Numerical simulation of ionic transport in cement paste under the action of externally applied electric field

This paper presents a numerical investigation on the penetration of chloride ions in a saturated cement paste with considering the interactions between different ionic species in pore solution. The work is performed by solving the equations of mass conservation of individual ionic species with electrostatic coupling of ions in a multi-component pore electrolyte solution. Unlike most of existing work where the electrostatic potential was determined based on the assumption of electro-neutrality, the present work uses the Poisson’s equation relating the spatial variation in the electric field to the charge distribution to determine the electrostatic potential. As numerical examples, chloride penetrations in saturated cement pastes of different initial concentrations are simulated. The results show that chloride concentration profiles are significantly different in the cement pastes of different initial concentrations. The dependence of chloride penetration on the initial composition of pore solution may explain why the experimentally obtained chloride diffusion coefficients published in literature varying from 10−12 to 10−10 m2/s.

► Transport of ionic species is heavily dependent on its initial concentrations.
► Initial concentrations have large effect on concentration distribution profiles.
► Rapid migration test is more reliable than the rapid chloride permeability test.