Effect of glass powder on the technological properties and microstructure of clay mixture for porcelain stoneware tiles manufacture

The present study focused on the use of waste glass powder with clay mixture, for manufacturing of porcelain stoneware wall and floor tiles. The raw materials were characterized in terms of mineralogical and chemical composition. Different mixtures with various amounts of glass were prepared and fired in the temperature range of 1000-1200 °C, for 2 h. The influences of waste glass content on the technological properties (linear shrinkage, water absorption, bulk density and flexural strength) were determined. Microstructural analysis of the fired samples was carried out by X-ray diffraction and SEM. The experimental results revealed that waste glass contributes to improve physico-mechanical properties of samples up to 30 wt% of glass content at 1150 °C. The final product (R50G20C30) showed weak absorbed water value (0.4%) and higher flexural strength (39.06 MPa). Thus, according to the ISO 13006 standard, it can be classified as porcelain stoneware tile, since it satisfies the standard requirements. The addition of high amounts of glass (>30 wt%) into the ceramic bodies is undesirable due to its adverse action on the physical properties of products. Moreover, the SEM micrographs of tiles specimens fired at 1150 °C and with 30 wt% of glass showed a very compact texture and dense microstructure with a mullite fibre. As a consequence, tiles exhibited noteworthy mechanical properties.