X-ray computed tomography to investigate steel corrosion in cementitious media: Experimental guidance, challenges and opportunities

X-ray computed tomography (XCT) provides unique opportunities to investigate steel corrosion in reinforced concrete, the primary degradation mechanism compromising infrastructure durability and safety. Its non-destructive nature, combined with high-resolution three-dimensional imaging and time-lapse capabilities, allows for detailed insights into corrosion processes without altering the specimen. However, applying XCT to reinforced concrete remains challenging due to recurring methodological issues, such as selecting appropriate tube voltage and current, defining pre-filtering combinations, mitigating imaging artefacts, and balancing image resolution with sufficient X-ray transmission. These challenges are particularly pronounced when imaging systems with components of widely differing X-ray attenuation, such as steel, concrete, air, and water.

This paper proposes a systematic guideline for designing XCT acquisitions tailored to the study of corrosion in reinforced concrete specimens, integrating theoretical considerations with practical examples. The guideline is supported by dedicated charts and design criteria, which guide researchers in selecting acquisition parameters, specimen configurations, and imaging strategies to achieve high-quality and reproducible results. This approach is built upon a critical review of previous studies, highlighting past limitations and identifying future research opportunities for the application of XCT to study corrosion in steel-concrete systems.

By providing a coherent framework for experimental design, this paper allows researchers to fully exploit the potential of XCT for studying in-situ steel corrosion and to advance understanding of reinforced concrete degradation, thereby addressing an important challenge in engineering.