Title:
Quantification of Electromigration and Chemical Activity Effects on Reactive Transport of Chloride Ions in Concrete Pore Solution
Author(s):
Feras Alsheet and A. Ghani Razaqpur
Publication:
Materials Journal
Volume:
117
Issue:
6
Appears on pages(s):
77-88
Keywords:
chloride; diffusion; electromigration; Fick’s law; finite element; ionic activity; Nernst-Planck Poisson model; reactive transport
DOI:
10.14359/51728126
Date:
11/1/2020
Abstract:
The Nernst-Planck Poisson (NPP) and a modified Fick’s diffusion models, including the reactions among the chemical species within the concrete pore solution, are implemented in a one-dimensional (1-D) finite element program. The program results are validated by comparison with available experimental data in the literature. The effect of the modeling method on chloride concentration, concrete pH, and changes in the concrete pore solution composition are investigated. It is demonstrated that among the three diffusion modes captured by the NPP model, molecular diffusion dominates chlorides diffusion in concrete followed by electromigration while the chemical activity gradient has negligible effect. Based on the model results, it is determined that for accurate and efficient prediction of concrete salt concentration, pH, and changes in its chemical composition engendered by the diffusion of salts, the full NPP model must be used rather than the Fick’s model even though the former is theoretically more complex and computationally more resource intensive than the latter.