Measurement and Characterization of Corrosion-Induced Cracking in Reinforced Concrete: A Review

Corrosion-induced cracking is one of the key factors affecting the durability and service life of concrete structures. Accurate measurement of crack initiation, propagation, and spatial distribution provides an important basis for structural durability assessment and maintenance decision-making. This paper systematically reviews the principles, technical characteristics, characterization methods, and development trends of techniques for measuring surface and internal corrosion-induced cracks in concrete, including geometric measurement, strain measurement, optical imaging, elastic-wave techniques, fiber-optic sensing, physical sectioning, X-ray computed tomography (X-CT), and artificial intelligence-assisted analysis. The results show that geometric and optical methods are suitable for quantifying surface crack geometry but have limited capability for identifying early internal damage. Acoustic emission, ultrasonic techniques, and distributed fiber-optic sensing can detect the initiation and evolution of internal cracks, although direct determination of absolute crack dimensions and three-dimensional morphology remains limited. X-CT can reconstruct internal crack networks, but field application is constrained by cost, specimen size, scanning time, and spatial resolution. Multi-source data fusion and artificial intelligence-assisted analysis offer opportunities to improve the comprehensiveness and automation of crack characterization, while improvements in measurement accuracy and reliability require further validation. Future research should focus on low-cost, wireless, long-term online multimodal measurement systems and stable, verifiable quantitative relationships between sensing signals and crack geometric parameters.