Recycling of glass waste in ceramics—part I: physical, mechanical and thermal properties

The study concentrated on the possibility to use glass waste nanoparticles with an original ceramic batch to produce wall and floor tiles. Eight different mixtures with various ratios of glass waste nanoparticles were prepared (0, 5, 10, 15, 20, 25, 30 and 35% having the symbols G0, G1, G2, G3, G4, G5, G6 and G7), respectively, and then fired in a temperature range of 1000–1200 °C for 2 h soaking. Results showed that the water absorption decreased as the glass content increased up to 35% if fired up to 1100 °C. On firing > 1100 °C, the water absorption decreased only up to 25% glass (G5), and then increased with G6 and G7. The bulk density of all batches increased up to 1100 °C. On firing > 1100 °C, the bulk density increased only up to up to 25% glass, and then decreased with further increase of glass content. The mechanical properties in terms of flexural and crushing strengths were displayed the same trend of bulk density. The dry shrinkage recorded zero reading, i.e. it was unchanged, while the firing shrinkage was slightly increased with both glass content and firing temperature. The experimental results revealed that the glass contributes to improve thermal, physical and mechanical properties as well as microstructure of the prepared samples containing up to 25 wt% of glass fired at 1150 °C. The addition of high amounts of glass (> 25 wt%) into the ceramic body is undesirable due to its adverse action on physical and mechanical properties of the fired products and moreover, the external appearance of the ceramic units are too bad. The dry shrinkage was unchanged, but the firing shrinkage was increased with both temperature and glass content. The coefficient of linear thermal expansion decreased with glass content.