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

Abstract

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°C for 2h, 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°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 2607–2739kg/m3, water absorption below 0.1%, Vickers hardness above 600MPa and elastic modulus of ∼96GPa were obtained. The fracture toughness Kic was in the range of 0.39–0.59MPam1/2. The chemical durability was considered excellent (with mass losses of ∼0.5mg/cm2), therefore these glass–ceramics can be good candidates for different applications in the construction sector.