Utilization of fly ash and red mud for thermal storage ceramics

Abstract

The solid wastes Red mud and fly ash were used as the raw materials in the production of thermal storage ceramics. Red mud was used to lower the firing temperature and fly ash powders were introduced to improve the mechanical properties. The physical properties of samples, including firing behavior, thermal storage properties and thermal shock resistance were evaluated. Also, the effects of fly ash and red mud on the properties of ceramics were investigated. The results showed that the thermal shock resistance of the sample improved by the addition of fly ash powders in the preparation of thermal storage ceramics. Besides, the addition of red mud promoted the formation of liquid phase. In particularly, sample R3 (40 wt % fly ash, 15 wt % clay shale, 20 wt % feldspar, 25 wt % quartz and addition of 15 wt % red mud) fired at 1140°C exhibited the best performance, in which the open porosity, bulk density, bending strength, thermal conductivity at 500°C and theoretical heat storage density (room temperature-500°C) were 0.37%, 2.54 g/cm³, 89.81 MPa, 3.62 W/(m·K), 1.56 KJ/cm³, respectively. Despite the bending strength of R3 sample fired at 1140°C decreased by 20.29% after 30 thermal shock cycles, it still maintained a flexural strength of 73.78 MPa.