Experimental study on bond performance of interface between concrete and UHPFRC incorporating recycled tyre fibers

This paper conducted single-side shear tests on 27 groups specimens with dimensions of 100 mm × 100 mm × 40 mm to investigate the shear bond performance of the interface between concrete and ultra-high performance fiber reinforced concrete (UHPFRC) incorporating recycled tyre fibers, as an eco-friendly and cost-effective material. The effects of concrete strength, interface roughness, interface adhesives, and the substitution rates of recycled tyre fibers in UHPFRC were analyzed by Response Surface Methodology model. The findings revealed the existence of two failure modes, specifically interface failure and concrete failure, and it was observed that the shear load-slip curves exhibited a similar trend across various specimens, characterized by a gradual increase accompanied by an escalating growth rate. The higher concrete strength and interface roughness as well as the lower substitution rates of recycled tyre fibers would enhance the shear bond strength, while interface adhesives had minor effects. Based on the micro-bonding mechanism and experimental data, two theoretical models for shear bond strength and shear load-slip curves were established, demonstrating good agreement between prediction and experimental results. Considering the shear bond strength, the environmental and economic analysis was carried out, and UHPFRC with 25 % substitution rates of recycled tyre fibers exhibited the best benefits.