Imaging-based detection and classification of corrosion damages in reinforced concrete using ultrasonic shear waves

Abstract

Corroded steel reinforcements in concrete members reduce the structural capacity and compromise safety. Prior detection of rebar corrosion and severity assessment of affliction helps in understanding durability and safety of Reinforced Concrete structures. An ultrasonic shear wave imaging-based approach is presented in this paper to determine the severity of rebar corrosion on a laboratory scale. The scattered wave data in the time domain is used for subsurface image reconstruction using a variant of the Synthetic Aperture Focusing Technique. The rebar has been subjected to an accelerated corrosive environment, and simultaneously, the deterioration process has been monitored using ultrasonic imaging at different stages of corrosion. The image amplitudes of the rebar signatures are clustered by the k-means technique to classify the corrosion severity. The observed changes in reconstructed rebar patterns at the final stage of corrosion are corroborated by examining the condition of extracted rebars from the test specimens. The measured corrosion potential measurements at the end of each stage support the ultrasonic imaging results. The deterministic imaging-based workflow presented in this study serves as a useful technique to assess and classify the severity of corrosion in reinforced concrete structures.