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Front. Mater. | doi: 10.3389/fmats.2019.00212

Inorganic polymers from CaO-FeOx-SiO2 slag: the start of oxidation of Fe and the formation of a mixed valence binder

 Arne Peys1*,  Alexios P. Douvalis2,  Vincent Hallet1, Hubert Rahier3, Bart Blanpain1 and  Yiannis Pontikes1
  • 1Department of Materials Engineering, KU Leuven, Belgium
  • 2Department of Physics, University of Ioannina, Greece
  • 3Department of Materials and Chemistry, Vrije University Brussel, Belgium

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 approximately 1, suggesting the participation of tetrahedral Fe3+ in the silicate framework, charge balanced by Na+.

Keywords: Alkali - activated materials, geopolymers, 57Fe Mössbauer spectroscopy, Non-ferrous slags, FTIR - spectroscopy

Received: 22 Feb 2019; Accepted: 14 Aug 2019.

Copyright: © 2019 Peys, Douvalis, Hallet, Rahier, Blanpain and Pontikes. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Arne Peys, KU Leuven, Department of Materials Engineering, Leuven, Belgium, arnepeys@hotmail.com