How to Pour Concrete in 100 Degree Temperatures

Set up some form of shade, as well as windbreaks, if working in a windy area. Shade is not always possible, but even just doing the mixing in the shade extends the concrete's working time.

Add additional water to your mix, as much as 4 gallons extra per 1 cubic yard of concrete. Be sure to also increase the dry mix to achieve a 3-inch slump to maintain the concrete's strength. A slump is a way to measure the desired thickness of the mix by noting how high the mix piles when poured before slumping, or spreading out. A mix that is too runny will be weak and will shrink as it dries.

Keep the work area hosed down. Spray water on forms, on rebar and on the surface where the concrete is to be poured. This lowers the ambient temperature by raising humidity and retards curing.

Wet down your tools and wheel barrow periodically. Cover mixed concrete that is waiting to be used with wet burlap between mixing and using to keep it viable longer.

Mix in a commercially available retardant to slow curing.

Cover the poured concrete with straw or sand once the surface has set to the point that it cannot be marred by debris. Keep it wet with a sprinkler to further slow curing and maintain the strength, integrity and beauty of your project. Concrete cures by evaporation, so slowing the evaporation also slows the curing on hot days.