Study on crack dynamic propagation behavior and fracture toughness in rock-mortar interface of concrete

To study crack extension behavior and fracture toughness in rock-mortar interface of concrete, a bi-material single cleavage triangle (BSCT) specimen was proposed in this paper. The BSCT specimen consists of two materials, i.e. granite and mortar. The dynamic loading of the BSCT specimen was conducted by split Hopkinson pressure bar (SHPB) system, and the velocity and time of crack extension were measured by using crack propagation gauges (CPGs). The effects of loading rate and the roughness of rock surface on crack dynamic behavior were investigated. The finite element numerical simulation was carried out by using the software AUTODYN, and the simulation results show that interface fractures in early stage were driven by tensile stress, and later, shear failure zone occurred in the rock-mortar interface. The shear stress was induced by the unbalance of stress waves travelling through the granite and mortar with different speeds. The complex stress intensity factors along rock-mortar interface were calculated using the software ABAQUS, and the complex fracture toughness was obtained combining with the test results of crack initiation time. The results show that the interface roughness and loading rate have great effect on crack propagation behavior along rock-mortar interface.