Foam glass gravel

Foam glass gravel is light and dimensionally stable, with a lambda rating of 0.08 W/mK and a specific weight of 150 kg per cubic metre. Being made from glass, the aggregate is non-combustive and inert, ageing resistant, pH neutral and insect and rodent resistant. The manufacturing process seals the air bubbles giving the gravel non-capillary properties. The material has a high compressive strength as well as insulatory properties making it ideal for insulated floor construction^[1]

Glass shards are cleaned and milled to a powder before a foaming agent, active carbon,^[2] is added in either liquid or solid form. The material is passed through a continuous tunnel furnace and heated to a temperature of 800–900 °C. Optimum temperatures produce maximum quantities of the foamed product. The foamed molten glass breaks into gravel on cooling.