Study on the corrosion patterns of rebar in concrete based on CT detection technology

Abstract

This paper studies the corrosion patterns of rebar in concrete using an accelerated corrosion method by applying electrical current. The experiment selected nine groups of samples with three different diameters and three different concrete covers. The corrosion process of rebar in concrete was simulated using a constant current method, and the samples were scanned before and after corrosion using CT detection technology. Avizo software was used to reconstruct the 3D visualization model of the scanned results, and a quantitative analysis of the corrosion degree on the rebar surface was conducted. The analysis results were compared with the corrosion results obtained by Faraday's law and weighing. The results showed that the rebar exhibited non-uniform corrosion in longitudinal and circumferential directions, with the corrosion degree at the rebar ends being more severe than the middle parts. The most severe corrosion occurred mainly on the rebar sections 2–5 mm from the concrete edge; the rebar surface near the concrete crack exhibited more severe corrosion than other parts. Under the same electrification conditions, reducing the cover led to more concentrated corrosion distribution, while increasing the cover or rebar diameter effectively mitigated corrosion damage and resulted in a more dispersed corrosion distribution. The maximum corrosion depth on the rebar cross-section showed uncertainty under the same electrification conditions; the larger the maximum corrosion depth, the more it conformed to a Gaussian distribution, while sections with smaller maximum corrosion depths tended to have multiple corrosion pits. The corrosion rate results calculated based on the CT model were used to correct Faraday's law calculations, and a predictive model for rebar corrosion rate under electrification conditions was established, considering the effects of Faraday's law and rebar diameter. For rebars of different diameters, there was a significant positive correlation between the corrosion rate and corrosion depth, and a linear correlation formula was fitted. This study also found that under the same electrification conditions, for cracks wider than 1 mm, the wider the crack, the smaller the maximum corrosion depth of the rebar.