Characterization and Evaluation of Ceramic Properties with Spherical and Prismatic Samples of Clay Used in Red Ceramics

The Brazilian red ceramic industry monthly consumes about 10.3 million tons of clay, its main raw material. In most potteries, characterization of the clay is made empirically, which can result in roof tiles and blocks not according to standards. In this sense, this paper aims to characterize clays used in the manufacturing of red ceramic products in a factory located in Colatina-ES, which appears as a ceramic pole with about twenty small and midsize industries. The clays were characterized by: X-ray fluorescence, X-ray diffraction, thermal analysis (DSC/TG), granulometry, Atterberg limits and content of organic matter. Specimens of clay and mixture containing four clays were shaped. Specimens were shaped, dried at 110°C, and burned at 850ºC in an industrial furnace-type tunnel for 24 hours. The ceramics and mechanical properties evaluated were: mechanic strength, water absorption, apparent porosity, apparent specific mass and shrinkage by drying and firing. The characterization showed that kaolinitic clay presents high plasticity, but high porosity. The mixture formed by the four clays does not meet the requirements of the Brazilian standard clays for red ceramic. It is possible to confirm the use of the methodology of the spheres in potteries for analysis of ceramics raw materials.