Detection of delamination and rebar debonding in concrete structures with ultrasonic SH-waveform tomography

The detection of delamination and rebar debonding is among the most frequently encountered issues for inspecting concrete for quality control and assurance. This paper presents a novel application of a 2D fullwaveform inversion of ultrasonic SH-waves (SH-FWI) for detection of delamination and rebar debonding in concrete structures. The ultrasonic data are collected by a commercial shear-wave tomography device (MIRA) and analyzed by the SH-FWI method to extract the material properties (density and S-wave velocity) at mmresolutions. Tested on a concrete slab with four delaminations of various sizes and depths and rebar debonding, the method was able to characterize all delaminations at accurate location and sizes, as well as identify the existence of rebar debonding. Compared to the synthetic aperture focusing technique (SAFT), the SH-FWI method provided clearer structural images with more detailed information of the delamination and rebar debonding.