\

THE EFFECT OF THE PELLET FORM OF CALCIUM CHLORIDE,

AS AN ADMIXTURE, ON THE STRENGTH OF
PORTLAND CEMENT CONCRETE

By
John Thompson.g£pall

A THESIS
submitted to the School of Graduate studies at Michigan
state College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
MASTER OF SClENOE

1951

I" #45“!

ACRE; O W LEM} M EN T

The author wishes to express his sincere thanks to
Dr. C.O.Harris and Broressor C.M.Cade, of the Civil Engin-
eering Department, and Mr. E.A.Finney, of the Michigan State
Highway Department, for their guidance and inspiration in
this investigation.

Grateful acknowledgment is also due to Mr. Roy Fulton,
of the Michigan State highway Department, for his assistance
in the design of the concrete mixes used.

The writer is indebted to the Dow Chemical Company

whose financial support made this project possible.

TABLE OF CONTENTS

CHAPTER PAGE
I 0 INTRODUCTION 0 C O O O O O O O O O O C O O O 1
Purpo S e c c o c o o c o c c c o o c c o 0

Reasons for conducting this project . . .

a: +4 rd

II. ORGANIZATION FOR TESTING SCHEDULE . . . . .

III. MATERIALS-dGENERAL DESCRIPTION,SOURCE,
MID STORAGE o o o o o c o o c o o c c o o c

Calcium.chloride . . . . . . . . . . . . .
Aggregate . . . . . . . . . . . . . . . .
Cement . . . . . . . . . . . . . . . . . .
Water . . . . . . . . . . . . . . . . . .
IV. DETAILS OF PROCEDURE . . . . . . . . . . . .

Design of the concrete mix used . . . . .

Oommxlxlmww

Proportioning, mixing, and molding cylinders
Curing . . . . . . . . . . . . . . . . . . 10
Testing . . . . . . . . . . . . . . . . . 10
V. RESULTS . . . . . . . . . . . . . . . . ... 12

VI. COMPARISON OF RESULTS WITH PREVIOUS TESTS
ON CALCIUM CHLORIDE . . . . . . . . . . . . 17

VII 0 CONCLUSIONS 0 0 O O I O O O O O 0 O O O O O 19

TABLE
I.
II.

III.

LIST OF TABLES

Sieve Analysis of Pellet Calcium Chloride . .
Specifications for and Sieve Analysis of
Aggregate . . . . . . . . . . . . . . . . . .
Increase of Compressive Strength of Concrete
due to the Addition of 2 Percent of Commercial

Calcium Chloride . . . . . . . . . . . . . .

PAGE

17

LIST OF FIGURES

FIGURE PAGE
1. Pellet Calcium.Chloride

Flake Calcium Chloride . . . . . . . . . . . . . h

2. Compressive Breaking Strength . . . . . . . . . 13

3. Compressive Breaking Strength . . . . . . . . . 1h

h. Slump . . . . . . . . . . . . . . . . . . . . . 15

5. Percent Entrained Air . . . . . . . . . . . . . l6

I. INTRODUCTION

11-311mm

It is the purpose of this thesis to determine the
effect of the pellet form of calcium chloride on the com»
pressive strength of portland cement concrete, at early

ages, when used as an admixture.
B. Reasons for Conducting this Project

Studies carried on by the Bureau of Standards in 193h
indicated that the use of the flake form of calcium chloride
as an admixture resulted in a portland cement concrete hav-
ing a higher compressive strength at ages up to 28 days than
concrete not containing the admixture. This project was
undertaken because improvements since 193h in the manufac-
ture of cement (such as better quality-control of raw mater-
ials and finer grinding) and the recent production of cal-
cium chloride in the form of pellets, rather than flakes,

has made some of the available information obsolete.

II. ORGANIZATION OF TESTING SCHEDULE

In order to allow for variations in different batches
of concrete, due to the impossibility of controlling the
gradation and moisture content of the aggregate exactly, it
'was decided to pour the cylinders in four series of five
batches each. The batches contained 0, l, 2, 3, and h per-
cent of pellet calcium chloride, respectively, and consisted
of five cylinders each. Four of these cylinders were used
for the tests reported in this thesis and the fifth was
stored for a long time study. (The percentages mentioned
‘were used because the previous tests in l93h indicated that
the optimum amount would fall somewhere within this range.
'Results of this test appear to have borne this fact out.)
The cylinders from each batch were tested at the ages of l,
3, 7, and 28 days. By this method it was possible to get
four test results (one from each series) for each percent
admixture at each of the ages mentioned. The value reported
for compressive strength is in each case the average of

these four test results.

III. MATERIALS--GENERAL DESCRIPTION, SOURCE, AND STORAGE
A. Calcium Chloride

The calcium chloride was obtained from the Dow Chemical
Company, Midland, Michigan. This product, as well as having
a different shape, has a different purity than the flake form.
The latter contains about 77 percent pure anhydrous calcium
chloride while the pellet form is about 96 percent pure. An
idea of the particle size, size distribution, and shape may
be obtained from the photograph in Figure l and the sieve
analysis in Table I. The calcium chloride used in this pro-
Ject was stored in moisture proof steel drums until immed-

iately before using.

TABLE I
SIEVE ANALYSIS OF PELLET CALCIUM CHLORIDE

Sieve Size Percent Retained Percent Passing

3/8" 0 100

#u 2.5 97.5
#8 63.2 3h.3
#10 25.7 8.6
#16 5.h 3.2
#30 ‘ 1.7 1.5
#50 0.5 1.0

#100 0.2 0.8

m

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A.
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E
K
A
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PELLET CALCIUM CHLORIDC

 

 

 

Figure l

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B. Aggregate

The aggregate used was obtained from the American Aggre-
gate Corporation, Brighton, Michigan. The sand was to meet
Michigan State Highway Department specifications for 2N3 and
the gravel the same specifications for 6A. As may be seen by
referring to Table II, the sand met specifications, but the
gravel did not. This gave a slightly harsher mix than would
have resulted if the gravel had contained a higher percentage

of fine material, but in no other way affected the test.

-6-

TABLE II
SPECIFICATIONS FOR AND SIEVE ANALYSIS OF AGGREGATES

Sieve Percent Specifications*
Size Passing Percent Passing
Coarse 2" 100.0 100.0
aggregate
1 1/2" 100.0 95-100
1" 63.1 60-90
1/2" 1h.O 25-55
#a 0.4 0-8
Fine 3/8" 100.0 100.0
aggregate .
#4 97.9 95-100
#8 8h.6 65-95
#16 66.2 35-75
#30 h6.9 20-55
#100 4.9 0-10

*Specifications are those of the Michigan
State Highway Department for "NS natural
sand and 6A gravel.

As the quantity of aggregate required for the project
exceeded the capacity of inside storage bins, it was stored
in outside bins which were rectangular in shape and two feet
high. Waterproof canvas tarpaulins were used to protect the
aggregate from dirt and freezing. Several days before being
used, the aggregate was placed in inside bins so that it

could come to room temperature.
C. Cement

Type I-normal portland cement was used in the project.
This is cement that contains no air entraining agent and is
suitable for use in general concrete construction. All
cement used in the project came from the same "grind" and
'was obtained from the Peerless Cement Company, Detroit, Michi-
gan. It was delivered in the customary moisture-resistant

paper bags and stored on platforms in the concrete laboratory.
D. Water

The water used was from the main supply to Michigan

State College.

IV. DETAILS OF PROCEDURE
A. Desigg of the Concrete Mix Used

The mix for the concrete used in this project was designed
using the Michigan State Highway Department mortar voids method
of proportioning. It was designed with a cement factor of 5.5
sacks of cement per cubic yard of concrete, a slump of three
inches to four inches, and a waterbcement ratio of 6.06 gallons
per sack of cement. The resulting prOportions, by weight of
dry materials, were 1 part cement, 2.h6 parts of sand, and 3.76
parts of coarse aggregate. Trial mixes were made up before the
project was started and resulted in a plastic, workable con-

crete having a slump of three inches.
B. Proportioning.gMixing.gand meldingggylinders

1. Proportioning
The ingredients used in making the concrete-dwater, cement,
and aggregates--were weighed on a Toledo platform scales having
a dial indicator reading to the closest one ounce. The calcium
chloride admixture was weighed on a Toledo laboratory balance,

accurate to the closest half gram.

2. Mixing
In order to prevent the caking of cement and sand to the

inside of the rotating drum type mixer, it was necessary to

add the materials to the mixer in the following manner:

Add the gravel (coarse aggregate) and then the sand (fine
aggregate) to the mixer, start the mixer rotating and add
cement, pour in water slowly so that it mixes with the
cement and aggregate as it is added and does not splash out
of the mixer, and finally throw in the admixture. .A mixing
time of two minutes was used; this started immediately after
the addition of water was completed and just as the calcium

chloride was added.

3. Molding Cylinders

After the completion of the mixing, the fresh concrete
was dumped into a large metal pan from.which it was placed by
a metal hand scOOp into 6 inch by 12 inch cylindrical steel
molds. The cylinders were filled by thirds, each third
being rodded 25 times with a five-eigth inch round steel rod
whaving a rounded end. After the final rodding the molds were
struck off with a steel trowel and then finiShed with a flat
wooden float.

The molds used were made by cutting six inch seamless
steel tubing in 12 inch lengths, splitting it, and attaching
brackets and thumbscrews to hold the longitudinal seam closed
and also to hold the cylinder to 10 inch by 10 inch by 1/2
inch steel base plates. Although all joints were machined it
was necessary to seal them to prevent leakage. Scotch mask-
ing tape proved satisfactory for the vertical longitudinal
joints, while paraffin was used on the joints where the cylin-

der and base plate came in contact.

.10-

C. Curigg

After the molding of the cylinders was completed they
were covered with damp burlap to prevent evaporation. Twenty
four hours later the burlap and steel molds were removed and
identifying marks placed on all cylinders. The one day speci-
mens were capped and tested at this time while the other cylin-
ders were placed in the moist room to be cured until tested.

The moist room is an insulated room of controlled humid-
ity and temperature. The temperature is 70 degrees Fahren-
heit and the relative humidity is 98 percent. Specimens

stored in the“ moist room were removed just prior to testing.

EM

1. Test Performed on Fresh Concrete
Slump. After dumping the concrete from the mixer and prior
to filling the molds, two slump tests were made on each

batch.

Air content. At the same time that the slump tests were
being made, another test was performed to determine the per-
cent of entrained air in the concrete. The Klein pressure-

type entrained air indicator was for this determination.

2. Testing Cylinders for Compressive Strength
Immediately upon removal from the moist room, specimens
to be tested were capped with plaster of Paris. (Note: Only

the top surfaces of the cylinders were capped as the bottom

surfaces which had been in contact with the base plates met
the American Society for Testing Materials specifications for
planeness.) After standing for about an hour so that the caps
could set and harden, the cylinders were placed in the
300,000 pound Rhiele hydraulic compression testing machine.
Load was applied at the rate of 35 pounds per square inch per
second until the cylinders failed.

Because the diameter of the individual molds varied
from top to bottom, and because the diameter of different
molds were not the same it was necessary to find an aver—
age area for each cylinder. This was done by measuring, with
caliphers, the daimeter at the top, middle, and bottom of each
cylinder, selecting each diameter so that it made an angle of

120 degrees with preceding one.

V. RESULTS

It may be easily seen by referring to Figure 2 that the
addition of calcium chloride in any of the percents used
results in a higher compressive strength, at ages up to
seven days, than if no calcium chloride is used. At 28
days, however, concrete to which 3 percent and A percent
calcium chloride was added, had a lower compressive strength
than concrete having no admixture; while the concrete con-
taining 1 percent and 2 percent still showed an improvement.

Figure 3 presents the same information as Figure 2 and
shows that the percent increase in compressive strength for
a given amount of calcium chloride was greatest at one day.

Slump, which was used as measure of consistency, showed
an increase as 1 percent and 2 percent calcium chloride were
added to the mix and then a decrease as 3 percent and h per-
cent were used. This is shown graphically in J-"igure A.
Although slump gives some measure of the workability, the
latter is impossible to measure exactly. It was noticed,
however, that concrete containing calcium chloride in any
percent seemed to be more sticky and plastic than concrete
containing none.

The air content of all mixes containing up to 2 percent
of admixture was constant. Beyond this point, as may be seen

in Figure 5 there was an increase in air content with an

increase in the percent of admixture.

-13-

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1 111111 1 - . . . . -1 1 1 . .111. ..1 111 ,7- 1-1- 1 1- 1-1.».
_ ET HUM-55 SHE-w xqbu-xmq _ . H H
_ H H H H 1 H
H
. H , H

H : H,

VI. COMPARISON OF RESULTS WITH PREVIOUS TESTS
ON FLAKE CALCIUM CHLORIDE
The results of tests using the pellet form or calcium
chloride may be compared, by means of Table III, to tests

performed by the listed agencies, prior to 193k.

TABLE III

INCREASE IN COMPRESSIVE STRENGTH OF CONCRETE DUE TO
THE ADDITION or 2 PERCENT OF COMMERCIAL CALCIUM CHLORIDE*

(All specimens stored in moist atmosphere)

Age at test Portland District National This

Cement of Bureau of Test
Assoc. Columbia Standards
percent percent percent percent

1 day 80 114 91

2 days h8 52

3 days #6 62 #6

7 days 25 21 29 19

28 days 7 1h 5

*Rapp, Paul. Effect of Calcium.Chloride on

Portland Cements and Concretes, Proceedings
of the Fourteenth Annual Meeting of the High-
way Research Board, December l93b. (Note:
Results of pellet calcium chloride were added
to original table.)

Tests on slump, as indicated in Figure A showed an

increase in slump up to 2 percent calcium chloride and then

I
AII‘
‘

v...- 1

A-
V—

—18-

a decrease. Previous tests, using flake calcium chloride
with a purity of about 77 percent, indicated an increase in
consistency up to 3 percent of commercial calcium chloride.
This curve was still increasing at 3 percent but its slope was
decreasing. Because of the lower purity of the flake calcium
chloride the difference in the maximum points of the curves
might be expected; however, in these previous tests the flow
of fresh concrete, and not slump, was used as a measure of
concistency and consequently an exact comparison is not

possible.

VII. CONCLUSIONS

1. The use of the pellet form of calcium chloride, in
amounts up to 2 percent by weight of cement, results in an
increase in the strength of portland cement concrete at all
ages up to 28 days. Two percent is the Optimum amount of
admixture to use as far as strength is concerned.

2. The consistency of concrete changes as calcium
chloride, up to 2 percent, is used as an admixture. This
results in a more workable concrete; however, it it is desired
to hold a given slump it would be possible to reduce the water
content. This would, of course, lower the water cement ratio
and result in a further increase in strength.

3. The percent of entrained air in concrete made with
Type I cement is not affected by the use of pellet calcium
chloride in amounts up to 2 percent. As the amount of cal-
cium chloride is increased up to h percent, the amount of air

entrained is also increased.

 

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