Identificação de fases cimentícias presentes em materiais cerâmicos a base de argila e resíduo de casca de ovo

Abstract

The manufacture of traditional ceramic products is essentially based on the use of clay as raw material. However, excessive extraction has been causing problems in its exhaustion, as well as damaging the areas in which it is explored. At this point, the reuse of solid industrial waste, such as avian eggshell residue (ER), in the incorporation into the ceramic mass, becomes an attractive alternative to be studied. In this way, the focus of this work is to obtain, characterize and technologically evaluate the ecological ceramic products based on clay and ER, as well, to identify the formation of cement phases due to the sintering temperature and the residue percentage used. The residue, from the commercial establishment of the food branch, was pre-treated and incorporated into the clay in 10, 20, 30, 40, and 50% (in weight). The raw materials were characterized concerning to the properties: physical by the threshold of Atterberg and granulometric distribution; chemicals by X-ray fluorescence (XRF); structural by X-ray diffraction (XRD); and thermal by thermogravimetric analysis (TA). The ceramic test bodies were pressed with load application of 49 MPa, and subsequently exposed to drying, and evaluated the physical properties through the humidity of conformation and linear drying contraction. The burning step was performed at temperatures of 900, 1000, 1100, and 1200 °C, a heating rate of 2.5 °C/min and landing of 30 min. The burning bodies were analyzed by scanning electron microscopy (SEM); physical properties by the linear contraction of burning, loss to fire, apparent porosity, water absorption and apparent specific mass; and mechanics by bending to three points. Specimen prepared with 10 ER % (in weight) presented the best results for the physicalmechanical properties evaluated. The values for the apparent porosity were 20.48% ± 0.43 (1200 °C) to 23.05% ± 1.46 (1000 °C), water absorption of 12.41% ± 0.38 (1200 °C) at 14.41% ± 0.66 (1000 °C) and mechanical strength of 9.23 MPa ± 1.06 (900 °C) at 16.19 MPa ± 1.38 (1200 °C). The results of analysis of the structural parameter of the products indicated that the incorporation of ER caused modifications in the diffraction patterns with the formation of the new phases as Gehlenite, Wollastonite, Portlandite, Ternesite, Akermanite, Sepiolite, Entantite, Gismondine and Diopside. These phases accelerated the development of vitreous phase and occurred lower values for apparent porosity, water absorption, and increased mechanical strength, mainly for specimens for 10% ER formulations at all evaluated burning step temperatures. Thus, the properties evaluated indicate the possibility of using the eggshell residue in a ceramic mass for the production of traditional ceramic products ecologically, contributing to the environmental impact reduction caused by the extraction of soil clay and disposal of the industrial solid waste.