Durability of Wet Bond of Hybrid Laminates to Cast-in-Place Concrete

Wet bond is a chemical bond developed to connect fiber-reinforced polymer (FRP) stay-in-place formwork to cast-in-place concrete for a composite action. Curing of chemical adhesive and fresh concrete occurs simultaneously in wet bond. Since FRP-concrete composite structure so designed is strongly dependent on the bond between FRP and concrete, a durable bond is of paramount importance. This paper presents a study on durability performance of wet bond exposed to sustained low temperature, freeze-thaw cycles, and wet-dry cycles. Single lap pull-off tests were conducted to evaluate the effect of exposure on bond. It was found that both first crack load and ultimate load of wet bond were reduced in comparison to dry bond. This reduction was more severe in first crack load than in ultimate capacity and was associated with voids, thickness, and surface of adhesive layer. The epoxy in wet bond had reached comparable degree of cure to dry bond and even gained a higher T-g. Environmental exposures did not show more impact on wet bond than on dry bond.