Experimental study on interfacial shear behaviour between ultra-high performance concrete and normal strength concrete in precast composite members

Abstract

Ultra-high performance concrete (UHPC) is increasingly applied in hybrid structures with normal strength concrete (NSC) due to the high performance and costs of UHPC, especially in making precast composite members. It is critical to understand the shear bond performance of the interfaces between UHPC and NSC. In this study, different types of interfaces between UHPC and NSC were experimentally tested, including bubble groove interfaces, flat-surface interfaces and water-jet-surface interfaces. The test parameters were the types of interfaces, existence of the dowel rebar and casting sequence of UHPC and NSC. In the series of bubble groove interfaces, three different sizes of bubble grooves were also considered and tested. The failure modes, shear strength and relationships between the loads and deformation were recorded and discussed according to the push-off test results. The test results show that NSC is the critical factor that determines the shear performance of the interfaces between UHPC and NSC. Different casting sequences of UHPC and NSC significantly affect the shear performance of different interfaces between UHPC and NSC.