Influence of hygrothermal ageing on the mechanical properties of CFRP-concrete joints and of their components

Externally bonded (EB) fiber reinforced polymer (FRP) composites have been effectively employed to strengthen existing reinforced concrete (RC) structures. However, relatively limited information is available regarding the long-term behavior of FRP-concrete joints. In this paper, different experimental tests are employed to investigate the effect of hygrothermal ageing on the bond behavior of a carbon FRP composite applied to a concrete substrate and on the mechanical properties of the epoxy resin and FRP composite considered. The experimental campaign includes tensile tests of epoxy resin, carbon FRP (CFRP) coupon, pull-off tests of the CFRP bonded to the concrete substrate, and single-lap direct-shear tests of CFRP-concrete joints. Specimens were conditioned in warm water (38 +/- 2 degrees C) for 500, 1000, and 1500 h to accelerate the possible degradation induced by a simulated high-moisture exposure environment. The parameters studied were the tensile properties of epoxy resin and CFRP coupons and the fracture energy of the CFRP-concrete interface, which was computed from the CFRP strain measured in the single-lap direct-shear tests using the digital image correlation (DIC) method. Results indicate that both the mechanical properties of the epoxy resin and the CFRP-concrete interface fracture energy were slightly affected by the exposure conditions.