Table 4. Admixtures that will produce strength at
low temperature, but it recovers full strength
10C at least as fast as normal concrete cured at 5C.
once warm weather returns. Thus, antifreeze
admixtures are sort of an insurance policy against
Dosage
Water to
unexpected freezing.
by wgt of cement
cement ratio
Admixture
Chemicals
(%)
(w/c)
The above discussion assumes that concrete
cast during cold weather must attain significant
1
Sodium nitrite
6.0
0.45
early or full late-age strength, or both, to be ser-
Potassium carbonate
0.06
viceable. However, attaining full strength may
2
Sodium nitrite
6.0
0.48
not be necessary. If less late-age strength can be
Sodium sulfate
2.0
tolerated, at least to the degree that now happens
3
Sodium nitrite
6.0
0.45
with concrete cast during hot weather, many of
Calcium nitrite
2.0
our everyday chemicals become potential anti-
4
Sodium nitrite
9.0
0.45
freeze admixtures. Chemicals such as automobile
antifreeze, alcohol, deicing salt, and common
even available. For short-term needs,
fertilizer can play an important role in protecting
there is another way to approach win-
ter concreting. This report shows that
Table 5. Everyday chemicals that allow concrete to gain at least
simply adding chemicals to the mix
75%* strength after being at low temperature for 28 days followed
water will make the resulting mortar
by room temperature for 28 days.
(concrete) resistant to freezing. These
Dosage
chemicals, called antifreeze admix-
by weight of
Strength (%) relative to mortar
cured 28 days at 20C
tures, serve to depress the freezing
cement
5C
10C
20C
w/c
(%)
point of water and to accelerate the
hydration rate of cement. Their effec-
Deicers
tiveness depends on temperature,
Calcium chloride
0.41
3
121.3
94.9
80.0
6
133.2
130.2
110.3
amount of chemical, and on how soon
9
108.3
100.2
110.5
the structure is needed.
Potassium acetate
0.41
4
76.0
77.5
78.0
In the situation where the tempera-
6
115.4
78.6
--
ture falls below freezing but the work
8
109.9
90.9
--
Calcium magnesium
0.41
4
87.7
--
--
must still get done in a hurry, there
acetate
6
96.2
--
--
are chemicals that will work very
8
97.9
75.8
96.4
well. Table 4 shows four admixtures
Water softener
that force mortars with internal tem-
Potassium Chloride
0.41
6
77.4
--
--
peratures of 10C* to gain strengths
9
85.3
79.5
--
as if they were cured above 5C.
Fertilizers
Calcium nitrate
3
98.1
88.1
76.8
Moreover, they gain more strength in
0.41
6
92.2
98.8
84.3
the long run than control mortar
9
105.5
99.6
na
cured at 20C (App. A). Thus, these
Potash
0.41
6
90.8
--
--
chemicals make cold concrete behave
9
86.6
78.9
--
Sodium nitrate
0.41
6
109.4
--
--
as if it were warm.
9
108.8
103.1
--
What happens to concrete if, soon
Car antifreezes
after it is placed, its temperature dips
below 10C? All is not lost. Appen-
Ethylene glycol
0.38
3
87.6
80.2
--
0.35
6
119.1
103.6
101.0
dix A shows that concrete made with
0.32
9
95.8
93.0
88.6
the Table 4 chemicals can avoid all
Propylene glycol
0.38
3
90.8
83.8
81.9
0.35
6
86.2
--
--
frost damage, even when cooled to
20C for a long time. The concrete
0.32
9
88.1
80.5
--
Alcohols
may not gain much strength at this
Methyl (wood)
0.38
3
75.7
--
--
0.35
6
96.9
88.4
--
* It is important to know that this is a concrete
0.32
9
79.3
83.7
--
temperature. Because of thermal inertia and
Ethyl (grain)
0.37
4.1
83.6
--
--
heat generated by cement hydration, air tem-
Iso-propyl
0.35
6
90.0
--
--
peratures can be much lower--further study is
needed to define how low. However, until addi-
* The 75% requirement reflects what happens to concrete strength when it is
cured at 50C. In the table, blank spaces indicate that the chemical did not pro-
tional information becomes available, the
duce enough strength; na means that tests were not conducted at that condition.
10C should be considered air temperature.
7
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