Concrete temperature for general concreting works 15 . should differ between0C to 250c to enable it to attain its absolute ultimate power within 28 days. If concreting is done in extremely hot weather, the rate of hydration of the cement is accelerated and the water in the concrete mix dries up faster. This in turn creates stress which causes shrinkage cracks and damage to the concrete.
Adverse effects of hot weather can be minimized by taking the following precautions while concreting in extreme hot weather conditions.
1. Use a retarding mix
Add a retarding agent to the concrete to reduce the rate of hydration of the cement.
2. reduce total temperature
Keep the temperature of the concrete material as low as possible. The temperature of aggregates can also be reduced by collecting them in shaded areas and by sprinkling cold water on the stock pile.
3. reduce water temperature
Use cold water to make concrete. In some cases, crushed ice can be used to lower the water temperature and achieve a concrete mix that has a temperature within the desired range.
4. rapid transport of concrete
Mixed concrete should be transported and kept in position within the shortest possible time, so as to minimize losses due to evaporation and rise in temperature.
5. Spraying on Formwork and Reinforcement
Spray cold water on the formwork and reinforcement just before applying the concrete. This prevents water loss from the concrete due to absorption by these materials.
In case of construction of roads, sprinkle water on the prepared sub-grade before pouring the concrete.
6. laying concrete at night
Schedule the pouring of concrete at night when the ambient temperature is much lower than during the day.
7. speed up work
The work should be executed with utmost speed, as delay will adversely affect the concrete due to hot weather conditions.
8. direct sunlight protection
Once in position, the concrete surface should be adequately protected from direct sunlight exposure by applying a sunshade.
9. wind protection
Direct air breaks on the finished concrete surface to protect the concrete surface from wind.
10. continuous treatment
Concrete should be continuously cured with sufficient water during the first few hours and thereafter the surface should be kept moist for the entire duration of curing.