Shear fracture performance of the interface between ultra-high toughness cementitious composites and reactive powder concrete

Abstract

This study used unnotched compression tests and digital image correlation technology to analyze the influence of two different casting intervals and three different roughness conditions on the fracture toughness of the interfaces between ultra-high toughness cementitious composite (UHTCC) and reactive powder concrete (RPC). UHTCC exhibits pseudo-strain-hardening responses and multi-cracking behaviors, and the most notable characteristic of RPC is its dense microstructure. The results show that the complete interfacial shear fracture process included three stages: crack initiation, steady crack propagation and unsteady crack propagation. A double-K crack propagation criterion for interfacial shear fracture of composite structures was proposed by introducing two parameters: initial and unstable fracture toughness. After introducing interfacial roughness via the scratch method, the unstable fracture toughness decreased. The 24-h casting interval group had a lower initial fracture toughness and higher unstable fracture toughness than the 2-h group. The unstable fracture toughness of all the composite specimens exceeded that of C60 concrete, indicating that they had excellent resistance to interfacial shear fracture.