At a location in Singapore, the temperature of plastic concrete as placed may be as high as 102 degrees F on a hot day. When the aggregate stockpiles are sprayed with water to promote evaporative cooling it is possible to keep the temperature of the plastic concrete below 95 degrees F but the plastic mix at the time of placing is seldom less than 90 degrees F. Is it possible that placing at such elevated temperatures leads to a drop in the strength of the concrete when compared with the same mix placed in a temperate climate, and thereby at a much lower temperature?
There are numerous publications that illustrate the detrimental effect of high temperatures on concrete strength. In particular, an article published in the July 1971 issue of the Journal of the American Concrete Institute provides a good discussion of this situation. The discussion referring to curing temperatures states there are substantial reductions in concrete strength as temperature increases above 90 degrees F. In the United States, the 90-degree temperature is the maximum limit for concrete at the time of placing.