Any operation of concreting done at atmospheric temperature above 400C may be put under hot weather concreting. The effect of hot weather may be as follows:
A higher temperature of fresh concrete results in a more rapid hydration and leads to reduced workability/ accelerated setting. This reduces the handling time of concrete.
Reduction in strength:
Concrete mixed, placed and cured at higher temperature normally develops higher early strength than concrete produced and cured at normal temperature but at 28 days or later the strength are generally lower.
Increased tendency to crack:
Rapid evaporation may cause plastic shrinkage and cracking and subsequent cooling of hardened concrete would introduce tensile stresses.
Effects of Cold Weather on Concrete
Any concreting operation done at a temperature below 50C is termed as cold weather concreting. In the absence of special precautions, the effect of cold weather concreting may be as follows:
When the temperature is falling to about 50C or below, the development of strength of concrete is retarded compared with development at normal temperature. Thus, the time period for removal of form work has to be increased.
Freezing of concrete at early stage:-
The permanent damage may occur when the concrete in fresh stage is exposed to freeze before certain pre-hardening period. Concrete may suffer irreparable loss in its properties to an extent that compressive strength may get reduced to 50% of what could be expected for normal temperature concrete.
Stresses due to temperature differentials:-
Large temperature differentials within the concrete member may promote cracking and affect its durability adversely.