In this article, we explain the step which can be taken to prevent or reduced the ill effects of concreting in hot weather
Concreting in Hot Weather
Any concreting operation done at a temperature above 40°C is called hot weather concreting.
IS 7861 (part-1): 1975 specifies precautious to be taken for concreting above 40°C temperature.
Precautions to Prevent Ill Effects of Concreting in Hot Weather
The following precautions must be taken:
- In hot weather, the Workability of concrete decreases and thus the addition of water without proper adjustments using refrigerated water. Precooling of aggregate and the addition of broken pieces of ice can reduce the ill effects of the weather concreting.
- The mix should contain minimum cement content. Low heat cement should be used.
- Accelerator must not be used in hot weather conditions. The use of water-reducing admixtures is beneficial.
- The period between the mixing and placing of concrete must be the minimum.
- The work area should be kept wet. Immediately after placing the concrete, steps should be taken to prevent the loss of water from the concrete. Continues curing is also very important. Moreover concreting can be done at right to reduce evaporation losses.
Following are some of the effects of hot weather concreting:
- High temperature leads to accelerated setting due to rapid hydration of cement. Workability of concrete decreases. This creates more demand for water in hot weather conditions.
- Long term strength of hot weather concrete is lesser than normally produced concrete.
- Hydration of cement takes place due to water present in the capillary pores which gets evaporated due to hot weather conditions. Thus more water is needed. Rapid hydration of cement gives rise to porous concrete thereby leading to lower strength.
- increased cracking results due to hot weather concreting. These cracks develop due to the plastic shrinkage of concrete.
- At high temperatures, it is more difficult to control the air content and thus air gets entrained in concrete.
This badly affects the workability of concrete.
Placing of Concrete in Cold And Hot Weather
Concreting in cold weather:
Any concreting operation done below 5°C is called cold weather concreting.
Low temperature makes the concrete develop its strength very slowly.
lee-lenses formed in the plastic
stage of concrete badly damages it.
Effects of Cold Weather Concreting
Following are the effects of cold weather concreting:
- Lower temperature leads to the delayed setting of concrete. This increases the time for removal of formwork thereby leads to increased cost of the project.
- Plastic concrete when exposed to low temperatures undergoes permanent damage like reduction in strength etc.