Durability of Bond between NSM CFRP Strips and Concrete under Real-Time Field and Laboratory Accelerated Conditioning

This investigation addresses the durability of the adhesive bond between near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips and concrete, under real-time field conditioning and laboratory-accelerated conditioning. Four natural outdoor environments were considered in the experimental program to induce aging mainly by carbonation, freeze-thaw cycles, elevated temperatures, and airborne chlorides from seawater. Additionally, a control environment (20°C and 55% RH) and a water immersion environment under controlled temperature (20°C) were considered. The durability was studied mainly throughout the mechanical properties obtained from (1) the involved materials (concrete, epoxy adhesive, and CFRP strips); and (2) the bond specimens, with a period of exposure up to 2 years. The bond performance of NSM-CFRP strips to concrete was slightly affected by environments under investigation, being water immersion and freeze–thaw cycles the most deleterious ones. A maximum average bond strength decrease of approximately 12% was registered for the specimens immersed in water, while in the case of the outdoor environments, the maximum bond degradation (approximately 8%) occurred for the specimens of freeze–thaw cycles after 2-year exposure.