Characteristics of clays and properties of building ceramics in the state of Rio de Janeiro, Brazil

The general characteristics and technological properties of four types of clays obtained from the same location at the north of the State of Rio de Janeiro, Brazil, have been investigated. These clays are intended for applications in ceramics such as bricks and roofing tiles. Clays were first analyzed by X-ray diffraction, chemical composition particle size distribution, thermal analysis and plasticity. Extruded samples were fired at temperatures varying from 850 to 1100 °C to determine the linear shrinkage, water absorption and flexural rupture strength. The results showed that three of the studied clays have adequate characteristics for brick fabrication. However, for two of these adequate clays it is necessary to add convenient materials to enhance the workability. The high porosity developed after firing impairs the use of these clays for roofing tiles. This is a consequence of the kaolinitic nature of the clays as well as their elevated loss on ignition.