Impact of Mg substitution on the structure and pozzolanic reactivity of calcium aluminosilicate (CaO-Al2O3-SiO2) glasses

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  • Shuai Nie, Aarhus University, Wuhan University of Technology
  • ,
  • René M. Thomsen
  • ,
  • Jørgen Skibsted

Calcium aluminosilicate (CAS) glasses are the main reactive component in supplementary cementitious materials such as fly ashes and slags, which may also include significant amounts of magnesium. Eighteen CAS glasses have been synthesized in six series with 0, 25, and 50 mol% of Ca substituted by Mg. Their structure, pozzolanic reactivity and impact on Portland cement hydration are investigated by 29Si and 27Al NMR spectroscopy and TGA analysis. The aluminosilicate network is only slightly affected by the Mg for Ca substitution, although an increased distortion of the network is observed, which is ascribed to a lowering of the Mg coordination state relative to Ca. The glass reactivity is mainly governed by the network depolymerization, which increases with the MgO + CaO content, with Mg substitution only having a minor impact. Increasing Mg contents in the glasses lead to OH-hydrotalcite formation and a smaller fraction of Al incorporated in the C-A-S-H phase.

Original languageEnglish
Article number106231
JournalCement and Concrete Research
Volume138
Number of pages16
ISSN0008-8846
DOIs
Publication statusPublished - 2020

    Research areas

  • Al NMR, Si NMR, Glass, Hydration products, Pozzolanic reactivity, Supplementary cementitious materials

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