Experimental study on bond performance between corroded reinforcement and basalt-polypropylene fiber reinforced concrete after high temperature

Abstract

High temperature damage and corrosion erosion degrade bond performance between steel reinforcement and concrete, subsequently affecting structural load-bearing capacity. Given that fiber reinforced concrete (FRC) exhibits superior mechanical properties and durability, this study experimentally evaluates the bond performance between corroded steel and basalt-polypropylene fiber (BF-PF) reinforced concrete after high-temperature exposure. Eccentrically loaded specimens with varying corrosion levels (0 %, 2 %, 5 %, and 10 %) were prepared for pull-out tests after exposure to high temperatures (20°C, 200°C, 400°C, 600°C, and 800°C). The results indicated that the incorporation of 0.1 % BF and PF improved the mechanical and bond properties of concrete, with a positive synergistic effect observed when the two types of fibers are combined. At temperatures of 200°C, 400°C, and 600°C, the average bonding strength of fiber-reinforced concrete (FRC) increased by 17.84 %, 12.68 %, and 15.93 %, respectively, with BPFRC exhibiting higher residual bonding strength at 400°C. However, As the level of damage increased, the contribution of fibers gradually diminished. At 800°C and a corrosion rate of 6.76 %, the bond strength of BPFRC increased by only 3.88 %, while that of PFRC decreased by 1.81 %. Additionally, fiber bridging effectively inhibits crack development and distributes the load, thereby positively impacting bonding stiffness and energy dissipation. A bond strength prediction model and constitutive relationship for the combined effects of corrosion and high temperature were proposed. The applicability of the model was further validated by predicting the flexural load capacity of reinforced concrete beams, considering bond slip after damage. This research provides data that support the performance evaluation of BF-PF reinforced concrete.