EFFECT OF MIXING RATIO ON BUBBLING PRESSURE OF POROUS CERAMIC DISCS PRODUCED WITH SAW DUST AS THE BURNT OUT MATERIAL

Abstract

The control of the amount of burnt out material in production of porous ceramics is important for the attainment of the desired pore size distribution which influences other characteristics such as bubbling pressure. Five different mixing percentage ratios of sawdust burnt out material to kaolinite clay, of 10:90, 20:80, 30:70, 40:60, 50:50 by volume, were therefore used in the moulding of porous ceramic discs 10.2 cm in diameter and 1.5 cm thickwhich were fired in a kiln to 1100 ^oC. The bubbling pressuresof three replicate discs per mixing ratiowere determined by the gas transport method. The corresponding sawdust content of the mixtures by weight were found to be3.33, 7.19, 11.72, 17.12 and 23.65 % respectively. Average bubbling pressure of the discs was found to vary inversely with sawdust content of the mixture and rangedfrom 10.33 MPa for the 50:50 Mixture to 66.33 MPa for the 10:90 Mixture. The regression relationship between the average bubbling pressures (MPa) and Mixture sawdust content by weight (%) was found to be best described in form of a decaying power function with a coefficient of determination of 0.986. It was therefore suggested that regression relationship could be useful in the specification of sawdust-kaolinite clay mixtures for the production of porous ceramics discs for special applications.