Hot & Cold Weather Concrete
Hot Weather Concrete
When it comes to mixing, curing, and placing concrete, hot weather can present a large array of problems. Included in these problems are variations in surface appearance and how water tight the concrete is. In terms of concrete, hot weather describes any combination of the following factors:
- High temperature in the concrete itself
- The level of solar radiation
- High wind velocity
- Low relative humidity
- High ambient temperatures
Rapid moisture evaporation is caused by combinations of the factors above. This rapid moisture evaporation leads to a few significant issues:
- Thermal cracking
- Cracks in plastic shrinkage
- Compression strength declines.
A way to prevent the issues listed above is to replace some of the water with ice while batching. Another option is to use Hydration Stabilizer (also known as Retarder). Hydration stabilizer is a chemical admixture that increases the amount of time it takes for concrete to settle. Ice and Hydration Stabilizer are often used together to achieve the best results for setting concrete in hot weather.
Cold Weather Concrete
Setting concrete in cold weather can also bring difficulties. In terms of what constitutes cold weather when setting concrete, the following apply if they’ve occurred for three consecutive days:
- The average daily air temperature is below 40 degrees F.
- The air temperature does not reach higher than 50 degrees F for more than 12 hours of any 24-hour period.
In order to expedite set up time and increase strength quickly, hot water can be added at the plant during batching.
Another cold weather concrete solution is to use Non Chloride Accelerator. This accelerator is non-corrosive, and as the name implies, does not use chloride. When you add this admixture to the plant during batching, it speeds up the setting time, and increases compression strength early on.
Calcium Chloride is also useful for concrete work in cold weather. The setup and results are very similar to using the Non Chloride Accelerator, but it is not recommended when reinforcements, such as steel, an electrical conduit, or metal decks are involved.