Mechanical properties and bond characteristics of different fiber reinforced polymer rebars at elevated temperatures

- FRP bars lost up to 55% of their tensile strength at a critical temperature of 325 °C.
- Concrete-FRP bond was significantly reduced upon exposure to high temperatures.
- FRP bars lost up to 81.5% of their bond strength at critical temperature of 325 °C.
- The analytical model, proposed in this study, showed good predictability.

This paper presents the results of an experimental study on the effect of elevated temperatures on the mechanical properties of FRP bars and the bond behavior between FRP bars and concrete. Four types of reinforcement bars namely: basalt fiber reinforced polymer (BFRP), CARBON fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), and steel bars of 10 mm diameter were used. The results showed that the FRP bars suffered significant reductions in their mechanical properties upon exposure to high temperatures of up to 450 °C at which the GFRP and BFRP melted and lost their total tensile strength capacity. At a critical temperature of 325 °C, the FRP bars lost as high as (55% and 30%) of their tensile strength and elastic modulus, respectively. The percentage reduction in mechanical properties and bond strength was more pronounced in specimens with FRP bars than those with steel bars under elevated temperatures; the percentage reductions in bond strength between concrete and FRP bars reached as high as 81.5% after exposure to 325 °C. Based on the experimental results, an empirical model was proposed to predict the post-heating bond stress-slip relationship between the FRP bar and the surrounding concrete: a good agreement was noticed between the experimental results and the proposed model.