Fracture toughness of high performance concrete subjected to elevated temperatures: the effects of heating temperatures and testing conditions (hot and cold)

In this study, the fracture toughness K_IC of HPC was determined by conducting three-point bending tests on eighty notched HPC beams of 500×100×100 mm at high temperatures up to 450ºC (hot) and in cooled-down states (cold). When the concrete beams exposed to high temperatures for 16 hours, both thermal and hygric equilibriums were achieved. K_IC for the hot concrete sustained a monotonic decrease tendency with the increasing temperature, with a sudden drop at 105ºC. For the cold concrete, K_IC sustained a two-stage decrease trend, dropping slowly with the heating temperature up to 150ºC and rapidly thereafter.