EFFECTS OF THERMAL TREATMENT OF AMA NGUZU CLAY FOR REFRACTORY BRICKS PRODUCTION

Abstract

The effects of thermal treatment on the properties of clay bricks produced from Ama Nguzu clay were studied through transformation processes in the clay matrix upon firing. The clay sample was collected, processed and characterized for mineralogical and chemical oxide composition using x-ray diffractometer (XRD) and x-ray Florence (XRF) respectively. The processed clay was used to develop test samples of the refractory brick. They were dried at 1100C and thereafter fired at different temperatures of 9000C, 10000C, 11000C and 12000C at the rate of 40C/min for 1 hour. The fired samples were tested for the refractory properties. The XRD results indicated quartz as the dominant mineralogical phase while that of XRF showed the presence of major oxides such as alumina, silica and iron oxide. The results obtained for the refractory property tests showed that the linear shrinkage, bulk density, modulus of rupture and refractoriness respectively increased from 4.77 – 6.75%, 1.605 – 1638g/cm3, 10.94 – 19.93N/mm2 and 14500C - 16500C when the fired temperature increased from 9000C - 12000C. With the same trend in the fired temperature, the apparent porosity, water absorption and thermal shock resistance decreased from 39.5 – 30.25%   24.61 – 22.14% and 31 – 28 cycles respectively. It was found that the properties are interrelated and are either directly or inversely related to the fired temperature. It was also found that the properties of the clay depended on other factors such as the mineral phase and chemical oxide constituents which are related to the fired temperature. Therefore, it was concluded that the firing temperature range of 1100 - 12000C is most appropriate to yield optimum performance for the refractory brick understudied. However, low porosity due to over firing does not yield impressive spalling resistance