Freeze–thaw resistance of epoxy/concrete interface evaluated by a novel wedge splitting test

Abstract

Abstract Externally bonding using epoxy is one of major applying method for FRP strengthening technology. The long-term performance of the epoxy/concrete interface has been proven to be a key for practical application of FRP strengthening, especially when the strengthened structures are exposed to severe environmental conditions. In this study, an experimental program has been carried out to examine the effect of freeze–thaw cycles (soaked in tap water and 5% sodium sulfate solution) on the deterioration of the epoxy/concrete interface through a novel wedge splitting test, which can directly measure the traction-separation law of the interface under mode I loading. The effect of silane treatment on the freeze–thaw resistance of the interface was also examined. A simplified tri-linear constitutive model of the epoxy/concrete interface was obtained according to the test results. Results showed that both the ultimate bond strength and the fracture energy decrease exponentially with the number of freeze–thaw cycles. Under mode I loading, the failure mode of the reference specimen is the tensile failure of the concrete. With the increase of freeze–thaw cycles, the failure mode gradually turns into adhesive failure along the epoxy/concrete interface. Testing results also confirm that the freeze–thaw resistance of the epoxy/concrete interface can be improved by application of silane coupling agent.