Q: I know ready-mix producers have to make an effort to deliver concrete at an appropriate temperature during hot weather. What steps should a concrete contractor take to keep concrete cool enough for hot-weather placement?

A: You can take several precautions during hot weather to maintain or reduce the concrete temperature.

  • Reduce the effect of solar heat on mixers, chutes, conveyors, hoppers, pump lines, and other handling equipment by shading or covering it with wet burlap. Painting the equipment white also helps.
  • Fog or sprinkle the forms, rebar, and subgrade with cool water just before placing concrete. Fog the area during placing and finishing to cool contact surfaces and the surrounding air, while also increasing its relative humidity. This slows the concrete's temperature rise and reduces the evaporation rate of mix water after placement.
  • When the weather is extremely hot, restrict placement to early morning, evening, or nighttime hours, especially in arid climates.