Properties of prepared samples
Determination of water absorption, bulk density, porosity and shrinkage are the tools for the degree of maturation or vitrification of a ceramic body. Fig. 5 shows the linear shrinkage behavior of the test specimens. It is clear from the graph that mostly shrinkage increased with increasing temperature whereas decreased with increasing rock dust percentages. Low shrinkage values were found for samples containing 30% rock dust, fired at 900 °C and 1000 °C. Above 1000 °C there was a tendency for linear shrinkage to increase for all samples with rock dust due to the presence of fluxing oxides. However, with increasing rock dust percentages shrinkage percentage decreased. It may be suggested that a high content of fluxing oxides in the system helps the formation of glassy phases which fill in the pores, thus leading to a shrinkage gain that decreases on firing.