Bond behavior of FRP-to-concrete interface under sulfate attack: An experimental study and modeling of bond degradation

• The bond behavior of an FRP-to-concrete interface under sulfate attack was tested.
• The effect of sulfate corrosion on the material degradation was revealed.
• The material-degradation-based interfacial bond strength model was proposed.
• The material-degradation-based interfacial bond-slip relation model was derived.
• The bond degradation significantly correlates with the sulfate diffusion depth.

Sulfate attack is one of the important environmental factors that cause the deterioration of concrete structural performance. It is also a potential risk factor that leads to the premature interfacial debonding failure of fiber-reinforced polymer (FRP) strengthened concrete structures. Externally bonded FRP-strengthened concrete structures are constructed from three materials, i.e., FRP, adhesive, and concrete. Therefore, the degradation of these materials is an important cause of the bond performance deterioration of an FRP-to-concrete interface. In this paper, (1) an experimental method for accelerated corrosion by a sulfate solution in a high-temperature dry-wet cycle was properly designed to simulate the external sulfate corrosion environment, (2) the mechanical performances of the three materials after sulfate attack and the bond performance deterioration of an FRP-to-concrete interface were tested and analyzed, (3) the material-degradation-based bond strength and bond-slip models of FRP-to-concrete interface were developed, and (4) as the performance degradation of concrete attacked by sulfates can be quantitatively characterized by the corrosion depth of concrete directly, the bond strength and bond-slip models related to the sulfate-induced corrosion depth of concrete were also derived. A comparison with experimental data showed that the models had relatively high prediction accuracy, and they can be used as the theoretical basis for the durability design of FRP-reinforced concrete structures under sulfate corrosion.