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WATER PERMEABILITY AND CHLORIDE ION DIFFUSION
IN PORTLAND CEMENT MORTARS:
RELATIONSHIP TO SAND CONTENT AND CRITICAL PORE DIAMETER

Pavla Halamickova and Rachel J. Detwiler
Department of Civil Engineering
University of Toronto
Toronto, Ontario M5S 1A4
Canada

Dale P. Bentz and Edward J. Garboczi
National Institute of Standards and Technology
Gaithersburg, Maryland 20899 U.S.A.

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.

• Introduction
• Experimental Procedure
  • Degree of Hydration
  • Pore Structure
  • Water Permeability
  • Chloride Ion Diffusion
• Determination of the Coefficient of Chloride Ion Diffusion
• Results and Discussion
• Conclusions
• References