Abstract:
To study the residual bond performance of glass fiber reinforced polymer (GFRP) bars and seawater coral aggregate concrete after exposure to high temperature, the pull-out tests were performed through 54 GFRP bars coral aggregate concrete specimens and steel bars coral aggregate concrete specimens. The highest temperature of 350℃ and concrete classes of C20 to C30 were considered in this experiment. The surface changes and bond failure modes of specimens after high temperatures were observed. The bond stress-slippage curves, bond strength, stiffness and peak slippage were obtained. The influences of temperatures, bar diameters and concrete strengths on the bond properties of GFRP bars and coral aggregate concrete after high temperatures were analyzed. Furthermore, the deterioration mechanism of GRFP bars seawater coral aggregate concrete after high temperatures was revealed based on the analysis of mass loss rate and XRD tests. Finally, the bond stress-slippage constitutive relation and residual bond strength of GFRP bars and coral aggregate concrete after high temperatures were proposed. The results show that even though the failure modes of specimens after high temperature are similar to those at room temperature, the interface of GFRP bar and coral aggregate concrete is degraded significantly due to the carbonization of GFRP bar and pyrolysis of coral aggregate concrete. The bond strength of specimens decreases and the peak slippage increases as the temperature increasing. The smaller the diameter of GFRP bars, the lower the residual bond strength and stiffness of specimens after high temperatures. The higher the strength classes of coral aggregate concrete, the greater the residual bond stiffness and the smaller the peak slippage. The calculated results of the proposed bond stress-slippage constitutive model and residual bond strength of GFRP bars-coral aggregate concrete after high temperatures show a good agreement with the experimental results.