point of around 3C. Its average temperature
temperature fluctuated daily. The maximum of
29.7C occurred at 4:10 p.m. on the 16th, and two
was 0.9C through 4 p.m., 22 March.
lows of 0.2C and 0.4C occurred at 3:30 a.m. on
Figure 4c shows the temperatures of the EY11H
the 19th and at 6:45 a.m. on the 20th respectively.
concrete and the outdoor air. The freezing point of
this concrete was 5C. The EY11H mix was cast
The two low temperatures were caused by a mal-
function of the heating equipment. The heat was
outdoors at 11:40 a.m., 16 March. It, too, began at
3.3C. But, instead of cooling off when exposed to
turned off at about 4 p.m. on 22 March. The aver-
the 7.3C air, it warmed to 11.8C at 2:10 p.m., be-
age air temperature in the shelter for the record-
ing period was 10.5C.
fore dropping off to 4.4C at 7 a.m., 17 March. It
reached its lowest temperature of 5.5C at 7 a.m.,
The control concrete was delivered to the site in
two separate shipments, at a temperature of about
20 March, 4 days after being cast. Its average tem-
12C for each shipment. (All other concrete was
perature was 2.4C through 4 p.m., 22 March.
delivered in one truck per section.) By the time
Figure 4d shows the temperatures of the DP
both control shipments had been placed and the
concrete and the outdoor air. The freezing point of
this admixture was 5C. The DP concrete section
shelter walls were reinstalled, the concrete had
cooled off to 1.3C (Fig. 4a). It wasn't until 5 p.m.
was cast outdoors at 1:10 p.m., 17 March. It was
delivered to the site at 7.2C, when the air temper-
of that same day that the heat supplied by cement
ature was 4C and falling. The concrete tempera-
hydration and the shelter warmed the concrete to
12C. The concrete continued to warm until it
ture rose to a high of 15.8C at 2:30 p.m. on 17
reached 20.3C at 7 a.m., 16 March, in spite of the
March. Because of a data recorder malfunction,
air cooling to 9.4C. Like the air, the concrete tem-
concrete temperatures were not recorded after
perature fluctuates throughout the recording pe-
midnight, 18 March. The average air temperature
riod. It reached a maximum temperature of
from the time of placement to midnight, 18 March,
25.3C at 4:10 p.m. on the 16th and a minimum of
was 1.6C and from placement through 4 p.m., 22
3.8C at 7:10 p.m. on the 20th, closely correspond-
March, was 1C. The average temperature of the
concrete through midnight, 18 March, was 6.3C.
ing to the high and low shelter air temperatures.
The average temperature of the control concrete
The DP concrete probably did not drop below
through 4 p.m. on 22 March was 13.3C. It never
5C through 22 March.
dropped below zero during this period.
Figure 4e shows the temperatures of two points
Two of the three antifreeze sections were
near the bottom surface of the EY11L slab. The
placed on 16 March, the coldest of the two days
EY11L slab had the lowest average surface tem-
that concrete containing antifreeze admixtures
perature of all the slabs. As can be seen in Figure
was placed. The outdoor air temperature (Fig. 4c
4e, the bottom surface of the concrete, which was
and d) through midnight on the 16th averaged
halfway between the two thermocouple positions,
8.7C, though it rose to slightly above freezing
could not have frozen. The lowest temperature of
the two thermocouples was 1.2C, 21 hours after
for a short time by midday. The minimum out-
door air temperature of 16.5C was recorded at
the concrete was placed. Recall that the freezing
temperature of this concrete was 3C. The EY11H
6:45 a.m. on 17 March. Winds created wind chills
down to 28C. Thereafter, the outdoor air tem-
slab, with a 5C freezing temperature, experi-
perature became much milder; the average
enced the lowest single surface temperature of all
through 4 p.m., 22 March, was 2.4C.
the slabs. Its bottom surface temperature reached
a low of about 3C (not shown), 4 days after the
Figure 4b shows the temperatures of the EY11L
concrete and the air inside the unheated shelter.
concrete was placed.
The EY11L mix was placed at 9:45 a.m., 16 March.
Figure 4f shows the temperatures of an EY11L
It was delivered at a temperature of 3.3C. As was
cylinder stored on grade in the unheated shelter.
The cylinder's temperature dipped below 5C on
done with the control section, two walls of the
unheated shelter were removed temporarily.
several occasions, the first at 8:00 p.m. on 16
When exposed to the 10C (but warming) air, the
March, about 10 hours after it was cast. The aver-
concrete temperature dropped to 2C, but almost
age temperature of the cylinder through 4 p.m., 22
immediately began rising, reaching 4.3C by 4
March, was 1.3C.
p.m. Then, the concrete temperature dropped to
3C, its lowest recorded temperature, at 3:30 a.m.
Strength development
Several 7.6- 15.2-cm cylindrical samples were
on 17 March. This concrete contained a low ad-
mixture dosage and had an expected freezing
cast from each type of concrete and stored in two
7
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