The use and recycling of filter-press cake wastes in eco-friendly porcelain tile formulations

This work investigates the possibility of improving the physical, mechanical, and microstructural performance of porcelain tile using a filter-press cake waste of a ceramic-tile factory. Before firing at the factory, the wastes (defective pre-products) formed in raw-material preparation, polishing-cutting lines, and after the glazing application accumulated in the sludge formed in the pools in the ceramic-tile factories. A waste cake mixture (WM) was prepared according to the daily production amounts in these pools; physical and chemical properties were investigated. For this purpose, sixteen different series of tile compositions have been prepared by replacing the clays and kaolin with the WM at 3, 6, 9, and 13% by weight. When the prepared samples are compared to a standard, the samples containing 6 wt% WM show high bending strength due to the high amount and relative aspect ratios of the needle-like mullite crystals, and firing shrinkage, water absorption, and color parameters values remained almost constant. The study reveals that the addition of 6 wt% WM in porcelain tiles results in about a 41% increase in strength. The WM is a potentially alternative material to be successfully recycled in the eco-friendly porcelain tile compositions as a partial replacement of clays and kaolins up to 13% level.