NATIONAL BUREAU OF STANDARDS REPORT

9343

Progress Report

INDUCED ACCELERATED DETERIORATION OF PORTLAND CEMENT CONCRETE

by

Raymond L. Blaine

Chemical Research Laboratory

RESEARCH LABORATORIES

Edgewood Arsenal, Maryland 21010

Contract D018-0-35=A6-02806

NATIONAL BUREAU OF STANDARDS

Washington, D. C, 20234

Semiannual

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
Distribution Statement

This document is subject to special export controls and each transmittal

to foreign governments or foreign nationals may be made only with prior

approval of the CO, US Army Edgewood Arsenal, Attn: SMUEA-TSTI-T, Edgewood Arsenal, Maryland 21010
NATIONAL BUREAU OF STANDARDS REPORT

NESS PROJECT NBS REPORT

421.04-12-4212442 9343

Progress Report

INDUCED ACCELERATED DETERIORATION OF PORTLAND CEMENT CONCRETE

Semiannual

by

Raymond L. Blaine

This document is subject to special export controls and each transmittal to

foreign governments or foreign nationals may be made only with prior approval

of CO, US Army Edgewood Arsenal, ATTN: SMUEA-TSTI-T , Edgewood Arsenal,

Maryland, 21010

Chemical Research Laboratory

RESEARCH LABORATORIES

Edgewood Arsenal, Maryland 21010

Contract D018-0-35-A6-02806

NATIONAL BUREAU OF STANDARDS

Washington, D. C. 20234

NATIONAL BUREAU OF ST

for use within the Government, and review. For this reason, th whole or in part, is not autho Bureau of Standards, Washing!

the Report has been specifically

IMPORTANT NOTICE

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

ss accounting documents intended

subjected to additional evaluation

listing of this Report, either in e Office of the Director, National

the Government agency for which apies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

FOREWORD

The work described in this report was authorized under Project No.

D018-0-35-A6-02 806 o This work was started in October 1965 and will continue

for 18 months. Experimental data are contained in Vol. 1 of notebook dated

October 1, 1965 assigned to R. L. Blaine.

Notices

Reproduction of this document in whole or in part is prohibited except with

permission of the CO, US Army Edgewood Arsenal, ATTN: SMUEA RPR, Edgev/ood

Arsenal, Maryland 21010; however DDC is authorized to reproduce the document

for United States Government purposes.

The information in this report has not been cleared for release to the general

public.

Disclaimer

The findings in this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents.

Disposition

When this document has served its purpose, DESTROY it.

- 3-
«

o n b 2
DIGEST

During the first six-month period most of the mortar and concrete speci- mens for use in this test series have been made. Tests have Indicated

the salt solutions which are most aggressive on mortar specimens, and

studies have been started on the feasibility of electrochemical corrosion

of reinforcing steel in concrete.

Mortar specimens, 4X4X16 cm, were made using a 1*3 and a 1:5 cement to sand

mix with both a Type I and a Type II cement. Of these specimens, 33 sets

of 10 were placed in various salt solutions and weekly measurements made

for six weeks of changes in fundamental resonance frequency, of weight

changes, and of electrical resistance. A number of failures were noted,

some as early as 2 weeks after being placed in the salt solutions.

Ammonium salts appear to be the most aggressive, and specimens made of the

Type II cement more resistant to attack than the specimens made of the

Type I cement.

Concrete cylinders, both 3X6 and 6X12 inches have been made from the same cements using silicions, aggregates and mixes designed for a 5000 psi and

a 2000 psi concrete. Additional small cylinders were made using a limestone aggregate. Reinforcing rods were placed in the axis of some of the

cylinders. These specimens are now being cured prior to test.

Preliminary tests have indicated that reinforcing steel in concrete can

be corroded by means of a direct electric current. The amount of corrosion

is dependent on the electrolyte used as well as the voltage and current.

Cracking of the concrete cylinders occurred in some trial experiments.

- 3-

TABLE OF CONTENTS

Page

Introduction 9

Cement s 9

Mortars 10

Concrete 11

Reagent s 12

Test Procedure 12

Results of Tests 13

Electrochemical Corrosion of Reinforcing 13

Bars in Concrete

Plans for Future Work 14

Table 1 Reagents Used 15

Table 2

Results of Tests with Type I Cement 16

Table 2B Results of Tests with Type II Cement 17

Appendix 1 Properties of Cements 19

Appendix 2 Properties of Concretes 21

Distribution List 23

Document Control Data - R&D , DD Form 1473, with 25

abstract and keyword list

-l-

INDUCED ACCELERATED DETERIORATION OF PORTLAND CEMENT CONCRETE

INTRODUCTION

There are many references in the literature to the deleterious effect on Portland cement concrete caused by certain chemicals. There is, however,

little information on the relative aggressiveness of the 4i^f£rent chemicals,

and to what extent the quality of the concrete or type of cement used in

the concrete may affect the degree of deterioration, or, how rapidly such

deterioration can be achieved. There are also references to cracking of

concrete caused by corrosion of the reinforcing steel, either by the pre- sence of salts in the concrete, or these in conjunction with stray electric

currents. Very little information is available on methods for accellerating such corrosion and cracking.

In order to determine the relative aggressiveness of various chemicals

which have been reported as being deleterious to concrete, a series of

screening tests were first made with low pressure steam cured mortars of

two qualities, of each of two types of cement, and after both moist and

dry storage. Concrete cylinders have been made and cured under more

normal conditions and will be exposed to the chemicals found to be the

most aggressive in the mortar tests. Reinforcing bars were inserted part

way into the axis of some cylinders, and these specimens will be used in

studies of electrochemical corrosion as a means of cracking reinforced

concrete.

This first progress report presents information on the cements used, the

proportions used for the mortars and concretes and their properties, the

chemical reagents used, as well as the methods of testing and the results

obtained with the more aggressive chemicals on the mortar specimens. Some

exploratory test results of electrochemical deterioration of concrete

specimens are also presented.

Cement s

Two lots of portland cement were procured from a mill supplying the Washington, D. C. area. Standard chemical and physical tests were made to

ascertain that the one lot was a Type I cement and the other a Type II

cement. Both lots of cement met Federal and ASTM specifications for low

alkali, non-air-entraining portland cements. The results of physical and

chemical tests are presented in Appendix 1.

-9-
Mortars

Two mortar proportions were used as follows:

Mortar "R" Mortar S 'L"

20-30 Ottawa sand, g 600 600

Graded Ottawa sand, g 600 600

#0 Gopher Silica sand, g 300 300

Cement, g 500 300

Water, ml 250 225

Mortar "R" has a 1:3 cement to aggregate ratio with a 0.50 water cement

ratio, whereas mortar "L" has a 1:5 cement to aggregate ratio with a water cement ratio of 0.75. The mortars were mixed in accordance with

Federal and ASTM specifications for portland cement. Trial mixes of

both mortars had a flow of 145 with 25 drops on the standard 10 inch

flow table. In making the 4X4X16cm prisms the 3 gang molds were vibrated

on a platform vibrator as filled in about 30 seconds. Vibration at

3600 vpm at 0.5 mm amplitude was continued an additional 90 seconds. The excess mortar was screeded off and a monel number tag placed in each

specimen for later identification. The molds were stored at 95- 100% re- lative humidity for 20 hours after which the molds were stripped and the

specimens weighed in air and in water. The specimens were then placed

in a container and steamed at 150°F for 24 hours after which they were

stored at 95 - 100% relative humidity for 3-4 weeks. After this, half of

the specimens of each of the groups of mortars were placed in laboratory

air. (The other specimens remaining in the high humidity room.) Each

specimen was placed on end with space between the specimens for circulation of air. With 2 cements, 2 mortars, and 2 conditions of storage,

there were 8 variables. A total of 480 prisms were made and cured.

The results of the specific gravity determinations indicated a slightly

higher specific gravity values than the theoretical:

Average

Theoretical

sp. gr.

Actual

sp. gr.

S.D.

Type I cement R mortar 2.307 2.317 0.007

Type I cement L mortar 2.285 2.315 0.006

Type II cement R mortar 2.307 2.356 0.007

Type II cement L mortar 2.285 2.321 0.004

S. D. is the estimated standard deviation of 12 determinations.

- 10-
The compressive strength of the moist stored specimens at the time of test was determined and the following results obtained;

PS 1 Type I cement

,

1:3 mortar 8665

Type I cement

,

1:5 mortar 4365

Type II cement , 1:3 mortar 10100

Type II cement , 1:5 mortar 4550

These compressive strength values were higher than anticipated for these

mixes

Concrete

Three concrete mix proportions were used as follows:

Mix A Mix B Mix C

cement , lb 24.2 15.95 24.2

3/8" aggregate, lb. 46.2* 46.2* 43.0**

sand, lb. 71.5 71.5 74.7

water, lb. 13.75 16.5 13.75

*Silicious, partially rounded.

**Crushed limestone.

Concrete mix proportions A and B were used with both the Types I and II

cements and mix C only with the Type I cement. The concrete was mixed in

a tilting drum mixer. The slump and weight per cubic foot was determined.

The mix A and C concretes were consolidated in the 1/2 cubic foot container

(for wt/ft^ determination) by means of vibration because of the low slump.

The 3X6 inch paper cylinder molds were filled in 3 layers and each layer

consolidated by vibration on a platform vibrator. Each layer was vibrated

until moisture appeared on the surface. With the lean, high slump con- crete, very little vibration was required.

Reinforcing rods, 3/8 inch size, were vibrated 4 inches into the axis of some of the cylinders after filling and held in place with clamps until the

molds were removed at 24 hours.

The specimens were stored at 100% relative humidity until they were 28 days

old when half of each group was placed in laboratory air and the remainder

(not used for compressive strength tests) remaining *in the high humidity

room.

The properties of the concretes are presented in Appendix B.

- 11 -
Using Type I cement and Mix A twelve 6X12 inch concrete cylinders were

made. Half of these cylinders had 3/8 inch reinforcing rods and the

others #6 reinforcing rods inserted into the axis. Twenty six 3X6 inch

cylinders with 3/8 inch reinforcing rods were also made with this mix

proportion. A total of 213 cylinders were made.

Reagents

Approximately 550 grams of each of the reagents listed in Table 1 was mixed with approximately 2750 ml tap water and placed in polyethylene

containers. In most instances there was complete solution, and in some there was an excess of the reagent. This quantity was adequate to cover

10 specimens placed in each container at the start of the test. The

containers were not covered and tap water was added to maintain coverage

of the specimens as water evaporated.

For the first series of tests, one specimen from each of the 8 variables

plus 2 duplicates, 1 from each of the cements, was placed in each

of the containers.

The one container with water only was used as a control to determine the

changes which occurred in resonance frequency with no reagent present.

Other reagents, such as DMSO, DMF, 1-2 Propanediol, DMSO with Aluminum

Potassium sulfate and sugar, and DMF with the same reagents were tried

but discontinued after a short time because of the difficulty of handling

these toxic solvents.

Some of the 4X4X16cm mortar bars have been placed on end in 3 to 4cm of

concentrated salt solutions.

Test Procedure

The 4X4X16cm specimens were each weighed to the nearest gram, after which

the fundamental resonance frequency was determined by means of a sonic

apparatus. Each specimen was then pressed against contacts about 3

inches apart to determine the electrical resistance. The measurements

were made prior to placing in the salt solutions and at weekly intervals

thereafter. Observations were also made of any cracking, checking or warping of the specimens. After being in the solutions, the specimens were washed in tap water, brushed with a soft bristle brush, allowed to

drain, and the adhering water blotted off with a paper towel before

weighing and other tests.

A reduction in the fundamental resonance frequency of 1300 cycles per

second was used as an arbitrary indication of failure. This corresponds

to an approximate 40% reduction in the dynamic modulus of elasticity for

the specimens used in this study. (A 40% reduction in the dynamic modulus

of elasticity is also used in freeze-thaw durability tests on concrete.)

- 12 -
Results of Test

A summary of the results obtained with the most aggressive solutions are presented in Table 2A for the Type I cement and in Table 23 for the Type

II cement. The approximate time required to attain a reduction of 1300

CFS in the fundamental resonance frequency where failure occurred is

presented in the one column, and in the last column is presented the re- duction in fundamental resonance frequency during a 6 week test period.

It may be noted in comparing the 1:3 cement to sand and the 1:5 cement to

sand mortars in these tables that the 1:3 mortars were more resistant to

attack. Also the specimens made of Type II cement (Table 2B) were more

resistant to chemical attack than were those of the Type I cement (Table

2A).

In addition to the effect of reagents listed in these tables, the speci- mens in citric acid solution sloughed off badly and at 6 weeks had lost

about 10% by weight. The sodium bisulfate and potassium bisulfate solutions had a severe surface reaction with the specimens at the start, after

which the specimens gained in resonance frequency. The specimens stored

in solutions of the other reagents have not indicated a significant loss

of strength nor loss of weight or cracking in 6 weeks of test. Specimens

stored in some of the salt solutions had an apparent increase in strength.

An analysis has not been made of the nature of the failure versus the

chemicals used. It was noted, however, that there was expansion in some instances, cracking in others, and softening and sloughing off of the sur- face with some specimens. A more complete description of the failures

will be presented in a later report.

The results of the duplicate specimens were in good agreement both with

respect to weight changes, and to changes in frequency.

The moist specimens stored in water for the same period as those stored in

the solutions indicated very little change in strength during the test

period.

Specimens placed on end in 3 to 4cm concentrated salt solutions have been

observed for signs of cracking or damage. The bottom part of specimens

stored in the concentrated ammonium acetate solution practically disintegrated in 24 hours and in 3 to 4 days severe sloughing occured up to

6 to 8 cm above the solution with both the Types I and II cements

Electrochemical corrosion of reinforcing bars in concrete

Some exploratory tests have been made of the time required to cause enough

corrosion of the reinforcing bars in concrete so that the concrete specimen splits open. The 3X6 inch cylinders with reinforcing rods in the

axis were placed on end in an electrolyte. The electrolyte came within

1/2 inch of the top of the cylinder. The protruding rod was connected to

the anode and the electrolyte to the cathode. Various electrolytes have

been used, including NaCl, NH^Cl, CaCl2

> NaAcetate, and Na2S0^. Two

voltages have been used, a HOdc and 18dc. Arrangements have been made

to obtain intermediate voltages.

- 13-
Small 2X4 inch cylinders could be cracked in about 1 hour with HOdc.

Enough heat was generated to boil the electrolyte surrounding the specimen. With the larger specimens (3X6 inch) cracks sometimes developed in

3 to 4 hours. Using 18 volts a number of days were required to crack

the cylinders. With both voltages, the corrosion product was extruded as

a liquid or suspension around the top where the reinforcing rod entered

the specimen. The corrosion product was then also forced out through

planes of weakness or through the cracks which sometimes formed in the

concrete cylinders. Although a fairly large quantity of the corrosion

product came out of the concrete into the electrolyte, no further damage

to the cylinder was observed. Concrete cylinders which were split open

manually after the electrochemical treatment indicated severe corrosion

of the reinforcing bar, and the presence of corrosion products in the

cracks. The use of chlorides reduced the resistance of the concrete

specimens and resulted in a greater current. However, it appeared that

a soluble corrosion product was formed which, when forced out, either

dried on the surface or precipitated in the electrolyte. When the acetate

salt was used, the corrosion product was extruded where the steel entered

the cylinder. When this cylinder was split, there was no corrosion on

the steel bar in the concrete. The problem of containing the corrosion

product where it will cause splitting of the concrete has not been solved.

Plans for future work

Measurements will be continued at less frequent intervals of the changes

of fundamental resonance frequency of the 4X4X16 cm mortar specimens re- maining in the salt solutions.

Non reinforced 3X6 inch concrete cylinders will be placed in solutions of

the more aggressive chemicals and measurements made of the changes in

fundamental resonance frequency.

Experiments will be continued to determine the electrolyte and voltages

best suited for the electrochemical corrosion of the steel in reinforced

concrete

- 14 -
No.

12

3

4

56

78

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

30

31

TABLE I

Reagents used

Water

Sodium Sulfate

Magnesium Sulfate

Stearic acid

Ammonium Sulfate

Ammonium Nitrate

Sodium Thiosulfate

Sugar

Sodium bisulfate

Potassium Sulfate

Ferrous Ammonium Sulfate

Ammonium Persulfate

Potassium acetate

Ammonium chloride

Sodium Sulfite

Ferric Ammonium Sulfate

Citric acid

Sodium Bisulfite

Ammonium Acetate

Sodium Acetate

Ferric Sulfate

Aluminum Potassium Sulfate

Potassium Bisulfate

Cupric Sulfate

Ammonium Sulfate, and sugar

Aluminum Potassium Sulfate and sugar

-13
TABLE 2

Time for Reduction in

Mortar Reagent

1300 cps reduction in resonance frequency

resonance frequency

in 6 weeks

weeks cps

Type I cement, NH4 C1 3

1:3 cement to sand nh4no3 4

moist (nh4 ) 2 s

2 08

5 NH/^Ac 750

(NH4 ) 2 S04 350

Type I cement

,

nh4no3

3

1:3 cement to sand (nh4 ) 2 s208

3

dry nh4ci 6

NH4 Ac 950

(nh4 ) 2 so4 90

Type I cement

,

(nh4

) 2 so4

2 1:5 cement to sand nh4no3 2

moist NH4 Ac 4

(nh4

) 2

s

2 0

8

3

nh4ci 3

k2 so4

4

MgS04

6

Type I cement

,

nh4no3

2 1:5 cement to sand

8<Ac 8

3

dry 4

NH4C1 5

k2 so4

5

(nh4 ) 2 so4

6

MgS04

6

_
TABLE 2B

Time for Reduction in

Mortar Reagent

1300 cps reduction in resonance frequency

weeks

resonance frequency

in 6 weeks

cps

Type II cement

,

nh4ci 1210

1:3 cement to sand NH^Ac 970

moist (nh4

) 2 s 2 o8 725

nh4no

3

640

(nh4

) 2 so4 200

Type II. cement,

1:3 cement to sand

dry

nh4 ci

NH4 Ac

(NH4

) 2 S

2 0

8

NH4N0

3

1010

900

780

770

Type II cement

,

NH4C1 2 1:5 cement to sand NH4 Ac 2 moist (nh4 ) 2 so4

5 NH4N0

3

1050

(nh

4

) 2

s 2 o

8 530

NaAc 110

Type II cement

,

NH4CI 3

1:5 cement to sand NIL Ac 1150

dry nh4no

3 1130

(nh4

) 2 so4 700

(nh4 ) 2s 2 o8 120

NaAc 90

-u-

Appendix 1 PROPERTIES OF CEMENTS

CHEMICAL ANALYSIS

Type I cement Type II cement

1st Test 2nd Test 1st Test 2nd Test

Loss on ignition, % 1.6 1.6 1.2 1.2

Insol, residue, 7, 0.14 0.18 0.18 0.14

S03 , 7o 2.1 2.1 1.9 1.9

MgO, % 2.5 2.5 2.1 2.1

Si02 , % 21.1 21.1 22.5 22.6

a12°3

, % 6.0 5.9 4.1 4.1

Fe2 03 , % 2.4 2.4 4.1 4.1

CaO, % 63.7 63.6 63.6 63.6

Total alkali as Na2 0, 70 0.52 0.54 0.43 0.42

C 3 A 12.0 11.6 3.9 3.8

c 3 s 48.8 49.3 48.8 48.4

c3 s 23.8 23.4 27.8 28.5

C

4 AF 7.3 7.4 12.4 12.6

PROPERTIES OF CEMENTS

PHYSICAL TESTS

Type I cement Type II cement

Autoclave expansion °/fO 0.11 0.01

Initial set hrs:min 3:35 4:25

Final set hrsrmin 5:40 5:50

Fineness cm^/g 3390 3420

Air 1:4 mortar 7. 8.2 9.4

Compressive strength Id psi 1260 1300

Compressive strength 3d psi 2801 2215

Compressive strength 7d psi 4095 3510

- 19 -

Appendix 2

Type I cement Mix A

Type I cement Mix B

Type I cement Mix C

Type II cement Mix A

Type II cement Mix B

PROPERTIES OF CONCRETES

Slump

in. wt/ft^ bags/yd^

Comp . ! 7d

Strength psi

28d

0.1 142 6.27 3590 5220

6.5 138 4.20 1160 2010

0.2 144 3730 4760

0.7 142 6.35 3520 5250

7.5 137 4.19 820 1820

-n-

DISTRIBUTION LIST

a. Twenty copies of the report shall be forwarded to Defense Documentation Center Headquarters, Attention: DDC-IRS, Cameron Station, Alexandria,

Virginia 22314.

b. Twenty- three copies of the report shall be forwarded to Commanding

Officer, U. S. Army Edgewood Arsenal, Attention: SMU1A-RCRP, Research

Laboratories, Mr. Gordon N. Jarman, Project Officer, Edgewood Arsenal, Maryland 21010.

- 23-

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20234

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2b. CROUP

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3 REPORT TITLE INDUCED ACCELERATED DETERIORATION OF PORTLAND CEMENT CONCRETE

4 DESCRIPTIVE NOTES (Type of report and inclusive dates)

5 AUTHORfS.) (Last name, first name, initial) Blaine, Raymond L.

6 REPO RT DATE 7a. TOTAL NO. OF PAGES 7b. NO. OF REFS

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8a CONTRACT OR GRANT NO. 9a. ORIGINATOR’S REPORT NUMBERfS,)

D018-0-35-A6-02806

b. PROJECT NO. Semiannual Progress Report

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10 A V A IL ABILITY /LIMIT A TION NOTICES This document is subject to special export controls and each transmittal to

foreign governments or foreign nationals may be made only with prior approval of

the CO, US Army Edgewood Arsenal, ATTN: SMUEA-TSTI-T , Edgewood Arsenal, Md. 2101

11 SUPPLEMENTARY NOTES 12 SPONSORING MILITARY ACTIVITY Ballistics Research Laboratories

Mortors Aberdeen Proving Ground, Maryland

13 ABSTRACT

Mortar specimens were made using a 1:3 and a 1:5, cement to sand ratio, with both

a Type I and a Type II cement. The specimens were placed in various salt solution

and measurements made for 6 weeks of weight changes and of changes in fundamental resonance frequency. A number of failures were noted,- some as early as 2 weeks

after being placed in the salt solutions. Ammonium salts appear to be the most

aggressive, and specimens of the Type II cements more resistant to attack than the

specimens of the Type I cement. Preliminary tests have indicated that reinforcing

steel in concrete can be corroded by means of a direct electric current. The

corrosion sometimes causes cracking of the concrete specimen.

.l- BEY WORDS: Aggressive salts, cement properties, concrete properties, corrosion,

electrochemical corrosion, mortar, reagents, and resonance frequency

DD FORM

1 JAN 64 1473

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