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

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  • Zhenguo Shi
  • ,
  • Mette Rica Geiker, Norges teknisk-naturvitenskapelige universitet, Trondheim
  • ,
  • Klaartje De Weerdt, Norges teknisk-naturvitenskapelige universitet, Trondheim, SINTEF Building and Infrastructure
  • ,
  • Tone Anita Østnor, SINTEF Building and Infrastructure
  • ,
  • Barbara Lothenbach, EMPA
  • ,
  • Frank Winnefeld, EMPA
  • ,
  • Jørgen Skibsted

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 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 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 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.

Original languageEnglish
JournalCement and Concrete Research
Volume95
Pages (from-to)205-216
Number of pages12
ISSN0008-8846
DOIs
Publication statusPublished - 1 May 2017

    Research areas

  • Calcium-silicate-hydrate (C-S-H) (B), Chloride (D), Metakaolin (D), pH (A), Thermodynamic calculations (B)

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