Preparation of high closed porosity foamed ceramics from coal gangue waste for thermal insulation applications

Resource utilization of industrial solid waste can be a preferred solution to waste management. This study proposes a new strategy to prepare high closed porosity foamed ceramic with coal gangue waste as the major material. The chemical composition and crystalline phase of the starting material, formation mechanism and the effects of sintering process parameters on the pore structure and properties of the samples are discussed. The results show that the density, compressive strength, and true porosity of the foamed ceramic are 0.22 g/cm3, 1.51 MPa, 91.38%, respectively, at the optimum sintering temperature and time of 1200 °C and 30 min. The high closed porosity of 83.95% compared to conventional foamed ceramics is a very favorable factor for the reduction of thermal conductivity and water absorption, resulting in a low of 0.11 W/(m·K) and 0.68%, respectively, which can be used as a cost-effective inorganic thermal insulation material in the building industry.