The application of sludge shale haydite in building materials

Sewage sludge might result in secondary pollution if there were unreasonable disposal methods. The traditional methods of disposing sludge included incineration, land use, reclamation, etc. If the sludge mixed with shale was fired to make haydite, the problem could be solved; in addition, it could produce high-performance artificial ultra-lightweight aggregate. Dehydrated sludge and shale was chosen to produce ultra-lightweight haydite by analysis of chemical and mineral composition for raw materials and considering haydite production processes and raw materials requirements. It had high strength and low water absorption at certain technical conditions. Optimal mixing ratio and baking system is obtained as follows: sludge dosage of 30%, preheating temperature of 400°C, preheating time of 10 min, baking temperature of 1150°C, baking time of 12 min. Haydite performances show: apparent density of 508 kg/m³, density level of 300, 1 hour water absorption of 6.0%, particle strength of 200N.