Influence of water immersion on the bond durability of CFRP-to-concrete and FRCM-to-concrete interfaces

This paper mainly focuses on the bond durability of CFRP-to-concrete and FRCM-to-concrete interfaces subjected to moisture attack, which was simulated by water immersion with different durations. Twenty-four notched concrete beams were manufactured with a 150 mm ×150 mm section and a 600 mm span, and were divided into two groups according to two different strengthening methods. The first group was comprised of 12 notched concrete beams strengthened with epoxy bonded CFRP sheet, while the second group was comprised of the rest 12 beams strengthened with CFRP grids bonded using engineered cementitious composites (ECC). For each group, the first three specimens were subjected to a normal environment, and every three of the rest nine specimens were immersed in the water with the temperature of 20 ^oC for 1 month, 3 months and 6 months, respectively. Test results showed that the shear bond strength of CFRP-to-concrete interfaces increased at the immersion duration of 1 month, but decreased afterwards. After 6 months exposure, the bond strength of the specimens reduced down to the value before exposure. On the other hand, the shear bond strength of FRCM-to-concrete interfaces increased obviously with the immersion duration up to 3 months, but almost kept constant afterwards.