Dynamic compressive behaviour of concrete after exposure to elevated temperatures

The aim of this paper is to investigate the high temperature performance of concrete under impact loading. A split Hopkinson pressure bar system was employed to determine the dynamic mechanical properties of concrete under different strain rates and temperatures. The results indicate that the hardening and toughening effects of strain rate on concrete are obvious under a given temperature. Moreover, high temperature exposure makes concrete more ductile and less resistant to impact loading. An increase in temperature leads to an obvious reduction in dynamic strength and toughness, and results in a larger strain rate and critical strain. Whereas for temperature of 200 degrees C, the dynamic strength barely changes even slightly increases. Meanwhile, the toughness at this temperature decreases firstly and later increases with strain rate in comparison to that at room temperature. Besides, as temperature increases, the dynamic fragmentation of concrete gets more violent, the stress-strain curve tends to flatten and the corresponding ascending branch becomes less steep. The stress-strain relationship of concrete under different strain rates and temperatures can be formulated by a modified model, which can well describe the dynamic mechanical behaviour of the heated concrete.