Avaliação das propriedades mecânicas e termomecânicas em compósitos cerâmicos refratários utilizando cinza de casca de arroz e lodo de estação de tratamento de água

Abstract

In order to reduce environmental impacts, the use of agro-industrial waste to produce new materials has been widely studied in recent decades. Aiming to develop more sustainable refractory ceramic composites (RCCs) using rice husk ash (RHA) as a source of silica from water treatment plant sludge (WTPS) as a source of alumina and silica, this study aimed to develop and evaluate the performance of CCRs using partial replacement of kaolin clay, in mass, by percentages of 10% of RHA and variations of 5%, 10% and 15% of WTPS. To characterize the raw materials, X-ray fluorescence and laser granulometry tests were carried out. The characterization of RCCs before and after firing was performed by X-ray diffraction. The physical properties were evaluated through tests of linear firing shrinkage and mass variation, bulk density, apparent porosity and water absorption. The mechanical behavior was determined from tests of compression strength and three-point bending tensile strength. To verify the thermomechanical behavior, the thermal shock test was performed. The chemical phases determined before and after sintering corroborated the X-ray fluorescence results. Typical phases of the Al-Si system were found, and the replacements used contributed to the formation of cristobalite, mullite, sillimanite and tridymite, as well as to the decrease in the intensity of quartz peaks. Regarding the mechanical properties, the composition with 100% kaolin clay resulted in greater compressive and tensile strength in bending. Among the replacement compositions, the worst performance occurred for ceramics with 10% RHA while the best performance occurred for ceramics with 10% RHA and 10% WTPS, and in both cases the less porous mixtures were the ones that showed better mechanical performance.Regarding to thermal shock resistance (TCR), the use of WTPS proved to be beneficial, especially the composition with 10% RHA and 10% WTPS. The use of RHA and WTPS showed potential for use as a ceramic precursor in the development of refractories, being sustainable sources of SiO2 and Al2O3. In general, all of the new refractories are within the range of use, demonstrating that they are viable for use in the siderurgy industry, contributing to the sustainable development of the country from a technical, environmental and economic point of view.