Incorporação de resíduos de quartzito em massa cerâmica para produção de porcelanato.

Abstract

The ornamental rock industry presents itself as a major producer of solid waste, which is usually disposed directly into the environment, compromising the flora and fauna. Finding applications for the waste from the extraction and processing of rocks is one of the current challenges for the scientific community. The objective of this work is to evaluate the potential of using quartzite residues, as a non-plastic raw material, in the composition of an industrial ceramic mass for porcelain tile production. Initially, the chemical, physical and mineralogical characterization of the raw materials was carried out. Central composite design was used to define the residue contents to be incorporated into the ceramic mass (1.76, 3, 6, 9 and 10.24 wt.%) and the firing temperatures (1143, 1160, 1200, 1240 and 1257°C). The compositions were characterized by the same techniques previously mentioned. For the conformation of the specimens, the uniaxial pressing process was used. The samples were dried at 110°C, sintered and subjected for tests of linear shrinkage, water absorption, apparent porosity, apparent specific mass and three-point flexural strength. After the statistical analysis of the results, other compositions with up to 20 wt.% of quartzite residue, sintered at 1240°C, were evaluated. The results showed that the firing temperature had a significant effect (D = 0,05) on all the investigated response variables, so that the elevation of its levels contributed to the decrease of the water absorption and increased the mechanical strength of the ceramic bodies. On the other hand, the residue content had no significant effect on the analyzed variables. The pieces containing up to 10.24 wt.% of residue, sintered at 1240 and 1257°C, met the criteria established by the international standard ISO 13006, for porcelain tiles (water absorption ≤ 0,5% and mechanical strength ≥ 35 MPa). Pieces with up to 15 wt.% of residue, sintered at 1240°C, was classified as porcelain tile while those with 20 wt.% was classified as stoneware.