CERAMIC PROPERTIES OF KAOLINISED TUFFACEOUS ROCKS IN KESAN REGION, THRACE, NW TURKEY

The Kesan-Karlikoy kaolin occurrence is located in the SW Thrace (Turkey) and was formed by the alteration of tuffaceous rocks. The tuff and tuffaceous units are made up of bentonite, kaolin and zeolite (mordenite-rich), from bottom to top. The 20-40 m thick kaolin level is beige, yellowish and whitish beige in colour and sandy tuff in appearance. The alteration of the rock to kaolin was explained by chemical, optical microscopy, SEM and XRD studies. The samples were generally rich in kaolinite and quartz, and some of them also contained minor amounts of smectite, feldspar, opal-CT and calcite. The kaolinite contents estimated by XRD-modal analysis ranged between 20 and 55 mass% in the kaolin zone. Representative samples from the kaolin zone were used for ceramic tests. Flexural strength and Young's modulus were measured and porosity, bulk density and water absorption were determined. For samples fired at 1140 C, the flexural strength was 9.78 MPa. The elastic modulus was 7.94 GPa. Water absorption and apparent porosity values were 12.7% and 22.9%, respectively. The apparent density was 2.33 g/cm3. Plasticity values of kaolin samples were also determined according to the Pfefferkorn plasticity test. The kaolinised tuff can be used for wall tiles, floor tiles, and tableware which are shaped by dry pressing and extrusion.