Patent Grant
7491267
The present invention relates to composite materials, and more particularly relates to composite materials made from reactive compounds such as metal oxides.
Conventional concrete materials are typically made of Portland cement, sand, stone and water. When water is mixed with the Portland cement, an exothermic reaction occurs.
Although conventional concrete is useful for many applications, the process for making concrete must be carefully controlled. Chemical ratios of the starting materials must be adhered to strictly. Precise quantities of water must be used, and controlled temperatures for curing are required. Furthermore, extreme care must be used when bonding conventional concrete to other structures. Such critical parameters increase costs, and result in relatively long process times for many applications.
Phosphate-containing ceramics have been proposed for encapsulating residual materials. U.S. Pat. Nos. 5,645,518, 5,830,815, 5,846,894 and 6,133,498 disclose phosphate ceramics which encapsulate various types of residual materials and contaminants such as heavy metals, asbestos, ash, lumber wastes, styrofoam, cellulose fibers, tires, textile wastes, and low-level radioactive waste. The residual materials act as fill materials which are encapsulated and do not participate in the chemical reaction of the product. Such processes use high-purity reagent grade dead burned MgO. The MgO requires further processing including calcining the MgO further to reduce its reactivity, requires additional buffers, such as oxides of boron to further control MgO reactivity, requires the use of hydroxides as an added buffer, and also requires pretreatment of the MgO by wash and acid wash techniques. Reagent grade fine powder forms of phosphates are required, and liquid phosphoric acid is used to initiate acid reactions in conjunction with the dry phosphate powders. These previous approaches require strict ratio control of the reagent grade MgO and phosphates. Chemical buffers are used to control reactivity of the precise formulas. Such precise chemical formulas are extremely sensitive to temperature during field implementation.
U.S. Pat. No. 5,002,610 discloses of the use of fiber additives to magnesium phosphate cements and non-reactive fill materials in order to achieve mechanical properties desirable for construction uses similar to those of Portland cement-based concrete.
U.S. Pat. No. 6,136,088 discloses the production of a cement and/or mortar based on the reactions of water, magnesium compounds, and potassium phosphate that utilize retardants such as boron oxide, polyphosphonic acid, carboxylic acid, hydroxycarbyloxylic acid, and salts of these acids. Additives such as silica, class F fly ash, talc, clay based sand, silica fume and mixtures of these materials are used as inert fillers.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
The present invention relates to composite materials made from reactive compounds such as metal oxides. In one embodiment, at least one of the reactive compounds is provided from a residual material such as ash, phosphate clay, residual phosphate slurries, mining waste, and the like. The materials are made by mixing chemically active components, including relatively low cost waste or residual materials, to produce the desired engineering properties for a particular application.
In accordance with an embodiment of the invention, metal phosphate compounds are formed with desired characteristics by controlling reactivity of acid-based reactions of metal/phosphate compounds and sources. Such control may be achieved by varying ratios of the metal (ion) phosphate, particle size of the compounds, surface area of the components, amount of water, purity of the compounds and oxide reactivity rate. The workability, set time and strength of the composite metal-phosphate compounds may be optimized by controlling reactivity of metal/phosphate compounds and sources.
An aspect of the present invention is to provide a composite material comprising a reaction product of metal oxide, phosphate, reactive residual material and water.
Another aspect of the present invention is to provide a composite material comprising a reaction product of a magnesium-containing material, phosphate, reactive residual material and water.
A further aspect of the present invention is to provide a composite material comprising a reaction product of metal oxide, phosphate and water, wherein at least a portion of the metal oxide and/or at least a portion of the phosphate is provided from a reactive residual material.
Another aspect of the present invention is to provide a composite material comprising a reaction product of a magnesium-containing material, phosphate and water, wherein at least a portion of the magnesium-containing material and/or at least a portion of the phosphate is provided from a reactive residual material.
A further aspect of the present invention is to provide a mix for making a composite material comprising metal oxide, phosphate and reactive residual material. Alternatively, the mix may comprise a magnesium-containing material, phosphate and reactive residual material. As another alternative, the mix may comprise metal oxide and/or magnesium-containing material and/or phosphate, wherein at least a portion of one or more of these materials is provided from a reactive residual material.
Another aspect of the present invention is to provide a rapid repair material comprising a reaction product of metal oxide, phosphate, reactive residual material and water.
A further aspect of the present invention is to provide a method of making a composite material. The method comprises reacting a mixture of metal oxide, phosphate and reactive residual material. Alternatively, the method comprises reacting a magnesium-containing material, phosphate and reactive material. As another alternative, the method comprises reacting a metal oxide and phosphate, wherein at least one of the metal oxide and phosphate is provided from a reactive residual material. As a further alternative, the method comprises reacting a magnesium-containing material and phosphate, wherein at least one of the magnesium-containing material and phosphate is provided from a reactive residual material. In each case, the reaction may be initiated by adding water to the mixture of starting materials.
These and other aspects of the present invention will be more apparent from the following description.
The composite materials of the present invention comprise chemical binders and may also comprise reactive particulates. The binders and/or reactive particulates may be provided from residual materials. The composite is a ceramic/concrete-like material which may include ionic and/or covalent chemical bonds. The present composite materials may use residual materials such as industrial by-products. The composite materials have a high tolerance for different types of starting materials, and are relatively insensitive to wide variations in composition and processing techniques.
As used herein, the term “reactive residual material” means residual materials that act as buffers, catalysts and/or activators, based upon their specific chemistry, and thereby contribute to the overall desired characteristics of the end product. The reactive residual material may react or chemically bond with the other starting material(s) during the present process to form chemical phases which may be determined, for example, by x-ray photoelectron spectroscopy techniques.
Suitable reactive residual materials may contain metal compounds such as metal oxides, metal hydroxides, metal halides, metal carbonates, metal nitrates, metal borates, metal sulfides, metal chromates, metal tungstates, metal molybdates, metal phosphates, metal arsenates, metal vanalydates, metal silicates, and pure metals. Suitable reactive residual materials may contain metal oxides such as MgO, Al2O3, ZnO, iron oxides, MnO2, FeTiO3, MgAl2O4, ZnAl2O4, and (Zn Fe Mn)(Fe Mn)2O4. Additional oxides include quarry fines, CCB's, wood ash, dredge materials, kaolin, ground recover glass, foundry sand, red mud, silica fines, coal fines, bauxite, volcanic ash and recycled concrete.
As a further example, suitable metal hydroxide-containing reactive residual materials may include Brucite—Mg—Mg(OH)2, Manganite—MnO(OH), Gibbsite—Al(OH)3, Diaspare—AlO—OH, Bachmite—AlO—OH, Geothite—FeO—OH and Bauxite.
In addition to the above-listed metal-containing reactive residual material compounds, other types of residual materials may be used in accordance with the present invention that include minerals such as Carnallite (KMgCl3—CH2), Boracite (Mg3ClB7O13), Epsomite (MgSO4-7H2O), Newberryite (MgHPO4), Magnesite (MgCO3), Olivine (MgFe)SiO4 and Dolomite (CaMg(CO3)2). In addition to the above listed metal-containing reactive residual compounds, other types of residual materials that may be used in accordance with reactive residual compounds, other types of residual materials that may be used in accordance with the present invention include calcium-containing dredge (oxides, carbonates, etc.), grain hulls and plant bark fiber.
One type of reactive residual material that may be used in accordance with the present invention comprises ash. Sources of ash reactive residual materials may include, for example, coal ash, wood ash, municipal solid waste ash (MSW), cellulosic waste ash, biosolids ash, fumes and collected particles from metal processes involving combustion. Typical sources of ash residual materials include coal-fired power plants, municipal waste furnaces and coal desulphurization residuals. Particularly suitable ash reactive residual materials include trace metal elements and/or metal oxides containing sulfur trioxide, phosphorous penta oxide, barium oxide, manganese oxide, strontium oxide, potassium oxide, aluminum oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide and sodium oxide. As a particular example, type C or F coal ash may be used.
Another type of reactive residual material that may be used in accordance with the present invention comprises phosphate compounds. For example, phosphate clays may be used as the reactive residual material. Phosphate clays typically comprised of Quartz, Dolomite, Apatite, Wavellite, Crandallite, Feldspar, Smectite, Illite, Palygorskite and Koalinite. Sources of phosphate clays include geologic sites, for example, south-central Florida.
Another type of phosphate-containing reactive residual material that may be used in accordance with the present invention is phosphate slime. Phosphate slime comprises a suspension of clays, minerals and phosphates in a liquid such as water. Typical phosphate slimes have solids contents of from about 5 to about 15 weight percent. When a phosphate slime is used as a reactive residual material in accordance with the present invention, the slime may be used directly in its as-is condition. Alternatively, the phosphate slime may be dried by removing some or all of the liquid content prior to use. Furthermore, additional liquid such as water may be added to the phosphate slime prior to use. Some sources of phosphate slime include toothpaste manufacturers, antifreeze manufacturers, motor oil producers and detergent and food processors/manufacturers. Florida phosphate and mine processing industries are examples of phosphate slime sources. In this case, the phosphate slime typically comprises a suspension of soluble and insoluble phosphates in water with a solids content of about 15 weight percent.
In addition to the above-noted types of reactive residual materials, other types of residual materials that may be used in accordance with the present invention include brake shoe dust, foundry sand, carbon black, dredge such as mining, harbor, island and manufacturing landfills. Such compounds may be provided from various industrial sources such as automotive parts manufacturers, naval shipyards, home health products manufacturers (shampoo, toothpaste, bath soap, Epsom salts), food manufacturers, beverage manufacturers, antifreeze producers and motor oil producers.
As shown in
The selection of an appropriate reactive compound may depend upon the specific reactive residual material that is used. For example, when ash such as calcium oxide rich ash is used as the reactive residual material, the reactive compounds may include MgO, Fe2O4, Al2O3, B2O3, etc. When phosphate compounds are used as the reactive residual material, the other reactive compounds may include, for example, MgO, iron oxides, Al2O3 and/or CaO. Some examples of phosphate reactive residual materials include phosphate clays, phosphate slurries, and the like.
In accordance with an embodiment of the present invention, the composite material may comprise a reaction product of metal oxide, phosphate, reactive residual material and water. The amount of metal oxide typically ranges from about 1 to about 90 weight percent, preferably from about 10 to about 50 weight percent, based upon the total weight of the combined metal oxide, phosphate and reactive residual material. The phosphate typically comprises from about 1 to about 90 weight percent, preferably from about 10 to about 50 weight percent, based upon the total weight of the combined metal oxide, phosphate and reactive residual material. The reactive residual material typically comprises from about 0.5 to about 95 weight percent, preferably from about 5 to about 80 weight percent, based upon the total weight of the combined metal oxide, phosphate and reactive residual material. The metal oxide, phosphate and reactive residual material may optionally be mixed with from about 0.1 to about 80 weight percent filler material, preferably from about 0.5 to about 60 weight percent filler material, based upon the total solids content of the metal oxide, phosphate, reactive residual material and filler.
When MgO is used as a metal oxide in accordance with the present invention, it may have a purity of at least 10 weight percent, e.g., from about 50 to about 99 percent, typically from about 90 to 98 weight percent. The MgO typically has a particle size of about 1 inch or less. For example, the MgO particles may range from about 0.25 inch to minus 325 mesh. As a particular example, the MgO particles may be minus 30 mesh. The MgO may have a structure corresponding to its as-mined condition (no heat treatment), or may be light burned, hard burned and/or dead burned. Preferably, the MgO is hard burned or dead burned. Light burned MgO is typically subjected to a heat treatment of from 700 to 1,000° C. Hard burned MgO is typically subjected to a heat treatment of from 1,000 to 1,500° C. Dead burned MgO is typically subjected to a heat treatment of from 1,500° C. to 2,000° C.
In accordance with an embodiment of the present invention, the phosphate component of the composite material may comprise mono-potassium phosphate, mono-ammonium phosphate, mono-sodium phosphate, hexa-meta phosphate, di-potassium phosphate, di-hydrogen potassium phosphate and/or di-ammonium phosphate. Typical phosphates include mono-potassium phosphate, mono-ammonium phosphate and mono-sodium phosphate. The phosphate typically has an average particle size of about 1 inch or less. For example, the phosphate may have an average particle size of from about 0.25 inch to minus 325 mesh. As a particular example, the phosphate particles may be minus 30 mesh. The phosphate may have a purity of at least 10 percent, e.g., from about 50 to about 99 weight percent, typically from about 30 to about 85 weight percent.
The metal oxide and phosphate may have any suitable weight ratio. For some type of materials, the metal oxide to phosphate weight ratio preferably ranges from about 0.8:1 to about 2:1. For example, where the metal oxide comprises MgO and the phosphate comprises mono-potassium phosphate, the MgO:phosphate weight ratio preferably ranges from about 0.9:1 to about 1.3:1, more preferably from about 1.01:1 to about 1.15:1 for some composite materials.
As shown in
In addition to the above-listed reactive residual materials and additional reactive compound(s), the solid components of the present composite materials may further comprise materials such as recycled concrete, recovered drywall, recycled asphalt, high chloride out of specification coarse aggregates and the like. Fibers (reactive and non-reactive), e.g., metal, polymeric, glass, e-glass, graphite, etc., may also be added.
Elemental analysis was performed for some of the present materials in comparison with conventional materials. Materials reacted according to the present invention show different chemical phases than conventional materials. In accordance with an embodiment of the invention, chemical bonding of the species occurs, rather than the encapsulation of additive materials.
Chemical data is shown in Tables 1 and 2. The first set of data listed in Table 1 is based upon x-ray diffraction and shows the atomic percentages of each element present in a reacted sample made from magnesium oxide, mono-potassium phosphate and fly ash in accordance with the present invention. The second set of data listed in Table 2 was accomplished using x-ray photoelectron spectroscopy, which measures the degree of bonding and can distinguish chemical compounds. It is clear from this data that the base materials in the reaction: magnesium oxide; mono-potassium phosphate; and the fly ash (primarily aluminum oxide and silicon oxide), form very complex chemical phases in the final product. These phases of the final product are present due to the direct chemical reaction of the magnesium oxide and the mono potassium phosphate with the fly ash constituents.
The quantitative x-ray photoelectron spectroscopy results for the elemental composition of a freshly fractured surface are expected to consist primarily of the surface of the particles which were bonded together during the chemical reaction. The depth of the analysis was about 5-6 nanometers, so the particle surface composition is not expected to be the same as the average bulk composition, given the nature of the material. Two principal surface potential states were found in the high energy resolution spectra, and are shown in Table 2. The respective component oxides and phosphates belonging to these potential states are shown in Table 2. Each of these complex phases differs only in the relative proportion of its constituent oxides and potassium phosphates. The remaining material (10.42 percent) is organic and this is distributed upon the two inorganic phases in proportion to their relative concentrations.
The following Table 3 lists some examples in accordance with the present invention. The primary starting materials are listed in Table 3 as “MOx” (e.g., MgO), “AB(PxOy)” (e.g., KH2(P2O4) or NH4H2(PO4)), and “residuals” (e.g., coal ash, calcium-containing dredge, municipal waste ash, phosphate slime, etc.). All numbers are in grams, unless otherwise noted. Unless otherwise noted, all mixing times are approximately 5 minutes.
Tables 4-10 list samples of additional materials. In the tables, the MgO designation “D-30” represents dead burned MgO −30 mesh, the MgO designation “D-325” represents dead burned MgO −325 mesh, the MgO designation “H-60” represents hard burned MgO −60 mesh, and the MgO designation “H-30” represents hard burned MgO −30 mesh. The phosphate designation “MKP” represents mono potassium phosphate, the phosphate designation “MAP” represents mono potassium phosphate, and the phosphate designation “MSP” represents mono sodium phosphate. The metal oxide, e.g., MgO, and/or the phosphate may be provided in the form of mixtures having different particle size distributions. For example, the MgO may comprise a relatively coarse particle size distribution, e.g., −30 mesh, and a relatively fine particle size distribution, e.g., −325 mesh. The “reaction time” is the time from initial mixing to the substantial completion of an exothermic reaction. “Initial set” is defined by the loss of workability. “Final set” is defined by the loss of elasticity or the start of hardening.
The composite materials of the present invention may be made by the selection and blending of properly sized reactants with water (potable and non-potable). During this process both endothermic and exothermic reactions may take place within the composite mixture. In many processes, the composite-forming reaction is exothermic. However, in some cases, at least a portion of the reaction may be endothermic. For example, upon mixing with water, an initial endothermic reaction may take place, followed by an exothermic reaction.
In accordance with the present invention, the composite-forming process may involve relatively short set times. Typical set times in accordance with the present invention are less than about 2 hours, preferably less than about 1 hour. For example, a typical set time of from about 10 to about 90 minutes may be achieved. In contrast, typical set times for Portland cement concrete mixtures may be several hours.
After achieving set, the composite materials of the present invention may possess favorable engineering properties such as high surface hardness, excellent bond to dissimilar materials, capability of expansion and shrinkage, rapid load carrying capability, zero cracking, resistance to spill, better flow and reduced effect from re-tempering. For example, the composite materials may have compressive strengths of at least 500 psi. Compressive strengths of 1,500, 2,000, 2500 or 3,000 psi may be achieved. In some embodiments, compressive strengths of 6,000 psi or higher may be achieved. In addition to relatively high compressive strengths, the present composite materials may exhibit the following improved mechanical properties: zero cracking, resistance to spill, zero shrinkage and better flow. In addition to favorable mechanical properties, the present composite materials may possess improved environmental properties such as non-caustic chemistry, use of non-potable water, high resistance to cyclic freeze-thaw and lower permeability (i.e. resistant to deicing salts).
The composite materials of the present invention may be used for many different applications. Suitable applications include pre-cast structures, in-situ structures, repair materials, very-rapid repair materials, ready mixes, grouts, coatings, counter tops, corrosion inhibitors, thermal barriers, armor, structural composites, anchor bonding materials, medical applications and catalysis. Some examples of pre-cast composite materials include railroad ties, high pressure pipes, retainer walls, railroad slab tracks and crossing platforms, bridge deck preforms, aircraft runway, taxi and apron pre-cast structures, armor panels, casting molds, stamping molds, combustion and combustion product catalysts, housing and building wall panels, countertops, and the like.
A pre-cast railroad tie 10 is illustrated in
Typical repair applications include rapid repair of surfaces such as road surfaces, aircraft runways, parking garage decking, building facades, and the like. A rapid repair material 20 in a road or runway surface 22 is illustrated in
Typical in-situ applications include repair of existing concrete materials, e.g., roadways, parking decks, facades, runways, marine applications, vertical columns, grouts, anchor materials, etc. Typical ready mix applications include various types of cast-in-place and pre-cast structures. Typical coatings applications include gunnites, shotcretes, overlaps, sealing membranes, concrete surface treatments, grouts, etc. For medical applications, the present composite materials may be used, for example, to mimic bone structure and morphology.
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/311,529 filed Aug. 10, 2001.
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