Bond durability of BFRP and GFRP bars in sulphoaluminate cement concrete under water immersion environment

To study the durability of bond performance between basalt-/glass-fiber reinforced polymer (BFRP/GFRP) bars and low alkalinity sulphoaluminate cement concrete (SAC), the bond test of 144 specimens were conducted after 30-, 90-, 180- and 360-day water immersion at 20, 40 and 55 °C. The test results indicated that the bond strength between BFRP/GFRP bars and SAC/ordinary Portland cement (OPC) concrete increased in the first 90 days due to the continuous cement hydration, and then decreased due to the long-term degradation. Moreover, the elevated temperature contributed to the more severe deterioration of bond performance. After 360-day aging at 55°C, the bond strength between BFRP (or GFRP) bars and OPC decreased by 24.8% (or 10.4%). Conversely, the FRP-SAC showcased superior durability than FRP-OPC counterpart (26% and 15.9% bond performance enhancement for BFRP- and GFRP-concrete, respectively). To profoundly investigate the inherent degradation mechanism between FRP bars and concrete, scanning electron microscopy (SEM) analysis was conducted. Finally, the long-term bond performance of BFRP/GFRP bars in SAC was comprehensively predicted, remaining a considerable bond strength retention of 92.84∼100% after 75 years of service in moisture saturated environment at 25 °C∼35 °C. •Bond durability of BFRP/GFRP-SAC pullout specimens were investigated.•Bond durability of FRP bars to SAC is superior than that to OPC.•Bond durability of GFRP bars is slightly superior than that of BFRP bars.•Bond performance of BFRP/GFRP-SAC specimens after 75 years was predicted.