Physical and mechanical properties of porcelain tiles made from raw materials in Uganda

Abstract

This study was intended to determine the physicomechanical properties of porcelain tiles made from raw materials in Uganda, hitherto not used for the same. The raw materials were mixed in proportions of 40–60% clays, 30–40% feldspar and 10–30% sand, the goal was to identify a mixture with properties that meet the ISO 13006 standards after firing. Test tile samples were formulated at a pressure of 40 MPa and fired from 1050 to 1250 °C in steps of 50 °C. A firing rate of 40 °C per minute and a dwell time of 2 h were applied. The microstructures and phase analysis of the fired samples were studied using a scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The XRD analysis revealed mullite and quartz as crystalline phases present in the fired bodies. At 1150 °C, the SEM micrograph depicted few, short and thick mullite fibers. At 1200 °C, the mullite population increased. The nature of the fibers (long, fine and more interlocking) resulted in an increase in flexural strength. A further rise in temperature had no significant change on the nature of the fibers and flexural strength of the samples. The best properties; flexural strength (33 MPa) and water absorption (0.08%) were exhibited at 1200 °C by samples with 30–40% kaolin, 30–40% feldspar, 20% ball clay and 10% sand. The results indicate that these samples are comparable to the ISO 13006 standards for porcelain tiles which are ≥ 35±2 MPa flexural strength and <0.5% water absorption. The other mix proportions did not meet these standards, specifically in terms of flexural strength (<25 MPa).