Preparation of Foamed Ceramic Materials from Fly Ash and Blast Furnace Slags

This is an article in the field of ceramics and composites.The high-temperature sintering method was used to prepare foamed ceramics by using fly ash and blast furnace slag as the main raw materials, adding silicon carbide (SiC) as a high temperature foaming agent and sodium borate (Na₂B₂O₇) as a flux. The effects of raw material ratio, SiC addition and Na₂B₂O₇ addition on the bubble structure, bulk density, water absorption, compressive strength and thermal conductivity of foamed ceramics were mainly studied. The experimental results showed that when the fly ash was 70%, the blast furnace slag was 30%, 0.3% SiC powder and 5% Na₂B₂O₇ were added additionally, and the sintering temperature was 1 100℃ for 40 min, the foamed ceramic had the best comprehensive properties, and its bulk density was 0.516 g/cm³, with water absorption rate of 3.82%, compressive strength of 3.62 MPa, thermal conductivity of 0.094 W/(m·K). The main phases of the sample under this condition included quartz phase (SiO₂), anorthite (CaAl₂Si₂O₈) and pyroxene phase (Ca(Mg,Al,Fe)Si₂O₆), the massive precipitation of crystals enhanced the strength of the material. This research provided a new method for converting industrial solid wastes such as fly ash and blast furnace slag into high value-added building insulation materials.