Conventional concrete repair methods are generally plagued by repair interface leakage. Although previous studies have attempted various measures, such as interface treatment and expansive agents, their efficacy remains debatable. As an emerging cementitious material, geopolymers exhibit high bond strength and offer promising potential for interface repair; however, their application in repair scenarios requires further investigation due to significant shrinkage. Therefore, this study employs geopolymer concrete supplemented with grooving techniques and expansive agents to enhance the bond performance of repair interfaces, and investigates the influences of grooving size, expansive agent type and dosage on the bond performance and impermeability of repair interfaces. The main scientific findings are as follows: 1) Under grooved treatment and externally restrained curing conditions, the mechanical interlocking effect between new and old concrete is enhanced, and the bond-impermeability performance of the repair interface is markedly improved. Optimal performance is achieved at a grooving width of 10 mm, which corresponds to approximately half the maximum particle size of the coarse aggregate in the repair material. 2) Among the four expansive agents tested, the high performance calcium sulpho aluminate (HCSA) expansive agent at a dosage of 10% exhibits the highest splitting tensile strength and resistance to chloride penetration performance at the repair interface, thereby maximally mitigating concrete shrinkage. 3). Additionally, it was observed that the impermeability of the repair interface exhibits a linear correlation with splitting tensile strength; thus, impermeability can be indirectly assessed via a simple splitting tensile test.
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