together. Rather than discuss each table in detail,
first came in contact with the cement. They
I summarized them into the tables and graphs
remained sealed until being tested for strength.
that follow and referenced them, as necessary, in
the text below. The reader is encouraged to re-
Test method
view Appendix A for additional detail.
Three samples of each mix from each tempera-
In reading this report, it is important to note
ture were tested in uniaxial compression accord-
that all strengths are referenced to the 28-day
ing to ASTM (1997) Standard C39 at 7, 14, 28, and
strength of control mortar cured at 20C. Table 1
56 days (some samples were not tested at 14 or 56
was organized in this manner. Likewise, Appen-
days owing to scheduling problems). Each sam-
dix A lists all strengths as percentages.
ple was capped with unbonded neoprene held
within a steel-retaining cup according to ASTM
(1993) Standard C1231. The samples from the cold-
Accelerators
rooms were allowed to thaw to 5C before being
One function of an antifreeze admixture is to
accelerate the hydration rate of portland cement.
tested.
Any increase in the early strength development
shortens the curing and protection periods neces-
RESULTS AND DISCUSSION
sary for the concrete to attain the desired
strengths. Table A1 highlights chemicals that
Appendix A shows freezing point and strength
force mortar to gain strength faster than it nor-
data for over 50 chemicals. Although many more
mally would. Table 2, extracted from Table A1,
could have been studied, I focused on a small
shows the best results.
portion of chemicals known to be compatible
It is clear that the seven chemicals shown in
with concrete. They are grouped into Tables A1
Table 2 increased the early strengths of mortar.
through A4 by their ability to accelerate the
They produced 7-day strengths at 20C that many
strength gain of mortar, by their ability to depress
times exceeded that of control mortar. In fact,
the freezing point of mixing water, by those that
compared to Table 1, they all far outperformed
are liquid, and by those that were combined
Table 2. Early age strength from the best accelerators from Appen-
dix A.
Percent by
Freezing
weight of
point
7 days*
(C)
20C
5C
10C
20C
Chemical
cement
Calcium chloride
1
2.5
108.5
10.5
1.8
na
2
3.8
109.9
19.0
3.6
na
3
6.2
108.5
30.0
5.3
na
Calcium bromide
4
2.9
108.4
4.9
3.2
0.8
6
4
109.4
11.0
6.2
1.8
na†
8
107.5
4.6
1.8
0.3
Fertilizer (calcium
3
5.3
114.3
3.8
3.4
3.4
nitrate)
6
6.7
107.9
3.2
3.1
1.9
9
8.3
96.7
6.8
6.4
5.3
Calcium nitrite
2
3.5
87.1
13.3
2.7
0.7
6
5.7
106.0
44.8
4.4
1.1
9
na
124.4
67.8
53.2
0.5
Calcium chloride
3
1.5
92.6
16.9
8.2
5.0
(deicer)
6
2.25
106.3
22.7
9.4
4.2
9
4
93.9
43.1
34.9
16.4
Calcium acetate
2
3
94.8
12.1
1.0
na
4
4.7
94.4
2.7
2.0
na
6
6.5
102.4
6.7
3.1
na
Calcium formate
2
3.3
96.2
14.4
2.0
0.2
4
4.5
91.1
17.9
3.3
0.4
6
5.5
91.7
7.3
3.3
0.7
* Strengths are given as percents of 28-day control mortar cured at 20C.
† Tests were not conducted, or information was not available.
3
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