Incorporation of quartzite fines in the production of red ceramics.

Abstract

The ornamental stone sector produces a substantial amount of solid waste and effluents that are discarded in a disorderly manner, a fact that has prompted the need for research aimed at reuse. Considering the concepts of sustainable development and conscious mining, this study proposed the incorporation of quartzite residues in the production of ceramics (using soil as raw material) and aimed to reduce production prices, minimize environmental impacts, and obtain a higher quality of ceramic products (with less water absorption and greater resistance). Ceramic bricks were made in accordance with the following variables: replacement percentage (10% and 15%), compaction pressure (28 and 35 MPa), drying temperature (65 C for 72 h and 110 C for 24 h), and firing temperature (950 and 1100 C). Technological tests evaluated the drying and firing linear shrinkage, firing specific weight, water absorption, and resistance to uniaxial compression. After determining the optimal conditions, a flexural tear test and microstructural characterization were also performed. The optimal conditions for making ceramic bricks were a replacement percentage of 15%, compaction pressure of 35 MPa, drying temperature of 65 C (72 h), and firing temperature of 1100 C. These results were favorable because of the partial thermal decomposition of the mineral phases with the recrystallization of mullite and cristobalite. The incorporation of the residue resulted in better quality ceramic products, placing them within the limits established for technological applications, whereas none of the compositions made entirely of clay met the technical specifications.