Depth estimation of surface-opening crack in concrete beams using impact-echo and non-contact video-based methods

Surface-opening crack is one of the main defects in concrete bridges, which results in degradation in the load-carrying capacity of these structures. Thus, estimating the depth of such surface-opening crack is vital. This study presents impact-echo (IE) and non-contact video-based methods to estimate the surface-opening crack of concrete beams in the laboratory, and the results are compared with visual inspection. Results show that the IE method estimates a considerably larger crack depth than the non-contact video-based method and visual inspection. Although the difference between the depth measured by non-contact video-based method and visual inspection is small, the depth estimated by non-contact video-based method is slightly larger than that measured by visual inspection because it can identify the unrecognizable micro-crack by visual inspection. Moreover, when adopting the IE method, the depth of inclined crack is more overestimated than the vertical crack.