Numerical study on steel corrosion in concrete exposed to carbonation and chloride attack

Abstract

Usually, steel embedded in concrete is recognized to be invulnerable to corrosion because the high alkalinity of pore solution in concrete generates the thin protective oxide layer on the surface of steel. However, recent observations in field and experimental evidences show that even steel in concrete can be corroded. The primary reasons for the corrosion are carbonation and chloride attack. Existing researches on the durability of RC structures are mainly focused on the estimation of time for the corrosion initiation due to carbonation or chloride attack. Reasonable estimation of steel corrosion rate after the initial depassivation of steel on the basis of the properly devised analysis system is still insufficient. Moreover, most of the existing researches on the analysis of steel corrosion are performed independently from the analysis of carbonation or chloride attack. For the realistic estimation of steel corrosion in concrete, these aspects should be considered simultaneously. The objective of this study is to develop a unified numerical analysis program which can investigate the steel corrosion behavior considering carbonation and chloride attack in the same time and space domain, so that the realistic behavior of steel corrosion in concrete can be reasonably estimated. To achieve this goal, three-dimensional finite element program which can performed the analysis of moisture transport, carbonation, and chloride attack simultaneously are developed first. In this program, the influence of convective flow on the chlorides penetration, and the change in binding property due to carbonation are considered, thereby the special cases, such as cyclic wetting and drying or combined deterioration (i.e. chloride attack accompanying carbonation), can also be analyzed reasonably. Developed program for penetration analysis is subsequently integrated with the analysis program for steel corrosion, so that the real-time behavior of steel corrosion in RC structures can be ...