Frontiers in Materials (Aug 2019)

Inorganic Polymers From CaO-FeOx-SiO2 Slag: The Start of Oxidation of Fe and the Formation of a Mixed Valence Binder

  • Arne Peys,
  • Alexios P. Douvalis,
  • Vincent Hallet,
  • Hubert Rahier,
  • Bart Blanpain,
  • Yiannis Pontikes

DOI
https://doi.org/10.3389/fmats.2019.00212
Journal volume & issue
Vol. 6

Abstract

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Belonging to the family of alternative cementitious materials, inorganic polymers are rising in importance because of the drive to decrease CO2 emissions of concrete production. A synthetic Fe-rich slag resembling industrial copper or lead slags, was mixed with a sodium silicate activating solution. 57Fe Mössbauer spectra analyses indicate that the oxidation reactions are taking place simultaneously with the polymerization reactions. The slag contains Fe2+ states and a small amount of Fe3+. During polymerization a new octahedral Fe2+ state is formed, while oxidation is manifested through the appearance of an additional Fe3+ state. The reactions continue after setting, lowering the relative contributions of the slag in the Mössbauer and FTIR spectra of the samples. The Na+/Fe3+ molar ratio in the mixture that makes up the binder after 28 days is ~1, suggesting the participation of tetrahedral Fe3+ in the silicate framework, charge balanced by Na+.

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