Long-term bond durability of fiber-reinforced polymer bars embedded in seawater sea-sand concrete under ocean environments

This paper presents an experimental study on the bond durability of basalt fiber-reinforced polymer (BFRP) bars, steel-fiber reinforced polymer (FRP) composite bars (SFCB), and steel bars embedded in seawater sea-sand concrete (SWSSC) and subject to a simulated ocean environment. The effects of the environment type, exposure period (i.e., 3, 6, and 9 months), and reinforcement type on bond durability were investigated. The degradation mechanism was analyzed using scanning electron microscopy (SEM). The test results showed that after being conditioned, the failure mode changed from shear failure at the BFRP rib-concrete occlusal interface to the peeling of the BFRP surface. For the BFRP bars, after 9 months of aging, the bond stress retention was 92% in the wet-dry cycling environment and 78% in the immersion environment. For the SFCBs, after 9 months of aging, the retention in the wet-dry cycling environment was 100% and that in the immersion environment was 90%. For the steel bars, although there was no reduction in bond strength, pitting corrosion was observed at the bar surface. The predicted bond stress retention of BFRP bars embedded in SWSSC after 50 years of service life in various environmental conditions ranged from 47% to 83%.