Circular Economy in the Production of Ceramic Materials (porcelain stoneware tiles, clay bricks and aggregates): Resource Efficiency and Waste Valorisation

The sustainability of the ceramic sector is challenged by its reliance on finite natural raw materials and the significant environmental footprint exerted by high-temperature firing processes. This is further intensified by the accumulation of massive volumes of industrial and environmental wastes, which currently lack effective recycling solutions. This study focused on two highly distinct types of waste materials, Mignano reservoir sediments and construction and demolition waste fine fractions, into porcelain stoneware tiles, clay bricks, and lightweight aggregates. A structured characterisation protocol was developed and validated for dam sediments. For construction and demolition waste, whose heterogeneity places it outside the range of conventional ceramic inputs, an innovative batch design strategy was proposed. Rather than the direct substitution approach common in the literature, the entire batch composition was redesigned around the chemical contribution of the wastes. In porcelain stoneware tiles, dam sediments and construction and demolition waste were successfully incorporated at 2-4 wt% and 10 wt%, respectively, achieving full compliance with ISO 13006 Group BIa at 1180-1200 °C. In fired clay bricks, both waste streams achieved compliant performance at 10 wt% substitution and 900 °C, the standard industrial firing temperature. For lightweight aggregates, dam sediments used as the primary material combined with 10 wt% of waste glass met EN 13055:2016 density requirements and exceeded the ASTM C330 compressive strength threshold at 1180 °C. Across all formulations, the targeted substitution levels preserved microstructural integrity and physico-chemical performance within the requirements of the applicable standards. Leaching tests for bricks further confirmed environmental safety across all systems. These results provide a credible foundation for pilot-scale validation and life cycle assessment, supporting a circular economy model for the ceramic sector through the productive reuse of waste streams currently landfilled or disposed of without value.