Preparation of glass-ceramic materials from coal ash and rice husk ash: Microstructural, physical and mechanical properties

Wastes such as coal and rice husk ashes, which are widely available in Colombia, were successfully used to synthesize glass-ceramics in the (Na2O)-CaO-Al2O3-SiO2 system, which are obtained from thermally treating the parent glasses. The raw materials were mechanically conditioned, and the glasses were designed based on the CaO/SiO2 molar ratio, which was varied between 0.25 and 0.39. The glasses were obtained by melting the powders at 1450 degrees C for 2 h, and the melted powder was then poured into water. To obtain the glass-ceramic material, the temperature of the glass thermal treatment, which was generally lower than 1000 degrees C in all cases, was determined by differential thermal analysis. The glass-ceramics obtained were microstructurally, physically and mechanically characterized. In addition, the durability was determined in acidic and alkaline environments (HCl and NaOH solutions). Glass-ceramics with densities of 2607-2739 kg/m(3), water absorption below 0.1%, Vickers hardness above 600 MPa and elastic modulus of similar to 96 GPa were obtained. The fracture toughness K-ic was in the range of 0.39-0.59 MPa m(1/2). The chemical durability was considered excellent (with mass losses of similar to 0.5 mg/cm(2)), therefore these glass-ceramics can be good candidates for different applications in the construction sector. (C) 2020 SECV. Published by Elsevier Espana, S.L.U.