Concreting in cold weather offers some special problems. If it is done at a freezing temperature, the mixing water freezes with a consequent increase in the overall volume of the concrete. Further, since no water is available for the chemical reactions, the setting and hardening of concrete are delayed, thus resulting in a poor concrete.
To avoid the ill effects of low temperature in fresh concrete certain precaution can be taken. The temperature at the time of casting can be raises by heating the ingredients of the mix. Water can be heated easily, but it is inadvisable to exceed temperature of 100 to 140°F as the flash setting of cement may result: the likelihood of this happening depends on the difference between the temperatures of water and cement. If heating the water does not sufficiently rise the temperature of the concrete the aggregate may also be heated. Heating the aggregate again above 125°F is inadvisable. You may want to read our article on: How Weathering Differs From Erosion
The temperature of the mix ingredients must be controlled to make sure that setting does not occur at too high a temperature as high temperature would adversely affect the development of the strength of the concrete. In addition, a high a temperature of fresh concrete lowers workability and may lead to high thermal contraction.
In this preferable for the concrete to set, say 50 to 70°F but it is essential that the temperature does not fall below about 50°F during the next three days. There are numerous precaution that should be taken in practice. For instance, concrete should not be allowed in cold weather unduly while being transported from the mixer to the formworks, and should not be placed against a frozen surface.
In cold weather concreting, temperature is needed to be controlled. Control of temperature after placing is obtained by insulating the concrete from the atmosphere and if necessary by constructing enclosures around the concrete and providing a source of heat within the enclosure. The form of heating should be such that the concrete does not dry out rapidly, that no part of it is heated excessively & that no high concentration of carbon-dioxide in the atmosphere results.