Introduction
The term “transport phenomena” covers a broad range of physical and chemical properties. These properties are important in at least three ways: as probes of microstructure (electrical impedance); as basic quantities that determine durability (ionic diffusivity, fluid permeability); and as important or potentially important engineering properties in and of themselves (elastic moduli, creep, shrinkage, and electromechanical response). The work on transport properties will include all three of these areas, with an important flow of research results among them. This back and forth flow of information is crucial for the success of these projects, and is made possible by the Center mode of operation. In addition, the work in transport properties draws heavily on results from the theme on microstructure. The levels of microstructure being considered in this work vary. Multi-scale models, with properties determined at a lower, more basic level being used in larger scale models, will be essential throughout this work.^Top

Creep And Shrinkage
Creep and shrinkage are important engineering properties of concrete structures. Previously, these properties have been examined only at the macroscopic level, due at least partly to the fact that micro scale experimental and theoretical data were not available. We will continue using the ESEM, along with new computer algorithms and image analysis techniques developed at ACBM, to map shrinkage in C-S-H at the micrometer scale. To understand shrinkage mechanisms at the microstructural level, these studies will be coupled with new developments in mathematical morphology, along with novel finite element shrinkage codes that have been developed for the digital image-based microstructural model. ^Top

Diffusivity And Permeability
Over the past five years, ACBM has contributed significantly to the understanding of microstructure-property relations for the ionic diffusivity and fluid permeability of cement-based materials, both of which are key parameters in controlling the long term durability of concrete. Diffusivity is predicted via application of the Nernst-Einstein equation to electrical conductivity measurements carried out by impedance spectroscopy, while permeability is estimated using electrical conductivity and mercury intrusion porosimetry (MIP) measurements and the Katz-Thompson relation. Agreement between predicted and measured properties is encouraging, but relevant experiments need to be carried out on the same specimens in a systematic way. ^Top

Sulfate Deterioration
The objective of this research is to determine the mechanism of sulfate attack on cement-based materials, both with and without mineral admixtures such as silica fume and slag. The use of concrete barriers to contain high sulfate content chemical wastes has prompted a renewed interest in this area of research. Some of the questions and ambiguities regarding the actions of sulfate in portland cement concretes, for example, the consequences of gypsum and ettringite formation, failure criteria, performance classification, and the effects of sulfate solution concentration, will be studied. The information obtained in this theme should form the development of new test methods to support performance-based standards and service life prediction models. ^Top

Coordinator: Edward Garboczi (NIST)

Mechanisms of Sulfate and Chloride Attack
PI: Menashi Cohen, Sidney Diamond, and Douglas Winslow (Purdue University)

Transport in Mortar and Concrete
PI: Thomas Mason and Hamlin Jennings (Northwestern University)

Cracking and Damage as a Mechanism of Drying Creep and Stress-Induced Shrinkage
PI: Zdenek Bazant and Hamlin Jennings (Northwestern University)

Microstructure and Shrinkage
PI: Dale Bentz (NIST)

Pore Structure and Permeability of Mortars
PI: Edward Garboczi (NIST)

Electrical-Mechanical Behavior in Cementitious Materials
PI: Dwight Viehlan (University of Illinois)