Alternative raw material; Ceramic properties; Recycling; Proper waste disposal; Sustainability.

The construction industry is increasingly looking for sustainable and economically viable alternatives for building materials production. In this context, drinking water treatment sludge (DWTS) has emerged as a potential alternative raw material to clay in the production of red ceramics. However, various authors have contested the use of this residue because the quality of the ceramic material has been compromised due to the characteristics of the sludge, such as particle size and high organic matter content. This study investigates the influence of DWTS calcination and grinding on the quality of ceramic materials produced from binary mixtures of DWTS and clay. Samples of DWTS and clay were collected in the Metropolitan Region of Recife (RMR), and physical, chemical, and mineralogical analyses were carried out. Binary mixtures of WTPS and clay in different proportions and beneficiation conditions were produced, and two types of clay were studied with substitution rates of 0, 5, 10, and 20% of sludge. The test specimens were molded and characterized for their physical, mechanical, chemical, and mineralogical properties. It was found that the properties of ceramics are affected by the incorporation of DWTS, tending to increase their shrinkage and water absorption and reduce their mechanical strength depending on the sludge content for any beneficiation type. The study showed that the form, calcination, and grinding have little influence on the properties of ceramics, with the type of clay and sludge content being more important. Therefore, priority should be given to the use of raw sludge as there is no additional energy expenditure for its beneficiation. Finally, the conclusions suggest that the particle size distribution of substituted clay should be observed seeking balance with respect to clay content and fluxing agents, avoiding significant changes in ceramics produced with DWTS. The incorporation of sludge in ceramic production contributes to the proper disposal of this waste and reduces the environmental impact caused by clay extraction in construction industry.