Construction of Gradient Interface for Concrete Repair and its Performance Evolution in Marine Environment
Author:
Affiliation:
1.South China University of Technology;2.CCCC Infrastructure Maintenance Group Co., Ltd;3.School of Materials Science and Engineering, South China University of Technology
Concrete repair interfaces in marine environments are prone to severe bond degradation under the coupled effects of mechanical loading and seawater wet-dry cycling. A cement-based repair mortar was developed which is modified with low-viscosity waterborne epoxy resin (WER) that subsequently penetrates from the mortar into the substrate to construct a gradient repair interface. Experimental results show that WER with a viscosity of 200 mPa·s can form a continuously gradient distribution at the interface between the repair mortar layer and the substrate, with a maximum penetration depth of approximately 9.4 mm, which is significantly greater than that achieved with high-viscosity systems. Compared to unmodified repair mortar, the 28 d interface flexural bond strength of the WER-modified system increases by approximately 77%. Under the combined action of seawater wet-dry cycles and compressive stress, the unmodified repair system exhibits a 50% reduction in interfacial bond strength after 180 d of cycling at a stress level of 0.5, whereas the degradation in the WER-modified system is limited to less than 30%. Moreover, the gradient interface formed by low-viscosity WER-modified repair mortar significantly decreases the ingress rates of magnesium and sulfate ions, inhibits the decalcification and deterioration of hydration products in the interfacial zone, and retards the degradation of interfacial performance. The study demonstrates that the gradient interface constructed with low-viscosity WER effectively enhances both the interfacial bonding properties and the long-term service durability of the repair system in marine environments.
