Table 2. Concrete mix design.
Table 1. Research work organization.
Cement type
ASTM C150, Type I
Phase no.
Description
362.8 kg/m3 for tasks 1A to 1F
Cement content
418.6 kg/m3 for task 1H
1
Effect of chemicals on strength gain
Water/cement ratio
0.48, or as indicated
2
Evaluation of best admixtures
Target slump
5 cm
3
Prototype slab-wall application
Aggregate gradation
ASTM C 33, # 6
4
Field application of new admixtures
Aggregate source
Lebanon, New Hampshire
5
Technology transfer
chemical formulations in search of an admixture
LABORATORY EXPERIMENTS
that would cause concrete to develop acceptable
strength at temperatures below 0C. Because cur-
Phase 1: Effect of chemicals
rent concrete construction standards cover con-
on strength gain
crete work down to 5C, the overall goal was to
produce an admixture that would promote con-
Objective
crete strength at 5C to meet or exceed the
To develop a chemical formulation that would
strength of admixture-free concrete at 5C.
allow concrete cured at 5C to gain strength at
least as fast as control concrete cured at 5C.
Another objective of this project was to recom-
mend changes that integrate the findings of this
research into relevant construction standards. It
Experimental approach
was the intention of the industry partner to de-
Early experiments with single chemical com-
velop an admixture that would provide adequate
pounds, experiences found in the literature,
strength at a sufficiently low temperature to jus-
physico-chemical data available for each chemi-
tify the investment involved in the implementa-
cal compound, and knowledge of the chemistry
tion of a new product line.
of cement hydration formed the basis for the for-
mulation of candidate admixtures. The candidate
admixtures were made of mixtures of two, three,
Approach
The research work was organized into five
or four chemical compounds. These formulations
phases (listed in Table 1). Phase 1 evaluated a
were tested for their ability to perform as anti-
large number of potential chemical compounds
freeze admixtures, i.e., chemicals that depress the
for their ability to promote concrete strength at
freezing point of water and accelerate the hydra-
5C. The admixtures that provided the best strength
tion of cement.
performance at low temperature were selected for
The experimental work began by screening a
Phase 2. This phase was a more comprehensive
set of chemical formulations using a strength gain
evaluation that included testing to determine the
criterion. A series of concrete mixes were made
effect of these chemicals on relevant concrete prop-
(Table 2), each including one candidate admix-
erties. Phase 3 consisted of a prototype concrete
ture at one of various dosages. A number of cylin-
application geared to explore practical job site is-
ders were cast and cured under one of several
sues such as placement, finishing, and curing of
temperatures using special coldrooms. Addition-
full-size concrete elements. Phase 4 integrated the
ally, control concrete (admixture free) was mixed,
experience gained in the prototype application
cast, and cured under the same conditions as the
into an actual field application built under winter
admixtured specimens (Table 3). At the prescribed
conditions; this demonstrated the advantage of
time, the cylinders were transported out of their
using antifreeze admixtures over conventional
coldrooms and allowed to thaw up to a controlled
temperature of about 10C at their center of mass.
thermal protection methods. Phase 5 consists of
technology transfer efforts, such as this report.
This was a necessary precaution to avoid testing
Table 3. Test parameters.
Chemical admixtures
As needed
(20C, 5C, 10C and 20C)
Curing temperatures
4
Testing ages
3
(7, 14, and 28 days)
0.04 m3
Mix size
Specimen replicates
3
7.6 cm 15.2 cm
Specimen size
Cylinders
2
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