Fired electrical porcelain scrap (chamotte waste) recycling and reuse as an alternative raw material for sustainable porcelain stoneware production

The development of new sustainable ceramic formulations that incorporate industrial waste is a practice that meets the efficiency and sustainability criteria that today's society demands for an industry with high energy and non-renewable mineral sources consumption. In this research, fired electrical porcelain scrap (chamotte waste) was recycled and reused in the porcelain stoneware manufacture, partially replacing the quartz and feldspar from the triaxial system at 5, 10, 15, 20, and 30 wt%. The experimental samples were obtained after uniaxial pressing of ceramic mixture powders at 30 MPa and firing at 1260 °C following a fast-firing process (90 min cold to cold). The technological properties were studied by bulk density, apparent porosity, linear shrinkage, water absorption, cold crushing strength, and Vickers microhardness. The microstructural aspects and the amount of crystalline and amorphous phases in the ceramic bodies were analyzed by scanning electron microscope and X-ray diffraction, respectively. The best technical characteristics were achieved with the incorporation of 15 wt% of chamotte in the new ceramic formulations, yielding a density value of 2.41 g/cm3, and percentages of linear shrinkage and water absorption of 11.2 and 0.08 %, respectively, as well as mechanical resistance of 314.94 MPa and microhardness of 7.07 GPa. The mechanical resistance achieved by the experimental sample containing 15 wt% of chamotte waste means six times the value obtained by the control sample (0 wt% of chamotte addition) and was attributed to a higher mullite phase content and well-dispersed crystals (primary and secondary mullite) in the ceramic body. The results suggest and advance in the design and development of a best-performance porcelain stoneware materials elaborated by a sustainable and ecological route.