ACI 305 defines hot weather as job site conditions that include high ambient temperatures, high concrete temperatures, low relative humidity, high wind speeds, and high solar radiation. 

 

This chart indicates when the risk of excessive moisture loss can occur.

If the rate of evaporation approaches 0.2 lb/ft2/h, precautions against plastic shrinkage cracking are necessary.

 

 

Try to minimize the addition of water on the jobsite by using admixtures appropriate for your placing needs. With the addition of water comes excessive bleed water, which can delay finishing operations and cause problems for the finisher.

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Hot Weather Concrete Tips:

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· Use mix designs suited for hot weather use

· Use retarding admixtures to slow the rate of slump loss

· Have adequate manpower for placing concrete in timely manner

· Dampen the subgrade with water prior to placement

· Use fibers to minimize the risk of plastic shrinkage cracking

· Use proper curing techniques under hot weather conditions. Use plastic sheeting   or membrane forming curing compounds to stop moisture loss, or use a water        cure technique remembering to never finish bleed or cure water into the surface

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