20
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――◇論 文◇

Development of the World’s Highest Strength
Cementitious Material
世界最高強度セメント系材料の開発

KONO, Katsuya*;

NAKAYAMA, Risa*;

TADA, Katsuhiko**

河

野

克

哉*, 中

山

多

田

彦**

要

克

莉

沙*,

旨

本研究では, 硬化モルタルにおいて最高の圧縮強度を達成することを目的として, 新しい
セメント系結合材に対する製造方法について検討した. ３成分系セメント結合材の粒子径と組成について, Furnas の最密充填理論を用いて算出した. この材料で打ち込まれた供試体は,きわめて少ない水量の練混ぜによって製造される. そのため, 最密粒度セメント系結合材を用いた脱型直後の硬化体に外部から水分を吸収させ, その後に二段階の熱養生を実施した.
その結果, 最密充填粉体設計と事前吸水処理によって, 460N/mm2 を超える圧縮強度を発現する
セメント硬化体を得ることができた．
キーワード：超高圧縮強度，最密充填，事前吸水処理，熱養生――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――* 中央研究所 第 2 研究部 ＴＢＣﾁｰﾑ TBC Team, Central Research Laboratory** 中央研究所 第 2 研究部 ＴＢＣﾁｰﾑ ﾘｰﾀﾞｰ Manager, TBC Team, Central Research Laboratory

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太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

ABSTRACTIn this study, new manufacturing methods have been investigated for cementitious
materials containing novel cement systems. The purpose of this work was to achieve thehighest level of compressive strength in hardened mortar. The grain size and proportionsof ternary blended cement systems were calculated using the closest packing theory of
Furnas. The cast specimens were prepared by mixing the constituents with an extremely
small amount of water. After removal from the mold, the hardened products with thedensest packing cement systems were subjected to water absorption from the outside
surface, followed by two-stage heat curing. As a result, the densest packing design andpre-soaking treatment enable the production of hardened cement having ultra highcompressive strength of more than 460N/mm2.

Keywords：Ultra high compressive strength, Closest packing, Pre-soaking treatment,
Heat curing

INTRODUCTION

Ultra high strength concrete is a material thatenables higher reinforced concrete buildings andlonger civil engineering concrete structures, andas shown in Fig.1, there is competition in thedevelopment of its strength. Since the company
commenced sale of Ductal (ultra high strength
fiber reinforced concrete) in 2000, our technology
for precast concrete with a compressive strengthof 200 N/mm2 has become the fastest spreading inJapan. Also in 2006 we launched SFPC (silica
fume premix cement) which develops acompressive strength of 80 to 150 N/mm2, and in2010 we developed SFPC200 (silica fume premix
cement) which develops a compressive strength of
200N/mm2, which established ultra high strength
ready mixed concrete technology. However,thereafter the competition for development of
ultra high strength concrete intensified within
Japan, and in 2013 the highest design strength
concrete in Japan of 300 N/mm2 was developed asa precast member by another company1). Notethat reactive powder concrete that develops acompressive strength of 673N/mm2 was developedin France in 19942), and this is currently thehighest strength ever recorded in the world.
However, this overseas technology was achieved
using a special method known as the hot press

molding method (temperatures 250 to 400C) as
shown in Fig.2(a), a method that is applied to the
manufacture of fine ceramics. The method is notpractical as it sacrifices the major advantage ofconcrete that it enables any shape to be obtainedby assembling formwork and pouring. Therefore
in this research the constituent materials, mixes,
and production methods were studied with theobjective of achieving concrete with the highest
compressive strength that could be expected to becommercialized by normal pour molding into
formwork as shown in Fig.2(b).

700Compressive strength （N/mm2）

1.

Reactive powder concrete (France)[Hot press molding method]

673

600

World-record concrete[Cast molding method]

500

464

400

Ultra high strength Ultra high strength
fiber reinforced
concreteconcrete

300
200

®

Rock

250〜300

Steel

SFPC200®

180〜220

100

Normalconcrete01990

Fig. 1

1995

SFPC®

2000

150〜200
80〜1502005(A.D.)

2010

2015

2020

The competition to develop ultrahigh strength concrete in Japan

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太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

Pressure
Fresh concreteElectrically-heated wire

Fresh concrete

Mold

Fresh concrete
Mold

Pressure(a) Hot press molding method(b) Pour molding method

Fig. 2 Casting method for fresh concrete
Table 1

Materials

Material

Type
SymbolCharacteristics
Low-heat Portland cement LC Specific surface area of 3330cm2/g, Density of 3.24g/cm2
BinderQuartz powder
QP Density of 2.59g/cm2(B)
Silica fumeSF
Specific surface area of 20m2/g, Density of 2.29g/cm2
Fine aggregate
Silica sandS
Maximum size of 0.3mm, Density of 2.29g/cm2
Superplasticizer
SP
Polycarboxylic acid typeChemical admixture
Defoaming agent
DFA Polyether type (Polyalkylene glycol)

Table 2

No.

W/B
(%)

Unit contents (kg/m3)

B
LC
QP
1
13
180
913
362
2
15
199
876
347
* Replacement as a part of unit water content.

2.

Mix proportions

W

TEST METHODS

2.1 Materials, mix proportions, and mixing used
(1) Materials used
As shown in Table 1, low heat Portland cement(hereafter, LC), fine quartz powder (hereafter,
QP), and silica fume (hereafter, SF) were used as
the binder (hereafter, B). Also silica sand (hereafter, S) was used as the fine aggregate, and asuperplasticizer (hereafter, SP) and a defoaming
agent (hereafter, DFA) were used as chemical
admixtures.

SF
107
102

S

SP *

DFA *

Flow
(mm)

927

B×
2.5%

B×
0.02%

230
295

Air
content
(%)
2.2
2.0

(2) Mix proportions
The mix proportions were as shown in Table 2.
Here the method of processing the bindermaterials in order to obtain the maximum density
grading was investigated, with the objective ofobtaining a powder mixture that can flow with asmall quantity of water (hereafter, W) by reducing
as much as possible the gap between particles ofeach of the powders from which B was formed. In
other words, the densest packing state of adiscontinuous particle size distribution system of
2 to 4 powder components was calculated basedon the densest packing theory of Furnas 3), which23
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

is a convenient calculation method for given
number of components, particle size, and ratio ofsize. In this calculation method, if the number of
powder components is n+1, the void ratio of eachpowder is  (assumed to be the same), themaximum particle size is D1, the minimum
particle size is Dn+1, the ratio of size of the
maximum particle size and the minimum particle
size K = Dn+1 /D1, and the particle size ratio ofadjacent particles in the maximum density
system Dn+1 /Dn = K1/n, the maximum density for 2,
3, or 4 components of powder is obtained for
mixing proportions (volume ratio) of the n+1
components, Primary particle : secondary
particle : tertiary particle : quaternary particle

Number of components n+1＝1/(1+) :  /(1+) :  2 /(1+) :  3 /(1+)each term being divided by the sum total up tothe (n+1)th particle.
Here, for the LC and SF powders shown in
Table 1, when it is assumed that the average
particle sizes are D1 = 20 m and D3 = 0.1 m
respectively, and the void ratios are 1 = 3 = 0.5,
the ratio of size K = D3/D1 = 5×10-3, from therelationship between the number of components
and the ratio of size to give the maximum density
for the powder mixture shown in Fig.3, thenumber of components to give the maximum

3.05

5×10-3
Ratio of size K

Fig. 3

Relationship between the numberof components and the ratio of size
to give the maximum density for the
powder mixture

density is n+1 = 3.05, so that means 3 components.
In addition from the relationship Dn+1 /Dn = K1/n,
the particle size that should be provided between
LC and SF is calculated to be D2=(D1.D3)1/2 = 1.41
m. The powder particle size of QP shown in
Table 1 (particle size D2 =1.41 m, void ratio 2 =0.5) was adjusted to be this intermediate particle,
and the mixing proportions of each powder LC :QP : SF = 5.71 : 2.86 : 1.43 ≒ 6 : 3 : 1 (volume
ratio) for the 3 component binder, and two criteria
for water binder ratio (hereafter, W/B) of 13% and
15% were used. For each mix the absolute volume
of S was 355 L/m3, the percentage of SP added
was B×2.5%, and the percentage of DFA added
was B×0.02%.
(3) Mixing
The B, W, SP, S, and DFA were placed in an
omni-mixer (capacity 5 L), mixed for 6 minutes,
and the mixed mortar was poured into a form
(internal dimensions 50100 mm). Note that asshown in Table 2, in the range W/B = 13 to 15 %the consistency of the flow was in the range 230 to
295 mm, and the air content was 2.0 to 2.2 %,indicating that each mix had high fluidity toenable normal pour molding.
2.2 Water soaking and heat curing(1) Water soaking
After pouring into a normal mold (internal
dimensions 50100 mm), the test specimens thatwere cured in a sealed condition (at room
temperature 20C) up to an age of 48 hours were
removed from the mold, and subject to deairing
water absorption or boiling water absorption as
described below.
i) As shown in Fig.4(a), with the test specimens
completely immersed in water within a closed
vessel, water was supplied from the externalsurface to the interior of the test specimen by
reducing the pressure by evacuating the top
layer air using a vacuum pump. The deaeration
duration was varied to 4 levels: 0 minutes, 1
minute, 30 minutes, and 90 minutes. Also, thetest specimens were weighed before and after
the deairing water absorption, and the quantityof water absorbed (Vw) was calculated.
ii) As shown in Fig.4(b), with the test specimens
completely immersed in water in an open vessel,

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太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

Deaeration

Open vessel

Closed vessel
Water
Specimen

Water
(a)

Specimen

HeaterDeairing water absorption method(b) Boiling water absorption method

Fig. 4 Pre-soaking treatment for test specimens just after removal moldthe temperature was raised at about 5C per
minute using an electrical heater until 100C
was reached, and boiling was continued for 30
minutes. Then the test specimens were cooled
naturally in water to room temperature 20C.
Note that the test specimens were weighed
before and after the boiling water absorption,and the quantity of water absorbed (Vw) was
calculated.
(2) Heat curing
The test specimens that had been subjected to
the water absorption process of i) or ii) weresteam cured (rate of rise in temperature 15C/h,maximum temperature 90C, duration at maximum temperature 48 hours, rate of reduction intemperature 15C/h, 1 atm), then heating curing
was carried out (rate of rise in temperature
60C/h, maximum temperature 180C, duration
at maximum temperature 48 hours, rate of
reduction in temperature 60C/h, 1 atm).
2.3 Test items(1) Compressive strength tests
The compressive strength of the test specimens(dimensions 50100 mm) that had completed the
2 stage heat curing was measured using acompression machine (capacity 1,000 kN) in
accordance with JIS A 1108 “Method of test forcompressive strength of concrete”.

(2) Analysis of the composition of the hardenedmaterial
Test specimens (W/B = 15%) whose length was
cut in half using a cutter after pouring into themold (dimensions 50100 mm) and removal fromthe mold were subjected to deairing water
absorption for 30 minutes or to boiling water
absorption for 30 minutes immediately after
removal from the mold as described in Section
2.2(1), and then subjected to 2 stage heat curing
as described in Section 2.2(2). Also the bottom
surface in contact with the mold and the finishedsurfaces after pouring were ground immediately
after removal from the mold. Test specimens ofdimensions 25255 mm were cut from thesetest specimens as shown in Fig.5, impregnatedwith resin, ground, and subjected to carbon
vapour deposition to provide thin specimens for

25mm Surface portion
25mm
50mm
Internal portion

50mm

Fig. 5 EPMA specimens prepared by
cutting the heat cured specimens

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太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――(3) Hardened material micropore size stribution
Using test specimens (dimensions 5050 mm)
produced under the same conditions as describedin Section 2.3(2), test specimens of about 5 mm
square were cut from the surface portion (therange up to a depth of 5 mm from the surface) andthe interior portion (a range of depths from 15 to20mm from the surface), and the pore size
distribution was measured using a mercury
penetration porosity meter.

3.
3.1

TEST RESULTS AND DISCUSSION

Effect of deairing water absorption on thehardened cement material(1) Water saturation ratio of air voids in test
specimens
Fig.6 shows the relationship between the water
saturation ratio of air voids and the deairing
duration for test specimens that were subjected todeairing water absorption immediately after
removal from the mold. The water saturation
ratio of air voids (quantity of absorbed water Vw)
is the quantity of water as a percentage of thevoids in the test specimen obtained bymultiplying the air content of the fresh mortar (a)shown in Table 2 by the test specimen volume

50
Water saturation ratioof air void (Volume %)observation. Ten backscattered electron images
using an electron probe micro-analyzer wereobtained at both the surface portion of the thin
specimens (in a range up to a depth of 1 mm fromthe surface) and the interior portion (in a range of
depth 15 to 20 mm from the surface). The graylevel of the backscattered images depends on the
average atomic number of the observed image, so
by binarization (a process that converts an image
with contrasting density into 2 tones of black andwhite) of pixels occupied by unhydrated cement ora void, area regions were extracted as a detection
image, and the respective volume percentages(percentage content) were calculated fromstereology theory (in stereology theory the area
percentage is equal to the volume percentage).
For comparison the same backscattering electron
image observation and image analysis was
carried out on test specimens that were notsubjected to water absorption immediately after
removal from the mold.

W/B=15%40
30
20
W/B=13%
10
0
0

30
60
Deairing duration (min)90Fig. 6 Relationship between the water
saturation ratio of air void and thedeairing duration for test specimens
subjected to deairing water absorption
after removal from mold(Vm) (Vw /(V m .a)×100) . In both cases of W/B = 13%
and W/B = 15%, the longer the deairing duration
the higher the water saturation ratio of air voids,
and for the same deairing duration the water
saturation ratio of air voids was higher for W/B =15% than for W/B = 13%. In particular when the
deairing duration was 30 minutes or higher, thewater saturation ratio of air voids further
increased for W/B = 15%, although it virtually
peaked for W/B = 13%. It is considered that thiswas because the higher the W/B the coarser the
microstructure of the hardened material whenremoved from the mold, so it still had a microstructure with high water permeability, andwater could be more easily absorbed from outside.
(2) Compressive strength of test specimens
Fig.7 shows the relationship between thecompressive strength after heat curing and thedeairing duration for test specimens subjected todeairing water absorption after removal from themold. When the deairing water absorption was
carried out for 30 minutes, the compressive
strength was an average of 411 N/mm2 for W/B =13% and an average of 464 N/mm2 for W/B = 15%,
so it can be seen that for both values of W/B an
extremely high compressive strength was26
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

500

500

450
W/B=13%400

350

Compressive strength2
after heat curing (N/mm )Compressive strength2
after heat curing (N/mm )W/B=15%

400

350

300

300
0
Fig.7

450

W/B 13% 15%
Untrearied
Dearing
Boiling30
60
Deairing duration (min)

0
10
20
30
40
50
Water saturation ratio of air voids (Volume %)90

Relationship between the compressive
strength after heat curing and the deairing
duration for test specimens subjected todeairing water absorption after removalfrom moldobtained. However, when deairing water
absorption was carried out for 90 minutes, a
reduction in compressive strength was seen for
W/B = 13% compared with 30 minutes deairing
water absorption, although for W/B = 15% thevalue was almost constant even though thedeairing duration was extended. For shortdeairing durations of 0 minutes (water absorption
not carried out) and 1 minute, there was no majordifference in the compressive strength for W/B =13% and W/B = 15%. In contrast when the
deairing water absorption was carried out for 30
minutes or longer, the water saturation ratio of
air voids of the test specimens was higher before
the start of heat curing in the case of W/B = 15%
compared with W/B = 13%, so an ultra highstrength of 460 N/mm2 or higher was obtained.
This suggests that the water supplied from theoutside surface to the interior of the test specimen
immediately after removal from the moldfunctioned as reaction water during thesubsequent heat curing. In other words, it isconsidered that the water forcibly absorbed fromthe outside was used for curing within the test
specimen, and by contributing to the formation ofan extremely dense hard microstructure,
dramatically increased the compressive strength.

Fig.8 Relationship between the compressive
strength after heat curing and the water
saturation ratio of air voids for test
specimens subjected to deairing water
absorption or boiling water absorption
after removal from mold

3.2

Effect of boiling water absorption on the
cement hardened material(1) Water saturation ratio of air voids in test
specimens
Fig.8 shows the relationship between thecompressive strength after heat curing and thewater saturation ratio of air voids in test
specimens for test specimens subjected to boilingwater absorption after removal from the mold.
In this figure the data for the test specimens
subjected to deairing water absorption from
Figs. 6 and 7 is also shown for comparison. The
water saturation ratio of air voids for the test
specimens subjected to boiling water absorption
for 30 minutes was 48.6% for W/B = 13% and44.0% for W/B = 15%. In the case of boiling water
absorption, substantially the same state of water
saturation was achieved as for deairing water
absorption, regardless of W/B. Also, for the W/B =15% test specimens, when boiling was carried out
for 30 minutes in water or when deairing was
carried out for 30 minutes or more in water, in allcases the state was substantially the same, thevoids of the test specimens being about half filledwith water. As a result, it is considered that thevoids within the test specimens that were
subjected to steam pressure expansion due to the27
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

3.3

Analysis of composition of hardened cement
and the pore structure(1) Unhydrated cement content
Fig.9 shows the backscattered electron imagesof the interior of the hardened material after heatcuring for (a) test specimens subjected to deairing
water absorption, (b) test specimens subjected toboiling water absorption, and (c) test specimens
not subjected to water absorption after removalfrom the mold. The backscattered electron images
display parts with heavy elements bright andparts with light elements dark, so it is also
referred to as a composition image. In other words,
unhydrated cement (legend: C) is displayed inlight gray, hydrates (legend: H) are displayed indark gray, and voids (legend: P) are displayed inblack. From these images it can be seen thatunhydrated cement is dispersed throughout

boiling gradually absorbed water into the interior
from the outside by the pressure reduction during
natural cooling in the water.
(2) Compressive strength of test specimens
As shown in Fig.8, the test specimens thatabsorbed the water by boiling for 30 minutes had
an average compressive strength of 411 N/mm2
for W/B = 13% and 450 N/mm2 for W/B = 15%.
With boiling water absorption, the test specimen
after removal from the mold is rapidly heated andexperiences a 100C environment at an early age,
but achieves an extremely high strength after
heat curing, so it is considered that initial defects
such as temperature cracking, etc., due tointernal constraint in the boiling and coolingprocess are not allowed to occur in the hardened
microstructure.

P

C

H

H

H

C

H

C
P
C

C

P
H

10m
(a) With deairing water absorption

P

P
10m

(b) With boiling water absorption

C

H

10m

(c) Without water absorption

Fig. 9Backscattered electron images of the internal of the hardened material after heat curing(C: Unhydrated cement, H: Hydrate, P: Air void) )Table 3Calculated unhydrated cement content obtained by the backscattered electron image
analysis for surface portion and internal portion of the hardened materialType of pre-soaking treatment
With deairing water absorption
With boiling water absorption
Without water absoption

Surface portion
22.4 volume %21.0 volume %25.4 volume %Interior potion
18.8 volume %16.9 volume %20.1 volume %28
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

uniform continuous hydrates, and the voids thatare displayed in black are extremely few. Table 3
shows the calculated unhydrated cement content
obtained by image analysis of the backscatteredelectron images for the surface portion andinterior portion of the hardened material. It canbe seen that by absorbing water by deairing or byboiling after removal from the mold, at both thesurface portion and the interior portion theunhydrated cement content was reduced compared with when water absorption was not
carried out. From this it can be deduced that thewater absorbed into the interior after removalfrom the mold reacts strongly with the cement
due to the heat curing, and forms a dense andhard microstructure.
(2) Pore size distribution
Fig.10 shows the pore size distribution at thesurface and the interior of the hardened material
subjected to the heat curing for test specimens
subjected to deairing water absorption, test
specimens subjected to boiling water absorption,and test specimens not subjected to water
absorption. From this figure it can be seen thatabsorbing water after removal from the mold bydeairing or boiling reduces the large pores both at
the surface and the interior more than whenwater absorption is not carried out, and in

Cumulative pore volume (ml/g)

0.016
0.014

With deairing water absorption
With boiling water absorption
Without water absorption

0.012
Surface

0.010
0.008
0.006

Internal

{
{

0.004
0.002 -5 -4 -3 -2 -1
0
1
2
3
10 10 10 10 10 10 10 10 10
Pore size (m)Fig. 10 Pore size distribution at the surface
and the interior of the hardenedmaterial subjected to heat curing

addition the total volume of pores is reduced. In
this way it is demonstrated that water absorption
after removal from the mold causes refinement
and reduction of pores in the hardened material,
which contributes to achieving extremely highstrength.

4.

CONCLUSION

In this research, an investigation was carriedout into new materials and methods for producing
hardened cementitious material with the aim ofobtaining extremely high compressive strength by
the normal method of pour molding into a mold.
The following is a summary of the results
obtained in this research.
(1) Fine quartz powder with average particle size
adjusted to about 1.4 m was added as anintermediate powder to a binder using low
heat Portland cement and silica fume, and themixing proportions of low heat portland
cement : fine quartz powder : silica fume were
set to 6 : 3 : 1 to provide a 3 component binder
with the theoretically highest density particle
size, and high fluidity to enable pouring into
the mold was obtained at a low water binder
ratio.
(2) Test specimens obtained by normal pourmolding of the mortar obtained from the 3component binder for the highest density
particle size and a water binder ratio of 15%
were subject to either deairing water
absorption or boiling water absorption after
removal from the mold, and water saturation
ratio of air voids of about 50% was achieved.
(3) The test specimens that had been subjected towater absorption after removal from the moldwere then given 2 stage heat curing (steam
curing at a maximum temperature of 90Cand heat curing at a maximum temperatureof 180C), and it was possible to obtain a newhardened cement material that achieved acompressive strength of 450 to 464 N/mm2,
which is a new record by the normal pourmolding method.
(4) The unhydrated cement content in thehardened cement material was reduced by theforcible water absorption by deairing or
boiling after removal from the mold. In29
太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第169号(2015)：河野, 中山, 多田――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

addition, it was confirmed that large size
pores were reduced and the total pore volume
was reduced in the test specimens that were
subjected to water absorption after removalfrom the mold. From this it is considered thatthe cement reactivity was increased by theheat curing after water absorption after
removal from the mold, and the pores werefilled with hydrates, which enabled an
extremely high strength to be achieved.

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