turned off about 4 p.m. on 22 March. The
average air temperature in the shelter for the
recording period was 10.5C (51F).
The control concrete was delivered to the
site in two separate shipments, at a tempera-
ture of about 12C (54F) for each shipment.
(All other concrete was delivered in one truck
per section.) By the time both control ship-
ments had been placed and the shelter walls
were reinstalled, the concrete had cooled to
1.3C (34F) (Fig. 8). It wasn't until 5 p.m. of
that same day that the heat supplied by ce-
ment hydration and the shelter warmed the
concrete to 12C (54F). The concrete contin- Figure 15. Temperature history of the center of mass of a 75-
150-mm (3 6 in.) cylinder of EY11L concrete stored on grade
ued to warm until it reached 20.3C (68.5F)
at 7 a.m., 16 March, in spite of the air cooling in the unheated shelter at Sault Ste. Marie, Michigan.
to 9.4C (48.9F). Like the air, the concrete
temperature fluctuated throughout the recording
ture dosage and had an expected freezing point
around 3C (26.6F). Its average temperature was
period. It reached a maximum temperature of
25.3C (77.5F) at 4:10 p.m. on the 16th and a
0.9C (33.6F) through 4 p.m. on 22 March.
minimum of 3.8C (38.8F) at 7:10 p.m. on the
Figure 14 shows the temperatures of the EY11H
20th, closely corresponding to the high and low
concrete and the outdoor air. The freezing point
of this concrete was 5C (23F). The EY11H mix
shelter air temperatures. The average tempera-
ture of the control concrete through 4 p.m. on 22
was cast outdoors at 11:40 a.m. on 16 March. It,
March was 13.3C (55.9F). It never dropped be-
too, began at 3.3C (37.9F). Instead of cooling
low 0C during this period.
when exposed to the 7.3C (18.9F) air, however,
it warmed to 11.8C (53.2F) at 2:10 p.m. before
The EY-11 mixtures were placed on 16 March,
dropping to 4.4C (24.1F) at 7 a.m. on 17 March.
the colder of the two days during which concrete
It reached its lowest temperature of 5.5C
was placed. The outdoor air temperature, shown
(22.1F) at 7 a.m. on 20 March, four days after
in Figure 13 and again in 14, averaged a chilly
8.7C (16.3F) through midnight on the 16th,
being cast. Its average temperature was 2.4C
(36.3F) through 4 p.m. on 22 March.
though it rose to slightly above freezing for a
short time by midday, the 17th. The minimum
Figure 15 shows the temperatures of an EY11L
outdoor air temperature of 16.5C (2.3F) was
cylinder stored on grade in the unheated shelter.
The cylinder's temperature dipped below 5C
recorded at 6:45 a.m. on 17 March. Winds created
wind chills down to 28C (18.4F) during the
(23F) on several occasions, the first at 8:00 p.m.
17th. Thereafter the outdoor air temperature be-
on 16 March, about ten hours after it was cast.
came much milder. The average outdoor air tem-
The average temperature of the cylinder through
4 p.m. on 22 March was 1.3C (29.7F).
perature from 16 March through 22 March was
Strength development. Several 75- 150-mm (3
Figure 13 shows the temperatures of the EY11L
6 in.) cylindrical samples were cast from each
concrete and the air inside the unheated shelter.
type of concrete and stored in two locations on
The EY11L mix was placed at 9:45 a.m. on 16
grade next to the slabs and overhead in the heated
March. It was delivered at a temperature of 3.3C
enclosure. A concrete testing laboratory in Michi-
(37.9F). As was done with the control section,
gan periodically tested the cylinders' compres-
two walls of the unheated shelter were removed
temporarily. When exposed to the 10C (14F)
The compressive strengths of the cylinders can-
(but warming) air, the concrete temperature
not be used as an indicator of the in-place strength
quickly dropped from its delivered temperature
of the antifreeze concrete because, as Figure 15
to 2C (35.6F), but almost immediately began
shows, the cylinders probably froze. Subsequent
rising, reaching 4.3C (39.7F) by 4 p.m. After that
petrographic analysis of the suspected frozen cyl-
the concrete temperature dropped to 3C (26.6F),
inders at CRREL revealed typical ice lens pat-
its lowest recorded temperature, at 3:30 a.m. on
terns in the cylinders. Strengths reported by the
17 March. This concrete contained a low admix-
testing laboratory indicate that the cylinders de-