antifreeze admixture code-named DP, which was
crete was exposed to ambient air and was in di-
developed in this project. A third slab contained
rect contact with the cold gravel base course, which
the admixture PolarSet (PS), a low-temperature
was placed directly on frozen ground. No insula-
accelerator newly marketed by WRG. The ad-
tion, shelter, or heater was used on the admixtured
mixtured slabs were cast and cured in the open
slabs. The plastic sheet was placed over the two
without shelter. The prototype application in New
exposed concrete sections for seven days to mini-
Hampshire provided some experience in deal-
mize water loss because no curing water was
ing with these admixtures in cold weather. The
added. The concrete in the heated shelter was left
slabs at the Soo Locks provided an opportunity to
uncovered for the seven-day curing period.
apply the new admixtures in a realistic cold
weather setting with conventional equipment and
Observations and results
conventionally trained labor.
Each reinforced slab on grade measured 5.5 m
Workability
wide by 6.1 m long by 15.2 cm thick. The slabs
The concrete stayed workable longer than it
were cast 1517 March 1994. The Corps' Soo Area
did in the prototype application in New Hamp-
shire. The mixtures were 36C colder in Michigan.
Office had scheduled 39 sections of concrete to be
replaced because of their advanced stage of freeze
thaw deterioration. The work area was located on
Finishability
the southwest pier, which borders the ship canal
The concrete workers indicated that the two
of the Soo Lock, the largest of four locks operated
mixes, DP and PolarSet, finished quite easily. The
and maintained by the Corps of Engineers, Sault
DP did seem to stiffen right at the end of the
Sainte Marie, Michigan. Inspection and repair of
finishing operation, about two hours after water
the locks themselves is normally done during the
was first added to the mix. However, the concrete
winter months, January through March, when
that was left over in a wheelbarrow from the
shipping is stopped. Other repair work, such as
sample-making procedure was still workable. The
the replacement of the slabs described here, is
DP contained a different water reducer than that
also most conveniently done during the winter
used in New Hampshire; WRDA-19 was used in
nonshipping season, making this test particularly
New Hampshire, while AA1D was used in Michi-
relevant.
gan. The first is a commercial product of WRG
The temporary heated enclosure erected over
while the second was still in research there.
the control slab provided a comparison between
conventional and antifreeze concrete operations.
Thermal records
The two admixtured slabs were placed on a cold
Four thermocouples were equally positioned
gravel bed. After consolidation and finishing op-
through the thickness of the PolarSet and DP slabs
erations were conducted conventionally, the fresh
at about 2.5 m from the edge. One thermocouple
slabs were covered with a plastic sheet. The con-
monitored air temperatures.
Figure 5 shows a 22-day record of
air temperature beginning at 9:50 a.m.,
20
16 March. The air temperatures from
15
1617 March were quite cold, averag-
ing 10C, with a low of 16.5C at
10
6:45 a.m. on the 17th. Steady winds
created wind chills of 28C. The air
5
temperature averaged only 0.5C for
0
the next seven days. The overall aver-
age air temperature for the first nine
5
days was 1.6C.
The control concrete was cast on
10
15 March. This slab was cast in a shel-
ter that was heated for the first seven
15
days; the heater was then turned off,
20
but the shelter stayed in place for
0
5
10
15
20
25
about a month. Nineteen days of tem-
Days
perature records from four positions
Figure 5. Air temperatures at the construction site.
15
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