Experimental Research on Fracture Behavior of Concrete after High Temperature

High-strength concrete has been widely used in various complex buildings. The fracture and mechanical properties of high-strength concrete after fire have great research value. Based on the double K fracture model, the fracture properties of C50 and C70 strength grade concrete after being processed by high temperature of 25 °C ~800 °C were studied by three-point bending beam test. The changes of fracture toughness Kic and fracture energy at different temperatures after being processed by high temperature were analyzed. The results showed that the initial crack toughness and instability toughness of the two kinds of concrete decreased with the increase of temperature; when the strength grade of concrete was C50, the fracture energy first increased and then decreased with the development of temperature; when the strength grade of concrete was C70, the fracture energy first decreased rapidly and then decreased slowly with the development of temperature.&nbsp