Effects of water immersion on the bond behavior between CFRP plates and concrete substrate

• The adhesive layer thickness and immersion affect the CFRP-concrete bond remarkably.
• The water diffusion in multi-material systems was modeled by FEM.
• The adhesive-concrete bond is susceptible to the moisture ingress.

Effects of water immersion on the behavior of bond between CFRP plates and concrete substrate were experimentally investigated and analytically modeled. The finite element method was used to simulate the distribution of the moisture content in the interfacial zone. Single lap shear test results showed that water immersion decreases the maximum bond stress, bond capacity, and fracture energy as well as the maximum slip. Increasing the immersion time led to more moisture uptake in the adhesive layers, and more degradation of the bonding properties. The thickness of the adhesive layers (i.e., 0.2 mm and 1 mm) affects the bonding properties and the resistance to the water immersion. The thinner the adhesive layer, the higher moisture content is found at the adhesive/concrete interface. Water immersion altered the debonding mode from cohesive concrete fracture to adhesive separation from the concrete substrate, which was attributed to the weakening of the bonding strength between silica and epoxy adhesive due to moisture ingress.