[CARE OF CONCRETE.]
After the concrete has been poured, care should be taken that it does not dry out too quickly, and in hot weather it must be protected from the sun. Exposed surfaces and objects made of dry concrete should be sprayed thoroughly with water twice or oftener each day for a week or 10 days. Sometimes surfaces are shielded with canvas, paper, boards, or layers of moist sand.
[PROTECTION FROM FREEZING WEATHER.]
CONCRETING IN FREEZING WEATHER.
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.