Ceramic products obtained from rock wastes

Residue powders resulting from cutting and machining operations in slate quarries were processed by a press and sintering route to manufacture ceramic products such as flooring and roofing tiles. The first part of this work consisted of a laboratory study carried out by uniaxially pressing the powders to shape and sintering in air using a muffle type furnace. A plan of sintering experiments was followed in order to evaluate the effect of some processing parameters: particle size distribution of the rock waste powders, compacting pressure and sintering cycle (heating and cooling rates, sintering temperature). The sintering tests have shown that the density of the sintered specimens increased gradually up to 1150–1170 °C and then started decreasing. The second stage of this study was carried out at an industrial scale. Since particle size of the raw material was found to be an important parameter, atomisation was used to homogenise the particle dimensions and ensure proper feeding of the pressing systems. Moreover, atomisation is the best way to treat very fine wastes, both for economical and technical reasons. Tiles with the dimensions 200 mm×100 mm×7 mm were then uniaxially pressed at 40 MPa and subsequently sintered at temperatures close to 1150 °C. The properties of the products obtained are suitable for flooring tiles.