Bond-slip behavior and failure mechanism of Basalt-FRP bars with different surface treatments in crumb rubber concrete

Recently, using crumb rubber aggregate has gained extensive attraction due to its ability to enhance ductility and energy dissipation of crumb rubber concrete (CRC). Fiber-reinforced polymer (FRP) bars have emerged as an innovative, sustainable and durable solution to improve the durability of reinforced concrete (RC) constructions in harsh environments. However, there is a notable lack of experimental research investigating the behavior of CRC in structural members , particularly concerning the interaction between CRC and FRP bars. Therefore, this study analyzes the bond performance between CRC and Basalt-FRP (BFRP) bars focusing on the effect of rubber particle sizes, volumetric replacement ratios. In addition, three different surface treatments (helically wounded, wrapped, and sand-coated) and three diameters; 10-, 12- and 16 mm of BFRP bars were examined to evaluate their influence on the bond-slip behavior. The experimental results revealed that different surface treatments significantly altered bond behavior and failure mechanisms. Moreover, replacing fine aggregate with 5 % of 5 mm rubber particles led to an increase in compressive and bond strengths by 13 and 8 %, respectively. However, increasing the replacement ratio beyond 5 % up to 20 % negatively affected the mechanical properties with only minor influence on the bond-slip curve characteristics. It was also observed that CRC mixes with No. 20 rubber particle sizes exhibited significant reductions in compressive and bond strengths across all replacement ratios. Regarding the surface treatment of BFRP bars, helically wounded BFRP bars demonstrated superior bond performance compared to all other BFRP and steel bars. Conversely, wrapped BFRP bars displayed inferior bond behavior characteristics compared to other BFRP bars. • Using 5 % of 5 mm crumb rubber particles enhances the mechanical properties of concrete. • For all substitutions, incorporation of finer rubber particles (No. 20) decreases the mechanical properties of concrete. • The surface treatment of BFRP bars has a significant effect on the failure mechanism and bond behavior. • Wounded BFRP bars have a superior bond performance compared to other BFRP and steel bars. • A new bond-strength equation was proposed incorporating rubber content, particle size, and bar diameter, validated with experimental data.