Mechanochemical Synthesis of Belite Cements from Coal Fly Ash/Portlandite Mixture
N. Števulova1, M. Balintova1, J. Briancin2 and Z. Szeghyova3
1Department of Environmental Engineering, Faculty of Civil Engineering, Technical University of KoЕЎice, VysokoЕЎkolska 4, KoЕЎice, 04120 (Slovakia)
E-mail: Nadezda.Stevulova@tuke.sk
2Institute of Geotechnics of the Slovak Academy of Sciences,
Watsonova 45, KoЕЎice, 04353 (Slovakia)
3Regional Public Health Authority,
Ipesska 1, KoЕЎice, 042 20 (Slovakia)
Pages: 225-229
Abstract
In this paper, the synthesis of the C2S cement by using reactive mixture containing fly ash (class F) from fluidized coal combustion and Ca(OH)2 (CaO/SiO2 ratio of 2) by mechanochemical treatment and subsequent heating is studied. Changes in structure and phase composition of milled and calcinated products of reactive mixture are compared with those of starting mixture. Two hours milling leads to mechanochemical decomposition of portlandite and to the structural and compositional metastability of mixture. The formation of the new compounds as C2S precursors (CSH and a-C2SH gels with low degree of ordering and a- and b-C2S nanocrystalline phases) was confirmed after 2 h milling by X-ray diffraction and infrared spectroscopy. Creation of a- and b-C2S and gehlenite in milled reactive mixture takes place at lower temperature (600oC) compared to non-milled starting mixture (1200oC). Mechanochemical synthesis in combination with thermal treatment offers opportunities for the increased utilization of coal fly ash as a basic raw material for belite production.
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