Bond Behavior between NSM CFRP Strips and Concrete Exposed to Elevated Temperature Using Cement-Based and Epoxy Adhesives

The repair and strengthening of existing concrete structures with composite material has become more common during the last decade. The near-surface-mounted (NSM) technique was used in this research, where fiber-reinforced polymer (FRP) laminates were bonded using an epoxy or cement-based adhesive in grooves cut into the concrete surface to study the behavior of the bond between the NSM carbon fiber–reinforced polymer (CFRP) strips and concrete after exposure to heating. Twenty-four heat-damaged concrete prisms were tested using a single-lap shear test. The results were compared with 24 reference specimens without heat damage. The results demonstrate that the residual bond strength after the repair of heat-damaged concrete with CFRP using epoxy adhesive is 94, 79, and 49% for temperature exposure of 1 h at 200, 400, and 600°C, respectively. The corresponding values for 2 h of exposure are 86, 75, and 41%, respectively. However, the residual bond strength after the repair of heat-damaged concrete with CFRP using cement-based adhesive is 91, 79, and 70% for temperature exposure of 1 h at 200, 400, and 600°C, respectively. The corresponding values for 2 h of exposure are 85, 69, and 66%, respectively.