C e Ca, vol.37, no.3, pp.145-154, 2007 (Scopus)
Sile Region, northeastern Istanbul, includes the most important underday deposit of Turkey. These days are composed of disordered kaolinite, illite, mixed-layer illite-smectite, smectite, gibbsite, quartz, pyrite, anatase, K-feldspar, goethite and organic matter. The underclays have been studied because this area is the biggest sedimentary industrial clay deposit of Turkey and economic importance. Mineralogical, chemical and technological tests have been conducted to assess their potentials in the ceramics industry for the production of tiles. They were tested at 50°C intervals from 1000 to 1200°C. The technological properties of underclays are characterized by low values of shrinkage and flexural strength after pressing, drying and firing. Water absorption values decreased below 5 wt. % at 1200 °C and these underclays can be used in the manufacture of vitrified tiles or sanitary ware. The chemical analyses generally show average silica, high potassium and medium alumina contents in all samples, typically of kaolinized and illitized materials. The Sile underclays exhibit very low S and Fe contents, but low plasticity and excessive refractory properties. Firing shrinkage increases slightly with increasing temperature, but there is a systematic increase in flexural strength ?