Role of calcium on chloride binding in hydrated Portland cement–metakaolin–limestone blends
- Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)
- SINTEF Building and Infrastructure, 7491 Trondheim (Norway)
- Laboratory for Concrete & Construction Chemistry, Swiss Federal Laboratories for Materials Science and Technology (Empa), 8600 Dübendorf (Switzerland)
Chloride binding is investigated for Portland cement–metakaolin–limestone pastes exposed to CaCl{sub 2} and NaCl solutions. The phase assemblages and the amount of Friedel's salt are evaluated using TGA, 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 CaCl{sub 2} 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 C-S-H for the pure cement. A linear correlation between the total bound chloride and the uptake of calcium from the CaCl{sub 2} solution is obtained and found to be independent on the type of cement blend.
- OSTI ID:
- 22697107
- Journal Information:
- Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 95; ISSN 0008-8846; ISSN CCNRAI
- Country of Publication:
- United States
- Language:
- English
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