Mechanical properties and bond strength degradation of GFRP and steel rebars at elevated temperatures

Abstract

Fiber reinforced polymer (FRP) rebars have recently been gaining popularity in the construction industry all around the world while steel rebars have been widely used so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this study, mechanical and bonding properties of glass fiber reinforced polymer (GFRP) and steel rebars subjected to elevated temperature effects were investigated throughout a correlative comparison. Axial tensile tests and pull-out tests of these materials were performed subsequent to exposing them into elevated temperature effects in the range of 23–800 °C. Severe effects on the tensile properties of bare steel bars were observed after 600 °C, while this critical limit is 300 °C for bare GFRP bars. Test results show that bond strength degradation is almost linear for both type of rebars, however, 600 °C is also the critical temperature regarding the serious deterioration on concrete. Additionally, an empirical modeling approach on the bond strength degradation of rebars at elevated temperatures was proposed and it was found that comparison results have quite promising consistency based on the modeling process.