Fracture properties of high-strength/high-performance concrete (HSC/HPC) exposed to high temperature

An investigation of the residual fracture properties of high-strength/high-performance concrete (C80 and C100) exposed to high temperatures is reported in this article. Three-point bending test specimens of 100 mm × 100 mm × 515 mm size were prepared according to the RILEM recommendation. The three-point bending beams were exposed to temperatures varying from 200 to 800 °C. The complete load-crack mouth opening displacement curves and load-deflection curves of the specimen were worked out after cooling. The fracture toughness, including the initial and unstable fracture toughness, fracture energy, and characteristic length, was calculated. These four parameters were shown to decrease monotonically with temperature. Other mechanical properties including the compressive strength, compressive Young’s modulus, and splitting strength of post-fire specimens were also obtained. The digital image correlation method was utilized to monitor the whole fracture process, and the results from the digital image correlation method fit well with those from the direct measurements.