Chloride ingress parameters derived from migration and diffusion tests for systems with calcined smectitic clay and limestone

Cement pastes made with ternary binders containing Portland cement, calcined smectitic clay and limestone were subjected to chloride migration and diffusion. Microstructural changes due to chloride ingress were studied by mercury intrusion porosimetry and SEM back-scattered electron image analysis, while chemical changes were investigated via chloride binding isotherms complemented by thermogravimetric analysis, X-ray diffraction and SEM-EDS. Chloride binding parameters were taken as inputs in a chloride diffusion model, to process chloride profiles obtained in diffusion experiments.

Refinement of the pore structure was observed for pure Portland cement samples in migration. No changes were observed in diffusion, nor with ternary blends. Moreover, ternary blends lead to more chloride binding compared to Portland cement, mainly due to more Friedel's salt. Effective diffusion coefficients, purely linked to transport properties, obtained from migration and diffusion experiments agree well. Conversely, apparent diffusion coefficients may differ by a factor two. Implications regarding chloride ingress are discussed.