Multiphase modelling of ionic transport in cementitious materials with surface charges.

This paper presents a two-dimensional, two-phase ionic transport model with a surface charge at solid–liquid interfaces. The present model is applied to investigate the effect of surface charges at the solid–liquid interface on the ionic transport in a cement paste when it is subjected to an externally applied electric field. The surface charge in the present model is considered by modifying the Nernst–Planck equation in which the electrostatic potential is dependent not only on the externally applied electric field but also on the dissimilar diffusivity of different ionic species including the surface charges. The coupled transport equations of individual ionic species are solved numerically using a finite element method built in commercial software COMSOL. Some important features about the effect of surface charge on the concentration distribution, migration speed and flux of individual ionic species are discussed. [ABSTRACT FROM AUTHOR]