Foamglass (foamed glass, cellular glass) - the insulating material, which is a foamed molten glass. For the manufacture of foam glass is used the ability of silicate glasses to soften and (in the case of the presence of a blowing agent) to foam at temperatures of about 1000 ° C. As the viscosity increases when the expanded glass mass is cooled to room temperature, the resulting foam acquires substantial mechanical strength.
It is believed that foam glass was invented in the 1930s by Soviet academic I. I. Kitaigorodsky and in the USA in the early 1940s by Corning Glass Work. At first it was supposed to use foam glass as a floating material. But it soon became clear that it additionally possesses high heat and sound insulating properties, it is easily subjected to mechanical processing and gluing. For the first time, concrete slabs with a heat-insulating layer of foam glass were used in 1946. during the construction of one of the buildings in Canada . This experience was so successful that the material immediately received universal recognition as durable insulation for roofs, partitions, walls and floors for all types of buildings. But in the USSR it was not widely used because of the high cost and the waste technology of production of this unique insulation material. However, by the 1970s, the production of foam glass in the USSR was carried out at 4 plants.
Foam glass manufacturing
Currently, the main technology of production of foam glass is the so-called. “Powder”: finely divided silicate glass (particles of 2–10 μm) is mixed with a blowing agent (usually carbon ), the resulting homogeneous mechanical mixture (mixture) in forms, or on a conveyor belt enters a special tunnel kiln. As a result of heating up to 800-900 ° C, the glass particles soften to a viscous-liquid state, and carbon is oxidized to form gaseous CO2 and CO , which foam the glass mass. The mechanism of the reaction of gas and foaming is rather complicated and is not limited only to the oxidation of carbon by atmospheric oxygen, the more important role is played by the redox processes of interaction of carbon with the components of softened glass. Used for this purpose wastes of ordinary glass or easily sintered rocks with a high content of alkalis — trachyte , syenite , nepheline , obsidian , volcanic tuff . As gas formers used coal coke , anthracite , limestone , marble . Carbon-containing gas generators create closed pores in the foam glass, and carbonates - communicating.  Do not confuse foam glass with the products of the foaming of aqueous solutions of soluble glass . Foaming t. " Liquid glass " occurs at temperatures of about 100-200 ° C as a result of the rapid removal of water from a viscous solution. The product of instant glass foaming is absolutely not resistant to the action of even cold water, unlike foam glass, whose chemical resistance is comparable to the original sheet or container glass.
Foamglass produced in the form of blocks, plates, rubble and granules. Foamglass density - 100-600 kg / m. cc Sorption moisture content of foam glass is 0.2-0.5%, with f = 97%. The thermal conductivity of foam glass is 0.04-0.08 W / (m · K) (at + 10 ° С). The vapor permeability of foam glass - 0-0.005 mg / (m.h. Pa.). Compressive strength - 0.7-4 MPa. Flexural strength - 0.4-0.6 MPa. The temperature of the beginning of the deformation of foam glass - 450 ° C. Foamglass water absorption 0-5% of the volume. Sound absorption: up to 56 dB. Effective temperature range: from −260 ° С to + 500 ° С.  The real range of application without loss of properties and destruction of foam glass from −260 ° С to + 230 ° С
Along with excellent thermal insulation properties and complete environmental and hygienic safety, foam glass has high strength, non-inflammability, ease of processing and ease of installation, the ability to maintain these indicators for a long time constant. The material is resistant to all commonly used acids and their vapors, does not allow water and water vapor, is not affected by bacteria and fungi, is impassable for rodents, does not support combustion, does not emit smoke and toxic substances.
Foamglass is mainly used as a universal heat insulator: in the building complex; housing complex; in agriculture; energy; mechanical engineering; chemical and petrochemical industries; food; paper; pharmaceutical and other industries.
Production of high-quality block (slab) foam glass (and especially molded products from it) is rightly considered a very technically difficult task. The reason for this is the complexity of physico-chemical processes directly during foaming, as well as strict requirements for the processes of fixation and cooling (annealing) of the finished foam. So, for example, fixing is complicated by the fact that glass is not characterized by a sharp hardening during cooling (like crystallization during the transition of water to ice), and fixing of foam glass may be accompanied by such “interfering” processes as exothermic reactions in a glass melt, spontaneous crystallization (devitrification) of glass melt , substantial heterogeneity of the temperature field in the foam mass, etc. It is also not easy to cool the foam block correctly - the material has an extremely low thermal conductivity with known rupkosti thin glass foam cells. As a result, the annealing stretches for 10–15 hours and imposes significant restrictions on the height (thickness) of the annealing blocks (the permissible cooling rate is inversely proportional to the square of the thickness). Significantly less complex is the production of granulated foamed glass, the mass production of which is less demanding on the composition of glass and the perfection of thermal engineering units. Granulated foamed glass is somewhat inferior in thermal efficiency block efficiency, however, having a significantly lower price, is in certain demand in the production of lightweight concrete, heat insulating backfill and the manufacture of geometrically complex products, including sound insulation.