Numerical Modelling of Non-uniform Steel Corrosion Development and its Mechanical Influences on Reinforced Concrete Structures

Steel corrosion and the associated cracking of the concrete cover can significantly reduce the service life of reinforced concrete (RC) structures. In most studies on corrosion-induced cracking, the distribution of rust was assumed to be uniform around the steel bar. However, under practical situations, steel reinforcement corrosion should start at the position nearest to the exposed surface and gradually spreads to other parts along its circumference. As a result, the chloride attack- penetration and the build-up of rust around the bar are far from being uniform. The present work will focus on non-uniform corrosion due to chloride penetration. The time-varying corrosion penetration around the rebar is first obtained by solving the diffusion equation numerically by Matlab. In the calculation, corrosion is assumed to initiate at a point when a specified chloride threshold value is reached at that position. The effects of cover thickness and corrosion rate on the non-uniformity of corrosion penetration are studied. To analyze crack propagation in the concrete cover due to rust expansion, the numerically formed shapes of rust and corroded steel configuration at different corrosion levels are employed in the finite element analysis. Discrete crack model is adopted to simulate the crack propagation in concrete. The surface crack width evolution with increasing corrosion level is examined for both non-uniform and uniform corrosion cases with different cover thicknesses (c/d=1 and c/d=2). It has been found that: 1) Cover cracking is more severe for non-uniform corrosion than uniform corrosion under similar percentage of steel loss. As a result, it is important to consider non-uniform corrosion in the analysis. 2) For larger cover thickness, the initiation of surface cracking is delayed, but its width becomes larger for the same amount of steel loss after surface cracking. This finding suggests that repair work should be performed immediately if corrosion-induced surface cracks are found in locations with large cover.