Properties of porous ceramics from two Cameroonian clays mixed with sawdust

Sawdust was mixed with two clays in a weight ratio varying from 1 to 10 %. Both clays are kaolinitic, but one named MY45g contains a few quantity of fine quartz (9.4 wt %) and the second denoted BEAC a larger quantity of large size quartz (27.2 wt %). Samples were shaped and fired between 1200 and 1350°C. At 1000°C, sawdust is reduced to a very small quantity of ashes, containing only SiO2 and Al2O3 oxides. During sintering the densification rate increases with the amount of sawdust, up to 15 % (MY45g) and 3,5 % (BEAC). This phenomenon is due to the increase of inter-connected large pores within the volume, but also to the role of a 3D network of large grains especially with BEAC. The addition of sawdust to clays leads to porous and insulating quality products, without changing the maximum temperature in service. However, the amount of sawdust must stay below 5 wt % to avoid the excessive reduction of the mechanical strength. © Lavoisier.