During hot weather, problems that may occur in concrete include the following.
Rapid slump loss
Reduced air content
Plastic shrinkage cracks
Therefore it is necessary to keep concrete temperature down. The most effective way to keep concrete temperature down is by controlling the temperature of its ingredients. Among all ingredients of concrete, the aggregate and mixing water exert most pronounced effect on temperature of concrete.
Controlling Temperature of Aggregate
The stockpiles of aggregates shall be shaded so as to avoid it from direct sun rays.
Stockpiles of coarse aggregate shall be sprinkled with water to keep it moist. When coarse aggregates are stockpiled during hot weather, successive layers should be sprinkled as the stockpiles built up.
Spray the coarse aggregate with cold water (if available), immediately before use, to have direct cooling action.
Coarse aggregates may also be cooled by inundating them in cold water or by circulating refrigerated air through pipes or by other suitable methods.
Controlling Temperature of Water
The temperature of mixing water has the greatest effect on the temperature of concrete. In practice the temperature of water is easier to control than that of other ingredients.
The mixing water shall be mixed with cold water to keep concrete temperature low.
Tanks or trucks used for transporting water shall be insulated and/or coloured and painted white or yellow.
If ambient temperature is very low, then crushed ice flakes can be incorporated directly into the mixer as part of the mixing water. It shall be ensured that ice crystals should be completely melted by the time mixing is completed.