Methods have been developed for predicting the overall diffusion coefficient of ions in concrete using a multi-scale interactive analysis, ignoring any chloride binding interactions. The analysis makes use of microstructure models of mortar/concrete and cement paste at the scales of millimeters and micrometers, respectively. When comparing experimental data to model results, one must be careful to consider the differing w/c ratio and degree of hydration of the interfacial transition zone (ITZ) and bulk paste regions, relative to a cement paste specimen containing no aggregates. The amount of aggregates influences the amount and properties of these two cement paste phases, leading to the designation of concrete as an interactive composite. The multi-scale analysis presented in this paper can quantitatively take this interaction of aggregates and cement paste into account when modelling the properties of concrete in terms of its microstructure. The analysis predicts that the contrast in diffusivity between the ITZ and the bulk cement paste is a function of the degree of hydration.
and Bentz, D.
Concrete: A Multi-Scale Interactive Composite, Proceedings of the International RILEM Conference, Haifa, IS, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860125
(Accessed December 8, 2023)