High-Strength Ceramsite Made with Sludge and Low-Quality Fly Ash

Sludge utilization has become the focus of sludge disposal, and this paper presents a study of using sludge, low-quality fly ash, and other raw materials from the Shanghai region to make high-strength ceramsite. The proportions of the mix and the firing conditions suitable to roast the calcined high-strength sludge ceramsite are discussed. The results show that pure sludge materials alone are not suitable for making high-strength ceramsite. High-strength sludge ceramsite was made with a silt–fly ash–waste glass powder of $60:35:5$ under a firing system with a preheating temperature of 600°C, a warm-up time of 20 min, a calcination temperature of 1,150°C, and a roasting time of 15 min. The high-strength sludge ceramsite provided particle strength of 7.1 MPa, apparent density of $\mathrm{1,580}\mathrm{kg}/{\mathrm{m}}^3$, and water absorption of 8.2%. All properties were better than the requirements in the national standards. In addition, the high-strength sludge ceramsite provides important environmental and social benefits due to its consumption of waste and industry by-products such as river sludge and low-quality fly ash.