Utilization of granite sludge for production of cordierite ceramics by direct coagulation casting

In this work, an attempt to produce cordierite ceramics from granite sludge waste, talc and alumina was performed by direct coagulation casting process. To optimize the conditions for cordierite formation, three mixcompositions were firstly prepared by processing the starting materials in different conditions. The first mix was prepared by firing the mix of granite sludge, talc and alumina up to 1300 degrees C while the second and third mixes were fabricated by firing alumina and talc at 1300 degrees C or 1350 degrees C, respectively, then the granite sludge was added. Both batches were fired at different temperatures. According to the percentage of formed cordierite, the third mix was selected to be solidified by direct coagulation casting method followed by sintering at different temperatures. The casted cordierite was examined by thermal analysis while the sintered bodies were tested for their physical, mechanical and electrical properties. The results indicated that the pre-heating of alumina and talc at 1350 degrees C (third mix) enhanced the formation of cordierite and some amounts of spinel. For the casted sintered specimens, the porosity was decreased with increasing the sintering temperature. Also, there was an increase in compressive strength for the samples sintered up to 1250 degrees C. The dielectric constant values were varied between 4.5 and 5.89 while the dielectric loss was varied between 2 x 10-3 and 7 x 10-3, at room temperature.