Alkali-activation of CaO-FeOx-SiO2 slag: Formation mechanism from in-situ X-ray total scattering

A. Peys, Claire Emily White, H. Rahier, B. Blanpain, Y. Pontikes

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The pursuit of low-CO2 technologies has led to a surge in research on alternative cementitious materials, of which alkali-activated materials are a large family. In recent years alkali-activated materials have expanded to encompass Fe-rich precursors in addition to the more commonly employed aluminosilicate precursors. The formation mechanism of alkali-activated materials from two Fe-rich synthetic slags has been assessed by employing in-situ X-ray total scattering and subsequent pair distribution function analysis. The evolution of the local atom-atom correlations reveals three reaction stages. After the dissolution of Fe-silicate clusters from the slag, a binder phase is formed with Fe in both Fe2+ and Fe3+ oxidation states. The Fe2+ state is present in the form of trioctahedral layers, similar to those in Fe(OH)2, while the Fe3+ is likely located in the polymerized silicate network. Exposure to air causes the Fe2+ species to transition to the Fe3+ state.

Original languageEnglish (US)
Pages (from-to)179-188
Number of pages10
JournalCement and Concrete Research
StatePublished - Aug 2019

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • General Materials Science


  • Alkali-activation
  • Amorphous
  • Fe-silicate
  • In-situ X-ray pair distribution function
  • Inorganic polymers


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