Innovative Glass Recipes Containing Industrial Waste Materials

The growth of the industrial production generates a high volume of waste materials. These products have a significant impact on the environment. Therefore, the valorization of industrial wastes, especially those produced in huge quantities, is an important social and ecological issue. Waste reuse and recycling could help to develop new products and aggregate value to materials that would have been previously discarded. Furthermore, it could reduce the consumption of natural resources and pollution. Blast furnace slag and fly ash are waste materials largely used in concrete production, mainly as an aggregate, and road construction, as porous asphalt and in other contexts. These wastes contain many elements that are also present in typical glass formulas, such as CaO, SiO2, Al2O3, and Fe2O3. However, these elements are highly refractory, and their presence in complex compositions leads to a high tendency to crystallize and to high working temperatures. For this reason, it is a challenge to get transparent materials at reasonable temperatures from these waste products. Glass is a material that allows large amounts of various elements in solution, and is suitable for assimilating the complex materials in its compositions. In this work, we produced transparent glass samples incorporating amounts up to 35% (in weight) of blast furnace slag or fly ash. The compositions were adjusted in order to allow for chemically durable glasses in relatively low melting temperature: the samples were successfully submitted to water durability tests and were obtained in melting temperatures between 1100°C and 1350°C, depending on the composition. The melting conditions were optimized in order to achieve a higher transparency. The optical, mechanical and thermal properties of the samples were measured and compared to the standard borosilicate and soda-lime glasses.