Shear Capacity Comparison of Four Different Composite Interfaces between FRP Plates and Concrete Substrate

The mechanical performance of four types of interfaces between fiber-reinforced polymer (FRP) plate and concrete was compared by double-lap-shear test. The study found that the failure characteristics of the four interfaces are obviously distinct. Among them, the shear capacity load of the shear key combined with wet-bond (SK-WB) interface was the highest, followed by the dry-bond and the coarse-aggregate-coating (CAC) interfaces; the wet-bond interface had the lowest shear load bearing capacity. The type of the resin used for the wet-bond adhesive has a slight influence on the bond strength, whereas the type of the resin used for the shear key bonding has a much more significant effect on the shear capacity load of these interfaces. The thickness of the wet-bond epoxy resin layer also has a significant impact on the bond performance of the wet-bond interface. The shear key forms has less influence when the flexural stiffness of the shear keys itself is sufficient; the load capacity of the SK-WB interface is often dependent on the bonding area between the shear key and the concrete. The concept of bond zone was put out when creating interface model of the SK-WB interface. Finally, unified form formulas of the shear capacity and the interface fracture energy are provided for the different interfaces, and the values of them are estimated.