Influence of the foaming process on the pore structure and properties of fly ash-based foamed ceramics

Fly ash and other solid wastes can be cooperatively coupled based on their physical and chemical characteristics to prepare foamed ceramics, which not only achieves a large-scale consumption of industrial solid waste but also mitigates the resource-environment conflict associated with industrial development. Foamed ceramics were prepared using fly ash, silica fume and red mud with a small amount of SiC as blowing agent and albite and microcline as fluxes. The influence of the foaming process on the pore structure of foamed ceramics was analyzed. The results show that the influence of foaming temperature on the pore size and its distribution uniformity of foamed ceramics is more obvious than the holding time. Moreover, the uneven temperature distribution in the foam container seriously affected the pore size distribution of the samples after foaming. Under the premise of ensuring uniform distribution of the temperature field, fly ash-based foamed ceramics can be obtained with a bulk density of 0.26 g/cm3, an average pore size of 0.58 mm, a bulk porosity of 93 % and a uniform aperture distribution at a foaming temperature of 1210 °C and a holding time of 20 min. Its flexural strength and thermal conductivity are 4.45 MPa and 0.09 W/(m·K), respectively.