Bond properties between FRP bars and coral concrete under seawater conditions at 30, 60, and 80 °C

•The bond properties between FRP bars and coral concrete under seawater conditions were investigated.•The bond strength of CFRP bars or GFRP bars to coral concrete decreased obviously after immersion at a high temperature.•The effect of the seawater immersion on the GFRP bars was significantly greater than that on the CFRP bars.•The coral concrete cover layer on the FRP bars has a weaker protective effect than ordinary concrete. The bond properties of glass-fibre-reinforced polymer (GFRP) bars, carbon-fibre-reinforced polymer (CFRP) bars, and coral concrete under seawater conditions at 30, 60, and 80 °C for 30, 60, and 120 days were studied. The characteristics of the bond stress-slip curve, failure modes and mechanisms, and changes in the bond strength of the fibre-reinforced polymer (FRP) bar-coral concrete immersed in seawater were analysed. The results show that the properties of the bar and the bond properties between the FRP bars and the coral concrete were reduced to different degrees. With increasing seawater temperature, the bonding performance significantly decreased, and the failure modes of the GFRP bar-bonded specimens gradually changed from pullout failure to bar fracture. The residual segments of the τ-s curves of some CFRP bar-bonded specimens show a wave-like uptrend. The surfaces of both types of FRP bars were obviously sheared and worn. The effect of the seawater immersion on the GFRP bars was significantly greater than that on the CFRP bars; after immersion at a high temperature, microcracks and voids appeared between the surface resin and fibre of the GFRP bars, and serious debonding and deterioration of glass fibres gradually occurred.