Civil Engineering Reference
In-Depth Information
Fig. 14-19. Stack of insulating blankets. These blankets trap
heat and moisture in the concrete, providing beneficial
curing. (43460)
the minimum required on Line 4 in Table 14-1, additional
insulating material, or material with a higher
R
value,
should be applied. Corners and edges of concrete are most
vulnerable to freezing. In view of this, temperatures at
these locations should be checked often.
The thermal resistance (
R
) values for common insu-
lating materials are given in Table 14-4. For maximum effi-
ciency, insulating materials should be kept dry and in
close contact with concrete or formwork.
Concrete pavements can be protected from cold
weather by spreading 300 mm (1 ft) or more of dry straw
or hay on the surface for insulation. Tarpaulins, polyeth-
ylene film, or waterproof paper should be used as a
protective cover over the straw or hay to make the insula-
tion more effective and prevent it from blowing away. The
straw or hay should be kept dry or its insulation value will
drop considerably.
Stay-in-place insulating concrete forms became
popular for cold-weather construction in the 1990s (Fig.
Fig. 14-18. (top) Tarpaulin heated enclosure maintains an
adequate temperature for proper curing and protection dur-
ing severe and prolonged winter weather. (bottom) Poly-
ethylene plastic sheets admitting daylight are used to fully
enclose a building frame. The temperature inside is main-
tained at 10°C (50°F) with space heaters. (69877, 69878)
sures that admit daylight are the most popular but tempo-
rary heat in these enclosures can be an expensive option.
When enclosures are being constructed below a deck,
the framework can be extended above the deck to serve as
a windbreak. Typically, a height of 2 m (6 ft) will protect
concrete and construction personnel against biting winds
that cause temperature drops and excessive evaporation.
Wind breaks could be taller or shorter depending on antic-
ipated wind velocities, ambient temperatures, relative
humidity, and concrete placement temperatures.
Enclosures can be made to be moved with flying forms;
more often, though, they must be removed so that the wind
will not interfere with maneuvering the forms into position.
Similarly, enclosures can be built in large panels like gang
forms with the windbreak included (Fig. 14-1).
INSULATING MATERIALS
Heat and moisture can be retained in the concrete by
covering it with commercial insulating blankets or batt
insulation (Fig. 14-19). The effectiveness of insulation can
be determined by placing a thermometer under it and in
contact with the concrete. If the temperature falls below
Fig. 14-20. Insulating concrete forms (ICF) permit con-
creting in cold weather. (69699)
