JSCE Guidelines for Concrete
No.16

STANDARD SPECIFICATIONS FOR CONCRETESTRUCTURES  2007
"Materials and Construction"

Japan Society of Civil Engineers

JSCE Guidelines for Concrete
No.16

STANDARD SPECIFICATIONS FOR CONCRETESTRUCTURES  2007
"Materials and Construction"

Published bySubcommittee on
English Version of Standard Specifications for Concrete Structures - 2007
Japan Society of Civil Engineers (JSCE)
Yotsuya 1-chome, Shinjuku-ku, Tokyo 160-0004, JAPANFAX +81-3-5379-2769 E-mail pub@jsce.or.jp
December 2010

Copyright  JSCE 2010 Concrete Committee
Printed in Japan
英文版 2007 年制定コンクリート標準示方書［施工編］ 1.1

ISBN 978-4-8106-0753-6

Preface
Concrete structures have supported our society as infrastructures. The society can only preserve itself inwholesome with tough, beautiful and durable concrete structures. Concrete Committee of Japan Society of Civil
Engineers (JSCE), leading organization for investigation, research, technological promotion and education of
concrete in Japan, considers the issuance and revision of Standard Specifications for Concrete Structures as its
most important activity. Standard Specifications for Concrete Structures (JSCE-SSCS), which show the model
for plan, design, execution, maintenance and repair of concrete structures, have been highly recognized in practiceand contributed to the development of concrete technology in Japan since its first publication as “Standard
Specifications for Reinforced Concrete – 1931.”
In order to cope with the development of concrete technology in Japan and the worldwide trend, Concrete
Committee converted all Specifications in JSCE-SSCS namely ‘Structural Performance Verification’, ‘Seismic
Performance Verification’, ‘Materials and Construction’, ‘Maintenance’, ‘Dam Concrete’ and ‘Pavement’, fromthe “Prescriptive Code” to “Performance-based Code” and completed the work in 2002.
This revised edition adopts the technological development after 2002 and intends to enhance theperformance-based nature in Standard Specifications. For practical efficiency, the three Specifications - ‘Design’,‘Materials and Construction’ and ‘Dam Concrete’ present not only general provisions for verification of specified
performance requirements but also standard methods as simplified methods to achieve the performancerequirements under certain conditions. JSCE-SSCS is ready for practical use as it describes the role of eachSpecification during the plan, design, execution, maintenance and repair phases as well as the relationship among
them. And for the first time, it also describes roles of engineers for construction works. This JSCE-SSCS is yet
an ultimate one. There are still remaining tasks, such as inclusion of provisions for scenario of concrete
structures during service life. What readers can find in this revised edition is rationality with “theperformance-based concept” and the applicability for practice, showing the high level of technology in Japan.
This revised JSCE-SSCS consists of five Specifications; ‘Design,’ which combines the previous ‘Structural
Performance Verification’ and ‘Seismic Performance Verification’ together, ‘Materials and Construction,’‘Maintenance,’ ‘Dam Concrete’ and ‘Test Methods and Specifications.’ Specification of ‘Test Methods andSpecifications’ was issued separately in May 2007. Specification of ‘Pavement’ was published as “Standard
Specifications for Pavements – 2007” by the Committee on Pavement Engineering of JSCE, which has taken overthe issuance and revision works from JSCE-SSCS.
Finally I would like to show my most sincere gratitude to Prof Taketo UOMOTO and Dr Tadayoshi ISHIBASHI,
Chairman and Secretary General of Sub-committee on Revision of Standard Specifications for Concrete
Structures as well as its Secretaries, Conveners and Members who devoted themselves continuously despite thetight drafting schedule. My gratitude also goes to Advisors, Secretaries, Executive Members and Members ofConcrete Committee, who reviewed the draft.
December 2007

Toyoaki MIYAGAWA, Chairman
Concrete Committee of Japan Society of Civil Engineers

Preface to the English Version
The Japan Society of Civil Engineers’ (JSCE) Concrete Committee has been publishing the Standard
Specifications for Concrete Structures in Japanese since 1931.

The English versions were published twice in1987 and 2005 when the limit state design and the performance-based concept were introduced in the 1986 and2002 editions of Standard Specifications for Concrete Structures (JSCE-SSCS) for the first time, respectively.

Since 2004 the Concrete Committee has put efforts to enhance information dissemination overseas by presenting
various English publications including the series of “JSCE Guidelines for Concrete.”also decided to prepare the English version of every edition of JSCE-SSCS.

Concrete Committee hasThis Sub-committee on English

Version of Standard Specifications for Concrete Structures was established in 2008.

Our task is to prepare the English version of four Specifications: ‘Design,’ ‘Materials and Construction,’‘Maintenance’ and ‘Dam Concrete’ of the 2007 edition of JSCE-SSCS.

Specification of ‘Test Methods andSpecifications’ of JSCE-SSCS is not included in this English version.

However, some of these standard test

methods and specifications have been translated for publication in a series of “JSCE Guidelines for Concrete.”
Please visit the website of Concrete Committee at http://www.jsce.or.jp/committee/concrete/e/index.html for the
information on the English publications.

This English version includes most of the contents in the original Japanese version.

Utmost efforts have been

made to ensure that the translation accurately convey the description in the original Japanese version. If there
were any discrepancy between the Japanese and English versions, however, reference should be made to theoriginal Japanese version.

Translation of technical work does not only require expertise but a lot of time and dedication.
the members for their tiring efforts.

I am grateful to all

My heartfelt appreciations go to Prof YOKOTA Hiroshi (Secretary General),

Dr SHIMOMURA Takumi (Head, WG for Design), Prof SUGIYAMA Takafumi (Head, WG for Materials andConstruction), Dr MAEDA Toshiya (Head, WG for Maintenance), Prof AYANO Toshiki (Head, WG for Dam
Concrete) and Dr ISHIZUKA Takayuki who proof-read all the translated Specifications. Without them thisEnglish version would not have been published.

December 2010

UEDA Tamon, Chairman
Sub-committee on English Version of Standard Specifications for Concrete Structures

JSCE Committee on
Revision of Standard Specifications for Concrete Structures
Taketo UOMOTO, Chairman
Tadayoshi ISHIBASHI, Secretary
Members
Hiroyuki IKEDA

Tomoya IWASHITA

Tamon UEDA

Kimitaka UJI

Hidetaka UMEHARA

Nobuaki OTSUKI

Hiroshi ONUMA

Satoshi OKAZAWA

Tsutomu KANAZU

Yuichi KANEKO

Toru KAWAI

Hirotaka KAWANO

Etsuo SAKAI

Koji SAKAI

Tsutomu SATO

Ryoichi SATO

Motoyuki SUZUKI

Shigeyuki SOGO

Koji TAKEWAKA

Takao CHIKADA

Yukikazu TSUJI

Tomoaki TSUTSUMI

Rokuro TOMITA

Kazuyuki TORII

Junichiro NIWA

Yoshinobu NOBUTA

Chikanori HASHIMOTO

Makoto HISADA

Tsutomu FUKUTE

Koichi MAEKAWA

Yasunori MATSUOKA

Kyuichi MARUYAMA

Tetsuya MISHIMA

Toyoaki MIYAGAWA

Hiroshi MUTSUYOSHI

Hiroshi YOKOTA

Keitetsu ROKUGOFormer Members
Takashi SASAKI

Yasuo INOKUMA

Working Group for 'Materials and Construction'
Hidetaka UMEHARA, Chairman
Hirotaka KAWANO, Vice Chairman
Shigeyuki SOGO, Secretary
Members
Takefumi SHINDO

Hidenori HAMADA

Takafumi SUGIYAMAToru KAWAI

Tetsuya ISHIDA

Takeshi INOUE

Michitoshi IWATA

Sakae USHIJIMASoji OHSHIRO

Tsutomu KANAZU

Yuichi KANEKO

Kenji KAWAI

Toshiharu KISHI

Satoru TERAMURA

Tatsuhiko SAEKI

Etsuro SAKAI

Noboru SAKATA

Fuminori SATO

Hideaki TANIGUCHI

Ryuichi CHIKAMATSU

Masamichi TEZUKA

Masayuki HASHIMOTO

Makoto HISADA

Shigemi MATSUO

Tetsuya MISHIMA

Hidenori MORIKAWA

Keiichi WATANABE

Former Members
Hideaki GOMI

Koji OSADA

Subcommittee on English Version of Standard Specifications for Concrete Structures
Tamon UEDA, Chairman
Hiroshi YOKOTA, Secretary General

Secretaries
Toshiki AYANO

Takayuki ISHIZUKATakafumi SUGIYAMA

Toshiya MAEDA

Takumi SHIMOMURA

Members
Tetsuya ISHIDA

Hajime ITO

Mitsuyasu IWANAMI

Takao UEDA

Atsushi UENO

Masahiro OUCHI

Yoshinobu OSHIMA

Yoshitaka KATO

Minoru KUNIEDA

Yoshimori KUBO

Hirohisa KOGA

Koichi KOBAYASHI

Shigehiko SAITO

Goro SAKAI

Yasutaka SAGAWA

Toshiya TADOKORO

Hiroaki TSURUTA

Hideki NAITO

Kohei NAGAI

Kenichiro NAKARAI

Akira HOSODA

Tomohiro MIKI

Maki MIZUTA

Hiroshi MINAGAWA

Shinichi MIYAZATO

Toshinobu YAMAGUCHI

Ken WATANABE

Working Group for 'Materials and Construction'
Takafumi SUGIYAMA, Chairman

Members
Tetsuya ISHIDA

Takao UEDA

Yoshitaka KATO

Minoru KUNIEDA

Yoshimori KUBO

Goro SAKAI

Yasutaka SAGAWA

Akira HOSODA

Shinichi MIYAZATOJSCE Guideline for Concrete No. 16

Standard Specifications for Concrete Structures -2007“Materials and Construction”
CONTENTS
Application of Standard Specifications for Concrete Structures ................................................... i

GENERAL REQUIREMENTS
CHAPTER 1 GENERAL PROVISIONS ...................................................................................... 1
1.1 General ..................................................................................................................................... 1
1.2 Definitions ................................................................................................................................ 3
CHAPTER 2 CONSTRUCTION PLAN ....................................................................................... 4
2.1 General ..................................................................................................................................... 4
2.2 Considerations in Construction Planning ................................................................................. 6
2.3 Determination of Concreting Method .................................................................................................... 7
2.4 Determination of Construction Performance of Concreting .................................................... 7
2.5 Materials ................................................................................................................................... 8
2.6 Concrete Mix Design ............................................................................................................... 8
2.7 Verification of Concrete Performance ...................................................................................... 9
2.8 Confirmation and Alteration of Construction Plan ................................................................ 10
CHAPTER 3 CONSTRUCTION ................................................................................................. 11
3.1 General ................................................................................................................................... 11
CHAPTER 4 QUALITY CONTROL .......................................................................................... 12
4.1 General ................................................................................................................................... 12
CHAPTER 5 INSPECTION ......................................................................................................... 13
5.1 General ................................................................................................................................... 13
5.2 Inspection Plan ....................................................................................................................... 15
5.3 Conduct of Inspection ............................................................................................................ 16
5.4 Maintenance of Inspection Records ....................................................................................... 16
CHAPTER 6 CONSTRUCTION RECORDS ............................................................................ 17
6.1 General ................................................................................................................................... 17

CONSTRUCTION STANDARDSCHAPTER 1 GENERAL .............................................................................................................. 19(1)

1.1 General ................................................................................................................................... 19
1.2 Definitions .............................................................................................................................. 21
CHAPTER 2 QUALITY CONTROL .......................................................................................... 32
2.1 General ................................................................................................................................... 32
2.2 Qualitative Consistency ......................................................................................................... 33
2.3 Workability ............................................................................................................................. 33
2.3.1 Filling ability ................................................................................................................... 34
2.3.2 Pumpability ..................................................................................................................... 37
2.3.3 Setting properties ............................................................................................................ 38
2.4 Strength .................................................................................................................................. 39
2.5 Durability ............................................................................................................................... 40
2.5.1 General ............................................................................................................................ 40
2.5.2 Durability of concrete ..................................................................................................... 41
2.5.3 Steel protection performance .......................................................................................... 42
2.6 Water-tightness ....................................................................................................................... 44
2.7 Cracking Resistance ............................................................................................................... 44
CHAPTER 3 CONSTITUENT MATERIALS ............................................................................ 47
3.1 General ................................................................................................................................... 47
3.2 Cement ................................................................................................................................... 47
3.3 Mixing Water .......................................................................................................................... 49
3.4 Aggregates.............................................................................................................................. 50
3.4.1 Fine aggregate ................................................................................................................. 50
3.4.2 Coarse aggregate ............................................................................................................. 56
3.5 Admixtures ............................................................................................................................. 59
3.5.1 General ............................................................................................................................ 59
3.5.2 Mineral admixtures ......................................................................................................... 61
3.5.3 Chemical admixtures....................................................................................................... 63
3.6 Reinforcing Materials............................................................................................................. 65
3.6.1 Reinforcing bars .............................................................................................................. 65
3.6.2 Prestressing steel ............................................................................................................. 66
3.6.3 Structural steel................................................................................................................. 68
3.6.4 Other reinforcing steel..................................................................................................... 68
3.7 Storage of Materials ............................................................................................................... 69
3.7.1 Storage of cement ............................................................................................................ 69
3.7.2 Storage of aggregates ...................................................................................................... 70
3.7.3 Storage of admixtures ..................................................................................................... 72
3.7.4 Storage of chemical admixtures ...................................................................................... 73
3.7.5 Storage of steel ................................................................................................................ 73
CHAPTER 4 MIX DESIGN ......................................................................................................... 75
4.1 General ................................................................................................................................... 75
4.2 Mix Design Procedure............................................................................................................ 77
4.3 Target Performance of Concrete............................................................................................. 80
4.3.1 Defining target performance ........................................................................................... 80
4.3.2 Workability of concrete ................................................................................................... 80
4.3.3 Specified strength ............................................................................................................ 81
4.3.4 Durability ........................................................................................................................ 81
4.4 Determination of Mix Requirements ..................................................................................... 83
4.4.1 Maximum size of coarse aggregate ................................................................................. 83(2)

4.4.2 Slump .............................................................................................................................. 84
4.4.3 Required strength ............................................................................................................ 92
4.4.4 Water/cement ratio .......................................................................................................... 94
4.4.5 Air content in air-entrained concrete............................................................................... 96
4.5 Determination of Provisional Mix Proportions ...................................................................... 96
4.5.1 Water content .................................................................................................................. 96
4.5.2 Cement content................................................................................................................ 97
4.5.3 Powdery material content............................................................................................... 98
4.5.4 Sand-aggregate ratio ....................................................................................................... 99
4.5.5 Unit quantities of admixtures ........................................................................................ 101
4.6 Trial Mixing ......................................................................................................................... 101
4.6.1 General .......................................................................................................................... 101
4.6.2 Trial mixing method ...................................................................................................... 102
4.7 Representation of Mix Proportions ...................................................................................... 103
CHAPTER 5 CONCRETE PRODUCTION............................................................................. 104
5.1 General ................................................................................................................................. 104
5.2 Production Plant ................................................................................................................... 105
5.2.1 Storage facilities ............................................................................................................ 105
5.2.2 Measuring equipment .................................................................................................... 106
5.2.3 Mixers ........................................................................................................................... 107
5.3 Measurement of Materials.................................................................................................... 108
5.4 Mixing ...................................................................................................................................111
5.5 Plasticization of Concrete .................................................................................................... 112
CHAPTER 6 READY-MIXED CONCRETE ........................................................................... 114
6.1 General ................................................................................................................................. 114
6.2 Selection of Plants ................................................................................................................ 115
6.3 Specification of Qualities ..................................................................................................... 116
6.4 Receiving.............................................................................................................................. 119
CHAPTER 7 TRANSPORTATION, PLACEMENT, COMPACTION AND
FINISHING .......................................................................................................... 122
7.1 General ................................................................................................................................. 122
7.2 Time from Mixing to Finishing the Placement .................................................................... 124
7.3 Transportation ...................................................................................................................... 125
7.3.1 Transportation to the construction site .......................................................................... 125
7.3.2 On site transportation .................................................................................................... 125
7.3.2.1 Concrete pump ....................................................................................................... 125
7.3.2.2 Buckets ................................................................................................................... 129
7.3.2.3 Chutes .................................................................................................................... 130
7.3.2.4 Other transportation equipment ............................................................................. 130
7.4 Placement ............................................................................................................................. 131
7.4.1 Preparation .................................................................................................................... 131
7.4.2 Placement ...................................................................................................................... 132
7.5 Compaction .......................................................................................................................... 135
7.6 Finishing ............................................................................................................................... 137
7.6.1 Surface finish of placed concrete .................................................................................. 137
7.6.2 Correction of surface finish defects .............................................................................. 138
7.6.3 Special finishing ............................................................................................................ 138(3)

CHAPTER 8 CURING ............................................................................................................... 140
8.1 General ................................................................................................................................. 140
8.2 Moist Curing ........................................................................................................................ 141
8.3 Temperature-Controlled Curing ........................................................................................... 142
8.4 Protection Against Harmful Effects ..................................................................................... 143
CHAPTER 9 JOINTS ................................................................................................................. 145
9.1 General ................................................................................................................................. 145
9.2 Construction Joints ............................................................................................................... 145
9.3 Horizontal Construction Joints ............................................................................................. 146
9.4 Vertical Construction Joints ................................................................................................. 148
9.5 Construction Joints in Columns and Walls Integrated with Floor Systems ......................... 149
9.6 Construction Joints in Floor Systems ................................................................................... 149
9.7 Construction Joints in Arches............................................................................................... 150
9.8 Expansion Joints................................................................................................................... 150
9.9 Joints to Control Cracking ................................................................................................... 151
CHAPTER 10 REINFORCEMENT ......................................................................................... 153
10.1 General ............................................................................................................................... 153
10.2 Fabrication of Reinforcement ............................................................................................ 154
10.3 Assembly of Reinforcing Bars ........................................................................................... 155
10.4 Joints of Reinforcing Bars ................................................................................................. 157
10.5 Placement of Pre-assembled Reinforcing Bars .................................................................. 158
CHAPTER 11 FORMWORK AND SHORING....................................................................... 159
11.1 General ............................................................................................................................... 159
11.2 Load ................................................................................................................................... 159
11.2.1 General ........................................................................................................................ 159
11.2.2 Vertical loads .............................................................................................................. 160
11.2.3 Horizontal loads .......................................................................................................... 160
11.2.4 Lateral pressure of concrete ........................................................................................ 161
11.2.5 Special loads ............................................................................................................... 166
11.3 Materials ............................................................................................................................ 166
11.4 Design of Formwork .......................................................................................................... 169
11.5 Design of Shoring .............................................................................................................. 170
11.6 Preparation of Formwork ................................................................................................... 171
11.7 Preparation of Shoring ....................................................................................................... 171
11.8 Removal of Formwork and Shoring .................................................................................. 172
11.9 Special Formwork and Shoring ......................................................................................... 173
11.9.1 General ........................................................................................................................ 173
11.9.2 Slipform ...................................................................................................................... 174
11.9.3 Movable shores ........................................................................................................... 175
CHAPTER 12 COLD WEATHER CONCRETING ................................................................ 177
12.1 General ............................................................................................................................... 177
12.2 Materials ............................................................................................................................ 177
12.3 Mix Proportions ................................................................................................................. 179
12.4 Mixing ................................................................................................................................ 179
12.5 Transportation and Placing ................................................................................................ 180
12.6 Curing ................................................................................................................................ 182(4)

12.7 Formwork and Shoring ...................................................................................................... 184
CHAPTER 13 HOT WEATHER CONCRETING .................................................................. 186
13.1 General ............................................................................................................................... 186
13.2 Materials ............................................................................................................................ 186
13.3 Mix Proportions ................................................................................................................. 187
13.4 Mixing ................................................................................................................................ 188
13.5 Transportation .................................................................................................................... 189
13.6 Placing ............................................................................................................................... 189
13.7 Curing ................................................................................................................................ 190
CHAPTER 14 MASS CONCRETE .......................................................................................... 192
14.1 General ............................................................................................................................... 192
14.2 Materials ............................................................................................................................ 193
14.3 Mix Proportions ................................................................................................................. 195
14.4 Production .......................................................................................................................... 195
14.5 Construction ....................................................................................................................... 196
14.5.1 Partitioning into blocks, lift height and joints ............................................................ 196
14.5.2 Placing ........................................................................................................................ 196
14.5.3 Curing ......................................................................................................................... 197
14.5.4 Formwork ................................................................................................................... 197
14.5.5 Crack-inducing joints.................................................................................................. 198
CHAPTER 15 QUALITY CONTROL...................................................................................... 199
15.1 General ............................................................................................................................... 199
15.2 Quality Control of Concrete Materials and Reinforcing Materials ................................... 200
15.3 Quality Control in Concrete Production ............................................................................ 200
15.4 Quality Control of Concrete .............................................................................................. 201
15.5 Quality Control during Construction ................................................................................. 202
15.6 Quality Control of Concrete Structures ............................................................................. 204
CHAPTER 16 INSPECTION CONDUCTED BY CONTRACTOR ..................................... 206
16.1 General ............................................................................................................................... 206
CHAPTER 17 CONSTRUCTION RECORDS ........................................................................ 207

INSPECTION STANDARDSCHAPTER 1 GENERAL ............................................................................................................ 209
1.1 General ................................................................................................................................. 209
1.2 Definitions of Terms............................................................................................................. 210
CHAPTER 2 INSPECTION PLAN ........................................................................................... 211
CHAPTER 3 INSPECTION FOR ACCEPTANCE OF CONSTITUENT MATERIALSOF CONCRETE................................................................................................... 214
3.1 General ................................................................................................................................. 209
3.2 Cement ................................................................................................................................. 215(5)

3.3 Mixing Water ........................................................................................................................ 216
3.4 Aggregates............................................................................................................................ 217
3.5 Admixtures ........................................................................................................................... 220
CHAPTER 4 INSPECTION OF CONCRETE PRODUCTION FACILITIES .................... 222
CHAPTER 5 INSPECTION FOR ACCEPTANCE OF READY MIXED CONCRETE ..... 224
CHAPTER 6 ACCEPTANCE INSPECTION FOR REINFORCEMENT ............................ 229
CHAPTER 7 INSPECTIONS OF CONSTRUCTION ............................................................ 231
7.1 General ................................................................................................................................. 231
7.2 Inspection of Concreting ...................................................................................................... 231
7.3 Inspection of Reinforcement ................................................................................................ 237
7.3.1 Inspection of fabrication and assembly of reinforcing bars .......................................... 237
7.3.2 Inspection of joint of reinforcing bars........................................................................... 240
7.4 Inspection of Formwork and Shoring .................................................................................. 242
CHAPTER 8 INSPECTION OF CONCRETE STRUCTURE ............................................... 243
8.1 General ................................................................................................................................. 243
8.2 Inspection of Surface Texture .............................................................................................. 244
8.3 Inspection of Locations and Dimensions of Concrete Members ......................................... 246
8.4 Inspection of Concrete Properties in Structure .................................................................... 246
8.5 Inspection of the Cover ........................................................................................................ 247
8.6 Loading Test of Member and Structure................................................................................ 248
CHAPTER 9 RECORDS ............................................................................................................ 250
9.1 General ................................................................................................................................. 250
9.2 Identifiers of Structures ........................................................................................................ 250

SPECIAL CONCRETE
CHAPTER 1 GENERAL ............................................................................................................ 251
1.1 Scope .................................................................................................................................... 251
1.2 Definitions ............................................................................................................................ 253
CHAPTER 2 EXPANSIVE CONCRETE ................................................................................. 261
2.1 General ................................................................................................................................. 261
2.1.1 Scope ............................................................................................................................. 261
2.1.2 General .......................................................................................................................... 262
2.2 Quality of Expansive Concrete ............................................................................................ 262
2.2.1 General .......................................................................................................................... 262
2.2.2 Expansivity.................................................................................................................... 263
2.2.3 Strength ......................................................................................................................... 264
2.3 Materials ............................................................................................................................... 265
2.3.1 Cement .......................................................................................................................... 265
2.3.2 Expansive admixture ..................................................................................................... 265(6)

2.4 Mix Proportion ..................................................................................................................... 266
2.4.1 General .......................................................................................................................... 266
2.4.2 Quantity of expansive admixture per unit volume of concrete ..................................... 267
2.4.3 Quantity of cement per unit volume of concrete ........................................................... 268
2.4.4 Presentation of mix proportion ..................................................................................... 268
2.5 Production and Construction ................................................................................................ 268
2.5.1 Mixing ........................................................................................................................... 268
2.5.2 Curing............................................................................................................................ 269
2.6 Inspections............................................................................................................................ 270
2.6.1 Expansive admixture acceptance tests .......................................................................... 270
2.6.2 Concrete acceptance tests .............................................................................................. 271
CHAPTER 3 LIGHTWEIGHT AGGREGATE CONCRETE ............................................... 273
3.1 General ................................................................................................................................. 273
3.1.1 Scope ............................................................................................................................. 273
3.1.2 General .......................................................................................................................... 273
3.2 Quality of Lightweight Aggregate ....................................................................................... 273
3.3 Quality of Lightweight Aggregate Concrete ........................................................................ 275
3.4 Mix Proportions ................................................................................................................... 279
3.4.1 General .......................................................................................................................... 279
3.4.2 Mass of unit volume ...................................................................................................... 279
3.4.3 Water-cement ratio ........................................................................................................ 280
3.4.4 Slump ............................................................................................................................ 280
3.4.5 Air content..................................................................................................................... 281
3.4.6 Presentation of mix proportion ..................................................................................... 282
3.5 Production and Construction ................................................................................................ 282
3.5.1 Selection of plant .......................................................................................................... 282
3.5.2 Transportation and storage of lightweight aggregates .................................................. 283
3.5.3 Control of moisture content of lightweight aggregate .................................................. 283
3.5.4 Mixing ........................................................................................................................... 284
3.5.5 Transportation within the construction site ................................................................... 285
3.5.6 Placing and compaction ................................................................................................ 285
3.5.7 Surface finishing ........................................................................................................... 286
3.6 Inspection ............................................................................................................................. 287
3.6.1 Inspection for acceptance of lightweight aggregate ...................................................... 287
3.6.2 Inspection for acceptance of lightweight aggregate concrete ....................................... 287
CHAPTER 4 CONCRETE USING CONTINUOUS FIBER REINFORCING
MATERIALS (CFRM) ........................................................................................ 289
4.1 General ................................................................................................................................. 289
4.1.1 Scope ............................................................................................................................. 289
4.1.2 General .......................................................................................................................... 289
4.2 Materials ............................................................................................................................... 290
4.2.1 Continuous fiber reinforcing materials (CFRM)........................................................... 290
4.2.2 Reinforcing steel bars.................................................................................................... 290
4.2.3 Anchorages and couplers on protection materials ........................................................ 291
4.3 Construction ......................................................................................................................... 291
4.3.1 Handling and storage of materials................................................................................. 291
4.3.2 Shaping, assembly and placing in position of CFRM tendons,
CFRM reinforcements etc. ............................................................................................ 292
4.3.2.1 Shaping and assembly of CFRM tendons .............................................................. 292(7)

4.3.2.2 Shaping and assembly of CFRM reinforcement .................................................... 293
4.3.2.3 Making ducts other than sheaths ............................................................................ 294
4.3.2.4 Placing sheaths and CFRM tendons....................................................................... 294
4.3.3 Placement of concrete ................................................................................................... 295
4.3.4 Prestressing ................................................................................................................... 295
4.4 Inspection ............................................................................................................................. 296
4.4.1 Inspection for acceptance of materials .......................................................................... 296
4.4.2 Inspection for protection of CFRM ............................................................................... 298
CHAPTER 5 SHORT FIBER REINFORCED CONCRETE ................................................. 299
5.1 General ................................................................................................................................. 299
5.1.1 Scope ............................................................................................................................. 299
5.1.2 General .......................................................................................................................... 300
5.2 Quality of Short Fiber Reinforced Concrete ........................................................................ 300
5.2.1 General .......................................................................................................................... 300
5.2.2 Strength properties ........................................................................................................ 301
5.2.2.1 Compressive strength ............................................................................................. 301
5.2.2.2 Tensile strength ...................................................................................................... 301
5.2.2.3 Flexural strength .................................................................................................... 301
5.2.3 Deformation characteristics .......................................................................................... 302
5.2.3.1 Deformation characteristics under compression .................................................... 302
5.2.3.2 Tension softening properties .................................................................................. 303
5.2.3.3 Flexural toughness ................................................................................................. 304
5.2.4 Prevention of explosion................................................................................................. 305
5.2.5 Prevention of spalling ................................................................................................... 306
5.2.6 Other performance ........................................................................................................ 306
5.3 Short fibers ........................................................................................................................... 307
5.3.1 Steel fibers..................................................................................................................... 307
5.3.2 Synthetic fibers ............................................................................................................. 307
5.4 Mix Proportions ................................................................................................................... 308
5.5 Production and Placement/Application ................................................................................ 310
5.5.1 Fiber addition and mixing ............................................................................................. 310
5.5.2 Transportation ............................................................................................................... 311
5.6 Inspection ............................................................................................................................. 312
5.6.1 Inspection for acceptance of short fibers ...................................................................... 312
5.6.2 Inspection for acceptance of concrete at delivery ......................................................... 313
CHAPTER 6 HIGH-STRENGTH CONCRETE ..................................................................... 315
6.1 General ................................................................................................................................. 315
6.1.1 Scope ............................................................................................................................. 315
6.1.2 General .......................................................................................................................... 316
6.2 Quality of High-Strength Concrete ...................................................................................... 316
6.3 Materials ............................................................................................................................... 317
6.3.1 Cement and admixture .................................................................................................. 317
6.3.2 Aggregate ...................................................................................................................... 317
6.3.3 Chemical admixture ...................................................................................................... 318
6.4 Mix Proportion ..................................................................................................................... 318
6.4.1 Srength .......................................................................................................................... 318
6.4.2 Slump or slump flow ..................................................................................................... 319
6.4.3 Air content..................................................................................................................... 319
6.4.4 Water-binder ratio ......................................................................................................... 319(8)6.4.5 Water content ................................................................................................................ 320
6.4.6 Unit content of coarse aggregate ................................................................................... 320
6.5 Production ............................................................................................................................ 321
6.5.1 Selection of plants ......................................................................................................... 321
6.5.2 Mixing ........................................................................................................................... 321
6.5.3 Production control ......................................................................................................... 321
6.6 Construction ......................................................................................................................... 322
6.6.1 Transportation within construction site ......................................................................... 322
6.6.2 Placement and compaction............................................................................................ 323
6.6.3 Finishing and curing...................................................................................................... 323
6.6.4 Formwork ...................................................................................................................... 324
6.7 Inspection ............................................................................................................................. 324
CHAPTER 7 HIGH–FLUIDITY CONCRETE ........................................................................ 326
7.1 General ................................................................................................................................. 326
7.1.1 Scope ............................................................................................................................. 326
7.1.2 General .......................................................................................................................... 326
7.2 Quality of High-Fluidity Concrete ....................................................................................... 327
7.2.1 General .......................................................................................................................... 327
7.2.2 Self-compactability ....................................................................................................... 327
7.3 Materials ............................................................................................................................... 329
7.4 Mix Proportion ..................................................................................................................... 329
7.4.1 Selection of types of high-fluidity concrete .................................................................. 329
7.4.2 Mix design..................................................................................................................... 330
7.4.3 Representation of mix proportion ................................................................................. 332
7.5 Production ............................................................................................................................ 333
7.5.1 Selection of plants ......................................................................................................... 333
7.5.2 Storage of aggregates .................................................................................................... 333
7.5.3 Mixing ........................................................................................................................... 334
7.5.4 Quality control during production................................................................................. 335
7.6 Construction ......................................................................................................................... 336
7.6.1 Transportating and placing ............................................................................................ 336
7.6.2 Finishing and curing...................................................................................................... 337
7.6.3 Construction joints ........................................................................................................ 337
7.6.4 Formwork ...................................................................................................................... 338
7.7 Inspection ............................................................................................................................. 338
CHAPTER 8 SHOTCRETE ....................................................................................................... 340
8.1 General ................................................................................................................................. 340
8.1.1 Scope ............................................................................................................................. 340
8.1.2 General .......................................................................................................................... 341
8.2 Quality of Concrete .............................................................................................................. 341
8.2.1 General .......................................................................................................................... 341
8.2.2 Mechanical properties of concrete ................................................................................ 342
8.3 Materials ............................................................................................................................... 343
8.3.1 Cement .......................................................................................................................... 343
8.3.2 Aggregate ...................................................................................................................... 344
8.3.3 Set accelerator ............................................................................................................... 344
8.3.4 Admixtures and short fibers .......................................................................................... 345
8.4 Mix Proportions ................................................................................................................... 346
8.5 Production ............................................................................................................................ 348(9)8.5.1 General .......................................................................................................................... 348
8.5.2 Production facilities ...................................................................................................... 348
8.5.3 Shotcrete machine and accessory equipment ................................................................ 349
8.6 Construction ......................................................................................................................... 350
8.6.1 General .......................................................................................................................... 350
8.6.2 Preliminary treatment of shotcrete surface ................................................................... 350
8.6.3 Shotcreting work ........................................................................................................... 351
8.6.4 Dust control measures ................................................................................................... 352
8.6.5 Concrete protection ....................................................................................................... 353
8.7 Inspections............................................................................................................................ 354
8.7.1 Acceptance tests for concrete materials ........................................................................ 354
8.7.2 Concrete acceptance tests .............................................................................................. 355
8.7.3 Inspection of concrete work .......................................................................................... 356
CHAPTER 9 PRE-PLACED AGGREGATE CONCRETE .................................................... 359
9.1 General ................................................................................................................................. 359
9.1.1 Scope ............................................................................................................................. 359
9.1.2 General .......................................................................................................................... 359
9.2 Quality of Pre-Placed Aggregate Concrete .......................................................................... 360
9.2.1 Quality of concrete ........................................................................................................ 360
9.2.2 Quality of grouting mortar ............................................................................................ 360
9.3 Mix Design ........................................................................................................................... 361
9.3.1 Materials........................................................................................................................ 361
9.3.2 Mix proportion of grouting mortar................................................................................ 363
9.3.3 Representation of mix proportion ................................................................................. 365
9.4 Production and Placing ........................................................................................................ 365
9.4.1 Production and placing of grout mortar ........................................................................ 365
9.4.1.1 Production plant ..................................................................................................... 365
9.4.1.2 Mixing .................................................................................................................... 366
9.4.2 Construction and control ............................................................................................... 367
9.4.2.1 Shuttering ............................................................................................................... 367
9.4.2.2 Charging coarse aggregate ..................................................................................... 369
9.4.2.3 Grouting equipment and injection pipes ................................................................ 370
9.4.2.4 Pumping ................................................................................................................. 370
9.4.2.5 Grouting ................................................................................................................. 372
9.4.2.6 Construction joints ................................................................................................. 374
9.4.2.7 Construction in cold weather ................................................................................. 375
9.4.2.8 Construction in hot weather ................................................................................... 375
9.5 Inspection ............................................................................................................................. 376
9.5.1 Material acceptance tests............................................................................................... 376
9.5.2 Acceptance test of pre-placed aggregate concrete and mortar for grouting.................. 377
CHAPTER 10 UNDERWATER CONCRETE ......................................................................... 378
10.1 General ............................................................................................................................... 378
10.1.1 Scope........................................................................................................................... 378
10.1.2 General ........................................................................................................................ 378
10.2 Ordinary Underwater Concrete .......................................................................................... 379
10.2.1 Mix proportions .......................................................................................................... 379
10.2.2 Placement .................................................................................................................... 380
10.2.2.1 General…………………………………………………………………………380
10.2.2.2 Placement using tremie pipes…………………………………………………381(10)

10.2.2.3 Placement by pumping…………………………………………………………382
10.2.2.4 Placement using bottom discharge buckets or bags……………………………383
10.3 Anti-Washout Underwater Concrete .................................................................................. 383
10.3.1 Materials ..................................................................................................................... 383
10.3.2 Mix proportions .......................................................................................................... 384
10.3.3 Mixing......................................................................................................................... 386
10.3.4 Placement .................................................................................................................... 387
10.3.5 Protection of concrete surface .................................................................................... 387
10.4 Underwater Concrete Used for Cast-In-Place Piles or Diaphragm Walls ......................... 388
10.4.1 Mix proportions .......................................................................................................... 388
10.4.2 Pre-assembled reinforcement...................................................................................... 389
10.4.3 Placement .................................................................................................................... 390
10.5 Inspections ......................................................................................................................... 392
CHAPTER 11 CONCRETE FOR MARINE STRUCTURE .................................................. 395
11.1 General ............................................................................................................................... 395
11.1.1 Scope........................................................................................................................... 395
11.1.2 General ........................................................................................................................ 395
11.2 Materials ............................................................................................................................ 396
11.3 Mix proportions ................................................................................................................. 398
11.4 Construction ....................................................................................................................... 400
11.5 Concrete Surface Protection .............................................................................................. 401
11.6 Installation of Precast Concrete Members ......................................................................... 401
11.7 Inspections ......................................................................................................................... 402
CHAPTER 12 PRESTRESSED CONCRETE ......................................................................... 403
12.1 General ............................................................................................................................... 403
12.1.1 Scope........................................................................................................................... 403
12.1.2 General ........................................................................................................................ 403
12.2 Quality of Concrete ............................................................................................................ 404
12.2.1 Required compressive strength of concrete at the time of prestressing ...................... 404
12.2.2 Required workability of concrete ............................................................................... 405
12.3 Required Performance of Grout ......................................................................................... 405
12.3.1 General requirements .................................................................................................. 405
12.3.2 Consistency ................................................................................................................. 406
12.3.3 Bond strength between concrete and tendons ............................................................. 411
12.3.4 Corrosion resistance of steel ....................................................................................... 412
12.4 Material .............................................................................................................................. 414
12.4.1 Prestressing steel ......................................................................................................... 414
12.4.2 Anchorages, couplers, and deviators .......................................................................... 414
12.4.3 Sheaths ........................................................................................................................ 416
12.4.4 Grout for prestressed concrete .................................................................................... 417
12.4.5 Auxiliary materials for injecting grout for prestressed concrete ................................ 417
12.4.6 Protecting duct ............................................................................................................ 418
12.4.7 Coating material for unbonded tendons ...................................................................... 418
12.4.8 Material for jointing precast concrete members ......................................................... 419
12.4.9 Storage of materials .................................................................................................... 419
12.5 Proportioning of Grout Mix ............................................................................................... 420
12.6 Execution ........................................................................................................................... 421
12.6.1 Installation of tendons................................................................................................. 421
12.6.1.1 Cutting, bending and placing of prestressing steel .............................................. 421(11)

12.6.1.2 Installation of sheaths, protecting tubes and tendons .......................................... 422
12.6.1.3 Formation of ducts ............................................................................................... 423
12.6.1.4 Assembly and installation of anchorages, couplers and deviating devices ......... 423
12.6.1.5 Arrangement of openings for grouting, exhaust and discharging........................ 424
12.6.2 Formwork and shoring ................................................................................................ 425
12.6.3 Casting and compaction of concrete ........................................................................... 425
12.6.4 Prestressing ................................................................................................................. 426
12.6.4.1 General requirements ........................................................................................... 426
12.6.4.2 Calibration of tensioning equipments .................................................................. 428
12.6.4.3 Control of prestressing......................................................................................... 429
12.6.4.4 Protection of anchorages and end surfaces of members ...................................... 432
12.6.5 Grouting ...................................................................................................................... 433
12.6.5.1 General requirements ........................................................................................... 433
12.6.5.2 Mixing and agitating ............................................................................................ 433
12.6.5.3 Grouting ............................................................................................................... 434
12.6.5.4 Treatment of injection inlet, openings for air vent and grout discharge .............. 435
12.6.5.5 Grouting in cold weather ..................................................................................... 435
12.6.5.6 Grouting in hot weather ....................................................................................... 436
12.6.6 Manufacture and construction of precast members .................................................... 436
12.6.6.1 Manufacture ......................................................................................................... 436
12.6.6.2 Transportation ...................................................................................................... 437
12.6.6.3 Storage ................................................................................................................. 438
12.6.6.4 Jointing ................................................................................................................ 439
12.6.6.5 Erection ................................................................................................................ 442
12.6.7 Construction of external cable structures ................................................................... 442
12.6.7.1 Handling of tendons............................................................................................. 442
12.6.7.2 Assembly and arrangement of anchorage zone ................................................... 443
12.6.7.3 Assembly and installation of deviating devices .................................................. 443
12.6.7.4 Handling of protective tube ................................................................................. 443
12.6.7.5 Control of prestressing......................................................................................... 444
12.6.7.6 Injection of anticorrosives ................................................................................... 445
12.7 Inspection ........................................................................................................................... 445
12.7.1 Material acceptance tests ............................................................................................ 445
12.7.1.1 Prestressing steel.................................................................................................. 445
12.7.1.2 Anchorage and coupler ........................................................................................ 446
12.7.1.3 Sheaths ................................................................................................................. 447
12.7.1.4 Adhesive agents for jointing precast members .................................................... 449
12.7.2 Inspection of grout ...................................................................................................... 450
12.7.2.1 Acceptance test of grout ...................................................................................... 450
12.7.2.2 Inspection of grouting .......................................................................................... 451
12.7.3 Inspection of execution ............................................................................................... 453
12.7.3.1 Inspection of sheaths, protecting tubes and tendon arrangements....................... 453
12.7.3.2 Inspection of anchorage and coupler assembly and arrangement ....................... 454
12.7.3.3 Inspection of opening layout for grouting, exhaust and discharging................... 455
CHAPTER 13 STEEL-CONCRETE COMPOSITE STRUCTURES ................................... 456
13.1 General ............................................................................................................................... 456
13.1.1 Scope........................................................................................................................... 456
13.1.2 General ........................................................................................................................ 457
13.2 Materials ............................................................................................................................ 457
13.2.1 Steel ............................................................................................................................ 457(12)13.2.2 Concrete ...................................................................................................................... 458
13.3 Production of Steel Members ............................................................................................ 459
13.3.1 Processing of steel ...................................................................................................... 459
13.3.2 Factory welding .......................................................................................................... 461
13.3.3 Temporary assembly, assembly symbol and transportation........................................ 462
13.4 Erection of Steel Members ................................................................................................ 462
13.4.1 Erection ....................................................................................................................... 462
13.4.2 Temporary placement and assembly of steel members .............................................. 463
13.4.3 Jointing using high-strength bolts ............................................................................... 463
13.4.4 Welding in construction site ....................................................................................... 466
13.5 Concrete Construction ....................................................................................................... 466
13.6 Inspection ........................................................................................................................... 467
13.6.1 General ........................................................................................................................ 467
13.6.2 Inspection for acceptance ........................................................................................... 468
13.6.2.1 Inspection for acceptance of steel ........................................................................ 468
13.6.2.2 Inspection for acceptance of jointing materials ................................................... 468
13.6.2.3 Inspection for acceptance of concrete ................................................................. 469
13.6.3 Inspection for production of steel members ............................................................... 470
13.6.3.1 Inspection of welding .......................................................................................... 470
13.6.3.2 Inspection for tightening of high-strength bolt .................................................... 471
13.6.4 Inspection for filling condition of concrete ................................................................ 471
CHAPTER 14 FACTORY PRODUCTS ................................................................................... 473
14.1 General ............................................................................................................................... 473
14.1.1 Scope........................................................................................................................... 473
14.1.2 General ........................................................................................................................ 473
14.2 Concrete Quality ................................................................................................................ 474
14.2.1 General ........................................................................................................................ 474
14.2.2 Strength of factory products ....................................................................................... 474
14.3 Materials ............................................................................................................................ 476
14.3.1 Cement ........................................................................................................................ 476
14.3.2 Fine and coarse aggregates ......................................................................................... 477
14.3.3 Admixtures ................................................................................................................. 478
14.3.4 Reinforcing steel ......................................................................................................... 479
14.4 Mix Proportions ................................................................................................................. 480
14.4.1 General ........................................................................................................................ 480
14.4.2 Workability ................................................................................................................. 480
14.5 Production .......................................................................................................................... 481
14.5.1 Factory production ...................................................................................................... 481
14.5.2 Assembly of reinforcement......................................................................................... 481
14.5.3 Formwork ................................................................................................................... 482
14.5.4 Molding....................................................................................................................... 482
14.5.5 Curing ......................................................................................................................... 484
14.5.6 De-molding and prestressing ...................................................................................... 485
14.6 Transportation and Storage ................................................................................................ 486
14.7 Erection and Jointing ......................................................................................................... 487
14.8 Inspection ........................................................................................................................... 487
14.8.1 Material acceptance tests ............................................................................................ 487
14.8.2 Acceptance tests for factory products ......................................................................... 488(13)

Application of Standard Specifications for Concrete Structures

Application of Standard Specifications for Concrete Structures
Editorial notes for the English Version:(1) The Standard Specifications for Concrete Structures are a model code which is supposed to be
applied in Japan and have no legal bindings.
(2) Therefore, some contents, such as Chapters 2 and 3 of “Application of Standard
Specifications for Concrete Structures,” may not fit to practical scheme in construction industry inthe other countries.
(3) However, it is hoped that the Standard Specifications for Concrete Structures could be amodel code for the other countries after necessary modifications of the contents considering the
local conditions.

1. Basic concept concerning the organization of the Standard Specifications for Concrete
Structures
The Standard Specifications for Concrete Structures are regularly revised reflecting thestate-of-the-art concrete technologies developed in Japan and other countries, and provide standards
concerning the technical aspects of concrete structures in a series of phases from planning to design,
construction and maintenance.
In this revised edition, the “Standard Specifications for Concrete Structures, Design” iscomposed of the “Standard Specifications for Concrete Structures, Structural Performance
Verification” and “Standard Specifications for Concrete Structures, Seismic Performance
Verification” to enhance the convenience of design practice. Durability check and initial cracking
check, which should be discussed in the “Standard Specifications for Concrete Structures, Design”
have been transferred from the “Standard Specifications for Concrete Structures, Materials andConstruction” to “Standard Specifications for Concrete Structures, Design”. The preparation andrevision of the “Standard Specifications for Concrete Structures, Pavement” has been handed overto the Committee on Pavement Engineering, JSCE (Japan Society of Civil Engineers). The results
are now published separately under the title of the Standard Specifications for Pavement. Thus, theStandard Specifications for Concrete Structures include five components: Design, Materials andConstruction, Maintenance, Dam Concrete, and Test Methods and Specifications.
The General Requirements for “Design”, “Materials and Construction” and “Dam Concrete” aredescribed based on the concept of performance-based code. Performance requirements are specified
for structures and the methods for checking the compliance with requirements are shown in the
General Requirements. In the Standard Methods, standard methods for satisfying the General
Requirements under certain conditions are given for more efficient and simpler design andconstruction. In cases where no conditions specified in the Standard Methods are met, performanceverification should be conducted in accordance with the General Requirements. For establishing
new standards fitting for structures or regions to which no Standard Methods are applicable, theStandard Methods may be referred to.
Concrete structures are generally constructed for providing services in the phases of planning,
design, construction and maintenance in accordance with the respective components of the Standard
Specifications. Each type of work is not independent of the others. Data are handed over from an(i)Standard Specifications for Concrete Structures-2007, Materials and Construction

upstream to a downstream phase that are required for carrying out the work downstream to meet theconditions specified upstream. Handing over the data is therefore important to proper
implementation of work in respective phases. In the Standard Specifications for Concrete Structures,“Design”, “Materials and Construction” and “Maintenance” are closely interrelated to one another.
Then, the required data shown in each Specifications should be accurately handed over to the next
phase without fail.
Performance requirements for durability, safety, serviceability and restorability that are specified
in the “Standard Specifications for Concrete Structures, Design” are determined in the design phase.
Construction and maintenance methods are roughly determined in the phase. The data that affectconstruction and maintenance should therefore be handed over to the next phase without fail in theform of design drawings.
Construction records that are specified in the “Standard Specifications for Concrete Structures,
Materials and Construction” provide important data for assessment, deterioration prediction andimplementation of remedial measures in the maintenance phase. Accurate construction records
should therefore be handed over to maintenance engineers. Construction plans and various
inspection reports should also be provided to engineers as required.

Planning

Data
Feedback

DesignData

Construction

Data

MaintenanceFeedback
Fig. 1

Flow of work

Figure 1 shows a flow of work from the planning of a concrete structure to service
commencement. Data collected in the maintenance phase are not transferred to engineering works
in the planning, design or construction phase. It should, however, be taken into consideration thatreflecting the data in the maintenance phase in the planning, design and construction of anotherstructure for improvement is important to extend the service life of the structure. Theinterrelationship is basically the same for design, construction and maintenance described in the“Standard Specifications for Concrete Structures, Dam Concrete.”
Each component of the Standard Specifications for Concrete Structures is described below.
The “Standard Specifications for Concrete Structures, Design” shows standard methods for
performance verification of concrete structures such as reinforced concrete, prestressed concreteand steel-concrete composite structures, and stipulates the preconditions for checking and structuraldetails. The revised Standard Specifications for Concrete Structures are not applicable tounreinforced concrete structures. Material design values or other applicable items may, however, beapplied to unreinforced concrete structures.
The “Standard Specifications for Concrete Structures, Materials and Construction” provides
basic general rules concerning the construction of concrete structures. In the construction phase, theconstruction method and the performance during the construction work are determined based on thedesign drawings and restrictions on construction. Then, materials are selected and concrete mix(ii)Application of Standard Specifications for Concrete Structures

proportions are determined, where a concreting plan is developed so as to meet the requirements forwater content, cement amount, cement type and other parameters. Whether the concreting plan
meets the construction requirements or performance requirements of the structure or not is verified
by an appropriate method. If the requirements are not satisfied, the concreting method is
re-specified or the mix proportions are modified as long as the conditions handed over from thedesign phase are met.
The “Standard Specifications for Concrete Structures, Maintenance” provides general basic
principles concerning the maintenance of concrete structures. In the maintenance phase, documents
such as the design drawings and maintenance plans handed over from the design phase, and theconstruction plans, as-built drawings, construction records and inspection reports handed over fromthe construction phase should be fully used for efficient and effective maintenance work. In cases
where the use or functions of the structure change due to social changes, performance verification
should be made to verify whether the structure meets the resultant performance requirements or not.
If designated performance requirements are not ensured, repair, strengthening or other remedial
measures should be considered.
The “Standard Specifications for Concrete Structures, Dam Concrete” stipulates performanceand quality requirements for dam concrete, and describes the methods for verifying the compliancewith the requirements and the basic design and construction principles. The descriptions concerning
design, construction and maintenance in the “Standard Specifications for Concrete Structures, Dam
Concrete” are different from the contents of the Standard Specifications “Design”, “Materials andConstruction” and “Maintenance” with many respects because of the factors unique to dam concretesuch as the unreinforced nature and low or zero slump of dam concrete. The “Standard
Specifications for Concrete Structures, Dam Concrete” therefore describes the matters concerning
the design, construction and maintenance of dam concrete.
The “Standard Specifications for Concrete Structures, Test Methods and Specifications” lists theJapan Industrial Standards, provisions of JSCE and other standards for the methods mentioned in
the other four components of the Standard Specifications. Figures 2 through 4 show work steps inrespective phases described in the Standard Specifications for Concrete Structures “Design,”“Materials and Construction” and “Maintenance.”

2. Roles and deployment of responsible engineers
To produce and maintain a reliable structure that meets the performance requirements, theengineers involved should have a capacity to carry out the work and a high level of ethics.
In the planning, design, construction and maintenance of a concrete structure, the engineers
should make appropriate decisions under varying work conditions. Therefore, the engineers withrequired technical skills should be deployed according to the level of difficulty of work. In theplanning, design, construction and maintenance, therefore, responsible engineers not only withrequired technical expertise but also with responsibility and authority should be deployed inorganizations of the owner, the consultant and the contractor.

(iii)

Standard Specifications for Concrete Structures-2007, Materials and Construction

Use and functions of structure

Plan for the structure
Specifications for Design
Specification of performancerequirements
Structural planning

Design plans(Structural format, materials used, dimensions ofmajor elements, construction method, etc.)

Design of the structure
Specifications for Design
Specification of structural details
Structural details (Cross section,materials, bar arrangement, etc.)
NG

Performance verification
for the structure
OK

Design drawings and other materials(Structure, materials, construction method,maintenance plan, etc.)

Construction of the structure

Fig.2

Work steps described in “Specifications for Design”(iv)Application of Standard Specifications for Concrete Structures

Planning of the structure

Design of the structure

Construction of the structure
Specifications for Materials andConstruction
Construction planning

NG

Verification and approval
OK

Construction

Quality control

NG

Inspection
OKAs-built drawings and construction records

Maintenance of the structure

Fig. 3Work steps described in “Specifications for Materials and Construction”(v)Standard Specifications for Concrete Structures-2007, Materials and Construction

Planning of the structure

Design plans

Design of the structure

Design drawings and other materials

Construction of the structure

As-built drawings and construction
records

Maintenance of the structure
Specifications for Maintenance
Maintenance plan

Investigation, deterioration
prediction and evaluation
Recording

Not required

Assessment
Remedial measuresrequired or not?
Required

Recording

Implementation ofremedial measures

Storage of maintenancerecords

Fig. 4Work steps described in “Specifications for Maintenance”(vi)Application of Standard Specifications for Concrete Structures

The technical skills required for responsible engineers should be defined according to a scale of
the work, importance and difficulty of planning, design, construction or maintenance.
As capacity classifications of engineers, engineer qualifications authorized by JSCE are listed inTable 1. The qualifications for the special senior engineers and senior engineers are generally
required for responsible engineers.
The JSCE technical qualifications cover several fields. Responsible engineers to be deployed inprojects need to have qualifications only for major fields related to the specific project.

Table 1Engineer qualifications authorized by JSCE

Qualification

Required skills

Executive
Professional
Civil Engineer

Japan’s leading civil engineer with high-level knowledge andexperience in his or her field of specialty, or with comprehensive
civil engineering expertise

SeniorProfessional
Civil Engineer

Engineer with high-level knowledge and experience in multiple
fields or with comprehensive knowledge on civil engineering who
can solve key problems as a leader

Professional
Civil Engineer

Engineer with knowledge and experience at least in one special field
who can carry out task at his or her discretion

Associate
Professional
Civil Engineer

Civil engineer with required basic knowledge who can carry out
assigned task

3. System for ensuring reliability
Many groups are involved in the planning, design, construction and maintenance of a structure.
In order to ensure the high reliability of the structure in each work phase, the organizations involved
should play their role providing their know-how and assuming due responsibility.
To ensure reliability in the design (and planning) phase, two independent groups should
basically check the design. After the design and check by the design company, engineers of thecontractor should re-check the design, or request a third party to check the design. Then, fully
skilled engineers should be selected for checking so that safety or other reliability parameters may
be satisfied. The design drawings serving as a basis for contracting should carry the signatures of
responsible engineers of the two groups that assume responsibility.
In the construction phase, reliability is ensured through the quality management by thecontractor and the quality verification by the inspector independent of the contractor. Inspections
have generally been conducted directly by the Owner and/or Consultant. Completed structures
should be inspected wherever possible. If inspecting completed structures is impossible, inspections
should be conducted while the structure is being constructed. If the Owner cannot directly inspect(vii)

Standard Specifications for Concrete Structures-2007, Materials and Construction

the structure under construction, the Owner may request an agent independent of the contractor.
Adopting as many highly reliable methods as possible can reduce the labor required for quality
management and inspection. In cases where adopting not so reliable methods is inevitable, the levelof quality management should be raised or inspections should be conducted more frequently to
improve reliability. Inspection items and decision criteria should be specifically presented at thetime of contracting because they greatly affect the quality of the structure and the construction cost.
Ensuring safety requires regular investigations. When defects are detected, decision should bemade as to remedial measures. For decision making concerning remedial measures for extremely
difficult deformation, listening to the opinions of engineers with high skills who have experienced
numerous cases is important.
In order for a system for ensuring reliability to work properly, the people or organization withtechnical skills fit for the specific work should be granted explicit responsibility and authority andassigned to the work. The compensation for the work and time required for the work should also be
provided.

(viii)

General Requirements

Chapter 1

General Provisions

CHAPTER 1 GENERAL PROVISIONS

1.1

General(1) Standard Specifications for Concrete Structures “Materials and Construction:
General Requirements” (hereafter referred to as the "Construction: General
Requirements” of this Specification) describe basic concepts for the construction of
concrete structures specified in design drawings and specifications.
(2) As a general rule, to construct a concrete structure, it is necessary to develop a
construction plan based on the design drawings and specifications, construct thestructure in accordance with the construction plan while performing proper quality
control, and inspect the structure to confirm that the structure has been constructed inaccordance with the design drawings and specifications.
(3) If it is not possible to develop a rational construction plan in accordance with thedesign drawings and specifications, it is mandatory to revert to the design stage andmodify the conditions set out in the design drawings and specifications.
(4) For ordinary concrete works, it is advisable to refer to Standard Specifications forConcrete Structures “Materials and Construction: Construction Standards” (hereafterreferred to as the "Construction: Construction Standards” of this Specification) andStandard Specifications for Concrete Structures “Materials and Construction: Inspection
Standards” (hereafter referred to as the "Construction: Inspection Standards” of thisSpecification). For concrete works described in Standard Specifications for Concrete
Structures “Materials and Construction: Special Concretes” (hereafter referred to as the"Construction: Special Concretes” of this Specification), a construction plan shall be
developed with reference to the provisions of the “Construction: Special Concretes” ofthis Specification.

[Commentary] (1) The “Construction: General Requirements” of this Specification describes
basic concepts for developing a rational construction plan and carrying out construction work inaccordance with the construction plan in order to construct a concrete structure specified in design
drawings and specifications on the assumption that the structure has been designed appropriately sothat the performance requirements for the structure can be met.
(2) Design drawings and specifications for a concrete structure, which are the result of a design
developed to meet the performance requirements for the structure, show structural drawings,
reinforcement drawings, concrete properties, and materials, mix proportions and other details
needed to meet these properties. It is a basic requirement, therefore, to plan the construction of aconcrete structure in accordance with the design drawings and specifications. In cases where aconstruction plan can be drawn up in accordance with the “Construction: Construction Standards”
or “Construction: Special Concretes” of this Specification, it may be assumed that the concrete
structure as described in the design drawings and specifications can be constructed.
Fig. C1.1.1 illustrates the scope of the Construction section of this Specification and the flow of
the construction process.
A construction plan drawn up in accordance with the design drawings and specifications must1

Standard Specifications for Concrete Structures-2007, Materials and Construction

be confirmed and approved before construction is started. All tasks in the construction process mustbe performed in accordance with the construction plan after proper quality checks are done at eachstage. The completed structure is taken over by the owner after it is confirmed through inspectionthat the structure has been constructed as designed.
(3) The conditions assumed for construction planning at the design stage may differ from theactual construction conditions. In such cases, conditions such as the selection of materials, mix
design and plans at each stage of construction are altered to the extent that the properties indicatedin the design drawings and specifications are achieved. If, however, it is difficult to develop arational construction plan while achieving the properties indicated in the design drawings andspecifications, it is necessary to return to the design stage and alter the design and prepare new
design drawings and specifications so that the performance requirements for the structure can bemet.
(4) The “Construction: Construction Standards” of this Specification applies to ordinary
concreting that involves few or no special requirements. The “Construction: Inspection Standards”
of this Specification describes an inspection system corresponding to such concreting. If theserequirements are met, it may be construed that the requirements described in the “Construction:
General Requirements” of this Specification are met.
The “Construction: Special Concretes” of this Specification deals with the types of concrete thathave proven performance but are not covered by the “Construction: Construction Standards” of thisSpecification. It is therefore necessary to fully understand the indicated requirements andincorporate them into the construction plan.

DesignConstruction
planning

Confirmed/
approved?

No

Yes

No

Construction

Quality control

Inspection

Standard Specifications forConcrete Structures:Construction

Yes

MaintenanceFig. C1.1.1 Scope of Construction: General Requirements and the flow of the concrete structure
construction process2Chapter 1

1.2

General Provisions

Definitions

The terms used in Standard Specifications for Concrete Structures “Construction: General
Requirements” are defined as follows:
Verification – The act of judging whether something meets performance requirements
through experiments using full-scale specimens, empirically and theoretically provenanalysis methods, etc.
Inspection – The act of judging whether the quality satisfies the required criteria
Quality control – Effective and organized technical activities for quality assurance
performed at all stages of construction work in order to economically construct a concrete
structure that matches its purpose
Domain engineer – A person who is authorized by the responsible engineer andpart of his responsibilities

perform[Commentary] Quality control, which is carried out to make a concrete structure that meets
performance requirements, should be performed by a method that is as economical as possible.
A person who has been ordered to assume part of the responsibility and authority of theContractor for particular construction work to be carried out in connection with the construction ofa concrete structure is referred to as a "domain engineer." Before carrying out construction work, it
is necessary to clearly define the scope of responsibility and authority of each domain engineer. A
domain engineer must be a person who is qualified as a First-Class Civil Engineer certified by theJapan Society of Civil Engineers, First-Class Civil Engineering Works Execution Managing
Engineer (Japan Federation of Civil Engineering Works Execution Managing Engineers
Associations), Chief Concrete Engineer (Japan Concrete Institute), Concrete Engineer (Japan
Concrete Institute), key technician specializing in a particular type of construction-related work or aperson with equivalent expertise.

3

Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 2 CONSTRUCTION PLAN

2.1

General(1) An appropriate construction plan shall be prepared to construct a concrete
structure indicated in the design drawings and the specifications.
(2) The construction plan shall meet the requirements for the construction work
concerned and shall be approved by the Owner after it is confirmed that the concrete
structure indicated in the design drawings and specifications can be constructed.

[Commentary] Preparation for an appropriate construction plan and carrying out the construction
work in accordance with the construction plan are essential for the construction of a concrete
structure that has the performance attributes (e.g., safety, serviceability, restorability, durability)
specified at the design stage.
Fig. C2.1.1 shows the flow of the process from the design of a structure through thedevelopment and approval of a construction plan to construction.
In order to construct a concrete structure indicated in the design drawings and specifications,appropriate concreting methods and construction performance of concrete must be determined, anda construction plan is drawn up taking into consideration the construction requirements, namely,
quality, construction safety, economy, construction period and environmental loading.
Information to be provided by the designer to the Contractor consists of characteristic values forconcrete determined according to the performance requirements for the structure, the maximum sizeof coarse aggregate and reference values related to concrete mix proportions such as cement content
and the water-to-cement ratio. When developing a construction plan, it is necessary to concretely
specify the concrete performance requirements and mix proportions determined at the design stage.
The Contractor prepares a construction plan in accordance with the design drawings andspecifications and submit the construction plan to the Owner. After the construction plan isapproved by the Owner, construction work is carried out according to the plan.
Structural performance does not need to be verified again if the construction conditions
determined in this chapter are the same as the conditions assumed at the design stage or if astandard construction method indicated in the Construction Standards section of this Specification isused. If, however, the actual construction conditions differ significantly from the conditions
assumed at the design stage, the performance of the structure must be verified again on the basis of
the actual construction conditions. If the verification has revealed that the structure does not meetthe performance requirements, the construction plan needs to be altered according to the situation.

4

Chapter 2

Construction Plan

Performance requirements for structure

Requirements for construction work

Design of structure
Determination of structural details
Determination of concrete details

Determination ofcharacteristic
values forconcrete

Determination of reinforcement details
Determination of construction method

Determination of maintenance details

Verification of performanceof structure• Verification related to earthquake action• Verification related to safety and serviceability• Verification related to environmental action• Verification related to initial cracking

NG

Designreview

OK

Design documents (specifications, inspection plan)
Construction planning
Concrete mix design
Determinationof construction
methods• Transportation• Reinforcement
work• Form work
• Placing• Compaction• Curing• Joint work
• FinishingNG

Determination of
manufacturing method

Selecting materials
Selecting mix proportions

Determination of
construction
performanceNG
Environmental andsafety planning

Verification of
concrete performance

OK
Quality control
planning
Inspection planning

Determination of mix proportions

Confirmation of
construction plan
OK

Start of construction work

Fig. C2.1.1 Flow of structure design and construction planning5Standard Specifications for Concrete Structures-2007, Materials and Construction

2.2

Considerations in Construction Planning

The construction plan shall be prepared taking into consideration the environmental
conditions and construction conditions at the construction site, giving consideration to
construction safety and environmental loading and developing plans for details such as
the overall schedule, construction methods, concrete manufacturing methods,
construction performance of concrete, concrete mix proportions, quality control,
inspection, environmental impact and safety.

[Commentary] A construction plan must be developed in due consideration of quality
achievement, construction period, safety, economy and environmental impact so that theconstruction can be carried out successfully. Safety measures against risks expected at theconstruction stage must be carefully studied in advance. Environmental conservation plans mustcomply with all environmental laws and regulations and standards related to the construction work.
It is also good practice, when preparing a construction plan, to take into consideration items forwhich there is as yet no standard to meet so that environmental loading can be minimized. Table
C2.2.1 lists examples of items to consider when drawing up a construction plan.

Table C2.2.1

Examples of considerations in construction planning

Item

Description

1. Plan for transporting andreceiving concretePlans for assigning and operating agitator trucks; haul roads, onsite tests, inspection areas;
inspection of concrete mix proportions (slump, air content, water content, water-to-cement
ratio), etc.

2. Haul road plan

Hauling method, concrete supply capacity, standby pump trucks, etc.

3. Placement plan

Construction organization (organization chart), placing intervals, hourly placing rate, safety,etc.

4. Compaction plan

Type and number of vibrators corresponding to hourly placing rate of concrete, personnel
requirements, preparation of standby vibrators, replacement personnel, etc.

5. Finishing plan

Skill level of finishing workers, plan for time of finishing, finish accuracy plan, confirmationof equipment to be used for finishing work, etc.

6. Curing plan

Time of initiation of curing, curing method, confirmation of curing period, confirmation of
curing equipment, confirmation of persons responsible for concrete curing control, etc.

7. Jointing plan

Jointing method, treatment method, equipment, time of jointing, etc.

8. Reinforcement work plan

Confirmation of reinforcing bar diameters, spacing, method for ensuring concrete cover,assembling method, type of reinforcing steel, fabrication method, skill level of reinforcement
workers, etc.

9. Formwork and falsework
plan

Design of formwork (lateral pressure), confirmation of formwork materials and falseworkmaterials, formwork designer, timing of form removal, timing of falsework removal, lateralpressure control method, etc.

10. Environmental conservationplan

Washing water, curing water, drainage of bleeding water etc., checks on noise and vibration,
dust, and environmental impact, etc., at and around jobsite

11. Safety and health plan

Confirmation of matters related to safety and health of construction workers, etc.

12. Others

Confirmation of troubleshooting methods, etc.

6

Chapter 2

2.3

Construction Plan

Determination of Concreting Method(1) Appropriate methods of concreting including hauling, placing, compacting,finishing, curing, etc., at the construction site shall be selected in due consideration of theinfluence on the quality of the concrete in the structure.
(2) In cases where a new construction method that is thought to be more suitable for theconstruction work concerned than a standard construction method assumed as the design
stage is used, the influence of the new method on the quality of the concrete in the
structure shall be ascertained through experiments or by other means.

[Commentary] (1) and (2) In order to achieve the required quality of concrete, it is important toemploy an appropriate construction method and carry it out in a reliable way. At the design stage,
structural details and various material properties are determined assuming the use of a widely used
standard construction method. As construction details such as construction requirements, weather
conditions, environmental conditions and concreting-related conditions become concrete andspecific, however, it may be more appropriate to alter the construction method. It is good practice,therefore, to take a flexible approach and select the most appropriate method in view of theconditions of the construction project. Decisions on construction methods in such cases may bemade with reference to the construction methods described in the Construction Standard section. If
a newly developed, poorly field-tested method is to be used, it is necessary to conduct construction
tests, etc., under realistic conditions in advance to fully ascertain the quality of concrete in the
structure that can be achieved by that method.

2.4

Determination of Construction Performance of Concreting(1) Appropriate construction performance of concrete shall be specified according to
the construction method to be used.
(2) If construction performance of concrete cannot be specified, previously determineddetails such as the construction method shall be reconsidered.

[Commentary] (1) Construction performance of concrete includes workability such as filling
ability and pumpability, setting properties and strength development properties. It is important tospecify construction performance of concrete needed at different stages of construction in due
consideration of changes over time in the properties of fresh concrete.
Concrete with appropriate workability is easy to handle, pour and compact appropriately
according to the conditions such as the placing site location, the cross-sectional shapes anddimensions of members and the reinforcing steel arrangement. Workability, however, is a property
that can change over time at different stages of construction from manufacturing, transportation,
pouring and compaction. Changes over time in slump vary considerably depending on concrete mix
proportions, the types of materials used and the environmental and weather conditions during
construction. Workability must be specified, therefore, after carefully considering suchtime-dependent changes.
In cases where concrete is pumped at the construction site, it is desirable that concrete can bepumped at the required rate under the planned pumping conditions without encountering theclogging of piping, and the quality of fresh concrete be not severely affected by pumping. Concrete7

Standard Specifications for Concrete Structures-2007, Materials and Construction

with excellent pumpability is concrete that has a well-balanced combination of three properties,
namely, the ability to flow smoothly in straight pipes (fluidity), the ability to pass through bent
pipes and tapered pipes (deformability) and the resistance to segregation due to changing pressuresin pipes (segregation resistance).
Setting properties are related to conditions such as the compaction of concrete, lateral pressure
acting on the formwork, placement intervals and the timing of finishing. In the case of hot weather
concrete or cold weather concrete, it may be necessary to adjust setting properties appropriately toaccelerate or retard setting.
Appropriate strength development properties are needed to ensure safety of the structure being
constructed against loading expected during the construction of the structure and achieve rational
construction and the required performance of the completed structure.
Concrete strength during construction is under the influence of factors such as placing
temperature, the material of formwork, curing method and ambient temperature. It is therefore
necessary to take these into consideration when deciding on the timing of formwork and falsework
removal. Strength development properties may be necessary in order to remove formwork andfalsework or achieve early initiation of prestressing tendon tensioning for prestressed concrete.
(2) If the required construction performance of concrete cannot be achieved, the construction
method must be reconsidered. For example, if the required workability or pumpability cannot be
achieved by carrying out a long-distance pumping plan, it is necessary to revert to the concreting
method determination stage and make necessary changes such as changing the concrete haulingmethod within the construction site.

2.5

Materials
Only materials of proven quality shall be used as concrete materials.

[Commentary] Using appropriate materials is very important for producing concrete with therequired performance. Whether particular materials are suitable for use can be judged from test
results or past performance data. In general, materials conforming to JIS, JSCE standards or otherquality standards may be deemed to be materials of proven quality. It is possible, however, to meetthe performance requirements for concrete even if materials not conforming to quality standards areused. If such materials are used, it must be ascertained in advance that the performancerequirements for the concrete structure can be met.
Concrete materials of any quality may be used as long as the concrete made by using thosematerials meets the performance requirements. In the case of poorly field-tested materials, however,
it is necessary to carefully evaluate their quality and the performance of the concrete, including
long-term stability of quality and the influence on the durability of the structure, made of thosematerials.

2.6

Concrete Mix Design

Concrete mix proportions shall be determined, taking into consideration of suchfactors as constraints related concrete plants, availability of materials and economy
including transportation cost, so that the required performance of concrete can be8Chapter 2

Construction Plan

achieved.

[Commentary] Mix design refers to a series of tasks performed to specify materials and their mix
proportions so that performance requirements for concrete can be met. Usually, in the mix design
process, materials and their mix proportions are assumed and trial mixing is carried out, and thiscycle is repeated until it is confirmed that the concrete mixes made in this way meet all performancerequirements (characteristic values). Because there are many combinations of materials and theirmix proportions that meet performance requirements, what is to be done in the mix design stage isto select appropriate ones from those combinations. Performance attributes required of concrete
here include the characteristic values for concrete indicated by the design and construction
performance of concrete, material conditions and mix requirements shown for reference only.

2.7

Verification of Concrete Performance(1) It shall be verified that the concrete made with the selected materials and mix
proportions meets the characteristic value criteria indicated by the design.
(2) If the design indicates reference-only values related to construction besides
characteristic values, it shall be verified that the selected materials and mix proportions
meet the reference-only values or meet the concrete performance requirements on which
the reference-only values are based.

[Commentary] Commonly used methods of concrete performance verification as of this writing
include experiment-based methods and the method of making inference from past performancedata.
Characteristic values for concrete to be verified include strength, carbonation rate coefficient,diffusion coefficient of chloride ions, freeze–thaw resistance, chemical attack resistance,
alkali–silica reaction resistance, water permeability coefficient, fire resistance and drying shrinkage
strain. Values indicated for reference only, such as material conditions and mix requirements and theworkability, pumpability, setting properties, strength development properties, etc., specified in theconstruction plan, also need to be verified. The following criteria may be used for verification:

p

Ap
Ak

 1.0,

or

p

Ak
 1.0
Ap

(C2.7.1)

where Ak: characteristic value for a performance attribute of concrete, Ap: predicted value for a
performance attribute of concrete, p: factor of safety for accuracy of Ap
If even a single characteristic value among the specified values is not met, the selected materials
and mix proportions are altered and verification is performed again. If rational mix proportions forconcrete cannot be determined by this method, all conditions including the structural conditions,reinforcement material conditions, concrete manufacturing conditions, placement conditions andmaintenance conditions shall be reconsidered.

9Standard Specifications for Concrete Structures-2007, Materials and Construction

2.8

Confirmation and Alteration of Construction Plan

(1) It must be confirmed by an appropriate method that the concrete construction plan
meets the requirements for the construction work and that the performance requirements
for the structure are met.
(2) Any change in the construction plan should be made so as to minimize its
influence. As a general rule, changes in the construction plan should be limited toconcrete mix proportions and construction methods.
(3) If the construction plan differs from the reference values indicated at the design
stage, cracking checks at the construction stage shall be made again under conditions
reflecting the construction plan.

[Commentary] (1) The construction plan must meet the requirements for the construction workand must be such that the concrete structure built in accordance with the plan meet the performancerequirements. The Contractor submits a construction plan in writing to the Owner, and the Owner
checks whether the structure shown in the design drawings and specifications can really beconstructed, and approves the construction plan. To be more specific, it is necessary to check eachtask in accordance with the items and descriptions shown in Table C2.2.1 to determine whether the
standard construction methods specified in the “Construction: Construction Standards of thisSpecification” are used, whether the plan has an adequate margin of safety against variable factors
expected in connection with each task, whether the plan incorporates troubleshooting methods, etc.
If new technologies or new construction methods are to be used, it is necessary to evaluate theirfeasibility and reliability by referring to reliable documents or conducting full-scale field trials.

(2) If the construction plan is to be changed, resultant changes in other conditions should be
minimized. A realistic way is to stay within the framework of reconsidering the construction planinstead of reverting to the design of the concrete structure. Usually, making changes in the concrete
mix proportions or construction methods specified in the construction plan suffices.
(3) At the design stage, concrete and its placement methods are assumed, checks are made on
initial cracking, and characteristic values for concrete are determined. If these conditions in theconstruction plan differ from the conditions assumed at the design stage, verification on cracking
shall be made again, on an as-needed basis, at the construction stage.

10

Chapter 3

Construction

CHAPTER 3 CONSTRUCTION

3.1

General(1) The construction of a concrete structure shall be carried out in accordance with theconstruction plan.
(2) The construction of a concrete structure shall be carried out under the supervisionof a domain engineer with sufficient knowledge and experience in the construction of
concrete structures stationed at the construction site.
(3) If the construction plan cannot be followed at the construction stage, appropriate
measures shall be taken so that the performance requirements determined at the design
stage can be met.

[Commentary] (1) The basic rule for construction is to carry out construction work economicallyand efficiently by using an appropriate construction method on condition that construction safety is
maintained. Because concreting work involves a variety of tasks such as tasks related to formwork,
reinforcing steel and the placing of concrete, it is desirable that concreting work be thoroughly
coordinated with other types of work so that the construction work can be carried out efficiently.
To construct a concrete structure, the constructor prepares a construction plan that details
necessary construction processes based on the design drawings and specifications. The constructionof the concrete structure, therefore, must be carried out in accordance with the construction plan.
(2) In general, the quality of construction is heavily dependent on human factors such as theexperiences and qualities of constructors. It is very important, therefore, to station domain engineers
with sufficient knowledge and experience in the field of the construction of concrete structures atthe construction site so that the construction work carried out under the direction of those domain
engineers.
(3) In a construction project, incidents not expected at the planning stage may occur at theconstruction stage. It is not always possible, therefore, to carry out construction in accordance withthe construction plan. If it is difficult to follow the construction plan in a real construction project,appropriate measures must be taken, following the domain engineers' instructions, so that therequired performance can be achieved.

11Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 4 QUALITY CONTROL

4.1

General(1) The Contractor shall perform quality control at each stage of construction in orderto create a concrete structure that meets the performance requirements.
(2) Quality control shall be performed, as a voluntary activity of the Contractor, byusing a method that can be expected to be effective.
(3) If quality control has revealed a possible quality problem, appropriate measures
shall be taken, in accordance with a domain engineer's instructions, so that theperformance requirements specified at the design stage can be met.

[Commentary] (1) In order to create a concrete structure that meets the performancerequirements, the Contractor must carry out construction in accordance with the construction planand perform quality control by appropriate methods for appropriate items such as concrete materials,
reinforcing materials, equipment and construction methods to ensure that the required quality isachieved at each stage of construction.
It is advisable, however, to perform quality control only for necessary items only as often asnecessary, instead of conducting many types of tests and collecting a large amount of data. One way
to check on quality on the basis of test results, besides actually conducting tests, is to examine
manufacturers' test reports as in the case of JIS-conforming products.
Usually, wide variations in the quality of concrete placed to build a structure not only increases
the possibility of occurrence of problems at the construction stage but also necessitates the use of alarge factor of safety at the mix design stage so as to achieve the required strength. That makes theconstruction process uneconomical and, in many cases, causes decreases in durability, cracking
resistance and appearance. Always producing concrete of stable quality, therefore, is essential, and
it is important to control the quality of materials and the concrete manufacturing process carefully.
(2) The Contractor must prepare a reliable, efficient and economical quality control plan inaccordance with the construction plan and carry out the construction work in accordance with thequality control plan. Quality control results may be used as substitutes for the results of inspection
conducted by the owner at each stage of construction. It is desirable, therefore, that quality control
be performed, wherever possible, by a technically or otherwise proven method.
(3) If quality control has revealed a sign of considerable variation in quality, it is necessary to
conduct an investigation to identify the cause of such variation and take corrective measures so thatvariations can be kept within the predetermined range. In the event of an abnormality or a possible
quality problem, appropriate measures must be taken in a timely manner in accordance with adomain engineer's instructions.

12

Chapter 5

Inspection

CHAPTER 5 INSPECTION

5.1

General(1) The Owner shall conduct inspection at each stage of construction and uponcompletion of a structure on the Owner's own responsibility.
(2) The Owner of a structure shall draw up an inspection plan in accordance with thedesign drawings and specifications, taking into consideration the degree of importance,
intended use and purpose of the structure.
(3) Inspection shall be conducted in accordance with the inspection plan by a methodof proven reliability.
(4) If inspection is failed, corrective measures to be taken shall be considered. If
corrective measures cannot be taken, the stage of construction that failed to pass theinspection shall be redone.
(5) The inspection plan and inspection results shall be maintained during the service
period of the structure.

[Commentary] (1) In order to construct a concrete structure as indicated in the design drawings
and specifications, inspection is conducted at each stage of construction to check whether theconstruction work being carried out is adequate. The required performance of the concrete structure
can be ensured by checking on the performance requirements such as safety at the design stage andconducting inspection at the construction stage. Inspection, therefore, must be conducted on the
responsibility of the Owner of the structure.
The performance of a newly completed concrete structure should ideally be inspected directly.
The items related to a concrete structure that can be inspected, however, are limited to only afraction (e.g., concrete surface condition, the locations, shapes, dimensions, etc., of structuralmembers) of all inspection items. A realistic approach, therefore, is to conduct necessary
inspections at each stage of construction to make sure, through a series of inspections, that theconcrete structure is being constructed as indicated in the design drawings and specifications.
(2) The Owner of the structure needs to draw up a reliable, efficient and economical inspection
plan with reference to the design drawings and specifications in view of the degree of importance,
intended use and purpose of the structure. In general, inspection is planned taking into considerationsuch factors as the type and scale of construction work, staffing, timing of construction,
construction period, reliability of the materials and construction methods used, skill level ofconstruction workers, the degree of influence on the work schedules at subsequent stages, andefficiency. The inspection plan must describe things to be done, inspection criteria, etc.
It is not practical that the Owner inspects all items because inspection items are diverse at eachconstruction stages. In this way the Contractor inspects quality inspection items for materials except
for inspections related to construction works and the structure on their own responsibility and the
Owner ensures the inspection results. To make this practice worked the Owner should discuss
13

Standard Specifications for Concrete Structures-2007, Materials and Construction

inspection methods with the Contractor before actual construction begins. Results of the discussion
should be recorded with written documents where the Owner records on an inspection planningdocument while the Contractor records on a construction planning document.
(3) Because the Owner of the structure has to judge the acceptability of the concrete structure
through inspection, the reliability of the inspection method needs to be ensured by supportive
technical information or other evidence. Acceptability criteria are one of the important items agreed
upon in the contract, so they must be objective. Common practice is to use methods specified in theJapanese Industrial Standards (JIS) or the JSCE standards. The Construction: Inspection Standardsof this Specification indicates standard inspection methods and criteria for evaluating theacceptability of inspection results based on those standards and specifications.
The Owner specifies, in advance, inspection-related requirements such as inspection items,
inspection methods and acceptability criteria in the contract documents, etc., and, as a general rule,
specifies all requirements in the contract documents. Since, however, inspections that need to be
conducted at different stages of construction involve a wide range of inspection items, it is desirable
that studies be conducted in advance on such details as inspection items, inspection methods, timing,
frequency, staffing, cost and required time and agreement be reached with the Contractor
concerning particularly detailed matters so that inspections can be conducted in a reliable, efficientand economical way. If a newly developed construction method or material is used, conventional
inspection methods may not be adequate. It is therefore important for the Owner to draw up an
inspection in consultation with the contractor.
(4) If an inspection has been failed at a stage of construction, it is necessary either to redo thestage of construction or take corrective measures. In this case, it must be confirmed that the required
performance of the concrete structure can be achieved by taking the corrective measures. The
Contractor, therefore, needs to carefully determine construction procedures and details in advancein connection with construction tasks that are difficult to redo.
If an inspection has been failed and neither taking corrective measures nor redoing construction
is possible, it is necessary to evaluate the influence of the problem on the required performance ofthe concrete structure and take appropriate measures such as demolishing and reconstructing thestructure or altering the maintenance plan and using the existing structure.
(5) Inspection records are documents that certify that the concrete structure has been constructedin accordance with the construction plan and as indicated in the design drawings and specifications.
Inspection records, therefore, must be maintained during the service period of the concrete structure.
If an inspection is failed at one or more stages of construction, it is important to record in detail thefacts including the corrective measures taken.

14Chapter 5

5.2

Inspection

Inspection Plan

(1) The inspection plan shall specify inspection items, inspection methods andrequirements such as acceptance criteria, timing and frequency of inspection and staffing
requirements needed to ascertain that the structure concerned is being constructed asindicated in the design drawings and specifications.
(2) In the event of any change in the design drawings or specifications, the inspection
plan shall be reviewed.

[Commentary] (1) Inspection items, inspection methods and requirements such as acceptancecriteria, timing and frequency of inspection and staffing requirements needed to ascertain that thestructure concerned is being constructed as indicated in the design drawings and specifications must
be determined and specified in the inspection plan.
Standard inspections usually consist of the following:(i) Inspection of the quality of concrete materials(ii) Inspection of the performance of concrete plant(iii) Inspection of the quality of concrete(iv) Inspection of the quality of reinforcing materials(v) Inspection of construction(vi) Inspection of structure
A series of inspections conducted in connection with the construction of a concrete structure
includes the inspection of materials (concrete and reinforcing bars) conducted to ensure that thematerials used are appropriate, the inspection of construction conducted mainly to ensure that thestructure and its members meet the dimensional requirements, specified reinforcing bars have beenplaced at specified locations, concrete has been uniformly placed and compacted, and curing has
been carried out as required, and the inspection of the concrete structure. After these inspections are
passed, it may be judged that the concrete structure has been constructed as indicated in the design
drawings and specifications.
It is desirable that inspections be conducted only for essential items in view of construction
efficiency and economy. Inspections that are deemed necessary in order to check whether theconcrete structure indicated in the design drawings and specifications can be constructed must be
conducted after their reliability is ascertained. For example, if it is thought likely that the adequacyof construction when newly developed materials or construction methods are used cannot be judged
by means of the inspections (i) through (vi) listed above, inspection methods suitable for suchmaterials or construction methods must be adopted. In such cases, it is very important to confirm
inspection details through in-depth discussion between the Owner and the Contractor.
(2) Because the inspection plan is drawn up on the basis of the design drawings andspecifications, if the inspection plan has been changed, it must, of course, be reviewed.

15

Standard Specifications for Concrete Structures-2007, Materials and Construction

5.3

Conduct of Inspection(1) Inspection shall be conducted in accordance with the inspection plan.

(2) The person responsible for inspection shall judge the acceptability of inspection
results according to predetermined evaluation criteria.

[Commentary] (1) Basically, the inspection of a structure must be conducted by the Owner of thestructure on the responsibility of the Owner in accordance with the inspection plan. Inspection tasksneed to be performed under the direction of a person who has experience in working in theconstruction work concerned or who has technical experience.
(2) If an inspection at a stage of construction has been failed, either the construction work
concerned is redone or corrective measures are taken after discussion between the Owner and theContractor. Inspection methods used after corrective measures are taken must also betechnically-proven, reliable methods. The person responsible for inspection must be the Owner or
the Owner's agent and needs to be a senior professional engineer certified by the Japan Society of
Civil Engineers, consulting engineer (concrete specialist), chief concrete engineer or an equallycompetent person.

5.4

Maintenance of Inspection Records(1) Inspection records shall be maintained during the service period of the concrete
structure.
(2) Inspection records covering necessary items shall be maintained in an appropriate
format with reference to the maintenance guidelines.

[Commentary] (1) Inspection records are important records confirming the required performanceof a concrete structure. Like the design drawings and specifications and the inspection plan,
therefore, inspection records must be maintained. If an inspection has been failed and corrective
measures have been taken, the records regarding their details must also be maintained.
(2) Because inspection records are important as the initial values for the maintenance of a
newly completed concrete structure, they must be maintained as a source of reference information
so that the safety, serviceability, etc., of the concrete structure can be ascertained.

16

Chapter 6

Construction Records

CHAPTER 6 CONSTRUCTION RECORDS

6.1

GeneralThe Owner of a concrete structure shall maintain the construction records during theservice period of the concrete structure.

[Commentary] The term "construction records" here refers to the design drawings andspecifications (including changes), the construction plan (including changes), the inspection plan(including changes) and the inspection records. It is also good practice to maintain records
concerning construction management depending on the degree of importance and necessity.
These documents contain all information concerning the newly constructed concrete structurethat can be used as basic data for ensuring the required performance of the structure during its
service period. It is desirable that these documents indicate the affiliations, names, etc., of thepersons who performed the relevant tasks.

17

Construction Standards

Chapter 1

GeneralCHAPTER 1 GENERAL

1.1

General(1) The purpose of this Specification “Materials and Construction: Construction
Standards” of the Standard Specifications for Concrete Structures is to make it possible,
in concreting work for new construction of an ordinary civil engineering structure, toconstruct a concrete structure of a certain level of quality by carrying out the items
indicated herein without paying painstaking attention.
(2) Prior to the commencement of concreting work, it is necessary to fully understandthe content of the design drawings and specifications and prepare an appropriate
construction plan.
(3) If details such as the materials used, construction conditions, construction
environment or construction methods deviate from the conditions indicated in the“Construction: Construction Standards” of this Specification, a construction planconsistent with the “Construction: General Requirements” of this Specification shall be
prepared and construction shall be carried out accordingly. For the items indicated in the“Construction: Special Concretes” of this Specification should be referred to.

[Commentary] (1) Concreting work varies very widely because of diverse elements andconditions such as the type of structure, materials used, construction conditions, construction
environment and equipment used for construction. It is also true, however, that most of concrete
construction projects involve very few special items. Numerous concrete construction projects ofthis type have already been successfully carried out. In many cases, therefore, it is rational to adopt
a construction plan that can be drawn up by making minor modifications to an ordinary construction
plan to suit the site-specific conditions. The “Construction: Construction Standards” of thisSpecification is intended for application to such ordinary concreting work as a standard guideline.
The “Construction: General Requirements”, “Construction: Construction Standards” and“Construction: Special Concretes” of this Specification should be used as follows:
The “Construction: Construction Standards” (i.e., this document) indicates typical items to be
carried out in connection with the types of structure, materials used, construction equipment andconstruction conditions within the range applicable to a typical civil engineering construction
project. The 2002 edition of the Construction section of this Specification had an independent
chapter on inspection. The other chapters dealt with items to be carried out by the Contractor, while
the chapter on inspection dealt extensively with items to be carried out by the Owner of thestructure. The Construction section of the current Specification, therefore, has separate volumes“Construction: Construction Standards” and “Construction: Inspection Standards” for"construction" and "inspection" to clarify the responsibilities of each party and make thisSpecification easier to use. Inspection-related items to be carried out by the constructor, such as
items related to receiving of materials, are described in “Construction: Construction Standards”.
“Construction: Construction Standards” and “Construction: Inspection Standards” are designed foruse as a kind of "standard specifications" for many construction projects.
Typical construction work to which the “Construction: Construction Standards” of thisSpecification is applicable involves, for example, specified strengths of concrete of up to about 60
19

Standard Specifications for Concrete Structures-2007, Materials and Construction
2

N/mm , minimum slump at the time of placement of 16 cm or less, the use of agitator trucks foroff-site transportation, the use of pumps for on-site transportation over equivalent horizontal
pumping distances of about 150 m or less, and the use of internal vibrators for compaction (seeTable C4.4.1). Among the items related to materials, construction conditions, construction
environment beyond these ranges, those that have been field-tested to a certain extent are describedin the “Construction: Special Concretes” of this Specification. It is assumed that in cases where
items related to materials, construction conditions and construction environment beyond theseranges are involved, in cases where special attention is required or in cases where special expertiseis to be used effectively, a construction plan is drawn up on a case-by-case basis in accordance withthe “Construction: General Requirements” of this Specification, verification is made, and thenconstruction is carried out.
(2) In all civil engineering construction projects, it is important to draw up an appropriate
construction plan according to the site-specific conditions prior to the commencement ofconstruction. In concreting work, it is necessary to fully understand the content of the design
drawings and specifications and draw up an appropriate construction plan prior to thecommencement of construction, taking into consideration such factors as the functionality, strengthand durability required of the structure and important things to keep in mind in carrying out
construction work. As mentioned in the explanation about Commentary (1), however, concreting
work in most cases consists of a combination of more or less standard tasks that include very few
special items. Furthermore, in cases where the concrete structure to be constructed has been
carefully designed so as to avoid special construction conditions such as excessively dense
reinforcement patterns, a sufficient level of quality can usually be achieved by performing standard
construction management. In such cases, a rational approach is to use the items indicated in the“Construction: Construction Standards” of this Specification by making minor changes to those
items. By following the procedures described herein, it is not necessary at many construction sites
to draw up a special construction plan.
Many troubles encountered in connection with the construction of concrete structures result
from inadequate attention paid to construction at the design stage. The designer and the constructor,
therefore, need to know the assumptions made by the other party within their respective scopes ofwork. In the case of the construction of an ordinary concrete structure, design and construction areusually performed separately, and information is seldom exchanged directly between the designer
and the constructor. In an ordinary project, therefore, the designer needs to perform design tasks
with a full understanding of the scope of the “Construction: Construction Standards” of thisSpecification. If design tasks are to be performed on the basis of assumptions that deviate from that
scope, it is necessary to clearly indicate it in the design drawings and specifications in order toprevent problems at the construction stage.
(3) When using special materials, production or construction methods that are not covered in the“Construction: Special Concretes” of this Specification, separate specifications in which theprovisions of this specification are appropriately reflected shall be prepared. For reference, thefollowing list provides guidelines and manuals dealing with special materials and construction
methods, published by the JSCE.
“Recommended Practice for Concrete Made by Continuous mixer”, 1986 (In Japanese)“Recommendations for Design and Construction of Reinforced Concrete Structure Using D57 and
D64 Large-diameter Threaded Reinforcing Bars”, 1992
“Recommended Practice for Concrete Containing Air-entraining and High-range Water-reducing

20Chapter 1

GeneralAgents – Recommendations for construction of high fluidity concrete”, 1993
“Guideline for Construction Using Blast-furnace Slag Aggregate”, 1993
“Recommendations for Design and Construction of Concrete Structures Using Silica Fume inConcrete -Draft-”, 1995
“Recommendation for Construction of Concrete Using Ferro-nickel Slag Fine Aggregate”, 1998 (InJapanese)“Recommendation for Construction of Concrete Using Copper Slag Fine Aggregate”, 1998 (InJapanese)“Recommendation for Construction of Concrete containing Fly Ash”, 1999 (In Japanese)“Recommendation for Concrete Pumping”, 2000 (In Japanese)“Recommendations for Design and Construction of Concrete Structures Using Electric Arc Furnace
Oxidizing Slag Aggregate”, 2003
“Recommendations for Design and Construction of Reinforced Concrete Structures Using
Epoxy-Coated Reinforcing Steel Bars”, 2003
“Recommendations for Mix Design and Construction of Concrete Based on Placeability”, 2007
“Recommendations for Design, Fabrication and Evaluation of Anchorages and Joints in Reinforcing
Bars”, 2007
“Recommendations for Concrete Repair and Surface Protection of Concrete Structures”, 2005

1.2

Definitions

The terms used in Standard Specifications for Concrete Structures “Construction:
Construction Standards” are defined as follows:
Concrete - A composite material, or its hardened form, consisting of materials such as
cement, water, fine aggregate, coarse aggregate, and admixtures added if necessary, to be
blended together by mixing or other methods.
Mortar - A composite material, or its hardened form, consisting of materials such as
cement, water, fine aggregate, and admixtures added if necessary, to be blended together
by mixing or other methods.
Cement paste - A composite material, or its hardened form, consisting of materials such as
cement, water, and admixtures added if necessary, to be blended together by mixing orother methods.
Plain concrete - Concrete without reinforcing materials, including concrete containing only
secondary reinforcement as a precaution against cracking due to shrinkage or otherreasons.
Reinforced concrete - Concrete strengthened by reinforcing bars, designed on theassumption that the two materials act together in resisting external forces.
Prestressed concrete - A type of reinforced concrete prestressed by means of prestressing
21

Standard Specifications for Concrete Structures-2007, Materials and Construction

steel, etc.
Aggregate - Sand, gravel, sea sand, crushed sand, crushed stone, blast-furnace slag fineaggregate, blast-furnace slag coarse aggregate and other similar materials which are
mixed with cement and water to produce mortar or concrete.
Sieve – A wire sieve specified in JIS Z 8801-1 used for tests of concrete and concretematerials
Fine aggregate - Aggregate entirely passing the 10 mm sieve with more than 85 % of its
weight passing the 5mm sieve.
Coarse aggregate - Aggregate with more than 85 % of its weight retained on the 5 mmsieve.
Sand - Fine aggregate formed from rocks through natural processes.
Gravel - Coarse aggregate formed from rocks through natural processes.
Recycled aggregate – Aggregate for use as a concrete material manufactured by
performing crushing and other processing of concrete fragments recovered fromdemolished structures.
Grading of aggregate - The size distribution of aggregate particles.
Fineness modulus of aggregate (F. M. ) - A factor obtained by adding the total percentages
by weight of an aggregate sample retained on each of a specified set of sieves, i.e., 80, 40,
20, 10, 5, 2.5, 1.2, 0.6, 0.3, 0.15mm, and dividing the sum by 100.
Solid volume percentage of bulk aggregate - The ratio of the solid volume of aggregate
filled in a container to the volume of that container, expressed as a percentage.
Maximum size of coarse aggregate - The size of coarse aggregate specified by the nominal
size of the smallest of all the sieves through which at least 90% of the aggregate by weightpasses.
Surface moisture of aggregate - Free water retained on the surface of aggregate particles. It
is accounted for as a portion of mixing water and obtained by subtracting the amount ofwater absorbed inside aggregate particles from the total amount of water retained by theaggregate.
Surface-dry state of aggregate - The state of aggregate particles in which there is no wateron the exposed surfaces and the permeable voids inside are filled with water. (Saturated
surface-dry state for ordinary aggregate)
Oven-dry State of aggregate - The state of aggregate particles in which all of watercontained in their permeable voids is removed by drying at the temperature between 100
and 110 degree C. until their mass becomes constant.
Density of surface-dry aggregate - The density obtained by dividing the weight ofaggregate in saturated surface-dry state into its absolute volume.
Density of oven-dry state aggregate - The density obtained by dividing the weight ofaggregate in oven-dry state into its absolute volume.
Total moisture content of aggregate - The percentage of the total weight of water inside andon the surfaces of aggregate to the weight of aggregate in oven-dry state.

22Chapter 1

GeneralAbsorption capacity of aggregate - The percentage of the total weight of water in thesurface-dry state of aggregate to the weight of aggregate in oven-dry state.
Effective absorption of aggregate - The percentage of the weight of the water that
aggregate absorbs to reach saturated surface-dry state to the weight of aggregate inoven-dry state.
Surface moisture content of aggregate - The percentage of surface moisture of aggregate
to the weight of aggregate in saturated surface-dry state.
Powdery material – A collective term for cement or other solid material used as a concretematerial that is as fine as or finer than cement.
Binder - Generic name for materials which react with water or/and participate in thestrength development of concrete such as cement, granulated blast-furnace slag fine
powder, fly ash, etc.
Admixture - Materials other than cement, water and aggregates, added to concrete before
placing to impart special properties.
Mineral admixture – Kinds of admixture which are used in comparatively large quantities
and the volumes of which are taken into account in calculating the mix proportion of
concrete.
Chemical admixture - Kinds of admixture which are used in small quantities and thevolumes of which are neglected in calculating the mix proportion of concrete.
Entrained air - Tiny isolated air bubbles introduced in concrete by using air entraining
agents or chemical admixtures.
Entrapped air - Air bubbles formed in concrete naturally without the use of chemical
admixtures.
Air-entrained concrete - Concrete that contains entrained air.
Steel - A general term for structural carbon steel consisting of iron as its principal
ingredient. This includes steel bars for reinforced concrete, prestressing tendon, hot rolled
section steel, steel plates.
Reinforcing bar - Steel bars embedded in concrete for reinforcing purpose.
Plain bars - Circular steel bars with uniform round cross section.
Deformed reinforcing bar, deformed rebar - Steel bars that have surface projections suchas ribs to improve the bond with concrete.
Prestress - Stress introduced in concrete before application of service loads to reduce
tensile stresses induced in concrete by loads.
Prestressing Steel - High strength steel used for prestress concrete.
Spacer - Devices used to provide a given cover to the reinforcing bar, tendons or sheaths
etc. and maintain the correct space between them. .
Creep - Time-dependent phenomenon in which the deformation (except elastic strain anddrying shrinkage strain) increases under constant sustained load.
Clearance - Clear distance between adjacent reinforcing bars.
Cover - Concrete thickness expressed by the least distance between the outer surface of23

Standard Specifications for Concrete Structures-2007, Materials and Construction

concrete and the surface of steel or sheaths.
Mix proportion - Proportion or quantity of constituent materials to produce a desiredquantity of concrete or mortar.
Trial mixing – Mixing carried out to determine whether a specified concrete can be obtained
from a designed mix.
Characteristic compressive strength of concrete - The strength on which structural designis based. Generally it is the compressive strength at 28days. Notation : f'ck
Mix proportioning strength (target strength) - Compressive strength used to select the mix
proportion of concrete. Generally it is a compressive strength at 28 days. Notation :f'cr
Allowance factor - A factor by which the specified average strength is multiplied to take
into account the variations of material quality in determining target strength.
Water-cement ratio - The ratio by weight of water to cement in cement paste in fresh
concrete or fresh mortar. It is generally expressed in percentage.
Unit content - Quantity of material used for producing one cubic meter of concrete or
mortar (i.e. unit cement content, unit water content, unit weight of coarse aggregate, unit
weight of fine aggregate, unit weight of admixture mineral and unit weight of admixture).
Powdery material content – A total quantity of powdery material used to make one cubic
meter of concrete or mortar.
Cementitious material content – The quantity of cementitious material used to make one
cubic meter of concrete or mortar.
Sand-aggregate ratio - The ratio of the absolute volume of fine aggregate to that of total
aggregate, expressed in percentage. Notation : s/a
Unit volume of dry-rodded coarse aggregate - The bulk volume of coarse aggregate toproduce one cubic meter of concrete. It is obtained by dividing the unit weight of coarse
aggregate into its weight per unit bulk volume (bulk density).
Fresh concrete, Fresh mortar, Fresh paste - Concrete, mortar or paste which has nothardened yet, respectively.
Slump – An indicator of the degree of softness of fresh concrete measured as the distanceby which the concrete surface falls after the slump cone is lifted.
Bleeding - The phenomenon in which a portion of mixed water emerges from fresh
concrete, mortar or paste due to sedimentation or segregation of solid materials.
Laitance - A relatively weak layer formed on the surface of concrete, mortar or cement
paste by tiny particles brought to the surface during bleeding.
Consistency - The property of fresh concrete, fresh mortar, or fresh paste, which is mainly
dependent of water content, shown by the degree of resistance to its movement or
deformation.
Workability - The property indicating the level for a fresh concrete to be easily transported,
cast, compacted and finished without occurrence of material segregation.
Filling ability – Among workability attributes, the ability of concrete to densely fill the coverregions and corners of concrete forms without undergoing segregation.

24

Chapter 1

General

Pumpability – The degree of ease with which fresh concrete or fresh mortar can betransported by a concrete pump.
Placing height – The height of concrete placed in one lift.
Free fall height – The height from which concrete falls in an exposed condition from achute or pipe end when concrete is placed.
Compaction height – The maximum height from the bottom of the concrete form or thesurface of previously placed concrete to the surface on which construction workers standwhile performing the compaction of concrete.
Durability - The resistance to degradation with time in performance of concrete structure.
Alkali-aggregate reaction - The phenomenon in which alkali-reactive aggregates react withcement or other alkali components in concrete over a long time, causing expansion cracks
or pop-out.
Freeze-thaw resistance - The resistance against repeated freezing and thawing action.
Frost damage - The damage of concrete due to freezing action in the initial period ofsetting and hardening.
Chemical attack – Dissolution or deterioration due to the generation of expansive
compounds of concrete caused by erosive substances such as acids and sulfates.
Chemical attack may cause a loss of concrete cross section or volumetric expansion andmay even cause cracking, spalling of cover concrete and steel corrosion.
Water-tightness - The property of having low water and moisture permeation.
Autogeneous shrinkage - The phenomenon in which concrete, mortar and cement paste
shrink due to reduction in volume during cement hydration.
Crack resistance -The resistance of concrete to crack initiation

Placement interval – The time from the completion of the placement of concrete in theunderlying layer to the initiation of the placement of concrete in the overlying layer.
Cold joint – A discontinuity between a previously placed layer of concrete and the nextlayer of concrete.
Batch mixer - A type of mixer in which the materials for concrete, mortar or paste are mixed
for each batch.
Continuous mixer - Mixing equipment which contains a set of devices for batching,supplying, and mixing materials for concrete, and therefore can produce fresh concrete
continuously.
Ready-mixed concrete - Fresh concrete that can be purchased at anytime from plants
which possess facilities for manufacturing concrete with desired properties.
Sheathing - Wooden, metal or plastic panel-type formwork directly adjacent to concrete.
Equivalent horizontal conveying distance - Total distance of horizontal concrete pipe andthe equivalent horizontal distance converted from the length of vertical pipe, bending pipe,
taper pipe, flexible hose etc.
Quality control - Effective and systematic technical activities for ensuring the quality ofconcrete in each stage of construction so that functional requirements of concrete25

Standard Specifications for Concrete Structures-2007, Materials and Construction

structures are satisfied.
Inspection - The work of judging whether the quality of concrete meets required criteria ornot.
Control chart - Chart used to determine whether the construction is proceeding asscheduled, or to maintain a steady construction process
Mass concrete - Concrete member or structure whose size is relatively large and theconsideration of temperature rise due to heat of hydration is of great concern during
design and construction.
Plasticized concrete - An already-mixed concrete is called plasticized concrete if
superplasticizer is added into it and a thorough mixing is carried out afterward to increase
the flowability.
Standard curing - A method of curing in water or in a moist condition under nearly 100% of
humidity while temperature is kept at 20±3°C.
Moist curing - A method of curing where concrete is kept in a moist condition for a certain
period of time after placing.
Temperature controlled curing - A method of curing where the temperature of concrete iscontrolled for a certain period of time after placing. .
Insulated curing - A method of curing where the necessary temperature is maintained byutilizing the heat of hydration of cement and preventing escape of heat to the utmost, bycovering the surface of concrete with highly insulating materials
Heat curing - A curing method in which concrete is heated by any source of heat during aperiod of curing.
Accelerated curing - A curing method used to accelerate the hardening process andstrength development of concrete.
Centrifugal compaction - Compaction of concrete by centrifugal force using a formwork
revolving at an extremely high speed.
Casting - Production of factory products by placing concrete into a form and applying
compaction to the placed concrete.
Instant demolding - Removal of a part or all of the formworks for concrete with anextremely stiff consistency immediately after placing and compacting using strong
vibration or pressure.

[Commentary] Reinforced concrete: Reinforced concrete, in a wide sense, also includes
prestressed concrete, steel framed reinforced concrete in which hot rolled section steel and shaped
steel are used as reinforcing materials. However, in this Specification, the term refers to concrete
containing reinforcing steel bars specified in JIS G 3112 or similar steel bars.
Sieves: “Standard Sieves for Concrete” of JSCE-C 501 is a series of the net-like sieves for thesieve analysis of aggregate chosen from the sieves specified in JIS Z 8801 “Standard Sieve”. In the
JSCE Standard, only their nominal sizes are given for convenience, although their actual mesh sizes,
diameters of wires, openings, and so forth are the same as those specified in JIS Z 8801.
Fine aggregate and coarse aggregate: The distinction between fine aggregate and coarse
aggregate is quite freely decided, and has no theoretical grounds. These definitions were made26

Chapter 1

Table C1.2.1

GeneralExample of the calculation of fineness modulus of aggregate

Quantity of sample retained on 80 mm
40 mm
20 mm
10 mm
5 mm
2.5 mm
1.2 mm
600 μm300 μm
150 μmFineness modulus of fine aggregate Fineness modulus of coarse aggregate Fine Aggregate
0％
0％
0％
0％
1％
16％
38％
61％
82％
97％

Coarse Aggregate
0％
0％
28％
78％
97％
100％
100％
100％
100％
100％

0  0  0  0  1  16  38  61  82  97
 2.95100
28  78  97  100  100  100  100  100
 7.03100

considering the customary practice. As the aggregate prepared on the construction site is notscreened thoroughly, aggregate particles passing the 5 mm sieve are frequently included in coarse
aggregate and particles retained on the 5 mm sieve in fine aggregate. Therefore, a 15 % allowancein each case has been given.
Sand: In a broad sense, sand is used as a synonym of fine aggregate, but it treated as genericname for natural fine aggregates in this specification.
Grading of aggregate: This term represents the degree that small and large size aggregates are
mixed moderately. It is expressed by the volume ratio of particles. However, for simplification, it isgenerally expressed by the cumulative weight percentage of aggregates passing each size of sieve.
When aggregates with different densities are mixed together, the cumulative weight percentage isalso converted to the volume percentage in order to adjust the grain size distribution.
Fineness modulus of aggregate: For example, the sum of the total percentage by weight ofaggregate retained on the 10mm sieve means the sum of the weight percentages of sample retainedon each of the 80, 40, 20 and 10mm sieves. Table C1.8.1 shows an example of the calculation offineness modulus from the result of the sieve analysis of coarse aggregate. Fineness modulus is apractical index to show the approximate grading of aggregate, and it is conveniently used to judge
the state of change in the grading of aggregate and to estimate the unit water content in the mix
design of concrete. However, attention shall be paid that the grading of aggregate which has thesame fineness modulus is unlimited.
Maximum size of coarse aggregate: Attention shall be paid that the maximum size of coarse
aggregate does not represent the maximum size of the largest particle. It is defined so based on thefact that coarse aggregates actually compose of thin and/or slender particles, the maximum size ofthe largest particle therefore does not represent the characteristics of all aggregate particles.
Surface moisture of aggregate: Water contained in aggregate (moisture of aggregate) is
distinguished between the surface moisture and the absorbed water inside aggregate particles. The
surface moisture of aggregate shall be counted as a part of mixing water of concrete.
Densities of surface-dry aggregate and oven-dry aggregate: The term “density” mentioned here27

Standard Specifications for Concrete Structures-2007, Materials and Construction

is not the actual one obtained using powdered aggregate, but the apparent one. In determining themix proportions of concrete, density of aggregates in saturated surface-dry state is usually needed,because the saturated surface-dry state is defined as the standard one. However, in case of lightweight aggregate, it is more appropriate to regard the apparent density in oven-dry state as thestandard one, so the density in oven-dry state is used.
Powdery material: Powdery materials (cementitious materials) include not only materials that
contribute to the strength development of concrete by reacting with water, such as cement, blast
furnace slag and fly ash, but also nonreactive mineral powder such as limestone powder.
Binder: It, in a broad sense, means materials which bind aggregates together. For example, incase of asphalt concrete, it indicates asphalt. Cement paste is also treated as binder in cement
concrete, but in the narrow sense, it indicates powder which is responsible for cement hydration. In
this specification, binder is a generic name of powders which binds other materials such as cement,
granulated blast-furnace slag fine powder, fly ash, silica fume, expansive admixture etc.
Admixture: Several kinds of admixtures are available on the market. Their types, properties andpurposes of use differ widely. In this Specification, admixtures are classified into mineraladmixtures and chemical admixtures according to their amount to be used in concrete.
Mineral admixture: Fly ash, ground granulated blast-furnace slag and expansive admixtures are
typical mineral admixtures.
Chemical admixture: Air-entraining agent, water-reducing agent, air-entraining andwater-reducing agent, superplasticizer, high-range water reducing agent, retarder, accelerator,
corrosion inhibitor for reinforcing steel, gas generating agent, waterproofing agent are the examplesof chemical admixtures.
Entrained air and entrapped air: Entrained air means microscopic and independent air bubbles
distributed uniformly in concrete intentionally, by using an air-entraining agent or an air-entraining
and water-reducing agent, for the purpose of improving the quality of concrete. Entrapped air means
air contained in concrete naturally without using any air-entraining agent, and the sizes of the air
bubble are larger than those of entrained air. Although about 1-2 % entrapped air may be usuallycontained in air-entrained concrete, it is difficult to distinguish between entrained air and entrapped
air. Therefore, air content of air-entrained concrete means the sum of the amount of entrained air
and entrapped air in the concrete.
Reinforcing bars: In a wide sense, reinforcing bars include all kinds of steel bars embedded inconcrete to reinforce concrete. However, generally it means steel bars for reinforced concrete
specified in JIS G 3112 and steel bars with equivalent quality as those in the JIS. This Specification
makes it a rule to use only steel bars that conform to the JIS except those confirmed usable by a test.
Prestressing steel used for prestressing and rolled section steel used for steel frame are not called
reinforcing bars in this Specification.
Deformed bars: In a wide sense, deformed bars are any kinds of steel bars which possess surface
deformations such as ribs. In this Specification, however, it is prescribed that only the bars
conforming to hot- rolled deformed bars specified in JIS G 3112 or those confirmed by tests are to
be used.
Mix proportion: In the definition, the term “materials” means cement, water, fine aggregate,coarse aggregate and admixture.

28

Chapter 1

GeneralCharacteristic compressive strength of concrete: In this Specification, the compressive strengthof cylindrical specimens is used as the standard one to represent the strength and the quality ofconcrete. Generally, the characteristic compressive strength is determined on the basis of thecompressive strength at 28 days. The compressive strength of concrete varies to a certain degreeaccording to the quality of materials, construction condition, etc. Therefore, the mix proportioning
strength shall be determined on the condition its probability of being equal to or higher than thecharacteristic compressive strength is higher than a pre-determined margin. In the case where thedesign is based on the tensile strength or flexural strength of concrete, characteristic tensile strength
or characteristic flexural strength is used. In the case where the design is based on the strength of
specimens tested at 91 days, or 7 days, the strength is called the characteristic strength at 91 days or
7 days, respectively. However, characteristic strength generally implies the strength at 28 days.
Mix proportioning strength: Mix proportioning strength is the desired strength in determining
the mix proportion of concrete. It is obtained by multiplying the characteristic compressive strength
to the overdesign factor, taking into account the variation in the quality of concrete.
Unit content: The term “unit content” is used for making short “the quantity of a specificconstituent material used for producing 1 m3 of concrete or mortar”. Unit cement content (C), unit
water content (W), unit content of aggregate, unit content of fine aggregate (S), unit content ofcoarse aggregate (G), unit content of air entraining agent, unit content of Pozzolan, and so on areused.
Powdery material content and cementitious material content: The powdery material content is
the total of the unit contents of different powdery materials including cement and other cementitious
materials and admixtures (Fig. C1.2.1) and is regarded as a major indicator of segregation resistance.
The cementitious material content and the cement content may be thought to as indicators used toevaluate strength development properties, heat of hydration and durability. Mixed cement may bedescribed, strictly speaking, as a binder, but it is conventional practice to classify mixed cement as
cement, and the term "cement content" may be used.

Powdery materials
BinderCementFig.C1.2.1 Definition of powdery materials, binder and cement
Slump: Slump is measured in accordance with JIS A 1101. Although the concept of "minimum
slump at the time of placement" is indicated in the Construction: Construction Standards of thisSpecification, unless otherwise specified herein, the term "slump" is construed to mean the averageof measured slumps.
Consistency and workability: Consistency is an important factor of workability and can be29

Standard Specifications for Concrete Structures-2007, Materials and Construction

measured fairly accurately by the slump test. Although many testing methods for measuring
workability were studied and proposed in the past, there are no testing methods universally
adaptable in field. Therefore, workability suitable for a work needs to be judged by an expert.
Slump test is effectively used as a supplementary mean of judging the workability of concrete.
Pumpability: Factors determining pumpability include the ability to achieve a high pumping rate
under a light pumping load and the ability to resist clogging of concrete piping.
Placing height and compaction height: In conventional concreting projects, the placing height
for each layer or lift of concrete is specified, but placeability varies widely depending on how
compaction is done. “Construction: Construction Standards” of this Specification, therefore, defines
the new term "compaction height" to distinguish it from "placing height." For example, to place
concrete for wall members or column members in a typical project, workers enter the concrete
forms to perform compaction. Depending on member sizes and reinforcement patterns, however,this method of compaction may be difficult to perform, and placing height per layer or lift differsfrom compaction height.
Durability: External actions which adversely affect the durability of concrete include freezing
and thawing action, attack by chemical substances, and rubbing action. Furthermore, whenmaterials of poor quality are used, the long-term stability of concrete is deteriorated. In the case of
members of reinforced concrete and prestressed concrete, corrosion of embedded steel progresses
and their durability is damaged, if their concrete is neutralized or chloride is accumulated beyond acertain limit in the members.
Alkali-aggregate reaction: Alkali aggregate reaction is classified broadly into alkali-silica
reaction and alkali-carbonate reaction depending on the kind of mineral substance which reacts withalkali, but most of the reported cases of alkali-aggregate reaction in Japan are alkali-silica reaction.
When alkali-silica reaction occurs, cracks develop in concrete because the resulting alkali-silica gel
swells when absorbing water
Freeze-thaw resistance: When concrete and/or aggregate particles containing water are frozen,
expansive pressure develops due to the freezing of free water inside these materials. Freezing andthawing action induces slack or damage in the structure of materials due to the expansive pressure.
The degree of damage increases with the repetition of freezing and thawing action. Entrained air inconcrete plays a role of relieving the expansive pressure during the freezing of concrete.
Crack resistance: It is very difficult to avoid cracking but controlling the number of cracks andthe crack width is comparatively simple. Controlling crack is very important as long as the
durability of concrete, water-tightness and its appearance are concerned. Cracks may be induced bymany causes, but it is possible to improve the crack resistance by properly selecting materials, mix
proportion, construction method. In addition, appropriate design of concrete structure is also very
effective in crack controlling.
Inspection: The inspection is carried out on the qualities of materials, concrete, construction
process and constructed structure, using various inspection systems. Generally, the inspection ofmaterial and product is carried out by the purchaser. In many cases, the structure owner justconfirms the inspecting results based on inspecting records afterward. In case of ready-mixed
concrete, the constructor usually carries out the inspection because they purchase materials.
However, designated inspector often carries out inspection when ready-mixed concrete of JIS isused. Inspections during construction or at completion are commonly carried out by the structureowner.

30

Chapter 1

GeneralMoist curing: It is to ensure the necessary amount of water for the hydration of cement in
concrete since it is not sufficient just by preventing the evaporation of water from the placed
concrete. This curing method is also effective in preventing cracking due to drying shrinkage duringinitial hardening stage.
Temperature controlled curing: This curing method is to control the temperature in each part ofthe concrete to facilitate the normal hardening process and to avoid the cracking after hardening aswell as and the development of excessive internal stress. In utilizing this curing method, it isnecessary to take into account both the size of members and the effect of construction condition.
Accelerated curing: There are some curing methods to accelerate the hardening rate of concrete,such as steam curing, autoclave curing, hot water curing, electrical curing, infrared curing, and highfrequency curing. However, in general, steam curing is widely used.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 2 QUALITY OF CONCRETE

2.1 General
The concrete used shall be one that has consistent quality and workability suitable forthe construction tasks to be performed and, after hardening, has the required properties
such as strength, durability, water-tightness and cracking resistance.

[Commentary] In order to create a concrete structure that has the required performance attributes,
it is necessary to use concrete that provides the structure with those performance attributes andmakes proper concreting possible. In accordance with this principle, this chapter specifies basic
quality requirements for concrete.
The basic quality requirements for concrete specified in this chapter are qualitative consistency,
workability, strength, durability, water-tightness and cracking resistance.
(a) Qualitative consistency: Highly variable quality of concrete supplied for the construction ofa structure not only increases the possibility of occurrence of defects during construction but also
necessitates the use of a large factor of safety in mix design to achieve the required strength, making
the construction project uneconomical. Inconsistent quality of concrete may also degrade durability,
cracking resistance and appearance. When manufacturing concrete, therefore, it is very important tosecure a supply of concrete of stable quality. To do that, it is important to perform thorough material
quality control and concrete manufacturing control.
(b) Workability: In order to carry out construction work efficiently and create a concrete
structure with as few defects as possible, the concrete used shall have the type of workability
suitable for such tasks as hauling, placing, compacting and finishing. In other words, workability
attributes such as filling ability by which to completely cast formwork including the regions aroundreinforcing steel and corners, pumpability necessary for on-site pumping, and appropriate setting
properties are very important in order to carry out construction appropriately and efficiently andconstruct a concrete structure with as few defects as possible.
(c) Strength: If a concrete structure is to maintain the required safety and serviceability during
its service period, the concrete used shall have the strength assumed at the design stage, that is, thedesign strength. Initial strength development properties are an important factor affecting the speedof construction.
(d) Durability: If a concrete structure is to maintain the required safety and serviceability during
its service period, the concrete used shall have the required durability as well as the design strength.
In order for the reinforcing steel placed in the concrete structure to perform the required functions
over a long period of time, the concrete needs to be capable of effectively protecting the reinforcing
steel from corrosion. The durability attributes required of concrete can be classified into (1)physical action such as freeze–thaw action, (2) chemical action caused by sulfates, acids, etc., (3)durability of concrete itself against its own deterioration attributable to the quality of the materials
used such as alkali–silica reaction, and (4) the ability to protect steel from the action of chloride
ions, carbon dioxide, etc., that accelerate steel corrosion by infiltrating the concrete. It is therefore
necessary to take these into consideration on an as-needed basis.
(e) Water-tightness: Water-tightness is a quality attribute indicating resistance to water or
moisture permeability. Concrete structures that require water-tightness are structures whose safety,
32

Chapter 2

Quality of Concrete

durability, functionality, maintenance, appearance, etc., are affected by water permeability.
Examples are storage facilities, underground structures, hydraulic structures, water storage tanks,
drinking water and sewer facilities, and tunnels. Leaching of calcium from concrete might also
cause performance degradation of the structure over a long period of time. Thus, water-tightness is aquality attribute that needs to be taken into account when considering structures that come into
contact with water.
(f) Cracking resistance: Excessive cracking in a concrete structure not only has adverse effects
on durability and water-tightness but also degrades the appearance of the structure. It is very
important, therefore, to use concrete that is highly resistant to cracking.
There may be cases, depending on the type of structure or member, where quality attributes ofconcrete other than those described in this chapter are required. In such cases, the quality ofconcrete shall be determined so that the required performance of the structure can be achieved.

2.2 Qualitative Consistency
Concrete shall be reasonably consistent in terms of the quality of materials andmanufacture and shall have consistent quality.

[Commentary] Great variation in the quality of materials used to manufacture concrete and thequality of manufacture could make it difficult to supply concrete of the required quality in aconsistent way, causing adverse effects on the performance of the resultant concrete structure. In
manufacturing concrete, therefore, it is important to control the quality of materials and the
manufacture of concrete carefully so that batch-to-batch variation in the quality of concrete can be
minimized and concrete of consistent quality is always available. Quality attributes such as thecontent of fines attached to the surfaces of aggregate particles, the surface water content of fineaggregate, and the grading of fine aggregate and coarse aggregate are highly variable and are factorsthat could greatly affect the quality of concrete. In order to ensure qualitative consistency, therefore,
it is important to control those quality attributes so that their variations can be minimized.

2.3 Workability
Concrete shall have workability suitable for the works to be performed such as
hauling, placing, compacting and finishing according to the construction, structural andenvironmental conditions.

[Commentary] In order to construct a concrete structure with the required performance, it isnecessary to perform construction. Since these tasks greatly affect the quality and setting propertiesof fresh concrete, concrete needs to have workability suitable for the tasks to be performed such as
hauling, placing, compacting and finishing. Although workability includes all items related to thedegree of ease of placement of fresh concrete until it hardens, it is difficult to describe all of them indetail. In the construction: Construction Standards in this specification, therefore, importance is
attached to smooth execution of construction work in ordinary concreting projects, and filling
ability, pumpability and setting properties are described as workability attributes.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

2.3 1 Filling ability(1) Filling ability is defined as a performance attribute that can be obtained through theinteraction of fluidity and segregation resistance in the case of vibrating compaction.
Filling ability shall be determined by considering both terms. Slump is used as anindicator of fluidity, and the cement content or powdery material content is used as anindicator of segregation resistance.
(2) Filling ability shall be specified within a practical range in view of the type ofstructure, the type and size of member, reinforcement conditions such as the amount ofreinforcing steel and the minimum steel spacing, on-site transportation methods andcompaction methods.
(3) It shall be assumed that the fluidity needed to fill formwork with concrete smoothly
and completely, and can be achieved by securing the minimum slump for placement. The
minimum slump for placement shall be determined after carefully considering the detailsof construction method such as placing locations, the parts of the structure to be
concreted, compaction height, internal vibrator spacing, placing height per concreting
cycle, and the placing rate in advance, so that slump can be made as small as practicable.

High[Commentary] (1): Filling ability required of concrete is the ability of concrete to pass throughreinforcing bars without undergoing segregation and completely fill complicated regions such asconcrete cover regions, internal corners or prestressing tendon zones. It is generally known fromexperience that filling ability is determined by the interaction of fluidity and segregation resistanceduring vibratory compaction. It is assumed here, therefore, the quality of filling ability isdetermined by the balance between fluidity and segregation resistance as shown in Fig. C2.3.1.
大↑Fluidity流
動性Workability
充てん性
Segregation
材
料分離
resistance
抵抗性

Low

↓
小

Low Segregation resistance High

Small
Slump → Large
小← スランプ
大

大
↑
材
料
分
離
抵
抗
性
↓
小

Slump → Large
Small
小← スランプ
大

Fluidity
流動性

良Better好↑必要な
充てん
Requiredfilling
レベル
ability level

密実な充てんが可能な範囲
Range
in which concrete can be cast completely

Lower
limit of slump
Upperlimit of slump
下限のスランプ
上限のスランプ
Small
Slump → Large
小← スランプ
大Fig. C2.3.1 Concept of workability of concrete

34

Chapter 2

Quality of Concrete

Fluidity and segregation resistance are affected by not only the water content, cement content
and the powdery material content (hereinafter powder content) but also other factors such as thetype of cement or powder, grading and shapes of fine and coarse aggregate, and the types ofchemical admixtures. In general, segregation resistance can be quantified by use of plastic viscosityand a rheological constant such as the yield value. In this specification (Construction Standards), inview of engineering practice, fluidity is expressed with slump, and the powder content is used as anindicator of segregation resistance. The powder content is the total of the unit contents in concreteof powdery materials, whether reactive or nonreactive, such as cement, ground granulated blast
furnace slag, fly ash, limestone powder, etc. In the case of concrete that uses only cement, thepowder content is synonymous with the cement content. As mentioned earlier, the powder content is
an indicator of segregation resistance, while the cement content and the cementitious material
content, which indicate the contents of only reactive powdery materials, are indicators related to theheat of hydration, strength, durability, etc.
It is assumed that the filling ability of concrete is not uniquely determined by slump as arepresentative indicator of the consistency of fresh concrete and that it can be evaluatedquantitatively in terms of a combination of slump, the powder content as an indicator of segregation
resistance, and the structural conditions and construction conditions. On this assumption, Chapter 4,
Mix Design, describes detailed concrete mix design methods. Chapter 4 requires that the standard
value of the minimum slump during placement be selected from the construction conditions, and thepowder content be determined according to slump, taking the construction conditions into
consideration. The powder content, however, needs to be greater than a certain value in order toprevent initial defects resulting from segregation. The lower limit is 270 kg/m3, and 300 kg/m3 or
more is recommended. The balance with the filling ability is also important. The reason is that thecement content cannot be increased infinitely because of the need to prevent thermal cracking andeconomy-related problems. Methods for attaining the required powder content in cases where theheat of hydration is an important consideration include the method of using low-reactivity powder
such as fly ash or limestone powder. Setting the fine aggregate content at an appropriate level isalso effective in improving segregation resistance. For further details on the determination of thefine aggregate content, refer to the values shown in Section 4.5.4.
(2) and (3): Filling ability requirements vary with the conditions for different tasks. It istherefore necessary to determine the required slump and corresponding powder content in view ofvarious construction conditions. As shown in Fig. C2.3.2, slump varies depending on the time fromthe manufacture of concrete to the placement of concrete and the transportation of concrete. In orderto ensure the required placing performance of concrete, slump needs to be at or higher than the level
required during placement. However, Construction Standards of this Specification requires that thefluidity needed to achieve the required filling ability be determined according to the minimum
slump during placement.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

設定スランプSpecified slump

Target slump
upon
練上りの
completionof mixing
目標スランプDecreasein slump due to
現場までの運搬に伴う
transportation
to construction site
スランプの低下

Targetslump
荷卸し箇所の
at delivery
point
目標スランプ

Minimumslump
打込みのfor placement
最小スランプSlumptolerance at delivery point
荷卸し箇所のスランプの許容差
Normaldistribution curve
荷卸し箇所のスランプの正規分布曲線
for slumpat delivery point

Decreasein slump due to
現場内での運搬に伴う
on-sitetransportation
スランプの低下練上り
Completionof mixing

荷卸し
打込み
Delivery
Placing
製造から打込みまでの時間・空間的移動
Temporal and spatial movement at stages from manufacture to placement

Fig. C2.3.2 Relationship between specified slump at each stage of construction and changes inslump over time
If the required minimum slump for placement is to be achieved, it is necessary to determine theslump upon completion of mixing and the slump at the delivery point in view of various conditions(e.g., transportation method, time from completion of mixing to completion of placing, ambient
temperature). To be more specific, the slump upon completion of mixing is determined in view ofthe slump loss during transportation so that the required slump is achieved at the delivery point, andthe slump at the delivery point is determined in view of the decrease at the construction site (due tothe elapse of time and on-site transportation) so that the required slump can be achieved at theplacing point. Since the slump loss due to the elapse of time or transportation varies depending on
various conditions, it is important to appropriately allow for decreases in slump by carefully
considering the construction conditions in advance. The procedure for determining slump at eachstage is described in detail in Section 4.4.2.
As mentioned above, different slumps are required at the placing site, at the delivery and uponcompletion of mixing. In order to secure the required workability at the placing site, therefore, it isnecessary to achieve quality control goals by requiring greater values for the slump uponcompletion of mixing and the slump at the delivery than the slump at the placing site. Strictly
speaking, however, mix proportions differ depending on how long it takes before placing assumed
for the purposes of mix design optimization (i.e., upon completion of mixing, at the time of delivery
or at the time of placing). The basis concept: Construction Standards of this Specification is todetermine mix proportions so that the optimum workability can be achieved at the placing site. If,
however, the target slump upon completion of mixing or at the delivery is considerably larger than
the required minimum slump for placement as when the amount of slump loss due to off-sitetransportation or the elapse of time is long or when the amount of decrease in slump during on-sitetransportation by means of pumping is expected to be large, it is necessary to select appropriate mix
proportions. It should be taking into consideration such factors as segregation at the time of
manufacture or during off-site transportation and possible decreases in pumpability due to, forexample, clogging of pipes during on-site pumping. In such cases, it is good practice to determine
mix proportions, in terms of target slumps upon completion of mixing or at the delivery, so that
concrete with excellent workability can be obtained, in order to prevent problems related to
manufacturing control, quality control or acceptance inspection at the delivery. If ready-mixed
concrete is used, it is good practice to specify a slump that is the same as the target slump at thetime of delivery so that the required minimum slump for placement can be achieved.
The minimum slump for placement is determined in view of the structural conditions such as
the types and sizes of structural members and reinforcement (reinforcing bars and other reinforcing

36Chapter 2

Quality of Concrete

steel) patterns and the construction conditions such as on-site transportation methods (type ofconcrete pumper truck, pumping distance, piping direction), placing methods (drop height, height oflayer of concrete to be placed) and compaction methods (type of vibrator, spacing, insertion depth,
vibration time, compaction height).
There may be cases where construction workers can enter the formwork to perform compaction
work near the concrete placement surface or where construction workers cannot enter the formwork
but to perform compaction work from locations relatively far from the concrete placement surface.
Thus, the conditions under which compaction work is carried out vary with the cross section of thestructural member concerned and the density of steel reinforcement, and the difficulty in performing
construction tasks also varies. Usually, the term "placing height" is used to refer to the height of alayer or lift of concrete to be placed. In the Construction: Construction Standards of thisSpecification, the commonly used term "placing height" and the working height related to thedifficulty in performing compaction work are distinguished, and, as shown in Fig. C2.3.3, the heightfrom the surface of the worker's platform to the bottom of the formwork or the concrete placement
surface is defined as the "compaction height."

Compaction
height
締固め作業高さ

It is a basic rule that the minimum slump for placement corresponding to the compaction heightshould be determined after carefully considering construction method details such as placing
locations and areas, compaction height, internal vibrator spacing, the height of concrete placed in asingle cycle, and the placing rate so that slump can be made as small as practically possible.

Fig. C2.3.3 Example of compaction height in case where a construction worker enters theformwork for a concrete member

2.3.2 Pumpability(1) When concrete is pumped, fresh concrete shall have a slump suitable for the task.
(2) Proper segregation resistance during pumping shall be achieved so that pipes used
for pumping are not clogged.

[Commentary] (1) and (2): When concrete is pumped, it is necessary to achieve the required
pumping rate under the planned pumping conditions without clogging the piping. The quality offresh concrete, therefore, should not change substantially during pumping. Ideally, in order to meetthese requirements, an appropriate set of conditions should be selected by considering alterations in
not only concrete performance but also construction conditions such as the type of pump, thediameter of pipes and the transportation distance. The properties of fresh concrete keep changing a37

Standard Specifications for Concrete Structures-2007, Materials and Construction

series of tasks from manufacturing and shipping through transportation to the construction site andon-site transportation to placement and compaction. Since slump may decrease considerably if
concrete is pumped for on-site transportation, it is necessary to select mix proportions allowing for
decreases in slump due to pumping so that the workability required for placement can be achieved.
The slump loss due to pumping should be estimated by referring to Table 4.4.7 or other data.
Clogging of piping is a phenomenon peculiar to pumping. It is necessary to select mix
proportions for excellent pumpability so that clogging of piping can be prevented and then estimate
the slump loss due to pumping appropriately. The powder content (or the cement content if cement
is the only powdery material used) and the fine aggregate ratio required careful attention because an
excessively low powder content or fine aggregate ratio increases the possibility of pipe clogging.
Since, however, the viscosity of concrete increases and the pumping load increases as the powder
content increases, it is important to find an appropriate balance. More information on concrete
pumping planning can be found in Recommendations for Placement of Concrete by Pumping(2000).
Standard slumps and powder contents needed to achieve good pumpability range from 8 to 18
cm and about 270 kg/m3 to 300 kg/m3 or more, respectively. Because the water content needed toobtain the required slump may be excessively high depending on the quality of aggregate or otherfactors, it is important to make the water content as low as possible by making proper use ofchemical admixtures such as air-entraining water reducers and air-entraining high-range water
reducers.
In cases where clogging of piping does not occur, pumpability can be expressed in the form of
the relationship between the discharge rate and the pressure loss in pipe, and the pumpability thus
obtained is used as an indicator of whether the required amount of concrete can be transported
efficiently. The relationship mentioned above is shown in Section 7.3.2 of Chapter 7.

2.3.3 Setting properties
Setting properties of fresh concrete shall be suitable for the construction tasks to be
performed such as compaction, placing on fresh concrete and finishing.

[Commentary] Setting properties are related to the compaction of concrete, allowable placing
time interval, timing of finishing, lateral pressure acting on the formwork, etc. For hot-weather
concrete and cold-weather concrete, it is necessary to control setting properties by, for example,
delaying or accelerating setting according to the timing of placing and placing temperature.
Setting properties are evaluated in terms of the time of the start of setting and the time of theend of setting. In the construction of an ordinary concrete structure, the time to the start of setting
and the time to the end of setting as determined in accordance with JIS A 1147, Method of Test forTime of Setting of Concrete Mixtures by Penetration Resistance, are roughly 5 to 7 hours and 6 to
10 hours, respectively. The time of setting of concrete can be controlled to some extent by using
appropriate types of chemical admixtures, but it is common practice to decide on construction plans
and construction methods according to the time of setting.

38

Chapter 2

Quality of Concrete

2.4 Strength(1) The strength of concrete at a specified age shall not be lower than the design
strength with a probability equal to or higher than a specified percentage.
(2) As a standard practice, the strength of concrete should be expressed with ameasured value for a standard curing specimen at a material age of 28 days.
(3) Compressive strength tests and tensile strength tests on concrete shall be
conducted in accordance with JIS A 1108 and JIS A 1113, respectively. Specimens forthese tests shall be prepared in accordance with JIS A 1132.
(4) The strength development properties of concrete required at each stage of
construction shall be checked on an as-needed basis.

[Commentary] (1): While in service, a concrete structure shall be sufficiently safe against theloads considered at the design stage. The quality of the concrete used, therefore, shall be highenough to meet the strength requirements for the structure specified at the design stage. Since,
however, the quality of concrete, like other types of materials, inevitably varies, in theory it is notpossible to ensure that the strength of any part of the structure is higher than the design strength.
The Design: General Requirements of this Specification, therefore, defines a material strength as avalue that guarantees that a measured value becomes smaller than that with a certain probability,
and uses that value as design strength. This provision has been adopted to ensure that the strength
considered when a structure is designed is attained with a predetermined probability. For the
probability with which a measured value becomes smaller than the design strength, usually a value
of 5% is used in view of economy and other factors.
(2): If concrete has been properly cured in a wet condition, the strength of the concrete increases
as it ages. In the case of an ordinary structure, however, in many cases curing of concrete cannot be
expected to be performed in such a way that the curing period is more/less than 28 days. In view ofthis, the strength of concrete at the start of use of the structure is expressed, as a standard practice,with a measured value of strength obtained from a 28-day specimen cured by the standard curingmethod.
In the case of a structure to be subjected to loading at a relatively early stage, the strength of
specimens at an earlier-than-28-day material age shall be used as a standard of reference in view ofsuch factors as the nature of working loads, the dimensions of structural members and the curingconditions. If concrete whose strength increases considerably over a long period of time is used andthe curing period before loads begin to act is long, the strength of an older-than-28-day specimen
may be used as a standard of reference. This may make it possible to reduce the cement content sothat the occurrence of cracking due to the heat of hydration can be prevented.
There are cases where strength test specimens are cured at the construction site in order toaccurately reflect the effect of the field curing conditions on concrete strength. For example,
strength development of specimens are delayed at low temperatures in winter, but in the case of astructure with a large cross section, strength development of the structure may occur relatively fast
because of the temperature rise due to the heat generated by the hydration of cement. Thus, careneeds to be taken because field curing results do not always indicate the strength development
characteristics of structural concrete, and evaluation based on standard curing may be more
appropriate.

39

Standard Specifications for Concrete Structures-2007, Materials and Construction

In the case of high-strength concrete with a high cement content, early-stage exposure to hightemperature may result in poor strength development at the subsequent stages. The influence of thisis described in detail in the Construction: Special Concretes of this Specification (Chapter 6,
High-Strength Concrete).
Concrete strengths used in the design of structures includes compressive strength, tensile
strength, flexural strength, shear strength, bearing strength and the strength of bond with steel. It is
common practice to use compressive strength as a standard of reference because compressive
strength is easy to test and measured values are large enough to indicate changes in quality clearly.
Strengths other than compressive strength are not necessarily proportional to compressive strength,
but they can be judged in many cases by evaluating compressive strength. Thus, compressive
strength is widely used as a convenient indicator because it accurately reflects the quality ofconcrete. Except in the case of certain types of concrete such as pavement concrete designed on thebasis of flexural strength, therefore, compressive strength can be usually used as a standard ofreference of concrete strength.
(3): Concrete strength varies with concrete mix proportions, curing methods and material ages,
and measured values of concrete strength also vary with such factors as the shapes and dimensionsof specimens and loading methods. The compressive strength and tensile strength used in thisSpecification, therefore, shall be determined by the test methods described in JIS.
Preparing test specimens and testing the strength of concrete strictly by the JIS-specified
methods is very important in order to minimize test error.
(4): In-process strength checks are necessary in cases where, for example, formwork or
falsework is removed or the tensioning of prestressing tendons for prestressed concrete is carriedout early. In these cases, strength development properties shall be checked in view of the influenceof placing temperature, ambient temperature, etc.

2.5 Durability
2.5.1 General
Concrete shall be sufficiently durable against various physical and chemical actions towhich a concrete structure is exposed during its service period and shall be capable ofprotecting steel.

[Commentary] Concrete used in a concrete structure shall have the durability needed by the
structure to perform necessary functions during the specified period. To do this, concrete needs tobe durable and capable of protecting the reinforcing steel in the concrete. Factors impairing the
durability of concrete include freeze–thaw cycles, chemical attack and alkali–silica reaction. If one
or more of performance attributes such as freeze–thaw resistance, chemical resistance andalkali–silica reaction resistance are required, concrete of the quality that meet all performancerequirements shall be used. Major factors contributing to the corrosion of the steel in the concrete
include chloride attack and carbonation, and cracking is also a contributing factor because it could
accelerate those phenomena.
Various durability verification techniques have been proposed as methods for ascertaining that a
concrete structure or the concrete itself is sufficiently durable against those degradation phenomena,and some of those methods are described in the Design: General Requirements of this Specification
40

Chapter 2

Quality of Concrete(Chapter 8, Verification of Durability). The design drawings and specifications indicate design
values for materials based on verification and reference values related to the materials used and mix
proportions for achieving the design values, so construction can be carried out in accordance withthose values. If changes have been made in the materials to be used or mix proportions at theconstruction stage, it is necessary to return to the design stage and make durability verification
again. Since, however, verification methods for alkali–silica reactivity are not described in the
Design: General Requirements of this Specification, control measures described in the explanation(Item (1)) in Section 2.5.2 need to be taken.

2.5.2 Durability of concrete(1) Materials used in concrete shall not be ones that have adverse effects on therequired durability of the concrete.
(2) As a general rule, the water/cement ratio of concrete should be 65% or less.
(3) As a general rule, the concrete used should be air-entraining concrete.

[Commentary] (1): The durability of concrete is determined by environmental action, materials
used, mix proportions and construction work. The materials used, therefore, shall not have adverse
effects on the durability of concrete, and mix proportions need to be selected properly. As a generalrule, materials that meet the requirements described in Chapter 3, Materials, should be used.
In order to prevent alkali–silica reaction from reaching a harmful level during the service period,
one of these three methods shall be used: (1) reducing the total alkali content of the concrete, (2)using Type B mixed cement that is effective in suppressing alkali–silica reaction and (3) using
aggregate that is classified as Category A (harmless) in an alkali–silica reactivity test. Further
details of control methods are described in Section 3.2. If the intrusion of alkalis from an externalsource is inevitable as in a marine environment or in a region where deicing agents are used and if
the use of alkali-reducing measures relying solely on materials used is deemed to be inadequate, itis necessary to consider the use of additional measures such as surface covering.
(2): The water/cement ratio is the most important mix-proportion-related factor affecting the
durability of concrete. As the water/cement ratio increases, concrete becomes less durable. Because
the water/cement ratio of concrete that is required to have durability is usually lower than 65%, thissection requires that the maximum water/cement ratio of ordinary concrete be, as a general rule,65%. The water/cement ratio to be actually used varies depending on expected degradation factors,
and specific details of the determination method are described in the Design: General Requirementsof this Specification (Chapter 8, Verification of Durability). It should be kept in mind, however, that
if the water/cement ratio is too low, the cement content becomes relatively large and the heat ofhydration and autogenous shrinkage increase so that the durability of concrete adversely affected
depending on the type of structure. The water/cement ratio of concrete subjected to chemical attack
shall meet the requirements described in Section 4.3.4 of Chapter 4.
Verification as to whether a concrete structure meets the freeze–thaw resistance requirements ismade by use of the relative dynamic modulus of elasticity in freeze–thaw testing. Reference values
shown in the design drawings and specifications are water/cement ratios that meet the required
relative dynamic modulus of elasticity in the Design: General Requirements of this Specification(Chapter 5, Design Values for Materials). The water/cement ratio, therefore, may be determined on
the basis of those reference values.

41

Standard Specifications for Concrete Structures-2007, Materials and Construction(3): In an environment under the influence of freeze–thaw cycles, entrained air bubbles reducewater pressure increases due to freezing of internal water. The use of air-entrained concrete,
therefore, is very effective in improving freeze–thaw resistance. Furthermore, the use of
air-entrained concrete substantially reduces the amount of water needed to achieve the required
workability so as to facilitate complete filling with concrete and improve durability attributes otherthan freeze–thaw resistance. This is why it is required, as a general rule, that air-entrained concrete
be used not only in cases where severe weather action is involved but also in cases where severe
weather action is not involved.

2.5.3 Steel protection performance(1) Concrete shall be capable of protecting the steel placed in the concrete so that thesteel can perform its intended functions during the service period.
(2) As a general rule, the total amount of chloride ions contained in concrete when it ismixed should not exceed 0.30 kg/m3.

[Commentary] (1): Concrete has the function of protecting the steel in the concrete from external
corrosion factors and heat from fires and other heat sources. Many of the concrete structures havereinforcing bars and other reinforcing steel in the concrete. If the reinforcing steel corrodes,
therefore, the durability of those concrete structures decreases considerably. The reason why theprotective function of concrete is lost is the protective passive film on the steel surface is destroyed.
The destruction of the protective passive film is caused mainly by a decrease in alkalinity due tocarbonation and the presence of chloride ions in the concrete. If, therefore, the protective functionof concrete is to be performed effectively, the depth of carbonation of concrete shall not reach thecritical depth for steel corrosion, which is the level at which steel corrosion occurs, during theservice period, and the chloride ion content of the concrete at the steel location shall not exceed thelevel at which the protective passive film on the steel is destroyed. Thus, from the viewpoint of theprotection of steel, it is necessary to select materials and mix proportions so that concrete isprovided with appropriate mass transfer resistance according to the concrete cover determined at thedesign stage. The water/cement ratio is determined at the design stage along with the concrete cover,
and whether the required durability is achieved is verified. It is a general rule, therefore, to use awater/cement ratio not greater than the value used for the purpose of verification.
The use of air-entraining agents, water reducers, air-entraining water reducers, superplasticizer,
etc., improves workability and reduces segregation such as bleeding so that homogeneous concretewith relatively few defects can be obtained. The use of those chemical admixtures, therefore, iseffective in improving the steel protection function of concrete.
Also, if blast furnace cement or fly ash cement is used or if an appropriate amount ofhigh-quality pozzolan is used as an admixture, fine-textured concrete is obtained. If blast furnace
cement is used, the ability to fix chloride ions in the concrete is enhanced. Thus, the use of these
admixtures can be expected to reduce the intrusion of elements that cause steel corrosion into theconcrete. It should be kept in mind, however, that the steel protection performance in the cases
where these types of cement or pozzolan is used can be achieved only if a sufficient initial wet
curing period is secured.
Cracks in the cover concrete can considerably degrade steel protection performance. It istherefore necessary to achieve durability by exercising control so that the critical crack width (seeSection 8.3.2 of the Design: General Requirements of this Specification) for steel corrosion is not
42Chapter 2

Quality of Concrete

exceeded.
If the measures mentioned above are not effective enough to protect the steel or if it is thoughtthat the maintenance or repair of the structure is difficult to perform, measures such as using
epoxy-coated reinforcing bars or coating or finishing the concrete surface should be taken. It isadvisable to refer to the Recommendations for Design and Construction of Reinforced Concrete
Structures Using Epoxy-Coated Reinforcing Steel Bars (Revised Edition) if epoxy-coatedreinforcing bars are used and the Recommendations for Concrete Repair and Surface Protection ofConcrete Structures if the concrete surface is protected to reduce the infiltration of chlorides.
(2): If chlorides exist in concrete in a quantity exceeding a certain limit, the corrosion of thesteel in the concrete is accelerated so that early deterioration of the structure results. Such chlorides
may enter the concrete from an external environment such as a marine environment or be supplied
to the concrete from materials such as cement, aggregate, chemical admixtures and mixing water. In
order to achieve the steel protection performance of the concrete, therefore, it is very important tocontrol and keep the total quantity of chloride ions supplied to the concrete from those materials
within the range that does not cause steel corrosion. The Construction: Construction Standards ofthis Specification requires, therefore, that the total quantity of chloride ions be controlled in termsof the total chloride ion content of concrete during mixing. The total chloride ion content of
concrete during mixing is the total of the quantities of chloride ions that are thought to be supplied
from the materials used to the concrete calculated on the basis of mix proportions. When mixing
concrete, therefore, it is necessary to know in advance the chloride ion content of each material. If
tap water is used as mixing water and the chloride ion content of that water is not known, thequantity of chloride ions supplied from the mixing water to the concrete may be assumed to be 0.04
kg/m3.
If the total quantity of chloride ions calculated on the basis of mix proportions is greater than theallowable limit, part or all of the materials to be used shall be changed. As a result of the recent JIS
revision, the allowable upper limit of the chloride ion content of normal Portland cement has been
increased from 0.02% to 0.035%, the amount of increase in the chloride content of concrete is notlarge enough to cause a serious problem unless the cement content is extremely high.
The limit value stipulated in this section, namely, the chloride ion content of 0.30 kg/m3, is notintended to guarantee that steel corrosion will never occur. Instead, the value has been determined,on the basis of research and study results, as a feasible value that can keep the deterioration of astructure due to steel corrosion at or below an acceptable degree. Therefore, in the case of, forexample, prestressed concrete subject to stress corrosion or reinforced concrete that is used in anenvironment with chloride attack due to chloride ion intrusion or electrolytic corrosion and that isrequired to be highly durable, the quantity of chlorides in the concrete should be made as small as
possible in comparison with the specified value.
In the case of reinforced concrete or plain concrete with nonstructural reinforcement to be used
under normal conditions, if materials with a low chloride content are very difficult to obtain, theallowable upper limit of the total chloride ion content of concrete may be raised to 0.60 kg/m3. In
this case, however, it is necessary to carefully carry out construction, taking particular care, among
other things, to make the water/cement content or the water content as small as possible and place
concrete properly.
The provision of this section does not apply to a structure built with plain concrete without
nonstructural reinforcement. It has been pointed out, however, that even in the case of concrete used
for structures of this type, there may be adverse effects such as poor strength development over along period of time and increased proneness to efflorescence deposition as the chloride ion content
increases. The total quantity of chloride ions, therefore, should be minimized.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

2.6 Water-tightness
Concrete shall have the required water-tightness so that the functions of the structure
are not lost because of water permeation.

[Commentary] Water-tightness includes the water-tightness of concrete and the water-tightnessof a structure or member. In general, the former is evaluated in terms of the permeability coefficientof concrete, and the latter in terms of the permeation rate.
The permeability coefficient is basically dependent on the solidity of concrete, and concretewith high solidity, that is, concrete with a small permeability coefficient is desirable from theviewpoint of durability, too. The permeability coefficient is governed by the degree of compactnessof hardened porous cement, void structure characteristics such as void continuity, and the nature of
the relatively-coarse-textured transition zones formed around aggregate particles. The void structureof hardened cement is usually dependent on the water/cement (cementitious material) ratio and thetype of cementitious material. Transition zone formation and continuity vary with the water/cement
ratio and the degree of segregation (bleeding), and as the width of the transition zone increases andthe distance between aggregate particles decreases, the continuity of transition zones tends toincrease and the permeability coefficient of the concrete tends to increase. It is generally known thatas the water/cement ratio increases, the permeability coefficient of concrete increases exponentially.
In order to achieve the required permeability coefficient, therefore, it is effective to reduce thewater/cement ratio and the water content to the extent that workability suitable for the construction
tasks to be performed can be achieved by using admixtures, etc., appropriately so that homogeneousand compact concrete can be obtained. Past experience confirms that water-tightness required ofordinary concrete can be achieved if the water/cement (cementitious material) ratio is 55% or less.
Whether the functionality of a structure is not hampered by water permeation is verified as
described in the Design: General Requirements of this Specification (Section 10.6, Verification of
Water-tightness). Because the permeation rates are indicated in the design drawings andspecifications as characteristic values, it is necessary to carry out construction so that those values
are met. The water-tightness of a concrete structure is closely related to not only the water-tightnessof the sound regions of concrete but also the water-tightness of discontinuous surfaces such as crack
and joint regions. In general, the rate of permeation through cracks and vertical construction joints
tends to be much higher than the rate of permeation in sound regions of concrete. If water-tightness
is required of a structure, therefore, the occurrence of cracking should be prevented. The use ofreinforcing bars for crack control and expansive admixtures is effective in controlling theoccurrence of cracking and crack width. Also, it is a basic rule to treat construction joints properly
and use waterstops at vertical construction joints (see Chapter 9, Joints). Construction-related
measures that can be taken include laying waterproof membrane in regions where water-tightness isrequired, and using crack-inducing joints and taking appropriate waterproofing measures after
cracking. When taking these measures, it is important to properly evaluate those measures including
the maintenance plan and decide on details accordingly because the effectiveness of such measuresdiffer depending on factors as the materials and methods used.

2.7 Cracking ResistanceConcrete used shall be one that is free as much as possible from settlement cracking,plastic shrinkage cracking, thermal cracking, autogenous cracking, drying shrinkage
44

Chapter 2

Quality of Concrete

cracking, etc.

[Commentary] Many cracks that have occurred at the surface of a concrete structure may mar theappearance of the structure or cause the performance of the concrete such as durability, steel
protection performance, water-tightness and airtightness to be degraded severely. Cracks resulting
from excessive shrinkage may also have adverse effects on the stiffness and deflection of structuralmembers. The influence of cracks occurring at the construction stage on the performance of astructure during its service period has not yet been fully understood. The verification, however, ofvarious performances attributes described in the Design: General Requirements of this Specification
assumes that initial cracking that is so harmful as to affect the required performance of the structure
does not occur at the construction stage. It is necessary, therefore, to minimize the occurrence of
cracking and control cracks so that they do not affect performance, that is, keep crack width withintolerance. The intent of the Construction: Construction Standards of this Specification is not tocompletely prevent cracking. Instead, it is to prevent harmful cracks that degrade the performanceof concrete.
Possible causes of cracking of concrete include those attributable to materials or mix
proportions, those attributable to construction work and those attributable to external forces. Causesof cracking attributable to external forces can be taken into consideration at the design stage, andthere are even types of cracking such as flexural cracking that are allowed to some degree.
The initial cracking verified in the Design: General Requirements of this Specification (Chapter
12, Verification of Initial Cracking) is cracking due to the hydration of cement and cracking due toshrinkage. The intent is to verify that these types of initial cracks do not affect the required
performance of the structure. Since the design drawings and specifications indicate design values
for materials based on verification and reference values related to the materials used and mix
proportions, construction can be carried out according to those values as in the cases where
durability is to be achieved. The occurrence of these types of cracks, however, is attributable to not
only the nature of concrete determined by such factors as materials and mix proportions but also
various other factors such as environmental conditions, the dimensions and shape of the structure,and construction methods, and there may even be cases where other factors that cannot be expected
at the design stage are involved. It is therefore necessary to select concrete materials, mix
proportions and construction methods after careful consideration of those factors and their effects.
In order to reduce rises in concrete temperature, it is important to make the cement content(cementitious material content) as small as possible. Taking measures such as keeping material
temperature low is a good construction practice.
From previous studies, it has shown that autogenous shrinkage increases while the water/cement
is low and that the amount of shrinkage varies widely depending on the type of cement and theadmixtures used. In the case of high-strength concrete with a smaller-than-normal water/cement
ratio, it is important to select appropriate materials and mix proportions. In order to control drying
shrinkage, it is important to make the water content as small as possible. It is also important not touse high-absorption aggregate or aggregate with a small Young's modulus.
It should be kept in mind that shrinkage strain should be small, but it is important to ascertain in
advance by referring to past construction data or reliable literature that the concrete materials andmix proportions to be used are free from cracking due to shrinkage. The Design: General
Requirements of this Specification requires that the maximum allowable shrinkage strain in
concrete should be 1,200 μ if past construction data or other relevant information is not available
concerning the shrinkage of the concrete to be used. This value was obtained by assuming thatmeasured values of length change obtained by water-curing 100×100×400 mm specimens for 7
days at 20±2°C and measuring length changes at 20±2°C and relative humidities of 60±5% in
45

Standard Specifications for Concrete Structures-2007, Materials and Construction

accordance with JIS A 1129, Methods of Test for Length Change of Mortar and Concrete, are 1,000
μ or less and that autogenous shrinkage occurring during the water curing and the subsequent six
months is 200 μ.
Judging from past construction data, it may be thought that shrinkage strain in ordinary
ready-mixed concrete is not greater than the maximum value mentioned above. If, however, a very
important structure is involved or shrinkage cracking has a serious impact on the performance of thestructure concerned or if a smaller shrinkage strain is specified at the design stage, the value
mentioned above needs to be verified through testing.
Common types of cracks that occur at the construction stage besides the shrinkage-induced
cracks mentioned above include settlement cracks and plastic shrinkage cracks. An effective way toprevent settlement crack is to use admixtures with a water-reducing agent and mix proportions witha low water content. Cracking can also be prevented by careful construction, and settlement
cracking can be prevented by reducing bleeding and carrying out tamping or revibration at
appropriate timing. Plastic shrinkage cracking can usually be prevented if rapid drying from thesurface following the placement of concrete is prevented. Plastic shrinkage cracking may occur
when the rate of evaporation of water from the surface is higher than the rate of rise of bleedingwater. In the case of high-strength concrete that is relatively free from bleeding, therefore, it isimportant to prevent the dissipation of moisture.

46

Chapter 3

Constituent Materials

CHAPTER 3 CONSTITUENT MATERIALS

3.1

GeneralConstituent materials used for concrete, of which quality has been confirmed, shall beselected.

[Commentary] Choice of appropriate constituent materials is very important in ensuring that theconcrete meeting the required performance criteria is made. The suitability of the constituent
materials can be confirmed using by quality control tests or service records. Also constituent
materials conforming to standards of quality such as those laid down by JIS or JSCE Standards may
be confirmed as good quality materials. Materials to be used for concrete shall be determined so as
to satisfy the required performance taking into consideration of the limitations of the production
plant, economy including ease of material procurement and cost of transportation, etc.(6.1 General).

3.2

Cement(1) Appropriate cement shall be selected according to the intended use.

(2) Cements shall comply with the requirements of JIS R 5210 or JIS R 5211 or JIS R
5212 or JIS R 5213.
(3) When cement other than the types of cement mentioned in Item (2) is used, it shallbe ascertained that the performance requirements for concrete are met.

[Commentary] (1) It is necessary to select the most appropriate cement for construction byconsidering the types, sizes and locations of structures, weather conditions, time and duration of
construction, construction procedures, etc. to produce concrete of required performance steadily andeconomically.
(2) The types of cement specified in JIS include normal, high-early-strength,very-high-early-strength, moderate-heat, low-heat, and sulfate-resistant Portland cement
conforming to JIS R 5210, Portland Cement, blended cement conforming to JIS R 5211, Portland
Blast-furnace Slag Cement, JIS R 5212, Portland Pozzolan Cement, and JIS R5213, Portland
Fly-ash Cement, and cement conforming to JIS R 5214, Ecocement. In many projects, normal
Portland cement is used. Other widely used types of cement include high-early-strength andmoderate-heat cement in the Portland cement category and blast furnace slag cement and fly ash
cement in the blended cement category. In recent years, the use of Type B blast furnace slag cement
has increased. Today, cement is being expected to contribute to the realization of a zero waste
society by making it possible to reuse by-products from other industries. In 2003, in order to meetgrowing demand for industrial by-products that can be used as materials for normal Portland
cement, the allowable upper limit to the chloride ion content was raised from 0.02% to 0.035%.
In general, the use of high-early-strength Portland cement in a low temperature environment
decreases the degree of delay in strength development at early material ages in the case of low
temperature curing, thereby making the concrete less susceptible to the damage by freeze–thaw
cycles. The use of high-early-strength Portland cement in a high temperature environment, incontrast, contributes to a rise in concrete temperature because of a large amount of heat generated
47

Standard Specifications for Concrete Structures-2007, Materials and Construction

by hydration, making spreading of concrete more difficult because of stiffness of concrete resulting
from high temperature and making the concrete more prone to cracking. In a high temperatureenvironment, therefore, it is desirable that low-heat, moderate-heat or normal Portland cement orType B blended cement be used so as to reduce the amount of concrete temperature rise andsubsequent cracking due to temperature fall.
Type B blast furnace slag cement is effective in reducing alkali–silica reaction and chloride
infiltration. Type B blast furnace slag cement in recent years, however, tends to be formulated sothat, depending on the slag content, the powder content, etc., the initial strength becomes high.
Consequently, there are cases where the adiabatic temperature rise rate of concrete is higher thanthat of normal Portland cement, and there have been reports of increases of cracks due to thermal
stress depending on member sizes, constraint conditions, environmental conditions, etc. Since TypeB blast furnace slag cement includes low-heat types, it is important, when using it, to check on its
thermal and other properties and guarantee strength at a relatively old material age.
Thanks to recent advancements in production technology, today it is possible to achieve therequired strength of cement even if the water/cement ratio is high. Cement today, therefore, iscapable of meeting high-early-strength-oriented performance requirements aiming to achieve therequired strength at a material age of 28 days. Some point out, however, that as a result, durability
suffers. In the coming years, there will be a need for cement that develops appropriate strength at
the water/cement ratio determined by durability, that is, cement that has different strengths forconcrete with different strengths. In this case, however, curing that takes early-age strength
development into consideration is important.
Ecocement, which was newly standardized in 2002, can be largely classified into two types:
normal ecocement and rapid-hardening ecocement. Ecocement, which contains chloride ions in thequantity equal to 0.1% or less of the mass of cement, has properties similar to those of normal
Portland cement. Ecocement has made application to ordinary reinforced concrete possible.
If the quantity of Na2O or K2O contained in cement is large, particular types of minerals in theaggregate may cause alkali–silica reaction under certain conditions, thereby causing thedeterioration of the concrete. Appendix 2 (regulation), Methods for Suppressing Alkali–Silica
Reaction, of JIS A 5308 describe three methods for preventing or reducing such alkali–silica
reaction to choose from: (1) reducing the total alkali content (total quantity of alkalis supplied byvarious materials) of concrete to an Na2O equivalent of 3.0 kg/m3 or less, (2) using blended cement
containing a reaction-suppressing effect such as Type B or Type C blast furnace slag cement or TypeB or Type C fly ash cement and (3) using aggregate that has been judged to be harmless withrespect to alkali–silica reaction. Reaction control methods are described in greater detail in the
explanation about Item (4) of Section 4.3.4.
(3) Cement used mainly for civil engineering projects includes not only the types specified in
JIS but also cement with special performance characteristics.
The use of ultra-rapid-hardening cement makes it possible to achieve high strength in a shortperiod of time and begin to use the structure in only several hours even in winter. Since theconsolidation and hardening properties of cement of this type vary considerably depending on thequantity of hardening time modifiers used, it is necessary to obtain accurate information on the
consolidation properties at the temperatures at which the cement is used. Other special types of
cement include ultra-fine cement, alumina cement, oil well cement, geothermal well cement, white
Portland cement and colored cement. When deciding on using these special types of cement, it isgood practice to carefully study past construction records and conduct thorough tests in advance.
The use of a combination of two or more types of cement may result in an unexpected result such as
48

Chapter 3

Constituent Materials

quick setting of a mixture of alumina cement and Portland cement. When mixtures of different
types of cement are used, it is necessary to ascertain that such mixtures would not have adverse
effects on the performance of concrete.

3. 3

Mixing Water(1) Mixing water should be tap water complying with the provisions of JSCE-B101 or
Appendix 3 of JIS A5308, as standard.
(2) Recovered water shall meet the requirements described in Appendix 3 of JIS A
5308.
(3) Sea water should not be used as mixing water in general.

[Commentary] (1) Mixing water must not contain substances that cause the consolidation or
hardening or concrete, strength development, volume changes, degradation in quality such as
workability, or steel corrosion in harmful quantities. In many cases, water that does not have any
unusual taste, odor, color or turbidity and that is suitable for drinking can be used for mixing of
concrete.
Service water, water from rivers and lakes, groundwater, industrial water, etc. may be used as
mixing water. River, pond or lake water may be contaminated by industrial waste water or sewage
and may contain sulfates, iodides, phosphates, borates, carbonates, compounds of lead, zinc, copper,
tin, manganese, etc., inorganic alkali compounds, organic impurities such as sugar pulp waste wateror corrosive materials. The presence of even very small amounts of these impurities in the mixing
water, of concrete may have adverse effects on concrete properties such as the setting, hardening,
strength development, volume change, workability, etc. When mixing water containing chlorides,
nitrates, sulfates, etc. is used for concrete, the corrosion of steel may be accelerated. In particular,
for highly stressed prestressing tendons in prestressed concrete, stress corrosion is likely to occur. In
steel where a stray current is flowing, electrolytic corrosion may be accelerated. Therefore, in casesof using water other than service water as mixing water, the water should conform to therequirements of JSCE-B101 “Recommended Practice for Quality of Mixing Water for Concrete" orAppendix 3 of JIS A 5308 “Water for Mixing of Ready-Mixed Concrete”.
(2) The supernatant liquid of washing water in mixers, truck agitators, etc., at ready-mixed
concrete plants or precast concrete plants may be used as mixing water if it has been ascertainedthat there will be no adverse effect on the strength, workability, etc., of the concrete. Sludge waterwith suspensions of cement and other fine particles generated when aggregates are covered form
excess concrete or mortar may be used as mixing water, if its suspension concentration, the ratio of
the quantity of suspended solids to the cement content, etc., can be controlled adequately, only after
it is ascertained that there will be no adverse effect on the quality of concrete. Since, however,recovered water contains chlorides and alkalis, it is necessary to consider their concentrations
before using recovered water. Thus, only recovered water meeting the requirements described inAppendix 3 of JIS A 5308 may be used.
(3) If seawater is used, old-age strength of concrete becomes smaller, concrete becomes more
prone to efflorescence, and concrete become less durable. The use of seawater, therefore, is usually
not permissible. Since well water near a seacoast often contains chlorides, seawater may be used
only after the chloride content is checked. In the case of plain concrete without nonstructural
reinforcement, seawater may be used as mixing water after ascertaining that there will be no49

Standard Specifications for Concrete Structures-2007, Materials and Construction

adverse effect on the quality of concrete.

3.4

Aggregates

3.4.1

Fine aggregate(1) Fine aggregates shall be clean, hard, firm, durable, chemically or physically soundand not contain a harmful amount of dust, mud, organic impurities, chlorides, etc.
(2) Fine aggregates should comply with Table 3.4.1.
Table 3.4.1

Properties of fine aggregate

Item

Quality

Test method▪ Oven-dry particle density g/cm3≥2.5

JIS A 1109

▪ Water absorption %≤3.5

JIS A 1109

▪ Clay lumps %≤1.0 1)JIS A 1137

▪ Particles passing standard sieve size of 75μm

JIS A 1103

/ When concrete surface is subjected toabrasion %≤3.0 2)/ Other than the above %≤5.0 2)▪ Organic impurities▪ Content of chlorides %▪ Soundness %Darkerthanthestandardcolor
orsamplecolor

JIS A 1105

≤0.04 3)

JSCS C 502≤10

JIS A 1122

1) Test samples are the residual materials retained on the sieve after the test JIS A 1103.
2) In the case of crushed sand or slag fine aggregate, if the washed-out materials consist of dust from fracturing,
and are essentially free from clay or shale, these limits may be increased to 5.0 and 7.0%, respectively.
3) This value is a percentage for oven-dry mass of a fine aggregate, and it is shown as the value converted into
NaCl.

(3) Crushed sand should comply with the provisions specified in JIS A 5005.
(4) Blast-furnace slag fine aggregate, ferro-nickel slag fine aggregate, copper slag fineaggregate and electric arc furnace reducing slag fine aggregate should comply with theprovisions specified in JIS A 5011-1, JIS A 5011-2, JIS A 5011-3 and JIS A 5011-4
respectively.

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Chapter 3

Constituent Materials(5) Recycled fine aggregate should comply with the provisions specified in JIS A 5021.
(6) Grading of fine aggregate should lie in the range specified in Table 3.4.2 withappropriate mix conditions of large and small particles.
Table 3.4.2

Standard grading of fine aggregate

Nominalopenings ofsieve (mm)Percentage of masspassing throughsieve

Nominalopenings ofsieve (mm)Percentage of masspassing through sieve

10.0

100

0.6

20 – 65

5.0

90 – 100

0.3

10 – 35

2.5

80 – 100

0.15

2 –10 1)

1.2

50 - 901) When only crushed sand or slag fine aggregate is used as fine aggregate, this range may be 2-15%. When mixed
fine aggregate is used and most of passing through 0.15 mm sieve are crushed sand or slag fine aggregate, 15%
may be accepted.
2) It is desirable that the percentage of aggregate remained between two successive sieves may not be larger than
45%.

(7) When using mixtures of different types of aggregate, the quality of each type of
aggregate before mixture should comply with (2), (3), (4) and (5). As for the content ofchlorides and grading, mixed fine aggregate should comply with the provisions in Table
3.4.1 and Table 3.4.2.

[Commentary] (1) As a standard requirement, this item stipulates that fine aggregates that meetthe requirements related to the grading of fine aggregate stipulated in Item (6) and the requirements
related to the limits of the contents of harmful substances such as organic impurities and chlorides
and the durability of fine aggregates stipulated in Item (2) should be used. The degree of hardnessof fine aggregates should be judged from the results of strength and other tests for mortar or
concrete produced by using those fine aggregates because there is as yet no standard for appropriate
testing methods. It has been reported that even in the case of aggregate conforming to the quality
standard of JIS, the shrinkage of concrete increases as the aggregate shrinks if the aggregate isporous and the specific surface area of interval voids is large. Although there is still room forargument, when selecting aggregate, it is important to ascertain, on the basis of past construction
records or reliable literature, that the aggregate under consideration is a material that does not pose
any shrinkage-related problem in a actual structure.
One item related to the chemical stability of aggregate is alkali–aggregate reaction. Concrete has
undergone alkali–aggregate reaction expands considerably and cracks in a characteristic way.
Alkali–aggregate reaction, therefore, can greatly reduce the durability of a structure. The types ofaggregate that are subject to alkali–aggregate reaction include those described below. In most cases,
concrete with typical mix proportions can be used by taking the control measures described in
Section 4.3.4.
Alkali–aggregate reaction used to be classified largely into alkali–silica reaction andalkali–carbonate reaction according to the type of minerals that react with alkalis. Recent research,however, has made widely accepted the hypothesis that the phenomenon that was once believed to
be alkali–carbonate reaction is actually alkali–silica reaction by microcrystalline silica in limestone.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Minerals which may cause alkali-silica reaction are opal, chalcedony, cristobalite, tridimite,
volcanic glass, quartz with deformed crystal lattice, cryto-crystalline quartz and so on. There aremany types of rocks which contain these minerals, such as andesite, ducite, rhyolite and their tuff,
basalt, slate, sandstone, chert, muddy slate and so on. It is impossible to judge the reactivity by only
the type of rock.
Usually, soundness for the alkali-silica reaction is tested by the method specified in Appendix 7
of JIS A 5308 “Method of Test for Reactivity of Aggregate for Alkali-Silica Reaction (Chemical
Method)” or Appendix 8 of JIS A 5308 “Method of Test for Reactivity of Aggregate for
Alkali-Silica Reaction (Mortar Bar Method)”. The petrological tests as polarization microscopy andpowder X-ray diffraction method can be used for detection of the reactive minerals.
In case of the alkali silica reaction, when non-reactive aggregate was mixed with reactive
aggregate, the expansion of mortar or concrete may become a maximum. This is called pessimum
phenomenon. The region of “Potentially Reactive” (region where Sc and Rc are high together) in
the chart of ASTM C 289 (Chemical Method) shows the region confirmed by the mortar bar method
where the most of aggregates have high reactivity and cause the pessimum phenomenon. When theaggregate in this region was used with non-reactive aggregate, harmful expansion may take place ata mix ratio (below 50%). In Japan, the aggregate in the region of “Potentially Reactive” areconsidered as “Low-reactive aggregate”. But, it is “essentially harmful aggregate” which causes thepessimum phenomenon, since the reactivity is very high. Therefore, it is necessary to test thealkali-aggregate reaction of each aggregate by chemical method for the case in which aggregates are
mixed. The mortar bar method on the aggregate, which is mixed at the ratio used, actually isnecessary in order to examine the reactivity, when even one result with “Not harmless” is obtainedby the chemical method. Aggregates in the “Reactive” area of ASTM C 289 do not show thepessimum phenomenon in the mortar bar test, and it causes the harmful expansion. Unsoundness
minerals except for the alkali-aggregate reactivity are smectites, laumontite, ferruginous brucite,
pyrite, etc.
Various chemically and physically unsound minerals mentioned above may be included inaggregate. It is important therefore to examine various points mentioned above in order not to lower,
the quality of the concrete when the aggregate without practical application is used.
(2) The low density and high water absorption means that a fine aggregate particle generally isporous and the strength is low. The low strength of the aggregate particle results in increased unit
cement content for making the concrete with the required strength in addition to the decreased crack
resistance against drying shrinkage and less predicted value of Young’s modulus of elasticity fromthe compressive strength of concrete. And, the porous particle of fine aggregate may cause
deterioration of concrete due to freezing and thawing action, even if the recommended amount ofentrained air is incorporated. Therefore, a natural fine aggregate should conform to JIS A 5308
Appendix 1 “Aggregate for Ready Mixed Concrete”. However, the sand may be used, when it has
been confirmed that the concrete made from it conform to the required performance throughpractical applications in the past or appropriate performance verification, even if it is the sand which
does not conform to these regulations.
Clay is not always harmful to concrete of low cement content, if that clay in fine aggregate is
distributed evenly without adhering firmly to particle surface. But if clay adheres firmly to particle
surfaces, it prevents bonding between cement paste and sand. When clay remains in concrete as
lumps, their destruction by wetting and drying or freezing and thawing may leave cavities in
concrete, or concrete surface may be stained. In the test for the content of clay lumps, the residualmaterials retained on the sieve for amount of materials passing standard sieve 75μ test are used as
52

Chapter 3

Constituent Materials

its sample in order to clarify the harmful clay lumps. The amount of clay or other fine materials
which are not in lump form and do not adhere firmly to particle surfaces of fine aggregate can be
determined by the amount of materials passing standard sieve 75μ test. In the case of natural fineaggregates, however, fine grains and clay in many cases have similar influence on concrete.
In the Standard Specification: Materials and Construction in 2002 the item on the substances,like coal and lignite, lighter than liquid having a specific gravity of 1.95 was specified. However thecase where river sand and other aggregates that are delivered by a train used to transport coalcontain coal and lignite becomes less and less. This is why this item is removed in this specification.
In case where JIS A 1141 Test Method for Substances Lighter than Liquid Having a Specific
Gravity of 1.95 is conducted, chemical agents specified in this JIS A 1141 are harmful to theenvironment and human body precautions must be taken in their handling.
Organic impurities contained in fine aggregates are tested in accordance with JIS A 1105,
Method of Test for Organic Impurities in Fine Aggregate. In this case, the standard method is to use
fine aggregate that produces a supernatant color lighter than the standard color. In cases where thecolor of the supernatant over the sand is darker than the standard color, if the compressive strengthof mortar specimens made by using the sand is equal to or higher than 90% of the compressive
strength of mortar specimens made by washing the sand in a 3% sodium hydroxide solution andthen washing the sand thoroughly with water, the sand may be used. The test for sand by thecompressive strength of mortar must be conducted in accordance with JIS A 1142, Method of Test
for Fine Aggregate Containing Organic Impurities by Compressive Strength of Mortar.
As a fine aggregate including the chloride, there are sea sand and mixed sand including sea sandcollected from seabed, beach, river mouth, etc. Sea sand has been used in the west part of Japanaround the Setouchi-Sea area but the using of sea sand is tend to be prohibited from theenvironmental view point. In case of the concrete using a fine aggregate including the chloride,the most part of the chloride content in the concrete is supplied from a fine aggregate. And generally,
the chloride content in the concrete may exceed allowable limit 0.30kg/m3, which is decided for the
steel product protection, when a fine aggregate including the chloride was used. Therefore, it isnecessary to establish some restrictions for chloride content in fine aggregate in order to keep thechloride content in the concrete under the allowed value. In Table 3.4.1, the upper limit of chloride
content for fine aggregate is a value determined which the regulation for the chloride content in theconcrete was almost satisfied in synthetic consideration with actual condition of salt removal
processing of sea sand and reliability of test for quality control.
It is necessary to consider not only the water to cement ratios and air content but also quality offine aggregate for acquiring a durable concrete against freezing and thawing. The durability of thefine aggregate may be judged by the results of test such as JIS A 1122 “Soundness Test ofAggregate Using Sodium Sulfate”. The fine aggregate to be used for concrete requiring theresistance freezing and thawing action should have a weight loss of not larger than 10% after being
subjected to 5 repetitions of the test procedure prescribed in the test for soundness using sodium
sulfate. However, fine aggregate may be accepted, provided it is proved that concrete made up of asimilar aggregate obtained from the same source has satisfactory freeze-thaw resistance when
exposed to weather conditions similar to those to be encountered, or provided that the concrete
composed of the fine aggregate shows satisfactory results in the freezing and thawing tests, even if
the weight loss of fine aggregate is larger than 10%.
There are lime, Pelli cress, hauyne, anhydrite (calcium sulfate anhydrite) as the result, whichbrings about the harmful effect for the concrete, when it is entrapped in a fine aggregate. Lime andPelli cress may be included for materials such as calcined lime, plaster, lime system expanding
material, baking fertilizer, dolomite clinker, fire brick, converter slag, artificial light-weight53

Standard Specifications for Concrete Structures-2007, Materials and Construction

aggregate. If these lumps exist in the concrete, pop-out at the concrete surface is caused byhydration reaction. Therefore, the attention is needed so that it may not entrap these in a fineaggregate. The damage may be received after several years, when the Pelli cress is included for afine aggregate since the hydration of Pelli cress is slower than that of lime.
(3) Crushed sand has angular particle shape and often contains a large amount of rock powder.
For these reasons, when crushed sand is used, the unit water content shall be increased
appropriately to acquire the required workability. The shape of the particles of crushed sand varies
according to the types of the original rocks or crushing processes in production. The shapes of sandparticles have a strong influence on the required unit water content or the workability of concrete.
When crushed sand is used, it is better not only to confirm the quality of the original rocks but also
to select sand, which is of particles of low angularity and contains little amount of slender or flat
particles. JIS A 5005 “Crushed Stone and Manufactured Sand for Concrete” specifies the method oftest for measuring the solid volume percentage of bulk aggregate in order to judge the adaptabilityof sand by particle shapes, specifying that the value shall not be less than 53%.
The Blaine specific surface area of rock powder in crushed sand is generally in the range of
1500-8000cm2/g. Although the powder increases the unit water content, it also prevents thesegregation of concrete materials. For this reason, when crushed sand is used, it is rather desirable
to use crushed sand, which contains 3-5% of rock powder. However, it shall be also noted that
excessive amount of rock powder in crushed sand will greatly increase unit water content for a same
slump value, decrease concrete strength and increase the rate of drying shrinkage. The weight lossof crushed sand in test of fine particle amount, which results from the washing out of rock powder,etc., is also specified to be not larger than 7%. If crushed sand conforms to these specifications,particle shape and rock powder content pose no significant problem as far as the quality of concrete
is concerned.
(4) Blast-furnace slag fine aggregate may be used alone as fine aggregate. However, in generaluse, it is frequently blended with other fine aggregates such as mountain sand to a percentage by
weight of 20-60% for the purpose of adjusting grading, decreasing the chloride content, etc.
Considering such blended use, JIS A 5011-1 “Granulated Blast-Furnace-Slag Fine Aggregate forConcrete” classifies blast-furnace slag fine aggregate into 4 types according to grading. When any
specific type of blast-furnace slag fine aggregate is used for concrete, the final grading of fineaggregate shall conform to the requirements in Table 3.4.2.
As blast-furnace slag fine aggregate has latent hydraulicity, when the daily mean temperature isover 20˚C, it may be adhered in stock bins, causing a difficulty in its drawing. Therefore, underthese conditions, it is advised to select blast-furnace slag fine aggregates rated as grade A by “The
Test for Soundness in Storing Blast-Furnace Slag” in Appendix 2 of JIS A 5011-1 which rarely form
lumps. It is necessary to avoid storing them for a long period. It is necessary to care the case of the
combination of alumina cement and blast-furnace slag fine aggregate, as it may occur the rapid
hardening. When blast-furnace slag is used, “Recommendation for Blast-Furnace Slag Aggregate
Concrete” should be referred to.
Ferro-nickel slag fine aggregate, copper slag fine aggregate and electric arc furnace reducing
slag fine aggregate are frequently blended with mountain sand as same as blast-furnace slag fineaggregate. JIS A 5011-2, JIS A 5011-3 and JIS A 5011-4 classify these fine aggregates into 4 types
according to grading. Ferro-nickel slag fine aggregate and copper slag fine aggregate are anadvantageous materials for precast concrete armor units, concrete blocks for revetment, etc. because
the density is very high. When ferro-nickel slag is used, “Recommendation for Ferro-Nickel Slag
Fine Aggregate Concrete” should be referred to. When copper slag fine aggregate is used,“Recommendation for Copper Slag Fine Aggregate Concrete” should be referred to. In general,54Chapter 3

Constituent Materials

electric arc furnace reducing slag tends to cause expansive reaction because it contains a large
amount of quicklime. Furthermore, because the composition of electric arc furnace reducing slag
varies widely among different types of steel to be refined, it is difficult to achieve consistent quality.
It is therefore necessary to use electric arc furnace oxidizing slag aggregates produced at factories
where measures are taken to keep electric arc furnace reducing slag away. For more information on
considerations in using electric arc furnace reducing slag fine aggregates, refer to
Recommendations for Design and Construction of Concrete Structures Using Electric Arc Furnace
Oxidizing Slag Aggregate.
(5) JIS classifies recycled aggregate, according to processing methods and the quality ofaggregate, into four classes, namely, H, M and L. JIS A 5021, Recycled Aggregate forConcrete—Class H, specifies the quality of Class H recycled aggregate, and JIS A 5022, Recycled
Concrete Using Recycled Aggregate Class M, and JIS A 5023, Recycled Concrete Using Recycled
Aggregate Class L, specify the quality of Class M aggregate and Class L aggregate and the qualityof concrete made with aggregate in those classes.
Class H recycled aggregate is aggregate for concrete applications produced throughsophisticated processing such as crushing, milling and grading of concrete fragments. Class H
recycled aggregate is nearly comparable in quality to ordinary aggregate and can be used inready-mixed concrete. Test methods for the alkali–silica reactivity of Class H recycled aggregate
include JIS A 1145, Method of Test for Alkali–Silica Reactivity of Aggregates by Chemical Method,
JIS A 1146, Method of Test for Alkali–Silica Reactivity of Aggregates by Mortar-Bar Method, and
JIS A 1804, Methods of Test for Production Control of Concrete—Method of Rapid Test for
Identification of Alkali–Silica Reactivity of Aggregate. If Class H recycled aggregate that has notbeen preprocessed is subjected to a test conducted in accordance with JIS A 1145 (chemical
method), even a very small amount of cement paste sticking to aggregate surfaces causes alkali
consumption and silica dissolution to increase so that the evaluation of test results is affected. It istherefore necessary to take measures in advance such as removing cement paste sticking toaggregate surfaces by use of hydrochloric acid. It is also necessary to ascertain by use of go/no-go
samples that the total quantity of impurities does not exceed 3% of the total mass of aggregate
because debris of demolished structures may contain impurities such as tiles, brick, ceramic ware
fragments, asphalt concrete fragments, glass fragments, gypsum board fragments, plastic fragments,
wood fragments and waste paper.
Class M and Class L recycled aggregate is produced by methods different from the method used
to produce Class H recycled aggregate from the economic point of view. The quality of Class M andClass L recycled aggregate, therefore, differs from that of Class H recycled aggregate in thatconsiderable amounts of cement paste and mortar are sticking to the surfaces of aggregate particles.
For this reason, Class M and Class L recycled aggregate and Class H recycle aggregate are coveredby different JIS specifications, and the former is specified not as aggregate but as concrete (JIS A
5022, JIS A 5023). The upper limits of nominal strength and slump of concrete made with Class M
recycled aggregate are 36 and 18 cm, respectively. The upper limits of nominal strength and slumpof concrete made with Class L recycled aggregate for civil engineering construction and building
construction are 24 and 10 cm and 18 cm, respectively. The use of concrete made with Class L
recycled aggregate is limited to plain concrete structures that do not need to be highly durable,
easily replaceable members, small reinforced concrete structures, concrete blocks reinforced withsteel bars, etc. The use of concrete made with Class M recycled aggregate is limited to membersthat are relatively free from drying shrinkage and freeze–thaw cycles because concrete of this typemay not be durable enough although the quality of concrete is higher than that of concrete madewith Class L recycled aggregate.
It is for these reasons that Class H recycled fine aggregate conforming to JIS A 5021 must be
55

Standard Specifications for Concrete Structures-2007, Materials and Constructionused if recycled fine aggregate is to be used.
(6) When properly graded fine aggregate with large and small particles is used, it is rather easy
to make concrete of the required quality economically and with relatively low unit cement content,
as opposed to using aggregate with single-size sand particles or sand having an excessive amount offine particles. As far as fine aggregate conforming to the specified grading range in Table 3.4.2 isused, concrete of required qualities can be made economically.
Since slag fine aggregate conforming to JIS A 5011 “Slag Aggregate for Concrete” is glassy andhas a smooth particle surface, its water retaining capacity is smaller than that of natural sand.
Crushed sand or crushed slag fine aggregate conforming to JIS A 5005 “Crashed Sand and Crashed
Stone for Concrete” contain more angular particles. In cases when such aggregates are used as fineaggregates, there is an improvement in the workability and bleeding characteristics of concrete
provided the mineral fines content is slightly higher. In the case of slag fine aggregate, the finer theparticles, the greater the density. Thus, when the particle size distribution of the aggregate byvolume is kept equal to that of other types of fine aggregates, the numerical value of the weightpercentage of the finer part becomes greater. Considering the above characteristics, in cases where
only crushed sand or slag fine aggregate is used, the upper limit of percentage by weight of fineparticles passing a 0.15 mm sieve has been set at a value higher than that for other types of fineaggregates.
According to the definition of the terminology, grading means “the degree of the distribution ofparticle size”. Therefore, it should be shown as the volume fraction of the particles. However, in
real practices or JIS, the grading in mass percentage has been adopted, because the maximum
difference between volume percentage and mass percentage is about 1%, when the difference ofdensity of used fine aggregates is under 0.2g/cm3. However, it is desirable that mass percentage ofTable 3.4.2 is replaced in the volume percentage, when used fine aggregates in which the density
differs over 0.2g/cm3.
(7) With the declining availability of high-quality aggregate for concrete, a growing number of
construction projects are using mixtures of two or more types of aggregate in order to achieve therequired quality and secure the required quantity of aggregate. In cases where mixtures of different
types of aggregate are used, the quality of mixtures is greatly affected by the quality of the different
types of aggregate used. When using mixtures of different types of aggregate, therefore, it isnecessary to ascertain the quality of each type of aggregate as described in Appendix 1 of JIS A
5308.
3.4.2

Coarse aggregate(1) Coarse aggregates shall be clean, hard, firm, durable, chemically or physicallysound and not contain a harmful amount of dust, mud, organic impurities, chlorides, etc.
When fire resistance is specially required, fire resistant coarse aggregates should be
used.
(2) Coarse aggregates should comply with Table 3.4.3.
Table 3.4.3

Properties of coarse aggregate

Item

Quality

Test method▪ Oven-dry particle density g/cm3≥2.5

JIS A 1109

▪ Water absorption %≤3.0

JIS A 1109

56

Chapter 3

Constituent Materials▪ Clay lumps %≤0.25 1)JIS A 1137

▪ Particles passing standard sieve size of 75μ %≤1.0 2)JIS A 1103

▪ Soundness %≤12

JIS A 1122

▪ Weight loss by abrasion %≤35

JIS A 1121

1) Test samples shall be drawn from the residue retained on the sieve after the test for determining the amount ofmaterials passing standard sieve 75μ test of coarse aggregate has been carried out in accordance with JIS A
1103.
2) In the case of crushed stone, the limit may be increased to 1.5%, provided the washed-out material consists ofdust from fracturing.
3) In the case of blast-furnace slag coarse aggregate, it may be increased to 5.0%.

(3) Crushed stone should comply with the provisions specified in JIS A 5005.
(4) Blast-furnace slag coarse aggregate and electric arc furnace reducing slag fineaggregate should comply with the provisions specified in JIS A 5011-1 and JIS A 5011-4
respectively.
(5) Recycled coarse aggregate should comply with the provisions specified in JIS A
5021.
(6) Grading of coarse aggregate should lie in the range specified in Table 3.4.4 withappropriate mix conditions of large and small particles.
Table 3.4.4

Nominalopeningsof sieve(mm)Max. sizeof coarse
aggregates(mm)Standard grading of coarse aggregate

Percentage of mass passing through sieve
50

40

30

25

20

15

10

5

2.5

40

100

95-100

・

・

35-70

・

10-30

0-5

・

25

・

・

100

95-100

・

30-70

・

0-10

0-5

20

・

・

・

100

90-100

・

20-55

0-10

0-5

10

・

・

・

・

・

100

90-1000-40

0-10(7) When using mixtures of different types of aggregate, the quality of each type of
aggregate before mixture should comply with (2), (3), (4) and (5). As for the grading, mixed
coarse aggregate should comply with the provisions in Table 3.4.4.

[Commentary] (1) The hardness and firmness may be judged from the results of adequate
tests such as JIS A 1121 “Method of Test for the Abrasion of Coarse Aggregate by Use of Los
Angeles Machine”, JIS A 1126 “The Method of Test for Soft Particles in Coarse Aggregate”, JIS A
57

Standard Specifications for Concrete Structures-2007, Materials and Construction

1110 “Method of Test for Specific Gravity and absorption of Coarse Aggregate” or a strength test of
concrete made with that coarse aggregate. As for chemical soundness, comment of Section 3.4.1 forfine aggregate should be referred to.
The fire resistance of concrete is largely affected by the properties of aggregates used. Graniteand quartziferous sandstone are inferior in durability. For concrete requiring not only fire resistancebut also strength and durability, it is advisable to use blast-furnace slag coarse aggregate, durable
andesite, basalt, hard tuff, etc.
(2) The reasons for prescribing these limits are similar to those given in the comments for
Section 3.4.1 in the case of fine aggregate. It has been reported in previous experiments that eventhough the weight loss in the soundness test (Appendix 2 of JIS A 6204 “Chemical Admixtures forConcrete”) is as higher as 12-40%, but the water absorption is less than 3%, or when the weight loss
less than 12%, but water absorption rate is around 5%, the durability factor (300 cycles) of concrete
can be higher than 60. In cases when concrete is required to have freezing-thawing resistance, thecoarse aggregate used should have a weight loss not larger than 12%, when subjected to 5 cycles ofsoundness test in accordance with JIS A 1122.
(3) As far as crushed stone is produced from durable basalt, andesite, hard and stone, hard tuff
or rocks similar to these, there is no intrinsic difference between crushed stone and river gravel as
concrete aggregate. Crushed stone aggregate is rather superior to river gravel as far as theuniformity of particles and its effect on the strength of concrete are concerned. However, because of
the angular shape and rough surface texture of its particles, it is necessary to increase the unit watercontent and sand-aggregate ratio of concrete in order to acquire a concrete of the same workability
as that of concrete with river gravel. Since these effects become quite significant especially when
the particles are flat and/or slender, it is necessary to examine the suitability of particle shapes
whenever the use of crushed stone is considered.
JIS A 5005 “Crushed Stone and Manufactured Sand for Concrete” prescribes a method of test
for solid volume percentage of bulk aggregate in order to judge the suitability of the aggregate byparticle shape, and specifies that the value shall be not less than 55% for crushed stone aggregate
whose maximum size is 20 mm. When the maximum size is around 40 mm, the value is equivalent
to 58%.
(4) Blast-furnace slag coarse aggregate is produced by crushing air-cooled blast-furnace slag.
Some blast-furnace slag coarse aggregates may not possess adequate quality as concrete aggregate
depending on the processes such as cooling and crushing during their production. Even when theblast-furnace slag coarse aggregate is produced in the same steel plant, the quality may be different
according to the time of production. In JIS A 5011-1 “Air-Cooled Iron- Blast-Furnace Slag
Aggregate for Concrete”, blast-furnace slag coarse aggregate is classified into the classes L and N.
Generally, blast-furnace slag coarse aggregate of Class N is used. Class L aggregate is used only inconcrete whose freeze-thaw resistance needs not be so high and characteristics compressive strengthis less than 21 N/mm2.
It shall be noted that flash setting may be caused when high alumina cement is used together
with blast-furnace slag aggregate. When using blast-furnace slag coarse aggregate, the“Recommendation for Blast-furnace Slag Aggregate Concrete” should be referred.
(5) It is a standard requirement that Class H recycled coarse aggregate conforming to JIS A
5021 be used if recycled coarse aggregate is to be used. In order to produce Class H recycled coarse
aggregate with stable quality, it is important to check on the quality of at least the original concreteand the original aggregate contained in the concrete by referring to past records, literature, etc. If

58

Chapter 3

Constituent Materials

such information is not available, it is necessary to take concrete samples from the structure at
appropriate frequencies and observe the color, shape, size, etc., of the samples.
If the particle size range of Class H recycled coarse aggregate is too wide, the aggregate
becomes prone to segregation between coarse particles and fine particles at the production andstorage stages so as to greatly affect the water content of concrete. JIS A 5021 defines six particle
size classes of recycle coarse aggregate, namely, H2505, H2005, H1505, H4020, H2515 and H2015.
Care needs to be taken here because there is no wide particle size category such as 4005. In the caseof Class H recycled coarse aggregate, the abrasion loss is affected by the amount of mortar sticking
to the aggregate surface. The abrasion loss, therefore, is not suitable for use as an indicator ofphysical properties. It may be thought that because of actions similar to abrasion tests such as
crushing and milling, Class H recycled coarse aggregate is free from weak regions. This is why
abrasion loss requirements are not specified except in cases where recycled coarse aggregate in thisclass is used in pavement slabs.
(6) The effects of grading of coarse aggregate on the workability of concrete are not sosignificant when compared with those of fine aggregate. But it is advisable to use coarse aggregatewith properly mixed large and small particles to make concrete of the required properties
economically. When coarse aggregates conforming to the grading in Table 3.4.4 are used, concretewith the required qualities can generally be made economically. For some precast concrete products,
it is better to use coarse aggregate whose maximum size is 10 mm. Therefore, the standard gradingof coarse aggregate whose size is 10-5 mm is also specified.
(7) This clause is provided due to the same reason as that shown in the comment for fineaggregate.
3.5

Admixtures

3.5.1

GeneralChemical admixtures and mineral admixtures used for concrete shall be of confirmed
quality.

[Commentary] The advantage of properly using quality mineral admixtures and chemical
admixtures has been confirmed by their application records. It is recommended to improve concrete
quality by the positive use of admixtures of confirmed quality and effect. However, there are also
many admixtures which only have insufficient application records and are not specified in JIS or
JSCE Standards. Such admixture shall be used after thoroughly confirming their quality byexamining their performance records or by testing.
In addition those admixtures are classified depending on their dosages, they may be further
sub-classified as follows according to their usage.
▪ Mineral admixtures(a) Those to which pozzolanic activity can be expected: Fly ash, Silica fume, Volcanic ash,
Siliceous white clay, Diatomite(b) Those which latent hydraulicity can be expected: Ground granulated blast-furnace slag.
(c) Those which cause expansion in hardening process: Expansive admixtures(d) Those which contribute in gaining high strength during autoclave curing: Siliceous fine
powder59

Standard Specifications for Concrete Structures-2007, Materials and Construction(e) Those for coloring: Pigments(f) Those which decrease material segregation and/or bleeding of concrete with high flowability:
Lime stone powder(g) Miscellaneous: Admixtures for high strength, polymers, fillers, etc.
▪ Chemical admixtures(a) Those for improving workability and freeze-thaw resistance: Air-entraining agent,
air-entraining and water-reducing agents(b) Those for improving workability, reducing unit water content and unit cement content:
Water-reducing agents, air-entraining and water-reducing agents(c) Those for increasing strength greatly by reducing water: High-range water reducing agent,
air-entraining and high-range water reducing agent(d) Those for considerably reducing unit water content and improving freeze-thaw resistance:
High-range water reducing and air-entraining agent(e) Those for considerably improving flowability without changing mix proportions or qualityof hardened concrete: Superplasticizers(f) Those for controlling material segregation in underwater concreting by increasing viscosity:
Antiwashout agents for underwater concrete(g) Those for controlling setting and hardening time: Accelerators, fast-set agents, retarders,retarders for construction joint(h) Those for improving the filling-up ability or controlling density by introducing foam:
Foaming agents and gas generating agents(i) Those for controlling material segregation by increasing viscosity or by controlling cohesion:
Agents for improving pumpability, segregation-reduction agents, and viscosity-modifying
admixture(j) Those for increasing filling-up ability and the strength development of concrete by providing
proper expansion and improving flowability: Agents for preplaced concrete aggregate
concrete, Agents for high-strength preplaced aggregate concrete, Agents for grouting mortar(k) Those for preventing corrosion of reinforcing bars by chloride: Corrosion inhibitors forreinforcing bars in concrete(l) Miscellaneous: Water-proofing agents, Nonfreezing agents, Drying shrinkage reducing
agents, Agents for controlling heat of hydration, Dust-reducing agents, etc.
Chemical admixtures generally used for hot weather concreting are air-entraining agents,
water-reducing agents, air-entraining and water-reducing agents and air-entraining and high-range
water reducing agents. When using water-reducing agent, air-entraining and water-reducing agent
or air-entraining-high-range water reducing agent, a retarding type rather than a ordinary type iseffective and practical. When a retarding agent is applied with the purpose of preventing cold joints,
the method shall be fully considered and especially, its dosage shall be determined properly. When
air-entraining and high-range water reducing agent is used for hot weather concreting, it is also
possible to considerably reduce unit water content and unit cement content. However, it is necessary
60Chapter 3

Constituent Materials

to pay the attention to the possible loss in slump value with time for some type of high-range water
reducing agent.
For mass concrete, there are fly ash and blast-furnace slag as mineral admixtures, andair-entraining agents, water-reducing agents, air-entraining and water-reducing agents andair-entraining and high-range water reducing agents as chemical admixtures. Using of fly ash with
sufficient quality has many advantageous effects on the properties of concrete such as improvement
in workability, reduction of unit water content, increase in long-term strength. Besides, fly ash is anadvantageous material in order to control cracking due to thermal stresses, because the temperaturerise resulting from hydration heat of concrete becomes lower. When blast-furnace slag with quality
is properly used, it becomes possible not only to increase long-term strength but also slow thegeneration rate of heat of hydration. (see “Recommendation for Blast-furnace Slag Concrete”)
On the other hand, when a air-entraining agent, water-reducing agent, air-entraining andwater-reducing agent or air-entraining high-range water reducing agent is properly used, it ispossible to reduce unit water content and unit cement content, since the workability of the concrete
is improved. And this results in lower temperature rise of the concrete. When a large quantity ofconcrete is placed, a retarding type of a water-reducing agent or air-entraining and water-reducing
agent may be used in order to slow the generation rate of heat of hydration and prevent cold joints.
However, in this case, it is important to confirm the effect on the degree of set-retarding andstrength development of concrete by testing and so on prior to the application, because the setting
time may be considerably retarded according to combined effect of using admixtures andtemperature condition at the application.

3.5.2

Mineral admixtures(1) Fly ash used as mineral admixture should comply with the provisions specified in
JIS A 6201.
(2) Expansive admixtures used as mineral admixtures should comply with theprovisions specified in JIS A 6202.
(3) Ground granulated blast-furnace slag used as mineral admixture should comply
with the provisions specified in JIS A 6206.
(4) Silica fume used as mineral admixture should comply with the provisions specified
in JIS A 6207.
(5) The quality and utilization method of mineral admixtures other than Clauses (1), (2),(3) and (4) shall be investigated thoroughly.

[Commentary] (1) When properly used, high quality fly ash has many excellent effects on theproperties of concrete such as improving workability, reducing unit water content, controlling heatof hydration, increasing long-term strength, reducing drying shrinkage, improving water tightness
and improving resistance to chemical attack, etc. However, the quality of fly ash widely varies
according to the quality of coal, combustion mechanism and processes of collection. Therefore, thefly ash used should comply with the provisions specified in JIS A 6201 “Fly Ash.” Recently,
production of fly ash has been increasing, but except for some regions, it is difficult to obtain alarge amount of fly ash with quality continuously. Therefore, it is advised to confirm whether or not
61

Standard Specifications for Concrete Structures-2007, Materials and Construction

a required amount of fly ash can be supplied. When fly ash is used, “Recommendation for Fly Ash
Concrete” should be referred to.
(2) By properly using expansive admixtures, it is possible to reduce cracking of concrete causedby hardening shrinkage or to increase cracking strength of concrete by introducing chemicalprestress. As these effects vary according to chemical composition, fineness, etc. of expansive
admixtures, expansive admixtures to be used should comply with the provisions specified in JIS A
6202 “Expansive Admixtures for Concrete“ (see Chapter 4 in the part of special concrete and the“Recommendation for Expansive Cement Concrete”) as standard.
(3) By using properly ground powder of granulated blast-furnace slag, which has been cooled
rapidly and has a glassy quality, it is possible to produce concrete having higher long-term strength,
lower heat of hydration, better water-tightness and permeation of chloride ion into concrete, higher
chemical resistance to sulfates or sea water, and also possible to suppress alkali-aggregate reaction
and obtain higher strength. Moreover, the workability of concrete is not adversely affected by its
use, and unit water content needs no to be increased even when very finely ground slag is used. But
these effects vary according to the chemical compositions of slag, cooling rate, fineness anddosages of ground slag, the addition or non-addition of gypsum, the quality of cement to be mixed
with, unit cementitious material contents, etc., so that this material should comply with theprovisions specified in JIS A 6206 “Blast-furnace Slag“. As the quality of concrete containing
ground slag is easily affected by the curing temperature and the term of wet curing, if construction
methods are not suitable for the concrete, insufficient development of the required strength or the
rapid carbonation of concrete may be induced. In addition, since the unit dosage of ground slag isquite large in comparison to that of other admixtures and ground slag is expected to play aimportant role as a cementitious material, if batching and mixing machines are unsuitable or controlof the work-process is not adequate, concretes of the required qualities can not be acquired. This
point shall be sufficiently taken into account during the planning and execution of construction. (seethe “Recommendation for Blast-furnace Slag Concrete”)
At present, 3 types of ground granulated blast-furnace slag are specified in JIS. They areblast-furnace slag 4000, 6000 and 8000. Therefore, it is necessary to determine the type of
blast-furnace slag and its replacing ratio in consideration with the purpose of use. Generally,
blast-furnace slag 4000 is used in many cases. For the special applications, i.e. strength
improvement in early ages, blast-furnace slag 6000 or 8000 may be used.
(4) Silica fume is a by-product of silicone or ferro-silicone production and consists of super-finespherical particles. The average particle size is about 0.1μm, specific surface area (by gas
absorption method) is about 20 m2/g and density is about 2.2 g/cm3. The main component of silica
fume is amorphous SiO2. Mixing silica fume in concrete has some advantages such as theprevention of material segregation, the reduction of bleeding, a remarkable increase of strength, andthe improvement of water-tightness and chemical durability in comparison to ordinary concrete. On
the other hand, it has disadvantages such as increasing the unit water content and increasing drying
shrinkage. Therefore, in application, it is necessary to take some counter-measures such as using
high-range water-reducing admixtures. The quality of silica fume is considerably different bylocalities, stock periods and form of the product, - powder or grain-, etc. because most part of the
supply depends on the import. It is important to confirm that the silica fume used should comply
with the provisions specified in JIS A 6207 “Silica Fume for Concrete”. When silica fume is used,
the “Recommendation for Silica-Fume Concrete” should be referred to.
(5) As mineral admixtures other than Clauses (1), (2), (3) and (4), there are siliceous fine
powder, pozzolans, limestone fine powder admixtures for high strength and so on. There is atpresent, no specification of quality for these mineral admixtures, and methods of their use are62

Chapter 3

Constituent Materials

different. When using these materials, therefore, it is necessary to confirm their quality andinvestigate the methods of use by referring to information and by testing. In other words, it isnecessary to investigate not only their quality, performance, service records, uniformity, prices andother items, but also the effects of their use on the workability, strength, durability, water-tightness,volume change, capability of protecting steel and prices of concrete.
Siliceous fines, which are composed mainly of quartz, are often used to provide concrete to be
cure in an autoclave with extra strength. Other pozzolans that generate calcium silicate hydrates byreacting with calcium hydrate at room temperature include the fly ash and silica fume mentioned
above and natural materials such as siliceous white clay, volcanic ash and diatomite, and artificial
materials such as burnt clay.
Limestone powder is a powdery material produced by grinding limestone so that the Blaine
specific surface area becomes 3000 to 7000 cm2/g. Limestone powder is used to prevent
segregation and bleeding of concrete. It has been reported that limestone powder reacts with C3A,
etc., to generate hydrates such as monocarbonates (C3A, CaCO3, 11H2O). This Specification,
however, does not regard limestone powder as a binder because the reaction with C3A in cement
and the relationship between the generation of C3A and strength are as yet not clarified. Standards
for limestone powder that can be used as guides include JCI-SLP, Standard for Quality ofLimestone Powder for Concrete, JIS A 5008, Limestone Filler for Bituminous Paving Mixtures, andstandards proposed by other organizations such as the former Honshu–Shikoku Bridge Authority
and the former Japan Railway Construction Public Corporation.

3.5.3

Chemical admixtures(1) Air-entraining agents, water-reducing agents, air-entraining and water-reducing
agents and air-entraining, high-range water reducing agents and superplasticizers used as
chemical admixtures should comply with the provisions specified in JIS A 6204.
(2) Corrosion inhibitors for reinforcing steel used as chemical admixtures should
comply with the provisions specified in JIS A 6205.
(3) The quality and utilization method of chemical admixtures other than Clause (1) and(2), shall be investigated thoroughly.

[Commentary] (1) Though several types of air-entraining agents, water-reducing agents,
air-entraining and water-reducing agents or air-entraining and high-range water reducing agents areavailable, their quality and performance are quite different. Therefore, only good quality chemical
admixtures conforming to the requirements of JIS A 6204 “Chemical Admixtures for Concrete”
should be used. In JIS A 6204, chemical admixtures for concrete are classified into air-entraining
agents, water-reducing agents (standard, retarding and accelerating types), air-entraining andwater-reducing agents (standard, retarding and accelerating types) and air-entraining and high-range
water reducing agents (standard and retarding types). And, chemical admixtures are also classified
into the types 1, 2, and 3 by the amount of chloride ions supplied from admixtures to concrete.
Therefore, when chemical admixtures are used, the adequate type of chemical admixture shall beselected in consideration with purpose of its use, setting time, hardening rate or limit of chloride
content in concrete, etc. Proper use of air-entraining agents, water-reducing agents, air-entraining
and water-reducing agents and air-entraining and high-range water reducing agents in concrete may
results is many desirable effects such as reduction of unit water content, improvement of
workability, increase in resistance to freezing and thawing, improvement in water-tightness, etc.
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The effect of these agents may, however, vary depending on the quality of cement, aggregates andthe agents themselves, mix proportions, method of construction, etc. Even in cases when the aircontent is the same, the effect may actually be different depending upon the average size of air
voids or their distribution.
Air-entraining and high-range water reducing agent has an ability of air-entraining itself. It candecrease water content more than ordinary air-entraining and water-reducing agents, and slump loss
becomes small. Therefore, it is possible not only to reduce the unit water content rather than whenusing ordinary air-entraining and water-reducing agents, but also to make the concrete which has
the same flowability as superplasticized concrete in ready-mixed plants. And, it is possible tochoose the dosage for its purpose of use within the wide range. However, when air-entraining andhigh-range water reducing agent is used, performance of concrete such as less change in slump or
workability is easily affected by service conditions like as atmospheric temperature, materials andso on in comparison with ordinary concrete. Therefore, when using air-entraining and high-range
water reducing agent, the characteristics of concrete and the limit of the effect must be sufficiently
understood. And, it must be sufficiently examined that the appropriate usage of air-entraining andhigh-range water reducing agent in order to surely obtain the effect for the purpose prior to the realapplication. And, it is also important to appropriately treat the concrete with air-entraining andhigh-range water reducing agent, because of the different workability from the ordinary using usual
air-entraining and water reducing agent. (see “Recommended Practice for Concrete used
Air-entraining and High-range Water-reducing Agents”)
High-range water-reducers are characterized by high water-reducing, low set-retarding and low
air-entraining effects and can be classified, according to chemical composition into a number ofgroups including polycarboxylic acid, naphthalene, melamine and other types. With their highwater-reducing and low air-entraining effects, high-range water reducers make it possible to easily
obtain high-strength concrete with a compressive strength of about 80 to 100 N/mm2. If, however,naphthalene and melamine type high-range water reducers are used, care needs to be taken becausea large slump loss may occur or freeze–thaw resistance may become low if an air-entraining agent
is not used.
Standard-type superplasticizers are used in ordinary concreting work and have been used inmany projects. Retarder-type superplasticizers have both a superplasticizing effect and a
set-retarding effect and are used to reduce post-superplasticization slump losses when concrete isplace under hot weather or the transportation of concrete takes long time. Since the setting delay
time of a set-retarding type superplasticizer varies with the quantity of the admixture used, it may
not be possible to achieve the required set-retarding effect depending on the service conditions or
mix proportions of concrete. It is good practice to trying to control the set-retarding effect suitable
for the purpose by paying attention to chemical admixtures added to the base concrete. Care needs
to be taken because the setting of concrete containing a retarder-type superplasticizer may be
excessively delayed under the influence of the chemical admixtures added to the base concrete sothat the durability of the concrete decreases (see Recommended Practice for Concrete Containing
Superplasticizers).
(2) Corrosion inhibitors for reinforcing bars in concrete are chemical admixtures to be used forsuppressing the corrosion caused by chloride from the use of sea sand. Corrosion inhibitors may beclassified into the following 3 types : (i) Corrosion inhibitors of passive film-forming type, (ii)Corrosion inhibitors of precipitation film-forming type and (iii) Corrosion inhibitors of adsorption
film-forming type. At present, all of the inhibitors available in the market have a nitrite component
as main constituent and suppress corrosion by oxidizing the metal surface and form the passive film.
All types of inhibitors are required not only to inhibit corrosion sufficiently for a long time, but also64Chapter 3

Constituent Materials

not to disturb the setting, hardening and durability of concrete. Moreover, they are required to beeasy to use and not to contain harmful components to the human body. Some papers report that
local corrosion of steel becomes remarkable under the environment where much chloride ionspermeate from outside of concrete structure because of insufficient effect of inhibitors even if therequired quantity of inhibitors for corrosion protection of steel against chloride in sea sand is added.
Therefore, when a inhibitor is applied for construction of concrete structures under theseenvironmental conditions, the dosage and the effect of inhibitor shall be examined sufficiently.
(3) For chemical admixtures other than Clauses (1) and (2), there are no specifications on their
quality, and the methods of use are different. It is necessary in the employment of them to confirm
their quality and investigate the methods of use by researching the service records and doing
sufficient tests. That is to say, it is necessary to research the quality, performance, service records,
uniformity, price, etc., and to investigate their effects on workability, strength, durability,
water-tightness, volume change, steel-protective quality, and cost of concrete.

3.6

Reinforcing Materials

3.6.1

Reinforcing bars

(1) It is a standard requirement that all reinforcing bars used conform to JIS G 3112, JIS
G 3117 or JSCE-E 121.
(2) If reinforcing bars not conforming to JIS G 23112 or JIS G 3117 are to be used, tests
shall be conducted to verify that the design values are met and determine the method ofusing those reinforcing bars.
(3) It is a standard requirement that all epoxy-coated reinforcing bars used conform to
JSCE-E 102.

[Commentary] (1) It must be ascertained that all reinforcing bars used meet the values
specified in JIS G 3112, Steel Bars for Concrete Reinforcement, JIS G 3117, Rerolled Bars forConcrete Reinforcement, and JSCE-E 121, Standard for Quality of D57and D64 Threaded andRibbed Steel Bars for Concrete Reinforcement. Steel bars used for concrete reinforcement can beclassified into two types, namely, those made from pig iron and those made from steel scraps byusing blast furnaces. Most of the steel bars for concrete reinforcement in use today are those madeby use of blast furnaces. Rerolled steel bars for concrete reinforcement are steel bars made fromiron scraps by cold rolling. Steel bars of this type are seldom used today because of concern about
their quality.
JIS G 3112 specifies (1) chemical composition, (2) mechanical properties and (3) shapes,
dimensions, masses and tolerances for seven types of steel bars, namely, SR235, SR295, SD295A,
SD295B, SD345, SD390 and SD490. For SD295B, SD345, SD390 and SD490, JIS G 3112
specifies not only lower limits but also upper limits to the yield point and 0.2% strength.
In JIS G 3117 “Rerolled Steel Bars for Concrete Reinforcement” mechanical properties, shapes
and dimension, mass, allowable difference and so on are specified for SRR235, SRR295, SDR235,
SDR295 and SDR345. These specifications are used as its quality. The specifications of shape anddimension and mass are the same as those of JIS G 3112. In addition specifications of themechanical properties of SRR235, SRR295 and SDR295 are the same as those of SR235, SR295
and SD295A, respectively.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Nominal diameter, cross section area, unit mass and so on are specified for D6 to D51 in the JIS
G 3112. Their allowance limits are also provided. Recently a steel bar of D51 or larger diameters
has been used with constructions of larger sizes to implement a rational design. For the use of D57
or D64 the JSCE-E121 “Quality Specification for Larger Size Steel Bars of D57 and D64” isreferred for the specification. Chemical constituents, upper limit and lower limit of yield strength,
elongation, inside radius of a moment curvature and so on are specified for SD295-N, SD345-N,
SD390-N and SD490-N. In the case of using steel bars of D57 or D64, design values and method to
use should be determined by the Standard Specifications for Concrete Structures “Design”.
(2) Reinforcing steel bars that do not conform to JIS G 3112 and JIS G 3117 may not only beunreliable in terms of quality but also have inappropriate details such as inappropriate rib shapes.
For steel bars that do not conform to JIS G 3112 and JIS G 3117, it is important for the responsible
engineer to verify by conducting reliable tests in advance that the specified design values are met
and, on the basis of the results thus obtained, judge the usability of the steel bars and specify themethod of using them.
Using epoxy-coated reinforcing bar may be beneficial for reinforced concrete structures in amarine environment as to prevents chloride ions from directly reaching the surface of the steel bar.
Powder type epoxy coating is applied to the surface of a steel bar using static powder coating
technique. Performance of epoxy coated reinforcing bars in terms of corrosion inhibition depends
on the quality of epoxy coating, surface preparation of steel, thickness of coating and the presenceof pinholes. Impact and bending of bars could cause cracking and delamination of the coating, andadversely affect the corrosion inhibition performance. Details of the materials used and the relevant
test methods are described in JSCE-E 102 “Quality Specification for Epoxy Coated Reinforced Bar(Draft)”. Therefore, an epoxy coated reinforcing bar that complies with the provisions of JSCEE102 may be considered to be suitable for use. Epoxy coated reinforcing bar used shall comply withthe provisions of the “Recommendation for Design and Construction of Concrete Structures Using
Epoxy-coated Reinforced Steel Bar”.

3.6.2

Prestressing steel(1) The prestressing wires and strands should conform to JIS G 3536 in general.
(2) The prestressing bars should conform to either JIS G 3109 or JIS G 3137 in general.
(3) When prestressing steel that is not mentioned in Item (1) or (2) is, tests shall be
conducted to verify that the design values are met and determine the method of using theprestressing steel.
(4) In cases when prestressing steel is reprocessed, or heat-treated for use inanchoring, coupling, assembling or layout, it shall be experimentally ensured that thequality of the prestressing bars has not been adversely affected.

[Commentary] (1) JIS G 3536 “Prestressing Wires and Strands” describes the mechanicalproperties, shapes, dimensions, tolerances, etc. for two types of prestressing wires and five types ofprestressing strands. These descriptions may be used as the quality specification. Mechanicalproperties have been specified in terms of loads corresponding to 0.2% permanent elongation,
tensile capacity of load, elongation and the ratio of relaxation. The surface irregularities of adeformed prestressing wire aren’t particularly specified. However the bond strength and fatigue
66

Chapter 3

Constituent Materials

strength of wire itself often depend on the surface irregularities. Therefore, the characteristic
strength should be determined by tests.
(2) In JIS G 3109 “Steel Bar for Prestressed Concrete” and JIS G 3137 “Deformed Prestressing
Bars of Small Diameter”, the descriptions relating to a)chemical constituents, b)mechanicalproperties and c)shapes, dimension, and tolerances are shown for three types of prestressing steel
bars and three types of deformed prestressing steel bars of small diameter, respectively. These
descriptions may be used as the quality specification. Mechanical properties of different types ofprestressing steel have been specified in terms of stress corresponding to 0.2% permanentelongation, tensile strength, elongation, and the ratio of relaxation.
Although the strength of prestressing steel bars is normally lower than those of prestressing
wires and prestressing strands the modification of the ends of prestressing steel bars results inbeneficial effects that anchoring is easily achieved. The relaxation of prestressing steel bars is lower
than those of normally used prestressing wires and prestressing strands but is similar to those ofparticular ones with lower relaxation. Prestressing steel bars of larger diameter exhibit larger
reductions of the quality due to bending. In addition the quality of the portion that is modified foranchoring must be examined if it can ensure sufficient performance. It is sometimes encounteredthat prestressing steel bars are hardly normal to anchoring cross section in the anchoring portion andbecomes never straight at the portion with connection devices. For those cases a local bending of
the prestressing steel bars will be induced resulting in rapture due to stress corrosion or delayed
failure. To avoid those it is recommended that prestressing steel bars of large elongation capacityand ductility be used.
When an end of the prestressing steel bar is threaded for anchoring or coupling roll-threading
must be conducted instead of thread-cutting because the thread-cutting reduces the effective
diameter of the threaded portion, thereby largely adversely affecting the tensile strength of the bar.
When large-diameter prestressing steel bars are threaded using the roll-threading method, only
minor reduction of the effective diameter occurs and the tensile load carrying capacity at thethreaded portion may be increased due to the effect of cold-working. In case of small-diameter
prestressing steel bars, however, major reduction of the effective diameter occurs, which may cause
reduction of the tensile load carrying capacity at the threaded portion. In this case, the threaded
portion may not meet the standard of the prestressing steel bars. Therefore, the prestressing steel
bars must be tested to confirm that they satisfy the design requirements. The design tensile load
carrying capacity of the prestressing steel bars may be calculated by multiplying the tensile strengthand the nominal sectional area specified in JIS G 3109. When the roll-threaded or headed portion of
the bar does not meet the specified tensile load carrying capacity of the bar itself the design values
must be modified in the same manner as prescribed in Clause (4) of this Section.
(3) Usually, JIS-specified prestressing steel is the safest and is also economical. If special
prestressing tendons that are not described in Item (1) or (2) of Section 3.6.2 are used, it isnecessary to determine the variability of quality by conducting tests on a sufficient number of
specimens. In such cases, it must be ascertained on the basis of values reflecting an appropriate
defect percentage in accordance with JIS Z 9004, Single Sampling Inspection Plans Having Desired
Operating Characteristics by Variables (Standard Deviation Unknown and Single Limit Specified)that the specified design values are met. The requirements related to tensioning materials other thanprestressing tendons are described in Section 3.6.4, Other Reinforcing Materials.
(4) When prestressing steel bar is subjected to grinding or bending, or rolled-threaded, headedor heated for anchoring, coupling, assembling and arranging the strength and the other quality of thesteel may deteriorate depending on the treatments. If the deterioration is minor it can be coped within consideration of the proper arrangement of the prestressing steel, anchorage or couplers. In turn if
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Standard Specifications for Concrete Structures-2007, Materials and Construction

the deterioration occurs on a large scale it is difficult to make up for this by only such consideration.
Therefore, for the deteriorated steel the strength and the other design values shall be modified bytests, if needed.
In case for the prestressing steel bar treated of re-bending or heated, following considerations
may be referred for a new specification corresponding to the reduction rate of the strength of thetreated prestressing steel bars.
(a) In a case when the strength reduction is equal to or less than 5 %: if the tensile strength ofprestressing steel bars which have been re-bent or heated is equal to or greater than 95 % of theoriginal value can be applied in the design under condition that the proper arrangement ofprestressing steel, anchorages and couplers is implemented.
(b) In a case when the strength reduction is greater than 5 % but less than 10 %: if the tensile
strength of prestressing steel which has been re-bent or heated is more than 90 % but less than 95 %of the original standard value, the standard value to be used in the design shall be modified by
testing.
(c) In a case when the strength reduction is equal to or more than 10 %: if the tensile strength ofprestressing steel bar which has been re-bent or heated is equal to or less than 90 % of the original
standard value, such re-bending or heating method must be generally avoided.
3.6.3

Structural steel

The structural steel should conform to JIS G 3101, JIS G3106 or JIS G 3136 in general.

[Commentary] JIS G 3101 “Rolled Steels for General Structures” specifies for four types ofrolled steels, SS330, SS400, SS490 and SS540 on a) chemical constituents, b) mechanicalproperties, c) shapes, dimensions and mass, and their allowances. Similarly JIS G 3106 “Rolled
Steels for Welded Structures” specifies for eleven types of the rolled steels ranging from SM400A
to SM570 and JIS A 3136 “Rolled Steels for Building Structures” that has been standardized in
1996 specifies for the heated rolled steels that are used mainly for steel-made structures of buildings.
These specification described in each standard may be considered to be the quality of the rolled
steels. The mechanical properties include yielded strength or load carrying capacity, tensile strength,
elongation, and inner radius of the bent-over. Steel bars for steel-reinforced concrete structures arein principal selected on the basis of its yielded strength similar to that of reinforcement bar used
together.

3.6.4

Other reinforcing steel

The quality of other reinforcing steel shall be appropriately confirmed and carefulattention paid to the method of using them.

[Commentary] There are many reinforcing materials, other than those mentioned above, forwhich there is as yet no quality standard, and there are many types and many methods for using
them. When using those reinforcing materials, therefore, it is necessary to conduct thorough studies
and tests to ascertain quality and identify methods for using those materials.
There are cases where reinforcing materials composed partially of fibers are used with the aim

68Chapter 3

Constituent Materialsof achieving higher quality of hardened concrete or preventing spalling of concrete used in tunnels
or other structures. Fibers used in such cases can be largely classified into two categories: shortfibers and continuous fibers. Examples of short fibers are inorganic fibers including metal fibers
such as steel fibers and stainless steel fibers, glass fibers, carbon fibers and ceramic fibers. There
are also organic fibers such as aramid, nylon, vinylon, polyethylene and polypropylene. When using
short fibers, it is good practice to conduct tests in advance to check on the quality of the fibers to be
used because suitable diameters, lengths and shapes vary with the intended use of the fibers.
JSCE-E 101, Standard for Quality of Steel Fibers for Concrete, can be used as a guide for thequality of steel fibers. Concerning the production of short fiber-reinforced concrete, theConstruction: Special Concretes of this Specification (Chapter 5, Short Fiber Reinforced Concrete)
can be used as a guide.
Continuous fiber reinforcing materials are continuous fibers cemented either into bars to be usedas substitutes for steel bars or prestressing tendons or into sheets. The former are used mainly as
concrete reinforcing or tensioning members, while the latter are used for the repair or reinforcementof concrete. There are five types of fibers used in continuous fiber reinforcing materials: carbon
fibers, aramid fibers, glass fibers, vinylon fibers and their mixtures. Continuous fiber reinforcing
materials can also be broadly classified, according to shapes, into five types: rod, strand, braid,mesh, and rectangular plate. Because the material, shape, quality and other characteristics ofcontinuous fiber reinforcing materials vary widely among different types, it is recommended thatstandard-conforming tests be conducted in advance as in the case of steel fibers to verify quality(see the standard section of this Specification). Also, when producing continuous fiber reinforced
concrete, it is good practice to refer to the Construction: Special Concretes of this Specification(Chapter 4, Continuous Fiber Reinforced Concrete).
Continuous fiber reinforcing materials are easily damaged when placed directly on the groundor floor surface and are subject to quality degradation. Furthermore, continuous fiber reinforcing
materials may deteriorate, depending on the type of fiber, if placed at a place exposed to hightemperature or ultraviolet rays or under the influence of chemicals. When storing continuous fiber
reinforcing materials, therefore, it is necessary to protect them from those influences.
3.7

Storage of Materials

3.7.1

Storage of cement(1) Different types of cement shall be stored separately in damp-proof silos,
warehouses or other storage facilities.
(2) Silos shall be designed so that there is no dead storage area near the bottom of thestorage space.
(3) When cement that has been stored for a long period of time is, the cement shall betested to ascertain its quality prior to the use.
(4) When the temperature of cement is excessively high, the temperature of the cement
shall be lowered prior to the use.

[Commentary] (1) When in contact with air while in storage, cement undergoes light
hydration by absorbing moisture from the air and simultaneously reacts with carbon dioxide in the
air. This process is referred to as weathering of cement. As cement weathers, the ignition loss
increases and density decreases so that setting is delayed or strength decreases with the progress of69

Standard Specifications for Concrete Structures-2007, Materials and Construction

weathering. It is necessary, therefore, not only to keep moisture away from cement but also to store
cement in an unventilated condition. If cement is stored in a highly airtight silo designed to prevent
internal condensation, the quality of the cement hardly changes even if the cement is stored for a
relatively long period of time. It is desirable that the capacity of a silo be equal to or greater than
three times the average quantity of cement used in one day. If cement can be supplied smoothly
because there is a concrete mixing plant at a relatively short distance from the cement service
station, silo capacity can be made smaller.
If bags of cement are stored for a relatively long period of time or during a high-humidity period,
it is good practice to take weathering prevention measures such as using bags lined with a
damp-proof membrane. In order to protect bags of cement in storage from moisture from the ground,
the warehouse floor needs to be kept a sufficient distance away from the ground. In the case of awooden warehouse, for example, at least 30 cm is required. In order to protect cement in storage
from condensation due to rain or the difference between internal and external temperatures, it isimportant to stack bags of cement so that they do not come into contact with the warehouse walls. Ifbags of cement are stacked while in storage, the cement in the lower bags might consolidate. A
recommended limit to the number of layers of stacked bags of cement, therefore, is about 13.
(2) Cement silos should have features or provisions to prevent the occurrence of dead storage
areas where stored cement does not flow out or is stuck, such as nonsymmetrical structure, a steep
bottom cone to facilitate flow, or vibrators or aerators to facilitate flow movement. It is also
necessary to inspect and clean silos at appropriate frequencies.
(3) Needless to say, cement containing lumps formed while the cement is storage must not be
used. In the case of cement that may have been exposed to moisture because of storage over a long
period of time, it is necessary to conduct tests (e.g., mortar tests) and evaluate the usability of thecement.
(4) As the temperature of cement changes by 8°C, the as-mixed temperature concrete rises orfalls by 1°C. The influence of cement temperature on concrete temperature is smaller than theinfluence of aggregate and water. If, however, cement with an excessively high temperature is used,
the as-mixed temperature of concrete may rise so as to cause abnormal consolidation or a decreasein slump. It may be necessary, therefore, to impose limits on cement temperature at the time ofshipping from a factory or at the time of delivery at the construction site. The temperature ofdelivered cement varies with the transportation route from the cement factory and the time of year.
For example, the average temperature of cement shipped directly from a cement factory ranges
from 50 to 80°C. If cement is transported by ship or stored at a service station, cement temperaturetends to be slightly lower. In general, no problem arises if cement with a temperature of 50°C or
lower is used.

3.7.2

Storage of aggregates(1) Fine aggregate and coarse aggregate and aggregate of different types, fromdifferent places of origin or of different particle sizes shall be isolated and stored
separately.
(2) Aggregates shall be received, stored and handled carefully by using machinery andequipment of appropriate structure in order to prevent problems such as the separation oflarge and small particles, the inclusion of foreign matter and damage to coarse aggregate.

70Chapter 3

Constituent Materials(3) Aggregate storage facilities shall be provided with appropriate drainage facilities sothat surface moisture conditions become uniform.
(4) In times of cold weather, aggregates shall be stored by use of appropriate facilities
to prevent the inclusion of ice and snow and freezing.
(5) Aggregates shall be stored by use of appropriate facilities to, for example, keep
cement away from direct sunlight in order to prevent aggregate from drying andtemperature from rising under hot weather.

[Commentary] (1) In order to produce concrete of consistent quality, it is necessary to makesure that the quality of aggregate used is always consistent. Different types of aggregate such as
gravel, sand, crushed stone, blast furnace slag aggregate and lightweight aggregate, aggregate ofdifferent particle sizes or maximum particle sizes, aggregate that has been graded in advance, andthe like must be isolated from one another by using appropriate dividing devices and be stored
separately. If the particle sizes of coarse aggregate fall within the range from 20 to 5 mm, it is goodpractice to divide the aggregate into two classes, namely, 20 to 10 mm and 10 to 5 mm, and store
them separately. Similar care needs to be taken in connection with the receiving of delivered
aggregate and the handling of aggregate from the storage area to the mixing area.
(2) In order to prevent the segregation of aggregate, it is necessary to take preventive measures
such as avoiding a sloping area where aggregate rolls down. One way to prevent the inclusion offoreign matter is to store aggregate on a concrete floor and surround the storage area with trenches
or walls. Care should be taken to make sure that mud and other foreign matter sticking to the tiresof aggregate hauling vehicles is not mix into the aggregate. Shovel loaders with rubber tires should
be used to handle aggregate because crawler-mounted loaders crush aggregate and wear theconcrete floor. Top-feed bottom-discharge silos are recommended.
(3) If concrete of consistent quality is to be produced, it is desirable that aggregate withconsistent particle size distribution be used and the surface moisture content of aggregate be stable
so that the water content can be kept constant. If the surface moisture content of aggregate is notconstant, it is necessary to adjust the water content on a batch-by-batch basis, making production
control almost impossible to perform. The basic rule, therefore, is to store aggregate so that thesurface moisture content of aggregate can be kept uniform. If delivered aggregate is used
immediately, it is difficult to cope with changing particle size distributions and surface moisture
contents by, for example, changing mix proportions. Good practice, therefore, is to use storage
facilities of appropriate capacity and provide drainage facilities so that the surface moisture
conditions become uniform. It is therefore important to prepare facilities and perform management
so that delivered aggregate is used in the order of delivery.
In cases where blast furnace slag aggregate or lightweight aggregate is stored, it is desirable thatwatering devices such as sprinklers as well as drainage facilities be provided. The reason is that
because pumping of concrete has increased in recent years, in the case of blast furnace slag
aggregate or lightweight aggregate, both of which are more absorptive than gravel and crushedstone, the slump of concrete may decrease considerably during pumping if water is not sprayed tosome extent in advance.
(4) If frozen aggregate or aggregate containing ice or snow is used as is under cold weather, thetemperature of concrete may decrease so that concrete freezes or the water content increases. In
order to prevent the intrusion of ice and snow, therefore, it is important to cover aggregate withsomething or store aggregate in roofed storage facilities.
71

Standard Specifications for Concrete Structures-2007, Materials and Construction(5) If aggregate that has been exposed to baking heat under hot weather for a long period of time
is used, concrete temperature may rise. If this occurs, workability may change considerably while
the concrete is being transported or handled or consolidation may be extremely accelerated so thatsatisfactory construction work cannot be carried out. In order to prevent this problem, it is importantto provide appropriate covering or water spraying facilities at the places where aggregate is stored.
If blast furnace slag fine aggregate is to be stored for a long period of time during a period in whichdaily mean temperature exceeds 20°C, it is necessary to pay careful attention to the management of
its storage. In the case of a cylindrical silo made of corrugated metal members or other materials
that greatly reduces work efficiency in the event of consolidation, the silo should be designed toprevent the occurrence of near-bottom dead storage areas from which stored aggregate cannot be
extracted, and attention should also be paid to the level of consolidation control.

3.7.3

Storage of admixtures(1) Different types of admixtures shall be stored separately in damp-proof silos,
warehouses or other storage facilities.
(2) When an admixture that has been stored for a long period of time is used, theadmixture shall be tested to ascertain its quality prior to the use.
(3) Admixtures shall be handled carefully so that they are not scattered about.

[Commentary] (1) Admixtures are usually absorptive, and an admixture that has absorbed
moisture may consolidate or deteriorate in performance so that the required quality cannot be
achieved. For example, fly ash consolidates when a very small amount of gypsum contained in the
fly ash absorbs moisture, and silica fume, which is very fine-grained, is more absorptive than otheradmixtures and is therefore prone to consolidation. Because expansive admixtures for concrete
contain a large quantity of free calcium oxide, they are more prone to weathering than cement. If
different types of admixtures are mixed together, it may not be possible to attain the expected effect.
It is therefore necessary to separate different types of admixtures and store them separately in
damp-proof silos, warehouses or other storage facilities. Bagged, canned or otherwise packaged
admixtures must be stored so that the packages are not broken or damaged and can be easily
identified and inspected.
(2) If admixtures are stored for a long period of time, the quality of the admixtures may changeeven if they are carefully stored. If, therefore, the storage period has become long, the usability of
the admixture must be evaluated after conducting a test again and ascertaining the degree of
influence of the long storage period on the concrete.
(3) Powdered admixtures tend to be scattered about in bag splitting areas and around silo outlets
so as to cause measuring instruments to break down. During humid periods, scattered powder tends
to stick to the surfaces of silos and transportation equipment. It is important, therefore, to carefully
handle powdered admixtures so that powder is not scattered about. It may also be necessary toprovide dust control equipment.

72

Chapter 3

3.7.4

Constituent Materials

Storage of chemical admixtures(1) Chemical admixtures shall be stored so that impurities such as waste materials are
not mixed into the admixtures. Liquid chemical admixtures shall be stored so that neither
segregation nor alteration results. Powdered chemical admixtures shall be stored so thatthey do not absorb water moisture or consolidate.
(2) Chemical admixtures that have been in storage for a long period of time or thathave been found to be in an anomalous condition shall be tested prior to the use to makesure that their performance had not deteriorated.

[Commentary] (1) Impurities such as waste materials in a chemical admixture may alter thequality of the chemical admixture so that the expected effect cannot be achieved. In the case of achemical admixture that is used in very small quantities such as an air-entraining agent, impurities
could hamper accurate measurement of required quantities. Impurities in a liquid chemical
admixture could cause malfunctioning of feed pumps or instrument valves. When storing chemical
admixtures, therefore, it is necessary to exercise due care to prevent the inclusion of waste materials
and other impurities. In the case of a liquid chemical admixture, not only the inclusion of impurities
but also changes in concentration due to the evaporation of moisture or the intrusion of rainwater
can be prevented by storing the admixture in a closed tank. When different types of chemical
admixtures are stored, it is necessary to exercise due care so as not to use the same containers formore than one type of chemical admixture or inadvertently mix different types of chemical
admixtures.
When a chemical admixture freezes, segregation of ingredients occurs. It is therefore necessary
in winter to take measures to prevent chemical admixtures from freezing. It is in many cases
possible, however, to restore the performance of a chemical admixture that has undergone
segregation because of freezing by completely melting and remixing the frozen admixture.
Powdered chemical admixtures are highly hygroscopic, and certain types of powdered chemical
admixtures even deliquesce. These types of chemical admixtures must be stored in damp-proof,
unventilated storage facilities.
In view of these factors, when storing chemical admixtures, it is necessary to take meticulous
preventive measures such as shielding sunlight, keeping fire away and preventing freezing.
(2) If chemical admixtures are stored for a long period of time, the quality of the admixtures
may change even if they are carefully stored. For example, storing a liquid chemical admixture for along period of time may result in not only segregation but also decomposition or alteration due torust forming on iron containers. The evaporation of moisture may result in a higher concentrationand the solidification of the surface layer. If, therefore, chemical admixtures have been stored for along period of time or have been found to be in an anomalous condition, it is necessary to evaluate
the influence on the concrete by testing them again and determine whether they can be used. Even if
the quantity of a chemical admixture used is small, its influence on the concrete is great. Care must
be taken because even a small change in the quality of a chemical admixture may result in asignificant difference in the quality of concrete.

3.7.5

Storage of steel(1) Reinforcing bars and structural steel shall be supported at appropriate spacing andstored in storage facilities or, if stored outdoors, under appropriate cover instead of being73

Standard Specifications for Concrete Structures-2007, Materials and Construction

placed directly on the ground surface.
(2) Prestressing steel shall be supported at appropriate spacing and stored in storage
facilities or, if stored outdoors, under appropriate cover for protection from harmful
substances such as oil, chlorides and waste materials and harmful processes and effects
such as corrosion, damage and deformation.

[Commentary] (1) The reason why steel reinforcing bars and structural steel must not be
placed directly on the ground surface is that they need to be protected from rusting or contamination.
The reason why reinforcing bars and structural steel are stored in storage facilities or underappropriate cover is that the corrosion of reinforcing bars and structural steel due to rain,condensation, corrosive salt air, etc., needs to be prevented. When storing steel reinforcing bars andstructural steel, it is necessary to support them at appropriate spacing for easy handling andconvenience in inspection. Steel reinforcing bars and structural steel of different material types
should be stored separately. Steel reinforcing bars of different diameters and structural steel items ofdifferent cross-sectional shapes and dimensions should also be stored separately.
(2) When storing prestressing steel, it is necessary not only to be as careful as with steel
reinforcing bars and structural steel but also to make special arrangements. The reason why
prestressing steel must not be placed directly on the ground surface is that it is necessary not only toprevent rusting and corrosion due to moisture and prevent foreign matter such as oil, wastematerials and mud from sticking to prestressing steel but also to make handing of prestressing steel
easier. The reason why prestressing steel must be stored in storage facilities or under appropriate
cover is that rusting and corrosion due to rain, condensation, corrosive salt air, etc., needs to beprevented.
Prestressing steel requires careful attention because oil, waste materials, mud, etc., sticking tosteel surfaces may cause steel–concrete bond strength to decrease. Because threaded portions ofsteel items are particularly prone to strength loss due to corrosion, they must be stored so that they
are perfectly protected from corrosion. If coils of prestressing steel wire and prestressing steel
strand are stacked in multiple layers for storage, harmful flexural loading from the upper coils may
cause stress-induced corrosion. It is therefore necessary to take such measures as restricting thenumber of stacked layers. In the case of prestressing steel wire and prestressing steel strand, which
are shipped in the form of coils, the property of restoring linearity when unwound is important fromthe viewpoint of efficiency in construction. In order to prevent wire or strand from being bent sothat their ability to return to the original shape is lost, it is desirable that the coil diameter be kept at
or greater than 150 times the diameter of the steel wire or strand.
The quality of prestressing steel may be altered if it is heated to about 300°C or higher. Caremust be taken, therefore, to keep prestressing steel away from fire.

74

Chapter 4

Mix Design

CHAPTER 4 MIX DESIGN
4.1 General(1) In mix design, unit quantities shall be determined after specifying mix requirements
such as the slump, required strength and water/cement ratio of concrete so that theworkability, strength and durability requirements can be met.
(2) Concrete mix proportions shall be determined by minimizing the water content inorder to meet the performance requirements.

[Commentary] (1): This chapter describes methods for determining concrete mix proportions tomeet three performance requirements. Those are workability, specified strength and durability forconcrete. The mix design methods described in this chapter are applicable to concrete whose
specified strength is about 60 N/mm2 or lower and whose workability in a fresh state is evaluated interms of slump. In cases where concrete is to be placed under unusual conditions such as whenplacing concrete into constricted spaces or through densely packed reinforcing steel or whenplacing a new layer of concrete under a previously placed layer of concrete (inverted construction
method), high-fluidity concrete with self-compacting ability should be used. Mix proportions forhigh-fluidity concrete (self-compacting concrete) shall be determined as described in the Special
Concrete section of this Specification (Chapter 7, High-Fluidity Concrete). If concrete with a slumpof 21 cm or less is inadequate in terms of filling ability but performance as high as that ofhigh-fluidity concrete is not necessary, mix proportions somewhere in-between should be selectedunder the guidance of an expert well versed in concrete mix design and construction technology.
When designing concrete mixes, it is necessary not only to meet the requirements for the
specified strength necessary for the purpose of structural design and the durability requirements but
also to select mix proportions that ensure workability suitable for the structural and construction
requirements for the structure to be constructed. The design drawings and specifications indicate theranges of reference values (e.g., maximum size of coarse aggregate, slump, water/cement ratio, typeof cement, cement content) to be reflected in actual mix designs, derived on the basis of theverification of structural performance, durability of various types, water-tightness, cracking
resistance, steel protection performance. Mix design in this chapter, therefore, is the act ofdetermining unit quantities of various materials including the water content suitable for thematerials to be actually used at the construction stage and the construction requirements on the basisof the reference values indicated on the design drawings and specifications mentioned above.
Figure C4.1.1 illustrates the concept for the determination of mix proportions to meet theworkability, specified strength and durability requirements for concrete. Workability, which is anindicator of ease of construction by use of concrete, is a performance attribute needed for ensuringsmooth and reliable execution of a series of tasks including hauling, placing, compacting andfinishing. This chapter focuses mainly on the ability of concrete to smoothly pass through the space
between reinforcing steel and completely fill the concrete cover regions, corners in formwork andprestressed concrete anchorage zones (filling ability) without undergoing the segregation ofingredients.
Filling ability is a performance attribute determined by the interaction between fluidity andsegregation resistance. In order to obtain concrete with satisfactory filling ability, it is necessary toprovide appropriate segregation resistance according to fluidity. Fluidity and segregation resistance
are affected by not only the water content, binder content and the water/binder ratio but also other75

Standard Specifications for Concrete Structures-2007, Materials and Construction

factors such as the type of the powder used, the particle sizes and shapes of fine and coarse
aggregate, and the type of chemical admixture. In the Construction: Construction Standards, slump
is used as an indicator of fluidity in view of practical convenience. In general, segregation
resistance is numerically expressed with rheological constants such as plastic viscosity and the yieldvalue. Since, however, segregation resistance can be controlled with relative ease by increasing or
decreasing the binder content, the binder content is used as a practical indicator of segregation
resistance.
In Fig. C4.1.1, the basic mix design approach to be taken in order to achieve the desired
performance of concrete is to use a water/cement ratio not higher than the ratio indicated in thedesign specifications. Cement content is also not higher than the upper limit indicated in the design
specifications, and the water content should be minimized to the extent that the binder content
needed to achieve complete and smooth filling is secured. In mix design, it is also very important toachieve appropriate segregation resistance by increasing or decreasing the binder content according
to slump instead of simply increasing or decreasing the water content according to the specified
slump.
Figure C4.1.2 illustrates the concept of mix proportion in the case where the cement content
indicated in the design specifications is lower than the binder content needed to achieve the required
filling ability. This case may occur when it is desired that the cement content be lowered as much as
possible in order to minimize the heat generated by hydration as in the case of mass concrete. With
this cement content, however, excellent filling ability from the viewpoint of workability cannot be
achieved. In this case, it is necessary to use concrete of the type generates a smaller quantity of heator blended cement or use admixtures such as limestone powder in order to increase the powder
content to the level needed to achieve the required filling ability.

Water content

単
位
水
量

単位水量
の上限

Upper limit of water content

Upper
limit of cement content determined
耐久性および水和熱制御から
bydurability
and heat of hydration control
定まる単位セメント量の上限
ら
か 比
性 ト
久 ン
耐 メ
・ セ
度 水
強 る
ま
定

Mix
proportions are to be
この領域からselectedfrom this area.
配合を選定

ワーカビリ
Lower limit of watercontent
ティーから
required from the viewpoint
必要な単位
of workability
水量の下限
ワーカビリティーから必要なLower limit of binder content
単位粉体量の下限
required fromthe viewpoint of workability

単位粉体量
Bindercontent

Fig. C4.1.1 Concept of mix proportioning (in normal case)76

Water content

Chapter 4

単位
水量

Mix Design

Upper limit of cement content determined
耐久性および水和熱制御からby durability and heat of hydration control

Upper limit of water単位水量
contentの上限

ワーカビリ
Lower limit of watercontent
required from the ティーから
viewpointof workability 必要な単位
水量の下限定まる単位セメント量の上限

ら
か 比
性 ト
久 ン
耐 メ
・ セ
度 水
強 る
ま
定

Mix
proportions are to be
この領域からselectedfrom this area.
配合を選定

Increasing binder ingredients such as cement and admixtures
セメントや混和材等の粉体の増量
Lower limit of binder content
ワーカビリティーから必要な
required fromthe viewpoint of workability
単位粉体量の下限

単位粉体量
Bindercontent

Fig. C4.1.2 Concept of mix proportioning(in the case where the powder content is too low from the viewpoint of filling ability)

In almost all ordinary concreting projects, ready-mixed concrete is used. Even in such cases, it
is important to select mix proportions on the basis of the mix design methods described in thischapter and select appropriate mixes from available types of ready-mixed concrete with reference tothe mix proportions thus selected.
(2): A high water content not only makes uneconomical concrete that requires a high cement
content to achieve the same water/cement ratio but also makes concrete prone to segregation so as
to make it difficult to produce homogeneous and relatively defect-free concrete. Reducing the watercontent to the extent that suitability for the construction work to be carried out is not compromised
makes it possible to use a lower cement content so as to achieve the required concrete quality and toenhance cracking resistance. An excessively low water content, however, makes the concrete very
difficult to place, increasing the possibility of initial defects such as incomplete filling. In order toproduce concrete that has the required levels of strength, durability, water-tightness, cracking
resistance and steel protection performance, it is very important to make the water content as low as
possible to the extent that the concrete is suitable for the construction work to be carried out and iscapable of filling the formwork completely.

4.2 Mix Design Procedure(1) In mix design, characteristic values related to the strength and durability ofconcrete described in the design specifications, as well as the maximum sizes of coarse
aggregate, slumps, water/cement ratios, cement types and cement contents indicated as
reference values, are ascertained.
(2) Mix proportions are determined on the basis of the reference values for concrete
indicated in the design specifications mentioned in Item (1) above.
(3) Provisional mix proportions to be used as reference mix proportions for trial mixes
are determined according to the mix proportions determined as mentioned above.

77

Standard Specifications for Concrete Structures-2007, Materials and Construction(4) On the basis of the provisional mix proportions thus determined, trial mixes areprepared by using materials identical to the materials to be used to ascertain that theperformance requirements for concrete can be met. If trial mixing has revealed that theperformance requirements cannot be met, the materials or mix proportions to be used arechanged, and mix proportions needed to achieve the required quality are determined.

[Commentary] (1): The design specifications indicate characteristic values for concrete
determined on the basis of the structural performance and durability of structures such as the
specified strength of concrete, the carbonation rate and the chloride ion diffusion coefficient. The
design specifications also indicate the maximum sizes of coarse aggregate, slumps, water/cement
ratios, cement types and cement contents as reference values to be used in cases where provenconcrete mix proportions are used or mix design is conducted concretely. In mix design, therefore, itis necessary as the first step to check on these characteristic values and reference values indicated in
the design drawings and specifications.
(2): Fig. C4.2.1 shows the concrete mix design procedure at the construction stage. As shown in
the figure, mix requirements such as the maximum size of coarse aggregate, slump, required
strength, water/cement ratio and the air content are determined on the basis of the reference values
indicated in the design specifications. If the reference values indicated in the design specifications
are thought to be inadequate in view of the materials to be actually used or the construction
requirements, it is necessary to change those values into the values suitable for the actual conditions
after ascertaining that the characteristic values for concrete indicated in the design specifications are
met.

78

Chapter 4

Mix Design

コンクリートの目標性能
Targetperformance of concrete

Check items of設計図書の確認項目
design drawings and specifications<特性値> values
Characteristic
Specifiedstrength, carbonation rate, chloride ion diffusion
設計基準強度，中性化速度係数，塩分物イオンに対するcoefficient,permeation rate (permeation coefficient),
拡散係数，透水量（透水係数），凍結融解試験における
relativedynamic modulus of elasticity, shrinkage strain, etc.
相対動弾性係数，収縮ひずみ，等Referencevalues<参考値>
Maximum
size of coarse aggregate, slump, water/cement ratio,
粗骨材の最大寸法，スランプ，水セメント比，
cementcontent, type of cement, air content
単位セメント量およびセメントの種類，空気量

Step
1: Define target performance【STEP-1】目標性能の設定• Placeability
・施工性能• Specified
strength
・設計基準強度• Durability
・耐久性

Step【STEP-2】配合条件の設定
2: Determine mix requirements(1)
Maximum size of coarse aggregate（１）粗骨材の最大寸法
(2)
Slump
（２）スランプ(3) Required strength（３）配合強度(4) Water/cement ratio, cement content and the type of cement（４）水セメント比，単位セメント量およびセメントの種類(5)
Air content（５）空気量Appropriate
適正配合の
mix
proportions
選定が困難
difficultto select

Step 3:【STEP-3】使用材料の選定および暫定の配合の設定
Select materials and determine provisional mix proportions
Trial
mix
試し練り
Step
4: Adjust unit quantities of materials【STEP-4】使用材料の単位量の調整
3(1)
Adjust water content (water content: 1753kg/m（１）単位水量の調整（単位水量175kg/m以下）or less)(2) Adjust cement content (control of heat of hydration: confirmation of（２）単位セメント量の調整（水和熱の抑制：単位セメント量の確認）
cement content)（３）細骨材率の調整(3)
Adjust sand percentage（４）混和材料の単位量の調整(4)Adjust admixture content

Is fresh concrete quality acceptable?
フレッシュコンクリートの品質の確認

NO

YES

Is hardened
concrete quality acceptable?
硬化コンクリートの品質の確認

NO

YES

Step【STEP-5】
5: Determine 配合の決定（使用材料の単位量の決定）
mix proportion (determine ingredient content)

Fig. C4.2.1 Mix Design Flow(3) and (4): According to the determined mix requirements, provisional mix proportions forconcrete consisting of the materials to be actually used are determined. After that, trial mixes areprepared to make sure the mix proportion thus determined meets the performance requirements. If
the performance requirements are not met, the mix proportion is modified, and trial mixing iscarried out again. If the performance requirements cannot be met by mix proportional modification
alone, the materials to be used are changed, and this process is repeated until the performance79Standard Specifications for Concrete Structures-2007, Materials and Construction

requirements are met.
If trial mixing has revealed that the water content needed to achieve the required consistency
would increase considerably, it is important to reconsider and modify the physical properties ofaggregate by, for example, using other types of aggregate, increasing the solid content or adjusting
the particle size distribution. If the water content of concrete containing an air-entraining
water-reducing agent exceeds the upper limit (175 kg/m3; see Section 4.5.1), the water content
should be reduced by using a superplasticizer. As a means of enhancing cracking resistance,measures such as changing the type of cement used to a low-heat type or using expansive
admixtures should be taken.

4.3 Target Performance of Concrete
4.3.1 Defining target performance
On the basis of the characteristic values and reference values for concrete indicated in
the design specifications, workability, specified strength and durability suitable for theenvironmental conditions, construction requirements and the materials used are definedas the target performance of concrete.

[Commentary] The target performance of concrete to be taken into consideration in mix design
consists of workability, specified strength and durability. Mix design is a series of tasks performed
to specify concrete ingredients and their mix proportions reflecting the actual environmental
conditions, construction requirements and the characteristics of the materials used on the basis of
the reference values indicated in the design drawings and specifications determined so as to achieve
the target performance of concrete. Concrete ingredients and mix proportions are determined, andthe concrete performance verification process by the trial mix method is repeated until theperformance requirements for concrete are met. In mix design, the upper and lower limits or rangesof parameters such as slump, water/cement ratio, water content and the cement content are specified
as mix requirements so that the workability, specified strength and durability requirements are met.
Commonly used indicators of concrete durability include the carbonation rate, the chloride ion
diffusion coefficient, freeze–thaw resistance, chemical attack resistance and fire resistance. The
reference values indicated in the design specifications are values determined on the basis ofdurability-related indicators such as the carbonation rate, the chloride ion diffusion coefficient,
freeze–thaw resistance and the permeability coefficient (permeation rate). If, therefore, mix
requirements are determined according to the reference values indicated in the design specifications
such as the water/cement ratio, the type of cement and the cement content, it may be assumed thatthe required durability related to carbonation, chloride attack, freeze–thaw damage andwater-tightness can be met.

4.3.2 Workability of concrete(1) Filling ability is determined as described in Section 2.3.1.
(2) Pumpability is determined as described in Section 2.3.2.
(3) Setting properties are determined as described in Section 2.3.3.

[Commentary](1), (2) and (3) In order to construct a concrete structure with the required
80Chapter 4

Mix Design

performance, it is necessary to specify requirements in accordance with Sections 2.3.1 to 2.3.3
appropriately so that the concrete has the filling ability, pumpability and setting properties suitablefor construction tasks such as hauling, pouring, compacting and finishing.

4.3.3 Specified strength
Specified strength is determined based on characteristic values given in the design
drawing.

[Commentary] Specified strength indicated in the design specifications, etc., mix requirements
such as required strength and the water/cement ratio are determined in view of the materials used,production equipment and the variability of concrete quality in past projects.

4.3.4 Durability(1) Durability is specified in accordance with section 2.5.
(2) Appropriate mix requirements and materials to be used are determined on the basisof the durability-related reference values indicated in the design drawings andspecifications so that the required durability against carbonation, chloride attack andfreeze–thaw cycles can be achieved.
(3) If the reference values indicated in the design drawings and specifications are notused as a reference, either past mix proportion data or other reliable data are used as areference or appropriate mix requirements are determined after conducting tests inadvance and ascertaining that the characteristic values indicated in the design drawings
and specifications are met.
(4) Appropriate control measures are taken against alkali–silica reaction.
(5) Appropriate mix requirements are specified so that the required durability can beachieved against chemical attack and in terms of water-tightness.

[Commentary] (1), (2) and (3): The reference values indicated in the design specifications arevalues determined on the basis of durability-related characteristic values such as the carbonation
rate, chloride ion diffusion coefficient and the relative dynamic modulus of elasticity. Appropriate
mix requirements and materials to be used, therefore, are determined on the basis of the reference
values indicated in the design specifications such as the water/cement ratio, cement content and thetype of cement so that the required durability can be achieved. The reference values indicated in thedesign drawings and specifications assumes the case in which concrete with an appropriate amountof entrained air and adequate filling ability is carefully placed, compacted and cured at appropriate
temperature and under adequate humidity conditions.
If different types of materials are used or if it is necessary to specify mix requirements otherthan the reference values indicated in the design drawings and specifications in order to achieve
durability other than the durability against carbonation, chloride attack and freeze–thaw cycles, it isnecessary either to refer to past mix proportion data or other reliable data or ascertain through trial
mix or other tests conducted in advance that the characteristic values indicated in the design
specifications can be attained.
81

Standard Specifications for Concrete Structures-2007, Materials and Construction(4): There is as yet no established method for appropriately checking on alkali–silica reaction ina short period of time, and the characteristic values and reference values indicated in the design
specifications do not reflect study results on alkali–silica reaction. In the Construction: Construction
Standards, therefore, it is assumed that the durability against alkali–silica reaction is achieved if oneof the three control measures described below is taken.
(a) Controlling the total alkali content of concrete
Portland cement, etc., whose total alkali content is indicated in test records is used so that the
total quantity of alkalis including the alkalis contained in chemical admixtures in a cubic meter ofconcrete is 3.0 kg or less (Na2O equivalent).
(b) Using blended cement with the alkali–aggregate reaction control effectType B (slag content: 40% or more) or Type C blast furnace slag cement conforming to JIS R
5211, Portland Blast-Furnace Slag Cement, or Type B (fly ash content: 15% or more) or Type C fly
ash cement conforming to JIS R 5213, Portland Fly-Ash Cement, is used; or a cementitious material
that is composed of portland cement and admixtures such as blast-furnace slag or fly ash and thathas a proven alkali–aggregate reaction control effect is used.
(c) Using aggregate rated as Category A (harmless) in alkali–silica reactivity test
Aggregate that has been rated as "harmless" in a test conducted in accordance with JIS A 1145,
Method of Test for Alkali–Silica Reactivity of Aggregates by Chemical Method, and JIS A 1146,
Method of Test for Alkali–Silica Reactivity of Aggregates by Mortar-Bar Method, is used.
If ready-mixed concrete is used, the basic rule is to take control measure (a) or control measure(b). If the intrusion of alkalis from external sources is unavoidable as in a marine environment or ina region where deicing agents are used, Category B aggregates are used, and alkali reduction
measures are taken on condition that there is little or no possibility of intrusion of alkali metal ionsfrom an external source.
(5): If it is required that chemical attack should not affect the required structural performance,
the water/cement ratio should be set at or below the levels shown in Table C4.3.1 depending on thedeterioration-causing environmental conditions in order to achieve the required chemical attack
resistance.

Table C4.3.1 Maximum water/cement ratio for ensuring chemical attack resistance
Deterioration-causing environment

Maximum water/cement ratio (%)

When in contact with soil or water containing 0.2% or more sulfate (SO4)50

When deicing agent is used

45

Note: If verification can be made by using past project data, research results, etc., a value of 5 to 10 may be added to the values
shown above.

Water-tightness includes the water-tightness of the concrete itself evaluated in terms of thepermeability coefficient and the water-tightness evaluated in terms of the permeation rate by taking
into account such factors as cracking in the structure or its members. In mix design, it is necessary
to take into account the former, namely, the water-tightness of the concrete itself. The permeability
coefficient is governed by such factors as the density of hardened cement with many fine voids,
void structure characteristics such as void continuity, and the nature of relatively rough-textured
transition zones formed around aggregate particles. In general, the void structure of hardened82

Chapter 4

Mix Design

cement is dependent on the water/cement ratio and the type of cement. In order to achieve therequired permeability coefficient, therefore, it is good practice to reduce the water/cement ratio andthereby reduce the water content so as to produce homogeneous and voidless concrete to the extent
that the filling ability suitable for concreting work can be maintained. Past research results haveshown that the water-tightness of concrete required for ordinary concrete structures can be attained
if the water/cement ratio is 55% or less.
In the case of a concrete structure that is required to be watertight, the permeability coefficientand the permeation rate are verified at the design stage. When the water/cement ratio needs to be
determined from the viewpoint of water-tightness, therefore, it may be determined on the basis of
the reference values for the water/cement ratio, cement content, type of cement, etc., indicated in
the design specifications.

4.4 Determination of Mix Requirements
4.4.1 Maximum size of coarse aggregate(1) The maximum size of coarse aggregate is determined, taking into account the sizesof structural members and reinforcing bar spacing, so that defects such as honeycombing
and incomplete filling do not occur.
(2) The maximum size of coarse aggregate shall not exceed one-fifth of the smallest
member size, three-fourths of the smallest reinforcing bar spacing and three-fourths ofthe concrete cover. The maximum size of coarse aggregate shall not exceed 20 or 25 mm
for ordinary members, 40 mm for large-cross-section members, and 40 mm or one-fourthof the smallest dimension of the member.
(3) The maximum size of coarse aggregate should be as shown in Table 4.4.1 as astandard.
Table 4.4.1 Maximum size of coarse aggregate
Structural conditions

Maximum size of coarse aggregate

If the smallest dimension of the cross section is 1,000 mm or larger andthree-fourths of the smallest reinforcing bar spacing and the concrete cover isgreater than 40 mm

40mm

In other cases

20 mm or 25 mm[Commentary] (1), (2) and (3): In general, increasing the maximum size of coarse aggregate isadvantageous in producing concrete economically. If, however, the amount of steel is large orreinforcing bar spacing is small, coarse aggregate of a large maximum size obstructs concrete flow
between reinforcing bars, causing the possibility of occurrence of defects such as honeycombing
and incomplete filling. This section, therefore, specifies the conditions to be met and indicates the
maximum sizes of coarse aggregate that are deemed appropriate judging from past project data andexperience. In the case of plain concrete, coarse aggregate of considerably larger sizes may be
usable because cross sections tend to be large. In general, however, coarse aggregate with a particle
size of around 40 mm are commonly used.

83

Standard Specifications for Concrete Structures-2007, Materials and Construction

4.4.2 Slump(1) Prior to slump determination, thorough studies shall be conducted on construction
method details such as placing locations and sites, compaction height, spacing of internal
vibrators, placing height per cycle and the placing rate so as to reduce slump as much aspractically possible.
(2) Slump shall be determined so as to prevent segregation to the extent suitable forconcreting tasks such as transportation, placing and compacting.
(3) In mix design, as the first step, the minimum slump for placement shown in Item (4)below is determined. As the next step, by using the minimum slump as a criterion, target
slumps for unloading and mixing are determined, allowing for the decrease in slump due
to on-site transportation, the change in slump during the period from production toplacement, the change in slump due to transportation to the construction site and thequality tolerance at the production stage.
(4) The minimum slump for placement is determined according to the type of structure,
the type of member, reinforcement conditions such as the amount of steel and steel
spacing, and other conditions such as compaction height by selecting an appropriate
value from Tables 4.4.2 to 4.4.6, which show slump values under different combinations ofthese conditions for different types of structural members. The term "minimum slump forplacement" refers to the minimum slump needed to place concrete smoothly andvoidlessly into the formwork.
Table 4.4.2 Typical values of minimum slump for placement of slabs
Amount of steel

Minimum steel

1)

1)

spacing

3（kg/m ）

(mm)

100 to 150

Compaction height

Placementinterval

2)

Less than 0.5 m 0.5 m to less than 1.5 m

3.0 m or less

At any location

5

7

－

2 to 3 m

－

－

10

－

－

12

100 to 150

3 to 4 m
31) The amount of steel shall be 100 to 150 kg/m , and the minimum steel spacing shall be 100 to 150 mm as
standard.
2) The drop height of concrete shall be 1.5 m or less as standard.

Table 4.4.3 Typical values of minimum slump for placement of columns
Effective equivalentCompaction heightamount of steel in the Minimum steel spacing
Less than 3 m

3 m to less than 5 m

5 m or more

50 mm or more

5

7

12

Less than 50 mm

7

9

15

50 mm or more

7

9

15

Less than 50 mm

9

12

15

1)

concrete cover zone

3

Less than 700 kg/m

3

700 kg/m or more84

Chapter 4

Mix Design

1) The effective equivalent amount of steel in the concrete cover zone is the amount of steel per unit volume in
the regions shown below.

Distance from concrete surface
to center of主鉄筋の中心までの幅
main reinforcing bar

Unit height (1 m)

単
位
高
さ
(1m)

Hoop
帯鉄筋
Main
reinforcing
主鉄筋barIntermediate
中間帯鉄筋
hoop
:１段配筋の有効換算鋼材量算出対象領域:複数段配筋の有効換算鋼材量算出対象領域: Calculation zone for effective equivalent amount of steel for single-layer reinforcement: Calculation zone for effective equivalent amount of steel for multi-layer reinforcement

Table 4.4.4 Typical values of minimum slump for concrete placement of beams
Compaction height

Minimum steel spacing

1)

Less than 0.5 m

0.5 m to less than 1.5 m

1.5 m or more

150 mm or more

5

6

8

100 mm to less than 150 mm

6

8

10

80 mm to less than 100 mm

8

10

12

60 mm to less than 80 mm

10

12

14

Less than 60 mm

12

14

16

1) Examples of members for which different compaction heights are used•

Less than 0.5 m: small beams, etc.
0.5 m to less than 1.5 m: standard beams
1.5 m or more: deep beams, etc.

•

The minimum slump for placement is selected according to whether it can be judged that adequate
compaction can be done by inserting bar-shaped vibrators about 40 mm in diameter.
(i) If it is judged that adequate compaction can be done, a minimum slump for placement of 14 cm is used.
(ii) If it is judged that adequate compaction cannot be done, high-fluidity concrete is used.

•

If slump exceeds 21 cm, high-fluidity concrete should be used in order to achieve the required segregation
resistance and place concrete voidlessly.

Table 4.4.5 Typical values of minimum slump for concrete placement of walls
Amount of steel

Minimum steel spacing

Compaction heightLess than 3 m

3 m to less than 5 m

5 m or more

100 mm or more

8

10

15

Less than 100 mm

10

12

15

100 mm or more

10

12

15

less than 350 kg/m

Less than 100 mm

12

12

15

3

－

15

15

15

3

Less than 200 kg/m
3

200 kg/m to3

350 kg/m or more

85

Standard Specifications for Concrete Structures-2007, Materials and Construction

Table 4.4.6 Typical values of minimum slump for concrete placement of prestressed
concrete members
Type of structure

1)

Average amount of reinforcing steel

Design strength

Minimum slumpof concrete

for placement

3Less than 120 kg/m (reinforced
2)

concrete equivalent : less than about

7

3

250 kg/m )3

120 kg/m to less than 140 kg/m

3

2)

(reinforced concrete equivalent : about

93

250 to less than 300 kg/m )3

140 kg/m to less than 170 kg/m

3

2)

(reinforced concrete equivalent : about

36 or 4012

3300 to less than 350 kg/m )3

3)

Girder of prestressed concrete
superstructure tensioned mainly withinternal tendons

170 kg/m to less than 200 kg/m

3

2)

(reinforced concrete equivalent : about

15

3350 to less than 400 kg/m )3

200 kg/m or more (reinforced concrete
2)

－

3

equivalent : about 400 kg/m or more)
3

Less than 170 kg/m (reinforced
2)

concrete equivalent : less than about

123

350 kg/m )3

170 kg/m to less than 200 kg/m

3

2)

(reinforced concrete equivalent : about

50

15

3

350 to less than 400 kg/m )3

200 kg/m or more (reinforced concrete
2)

－

3

equivalent : about 400 kg/m or more)
Cross beams and unsupported floorslabs of a T-girder bridge
Unsupported floor slabs other thanthose mentioned above

-

30

7

-

30

5

－

－

3

Members including densely reinforced 300 kg/m or more (reinforced concrete
regions4)2)3equivalent : about 500 kg/m or more)

1) The average amount of reinforcing steel is a value obtained by dividing the amount of reinforcing steel in asection in which concrete is placed continuously by the volume of concrete.
2) The reinforced concrete equivalent amount of reinforcing steel is a reference value calculated by assuming thatthe entire cross section of the sheath is equivalent to reinforcing steel.
3) Girders include the superstructure of a hollow slab bridge. Prestressed reinforced concrete bridges are notincluded in the table. Since it is difficult to determine the standard value, the amount of prestressing steel isrelatively small compared with the amount of reinforcing steel.
4) "Densely reinforced regions" are regions where the amount of reinforcing steel is particularly large such as
anchorage zones of cable stayed bridges and structures prestressed with external tendons.

(5) When a number of concrete members can be cast separately, the minimum slump
for placement shall be specified for each member. If it is not possible to change slumps
during the placement process as when a number of members are to be cast consecutively,
the method of using the largest of the minimum slump values required for placement
should be used as a standard.
(6) When concrete to be placed is pumped for on-site transportation, slump loss under
different conditions such as the pumping conditions, minimum slumps and theenvironmental conditions shown in Table 4.4.7 shall be considered.

86Chapter 4

Mix Design

Table 4.4.7 Typical slumps under different conditions
Construction conditions

Slump loss

Pumping distance

When the minimum slump is

When the minimum slump is(equivalent horizontal distance)

smaller than 12 cm

12 cm or greater

―

―

1 cm

―

2 cm to 3 cm

1 cm

Less than 150 m(including placement by bucket, etc.)
150 m to less than 300 m
300 m to less than 500 m
500 m or more

To be determined on the basis of past project data or field trial results

For reference, when daily average temperature exceeds 25°C (during summer), it is recommended that 1 cm
be added to each of the values shown above.

[Commentary] (1) and (2): When determining slump requirements, it is necessary to take into
account not only structural conditions such as the type and dimensions of the member concerned
and the arrangement of reinforcing materials (reinforcing bars and other steel) but also construction
conditions such as on-site transportation methods (type of concrete pumper, pumping distance,
piping direction), concrete placement methods (drop height, height of each layer of concrete to beplaced) and compaction methods (type of internal vibrator, vibrator spacing, insertion depth,
vibration time). The basic rule is to minimize slump of the concrete being placed to the extent thatworkability requirements can be met. It is important to carefully consider construction methods
such as concrete placement methods (drop height, height of each layer to be placed) and compaction
methods (compaction height, type of internal vibrator, vibrator spacing, insertion depth, vibrationtime).
(3): The slump and other properties of fresh concrete continue to change throughout the processfrom the transportation from the concrete plant to the construction site, on-site transportation,
placement and compaction. In order to achieve smooth and complete filling, it is important to makesure, in view of the changes during these stages of construction work, that appropriate filling ability
is retained at the stages of placement and compaction. The Construction: Construction Standards,
therefore, first defines the minimum slump necessary at the time of placement and requires that atarget slump to be used for quality control at the unloading location and a target slump uponcompletion of mixing (production) to be used for quality control at the production stage be specified
as criteria for the minimum slump.
Slumps at the placement, unloading and production stages determined in mix design aredetermined, in view of the occurrence of slump changes as shown in Fig. E4.4.2, by following theprocedure described below (Fig. C4.4.1).
Step 1: Determine minimum slump for placement
Select the minimum slump needed to fill the formwork reliably and completely according to thestructural conditions such as the type of member, the amount of reinforcing steel and reinforcing bar
spacing and the construction conditions such as compaction height (see Table 4.4.2 to Table 4.4.6).
Step 2: Determine target slump at unloading location
Determine a target slump at the unloading location on the basis of the minimum slump forplacement in view of the slump loss during on-site transportation such as pumping, changes inslump due to the passage of time during the process from unloading to placement, and quality
variation at the production stage. As for JIS-certified articles, as a standard procedure, the quality
control and acceptance inspection of concrete are performed with respect to this target slump at theunloading location.
87

Standard Specifications for Concrete Structures-2007, Materials and Construction

The slump loss (compensation) due to on-site transportation such as pumping is selected from
Table 4.4.7 (shown below) according to the construction conditions such as pumping distance. The
amount of quality variation at the production stage is determined appropriately according to theconditions of the production equipment and the quality control within the allowable ranges (2.5 cm
for 8 to 18 cm slump; 1.5 to 2 cm for 21 cm slump) for JIS-certified articles. Changes in slump dueto the passage of time during the process from unloading to placement are estimated from past
project data or time-dependent changes observed during trial mixing mentioned in Section 4.7.
However, the decrease in slump over time during the period of time necessary for construction work
should be minimized. It is therefore important to select mix proportions, at the trial mixing stage,that make it possible to retain the required slump by, for example, using appropriate chemical
admixtures.
Step 3: Determine target slump for freshly mixed concrete
Determine a target slump for freshly mixed concrete, taking into account the decrease in slump
due to off-site transportation to the unloading location. A rule of thumb about the relationshipbetween the time required for transportation to the construction site and slump is that the amount ofdecrease in slump during spring and autumn is about 1 cm per 30 minutes of transportation. In
winter, the slump loss due to an increase in transportation time is low, and the slump loss is about 1
to 1.5 cm per 60 minutes of transportation. However, during summer (hot weather), the concrete
shall be taken care, because the slump loss over time tends to be higher (about 1.5 cm per 30
minutes of transportation).

Step 1
手順１

Minimumslump for placement
打込みの最小スランプ

To部材の種類，鉄筋量や鉄筋間隔等に基づき，表4.4.2～表4.4.6
be determined according to Tables 4.4.2 to 4.4.6 on the basis of conditions such as
theより定める
type of member, the amount of reinforcing steel and reinforcing bar spacing

Variability
during the production process from unloading to placement and the amount
荷卸しから打込みまでの製造のばらつきや現場内の運搬におけるスランプがofdecrease in slump due to on-site transportation are allowed for.
低下する分を見込む
Step 2
手順２

Target slump for unloading
荷卸しの目標スランプ

Value
obtained by adding the amount of decrease in slump (see Table 4.4.7) due to
打込みの最小スランプ（手順１）に，荷卸し箇所から打込みまon-sitetransportation from the unloading location
to the placement location and a
での現場内運搬によるスランプの低下（表4.4.7参照）,さらに
slump
tolerance at the unloading location to the minimum slump for placement (Step 1)
荷卸し箇所におけるスランプ管理幅（許容差）を加えた値

The amount of decrease in slump due to transportation from an off-site plant to the
工場から現場荷卸しまでの運搬においてスランプが低下する分を見込む
unloadinglocation at the construction site is allowed for.
Step 3
手順３

Targetslump upon completion of mixing
練上りの目標スランプ

荷卸しの目標スランプ（手順２）に，現場プラントあるいはレValueobtained by adding the slump loss due to transportation from an on-site plant or
ディーミクストコンクリート工場から工事現場までの場外運搬
off-sitetransportation from a ready-mixed concrete plant to the target slump for
によりスランプが低下する分を加えた値
unloading(Step 2)：スランプ設定の流れ
flow of slump determination
movement of concrete：コンクリートの移動

Fig. C4.4.1 Flow chart for slump determination at different stages

88Chapter 4

Mix Design

In mix design, it is a basic rule to secure the required minimum slump for placement so as toachieve good filling ability. If, however, a large amount of decrease in slump is expected because
the construction tasks such as the transportation to the construction site and a series of tasks from
unloading to placement are time consuming or if slump loss due to pumping is expected, it may benecessary to set a target slump at the unloading location or upon completion of mixing that is larger
than the target slump. In such cases, simply increasing the slump at the unloading location or uponcompletion of mixing might cause segregation during production or off-site transportation, resulting
in not only quality control and acceptance inspection problems at the unloading location but also
clogging of piping during pumping. In order to prevent these problems, mix proportions may be
adjusted so that the concrete has good workability at the target slump at the unloading location.
The same mix-design procedure may be used in cases where ready-mixed concrete is used. As
the first step, the minimum slump for placement is determined, and the target slump upon unloading
is determined so that the minimum slump for placement can be achieved. This target slump upon
unloading is used as the specified slump for ready-mixed concrete. A simple method for specifying
this target slump upon unloading for JIS-certified items is described in JSCE's Recommendations
for Design and Placement of Concrete Based on Placeability.

89

Standard Specifications for Concrete Structures-2007, Materials and Construction
Step 1
手順１
Slump
スランプ

Determinedon the 4.4.6
basis of
表 4.4.2～表
Tables
4.4.2 to 4.4.6に基づいて設定

Minimum
slump
打込みの
for
placement
最小スランプ圧
打On-site送 ⇒現場内での運搬⇒
込⇒開 ⇒ Transportation（ポンプ圧送）み(pumping)
始Placement

Start of pumping

site

UnloadingCompletion of
mixing荷練上 Transportation⇒現場までの⇒ 卸⇒しり ⇒to construction
運搬

Duration
作業の流れ
in terms of work

Step 2
手順２

Slump
スランプ

Target slump at
unloading
荷卸し箇所のlocation
目標スランプ

品質の許容差Qualitytolerance

品質のばらつきQualityvariation

経時にともなうスランプ低下Slump loss over timeSlumploss due to on-site
現場内運搬(ポンプ圧送)transportation(pumping)にともなうスランプ低下(See（表Table4.4.7参照）
4.4.7.)

Minimum
slump
打込みの
for
placement
最小スランプPlacement

圧
打On-site送 ⇒現場内での運搬⇒
込transportation
開 ⇒（ポンプ圧送） ⇒ み(pumping)
始Start of pumping

site

UnloadingCompletion of
mixing練荷上 ⇒現場までの⇒Transportation 卸⇒しり ⇒to construction
運搬

Duration
作業の流れ
in terms of work

Step 3
手順３

Slump
スランプ
Target slump
練上りのupon completionof目標スランプmixingSlumploss due to
現場までの運搬によるスランプ低下
transportation
to jobsite

Targetslump at
荷卸し箇所の
unloading
目標スランプlocation

品質のばらつきQualityvariation

Qualitytolerance
品質の許容差経時にともなうSlumploss over time
スランプ低下Slumploss due to on-site
現場内運搬(ポンプ圧送)transportation(pumping)にともなうスランプ低下

Minimum
slump
打込みの
for
placement
最小スランプPlacement

圧
打On-site送 ⇒現場内での運搬⇒
込transportation
開 ⇒（ポンプ圧送）
み(pumping)
始Start of pumping

site

UnloadingCompletion of
mixing練荷上 ⇒現場までの⇒Transportation 卸⇒しり ⇒to construction
運搬

Duration
作業の流れ
in terms
of workFig. C4.4.2 Changes in slump over time at different stages of construction(4): In order to construct a highly durable and densely cast concrete structure, it is necessary toprovide concrete with workability suitable for the structural conditions. The Construction:
Construction Standards shows typical values of the minimum slump for placement suitable for the
structural conditions for different types of structure or member. Tables 4.4.2 to 4.4.6 show typical
90

Chapter 4

Mix Design

minimum slumps needed at the placing location for different types of structural members
determined on the basis of past construction experience, etc., on condition that standard
construction methods shown in Table C4.4.1 are practiced. From this table, standard values of theminimum slump for placement can be selected according to the structural conditions of the structure
to be constructed.
Table C4.4.1 Standard construction methods specified in the construction: construction
standards of this specification
Task category
Transportation

Placement

Item
Transportation to construction site

Agitator

On-site transportation

Concrete pump

Dropping height

Within 1.5 m

Placing height per layer

40 to 50cm

Allowable
placement interval

Compaction

Standard method

Outdoor air temperature: 25°C or below

2.5 hours

Outdoor air temperature: higher than 25°C

2.0 hours

Compaction method

Internal vibrator

Vibrator spacing

About 50 cm

Vibrator depth

About 10 cm in the underlying layer of concrete

Vibration time per point

5 to 15 sec

In the Construction: Construction Standards, compaction height, which is related to the degreeof ease/difficulty of compaction, and placing height, which is a widely used term, are distinguished.
As shown in Fig. C4.4.3, "compaction height" is defined as the height from the working platform on
which construction workers stand to the lower end of the formwork or the upper surface ofpreviously cast concrete layer. If concrete is placed continuously and compaction is performed
while moving upward as the height of newly placed concrete increases, the distance from the moved
working platform to the surface of the previously placed concrete is the compaction distance.

締固め

Compaction
height
作業高さ

先行層

Previously placed layer

Compaction height

締
固
め
作
業
高
さ
先行層
Previouslyまたはorplaced既設部
existing
layer

Example:Beam例）はり部材Compaction height例）スラブ部材
Example: Slab

締
固
め
作
業
高
さ

例）柱部材
Example:ColumnExample:Wall (compaction in the wall)
例）壁部材（部材内での締固め）

Fig. C4.4.3 Examples of compaction height
91

Compaction height

締
固
め
作
業
高
さ

Standard Specifications for Concrete Structures-2007, Materials and Construction(5): The minimum slump for placement is determined for each type of member. The use ofdifferent types of concrete mixes with different slumps, however, when different types of members
such as columns, beams, walls and slabs are cast continuously would make construction work andmanagement cumbersome and lower construction efficiency. A rational approach in such cases is toselect concrete mixes suitable for members that are relatively difficult to construct and require
relatively large minimum slumps for placement. It is important, however, to carefully consider inadvance whether problems can be prevented by modifying concreting-related arrangements such asconcrete placement and compaction methods.
(6): In order to keep the performance of fresh concrete necessary for placement, it is necessary
to predict changes in concrete quality due to the influence of pumping conditions andenvironmental temperature and allow for such changes in determining slump requirements. Typicalchanges in slump corresponding to different construction conditions such as pumping conditions areshown in Table 4.4.7. If relevant information such as past construction records and pumping test
results is available, slump requirements should be determined on the basis of such information.

4.4.3 Required strength(1) The required strength of concrete is determined in view of the specified strengthand the variability of concrete quality at the construction site.
(2) The required strength f'cr of concrete is determined so that the probability that ameasured value of the compressive strength of concrete obtained as an on-site test resultis smaller than the specified strength is 5% or less.

[Commentary] (1): Usually, the quality of concrete at a construction site varies during theconstruction period depending on such factors as changes in the quality of aggregate, cement, etc.,
measuring errors and changes in the way concrete ingredients are mixed. The required strength of
concrete, therefore, needs to be made higher than the specified strength according to the variabilityof concrete quality at the construction site, in order to ensure that the compressive strength of
concrete in any part of the structure is not lower than the compressive strength assumed when
designing the structure. The required strength of concrete needed relative to the specified strength isusually determined in accordance with the conditions described in Item (2).
(2): This clause describes the compressive strength requirements for test specimens to be used toachieve the specified strength of concrete. Inevitably, measured values of the compressive strengthof concrete vary to some extent depending on changes in the quality of cement, aggregate, etc.,
measuring errors, differences the conditions under which mixing and other tasks are performed, test
errors, etc. It is known from experience that variations in the compressive strength of concrete
under ordinary quality control conditions are more or less distributed normally. Assuming astochastic distribution, therefore, this guideline requires the probability that a measured value of thecompressive strength of concrete used for an ordinary structure is smaller than the specified strength
be 5% or less. A measured value of the compressive strength of concrete obtained as an on-site test
result is the average value of compressive strength obtained through standard curing of threeconcrete specimens sampled at the construction site.
In order to ensure that the probability that a measured value of compressive strength is smaller
than the specified strength is not higher than a predetermined percentage, it is necessary to select astrength value obtained by increasing the specified strength appropriately according to the variation
92

Chapter 4

Mix Designin measured values of compressive strength as a required strength. Fig. C4.4.4 shows therelationship between the coefficient of variation and the overdesign factor in the case in which thepredetermined percentage mentioned above is 5%. A recommended standard procedure is todetermine the overdesign factor corresponding to the coefficient of variation in the compressive
strength of concrete at the construction site from the figure mentioned above. After that, theoverdesign factor and the specified strength or an appropriate value are selected, and it should not
be smaller than the required strength of that structure.
In the case of concrete to be used for a very important structure, the abovementioned
predetermined percentage should be reduced to a smaller value, and another overdesign factor
determined from that percentage and the coefficient of variation in compressive strength should be
used.
As mentioned above, in order to determine the required strength of concrete, it is necessary tofind out the coefficient of variation of measured compressive strengths of concrete at theconstruction site and determine the overdesign factor accordingly. This value should be determinedby past experience, equipment at the construction site, variations in the quality of the materials used,
the skill levels of construction workers, etc. At early stages of construction, however, it is notuncommon that it is difficult to estimate the coefficient of variation appropriately because there isdearth of information on the equipment at the construction site, variations in the quality of materials,
etc. An appropriate method to be used in such cases is to determine the required strength by using asomewhat larger overdesign factor. After concrete work is started, the required strength can be
modified according to the actual coefficient of variation.

93

Standard Specifications for Concrete Structures-2007, Materials and Construction
1.7

Overdesign
factor
割増し係数
αα

1.6

α＝1/（1-1.645Ｖ/100）
4.4.3（2）の条件
Condition
indicated in 4.4.3 (2)

1.5
1.4
1.3
1.2
1.1
1.0
5

10

15

20

25

Expected予想される圧縮強度の変動係数
coefficient variation in compressive strength,
V（％） V (%)

Fig. C4.4.4 Overdesign factor in a normal case

4.4.4 Water/cement ratio(1) The water/cement ratio is determined by selecting the smallest values determined inview of the strength, durability, water-tightness, cracking resistance and steel protection
performance required of concrete on the basis of the reference values indicated in thedesign specifications.
(2) When the water/cement ratio is determined on the basis of the compressive
strength of concrete, it is determined as follows:(a) As a general rule, the relationship between compressive strength and thewater/cement ratio shall be determined experimentally. The testing age is 28 days as
standard. Other testing ages, however, may be used depending on the type of cement to
be used if high-early-strength cement is used or if low-heat cement is used for the
purpose of thermal stress control.
(b) The water/cement ratio to be used for mix proportion shall be the reciprocal of thecement–water ratio corresponding to the required strength f'cr in the relationship between
the cement/water ratio (C/W) and compressive strength f'c at the reference age.
(3) In cases where the water/cement ratio is determined in view of the durability ofconcrete against carbonation, chloride attack and freeze–thaw cycles, the water/cement
ratio is determined so that it is not greater than the reference values indicated in thedesign specifications.
(4) In cases where the water/cement ratio is determined in view of the durability ofconcrete against chemical attack, the water/cement ratio shall be determined on the basis
of Table E4.3.1. The water/cement ratio in the case where water-tightness is taken into
account should be set at 55% or less as a standard.

[Commentary] (1): The water/cement ratio to be used shall be the smallest among thewater/cement ratios determined from the required strength, durability, water-tightness, cracking
resistance and steel protection performance of concrete. Under normal conditions, the water/cement
ratio determined taking the abovementioned factors into account rarely exceeds 65%. Since,
94

Chapter 4

Mix Design

however, many of the problems encountered in the past occurred in structures built with concretewith a water/cement ratio exceeding 65%, it is a basic rule to specify a water/cement ratio of 65%
or less. When determining the water/cement ratio for concrete to be used for offshore structures, theConstruction: Special Concretes (Chapter 11, Offshore Concrete) of this Specification should be
used as a guide.
The water/cement ratio is to be determined on the basis of the reference values indicated in thedesign specifications such as the upper and lower limits or range of the water/cement ratio, thecement content and the type of cement. If it is judged that these values and ranges are not adequate
because of the quality of the materials to be used, the system for supplying materials or otherfactors, it is necessary to select an appropriate realistic value after ascertaining that thecharacteristic value requirements specified in the design specifications are met.
(2) (a): The fact that the cement/water ratio (C/W) and compressive strength (f'c) are linearly
related within a certain range can be used to determine the relationship between the compressive
strength of concrete and the water/cement ratio. A universal linear formula applicable to any type ofmaterial, however, has not yet been derived for determining the relationship between the
cement/water ratio and compressive strength. As a general rule, therefore, this specification requiresthat the relationship between the compressive strength of concrete and the cement/water ratio be
determined experimentally.
The C/W–f'c relationship is determined as follows:
Three or more types of concrete mixes with different cement/water ratios are tested within arange that is deemed appropriate to derive C/W–f'c curves. In the case of air-entrained concrete, test
specimens are prepared by using concrete mixes with the required air content.
In order to minimize errors in mix tests, the average value for specimens prepared from two or
more batches of concrete should be used as the value of f'c for each C/W. If a mineral admixture
that can be expected to act as a binder such as ground granulated blast furnace slag or fly ash is used,
the numerator of C/W may be taken as the sum of the mass of the cement and the mass of the
admixture.
In the case of air-entrained concrete, the relationship between C/W and f'c varies depending on
the air content, but if the air content remains constant, the relationship between C/W and f'c can beapproximated by a linear equation.
In the cases where the specified strength age is not 28 days and where mix proportions need to
be determined early and the 28-day strength and the relationship with the strength at that age isknown, the water/cement ratio may be determined by using a reference age other than 28 days.
If the relationship between the cement/water ratio and the compressive strength at the age of 28days has been fully ascertained, the abovementioned tests may be downscaled or omitted.
(2) (b): If homogeneous concrete is to be made, it is necessary to use homogeneous materials,
measure them accurately and mix them sufficiently. Even if these tasks are performed, however, thevariation in the quality of concrete is inevitable. In order to ensure the level of safety considered at
the structural design stage, therefore, it is necessary to determine a required strength value by
increasing the specified strength according to the variation as a compressive strength value needed
when the relationship between the cement/water ratio and compressive strength mentioned in Item(a).
(3): In the cases where the durability of concrete against carbonation, chloride attack andfreeze–thaw cycles must be taken into account for design purposes, verification is made as95

Standard Specifications for Concrete Structures-2007, Materials and Construction

described in the Design: General Requirements (Chapter 8, Verification of Durability) of thisSpecification, and the necessary upper limit of the water/cement ratio is indicated in the design
specifications as reference values. It is necessary, therefore, to determine the water/cement ratio sothat the value is not exceeded. When a high-quality mineral admixture is used appropriately, thedenominator of the water/cement ratio needed from the viewpoint of durability may be taken as thesum of the mass of cement and the mass of the admixture (binder content).
(4): When coming into contact with soil or water containing a substantial quantity of sulfate,concrete is eroded by chemical reaction. The aim of this clause is to ensure that strong and voidlessconcrete that is highly durable against such chemical reaction can be obtained.

4.4.5 Air content in air-entrained concrete(1) The air content in air-entrained concrete should be 4 to 7% of the concrete volume
depending on the maximum size of coarse aggregate and other conditions as a standard.
(2) Air content tests for concrete shall be conducted in accordance with JIS A 1116, JIS
A 1118 or JIS A 1128.

[Commentary] (1): Concrete with an appropriate amount of entrained air is highly durable
against freeze–thaw cycles. As a general rule, therefore, air-entrained concrete shall be used in cases
where concrete is to be subjected to severe weather conditions. It is common practice to specify astandard air content of about 4 to 7% of the concrete volume upon completion of mixing. The aircontent during the production process shall be determined in view of time-dependent changes
during the process from production to placement and changes during transportation.
Entrained air is highly effective in improving the workability of concrete. By using air-entrained
concrete, therefore, the water content needed to achieve the required level of workability can be
reduced substantially. The strength of concrete, however, decreases as the air content increases, andthe variability of concrete quality tends to increase as the air content increases. It is advisable,
therefore, not to increase the air content excessively if weather conditions are not severe.
The air content of air-entrained concrete varies considerably depending on various conditions
even if the air entraining agent content remains unchanged. An air content test shall be conducted,
therefore, prior to the placement of air-entrained concrete.
(2): Air content tests may be conducted by the mass method (JIS A 1116), the volumetricmethod (JIS A 1118) or the pressure method (JIS A 1128).

4.5 Determination of Provisional Mix Proportions
4.5.1 Water content(1) The water content is determined experimentally and be made as low as possible tothe extent that concreting tasks can be performed.
(2) The upper limit of the water content of concrete should be 175 kg/m3 as a standard.
If the water content exceeds this upper limit, it shall be ascertained that the required
durability is attained.
96Chapter 4

Mix Design[Commentary] (1): A higher water content tends to result in a degradation in the quality ofconcrete such as a degradation in segregation resistance and an increase in drying shrinkage. It istherefore necessary to make the water content as low as possible to the extent that concreting tasks
can be performed. Because the water content of concrete needed to achieve the required slump
differs depending on such conditions as the maximum size of coarse aggregate, the particle size
distribution and particle shape of aggregate, the type of admixture, and the air content of concrete,
this Specification requires that the water content be determined through trial mixing by use ofmaterials to be actually used for construction.
The water content can be reduced considerably by making appropriate use of air-entraining
agents, air-entraining water-reducing agents, superplasticizer, etc. The percentage of water
reduction, which varies depending on the air content, the type of admixture, concrete mix
proportions, etc., is about 6 to 10% for air-entraining agents conforming to JIS A 6204, Chemical
Admixtures for Concrete; 10 to 14% for standard-type or retarder-type air-entraining
water-reducing agents; 8 to 12% for accelerator-type agents; and 16 to 20% for superplasticizer. The
water content in the case where crushed stone or blast furnace slag coarse aggregate is used is about
10% higher than in the case where gravel is used although it varies depending on the shape ofparticles.
(2): Because the water content greatly affects the quality and durability of concrete, thisSpecification requires that the water content be specified at or below the upper limit of 175 kg/m3 asstandard. In this Specification, the water content of concrete refers to the water content specified at
the mix design stage. It does not mean, therefore, that the upper limit of the water content reflecting
the quality variations in actual construction work is 175 kg/m3.
If the water content of concrete containing an air-entraining water-reducing agent exceeds 175
kg/m3, a superplasticizer instead of an ordinary air-entraining water-reducing agent should be used
so that the water content becomes 175 kg/m3 or less. In the case of plain concrete, however, or in
the case where it can be ascertained that the durability of concrete will not be adversely affected, awater content higher than 175 kg/m3 may be adopted.
The lower limit of the water content is not specified, but a water content should be 145 kg/m3 or
higher when using crushed stone or crushed sand. Table C4.5.1 shows the recommended ranges of
the water content. If the water content of ordinary concrete deviates from the ranges shown in Table
C4.5.1, appropriate actions such as using a high-performance water-reducing admixture such as an
air-entraining water-reducing agent or super plasticizer should be taken. In the case of concrete
whose fluidity is evaluated in terms of slump flow such as high-fluidity concrete, too, the watercontent should be determined with reference to the ranges shown in Table C4.5.1.
Table C4.5.1 Recommend ranges of the water content of concrete
Maximum size of coarse aggregate (mm)Range of water content (kg/m3)

20 to 25

155 to 175

40

145 to 165

4.5.2 Cement content
The cement content shall be determined on the basis of the reference values indicatedin the design specifications. If an upper or lower limit is specified for the cement content,
that specification shall be met.
97

Standard Specifications for Concrete Structures-2007, Materials and Construction[Commentary] The cement content shall be determined on the basis of the reference values
indicated in the design drawings and specifications. If an upper or lower limit is specified for the
cement content, it shall be ascertained that the cement content determined from the water content
and the water/cement ratio falls between the upper and lower limits specified for the water content.
If it does not fall within the range between the upper and lower limits, it is necessary to change thematerials used or the mix proportion. In the case of concrete made by using a superplasticizer, and if
the cement content is too small, it tends to result in poor workability and a degradation in slump
over time increases. It is recommended, therefore, that if the maximum size of coarse aggregate is
20 to 25 mm, a cement content of at least 270 kg/m3 (250 kg/m3 if the maximum size of coarse
aggregate is 40 mm) and preferably 300 kg/m3 or more be secured.
By increasing the cement content, the cracking due to hydration of cement may cause theproblem. To solve this problem, the chemically-inactive powder, such as limestone powder, can beapplied. In the case of mass concrete, which is subject to cracking due to the hydration of cement, itis necessary to determine an appropriate cement content with reference to Chapter 14, Mass
Concrete. If the cement content does not fall within the upper and lower limits indicated in thedesign specifications or if the type of cement to be used is changed, verification needs to be
conducted again concerning cracking due to the hydration of cement.
The cement content of offshore concrete and underwater concrete shall be determined as
stipulated in the Construction: Special Concretes (Chapter 10, Underwater Concrete, and Chapter
11, Offshore Concrete) of this Specification.

4.5.3 Powdery material content(1) The powdery material content is determined so that segregation resistanceappropriate for the slump can be attained.
(2) The powdery material content is determined within the range appropriate forpumping and placement.
(3) If a lower or upper limit is specified for the powdery material content, all of suchspecifications shall be met.

[Commentary] (1): "Powder" is a collective term for any material with a fineness equivalent or
higher than that of cement including not only cement but also blast furnace slag, fly ash, silica fumeand limestone powder. The powdery material content (hereinafter powder content) is the sum of thecontents of those powdery materials, and the powder content is a primary mix design factor
affecting the segregation resistance of concrete. If only cement (including blended cement) is used,
the powder content is the same as the cement content.
Concrete ingredients are prone to segregation if a powder content appropriate for slump is notsecured, and an inappropriate powder content may result in defects at the construction stage such as
honeycombing and incomplete filling. In order to achieve excellent pumpability and placeability,
therefore, it is recommended that a powder content of at least 270 kg/m3 be kept if the maximum
size of coarse aggregate is 20 to 25 mm (at least 250 kg/m3 if the maximum size of coarse aggregate
is 40 mm) and preferably a powder content of 300 kg/m3 or more be secured in order to ensure
construction safety. The fine grains contained in aggregate are not taken into consideration here. An
excessively high fine grain content of aggregate, however, may result in excessively viscosity ofconcrete so that workability declines. If, therefore, the fine grain content of the aggregate to be usedis high, the powder content is reduced on as-needed basis.
98

Chapter 4

Mix Design

It is recommended that when determining a rough level of the powder content appropriate forthe specified slump, Chapter 2 of JSCE's Recommendations for Mix Design and Construction ofConcrete Based on Placeability be used as a guide.
(2): In order to perform smooth, clogging-free pumping, it is necessary to keep the powder
content at or above a certain level.
(3): If the design specifications indicate an upper or lower limit of the cement content, it isnecessary to compare that upper or lower limit with the powder contents determined as described in
Items (2) and (3) above and determine the powder content so that both requirements are met. If it isjudged that meeting both requirements is not possible, the materials or mix proportions to be usedneed to be changed.

4.5.4 Sand-aggregate ratio
The sand-aggregate ratio is determined experimentally so that the water content canbe made as small as possible to the extent the required workability can be attained.

[Commentary] In the mix design of concrete, an appropriate sand percentage shall be selected. In
general, as the sand-aggregate ratio is reduced, the water content needed to obtain concrete with therequired slump tends to decrease so that the cement content decreases accordingly and the mix
proportion becomes more economical. If the sand percentage is reduced excessively, the resultant
concrete may tend toward segregation, so it may cause poor workability of concrete. For a given
combination of fine aggregate and coarse aggregate, there is an optimum sand percentage thatprovides the required workability and minimizes the water content. Because this sand percentage
varies depending on the particle size distribution of fine aggregate, the air content of concrete, thecement content, the type of mineral admixture, etc., the sand percentage needs to be determined sothat the water content is minimized. It shall be kept in mind that the sand percentage is thepercentage by absolute volume, not by mass, of fine aggregate in total amount of aggregate inconcrete.
The particle size distribution of aggregate should remain stable throughout the construction
period. If the fineness modulus has deviated by 0.20 or more from that of the fine aggregate actuallyused for mix proportion during construction, workability is also affected considerably. In such cases,
the mix proportions need to be modified. On such occasions, the validity of sand percentage values
should also be verified by testing.
In the case of concrete pumping, it is necessary to select an appropriate sand percentage, on thebasis of available data and past construction data, according to concrete pump performance, piping,pumping distance, etc. If superplasticized concrete is used, the sand percentage needs to be
determined taking into account the workability of superplasticized concrete (see Recommended
Practice for Concrete Containing Superplasticizers).
In the case of concrete containing a superplasticizer, a satisfactory result can often be obtainedby using a sand percentage that is 1 to 2 percent higher than that of concrete that contains an
ordinary air-entraining water-reducing agent and has the same water/cement ratio and slump (seeRecommended Practice for Concrete Containing Air-Entraining High-Range Water-Reducing
Agents).
The percentages of fine aggregate (sand) and coarse aggregate may be determined on the basisof the unit mass of coarse aggregate instead of the sand percentage as mentioned above. If slump islarge, the relationship between the sand percentage and workability tends to become unclear. There99

Standard Specifications for Concrete Structures-2007, Materials and Construction

are cases, therefore, where appropriate mix proportions can be better selected by determining theunit mass of coarse aggregate first. By using this method, in the case of plastic concrete, the bulk
volume of coarse aggregate per cubic meter of concrete (unit bulk volume of coarse aggregate) canbe made nearly constant, regardless of slump and the water/cement ratio, according to the
maximum size of coarse aggregate and the particle size distribution of fine aggregate so that thecoarse aggregate content can be determined easily even when using angular aggregate such as
crushed stone.
Table C4.5.2 shows typical values of the unit bulk volume of coarse aggregate, the sandpercentage and the water content for concrete with a water/cement ratio of about 55% and a slumpof about 8 cm. When air-entrained concrete is used in ordinary reinforced concrete construction, aconcrete mix obtained from the unit bulk volume of coarse aggregate tends to contain a somewhathigh percentage of sand. Table C4.5.3 shows approximate amounts of correction for the sandpercentage and the water content in the cases where the materials used and concrete quality shownin Table C4.5.2 are changed. In general, as the sand percentage decreases and the coarse aggregate
content increases, the workability of concrete such as pumpability and void-penetrating ability
decreases. It is necessary, therefore, to select appropriate minimum values of the sand percentage
and appropriate maximum values of the coarse aggregate content appropriate for the specified
slumps. When determining a sand percentage or coarse aggregate content appropriate for a slump, it
is recommended that Table C4.5.2 and Table C4.5.3 and Chapter 4 of JSCE's Recommendations forMix Design and Construction of Concrete Based on Placeability be used as guides.

Table C4.5.2 Approximate values of the unit bulk volume of coarse aggregate, sand percentage
and water content of concrete
Air-entrained concrete
Maximum size

Unit bulkof coarse

volume of coarse

aggregate

aggregate

With air-entraining agent
Air content

With air-entraining
water-reducing agent

Sand percentage

Water content

Sand percentage

Water content

s/a

W

s/a

W

(mm)

(m3/m3)

(%)

(%)

(kg)

(%)

(kg)

15

0.58

7.0

47

180

48

170

20

0.62

6.0

44

175

45

165

25

0.67

5.0

42

170

43

160

40

0.72

4.5

39

165

40

155

The values shown above are average values determined with reference to the standard mix proportions adopted by ready-mixed
concrete industrial associations in Japan and are for concrete made by using sand of an ordinary particle size distribution (finenessmodulus: about 2.80) and crushed stone.

100Chapter 4

Mix Design

Table C4.5.3 Approximate amounts of correction for the sand percentage and the watercontent due to variations in the quality of materials used or concrete
Category
For every 0.1 in fineness modulus of sand greater

Correction of s/a (%)

Correction of W

Increase (decrease) by 0.5.

No correction

No correction

Increase (decrease) by 1.2%.

Decrease (increase) by 0.5 to 1.

Decrease (increase) by 3%.

Increase (decrease) by 1.

No correction(smaller) than reference value
For every 1 cm in slump greater (smaller) than referencevalue
For every 1% in air content higher (lower) thanreference value
For every 0.05 in water/cement ratio higher (lower) thanreference value
For every 1% in s/a higher (lower) than reference value
When river gravel is used―
Decrease by 3 o 5.

Increase (decrease) by 1.5 kg.
Decrease by 9 to 15 kg.

If the unit bulk volume of coarse aggregate is used, the unit bulk volume of coarse aggregate is decreased (increased) by 1%
for every 0.1 in the fineness modulus of sand greater (smaller) than the reference value.

4.5.5 Unit quantities of admixtures
The unit quantities of admixtures are determined so that the required effect can beobtained.

[Commentary] The effect of admixtures varies depending on not only the characteristics of eachadmixture but also the nature of cement and aggregate, the type of other admixtures used, concrete
mix proportions, construction conditions, environmental conditions, etc. The quantities ofadmixtures to be used, therefore, need to be determined according to these conditions by testing
their performance under realistic service conditions or consulting literature or experience.
Combined use of two or more types of admixtures may have unexpected adverse affects on theproperties of fresh concrete and the performance of hardened concrete. When using a new
combination of admixtures, therefore, a thorough study should be conducted in advance.

4.6 Trial Mixing
4.6.1 General(1) Concrete mix proportions shall be determined through trial mixing so that concretethat meets the mix requirements can be obtained.
(2) Trial mixing of concrete should be conducted in the form of laboratory testing as astandard.
(3) Trial mixing may be omitted if it can be ascertained from performance data, etc., thatthe planned mix proportion meets the mix requirements.

[Commentary] (1): Trial mixing shall be conducted in order to ascertain that the mix proportion
determined at the mix design stage meets the mix requirements. Concrete performance changes
under the influence of various factors. The performance of fresh concrete is subject to considerable
change depending on the time after completion of mixing, ambient temperature, on-sitetransportation methods, etc. When designing concrete mixes, therefore, it is important to set quality
goals at each stage (i.e., production and unloading) so that concrete workability needed at the101

Standard Specifications for Concrete Structures-2007, Materials and Construction

placement stage can be attained. This section requires, therefore, that concrete mix proportions be
determined through trial mixing prior to the placement of concrete so that concrete that meets theperformance requirements can be obtained. Trial mixing shall be conducted, on an as-needed basis,
under the direction of a Chief Concrete Engineer or Concrete Engineer certified by the Japan
Concrete Institute or an equally qualified engineer.
(2) and (3): In order to determine concrete mix proportions through trial mixing, it is necessary
to measure materials of proven quality accurately and mix them thoroughly. This is why laboratory
testing is required as a standard method. If, however, the conditions under which concrete is
produced in a laboratory test environment differ from the conditions under which concrete is to be
produced for construction or if changes in concrete quality over time are to be evaluated, trial
mixing of concrete should be conducted by using real mixers.

4.6.2 Trial mixing method(1) Trial mixing is conducted in the form of laboratory testing so that concrete thatmeets the mix requirements can be obtained.
(2) When trial mixing is conducted in a laboratory test, workability upon completion of
mixing is evaluated taking into account the difference in slump from the results of tests
conducted by use of real equipment, concrete temperature at the time of construction,
mixing performance, transportation time, etc.
(3) Trial mixing of concrete should be conducted at 20±2°C as a standard. If trial mixing
cannot be carried out under such test conditions, mix proportions shall be determined
after making corrections for temperature differences.
(4) In a mix test using a test mixer, appropriate test items shall be selected so as toevaluate the workability of concrete.

[Commentary] (1) and (2): At the mix design stage, the target slump at the unloading locationand the target slump upon completion of mixing shall be determined on the basis of the minimum
slump for placement, taking into account transportation time, waiting time at the construction site
and the decrease in slump due to on-site transportation. In trial mixing conducted in the form oflaboratory testing, therefore, it is necessary to make repeated corrections for mix proportions toachieve the target slump at the unloading location or the target slump upon completion of mixing
until the required minimum slump for placement can be attained, taking into account the decreases
in slump not only immediately after completion of mixing but also after the passage of time.
Concerning mix proportion corrections, Table E4.5.2 should be used as a guide.
If a large amount of decrease in slump is assumed at the mix design stage, time-dependentchanges in slump during the time from the completion of mixing to the placement of concreteshould be estimated. If trial mixing has indicated the possibility of a large amount of decrease inslump over time, it is important to select mix proportions with an excellent slump-retaining property
and take necessary measures such as using appropriate chemical admixtures so that the minimum
slump for placement can be attained. In general, the amount of decrease in slump of a concrete mix
uninterruptedly agitated in a mixer tends to be smaller than that of small-batch concrete kept in astatic state in a laboratory test. As a rule of thumb, it may be assumed that slump retention time in amixer test is about 30 minutes longer than that in a laboratory test.
Mixing performance varies widely depending on mixer types so that the quality of freshly102Chapter 4

Mix Design

mixed concrete and subsequent changes in quality are greatly affected. Mixers used in laboratory
testing, therefore, should be of the same type as the mixers used for construction.
(3): Trial mixing in a laboratory test should be conducted at constant temperature conditions(20±2°C). If the time of year when trial mixing is conducted differs from the time of year whenconstruction is carried out and a considerable difference in placing temperature is expected, mix
proportions need to be determined taking into account that temperature difference. It is also goodpractice to conduct trial mixing by using mixers and correct mix proportions derived throughlaboratory testing.
(4): Concrete shall be provided with workability suitable for construction tasks such as hauling,placing, compacting and finishing according to the construction requirements, structuralrequirements and the environmental conditions. In concrete mix tests, it is important to check
whether the mix proportions specified at the mix design stage have the targeted performance withrespect to filling ability, pumpability, setting properties and strength development characteristics.

4.7 Representation of Mix Proportions
As a general rule, mix proportions should be presented as shown in Table 4.7.1.
Table 4.7.1 Representation of mix proportions
Maximum Slumpsize of

1)

Air

3

Content (kg/m )

Sand
3)

content cement percentage Water
2)

coarseratio

aggregate(mm)

Water/

CementMineraladmixture

s/a

Fine
3)4)

Coarse aggregate ChemicalGaggregateadmixture

5)

W/C
(cm)

(％)

(％)

(％)

W

C

F

S

(mm)

(mm)

A

Notes 1) The standard method is to indicate the target slump at the unloading location. If necessary, the minimum slump
for placement and the target slump upon completion of mixing are also indicated.
2) If a mineral admixture with pozzolan reactivity or latent hydraulic property is used, the water/cement ratio becomes thewater/binder ratio.
3) The powder content should be indicated as the combined content of cement and mineral admixtures as an
approximate indicator of segregation resistance.
4) If two or more types of mineral admixtures are used, mix proportions for different types are indicated separately on an
as-needed basis.
335) The chemical admixture content is indicated in ml/m or g/m , and the quantity of undiluted and undissolved liquidmust be indicated.

[Commentary] As a general rule, mix proportions should be indicated by mass, and the content
of each ingredient used in each cubic meter of mixed concrete must be indicated in the form of amix table like Table 4.7.1. Mix tables should also show information such as the type of structure,
specified strength, required strength, the type of cement, the fineness modulus of fine aggregate, thetype of coarse aggregate, the solid content of coarse aggregate, transportation time and the time ofyear of construction. A recommended standard practice is to indicate the target slump at theunloading location in mix tables and, if necessary, determine the slump at each stage of construction
from immediately after completion of mixing to the placement of concrete. It is also good practice
to indicate the combined content of powdery materials such cement and mineral admixtures to showwhether segregation resistance appropriate for the slump level is being maintained.

103

Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 5 CONCRETE PRODUCTION

5.1 General(1) Concrete with the required quality shall be produced.
(2) Equipment used for the storage, batching and mixing of materials shall be one thathas been verified to have the required performance.
(3) Methods of storing, batching and mixing materials by using equipment with therequirement performance shall be determined prior the production of concrete.
(4) Specialists with sufficient knowledge and experience shall be assigned to the
production of concrete to control the quality of concrete materials, production equipment
and concrete.

[Commentary] (1): In order to produce concrete with the required quality, it is important to use
equipment with the required performance, use appropriate production methods and have specialists
capable of ensuring stable quality of concrete perform quality control.
(2) and (3): Use of equipment with the required performance is most fundamental and important
for the production of concrete. Even if the concrete materials meet the quality requirements
specified in Chapter 3, inadequate production equipment increases the possibility of fluctuations or
degradation of the quality of stored materials, fluctuations in mix proportions due to batching errors,
and fluctuations of the properties of mixed concrete, thereby making it difficult to obtain concretewith the required quality stably. Even when the storage, batching and mixing equipment meet theperformance requirements, it is difficult to obtain concrete with the required quality if concrete is
produced without ascertaining in advance that the storing, batching and mixing methods areappropriate as in the case where inadequate equipment is used. The performance requirements for
production equipment are described in Section 5.2, and appropriate production methods aredescribed in Sections 3.7, 5.3 and 5.4.
(4): Even when production equipment meets the performance requirements and appropriate
production methods are used, it is difficult to obtain concrete of stable quality if production
specialists lack the ability to control the quality of concrete stably. Since the quality of concrete iseasily affected by various factors, it is important for the specialists who produce concrete to haveexpert knowledge and experience related to the quality and production of concrete. For example, it
is important that a specialist qualified as a Chief Concrete Engineer or a Concrete Engineer stay at
the construction site and perform quality control. Since the operation and maintenance of
production equipment requires specialized knowledge about mechanical and electrical equipment, it
is good practice to make effort to enhance the operators' ability and knowledge about operation andconsider ways to contact outside specialists so that troubleshooting actions can be taken in times ofequipment failures.

104

Chapter 5

Concrete Production

5.2 Production Plant
5.2.1 Storage facilities(1) Storage facilities for cement and mineral admixtures shall have a structure to keep
the inside free of moisture, and the cement and admixtures shall be stored separately
according to their types.
(2) Storage facilities for aggregates shall have a structure that stores aggregates
separately according to their type, size and grading such that they do not segregate in thesize easily. Also, the storage facilities shall have an adequate drainage such that thesurface moisture content of aggregate can be maintained at a uniform level.
(3) Storage facilities for chemical admixtures shall have a structure that stores the
admixtures separately according to their types, and shall prevent any contamination with
impurities, changes in properties, segregation in liquid admixtures, etc.

[Commentary] (1): In general, cements and mineral admixtures should be stored in storage
facilities equipped with a structure to keep the inside free of moisture. The volume of a silo should
be more than three times the average volume of use per day. A storage silo for cements and mineraladmixtures should be of structure as to have no dead stock of cement at the bottom, and beequipped with vibrators, knockers or an aeration system in the vicinity of the bottom to prevent thearch formation of the powder particles and to ensure a smooth discharge of the materials.
In case when using the cement silo of which inside is separated into some smaller storage by thesteel plate separators etc., attention need to be paid for the leakage of cement from the welding part.
Furthermore, it shall be prevented that different types of cements or mineral admixtures mix eachother through a hole due to corrosion on the steel separator.
If cement cannot be sent directly from a cement silo to a batching bin, it is necessary to install astorage bin over the batching bin. Two or more cement storage bins should be available. If mineraladmixtures that are not used for the production of ordinary concrete are stored as when high-fluidity
concrete is produced, care shall be taken to prevent problems such as clogging or malfunctioning oflevel indicators due to the compaction of admixtures resulting from long-term storage.
(2): It is important that aggregate storage facilities be capable of storing aggregates of different
types or different sizes separately and have sufficient capacity so that stored aggregate can be used
on a first come, first used basis. The storage facilities shall also be structurally designed so that
aggregates do not become segregated when they are received or handled. Since the quality ofconcrete is easily affected by fluctuations in the surface moisture content of aggregate, control
measures need to be taken so that the surface moisture content of aggregate is kept uniform.
Aggregate storage facilities include stockyard types and silo types. For stockyard type storage
facilities, it is important to provide roofing so that aggregate is not affected by rains and direct
sunlight, prevent the intrusion of other aggregates, mud, dead leaves, ice, snow, etc., and provide agentle drainage slope for effective drainage. For silo type storage facilities, the bottom of a fineaggregate storage silo should be designed for efficient drainage, and devices such as air blasters
should be provided so that the aggregate accumulated at the bottom of the silo can be removed.
Even for silo type storage facilities, if the hopper for receiving aggregate from a transportation
vehicle is located outdoors, it is important to provide a roof over the hopper to prevent the intrusionof rain and the accumulation of aggregate in the hoppers.

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In order to minimize fluctuations in the particle size distribution of aggregate, for example, 20
to 5 mm aggregate should be divided into 20 to 10 mm aggregate and 10 to 5 mm aggregate and be
stored and batched separately. It is also necessary to take measures so as to prevent the freezing of
aggregate or a rise in temperature of aggregate because of outdoor air temperature.
Aggregates stored in stockyard facilities or silos are transported by a belt conveyor to theconcrete plant, distributed by turn chutes, and dropped into the aggregate storage bins. Thesefacilities shall be inspected periodically for problems such as clogging of drainage troughs, leakage
from the gates, intrusion of water into the aggregate carried on the belt conveyor, or theaccumulation of aggregate on the belt conveyor or in the storage bins.
If highly absorptive aggregates such as artificial lightweight aggregates or blast furnace slag
coarse aggregates are stored, watering facilities such as sprinklers should be provided in addition todrainage facilities. Concerning the storage of artificial lightweight aggregate, Construction: Special
Concretes (Chapter 2, Lightweight Aggregate Concrete) of this Specification should be consulted.
Because of its latent hydraulic property, blast furnace slag fine aggregate may become difficult towithdraw during the time of year when daily mean temperature exceeds 20°C so that consolidation
occurs in the aggregate storage facilities or storage bins. It is therefore necessary to avoid long-term
storage during such periods. When producing concrete by using blast furnace slag fine aggregate,
the Guidelines for Construction Using Blast-Furnace Slag Aggregate Concrete should be consulted.
(3): Chemical admixtures shall be stored in such a way as to prevent the incursion of dirt orother impurities. Chemical admixtures of liquid form shall be stored so as to prevent theirsegregation, quality change or freezing. Chemical admixtures of powder form shall be stored so as
to prevent their moisture absorption and lumping. Chemical admixtures which have been stored fora long time or are found to be of unsure quality shall be tested to confirm their quality before use.
The storage facilities for the chemical admixtures of liquid form shall be of structure that canprotect from the contamination of impurities, and should have a mixer or a circulator protectingfrom the segregation due to sedimentation. In case that the storage tanks or the transportation pipes
are made of steel, attention needs to be paid for corrosion. Though the liquid type of chemical
admixtures is, generally, controlled its pH to neutral or week alkali condition, special attention
should be required for use of the acid admixture.
For storage facilities (tanks) for water and liquid chemical admixtures, it is also important totake measures to reduce batching errors by using the automatic water supply method or overflow
piping to keep water pressure, water level or concentration constant or protection measures toprevent freeze damage to the piping from the storage tanks to the storage bins and a breakdown due
clogging of electromagnetic valves because of foreign matter or precipitates.

5.2.2 Measuring equipment(1) Equipment used to weigh each material shall be compatible to the production of
concrete, and be capable of batching each material within the required accuracy.
(2) Equipment used to weigh each material shall be periodically inspected before andduring the operation, and appropriately adjusted.

[Commentary] (1): It is necessary to choose the measuring equipment suitable for producing
volume of concrete, the scale and importance of the construction, etc. Furthermore, the equipments

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Concrete Productionused to weigh each material shall be capable of batching each material within the required accuracy.
Though there are both mechanical and electrical types of measuring equipment, the mostpopular is the electrical type because remotely-monitoring can be operated and a digital control isdone with an analog digital converter, at present.
Since the setting of batching values is fundamental to batching, batching equipment needs to becapable of performing batching correctly according to the mix proportion settings. Punch card
equipment is used for the setting of batching values, but today most plants use CPU-memory typeequipment based on computer keyboard entry. Recent years saw widespread use of operation room
equipment with comprehensive quality control capability, as well as batching control, thatincorporates various other systems such as automatic material feed control systems, automatic
surface moisture content measuring systems and automatic batching value correction systems.
Chemical admixtures such as air-entraining water-reducing agents greatly affect the quality ofconcrete. Devices for preventing excessive water flow may be installed at the water inlets.
(2): The batching equipment for each material shall be checked before the start of the use andadjusted so as to weigh each material within the prescribed limits for errors in batching. Even whenbatching equipment is adjusted in this way, the accuracy deteriorates with time. Therefore, theequipment shall be regularly checked and readjusted as required.
If the inside surface of the aggregate batching bin is not smooth, residual aggregate may lower
batching accuracy. It is therefore necessary to make improvements such as bonding rubber sheets.

5.2.3 Mixers(1) As a general rule, batch mixers should conform to JIS A 8603.
(2) Continuous mixers shall be ones that have been verified to have the required
mixing through a mixing performance test conducted in accordance with JSCE-I 502.

[Commentary] (1): Batch mixers are classified into two types; the gravity type and the forced
mixing type. Regarding the gravity type, there are tilting and drum mixers. Forced mixing typebatch mixers come in pan types, single- horizontal- axis and double-horizontal-axis types. Mixing
efficiency is tested on mixed concrete by a compressive strength test, an air content test and a slump
test, in accordance with JIS A 1119 “Method of Test for Variability of Constituents in Freshly Mixed
Concrete” and JIS A 8603 “Concrete Mixer”. When the testing results do not satisfy the thresholdvalues shown in Table C5.2.1, it is often considered that the structure of the mixer is not appropriate,or the blade for mixing is abraded.

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Table C 5.2.1

Mixing Capacity of batch mixer

Items
Variability of mass per unit volume ofmortar in concrete
Variability of content of coarse
aggregate in concreteCompressive strength
Variability
Air content
from average
value
Slump value

Mixing volume of concrete
Nominal volume
A half of nominal volume
0.8% or less

0.8% or less

5% or less

5% or less

7.5% or less
10% or less
15% or less－－－In the upper bound of the nominal capacity of the mixer targeted by JIS A 8603 "Cement mixer",
both the gravity type mixer and the forced mixing type mixer are 3m3. The suitability should be
judged by applying regulations of JIS A 8603 correspondingly about the mixer for nominal capacity
to exceed this. Recently, a mass mixer of nominal capacity 6m3 has come to be used.
The forced mixing type mixer is suitable for the stiff concrete, the concrete of the rich mix and
the Special Concretes (Chapter3 Lightweight Aggregate Concrete, Chapter6 High Strength
Concrete, Chapter7 High Fluidity Concrete, etc). In general, the forced mixing type mixer canshorten necessary mixing time than the case of the tilting mixer.
(2): Continuous mixers may be used when large-scale production equipment cannot be installedat the sites of tunnel construction, rehabilitation, offshore construction, etc. Concrete production byuse of continuous mixers, however, differ in many ways from concrete production by use of batchmixers (e.g., the batching of materials by volume, sufficient calibration necessary for stable supply,
the possibility of poor quality concrete output immediately after the commencement of operation).
Continuous mixers, therefore, shall be used after referring to the Recommendations for Job-Mixed
Concrete Construction Using Continuous Mixers to fully understand the characteristics ofcontinuous mixers and conducting a test in accordance with JSCE-I 502, Method of Test for Mixing
Performance of Continuous Mixers.

5.3 Measurement of Materials(1) Materials shall be batched according to mix proportions modified in view of suchfactors as the state of materials, concrete temperature and slump retention time so that
concrete with the required quality can be obtained.
(2) The size of batch shall be determined considering the type and properties ofconcrete, performance of mixing equipment, method of transportation, type of
construction, quantity of concrete to be placed, etc.
(3) All materials for each batch shall be measured by weight. Errors in batching foreach measurement shall not be greater than the values given in Table 5.3.1.

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Table 5.3.1

Concrete Production

Permissible errors in measurements

Material

Error in measurements (%)

Water

1

Cement1
3
2 1)

Aggregate
Mineral admixture

3

Chemical admixture1) In case of finely ground blast furnace slag, the error in batching shall be taken as 1.

(4) In cases when a continuous mixer is used, the materials may be measured byvolume. The error in measurement shall not be greater than the values given in Table 5.3.1
in which the error should be calculated in mass weight that is converted from the volumeof each material per an appropriate specified period depending on the capacity of themixer. The measured volume of each material per the specified period shall be properly
determined on the basis of the type of concrete mixer, mixing time, etc.

[Commentary] (1): The materials in storage should be in as stable a state as possible, but thesurface moisture content and particle size distribution of aggregate, for example, are always in astate of change. The temperature of freshly mixed concrete also varies depending on such factors as
the temperature of the materials in storage and outdoor air temperature. These various changes
affect the slump and air content of freshly mixed or subsequent concrete. Concrete materials to be
used, therefore, shall be batched after corrections for such changes are made so that concrete of therequired quality can be obtained.
The surface moisture content and effective absorption of aggregate change easily, and suchchanges affect the slump and water/cement ratio of concrete. The surface moisture content oreffective absorption, therefore, shall be measured at an appropriate frequency and the measurement
results shall be reflected in batching. The surface moisture content shall be tested in accordancewith JIS A 1111, JIS A 1125 or other appropriate method, and particle size distribution shall betested in accordance with JIS A 1102 or other appropriate method. Effective absorption values in thecases where aggregate is dry shall be determined after letting the aggregate absorb water for an
appropriate period of time.
Methods for testing the surface moisture content include JIS A 1111, Method of Test for Surface
Moisture in Fine Aggregate, and JIS A 1125, Method of Test for Moisture Content of Aggregate andSurface Moisture in Aggregate in Drying. Other methods include the graduated cylinder method,
methods using infrared rays or other means for drying, methods using electrical resistance or the
dielectric constant, neutron-based methods and many other methods. Test methods most appropriate
for the jobsite should be selected in view of factors such as the time required for the task to be
performed, the number of test cycles, test accuracy and economic efficiency. In recent years, it has
become possible to make water and aggregate batching corrections for all batches of fine aggregate
according to changing surface moisture contents by installing surface moisture sensors in theaggregate storage bins and at their outlets.
The water used for the dissolution or dilution of chemical admixtures is deemed to be included
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Standard Specifications for Concrete Structures-2007, Materials and Constructionin the water content. The solids contained in chemical admixtures may be ignored for the purpose of
concrete volume calculation.
(2): As the size of each batch of concrete produced especially in a plant at the construction site
is closely related to the efficiency of work and construction cost, it is important that the proper size
is determined considering the type of work, concrete quantity to be placed, the capacity of mixing
plant and transportation method.
(3): As a general rule, materials shall be batched by weight. However, water and the liquid
chemical admixtures may be measured by volume, in the case where they are confirmed to bewithin the acceptable error described in Table 5.3.1. In the case where cement and mineraladmixtures are supplied in bags, and the difference between the net mass of 1bag and the printed
value on the mass is confirmed to be within the acceptable error described in Table 5.3.1, they may
be batched on the basis of the number of bags. However, a quantity which is less than 1 bag shall bemeasured by mass.
Material batching errors include errors attributable to the batching equipment and errors that
occur when materials are fed to the batchers. Errors of the former type can be reduced sufficiently
by the daily inspection and maintenance of the batchers because the inaccuracy of the batchers canbe determined by use of the proof mass. In general, the accuracy of batchers used for concrete
construction is about 0.5% of the maximum capacity. Errors attributable to material feeders, etc.,
however, can only be reduced to a limited extent. Batching devices, therefore, shall be managed sothat material batching errors of the batching system including the measuring instrument and thefeeder can be kept within an appropriate range in relation to the target value. JIS A 5308 requiresthat cement and mineral admixtures be batched by use of separate measuring instruments.
The batching errors specified in this article are the maximum limits of batching error allowable
at general construction sites. In the case of important structures, proper batching methods whosebatching error is less than the value shown in Table 5.3.1 should be adopted. As batching error
become large particularly when the quantity to be measured is small in comparison with thecapacity of the batching machine, it is necessary to confirm that a batching machine can measure
the quantity of each batch accurately. The finely ground blast furnace slag is usually used for
concrete in the range of 30 to 70 % in the total mass of binder, and is the mineral admixture having
a latent hydraulic property. Therefore, the error in batching of the slag shall be taken as 1% or less,which is same regulation as the cement.
In a case of the batching in construction site, it is important to provide such supply equipmentthat batching errors does not increase. Furthermore, it is important to prescribe the capacity of abatching machine so as to measure the quantity of each batch accurately and to modify theequipment as required. Particularly the batching machine for water needs to be devised to improve
its accuracy. Since the batching machine often get out of order due to dust, they shall always be kept
clean by installing a dust collector and so on. Then the batching value should be controlled by aprinting record.
(4): In the case of the continuous mixer, which is different from the batch mixer, the quantity ofmaterials is usually measured by volume by adjusting the quantities of the supply of aggregate,
water and admixtures according to mix proportions on the basis of the quantity of supply of cement
per unit hour. If a continuous mixer is used, its measuring equipment shall necessarily be inspectedprior to the commencement of work by using materials which are to be used for the work. This
inspection shall be conducted by measuring the weight of each material supplied during a fixed time.
Measuring by volume generally results in more measuring errors than measuring by weight.

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Therefore, when the inspection is performed, in order to obtain quantity-per-prescribed-time mostaccurately, it is important that the capacity of the measuring machine is properly determined and themeasuring equipment is adjusted as required, to reduce measuring errors to the utmost, so thatmeasuring errors for each material will be within the allowable limits.

5.4 Mixing(1) Constituent materials of concrete shall be thoroughly mixed until a uniform
concrete is obtained.
(2) The sequence of charging materials into the mixer shall be appropriately examinedand decided in advance.
(3) As a general rule, time for mixing should be determined through experiments.
(4) Mixing shall not be continued for more than three times the predetermined time of
mixing.
(5) As a general rule, the inner surface of the mixer should be covered with mortar
before commencing mixing.
(6) Materials for a new batch shall not be loaded into the mixer before the previous
batch has been completely discharged.
(7) Mixers shall be properly washed prior to and after the use.
(8) When a continuous mixer is used, the first portion of discharged concrete shall not
be used.

[Commentary] (1): In order to obtain a uniform concrete, mixing needs to be performed using amixer with high efficiency by feeding the materials in the proper order and mixing them for aproper period of time.
(2): Since the suitable order of changing materials into the mixer varied depending on the typeof mixer, mixing time, type and grading of aggregate, unit water content, unit cement content andtype of admixtures, this should be determined with reference to the past experience or the results ofthe test performed in accordance with JIS A 1119, strength test and bleeding tests.
(3): Since the time necessary for sufficient mixing in batch mixers varies considerably
depending on the type of mixer, mixer capacity, concrete mix proportions, type of admixture andorder of feeding materials, it shall be determined based on the results of test of JIS A 1119 and othertests as a general rule.
In the case where the difference in the mass of the unit volume of mortar is less than 0.8% andthe difference in the content of coarse aggregate is less than 5%, which are specified in JIS A 1119,
it can generally be considered that satisfactory mixing has been carried out. Furthermore, if therelationship between the load current of the mixer and the operation time can be measured, the time
until the load current changes in the stable condition after some amount of increasing anddecreasing will be suggestive to determine the mixing time.
If tests for mixing time are not performed, the minimum time may be set at 1.5 minutes fortilting batch mixers and 1 minute for compulsory batch mixer. These are maximum value based on
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Standard Specifications for Concrete Structures-2007, Materials and Construction

the results of investigation of batching equipment and mixers in use conducted in 1984, and theaverage time which can obtain by the test are about 70% of those times.
In the case of small-slump concrete, concrete made by using lightweight aggregate or
admixtures or high-strength concrete, it is in many cases appropriate to use long mixing time. Whenlightweight aggregate concrete, high-strength concrete, etc., are mixed, Construction: Special
Concretes of this Specification should be used as a guide.
(4): If concrete is mixed for a long time, especially in the case where mixer capacity is large, orthe aggregate is not stiff and its maximum size is large, not only the workability of concrete atdischarging time is reduced but also its slump loss with time becomes larger, because the aggregate
is crushed to increase the amount of powder and the air content deceases during the prolonged
mixing period. Therefore, it is specified that the mixer shall not be continued for more than threetimes the predetermined mixing time.
(5): The concrete of the required mix proportions can not be obtained in the first batch since apart of its mortar component will adhere to the bare surface of the mixer. Therefore, an appropriate
amount of concrete should be mixed to adhere its mortar to the inside of the mixer, and theprescribed materials should be charged into the mixer to be mixed after discharging the priorconcrete.
(6): If new materials are put into a mixer in which there is residual concrete and mixed together,
concrete of the required quality cannot be obtained because inadequate mixing occurs locally.
Mixing of new materials, therefore, shall not be started until it is confirmed that previously mixed
concrete is completely discharged.
(7): In cases where the quality of mixed concrete may vary because of differences in thematerials used in different batches, the measures described in Item (6) in this section should betaken after the mixer is cleaned.
(8): When a continuous mixer is used, since the concrete of undesirable quality may bedischarged at the start of its operation, such concrete shall not be used. The amount of concrete to
be disposed of shall be greater than the volume of mixing part as standard. This precaution needs tobe taken also when the mix proportions are changed (see the JSCE Recommendation“Recommended Practice for Field Mixed Concrete by Continuous Mixer”).

5.5 Plasticization of Concrete
Plasticization of concrete shall be carried out after considering details such as
materials, mix proportions, fluidity-enhancing method, and the time until the completionof placement so that the quality requirements for concrete can be met.

[Commentary] Slump can be increased by adding plasticizer to the concrete in the drum of thetruck agitator that has transported the concrete from the concrete plant to the construction site andstirring the mix until it becomes homogeneous. The use of plasticizers is effective when therequired slump cannot be maintained until the placement of concrete is completed. Superplasticized
concrete with a slump comparable to that of ordinary concrete helps prevent thermal cracking andachieve higher quality because the water content and the cement can be reduced. Changes in slumpof superplasticized concrete over time, however, differ considerably from those of ordinary concrete,and excessive use of plasticizers may have adverse effects, such as segregation and changes in the112

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Concrete Production

air content, on the quality of concrete. When trying to increase the fluidity of concrete, therefore, itis necessary to carefully study details such as materials, mix proportions, fluidity-enhancing method(e.g., timing, the quantity of superplasticizer to be added, mixing time and method), themanagement of time until the completion of placement taking into account the slump retention timeafter plasticization, and noise control so that the quality requirements for concrete can be met.
Chemical admixtures added to concrete before plasticization may not go well with plasticizers,
and there may be adverse effects on their respective effects. Undesirable combinations, therefore,
need to be identified in advance. The amount of increase in slump needs to be kept within the rangethat does not cause segregation of plasticized concrete. As a general rule, therefore, the amount of
increase in slump shall not exceed 10 cm, and 5 cm to 8 cm shall be regarded as standard values.
Post-plasticization slump varies widely depending on the pre-plasticization quality of concrete,
the type and dosage of superplasticizer, concrete temperature, etc. Because slump retention time
may become shorter, the time until completion of placement should be managed by checking in
advance on the slump retention time.
Re-flowing of the plasticized concrete may generate the segregation or the delay of setting timeof concrete due to an oversupply of plasiticizer, and consequently, have a bad influence on theperformances of hardened concrete, such as durability, strength in the long term and so on.
Therefore, the re-flowing should be avoided in the plasticized concrete.
There are also many other considerations such as methods of adding plasticizers, noise due tohigh-speed rotation of truck agitators, and exhaust gas control. When using plasticized concrete, theRecommended Practice for Concrete Containing Plasticizers should be consulted in advance.

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CHAPTER 6 READY-MIXED CONCRETE

6.1

General(1) As a general rule, ready-mixed concrete used should be one that conforms to JIS A
5308 and bears a JIS Mark indicating JIS certification (hereafter referred to as a"JIS-certified product").
(2) Prior to purchasing ready-mixed concrete, a plant shall be selected so that therequired quality of concrete can be obtained, and the requirements specified in JIS A 5308
such as materials, quality and mix proportions shall be discussed with the producer.

[Commentary] (1) and (2) JIS A 5308, Ready-Mixed Concrete, specifies requirements such as
the type and quality of ready-mixed concrete, mix proportions, materials, manufacturing, quality
control, and test methods, and the appendices specify details such as the requirements for
aggregates to be used for ready-mixed concrete and test methods to be used. Although JIS A 5308
does not necessarily agree with this Specification, the requirements specified in JIS A 5308 aredesigned to cover a wide range of requirements. It is usually possible, therefore, to procure concreteof the quality specified in this Specification by purchasing JIS-certified ready-mixed concrete
conforming to JIS A 5308.
When purchasing JIS-certified ready-mixed concrete, it is necessary to carefully consider thequality of concrete specified in this Specification and select a plant, specify quality requirements
and conduct acceptance inspections so that the concrete of the required concrete can be obtained. If
the provisions in this Specification differ from the provisions of JIS A 5308, the standard method is
to follow the more stringent of the two sets of provisions, but the constructor needs to make an
informed decision with the full understanding of the differences between the two sets of provisions
and the reasons for those differences.
If concrete that does not conform to JIS A 5308 in terms of materials, mix proportions, quality
criteria, etc., is purchased for reasons such as the purpose of use of concrete or construction
conditions, mix requirements and other details must be fully discussed with the producer and trial
mixing must be conducted on an as-needed basis to verify quality and determine mix proportions.
With respect to matters not specified in this Specification or relevant JSCE guidelines, JIS A 5308
should be followed. In other words, even in cases where ready-mixed concrete that does notconform to JIS A 5308 is used, it is necessary to select a plant that manufactures JIS-certified
products. For matters not specified, it is necessary to determine specifications in due considerationof the intent of the JIS A 5308 provisions and select plants, specify quality requirements andconduct acceptance inspections accordingly.
Although JIS A 5308 includes provisions related to pavement concrete, this chapter does notinclude provisions related to pavement concrete because this Specification does not deal withpavement work.

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6.2

Ready-mixed Concrete

Selection of Plants(1) Ready-mixed concrete plants shall be selected from JIS-certified plants, andpreferably from plants that have been permitted by the Namakon Quality Control Inspector
Conference to use its certification mark. If other plants need to be selected, a certified
Chief Concrete Engineer or Concrete Engineer or an equally knowledgeable andexperienced engineer shall be permanently posted, and plants shall be selected from thosecapable of performing mix design and quality control appropriately.
(2) Matters to be considered for the selection of concrete plants shall include thetransportation time to sites, unloading time, concrete production capacity, number oftransporting vehicles, manufacturing equipment condition of quality control and so on.

[Commentary] (1) Ready-mixed concrete plants vary widely in terms of production facilities,
production technology, quality control, etc. Under the Industrial Standardization Act, therefore, atthe request of ready-mixed concrete plants, state-authorized private-sector certifying organizations
examine the plants in accordance with JIS Q 1001, Conformity Assessment—Conformity
Assessment for Japanese Industrial Standards —General Guidance on a Third-Party Certification
System for Products, and JIS Q 1011, Conformity assessment— Conformity Assessment forJapanese Industrial Standards—Guidance on a Third-Party Certification System for Ready-Mixed
Concrete Products, and authorize the certified plants to put a JIS mark on their JIS-conforming
products. This plant certification shows that the certified plant meets the equipment, operation,
management and other requirements for the production of JIS-conforming ready-mixed concrete
and ready-mixed concrete produced at the plant conforms to JIS.
The number of JIS-certified plants has reached about 3,800, and the state of quality control
differs considerably even among the certified plants. National Ready-Mixed Concrete Industrial
Association, therefore, upgraded the national uniform quality control audit system administeredjointly by an industry–government–academia organization. Under the new system, regional quality
control audit conferences established in each prefecture conduct on-site audits of plants every yearin accordance with the uniform audit criteria adopted by the Namakon Quality Control Inspector
Conference. The plants that have passed these audits are granted a certificate and are permitted touse a certification mark after undergoing an deliberation by the National Ready-Mixed Concrete
Industrial Association. The newly introduced system has enhanced transparency and fairness in thequality control of ready-mixed concrete and has made it possible to supply even more reliableconcrete. According to 2006 survey results, the plants that have been permitted by the Namakon
Quality Control Inspector Conference to use its certification mark accounts for 80% of all
ready-mixed concrete plants.
In view of this situation, this Specification requires, as a general rule, that ready-mixed concrete
plants be selected from JIS-certified plants and recommends that ready-mixed concrete plants beselected from the plants that have been permitted by the Namakon Quality Control Inspector
Conference to use its certification mark. If other plants need to be selected for reasons related toplant locations or other reasons, a Chief Concrete Engineer or Concrete Engineer or an equallyknowledgeable and experienced engineer must be permanently posted, and plants that are capableof performing concrete mix design, quality control, etc., appropriately.
(2) Besides the considerations mentioned in Item (1), the time required for transportation to theconstruction site is also an important consideration in selecting plants. In view of changes in thequality of concrete during transportation, transportation time should be made as short as possible.
Since transportation time varies depending on the traffic conditions of the transportation route,115

Standard Specifications for Concrete Structures-2007, Materials and Construction

weather, etc., it is also necessary to take varying transportation time into account. In the case of
JIS-certified concrete, a plant located within a distance that makes it possible to transport andunload concrete within the time limit specified in JIS A 5308 must be selected. Even in the case of
concrete that does not conform to JIS A 5308, it is good practice to select a plant in accordance withthat standard. Chapter 6 of this Specification specifies the time limit for completing the placementof concrete. The constructor must select plants and transportation routes, taking into consideration
the time from unloading to the completion of concrete placement.
In order to perform concrete placement smoothly, it is necessary to supply ready-mixed concreteat a rate appropriate for the rate of concrete placement. When selecting plants, therefore, suchfactors as production capacity and transportation capacity must also be taken into consideration. If
the capacity of a plant is not sufficiently large, it is necessary to purchase ready-mixed concrete
produced at two or more plants. Since the quality of materials, concrete mix proportions, slump, aircontent, quality control systems, etc., differ from plant to plant, the constructor must ascertain thosedifferences and plan and manage vehicle arrangements and concrete placement appropriately.

6.3

Specification of Qualities(1) When JIS-certified ready-mixed concrete is purchased, the type of ready-mixed
concrete and other necessary specification items shall be specified so that concrete of
the required quality can be obtained.
(a) Type of ready-mixed concrete
The type of ready-mixed concrete shall be specified on the basis of the maximum
size of coarse aggregate, nominal strength, the target slump or target slump flow at theunloading location and the type of cement in view of the requirements for fresh
concrete such as filling ability, segregation resistance, and changes in quality duringtransportation and during the process from unloading to placement.
(b) Specification items
The type of cement, the type of aggregate, the maximum size of coarse aggregate
and the method of alkali–silica reaction control shall be specified through consultation
with the producer. Details such as the age for nominal strength guarantee, the upper
limits of the water/cementitious material ratio and the water content, the upper or lower
limit of the cement content, and the air content shall be specified through consultation
with the producer on an as-needed basis in view of such factors as the specified
strength age, durability and cracking resistance.
(2) When non-JIS-certified ready-mixed concrete is ordered, details such as nominal
strength, the target slump or target slump flow at the unloading location, and the
maximum size of coarse aggregate shall be specified as set forth in Item (1) so that
concrete of the required quality can be obtained.

[Commentary] The types of ready-mixed concrete specified in JIS A 5308 are determined by
a combination of the specification items shown in Table C6.3.1, namely, the type of concrete, themaximum size of coarse aggregate, the target slump or target slump flow at the unloading location,and nominal strength. The type of ready-mixed concrete, therefore, must be selected from their116

Chapter 6

Ready-mixed Concrete

combinations so that concrete of the quality specified in this Specification can be obtained. In thisSpecification, the lightweight concrete and high-strength concrete shown in Table C6.3.1 are dealt
with in Chapter 3, Lightweight Aggregate Concrete, and Chapter 6, High-Strength Concrete, of thepart regarding special concretes. It should be kept in mind that for high-strength concrete, forexample, specified strengths ranging from 60 N/mm2 to 100 N/mm2 are considered, and thespecifications regarding slump, slump flow, air content, etc., do not necessarily the same as the JIS
specifications.
Table C6.3.1 Types of ready-mixed concrete specified in JIS A 5308 (normal concrete,
lightweight concrete, high-strength concrete)
Types of concrete

Maximum size of Slump orcoarse aggregate slump flow
(cm)
(mm)

Nominal Strength
18 21 24 27 30 33 36 40 42 45 50 55 60

8, 10, 12
15, 18

○

○

○

○

○

○

○

○

○

○

-

-

-

21

-

○

○

○

○

○

○

○

○

○

-

-

-

40

5, 8, 10, 12,
15

○

○

○

○

○

-

-

-

-

-

-

-

-

Lightweight
concrete15

8, 10, 12,
15, 18, 21

○

○

○

○

○

○

○

○

-

-

-

-

-

High-strength
concrete

20,25

10, 15, 18

-

-

-

-

-

-

-

-

-

-

○

-

-

50, 60

-

-

-

-

-

-

-

-

-

-

○

○

○

Ordinary
concrete

20,25

The specification specifies standard values of the minimum slump for placement in Section
4.4.2. The target slump at the unloading location needs to be selected in view of changes in and thetolerance for slump expected to occur until concrete is placed. The JIS specifications refer toconcrete with a slump of 21 cm and slump flows of 50 cm and 60 cm as shown in Table C6.3.1, but
the Materials and Construction: Construction Standards of this Specification does not assume theuse of those kinds of concrete. The quality of those concretes must be determined in accordancewith the Materials and Construction: Standard Specification before their uses.
Strength requirements are often indicated in terms of "specified strength." "Nominal strength,"which is a term used for distinction from the "specified strength" used in this Specification, is adimensionless number indicating the strength guaranteed under the conditions indicated in Section
4, Quality, of JIS A 5308.
In the Materials and Construction: Construction Standard the target strength for mix proportions
is determined so as to satisfy the condition that the probability that the test value set forth in Section
4.4.3 becomes 5% or less. On the other hand in the JIS A5308 the target strength is determined so as
to satisfy the percent defective under the quality requirements that is 0.0013% (about 1/741).
Therefore, the target strength that is determined by the JIS A5308 is larger than that by this standard
as shown in Fig. C6.3.1. In this way by regarding the specified strength of concrete as nominal
strength, the probability that the strength of ready-mixed concrete becomes lower than the specified
strength can be made to remain at or below the probability specified in Section 4.5 (2) of thisSpecification.

117

1.60
1.60
*1) Overdesign factor:
1.55
0.85
1.50
1.50
Conditions
in
JIS
A5308
1

3
 V 100
Requirement
of
1.45
*1)
4.1a)
JIS A 5308 3.1(1)(a) *1)*2) Overdesign factor:
1.40
1.40
1
1.35
→
1  3 V 100
1.30
1.30
RequirementofConditionsin
1.25
A 5308,←Requirement*3) The probability of the test value
JISJIS
A5308
Conditions in
1.20*2)
1.20 4.1a)of compressive strength of*2)→
3.1(1)(b)of Clause*3)6.4.2.(1)4.4.3 (2)concrete being lower than the*3)
1.15
characteristic
compressive
1.10
1.10
strength is 5% or less.
1.05
1.00
1.00
20
55
15
25
10
15
20
000 Coefficient
5
20
of10
variation15
V(%)

Overdesign factor

割増し係数Standard Specifications for Concrete Structures-2007, Materials and Construction

Coefficientof variance
V (%)
変動係数
Ｖ（％）

Fig. C6.3.1 Comparison of overdesign factors

JIS A 5308 allows items a) to d) and, on an as-needed basis, items e) to q) to specified throughconsultation with producers. It is required, however, that items a) to h) be specified within theranges stipulated in JIS A 5308. Even if specifying types is not enough, concrete of the required
quality can be obtained by specifying necessary items among these items.
a) Type of cementb) Type of aggregatec) Maximum size of coarse aggregated) Alkali–silica reaction control methode) Classification of aggregate by alkali–silica reactivityf) Classification of waterg) Type and quantity of mineral admixtureh) Upper limit of chloride content (if different from standard upper limit)i) Age at which nominal strength is guaranteedj) Air content (if different from standard air content)k) Unit mass of concrete (in the case of lightweight concrete)l) Highest or lowest temperature of concretem) Upper limit of water/cementitious material ratio

118

Chapter 6

Ready-mixed Concreten) Upper limit of water contento) Lower limit or upper limit of cement contentp) Amount of increase in slump from that of ready-mixed concrete before fluidization (in thecase of superplasticized concrete)q) Other necessary items
Since the specified strength of concrete is usually indicated in terms of 28-day strength, nominal
strength used in JIS A 5308 is also based on measured values at the age of 28 days. In the case,however, of concrete that requires high initial strength and is made by using high-early-strength
cement such as prestressed concrete or in the case of mass concrete made by using low-heat cement,
etc., it may be necessary to use an age other than 28 days as the reference age for the specified
strength of concrete and secure the required strength at that age. In such cases, the reference age forthe specified strength must be specified as the age at which nominal strength is guaranteed.
In cases where the upper limit of the water/cementitious material ratio needs to be controlled inorder to secure the durability, watertightness, chemical resistance, etc., of concrete, the limit value
must be specified.
Standard air contents in this Specification are 4 to 7% depending on the maximum size of coarse
aggregate. In JIS A 5308, standard values are 4.5% for normal concrete and high-strength concrete,
and 5.0% for lightweight concrete. If the air content is to be made higher than the JIS value in orderto enhance freeze–thaw resistance, the value must be specified. In Section 6.4.3 of the Materials andConstruction: Special Concretes of this Specification, the air content of high-strength concrete is
specified for the freeze–thaw resistance.
As stipulated in Section 4.5.2, the cement content is usually determined from thewater/cementitious material ratio and the water content. In cases, however, where the cement
content needs to be reduced for the purpose of thermal cracking control or where the type of cement
or concrete temperature requires special consideration, it is necessary to specify the upper limit of
the cement content, the type of cement or concrete temperature through consultation with the
producer. If placeability determines the lower limit of the cement content in Chapter 4, Mix Design,
the cement content must be specified through consultation with the producer.
In order to prevent alkali–silica reaction of aggregate, it is necessary to take any of thealkali–silica reaction control measures (listed below) stipulated in Appendix 2 of JIS A 5308. The
alkali–silica reaction control method must be specified through consultation with the producer.
a) Measures to control the total alkali content of concreteb) Control measures using blended cement or other materials that are effective in controlling
alkali–silica reactionc) Control measures using aggregate that is deemed safe

6.4

Receiving(1) For smooth placement of concrete, consultation shall be held with the producer,
and details such as the delivery date, the type and quantity of ready-mixed concrete,unloading location and the rate of delivery shall be determined.
119

Standard Specifications for Concrete Structures-2007, Materials and Construction(2) Planning and management shall be performed so that transportation vehicles do
not stay long at the construction site.
(3) Good communication with the producer shall be maintained even during theplacement of concrete so that the placement work is not interrupted.
(4) Unloading shall be done at a location where the transportation vehicle can safely
and smoothly enter and exit and unloading work can be performed easily.
(5) Unloading shall be done by a method that minimizes the segregation of concretematerials.
(6) Receiving inspections of ready-mixed concrete shall be conducted in accordancewith Chapter 5 of Materials and Construction: Inspection Standards of theseSpecifications.

[Commentary] (1), (2), (3) and (4) In many cases, ready-mixed concrete plants are
considerably distant from construction sites. In order to carry out the placement of concrete asplanned, it is very important to discuss arrangements in detail with the producer, taking into
consideration such factors as the production capacity of the ready-mixed concrete plant,
transportation capacity, transportation time, receiving facilities, placing rate, waiting time, and their
possible changes.
With respect to transportation time, JIS A 5308 requires that transportation be carried out so that
unloading can be done within 1.5 hours after mixing is started. This Specification (Chapter 6),
however, requires as a standard method that the process from mixing to concrete placement becompleted within 2 hours when outdoor air temperature is 25°C or lower and 1.5 hours when it ishigher than 25°C. In view of unpredictable circumstances such as traffic regulation, traffic
congestion and emergencies on the transportation routes, it will be difficult to complete concrete
construction within those spaces of time when outdoor air temperature is high unless effort is madeto complete transportation to the construction site in one hour. It is important for the constructor to
select a plant with a short transportation time, keep an eye on time-dependent changes in concrete,draw up a plan so as not to keep truck agitators that have arrived at the job site waiting long, andperform time management by keeping in close contact with the producer.
It is important to take measures in advance such as organizing the construction site, securing
access roads for transportation vehicles and deploying traffic control personnel to guidetransportation vehicles to the unloading location appropriately so that transportation vehicles cansafely and smoothly arrive at and leave the concrete unloading location and perform unloadingtasks easily.
If concrete is to be plasticized on-site by using a truck agitator, it is necessary to discuss theprocedure in detail with the producer and the person in charge of plasticization in due considerationof the transportation capacity in the case where the load capacity of the agitator is reduced in viewof its agitating performance, transportation time of base concrete, receiving facilities, the rate ofplacement, etc. (Refer to Section 5.5)
(5) Transportation vehicles used must be ones that minimize the segregation of concrete during
unloading. In the case of ready-mixed concrete as per JIS A 5308, problems seldom arise because
truck agitators that have passed a performance test are used. Ready-mixed concrete that is found tohave undergone segregation, even if slightly, at the initial stage of discharge from a truck agitator
120

Chapter 6

Ready-mixed Concreteshould be agitated for a short period of time at a high speed in the agitator before unloading. In thecase of high-viscosity concrete, however, high-speed agitation may cause air entrainment. In suchcases, preventive measures such as reducing the rotation speed need to be taken.

121Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 7 TRANSPORTATION, PLACEMENT,COMPACTION AND FINISHING

7.1

General(1) Transportation, placement and finishing tasks shall be determined so as to satisfy
the required quality of concrete structures by specifying each methods in details.
(2) Transportation, placement, compaction and finishing shall be performed bymethods that make it possible to obtain the required quality of concrete.

[Commentary] (1) The construction plan drawn up prior to the commencement of construction
work outlines each construction task to be carried out with reference to similar types of construction
work carried out in the past. In the course of construction work, the content of construction work
may deviate from the construction plan, or methods better than the planned methods may be found.
Before starting the transportation, placement and finishing tasks, therefore, it is necessary to discuss
details with the people who will be engaged in those tasks to find better methods.
It is also important to double-check the content of not only the construction plan but also thedesign drawings and specifications. For example, it is of course necessary to install formwork andperform reinforcement and joint construction just as designed. It is also necessary, however, todouble-check whether there are any areas where the placement or compaction of concrete isdifficult to carry out by comparing the design drawings and specifications with the actual state ofconcrete construction. If such preconstruction studies and preparatory measures are inadequate, thepossibility of occurrence of defects during or after construction increases. Changes from the initialconstruction plan may affect the overall construction schedule, cause structural design problems
that cannot be predicted by the constructor, or affect the contracts or other arrangements with thelocal community such as traffic regulation, noise and vibration control, environmental measures, etc.
Both the owner and the designer, therefore, must participate in discussions and take appropriate
measures.
Major considerations are summarized as follows:(a) Concreting schedule
The schedule for concreting work should be determined taking into account various factors suchas the type and shape of the structure to be constructed, the relationship with other construction
tasks in the overall construction schedule, the total quantity of concrete, the method of obtaining
concrete, the quantity of concrete that can be obtained at a time, the difficulty level of construction,
the influence on previously placed concrete, season and weather.
(b) Equipment and personnel deployment for transportation, placement and finishing
The type, model, capacity and number of equipment necessary for transportation, placement andother tasks and personnel deployment should be determined in view of such factors as theconditions at the construction site, the type and shape of the structure, transportation distance,
concreting block size, the quantity of concrete to be placed, the order of placing, the rate of placing,availability of concrete, compaction capacity, materials used and mix proportions. It is necessary to
select a concrete transportation method that makes it possible to transport concrete speedily and122

Chapter 7

Transportation, Placement, Compaction and Finishingeconomically while minimizing changes in workability and other properties due to the segregationof concrete, changes in air content, decreases in slump, etc.
On-site pumping of concrete greatly affects not only the quality of hardened concrete but also
pumpability and causes the rate of placing higher than in other methods. It is therefore important todraw up a well-balanced plan for a series of construction tasks. On-site pumping, therefore, requires
prior studies on details such as concrete mix proportions, the type and number of concrete pumps,
pump locations, piping, and pumping conditions.
Surface finishing of newly placed concrete needs to be planned so that it can be carried out at an
appropriate time, judging from various factors such as outdoor air temperature, humidity, solar
radiation and other construction environment conditions, the amount of bleeding of concrete, setting
time, the length of time after the placement of concrete in each concreting block. If concreting
blocks are large, work efficiency can be improved by using finishing equipment. Care should betaken, however, because surface finishing adjustments may be more difficult to make in machine
finishing than in manual finishing.
(c) Transportation routeTransportation routes should be determined so that concrete can be transported easily, speedilyand smoothly and transportation time and transportation distance can be minimized.
(d) Concreting blocks, joint locations and construction joint treatment methods
Concreting blocks should be determined according to the volume of concrete that can be placed
in one day with reasonable effort after studying conditions such as concrete supply capacity,
construction schedule, the shape of the structure, placing capacity, allowable placement interval,
formwork and construction joints. Consideration should also be given to cracking due to heatgenerated by the hydration of cement, autogenous shrinkage and drying shrinkage. If construction
joints that are not indicated on the design drawings are to be provided, the location of construction
joints and joint treatment methods need to be determined after carefully considering such factors as
the structural performance of the structure, durability and reinforcing patterns. Thus, it is important
to determine concreting blocks, construction joint locations and joint treatment methods in view ofthe structural performance requirements, durability and cracking instead of solely on the basis of theplaceability of concrete.
(e) Order and rate of concrete placement
The order and rate of placement in each concreting block must be determined in view of the
shape of the structure, the state of supply of concrete, placing capacity, allowable placement interval,
the organizational system for concrete placement, formwork and falsework deformation, etc.
Common practice when placing concrete in a large concreting block is to begin at the end far fromthe source of concrete supply and end at the near end.
In the cases of certain types of structures such as continuous girders and arches, the placementof concrete may have adverse effects on previously placed concrete or change the dimensions of thecompleted structure because of formwork or falsework deformation. The order and rate ofplacement, therefore, must be determined taking those possibilities into consideration. There were
projects in which falsework collapsed because of careless placement of concrete. The order ofplacement needs to be determined so that loads on falsework can be distributed as evenly as
possible.
(2) The quality of fresh concrete is easily affected by not only time as mentioned in Item (1) but
123

Standard Specifications for Concrete Structures-2007, Materials and Construction

also the transportation method. In general, the use of truck agitators is effective in maintaining
slump and preventing segregation when transporting concrete from the plant to the construction site.
In some cases such as when the volume of concrete being transported is small or when the concrete
is exposed to sunlight during transportation, the amount of decrease in slump may be large.
Methods of on-site transportation include the concrete pump, bucket and chute methods. When aconcrete pump is used, it is necessary to take into account slump and powder content settings
allowing for pumpability and decreases in slump during pumping as mentioned in Chapter 4, Mix
Design. In transportation by use of buckets, which do not have an agitating function, there may becases where changes in slump over time are larger than the changes assumed in Item (1) orvibration causes segregation. It is therefore necessary to select a transportation method so that therequired quality of concrete can be attained.
Even in cases where mix proportions are appropriate, if the method of transportation, placement,
compaction or finishing is not appropriate, the segregation of concrete may result during any of
those tasks. During transportation, placement, compaction and finishing, concrete needs to beprotected from sunlight and weather. It is also important to consider the order of placement in orderto prevent cold joints by placing concrete within the allowable placement interval.

7.2

Time from Mixing to Finishing the Placement

As a standard, the time from the completion of mixing to the completion of placement
should be 2 hours or less or 1.5 hours or less when outdoor air temperature is 25°C or
lower or higher than 25°C, respectively.([Commentary] Since the quality of fresh concrete changes over time after completion of mixing, it
is desirable that transportation, placement and compaction be completed as soon as possible. In
concreting work, however, it is often not possible to complete the placement of concrete in a shorttime after it is mixed because of transportation-related constraints concerning available plants,
available transportation routes, the location of the structure, etc., and placement- andcompaction-related constraints concerning the shape of the structure, reinforcement patterns,
available personnel and equipment, etc. It is therefore important to perform planning andmanagement, taking those constraints into consideration, so that various tasks can be smoothly
carried out within scheduled time frames and to check in advance on changes in the quality of fresh
concrete over time. Because the limit of time within which the placement of concrete can becompleted after completion of mixing varies depending on conditions such as concrete mix
proportions, materials used, temperature, humidity and transportation methods, good practice is toset a limit suitable for each concreting work in view of these conditions. In general, the time limit isabout 2 hours at or below 25°C and 1.5 hours when outdoor air temperature is higher than 25°C.
These time limits, therefore, are specified in this Specification.
If the minimum slump for placement cannot be achieved by the time the placement of concrete
is completed, it is necessary to take measures such as considering the use of a construction method
for completing the task in a shorter time than the specified standard time, modifying the mix
proportion so as to reduce changes in slump over time or increasing the slump upon completion of
mixing. An effective method for reducing changes in slump over time is to use a chemical
admixture that excels in slump retention such as an air-entraining high-range water-reducing agent.
If slump upon completion of mixing is to be increased, it is advisable to consider a switch to a124

Chapter 7

Transportation, Placement, Compaction and Finishingchemical admixture that functions as an effective water reducer such as an air-entraining high-range
water-reducing agent because the water content tends to increase if slump upon completion of
mixing is increased. When taking these measures, it is necessary to conduct studies on thosemeasures well in advance to verify their effectiveness.

7. 3

Transportation

7.3.1

Transportation to the construction site(1) In cases where ready-mixed concrete is used, the provisions of JIS A 5308
regarding transportation shall be followed.
(2) In cases other than those mentioned in Item (1), it shall be ascertained that thetransportation method used permits easy unloading, causes little segregation duringtransportation and minimizes changes in slump, air content, etc.

[Commentary](1) JIS A 5308, Ready-Mixed Concrete, specifies the performance oftransportation vehicles and requires that as a general rule, the process from mixing to unloading becompleted within 1.5 hours. Since, however, this Specification requires that when outdoor air
temperature is higher than 25°C, after completion of mixing, the placement of concrete, as a generalrule, be completed within 1.5 hours, it is recommended that the transportation from the plant to theconstruction site be completed in about one hour.
(2) If the transportation distance is long or the slump of concrete is large, truck mixers with anagitation function or truck agitators must be used for transportation. In cases where concrete with aslump of 5 cm or less is transported over a distance of 10 km or less or such concrete can betransported within one hour, the method of using dump trucks or dumpers or buckets loaded on
automobiles may be used after ascertaining that segregation does not occur and changes in slump,
air content, etc., are small. In cases where there is no empirical knowledge about combinations ofconcrete quality and transportation methods, it is necessary to conduct tests under realistic
conditions to determine the influence on changes in the quality of concrete.

7.3.2
7.3.2.1

On-site transportation
Concrete pump

(1) Prior to the pumping of concrete, details such as the type of concrete pump, pipe
diameter, piping route and discharge rate shall be determined, taking the pumpability ofconcrete into consideration, so that concrete of the required quality can be obtained.
(2) Pipe diameters shall be selected in view of the type and quality of concrete, themaximum size of coarse aggregate, pumping conditions, ease of pumping, safety, etc., sothat pumping capacity is sufficiently large. It is desirable that concrete pump locations
and piping routes should be determined so that the piping distance and the number ofbends are minimized.
(3) The type and number of concrete pumps shall be determined in view of pumping
load, discharge rate, the rate of placement and the environmental conditions at the job

125

Standard Specifications for Concrete Structures-2007, Materials and Construction

site.
(4) If difficulty in pumping is expected, test pumping shall be conducted in advance tocheck on the pumpability and quality of concrete.
(5) It is recommended that prior to the pumping of concrete, mortar with a mix
proportion equivalent to that of the mortar in the concrete should be pumped so thatmortar sticks to the inside surfaces of the concrete hopper and piping. As a general rule,
however, the mortar should not be pumped into the formwork.
(6) Pumping shall be planned and controlled so that pumping can be carried out ascontinuously as possible. When pumping needs to be interrupted for a long period oftime, appropriate measures shall be taken so that the pumpability and quality of concrete
are not lost after pumping is resumed.

[Commentary] (1) Concrete to be pumped must have pumpability suitable for pumping. This
Specification, therefore, provides for mix requirements such as the powder content in Chapter 4,
Mix Design, and requires that slumps be determined taking into account changes over time anddecreases due to pumping. Prior to the pumping of concrete, the type, locations and number ofconcrete pumps, piping routes, the diameter and type of pipe, discharge rates, etc., must be
determined appropriately so that the assumed conditions are met.
It is also important that not only the slump but also the air content, unit mass, temperature, etc.,
of pumped concrete be within the required ranges. If changes in the quality of pumped concrete falloutside the expected ranges, it is necessary to reconsider the concrete mix proportion, slump,pumping methods, etc., and take appropriate measures.
For matters not described in this section, the Recommendations for Placement of Concrete by
Pumping should be consulted.
(2) Piping diameters should be determined after considering the maximum size of coarse
aggregate, the amount of pumping load, etc. As the pipe diameter increases, the pumping loaddecreases. The use of large-diameter pipes, therefore, is desirable, but it is recommended that pipe
diameters be determined in view of the fact that large-diameter pipes lower the efficiency of work
associated with the handling of pipes.
In concrete pumping, pipes with a nominal diameter of 100A (4B) or 125A (5B) are used inmany cases. In large-scale construction, 150A (6B) pipes may be used. In general, pipes with anominal diameter of 100A (4B) can be used in cases where the maximum size of coarse aggregate is
25 mm or less and the piping distance is relatively short. The "nominal diameter" here refers to theinside diameter of pipe expressed in millimeters and inches. For example, "100A (4B)" means an
inside diameter of about 100 mm, or about 4 inches.
In order to reduce the overall pumping load and prevent the clogging of piping, it is desirable
that concrete pump locations and piping routes be determined so that the piping distance and thenumber of bends in piping are minimized. The pipe sections near bent or tapered pipe sections are
particularly subject to flow velocity fluctuations, pressure loss and clogging. Good practice,therefore, is use bent pipes with a large radius of curvature and gently tapered pipes.
In order to perform stable pumping, it is necessary to inspect the pipes for deposits on theirinside surfaces, wear, etc., and consider vehicle allocation methods for smoothly supplying concrete
from the transportation vehicles to the concrete pumps and methods for facilitating tasks such as
126

Chapter 7

Transportation, Placement, Compaction and Finishingassembling the pipes for pumping, washing the inside surfaces of the pipes after pumping andmoving and removing the pipes. Appropriate piping routes, pipe support methods, working
platforms, etc., need to be selected so that the formwork, reinforcement and previously placed
concrete are not adversely affected by the vibration and loads from the pipes during pumping
operations.
(3) Selection of the type of concrete pump is the most important item for carrying on placementof concrete with pump smoothly. The maximum pumping load on the concrete pump (Pmax) can beestablished on a basis of the result in the similar type of construction site or the one from thepreliminary pumping test. However, in general, Pmax is calculated by using a following equation,then the type of concrete pump is selected in a manner that the calculated maximum pumping load
is no more than 80 % of the pump capacity. If some restraints may exist in a size of the setting yard,
the size and dimension are also decisive conditions for selecting the pump type.
Pmax = (Loss in pressure per 1m length of horizontal pipe) x (Equivalent horizontal pumping distance)

Pressure loss per 1meter length of the horizontal pipe can be decided by using data of the typeand quality of cement, rate of pumping, diameter of the pipe, and the loss is larger with the smaller
value of slump, the smaller value of transportation pipes and the larger rate of pumping. Fig. C 7.3.1
shows the standard values of the loss in pressure in the case of concrete using 20~25mm of
maximum size of coarse aggregates. When using the coarse aggregates having 40 mm of maximum
size, the values should be increased 10% from the values shown in this figure. Here, as for theequivalent horizontal pipe length for each type of pipe, which is for calculating the equivalenthorizontal pipe distance, the values shown in Table C7.3.1 can be used.

Loss of pressure in the pipe
10-1 (N/mm2/m)*

Slump: 8cm** Slump: 12cm

*
**
*
**

*

**
Rate of pumping (m3/h)

Fig. C7.3.1 Standard values of the loss in pressure(maximum size of coarse aggregate: 20 to 25 mm, cement content: about 300 kg/m3,
air-entraining water-reducing agent used)127

Standard Specifications for Concrete Structures-2007, Materials and Construction

Table C7.3.1 Equivalent horizontal pipe length
Item

Unit

Vertical pipe

1 meterTapered pipe＊＊1 piece

Bent pipe

1 piece

Flexible hose

Nominal diameterof pipe

Equivalent horizontal pipe
length＊ (ｍ)100A(4B)
125A(5B)
150A(6B)
175A(4B)->150A
150A(5B)->125A
125A(6B)->100A

3
4
5

90 ° r＝0.5 m
r＝1.0 m
5~8 m/one piece

3

6
20

* The value for the pumping of the normal concrete** The value for Tapered pipe with 1m of the length as the standard, and established on thebasis of the diameter of the smaller pipe

The volumetric efficiency of a pump varies depending on concrete mix proportions, theproperties of fresh concrete, etc., and the actual discharge rate is smaller than the theoreticaldischarge rate. Since the rate of placement in the construction plan is the average rate of placement
work including such tasks as moving the pipe end and compacting the concrete, the actual discharge
rate is higher than the rate of placement. The discharge rate assumed for calculation purposes,
therefore, must be a value reflecting the volumetric efficiency of the pump and work efficiency, and
it is necessary to draw up a plan so that pumping can be performed smoothly even at that discharge
rate. The number of concrete pumps is determined in view of the rate of pumping, the discharge rate
for the type of pump to be used, the size of concreting blocks, the volume of concrete to be placed,the order of placement, the rate of placement, the state of supply of concrete, compaction capacity,
the number of placing locations, etc. For concreting work that requires continuous placement of
concrete, it is good practice to prepare backup concrete pumps.
(4) If difficulty is expected in the pumping of concrete, it is necessary to check the functioningof concrete pumps, pumping loads, the condition of discharged concrete, etc., by taking appropriate
measures in advance such as conducting test pumping under realistic piping conditions.
Pressure losses in pipes and changes in the quality of concrete due to pumping are largely
unknown because they vary depending on the type of concrete used, construction conditions andenvironmental conditions. The types of concrete and the construction and environmental conditions
that require careful consideration in connection with pumping include the following:(a) Pumping of lean concrete with a cement content of less than about 270 kg/m3 or richconcrete with a cement content of more than about 350 kg/m3(b) Pumping of concrete with a pre-pumping slump of less than 8 cm(c) Pumping of concrete containing plasticizer or air-entraining high-range water-reducing agent(d) Pumping of concrete in a construction environment described in Chapter 12, Cold-weather
Concrete, or Chapter 13, Hot-weather Concrete

128

Chapter 7

Transportation, Placement, Compaction and Finishing(e) Pumping from a higher point to a lower point or over a long distance(f) Pumping or lightweight aggregate concrete, high-strength concrete, high-fluidity concrete,
fiber-reinforced concrete, antiwashout underwater concrete or shotcrete for tunnel
construction mentioned in the Construction: Special Concretes of this Specification
If difficulty in the pumping of concrete is expected, it is desirable that test pumping be
conducted under realistic piping conditions in advance to check on how concrete pump operation,
pumping loads, the condition of discharged concrete, etc. If test pumping under realistic conditions
is not possible because of constraints associated, for example, with cost, time or site conditions,pumpability may be evaluated on the basis of available pumping data obtained under similar
conditions or by conducting test pumping under short piping conditions. Simple methods forevaluating the pumpability of fresh concrete in advance include JSCE-F 502, Method of Test of
Bleeding under Pressure.
(5) Prior to the pumping of concrete, measures to prevent interruption due to clogging, such as
pumping mortar in advance, for the purpose of lubricating the inside surfaces of concrete pumps
and pipes. Although the quantity of mortar pumped in advance is small, the mortar, as a general rule,
must not be pumped into the formwork.
(6) Concrete leaving inside of pipe during an interruption of pumping may causes blocking due
to the decrease of pumpability because of segregation and loss of workability. Also, quality of theconcrete may be adversely affected. Therefore, concrete sent to hopper of concrete pump should bepumped continuously, and placed and compacted rapidly. In cases when an interruption cannot be
avoided because of segregation and loss of workability. Also, quality of the concrete may be
adversely affected. Therefore, concrete conveyed to hopper of concrete pump should be pumped
continuously, and placed and compacted rapidly. In cases when an interruption is not avoidable
because of movement of pipes, shift of workers, a rainfall, or any other unexpected situations, a
resuming time should be informed to the persons concerned. In the case of interruption over a long
period, interval operations shall be done to prevent blocking. If possibility of occurring blocking ishigh due to the interruption of pumping for a long time, all of the concrete in the pipes shall bedischarged.

7.3.2.2

Buckets

Buckets shall be fabricated so that segregation is minimized when concrete is poured
in and discharged, concrete can be easily discharged, and, when closed, concrete andmortar do not leak.

[Commentary] The method of receiving concrete discharged from a mixer with an appropriately
structured bucket and immediately transporting the bucket to the placing location is convenient
because concrete can be transported to the placing location by moving it in the vertical andhorizontal directions easily.
For the bucket method of placement, as shown in Table 4.4.6, slump correction values under
different construction conditions are not specified as for the concrete pump method. Bucket
transportation, however, is often more time-consuming than concrete pumping. The method ofmoving a bucket with a crane is one of the transportation methods that are effective in reducing thesegregation of concrete. If concrete is left in a bucket, which does not have an agitating function, fora long time, the possibility of segregation and the occurrence of changes in workability increases.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

When using the bucket method of transportation, therefore, it is necessary to draw up a plan andperform quality control in view of the rate of placement in the bucket method and changes in thequality of concrete. A bucket used in this method should have an outlet at the center of the bottom
because an outlet located off-center tends to cause segregation when the concrete is discharged.

7.3.2.3

Chutes(1) As a general rule, a vertical chute should be used if the chute method is used.
(2) When an inclined chute has to be used, as a general rule, the slope of the chuteshall be steep enough to prevent the segregation of concrete and should not be gentler
than 1 vertical to 2 horizontal.
(3) The structure and method of use of a chute shall be conducive to the prevention of
the segregation of concrete.

[Commentary] (1) and (2) Concrete transported in an inclined chute is prone to segregation. The
tendency to use large-slump concrete with the aim of facilitating concrete flow may aggravates
segregation. It is required as a standard practice, therefore, that when a chute is used, a vertical one
should be used. Depending on construction conditions, however, there may be cases where an
inclined chute needs to be used. In such cases, the slope of the chute must be steep enough toprevent the segregation of concrete, and must not be gentler than 1 vertical to 2 horizontal. If
concrete does not flow down the chute smoothly, it may be necessary to change the inclination ofchute or modify the concrete mix proportions. It is desirable, therefore that the condition of concrete
flow be observed in advance by using the planned chute and concrete.
(3) Chutes must be structured to minimize the segregation of concrete. Vertical chutes include
ones that has a funnel tube and ones made by using flexible tubes. Vertical chute joints must be
sufficiently strong so that they do not come off because of the impact of falling concrete. Inclined
chutes include iron chutes, chutes with sheet iron linings, chutes consisting of iron pipes andflexible tubes, and lightweight FRP chutes. When using an inclined chute, it is necessary to provide
the outlet with a funnel tube and baffle plates to reduce segregation.
It is good practice, when using a chute, to wash it with water before and after it is used and let
mortar flow down the chute before using it. Care should be taken, however, so as not to let thewater or mortar that has flowed down the chute flow into the concrete or the formwork.
The lower end of the funnel tube needs to be kept as close to the concrete placement surface aspossible. Because pouring too much concrete at one location would necessitate moving concrete
laterally and cause segregation, it is necessary to carefully consider details such as the spacing of
concrete inlets and the order of pouring. If concrete transported in an inclined chute is found to havesegregated, it is necessary to receive the concrete at the outlet and remix the concrete before usingit.

7.3.2.4

Other transportation equipment(1) If a pneumatic concrete placer is used, careful studies shall be conducted to decideon which concrete placer to use and the method of use because the transportation

130Chapter 7

Transportation, Placement, Compaction and Finishingdistance varies depending on the model and type of concrete placer.
(2) If a belt conveyor is used, appropriate measures shall be taken for protection fromsunlight and weather, and, in order to prevent the segregation of concrete, baffle plates
and a funnel tube shall be provided at the discharge end of the conveyor.
(3) When wheelbarrows, tramcars, etc. is used, the transportation distance shall not belonger than 50 to 100 m, if a flat haul way can be provided and if the segregation of
concrete can be prevented.

[Commentary] (1) Like a concrete pump, a pneumatic concrete placer, which pumps concrete in
the conveyance pipe by compressed air, is useful in delivering concrete to a constricted space suchas a tunnel. The distance over which concrete can be transported with a pneumatic concrete placer
varies with air pressure, air consumption, etc. The model, type and other details of a pneumatic
concrete placer to be used, therefore, need to be selected after careful study.
The number of bends in conveyance piping should be minimized. Only horizontal or upward
sloping piping must be used, and downward sloping piping must not be used. In a downward
sloping pipe, concrete moves under its own weight and the state of flow in which the pipe is filledwith concrete is destroyed so that pumping becomes difficult and a blowout of compressed air may
result.
If the segregation of concrete occurs when concrete is discharged from the pipe, it is goodpractice to take such measures as mitigating the impact at the time of discharge and letting thedischarged concrete hit a straw mat, hemp cloth or other similar material suspended in front of theoutlet of the conveyance pipe. Using highly viscous concrete, that is, concrete with a high sandpercentage and a relatively high mortar content may be effective in reducing segregation.
(2) A belt conveyor is convenient for the continuous conveyance of concrete. In the arrangementof conveyors, not only the difference in each conveyor level should be as small as possible, but also
the conveyors should keep their slope within a certain level in which any segregation does not occur
in concrete. The longer the conveyance distance, the longer the concrete is exposed to air, causing
drying, or changing of its slump. Therefore, steps must be taken to top the belt conveyor with acover. A device shall be installed at the end of the conveyor to prevent the deposition of mortar on
the return belt. Provision of baffle plates and a funnel tube is effective to prevent the segregation of
concrete. If the concrete is deposited in a set position by the belt conveyor, it must be shiftedlaterally within the forms resulting in a larger segregation, therefore, the end of the belt conveyor
shall be able to be moved.

7. 4

Placement

7.4.1

Preparation(1) Prior to the placement of concrete, it shall be ascertained that the reinforcing steel,formwork and others have been placed in accordance with the construction plan.
(2) Just before the placement of concrete is started, the insides of the transportationequipment, placing equipment and formwork shall be cleaned, and the intrusion of wood
fragments or other foreign matter shall be prevented. Any thing that may absorb water
when in contact with concrete shall be wetted in advance.

131Standard Specifications for Concrete Structures-2007, Materials and Construction(3) Water remained in the formwork shall be removed prior to the placement of
concrete. Appropriate measures shall be taken so that water flows into the formwork towash newly placed concrete.

[Commentary] (1) Besides the checks to be made prior to the placement of concrete, it isnecessary to ascertain that neither the reinforcing steel nor the formwork is likely to be moved by
the concrete placement work, the pressure from the concrete being placed, etc. (see Chapter 10,
Reinforcement, and Chapter 11, Formwork and Falsework).
(2) If transportation equipment is dry, concrete may stick to the equipment so that transportation
becomes difficult to carry out. If the moisture in newly placed concrete is absorbed by theformwork, it is often not possible to obtain a good surface finish after the formwork is removed. It
is therefore necessary to moisten the potentially water-absorbent regions in advance. Care must be
taken, however, not to be excessive in wetting so that pools of water form.
(3) If concrete is poured into the formwork where there is a pool of water due to rain,
groundwater inflow, curing water, bleeding water from previously placed concrete, etc., the quality
or integrity of concrete may be lost. Such water, therefore, needs to be removed before theplacement of concrete. If rainwater or groundwater enters the formwork, the concrete surface may
be washed. It is therefore necessary to take rainproofing or waterproofing measures in advance.

7.4.2

Placement(1) Concrete shall be placed carefully so that neither the reinforcing bars nor theformwork move out of position.
(2) Placed concrete shall not be moved laterally in the formwork.
(3) If severe segregation is identified during the placement of concrete, the placement
shall be stopped, and a method for reducing segregation shall be determined andimplemented.
(4) Except at planned construction joints, the placement of concrete shall be carriedout continuously until the placement is completed.
(5) As a general rule, concrete should be placed so that the surface of the newly placed
concrete becomes nearly horizontal. The standard lift height for concrete placement shallnot be greater than 0.4 to 0.5 m in view of the performance of the internal vibrators used.
(6) If concrete is placed in two or more layers, placement shall be carried out so that an
overlying layer becomes integral with an underlying layer. The area of each concretingzone, concrete supply capacity, allowable placement interval, etc., shall be determined sothat cold joints do not result. The term "allowable placement interval" is the time after
completion of the placement and compaction of the underlying layer of concrete until theoverlying layer of concrete is placed after a period of standing time. Standard allowable
placement intervals are shown in Table 7.4.1. When a new layer of concrete is placed on apreviously placed layer, vibrators shall be inserted into the underlying layer, too, for132

Chapter 7

Transportation, Placement, Compaction and Finishingcompaction in accordance with Section 7.5 (4)..

Table 7.4.1

Standard for the allowable time lag between two placing lifts

Temperature in the environment

Allowable time lag between two placing lifts

Over 25˚C

2.0 hours

25˚C or less

2.5 hours(7) When placing concrete into high formwork, the inlet shall be positioned in theformwork, or the discharge location of the vertical chute or pipe shall be lowered close to
the surface. In such cases, the distance of the surface of placing from the outlet of thechute, pipe, bucket, hopper or other devices, should, in principle, not exceed 1.5m.
(8) In cases when bleeding water appears at the surface during the placement of
concrete, the water shall be removed using appropriate methods, before placing more
concrete.
(9) The standard rate of placement under normal conditions is about 1 to 1.5 m per 30
minutes. It is desirable, however, that adjustments should be made according to the sizeof the cross section, concrete mix proportions, compaction methods, etc.
(10) If the concrete of a slab or beam is continuous with the concrete of a wall orcolumn, it is a standard requirement that the placement of the concrete of the slab or
beam should be started after the settlement of the concrete of the wall or column haslargely ended in order to prevent settlement cracking.
(11) In cases when concrete is to be placed directly onto the ground, a layer of levelingconcrete should be placed beforehand.

[Commentary] (1) As concrete placing may disturb the reinforcement and forms arrangements, it
shall be placed carefully, and it is also desirable that reinforcement workers stand by during placing,in preparation for reinforcement disturbance by any chance.
(2) If concrete is deposited at the point far away from the intended casting place, it needs to be
moved again to the planned point. As segregation is likely to occur after each handling, it isimportant to deposit the concrete at the placement point to avoid segregation.
(3) If severe case of segregation is observed during placement, it is difficult to obtain
homogeneous concrete by remixing. Therefore, the placing of the concrete into the form must be
discontinued and the cause of the segregation studied and corrected for subsequent concrete
placement.
(4) Since construction joints tend to become structural weak spots, it is necessary to draw up aplan for continuous placement of concrete and control vehicle operation and placement work so that
construction joints are not made except at the planned locations.
(5) To obtain uniform concrete, it is necessary that the concrete be placed as to result in a nearly133

Standard Specifications for Concrete Structures-2007, Materials and Construction

flat surface within the forms and be uniformly compacted by vibration. In case when a lot of
concrete is placed in the large area, it is recommended to limit the concrete placing rate at one pointaccording to the capacity of compaction by preparing the placing points as many as possible, so thatthe surface of concrete in the whole area for placing should keep its flat level. If the number of theplacing points is a few, the placing rate in each point tends to increase, and the works may change to
be rough. Consequently, the possibility not to place the dense concrete becomes high. Therefore, it
is important that the balance between number of the placing points and the placing speed iscontrolled properly.
If the height of a layer is about 0.4 to 0.5 m or less, which is smaller than the length of thevibrating part of an internal vibrator, lateral movement of concrete can be reduced. This is why that
range is specified as a standard ranged in this Specification. If a layer exceeding that range is placed,
it must be ascertained, for example by conducting a test, etc., using a realistic structural model, that
there will be no adverse effect, and an appropriate construction method must be determined.
(6) This clause is given to ensure a consolidated condition between layers when concrete isplaced in separate layers. Cold joints may develop if the upper layer is placed when concrete of thelower layer has begun to harden. For preventing the cold joint, it is important that the time span
until placing new concrete on consolidated fresh concrete shall be specified and controlled, inconsideration of the effects of type and, quality or performance of concrete, elapsed time between
the start of mixing concrete to the finishing of placing, concrete temperature, compaction method
and so on. Especially, due to rapid setting, the possibility of the occurrence of cold joints in hot
weather concrete is higher than that of normal condition concrete. In case when a lot of concrete isplaced in the large area, the same attention should be paid for taking long time until placing
concrete on previous compacted concrete.
The available time elapsed for placing concrete on previously compacted concrete is different
depending on type of cement, type and dosage of chemical admixture, concrete temperature,temperature in atmosphere and etc. and etc. for normal concrete. Values given in Table 7.3.1 should
be taken as standard for the time elapsed for placing concrete on previous compacted one. If thecold joint is highly susceptible to occur, some of countermeasures shall be taken; such as use of aretarding type of air-entraining and water-reducing admixture, reduction of the height of one lifts
and so on. As the method to establish the available time elapsed for placing concrete on previously
compacted concrete before construction and to judge the possibility of continuation of the placing
under the problem in construction, there are Proctor penetration resistance test and the method
inserting the reinforcing bar or the steel bar for slump test to concrete at the construction site. Whenthese methods are carried out, Concrete Library ”Cold joint in concrete structures and its’countermeasures” should be referred to.
(7) When concrete is deposited from high position or discharged from above to build a high walland so forth, segregation is often caused due to striking of concrete, forms and reinforcing bars. It isalso possible that concrete deposited on the forms and bars subsequently harden, causing
interference to subsequent jobs or becoming a defect in the structure. In such a case, it is necessary
to provide an opening in the form or to lower the discharging outlet of the vertical chute or to movethe pump pipe closer to the surface of placement. Therefore, to prevent material segregation beingcaused by dropping concrete from overhead, the falling distance from the discharge outlet to theplacement surface must be defined.
(8) If water left on the surface of newly placed concrete is not removed, it may wash the surface
in contact with the formwork and cause sand streaking and the formation of a weak layer near theconcrete surface. It is therefore necessary to remove water by appropriate means such as sponges,

134Chapter 7

Transportation, Placement, Compaction and Finishingladles and small submersible pumps.
(9) When concrete is placed continuously to build a high wall or column, it is possible that largepressure will be applied to the form or adverse effects due to bleeding will arise if the concrete isplaced too quickly, making the upper concrete weak or drastically reducing the bonding strength of
the horizontal reinforcing bars. To avoid this defect, the placing speed must be adjusted. It is
desirable that the speed be changed in accordance with the size of the cross section, concrete mix
proportion, method of compaction and so on, but ordinarily a speed of 2 m to 3 m per an hour isdesirable.
(10) In the case of certain types of concrete cast in the shape of a cantilevered member andconcrete cast as a wall or column continuous with a slab or beam, the degree of settlement of
concrete differs at different parts of the concrete with different cross sections. Consequently, if
concrete is placed at a time, cracking tends to occur in the boundary zones between different crosssections. This Specification requires, therefore, that the placement of concrete be interrupted at alocation where the cross section changes, and after the settlement of the concrete has largely ended,
the placement of an overlying lying lay of concrete, such as concrete to be cast in the shape of a
cantilever, be started. The time needed for the settlement of concrete varies with the materials used,temperature, etc., and cannot be indicated specifically, but it is usually 1 to 2 hours.

7. 5

Compaction(1) In principle, internal vibrators should be used for compacting concrete. Form
vibrators may be used for such structures as thin walls where the use of internal vibrators
is difficult.
(2) Scaffold installation and concreting methods shall be determined so that thecompaction height does not exceed the planned value.
(3) Concrete adjacent to the sheathing board shall be properly compacted around thesheathing board to ensure that the final concrete surface is as flat as possible.
(4) During compaction using vibration, the internal vibrator shall be inserted about
10cm into the lower layer of concrete.
(5) The spacing of interval vibrators and the vibration time at each location shall be
determined so that concrete can be adequately compacted. Internal vibrators shall bewithdrawn gradually so that holes are not left in the concrete.
(6) The time for revibration should be as late as possible to the extent that thecompaction of concrete is possible and there is no adverse effect such as cracking on theconcrete.

[Commentary] (1) Civil engineering structures are built with relatively thick members, often
made of stiff concrete. As a general rule, therefore, this Specification requires the use of internal
vibrators for compaction. Because there are many types of vibrators and performance varies among
different types, it is necessary to use vibrators suitable for the construction work to be carried out.
Internal concrete vibrators are specified in JIS A 8610, Internal Vibrators for Concrete, and concrete
form vibrators are specified in JIS A 8611, External Vibrators for Concrete. When using external(form) vibrators, it is important, among other things, to select vibrators of an appropriate type,135

Standard Specifications for Concrete Structures-2007, Materials and Construction

firmly secure the vibrators to the formwork and select appropriate installation locations andvibrator-moving methods.
(2) In order to achieve the required quality and filling ability of concrete, it is necessary to pourconcrete from an appropriate height and determine a compaction height from which the filling
process can be visually observed. Chapter 2 and Chapter 4 of the Construction: Construction
Standards of this Specification require that an appropriate slump be determined in view of thecompaction height. It is important to determine scaffold installation and concreting methods so thatthe compaction height does not exceed the planned value.
Details such as concrete mix proportions and workability are determined according to thedimensions of structural members and reinforcement patterns. In regions that are difficult to fillwith concrete such as densely reinforced regions, therefore, it is necessary to carefully compact
concrete before the workability of concrete decreases.
(3) Exposed surfaces of concrete must be flat. This is important not only for appearance but also
for the durability and water-tightness of the structure. It is therefore necessary to make sure thatsheeting surfaces are flat and mortar does not leak through sheeting joints and carefully place andcompact concrete.
(4) The aim of this provision is make sure that a newly placed layer of concrete is integrated
with the underlying layer.
(5) It is necessary to determine internal vibrator spacing and vibration time at each location sothat newly placed concrete is vibrated uniformly and to inform the construction workers of them inadvance. Important considerations in using vibrators include the following:(i) Internal vibrators should be inserted as vertically as possible at a uniform spacing. The
spacing should not be greater than a diameter in the range in which vibration is effective,
which is usually 50 cm or less for concrete with the average level of fluidity and viscosity.
The range in which vibration is effective, however, varies depending on various factors suchas the diameter of internal vibrators, compaction capacity at different frequencies, the fluidity(slump) and viscosity of concrete, the dimensions of structural members, and reinforcement
patterns. Decisions must be made, therefore, paying attention to the filling ability andsegregation of concrete.
(ii) The appearance of a cement paste line along the concrete–sheeting interface is an indicatorof adequate compaction. There are also other indicators: for example, the volume of concrete
ceases to decrease, the surface becomes glossy, and the entire concrete increasingly looks likea uniformly blended mixture. As a rule of thumb, vibration time is about 5 to 15 seconds.
Pulling out vibrators slowly is very important in order to make sure that holes are not left in
the concrete.
(iii) Internal vibrators must not be used for lateral movement, which may cause segregation.
(iv) The type, size and number of vibrators need to be suitable for the compaction of the entire
volume of concrete to be compacted at a time. To this end, it is necessary to select the type,size and number of vibrators according to the thickness and area of structural member crosssections, the maximum volume placed per hour, the maximum size of coarse aggregate, mix
proportion (particularly the sand percentage), the slump of concrete, etc. Although the volume
of concrete that can be compacted with a single internal vibrator varies depending on the site
conditions, it is about 4 to 8 cubic meters per hour for concrete to be used for an ordinary136

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Transportation, Placement, Compaction and Finishing

structure.
(6) Re-vibration refers to the second application of vibrations at a certain time after the firstcompaction of concrete, and to do this, the timing has to be adequately determined. Re-vibration
given at the proper time plasticizes the concrete again to reduce air/water cavities in the concrete. It
is also effective in enhancing the concrete strength and the bonding strength to the reinforcement,
and preventing the development of settlement cracks. The benefits of the re-vibration are best
attained when it is done as late as possible while the concrete still holds its plasticity. However
problems such as the development of cracks within the concrete will arise if re-vibration is done toolate. Moreover, it shall be confirmed that the vibration transporting to reinforcing bars does notinjure the concrete that has already been in the setting condition.

7. 6

Finishing

7.6.1

Surface finish of placed concrete(1) Upon completion of compaction, the upper surface of concrete shall be leveled at
the specified height and shaped as specified, and the finishing procedure shall be
repeated while removing the water on the upper surface of the concrete until the water
having seeped out from the concrete is completely removed. This finishing work,
however, shall be performed carefully so that it is not excessive.
(2) Cracks that have occurred after finishing work until the concrete begins to set shallbe repaired by tamping or refinishing.
(3) When a smooth and dense surface is required, the surface finishing shall bedelayed to the possible extent and carried out by applying reasonable pressure using asteel trowel.

[Commentary] (1) It is necessary to remove the excess bleeding water accumulated at the top. A
layer of laitance or fine cracks at the top may exist when the excess bleeding water remains after
finishing.
Normally surface finishing is roughly done by a wooden float followed by finished with a steel
trowel if necessary. However excessive finishing tends to cause shrinkage cracking because of theaccumulation of cement paste at the top. Furthermore, a layer of laitance may be formed and reduceabrasion resistance.
The use of equipment capable of smoothly finishing the entire concrete surface is helpful inobtaining a densely compacted concrete surface finish. Because finishing equipment is easy to workwith, it is possible that regions of concrete in different states of surface due to differences in thetime elapsed after placement and the degree of drying are finished in a similar way. Before using
finishing equipment, therefore, it is necessary to conduct careful studies on the quality of concrete,
the performance of equipment and construction methods.
In cases where the water/cementitious material ratio is low or high-early-strength portland
cement is used, a small amount of bleeding may result in localized hardening of the concretesurface from immediately after placement. For details about the finishing of low-bleeding concrete,refer to Chapter 6, High-Strength Concrete, of the Construction: Special Concretes of thisSpecification.

137

Standard Specifications for Concrete Structures-2007, Materials and Construction(2) About the time when bleeding water disappears from the concrete surface, the concrete
becomes subject to cracking due to factors such as shrinkage caused by rapid drying of the surface.
It is important to carry out appropriate curing in accordance with Chapter 8, Curing, in order toreduce drying due to sunlight or wind. Surface areas near reinforcing bars are particularly prone to
cracking due to the subsidence of concrete. The time needed before the settlement of concrete ends,
which cannot be indicated clearly because it varies depending on such factors as concrete mix
proportions, materials used and temperature, is usually one to two hours. Measures that can betaken against cracks include tamping with a trowel and revibration by use of vibrators, etc.
Revibration needs to be carried out carefully in accordance with Section 7.5 so as not to cause adegradation in quality.
(3) Finishing with steel trowels may be commenced when the surface has hardened enough tothe degree that the surface remains without leaving an indentation when pressed with the finger. The
mixture proportions, weather conditions, atmospheric temperature and other factors influence thetiming for the commencement of finishing operation. This operation shall be performed with heavypressure to consolidate the surface cement paste and produce the dense and hard surface.
In certain types of concrete such as low-bleeding concrete, even if the surface of newly placed
concrete hardens because of the evaporation of moisture, the inner part of the concrete may still besoft and water may seep out as the concrete surface is troweled. The time for final finishing needs tobe determined in view of the setting time, the degree of dryness of concrete, etc.

7.6.2

Correction of surface finish defects

If a hardened surface is not in a satisfactory condition or if cracking has occurred,appropriate repairs shall be performed on an as-needed basis.

[Commentary] Protrusions, streaks, etc., on the surface of concrete must be removed to make thesurface flat. Honeycombed surfaces, cross-sectional loss regions, etc., must be repaired by selecting
appropriate materials and repair methods on an as-needed basis in view of such factors as durability,
appearance and safety. If a cross-sectional restoration method of surface treatment method is used,refer to the Recommendations for Concrete Repair and Surface Protection of Concrete Structures.
Possible causes of cracking during construction include those attributable to materials used or mix
proportions, those attributable to construction methods and those attributable to design. The causeof cracking must be identified, and appropriate repairs must be made if necessary. For theestimation of the causes of cracking and the selection of repair methods, refer to the Practical
Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures (Japan
Concrete Institute). It is desirable that records of problem locations, their causes and repair methods
be kept for reference at the maintenance stage.

7.6.3

Special finishing(1) When the surface is subjected to abrasion, concrete having the required strength
shall be fully compacted and finished flat. After finishing, it shall be kept moist for aperiod longer than normal concrete and adequately cured.
(2) When special finishing is carried out, it shall not cause reduction in the138

Chapter 7

Transportation, Placement, Compaction and Finishingcross-section or loosening of the concrete, which may adversely affect the whole
structure.

[Commentary] (1) Finished surfaces of water channels, sediment flush channels, etc., may berequired to be resistant to abrasion. The use of hard and highly friction resistant high-quality
aggregate and concrete with a low water/cementitious material ratio is helpful in increasing theabrasion resistance of concrete. In order to obtain well-compacted, homogeneous concrete, careful
compaction and adequate curing must be carried out. Abrasion resistance can be enhanced byextending the curing period because the hydration of cement progresses that much.
When using abrasion-resistant materials such as silica fume, iron powder, iron aggregate,
polymer and steel fibers, it is important to carefully check in advance on the quality of concrete
made by using those materials and methods for producing and placing concrete made with thosematerials.
Rough surfaces or joints of concrete make the concrete prone to abrasion and cavitation.
Regions of concrete in contact with inclined form surfaces tend to attract air bubbles so that weaklayers are formed. Because it may be possible to alleviate this problem by using devices such aspermeable forms and absorptive sheeting, such devices should be used after verifying theireffectiveness by conducting realistic model tests.
(2) When producing a special finish or washed finish, it is necessary to be careful so as not tocause adverse effects on the structure such as a reduction in cross-sectional area or loosening of
concrete. Since there are various methods of producing special finishes and various rules associatedwith them, it is also necessary to follow those rules when producing special finishes. If a surface
treatment (protection) method is used for the purpose of enhancing durability, appearance, etc., referto the Recommendations for Concrete Repair and Surface Protection of Concrete Structures.

139

Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 8 CURING

8.1

GeneralFor the curing of concrete, a method that maintains the temperature and humidity
required by concrete to harden for a certain period of time after the placement of concrete
and is not adversely affected by the environmental conditions shall be selected.

[Commentary] In order for concrete to develop, through hydration, its required performance suchas strength, durability, cracking resistance, water-tightness and protection of steel, it is necessary tokeep the newly-placed concrete in a sufficiently wet condition at an appropriate temperature for acertain period of time after the placement of concrete and to protect the concrete from adverse
effects. The series of tasks performed for this purpose is referred to as "curing."
Fig. C8.1.1 classifies curing tasks into three categories – keeping concrete in a wet condition,
controlling the temperature of concrete and protecting concrete from adverse effects – , andsummarizes the curing method in each category. Some of the curing methods are interrelated, andcuring is often carried out for two or more purposes.
It is important to determine specific curing methods and the number of days required for curingconsidering project-specific conditions such as the type of structure, construction conditions, site
conditions and environmental conditions in accordance with the applicable provisions. For further
information on curing methods for cold-weather concrete, hot-weather concrete and mass concrete,refer to Chapters 12, 13 and 15, respectively. For details of accelerated curing by use of steam, etc.,
refer to Chapter 14, Industrial Products, of the Construction: Special Concretes of thisSpecification.
Underwater
curingUnderwater
curing

Keeping
humidity humidity
Keeping

Ponding

Ponding

Sprinkling

Sprinkling

Moist(CuringMoistcuringcuring(Curing mat
or clothes)mat or clothes)
Wet sandWet sandMembraneMembrane
curingcuring(Solvent,
Fat Fattype type(Solvent,
Emulsion) Emulsion)Resintype (Solvent,Resintype(Solvent,Emulsion) Emulsion)Basis
ofofcuring
Basis
Curing

ThermalControl
Thermalcontrol

Mass concrete
Mass concrete

Ponding,
pipe cooling
Ponding,
pipe cooling

Cold Cold
weatherweather
concreting concreting

Insulation,
heat supply,
Insulation,
heat supply
steam,
electric
heating heating
steam,
electric

Hot weather
concreting concreting
Hot weather

Sprinkling,sunshadesunshade
Sprinkling,

Accelerated
curingAccelerated
curingSteam,
heat supply
Steam,
heat supply

Protection
againstProtection
against harmful
actions harmful

Fig. C8.1.1 Basis of Curing

140

Chapter 8

8.2

CuringMoist Curing(1) After placing, the loss of moisture due to exposure to sunshine and wind shall be
prevented until the concrete begins to harden.
(2) When the concrete hardens to the extent that further activities can be undertaken
without damaging its surface, the exposed surface shall be kept wet using methods suchas covering with a moist curing mat, clothes, etc., sprinkling or ponding with water. The
periods of time given in Table 8.2.1 should be taken as the standard duration formaintaining the wet condition.
Table 8.2.1 Standard curing duration
Daily mean
temperature

Ordinary portland cement

Blended cement B

High-early-strength cement

More than 15˚C

5days

7days

3days

More than 10˚C

7days

9days

4days

More than 5˚C

9days

12days

5days(3) If membrane curing is carried out, it is necessary to clarify the purpose of use, usea liquid membrane-forming compound with proven quality, effectiveness and ease of use,and shall uniformly apply the membrane-forming compound in the specified quantity at
an appropriate time.

[Commentary] (1) If the concrete surface becomes dry relatively quickly after placing and its
moisture is lost, the hydration reaction of cement does not progress satisfactorily, and if the surface
alone is quickly dried by exposure to sunshine and wind, cracks may be induced. Therefore, it isdesirable to provide a shelter made of sheets, etc., over the top of newly-placed concrete. Thus, it isnecessary to proceed with the curing of concrete concurrently with not only the post-hardening
construction tasks but also the pre-hardening tasks at the placement and finishing stages.
(2) To improve quality of concrete such as strength, durability and other performances, it isdesirable to keep the concrete wet as long as possible. As a result, concrete can harden sufficiently
and drying shrinkage during hardening can be minimized. However, for general structures it is bothdifficult and uneconomical to perform moist curing for a long period. In addition, most effects ofmoist curing are limited to the early age of curing. Therefore, standard periods for curing aredetermined as in the table mentioned above, although the effect of curing might be different
depending on the curing temperature. Even in cases where the compressive strength required forformwork and shoring removal shown in Table C11.8.1 has been obtained at an early stage, theconcrete needs to be kept in a wet condition during the curing period shown in Table 8.2.1.
Today, various types of cement, such as low-heat portland cement, moderate-heat portland
cement and three-component cement, other than the types shown in Table 8.2.1 are in use. There arealso cases where the curing period for concrete needs to be determined according to theconstruction period, construction methods, etc. It is difficult to specify curing periods for different
types of cement, construction methods, etc., in this Specification. It is desirable, therefore, that the141Standard Specifications for Concrete Structures-2007, Materials and Construction

curing period be determined in view of factors such as the type of cement, cement content, the typeand location of the structure, and weather conditions by conducting, if necessary, tests forverification. If concrete is likely to be subjected to seawater, alkalis, acidic soil or water or othererosive substances, it is necessary to use a longer curing period than in ordinary cases. If concrete is
likely to be exposed to seawater, refer to Chapter 11, Offshore Concrete, of the Construction:
Special Concretes of this Specification.
(3) Membrane curing is a curing method in which the evaporation of water is prevented byapplying a liquid membrane-forming compound to the concrete surface. Membrane curing is
usually used in cases where wet curing by means of moist curing (curing mat or clothes) or water
spraying is difficult to perform or there is a need to prevent the dissipation of moisture for a long
period of time after the specified wet curing is carried out. Membrane curing may also be used toreduce the evaporation of water after the placement of concrete or, in the case of high-viscosity
concrete such as high-strength concrete, to assist in finishing the concrete surface.
In order to form a watertight membrane, it is necessary to uniformly apply a sufficient quantityof liquid membrane-forming compound at an appropriate time. In general, it is necessary to carryout membrane curing immediately after the gloss of the water on the concrete surface disappears. If
membrane-forming compound cannot be applied immediately, the concrete surface needs to be kept
in a wet condition until membrane-forming compound is applied. If the membrane-forming
compound has adverse effects on the bond between concrete and reinforcing steel or between
concrete surfaces, the membrane-forming compound shall be applied so that it does not stick to thereinforcing bars or the construction joints. In cases where surface treatment of the finished surface
is carried out, if the membrane-forming compound could have adverse effects on the bond between
the finished surface and the coating material, it is necessary to perform appropriate surface
preparation, such as polishing the membrane-cured finished surface to remove themembrane-forming compound, after performing the required curing.
Requirements for liquid membrane-forming compounds include (1) impermeability to humidity(moisture), (2) ease of application, workability and no harm to human health, (3) excellent bond to
concrete, (4) excellent durability against weather and sunlight and (5) the absence of adverse effects
on the bond to coating materials, etc. When using liquid membrane-forming compounds, it is goodpractice to clarify the purpose of use, select liquid membrane-forming compounds appropriate forthe purpose of use and the performance requirements, and ascertain the dosage, construction
methods and other details needed to meet the performance requirements by referring to reliable
literature or conducting tests.

8.3

Temperature-Controlled Curing(1) Until the concrete has hardened to a certain extent, it shall be maintained undertemperature conditions required for hardening. Temperature-controlled curing shall be
carried out if required to protect concrete from the harmful effects of low and hightemperatures, as well as sudden changes in temperature.
(2) When temperature-controlled curing is carried out, the temperature-controlling
method, curing control method and duration shall be appropriately determined taking
into account the type of concrete, the shape and size of the structure, construction
method, and environmental conditions.

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Chapter 8

Curing[Commentary] (1) and (2) Cement hydration is remarkably influenced by the curing temperatureof concrete. Except in special cases, the concrete temperature begins to be influenced by the outside
temperature just after the concrete is mixed. In particular, concrete surfaces or thin members such as
walls and slabs are easily affected by the outside temperature. In general, the relationship between
curing temperature, concrete age and compressive strength can be expressed by the concept ofmaturity. When the curing temperature is lower, the period to obtain necessary compressive strength
becomes longer; on the other hand, when the curing temperature is higher it becomes shorter (seeChapter 12). However, the effect of curing temperature depends on the type of cement. Blended
cements such as fly ash cement or blast furnace cement tend to be sensitive to the curing
temperature. Therefore, for blended cements, a longer curing period than ordinary portland cement
is required, especially when the curing temperature is low. The hydration of ground granulated blast
furnace slag is highly dependent on temperature, and the temperature history and strength
development properties of structural members may differ considerably depending on factors such as
the dimensions of the members and the heat insulation property of the formwork.
Very low temperatures interfere with the hydration reaction of cement and may delay thedevelopment of strength. The concrete may also be subjected to initial frost damage. It is therefore
necessary to perform temperature control by heat supply or heat insulation for a given period tomaintain the necessary temperature conditions. For cases when the daily mean temperature is lessthan 4℃, it needs to be treated as cold weather concreting (see Chapter 12).
If the atmospheric temperature is extremely high, initial strength tends to develop quickly.
However, increase of strength over the long term tends to be small and durability or water-tightness
is sometimes inferior. In addition, special attention needs to be paid to keeping the concrete surface
wet. For cases when the daily mean temperature is greater than 25 ℃, it needs to be treated as hot
weather concreting (see Chapter 13).
If the member size is large and a considerable temperature increase according to hydration is
anticipated, or if a big temperature differential is anticipated, cracks may be induced by thermal
stress. Therefore, the concrete temperature and temperature differential have to be controlled bypipe cooling, surface heat insulation or a combination of both. Furthermore, when the atmospherictemperature is high, the additional effect due to the acceleration of cement hydration needs to beconsidered (see Chapter 14).
Accelerated curing includes atmospheric-pressure steam curing, autoclave curing and heatcuring. For further information on atmospheric-pressure steam curing and autoclave curing, which
are widely used for the factory production of concrete, refer to Chapter 14, Factory-Made Products,of the Construction: Special Concretes of this Specification. When heat curing is carried out by
using heater mats, jet heaters, etc., the concrete surface is subject to drying and cracking. In suchcases humidifying devices may be used. In accelerated curing, care needs to be taken because
cracking may result if the temperature is not lowered gradually after the completion of curing.

8.4

Protection Against Harmful Effects

Concrete shall be protected against harmful effects, such as vibration, impact andother loads, etc., that are likely to arise during the curing period.

[Commentary] Concrete which has not yet sufficiently hardened is likely to suffer damage,including cracks, due to impacts, excessive loads, vibrations, etc. Therefore, it is necessary to avoid
placing material or dropping heavy articles on the surface of the concrete during the hardening
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Standard Specifications for Concrete Structures-2007, Materials and Construction

period. Harmful conditions also include rain showers during placement, poor quality of curing water,
overheating during heat supply curing, etc. It is necessary to prevent the occurrence of theseharmful effects with full understanding of the properties of early-age concrete or, if it is unavoidable,
to protect the concrete from their influences. If concrete is likely to be exposed to seawater, refer to
Chapter 11, Offshore Concrete, of the Construction: Special Concretes of this Specification.

144

Chapter 9

JointsCHAPTER 9 JOINTS
9.1

General(1) Joints shall be located and structured as specified in the design drawings and thespecifications.
(2) If joints not specified in the design are to be provided, their locations, directions
and construction methods shall be specified in the construction plan so that the strength,
durability, watertightness and appearance of the structure are not degraded.

[Commentary] (1) Joints in a structure greatly affect the strength, durability and appearance ofthe structure. Joints shall be provided carefully because they may become structural weak links inthe event of an earthquake. Since the location and structure of joints are determined at the design
stage considering factors such as the strength, durability, appearance and constructability of thestructure, joints shall be located and structured in accordance with the design drawings andspecifications.
(2) If joints are to be located or structured in ways that are not specified in the design, theirlocations, directions, structure and construction methods are to be specified in the construction plan
after ascertaining that the performance requirements for the structure are met through consultation
with the designer.

9.2

Construction Joints(1) A construction joint should, in general, be designed at the position where the shear
force is as small as possible. The joint surface should be perpendicular to the direction of
the compressive force acting in the member.
(2) Construction joints shall be planned taking into consideration cracking due tothermal stress, drying shrinkage, etc.
(3) When the concrete structure is required to be watertight, construction joints shallbe made at appropriate intervals to ensure necessary water-tightness.
(4) In concrete structures which could be damaged by external chloride attack, such as
marine and port structures, it is highly recommended that construction joints are notprovided. In cases when construction joints cannot be avoided, it should, in general, be
ensured that the construction joints do not impair the durability of the structure.

[Commentary] (1) The construction joint often proves to be a weak point for the acting shear
force. It is therefore necessary to form construction joints in locations at which the shearing force issmall and to maximize the shearing resistance of the construction joint by positioning theconstruction joint at right angles to the direction along which the compressive force acts in themember. If a construction joint is provided for a compelling reason at a location where large shear
force occurs, measures to ensure safety against shear force may be taken, such as using
mortise-and-tenon or groove-and-tenon type shear keys or reinforcing construction joints withdowel bars or other types of reinforcing bars. These measures need to taken after verifying at the145

Standard Specifications for Concrete Structures-2007, Materials and Construction

design stage that the performance requirements are met.
(2) Construction joints need to be located and structured by predicting the possible occurrenceof cracking due to thermal stress caused by changing outdoor air temperature, drying shrinkage, etc.
(3) When concrete is placed in considerably large blocks at a time, the expected property ofstructures which require water-tightness cannot be achieved due to cracks caused by dry shrinkage
or thermal stress. Therefore, this requirement is prescribed.
(4) The use of construction joints in marine and port concrete structures should be avoided asmuch as possible because external chlorides may penetrate through the construction joints to cause
the corrosion of reinforcing bars. For further information about the jointing of marine concrete
structures, refer to Chapter 11, Marine Concrete, of the Construction: Special Concretes of thisSpecification.

9.3

Horizontal Construction Joints(1) If appearance requirements need to be met, the lines formed by horizontal
construction joints in contact with the formwork should be made as straight horizontal
lines wherever possible.
(2) Before fresh concrete is placed, laitance, poor-quality concrete, loosened
aggregate, etc. on the old concrete (previously placed concrete) surface shall becompletely removed, and the surface of the old concrete shall be wetted sufficiently.
(3) In cases when concrete is inversely placed, construction joints shall be provided ina manner that concrete layers at the joint position are well integrated, with due
consideration to bleeding and settlement.

[Commentary] (1) For good appearance, attention shall be paid to ensure the line of a horizontal
joint on the concrete surface looks straight. To this end, it is appropriate that the joint positions
coincide with form panel joints or markers showing the height of the construction joint should be
used.
(2) To produce a construction joint of sufficient strength, durability and water-tightness, it isnecessary to remove any laitance, poor-quality concrete, loosened particles of aggregate, etc., on theold concrete surface before placing the fresh concrete.
For processing the joint surfaces on old concrete, pre-hardening processing, post-hardening
processing or a combination of both can be used.
A common method of pre-hardening processing is to expose the coarse aggregate by removing
the thin film on the concrete surface with high-pressure air and water after the final set of concrete.
If the surface of the construction joint is large, this processing method proves to be efficient.
However this method may spoil the concrete unless it is performed in a proper manner and at theproper time after concrete placing. The program has to be carefully controlled during processing. In
general, the possible working time to process construction joints is short. If construction joint
treatment cannot be done during this period, it may become difficult to attain the required joint
performance because of problems such as excessively high concrete strength that makes it difficult
to expose coarse aggregate grains and weakening of the matrix around coarse aggregate grains

146

Chapter 9

Jointscaused by excessive scraping. To ease this working restriction, it is effective to apply a retarder, of
which the principal ingredient is sodium gluconate, on the surface of concrete to process theconstruction joints. By using this kind of retarder, processing time can be extended because
hardening of the concrete joint surface is intentionally delayed.
In the case of post-hardening processing, the surface is roughened with either high-pressure air
and water sprayed for careful cleaning or a wire brush with pouring water if the old concrete surface
is not too hard. If the old concrete is hard, the most reliable way to prepare the surface is to wash itwith water after scraping the surface with a wire brush or sandblasting. Incidentally, the remaining
water on the old concrete surface has to be removed before placing fresh concrete.
If mortar is laid just before a new layer of concrete is placed, the water-cement ratio of thismortar should be lower than that of the concrete used.
(3) In the case of the inversely placed concrete, a construction joint is always located under theold concrete and the surfaces of the construction joint are not usually integrated because of bleedingor settlement of the newly-placed concrete. In the case of the inversely-placed concrete, methods ofconstruction in Fig.C9.3.1 are employed to ensure the integration of the surfaces of construction
joint. Regardless of which method is used, it is necessary to remove laitance and dirt from theconstruction joint surfaces in order to achieve the structural integrity of the newly- andpreviously-placed concrete.
In the direct method, the lower end of the previously-placed layer of concrete is used as aconstruction joint surface to achieve close contact with a newly-placed layer of concrete. In thismethod, the lower end of the previously-placed layer of concrete is often formed as a single-slope
surface or a double-slope (V-shaped surface) in order to help air bubbles and bleeding water escapeeasily. The mix proportion of the newly-placed concrete is designed to minimize the bleeding andsettlement and it should be sufficiently compacted by a vibrator. In this case, hanging parts shall be
removed at a proper time after construction to prevent falling during the service life of the structure,or shall be checked regularly for safety according to in-service maintenance control. If aluminum
powder is mixed into newly placed concrete to give the concrete a pre-hardening expansion
property and thereby achieve the structural integrity of the newly- and previously-placed concrete, it
shall use concrete forms that are strong enough to confine the expansive concrete.
In the filling method, the pouring of newly-placed concrete is stopped a little below the jointing
surface and a hollow between the old and newly placed concrete is filled with mortar containing an
expansive agent or aluminum powder. As in the direct method, concrete forms that are strong
enough to withstand expansion pressure are necessary.
The injection method is used either independently or in conjunction with the direct method. The
injection tube for grouting is arranged beforehand, and after the newly-placed concrete is hardened,
cement paste, resin, or another material is injected. A cement paste or resin which is fluid and mixed
with an expansive agent is recommended for injection to thoroughly fill small spaces.

147

Standard Specifications for Concrete Structures-2007, Materials and Construction
casting
old concrete
deflation
tube

old concrete

old concrete
grouting

injection tube

excess casting

mortarnewly placed

newly placed

concreteconcrete

Direct method

Filling method

newly placed
concrete

Injection method

Fig. C 9.3.1 Construction joint of inversely placed concrete

9.4

Vertical Construction Joints(1) The formwork of vertical construction joints shall be firmly supported.

(2) Before placing the fresh concrete, the surface of the old concrete shall be
sufficiently moistened and coated with cement paste, mortar or epoxy resin afterroughening the surface by scraping with a wire brush or chipping.
(3) Placement and compaction shall be performed so that newly-placed concrete
reaches every corner of the joint surface to achieve close contact with the joint surface.
(4) As a general rule, a water stop should be used for vertical construction joints inconcrete structures that require water-tightness.

[Commentary] (1) Formwork for vertical construction joins must be designed to prevent thespilling of mortar and must be supported firmly.
(2) The typical method to roughen the surface of old concrete is wire brushing, hand picking,picking by machine and so on. Another method is processing construction joints before hardening
with a spreading retarder, of which the principal ingredient is sodium gluconate, on the surface of
formwork prior to placing concrete. In this case, processing time is properly adjusted by intentional
delay of hardening time at the concrete surface. Furthermore, an alternative method to roughen thevertical construction joints is using wire net as formwork at construction joints (see Fig. C9.4.1). If
a new layer of concrete is to be placed after the surface of the previously-placed layer of concrete isroughened, structural integrity can be enhanced by applying cement paste, mortar or epoxy resin toa wet surface just before the placement of the new layer. A recently-developed method attachs
set-retarding sheets to concrete forms and washing them away after removing the forms. Whenusing these methods it is necessary to check, in advance, their effectiveness and practicality byconducting tests or referring to reliable literature.
(4) Since it is very difficult to achieve water-tightness without a water stop, a water stopper
should be used in vertical construction joints. When a water stop is used, special attention shall be
paid to the installation work, otherwise water-tightness might be worse than the case where a waterstop was not used.

148

Chapter 9

JointsWire netting
Old concrete
Reinforcing
barTemporary support

Wire netting

Reinforcing bar

Fig. C 9.4.1 Vertical joint using wire net

9.5

Construction Joints in Columns and Walls Integrated with Floor Systems(1) Construction joints in a column or wall integrated with a floor system should beformed adjacent to the border between them.
(2) Concrete in haunches shall be placed at the same time as the floor concrete.
(3) Similar procedures shall be used in structures with an overhang.

[Commentary] Concrete of the haunch must be placed in continuity with the floor construction inview of the fact that, as it is directly supported with shuttering, it cannot shrink or settle together
with concrete of the column or wall, so the haunch behaves as part of the slab.

9.6

Construction Joints in Floor Systems(1) Construction joints in floor systems should be made in the middle of the slab or
beam.
(2) In cases when a beam crosses a joist at the middle of the span, the construction
joint in the beam shall be provided at a position apart from the joist by about twice thewidth of the joist. The construction joint shall be reinforced against shear by providing
additional diagonal tensile reinforcements crossing the joint.

[Commentary] A construction joint is formed in the middle of a slab or beam because theshearing force in this area is usually small and the compressive stress works at right angles to thevertical construction joint, hence the formation of a construction joint has little effect on thestrength capacity of the slab or beam. If a joist crosses the beam at the middle of its span, however,
it is advisable to position the construction joint at about twice the width of the joist away from thejoist in order to avoid coincidence of the construction joint with a point at which the stress changes
sharply. As a considerable shear force is applied to the construction joint in that case, the joint has tobe reinforced using tension bars that cross the construction joint at an angle of 45˚ (see Fig. C9.6.1).

149

Standard Specifications for Concrete Structures-2007, Materials and Construction

Construction joint

About 2b0

Joist

Fig. C 9.6.1 Reinforcement for construction joint

9.7

Construction Joints in Arches(1) Construction joints in arches should, be provided at a right angle to the axis of thearch.
(2) In cases when a construction joint is obliged to be parallel to the axis of the arch,
the location, reinforcing methods for strengthening, etc. shall be carefully examined.

[Commentary] (1) Since the shear force acts along the joint when the construction joint in thearch is not formed at right angles to the arch axis, the joint is likely to be a structural weak point.
Therefore, this requirement is prescribed for the purpose of avoiding shear force acting along thejoint.
(2) If a vertical construction joint is formed parallel to the arch axis, an action such as eccentric
live loads might cause shear force along the joint. Therefore, sufficient countermeasures against
these problems are required.

9.8

Expansion Joints(1) The structure of expansion joints shall be such that the structures or members on
both sides can be free from restraint.
(2) Joint filler, water stop, etc. shall be provided at expansion joints, if necessary.
(3) In cases when evenness at the expansion joint is required, a protrusion or groove
should be introduced or dowel bars provided.

[Commentary] (1) To form an expansion joint, either both joined structures must be perfectlydiscontinuous or, depending on the type of structure and the location of the installation, the concrete
may be discontinuous and the reinforcing bars may remain continuous (see Fig. C9.8.1).
(2) If an expansion joint gap is likely to become filled with soil, sand and so forth, joint filler
materials shall be used. Examples of the filling materials are sheets of asphalt, rubber foam, resin
foam,, or other sealing and filling materials. For the expansion joint of a structure that requires
water-tightness, a water stop with proper flexibility must be used. Examples of a water stopper arecopper plates, stainless plates, vinyl chloride resin sheets and rubber sheets.

150

Chapter 9

JointsInsulation by asphalt etc.

Dowel bar

Water stop(a)-(d): Wall structures

Sealing materials(e), (f): Water tightness forwall and slab
Water stop
Filling materials
Water stop
Filling materials

Filling materials

Filling materials(g), (h): Base of water tank

Asphalt membrane

Rubber ring

Hinge

Fig. C 9.8.1 Examples of expansion joints

9.9

Joints to Control Cracking

In cases when a joint is introduced to control cracking, its structure and location shallbe in accordance with the design documents.

[Commentary] In the case of a concrete structure, there are many factors that cause deformation
besides applied forces, including the temperature change due to the heat of hydration and the outer
temperature, drying shrinkage and so on. Cracks may develop if such deformation is restrained. It istherefore desirable to control the cracks by forming notches in the cross section at given intervals inorder to concentrate cracks in a given area. Crack-inducing joints need to be considered at thedesign stage. If the design drawings and specifications do not deal with crack-inducing joints, it isnecessary to refer to the Design section of this Specification and provide appropriately-locatedand -structured crack-inducing joints through consultation with the designer.
When the joint to control cracking is used, sufficient consideration is necessary to decide thespacing intervals, the reduction ratio of cross section, the method to prevent steel corrosion, and themethod to assure required cover and filling material in the notches. In general, spacing interval of
joints may be 1 to 2 times the wall height, and the reduction ratio of cross section is advisable to be
more than 30 to 50%.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Some examples of joints to control cracking in wall structures are shown in Fig. C9.9.1. Inthese figures, the notches are vertically arranged on the both side of the wall and the insulation isembedded in the wall, if necessary, to obtain the required cross section reduction ratio. Examples (c),(e), and (g) show that vinyl chloride pipe, pre-cast concrete block and steel plate with remover on
their surfaces are respectively arranged in the wall to cut the bond of concrete and to induce stressconcentration. The cross section reduction rate of is defined as the value obtained by dividing theadditional depth of the notches on both sides and width of the embedded insulation by the originalwall thickness. If a crack-control joint is formed in a water-tightness structure, it is advisable to takeproper water-preventive measures, including the advance installation of a water stopper. In the caseof mass concrete, see Section14.5.5.
Water stop

Spacing interval of joint
to control cracking

Water stop

Pipe
Wall
heightRemover

Precastconcreteblock Half
pipe

Remover

Shape of notch
t=0.6-1.2mm plate
Distribution
bar

Water stop

Filling materials (sealing or resin mortar)

Fig. C 9.9.1 Examples of joints to control cracking

152Chapter 10

Reinforcement

CHAPTER 10 REINFORCEMENT

10.1

GeneralReinforcing bars shall be fabricated to the shape and size specified in the design
documents using appropriate methods that do not cause any damage to the quality of thebars. Furthermore, the reinforcing bars shall be accurately placed in the required positionand securely fixed in place.

[Commentary] The main matters which should be examined in general reinforcement work are
explained as follows.
(1) Master planning
Prior to reinforcement work, a plan shall be drawn up after carefully considering the schedule
for reinforcement work, personnel requirements, storage locations for reinforcing bars, bar
processing equipment, and so forth. Those involved in reinforcement work should preferably havesufficient knowledge and experience associated with reinforcement work, the quality of reinforcing
bars, the preparation of reinforcement drawings, the fabrication and assembling of reinforcing bars,
and so forth. There are a variety of jointing methods, and each method requires specialized
knowledge and experience. It is desirable, therefore, that the personnel for reinforcement work
include persons with officially recognized qualifications, such as Certified Reinforcing Steel
Erectors, various technicians certified by Japan Pressure Welding Society or Japan Welding
Engineering Society, or other equally knowledgeable and experienced persons.
It is necessary to check the requirements indicated in the design drawings and specifications
such as concrete cover, clearance, bending configuration, anchorage, joints and nonstructural
reinforcement and verify that the reinforcing bars can be erected as designed. Reinforcementdrawings are supposed to have been thoroughly checked at the design stage, but there may havebeen errors at the drafting stage. If the designer does not understand the actual tasks involved inreinforcement work or form work, it may not be possible to place reinforcing bars as indicated on
the drawings at the erection stage. It is important, therefore, to correctly understand the design
drawings and specifications and confirm the tasks to be performed together with the technicians
who will be involved in the reinforcement work before the construction work begins. If, as a result,placing the reinforcing bars as specified in the design turns out to be difficult to perform, it isnecessary to decide on the measures to be taken through consultation with the owner and thedesigner.
(2) Ordering, delivery and storage of reinforcement
It is necessary to check the type, diameter, length and quantity of reinforcing bars before
ordering reinforcing bars and after they are delivered. Since the quality of reinforcing materials
such as reinforcing bars is described in Section 3.6, it is important to refer to and understand therelevant JIS and JSCE standards in advance. It is also necessary to refer to Section 3.7.5 for
information on the storage of reinforcing bars and other steel products and take measures to protect
reinforcing bars from corrosion and dirt in order to maintain their quality.
(3) Fabrication of reinforcement
In connection with the fabrication of reinforcing bars, fabrication instructions shall be given
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Standard Specifications for Concrete Structures-2007, Materials and Construction

to construction workers in accordance with Section 10.2 so that there will be no error in the type ofreinforcing bars, inside bend radius, etc. After reinforcing bars are fabricated their type, number andfabrication accuracy need to be checked. Fabrication accuracy shall be kept within the tolerance
indicated in Chapter 7 of the Construction: Inspection Standards of this Specification.
(4) Placement and assembly of reinforcing bars
In connection with the placement and assembly of reinforcement, checks must be made inaccordance with Sections 10.3, 10.4 and 10.5 on details such as fixing by use of spacers and tie wire,
relationship with formwork, specified locations and bar spacing, effective depth, concrete cover,development length, adequacy of joint method and the treatment of pressure-welded bar ends.
Assembly accuracy needs to be controlled so that it can be kept within the range indicated in
Chapter 7 of the Construction: Inspection Standards of this Specification.

10.2

Fabrication of Reinforcement(1) Reinforcing bars shall be fabricated to the shape and size specified in the design
documents using methods that do not cause any damage. As a general rule, bars thathave been bent once should not be re-bent.
(2) Epoxy resin-coated reinforcing bars shall be processed by an appropriate method
suitable for their characteristics.
(3) As a general rule, reinforcing bars shall not be welded. If reinforcing bars are
welded for a compelling reason and welded reinforcing bars are bent, the welded portionsof the bars shall not be bent. As a general rule, bending should not be done within adistance calculated as 10 times the bar diameter.
(4) If the bend radius requirements for reinforcing bars are not indicated in the design
drawings and the specifications, reinforcing bars shall not be bent with a radius smaller
than the inside bend radius indicated in the Design section of this Specification.
(5) Reinforcing bars should be fabricated at a normal temperature.

[Commentary] (1) It shall refer to the shapes and dimensions indicated in the design drawings
and specifications and fabricate reinforcing bars so that their dimensions fall within the specified
dimensional tolerance. In order to fabricate reinforcing bars so that their dimensions fall within thetolerance, it is desirable that equipment suitable for the type of reinforcing bars be used for bar
bending.
Re-bending of bent bars may have adverse effects on the quality of the bars. Re-bending,therefore, shall be avoided as much as possible. If reinforcing bars are provisionally bent at alocation such as a construction joint and later bent back into the specified position, it is necessary
either to bend and re-bend the bars at the largest possible radius or to heat the bars to 900 to
1,000°C before bending.
(2) Fabrication and assembly of epoxy resin-coated reinforcing bars shall be done by anappropriate method so that the quality of the coating film is not degraded. Because this requires
specialized knowledge about epoxy resin-coated reinforcing bars, refer to the Recommendations for
Design and Construction of Reinforced Concrete Structures Using Epoxy-Coated Reinforcing Steel154

Chapter 10

Reinforcement

Bars.
(3) Reinforcing bars shall not be welded, in general, because it may harm the quality of thebars. When it is impossible to avoid the bending for repair or strengthening, effects of welding on
welded reinforcement and performance of the structure should be investigated sufficiently. On-site
welding should necessarily be sufficiently managed. No bending should be made at a location
closer than 10 times the bar diameter to the nearest welded portion because of its fabricability andreliability.
(5) As a bar bending machine facilitates the bending work of bars even with large diameters
under normal temperature, bending shall, in general, be carried out at normal temperature. Whenheat must be applied to normal hot rolled reinforcing bars, it shall be within the temperature rangeof 900 to 1000℃. Rapid cooling should be avoided. As bars might be harmed by an inadequate
heating temperature, rate of cooling, or bending procedures, it is important to control the heating
temperature sufficiently and avoid rapid cooling for bending of bars with large diameters.

10.3

Assembly of Reinforcing Bars

(1) Before being assembled, the reinforcing bars shall be cleaned, and rust or any
other foreign matters, which may adversely affect the bond between the bar and concrete,
shall be removed.
(2) Reinforcing bars shall be accurately placed and secured against any movement
during the placement. For this purpose, erection bars shall be used if necessary. In
addition, annealed wire having a diameter of not less than 0.8mm or appropriate clips
shall be used at the intersection of the reinforcing bars to keep them in position.
(3) Spacers shall be provided at required intervals to achieve the required concrete
cover for the reinforcing bars. In selecting and placing the spacers, conditions at thelocation of the spacers, the method used for fixing the spacers, amount of reinforcing
bars, and working loads should be considered.
(4) As a general rule, spacers in contact with formwork should be made of mortar or
concrete.
(5) If part of the assembled reinforcement is exposed to the air for a long time, thereinforcing bars should, be rust-proofed.
(6) If a considerable amount of time has passed after reinforcing bars are assembled,
the surfaces of the reinforcing bars should be cleaned again before the placement of
concrete.

[Commentary] (1) Rust, mud, oil, paint, etc. may adversely affect the bond strength ofreinforcing bars with concrete. Hardened mortar adhered to reinforcing bars shall be removed bywire brush.
(2) This provision has been made because the strength of reinforced concrete members may
be affected and their durability may be degraded if reinforcing bars are not located as specified in
the design drawings and specifications.
In some design drawings, positions of reinforcing bars are shown only in their central lines, and155

Standard Specifications for Concrete Structures-2007, Materials and Construction

the cover may not be appropriately displayed. Therefore, the accuracy of the reinforcing bars’
arrangement should be confirmed beforehand by the preparation of the assembly diagram inconsideration of outer diameter and bending radius, assembly sequence of reinforcing bars, etc.
Erection bars are required for not only preventing bars from movement but also for facilitating
erection. Sometimes, erection bars are not shown in design drawings but it is recommended thatthey be used. From the viewpoint of durability, the cover of erection bars should also be ensured.
To ensure the correct spacing of bars, intersections of bars are usually tied up with wires ofdiameter 0.8 mm or greater. To fix intersections, clips of various types or spot welding can beutilized instead of wire. Spot welding may damage the quality of the bars and lower the fatigue
strength considerably due to local heating. Therefore, care should be taken to ensure that harmful
effects do not occur to the bars in consideration of the type of loads, the importance of the structure,
the materials and diameters of bars, inadequate bar diameter, welding workmanship or welding
method.
(3) and (4) Spacers which are made of proper materials for use position should be placed at theappropriate position in order to retain reinforcing bars for the appropriate position and to ensure therequired cover. Generally, spacers made of mortar, concrete, steel, plastic or ceramic are used.
Materials for spacers should be determined in consideration of the site location and environmental
condition. The mortar or concrete spacers shall, in general, be used in this Specification. The
dimension of the spacers used shall be appropriately selected in order to ensure the minimum
required cover and to place reinforcing bars at the position within the tolerance.
If steel spacers are exposed at the concrete surface, the portions in contact with the formwork
begin to rust even if they have been rust-proofed. Consequently, those portions may cause thecorrosion of the inner portions of the reinforcing bars, create corrosion-vulnerable regions, anddegrade the appearance of the structure. In a highly corrosive environment, steel spacers are
particularly prone to rusting, and rusty water may turn the concrete surface brown. Steel spacers
must not be used, therefore, in highly corrosive environments. Although there arecorrosion-resistant spacers made of stainless steel or other materials, there are still unknown factors
such as corrosion due to the contact between different kinds of metal. Plastic spacers pose othertypes of problems such as differences in the coefficient of thermal conductivity from concrete andinsufficiency in bond and load-carrying capacity. As a general rule, therefore, this Specification
shall require the use of mortar or concrete spacers. The quality of mortar or concrete spacers usedshall be equivalent to or higher than that of the structural concrete.
Generally, the number of spacers is about 4 per 1 m2 in beams and slabs, and between 2 to 4 per
1 m2 in webs, walls and columns. Spacers should be placed in zigzag with an interval of 50 cm
when the number of spacers is 4 per 1 m2. The position of spacers should be described in thedrawing in which the reduced scale is large for arrangement of reinforcing bars.
“Spacer Design and Construction Guideline for the Reinforcement Work” by the Japan Civil
Engineering Contractors’ Association shall be referred to for selection and placement of spacers.
(5) and (6) If assembled reinforcing bars are left un-concreted for a long time, they collectloose rust, dirt, oil, etc. As a general rule, therefore, if the time after completion of reinforcing bar
assembly until the placement of concrete is expected to be long, the reinforcing bars shall be either
rust-proofed or protected with sheeting or other devices. If a long time has passed after reinforcing
bars are assembled until the placement of concrete, the reinforcing bars shall, in general, be cleaned
again.

156

Chapter 10

10.4

Reinforcement

Joints of Reinforcing Bars

(1) Reinforcing bar joint locations and jointing methods shall conform to the design
drawings and specifications. If a reinforcing bar joint that is not indicated in the design
drawings and specifications needs to be provided, the location of the joint and the jointing
method shall be determined in accordance with the Design section of this Specification.
(2) In a lapping joint, the reinforcing bars should be lapped over the required lapping
length, and be tied at several points with annealed wires having a diameter of at least
0.8mm.
(3) If lap joints, gas pressure welded joints, welded joints or mechanical joints are used
for reinforcing bars, the Recommendations for Design, Fabrication and Evaluation of
Anchorages and Joints in Reinforcing Bars should be followed.
(4) Reinforcing bars extending out of finished concrete shall be protected against
possible damage and corrosion to ensure good continuity with further construction.

[Commentary] (1) When selecting a joint method it shall consider the type of reinforcing bar,
diameter, state of stress, joint location, joint performance requirements, etc. At the design stage,
joint locations are specified in the design drawings and specifications in due consideration of thosefactors. For this reason, the design drawings and specifications shall be followed with respect toreinforcing bar joint locations and joint methods. It may become necessary, however, at theconstruction stage to provide reinforcing bar joints that are not indicated in the design drawings andspecifications. In such cases, the Design section of this Specification must be followed with respect
to joint locations and joint methods, and decisions are to be made through consultation with theowner and the designer.
(2) Lap length requirements for lap joints are specified in the Design section of thisSpecification. It is important to firmly connect the lapped portions with iron wire. The length of thesection wound by annealed iron wire should be made as short as possible because an excessive
length may cause a decrease in bond strength between concrete and reinforcing bars and, as aconsequence, a decrease in the strength of the joint.
(3) The Recommendations for Design, Fabrication and Evaluation of Anchorages and Joints
in Reinforcing Bars specify gas pressure welding joints (manual gas pressure welding joints,
automatic gas pressure welding joints, gas pressure welding and hot shearing joints), welding joints(butt welding joints, butt arc stud welding joints, butt resistance welding joints, flare welding joints)
and mechanical joints (crimped sleeve joints, crimped sleeve screw joints, threaded deformed bar
joints, mortar grouted joints, friction welding screw joints, wedged joints, combination joints). This
Specification provides for the equipment and methods for construction and inspection, qualification
requirements for inspectors, reliability attributable to these factors, etc. Construction and inspection,
therefore, need to be carried out with prior understanding of those provisions.
(4) To prevent the corrosion of bars, methods such as cement paste coating on bars or coatingwith high polymeric film are generally used. Such materials may cause a reduction in bond strengthwith the concrete and should therefore be removed completely before jointing is undertaken. It iseffective to put a vinyl bag on the jointing part of reinforcing bars to protect them from rainwater.

157

Standard Specifications for Concrete Structures-2007, Materials and Construction

10.5

Placement of Pre-assembled Reinforcing Bars

(1) Pre-assembled reinforcing bars shall be placed accurately at the specified locationsin the formwork.
(2) Pre-assembled reinforcing bar segments shall be connected together by a methodthat makes it possible to achieve the required joint performance.

[Commentary] (1) In cases where pre-assembled reinforcing bars are to be placed at a specified
location, it is necessary to select an appropriate lifting method, such as providing lifting frames or
steel reinforcements for lifting, in due consideration of safety so that there are no adverse effects
such as irregularities in the shape or dimensions or excessive deformation of the pre-assembled
reinforcement cage due to lifting.
In order to place pre-assembled reinforcing bars accurately into position, it is recommended
that positioning marks be indicated on the upper part of the formwork or other appropriate places.
(2) In order to achieve the required strength of the structure, it is important to connect together
pre-assembled reinforcing bar segments by a highly reliable method. Lap joints must be placed sothat the lapped portions of the reinforcing bars are in contact with each other. If it is difficult toplace reinforcing bars to be connected so that they are in contact with each other as in the case of adiaphragm wall, it is necessary to ascertain that the joint meets the performance requirements. For
further information about pre-assembled reinforcing bars for diaphragm walls, refer to Section
10.4.2 of the Construction: Special Concretes of this Specification.

158

Chapter 11

Formwork and Shoring

CHAPTER 11 FORMWORK AND SHORING

11.1

General(1) Construction plans for formwork and shoring shall be prepared in advance andformwork and shoring shall be designed and constructed in accordance with those plansso that the concrete structure has the shape and dimensions indicated in the design
drawings and specifications.
(2) Formwork and shoring shall be designed and constructed so as to ensure therequired strength and rigidity against loads specified in Section 11.2 and also to ensure
the required shape and dimensions of the structure.
(3) In order to achieve the required accuracy of the concrete structure, the accuracy ofassembled formwork and shoring shall be confirmed before placing concrete.
(4) In addition to the provisions of this Standard Specification, the design andconstruction of formwork and shoring shall also comply with the “Ordinance on
Industrial Safety and Health” issued by Ministry of Health, Welfare and Labor of Japan.

[Commentary] It is usually not necessary to allow for a very large factor of safety when
designing formwork and shoring because the period from the placement of concrete to its hardening
is short. There must, however, be neither adverse effects on the structure nor unsafe practices.
Formwork and shoring are important for obtaining a structure that meets the positional anddimensional requirements and ensures the safety of the workers involved in compaction and otherconstruction tasks and the engineers who manage those tasks. Formwork and shoring, therefore,
need to be designed by engineers who have specialized knowledge about formwork design. It isalso desirable that those construction tasks be performed by experienced and skilled technicians
who are capable of determining whether anomalous erection work is in progress – for example,
persons certified as chief assembly technicians by a public institution.

11. 2

Load

11.2.1

GeneralFormwork and shoring shall be designed considering the type, scale and importanceof the structure and the conditions of construction and environment, referring to Section
11.2.2 to 11.2.5 for the various loads. Not only strength but also deformation shall beconsidered in the design of shoring.

[Commentary]
The loads imposed on the formwork and shoring are complicated. However, forthe convenience of design, they are categorized into four cases, such as vertical loads, horizontal
loads, lateral pressure of concrete, and special loads. Minimum values are given for the specified
loads in Section 11.2.2 through Section 11.2.5. These values should be increased properly taking
into account structural conditions.

159

Standard Specifications for Concrete Structures-2007, Materials and Construction

11.2.2

Vertical loads(1) The mass of formwork, shoring, concrete, reinforcing bars, workers, construction
machinery and equipment, temporary facilities, and any impact, shall be considered.
(2) It shall be a standard requirement to assume a unit mass of 2,400 kg/m3 forconcrete in formwork and shoring calculations. In the case of reinforced concrete, it shallbe a standard requirement to assume a mass of 150 kg/m3 for reinforcing steel incalculations associated with ordinary structures.
(3) The unit mass of concrete made with aggregate consisting solely or partially of
artificial lightweight shall be determined appropriately with reference to the Construction:
Special Concretes (Chapter 3, Lightweight Aggregate Concrete) of this Specification.
(4) Other than the dead loads, working and impact loads should, in general, be taken atleast 2.50kN/m2.

[Commentary] (1) and (2) In the case of an ordinary structure, vertical loads may be calculatedon the basis of the values indicated in the provisions. If the amount of steel is greater than inordinary cases or if the actual mass is known, calculation shall be performed taking those factors
into account. Although the Design section of this Specification specifies unit weights for hardened
concrete of 22.5 to 23.0 kN/m3 and unit weights for reinforced concrete of 24.5 kN/m3, moreconservative values (unit weight = 23.5 kN/m3) are required as standard in formwork and shoring
calculation.
(4) Generally, it is difficult to assume the values of working and impact loads. However, theseloads can be assumed as uniform loads for the convenience of design.

11.2.3

Horizontal loads(1) Horizontal loads shall include loads caused by inclination of formwork, vibration,
impact, commonly used eccentric loads, loads due to erection errors, loads due to windpressure, hydrostatic water pressure and earthquakes, etc., depending on therequirements.
(2) In design, the horizontal load, which actually acts on formwork, should be taken
into consideration. However, in cases when actually acting horizontal load is smaller than
the reference horizontal load, the latter shall be used to evaluate the safety.
(3) In cases when the formwork is almost level and shoring is assembled using pipe
support, a single pipe support, steel pillar, a shoring beam, etc., reference horizontal load
acting at the top of shoring, shall be taken to be 5% of the design vertical load. When ashoring is assembled using framed steel-pipe support with factory accuracy, thehorizontal load equivalent to 2.5% of design vertical load shall be assumed. Formwork
for walls such as retaining walls shall be designed for a horizontal load of at least
500N /m2.

[Commentary] (1) As collapse of shoring is mainly caused by horizontal load, it is necessary tocarefully assume this load in the design. It is thought that the horizontal load acting on shoring acts
160

Chapter 11

Formwork and Shoringon the top of shoring or horizontally on the side.
(2) The reference horizontal load should be used in order to secure the rigidity and stability offormwork and shoring against horizontal force, even when horizontal load does not actually act.
(3) This clause is based on Article 240 (3) (iii) and (iv) of the Ordinance on Industrial Safety
and Health. This is based on the empirically known fact that a collapse often results frominadequate consideration of horizontal loads. In normal cases, horizontal loads may be determinedon the basis of the values indicated in this clause, but it is desirable that they be determined after
carefully considering factors such as the degree of importance of the structure, construction
conditions and the construction period.

11.2.4 Lateral pressure of concrete(1) Formwork shall be designed taking into consideration the lateral pressure ofconcrete.
(2) Since the lateral pressure of concrete varies depending on the structural
conditions, concrete conditions and construction conditions, its value shall be
determined taking these factors into consideration.

[Commentary] The lateral pressure acting on the formwork differs depending on the structural
conditions, concrete conditions and construction conditions. Major factors affecting lateral pressure
include the following:(a) Structural conditions: cross-sectional dimensions of structural members, the amount ofreinforcement, etc.
(b) Concrete conditions: materials used, mix proportion, slump and its retention time, setting
time, concrete temperature, etc.
(c) Construction conditions: placing rate, placing height, compaction method, whether
re-vibration is to be performed, etc.
If factors contributing to an increase in lateral pressure are involved, it is necessary toappropriately increase lateral pressure values used for calculation. The setting time, temperature andplacing rate of concrete vary considerably depending on outdoor air temperature, materials used,production and construction conditions, etc. If slump retention time is long, setting is delayed or theplacing rate is increased as in the case of concrete placement during winter, care needs to be taken
because higher-than-expected lateral pressure may act on the formwork.
It is difficult to indicate, in the Construction: Construction Standards of this Specification, alateral pressure formula reflecting the influence of various factors affecting lateral pressures. Lateralpressure values to be used for formwork design shall be determined appropriately on theconstructor's own responsibility, taking into consideration the construction speed, economy, safety
and other requirements of the constructor and various factors affecting them. One way to do this is
to design formwork by measuring actual lateral pressure by installing lateral pressure cells or checkon lateral pressure during the placement of concrete.
One way to design conservatively is to determine the lateral pressure acting on the formwork
by regarding lateral pressure as fluid pressure. The term "fluid pressure" refers to pressure(hydrostatic pressure) in the case where gravity acts on fluid in a stationary state. Fluid pressure is161

Standard Specifications for Concrete Structures-2007, Materials and Construction

calculated by assuming concrete as fluid and multiplying the unit mass of concrete by gravitational
acceleration and the placing height as follows:

pw = WCH(C11.2.1)

where,
pw: fluid pressure (kN/m2)
WC: unit weight determined by multiplying the unit mass of concrete by gravitational
acceleration (23.5 kN/m3 when unit mass = 2,400 kg/m3)
H: placing height of fresh concrete (m)Measured lateral pressures of high-fluidity concrete such as self-compacting concrete andhigh-strength concrete often show distribution patterns resembling those of fluid. The Construction:
Special Concretes (Chapter 6, High-Strength Concrete, and Chapter 7, High-Fluidity
Concrete)therefore require, as a general rule, that design be conducted assuming fluid pressure. If
the unit mass of concrete has been determined, it may be substituted in the equation, taking itschanges into account.
Designing formwork assuming fluid pressure is a conservative approach, and this approach isneither economical nor practical if the actual lateral pressure is substantially lower than the fluidpressure. If relatively-low-slump concrete as mentioned in the Construction: Construction Standards(Chapter 4 and Chapter 7) is placed under certain conditions, such in layers of thickness 0.4 to 0.5m or less and at a placing rate of about 1.0 to 1.5 m, the lateral pressure acting on the formwork isoften substantially lower than the fluid pressure. Various practical lateral pressure formulas havetherefore been proposed based on the results of experiments paying attention to various factors
affecting lateral pressure. The equations shown below are long-used practical formulas for roughly
calculating lateral pressure in the case where normal Portland cement is used and concrete with aslump of about 10 cm or less is poured into formwork and compacted by use of internal vibrators.
Fig.C11.2.1 and Fig.C11.2.2 show the relationship of the lateral pressure calculated by using theseformulas with the placing rate and concrete temperature.
In view of the experiment conditions under which the formulas were derived, the upper limitof the values calculated from the formulas is 150 kN/m2 for columns and 100 kN/m2 for walls.
Because these formulas do not consider the final placing height, calculated lateral pressure values
may become greater than fluid pressure values depending on the placing rate, concrete temperatureand the final placing height. Since, however, the maximum value of the lateral pressure is usually
not greater than the fluid pressure, the fluid pressure is used when the calculated value is greaterthan the fluid pressure. In the case of a wall, there are no significant differences from the lateralpressures for a column. The formula for columns, therefore, may also be used for walls.

(a) ColumnpWC 
100 R 1 

3  T  20 

 150

(C11.2.2)

162

Chapter 11

Formwork and Shoring(b) Wall(i) R ≥ 2m/hpWC  150  30 R 
1 

3 
T  20 

 100(C11.2.3)(ii) If R < 2m/h, the formula for columns may be used.
where,
p: lateral pressure (kN/m2); but if the calculated value of p becomes greater than pw, p is
assumed to be equal to pw.
pw: fluid pressure (kN/m2)
WC: unit weight obtained by multiplying the unit mass of concrete by gravitational
acceleration (kN/m3)
R: placing rate (m/h)

2

p (kN/m) 2)
Lateral側圧
pressurep (kN/m

T: concrete temperature in formwork (°C)

160

Maximum value of lateral pressure permissible
2
式 を 適 用 でofきformula:る側圧の最 大 値 2150kN/m
for application
150kN/m

140

①柱
の場合
(1)
Column

120

T=10℃

T=5℃
T=0℃

T=15℃
T=20℃

100

T=25℃

80

T=30℃
T=35℃

60
40
標準的な
打上り
速度
Standard
placingrate
2～m/h
3m/h(7.4.2による)
2–3(as per 7.4.2)

20
0
0

1

2

3

4

5

Placing rateRR(m/h)
(m/h)
打上り速度

Fig. C11.2.1 Lateral pressure of concrete with a slump of about 10 cm or less (column)

163

Standard Specifications for Concrete Structures-2007, Materials and Construction(2)②Wall
壁の場合
Maximum value of lateral pressure permissible
2
100kN/m2
for式を適用できる側圧の最大値
application of formula: 100kN/m

120

T=5℃
T=10℃

2

側圧 p (kN/mLateral pressurep (kN/m
) 2)

100
T=0 ℃

80

T=15℃

T=5 ℃

T=20℃

T=10℃

60
40

T=25℃
T=30 ℃

T=15℃
T=20
T=25℃

T=35 ℃

標 準 的 なplacing
打 上 りrate
速度
T=30℃ Standard

20

T=35℃

実線は壁の
2～ 3m/h(7.4.2にwall formula
2–3
m/h (as per 7.4.2)
よ る ) Solid line:
式，点線はDotted line:
column formula

1

2

柱の式

0
0

3

4

5

R (m/h)
打上り速度
Placing rate
R (m/h)Fig. C11.2.2 Lateral pressure of concrete with a slump of about 10 cm or less (wall)Fig. C11.2.3 shows the changes in the distribution of the lateral pressure due to concrete. As
indicated by the formula, lateral pressure increases as the placing height increases. If two or more
0.4–0.5 meter-thick layers of low-slump concrete are placed one on top of another, the increase inlateral pressure is in many cases hampered, especially at locations lower than a certain level,
because of a decrease in the slump of concrete in the formwork, the progress of setting, bonding
with reinforcing bars, etc. In view of the possibility of such changes, therefore, if tall forms are used,
formwork is sometimes designed assuming that lateral pressure is constant at or below a certain
height. This assumption is based on the fact that because the abovementioned formulas forcalculating lateral pressure from the placing rate and concrete temperature do not include a term forthe placing height, calculated lateral pressures remain constant. Thus, formwork is designed
assuming that the calculated lateral pressure is the maximum value.

Maximum
側圧の最大
値pof
value
maxlateralpressure pmax
コンク
Concrete
リート

コンク
Concrete
リート

Maximum
valuep of
側圧の最大値max
lateral pressure pmax

(a)

側圧p
Lateralpressure p

側圧p
Lateralpressure p

(b)

H-HC

コンク

Concrete
リート
Maximum
側圧の最大
valueof lateral
値p maxpressure pmax

一定と見なす高さ HC

打上り高さ
H1 H 1
PlacingheightCompaction
by use内部振動機による締固め
of interval
vibrator

型枠
Form

型枠
Form

最終的な打上り高さ
Final
Placing heightHH

Form
型枠

Final
Placing height H
H
最終的な打上り高さ

内部振動機にby use
Compactionofよる締固めinterval vibrator

Height at whichconstancy is assumed HC

側圧p
Lateralpressure p(c)Fig. C11.2.3 Distribution of lateral pressure of concrete with a slump of about 10 cm or less(a) Lateral pressure distribution at initial stage of placement, (b) Lateral pressure distribution
upon completion of placement, (c) Lateral pressure distribution calculated at design stage
164

Chapter 11

Formwork and Shoring

Chapter 4 of the Construction: Construction Standards of this Specification specifies a methodfor determining the appropriate minimum slump for placement considering the concrete structure
and reinforcement conditions. It is therefore possible that concrete with a larger slump than that ofconventional concrete will be used in civil engineering projects. Because the minimum slump needs
to be retained until the placement of concrete is completed, the slump of the concrete at the time
when it is actually placed becomes greater than the minimum slump. Since the lateral pressure ofconcrete tends to increase with slump, it is necessary to determine lateral pressure in view ofpredetermined slump values and tolerance during construction planning.
The equations shown below are practical formulas for calculating lateral pressure in the casewhere high-slump (about 18 cm) concrete is placed at a rate of 10 m/h or less and at a final placing
height of 4 m or less. Fig.C11.2.4 shows distributions of lateral pressures calculated by using theformulas. These distributions can be used as reference data when considering the lateral pressure ofhigh-slump concrete. Note, however, that the formulas reflect neither placing rates lower than 10
m/h nor the influence of concrete temperature. In general, lateral pressure increases with slump. If,
therefore, the lateral pressure calculated by using these formulas is equal to or smaller than acalculated lateral pressure of concrete with a slump of about 10 cm or less, it is desirable that lateralpressure be determined taking a factor of safety into consideration.
(a) If the placing height is in the range of 0 m to 1.5 m, it is assumed that fluid pressure acts.
(b) If the placing height is greater than 1.5 m and not greater than 4.0 m, lateral pressure is
calculated for each structural type using the following formulas:(i) Column:p  1.5WC  0.6WC ( H  1.5)

(C11.2.4)(ii) Wall (with length 3 m or less):p  1.5WC  0.2WC ( H  1.5)

(C11.2.5)(iii) Wall (with length greater than 3 m): p  1.5WC(C11.2.6)

where,
p: lateral pressure (kN/m2)
WC: unit weight determined by multiplying the unit mass of concrete by gravitational
acceleration (kN/m3)
H: placing height (m)165打上り面からの高さ(m) H (m)Height fromnewly placed concreteH surface

Standard Specifications for Concrete Structures-2007, Materials and Construction
3

3
コン
ク リof
ート
の単位容
積質量
2400kg/m
，
Unit
mass
concrete:
2,400
kg/m
打 上 りrate:
速 度 1010m/h以下，
打込
み 高 さheight:
4m以 下 4 m or less
Placing
m/h orless,
Placing0

柱column壁(Lがwall(L:3m以
3 m下
or）
less)
壁
(Lが
え るthan） 3 m)wall(L:3m超greater
液
圧 pressure
fluid

1

L：wall
壁 のlength
長さ

2

3

4
0

20

40

60

80
2

100

2

)
圧 P (kN/m
Lateral側pressurep (kN/m)Fig. C11.2.4 Distributions of lateral pressure of concrete with a slump of about 18 cm

11.2.5Special loads

If the influence of special loads expected to occur during construction cannot beignored, those loads shall be taken into consideration when designing formwork andshoring.

[Commentary] Special loads defined here are eccentric loads caused by the unsymmetricalplacement of concrete, horizontal component forces at the placement caused by inclination of formbottoms, uplift force effective to the embedded sheaths in hollow slabs, and other forces. Suchspecial loads shall also be considered in the design where their effect may be anticipated.

11.3 Materials(1) Materials used for formwork and shoring shall be selected taking into accountstrength, rigidity, durability, workability, effect on the placed fresh concrete, aesthetics andeconomy of concrete structures.
(2) Materials such as timber, plywood and steel plate used for formwork should meetthe requirements of the relevant JIS or JAS (Japanese Agricultural Standard) standards.
(3) In cases when the concrete structure requires water-tightness, formwork bolts shallbe such that they do not impair the water-tightness.

[Commentary] (1) Formwork and shoring tend to be damaged, deformed and corroded throughrepeated use and relatively large loads. However, the selection conditions differ depending on thetype of structure, the frequency of use, or the importance of the location where the formwork andshoring are to be used. Therefore, the most suitable material should be selected after taking into
consideration the factors described in this section.
Formwork shall meet the required performance, construction accuracy and construction safety.
Although formwork are usually used more than once, the maximum usage should be about 5 times
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Formwork and Shoringfor plywood, about 20 times for plastic forms, and about 30 times for steel forms.
(2) Specifications for pipe support, steel panel for formwork and plywood for concrete
formwork are provided in JIS A 8651 “Tubular Steel Adjustable Shore,” JIS A 8652 “Metal Panels
for Concrete Panel,” and in the Japanese Agricultural Standard, respectively.
Recently, there is a trend to change the plywood formwork material, from trees such as the lauan
in Southeast Asia to needle-leaf trees, as part of the countermeasures against global environment
problems. In the case of formwork made from needle-leaf trees, it is necessary to consider thatneedle-leaf trees have many knots and formwork made from these trees may curve easily, resulting
in inadequate hardening of the concrete. Compound plywood made of lauan for the surface layer
and needle-leaf tree on the inside, or with surface painting or other methods, may be used so as toprevent adverse effect on concrete quality.
A plastic form can serve not only as a substitute for timber from Southeast Asia but is also
effective for construction management.
Clause No. 241 of the “Ordinance on Industrial Safety and Health” specifies the allowable stressof materials for formwork and shoring as follows;
1) Allowable bending stress and allowable compressive stress of steel members shall not
exceed two-thirds of the lower of the following values: the yield strength or three-fourthsof the tensile strength.
2) Allowable shear stress shall not exceed thirty eight-hundredths of the lower of thefollowing values: the yield strength or three-fourths of the tensile strength.
3) Allowable buckling stress of steel members shall not exceed the value calculated by thefollowing formulas
for l / i   ,c 

1 0.4(l / i /  ) 2

F

for l / i   ,

c 

0.29
F
(l / i /  ) 2

where, l : effective length of support (the longest span of restrained positions, if the
support is restrained from lateral displacement) (mm)i : minimum radius of gyration of the support section (mm)

 : limit ratio of length to width =

 2E

0.6 F

 : the ratio of the circumference of a circle to its diameter
E : Young’s modulus of steel member (N/mm2)

 c : allowable buckling stress (N/mm2)

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Standard Specifications for Concrete Structures-2007, Materials and Construction

 : safety factor = 1.5  0.57 (l / i /  ) 2
F : lower of the following values: the yield strength or three-fourths of tensile
strength (N/mm2)4) The value of allowable bending stress, allowable compressive stress and allowable shear
stress of timber parallel to the grain of various species of timber shall not exceed thoselisted in Table C10.7.1.

Table C11.3.1

Standard allowable stress of materials for formwork and shoring
Allowable stress (N/mm2)
Species

Bending
stressCompressive
stressShearstress

13.5

12.0

1.0

Japanese cedar, Fir, Japanese spruce, Abies,
Western red cedar, Western hemlock

10.5

9.0

0.7

Oak

19.5

13.5

2.1

Chestnut tree, Japanese oak, Beech, Zelkova
tree

15.0

10.5

1.5

Japanese red pine, Japanese black pine,
Japanese larch, Arborvitae, Japanese cypress,
Needle-leaf Japanese hemlock, Oregon pine, Port Orford
trees
cedar

Broad-leaf
trees5) Allowable buckling stress of timber parallel to the grain shall not exceed the value
calculated by the following formulas,
for lk / i  100 ,f k  f c (1  0.007 lk / i ) fk

for lk / i  100 ,fk 

0 .3 f c(lk / 100i ) 2

where, lk : effective length of support (the longest span of restrained positions, if the
support is restrained from lateral displacement) (mm)i : minimum radius of gyration of the support section (mm)fc: allowable compressive stress (N/mm2)
fk: allowable buckling stress (N/mm2)
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Chapter 11

Formwork and Shoring(3) Bleeding water accumulates under the bolts and steel bars used as tie members and causes
water leakage after the hardening of concrete. Therefore, it is efficient to attach a brim so as tolengthen the waterway. The hole at the concrete surface should be carefully filled using resin mortar
or other materials while taking into consideration the water-tightness requirements of the whole
structure.

11.4

Design of Formwork(1) Formwork shall be able to maintain its shape and position accurately under theaction of loads by using appropriate bolts.
(2) The structure of formwork shall be such that it can be easily erected and removed.
Vibration or impact resulting from the removal shall not adversely affect the concrete, etc.
Joints in the sheathing or form panels should, as much as possible, be at right angles orparallel to the member axis and be sealed to prevent mortar from leaking.
(3) Even if not specified, formwork should be designed to incorporate chamfers at all
corners.
(4) If necessary, temporary openings shall be provided at appropriate positions in theformwork to facilitate cleaning, inspection, and placement of concrete.

[Commentary] (2) It is important to erect boards or panels at right angles or parallel to themember axis so as to ensure the accuracy of formwork position, shape and dimension, and also toprevent mortar leakage from sheathing joints or form panels.
(3) The proper chamfer strip at the corner of formwork is useful for protection against impact
damage during removal work or after the completion of construction. Furthermore, such chamfers
are effective in order to minimize the effect due to atmospheric conditions or physical action.
Chamfer is sometimes used at joints in consideration of appearance and constructability.
(4) This requirement is necessary when the inside of formwork is blockaded cleaning andinspection are difficult after assembly or before concrete placing, or when the height of formwork ishigh and predetermined placing height cannot be secured during placement.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

11.5

Design of Shoring(1) Shoring shall be appropriately designed to ensure that all loads acting on it aretransmitted to the foundation.
(2) Shoring shall be easy to erect and remove, with joints and connections being
appropriately designed to carry all loads.
(3) Foundations of shoring shall be such that excessive and differential settlement
does not occur.
(4) Additional measures to appropriately raise the shoring shall be provided to offset
any settlement and/or deformation during or after placing of concrete.

[Commentary] (1) It is necessary for the shoring members to stabilize the supports using
sufficient lateral or diagonal bracing so as to possess sufficient strength and to be safe against
buckling under vertical loads. When the variance of load distribution occurs with the differential
settlement of foundation, temporary beams or other members should be used to distribute loads toall vertical supports.
Shoring should be designed to resist horizontal loads by fixing both sides of the beam at theupper part of shoring onto existing structures or other supports, or by employing lateral anddiagonal bracing. Also, for inclined formwork, care should be taken to ensure that shoring should
not deform adversely under concrete pressure.
(2) Shoring should be designed to be removed easily and safely without any impact on the
structures due to jacks, wedge anchors, or other measures.
For load transmission at joints and connections, it is effective to firmly fix the supports using
butt joint or plug joint and the connections and intersections between the steel materials using metal
devices such as bolt and clamp.
Beams of considerable height should be connected together with lateral bracings to prevent
rotation and collapse.
(3) To avoid the settlement of foundations in soft ground conditions, the distribution of loads oradequate strengthening of foundations should be required.
(4) Deflection of the structure or settlement of shoring caused by the weight of concrete may
affect the settlement or deformation of the structure during construction. Therefore, it is requiredthat the shoring be raised to ensure that the structure is constructed in conformity with the design
drawings.
Also, deflection caused by creep after construction may also require shoring adjustment.
Generally, it is necessary to show the amount of additional lift in the design drawings.
The settlement and deformation of shoring is normally caused by the settlement of foundations,compressive deformation and deflection of shoring members, looseness of joints or connections inthe shoring, and the thrust of contact faces. The amount of settlement and deflection should be
estimated by calculations, past experiences or a simple field measurement, etc., and be taken into
consideration in construction, if necessary.

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Formwork and Shoring

Generally, the looseness at joints or connections, the thrust of contact faces, etc. in the shoring
may be approximately 1 mm to 2 mm per location.

11.6

Preparation of Formwork(1) Formwork should be secured using bolts or steel bars. These bolts or bars shallnot remain on the surface of the concrete after the removal of formwork.
(2) Contact surfaces of formwork should be coated with a form release agent.
(3) The dimensions of the formwork and any defects therein shall be appropriately
managed prior to and during the placing of concrete.

[Commentary] (1) Steel wire in particular shall not be used for tying members of important
structures because it may easily expand or be cut.
When bolts and steel bars are exposed to concrete surfaces, the exposed portion may cause
water infiltration, rust spots, or cracks on the concrete surface. Embedded parts of bolts or steel bars
within 2.5 cm of the concrete surface should be removed after chipping the concrete. The holecreated by the chipping should be filled up with high quality mortar.
(2) The form release agent should efficiently prevent the formwork from adhering to theconcrete surface and facilitate the removal work of the formwork. For the form release agent, manykinds of products are marketed for use with wood, steel, or other forms. The main components ofform release agents are classified into paraffin, mineral oil, animal oil, vegetable oil, synthetic resinand surface-active agents, among others. Each form release agent differs widely in usage,
application amount, maximum number of applications, etc. Depending on the type or usage, a form
release agent may flow out by washing with water at the time of cleaning, rain, etc., so that the form
release effect may decrease. Also, construction joints may be polluted, or a form release agent may
be entrapped in the concrete during placement. Therefore, it is important to first confirm theproperty and usage before using a form release agent.
(3) Formwork shall be erected so that the completed structure is within the tolerances specified
in Section 15.7.3 of the Construction: Inspection Standards of this Specification. There may be
deflection of formwork, leakage of mortar, movement, inclination, settlement, looseness ofconnections, etc. caused by formwork prior to and during the placement of concrete. When suchtroubles arise, it is important to take suitable measures immediately, if necessary, to prevent danger.

11.7

Preparation of Shoring(1) Shoring shall be prepared in a manner that ensures sufficient strength and stability.
(2) The dimensions of the shoring and any defects therein shall be appropriately
managed prior to and during the placing of concrete.

[Commentary] (1) In order to provide sufficient strength and stability for shoring, prior to theshoring erection adequate preparation and strengthening of the ground should be completed so as toprovide the required bearing capacity or to avoid differential settlement. Sufficient compaction
should be applied to back-filled soil when it is used as the foundation material. When there is thepossibility that water may erode the underside of a shoring, precautions for treatment of water shall171

Standard Specifications for Concrete Structures-2007, Materials and Construction

be taken. Care should always be taken to the inclination, height, alignment and other factors so as toensure that there will be sufficient strength and stability during the erection of shoring.
Joints, connections and intersections of the members should be tight and free from gap andlooseness. All joints should be aligned correctly.
(2) There may be movement, inclination, settlement, etc. caused by the shoring prior to andduring the placement of concrete. When such troubles arise, it is important to take suitable measures
immediately, if necessary, to prevent danger.
Shoring shall be erected so that the completed structure is within the tolerances specified in
Section 15.7.3 of the Construction: Inspection Standards of this Specification. Even in cases where
the tolerance for each part of shoring is small enough to be commonly acceptable, if there is any
part that is affected by the cumulative effect of such tolerances it is necessary to evaluate such
effects and specify tolerances considering the cumulative error.

11.8

Removal of Formwork and Shoring(1) Formwork and shoring shall not be removed until the concrete has achieved
sufficient strength to carry its own weight and any loads superimposed during the courseof further construction.
(2) The timing and sequence of the removal shall be determined taking the strength of
concrete, the structure type and importance, member types and dimensions, loads
imposed on all members, temperature, weather and ventilation, etc. into appropriate
consideration.
(3) In cases when the structure is subjected to loads immediately after the removal offormwork and shoring, the concrete strength, the structure type, and the characteristic
and value of imposed loads shall be carefully considered in order to avoid harmful cracks
and other damage to the structure.

[Commentary] (1) The removal of formwork and shoring should be carried out after the concrete
has achieved sufficient strength. Removal of formwork and shoring should be carried out carefully
so as not to damage the structure.
The timing of removal should be determined considering the compressive strength of concrete
specimens cured under the same condition as the actual structure. Since specimens tend to be
influenced by outside temperature or dryness, it is desirable to judge the timing of the removal
based on the curing method in consideration of these effects.
(2) It is difficult to provide general criteria for removal time of formwork and shoring because
the various factors mentioned in this section may greatly influence the removal time. As many
construction accidents can be attributed to erroneous judgment of removal time, sufficientconsideration is required for the removal work.
Table C11.8.1 provides the suggested compressive strengths for the determination of theremoval time of formwork for RC structures. When the total load acting on a structure consists
almost entirely of dead load, a longer period of curing may be required than that given in Table
C11.8.1. Even after the compressive strength shown in Table C11.8.1 is achieved and the formwork
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Chapter 11

Formwork and Shoringis removed, wet curing needs to be continued for the period shown in Table 8.4.1.
Generally, the parts of formwork which bear relatively smaller loads should be removed prior toother parts which are more important and bear more load. For example, the formwork for verticalmembers like columns and walls can be removed before those for horizontal ones like slabs andbeams. The formwork on the lateral sides of beams can be removed before those at the bottom.

Table C11.8.1 Reference values of compressive strength of concrete required
for the removal of formwork and shoring
ExampleCompressive
strength (N/mm2)

Vertical or almost vertical surfaces of thick member
Upper surfaces of inclined members
Outside surfaces of small arch structures

Sides of footings

3.5

Vertical or almost vertical surfaces of thin member
Lower surfaces of members inclined at 45 degrees or more
Inside surfaces of small arch structures

Sides ofcolumns, walland beams

5.0Type and position of surface

Slabs and beams of bridges and buildings
Lower surfaces of members inclined at 45 degree or less

Bottoms of slabs
and beams,
Inside surfaces ofarch structures

14.0(3) Immediately after the removal of formwork, the concrete structure may not yet haveacquired the specified concrete compressive strength and the structural system may be different
from the one expected in the design. Loading may cause harmful cracks or damage to the structure
due to excessive stress. Therefore, it should be confirmed that loads imposed immediately after theremoval of formwork and shoring will have no harmful effect on the structure.

11.9
11.9.1

Special Formwork and Shoring
GeneralVarious types of special formwork such as slip forms, embedment forms, vented forms,
water absorbing forms, etc. are available. Various types of special shoring such as moving
shores, erection cars, etc. are also available. These formwork and shoring shall be used inaccordance with the special requirements for their use.

[Commentary] There are various types of special formwork; for instance, slip forms which movevertically for the construction of high bridge piers and water tanks, forms which move horizontallyor diagonally for waterways, tunnel forms for secondary lining, and so on. And there are various
types of special shores such as a moving or truss shores for viaducts and erection cars for cantilevererection of arch bridges. Formwork which is made from polymer cement mortar,polymer-impregnated concrete, fiber reinforced concrete, etc., and is used as a part of member, as
well as vented forms and water-absorbing forms which decrease surface air bubbles and rockpockets while reducing the water cement ratio at the concrete surface and raise the impermeability
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Standard Specifications for Concrete Structures-2007, Materials and Constructionof the surface part of a structure, are used in environments where high durability is required. In
addition, when using vented forms or water-absorbing forms for a thin concrete member, it isespecially important to delay the removal or to assure sufficient curing in order to avoid drying at
the initial stage. When using such forms care should be taken to meet the special requirements forthe use.
Since an embedment form is generally a thin component, cracks and chips may occur due to its
own weight, impact, etc. during conveyance and installation. Therefore it is necessary to pay
attention to the conveyance method or the method of hanging. Also, since rigidity of an embedment
form is generally small, it should be sufficiently examined in advance and, if necessary, reinforced
so that cracks do not occur due to lateral pressure of concrete.
Fiber sheet attached to forms for the purpose of water permeation or water absorption should besecurely fixed to the forms with adhesive tape, stapler, etc. so that neither slack nor wrinkle mayarise. When the fiber sheet is reused, any attached waste shall be removed and the sheet properly
cleaned to ensure full functional performance of the fiber sheet.

11.9.2

Slipform(1) In the design of slipform, in addition to loads referred to Section 11. 2, special loads,
such as frictional forces, shall be appropriately considered.
(2) The slipform shall be moved continuously until the structure is completed orconstruction of the planned section is finished.
(3) The formwork system shall have sufficient strength and rigidity, and all ancillaries
should have the required capacity and be safe for use. Formwork made of metal plates
should be used.
(4) The rate of movement of slipform shall be determined in a manner that ensures thatthe strength of concrete immediately after the removal of slipform is sufficient to resist all
possible loads, taking into account the quality of concrete and the conditions ofconstruction.
(5) Appropriate measures for securing concrete durability shall be taken whenconstructing using slipform.

[Commentary] (1) When a slipform is used, in addition to the loads expected on general
construction methods, the following special loads shall be considered at the top of steel frames orjacking rods during placing of concrete: the weight of deck, the friction between concrete andformwork, the weight of reinforcing bars temporarily placed on the deck, and the weight of concrete
acting on the temporary deck or working deck which can be used as shores or bottom formwork.
When the theoretical loads are difficult to calculate, the design should be based on the result
from an experiment unless the safety of the formwork has been proven from previous experience.
(2) and (3) Formwork system should have sufficient rigidity so as to ensure that deformations of
the structure do not exceed the tolerance during sliding operations.
The yoke, a member like a gate frame supporting the formwork and working deck, should be

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Chapter 11

Formwork and Shoring

able to resist the lateral pressure of concrete, and to transmit the full weight of shuttering,accessories and decks to the jacks. The yoke should also secure adequate clearance to enableembedded material to be located correctly prior to being arranged in the rising concrete. In thedesign of a vertical slipform, in which jacks are supported on vertical rods, care should be taken toplace jacks in such a manner that the vertical loads to each jacks are as nearly equal as possible andthat the capacity of the jacks are not exceeded. The jacking system should also provide for the
precise simultaneous movement of the entire form at a constant sliding rate.
When placing of concrete is interrupted, before resuming construction it is necessary to perform
joint treatment. This is necessary in order to prevent a weak point in the concrete which may reducethe durability performance.
(4) In general, the required compressive strength of concrete immediately after removal offormwork should be more than two times larger than the stress induced by the full loads. As thesliding rate is greatly affected by the type of cement used, mixture proportion, temperature of fresh
concrete and other factors, the intended standard rate should be determined based on preliminary
tests. When the concrete immediately after removal is not expected to achieve the required strength
due to changes in the weather or construction conditions, it is necessary to alter the rate of
movement or to take proper measures to achieve adequate strength. In addition, if concrete strength
becomes too large, slip resistance may also increase and may exceed the capacity of the jack.
Therefore, sufficient attention shall be paid to the rate of movement.
(5) Since the removal of slipforms will be carried out at an early age and it is hard to carry out
sufficient curing in slipform method compared with general construction method, the curing methodshould be fully examined beforehand in order to secure the durability of concrete. Moreover, there
is a possibility that wrinkles may arise with movement of slipform. Since this will have an adverse
effect not only on appearance but also on durability, when a fault is discovered after movement ofslipform the extent of the fault shall be evaluated and measures shall be taken, if necessary.

11.9.3

Movable shores(1) Movable shores shall be designed to have sufficient strength, safety and required
performance.
(2) In cases when loads from movable shores are to be supported by existing
structures, safety of such structures shall be confirmed for all load conditions.
(3) All supports on the movable shores shall be regularly inspected after erection andduring the period of operation to ensure their performance and safety.
(4) Movement of movable shores shall be carried out accurately and safely.
(5) In cases when movable shores are used, it shall be ensured that assembly andoperation will not cause any adverse deformation in concrete.
(6) Adequate camber shall be provided for movable shores, depending on therequirement.

[Commentary] (1) Movable shores referred to here involve movable shores, movable suspended
shores, working cars for overhanging erection, movable erection beams, and so on. Movable
shores consist of formwork, shoring beams, extending beams, supporting posts transmitting the175

Standard Specifications for Concrete Structures-2007, Materials and Construction

loads to the existing part or ground, other supports for horizontal or vertical movements, andcombined apparatus, if necessary. Movable shores, because of their long service period, shall be
designed for stability against the uplift force of wind as well as horizontal loads due to seismic andwind loads.
(2) In general, the structure may face unstable conditions during the movement of the shores.
Therefore, care should be taken.
(3) If necessary, loading tests should be conducted after the erection of shores to confirm theirsafety.
(4) Movable shores should be moved while monitoring the direction, height, and other factors toensure that the specified positions are obtained accurately and safely.
(5) If the shores are moved before the concrete achieves the specified elastic modulus, theconcrete beam may be harmfully deformed. Consideration should be taken to avoid such a situation
before the commencement of construction work.
(6) The value of the camber should be determined based on the deflection caused by the weightof concrete and other factors. Especially for prestressed concrete beams, the camber should bedetermined considering the elastic deformation and creep caused by the prestressing. For
information on the placement of prestressed concrete, refer to the Construction: Special Concretes(Chapter 12, Prestressed Concrete) of this Specification.

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Chapter 12

Cold Weather Concreting

CHAPTER 12 COLD WEATHER CONCRETING
12.1

General(1) When the mean daily temperature is likely to drop below 4℃, the provisions for cold
weather concreting shall apply.
(2) In cold weather concreting, adequate care shall be taken in regards to transportation
to the site, placing, curing, formwork and shoring, etc. to ensure that fresh concrete does
not freeze and that it has the required qualities despite being placed in cold weather.

[Commentary] (1) Under weather conditions when the mean daily temperature is 4˚C or below,
the casting of concrete should be carried out according to the provisions for cold weather concreting
since the setting and hardening reactions of the concrete are markedly retarded and the concrete
may freeze even in the daytime as well as at night or early in the morning. When concrete is
exposed to temperatures below freezing before hardening, it easily freezes, expands and suffersfrom frost damage at early ages. Concrete having suffered from the frost damage at early ages will
never be restored to its strength even if followed by adequate curing. Consequently properties assuch as durability and water-tightness will be greatly deteriorated. When concrete is exposed to lowtemperature of about 5˚C or below, the setting and hardening reactions are considerably retarded,even though no freezing occurs. Hence, in structures subjected to an early application of
construction loads, problems such as cracks and residual deformation will arise. When the windblows directly against exposed surface or steel-made shuttering, the temperature fall in the concrete
becomes much larger.
The freezing temperature of concrete is about -0.5 to -2.0˚C, although it slightly varies
depending upon the water-cement ratio and the type and amount of admixtures. According totemperature data in Japan, freezing of concrete may occur not only in Hokkaido and Tohoku but
also in other parts of the country, including Shikoku and Kyushu.
(2) Important actions during cold weather concreting are to prevent the concrete from freezing
and to take necessary measures to prevent the quality of concrete from deteriorating even undercold weather. Particularly important considerations when trying to achieve these goals are as
follows:
1) Concrete shall be protected from freezing at the early stage of setting and hardening.
2) Concrete shall be given sufficient resistance against freezing and thawing action during theperiod from completion of curing till the weather gets warm.
3) Sufficient strength shall be provided to withstand possible loads at different stages of
construction.
12.2

Materials(1) It is a standard requirement that portland cement or Type B blended cement should
be used.
(2) Neither frozen aggregate nor aggregate containing ice or snow shall be used in that177

Standard Specifications for Concrete Structures-2007, Materials and Construction

state.
(3) Chemical admixtures shall be selected so that stable concrete quality can beobtained. Chemical admixtures whose quality is not specified in JIS or JSCE standards,
such as freeze-preventing additives and cold-resistant additives, may be used only when
their quality and the quality of concrete made by using such additives are fully verified.
(4) If materials are to be heated, only water or aggregate shall be heated; cement shallnot be heated directly under any circumstances. Aggregate shall be heated uniformly andby a method that does not cause the aggregate to become dry.

[Commentary] (1) The use of portland cement or Type B blended cement is required as standard
for cold weather concreting because the degree of delay in strength development at early ages ofconcrete is low even when the concrete is cured at low temperature.
In the case of normal portland cement, it is difficult to attain the required curing temperatureand initial strength. In the absence of problems associated with cracking due to heat generated byhydration, it is desirable that high-early-strength portland cement be used.
(2) If frozen aggregate or aggregate containing ice or snow is used in that state, concrete
mixes become prone to problems such as lower mix temperature and fluctuations in water content
such that the concrete quality is adversely affected. When conducting cold weather concreting,therefore, it is desirable that aggregates are stored in facilities where freezing and the intrusion of
ice and snow can be prevented.
(3) It is a standard requirement that chemical admixtures to be used for cold weather
concreting be selected from those that meet the requirements specified in JIS A 6204, Chemical
Admixtures for Concrete, or the JSCE standard. Chemical admixtures to be used shall also ensurestable quality of concrete even at low temperatures. Lowering the water-cement ratio by using an
air-entraining high-range water-reducing agent is effective for enhancing freezing resistance.
Concrete made using an air-entraining high-range water-reducing agent has a smaller slump at
lower temperatures than at higher temperatures after mixing, but the slump of such concrete may
become larger over time. It is therefore important to exercise care in using air-entraining high-range
water-reducing agents and pay close attention to water-reducing performance at low temperatures,changes in workability, etc.
Besides the chemical admixtures mentioned above, other chemical admixtures that may be
used include freeze-preventing and cold-resistant additives, accelerator-type air-entraining
water-reducing agents, and accelerators used to accelerate strength development. When using thesechemical admixtures, it shall conduct careful studies on their composition, effects, etc., andascertain their quality. For liquid chemical admixtures, it is also necessary to take measures toprevent them from freezing because segregation occurs when they freeze.
(4) If high-temperature cement is allowed to come into contact with water, the cement may
harden quickly, with adverse effects on the concrete. Cement, therefore, shall not be heated. Ifmaterials are to be heated, it is desirable that water also be heated because it is simple to perform
and the heat capacity of water is large. The temperature of heated water shall be controlled so that
cement does not harden quickly. The capacity of the equipment and methods used to heat waterneeds to be sufficiently large so that the temperature of the materials to be heated is raised
uniformly and the target temperature can be obtained for the selected materials
Raising the temperature of aggregate to 65°C or higher may make the aggregate difficult to178

Chapter 12

Cold Weather Concreting

handle and cause cement to harden quickly. In general, these problems can be prevented by keeping
the temperature of water–aggregate mixtures at or below 40°C. The method of using steam to heataggregate is relatively easy to control.
When materials are heated, the concrete temperature (°C) just after mixing can be calculatedby the following equation;T

cs (TaWa  TcWc )  TmWm
cs (Wa  Wc )  Wm

(C12.2.1)

where,
Wa, Ta: weight and temperature of aggregate in kg and ºC, respectively,
Wc, Tc: weight and temperature of cement in kg and ºC, respectively,
Wm, Tm: weight and temperature of mixing water in kg and ºC, respectively,
cs: specific heat of cement and aggregate, assumed to be 0.2.

12.3

Mix Proportions(1) As a general rule, concrete placed under cold weather should be air-entrained
concrete.
(2) In order to prevent initial freeze damage, the water content shall be made as low as
possible while maintaining the required workability.

[Commentary] (1) The use of an air-entraining agent or air-entraining water-reducing agent
makes it possible to entrain air bubbles so as to reduce the water content needed to attain therequired workability and to reduce adverse effects due to the freezing of water in concrete. This is
why it is required that air-entrained concrete be used when concrete is to be placed under cold
weather. The standard air content is 4% to 7% of the volume of concrete upon completion of mixing.
In cases where concrete is likely to be subjected to freeze–thaw cycles over a long period of time –for example, in a cold region – it is good practice to use an air content of about 6% after confirmingthat the strength requirements are met.

(2) In general, slump increases as concrete temperature rises. When concrete is produced in
winter, therefore, the water content tends to be lowered to attain the required slump. Lowering thewater content not only reduces the amount of water that can freeze but also reduces bleeding, whichtends to increase considerably at lower temperatures, and prevents concrete temperature fromfalling. The basic rule, therefore, is to reduce the water content as much as possible to the extent
that the required workability can be achieved.

12.4

Mixing(1) Concrete temperature just after mixing shall be such that the required temperature at
the time of placing can be obtained, taking into consideration the effect of weather

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conditions, time of transportation, etc.
(2) In the case that heated materials are used, the order in which the materials are put
into the mixer shall be decided such that cement does not harden quickly.
(3) The concrete temperature just after mixing shall be controlled so as to minimize
batch-to-batch variations.

[Commentary](1) Concrete temperature at completion of placing is lower than that just after
mixing in a mixer due to heat loss during transportation and placing. The extent of the concretetemperature drop is usually regarded to be about 15% of the difference in the temperature between
the concrete and ambient air for each hour of transportation and placing. It can be calculated by thefollowing equation;
T2  T1  0.15(T1  T0 )t(C12.4.1)

where,
T0 : ambient air temperature, in ºC,
T1 : concrete temperature just after mixing , in ºC
T2 : concrete temperature at completion of placing, in ºCt : time from mixing to completion of placing, in h.
Therefore, the concrete temperature at mixing needs to be the sum of the required placing
temperature and heat loss during transportation and placement. In the selection of ready-mixed
concrete plants, such factors as temperature drop during transportation, transportation time and theheating capacity of the plant facilities shall be considered.
(2) Cement may harden quickly if high-temperature water comes into contact with cement. A
recommended procedure, therefore, is to put heated water and coarse aggregate and then fineaggregate into the mixer and finally, after the temperature of the materials in the mixer becomes
40°C or lower, put cement into the mixer.
(3) If the rate of supply of concrete exceeds the capacity of the heating equipment, it is nolonger possible to attain the required as-mixed temperature. When planning for concrete placement,
therefore, it shall take material-heating capacity into consideration. It shall also take considerable
care with the first batch of the day because low equipment temperature may result in low as-mixed
temperature.
12.5

Transportation and Placing(1) Concrete shall be transported and placed so as to minimize the reduction intemperature of the concrete. The reduction in concrete temperature during transportationand placing shall be prevented by reducing the time elapsed between mixing and placing of
concrete as much as possible.
(2) The temperature of concrete at placement shall be in the range of 5 to 20˚C
considering of the cross-sectional dimensions of the structure and the weather conditions.

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Cold Weather Concreting(3) It shall be ensured that snow and/or ice are not adhering to the reinforcement,
formwork, etc., at placing.
(4) In cases when the surface of concrete at a construction joint is frozen, it shall beappropriately thawed and fresh concrete shall be placed in accordance with provisions
given in Chapter 9 of this specification..
(5) Surfaces of freshly-placed concrete shall be protected from exposure to theatmosphere for a long time.

[Commentary] (1) It is necessary to check on the time required for the transportation from theplant to the construction site, for waiting at the construction site, and for the process from unloading
to the completion of placement as well as temperature falls during those processes and to takeappropriate measures on an as-needed basis. When a concrete pump is used, if the temperature of
the conveyance pipe is too low, frozen mortar may stick to the inside surface of the pipe and may
result in unexpected trouble. In order to prevent such trouble, it is necessary to carefully performtasks such as maintaining the temperature of piping, preheating by use of heated water prior toplacement and cleaning after the completion of placement. Concreting tasks need to be controlled
so that the placement of concrete is not interrupted.

(2) For cold weather concreting the hardening of concrete may be retarded remarkably and theconcrete is likely to freeze when ambient air temperature drops rapidly. Therefore, adequate
concrete temperatures shall be secured at placing of concrete considering the type and size of thestructures, weather conditions, the ambient air temperature and the curing method. For the case of
severe weather conditions and a thin concrete member, the minimum temperature at the placement
shall be secured at around 10˚C. On the other hand, for a thick concrete member, thermal cracking
tends to occur due to the heat generated by cement hydration when the temperature of placing
concrete becomes higher. Therefore, the temperature at the placement of concrete may be controlled
at 5˚C or slightly higher for thick concrete members. When the temperature is overly high the unit
water content normally increases and the hardening process of the concrete is accelerated resulting
in decrease of strength at later ages. Furthermore, the concrete surface becomes susceptible todrying and may cause cracking. Hence, considering such factors as the size of structural members
and the weather conditions, concrete temperature at placing should be determined to within a rangeof 5 to 20˚C so that freshly-placed concrete will not be subjected to frost damage at early ages.
Since low concrete temperature may cause lateral pressure and bleeding to increase, it shall pay
attention to the placing rate, placing height, etc.
(3) It is effective to spray hot water or steam on reinforcement and shuttering to melt the ice
and/or snow. However, in the case of lower temperatures precautions should be taken because
re-freezing of the water may cause adverse effects. The combined use of such equipment as burners
and heaters with propane gas or kerosene is also effective. Melted water and the water used for
melting shall be removed prior to the placement of concrete.
In cases where concrete is placed on the ground, if the ground is frozen concrete temperature
falls sharply and the frozen ground melts so that the concrete settles. When placing concrete on the
ground, therefore, it is necessary to cover the ground with sheeting, etc., and, if necessary, usefloodlighting equipment, heater, etc., to prevent the ground from freezing before the placement of
concrete and prevent water inflow. In cases when the ground is already frozen concreting shall be
carried out after it is properly melted.
(4) To state herein that concrete is frozen does not mean that the concrete is subjected to frost

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damage, but just describes the state of concrete.
(5) It is likely that the temperature of the concrete surface may rapidly drop during the elapsed
time between the completion of placing and the start of curing. Therefore, the concrete surfaces
shall be covered immediately after placing with appropriate materials such as a plastic sheet. It isespecially important to protect the concrete surface from the wind.

12.6

Curing(1) The method and duration of curing shall be decided considering such factors as theambient air temperature, mix proportions and the type and size of the structures.
(2) During the early age after placement, freshly-placed concrete shall be sufficiently
protected from being frozen, particularly from wind. Furthermore, during construction thetemperatures of concrete and the surrounding atmosphere shall be periodically measured
and the plan for construction may be changed accordingly, if necessary.
(3) The temperature of concrete exposed to severe weather should be maintained at 5˚Cor higher until the compressive strength reaches the values given in Table 12.6.1, and at
0˚C or higher for a further period of two days.

Table 12.6.1 Required compressive strength of concrete at the end of curing under severe weather
conditions (N/mm2)
Sections
Exposure condition of structure(1) Portions continuously or frequently saturated with water(2) Portions exposed to ordinary conditions other than (1)Thin

Ordinary

Thick

15
5

12
5

10
5

(4) When heating up concrete, rapid drying of concrete shall be avoided and heating
shall be conducted uniformly in the concrete.
(5) Concrete shall be cured until it achieves required strength that can withstandpossible loads during construction.
(6) After completion of insulation curing or heat curing, concrete shall not be cooled
rapidly.

[Commentary] (1) Curing methods for cold weather concreting are classified into insulated
curing and heat curing. Regarding insulated curing, the concrete’s surroundings are covered withmaterials of high insulation performance and curing is continued until the required strength
develops by utilizing the heat of hydration of the cement itself. Heat curing is conducted for lower
ambient air temperatures and thin concrete sections when it is impossible to adequately keep thetemperature above the freezing point by insulation alone. It is recommended to combine the heatcuring with insulated curing using sheets in order to optimize its effectiveness. Heating apparatusesof various properties are available, and the effectiveness of their capacities, the number of apparatus
to be used and the arrangement of the locations need to be examined. Since carbon monoxide may

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Cold Weather Concreting

be produced depending on the types of apparatuses used, close attention shall be paid to the safetycontrol. When curing temperature increases, the strength development of concrete is expedited andthe duration of curing can be shortened though cracking is likely to occur during the cool-down
period after the termination of curing. On the other hand, when the curing temperature decreases,
the curing time until the required concrete strength is achieved is prolonged. Therefore, it shall plan
the curing method, duration and curing temperature while considering concrete mixture proportions,strength, structural type, thickness of cross-sectional area, ambient air temperature, and so on.
(2) Once concrete suffers frost damage at early ages the strength develops only slightly even if
curing is continually performed. Therefore prevention of concrete freezing placed at any location
shall be implemented until required strength is obtained. Particular care should be taken for the
curing of corners and edges of concrete structures, as these locations are the most difficult toproperly insulate and are vulnerable to frost damage at early ages. For cold weather concreting thetemperature of both concrete and its surrounding atmospheric air should always be monitored so as
to avoid any problems related to the concrete strength development. When the construction
conditions differ from the plans such that the concrete may be adversely affected, necessary
countermeasures such as increased temperatures of concrete materials, insulated curing and heatcuring shall be taken.
Since wind expedites moisture evaporation from the concrete surface and lowers the concretetemperature at and near the surface, the surface concrete shall be protected from the cold wind
immediately after placing.
(3) It shall determine curing temperature considering mixture proportions, ambient air
temperature, structuralsize and dimensions, curing methods and their periods and temperature
control systems. The lowest curing temperature with regard to the protection from the frost damageat early ages is 5˚C. However, for severe cold weather or a thin concrete member it may be
increased to 10˚C. Rapid cooling after curing shall be avoided for concrete with a thick crosssection since the temperature sometimes increases up to 20˚C due to the heat of hydration. In
general appropriate curing methods are required so as not to increase the temperature of the surface
concrete higher than 20˚C.
Since concrete suffers from frost damage depending on factors such as strength, moisture
content and the amount, size and distribution of entrained air, the required performance to withstandfrost damage cannot be specified by strength alone. However, it is reported that concrete with acompressive strength of not less than 4 N/mm2 rarely suffers from frost damage after several
freezing and thawing cycles. However, in the case of wet concrete continuously subjected to severe
weather conditions, the curing shall be continued until further strength development is achieved.
Concrete strength necessary to withstand frost damage at the end of curing depends on factors suchas weather conditions, size of members, exposure conditions, etc. Standard concrete strength isprovided in Table 12.6.1 according to the classification prescribed therein. These strength values are
specified to ensure that the post-curing concrete can resist the freezing and thawing actions. For theprevention of concrete under rapid cooling, it has been concluded that the concrete temperature
should be kept above 0˚C for the following two consecutive days after the end of curing. When the
curing practice prescribed herein is carried out, resistance against the long-term weather actions isgenerally considered to be satisfactory owing to the proper development of the strength.
In principle, curing period should be determined by testing since the types of cement, mixture
proportions and curing temperature affect the curing period necessary to achieve the strength
specified in Table 12.6.1. Table C 12.6.1 shows general curing criteria at 5 and 10˚C. In order tomaintain wet conditions, the periods specified in Section 8.2 for wet curing shall be satisfied as
well.
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Table C 12.6.1 Criteria for curing periods to achieve specified compressive strength
SectionOrdinary

Types of cement
CuringTemp.
(1) Portions continuously or
5˚C
frequently saturated with
10 ˚C
water
5˚C
(2) Portions exposed to ordinary
conditions other than (1)10˚CExposurecondition of surface

Ordinary
portland
9days

High-earlystrength portland
5days

Blended cement(type B)
12 days

7days

4days

9days

4days
3days

3days
2days

5days
4days

Note: Applicable to W/C＝0.55. Need to be modified for different W/Cs

(4) When heat is provided to concrete, it shall keep the concrete at the appropriate temperatureand provide the concrete with sufficient moisture so as to prevent the concrete from drying. Whenconcrete is heated, evaporation of water from the concrete is accelerated. It is therefore necessary to
prevent the concrete from drying by taking appropriate measures such as watering. In this sense, themethod of heating concrete by use of steam is advantageous, but water needs to be supplied because
drying can result even if the steam method is used.
In heat supply curing, it is important to avoid local heating since it may increase the possibilityof cracking due to temperature gradients generated within the concrete.
(5) Concrete placed in cold weather is exposed to low temperatures after insulated or heatcuring, and the successive strength development is slow. Therefore, except for cases when the timeof load application is considerably late, it is recommended that the curing be continued after thestrength of concrete reaches the requirement for resistance against frost damage at early ages until it
can sustain an anticipated load.
(6) Cracking may occur at the concrete surface when concrete of relatively higher temperature
after insulated or heat curing is quickly exposed to the cold air. The concrete surface shall beprotected by an appropriate method so as to be gradually cooled down. In cases when concrete isvulnerable to freezing under cold air after the end of curing, watering just before the termination of
curing shall not be done.

12.7

Formwork and Shoring(1) The formwork should have good heat retention.
(2) Lateral pressure acting on formwork shall be determined, taking concretetemperature into consideration, with reference to Section 11.2.4.
(3) Shoring shall be placed firmly on the ground without any deformation on account offrost heaving of the ground or thawing of the frozen ground.
(4) Removal of formwork shall be carried out in a manner that the temperature ofconcrete does not drop rapidly.

[Commentary] (1) Compared with steel forms, wooden forms have lower thermal conductivity
and therefore provide better heat retention. If the concrete section is thick it is efficient to take
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Cold Weather Concreting

advantage of the effect of temperature rise due to the heat of hydration of cement. Even when theconcrete section is thin it may be possible to provide insulation without a heat supply by the
combined use of foamed resin and shuttering. When steel forms are used, it is necessary to pay
sufficient attention to the insulation since the steel is readily influenced by rapid change in ambient
air temperature.
(2) As concrete temperature falls, lateral pressure acting on formwork tends to increase. It isnecessary, therefore, to determine lateral pressure values to be used in formwork design taking thistendency into consideration, with reference to Section 11.2.4.
(3) When shoring is directly based on the ground, the proper location, configuration ordimensions of the structure may not be secured due to the frost heaving or thawing of the ground; insome cases the shoring may collapse. Therefore, when the above-mentioned is predicted, it shallprevent frost heaving or to avoid the adverse effect of displacement caused by frost heaving or
thawing by adopting measures such as a pile foundation.
(4) The inner temperature of a structure with a thick section rises considerably due to the heat ofhydration. Temperature differences may develop when the concrete is rapidly cooled down after the
shuttering removal and cracking may occur. Therefore, it is desirable to remove shuttering after
minimizing the temperature differences by adjusting the temperature within the enclosures or toretain the shuttering until the concrete surface will not be subjected to rapid cooling even after the
specified strength for the removal has developed. For example the maximum allowance on atemperature drop within 24 hours after the end of curing is 22 to 28˚C for a thin section and 17˚C
for a thick section.

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CHAPTER 13 HOT WEATHER CONCRETING
13.1

General(1) When the mean daily temperature is likely to exceed 25°C, the provisions of
hot-weather concreting should apply.
(2) In hot-weather concreting, appropriate measures shall be adopted duringtransportation within the site, placing, and curing, so that the quality of concrete is not
impaired due to high temperatures.

[Commentary] (1) It is quite difficult to accurately define in which period of the year
hot-weather concreting should be applied. It is desirable, however, to prepare for hot-weather
concreting when the mean daily temperature exceeds 25˚C because the characteristics of
hot-weather concreting become remarkable if the temperature at placing time exceeds 30˚C.
Measures to be taken in connection with hot weather concreting should be implemented well inadvance.
(2) High (atmospheric) temperatures result in high concrete temperature and large slump loss
during transportation as well as loss of entrained air. High temperatures also increase the risk ofcold joint development, cracking due to the rapid evaporation of water on concrete surface, thermal
cracking, etc. Therefore, in order to minimize the concrete temperature during and after placing,
special care should be given to handling materials, mixing, transporting, placing, and curingconcrete.
It is also desirable that a construction plan be drawn up and construction work be controlled
appropriately in due consideration of the fact that in a higher-than-normal-temperature environment,
work efficiency tends to decline and workers are susceptible to heat stroke.

13.2

Materials(1) When the required concrete temperature cannot be attained, a method for lowering
the temperature of materials shall be determined and its effectiveness verified in advance.
(2) It is a standard requirement that air-entraining water-reducing agents andsuper-plasticizers used should be retarder type admixtures conforming to JIS A 6204. It isalso a standard requirement that air-entraining high-range water-reducing agents usedshould conform to JIS A 6204.

[Commentary] (1) The temperature of cement upon delivery may be quite high temperaturedepending on the shipping conditions from the factory. Although the temperature of the cement
does not severely affect the temperature of the concrete (in general, ±1ºC in concrete temperature),
the use of high temperature cement under hot weather conditions is unfavorable as it raises thetemperature of concrete.
The temperature of the aggregates affect the temperature of concrete greatly (in general, ±2ºC
change in aggregate temperature corresponds to ±1ºC in concrete temperature); therefore, the use of186

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Hot Weather Concreting

aggregates exposed to sunlight for an extended time period may produce a concrete temperature
over 40ºC. This will cause an increase in unit water content, an increased rate of slump loss duringtransporting and an increased rate of setting after concrete placement. Thus, the aggregate should be
kept away from direct sunlight using adequate facilities or kept in an appropriate condition bywatering them. In general, the purpose of the method of watering over coarse aggregate is to lower
the temperature by means of water evaporation. The method can be made even more effective bydirectly cooling coarse aggregate by use of cold water. The method of lowering the temperature of
aggregate by use of liquid nitrogen is used in some cases. Because of its latent hydraulic property,
ground granulated blast furnace slag may consolidate in aggregate storage facilities or storage bins
during periods when daily mean temperature is higher than 20°C, thereby making it difficult toremove from the storage facilities or storage bins. During such periods, it is important to avoid
long-term storage.
In order to reduce the temperature of mixed concrete, it is desirable that the mixing water be
as cool as possible (in general, ±4ºC change in water temperature corresponds to ±1ºCin concretetemperature). It is necessary for water-storage tanks and pipelines to keep the water temperature
low by means of adequate methods such as shading, painting storage silos white, and so on. The useof ice is a very effective means of reducing the concrete temperature though it is generally not easy
to possess ice-crushing facilities.
(2) When water-reducing agents or air-entraining water-reducing agents are used,retarder-type agents instead of standard types should be used. If retarder-type admixtures, etc., areused with the aim of preventing cold joints, it is necessary to carefully consider how to use themand determine the quantity to be used appropriately. Air-entraining high-range water-reducing
agents substantially reduce the water content and the cement content even in the case of hot weather
concreting. Depending on the type of admixtures, however, the amount of decrease in slump overtime may be large at high temperatures. Regardless of the type of chemical admixture to be used,
therefore, it is important to select chemical admixtures that make it possible to maintain therequired minimum slump until the planned time of completion of placement.
Super-plasticized concrete dramatically improves the placeability and quality of concrete. In
general, however, the slump of super-plasticized concrete decreases considerably over time, and thistendency may become particularly pronounced under hot weather. It is therefore desirable thateither retarder type super-plasticizers are used for hot weather concreting or retarder-typewater-reducing agents, air-entraining water-reducing agents or other similar admixtures be used forbase concrete.

13.3

Mix Proportions

In the mix design of hot weather concreting, appropriate measures shall be taken sothat the water content and the cement content do not become too high to the extent thatthe required strength and workability can be attained.

[Commentary] There is a certain relationship between the water content needed to attain therequired workability and concrete temperature just after mixing. In general, the water content tends
to increase by 2% to 5% for every 10°C of temperature rise. In many cases, as concrete temperaturerises the amount of change in slump and air content also increases. Consequently, when slump isadjusted by using such methods as adjusting the surface moisture content of aggregate without
taking control measures associated with hot weather concreting, concrete with higher water content
and lower compressive strength than that of low temperature seasons might be placed. When the187Standard Specifications for Concrete Structures-2007, Materials and Construction

water-cement ratio is kept constant and the cement content is increased according to the increase in
the water content with the aim of attaining the required compressive strength, conditions that are
disadvantageous in preventing cracking due to the hydration of cement result. It is necessary,
therefore, to take appropriate measures (after conducting prior studies) to prevent the water content
and the cement content from becoming excessively high to the extent that the required strength andworkability can be obtained. To be more specific, it is necessary to determine the amount ofdecrease in slump due to temperature rise and changes in slump over time and check whether therequired minimum slump can be attained until the completion of placement. If the water content
needs to be increased substantially, it is necessary to take appropriate measures such as increasing
the usage of chemical admixtures, switching from air-entraining agents to air-entraining high-range
water-reducing agents or adding super-plasticizers.

13.4

MixingConcrete temperature just after mixing shall be such that the required temperature at
the time of placing can be obtained while taking into consideration the effect of weather
conditions, time of transportation, etc.

[Commentary] Lowering the temperature of concrete materials is a good way to lower theconcrete temperature just after mixing. When, however, ice is used as part of mixing water, it isnecessary to ascertain in advance that ice melts completely during mixing. There are also othermethods such as the method of injecting liquid nitrogen into the mixer to lower concretetemperature directly. The temperature of mixers installed in a poorly-ventilated plant with highindoor temperature due to solar radiation and heat generated by machinery might also be affectedby heat supplied by premixed concrete. Such mixers need to be cooled on an as-needed basis.
In order to deduce the temperature of fresh concrete from the temperatures of the materials
with which the concrete is made, the equation shown in Eq. C.12.2.1 may be applied. However, theequation does not consider the effect of the heat of hydration and the frictional heat during mixing,
so that the actual concrete temperature under hot weather conditions may be about 1ºC higher thanthe calculated temperature.
The rise in concrete temperature during transportation is generally 2 to 4ºC, and 1 to 5ºC forpre-cooled concrete. When calculating the temperature increase during the period between thefinish of mixing and the finish of transportation or placing concrete, Eq. C.13.4.1 may be
applicable.
T2  T1  0.15(T0  T1 )t

C13.4.1

where,
T0 : ambient air temperature, in degree C.
T1 : concrete temperature just after mixing , in degree C.
T2 : concreter temperature at completion of placing, in degree C.
t : time from mixing to completion of placing, in hours.

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13.5

Hot Weather Concreting

Transportation

Transportation of concrete shall be carried out using means and methods so that theconcrete does not dry or get heated during transportation.

[Commentary] Concrete shall be transported using means and methods that minimize concretetemperature rise and drying of concrete. To do that, it is good practice to transport and place
concrete as quickly as possible. For ready-mixed concrete, it is required that the process frommixing to unloading be completed in 1.5 hours. Section 13.6, however, requires as a general rulethat the placement of hot weather concreting be completed in 1.5 hours. At the construction
planning stage, therefore, it is necessary to check whether construction work needs to be carried out
during a hot weather concreting period and, if concreting during such a period is expected,
determine the plant and transportation routes to be used, estimate transportation time and takeappropriate measures, through consultation with the plant, so that transportation time can be madeas short as possible. It is also important to plan and control vehicle operation so that truck agitators
will not be kept waiting for a long time under hot weather. In connection with on-site transportation,
it is necessary to study and find, in advance, methods for transporting and placing concrete as
quickly as possible. Care shall be taken, however, so that a higher transportation speed does notincrease pipe pressure such that pumping becomes difficult or there is a delay in compaction,finishing and curing. If concrete is transported by pumping, it is important, for example, to selectlocations so that pipes are not exposed directly to sunlight, to prevent pipe temperature from risingby covering the pipes with wet cloth and to avoid interruption in order to prevent clogging due to adecrease in slump.

13.6

Placing(1) In areas where water absorption is expected, such as on the ground or in formwork,
the areas shall be saturated with water prior to placing. Furthermore, when the temperatureof formwork or reinforcement is anticipated to rise substantially due to direct exposure to
sunlight, appropriate measures such as water sprinkling or covering shall be taken.
(2) Concrete placing shall be completed as promptly as possible and the elapsed timefrom start of mixing to completion of placing should, in general, not exceed 1 and a half(1.5) hours.
(3) Temperature of concrete at the time of placing shall not exceed 35°C. Furthermore,during construction, the temperatures of concrete and surrounding atmosphere shall be
periodically measured and the plan for construction may be changedaccordingly, if
necessary.

[Commentary](1) When placing concrete in high temperature conditions, areas such as theground and formwork may easily dry out; this drying process affects the flowability of concrete byabsorbing concrete water. Therefore, it is necessary to saturate these portions with water before
placing concrete. The temperature of the formwork and reinforcing bars may rise substantially
under direct exposure to sunlight. This results in quick-setting of concrete and adversely affects thequality of hardened concrete; therefore, covering or sprinkling should be carried out to keep theformwork and reinforcing bars at a low temperature. It is necessary, however, to avoid excessive
watering so that water is not left in the formwork and to observe the condition in the formwork andshall remove water left in the formwork before placing concrete.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(2) The slump of hot weather concreting is highly susceptible to decreases over time.
Consequently, concrete that has been left unplaced after being mixed may become difficult to place.
If, therefore, construction during a period when outdoor air temperature is higher than 25°C is
expected, it is important to check on the time-dependent changeability of concrete in advance sothat the required minimum slump for placement defined in Section 4 can be met. In general, theamount of decrease in slump is small for 1.5 hours after the completion of mixing, and concrete canbe placed without any problem during that period. Since, however, such changes in quality tend toincrease as air temperature rises, it is desirable that concrete be placed continuously and as quickly
as possible so as not to cause problems such as cold joints. Although Table 7.4.1 shows that theallowable placement interval at an outside air temperature exceeding 25°C is 2.0 hours or less, it isdesirable in the case of hot-weather concrete that a shorter placement interval be specified in orderto prevent the occurrence of cold joints.
(3) The temperature at concrete placing time shall be as low as possible in order to prevent
adverse effects. The upper limit of concrete temperature at placing time has been determined to belower than 35°C based on the following reasons. 1) When temperature is lower than 30°C, theadverse effect of temperature on concrete quality is relatively small; under hot weather conditions,
it has been observed that the temperature of ready-mixed concrete at the point of discharge is
between 30 to 33°C and this temperature rises approximately 2°C during transportation of concrete
to the site. 2) With currently-available facilities, it is difficult for concrete plants to cool down
concrete materials before mixing. 3) The required concrete quality can be assured if the concretetemperature is kept between 30 to 35°C by using a retarding agent or by rapid construction. Whenthe development of thermal cracks is anticipated, verification of thermal cracking shall be carriedout and concrete placing temperature determined.
In hot weather concreting, temperatures of materials and concrete should be measured. If thepredicted placing temperature or actual measured concrete temperature exceed the planned
temperature, the construction plan shall be modified and appropriate construction methods selectedbased on measured temperatures of materials and concrete.

13.7 Curing
Curing shall be started immediately after placing concrete, so that the concrete surface
can be protected from drying. Appropriate measures shall be taken to protect the concrete
against direct sunlight and wind so that cracks due to rapid drying can be avoided.

[Commentary] The surface of concrete placed under hot weather dries up quickly when exposed
directly to sunlight or wind so that the concrete becomes difficult to finish and the potential forcrack formation increases. Therefore, the placed concrete should be cured as soon as possible sothat the surface does not dry out. Moist curing period shall be decided in accordance with theprovision stipulated in Table 8.2.1. In the case that wooden formwork is used, they shall be kept in asaturated condition during the curing period since this formwork is likely to dry out.
Moreover, the exposed concrete surface should also be kept in saturated conditions during thecuring period after formwork is removed. Especially in the case of high temperature or low
humidity, cracking is likely to occur due to rapid drying. Therefore, measures such as sprinkling or
covering should be conducted in order to prevent the surface from drying. For structures with widesurface area like slabs, where sprinkling or covering is difficult, membrane curing may be appliedin accordance with regulations stipulated in Section 8. The membrane curing agent should be of the190Chapter 13

Hot Weather Concretingtype which absorbs only little thermal energy from direct sunlight.
If cracking due to the rapid drying of the surface is recognized while concrete has not hardened
after placing, re-vibrating or tamping should be conducted to eliminate cracking.

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CHAPTER 14 MASS CONCRETE

14.1 General(1) In cases where thermal stress due to heat generated by the hydration of cement is
problematic, the concrete is regarded as mass concrete and measures to be taken shall becarefully determined.
(2) For mass concrete, verification concerning thermal stress and thermal cracking due
to heat generated by the hydration of cement shall be performed in advance in accordancewith the Design: General Requirements (Chapter 12, Verification Related to Initial Cracking)of this Specification.
(3) It shall be ascertained prior to the commencement of construction that theconditions assumed in the Design section of this Specification agree with the actual
construction conditions. If the conditions assumed in the Design section do not agree withthe actual construction conditions, verification concerning thermal stress and thermal
cracking due to heat generated by the hydration of cement shall be performed prior to thecommencement of construction on the basis of the actual construction conditions.
(4) Prior to mass concrete construction, appropriate plans for concrete temperature
control, transportation, placement, curing, etc., shall be made so that the effects of thermal
crack control measures determined in advance can be achieved.

[Commentary] (1)Together with recent developments in advanced construction methods, there havebeen increasing demands for the construction of large-sized concrete structures. It has been frequently
observed that thermal stress, which develops due to temperature variation during cement hydration
process, causes thermal cracking of large-sized concrete structure. These problems were once
considered peculiar to concrete dams or concrete structures with especially large-sized members.
However, harmful cracks are often recognized even in relatively small-sized structures, depending on
cement materials used and construction conditions. Therefore, concrete structures which face
above-mentioned problem of thermal stress due to heat of hydration shall be dealt with as massconcrete and, consequently, special considerations are necessary.
Though it cannot be absolutely determined due to the fluctuation of the type of structure,materials used and construction conditions, the size of the member regarded as mass concrete isroughly considered to be not less than 80-100cm in thickness for wide slabs, or to be not less than
50cm for walls restrained at the lower end. For concrete with rich mix proportion as in the case ofprestressed concrete structures, thin members may also be included in the scope of this chapter,depending on the restraining conditions. Dam concrete is not stipulated in this chapter but in theStandard Specifications: Dam Concrete.
(2) The crack controlling measures, such as crack prevention or restriction of crack position andwidth, should be taken at each stage of design, selection of materials, determination of mix
proportions and construction. The method for evaluating the effectiveness of each crack controllingcountermeasure, by quantitatively estimating the influence of these measures on the development ofthermal crack at various stages, has been almost established from recent researches The verification
for thermal crack in the construction of mass concrete should be carried out in advance by following
Chapter 4, which stipulates the verification methods for thermal stress and thermal crack caused by
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heat of hydration. In mass concrete, where large amount of concrete is used continuously, in order tosatisfy the desired concrete quality, it is especially important that all processes of production, supply,transportation and compaction of concrete are controlled completely based on the construction plans.
During the construction of mass concrete structures, concrete may be delivered form several
ready-mixed concrete plants. As a general rule, cement and chemical admixture produced by thesame manufacturer, coarse and fine aggregates produced from the same region should be used whenpossible. When materials differ for each ready mixed-concrete plant, the trial mixing should be
carried out in advance in order to confirm the safeness of mixing before construction. When usingchemical admixture, great attention is required because incompatibility between chemical admixtures
may be observed.
(3) Chapter 12 of the Design section of this Specification requires as a general rule thatverification be performed concerning initial cracking. The same chapter also requires that a limit forcrack width be set if cracking is to be prevented or permitted. Although the Design section assumes
construction conditions for the purposes of design studies, actual construction conditions such as
weather conditions (e.g., air temperature, wind) may change considerably. Prior to thecommencement of construction, therefore, it must be checked whether the pre-assumed conditions
agree with the actual construction conditions. If the pre-assumed conditions have turned out to differ
from the actual construction conditions and the study results based on the Design section need to bemodified, studies must be conducted again before starting construction by the method specified in the
Design section of this Specification on the basis of the actual construction conditions.
(4) In controlling thermal cracking during mass concrete construction, various measures forpreventing cracking, controlling the position, interval and width of cracks shall be carried out atconstruction stage in order to satisfy the required function and performance of the structure.
In order to control thermal cracking, not only the selection of cement type, materials, admixtures,mix proportions as well as the adjustment of concrete placing temperature, but also the selection of
formwork dimension, lift height, joint position, placing time interval, material and fabrication of
formwork as well as curing method should be considered thoroughly from production to construction
stages. Depending on the structure type, controlling the crack position by crack-inducing joints may
be effective in some cases. Regarding these measures in making concrete and construction forcontrolling and preventing cracking, construction of mass concrete should, in general, be carried out
in accordance with Standard Specification: Design in which the requirements on material, mix
proportion, production and construction method are described in details based on prior examination
related to thermal cracking.
Other methods for controlling or preventing thermal cracking such as using pipe cooling for dam
concrete or large bridge pier, using expansive concrete or arranging reinforcing bars for crack control
can be adopted. However, since these methods lead to cost rise, their technical and economical
efficiencies should be valuated.

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14.2 Materials(1) As a general rule, cement and admixtures used in mass concrete should be ones
specified in the design.
(2) If cement or admixtures mentioned in Item (1) are to be used, verification concerningthermal stress and thermal cracking due to heat generated by the hydration of cement shallbe performed.

[Commentary] As a general rule, cement and admixtures used in mass concrete must be selected
after verification concerning thermal stress and thermal cracking due to heat generated by thehydration of cement.
This Specification requires that cement be selected on the basis of verification concerning thermal
stress and thermal cracking. Since, however, actual construction conditions cannot always be
predicted at the design stage, there may be cases where prior to the commencement of construction,
cement and other materials are reconsidered and selected again through similar verification.
In the case of mass concrete, the quality of cement greatly affects the strength of concrete, heatgenerated by hydration, etc. When selecting cement to be used in mass concrete, therefore, it isnecessary to thoroughly study the characteristics of different types of cement and select cement
appropriately so that concrete of the required quality can be obtained. In general, it is desirable that
low-heat cement such as moderate-heat portland cement, low-heat portland cement, blast furnace slag
cement and fly ash cement be used. When selecting cement, it should be kept in mind that thegeneration of heat by blast furnace slag cement tends to be accelerated as temperature rises.
In cases where blended cement made by mixing portland cement with relatively large quantities
of admixtures such as ground granulated blast-furnace slag and fly ash is used, the quality andproperties of such blended cement often vary considerably among manufacturers. When using suchcement, therefore, it is necessary to fully identify its quality and properties in advance by, for example,
conducting tests. In general, in the case of cement whose heat generation is suppressed, the degree of
long-term strength increase is relatively high, compared with normal portland cement. When using
such cement, therefore, it is good practice to check the stresses that occur in the member during theperiod until the specified strength is reached and use a relatively old age (around 91 days) as areference age at which the specified strength is determined.
Admixtures commonly used for mass concrete include mineral admixtures such as fly ash andground granulated blast-furnace slag and chemical admixtures such as air-entraining agents,
water-reducing agents, air-entraining water-reducing agents and air-entraining high-range
water-reducing agents. The use of expansive admixtures has been increased in recent projects. The
use of high-quality fly ash brings about a number of beneficial effects such as improving theworkability of concrete, reducing the water content, increasing old-age strength development andreducing temperature rise due to the heat of hydration of concrete. Fly ash, therefore, is advantageous
for the purpose of controlling the occurrence of cracking due to thermal stress. Furthermore,
appropriate use of fine-grained blast-furnace slag powder makes it possible not only to increase thelong-term strength of concrete but also to slow down the generation of heat due to hydration.
Appropriate use of air-entraining agents, water-reducing agents, air-entraining water-reducing
agents or air-entraining high-range water-reducing agents makes it possible to improve theworkability of concrete, reduce the water content and thereby reduce the cement content. By using
these chemical admixtures, the amount of rise in concrete temperature can be reduced.
194Chapter 14 Mass Concrete

If a large volume of mass concrete is to be placed, it is recommended that retarder typewater-reducing agents or air-entraining water-reducing agents be used to lower the rate of generationof the heat of hydration and prevent the occurrence of cold joints. In such cases, however, setting may
be retarded considerably depending on such factors as the combination with mineral admixtures to be
used and air temperature during construction. It is therefore important to check in advance on the
degree of retardation of concrete setting and the influence on strength development characteristics bymeans of tests, etc.

14.3 Mix Proportions(1) As a basic rule, the cement content of mass concrete should be as specified at thedesign stage.
(2) If it is not possible to achieve the required workability, strength, durability,
watertightness, cracking resistance or steel protection performance with the cement
content specified at the design stage or if the type of cement or admixture to be used has
been changed, verification concerning thermal stress and thermal cracking shall be
conducted again, and the cement content determined accordingly.

[Commentary] The rate of heat generation of concrete is roughly proportional to the cement content,
and, in general, concrete temperature increases or decreases by about 1°C for every 10 kg/m3 ofincrease in the cement content. A substantial increase in the cement content determined as a result of
verification concerning thermal stress and thermal cracking must be avoided. If, however, it isdifficult to achieve the required workability, strength, durability, watertightness, cracking resistanceor steel protection performance with the cement content specified at the design stage, it may benecessary to reconsider the cement content. If the type of cement or admixture to be used is changed,
it is necessary to perform verification concerning thermal stress and thermal cracking again anddetermine a cement content (or a binder content if non-cement binder is used) that does not cause any
problem associated with thermal cracking.

14.4 Production
Mass concrete shall be produced, taking into consideration such factors as concrete
transportation distance, transportation methods, placing methods, weather conditions andother conditions, so that the placing temperature does not exceed a specified limit.

[Commentary] Lowering the concrete placing temperature is effective in thermal stress and thermal
cracking because doing so reduces the difference between the temperature in the member and thetemperature outside the member and lowers the highest temperature in the member. One method oflowering the placing temperature is precooling, in which ingredients such as water and aggregate arecooled in advance when concrete is produced. The effect of the temperature of each material on the
as-mixed temperature of concrete is as follows: a change of ±2°C in aggregate temperature resulting
in a change of ±1°C in as-mixed temperature, a change of ±4°C in water temperature resulting in achange of ±1°C, and a change of ±8°C in cement temperature resulting in a change of ±1°C.
Precooling methods include a method that uses cold water, a method that uses flake ice or small ice
fragments independently or in combination as part of mixing water, a method that uses cooled
aggregate and a method that cools materials or concrete by using liquid nitrogen. If small ice
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fragments are used as part of mixing water, it must be ascertained before the placement of concretethat the ice has completely melted. If liquid nitrogen is used for cooling, care needs to be taken to
ensure safety, particularly in the control of the concentration of oxygen at and around the place whereliquid nitrogen is used.
Even if the temperature of concrete at the time of production is lowered, concrete temperature may
rise during transportation so that the placing temperature becomes higher than expected at theplanning stage. It is important, therefore, to determine the temperature of concrete at the time of
production, taking into account likely amount of rise in concrete temperature due to such factors astransportation distance, transportation methods and weather conditions.

14.5 Construction
14.5.1 Partitioning into blocks, lift height and joints
In placing mass concrete, size of blocks, height of lift, the location and structure ofjoints, and interval between successive castings, should be decided based on the results ofthermal verification.

[Commentary] In mass concrete, large volume of concrete is placed in many blocks which areseparated by joins. The location and structural details of joints as well as the size of blocks(dimensions of horizontal and vertical partitioning) need to be determined with comprehensive
consideration of heat dissipation and restraining conditions, as well as various construction
conditions, one of which is concrete placing capacity each time. When mass concrete is placed into
blocks partitioned vertically or into lifts divided horizontally, stresses will develop with the variationof temperature in concrete structure because the newly-placed concrete is restrained by thepreviously-placed one.
These stresses grow larger when the differences in the effective Young's modulus as well as in thetemperature between new and old concretes increase. Therefore, concrete placing time interval
should be kept as short as possible. However, where concrete is placed lift by lift on such bodies asrock beds which provide significant restraint, too short placing intervals may result in hightemperature in mass concrete and, consequently, high potential of crack development. As a result, theplacing interval at the construction site shall be determined with due consideration, together withother measures, to deal with the development of thermal stress.

14.5.2 Placing
The placing temperature of mass concrete shall not exceed the planned temperature.
During placing process, the temperature of concrete shall be measured, The thermal historyof placed concrete shall be monitored, and the plan for construction may be changed
accordingly, if necessary.

[Commentary] The verification method for placing temperature of mass concrete is included in the“verification for thermal crack”. One must keep in mind that the assumed conditions at design stageof thermal characteristic of materials and environmental conditions may differ from those atconstruction stage. When actual placing temperature exceeds the assumed placing temperature ofmass concrete, the prevention of thermal cracking as well as the control of crack width may become
difficult. As a result, the desired function and performance may not be satisfied. Therefore, concrete
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Chapter 14 Mass Concretetemperature and temperature rise of placed concrete should be confirmed at the time of construction.
The construction plan should be modified if the actual condition is too much different from theassumed one. Especially, when placing concrete under the scorching sun, special cares on the
management of materials, concrete production, transportation, placing, etc. shall be applied to makesure that the actual placing temperature will not exceed the planned one. Since the exothermic
properties of portland blast furnace slag cement is accelerated if temperature is high, the placing
temperature should be as low as possible in order to control the temperature rise.

14.5.3 Curing
In curing mass concrete, appropriate care shall be taken to control concretetemperature, so that thermal cracks can be controlled as per plan.

[Commentary] In the curing of mass concrete, adequate measures for thermal crack control basedon the results of the verification and curing methods specified in the construction plans need to betaken additionally with the conditions required for the curing of normal concrete. Specifically, it isnecessary to apply appropriate measures to cool down the concrete temperature as close to theambient air temperature as possible, to keep the temperature difference between the interior andexterior of the concrete member as low as possible and to maintain the temperature drop rate of thewhole member at acceptable level . If necessary, such measures as thermal insulation and protectionof the concrete surface with adiabatic materials (styrol or sheet) should be implemented. The sprinkleof more water that necessary may lead to the formation of cracking by the decrease in the surface
temperature of conceret..
The pipe cooling is used in order to reduce maximum internal temperature of young concrete andoverall temperature of members to average temperature of concrete structure. Pipe cooling is carriedout by pumping chilled water or natural river water through the pipes previously placed in concrete.
In pipe cooling practice, thin-walled steel pipes of external diameter of approximately 25mm areusually used. Factors such as the space between pipes, water flow, and length of a coil as well as
cooling-off duration should be determined to obtain the required effect. The temperature of coolingwater also should be determined by considering placing time intervals, construction period, thicknessof members, etc. If the temperature of cooling water is too low, temperature difference within amember or between members may cause crack initiation. Therefore, sufficient caution needs to betaken. Temperature difference between the circumference of cooling pipe and cooling water should
be maintained less than 20°C. In pipe cooling practice, air can be used in stead of water.
Mass concrete using moderate-heat portland cement, low-heat portland cement and blast furnace
slag cement requires sufficient curing with thermal insulation to obtain sufficient strength.

14.5.4 Formwork
The material and structure of formwork for mass concrete, and the timing of formwork
removal shall be appropriately decided so that the thermal cracking can be effectively
controlled.

[Commentary] Concerning formworks for mass concrete, the material and structural details arerecommended to be selected with consideration to the control of concrete temperature for the purposeof thermal crack control.
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To minimize the temperature rise, formworks which have high heat dissipation may be used.
However, in the case of mass concrete, control range of temperature rise is restricted and ambient
temperature may drop drastically after placing, the use of exoteric metal formwork may cause large
temperature differences between internal part of concrete and its surface. Therefore, sometimes theuse of insulated formworks is effective. When insulated formworks are used, the retaining duration is
prolonged, in principle, compared with the conventional formworks, and the thermal insulation of theconcrete surface is recommended to be continued after formwork removal by such measures ascovering the concrete with plastic sheets so as to protect the concrete surface from rapid cooling.

14.5.5 Crack-inducing joints
In cases when crack-inducing joints are provided to control the position of thermal
cracks, the structural details and positions of these joints shall be determined as specified
in the design documents.

[Commentary] In general, it is difficult to control the thermal cracking occurring in massive
wall-type structures by taking measures from material or mix design aspect. In such cases, there ismethod in which reduced sections are provided at a certain spacing intervals on the longitudinal
direction of the structure, to induce cracking at these sections, to prevent cracking at other portions,and to easily take care of the cracked sections. Details should be in accordance with Section 9.9 andthe Design section 14.8 Crack-inducing joints.

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CHAPTER 15 QUALITY CONTROL

15.1 General(1) For the execution of concreting work, quality control shall be performed
appropriately in all aspects of the work including concrete materials, reinforcing materials,
equipment, concrete production methods, construction methods and the concrete
structure until completion in order to construct a concrete structure with the required
quality economically.
(2) Quality control is a series of voluntary activities of the Contractor, and theContractor shall develop plans for methods that the Contractor can expect to be effective
and carry them out appropriately.
(3) Records of quality control shall be kept for a certain period of time even after thedelivery of the constructed structure so that they can be used for the quality assurance ofthe constructed structure and quality control for future construction work.

[Commentary] (1) Progress control, quality control, cost control and safety control are important in
concreting work. Of these, quality control is a series of effective and organized activities performed at
all stages of construction work in order to economically construct a concrete structure that matches its
purpose of use. Quality control needs to be performed appropriately in all aspects of the work
including concrete materials, reinforcing materials, equipment, concrete production methods,
construction methods and the concrete structure until completion. Quality control in production andconstruction may be referred to as production control and construction control, respectively.
(2) A concrete structure can be made to rationally meet the owner's requirements if constructedunder appropriate quality control. Because the owner receives a structure that has been constructedunder the quality control of the Contractor and has passed inspection, inspection may be simplified by
performing appropriate quality control.
Quality control should be performed so that the quality should be stayed in a stable condition.
Warning in all stage of construction work should be found as soon as possible and make an action for
it. It is important to establish the system contains PDCA cycle (Plan-Do-Check-Action). Whendrawing up a quality control plan, it is important to identify a person responsible for each process andconstruct an organizational system for quickly responding to an abnormality.
Since quality control is a series of voluntary activities performed by the Contractor, theContractor can perform only activities that the Contractor deems necessary. If the Contractor's
inspection covers all items and frequency of the inspection conducted by the owner, themeasurements conducted by the Contractor are deemed to be equivalent to the measurements
conducted by the owner. It is possible, therefore, to make passing the owner's inspection easier bychecking, in advance, the design drawings and specifications and inspection criteria (inspection plan)
shown by the owner and reflect them in the quality control plan. Hence, if tests are conducted as partof the quality control activities associated with production and construction, it is good practice to use
methods that permit objective evaluation and that are easy to understand to the owner and methods
specified for inspection purposes. For general tests, refer to the test methods specified in JIS, JSCE orother standards. It is difficult, however, to make a comprehensive judgment solely on the basis ofquantifiable data such as measurement results obtained by means of tests and inspection devices
specified in JIS or other standards. It is also important, therefore, to deploy experienced specialists
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and make judgments based on visual inspections.
(3) Quality control records are documents certifying that the required quality has been achieved,
and are also invaluable data that can be used to improve quality and prevent problems in future
projects. The Contractor, therefore, needs to store records for a certain period of time. For further
information on record keeping, refer to Chapter 17.

15.2 Quality Control of Concrete Materials and Reinforcing Materials
In the quality control of concrete materials and reinforcing materials, materials shall be
managed so that they meet their respective quality requirements and stay in a stablecondition as much as possible.

[Commentary] In order to construct a concrete structure of the required quality economically, it isrequired, needless to say, that the quality of concrete materials, namely, cement, water, aggregate andadmixtures, and reinforcing materials meet the specified requirements. In addition, it is desirable thatvariations in the quality of those materials be small. The state of storage of concrete materials andreinforcing materials should be controlled appropriately so that their quality does not change. The
state of control should also be checked periodically.
Although the quality of admixture such as superplasticizer and quick setting admixture or
reinforcing materials, which is used at construction site, depends on the conditions of construction
site, the quality control at construction site is important. For the quality of aggregate, when theContractor produces concrete, the Contractor shall tests related to the quality control of aggregate,
and shall keep the storage conditions. Grading of aggregate and percentage of surface moisture may
be used as an index in quality control of aggregate, for instance.

15.3 Quality Control in Concrete Production
In the quality control in the production of concrete, concrete production equipment andproduction processes shall be controlled appropriately so that concrete of the required
quality can be produced stably and smoothly.

[Commentary] In the production of concrete, the storage facilities, measuring equipment andmixers must be stored appropriately during the production period so that the requirements specified in
Section 5.2 are met. In order to continue to produce concrete of stable quality, it is good practice tomeasure the surface moisture content of aggregate with moisture meters on a continual basis and, if aconsiderable change or any abnormality in the property of concrete has been observed, take aggregate
samples and compare surface moisture contents. Because it is necessary to ascertain thatmeasurement errors are small enough to stay within an allowable range, if an automatic batchingrecorder (recorder–printer) is available, records from the recorder should be used to check whether
measured values are stable. In mixing control, changes in the quality of concrete can be identified byobserving the state of mixing of concrete on the monitor screen and checking the mixer load current.
The success or failure of quality control can be evaluated by checking, for example, theoperation and cleaning status of production equipment, equipment deterioration and damage, and theproperties of concrete during and after mixing. In many cases, evaluation can be made by visualobservation or by listening to the sound of machines in operation.
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Test results such as compressive strength, slump and air content of concrete can be recognizedby quality chart. Obtained data is plotted in the chart with mean value, upper and lower control lines
for quality control. The range of the control line should be defined appropriately. When the result outof the range is observed, it should be investigated whether the reason of the change causes the changeof quality permanently, and a provision for it should be conducted. The control limit line shall bechanged based on the quality control data during the construction period. A histogram is useful torepresent the distribution of quality, and ratio of passed/false and margin for quality can be assessedby the histogram with criteria. The shape of histogram indicates warning in construction process(quality of the used materials, production of concrete and testing).

15.4 Quality Control of Concrete
The quality of fresh concrete and hardened concrete shall be controlled so that
concrete of stable quality can be obtained.

[Commentary] The quality of concrete in a structure is greatly affected by the quality of the concreteused. When controlling the quality of concrete, therefore, it is important to accumulate quality control
data and analyze data on a daily basis so that the relationship of the quality of concrete with the
production of concrete materials and concrete can be quantified. The quality control should be
conducted at appropriate period and frequency, refer to inspection standard Chapter 5 in thisspecification.
(a)Confirmation of mix proportions The mix proportions indicated in the mix plan do notnecessarily agree with the mix proportions of the concrete actually produced. It is recommended,
therefore, that production-related records such as the printed records be checked for comparison withthe actual mix proportions.
(b)Quality control of fresh concrete If concrete is not homogeneous and does not haveworkability suitable for the types of work to be done such as transportation, placement andcompaction, poor placeability or defects might result. The workability of fresh concrete can be judged
to some extent by observing the state of concrete during unloading and placement even if tests are notconducted frequently. If quality fluctuates considerably, tests should be conducted on an as-neededbasis to identify the causes of problems and take early corrective measures. It is also desirable that thefrequency of quality control checks be increased until quality becomes stable.
i) Slump: Slump test is conducted to ensure the workability of concrete as well as homogeneityof concrete. It is necessary to check the production of concrete with given materials, the particle size
distribution of aggregates, surface moisture content of aggregate and so on when the change of slump
is acknowledged. Slump cone test can also provide an indicator of the quality of fresh concrete. Sinceslump will change wit time after the finish of mixing it is necessary to take into account the differencein time in which slump test and actual placement of fresh concrete are conducted.
ii) Air content: Change in air content results in the change of workability, strength and durability.
In order to ensure air content in fresh concrete air content test is conducted. Since change in the aircontent results in the change in the slump the cause should be clarified and in case to takecountermeasures surface moisture and particle size distribution of aggregates, temperature of fresh
concrete and change in the air content are taken into account.
iii) Temperature of concrete: Temperature of concrete have influences on slump, air content,
thermal temperature due to hydration, development of strength and properties of the hardened
concrete. Therefore it is an important item for the quality control for the construction of mass
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concrete, cold weather concrete and hot weather concrete. Besides it is necessary to check thetemperature of concrete during the curing.
(c)Quality control of hardened concrete Because the time required to get results of concrete
strength tests conducted to test the quality of hardened concrete is long, those tests are usually notsuitable for use in quality control. It is more rational, therefore, to spend effort in the quality control ofmaterials and production. When rarely produced concrete is used or during a certain period of timeafter production is started or during a period when air temperature changes considerably, it is goodpractice to check on changes in compressive strength.

15.5 Quality Control during Construction
In the quality control during construction, it should be checked whether each type of
construction work in progress such as the work related to concrete, reinforcement, andformwork and falsework agrees with the plan, and, if necessary, the methods being usedshould be changed to more effective methods so that concreting work can be carried out
smoothly.

[Commentary] At the construction stage, it is important to check whether each type of construction
work in progress such as the work related to concrete, reinforcement, and formwork and falseworkagrees with the plan so as to carry out concreting work smoothly, attain the required quality andcomplete the work by the planned date. It is often not possible to proceed with the work as planned
because of, for example, the changing quality of concrete, changing environmental conditions,differences in the experience of workers and differences in the performance of equipment. It is
desirable that the Contractor carefully observe the state of construction work and, if improvement
needs to be made, give the workers appropriate instructions as to specific methods to be used forfurther improvement of the methods used.
(a) Quality control in preparation Since weather during construction is always in a state ofchange, it is important to check on weather forecasts in advance and make preparation such as
rescheduling the work to be done on the day or during the coming week or taking rain protection
measures. Adequate preparation for each type of work minimizes problems encountered during
construction.
(b) Quality control in concreting work If the methods used for transportation, placement,
compaction, finishing and curing are not appropriate, it is difficult to construct a concrete structure of
the required quality. It is important, therefore, to fully understand the points to remember described in
Chapters 7, 8, 9, 12, 13 and 14 and check whether the methods described there are appropriate on thebasis of the construction plan and the quality control plan. In the quality control for each type of work,
the basic rule is to control the facilities and equipment used, staffing and construction methods. Prior
to the placement of concrete, it must be carefully ascertained that the reinforcement and formwork
and falsework have been placed and constructed as planned.
i) Transportation to the site: Transportation time of agitator truck should be checked to keep the
given time until the finish of the placement of concrete so that placing concrete can be continued. The
number of agitator truck based on the amount of placing concrete and its placing rate should bedetermined and transportation plan for these agitator trucks should be prepared before the actual
construction. Schedules of managing transportation should be prepared in which planed and actual
time for shipping, arrival, finishing of discharge and tests, estimated time interval, the numbering of
agitator trucks, the amount of loading and accumulation, either quality control or inspection of
acceptance are indicated. In addition it is a good practice to make close contact with a person in202

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charge of quality control at the factories and at the placing site. These practices make it easy inplacing concrete continuously.
ii) Transportation within the site: It is necessary to manage types of transportation equipments
needed, its form and capacity, arrangement of personnel and method of transportation according to
the prepared plan within the site. Concrete pump is usually used for the transportation within the siteand concrete pumping works will be left the management to the specialist. However it is importantthat person in charge of quality control should advice properly the method of pumping by considering
quality of concrete, transportation using agitator trucks, compaction, pressure to the formwork.
iii) Placement and compaction: In placing and compacting concrete the order of the placement,
the placement rate and its height, interval of layered concrete, the position of joints, the height ofcompacting and method of compaction are needed to be checked. Proper countermeasures should betaken when actual workability is reduced though periods of time for the placement is within theallowable time. It is necessary to point out compaction time and its interval since the effectiveness ofcompacting with vibration may be different by the conditions of concrete and reinforcement
arrangement.
iv) Finishing: In finishing concrete the number of finishing actions, the period and the methodsof the finishing are managed if they follow to the initial planning. The appropriate period of thefinishing may be varied depending on the weather conditions and the ability of workers. When thefinishing time of placing concrete is delayed the finishing actions may be carried out during night.
Subsidence cracks and separation occur by finishing with bleeding water. It is necessary to manage
the schedule of the completion of finishing and its methods.
v) Curing: Equipments, workers arrangement and methods need to be checked if they follow to
the initial planning. For wet curing a person in charge of quality control must understand theprocedures of the curing to avoid improper curing. Inadequate wet curing may result from improper
curing with sprinkling water, sheet and mat at locations of the projection of reinforcements. With
inadequate wet curing the quality of concrete is reduced as compared with that of water-cured
concretes. For strength and durability of structure the quality control of curing is important.
(c) Steel works: Followings are important notices for steel works. They also can be applied tothe quality control for other types of reinforcement.
i) Drawing of bar arrangement: Types, diameter and length of steel, cover and space, bending
shape and the position of anchor and joint are checked if they follow to the drawing. It is necessary tocheck if supportive and temporal bars are needed, there are positions at which bar is not arranged inaccordance with the drawing and there are mistakes in the drawingii) Planning: A standard procedure for the planning of bar and personnel (for considering ability)
arrangement, storage site within construction site and selection of equipments for bending bars is
prepared. By considering load on the spacer necessary spaces of bar arrangement need to be secured.
iii) Acceptance and storage: Types, diameter, length and the number of bars needed arerecognized. It is checked if the length is enough for the transportation and the no-use during
processing is reduced. By ensuring if transported steels are ordered ones at acceptance the they arestorage so as to prevent corrosion and dirt.
iv) Processing: Drawing of processing, the content of standard procedure and the specificationof a slice processing machine (same as the radius of bending bar) are ensured. Types and the numbersof bars after the processing and the accuracy in the processing are needed to be checked and thecontrolling within own target values reduces the risk of failure in inspecti,
203

Standard Specifications for Concrete Structures-2007, Materials and Constructionv) Fabrication: Spacer, band wires, space of formwork, given position and the interval of center,
effective depth, cover, anchor length, position of bending, position, length and methods of joint, end
treatment for compressive steel and weathering are checked. These checks must be completed before
the placement of concrete. Allowable error in the target of control which is determined based on thetypes and importance of structures is set up with own values more severe than those employed at
inspection so that the risk for failure in inspection is reduced. Re-fabrication of steel requires a great
deal of labor and hence it is advisable to ensure each steps in fabrication to avoid mistakes. Whentime is elapsed after fabrication corrosion, contacting mud and oil and the displacement of bar
arrangement take place. It is advisable to clean steel and ensure the accuracy of fabrication before theplacement of concrete.
(d) Formwork and shoring: Followings are important notices for formwork and shoring.
i) Calculation and control: Sufficient strength and safety against expected load are required forformwork and shoring. A person in charge of quality control ensures the results of calculation of
formwork and shoring. Attention is paid for the expectation of load since lateral pressure and externalload that is beyond initial expectation may occur. By considering the minimum slump at theplacement of concrete and the change of slump with time target slump is determined at the dischargeof fresh concrete in this specification. Increase in the lateral pressure due to larger slump than theminimum slump specified must be taken into account. It is safe to consider the change in the rate ofplacing and temperature of concrete.
ii) Drawing and construction; Construction is ensured if it follows to the drawing and procedures.
Construction accuracy for formwork and shoring is determined so as to obtain a given position, shapeand size of structure. It is noticed that the accumulated error associated with each works must be still
within the allowable error. Before re-use of formwork and shoring it is checked if the degradation is
not influential to concrete and separation agents are removed. When these care are not properly taken
into account surface concrete contacted with the formwork is affected. Corrosion of steel bars used asa fasten material and improper welding wires may result in the failure of formwork. These must be
paid attention not to occur.
iii) Control in use: During placing concrete the leakage of pastes and mortar from the gap,
widening, movement, slant and subsidence of formwork and shoring, softening in joints floating
cylindrical mould need to be checked to prevent accident and take any actions if taking place.
Workers in charge of not only concrete works but also formwork and shoring works are placed during
placing concrete. Communication with a person in charge of quality control for concrete works
should be made to ensure the use of concrete with expected slump, the rate of placement andtemperature which are assumed in calculation for the formwork and shoring.
iv) Removal time: By considering temperature, conditions of structures and the formation ofthermal cracks the formwork and shoring are removed. Strength development is slow in low
temperature and displacement and cracks may occur when bottom plate formworks used in decks are
removed.

15.6 Quality Control of Concrete Structures
Until a concrete structure is taken over by the Owner, the structure shall be kept undercontrol so that a concrete structure of the required quality can be delivered to the owner.

[Commentary] Passing the owner's inspection of a concrete structure can be made easier bychecking, during construction, on the state of concrete surfaces, the positions and dimensions of204Chapter 15 Quality Control

concrete members, the quality of the concrete in the structure, and concrete cover. For example,
cracking might be caused by long-term temperature changes, drying shrinkage or changes in the stateof stress in the course of construction even if there was no visible crack immediately after thecompletion of the structure. A concrete structure may also be affected by environmental factors suchas natural phenomena including typhoons and earthquakes, the deformation of the surrounding
ground, and vibration caused by transportation facilities. It is therefore advisable to periodicallyobserve the concrete structure, the protection works around the structure, etc., to check whether there
is no abnormality during construction and after the completion of the structure until the completion ofdelivery to the owner. If any abnormality has been discovered, quality control personnel need toreport it to the quality control manager or the responsible engineer and take appropriate corrective
measures.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 16 INSPECTION CONDUCTED BY CONTRACTOR

16.1 General(1) The Contractor shall conduct inspections for acceptance of materials andinspections of concrete production facilities at each stage of construction in accordancewith the construction plan and have the inspection results confirmed by the owner.
(2) Standard inspections to be conducted by the Contractor shall be inspections for
acceptance of concrete materials, inspections of concrete production facilities,
inspections for acceptance of concrete and reinforcing materials.
(3) As a general rule, inspection shall be conducted in accordance with predetermined
criteria by using a method based on testing or measurement that permits objective
evaluation. With respect to inspection methods and evaluation criteria, refer to theConstruction: Inspection Standards of this Specification.
(4) No item that has failed to pass an inspection shall be received.

[Commentary] (1) and (2) Main inspections conducted by the Contractor are inspections for
acceptance of materials for concrete production, inspections for acceptance of structural reinforcing
materials and inspections of concrete production facilities. The results of inspections conducted by
the Contractor must be documented and kept in storage and, on an as-needed basis, be reported to andconfirmed by the owner. It is good practice for the Contractor, therefore, to incorporate the plans forinspections to be conducted by the Contractor on its own responsibility into the construction plan.
From the viewpoint of quality control to be performed by the Contractor, the inspections for
acceptance of materials are essential for successful execution of concreting work of the required
quality. Usually, therefore, inspections to be conducted by the Contractor are included in the tasks
specified in the construction plan drawn up with the approval of the owner of the structure.
Even in an inspection conducted by the Contractor, a final decision may be made by the owner ofthe structure depending on the technical level, reliability, etc., of the inspection. It is therefore
necessary to clarify the inspection system in advance through consultation with the owner of thestructure.
(3) An inspection is done by comparing the results of a necessary measurement or test withpredetermined criteria. Tests must be conducted by using a method that permits objective evaluation.
As a general rule, methods specified in the Japanese Industrial Standards, JSCE standards, etc.
(4) Basically, an inspection is conducted to determine whether something is acceptable. As ageneral rule, therefore, an item that has failed to pass an inspection must be rejected.

206

Chapter 17 Construction Records

CHAPTER 17 CONSTRUCTION RECORDS

The constructor shall record the schedule of concreting work, the state of production
and construction, curing methods, weather and atmospheric temperature on the date on
which construction work is performed, quality control and inspection results, etc., during
construction and deliver the construction records thus prepared to the Owner of thestructure.

[Commentary] Construction records provide basic information for the maintenance of the structure.
Construction records, therefore, are also necessary for the progress of technology. Records should
cover the following:a) Records related to the quality of concrete: mix proportions, materials, quality control andinspection results, the name of the ready-mixed concrete plant, etc.
b) Records related to concreting work: quantities of concrete to be placed, methods, date, placing
time, air temperature, humidity, pump type, pumping distance, pipe diameter, pumping company,
personnel and organizational system, curing methods and periods, etc.
c) Material inspection results: results of concrete receiving inspections (e.g., slump, air content,
specimen strength, chloride ion content), results of reinforcing bar receiving inspectionsd) Other information: changes related to the quality of concrete, construction, etc.

207

Inspection Standards

Chapter 1

GeneralCHAPTER 1 GENERAL

1.1

General(1) The Owner shall assume the responsibility for inspecting the completed structure
for acceptance.
(2) These Specifications present the standards for inspections that are conducted ineach phase of concrete work during the construction of a new ordinary civil engineering
structure and at the completion of the structure.
(3) In cases when experiments are carried out, the adapted methods should be thosethat enable an objective evaluation. In principle, methods adapted by JIS or JSCE
Standards should be carried out.
(4) In cases inspection results indicate that the required performance criteria are notsatisfied, appropriate countermeasures shall be taken.

[Commentary] (1) and (2) Inspections are conducted by the Owner of the project to determine
whether the produced and constructed concrete, member and structure meet the designatedperformance requirements or not and whether the completed structure is acceptable or not. Various
inspections are required in each phase of concrete production and structural construction. It is noteffective or practical for the Owner to perform all the inspection work. It is stipulated that the
Owner should assume the responsibility for conducting inspections to explicitly define theresponsibility of the Owner of the structure. In some cases, the Owner carries out actual inspection
work including measurements and testing in each phase. In other cases, the Contractor carries out
measurements and testing and transfers the responsibility for inspections to the Owner by having
the Owner verify inspection results. For the inspections conducted by the Contractor, refer to"Materials and Construction: Construction Standards".
If the ultimate goal of constructing a structure is to ensure the achievement of its performancerequirements, it is ideal to inspect the performance of the completed structure firsthand. At present,
however, only limited items can be inspected in a completed structure such as the surface conditionof concrete and the locations and dimensions of members. Whether the performance requirementsof the structure are met or not should therefore be verified by preparing an effective, economicaland systematic inspection plan, consulting the design drawings and construction plans, andconducting appropriate inspections in each phase of construction in accordance with the plans. Mostof the inspection standards described in this chapter are intended for application to ordinary work
and incorporation into contract documents.
(3) Since the method of inspection varies depending on the type of the structure, materials,
construction methods, etc., the inspection items, test methods and frequencies should be examinedand planned beforehand. Objective testing methods and decision criteria should be used forinspections. To that end, tests shall be conducted using the methods that are in compliance with theJapan Industrial Standards or the standards of the Japan Society for Civil Engineers. The methods
for inspections should generally be specified in contract documents.
The reliability of the inspection, which comprises visual observation and testing, as well as cost
and time required, should also be examined beforehand. In the case of inspection of reinforcing bar
arrangement for instance, it is currently more reasonable in terms of cost and reliability to give209

Standard Specifications for Concrete Structures-2007, Materials and Construction

observation before concrete placing than to conduct nondestructive inspection after the constructionof the structure, though technically feasible. Judgment criteria also significantly depend on theaccuracy and reliability of testing. Since any current inspection method can be not infallible, it is
not reasonable for the cost of inspection to select the nearly infallible inspection method.
(4) Inspection is basically carried out to judge whether or not the product is acceptable. It
follows that, if the product is judged unacceptable, it should as a rule be rejected. However, incontrast to the case of mass-produced goods, rejection is not the best solution in most cases inconsideration of the complicated processes, long construction period and social effects of delayedcompletion. It is more realistic to ensure the specified performance of the structure by taking
appropriate remedial measures. A wide variety of remedial measures may be possible. Whereas
corrective work in an intermediate stage may be sufficient in some cases, correction orstrengthening in the final stage may be required in other cases. When any of these measures cannot
ensure the specified performance, demolition and reconstruction are inevitable.

1.2

Definitions of Terms
The following definitions of terms are used in these Inspection Standards.

Inspection: Act of determining whether the quality meets the decision criteria or not.
Quality control: Effective and systematic technical activities performed in all construction
phases for ensuring quality in order to construct concrete structures economically that
achieve the requirements for their intended use.

[Commentary] Inspection As described in Section 1.2 of "Materials and Construction:
Construction Standards", the items to be inspected include the qualities of materials, concrete,construction and completed structure. The qualities of materials and products are generally
inspected by the purchaser and the Owner of the structure verifies the inspection results in writing.
Inspections of construction work and the completed structure are generally conducted by the Ownerof the structure.
Quality control Quality is controlled during the production of materials, during construction andfor a structure or members. Quality control is voluntarily executed to construct the structure that iscomplied with the requested quality by the Contractor of construction work. The Contractor shallapply the needed quality control on their own judgments and shall execute the economical andreasonable quality control.

210

Chapter 2 Inspection Plan

CHAPTER 2 INSPECTION PLAN

(1) Inspection plans shall be prepared in accordance with the design drawings andthe specifications to specify the selected inspection items, testing and inspection
methods, timing and frequency of testing and inspections, decision criteria in testingand inspections, required human resources to be assigned and other matters.
(2) Inspection shall be planned in consideration of the importance of the structure,
type and scale of construction, construction period, reliability of the materials andconstruction methods, experience of the engineers, time of construction, effects on
subsequent processes, efficiency, etc.
(3) The plan for inspection shall be established for all stages including concrete
production and completed concrete structure. In the case of standard construction,
inspections shown in Table 2.1 should be applied.

Production

Concrete materials
Manufacturing
facilities and process
Transportation to theconstruction site

Ready-mixed concrete

Construction

Reinforcement

CH7 7.3

CH7 7.4

CH8 8.2

CH8 8.3

CH8 8.4

○
○

○
○

（△）
○

Transportation within
site

○

○

（△）

Placement(or casting)

○

○

（△）

Compaction

○

○

（△）

○

Surface finish

211

cover

CH7 7.2of concrete
members
concrete
properties instructure

CH6

Inspection of structures
Surface texture
position, shape anddimensionof concrete
members
position, shape anddimension

CH5

formwork andshoringCH4

reinforcement

CH3

Inspection during execution

concreting

Inspection

Inspection of concreteat time of delivery at
site

Items forInspection of concreteat time of delivery at
site

Reference

Inspection of production

Inspection requirement systems for insurance of structural performance
Inspection of constituent
materials of concrete (foracceptance)

Table 2.1

CH8 8.5

construction

Standard Specifications for Concrete Structures-2007, Materials and Construction
Curing○Joints○Reinforcement

（△）
○
○

Formwork
and shoring

（○）
○

○

（○）

Explanatory notes○ : possible (able to verify)(○) : possible as required(△) : possible as required (able to inspect the limited part of performance)(4) The inspection plan should be flexible enough to cope with normal anticipatedvariations. However, in cases when the changes are beyond the anticipation, theinspection plan should be appropriately modified.

[Commentary] (1) and (2) The ultimate objective of inspections is to verify that the structure isdesigned in accordance with the design drawings so as to achieve the designated performancerequirements. Though formulating an inspection plan is essentially an action to determine the items
presented in Clause (1), the inspection systems to achieve the goal are not single but numerous.
When determining the inspection system, the items given in Clause (2) should be considered.
The standard inspection presented in Section 3 and subsequent sections may be reasonably
applied to common construction on a small scale. In the case of a large-scale and/or long-term
project, or project involving special materials and/or methods, however, formulation of its own
inspection system could be more reasonable.
Inspection is an act of ensuring the reliability of the structure. Varying the inspection method
according to the reliability of the construction method is important. For the methods that are likely
to involve human errors, the frequency of inspections should be increased. For the methods
involving few errors in the process of construction, the frequency of inspections may be reduced. It
may be reasonable for instance, even in a newly introduced method, to carry out inspection at shortintervals in the beginning and progressively reduce the frequency of inspection when the sameprocess is repeated, though such practice may be incompatible with the current system of agreement.
When a new method is adopted for multiple projects, it may be reasonable to formulate a strict
inspection system in the first project to which the method is introduced for the first time and reduce
the frequency of inspection as the field experience accumulates. It is also worthwhile to consider
simplifying the inspection for those who have received ISO 9000 series or other certifications or
those who have remarkable track records. For instance, the inspection frequencies for ready-mixed
concrete producers could be reduced for not only JIS accredited producers but also recipients of thecompliance certificate by the National Quality Control Committee of the Ready-mixed Concrete
Producers; and the inspection frequencies could also be reduced for pressure welders having an“excellence” certificate by the Japan Pressure welding Society in the recommendation system forexcellent pressure welders.
It is also worthwhile to consider changing the inspection method according to the importanceof the structure or members. For instance, the current JIS A 5308 “Ready-mixed Concrete” requires
the same acceptance tests for both concrete for prestressed concrete elements and concrete forleveling concrete, but the former should normally be subjected to a closer inspection than the latter,212

Chapter 2 Inspection Plan

while the inspection for the latter may be simplified compared with that for structural members.
From the viewpoint of the reliability of materials, inspection methods are sometimes
employed that take the state of quality management in the production phase into consideration. For
instance, whereas ready-mixed concrete is basically inspected by testing, inspection of reinforcing
bar consists only of control of the mill sheet, as it is produced with little scatter of qualities and thequalities scarcely change after production.
In cases where quality management is considered inadequate in the field, conducting
inspection without notification is worth considering in order to increase inspection efficiency.
Inspection without notification, if conducted properly, may serve as an incentive for quality
improvement.
It should be noted that introduction or improvement of an inspection method can produce a
decisive effect on the inspection system. The restrictions of the chloride content in sea sand, forinstance, used to be ineffective without a suitable inspection method when they were established but
later became very effective after the development of a practical method of measuring chloride
content in concrete. This indicates the importance of the improvement in the inspection equipment,
the hardware. When a new inspection technology is developed, the inspection system should be
actively reviewed.
(3) As shown in Table 2.1, materials are inspected for acceptance and production facilities areinspected in the phase of concrete production. In the construction phase, concrete and reinforcement
are inspected for acceptance and concrete work, reinforcement work, form work and support work
are inspected. For a completed structure, surface conditions, locations and dimensions of concrete
members, concrete in the structure and concrete cover are inspected. Defects can be detected in theconstruction phase by inspections of surface conditions, locations and dimensions of members,
concrete in the structure and concrete cover.
(4) A review of the inspection plan becomes necessary when the construction plan is modified.

213

Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 3 INSPECTION FOR ACCEPTANCE OF
CONSTITUENT MATERIALS OF CONCRETE

3.1 General(1) The party accepting concrete materials such as cement, water, aggregate andadmixtures shall inspect the materials responsibly to verify whether they meet thedesignated quality requirements or not. The Owner of the structure shall verify theinspection results. Cement and admixtures may be inspected by confirming the lists oftest records prepared by the production plants.
(2) If the quality of materials is determined to be inadequate in inspections, thematerials shall be replaced or other measures shall be taken.

[Commentary] (1) It is important that cement, mixing water, aggregate and admixtures shall havethe qualities prescribed in mix proportioning process to manufacture the requisite performance. The
party producing concrete shall assume the responsibility for testing concrete materials to verify their
quality when they are accepted. When producing concrete using the production facilities installed at
the site as in dam or tunnel construction, the contractor shall assume the responsibility for testingmaterials to verify their quality. The Owner of the structure shall finally verify the results ofinspections of concrete materials conducted by the contractor, fulfilling the responsibility of theaccepting party.
(2) When the inspection results for the quality of materials were judged not to be conform to therequirement, if that cause can improved by engineer, such as the grading of aggregate or chloride
ion content of sand, it may continue to use the material in condition of the improvement of that
quality. But, if dealing with that come is not possible by engineer, such as the density or water
absorption of aggregate, the measures such as the change of that material must be executed.
In cases where unacceptable materials have been used, whether the concrete using thematerials achieves the designated performance requirements or not should be verified andappropriate measures should be taken based on the results.

214

Chapter 3 Inspection for Acceptance of Constituent Materials of Concrete

3.2

CementInspection of cement should be carried out in accordance with Table 3.2.1 as astandard.

Table 3.2.1

Inspection of cement

Type

Item

Testing or Inspection
methodCements
specified in JIS
specification

Items specified
in JIS for thedifferent types of
cementConformation of test
results provided bymanufacturer or inaccordance with JIS
R 5201

Cements not
specified in JIS
specifications

Items arranged
for achievementof usual purpose

Conformation of test
results provided bymanufacturer orreferring to JIS R
5201

Period/Frequency

Criteria for judgment-Prior toconstruction work

Complying with
relevant JIS
specification-At least once amonth during
construction work
-After the cement
has been stored fora long timeComplying withspecifications arranged
for achievement ofusual purpose[Commentary] Cements not specified in JIS have generally the unique properties, and are used
for special purpose. For these cements, it is needed that quality items and specifications shall bearranged adequately for achievement of usual purpose and judgment must be led under these items
and specifications.

215

Standard Specifications for Concrete Structures-2007, Materials and Construction

3.3 Mixing Water
Inspection of mixing water should be carried out in accordance with Table 3.3.1 as astandard.
Table 3.3.1 Inspection of mixing water
Type

Item

Servicewater(drinkablewater)-

Servicewater (notdrinkable
water)

Items specified
in JSCE-B101oritems specified
in JIS A 5308
appendix 3

Testing method/
Inspection method
Confirmation of the
document about
service water

Period/Frequency

Criteria for judgment

Prior to the construction
work

Shall be service water(drinkable)-Prior to construction
workin accordance with
JSCE-B101or JIS A
5308 appendix 3-At least once a year
during construction work

Complying with
JSCE-B101or JIS A
5308 appendix 3-In case the water qualitychanges-Prior to construction
work

Recovered
water

Items specified
in JIS A 5308
appendix 3

Referring to JIS A
5308 appendix 3-At least once a year
during construction work

Complying with JIS
A 5308 appendix 3-In case the water qualitychanges[Commentary] When drinkable service water is used for mixing water, this should be
documented without requiring a special inspection test.
When drinkable service water is not used for mixing water, it shall be confirmed by inspection
test in accordance with JSCE-B 101 “Quality Specifications of Mixing Water of Concrete” or JIS A
5308 appendix 3 “Mixing Water for Ready-mixed Concrete”, as standard. On JSCE-B 101, thefollowing items, quantity of suspended solids, quantity of dissolvable evaporating remainders,chloride ion content, hydrogen ion content, strength ratio of mortars and increment of air content
were specified, and on JIS A 5308 appendix 3, the follow items, quantity of suspended solids,
quantity of dissolvable evaporating remainders, chloride ion content, difference of setting time ofmortars, strength ratio of mortars and increment of air content were specified. Then thespecification items for hydrogen ion content and difference of setting time of mortars are different
in these specifications, respectively. When drinkable service water is not used for mixing water,
inspection test shall be executed by either method in consideration of general use, as standard, sothat the concrete would be satisfied the prescribed performance.
When recovered water is used, the quality must be confirmed in accordance with JIS A 5308
appendix 3 “Mixing Water for Ready-mixed Concrete” once in a year by the approximate test of JIS
A 5308 appendix 3.

216Chapter 3 Inspection for Acceptance of Constituent Materials of Concrete

3.4 Aggregates(1) Inspection of fine aggregate should be carried out in accordance with Table 3.4.1
as a standard.

Table 3.4.1 Inspection of fine aggregate
Type

Item

Testing method/
Inspection method

Oven-dry density

Method in JIS A
1109

Water absorption

Method in JIS A
1109

Grading

Method in JIS A
1102

Clay lumps

Approximate
method in JIS A
1137

Loss in washing test

Method in JIS A
1103

Chloride ion content

Method in
JSCE-C 502 or
Method in
JSCE-C 503

Period/Frequency-Prior to construction work
-At least once a month 1)during construction work
-Incase the source of the sandis changed-Prior to construction work

Sand
Organic impurities

Method in JIS A
1105-At least once a year during
construction work
-In case the source of the sandis changed

Chemical soundness(alkali-silicate
reactivity)

Method in JIS A
1145
Method in JIS A
1146

Criteria forjudgment

Complyingwithspecificationsof Section 3.4.1
in "Materials

andConstruction:
Construction
Standards"-Prior to construction work
-At least once every 6 months
during construction work
-Incase the source of the sandis changed.
-Prior to construction work

Soundness(Freeze-Thaw
resistance)

Method in JIS A
1122-At least once a year during
construction work
-Incase the source of the sandis changed.

-Prior to construction work
Crushedsand

Items specified in
JIS A 5005

Method in JIS A
5005-At least once a month 2)
during construction work
-Incase the source of the sandis changed

217

Complying
with JIS A
5005

Standard Specifications for Concrete Structures-2007, Materials and Construction

Blast-furnace slagfineaggregate

Items specified in
JIS A 5011-1

Method in JIS A
5011-1

Complying
with JIS A
5011-1

Ferro-nickel slagfine
aggregate

Items specified in
JIS A 5011-2

Method in JIS A
5011-2Complying
with JIS A
5011-2-Prior to construction work
-At least once a month 3)
during construction work

Copperslag fineaggregate

Items specified in
JIS A 5011-3

Method in JIS A
5011-3

Electric
furnaceoxidizingslag fineaggregate

Items specified in
JIS A 5011-4

Method in JIS A
5011-4Complying
with JIS A
5011-4

Recycledfine
aggregate
H

Items specified in
JIS A 5021

Method in JIS A
5021

Complying
with JIS A
5021-Incase the source of the sandis changed

Complying
with JIS A
5011-3

1) In case of hill sand, loss in washing test shall be tested at least once a week.
In case of sea sand or blended sand of sea sand and others, chloride ion content shall be tested once in a week at
least2) Alkali-silicate reactivity shall be tested once in 6 months at least, soundness shall be tested once in a year at least3)For ferro-nickel slag fine aggregate, copper slag fine aggregate, electric furnace oxidizaing slag fine aggregate andrecycled fine aggregate H, alkali-silicate reactivity shall be tested at least once every 6 months(2) Inspection of coarse aggregate should be carried out in accordance with Table 3.4.2
as a standard.
Table 3.4.2 Inspection of coarse aggregate
Testing method/Type

GravelItem

Inspection
methodPeriod/Number

Criteria forjudgment

Complying
with thespecificationsof Section 3.4.2
in "Materials

Oven-dry density

Method in JIS A
1110

Water absorption

Method in JIS A
1110-Prior to construction work

Grading

Method in JIS A
1102-At least once a month
during construction work

Clay lumps

Approximate
method in JIS A
1137-Incase the source of thesand is changed

Loss in washing test

Method in JIS A
1103

218

and
Construction:
Construction
Standards"

Chapter 3 Inspection for Acceptance of Constituent Materials of Concrete-Prior to construction work
Chemicalsoundness(alkali-silicate
reactivity)

Method in JIS A
1145
Method in JIS A
1146-At least once every 6months during construction
work-Incase the source of thesand is changed-Prior to construction work

Soundness(Freezing-Thawing
resistance)

Method in JIS A
1122-At least once a year during
construction work
-In case the source of thesand is changed-Prior to construction work

Crushedstone

Items specified in
JIS A 5005

Method in JIS A
5005-At least once a month 1)during construction work
-Incase the source of thesand is changed

Blast-furnace slagcoarseaggregate

Items specified in
JIS A 5011-1

Complying
with JIS A
5005

Complying
with JIS A
5011-1

Method in JIS A
5011-1-Prior to construction work

Electric
furnaceoxidizingslag fineaggregate

Items specified in
JIS A 5011-4

Recycledfine
aggregate
H

Items specified in
JIS A 5021

Method in JIS A
5011-4-At least once a month2)
during construction work
-Incase the source of thesand is changed

Method in JIS A
5021

Complying
with JIS A
5011-4Complying
with JIS A
5021

1) Alkali-silicate reactivity shall be tested at least once every 6 months, percentage of abrasion and soundness shallbe tested at least once a year
2) For electric furnace oxidizaing slag fine aggregate, alkali-silicate reactivity shall be tested at least once every 6months[Commentary] Items of inspection test and methods shall be decided from character of
construction work and/or experiences for same kinds of works. As concrete consists of large amountof aggregates, to ensure the durability of concrete, the following tests shall be carried out: namely
density, water absorption, grading, deleterious substance content, soundness, chloride ion content
and alkali-aggregate reactivity.
Test period and frequency of aggregates must be decided based on the tendency of alteration of
the grading and moisture content. The inspection tests should be performed at least twice a day inthe beginning of construction work. It may be decreased the frequency of test based on the
judgment from the appropriate storage and treatment, and small variation of the grading andmoisture content of aggregates.
When the sea sand is used, frequency of tests for chloride ion content, grading and moisture219

Standard Specifications for Concrete Structures-2007, Materials and Construction

content must be increased compared to the other kind of aggregate. And in case the large content ofshells in sea sand adversary affect the quality of concrete, the quantity of shells must be examined.
When the source of product is changed, it is necessary to confirm the qualities by inspection test. As
the considerable variations of quality shall be occurred in case the source of product would be samebut position in the source different, a special care must be taken for the alteration of out-looks ofaggregates on receiving of materials.

3.5 Admixtures(1) Inspection of mineral admixtures should be carried out in accordance with Table
3.5.1 as a standard.

Table 3.5.1 Inspection of mineral admixtures
Testing method/Item

Fly ashItems specified
in JIS A 6201

Conformation of test results
provided by manufacturer
or in accordance with JIS A
6201

Complying
with
JIS A
6201

Expansive
admixture
for concrete

Items specified
in JIS A 6202

Conformation of test results
provided by manufacturer
or in accordance with JIS A
6202

Complying
with JIS A
6202

Groundgranulated
blast-furnaceslag

Items specified
in JIS A 6206

Conformation of test results
provided by manufacturer
or in accordance with JIS A
6206

Silica fumeItems specified
in JIS A 6207

Conformation of test results
provided by manufacturer
or in accordance with JIS A
6207

Required items

Conformation of test results
provided by manufacturer
or in accordance withrequired method

Other thanthose listed
mineraladmixture

Inspection method

220

Period/Frequency

Criteria forjudgment

Type-Prior to construction
work-At least once a month
during construction
work- In long term storage
case

Complying
with
JIS A
6206
Complying
with JIS A
6207
Complyingwithspecifications
arranged forachievement ofusual purpose

Chapter 3 Inspection for Acceptance of Constituent Materials of Concrete(2) Inspection of chemical admixtures should be carried out in accordance with Table
3.5.2 as a standard.

Table 3.5.2 Inspection of chemical admixtures
Type

Item

Air-entraining
agent,
Water-reducing
agent,
Air-entraining andHigh -range
Items specified inwater-reducing
JIS A 6204
agent, Fluidity
agent,
Superplasticizer,

Testing method/
Inspection method

Conformation of test
results provided bymanufacturer or inaccordance with JIS
A 6204

Corrosion
inhibitor for
reinforcing bar inconcrete

Other than thoselisted chemical
admixture

Criteria forjudgment

Complying with
JIS A 6204
-Prior toconstruction work

Rapid hardened
agent

Antiwashout
agent

Period/Number-At least once every
3 months during
construction work

Items specified in
JSCE-D 104

Conformation of test
results provided bymanufacturer or inaccordance with
JSCE-D 104

Items specified in
JIS A 6205

Conformation of test
results provided bymanufacturer or inaccordance with JIS
A 6205Complying with
JIS A 6205

Required items

Conformation of test
results provided bymanufacturer or inaccordance withrequired method

Complying withspecifications
arranged forachievement ofusual purpose- In long term
storage caseComplying with
JSCE-D 104[Commentary] On the acceptance inspections of admixture, it shall be confirmed that brand andkind would be proper materials by carrying out control of the acceptance document and/or the label
expression by visual observations. Inspection tests may be generally substituted for follow method,
certification of conformity to the specification on the mill sheet expressed the test results by public
testing organization or by product company for respective specification items. Inspection tests
should be carried out when needed.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 4 INSPECTION OF CONCRETE PRODUCTION
FACILITIES(1) The party accepting concrete shall assume the responsibility for inspecting
concrete production facilities. The Owner of the structure shall verify the inspection
results.
(2) Inspection of concrete production facilities should be carried out in accordancewith Table 4.1 as a standard.

Table 4.1 Inspection of concrete production facilities
Type

Item

Testing method/
Inspection
methodPeriod/Frequency-Confirmation byvisualobservations
Material storage
facilities

Required
items-Confirmation of
the structural
figures ofstorage facilities-Prior to theconstruction work
-Anytime during
construction work

-Measurement of
temperature andhumidity

Weighing
machineBatching
facilities

Accuracy ofbatching(dynamicloading)

Measurement oferror between set
up value andcounting value

Bach mixer

Performanceof mixing

Method in JIS A
1119

Continuous
mixer

Performanceof mixing

Method specified
in JSCE-I 501
and JSCE-I 502

Weighing
controlequipment

Mixer

Accuracy ofbatching(static
loading)

Measurement oferror between theload andindicated value
using weights oran electricaltesting apparatus-Prior to theconstruction
work, -At least
once every 6months during
construction work

-Prior to theconstruction
work, -At least
once a year during
construction work

Criteria for judgment

Complying with thespecifications ofSection 5.2.1 in"Materials andConstruction:
Construction
Standards"

Shall be weighing
within permissible
limit specified in low

Shall be weighing
within prescribed
permissible limit
Complying with
A 1119JIS

Complying with
JSCE-I 501 and
JSCE-I 502[Commentary] (1) Verifying the performance of concrete production facilities such as material
storages, measurement facilities and mixers at the start of or during construction is required for
producing concrete with designated performance economically. In order to produce concrete with

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Chapter 4 Inspection of Concrete Production Facilities

designated performance, the accepting party shall assume the responsibility for verifying that theconcrete production facilities meet the performance requirements specified in Section 5.2 of"Materials and Construction: Construction Standards". The owner of the structure shall verify theinspection results.
(2) The weighing of materials is controlled by a weighing control system. The variance between thedesignated and actual weights shall be measured to verify that the precision of weighing is within
the specified range. For inspecting the weighing meters, static loading tests shall be conductedusing a weighing meter or electric detector to verify that the weighing meter can detect loads as
precisely as designated.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 5 INSPECTION FOR ACCEPTANCE OF READYMIXED CONCRETE(1) The accepting party shall assume the responsibility for conducting acceptancetests for ready mixed concrete. The Owner of the structure shall verify the inspection
results.
(2) Acceptance tests for ready mixed concrete shall be conducted at the time of
unloading.
(3) Inspections should be conducted in accordance with Table 5.1 as a standard.
(4) Professional engineers of the accepting party shall visually verify that concrete
achieves a high level of workability at the time of unloading. No concrete with poor
workability shall be placed.
(5) Water content of unit volume of fresh concrete should be inspected after the
consultation between the accepting and producing parties concerning the inspection
method and decision criteria.
(6) Mix proportions should be inspected by verifying that each material is produced at
the designated proportion based on the printed weighing records. For inspection, watercontent per unit volume of concrete should be obtained by calculation using the printed
weighing records for water and the calibrated volume of aggregate surface water.
(7) Water-cement ratio should be obtained from the printed weighing records of cement
content per unit volume of concrete, and the water content per unit volume of concretethat is calculated based on the printed weighing record of water and the calibrated volume
of aggregate surface water. Alkali-aggregate reaction should be verified based on theconcrete mix proportion list.
(8) Strength shall be inspected in compressive strength tests. If the test result is
unacceptable, the strength of concrete in the structure shall be examined.
(9) Shrinkage strain should be verified as required for important structures.
(10) When applying a fluidity agent to concrete, the slump and volume of air should bemeasured before and after the application at a rate of once per 50 m3.
(11) Concrete determined to be inappropriate as a result of inspections shall not be
used.

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Chapter 5 Inspection for Acceptance of Ready Mixed Concrete

Table 5.1 Acceptance inspection of concrete
Testing method/

Item

Inspection method

Condition of fresh
concrete

Confirmation by visualobservations ofengineer in charge orappropriate engineer

Period/Frequency

Criteria for judgment-When unloading

Shall have the suitableworkability and minimum
variation in quality-Anytime as required

Allowable error:

Slump

Method in JIS A 1101

Method in JIS A 1116
Air content±1.5cm in the case ofslump higher than 5cm
and less than 8cm

Method in JIS A 1118
Method in JIS A 1128

When unloading, once in a
day or once every
20~150m3, depending upon
the importance of structure
and the scale of theconstruction work, and in
the event of any appreciablechange in the quality on
unloading±2.5cm in the case ofslump 8cm to 18 cm

Allowable error:±1.5%

Unit weight ofwater of fresh
concrete

By tests on the unit
weight of fresh
concrete

Temperature ofconcrete

By temperature
measureShall be conform to theprescribed conditions

Bulk density

Method in JIS A 1116

Shall be conform to theprescribed conditions

Chloride ioncontent

Method in JIS 1144 or
Recognized method byreliable testingorganization

Preventive ofalkali-aggregate
reaction

Confirmation of mix
proportion report

Unit
water
content

Confirmation of thecount surface moistureof aggregates andprinted record forweighing
measurements of waterMix
proportionUnitcementcontent

Water
tocementratio

Confirmation of
printed record forweighing
measurements of water
Confirmation of thecount surface moistureof aggregates andprinted records forweighing
measurements of
cement and water

Shall be in permissible
limit

When unloading,3
In the case of sea sand twice Shall not exceed 0.3kg/m
in principle
a day, the other case once ina weekPrior to the construction
work and in which thematerial or mix proportion
changes

Shall be confirmed thepreventive-When unloading-Twice in before noon andafternoon, respectively
Shall be in permissible
limit

Prior to the construction
work and in which thematerial or mix proportion
changes225

Standard Specifications for Concrete Structures-2007, Materials and Construction

Unit
contentofothermaterials

Compressive
strength (at28-day age, in
general)Confirmation of
printed record forweighing
measurements ofconcrete materials

Method in JIS A 1108

-When unloading- Twice in before noon andafternoon, respectively

When unloading, once a day
or once every 20~150m3,
depending upon theimportance of structure andthe scale of the constructionwork

The probability forcompressive strength tobe lower thancharacteristic
compressive strength of
concrete is less than 5%(Estimated using
production risk)[Commentary] (1) and (2) In order to verify whether the concrete delivered to the site meets thedesignated performance requirements or not, the party accepting ready mixed concrete shall assume
the responsibility for conducting inspections. The Contractor shall basically assume theresponsibility for conducting acceptance tests for ready mixed concrete at the time of unloading
because the Contractor generally purchases ready mixed concrete.
(3) The Contractor shall verify responsibly that fresh concrete meets the designated construction
performance requirements. The Owner of the structure should inspect the parameters related toperformance after concrete hardens such as the amount of chloride ions, measures to control
alkali-aggregate reaction, volume of air, water-cement ratio and strength. The Owner of thestructure shall assume the ultimate responsibility for these parameters.
Slump: Slump tests are widely employed for evaluating the consistency of concrete. The
plasticity of concrete can also be determined to some extent by slump tests. Not only the values
obtained in slump tests should be used but also the shape and homogeneity of concrete shouldcarefully be observed after the tests to determine workability. For the allowable margin of error for
special concrete with a slump lower than 3 cm or higher than 18 cm, refer to relevant standards.
Air content: The volume of air entrained in AE concrete may sometimes vary greatly withchanges in aggregate grading, temperature or other parameter even where concrete of the same mix
proportions is produced using the materials in one and the same lot. The changes in volume of air
entrained have great impact on workability, strength and durability of concrete. It should therefore
be verified by testing that the designated volume of air is entrained at the time of acceptance.
Temperature of concrete: The temperature of concrete greatly affects the quality of fresh
concrete, rise of concrete temperature due to the heat of cement hydration and characteristics ofstrength development. This parameter is an important determinant of concrete quality during theconstruction of mass concrete and during the concreting in cold or hot weather.
The temperature of fresh concrete should be measured in accordance with JIS A 1156 Methodof Measuring the Temperature of Fresh Concrete.
Mass of unit volume: Inspecting the mass of unit volume is essential to the verification ofwhether or not the mass of unit volume in an actual structure is appropriate as compared with themass of unit volume specified in the design of the structure. The inspection is particularly importantin the case of light-weight aggregate concrete because substantial changes in mass of unit volume
226

Chapter 5 Inspection for Acceptance of Ready Mixed Concrete

determine the quality of the structure.
Chloride ion content: Chloride ion concentration greatly affects the resistance to steel corrosion.
In cases where a large number of chloride ions are highly likely to intrude into concrete as in cases
where sea sand is used, the frequency of testing shall be increased.
As a method of inspecting chloride ion concentration in fresh concrete, JIS A 1144 Method ofInspecting Chloride Ion Concentration of Water in Fresh Concrete is available.
(4) Concrete needs to be homogeneous and sufficiently workable for transport, placement andcompaction. Whether fresh concrete is sufficiently workable or not may be visually determined tosome extent. Then, an engineer of the accepting party shall visually verify the state of concrete forany defects at the time of unloading or placement at the site. No concrete determined to be
insufficiently workable should be placed. In order to enhance the reliability and precision of visualinspections, engineers with adequate knowledge and experience concerning concrete should
conduct inspections. Visual inspections shall be conducted by professional engineers of theaccepting party such as chief concrete engineers and concrete engineers. If questions are expected
to arise during determination, the producing and accepting parties should consult with each other inadvance and define appropriate decision criteria with mutual consent.
(5) For estimating the water content per unit volume of fresh concrete, such methods have beendeveloped as the heating and drying method (drier method, microwave heating method, etc.), drying
under reduced pressure method, air meter method and capacitive method. At present, however, theprecision of measurement is limited. In testing, therefore, water content per unit volume of fresh
concrete should be inspected exclusively to remove concrete containing excessive volume of water.
The precision of testing and the method of calibration vary from method to method. Inspections
should therefore be conducted after prior mutual consultations between the accepting and producing
parties concerning the method or decision criteria to be applied.
(6) and (7) In cases where the condition of concrete production has been inspected and thequalities of concrete materials have been inspected for acceptance, concrete mix proportions may beverified based on the printed records of measurements. Unit quantity of water shall in principle beobtained through calculation using the measurements in respective batches and the percentage ofaggregate surface water.
Water-cement ratio (water-binder ratio) is an important factor affecting strength andcoefficient of carbonation velocity, coefficient of chloride ion diffusion, resistance to frost damage,resistance to chemical intrusion and permeability coefficient, which determine the durability ofconcrete. Inspecting water-cement ration (water-binder ratio) is therefore important. Water-cement
ration (water-binder ratio) shall in principle be obtained by calculation using the printed records ofmeasurements for cement (binder) and the unit quantity of water obtained from the percentage ofaggregate surface water and the printed records of unit quantity of water.
When accepting concrete from a ready mixed concrete production plant with no equipment for
printing measurement records, verification may be made by an appropriate method through theconsultation with the producing party. Whether corrective measures are taken or not to control
alkali-aggregate reaction shall be verified using the lists of mix proportions.
(8) In cases where highly reliable production facilities and production and quality management
systems are in place, concrete strength may be inspected before concrete placement by verifying thequalities of concrete materials and mix proportions. In cases where production facilities or
production management systems are not reliable or where the conditions of concrete production are
unknown or concrete is not produced as specified, however, no concrete strength can be verified in
227

Standard Specifications for Concrete Structures-2007, Materials and Construction

mix proportion inspections. Then, verification shall be made by strength tests after concrete
placement. At present, JIS A 5308 Ready Mixed Concrete stipulates that strength tests should be
conducted.
(9) Shrinkage strain should be measured in accordance with JIS A 1129 Methods of Test for
Length Change of Mortar and Concrete. It should be verified that the measurement does no exceed
a shrinkage strain of 1000 micro meter. The standard value is the shrinkage where concrete isplaced under dry conditions for six months after wet curing for seven days. When applying ordinary
ready mixed concrete with a proven track record to a structure, inspections by shrinkage tests may
be eliminated.
(10) Even if the slump and air content of base concrete before a fluidity agent is within theallowable limit, slump and air content of the fluidity concrete may show considerable fraction for
determined fluidity agent dosage. Therefore frequency of inspection test shall be increased
compared to the case of ordinary concrete and these tests shall be performed to the both of the baseconcrete and the fluidity concrete.
For the slump of the both of the base concrete and the fluidity concrete, test shall be performed
in high frequency from prior to the placing works to the period confirming the stabilized qualities
on manufacturing, after that test may be performed in every 50m3 s. And visual inspection shall be
conducted for each agitator tracks to monitor the properness of workability of fluidity concrete.
(11) It is no doubt that the concrete judged not to be in conformity with requirements on the
results of acceptance inspection must not be placed. If the concrete was already placed into thestructure, the inspection as the structural concrete must be performed. That inspection shall be
executed on Section 8.4.

228

Chapter 6 Acceptance Inspection for Reinforcement

CHAPTER 6 ACCEPTANCE INSPECTION FOR
REINFORCEMENT(1) The accepting party shall assume the responsibility for verifying before
construction that the reinforcement delivered to the site meets the quality requirements
specified in design. The Owner shall verify the inspection results.
(2) Inspection of qualities of reinforcement should be carried out in accordance with
Table 6.1 as a standard.

Table 6.1

Inspection of qualities of reinforcement
Testing method/

Period/Inspection method

Frequency

Criteria forjudgment

Type

Item

Steel bars forconcretereinforcement

Items specified
in JIS G 3112

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3112

Complying with
JIS G 3112

Re-rolled steel bars
for concrete
reinforcement

Items specified
in JIS G 3117

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3117

Complying with
JIS G 3117

Reinforcing bars
not conforming to
the requirements of
JIS G 3112 and JIS
G 3117

Required items

Confirmation of test results
provided by manufacturer orreferring to JIS G 3112

Complying withspecifications
arranged forachievement ofusual purpose

Epoxy-coatedreinforcing bars

Items specified
in JSCE-E102

Confirmation of test results
provided by manufacturer orin accordance with JSCE-E102

Complying with
JSCE E-102

Threaded rugged
reinforcing bars
with large diameter

Items specified
in JSCE-E121

Confirmation of test results
provided by manufacturer orin accordance with JSCE-E121

Prestressing wire
Prestressing strands

Items specified
in JIS G 3536

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3536

Complying with
JIS G 3536

Prestressing bars

Items specified
in JIS G 3109
or JIS G 3137

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3109
or JIS G 3137

Complying with
JIS G 3109 or JIS
G 3137

Required items

Confirmation of test results
provided by manufacturer orin accordance with JIS G
3536,JIS G 3109 or JIS G 3137

Complying withspecifications
arranged forachievement ofusual purpose

Prestressing steel
not conforming to
the requirements of
JIS G 3536, JIS G
3109 and JIS G
3137

229

At delivery

Complying with
JSCE E-121

Standard Specifications for Concrete Structures-2007, Materials and Construction

Rolled steels forgeneral structures

Items specified
in JIS G 3101

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3101

Complying with
JIS G 3101

Rolled steels for
welded structures

Items specified
in JIS G 3106

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3106

Complying with
JIS G 3106

Rolled steels forbuilding structures

Items specified
in JIS G 3136

Confirmation of test results
provided by manufacturer orin accordance with JIS G 3136

S Complying
with JIS G 3136

Required items

Confirmation of test results
provided by manufacturer orreferring to JIS G 3101,JIS G
3106 or JIS G 3136

Complying withspecifications
arranged forachievement ofusual purpose

Steels for structures
not conforming to
the require-ments
of JIS G 3101, JIS
G 3106 and JIS G
3136[Commentary] It is only right and proper that reinforcement shall process the required quality as
specified for the design of the structure. Inspection to ensure the quality of reinforcement should be
performed on prior the placing works in advance. The Contractor shall assume the responsibility for
conducting acceptance tests for reinforcement. The Owner shall verify the results of inspections
conducted by the Contractor.
The shipment of the reinforcement is generally made to the field directly from factories in theform of bundle with the manufacture’s certified mill sheet where the name (or abbreviation) of the
manufacture, the name and type of reinforcement are legibly identified.
General inspection shall be performed by confirming that the description and kind shall be
adapted to the prescribed reinforcement by visual observations, and that material properties, shape,size and weight of reinforcement shall conform to the specifications prescribed by JIS G 3112 or
JIS G 3117 respectively by examination on mill sheet from product company. In this case, outlooksof reinforcement shall be examined and the measured the diameter shall be measured of reinforcing
bars by calipers, etc.
When the reinforcements except for reinforcing bars are accepted, the same method forreinforcing bars shall be approximately taken. When epoxy-coated reinforcing bars or galvanizedreinforcing bars are accepted, it is important to confirm that the coating or galvanizing parts have no
defects. For other types of steel than reinforcing bars, inspections may be conducted as forreinforcing bars

230

Chapter 7 Inspection of Construction

CHAPTER 7 INSPECTIONS OF CONSTRUCTION

7.1 General
The Owner of the structure shall assume the responsibility for inspecting constructionin accordance with the inspection plan.

[Commentary] The Contractor shall manage quality in each construction phase. The Owner ofthe structure shall assume the responsibility for inspection construction. Verifying the quality of acompleted concrete structure is generally difficult in numerous cases. Construction shall therefore
be inspected before concrete placement or during concrete construction as a standard practice.

7.2 Inspection of Concreting(1) Inspection for transportation should be carried out in accordance with Table 7.2.1
as a standard.

Table 7.2.1 Inspection for transportation
Item

Testing method/
Inspection method

Period/Frequency

Criteria for judgment

Equipment and labor
required for transportation

Confirmation by visualobservations

Shall conform to theconstruction plan

Method of transportation

Confirmation by visualobservations

Shall conform to theconstruction plan

Quantity of transportation

Confirmation of the quantityof concrete

Transporting time

Confirmation of the time of
shipment and arrival on site

Prior to theplacing work andduringtransportation

Shall be prescribed
quantityComplying with Section
7.3 in "Construction:
Construction Standards"
based on the placing hours(2) In the inspection of pumping, it should be verified as a standard practice that the
maximum pumping load on the pump during pumping is equal to or less than 80% of the
maximum theoretical pumping pressure of the concrete pump.
(3) Inspection of placing should be carried out in accordance with Table 7.2.2 as astandard.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Table 7.2.2 Inspection of casting
Item

Testing method/

Period/Frequency

Inspection method

Equipment and labor
required forplacement

Confirmation by visualobservations

Method of placement

Confirmation by visualobservations

Quantity ofplacement

Confirmation of quantity fromshape and size of placing zone

Criteria for judgment
Shall conform to theconstruction plan

Prior to the placing
work and during
placement

Shall conform to theconstruction plan
Shall be prescribed
quantity(4) Inspection of curing should be carried out in accordance with Table 7.2.3 as astandard.
Table 7.2.3 Inspection of curing
Item

Testing method/

Period/Frequency

Inspection method

Equipment and labor
required for curingConfirmation by the visualobservation

Method of curingConfirmation by visualobservations

Period of curingConfirmation of curing days
and curing time

Criteria for judgment
Shall conform to theconstruction plan

During curing

Shall conform to theconstruction plan
Shall be conform to theprescribed conditions(5) In cases when inspection for transportation, placing or curing of concrete before
construction shows non-compliance with the required standards, appropriate measures,such as improvements of equipment, labor arrangement or improvements of construction
method should be taken, so that required objectives are achieved. In cases when concrete
has already been placed, it shall be determined whether the concrete within the structure
meets the required purposes, and appropriate countermeasures should be taken as
needed.
(6) In cases when it is required to determine the adequacy of curing, timing of
formwork removal, introduction of prestress, or the load applicability at early stage, it isdesirable that tests for strength are carried out using specimens cured under conditions
as close as possible to the concrete at site.
(7) In the case of cold weather concreting, inspection should be carried out inaccordance with Table 7.2.4, besides the provisions of (1) to (6). The timing for terminationof curing, or formwork removal and shoring dismantlement, should be determined on thebasis of strength of specimens cured under conditions as close as possible to theconcrete at site, or on the basis of strength estimated using the records of temperature of232Chapter 7 Inspection of Construction

concrete.
Table 7.2.4 Inspection of cold weather concreting
Testing method/
Item

Inspection
methodPeriod/Frequency

Criteria for judgment

Prior to theconstruction work andduring construction
work

Refer to Section 12.1 in "Materials
and Construction: Construction
Standards" based on mean daily
atmospheric temperature
Be within the limits of provided
planning temperature, planningtemperature range shall comply with
Section 12.5 in "Materials andConstruction: Construction
Standards"
Be within the limits of provided
planning temperature, planningtemperature range shall comply with
Section 12.6 in "Materials andConstruction: Construction
Standards"

Circumferential
temperature

Concrete temperature at
placing

Measurementof temperature

Concrete temperature on
curing or circumferential
temperature under theheat curing(8) Inspection of hot weather concreting should be carried out in accordance with
Clauses (1)-(6) and Table 7.2.5.

Table 7.2.5 Inspection of hot weather concreting
Item

Testing method/
Inspection method

Prior to the construction
work and during
construction work

Circumferential
temperature

Concretetemperature at
placing

Transportingtime

Period/Frequency

Measurement of
temperature
During construction
work

Confirmation oftransporting time

Prior to the construction
work and during
construction work

Criteria for judgment
Refer to Section 13.1in " Materials
and Construction: Construction
Standards" based on mean daily
atmospheric temperature
Be within the limits of provided
planning temperature, planningtemperature range shall comply with
Section 13.6 in " Materials andConstruction: Construction
Standards"
For mass concrete, refer to Section
14.5.2 in " Materials andConstruction: Construction
Standards"
The time from the start of mixing to
the completion of the placing shallnot exceed 1.5 hours and within thelimits of provided planningtemperature(9) Inspection of mass concrete should be carried out in accordance with Clauses

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Standard Specifications for Concrete Structures-2007, Materials and Construction(1)-(6) and Table 7.2.6.

Table 7.2.6 Inspection of mass concrete

Item

Testing
method/Inspection
methodConcrete temperature on
placing
Concrete temperature on
curing or circumferential
temperature under thetemperature-controlled curing

Measurementof temperature

Period/Frequency

Criteria for judgment

During theconstruction
works

Shall comply with the requirements
of provided plan.

[Commentary] (1), (2) and (3) In the inspections of concrete transport and placement, the types,
models, capacities and quantities of transport and placement facilities, human resources assigned,transport channels to the site, methods of transport at the site, sections of concrete placement,
locations of construction joints, and order and speed of placement shall be verified for compliancewith the construction plan.
It shall be verified that the pumping equipment has sufficient pumping capacity for theconcrete and piping conditions.
Sufficiency of the quantity of transportation and quantity of placement shall be controlled on
the period of transporting and placing respectively. Required volume for practical placing is
generally about 2% larger than the design volume as the reasons of counting error of materials,
variation of density of aggregates, variation of air content, loss on unloading from agitator track,
bleeding after placing and deforming of the form.
Transporting time means the period from the start of mixing to completion of placing. The
variation of transporting time shall lead the change of workability and other properties due to thechange of air content and the loss of slump. If the transporting time shall become extremely long, it
would be difficult to construct in proper condition. Then the transporting time must not be longer
than the specified period.
(4) In the inspection of curing equipments, labor arrangement for curing and curing method, it shallbe confirm that the moist curing, temperature-controlled curing and protection from harmful effects
would be executed according to the description of the construction planning documents. The curing
period (curing days or hours) is specified on Sections 8.2, 8.3 and 8.4 in “Materials andConstruction: Construction Standard” for moist curing, temperature-controlled curing andprotection from harmful effects, respectively. These specifications are determined from theconsideration for curing method, kind of structure, location, weather conditions, kind of cement
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condition would be conformed.
(5) In cases where concrete is found to be unacceptable as a result of inspections of transport,
placement and curing, the facilities and construction plan are considered unsatisfactory. Then,facilities should be improved and the construction plan should be reviewed as required. In cases
where the structure has been completed, it should be verified that the structure meets the designatedperformance requirements. Inspections should be conducted during construction and improvement
should be made immediately. Measures as preventive as possible should be taken.
(6) In order to estimate the adequacy of curing, appropriate time for form removal and prestressing
or to ensure safety of the structure under working condition, real concrete strength in the structure
must be estimated in some cases. For this purpose, the concrete test specimens shall be cured underconditions as close to the field conditions as possible. In cold weather concrete works,
above-mentioned specification is extremely important.
(7) As specified on Section 12.1 in “Materials and Construction: Construction Standard”, if mean
daily temperature is 4˚C or below during construction, construction practice as cold weather
concreting shall be required.
The times of the curing termination, form removal and shoring dismantlement shall bedecided by using the strength of specimens cured under similar conditions to in-place concrete, orusing the records of concrete temperature whose relationship between the concrete temperature andcompressive strength has been obtained by advance tests. It is desirable that curing conditions forfield-curing specimens are the same as those for real concrete structure, but the same temperature
conditions cannot be realized by simply putting the specimens at the same place as the structure.
Therefore, it is recommended to measure the temperature of the field-cured specimens, and toinvestigate the temperature difference between the specimen and structure.
When the temperature of the structure is measured, concrete strength can be estimated from
integrated temperature, or maturity. The maturity is generally expressed by the follow equation.
M=  A) t
where,(C7.2.1)

M : integrated temperature, or maturity, in [(degree C.) x(day)] or [(degree C.) x(hour)] concrete temperature during t, in [degree C.]
A : constant, generally 10 [degree C.] is used,t : time, in [day] or[ hour].

The relationship between maturity M and concrete strength varies depending on several
factors, such as the materials used, the mix proportions and the degree of drying or moisture
condition. Therefore, it is recommended that the relationship is confirmed by advance tests.
(8) Concrete considered as hot weather concreting is prescribed in Section 13.1 in “Materials andConstruction: Construction Standard”.
(9) Concrete considered as mass concreting is prescribed in Section 14.1 in “Materials andConstruction: Construction Standard”.

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The principle of reliable thermal cracking control in mass concrete is to evaluate thetemperature or thermal stress of structures in advance. However, in actual practice, due to thecomplicated influence of many uncertain factors at the construction stages, the behavior of thestructure may often differ from the prediction no matter how detailed tests or advanced analysis are
conducted at planning stage. Therefore, in mass concreting it is necessary to measure concretetemperatures of the structures continuously from the time of placing to the time when thetemperature of the concrete becomes nearly equal to atmospheric temperature, and to examine
whether the temperature change is kept within a range predicted in advance.
When the measured temperature at each portion of the concrete after placement largely differsfrom the predicted value, the measures such as curing method and placing interval shall bereexamined, and care shall be taken for the succeeding concreting.

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7.3 Inspection of Reinforcement
7.3.1 Inspection of fabrication and assembly of reinforcing bars
(1) Inspection of fabrication and assembly of reinforcing bars should be carried out inaccordance with Table 7.3.1.
(2) When the inspection results reveal that fabrication and assembly of reinforcing bars
is not in conformity with the requirement, the works for fabrication and assembly of
reinforcing bars shall be modified.

Table 7.3.1

Inspection of fabrication and assembly of reinforcing bars
Testing method/

Item

Inspection method- Confirmation of test results
provided by manufacture,
Kinds, diameter andConfirmation by visualquantity of reinforcing bars
observations,- Measurement of diameter
Prepared dimensions ofreinforcing bars

Period/Frequency

Criteria for judgment
Shall conform to therequirements of design

Completion of
cutting and bending

document
Shall be withinprescribed permissible
limit

Measurement by scale, etc.

For deck, beam etc.,
Kinds, placement andquantity of spacers

Min. 4 spacers/m2

Confirmation by visualobservations

For column,
Min. 2 spacers/m2

Fixing method of arranged
reinforcing bars

Arrangement ofassembled
reinforcing
bars

Arrangemen
t and lengthof joint andanchorage

Confirmation by visualobservations

Completion ofassembly of
reinforcing bars, andwhen concrete is notplaced immediately
right after
completion ofassembly of
reinforcing bars

Shall be sufficiently
secured against
displacement andmovement ofreinforcing bars causedby concrete placing

Shall conform to therequirements of design
document

Measurement by scale andconfirmation by visualobservations
More than designed
cover according toverification ofdurability

Concrete
cover

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Allowable error:
Effective
depth

Smaller value±3% ofdesign dimension
or±30mm (as standard)

Spacing
betweencenter of
reinforcing
bars

Allowable error:±20mm (as standard)[Commentary] (1) After the completion of bar placing and before the placement of concrete, thenumber and size of the bars should be inspected together with the location of bends, location andlength of joints, spacing of bars, and bar support in the form in order to whether those items are
satisfied with the required accuracy in design documents. The allowable error of criteria forjudgment shall be decided under the consideration with kind and importance of the structure. The
prescribed allowable errors for general concrete structure with columns, beams and walls are
expressed in Table 7.3.1.
It is advisable to make as many inspections as possible during placing of reinforcing bars to
avoid errors and to prevent the re-placement of bars that may require further time and cost.
Following a long interval from the completion of bar placement to concrete placement, theinspection and cleaning of bars shall be undertaken to ensure that the bar positions are correct andany mud, oil or other materials which have been deposited are removed. Concrete should therefore
be placed quickly after the cleaning and inspection at the end of the assembly of reinforcement.
As the allowable error of prepared dimension of reinforcing bars affects directly to theallowable error of location of assembled reinforcing bars, it shall be decided based on the kind andimportance of the structures, member sizes, and directions of such tolerances. An example forgeneral case is shown in Table C7.3.1.
The allowable error for the arrangement of the assembled reinforcing bars shall be ranged
from 5 to 20mm. However, the least cover must be kept at every location containing the joint
parts.
The relationship between the concrete cover specified in the design drawing and that specified
in durability check shall be verified, and decision criteria should be determined using the following
equation(C7.3.1).
Cm>Cd(C7.3.1)

where, Cm: measured concrete cover, andCd: concrete cover specified in durability check, which is expressed by the following
equation.
Cd= C – Ce

(C 7.3.2)

where, C: concrete cover shown in the design drawing∆Ce: construction error assumed in design.
If the spacers installed properly are larger than the concrete cover specified in durability
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check, it may be determined that the designated concrete cover is available.
Table C7.3.1 Allowable error of prepared dimensions of reinforcing bars

Type of reinforcing bars

Sign (on lightside figure)

Allowable
error
(mm)

Stirrup, hoop reinforcement,
helical reinforcement

a, b

±5

Round bars of
28mm or below
diameters,
deformed bars
25mm or below
diameters

a, b

±15

Round bars of
32mm or below
diameters/
deformed bars
29mm to 32mm
diameters

a, b

±20

Total length after completionof cutting and bending

L

±20

Other
types ofreinforcing
bars

Stirrups, ties, spiral
Reinforcement
reinforcement
other than the left

Overall length ( l )Overall length ( l )(2) When the inspection results were judged that preparation and assembly of reinforcing bars
was not in conformity with the requirement, it shall be modified properly. For the bended
reinforcing bars, re-bending shall not be undertaken in principle due to the fact that it may harm thequality of the bars.

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7.3.2

Inspection of joint of reinforcing bars

(1) When connecting reinforcing bars using gas welded joint, welded joint, mechanicaljoint etc. as the joint of reinforcing bars, the strength of joint shall be examined before
using.
(2) Inspection of joint of reinforcing bars should be carried out in accordance with
Table 7.3.2. as a standard. The detailes should be referred to the Guidelines of Anchorageand Joint for Reinforcing Bars.

Table 7.3.2 Inspection of joint of reinforcing bars
Type

Item

Lap joint

Location
Joint length
Location

Gas
pressure
welding
joint

Outlook
inspection
Super sonicflow
detectingtest2)
Measureme-nt,
Outlook
inspection

Testing method/

Period/Number

Criteria for judgment

Completion ofassembly of
reinforcing bars

Complying with therequirements of design
document

Confirmation by visualobservations, andmeasurement by scaleand calipers carried as
requiredOn all joints

Complying with therequirements of design
document

Method specified in JIS
Z 3062

Sampling 1)

Measurement by scaleand confirmation byvisual observations

On all joints

Inspection method
Measurement by scaleand confirmation byvisual observations

Complying with “Standard
Qualification Procedure for
Gas Pressure Welding
Technique” published by“Japan Pressure Welding
Society”, Refer to
Guidelines of Anchorageand Joint for Reinforcing
Bars
Complying with therequirements of design
document, Be without
surface defectEccentricity:

Buttarc-welded
joints

Not more than one-tenth ofbar diameter
Detailed
outlook
inspection

Measurement bycalipers and otherappropriate apparatus

More than 5%

Slope of joint parts:Not
more than one-tenth ofmeasured length
For detail, refer to
Guidelines of Anchorageand Joint for Reinforcing
Bars

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Super sonicflow
detectingtest
Mechanicaljoint

Sampling rate:
Method specified in JIS
Z 3062more than 20%
and more than 30
samples

For detail, refer to
Guidelines of Anchorageand Joint for Reinforcing
Bars

Inspection test shall be executed on the consideration with the types of joint method
For detail, refer to Guidelines of Anchorage and Joint for Reinforcing Bars

1) One inspection lot is assumed to be pressure welding parts that the same working party constructed on thesame day, and the standard of the lot size is about 200 samples. In the case of manual gas pressure welding, all
SD490 bars shall be inspected. Sampling inspections shall be conducted at 30 locations per inspection lot forother types of bars. In the case of automatic gas pressure welding, sampling inspections shall be conducted at ten
locations per inspection lot.
2) Inspections may be eliminated in the case of the hot punching method.

(3) When the inspection results for joints were judged not to satisfy the requirement,
appropriate countermeasures shall be taken.

[Commentary] (1) and (2) Various joints have been developed for reinforcing bars to facilitate
the construction of joints. Inspections shall be conducted to verify that all joints for reinforcing bars
meet the designated performance requirements. Gas welded joints include manually gas welded
joints, automatically gas welded joints and hot punching gas welded joints. Welded joints include
butt arc-welded joints, butt arc stud welded joints, butt resistance welded joints and flare welded
joints. Mechanical joints include crimped-sleeve joints, crimped-sleeve threaded joints, threaded
deformed bar joints, mortar grouted joints, friction welded and threaded joints, wedged joints andcombination joints. The performance of welded, mechanical and other types of joints varies
according to the type of joint, materials used, skill of engineer performing jointing and method of
jointing.
For details, refer to the Guidelines of Anchorage and Joint for Reinforcing Bars. Gas welded
joints may be inspected in accordance with the Standard Specifications for Gas Welding ofReinforcing Bars prepared by the Japan Reinforcing Bar Joints Institute.
In generals, an inspection test for gas pressure welding joint is approximately executed
according to the “Standard Qualification Procedure for Gas Pressure Welding Technique” publishedby “Japan Pressure Welding Society”.
(3) When the judgment does not comply with the specifications, the measures shall be performed
according to the recommendations of “Standard Qualification Procedure for Gas Pressure Welding
Technique”.

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7.4

Inspection of Formwork and Shoring(1) Inspection of formwork and shoring should be carried out in accordance with Table

7.4.1 as a standard.
Table 7.4.1
Item

Inspection of formwork and shoring

Testing method/
Inspection method

Period/Frequency

Criteria for judgment
Shall conform toprovided qualities andsizes

Materials of form andshoring and kinds,
material, shape and sizeof form tie

Confirmation by visualobservations

Prior to construction ofform and shoring

Placement of shoring

Confirmation by visualobservations andmeasurement by scale

Completion of
construction of shoring

Position and quantity ofform tie

Confirmation by visualobservations andmeasurement by scale

Prior to placing of
concrete

Shape and size, positionof form

Measurement by scale

Clear distance between
form and reinforcing bar
placed near side of form

Measurement by scale

Prior to placing of
concrete and during ofplacement

The concrete members
shall comply with thespecifications on
Sections 8.2 and 8.3 as
hardened concrete
members
Complying with thespecifications for coveron Section 7.3.1(2) When the inspection for formwork and shoring shows unsatisfactory results,
appropriate countermeasures shall be taken.

[Commentary] If the structure is inspected upon completion, inspecting the formwork or supports
may not be necessary. Defective formwork may, however, frequently cause problems during
construction or after the hardening of concrete. Then, formwork and supports shall be inspected.
(1) Formwork and shoring must provide the sufficient strength and safety against the mostunfavorable combination of actual loads prior to and during placing of concrete. Thus, inspections
for those kinds of loads should be performed according to Table 7.4.1 not to cause such unusualmatters as expansion of forms, leakage of mortar, sliding, leaning, settlement, looseness ofconnections, etc., and the configuration and dimensions of structures or members, and safety of
construction must be ensure additionally.
Construction accuracy of formwork and shoring shall guaranty the required position, shapeand dimension of the structure. Even if individual errors may be generally acceptable, thecumulative effects of these errors may have an adverse affect on the structures. Thus, it must ensurethat the cumulative error does not exceed the prescribed allowable error.

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CHAPTER 8 INSPECTION OF CONCRETE STRUCTURE

8.1 General(1) The Owner shall inspect the surface condition and locations and dimensions ofmembers of concrete structures.
(2) Concrete cover shall be inspected by nondestructive testing in accordance with
Section 8.5 for key structures, slabs that are likely to have inadequate concrete cover andmembers that are highly likely to be subjected to chloride attack or carbonation under
severe conditions.
(3) In cases where it is doubtful whether the structural performance requirements areachieved because of trouble during construction, structural performance shall beinspected as required.
(4) In cases where the structure is found to be unacceptable, or where detailed
inspections become necessary based on the results of inspections including
nondestructive tests, the safety and serviceability of the structure shall be verified byloading tests in accordance with Section 8.6.

[Commentary] (1) Concrete structures should be constructed as initially planned as possible
within the allowable range if they are to meet the designated performance requirements. For
verification, the Owner of the structure who accepts it should assume the responsibility for
conducting inspections for verifying whether the surface condition is satisfactory or not andwhether the location, shape and dimensions of the structure are within the allowable range or not.
Concrete structures like pile foundations constructed underground and high bridge piers forwhich no inspections are possible after the removal of formwork can be inspected only during
construction or at the completion of part of the work.
For structures constructed under severe conditions, items for detailed inspections should bespecified considering subsequent maintenance, and not only the appearance should be inspected byvisual observation or measurement of dimensions but also nondestructive testing should be
conducted for inspecting the quality of concrete and condition of reinforcement.
(2) In order for the structure to meet the performance requirements, the concrete cover as
designed should be made available. For slabs in which concrete cover is likely to be insufficient or
for members that are expected to cause damage to third parties in the case of spalling,nondestructive testing should be conducted for inspecting the concrete cover. For members that arelikely to be subjected to steel corrosion due to chloride attack or carbonation, nondestructive testingshould be conducted also for inspecting the concrete cover.
(3) Problems expected during construction include the frost damage to the concrete of thestructure, poor concrete strength as determined based on the results of concrete acceptance tests andsuspicion about structural safety for some well-founded reasons. In these cases, inspections should
be conducted to verify that the designated performance requirements are achieved.

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8.2. Inspection of Surface Texture(1) Inspection of surface texture should be carried out in accordance with Table 8.2.1.
Inspection shall be performed before any surface treatment.

Table 8.2.1 Inspection of surface texture
Item
Situation of
exposedconcretesurface(2)

Inspection method

Criteria for judgment

Shall be flat and shall not be recognizable defects such as
Confirmation by visual from honeycombs, ridges, air bubbles and etc.
observations
Shall not be shown the insufficient cover and shall have anormal surface
Shall be within the permissible limit to satisfy of therequirement as the structure

Crack

Measurement by scale

JointsConfirmation by visual
Shall ensure the mutually tight bond between lower andobservations andupper layers
measurement by scale

When

the

defectsarerecognized

duringtheinspection,

thefollowing

counter-measures shall be conducted as required.
(a) Defects on a concrete surface such as abrupt bulges and ridges shall be removed
to flatten the surface. Other surface imperfections such as honeycombs andfractured portions shall be removed and repaired appropriately.
(b) If initial cracks larger than allowed occur, the structure shall be repaired properly.
(3) In the case of mass concrete, besides inspection carried out as stipulated in
Clauses (1) and (2) above, the inspection of thermal crack shall be conducted by visualobservations after formwork removal. The timing of inspection of thermal cracks shall bedecided taking into account temperature change in the structure. When the inspection
points out the harmful cracks, adequate countermeasures shall be taken. When repair isnecessary, appropriate materials and methods shall be selected so as to satisfy therequirement of the structure.

[Commentary] (1) and (2) Inspection of surface texture shall be performed prior to theundertaking of measures such as repair or refinishing. It is important to inspect the surface just after
removal of formwork and curing. The visual inspection for surface defects such as cold joints,
honeycombs, ridges, abrupt bulges, bubbles and different tone of colors will be conducted by visualobservation shall be performed. Also, the location where the reinforcing bars have been visibly
exposed or where the shapes of the reinforcing bars are clearly recognized due to insufficient
concrete cover even before the reinforcing bars have not been exposed. Prior to repair, theexamination on the service environment, location and status of defects shall be performed. Repair
should be applied while implementing adequate quality management programs so as to eliminate
the need of re-repair in the maintenance phase, by selecting concrete, mortar or polymer
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cementitious mortar with appropriate mix proportions considering the environment, location andsize.
Initial cracks are ascribable to thermal stress due to the heating of concrete, drying shrinkage
or loading. Although some cracks have little influence on the structure, other types of cracks may behazardous to the structure. Therefore, allowable criteria of judgment shall be prescribed properly
depending on the degree of necessity. The allowable crack width shall be determined in accordancewith Section 8.3.2 of the Standard Specifications for Design and Construction of Concrete
Structures: Design. The threshold crack width for steel corrosion specified in Table 8.3.2 shall beapplied. In addition, it may refer to the “Limits of crack width concerning with requirement of
repair” on “Recommendation for Repair and Reinforcement of Cracking in Concrete” that is
published by Japan Concrete Institutes.
At the joints between placed layers, the uniformity of the existing concrete and newly placing
concrete shall be inspected by visual observations. When the performance of joints between theboth concretes is considered insufficient from the inspection results, it should be repaired by theeffective method for repairing for cracks.
Works shall be conducted in accordance with the “Recommendation for Repair andReinforcement of Cracking in Concrete” published by Japan Concrete Institute.
(3) Concrete to be regarded as mass concrete is outlined in the commentary of Section 14.1 in“Materials and Construction: Construction Standard”.
For mass concrete, the investigation with special caution shall be made in addition to theordinary inspection of general structures due to the possible development of the thermal cracking
which may impair the required quality or function of the structure. Period of inspection for thermal
cracking shall be decided in connection with the alteration of the temperature in the structure, suchas after the removal of forms, when the temperature of the concrete becomes nearly equal to that of
the atmosphere and when the average temperature of the member becomes the lowest during thewinter.
Materials used for crack repairs and their application methods are very diverse. Filling, grout
injection and surface treatment with resins are generally adopted. Epoxy resins are frequently used
for repairing cracks. The physical properties, applicable temperature, usable life, cohesion and use
condition vary even for one and the same type of resin. In the related field, developments have been
made both for materials and methods. Decision should be made based on the latest data. For
structures that function properly only by cutting water leakage, cutting off water may replace repair.

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8.3. Inspections of Locations and Dimensions of Concrete Members(1) The locations and dimensions of concrete members should be inspected inaccordance with Table 8.3.1 as a standard practice.

Table 8.3.1 Inspection of location, shape and dimension of concrete members
Item

Inspection method

Criteria for judgment

Plane position
Height in design
Section size

Allowable error: 30mm (as standard)
Measurement by
scale, transit, leveland etc.

Allowable error: 50mm (as standard)
Allowable error: 0~+50mm of designed length (as standard)(2) When the inspection results reveal that the criteria of judgment are not satisfied, thecountermeasures such as chipping, reconstruction and additional casting of concrete
shall be taken.

[Commentary] (1) Inspection of location, shape and dimension of concrete members shall be inconformity with the prescribed accuracy based on the design documents. Allowable errors shall bedecided considering the type and importance of the structure. The decision criteria in Table 8.3.1
present the standard tolerance for concrete structures constructed under ordinary structural andconstruction conditions. Tolerances for sectional area or length may vary according to the type ofthe member, e.g. columns, beams or walls.

8.4 Inspection of Concrete Properties in Structure(1) Inspection of concrete in the structure shall be carried out, in the case the concrete
is judged unacceptable during the acceptance inspection or in the inspection during
construction, or when these inspections are not properly carried out. The following
inspections shall be applied:(a) Tests on the specimens taken upon delivery and subjected to the same
conditions as the structure.
(b) Tests on the specimens taken from the structure.
(c) Nondestructive tests will be applied on the concrete in structures.
(2) In case the inspection evokes suspicion on the performance of the structure, tests
shall be conducted to comprehensively judge the structural performance from various
aspects, combining nondestructive tests, tests on drilled cores or sawed beams andloading tests on the structure. The loading test for confirming safety and serviceability of246

Chapter 8 Inspection of Concrete Structures

the structure shall be conducted in accordance with Section 8.6. In case the structure
does not conform with the performance requirements, appropriate countermeasures shallbe taken, including removal of defective concrete, re-placing of concrete andstrengthening of the structure.

[Commentary] (1) A simple and reliable test method for concrete in the structure is yet to beestablished. Judging from the field experience, the required performance of concrete in the structure
can be assured by carrying out an acceptance inspection as specified in Chapter 5 and inspection
during concreting as specified in Section 7.2 and ensuring conformity. Accordingly, omission of theinspection of concrete in the structure is permitted, provided that the acceptance inspection of the
as-delivered concrete and placement-related inspection regarding transportation, depositing andcuring is duly carried out and that the concrete is judged acceptable.
However, achievement of the required performance cannot be assured when concrete judged
unacceptable by the acceptance inspection has already been placed in the structure or when theinspection of concreting work cannot be duly carried out. In such a case, concrete in the structure
should be inspected as required.
Three methods are generally practiced for confirming the quality of concrete in the structure
as given in the items (a), (b) and (c). Concrete structures are generally designed based on thecompressive strength of concrete. Identifying concrete strength is therefore extremely important. In
addition to the inspections described in Chapter 5 and Section 7.2, nondestructive tests such as
Shmidt hammer tests (JSCE-G 504) should be conducted for inspection. The decision criteria
should be determined fully considering the variations of test results. Decision should be madecomprehensively by integrating the results of inspections described in Chapter 5 and Section 7.2.
(2) This is a requirement for confirmation of the performance of a structure when theinspection evokes suspicion about the development of the required performance of the concrete in
the structure, such as concrete damage due to freezing, etc. In such a case, detailed quality tests
should be conducted on concrete in the structure to examine if the structure can achieve the required
purposes.
Test methods include nondestructive tests such as Shmidt hammer tests (JSCE-G 504) andultrasonic testing, tests using concrete specimens (cores or beams) cut from the structure, in-situ
tests for surface air permeability, tests for estimating concrete mix proportions and loading tests.
The qualities of concrete in the structure may not be accurately judged by a single test method.
Multiple tests should be combined to make a comprehensive judgment.
When the test results indicate that the performance requirements of the structure are notfulfilled, appropriate measures should be taken including strengthening of the structure, instead of
removal of defective concrete and re-placing of the part.

8.5

Inspection of the Cover(1) For structures or members for which inspections of concrete cover are foundnecessary after the hardening of concrete, the availability of designated concrete cover
should be verified by nondestructive testing.
(2) Concrete cover should be inspected by nondestructive tests based on the decision
criteria shown in Table 7.3.1.

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Standard Specifications for Concrete Structures-2007, Materials and Construction(3) If the concrete cover is found unacceptable as a result of inspections, comparison
shall be made among such methods as the chipping and re-construction of concrete andthe application of protective measures like the coating of concrete surface. Then,appropriate measures should be taken to ensure the protection of steel.

[Commentary] (1) and (2) Though the cover is investigated at the time of the inspection of
fabricated reinforcement, the cover can change depending on the degree of security of the formwork,
reinforcement and spacers. The concrete cover of a completed structure should be measured by suchnondestructive testing methods as electromagnetic induction, electromagnetic wave reflection andradiography. For important structures, members that are frequently likely to be subjected to steel
corrosion under severe conditions and members that greatly affect third parties in particular, theconcrete cover should be measured by nondestructive tests.
The criteria for estimating the concrete cover by nondestructive tests may be the same asshown in Table 7.3.1. When applying the criteria, the precision of the measurement equipment
should also be considered. The precision should generally be approximately 5 mm. The
measurement error due to the precision of equipment is assumed to be a risk in inspection whenmeasuring the concrete cover.
Sampling inspections are generally conducted. Cross sections should be specified formeasurement at certain intervals along the length of the structure or each time the cross section
varies. Measurements should be taken at one point at the least in each element in the measurement
cross section. Measurements should be made for a length of one meter or more transverse to theoutermost reinforcement of each element.
For structures in which concrete cover is found insufficient as a result of sampling inspections,detailed investigations should separately be conducted.
(3) Insufficient cover reduces the performance of concrete to protect steel reinforcement. Thisrequirement was established to ensure the performance.

8.6

Loading Test of Member and Structure(1) In cases where a structure is considered unacceptable in inspections conducted
before the completion of the structure, or where verification of structural performance isconsidered necessary because of well-founded suspicion about the performance of thestructure, the performance of the structure should be verified.
(2) When confirming the safety and serviceability of the structure or members by theloading tests, the method of loading test shall be determined in order to certainly examine
the required performance. Special care shall be taken when determining timing andmethods of loading, the magnitude of the load, etc, so as not to exert harmful influence on
the structure or members.
(3) It shall be ensured that the amount of deflection and strain during and after theloading test are not unusual in comparison with the values estimated in the original
design.
(4) Appropriate countermeasures such as strengthening the structure or members

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shall be taken in case that the safety and serviceability of the structure or members areprobably insufficient based on results of loading test.

[Commentary] (1), (2) and (3) When the confirmation by loading tests shall be performed, it
shall be considered the conforming tests for the performance of elements such as members andloading tests of structure. In the application of the test results, special attention needs to focus onthat fact that the performance assessed in loading tests is generally limited to the part of elastic
behavior.
The loading tests specified in this section shall be conducted by a responsible engineer who
recognizes the need of the tests to verify the safety, serviceability or other parameters of thestructure in cases where concrete strength is considered to be poor based on the results of concrete
acceptance tests or concrete inspections during construction or where there is well-foundedsuspicion about the safety and serviceability of the structure during construction. The testing period
shall be determined so that the loading tests could be performed after sufficient concrete strength isattained so that introduction of weak spots on the structure due to the early application of load can
be avoided.
In case a new concept, a new construction method or a special material is adopted during theconstruction of structures, the loading test method shall be required as prescribed in the construction
specifications concerned.
Behaviors applied to the structure or on the members by loading tests therein were varied
depending upon the magnitude and type of the load, therefore it is important to select an appropriate
method of testing so that it can be judged whether the structure or members of the structure have thestrength and performance prescribed in the design or not. Loading tests may generally be done by
the static load application, but the rate of application and the magnitude of a load shall be selectedso as not to create weak spots by an expensive load.
To examine the behavior of members and structures, measurement of deformation in thewhole structure, deflection of respective members, and the strain of the respective parts is required.
The position for monitoring and the loading method of those examinations shall be properly
selected based on the purpose of the test, the method of analysis and the degree of importance of thestructure.
In the static loading tests, it shall be required to take care not to be affected by vibration,
impact or other dynamic movement. The measurement errors that are largely affected byatmospheric temperature change during the test shall be kept as small as possible or an adjustmentof the errors in the test results shall be prepared in advance.
Cracking that may exert harmful effects on the strength and durability of the structure, notably
large residual deformations or other defects in the structure must be carefully observed not only
during but also after the test. In addition, the propriety of the testing method shall be confirmed
together with the performance of the structure. For the confirmation of the dynamic properties of astructure, such as natural frequency, a vibration loading test should be performed.

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CHAPTER 9 RECORDS

9.1 General(1) The results of inspections of concrete structures shall be organized and stored as
inspection records.
(2) If repair, renovation or other corrective measures are taken based on the results ofinspections, the reasons, repaired locations and range and materials used shall also berecorded.

[Commentary] (1) The results of inspections conducted before the structure is put into service
serve as the initial values in inspections in the maintenance of the structure. The performancerequirements for concrete structures in such terms as durability, safety, serviceability andrestorability should be met throughout the design useful life. The inspection results for concrete
structures are important data for identifying the initial conditions of the structure for maintenance,
preparing inspection and investigation plans and analyzing the progress of the alteration and theircauses. Inspection results shall therefore be kept with the construction records received from thecontractor. These records should in principle be retained as long as maintenance is continued.
When maintaining a structure, not only the construction records received from the contractor
but also (i) results of crack investigations upon completion of the structure, (ii) results ofinspections of concrete cover, (iii) investigation results at the time of inspection of concrete during
construction e.g. results of concrete strength tests based on rebound, (iv) results of inspection ofcompleted part of the structure and (v) results of inspections of initial defects and past repair shallbe recorded. In relation to crack investigations, recording crack widths, lengths and locations even
where the width is within the allowable range may sometimes be useful during maintenance(Records in Chapter 12 of Part I Maintenance). The minimum number of records should be stored
to ensure the use and organization of records.

9.2

Identifiers of Structures

Identifiers should be attached to structures in which such information is described as
the name of the structure, load, design and construction organizations, date ofcommencement of construction, date of completion, and persons responsible for design,material supply, construction and construction control.

[Commentary] Specifying the names of chief design engineer and persons responsible forconstruction and construction management is explicitly defining the positions of respectiveengineers and paying tribute to the engineers engaged in the construction work. This is expected tocontribute to the improvement of the durability of the structure and is also important tomaintenance.

250Special Concrete

Chapter 1

GeneralCHAPTER 1 GENERAL

1.1

Scope

"Materials and Construction: Special Concrete" covers standards concerning thematters required for producing or constructing concrete structures that involve special
materials, functions, construction methods, construction environment, structural formats
and production methods.

[Commentary] In order to enable concrete structures to meet the designated performancerequirements, it is sometimes necessary to use concrete that involves special materials, functions,construction methods, structural formats and production methods or to construct concrete under aspecial construction environment.
"Materials and Construction: Special Concrete" presents standards concerning the mattersrequired for producing or constructing special concrete. Concrete that uses special materials andprovides special functions includes expansive cement concrete, lightweight aggregate concrete,concrete using continuous fiber reinforcing materials, short fiber reinforced concrete and highstrength concrete. Concrete that is constructed by a special method includes high fluidity concrete,
shotcrete and prepacked concrete. Concrete that is constructed under a special environment includes
underwater concrete and offshore concrete. Concrete that is of special structural format or is
produced by a special method includes prestressed concrete, steel-concrete composite structures andindustrial products.
There may be cases where special concrete is actually constructed or applied under different
conditions from those described in this chapter. Then, special concrete shall be constructed inaccordance with "Materials and Construction: General" or "Materials and Construction:
Construction Standards". In cases where the stipulations in "Materials and Construction: Special
Concrete" are inadequate or where applying the stipulations is not necessarily appropriate, special
concrete should be constructed so as to be fit for the actual conditions fully considering the
stipulations of "Materials and Construction: Special Concrete". For the special materials, methods
and types of construction not sufficiently stipulated in this Specification, the following guidelines
and manuals prepared by the Japan Society for Civil Engineers should be consulted.
“Recommendation for Design and Construction of Steel Fiber Reinforced Concrete”, 1983.
“Manual of Design and Construction for Lightweight Aggregate Concrete Structures”, 1985 (InJapanese)“Recommended Practice for Concrete Made by Continuous mixer”, 1986 (In Japanese)“Recommendations for Design and Construction of Structures by Prestressed Concrete Panel
Composite Slab Method”, 1987
“Recommendations for Design and Construction of Prestressed Concrete”, 1991 (In Japanese)“Recommendations for Design and Construction of Anti-washout Underwater Concrete”, 1991
“Design Code for Steel-concrete Sandwiches Structures”, 1992
“Recommended Practice for Concrete Containing Air-entraining and High-range Water-reducing
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Agents – Recommendations for construction of high fluidity concrete”, 1993
“Recommended Practice for Expansive Concrete”, 1993
“Recommendations for Design and Construction of Concrete Structures Using Silica Fume inConcrete -Draft-”, 1995
“Recommendations for Design and Construction of Concrete Structures Using Continuous Fiber
Reinforcing Materials”, 1995
“Recommendation for Design and Construction of Composite Structure”, 1997 (In Japanese)“Recommendation for Construction of High Fluidity Concrete”, 1998 (In Japanese)“Recommendation for Design of Pillar Member using Reinforced Concrete strengthened with Steel
Fiber”, 1999
“Recommendation for Concrete Pumping”, 2000 (In Japanese)“Recommendation for construction of tunnel concrete”, 2000
“Recommendation for Design and Construction of Electro-chemical Protection against Corrosion”,
2001“Recommendation for Design and Construction of structure using self-compacting, high-strengthand durable concrete”, 2001
“Guidelines for Design and Construction of Concrete Using High Strength Fly Ash As Artificial
Aggregate (draft)”, 2001
“Present and Problems Concerning the Leaching of Micro-components from Concrete”, 2003
“Guidelines for Design and Construction of Reinforced Concrete Using Epoxy Resin Coated
Reinforcing Bars (revised edition)”, 2003
“Guidelines for Design and Construction of Ultra High Strength Fiber Reinforced Concrete (draft)”,
2004“Guidelines for Design and Construction for Surface Protection Methods (draft)”, 2005
“Guidelines for Shotcrete (draft): Tunnels”, 2005
“Guidelines for Shotcrete (draft): Slopes”, 2005
“Guidelines for Design and Construction of High Performance Fiber Reinforced Cement Composite
Materials (draft)”, 2007
Constructing the special concrete discussed in "Materials and Construction: Special Concrete"frequently requires professional skills. It is stipulated that special concrete should be constructedunder the guidance of professional engineers with adequate knowledge and experience concerning
the specific types of special concrete. The acceptance tests for the special concrete discussed in"Materials and Construction: Special Concrete" shall be conducted either by the Contractor or the
Owner according to the type of concrete. When the acceptance tests for special concrete areconducted by the Contractor, the Owner needs to verify the results of inspection. The
responsibilities of the Contractor and the Owner should therefore be defined explicitly.

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1.2

GeneralDefinitions

The terms used in Standard Specifications for Concrete Structures “Materials andConstruction: Special Concrete” are defined as follows:
Expansive concrete - A type of concrete to which an expansive admixture has been added
as a mineral admixture.
Expansive admixture - An admixture that is mixed with cement and water to generate
ettringite or calcium hydroxide for causing concrete to expand.
Chemical prestress - Compressive stress that is applied to concrete when the expansion of
expansive concrete is restrained by such objects as reinforcing bars.
Chemical prestrain - Initial strain that is applied to the restraining objects when the
expansion of expansive concrete is restrained by such objects as reinforcing bars.
Shrinkage-compensating concrete - Expansive concrete with expansion capacity to offset
or reduce tensile stress caused by the drying shrinkage using chemical prestress.
Chemical prestressing concrete - Expansive concrete with expansion capacity sufficient toleave chemical prestress even in case of drying shrinkage.
Shrinkage-compensated concrete - Reinforced concrete to which chemical prestress isapplied to offset or reduce the tensile stress caused by drying shrinkage, mainly by using
shrinkage-compensating concrete and restraining the expansion of concrete withreinforcing bars or other materials.
Chemical prestressed concrete - Reinforced concrete to which high expansion capacity isprovided, mainly by using chemical prestressing concrete so that the chemical prestressthat is introduced into concrete by restraining expansion and the chemical prestrain that is
introduced to reinforcing bars may remain even where the chemical prestress andprestrain are partly eliminated by drying shrinkage
Lightweight aggregate - A kind of aggregate whose density is lighter than that of normal
rock, used for reducing concrete weight or for the purpose of thermal insulation, etc.
Lightweight aggregate concrete - Concrete with specific gravity lower than that of normal
concrete, produced using lightweight aggregate.
Surface-dry state of lightweight aggregate - The state of lightweight aggregate in which
only water on the exposed surfaces is removed from its wet state.
Specific gravity of surface-dry lightweight aggregate - The density of a lightweightaggregate particle in a surface-dry state.
Prewetting - The work of soaking aggregates before using it.
Continuous fiber reinforcing material - Concrete-reinforcing materials made of continuous
fibers bound together by adhesive. They can be unidirectional reinforcing materials,

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round-up or wove continuous fibers.
Continuous fiber tendon - Continuous fiber reinforcing material used for applying
prestress on concrete.
Continuous fiber - Continuous fiber for reinforcing the concrete such as carbon fiber,aramid fiber and glass fiber.
Fiber binder - Binder that solidifies fibers. Plastics such as epoxy resins and vinyl ester
resins.
Short fiber reinforced concrete - Steel fiber reinforced concrete or synthetic fiber
reinforced concrete.
Steel fiber reinforced concrete - Concrete made by mixing steel fiber into concrete, mainly
to improve its toughness and abrasion resistance.
Synthetic fiber reinforced concrete - Concrete mixed with synthetic fibers mainly toenhance the effectiveness for preventing explosive fracture or spalling.
Short fiber content - Volume percentage of short fibers per cubic meter of short fiber
reinforced concrete (%).
Steel fiber content - The volume percentage of total volume of steel fiber present in one
cubic meter of steel fiber reinforced concrete.
Tension softening curve - The curve expressing the relationship between tensile stress andcrack width.
Explosive fracture - Delamination or spalling of concrete surface when the concrete is
subjected to fire.
Unit volume of dry-rodded coarse aggregate - The bulk volume of coarse aggregate toproduce one cubic meter of concrete. It is obtained by dividing the unit weight of coarse
aggregate into its weight per unit bulk volume (bulk density).
High fluidity concrete - Concrete with greatly enhanced flowability but still possesses highresistance to segregation.
Self-Compactability - The property of fresh concrete to uniformly fill all corners offormworks by its own weight without the need of external compaction.
Segregation resistance - The property of fresh concrete that enables to maintain its
uniform distribution, i.e. avoiding the segregation, of constituent materials under gravity
or application of external forces.
Flowability - The property expressing the level to which fresh concrete moves undergravity or application of external force.
Passability for narrowed area - The ability of fresh concrete to pass through narrowed
gap(s) between reinforcing bars and fill up space by its own gravity without the risk of254

Chapter 1

Generalsegregation.
Viscosity agent - A type of admixture that increases viscosity and segregation resistance.
Some of them have the ability to reduce the variations in quality of fresh concrete.
Unit absolute volume of coarse aggregate - The value is obtained by dividing the unit
content of coarse aggregate by its density in saturated surface-dry state. Notation: m3/m3.
Shotcrete - Concrete conveyed by compressed air (using pump or compressor) throughthe conveying hose and sprayed from the nozzle at the end of the hose onto the target
surface.
Lining concrete - Cast-in-place concrete inside the shotcrete sprayed in a tunnel
constructed by the drill-and-blast method. Concrete is generally unreinforced. Where thelining is subjected to earth pressure or asymmetric pressure, however, reinforcing bars areused for reinforcement.
Wet spraying: Spraying of concrete mixed with all the materials using compressed air.
Dry spraying - Spraying of dry-mixed materials by pumping them using compressed air
and adding designated amounts of water at and before the spray nozzle.
Set-accelerating agent - The chemical admixture added to shotcrete in order to shorten thesetting time and increase the early strength of shotcrete.
Percentage of rebound - Percentage of the mass of concrete that rebounds without being
attached to the surface in the total mass of concrete sprayed.
Dust concentration - Mass of solid fine particles that rebound or fly from nozzles and float
in the air during spraying, expressed in milligrams per cubic meter of air.
Prepacked concrete - A kind of concrete produced by packing coarse aggregate particles
of a specified grading into formwork and grouting mortar between the voids of the
prepacked aggregates.
Grouting mortar - A mixture of cement, fly ash or other mineral admixtures, sand, chemical
admixture, and water; used for injection into pre packed concrete, etc.
Minimum size of coarse aggregate - The size of coarse aggregate specified by the nominal
size of the largest of all the sieves on which at least 95 % (by weight) of the aggregate isretained.
Underwater concrete - Any concrete used for construction under normal water, slurry or
sea-water.
Stabilizer - Liquid used mainly for preventing the collapse of tunnel walls. Composed
mainly of water and also of bentonite and polymer.
Anti-washout underwater concrete - Underwater concrete with segregation resistanceenhanced by using anti-washout admixture.
Underwater washout resistance - The ability of preventing segregation under the washout

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action of water.
Test piece made in water - The test piece made by dropping anti-washout underwater
concrete into the mold placed underwater as specified by JIS A 1132.
Test piece made in air - The test piece made by filling anti-washout underwater concrete
into the mold in air as specified by JIS A 1132.
Strength ratio of underwater concrete to normal concrete - The ratio of compressive
strength of the test piece made in water to the test piece made in air at the same age.
Prestressed concrete - A type of reinforced concrete prestressed by means of prestressing
the steel etc.
Prestressing Steel - High strength steel used to prestress concrete.
Prestress - Stress introduced in concrete before application of service loads to reduce
tensile stresses induced in concrete by loads.
Tendon - A prestressing bar or strand.
Duct - Space created through the concrete of a posttensioned prestressed concrete
member for enclosing a tendon.
Sheath - A case that forms a duct.
Anchorage fixture - A fixture for anchoring the ends of a tendon to concrete fortransmitting prestress to the member.
Connection fixture - A fixture for connecting one tendon to another.
Pretensioning - Placing concrete while tendons are provided with tension, and transmitting
the tension provided to tendons to concrete through the bond of the tendons and concrete
after the hardening of concrete, to apply prestress.
Posttensioning - Providing tension to tendons after the hardening of concrete and applying
prestress by anchoring the ends of tendons to concrete.
Grout for prestressed concrete - A mixture of cement, water and admixtures to fill the gap
between the duct and tendon after prestressing in posttensioning.
Internal prestressing method - Method of prestressing using tendons placed in theconcrete member.
External prestressing method - Method of prestressing using tendons placed outside theconcrete member.
Deviation fixture - A fixture used for maintaining or deviating the position of tendon in theexternal prestressing method.
Deviation zone - A zone where the deviation fixture is fixed to the concrete member and acomponent of the tension generated by deviating the tendon is transmitted to the member.

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Chapter 1

GeneralConcrete product - Precast concrete products manufactured in succession in controlled
factories.
Moist curing - A method of curing where concrete is kept in a moist condition for a certain
period of time after placing.
Insulated curing - A method of curing where the necessary temperature is maintained byutilizing the heat of hydration of cement and preventing escape of heat to the utmost, bycovering the surface of concrete with highly insulating materials
Accelerated curing - A curing method used to accelerate the hardening process andstrength development of concrete.
Steam curing temperature

An accelerated method of curing concrete in water vapor at highSteam curing at atmospheric pressure - Steam curing at atmospheric pressures.
Autoclave curing - A method of curing in a steam boiler (autoclave) at high temperatureand high pressure.
Centrifugal compaction - Compaction of concrete by centrifugal force using a formwork
revolving at an extremely high speed.
Casting - Production of factory products by placing concrete into a form and applying
compaction to the placed concrete.
Instant demolding - Removal of a part or all of the formworks for concrete with anextremely stiff consistency immediately after placing and compacting using strong
vibration or pressure.
Hot concrete – A concrete product of which temperature is over 40°C. immediately after thecompletion of mixing.

[Commentary] Lightweight aggregate: Lightweight aggregate is classified into artificial
lightweight aggregate, natural lightweight aggregate and by-product lightweight aggregate. In thisspecification, only structural lightweight aggregate which is consistent in quality and can be used
for making lightweight concrete is dealt with.
Surface-dry state of lightweight aggregate: For ordinary aggregates, such as river sand, rivergravel and crushed stone, the saturated surface-dry state is defined as one of the standard states of
their moisture content to be considered in expressing specified mix and other matters. In the case oflightweight aggregate, however, it is almost impossible to obtain its saturated surface-dry state,because lightweight aggregate generally absorbs much water and it takes a long time to saturate theinsides of aggregate particles. Accordingly, in the case of lightweight aggregate, the state in which
only the parts near the surfaces are nearly saturated with water and there is no water on the surface
even if the insides of aggregate particles are not saturated is defined as surface-dry state. For
practical purposes, this state is treated as the state to which saturated surface-dry state of ordinary
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aggregate corresponds. Therefore, the surface-dry state of lightweight aggregate is not a constantone, and it shall be noted that specific gravity in a surface-dry state varies depending on the degreeof water saturation.
Prewetting: Aggregates in dry state absorb water of concrete during mixing and transporting. In
order to minimize the degree of water absorption, it is necessary to conduct the work of soaking
aggregate in water before using it. This operation is called prewetting.
Continuous fiber reinforcing material: Continuous fiber reinforcing material is the generic nameof a material made of continuous fibers tied together by fiber binder for use as reinforcing material
in concrete instead of steel bar or prestressing tendon. Continuous fibers like carbon fiber, Aramid
fiber, glass fiber, or Vinylon fiber, etc, and binders like epoxy resin, vinyl ester resin, etc are usuallyused.
Steel fiber content: The reason for expressing the content of steel fiber in the unit of volume
percentage of steel fiber in one cubic meter of concrete is that the volume, not the weight, of steel
fiber in the matrix is the most directly influencing factor of the strength and deformation in steel
fiber composite material.
Tension softening curve: It is believed that at the crack tip, there is a so-called fracture processzone governed by on the formation and the development of micro-crack (Fig. C1.2.1).
Fracture process zone is classified into micro-cracking zone with many micro-cracks such as
peeling-off of mortar at the surface of aggregate and the bridging zone with aggregates or steel
fibers lying across the crack. Tension softening curve shows the relationship between tensile stresstransferred in fracture process zone at the crack tip and the crack width.
Micro cracking zone

Tensile stress

Bridging zone

Crack width
ひび割れ幅
Fracture process zone

Fig.C1.2.1
Fig.
C1.2.1 Fracture
Fractureprocessprocess zone
zone

High fluidity concrete: The definition of high fluidity concrete is in fact the definition used by
Japan Concrete Institute or Architectural Institute of Japan. However, high fluidity concrete in this258

Chapter 1

Generalspecification indicates the one with self-compactability.
Passability for narrowed area: The ability of fresh concrete which passes and fill into narrowed
areas, such as the space between reinforcing bars, by its own weight without the need of external
compaction. Passability can be approximately measured by U-shape filling test, box filling test or
funnel flow test.
Absolute volume of dry-rodded coarse aggregate per unit volume of concrete and Bulk volume
of coarse aggregate per unit volume of concrete: These values must be considered during mix
design because they affect the self-compactability of high fluidity concrete or passability. Generally,
as absolute volume of dry-rodded coarse aggregate per unit volume and bulk volume of coarse
aggregate per unit volume of concrete become small, the Young's modulus of high fluidity concrete
becomes lower, therefore, appropriate value must be determined. The weight of coarse aggregate
per unit volume of concrete depends on density of coarse aggregate even if absolute volume ofdry-rodded coarse aggregate per unit volume is the same.
Prepacked concrete: Coarse aggregate of a specific grading means the one which contains alittle amount of particles passing the 15 mm sieve. Special mortar means mortar which possesses
such properties as high flowability, little segregation, small shrinkage and expansibility.
Minimum size of coarse aggregate: The terms “minimum size of coarse aggregate” doesn’tmean the minimum size of the smallest particle. The definition was given based on the reason that it
is not practical and improper to determine the actual minimum size by measuring the individual
minimum size of particles, since coarse aggregate contains particles with various shapes. This term
is used only in the case of pre-packed concrete.
Concrete product: Some example of concrete products are Hume pipes, piles, blocks, railroad
sleepers, shield segments and precast composite slabs. They are mass-produced in succession infactories for different applications. Concrete members produced in factories are usually calledfactory product, precast product, concrete product, cement product, or prefabricated product. In thisSpecification, however, the term "concrete product" is used.
Moist curing: It is to ensure the necessary amount of water for the hydration of cement in
concrete since it is not sufficient just by preventing the evaporation of water from the placed
concrete. This curing method is also effective in preventing cracking due to drying shrinkage duringinitial hardening stage.
Temperature controlled curing: This curing method is to control the temperature in each part ofthe concrete to facilitate the normal hardening process and to avoid the cracking after hardening aswell as and the development of excessive internal stress. In utilizing this curing method, it isnecessary to take into account both the size of members and the effect of construction condition.
Accelerated curing: There are some curing methods to accelerate the hardening rate of concrete,such as steam curing, autoclave curing, hot water curing, electrical curing, infrared curing, and highfrequency curing. However, in general, steam curing is widely used.
Steam curing: Steam curing is usually conducted at a higher temperature than 35°C. Such curing
as that to maintain the temperature of concrete at a lower temperature than 35°C is not included
here.
Centrifugal compaction: Centrifugal compaction is used for the placing of concrete products of259

Standard Specifications for Concrete Structures-2007, Materials and Construction

hollow cylinders such as poles, piles, pipes and so on. The effect of centrifugal compaction isrelated to the magnitude of force originated by the revolution of formworks. The acceleration ofcentrifuge usually adopted is 20-40G.
Casting: In the production of concrete products, the process of placing concrete into a formwork
and, then, providing compaction to the placed concrete is called casting, while stripping formworks
is called demolding.
Hot concrete: Hot concrete of a temperature of 40 to 60C is used to place in a formwork andremove the form in a short time after hot curing.

260

Chapter 2

Expansive Concrete

CHAPTER 2 EXPANSIVE CONCRETE

2.1

General2.1.1 Scope
This chapter specifies standards on essential matters particularly needed for achieving
required qualities and performances of expansive concrete. ‘Expansive concretes’
referred to in this chapter are shrinkage compensating concrete and concrete forchemical prestressing.

[Commentary] Expansive concrete is a general term for a type of concrete which consists ofexpansive admixture mixed together with cement, water, fine aggregate, coarse aggregate and otheradmixtures and which possesses volume expansion even after the start of hardening. There arevarious types of expansive concrete with different qualities depending on materials and mix
proportions. In a case when expansive concretes are classified based on the expansive extent, they
are roughly divided into shrinkage compensating concrete and concrete for chemical prestressing.
And when reinforced concretes using expansive concretes are functionally classified, they areroughly divided into shrinkage compensated concrete and chemically prestressed concrete.
By restraining the expansion of expansive concrete with objects such as reinforcing bars,
compressive chemical prestress will be induced in concrete, while in the objects, tensile chemicalprestrain will be induced. Shrinkage compensated concrete is reinforced concrete imparted with asmall chemical prestress at such a level to offset or reduce tensile stress occurring due to drying
shrinkage or other causes. Chemically prestressed concrete is reinforced concrete imparted with alarge chemical prestress by the addition of a large amount of expansive admixture compared withthat in shrinkage compensated concrete, so that chemical prestress will remain even when drying
shrinkage has been offset. As a result, it is possible to demonstrate the effectiveness of chemicalprestress and chemical prestrain in the design of members and structures by utilizing chemicallyprestressed concrete.
Even when the expansive concrete having same expansive property is used for reinforced
concrete, as shown in Table C2.1.1, it is possible to functionally classify that concrete as either
shrinkage compensated concrete or chemically prestressed concrete, depending on the degree ofrestraint induced by objects such as reinforcing bars. Therefore, expansive concretes are roughly
divided into shrinkage compensating concrete and chemical prestressing concrete based on the
expansive capacity, which is totally different from the classification based on function.
In chemical prestressing concrete, the strength loss due to expansive action will not occur if
proper restraining objects are provided. However, if the provision of restraining objects is improper,
the strength loss will occur. In contrast, for shrinkage compensating concrete, expansive admixture
is used in such an amount that the obtained concrete strength is almost equal to that of concrete withthe same water-binder ratio and without expansive admixture in mix proportion.
Expansive concrete (mortar) has been applied mainly as cast-in-place concrete using
shrinkage-compensating concrete, concrete products using shrinkage-compensating concrete or261

Standard Specifications for Concrete Structures-2007, Materials and Construction

chemical prestressing concrete, various fill concrete and mortar for filling the voids in inverse lining
or below the bridge bearing. Chemical prestressing concrete is also used for cast-in-place concrete.

Table C2.1.1 Classification of expansive concrete
Type

2.1.2

Function

Shrinkage compensating concrete

Shrinkage compensating concrete

Chemical prestressing concrete

Chemically prestressed concrete

GeneralWhen using expansive concrete, materials, mix proportions, production methods,
quality management methods and construction methods shall be determined so as toproduce designated quality.

[Commentary] The expansivity of expansive concrete varies according to the type of the
expansive admixture or cement used, amount of expansive admixture per unit volume of concrete,age, method of curing, environment of the structure and dimensions of member cross section. The
performance requirements for expansive concrete vary according to whether
shrinkage-compensating or chemical prestressing concrete is used. The materials, mix proportions,production method and quality management method should therefore be determined so as toproduce designated expansivity. When applying expansive concrete, it should be managed in thephases of mix proportions design, production and construction under the guidance of professional
engineers who understand the characteristics of the concrete and have learned the use techniquesand have adequate knowledge and experience.

2.2

Quality of Expansive Concrete

2.2.1 General
Expansive concrete shall meet performance requirements in terms of workability,
strength, expansivity, durability, water tightness and steel protection. Variations of quality
shall be minimized.

[Commentary] Expansive concrete as well as ordinary concrete should have designatedworkability and expansivity with minimum variations. Variations of expansivity may prevent
shrinkage compensation or application of chemical prestress from producing an intended effect, orlead to strength reduction due to excessive expansion. The quality of expansive concrete should
therefore be fully managed.

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Expansive Concrete

2.2.2 Expansivity(1) The expansivity of expansive concrete shall be expressed in rate of expansion
obtained in accordance with JIS A 6202. The test value at an age of seven days shown in
Attachment 2 (Reference) should be used as a standard value.
(2)

The standard range of expansion coefficient of expansive concrete is shown below.

- Expansion ratio of shrinkage compensating concrete: between 150×10-6 and 250×10-6- Expansion ratio of chemical prestressing concrete: between 200×10-6 and 700×10-6
For chemical prestressing concrete used for concrete products, the upper limit ofexpansion coefficient may be set at 1000 x 10-6.

[Commentary] (1) The coefficient of expansion of expansive concrete varies according not only tothe concrete mix proportions, curing method and age but also to test conditions such as thedimensions of specimens and restraining conditions. The coefficient of expansion of expansive
concrete shall therefore be expressed in the rate of uniaxially restrained expansion obtained inaccordance with Attachment 2 (Reference) "Restrained Expansion of Expansive Concrete andShrinkage Test Method" in JIS A 6202 "Expansive Additive for Concrete". In the method,
specimens are used that have a rate of uniaxially retrained reinforcement of 0.95% provided byusing restraining fixtures (namely, restraining end plates and restraining bars (prestressing steel)). It
should be noted that the reinforcement rate is lower and the expansion rate is higher in ordinary
concrete than when the above method is employed even where the same expansive concrete is used.
The rate of expansion and the velocity of expansion vary according to the type of expansive
admixture, quantity of expansive admixture per unit volume of concrete, curing temperature and thedegree of wetting and drying. If a test is conducted in accordance with Attachment 1 (Regulations)"Method for Testing the Expansion of Expansive Admixtures by Mortar", expansion is completed at
an age of seven days. The rate of expansion is therefore expressed in uniaxially restrained
expansion rate at an age of seven days also in the testing of expansion by concrete as a standardpractice.
(2) Expansive concrete is roughly classified by major use into shrinkage-compensating concreteor chemical prestressing concrete. The standard range of expansion rate is shown for each type ofconcrete. The range of expansion rate is the same for shrinkage-compensating concrete andchemical prestressing concrete in the range between 200 x 10-6 and 250 x 10-6. The user may selectan appropriate type considering the use of expansive concrete.
When applying an expansive admixture to shrinkage-compensating concrete with a water-binder
ratio of 30% or lower such as high strength concrete and high-fluidity concrete, expansion may becontrolled at an early age because of the lack of water required for the hydration of the expansive
admixture and abnormal expansion occurs after the elapse of some time. When using an expansive
admixture for concrete with a low water-binder ratio, therefore, it is necessary to verify in advancethe type and quantity per unit volume of concrete of the expansive admixture, curing method andage at which expansivity should be determined by testing, in order to prevent abnormal expansion.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

In chemical prestressing concrete, inappropriate arrangement of reinforcing bars or steel pipes
for restraining expansion not only prevents the development of effective chemical prestress but also
deteriorates the quality of expansive concrete as described above. The area and arrangement ofreinforcing bars when using chemical prestressing concrete should be determined considering the
expansivity of concrete, type of structure, characteristics of loads, dimensions of members andconstruction method. Highly unbalanced arrangement of reinforcing bars in the cross section creates
sections with extremely high expansivity where concrete quality is deteriorated. Full attention
should therefore be paid to the area and arrangement of reinforcing bars. In ordinary reinforced
concrete structures, the area and arrangement of reinforcing bars should be determined so that the
maximum expansivity in member cross section may be held to approximately 1000 x 10-6 or lessduring and at the completion of construction. The possibility that reinforcement yields or fractures,
exhibiting brittle failure, when flexural cracks occur due to the increase of moment that induces
flexural cracks owing to chemical prestress is greater than in ordinary reinforced concrete. In orderto prevent brittle failure even at a strain of reinforcement of approximately 700 x 10-6, the tension
reinforcement ratio in rod members of rectangular cross section should be set at 0.25% or higher. In
the case of a T-shaped cross section, longitudinal reinforcement should be arranged in 0.35% ormore of the effective cross-sectional area of concrete.
For chemical prestressing concrete used for factory products, it was made permissible for theupper limit of expansion rate to be 1000×10-6, which is higher than the 700×10-6 rate forcast-in-place concrete because the control of expansion rate and of reinforcing bars arrangement, etc.
of factory products are superior compared with cast-in-place concrete.

2.2.3 Strength(1) The compressive strength of expansive concrete should be the compressive strength
at the age of 28 days
(2) The compressive strength of shrinkage compensating concrete shall be determinedin accordance with JIS A 1108 and JIS A 1132.
(3) The compressive strength of chemical prestressing concrete should be determined inaccordance with Appendix 3 of JIS A 6202.

[Commentary] (1) and (2) The compressive strength of expansive concrete shall be thecompressive strength at the age of 28 days as for ordinary concrete. For shrinkage-compensatingconcrete, compressive strength and strength development identified in JIS (Japan Industrial
Standards)-designated testing are similar to those for concrete with no cement replaced withexpansive admixtures, so compressive strength shall be obtained in the same tests as those forordinary concrete.
(3) Chemical prestressing concrete has higher expansivity than shrinkage-compensatingconcrete. There are therefore cases where the compressive strength obtained in accordance with JIS

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A 1108 "Method of Test for Compressive Strength of Concrete" and JIS A 1132 "Method of Making
and Curing Concrete Specimens" is greatly reduced due to excessive free expansion. Thus, usecondition may be much different from actual conditions. Then, it becomes necessary to obtaincompressive strength using specimens that are left in the formwork up to the start of compressive
strength tests in accordance with Attachment 3 (Reference) "Method for Testing Compressive
Strength by Curing Expansive Concrete Under Restrained Condition" to JIS A 6202.

2.3

Materials

2.3.1 Cement
Cements that comply with JIS R 5210, JIS R 521 1, JIS R 5212, and JIS R 5213 should be
used.

[Commentary] Cements generally used for expansive concrete are ordinary Portland cement,
moderate heat Portland cement, high-early-strength Portland cement, fly ash cement type B andblastfurnace slag cement type B. As long as these types of cements have been used, no abnormal
expansion characteristics have been recognized. Then, it has been verified that the type of cement
has little effect on expansivity. When using low-heat Portland cement or blended cement containing
three cementitious materials with high content of blast furnace slag or fly ash, expansion sometimes
occurs early or expansivity increases as setting of concrete or development of strength varies. These
cements should therefore be used only after the achievement of designated performancerequirements is verified by conducting tests or based on the records of use.

2.3.2 Expansive admixture(1) The expansive admixture that complies with JIS A 6202 should be used.
(2) When using other expansive admixtures than those described in (1) above, their
quality shall be verified and the method of use should be fully examined.
(3) Expansive admixtures shall be stored so as to maintain their quality.

[Commentary] (1) Expansive admixtures used for expansive concrete are divided into two major
types according mainly to chemical composition: calcium sulfo-aluminate type (CSA type) andcalcareous type (CaO type). In shrinkage-compensating concrete using these types of admixtures,the quantity of expansive admixture per unit volume of concrete has conventionally been set at 30kg/m3 as a standard. In recent years, calcium sulfo-aluminate/calcareous composite expansive
admixtures and expansive admixtures with high content of calcareous components and low ratio ofadditives have been put to practical use, and the standard quantity of expansive admixture per unit
volume of concrete has been set at 20 kg/m3 in numerous applications. It has been reported that
expansive admixtures with a low ratio of additives produce similar expansivity as in the past even at
20 kg/m3. JIS A 6202 has, however, been established for expansive admixtures that are used at 30kg/m3, the amount used for conventional shrinkage-compensating concrete. It was then stipulated265

Standard Specifications for Concrete Structures-2007, Materials and Constructionthat a quantity of expansive admixture of 20 kg/m3 per unit volume of concrete may be used as astandard when conducting tests in accordance with JIS A 6202 for expansive admixtures with a low
ratio of additives. It was also stipulated that either conventional expansive admixtures or expansive
admixtures with a low ratio of additives should meet the quality requirements for expansive
admixtures specified in JIS A 6202.
(2) As other expansive admixtures than those described in (1) above, expansive admixtures formass concrete (also referred to as hydration heat control type) for reducing cracks due to thermal
stress, and high-early-strength expansive admixtures for concrete products have been put topractical use. These admixtures are sometimes mixed with additives for controlling the heat ofhydration or developing strength early. Then, the requirements for ignition loss stipulated in JIS A
6202 may sometimes not be met. This is because in the tests of ignition loss, the additives
mentioned above are detected while ignition loss provides guidelines for determining theweathering of expansive admixtures. These expansive admixtures should therefore be used only
after verifying other quality parameters than ignition loss that are specified in JIS A 6202 andverifying that the quality requirements for expansive concrete are met based on the existing records
or by conducting tests.
(3) Since expansive admixtures contain large amount of free calcium oxide, it can be moreeasily weathered compared with cement. If expansive admixture is weathered by atmosphericmoisture or carbon dioxide, its expansive property is reduced and, consequently, the required
performance of expansive concrete may not be obtained. Therefore, the following points should beconsidered when storing expansive admixtures:
1) The expansive admixture shall generally be stored in a silo having humidity-proof structure
exclusively used for expansive admixture in such a way that it will not become mixed withcement and other materials.
2) Bagged expansive admixture shall be stored in such a manner that it will not be in directcontact with the floor inside the storeroom, and arranged in a convenient order for hauling out
and inspection.
3) Bags of expansive admixture shall be opened just before using, and admixture bags broken
during storage shall not be used.
4) If the storage period is relatively long, tests shall be performed before using, to confirm all
the required properties

2.4

Mix Proportion

2.4.1 General
When designing expansive concrete mix proportions, the quantity of water per unit
volume of concrete should be minimized while ensuring the achievement of performancerequirements in terms of strength, expansivity, durability, resistance to cracking,watertightness and steel protection, and providing appropriate workability.

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Expansive Concrete[Commentary] It is extremely important to minimize the quantity of water per unit volume of
expansive concrete as long as the designated performance requirements are met as for ordinary
concrete.

2.4.2 Quantity of expansive admixture per unit volume of concrete
The quantity of expansive admixture per unit volume of expansive concrete should bedetermined through testing so as to provide the designated expansivity. For
shrinkage-compensating concrete, the quantity of expansive admixture may generally be
determined based on reliable documents.

[Commentary] The effectiveness of the shrinkage compensation and chemical prestressing of
expansive concrete in a structure is higher with larger expansion rate. However, when the expansion
rate is too high, the compressive strength of concrete is lower compared with non-expansive
concrete of the same mix proportions. Therefore, it is important to find an appropriate range of
expansion rate within that the strength declination does not occur.
When air content and slump are constant, the expansion rate of expansive concrete is mostly
decided by the unit expansive admixture content regardless the water-cement ratio and the unit
cement content. Therefore, in order to experimentally determine a unit expansive admixture content,
concrete with a properly selected mix proportions and three different expansive admixture contents
is tested in accordance with the Appendix 2 “Testing Method for Restrained Expansion and
Shrinkage of Expansive Concrete” in JIS A 6202. Basing on the experimental results, the unit
expansive admixture content corresponding to the desired concrete expansion rate will be selected.
In addition, expansive admixture content for shrinkage compensating concrete can also be
determined based on available data of reliable sources. Table C2.4.1 shows the types of expansive
admixtures and standard quantities per unit volume of concrete for shrinkage-compensating andchemical prestressing concrete.
Table C2.4.1 Types of expansive admixtures and standard quantities of expansive admixtures perunit volume of concreteType of expansive concreteType of expansive admixture

For ordinary
concrete
Shrinkage-compensatingconcrete
For mass concrete

Chemical prestressing
concrete

Standard quantity of
expansive admixture per unit
volume of concrete (kg/m3)

Conventional type30

Low ratio ofadditives

20

Conventional type30

Low ratio ofadditives

20

For ordinary concrete

35～50

For concrete products

30～60

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Standard Specifications for Concrete Structures-2007, Materials and Construction

2.4.3 Quantity of cement per unit volume of concrete
The standard quantity of cement per unit volume of expansive concrete should be 260
kg/m3 or larger.

[Commentary] The strength and rate of expansion of expansive concrete are determined by thequantities of cement and expansive admixture, which are components of expansive concrete, perunit volume of concrete. The quantity of expansive admixture required to obtain the designated rateof expansion is generally determined based on the assumption of a constant quantity of binders(cement and expansive admixture) per unit volume of concrete identified by replacing the expansive
admixture with cement in numerous cases. Then, increasing the quantity of expansive admixture perunit volume of concrete to obtain higher rate of expansion is likely to increase the ratio of the unit
quantity of expansive admixture to the unit quantity of cement and deteriorate the strength anddurability of concrete. These phenomena are found in concrete with a small quantity of binder per
unit volume. Then, the standard minimum quantity of cement per unit volume of concrete shall be
set at 260 kg/m3.

2.4.4 Presentation of mix proportion
As a general rule, mix proportions should be presented as shown in Table 2.4.1.
Table 2.4.1 Representation of mix proportion

Maximum
size of coarse Slumpaggeregate
(cm)
(mm)

Air
content(%)

Water-tobinder ratio

Volumeof sand

W/(C+F)

s/a

(%)

(%)

Unit content (kg/m3)

Admixtures F
Water

CementW

C

Expansive
agent

Other
admixtures

E

F’

CoarseFine
aggregate
S

Aggregate G
mm -

mm -

mm

mm

Chemical
admixture

A unit for amount of chemical admixture that should not be diluted and dissolved is ml/m3 or g/m3.

[Commentary] Water-cement ratio is regarded as water-binder ratio and unit quantities arepresented for expansive admixture E and other admixture F' in accordance with Table 4.4.1 Methodof expression of mix proportions in Section 4.7 of "Material and Construction: Construction
Standards".

2.5

Production and Construction

2.5.1 Mixing(1) For mixing, mixers with the designated mixing capability should be used as a

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Expansive Concrete

standard practice.
(2) Method for putting expansive admixtures into the mixer and mixing time should bedetermined by testing so that concrete may meet the designated quality requirements as astandard practice. The method and mixing time may be determined based on reliable
documents or records whenever available.

[Commentary] (1) If mixing of expansive admixtures is insufficient although admixtures areaccurately measured and input, expansive admixtures may sometimes be distributed unevenly inconcrete and form masses or are provided in excessive quantities in some sections. Then, thestrength of concrete may be reduced after hardening or expansion failure may occur locally. For
mixing, therefore, the mixers specified in Section 5.2.3 of "Material and Construction: Construction
Standards" should be used as a standard practice so that expansive admixtures or other concretematerials may be distributed fully evenly.
(2) Expansive admixtures should be mixed only after appropriate input procedure and mixing
time are determined through testing so that expansive admixtures may be mixed in concrete fully
evenly.
Generally, expansive admixture should be charged in at the same time with cement. If expansive
admixture is charged in the mixer to the mixture either together with other materials or separately,
the confirmation on whether it is thoroughly mixed or not shall be carried out in advance by
experiments.
If expansive admixtures adhere to the inlet, inner wall of the mixer or mixing blades and form
masses when expansive concrete is continuously mixed, the mixing of masses or fragments into
concrete is likely to cause local expansion failure as in the cases described above. Masses of
expansive admixtures should be removed immediately after they are formed. The location andprocedure of input should be reviewed to prevent masses of admixture from forming.

2.5.2

Curing(1) Expansive concrete should be maintained in a moist condition at all times for at least
5 days after placement(2) In cases when steam curing or other accelerated curing methods are used, a test
should be carried out to ensure in advance that the required quality can be obtained
through the considering curing method.

[Commentary] (1) The purpose of expansive concrete is to compensate shrinkage, reduce crack
generation due to shrinkage and introduce chemical prestress in order to improve mechanicalpropertied of concrete structure. For expansive concrete, the moist curing at the early stages is very
important, not only for the strength development but also to obtain the required expansion.
Therefore, if there is a possibility of formworks being dried due to small thickness or hightemperature, formworks should be sprinkled with water and maintained in a moist condition. Whenformworks are removed within 5 days after placing concrete, exposed surfaces should bemaintained in a moist condition. Expansive concrete generally ceases expanding at an age ofapproximately five days at normal temperatures. Expansive concrete shall therefore be kept
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Standard Specifications for Concrete Structures-2007, Materials and Construction

constantly wet for at least five days after placement as a standard practice. If the shoring is removed
within five days of placement, wet curing is required such as spraying water on the exposed surface
or laying curing membrane over the concrete.
(2) If special curing methods, such as steam curing, insulated curing or heating, are applied, it isimportant to confirm in advance by experiments that the required properties of concrete will besatisfied.

2.6

Inspections

2.6.1 Expansive admixture acceptance tests
Conducting acceptance tests for expansive admixtures shall be the responsibility of theaccepting party. Inspections should be conducted in accordance with Table 2.6.1.
Table 2.6.1
Type

Expansive
admixture

Item

Quality

Expansive admixture acceptance tests

Testing methods/ Inspection
methodVerification based on the test records
prepared by the manufacturer or by
the method specified in JIS A 6202

Period/Frequency

Criteria for judgment

At the delivery ofmaterials

Compliance with JIS A 6202
(or through consultation with
the Owner)[Commentary] The party accepting expansive admixtures in the acceptance tests means the
manufacturer of expansive admixtures. The results of inspections shall be confirmed by the Ownerof the structure. Expansive admixtures may be inspected by verifying the test records prepared by
the manufacturer. For expansive admixtures not meeting the quality criteria of JIS A 6202 such as
expansive admixtures for mass concrete and high-early-strength expansive admixtures described in
Section 2.3.2 (2), decision criteria should be defined through mutual consultations with the Owner.

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2.6.2

Expansive Concrete

Concrete acceptance tests

Conducting acceptance tests for expansive concrete shall be the responsibility of theaccepting party. Inspections should be conducted in accordance with Table 2.6.2.

Table 2.6.2
Type

Acceptance tests for expansive concrete

Item

Testing methods/ Inspection
methodPeriod/Frequency

Criteria forjudgment

Expansion

Confirmation of used
expansive admixture content

When unloading,for all batches

Within ±3% ofexpansive admixture
content stipulated in
the Specification

Testing method in JIS A
1108 and JIS A 1132

Determined byconsidering theimportance and thescale of structure

It shall be madepossible to estimatethat the probability ofthe strength of
expansive concretedecreasing below thedesign strength is 5%
or lower based on the
producer's risk ratio.

Testing method in reference
No. 2 of JIS A 6202

When unloading, once a
day or once every
20-150m3, depending
upon the importance ofstructure and the scaleof the construction
work

Within ±15% ofexpansion ratio asprescribed

Determined byconsidering theimportance and thescale of structure

It shall be madepossible to estimatethat the probability ofthe strength of
expansive concretedecreasing below thedesign strength is 5%
or lower based on the
producer's risk ratio.

Shrinkagecompensatingconcrete
Strength

Expansion

Chemicalprestressing
concrete
Strength

Testing method in reference
No. 3 in JIS A 6202

[Commentary] The party accepting expansive concrete in the acceptance tests means the Ownerof the structure. There are, however, cases in which the Contractor of expansive concrete conducts
tests and the Owner confirms the results. In the design of mix proportions of expansive concrete, it
has been verified that the rate of expansion of expansive concrete is nearly proportional to thequantity of expansive admixture per unit volume of concrete. Therefore, the inspection of the
expansion for shrinkage compensating concrete can be replaced by confirming the expansive
admixture content in the mix proportion record when concrete is unloaded at construction site.
The meaning of “when unloading, for all batches” in Table 2.6.2 is that the confirmation must
be made if the fluctuation of the expansive admixture content in all mixing batches is within ±3% of
the content stipulated in specified mix proportion when concrete is unloaded from agitator trucks tothe site.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

For chemical prestressing concrete, the required expansion ratio is substantially larger and thelack of expansion also causes more negative effect on the structure compared with shrinkage
compensating concrete. Therefore, the inspection of expansion must be carried out by expansion
tests. Regarding the inspection of concrete strength, tests on compressive strength should be carriedout by compression test considering characteristics of expansive concrete.
Other concrete inspections shall be conducted in accordance with Chapter 16 of "Materials andConstruction: Construction Standards" and "Materials and Construction: Inspection Standards".

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Chapter 3

Lightweight Aggregate Concrete

CHAPTER 3 LIGHTWEIGHT AGGREGATE CONCRETE

3.1

General

3.1.1

Scope

This chapter specifies standards on essential matters particularly required for theconstruction of lightweight aggregate concrete.

[Commentary] Over 40 years have passed since lightweight aggregate concrete was first used for
civil structures in Japan. Consequently, the reliability to its durability is gradually increasing withincrease of the experiences related to the design and construction. At present, it is possible to handle
lightweight aggregate concrete in almost the same manner as normal aggregate concrete, except foritems that require special attention. This chapter focuses on the matters required. For matters notreferred to in this chapter, lightweight aggregate concrete shall be handled as if it were concrete
using ordinary aggregate.
In this chapter, it is noted that concrete with artificial lightweight aggregate is simply called aslightweight aggregate concrete and artificial lightweight aggregate is also called as lightweightaggregate.
For the construction of lightweight aggregate concrete, “Manual of Design and Construction forLightweight Aggregate Concrete” and “Recommendation on Design and Construction of Concrete
Using High Strength Lightweight Aggregate Made of Fly Ash” published by JSCE are referred.

3.1.2

GeneralWhen constructing lightweight aggregate concrete, the qualities of lightweightaggregate and of lightweight aggregate concrete shall be fully examined so as to meet thedesignated performance requirements.

[Commentary] The basic matters to be considered when using lightweight aggregate concrete aredescribed in detail in 3.2 Quality of Lightweight Aggregate and 3.3 Quality of Lightweight
Aggregate Concrete. These sections should be consulted during construction.

3.2

Quality of Lightweight Aggregate(1) Lightweight aggregate should comply with the aggregate classified in category 3

and 4 for concrete compressive strength specified in the JIS A 5002.
(2) In principle, when using lightweight aggregate concrete for structures subjected tofreezing and thawing action, the freeze-thaw resistance of the concrete using thatlightweight aggregate should be confirmed based on past experiences and records.
However, it may be sufficient to confirm the freeze-thaw resistance of aggregate byreferring to the result of freezing and thawing test on concrete carried out in accordance273

Standard Specifications for Concrete Structures-2007, Materials and Construction

with JIS A 1148.
(3) Whether alkali-silica reaction of lightweight aggregate occurs or not shall be verified
based on the use records or in the concrete prism test.

[Commentary] (1) Because different types of lightweight aggregate are characterized by different
properties, not all types of lightweight aggregate are necessarily suitable for the use in civil
structures. Therefore, in this standard specification, lightweight aggregates made of expanded shale,
expanded clay, pearl stone, fly ash, etc. that can be used for the concrete with adequate lightweightand strength are specified. These lightweight aggregates used as fine and coarse one are classified in
the level 3 and 4 concerning compressive strength of concrete specified in JIS A 5002 “Structural
Lightweight Aggregate for Concrete”.
They are generally clean, hard and properly distributed in the particle size and less scattered in
the quality because of manufacturing in factories. However poor manufacturing processes andquality control will result in producing low quality aggregates and hence inadequate properties ofconcrete. Therefore, good quality products shall be selected for the use of lightweight aggregate. In
addition, the properties of fresh and hardened lightweight aggregate concrete, such as workability,
strength, durability, may be adversely affected because of lower strength characteristics and higher
water absorption of the lightweight aggregate compared with the natural aggregates or the normal
aggregates. Therefore it is important to acknowledge the properties of lightweight aggregate.
High-strength and low-water-absorption lightweight aggregates have recently been developedby improving the materials used and the methods of production. High strength lightweightaggregate made of fly ash (HFA) is an example. These aggregates, with no continuous air voids,
have low water absorption and high strength. The lightweight aggregate concrete using theselightweight aggregate has much better basic quality in such terms as the ease of construction,
strength and durability than conventional lightweight aggregate concrete and compares favorablywith ordinary aggregate concrete. Table C3.2.1 compares the absolute dry density (standards) ofaggregates. The absolute dry density of lightweight aggregates actually put to use varies greatly
from 0.75 g/cm3 to 2.0 g/cm3. The characteristics of lightweight aggregates also vary accordingly.
For constructing lightweight aggregate concrete structures that meet performance requirements,
therefore, aggregates should be selected that are fit for the use, and construction should be carriedout considering the quality of aggregates.
Table C3.2.1

Comparison of absolute dry density (standards) of aggregate

Aggregate
JIS A 5005 Crushed stone for concrete
JIS A 5002 Class H, Lightweight Coarse aggregate
aggregates for structural concrete
Fine aggregate
JIS A 5002 Class M, Lightweight Coarse aggregate
aggregates for structural concrete
Fine aggregate
JIS A 5002 Class L, Lightweight Coarse aggregate
aggregates for structural concrete
Fine aggregate
High strength aggregate of fly ash (HFA)

Absolute dry density (g/cm3)
Over 2.5
Over 1.5 and below 2.0
Over 1.8 and below 2.3
Over 1.0 and below 1.5
Over 1.3 and below 2.8
Below 1.0
Below 1.3
Not more than 2.0(2) JIS A1122 “Test Method for the Stability of Aggregate Using Sodium Sulfate” is employed
to test the performance of aggregate under weathering actions such as freezing and thawing action.
However, in general, lightweight aggregate is hardly tested for its performance against frost damage
by this method. The internal factor that affects the resistance of lightweight aggregate concrete274

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Lightweight Aggregate Concrete

against frost damage is the relationship between pore structures of the lightweight aggregate andthose of interfaced mortar. Therefore the performance against frost damage of lightweight aggregate
itself is not specified but is to be investigated as lightweight aggregate concrete on the basis of pastrecords. In addition, the freeze-thaw resistance of lightweight aggregate may be investigated byusing the result of the freezing and thawing test according to JIS A 1148 “Test Method of Freezing
and Thawing for Concrete”.
In case where the concrete with lightweight aggregate of high water absorption ratio istransported using a concrete pump, large amount of pre-wetting is necessary to prevent the blockade.
However, Concrete that uses adequately pre-wetted low water absorption lightweight aggregate ispoorly resistant to freezing and thawing action and should not be used in structures that are
subjected to freezing and thawing.
Conventional lightweight aggregates have continuous pore spaces and hence need to be used
under high water content by pre-wetting. On the other hand, nowadays, the lightweight aggregatewith the water absorption lower than 5% is being used. The low water absorption type oflightweight aggregates has isolated pore spaces in the pore structure. Their use with carefully
designed mixture proportions enables to transport the concrete using a concrete pump without large
amount of water brought into concrete. It also turns out to increase the freeze-thaw resistance.
(3) When a glass phase is formed on the surface of the shell of aggregate in the course ofburning of lightweight aggregate, alkali-silica reaction is likely to occur in the concrete using thelightweight aggregate. For using the aggregate, therefore, whether alkali-silica reaction of theconcrete to be produced occurs or not should be verified in advance.
The reactivity of lightweight aggregate to alkali-silica reaction should be determined based on
the use records. If use records are unavailable or unknown, verification should be made by
conducting tests.
Using crushed lightweight aggregate in testing creates a condition different from that inconcrete. JIS A 1145 "Method for testing alkali-silica reactivity of aggregate (chemical method)"therefore stipulates that no chemical methods should be applied to lightweight aggregate. JIS A
1146 "Method for testing alkali-silica reactivity of aggregate (mortar-bar method)" uses crushed
aggregate with the grading of fine aggregate. Crushed and non-crushed lightweight aggregates areof highly different physical and chemical nature. Neither chemical nor mortar-bar method candetermine the alkali-silica reactivity of lightweight aggregate itself. The alkali-silica reactivity oflightweight aggregate needs to be evaluated in tests using concrete using the aggregate. Concretebar methods using concrete include the promotion of alkali-silica reaction by adding alkali inside
the concrete (e.g. JCI method (JCI AAR-3) and Canadian method) and the promotion of alkali-silica
reaction by supplying alkali (NaOH, NaCl, etc.) from outside (e.g. ASTM method and Danish
method). A test method fit for the specific use should be selected.

3.3

Quality of Lightweight Aggregate Concrete(1) Lightweight aggregate concrete shall be of homogeneous quality, fit for work andsufficiently workable to enable tight placement in the formwork. After hardening,lightweight aggregate concrete shall have the designated strength, durability and watertightness.
(2) When concrete pumps are used for transport at the site, lightweight aggregate
concrete shall have adequate pumpability.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(3) Bulk density of lightweight aggregate concrete shall be appropriately specified andfall in the range of the bulk density determined in structure design. Lightweight aggregate
concrete are classified into two types – lightweight aggregate concrete Type I andlightweight aggregate concrete Type II. Table 3.3.1 gives the standard range of the bulk
density of the two types, respectively.
Table 3.3.1 Range of bulk density and combination of aggregate
Type oflightweightaggregateconcrete

Range ofbulk density(kg/m3)

Type I

1,600～2,100

Either lightweight aggregate
or partially normal aggregate

Normal aggregate

Type II

1,200～1,700

Either lightweight aggregate
or partially normal aggregate

Either lightweight aggregate
or partially normal aggregate

Aggregate used
Coarse aggregate

Fine aggregate[Commentary] (1) The quality of lightweight aggregate concrete in such terms as strength, massof unit volume, durability and water tightness should reach the designated level specified in thedesign of members and be able to facilitate construction. The quality varies greatly according to thetype and combination of aggregates, and concrete mix proportions, so full examination should be
made.
Lightweight aggregate concrete shall be classified into type I or II according to the combinationof aggregates (Table 3.3.1). For making an effective use of light weight of lightweight aggregate
concrete, using lightweight fine and coarse aggregates can reduce the mass of unit volume oflightweight aggregate concrete to approximately 1,200 kg/m3. In cases where increasing thestrength and durability is required, lightweight aggregates may partly be replaced with ordinary
aggregates. Some of the coarse aggregates may be replaced with ordinary aggregates or some of thecoarse and fine aggregates may be replaced with ordinary aggregates (Table 3.3.1). Table C3.3.1
roughly shows the range of masses of unit volume of concrete using various types of aggregates(using ordinary Portland cement and with a water-cement ratio of 40 to 60%). The mass of unit
volume of concrete made of high strength lightweight aggregate made of fly ash (HFA) is slightly
larger than that of lightweight aggregate concrete type I but is smaller than that of ordinary
aggregate concrete by approximately 10%.
Table C3.3.1 Bulk density of concrete
Aggregate
Coarse aggregate

Fine aggregate

Bulk density of concrete(kg/m3)

Crushed stone

Pit sand

2,200〜2,400

HFA

Pit sand

2,000〜2,100

Lightweight aggregate

Pit sand

1,900〜2,100(i) Fresh properties : The construction of lightweight aggregate concrete, unlike the constructionof ordinary aggregate concrete, generally involves the pre-wetting of aggregate and requires
construction as air-entrained concrete. In the case of pumping, high performance air-entraining276

Chapter 3

Lightweight Aggregate Concrete

agents should be used. The properties of air-entraining agents need to be evaluated by testing
before construction.
(ii) Strength : Lightweight aggregate concrete provides similar compressive strength to that ofordinary aggregate concrete. Other types of strength than compressive strength can be
estimated based on the compressive strength. Aggregates, however, have strength limits. It
should therefore be noted that the limit of compressive strength of generally used lightweightaggregate concrete is approximately 60 N/mm2 and that the tensile and shear strengths(approximately 60 to 80% of those of ordinary aggregate concrete) and Young's modulus(approximately 40 to 80% of that of ordinary aggregate concrete) are much smaller than thoseof ordinary aggregate concrete. Lightweight aggregate concrete is easy to crumble due to highlocal impact. In sections that are likely to be subjected to impact, therefore, arranging
additional reinforcement or making a relatively large chamfer by cutting off the corner of themember is required. In the points where extremely large impact is expected to act, nolightweight aggregate concrete should be used.
For some of the high-strength, low-water-absorption lightweight aggregates that haverecently been developed, the above description may not be applicable because there may be a
linear relationship between compressive strength and water-cement ratio as long as thewater-cement ratio is less than approximately 25% (compressive strength is approximately 70
to 80 N/mm2).
(iii) Resistance to freezing and thawing action : Lightweight aggregate concrete generally
exhibits lower performance against freezing and thawing action because of larger water
absorption of the lightweight aggregate. On the other hand, sufficient performance against
freezing-thawing action can be generally given in the lightweight aggregate concrete, whenusing the lightweight aggregates whose adequate freeze-thaw resistance has been proved by thepast experiences or freezing and thawing tests and the concrete being an air entrained one ofwhich water to cement ratio is smaller than that described in Section 3.4.3(2). Increasing air
content slightly, using lightweight aggregate under a dry condition as long as reliable
construction management is possible, and replacing part or all of the coarse aggregates withordinary aggregates are effective for increasing the durability of lightweight aggregate concrete.
It should, however, be noted that concrete using lightweight aggregates that are considerably
pre-wetted to prevent pump clogging suffer the reduction of resistance to freezing and thawing
action. Concrete using high strength, low-water-absorption aggregates contains little waterowing to low absorption and provides for pumping without increasing pre-wetting. The
concrete therefore has similar resistance to freezing and thawing action as ordinary aggregate
concrete with the same water-cement ratio and air content.
The freezing and thawing test that is generally employed in Japan is either the one
conducted under submerged in water conditions, provided in JIS A 1148 “Freezing andThawing Test for Concrete, Method A”. In the case when the frost resistance of lightweightaggregate concrete is tested using this method, the concrete with the pre-wetted lightweightaggregate, having 25 to 30% of the water content, normally shows significantly lower
performance as compared with normal weight concrete that is used for the same mixture
proportioning. However it is not always true that the result of the freezing and thawing test canaccurately represent the actual performance of lightweight aggregate concrete structures. Thisis because the test conditions such as the speed of a freezing and thawing cycle, the minimum
temperature, the number of cycles given continuously and the degree of the saturation anddryness in specimens are much more severe than those actually encountered under service
conditions.
Considering above reasons it is practically impossible to predict the service life period of277

Standard Specifications for Concrete Structures-2007, Materials and Construction

lightweight aggregate concrete structures and to judge if lightweight aggregate concrete is to
be used based on the results obtained only from the freezing and thawing test undersubmergence in water like JIS A 1148, Method A. Therefore other test methods, such as JIS
A1148, Method B for the freezing and thawing test under an air condition, may be used for theverification to account for the weather and other environmental conditions of concrete
structures and members under consideration. In addition, when past records and practices
under similar conditions are available they can be regarded as important such that theproperties of lightweight aggregate used and the entrained air content may be used to verify the
frost resistance of concrete under consideration.
(iv) Water tightness : The water tightness of lightweight aggregate concrete, if the concrete
causes little bleeding and is homogeneous, is the same as that of ordinary aggregate concrete.
Air-entrained concrete with a water-cement ratio shown in Section 3.4.3 (3) using aggregates
for which water tightness has been confirmed based on the past examples and by conducting
permeability tests for the concrete may have practical water tightness.
(2) For the transportation of lightweight aggregate concrete using a concrete pump theworkability is significantly reduced due to the absorption of water into the lightweight aggregate by
the pumping pressure and its reduction is followed by the blockage of the concrete inside the pump.
These are different from the cases with normal weight concrete. To avoid this, the maximum
pumping load (Pmax) on a concrete pump is generally ensured to be less than 80% of the maximum
theoretical discharging pressure of the pump described in Section 7.3.2 of "Construction:
Construction Standards" by properly specifying the absorption of aggregate, the water content of
aggregate, the workability of concrete and the types of concrete pump considering the properties oflightweight aggregate. In addition, it may be referred to the past similar construction records andexperimental data.
Lightweight aggregate concrete with a slump of 18 cm or higher and with mix proportions
leading to low cohesiveness provides an excellent pumpability. Standard pressure loss in pipeduring the pumping of lightweight aggregate concrete required for calculating Pmax is shown in Fig.
C3.3.1 for reference.
For pumping lightweight aggregate concrete, pre-wetted lightweight aggregates are used andhigh performance water reducers are used to increase the slump of concrete during transportation.
Lightweight aggregates with low water absorption that have recently been developed for higher
durability may not cause pumpability to be deteriorated even when used without increasing thelevel of pre-wetting.

Fig. C3.3.1 Standard values of the loss in pressure of lightweight aggregate concrete278Chapter 3

Lightweight Aggregate Concrete(3) Since the purpose of the use of lightweight aggregate concrete is to reduce the dead weightof the structure, the bulk density should be specified as the required performance. Type and bulk
density of lightweight aggregate concrete shall be established considering the size and shape ofstructure and member, types of structure, construction method, environmental conditions and the
purpose of structure.
In general, if actual bulk density is larger than that specified at design, the results become
improper due to increase of weight of structures. However, it may not be always safe even when theactual bulk density is smaller than the specified value. In this way the verification is to be made.

3.4

Mix proportions

3.4.1

GeneralLightweight aggregate concrete should be used as air-entrained concrete. Unit watercontent should be minimized by conducting testing as long as the designated strength,
unit mass of volume, resistance to freezing and thawing action, water tightness, resistanceto cracking and workability sufficient for work are available.

[Commentary] Lightweight aggregates have varying grain size, density, water absorption andstrength according to the type. Mix proportions should therefore be determined after verifying
whether the specific lightweight aggregate produces concrete of designated quality or not in testing.
In the case of lightweight aggregate concrete as in the case of ordinary aggregate concrete, using
concrete with a high unit water content is likely to increase unit cement content, resulting in cost
increase, and cause aggregate segregation and cracking. Thus, producing flawless concrete may bedifficult.
For certain types of lightweight aggregates, the unit water content required for obtaining
workability as designated is higher than for ordinary aggregates and the resistance to freezing andthawing action may sometimes be reduced. Then, unit water content should be reduced using water
reducers, air-entraining agents, high performance water reducers, etc. Using these agents may also
improve the resistance of lightweight aggregate concrete to freezing and thawing action. Thus,lightweight aggregate concrete shall in principle be used as air-entrained concrete as well as
ordinary aggregate concrete.

3.4.2

Mass of unit volume

In order to achieve the mass of unit volume of lightweight aggregate concrete as
specified in design, lightweight aggregates shall be properly combined with ordinary
aggregates.

[Commentary] The objective of using lightweight aggregate concrete is to obtain the benefit ofweight reduction. Mix proportions should therefore be determined in design to achieve thedesignated mass of unit volume of concrete. The most important factor that determines the mass ofunit volume of concrete is density. The type and combination of aggregates should be specified
properly based on the concrete quality shown in Section 3.3. Combining aggregates is naturally
important to the satisfaction of performance requirements for concrete in such terms as strength anddurability. The ordinary aggregates used for lightweight aggregate concrete should in principle
satisfy the stipulations in Section 3.4 of "materials and Construction: Construction Standards".
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Standard Specifications for Concrete Structures-2007, Materials and Construction

3.4.3

Water-cement ratio(1) When determining the water-cement ratio based on the compressive strength of
concrete, the procedure shall conform to Section 4.4.3 of "Materials and Construction:
Construction Standards".
(2) When determining the water-cement ratio based on the resistance of concrete to
freezing and thawing action, the ratio should be 5% lower than that used in ordinary
aggregate.
(3) When determining the water-cement ratio based on the water tightness of concrete,
the ratio should be 55% or lower.

[Commentary] (2) In relation to the actual resistance of lightweight aggregate concrete to
freezing and thawing action, no report has been made on the deterioration of resistance oflightweight aggregate concrete to freezing and thawing action which has been in service for morethan 15 years in cold areas in Japan. According to the results of tests for freezing and thawing
resistance of concrete under severe conditions in laboratory, however, lightweight aggregate
concrete has been found slightly less resistant to freezing than ordinary aggregate concrete. The
maximum water-cement ratio shall therefore be set 5% lower than that given ratios in Table C5.2.11of “Design: Main Text”, Standard Specifications for concrete Structures to ensure safety. The
water-cement ratio is obtained in cases where concrete is properly placed, compacted and cured. In
cases where no adequate curing is expected, a value lower than that shown in the table should bespecified.
The water-cement ratio determined by durability in cases where lightweight aggregate concreteis used for offshore structures may be equivalent to that for ordinary aggregate concrete in cases
where the temperature rarely falls below zero and no concrete is saturated with water. For structuresthat are saturated with water because of severe meteorological conditions, water-cement ratio
should be determined based on the comprehensive consideration of materials used, construction
conditions, measures to enhance durability and the importance of the structure. In the field,
water-cement ratio should be set at a value 2 to 3% lower than designated considering the change inwater content of aggregate and errors in material measurement.
(3) Water tightness of lightweight aggregate concrete may be assumed to be the same as that ofordinary aggregate concrete and is specified according to Section 2.6 of "Materials andConstruction: Construction Standards".

3.4.4

Slump

(1) Slump of concrete shall be set at the minimum level possible as long as the concrete
is fit for work.
(2) Slump of concrete should conform to Section 4.4.2 of "Materials and Construction:
Construction Standards".
(3) When pumping lightweight aggregate concrete, slump before pumping should be set
at 18 cm as a standard practice.
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Chapter 3

Lightweight Aggregate Concrete[Commentary] (2) Lightweight aggregate concrete tends to exhibit lower slump than that ofnormal weight concrete having the same consistency due to the smaller mass per unit volume.
Therefore, specified slump for lightweight aggregate concrete may have the same or lower value
than that of normal weight concrete.
(3) In case where lightweight aggregate concrete is transported by a concrete pump or placed
into the dense space of large amount of reinforcements either superplasticized concrete or
self-compacting concrete is employed so that the quality of concrete can be maintained andsufficient construction work can be executed. Water reducers with a rate of water reduction
exceeding approximately 15%, higher than the rate for conventionally adopted water reducers, haverecently been used for pumping lightweight aggregate concrete. Then, reduction of slump with timeor due to transportation should properly be estimated based on the construction records orconstruction tests under similar conditions. In order to obtain high-fluidity concrete, segregation oflightweight aggregate should be carefully examined. For construction, refer to Chapter 7
High-fluidity Concrete.
3.4.5

Air content(1) Taking into consideration the freeze-thaw resistance, workability, etc. the air content
after mixing should be 1% higher than that of normal aggregate concrete as standard.
(2) Test of air content should be carried out in accordance with JIS A 1118. Whenmeasuring

air

contentforthepurposeofquality

management

or

using

low-water-absorption lightweight aggregates, tests may be conducted in accordance with
JIS A 1128. When calculating the air content, the correction factor to account for the water
absorption of lightweight aggregate should be accurately understood and used.

[Commentary] (1) The freeze-thaw resistance of lightweight aggregate concrete under severe
weather and water saturated conditions is considered in some case to be lower than that of normal
weight concrete. Therefore, the air content needs to be increased to overcome this.
(2) In order to prevent the measured value from being inaccurate due to the pressurized water
absorption, test method for air content should be followed such as the volumetric method provide in
JIS A1118 as the standard method.
The volumetric method generally requires considerable time and may sometimes not be fit fortests for quality management. Then it has been stipulated that the "method of test for air content offresh concrete by pressure method" (JIS A 1128) may be adopted. When adopting the method, theaggregate correction factor for the absorption of lightweight aggregate should be measured
accurately and the measurement should be corrected. Whenever using lightweight aggregates
shipped at different dates or whenever the water content of lightweight aggregate varies
considerably while the same lightweight aggregate is used continuously, the aggregate correction
factor should be measured.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

3.4.6 Presentation of mix proportion
As a general rule, mix proportions should be presented as shown in Table 3.4.1.
Table 3.4.1 Representation of mix proportion
Mass
Maximumpersize ofunit
coarsevolumeaggregate(mm)(kg/m3)

Note

Slump
(cm)

WaterSandAir cement Aggregate
ratio1)
ratio
(%)

W/C
(%)

s/a
(%)

Unit content (kg/m3)
Water Cement1) Admix- Normal
ture2),3)
fine
aggregate

Ｗ

Ｃ

Ｆ

LightNormal
LightChemical
weightcoarseweightadmixFine
aggregatecoarseture6)
4),5)4),5)
aggregate4),5)
aggregate4),5)
S1
S2
G1
G2
A

1) When mineral admixtures with pozzolanic reactivity or latent hydraulicity are used, the term "water-binder ratio" should
be used instead of "water-cement ratio".
2) As an indicator of resistance to material segregation, the unit amount of fine powder should be presented as a combined
total for cement and admixtures.
3) When several materials of the same category are used, they should be detailed separately.
4) Fine and coarse aggregates should be presented in separate columns for lightweight and ordinary aggregates.
5) Quantity of lightweight aggregate per unit volume of concrete should be presented as the mass in an over-dry condition.
6) Quantity of ordinary aggregate per unit volume of concrete should be presented as the mass in a surface-dry condition.

[Commentary] The mass of lightweight aggregate varies greatly according to the moisture stateof aggregate. In the mix proportions, therefore, the mass in an over-dry condition should bepresented unlike for ordinary aggregate. When both lightweight and ordinary aggregates are usedsimultaneously, quantities of respective types of aggregates per unit volume of concrete should bepresented. Types of structures, characteristic compressive strength, mix proportioning strength, themass per unit volume used in design, types of cement, fine and coarse aggregates, types of chemical
admixtures is also desirable to be described in the table of the specified mix proportion.
In batching, when lightweight aggregate is used under dry condition, corrections related to theeffective water absorption should be conducted. Also, when lightweight aggregate is used under thesurface water content, the amount of pre-wetting should be concerned and corrections related to thesurface water content should be conducted.
In a format of field mix proportion, shown in Table 3.4.1, not only the bulk density but also thewater absorptions, surface water contents of both fine and coarse aggregates and mix proportioning
strength are preferably to be provided.

3.5

Production and Construction

3.5.1

Selection of plant

For producing lightweight aggregate concrete, a plant producing JIS-authorized
lightweight concrete products that has been officially authorized, or a plant with equivalent
production facilities and management systems should be selected considering the timerequired for transport to the site, concrete shipping capacity and quality management
capability.

[Commentary] Ready mixed concrete plants have varying production facilities, production
technology and quality management capability. Lightweight aggregate concrete should be282

Chapter 3

Lightweight Aggregate Concrete

purchased from a plant that manufactures JIS-authorized lightweight concrete products andconducts inspections in conformity with the uniform inspection standards established by the
Namakon (ready mixed concrete) Quality Control Inspector Conference of Japan, and has been
officially authorized.
In cases where no plants produce JIS-authorized products that can be transported to theconstruction site within the designated time, a production plant should be selected for which it has
been verified in testing that it can steadily supply concrete of designated quality, considering the
production facilities, quality management systems and expertise concerning lightweight concrete.

3.5.2

Transportation and storage of lightweight aggregates(1) Coarse and fine lightweight aggregates shall be transported and stored separately.
(2) Lightweight aggregate shall be handled taking care to avoid crushing, separation ofparticles of different sizes, and being mixed with normal aggregate, dirt and foreign
matters.

[Commentary] To produce a uniform quality of concrete the grading of aggregate must be
constant. For this reason coarse and fine aggregates need to be transported and stored separately sothat aggregates of different sizes do not mix. When transporting lightweight aggregate to theconstruction site, it is necessary to use a rubber-tire vehicle as the aggregate will be broken if othertypes of transportation, such as caterpillar bulldozer, excavator, etc. are used. The mix of broken
aggregates results in non-uniform quality concrete and the required strength will not be obtained.
Lightweight aggregates are often stored in open-air but when stored in conical heaps large
grains and small grains tend to become separated from each other. Therefore, it is suggested that
aggregates should be stored in cylindrical silos or be enclosed in by walls in order to keep theirlevel horizontally.
When a belt conveyer is used to convey lightweight aggregates, the care needs to be exercised
not to make the inclination too steep and to clean the conveyer after conveying river sand to preventthe river sand from mixing with the lightweight aggregates.

3.5.3

Control of moisture content of lightweight aggregate(1) Moisture content in lightweight aggregate shall be maintained at a pre-determined
level.
(2) Moisture content of lightweight aggregate in case of pre-wetting shall be determinedconsidering the possibility of pumping transportation, conditions of pumping, freeze-thaw
resistance, etc.

[Commentary] (1) As the lightweight aggregate tends to absorb water more easily than ordinary
aggregate, the concrete quality tends to vary during mixing, transportation and placing. Therefore, it
is better to use them in a thoroughly wet condition. The presoaking of lightweight aggregate needs
to be enough when pumping lightweight aggregate concrete. However, when concrete pump is not
used for the transportation of the lightweight aggregate concrete, only controlling the moisture
content in such a way that it hardly varies at the departure from a production factory is necessary.
Lightweight aggregate that is largely presoaked at a production factory is used to prevent the water283

Standard Specifications for Concrete Structures-2007, Materials and Construction

absorption during pumping. In these cases it is important to control the moisture content during thestorage of the aggregates by providing a water spraying device such as a sprinkler, so that thelightweight aggregate does not become dry in the concrete plant.
It is possible for lightweight aggregate with lower water absorption capacity to be used under
dry condition since the change of the properties during the mixing, transporting and placing is small
and also the water absorption due to pressure is small as well. In these cases the moisture content of
the lightweight aggregate that is stored under dry condition may be controlled so as to be constant.
Unless the moisture content of lightweight aggregate is uniform, the control of weighing mixing
water becomes difficult. Therefore the moisture content must be controlled so as to maintain auniform value not only in presoaking the aggregates but also in storage. The place of storage mustbe such that the aggregates are protected from rain and sunshine and well-drained. Also the volume
of a storage facility shall be sufficient to store an enough amount of aggregates for one day
consumption.
(2) Generally the use of lightweight aggregates containing excessive water will adversely affect
the quality of the concrete by increasing the density or by reducing the freeze and thaw resistance.
As adequate pre-wetting is required when pumping lightweight aggregate concrete, the resistance oflightweight aggregate concrete to freezing and thawing action is generally reduced. When
constructing lightweight aggregate concrete that is subjected to alternative freezing and thawing incases where the absorption of aggregate is not an issue in a series of work from concrete mixing toplacement, reducing the water content of lightweight aggregate and constructing concrete using
buckets should be considered.

3.5.4

Mixing(1) The sequence of charging materials into the mixer shall be determined considering
efficiency of mixing and water absorption by aggregate during mixing, so as to ensure thatthe lightweight aggregate concrete meets the required performance.
(2) The duration of mixing should, in principle, be determined through tests.

[Commentary] (1) The sequence of introducing lightweight aggregate concrete materials into themixer has a large effect on the mixing efficiency, degree of water absorption of aggregates in themixer and the like.
When using dry lightweight aggregate with high water absorption capacity, the materials in themixer absorb a considerable amount of water causing variation in the quality of concrete such as
slump or strength. Therefore, the care must be exercised in their use.
(2) As the mixing efficiency of lightweight aggregate concrete differs greatly depending on thetype of aggregate, the consistency of the concrete, the type of mixer, the capacity of the mixer andthe like, the required mixing time is specified and determined, mainly by tests such as JIS A1119“Method of Test for Variability of Constituents in Freshly Mixed Concrete” and JIS A 8603
“Concrete Mixer”. The standard mixing time will be not less than one minute in the case of theforced mixing type mixer, and not less than two minutes in the case of the tilting type mixer, after
all materials have been introduced into the mixer.
When a gravity type mixer is used, the mixing of lightweight aggregate concrete becomesineffective compared with ordinary concrete, depending on the type of mixer. Therefore theminimum mixing time may be extended when tests are not performed. When the type of mixer and284

Chapter 3

Lightweight Aggregate Concrete

its method of use are adequate and the mixing performance can be confirmed by tests, the mixing
time will be the same as in the case of ordinary concrete. In the case of using a small tilting typemixer at the construction site, because concrete may adhere to the inner wall of the mixer lowering
the mixing efficiency, it is suggested that the sequence of introducing materials and mixing timeshould be determined by tests. If reliable documents or records are available, they may beconsulted.
For the use of a continuous mixer, see Comments of Sections 5.2.3 and 5.4 of "Materials andConstruction: Construction Standards"

3.5.5

Transportation within the construction site(1) When lightweight aggregate concrete is transported using concrete pumps, it should
be superplasticized concrete or concrete using high-range water reducing AE agents asstandard.
(2) For the use of lightweight aggregate having larger water absorption, the watercontent of the aggregate should be reduced and buckets should be used for transportingthe concrete to ensure the frost resistance.

[Commentary] (1) It is possible to transport lightweight aggregate concrete by a concrete pumpwhen the concrete of the slump ranging from 8 to 12 cm is superplasticized so that the slump isincreased to about 18 cm. Lightweight aggregate concrete in which high-range water reducing AE
agent is added at the mixing may be also used for pumping. However, the use of lightweightaggregate with insufficient pre-wetting may cause blockage in the conveying pipe because ofincreasing frictional resistance of concrete in the pipe due to the large amount of water absorption
by the aggregate under high pressure. Self-compacting concrete may be used with careful attention
to the mixture proportion so that it does not cause the segregation of lightweight aggregate. In thiscase, refer to Chapter 7 High-fluidity Concrete.
There remain air voids in lightweight aggregate not absorbing water after pre-wetting. Whenpumping concrete, slump should be set slightly high and discharge should be reduced to prevent
pressure in the pipe from increasing.
In case when a concrete pump is used for the transportation of lightweight aggregate concrete,
the JSCE Recommendation “Recommended Practice for Concrete with High Range Water Reducer
with AE Effect”, “Specification for Self-Compacting Concrete” and “Specification for Construction
using Concrete Pump” may be referred to.
(2) Lightweight aggregate concrete with pre-wetted aggregates shows less frost resistance. In
cases where there is no problem on the absorption of aggregates during mixing and placement forthe construction with lightweight aggregate concrete subject to freeze thaw cycles, the water content
of the aggregate should be reduced and buckets may be used for transporting the concrete to ensure
the frost resistance.

3.5.6

Placing and compaction(1) Concrete shall be placed taking into account the floating-up of lightweight aggregate
and using methods that ensure the least segregation.

285

Standard Specifications for Concrete Structures-2007, Materials and Construction(2) When internal vibrator for lightweight aggregate concrete is used, an appropriate
method shall be selected with due consideration of the thickness of each compacted layer,
duration of vibration, spacing interval between vibrated points, etc.

[Commentary] (1) Segregation of lightweight aggregate concrete occurs because the coarse
aggregate tend to float and mortar tends to sediment, which is the reverse tendency to that of normal
weight concrete.
(2) When consolidating lightweight aggregate concrete using an internal vibrator, the effective
consolidation range is smaller than that for normal weight concrete and tendency of the concrete toextend to the corners of the formwork and around the reinforcing bars by dead weight is weak.
Therefore concrete shall be consolidated thoroughly by making the insertion intervals of thevibrator shorter and the duration of vibration slightly longer. However care must be exercised
during vibration or the coarse aggregate may tend to float.

3.5.7

Surface finishing

When finishing the surface of concrete, floated coarse aggregates shall be pushed backinto concrete.

[Commentary] As there may be cases where the lightweight coarse aggregates float to thesurface, becoming the subject of deterioration due to weather conditions and mechanical action,
concrete should generally be finished in such a way that floated coarse aggregates are pushed backinto the mortar. In this case, the care must be exercised not to increase the bleeding significantly asa result of excessive finish operations. To finish the surface smoothly, it is suggested that refinishingshould be performed after an adequate time has elapsed. When lightweight aggregate concrete isused in a floor slab, micro cracking tends to occur in a tortoise-shell pattern 30 minutes to 1 hour
after finishing. Therefore, it is necessary to remove such micro cracks by lightly striking using atamper and the like about 1 hour after the initial surface finishing. When excess bleeding water isgenerated after placing concrete in winter, it is recommended to remove the bleeding water properly
and the surface should be finished in such a way as mentioned above.

286

Chapter 3

3.6

Lightweight Aggregate Concrete

Inspection

3.6.1

Inspection for acceptance of lightweight aggregate

The accepting party shall be held responsible for conducting acceptance tests forlightweight aggregates. The tests should be carried out in accordance with Table 3.6.1.
Table 3.6.1

Inspection for lightweight aggregate

Item

Testing method/Inspection method

Period/Frequency

Criteria for judgment

Items related
to quality in
JIS A 5002

Confirmation based on test results
provided by manufacturer, or inaccordance with JIS A 5002

Before the start ofconstruction and oncea month during
construction

Compliance with JIS A
5002

Moisturecontent

In accordance with JIS A1134 andJIS A 1135

At least once a day

Falling within the range
given in construction plan[Commentary] The accepting party conducting acceptance tests for lightweight aggregates is the
producer of lightweight aggregate concrete. The results of acceptance tests shall be confirmed by
the Owner of the structure.
It is important to exercise proper quality control for lightweight aggregate to ensure thatlightweight aggregate concrete which meets required properties is manufactured and constructed.
Lightweight aggregate that is prescribed in this chapter complies with the JIS A5002: “Lightweight
Aggregate for Concrete for Structural Use”. Quality control for the lightweight aggregate shall be
exercised for the items prescribed in JIS A5002. Since artificial lightweight aggregate for concrete
for structural use is normally controlled better than natural aggregate the data sheet of test results
submitted by a production company may be used for the quality control like cement.
The water content of lightweight aggregate used for concrete plays an important role not only
for the production of consistent quality of concrete but also for the transportation, such as pumping,
and the placing. Care should be exercised in the case of pre-wetting because water content is likely
to vary. Then the quality control for the water content becomes important during the production of
concrete. The test for the water content shall be carried out once per day or more similar to thenumber of the test for the surface saturation of aggregate. It is difficult to specify an uniform
standard judgment for test results on water content. However, the standard of water content can be
specified by considering conditions for transporting concrete and consistent quality. It can becontrolled within the range of ±2% for example, based on the standard value.

3.6.2

Inspection for acceptance of lightweight aggregate concrete(1) The accepting party shall be held responsible for conducting acceptance tests forlightweight aggregate concrete. It should be verified by tests that concrete has thedesignated mass of unit volume when it is unloaded.
(2) Test for mass of unit volume of concrete should be carried out in accordance with
JIS A 1116.
287

Standard Specifications for Concrete Structures-2007, Materials and Construction(3) Mass of unit volume of concrete shall be within the range specified at the design
stage. In addition, the difference between the bulk density obtained by test and the one
calculated from specified mix proportion shall be less than 50kg/m3.

[Commentary] The accepting party conducting acceptance tests for lightweight aggregate
concrete is the Owner of the structure. There may be cases, however, where the Contractor
constructing lightweight aggregate concrete has conducted tests and the Owner has verified the test
results.
The mass of unit volume of lightweight aggregate concrete does not vary greatly according to
the degree of drying. The mass shall therefore be measured for fresh concrete to ensure safety. The
density of fresh concrete is influenced by the variation of water content in the lightweight aggregate.
Accordingly for the inspection of the density, a provision on the difference between the result
obtained from the field inspection and the calculation one based on the specified mixture proportionis introduced, in addition to that the result of the inspection should fall within the range used at thedesign stage.
The mass of unit weight of lightweight aggregate concrete should be calculated using thefollowing equation.
Uw=G0(1+ag/100)+S0(1+as/100)+G’+S’+C+W (kg/m3)（C 3.6.1）

where
Uw : bulk density of fresh concrete based on specified mix proportion (kg/m3)
G0 : mass of coarse lightweight aggregate (oven dry state) in mix proportion (kg/m3)
S0 : mass of fine lightweight aggregate (oven dry state) in mix proportion (kg/m3)
G’ : mass of coarse normal aggregate (saturated surface-dry state) in mix proportion (kg/m3)
S’ : mass of fine normal aggregate (saturated surface-dry state) in mix proportion (kg/m3)
C : cement content in mix proportion (kg/m3)
W : water content in mix proportion (kg/m3)
ag : moisture content of coarse lightweight aggregate to be used (%)
as : moisture content of fine lightweight aggregate to be used (%)
Inspections for other parameters than the mass of unit volume of lightweight aggregate concreteshould be conducted in accordance with Chapter 16 of "Materials and Construction: Construction
Standards" and "Materials and Construction: Inspection Standards".

288

Chapter 4

Concrete using Continuous Fiber Reinforced Materials (CFRM)

CHAPTER 4 CONCRETE USING CONTINUOUS FIBER
REINFORCING MATERIALS (CFRM)

4.1

General

4.1.1

Scope

(1) This chapter specifies standards on essential matters particularly required for theconstruction of concrete using continuous fiber reinforcing materials (here-in-after called
as “CFRM”).
(2) In the case of prestressed concrete using CFRM as tendons, Chapter 12 shall bereferred, whenever required.

[Commentary] (1) This chapter presents the matters required for construction when applying
concrete using CFRM to a new structure. For continuous fiber reinforcing materials, continuous
fibers are hardened with a binder into a bar shape as a substitute for reinforcing iron bar, into a bar
or stranded shape as a substitute for prestressing steel member, and into a sheet shape. The latter is
not discussed in this chapter because it is used mainly for repair or retrofit. The concrete using
CFRM presented in this chapter is either of reinforced concrete structure in which CFRM,
bar-shaped continuous fiber consolidated with binders, are used in place of steel bars (CFRM
reinforcements) or with steel bars; or of prestressed concrete structure in which CFRM are used as
tendons (CFRM tendons) in place of or with prestressing steel.
Five types of fiber are used for CFRM: carbon fiber, aramid fiber, glass fiber, vinylon fiber andcombination thereof. They come in five shapes: rod, strand, braid, grid or rectangle. For the fiber
binder (matrix), epoxy or vinyl ester type is used.
For members made of concrete using CFRM, the examination of corrosion of CFRM
reinforcements due to environmental action such as carbonation and chloride chloride induced
deterioration can be eliminated because CFRM are generally highly resistant to corrosion.
Continuous fiber reinforcing materials (CFRM) are non-magnetic and fit for concrete structures ormembers that need to be non-magnetic. What is not mentioned in this chapter shall be prescribed in“Draft of Design and Execution Guide for Structure Made with Concrete Using Continuous Fiber
Reinforcing Materials”.
(2) Prestressed concrete with CFRM should be referred regarding exactly the same items as theordinary prestressed concrete of PC grout, for example. Therefore, see Chapter 12, "Prestressed
Concrete" for details.

4.1.2

GeneralWhen constructing concrete CFRM, methods for storing and assembling CFRM and forconstructing concrete shall be determined under the guidance of professional engineers tomeet the designated performance requirements.

[Commentary] Generally, CFRM are subject to surface damage because fiber resin is generally asynthetic resin. A deep scratch of the materials by a sharp edge of steel member will reduce its load289

Standard Specifications for Concrete Structures-2007, Materials and Construction

performance remarkably. Especially if CFRM are used as tendons, a careless error at construction isgreatly anticipated to result in a serious accident. In addition, CFRM may lose their quality if left ina high temperature, ultraviolet ray, or chemical environment. Various matters should be consideredwhen constructing concrete using CFRM. When constructing concrete using CFRM, therefore,
methods should be established for storing and assembling CFRM and for placing and curingconcrete using CFRM under the guidance of professional engineers with sufficient knowledge andexperience so that concrete using CFRM may meet the designated performance requirements.

4.2

Materials

4.2.1

Continuous fiber reinforcing materials (CFRM)

CFRM should comply with the provisions stated in JSCE-E 131 as a standard.

[Commentary] JSCE-E 131 “Specific Properties for Continuous Fiber Rods” specifies theproperties of five types of fibers, namely carbon fiber, alamid fiber, glass fiber, vinylon fiber andthe mixed fiber. It contains mechanical properties, nominal diameter and the maximum dimension
for fiber types, namely rods, strands, lattices and rectangular shapes. These specifications may be
used as the properties. Due to the fact that the types of fibers and the volume ratio of its amountcontained control the mechanical properties of continuous fiber rods, the assured tensile strength,
Young’s coefficient, elongation, relaxation and so on are specified according to an combination ofrod types and fibers used. Similarly nominal diameters and the maximum dimension are specified
for each combination.
The JSCE standards specify seven methods for verifying the performance of CFRM in addition
to these standards. The performance of CFRM should be verified by any of the methods according
to the purpose.

4.2.2

Reinforcing steel bars

(1) Reinforcing steel bars that are used with CFRM shall be fit for the intended purposeof CFRM.
(2) In cases when CFRM are used to enhance the corrosion resistance in a concrete
structure, the reinforcing steel bars used in conjunction should be epoxy coatedreinforcing bars that conform to Clause 3.6.1(4) of "Materials and Construction:
Construction Standards".
(3) In cases when ordinary reinforcing steel bars not specially treated for enhanced
corrosion resistance are used, they should conform to Clause 3.6.1(1) of "Materials andConstruction: Construction Standards".

[Commentary] (1) CFRM are corrosion-resistant and non-magnetic and used mainly for the
structures and member that need to have such characteristics. CFRM may be used also because ofsuch characteristics as lightweight, high strength and low elastic modulus. Therefore, reinforcing
bars used in conjunction with CFRM must be selected in accordance with the intended purpose. It
should be noted in this connection that non-magnetic reinforcing bars have also been developed inrecent years.
290Chapter 4

Concrete using Continuous Fiber Reinforced Materials (CFRM)(2) Considering the characteristics, CFRM are generally applied to structures in saline and othersevere environments. From the viewpoint of corrosion resistance, reinforcing bars for use inconjunction with CFRM should be epoxy coated reinforcing bars that conform to Clause 3.6.1(4) of"Materials and Construction: Construction Standards".
(3) For ordinary reinforcing bars of no corrosion resistance, ones conforming to JIS G 3112
"Steel Bars for Concrete Reinforcement", which is described in Clause 3.6.1(1) of "Materials andConstruction: Construction Standards", shall be basically used.
In recent years, stainless-steel and corrosion-proof reinforcing bars have been developed. Whenusing these reinforcing bars, including non-magnetic reinforcing bars it is necessary to confirm theperformance conforming to the above JIS standard.

4.2.3

Anchorages and couplers(1) It shall be ensured that structure and strength of anchorages and couplers is suchthat they do not fail below the required capacity or undergo excessive deformation.
(2) It should be ensured that the performance of anchorages and couplers complies with
JSCE-E 537.
(3) When selecting the material for the anchorages and couplers, it shall be ensured thatthey conform to the required performance.

[Commentary] (1) Anchorage or couplers shall be of a structural and strength corresponding toor superior to the anchoring or coupling system using CFRM, allowing for safety during
prestressing work, prevent excessive set in anchorage etc. In this case, the guaranteed capacity of
the anchorages or couplers and that of the tendons are treated separately. Because, the tensile
strength of CFRM is evaluated totally, including the influence of anchorages, but the anchoring
device itself cannot exhibit the tensile strength of CFRM completely in many cases. This tendency
is more remarkable in multi-cables. “Anchoring or coupling system” here refer respectively tosystems configured with CFRM and anchorages, and CFRM and couplers.
(2) It is recommended to verify the performance of anchorages or couplers by “Test Method for
Performance of Anchorages and Couplers in Prestressed Concrete Using Continuous Fiber
Reinforcing Materials” in JSCE-E 537. However, this test is intended for new types or types forwhich adequate test data is not available; testing may be omitted for quality-assured types whose
test data is given in the appendix of the “Recommendation for Design and Construction of Concrete
Structures Using Continuous Fiber Reinforcing Materials".
(3) “Materials used for anchorages and couplers” refers to synthetic resins, anchoring expansion
agents, grouts, anchor bars etc. These materials are used for anchoring and coupling that are mostimportant for prestressed concrete structures. Therefore, the materials must be confirmed to bestable in quality and excellent in durability.

4.3

Construction

4.3.1

Handling and storage of materials(1) CFRM should be handled carefully. For example, they should be applied with291

Standard Specifications for Concrete Structures-2007, Materials and Construction

protection to prevent damage to their surface.
(2) In cases when CFRM are stored outdoors, placing them directly on the groundshould be avoided, and they shall be suitably covered. Even in cases when CFRM are
stored indoors, placing them directly on the floor should be avoided and, if required, theyshall be suitably covered. In any case, they shall be stored in a manner that they areprotected against environmental factors such as high temperature, ultraviolet rays,
chemicals etc, which could impair the CFRM, and also protected against being damaged ordeformed.

[Commentary] (1) CFRM is likely to be subjected to deep scars when a sharp edge tool or anacute part of steel touches their surface. CFRM should therefore be handled carefully during theirtransport and storage, and assembly of steel bars and placement of concrete by taking suchmeasures as protection. CFRM using glass fibers in particular should be handled carefully because
alkali intrusion through the scars on the surface is likely to deteriorate durability.
(2) Placing CFRM directly on the ground or on a concrete floor should be avoided, even in awarehouse because they may be damaged or lose their quality. Placing CFRM in a high temperature,
ultraviolet ray, or chemical environment should be also avoided, because their quality may
deteriorate. In both cases, CFRM must be stored in a state free of harmful environmental
conditions.
CFRM that are shipped in the form of coils should be stored in coils with an increased diameteror linearly to prevent twists when CFRM are uncoiled.

4.3.2

Shaping, assembly and placing in position of CFRM tendons, CFRM reinforcementsetc.
4.3.2.1

Shaping and assembly of CFRM tendons(1) CFRM tendons shall be shaped and assembled in a manner that results in the shapeand dimensions specified in the design, without damaging the material. CFRM tendons
found to be damaged at the surface, bent, affected by exposure to high temperatures orstored outdoors for long periods, shall not be used.
(2) CFRM tendons should not be bent to shape.
(3) CFRM tendons expected to develop bond shall be cleaned of any oil, fat or foreign
matter, which may impair the bond before assembly.

[Commentary] (1) CFRM must to be processed correctly in order to achieve the designed shapes
and dimensions without damaging the materials. These tendons must be cut, processed foranchoring, or attached to anchorages by appropriate methods prescribed for each CFRM. For
cutting CFRM, it is preferable to use an efficient high-speed rotary grinder which does not damage
the material.
CFRM tendons which are bent or scratched on the surface must not be used because their tensile
strength is greatly anticipated to be reduced. In addition, CFRM tendons which have been subjected
to high temperature must not be used because the thermal deterioration of the resin may lower their292

Chapter 4

Concrete using Continuous Fiber Reinforced Materials (CFRM)

performance as the binder and reduce the tensile strength of tendons. Under direct sunlight, somekinds of CFRM tendons may be deteriorated by ultraviolet rays, therefore CFRM tendons that havebeen stored outdoors for long periods should not be used.
(2) In general, thermosetting resins are used as binding materials for CFRM tendons. Since it israther difficult to form such a material by bending on site in terms of both technically and quality,
the bend forming of CFRM is basically avoided. If bend forming is not avoidable, however, factory
processing that does not impair the materials is permitted. Since the tensile strength of CFRM
tendons may be reduced under the influence of bend forming and internal bending radius, it isnecessary to check whether the tensile strength satisfy the strength required in design by anappropriate test method that reproduces the actual state of use.
(3) Grease, paint, dirt, and other foreign substances may disturb to develop bond between
concrete or PC grout and CFRM tendons and cause tendon slippage. Therefore, CFRM tendonsmust be used after full surface cleaning.

4.3.2.2

Shaping and assembly of CFRM reinforcement(1) CFRM reinforcements shall be shaped and assembled in a manner that results in the
shape and dimensions specified in the design, without damaging the material. CFRM
reinforcements found to be damaged at the surface, bent except shaping, affected byexposure to high temperatures or stored outdoors for long periods, shall not be used.
(2) CFRM reinforcement should be bent to shape in the factory.
(3) In cases when the inside radius for bending CFRM reinforcement is not specified in
the designs, the inside radius and method of bending shall be determined in a manner that
ensures that the tensile strength of the bent-to-shape CFRM is not below the value
considered in the design.
(4) CFRM reinforcement shall be cleaned of any oil, fat or foreign matter, which may
impair the bond before assembly.
(5) CFRM reinforcements shall be placed accurately and adequately supported without
damaging the material to ensure that no displacement or deformation is caused by
concrete casting. The CFRM reinforcement shall be fixed using a method that does notdamage the CFRM or harm its durability.

[Commentary] (1) CFRM reinforcement must be handled in the same way as CFRM tendons,
according to the comment of Clause 4.3.2.1 (1).
(2) For the reason given in Clause 4.3.2.1 (2), the bend forming of CFRM reinforcement into
stirrups or spirals is basically done at the factory. Certain types of CFRM reinforcement can beformed by bending and thermosetting on site or by heating on site using thermoplastic resins,
however, the tensile strength of the bend-formed section of CFRM reinforcement bent in these ways
should be confirmed by an appropriate test method.
(3) Bend to shaped section of CFRM reinforcement is known to reduce the tensile strength to adegree depending on the type of continuous fiber, the reinforcement manufacturing method of thereinforcement, and the inside radius of bending. Therefore, the inside radius of bending and bend
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Standard Specifications for Concrete Structures-2007, Materials and Construction

forming method should be determined after the decrease in tensile strength is confirmed by testing.
It is preferable to maximize the inside radius of bending.

4.3.2.3

Making ducts other than sheaths

When making ducts other than sheaths, the material and method used shall notadversely affect the CFRM tendons, CFRM reinforcement and concrete.

[Commentary] A duct is used to reserve space for tendon placement and to insulate tendons fromconcrete. The duct material must be selected after it is verified not to corrode the CFRM tendon or
CFRM reinforcement or to decompose the concrete. The forming shall not cause racking in theconcrete, increase the friction remarkably at prestressting, or damage the CFRM tendons.

4.3.2.4

Placing sheaths and CFRM tendons(1) Damaged sheaths or sheaths having corrosion inside shall not used.
(2) Sheaths and CFRM tendons should be placed accurately and adequately supported
without damaging the material, to ensure that no displacement or deformation is caused by
concrete casting.
(3) CFRM tendons shall be placed within the sheath without being tangled.
(4) In cases when pre-tensioned CFRM tendons are used, the CFRM shall be handled ina manner that does not cause damage at edges of contact.
(5) CFRM tendons and sheaths should be inspected after they are placed. In cases when
inadequacies such as damage or an error in placing, etc. are found, required corrective
action and changes shall be undertaken.
(6) Allowable error during placement of CFRM tendons should be determined to bewithin a range that does not adversely affect the concrete member, considering its size.

[Commentary] (1) Steel sheaths having corrosion inside shall not be used because this may
increase the friction at prestressing, damage the CFRM tendons, or disturb to develop bond. Before
use, the external surface of a sheath shall be made free of oils, loose rust, and other foreign
substances that may disturb adhesion.
To prevent the damage of CFRM tendons in a sheath, a plastic sheath may be used after its
performance is fully verified.
(2) Sheaths and CFRM tendons shall be held securely at comparatively short intervals withappropriate supports not damaging concrete members so that the concrete weights at concrete
placing or vibrations by vibrator will not misalign the positions. The support intervals shall be
determined appropriately by considering the types and rigidities of CFRM tendon and sheath andalso the coefficient of friction. Since CFRM tendons have lower density than steel members, theyshould be fixed with respect to ascending force also at concrete placing.
(4) Pretension may break a continuous-fiber tendon placed through an arrangement hole of anend frame if the tendon is damaged by contact with the arrangement hole at tensioning or concrete294Chapter 4

Concrete using Continuous Fiber Reinforced Materials (CFRM)

compaction. Therefore, it is preferable to prevent the CFRM tendon from direct contact with theframe by using a cushioning material at the arrangement hole of the edge frame for CFRM tendon.
(5) Error in placing or damage during the placement of sheaths or CFRM tendons shall becorrected not only during the placement. The sheaths and CFRM tendons shall be inspected
carefully also during concrete placing after the placement and corrected if necessary.
(6) The allowable error during placing of sheaths and CFRM tendons differ depending on themember dimensions and tendon placement method. As a rule, it is preferable to keep the centroid
deviation within 5 mm if the cross-sectional dimension of the member is less than 1 m and within
10 mm besides less than 1/200 of the member dimension if the cross-sectional dimension of themember is 1 m or more. Deviation over 10 mm shall be corrected in any case.

4.3.3

Placement of concrete(1) Concrete shall be placed and compacted taking care that the placement of CFRM,
reinforcing steel bars, anchorages, sheaths etc., is not disturbed, and no damage occurs to
the CFRM.
(2) In cases when steam curing is carried out, the tensile force and temperature ofcuring, etc. shall be determined considering the thermal behavior of the CFRM, anchorages,
couplers etc.

[Commentary] (1) Concrete placing must be done with care because it may disturb not only theplacement of CFRM, reinforcing bars, and frames but also the placement of anchors and sheaths forprestressed concrete. It should also be noted that CFRM migrate easily due to ascending forces
because they are more lightweight and less rigid. In case that the placement of CFRM, reinforcing
bars, anchors, and sheaths is disturbed, an iron worker should be present even during concrete
placing.
CFRM may be damaged by direct contact with an internal vibrator. To prevent this damage, aninternal vibrator with urethane or a similar cushioning material is preferable.
(2) The coefficient of thermal expansion in the axial direction of a CFRM differs depending on
the fiber type. All fibers except glass fiber show very different coefficients from that of concrete.
The coefficient of carbon fiber is almost 0 but the coefficient of Aramid fiber indicates an opposite
property to concrete. For steam curing of a pretension member using a tendon, the initial tension
must be determined by considering the temperature history. Temperature correction is necessary
even for the post-tension method, in cases when the hydration heat of a concrete is remaining. This
regulation was prescribed because some CFRM and their anchors, couplers, and sheaths are subject
to quality changes of materials at steam curing temperature. The increase in relaxation and thedecrease in adhesion strength must be noted for CFRM especially at high temperature. For steam
curing, heating shall be started three hours or more after concrete placing and the temperature riseshall generally be 15C or less per hour. The temperature during curing shall be 65C or less andshall not adversely affect the quality of CFRM and their anchors and couplers.

4.3.4

Prestressing(1) The required tensile force in CFRM, method of prestressing, preventative measureagainst emergency situations during prestressing, calibration of tensioning equipment,295

Standard Specifications for Concrete Structures-2007, Materials and Construction

required compressive strength of concrete for prestressing and control of prestressing,should be determined as per relevant methods.
(2) The coefficient of friction and apparent modulus of elasticity of CFRM for control ofprestressing should be determined by testing at site.
(3) The coefficient of friction of tensioning apparatus and anchorage should bedetermined by testing.
(4) Prestressing tendons shall be tensioned and anchored in a manner that each of the
CFRM is tensioned to the required level.

[Commentary] Tension shall be as prescribed in Section 12.6.4. When using a process prescribedin the data section of “Draft of Design and Execution Guide for Structure Made with Concrete
Using Continuous Fiber Reinforcing Materials”, the control method prescribed for the process must
be used.
(1) Since a CFRM tendon shows more elongation than a PC steel member to the same tension
force, it may be necessary to reposition the jack or use a jack with a longer stroke.
(2) The coefficient of friction and the apparent Young's modulus must be measured at theinitiation of works and again if the trouble found during control. Tension had better be controlledwith the measured coefficient of friction μ. The allowable standard limit of μ given in Table
C13.7.1 is for PC steel member. For CFRM tendon, it is necessary to determine the allowable
standard limit of μ in the same way as for PC steel member.
(4) A CFRM tendon shows a linear stress-strain curve with no yielding and its ultimate strain issmaller than that of a PC steel member. Since a CFRM tendon has a property of great strength
decrease by bending, tensioning of CFRM tendons and anchoring to the anchorage must be carriedout carefully to avoid brittle failure. The tensioning section lengths of CFRM tendons should bemade uniform from the beginning and the elongation of each CFRM tendon at tensioning must be
controlled more strictly than when a tension is given to a PC steel member. At the tensioning of a
CFRM tendon, the tension should be increased not quickly but gradually. When a CFRM tendon isfixed on an anchor, slippage may become greater than for a PC steel member. Because of small
tensile rigidity, however, the decrease of tendon tensile force attributable to slippage at anchorage
generally becomes small.

4.4

Inspection

4.4.1

Inspection for acceptance of materials(1) The accepting party shall be held responsible for conducting acceptance tests for
CFRM. The tests should be in accordance with Table 4.4.1.
Table 4.4.1
Item
Quality item of
JSCE-E 131

Inspection for acceptance of CFRM

Testing method/Inspection method
Verification based on the test
records prepared by the
manufacturer, or test using a method
specified in JSCE-E 531, 533, 534

296

Period/Frequency

Criteria for judgment

On acceptance

Shall confirm to
JSCE-E 131

Chapter 4

Concrete using Continuous Fiber Reinforced Materials (CFRM)(2) Conducting acceptance tests for anchorages and couplers for continuous fiber
reinforcing materials (CFRM) tendons shall be the responsibility of the accepting party.
Inspections should be conducted for the anchorage or coupler in combination with the
CFRM tendon in accordance with Table 4.4.2. Note that the inspection may be avoided formaterials of the quality assured.

Table 4.4.2
Item
Tensile strength(or Tensile load)
Anchorages
and couplers

Fatigue strength

Relaxation value

Inspection for acceptance of anchorage or coupler

Testing method/
Inspection method
Verification based on the test
records prepared by the
manufacturer, or test using amethod specified in JSCE-E 537
Verification based on the test
records prepared by the
manufacturer, or testing of asystem incorporating theanchorage or coupler using amethod specified in JSCE-E 535
Verification based on the test
records prepared by the
manufacturer, or testing of asystem incorporating theanchorage or coupler using amethod specified in JSCE-E 534

Period/Frequency

Criteria for judgment

On acceptance(Inspections may
be eliminated for
those of guaranteed
quality and withgood trackrecords.)

Anchorage or coupler
should confirm tostandards to achieve
the designatedobjective.

[Commentary] The accepting party held responsible for conducting acceptance tests means the
Owner. Generally, however, the Contractor constructing concrete using CFRM conducts tests andthe Owner confirms the test results.
(1) In terms of mechanical properties, durability, and handling method, CFRM generally differ
greatly from steel members. This must be kept in mind for appropriate inspection. The performancerequirements and inspection details for reinforced or prestressed concrete using CFRM are similar
to those using ordinary reinforcing materials. Acceptance tests shall therefore be conducted inaccordance with "Construction: Construction Standards".
(2) The mechanical properties of the CFRM tendon are greatly affected by the performance ofanchorages and couplers. Whether the type is single or multiple, the general system performancetends to be lower than that of the CFRM tendon itself. When using CFRM tendons, therefore, theentire system, including anchorages and couplers shall be tested with respect to items thatseemingly affect the CFRM tendons to verify the performance.
The shape, performance, and state of use of anchorages or couplers differ greatly depending on
the model of anchorages or couplers and the type of CFRM tendon. Therefore, it is necessary to
determine an appropriate test that can reproduce the state of use and the tensile force effecting state.
This test shall verify that the anchorages and couplers have structures and strengths not to be
fractured or remarkably deformed under each proof tensile load or less and that they have theprescribed fixing efficiency and coupling efficiency for CFRM tendon. Depending on the type ofanchorages and couplers, it is also important to check that set loss due to tendon slippage is withinallowable limits; furthermore, given that continuous fiber reinforced concrete structures are often
located in extreme environments, any steel anchorages and couplers must be confirmed to be
sufficiently durable.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

This test may be omitted if the CFRM tendon has verified quality and the anchorages andcouplers are given in the data section of “Draft of design and execution guide for structure madewith concrete using continuous fiber reinforcing materials” exclusively for the CFRM tendon andhave assured quality and history of use.

4.4.2

Inspection for protection of CFRM

(1) The accepting party shall be held responsible for conducting inspection forprotection of CFRM. The tests should be in accordance with Table 4.4.3 as a standard.
(2) In cases when from the results of the inspection, protection to the CFRM isdetermined to be inadequate, the method of protection shall be appropriately modified.
Table 4.4.3 Inspection for protection of CFRM
Item

Method for testingand inspection

Period/Frequency

Method of storage

At the time ofacceptance

Method oftransportation

At the time oftransportation

Visual observation

Method of fixing

Prior to placing
concrete

Method of concrete
placing

During concrete
placing

Criteria for judgment

As per the document
giving details of theconstruction plan[Commentary] At each stage of work, CFRM shall be inspected to verify that they are protectedfrom damage as prescribed in the construction plan.
Inspection of concrete must refer to Chapter 16 in “Materials and Construction: Construction
Standard” and “Inspection Standard”.

298Chapter 5

Short Fiber Reinforced Concrete

CHAPTER 5 SHORT FIBER REINFORCED CONCRETE

5.1

General

5.1.1

Scope

This chapter presents standards for necessary matters concerning the quality andconstruction of short fiber reinforced concrete. The short fibers to be discussed in thischapter are steel fibers and synthetic fibers.

[Commentary] Short fiber reinforced concrete is a composite material with tensile strength,
flexural strength, cracking resistance, ductility, shear strength and impact resistance enhanced by
uniformly distributing discontinuous short fibers in concrete. Fibers used for short fiber reinforced
concrete include metal fibers such as steel and stainless fibers, inorganic fibers such as glass, carbon
and ceramic fibers, and synthetic fibers such as aramid, nylon, polyvinyl alcohol(PVA),
polyethylene and polypropylene. This chapter discusses steel and synthetic fibers as they have goodtrack records. When using carbon and other fibers, this chapter should be consulted whileconsidering the characteristics and track records of respective fibers.
Steel fiber reinforced concrete has been applied not only in non-structural members but also in
structural members of various structures because it provides greatly improved mechanicalproperties. Steel fiber reinforced concrete is highly resistant to crack opening. Using steel fiber
reinforced concrete for unreinforced concrete reduces crack width and enhances fatigue strength. As
the content of steel fibers increases, therefore, the thickness of pavement or tunnel lining can be
reduced. Resistance to freezing and thawing action and durability can also be improved. Using steel
fiber reinforced concrete for reinforced concrete increases the shear strength of members. Steel fiber
reinforced concrete is therefore effective for structures that require particularly high shear strength.
High toughness against compression during compressive failure and against bending during flexural
failure means high resistance to impact or explosive loads.
The above characteristics of steel fiber reinforced concrete are determined by the shape,
dimensions, content, orientation and dispersion of steel fibers in concrete, and by the quality ofconcrete. The quality of steel fiber should be verified in testing before use. Steel fibers with a lengthof 20 to 60 mm, diameter of 0.3 to 0.9 mm and aspect ratio (diameter-length ratio) of 30 to 100 are
generally used. The percentage of steel fiber in concrete ranges from 0.5 to 2.0%, which isequivalent to a unit quantity of approximately 40 to 160 kg/m3. When constructing steel fiber
reinforced concrete, the "Recommendations for Design and Construction of Steel Fiber Reinforced
Concrete (draft)" and "Recommendations for Design of Steel Fiber Reinforced Concrete Column
Members (draft)" should be consulted. For shotcrete using steel fibers, refer to Chapter 8 Shotcrete,"Recommendations for Design and Construction of Steel Fiber Reinforced Concrete (draft)" and"Recommendations for Construction of Steel Fiber Reinforced Shotcrete (draft)".
Ultra high strength fiber reinforced concrete has recently been put to practical use that has acharacteristic value of compressive strength of 150 N/mm2 or higher owing to the use of extremely
fine powder like silica fume and has high cracking strength and tensile strength with the mixing ofsteel fiber of approximately 2%. Steel fibers with a length of 10 to 20 mm and a diameter of 0.1 to
0.25 mm, unlike the conventional steel fibers, are now being used. For super high strength fiber
reinforced concrete, refer to the "Recommendations for Design and Construction of Ultra HighStrength Fiber Reinforced Concrete Structures (draft)".

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Synthetic fibers are generally inferior to steel fibers in terms of mechanical reinforcement. The
former are, however, difficult to corrode and can be easily shaped during manufacturing. They havea low density and can be deformed easily, facilitating construction. Short fiber reinforced concrete
using synthetic fibers as that using steel fibers sees its toughness against bending and othermechanical properties enhanced with the increase of the percentage of short fibers. In tunnel lining
concrete, synthetic fibers with a length similar to that of ordinary steel fibers are used as well as
steel fibers. Recently, small quantities of synthetic fibers are mixed to reduce plastic shrinkage,
prevent cracking due to drying shrinkage and concrete spalling and prevent explosion during firerather than to improve mechanical characteristics in numerous cases. For these applications,
synthetic fibers with a length of 10 to 20 mm and a diameter of 0.02 to 0.3 mm are frequently used.
The length is shorter and the diameter is smaller than steel fibers. Synthetic fibers come in a large
number of types with the aspect ratio between 40 and 700. The percentage of short fibers inconcrete varies with the objective of use. The percentage is 0.04 to 0.1% for preventing concrete
from spalling from viaducts, 0.2 to 0.3% for preventing the explosion of high strength concrete ormore than 0.3% for controlling the cracking of tunnel lining concrete. Synthetic fibers have a low
density. The quantity used per unit volume of concrete is 0.3 to 5 kg/m3. The characteristics of shortfiber reinforced concrete vary according to the shape, dimension and percentage of synthetic fiber.
The quality and effect of the synthetic fiber to be used should be verified in testing before used.
Mixing approximately 2% of high strength synthetic fiber such as polyvinyl alcohol fiber(PVA) and high strength polyethylene fiber enables the production of short fiber reinforced mortar
with high mechanical properties, which is proposed as ductile material with multiple fine and highdensity cracks. When using ductile materials, refer to the "Recommendations for Design andConstruction of High Performance Fiber Reinforced Cement Composites with Multiple Fine Cracks(HPFRCC) (draft)".

5.1.2

GeneralWhen using short fiber reinforced concrete, materials of proven quality shall be
employed, mix proportions shall be determined to meet the designated performancerequirements and the concrete shall be manufactured and constructed properly.
Inspections shall be conducted as required in each phase.

[Commentary] To obtain the designated quality of short fiber reinforced concrete, short fibers
should in principle be dispersed evenly. Quality is greatly influenced by the length, shape andpercentage of short fiber, maximum size of coarse aggregate, water-cement ratio, percentage of fineaggregate, mixing method, compaction method and other factors. These parameters shall therefore
be fully examined before construction.

5.2
5.2.1

Quality of Short Fiber Reinforced Concrete
GeneralShort fiber reinforced concrete shall have the designated strength, toughness,durability, cracking resistance and workability and be of uniform quality.

[Commentary]

In cases where short fibers are not uniformly distributed or oriented in a specific300

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Short Fiber Reinforced Concrete

direction, the designated strength or toughness may not be achieved. Tensile strength, flexuralstrength, shear strength and toughness increase nearly in proportion to the percentage of short fibers
in concrete. Compressive strength, however, does not change greatly. Steel fiber reinforced concreteand short fiber reinforced concrete with a relatively large quantity of synthetic fibers gradually failwhile maintaining a certain level of ductility even after cracking occurs. The brittleness of concrete
is improved considerably and the toughness is increased greatly.
In cases where steel reinforced concrete is used in reinforced concrete structures, cracking
seldom occurs and electrical resistance varies. It has been reported that the corrosion ofreinforcement is controlled even under severe conditions as in marine environments.

5.2.2
5.2.2.1

Strength properties
Compressive strength

Compressive strength of short fiber reinforced concrete shall be determined inaccordance with JIS A 1108.

[Commentary] The compressive strength of concrete increases marginally due to addition ofshort fibers to the concrete. The compressive strength shall be specified in a manner similar tonormal concrete. The probability of not attaining design characteristic compressive strength shouldbe less than 5%, when tests are carried out in accordance with JIS A 1108 “Method of Test for
Compressive Strength of Concrete”. It is noted that the coefficient of variation of compressive
strength of short fiber reinforced concrete may be equal to that of normal concrete.

5.2.2.2

Tensile strength

Tensile strength of short fiber reinforced concrete shall be determined in accordancewith JIS A 1113 or by the direct tension tests using concrete specimens.

[Commentary] Though it is desirable that the tensile strength be determined by direct tension
tests, an accurate test method using a general-purpose test apparatus is not yet to be established.
Thus, the tensile strength of short fiber reinforced concrete shall normally be determined using JIS
A 1113 “Method of test for splitting tensile strength of concrete.” In this case, the strength at thefirst crack may be taken as the tensile strength. The tensile strength should be specified in a mannerthat the probability of failure at a value lower than the characteristic value of tensile strength is lessthan 5%.

5.2.2.3

Flexural strength

Flexural strength of short fiber reinforced concrete should consider its size effect as astandard.

[Commentary] Due to the significant size dependence, it is difficult to think of flexural strength
as an index for characterization of material properties of short fiber reinforced concrete. However,301

Standard Specifications for Concrete Structures-2007, Materials and Construction

on the basis of the full-scale testing, the experimental value can be taken as the characteristic value
for the actual structure. In general, flexural strength is generally determined in accordance with
JSCE-G 552 “Test Method for Flexural Strength and Flexural Toughness of Steel Fiber Reinforced
Concrete”.

5.2.3
5.2.3.1

Deformation characteristics
Deformation characteristics under compression(1) The stress-strain curve of short fiber reinforced concrete should be determined by amethod in accordance with JSCE-G 502 as a standard.
(2) The stress-strain curve of short fiber reinforced concrete may be assumed using
reliable data.

[Commentary] As in the case of normal concrete, the stress-strain curve of short fiber reinforced
concrete also varies widely depending on the type and age of concrete, state of stress of concrete,
and rate and path of loading. However, the inclusion of fibers scarcely affects the compressive
strength and the deformation characteristics in compression, as long as the applied load is less thanthe compressive strength. Accordingly, this specification allows use of provisions of JIS A 1149
“Test Method for Static Modulus of Elasticity of Concrete” for determination of the stress-strain
curve and the deformation properties of short fiber reinforced concrete in compression.

Compressive stress (N/mm2 )40

30Steel fiber reinforced concrete
20
Normal concrete
10
0

0

0.02
0.01
Compressive strain

Fig. C5.2.1

0.03

Example of compression test results

The inclusion of short fibers is however known to improve the deformation characteristics ofconcrete after the peak load as shown in Fig.C5.2.1. In the case of synthetic fiber, improvement of
deformation characteristic depends on fiber content significantly, and much fiber content improves
the deformation characteristics of concrete after the peak load.
When a high accuracy is required in calculation of stresses, etc., a stress-strain curve
representing the actual conditions should be used. In such cases, compression-softening should be302

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Short Fiber Reinforced Concretetaken into consideration.

5.2.3.2

Tension softening properties(1) Tension softening properties of short fiber reinforced concrete should bedetermined by the results of the direct tension tests or flexure tests using test specimens.
(2) The tension softening curve of short fiber reinforced concrete may be specified
using a linear or any other suitable model based on reliable data.

[Commentary] (1) Since short fibers transfer stress after cracking, the effect of short fiber
reinforced concrete on the tensile fracture property remarkably appears in the tension softening
curve, which shows the relationship between tensile stress and crack width. In case when thetension-softening property of short fiber reinforced concrete needs to be specified, for example inthe case of columns, it may be specified using a tension-softening curve. Though direct tensile test
can be carried out to determine the tension softening curve, it shall be required to have a highly
rigid testing machine completed with precise displacement control. In certain cases, it may be
impossible to apply as method of verification for short fiber reinforced concrete. The tension
softening curve may be calculated from flexural test results, while recommending determination of
the curve based on tests under direct tension. Several methods of estimating a tension softening
curve on the basis of the flexure test results have been proposed. Appendix 1 of “Design
Recommendations for Concrete Columns Reinforced with Steel Bars and Fibers” gives a brief
outline of such method, and Test Method 2 “Recommendations for Design and Construction ofHigh Performance Fiber Reinforced Cement Composites with Multiple Fine Cracks (HPFRCC)(draft)” provides an example of the direct tensile test. It may be noted that, in principle, only
machine with displacement control should be used for direct tensile test and flexure test.
(2) The tension softening curve of short fiber reinforced concrete generally shows a reduction instress immediately after cracking. As the softening behavior after cracking has been known todepend on the type, shape, and content of short fibers, the tension softening curve of short fiber
reinforced concrete may be specified using a linear or any other suitable model, depending upon theapplication. A tension softening curve obtained from direct tension tests can be divided into twozones as shown in Fig. C5.2.2 – one is the region immediately after cracking, where the stressabruptly decreases, and, the other is the region where the stress decreases slowly as the crack-width
increases. The area under the tension softening curve, i.e., fracture energy GF, represents theresistance of concrete to cracking.
A typical tension softening curve is shown in Fig. C5.2.3. This curve is quoted from “Design
Recommendations for Concrete Columns Reinforced with Steel Bars and Steel Fibers” and may be
used as a reference.
For short fiber reinforced concrete with synthetic fiber, fiber content significantly depends on
the application, tension softening properties of concrete is dramatically improved with increasing offiber content.

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3

2
Steel fiber reinforced concrete
1Normal concrete
0

0

1

2

3

4

5

Crack width (mm)Tensile stress (N/mm2)

Fig. C5.2.2

A typical tension softening curve

ftk: Characteristics of tensile strength
μ: Rate for residual strengthωk: Limit of crack width

ftk
μftk

Crack width (mm)Fig. C5.2.3

5.2.3.3ωk

A typical specified tension softening curve

Flexural toughness

In cases when the performance of short fiber reinforced concrete in terms of flexural
toughness is specified on the basis of field experience without using a tension softening
curve, indices as the coefficient of flexural ductility determined from test values inaccordance with JSCE-G 552, the load-deflection curve and load-crack width curve
obtained from flexural test of concrete specimens, may be used.

[Commentary]

In the past, short fiber reinforced concrete has been used in applications such as

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Short Fiber Reinforced Concretetunnel lining, paving, slope protection, and repair and reinforcement without carrying out
calculations for stress or numerical analysis. In these cases, flexural toughness may be adequately
specified on the basis of field experience or shall be specified by the coefficient of flexural ductility
based on values determined through tests carried out in accordance with JSCE-G 552 “Test Method
for Flexural Strength and Flexural Toughness of Steel Fiber Reinforced Concrete”. Also, it may be
specified by the post-cracking period in the load-deflection curve or the load-crack width curve,
obtained from flexural testing of concrete specimens.
The scale effect between the actual structure and specimens should be adequately considered, as
the results of flexural toughness can vary widely, depending on the size of the specimen.

5.2.4

Prevention of explosion

When using short fibers to prevent explosion during a fire, the types and quantities ofsynthetic fibers to be used should be verified by an appropriate method as a standardpractice. The percentage of short fibers to be mixed for preventing explosion may be
determined according to the type of synthetic fiber to be used based on reliable data.

[Commentary] In concrete with a low water-cement ratio such as high strength concrete and highfluidity concrete, vapor pressure sometimes increases in concrete during a fire and surface concrete
is exploded. Mixing synthetic fibers, however, provides a route for vapor to pass during a fire while
synthetic fibers are burned and is effective for preventing explosion. Polypropylene short fibers are
fully effective for preventing explosion in a range of fiber content (volume percentage) between
0.165 to 0.33% (a range of quantity mixed between 1.5 to 3.0 kg/m3). Mixing of synthetic fibers has
little influence on the strength or durability of concrete. Short fiber reinforced concrete with
explosion prevention capacity has frequently been used in columns of high rises with a design
strength of 80 N/mm2 or higher. Use is also being considered in tunnels with an ordinary strengththat are subjected to a fire under severe conditions.
Polypropylene is frequently used, and polyacetal and polyvinyl alcohol (PVA) are also adopted.
Effectiveness for preventing explosion varies because fusion point varies according to the type ofsynthetic fiber. The larger quantity, the smaller diameter and the longer length of the fiber give themore effective for preventing explosion. Melting point and burning temperature are different for
polypropylene and polyacetal. Synthetic fibers provide adequate explosion prevention capacity at a
mixing percentage by volume of 0.2 to 0.3%. It should, however, be notes that some of the synthetic
fibers are likely to emit toxic gas when they are burned.
When using a synthetic fiber for which no data is available on the standard percentage formixing to provide explosion prevention capacity, the quantity of the synthetic fiber effective forpreventing explosion should be verified for the specific type of synthetic fiber in appropriate
heating tests while varying the percentage of the synthetic fiber to be mixed. The heating
temperature should be specified considering the RABT curve (ZTV Tunnel Curve) for testing tunnel
fire specified in recommendations concerning highway tunnel facilities and operation in Germany,or the RWS tunnel curve of the Ministry of Transport, Public Works and Water Management of theNetherlands.

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5.2.5

Prevention of spalling

When using short fibers to prevent concrete from spalling from the structure, the types
and quantities of short fibers to be used should be verified by an appropriate method as astandard practice. The standard percentage of short fibers to be mixed for preventing
concrete spalling may be determined according to the type of short fiber to be used basedon reliable data.

[Commentary] Concrete spalling from concrete viaducts is likely to cause damage to third
parties. When using short fiber reinforced concrete to prevent spalling, small quantities of synthetic
fibers with a percentage of 0.04 to 0.1% are applied. Synthetic fibers are used on the slabs andbeams at upper and middle levels of concrete viaducts, and on curbs and railings where concrete is
cast in-situ.
In order to determine the quantity of short fiber effective for preventing concrete spalling forthe specific type to be used, the effectiveness should be verified in tests in which damage is causedby hammering to induce concrete spalling. Fig. C 5.2.4 shows an example of method for verifying
the effectiveness of short fibers for preventing concrete spalling. In the tests using the method, an
expansive agent is injected into holes at the positions of reinforcement in the specimen, expansion
pressure is used to cause cracking and the spalling of concrete cover is induced by hammering inorder to simulate concrete spalling due to the corrosion of reinforcement. The ratio between thefrequency of hammering until spalling occurred in the case with short fibers and the frequency inthe case with no short fibers (hammering frequency ratio) is obtained while varying the quantity ofshort fibers mixed to evaluate the effectiveness of short fibers for preventing spalling. The shortfiber mixing ratio at a hammering frequency ratio of approximately eight was regarded as a
guideline for the standard quantity of short fibers to be mixed. In order to prevent the expansive
agent injected into the holes at the positions of reinforcement from expanding excessively andexploding, the designated quantities of expansive agent should be used by the designated method.

膨張圧によりCracking
induced by
発生するひび割れ
expansion pressure

Holes 鉄筋位置に設けた孔
created at the positions ofreinforcement (into which static（静的破砕材を注入する）
expansive demolition agent is injected)

150mm

600mm
150mm

鉄筋位置に
of hammering
Crack at theposition Point
打撃箇所
沿ったひび割れof reinforcement

Fig. C5.2.4 Test for verifying the effectiveness for preventing concrete spalling

5.2.6

Other performance

In cases where performance other than strength and deformation characteristics areespecially required, these shall be appropriately confirmed on the basis of tests using
scaled specimens and models, testing of conventional specimens, or analysis.

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Short Fiber Reinforced Concrete[Commentary] Performance of short fiber reinforced concrete other than strength anddeformation characteristics include abrasion and impact resistance. However, enough relevant data
is not available from past research work and no standard test or method of analysis is currently
available to determine these properties. Therefore, in case when these properties are specified, theyshould be appropriately evaluated.

5.3

Short fibers

5.3.1

Steel fibers(1) Steel fibers used should comply with JSCE-E 101 as a standard.
(2) When steel fibers other than those specified in (1) above are used, the quality shallbe appropriately confirmed and the application shall be thoroughly investigated.

[Commentary] The reinforcing effect of short fibers increases as the fiber length increases. A
fiber length of at least 1.5 times the maximum aggregate size is recommended considering the easeof fiber dispersion. While a fiber length of 30mm or more is generally recommended for short fiber
reinforced concrete, the fiber length for shotcrete should be selected considering the fact that shortfibers are more workable but less effective in reinforcing concrete.
Short fibers of 20mm or less, which permit easy spraying, are used for shotcrete, while longer
fibers of about 60mm with a high reinforcing effect are used for slabs. Therefore, JSCE-E 101“Quality Specifications for Steel Fibers for Concrete” requires the nominal length and aspect ratioof short fibers to be between 20 and 60mm and between 30 and 80, respectively. When the fiber thatis no specified in JSCE-E 101 is used, quality of the used fiber and usage of the fiber shall be wellinvestigated referring to JSCE-E 101.

5.3.2

Synthetic fibers

Synthetic fibers shall have proved quality so that the short fiber reinforced concrete
using the synthetic fibers meets the designated performance requirements.

[Commentary] Synthetic fibers are less effective for mechanical reinforcement than steel fibers.
The former, however, have several benefits. For example, they are free from corrosion, thethickness and surface shape of the fiber can be treated relatively freely according to the objective
and they have a low density and are easily deformed, so they are easy to construct. Synthetic fibers
are used for varieties of purposes including the control of cracking due to plastic shrinkage ordrying shrinkage, prevention of spalling, improvement of toughness against bending and preventionof explosion during a fire. Examples of physical properties of typical synthetic fibers are listed inTable. C5.2.4. Most of the organic fibers used for short fiber reinforced concrete are synthetic fibers.
For producing high strength short fiber reinforced concrete using synthetic fibers, polyvinyl alcohol(PVA) fibers and high strength polyethylene fibers are used.

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Table. C5.2.4
Type

Examples of physical properties of synthetic fibers

Tensilestrength（N/mm2）Modulus of
Densityelasticity in （g/cm3）
tension（kN/mm2）

Heat resistanceSoftening
point（℃）

Melting
point（℃）

Polyethylene fiber

200

2.5

0.94～0.96

100～115125～135

Polypropylene fiber

300～980

3～10

0.91

140～160

165～173

Polyvinyl

800～150020～40

1.26～1.30

220～230

Not explicitly

Alcohol

fiber

known

When using synthetic fibers to reinforce concrete, the bond between hardened cement and fiber
is important. If the bond is extremely lower than the limit elasticity stress of the fiber, fibers startejecting from the hardened cement as soon as cracking occurs. Then, reinforcement is insufficient.
Polyvinyl alcohol fiber is highly hydrophilic because the material contains hydroxyl, and provides ahigh bond strength. Polypropylene fiber and polyethylene fiber have a low bond strength withhardened cement. For these types of fibers, the bond is improved by using fibers of a special shapeor treating the surface.
The chemical properties of synthetic fiber varies according to the type. The deterioration ofsynthetic fibers due to alkali reaction induced by cement has a great impact on the durability ofshort fiber reinforced concrete. A method has therefore been proposed for verifying the deteriorationof flexural strength and toughness by dipping a specimen of short fiber reinforced concrete usingsynthetic fiber in hot alkali water.
In short fiber reinforced concrete using synthetic fibers, the larger the quantity of short fibers
mixed and the shorter the diameter of the short fiber, the greater the performance but the lower theworkability. At the same percentage of short fibers mixed in concrete, slump is lower for longer
fibers and for thinner fibers.

5.4

Mix proportions(1) Short fiber reinforced concrete shall be appropriately proportioned in a manner that itmeets the requirements for design concrete.
(2) The shape, size and content of short fibers should be determined considering therequired strength and deformation characteristics of the short fiber reinforced concrete.
(3) Short fiber reinforced concrete shall be proportioned in a manner that the watercontent is kept to a minimum, while meeting the required performance.
(4) The shape, size and content of short fibers shall be clearly indicated in the mixture
proportions.

[Commentary] (1) Short fiber reinforced concrete shall have the required strength anddeformation properties, durability, and capability to protect the reinforcing bars, while having
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Short Fiber Reinforced Concrete

workability for proper placing.
Fibers in short fiber reinforced concrete should, in principle, be uniformly dispersed to achieve
the required qualities or performance, which are strongly affected by the length, shape, and content
of short fibers, maximum size of aggregate, water-cement ratio, sand-aggregate ratio, and methodsof mixing and consolidation. Especially, a very high fiber content needs a high unit water content
and sand-aggregate ratio, which could induce bleeding and segregation, and hamper mixing,
transportation, placing, and consolidation. Such issues should, therefore, be thoroughly looked into
before start of operations such as production and placement/application.
Whereas the flexural strength and toughness of short fiber reinforced concrete increase as thefiber content increases, the compressive and tensile strengths do not change much with the fiber
content.
(2) The compressive strength of short fiber reinforced concrete is determined primarily by thewater-cement ratio, as in the case of normal concrete, and not by the fiber content, though anincrease in the fiber content may increase the flexural and bond strengths, and toughness. Further,
this increase, particularly in the case of toughness, depends on the shape and size of fibers. Thus, inthis section the compressive strength shall be considered on the basis of the water-cement ratio, asin the case of normal concrete, and the shape, size, and content of short fibers for short fiber
reinforced concrete shall be determined taking the required flexural or bond strength anddeformation properties into consideration. However, it has been found that the fiber content should
be up to 0.5 to 2% by volume of concrete to be adequately mixed using normal mixing methods.
It also is noted that the fiber content, raw material, method of production, surface treatment, andshape of short fibers for concrete columns should be selected in accordance with “Design
Recommendations for Concrete Columns Reinforced with Steel Bars and Steel fibers”. In cases
when the fibers used do not conform to these requirements, it should be ensured that the tension
softening properties of the resulting short fiber meet the specified requirements.
The deformation properties of short fiber reinforced concrete are also affected by the maximum
size of aggregate. Thus, the short fibers used short fiber reinforced concrete should be sufficiently
long compared to the maximum aggregate size in order to satisfy the desired deformation properties.
Therefore, the length of short fibers should be specified to be at least 1.5 times the maximum
aggregate size. In the case of short fiber reinforced mortar, maximum aggregate size of fineaggregate should be considered. The short fiber with the length of 12mm or less can be, therefore,
used in the application to prevent spalling or explosion of concrete.
(3) In addition to compressive strength but also deformability is an important performance item
for short fiber reinforced concrete. It is therefore necessary, that the proportioning of short fiber
reinforced concrete be carried out in a manner that the resulting concrete satisfies the deformability
requirements also.
The unit water content required for short fiber reinforced concrete linearly increases as the fiber
content increases, and for each fiber percent by volume of concrete, an increment of as much as 20
kg/m3 may sometimes be required. It is therefore essential to minimize the unit water content ofshort fiber reinforced concrete within the range that produces concrete satisfying the quality
requirements. From this point of view, that use of admixtures such as air-entraining andwater-reducing admixtures, high-range water reducing AE admixtures is recommended. In the caseof short fiber reinforced concrete, in order to maintain the workability, the sand-aggregate ratio mayneed to be substantially increased as the aspect ratio of the fibers increases (see “Recommendations
for Design and Construction of Steel Fiber Reinforced Concrete Structures”).
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5.5

Production and Placement/Application

5.5.1

Fiber addition and mixing(1) In principle, a revolving-blade mixer should be used.
(2) Short fibers shall be added to concrete in the mixer in a manner that ensures theiruniform dispersion in the concrete.
(3) Short fiber reinforced concrete shall be thoroughly mixed in order that the required
qualities can be obtained.
(4) In principle, the mixing time should be determined by relavant tests.
(5) In cases when short fibers are added to concrete in an agitating truck, the concrete
shall be mixed at high speed, and shall be confirmed that the quality requirements are met.

[Commentary] (1) Since short fiber reinforced concrete is a composite material, in which shortfibers are uniformly dispersed and formed a homogenous composite material, it is important thatfibers are thoroughly mixed with the concrete. As concrete including short fibers may require
greater energy for mixing, than concrete without fibers, the present specification recommends useof a revolving-blade mixer as a standard mixer instead of a gravity mixer. It is noted that the mixing
load of short fiber concrete using the revolving-blade mixer may require between 2 to 4 times theenergy required in the case of normal concrete.
(2) Dispersing short fibers uniformly in concrete without forming fiber balls is of paramountimportance for obtaining short fiber reinforced concrete having the required properties. The methodof adding fibers to the concrete including selection of fiber type and the points and sequence offiber addition is therefore a critical factor requiring utmost care for producing short fiber reinforced
concrete having the desired properties. When the fiber having the length over 40mm is used, mix
proportions, mixing and transportation should be confirmed to meet the required performance, suchas mechanical properties. When a fiber-ball is found in the mixed concrete, the concrete shall not be
used in a concrete structure.
(3) In order to obtain short fiber reinforced concrete having the required qualities, it is necessarythat fibers should be uniformly dispersed in the concrete, which should form a homogenous
composite material. Therefore, the method of charging short fibers into the mixer and mixing so thatthe short fibers can be dispersed uniformly should be established.
For adding normal steel fibers, devices such as dispersing dispensers may be used. In the case offlat fibers and fibers bundled with water-soluble adhesive, addition may be made at a time without
forming fiber-balls.
(4) As the mixing time to be necessary for adequate dispersion of added fibers varies dependingon the type and content of fibers, it is recommended that, in principle, the mixing time for shortfiber reinforced concrete shall be determined using test mixes and confirming that the properties of
the concrete obtained meet the specifications. Mixing time can be also determined through thereliable data or track records.
(5) In general, the high speed mixing in cases when short fibers are added to concrete in an

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Short Fiber Reinforced Concrete

agitating truck is conducted. Although synthetic fibers of 0.1% or less in volume are used forprevention of spalling, adequate fiber is put in the agitating track. High speed mixing using anagitating truck shall be adopted for 2-4 min. to obtain well dispersion of fiber itself. In the case ofsynthetic fibers, high speed mixing, however, increases air content of concrete.
In cases when steel fibers are added to the concrete in an agitating truck, the qualities of theresulting concrete are affected by the method of addition and mixing time. The method of addition
and the mixing time should therefore be appropriately specified to ensure that the resulting shortfiber reinforced concrete meets the specifications.

5.5.2

Transportation

When using concrete pump for transportation, the pumping loads are greater thanthose for normal concrete. This shall be appropriately considered when making theselection of the type of pump, etc.

[Commentary] When concrete pumps are used to transport short fiber reinforced concrete, theyshould have a sufficiently large capacity, as losses in internal pressure may be larger than those fornormal concrete. Also, the piping layout should be such that an increase in the pumping loads isavoided. Further, since flexible pipe sections are particularly vulnerable to abrasion, their material,
diameter, and pipe thickness should be appropriately selected according to the placing conditions.

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5.6 Inspection
5.6.1 Inspection for acceptance of short fibers
Inspection for acceptance of short fibers shall be conducted under the responsibility ofacceptance side. The inspection should be carried out in accordance with Table 5.6.1.

Table 5.6.1

Inspection of short fibers

Type

Item

Testing
method /inspection
methodPeriod/Frequency

Criteria forjudgment

Steel
fiber

Quality

Data sheet of thetests provided bymanufacturer

Prior to construction, during
construction, and when the type offiber is alteredConformance to
JSCE-E 101

Quality

Data sheet of thetests provided bymanufacturer

Prior to construction, during
construction, and when the type offiber is alteredConformance toquality control
level ofmanufacturer

Synthetic
fiber[Commentary] Acceptance side of short fiber means manufacturer of short fiber reinforced
concrete, and the inspection results shall be confirmed by the Owner of the concrete structure. In thecases of fibers not conforming to JSCE-E 101 “Specification for Steel Fiber for Concrete”,
inspection should be carried out by the same test and inspection methods as conforming fibers andbe judged in accordance with JSCE-E 101. Criteria for the judgment should be verified through thevarious tests of short fiber reinforced concrete. Although a standard or specification for a synthetic
fiber is not established, the criteria for the judgment should be specified conforming to quality
control level of manufacturer.

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5.6.2

Short Fiber Reinforced Concrete

Inspection for acceptance of concrete at delivery

Inspection for acceptance of short fiber reinforced concrete shall be conducted under
the responsibility of the acceptance side. The inspection should be carried out inaccordance with Table 5.6.2 as standard.

Table 5.6.2

Item

Steel fiber content by
volume (whendeformation properties
are specified as
performancerequirements)

Inspection for acceptance of concrete

Testing method/
Inspection method
In accordance with
JSCE-F 554

In accordance with
JSCE-F 555(Shotcrete)

Period/Frequency

Criteria of judgment- When unloading- Once in a day or once
every 20-150 m3,
depending upon theimportance of structure
and the scale of theconstruction work

Steel fiber content by
weight (when only
strength properties are
specified as
performancerequirements)

Mass of fiber added
to concrete- At the time of unloading

Mass of fiber added
to concrete, or
number of bags

- At the time of unloading

Synthetic fiber content- All batches- All batches

Within the specified
range of fiber content
by volume

Within the specified
range of fiber content
by weight

More than the specified
fiber content[Commentary] The acceptance side of short fiber reinforced concrete means the Owner of theconcrete structure. Occasionally, constructer of the short fiber reinforced concrete tests and the
Owner of concrete structure confirms the test results.
As in the case of compressive strength of normal concrete, it is difficult to directly inspect forthe strength and deformability of the short fiber reinforced concrete at the time of delivery.
Nevertheless, these properties significantly depend on the materials used and their proportions andtheir relationships have been confirmed in the verification stage. At this stage, therefore, it isconsidered enough to ensure that the materials and their proportions used in the concrete conform to
the original specifications.
In cases when steel fiber is used, as part of the inspection for acceptance of short fiber
reinforced concrete for which the deformability is specified as one of the performance requirements,
direct measurement of short fiber content in samples taken from as-delivered concrete shall be
carried out in accordance with JSCE-F 554 “Test Method for Content of Steel Fiber in Steel Fiber
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Reinforced Concrete” or JSCE-F 555 “Test Method for Content of Steel Fiber in Sprayed Steel
Fiber Reinforced Concrete.”
As far as the inspection for acceptance of short fiber reinforced concrete for which performancerequirements are specified only in terms of strength, only a measurement of the mass of added shortfibers may be carried out. The fiber content may be measured on the basis of the number of bags ofshort fibers added to the concrete at the time of mixing from the charging hole. Fractions of a bagmust be measured by mass.
In cases when synthetic fiber is used, fiber content in concrete shall be inspected through themeasurement of fiber weight. When the fiber is added into concrete at agitating truck, the fiber
content may be measured on the basis of the number of bags of short fibers added to the concrete.
Regarding the allowable range on fiber content for the criteria of the inspection, not only
allowable value of variation for each measurement but also averaged values of several
measurements can be used. For example, a change of ±20% for median can be used as the criteria
for each measurement, and the criteria that the mean value of three measurements should be morethan 95% of median can be also used.
For short fiber reinforced concrete, inspection of acceptance, which is similar to that of normal
concrete, is required. Although the slump and air content of concrete before and after adding offiber might be changed, the occasion for the inspection should be decided consulting with the
Owner of a structure.
The inspection except for the above shall be carried out in accordance with this specification(Materials and Construction, Construction Standards Chapter16 and Inspection Standards).

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 6 HIGH-STRENGTH CONCRETE
6.1 General
6.1.1 Scope
This chapter specifies requirements particularly for construction of high-strength
concrete with characteristic compressive strength of 60 N/mm2 to 100 N/mm2.

[Commentary] For structures such as prestressed concrete bridges, tanks and diaphragm walls,
and for industrial products such as poling boards, precast prestressed concrete beams andprestressed concrete piles, concrete with strength higher than that of ordinary concrete is used. It is
recently possible to manufacture high-strength concrete with a compressive strength of 200 N/mm2
or higher, or a design strength of 150 N/mm2. High-strength concrete with a design strength of 100
N/mm2 or higher can be manufactured only at a limited number of plants. Special considerations
are required throughout the production, construction and quality management phases. Then, thischapter discusses high-strength concrete with a design strength of 60 to 100 N/mm2 and describes
the matters required in the construction of the concrete. When using concrete with a design strengthof more than 100 N/mm2 or less than 60 N/mm2, this chapter may also be consulted because they
are similar to those types of concrete discussed in this chapter at a certain design safety factor
specified in the design of mix proportions.
In general, one basic way to achieve high strength for concrete is to keep the water to cement
ratio as low as possible in the range to achieve the required performance of concrete. In recent years,
the development of high-range water reducuing AE (air-entrainig) agents or high-range water
reducing agents has made it possible to produce high-strength concrete with a characteristic
compressive strength of around 60 N/mm2 with relative ease by lowering the water-cement ratio toabout 30%, while retaining required workability. In cases where a design strength of 80 to 100
N/mm2 is required, producing concrete of the designated quality simply by reducing the watercement ratio is difficult. In numerous cases, therefore, various types of cements or admixtures areused or compressive strength is determined for an age older than 28 days. When purchasing highstrength concrete as ready mixed concrete, the difference in description between Chapter 6 Ready
Mixed Concrete of "Construction: Construction Standards", JIS A 5308 Ready Mixed Concrete andthis chapter should be considered.
When providing self-compactibility to high-strength concrete, Chapter 7 High Fluidity Concreteor the "Recommendations for Design and Construction of Self-compactible, High-strength, Highdurability Concrete Structures (draft)" should be consulted. When using organic short fibers toenhance resistance to explosion during a fire, Chapter 5 Short Fiber Reinforced Concrete should be
consulted. Chapter 10 Underwater Concrete, Chapter 12 Prestressed Concrete, Chapter 14 Industrial
Products and other chapters should be consulted according to the use of high-strength concrete tounderstand the characteristics of respective types of concrete and to verify strength enhancement
and construction considerations.
Ultra high strength fiber reinforced concrete has recently been developed with a design strengthof 150 N/mm2 or higher and with great toughness owing to the use of short fibers. Concrete using
high strength lightweight aggregate made of fly ash (HFA aggregate) also enables the design andconstruction of concrete with a design strength of up to 80 N/mm2. For using these types of concrete,refer to the "Recommendations for Design and Construction of Ultra High Strength Fiber
Reinforced Concrete (draft)" and "Recommendations for Design and Construction of Concrete
Using HFA Aggregate".
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Chapter 6 High Strength Concrete

6.1.2 General
When constructing high-strength concrete, methods for selecting materials, determining
mix proportions, production and quality management shall be selected properly under theguidance of professional engineers with adequate knowledge and experience concerning
high-strength concrete so as to meet the designated performance requirements.

[Commentary] Numerous plants have never produced high-strength concrete. In the early stagesof construction planning, therefore, the facilities of plants, quality of aggregate and other materials
and production management capacity should be investigated, plants should be selected fit for
producing high-strength concrete and appropriate mix proportions should be determined based on
the results of trial mixing. Construction should be carried out more carefully than for ordinary
concrete in the transport, placement, compaction, finishing, curing and formwork design phases. In
order to ensure that the designated quality of high-strength concrete is obtained, the methods forselecting the high-strength concrete materials, determining mix proportions, production and quality
management should be fully examined and construction should be carried out according to carefully
prepared plans under the guidance of professional engineers with adequate knowledge andexperience concerning high-strength concrete.

6.2 Quality of High-Strength Concrete
High-strength concrete shall meet the designated performance requirements in terms ofstrength, durability, resistance to cracking, watertightness and fire resistance, haveworkability fit for work and be of highly homogeneous quality.

[Commentary] The quality of high-strength concrete is different from that of ordinary concrete insome respects. The quality characteristics of high-strength concrete are described below.
(i) Strength: High-strength concrete achieves high strength by reducing the water-binder ratio. The
compressive strength of concrete in the structure may, however, sometimes be lower than thecompressive strength of the specimen because of the initial high temperature hysteresis causedby the heat of hydration since the unit binder content is high.
(ii) Durability: High-strength concrete is highly resistant to the progress of carbonation and chloride
intrusion because it is of a more compact structure than ordinary concrete. With the increase ofunit binder content for enhancing strength, however, the total alkali content of concrete
increases. Then, non-reactive aggregates for alkali-silica reaction should be used. In order toensure resistance to freezing and thawing action, setting and controlling air content properly isimportant even in high-strength concrete.
(iii) Resistance to cracking: High-strength concrete provides superior protection for steel. The
performance of steel may, however, be deteriorated due to cracking caused by the heat ofhydration of the binder because the unit binder content is higher in high-strength concrete thanin ordinary concrete. It is important to make stress analysis of volumetric changes due to bothtemperature distribution and autogenous shrinkage, and to take appropriate measures toprevent damaging cracking.
(iv) Watertightness: High-strength concrete is of such a compact structure that it is highly watertight.
It should, however, be noted that unless appropriate measures are taken against cracking, water
permeates the cracks and the designated watertightness may not be obtained.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(v) Fire resistance: High-strength concrete is of a compact structure. If concrete surface is heatedconsiderably during a fire, therefore, the lower the water-binder ratio, the more likely is
explosion to occur and the greater the degree of damage. When using high-strength concrete instructures that need to be fire-resistant, measures should be taken to prevent explosion.
Explosion is generally prevented by mixing organic fibers in concrete, preventing thesplashing of fragments by explosion using steel plates or controlling temperature rise by
applying fire-proof coating. A method should be adopted for which effectiveness has been
fully verified.
(vi) Workability: High-strength concrete is highly cohesive, increasing the resistance in the pipeduring pumping and making vibratory compaction less effective. Efficiency of concrete
placement in the formwork may sometimes be reduced. High fluidity concrete should therefore
be used to ensure the designated workability.

6.3 Materials
6.3.1 Cement and admixture(1) Cement and admixture should comply with the requirements of JIS.
(2) When using cement or admixture not conforming to JIS, whether the designatedquality requirements are met or not shall be verified based on reliable documents or by
conducting tests.

[Commentary] (1) In high-strength concrete with a design strength of 80 N/mm2 or higher, lowor moderate-heat Portland cement conforming to JIS R 5210 is frequently used. Reducing thewater-cement ratio is insufficient for ensuing the designated strength. Silica fume conforming to JIS
A 6207 is generally used as an admixture. Also used are ground granulated blast-furnace slag, fly
ash and expansive additive conforming to JIS A 6206, 6201 and 6202, respectively.
(2) In high-strength concrete, binders such as ground granulated blast-furnace slag, gypsumtype admixtures and ettringite-type admixtures are used in place of cement. Cements premixed withsilica fume have been adopted in an increasing number of cases in view of the complexity ofmanagement and varying quality of silica fume composed of ultra-fine particles. When using
cements or admixtures not conforming to JIS, whether the designated quality requirements are met
or not should be verified based on reliable documents or by conducting tests.
6.3.2 Aggregate(1) Aggregate should be used that meets the quality requirements described in Chapter
3 of "Construction: Construction Standards" and enables high-strength concrete to obtain
the designated strength.
(2) Aggregate that has been determined to be harmless in relation to alkali-silica
reaction by testing specified by JIS A 1145 or 1146 should be used.

[Commentary] (1) Attributes such as the strength, which describe the quality of high-strength
concrete may vary considerably with the type of aggregate used. The reason for this is that as thestrength of the cement matrix approaches the strength of the aggregate, the compressive strength ofthe concrete is greatly affected by the aggregate strength. Selecting aggregates to be used in highstrength concrete, therefore, is a very important task, and the use of hard aggregates such as crushed
hard sandstone is desirable. In some regions, however, acquiring excellent aggregate is difficult. It
should be verified in preliminary testing that the designated compressive strength can be provided.
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Chapter 6 High Strength Concrete(2) In high-strength concrete, unit cement content is high and the total alkali content of concreteis also high. Aggregates inducing no alkali-silica reaction shall be used in high-strength concrete.
Local availability of aggregate should be identified in the planning phase and methods for acquiring
aggregates causing no alkali-silica reaction should be examined.

6.3.3 Chemical admixture(1) Chemical admixure should be air-entraining and high-range water reducing agentsor high-range water reducing agents that conform to JIS A 6204.
(2) When using admixtures not conforming to JIS, whether the concrete meeting thedesignated performance requirements can be obtained or not shall be verified based onreliable document or by conducting tests.

[Commentary] (1) In high-strength concrete, the water-binder ratio should be set at a level lower
than in ordinary concrete. Setting the unit water content greatly influences the unit binder content.
For improving concrete workability and preventing cracking due to the hydration of the binder,
admixtures highly effective for reducing water and maintaining slump are required. When
producing high-strength concrete, therefore, high performance air-entraining and water-reducing
agents or high performance water reducing agents that conform with JIS A 6204 Chemical
Admixtures for Concrete shall be used as a standard practice.
(2) High-strength concrete is subjected to greater autogenous shrinkage than ordinary concrete.
Expansive additives or shrinkage reducing agents are sometimes used to control cracking. Whenusing admixtures for which quality requirements have not been specified in JIS such as shrinkage
reducing agents, it should be verified that quality is improved as intended or the admixture iscompatible with other materials
6.4 Mix Proportion
6.4.1 Strength
In cases where the compressive strength of concrete in the structure is likely to be
reduced below the compressive strength of the specimen as the concrete is subjected tohigh temperature hysteresis in the initial stages, the mix proportions of high-strength
concrete should be determined considering the effect of the reduction of compressive
strength as a standard practice.

[Commentary] High-strength concrete, with a high unit binder content, is subjected to hightemperature hysteresis in the initial stages if it is placed in a member of large cross section. The
compressive strength of concrete in the structure may sometimes be reduced below the compressive
strength of the specimen used for management. If the temperature of concrete exceeds
approximately 50°C due to heating, the effects should be considered in numerous cases. Testing
methods include using the compressive strength of a core sample collected from a specimen of
simulated member, and using the compressive strength of a cylindrical specimen cured in a tank towhich temperature hysteresis equivalent to that of the member or in a device in which temperaturehysteresis can be followed.
No strength reduction has been reported in cases where cement with a low calorific value e.g.
low-heat portland cement was used or where mixing temperature was held low by pre-cleaning orother means. In structures using cements that have a low-calorific value or in which strength318

Standard Specifications for Concrete Structures-2007, Materials and Construction

develops slowly, therefore, temperature rise due to heating should be minimized by taking measures
such as increasing the age as a basis for compressive strength above 28 days.

6.4.2 Slump or slump flow
The workability of high-strength concrete should be specified based on the slump or
slump flow according to the properties or construction method of concrete. At the time of
concrete placement, slump should be 18 to 21 cm, or slump flow should be 50 to 65 cm.

[Commentary] High-strength concrete is highly cohesive and should be provided with greater
fluidity than ordinary concrete. A criterion fit for evaluating the workability of high fluidity
concrete is slump flow. In order to ensure the designated workability, slump is set to be 18 to 21 cm
for high-strength concrete with a design strength of approximately 60 N/mm2, and slump flow is set
to be 50 to 65 cm for high-strength concrete with a greater strength in numerous cases. For the highstrength concrete discussed in this chapter, slump at the time of placement is set to be 18 to 21 cm,
or slump flow is set to be 50 to 65 cm as a standard practice. A standard for judgement, as towhether slump or slump flow tests should be used for workability evaluation may be as follows;
using slump for concrete with a slump of 21 cm or less, and using slump flow for concrete with aslump of 24 cm or more. Slump and slump flow should be specified properly considering thecompactibility and fluidity at the time of placement and changes in these parameters in production
through placement. Having the same slump flow as high-strength concrete does not always ensureself-compactibility. If self-compactibility is required, mix proportions should be determined inaccordance with Chapter 7 High Fluidity Concrete. For industrial products, slump may be specified
regardless of the value shown here. Slump may be reduced as long as compaction is possible.

6.4.3 Air content
For high-strength concrete that needs to be resistant to freezing and thawing action, thestandard air content should be set as shown below.
For characteristic compressive strength of 60 N/mm2

4.0%

For characteristic compressive strength of 80 N/mm2

3.5%

For characteristic compressive strength of 100 N/mm2

3.0%[Commentary] In cases where high-strength concrete needs to be resistant to freezing and thawing
action, the designated water content should be achieved. Air content greatly influences concrete
strength. Air content should therefore be minimized as long as the designated resistance to freezing
and thawing action can be obtained. Generally, the greater the concrete strength, the more resistantto freezing and thawing action. Standard air content is shown here according to the design strength.

6.4.4 Water-binder ratio
Water-binder ratio shall be determined so as to obtain the designated strength.

[Commentary] For high-strength concrete, various admixtures are used in addition to cement suchas silica fume and ground granulated blastfurnace slag. Water-binder ratio rather than water-cement
ratio is therefore discussed here. More factors affect the compressive strength of high-strength319

Chapter 6 High Strength Concrete

concrete than that of ordinary concrete. In cases where the aggregate has a low strength, no linear
relationship may be established between water-binder ratio and compressive strength. Preliminary
verification should be made in testing.
The type, air content and base materials of the binder vary according to the construction project.
Presenting a water-binder ratio corresponding to the design strength is therefore difficult. According
to the past construction records, the water-binder ratio is approximately 30 to 35% at a design
strength of 60 N/mm2, and approximately 25 to 30% at a design strength of 80 N/mm2. At a design
strength of 100 N/mm2, 7 to 15% of silica fume is used and the water-binder ratio is frequently set
at 18 to 22%.

6.4.5 Water content
The standard water content shall be less than 175 kg/m3. Water content shall beminimized by conducting testing as long as the designated performance requirements canbe met.

[Commentary] The increase of unit quantity of binder is closely related to the occurrence of
cracking due to cement hydration and to the increase of the total alkali content of concrete. Water
content should therefore be minimized to prevent the unit quantity of binder from increasing.
Excessively reducing water content, however, may lead to the deterioration of workability or to thedelay of setting due to the increase of chemical admixtures used. Therefore, the standard watercontent shall be less than 175 kg/m3. Water content should be minimized by conducting testing as
long as the designated performance requirements can be met.

6.4.6 Unit content of coarse aggregate
The unit content of coarse aggregate should be as high as possible to the extent that therequired workability is achieved.

[Commentary] In high-strength concrete, the greater the unit quantity of coarse aggregate, thebetter the quality of hardened concrete as long as the designated workability is obtained. An
optimum unit quantity of coarse aggregate should be obtained so that workability may be achievedin a wide range between a slump of 18 cm or more and a slump flow of 65 cm for high-strength
concrete. Guidelines for the absolute volume of coarse aggregate in a unit volume of concrete incases where coarse aggregates with a maximum size of 20 mm are used are listed in Table C6.4.1.
When self-compactibility is required, refer to the absolute volume of coarse aggregate in a unit
volume of concrete shown in Chapter 7 High Fluidity Concrete.
Table C6.4.1 The range of unit bulk volume of coarse aggregate(for the case of the maximum size of aggregate being 20mm)
Slump or slump flow

Unit bulk volume of coarse aggregate (m3/m3)

18 to 21 cm of slumpfrom 0.40 to 0.34

50 to 65cm of slump flow

form 0.36 to 0.31

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6.5 Production
6.5.1 Selection of plants
For producing high-strength concrete, a plant that has been officially authorized, or aplant with equivalent production facilities and management systems shall be selectedconsidering the time required for transport to the site, concrete shipping capacity andquality management capability.

[Commentary] Producing high-strength concrete requires high-level management. A plan that has
been officially authorized or a plant with equivalent production facilities and management systems
shall be selected. Some of the officially authorized plants, however, may not have produced highstrength concrete. A plant should therefore be selected considering the type and quality of materials
that can be used, quantities of storage facilities and conditions of materials stored, mixing
performance of mixers, time required for transport to the site, quality management capability andother factors.
The quality of high-strength concrete is likely to be influenced by the grading of aggregates andchange in surface moisture. Plants should therefore be equipped with such facilities as storages withhigh drainage capacity divided according to the grading of aggregates and devices capable ofautomatically measuring surface moisture. Plants should preferably be selected where the load
currents in the mixer while mixing can be verified or automatic measurements can be output.
6.5.2 Mixing(1) Batch-type forced-action mixers should be used in principle for mixing high-strength
concrete.
(2) The method for mixing high-strength concrete shall be determined based on therecords or by conducting testing so that the designated quality may be obtained.

[Commentary] (1) High-strength concrete is highly cohesive and places heavier burdens on themixer than ordinary concrete. High-strength concrete therefore shall be produced in principle usingbatch-type forced-action mixers with high mixing capacity.
(2) Mixing high-strength concrete tends to require longer time than mixing ordinary concrete
because dispersing materials uniformly such as fine grained silica fume, high performance airentraining and water-reducing agents and high performance water reducing agents is required.
Mixing time varies according to the mix proportions of high-strength concrete, performance of themixer and quantity of concrete to be mixed in each batch. The lower the water-binder ratio, thelonger the mixing time tends to be. At a water-binder ratio of more than 20%, the mixing time may
exceed 180 seconds. The dispersion of high performance air-entraining and water-reducing agentsand high performance water reducing agents is determined by the quality of materials used, order ofmaterial input and mixing capacity of the mixer. For mixing high-strength concrete, therefore,
selecting an appropriate method to ensure the designated quality is important.

6.5.3 Production control
The production of high-strength concrete shall be managed so that the designatedperformance can be obtained steadily.

[Commentary] The workability and compressive strength of high-strength concrete are likely to
be influenced by the grading of aggregates and change in surface moisture. In cases where the321Chapter 6 High Strength Concretesurface moisture of aggregates is expected to vary greatly, it should be measured frequently and theaccuracy of moisture correction should be increased to secure the designated water content.
Variations in material quality or concrete temperature may cause the water reduction capacity ofhigh performance air-entraining and water-reducing agents and high performance water reducing
agents to vary. If the load currents in the mixer during mixing vary greatly, fresh concrete should betested promptly and measures should be taken to reduce the variation of concrete quality.

6.6 Construction
6.6.1 Transportation within construction site
(1) Transport facilities are specified in Chapter 7 of "Materials and Construction:
Construction Standards" and should be selected considering the properties and change inquality of high-strength concrete.
(2) Concrete pumps with adequate pumpability should be selected.
(3) When pumping concrete under a condition under which no pumping has been done,
the type and pumping rate of the concrete pump and the diameter of pumping pipe should
be determined based on the results of full-scale pumpability tests simulating actual
pumping work.

[Commentary] (1) Concrete pumps are frequently used for transporting high-strength concrete at
the site as well as ordinary concrete. High-strength concrete is, however, so cohesive that theresistance in the pipe is increased. Pumping at the required rate for the required length may
therefore be difficult, or the quality of concrete is substantially changed during pumping. Then,
high-strength concrete may be transported using buckets. When concrete is transported in buckets,the rate of placement may be lower than in the case where concrete pumps are used, and concrete
may not be placed continuously. Care should therefore be exercised concerning the daily quantity ofconcrete to be placed, division of places for concrete placement, allowable time lag between two
placing lifts and post-placement curing. It should also be noted that placing high-strength concrete
using buckets with no agitation capacity for a long time induces surface stiffness and thereby
deteriorates the quality of high-strength concrete. Thus, appropriate facilities should be selected forthe transport of high-strength concrete at the site fully considering the deterioration of workability
during transport by pumping or other means and the change in quality of high-strength concreteduring transport.
(2) and (3) High-strength concrete is highly cohesive, so pumping load is higher for highstrength concrete than for ordinary concrete. The higher the pumping rate, the more serious the
problem. The pressure loss in the pipe for one meter of horizontal pipe for high-strength concrete
may sometimes exceeds the level five times as large as the standard value for ordinary concrete
shown in Fig. C 7.3.1 in Chapter 7 of "Materials and Construction: Construction Standards". After
pumping, the slump or slump flow and air content may be changed greatly in some cases. The
pressure loss in the pipe and quality change for high-strength concrete vary considerably according
to the mix proportions or pumping condition. They cannot be presented quantitatively. Whenpumping high-strength concrete under a unprecedented condition, therefore, the type and pumping
ratio of the concrete pump and the diameter of the pipe shall be determined properly by conducting
full-scale pumping tests simulating actual pumping work, as a standard practice. Conducting
pumping tests under actual pumping conditions before the start of construction work is, however,difficult. Tests may be eliminated if reliable data is available. After the start of construction work,
work should be carried out while confirming the oil pressure gauge readings or the state of concrete
discharged at the outlet as required.
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6.6.2 Placement and compaction(1) The time from the mixing to the end of placement of high-strength concrete should
be set to be two hours or less in cases where it has been verified that the quality of highstrength concrete remains unchanged when outdoor temperature exceeds 25°C.
(2) The method of placement, compaction time, interval of vibrator insertion and otherparameters shall be determined after preliminary verification by testing.

[Commentary] (1) If appropriate quantities of appropriate types of high performance airentraining and water-reducing agents or high performance water-reducing agents are used, slump or
slump flow of high-strength concrete varies little with time. Using high performance air-entraining
and water-reducing agents or high performance water-reducing agents helps delay the setting of
concrete. If the surface of placed concrete is kept sufficiently wet, integrity may be ensured even
where the time lag between two placing lifts is long. Then, the time from mixing to the end ofplacement may be set to be longer than 1.5 hours stipulated in 7.2 in Chapter 7 of "Materials andConstruction: Construction Standards" as long as it does not exceeds two hours in cases where it
has been verified that outdoor temperature increase above 25°C would have no adverse effects on
the quality of high-strength concrete.
(2) High-strength concrete is so cohesive that vibrators have difficulty in transmitting vibration
through the concrete and are not fully effective for compacting concrete. It is therefore necessary toverify in advance the time required for compaction and the interval of vibrator insertion. In
numerous cases, high-strength concrete is designed to have higher slump or slump flow thanordinary concrete (6.4.2). It should therefore be noted that high-strength concrete may flow
excessively toward lower sections affecting the scheduled progress of placement or compaction orthat finishing the surface of freshly placed concrete may become difficult.

6.6.3 Finishing and curing
High-strength concrete shall be finished and cured by such a method that prevents thedrying of concrete surface at the end of placement and provides the designateddimensions, surface condition and quality.

[Commentary] In high-strength concrete, bleeding rarely occurs and concrete surface dries rightafter the placement and stiffness occurs. Setting is delayed and surface finishing may sometimes
become difficult. In high fluidity high-strength concrete that is managed based on slump flow,
highly cohesive paste adheres to the trowel, pulling the surface. Smoothing the surface may
sometimes be difficult. In these cases, an appropriate amount of water should be sprayed over thesurface using atomizers during finishing. Drying of concrete surface may sometimes shorten theallowable time lag between two placing lifts or cause plastic shrinkage cracks. In order to protect
concrete surface from direct radiation or wind, concrete surface should be covered with membranes
or curing mat immediately after placement and water should be sprinkled on the surface or concreteshould be cured using membranes. Liquid membrane-forming compounds for curing are applied
either during or at the end of finishing. The quantity to be applied and the timing of application vary
according to the type of the compound. When using compounds, the method of application and theeffects of compounds should be verified in advance based on reliable documents or by conducting
tests.

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Chapter 6 High Strength Concrete

In high-strength concrete, binders such as moderate- and low-heat Portland cements, silica fumeand ground granulated blast-furnace slag are frequently used. No standard period of wet curing has,
however, been specified for these binders in Table 8.2.1 in "Materials and Construction:
Construction Standards" . The period of wet curing should therefore be determined according to thetype of the binder, combinations of binders or design strength of the binder. High-strength concrete
has a low water-binder ratio. The compressive strength of concrete at an early age when forms canbe removed (Table C 11.8.1 in Materials and Construction: Construction Standards) can sometimes
be obtained. At the age, however, the temperature of members is extremely high. If forms are
removed at an inappropriate time or if concrete is cured improperly after the removal of forms,
cracking is likely to occur. The method of curing or the timing of form removal shall therefore be
determined based on reliable documents or by conducting tests considering the period of wet curing
required to ensure the designated strength and durability and the change in thermal stress at the endof curing.

6.6.4 Formwork
The lateral pressure of high-strength concrete on the formwork should, in general, be
treated as hydrostatic.

[Commentary] High-strength concrete is designed to have workability in the range between astandard slump of 18 cm and a slump flow of 65 cm. The lateral pressure acting on formwork is
nearly fluid pressure. Setting takes a long time and the lateral pressure acting on the formwork is
reduced slowly. Formwork shall therefore be designed on the assumption of fluid pressure. In cases
where sufficient management is possible, however, by adjusting the rate of placement or measuringlateral pressure by pressure gauges, pressure lower than fluid pressure may be assumed when
designing formwork.
6.7 Inspection
The accepting party shall be held responsible for conducting acceptance tests forhigh-strength concrete in accordance with Table 6.7.1.
Table 6.7.1 Inspection for acceptance of high-strength concrete
Item

Slump orslump flow

Testing method/Inspection
methodPeriod/Frequency

Criteria for judgment

In accordancewith JIS A 1102
or JIS A1150

When accepting,once a day or once
every 20~150m3,
depending upon theimportance ofstructure and thescale of theconstruction work

Slump:
Specified value ±2.5cm(when specified value is 18cm)
Specified value ±2.0cm(when specified value is greaterthan 18cm and smaller than 21cm)
Slump flow:
Specified value±7.5cm[Commentary] The accepting party conducting acceptance tests for high-strengh concrete is the
Owner of the structure. There may be cases, however, where the Contractor constructing highstrength concrete has conducted tests and the Owner has verified the test results.
It should be noted that the compressive strength of high-strength concrete is more likely to beaffected by the smoothness of the surface of the loading test specimen subjected to loading and the324

Standard Specifications for Concrete Structures-2007, Materials and Construction

stiffness of the loading test apparatus than ordinary concrete. There is a risk of fragments of thespecimen splashing at the time of compressive failure. Tests should therefore be conducted after
taking measures to prevent fragments from splashing.
The decision criterion for slump flow has been specified at plus or minus 7.5 cm as comparedwith the set value. In cases where slump flow exceeds 70 cm in testing, the segregation of
aggregates may occur at certain mix proportions. The setting and the range for management should
therefore be determined after verifying no occurrence of segregation.
Inspections of concrete other than those listed in Table 6.7.1 shall be conducted in accordancewith Chapter 16 of "Materials and Construction: Construction Standards" and "Materials andConstruction: Inspection Standards".

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Chapter 7

High Fluidity Concrete

CHAPTER 7 HIGH-FLUIDITY CONCRETE

7.1

General

7.1.1

Scope

This chapter specifies standards on essential matters particularly required for theconstruction of high-fluidity concrete.

[Commentary] High-fluidity concrete refers to a concrete with greatly enhanced flowability
while retaining high resistance to segregation. The performance evaluation method of freshhigh-fluidity concrete widely differs depending on whether vibration is given to the concrete during
placing. This chapter is applicable to high-fluidity concrete having self-compactability with whichconcrete can be placed in every corner of formwork without causing segregation even without
vibration. For this reason, concrete with relatively high fluidity but with no needs of self
compatibility to which vibrations are applied to help compaction is not discussed in this chapter.
High-fluidity concrete not only increases the reliability of structures from the viewpoint ofquality or durability but also permits energy/labor-saving at construction sites and rationalization of
construction. In pre-cast product plants as well, high-fluidity concrete is highly effective in reducing
noise as it requires no vibration. One of the major characteristics is the properties of fresh concretethat are greatly different from those for ordinary concrete. To use the characteristics, production of
concrete is important and numerous points should be considered. This chapter specifies matters that
require attention to ensure its performance in selecting materials, proportioning, producing, andplacing.
For matters not described in this chapter, refer to the "Construction Guidelines for High Fluidity
Concrete". For high strength concrete using high fluidity concrete and industrial products using
high fluidity concrete, refer to Chapter 6 High Strength Concrete and Chapter 14 Industrial Products,
respectively.

7.1.2

GeneralWhen constructing high-fluidity concrete, methods for selecting materials, determining
mix proportions, production and quality management shall be selected properly under theguidance of professional engineers with adequate knowledge and experience concerning
high-fluidity concrete so as to meet the designated self-compactability.

[Commentary] Various types of materials are used for high fluidity concrete. Mix proportions
can be determined freely. High fluidity concrete has unique characteristics as compared withordinary concrete. For example, the quality of high fluidity concrete is determined by the effects ofchange in surface moisture of aggregate. High fluidity concrete should therefore be produced andconstructed by understanding its characteristics, learning the methods for using it, determining thematerials to be used, mix proportions, production method and quality management method and fully
identifying the properties of high fluidity concrete so that the designated self-compactibility may beachieved steadily under the guidance of professional engineers with adequate experience.

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7.2

Quality of High-Fluidity Concrete

7.2.1

GeneralHigh-fluidity concrete shall meet the designated performance requirements in terms ofstrength, durability, resistance to cracking and self-compactability, and shall be of highly
homogeneous quality.

[Commentary] One of the major characteristics of high fluidity concrete is self-compactability.
Reduction of self-compactability due to the heterogeneous nature of fresh concrete leads directly tosuch problems as pipe clogging during pumping, fall from a large height or material segregation
during long-distance flow, poor injection in densely arranged reinforcement and honeycombing on
the surface of formwork. Care should therefore be exercised especially as to the quality of fresh
concrete as compared with the case for ordinary concrete.

7.2.2

Self-compactability(1) For high-fluidity concrete, the level of self-compactability should be determinedconsidering the shape, dimensions and bar arrangement for the structure in whichconcrete is placed.
(2) The level of self-compactability shall be appropriately determined for the concrete
just before placing in the formwork.
(3) Three ranks of self-compactability are defined as follows:
Rank 1: Self-compactability for high-fluidity concrete placed into members or
segments having complicated shapes and/or small cross-sectional areas with aminimum clearance of 35 to 60 mm between reinforcing bars.
Rank 2: Self-compactability for high-fluidity concrete placed into reinforced
concrete structures or members with a minimum clearance of 60 to 200 mm
between reinforcing bars.
Rank 3: Self-compactability for high-fluidity concrete placed into structures having
large cross-sectional areas, with little or no reinforcement, such as structures
where the minimum clearance between reinforcing bars exceeds 200 mm or plain
concrete structures.
(4) It is advisable to select the Rank 2 level of self-compactability as a standard fornormal reinforced concrete structures or members.

[Commentary] (1) and (2) The level of self-compactability should be determined for concreteright before placement in the formwork considering the shape, dimensions and bar arrangement forthe structure in which concrete is placed. Construction conditions such as the height of fall, distanceof flow and the height of a lift should be determined according to the specified level ofself-compactability for reflection in the construction plan.
(3) and (4) Ranks 1 to 3 are defined as the levels of self-compactability of concrete. These ranks
are set based on the dimensions and reinforcement arrangement of the structures or members. Rank
2 is defined as the capability of concrete with which it can be self-compacted through a minimum
bar clearance of 60 to 200 mm. This normally corresponds to the steel content of 350 to 100 kg/m3.
Rank 1 is a level on which concrete meets severer requirements than for Rank 2, representing theminimum cover depth and clearance specified in the Clause 13.3 of Standard Specifications for327

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High Fluidity Concrete

Concrete Structures “Design: Main”. Rank 3 is a level on which concrete meets easier conditions
than Rank 2, requiring the self-compactability demonstrated where the minimum bar clearance ismore than 200 mm and maximum steel content is less than 100 kg/m3. In normal concrete structuresand members, the minimum bar clearance is 60 to 200 mm and the steel content is roughly 100 to
200 kg/m3. Therefore, a self-compactability level of Rank 2 is selected as a standard for ordinary
reinforced concrete structures and members. In cases where high-fluidity concrete is applied forfilling narrow space like concrete joined under existing concrete members or for filling steel shellsof a steel-concrete composite structure, Rank 1 or 2 self-compactability high-fluidity concreteshould be used regardless of bar arrangement. High-fluidity concrete in respective ranks
corresponds to high-fluidity concrete with performance represented by a filling height of more than
300 mm (restriction R1, restriction R2 and with no restrictions) in U- or box-shaped container (Fig.
C7.2.1) in tests using a filling tester specified in JSCEF-F511 "Void Passing Tests Using
High-fluidity Concrete Filling Tester (draft)" (Table C7.2.1).
Grip

Grip

[Obstacles][Obstacles]
A
room

A
room

B
room

Partition board(t=5mm)Partition board(t=10mm)
R1

R1
Partition gate
(t=10mm)

R2

B
room

Obstacle

Partition gate(t=5mm)Sampling gate

R2(a) U-shaped container

Obstacle

Sampling gate(b) Box-shaped container

Fig. C7.2.1 Shapes and dimensions of apparatuses for self-compactability test

Table C7.2.1

Rank of self-compctability of high-fluidity concrete

Rank of self-compactability
123Condition
Minimum barover 200
35〜60
60〜200clearance (mm)Steel content
over 350
under 100
100〜350(kg/m3)Filling height in a U- orover 300
over 300
over 300
box-shaped container* (mm)(restriction R1)(restriction R2)(without restriction)* Filling height specified in JSCEF-F511 "Void Passing Tests Using High-fluidity Concrete Filling
Tester (draft)"328

Standard Specifications for Concrete Structures-2007, Materials and Construction

7.3

Materials(1) Materials used in high-fluidity concrete should be those of which quality has been
confirmed to JIS or the JSCE standards.
(2) In the case of using materials having qualities not specified in the standards of JIS
or the JSCE standards, the fulfillment of both the self-compactability of the fresh concrete
made using them and the properties of the hardened one shall be confirmed by reliable
documents or by conducting tests.

[Commentary] (2) The self-compactability of concrete made using materials not covered by the
JSCE Standard Specification or those that will be newly developed can be used after verifying
self-compactability of concrete. In this case as well, it should be confirmed that such concrete
satisfies the quality requirements for hardened concrete specified in the JSCE Standard
Specification by reliable documents or by conducting tests.
Amongst the materials not specified by JIS or the JSCE standards, limestone powder, crush stone
powder and viscosity agent are examples of materials for high-fluidity concrete for which sufficientfield experience has already been acquired. When increasing the amount of powder to enhance theresistance to material segregation, increasing the binder as powder is likely to promote heating or
shrinkage. Limestone powder and crushed stone powder are therefore used as powder with poor or
no reactivity. Viscosity agents are classified into two types: one used simply to introduce
segregation resistance to fresh concrete, and another used both for imparting segregation resistanceand for reducing the influence of fluctuation of the material qualities on the performance ofconcrete. On the other hand, some of the viscosity agent may interact with other chemical
admixtures, producing adverse effects on each other’s performance each other. Therefore, theseshould be used after checking the performance, with due attention to their combinations.

7.4
7.4.1

Mix proportion
Selection of types of high-fluidity concrete

When designing mix proportions for high-fluidity concrete, an appropriate type ofhigh-fluidity concrete should be selected from among powder type, viscosity agent typeand combination type considering the type of the structure, structural conditions,construction conditions, types of materials available and restrictions at concrete
production plants.

[Commentary] High-fluidity concrete is classified into three types: powder type, viscosity agent
type or combination type based on the type and quantity of the material used. In powder-typehigh-fluidity concrete, the resistance to material segregation is generally enhanced by increasing theamount of powder without using viscosity agents. In viscosity-agent-type high-fluidity concrete,
resistance to material segregation is increased using viscosity agents. Viscosity agent and powder
types can be clearly classified according to whether viscosity agents are used or not.
Combination-type high-fluidity concrete uses viscosity agents like viscosity-agent-typehigh-fluidity concrete. In the combination type, resistance to material segregation is provided
basically by increasing the unit amount of powder as in powder-type high-fluidity concrete andself-compactability is provided by considerably enhancing fluidity using high performance
air-entraining and water-reducing agents or high performance water reducing agents. In
combination-type high-fluidity concrete unlike in powder or viscosity agent types, viscosity agentsare used not only to provide slight resistance to material segregation but also to produce and329

Chapter 7

High Fluidity Concrete

construct steady and self-compactible high-fluidity concrete relatively easily by minimizing thevariations of fresh concrete properties due to variations of quality and condition of materials.
What type of fluidity concrete is appropriate varies according to the conditions unique to eachstructure such as the type of the structure, structural condition, construction condition, types ofmaterials available and restrictions at concrete production plants. An appropriate type ofhigh-fluidity concrete should be selected considering the following points.
(i) In cases of severe structural conditions or inappropriate grading or grain size of coarse
aggregate, using powder- or combination-type fluidity concrete should be considered with a view to
reducing the quantity of aggregate.
(ii) In cases where thermal stress or autogenous shrinkage is an issue as in mass concrete,
selecting a viscosity agent type with relatively low unit binder content for reducing the amount ofbinder or reducing the heat of hydration in powder or combination type by adjusting the types andcombinations of powder should be considered. In cases where varieties of types of admixtures are
required and only a few cement silos are available on a standby basis, using premixed powder suchas blended cement containing three cementitious materials should be considered.
(iii) In cases where high strength is required, powder- or combination-type high-fluidity concrete
is applicable as a relatively low water-binder ratio can be specified. Conversely, in cases where highstrength is not required or is structurally detrimental, selecting the viscosity agent type with arelatively high water-binder ratio or preventing strength from increasing excessively by adjusting
the type and combination of powder in powder- or combination-type high-fluidity concrete should
be considered.
(iv) In cases where steadily securing self-compactability by minimizing the variations of fresh
concrete properties is required while fine aggregate grading and surface moisture vary in a wide
range, using the combination type should be considered.
(v) In cases where aggregates contain few fine particles, using the powder or combination typeto increase the amount of powder should be considered. In cases where aggregates containnumerous fine particles, using the viscosity agent type should be considered.

7.4.2

Mix design

The mix proportions of high-fluidity concrete should be determined so that the concrete
may have the designated fluidity, resistance to material segregation andself-compactability according to the structural condition of the structure, construction
condition and environmental condition, and that the designated performance requirements
may be achieved in such terms as strength and durability.

[Commentary] In high-fluidity concrete, resistance to material segregation and fluidity, which
are mutually conflicting performance requirements for fresh concrete, are achieved by combining
different types and quantities of materials. Various materials and mix proportion design methods are
therefore used. Various mix proportions can achieve the same performance goal. This is a great
difference from the conventional concept of concrete mix proportions.
In the design of mix proportions of high-fluidity concrete, the maximum size of coarse aggregate
and absolute coarse aggregate content are first determined to ensure the designatedself-compatibility and excellent passage through voids after the type of high-fluidity concrete is
selected. Next, water content, water-powder ratio and unit amount of powder required for ensuring
the designated self-compactability are determined. Then, water-binder ratio and unit binder content
are specified to achieve the performance requirements in such terms as strength and durability. Air
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Standard Specifications for Concrete Structures-2007, Materials and Construction

content, unit content of fine aggregate and quantities of admixtures used are also determined.
Whether or not the fresh concrete to be obtained is provided with the designated fluidity, resistanceto material segregation and self-compactability is then verified.
The goals to be achieved at respective ranks of self-compactability in evaluation tests for powder-,viscosity-agent- and combination-type high-fluidity concrete during the design of mix proportions
are shown in Tables C7.4.1 through C7.4.3. For the resistance to material segregation, any one ofthe parameters listed in the table should be satisfied. For the general procedure of mix proportions
design for each type of high-fluidity concrete, refer to the mix proportions design manual in the"Guidelines for Construction of High-fluidity Concrete". In the powder- or combination-typehigh-fluidity concrete, the unit amount of powder is generally large. In cases of a large amount of
cement, the total alkali content increases and there is a concern about alkali-aggregate reaction. For
mix proportion design considerations in such a case, refer to Chapter 6 "High Strength Concrete."

Table C7.4.1 Self-compactability ranks of powder-type high-fluidity concreteand targets to be achieved in evaluation tests
Rank of self-compactability
123Absolute volume of coarse aggregate
0.28〜0.30
0.30〜0.33
0.32〜0.35
content (m3/m3)
Fluidity
Slump flow (cm)
60〜70
60〜70
50〜65
Funnel flow time of V75 funnel
9〜20
7〜13
4〜11
Resistance toor O funnel (s)segregation
50 cm flow time (s)
5〜20
3〜15
3〜15

Table C7.4.2 Self-compactability ranks of viscosity-agent-type high-fluidity concreteand targets to be achieved in evaluation tests
Rank of self-compactability
123Absolute volume of coarse aggregate
0.28〜0.31
0.30〜0.33
0.30〜0.36
content (m3/m3)
Fluidity
Slump flow (cm)
55〜70
55〜70
50〜65
V75 funnel
10〜20
7〜20
7〜20
Funnel flowor O funnel
Resistance totime (s)S100 funnel*
4〜8
3〜8
3〜8
segregation
50 cm flow time (s)
5〜25
3〜15
3〜15
* Reference "Flow test method using S funnel" in "Guidelines for construction of high-fluidity concrete"331Chapter 7

High Fluidity Concrete

Table C7.4.3 Self-compactability ranks of combination-type high-fluidity concreteand targets to be achieved in evaluation tests
Rank of self-compactability
123Absolute volume of coarse aggregate
0.28〜0.30
0.30〜0.33
0.30〜0.35
content (m3/m3)
Fluidity
Slump flow (cm)
65〜75
60〜70
50〜65
Funnel flow time of V75 funnel
10〜25
7〜20
7〜20
Resistance toor O funnel (s)segregation
50 cm flow time (s)
5〜20
3〜15
3〜15

7.4.3

Representation of mix proportion

As a general rule, mix proportions should be presented as shown in Table 7.4.1.

Table 7.4.1 Representation of mix proportion
Maximum
size ofcoarseaggregate
(mm)

Notes

Rank ofselfcompactability

Water
to
binder
ratio
(%)

Water
to
powderratio
byvolume(%)

Aircontent(%)

Unit
volumeofcoarseaggregate(m3/m3)

Unit weight (kg/m3)
Chemical admixture
Water
W

CementC

AdmixtureF

Fine
aggregate
S

Coarseaggregate
G

Superplasticizer

Viscosity
agent

Others1) When more than one material of the same kind is used, each shall be indicated in a separate box.
2) Shown in the columns for self-compactability ranks are the types of obstacles in void passage tests using filling
equipment.
3) The dosage of an air-entraining and high-range water-reducing admixture shall be expressed in kg/m3 and shall be
included in the unit water content.
4) The dosage of other chemical admixtures sham be expressed in ml/m3 or g/m3 and shall be indicated undiluted andundissolved.
5) The viscosity agent content shall be expressed in kg/m3.

[Commentary] The mixture proportions shall be expressed as the content of each material in termsof mass per cubic meter of concrete. It should be noted that the water-powder ratio by volume andunit volume of coarse aggregate which affects passability through narrowed area should beindicated in the format, in addition to the water-binder ratio, as the volume of powder strongly
affects the deformability and segregation resistance of high-fluidity concrete.
It is desirable that the format include the type of structure, type of high-fluidity concrete,characteristic compressive strength, age at which the characteristic strength is assured, type of
cement, type and physical properties of mineral admixtures, type and physical properties of coarse
and fine aggregates and type of chemical admixtures. It is also desirable that it includes the
structural conditions of the structure like reinforcement conditions, as well as the construction
conditions, such as the transportation time, construction methods and seasonal conditions. The
inclusion of the slump flow, flow time to 50 cm and funnel efflux time in the data sheet isrecommended because these are useful for the control of self-compactability.

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7.5

Production

7.5.1

Selection of plants

For producing high-fluidity concrete, a plant that has been officially authorized, or aplant with equivalent production facilities and management systems shall be selectedconsidering the time required for transport to the site, concrete shipping capacity andquality management capability.

[Commentary] Plants should be selected considering the production management capability,
availability of engineers with adequate knowledge about high-fluidity concrete and other factors.
The quality of high-fluidity concrete is easily affected by changes in the surface moisture andgrain size distribution for aggregate. Plants should therefore be selected that use storage andmanagement methods for minimizing the changes. Plants should also be equipped with equipment
for monitoring the mixer loads during concrete mixing and facilities for outputting measurement
records.

7.5.2

Storage of aggregates

Aggregates should be stored so as to minimize the change in surface moisture.

[Commentary] High-fluidity concrete is generally more susceptible to fluctuation in unit watercontent than normal concrete. For this reason, in order to produce high-fluidity concrete having
stable qualities, it is necessary to control the fluctuation of the surface moisture of aggregate,particularly fine aggregate by the following methods.
(i)

The storage facility is covered with a roof to prevent aggregates from being weathered.

(ii) When piling aggregates in open yards for storage, the aggregates are covered with curing
membranes to protect them from weathering or solar radiation.
(iii) When the surface moisture of fine aggregate is high, the surface moisture tends to beheterogeneous even where the aggregate is stored in facilities with a roof. Surface moisture shouldbe held to 5% or less. For coarse aggregates, surface moisture of 1% or less is desirable. To that end,
aggregates should be retained in storages several days ahead of placement and surface moisture of
aggregates should be reduced throughout the storage facilities.
(iv) Adequate quantities of aggregates should be stored to prevent aggregates in another lot frombeing used in a round of construction.
(v) In cases where aggregates in another lot need to be used frequently because large quantities
are placed at once, systems that mechanically maintain surface moisture at a certain level such as byusing centrifugal forced dewatering equipment should be used.

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7.5.3

High Fluidity Concrete

Mixing(1) Batch-type forced-action mixers should be used for mixing high-strength concrete.
(2) The high-fluidity concrete mixing method should be determined based on theexisting records or by conducting tests.
(3) The batch of high-fluidity concrete should be determined considering the type ofhigh-fluidity concrete, mixing capacity of the mixer, transport volume and rate of shipment.
The standard batch should be 80 to 90% of the maximum capacity of the mixer.
(4) The high-fluidity concrete mixing time for each batch should be determinedconsidering the type of high-fluidity concrete, mixing capacity of the mixer and otherfactors. The standard mixing time should be 90 seconds or more in the case where arevolving-paddle mixer is adopted.
(5) It shall be verified by mixing using an actual mixer at the plant that high-fluidity
concrete meets the designated performance requirements for fresh concrete.

[Commentary] (1) High-fluidity concrete has a lower yield value and higher plastic viscosity
than ordinary concrete. Batch-type revolving-paddle mixers with high mixing capacity shall be usedin principle for producing concrete. Horizontal biaxial revolving-paddle mixers should generally be
used that can reduce mixing time and takes a short time for discharging.
(2) Materials are input to the mixer in a similar sequence to that for ordinary concrete innumerous cases. In high-fluidity concrete, however, the mixing load is larger than in ordinary
concrete. Excessively large loads are imposed at the time of input of coarse aggregates. The mixer
may discontinue operating or is enforced to cease. Care should therefore be exercised. The
effectiveness of high performance air-entraining and water-reducing agents or high performancewater reducing agents for dispersion is affected by the type of powder used, quality of aggregates,order of material input and capacity of the mixer. Then, a high performance mixer should be used,
and the material input order, mixing volume and mixing time should be determined properly basedon the existing records or by conducting tests so that the mixed concrete may meet the designatedperformance requirements.
(3) In high-fluidity concrete, the load on the mixer tends to increase during mixing. The batch istherefore frequently reduced to obtain adequate mixing capacity. In existing records, the batch is set
to be 80 to 90% of the maximum capacity of the mixer in numerous cases.
(4) In high-fluidity concrete, unit amount of powder is increased or thickening agents are used
to enhance resistance to material segregation. High-fluidity concrete therefore tends to be morecohesive and require more mixing time for obtaining the designated quality than ordinary concrete.
The mixing time required for obtaining the designated quality uniformly varies according to themixing capacity of the mixer and the batch. An appropriate mixing time should be verified byconducting tests. In existing records of construction, the mixing time in the case where arevolving-paddle mixer is used is set to be 90 to 150 seconds in numerous cases. The mixing time
for revolving-paddle mixers should therefore be set to be 90 seconds or longer as a standardpractice.
(5) The properties of fresh high-fluidity concrete produced in the plant to be used for actual
construction may frequently differ from those of high-fluidity concrete proportioned in advance inlaboratories. This results from different mixing efficiency of the mixer. In such a case theproportions are normally corrected by adjusting the dosage of high-range water reducing AE agent.
The manual for production and construction in the “Recommendation for Construction of334

Standard Specifications for Concrete Structures-2007, Materials and Construction

High-fluidity Concrete” may be instructive in understanding details of such adjustment.

7.5.4

Quality control during production(1) The frequency of measurement of surface moisture should be increased as required
to accelerate the correction of surface moisture of aggregate.
(2) The quality of fresh concrete is likely to vary at the start of production. Tests should
be conducted frequently for quality control until stable quality is obtained.

[Commentary](1) In high-fluidity concrete, the properties of fresh concrete are vulnerable tothe effects of change in aggregate surface moisture. In the first several batches, the surface moistureis high even in an aggregate storage covered with a roof. Measurements should therefore be taken
the required number of times until the value of surface moisture is stabilized and equipment should
be adopted that provides for prompt correction of measurements.
(2) The surface moisture of aggregate is likely to vary right after the start of production, so thequality of fresh concrete is also likely to vary. The frequency of quality management tests should be
increased until the quality is stabilized for reflection in production management. For high-fluidity
concrete, quality management tests should be conducted in terms of fluidity, resistance to material
segregation and self-compactability in addition to the verification of power consumption by themixer during mixing and the quality verification tests of fresh concrete as practiced for ordinary
concrete, so as to obtain the designated properties. Generally, fluidity is controlled by conducting
slump flow tests and resistance to material segregation is controlled based on the 50 cm flow time
and the funnel flow time. Self-compactability should be controlled by conducting tests forpassability through narrowed area using a filling tester as required.

335

Chapter 7

7.6
7.6.1

High Fluidity Concrete

Construction
Transporting and placing(1) When using concrete pumps for transport at the site, the pump diameter, piping
route and pipe length should be determined considering the quality of concrete, pumptype, pumping condition, ease of work and safety. The types and quantities of pumps
should be determined considering the quality of concrete, pump diameter, pumping
distance, pumping load and pumping rate. Pumping condition should be determinedbased on the test results or records.
(2) The placing rate of high-fluidity concrete should be adequately establishedaccording to the mixture proportions, shapes and dimensions of members andreinforcement arrangement conditions on the basis of test results and field experience.
(3) The maximum permissible drop height and flow distance of high-fluidity concreteshould be determined in advance considering the mix proportions, structural conditions
and construction conditions.
(4) The designated quality needs to be maintained during the work from the productionof high-fluidity concrete to the end of placement.

[Commentary] (1), (2) and (3) When high-fluidity concrete is conveyed by pumping, anincrease in the pumping rate tends to lead to a greater pressure loss than normal concrete. Fig.
C7.6.1 shows an example of relationship between the pumping rate and the pressure loss in the pipe.
The relationship varies greatly according to the quantity of powder. The larger the quantity of
powder, the greater the pressure loss in the pipe. Also, pumping generally tends to reduce the slump
flow of high-fluidity concrete.
When no test results are available, the following pumping conditions should be applied as astandard: The length of the pipeline should not be more than 300 m with 4- or 5-inch pipes; the free
drop height of concrete should be around 5 m or less; and the maximum lateral flow distance shouldbe 8 to15 m or less.
Excessively quick placing of high-fluidity concrete can entrap air or cause defective filling incertain structures. It is, therefore, necessary to establish the placing rate adequately according to the
mixture proportions, shapes and dimensions of members and reinforcement arrangement based on
test results and field experience. The rate of placement is generally lower than for ordinary concretein numerous cases. In approximately 50% of cases, the rate of placement has been 10 to 40 m3/hr.
The mean rate is approximately 30 m3/hr. When placing concrete in closed space, an appropriate
concrete flow slope, rate of placement and locations of air vents should be determined to prevent
incomplete filling. Though high-fluidity concrete is proportioned to provide high flowability andresistance to segregation, segregation can occur when it is dropped or flowed for an excessively
long distance. The maximum permissible drop height and flow distance should, therefore, beestablished in advance in consideration of the mix proportions and structural and construction
conditions.
In structures in which air voids are aesthetically detrimental, lightly striking the surface of
formwork may be necessary. It has, however, been known that lightly striking the surface may
remove or embed air voids. Great care should therefore be exercised when striking the surface of
formwork. The effects of striking should be confirmed in advance.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Fig. C7.6.1

Example of pressure loss in pipe under pumping of high-fluidity concrete(4) It is functionally important that high-fluidity concrete maintains the designatedself-compactability until the end of placement. Placement in densely arranged reinforcement or
filling in narrow space may take longer time than for ordinary concrete in numerous cases. With therecent enhancement of high performance air-entraining and water-reducing agents, the quality offresh concrete can now be maintained for a long time. It is necessary to use appropriate admixturesthat enable the maintenance of fresh concrete quality and to select mix proportions that provide forthe provision of designated self-compactability in the production phase through the end ofplacement.

7.6.2

Finishing and curing

Until the time of surface finishing, measures to prevent drying of the concrete surface
shall be taken. Also, care should be exercised not to miss the time to take such measures.

[Commentary] Finishing work is difficult to perform on high-fluidity concrete, due to its highviscosity and little amount of bleeding water. It is, therefore, necessary to take measures to prevent
surface drying until the time of finishing, and care should be exercised not to miss the time fortaking such measures.

7.6.3

Construction joints

Treatment at construction joints of high-fluidity concrete may be simplified if it can beensured that the required performance can still be achieved.
337

Chapter 7

High Fluidity Concrete[Commentary] The small amount of bleeding water of high-fluidity concrete forms less laitanceon the construction joint surfaces than normal concrete. For this reason, simplified treatment ofconstruction joint surfaces is permitted, provided the required performance of the joint surface isconfirmed.

7.6.4

Formwork(1) The lateral pressure of high-fluidity concrete on the formwork should, in general, be
treated as hydrostatic.
(2) When placing high-fluidity concrete into closed spaces, vent holes shall be provided
at appropriate positions in the top forms.
(3) In the case when the presence of surface voids impairs the aesthetics of thestructures, care shall be exercised in selecting the sheathing materials and type of form
removers.

[Commentary] (1) The lateral pressure of high-fluidity concrete placed in formwork acts
similarly to liquid pressure on the formwork, due to its high flowability. In addition, the longer
setting time of high-fluidity concrete than that of normal concrete generally tends to retain the highlateral pressure for a longer time. Therefore, the lateral pressure of high-fluidity concrete on theformwork should be designed as liquid pressure.
(2) Air in closed spaces should be allowed to escape out of the forms as concrete is filled inthem. To this end, vent holes should be provided at appropriate positions in consideration of theplacing method and shapes and dimensions of the portions to be placed.
(3) High-fluidity concrete can leave many voids on the formed surfaces. For structures on whichsuch voids will damage their aesthetic appearance, the sheathing materials and type of form
removers should be selected with care, as these can affect the state of air-voids being left on formed
surfaces.

7.7

Inspection

The accepting party shall assume the responsibility for conducting acceptance tests ofhigh-fluidity concrete. Self-compactability should be inspected before concrete placement
as a standard practice (Table 7.7.1).

Table 7.7.1 Inspection of self-compactability
Ranks ofself-compactability

Testing method/
Inspection method

Period/Frequency

Criteria for judgment

Rank1 to 3

In accordance with
JSCE-F511

At least once foreach 50 m3

Filling height is not lessthan 300 mm[Commentary] The accepting party conducting acceptance tests for high-fluidity concrete is the
Owner of the structure. There may be cases, however, where the Contractor constructing
high-fluidity concrete has conducted tests and the Owner has verified the test results. The
performance of concrete produced and transported for actual construction can differ from that of338

Standard Specifications for Concrete Structures-2007, Materials and Construction

designed concrete. It is, therefore, important to conduct inspection before placing, even if theconcrete has been verified at the construction planning stage. It is particularly important to examine
before placing that produced and transported concrete attains the established self-compactability forensuring reliability of the structure. Since the changes in the temperature and transportation time
during the construction can alter the self-compactability from the designed level, it has to be
confirmed by a suitable method by the time the placing begins.
The inspection is generally carried out at the point of unloading after production/transportation.
In this case, it should be confirmed that the changes in the self-compactability due to conveyancewithin the site, such as pumping after unloading, are sufficiently small. Furthermore, the time after
production and before shipping may be specified for inspection, if it is also confirmed that thetransportation after production causes only marginal changes in the self-compactability.
Self-compactability inspection is required as a rule by the test for passability through narrowed
areas with a filling tester.In the test for passability through narrowed areas using a filling tester, theobstacle conditions corresponding to the established self-compactability rank should be used. An
inspection frequency of at least once for each 50 m3 was adopted referring to the frequency ofinspection specified for superplasticized concrete.
A simple alternative test method may be applied in place of the inspection testing, if the possible
factors for quality fluctuation of concrete during production are identified and if such a simple test
method can be established with clear criteria corresponding with the criteria for rejection in theinspection by passability test using a filling tester. In cases where quality change is ascribable to thechanges in moisture and quantities of high performance air-entraining and water-reducing agentsand the changes can be corrected sequentially based on the verification of the measurements at thetime of production based on records, evaluation may be conducted based both on the slump flow
and 50 cm flow time and funnel flow time. In this case, it is necessary to establish judgment criteria
corresponding to rejection by the test for passability through narrowed areas using a filling tester or
100% testing with passability test equipment.
The best means of inspecting self-compactability is the implementation of 100% testing withpassability test using void passage equipment. If 100% testing with passability test using void
passage equipment installed between the truck agitator and pump is possible, it may be conducted.
For the methods of testing, refer to the production and construction manual described in the"Guidelines for Construction of High-fluidity Concrete".
When a concrete is rejected by inspection because of insufficient flowability, the concrete may
be added with a high-range water-reducing AE agent at a dosage in a predetermined range forre-inspection. When rejected because of segregation, the concrete must not be used. In any case, thecauses for rejection must be identified for adequate and prompt remedial measures to improve
subsequent production.
Other concrete inspections than those described here shall be conducted in accordance with
Chapter 16 of "Materials and Construction: Construction Standards" and "Materials andConstruction: Inspection Standards".

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 8
8.1

General

8.1.1

Scope

SHOTCRETEThis chapter presents the standards concerning shotcrete used for the construction oftunnels and slopes.
Shotcrete is classified into three major types: tunnel shotcrete used as theprimary tunnel lining, slope shotcrete used to protect slopes from weathering and erosion, andrepair or retrofit shotcrete for repairing or retrofitting concrete structures. Repair or retrofit
shotcrete is not discussed in this chapter because materials and mix proportions for this type of
shotcrete are greatly different from those for tunnel and slope shotcrete in certain members andunder certain construction conditions and because few records or reliable data is available. This
chapter is applicable to tunnel shotcrete (study structures include inclined and vertical shafts andlarge-cavity structures) and slope shotcrete. The shotcrete for repairing or retrofitting concrete
structures should be constructed under the guidance of professional engineers with adequate
knowledge and experience in accordance with the "Guidelines for Shotcrete (draft): Repair andRetrofit".

[Commentary]

Tunnel shotcrete as well as the rock bolts and steel supports is a major component of support
system, a standard system for a mountain tunnel. Tunnel shotcrete provides excellent adhesion to
the soils excavated earlier and develops the designated early strength right after shotcreting, and is
expected to be effective for preventing soil spalling or reinforcing the soil, preventing weathering,
applying internal pressure to the soil and distributing external forces.
Slope shotcrete is used for shotcreting for preventing the weathering of exposed rock surface,slope erosion and water seepage in the soil and for constructing shotcrete cribbing for preventing
small-scale or thin surface collapses.
Shotcrete offers numerous benefits. Factors related to the shotcreting method, however, greatly
affect the quality of shotcrete and the accumulation of dust has serious impact on the environmentand on the health and safety of workers. For dust, the Labor Standards Bureau of the Ministry of
Health, Labor and Welfare presented the "Guidelines Concerning the Dust Control during theConstruction of Tunnels and Other Structures" in December 2000. Reducing dust is an important
issue in shotcreting. With the increase of tunnel cross section, demand has been increasing formechanical performance enhancement such as higher strength and tougher shotcrete. To meet thedemand, efforts have been made to improve the quality, ease of work, cost performance, safety andwork environment through the development of such admixtures as silica fume and fine limestone
powder, dust reducing agents, acid set accelerators for liquid, such admixtures as set accelerators for
slurried powder and shotcrete machines using rotational or centrifugal force instead of compressedair.
For matters not described in this chapter, refer to the "Standard Specifications for Tunnels:
Mountain Tunnel Construction Methods". Related guidelines should also be consulted such as "Part2 Shotcrete in Mountain Tunnels" of the "Tunnel Concrete Construction Guidelines (draft)","Shotcrete Guidelines (draft): Tunnels", "Shotcrete Guidelines (draft): Slopes", "Highway
Earthworks Series – Manual for Slope Protection" of the Japan Road Association (March 1999) andthe "Design and Construction Guidelines for Slope Cribs" of the Japan Slope Protection Association(revised in March 2003).

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8.1.2

Shotcrete

GeneralWhen constructing shotcrete, the materials, mix proportions, shotcreting type, shotcretemachine and facilities and construction method should be determined under the guidanceof professional engineers with adequate knowledge and experience so that the designatedperformance requirements may be met.

[Commentary] Tunnel and slope shotcrete has both benefits and drawbacks as described below.
The materials, mix proportions, shotcreting type, shotcrete machine and construction method should
be determined under the guidance of professional engineers with skills required for the constructionof shotcrete so that the shotcrete may meet the designated performance requirements.
Shotcreting is classified into wet or dry shotcreting. In wet shotcreting, concrete is mixed in a mixer
and is pumped using compressed air as in the production of ordinary concrete. Then, set
accelerators are applied at the nozzle as required and the concrete is sprayed. In dry shotcreting, set
accelerators are applied to dry mixed cement and aggregate and the mixture is pumped using
compressed air. Pressure water is added to the mixture at the nozzle before the concrete is sprayed.
Examples of dry and wet shotcreting systems are shown in Exp. Fig. 8.1.1. In cases where the crosssection of excavation is small and the tunnel has a great length, the dry shotcreting system isadopted because a small shotcrete machine can pump materials over a long distance. In tunnels oflarge cross section like highway or railway tunnels, the wet shotcreting system is used in numerous
cases.
For tunnel shotcrete, the wet shotcreting system has recently been adopted in numerous cases inorder to improve the work environment and reduce the loss of materials. Also for slope shotcrete,
use of the wet shotcreting system is moving into the mainstream.

cement
water

mixer

Transport

ShotcretemachineCompressed airCompressor

fine aggregate
coarse aggregate

HosenozzelSpray wall

Set accelerator (forpowder and liquid)

Wet shotcreting system
Set accelerator (for powder)cementShotcretemachineCompressed air

mixer

fine aggregate
coarse aggregate

HosenozzelSpray wall

Water conveyance
Set accelerator (for liquid)
hose
Water supply pump (water)

Compressor

Dry shotcreting system

Fig. C8.1.1 Examples of shotcreting systems

8.2

Quality of Concrete

8.2.1

General

Shotcrete shall have mechanical properties, provide workability during shotcreting and341

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be able to control the dust concentration and percentage of rebound as designated, andshould be of homogeneous nature. Slope shotcrete shall be sufficiently durable as
designated.

[Commentary] For shotcrete, the 28-day strength shall be specified as the design strength as inordinary concrete. Tunnel shotcrete needs to meet the mechanical property requirements including
the early strength up to an age of 24 hours to ensure early stabilization of the tunnel andsurrounding ground during tunnel construction. When determining the performance requirements
for shotcreting, workability should be designated to reduce quality variations, and the percentage ofrebound and dust concentration should be minimized to improve the construction environment.
Slope shotcrete should keep the third party free from adverse effects of delamination or spalling,
keep aesthetic and landscape performance within the allowable range, and be sufficiently durable tocontrol the expansion of reinforcement due to corrosion caused by carbonation or chloride attack
and the cracking due to freezing and thawing action or alkali-silica reaction.

8.2.2 Mechanical properties of concrete(1) The mechanical properties of tunnel shotcrete should be expressed by the 28-daycompressive strength and the 24-hour strength as a standard practice.
(2) Compressive strength tests for tunnel shotcrete at an age of 28 days should be
conducted in accordance with JIS A 1107 using core samples produced as stipulated in
JSCE-F 561 and 553. The early strength should be tested in accordance with JSCE-G 561 or
562.
(3) The mechanical properties of slope shotcrete should be expressed by the 28-daycompressive strength.
(4) Compressive strength tests for slope shotcrete at an age of 28 days should be
conducted in accordance with JIS A 1107 using core samples produced as stipulated in
JSCE-F 561 and 553.
(5) Other mechanical properties than compressive strength shall be determined as
required. Tests should be conducted after identifying the quality standards and test method.

[Commentary] (1) : The strength of tunnel shotcrete as a mechanical property requirement varies
according to the use of the tunnel, e.g. railway, highway or water conveyance channel, and thestructural condition including the cross section and geological condition. The 28-day design
strength obtained based on the design of the tunnel supports is generally set to be approximately 18
N/mm2 in numerous cases. Tunnel shotcrete should be applied immediately following the
excavation to retain the earth. The designated strength therefore should be secured at an early age so
as to prevent the attached concrete from spalling due to its own weight and to provide resistance tovibrations induced by blasting. As the strength at an early age, a 24-hour compressive strength of 5or 8 N/mm2 is frequently specified.
(2): The 28-day strength of tunnel shotcrete shall be tested as a standard practice by testing coresamples produced by shotcreting in accordance with JIS A 1107 "Method of Collection of Core
Samples from Concrete and Method of Test for Compressive Strength". Test samples are producedin accordance with JSCE-F 561 "Production of Samples for Compressive Strength Test of Shotcrete(Mortar)". For steel fiber reinforced shotcrete, refer to JSCE-F 553 "Production of Samples forStrength and Toughness Tests of Steel Fiber Reinforced Shotcrete". Samples of tunnel shotcrete are342

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produced by shotcreting. Voids or cavities in the sample reduce the compressive strength. At thetime of testing, therefore, the method of shotcreting and the condition of the shotcrete machine
should be determined by verifying the continuity of spray walls for the sample, monitoring thevoids or cavities and measuring the apparent concentration (mass of unit volume) of the sample. In
the wet shotcreting system, the compressive strength of concrete before the application of set
accelerators may sometimes be tested by JIS A 1108 "Method of Test for Compressive Strength ofConcrete" to estimate the design strength of concrete.
The early strength up to an age of 24 hours after the start of shotcreting is low. It is therefore
difficult to measure strength by processing and shaping the sample and subjecting it to a directcompressive test as for ordinary concrete. As a standard practice, therefore, a guideline shall beobtained for early strength by measuring the pullout resistance by JSCE-G 561 "Method of Early
Strength of Shotcrete by Pullout Method", or tests shall be conducted by JSCE-G 562 "Method of
Test of Early Compressive Strength of Shotcrete in Beams".
(3) and (4): The 28-day strength of slope shotcrete shall be tested by a method similar to that for
testing the 28-day compressive strength of tunnel shotcrete described in (1) above. The design
strength is generally set to be 15 N/mm2 in numerous cases, but is sometimes set to be 18 or 21
N/mm2.
(5): Other mechanical properties of shotcrete include flexural strength and flexural toughness incases where short fibers are mixed. Flexural strength should be tested by JIS A 1106 "Method of
Test for Flexural Strength of Concrete". Flexural toughness should be tested by JSCE-G 552"Method of Test for Flexural Strength and Toughness of Steel Fiber Reinforced Concrete" using thesamples produced in accordance with JSCE-F 553.

8.3 Materials
8.3.1 Cement(1) Ordinary Portland cement complying with JIS R 5210 should be used as a standardpractice.
(2) Other types of cements than that mentioned in (1) above shall be used only after
verifying that the shotcrete meets the designated quality requirements.

[Commentary] (1) and (2): For shotcrete, ordinary Portland cement is generally used. In cases
where the shotcrete is exposed to a sulfate environment (e.g. in hot spring areas) or to an
environment affected by salt as in an ocean, Portland blastfurnace cement type B is used. It should
be noted that when using Portland blastfurnace cement, applying acid set accelerators containing
aluminum salts may sometimes cause the components of blastfurnace slag and acid set accelerator
to react to each other to form hydrogen sulfide gas. In cases where high early strength is required asin slope shotcrete construction in cold areas or in placing concrete in arch and then in sidewalls
during tunnel excavation, high early strength Portland cement is used.

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8.3.2 Aggregate
For shotcrete, aggregates inducing no alkali-silica reaction should be used as a standardpractice.

[Commentary] Shotcrete has higher cement content than ordinary concrete. Set accelerators fortunnel shotcrete contain alkali components in numerous cases. The total alkali content of concrete
generally exceeds 3.0 kg/m3. For shotcrete, aggregates shall be used as a standard practice that are
determined to induce no alkali-silica reaction by conducting tests using JIS A 1145 "Method of Test
for Alkali-silica Reaction of Aggregate (chemical method)" or JIS A 1146 "Method of Test for
Alkali-silica Reaction of Aggregate (mortar bar method)".
In cases where aggregates inducing no alkali-silica reaction are unavailable, blended Portland
cement should be used that is effective for controlling alkali-silica reaction, and acid set acceleratorswith a low alkali content should be adopted.

8.3.3 Set accelerator
Set accelerators used for shotcrete shall comply with JSCE-D 102.

[Commentary] Set accelerators promote the hydration of cement and accelerate the setting(hardening) of concrete. Set accelerators prevent sprayed concrete from sagging or falling due to its
weight, secure the designated thickness of shotcrete, reduce rebound and enhance early strength of
concrete; and thereby provide sufficient strength to resist ground deformation and vibrations causedby blasting. These are the reasons for generally adopting set accelerators for tunnel shotcrete. At thesame time, however, set accelerators are likely to deteriorate the long-term strength of concrete orcause damage to the health of workers as part of the dust. Set accelerator of guaranteed quality
should therefore be used. Set accelerators that comply with JSCE-D 102 "Quality Standards for Set
Accelerators for Shotcrete (draft)" should be used.
Major set accelerators currently used for tunnel shotcrete are listed in Table C8.3.1 with theirshape and components. Cement mineral set accelerators promote the hydration of cement, and istherefore effective for setting and developing early strength. Acid set accelerators are slightly lesseffective for developing early strength but effective for reducing dust concentration or rebound.
They are therefore used also as a measure for controlling total alkali content in cases where
aggregate that is unavailable for inducing no alkali-silica reaction is used. Appropriate set
accelerators should be selected considering the use, materials, mix proportions, construction method
and other factors because they have varying characteristics although they comply with JISCE-D
102.
Methods have recently been reported for reducing the dust concentration in cases where powder
set accelerators are used, using slurries produced by mixing powder set accelerators with water; orfor enhancing early strength using both powder and liquid set accelerators.
For slope shotcrete, set accelerators are also used in some cases to prevent the sagging of
concrete or help develop early strength in the shotcreting on sharp slopes. Then, appropriate typeand quantity of set accelerator should be determined fully considering such conditions as thecondition of construction site, method of construction and temperature.

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Table C8.3.1 Classifications of set accelerators used for tunnel shotcrete
Components

Shape

Type

PowderCement mineral

LiquidAcid
Alkaline

Calcium aluminate cement
Calcium sulfoaluminate
Water-soluble aluminum salt
(alkali-free)
Inorganic salt and aluminate

8.3.4 Admixtures and short fibers(1) Standard admixtures used for shotcrete should comply with JIS A 6201, 6206 or 6207.
(2) Standard fine limestone powder should comply with JCI-SLP "Quality Standards forFine Limestone Powder for Concrete (draft)".
(3) Standard steel fibers should comply with JSCE-E 101. Other types of short fibers shallbe used only after verifying that the designated quality requirements are met for the
shotcrete.
(4) Standard chemical admixtures should comply with JIS A 6204.
(5) Other types of admixtures shall be used only after verifying that the designatedquality requirements are met for the shotcrete.

[Commentary] (1): For shotcrete, JIS-complying fly ash, ground granulated blastfurnace slag andsilica fume are used. It has been verified that these admixtures not only enhance the mechanicalproperties of concrete but also improve concrete resistance to material segregation, enhance the easeof work in such terms as concrete pumpability and reduce the dust concentration and rebound.
When using admixtures, it should be verified in advance by conducting testing that the designatedquality requirements are met for the concrete..
(2) Shotcrete using fine limestone powder as well as that using admixtures has been determined
to improve the ease of construction and work and reduce the dust concentration and rebound. Fine
limestone powder is sometimes used with other types of admixtures. When using fine limestone
powder, it should be verified in advance by conducting testing that the designated quality
requirements are met for the concrete.
(3): Shotcrete using steel fibers is used in sections subjected to structurally high stress such as
tunnel portals, intersections of tunnels and enlarged sections; or in sections under poor geologicalconditions that are subjected to great earth pressure such as fault fracture zones and expansive
ground, mainly for improving toughness. Increasing the flexural strength, tensile strength, shear
strength and flexural toughness of shotcrete is expected to reduce shotcrete thickness and prevent
shotcrete from spalling. In cases where steel fibers are used in shotcrete, however, steel fibers may
be deformed during mixing or shotcreting. In some cases, the designated mechanical properties andtoughness may not be available for shotcrete even if the designated percentage of steel fibers is
attained. Steel fibers should therefore be of a shape that prevents deformation during mixing or
shotcreting and causes no clogging of the hose. Steel fibers used in shotcrete should generally
comply with JSCE-E 101 "Quality Standards for Steel Fiber Products for Concrete" and have alength of approximately 30 mm and have both ends treated.
When using steel fibers in shotcrete, the pumping load of concrete, quantity of steel fibers in thematerial that rebounds, orientation and deformation of steel fibers in concrete and wear of shotcrete345

Standard Specifications for Concrete Structures-2007, Materials and Construction

machine or auxiliary equipment should be fully considered. For the mix proportions and methods ofproduction and construction of shotcrete using steel fibers, refer to "Design and Construction
Guidelines for Steel Fiber Reinforced Concrete (draft)".
Other synthetic fibers than steel fibers such as vinylon and polypropylene fibers are used insome cases. When using these types of fibers, it should be verified in advance by conducting testingthat the designated quality requirements are met for the shotcrete based on Chapter 5 Short Fiber
Reinforced Concrete as for steel fibers.
(4): Chemical admixtures for concrete has been used in an increasing number of cases to reduce
the water content of shotcrete, improve resistance to material segregation and obtain designatedworkability. For slope shotcrete in particular, the designated resistance to freezing and thawing
action is frequently demanded. It is therefore necessary to use air-entraining agents, air-entraining
water-reducing agents and high performance air-entraining water-reducing agents. The effectivenessof these admixtures, however, varies according to the quality, mix proportions and construction
method of cement and aggregate. The effectiveness should therefore be verified in advance byconducting tests. When using a chemical admixture, appropriate type and quantity should bedetermined after verifying that the designated quality requirements may be met for the shotcrete.
(5): Other admixtures used in shotcrete include thickening agents and retarding agents.
Thickening agents are frequently used mainly to reduce dust and are generally referred to as dust
reducing agents. Thickening agents are used also to prevent material segregation during pumping
and to reduce rebound. Retarding agents may sometimes be used to delay the setting of concretewhen the duration from the start of mixing to the end of shotcreting (placement) is expected to
exceed the duration stipulated in Section 7.2 of "Construction: Construction Standards" in cases oftransport of ready-mixed concrete from the plant to the site or of intensive nighttime shotcreting. If
these admixtures are used in large quantities, the designated quality may be adversely affected by
the reduction of early strength and design strength. Appropriate type and quantity should bedetermined only after verifying that the designated quality requirements can be met for the
shotcrete.

8.4 Mix Proportions(1) When determining the mix proportions, the following parameters shall be determinedso that the designated quality requirements may be met for the shotcrete.
(a) Maximum size of coarse aggregate(b) Percentage of fine aggregate(c) Water-cement ratio, unit cement content and water content(d) Type and unit quantity of admixture(e) Type and quantity of set accelerator(2) Mix proportions should be determined by conducting testing before the start ofconstruction work based on reliable data.

[Commentary] (1): The workability of wet-type tunnel shotcrete is frequently controlled in aslump range between 8 and 14 cm. For the workability of slope shotcrete, flow value is set to beapproximately 120 mm as stipulated in JIS R 5201 "Physical Test Method for Cement" in numerous
cases. In the dry system, materials are mixed with water at the nozzle. The surface moisture of fineaggregate is mainly used as a parameter for controlling the ease of work.
For shotcrete, mix proportions should be determined for respective shotcrete type by selecting
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the maximum size of coarse aggregate, percentage of fine aggregate, water-cement ratio, unit
cement content and unit water content, type and unit quantity of admixture and type and quantity of
set accelerator, based on the reliable data and construction records so that the designatedperformance requirements may be met in such terms as quality of the sprayed concrete, cost
performance and ease of shotcreting work.
When determining the mix proportions of shotcrete, the following parameters should beconsidered to meet performance requirements for shotcreting work.
(i) Freedom from clogging or pulsation during pumping(ii) Low rebound ratio and dust concentration(iii) Nonoccurrence of delamination, spalling and surface sagging of sprayed concrete(a) Maximum size of coarse aggregate: Increasing the maximum size of coarse aggregate reduces
the unit water content and unit cement content, and is beneficial from a viewpoint of durability
and cost performance. In shotcrete, however, the rebound of aggregate increases and the content
of aggregate in the sprayed concrete is reduced. Clogging and pulsation are also likely to occur
during pumping. These are the reasons for specifying the maximum size of coarse aggregate at
10 to 15 mm in most of the cases either in tunnel or slope shotcrete.
(b) Percentage of fine aggregate: In shotcrete, the higher the percentage of fine aggregate, the lower
the rebound ratio and the higher the water content. On the other hand, the lower the percentage
of fine aggregate, the smaller the resistance to material segregation resulting in a higher reboundratio, and the more frequently the clogging of the hose occurs. These are the reasons for using
fine aggregates in tunnel shotcrete in a range between 55 to 70% in numerous cases. For slope
shotcrete, there are cases of a range between 70 to 100%. In numerous cases, mortar is usedwithout using any coarse aggregate. When using short fibers, a large percentage of fineaggregate should be selected as for ordinary concrete.
(c) Water-cement ratio, unit cement content and water content: The water-cement ratio of tunnel
shotcrete is generally approximately 50 to 60% for the wet system, or 45 to 55% for the dry
system. The standard water-cement ratio for slope shotcrete should be 60% or lower. In the wet
system, the ratio is frequently set to be approximately 55 to 60%. In the wet system, unit watercontent tends to be higher than in the dry system because the designated slump is secured while
not affecting concrete transport and pumping. In the dry system, the water-cement ratio iscontrolled by adjusting the amount of water added at the nozzle according to the surface
moisture of the fine aggregate used. It is therefore important to control the amount of water at
the nozzle using a flow meter considering the surface moisture of fine aggregate and theperformance requirements for shotcreting.
The unit cement content of tunnel shotcrete is set to be 360 kg/m3 at a design strength ofapproximately 18 N/mm2 in most cases. Generally, the lower the unit cement content, thehigher the rebound ratio. The higher the unit cement content, the more likely is pulsation to
occur during pumping, resulting in smaller pumpability. If aggregates with low solid volume
percentage are used, the unit water content increases and problems are likely to occur such as
clogging during pumping and sagging during shotcreting. Measures may be sometimes required
like increasing the unit cement content or increasing unit powder content by applying
admixtures. In tunnel shotcrete with a design strength of approximately 36 N/mm2, the unit
cement content is increased nearly to 450 kg/m3 and the unit water content is reduced by usingchemical admixtures. In slope shotcrete, the unit cement content should be set to be 400 kg/m3
or higher to ensure shotcreting work.
(d) Type and unit quantity of admixture: In shotcrete, admixtures are used to make high strength
concrete, enhance concrete resistance to material segregation and reduce rebound ratio and dust
concentration (Section 8.3.4). Excessively large quantities of admixtures, however, may place347

Standard Specifications for Concrete Structures-2007, Materials and Construction

large burden on pumpability or ease of shotcreting work. When using admixtures, therefore, theunit volume of admixture should be verified in advance by conducting tests considering the typeof set accelerator used so that the designated requirements for shotcrete quality and shotcreting
work may be met.
(e) Type and quantity of set accelerator: The quantity of set accelerator used in tunnel shotcrete isfive to 10% of the unit cement content in most of the cases. The quantity of set accelerator
varies according to the type of accelerator, and is affected by various parameters such as thematerial, mix proportions, slump and temperature at the end of mixing of shotcrete; conditionsof the sprayed surface such as the temperature and seepage in the tunnel; method of injection of
set accelerator into the nozzle and the method of shotcreting.
When spraying slope shotcrete, set accelerator is used to reduce rebound and to secure shotcrete
thickness early on sharp slopes or under overhangs. Then, set accelerator is likely to deteriorate
resistance to freezing and thawing action. Careful attention should therefore be paid to the typeand quantity of set accelerator.
The type and quantity of set accelerator should therefore be determined based on reliable data or
construction records, or by conducting preliminary tests so that designated quality requirements
may be met for the shotcrete. The quantity of set accelerator is generally not included in volume
calculation for mix proportions.
(2): The quality and ease of work of concrete vary according to the component of the mix. Mix
proportions therefore shall be determined after conducting tests before the start of constructionwork.

8.5 Production
8.5.1 General
When producing shotcrete, facilities for storing, measuring and mixing the materials andshotcrete machines shall be selected so as to meet quality requirements for the shotcrete.

[Commentary] For producing shotcrete, facilities meeting designated performance requirements
should be used. In this section, the process of shotcrete production is assumed to end at the point
where set accelerator and water are added at the nozzle. Necessary matters concerning the
production facilities and shotcrete machines are described in this section.

8.5.2 Production facilities(1) For measuring the volume of materials, equipment with designated measurement
accuracy should be used as a standard practice.
(2) For mixing, mixers with designated mixing capacity should be used as a standardpractice. The method for inputting materials and mixing time should be determined so thatthe designated quality requirements are satisfied.

[Commentary] (1): In the dry shotcreting system, continuous mixers are sometimes used thatmeasure the volume of materials for producing concrete. When using continuous mixers, themeasuring equipment for respective materials should be inspected using the materials to be used in
the work before the start of construction work. Measuring the volume of materials generally results
in a larger margin of error in measurement than measuring the mass of materials. Equipment should348

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Shotcrete

therefore be adjusted to maximize the accuracy of measurement of materials and to hold the marginof measurement error below the allowable level.
In cases where measuring the mass is difficult when measuring the volume of water to be addedin the dry shotcreting system or when measuring the quantity of chemical admixtures applied in thewet shotcreting system, flow meters or other equipment should be used for measurement. Whenusing a small quantity of admixtures like dust reducing agents, it should be verified in advance thatthe margin of measurement error is below the allowable level by calibrating the equipment for
applying admixtures. The margin of measurement error should be held below the level specified in
Section 5.3 of "Construction: Construction Standards". When using equipment for measuring thevolume like continuous mixers, the "Guidelines for Construction of Concrete Mixed in Place Using
Continuous Mixers (draft)" should be consulted for reference.
(2): For mixing, appropriate material input procedure and mixing time should be specified sothat concrete materials may be mixed uniformly. For mixing, mixers shall be used as a standardpractice that have capacity as stipulated in Section 5.2.3 of "Construction: Construction Standards".
If no designated quality requirements are met, appropriate measures should be taken like increasing
the mixing time.

8.5.3 Shotcrete machine and accessory equipment(1) Shotcrete machines shall be able to uniformly and continuously pump and sprayconcrete of designated quality.
(2) Accessory equipment shall be able to help shotcrete machines meet the designatedperformance requirements.

[Commentary] (1): Shotcrete machines need to be able to uniformly and continuously transportmaterials so that the designated quality of concrete and work efficiency may be secured. When
constructing shotcrete, the nozzle is either remote-operated by an automatic shotcrete machine oroperated manually. In cases where a wide work area is available and no scaffolding is required,automatic shotcrete machines are generally adopted. In a tunnel cross section of 30 m2 or less orwhen spraying concrete on a slope, concrete is sprayed manually in numerous cases.
Shotcrete machines have been put to practical use in numerous types and have varying capacity.
Shotcrete machines should be selected based on the existing records. It should be verified byconducting preliminary tests that the designated quality requirements are met for the concrete.
Using compressed air for transporting materials or for spraying concrete may cause the pressure to
rise temporarily due to clogging with materials or for other reasons. It should be made sure that
adequate strength is available at the points of hose connection and attachment. Shotcrete machines,
without the capacity for pumping materials uniformly and continuously, may fail to provide
designated quality and excellent finished surface and deteriorate work efficiency. For
remote-operating the nozzle, automatic shotcrete machines are required that can maintainappropriate distance and angle between the shotcrete surface and nozzle and enable the shotcrete tomeet the designated quality requirements. Pumping distance for slope shotcrete in particular isaffected by the area where shotcreting work takes place. If the pumping distance or vertical height isincreased, pumping becomes difficult and concrete quality is likely to become heterogeneous. A
hose length of 100 m or a height of 45 m is therefore specified as a standard.
(2): Accessory equipment to be used with shotcrete machines include compressors and equipment
for applying water and admixtures including set accelerators. Compressors should be provided withadequate capacity considering the piping resistance and leakage because insufficient volume orpressure of compressed air may cause clogging or production of non-uniform shotcrete. Then, no349

Standard Specifications for Concrete Structures-2007, Materials and Construction

designated quality requirements are met.
If no appropriate equipment is used for applying water and admixtures including set accelerators,
application may not be stable causing rebound and generating dust. Then, no designated quality
may be obtained. Methods of adjustment to secure the designated quantities should be verified inadvance by conducting material pumping tests. Compressed air used for pumping contains moisture.
When using powder set accelerators, therefore, the moisture in compressed air should be removed
using a drier.
When storing powder set accelerators in the tunnel, moisture should be removed because humidity
is high in the tunnel and set accelerators are likely to be weathered. When storing liquid set
accelerators outside the tunnel, dissolved components may sometimes precipitate when thetemperature of liquid set accelerators lowers. These points should be taken into consideration for
selecting appropriate storage methods and installing appropriate facilities.

8.6 Construction
8.6.1 General
An appropriate construction plan shall be prepared concerning the transport andapplication of shotcrete to ensure the safety of shotcreting workers.

[Commentary] Tunnel or slope shotcrete is applied in closed work space, on sharp slopes or athigh altitudes. Work space is frequently limited. There are risks of rock falls from the rock mass orearth and of collapse. In order to ensure that the designated quality requirements are met for
shotcrete under such a work environment, safety measures should be taken thoroughly by providing
protective appliances to workers or other means and a good construction plan should be prepared
concerning the specific spraying work.

8.6.2 Preliminary treatment of shotcrete surface(1) Loose rocks expected to fall during shotcreting shall be removed carefully.
(2) Any seepage on shotcrete surface shall be drained properly to prevent shotcreting
work or sprayed concrete from being adversely affected.

[Commentary] (1): Loose rocks that are expected to fall, if any, should be removed carefully inadvance to ensure the safety of shotcreting work and the bond between the earth and shotcrete.
When spraying concrete on the slope, steel wire mesh is installed to control or disperse the cracks
on the earth or rock and to prevent the delamination and falling of mortar to be sprayed. In cases
where wire mesh needs to be installed at a certain distance from the earth, welded wire mesh with asteel diameter of 2 mm and a mesh size of 50 mm is adopted. One or two anchor pins with adiameter of 13 to 16 mm and a length of 200 to 400 mm are generally arranged per cubic meter.
(2): Seepage on the shotcrete surface not only deteriorates the bond between the shotcrete andsurface but also causes the water to enter the concrete, degrading concrete quality, washes away
concrete before hardening or causes water pressure to act behind the hardened concrete, inducing
cracking or delamination.
In cases of large quantities of seepage in the tunnel, drainage pipes or filters should be installed.
In cases of small quantities of seepage, concrete is sprayed after changing the mix proportions suchas increasing the cement or set accelerator content or reducing the water content as long as the ease350

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Shotcreteof shotcreting work can be ensured. For controlling seepage on the slope, 20- to 30-cm square
geomembranes or drainage mattresses are installed at intervals of one meter or longer, or othermeasures are taken. In ordinary wire netting works, drainage pipes are installed.
For seepage control measures, refer to Section 6.4.3 of II Shotcrete in Mountain Tunnels of the"Tunnel Concrete Construction Guidelines (draft)", Section 7.7.1 of "Shotcrete Guidelines (draft):
Tunnels" and Section 7.2 of "Shotcrete Guidelines (draft): Slopes".

8.6.3 Shotcreting work
(1) Shotcreting should be carried out under the guidance of professional engineers withadequate knowledge and experience concerning shotcrete.
(2) In the wet shotcreting system, shotcreting shall be completed as soon as possible
after the unloading of shotcrete.
(3) The nozzle and shotcrete surface shall be positioned at right angles inasmuch as
possible and appropriate shotcreting distance and pressure should be maintained.
(4) Concrete shall be sprayed so as to minimize the rebound and dust concentration.
(5) Concrete shall be sprayed for an appropriate thickness so as to prevent delamination,
spalling or sagging of concrete. Concrete shall be sprayed the required number of times
until the designated thickness is reached.
(6) When spraying concrete in areas where steel supports are installed, concrete shall be
sprayed so as to leave no gap between the earth and the steel supports to ensure the bond.
(7) When spraying concrete, care shall be exercised to prevent rebound materials frombeing embedded in the concrete layer.

[Commentary] (1): The quality of shotcrete is greatly affected by the shotcreting method and theskill of nozzle operator. The shotcreting method should therefore be selected under the guidance ofprofessional engineers with adequate shotcrete knowledge and experience, and nozzle operators
well versed in spray nozzle handling should carry out the work.
Shotcreting on the slope is subjected to the effects of weather or temperature. Then, the quality of
shotcrete is somewhat affected. In cases where no appropriate curing is expected to be possible insuch a case where temperature may falls close to the freezing point after shotcreting, no shotcreting
work should be carried out.
(3): The greatest bond can be achieved between the shotcrete and shotcrete surface in cases
where the materials are sprayed from the nozzle at an appropriate rate at right angles to the
shotcrete surface. Shotcreting should therefore be carried out while maintaining the appropriate
shotcreting distance and pressure so that the nozzle may be positioned at right angles to the
shotcrete surface inasmuch as possible.
(4): The rebound and the generation of dust during shotcreting may be reduced by selecting the
shotcrete method described in (3) above. The rebound and dust increase unless set accelerators or
concrete is supplied steadily at the start of shotcreting. In order to carry out shotcreting steadily as
early as possible, therefore, equipment for applying set accelerators or other admixtures andconcrete pumps should be adjusted.
(5): The allowable shotcrete thickness varies according to the position of the shotcrete surface,whether the surface is wet or dry, shotcrete material, type and quantity of set accelerator, shotcrete
system and skill of nozzle operator. The shotcrete thickness per round of work should be specified
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Standard Specifications for Concrete Structures-2007, Materials and Construction

so as to prevent the delamination, spalling or sagging of sprayed materials. Concrete should besprayed only after the layer of concrete sprayed earlier hardens sufficiently to hold the next layer ofconcrete.
(6): In cases where the shotcrete thickness is smaller than the thickness of steel supports,
securing the continuity of supports and wall surface may become difficult. Concrete should
therefore be sprayed as shown in Exp. Fig. 8.6.1 (a). is of concern.
The grid opening should be large enough to allow shotcrete to readily fill the spaces behind thegrid. It is normally 100 by 100 mm or 150 by 150 mm, with the wire diameter being 3.2 to 6.0 mm.
A grid size of 10 by 10 mm has been used for a tunnel in soil ground to prevent soil outflow due toshotcreting.
GroundGroundDesirable finishing
Fig. C8.6.1

Undesirable finishingfinishing of shotcrete(7): In swelling or weak ground, shotcrete is sometimes used for closing the invert early. Then,
concrete is sprayed downward rather than horizontally. Rebound concrete is likely to be embedded
as it is, creating voids. Shotcrete with voids sees its strength deteriorated. Care should therefore be
exercised during shotcreting not to embed rebound materials.
8.6.4 Dust control measures(1) The rebound ratio and dust concentration during shotcreting shall be minimized.
(2) In cases where the rebound ratio and dust concentration are likely to be at detrimental
levels, appropriate corrective measures shall be taken.

[Commentary] (1) and (2): Dusts are produced during tunneling by excavation, machine
operation or shotcreting. This chapter discusses the rebound and dusts produced during the sprayingof tunnel concrete.
The dusts produced during shotcreting or rebound materials contain highly alkaline cement or set
accelerators. Shotcreting workers should therefore use appropriate protective appliances (e.g. hard
hats, goggles, dust masks, protective gloves, safety coats and safety boots) for their health andsafety.
Even with the installation of blowers for injecting indoor or outdoor air in close space like a tunnel,
completely removing dusts is difficult. While spraying concrete, the dust concentration should bemeasured by digital dust meters or high-volume suppliers, and dust control measures should betaken as required.
Methods for controlling dusts produced during shotcreting are described below.
(i) Measures taken at the source of dust(a) Selecting shotcreting methods that minimize dust production (e.g. reviewing shotcreting
distance or pumping pressure, adopting the wet shotcreting system, and employing shotcreting352

Chapter 8

Shotcreteusing rotational or centrifugal force)(b) Selecting materials that minimize dust production (e.g. using dust reducing admixtures, or liquidor powder set accelerators in the form of slurry; and using such admixtures as silica fume and finelimestone powder)(ii) Measures to control the dusts produced(a) Discharging or diluting dusts by air conditioning(b) Installing dust collectors
For controlling the dusts that are produced during tunnel excavation, refer to the "Guidelines
Concerning Dust Control during Tunnel Construction" prepared by the Labor Standards Office ofthe Ministry of Labor of Japan in December 2000..
8.6.5 Concrete protection
In cases where the shotcrete is exposed under severe conditions, appropriate concrete
protection measures shall be taken.

[Commentary] In the tunnel, temperature is stable and humidity is high except in sections near
the tunnel portals. Shotcrete is in contact with the soil and drastic drying hardly occurs. Tunnel
shotcrete is covered with geomembranes or lining concrete and is not exposed for a long time. At
present, sprayed concrete is not generally cured. In cases where a dry condition is created rapidly
after the construction of shotcrete or no lining concrete is constructed, appropriate concrete
protection work should be done such as the application of curing admixtures to prevent drying andthe atomization.
For slope shotcrete, wet curing and heat curing are required. Slope shotcrete is applied over a wide
area in numerous cases. Shotcreting should therefore be carried out at an appropriate time so as toeliminate the need of special curing.

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8.7 Inspections
8.7.1 Acceptance tests for concrete materials
The accepting party shall be held responsible for conducting acceptance tests foradmixtures used in the shotcrete. Acceptance tests should be conducted in accordance with
Table 8.7.1 as a standard practice.
Table 8.7.1 Admixture Acceptance Tests
Type

Set
accelerator

Dust
reducer

Item

Test or inspection method

Timing andfrequency

Quality

Verification based on the test
records prepared by the
manufacturer or using amethod specified in JSCE-D
102

At the time ofdelivery ofmaterials

Conformity with JSCE-D
102

Quality

Verification based on the test
records prepared by the
manufacturer

At the time ofdelivery ofmaterials

Conformity with thevalues specified in the test
records or the specified
range

Decision criteria[Commentary] Major admixtures used for shotcrete are set accelerators and dust reducers. In theacceptance tests of these admixtures, their conformity is determined at the time of delivery based on
the test records prepared by the manufacturer in most cases. Table 8.7.1 shall be used as standards.
In cases where these admixtures are stored for a long time or some defects are detected during theinspection of concrete work, specified admixtures are inspected at the instruction of the accepting
party. The inspection results are verified by the Owner.
For admixtures for which no standards have been established like JIS such as dust reducers, their
quality should be verified in advance and the decision criteria that should be adopted in acceptancetests should be determined based on the test records provided by the manufacturer.
For maintaining and managing the quality of shotcrete properly, Material Safety Data Sheet(MSDS) should be consulted that presents storage methods for respective components orcompositions of materials.eting. Shooting methods using pumps should conform to the“Recommendations for Pumping of Concrete”.

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Shotcrete

8.7.2 Concrete acceptance tests(1) The accepting party shall be held responsible for conducting acceptance tests forconcrete in the wet shotcreting system. Acceptance tests should be conducted inaccordance with Table 8.7.2 as a standard practice.
(2) Acceptance tests for concrete in the dry shotcreting system may be replaced withinspections based on the material measurements.
Table 8.7.2 Acceptance tests for shotcrete
Item

Workability ofconcrete in thewet shotcretingsystemMeasurementsof concretematerials in thedry shotcretingsystemCompressive
strength of
concrete in thewet shotcretingsystemTest or inspection method
Method specified in JIS A
1101

JIS R 5201 flow test

Timing and frequency
Before the start of
shotcreting and at thedesignated frequency
during construction
10) Before the start of
shotcreting and at thedesignated frequency
during construction

Decision criteria
Should be within thedesignated range of slump
Should be within thedesignated range of flow
value

Method specified in JIS R
5308 or JSCE-I 501

Before the start of
shotcreting and at thedesignated frequency
during construction

Should be within thedesignated range ofmeasurement

Method specified in JIS A
1108

Before the start of
shotcreting

Compressive strength
should be higher thandesignated (for reference
value)[Commentary] The accepting party in shotcrete acceptance tests means the Owner of the project.
The Contractor for shotcreting, however, usually conducts tests and the Owner verifies the test
results.
Acceptance tests for shotcrete should be conducted for the items listed in Table 8.7.2 as the tests forordinary concrete.
Concrete in the dry shotcreting system, unlike ordinary concrete, cannot be inspected based on theproperties of fresh concrete including slump. Acceptance tests for concrete in the dry shotcretingsystem may be replaced with the tests based on the measurements of materials obtained bymeasurement equipment used in concrete mixing.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

8.7.3 Inspection of concrete work
The Owner shall be held responsible for inspecting shotcreting work. Inspections forshotcrete used for tunnels and slopes should be conducted in accordance with Tables 8.7.3
and 8.7.4, respectively as a standard practice.
Table 8.7.3 Inspections of tunnel shotcrete work
Type

Inspection
ofshotcreting
work

Inspectionof shotcrete
thickness

Inspectionof conditionin the tunnel

Item

Test or inspection
methodRebound ratio

Method specified
in JSCE-F 563

Dust
concentration

Method specified
in JSCE-F 564

Timing and frequency
Before the start of
shotcreting and at thedesignated frequency
during construction
Before the start of
shotcreting and at thedesignated frequency
during construction

Decision criteria
Rebound ratio should be
below the designatedlevel.
Dust concentration should
be below the designatedlevel.
A five-percent or lower
probability ofcompressive strength
falling below the design
strength can be estimatedfrom an appropriate
producer's risk ratio.

Compressive
strength of
shotcrete

Method specified
in JIS A 1107 or
1108

Before the start ofconstruction andwhenever thedesignated mixing
condition is changed
during construction

Early strengthof shotcrete

Method specified
in JSCE-G 561(pull-out tests) or
JSCE-G 562(beam)

Before the start ofconstruction andwhenever thedesignated mixing
condition is changed
during construction

Early strength should
exceed the designatedlevel.

Shotcrete
thickness

Visual inspection,use ofmeasurement pins,
inspection bydrilling, etc.

At the designatedfrequency during
construction and at theend of construction

Shotcrete thickness should
exceed the design
thickness.

Deformation of
shotcrete

Visual inspection
or based onrecords

Dust
concentrationin the case ofventilation in
the tunnel

Refer to themethod describedin the Explanationin Section 8.6.4

At the designatedfrequency during
construction and at theend of construction
At a point where the
excavated length
exceeds 50 m, and at
the designatedfrequency in subsequent
construction

Shotcrete should be freefrom damaging
deformation or cracking.

3 mg/m3 or less

Table 8.7.4 Inspections of tunnel shotcrete work
Type
Inspection
ofshotcreting
work

Item

Compressive
strength of
shotcrete

Test or inspection
methodTiming and frequency

Decision criteria

Method specified
in JIS A 1107 or
1108

At the designatedfrequency during
construction and at theend of construction

A five-percent or lower
probability ofcompressive strength
falling below the design
strength can be estimatedfrom an appropriate

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Chapter 8

Inspectionof shotcrete
thickness

Inspectionof the sizeand positionof shotcrete
cribwork

Shotcrete

Shotcrete
thickness

Use ofmeasurement pins,
inspection bydrilling, etc.

At the designatedfrequency during
construction and at theend of construction

Deformation of
shotcrete

Visual inspection
or based onrecords

At the designatedfrequency during
construction and at theend of construction

Sectional sizeof crib
Center tocenter distance
betweenvertical andhorizontal cribs

At the designatedfrequency during
construction and at theend of construction

Measurement
using a scale

producer's risk ratio.
- 1 cm at a design
shotcrete thickness of lessthan 5 cm. -2 cm at adesignated shotcrete
thickness of 5 cm or more.
The minimum shotcrete
thickness in cases ofrough shotcrete surface
should be 50 or higher
percentage of design
shotcrete thickness. The
mean thickness should belarger than the design
thickness.
Shotcrete should be freefrom damaging
deformation or cracking.
Height: -3 cm. Width: -3
cm.
26) Center to center
distance between verticaland horizontal cribs: ± 10cm

[Commentary] In the inspection of shotcrete, one of concrete work inspections, rebound ratio,
dust concentration, early strength and compressive strength, four performance parameters related toshotcreting, are inspected. Early strength and compressive strength are investigated in daily
inspections. Rebound ratio and dust concentration are investigated as required.
Methods for investigating rebound ratio for tunnel shotcrete are affected by the condition of soil
excavation, shotcreting method and skills of workers. Investigation accuracy is not sufficiently
reliable. Investigations themselves require much effort. Rebound ratio shall therefore be
investigated as required. Rebound in the tunnel is frequently inspected near the point of excavation.
Inspections should be conducted while ensuring safety in the work environment considering thestability of soil or excavated face and the strength development of tunnel shotcrete. In cases where
good track records on the past shotcreting are recognized based on the mix proportions of tunnel
shotcrete, inspections of rebound ratio may be replaced with inspections of dust concentration andvisual examinations. Inspection timing and frequency of tunnel shotcrete strength and decision
criteria are listed in Table C8.7.1.
Table C8.7.1 Examples of timing and frequency of strength inspections and decision criteria
Timing and frequency
Once per a tunnel length of 20 m or 40 m
Once each time tunnel is excavated for 50 m
Once each time tunnel is excavated for 25 m
Once per tunnel length of 20 m in the initialstages of excavation (approximately 200 m
from the start of excavation). Subsequently,
once in 50 m.

Decision criteria
28-day compressive strength should be 18 N/mm2 or
higher.
28-day compressive strength should be 18 N/mm2 or
higher, or 36 N/mm2.
One-day compressive strength should be 5 N/mm2 or
higher, or 8 N/mm2.
One-day compressive strength should be higher than
5 N/mm2.
28-day compressive strength should be higher than
18 N/mm2.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Slope shotcrete may sometimes have different compressive strengths in trial mixing and during
actual construction owing to the difference in spraying or curing condition. The mean 28-daycompressive strength should therefore be set to be 25 N/mm2 or higher. Parameters for eachinspection items of slope shotcrete are frequently inspected each time 50 to 100 m3 of the volume ishandled or at least once during construction work.
For direct measurement of shotcrete thickness, measurement pins are installed, measurement pins
are inserted into the shotcrete layer while the shotcrete is sill soft, or measurement holes are drilled
after shotcreting. Tunnel shotcrete is generally sprayed on the surface of steel supports that are
erected right after excavation (Fig. C8.6.1). It may be inspected visually that shotcrete is sprayed on
the surface of steel supports for a thickness larger than the designated thickness. The construction of
shotcrete should be visually inspected daily or regularly for cracking, leakage, deformation, etc. andrecords should be kept. Examples of the timing and frequency of shotcrete thickness inspections
and decision criteria are listed in Table C8.7.2. For shotcrete inspections, measurement holes of adiameter of 32 mm or longer are drilled mainly using electric augers in numerous cases. The timing
and frequency of inspections should be determined to the specifications established by the receiving
party. Shotcrete thickness should be evaluated based on the soil excavation condition.
Table C8.7.2 Examples of timing and frequency of shotcrete thickness and decision criteria
Testing or inspection
method-Drilling holes of a diameterof 32 mm or longer withelectric augers or otherdevices-Installing measurement
pins (nail wire or round steelbars) at post-shotcretingmeasurement points andspraying concrete whiledisplaying shotcrete
thickness

Timing and frequency

Decision criteria-Measurement points are set in across section each time an advanceis made for 40 m, and measurements
are taken at five points in the crownand one each on either sidewall at
the least.

-Thickness should be larger thandesign thickness. In special areas
such as the ends or injections in
an excellent rock mass, theminimum thickness should be 1/3
of design thickness.

-Measurement points are set in across section within a length of 20 m
or less, and measurements are taken
at five points in the crown and one
each on either sidewall at the least.

-In cases where the design
thickness is the minimum
thickness, measurement should beequal to or larger than design
thickness. In cases where thedesign thickness is the mean
thickness, the mean thickness
measurement should be equal toor larger than design thickness.

The tunnel environment for tunnel shotcrete is determined not only by the temperature and humidity
during work but also by the dust that affects workers' health. The latter parameter is therefore also
inspected to determine the environment in the tunnel. This parameter is defined as "dustconcentration while a tunnel ventilation system is in operation" to distinguish it from shotcrete dust.

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Chapter 9 Pre-Placed Aggregate Concrete

CHAPTER 9 PRE-PLACED AGGREGATE CONCRETE
9.1 General
9.1.1 Scope
This chapter presents the standards for the matters required for the construction of preplaced concrete.

[Commentary] Pre-placed aggregate concrete or Prepacked conceret is concrete made by filling
forms with coarse aggregate of selected grading and by grouting the voids of the aggregate with a
specially prepared mortar under sufficient pressure. Special mortar means high fluidity grouting
mortar that hardly causes material segregation and has adequate expansibility.
Pre-placed aggregate concrete is used for grouting, repair and retrofit, as a shield against
radioactivity, as unreinforced offshore concrete and for other purposes. Pre-placed aggregate
concrete is applied to wide varieties of structures of varying type, importance and scale.
High strength pre-placed aggregate concrete has been put to practical use that can produce a 91-day
compressive strength of 40 to 60 N/mm2 by using high performance water reducing agents. Mortar
injected into high strength pre-placed aggregate concrete has higher compactibility than ordinary
pre-placed aggregate concrete but requires special construction methods because of its highviscosity. This chapter presents the construction standards for ordinary pre-placed aggregate
concrete and also for high strength pre-placed aggregate concrete.
9.1.2 General(1) In order to construct pre-placed aggregate concrete structures of the designatedquality, the place of construction, meteorological condition and construction method shallbe examined under the guidance of professional engineers with adequate knowledge andexperience.
(2) Pre-placed aggregate concrete construction methods shall be selected properly
depending on ordinary concrete or high strength concrete.

[Commentary] (1) Pre-placed aggregate concrete differs considerably depending on whether theconcrete is ordinary, large scale or high strength. In ordinary pre-placed aggregate concrete, theconstruction method which uses the close spacing of injection pipes has been adopted to obtainbetter quality concrete. Contrary to this, in construction of large-quantity pre-placed aggregate
concrete where construction efficiency is essential, the close spacing of injection pipes may not
only reduce concreting efficiency but also make it difficult to provide a proper capacity mortar plant
due to the huge number of injecting pipes required. In this sense, a method which allows increased
spacing of the injecting pipes by using larger size coarse aggregate with a rich mix proportion has
been applied. In pre-placed aggregate concrete work where hi-strength is required, a high-range
water-reducing agent is used as the chemical admixture to produce a grout mortar of low watercementitious material ratio and high efficiency in intruding into the voids of coarse aggregate.
Thus, in pre-placed aggregate concrete, the most adequate materials and construction methods
including chemical admixtures, mix proportion of grout mortar, gradation of coarse aggregate,
spacing of injecting pipes, and construction equipment shall be selected depending on the structures.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(2) Pre-placed aggregate concrete construction methods vary greatly according to whether ordinaryor high strength concrete is required.
For high strength pre-placed concrete, a grout mortar of low water-cementitious material ratio
should be used. Grouting mortar can be injected smoothly into the voids between coarse aggregates
despite its high viscosity by mixing admixtures composed of high performance water reducing
agents and various types of additives.

9.2 Quality of Pre-Placed Aggregate Concrete
9.2.1 Quality of concrete(1) Pre-placed aggregate concrete shall have the designated strength, durability and crack
resistance and be of homogeneous quality.
(2) The 91- or 28-day compressive strength should be adopted as the standard strength of
pre-placed aggregate concrete according to the construction condition or use.
(3) The compressive strength test of pre-placed aggregate concrete shall be conductedfollowing JSCE-G 522.

[Commentary] (2) Due incorporation of mineral admixtures such as fly ash in many cases, preplaced aggregate concrete cannot be expected to have sufficient compressive strength in earlystages. However, if adequate curing is allowed, the compressive strength will continue to increase,and after approximately 13 weeks of aging, the long-term strength will be equivalent to or higher
than that of concrete composed of ordinary portland cement only. For concrete which develops its
strength slowly like the above mentioned, Concrete strength should be evaluated at old age.
Pre-placed aggregate concrete is especially adaptable to such applications as underwater
concrete, concrete to be injected into voids, and filling concrete. In these cases, most curingconditions will be satisfactory, and only after a considerably long period the concrete structure will
be subjected to design load. Therefore, it is reasonable to apply 91-day compressive strength as thecharacteristic compressive strength when pre-placed aggregate concrete is used for such structure.
However, when pre-placed aggregate concrete be used for general structures where the proper
curing over a long period cannot be expected or structures on which the design load may act within
91-days after concreting, the application of 28-day compressive strength is advisable. In the above
sense, the characteristic compressive strength of pre-placed aggregate concrete shall be determinedbased on either the 28-day or 91-day test specimen cured under the standard condition, depending
upon the intended use of the concrete.
(3) Since the strength of pre-placed aggregate concrete made by grouting expansive mortar whichcontains aluminum powder is considerably affected by the degree of restraint of mortar expansion
and the amount of bleeding water squeezed out, its compressive strength shall be tested according to
JSCE-G 522 “Test Method for Compressive Strength of Pre-placed Aggregate Concrete”.

9.2.2 Quality of grouting mortar
Grouting mortar shall be able to produce concrete that hardly causes material segregationand has the designated fluidity, strength, durability and crack resistance.

[Commentary] Grouting mortar needs to have the following characteristics to produce pre-placed
aggregate concrete of the designated quality.
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Chapter 9 Pre-Placed Aggregate Concrete(i) In the fresh state, grouting mortar needs to facilitate pumping and injection, to have high fluidity
and pumpability to enable the filling of the voids between coarse aggregates and to maintain the
aforementioned characteristics until the end of injection.
(ii) While it is injected into the voids between coarse aggregates, mortar should seldom causematerial segregation and induce little bleeding and expand adequately during the period between
injection and hardening.
(iii) After it hardens, mortar should have the compressive strength required to produce concrete ofthe designated quality, have bond with coarse aggregate and have sufficient durability and crack
resistance.
9.3 Mix design
9.3.1 Materials(1) The cementitious material shall be used either an appropriate mixture of ordinary
portland cement meeting the requirements of JIS R 5210 and fly ash meeting therequirements of JIS A 6201, or, fly ash cement meeting the requirements of JIS R 5213.
(2) When cementitious materials other than those given in (1) above are used, it shall beensured through tests that pre-placed aggregate concrete meeting quality of requirements,
can be obtained.
(3) Appropriate admixtures shall be used considering the fluidity and resistance to material
segregation of grouting mortar.
(4) Fine aggregate with an adequate grading shall be used considering the fluidity andpumpability of grouting mortar.
(5) Minimum size of coarse aggregate shall be more than 15 mm.
(6) The maximum size of coarse aggregate should not be more than 1/4 the minimum
thickness of the member. Further, in the case of reinforced concrete, the maximum size ofthe coarse aggregate should not exceed 1/2 the clearance between the reinforcing bars.

[Commentary] (1) For the binder of the grout mortar used for pre-placed aggregate concrete, amixture of ordinary portland cement and mineral admixture such as fly ash are used as cementitious
material to improve fluidity, resistance against chemical intrusion, and to control hydration heat,ordinary Portland cement with fly ash, or fly ash cement conforming to JIS R 5213 are generally
used.
(2) If high-early strength portland cement instead of ordinary portland cement, portland blastfurnace slag cement or low-heat portland is used, it must be ascertained before use by testing thatthe required quality of pre-placed aggregate concrete obtainable.
(3) Chemical admixtures to be used in the grout mortar of pre-placed aggregate concrete shallpromote the fluidity, prevent segregation, retard setting, and give expansibility to the mortar.
Pre-blended chemical admixtures for pre-placed aggregate concrete containing the optimum
amount of water-reducing agent, gas generating agent, viscosity agent, and set-retarding agent
required for furnishing these properties to the grout mortar, are available commercially. Therefore,
for general use pre-placed aggregate concrete, this pre-blended type of chemical admixture isrecommended.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

The gas generating agent contained in this type of chemical admixtures is generally scaly
aluminum powder equivalent to JIS K 5906 “aluminum powder for paints” type 2. The
expansibility by the aluminum powder is subtly altered by the quality of the aluminum powder, thequality of cement, the temperature, the mix proportion, the mixing time, the pressure after grouting,etc. At 10 to 20 C, many of previous experience indicate that the weight ratio of aluminum powder
to cementitious material Al/(C+F) is generally from 0.010 to 0.015 %. Under the conditions withthe construction of special attention needed the amount of aluminum powder is increased or
decreased so as to satisfy the expansion with the standard values given in Section 9.3.2.
If pre-blended chemical admixtures for pre-placed aggregate concrete are not used, a mixture ofwater-reducing agent conforming to the provisions of JIS A 6204, aluminum powder and otheragents shall be used.
Grouting mortar tends to lose fluidity at high temperatures. Retarders and thickening agentsshould therefore be used simultaneously to maintain fluidity.
Grout mortar with a low water-cement ratio tends to rapidly lose its fluidity under hightemperatures. To preserve the fluidity, use of a set-retarding agent and water retentive agent may beeffective. However, prior to using a water retentive agent, it shall be carefully examined since thisagent may seriously affect the properties of concrete, especially the strength.
(4) To improve the fluidity and the resistance against segregation of the grout mortar, a finer
fine aggregate than for conventional concrete shall be used.
If the water-cementitious materials ratio is the same, a fine aggregate with greater F.M. allows
less cementitious material and water needed to obtain an equivalent fluidity. However, an excessive
F.M. will make grout mortar segregate and block pumps or delivery pipes. Furthermore, defective
filling of the voids of the aggregate by grout mortar may result. If F.M. is too low, an excessive unit
content of cementitious materials and water will be necessary to obtain the required fluidity. The
maximum size of fine aggregate shall thus be 2.5 mm and F.M. shall be between 1.4 and 2.2. The
standard grading of fine aggregate is shown in Table C9.3.1.
Table C9.3.1 Standard grading of fine aggregate
Nominal sieve (mm)Percentage of mass passing through sieve

2.5
1.2
0.6
0.3
0.15

100
90-100
60-80
20-50
5-30

The grout mortar for high-strength pre-placed aggregate concrete is normally used where highquality pre-placed aggregate concrete with a low water-cementitious materials ratio and a lesser
water content than grout mortar for normal pre-placed aggregate concrete is required. Therefore,
great care must be exercised in controlling the materials. Furthermore, particular attention should be
paid to the surface moisture content in the fine aggregate since it may considerably affect thefluidity of grout mortar and the compressive strength of pre-placed aggregate concrete. The finenessmodulus of fine aggregate should be between 1.8 and 2.2 to minimize the cementitious material
content within the limit for obtaining the required fluidity.
(5) As minimum size of coarse aggregate is larger, it will be easier for the grout mortar to flow
into and fill out voids. Therefore, the minimum size coarse aggregate selected should be the largest
possible in a practically permissible range. If small size particles are abundantly contained in coarse
aggregate, sufficient grouting may not be possible due to the extremely reduced void space of the362

Chapter 9 Pre-Placed Aggregate Concrete

aggregate. The lower limit of the minimum size of coarse aggregate has therefore been specified as
15 mm.
(6) The maximum size of coarse aggregate is generally two or four times the minimum size. A
smaller difference between the maximum size and the minimum size of coarse aggregate will not
impede the grouting. However, the grout mortar needed will be increased with the decreased solid
volume percentage. Therefore, an appropriate grading shall be selected.
The volume of the void of coarse aggregate varies according to the grading of the aggregate andthe shape of particles. In general, it ranges from 40 to 48 %. The apparent void ratio tends toincrease when the shape of particles is plate type and to decrease when the shape of particles isspherical type.
9.3.2 Mix proportion of grouting mortar
The mix proportions of grouting mortar shall be determined so as to meet the following
conditions.
(1) The flowability shall be determined using the flow time in accordance with JSCE-F 521.
The standard flow time should be taken to be between 16 and 20 seconds. For highstrength pre-placed aggregate concrete, the standard flow time should be between 25 and
50 seconds.
(2) The amount of bleeding at three hours after the start of the experiment shall not exceed
3% when tested according to JSCE-F 522. For high-strength pre-placed aggregate concrete,
this amount shall not exceed 1%.
(3) The amount of expansion at three hours after the start of the experiment should, ingeneral, be between 5 and 10% when tested according to JSCE-F 522. For high-strength
grouting mortar, this amount should be between 2 and 5%.
(4) Required compressive strength shall be obtained when tested according to JSCE-G 521.

[Commentary] In order to obtain grouting mortar of the designated quality, construction
conditions should be fully identified, appropriate materials should be selected and mix proportionsof grouting mortar should be determined so that the mortar may meet conditions (1) through (4)described in Section 9.3.2.
(1) The flow time specified in this section is only a general standard. Mortar with flow time outof the specified range may be injected in some cases. However, The flow time of low flowability
mortar will be more significantly influenced by variations in the water content. If the target flowtime exceeds 20 seconds, mortar injection may be impended by slight measuring errors, thevariation in the fine aggregate surface moisture content, elapsed time, temperature rise during
mortar delivery and so on. On the other hand, a mortar with a flow time of less than 16 seconds will
have large possibility of segregation. Therefore, the standard flow time may be taken to be between
16 and 20 seconds.
If the flow time of mortar for high strength pre-placed aggregate concrete, which is tested
according to JSCE-F 521, is not more than 25 seconds, segregation of mortar tends to occur and if
the flow time exceeds 50 seconds, penetration into voids to the bulk of coarse aggregate isdecreased. The standardized flow time of grout mortar is, therefore, 25 to 50 seconds. However, agrout mortar with a flow time of approximately 20 seconds may be used when it can be proved that
appreciable segregation does not occur.
(2) Bleeding of the mortar is not only caused by the water ascension resulting from the settlingof solid particles as generally seen in conventional concrete, but also includes water displacement in363

Standard Specifications for Concrete Structures-2007, Materials and Construction

the course of generating hydrogen bubbles. This may interrupt the bond between grout mortar andcoarse aggregate or reduce the strength of the upper portion of the concrete and increase laitance,
and therefore, it should be minimized. The bleeding limit of 3% specified here has been determinedby examining past construction records.
The bleeding ratio of the mortar for grouting for high-strength pre-placed aggregate concrete using
a high range water-reducing agent is usually very small, less than 1 % for a water-binder ratio ofless than 40 %.
(3) The purpose of making the mortar for grouting expansive is to increase the bond strength
between coarse aggregate and mortar and to prevent spaces between those coarse aggregates and themortar by allowing the mortar to expand while it is settling and shrinkage due to the bleeding.
Therefore, the expansion shall be higher than the bleeding. If possible, the expansion more than
twice the bleeding is recommendable. However, an excessively high expansion is also undesirable
since it results in increased voids in the mortar.The expansion of the mortar actually injected into
the voids of the coarse aggregate may differ from that obtained from tests. However, satisfactory
results have generally been obtained, as long as the expansion according to the JSCE-F 522is within
5 to 10 %.
The expansion can be adjusted by the aluminum powder content and will fluctuate according to
the properties of the cement, type and content of admixture, temperature of mortar, acting pressure,etc. Moreover, the expansion process may be considerably different even though the expansion at
three hours after starting the test is same. The targeted expansion should be determined byconsidering the actual working conditions after examining the time change of the expansion of thesampled mortar.
Considering that the expansion will be much lower in cold weather and considerably higher
with more rapid expansion in hot weather, it is necessary to determine the proper expansion byadjusting the aluminum powder content. In deep sea construction, the adjusted value of the
expansion under the atmospheric pressure should be estimated by applying Boyle’s law, and an
adequate amount of aluminum powder should be added to obtain the optimum value of the
expansion of such pressurized mortar. In such cases, however, rapid expansion may occur, so it isimportant to shorten the time required from the mixing till mortar injection and to provide proper
measures to prevent excessive expansion of the mortar before the completion of the injection byminimizing the temperature rise.
A lower expansion ratio of mortar can be accepted for grouting for high-strength pre-placed
aggregate concrete due to its small bleeding. In cases where the expansibility of grouting mortar forhigh strength concrete is 0.5 to 1.0%, the compressive strength of concrete reaches the maximum
value. Compressive strength is affected little until the expansibility reaches approximately 5%.To
increase the freeze-thaw resistance, the expansion ratio of the mortar for grouting for high-strengthpre-placed aggregate concrete shall be not less than 2 %. Therefore, the expansion ratio of themortar for grouting for high-strength pre-placed aggregate concrete is specified as 2 to 5 %.
(4) The compressive strength of grouting mortar must satisfy the required strength, and shall betested according to JSCE-G 521 “Test Method for Compressive Strength of Grouting Mortar of Preplaced Aggregate Concrete”. When mix proportion of pre-placed aggregate concrete is decided, thecompressive strength should be obtained according to JSCE-G 522 “Test Method for Compressive
Strength of Pre-placed Aggregate Concrete.” As a rule of thumb, however, the compressive strength
may be estimated as 70-80 % of that of grouting mortar.

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9.3.3 Representation of mix proportion
Mix proportions of pre-placed aggregate concrete shall be given in the format given in
Table 9.3.2.
Table 9.3.2 Representation of mix proportion
Coarse aggregate
Minimum
size
(mm)

Note

Maximumsize(mm)Mortar used for grouting
Voidcontent(%)

Range
to time
of
flow

Water
binderratio

Admixture
substitutio
n ratioSandbinderratio

W/(C+F)

F/(C+F)

S/(S+F)

(%)

(%)

(%)

Unit content (kg/m3)
W

C

F
(*)

S

Chemical
admixture(**)

Aluminumpowder(***)(*): F is shown administers(**): A unit for amount of chemical admixture that should not be diluted and dissolved is ml or g.
(***): A unit for amount of Aluminium powder is g. It is differently displayed with the chemical admixture forpre-placed aggregate concrete[Commentary] The description of the type of structure, characteristic compressive strength, mix
proportioning strength, the type of cement, F.M. of the fine aggregate, type of coarse aggregate, thetype of admixture, etc. should be written in addition to the table of the mix proportion.

9.4 Production and Placing
9.4.1 Production and placing of grout mortar
9.4.1.1 Production plant(1) Production plant of grout mortar shall have the material supply system, a weighing
system and mixer which possess specified performance so that mortar having required
performances can be obtained.
(2) Mortar mixers shall be capable of producing a mortar of the required performance[Commentary] (1) The performance of grout mortar and the quality of pre-placed aggregate
concrete are greatly influenced by the production plant. Control of each equipment whichconstitutes production plant needs to be performed appropriately.
The quality of grout mortar varies noticeably according to the materials used, the mortar production
facilities and, in particular according to the performance of the mixer and mixing temperature.
Therefore, prior to starting construction, the quality of grouting mortar should be verified before
construction by mixing on a trial basis under the conditions similar to actual conditions. An
example of arrangement of construction facilities in the phase of grouting mortar production
through the construction phase is shown in Fig. C9.4.1.
Since the grout mortar for high strength pre-placed aggregate concrete has larger mass of unit
volume and higher plastic viscosity than grout mortar for normal pre-placed aggregate concrete, theenergy required for mixing is about 1.5 times that for normal pre-placed aggregate concrete. It
should, therefore, be mixed using a mixer with high mixing efficiency.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Mortar plant
Storage bottle

Cement silo

Measuring device
Mortar mixer

Inspection machine
Grouting
platform

grouting pipe
Conveying pipe

Sand pit

agitator
Leakage Inspection
prevention pipe

shuttering

Mortarpump

Fig.C9.4.1 Example of arrangement of construction equipments in grouting of mortar(2) The capacity of a grout mortar mixer per drum is normally 0.2 to 1.5 m3, and mixers having
a single drum, double drums, or triple drums are commonly employed. The order of charging
materials into the mixer is water, admixtures, fly ash, cement and fine aggregate. The mixer should
be designed to mix the materials uniformly and to disperse the cement and admixtures efficiently.
If the mixer has a low mixing capacity, the working efficiency will be decreased as mixing timeis prolonged to obtain the required fluidity of the grout mortar. High-speed mixing provides higher
mixing efficiency but due care should be taken with high-speed mixing as it increases temperatureof the grout mortar, resulting in an earlier gas generating of the aluminum powder and decreased
fluidity of grout mortar.
A mixer having a paddle rotation speed of 125 to 500 r.p.m. is commonly employed and themixer should be able to produce grout mortar having the required fluidity and quality within 2 to 5
minutes.

9.4.1.2 Mixing(1) The time of charging materials and the mixing time shall be controlled to carry out
within given time.
(2) Agitators shall be capable of stirring the mortar for grouting slowly in a manner thatthe mortar retains the required properties till the completion of grouting.

[Commentary] (1) The time of charging materials into the mixer and mixing time shall becontrolled to minimize the range of variations because these variations are major cause of variationof fluidity of grout mortar.
Since high-speed mixing for a long time will increase the temperature of the grout mortar anddecrease the fluidity of the grout mortar, due care shall be taken when grouting in hot weather or366

Chapter 9 Pre-Placed Aggregate Concretewhen grouting for a long period. Because of this, the grout mortar should be delivered to a grout
agitator tank immediately after mixing.
(2) Agitators store the mixed grouting mortar and stir it at low speed to prevent material
segregation and the change in fluidity. Agitators enable continuous supply of grouting mortar topumps.
If the capacity of the grout agitator tank is excessive, the quality of the grout mortar will be
adversely affected by prolonged storage, and too small a capacity of the grout agitator tank will
make the use of the grout agitator tank meaningless. The suitable grout agitator tank capacity should
thus be determined by considering the required hourly rate of mixing quantity and the capacity of
the grouting pump to be used. A grout agitator tank having a capacity of three to five times that of
the mixer is commonly employed.

9.4.2 Construction and control
9.4.2.1 Shuttering(1) Shuttering shall be designed to sufficiently resist the lateral pressures of pre-placed
aggregate concrete and any other external forces during construction.
(2) Leakage of mortar for grouting through joints in the shuttering and the interface
between the foundation and the shuttering shall not be allowed to occur.

[Commentary] (1) Wood forms have been commonly employed in the repairing and strengtheningof existing concrete structures using pre-placed aggregate concrete. Steel forms, on the other hand,
have been commonly employed in under-seawater construction, construction of important structuresand for the formwork subjected to high lateral pressure of pre-placed aggregate concrete duringexecution of work.
Formwork for pre-placed aggregate concrete greatly differs from those for conventionallyplaced concrete such that greater care is needed to prevent grout mortar leakage in the forms, theform must be prefabricated on the shore for under-seawater construction, and coarse aggregate is
pre-placed into the forms before the mortar is grouted into the voids of the coarse aggregate.
Therefore, the forms shall be designed to be strong and rigid enough to prevent harmful
deformation and breakage.
In under-seawater construction, it is especially important to seize accurately, in the design stageof the formworks, impact loads during installation of the forms, water pressure caused by variationsof tidal level.
1) Influence for the impact during coarse aggregate placement
Estimation of impact loads during coarse aggregate placement and lateral pressure of pre-placed
aggregate concrete should be calculated as follows:
Pressure during coarse aggregate placement:p  (1  i )  Wwa ha
Where,
p: pressure acting upon forms during coarse aggregate placement (kN/m2)
i : impact coefficient during coarse aggregate placement 0.6 to 0.7
ha: depth of coarse aggregate367

Standard Specifications for Concrete Structures-2007, Materials and Construction

Wwa: unit weight of coarse aggregate (kN/m3). In general, Wwa=10*Wa
where, in air: Wa 

100  Va
100

in water: Wa 

100  V(  a  1)100

V: percentage of voids of coarse aggregate, commonly 40 to 48%
ρa: density of coarse aggregate (t/m3)

2) Lateral pressure of pre-placed aggregate concrete
The lateral pressure of pre-placed aggregate concrete depends on the mix proportion of the grout
mortar, temperature of the grout mortar, rising rate of the grout mortar surface, height of placement,
percentage of voids of the coarse aggregate mass and stiffness of the formwork. In general, themaximum lateral pressure of pre-placed aggregate concrete may be considered as the sum of coarse
aggregate pressure and mortar pressure, and should be calculated as follows:
Pmax  K a  Wwa  ha  2  Wwm  Rt  V 100
The term “2Rt” is the depth of grout mortar while the influence of setting of grout mortar is
negligible.
Where,
Pmax: maximum lateral pressure of pre-placed aggregate concrete (kN/m2)
Ka: coefficient of lateral pressure of coarse aggregate, commonly Ka=1
Wwm: unit weight of mortar (t/m3), Wwm=10·Wm, which is Wwm-10 in water
R: rising rate of mortar surface level (m/h)
T: time of initial setting of mortar (h)(2) As grout mortar has high fluidity and a long setting time, mortar leakage can readily occur
from small openings between the foundation and forms and from joints of the forms. Therefore, theforms for pre-placed aggregate concrete should be sufficiently tight to prevent mortar leakage.
Mortar leakage from the mortar-foundation interface is prevented by caulking the gaps withbagged sand, bagged concrete, or soil cement or by placing cloth sheets in front of the forms or
putting special sponges at the bottom of forms prior to forms installation. The surface of thefoundation contacting with the forms should be finished as flat as possible, the gap between thebottom edge of the form and foundation should be eliminated by sealing it with highly viscous
cement or other means. As for the prevention of mortar leakage from the joints of forms, several
methods are commonly used such as tightening forms after putting cloth and/or sponges in theinterfaces of the form joints, spreading sealing materials on the inside surface of forms and caulking
the joints of forms with gum tape.

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Chapter 9 Pre-Placed Aggregate Concrete

9.4.2.2 Charging coarse aggregate(1) When any damage to embedded items such as injection pipes and sounding wells is
anticipated in charging coarse aggregate, they shall be suitably protected.
(2) Coarse aggregate charged within the shuttering shall be kept clean till grouting iscarried out.
(3) The coarse aggregate shall be so charged as to obtain a uniform distribution and toprevent the coarse aggregate from breaking.

[Commentary] (1) In cases where the injection height is low, injection pipes are erected after the
input of coarse aggregate. However, generally, embedded items such as injection pipes andsounding wells are commonly installed prior to the placing of coarse aggregate. These shall beadequately protected by caps on the top of the pipes and by tightly securing the pipes to the forms
so that they do not suffer breakage, bending and movement due to the falling impact of the fallingcoarse aggregate during placing operation. If the coarse aggregate particle size is small and thegrouting depth is shallow, injection pipes may be installed after placing coarse aggregate.
(2) If the coarse aggregate is contaminated with mud or other materials the bonding of themortar to the aggregate may be impeded and the grout mortar may not penetrate completely into thevoids of the coarse aggregate. Therefore, mud and contaminations on the coarse aggregate surface
should be eliminated by screening and washing.
The coarse aggregate should be screened and washed again before being placed in the forms
considering that it will have collected mud and contaminants during transportation and handlingeven though it was clean originally. In the under-seawater construction, marine life such as seaweed
and shells, and others may grow on the surface of the coarse aggregate after it is placed. Therefore,
the mortar should be grouted as soon as possible after placing coarse aggregate. The fine materials
which settle or are deposited on the surface of the foundation should be removed by using an air-lift
pump or suction pump, and due care shall be taken to prevent the contamination of the coarse
aggregate surface by suspended fine materials during placing.
(3) Coarse aggregate is commonly discharged directly into the forms from a grab-bucket
mounted on bottom-door-type barges or from a grab bucket mounted on hopper barges when theforms are underwater. When the tops of the forms are above water, the coarse aggregate iscommonly placed using a hopper temporarily installed on the forms with a belt conveyor. In thiscase, if the coarse aggregate is discharged from one fixed place, the uniform grain size distributionof the aggregate throughout the forms will not be expected resulting in non-uniform penetration of
the mortar. Therefore, coarse aggregate should be placed so as to give uniform distribution
throughout the form by shifting the hopper gate. If aggregate breaks due to excessive impact during
the placement, rock fragments will get mixed with the coarse aggregate, with the result that grout
mortar will not penetrate completely into the voids of the aggregate. As abovementioned, it isnecessary to have a low free falling height from the hopper gate and/or to flood the forms withwater to absorb the impact of aggregate during the placement.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

9.4.2.3 Grouting equipment and injection pipes(1) A sufficient amount of equipment of the proper capacity for mortar grouting shall be
provided considering the constructing conditions and construction methods.
(2) Injection pipes shall have structures in which the injecting work can carry out reliably
and smoothly. The inside diameter of the pipes should be the same or less than that of thedelivery pipes.
(3) In general, the horizontal spacing of vertical injection pipes should be approximately
2 meters.
(4) In general, the horizontal and vertical spacing for horizontal injection pipes shall beapproximately 2 and 1.5 meters respectively. In principle, horizontal injection pipes shallhave valves to prevent backflow.

[Commentary] (1) Mortar grouting shall be planned adequately with regard to the supply ofmaterials, the capacity of the mortar plant, the distance from the mortar plant to the injection points,
the capacity of the grout pump, and the number of pumps to be used considering the grouting
quantities, the working time, site conditions and others so that mortar grouting can be continuousand smooth. When the grouting operation may need a considerably long time, it is desirable toprovide standby pumps for any unforeseen line blockage or other breakdown.
(2) Grout mortar injection should proceed as a smooth process in which the height of the lower
end of the injection pipes may be adjusted and the injection pipes may be withdrawn due to any
temporary shutdown in the injection operation. The lower end of the injection pipes should be kept
approximately 5 cm above the bottom of the aggregate, the end should be cut slant, or there should
be a chair made of reinforcing steel bars which is provided under the lower end of the injection
pipes so that plugging and excessive free falling underwater can be prevented at the start of injecton.
Steel pipes of 25 to 60 mm inside diameter are normally used as injection pipes. The inside
diameter of injection pipes should be the same as delivery pipes. Should injecton pipes of smaller
inside diameter than that of delivery pipes be used, the injection pipe should be connected to thedelivery pipes through tapered jointing pipes to prevent any segregation of mortar due to the sudden
increase of pressure in the pipe.
(3) and (4) Spacing of injection pipes should be determined properly so as to minimize thesegregation of the mortar to be injected into the voids of the coarse aggregate, and to obtain therequired quality of pre-placed aggregate concrete considering the minimum size of coarse aggregate,
grouting rate of mortar and other factors. Large distance between injection pipes will cause
segregation of mortar while penetrating into the aggregate mass and many decrease concrete
strength.

9.4.2.4 Pumping(1) Mortar pumps shall have sufficient pumping capacity. They shall be suitable forinjecting mortar continuously and preventing air intrusion.
(2) Delivery pipes shall be suitable for delivering grout mortar smoothly.

[Commentary] (1) In determining the type of grout mortar pump to be used, carefully
consideration shall be made of the job conditions such as coarse aggregate size, the area to be
grouted, and the inside diameter of the injection and delivery pipes. For example, if a high-capacity370

Chapter 9 Pre-Placed Aggregate Concrete

grout mortar pump is used with a small particle coarse aggregate, the grout mortar flow gradientbecomes large and the segregation of grout mortar will be accelerated. A pump having a discharge
capacity from 100 to 150 liter per minutes has commonly been employed.
An approximately 5mm sieve screen and a hopper having a suitable size should be provided
between the mixer and the pump to prevent the intrusion of foreign materials and air into the grout
mortar pump.
(2) A delivery pipe is used to carry the grout mortar discharged from the grout mortar pump to
the injection pipes. The delivery pipe shall be selected and arranged with due care because theplugging of delivery pipes will cause delays in the grouting operation, decrease of working
efficiency and deterioration of the quality of pre-placed aggregate concrete.
The pumping pressure of the grout mortar pump is mostly due to the resistance in the delivery
pipe. The resistance in the delivery pipe varies according to the diameter of the delivery pipe, thegrout velocity inside the pipe, fluidity of the mortar, the shape of joints used, and the material of thedelivery pipe. Therefore, the following measures shall be taken so that pressure head loss will beminimized:a) The length of the pipe line between the grout pump and injection points be kept to thepractical minimum.
b) A relay grout agitator tank and relay pump, if the delivery pipe length exceeds 100 meters,
be provided.
c) Sharp bends and sudden changes in the sectional area of the delivery pipe line be avoided.
d) Watertight joints which can be removed easily be provided to prevent blockage at thepipe joints resulting from the dehydration of the grout mortar caused by the pressureduring pumping.
e) The inside diameter of the delivery pipes is normally the same as the outlet inside
diameter of the pumps. However, the inside diameter of delivery pipes shall be sodetermined that the average flow rate of mortar (pumping rate/cross sectional area ofdelivery pipe) is between 0.5 to 2 m/s. Because the solid particles will settle due to thesegregation of the grout mortar where the grout mortar flow rate inside the pipe is too low,
and the pressure head loss is too high when the flow rate is too high.
A delivery manifold system may be used when the grout mortar is delivered through pluraldelivery pipe lines using one pump. However, if such plural delivery pipe lines are operated at thesame time, an uniform flow rate of grout mortar will not be expected. Therefore, the grout mortar
should be delivered from one pipe to another pipe in series using a manifold system. Due care shallbe taken to prevent the plugging of delivery pipes which may be caused by intermittent mortardelivery when the delivery interval to each delivery pipe is prolonged.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

9.4.2.5 Grouting(1) The grouting mortar shall be injected continuously until the mortar surface hasreached the elevation designated in the design or construction plan.
(2) Injection of the grouting mortar shall be started from the lowest point and be carriedout in heading for the upper area. The rising rate of the mortar surface should be about 0.3
to 2.0 m/hr.
(3) In principle, mortar shall be injected while the vertical injection pipes are salvaged.
The tip of pipe shall be kept the condition inserted in the mortar, 0.5 to 2.0 meters below themortar surface.
(4) To inspect the rising of mortar, a monitoring system shall be provided to measure themortar surface level.

[Commentary] Prior to grouting, the grouting pipe line should be inspected for foreign materials,
the grout pump and pipe line should be washed out by passing water through them, then cement
paste should be injected to lubricate the inside surface of the pipe line and to insert the lower end of
the injection pipes in the placed cement paste. This prior cement paste injection is especially
important for underwater construction. Since without this operation, the lower end of the injection
pipes are not in the grout mortar, and the grout mortar fall freely into the water, and may experience
the segregation of mortar, and the possible blockage of pipes as well as voids of coarse aggregate,causing serious weakness in the concrete. The quality and quantity of the cement paste should bedetermined that the subsequent injected grout mortar does not serve a weak point, in consideration
with the type and capacity of the pump, scale of the structure and so on.
(1) Construction joint, made due to the interruption of grouting which will cause a serious
weakness in the pre-placed aggregate concrete shall be avoided unless indicated in the design orworking plan. If the grouting is interrupted through unavoidable circumstances such as the
temporary shutdown of the grouting equipment or sudden changes in weather conditions which
results in the provision of a construction joint, particular attention shall be paid according to Section
9.4.2.6.
When the grouting operation is interrupted for not more than about 2 to 3 hours and the grout
mortar has not yet set retaining sufficient fluidity, the mortar injection may be resumed without
special measures. However, if the injection pipes have been withdrawn, the lower end of theinjection pipes should be inserted a sufficient depth below the grouted surface and rich cement paste
should be injected prior to resuming grout mortar injection. In other cases, it is quite risky to resume
injection of grout mortar without taking proper measures.
The quality of the mortar near the grout surface tends to be considerably lower than that of themortar inside due to adverse effects such as dilution with water and fall of the expansion restraint ofmortar and other factors. The deteriorated part of the mortar should be eliminated by re-injecting
rich mortar with shorter injection pipes. Alternatively, grout mortar shall be injected 50 cm above
the design level then the excess portion be removed after hardening.

372

Chapter 9 Pre-Placed Aggregate Concrete(2) Fundamentally, grout injection shall be started at the lowest point, then grout mortar should
be gradually injected to the higher points and be prevented from falling freely in the water so that it
can fill all the voids of the coarse aggregate completely.
The grout mortar should be injected as slowly as possible. If the grout mortar is injected rapidly,
the elimination of water and air bubbles in the coarse aggregate will become difficult, and inunderwater construction, the grout mortar will be diluted with water and considerable laitance willdevelop. Therefore, injection rates which will depend on the fluidity of grout mortar, the grouting
area and the grouting depth should be so determined that the rising rate of the grout mortar isapproximately 0.3 to 2.0 m/hr.
The grout should be brought up in a horizontal layer by moving the injection points. For theabove purpose, a constant discharge rate of grout mortar shall be maintained and grout mortar shallbe delivered to the injection pipes in sequence at adequate regular intervals. However, when the
grouting area is relatively small, the mortar may be injected into the entire area at the same timewith all injection pipes being connected to the pump.
When the grouting depth is relatively shallow and the grouting area is relatively wide, the grout
mortar may be injected from a row of injection pipes provided at one end of the forms over theentire width of the forms at the same time by advancing injection points from one end to the otherend by changing the valves.
(3) Mortar should be injected by a vertical pipe withdrawing the injection pipes in sequence, butwhen the grouting depth is relatively shallow, grout mortar may be injected without withdrawing
the injection pipe. When the grouting depth is relatively deep and withdrawing the injection pipe isdifficult, grout mortar may be injected through closely arranged injection pipes, or double injection
pipes with punched pipes adopted as external pipes should be used (Fig. C9.4.2) so that they can bewithdrawn readily from the injected mortar.
In either case, the lower end of the injection pipe shall always be inserted below the grout
surface to prevent segregation of the mortar during the operation. Due care shall also be taken if theembedded injection pipes are relatively deep, since there may be difficulty in injecting grout mortar
due to the setting of grout mortar around the lower end of the injection pipe. The proper inserted
depth of the injection pipe, which may depend on the grout mortar injection rate, shall bemaintained 0.5 to 2.0 meters below the grout surface.
Groutingof mortar

Internal pipe

PackerExternal pipe

Coarseaggregate

Fig.C9.4.2 Double injection pipes
373

Standard Specifications for Concrete Structures-2007, Materials and Construction(4) There are several methods of measuring the flow conditions and the rising surface level ofthe grout mortar within the aggregate mass. A suitable method shall be employed considering job
conditions.
The measurements are commonly conducted by means of a sounding well which consists of 38
to 65mm diameter steel pipes provided with slots at frequent intervals so that the grout surface levelis the same inside and outside the pipes. The sounding well is set up in the same manner as theinjection pipe. And the measuring will be made using the sounding line equipped with a float andweight or with electronic sensors. Also used is an ultrasonic sensor mounted on the top of thesounding well to automatically measure the location of the grout mortar surface in the sounding
well.
The ratio of the number of sounding well to that of injection pipes usually ranges from 1 : 1 to
1 : 2 depending on the importance of the structure. Another method of measuring the grout mortar
surface level is conducted using an electrical detector installed in the voids of the aggregate massprior to mortar grouting. This method can estimate the location of the grout mortar surface by thevariations of the electric current and resistance.
When grouting is being made in dry areas, a measuring method using small holes made in theforms a regular intervals beforehand, is normally adopted by which the mortar surface position canbe known by the grout mortar seepage through the small holes. These methods enable the locationand slope of the grout surface to be known at all times with reasonable accuracy. The lower end of
the injection pipe shall be adjusted and the injection point shall be moved accordingly.
The flow gradient of grout mortar surface should be maintained at not more than 1 : 3.

9.4.2.6 Construction joints(1) In principle, horizontal construction joints shall not be made in underwater
construction.
(2) At horizontal construction joints in construction in the air, new concrete shall becarefully placed in an appropriate manner after removing the surface laitance of thepreviously placed pre-placed aggregate concrete.

[Commentary] (1) In pre-placed aggregate concrete construction, grout should be injected
continuously, and horizontal construction joints shall be avoided unless indicated in the working
plan because the joint may seriously weaken the surface due to the difficulty in removing laitance inthe joint. When the horizontal construction joint is made due to unforeseen circumstances, thesurface should be prepared for the succeeding lift by removing loose aggregate and all laitance. The
joint shall then be provided with a dowel or groove, or steels shall be inserted to reinforce the joint.
The work should then be resumed after the grout mortar hardens.
(2) The laitance of the placed concrete surface should be removed thoroughly by means of an
air-jet or water-jet, and in cases that the quality of the concrete or mortar in the surface layer isjudged to have deteriorated, those portions shall be removed using a concrete breaker or otherequipment. Water containing fine solids suspension formed by the debris of removed laitance andconcrete shall be discharged.
In placing the succeeding lift, rich cement paste shall be injected prior to the start of grouting mortar
to prevent segregation by the free fall of grout mortar through the water.

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9.4.2.7 Construction in cold weather
In the case of construction in cold weather, freezing of aggregates and the mortar for
grouting shall be prevented. Appropriate insulation and heat shall be carried out to prevent
delay of expansion of the mortar.

[Commentary] When injection work is conducted in cold weather, due care shall be taken toprevent excessively low temperature of the materials. The extremely lowered temperatures ofmortar at night will cause a considerable decrease in its expansion ratio and delay the setting time of
the grout mortar. The aggregate shall be stored with cover sheets and protected from snow duringtransportation and handling to prevent it from freezing. The mixing water may be preheated to raise
the temperature of grout mortar, however the temperature of water shall be less than approximately
40˚C to prevent the rapid setting of grout mortar.
The early strength of the grout mortar using fly ash, portland blast-furnace slag cement or fly
ash cement is usually lower than that made using ordinary portland cement alone, and so the mix
proportion shall be determined in advance using trial batch. When necessary, mortar with small
water to cement ratio should be used.

9.4.2.8 Construction in hot weather
In the case of construction in hot weather, temperature increase, early expansion anddecrease in flowability of the grouting mortar shall be prevented, and appropriate measures
for materials and construction methods shall be taken.

[Commentary] When the temperature of the mixed up grout mortar exceeds 25˚C, the fluidity ofgrout mortar tends to decrease rapidly, the flow gradient may become steeper, expansion may occur
too early and the expansion ratio may be excessively high. As a result, the injection pipes anddelivery pipes may get readily plugged, the grout mortar may undergo excessive segregation andquality of concrete may deteriorate. Therefore, when grouting in hot weather, the temperature of
mixed up grout mortar shall be reduced as much as possible by keeping the cement temperature as
low as possible and pre-cooling the water and the fine aggregate. During injection, great care shallbe taken to prevent the early expansion and decrease in fluidity of the grout mortar by minimizing
the storage time in the grout agitator tank, injecting it soon after mixing, lowering the temperatureof the delivery pipe, retarding setting time, improving fluidity, strictly controlling fluidity and flow
gradient of the grout mortar and preventing the interruption on injection.

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9.5 Inspection
9.5.1 Material acceptance tests
The receiving party shall be responsible for conducting acceptance tests for grouting
mortar materials. Acceptance tests should be conducted in accordance with Table 9.5.1.

Table 9.5.1 Inspection of materials for grouting mortar
Type

AluminumpowderItem

Quality

Expansion ratioof mortar

Testing method/
Inspection
methodConformation oftest results
provided bymanufacturer orin accordancewith JIS K 5906
Method in
JSCE-F 522

Chemical
admixture forpre-placed
aggregateconcrete

Performance ofmortarMethod in
JSCE-F 522

Coarseaggregate

Minimum sizeof coarse
aggregate

Mehotd in JIS A
1102

Period/Frequency-Prior toconstruction work
-Once a month
during construction
work-Prior toconstruction work
-Once a month
during construction
work-Prior toconstruction work
-When material ischangedCriteria for judgment

Complying with JIS K5906

Complying with thespecifications of Section 9.3.2
Complying with thespecifications of Section 9.3.2

Larger than 15mm

[Commentary] The accepting party that conducts acceptance tests for grouting mortar materials is
the producer or contractor. The producer or contractor shall conduct acceptance tests and the Owner
shall verify the test results.
Specifications for aluminum powder and pre-blended chemical admixture for pre-placed
aggregate concrete have not been defined. Therefore, mortar using these materials should be tested
to check that the materials can give the required performance to the pre-placed aggregate concrete.

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9.5.2 Acceptance test of pre-placed aggregate concrete and mortar for grouting
The receiving party shall be responsible for conducting acceptance tests for concreteand grouting mortar. Acceptance tests should be conducted in accordance with Table 9.5.2.
Table 9.5.2 Acceptance test of concrete and grouting mortar
Performance

Inspection of
concrete

Inspection ofgrouting
mortarItem

Testing method/
Inspection method

Compressive
strength

Method in JSCE-G
522

Temperature ofgrouting mortar

bar thermometer
etc.

Compressive
strength

Method in JSCE-G
521

Flowability(flow time)
Resistance tosegregation(bleeding ratio)
Expansion(expansion ratio)

Method in JSCE-F
521
Method in JSCE-F
522

Period/Frequency

Once each time 20
to 150 m3 ofmortar is applied
according to theimportance of thestructure and thescale of theconstruction
project

Criteria for judgment
It can be estimated at
appropriate producer's riskthat the probability offailing to provide thedesign strength is 5% or
less.
Shall conform to therequirements ofconstruction plan
It can be estimated at
appropriate producer's riskthat the probability offailing to provide thedesign strength is 5% orless.
Within the standard value
in 9.3.2
Satisfying the specified
value in 9.3.2
Within the standard value
in 9.3.2[Commentary] The receiving party that conducts acceptance tests for pre-placed aggregate
concrete and grouting mortar is the Owner. There are, however, cases where the Contractor that
produces pre-placed aggregate concrete conducts acceptance tests for pre-placed aggregate
concrete and the Owner verifies the test results.
The quality of grouting mortar greatly affects the quality of pre-placed aggregate concrete. In
order to produce pre-placed aggregate concrete of the designated quality, therefore, grouting mortar
also needs to be of the designated quality. The temperature, fluidity, resistance to material
segregation and expansibility of grouting mortar should be inspected.
Fluidity shall be inspected by conducting fluidity tests focused on flow time, and resistance tomaterial segregation shall be inspected by conducting bleeding tests as a standard practice. In cases
where other parameters need to be inspected than fluidity, resistance to material segregation andexpansibility, appropriate inspection methods should be selected.
For other types of concrete inspections than those described above, refer to Chapter 16 of"Materials and Construction: Construction Standards" and "Materials and Construction: Inspection
Standards".

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CHAPTER 10 UNDERWATER CONCRETE

10.1 General
10.1.1 Scope(1) This chapter presents the standards for matters required during the construction ofordinary underwater concrete, anti-washout underwater concrete and underwater
concrete used for cast-in-place piles or diaphragm walls.
(2) In cases when preplaced aggregate concrete is used under water, Chapter 9 shallapply.

[Commentary] (1) Ordinary underwater concrete and anti-washout underwater concrete areconstructed over a relatively wide area in the ocean or in other underwater areas. Ordinary
underwater concrete is used mostly for unreinforced concrete. Anti-washout underwater concretewith increased resistance to washout is used for unreinforced or reinforced concrete. Underwater
concrete is also used for cast-in-place piles or diaphragm walls that involve the construction ofreinforced or steel framed reinforced concrete in water or in stabilizing fluid.
The type and construction method vary according to the type of underwater concrete. Ordinary
underwater concrete, anti-washout underwater concrete and underwater concrete used forcast-in-place piles or diaphragm walls are discussed in Sections 10.2, 10.3 and 10.4, respectively.

10.1.2 General
Performance varies according to the type of underwater concrete. When constructing
underwater concrete, therefore, appropriate materials, mix proportions, methods ofplacement and construction machinery shall be selected under the guidance ofprofessional engineers with adequate knowledge and experience concerning underwater
concrete to minimize material segregation.

[Commentary] There is no proper method to confirm the uniformity of placed concrete, thereliability of a construction joint for normal underwater concrete in a wide area. Considerations are
therefore required for such measures as the enhancement of strength requirements to a level higher
than during the construction in the air. The quality of underwater concrete is determined by thequality of construction in particular. An appropriate construction method that minimizes material
segregation should therefore be selected.
Anti-washout underwater concrete may be of much higher quality than ordinary underwater
concrete if appropriate materials, mix proportions and construction methods are selected. Anotherbenefit is a small amount of leaching of suspended solids into surrounding water during
construction. Anti-washout underwater concrete has therefore been frequently adopted forconstructing high quality underwater concrete structures or in cases where preventing waterpollution is required. The properties of fresh concrete are, however, much different in anti-washout
underwater concrete from those of ordinary underwater concrete, and more considerations are
required in construction. These points should be taken into consideration when constructing
anti-washout underwater concrete. For the matters not mentioned in 10.3 concerning anti-washout
underwater concrete, refer to the "Design and Construction Guidelines for Anti-washout
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Underwater Concrete (draft)".
Underwater concrete used for cast-in-place piles or diaphragm walls is also used for such
structures as earth retaining walls and wall members of main structures. Reliable construction
requires high-level construction management including the management of construction accuracy,
stabilizing fluids and concrete quality.
When using underwater concrete in the ocean, attention should also be paid to durability. The
stipulations described in Chapter 11 "Offshore Concrete" should be honored.
In order to use an underwater concrete method that prevents material segregation by blocking
the contact of concrete and water through the improvement of construction equipment, the methodshould be fully examined considering the field conditions and adequate construction management
should be performed so as to achieve the designated quality of concrete.
Performance varies greatly according to the type of underwater concrete. Each type ofunderwater concrete should therefore be constructed under the guidance of professional engineers
with adequate knowledge and experience concerning the type.

10.2 Ordinary Underwater Concrete
10.2.1 Mix proportions(1) Standard slump values at the time of placement are listed in Table 10.2.1.

Table 10.2.1

Slump of underwater concrete

Construction method
Tremie pipes or concrete pumps
Bottom discharge buckets or bags

Range of slump (cm)
13～18
10～15

(2) The standard strength should be determined on the assumption that the strength
during underwater construction is 0.6 to 0.8 time the strength of a standard specimen.
(3) The standard water-cement ratio should be set at 50% or lower.
(4) The standard unit cement content should be set at 370 kg/m3 or higher.

[Commentary] (1) Underwater concrete cannot be compacted and so requires an appropriate
amount of fluidity. The standard slump at the time of placement has been specified as shown in
Table 10.2.1 according to the construction method. For underwater concrete, highly cohesive mix
proportions are required so as to minimize material segregation. To that end, using appropriate
admixtures and increasing the percentage of fine aggregate to an appropriate level are required. The
standard percentage of fine aggregate should be set at 40 to 45% in cases where gravel is used forcoarse aggregate and should be increased 3 to 5% in cases where crushed stone is used.
(2), (3) and (4) Existing survey results show that the compressive strength of underwater
concrete placed by tremie may sometimes be reduced to approximately 60% of compressive
strength of a standard specimen if the distance of flow from the tremie exceeds 3 m. This suggeststhat concrete is likely to be subjected to washout in the vicinity during underwater placement andhave its strength reduced.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

In order to minimize strength reduction and resultant concrete quality deterioration and toensure the ease of construction, rich mixes are desirable for underwater concrete. The standard
maximum water-cement ratio and minimum unit cement content have been set at 50% and 370
kg/m3, respectively.
When using fly ash meeting the requirements in JIS A 6201 "Fly ash for concrete" or granulated
blast-furnace slag meeting the requirements in JIS A 6206 "Granulated blast-furnace slag for
concrete", the fly ash or blast-furnace slag may be regarded as part of the unit cement content.

10.2.2 Placement
10.2.2.1 General(1) Concrete shall be placed in static water.
(2) Concrete shall not be made to fall in water.
(3) Concrete shall be placed continuously until it reaches the designated height orwater surface while keeping the surface as horizontal as possible.
(4) Concrete shall not be stirred during the placement.
(5) Flow of water shall be prevented until the concrete hardens.
(6) Surface laitance shall be removed at the end of placement of a lift before starting
the placement of another lift.
(7) Concrete should be placed in general using tremie or concrete pumps.

[Commentary](1) Underwater concrete should be placed while building an appropriate temporary
enclosure to control the flow of water to prevent water contamination due to the washout of cement and theformation of laitance. Even if no complete enclosure can be built, concrete should be placed while the flow
velocity is 5 cm/sec or lower.

(2) Letting concrete fall in water causes material segregation and washout of cement. Concrete
is likely to fall in water in cases where construction tools are handled improperly. The handlingprocedure should be thoroughly examined and preventive measures should be taken.
(3) Before resuming the placement of concrete after suspension, laitance should be removed as
per stipulation (6). Removing laitance is very demanding. The placement of concrete should
therefore not be suspended until the designated height or water surface is reached unless suspension
is inevitable.
In the case of a continuous lift of several meters, placement in short time may sometimes cause
the form to swell due to the lateral pressure acting on the form and the mortar to leak. Due attention
should therefore be paid to the strength and assembly of the form.
(4) In order to minimize concrete material segregation at the contact with water, the tip of thetremie or pump should be fixed during placement.
(7) Tremie or concrete pumps are fit for the construction of underwater concrete while
preventing cement washout. No bottom discharge buckets or bags should be used except forstructures that are not so important because they cannot enable continuous concrete placement and380

Chapter 10

Underwater Concrete

the quality of concrete placed is not sufficiently reliable.

10.2.2.2 Placement using tremie pipes(1) Tremie pipes shall be watertight and be sufficiently large to enable the free fall ofconcrete.
(2) The area where concrete is placed by a single tremie pipe should be determined so
as not to deteriorate the quality of concrete.
(3) The tip of the tremie pipe shall be placed in the concrete already placed duringconcrete placement.
(4) The tremie must not be moved laterally during concrete placement.
(5) The handling of the tremie from the start to the end of concrete placement shall be
studied in detail in advance, and measures shall be taken to prevent material segregationin the concrete being placed.
(6) When using a special tremie pipe, its applicability and use shall be examined
carefully.

[Commentary]
C10.2.1.

An example of underwater concrete placement by a tremie is shown in Fig.

(1) In actual concrete placement by a tremie, 25-cm-inner-diameter tremie pipes are frequently
adopted where water depth is 3 m or less, or 30- to 50-cm diameter tremie pipes are used wherewater depth is 5 m or more. The inner diameter of tremie pipe should be approximately eight times
the maximum size of coarse aggregate(2) Letting the concrete that flows out at the bottom end of the tremie flow in the water for along time deteriorates concrete quality. The area where concrete can be placed by a single tremie
pipe is generally limited to approximately 30 m2. In an example, concrete was placed in an area ofapproximately 60 m2 for an unreinforced concrete structure of simple shape with large height andarea.
(3), (4) and (5) Dropping concrete in the water causes considerable material segregation. The
contact of water and concrete should therefore be prevented by using a tremie pipe with a cap at the
tip or inserting a plunger at the start of concrete placement. In order to prevent water from entering
the tremie pipe during concrete placement, the bottom end of the tremie should be embedded in theconcrete already placed.
(6) A special tremie is equipped with a flexible hose in the pipe section to leave no concrete in
the pipe using the pressure balance with the water outside the pipe. Another special tremie has aremote-controlled valve and a concrete surface sensor at the tip. These tremies eliminate the need ofinsertion of their bottom end into the concrete already placed and therefore can place concrete in a
wider area than by ordinary tremies. When using a special tremie, its applicability under theconstruction conditions should be verified and the method of its use should be fully examined381

Standard Specifications for Concrete Structures-2007, Materials and Construction

TremieFlange joint

Scaffolding

Ｗ．Ｌ．

Concrete

Fig. C10.2.1 Placement of underwater concrete by a tremie

10.2.2.3 Placement by pumping(1) Concrete pump piping shall be watertight.
(2) Concrete shall be placed by the method described in Section 10.2.2.2.

[Commentary] (1) Underwater concrete is pumped to a lower area, so negative pressures are
frequently created. Then, the water in the vicinity penetrates the concrete and concrete quality isdeteriorated unless the piping is watertight.
(2) In actual construction, pipes of 10- to 15-cm diameter, three to four times the maximum sizeof coarse aggregate, are used in numerous cases. The area in which concrete can be placed by asingle pipe is approximately 5 m2.
The contact between water and concrete in the pipe should be prevented by inserting a spongeball at the start of concrete placement, and the pipe should be filled with water and the tip of thepipe should be embedded into the concrete already place to a depth of 30 to 50 cm during
placement, to prevent the deterioration of concrete quality. When moving the pipe, it should beequipped with a check valve at the tip to prevent the reverse flow of water into the pipe or theunderwater drop of concrete in the pipe.
In the case where the pumping pressure is high, the tip of the pipe should be provided withadequate mass or fixed so as to prevent concrete from being stirred owing to the shaking of the pipetip.
A method involves concrete placement by placing the tip of the concrete pump in the tremie (orsteel casing) installed at the point of placement. The tremie prevents the tip of the pumping pipe
from shaking. If the tip of the tremie is inserted into the concrete already paced, the tremie also
prevents material segregation due to concrete fall in the pipe or reverse water flow in the pumpingpipe.
A report has been made on a number of quality tests of underwater concrete placed by inserting
the tip of the concrete pump into a steel casing. The concrete was placed in an area ofapproximately 38 m2 per casing and the flow distance in the water was less than 5 m. The test
results show that the core samples collected from the underwater concrete structure had strengthwith a small amounts of variations and had designated resistance to freezing at a unit cement
content of 340 kg/m3, water-cement ratio of 50% and a percentage of fine aggregate of 43% or382

Chapter 10

Underwater Concrete

higher. In cases where the mix proportions and construction conditions are clearly known and theguarantee of quality has been verified as in the above case, the unit cement content may be reduced
to some extent despite the stipulations in Section 10.2.1.

10.2.2.4 Placement using bottom discharge buckets or bags
(1) Bottom discharge buckets and bags shall be designed to open easily when
discharging concrete as their bottom reaches the concrete placement surface.
(2) Bottom discharge buckets and bags shall be slowly lowered in the water duringconcrete placement. After the discharging of concrete, bottom discharge buckets andbags shall be raised gradually until they are fully away from the concrete surface.

[Commentary] Numerous types of membrane are used for bottom discharge bags. Placing
underwater concrete using bottom discharge buckets or bags causes the concrete to be piled andresults in insufficient filling of the form. When adopting these means, therefore, water depth shouldbe measured and the concrete should be placed at low points on the top surface of concrete.
The use of the underwater concrete placed by the above method should be selected considering
the fact that concrete may not be uniform in different buckets or bags.

10.3 Anti-Washout Underwater Concrete
10.3.1 Materials(1) The anti-washout admixture for underwater concrete shall conform to JSCE-D 104.
(2) High performance water reducers, plasticizers, high performance air-entraining
water reducers, water reducers, air-entraining water reducers and other admixtures shallcomply with JIS A 6204 and should not have adverse effects when used in combination
with anti-washout admixtures.
(3) Aggregate that has been found safe in alkali-silica reaction tests shall be used.

[Commentary] (1) Underwater concrete, at the time of placement, should have designatedanti-washout capacity and fluidity sufficient to enable construction without compaction. Hardened
concrete should have designated strength, durability and crack resistance. In order to provide
anti-washout underwater concrete with these properties, anti-washout admixtures with designatedcapacity should be used.

There are many types of chemical admixtures available to enhance the resistance to segregation
underwater. Then, the quality and performance of these admixtures vary in wide range. Therefore,chemical admixtures for enhancing the resistance to segregation used in the construction shallconform to JSCE-D 104 “Quality Specifications for Anti-washout Admixtures for Underwater
Concrete”.
(2) The amount of water content of anti-washout underwater concrete to obtain the required
flowability is more than that of normal underwater concrete because of the increasing viscosity
effect of the admixture. However, in order to avoid the excessive increasing of water content,
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Standard Specifications for Concrete Structures-2007, Materials and Construction

high-range water-reducing agent conformed to JSCE-D 101 “Quality Standards forSuperplasticizers for Concrete” or water-reducing agent conformed to JIS A 6204 shall be used at
the proper amount. It is known that some combinations with these agents and the chemical
admixtures for the resistance to segregation underwater may have a negative influence on theperformance each other. Therefore, it is necessary that the combination with admixtures is
examined thoroughly and the performance is confirmed before use.
(3) If antiwahsout underwater concrete is used in the sea, alkali metal is supplied by theseawater in addition to alkali contained in concrete. Both fine and coarse aggregates that have beenfound safe in alkali-silica reaction testing should therefore be used to ensure safety.

10.3.2 Mix proportions(1) The mix proportions shall be determined by test so that the requirements ofstrength, resistance to segregation under water, flowability, etc. are satisfied.
(2) The target strength of anti-washout underwater concrete shall be determinedconsidering the design strength and variation of concrete quality.
(3) Strength shall be determined based on the 28-day compressive strength of a
specimen prepared in the water in accordance with JSCE-F 504.
(4) The underwater segregation resistance of anti-washout underwater concrete shallbe determined based on the degree of underwater segregation or ratio between strengths
in the water and in the air.
(5) The fluidity of anti-washout underwater concrete shall be represented by slump
flow. Slump flow tests should be conducted in accordance with JIS A 1150.
(6) The air content of anti-washout underwater concrete should not be more than 4% as
a standard.
(7) The maximum size of coarse aggregate should not exceed 40mm, and also not
exceed 1/5 of the least dimension of a member, nor 1/2 of the minimum spacing of
reinforcing bars.

[Commentary] (1) Anti-washout underwater concrete is used for various structural construction
from small-scale consolidation of rubble mounds to large-scale bridge pier construction, and comesin a wide variety of types such as unreinforced concrete, reinforced concrete and steel framed
reinforced concrete. The mix proportions of anti-washout underwater concrete should therefore be
determined by conducting tests fully considering the construction conditions such as the underwaterflow distance, degree of water pollution prevention and underwater drop height, and the structural
conditions such as the clearance of reinforcing bars so as to achieve designated strength, underwater
resistance to segregation, fluidity and durability.
(2) and (3) The 28-day compressive strength of a core sample of anti-washout underwater
concrete placed at an underwater drop height of 50 cm or lower and an underwater flow distance of
5 m or less is equal to or higher than the compressive strength of a specimen created underwater at
the same age. Concrete strength shall therefore be determined based on the 28-day compressive
strength of a specimen created in accordance with JSCE-F 504 "Method of preparing underwater
specimens for testing the compressive strength of anti-washout underwater concrete (draft)".
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Underwater Concrete

The target strength of anti-washout underwater concrete should be obtained by multiplying thedesign strength by a premium coefficient obtained in accordance with Section 4.4.3 (2) in"Materials and Construction : Construction Standards" according to the coefficient of variance ofconcrete compressive strength estimated at the site.
Anti-washout underwater concrete has chloride intrusion resistance and resistance to corrosion
due to various types of salt similar to those for ordinary concrete. When applying anti-washout
underwater concrete in the ocean, therefore, Section 11.3 should be consulted. Then, thewater-cement ratio should be determined based on the results of check of chloride intrusion
resistance. When determining the water-cement ratio considering the effect of corrosion on
reinforcing bars and chemical action on concrete, the standard maximum ratio should be determined
as shown in Table C.10.3.1

Table C.10.3.1

Maximum water-cement ratio of concrete determined from durability (%)

Type of concrete
Environment
In fresh water
In seawater

Unreinforced concrete

Reinforced concrete

65
60

55
50

(4) As for the degree of underwater segregation, tests should be conducted by Attachment 2"Method for testing underwater segregation in anti-washout underwater concrete (draft)" to JSCE-D
104 "Quality standards for anti-washout admixtures for concrete", and the suspended solids andpotential of hydrogen may be set to be 50 mg/l or lower and 12.0 or lower, respectively. The ratio
between strengths in the water and in the air may be set to be 0.8 or higher where relatively highresistance to underwater segregation is required as in reinforced concrete, or 0.7 or higher undernormal conditions.
(5) The values of slump flow representing the fluidity of anti-washout underwater concrete arelisted in Table C.10.3.2 under various construction conditions. The slump flow is measured fiveminutes after the slump cone is lifted in the test conducted in accordance with JIS A 1150 "Concrete
slump flow test (draft)".
Table C.10.3.2

Slump flow of anti-washout underwater concrete

Range of slump flow (cm)Construction condition
In cases where fluidity needs to be minimized as in the
consolidation of plastering on the surface of a steep slope
35 - 40(1:1.5 to 1:2) or in the construction of thin slabs on a slope(up to 1:8)
In cases where concrete is placed in an area of simple
40 - 50
shape
Under normal conditions and in cases where concrete is
45 - 55
placed in standard reinforced concrete structures
In cases where concrete is placed in an area of
55 - 60
complicated shape and in cases where high fluidity isrequired(6) In the case of excessive amounts of air, not only compressive strength is reduced but also385

Standard Specifications for Concrete Structures-2007, Materials and Construction

raising of air foam in the concrete during concrete flow causes water pollution and quality
variations.
(7) Underwater concrete cannot be compacted in most cases. In order to increase concrete
compactibility, therefore, more strict conditions have been specified for anti-washout underwater
concrete concerning the minimum spacing of reinforcing bars than for ordinary concrete. In actual
construction, the maximum size of coarse aggregate is mostly 20 mm or 25 mm because increasing
the size of coarse aggregate is not expected to greatly reduce unit water content or unit cement
content and because the segregation of coarse aggregate is more likely to occur as the size
increases.

10.3.3 Mixing(1) For anti-washout underwater concrete, cement, aggregate and anti-washout
admixtures should be dry mixed preliminarily and then all the materials shall be mixed.
Authorized plants equipped with manufacturing facilities should be used in general.
(2) Forced-action batch mixers should be used in general.
(3) The standard batch should be 80% of nominal mixer capacity or less.
(4) The mixing time should be determined by conducting tests.

[Commentary] (1) For producing homogeneous anti-washout underwater concrete by mixing,
cement, aggregate and anti-washout admixtures should be dry mixed in a plant and then water anddesignated admixtures should be mixed. The standard dry mixing time may be set at 20 to 30
seconds. When mixing anti-washout underwater concrete at a ready mixed concrete plant, the slump
flow, compressive strength of a specimen created underwater, ratio between strengths in the air andin the water, and the type and quantity of anti-washout admixtures should be determined in addition
to ordinary parameters through consultation with the manufacturer.
(2) Forced-action batch mixers with performance specified in Section 5.2.3 of "Materials andConstruction: Construction Standards" should be used in principle because adequate capacity of
mixing anti-washout underwater concrete is required. When using tilting mixers, care should be
exercised because concrete may sometimes adhere to the inner wall of the drum resulting ininadequate mixing.
In small-scale construction work, anti-washout underwater concrete may sometimes be mixedby agitation in a truck agitator to which anti-washout admixtures are input. Then, the availability ofconcrete of designated quality owing to adequate mixing should be verified before using theconcrete.
(3) Anti-washout underwater concrete places heavier burden on mixers than ordinary concrete.
A batch should therefore be 80% of nominal mixer capacity or less so as to obtain concrete ofdesignated quality.
(4) Mixing time should be determined in accordance with the stipulations of JIS A 1119
"Methods of testing the differences in mortar and in fine aggregate in the concrete mixed using amixer". Mixing time should be determined only after conducting mixing tests to verify whether theconcrete is of designated quality or not. The mixing time for forced-action mixers is generally 90 to
180 seconds.
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Underwater Concrete

10.3.4 Placement(1) Concrete should be placed in static water at an underwater height of fall of 50 cm orless as a standard practice.
(2) Concrete shall be placed either using tremies or concrete pumps. Care shall betaken not to deteriorate the quality of anti-washout underwater concrete.
(3) The standard underwater flow distance should be 5 m or shorter.

[Commentary] (1) Placing anti-washout underwater concrete in water flowing at low speed or
dropping concrete in water is likely to make reliable concrete. Methods should, however, beavoided that may deteriorate quality for no reason. Static water means the water with a flow
velocity of 5 cm/sec or lower.
(2) The tip of the tremie or concrete pump should be kept embedded into the concrete alreadyplaced during concrete placement for the same reason as described above. When suspending
concrete placement or moving the pipe tip of the tremie or concrete pump, reverse water flow
should be prevented.
When pumping anti-washout underwater concrete, the pump pressure is two to three times thatfor ordinary concrete and the rate of pumping 1/2 to 1/3 of that for ordinary concrete. Care should
therefore be taken when developing a construction plan.
Buckets may sometimes be used for placing anti-washout underwater concrete with low slump
flow in relatively small-scale construction or on slope ways. Placement using buckets results indiscontinuous placement. Care should be taken to prevent water from entering the gap from thepreviously placed lift.
(3) Anti-washout underwater concrete has higher fluidity than ordinary concrete and causes little
quality deterioration due to flow. The area to be covered by a tremie or a fixed pump pipe may be
increased over that for ordinary underwater concrete. The underwater flow distance should,
however, be held to 5 m or less because letting concrete flow excessively induces quality
deterioration and heterogeneity. In cases where the underwater flow distance needs to be longer
than 5 m, the achievement of concrete of designated quality should be verified by testing or basedon the existing construction records.

10.3.5 Protection of concrete surface
Since anti-washout underwater concrete requires a long setting time, the concrete
shall be protected from surface scour by flowing water or waves before concrete hardens
after placement.

[Commentary] Anti-washout underwater concrete has adequate resistance to underwater
segregation. If subjected to direct effect of flowing water or waves, however, cement may flow out
or concrete surface may be scoured. Then, protective measures should be taken by covering theconcrete surface with membrane or installing a form to the height required to prevent the flowing
water or waves from directly affecting the concrete surface.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

10.4 Underwater Concrete Used for Cast-In-Place Piles or Diaphragm Walls
10.4.1 Mix proportions(1) For underwater concrete used for cast-in-place piles or diaphragm walls, strength
shall be determined considering the strength reduction during construction.
(2) The standard maximum size of coarse aggregate should be specified at 1/2 or lessof the spacing of reinforcing bars and 25 mm or less.
(3) The standard slump should be 18 to 21 cm. Slump flow shall be set in a range
between 50 to 70 cm in cases where the design strength f'ck exceeds 50 N/mm2 because
especially high fluidity is required.
(4) The standard water-cement ratio should not exceed 55%.
(5) The standard unit cement content should be 350 kg/m3 or higher.

[Commentary] (1) For underwater concrete used for cast-in-place piles or diaphragm walls, thestrength during underwater construction shall be set at approximately 0.8 time that during air
construction and the strength during construction in stabilizing fluid shall be set approximately 0.7
time that during air construction based on the past records.
(2) In underwater concrete, the larger the coarse aggregate, the more likely is material
segregation to occur. If the reinforcing bars are arranged at small spacing, concrete is unlikely toflow outside the pre-assembled reinforcing bars, resulting in inadequate filling or segregation is
likely to occur in the concrete outside the pre-assembled reinforcing bars due to the fall of concrete.
The standard maximum size of coarse aggregate has been set to be 1/2 or less of the spacing of
reinforcing bars and 25 mm or less. In cases of large wall thickness and pile diameter, and large
spacing of reinforcing bars, the maximum size of coarse aggregate may be set at 40 mm or less on
condition that concrete mix proportions and slump are fully examined.
When using lapped joints or bundled bars, concrete is not likely to fill neatly. Attention should
therefore be paid not to reduce the spacing of reinforcing bars excessively.
(3) Underwater concrete used for cast-in-place piles or diaphragm walls is generally placed inwater using tremies, so the concrete should be highly fluid. In the case of low fluidity, concrete isplaced in a mound with the tremie at the midpoint, slimes composed of debris and cuttings areformed at the joints, and concrete is locally deteriorated or voids are created as the slime or
stabilizing fluid is entrained. In the case of a small spacing of reinforcing bars, concrete may not fillcompletely. It should be noted that segregation is likely to occur when the slump exceeds 21 cm andthat fluidity is reduced at a slump of 18 cm or less.
Diaphragm walls with a design strength of 50 N/mm2 or greater have recently been constructed.
Then, the spacing of reinforcing bars is reduced as the amount of reinforcement increases. In orderto obtain high concrete compactibility, concrete should be provided with high fluidity. Fluidity may
be required in numerous cases that should be managed in terms of slump flow not slump. High
fluidity is generally achieved by adding high performance air-entraining water reducers. Adding an
excessively large amount of high performance air-entraining water reducers, however, may causematerial segregation or extraordinarily delay setting. When using concrete with a design strength of
50 N/mm2 or greater, the range of fluidity that provides adequate quality should be verified inadvance in testing and proper construction management should be exercised.
For underwater concrete used for diaphragm walls with a design strength of 50 N/mm2 or
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Underwater Concrete

greater, rich concrete mix is used. Low-heat cement is therefore generally used to prevent theoccurrence of thermal cracking. Low-heat cement comes in various types. Moderate heat Portland
cement, low-heat Portland cement, blast-furnace slag cement type B with a ground granulated
blast-furnace slag content of 50% or higher, ordinary Portland cement or multicomponent cement,
which is moderate heat Portland cement with one or two types of admixtures, is frequently adopted.
In order to prevent thermal cracking, 91-day design strength is generally adopted and unit
cement content is reduced in numerous cases.
(4) and (5) The design strength varies for underwater concrete used for cast-in-place piles ordiaphragm walls according to the use. The design strength is generally set at 24 to 30 N/mm2 innumerous cases. Mix proportions may be specified to achieve the design strength even at awater-cement ratio of approximately 60% and a unit cement content of approximately 300 kg/m3.
The water-cement ratio and unit cement content have been specified as described above because acertain amount of viscosity is required to prevent segregation in water and because strength
reduction needs to be considered due to the entraining of slime or mixing of stabilizing fluid.
When using diaphragm walls only as temporary structures, water-cement ratio may be set at 300
kg/m3 or higher. When using fly ash complying with JIS A 6201 or ground granulated blast-furnace
slag complying with JIS A 6202, the fly ash or the ground granulated blast-furnace slag may be
regarded as part of the unit cement content.

10.4.2 Pre-assembled reinforcement(1) Pre-assembled reinforcement shall be sufficiently hard to prevent damaging
deformation during storage, transport or erection.
(2) Sufficient concrete cover shall be provided.
(3) Spacers of appropriate shape shall be arranged properly so as to secure covering
as per design documents.
(4) Pre-assembled reinforcement shall be erected as early as possible after thecompletion of excavation. Reinforcement shall be kept in position and vertical to prevent
bending, buckling, omission and contact with the wall of the drill-hole during erection.

[Commentary] (1) The deformation of pre-assembled reinforcement (also referred to as the cageof reinforcement) causes the reduction of concrete cover, collapse of the wall of the drill-hole,
impossibility of erection of reinforcement and simultaneous rising of pre-assembled reinforcementin the case of pile construction using casing. Pre-assembled reinforcement should therefore be
assembled properly to form the designated shape at the designated size, and should be madesufficiently hard so as to prevent damaging deformation during lifting, transport or erection.
Pre-assembled reinforcement may be reinforced by reinforcing the steel wire hanger clamping
fixture or reinforcing for protection from twisting or crushing of pre-assembled reinforcement. For
reinforcement work, large-diameter erection bars or steel plates with designated dimensions should
be used. In rectangular pre-assembled reinforcement as for diaphragm walls, reinforcing bars should
be arranged externally in a diagonal grid pattern. Then, reinforcing bars should be arranged so as
not to prevent the insertion of the tremie. When stacking previously arranged reinforcement forstorage or transport, deformation should be prevented by taking measures such as inserting
temporary supports in the pre-assembled reinforcement.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

When producing pre-assembled reinforcement, vertical and horizontal reinforcements may bewelded rather than bundled to enhance the ease of construction as long as designated conditions aremet.
(2) No underwater concrete used for cast-in-place piles or diaphragm walls can be compacted.
Concrete may not fill completely in cases where the clearance between the drill-hole wall andreinforcement is small. For underwater concrete, constructed in water or stabilizing fluid, the resultof construction can hardly be determined. Considering these points, concrete cover should be set at
10 cm or more. Concrete cover may, however, be set at 8 cm or more for temporary walls or water
cutoff walls. Concrete cover here means the distance from the outer edge of hoop to the outer edgeof the design cross section of a pile or wall.
(3) Pre-assembled reinforcement should be applied with spacers and designated concrete cover
should be secured. Spacers should be of a shape that prevents the removal or scraping of thedrill-hole wall when inserted into the pre-assembled reinforcement.
Spacers should be arranged at vertical intervals of 3 to 5 cm and in four to six locations at thesame depth, and should be attached to the main reinforcement. The projection height of spacers andthe clearance from the drill-hole wall and from the inner surface of casing should be determinedconsidering the accuracy of excavation of drill-hole wall surface and the prevention of simultaneous
rising of pre-assembled reinforcement at the time of extraction of casing. Spacers should be shaped
so as to prevent the formation of slime.
(4) Pre-assembled reinforcement should be erected as early as possible after the completion of
excavation because the drill-hole wall is likely to collapse and slime is likely to settle.
Pre-assembled reinforcement should be lifted and erected so as not to induce deformation
detrimental to the pre-assembled reinforcement itself. For piles using no casing, due care should betaken not to cause the shaking or inclination of pre-assembled reinforcement to induce the collapseof drill-hole walls. Pre-assembled reinforcement should be erected moderately at the predetermined
position while keeping the reinforcement vertical and preventing lateral shaking. Pre-assembled
reinforcement is generally erected by lifting reinforcing bars at the top edge of pre-assembled
reinforcement or steel plates using steel hangers in numerous cases.
In cases where no pre-assembled reinforcement can be inserted smoothly during erection, thepre-assembled reinforcement should be lifted, causes should be identified and corrective measures
should be taken.

10.4.3 Placement(1) Slime shall be completely removed before concrete placement.
(2) Concrete shall be placed using tremies.
(3) Concrete shall be placed to a height 50 cm or more above the design surface, andshall be removed after hardening.
(4) Due consideration shall be given when disposing of the used stabilizing fluid.

[Commentary] (1) Placing concrete while slime is deposited at the bottom of the drill-hole has
adverse effects such as the deterioration of the end bearing capacity of the pile and the deteriorationof concrete quality due to the entrainment of slime. It should therefore be ensured that slime beremoved. Slime should be removed twice: at the end of excavation and right before concrete390Chapter 10

Underwater Concrete

placement. Removal may take place once at an appropriate time for some methods or under certain
conditions.
(2) Underwater concrete used for cast-in-place piles or diaphragm walls should be placed using
tremies to ensure construction because concrete placement generally takes place in stabilizing fluid,
concrete is placed to a great height, construction is carried out over a wide area and high quality
concrete is required.
The inner diameter of tremie should be approximately eight times the maximum size of coarse
aggregate. In cases of a maximum size of coarse aggregate of 25 mm, therefore, tremies 20 to 25
cm in pipe diameter should be used.
If the tremie is embedded to an extremely small depth during concrete placement, concrete may
rise through the tremie and segregation may occur, or the top end of the tremie may be raised above
the concrete surface. The tremie should therefore be embedded to a depth of 2 m at the minimum inthe concrete during concrete placement. The depth of embedment may, however, be set at 2 m orless in cases where the concrete surface can be verified easily when placement is expected to becompleted soon.
Embedding the tremie to an extraordinary depth is likely to cause concrete to flow poorly,
induce inadequate filling, make the lifting of the tremie difficult, increase the height of lifting of thetremie, and cause the concrete to fall drastically in the tremie leading to segregation. The depth ofembedment should therefore be set at approximately 9 m at the maximum or at 6 m under normal
conditions.
When constructing diaphragm walls, concrete flows a longer distance than when constructing
cast-in-place piles. An excessively long flow distance from the tremie results in segregation.
Tremies should therefore be installed at intervals of less than 3 m longitudinally, and should beplaced even at ends or in corners.
Placing concrete extremely slowly causes the deterioration of concrete quality due to theentrainment of stabilizing fluid. Extremely high speed of placement on the other hand deforms
connection steel plates at joints or causes concrete inflow into joints in the case of primary elementsof diaphragm walls. Concrete is generally placed at a rate of 4 to 9 m/hr for primary elements or 8
to 10 m/hr for secondary elements in most cases.
When placing concrete using multiple tremies, concrete should be placed so that concretesurfaces may rise simultaneously to minimize the difference in concrete height.
(3) Quality is deteriorated on the top surface of concrete due to the mixing of the stabilizing
fluid and slime and bleeding-induced laitance during concrete placement. Concrete should therefore
be placed more than 50 cm above the design surface. The extra height of placement for diaphragmwalls used for temporary walls or cutoff walls may be set to be 50 cm or less if adequate
examination is made.
(4) Mishandling of used stabilizing fluid is likely to cause the clogging of drain pipes in thevicinity of the site or pollute surrounding roads. Considerable attention should be paid to thedisposal of used stabilizing fluid by preparing disposal facilities such as settling tanks and vacuum
vehicles. The drainage and environmental standards concerning the construction work in question
should be fully investigated in advance and disposal plans should be developed accordingly.

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10.5 Inspections(1) The accepting party shall conduct acceptance tests for ordinary underwater
concrete. The tests and inspections should be in accordance with Table 10.5.1.
Table 10.5.1 Acceptance tests for ordinary underwater concrete
Item
Compressive
strength

Water-cement
ratio

Unit cement
content
Slump

Testing or
inspection method
Method shown in
JIS A 1108

Timing and frequency

Decision criteria

It can be estimated at
appropriate producer's riskthat the probability of failingto provide the design strength
considering the allowance
duringunderwater
construction is 5% or less.
Obtainedfrom At the start of construction 50% or lesswork, and when materials or
automatic
measurements of mix proportions vary.
cement, aggregate
surface water ratio
and water content.
Automatic
measurements
Method shown in
JIS A 1102

At the time of unloading,daily or once in 20 to 150 m3
according to the importanceof the structure or the scaleof work.

Same as above.

370 kg/m3 or higher

At the time of unloading,daily or once in 20 to 150 m3
according to the importanceof the structure or the scaleof work.

Value shown in Table 10.2.1(2) The accepting party shall conduct acceptance tests for anti-washout underwater
concrete. The tests and inspections should be in accordance with Table 10.5.2.
Table 10.5.2 Acceptance tests for anti-washout underwater concrete
Testing or
Item
Timing and frequency
Decision criteria
inspection method
Compressive
Method shown in At the time of unloading, It can be estimated atstrength of
JSCE-F504
daily or once in 20 to 150 m3 appropriate
producer's
specimenaccording to the importance risk that the probability ofmade in theof the structure or the scale of failing to provide the
water
work.
design strength is 5% orless.
MaximumMix proportions
At the start of construction 40 mm or less.
size of coarse
testing
work, and when materials or Not exceeding 1/5 or theaggregate
mix proportions vary.
minimum size of themember and 1/2 of thespacing of reinforcing
bars
Degree of
Method shown inSame as above
Suspended solids should
underwater
JSCE-D104
not exceed 50 mg/l.
segregation
Potential of hydrogenshould not exceed 12.0.

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Chapter 10

Ratio between
strengths in
the water andin the air
Slump flow

Method shown in
JSCE-F504

Method shown in
JIS A 1150

Underwater Concrete

Same as above

For ordinary concrete, 0.7
or higher.
For reinforced concrete,
0.8 or higher.
At the time of unloading, Designated value plus or
daily or once in 20 to 150 m3 minus 3 cm
according to the importanceof the structure or the scale ofwork(3) The accepting party shall conduct acceptance tests for underwater concrete used
for cast-in-place piles or diaphragm walls. The tests and inspections should be inaccordance with Table 10.5.3.
Table 10.5.3 Acceptance tests for underwater concrete used for cast-in-place piles ordiaphragm walls
Item
Compressive
strength

Testing or inspection
methodMethod shown in JIS
A 1108

Timing and frequency

Decision criteria

At the time of unloading,daily or once in 20 to 150
m3 according to theimportance of the structureor the scale of work.

It can be estimated at
appropriate
producer's
risk that the probability offailing to provide thedesignstrengthconsidering the allowance
duringunderwater
construction is 5% orless.
Maximum size
Mix proportions
At the start of construction 25 mm or less.
of coarse
testing
work, and when materials Not exceeding 1/2 of theaggregateor mix proportions vary.
spacing of reinforcing
bars
Water-cement Obtainedfrom
Same as above
55% or lessratio
automatic
measurementsofcement,aggregate
surface water ratio
and water content.
Unit cement
Automatic
Same as above.
350 kg/m3 or higher
content
measurements
Slump or slump Method shown in JIS At the time of unloading, Value in the constructionflow
A 1102 or 1150
daily or once in 20 to 150 plan.
m3 according to the Slump in cases with noimportance of the structure specifications: 18 to 21
or the scale of work.
cm.
Specified slump flowplus or minus 5 cm.

[Commentary] The accepting party conducting underwater concrete acceptance tests means the
Owner. There may, however, be cases in which the Contractor conducts acceptance tests forunderwater concrete and the Owner verifies test results.
The segregation resistance underwater is affected by the variation of materials and mix
proportion on producing and by the little difference on producing conditions. Therefore, theinspection of the resistance to segregation underwater for normal underwater concrete and393

Standard Specifications for Concrete Structures-2007, Materials and Construction

underwater concrete for cast-in place piles or diaphragm walls is specified to be carried out by
confirming the mix proportion and the type of used materials. Moreover the inspection of theresistance to segregation underwater for anti-washout underwater concrete is specified to be carriedout by tests of level of segregation resistance underwater and ratio of strength underwater to in airand so on.
For inspections of other concrete than described here, refer to Chapter 16 of "Materials andConstruction: Construction Standards" and "Materials and Construction: Inspection Standards".

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Standard Specifications for Concrete Structures-2007, Materials and Construction

CHAPTER 11 CONCRETE FOR MARINE STRUCTURE

11.1

General11.1.1 Scope(1) This chapter presents the standards for matters required during the construction of
concrete marine structures.
(2) When constructing underwater concrete structures, Chapters 9 and 10 shall also be
consulted.

[Commentary] (1) In this chapter, ports, seashores and sea are collectively referred to as oceans.
Not only the concrete used for the structures that are located in tidal areas or below the sea level andare subjected direct to the action of seawater but also the concrete used for the structures that are
constructed on land or above the sea level and are subjected to the actions of waves, seawater orsplash are regarded as concrete for marine structures. The marine structures discussed in thischapter include small members installed on the seashore, large marine floating structures and large
or deep-sea marine structures. Structures using concrete for marine structures in parts of or
throughout the structure are referred to as marine concrete structures. Marine concrete structures
include breakwaters, moorings, revetments, marine bridges, offshore terminals, docks, submarine
tunnels, offshore airports, offshore power plants and offshore cities. For these structures, members
are produced as precast concrete members and assembled at the site in numerous cases. Then,
concrete is of uniform quality.
This chapter describes the construction of concrete for marine structures and the construction
work for marine concrete structures. Marine concrete structures come in wide varieties of types.
Establishing stipulations covering all of the types is extremely difficult. When constructing a
specific structure, therefore, it is necessary to fully understand the performance requirements for the
structure, and apply the stipulations in this chapter considering the service life, functions, effects offailure or damage on the functions, difficulty of repair or retrofit, uncertainties including natural
conditions, and construction conditions. The "Corrosion Protection Guidelines for Marine Concrete
Structures (draft)" prepared by the Japan Concrete Institute or other documents may be consulted as
required.

11.1.2

General(1) Measures shall be taken to prevent the quality degradation of marine concrete
structures during their service life due to concrete deterioration or steel corrosion.
(2) Concrete for marine structures shall be constructed fully considering the construction
conditions, environmental conditions and the effects of sailing ships.
(3) When constructing concrete for marine structures, due care shall be exercised forenvironmental protection to prevent the pollution of the marine environment or the adverse
effect on the ecosystem.

[Commentary] (1) Marine concrete structures are more vulnerable to chloride intrusion thanordinary structure on land. Once the corrosion of the steel in concrete due to chloride intrusion
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Chapter 11

Concrete for Marine Structures

becomes outstanding, completely restoring the functions of the structure by repair or retrofit isdifficult. In marine concrete structures, therefore, due attention should be paid to the durability ofconcrete and the corrosion protection of steel in concrete. The corrosion of steel in concrete cangenerally be prevented by producing compact concrete, increasing the concrete cover, preventing
cracks due to thermal stress or drying shrinkage or adopting appropriate materials and construction
method. In important structures or structures for which repair is difficult, more active corrosion
protection measures may be required using steel corrosion protection methods with good trackrecords such as using epoxy resin coated reinforcement, coating concrete surface and providing
cathode protection. For these corrective measures, refer to the "Construction and Design Guidelines
for Reinforced Concrete Using Epoxy Resin Coated Reinforcement (revised edition)","Construction and Design Guidelines for Electrochemical Corrosion Protection Methods (draft)","Construction and Design Guidelines for Surface Protection Methods (draft)", "Manuals for
Respective Methods" and the "Corrosion Protection Guidelines for Marine Concrete Structures(draft)" prepared by the Japan Concrete Institute.
(2) When constructing concrete for marine structures, sea breezes, waves and tidal currents
should be taken into consideration. The effects on the passage of ships or on the fishing grounds inthe vicinity, and the adverse effects of passing ships at night or in heavy weather should be
examined in advance, and adequate corrective measures should be prepared.
Concrete for marine structures is constructed under more severe conditions and greater
performance requirements are required than for ordinary concrete on land. Concrete placement at an
offshore site should be avoided wherever possible. Precast members produced at land or marine
yards under better construction conditions should be used. Precast members should be installed at
an offshore site in accordance with Section 11.6.
(3) When constructing cast-in-place concrete for marine structures, measures should be taken toprevent the contamination of sea water. While concrete for marine structures is being constructed oris in service, the environment should be protected and the surrounding environment should be kept
free from any adverse effects. For these matters, refer to "Present conditions and problems
concerning the leaching of minute components of concrete" or other works.

11.2 Materials
Materials used for marine concrete structures shall not impair the durability ofconcrete[Commentary] Concrete for marine structures is subject to gradual damage due to damaging
actions such as the physical and chemical actions of sea water, meteorological actions, and impact
or friction caused by waves or drifting solids. Chloride ion intrusion into the concrete is highly
likely to corrode internal steel. In order to ensure the durability of concrete and the protection ofsteel under the above conditions, materials resistant to the action of sea water should be used for
producing concrete for marine structures, and construction should be carried out carefully. In cases
where concrete alone cannot fully meet the above performance requirements under certain marine
environments, concrete surface should be coated to provide adequate protection in the marine
environment, or epoxy resin coated reinforcement or other types of reinforcement should be usedthat are unlikely to be corroded.

Cement: Highly resistant to the action of sea water are blastfurnace slag cement and fly ash
cement. For the concrete for marine structures, Portland cement with a low content of C3A is highly
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Standard Specifications for Concrete Structures-2007, Materials and Construction

resistant to sea water, to sulfate in particular. Care should, however, be exercised from a viewpointof steel corrosion. Sulfate-resistant Portland cement, moderate heat Portland cement and low heat
Portland cement have a low content of C3A. Concrete using these types of cement has a low
capacity of immobilizing chloride ions. Then, chloride ion intrusion into concrete is likely to beaccelerated. These types of cement have a lower capacity of immobilizing chloride ions thanordinary Portland cement. When using these types of cement, therefore, the water-cement ratio
should be reduced to produce the concrete of low permeability. Blast furnace slag cement on theother hand has a high capacity of immobilizing chloride ions and is highly resistant to sea water, so
it is considerably effective for preventing steel corrosion. Ordinary blast furnace slag cement type B
may have a high early age strength at certain levels of slag content and fineness, and the adiabatic
temperature of concrete sometimes rises higher than in ordinary Portland cement. Cracking due tothermal stress has been reported at certain member dimensions or under certain restraining or
environmental conditions. Some variations of blast furnace slag cement type B are of low-heat type.
When using the type of cement, the heating conditions should be verified and a longer design age
should be specified.
Moderate- and low-heat Portland cements or fly ash cement produces low heat of hydration andmay be adopted to control thermal cracking. The concrete using these types of cement, however, hasa low early age strength. When using these types of cement, therefore, special attention should be
paid to early age wet curing to develop an appropriate level of strength. Early age wet curing is also
important to blast furnace slag cement.
Aggregate: Materials that crumble easily, have joints, have low strength, have high absorption
and swell are unfit for aggregate because they are not sufficiently durable. Sea water may
sometimes accelerate alkali-aggregate reaction. The reactivity of aggregate should therefore be fully
examined.
Admixtures: Admixtures complying with JIS A 6201 "Fly ash for use in concrete", JIS A 6202
"Expansive additive for concrete", JIS A 6206 "Ground granulated blastfurnace slag for concrete"and JIS A 6207 "Silica fume for concrete" should be adopted as a standard practice. Replacing
cement with an appropriate amount of ground granulated blast furnace slag or fly ash produces
watertight concrete highly resistant to the chemical actions of sea water. These admixtures are said
to control chloride ion intrusion into or movement in concrete. The effectiveness of these
admixtures, however, varies according to their physical and chemical properties, the ratio of cement
replacement and the curing conditions of the concrete using these admixtures. Their effectivenessshould be verified by testing before using them, or appropriate methods of their use should bedetermined based on the past examples of their use. Using silica fume properly is also said toimprove the resistance of concrete to sea water or the capacity of concrete for controlling chloride
intrusion. When using silica fume, however, the performance of concrete using silica fume shouldbe verified in advance by conducting tests. For the use of expansive additives, refer to Chapter 2
Expansive Concrete.
Chemical admixtures: Using chemical admixtures complying with JIS A 6204 "Chemical
admixtures for concrete" such as air-entraining agents, water reducers, air-entraining water reducers,
high performance air-entraining water reducers, high performance water reducers andsuperplasticizers improves concrete workability, resulting in the production of highly durable
watertight concrete. These chemical admixtures provide high resistance to heavy meteorologicalactions, and are fit for use in concrete for marine structures.

Anticorrosives: Anticorrosives that have been applied to concrete surface coating or lining
include organic materials such as epoxy, urethane and polyester resins; and materials mainly
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Concrete for Marine Structures

composed of polymer cement mixed with SBR (styrene-butadiene rubber), acrylic andethylene-vinyl acetate copolymer. Some materials have not yet proved effective in actual structures
over a long time. Quality varies greatly for one and the same material according to the construction
condition. When selecting anticorrosives, therefore, tests should be conducted or selection should
be made based on the past examples of construction. For selecting or using surface protection
methods using surface lining materials, refer to the "Design and Construction Guidelines for
Surface Protection Methods (draft)" and "Manuals for Respective Methods". There may be cases
where embedded forms using polymer-impregnated concrete, cement concrete with synthetic resin
impregnated into the voids, are used as anticorrosives.
Steel: When using epoxy resin coated reinforcement, the "Design and Construction Guidelines
for Reinforced Concrete Using Epoxy Resin Coated Reinforcement (revised edition)" should be
consulted.
Corrosion of steel greatly deteriorates fatigue strength. In cases where steel is subjected tocyclic loading, special care should be exercised to prevent steel corrosion. In cases where hightension steel like prestressing steel is subjected to stress exceeding 60% of tensile strength, the steel
is likely to suffer stress corrosion. Construction should therefore be conducted carefully.
Continuous fiber reinforcing materials have recently been used as non-corrosive reinforcing
materials. When using continuous fiber reinforcing materials, Chapter 4 Concrete Using Continuous
Fiber Reinforcing Materials should be consulted.

11.3 Mix proportions(1) For concrete for marine structures, the water-cement ratio shall be determined so as
to meet the designated performance requirements.
(2) Unit cement content shall be determined so as to meet the designated performancerequirements considering the sectional area, importance and environmental conditions of
the structure.
(3) The standard air content of concrete for marine structures should be set as shownin Table 11.3.1.
Table 11.3.1

Standard air contents of concrete for marine structures (%)
Maximum size coarse aggregate (mm)Classifications of environmental conditions

Freezing and thawing
actions

20 or 2540(a) Offshore air

5.0

4.5

(b) Splash zone

6.0

5.5

[Commentary] (1) On the offshore, reinforced concrete and prestressed concrete members arelikely to be subjected to various actions such as freezing and thawing actions and chemical actionsof various types of salt contained in sea water. Material deterioration and steel corrosion are likely
to occur with the elapse of time. In order to provide adequate resistance to these severe actions,water-cement ratio, unit cement content and air content should be determined so as to meet the398

Standard Specifications for Concrete Structures-2007, Materials and Construction

designated performance requirements.
The splash zone in particular is between the mean low water level and the sum of mean highwater level and wave height, and is subjected to tidal actions and alternate wetting and drying by
the splash of waves. Thus, the zone is under the most severe condition from a viewpoint of
durability. Concrete is therefore likely to be subjected to internal steel corrosion, freezing andthawing actions, chemical intrusion and other types of damage. In the offshore air above the splash
zone, sea breezes are constantly active and the splash of waves sometimes affects the environment.
The condition is second severest following the splash zone. In the sea at depths below the meanhigh water level, sea water applies chemical and frictional actions but internal steel corrosion ismore moderate than in the splash zone or in the offshore air. It should be assumed that the structuressubjected to severe actions of sea breezes are under the similar conditions to those in the offshore
air. When constructing concrete under unfavorable conditions affected by sea water or tidal actions,
the water-cement ratio of the concrete should be reduced below that at ordinary construction sites.
Table C11.3.1 shows standard maximum water-cement ratios of air-entraining concrete thatare determined from durability. The water-cement ratio should be set below the values listed in thetable. The water-cement ratio should also be lower than the design ratio determined based on the
results of check of resistance to chloride ion intrusion considering the concrete cover.
(2) Increasing the unit cement content produces homogeneous compact concrete, andincreases resistance to chemical intrusion of various types of salt contained in sea water and tointernal steel corrosion. The unit cement content determined from the durability of reinforced
concrete for marine structures should be higher than the values listed in Table C11.3.2.
Water-cement ratio should be determined as per (1) above. The unit water content should be 175
kg/m3 or lower to ensure durability. The unit cement content determined accordingly should behigher than the values shown in Table C11.3.2. The unit water content is not expected to be lower
than the values in view of the upper limits of the water-cement ratio determined to ensure resistanceto chloride ion intrusion and of the unit water content. Admixtures complying with JIS A 6201 "Flyash for use in concrete", JIS A 6206 "Ground granulated blastfurnace slag for concrete" and JIS A
6207 "Silica fume for concrete" may be regarded as part of cement.
With excessive increase of the unit cement content, concrete cracking becomes more likely tooccur due to drying shrinkage in small cross section or due to thermal stress ascribable to the heatof hydration in large cross section. In cases where no performance requirements are determined tobe met in thermal cracking check, corrective measures should be taken including the replacement ofmaterials through the use of blended cement, low heat cement or admixtures. Early age cracking
accelerates chloride ion intrusion into concrete and steel corrosion. Care should therefore be
exercised to prevent thermal cracking and autogeneous shrinkage cracking.
(3) Standard air content of concrete for marine structures should be set as shown in Table
11.3.1. Concrete for marine structures is subjected to the actions of chlorides contained in sea waterand sees its resistance to freezing and thawing actions deteriorated. In the splash zone, therefore, theair content of fresh concrete should be set as shown in Table 11.3.1 (b) using chemical admixtures.
For members that are frequently subjected to the effects of meltwater in the offshore air, air content
shown in Table 11.3.1 (b) should be used.
Structures are free from freezing and thawing actions if they are constantly in the sea ortemperature rarely falls below zero.

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Table C11.3.1

Concrete for Marine Structures

Maximum water-cement ratios determined from durability(%)
Construction conditions

Environmental
classifications

Ordinary construction

Concrete products, or the quality equal
to or higher than concrete products

Offshore air

45

50

Splash zone

45

45

Undersea50

50

Note: If verified based on research results, the value specified in Table C11.3.1 plus 5 to 10 may be
specified as the maximum water-cement ratio.

Table C11.3.2 Minimum cement content of concrete determined to ensure durability (kg/m3)
Maximum size coarse aggregate (mm)Offshore air,Environmental
classifications

Splash zone
Undersea

11.4

20 or 25

40

330

300

300

280

Construction(1) When constructing concrete marine structures, care shall be exercised especiallyduring transport, placement, compaction and curing.
(2) Construction joints shall be avoided wherever possible. In cases where construction
joints are inevitable, Chapter 9 of "Materials and Construction: Construction Standards"
shall be honored and appropriate measures shall be taken to prevent adverse effects on
durability.
(3) Concrete shall be protected from sea water until it reaches an age of five days.
(4) An appropriate gap shall be provided between the steel and formwork to secure
designated concrete cover.

[Commentary] (1) Even under severe conditions as in the marine environment, structures forwhich proper construction management is exercised keep functioning as designated over a long
period of time. It has, however, been verified that a slight defect greatly reduces structural durability
under severe conditions. Poor construction results in the acceleration of structural deterioration in
the poorly constructed sections. Careful process control should therefore be exercised throughout
the process from transport to placement, compaction and curing.
(2) In ordinary structures, avoiding constructing joints is important. In marine structures inparticular, construction joints should be avoided because deterioration frequently starts at the joints.
Construction should be planned so as to make no construction joints in the low water section
between a point 60 cm above the high water level and another point 60 cm below the low water400

Standard Specifications for Concrete Structures-2007, Materials and Constructionlevel. In the case of a great tidal range and a lift of a large depth or in the case where the formationof construction joints is inevitable, Chapter 9 of "Materials and Construction: Construction
Standards" should be strictly adhered to.
(3) If concrete that hardens only incompletely is inundated in sea water, mortar washout andother damage are likely to occur. Concrete should therefore be protected from direct contact withsea water until it completely hardens and certain levels of strength and watertightness are achieved.
Approximately five days are required for ordinary Portland cement to achieve the goal. The period
should be increased for blended cement like blast furnace slag cement above the period for ordinary
concrete to achieve the designated levels of strength and watertightness.
(4) Repairing marine concrete structures is difficult in numerous cases. An appropriate
method should be employed to provide designated concrete cover to prevent internal steel corrosion.
Mortar or concrete spacers with performance equivalent to or higher than that of mainframe
concrete should be used where the spacers are in contact with the formwork.

11.5

Concrete Surface Protection

In sections subjected to abrasion or impact, concrete surface shall be protected using
appropriate materials or concrete cover, or sectional area shall be increased.

[Commentary] In structures subjected to flowing water containing sand particles, waves
containing gravel or the impact of ships, the areas to which abrasion, impact or other severe actions
are applied should be provided with surface protection using appropriate materials such as rubber
fenders, wood, excellent stones, steel and high polymetric materials, concrete cover or sectional
area should be increased. Special care should be exercised in the prestressing steel anchorage zones
because they may be detrimental to durability.

11.6

Installation of Precast Concrete Members(1) When constructing precast concrete members, measures shall be taken to safely
transport and tow the members to the site of installation so as to prevent durability
defects.
(2) When installing precast concrete members, the soil in which the members are installed
and the method of installation shall be selected so as to achieve the designated accuracy.
(3) Appropriate methods meeting the designated requirements for load bearing capacityand durability shall be used for connecting precast members to each other or connecting
precast members to other members..

[Commentary] (1) When transporting or towing precast members constructed on land or offshore
for installation at designated locations, meteorological, oceanographic, marine and other conditions
should be investigated in advance and allowance should be provided for construction machinery toensure safe construction. Considering in advance the emergency escape methods or shelters is very
important to the safety of construction. Verifying whether the loads acting on the precast concrete
members during the transport or towing is estimated or not in the design phase is important in orderto keep the members safe against the loads and prevent them from damage due to the loads.
(2) The soil in which precast members are installed should have designated load bearing
401

Chapter 11

Concrete for Marine Structures

capacity and be sufficiently flat. To that end, the soil is frequently improved by replacement, rubble
beds are leveled or underwater concrete is constructed. For installing precast members at thedesignated locations, a less tight schedule should be developed, fully capable construction
machinery and skilled divers should be made available and work should be performed under
excellent conditions.
(3) Connecting precast members is more difficult in offshore construction than in construction
on land. The connections are likely to become weak points of the structure. The structural format
should therefore be selected so as to minimize offshore connecting work, or connection methods
should be selected that facilitate offshore construction work and ensure load transmission. Synthetic
resins used for adhesion include epoxy resins for hardening by wetting. Synthetic resins of known
composition and with verified performance and environmental safety should be used.
Waterproofing work should be applied as required. Efforts should also be made to prevent chloride
ions or water from permeating the connections.

11.7

Inspections

Concrete for marine structures shall be inspected for cracking responsibly by the Owner. If
the inspection results suggest the possibility of durability deterioration, appropriate
measures shall be taken.

[Commentary] In concrete for marine structures, outstanding surface cracking and early age
defects accelerate the intrusion of chloride ions and the corrosion of steel in concrete. If cracks aredetected in inspections that are expected to be detrimental to use and deteriorate durability,
appropriate corrective measures should be taken. For other matters, refer to "Materials andConstruction: Inspection Standards".

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Prestressed Concrete

CHAPTER 12 PRESTRESSED CONCRETE

12.1

General12.1.1

Scope

This chapter describes standards on essential matters particularly needed forconstruction of prestressed concrete with prestressing steel.

[Commentary] (1) Although various kinds of prestressing methods have already been developed,
this chapter only covers the methods where the prestressing force is introduced to the concrete
members as a reaction force by a tensile force which is mechanically applied to tendons placed
inside or outside of the concrete. Prestressing methods are classified into two categories; thepost-tensioning system and the pretensioning system, depending upon whether the tensile force isapplied before or after placing the concrete. The post-tensioning system is again divided into twogroups; the bonded method where the tendons and the concrete members are bonded together as one
element, and unbonded method where they are not. In the pretensioning system, the tendons and theconcrete are directly bonded and the prestressing is introduced due to the bond stress between
concrete and tendon. The pretensioning system is mainly used for concrete products. The internalcable method where the tendons are placed inside of the concrete has mainly been used up to now,
however, recently, the external cable method where the tendons are placed outside of the concrete
has often been used as it reduces the cross section area of the concrete members and makes
maintenance easy.
This chapter refers to the case where prestressing steel is used as tendons. In case wherecontinuous fiber reinforcements are used for prestressing tendon, execution should follow 'Chapter
4, Continuous fiber reinforced concrete'.
The items that are not covered in this chapter should follow the “Recommendations for Design
and Construction of Prestressed Concrete Structures”.

12.1.2(1)

GeneralDuring the construction of prestressed concrete structures, work shall be carriedout carefully in accordance with the sequence specified in design documents. The effect of
accuracy in construction on the safety of the structure during different stages of the work
shall also be considered.
(2)

Construction of prestressed concrete structures shall be managed at the presenceat the site of professional engineers with adequate knowledge and experience concerning
prestressed concrete.

[Commentary] (1) In the construction of prestressed concrete structures, stresses occurring in themember vary extremely depending on the construction method or sequence, and sometimes stresses
may reach critical levels. Therefore, it is particularly important to perform the work carefully inaccordance with the design documents.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

When making a plan for prestressed concrete construction work, items peculiar to prestressed
concrete should be included in addition to the items for general concrete construction work.
Construction work should be planed to be executed smoothly taking account of safety, economy
and influence on environment.
1. Prestressing steel shall be placed with proper method in the location as specified in the design
documents without any impairment on the quality of the material. Location accuracy shall be
determined by taking account of dimensions of the structure to keep the quality of thestructure as specified in the design documents.
2. Anchorages and couplers shall be assembled in the accurate shape and dimensions as
specified in the design documents, and shall be properly installed in the location and direction
specified in the design.
3. Prestressing shall be planed so that the required tension force is applied to each of theconstituent prestressing steel of the prestressing tendons.
4. Grouting shall be performed as earlier as possible after prestressing. The plan for grouting
shall be determined taking account of selection of materials, mix proportion and injection
method so as to satisfy the required performance of grout.
(2) In prestressed concrete work, construction accuracy greatly affects the safety of thestructures. Accordingly, it is necessary to understand the extent of its influence when executing theconstruction work. In turn, when construction errors occur, proper correction can be taken if theengineer has full knowledge of the influence on the safety. Therefore, in the construction ofprestressed concrete structures, it is desirable that the engineer with full knowledge; e.g. Prestressed
Concrete Engineer authorized by Japan Prestressed Concrete Engineering Association, must station
the construction site and supervise the construction works.

12.2
12.2.1

Quality of Concrete
Required compressive strength of concrete at the time of prestressing(1) The strength shall be set so as to prevent any defects due to tensioning.
(2) The strength should be more than 1.7 times the maximum compressive stressoccurring in concrete just after prestressing. In the case of the pretensioning system, thecompressive strength of concrete shall not be less than 30N/mm2.
(3) The strength around the anchorages shall be more than the strength required toresist anchoring forces.

[Commentary] (1) and (2) The required compressive strength of concrete at prestressing of
tendons must be on the conservative side with a certain factor of safety against the maximum
compressive stress that may occur just after prestressing. This maximum compressive stress will be
reduced later by the relaxation of tendons, the creep and drying shrinkage of concrete and thepermanent loads, so that the safety factor considered above can be smaller than that against thedesign loads. However, if the given stresses become too large compared with the compressive
strength of the concrete, the creep of concrete exceeds the range in which the creep is in proportion
with the applied stress. Therefore, in this standard the required compressive strength must not beless than 1.7 times the maximum compressive stress occurring just after prestressing. However, it isrecommended that the safety factor for the required compressive strength must be increased for the404

Chapter 12

Prestressed Concrete

members which have relatively large dead load, because the stresses larger than calculated in thedesign may occur depending upon the support conditions.
When a structure is designed using the creep coefficient shown in Table C5.2.7 and C5.2.8 of
the Standard Specifications for Concrete Structures “Design” and constructed without applying any
special curing methods such as the elevated-temperature accelerated curing, the time forprestressing the concrete must be determined not only by the condition of the compressive strength
but also by the condition on the concrete age that shall be not less than the one corresponding to thecreep coefficient used in the design. In addition, when the creep coefficient specified in Clause
5.2.9 (2) of the Standard Specification “Design” is applied, the required conditions for prestressing
must be determined to meet the conditions considered in the design.
The reason for specifying the compressive strength not less than 30 N/mm2 at the transfer ofprestresses in the pretensioning system is not only to take into account the safety factor against theactual maximum compressive stress but also to ensure the sufficient bond strength between thetendons and concrete. In addition, when large bending moments or shear forces are expected to act
in a short member or near an end of a member, the required compressive strength at transfer ofprestresses should be not less than 35 N/mm2.
(3) Safety of concrete around the anchorages must be examined considering the bearing stressesof concrete in contact with the anchorages and the design bearing strength of concrete prescribed in
Clause 5.2.1(4) of the Standard Specification “Design”. The anchorage and anchoring method varydepending upon the kind of the prestressing system, so that the required concrete strength aroundthe anchorages at prestressing of tendons should be determined in advance by tests corresponding to
the anchorage and anchoring method applied.

12.2.2Required workability of concrete(1) Workability should be determined so as to ensure the placement of concrete aroundthe tendons, sheaths, reinforcement and anchorages.
(2) For standard slump, Section 4.4.2 of "Materials and Construction: Construction
Standards" should be referred.

[Commentary] Tendons, sheaths, reinforcement and anchorages are frequently arranged in acomplex manner in a prestressed concrete member which is thinner than a reinforced concrete
member. The concrete near the anchorage is subjected to considerably large local forces. It istherefore important to ensure that appropriate fluidity is provided so that concrete may beadequately placed in the vicinity of anchorages to create dense concrete.
The minimum slump during concrete placement in prestressed concrete members is shown in
Table 4.4.6 of "Materials and Construction: Construction Standards". The slump has been
calculated from the relationship between the area of reinforcement and the slump obtained based on
the results of investigations of approximately 600 prestressed bridge superstructures.
12.3

Required performance of grout

12.3.1

General requirements

Grout shall completely cover the tendons to prevent corrosion and fill all voids in theducts to properly bond the tendons and concrete.
405

Standard Specifications for Concrete Structures-2007, Materials and Construction[Commentary] There are two aims for grout applying for internal cable method; one is to preventthe tendons from corrosion, the other is to bond the tendons and concrete together as one element.
If the grouting is not perfect, it is expected that corrosion of the tendons induce concentrated
cracks, and in the worst case, sudden deterioration of the load-carrying capacity would occur. The
qualities of the grout greatly affect the durability of the prestressed concrete members. Therefore,
the grout shall be filled in the ducts so that the two aims mentioned above are achieved.
Particularly in a severe environment, multi layer protection; e.g. waterproofing of anchorages,
waterproofing of the joints, post-waterproofing of the grout hose and using high density
polyethylene sheath in an area where measures against salt damages are needed, in addition tofilling grout in the ducts, is recommended in order to protect the tendons from corrosion. In theareas where measures are required to prevent chloride intrusion, protection should be provided bymultiple measures including the adoption of plastic instead of steel sheaths.
12.3.2

Consistency(1) Consistency, which includes flowability, segregation resistance and volumetricchanges, shall be determined considering the length and shape of ducts, changes inclimate and weather conditions, type of prestressing steel and the proportion of thesectional area of the prestressing steel to that of the duct.
(2) In cases where standard structural and construction conditions are selected, thefluidity, resistance to material segregation and rate of volumetric change of the grout for
prestressed concrete may be specified in the following range. Resistance to material
segregation may be specified based on the bleeding rate. In daily construction
management, water-cement ratio that is obtained from the mass of unit volume may be
used instead of bleeding rate and rate of volumetric change.
(a) As a standard for fluidity, the flow time obtained in fluidity tests (JSCE-F 531)
should be within the range identified in full-scale tests or based on the pastrecords.
(b) The bleeding rate obtained in bleeding tests (vertical pipe method) (JHS 420-2004)
should be 0.3% or lower and be 0.0% in 24 hours.
(c) The rate of volumetric change obtained in the tests of volumetric change (verticalpipe method) (JHS 420-2004) should be between -0.5% and 0.5%.

[Commentary] (1) The characteristics of flowability of grout in ducts vary from not only theviscosity and the flow properties but also the area and size of the space through which grout flows,
the gradient of the ducts in the flow direction, the shape of ducts, the shape of tendons and thepressure of grout injection. Also, the length of ducts and the thermal change may affect thecharacteristics of flowability. It is difficult to control consistency of the grout only with thecharacteristics of the grout.
It is needed to specify the space ratio in ducts and location of the inlets, outlets and vents forgrout, considering the length and the shape of ducts adequately, taking into account the influence on
the members, as well as to select a mix proportion of grout with flowability, in order to fully ensure
the filling performance of the grout in the ducts. Also, it is important to choose suitable materials
406

Chapter 12

Prestressed Concretefor the grout to meet the construction and the weather conditions during grout injection.
In cases such as the injection of grout with low viscosity in ducts arranged in a curved shape,
grout does not flow through the full section of the duct but along the lower side of the duct towards
the down slope of the duct, and the grout is filled up from the bottom portion of the duct as thegrout is injected. As a result, some air may be trapped in the duct and remains at the upper portionof the duct as a void. The lower the viscosity of grout become, the bigger would be the space in theduct and the lower the flow rate become, the higher would be the rate of probability of occurrenceof the air void. (see Fig. C12.3.1)
In order to achieve 'full section flow' where grout flows through the full section of the duct,
viscous plasticity and flow rate shall be determined adequately considering the area of space andinclination of the duct.
When the “full section flow” is not adopted, arrangement of the inlets, vents and outlets and theflow rate shall be determined adequately understanding the occurrence mechanism of the air void.
Recently, the grout with super low viscosity has been developed, and an increasing number of
construction methods using no full face placement system have been adopted. The grout with low
viscosity has advantages in terms of controlling the injection pressure and to shorten the injection
time when the length of the duct is relatively long.

(i)
(ii)

Air void(i)-(iii): Injection process(iii)(a) Low viscosity

(i)
(ii)

Without air void(iii)(b) High viscosity

Fig. C12.3.1

Occurrence mechanism of void at a down slope of duct

As described above, whether grout for prestressed concrete is adequately injected into the duct
or not is comprehensively determined by numerous factors such as the structural design, quality of
the grout and construction method. Excellent pumpability may not always be ensured even if
respective parameters are specified separately. Then, full-scale tests should be conducted under the
structural and construction conditions similar to those for the actual structure, or examples ofsimilar past construction that produced no damaging residual air should be used for reference tospecify the materials and quality of grout for prestressed concrete, construction method,management method and other parameters.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

If the cables are of a shape different from that in past full-scale tests, other full-scale tests are
required. It should therefore be verified based on the design drawings in the first place whether the
shape of the cables is in the range identified in the past full-scale tests. The type of fluidity of grout
admixtures selected and the rate of injection determine the position of the air outlet. The type of
fluidity of grout admixtures should be selected by fully examining the construction condition in theplanning phase. The positions of injection inlet, air outlet and discharge outlet are determinedaccording to the type of fluidity. Unless the positions can be determined, they should be confirmed
by conducting full-scale tests. For construction, the grout admixtures should be selected according
to the type of fluidity specified, and the mix proportions providing the designated quality should bedetermined by mixing on a trial basis. A flowchart in the planning through construction phases forgrout for prestressed concrete is shown in Fig. C12.3.2.
Production of no residual air damaging in construction is generally verified by confirming thatthe grout injected and confined in grout hoses at air outlets and discharge outlets has not gone away
by hardening, or by using sensors to confirm injection. If the results of verification is determined tobe similar to the excellent results obtained in the past tests, the past results may be used.
An example of cable arrangement for which designated pumpability has been confirmed in past
full-scale tests is shown in Table C12.3.1. For details, refer to the "Design and Construction
Guidelines for Grout for Prestressed Concrete" of the Japan Prestressed Concrete Engineering
Association and the "Construction Manual for Grout for Prestressed Concrete and Pregrouted
Prestressing Steel (revised edition) 2006" of the Japan Prestressed Concrete Contractors
Association.

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Prestressed Concrete

Structural Design

Plan of grouting
Confirmation of Design Documentation
・Shape of Cable
・Combination of PC steel andSheath diameter (void ratio)

・Gradient =< Past experiences

NO・Void ratio = Past experiences

YES
・Selection of type of flowability
・Setting of grouting speed

・Type of flowability = Past experiences

NO

Experiment withreal size specimen

・Grouting speed >= Past experiences

・To confirm notremaining of harmful
remained air

YES・Arrangement of openings
for grouting, exhaust, discharging

・Arrangement of openings
for grouting, exhaust, discharging
is the same or more thanpast experiences

NO

YES

・Selecting agent for grout

・Adjustment of unit water content

NO・Flowability is within recommendation

YES
・Qualities other than flowability
Satisfies specified values

NO

Analysis of Causes

YES

Execution of Grouting

Fig.C12.3.2

Flow of planning and execution of grouting
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Standard Specifications for Concrete Structures-2007, Materials and Construction

Table C12.3.1

Examples of cable arrangement for which designated pumpability has
been verified based on the results of past full-scale tests

direction of cable

tendonInnerdiameter ofsheath（mm）

Void ratio（％）

Maximum descending
gradient of cable
（°）

63.5

63

9

65

64

15

70

69

15

75

62

15

80

67

5

1S21.8

35

67

0

1B26

35

45

0

39.3

34

12

41

39

12

1B32

50

59

-

1B40

50

36

-

12S12.7
Direction of axisof bridge
12S15.2

normal direction
to axis of bridge

1B32

Vertical direction(2) Filling conditions have been examined by the injection test using full scale specimens withspecified range of flowability, bleeding ratio and expansion ratio of the grout. The filling
performance of the grout can be controlled with the flowability, bleeding rate and expansion ratio of
the grout. In cases where it has been verified that the bleeding rate and the rate of volumetricchange are in the designated range at designated mix proportions, using the water-cement ratio thatis obtained from the mass of unit volume instead of bleeding rate and rate of volumetric change indaily management is recommended. Efficiency is the reason for the recommendation because theprocess enables immediate check for calculation errors for materials and quality verification before
injection.
(a) Fluidity should be controlled so that the flow time of grout for prestressed concrete during
construction may be within the range of flow time that is obtained by full-scale tests orbased on the past records. The position of the air outlet is determined by the range of flow
time. The position should therefore be specified that is fit for the range of flow time.
JP funnel flow time is classified into three major types according to the type of grout
admixture: more than 14 seconds for highly viscous type, 6 to 14 seconds for low viscous
type and less than 6 seconds for ultra-low viscous type. One of these types should beselected.
(b) For the bleeding rate for grout for prestressed concrete, the rate specified in JSCE-F 532"Bleeding Rate of Grout for Prestressed Concrete and Expansibility Test Method(polyethylene bag method)" has been adopted. It has, however, recently been confirmedthat bleeding and settlement are more outstanding in tests using one- to 1.5-m long
vertical pipes at the center of which prestressing strands are installed. This is because theprestressing strands, working like the wick of an oil lamp, cause the bleeding water tobe concentrated at the top of the pipe. As a more strict test method than conventional
methods, JHS 420-2004 "Method for Testing Bleeding Rate and Rate of Volumetric
Change of Grout for Prestressed Concrete (vertical pipe method)" shall be adopted.
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Chapter 12

Prestressed Concrete(c) The rate of volumetric change is determined on the assumption of use ofnon-bleeding-type grout admixtures. The standard rate of volumetric change has been set
to be in a range between -0.5% and 0.5% in view of the margin of error. JHS 420-2004
shall be adopted also for the rate of volumetric change as a more strict test method.
It has been stipulated that in daily construction management, the water-cement ratio thatis obtained from the mass of unit volume may be used instead of the bleeding rate and therate of volumetric change. Whether the bleeding rate and the rate of volumetric change
are in the designated range or not is verified indirectly by confirming whether thewater-cement ratio that is calculated from the mass of unit volume of mixed grout for
prestressed concrete is in the recommended range of water-cement ratio (range in which
the manufacturer has confirmed that the designated bleeding rate and the rate ofvolumetric change are achieved, and the range recommended by the manufacturer
including the margin of error). It is also verified that there are no calculation errors formaterials and that materials are mixed at the designate water-cement ratio.
The water-cement ratio that is calculated from the mass of unit volume of mixed grout for
prestressed concrete should be the recommended water-cement ratio specified for eachgrout admixture product plus or minus 1.5% and should be in the serviceable range(marginal range in which the manufacturer has confirmed that the designated bleeding
rate and rate of volumetric change can be achieved). This is because a largest margin oferror of approximately 15% has been confirmed due to the mixing of air for thewater-cement ratio in cases where cement, water and admixtures were accurately
measured, and because exceeding the serviceable range is not allowed even where themargin of error is taken into consideration. If the test results are in the designated range,
therefore, injecting mixed grout is allowed.

12.3.3

Bond strength between concrete and tendons(1) The bond strength to ensure monolithic behavior of concrete and tendons shall be
determined in an appropriate manner considering the type and shape of ducts, as well as
the type of tendons.
(2) In general, the bond strength between concrete and tendons may be determinedusing the compressive strength at the age of 28 days. Compressive strength should bedetermined in accordance with JSCE-G 531. The standard value should be taken as
30N/mm2 or more.

[Commentary] (2) The Standard Specification for Concrete Structures, “Part 2: Materials andConstruction” (1996) specified a uniform compressive strength of grout of 20N/mm2. This
provision is a carryover from the "formwork method" provisions in the Guidelines for Grout for
Prestressed Concrete, a document attached to the revision of the “Recommendation for Design andConstruction of Prestressed Concrete Structures” published by JSCE in 1961. In the “formwork
method,” the strength of expansive grout that is formed and weighted down is determined.
Considering the fact that the grout strength thus determined is lower than the strength of sheathedgrout, relatively low levels of strength were specified. The rationale for that provision was asfollows:
1) At the time the provision was adopted, expansive grout containing aluminum powder was themost widely used type of grout.
411

Standard Specifications for Concrete Structures-2007, Materials and Construction2) Obviously the strength of grout that is allowed to expand freely is considerably lower than
the strength of grout confined in a sheath. It is not easy, however, to reproduce the degree ofgrout confinement used to prepare test specimens.
3) Strength is also influenced by the degree to which water is allowed to flow out of grout. It isalso very difficult, however, to reproduce the degree to which water is allowed to flow out ofsheathed grout.
The conditions under which the above provision was adopted 30 years ago have changed
dramatically now. Today, non-bleeding type chemical admixtures are used, and non-expansive
grout is used in most projects. The new provisions of this specification have been adopted in viewof the fact that the required performance of grout is to protect tendons from corrosion and toachieve structural integrity of structural concrete and tendons and act as integral part of theconcrete.
Although the relationship of bond strength needed to achieve structural integrity withcompressive strength has not yet been elucidated, the compressive strength of concrete for internalcable method should be 30 N/mm2 or more, by referring to standards in other countries.
12.3.4 Corrosion resistance of steel(1) The designated performance requirements for structures shall not be deteriorated
due to steel corrosion caused by corrosive materials contained in grout for prestressed
concrete.
(2) Resistance to steel corrosion shall generally be determined based on the total
chloride ion content in grout during mixing. The total ion content shall be less than 0.08% of
the mass of cement.

[Commentary] (1) The mechanism of electrochemical corrosion of tendons is the same as the
corrosion mechanism of reinforcing bars. Because of the service conditions, the tensile strength oftendons is higher than that of reinforcing bars, and tendons are always subjected to tensile stresses
equal to nearly 60% of the normal tensile strength. Breaking of tendons could, therefore, result froma decrease in cross sectional area due to corrosion, strength reduction due to pitting corrosion, ordelayed failure such as stress corrosion cracking and hydrogen embrittlement.
In general, stress corrosion cracking of a material results from the simultaneous action of tensilestress and a chemical component such as chlorides, nitrates, carbonates or liquid ammonia.
Hydrogen embrittlement is a phenomenon that occurs under stress because of hydrogen dissolved ina solid material during the manufacturing process or due to steel corrosion. These phenomena
progress with time and eventually cause a brittle failure.
As a matter of fact, it is difficult to quantitatively describe environments conducive to delayed
failure. At least it can be said, however, that in order for prestressing tendons to break in stresscorrosion or hydrogen embrittlement tests, it is necessary to conduct tests under considerably
stringent, accelerated conditions. Therefore, as long as grouting is performed adequately by using
standard procedures, the possibility of delayed failure should be very low. Since delayed failureoften causes internal cracks that are difficult to detect and causes extensive failure of tendons, it
must be kept in mind that delayed failure not only could impair the required performance of thestructure but also is very dangerous.
(2) In some countries, the use of nitrates and thiocyanates as grout ingredients is prohibited. In
Japan, under the present conditions the possibility that grout contains chemical components that412

Chapter 12

Prestressed Concrete

could cause delayed failure such as stress corrosion cracking and hydrogen embrittlement is low.
For this reason, on condition that Material Safety Data Sheet (MSDS) for grout admixtures should
be consulted to verify that no chemical components are contained that cause delayed failure, only
the chloride ion content at the time of mixing is specified in order to achieve the required level ofcorrosion resistance of steel on condition that the steel manufacturers' certificates should be checkedin advance.
As the total chloride ion content during mixing, 0.3 kg/m3, the same as in concrete, has been
adopted. This is because the chloride ion contained during the mixing of grout for prestressed
concrete is mostly supplied from the cement and because there were no operation problems as longas the limit chloride ion content was less than 0.02%. In 2003, however, JIS R 5210 concerning
Portland cement was revised and the limit chloride ion content of ordinary Portland cement wasincreased to 0.035%. In grout for prestressed concrete using a unit cement content of approximately
1300 kg/m3, the total chloride ion content exceeded 0.3 kg/m3 causing some problems.
Steel corrosion in NaCl-NaOH solutions is determined by the ratio between the molar
concentration of chloride ion and that of hydroxide ion (OH-) ([CL-]/[OH-]). The limit [CL-]/[OH-]for corrosion in hardened cement has been reported to be higher than that in solutions in numerous
researches.
The chloride ion in hardened cement is classified into free chloride ion dissolved in pore wateror chloride ion immobilized in hydrate. Only the free chloride ion is involved in steel corrosion.
Cement hydrates immobilize chloride ion. Then, the free chloride ion concentration decreases as theunit cement content increases while the chloride ion content per unit volume remains constant.
In western countries, the same percentage of cement mass is used both in concrete and grout for
prestressed concrete as the limit of chloride ion content during mixing. In the United States(American Concrete Institute), the limit chloride ion content has been set at 0.06% or lower of
cement mass for free chloride ion in pore water, and at 0.08% or lower of cement mass for total
chloride ion content. In Europe (EN), the limit is set at 0.10% or lower of cement mass for total
chloride ion content.
The Japan Prestressed Concrete Engineering Association conducted tests concerning the limit
state for the occurrence of steel corrosion based on the chloride ion content in grout for prestressed
concrete for preparing the "Design and Construction Guidelines for Grout for Prestressed Concrete".
In the tests, changes in self-potential and polarization resistance with time were measured under wet
conditions at eight different levels of chloride ion in the grout for prestressed concrete in the range
between 0.02% of cement mass (0.3 kg/m3) and 2.4% of cement mass (31.3 kg/m3), and a bridge
girder in service for a long time was dismantled and investigated. As a result, it was reported thatthe chloride ion in the limit state for the occurrence of steel corrosion in the grout for prestressed
concrete accounted for approximately 0.3% of cement mass (3.9 kg/m3) and that similar results
were obtained in tests in which steel was subjected to stress. A bridge girder that had been inservice for 17 years was removed due to chloride intrusion and dismantled for investigation. As aresult, it was confirmed that the rate of mass reduction increased rapidly due to steel corrosion when
the chloride ion in the grout for prestressed concrete around the prestressing steel exceeded 0.4% of
cement mass (5.2 kg/m3) and that small amounts of corrosion occurred at a cement mass of 0.08%
or lower. The "Design and Construction Guidelines", based on the above results and on thespecifications in the West, stipulate that the chloride ion contained in the grout for prestressed
concrete should be 0.08% or less of cement mass. The limit value of chloride ion has therefore beenrevised from 0.3 kg/m3 to 0.08% or less of cement mass.
While checking on the possibility of the corrosion of tendons due to intrusion of chloride ions, it
is advisable to consider the thickness of cover over ducts because tendons are often in contact with413

Standard Specifications for Concrete Structures-2007, Materials and Construction

ducts.

12.4
12.4.1

Material
Prestressing steel(1) Prestressing steel wire and prestressing steel strands that conform to JIS G 3536
should be deemed to be standard.
(2) Prestressing steel bars that conform to JIS G 3109 or JIS G 3137 should be deemed to
be standard.
(3) If prestressing steel that is not mentioned in Item (1) or (2) is to be used, tests shall be
conducted to verify that the design values are met and determine the method of using theprestressing steel.
(4) When subjecting prestressing steel to re-processing or thermal treatment foranchorage, connection, assembly or arrangement, it shall be verified by testing that thequality of prestressing steel is not deteriorated due to such treatment.

[Commentary]
12.4.2

Refer to "Materials and Construction: Construction Standards" 3.6.2.

Anchorages, couplers, and deviators(1) Structure and strength of anchorages and couplers shall be such that breakage andexcessive deformation is avoided before the applied tensile load reaches the value as may
be specified for anchoring or coupling prestressing steels.
(2) The performance of anchorages and couplers should be determined in accordancewith JSCE-E 503 as standard.
(3) Deviators used for external cable structures shall have sufficient strength to resist
active deviation forces of the cable and shall conform to a shape that does not damage thetendons.

[Commentary] (1) Tendon anchorages used in the post-tensioning method can be classified asfollows:(a) Those that anchor prestressing steel wires, prestressing steel strands, or parallel prestressing
steel bar groups or prestressing steel bars by using the wedge action in the radial direction or
the circumferential direction(b) Those that anchor prestressing steel wires or prestressing steel bars by cutting threads ontheir ends and installing nuts(c) Those that anchor prestressing steel wires or prestressing steel bars by fabricating a head at
the wire or bar end(d) Those that anchor multi-layered prestressing steel strands by securing the strand end into asteel socket with a low-melting point alloy poured into the socket(e) Those that anchor prestressing steel strands or multi-layered prestressing steel strands by414

Chapter 12

Prestressed Concretepress-fitting a sleeve onto the strand end (by, for example, cold drawing) and using thebearing pressure of the strand-end of the sleeve or cutting threads on the outside of thesleeve and installing a nut(f) Those that anchor prestressing steel wires or prestressing steel strands by bending them in awavy pattern or in loops and embedding them directly in concrete so as to use the bond withthe concrete or the bearing pressure of the concrete(g) Those that anchor prestressing tendons by anchoring them, by some means, to an anchor
head, tensioning them through pull rods and grouting the space behind the anchor head sothat the tendons are anchored by bearing pressure and bond after the grout hardens
Couplers include ordinary couplers that connect together untensioned tendons and anchoring
couplers that connect tensioned tendons to untensioned tendons.
Depending on anchorage or coupler location or in cases where prestressing tendons are bonded
for use, it may not be necessary for anchorages or couplers to be capable of withstanding the fulltensile load capacity of the tendons. However, in order to ensure safety in tensioning work andprevent increases in anchorage settings, this specification requires the structure and strength ofanchorages and couplers to be able to withstand the full specified tensile load capacity of thetendons.
Even if anchorages or couplers are capable of withstanding the full tensile load capacity ofprestressing tendons under static loads, the fatigue strength of anchorages or couplers is often lower
than that of the tendons. If variable stresses due to normal variable loads are large relative to thefatigue limit of anchorages or couplers, they need to be located in a cross section where bending
moment is small or in an area close to the neutral axis of a cross section where variable stresses are
small.
(2) It is usually very difficult to check by calculation whether or not an anchorage or couplersatisfies the requirement of Clause (1) above. It is therefore a good practice to conduct a test inaccordance with JSCE-E 503 “Method of Performance Test of Anchorages and Couplers for
Prestressed Concrete Construction”. Such a test, however, does not need to be conducted if thequality of anchorages or couplers is guaranteed by their manufacture on the basis of sufficient test
data. It is advisable to refer to the “Recommendations for Design and Construction of Prestressed
Concrete Structures” while selecting anchorages or couplers. However, when using a new type ofanchorages or couplers or when sufficient test data are not available, it is necessary to conduct tests
on a sufficient number of test specimens in order to ensure safety.
The number of anchorage sets needed and the amount of play in couplers vary with the type ofanchorage or coupler. These requirements, therefore, must be determined by studying existing test
data and, if necessary, conducting tests for verification.
(3) Deviators must be strong enough against deviation forces of tendons and must be capable of
mitigating stress concentration due to acting forces and adequately transferring acting forces tostructural members. The inside surfaces of deviators must be smooth because projecting parts or
steps on the inside surfaces of deviators could damage tendons or tendon sheaths. If a tendon is
sharply bent on an edge of a deviator or in contact with only an edge of a deviator, durability of
tendons could be adversely affected because of fretting. In cases, therefore, where a bent steel pipe
is used as a deviator, it is, therefore, necessary to enlarge both ends of the pipe so that the tendonsand sheath do not come into contact with an edge of the deviator.

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12.4.3

Sheaths(1) Sheaths used shall be such that they are not deformed during handling and castingof concrete, and also be capable of preventing any leaking-in of cement paste through laps
or joints.
(2) The shape and size of sheaths should be determined considering the procedures toinsert the prestressing steel, consistency of grout, the requirement of sufficient bondstrength and its friction against prestressing steels.
(3) In cases when high level of durability particularly against chloride induced corrosion
is required, plastic sheath should be used.

[Commentary] (1) Sheath is used as materials to form ducts for the prestressing steel. The duct
may otherwise be made in a way that rubber pipes or steel pipes are used instead of sheaths andafter concreting they are removed at an appropriate time before the concrete is hardened.
Sheath should be selected confirming that it will not easily deform or crush and that it will not
let the cement paste leak into it, since otherwise the friction during tensioning will remarkably
increase.
(2) The shape and the size of the sheath should fulfill the required function. The diameter of thesheath is determined depending on easiness of inserting the prestressing steel or easiness of filling
the grout. As the latter is the most essential for the durability of the prestressed concrete structures,it should be fully taken into account when determining the size of the sheath.
For the structures requiring the bond after tensioning, steel sheath is usually used. Ribbed or
corrugated sheaths are relatively stiff against the deformation during handling and effective for thebond between the concrete and the grout.
For the un-bonded construction requiring no bonds, steel or plastic sheath is used.
(3) In cases where durability is required including chloride intrusion control, high cut-off
capacity against chloride ion, water and air as well as ordinary requirements for sheaths is highly
important to the protection of prestressing steel from corrosion. Plastic sheaths shall therefore be
adopted in principle because they have proved to be effective for meeting the requirements.
Plastic sheaths are made of polyethylene or polypropylene. Polyethylene is available at high,intermediate or low density.As a polyethylene sheath to be used for the prestressed concrete
structures, hard high-density polyethylene sheath should be used since it meets the requirement of
the strength, abrasion resistance and so on. Care must be taken, however, to avoid deformation of
the connections or the fittings due to steam curing or so, as the polyethylene sheath may easily
deform under high temperature.

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Chapter 1212.4.4Prestressed Concrete

Grout for prestressed concrete(1) In general, the cement used for grouting should comply with JIS R 5210.
(2) Water used for grouting shall not contain harmful amounts of substances, which may
adversely affect the grout or the prestressing tendons.
(3) Use of admixtures in grouts as well as the quality and method of application of these
admixtures shall be appropriately examined beforehand.
(4) Admixtures used in grouts should be of a non-bleeding type to avoid bleeding.

[Commentary] (3)and(4) Grout used for prestressed concrete is required to maintain the required
levels of flowability and filling ability during grouting and to develop sufficient bond strength
between the tendons and sheath after hardening so as to achieve watertightness and protect thetendons.
Common practice today is to use high-range water reducing agent as dispersing agents toachieve an adequate level of flowability and viscosity-modifying agents for bleeding control.
Admixtures capable of performing these functions are called non-bleeding type admixtures and areavailable as either high-viscosity types or low-viscosity types for the use in grouting methods andunder different grouting conditions. This specification thus requires the use of non-bleeding typechemical admixtures because they make it possible to achieve the desired level of flowability andtheir bleeding control effect is relatively unaffected by other conditions.
Since it takes some time to completely dissolve viscosity-modifying agents in water, it isimportant to use them after mixing them with water thoroughly and uniformly.

12.4.5 Auxiliary materials for injecting grout for prestressed concrete(1) Grout caps shall be able to prevent any air from being left inside, be resistant toinjection pressure and provide air tightness at joints with the anchorage fixture.
(2) Grout hoses shall be semi-transparent and form the injection inlet, air outlet anddischarge outlet. The hose cross section should be held at the time of assembly or concrete
placement. Grout hoses shall have adequate strength against injection pressure.

[Commentary] (1) Grout caps should have an appropriate injection inlet or discharge outlet and air
outlet so as to leave no air inside. The grout cap on the injection side is subjected to extremely highgrout injection pressure. Grout caps therefore should have adequate strength to prevent deformationor breakup and should be able to structurally prevent grout for prestressed concrete from leaking
through the joint with the anchorage fixture. Grout caps should be of a structure that enables theverification of grout filling. In cases where durability is required in particular as for controllingchloride intrusion, plastic grout caps should be adopted.
(2) Grout hoses should be semi-transparent so that the filling of grout may be verified. The diametershould be at an appropriate level to prevent injection pressure from rising extremely. Grout hoses
should have adequate strength to prevent bending and provide resistance to the impact of concrete
placement or injection pressure. At the end of injection, the end of the grout hose needs to be closed
to prevent grout leakage or air inflow. Hoses therefore should be made of materials that can ensure417

Standard Specifications for Concrete Structures-2007, Materials and Construction

air tightness. Tetron blade hoses of an inner diameter of 19 mm or larger should be used for
multiple strands. Tetron blade hoses of an inner diameter of 15 mm or longer should be used forsingle strands or prestressing bars.

12.4.6

Protecting ductProtecting ducts for external cable structures shall be selected considering their ability
to protect tendons, and function as a duct for grouting anti-corrosive materials, specified
strength/durability, and their erosion resistance performance.

[Commentary] Since protection tubes are placed outside the concrete and in many cases theenvironmental conditions to them are more severe than those for the sheath inside the concrete,materials for the protection tubes should be so selected as to secure the easiness of maintenance andthe durability against corrosion. Furthermore they should have enough strength against the injection
pressure of the filling material or the contact pressure at the bent.

12.4.7

Coating material for unbonded tendons

Coating material for unbonded tendons shall not cause corrosion of the tendons or
deterioration of concrete, and shall not cause bond stresses between the tendons and theconcrete while prestressing.

[Commentary] The reason for the use of coating materials for the un-bonded tendons is that it isrequired to coat and protect the prestressing steel in the prestessed concrete preventing from rusting
but not necessarily required to develop the bond between the prestressing steel and the surrounding
concrete. In the following cases it is required to break the bond between the prestressing steel andthe surrounding concrete partly or entirely.
(a) where in the pre-tensioned prestressed concrete members excessive tensioning is to be
decreased in the particular area,(b) where in the post-tensioned prestressed concrete members un-bonded system is adopted tominimize the construction eliminating sheathing or grouting,(c) where in the post-tensioned prestressed concrete members stress concentration in theprestressing steel induced around the cracks during earthquake,
For such un-bonding, asphalt emulsion, cut-back asphalt, grease, wax, epoxy or other plastics
are reported to have been used. It is required for them not to crack, become brittle, liquefy, but to bechemically stable, water-tight, and not to cause chemical change harmful to the concrete or theprestressing steel. Since contamination of other places with or mixing in the concrete of the coating
materials of the prestressing steel not only cause harmful effects on the surrounding but also
damage the coating materials themselves, it is required to take measures such as protecting thesurface with tapes or others, or hardening the surface of the coating materials themselves.

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Chapter 1212.4.8Prestressed Concrete

Material for jointing precast concrete members

Concrete, mortar and adhesives used for jointing precast concrete members shall havethe required strength and watertightness, and shall comply with the on-site work conditionsof jointing.

[Commentary] For the prestressed concrete structures to be unified by jointing precast members
and tensioning them, concrete, mortar or adhesives are usually used as jointing materials.
Kinds or qualities of materials used for jointing are determined depending in many cases on thekinds of the structures or the details of the joint and sometimes on the working conditions. It shouldbe paid attention that the jointing materials with inadequate kinds or quality may lower the strengthof the joint or the water-tightness and shorten the life of the entire structure.
As a rule, epoxy resin adhesives to be used for jointing precast members should meet therequirement of JSCE-H 101 “Specification for Epoxy Resin Adhesive in Precast Concrete (forBridge Girders)”. Epoxy resin adhesives have usually been mixing types of two liquids, a main anda hardening liquid but recently one liquid, moisture-hardening types which harden with moisture
contained in the atmosphere or in the concrete. Despite a difference of applicable period andhardening period between two types, performances of hardened epoxy resin are nearly the same,
quality standard for one liquid, moisture-hardening type epoxy resin can be based on JSCE-H 101“ Specification for Epoxy Resin Adhesive in Precast Concrete (for Bridge Girders)”.

12.4.9Storage of materials(1) Prestressing steel shall not be placed on the ground but shall be stored inwarehouses by supporting it at appropriate intervals, or shall be properly covered whenplaced outdoors. The objective is to prevent the attachment of toxic oil, salt and dust anddamaging corrosion, flaws and deformation.
(2) Anchorages and couplers shall be stored in a warehouse and protected fromcorrosion. No oil or dust shall be allowed to adhere to the surface that comes in contact
with concrete.
(3) Deviating devices, sheaths and protecting tubes shall be stored in a warehouse, or
when stored out-doors, shall be properly covered to protect them against corrosion,
harmful scarring and deformation, and against adhesion of harmful oil, salt or dust.
(4) Adhesives shall be stored in a manner that any segregation of materials,
deterioration in quality is prevented and no impurities get mixed. Materials stored over a
prolonged period shall be tested before use to check the quality.

[Commentary] (1) See "Materials and Construction: Construction Standards" 3.7.5(2).
(2) As the anchorages and the couplers are essential materials in the prestressed concrete, it has
been specified that they should be stored in a warehouse.
Rusting screws may bring about the declined strength of the screws, the difficulty of assemblinganchorages and couplers and the difficulty of tensioning. Therefore, the screws must be prevented
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Standard Specifications for Concrete Structures-2007, Materials and Construction

from rusting by coating oils or so. The parts of contact of anchorages and couplers with the concretemust be prevented from contamination with oil, dust or dirt to secure the bond strength.
In cases where combined action of sleeve and wedge is required as for wedge-type anchorage
fixtures, special care should be exercised to prevent the combined action from being deteriorated
due to corrosion or damage during storage.
(3) When deviators, sheaths and protection tubes are contaminated with dust, damaged ordeformed, tensioning will be hindered and in the bonded construction oil, dust or dirt will harm thebond. Therefore, storage must be done so as to prevent these harmful effects preferably stored in awarehouse. Even in short period of storage outside they should at least be covered to prevent
harmful effects.
(4) As adhesives may deteriorate in quality when exposed to temperature higher than 30℃ suchas that in summer season, they should be stored inside a cool and dark place in a lidded can which
has to be opened just before the use of the adhesives.
Furthermore, as passing longer period than six months after production may cause segregationof the materials or mixing rust of the can, storage period should not be too long.

12.5

Proportioning of grout mix(1) In the design of mix proportions of grout for prestressed concrete, grout admixtures
shall be selected considering the construction condition so that the designated quality may
be achieved.
(2) Mix proportions of grout for prestressed concrete shall be planned considering theenvironmental and meteorological conditions for the selected grout admixtures so that thedesignated quality and specified fluidity may be achieved, and the performance shall beverified by trial mixing.
(3) The water to cement ratio of the grout should not be more than 45%.
(4) Mix proportions of grout for prestressed concrete shall be adjusted during
construction as required.

[Commentary] (1) In the design of mix proportions of grout for prestressed concrete, grout
admixtures should first be selected so as to meet the requirements in Section 12.3.
(2) Grout for prestressed concrete on the market has its unique properties, which should betaken into consideration when determining appropriate mix proportions. The properties of grout for
prestressed concrete are affected by the environmental and meteorological conditions at the time of
construction. The temperature of mixed concrete in particular affects the fluidity and the duration ofservice of grout for prestressed concrete. The temperature of mixed concrete should be predicted
during construction and mix proportions should be determined so that the design fluidity can beachieved. The designated quality and fluidity should be verified for the planned mix proportions bytrial mixing.
(3) The standard water-cement ratio should be set to be 45% or less, and should be minimized
as long as the designated fluidity can be obtained. Care must be taken, however, not to make itlower than necessary in cases, for example, where the duct is long, the void ratio of the duct is small,grout temperature could become high or the grout is apt to lose water. Use of water reducing
retarders is very effective in lowering the water to cement ratio without compromising the420Chapter 12

Prestressed Concrete

flowability of grout.
(4) Mix proportions for grout for prestressed concrete are determined based on theenvironmental and construction conditions during construction. In actual construction, however,conditions may be sometimes different from those assumed. Mix proportions should be adjusted
properly in cases where the designated fluidity or performance cannot be achieved before grout
injection or in cases where no designated performance is expected to be achieved after grout
injection.

12.6

Execution

12.6.1
12.6.1.1

Installation of tendons
Cutting, bending and placing of prestressing steel(1) Prestressing steel shall be fabricated and placed in the accurate shape anddimensions as specified in the design documents without impairing the quality of thematerial. Prestressing steel, which has been excessively bent, affected by extreme heating
and/or exposed to high temperatures, shall not be used.
(2) All loose rust, oil and other harmful substances, which may impair the bond of theprestressing steel used for the pretensioning or the bonded post-tensioning system, shallbe removed before use.

[Commentary] (1) Prestressing steel should be fabricated in a way to keep the accurate shape anddimensions and not to damage the quality of the material. For this purpose the bending of theprestressing steel should always be carried out mechanically in the cold working to achieve thesmooth curve. Fixing to the anchorages or fabricating for the anchoring should be carried out inaccordance with the specified methods, referring to the “Recommendation for Design andConstruction of Prestressed Concrete Structures, JSCE” and so on. Excessively bent prestressing
steel should not be used since its straightening back will damage its material quality. Prestressing
steel exposed to spark due to arc-welding or rapidly cooled after heated with high temperature
should never be used, since its material quality has been changed to brittle. When arc-welding
nearby the prestressing steel is inevitable, it should not be allowed to let the arc-electrode contact
the prestressing steel and an earth wire should never be taken from either the prestressing steel orthe arranged reinforcing bars.
Mechanical method is recommended in case of cutting the end of the prestressing steel after
tensioning, but when inevitably cutting by heat such as fusing, it should be carried out confirmingthat its effect will not reach the anchorage. Screws of the prestressing bar in the coupler should not
be cut by heat, since their quality may be damaged by heat.
(2) When fixing the prestressing steel to the anchorage, the surface of the prestressing steel near
the anchorage should be cleaned with particular care since oil or surfaced rust may often cause
slipping of the tensioning steel.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

12.6.1.2

Installation of sheaths, protecting tubes and tendons(1) Sheaths shall be appropriately installed in position and orientation without being
damaged. Sheaths shall be rigidly supported using spacers or steel frames so as to preventany disturbance or deformation during concrete casting. The joints of sheaths shall be
securely sealed to prevent the penetration of cement paste when casting of concrete.
(2) Tendons shall be installed in sheaths without any entanglement.
(3) Unbonded tendons shall be carefully installed without inflicting any damage to thecoating.
(4) Inspection shall be carried out after installation of sheaths and tendons, andcorrective actions shall be taken in case any damage, etc. is found.
(5) Tolerances for installation of tendons in the formwork shall be determined so that theconcrete members are not adversely affected considering factors such as the size of themembers, etc.

[Commentary] (1) Prescribed tensioning of the prestressing steel can still fail to give theprescribed prestress if the position of the prestressing steel is inaccurate. Therefore the prestressing
steel should be accurately positioned. During concrete placement, since incomplete sheath joints,
joints with the anchorages and prestressing steel joints will occur the same defects as described in
the commentary of Clause 13.6.2 (1), leaking of the cement paste into the sheath should be
prevented by lengthening the lap length, taping around the joints or so. The prestressing steel andthe sheaths should be firmly fixed using appropriate supports at shorter intervals so as not to shift
the position because of the weight of the concrete or the strong vibration of the vibrator duringconcrete placement. The interval of such supports should be determined according to the kinds ofthe prestressing steel and the sheath.
(2) When accommodating several prestressing wires or strands in a sheath, care must be taken
not to tangle the prestressing wires or strands using anti-tangling devices or so, since tangling ofthem will not only increase the friction during tensioning but also can cause uneven stresses inthem.
(3) Prestressing steel used for the un-bonded construction is usually coated. Since exfoliation of
the coating not only cause the difficulty of the tensioning but also eliminate the effect of corrosion
protection, care should be taken when installing the un-bonded prestressing tendons and in case of
exfoliation it should be repaired.
(4) Shift of the position of the prestressing steel or damage of the sheath caused during
arranging the prestressing steel should be repaired either during arranging or after arranging, withcareful inspection to find any shift or damage, before concrete placement.
(5) Tolerance of the position varies depending on the size of the members or on the way ofarrangement of the prestressing steel. For the prestressing steel, the sheath and the protection tube
tolerance should be not more than 5mm in case of not more than 1m of the distance between thecenter of the prestressing tendon and the extreme fiber of the member, and not more than 1/200 of
the size of the member or 10mm whichever is the less in case of not less than 1m.

422Chapter 1212.6.1.3

Prestressed Concrete

Formation of ducts

The material and the method for forming the ducts shall not adversely affect theprestressing tendons and concrete in cases when sheaths are not used.

[Commentary] Although the duct is prepared in order to insulate prestressing tendon withconcrete, while securing the space for arranging prestressing tendon, the material used for theformation shall be investigated the character and confirmed that prestressing tendon does notcorrode or concrete does not deteriorate. Moreover, the method to form duct shall not be such to
make concrete produce a crack, or not to increase friction remarkably during prestressing. In case of
producing bond later, as concrete and prestressing tendon shall act uniformly, its bond between
concrete and grout shall be large and sufficient. In case of forming the duct without using sheath,generally the following methods are applied.
(i) The method to form duct by covering prestressing tendon with insulating material such asasphalt, a polymer material and oil, and embedding into concrete: In this case, theinsulating material which can achieve insulation between concrete and prestressing
tendon completely and does not produce big friction shall be chosen. Moreover, covering
shall be done with the manner such that material does not exfoliate at the time during
handling and placing of concrete. This method is used for the case not to produce bond
between duct and concrete.
(ii) The method to form a duct by embedding mold etc. into concrete (a steel pipe, steel bar,plastic pipe, wood stick, rubber hose, etc.), and pulling out this before hardening of
concrete: In this case, the mold etc. shall not deform easily at the time of placing concrete.
Moreover, in case of producing bond later, the material used for it shall be such that it
does not leave anything what injures bond into duct.
(iii) The method to drill to the hardened concrete and form a duct: The method to drill shallbe to secure the position of duct correctly and not to produce big friction between
prestressing tendon and concrete. Moreover, foreign substances such as powder by drill
which serves as a fricative basis or injures bond shall be removed before insertingprestressing tendon.

12.6.1.4

Assembly and installation of anchorages, couplers and deviating devices(1) Anchorages and couplers shall be assembled in the accurate shape and dimensions
as specified in the design documents, and shall be appropriately installed at the locationand in the direction specified in design.
(2) The bearing surface of the anchorage shall be perpendicular to the tendons.
(3) In cases when tendons are coupled, sufficient space shall be provided in the duct on
the pulling side of the coupler to permit movement of the coupler when tensioning thetendons.
(4) An inspection shall be carried out after installation of the anchorages, couplers anddeviation devices, and damaged hardware shall be replaced or repaired. Any disturbanceerror in the position of the hardware shall also be corrected.
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Standard Specifications for Concrete Structures-2007, Materials and Construction[Commentary] (1) and (4) As the large scale force are applied to the anchorage and theconnection implement by prestressing, it is important to assemble correctly as plan and to arrange toaccomplish the right transfer of stress and accident prevention.
(2) If the prestressing tendon is not installed perpendicular to the bearing plate, at the time whenprestressing tendon is tensioned or it is anchored, prestressing tendon fractures may occur or there
is a possibility that anchoring prestressing tendon may become impossible due to the occurrence of
local bending stress. Therefore, it is preferable to assemble them so that the anchor and prestressing
tendon may become perpendicular correctly, and to maintain the straight line part of suitable length
in the prestressing tendon near anchorage.
(3) In the case that the prestressing tendon coupling is done, it is necessary to calculate
beforehand the amount of movements of the coupler by giving tension force to prestressing tendon
and to provide space, which is generous enough to this at a tension side. Moreover, it is required toconfirm the position of a joint after the assembly of a coupler.

12.6.1.5

Arrangement of openings for grouting, exhaust and discharging(1) Openings for grouting, exhaust and discharging shall be appropriately installed interms of their location and orientation.
(2) Grout caps should be used for anchorage fixtures.
(3) Hoses used for grouting, exhaust and discharging openings shall not be
concentrated in regions at the rear of anchorages.
(4) In cases when the ducts are very long or large-sized ducts are used, extra inlets inthe middle should preferably be provided.
(5) Hoses for grouting shall be securely installed in a manner that during the concrete
casting, they do not become detached or bend.

[Commentary] (1) The positions of injection holes, vent, and outlet shall be planned andarranged by considering the cable form or the grouting direction. The direction of a grout injection
hole is made into the direction according to the grouting position, and a vent and an outlet shall be
attached on the upper side of the duct. An outlet shall be prepared in consideration of the generating
mechanism of the remaining air depending on the viscosity of grouting etc.
(2) As the rising of an air bubble is influenced by a height difference near anchorage used as agrout injection part and a discharge part and it is easy to become an air void, an anchorage end cap
shall be used to avoid it. An anchorage end cap used for grout is preferable to have thecharacteristics of the non-iron and the structure where grout filling can be easily checked. A grout
hose need to be held vertically about 1.0m above from the girder surface. This is for replacing the
air bubble etc. and grout, which exist inside duct.
(3) Distribution of the grout hoses is needed in order to avoid a risk of air void concentrating
until grout injection is done, becoming a cross-sectional deficit and becoming lack of bearing
capacity against the prestressing force in the case that intensive arrangement of the grout hose iscarried out at the back side of anchorage.
(4) In cables used for such as a continuation girder, if a cable length is long, it is possible thatgrout injection pressure becomes high and pouring speed becomes slow, and it tends to be the cause424Chapter 12

Prestressed Concreteof trouble generation. In the case that cable length exceeds about 50m; it is preferable to prepare
injection holes also in the middle of over cable length to inject by the step-by-step formula (asystem which injection is gradually done by the use of the outlets which the outflow was checked asa injection hole).
(5) To prevent the connection part of a grout hose from separating during the casting concreteor to prevent grout hose bend deformation, it shall be connected each other using a strong
attachment band. Moreover, the middle support to the concrete side of a grout hose is strongly
attached to reinforcing bars etc. by the steel wire etc.

12.6.2Formwork and shoring(1) Formwork and shoring shall be designed so as not to obstruct deformation of
concrete members on account of prestressing. Formwork that may obstruct deformation of
concrete members during prestressing, should be removed before prestressing, unless theremoval adversely affects the concrete members. However, formwork and shoring, which
are provided for the reaction forces of gravity loads after prestressing, shall not be
removed.
(2) Formwork shall be adequately cambered considering deformations in concrete
members during and after prestressing so that the members will be in the required shapeand configuration upon completion.

[Commentary] (1) In case of the prestressing, it is preferable to remove some forms before
prestressing, and it is also preferable to consider as the structure, which can remove a part of sole
plate of formwork so that a concrete member can contract freely. As the deformation of the member
while prestressing, the reaction force acting on a form will change a lot with places. Therefore, theportion which receives self-weight and other loads for the first time after prestressing, unless after
giving the prestress to bear those loads at least, removal of the formwork and shoring shall not be
performed.
Shoring shall be arranged so that the concrete member’s stability is maintained as theassumption in design calculation after prestressing. If lifting of shoring is large, it is also required totake the measures which sink timbering simultaneously with prestressing.

12.6.3

Casting and compaction of concrete

During casting and compaction of concrete, great care shall be taken to avoid any
disturbance to reinforcing bars, anchorages, couplers and sheaths, and ensure that voids
surrounding reinforcing and tensioning materials are removed by compaction.

[Commentary] In a prestressed concrete structure, as an arrangement of prestressing tendons andreinforcing bars is complicated, it is necessary to pay careful attention in casting and compaction of
concrete.

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12.6.412.6.4.1

Prestressing
General requirements(1) Prestressing tendons shall be tensioned in a manner that imparts the required tensile
force to each of the constituent prestressing steel tendons or strands.
(2) In cases when the tendons are tensioned sequentially, care shall be taken to ensurethat the concrete is not subject to harmful stresses at any stage.
(3) In cases when a particular tensioning apparatus is specified for a specific prestressing method, such a specific apparatus shall be used. When no specific tensioning
apparatus and load-measuring device are specified, a tensioning apparatus that is capableof giving the required tensile force accurately shall be used.
(4) Special care shall be taken to avoid accidents during prestressing.

[Commentary] (1) and (2) In the case that multi-strand prestressing tendons are simultaneously
tensioned as one bundle of cable, it is needed to maintain the length of each strand so that equaltension force is given to each strand prior to the beginning of stressing operation. Moreover, there
shall be no slip at the anchor of prestressing tendon.
The following specific points should be taken into consideration.
(i) Since there is a possibility that slips may occur in wedge type anchorages during prestressing,each prestressing tendon shall be marked to control the existence of such slips.
(ii) In pretensioning system, in the case when the prestresing is done in a manner such thatseveral prestressing tendons are beforehand anchored to the anchorage abutment, and the tension
force is going to be given simultaneously to all prestressing tendons by the anchored abutment to be
moved, the preliminary tensioning pulling and arrangement of each prestressing tendons by suitable
force is required in order to eliminate the differences of the tendon lengths due to the slack of eachprestressing tendon before fixing.
(iii) In post-tensioning system, in the case when several to about ten prestressing tendons are
made into a bunch and prestressing is done simultaneously, it is important to arrange the lengths ofthe prestressing tendons before prestressing.
In measurement of elongation of prestressing tendon, a measuring point shall be prepared after
giving suitable tension force for prestressing tendon so that the slack of prestressing tendon or theslack of a connection implement may not be included in measured value.
(iv) Tension force value given to prestressing tendon shall be predetermined in consideration of
the slip of the anchoring equipment, and the influence of high temperature during accelerated curingetc. in the case of pre-tensioning system. Anchorage equipment shall be loosened gradually so thateach prestressing tendon enables to be loosened uniformly to give prestress.
In the case when each prestressing tendon is tensioned separately and anchored by using thewedge type anchorage, a certain amount of set loss will occur at the anchorage. Although theamount of reduction of the tension stress due to the amount of set loss can be disregarded to someextent in such case when the length of tendon is comparatively long, it is not ignorable in the casesuch that moving bench system with the use of comparatively short length tendon is used, or in thecase that the anchorage system with a large amount of set loss is used.
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To arrange the prestressing tendon on a polygonal line, there are methods to give predetermined
tension force by carrying out whether prestressing tendon being raised or lowered at the position ofbending point after arranging prestressing tendon in the shape of a straight line beforehand and totension from the end of prestressing tendon after arranging prestressing tendon on a polygonal line.
By arrangement of these prestressing tendon and the order of tensioning, as the states of the friction
loss between support equipment and prestressing tendon differ, a proper investigation of the relation
between the order of tensioning and friction loss in prestressing tendon shall be carried out
beforehand.
In the case when the loss of tension force takes place due to such a cause, the amount of
reduction shall be calculated beforehand by calculation or survey, and tensioning of prestressing
tendon shall be done so that the predetermined tension force may be given in consideration of theselosses.
Since there is a possibility of giving a shock to concrete and spoiling bond between prestressing
tendon and concrete if the anchoring equipment of prestressing tendon is loosened rapidly during
prestressing, loosening of anchoring equipment shall be carried out gradually.
In addition, if tension force of each prestressing tendon does not loosen uniformly
simultaneously at the same time, unexpected bending moment may arise and it may have a
detrimental influence on concrete member and anchoring equipment. Moreover, in the case when
the concrete member is manufactured with the method that a part of prestressing tendon is arranged
being bent up and vertical reaction force raised by the tension force of prestressing tendon istransferred to the manufacture bench, generally, support equipment at the bending up point must beloosened prior to the loosening of the anchoring equipment. However, in such a case that thevertical reaction force of a bending up point is large compared with the mass of concrete member,as it may have a detrimental influence on concrete by loosing the support equipment previously,prestressing shall be carried out after confirming that the order of loosening will not have any
detrimental influence on the concrete member.
In addition, if it is made to cool completely after the rapid curing with high temperature is
performed before prestressing, as there is also a possibility that the prestressing tendons exposed
between concrete members may fracture, it is preferable to give prestress to members before atemperature falls.
(v) Tension force given to prestressing tendon shall be determined in accordance with thedesign value in consideration of friction loss, deformation of anchorage or a slip in case of
post-tensioning system. In the case that the prestressing tendon is tensioned one by one, it shall bedone not to cause detrimental stress to concrete in each stage. Moreover, tension force given to eachprestressing tendon shall be determined so that tension force of prestressing tendon may become
equal respectively in consideration of elastic deformation of concrete in this case.
Tension force of prestressing tendon decreases as it becomes farer from the tensioning end dueto the friction between prestressing tendon and duct. Therefore, if tension force given to thetensioning end is not enlarged considering this friction loss, it becomes impossible to give
predetermined tension force to prestressing tendon in a design section.
As the actual quantity of the friction loss may differ from that assumed in the design, tension
force given to prestressing tendon end shall be defined based on the friction value measured by thetest in on-situ construction.
In the case that the prestressing tendon is anchored to concrete with an anchorage, that has a set,
the amount of permissible set loss should be decided beforehand. If this amount of permissible set
loss is exceeded at the anchorage, it is necessary to redo prestressing.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

In the case that the prestressing tendons are tensioned one by one every single or every several
groups and anchored, only a part of prestressing tendon is tensioned before all prestressing tendons
are stressed to the required tension force and anchored. Due to this reason, depending on theposition and size of the prestressing tendons, the torsional moment, bending moment in transverse
direction and stress detrimental to a part of member may arise due to statically indeterminate force
in a statically indeterminate structure. Therefore, the order of tensioning of prestressing tendons,
method and value of tension force shall be determined considering these effects so that detrimental
stress shall not arise on concrete in each stage.
In post-tensioning system, the elongation of prestressing tendon is generally calculated bymeasuring the extract length of the prestressing tendon from a concrete member with deduction ofelastic deformation of concrete. When all the prestressing tendons are tensioned simultaneously, theamount of elastic deformation of concrete shall not be disregarded. In the case that tensioning isdone for each group of prestressing tendons, as the amount of elastic deformation of the concrete ismostly in inverse proportion to the number of groups divided, if there are many groups, it does notinterfere even if extract quantity of the prestressing tendon is considered to be the elongation to fulllength as it is. However, the original tension forces of the prestressing tendons tensioned previously
generally decrease due to the elastic deformation of the concrete occurred by the prestressing
tendon which is subsequently tensioned. Therefore, according to the method shown in thecommentary (1) (i) of Section 15.3 of the Standard Specifications for Concrete Structures “Design”,
tension forces given to each prestressing tendon shall be adjusted considering the reduction of theaverage tension force of prestressing tendons.
For the calculation of prestressing tendon extract, the Young's modulus of the prestressing
tendon examined on site shall be used. In the value of apparent Young's modulus, theabove-mentioned prestressing tendon extracts and the influence by the difference of quantity andelongation, etc. should be included.
(3) Prestressing jack may be prescribed in the “Guideline of Design and Construction of
Prestressed Concrete” for every type of prestressing tendon with specific prestressing method. Insuch a case, specific prestressing jack shall be used.
(4) During the stressing operation, prestressing tendon has possibilities of doing harm as a resultof releasing tremendous stored energy rapidly if the breakage of prestressing tendon, anchorage or
tensioning equipment occurs. It is preferable to place a protection board behind the tensioning
equipment. Moreover, the workers engaged in prestressing work as well as neighboring workers
must be careful enough about the harm prevention and must not stand behind the tensioning
equipment or anchored equipment during stressing operation in any cases in order to prevent a
worker's harm. In addition, it is also preferable to train skillful workers and the stressing operation
shall always be carried out by these workers on the basis of the engineer presence that has sufficientknowledge such as prestressed concrete engineer authorized by the Japan Prestressed ConcreteEngineering Association.

12.6.4.2

Calibration of tensioning equipments

Tensioning equipments shall be calibrated before use. The equipments shall berecalibrated periodically and the results shall be recorded. In cases when the tensioning
equipments are subjected to an impact, while in use, recalibration shall be carried out.

[Commentary] Since load-measuring devices of tensioning apparatus may not show the actual
tensile force due to the internal friction of the device or the friction between prestressing tendonsand anchoring device, calibration must be carried out beforehand for these friction losses so that the428Chapter 12

Prestressed Concretetensile force applied to prestressing tendons can be correctly read from the load-measuring device.
The load-measuring devices of tensioning apparatus may often be incorrect so that periodical
calibrations shall be carried out to check the function and precision.
The most precise range of the load-measuring device is different in accordance with the typeand capacity. The type and capacity should be selected so that it can be constantly used in the rangeof highest precision.
Calibration of tensioning apparatus is one of the most important works for stressing operation,
therefore, it is necessary to frequently carry out calibrations. Dual-pointer standard gauge ordynamometer for calibration shall be prepared at the work site. In general, tensile force should bedirectly checked by dynamometers. Nevertheless, such devices are mostly expensive and it may be
acceptable to use dual-pointer standard gauges at the general work site. Attention must be paid,
however, to the inability of knowing increase of internal friction losses due to mechanical failure of
jack, though the calibration by standard gauge can show whether the pressure indication by theload-measuring device is correct or not.

12.6.4.3

Control of prestressing(1) Prestressing shall be controlled so that the tensile force in each tendon is not lessthan the specified value, taking into account the deviations due to various reasons.
(2) The tensile force applied to the tendons shall be measured by the readings of theload as well as the elongation or extension of the tendons. Moreover, the linear relationshipbetween the two shall be confirmed during the prestressing work. If the relationship is not
linear, prestressing shall be carried out again. In case the anomaly still remains for thesecond time, work shall be suspended and the cause of the anomaly shall be determined.
(3) In cases when several tendons are placed in a concrete member and the tendons aregrouped, tensioning of the tendons shall be controlled both as a group and individual
tendon.
(4) In cases when the number of the tendons placed in a concrete member is extremely
small, as in the case of concentrated cable system, special attention shall be paid to thecontrol of prestressing.
(5) In principle, the friction coefficient and the apparent Young’s modulus of a tendon
should be determined through tests carried out at site.

[Commentary] This article provides the control of prestressing for main prestressing tendons.
For the tendons with little change in angle and with a small length as in the case of transverse
prestressing, applying all the conditions may not be appropriate. Then, the tendons should bemanaged under the conditions inasmuch as possible.

(1) In the case of prestressing tendons with friction, even when friction coefficient and apparent
Young's modulus of a tendon are measured, the measured results can only show the average
condition of prestressing tendons at the time. Accordingly, prestressing tendons are fairly different
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for each other. Tension forces applied to prestressing tendons must be determined so as not be lessthan the design values considering these differences.
For this reason, it may be safe to stress the tendons with approximately 2-3% larger tensile force
than the design values.
For controlling the prestressing in the case when several tendons are arrenged on a member,
followings are convenient and widely used to determine the anchoring point of prestressing
tendons;
The apparent Young's modulus are measured on considerable numbers of prestressing tendonsand the average value Ep is calculated. Prestressing calculations are carried out for any more than
two friction coefficient μ using Ep. Indications of load-measuring device and extraction amount oftendons for applying specified tensile force are calculated for each friction coefficient, and they areplotted in a diagram as Points A, B,…… When the apparent Young's modulus is correct, the line
which connects Points A and B becomes the theoretical anchoring line to the corresponding friction
coefficient (see Fig. C12.6.1).
In such a case, additionally, the relationship between the actual indication of load-measuring
device and the extraction amount shall be plotted on the figure, and the friction coefficient μ
corresponding to the intersection point of the line which connects Point A and B should becontrolled within the tolerance of the friction coefficient calculated from the test. Although, thefriction coefficient corresponding to the intersection point of the line which connects Point A and B
may be a negative value, it does not mean that the actual friction coefficient becomes negative.
Difference of the apparent Young's modulus may produce such value.

Indications ofload-measuring device

Anchoringline

Extraction amount of tendonsFig. C12.6.1

Diagram for controlling the presterssing(2) The relationship between the indication of load-measuring device and the extraction amountof prestressing tendon does not become linear when the measuring results are incorrectly read
during prestressing, in cases of something wrong with the pointer of load-measuring device or any
other abnormalities. In such cases, not only the reliability for the results of prestressing declines, butalso it may cause a large error on the correction value of elongation or extraction amount, which
gives adverse effects to the control of prestressing. For this reason, when the relation between theindication of load-measuring device and the extraction amount of prestressing tendon does not
become linear, the work must be stopped to redo the prestressing.
(3) Considerable differences cannot be avoided for tensioning each prestressing tendon.
Accordingly, even when there is a considerable error, it cannot be easily found on the control of430

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prestressing for each tendon. As a result, predetermined tensile force cannot be applied in somecases. For this reason, prestressing tendons should be grouped, and the average tensile force in eachgroup should be calculated. Moreover, the influence of dispersion due to accidental errors should be
minimized so that the causes of abnormality can be promptly and correctly found.
The following method is convenient when controlling prestressing by grouping tendons.
The relationship between the indication of load-measuring device and the extraction amount foreach prestressing tendon is plotted on the figure, and the intersection point to the line whichconnects Points A and B (See Fig. C12.6.1) is obtained. The coefficients of frictions for theintersection points are calculated for each group and are adopted as statistics values. The averagevalue of such the statistic ones is controlled so that it is within the tolerance, as shown in Table
C12.6.1, against the friction coefficient value μ calculated through the measurement.
Table C12.6.1

Standard value of tolerance for friction coefficient

Number of prestressing tendonsin the group1
4
6Above 10Tolerance of μ
±0.4
±0.2
±0.16
±0.13

The tolerance is based on prestressing control data at many sites. Even in the normal control
condition, approximately 5% of standard deviation is considered to be unavoidable in therelationship between the tensile force on the designed cross section estimated from the indication ofload-measuring device when prestressing and the tensile force of the same cross section estimatedfrom the extraction amount. Accordingly, the tolerance is calculated for μ value so that the 95%
is within the tolerance under the normal controlled condition. Even in the normal condition, it may
be deviated from the tolerance in a rate of once in 20 times.
When manufacturing very large numbers of prestressed concrete members, it is recommended
to calculate the standard deviation of the differences based on the actual field results and determine
the tolerance.
In group control of prestressing, deviation from the tolerance does not mean that specified
tensile force is not be able to applied, but that designed prestress may not be applied with higher
possibility when prestressing is continued under the condition out of the tolerance, and is to judge if
prestressing condition is favorably maintained.
(4) In concentrated cable systems, accidental errors during prestressing are the errors of tensile
force which will affect the safety of members. Accordingly, measures must be taken to reduce such
accidental errors.
Consequently, the following measures must be taken:(a) Continue the measurement of friction coefficient and apparent Young's modulus until
stable measured value can be obtained sufficiently, and calculate the required tensile force
using such the value.
(b) Repeat prestressing several times until the relationship between the elongation or
extraction amount of prestressing tendons and the reading of load-measuring device isstabilized before anchoring.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(c) In the case of extremely long prestressing tendon, provide an observation window in the
middle and check the traveling amount of prestressing tendon at the midpoint.
(5) The friction coefficient of tensioning apparatus and anchorage should be measured by tests,
in principle. When there is enough test data on the prestressing method that has been widely used,friction coefficient may be estimated using such the results.
Friction coefficient between prestressing tendons and the duct largely affects on the tensile
force. Moreover, it often changes even at the same site as time passes. Accordingly, measurements
must be carried out not only when starting the construction but also during the construction.
Young's modulus of prestressing tendons is employed to calculate the tensile force from theextraction amount of prestressing tendons. Extraction amount of prestressing tendons relates to not
only the elastic elongation of prestressing tendons but also the shortening of members. The apparent
Young's modulus calculated from the extraction amount of prestressing tendons during prestressing
usually becomes considerably lower than that indicated on the mill sheet of prestressing steel
materials. Accordingly, the apparent Young's modulus calculated from the extraction amount must
be used to calculate the tensile force for prestressing.
Since the apparent Young's modulus changes depending on the conditions of the site and thearrangement of tendons, it must be calculatedfor each layout of the tendon on the site. Generally,
the apparent Young's modulus is approximately 1.81～1.96×105 N/mm2 when the Young's
modulus indicated on the mill sheet of prestressing steel materials is 2.01×105 N/mm2. However, it
may become smaller value in some special cases.
The apparent Young's modulus is able to be estimated to be 1.95×105 N/mm2 when a small
number of members in which prestressing wires are arranged with the normal layout, areprestressed. However, the suitability of this estimation shall be ensured on the prestressing control.

12.6.4.4

Protection of anchorages and end surfaces of members(1) In the pre-tensioning system, tendons shall be cut evenly after prestressing at theends of the members, and shall be protected from corrosion.
(2) In the post-tensioning system, the anchorages and the end surfaces of the members
shall be protected from damage or corrosion.

[Commentary] (1) In general, prestressing tendons should be cut so as to be less than 5mm fromthe ends of members in length, even if not indicated on design document. As much as possible, amechanical cutting method should be applied. Only when it is unavoidable, a gas cutting method
can be applied. Then, the end surfaces of the members should be protected from corrosion by
painting asphalt or coal tar, or wrapping with mortar.
(2) In many cases, as anchorages of the post-tensioning system are arranged at the surfaces ofthe members, they are easy to be suffered from external shocks and permeation of the rain water. In
addition, the anchorages are always in the state on which high force acted after prestressing.
Consequently, they should be sufficiently protected from damage by the shock from the exterior or
corrosion due to the rain water.
Therefore, the anchorages should be placed in depressions which are completely filled withconcrete or mortar subsequently. Construction joint should be cleaned up and chipped before432Chapter 12

Prestressed Concrete

casting the concrete or the mortar, for which the non-shrinkage types are used, at the depressions forthe anchorages. Moreover, the waterproof processing should be carried out at the surface of joint.
When the anchorages are exposed to the weather for comparatively long time during
construction, or when there are necessary to be exposed in atmosphere for re-prestressing, acorrosion inhibitor with high quality shall be painted on the anchorage surface and shall be easily
re-painted.
12.6.512.6.5.1

Grouting
General requirements(1) Grouting should be carried out as soon as possible after prestressing to protect thetendons against corrosion, in principle.
(2) When constructing grout for prestressed concrete, professional engineers withadequate knowledge about grout for prestressed concrete shall manage construction.

[Commentary] (1) If prestressing tendons without grouting are left as they are after prestressing,
there are possibilities of breaking out of the tendon, incidence of an accident, or incidence of amember breakage due to an accident occurring on the anchorages of the prestressing tendon.
Additionally, in a case when the prestressing tendons without grouting are left for a long period oftime, the intruded rainwater may cause corrosion in the tendons. Therefore, grout should be injected
as soon as possible after prestressing, and it is necessary to unify the tendons with the member so as
to protect the tendons from corrosion.
(2) Developing construction plans and injecting grout for prestressed concrete after
understanding the necessity, importance and filling mechanism of grout for prestressed concrete
helps eliminate human errors or eliminates unnecessary tests or inspections. Professional engineers
with adequate knowledge about grout for prestress concrete should therefore manage theconstruction of grout for prestressed concrete. Professional engineers here means the prestressing
engineers authorized by the Japan Prestressed Concrete Engineering Association who have attended
the training sessions on grout for prestressed concrete conducted by the Japan Prestressed ConcreteContractors Association.

12.6.5.2

Mixing and agitating(1) The grout should be mixed using a grout mixer capable of mixing one batch of grout
sufficiently within 5 minutes.
(2) The grout should be steadily agitated until grouting operation is finished.

[Commentary] (1) The grout mixer should have sufficient function which can disperse cement
particle. The mixing procedure of grout materials is able to be determined so as to be suitable forthe admixture to be used. However, followings must be avoided; these are, giving excessive load toa motor due to not enough mixing of cement and water, intruding excessive entrapped air into thegrout during mixing, and obtaining not well mixed grout in a prescribed mixing time.
In case that the cement particles coagulate, the cement should let a 1.2mm-sieve pass before433

Standard Specifications for Concrete Structures-2007, Materials and Construction

mixing.
Since the temperature of grout will rise and its flowability will decline in case when intense
mixing continues for a long time, a special attention is required when mixing time is prolonged, or
grouting is executed in a high temperature. In such a case, countermeasures to prevent risingtemperature of grout, for example, using retarder or fly-ash, and mixing grout slowly, must be
carried out.
(2) Because grout will cause a segregation of material and/or declination of flowability, grout
must be agitated gradually during grout injection.

12.6.5.3

Grouting(1) Prior to grouting, the duct shall be flushed with compressed air to confirm that there
are no blockages and that the duct is air-tight.
(2) Just after mixing the grout, the grouting shall be carried out gradually with adequate
pressure using a grout pump capable of injecting the grout without entrapping air in theprocess.
(3) The grout shall be screened through an appropriate sieve before pumping.
(4) The grouting shall be continued without an intermission until the grout with the sameconsistency comes out of the vent openings and free ends.
(5) While grouting, the injected volume of grout should be controlled using a flow meter.

[Commentary] (1) Before grouting, ducts shall be checked to be air-tight without any blockage.
When blockages cannot be checked, and when there is a leakage from the duct, it is necessary toprovide some suitable measure.
(2) In a case when grout is injected quickly, there is a possibility that the grout may not be
sufficiently injected. Therefore, the injecting pressure should be maintained adequately during
grouting. A power grout pump that can be equipped with a function of gradual injection isconvenient, but also good as using a handy type pump that has same performance. Use of the pumpthat presses the grout directly with air is prohibited, because there is a risk of entrapping the air into
the grout.
(3) Generally, 1.2mm sieve is used for screening the grout before pumping.
(4) Grouting has better to be injected toward the higher place from the lower place, in order tofill up a duct fully with the grout. In case when most of the portion of the duct is lower than theinjection inlet, vent openings for the water drain as well as the grout discharge shall be provide as
many as possible. When injection is performed downward in an inclined duct, grout flows along thebottom of the sheath and fills the duct up gradually from the lowest toward the top of the duct. So
air voids tend to appear around the upper potion of the duct. And in case where a duct has convex
portions, grout flows along the bottom of the sheath after passed the highest point, and air voids
tend to appear near the highest point. Therefore, when there are convex portions in the middle of aduct, openings combined air vent with grout discharge shall be provided so as to eject the entrapped
air considering above mentioned phenomenon.
The vent openings are closed after confirming the steady coming-out of the grout without434

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dilution. It is required that injection is carried out using sufficient amount of grout without any
hesitation to discharge the necessary amount of grout. Finally, backward flow of the grout should be
avoided by closing all vent openings so that the pressure should be raised and maintained a little
higher than that of injection, then the grouting should be terminated.
Care must be taken so that the pressure will not become excessively high during injection. For
the high viscosity type of gout, it may be effective in control of injecting pressure that grout isinjected after passing water in advance. In general, the injection pressure should be not more than 2
Mpa considering capacities of grouting hoses, joints and caps. Grouting hoses should be held
vertically not less than 1 m in length from the surface of the girder in order to confirm that no air
void is left in the sheath. In case when the grout level drops, counter measures, e.g. re-injection,
have to be carried out.
(5) Grout flowmeter is available for the both types, a printer-type and a chart-type. The
printer-type is a type that prints construction date, cable number, time, and amount of injected grout
on a sheet. The chart-type records the amount of flow and pressure on a graph as well as prints them.
The type of flowmeter shall be chosen so as to be suitable for the location of grouting and theamount of grout. In advance of injection, flowmeter must be calibrated.

12.6.5.4

Treatment of injection inlet, openings for air vent and grout discharge

The cut faces of the hoses used in injection inlet and openings for air vent and grout
discharge, shall be appropriately treated and finished to achieve sufficient density of thesurface to prevent water and any other harmful substance from penetration into the hoseand become a cause for corrosion of sheaths or steels.

[Commentary] Since a coefficient of thermal expansion differs from that of concrete, there is apossibility that a gap is formed between concrete and the hose and it can be a water path in a long
period. And also concerning the concrete cast in depressions, if its water-tightness is not maintained,
water will penetrate into the joint, and there is a possibility of occurrence of cracks induced byfreezing and thawing, consequently steel corrosion. Therefore, in principle, grouting hoses shallbe cut 1cm or more in depth below concrete surface, and depressions after cutting the hoses shall befilled with epoxy resin. Especially in a cold district, since there is a possibility of permeation of
calcium chloride scattered on the road for freezing prevention, care must be taken in the execution.
Furthermore, waterproofing must be carried out for the road surface of bridge, which are directly
influenced by rain water or de-icing agents.

12.6.5.5

Grouting in cold weather

When grouting is carried out during cold weather, the temperature around the ducts
shall be maintained at not less than 5 C before injection. The standard temperature of grout
during injection should be between 10 and 25 C. In principle, the temperature of the grout
should be kept at not less than 5 C for at least 5 days after completion of injection.

[Commentary] If grouting is performed in the cold season when the averaged temperature
becomes 4 C or less, the grout may freeze and may not have required intensity. Moreover, thefrozen grout may expand and surrounding concrete may crack along with a duct. Therefore, it isrequired to carry out the grouting with careful attention to weather conditions.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

From the results of previous experiments, it was found that the hydration reaction will progress,
and grout with a required quality can be obtained under the following conditions: the temperature of
the duct circumference when grouting is 5C or more, the temperature when grouting is in the rangeof 10-25C, and the temperature of grout is kept at 5C or more over five days after grouting.
However, according to another report, when the unit water content is minimized by using ahigh-range water-reducing agent, the required strength can be obtained, without expansion byfreezing, if it takes at least 10 hours for the grout temperature to reach -5 C after injection with thesame initial conditions, and if even after that the temperature is kept at -5 C for two days off and on.
Therefore, grouting can be carried out if weather conditions can be stabilized, and grouting can becompleted when temperature in the daytime is 5C or more, when the prediction of the lowest
temperature several days after is possible, and the temperature of subsequent grout can be kept at 0
C or more over five days. In this case, the temperature of the grout shall be recorded for 5 days
after injection and it shall be confirmed that the temperature has stayed not below 0C.

12.6.5.6 Grouting in hot weather
In cases when grouting is carried out during hot weather, appropriate measures shall betaken to prevent an unacceptable rise in the grout temperature and early hardening ofgrout.

[Commentary] Since a blockade will tend to take place by set that is too early if grouting iscarried out in the hot season where the averaged temperature exceeds 25C, consideration tomaterial and construction must be adequately given for prevention of uncertain grouting.
In hot weather grouting, the temperature of grout for prestressed concrete should be minimized.
It is important to finish grouting in a short period of time as much as possible.In order to lower thetemperature of grout, it may be effective to reduce the water temperature by feeding ice into a watertank or using a water cooler.

12.6.612.6.6.1

Manufacture and construction of precast members
Manufacture(1) The structure of the production platform shall be such that precast members
obtained are accurate in shape and size. It shall be constructed considering deformation of
the members and change in the reaction force due to prestressing.
(2) Precast members shall be carefully manufactured to ensure accurate jointing andassembly.

[Commentary] This paragraph covers precast members except factory products explained in
Chapter 14. Regarding the other items not explained here, “Guideline of Design and Constructionof Precast Concrete Block System (Draft)” published by Japan Prestressed Concrete Contractors
Association and “Specification of Design and Construction of External Cable Structures and Precast
Segmental Method (Draft)” published by Japan Prestressed Concrete Engineering Association canbe referred.
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Prestressed Concrete(1) Generally, many precast members are manufactured using a few production platforms.
Hence, in such cases, the structure of the production platform should be so as to avoid unevensettlement caused by casting concrete and the softening of the ground by due to curing water. The
production platforms shall be designed and manufactured after surveying and investigating the
topographic and geological features, and considering the vertical and horizontal loads act on the
production platforms during manufacture.
Some prestressed members may be supported on the both sides of themselves due to warping
induced by prestressing. Consequently, the production platforms shall be manufactured so that theharmful settlement and deformation may not occur by the load at both end supports of the members,
and so as not to restrict the shortening of the member by the elastic deformation resulting fromprestressing.
(2) In order to ensure monolithic behavior of precast members by prestressing, the members
shall be such that the construction work for the joint portion can be performed properly, theprestressing tendons can be easily installed in the ducts and the shape and dimensions of thestructure will be such as planned.
Therefore, in the manufacture of the precast members, the work shall be carefully performed,
taking these matters well into consideration, so that the shape and dimensions of the members andjoint surfaces can be accurately secured and the locations of the ducts can be arranged correctly.
When producing the members using an adhesive as a bonding material and in case of match
casting members, in which the joint surface of a precast member is cast against the joint surface of
the already-made unit, guide-keys (dowels, slots, etc.) shall be provided on both surfaces in advanceso as to enable accurate and easy jointing of the two surfaces.
When detaching the members, it is advisable to separate them perpendicular to the joint surface.
Cracking, breaking and lacking at the corner of concrete may occur at the joint surface if themembers are lifted up parallel or diagonal to the joint surface. Consequently, the production
platforms and the forms shall be manufactured with consideration of the above-mentioned matters.
Release agents are generally applied on the joint surfaces to reduce the resistance of detaching. The
release agent shall be effective in easy stripping and be thinner film as possible without bondstrength loss and durability of adhesives.
It is difficult to adjust the direction of the jointed members during erection since the accuracy oferection of members produced with mach casting method is determined at manufacturing. Hence, if
an erection error may be much larger than expected at the final stage, the error should be modified
as soon as possible during construction.
When precast members are introduced prestress, deformations such as warping and shortening
will occur, and further time-dependent deformation will take place due to creep and shrinkage ofconcrete. If these deformations are predicted to cause harmful effects on the shape and dimension of
the structure, the members shall be manufactured in anticipation of such deformations.

12.6.6.2 Transportation(1) Precast members shall be transported such that they are not damaged in any
manner.
(2) When transporting precast members, they shall be supported at predetermined
locations. In cases when support needs to be inevitably provided at other locations, it shall437

Standard Specifications for Concrete Structures-2007, Materials and Construction

be verified in advance that the members are not adversely affected.

[Commentary] (1) Since the loads acting upon the precast member vary according to the phasesof the work depending on the methods of handling during transportation and erection, the members
shall be handled in such a way as to avoid harmful effects on themselves. If the member is largely
inclined from side to side during transportation, the dead load may cause the bending moment
laterally and the tensile stress may occur on the side and at the top fiber. Generally, a member witha relatively narrow width, compared with the span between supports, tends to become unstablesidewise.
Hence, when a member with a narrow width and long span between the supports is to betransported or erected, sufficient safety shall be ensured in advance against the tensile stress and thelateral buckling caused by the effect of the lateral load. If the analysis shows that the safety of themember is comparatively small, the sufficient countermeasures as followings shall be taken. For
instance, to arrange tensile reinforcements within a portion in tension, or to restrain the lateral
deformation by installing temporary bracings on the side of the member, or to shorten a hanging up
span, or to increase the degree of restriction against torsion at the ends of the member.
Thus, safety against cracking and lateral buckling shall be improved in advance, andfurthermore, the members shall be handled carefully upon transportation and erection.
(2) Since, during transportation, the prestressed concrete members are in general subjected tothe combined stresses only corresponding to the prestressing and the bending due to the dead load,
the stress at the top fiber of the member is usually zero or nearly zero. Therefore, upontransportation, the member shall be supported at positions designated in the design drawings ordesign calculation documents, otherwise a large tensile stress may be induced at the top fiber of themember and may result in cracking when a bending moment acts on the member in a direction not
originally considered.
If the member cannot be inevitably supported on the proper positions at the designated positions,and the cantilever portion of the member may be longer than expected, the negative bending
moment by the dead load at the supports and the prestress may cause high tensile stress at the top
fiber of the member. Hence, when the member is supported at the unexpected positions, it isnecessary to ensure the safety by calculation in advance. Also, even if the position of the support is
not prescribed, the safety of the handling method shall be ensured in advance.

12.6.6.3 Storage(1) Supports shall be provided for precast members at prescribed locations duringstorage, and appropriate measures shall be taken to ensure that the members do not fall. In
cases when members are stored in a pile, supporters shall be firmly placed at proper
positions to prevent a collapse of the pile.
(2) When precast members are stored, appropriate measures shall be taken to prevent
any ingress of water into ducts that may freeze or have an adverse effect such as corrosionof sheaths and couplers.

[Commentary] (1) During storage, precast members shall be firmly supported on the prescribed
positions. Also, measures shall be taken to prevent the members from being inclined and fallen
because of an uneven settlement of the ground or an earthquake.
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In cases when the members are stored in a pile, the positions of supporters for each layer shallbe carefully arranged to be in a vertical line. If not, the unexpected bending moment at designing
may occur in the member below the supporters due to the weight of the members stacked above.
Also if the dimensions or the quality of the supporters differs from that of designated, for instance,
if the heights of the supports at two points are extremely different or if the supports are not of therequired length, or if the strength of the supports is insufficient, not only may unexpected loads act
upon the members but the members may be damaged by the collapse of the stack. Hence, sufficientattention shall be paid to the dimensions or strength of the supporters.
(2) Post-tensioned members without grout shall not be stored for a long time in cold weather,since the frozen water in the ducts may cause cracking of the members. If the storage in suchcondition is inevitable, appropriate measures such as drain-holes at the lower position of the ducts
shall be provided to prevent any ingress of water. Also, as the prestressing tendons rust or corrode if
they are left in the ducts for a long time without grouting, such a situation shall be avoided. If thestorage in such condition is inevitable, sufficient preventive measures against rusting or corrosionof the tendons shall be taken.
12.6.6.4

Jointing(1) Joint surface of precast members shall be maintained sound and clean by completely
removing any harmful substances, such as loose particles of aggregate, poor-quality
concrete, laitance, mud, and oil.
(2) At the time of jointing the members, they shall be so aligned with the ducts in termsof their position and shape that no gaps or twists are caused during jointing andprestressing.
(3) Jointed parts of ducts shall be appropriately treated to prevent concrete, mortar andbonding agents used for jointing, from flowing into the duct as well as to avoid conjunction
with adjacent ducts.
(4) The structure and strength of shoring for jointing the members shall be such that it
can withstand the loads applied during jointing and elastic deformations due toprestressing.
(5) Waterproofing shall be applied at all locations from where water or chloride ions
could flow into a duct.

[Commentary] (1) Poor-quality concrete at joint surfaces brings a poor-quality joint for precast
members even if a bonding material is of good quality.
Consequently, the joint surfaces of the members shall be carefully finished up. In case whenloose particles of aggregate and poor-quality concrete remain on the joint surfaces, they shall be
removed, and treatments shall be taken so that the joint surfaces are clean and sound. Laitance andrelease agent for a form may remain, and mud and oil may stick to the joint surfaces duringtransportation and storage even if the elaborate work is done. Thus, any substances, whichharmfully affect the jointing, shall be removed with a wire blush and others in advance.
When concrete or mortar is used as a bonding material, the joint surface shall be kept wet before
casting.
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Standard Specifications for Concrete Structures-2007, Materials and Construction

On the other hand, when using adhesives as a bonding material, the thickness of the joint is
negligible thin after assembling members. Therefore, if there is a projection, such as a roll-up end ofa sheath, on the joint surfaces, even if relative small, it may cause a harmful effect including stressconcentration on them. Thus any projection on the joint surfaces shall be removed. Also, the joint
surface shall be sufficiently kept dry before applying adhesives.
The most suitable manner shall be taken for the jointing of precast members, concerning thebonding material, in order to achieve the required quality such as strength, durability andwater-tightness.
When the concrete or mortar is used as the bonding material, thickness of the joint is usuallyrelatively thin, 10 to 500 mm, compared with the depth of the members. Hence, it is necessary tochoose a mix proportion in order to obtain the most suitable flowability for each location and therequired quality. Also, the concrete or mortar shall be sufficiently compacted by vibrators so that
it will fill around the ducts and enter all the corners of the form. In this case, the joint portion shallbe made firm enough to prevent the sheaths from being crushed or being out of place, or the cement
paste from flowing into the sheaths.
If an adhesive is to be used as the bonding material, the work shall be performed with particularcare to the following points as the nature of the material is quite different from that of the concrete
or mortar.
(a) To choose an adhesive suitable for conditions of execution:
The characteristics of adhesives with same kind of resin are more or less different
depending on the manufacturers, and a mix proportion and others. Hence, the adhesivethat is most suitable for the conditions of execution such as temperature and working hours
and that has required quality shall be chosen.
(b) To weigh and mix accurately:
The adhesive consists of two agents, the principal agent and the hardening agent.
Accurate measurement of these two agents is required during execution in accordance withthe specified mix-proportion.
In general, mechanical mixing is preferred to evenly mix the principal agent and thehardening agent although manual mixing may be allowed for a small quantity. If the amountof a batch is too large and is beyond a capacity of a container, the great heat is generated andthe pot life is reduced. Thus, particular attention shall be paid on mixing by machines.
(c) To consider the weather condition such as temperature and rain during execution:
Excessive low temperature of concrete at the joint surface will cause a higher viscosityof adhesive, difficulties of the work and a slow hardening reaction. On the other hand,excessive high temperature will lead to a smaller viscosity, a flagging increase, a rapid
progress of the hardening reaction and a short pot life. Therefore, it is recommended that theexecution will be done when the concrete temperature is between 15 to 25 . When theexecution is done at the temperature other than these, the adhesive suitable for thetemperature at use shall be chosen.
The adhesive wet with rain shall be removed from the surfaces.
(d) To be careful in the application of adhesives and attentive to the safety of work:
Adhesives shall be applied as thin as possible, with no missing areas, in even thickness,quickly and elaborately. Also, when jointing the members by compression, the appropriate
440Chapter 12

Prestressed Concrete

treatment is needed in advance to prevent the adhesive from flowing into the ducts.
Some kinds of adhesives may have harmful effects on skin by direct touch. Thus, it isnecessary to protect skin by wearing rubber gloves from being inflamed while working.
(e) To cure and protect members sufficiently after jointing in order to obtain the required
quality:
After precast members are temporarily jointed during the pot life, moderate compressive
stress shall be applied to the joint surfaces to prevent the generation of tensile stress until
hardening of the adhesives. If the temperature of the joint surface after jointing is lower than
expected, it will take a much time to harden the adhesive. Hence, the insulated curing by theappropriate method shall be taken to avoid it. Also, since rainwater may intrude if it rains
immediately after the bonding, the jointed portion shall be protected with sufficient care, bycovering it with sheets, for instance, to avoid adverse influences on the bonding effect.
(2) Members shall be carefully manufactured so as to have exact shapes, dimensions andlocations of ducts and to adhere closely each other. When they are installed in the field, fineadjustments shall be enable so that the member sections and the ducts will fit precisely at the joint
and the prestressing tendons can be easily inserted. If an adhesive is used as the bonding material in
the cantilevering erection in which the members are jointed in succession as they are being
prestressed, it is difficult to adjust the length or direction of the members at the joints as the
thickness of the joints is negligibly thin. Hence the manufacture and installation of members,
especially installation of the first member which is to be used as the basis, shall be done accurately
with particular care. Also, in case when a large deviation in length or direction is predicted, amethod of modifying them shall be planned in advance. Furthermore, members shall be securely
held on shoring to avoid discordance or twisting during the jointing and prestressing.
(3) In case of jointing of ducts, it shall be required to prevent a bonding material from flowing
into the ducts since the inflow has a harmful effect on insertion of tendon and injection of grout. It
is necessary to confirm whether the inflow is in the duct or not after jointing. If any inflow is found,it shall be removed as soon as possible. Also, care must be taken that, if the spaces between
adjacent ducts are not filled with bonding material, the grout may flow into the adjacent ducts.
(4) Temporary shoring for jointing operation shall withstand the dead load of the members, themass of the erective machines and the elastic deformations due to prestressing.
Erection and prestressing sequences prescribed in the design drawings shall be followed strictly.
Since these sequences are determined considering the stress condition of each member at eachphase of work or the statically-indeterminate forces due to prestressing, the members being underconstruction may be damaged or the stress conditions specified for the structure may not appear if
these sequences are unreasonably changed.
(5) The initial defects such as detachments and gaps can easily occur at a joint. Also, a joint canbe a path of water or chloride ions in a long-term even if the elaborate work is done. Waterproofing
shall be applied at the joint with couplings of ducts to prevent a tendon from corrosions. The same
treatment shall be needed for bridge decks that are directly affected by rainwater and de-icing
agents. It is desired that waterproofing is applied to the side and the bottom of bridge, although thechance of penetrations of water and chloride ions is rare except for in seashore area.

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12.6.6.5

Erection(1) Erection shall be carried out safely taking into account the characteristics of themembers and the structure after examining the erection plan.
(2) In cases when an erection method different from that planned at the design stage isadopted, its safety shall be ensured by carrying out a prior examination of stresses anddeformations expected during erection.
(3) Erection shall be carried out, whenever necessary, after safety is ensured throughevaluation of stresses and deformations in each member.

[Commentary] In general, prestressed concrete members are given prestress corresponding to thedead load of the members. Therefore, if the state of the stresses due to the dead load differs greatly
from that being designed because of the modification in the erection method or mishandling in thecourse of the erection work, the balance in stresses may be lost and the prestressed concrete
members may have cracks, or may even break in some. Thus, it is essential to carry out the erection
in compliance with the instructions shown in design documents. In case when the erection shouldbe performed in a different way from that of the design documents, sufficient study shall be
required on the state of stresses and deformations.

12.6.712.6.7.1

Construction of external cable structures
Handling of tendons(1) Tendons shall be transported and stored so that no damaging deformation or otherdamage may be incurred.
(2) Tendons shall be placed in protective tubes so as not to be entangled.
(3) Coated tendons and cables to which anticorrosives have been applied shall bearranged so as not to damage the protective coating or anticorrosives.
(4) Protective tubes and tendons should be placed on appropriate supports under acondition close to the designated cable shape except at the deviator.

[Commentary] (1) Tendons should naturally be transported and stored considering the physicaland chemical properties of coating materials and anticorrosives. In cases where tendons are stored
in hot places, the resin coating the steel is likely to soften. In cold and humid conditions,condensation is likely to corrode the steel.
(2) When arranging tendons, freedom from entanglement of tendons near the anchorage fixture
should be confirmed because the entanglement of tendons not only increases friction but also causes
the cable to fracture near the anchorage fixture.
(3) The thickness of coating of tendons is determined to ensure anticorrosive performance.
Unless the coating is arranged so as not to be subjected to damage, anticorrosive performance is not
ensured. The same is true for cables coated with anticorrosives. Adequate care should therefore be
exercised when arranging tendons. When inserting the steel, the exterior of the coating should be
inspected for damage or peeling. Measures should also be taken to prevent damage to the coating in
442

Chapter 12

Prestressed Concrete

the areas that are likely to interfere with the deviator. Even in the case where damage to the coating
is detected, repair may be applied in the field if the repair can provide the designated anticorrosive
performance.
(4) Arranging protective tubes and tendons in a shape greatly different from the designatedcable shape may not only complicate subsequent handling but also increase the loss of tension.
Protective tubes and tendons shall therefore be arranged in a shape as similar to the designated cable
shape as possible.

12.6.7.2

Assembly and arrangement of anchorage zone

(1) Anchorage fixture in which tendons can be replaced shall be installed so that thepositions of parts may be properly maintained.
(2) Protective caps shall be attached at the end of the anchorage fixture to protect theanchorage fixture and tendons from corrosion.

[Commentary] (1) In systems that adopt a double-tube structure near the anchorage zone andenable the replacement of tendons, a pre-assembled anchorage zone should be attached to theformwork so as to maintain the positions of parts as designated.
(2) External prestressing systems shall be covered with protection cap at the ends, and inside ofthe ducts shall be filled with corrosion inhibitor or be grouted in order to protect the externaltendons and the anchorages from the corrosion. Protection cap should be waterproof and be rustprevention itself.

12.6.7.3

Assembly and installation of deviating devices

At the time of construction at the deviator, it shall be ensured that no tendons arebroken locally due to an error of installation.

[Commentary] The arrangement form of an external cable is determined by the installation
position of anchorage and a deviation device. For this reason, regardless of the arrangement
position size of a deviation device, it shall be arranged with full care of the direction of a continuous
deviation part and anchorage part.
As dense reinforcing bars arrangement is served at a deviation part, it is strictly needed tomaintain the placing space of concrete and the fixing method of a deviation device.
12.6.7.4

Handling of protective tube

(1) During the transportation and storage of protective tubes, appropriate packing for the
tubes shall be conducted considering the properties of materials of the tubes.
(2) When protective tubes are connected, jointed parts shall not be weak points.
(3) When protective tubes are arranged, required space between prestressing steels andprotective tubes shall be kept.
443

Standard Specifications for Concrete Structures-2007, Materials and Construction[Commentary] (1) As protective tubes, polyethylene (PE), polyvinyl chloride (PVC), fiber
reinforced plastic (FRP), polypropylene (PP) or steel tubes are used. Methods of handling protective
tubes should be determined according to the characteristics of respective materials.
(2) For the joints of protective tubes, adhesion, welding, thermal shrinking, clamping or othermethod is adopted. Bonding methods should be selected so that joint zones may be fully resistant to
the pressure of injection of anticorrosives and fully waterproof to protect tendons.
(3) Tendons and protective tubes should be arranged properly using internal spacers or racks sothat anticorrosives may evenly wrap tendons.
12.6.7.5

Control of prestressing

Tension shall be controlled for each external cable to prevent the tension given to theexternal cable from decreasing below the designated level considering the characteristicsof the external cable structure.

[Commentary] In the arrangement of external cables, changes in angle are generally smaller thanfor internal cables and the loss of tension due to friction is smaller. Methods of management using
the coefficient of friction as parameters (12.6.4.3 Commentary) may sometimes be inappropriate.
Then, the readings from load cells should be assumed at a certain level and the variation should beheld to plus or minus 5% of a designated level (Fig. C12.6.2a). Another method involves holding
the readings from load cells and variations to 0 to plus 5% of designated levels because a shortageof tension is of concern when the apparent coefficient of friction is expected to exceed thecoefficient of friction assumed in design (Fig.C12.6.2b). In either case, no trial stressing is generally
carried out on grounds of a small amount of friction loss, and the values shown in Fig. C15.3.2 inthe "Standard Specifications for Concrete Structures: Design" may be used for calculating thetension. In cases where the total variation of cable angle exceeds 30 degrees according to theexisting records, however, trial stressing should be done and tension should be managed using thecoefficient of friction as a parameter.
Stopping line

Absolute upper limit

Control band

Manometer height

Manometer height

Absolute upper limit

Elongation

Stopping line

Control band

Elongationa) ±5% controlb) 0 - +5% control

Fig.C12.6.2 Example of controlling of prestressing

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Prestressed Concrete

Injection of anticorrosives(1) The injection of cement grout shall be planned and implemented as for the grout for
prestressed concrete for internal cables.
(2) The injection of other materials shall be planned and implemented fully identifying
their characteristics.

[Commentary] (2) Other materials include grease, wax and polyurethane. Soft materials inparticular should be used fully considering the effects of their post-injection expansion or shrinkage
due to thermal changes on protection tubes.

12.7

Inspection

12.7.1
12.7.1.1

Material acceptance tests
Prestressing steel

The accepting party shall assume the responsibility for prestressing steel acceptance tests.
The tests should be carried out in accordance with Table 12.7.1 as a standard practice.
Table 12.7.1 Acceptance test of prestressing steel
Type

Item

Prestressing
wires and strands

Quality items
in JIS G 3536

Prestressing bars

Quality items
in JIS G 3109
or 3137

Prestressing steel
other than thosespecified in JIS G Required items
3536, 3109 or
3137

Test or Inspection method
Verification based on a listof test records prepared by
the manufacturer or by amethod specified in JIS G
3536
Verification based on a listof test records prepared by
the manufacturer or by amethod specified in JIS G
3109 or 3137
Verification based on a listof test records prepared by
the manufacturer or by amethod specified in JIS G
3536, 3109 or 3137

Timing andfrequency

Criteria forjudgment

Upon delivery

Compliance with
JIS G 3536

Upon delivery

Compliance with
JIS G 3109 or
3137

Upon delivery

Compliance withspecifications
defined toachieve thedesignated goal

[Commentary] The accepting party conducting acceptance tests means the Owner. Generally,
however, the prestressed concrete contractor conducts tests and the Owner verifies test results. This
holds true also in the acceptance tests for anchorage and connection fixtures (12.7.1.2), sheaths(12.7.1.3) and for adhesives used for connecting precast members (12.7.1.4).
Prestressing steel is generally delivered in bunches of rolls. The certificate of inspection,
symbol indicating the type, nomenclature and manufacturer (or logo) are indicated on the surface ofthe bunch. General acceptance tests involve the visual verification of the brand and type of445

Standard Specifications for Concrete Structures-2007, Materials and Construction

prestressing steel and verification that the type, diameter, size and mass of the prestressing steel arein agreement with the specifications in JIS G 3536 "Prestressing wires and strands", 3109
"Prestressing bars" or 3137 "Small-diameter deformed prestressing bars" based on the lists of test
records prepared by the manufacturer. At the same time, the diameter of the prestressing steel
should be measured using calipers and the appearance should be inspected.

12.7.1.2

Anchorage and coupler

The accepting party shall assume the responsibility for anchorage and coupler
acceptance tests. The tests should be carried out in accordance with Table 12.7.2 as astandard practice.
Table 12.7.2 Acceptance test of anchorage and coupler
Item

Performance items
in JSCE-E 503

Method fortest/inspection
Verification based ona list of test records
prepared by the
manufacturer or by amethod specified in
JSCE-E 503

Timing and frequency

Criteria for judgment

Upon delivery

Compliance withspecifications in “Guidelineof Design and Constructionof Prestressed Concrete”[Commentary] The shapes, performance and service conditions of anchorages and couplers vary
widely depending on the type of anchorage or coupler. It is, therefore, necessary to determine test
methods so that their service conditions and the way of tensile forces can be accurately reproduced.
For this reason, in cases where the performance of an anchorage or coupler is to be tested, it iscommon practice to test the combinations of anchorages and concrete or of anchorages or couplers
and tendons.
Test results obtained must satisfy the conditions listed below.
(a) Test on combinations of anchorages and concrete:
Anchorages must be able to withstand 100% of the rated tensile strength of the tendons.
(b) Test on combinations of anchorages or couplers and tendons:
In the static tension tests that do not involve bonding, the anchoring efficiency ofanchorages or the connection efficiency of couplers must be 95% or more of the rated
tensile strength of tendons. In cases, however, where the anchoring efficiency orconnection efficiency becomes lower than 95% because of a modification made to
tendons but not lower than 90%, new standard values may be set.
The anchoring efficiency and connection efficiency here refer to the percentage of the
maximum tensile load to the rated tensile strength of the tendons.
These tests of anchorages and couplers should be conducted in accordance with the test methods
described in JSCE-E 503 “Method of Performance Test of Anchorages and Couplers for Prestressed
Concrete Construction”.
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Even in cases where neither anchorages nor couplers are used, but materials, such as reinforcing
bars, concrete, grout and auxiliary materials, are used as integral parts of anchoring or connection
systems, equal care must be taken in determining test methods.
Anchorages or couplers, which are used at the locations subjected to large variable stresses due
to permanent variable loads, need to be tested for the fatigue strength under appropriate stressamplitude and cycling loading conditions. In cases where prestressing tendons are to be usedwithout being bonded with concrete, the fatigue strength test is very important.
For the anchorages and couplers, that are covered by the “Recommendations for Design andConstruction of Prestressed Concrete Structures (JSCE)” and that have proven performance, may be
used without conducting this test.
Anchorages and couplers that have undergone corrosion of steel or have been fouled damaged ordeformed while being stored at the construction site for a long period of time must be used only
after their quality is verified through testing even if those anchorages and couplers were in goodcondition when they arrive at the construction site. Damaging steel corrosion here means the loss ofcross section like pitting corrosion. Rust cannot be removed with sandpaper.

12.7.1.3

Sheaths

The accepting party shall assume the responsibility for sheath acceptance tests. The
tests should be carried out in accordance with Table 12.7.3 as a standard practice.
Table 12.7.3 Acceptance test of Sheath
Item
Quality items
regarding leakageof paste

Method fortest/inspection
Verification based ona list of test records
prepared by the
manufacturer or
specified leakage test

Timing and frequency

Criteria for judgment

Upon delivery

No leakage of paste in
the specified method[Commentary] Since sheaths are likely to be stepped on during pre-concreting work andsusceptible to impact by vibrators or other equipment before the concrete placement, they shall bestrong enough to withstand such physical interference. They shall also be rigid and strong enough toretain its shape against the pressure of placed concrete and be sealed sufficiently to prevent the
inflow of cement paste in concrete.
In general, the following tests shall be performed to determine the quality of sheath:(a) Inject cement paste with a water-cement ratio of 50% (Fig. C12.7.1) into sheath specimens
produced in accordance with (i) to (ii) below, and leave for 30 minutes. Water leakage isallowed, but there shall be no leakage of cement paste through the sheath.
[Sheath specimen preparation procedures](i) Specimen for testing resistance to local external force
Place a sheath specimen of length four times its inner diameter with a round steel bar
with a diameter 0.8 times that of the sheath inner diameter inserted onto a flat surface.
Then, apply a short period loading to the sheath using a 9 mm diameter round steel bar
weighing 1 kN placed at its center and perpendicular to its axis (see Fig. C12.7.2).
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Standard Specifications for Concrete Structures-2007, Materials and Construction

If the sheath is made of material that varies significantly in hardness depending on thetemperature, this loading test shall be performed at -10℃, +20℃, and +50℃.
(ii) Specimen for testing resistance to uniform external force
Apply a force of P=100πD2 (N) to a sheath specimen with an inner diameter of D(cm) and a length of 4D in the manner shown in Fig. C12.7.3 at the ambient temperaturefor 10 minutes.
(b) Inject cement paste with a water-cement ratio of 50% into a sheath specimen bent to a radiusequal to 30 times the sheath inner diameter. There shall be no leakage of cement paste
through the sheath (see Fig. C12.7.4).
Cement paste with a waterto cement ratio of 50%

9 mm diameterround steel bar

Load: 1 kN

Sheath specimens produced inaccordance with (i) and (ii)Roundsteel bar

Rubber, clay, etc
Sheath specimen

D: Inner diameter of sheathFig. C12.7.1

Load P

D: Inner diameter of sheath

Sheath test method (a)Fig. C12.7.2 Sheath specimen for testing
resistance to local external force

Loadingplate
10 mm thick sponge
Sheath specimen

Cement paste

Loading plate

Sheath specimen
R: Radius of curvature
D: Inner diameter of sheath

D: Inner diameter of sheathFig. C12.7.3 Specimen for testing resistanceto uniform external force

Fig. C12.7.4

Sheath test method (b)The above tests may be omitted if the sheath has been tested and found suitable for its intended
use by the manufacturer.
In order to ensure the correct injection of grout, the sheaths shall be inspected immediately prior
to the use and concrete placement for defects such as corrosion, grime, scratches, and deformation.
If any defects are found during this inspection, the sheaths shall be repaired or replaced. Damaging
corrosion here means corrosion in which the coefficient of friction with the tendon seems to havevaried greatly.

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Chapter 1212.7.1.4

Prestressed Concrete

Adhesive agents for jointing precast members

The accepting party shall assume the responsibility for conducting acceptance tests foradhesive agents used for jointing precast members. The tests should be carried out inaccordance with Table 12.7.4.
Table 12.7.4 Acceptance test of adhesive agents for jointing precast members
Item
Quality items in
JSCE-H101

Method fortest/inspection
Verification based ona list of test records
prepared by the
manufacturer or
JSCE-H101

Timing and frequency

Criteria for judgment

Upon delivery
Before the commencement ofconstruction work

Compliance with
JSCE-H101[Commentary] Where an epoxy resin bonding agent is to be used for jointing precast members, it
shall conform to JSCE-H 101 “Specification for Epoxy Resin Adhesive in Precast Concrete (forBridge Girders)”. If the bonding agent is used under special conditions or circumstances, it shall betested as required for the properties such as tensile strength at high temperature, tensile strength
when hardening in water, impact strength, compressive Young’s modulus, thermal expansion
coefficient, hardening shrinkage ratio, and water absorption coefficient. Degree of decrease intensile strength at high temperature shall be tested, if usage is for structures and road surfaces withasphalt pavement subject to direct sunlight, because bonding agents tend to lose strength when
exposed to high temperatures, even after hardening. If it is necessary to joint precast members while
they are still wet, the bonding agent shall be tested in advance for any decrease in tensile strength
when hardened in water.
It is also recommended to check in advance whether the form releasing agent used in the
production of the precast members is compatible with the bonding agent and has no detrimental
effect on the bond strength.
Tests on epoxy resin bonding agents may be difficult to perform on site, since they generally
require special apparatus and measurement techniques. For this reason, some of the tests may beomitted if the review of the test data issued by the manufacturer reveals no problems, or if thebonding agent is used within a reasonably short period of time after delivery to the site, or if the
major factors (e.g., construction period, construction conditions, and structure size) arecomprehensively reviewed.
However, since properties of epoxy resin bonding agents such as workability before hardening
are greatly affected by temperature, it is necessary to carry out a test to verify that the bonding agent
is suitable for use under the prevailing temperature fluctuations. Tests shall also be performed if thebonding agent has been stored for a long period of time before use, since the properties of suchmaterials may change with storage time.

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12.7.2

Inspection of grout

12.7.2.1

Acceptance test of grout

The accepting party shall assume the responsibility for conducting acceptance tests forgrout. The tests should be carried out in accordance with Table 12.7.5.
Table 12.7.5
Item

Method fortest/inspection

Flowability

JSCE-F 531

Bleeding Ratio

JSCE-F 532

Volume change
ratio

JHS 420

Compressive
Strength

JSCE-G 531

Chloride
Content

Using a reliable
test method, andcarried out by
an organizationof repute.

Acceptance test of grout
Timing and frequency

Criteria for judgment

Prior to grouting and when
variation in quality is found:
once per day or more

Falling within the range specified
in the construction plan
Less than 0.3%
0.0% (24 hours later)

Prior to grouting and when
variation in quality is found:
once per day or more

-0.5% - +0.5%

30N/mm2 or more at 28 days
Prior to grouting and when
variation in quality is found:
once per day or more

Should be 0.08% or less of cement
weight[Commentary] The accepting party conducting acceptance tests means the Owner. The
prestressed concrete contractor, however, generally conducts tests and the Owner verifies test
results.
Grout quality varies considerably depending on conditions such as the materials used, mixer
capability and temperature. Prior to grouting, therefore, it is necessary to conduct tests on
flowability, bleeding ratio, expansion ratio and compressive strength under conditions designed toreproduce the same as actual conditions as much as possible. Since the grout quality also varies
slightly depending on the site conditions, sufficient testing is needed for management purposes.
In actual construction, at mix proportions at which it has been verified that the bleeding rate andthe rate of volumetric change are in the designated range, the water-cement ratio that is obtained
from the mass of unit volume and enables quick interpretation of results may be used for quality
inspection instead of the bleeding rate and the rate of volumetric change generally inspected before
injection on a daily basis. Then, specimens should be prepared in accordance with JSCE-F 506"Method for preparing cylindrical specimens for compressive strength tests of mortar or cement
paste", and the water-cement ratio estimated by measuring the mass should be plus or minus 1.5%of the recommended range for water-cement ratio specified for each admixture and be in theserviceable range.
The variance occurs between the estimated water-cement ratio obtained from the mass of unit
volume and the specified water-cement ratio because of the variations of the mass of packed cement,
mismeasurements or measurement errors, too much or too little mixing time and the mixing of air.
In the preliminary mixing, the mass of packed cement should be measured, water should be
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Prestressed Concretemeasured to achieve the specified water-cement ratio, the air content of the grout for prestressed
concrete mixed accurately should be measured and a reference value based on the air content shouldbe specified. Measuring the mass of packed cement, water and air content in the field with a proper
frequency is also effective for correcting errors. For details, refer to the "Design and Construction
Guidelines for Grout for Prestressed Concrete" of the Japan Prestressed Concrete Engineering
Association and the "Construction Manual for Grout for Prestressed Concrete and Pregrouted
Prestressing Steel 2006 (revised edition)" of the Japan Prestressed Concrete Contractors
Association.
In the inspection of chloride ion content, a testing method appreciated by a reliable organizationand for which accuracy has been verified by the Japan Institute of Construction Engineering or anequivalent third-party organization should be adopted.

12.7.2.2

Inspection of grouting(1) The Owner shall assume the responsibility for conducting inspection prior to
grouting. The tests should be carried out in accordance with Table 12.7.6 shown below.
Table 12.7.6 Inspection prior to grouting
Item
Preparation ofMaterials

Method fortest/inspection
Visual inspection,
Number of Cement
Bags

Production
Facility
and Labor
Charging ofmaterials

Visual inspection

Mixing Time

Stop watch

Timing and frequency

Before and during execution

Criteria for judgment

Compliance with theconstruction plan

During execution(2) The Owner shall assume the responsibility for conducting inspection during
grouting. The tests should be carried out in accordance with Table 12.7.7 shown below.
Table 12.7.7 Inspection of grouting process
Item
Facility and Labor

Method fortest/inspection

Timing and frequency

Criteria for judgment

Visual inspection

Before and during execution

Compliance with theconstruction plan

Flow meter

Total volume

The amount applied is
as predetermined

Grouting Method
Volume(3) The Owner shall assume the responsibility for conducting inspection after grouting,exhaust and discharge. The tests should be carried out in accordance with Table 12.7.8
shown below.

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Standard Specifications for Concrete Structures-2007, Materials and Construction

Table 12.7.8 Inspection after grouting

Item

Method fortest/inspection

Timing and frequency

Criteria for judgment

Treatment of
openings after
Grouting/Exhaust/
Discharging

Visual inspection

Upon completion of grouting

Compliance with theconstruction plan(4) In the case that the production or grouting process is found to be unacceptable
during the inspection carried out prior to the commencement of construction, appropriate
corrective measures, such as improvement in the systems, reassignment of labor, orchanging the methods, should be taken to ensure that the predetermined requirements are
met. In the case that the grouting has already been completed, other appropriate measures
shall be taken to ensure that the predetermined requirements are met.

[Commentary] (4) Grouting inspection methods include the direct and nondestructive inspection
methods. In the direct inspection method, the concrete cover is directly removed to inspect the groutin the sheath, hence, this is the most reliable method for inspection. However, since only one crosssection of prestressing tendons can be observed in this method, in order to inspect the degree ofcompleteness of continuous grouting, it is necessary to conduct inspection at two or more locations.
In this case, care must be taken not to damage prestressing tendons when drilling holes.
Nondestructive inspection methods are inspection methods that do not damage the members.
Nondestructive inspection methods that have been proposed include the following:(i) X-ray inspection method
In the X-ray inspection method, images are taken by using the principle that when X-ray
passes through a substance, the intensity of X-ray transmitted through the substance varies
with such factors as the type and thickness of the substance. The methods of using X-ray
film, such as a photosensitive recording medium (film method), the method of using an“imaging plate” (IP) and processing images on a computer (IP method), are already in use.
(ii) Sounding methods
In sounding methods, a concrete member, which is used for inspection, is impacted, or
ultrasonic pulses are transmitted through the member, and then the response of the member
is analyzed. Techniques using hammer impacts and ultrasonic pulses have been developed.
If a part of a member is found that there is some defect due to grout, regrouting shall be
performed. Materials used for regrouting must meet the following requirements:• High flowability and penetration• High rust resistance• Strength according to its design requirement• High workability
For materials used for regrouting, the ability to penetrate fine spaces is important.
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Prestressed Concrete

Materials used for regrouting should be cement materials (inorganic materials).
Cement materials include the following:• Fine-grained cement• Fine-grained cement + polymer• Cement + calcium sulfoaluminate• Cement + aluminum + sulfonate compounds
In general, the cement materials form an alkaline zone around prestressing tendons and suppress
the progress of steel corrosion even if penetration is not complete.
No non-cementitious materials (organic materials) should be used for re-injection because thepotential of hydrogen is low and the passive film on the steel surface is likely to be unstable in thecase of incomplete filling and because there may occur a gap from the area where grout is applied
for prestressed concrete in the vicinity.
12.7.3

Inspection of execution

12.7.3.1

Inspection of sheaths, protecting tubes and tendon arrangements

The Owner shall assume the responsibility for conducting inspection of sheaths,
protecting tubes and tendon arrangements. The tests should be carried out in accordancewith Table 12.7.9 shown below.
Table 12.7.9
ItemType/Diameter/
Quantity
Anchorage
MethodLayoutInspection of sheaths, protecting tubes and layout of tendons

Testing method/
Inspection method
Visual inspection，
measurement of
diameter

Period/Frequency

Criteria for judgment

After layout

Compliance with design documentation
No potential deformation or disturbanceduring casting concrete

Visual inspection

Visual inspection，
measurement oflocation

Before casting
concrete

Tolerance: As specified in design
documentation. In cases when the distance
between the center of the tendon and theedge of concrete is less than 1m, thetolerance shall be ±5mm, for 1 m or
more 1/200 or less of the size of concrete
or ±10mm whichever is smaller.

[Commentary] The purpose of the inspections is to ensure that the structure will satisfy thequality requirements. Since, in terms of structural safety, prestressing tendons are the mostimportant component of prestressed concrete structures, they shall be carefully inspected. However,since prestressing tendons are inserted into ducts created in the concrete by embedding sheaths andprotective conduits, the accuracy of tendon installation and the ability to induce the specified stresson the tendons are determined by the accuracy of sheath and conduit alignment. Furthermore, thestructural integrity of the interface between tendons and concrete, and thus the long-term durabilityof the structure, is dependent on whether grout is properly injected into the sheaths and protective
conduits. This means that the sheaths and protective conduits also indirectly play an important rolein the safety of the structure, and the inspections shall be performed with the consideration of this453

Standard Specifications for Concrete Structures-2007, Materials and Construction

crucial function.
In general, the most desirable approach to structure inspections is non-destructive inspection
after completion. However, given the imperfect inspection techniques currently available, the only
practical choice is to use the results of tests carried out before concrete placing to evaluate thecharacteristics of the completed structure. This approach is based on the assumption that theconditions prevailing, when the inspections are performed, remain unchanged after concreting. Thismeans that it should be confirmed during the inspections that all components and materials willremain free from deformation and displacement, and they will maintain in the same condition evenif subjected to disturbances during concrete placement.
Although it is desirable that a structure should follow the drawings as accurately as possible,
discrepancies may arise due to various constraints and site conditions. To cope with this, certainalignment tolerances are usually incorporated into structure designs. If such tolerances (allowable
tolerances) are specified in the drawings, the inspections must include the checks to determine
whether the components and materials have been installed in such a manner that they are satisfied.
When the alignment tolerances are not specified in the drawings, Table 12.7.9 should be followed.

12.7.3.2

Inspection of anchorage and coupler assembly and arrangement(1) The Owner shall assume the responsibility for conducting inspection of anchorage
and coupler assembly and arrangement. The tests should be carried out in accordancewith Table 12.7.10 shown below.
(2) It shall be confirmed that the arrangement of the couplers is such that the concrete
close to the perimeter is not adversely affected by the tension of tendons.
Table 12.7.10
ItemType/Diameter /Quantity
Anchorage
MethodInspection of anchorage and coupler assembly and arrangement

Testing method/
Inspection method
Visual inspection，
measurement of diameter

Period/Frequency

Criteria for judgment

After layout

Compliance with Design
Documentation

Visual Inspection

LayoutMeasurement using scales
and visual inspection

Arrangement ofReinforcing Bars

Visual inspection

Prior to casting
Concrete

After layout

No potential deformation or
disturbance during casting concrete
Tolerance: As specified in design
documentation or, if the distance
between the center of a tendon andthe edge of concrete is less than 1m,
the tolerance shall be ±5mm, for 1
m or more, 1/200 or less of the sizeof concrete or ±10mm, whicheveris smaller (standard)Compliance with design
documentation[Commentary] (1) If allowable tolerances for the installation of anchorage devices and couplers
are not given on the drawings, in general, Table 12.7.10 should be followed.
Anchorage devices and couplers are usually tested for performance in combination withreinforcement bars under specified conditions. Therefore, the inspections shall determine whether
the actual installation completely matches the conditions guaranteed by the test.
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Even if anchorage devices are properly placed, they may not fulfill their specified function if
the concrete surrounding the anchorage has defects. Therefore, the inspections shall determine not
only whether the installation of the anchorage devices is correct, but also whether the reinforcement
bars and other materials are arranged in such a way that the concrete surrounding the anchorage isprevented from any defects that may occur.
(2) In some designs, the couplers are free to move when prestress is applied to the tendons. With
such designs, if movement is restricted, not only is application of the specified prestress inhibited,
but there may also be adverse effects on the concrete surrounding the tendons. For this reason, theinspections shall determine whether the adequate space (duct) is provided to allow the movement of
the couplers.

12.7.3.3

Inspection of opening layout for grouting, exhaust and discharging

The Owner shall assume the responsibility for conducting inspection of opening layoutfor grouting, exhaust and discharging. The tests should be carried out in accordance with
Table 12.7.11 shown below.
Table 12.7.11

Inspection of opening layout for grouting, exhaust and discharging

Type/Diameter /Quantity

Testing method/
Inspection method
Visual inspection,measurement of diameter

Anchoring Method

Visual inspection

LayoutVisual inspection

Item

Period/Frequency
After layout

Prior to casting
concrete

Criteria for judgment
Compliance with theconstruction plan
No potential deformation or
disturbance during casting
concrete
Compliance with theconstruction plan[Commentary] The layout of prestressed concrete grout injection, air exhaust port, and grout
discharge port plays a very important role in injecting grout into the ducts and allowing air bubbles
to escape. The inspections shall determine whether the type, diameter, number, and location ofgrout hose to be used are in conformity with the work plan. The inspections shall include checking
for vent looseness or damage, which may cause the vents to come away during concrete placement,
and whether the vents will maintain functionality as grout injection, air exhaust port, and grout
discharge port.

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Chapter 13

Composite Steel-Concrete Structures

CHAPTER 13 STEEL-CONCRETE COMPOSITE STRUCTURES

13.1 General
13.1.1 Scope
This chapter presents the standards for filling concrete and for producing, transportingand erecting steel members that are required for meeting the construction andperformance requirements for structures during the construction of steel framed
reinforced concrete members, concrete-filled columns and sandwiched members, all ofwhich are of steel-concrete composite structure.

[Commentary] This chapter refers to the construction described in Chapter 16 Steel-Concrete
Composite Structure of the Standard Specification for Concrete Structures, "Design: Main Text".
For matters concerning the filling of concrete, refer to the "Design and Construction Guidelines for
Composite Structures (draft)" and "Performance Check Guidelines for Composite Structures(draft)". For matters concerning steel members, refer to the "Steel Structure Design Guidelines","Standard Specifications for Steel-Concrete Composite Structures", "Specifications for Highway
Bridges: Part II Steel Bridges" (Japan Road Association).
This Specification takes up:
Steel reinforced concrete member: A structure consisting of such steel frames as H beams,
Warren truss members in reinforced concrete to resist external forces by frames and concrete. A
structure with main bars and anti-shear reinforcing bars around steel frames is intended here. For
construction-related matters not explained herein, refer to “Standard for Designing Railway
Structures with Explanation - Composite Steel and Concrete Structures” (Railway TechnicalResearch Institute).
Concrete-filled steel column: A structure consisting of a circular or square pipe filled withconcrete. For construction-related matters not explained herein, refer to “Standard for Designing
Railway Structures with Explanation - Composite Steel and Concrete Structures” (Railway
Technical Research Institute).
Sandwich member: A structure consisting of two plates linked using steel reinforcements andfilled with concrete. For construction-related matters not explained herein, refer to “Design Codefor Steel-Concrete Sandwich Structures (Draft)”.

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13.1.2 General(1) When constructing steel-concrete composite structures, examinations should bemade in advance of the production, transport and erection of steel members and of thefilling of concrete, and adequate construction plans should be prepared.
(2) Steel-concrete composite structures should be constructed properly in accordancewith the construction plans.
(3) Inspections should be conducted as required in respective construction phases forstructures to meet the designated performance requirements.

[Commentary] (1) When constructing composite steel-concrete structures, general parameters
and the materials and parts, production methods (original size, cutting and processing, welding),
production process, temporary assembly, transport, erection and connection of steel members
should be examined. For concrete, the filling capacity and construction methods should be
examined.

13.2 Materials
13.2.1 Steel(1)Qualities of steel used, such as steel plates, shape steel, steel pipes and re-bars
should conform to the quality specifications provided in JIS or JSCE Standards, etc.
(2)Jointing materials such as welding materials, high-strength bolts, etc. should
conform to JIS, etc.

[Commentary]used.

For composite steel-concrete structures, materials of verified quality should be

The materials used for composite steel and concrete structures refer to concrete, steel
reinforcements, and jointing materials.
(1) The standard materials of such structural steel as plates and shape steel conform to JIS G
3101 “Rolled Steels for General Structure”, JIS G 3106 “Rolled Steels for Welded Structure”, or JIS
G 3136 “Rolled Steels for Building Structure”.
The standard pipes conform to JIS G 3444 “Carbon steel tubes for general structural purposes”,
JIS G 3466 “Centrifugally Cast Steel Pipes for Welded Structure”, and JIS G 5012 “Carbon Steel
Pipes for Ordinary Piping”.
The standard type of stud for shear connector conforms to JIS B 1198 “Headed Studs”.
Reinforcement complying with Section 3.6.1 of "Materials and Construction: Construction
Standards" should be used as a standard practice. When welding the reinforcement to steel plates or
steel sections for shear connectors, due care should be exercised to provide the quality of welding
described in this chapter.
To enhance the composite action with concrete, such composite structural steel as checkered
plates, ribbed pipes, and H-shape steel with indentations have been developed. Whether it isappropriate to use these steel may be judged by testing or from past data.
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Composite Steel-Concrete Structures(2) The welding materials are prescribed in JIS Z 3211 “Covered Electrodes for Mild Steel”, JIS
Z 3212 “Covered Electrodes for High Tensile Strength Steel”, JIS Z 3351 “Submerged Arc Welding
Solid Wires for Carbon Steel and Low Alloy Steel”, and JIS Z 3352 “Submerged Arc Welding
Fluxes for Carbon Steel and Low Alloy Steel” and the high-strength bolts are prescribed in JIS B
1186 “Sets of High Strength Hexagon Bolt, Hexagon Nut, and Plain Washers for Friction Grip
Joints”. Torcia high-strength bolts now very popular are prescribed not in JIS, but in “Set of Torcia
High-strength Bolt, Hexagon Nut, and Plain Washer for Friction Jointing” (Japan Road Association).
Therefore, this standard may be used instead.

13.2.2 Concrete(1) Concrete should have designated filling capacity so that concrete and steel are inmonolithic form and meet the designated performance requirements.
(2) In cases where compaction is difficult between steel plates or verifying the inside is
impossible as for sandwiched structures and concrete filled columns, self-compactiblehigh fluidity concrete should be used as a standard practice.

[Commentary] (1) In composite steel-concrete structures, selecting concrete quality so as toensure integrity between concrete and steel is important. The filling capacity of concrete should
therefore be determined properly according to the structural format, dimensions and concrete
construction method.
If the relationship between concrete compactability, flowability, and segregation resistance isclear, the concrete compactability can be represented by flowability and segregation resistance.
The concrete flowability is represented by a slump or slump flow. The segregation resistance isevaluated from that in a static state expressed by a bleeding rate and from that when the concrete
moves. If highly flowable concrete is used, the segregation resistance when the concrete moves canbe expressed with the flow arrival time and the efflux time.
The concrete compactability of a composite steel and concrete structure depends greatly on
structural conditions (structural form, shape, and dimensions of a structure or member), concreteconditions (materials, mixing, consistency of fresh concrete, and bleeding characteristic), andconstruction conditions (concrete placement method). Composite steel and concrete structures mustbe filled with concrete in order to prevent detrimental voids (defective compacting) between theconcrete and steel. However, voids tend to occur under the upper or lower flanges of a steel framein steel reinforced concrete, under a diaphragm in a concrete-filled steel column, and under theupper plate of a sandwich structure. In order to eliminate these defects, concrete compactability
must be set appropriately. Also, whether the required concrete compactability is achieved or not
must be verified based on past data or by concrete compacting test and compactability analysis.
Even if concrete fills properly, bleeding occurs in ordinary concrete and a gap of a few
millimeters may occur in places where bleeding water is retained. When using ordinary concrete,
therefore, corrective construction measures should be taken by injecting shrinkage compensatingmortar or equivalent paste in the gaps created by bleeding, or the structure should be designed tomeet the designated performance requirements.
(2) In cases where compaction is difficult between steel plates or verifying the inside is
impossible as for sandwiched structures and concrete filled columns, there is a concern thatdamaging voids (that cannot be filled completely) may remain between concrete and steel.
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Self-compactible high fluidity concrete should be used. When using high fluidity concrete, refer to
Chapter 7 High Fluidity Concrete.
However，if the space surrounded with steel plates is large enough for a worker to enter forconcrete placement or if a work method to secure concrete compacting is established, the concrete
compactability may be set in the same way as for ordinary reinforced concrete or steel reinforced
concrete.
Even in cases where self-compactible high fluidity concrete is used, autogeneous shrinkage ofconcrete sometimes causes slight delaminations from steel in large cross section. The gaps createdby delaminations are small, less than 1 mm. Considerations should be made in the design phase toensure that the structure meets the designated performance requirements even in case ofdelaminations, or it should be verified in the design phase that delaminations have only limited
effects. In cases where injection is required in small delaminations, injecting mortar is difficult.
Shrinkage compensating paste should be used.

13.3 Production of Steel Members
13.3.1 Processing of steel(1) In the processing of steel, the mechanical properties required in design or otherperformance requirements shall be satisfied. High strength bolt holes should beprocessed so that they may be of such a quality that the design joint strength may
develop.
(2) For easy compacting, steel members shall have concrete placing holes and ventholes arranged appropriately.
(3) Before production starts, a full-size drawing or the equivalent shall be prepared toconfirm the basic shape and the existence of obstacles in production.
(4) In the plank layout of main members, in principle, the main stress direction on eachmember shall in general coincide with rolling direction.
(5) For marking the lines on the steel plate, in principle, a chisel or a punch should not
be used where a tensile stress is large or a repeated load is applied.
(6) In principle, main members shall be cut by automatic gas cutting. Each cut crosssection, processed edge surface or chipped surface shall satisfy the prescribed quality.
(7) In cases when there is shoulder-down, warp or uneven at the cut line, it shall befinished flatly by edge polishing or grinder finishing.
(8) A drill or both a drill and a reamer should be used for boring holes of specified
diameters in a main member. However, a punch may be used for boring holes in a board
less than 12 mm thick for the secondary member.
In cases when boring bolt holes of specified diameters in a main member before
tentatively assembled, in principle, template should generally be used except when an NC
punching machine is used.
(9) The cold bending of a main member should be processed with due care regarding459

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Composite Steel-Concrete Structures

the deterioration of toughness and cracking caused after the processing.

[Commentary] (2) When holes in steel members are made and followed by welding it isnecessary to confirm that there is no structural problem.
(3) The design drawing also shall be checked to ensure that the concrete placing holes and thevent holes are arranged appropriately and that site welding is minimized. The basic shape before
production and problems during production are checked by life-size fabrications on the floor orusing numerical control (NC).
(4) In general, the mechanical properties of steel plates do not differ greatly between the rolling
direction and the rolling perpendicular direction about the tensile strength and yield point. However,
the elongation is smaller by 10 to 15％ and the squeeze smaller by 5 to 15％ in the direction
perpendicular to rolling. Also, since the Charpy impact value in the direction perpendicular torolling may be about half that in the rolling direction, the main stress direction and the rolling
direction shall basically be matched for the plank layout of a main member.
(6) Plates are cut by gas cutting or shearing. To ensure high-quality cut sections, main members
shall basically be cut by auto gas cutting. However, a filler, a tie-plate, a steel section, a gusset plateof 10 mm or less in thickness, and a stiffener may be cut by shearing.
(8) For the diameters, diameter tolerances, penetration ratios, and stopping ratios of bolt holes,“Standard for Civil Engineering Works” (Japan Railway Construction Public Corporation) and“Specifications for Highwaybridge with Explanation II - Steel Bridges” (Japan Road Association)
shall be referred.
(9) Cold bending may lower the toughness of steel or cause them to crack. For the cold bendingof main members, therefore, the internal diameter shall be basically 15 times the plate thickness ormore to prevent great local strains. However, the internal diameter may be seven times or five times
the plate thickness or more for steel reinforcements whose results of the Charpy impact test
prescribed in JIS Z 2242 “Method of impact test for metallic materials” satisfy the conditions given
in Table C13.3.1 below and chemical components do not contain nitrogen more than 0.006％. For
cold bending in the rolling perpendicular direction, the Charpy absorbed energy value in the
direction perpendicular to rolling applies.

Table C13.3.1

Tolerance of cold bending radius against Charpy absorbed energy

Internal radius of cold bending
Charpy absorbed energy：J
150 or more
Seven times the plate thickness or more
200 or more
Five times the plate thickness or more
The test temperature, the number of test samples, and the sampling position for
the Charpy impact test conform to JIS G 3106 or JIS G 3114

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13.3.2

Factory welding(1) In order to satisfy the required joint performance, factory welding shall be done.
(2) For factory welding, the items shall be described in a work plan
(3) Factory welding must be done indoors or in a similar environment.

[Commentary] (1) This article gives the minimum necessary items, with respect to welding, thatshould be described in a construction plan and confirmed at execution. In general, welded joint
performance is not only determined by the indication of a welding symbol but is also affected
greatly by the metallurgical properties related to execution and the degree of existing defects. These
items require due care at work. Verifying the following points is important to the satisfaction ofdesignated joint performance requirements.
(a) Type and characteristics of a steel(b) Welding method, open edge shape, and type and characteristics of a welding material(c) Qualifications for welding engineers (refer to JIS Z3801 "Standard qualification procedure
for manual welding technique" and JIS Z3841 "Standard qualification procedure for semi-automatic
welding technique".
(d) Welding environment and facilities(e) Shape of joint (groove), Processing of steel pieces to be joined, assembling accuracies(f) the cleanness and Dry state of a section to be welded(g) Drying condition of a welding material(h) Welding conditions and order(i) Other points to remember(2) The following items should be described in construction plans concerning welding as aminimum.
1. Qualification of a welder
2. Welding test
3. Assembling method of work piece and accuracy in combination
4. Assembly welding (Temporary welding)
5. Cleaning and drying of member before welding
6. Selection and charge of welding materials
7. Preheating
8. General notes on welding work
9. Inspection of welding
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10. Attachment of hangers and apparatus for erection
11. Defect repairing method
12. Strasin release method, etc.

13.3.3

Temporary assembly, assembly symbol and transportation(1) For temporary assembly, appropriate supports should be set up to make eachmember free from stress.
(2) Before transportation, assembly symbols shall be marked on each member. If amember having 5 tons or more in weigh, its weight and center of gravity shall be marked.
(3) Members should be transported carefully not to damage them or to prevent salt
adhesion on the way.

[Commentary] (1) The purpose of temporary assembly is to check the shape and dimensions ofeach produced member, the status of jointing between members, the assembled status, the welded
status, and disturbances to site erection. If a method different from temporary assembly can ensure
inspections of equivalent precision, temporary assembly may be performed partially or totallyomitted.
As a rule, members shall be assembled temporarily with no stress in individual members. If thejoints of temporary assembly can be reproduced at the erection site, the specified shape can beobtained. However, due to the specific requirements of certain erection methods, it may not be
possible to support a member in a stress-free arrangement. In such a case, an appropriate temporary
assembly method shall be selected in consideration of the design and the erection method.
(2) Assembly symbols, masses, and gravity centers are usually indicated by painting. Even if theunit mass is less than 5 tons, the mass and the center of gravity should be indicated in the casewhere the member is of a complicated shape.
(3) Care should be exercised not to damage members during loading, unloading and transport.
Special care is required in particular in cases where field welding is involved or where chloride
adhesion is expected during offshore or coastal transport.

13.4
13.4.1

Erection of Steel Members
Erection

Steel members shall be erected in accordance with the method and the procedure ofconstruction determined in design. If an erection method different from that planned at thedesign stage is adopted, safety shall be insured by reexamining the stress anddeformation to be expected during the erection.

[Commentary] For construction methods and procedures that differ from those originallyprescribed, it is necessary to be considered safety before erection because stresses due to dead loads,
such as those of steel reinforcements and pre-hardened concrete, may change drastically, causing
such problems as concrete cracking and steel frame buckling or deformation.
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13.4.2

Temporary placement and assembly of steel members(1) In the case of temporary placement of steel members at the construction site, themembers shall be placed to avoid contact with the ground. For long-term temporarystorage, appropriate measures shall be taken to prevent contamination, damage, rusting,and deformation.
(2) Members shall be assembled according to the specified assembling order.

[Commentary] (1) Special care must be taken to prevent toppling because a temporary
installation place may not always be topographically flat.
(2) When assembling members, adjust the positions of high-strength bolt holes by using
temporary tightening bolts and drift pins, and then tighten the high-strength bolts. Since members
may be damaged and slightly deformed during transportation, it is necessary to take great care notto produce root gaps between members.
13.4.3

Jointing using high-strength bolts(1) Contact surfaces of the both work pieces to be jointed shall be treated to achieve a
0.4 or greater of slip factor except for bearing connection.
(2) Table 13.4.1 gives the standard values of the axial forces for bolt tightening.
Table 13.4.1 Axial force for bolt tightening
Nominal diameterof screw

Axial Force for Bolt Tightening (kN)
Ｆ8Ｔ

Ｓ10Ｔ, Ｆ10Ｔ

Ｍ 20

144

178

Ｍ 22

178

221

Ｍ 24

207

257

(3) Bolts shall be fastened as follows:(a) For the full tightening of a Torcia type high-strength bolt, a dedicated tightening
machine shall be used.
(b) For the tightening of a high-strength hexagonal bolt by the torque method, thetightening torque shall be adjusted to apply the axial force for bolt tightening equally toeach bolt.
(c) In principle, the axial force should be applied to a high-strength hexagonal bolt by
turning the nut.
(4) Bolts should be tightened sequentially beginning from the one at the center of aconnection plate, then this procedure shall be repeated again. After initial tightening, inprinciple, bolts, nuts, and washers should be marked in order to find out easily thetightening errors and co-turning.
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Composite Steel-Concrete Structures(5) In the case when both welding and high-strength bolt friction jointing are used
together, in principle, a high-strength bolt should be tightened after welding is completed.

[Commentary] (1) In the design of friction jointing, the slip strength of a joint is calculated withthe slip factor on the joint surface as 0.4. Therefore, a joint surface must be processed to make its
slip factor 0.4 or more. The slip factor here means a kind of coefficient of friction but is adopted
here because the term is used in previously published standard documents.
Up to the present, making a joint surface rough by removing black rind is known to produce 0.4
or greater slip factor. Even when this kind of processing is done at shop production, it is difficult tomaintain this status until jointing at site. The joint surface is often rusty, greasy, or dusty. Therefore,
it is important to clean the joint surface well immediately before jointing at site.
Bolt tightening must be made to connect members with connection plates.
(2) It is a standard to increase axial force for tightening bolt at execution by 10% from thedesign axial force when considering the dispersion of torque coefficient, the creep, the relaxation,and the dispersion of slip factor.
A Torcia high-strength bolt produces a tightening torque when an axial force twists and breaks
the rupture groove at part of the bolt. This bolt is produced with a purpose to carry the axial force
for tightening bolt. Therefore, setting the bolt itself will ensure a axial force equivalent to that for ahigh-strength hexagon bolt.
“Specifications for Highway Bridges, Part II Steel Bridges” (Japan Road Association) prescribesthat the average axial force for tightening bolt of Torcia high-strength bolts at room temperature (10to 30C) shall be within the range in Table C13.4.1 below when five samples taken randomly fromone production lot are tested.
Table C13.4.1

Average axial force for tightening bolt at room temperature (10 to 30C)

Set

Screw nominal
diameter
M 20

Average of axial forces for tightening
bolt in a set from one production lot: kN
172～202

S10T

M 22

212～249

M 24

247～290(3) A Torcia high-strength bolt has its pin tale cut by a certain tightening torque. For fulltightening, a special tightening device for Torcia high-strength bolts is necessary.
High-strength hexagon bolts are jointed roughly by the torque method and the turning-nut
method depending on the control of tightening bolt axial force. This article prescribes the torquemethod that is frequently used. In the torque method, a bolt is basically tightened by turning its nut,
because the torque coefficient of a bolt set is specified for nut turning. If it is inevitable in aconstruction procedure to turn a bolt head, it is necessary to check the value again. Prior to
execution, an appropriate tightening torque must be selected to reach the standard bolt axial force.
The bolt tightening machine and measuring instruments must be inspected at appropriate
timings to check their precisions.
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Standard Specifications for Concrete Structures-2007, Materials and Construction(4) If bolts at a joint are tightened from outer edge, the connection plate is lifted and does notconnected tightly. To prevent this problem, the bolts shall be tightened from the center to the edge.
If each bolt is tightened with the required axial force, the first tightened bolt tends to become
loose. As a rule, each bolt shall be tightened in two steps. For the initial tightening, about 60% of
the axial force for tightening bolt given in Table 13.4.1 is recommended.
(5) As a rule, bolts shall be tightened after welding to reduce welding constraints and to prevent
deformation by welding from lowering the slip strength. When tightening high strength bolts after
welding, deformation due to welding should be prevented by temporarily tightening the bolts or
attaching restraining materials during welding.
Also, for welding after the tightening of high-strength bolts, therefore, the influences of
constraints must be considered.

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13.4.4Composite Steel-Concrete Structures

Welding in construction site(1) For the site welding, it is necessary in advance to examine the effects of shrinkage,
deformation, constraints, and etc., which accompany the welding, on the overall and detailstructures to be welded(2) Notes on the site welding work should be the same as those given in Section 13.3.2.

[Commentary] Site welding described in this article means welding for site jointing during
erection.
The checking items for execution of site welding are in accordance with Section 13.3.2.
However, site welding generally requires stricter control than shop welding in factory because thegroove accuracy, groove cleaning, drying, fluctuation of secondary current, and drying of welding
materials are difficult to maintain in good condition, compared with shop welding in factory.
For site welding, the side welding method and measures against anticipated on-site deformationmust be determined at the stage before factory production and must be reflected in factory
production and site welding. The relationship between the bolt tightening method or bolt hole sizeand shrinkage, and how to create the designated shape of the welding plane at the end of themember should be considered in the phase of production in plant.
If weather conditions on the welding site are as listed below, welding shall be avoided toprevent welding defects, except when the working conditions for welding can be set with awindbreaker or a pre-heater.
1) Raining or case when rain is anticipated during execution2) Immediately after raining
3) Strong wind4) Temperature of 5C or below

13.5 Concrete Construction(1) Concrete shall be placed and compacted carefully to prevent imperfect filling
between the concrete and steel.
(2) When using self-compactible high fluidity concrete in a bulkhead section, a closed
space encircled by steel plates, the concrete should be placed continuously as a standardpractice.

[Commentary] (1) Steel reinforced concrete tends to have voids under the upper or lower flangesof a steel member in a beam, at a joint between a column and a beam, and at a splice. To preventthese defects, make concrete overflow through the air vents at concrete placement and compacting
to ensure full compacting and also take the measures such as followings.
(a) For a beam, place concrete from one side of the web of steel beam while ensuring fullcompaction. After checking the full compacting of concrete under the flange, start placing concrete466

Standard Specifications for Concrete Structures-2007, Materials and Construction

on the other side.
(ii) In a column-beam connection, concrete placement should be suspended at the bottom of thebeam, concrete should be fully compacted and additional concrete should be placed from two or
more points on the side of the column. Then, concrete should be fully compacted.
In composite steel-concrete structures, steel arrangement and concrete-steel contact conditions
are considerably different from those in ordinary concrete. The quality and filling method of
concrete should be fully examined in the construction planning phase.
(2) In cases where compaction is difficult between steel plates or verifying the inside is
impossible as for sandwiched structures and concrete filled columns, self-compactible high fluidity
concrete should be used as a standard practice. Then, continuously placing concrete in a bulkhead
section, a closed space, is important. Self-compactible high fluidity concrete is greatly different
from ordinary concrete. In order to make best use of its characteristics, the rate and locations ofplacement should be selected properly.

13.6

Inspection

13.6.1

GeneralIn order to verify that the completed structure meets the designated performancerequirements, effective and economical inspection plans should be prepared and theaccepting party should assume the responsibility for conducting necessary inspections ineach construction phase.

[Commentary] Since the construction of a composite steel and concrete structure requires steel
member production and erection as well as concrete works, it is important to plan appropriately theinspection including steel member production and erection.

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13.6.2Composite Steel-Concrete Structures

Inspection for acceptance

13.6.2.1

Inspection for acceptance of steel

The accepting party shall assume the responsibility for conducting acceptance tests forsteel. The tests should be carried out in accordance with Chapter 6 of "Construction:
Inspection Standards". For the inspection of steel not mentioned in Chapter 6 of"Construction: Inspection Standards", Table 13.6.1 should be referred.
Table 13.6.1
Classification
Carbon steel pipe
forgeneralstructures
Square steel pipe forgeneral structures
Centrifugal
cast-steel pipe forwelded structures

Inspections for acceptance of steel pipes

Testing method/
Period /Inspection method
Frequency
Manufacturer's
test
Quality item insheet or the method in
JIS G 3444
JIS G 3444
Manufacturer's
test
Quality item inAtsheet or the method in
JIS G 3466
delivery
JIS G 3466
Manufacturer's
test
Quality item insheet or the method in
JIS G 5201
JIS G 5201
Item

Criteria forjudgment
Compliance
JIS G 3444

withCompliance with
JIS G 3466Compliance
JIS G 5201

with[Commentary] The accepting party conducting acceptance tests for steel is the contractor ofcomposite steel-concrete structures. The results of acceptance tests should be verified by the Owner.

13.6.2.2

Inspection for acceptance of jointing materials

The accepting party shall assume the responsibility for conducting acceptance tests forjointing materials. Inspection for acceptance of jointing materials should be carried out inaccordance with Table 13.6.2.
Table 13.6.2 Inspections for acceptance of jointing materials
Testing method/
Period /Inspection method
Frequency
Manufacturer's test sheet
Covered electrode Quality item inor the method in JIS Z
for mild steel
JIS Z 3211
3211
Covered electrode
Manufacturer's test sheet
Quality item infor high-tension
or the method in JIS Z
JIS Z 3212
steel
3212
Submerged-arc
Quality item in
welding solid wire
Manufacturer's test sheet
JIS Z 3351
and
flux
for
or the method in JIS Z
At
and JIS Z
carbon steel and
3311 and JIS Z 3352
delivery3352
low-alloy steel
Classification

Item

Criteria for judgment
Compliance with JIS
Z 3211
Compliance with JIS Z
3212
Compliance with JIS
Z 3311 and JIS Z
3352

Torciahigh-strength bolt

Necessary
item

Manufacturer's test sheet
or necessary method

Compliance withstandards prescribedfor achieving the
purpose of use

High-strength
hexagonal bolt

Manufacturer's test sheet
Quality item inor the method in JIS B
JIS B 1186
1186

Compliance with JIS
B 1186468

Standard Specifications for Concrete Structures-2007, Materials and Construction[Commentary] The accepting party conducting acceptance tests for connection materials is thecontractor of the composite steel-concrete structure. The results of acceptance tests should beverified by the Owner.
Welding materials and jointing materials such as high-strength bolts are usually inspected evenat the manufacturing factory. Therefore, the material properties, strengths, shapes, dimensions, andothers may be checked with inspection sheets submitted from the manufacturing factory. Torcia
high-strength bolts are specified not in JIS, but in “Set of Torcia High-Strength Bolt, Hexagon Nut,and Plain Washer for Friction Jointing” (Japan Road Association). Therefore, this standard may be
used instead.
Data for torque coefficient of high strength bolts are also submitted from the manufacturing
factory. The data need to be checked because the storage conditions after shipping may change thetorque coefficient from that at factory inspection.

13.6.2.3

Inspection for acceptance of concrete

The accepting party should assume the responsibility for conducting the acceptancetests for concrete.

[Commentary] When using ready-mixed concrete, refer to Chapter 5 of "Materials andConstruction: Inspection Standards". The stipulations concerning the use of special concrete should
be adhered to. In cases where concrete not mentioned in "Materials and Construction" is used orwhere the structure needs to meet special performance requirements, appropriate acceptance tests
should be conducted considering the characteristics of concrete or the performance requirements forthe structure.

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13.6.313.6.3.1

Composite Steel-Concrete Structures

Inspection for production of steel members
Inspection of welding

The Owner should assume the responsibility for inspecting welding by an appropriate
method fit for the objective. External and internal flaws should be inspected in accordancewith Tables 13.6.3 and 13.6.4, respectively.
Table 13.6.3
Item
Weld cracking
Appearance and shape ofthe bead
Reinforcement andfinishing of groove weld

Inspection of external flaws

Testing or inspection method
TimingVisual inspection and magnetic At the time ofparticle inspection as required
production
At the time ofVisual inspection
production
At the time ofVisual inspection
production

Table 13.6.4

Decision criteria
No cracking is foundAs stipulated in theconstruction planAs stipulated in theconstruction plan

Inspection of internal flaws

Item

Testing or inspection method

Radiography

Method specified in JIS Z 3104

Ultrasonic testing

Method specified in JIS Z 3060

TimingAt the time of
production
At the time of
production

Decision criteriaLess than specified size
Less than specified size

[Commentary] The welding quality is affected by joint type, material properties, plate thickness,
welding conditions, precision of groove and assembly, cleanness of groove, control of preheating,postheating and inter-layer temperatures, and welding skill. Therefore, these conditions must be
well considered at inspection. In the field, achieving the same level of welding quality as at theplant is difficult in numerous cases. Inspection methods are also restricted. Due care should
therefore be exercised in field welding as compared with plant welding.
Welding is usually checked by visual inspection, radiographic testing, ultrasonic testing,magnetic particle testing and penetration testing. As a rule, the external flaws is to be visuallyinspected from end to end. In inspection, priority is given to undercuts, overlaps, cracks, pits, andbead irregularities. Cracks are mainly checked by visual inspection, but magnetic particle testing or
penetration testing may be used as required.
Internal flaws during welding should be inspected by JIS Z 3104 "Methods of radiographic
examination for welded joints in steel" and JIS Z 3060 "Methods for ultrasonic examination forwelds of ferritic steel".
For details of welding quality control and inspection, refer to 17.4 Welding of the"Specifications for Highway Bridges: Part II Steel Bridges" prepared by the Japan Road Association.
Decision criteria should be established based on the document.
Ultrasonic examination methods are generally used in the field for inspecting internal flaws
during field welding because using radiation is difficult in the field. Flaws should be repaired
carefully considering the effect of repair on the parent materials.

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13.6.3.2

Inspection for tightening of high-strength bolt

The Owner should assume the responsibility for inspecting the tightening of highstrength bolts in accordance with Table 13.6.5.
Table 13.6.5
Item
Torque-shear highstrength bolt

Hexagonal-headedhigh strength bolt

Inspection of high strength bolt tightening

Testing or inspection method
Cutting of pin-tail nut is verified
for all samples.
Visual inspections are conductedusing markings.
Testing using a torque trench
Ten percent of bolts in a group areused as a standard practice.

TimingDecision criteria

At the timeof
production

Visual inspection

At the timeof
production

Bolt tightening torque isplus or minus 10% of thetorque specified at thetime of calibration[Commentary] A Torcia high-strength bolt can be confirmed to be tight if the pin tale is broken.
Therefore, only the cutting pin tale as well as a co-turn with marking should be checked.
If abnormal tightening is detected in tightening test of a high-strength hexagonal bolt using an
automatic recorder, the bolt may be found by referring the recording paper and the marking and be
retightened.
When a torque wrench is used, a high-strength hexagon bolt must be checked immediately aftertightening because the torque coefficient changes if the tightened bolt is left for a long time.
When welding follows the tightening of high strength bolts, the effects of restraining should betaken into consideration.
“Steel Highwayridge Construction Handbook” (Japan Road Association) may be referred to forthe acceptance criteria and other details.

13.6.4Inspection for filling condition of concrete

The Owner should assume the responsibility for verifying by an appropriate methodthat concrete fills so that the composite steel-concrete structure may meet the designatedperformance requirements.

[Commentary] In cases where directly verifying the compaction is difficult between steel plates,
inspection should be made by a method the reliability of which has been verified. Inspection
methods include infrared thermography, hammering tests, ultrasonic tests and application ofradioisotope. Inspection should be conducted at the end of placement to verify concrete filling andafter the hardening of concrete to verify the effects of bleeding and other phenomena.
Damaging voids (poorly filled areas) are likely to occur below the top and bottom flanges ofsteel members in steel framed reinforced concrete structures, below the diaphragm in concrete filledcolumns, and under the top steel plate in sandwiched structures. Careful inspections are therefore
required.
In cases where air vents are installed in steel plates at appropriate locations, whether concrete
fills completely or not can be determined by verifying concrete overflow through the air vents.
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In cases where voids that are not allowed (poorly filled areas) are detected andshrinkage-compensating mortar or paste of equivalent performance is injected, care should be
exercised not to deteriorate the performance of steel members due to punching or welding.

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CHAPTER 14 FACTORY PRODUCTS

14.1

General14.1.1

Scope

This chapter presents the standards required for production and construction offactory products.

[Commentary] This chapter provides the general performance requirements for factory products,
including not only plain and reinforced factory products but also prestressed factory products, to be
produced continuously in large quantities in a well-controlled plant. However, provisions of thischapter are not applicable to plants with insufficient control, or pre-cast units produced in a
temporary yard near a construction site.

14.1.2 General
Factory products should be produced under the guidance of professional engineers
with adequate knowledge about factory products, paying due attention to the materials,
mix proportions, mixing, application of reinforcement, shaping and curing, with a view tomeeting the designated quality requirements for the factory product.

[Commentary]
Factory products have several characteristics. First, the materials, mix
proportions, production facilities and construction can be managed easily. Second, factory products
can be produced constantly by skilled workers. Third, production, transport and assembly of factory
products can easily be mechanized to save manpower. Fourth, concrete can be placed at locations
rarely affected by the weather where simple work is possible. Fifth, full-scale tests are stipulated inappendices to JIS documents and can be conducted for most of the factory products. Sixth, somefactory products have very small cross section.
Since it is assumed that factory products are manufactured in highly controlled plants,
restrictions on the maximum size of coarse aggregates and the minimum cover for steel may berelaxed as stated elsewhere.
Since early age strength, instant demolding ability, and, in some cases, high strength arerequired, stiff concrete with low W/C may be used in the manufacture of factory products.
Compaction using strong vibration, centrifugal compaction, pressing compaction, instant demolding,accelerated curing and other special manufacturing techniques are normally used in producing large
numbers of high quality factory products. However, when these special techniques are used,characteristic care shall be taken during manufacture, because the special techniques differ fromthose used when producing normal concrete.
Numerous factory products are transported to the construction site for assembly and connection.
Then, the connection is likely to become vulnerable. Due care should therefore be exercised duringtransport and connection so as not to deteriorate the quality and performance of the product.
In manufacturing factory products with lightweight concrete, high strength concrete andself-compacting concrete, the following chapters should be referred to: Chapter 3 “Lightweight
Aggregate Concrete”, Chapter 6 “High Strength Concrete” and Chapter 7 “High Fluidity Concrete”,
respectively. Also, when using expansive admixture, continuous fiber reinforcing materials and steel
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Factory Products

fiber reinforcing materials for factory products, the following chapters should be referred to:
Chapter 2 “Expansive Concrete”, Chapter 4 “Continuous Fiber Reinforced Concrete” and Chapter 5“Steel Fiber Reinforced Concrete”, respectively. For prestressed concrete and composite
steel-concrete structures, refer to Chapter 12 Prestressed Concrete and Chapter 13 Composite
Steel-concrete Structures.
Chief concrete engineers and concrete engineers authorized by the Japan Concrete Institute; andcivil engineering concrete block engineers, factory products production supervising engineers andother engineers authorized by factory production associations should permanently be present atfactory products production plants.

14.2 Concrete Quality
14.2.1 General
Concrete used for factory products shall have the designated strength, durability,
resistance to cracking and watertightness, and shall be of homogeneous quality.

[Commentary] In many cases, accelerated curing is used to make factory products, which can be
demolded at an early age and transported within the factory or to the construction site. Also,
factory products, such as concrete piles and sheet piles, may be subjected to impact loads or
localized and concentrated loads under erection or construction. Further, some factory products may
be located in severe environmental conditions such as marine or other corrosive environments. Thus,
Concrete for factory products should have the strength, durability, resistance to cracking,watertightness and protection for steel fit for the type. In cases where concrete is used under special
conditions, it should also meet other quality requirements. Appearance is also an essential quality
factor for factory products, so it should present a designated appearance.
The total amount of chloride ion contained in concrete should be 0.30 kg/m3 or less forprestressed and reinforced factory products as for ordinary concrete in order to prevent thecorrosion of steel used in factory products. In cases where chloride ions have little effects on
reinforced factory products used under normal conditions and unreinforced factory products withadditional reinforcement, the upper limit of total chloride ion in concrete may be set at 0.6 kg/m3 or
less.

14.2.2

Strength of factory products(1) The strength should be specified on the basis of the compressive strength
determined using one of the following methods:(a) In the case of general factory products, the value of the compressive strength at
the age of 14 days.
(b) In cases when special accelerated curing such as autoclaving is used, the valueof compressive strength at an appropriately lower age than 14 days.
(c) In cases when accelerated curing is not used, or in the case of relatively thickmembers, the value of compressive strength at the age of 28 days.
(2) Compressive strength tests for concrete used for factory products shall be474

Standard Specifications for Concrete Structures-2007, Materials and Construction

conducted as described below.
(a) Specimens should be made under the same compaction and curing conditions as
those for factory products.
(b) Typical specimens should be 10 cm in diameter and 20 cm in height, and be
cylindrical.
(c) Compressive strength should be specified as stipulated in JIS A 1108.
(3) In cases when factory products are manufactured in a manner similar to that ofordinary reinforced concrete members, or in cases when it is difficult to meet theprovisions in Clause (2)(a) above, the strength of concrete in the products, shall be
specified in terms of compressive strength tests carried out according to JIS A 1132 andJIS A 1108.
(4) Compressive strength at the stage of demolding, application of prestressing, ordelivery, shall meet the required value determined for each stage of manufacture.

[Commentary] (1) Compressive strength is almost always required for evaluating the quality offactory products as well as for normal concrete. Because, as it is rare that tensile strength andbending strength, etc. are specified as a quality of the factory products, the compressive strength isspecified as the representative property for the quality of factory products. In cases when the qualityof factory products is specified on the basis of strength except for the compressive strength, thestrength of the determined requirement shall be satisfied.
As various methods in curing factory products are used, with the progress in age, considerable
differences appear in development of the strength. In general, the strength of the factory products
develops rapidly in the early stage because the members of factory products are usually thinner,
accelerated curing is more often used, and because the water-cement ratio is less than that used in
the production of the conventional concrete. However, the rate of increase in the strength of factory
products in the long-term is less than that of conventional concrete. Therefore, the strength ofgeneral factory products under atmospheric-pressure steam curing, shall be specified, whilereferring to results of experiments, on the basis of compressive strength at 14 days determined using(a).
As the strength of the factory products using a high-pressure steam curing method (autoclave
curing method) can only be increased with time after the curing ends, the compressive strength
should be determined using (b). The strength of factory products not using accelerated curing or
factory products with comparatively thick section shall be specified, as well as the conventional
reinforced concrete structures, on the basis of compressive strength at the age of 28 days determinedusing (c). In the above case, comparatively thick sections of factory products denote sections withthicnesses greater than 45 cm.
In cases where the factory product is shipped before it reaches a designated age through mutual
consultation between the accepting party and the manufacturer, it should be verified at the time of
shipment that the designated compressive strength is available.
Furthermore, in some types of factory products, the compressive strength can be specified at
appropriate age that is less than 14 days or more or less than 28 days by using a combination ofmaterial used and the curing method.
(2) In the manufacturing of factory products, some factory products are compacted using
centrifugal force, strong vibration and pressure. Further, steam curing is generally used for
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Factory Products

accelerated curing. Therefore, it is not adequate that the compressive strength of the factory
products in such manufacturing conditions is evaluated on the basis of the compressive strength oftest specimens under standard curing. Thus, as it is necessary that, in order to appropriately evaluate
the quality of factory products, test specimens and manufacturing conditions of the factory products
are as equal as possible, the test specimens are determined as mentioned in Clause (a).
The maximum size of coarse aggregate used in factory products is smaller than that used innormal concrete, because the thickness of members in factory products is less than that of members
in conventional reinforced concrete structures. Also, the usual strength test can easily be carried out
using cylindrical specimens whose size is 10cm in diameter and 20cm in height. Further, cylindrical
specimens whose size is 10 cm in diameter and 20 cm in height have been used in the compressive
strength of factory products. Therefore, the test specimen in which the cylinder size is determinedas mentioned in Clause (b). However, in cases when using coarse aggregates having a maximum
size of 30 mm or more, it is necessary to use cylindrical test specimens of large type, at least 12.5
cm in diameter and 25 cm in height. Factory products compacted using centrifugal force should, inprinciple, be prepared according to the JIS A 1136 “Method of Test for Compressive Strength of
Spun Concrete”. In the case when cylindrical specimens whose size is 5 cm in diameter and 10 cm
in height are used in factory products using mortar or when a test specimen of hexagonal cylinder,
etc. which has no capping is used, the comparative test with cylindrical specimen as mentioned
above needs to be sufficiently carried out, and these characteristics shall be understood when in use.
(3) It is proper that a compressive strength test is carried out in order to investigate the qualityof factory products in accordance with the following standards; the JIS A 1132 “Method of Making
and Curing Concrete Specimens” and the JIS A 1108 “Method of Test for Compressive Strength ofConcrete”. When the manufacturing method of factory products is similar to that of ordinary
reinforced members, it is quite natural that compressive strength tests using standard test specimens
can be the basis for determining the concrete strength of factory products without carrying out any
special tests. When factory products require special compaction and curing methods, and the testing
method for test specimens made in the same condition has not been prescribed, the compressive
strength of standard test specimens can be utilized to determine the compressive strength of factory
products. In this case, the relation between the compressive strength and the actual strength offactory products should be investigated sufficiently.
(4) In cases when the compressive strength used in factory products at the stage of demolding,application of prestressing, or delivery is determined, the determined strength shall be satisfied. In
cases when the strength has not been determined even in the manufacturing process, it is importantto satisfy the required value which the Engineers in charge of manufacturing indicate, if necessary.

14.3 Materials
14.3.1 Cement
Cement shall be selected properly so as to obtain factory products that meet thedesignated quality requirements.

[Commentary] For factory products, ordinary Portland cement is used in most cases. High earlyPortland cement is frequently used for prestressed factory products because it enables early
development of high strength. It is also fit for factory products that need to be shipped quickly or
for factory products that are produced during the cold period. In order to enhance the resistance tosea water and control thermal cracking in large factory products, blended cement such as
blastfurnace slag cement and fly ash cement, and moderate heat cement are used. For these types of476

Standard Specifications for Concrete Structures-2007, Materials and Construction

cement, adequate curing is required because the development of early age strength is generally
delayed. When using cement for which no JIS stipulations are available such as white Portland
cement for producing colored concrete, and ultra rapid hardening cement, its quality should beverified by testing.
The cement for factory products should be selected based on Section 3.2 of "Materials andConstruction: Construction Standards" considering the characteristics of factory product production
methods and the performance requirements for the product.

14.3.2Fine and coarse aggregates(1) Fine and coarse aggregates shall be appropriately selected, depending upon thetype of products, method of manufacture, etc. in a manner in which the required quality isimparted to the factory product.
(2) Maximum size of coarse aggregates shall not be more than 40 mm and shall not
exceed 2/5 of the minimum dimension of the product or 4/5 of the minimum clearance
between reinforcing bars. However, in cases when conditions for sufficient compaction
are confirmed, every aggregate can be used without any limitations.
(3) In the case of pre-stressed factory products, recycled aggregates shall not be used.

[Commentary] (1) Factory products need to have not only excellent quality and performance but
also good appearance in numerous cases. The type and properties of the aggregate to be used should
therefore be fully investigated by referring to Sections 3.4.1 and 3.4.2 of "Materials andConstruction: Construction Standards". The grading of fine aggregate has great impact on theappearance. Appropriate mixes of large and small particles should therefore be used.
The concrete for factory products that require high strength is greatly affected not only by
mixing, curing and other production conditions but also by the quality of aggregate. Selecting fineand coarse aggregates of excellent quality is especially important.
Use of crushed fine aggregates or fine aggregates made from granulated iron-blast-furnace slag
has an advantage in terms of better control of deformation of factory products at the time of instantdemolding. Also, use of lightweight aggregates leads to lighter factory products, which not only
reduce the dead load of the structure, but also are advantageous from the point of view oftransportation and erection. When using lightweight aggregates, refer to Section 3.2.
When using recycled aggregates, recycled concrete aggregate can be used for factory products
only when it is confirmed through a careful survey of previous results that the required performanceof factory products, such as compressive strength, drying shrinkage and durability, are not adversely
affected.
(2) Generally, coarse aggregates having a maximum size of 20 or 25 mm may be used in factory
products. For products with particularly smaller thicknesses, aggregates with a maximum size of 10mm or 15 mm may be used. Further, in cases of factory products with a relatively large crosssection, aggregates with a maximum size of 40 mm have been used and thus the maximum size ofcoarse aggregates that may be used has been kept at 40 mm.
It is probable that concrete will spread to the edge of the framework because (a) coarse
aggregates used for factory products are controlled to keep a constant grading, (b) aggregates ofexcessively large particle size are seldom used, and (c) concrete can be sufficiently compacted.
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Therefore, the maximum size of coarse aggregates is specified as 2/5 of the minimum thickness offactory products and 4/5 of the minimum clearance between reinforcing bars.
Since compactability can be checked by a test of real-size specimens (products), some factories
especially manufacture factory products with a little thickness or densely reinforced bar
arrangement without any limitation on aggregate size for reduction of the shrinkage or economical
efficiency. In such cases, factory products can be manufactured without any limitations on
aggregate size.
(3) It is known that drying shrinkage and creep in concrete using recycled aggregate are larger
than those using normal aggregate, and in cases in which concrete is used in prestressed factory
products, the loss of prestress become large. Especially, performance of such concrete in terms of
its ability to protect the reinforcing bar is not clear yet. Thus, the use of recycled aggregate inprestressed factory products is not allowed.

14.3.3Admixtures

Admixtures shall be used in factory products only after appropriately considering thepeculiar mix proportion, compaction, accelerated curing, etc., and the effect on the qualityof the product and improvement in the efficiency of production.

[Commentary] Chemical admixtures, such as air-entraining agents, water-reducing agents,
air-entraining and water-reducing agents, high-range water-reducing agents, high-range
water-reducing and air-entraining agents, and high viscosity agents are normally used during
manufacture of factory products. In general, high-range water-reducing agents, or high-range
water-reducing and air-entraining agents are used in cases when high strength concrete in products
is required.
Mineral admixtures, such as expansion admixtures, admixtures for high strength concrete(mainly composed of anhydrous gypsum), ground granulated blast-furnace slag, fly ash and silica
powder are normally used during manufacture of factory products. Recently, special factory
products, made with high strength concrete or high durability concrete, which contain high-range
water-reducing agents, or high-range air-entraining and water-reducing agents, and silica fume havebeen manufactured. Additionally, some mineral admixtures, which can be used to make factory
products that can be demolded early and ensure rapid manufacturing, have been developed. Suchmineral admixtures have enabled development of factory products that have an advantage from theview point of shortening the curing period and releasing formwork at earlier ages, especially during
winter’s season.
Nowadays, texturized or colored factory products have been developed from the considerationthat they harmonize with their environment better. Although there are many coloring agents, it
should be ensured that the quality of factory products is not adversely affected.

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14.3.4

Reinforcing steel(1) Reinforcing steel, wires, and rebar used in factory products shall be complies with
Sections 3.6.1 and 3.6.2 of “Materials and Construction: Construction Standards”. If thesematerials are complied with one of the following standards, they can satisfy the required
qualities.
Hard Drawn Steel Wires

JIS G 3521

Low Carbon Steel Wires

JIS G 3532

Low Carbon Steel Wires and Rods

JIS G 3505

High Carbon Steel Wires and Rods

JIS G 3506

Welded Steel Wire and Bar Fabrics

JIS G 3551

(2) Steel wires for pre-stressed factory products shall follow Sections 3.6.2 of“Materials and Construction: Construction Standards”. If that material is complied withthe following standard, it can satisfy the required qualities.
Hard Drawn Steel Wires for Pre-stressed Concrete

JIS G 3538

(3) In cases when reinforcing steel other than Clauses (1) and (2) above is used, or incases when the reinforcing steel is re-processed or heat-processed, the qualities of thematerial should be confirmed by the tests. Also, the appropriate strength, other design
parameters, and the method of use shall be determined by other manners.

[Commentary] (1) and (2) Since the factory products are generally manufactured with thinnerunit members, reinforcing steel with a size of 10 mm or smaller is often used. Also, low carbon steel
wires and rods often are used for manufacturing factory products. In addition, many factory
products are specified by JIS which allows the use of these steel materials.
According to Clause (1), reinforcing materials, which are not specified in either Sections 3.6.1 of“Construction: Construction Standards” or Sections 3.6.3 of “Construction: Construction Standards”,
shall be checked in terms of their strength, parameters for design, and application method with theconsideration of the yield point and crack controlling properties for their kind or purpose of use.
(3) The application method of steel materials not explained in Clauses (1) and (2) above shall be
determined after the confirmation of their qualities.
If the epoxy-coated reinforcing bar mentioned in Sections 3.6.1 of “Materials and Construction:
Construction Standards”, satisfy the certain quality, they do not need to undergo the confirming tests,
since manuals or specifications for those materials have been published. However, theirperformance must be checked to satisfy requirements if those materials have the chance ofundergoing a hot curing process or other special manufacturing process. When reinforcing steel isprocessed for thread rolling, bluing, and so on, the performance of reinforcing steel shall be
specially checked so that the quality does not alternate.
Short fibers may be used for reinforcement of mortar such as alkali-resistant glass fibers, carbon
fibers, polypropylene fibers, polyethylene fibers and vinylon fibers. Then, appropriate tests should
be conducted considering the type of fiber and the product manufacturing method to verify that thefactory product is of the designated quality. When using synthetic fibers, a variation of short organic
fibers, refer to Chapter 5 Short Fiber Reinforced Concrete.
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When replacing the reinforcement or prestressing steel of factory products with continuous
fiber reinforcing materials made by converging carbon fibers, aramid fibers and other continuous
fibers with resins, the continuous fiber reinforcing materials should comply with JSCE-E 131"Quality Criteria for Continuous Fiber Reinforcing Materials (draft)". In cases of non-compliance,
adequate tests should be conducted. When using continuous fiber reinforcing materials, refer to
Chapter 4 Concrete Using Continuous Fiber Reinforcing Materials.

14.4
14.4.1Mix Proportions
GeneralMix proportions for factory products shall be determined appropriately considering themethod of molding and curing in order that the products have the required strength,
durability and water-tightness.

[Commentary] Properties of factory products such as strength, durability and water-tightness
should be determined through tests carried out on actual factory products directly, or on concrete
specimens produced under equivalent conditions. Thus, the mix proportions for factory products
should be determined to satisfy the required conditions. When factory products will be located inenvironments with cyclic freezing and thawing, the performance of freeze-thaw resistance shouldbe improved by using air-entrained concrete.
It is necessary to find the optimum condition by checking both the effect of mix proportions andthe effect of accelerated curing in cases when mix proportions are determined by considering therequired strength of concrete at the demolding stage or the required strength at the pre-stressing
stage for factory products.
The concrete mix proportions for factory products should be able to provide the factory productwith adequate compactibility, strength and durability and excellent concrete surface, and should be
fit for the factory product shaping method.
For factory products with instant demolding, care shall be taken to select the unit water content,
sand-aggregate ratio, and air content appropriately.
The required concrete strength should be determined considering the variation of concrete
quality in factory products. For factory products, mix design is developed under more severe
conditions than stipulated in Section 4.4.3 of "Materials and Construction: Construction Standards"
to enhance quality. The compressive strength of concrete obtained in a round of test has been set to
be 90% of design strength or greater, and the mean compressive strength obtained in three rounds oftests has been set to be greater than the design strength.

14.4.2

Workability(1) Workability of concrete shall be determined taking into consideration the shape andsize of the product, and the method of production.
(2) It should be verified that appropriate workability is achieved by conducting slump
tests, slump flow tests or other appropriate tests.

[Commentary](1) The method of production differs according to the type of product, because
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the variety of factory products abounds, and because the shape and size of products differ
considerably. Therefore, the workability of concrete shall be appropriately required for the methodof production in factory products. The shaping methods for factory products include vibratorycompaction with a great force and centrifugal compaction. Due care should be exercised not tocause material segregation.
Although most factory products are manufactured using concrete with 5-10 cm slump, someproducts are manufactured using concrete with 15 cm slump. In cases when factory products are
manufactured using self-compacting concrete, a test using slump flow may be applied to determine
the workability of factory products.
(2) When using concrete with a slump of 2 cm or higher, workability can be controlled byconducting slump tests. When shaping stiff concrete with a slump of lower than 2 cm by instant
stripping of forms, fresh concrete needs to be controlled by conducting other types of tests. The
methods for measuring the workability of stiff concrete with a slump lighter than 2 cm include
JSCE-F 508 "Method for testing the compactibility of extremely stiff consistency concrete (draft)",
EN 12350-3 "Testing fresh concrete - Part 3: Vebe test" and EN 12350-4 "Testing fresh concrete Part 4: Degree of compactibility". Concrete workability is generally determined by shaping factory
products using compaction methods for actual factory products in numerous cases. Shaking tableconsistency test methods for pavement concrete is not fit for measuring the workability of
extremely stiff consistency concrete because of extremely low amplitude and frequency.

14.5 Production
14.5.1 Factory production(1) Concrete should be produced in accordance with Chapter 5 of "Materials andConstruction: Construction Standards" as a standard practice.
(2) Ready-mixed concrete should be used in accordance with Chapter 6 of "Materials
and Construction: Construction Standards" as a standard practice.
(3) Appropriate batch mixers shall be used to mix the concrete used in the products.

[Commentary] (1) and (2) For factory products, relatively stiff concrete with a slump of 5 to 10
cm is frequently used. Workability needs to be achieved that is fit for the shaping method. A test
value of 14-day compressive strength is generally used. The premium coefficient in mix proportions
is specified under more severe conditions than for ordinary concrete. When using ready-mixed
concrete, an appropriate type of concrete fit for the factory product to be manufactured should bepurchased through full consultation with the manufacturer of the ready-mix concrete.
(3) Stiff consistency concrete having a low water-cement ratio is generally used forfactory products. For mixing such concrete, forced mixing type mixers are suitable. Care shallbe taken when tilting mixers are used, as mortar may adhere to the inner mixer lining and thebase of blades. This may adversely affect the uniformity of the concrete.

14.5.2Assembly of reinforcement(1) The reinforcement shall be assembled by tying annealed steel wire or appropriate
clips at the important area in the intersections of reinforcing bars.
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Factory Products(2) In cases when spacers are used, the material and the method of use shall beselected taking into consideration the durability and appearance of the product.
(3) The stirrups, additional steel bars, etc. should, in principle, not be welded toprestressing tendons.

[Commentary] (1) In general, reinforcing bars of factory products are tied using annealed steel
wire of 0.5 mm or larger in diameter, or adequate clips. Also, reinforcing bars of factory products to
be manufactured in large quantities are mostly pre-assembled, and spot welding is commonly used
for them. In all cases, reinforcing bars shall be carefully tied and assembled so as not to be
deformed in the manufacturing process.
(2) Using spacers for fixing reinforcing steel into a position is effective, however, care must be
exercised to prevent spacers from making weak points in the structure and to avoid deterioration of
the durability of factory products due to the harmful effect of corrosion of the reinforcing steel. It isadvisable to use spacers made of the same properties of concrete or mortar as the factory products.
When using plastic or other types of spacers, the one with a minimum thermal expansion coefficientand of large cross section (opening ratio) that hardly causes lateral buckling of steel due to its
weight should be selected. It should be verified before using a spacer that it has no adverse effects
on the durability of factory products, based on the records of its use.
(3) Since pre-stressing steel generally contains a large amount of carbon, it is unsuitable forwelding. Furthermore, since pre-stressing steel is always worked under high tension, a change in themechanical properties or a reduction in the sectional area due to welding may cause serious
accidents. Thus, the welding of pre-stressing steel is prohibited in principle. However, in the case of
pre-stressed concrete piles and other products, spot welding of additional bars to heat-treated
pre-stressing bars using the automatic machines, which contain a relatively low amount of carbon,
is widely used. When the welding current and time are fully controlled, the reinforcing steel can bespot welded to the pre-stressing steel. In these cases, it is required that the mechanical properties of
the tendons be checked to ascertain that they are not less than the design values.

14.5.3Formwork

The formwork shall have a rigid structure, have an accurate shape and size, and beeasy to assemble and remove.

[Commentary] During compacting, molds for factory products are subjected to strong vibrationand high pressure. In addition, the molds are repeatedly used, and steam curing usually generates
thermal stress in the molds. Accordingly, the molds must be strong and conveniently assembled anddisassembled. Steel molds are usually used for concrete forms, and synthetic resin molds are also
used. When using molds, sufficient consideration must be given to handling, cleaning, applicationof form releasing agents, maintenance, and so on.
For production of factory products with accurate dimensions, it is necessary that the tolerances
for mold dimensions be less than that for the dimensions of factory products.

14.5.4

Molding(1) Molding shall be appropriately done using mechanical compaction methods in482

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order to have factory products with the required quality.
(2) The surface of factory products shall be smoothly finished, taking their applications
into consideration.

[Commentary] (1) Compaction methods generally used for factory products include vibrationcompaction, centrifugal compaction, pressing compaction, vacuum compaction and methods
combining the above. Close relationships exist among the type of factory products, mix proportions,mixing and casting. Therefore, it is essential that a suitable mechanical compaction method relevantto the condition be adopted and that casting be performed with care.
Numerous houses have recently been built around plants, and the noise and vibration generated
by the manufacture of factory products has been an issue. The working environment for plant
employees has been another serious issue. For solving these problems, vibration-free shaping
methods using high fluidity concrete with self compactibility or shaping methods that vibrate highfluidity concrete for supplementing concrete filling have been adopted for shaping factory products.
(2) In general, surface finishing is done after compaction by using finishing tools such as rulers,trowels and external vibrators with a bottom plate. Factory products that are compacted by thepressing compaction method are mechanically finished by means of the pressing plate which is
attached to the top of the mold. In cases where factory products have an apparent limitation of sizein their design specification, the surface finishing shall be done with those considerations.
In cases where the concrete surface is not specially finished, the exposed concrete surface shallbe flat and dense. This is one of the most important points for improving the durability andwater-tightness of factory products, as well as its external appearance. Therefore, it is necessary tocompact concrete carefully with vibrating tables, form vibrators, rod type vibrators, and otherequipment, taking care of the surface smoothness of the forms and the leakage of mortar from thejoints between forms. Fine surface air voids created by entrained air are not detrimental to durability.
Large air voids, however, may deteriorate durability. Large air voids that are likely to deteriorate
durability should therefore be repaired during manufacturing regardless of whether the surface is
exposed or not upon completion.
For special concrete surface finishing, water jetting, washing using a wire brush, shot blastingby throwing abrasive, using grinders and polishing using sharpening stone are available.
The proper finishing method should be selected in order to meet the requirements.
For example, the contact surface of the factory product members jointed to cast-in-place
concrete members after their erection or assembly shall be scarred in order to obtain a good bond
between the old and new concrete.

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14.5.5

Factory Products

Curing(1) The method and duration of curing of factory products shall be determined suchthat the required quality is met, taking into consideration the type and method of
manufacture and use.
(2) No accelerated curing should cause concrete cracking, delamination ordeformation, or should have damaging effects on the long age strength or durability.
(3) Temperature should be controlled during accelerated curing in accordance with
Table 14.5.1.
Table 14.5.1
Item
Temperature

Temperature control during accelerated curing

Check
Heat generation speed
Cooling down speed
Maximum temperatureand its holding time

Timing and frequency
In cases where changes are
made to production plans,materials or mix proportions

Criteria for judgment
Compliance with thespecification ofdesignation[Commentary] (1) Concrete shall be cured sufficiently after casting in order to avoid harmful
effects on quality such as low temperatures, drying, sudden temperature variations, loads andimpact. It is necessary that proper curing methods such as wet curing and insulated curing beapplied for the specified period even after de-molding. When the hydration of cement is progressing
and sufficient strength is obtained by using an accelerated curing method such as steam curing, aperiod of additional curing, such as wet or insulated curing, can be shortened or be omitted
depending upon the type of factory product. In cases where adequate strength can be obtained andthe designated performance requirements can be met for factory products owing to the progress of
cement hydration as a result of steam curing or other types of accelerated curing, the period ofsubsequent wet curing or insulated curing may be reduced or such curing may be eliminated forcertain types of factory products.
It is generally recommended that factory products be additionally cured wet after accelerated
curing in order to continue the successive hydration of many un-hydrated cement particles in thehardened concrete after the application of steam curing, and to improve properties of the concretesuch as strength, water-tightness and durability. It is necessary that factory products requiring
specially high-strength, abrasion resistance, water-tightness, freezing-thawing resistance, or thosethat will be subjected to strong impact loads be cured wet until the required quality is obtained.
(2) Steam curing at atmospheric pressure is widely used to obtain high productivity. In cases
using steam curing, improper operations such as an immediate supply of steam just following
casting, rapid temperature rises, or curing at extremely high temperatures will undoubtedly have
harmful effects on the factory products. Also, the concrete surface is apt to crack when the factory
products are taken out from steam curing chambers at high temperature and rapidly cooled down.
Therefore, there are many examples of steam curing applications stipulated as follows;
1) Steam curing shall be started when 2-3 hours or more have elapsed after mixing.
2) Factory products after demolding are put into stream curing rooms and the curing room
temperature is raised uniformly.
3) The rate of temperature rise should be no more than 20C per hour, and the maximum484

Standard Specifications for Concrete Structures-2007, Materials and Construction

temperature should be 65C.
4) The temperature of the curing room shall be lowered slowly, and factory products should be
removed from the room when the temperature difference between the curing room and theatmosphere has nearly disappeared.
In general, the elapsed time from mixing to the start of steam curing may be shortened if thewater-cement ratio of the concrete is low. Conversely, if the water-cement ratio is high, it isnecessary to lengthen the elapsed time.
Cases have been reported overseas in which deterioration occurred due to the delayed ettringite
formation after hardening for factory products that were exposed to a cold wet environment after
they were cured at high temperature in normal-pressure steam curing. Deterioration is said to berelated to hot curing and alkali amount and likely to occur at 90C or higher temperature. In Japan,
deterioration due to delayed ettringite formation has not been outstanding because temperature ismaintained at a relatively low level and the alkali content of cement is held low during the steam
curing of factory products, but careful investigations will be required in the future. Concretetemperature rises above the curing temperature because of the heat of hydration. The difference
between curing temperature and concrete temperature should also be considered.
In addition to the above method, autoclave curing and pressure curing are generally used as
accelerated curing methods. Autoclave curing, used for the curing of PC pole or pile, is a curingmethod using a high pressure, 1N/mm2, and 180C vessel. Pressure curing is a method of curingconcrete cast in a mold at a high-temperature of about 100C under a pressure of 0.5-1.0 N/mm2.
Using these curing methods, sufficient strength can be obtained at an early age.
When the hot-concrete method is employed to shorten the pre-curing period or steam curing
period after mixing, it is important to verify the properties of the concrete by testing the slump loss
with the elapsed time after mixing. The long-term strength and other properties shall also be tested.
(3) The high productivity by the acceleration of curing and de-molding is the special
requirement for the manufacture of factory products. However, rapid heat generation or cooling
down causes porous and low durable factory products. Since The quality of concrete is frequently
determined by the method, temperature and time of curing. For concrete used for factory products,
temperature should be fully controlled in accelerated curing in particular.

14.5.6De-molding and prestressing(1) De-molding of factory products shall be done after achieving sufficient concrete
strength for handling.
(2) Pre-stressing shall be carried out after confirming that the required strength has
been reached(3) In cases where instantly removing the form has no adverse effects on factory
products, the form can be partly or completely removed before concrete hardens.
(4) The strength at the time of form removal or at the time of prestressing should becontrolled in accordance with Table 14.5.2.

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Table 14.5.2
Item
Strength at thetime of form
removalStrength at thetime ofprestressing

Factory Products

Strength control at the time of form removal or prestressing

Items to be verified

Timing or frequency

Standards

Compliance with the
In cases where changes are
In accordance withconditions specified bymade to production plans,
14.2.2JIS or in production
materials or mix proportions
plans[Commentary] (1) The form should naturally be removed after the strength reaches the level atwhich the factory product can be handled without any problem. When storing factory products overa long period of time, the de-molding time of factory products shall be scheduled with aconsideration not only of the concrete strength, but also of the properties of creep or drying
shrinkage.
(2) For prestressed factory products, the form is partly removed right before prestressing in
numerous cases. Then, the form should be removed only after verifying that the strength specified
at the time of prestressing is achieved.
The time of pre-stressing of factory products shall be decided and referred to in Section 12.2.1.
(3) When shaping factory products by strong vibratory compaction or application of pressureusing extremely stiff concrete, removing the form right after the shaping is not likely to adversely
affect the transport, curing or other work. Concrete is also free from any damaging effect on its
quality. For these factory products, the form may be removed immediately following the shaping
even before concrete hardens.
(4) It should be verified that concrete strength at the time of form removal should be higher thanthe designated level so as not to adversely affect factory products in form removal or subsequentwork. For prestressed factory products, it should be verified that the strength at the time ofprestressing is higher than designated.
The checking of the relation between the quality of factory products and strength property by
the compressive strength test at early age is useful for quality control in the manufacturing processof material, mixture proportion, curing, and so on.

14.6 Transportation and storage(1) Transportation of factory products shall be undertaken, paying attention to safety.
Also, factory products shall not be damaged during handling and transportation.
(2) In cases when factory products are stored, any extraordinary stress and plastic
deformation shall be not caused in the factory products due to their own-weight or due totheir stacking.

[Commentary] Great care shall be taken during transporting of factory products. Since factory
products are easily cracked and damaged during transporting, preventive measures should be done.
Especially when long factory products such as bridge girders, poles, piles, and sheet piles aretransported and stored, great care should be taken with respect to the suspension points and themethod of support so as to avoid generating any large bending moment in these products. When
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stacking factory products for storage, stacking methods shall be determined by taking into accountthe strength and the dead load of the factory products, as well as the stacking conditions. Whenstacking bridge girders, preventive measures shall be taken to prevent tumbling down caused byearthquakes or by other unexpected loads.
Furthermore, since factory products are usually de-molded, transported and stored at an earlyage, they may be deformed by the harmful effects of drying shrinkage, creep, etc., due consideration
shall be sufficiently given to support positions during transportation and storage.
However, when the safety of the members has been already checked, the required compressive
strength can be lowered according to instructions from the Engineer in charge.

14.7

Erection and Jointing

Erection and jointing of factory products shall satisfy matters considered in the design
stage.

[Commentary] Assembly and erection shall be fully planned. Since, in general, joints may
become the weak points, assembly and erection, and jointing of factory products shall be performedin good conditions. When jointing piles and transversely fastening bridge girders, great care shall betaken regarding the relative positioning among members in order to satisfy the joint performance
specified in the design stage.
When factory products are jointed to each other by using a bonding agent, the joints shall betightly bonded. Care shall be taken regarding the mix proportions, mixing, the surface preparation,
the workable time of the bonding agent, and the curing after bonding with the consideration ofSection 12.4.8 and 12.6.6.
14.8

Inspections

14.8.1 Material acceptance tests
The accepting party shall be held responsible for conducting acceptance tests forconcrete and reinforcing materials for factory products in accordance with Chapters 3 and
6 of "Construction: Inspection Standards".

[Commentary] The accepting party that conducts acceptance tests for the materials for factory
products is the manufacturer of factory products. The inspection results should be verified by the
Owner of the construction project.
In the acceptance tests for concrete and reinforcing materials for factory products, quality may
be verified based on the test result checklist prepared by the manufacturer as for ordinary structures.
If no test result checklist prepared by the manufacturer is available at the time of acceptancetests for JIS-authorized steel, JIS-authorization mark should be verified at the time of delivery. At
JIS-authorized plants, JIS Q 1012 "Conformity assessment - Conformity assessment for JapaneseIndustrial Standards - Guidance on a third-party certification system for precast factory products"
should be adhered to.

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Factory Products

14.8.2 Acceptance tests for factory products(1) The accepting party shall assume the responsibility for conducting acceptancetests for factory products by appropriate methods to verify that the factory products meetthe designated performance requirements.
(2) Appropriate methods, timing and frequency of inspection should be selected forrespective inspection items considering the type and use of the product.
(3) Factory products shall not have harmful defects in service, such as cracks, flaws,
warping, and twists. Dimensional tolerance shall be such that factory products satisfy therequired performances specified in JIS or the production scheme.
(4) Factory products shall have the strengths required by the design.
(5) In cases when the strength of concrete can be substituted for the required strengthof factory products, compressive strength of concrete shall be generally used. The
inspection method to measure the compressive strength of concrete shall be carried out
in accordance with JIS A 1108 or Section 14.2.2.
(6) For factory products in which the quality assurance of a JIS mark, etc. is shown, themill sheet of the final inspection can be substituted for inspection by specific agreement
between manufacturer and the accepting party.
(7) In cases when the products can not be accepted, appropriate countermeasures
shall be implemented under the agreement between the manufacturer and the accepting
party.

[Commentary] (1) The accepting party conducting acceptance tests generally means theContractor. The Contractor usually conducts acceptance tests through mutual consultation between
the Owner of the construction work and the Contractor, and the test results are verified by the
Owner.
As a characteristic of acceptance tests of factory products, actual factory products can be
sampled and tested. The inspection methods described in JIS A 5365 "Precast factory products General rules for method of inspection" are total inspections, sampling inspections and inspections
involving no testing based on the past records. Nondestructive and destructive inspections are alsoavailable.
Factory products come in varieties of types, are used for various purposes and have varying
performance requirements. Uniformly determining the inspection method is therefore difficult.
When inspecting factory products, the accepting party should select appropriate methods forrespective inspection items through mutual consultation with the manufacturer.
For inspecting factory products, the kinds of inspection methods and proposal selection
standards, specified in JIS A 5365 “Pre-cast Factory products - General Rules for Method ofInspection”, and the performance testing methods, specified in JIS A 5363 “Pre-cast Factory
products - General Rules for Methods of Performance Test”, can be referred to.
(2) and (3) The inspection items for factory products include the appearance, shape, size,
compressive strength, flexural strength, external pressure and internal pressure. The accepting party
should properly select inspection items according to the quality requirements through mutual
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Standard Specifications for Concrete Structures-2007, Materials and Construction

consultation with the manufacturer.
An example of inspection items due to the kinds of factory production is shown in Table
C14.8.1.
Table C14.8.1

An example of inspection items due to the kinds of factory production

Inspection items
appearance, shape, size and compressive strengthappearance, shape, size, outer pressure strength for the outer
Reinforced spun concretepressure pipe, inner and outer pressure strength for the innerpipepressure pipe
appearance, shape, size, flexural strength at the body, flexural
Pre-stressed concrete pilestrength, assembly of reinforcing steel
Kinds of factory products
Concrete bricks

The timing and frequency of inspections should be determined by the accepting party based on
the size of the lot for testing and the sampling method through mutual consultation with the
manufacturer.
The factory products described in the appendices to JIS documents should be inspected using
the testing and inspection methods specified in the appendices. The factory products not describedin the appendices should be inspected using the methods specified in the production plans. In cases
where no production plans have been prepared, factory products may be inspected based on thetesting and inspection methods for similar JIS products stipulated in JIS A 5365, JIS A 5371
"Precast unreinforced factory products", JIS A 5372 "Precast reinforced factory products" and JIS A
5373 "Precast prestressed factory products".
When the test or inspection cannot be done using actual factory products, it is important that thetest or inspection shall be done using a prepared specimen specified by the manufacturing scheme.
In addition, the placement of reinforcing steel, the state of the dimensional tolerance, and the depthof cover concrete should be tested and inspected by using specimens after the strength tests. The
freezing and thawing test shall be done, if necessary.
For the placement of reinforcing steel, inspection shall be done by the non-destructive testing
method, a test using destructive specimens, or by measurements before concrete casting. When it isclear that the placement of reinforcing steel does not move by casting concrete, the measurements
before concrete casting is better.
Dimensional tolerance strictly influences the assembling or jointing correction of factory
products. For factory products (class I) shown in JIS-recommended specifications, allowable
margin of error in size is presented in the corresponding standards.
The factory products not described by the JIS appendix must be followed by the specified
allowance of dimensional tolerance described in the manufacturing scheme.
Cracked factory products influence the durability of themselves. And the flaws or un-uniformed
color of factory products influence their aesthetics. Moreover, warping and twists of factory
products cause low assembling accuracy and low performance. Therefore, factory products shall befree from these harmful defects in service. Pre-tensioning pre-stressed factory products, since they
may become are possible to be warp, shall be inspected for harmful warping.
There is no uniformed testing method for the components, because the testing scale may
become large and uneconomical compared to the testing method of the unit product. Therefore, theperformance test results inspected at the verification stage are normally used instead of the actual489

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Factory Products

test results, by explicit agreement between the manufacturer and the ordering agents.
Construction performance, such as transportation, assembling and jointing, is normallyevaluated by the actual results of the appearance, shape, size and compressive strength of concrete.
Factory products with special construction methods are inspected for accuracy at the temporary
assembling stage.
(4) A test using actual factory products can show the performance requirement of flexuralstrength, shear strength, inner pressure strength, outer pressure strength, and so on. A proper
specimen can be used for the testing of complex-shaped or large-sized products. In addition,
the un-destroyed testing method using actual products can be done when considering
production uniformity, testing cost or testing time.
(5) As the substitute parameter, compressive strength of concrete specimen can be used for theinspection, when factory products are difficult to test directly. Compressive strength of concrete isnormally used for the substitute parameter. Therefore, this parameter was determined in thisspecification. Compressive strength should be determined considering the method for increasing thedesign strength as described in Explanation in Section 14.4.1.
In cases when other strength properties are specified for factory products, the proper test shallbe done for their requirements. In this case, bar arrangement should also be inspected for reinforced
factory products. Bar arrangement and wiring should also be inspected for prestressed factory
products. For factory products for pavement, flexural strength of concrete is important and isadopted as an alternative characteristic.
(6) When the qualities of factory products are certified by a third party such as JIS, or when thefactory products can be considered to have good performance, manufactured products can bethought of as having undergone well quality-controlled production. Therefore, for factory products,
which are certified by JIS or another third party, the inspection can be done with a mill sheet of the
final test made at the factory. The final test means the test which is done by the manufacturing
companies for their quality insurance. Generally, the appearance, the shape and the size arebasically checked in the final test. And the compressive strength, flexural strength, shear strength,
outer pressure strength, inner pressure strength, cracking load, bending strength at the joints,
assembly of reinforcing steel or thickness of cover concrete are optionally selected, if necessary.
(7) Sampling inspections are generally conducted at the time of acceptance of factory products.
The decision criteria at the time of inspection and the methods for handling unacceptable productsvary according to the type of product and inspection item. The inspected lots should therefore be
handled properly through mutual consultation between the accepting party and the manufacturer.

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