Effects of hot weather on concrete, in the absence of special precautions can be as follows.
- Accelerated setting of concrete
- Reduction in strength of concrete
- Increased tendency to crack
- Rapid evaporation of water during curing period
- Difficulty in control of air in air-entrained concrete
Accelerated Setting
The rate of setting time of the concrete increases due to high temperature. The duration of time during which the concrete can be handled is reduced. Quick stiffening may necessitate undesirable retempering by addition of water. It may also result in cold joints.
Reduction in strength
High temperature results in the increase of the quantity of mixing water to maintain the workability with consequent reduction in strength.
Increased tendency to crack
Either before or after hardening plastic shrinkage cracks may form in the partially hardened concrete due to rapid evaporation of water. Cracks may be developed in hardened concrete either by increased drying shrinkage resulting from greater mixing water used or by cooling of the concrete from its elevated initial temperature.
Rapid evaporation of water during curing period
It is difficult to retain moisture for hydration and maintain reasonably uniform temperature conditions during curing period.
Difficulty in control of air content in air-entrained concrete
It is more difficult to control air content in air entrained concrete. This adds to the difficulty of controlling workability. For a given amount of air entraining agent, hot concrete will entrain less air than concrete at normal temperature.