A review of waste glass as a raw material for whitewares

The use of waste glass as a raw material for whitewares is a subject that has been investigated for many years. This residue could be used in whitewares formulations as a fluxing agent for partial or total substitution of one of the natural raw materials, commonly alkaline feldspar and brings the opportunity to improve sustainability. The majority of the studies in this field are related to the production of porcelain tile, but there are also investigations about hard porcelain and sanitarywares. As a general result, the reviewed articles show that waste glass reduces the firing temperature of whitewares, and alters some properties, such as phase crystallization, microstructure, and mechanical strength. In addition, the presence of waste glass also changes some processing properties which have not been adequately highlighted yet. The present article presents a review of the waste glass in its composition and uses in whitewares formulations, as well as its influence on formulation dosage, milling parameters, conformation and firing processes, besides the alterations on mechanical strength, toughness, resistance to deep abrasion and thermal expansion coefficient. Based on the findings, indications are provided to determine the ideal amount of waste glass in a formulation, which may be related to the desired properties. The key findings are that waste glass can replace feldspar with technical and environmental advantages: reaching the desired properties required for commercial whitewares, with lower firing temperature, but with a few adjustments in the processing.