Processing of floor tiles bearing ornamental rock-cutting waste

In ornamental rock industry large amounts of wastes in the form of powder have to be discarded. The reuse of ornamental rock-cutting waste to produce floor tiles for civil construction is described. The waste was added gradually up to 47.5 wt.%. The tile manufacturing route consisted of dry powder preparation, uniaxial pressing at 50 MPa, and sintering between 1190 and 1250 °C using a fast-firing cycle. The development of the microstructure was followed by XRD and SEM. The technological properties (linear shrinkage, apparent density, water absorption, and flexural strength) as function of the waste addition and firing temperature are investigated. The results revealed that the gradual replacement of Na-feldspar with rock-cutting waste accelerated liquid phase formation and thus sintering, resulting in denser microstructures. All tile pieces consist of mullite and partially dissolved quartz embedded in a glassy matrix. The technological properties were found to be influenced by the waste addition. It was also found that the replacement of Na-feldspar with rock-cutting waste as part of the flux system, in the range up to 47.5 wt.%, allows the production of enhanced floor tiles at lower firing temperatures.