Water Permeability and Chloride Ion Diffusion in Portland Cement Mortars: Relationship to Sand Content and Critical Pore Diameter.
Water Permeability and Chloride Ion Diffusion in
Portland Cement Mortars: Relationship to Sand Content
and Critical Pore Diameter.
(828 K)
Halamickova, P.; Detwiler, R. J.; Bentz, D. P.;
Garboczi, E. J.
Cement and Concrete Research, Vol. 25, No. 4, 790-802,
1995.
Keywords:
cements; chloride ion; diffusion; interfacial zone;
mercury intrusion porosimetry; mortar; percolation;
permeability; transport; sand
Abstract:
The pore structure of hydrated cement in mortar and
concrete is quite different from that of neat cement
paste. The porous transition zones formed at the
aggregate-paste interfaces affect the pore size
distribution. The effect of the sand content on the
development of pore structure, the permeability to water
and the diffusivity of chloride ions was studied on
portland cement mortars. Mortars of two water-to-cement
ratios and three sand volume fractions were cast
together with pastes and tested at degrees of hydration
ranging from 45 to 70%. An electrically-accelerated
concentration cell test was used to determine the
coefficient of chloride ion diffusion while a high
pressure permeability cell was employed to assess liquid
permeability. The coefficient of chloride ion diffusion
varied linearly with the critical pore radius as
determined by mercury intrusion porosimetry while
permeability was found to follow a power-law
relationship vs. this critical radius. The data set
provides an opportunity to directly examine the
application of the Katz-Thompson relationship to
cement-based materials.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899