Abstract
Basalt fiber-reinforced polymer (BFRP) rebars offer a cost-effective, high-temperature, chemical-resistant, and eco-friendly alternative to steel bars. However, their widespread adoption hinges on understanding their structural and mechanical performance, particularly bond with concrete at elevated temperatures. This research investigates the bond of BFRP rebars in plain and fiber-reinforced concretes after high-temperature exposure via beam-end tests, comparing them to steel bars. The parameters considered in the study include concrete type (plain and steel fiber-reinforced), the type of rebar (steel and BFRP), and exposure temperatures (ambient temperature, 100°C, and 200°C). Twenty-four beam-end test samples were prepared and tested. The observed bond performance was evaluated based on failure modes, bond stress-slip behavior, and average bond strength. Interestingly, the bond strength of BFRP rebars showed a slight increase under elevated temperatures, with gains of about 8–17% at 200°C depending on the concrete type. Although initially lower than steel at ambient conditions, BFRP exhibited comparable or slightly higher average bond indices at 200°C, while both showed similar bond strength at 100°C. Given n = 2 per condition, these trends are indicative rather than definitive. These trends suggest potential thermal resilience of BFRP at moderate temperatures; however, the observations are based on limited replicates, and the bonded regions experienced equivalent thermal exposure. To model the bond stress–slip relationship of BFRP bars at higher temperatures, an existing model for FRP bars was modified. Comparisons of bond strength are made with available models from different codes and researchers.