Use of marble sludge waste in the manufacture of eco-friendly materials: applying the principles of the Circular Economy.

The marble industry generates enormous amounts of waste every year, whose incorrect management can lead to environmental problems. The Circular Economy model can provide an effective solution to this issue, an aspect that has been addressed in this research. The suitability of a marble sludge generated in the ornamental rock industry of Andalusia (Spain) has been assessed as raw material in ceramic bricks. Mixtures containing a clayey base and 0, 2.5, 5, 7.5, and 10 wt% of marble powder have been shaped into 60 × 30 × 10-mm3 prismatic specimens and sintered at 950 °C in a muffle. The main technological properties of the bricks related to color, shrinkage, porosity, water absorption, suction, and compressive strength have been determined. The addition of marble sludge has fostered the development of a lighter color, together with a significant increase of the open porosity. This aspect has implied, on the one hand, higher water absorption and suction results and, on the other hand, a decrease of the density and the mechanical strength. The correlations obtained after applying Shapiro-Wilk normality tests and r Pearson coefficients endorse the clear relationship between the addition of marble powder and the abovementioned effects on the technological properties of the sintered bricks. All the measured properties fully meet the brick standardized requirements, which would indicate that the recycling of marble wastes could be a promising alternative to obtain eco-friendly lightweight ceramic materials.