Interfacial Transport in Porous Media: Application to dc Electrical Conductivity of Mortars.
Interfacial Transport in Porous Media: Application to
dc Electrical Conductivity of Mortars.
Schwartz, L. M.; Garboczi, E. J.; Bentz, D. P.
Journal of Applied Physics, Vol. 78, No. 10, 5898-5908,
November 15, 1995.
Sponsor:National Science Foundation, Washington, DC
building technology; concretes; durability; effective
medium theory; electrical conductivity; interfacial
zone; mortar; percolation; fluid flow; sand
A mortar is a composite of inert sand grains surrounded
by a porous cement paste matrix. We investigate the
electrical conductivity of model mortars that include
enhanced electrical conduction in the matrix-sand grain
interfacial region. The electrical conductivity is
evaluated by a combination of finite element, finite
difference, and random walk methods for periodic and
disordered models of mortar. Since the effective
conductivity within the interfacial zone is often much
higher than the bulk matrix conductivity, the
qualitative features of transport in these systems is
often controlled by the connectivity of the interfacial
zone. Special attention is thus given to the
geometrical percolation of this zone. A family of
effective medium approximations give a good qualitative
description of the disordered model's electrical
properties. A simple four parameter Pade approximant is
found to successfully describe the electrical
conductivity of the periodic model over the entire range
of parameters studied. Finally, we show that our
calculations can be used to obtain a reasonable estimate
of the permeability to viscous fluid flow.