Ceramics-Silikáty 65, (2) 176 - 186 (2021)

Ceramsite was sintered using coal gasification slag, fly ash, construction spoils, and municipal sludge. The influence of the municipal sludge content on the ceramsite performance was studied by TG-DSC, XRD, MIP, and SEM. The optimal sintering conditions for the fabrication of ceramsite exhibiting the best performance were obtained through an orthogonal experiment. The highest cylindrical compressive strength was obtained under the following conditions: a preheating temperature of 500 °C with a preheating time of 30 min, and a sintering temperature of 1100 °C with a sintering time of 20 min. The compressive strength of the ceramsite was higher than 6.5 MPa when the municipal sludge content was 20% and prepared in optimal conditions. The porosity and the average pore diameter of the ceramsite increased with an increasing municipal sludge content, while the strength and apparent density decreased. The average pore diameter of the ceramsite with the 20% municipal sludge content increased by 490 nm compared with the ceramsite containing a 5% municipal sludge. In addition, the Al₂O₃ content was the factor affecting the strength of the ceramsite. When the Al₂O₃ content exceeded 20.5%, the main crystal phase of the ceramsite changed from a quartz phase to kyanite, significantly improving its strength.