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Journal of Spectroscopy
Volume 2013 (2013), Article ID 231843, 9 pages
http://dx.doi.org/10.1155/2013/231843
Research Article

Mössbauer, XRD, and Complex Thermal Analysis of the Hydration of Cement with Fly Ash

1Department of Physics, University of Mining and Geology, 1700 Sofia, Bulgaria
2Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Received 25 June 2012; Accepted 7 October 2012

Academic Editor: Renata Diniz

Copyright © 2013 Vili Lilkov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Hydration of cement with and without fly ash is studied with Mössbauer spectroscopy, XRD, and thermal analysis. Iron in cement is present as Fe3+-ions and occupies two octahedral positions, with close isomer shifts and quadrupole splittings. Iron in fly ash is present as Fe2+ and Fe3+, and the Mössbauer spectra display three doublets—two for Fe3+ in octahedral coordination and one for Fe2+. A third doublet was registered in the hydrating plain cement pastes after the 5th day, due to Fe3+ in tetrahedral coordination in the structure of the newly formed monosulphate aluminate. In cement pastes with fly ash, the doublet of tetrahedral iron is formed earlier because the quantity of ettringite and portlandite is low and more monosulphate crystallizes. No Fe(OH)3 phase forms during hydration of C4AF. The fly ash displays pozzolanic properties, which lead to lowering of the portlandite quantity in the cement mixtures and increasing of the high temperature products.