Random-walk algorithm for chloride diffusivity of concrete with aggregate shape effect

Owing to its importance to the assessment and design of reinforced concrete structures, it is essential to determine the chloride diffusivity of concrete. This paper develops a random walk algorithm for the chloride diffusivity of concrete with the aggregate shape effect. In this algorithm, an equivalent aggregate model is established by coating each aggregate particle with an interfacial transition zone (ITZ) layer and the equivalent ITZ thickness is estimated through stereological analysis. The chloride diffusivity of each equivalent aggregate is then formulated by an effective medium approximation. Finally, the random walk algorithm is adopted to compute the chloride diffusivity of concrete. After the validity of the simulation algorithm is verified with two sets of experimental data, the effects of the aggregate content, the aggregate aspect ratio, and the ITZ thickness on the chloride diffusivity of concrete are evaluated in a quantitative manner. The paper concludes that the random walk algorithm can estimate the chloride diffusivity of concrete with reasonable accuracy.