Crack depth measurement and 3D reconstruction for concrete structures: A review

Crack depth and three-dimensional (3D) morphology are critical for assessing durability and capacity in concrete bridges, yet routine inspections remain surface-focused. This recent review synthesizes advances in non-destructive evaluation (NDE) for quantitative crack depth and 3D reconstruction, emphasizing concrete material and bridge-scale applications. Methods are grouped by sensing physics: Ultrasonics, Ground-penetrating radar/electromagnetics, and Optical/Thermal approches. A staged workflow emerges: fast noncontact screening, volumetric localization, and defensible depth confirmation, with optional 3D reconstruction where morphology drives decisions. We highlight integration into finite-element (FE) models via surface meshes, volumetric fields, and scalar depths, all with uncertainty propagation. Remaining challenges include calibration, reinforcement effects, environmental variability, and lack of bridge-scale ground truth. Standardized benchmarks, multimodal fusion, and automation are identified as key levers for advancing from pilots to routine practice.