As we begin to hit the heat of summer, we should think about proper concrete placement practices to combat the heat. High temperatures can affect fresh concrete in a multitude of ways:
- Increase water demand
- Accelerate slump loss
- Accelerate set times
- Higher curing temperatures can reduce ultimate strength of concrete
- Increased chance of rapid surface evaporation leading to plastic shrinkage cracking
- Potential for thermal cracking resulting from rapid temperature drops (hot days/cool nights)
Planning for the summer heat can save you from problems down the road. Consider the use of set retarding admixtures to give you the time necessary to finish the concrete. Truck spacing should be such that delays in unloading are minimized. Also, placement in the early hours of the day are beneficial. If wind and low humidity are expected, be prepared with an evaporation retardant (such as Confilm by BASF), wind breaks or sun screens to avoid plastic shrinkage cracking.
If you have a smart phone, consider downloading WeatherApp by Holcim Cement Co. This app helps determine pouring conditions.
