Valorization of ceramic sludge waste as alternative flux: A way to clean production in the sanitary ware industry

The ceramic industry consumes a large amount of raw materials, much of which consists of fluxes. In view of the growing demand for infrastructure and sanitation, the waste valorization is a viable alternative for recycling materials, mitigating the extraction of natural resources. In this context, the present work studied the feasibility of replacing feldspathic flux by ceramic sludge waste (CS) in the sanitary ware production. The waste was characterized by particle size distribution, chemical composition, and mineralogical phases. The replacement ratios (by mass) were set in a wide range of 5, 10, 25, 50, 75, and 100%. The ceramic mass in fluid aspect was evaluated by means of density, viscosity, thixotropic index, setting rate and drying time. The hardened state was investigated through shrinkage, pyroplastic deformation, compressive and flexural strengths, water absorption and microstructure. The results showed that CS can be a stronger flux than granite. One of the proportions with total replacement (B-100) showed promising results, being the best option in terms of rheological behavior and physical-mechanical properties. An important finding concerns water absorption, which decreases with increasing the CS content. It is suggested that CS valorization on industrial scale may be sufficient to eliminate the entire volume of waste. This approach represents an eco-friendly solution, promotes the closing of waste loops and can be a way to cleaner production in the sanitary ware industry.