Interfacial Tensile Bond between Substrate Concrete and Repairing Mortar under Freeze-Thaw Cycles

Freeze-thaw cycle is one of the major damage factors of concrete patch repair. Not only the material itself but also the adhesive interface is damaged under freeze-thaw cycles (FTC). Air-entraining agent has long been used to increase the freeze-thaw resistance of concrete materials. However, the effect of air-entraining agent on the adhesive interface has not been explored. The degradation mechanism and failure mode of concrete repair system under FTC has not been studied, either. In this study, three kinds of substrate concrete were casted and repaired by two kinds of ordinary Portland cement mortars and one kind of polymer-modified cement mortar (PCM), respectively. With up to 150 FTC, splitting tensile strength and failure modes of composite specimens were experimented. Results showed that air-entraining agent in the repairing mortar greatly influenced adhesive tensile strength under FTC. The water cement ratio and air-entraining agent of substrate concrete insignificantly affected the adhesive interface, but affects failure mode. The adhesive tensile strength of PCM-repaired composite specimens decreased faster than that of ordinary Portland cement mortar-repaired composite specimens although PCM itself showed stronger freeze-thaw resistance than ordinary mortar.