Fracture toughness of high performance concrete subjected to elevated temperatures Part 1 The effects of heating temperatures and testing conditions (hot and cold)

In this study, the fracture toughness K-IC of high performance concrete (HPC) was determined by conducting three-point bending tests on eighty notched HPC beams of 500 mm x 100 mm x 100 mm at high temperatures up to 450 degrees C (hot) and in cooled-down states (cold). When the concrete beams exposed to high temperatures for 16 hours, both thermal and hygric equilibriums were generally achieved. K-IC for the hot concrete sustained a monotonic decrease tendency with the increasing temperature, with a sudden drop at 105 degrees C. For the cold concrete, K-IC sustained a two-stage decrease trend, dropping slowly with the heating temperature up to 150 degrees C and rapidly thereafter. The fracture energy-based fracture toughness K-IC' was found to follow similar decrease trends with the heating temperature. The weight loss, the fracture energy and the modulus of rapture were also evaluated.