Recycling of Silicon Carbide Sludge on the Preparation and Characterization of Lightweight Foamed Geopolymer Materials

This study used silicon carbide sludge (SCS) to prepare lightweight foaming geopolymer materials (FGPs) by the direct foaming method. Results showed that when the SCS replacement level was 10%, the bulk density of the lightweight FGPs with added foaming agent amounts of 0.5% and 2.0% was 0.59 and 0.49 g/cm³, respectively; at a curing time of 28 days, the lightweight FGPs with amounts of added foaming agent of 0.5% and 2.0% had bulk densities that were 0.65 and 0.58 g/cm³, respectively. When the SCS replacement level was 10%, and the amount of added foaming agent was 2.0%, the porosity ratio of the lightweight FGP increased from 31.88% to 40.03%. The mechanical strength of the lightweight FGPs with SCS replacement levels of 10% and 20% was 0.88 and 0.31 MPa, respectively. Additionally, when the amount of foaming agent increased to 2.0%, the thermal conductivity of the lightweight FGPs with SCS replacement levels of 10% and 20% were 0.370 and 0.456 W/m⋅K, respectively. When the curing time was 1 day, and the amount of added foaming agent was 0.5%, the reverse-side temperature of the lightweight FGPs with SCS replacement levels of 10% and 20% were 286 and 311 °C, respectively. The k value of the O₂ reaction decreased from 2.94 × 10^-4 to 1.76 × 10^-4 because the reaction system was affected by the presence of SiC sludge, which was caused the reaction to consume O₂ to form CO₂. The results have been proposed to explain that the manufactured lightweight FGPs had a low thermal conductivity (0.370-0.456 W/m⋅K). Therefore, recycling of silicon carbide sludge in lightweight foaming geopolymer materials has potential as fire resistance material for the construction industry.