Shear Performance of Interface Between Normal Concrete and Ultra-high Performance Concrete in Cryogenic Circumstance

Ultra-high performance concrete(UHPC) is known for its high strength, high toughness and durability, which makesUHPCbe seen as a promising repairing material for normal concrete(NC). In order to make sure the application of UHPC in reinforcement, especially in cryogenic circumstance, it is critical to characterize the bonding performance between UHPC and NC. Through 11 sets of normal concrete and ultra-high performance concrete specimens (UHPC-NC specimens) were tested by double shear tests, the shear properties of UHPC-NC specimens in normal and cryogenic environment (-60 degrees C) were evaluated and discussed. Different interface treatments were used, including untreated, water jetting and using retarder. The effect of interface agent was also studied. The results show that the shear strength of the interface was improved by increasing surface roughness degree. The failure mode presented brittle failure, no matter what kind of interface treatments. Cryogenic circumstance can improve the bonding strength of UHPC-NC, and the group without interfacial agent had a more significant improvement. The performance of interfacial agent in low temperature limits the improvement of interfacial bonding strength to a certain extent.