Abstract:To investigate the bonding property between basalt fiber-reinforced polymer (BFRP) bars and hybrid steel fiber ultra-high performance concrete (UHPC), pull-out tests were conducted to study the bonding property of BFRP bars and hybrid steel fiber UHPC. The effects of recycled tire steel fiber (RTSF) content, UHPC protective layer thickness, UHPC age, and different fiber replacement ratios on the bonding failure modes, bond-slip responses, and bonding strength of the BFRP bar-UHPC structure were examined. The results indicate three distinct bonding failure modes for the structure include pull-out failure, splitting failure, and combined pull-out and splitting failure. The ultimate bonding strength of the BFRP bar-UHPC structure gradually increases with greater UHPC protective layer thickness and longer UHPC age. Specifically, increasing the RTSF content from 0% to 3% enhances the ultimate bonding strength by 42.3%. However, a slight decrease in ultimate bonding strength is observed as the RTSF content increases. Based on the experimental results, a bond-slip constitutive model for the BFRP bar-UHPC structure is proposed. The model curves are in good agreement with the experimental curves.