Sintering properties of the Bornova shale (Turkey) and its application in the production of red fired ceramics

Abstract

The aim of this work was to evaluate the use of the Bornova shale (BS) from Bornova-Izmir, west Turkey, as a raw material in the production of red fired ceramics. The Bornova-Izmir area is a convenient region for establishing a ceramics factory in terms of climate and proximity to Izmir harbour. The BS consists of phyllosilicates (illite, chlorite, and smectite), quartz, feldspar, and calcite. The dominant clay minerals are either illite or chlorite with smectite making up 0-7%. Differential thermal analysis (DTA) reveals that an amorphous phase occurs above 918°C. For the production of red fired ceramics, we used illiteand chlorite-rich BS in the following proportions: addition of 40% Fe-rich Eymir (Havran) kaolin (EK) to the BS, addition of EK (40%) and 2% Bigadiç Borate Concentrator Waste (BBCW), addition of EK (40%) and 3% BBCW, and addition of only 2% BBCW. Representative samples were prepared by pressing clay bodies at 15 MPa, which were then fired at temperatures between 850 and 1200 °C. The physical properties of the representative samples (e.g., water absorption and bending strength) were obtained from specific tests. Based on the desired colour and physical characteristics, the optimum batch was that with 98% BS +2% BBCW fired at 1100 °C. Addition of BBCW to the BS imparts binding and fluxing properties during the production process. These properties, in turn, improve mechanical strength and reduce energy usage.