Recycling the Product of Thermal Inertization of Man-Made Vitreous Fibres for the Manufacture of Stoneware Tiles

In this paper, we present a process where the material deriving from the thermal inertization of exhaust hazardous mineral wool is recycled as secondary raw material in the production of “eco-friendly” ceramic tiles. The process proposed intends to: (1) promote the recovery and recycling of a material not served by the supply chain and therefore destined for landfill; (2) promote the use of alternative raw materials by encouraging an efficient use of resources from both an ecological and an economic point of view. In fact, this use will make it possible to: (a) replace natural mineral resources in production; (b) decrease importing raw materials over long distances, limiting energy cost; (c) avoid the risk of supply in the event of a blocking of exports. The glass material deriving from the inertization of the mineral wool is here fully characterized and, on the basis of its properties, it has been added to a batch for the production of porcelain stoneware tiles in substitution to fluxing component. The semi-finished products were characterized in terms of particle size distribution, powder moisture, green and dry bulk density, green and dry flexural strength, spring-back after pressing and drying shrinkage to highlight the eventual presence of bottleneck in the production cycle. The final products were fully characterized in terms of technological properties (linear firing shrinkage, water absorption, bulk density, open porosity, flexural strength, colorimetry). The final product properties resulted satisfactory, since the values of all the technological parameters recorded for the bodies realized with waste perfectly match the standard requirements for porcelain stoneware (ISO13600). Moreover, the introduction of inertized waste allowed to lower the firing temperature up to 40 °C with respect to the benchmark. The only drawback observed is related to the colour of the ceramic bodies: the amount of Fe intrinsically present in the inertized glass lead to a darker final colour. Graphical Abstract