Process for the preparation of a glass based cellular mineral and various articles made therefrom

A process for the preparation of a porous expanded glass which comprises the steps of:

• (a) providing a mixture comprising of 100 parts by weight of ground glass and 0.2 to 2 parts by weight of calcium carbonate and magnesium carbonate in a CaCO.sub.3 to MgCO.sub.3 weight ratio ranging from 20:80 to 80:20;
• (b) placing said mixture in open refractory vessels, the rims whereof have a minimum height of 15 cm, in such a way that said vessels are filled to a minimum height of 6 to 12 cm;
• (c) heating said filled vessels in a furnace until a temperature of approximately 800.degree. C. is reached, said heating being carried out so that after a temperature of 700.degree. C. is attained a maximum heating rate of 150.degree. C. to 170.degree. C. per hour is observed;
• (d) maintaining said temperature of approximately 800.degree. C. for at least half an hour;
• and then
• (e) cooling the heated vessels at a maximum rate of 80.degree. C. per hour with the proviso that a maximum cooling rate of 20.degree. C. per hour is observed in the temperature range of from 600.degree. C. to 500.degree. C., to obtain an expanded glass having a thickness exceeding 10 cm and having a density range of from 160 to 700 kg/m.sup.3 and a proportion of open pores of 30 to 90% by volume based on the total volume of pores.