Quantitative characterization of the microstructure of a porous material in the context of tortuosity

This paper focuses on the connection between the microstructure of a porous material saturated with electrolyte and the overall electric conductivity on examples of loamy sand and silt loam soils. We relate several micromechanical averaging methods (non-interaction approximation, differential scheme, Mori–Tanaka scheme and Kanaun–Levin method) to tortuosity and clarify the micromechanical meaning of this parameter. We also show how it can be estimated from the analysis of soil images. Tortuosity was evaluated from measurements of the bulk electrical conductivity of saturated soils at different levels of electrolyte content and different conductivities of the electrolyte. Image analysis has been done by image processing software Image J. It is shown that the geometrical parameter that describes tortuosity is the minimum value ψmin of the relative length of the cross-sectional line situated in the electrolyte domain.