Waste glass becomes thermal insulation

This article describes how waste glass can be transformed into thermally insulating, glass foam aggregate. Application as load bearing insulation underground slabs and insulating drainage layers of a roof garden are examples of how this loose fill aggregate can be used. In the first part the production procedures of wet foaming and dry foaming will be explained. Then the physical properties and the applications of the final foam glass gravel or cellular glass with lump size of 10 to 75 mm in structural and civil engineering will be described. Foam glass gravel is produced from more than five companies now and has been applied for more than ten years in Switzerland, Germany and other European countries. The insulation material is manufactured from recycled glass and mineral additives in a thermal process. The aggregates form when slabs of cellular glass crack while cooling down. In order to obtain the required hygrothermal properties, the manufacturing process must be carefully controlled. Despite its low density of approximately 110 to 250 kg/m³, celluar glass aggregate has a high pressure resistance, absorbs hardly any water and is fireproof. The expected service life is at least 50 years. According to German and European requirements this insulation material has been thoroughly tested and the effect of water clinging to the aggregate has been investigated in the laboratory and by in-situ investigations. This paper provides an overview of the processing from raw waste glass to building insulation material, summarizes aggregate properties of product from different manufactures, and reports on practical experience.