The effect of protective coating on the bond strength of CFRP sheets in some environmental conditions

Reliable long-term bond durability is required in order to have successful performance of concrete structures reinforced with CFRP sheets. In this paper, the results of investigating the effect of using protective coating applied on CFRP sheets in increasing the strength and bond durability of these sheets under acute environmental conditions are presented. The environmental conditions considered are: wet-drying cycles, freeze- thaw and temperature changes. The results show that the bond durability of CFRP-reinforced specimens without protective layer is reduced by 24, 40 and 75% under cyclic conditions of temperature change, wet-dry and freeze-thaw. In order to protect CFRP sheets, four types of mortar were used, consisting of cement-based fiber mortar, fiber mortar with air Entrainment, cement-sand mortar containing epoxy adhesive and epoxy-based waterproof mortar were applied on their surface. Tests performed include measuring the bond strength using the "pull-off" and "twist-off" methods, as well as determining the compressive strength of the protective coating mortars, before and after exposing specimens to acute conditions. The results obtained tend to indicate that the proper selection of protective coating had a significant impact on the performance and bond durability of the CFRP coated concrete cubes that were under harsh environmental condition. By applying these coatings on concrete specimens reinforced with CFRP sheets, under conditions of temperature change, wet-drying and freeze-thaw, the bond strength increased by 12%, 22% and 84% compared to the specimens without protective coating.