Experiment and calculation investigations 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 used strategy to enhance the durability of concrete structures in chloride environments. However, due to the distinct material properties of FRP and steel, conventional degradation theories and bond strength formulas 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. Various specimens were subjected to pull-out tests with exposure durations of 0, 3, 6, 9, and 12 months. The results showed that sustained deterioration was observed with increasing exposure duration. To predict the bond performance of GFRP-concrete after chloride exposure, a new bond strength model was proposed, considering the mechanical interlocking effect of ribs on the GFRP bars. The model was validated with the experimental results. Additionally, a finite element model accounting for the pull-out tests was established to further examine the effectiveness of the analytical model, showing a good agreement between them. These findings are expected to offer valuable insights into the long-term bond performance and service life prediction of GFRP-concrete members in chloride environments.