Mechanism of effect of elevated temperature on compressive strength of cement mortar

Compressive strength of cement mortar was studied from room temperature to 550°C with cement paste and different fine aggregate content. The result shows that development of compressive strength of cement or cement mortar with same m(C)/m(S) is divided into three stages: compressive strength increases to some extent when cement or cement mortar with m(C)/m(S)>1/3, but compressive strength decreases to some extent when m(C)/m(S)<1/3 in the first stage(room temperature to 150 °C); compressive strength changes gently in the second stage(150~180 °C); compressive strength decreases significantly in the third stage(180~550 °C). And compressive strength of cement mortar decreases with fine aggregate content increasing in the same temperature. Through the analyst of DSC, XRD and thermal expansion behavior measurement the mechanism how compressive strength changes with temperature is proposed.