Durability of FRP bars and FRP bar reinforced seawater sea sand concrete structures in marine environments

Fiber reinforced polymer (FRP) is one of the alternatives to steel, and can be directly used in seawater sea sand concrete (SSC). But FRP material still has durability problems in corrosive environments, which is one of the hot and difficult issues of current research. Based on the existing literature, this paper combs the degradation of the long-term property of FRP bars and the durability of FRP bar reinforced SSC (FRP-SSC) structures in the marine environment. The combination of the alkaline environment of concrete and the salt ions in sea sand and seawater aggravates the dissolution of the resin and debonding of the fiber-resin interface of FRP bars (particularly for BFRP bars). Therefore, the mechanical properties of FRP bars degrade with high variability which leads to the reduction of bonding between SSC and FRP bars. Additionally, the bearing capacity of FRP bar/steel-FRP composite bar (SFCB) reinforced SSC components in marine environments decreases, and the failure mode of components changes. The current codes use environmental reduction factors in the durability design of FRP bar reinforced concrete structures. But the values of reduction factors are conservative. Finally, it is pointed out that the quantification of variability for the mechanical property of FRP bars after long-term service, and the time-dependent reliability-based design methods of components are needed for further studies.