Raw material of the Corumbatai formation at the region of ceramic pole of Santa Gertrudes - Sao Paulo, Brazil, with natural characteristics for fabrication of expanded clay

This paper refers to the study of the bases material of the Corumbatai Formation (Parana Basin) from a clay mine, which presents limits for its use in ceramic tiles in dry grinding process due to its hardness and, especially, the high content of organic matter in relation to the clay overlaid. The characterization of the raw material and the product was accomplished by organic carbon analysis, X-ray diffraction, optical microscopy and test-firing. Firing conditions were determined to get expanded clay, using fast firing static kiln and a continuous roller kiln, both from laboratory equipment, getting samples with variable density up to the limit of expansion, with density that can reach values lower than 0,5g.cm-3 because of the formation of closed pores and an external vitreous foil which provide a high mechanical resistance to the particles. (author)