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THESIS

The Effect of Curing Conditions on the Ton-113

strength cf Super Cement Mortars.

A Thesis
Submiitod to the Faculty of
The
LICKIGAN STLIJ CULLSGE
of
Agricultura and Applied Science.
by

3.0.Avory.

Candidata for the Degree of
Baoholor of Science

June, 1926.

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Peerle s Super Cement is made by the Peerless Portland

(D

Cement Co. at Uxion City, Mich.It is a discovery of an Eng-
lishinvestigator and was successfully used in Great Britian
a number of years before its introduction into Canada in 1920.

Super Cement is merely a more efficient form of Port-
land Cement and is rendered so by the incorporation of a
substance known as “Catacoll” during the manufacturing Pro-
cess. Catacoll itself has no more cementing value than raw
gypsum ordinarily used in the manufacture of Portland Gem-—
ent, a portion of which Catacoll replaces.It occupies no
greater volume and is anything but a water repellant.The
strength and impermeability developed in Super Cement mcr-
tars are derived from the reactions which occur between the
m1Xing water and the constituents of the clinker. fhe fun—
ction which Catacoll accomplishes is to facilitate these
reactions and thus insure that they will be more complete
than in the case of Portland Cement.

Super Cement hydrates more thoroughly than Portland.
Cement depends upon this prOperty far its strength and den-
sity. Consequently, greater strength in bond, tension and
compression can be expected from Super Cement mortars.

Super Cement is more efficient as a lubricant to the
mix thus minimizing the tendency toward segregatin— in and-
ling. As a result of this greater efficiency, Super Cement
produces a concrete of sufficient density which is so im-
pervious that no other means of water proofing is necessary.

Exactly the same machinery is used to powder Super

Cement as is used for Portland, but the Super Cement seems

93813

to be more finely ground. It has no initial set but produces
a uniform set curve from cast to final set. The forgoing was
taken from a bulletin published by the Peerless Cement Co.

In testing for the effects on the tensile strength of
mortar produced by different methods Of curing, a 1:3 mix of
normal consistiency was used. The normal consistiency of neat
cement was 253 and of a 1:3 mix, 15% of water by weight. The
sand used was cleant sharp and dry,and passed a no. 20 sieve.
The specimens were of the standard size adOpted by the Amer-
ican Society of Testing Materials and were tested at the end
of I,2,3,5,7,I4, and 23 days. Four briquettes were used for
eacn test and the average strength of the four taaen as the
final result. If a.specimen showed signs of weakness, i.e.
POOTIY tamped etc. and the strength fell much below theaver-
age of the others, it was discarded.

Different methods of curing were obtained by varying the
time that the specimens were left in dry air, moist air,and
water and also by changinv the briquettes from one medium to
another at different ages of the curing. The standard method
adOpted by the A.S.T.M. is to place the specimens in moist air
'for the first 24 hours and the balance of the time in water.
This method was varied by curing the first day in moist air
and then changing to dry air the 2nd, 3rd, 4th and 5th, 6th
and 7th, 2nd week and tne last two weeks, testing the Spec-
imens at the above mentioned intervals. Also specimens were
cured by placing in moist airxlry air, and water for“ the fU1l
28 days. modifications were also made from these by changing

to other mediums at different ages of the curing.

The results obtained from the series of tests seem to be
rather mystifying. It is a recognized fact that to elpose
Portland cement concrete to dry air isdetrimental to the final
strength of the concrete. This does not seem true for Super
Cement mortars, unless the exposure to dry air is very pro-
longed. Exposure to dry air not only hastens the set of the
mortar but actually seems to increase the final strength at
the end of the 28 day period. It was found that the mortars
could be exposed to dry air for the first 5 days and the rest
of the time in water and no harm done. In fact, the strength
at the end of 28 days was greater than that obtained by our-
ing the standard way. The highest strength, tho, was obtained
by curing the standard way for the first two weeks and then
exposing to dry air the last two weeks. Curing the full 28
days in dry air gave practically no strength at all. the mortar
almost crumbling at the touch.

cured

The final strength of thosefithe full 28 days in water
was almost as much as those cured the standard way,but the set
for the first few days was greatly retarded. Also, great care
had to be exercised when placing the specimens in water or
much of the mortar would wash away.

The conclusions arrived at thru the series of tests ind-
icate that to get the strongest concrete, cure the standard
way,i.e. keep the concrete as wet as possible for the first two
weeks and then expose to dry air after that.Also great care
must be exercised when placing Super Cement concrete under
water or much of the fine mortar will wash out and the strength

of the concrete will be greatly reduced.

The following is a table of the actual strengths as tested.
The letters under the ages at which the specimens were tested
denote how the Specimen was cured from the precceding testing
day to the one at which the test was made.For example,D under
the second day means that the Specinen was cured in dry air for
the second day, or D under the 3rd day means that the Specimen
was cured in dry air the third day or from the 2nd testing
period to the 3rd testing period etc.
Legend: 3- dry air.
M- moist air.
3- water.
The numbers under the letters give the average strengths

in pounds per square inch as tested.

Table of tested strengths.

Age of specimen (days)

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I 2 3 5 7 I4 28
M iv ll, IJ v I 1u I VJ
- 60 90 I40 210 240 260
In D ‘I W .) VJ J d J
- 60 I45 185 200 220 260
h N D J 'J W J
- 6O IBC I85 200 250 295
i; 2': 5 w n u; v w
A 55 95 225 230 250 290
K W W W D ’H ‘H
- 60 85 I50 220 255 275
IS ?7 if if 3? I) ll
- 60 90 I45 20 245 500
It: I"; W Y; W w D
- 65 IOO I50 215 250 400
D D D D D D D

50 100 12 I30 150 IIO 80

m i 1 to 4-, L .1 tJ‘.‘;fi, .
fable 0; be tel tti--_tns

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continued.

in

Age of specimens (days)
I 2 3 5 7 14 28
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