Assessment of interfacial fracture energy between concrete and CFRP under water immersion conditions

Abstract

The interfacial fracture energy is a critical parameter for the bond between carbon fiber reinforced polymer (CFRP) plate and concrete, and is significantly influenced by the ingress of moisture. Exploiting the single-lap shear test, this paper studies the effect of water immersion on the interfacial fracture energy experimentally and analytically by taking into account the impacts of immersion time, concrete compressive strength, and concrete surface roughness. The results indicates that: 1) water immersion transforms the failure mode from concrete cohesive failure to debonding of the adhesive layer from the concrete substrate. 2) the interfacial fracture energy considerably drops in the first six months of immersion in water and then levels off; 3) the reduction of the interfacial fracture energy depends on the compressive strength of the concrete substrates. A higher compressive strength of concrete leads to a more significant reduction; 4) the impact of water immersion on the mechanical interlocking of concrete with epoxy is negligible. Finally, based on the reduction mechanism of the breakage of the van der Waals interactions and hydrogen bonding between SiO2 groups of concrete and hydroxyl groups (–OH) of epoxy with ingress of water, an analytical model is proposed for predicting the interfacial fracture energy.