Abstract: The blown granular glass consists of fragments of a blown glass element and comprises at least 100,000, preferably 1,000,000, per cm.sup.3 of bubbles approximately of the same size. It is obtained by grinding the race material into a flour; the flour is mixed into a hot gas by a blowing means; the mixture is blown into a flat base furnace in an amount of blown glass; this amount is cooled after blowing and directly after cooling it is crushed into a granulated material.

Abstract: An expanded glass aggregate has a granulometry of 0.2 to 3 mm and 10.sup.6 to 10.sup.7 cavities filled with gas per cm.sup.3. The diameter of the larger cavities is substantially smaller than 0.1 mm. All or a majority of the cavities are closed cells having a similar size. The expanded glass aggregate may contain in addition up to 85% of concrete, lava and/or tuff. For the preparation, the raw material is ground into a flour, mixed with a blowing organic and/or inorganic material appropriate to hot release gas, and a semi-finished aggregate is formed with a diameter of the granules of 0.1 to 1.5 mm. This aggregate is heated in a vibrating or suspended furnace during 5 to 180 seconds at a temperature of 600.degree. to 900.degree. C. The expanded glass aggregate is removed away from the furnace before a significant number of small cavities formed during the blowing gather to form larger cavities.