25
20
15
10
5
0
5
10
1.27 cm Below Top Surface
Middle of Slab
2.54 cm Above Slab Bottom
15
1.9 cm Below Slab
20
25
0
5
10
15
20
25
Days
Figure 6. Concrete temperatures at various depths for the heated con-
trol slab.
riod, averaging 6.7C and 6.3C for the PS and DP,
through the thickness of the slab are given in Fig-
respectively. Neither mix is expected to have
ure 6. The position 1.9 cm below the bottom of the
dropped below 5C through 23 March. By then it
slab was colder than the slab itself the first 2 1/2
would have been able to resist frost damage. Ex-
days. Over that same 2-1/2-day period, the top
cept for the heat of day when the sun was shining,
surface was slightly warmer than the middle,
each slab was of uniform temperature throughout
which was slightly warmer than the bottom of the
slab. Thereafter all temperatures throughout the
its thickness. Based on tests conducted previously,
slab were essentially the same. The heat was
it is expected that the temperature of the PS and
the DP slabs tracked that of the air temperature
turned off in the control shelter by midafternoon
after day 4. The surface may have gotten a few
on 22 March. By 10 a.m. on the 23rd, the control
degrees warmer than the air during midday.
concrete had equilibrated to ambient conditions.
The PolarSet and DP sections were cast on 17
Microscopic evaluation of
March. A malfunction in the data recorder pre-
the hardened concrete
vented temperatures from being recorded past
Core samples were cut from both slabs in July
midnight, 18 March. Consequently, a two-day tem-
1994 and examined for evidence of ice crystal im-
perature record of four positions through the thick-
ness of each slab is given in Figures 7 and 8. Both
prints. No icing was found. Similarly, no ice was
found in the 7.6- 15-cm core samples that were
mixes were relatively warm during this short pe-
20
15
1.27 cm Below Top Surface
Middle of Slab
2.54 cm Above Slab Bottom
1.9 cm Below Slab
10
5
0
5
10
0
5
10
15
20
25
Days
Figure 7. Concrete temperatures for the slab containing PolarSet.
16
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