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Effect of the Interfacial Transition Zone on the Conductivity of Portland Cement Mortars

John D. Shane¹, Thomas O. Mason¹, Hamlin M. Jennings ¹
Northwestern University
Department of Materials Science and Engineering
Evanston, IL 60208-3108

Edward J. Garboczi¹ and Dale P. Bentz¹
National Institute of Standards and Technology
226/B350
Gaithersburg, MD 20878 USA
¹ Denotes membership in the American Ceramic Society

Abstract

The electrical conductivity of portland cement mortars was determined experimentally as a function of the volume fraction of sand and degree of hydration. The results were analyzed using theoretical models that represent the mortars as three-phase, interactive composites. The three phases are the matrix paste, the aggregate, and the thin interfacial transition zone between the two. The microstructure and properties of the conductive phases (the transition zone and matrix paste) were determined by a micrometer-scale microstructural model, and were used in conjunction with random-walk algorithms and differential-effective medium theory to determine the overall mortar conductivities. The presence of the transition zone was not found to significantly affect the global electrical conductivity of the mortar. However, there were significant differences in conductivity between the transition zone and matrix pastes when examined on a local level. These differences were found to vary with hydration and were most significant when the degree of hydration was between 0.5 and 0.8.

• Introduction
• Conductivity Studies of Mortars
  • Experimental
  • Modeling
  • Discussion
  • Permeability and the ITZ
• Conclusions
• Acknowledgments
• References