Experimental and numerical study of the CFRP-to-concrete bonded joints after water immersion

The bond between a carbon-fiber-reinforced polymer (CFRP) plate and concrete is significantly and adversely affected by the ingress of moisture. In the present study, the effects of water immersion on the CFRP-to-concrete bonded joints were examined. A single lap shear test was utilized for the experimental test and the finite element (FE) method was adopted for the numerical study. Water immersion caused the failure mode to change from concrete cohesive failure to primer-concrete interfacial debonding. When the debonding changed from concrete cohesive failure to interfacial debonding, the interfacial stiffness increased. The interfacial stiffness increased with the immersion time. The interfacial fracture energy decreased rapidly during the initial period of 6 months and then leveled off with further immersion. The evolution of the interfacial fracture energy was proposed as a function of immersion time. The numerical model of the FRP-concrete with the proposed evolution of the interfacial fracture energy can accurately predict the experimental results. A reduction coefficient is proposed to evaluate the effects of water immersion on the bond performance.