Cellular glass – a unique material, by 100 % composed of glass cells. It has been created in 30th years last century in the USSR ( MHTI Mendeleev Chemical Technological University in Moscow ) and at the beginning of the fortieth years by firm Corning Glass Work. At first it was proposed to apply as a floating material. But it was soon found out, that it possesses also high heat and sound-insulating properties, easily it is subjected to machine processing and agglutination. For the first time concrete slab with heat-insulated layer from cellular glass have been applied in 1946 at construction one of buildings in . This experience was so successful, that the material has received a general recognition at once as durable isolation for a roof, partitions, walls and floors of all kinds of constructions.
Substantially cellular glass unique properties are caused by as a chemistry of an end-product (by 100 % coincident with structure of usual glass for glass-wares, bottles or a windowpane), as and thermal process of sponging and annealing. The algorithm of technological process in brief looks as follows.
Production technology of cellular glass.
Finely crushed glass and cullet are crushed, using ball mill in mixture with gasifier (coal) in a thin powder, are loaded into forms from heatproof steel with kaolin coating. Forms are given to the tunnel furnace on trolleys by the roller conveyor. Softening of particles of a glass powder and its sintering occur under action of high heat . Gases, escaping during gasifier burning and decomposition bloat viscous glass mass. Material with cellular structure forms during cooling. Slow cooling (annealing) promotes of uniform cooling of articles whole volume, therefore there are no internal stress or crack formation in them. The cooled products are sawed up then packed.
Foam glass blocks are got as a result of the given production phases. The chemistry of foam glass by 100 % coincides with a chemistry of classical glass and includes oxides silicon, calcium, sodium, magnesium, aluminium. Atmosphere completely closed glass cells does not interact with environment atmosphere and represents, basically, oxides and compound of carbon. Gas pressure in cells by the level below than atmospheric pressure since process of foaming occurs due to gassing with coke, anthracite and soot at temperature at about 1000°C. Owing to gasification and foaming of glass its volume increases in 15 times.
Cellular construction of foam glass where walls and units of cells consist of such strong material as glass, is caused its unique durability and ability to resist to mechanical loadings. The matrix of units and communications of foam glass structure represents the optimal space-volumetric configuration capable to stand the maximal loadings at the minimal density. Critical parameters of a foam glass cell are characterized by following parameters: at average diameter of a cell 2 000 microns walls cells´ thickness varies in an interval from 20 up to 100 microns.
The basic advantages of foam glass deserve more detailed consideration.
The guaranteed foam glass blocks life cycle with preservation of physical characteristics values is equal to term of building operation and exceeds 100 years.
Experimental researches of the objects warmed with foam glass more 50 years ago have shown absence of essential changes in a foam glass structure. The factor of preservation of heat-shielding properties during all building existence is especially important in view of inaccessibility heat-insulated material after the end of works. Foam glass is not subject to ageing for some reasons since its unique properties resist to active factors showing themselves eventually:
- oxidation. The active oxygen containing in atmosphere does not render influence on foam glass for the reason that this material consists exclusively of the higher oxides silicon, calcium, sodium, magnesium, aluminium;
- erosion. As foam glass has no soluble components in its structure, there is no dissolution and washout of a material with water;
- temperature drops. Foam glass has very low coefficient of linear expansion that allows to transfer daily and annual temperature perturbation without damage for structure of a material;
- freezing of water. At freezing water extends and can destroy even such strong minerals as basalt and granite, flowing in cracks. The surface of foam glass consists of hemispheres, the material represents closed cells at all excluding hit of water inside, therefore expansion of water does not destroy foam glass;
- deformation. . Cellular glass is not deformable absolutely and very strong material for its density, that completely excludes an opportunity of its shrinkage, whipping, etc. consequences of gravity and mechanical long influence;
- activity of biological forms. Foam glass is not a nutrient medium for a fungus, mould and microorganisms, it is not damaged with roots of trees, therefore activity of biological forms does not harm to a material structure during the time.
Cellular glass is the strongest of all effective heat-insulated materials. Its compression strength in some times above than fibrous materials and polyfoam. How much important is strength, and especially compression strength for heat-insulated materials in building industry? First of all the higher compression strength the less (that is logical) material subjected to external influence shrinks. At the same time compression of heat-insulated material reduces to increase of its heat conductivity and decrease of design´s heat-shielding properties. Foam glass is unique that is not compressed material absolutely. Moreover, less strong than foam glass heat-insulated material demands anchoring and pintle fastening to a bearing structure of a construction and the it less fast the more elements of fastening are used for fixing a heat-insulated layer and in that way number of foreign high-heat-conducting particulates generating additional « bridges of a cold » increase. Stronger heat-insulated material can bear a part of loading due to own physical properties, that allows do not apply additional metal fastenings reducing resistance to a heat transfer of a heat-insulated layer in some cases.
Stability of blocks´ sizes.
Owing to the fact that foam glass consists exclusively of glass cells, this material does not shrink and does not change geometrical sizes eventually under the action of building structures´ weight, exploitation loadings. All this has very essential value as for whole building structure as and for preservation of operational properties a heat-insulated layer.
Presence of the given factor is rather important since materials which sizes are not stable because of thermal expansion/compression or shrinkage during operation can cause damage of waterproofing and finishing layers, form « bridges of a cold » because of shrinkage, whipping or compression at cooling.
Foam glass is made of glass and has a coefficient of linear expansion comparable with coefficient of linear expansion of materials of which classical bearing structure consist: concrete, steel, ceramic or silicate brickwork. This affinity of values guarantees stability of foam glass blocks´ sizes are laid or mounted on a steel or concrete design.
Stability of physical parameters.
Foam glass is the material consisting from hermetically closed hexagonal and spherical cells. Such structure of a material excludes interaction of the gas environment of cells with an atmosphere and causes invariance in time of material´s characteristics. That is, there is no change of such parameters of foam glass blocks as heat conductivity, strength, stability, form, etc. Eventually a factor of keeping heat-insulated material`s properties is important especially at upkeep of buildings and constructions in view of inaccessibility of a material after end of works.
In a territory of the former , and also in the Europe and Northern America foam glass was used as a heater more than 50 years. Natural inspections, results of laboratory researches, measurement of physicotechnical parameters of foam glass blocks, taken of building structures with the useful life 40-50 years have shown that their characteristics practically have not changed, since results of measurements have coincided with the initial values.
Urgency of keeping the initial values of heater parameters has during an upkeep of building and a construction in modern construction primary value, as customers and the consumers to demand much of service performances of an all building or a construction, of a guarantee of their constancy in time. It is also important and at architectural complication of a building structure where expenses for major overhaul and replacement of the heater which has lost its property are comparable to expenses for erection and building.
Chemical and biological action stability.
Glass of which foam glass consists by 100 % , is not decomposed with chemical reagents (except for a hydrofluoric acid), is not nutrient medium for fungus, mould and microorganisms, is not damaged with roots of plants, is absolutely impassable for insects and rodents and represents an ideal barrier to similar pests.
Stability of foam glass to corruption and absence of a nutrient medium for distribution of mould and fungi especially is important at foam glass use in closed, non-aerated space of a roof, walls, a socle and a base. Absence of organic fertilizer allows avoid completely situations connected with destruction of heat-insulated material under the influence of biologically active medium.
Foam glass in addition is very good abrasive material. This feature of foam glass is used actively at a heat-shielding of granaries, industrial food refrigerators, warehouses since foam glass is reliable barrier on a way of wreckers besides a heat-protection layer.
Incombustibility and fire resistance.
Foam glass is completely non-inflammable material as it does not include oxidized or organic components. The "know-how" of foam glass is such, that a finished article is fabricated as a result of manufacturing in furnaces at the temperature close to 1000°C, therefore at foam glass heating up to warm temperature it only melts as usual glass without extraction of gases or vapor. This factor is important for fire-prevention properties of a construct.
The basic tests of fire safety of the material is incombustibility and absence of absorption capacity thanks to it is capable to provide the best fire protection of isolated objects.
Moisture resistance, water resistance and non hygroscopic property.
Water does not render on foam glass any influence for two reasons. First it consists of hermetically closed cells which walls` material is usual silicate glass. Secondly it does not absorb moisture and does not pass it, and it is an additional hydrobarrier at use in a building envelope. At damage of a waterproofing distribution of water is not supposed both in vertical and in horizontal directions.
Water resistance of foam glass allows it to prevent ice formation for long, to provide overall protection against corrosion and excellent thermoregulation. Foam glass is steady to action both fresh and salty water.
Ecological and sanitary safety.
Ecological and sanitary safety of foam glass allows to warm filler structures not only for housings in which the raised cleanliness of the air is necessary (buildings of educational and medical function, sports constructions; museums; hi-tech manufactures, etc.), but also for buildings with special sanitary-and-hygienic requirements (the food and pharmacological industry; baths and saunas; pools; cafe, restaurants, dining room, etc.
Simplicity of processing.
Foam glass is processed easily by the joiner's tool under any necessary sizes and the form. It communicates and sticks together with any type of a building mix, bitumen or glue. All this allows realizing foam glass assembly with use of various variants of fastening. It is caused by that sticking occurs not so much due to adhesion (which, none the less, is present), and due to extremely developed surface of foam glass and mechanical adhesion of surfaces by means of hardening structure.