Abstract
In this work, the non-uniform corrosion characteristics of steel bars in stressed reinforced concrete beams after accelerated depassivation and seven-year outdoor natural corrosion is analyzed using fractal theory. 3D laser scanning and 3D reconstruction technology are applied to collect the cross-sectional area along the steel bars and obtain the corrosion curves. The non-uniformity of corrosion is analyzed by fractal dimensions which is calculated by variation method. The results indicate that the initial loading level and loading zone have some influence on non-uniform characteristics of steel bars. For an ordinary concrete beam, the increase of load can cause a reduction of fractal dimension of corrosion curves by 5%, which indicates the non-uniformity of corrosion will increase with the increase of load level. The fractal dimension in the bending zone is lower than that in the tension–shear zone, which indicates that corrosion is more non-uniform in bending zone. However, the loading level and loading zone have a slight influence on corrosion level, and the maximum difference of corrosion level caused by load is merely 0.23%. Furthermore, the corrosion level increases with the decrease of fractal dimension, suggesting that the non-uniformity of corrosion increases with the growth of corrosion level. The incorporation of slag powder can help reduce the non-uniformity of corrosion, but the influence on reduction of the corrosion level is about 0.25%. For concrete structures under marine environment, application of slag powder is a good method to slow down the corrosion and reduce the non-uniformity of corrosion.
Highlights
As corrosion of steel reinforcement causes a remarkable performance deterioration of concrete structures, reliable monitoring and assessment methods of corroded reinforcement have drawn significant attention
As all reinforcement utilized in this study are deformed steel bars, the cross-sectional area, as shown in the reinforcement utilized in this study are deformed steel bars, the cross-sectional area, as shownthe in reinforcement utilized in this study are deformed steel bars, the cross-sectional area, as shown in Figure 7,7,fluctuates fluctuatesperiodically periodically along longitudinal direction in a narrow
The is incorporation of slag helps to plays recover www.mdpi.com/journal/materials role in weakening the by corrosion level. This canwill be attributed to the reaction caused thea micro-cracks caused initial loads, which reduce the pozzolanic non-uniform corrosion of by steel bars embedded in concrete beams
Summary
As corrosion of steel reinforcement causes a remarkable performance deterioration of concrete structures, reliable monitoring and assessment methods of corroded reinforcement have drawn significant attention. Materials 2019, 12, 3919 causes of non-uniform corrosion of steel reinforcement in concrete have been proposed, including the non-uniform spatial distribution of chloride at rebar surfaces [7,8], the stochastic nature of corrosion process [9,10], as well as the presence of cracks and defects at steel–concrete interfaces [11,12,13,14]. The failure of a corroded steel bar usually occurs at the location with the minimum cross-sectional area. The fractal theory was utilized to characterize the non-uniformity of corrosion along the steel bars obtained from long-term outdoor naturally-corroded reinforced concrete beams after being dispassivated by wetting–drying cycles under different load levels. The relationship between non-uniformity of corrosion and corrosion level is studied by fractal dimension for this case
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