Circular economy in marble industry: from stone scraps to sustainable water-based paints

Huge amounts of sludge waste are produced every day during the sawing and processing of carbonate ornamental stones. Most of these materials are landfilled and create serious environmental and health hazards. Thus, it is mandatory to find alternative solutions to recycle them. Since calcium carbonate is the most widely used mineral filler for interior and exterior emulsion paints, this investigation focused on the feasibility of trying out innovative methods of circular economy in a waste processing area. Focusing in the Orosei Marbles’ producing area (North-East Sardinia, Italy), the aim of this study was to compare the performance of water-based paints, through the use of marble sludge waste, as mineral fillers, rather than commercial CaCO3. According to standard normative tests were carried out on paint samples, prepared according to an experimental formulation, after a preliminary chemical and physical characterization of the fillers. The results indicate that the marble sludge waste can be successfully used as mineral filler in water-based paints, and that it requires only light pretreatments consisting of deagglomeration and mechanical dispersion in a wet medium, thus confirming its environmental and economic benefits.