Antifreeze Admixtures for Concrete
CHARLES J. KORHONEN, EDEL R. CORTEZ,
TIMOTHY A. DURNING, AND ARA A. JEKNAVORIAN
known as antifreeze admixtures, low-temperature
INTRODUCTION
admixtures, or freeze-protection admixtures. The
term "antifreeze admixtures" is adopted in this
Background
report to convey the implication that they work at
The American Concrete Institute (ACI) is the
temperatures below the freezing point of water.
technical authority on concrete technology in the
The concept of antifreeze admixtures for concrete
United States. In its guidance for cold weather
is found in foreign literature reporting early expe-
concrete (American Concrete Institute 1988), ACI
riences in Scandinavian countries and the former
outlines procedures to prevent early-age freezing,
Soviet Union (Korhonen 1990). With antifreeze
to ensure adequate strength for safe removal of
admixtures, there is little need for building enclo-
form work, and to avoid thermally induced crack-
sures, insulation, or heaters. The properties of the
ing. In order to produce quality concrete, several
concrete are more uniform, and thermal gradients
parameters must be carefully controlled. The air
are insignificant. Concerns about accidental early-
temperature as well as the concrete temperature
age freezeups are diminished because the internal
needs to be monitored constantly before and after
temperature of the concrete can be below 0C.
casting to avoid cold and hot spots. Despite care-
Antifreeze admixtures have two purposes: to de-
ful control, it is not uncommon to find excessively
press the freezing point of water and to accelerate
cold and hot areas in the same enclosure at the
the hydration of cement at low temperature.
same time. Neither is it uncommon to find spots
This research project combined the expertise of
where hot air has dried out the fresh concrete.
two organizations: the U.S. Army Cold Regions
Local dehydration and significant temperature
Research and Engineering Laboratory (CRREL),
gradients can result in concrete of nonuniform
which has studied low-temperature admixtures
properties and in concrete that is thermally
since 1990 (Borland 1994a, b; Korhonen et al. 1994a,
cracked.
b; Korhonen et al. 1995) and W.R. Grace (WRG),
If combustion heaters are used, carbonation of
which is a leading producer of admixtures for
the concrete surface may occur and cause soft
concrete, with extensive experience with concrete
surfaces and surface crazing. Carbon monoxide
accelerators.
from partial combustion presents a hazard to
workers. The risk of uncontrolled fire exists wher-
Project objectives
ever open flame heaters are used. Provisions for
these procedures date back to the 1930s. Basically,
The objectives of this project were to
the conventional practice today is to artificially
Evaluate the low-temperature strength per-
warm the environment where concrete is mixed,
formance of Daraset, a commercial concrete
cast, and cured, keeping it at or above 5C. The
strength accelerator.
high cost of thermal protection discourages win-
ter construction. Underutilization of resources and
Develop new cold weather admixtures.
seasonal unemployment are common among con-
Recommend changes in construction stan-
crete practitioners in cold regions.
dards.
One alternative to thermal protection methods
is the use of admixtures that allow fresh concrete
The performance of Daraset at warm tempera-
to achieve acceptable strength when cured in cold
tures was well known, but its performance below
0C was not. Daraset was tested along with other
environments. These admixtures are variously
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