Review on degradation behavior of fiber-reinforced polymer bars in marine environments

Fiber-reinforced polymer (FRP) composites are expected to serve as reinforcement materials for coastal and island infrastructure due to their high strength, lightweight, and good corrosion resistance. However, the performance of FRP bars as reinforcement materials in long-term service in the marine environment is also subject to deterioration. Therefore, for improving the durability performance of FRP bars, it seems necessary to understand their degradation behavior. This paper first analyzes the deterioration mechanisms of the fibers, resins, and fiber–resin interfaces that make up the FRP bars under the action of seawater/salt solution, seawater sea-sand concrete pore solution/alkali solution, and stress-marine corrosive environment coupling, respectively, and further investigated the mechanical property degradation of FRP bars under the action of various factors, including interlaminar shear strength, tensile strength, and bond strength with concrete. The degree of degradation of FRP bars exposed to the offshore environment was found to be more sensitive to the magnitude of alkalinity and stress levels; GFRP bars were more resistant to seawater corrosion than BFRP bars. Moreover, the long-term mechanical properties of FRP bars were predicted, and the predicted result is more conservative than the field data. Based on the summarized and analyzed results of this review, recommendations for future work are presented, also for a comprehensive and better understanding of the degradation behavior of FRP bars.