A damage index method for detection of localized corrosion in reinforcement bars using scattering of longitudinal guided waves

Corrosion of steel is a major cause of failure in reinforced concrete structures. Recently, the focus of research has been to identify different kinds of damage that could occur simultaneously in reinforced concrete. In the recent literature, it is reported that the presence of damage such as corrosion and debond in reinforced concrete could lead to a phenomenon called zero effect state due to their complementary effect on wave characteristics. In this paper, two different damage scenarios in reinforcement are considered. It is demonstrated that the guided wave mode L(0, 1) can be used to assess the level of pitting corrosion in the reinforcement bars. A novel damage index is developed using the reflection and transmission signatures of wave modes from the front and rear edges of the corroded region to assess the corrosion of steel rebars. The damage index at various points on the rebar is plotted, which gives the information on the location, intensity, and axial extent of the corrosion. The numerical modelling is carried out using Abaqus/CAE and results for various levels of corrosion are validated through laboratory experiments. The study is further extended to determine the minimum quantifiable corrosion size for the current experimental specimen.