Recycling of wastes in silicate ceramics: feasibility and effects

Chiara Zanelli (CNR-ISTEC Faenza)

The manufacture of ceramic products is constantly increasing all over the world, implying an ever-increasing demand for raw materials. On the other hand, the progressive depletion of the main mineral deposits that this production rate imposes is forcing the ceramic industry to look for suitable substitutes, which guarantee specific technological properties to the finished product. This situation represents a real challenge for the ceramic industry, to make production completely sustainable in the long run - in view to the transition to a circular economy - but ensuring the high technological performances of the product. Although to date the ceramic industry has proven to be able to recycle its own processing residues very efficiently, the use of wastes from other sources is currently rather limited, because of the lack of knowledge about their effect in ceramic manufacturing and firing behavior. Case-studies about the utilization of waste glasses, waste slags and construction and demolition wastes in different silicate ceramics (such as floor tiles, clay bricks and lightweight aggregates) will be discussed focusing on the main physical and chemical properties of the batches. The mineralogical transformations occurring during firing determine the final technological properties and performance of the ceramic products and, consequently, the feasibility of the transfer to industry.