Durability test on the flexural performance of seawater sea-sand concrete beams completely reinforced with FRP bars

Fibre-reinforced polymer (FRP) bars and seawater sea-sand concrete (SWSSC) is a very promising new combination. When seawater and sea sand are used, not only the tensile reinforcements but also the stirrups and top reinforcements should be FRP to avoid corrosion. In this paper, an accelerated ageing test was conducted on SWSSC beams completely reinforced with FRP bars in the marine environment. Two types of beams were tested. One had a basalt FRP (BFRP) bar as the tensile reinforcement, and the other had a steel-FRP composite bar (SFCB) as the tensile reinforcement. The stirrups and top reinforcements were all BFRP bars. The experimental results indicated that cracks in both types of beams after bending tests became sparse after environmental exposure. The load fluctuation during crack formation increases for environmentally conditioned SWSSC beams reinforced with BFRP bars. After immersion in 50 °C seawater for longer than 6 months, the failure mode of BFRP beams changed from concrete crushing to shear failure, and the contribution of BFRP stirrups to shear resistance capacity clearly decreased. For the SFCB beam, the failure mode changed from concrete crushing to SFCB rupture due to the reduction of tensile strength of SFCB after exposure, which causes a maximum of 11% reduction in load capacity.