Ceramic properties of clay from the Asseiceira quarry at Tomar, Portugal

The clay mined at the Asseiceira quarry near the city of Tomar, Portugal, has traditionally been used to manufacture hollow brick. However, since an assessment has shown the ceramic properties of the strata to vary, the quarry could potentially produce clay blends of different qualities to form raw materials appropriate for items demanded by different market segments, such as high quality facing brick and roof or floor tiles. The composition and texture of the various clay materials identified in the Asseiceira quarry were characterized using analytical techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), Atterberg limits and grain size analysis The phases resulting from the thermal transformations taking place during drying and firing were identified with thermogravimetric (TG), differential scanning calorimetric (DSC), and thermodilatometric (TD) techniques. Finally, certain relevant ceramic properties such as linear shrinkage, bending strength and water absorption at 875 °C, 950 °C, 1025 °C and 1100 °C were determined on the raw material after extrusion.