Mineralogical study of calcined coal waste in a pozzolan/Ca(OH)2 system

• Published in: Applied clay science 2015-05, Vol.108, p.45-54
• Main Authors: García, Rosario, Vigil de la Villa, Raquel, Frías, Moisés, Rodriguez, Olga, Martínez-Ramírez, Sagrario, Fernández-Carrasco, Lucía, de Soto, I.S., Villar-Cociña, E.
• Format: Article
• Language: English
• Subjects: Characterization; Hydration products; Pozzolan; Stability; Waste management
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2015.02.014

Activated carbon mining waste influences the formation of hydrated phases, their saturation indexes and mineral stability fields during pozzolanic reactions. The behavior of these reactions is predicted in this study by examining the influence of carbon waste at 600°C over 2h, by means of a thermodynamic model running on a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations (PHREEQC program: pH-REdox-Equilibrium in Program C). Experimental analysis of the solid phases shows early formation of monosulfoaluminate hydrate, C–S–H phases and subsequent precipitation of laminar minerals, tetracalcium aluminate hydrate, layered double hydroxide compounds (phyllosilicate/carbonate) (LDH) and stratlingite. Monosulfoaluminate hydrate was formed on day one of the reaction for samples with activated coal mining waste. The thermodynamic calculations confirmed the experimental observations. •The carbon waste shows phyllosilicates, quartz, calcite, dolomite and feldspars.•According to the kinetic parameter values, the reaction rate was 10−3h−1.•Carbonate and sulfate of low crystallinity have been formed in Portlandite solution.