Toward Reliable Interfacial Bond Characterization Between Polymeric Cementitious Composites (PCCs) and Concrete: Testing Standards, Methodologies, and Advanced NDT–AI Hybrid Approaches

The evaluation of interfacial bonds between polymeric cementitious composites (PCCs) and concrete is considered as a critical factor to determine structural safety, durability, and service life regarding the repair and strengthening of old concrete structures. Conventional evaluations of interfacial bond strength have primarily relied on destructive testing methods, such as the pull-off and slant shear tests. However, these methods inherently possess fundamental limitations, including localized damage, non-uniform stress distribution, and uncertainty in result interpretation. This review aims to provide a comprehensive overview of existing standards and methods for assessing interfacial bond strength. For this purpose, the evaluation methods and results for the interfacial bond strength between cementitious composites such as PCCs and concrete were systematically reviewed. It further examines the characteristics and sources of error of the representative destructive method (pull-off test), highlighting its inherent limitations. Furthermore, this study conducted an in-depth analysis of a hybrid evaluation strategy combining non-destructive testing (NDT) and artificial intelligence (AI) to overcome the limitations of conventional interfacial bond strength assessment methods and minimize prediction errors. The results demonstrated that the NDT–AI hybrid approach, based on an ANN–BFGS model, achieved the highest accuracy in bond strength prediction and was identified as the optimal method for quantitatively and non-destructively evaluating interfacial bond behavior.