X-ray and neutron imaging for steel corrosion in concrete: addressing challenges and revealing opportunities

A key challenge in experimental research on steel corrosion in reinforced concrete is the destructive nature of most experimental techniques, which limits the ability to monitor progressive deterioration over time.Advancements in research on steel corrosion in reinforced concrete, however, have been made through the application of non-destructive imaging techniques, particularly X-ray and Neutron Computed Tomography (XCT and NCT).These techniques enable qualitative and quantitative assessments of steel corrosion in concrete.X-ray attenuation generally increases with the atomic number (density) of the material, making XCT particularly effective for identifying voids in the specimen.In contrast, neutrons interact with the atomic nuclei and are sensitive to light elements, such as hydrogen, making NCT advantageous for identifying moisture and corrosion products in the sample.Effective implementation requires meticulously experimental planning to ensure high-quality data and efficient post-processing.Sophisticated image analysis methods, such as a multimodal approach that exploits the statistics of both the X-ray and neutron attenuation fields, facilitate phase segmentation of the sample, thereby enabling detailed insights into factors such as the corrosion morphology and the influence of interfacial voids on pitting corrosion.Additionally, time-resolved imaging combined with digital volume correlation enable for monitoring the evolution of steel corrosion and damage within the sample.This paper aims to provide insights into the effective application of XCT and NCT for investigating steel corrosion in reinforced concrete, focusing on the challenges and opportunities these techniques present for continuous, non-destructive monitoring.Through illustrative examples, this paper demonstrates how these imaging techniques can improve the understanding of steel corrosion in reinforced concrete.