Efeito do resíduo de quartzito nas propriedades tecnológicas de peças cerâmicas obtidas a partir de massas para fabricação de grés sanitários.

Abstract

During the extraction and processing of quartzite large amounts of waste are produced, which presents oxides that are present in the main raw materials used in traditional ceramic masses. In this context, this work investigated the technological properties of ceramic pieces obtained by masses used in the production of sanitary stoneware, containing quartzite residue, by the partial replacement of feldspar. Initially, a study of the physical and mineralogical characterization of the residue and of the conventional raw materials, clay, feldspar, quartz and kaolin, of the composition of the mass were carried out. The characterization was carried out using the following techniques: granulometric analysis by laser diffraction, X-ray diffraction, X-ray fluorescence, thermal analysis. Compositions have been formulated by varying the amount of the residue, replacing the feldspar at 10, 15, 20 and 25% by weight. The rheological properties of the slips were analyzed, emphasizing also the pH. The slip casting process was used in the conformation, the specimes were dry (110o) and sintered at the temperature of 1200 ° C, in two firing cycles. For characterization the following tests were performed: color variation after firing, fusibility, water absorption, loss on ignition, porosity, apparent specific mass, firing retraction, coefficient of thermal expansion, flexural strength, vickers hardness and modulus of elasticity. The microstructure was evaluated by scanning electron microscopy and X-ray diffraction analysis. The results showed that the rheological characteristics of the suspensions were adequate when the partial replacement of the feldspar by the quartzite residue was used for the bonding process. The specimes produced from compositions containing quartzite residue, in the range of 10 – 25%, presented the flexural strength values were greater than 35MPa, water absorption nearly 0.5% and linear retraction after burning below 12%, values within the range required for the manufacture of sanitary products. The presence of the quartzite residue did not alter the crystalline phases in the sintered pieces, was observed only the presence of quartz and mullite.