Incorporação de matérias primas alternativas em massas cerâmicas para grés sanitário.

Abstract

Medium-sized ceramic coating industries generally discard between 30 to 35 tons per day of waste from the tile polishing process, often in an indiscriminate manner. On the other hand, there is a severe shortage of good quality feldspars in the national ceramic industry. In this scenario, the incorporation to the ceramic mass of materials that allow the reduction of environmental impact of waste disposal and/or mitigate the difficulty of using good quality fluxes only adds to the value of the final product and reduces production costs. The objective of this work was to investigate the incorporation of alternative raw materials with high content of alkaline earths such as porcelain polish residue and mineral diopside in ceramic tiles for sanitary stoneware as partial replacement for feldspar. The raw materials were characterized by chemical analysis, X-ray diffraction, granulometric analysis, differential thermal analysis and thermogravimetric analysis; ceramic mass compositions were formulated for sanitary stoneware by replacing 2%, 6%, 10% and 20% of feldspar with residue or diopside. Rheological characteristics of the dispersions were analyzed and specimens were conformed by bonding. Dilatometry of the bodies was conducted followed by their respective firings at 1160o, 1180o and 1200o C. After burning, the physical-mechanical properties of water absorption, apparent porosity, apparent density, linear burning retraction and flexural strength were determined. The microstructure was evaluated by X-ray diffraction and scanning electron microscopy. Masses containing up to 6% of polishing residue as replacement for feldspar showed equivalent values of flexural strength and values of water absorption as well as porosity lower than the reference mass, a commercial mass. Using diopside allowed for the formation of anorthite in the ceramic pieces and reduction in the sintering temperature from 1200 to 1160oC. Masses with 10% and 20% of feldspars replaced with diopside presented higher values of flexural strength and water absorption as well as apparent porosity inferior to the standard mass. Results indicate the feasibility of using up to 20% of diopside and up to 2% of porcelain tile polishing residue (PPR) for replacing feldspar.