Role of calcium on chloride binding in hydrated Portland cement–metakaolin–limestone blends

Chloride binding is investigated for Portland cement–metakaolin–limestone pastes exposed to CaCl₂ and NaCl solutions. The phase assemblages and the amount of Friedel's salt are evaluated using thermogravimetric analysis (TGA), X-ray diffraction (XRD) and thermodynamic modeling. A larger amount of Friedel's salt is observed in the metakaolin blends compared to the pure Portland cement. A higher total chloride binding is observed for the pastes exposed to the CaCl₂ solution relative to those in the NaCl solution. This is reflected by the fact that calcium increases the quantity of Friedel's salt in the metakaolin blends by promoting the transformation of strätlingite and/or monocarbonate to Friedel's salt. Calcium increases also the amount of chloride in the diffuse layer of the calcium silicate hydrate (C-S-H) for the pure cement. A linear correlation between the total bound chloride and the uptake of calcium from the CaCl₂ solution is obtained and found to be independent on the type of cement blend.

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  • English

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  • Accession Number: 01634672
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 10 2017 10:49AM