Microwave Heating Application for Making Cellular Gravel Using Recycled Residual Flat Glass from Construction as Well as Alumina-Silicate Industrial By-Products (Fly Ash and Slag)

The production of cellular glass gravel based on glass waste and a suitable foaming agent has rapidly reached an industrial level in the last decades, satisfying the need for insulation-under slab and rooftops, light filling material for landscaping, roof gardens, green roofs, etc., having drainage and load bearing abilities. Not only glass waste was tested for the manufacture of cellular gravels, but also other material precursors, the most interesting being metallurgical slag and coal fly ash. They exhibited the capability to increase the mechanical strength of cellular products, but had a certain negative effect on their thermal insulation and physical properties. The current work aimed at finding an optimal correlation between the proportions of glass waste and those of slag and fly ash used in the material mixture. The own technical solution of applying predominantly direct microwave heating was maintained in this experiment.