frozen concrete, which could
Phase 1, Tasks 1A to 1H
Table 4. Experi-
m e n t a l tasks in
yield false high strengths that
Phase 1 contained ten tasks. During the early
Phase 1, and num-
vanish upon thawing. The
planning stages of this project, it was envisioned
ber of mixes.
that the search for a 5C admixture would re-
cylinders were compression
tested at various ages.
quire two or at most three tasks. However, we
Phase 1 was divided into
soon learned that a compromise between low-
ten tasks (Table 4). Each task
temperature strength development and workabil-
consisted of testing one set
ity of the fresh concrete was needed in order for
of chemical formulations.
the admixture to be practical. New admixtures
The objective was to identify
were formulated to address these issues and test-
chemical formulations that
ing continued. Next, differences in low-tempera-
ture (5C and 10C) performance indicated a
best promote the strength of
concrete cured at low tem-
need to reformulate some of the early admixtures
peratures. Slump, slump
loss, and set times were also
and freeze-point depression. Finally, after ten tasks,
measured for several mixes.
two admixtures code-named DPTC* and DP were
Retarders and some adjustments to the mix de-
selected for further study in Phase 2.
sign were implemented in later tasks to obtain an
In each task, a set of concrete mixes, each con-
adequate compromise between strength and work-
taining a given chemical admixture at a given
dosage, was mixed, and cylinders were cast, cured,
With the exception of Task 1G*, the specimens
and compression-tested to determine the effect of
were concrete cylinders (7.6 15.2 cm) cast in
each admixture on the strength development of
plastic molds. The cylinders were kept sealed in
concrete cured at various temperatures.
their plastic molds until ready for compression
All Phase 1 tasks were conducted on concrete
testing, and then were cast at room temperature
cylinders, except tasks 1Ga, 1Gb, and 1Gc, which
(hereby defined as approximately 20C) and
were conducted on mortar specimens. Mortar was
brought to their corresponding curing room within
used to expedite the study of a series of admixtures.
40 minutes after water was added to the mix.
On the date of their compression test, the cor-
responding cylinders were brought to room tem-
The data from only certain tasks will be dis-
perature environment, demolded, and allowed to
cussed in this report. For those wishing more de-
stand just long enough to ensure that no speci-
tail, the test data for all ten Phase 1 tasks are
men would contain ice during testing. Typically, a
presented in Appendix A. There, "N/A" stands
cylinder would be allowed to reach 10C before
for "not available," and it appears wherever a mix
testing. Replicate dummy cylinders containing a
number was not used in that particular task, or
thermocouple at their center of mass were also
the test was limited according to judgment of rel-
cast to monitor temperatures.
evance. For tasks with fewer than 20 mixes, the
charts show a blank space where a mix number
Mixing time and sequence
was not used. The blank spaces in the charts were
Mixing procedures followed ASTM C 192,
included to keep a consistent format that facili-
"Standard Method of Making and Curing Con-
tates comparison. The admixture code name, dos-
crete Test Specimens in the Laboratory," specifi-
age, and water/cement ratio for each mix are given
cally paragraph 6.1.2:
in separate tables. Code names were used rather
than chemical formulations where there was a
Add coarse aggregate.
need to preserve the industry partner's propri-
1/3 mix water (admixture free), start mixer.
Fine aggregate (stop mixer if needed).
The ACI 306 specifications for cold weather
Cement (stop mixer if needed).
concrete are valid for concrete cured at 5C or
Remaining water containing admixture.
above. In this project, an antifreeze admixture was
Mix for three minutes, stop mixing for three
required to deliver a seven-day strength for speci-
minutes, mix for two minutes.
* The chemical compositions are disclosed in Table 5 for the
selected admixtures, except for those protected by the in-
* Task 1G was conducted on mortar.
dustry partner's proprietary rights.