Effect of substitution of quartz by rice husk ash and silica fume on the properties of whiteware compositions

Active silica from rice husk ash (RHA) and silica fume (SF) were progressively incorporated in a whiteware composition in substitution of quartz. The Influence of the addition on the thermo-mechanical properties, vitrification behavior and microstructure has been investigated. It has been found that replacement of quartz by RHA(+) SF (1:1) reduced drastically both the maturing temperature (50-100 degreesC) and the thermal expansion (3.24-14.6%) at 600 degreesC with the improvement in the fired strength. Maximum improvement in the fired MOR (20.8%) was observed in a whiteware composition containing 10% (RHA + silica fume). On complete replacement of quartz (25%) by RHA + SF, the fired strength was noticed around 14.95% in whiteware body matured at lower temperature by 100 degreesC. The improvement in the properties is attributed to sharp changes in the microstructural features as a result of significant reduction in the content of the quartz phase and the simultaneous increase in glassy phase. The findings would be helpful to improve the properties of whiteware as well as to reduce the energy consumption during firing process. (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserve