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E. Samson, J. Marchand
Département de génie civil Université
Laval, CRIB, Ste-Foy (Qc), Canada, G1K 7P4
SIMCO Technologies Inc., 1400, Boul. du Parc Technologique
Québec (Qc), Canada, G1P 4R7
K.A. Snyder
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899 United States
and
J.J. Beaudoin
Materials Laboratory
Institute for Research
in Construction National Research Council
Ottawa, ON, Canada, K1A 0R6
A description of ionic transport in unsaturated porous materials due to gradients in the electro–chemical potential and the moisture content is developed by averaging the relevant microscopic transport equations over a representative volume element. The complete set of equations consists of time-dependent equations for both the concentration of ionic species within the pore solution and the moisture content within the pore space. The electrostatic interactions are assumed to occur instantaneously, and the resulting electrical potential satisfies Poisson's equation. Using the homogenization technique, moisture transport due to both the liquid and vapor phases is shown to obey Richards' equation, and a precise definition of the moisture content is found. The final transport equations contain transport coefficients that can be unambiguously related to experimental quantities. The approach has the advantage of making the distinction between microscopic and bulk quantities explicit.
Keywords: Diffusion; Transport properties; Degradation; Modeling; Homogenization