Hot weather concreting is always a challenging task for civil engineers. We are living in a world where you can explore different environments and weather conditions. Some places are soo cold but some places are too hot.
While constructing a building the concreting procedure is different for both conditions. You know that hydration of cement is basic operation during the setting and hardening of concrete.
During hydration, the basic mixture that is added to cement and aggregates is water. But the main problem is water changes its property with its surrounding weathering conditions.
During hot seasons, the evaporation rate will be very high. In other words, the rate of hydration will be very high. This leads to many problems. This is one of the main criteria for hot weather concreting.
This drives to the accumulation of higher earlier strength. Higher early strength is good but in terms of long-term aspect, this is not really good. There are several problems listed below during the hot weather concreting.
Different problems due to Hot weather concreting
1.Rapid evaporation of water from the concrete
Hot weather concreting normally takes in low humidity. In low humidity the evaporation rate i.s very high because of the low water content in the atmosphere.
This reduces the workability of concrete and makes unworkable. Due to this big voids will forms in the concrete and this makes the way for cracking of concrete.
2.The rate of hydration increases
As we know that the normal temperature for the setting process is around 27 degrees Celcius. But here the temperature goes above 40-degree Celcius. Due to this, the rate of hydration increases very much.
This results in the stiffening of concrete before placing concrete. This causes a reduction in the workability of concrete.
3.Finishing of concrete
While concreting, you must try finishing of concrete as soon as possible after mixing. But when concreting at high temperatures the water evaporates very fast.
This causes hydration faster and initial setting of concrete takes places before doing concreting. Hence the finishing of concrete will be of poor quality.
The plastic shrinkage will be higher. The higher plastic shrinkage is due to higher evaporation rate in concrete. The water particles will move faster from the interior to the surface of the concrete.
This creates large pressure gradients and results cracks in the concrete. You must take more care for concreting structures which has more surface area compared to its depth.
5.Curing of concrete.
Due to early strengthening, continuous curing is to be required. This continues curing cause more consumption of water. Curing at higher temperatures also increases the number of labor and project estimate.
6.Air entrained concrete.
You need to use a greater proportion of air entraining cement in order to overcome the lack of air entrainment due to higher temperatures.
What are the remedy or precautions for hot weather concreting?
- Select places for concrete mixing where doesn’t get a direct attack of sunlight.
- Try to make consistency to concrete which helps rapid placement.
- Keep all the ingredients of concrete in normal temperature places.
- Provide suitable methods of curing as soon as possible after finishing of concrete.
- Try to avoid mixing and placing at noon times. Early morning and night are most preferable time to avoid hot weather concreting.
- Spread fog above the surface of the concrete to increase the humidity.
- Before concrete placing, try to moisture steel reinforcement, formwork etc..