Effects of interface agent and cooling methods on the interfacial bonding performance of engineered cementitious composites (ECC) and existing concrete exposed to high temperature

Abstract

The interfacial bonding performance between engineered cementitious composites (ECC) and concrete exposed to high temperature was investigated in this paper, and the effects of the exposure temperature, cooling methods and interface agent on the interfacial bonding performance were considered. The crystal morphology of the interface was observed by SEM. The pore structure near the interface was analysed by X-CT. The relationship between the ECC residual bonding area (ERBA) on the failure surface and the splitting tensile strength of the repair systems was investigated. The results showed that the interfacial bonding strength decreases with increasing temperature. High temperature will not only reduce the compressive strength of sample, but also increase the porosity of ECC at the interface area. Although water cooling reduces the compressive strength of the substrate, the rehydration products sometimes fill the cracks and increases the chemical cohesive force between the cover and the substrate and thus enhances the interfacial bonding properties. The effect of interface agent is influenced by the damage degree of substrates, interface agent may improve the interfacial bonding strength of substrates with high damage degree and reduces that with less damage degree. The change trend of the splitting tensile strength and ERBA is consistent with increasing temperature, and they are approximately positively correlated.