A Three-Dimensional Random Walk Algorithm for Estimating the Chloride Diffusivity of Concrete

Abstract

The chloride diffusivity of concrete is an important parameter for assessing the long-term durability of coastal concrete structures. The purpose of this paper is to present a three-dimensional random walk algorithm (RWA) for estimating the chloride diffusivity of concrete. By analyzing the size distribution of aggregates, the equivalent interfacial transition zone (ITZ) thickness is derived in an analytical manner. Each aggregate is combined with the surrounding ITZ to construct an equivalent aggregate model (EAM) and the chloride diffusivity is formulated. It is found that the equivalent ITZ thickness decreases with the increase of practical ITZ thickness and aggregate volume fraction. The aggregate gradation influences the equivalent ITZ thickness to a certain extent. The relative chloride diffusivity of the equivalent aggregate is almost directly and inversely proportional to the equivalent ITZ thickness and the aggregate radius, respectively. The numerical results show that, when the EAM is adopted, the computational time is greatly reduced. With the EAM, concrete can be modeled as a two-phase material and the chloride diffusivity is estimated by applying the RWA. It is shown that, with the increase of mean square displacement and number of Brownian particles, the average chloride diffusivity of concrete approaches a stable value. Finally, through comparison with experimental data, the validation of the RWA is preliminarily verified.

Recent Advances in X-ray Computed Tomography for Alkali-Activated Materials: A Review

“…Tortuosity, deemed as the sinuosity and interconnection of the pores inside matrix, is often considered in porosityrelated research which influences the flux transport in porous materials (da Silva et al 2022). Random walk simulation is the most widely used method for determining tortuosity and pore connectivity, which can model and analyze the behavior of particles or entities moving in a random manner within a defined space (Rong et al 2020;Promentilla et al 2016). Combining with the CT image, tortuosity is quantified by random walk simulation in a 3D micro-geometry of the pore structure.…”