Large high density foam glass tile

[0001] The present invention relates generally to a building material to be used in building construction. More particularly, the present invention relates to large high density foam glass tiles to be used on both interior and exterior facades of buildings. Even more particularly, the present invention relates to large high density foam glass tiles to be used on interior and exterior facades of buildings which enable such buildings to have a greater resistance to explosions.

[0002] The present invention further relates to a composite of panels made from such tiles, and more particularly, to a blast energy absorbing structural laminate and a method of making the same by bonding layers of foamed glass or foamed siliceous materials with structural inorganic cementaceous materials, polymeric materials, metals and fibers which can be optionally used in laminates.

[0003] Over the past decades, there have been a significant number of terrorists attacks on government buildings owned by the United States and other countries both outside of the United States and within. For example, in 1993, terrorists exploded a car bomb inside the garage of the World Trade Center located in New York City, resulting in loss of life and significant property damage. Since then, in 1995, other extremists exploded a truck outside of the Federal Building located in Oklahoma City, Okla. also resulting in significant loss of life and property damage. In 1998, the United States embassies in Nairobi and Dar Es Salaam were also subject to terrorists attacks by car bombs, each of which resulted in significant loss of life and property damages. Most recently, the tragic events at the World Trade Center in New York City and the Pentagon in Virginia has further emphasize the long felt need to develop and manufacture building materials which are able to withstand the shock wave from car bomb explosions and other similar terrorist attacks.

[0004] While the concept of using foam glass as a construction material is well known in the prior art, generally such foam glass has been used as a high temperature insulator and thus seeks to minimize its density and weight and is not suitable for absorbing sufficient energy from a shock wave from unexpected explosions or to resist an earthquake. The shortcomings in such conventional foam glass as relevant to this long standing problem is now described.

[0005] For example, Pittsburgh Corning Corporation (“PCC”) of Pittsburgh, Pa. has developed and marketed a product known as Foam Glas® Insulation Systems, which is described in U.S. Pat. Nos. 3,959,541, 4,119,422, 4,198,224, 4,571,321 and 4,623,585. Because the focus of these developments are directed to making a foam insulating material, the Foam Glas® Insulation Systems tile commercially sold by PCC is relatively light, weighing 9.5 lbs. Furthermore, since the purpose of this tile is to be used as thermal insulation, it lacks surface strength, and can be dented very easily. Because the Foam Glas® Insulation Systems tile is of relatively low density, e.g., 9.5 lb./cu. ft., such tiles will easily break when exerted to forces typically asserted on exterior walls to a building or other structure. Thus, such tiles are not suitable to be used as tiling for an exterior wall. Similarly, this foam, when exposed to a shock wave from an explosion will absorb very little of the shock waves energy when it implodes. A shock wave is a measure associated with explosions which is easily understood by those skilled in the art as being a pressure front resulting from an explosion.

[0006] Others have also attempted to use foam glass tiles as the outer skin-surface of buildings. For example, U.S. Pat. No. 5,069,960 discloses a thermally insulating foam glass tile that is coated with an outside surface to make a hard skin to protect the outside of a building. The tiles disclosed are fabricated in extremely small sizes, i.e., 18 cm×18 cm×6 cm, and the interior foam material which makes up the bulk of the material is generally of a low density. Significantly, there is no indication that the strength of the material disclosed is capable of absorbing sufficient energy from an explosion, and indeed the size of the disclosed tiles would not be ideally suitable for absorbing such energy.

[0007] Prior work by the inventors and others have developed methods for making foam glass tiles of a wide a variety of densities as described in U.S. Pat. No. 4,430,108 that can be used for building materials. While the techniques and methods disclosed were useful to manufacture then-standard size tiles of 4.25 in.×4.25 in.×0.25 in., this disclosure does not teach how to manufacture tiles of a larger size, for example 2 ft.×2 ft.×3 in. Likewise the tiles manufactured under these methods were relatively light, e.g., less than 10 lbs., and were not manufactured to withstand the effects of an explosion. To the contrary, these methods sought to optimize the thermal insulation properties of the material, and thus made smaller, lighter and weaker tiles.

[0008] While still others have worked on trying to make some large-size porous shaped bodies, these have been smaller in critical dimensions and of lower density than the present invention and not suitable to absorb a substantial amount of a shock wave which impacts the bodies associated with an explosion or earthquake. For example, U.S. Pat. No. 5,151,228 describes a process for manufacturing large-size porous shaped bodies of low density by swelling, in order to manufacture large-size cellular ceramic structural elements, e.g., multi-story high wall elements having a low weight. In the example, it discloses a tile 8.2 ft.×1.64 ft.×2 in., with a density of 26 lb./cu. ft. and a mass of 60 lbs. It also teaches to obtain a low density in order to optimize thermal insulation. Thus, this foam when exposed to a shock wave from an explosion or earthquake will absorb very little of the shock waves energy when it implodes.

[0009] Unlike the prior art discussed above, the tiles of the present invention are designed and constructed of various materials so that such tiles have properties which are ideal for withstanding the shock wave associated with large explosions or make a building or other structure resistant to earthquakes.

[0010] Thus, while the prior art is of interest, the known methods and apparatus of the prior art present several limitations which the present invention seeks to overcome.

In particular, it is an object of the present invention to provide a large, high density foam glass tile which can be used as a facade on both exterior and interior building walls.

[0011] It is another object of the present invention to increase from the commercially recommended density of 9.5 lb./cu. ft. to have a higher density of between 30-100 lb./ cu. ft., and more particularly 40-60 lb./cu. ft.

[0012] It is a further object of the present invention to increase the weight of the foam glass tile to be greater than 30 lbs., and more particularly over 65 lbs. and even more particularly over 100 lbs.

[0013] It is a further object of the present invention to provide a large, high density foam glass tile which can be used on the critical surfaces of buildings at high risk for terrorist attacks, in combination with cement, steel or other high strength building materials.

[0014] It is also an object of the present invention to provide a glass foam tile that can be used in surfaces of typical buildings and has the advantage of having a rigid structure that when exposed to shock waves having blast energy, the tile can absorb a substantial portion of that blast energy. It also has the advantage of being more resistant to earthquakes.

[0015] These and other objects will become apparent from the foregoing description.

[0016] It has now been found that the above and related objects of the present invention are obtained in the form of a large, high density foam glass tile which can be used as a facade on both exterior and interior building walls. The foam glass tile can also be used with other material to form a panel or a composite. The present invention may be used on the critical surfaces of buildings at high risk for terrorist attacks, in combination with cement, steel or other high strength building materials. The present invention may also be used in surfaces of typical buildings. The present invention has the advantage of absorbing a substantial portion of a shock wave caused by an explosion. The present invention also has the advantage of being more resistant to earthquakes. It must be noted that the terms glass foam, foam glass, ceramic foam and foam ceramic are interchangable in the present invention.

[0017] One embodiment of the present invention is a larger, higher density foam glass tile with a closed pore outer skin that has an increased strength. These heavy foam glass tiles will absorb more energy from an explosion, withstand higher wind loading and other mechanical forces. The closed pore outer skin may either be formed naturally or mechanically by bonding a secondary glass surface. The closed pore outer skin may have various color and texture variations which will make the tile suitable for use as an exterior or interior facade of a building or other structure. The density of the foam glass tile of the present invention is increased from the commercially recommended density of 9.5 lb./cu. ft. to have a higher density of between 30-100 lb./cu. ft., and more particularly 40-60 lb./ cu. ft. The weight of the foam glass tile of the present invention is greater than 30 lbs., and more particularly over 65 lbs. and even more particularly over 100 lbs. And more particularly, the tile will have a closed pore structure.

[0018] The large foam glass tile of the present invention which is capable of being used as a building material for interior and exterior building surfaces and having less seams than smaller tiles and which has a surface area of 2 ft.×2 ft. or greater, and more particularly has a surface area of 4 ft.×4 ft. or greater. More particularly, such tile may have a thickness of at least 2 in. and, more particularly, at least 3 in., and even more particularly at least 4 in.

[0019] Another embodiment of the high density foam glass tile of the present invention is capable of absorbing a substantial portion of a blast shock wave when subjected thereto. More particularly, such high density foam glass tile has a density between 30-100 lbs./cu. ft. These high density foam glass tiles may be backed to form a composite building material by a rigid structure, such as an exterior concrete wall, building columns, structures located in or adjacent to garages or other building structures located in the interior or exterior of a building which are at risk of being exposed to potential blast shock waves. Even more particularly, such tile may be backed by cementaceous materials having a pozzolanic bond with the foam glass tile, or polymeric materials. Such tile may be part of a larger panel and such panel may also have hanging hardware provided therein, and may be mounted in a load bearing frame.

[0020] A further embodiment of the present invention is a ceramic-glass foam composite made from a surface layer, at least one layer of rigid foam glass and at least one backing layer. The surface layer may be made from materials suitable for absorbing blast energy, and more particularly suitable for protecting the composite from fragmentation, such as fibrous materials like graphite or Kevlar, or polymeric materials. The surface layer may also be a foam glass glazed outer surface of the rigid foam glass. More particularly, such tile has a density between 20-100 lb./cu. ft., and even more particularly between 30-80 lb./cu. ft. Such tile has a closed pore structure. The surface finish layer may either be formed naturally on the tile during the heating process or mechanically by bonding a secondary surface. The closed pore outer skin may have various color and texture variations which will make the tile suitable for use as an exterior or interior facade of a building or other structure. More particularly, the surface finish layer may be a non-foam layer, thus expanding upon the available color and texture variations available for architectural appeal. The backing protective layer may be comprised of one or more materials including, but not limited to, a fibrous composite, where such fibers are made of high tensile strength materials, such as graphite, Kelvar and/or fibreglass, or cementaceous materials, which may contain portland cement, reinforced portland cement, lime, aluminous cement, plaster, polymeric material, such as commercial thermosets and thermoplastics, concrete or reinforced concrete. Such backing layer may also be reinforced by metal, Kevlar or other supporting materials. A bonding promoter or adhesive may be applied between at least one foam glass layer and the backing layer. The composite may also have hanging hardware provided therein, and may be mounted in a load-bearing frame, and thus be capable of absorbing a substantial amount of shock waves and vibration energy.

[0021] Another embodiment of the present invention is a ceramic-glass foam composite comprising a foam glass tile and an inorganic cementaceous backing on the foam glass tile, whereby the composite is capable of absorbing a substantial portion of blast energy which it may be exposed to from a potential explosion. Such foam glass tile may have a closed pore outer skin, which may either be formed naturally or mechanically by bonding a secondary glass surface. The closed pore outer skin may have various colors and textures which will make the tile suitable for use as an exterior or interior facade of a building or other structure. More particularly, such tile has a density between 20-100 lb./cu. ft., and more preferably between 30-80 lb./cu. ft. Such tile may have a closed pore structure which may either be formed naturally or mechanically by bonding a secondary glass surface. Such inorganic cementaceous materials may contain portland cement, reinforced portland cement, lime, aluminous cement, plaster, polymeric material, concrete or reinforced concrete. The cementaceous backing may form a pozzolanic bond with the foam glass tile. Alternatively, the cementaceous material may bonded to the foam glass either by directly applying the cementaceous material or by applying a layer of bonding promoter, such as Elmer's pro bond concrete bonder adhesive-promoter. Even more particularly, hanging hardware may be installed in the cementaceous material either before the cementaceous material is fully cured or after the cementaceous material is cured. The present invention has the advantage of absorbing a substantial portion of a shock wave caused by an explosion, in particular, when the tile is exposed in the direction of the potential explosion.

[0022] An even further embodiment of the present invention is a foam glass panel comprised of one or more large, high density foam glass tiles which can be assembled into a lightweight building facade. Particularly, the closed pore structure is textured for architectural appeal, the tile has an interior portion and the tile outer skin includes an additive to make its surface appear a different color than the interior portion of the tile. More particularly, such panels can be used to make a building more resistant to earthquake damage than buildings made from conventional concrete panels.

[0023] The present invention relates to large, high density foam glass tiles which can be used as a facade on both exterior and interior building walls. The foam glass tile of the present invention can also be used with other materials to form a panel or a composite. The present invention may be used on the critical surfaces of buildings at high risk for terrorist attacks, in combination with cement, steel or other high strength building materials. The present invention may also be used in surfaces of typical buildings. The present invention has the advantages of being more resistant to earthquakes and/or wind loading.

[0024] Under one preferred embodiment of the present invention, the large, high density foam glass tiles are capable of absorbing more energy from an explosion than contemporary cement building materials, as well as withstand higher wind loads and other mechanical abuse. Such large, high density foam glass tiles may be fabricated in a variety of shapes, including but not limited to flat and/or curved shapes. Further, the large, high density foam glass tiles of the present invention are made from siliceous materials and gas forming foaming agents, including but not limited to carbonaceous organics (e.g., sugar and starch), carbon black, silicon carbide, carbonates and sulfates. There are many possible methods to fabricate ceramic foam panels with various densities, sizes, and surface finishes. U.S. Pat. No. 4,430,108 describes various foam glass products fabricated from fly ash and other additives with various densities, and surface finishes, the disclosure of which is incorporated by reference herein. Foam glass with various densities can be fabricated by varying the composition and type and concentration of cellulating agents. Viscosity of glass is the dominating parameter during the foaming process. In addition the pore structure, uniformity is dependent on the distribution and particle size of the cellulating agent.

[0025] In the preferred embodiment for use in resisting explosions, the foam glass tile of the present invention is larger and of a higher density than the traditional foam glass tiles discussed herein. In particular, the preferred foam glass tiles have a surface area of at least 2 ft.×2 ft. and more particularly at least 4 ft.×4 ft. in dimensions, and a depth of at least 2 in., and more preferably at least 3 in. and even more preferably at least 4 in.

[0026] Such large tiles are advantageous over conventional smaller tiles because the larger size allows the composite of tiles to have less seams than composites of smaller tiles conventionally used. Such seams can be detrimental to the structural integrity since seams in a tile surface weaken due to thermal expansion and contraction, and thus tend to crack. These seams are also a means by which water can penetrate behind the tiles, resulting in damage from a variety of processes, such as molds, insects, and the freeze-thaw cycle. In the freeze-thaw cycle, when water seeps into a tile and freezes it expands. When the water thaws, it contracts thereby causing the material to crack. When subjected to a shock wave caused by an explosion, an improperly sealed seam will allow the wave to penetrate behind the tiles, causing them to explode outward rather than absorbing the desired energy. Thus, by reducing the number of seams, the risk of having improperly sealed seams will be reduced. The larger tile surface also has the further advantage of reducing labor at the labor site, by requiring less pieces to be assembled, which in turn reduces labor costs.

[0027] Further, these foam glass tiles of the present invention are also denser and heavier than conventional foam glass materials used in construction. Preferably, the density of the foam glass tile of the present invention is increased from the commercially recommended density of 9.5 lb./cu. ft. to have a higher density of between 20-100 lb./cu. ft., and more particularly 30-80 lb./cu. ft. The weight of the foam glass tile of the present invention is greater than 30 lbs., and more particularly over 65 lbs. and even more particularly over 100 lbs. Although these densities and weights are higher than conventional foam glass, they still provide the advantage of being relatively less dense, and thus lighter than traditional cement products used in construction.

[0028] The foam glass tile of the present invention preferably has a closed pore outer skin, which thus provides the tile with increased strength and protects the tile against water, and the freeze, thaw cycle. The closed pore outer skin may either be formed naturally as taught in U.S. Pat. No. 4,430,108 or mechanically by bonding a secondary glass surface as taught in U.S. Pat. No. 5,069,960, the contents of which are incorporated by reference herein. Natural formation is advantageous because it does not require additional labor and quality control, and thus is more cost effective and less burdensome. Using a secondary glass surface may also be advantageous because such techniques allow the closed pore outer skin to have various color and texture variations which will make the tile architecturally attractive for use as an exterior or interior facade of a building or other structure. One way of making different color surfaces is by the use of different color additives, as is generally well known to those skilled in the art.

[0029] Another advantage of the high density foam glass tile of the present invention is that when it is exposed to a blast shock wave it is capable of absorbing a substantial portion of the shock wave. Because these tiles are capable of absorbing a substantial portion of a blast shock wave, they are particularly advantageous as building construction materials for interior and exterior surfaces of buildings which are at risk of exposure to explosions, such as government buildings, embassies and high visibility/famous buildings.

[0030] These high density foam glass tiles may be backed by a rigid structure, such as an exterior concrete wall, building columns, structures located in or adjacent to garages or other building structures located in the interior or exterior of a building which are at risk of being exposed to potential blast shock waves. To provide for additional reinforcement to exterior walls, such tiles may be backed by cementaceous or polymeric materials. Examples of cementaceous materials include, but are not limited to, concrete, reinforced concrete, portland cement, reinforced portland cement, lime, aluminous cement, plaster. Examples of polymeric materials include, but are not limited to, commercial thermosets such as polyesters, epoxies, polyurethane and silicones and commercial thermoplastic such as PVC, polyethylene, polystyrene, nylons and polyesters and fibers of various types, such as ceramic, carbon, glass, cellulose, graphite, Kevlar and polymer. The composition of the foregoing materials have properties which facilitate and improve the absorption of large forces. Such tile may also be part of a larger panel and such panel may also have hanging hardware provided therein, and may be mounted in a load bearing frame.

[0031] The foam glass tiles of the present invention are also thicker than conventional foam glass tiles. In particular, the foam glass tiles of the present invention are at least 2 in. thick, and are preferably at least 3 in. thick, and even more preferably at least 4 in. thick. The increased thickness of the tile adds to the volume and therefore, to the weight of the tile. The increased thickness gives the tile an increased stiffness, which reduces inadvertent fractures during handling, whether from manufacturing, transporting or building. The increased thickness will also permit the tiles to absorb more energy from explosions, exposures to earthquakes or other shock waves.

[0032] The selection of the particular size, thickness and density depends upon the use to which the tile is intended to be made. For example, if the tile is intended to be used to resist earthquakes, then the tiles should be optimized to be the lowest weight that can withstand the wind pressure. By contrast, if the tile is intended to protect a building or structure from shock waves associated with an explosion, then the tile should be optimized to increase its density to be strong enough to absorb such a shock wave. The desired thickness will depend upon the proximity of the exposed tile to the location of the potential explosion. For example, on the outside of a building, the thickness would have to take into account the distance of the tile to the nearest location where an automobile or truck with explosives may be parked. On the other hand, in an interior of a building, such as a support column, the proximity anticipated could be immediately next to such a column, although the likely anticipated explosive load would be substantially less.

[0033] For the purposes of resisting shock waves associated with an explosion, the tile of the present invention can be combined with a rigid backing to form a composite panel. When the composite panel is exposed to the shock wave, the exposed foam glass tile of the present invention will collapse or implode and thereby absorb a substantial amount of the shock wave energy to which it is exposed, thus protecting the rigid backing, which in turn protects the building or other structure. The rigid backing may be comprised of any one of the materials discussed above with respect to the rigid structure.

[0034] In the case of a tile to be used to make a structure resistant to earthquakes, a slighter lighter tile may be used with a rigid backing. The load caused by wind pressure which needs to be resisted by these tiles is related to the area between support columns. Thus, the greater the area between support columns, the more resistance and greater strength will be required from the composite tile with rigid backing. The thickness/density of the tiles to be used are accordingly defined by these parameters. Thus, selection of these properties should be optimized to provide the lightest system that can withstand the largest anticipated wind pressure sought to be resisted with an appropriate safety factor built in as is typically done in the construction industry. The tiles should be supported by a metal frame, which in turn is supported by structural metal supports of the building or other structure.

[0035] For aesthetic purposes, the tiles with a finished layer can be used on any surface subject to public view. Thus, if only one surface will be exposed to public view, than only that surface needs to have the tiles with a finished layer. On the other hand, if both sides of a wall sought to be protected by the present invention are subject to a public view, than a second tile with an appropriate finished layer can be used on the second exposed side, such as the interior of the building. Alternatively, other interior surfaces can also be used.

[0036] Another advantage of the tiles of the present invention is that such tiles are also heat insulating as well as fire proof. Thus, these tiles have an added advantage of being able to be used to protect a support column from a terrorist fire attack such as a Moltov cocktail, or other sources of fire. The use of the tiles of the present invention can thereby either prevent and/or delay the destruction of such support columns, thereby increasing the likelihood that occupants of an attacked building will have sufficient time to evacuate.

[0037] Another embodiment of the tiles of the present invention can be used to retrofit existing buildings or other structures. In particular, the tiles can be mounted on the potentially exposed walls. If such walls are already sufficiently rigid, then the tiles can be mounted directly thereon. If not, then the tiles can be mounted on an appropriate rigid structure or backing protective layer to form a panel, which in turn can be mounted on the exposed wall. Appropriate backing protective layer may be a fibrous composite, where such fibers are made of high tensile strength materials, such as graphite, Kelvar and/or fibreglass, or cementaceous materials, which may contain portland cement, reinforced portland cement, lime, aluminous cement, plaster, polymeric material, reinforced concrete. Such backing layer may be reinforced by metal, Kevlar or other supporting materials. A bonding promoter or adhesive, such as Elmer's pro bond concrete bonder adhesive-promoter, may be applied between the at least one foam glass layer and the backing layer. The composite may also have hanging hardware provided therein, and may be mounted in a load-bearing frame, and thus be capable of absorbing a substantial amount of shock waves and vibration energy.

[0038] In the preferred embodiment, the tile of the present invention can be manufactured using raw materials which include (but are not necessarily limited to) silica, fly ash, volcanic ash, diatomaceous earth, siliceous minerals, alkali carbonates, calcium and magnesium minerals such as dolomite, and gypsum, sodium silicate, borax, glass powders (such as cullet) and foaming agents. The foaming agent can be selected from carbonaceous organics such as sugar and starch, carbon black, silicon carbide, carbonates, sulfates and other like materials.

[0039] To make the tile of the present invention, various methods can be used. In one embodiment, the starting raw materials to make the tile are blended together with water to form a homogenous slurry. It must be noted that even though the preferred method of mixing is wet, nonetheless, dry blending may be selected depending on type of raw materials used in foam glass formulation. For instance, when glass powders (soda-lime glass cullet) is used as major raw material, the gasifier can be dry blended in a conventional mixer, such as a ball mill. When wet blending is used, the solid content of the slurry is preferably between 30-80 wt %, and more preferably between 50-70 wt %.

[0040] The slurry is then dried in a conventional dryer such as a spray dryer to produce dry powders. If a static dryer is used, then the dried aggregates are ground to form dried powders. The resulting powdery product is then calcined to a temperature at which the viscosity of the resulting foam glass is preferably between 10⁷ to 10² poise, more preferably between 10⁵ to 10³ poise. Calcination may be carried out in a reducing environment to effectively pyrolize organic gasifiers to microscopic carbon containing compounds. In the case of silicon carbide as foaming agent, calcination may be carried out in a neutral air atmosphere. When glass powders are used as major ingredients in the foam glass formulations, calcination step is the same as the foaming step. Calcination can be carried out in a rotary kiln, in stationary molds in a kiln, or in a fludizied bed reactor heated primarily by a hot gas.

[0041] The calcined product may require pulverization if calcination for instance is carried out in stationary molds. Calcination by fludization may not require pulverization, if particles do not agglomerates in the fludized bed. The calcined powders are screened preferably through 20 mesh screen, more preferably through 40 mesh screen to remove the coarse particles.

[0042] The powders are then molded into desired shapes, in a metal mold. The preferred metals are stainless steel and chromium containing alloys such as Inconel™ Inco Alloys. Inconel™ type alloys are preferred, since they can resist thermal cycles, and oxidation better than stainless steels. Mold release agents are preferably used to ease the de-molding process, and also minimize adhesion of the foam glass to the metal which can cause unwanted cracking in the finished foam glass product. The mold releasers should withstand the peak firing temperature, as a result inexpensive refractory oxides such as high silica minerals, high alumina mineral powders such as diatomaceous earth, silica, and various clays can be used. Secondary oxide glazing or surface coating can be applied over the molded foam glass powder precursor, to produce additional surface effect in the finish foam product.

[0043] The molds are then transferred into either electric or gas fired kilns that can accommodate the molds with a temperature uniformity better that 50° C. across any dimension of the mold, more preferably better than 20° C. The heating rate is selected based on the foam glass thickness, and product loading inside the kiln. Normally the heating rate may fall between 2-10° C./min., and preferredly between 3-5° C./min. At the peak foaming temperature the foam glass viscosity is between 10⁵ to 10³ poise. The soak time at the peak firing temperature depends on the foam glass dimensions. The soak time also effects the surface glazing thickness. Longer soak time results in the formulation of thicker surface glaze or skin. The larger foams may require longer soak times to ensure temperature equilibration throughout the foam body.

[0044] During cooling cycle to room temperature, thermal stresses across the foam glass need to be minimized to ensure a strong product free of residual thermal stresses. As a result the cooling rate around the annealing and strain point temperatures which correspond to an approximate viscosity range of 10¹² to 10¹⁶ will be relatively slow, between 1-5° C./min, preferably between 1-3° C./min. Above and below this temperature range, depending on the foam dimensions, the average cooling rate is from 2-10° C. min., preferably 3-5° C./min.

[0045] The annealed foam glass will be de-molded, and trimmed on its sides if needed. Trimming can be done by various means such as grinding and cutting. Cutting with an abrasive resistant blade such as carbide blade is preferred, since it produces less dust than grinding. It should be noted that the foam glass dust is primarily composed of non-crystalline silica, which is much less harmful than crystalline silica dust, such as concrete dust.

[0046] The foam glass board produced can be used as a stand alone tile, or be used in fabrication of foam glass composite panels. All the trimming and dust collected during the final step will be ground and added to the starting raw materials. In addition, any product reject, such as broken tiles or panels will be ground and recycled back into the starting raw materials.

[0047] It will be understood by those skilled in the art that the foregoing method of making the tiles of the present invention could be modified or other methods of fabrication can be used without departing from the spirit and scope of the invention.

[0048] As discussed above, an aspect of the present invention is the inclusion of backing materials to the foam glass tile. Examples 1 and 2, below illustrate the application of portland cement as backing material. These examples demonstrate that pozzolanic bonding occur naturally at the interface of the foam glass tile and the cement containing backing layer.

[0049] Alternatively, other inorganic cementaceous backing materials can be applied over the foam glass tile to a desired thickness, preferably initially as a paste which will harden to a solid backing. The backing can be made into a multilayer structure, where lime or portland cement will be the adjacent layer to the foam to develop pozzolanic bond, followed by other cementaceous over layers. The cement backing materials can be reinforced by addition of fibers of glass, graphite, ceramics, polymers such as cellulose, metals, Kevlar or alike.

[0050] It is also possible to join the foam glass tile with other solid layers via a joining compound. For instance, appropriate contact adhesives can be applied between a sheet of metal and foam glass. One such adhesive that can be used with aluminum sheets is a silicone based adhesive. Other examples are application of a polymeric foam between the foam glass and another backing material to protect the polymeric foam. Polyurethane foam and cement board are examples of this type of multilayer backing. The advantage of polyurethane foam is that, it can be applied in place into a gap between a pre-positioned foam glass board and a sheathing back layer. Polymeric backing are particularly useful to reduce fragmentation of the brittle layers such as foam glass and more so of the cementaceous layers. The backing layer may contain multiple layers of foam glass bonded together with cement, polymeric foams or other contact adhesives.

[0051] The foam glass backing may be selected to have different density than the main foam glass panel for maximum absorption of shock wave energy. The front face of the foam glass layer normally is glazed as discussed before. However, a surface finish may be applied according to the present invention to impart additional protection and aesthetic appearance to the composite foam glass structure. The surface finish can be applied before or after the backing layers are installed. The finish can be a textured cementaceous and/or polymeric overlayer to display for instance a brick facing or marble type appearances. These finishes can be molded in place over the foam layer or be adhered to the foam as a separate sheathing via a contact adhesive or a cement layer with pozzolanic activity. These finishes would impart additional architectural appeal to the foam glass composite structure. In addition, colorants can be used in surface finishes to impart desired colors to the structure. Fibrous materials can be added to the surface finishes to impart additional reinforcement and to reduce fragmentation upon shock wave reception. Various UV protecting compounds can be added to the surface finishes if desired.

[0052] The thickness of both backing layers and the surface finishes can vary upon design specifications, required energy absorption and strength. The application of a surface finish may be unnecessary since the natural glazing of the foam glass panel as fired may be aesthetically sufficient.

[0053] A foam glass tile was made by blending the raw materials set forth in Table 1 below:

[0054]

	TABLE 1
	Fly ash (calcined type F)	2000 g
	Silica flour	2000 g
	Sodium Carbonate	600 g
	Sodium meta silicate, penta hydrate	1600 g
	Potassium carbonate	0
	Borax	0
	sugar	120 g
	Water	1415 g

[0055] The resulting slurry was dried, and the powder mixture was calcined at 950° C. for about 45 minutes to react the raw materials, and decompose sugar to finely, and evenly dispersed carbonaceous phase. The calcined product was ground to fine powders, placed in an Inconel™ mold, and was foamed by heating to about 850° C. and soaked at that temperature for approximately 30 minutes. The resulting foam glass was annealed to room temperature and de-molded. The resulting foam glass had a density of about 25 lb./cu. ft., a dark greenish color, and a completely glazed surface. The pore structure was uniform with an average pore size of about 2 mm. After trimming the edges the tile had a dimension of approximately 16 in.×12 in.×3 in.

[0056] The foam glass-concrete composite tile according to the present invention was made by the following method. The foam was trimmed around its sides and was framed with strips of plywood around its perimeter with the glazed surface faced down, leaving a gap of about 1 in. above the tile to receive cement. A portland cement sand mix (Quickrete sand mix) was prepared according to the manufacturer instruction. The resulting paste placed over the exposed face of the foam which was in contact with the mold during firing, and was not trimmed to expose the cell structure before making the composite tile. The concrete was allowed to cure for about 28 hours, before being removed from the form. The interface between the foam and concrete layers were completely sealed indicating a strong cementaceous pozzolanic bond formation.

[0057] A foam glass tile was made by blending the raw materials set forth in Table 2 below:

[0058]

	TABLE 2
	Fly ash (calcined type F)	2000 g
	Silica flour	2000 g
	Sodium Carbonate	320 g
	Sodium meta silicate, penta hydrate	800 g
	Potassium carbonate	320
	Borax	400
	sugar	120 g
	Water	1370 g

[0059] The resulting slurry was dried, and the powder mixture was calcined at 900° C. for about 30 minutes to react the raw materials, and decompose sugar to finely, and evenly dispersed carbonaceous phase. The calcined product was ground to fine form powders, was placed in an Inconel™ mold, and was foamed by heating to about 860° C. with an average heating rate of about 3.5° C./min. The resulting foam was annealed to room temperature and de-molded. The foam glass had a density of about 52 lb./cu. ft., a greenish color, and a completely glazed surface. The pore structure was uniform with an average pore size of about 1-2 mm. After trimming the edges the tile had a dimension of approximately 17 in.×12 in.×1.4 in.

[0060] The foam glass-concrete composite tile according to the present invention was made by the following method. The foam was trimmed around its sides and was framed with strips of plywood around its perimeter with the glazed surface faced down, leaving a gap of about 1 inch above the tile to receive cement. A thin layer of Elmer's pro bond concrete bonder adhesive-promoter was applied to the foam. A portland cement mortar mix (Sakrete mortar mix) was prepared according to the manufacturer instruction. The resulting paste was placed over the exposed face of the framed foam glass tile and leveled. This was the face in contact with the firing mold, and was not trimmed to expose the cell structure before making the composite tile. The concrete was allowed to cure for about 28 hours, before being removed from the form. The interface between the foam and concrete layers were completely sealed indicating a strong cementaceous pozzolanic bond formation.

[0061] Now that the preferred embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is to be construed broadly and limited only by the appended claims and not by the foregoing specification.