If suitable methods are used, good concrete work can be done in cold
weather, but with more difficulty and at somewhat greater cost than when
the weather is warm. Ordinarily it is best not to attempt to do concrete
work during freezing weather. However, the extra cost at times may be
warranted by urgent need of the structure or the fact that other farm
work is not so pressing during the winter and the concrete work may be
carried on without seriously interfering with regular farm operations.
Concrete must be protected from alternate freezing and thawing until it
has set. Cold retards the setting and hardening of concrete; therefore,
even though the temperature is not at the freezing point, the concrete
should be protected and special care taken not to subject it to loads.
The forms should be kept in place until there is no doubt that the
concrete has properly hardened. Hot water should be poured on the
concrete to make sure that apparent hardness is real and not due to a
frozen condition. Just before the concrete is placed all ice and frost
should be removed from the forms and reinforcement, if used, by warming
the surfaces with steam or by other means.
Concrete that has been frozen once may, with proper care, attain its
ultimate strength, but should it freeze a second time the chances of
saving the work are very slight. Exposed surfaces are apt to scale or pit
if the concrete is allowed to freeze before it is thoroughly hardened.
Pleating the materials, protecting the green concrete, and the use of
salt are precautions generally taken to prevent freezing.