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 full-waveform 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 mm-resolutions. 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. • This paper presents a first-time application of 2D SH-FWI method on ultrasonic waves, for determining delamination and rebar debonding. • It was demonstrated on a concrete slab with delamination of various sizes and depths as well as rebar debonding at various severity. • The method was able to characterize the delamination at accurate location and sizes, as well as identify the existence of rebar debonding. • The SH-FWI shows the superiority over the conventional SAFT by providing clearer images with more detailed information.