Experimental study on the bond behavior of the CFRP plate-ECC-concrete composite interface under freeze–thaw cycles

A very important subject in the application of civil engineering reinforcement is the durability of interfacial bonding behavior between fiber reinforce plastic (FRP) and concrete under freeze–thaw cycles. Premature debonding of the FRP plates (underutilization of FRP plates) would results in the potential safety hazards in FRP plates reinforced concrete structures. The use of engineered cementitious composites (ECCs) can effectively delay the peeling off of the FRPs and improve the durability and bearing capacity of FRP reinforced concrete structures. To strengthen the concrete structures under freeze–thaw cycles environments more economically and safely, it is necessary to study the bonding performance of the FRP-ECC-concrete composite interface. In this research, single-shear tests were carried out on CFRP plate-ECC-concrete composite interface specimens under freeze–thaw cycles. Taking the concrete/ECC strength as the research variables, the bonding properties of the composite interface under different freeze–thaw cycles were studied. The results show that the CFRP plate-ECC-concrete composite interface can effectively delay the peeling off of the CFRP plate, and effect of delaying the peeling off of the CFRP plate is reduced with the increasing of freeze–thaw cycles. The bearing capacity of single-shear specimens decreased by 2.4%-27.3% with the increase of freeze–thaw cycles, but the bearing capacity increased by 12.6%–32.4% with the increase of concrete/ECC strength. The ultimate strain of the CFRP in single-shear specimens decreases by about 29.2% under freeze–thaw cycles. The proposed fracture energy prediction model considering freeze–thaw cycles can accurately predict the bearing capacity of single-shear specimens with the composite interface. The bond-slip constitutive relationship considering the interface softening descending stage is in good agreement with the experimental results.