Table 13. Shrinkage of concrete containing
slightly decreased the shrinkage. DP at 6% de-
antifreeze admixtures.
creased the shrinkage by 29% compared to the
control specimens.
Mixture
Dosage
Percent length change
The shrinkage test results suggest that the can-
no.
Admixture
(%)
at 4 days
at 7 days
didate antifreeze admixtures are benign to con-
1A
Control
0
0.008
0.024
crete at 6% dosage. The 8% dosage shows a ten-
1B
Control
6
0.007
0.025
dency toward increased shrinkage. The potential
2A
PolarSet
6
0.020
0.046
for shrinkage should be checked on actual job
2B
PolarSet
6
0.009
0.031
concrete when admixtures are used above 6%
3A
DPTC
6
0.003
0.022
3B
DPTC
6
0.005
0.023
dosage.
4A
DP
6
0.001
0.019
4B
DP
6
0.003
0.016
Phase 3: Prototype
5A
PolarSet
8
0.014
0.045
slab-wall application
5B
PolarSet
8
0.021
0.052
6A
DPTC
8
0.024
0.054
6B
DPTC
8
0.016
0.049
Objective
7A
DP
8
0.019
0.049
To assess the practicality of using the newly
7B
DP
8
0.015
0.045
developed antifreeze admixtures in a full-scale
structure with low risk and easy access for moni-
* Negative sign indicates shrinkage (negative expansion).
toring.
Experimental approach
not seem to have a significant effect on the overall
Numerous chemical combinations were inves-
quality of the air-void parameters. Therefore, it is
tigated for approximately two years before two
deduced that these admixtures do not adversely
formulations were selected for final consideration.
affect the freezethaw durability of concrete.
The two prototype admixtures are referred to as
Task 6: Shrinkage. In addition to strength and
DP and DPTC. Disclosure of their chemical com-
durability, concrete must exhibit adequate vol-
position is withheld as the formulations are pro-
ume stability. Excessive expansion or contraction
prietary.
of concrete elements can lead to joint damage,
At CRREL, a composting bin consisting of a
bulging, and cracking. Chemical admixtures have
16.5-cm-thick reinforced slab on grade 3.7 m wide
been known to affect the drying shrinkage of con-
by 4.6 m long with 0.9-m-high, reinforced 20.3-
crete during the curing period. Concrete mixtures
cm-thick walls on three sides was cast 1718 Feb-
containing the candidate admixtures and admix-
ruary 1994. Site preparation consisted of remov-
ture-free control mixtures were tested for drying
ing a meter of snow from the ground, placing
shrinkage that occurred during their first seven
days of curing. Beam specimens (25 mm2, 285 mm
about 10 cm of dry sand on the newly exposed
but frozen ground, and setting the forms and re-
in length) were cast and tested according to ASTM
inforcing steel. The concrete was placed in the
C 157. The specimens were mixed and cast at
forms, consolidated, and finished as usual. A plas-
room temperature. The control specimens were
tic sheet was placed over the concrete for three
cured at room temperature and the others were
cured at 7C. Their initial length was measured
days to minimize water loss. The wood forms
were removed from the walls 20 hours after the
24 hours after casting. The specimen lengths were
concrete was cast. No thermal protection was pro-
measured again four and seven days later. These
vided to the concrete. Plastic pullout cylinders 10
measurements were compared to the initial read-
cm in diameter by 15 cm long were cast into the
ing for each specimen. The length changes ex-
slab and the top of the wall to provide in-situ
pressed as a percentage of the initial lengths for
strength-gain results. No control concrete was cast
each specimen are presented in Table 13.
on this application.
The data show that there was a significant in-
Thermocouples were embedded in the concrete
crease in the shrinkage of all specimens contain-
at selected locations to monitor the air and con-
ing the admixtures at the higher percent (8%).
crete temperatures by means of electronic data
While PolarSet at 6% increased the shrinkage by
loggers. Special attention was given to work-
more than 50% compared to the shrinkage of the
ability, finishability, thermal effect of the con-
control specimens, use at the normal dosage range
crete mass, temperature gradients, and strength
recommended by the manufacturer conforms to
development.
the requirements in ASTM C 494. DPTC at 6%
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