Effect of high temperature on the bond performance between basalt fibre reinforced polymer (BFRP) bars and concrete

Abstract

The use of basalt fibre reinforced polymer (BFRP) bars as a reinforcing material has gained increasing interest worldwide. However, few studies have reported on the bonding performance of the bars in concrete when exposed to high temperatures. This paper investigates the effects of seven variable parameters, namely, temperature, bonded length, diameter and type of FRP bars, concrete strength, concrete cover thickness and a fireproof coating material on the concrete surface, on the bond stress-slip curves, failure modes, and bond strength of the BFRP bars. Glass fibre reinforced polymer (GFRP) bars were used for comparison. BFRP bar pullout specimens exhibited similar bond stress-slip curves at both room and high temperatures, but the peak bond stress and the slope decreased when the temperature increased. The bond strength declined gradually with the increase of the temperature, and the effect of temperature on the bond strength of the GFRP bar pullout specimens was more severe than that of the BFRP bar pullout specimens. At temperatures from 70°C to 220°C, the bond strength decreased by 2.45–14.24%. At 270°C, the bond strength declined by approximately 32%. At 350°C, the residual bond strength was 12.20–23.14% of their original values.