Experimental study on the interfacial shear performance between macro basalt fibers reinforced UHPC as repair material and normal concrete

The novel ultra high performance concrete (UHPC) reinforced with macro basalt fibers (MBFs), which has better performance of fiber distribution, electrochemical corrosion resistance and chloride resistance after cracking compared to UHPC with steel fibers, conforms to reinforce or repair marine structures. The interfacial performance between UHPC with MBFs and normal concrete (NC) urgently needs to be studied. Six kinds of UHPC, which were reinforced with MBFs, steel fibers and polypropylene (PP) fibers with various contents, were designed. A Double-sided direct shear test was conducted to study the effects of fibers in UHPC on the interfacial performance between UHPC and NC with different interface treatments. According to the test results, the interfacial shear strength (IFSS) between UHPC and NC increased and gradually approached the upper limit with the increasing fiber-UHPC bonding strength , content, aspect ratio and modulus of fibers. The interfaces processing method had a more significant influence on the IFSS compared to the fibers in UHPC. The group with two grooves had the highest IFSS of 6.57 MPa, representing a 242 % increase compared to the group with smooth interfaces. Semi empirical formulas fully considering the effects of fibers in UHPC were proposed based on tests results and cohesion, and it showed a reliable calculation accuracy with the prediction errors of most groups which were less than 15 %. • The interfacial performance between NC and UHPC with MBFs was innovatively studied. • Effects of cohesion influenced by fibers in UHPC on the interfacial performance of UHPC-NC was revealed. • The formulas considering the effect of fiber was proposed to calculate the interfacial shear strength of UHPC-NC.