Ultrasonic SH-Waveform Tomography Enables a Novel Structural Imaging Approach to Recover the Spatiotemporal Progression of Rebar Corrosion

The corrosion of rebar significantly impacts the service life of reinforced concrete structures, making the health monitoring of rebar corrosion crucial. This paper presents an innovative method for characterizing the spatiotemporal evolution of rebar corrosion using ultrasonic shear-horizontal (SH) wave full-waveform inversion (SH-FWI). By analyzing ultrasonic SH-waves using the FWI method, the density distribution of various media within the concrete can be reconstructed, enabling the imaging and characterization of different stages of rebar corrosion. This approach was validated through laboratory experiments using electrically accelerated corrosion specimens. The SH-FWI method was employed to perform inversion imaging over the full corrosion cycle of a reinforced concrete specimen. The imaging results were compared with a set of reference specimens featuring corroded rebar sections, which confirmed the accuracy of the SH-FWI method in capturing the spatiotemporal evolution of rebar corrosion. The experimental results further demonstrated the effectiveness of SH-FWI in characterizing the spatiotemporal evolution of rebar corrosion. A comparative analysis with the synthetic aperture focusing technique (SAFT) demonstrates that SH-FWI produces clearer structural images and provides more comprehensive information on the spatiotemporal evolution of rebar corrosion.