Placing, finishing, and curing concrete require extra care in hot weather. When temperatures rise above 80 degrees, fast setting, lower strengths, and cracking are all more likely. Some tips for minimizing hot weather effects are as follows:
CONCRETE PRODUCTION, DELIVERY, AND DISCHARGE:
- Minimize cement content by using water reducers and fly ash as a cement replacement.
- Use retarders to control fast setting and when long haul times are unavoidable.
- Shade aggregate stockpiles and wet them to promote evaporative cooling that lowers concrete temperature.
PLACING AND FINISHING:
- Have all forms, equipment, and workers ready to handle concrete, especially the first delivery of the day.
- Have at least one standby vibrator on hand for every three in use.
- Work fast but don't finish concrete while there's still bleedwater on the surface.
CURING AND PROTECTION:
- Start curing as soon as finishing is complete.
- Cure continuously, preferably with water.
- Cure for the specified period, but not less than three days.
TESTING AND INSPECTION:
- Make slump, air tests, and test cylinders immediately after obtaining the concrete sample.
- Don't leave test cylinders unprotected in the hot sun.
- Prevent test cylinders from drying by casting them in plastic molds with a plastic lid or by covering them with plastic sheets.