Perhaps the most satisfactory method of preventing freezing of concrete
is to heat the materials and to inclose or cover the completed work for
a few days or until most of the water has disappeared and sufficient
strength has developed. In extreme weather protection may be needed for
five or six days. When the weather is cold but not freezing, heating the
materials will be sufficient. If a freeze is expected the concrete work
should be protected by wood inclosures, paper, or canvas, over which, if
the surface is horizontal, may be spread a 6 or 8 inch layer of straw.
Manure should not be used to protect fresh concrete, since the acids in
it are destructive and cause unsightly stains. Splits or other openings
in coverings may admit cold, which may freeze parts of the work. As the
temperature drops (to about 20° F.) it will be necessary to arrange the
covering so that live steam can be turned in between it and the concrete
or that heat may be supplied from stoves or salamanders.
Mass work, except in very cold weather, will not require as careful
protection as thin sections and, as a rule, the forms are sufficient if
the exposed parts are covered.