A fracture failure criterion for concrete-concrete interface under mixed mode loading condition

Various important concrete structures are susceptible to imperfections, such as the presence of an interface.In some cases, the formation of an interface is an inevitable flaw, such as in the case of repair, dams and pre-cast concrete structures.These flaws can act as a weak link and could be responsible for the failure of the structures.One of the most widely used nondestructive techniques to monitor such damages in structures in real time is the acoustic emission (AE) technique.In this study, experimental tests are conducted on concrete-concrete interface specimens under four-point shear tests with different interface positions.The interfaces are formed between four different strengths of concrete on each side.The AE technique is used to monitor the crack growth.Based on the experimental results, A fracture criterion has been suggested based on simplified calculation of mode mixity ratio.Three different failure patterns have been identified depending on the mode mixity ratio, where cracks eventually kinked into the substrate material at a critical value of the mode mixity ratio.