Abstract
A simple technique has been developed for measuring the ionic ingress into the surface layers of sealing composite specimens exposed to a salt solution, from which the apparent diffusivities for chloride, sulphate, sodium, and potassium are derived. Results obtained have indicated that for a given composite, the depth of the ion diffusion is dependent upon the age of the specimens. If the sealing composite is older than about 2 years, i.e., the changes in its chemical compositions and microstructures are negligible compared to the rate of penetration of the ions, the apparent diffusivities determined from the diffusion equation according to the second Fick's law can realistically characterise the diffusion and sorption—coupled transport of ions into the mineral sealing composite materials.
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