Abstract: A dry binder premix includes, in mass proportions: Portland clinker having a Blaine specific surface area comprised from 4500 to 9500 cm2/g, the minimum quantity of the clinker by mass percentage relative to the total mass of the premix being determined according to: [?6.10?3×BSSk]+75, in which BSSk is the Blaine specific surface area of the clinker given in cm2/g; fly ash; an alkali sulphate; one source of SO3; complementary materials having a Dv90 less than or equal to 200 ?m selected from limestone powders, calcined shale, metakaolins, siliceous fillers, silica powders, pozzolans, slags, fly ash and mixtures thereof. A quantity of clinker+the quantity of fly ash is greater than or equal to 75% by mass percentage relative to the total mass of the premix and a total quantity of clinker in the premix is less than 60% by mass percentage relative to the total mass of the premix.

Abstract: The invention concerns a method of treating an alkaline granular carbonatable material which contains aluminium metal and which has in particular a pH of at least 10. The method comprises an oxidation step wherein at least a portion of said aluminium metal is oxidized by contact with moisture. The aluminium should be oxidized to avoid swelling problems when using the granular material as aggregate. In the method according to the invention this oxidation is accelerated by providing at least one oxidizing agent in said moisture, which oxidizing agent has a higher redox potential than the water contained in said moisture. The method further comprises a carbonation step wherein the granular carbonatable material is at least partially carbonated to lower the pH thereof. In this way the formation of ettringite, which may also release aluminium ions which causing further swelling problems, can be avoided in the granular material or any ettringite present therein can be destabilized.

Abstract: This invention relates to a formulation with the addition of low density additives of volcanic ash, hollow ceramic microspheres or a combination of microspheres and volcanic ash or other low density additives into cementitious cellulose fiber reinforced building materials. This formulation is advantageously lightweight or low density compared as compared to current fiber cement products without the increased moisture expansion and freeze-thaw degradation usually associated with the addition of lightweight inorganic materials to fiber cement mixes. The low density additives also give the material improved thermal dimensional stability.

Abstract: A process for control melting a mixture of coal ash, electric arc furnace dust, recycled glass and additives to create a feedstock. The feedstock is quenched or air dried in a mold to create useful products, such as fracking compounds, abrasives, construction products, building materials, landscaping materials, and the like.

Abstract: A cement composition for cementing an oil or gas well includes Portland cement, water and a sulfur component. The cement composition may be used to cement a well bore by creating a cement slurry including the sulfur component, pumping the slurry into the well bore to a selected location and allowing it to solidify.

Abstract: In a method of producing an activated construction mixture including cement, water, additives and superplasticizer the activation is performed with dimensionless criteria Reynolds and Power numbers within the limits of 20-800 and 4.0-0.1 respectively for increasing water adsorption with calcium silicate hydrate colloid formation and accelerating cement hydration.

Abstract: Disclosed are a system, a method and/or composition of reduction of carbon dioxide in the manufacturing of cement and concrete. In one embodiment, a method of producing a concrete, includes preparing a dried powder mixture of an alkali hydroxide, a sodium silicate, clay and a pozzolanic material. The dried powder with water may be reacted to form a cement paste. In addition, the cement paste may be mixed with at one of sand, an aggregate, a plasticizer and a nano additive to form the concrete.

Abstract: Cementitious formulations and their products with enhanced reactivity are provided. Formulations in certain embodiments may include at least one calcium source, a reactant and a filler in a hydrated environment, wherein the reactant, in one form, is crystalline silica that has been modified for reactivity. Enhancement of a reactant may include one or more modifications to its content, grind and/or the cement to silica ratio, as well as addition of one or more additives in the formulation, additives in the form of at least one alumina source, defoamer, catalyst and/or a clay.

Abstract: Shaped geopolymeric particles, fibers, and articles incorporating at least one geopolymer are provided; the geopolymeric particles, fibers, and articles having a structure that is solid, foamed, hollow or with one or more voids. Geopolymers are formed by alkali activation of an aluminosilicate and/or aluminophosphate material. The end-products are shaped as spheres, flakes, fibers, aggregates thereof or articles. Such products are formed at low temperatures; wherein forming includes processing using techniques such as spray drying, melt spinning, or blowing. The shaped geopolymeric particles and fibers have high chemical durability, high mechanical strength, application-targeted flowability and packing properties, and are specially suited for incorporating into composite materials, articles, and for use in cementitious, polymeric, paint, printing, adhesion and coating applications.

Abstract: A durable concrete composition includes a cementitious material comprising cement and ground expanded perlite, coarse aggregate, fine aggregate, and sufficient water for adequate workability. The resulting concrete displays a number of superior properties to conventional concrete, including extremely high thermal resistance coupled with high strength, low chloride ion permeability, and good early strength. The ground expanded perlite is a readily available material and the finished concrete is extremely cost effective for applications where a high strength structural concrete must withstand high temperatures. The mixture can be handled and placed by conventional methods and is compatible with existing conventional concrete additives.

Abstract: A low-calcium-cementitious material having a calcium oxide content less than or equal to 10 wt % which is processed at room temperature into a low calcium cement mainly composed of mullite and a method manufacturing of the low calcium cement are provided. The low-calcium-cementitious material includes low calcium fly ash, an alkaline agent, and a congealing agent, wherein the calcium oxide content of the low-calcium-cementitious material is less than or equal to 10 wt %. The low calcium fly ash has a calcium oxide content less than or equal to 10 wt %. The low calcium cement manufacturing method includes providing a low calcium fly ash having a calcium oxide content less than or equal to 10 wt %; providing an alkaline agent; providing a congealing agent; and mixing the low-calcium-content fly ash, the alkaline agent, and the congealing agent and standing the mixture at room temperature to form a low calcium cement.

Abstract: A geopolymer concrete formed by mixing about 3% to about 43% by weight incinerator fly ash, about 3% to about 35% by weight coal fly ash, about 7% to about 38% by weight alkaline activator liquid, and about 31% to about 70% by weight aggregate. The incinerator fly ash may be derived from a solid waste incinerator facility. The alkaline activator liquid may include a sodium hydroxide solution and sodium silicate. The aggregate may include a fine aggregate, such as sand, and a coarse aggregate, such as gravel.

Abstract: Methods and compositions are provided that relate to cementing operations, including a method of cementing that may comprise providing a settable composition that may comprise wollastonite, pumice, a calcium-ion source, and water, wherein the wollastonite may be present in an amount in a range of from about 25% to about 75% by combined weight of the wollastonite and pumice, and wherein the pumice may present in an amount in a range of from about 25% to about 75% by combined weight of the wollastonite and pumice. Embodiments of the method further may comprise allowing the settable composition to set.

Abstract: A method of making a rapid setting lightweight cementitious composition with improved compressive strength for products such as boards is disclosed. The method mixes fly ash, alkali metal salt of citric acid and lightweight aggregate with water. Compositions which include fly ash, alkali metal salts of citric acid and lightweight aggregate are also disclosed.

Abstract: Provided are cementitious compositions and related systems and methods. The cementitious compositions, or admixtures, according to the present invention generally comprise gypsum, a first alkaline component and glass. The admixture may further comprise fly ash, which is preferably obtained as a waste by-product from a coal-burning power plant. A method according to the present invention comprises an initial step of analyzing or receiving an analysis of a fly ash sample. Based at least in part on the analysis of the fly ash sample, a mix rate may be selected and an initial admixture can be formulated, which, when added to the fly ash sample, creates an alternative or additive to Portland cement for use in concrete, for example.

Abstract: Microparticles having crystalline needle or rod-shaped structures of, for example, an ettringite mineral grown and attached radially from their surface. A method including nucleating and growing crystalline needles/rods from the surface of a particle in the presence of a solution of calcium, sulfur, and aluminum such as calcium sulfoaluminate, lime and calcium sulfate is described. One example is the radial growth of ettringite needles on the surface of fly ash particles in calcium sulfoaluminate-based cement paste and concrete.

Abstract: A method of making a lightweight cementitious binder composition with improved compressive strength for products such as cementitious panels is disclosed. The method mixes fly ash, alkali metal salt of citric acid, alkali metal silicate, foaming agent for entraining air, water and in the preferred embodiment a foam stabilizing agent. Compositions which include fly ash selected from the group consisting of class C fly ash, class F fly ash and mixtures thereof, alkali metal salts of citric acid, alkali metal silicates, foaming agents, and preferably a foam stabilizer, such as polyvinyl alcohol, and do not require use of set retarders. Compositions containing class F fly ash can optionally contain Type III Portland cement.

Abstract: Method for suppressing antagonistic hydration reactions in Portland fly ash cement involves the use of unponded fly ash that is pre-hydrated, preferably as an aqueous slurry wherein fly ash, preferably having an alkaline earth metal oxide of at least 10% by weight, is soaked, whereby the hydration reaction of the resultant mixed fly ash and cement is accelerated when these components are mixed together with water to hydrate the cement. Blended Portland cement/fly ash compositions of the invention will also have higher early strength as well as shorter set time compared to untreated blends.

Abstract: A process for producing a cement binder composition including one or more magnesium carbonates having the general formula w MgCO3. x MgO. y Mg(OH)2 . z H2O in which w is a number equal to or greater than 1, at least one of x, y and z is a number greater than 0 and w, x, y and z may be (but need not be) integers is described. The process is characterised by (a) heating magnesite to liberate carbon dioxide gas and produce a solid product including magnesium oxide and (b) contacting an aqueous mixture including the magnesium oxide produced in step (a) with a source of carbonate ions at a temperature in the range 25 to 120° C. to produce at least one of the magnesium carbonates.

Abstract: A geopolymer mortar formed by mixing about 35% to about 45% by weight pozzolanic material, about 35% to about 45% by weight silicon oxide source, about 15% to about 20% by weight alkaline activator solution, and about 0.3% to about 2.5% by weight copper ion source. The pozzolanic material may be fly ash and the silicon oxide source may be sand. The alkaline activator solution may be a sodium hydroxide solution containing sodium silicate. The geopolymer mortar may have a viscosity in the range of about 25,000 to about 50,000 centipoise. The geopolymer mortar may be formed by further mixing one or more additives, such as surfactants, thermal spheres, anti-sagging agents, adhesion primers, or fibers. The geopolymer mortar may be applied as a protective coating on a surface of a structure.

Abstract: Sorbent components containing halogen, calcium, alumina, and silica are used in combination during coal combustion to produce environmental benefits. Sorbents such as calcium bromide are added to the coal ahead of combustion and other components are added into the flame or downstream of the flame, preferably at minimum temperatures to assure complete formation of the refractory structures that result in various advantages of the methods. When used together, the components reduce emissions of elemental and oxidized mercury; increase the level of Hg, As, Pb, and/or Cl in the coal ash; decrease the levels of leachable heavy metals (such as Hg) in the ash, preferably to levels below the detectable limits; and make a highly cementitious ash product.

Abstract: Provided herein are compositions, methods, and systems for cementitious compositions containing calcium carbonate compositions and aggregate. The compositions find use in a variety of applications, including use in a variety of building materials and building applications.

Abstract: Methods and compositions that comprise sub-micron alumina for accelerating setting of a cement composition. An embodiment includes a method of cementing in a subterranean formation. The method may comprise introducing a cement composition into the subterranean formation, wherein the cement composition comprises hydraulic cement, sub-micron alumina, and water. The method further may comprise allowing the cement composition to set in the subterranean formation. Another embodiment includes a cement composition that may comprise hydraulic cement, sub-micron alumina, and water.

Abstract: A composition comprising a metallic composition, an inorganic oxide-based polymer, and a solvent. A cure product of the metallic composition, inorganic oxide-based polymer, and solvent, the cure product having a network structure, are also disclosed.

Abstract: A novel binder system comprising at least one latent hydraulic binder, at least one amorphous silica, optionally at least one reactive filler and at least one alkali metal silicate is proposed. It was surprisingly found that the binder system according to the invention hardens in the form of a hybrid matrix which is acid-resistant, water-resistant and alkali-resistant. The binder system can be used for the production of a hydraulically setting mortar which, after setting, hardening for seven days and subsequent storage for three days in acid, base and/or water, has compressive strengths of more than 15 N mm?2, preferably more than 20 N mm?2 and in particular more than 25 N mm?2, according to DIN EN 13888.

Abstract: A method of making a rapid setting lightweight cementitious composition with improved compressive strength for products such as boards is disclosed. The method mixes fly ash, alkali metal salt of citric acid and lightweight aggregate with water. Compositions which include fly ash, alkali metal salts of citric acid and lightweight aggregate are also disclosed.

Abstract: To reduce cost of chemical by reducing quantity of foaming agent used when removing unburned carbon in fly ash with wet floatation and to prevent decrease in activity index of the fly ash. In wet decarburization of fly ash, the solution comprising the steps of: adding water to fly ash to generate slurry; adding hydrophobizing agent and foaming agent to the slurry and agitating them to generate bubbles; and adhering unburned carbon in the fly ash to the bubbles to float them to remove the unburned carbon in the fly ash, when sedimentation component at wet floatation separation is solid-liquid separated and liquid phase obtained by solid-liquid separation is reused for another floatation separation for new fly ash, the quantity of foaming agent added to the slurry is adjusted such that concentration of the foaming agent in liquid phase is in a predetermined range.

Abstract: In-process systems and methods for treating coal combustion products with property-enhancing additives are disclosed. Coal combustion products such as fly ash are collected upon their formation and are contemporaneously treated with additives such as dispersants, rheology modifiers, retarders and accelerators to improve properties of the treated products when they are used in cement, concrete, mortar and other hydraulic mixtures.

Abstract: Disclosed herein are an asphalt concrete mixture, an asphalt binder composition, and methods of preparing the related compositions. The asphalt binder compositions include heavy oil fly ash that contains more than about 90 wt. % carbon. The compositions are capable of being performance graded. The binder can be used to modify the asphalt and also as a filler in asphaltic concrete compositions.

Abstract: A heavy oil ash self-compacting concrete can include aggregate, heavy oil ash fines, water, and cement. The heavy oil ash can include more than 90% carbon, by weight. In an embodiment, the heavy oil ash self-compacting concrete can flow under its own weight and yet maintain a stable mixture consistency.

Abstract: To effectively utilize coal ash while reducing mercury concentration in cement kiln exhaust gas. Coal ash is received from a thermal power plant or the like; the received coal ash is separated into ash and unburned carbon; the separated ash is utilized in a cement manufacturing facility as a cement raw material; and the separated unburned carbon is utilized in the cement manufacturing facility in accordance with mercury concentration in gas exhausted from a cement kiln of the cement manufacturing facility. In case that the mercury concentration in the gas exhausted from the cement kiln of the cement manufacturing facility is high, in the coal ash, unburned carbon with high mercury content can be treated in facilities other than the cement manufacturing facility without feeding the unburned carbon to the cement manufacturing facility, or the quantity of such unburned carbon fed to the cement manufacturing facility can be adjusted.

Abstract: A thermal method to passivate the carbon and/or other components in fly ash significantly decreases adsorption. The passivated carbon remains in the fly ash. Heating the fly ash to about 500 and 800 degrees C. under inert gas conditions sharply decreases the amount of surfactant adsorbed by the fly ash recovered after thermal treatment despite the fact that the carbon content remains in the fly ash. Using oxygen and inert gas mixtures, the present invention shows that a thermal treatment to about 500 degrees C. also sharply decreases the surfactant adsorption of the recovered fly ash even though most of the carbon remains intact. Also, thermal treatment to about 800 degrees C. under these same oxidative conditions shows a sharp decrease in surfactant adsorption of the recovered fly ash due to the fact that the carbon has been removed. This experiment simulates the various “carbon burnout” methods and is not a claim in this method.

Abstract: Provided are cementitious compositions and related systems and methods. The cementitious compositions, or admixtures, according to the present invention generally comprise gypsum, a first alkaline component and glass. The admixture may further comprise fly ash, which is preferably obtained as a waste by-product from a coal-burning power plant. A method according to the present invention comprises an initial step of analyzing or receiving an analysis of a fly ash sample. Based at least in part on the analysis of the fly ash sample, a mix rate may be selected and an initial admixture can be formulated, which, when added to the fly ash sample, creates an alternative or additive to Portland cement for use in concrete, for example.

Abstract: A concrete mixture that includes aggregates, water and cement can include heavy oil ash instead of or in addition to a portion of the cement. In one embodiment, the heavy oil ash originates from heavy fuel oil burned in a power generation plant. The weight of the heavy oil ash used in the concrete mixture can be from greater than 0 to about 10% of the weight of the cement.

Abstract: A composition used for high-strength impermeable concrete. The composition contains sand, stone, cement, water reducer, water and reinforced impermeable sand. The reinforced impermeable sand includes aeolian sand and binder covering the surface of the aeolian sand. The reinforced impermeable sand can fill the gap between the sand and the stone, and well combine various components in the composition, and suppress the seepage phenomenon of the molded concrete, thereby greatly improving the strength and impermeability of the concrete.

Abstract: A dry cement mix based on a hydraulic binder and a glass aggregate for forming light concretes with low thermal conductivity, characterised in that said glass aggregate comprises a fine fraction consisting of granulated aggregate with a particle size from 0.5 to 2 mm, and a coarse fraction consisting of crushed aggregate with a particle size from 4 to 20 mm, obtaining for said glass aggregate a well-defined overall particle size distribution.

Abstract: A dry mortar mixture based on at least one hydraulic and/or latently hydraulic binder which in the made-up and not yet cured state has firm properties is claimed. The novel dry mortar mixture is characterized in that it contains at least one representative of a dispersant and at least one compound having superabsorbent properties. This mixture makes it possible to carry over the advantages of known tile adhesives for horizontal application to vertical application possibilities.

Abstract: Inorganic polymer compositions and methods for their preparation are described herein. The compositions include the reaction product of a reactive powder, an activator, optionally a retardant, and water. The reactive powder includes 85% by weight or greater fly ash. The ratio of water to reactive powder is from 0.06:1 to less than 0.15:1. Also described herein are building materials including the compositions.

Abstract: A lightweight structural concrete includes a hydraulic binder; effective water; a superplasticizer; and aggregates; the concrete having a density in the fresh state varying from 1.40 to a Dmax value calculated according to formula (I) Dmax=1.58+(a×AM) in which “a” represents a coefficient for which the value is equal to 1; “AM” represents the mass percentage of the amorphous materials contained in 1 m3 of fresh concrete; the concrete having a maximum fresh state density Dmax less than or equal to 1.85; the concrete having a Weffective/L ratio varying from 0.19 to 0.

Abstract: The invention relates to a hydraulic binder, comprising K, Ca, aluminosilicates, as well as optionally Li, Na, and Mg, wherein the binder comprises the following components: a) a latently hydraulic aluminosilicate glass with a ratio of (CaO+MgO+Al2O3)/SiO2>1 and b) an alkali activator of the empirical formula (I) a(M2O)*x(SiO2)*y(H2O)??(I) wherein M=Li, Na, K, a=0-4, and x=0-5 and y=3-20, wherein the molar ratio of Ca/Si is <1, the molar ratio of Al/Si is <1, and the molar ratio of M/Si is >0.1. Furthermore, it relates to binder matrices, mortars, concrete adhesives, and metal anodes made of such binder.

Abstract: The present invention relates to a cement-free alkali-activated binder. More particularly, the present invention relates to a cement-free alkali-activated binder having a novel combination ratio, which can improve the compressive strength of mortar and concrete in which the cement-free alkali-activated binder is used as a binding material instead of cement, and which can solve the low field applicability of mortar and concrete in terms of quick setting characteristics, fluidity loss, economic efficiency and the like, and to mortar or concrete comprising the same. The cement-free alkali-activated binder can improve field applicability by controlling the content and combination ratio of an alkali activator included in the cement-free alkali-activated binder, and can solve the problems of the toxicity of cement, the carbon dioxide (CO2) produced during the manufacturing of cement and the exhaustion of natural resources due to the production of cement.

Abstract: Provided are cementitious compositions and related systems and methods. The cementitious compositions, or admixtures, according to the present invention generally comprise gypsum, a first alkaline component and glass. The admixture may further comprise fly ash, which is preferably obtained as a waste by-product from a coal-burning power plant. A method according to the present invention comprises an initial step of analyzing or receiving an analysis of a fly ash sample. Based at least in part on the analysis of the fly ash sample, a mix rate may be selected and an initial admixture can be formulated, which, when added to the fly ash sample, creates an alternative or additive to Portland cement for use in concrete, for example.

Abstract: A method of making a rapid setting lightweight cementitious composition with improved compressive strength for products such as boards is disclosed. The method mixes fly ash, alkali metal salt of citric acid and lightweight aggregate with water. Compositions which include fly ash, alkali metal salts of citric acid and lightweight aggregate are also disclosed.

Abstract: The invention relates to an expanded concrete composed of binder-containing mixtures, preferably having binders composed of Portland cement as specified in DIN EN 197 or of mixtures of hydraulic, latent-hydraulic and/or pozzolanic binders, having binders, water with a fraction of 20-60% by mass based on the mass of the binder in the mixture, chemical gas-forming agent, preferably in the form of aluminum powder, at 0.05-0.25% by mass, based on the mass of the binder, for forming mostly air pores in the expanded concrete, wherein the gas-forming agent in the form of a powder forms a mixture of different particle sizes, concrete additives such as in particular microsilica and/or flyash with a fraction of 0.5-25% by mass, based on the mass of the binder, concrete admixtures of mostly liquefying character and at a fraction of 0.

Abstract: A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 40%, and in some cases less than 20%, of the foam index of the untreated fly ash. An optional alkaline activator may be mixed with the fly ash and SDA to facilitate the geopolymerization reaction. The alkaline activator may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.

Abstract: A CO2 control device and method for capturing CO2 from fluid flow, including: a flow-through apparatus and an CO2 absorbing filter treated with an alkaline material which is housed within the flow-through apparatus. The flow-through apparatus receives fluid flow and the CO2 from the fluid flow is absorbed by the CO2 absorbing filter. The absorbed CO2 is converted into CaCO3 which is combined with volcanic ash to form a useful cement material.

Abstract: Methods and compositions are disclosed that comprise cement kiln dust having a mean particle size that has been altered. An embodiment discloses a method of preparing cement kiln dust comprising: providing cement kiln dust having an original particle size; and altering the mean particle size of the cement kiln dust from the original size by grinding, separating, or a combination thereof. Another embodiment discloses a well treatment fluid comprising: cement kiln dust having a mean particle size that has been altered from its original size by grinding, separating, or a combination thereof; and water.

Abstract: A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with an activator solution sufficient to initiate a geopolymerization reaction and for a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 35% of the foam index of the untreated fly ash, and in some cases less than 10% of the foam index of the untreated fly ash. The activator solution may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.

Abstract: In accordance with an embodiment, a method for producing an aggregate is disclosed comprising mixing IBA and a second, silicoaluminous material having a calcium content less than the IBA. The method further comprises agglomerating the mixture, such as by pelletizing, and pyroprocessing the agglomerates, such as by sintering or vitrification, to form the aggregate. The second material may be a clay, such as bentonite or kaolin, a mining waste, such as granite sawing residues, waste glass, or furnace bottom ash, for example. The addition of the second material has been found to facilitate production of lightweight and normal weight aggregates. Preferably, the IBA or the mixture of IBA and the second material are wet milled prior to agglomeration. Methods for producing expanded aggregates are also disclosed.

Abstract: A method for the treatment of fly ash obtained from an incineration process of a waste incineration plant, in particular for municipal solid waste, whereby fly ash is separated from the incineration process. Furthermore, a method for the operation of a waste incineration plant, in particular for municipal solid waste or the like. The process for the treatment of fly ash is further characterized in that metals and/or metal containing compounds, in particular heavy metals and/or heavy metal containing compounds, are separated from the fly ash, which is separated from the combustion process and preferably non-fractioned, in a separation step and subsequently the fly ash reduced by the metals and/or metal containing compounds is, preferably dosed, mixed with or added to the waste to be incinerated so that the mineral parts of the fly ash, reduced by its metals and/or metal containing compounds, are returned to the combustion process.