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Low-temperature Synthesis of Belite Cement from Reactive Mixtures Based on Coal Fly Ash



Author(s)

Nadezda Stevulova1, Ivana Filkova1 and Kestutis Baltakys2

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DOI:10.17265/1934-7359/2012.02.007

1. Institute of Building and Environmental Engineering, Civil Engineering Faculty, Technical University of Kosice, 042 00 Kosice, Slovak Republic
2. Department of Silicate Technology, Faculty of Chemical Technology, Kaunas University of Technology, Radvilenu st. 19, C-144, LT – 50254 Kaunas, Lithuania

This paper summarizes the selected results of an extensive investigation of application of two methods (hydrothermal and mechanochemical) assisted by calcination for synthesizing belite cement from reactive mixtures (CaO/SiO2 molar ratio of 2) consisting of various waste kinds from fluidized brown coal combustion in Slovakian power plant and CaO addition. Based on XRD diffraction patterns and infrared spectra of pre-treatment products, the formation of the new profiles corresponding to CSH phases with low degree of ordering as belite precursors after hydrothermal treatment as well as metastables calcium silicates and aluminosilicates in mechanosynthesized products was confirmed. Calcination of hydrothermally treated products led to transformation of CSH phases to wollastonite (CS), belite and gehlenite phase, whereas creation of - and -C2S or wollastonite in milled reactive mixture took place. Differences in phase composition of products before and after calcination depend upon waste quality and precursor’s synthesis conditions. Bottom ash isn’t suitable as raw material for synthesizing belite phase because of high CaO content fixed in anhydrite form (44.1). Coal fly ash with low CaO content in anhydrite form (4.2) and its mechanochemical or hydrothermal treatment in combination with subsequent heating offer opportunities for the utilization of coal fly ash as raw material for belite production.

Coal fly ash, hydrothermal pre-treatment, mechanosynthesis, belite.