Newswise — As temperatures soar close to and above 100 degrees this week, the construction business is affected in more ways than the obvious toll of the heat on workers. Construction professionals say that temperatures above about 85 degrees begin to affect the concrete and when the thermometer reaches 95 and above, precautions to keep the concrete cool and ensure its strength become very important, said Fouad H. Fouad, Ph.D., professor and chair of the UAB Department of Civil, Construction and Environmental Engineering.
"High concrete temperatures will decrease the concrete setting time and, consequently, the time available for placement and finishing of the concrete," Fouad said. "The concrete also becomes vulnerable to lower ultimate strength."
When concrete is mixed, the addition of water to the cement initiates a chemical reaction referred to as hydration, a process which itself generates heat. If the hydration process happens too quickly, the resulting internal structure of the concrete will be weak and the ultimate concrete strength will be low. So when the temperature soars, contractors and builders must consider using set-retarding chemical admixtures that slow down the rate of hydration. Other hot-weather precautions include using ice in the mixture, keeping the mixing time of the concrete to the minimum required, protecting the concrete from drying winds and keeping the concrete shaded from direct sun as it is being transported and placed.
"Contractors also mist cool water on the steel forms in which the concrete is mixed," he said. "And working at night should be considered if it is too hot during the day."
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