Structural material with fire retardant properties and method of making same

Abstract

The invention relates to compositions for use as structural construction materials with fire retardant properties and methods of making same. The composition comprises 26-40 wt.% water glass, 2-5 wt.% NaOH, 18-28 wt. % FeSi, 30-40 wt.% fly ash, 1-10 wt.% metakaolin, and 1-6 wt.% mica. The methods of making the material controls two exothermic reactions to control the density of the material by adjusting the amount of NaOH and FeSi, or by starting the two exothermic reactions at separate times, where the first reaction provides optimal activation energy for the second reaction. The material is manufactured by dissolving the NaOH in water glass to obtain an aqueous solution, mixing ferrosilicon, fly ash, metakaolin, and mica all at once or individually into the aqueous solution to obtain a slurry, pouring the slurry onto a surface, leveling the slurry, and allowing the slurry to set to obtain the structural material.

Description

STRUCTURAL MATERIAL WITH FIRE RETARDANT PROPERTIESAND METHOD OF MAKING SAMECROSS-REFERENCE TO RELATED APPLICATION AND CLAIM TO PRIORITY

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 734,587, filed December 16, 2024, the disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION

[0002] The invention relates to structural material compositions for use as construction materials, e.g., in building construction, such as for residential or commercial buildings. In particular, the invention relates to structural material compositions with fire retardant properties and methods of making same.BACKGROUND OF THE INVENTION

[0001] Building or structural materials are manufactured with a wide array of materials and techniques. The materials are used in building for specific purposes, such as insulation, sound proofing, strength, etc. For example, gypsum board or cement board are commonly used to construct interior walls or exterior sheathing for buildings to provide insulation, water resistance, and / or strength to the wall surface.

[0002] U.S. Patent No. 10,730,796 to Kluj et al. discloses a hydraulically binding composition used to produce an inorganic fire-protection and / or insulation foam. The composition includes: (i) a hydraulic binder, (ii) a blowing-agent mixture, (iii) a thermally expandable compound, and (iv) optionally a foam stabilizer, where the at least one thermally expandable compound, depending ona particle size thereof and an adjusted density of a foamed composition, is present in a quantity such that a foam structure of the foamed composition is not destroyed by expansion thereof during heating of the composition above an onset temperature thereof.

[0003] U.S. Patent No. 10,427,977 to Reid et al. discloses a foamed geopolymer for use as a fire- resistant sealant material, a method of sealing an aperture or cavity for housing services in a building comprising (i) applying a curable foamed geopolymer composition to the aperture or cavity; and (ii) curing the foamed geopolymer composition, thereby creating a seal in the aperture or cavity; and wherein the cured foamed geopolymer has fire-resistant properties, and a kit of parts for preparing a foamed geopolymer for use as a fire-resistant sealant material, comprising (i) a container holding a dry mixture of components suitable for preparing a foamed geopolymer including a blowing agent and (ii) a container holding an aqueous alkaline liquid mixture of components suitable for preparing a geopolymer.

[0004] However, neither the hydraulically binding composition nor the foamed geopolymer described above have structural integrity to replace gypsum or cement board.

[0005] U.S. Patent No. 9,919,974 to Gong et al. discloses a composite binder comprising one or more Class F fly ash materials, one or more gelation enhancers, and one or more hardening enhancers, wherein each of the one or more Class F fly ash materials comprises 15 wt. % or less calcium oxide, and wherein the composite binder is a Portland cement-free binder for concrete. Also provided are Geopolymer Composite Cellular Concretes (GCCCs) including the composite binder and methods of making these GCCCs. This patent mentions high fire resistance as cellular concrete is approximately twice as fire resistant as dense concrete. However, cellular concrete is not a suitable replacement for gypsum or for use in cement board.

[0006] U.S. Patent No. 8,869,477 to Ha et al. discloses formed building materials comprising sequestered CO2. The building materials include a composition comprising a carbonate / bicarbonate component. Additional aspects of the invention include methods of making and using the formed building materials. In some embodiments, additives such as fire resistance agents such as perlite, vermiculite, boric acid, and combinations thereof are added. However, the primary goal of this patent is to sequester CO2 to reduce the risks of climate change.

[0007] U.S. Patent Nos. 6,264,734 and 6,350,308 to Dickens disclose a method for forming building products from heat insulated material and building products formed in accordance therewith including providing a mold configured with inner dimensions equal to the desired configuration of the building material block; providing a fluid mixture of heat insulating material formed from a predetermined composition of ingredients; providing at least one rigid reinforcement member and placing the reinforcement member in the mold; introducing the fluid mixture into the mold with the at least one reinforcement member and allowing the fluid mixture to harden within the mold and removing the mixture from the mold resulting in a block of reinforced heat insulating building material. The invention is also directed to a block of reinforced heat insulated building material according to the method described.

[0008] U.S. Patent No. 5,749,960 to Belyaeva discloses a formulation for producing a heat insulating material and a method for making same that uses an exothermic reaction, which depends on sodium silicate, sodium hydroxide, firing clay and iron silicon. The iron silicon reacts in the alkaline medium in an exothermic reaction that results in a high release of heat. As a result of the exothermic reaction, the formulation heats up to temperatures near 100° C. The formulation then starts to harden. The evolved water steam and hydrogen form pores, which allows for an increase of many times the volume of the resulting heat insulating material. The self-heating reaction causesthe formulation to lose water, which leads to an increase in the dielectric qualities of the material. Additionally, the iron silicon raises the heat resistance of the resulting heat insulating material.

[0009] The above-described building construction materials are directed to heat insulating building materials, but do not teach or suggest fire retardant properties.

[0010] U.S. Patent No. 4,946,811 to Tuovinen et al. discloses a method for preparing iron silicate slags, by means of mixing with ferroalloy slag, to a molten slag which can be defibrated into fire- resistant and chemically resistant fibers. The composition for the molten slag is 15-25% Fe, 45- 69%, SiO2 0-5% CaO, 4-10% MgO, 5-15% A12 03 and 0.5-3% Cr (percentages by weight).

[0011] U.S. Patent No. 4,262,055 to Russell et al. discloses a fire protection material, suitable for use as a coating for structural members, produced by mixing a lightweight refractory aggregate including magnesia with ammonium phosphates in aqueous solution, wherein the composition of the phosphates is at least about 20% by weight polyphosphates, balance orthophosphate, and allowing the mixture to set as a fire protection coating or body having a bulk density of not more than about 50 lb. / ft.3.

[0012] Although the above-described fibers and coatings disclose fire protection properties, they do not provide structural integrity as a building component.

[0013] It is therefore desirable to provide building materials that provide fire retardant properties and that may be used as a substitute for currently available structural building components such as gypsum board, cement board, or other analogous materials.SUMMARY OF THE INVENTION

[0014] An object of the invention is to provide compositions for use as structural construction materials with fire retardant properties and methods of making same.

[0015] It is another object of the invention to provide a structural composition to make materials and products to replace magnesium oxide board, cement board, or gypsum board in building construction and assemblies, as interior walls, exterior sheathing, fire stops, or area separation walls.

[0016] It is another object of the invention to provide a structural material composition comprising water glass (aqueous sodium silicate), sodium hydroxide, fly ash, ferrosilicon, metakaolin, and mica.

[0017] It is another object of the invention to provide a structural material composition comprising 26-40 wt.% water glass (aqueous sodium silicate), 2-5 wt.% sodium hydroxide (NaOH), 18-28 wt. % ferrosilicon (FeSi), 30-40 wt.% fly ash, 1-10 wt.% metakaolin, and 1-6 wt.% mica.

[0018] It is another object of the invention to provide a process of making the structural material without the use of enclosed molds or reinforcing elements to save on the cost of production and raw materials.

[0019] It is another object of the invention to provide a process of making the structural material by controlling two self-starting exothermic reactions in a way that results in control of the density of the structural material, preferably by adjusting the amount of sodium hydroxide and ferrosilicon, or by starting the two exothermic reactions at separate times, where the first reaction provides optimal activation energy for the second reaction.

[0020] It is another object of the invention to provide a method of making a structural material having fire retardant properties comprising the steps of dissolving sodium hydroxide in aqueous sodium silicate to obtain an aqueous solution, mixing ferrosilicon, fly ash, metakaolin, and mica into the aqueous solution to obtain a slurry, pouring the slurry onto a surface, leveling the slurry, and allowing the slurry to set to obtain the structural material.

[0021] It is another object of the invention to provide a method of making a structural material having fire retardant properties comprising the steps of dissolving sodium hydroxide in aqueous sodium silicate to obtain a aqueous solution, mixing ferrosilicon, fly ash, metakaolin, and mica to obtain a dry mixture, mixing the dry material into the aqueous solution to obtain a slurry, pouring the slurry onto a surface, leveling the slurry, and allowing the slurry to set to obtain the structural material.

[0022] It is another object of the invention to provide a method of manufacturing a structural material having fire retardant properties with a kit comprising a two or three component system, wherein each component contains pre-weighed materials that can be opened and mixed together to create a slurry that can be poured and set to make the structural material of the invention. In a two-component system, a first component is a container containing a mixture of fly ash, ferrosilicon, metakaolin, and mica, and a second component is a container containing a NaOH / sodium silicate aqueous solution. Alternatively, in a three-component system, the second component is a container containing NaOH and a third component is a container containing aqueous sodium silicate.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are incorporated in and constitute a part of the specification. The drawings, together with the general description given above and the detailed description of the exemplary embodiments and methods given below, serve to explain the principles of the invention. In the drawings:

[0024] FIG. 1 is a diagram showing the process for making a structural material composition of the invention;

[0025] FIG. 2 is a photograph of a sample of an exemplary embodiment of the structural material of the invention;

[0026] FIG. 3 is a graph comparing the set time and density as a function of the amount of silicon contained in the ferrosilicon alloy;

[0027] FIG. 4 is a graph comparing the set time and density as a function of the amount of ferrosilicon alloy in the structural material;

[0028] FIG. 5 is a graph comparing the set time and density as a function of the amount of aqueous sodium silicate in the structural material;

[0029] FIG. 6 is a graph comparing the set time and density as a function of the amount of fly ash in the structural material;

[0030] FIG. 7 is a graph comparing the set time and density as a function of the amount of sodium hydroxide in the structural material;

[0031] FIG. 8 is a graph comparing the set time and density as a function of the amount of metakaolin in the structural material; and

[0032] FIG. 9 is a graph comparing the set time and density as a function of the amount of mica in the structural material.

[0033] FIG. 10 is a photograph of a sample of an exemplary embodiment of the structural material of the invention;

[0034] FIG. 11 is a photograph of a sample of an exemplary embodiment of the structural material of the invention;

[0035] FIG. 12 is a photograph of a sample of an exemplary embodiment of the structural material of the invention;

[0036] FIG. 13 is a photograph of a sample of an exemplary embodiment of the structural material of the invention;DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Reference will now be made in detail to exemplary embodiments and methods of the invention. It should be noted, however, that the invention in its broader aspects is not necessarily limited to the specific details, representative materials and methods, and illustrative examples shown and described in connection with the exemplary embodiments and methods.

[0038] The invention provides a structural material composition for use to make structural materials having fire retardant properties. Preferably, the structural material composition may be used to make materials and products to replace magnesium oxide board, cement board, or gypsum board in building construction and assemblies. The structural material composition of the invention is comprised of water glass, sodium hydroxide, fly ash, ferrosilicon, metakaolin, and mica.

[0039] The structural material composition refers to the quantitative makeup of the initial chemical compound used to make the structural material composition, i.e., created by adding all of the ingredients together. The structural material composition is reported in weight ratio of the ingredients. The structural material composition and weight ratios used do not account for the mass loss from evaporation and gas evolution that occurs during hardening / setting. The weight ration of the initial composition is specified because the composition will change after the reactions occur and weight ratios may differ due to mass loss due to evolution of gasses during the reactions. Unless otherwise indicated, all percentages used herein refer to weight percent.

[0040] The following table summarizes the ingredients used to make up the structural material composition of the invention:TABLE 1 : Structural material composition (all % are weight ratios to the weight of the total mixture)

[0041] Water glass, also known as liquid glass, soluble glass, or aqueous sodium silicate, is a compound containing sodium oxide (Na2<3) and silica (SiCh) that forms a glassy solid that is soluble in water. The water glass reacts in the method of the invention to form a geopolymer structure in the structural material composition. For the structural material composition, the water glass preferably has a modulus (ratio of silica to sodium oxide) of 2.5 to 3.4, more preferably 3.00 to 3.25. For use herein, the water glass is preferably dissolved in water to become an aqueous solution of 35 to 42% solids, more preferably 37 to 39%. The aqueous water glass preferably has a pH of 11 to 12.5. The pH of the aqueous water glass refers to the intrinsic pH value of the water glass as sourced from a manufacturer (for example, PQ Corp aqueous sodium silicate (water glass) used in the invention has a reported pH of 11-12). The aqueous water glass used is preferably present at 26 to 40% by weight, more preferably 30 to 35%, of the structural material composition.

[0042] Sodium hydroxide (NaOH), also known as lye, soda, or caustic soda, used in the invention is preferably in non-aqueous form. The dissolution of sodium hydroxide during the manufacturing process provides energy for subsequent reactions as described below. The dissolved sodiumhydroxide also aids in the reaction to form the final product. Addition of sodium hydroxide to the water glass before the addition of the other ingredients aids in mixing and pouring by lowering the viscosity of the aqueous waterglass. The sodium hydroxide is preferably present at 2 to 5% by weight, more preferably 2.6 to 3.5%, of the structural material composition.

[0043] Ferrosilicon is an alloy of iron and silicon, preferably having a silicon content of 70% or more, and ferrosilicon of 75% Si works sufficiently. Low silicon content ferrosilicon may result in samples not expanding during setting. The ferrosilicon reacts with the aqueous solution of water glass and sodium hydroxide to provide energy to evaporate water and to provide a hardened final product. Silicon in the ferrosilicon also reacts to eventually form part of the geopolymer structure of the final product. For the composition of the invention, ferrosilicon is preferably present at 18 to 28% by weight, more preferably 19 to 22%, of the structural material composition.

[0044] Preferably, the fly ash used in the composition is Class-F ash. Any standard or common Class-F fly ash obtained from boilers and like furnaces used for the combustion of pulverized coal, particularly of a bituminous or anthracite type, and especially from coal-fired, steam-generating plants of electrical utilities, is suitable for use as the fly ash component of this invention. The fly ash provides cementitious properties to the composition and contributes to fire resistance. The fly ash also helps form the geopolymer of the final product. The Class-F fly ash is preferably present at 30 to 40% by weight, more preferably 33 to 35%, of the structural material composition. Fly ash used in experimentation was from Diversified Materials Inc., with a 16% particle size on a USS 325 mesh size, and a specific gravity of 2.3 to 2.7.

[0045] Metakaolin is the anhydrous calcined form of kaolinite, a clay mineral. Metakaolin is typically obtained by dehydrating kaolinite. The metakaolin is a pozzolan that helps improve the setting time of the composition and improve mechanical properties of the final product. Otherpozzolans can be substituted, in part or whole, for the metakaolin. For the invention, metakaolin is preferably present at 1 to 10% by weight, more preferably 4 to 6 % by weight, of the total initial composition While no specific metakaolin is preferred, the metakaolin used in experimentation was from Mineral Resources Inc. and had a median particle size of 1.4 micron.

[0046] Mica is a silicate mineral common in igneous and metamorphic rock. The crystal structure of mica lowers crack propagation and provides low thermal conductivity and fire resistance in the final product. For the invention, muscovite, also known as common mica, potash mica, or isinglass, is preferred. The mica is preferably present at 1 to 6% by weight, more preferably 2 to 3% by weight, of the total initial composition. An example of mica as used in experimentation is from Pacer Minerals, with a particle size specification of 25 to 45% on USS 325 mesh and 50 to 70% below USS 325 mesh. While no size range or distribution was experimented with, the size range / distribution used for experiments was 85% on 325 USS mesh size or less according to the manufacturer.

[0047] FIG. 1 outlines the process of making the structural composition of the invention. FIG. 2 is a photograph of a cross-section of the structural material of the invention.

[0048] First, the dry ingredients (ferrosilicon, fly ash, metakaolin, and mica) are mixed to prepare a dry mixture. There is no preferred type of mixing or mixer, although, in the experiments, the dry ingredients were mixed by hand with a stirring stick or by shaking the dry ingredients in a closed container. The order of addition does not matter when mixing ferrosilicon, fly ash, metakaolin, and mica together to form a dry dispersed mixture (box 100). Sufficiency of mixing was determined visually when the particles looked well mixed, which is easily determined because they are distinctly different colors. Once the dry ingredients are well mixed the dry mixture is set aside.

[0049] Next, sodium hydroxide is added to water glass in a vessel to obtain an aqueous solution. The vessel may be any open container such as a drum, bucket, vat, concrete mixer, etc. The sodium hydroxide is mixed into the water glass with a mixing device until the sodium hydroxide is dissolved (box 102). The dissolution of sodium hydroxide in the aqueous water glass starts a first exothermic reaction that raises the temperature of the aqueous solution until it reaches a maximum temperature, usually 130 to 140° F, but may vary depending on the cooling efficiency of the system. The first exothermic reaction is summarized by the following equation: NaOH <S) + H2O «-> Na+(aq) + OH'(aq) + H2O. Adding sodium hydroxide to the water glass before the addition of the dry mixture advantageously reduced the modulus of the water glass, which lowers the viscosity and makes the mixture easier to work with / pour and to mix in the other ingredients, while still allowing the final composition to have sufficient mechanical strength.

[0050] After the aqueous solution reaches its peak temperature and cools to a temperature of 95 to 110°F, the dry mixture is added to the vessel containing the aqueous solution (box 104) to obtain a slurry. The dry mixture is added all at once. Alternatively, the dry ingredients may be added to the aqueous solution individually while mixing. At that time, the heat generated from the first exothermic reaction is sufficient to drive (provide activation energy for) a second exothermic reaction between the ferrosilicon and the aqueous sodium hydroxide. For example, for 700-800 g of structural material, which is enough to pour a 1 ’xl’x 'A” sample, the optimal time to wait before adding the dry mixture is between 3-4 minutes after mixing the sodium hydroxide with the water glass for the temperature to reach around 1 10° F. The optimal time to wait will depend on the volume of the mixture, as a larger volume will require a longer time for heat to dissipate. Preferably, the optimal time to wait before adding the dry mixture is the time it takes for the reaction in the vessel to reach the maximum temperature and then cool to 95 to 110°F.

[0051] After all the dry mixture is added to the aqueous solution (box 104), the resulting slurry is stirred with a mixing device in the vessel before it is poured onto a setting surface (box 106). This setting surface is preferably a paper or fdm that acts as the backing / facing paper to provide a smooth surface to the final cured product. Although the use of paper or film is preferred, the structural material need not have the backing paper or film resulting in a bare surface. Alternatively, other backing materials, such as fiber glass cloth or mesh, may be used. These backing and facing materials are not needed to provide structural support but to create a uniform surface which may be more desirable for building products, particularly for their aesthetics. The slurry is then leveled with a lathe or some other sort of leveling device that is passed along the surface of the slurry to obtain uniform thickness of the slurry, resulting in a structural material of uniform thickness. For example, if the slurry is poured onto a conveyor belt, a scraping blade or a roller spaced at a fixed distance from the conveyor belt may be used to level the slurry. The fixed distance is determined by the desired thickness of the desired structural material composition. Other methods for leveling the slurry may be used.

[0052] Once leveled, a second sheet of paper, if desired, may then be applied to the top surface. Essentially, the slurry is preferably sandwiched between two layers of paper. With the use of the conveyor belt configuration described above, the structures of the conveyor only need to have inner dimensions that match the final width of the final product (e.g., fixed rails or guards on either side that prevent the slurry from spreading out wider than the intended width of the product). The thickness can be controlled by the expansion of the material and / or a flattening device, such as a roller or scraper, to set at the final thickness of the product (hardened structural material composition) before it has fully set. The length of the form can be set to the final length or continuous. In the continuous process (e.g., conveyor belt style method), the material can be setas a long piece with final width and thickness, and then cut to the final length similar to how traditional gypsum boards are made.

[0053] In another embodiment, a block mold or form is used to control the length and width of the slurry as it is poured onto the setting surface, which allows for material expansion as the material sets.

[0054] The structural material composition is then allowed to set, preferably in one hour to 90 minutes. Set means to harden, which is accompanied with expansion in this process (volume increase). The second exothermic reaction is summarized by the following equation: 2Na++ 2 OH' + Fe+ Si + H2O Na2SiOa + Fe + 2H2. By separating the two exothermic reactions, the overall energy produced is controlled, thus achieving desired expansion of the structural material composition. Expansion is limited to achieve higher density and thus mechanical strength while still providing porosity to aid in thermal properties such as thermal conductivity. There is expansion when the ferrosilicon starts to react, which is controlled by the amount of NaOH and FeSi used, as well as the temperature of the solution the ferrosilicon is mixed into. Excessive expansion is not desired because it causes 1) the material to set too early resulting in the inability to evenly pour the material on a settling surface; and 2) large, non-uniform pores throughout the material. Pore size is the open-air gaps in the bulk material, an ideal pore size is around 1 cm or less. The pores are desired to be large enough to promote insulating properties, but not so large that they compromise mechanical strength and negatively impact the mechanical properties of the material. The expansion should be controlled such that expansion occurs only after the structural material composition has been handled and distributed on its desired setting surface and should progress at a slow enough rate limiting the rate of reaction to minimize pore size distribution inthe hardened material. Final material is the material after expansion and setting is complete, and the mass and composition have changed due to evaporation of H2O and evolution of H2 gas.

[0055] When the structural material composition is finally set or hardened (box 108), it should have a final density of 0.38 to 0.5 g / cm3. This translates to a 4’x8’x5 / 8” board weighing around 40 to 55 lbs. This is noticeably lighter than Type X sheet rock (which is a fire-rated gypsum board reinforced with noncombustible glass fibers) of the same size which can weigh as much as 70 lbs., and the lightweight version of Type X sheet rock still weighs as much as 65 lbs. This is also lighter than 4’8’xl / 2” magnesium oxide (MgO) board and cement board, which can weight 75 lbs. or more. The final product replacing gypsum, MgO, or cement board includes the hardened structural material composition sandwiched between two layers of paper / film.

[0056] Overall, the method of the invention provides a structural material composition that is fire resistant. This process is superior to prior art processes in that enclosed molds or reinforcing elements are not required, which saves production cost as well as the cost of the raw materials needed.

[0057] The process is accomplished by controlling the two self-starting exothermic reactions in a way that results in control of the density of the material (controlling the density in turn allows for control of the dimensions of the final product, for example the thickness when width and length are fixed). The amount of energy produced by the reactions correlates to the speed at which the structural material composition expands and sets, and ultimately, the density of the final product. If energy is produced too quickly, the slurry will expand rapidly and set too quickly to be poured into the desired shape. The quick evolution of the reaction also creates large pores that are detrimental to the mechanical properties of the final product. If the reaction does not produce enough energy at the proper rate, the structural material composition takes too long to set resultingin a final product that may be too dense (not enough expansion). Long setting time also makes manufacturing costlier. Higher density also means more material is used for the same volume which increases cost. An even more detrimental effect of increased density is that it will make the material cumbersome to move / work with, and negatively impact the thermal properties of the material (less pores to absorb thermal energy due to the heat capacity of the air in the pores).

[0058] Due to these drawbacks, the process of the invention must optimize the speed of the reaction with the final density of the material to produce sheets of a desired thickness and density, which are self-supporting and do not need reinforcing elements. This allows the material to be handled like gypsum board or cement board, while also being lighter, more thermally insulating, quicker to set (dry and harden), and more energy efficient to produce (since the setting process is done by self-starting reactions instead of an external heat source).

[0059] The process of the invention controls the rate of the reaction in two ways: 1) by adjusting the amount of sodium hydroxide and ferrosilicon; or 2) by starting the two exothermic reactions at separate times, where the first reaction provides optimal activation energy for the second reaction. By mixing the sodium hydroxide into the water glass and letting them react first, the solution increases in temperature as the exothermic reaction progresses. After waiting for an amount of time (preferably after peak temperature of the first reaction is reached), the remaining dry ingredients, including the ferrosilicon, are mixed into the solution to start the second exothermic reaction. Activation energy for the second exothermic reaction is provided by the heat of the first exothermic reaction. Optimizing when to start the second reaction allows the amount of ferrosilicon needed to be decreased (saving cost) while causing the structural material composition to expand at an appropriate rate that balances a slow enough expansion to provideuniform and small pores, while not taking too long to set and harden, which is typically around 60 to 90 minutes.

[0060] ASTM E136 is a “fire-test-response test method” that “covers the determination under specified laboratory conditions of the combustibility of building materials”. “Materials passing this test are typically classified as noncombustible materials.” Samples were prepared in the manner set forth herein below and tested using the ASTM El 36 Standard in order to show that the material can be classified as a non-combustible building material. The invention passed the ASTM E136 test, which means the material is qualified as “non-combustible,” which means it can be used as a fire resistant / retardant / non-combustible building material.

[0061] For compressive strength, samples were made in the manner set forth below, then cut and sanded to dimensions as specified by ASTM D695. The length direction of the tested sample was perpendicular to the direction of material expansion during material setting. The samples were then tested for compressive strength using the ASTM D695 standard and compared to the prior art.

[0062] Samples were made in the manner set forth below. For thermal conductivity, the samples were cut and sanded as necessary to meet the dimensional specifications required for ASTM Cl 77. Samples were then sent to an external laboratory and thermal conductivity was measured using the ASTM Cl 77 standard.

[0063] The results are shown in Table 2.TABLE 2

[0064] Thermal conductivity comparable to the invention was found in US5749960, formulation C and D. For comparable thermal conductivity, the increase in density of the invention resulted in a greater increase in strength of the samples. Comparing the invention to US5749960, formula D, increased density of about 22% increased the compressive strength by more than 70%. Likewise, comparing the invention to US5749960, formula C, increased density of 50% resulted in an 86% increase in compressive strength.

[0065] Compared to the prior art, the invention has an increased density, without a substantial increase to thermal conductivity coupled with a desired substantial increase in strength of the material. Increased strength of the material provides better performance in building and sheathing applications, allows for the material to be fastened with bolts, nails, etc., while also allowing for the exclusion of any support structure as required for example in prior art US6350308. This simplifies production and reduces the excess parts needed. Also, as mentioned, the invention is also non-combustible, making it useful in fire resistance rated building assemblies.

[0066] Without further description, it is believed that one of ordinary skill in the art can, using the description and the illustrative examples make and utilize the invention. The following examples are given to illustrate the invention. It should be understood that the invention is not to be limited to the specific conditions or details described in the examples.

[0067] The samples in the following examples were prepared by:

[0068] - weighing out the desired quantities of dry ingredients, fly ash, FeSi, mica, and metakaolin,

[0069] - pouring the dry ingredients into a jar, sealing the jar, and shaking it until the dry ingredients are uniformly dispersed to obtain a dry mixture,

[0070] - weighing out the desired quantity of aqueous sodium silicate and placing it into a mixing apparatus,

[0071] - weighing out the desired quantity of NaOH and adding it to the sodium silicate and mixing until dissolved,

[0072] - waiting a certain amount of time T after the NaOH has been dissolved, T = x minutes, then pouring the dry mixture into the NaOH / sodium silicate solution, and mechanically mixing until it forms a slurry,

[0073] - pouring the slurry into 2” by 2” by 2” square molds with open tops, and paper on the bottom, and

[0074] - allowing the slurry to react and set, measuring the time it takes to harden.

[0075] The density of the samples were measured by removing the hardened samples from the molds, measuring the length, width, and height with a ruler or calipers, then weighing the samples on a gram scale. The samples were approximated to be rectangular, and the geometric density wasI X W X fl calculated from the above measurements using the formula d = — - — .

[0076] This procedure was followed to produce and measure each sample described in the tablesbelow.TABLE 3Formulas used for samples measured to create a plot of Si content in FeSi as shown in FIG.3

[0077] As seen in Table 3, having a FeSi powder that contains a high enough ratio of silicon is essential for the exothermic reaction between FeSi and FEO to produce enough energy to drive off the water liquid water as steam, which leads to expansion and setting (solidifying of the material). FeSi comes in varying grades defined by silicon content, ranging from as low as 15% up to 90%. FeSi72 (72% Si) and above is preferred for the invention. The tests show FeSi 15 will not drive a strong enough reaction, so no expansion occurs and setting is achieved by slow evaporation of water at ambient temperature and pressure. FeSi72 and FeSi75 showed very little difference and achieved desired setting time and expansion.TABLE 4Formulas used for samples measured to create plot of FeSi by weight as shown in FIG. 4

[0078] FeSi is responsible for the exothermic reaction that drives expansion and setting as hereindescribed. To test the effects of varying amount of FeSi, the weight percent of FeSi and Fly Ash were varied, while all other components were kept the same. Fly ash was chosen as the other variable because it is the base material in the formulation and varying its content does not play a major role in changing set time and density properties of the structural material.

[0079] By varying the amount of FeSi, it was noted that the more FeSi was added, the more intense the second exothermic reaction was, and therefore the faster the setting and the greater the expansion of the material during setting. Due to FeSi being more expensive than the other materials, it is preferred to minimize the amount of FeSi used while still achieving an adequate setting time (around 1.5 hours or less). These results showed that 22% by weight or less FeSi was preferred, and dropping below 15% FeSi started to show longer than desired setting times while the density started to become too high.TABLE 5Formulas used for samples measured to create plot of sodium silicate by weight as shown in FIG. 5* Too difficult to mix, mixture became impractical

[0080] Aqueous water glass provided a medium for the dry ingredients to be incorporated into a slurry that could be poured, as well as water which takes part in both exothermic reactions of the invention: first between H2O and NaOH, second between H2O and FeSi. By varying the amount of water glass in the formulation, the example showed that if the amount of waterglass was too low, the dry ingredients become too difficult to mix, and the overall slurry was too viscous, whichis impractical for manufacturing. Increasing the waterglass content by weight increased the reaction time as more time was needed to drive off all of the water. However, going above 40% made the slurry too watery and the slurry took too long to set, negating the advantage of having a fast-setting material and leading to less expansion of the material as it sets.TABLE 6Formulas used for samples measured to create plot of fly ash by weight as shown in FIG. 6* Too much fly ash, could not mix well enough to get homogeneous mixture

[0081] To test the effects of varying fly ash content by weight, the ratios of all the other ingredients were kept constant, while fly ash was varied. It was found that when the fly ash content was too high, the amount of water glass become too low and the mixture became too viscous and difficult to mix and pour. When the fly ash content was too low, more expensive FeSi was needed which is not practical in a commercial setting. Otherwise, varying the amount of fly ash did not have a great effect on density or set time when all other materials were kept in the same ratios.TABLE 7Formulas used for samples measured to create plot of NaOH by weight as shown in FIG. 7

[0082] Varying the amount of NaOH in the formulation by weight showed that the more NaOH was added, the faster the material set and the more it expanded. When the amount of NaOH in the formulation was too low, the material set more slowly and more importantly, the expansion was much less, leading to increased densities. When the amount of NaOH was too high, expansion was occurring too quickly, with foaming starting upon pouring into the mold. This decrease of set time is not conducive to material handling and manufacturing. Increased amount of NaOH also causes higher expansion which after around 3% in these examples lead to diminished material strength as well as difficulty handling.TABLE SFormulas used for samples measured to create plot of metakaolin by weight as shown in FIG. 8

[0083] Metakaolin also known as pozzolan, helps improve setting time and mechanical properties of the material. However, this example showed that too much metakaolin, 10% range and above, lead to the slurry being too viscous and difficult to handle. It also decreased the density too much which decreased the mechanical strength of the material. However, metakaolin below 4% diminished the positive effects on set time and mechanical properties. Density also started to increase with less metakaolin, and at 4% metakaolin, samples were at the higher end of the desireddensity range for the material.TABLE 9Formulas used for samples measured to create plot of mica as shown in FIG. 9

[0084] The crystal structure of mica can help to lower crack propagation in the material and also gives mica preferred thermal properties. Samples with mica were observed to better handle being nailed to structures and being sawed, as could occur in use as a building material. Additionally, mica has low thermal conductivity and is non-combustible, adding to the final material’s fire- resistant performance. The following observations were made by varying the weight % of mica, noting that varying the amount of mica had no noticeable effect on set time:

[0085] - at 6% mica and above: excess mica was filling pores, as found when the sample was cut in half. Material in pores is detrimental to density and thermal properties.

[0086] - at 5% mica: still noticeable excess mica in the pores.

[0087] - at 4% mica: very little excess mica found in the pores when the sample was cut in half.

[0088] - at 3% mica: level at which the mica stays in the material structure, and excess mica is not present in the pores after setting.

[0089] - going lower than 3% mica by weight showed negligible effect on density, once mica is at a level to not precipitate out when setting.

[0090] Four samples, using various concentrations of ingredients, were made in accordance to the above describe process for qualitative comparison of the resulting structural material. Table 10below shows the samples made.TABLE 10Formulas used for samples pictured in FIG. 10 to FIG. 13

[0091] The following results were observed from the results noted in Table 10 and FIGs. 10-13:

[0092] The sample shown in FIG. 10 did not expand much and only attained an about 0.25” final thickness. The sample was very flat with low porosity and high density.

[0093] The sample shown in FIG. 11 set after 1.5 hours and expanded to 'A” to about 5 / 8”. The pores were small in size; and the size distribution of the pores was not too large. Higher NaOH caused higher energy / heat to be produced in the first reaction, leading to more expansion caused by the second reaction despite slightly lower percentage of ferrosilicon in this formulation compared to the sample shown in FIG. 10.

[0094] The sample shown in FIG. 12 expanded about 3 / 8”. The pores were small and had adequate size distribution but there were less total pores. Due to this, the material’s density was too high. Despite the first reaction being the same as in the sample shown in FIG. 11, the density was higher since the second reaction did not contribute enough energy for expansion. However, it was a benefit to have the ferrosilicon percentage lowered for cost savings.

[0095] The sample shown in FIG. 13 expanded about 3 / 8”. The number of pores was greater than shown in the sample of FIG 12, but they were still small and uniform. This sample was also improved over sample FIG 12 as it was able to be screwed onto a support without cracking. Themica worked in increasing the mechanical properties, however, this sample had too much mica resulting in some of the excess mica ending up inside the pores.

[0096] An additional sample was prepared containing less mica than the sample shown in FIG. 13, wherein the additional sample contained 32% sodium silicate, 3% NaOH, 34% fly ash, 22% ferrosilicon, 5% metakaolin, and 4% mica. This additional sample did not exhibit as much excess mica as the sample shown in FIG. 13.

[0097] The foregoing detailed description of the certain exemplary embodiments has been provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. This description is not necessarily intended to be exhaustive or to necessarily limit the invention to the precise embodiments disclosed.

Claims

AMENDED CLAIMS received by the International Bureau on 09 June 2026 (09.06.2026)1. A fire-retardant structural material comprising 26-40 wt.% aqueous sodium silicate, 2-5 wt.% sodium hydroxide, 18-28 wt. % ferrosilicon, 30-40 wt.% fly ash, 1-10 wt.% metakaolin, and 1-6 wt.% mica.

2. The material of claim 1, wherein the aqueous sodium silicate comprises a ratio of silica to sodium oxide of 2.50-3.40.

3. The material of claim 2, wherein the ratio is 3.00-3.25.

4. The material of claim 1, wherein the aqueous sodium silicate comprises 35-42 wt.% solids.

5. The material of claim 4, wherein the aqueous sodium silicate comprises 37-39 wt.% solids.

6. The material of claim 1, wherein the aqueous sodium silicate comprises a pH of 11-12.5.

7. The material of claim 1, comprising 30-35 wt.% aqueous sodium silicate.

8. The material of claim 1, comprising 2.6-3.5 wt.% sodium hydroxide.

9. The material of claim 1, wherein the ferrosilicon comprises at least 70 wt.% silicon.

10. The material of claim 9, wherein the ferrosilicon comprises at least 75 wt.% silicon.

11. The material of claim 1, comprising 19-22 wt.% ferrosilicon.

12. The material of claim 1, wherein the fly ash comprises a Class-F ash.

13. The material of claim 1, comprising 33-35 wt.% fly ash.

14. The material of claim 1, comprising 4-6 wt.% metakaolin.

15. The material of claim 1, wherein the mica comprises muscovite.

16. The material of claim 1, comprising 2-3 wt.% mica.

17. A method of making a structural material having fire retardant properties comprising the steps ofa. Dissolving sodium hydroxide in aqueous sodium silicate to obtain an aqueous solution, b. Mixing ferrosilicon, fly ash, metakaolin, and mica into the aqueous solution to obtain a slurry, c. Pouring the slurry onto a surface, d. Leveling the slurry, and e. Allowing the slurry to set to obtain the structural material.

18. The method of claim 17, wherein the structural material comprises 26-40 wt.% aqueous sodium silicate, 2-5 wt.% sodium hydroxide, 18-28 wt. % ferrosilicon, 30-40 wt.% fly ash,1-10 wt.% metakaolin, and 1-6 wt.% mica.

19. A method of making a structural material having fire retardant properties comprising the steps of a. Dissolving sodium hydroxide in aqueous sodium silicate to obtain an aqueous solution, b. Mixing ferrosilicon, fly ash, metakaolin, and mica to obtain a dry mixture, c. Mixing the dry mixture into the aqueous solution to obtain a slurry, d. Pouring the slurry onto a surface, e. Leveling the slurry, and f. Allowing the slurry to set to obtain the structural material.

20. The method of claim 19, wherein the structural material comprises 26-40 wt.% aqueous sodium silicate, 2-5 wt.% sodium hydroxide, 18-28 wt. % ferrosilicon, 30-40 wt.% fly ash,1-10 wt.% metakaolin, and 1-6 wt.% mica.

21. A method of making a structural material, comprising:a. Dissolving sodium hydroxide in an aqueous sodium silicate solution to form an aqueous mixture, wherein dissolution of the sodium hydroxide initiates a first exothermic reaction that increases a temperature of the aqueous mixture; b. Allowing the aqueous mixture to reach a peak temperature and subsequently cool; c. Adding a mixture comprising ferrosilicon to the aqueous mixture after the temperature has decreased from the peak value, thereby initiating a second exothermic reaction; d. Mixing to form a slurry; and e. Allowing the slurry to expand and set to form the structural material, wherein the first exothermic reaction provides activation energy for the second exothermic reaction, and wherein a rate of expansion and a density of the structural material are controlled by timing of initiation of the second exothermic reaction.

22. The method of claim 21, wherein step c is performed after the aqueous mixture cools to a temperature of about 95°F to about 110°F.

23. The method of claim 21, wherein step c is performed after the aqueous mixture reaches the peak value of the temperature and begins to cool.

24. The method of claim 21, wherein the second exothermic reaction is delayed relative to the first exothermic reaction to control pore size distribution in the structural material.

25. The method of claim 21, wherein the timing of step c is selected to balance expansion rate and setting time of the slurry.

26. The method of claim 21, wherein the density of the structural material is controlled by adjusting relative amounts of sodium hydroxide and ferrosilicon.

27. The method of claim 21, wherein increasing an amount of sodium hydroxide increases energy and reaction rate of the first exothermic reaction, thereby increasing expansion and reducing setting time.

28. The method of claim 21, wherein increasing an amount of ferrosilicon increases energy and reaction rate of the second exothermic reaction, thereby increasing expansion and reducing setting time.

29. The method of claim 21, wherein the structural material has a density of about 0.38 to about0.5 g / cm3.

30. The method of claim 21, wherein the structural material comprises a porous structure having pores formed by gas evolution during the second exothermic reaction.

31. The method of claim 30, wherein timing of the second exothermic reaction is selected to produce smaller and more uniform pores.

32. The method of claim 21, wherein the slurry comprises: a. aqueous sodium silicate; b. sodium hydroxide; c. ferrosilicon; d. fly ash; e. metakaolin; and f. mica.

33. A method of controlling density of a structural material formed from a slurry comprising aqueous sodium silicate, sodium hydroxide, and ferrosilicon, the method comprising: a. initiating a first exothermic reaction by dissolving sodium hydroxide in the aqueous sodium silicate;b. delaying initiation of a second exothermic reaction involving the ferrosilicon until after the first exothermic reaction reaches a peak temperature; and c. initiating the second exothermic reaction such that heat from the first exothermic reaction provides activation energy, wherein the delay controls expansion behavior and resulting density of the structural material.

Images