Abstract: A numerical method is presented for calculating the chloride diffusivity of concrete with polygonal aggregates. Through uniform scaling and unidirectional scaling, we generate polygonal aggregates for a given gradation, aspect ratio and content, and reconstruct the mesostructure of concrete by placing the generated particles into a simulation element with periodic boundary conditions. The mesostructure of concrete is then discretized on a regular grid, and a pixel-counting method is used to analyze the convergence of aggregate content and interfacial transition zone content to determine the required number of pixels. By applying Fick’s first law, we derive a solution for the chloride concentration gradient in heterogeneous media in the Fourier space, and based on this solution, develop an iterative algorithm for calculating the chloride diffusivity of concrete. Compared with the finite element method, our numerical method has the advantages of no need for complicated mesh generation, smaller data storage, and easy calculation. Finally, the method is verified through comparison with two sets of experimental data, and the effect of aggregate aspect ratio on the chloride diffusivity of concrete is discussed.

Key words: concrete, chloride diffusivity, polygonal aggregate, discrete Fourier transform, iterative method