Drops in concrete strength in summer related to the aggregate temperature

International audienceDrops in compressive strengths may occur for hot weather concreting. They are observed on specimens for manufacturing control tested in laboratory at 28 days. On the other hand, 7-day compressive strength seems not to be affected.An experimental program was carried out. It constituted a quantitative approach to evaluate the effect of the aggregate temperature on the performances of plain concrete. So, this paper presents the results of tests for compressive and splitting tensile strengths conducted on normal strength concrete specimens. Cylinders (11 cm × 22 cm) were prepared with different aggregate temperatures ranging from 20–70 °C and cured under either controlled laboratory conditions (20 °C) or simulated conditions of hot weather (35 °C). Results show that both the 28-day compressive strength and the splitting tensile strength of concrete are reduced with the increase in aggregate temperature by as much as 15% and 17% respectively. The aggregate temperature rise also implies an increase in the water demand of the concrete mixes which, in turn, cannot fully explain the drops in strength