days. The optimum curing time was between 12
Effect of temperature on strength
and 16 hr. Thus, early-age freezing is not always
Experiments were conducted in the laboratory
harmful. One explanation for greater strengths of
to develop data that relate strength gain to curing
temperature. Strength tests were done on 50-
mortar subjected to freezing temperatures is that
100-mm (2- 4-in.) cylinders of admixture-free
these low temperatures slow the hydration of the
cement, resulting in a more controlled (less vio-
mortar and mortar that contained the chemicals
lent) chemical reaction rate.
shown in Table 7. The calcium chloride and KC1
chemicals were dosed by weight of cement, and
the two alcohols were dosed by weight as a per-
Antifreeze admixtures
cent replacement of water so as to maintain con-
Objective
stant plasticity of the mortar. The mortars were
The primary objective of the following tests
mixed to a moisture content of 16%, and cylinders
was to assess the practicality of using antifreeze
were cast at room temperature and brought into a
admixtures developed for concrete with masonry
given coldroom a few minutes after being cast. At
mortars. In addition, some alcohols were evalu-
the prescribed testing age, the cylinders were
ated for their ability to perform as antifreeze
brought back to room temperature and compres-
admixtures for mortar.
sion-tested as soon as the temperature at their
center of mass reached 5C (41F). (A dummy cyl-
Antifreeze admixtures are chemicals that pro-
tect mortar from freezing without the use of heat-
inder instrumented with a thermocouple served
ers. Currently, antifreeze admixtures are not rec-
as the temperature reference.) Some of the test
ommended for use in mortar. The concern is that
samples were kept in their respective coldrooms
such chemicals will harm compressive and bond
for as long as 28 days, then returned to room tem-
strengths or corrode embedded metals within the
perature for an additional 28 days (56 days curing
mortar. A similar concern existed for concrete a
time) to test for strength recovery.
few years ago. Since then, certain chemicals have
Table 7 presents a summary of the strength test
been shown to protect concrete from freezing
results expressed as a percentage of the same-age
without causing detrimental side effects (Kor-
strength of a control, admixture-free mortar
honen et al. 1994). The objective of this section
made with a type M masonry cement cured at
20C (68F). As seen in the 20C results, methanol
was to evaluate whether a similar result was pos-
sible for mortar. This study evaluated chemicals
retarded strength gain, especially at higher dos-
for their effect on low-temperature strength gain,
ages. At 7 days, methanol produced strengths
bond strength, and the freezethaw durability of
that were only 47 to 79.4% strong relative to the
control. At 5 and 10C (23 and 14F) the metha-
mortar.
Table 7. Compressive strength of mortars containing various admixtures. Strengths are
expressed as percentage relative to admixture-free mortar cured at 20C (68F).
Curing temp. (20C)
Curing temp. (5C)
Curing temp. (1C)
Day
Day Day Day
Day Day Day Day
Day Day Day Day
Admixture*
7
14
28
56
7
14
28
56
7
14
28
56
11.6% meth
79
90
94
100
8
36
63
103
0
5
29
96
17.4% meth
68
80
91
94
3
16
44
97
0
5
20
109
23.3% meth
47
63
78
92
0
6
23
91
0
0
8
105
2% CaCl2 , 11.6% meth
76
85
92
99
18
44
68
93
5
14
34
76
2% CaCl2 , 17.4% meth
67
72
87
91
12
29
51
101
4
10
22
96
2% CaCl2 , 23.3% meth
68
73
84
95
7
19
36
93
1
4
11
91
4% CaCl2 , 11.6% meth
72
80
87
91
7
33
52
95
0
4
22
88
4% CaCl2 , 17.4% meth
65
73
86
93
3
24
43
97
0
0
10
91
4% CaCl2 , 23.3% meth
55
62
79
86
2
14
34
93
0
0
5
87
1% CaCl2 , 23.3% IPA
68
80
94
103
5
18
37
102
0
4
17
104
17.4% IPA
83
93
100
104
2
0
31
104
0
0
2
90
6% KC1†
105
97
97
98
67
87
88
112
26
49
56
77
Control
100
100
100
100
5
10
13
NA
NA
NA
NA
NA
* meth = methanol; CaCl2 = calcium chloride; IPA = isopropyl alcohol; NA = not available.
† KC1 = U.S.-Army-patented admixture made of 3 weights of sodium nitrate + 1 weight of sodium sulfate.
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