Effect of Mechanical Interlocking Damage on Bond Durability of Ribbed and Sand-Coated GFRP Bars Embedded in Concrete Under Chloride Dry-Wet Exposure

The substitution of conventional steel reinforcement with fiber-reinforced polymer (FRP) bars is a widely adopted strategy for enhancing the durability of concrete structures in chloride environments. However, due to the distinct material properties of FRP and steel bars, conventional degradation theory and formulas of bonding strength cannot be directly applied. This study investigates the bond behavior between Glass fiber-reinforced polymer (GFRP) bars and concrete under long-term chloride dry-wet cycling exposure. Pull-out tests were conducted on various specimens subjected to exposure durations of 0, 3, 6, 9, and 12 months. The experimental results demonstrated that factors such as surface textures and effective bond length significantly influenced bond behaviors and the sustained deterioration was observed with increased exposure duration. To predict the GFRP-concrete bond performance after chloride exposure, a novel bond strength model for GFRP bars embedded in concrete, considering the mechanical interlocking by ribs, was proposed and validated by the test results. Additionally, a sensitivity analysis was conducted on the main parameters in the model. Finally, the long-term GFRP-concrete bond performance deterioration was estimated using the proposed model. These findings are expected to provide valuable insights into the long-term bond performance and service life prediction of GFRP-concrete members in chloride environments.