Method of making a mining tailings based aggregate and the aggregate

Abstract

Embodiments presented provide for a method of making aggregate from mining tailings, which includes incorporating a significant amount of the mining tailings in combination with a calciferous additive, sodium hydroxide, and water. The resulting mixture is cured into a desired shape under the influence of controlled pressure and temperature for a predetermined time to create the aggregate. The aggregate is characterized by a mineralogical crystalline phase.

Description

PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None. FIELD OF THE DISCLOSURE

[0002] Aspects of the disclosure relate to producing an aggregate material used in construction. More specifically, aspects of the disclosure relate to producing a mining tailings based aggregate as well as a method of making the aggregate for use in the construction industry. BACKGROUND

[0003] Environmentally clean technologies are becoming more important in the construction process. Unknown to most individuals, the construction industry is a major producer of waste. This waste may take many forms. The providing construction materials to a job site includes transportation of the materials to the job site. Production of the materials at a manufacturer can be complicated and large amounts of energy are often used in the production of the materials.

[0004] In the case of aggregate production, conventional production technologies include loosening material from a rock face. The loosening can be accomplished through several known production techniques. When the rock face has a segmented or fractured face, a backhoe or power shovel may be used to create a shearing force on the rock. When the shearing force exerted on the face is greater than the shear strength of the rock, material is loosened.

[0005] In rock quarries that have more heterogeneous rock faces, more extreme measures must be undertaken to loosen rock to make aggregate. Generally, a drill is used to make vertical bore holes extending down within a few inches of the rock face. The bore holes are filled with an explosive. A mining engineer detonates the explosive 1PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE that subsequently causes a shear force on the rock face. The rock may then fall from the rock face.

[0006] Each of the techniques described above uses large amounts of energy which produce greenhouse gases. The production of aggregate can be a major contributor to increases in greenhouse gases. In addition to the production of greenhouse gases, conventional aggregate production can cause the creation of major amounts of dust, which can be irritating to humans.

[0007] The mining industry uses well established technologies to maximize production and minimize costs. Often, the materials that are sought are incorporated with other base materials that do not have economic value. Production techniques seek to separate the base materials from the valuable ore. The result of the process is a usable ore which is separated from the base materials. The base materials, called mining tailings, are disposed within waste piles at the mining site. The mining tailings are merely stored on site due to contamination with heavy metals that were present during the formation of the rock. Fracture of the rock during mining may free the incorporated heavy metals. Acidic rainwater may also chemically react with the mining tailings causing significant local contamination. For these reasons, mining tailings are considered potentially hazardous.

[0008] There is a need to provide construction aggregate to construction sites without the drawbacks of excessive greenhouse gas production.

[0009] There is a further need to provide aggregate to construction sites that is economically beneficial to use.

[0010] There is a still further need to beneficially use mining tailings that incorporate heavy metals. 2PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0011] There is also a need to eliminate rainwater contamination concerns at mine disposal sites.

[0012] There is also a need to minimize mining activities on virgin ground; thereby eliminating unnecessary industrial development.

[0013] There is a further need to more efficiently use mining tailings produced on site, thereby effectively using energy used in production activities. SUMMARY

[0014] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized below, may be had by reference to embodiments, some of which are illustrated in the drawings. It is to be noted that the drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments without specific recitation. Accordingly, the following summary provides just a few aspects of the description and should not be used to limit the described embodiments to a single concept.

[0015] In one example embodiment, a method to produce a mining tailings based aggregate is disclosed. In one example embodiment, a method to produce a mining tailings based aggregate is disclosed. The method may comprise receiving a feedstock of mining tailings. The method may further comprise separating the feedstock of mining tailings into a size of 35 microns or less, to create a separated fraction of mining tailings. The method may further comprise combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of mining tailings to create a mixture. The method may further comprise dry mixing the mixture to create a mixed dry mixture. The method may further comprise adding water to the mixed dry 3PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE mixture to create a green mixture. The method may further comprise roller pressing the green mixture into a green aggregate and thermally curing the green aggregate in an autoclave to form the mining tailings based aggregate.

[0016] In another example embodiment, a method to produce a mining tailings based aggregate is disclosed. The method may comprise receiving a feedstock of mining tailings. The method may also comprise separating the feedstock of mining tailings into a size of 35 microns or less to create a separated fraction of sized mining tailings. The method may also comprise combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized mining tailings to create a mixture that has a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight. The method may also comprise mixing the mixture with water to create a green mixture. The method may also comprise roller pressing the green mixture into a pre-shaped mold to directly form a formed shape. The method may also comprise thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch and with a relative humidity over 90 percent.

[0017] In another example embodiment, a construction material based upon a mining tailings material is disclosed. The material may comprise a molded formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino-silicates with incorporated mining tailings, the material having a stable crystalline structure formed into an aggregate shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly 4PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE summarized above, may be had by reference to embodiments, some of which are illustrated in the drawings. It is to be noted; however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0019] FIG.1 is a systemized approach for producing a mining tailings based aggregate and a method of making an aggregate.

[0020] FIG. 2 is a method for producing an aggregate from mining tailings in conformance with the systemized approach of FIG.1.

[0021] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures (“FIGS”). It is contemplated that elements disclosed in one embodiment may be beneficially utilized in other embodiments without specific recitation. DETAILED DESCRIPTION

[0022] In the following, reference is made to embodiments of the disclosure. It should be understood, however, that the disclosure is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated for implementation and practice in the disclosure. Furthermore, although embodiments of the disclosure may achieve advantages over other possible solutions and / or over the prior art, whether or not a given embodiment achieves a particular advantage is not limiting the disclosure. Thus, the following aspects, features, embodiments, and advantages are merely illustrative and are not considered elements or limitations of the claims except where explicitly recited in a claim. Likewise, reference to “the disclosure” shall not be construed as a generalization of the inventive subject matter disclosed herein and should not be considered an element or limitation of the claims except where explicitly recited in a claim. 5PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0023] Although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another region, layer, or section. When used herein, terms such as “first”, “second”, and other numerical terms, do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed herein could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0024] When an element or layer is referred to as being “on”, “engaged to”, “connected to”, or “coupled to” another element or layer, it may be directly on, engaged, connected, coupled to the other element or layer, or interleaving elements or layers may be present. In contrast, when an element is referred to as being “directly on”, “directly engaged to”, “directly connected to”, or “directly coupled to” another element or layer, there may be no interleaving elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms.

[0025] Some embodiments will now be described with reference to the figures. For consistency, elements in the various figures will be referenced with numbers. In the following description, numerous details are set forth to provide an understanding of various embodiments and / or features. It will be understood; however, by those skilled in the art that some embodiments may be practiced without many of these details and that numerous variations or modifications from the described embodiments are possible. As used herein, the terms “above” and “below”, “up” and “down”, “upper” and “lower”, “upwardly” and “downwardly”, and other like terms indicating relative positions above or 6PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE below a given point are used in this description to more clearly describe certain embodiments.

[0026] Aspects of the disclosure provide a method for producing an aggregate that may be used in the construction industry. Embodiments of the method produce an aggregate with a significant amount of mining tailings in combination with a calciferous additive, sodium hydroxide, and water, to cure the shape under the influence of controlled pressure and temperature for a predetermined time, to create an aggregate which is characterized by a mineralogical crystalline phase. In some embodiments, mining tailings from gold, copper and molybdenum are especially beneficial. The mining tailings from gold, copper and molybdenum have been separately tested compared to other mining tailings and shown to be especially beneficial as the elements in these tailings are fixed during the treatment process described herein. In some embodiments, a filler material may be used. Filler materials may be sand, silt, clay, or other materials in non-limiting embodiments. The resulting aggregate does not leach toxic materials under environmental conditions that the aggregate will be exposed to. The aggregate may be shaped into different sizes and angularities. Different sized aggregates may be created such that an overall porosity can be achieved.

[0027] In the methods described, the aggregate produced encapsulates potentially toxic elements. These toxic elements may include lead, mercury, arsenic, and cadmium. In embodiments, the aggregate produced may also prevent other lighter metals from also leaching under certain conditions. The resulting aggregate produced by the systematic approach described in FIG.1, as well as FIG.2, has been tested through an exhaustive number of established testing methods to determine the properties of the aggregate.

[0028] Solid materials, such as aggregates, may develop structural defects in freezing and thawing. Standardized testing has been developed to place aggregate produced by the methods described in relation to the disclosure. In testing, a 50-cycle freeze / thaw 7PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE process is performed in conformance with AASHTO T 103. The test simulates the amount of weathering an aggregate would undergo in field conditions. The resulting aggregate shows acceptable results.

[0029] Mining tailings may incorporate many different types of materials. In some embodiments, hydrocarbons may be present. Coal mining tailings may incorporate many types of hydrocarbons. By conducting a loss of ignition test, the aggregate is subjected to a specific heating temperature for a specified amount of time. The heating temperature is over the combustion temperature required for ignition. Standard ASTM C 25 requires that the weight of a test sample is recorded prior to heating. After heating, the weight of the test sample is recorded. A difference in weight of the test sample is calculated. As provided in Table 1, the loss of ignition (LOI) is minimal.

[0030] Aggregate may be used in a variety of conditions. In other instances, the aggregate may be used in conjunction with concrete to produce a concrete building structure, such as a block or a brick. When incorporated into other building materials, materials such as sodium sulfate may interact with chemicals or elements in the surrounding media. To determine the amount of potential degradation that an aggregate may undergo in some instances, test ASTM C 88, was performed on the aggregate. In ASTM C 88, the aggregate was immersed in either a saturated sodium solution or magnesium sulfate solution. After immersion, the aggregate is then placed into an oven and dried. Upon drying, the salts that permeated into the aggregate may interact with other materials surrounding the aggregate. The salts may deposit into any pore spaces within the aggregate. Upon another immersion, the salts present within the pore spaces may rehydrate. This rehydration may cause an expansive force to be created within the aggregate, subsequently damaging the structure. The results indicate sufficient soundness of the aggregate. 8PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0031] Aggregate is often used to withstand different types of construction forces. These forces usually include compression or abrasive forces. Abrasive forces, when exerted on certain types of aggregate, may cause the aggregate to fracture or break. To determine the soundness of the aggregate to abrasive forces, an abrasion test was conducted in conformance with ASTM C 131. In the test, the forces are created using a standard Los Angeles testing machine.

[0032] In the Los Angeles testing machine, a screened and weighed load of aggregate approximately five pounds in weight is inserted into a drum of the test machine. Steel balls are also incorporated within the drum. The mixture of steel balls and aggregate are scooped up to the top of the drum and allowed to drop, creating an overall crushing force between the sides of the drum, the steel balls, and the aggregate. This test was conducted on aggregate smaller than three-fourths of an inch in diameter. This scooping action is repeated a standardized number of times, and the aggregate is removed from the drum and screened and weighed a second time. The amount of abrasion loss is then recorded. The resulting range for the tested aggregate shows little to no abrasion loss.

[0033] An evaluation of the amount of lightweight particles in the aggregate was performed. In this evaluation, a sample of the aggregate was submersed in a high-gravity liquid (over a specific gravity of 2.0), and the amount of floating aggregate was determined. This may be used to determine the amount of coal or lignite contained within the sample. As tested, the aggregate has little to no coal or lignite remaining in the material.

[0034] A petrographic analysis of the aggregate, as specified in ASTM C 295, was also performed. The petrographic examination establishes whether the aggregate contains chemically unstable minerals such as soluble sulfates or unstable sulfides that may form sulfuric acid. In these embodiments, the sulfuric acid may be created through hydration from weathering or by submersion of the aggregate within an aquatic environment. These 9PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE evaluations may be performed to analyze the potential distress the aggregate may create upon a surrounding concrete matrix. Variations of the methods specified under ASTM C 295 are also conducted. In these variations, temperatures are also increased during such tests to determine viability in different temperature regimes. Unstable materials, such as smectites, are also determined, as well as the presence of swelling clay materials. The results of such petrographic examinations upon example mining tailings based aggregate are acceptable.

[0035] Material stability is vital to concrete when different materials are incorporated into a matrix. Materials that expand or contract based upon environmental changes can cause cracking or spalling of the aggregate. As the amount of swellable clays and friable particles may be detrimental when the aggregate is incorporated into a concrete brick or block, a test in conformance with ASTM C 142 was performed. Clays and friable materials at or near the surface of a structural element may also result in the pitting of the surface through wear. Test results of the materials indicate a low percentage of clays and friable materials.

[0036] Other tests were also performed to identify the physical properties of the aggregate. These include determining bulk dry specific gravity, apparent specific gravity, and water absorption percentage. All tests recorded acceptable results. Test Parameter Test Method Result Range10PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE Clay lumps and friable particles %ASTM C 142 0 – 10

[0037] Referring to FIG.1, a process for making a mining tailings based aggregate is illustrated. The method 100 entails receiving a shipment of material to be processed. The material can be received directly from a mining site. In other embodiments, the processing equipment may be moved to the mining site where processing may occur. The materials may be in the form of sands, silts, clays or small aggregate. In embodiments, the materials may be the separated components from previous processing of the ore. Mining activities that may be used include mining for zinc, coal, iron and aluminum in non-limiting embodiments.

[0038] The materials, in embodiments, may be combined into a single non-homogenous mixture for processing. In embodiments where the processing is to be accomplished remotely from the mining tailings storage area the materials may be transported by rail, car, or truck in some embodiments.

[0039] As will be understood, providing a mobile unit that processes the mining tailings based materials provides advantages over conventional treatment methods. For example, trucking or transportation of materials over roads, rails, or ships is minimized. Permitting for transporting of potentially hazardous waste is eliminated. Other advantages include eliminating “double handling” of materials, where the hazardous materials are merely placed into the treating apparatus rather than the materials being 11PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE handled, transported, unloaded, and then treated. Such elimination of double handling is not possible with conventional treatment processes.

[0040] Remediation of mining tailings materials, when it occurs at the storage site, significantly reduces greenhouse gas emissions, as transportation emissions are virtually eliminated. Permitting for the treatment site is also avoided, as the treatment of the residual materials occur at a site that was previously permitted to store mining tailings. Additionally, because the ultimate aggregate produced renders any heavy metals inert or captured, the mining tailings may not need to be chemically treated or site permitted as the mining tailings will be ultimately treated.

[0041] Treatment of the mining tailings occurring on-site allows for minimization of environmental contamination. Potentially hazardous storm water generation is also minimized as the overall amount of mining tailings may be reduced at the mining location.

[0042] After receiving the materials at step 102, the method progresses to steps 104 and 106 as well as step 108. In step 104, smaller diameter materials are separated from other diameter materials within the mining tailings feedstock. The small diameter material at 104 is placed into a silo at 110. Materials larger in diameter than 35mm may be processed as noted in step 112. The material at 106, because it is larger in diameter size than the smaller diameter components at 104, is screened at step 112. If the mining tailings size is considered to be acceptable, it is placed in the silo at 110, along with the material from step 104. If the material is too large at step 112, the material is sent to a grinder or crusher at 114. The materials is then screened a second time at step 112. If the material is acceptable in size then the material is stored in the silos. If the material is too large for the screens at 112, the material may be sent again to a grinder or crusher at 114 and then reprocessed through to the screening step at 112. The acceptance size diameter may vary. In some embodiments, the acceptance size diameter is under 35 micron diameter. If the material is rejected in the screening process at 112, the material 12PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE may be sent to a grinder or crusher at 114 and reprocessed through the screening step 112. As will be understood, mining tailings are not conventionally recycled in this manner; therefore, the process illustrated incorporates materials into a final process that was previously not used by reclamation techniques.

[0043] Storage of the material constituents of the aggregate may be stored in a silo, or in other possible alternatives. Such alternatives may include bin storage, on-site pile storage, or open-pit storage. In some embodiments, the materials may come directly from the mining operations itself where the material is produced. This may provide a system that uses the mining tailings as soon as they are created. In such instances, a continual feed process eliminates storage requirements. In mining operations with minimal overall footprint, this additional processing allows for more efficient use of land at the mining site. Maintenance of mining tailings storage areas is minimized. As will be further understood, after extraction of the main ore that is of economic value, the mining tailings may be directly used for to produce aggregate.

[0044] Lye is stored at 108. Lime is stored at 116. Each of these materials may be stored in different silos for addition to other materials. As will be understood, materials may be metered from the silo at 110 to a separate vat or container such that specific amounts of lye and / or lime may be added to the contents coming from the silo at 110. The resulting mixture is then weighed at 118. Each of the lye and the lime may also be measured / metered to achieve a specific weight-based mix ratio. In embodiments, the provision of lye and lime may be performed on a “per batch” basis where the amounts of lye and / or lime may be pre weighed prior to addition to a mixing machine.

[0045] The dry materials may be mixed first to achieve a relatively uniform mixture of materials based on the dry batch formula. In some embodiments, a batch mixing process is performed where large amounts of each constituent are added to a hopper. The rotary motion of the hopper mixes the constituents. Other mixing forms, such as convective 13PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE mixing, may also be performed. In such convective mixing processes, a base material travels along a beltway or other transportation mechanism, and other constituents are added to the base material, thereby arriving at the end of the process with a mixed material. Still, further types of mixing may be used, such as paddle mixers, industrial ribbon mixers, double cone blenders, drum blenders, or shear mixers.

[0046] After the mixing of the dry components, water may be added. As illustrated, the materials are mixed at 122 with water added at step 120. In embodiments a deionized water may be added. In other embodiments, potable or non-potable water may be used. After addition of the water, the resultant material is defined as a “green” material or wet mix.

[0047] The wet mix of material is then passed through a press at step 124. As will be understood, a hydraulic press may be used at step 124. Additionally, to increase the efficiency of the process, a roller press may be used at step 124, thereby providing continuous processing ability for the method. The green mixture may be pressed to a specified compression value, such as processing through a 5000 pounds per square inch roller press. The use of a roller press is considered a valuable alternative to other presses as the amount of energy used by the roller press may be substantially less than other conventional hydraulic presses.

[0048] The use of the roller press is significant as the overall amount of energy usage and the reduction of emissions that occur during the process are reviewed and rated by governmental agencies, such as the EPA. A single roller cylinder may be used in one non-limiting embodiment as the green material is held captive in a tray or mold. Other possibilities for a roller press include a dual action or dual roller system with top and bottom rollers. 14PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0049] While the material constituents of the green mixture are designated by the batch design, the use of a dual-action or dual roller system may allow for additional grinding of materials, such as oversized mining tailings, if such a need arises. In the instance of a roller press, the amount of compressive force may be between 7000kN and 35,000kN.

[0050] Thicknesses of the green mixture, after compression, may vary. In some embodiments, the green product (prior to insertion into an autoclave for drying) may be 3 inches. Other values may be used. One such value may be thicknesses less than three- fourths of an inch. In such embodiments, relatively thin strips of material may be formed. These strips may be easily converted through additional processing steps to make large or small aggregates.

[0051] The green mixture, after being roller pressed at 124, is then sent to an autoclave at step 130. The green mixture is placed in the autoclave for a specific amount of time and dried. In the autoclave, a humid atmosphere may be achieved by water, at 126, being added to a boiler, at 128, providing a steam atmosphere for the autoclave 130. In some instances, the autoclave may be equipped with a separate heating system for water. The autoclave may be equipped to capture vapors that occur during the curing of the green mixture. These vapors may include those that are developed through the curing process. In embodiments, the heating process may drive off heavy metals that may be captured.

[0052] In some applications, the cured product from the autoclave may then be sent to a crusher to crush the material to a desired final size. The crushing may result in the desired size of aggregate. The material may also be tumbled, as necessary, in a tumbling machine if the final product to be achieved specifies a non-angular resultant product.

[0053] After completion of curing in an autoclave, samples of the material may be tested at 132 to see if they conform to expected standards. As will be understood, the testing may be related to any or all of the tests identified in Table 1. Additional tests, such as for 15PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE size, specific gravity, angularity, or other features, may also be performed. If the testing at 132 is acceptable, packaging may be accomplished at 134. To this end, packaging may take many forms. The materials may be ordered in small batches or larger batches by a customer. Smaller batches may be placed in 20 to 50 pound bags for direct delivery to a consumer or retailer. Larger batches may be separated according to the size of the material. Material may be put into large freestanding piles that may be loaded onto railcars, trucks, ships, or other transportation devices. In embodiments, different size aggregates may be combined to achieve an overall engineering specification. To this end, for example, one batch of three-fourths of an inch in diameter size material may be added to one batch of one-half of an inch in diameter size material. In further embodiments, three or more different size aggregates may be combined.

[0054] A unique feature of the method illustrated in FIG. 1, is that if testing is not acceptable at 132, the method may return to step 114 for further grinding and crushing the material. In these embodiments, the material that fails the testing is related to the size component of the aggregate that has been produced. Thus, the overall size of the aggregate is too large for a specified diameter by a customer. To achieve the size of the material as specified by the customer or project engineer, the size of the aggregate may be altered by an additional grinding or crushing at 114.

[0055] The use of lime at 116 involves the addition of an inorganic material composed primarily of calcium oxide and hydroxides. The type of hydroxides that may be incorporated with the calcium oxides may vary. In one possible alternative, calcium hydroxide is the type of hydroxide used. The source material for lime may be from quarried material. The quarried material may be, in non-limiting examples, limestone. As will be further understood, instead of directly using calcium hydroxide, a process may be used at the site or with equipment where quicklime is hydrated with water to produce calcium hydroxide. Quicklime is defined as calcium oxide. The hydration may be 16PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE performed with deionized water in some embodiments. Other embodiments may use potable water.

[0056] Although the process at 116 shows a single step, the step may be subdivided by using quicklime with an addition of water to produce lime that is then weighed at 118 with material from the silos at 110. The formation of the aggregate may occur in separate locations and then the results from the locations added together. Thus, the process of hydrating the quicklime may occur separate from the other components of the aggregate and then after the hydration, the hydrated quicklime may itself be added. In still further embodiments, the quicklime, water and other materials may be added together.

[0057] As will be further understood, different types of lime with other features may be used for the lime function at 116. These types of lime may include portlandite, brucite, magnesite, and other magnesium hydroxycarbonate compounds.

[0058] Lime in the building industry is characterized into three subcategories. Each of these subcategories may be used in combination with the process. The three types of lime include pure, hydraulic, and poor lime. In embodiments, hydraulic lime, also called water lime, contains lime with at least one of silica or alumina. They hydraulic lime may be set by exposure to water.

[0059] In one example embodiment, the mining tailings may resemble a clay. The amount of clay added to the hydraulic lime predicts the type of behavior of the hydraulic lime and the ultimate use of the materials. With greater use of clay materials, hydraulic lime can be used in more aggressive and freezing climates than limes with lesser amounts of clay added.

[0060] In some embodiments, pure lime may be used in a variety of possible exposure conditions. Pure lime consists primarily of calcium hydroxide, which is derived from 17PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE quicklime with the addition of water, and may contain up to 5 percent of other ingredients. Pure lime may be used in mixtures where the aggregate will be exposed to potential cracking due to loads or freeze-and-thaw conditions.

[0061] Pure lime allows for a self-healing process to occur for the aggregate produced, thereby preventing further degradation of the aggregate due to the conditions that are being experienced. In embodiments, water may dissolve calcium bearing components and transports the calcium from a zone rich in calcium, to voids and cracks. In this way, small cracks and voids are refilled with re-crystallized components in an autogenous self- healing process.

[0062] In some instances, poor lime may be used when the base material has little to no toxicity. Poor lime is characterized by comparatively longer set times and strength. To this end, poor lime may be used in low-quality aggregates that do not need extensive encapsulation for toxic elements or materials and that also require a relatively cost- effective treatment process for aggregate production. Uses of aggregate, not subjected to large forces, may be used for landscaping activities and a bedding for rural roadways with minimal truck traffic.

[0063] Alkali metal hydroxide is added when lye is incorporated. Different types of alkali metal hydroxides may be added, including sodium hydroxide or potassium hydroxide, as nonlimiting embodiments. The type of lye that may be added in the process may take several forms. The forms may be flakes, pellets, powders, solutions, or beads. One advantage of adding lye to the aggregate is to create an alkaline solution. The alkaline solution prevents a potential acidic attack upon the aggregate produced. In embodiments where the aggregate may experience a hostile environment that is acidic in nature, greater amounts of lye may be added to combat acid attack. 18PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0064] As will be understood, the amount of lye at 108 and the amount of lime at 116 may vary when added to the materials obtained from the silos at 110. In some instances, no lye at 108 is used. In some further instances, no lime at 116 is used. Thus, the process may include various amounts of each component according to the aggregate type needed for end production.

[0065] Referring to FIG.2, a method 200, in accordance with one example embodiment of the disclosure, is illustrated. The method entails receiving materials at step 202. The receiving of materials includes materials derived from mining tailings. The mining tailings may vary in diameter size. A specification for the maximum size of aggregate may be submitted by a customer related to a specific project. To that end, the material is sized at 204 according to the maximum size range desired. For example, the specification may state that the maximum diameter size of material may be three-fourths of an inch.

[0066] The material may be put through a screening process to separate out acceptable diameter sized material from unacceptable diameter sized materials. If the material is not of the proper size at 204, the material may be resized at 222 through the use of a grinding or abrasion method. Alternatively, material that will pass the required size may be found; therefore, resizing the material would not be necessary at 222. At 206, additives may be provided to the sized materials. The additives may be lime, lye, or other materials. Percentages and weights of different lime and lye may be incorporated into the sized material arriving from 204. In embodiments, sand or other materials may be added to manufacture what is defined as green material. The other materials may be filler materials such as sand. The addition of sand or other materials may be controlled such that the overall specifications required for the material are maintained. To ensure the proper mixture, each of the individual components may be weighed at 208.

[0067] The materials may then be dry mixed at 210. After completion of the dry mix at 210, water may be added directly to the mixture, or the contents of the dry mixture may 19PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE be emptied and placed into a wet mixer at 214, wherein water is added at 212 to the wet mixture at 214. The wet mix generated at 214 is placed into a mold and provided to a roller press at 216. The roller press compresses the green mixture to a desired thickness, and heat is applied at 218. Heat applied at 218 may be in a steam atmosphere in an autoclave. Heating sources other than an autoclave may be used in other embodiments. In embodiments, a mobile autoclave is used such that sized material from 204 is treated at the mining site directly, without the need for shipping.

[0068] The use of an autoclave allows for efficient use of energy and minimization of greenhouse gas emissions. The autoclave provides for identification, separation, and recycling of heavy metals that may be present within the mining tailings. The autoclave may also remove hydrocarbons that may be present within the tailings.

[0069] After the heating process at 218, the aggregate size produced may be evaluated at 220. The sizing operation performed at 220 may be through the performance of dumping materials onto mechanical screens to separate fractions of material. Acceptable sized material results in an end of the process. Material that is not sized appropriately may be resized at 222. After resizing at 222, a query is run if the process has been previously completed at 224. If the process has been previously completed at 224, then the resized material may be used, and the process ended. If the resized material has not been previously processed, the method may return back to 206, where additives of lime and lye are added. As will be understood, successive additions of additives such as lime and lye are prevented through the query run at 224. Thus, the batch process that creates the aggregate always maintains the correct chemical composition.

[0070] The roller press at 216 may be a dual roller press or a single roller press that impacts material into a predefined mold. In the process of making small aggregate, a dual roller press may be used to provide small or thin-size aggregate. In instances where a larger aggregate is needed, then a single-sided roller press may be used at 216. In either 20PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE embodiment, after heating the green mixture at 218, an additional step of abrasive mechanical action at 220, for example, may be accomplished to size the heated material correctly. As will be further understood, the roller press at 216 may directly determine the aggregate size from the rolling action in one step prior to heating. For example, such a roller press action may include mechanically separating components of an area into desired sizes such as one-half-inch, aggregate, maximum, and dimension size. The roller chosen, for example, may directly make materials in various sizes such that a specific void ratio for the aggregate, placed in an amendment, is maintained below a specific threshold.

[0071] In embodiments of the disclosure, 50 tons or more of aggregate can be processed per hour. Although described as using a roller press, other processes are possible, including an extrusion process where the green mixture is cut or shaped directly into desired sizes. In embodiments, when an extrusion process is used, a cutting mechanism may be used to separate portions of the extruded material into a desired aggregate size.

[0072] In embodiments, a separate step of drying the green mixture may occur after the roller press or extrusion process. The drying process may include holding the aggregate in trays for periods up to and possibly exceeding thirty-six hours. This drying process would be in addition to the heating in the autoclave at 130. Firing time at the autoclave may be determined by the aggregate size produced. Firing may take one-half-hour in the case of small aggregate to 10 hours for large-size material. Autoclave temperatures of between 180 degrees Celsius and 250 degrees Celsius may be used as a non-limiting temperature profile. After autoclave thermal treatment, a separate step of cooling may also occur prior to packaging at 134 or determining size acceptance at 220. In the embodiments using an autoclave, such embodiments minimize the amount of greenhouse gas emissions produced as the autoclave uses energy more efficiently than a kiln. 21PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0073] The autoclave used at 130 may be equipped to handle toxic element vaporization, thereby capturing vaporized hazardous emissions. Such emissions may include those of mercury or other heavy metals. As such, ordinary kiln technology, which does not provide this environmental benefit, is not used, as the fugitive emissions would be considered to be a generated waste, impacting the overall environmental clean-up capability of the process. In further embodiments, the autoclave times may be minimized for small aggregate production, providing an economic benefit for greenhouse gas emissions.

[0074] The autoclave used at 130 also has the advantage of keeping a controlled humidity and pressure inside the unit during the heating process. Pressures up to sixteen atmospheres may be exerted on the aggregate during the heating process, thereby chemically combining the lime and / or lye with the coal combustion residue to encapsulate toxic elements. Humidity levels up to 100 percent relative humidity may be used to provide a structurally sound final product.

[0075] Additives may be added to the green material in order to provide the desired architectural color. Additions of zinc and / or iron, as non-limiting possibilities, may be added to the green mixture to produce the required color of the material. Pigments may be incorporated into clay materials. The pigments may also be incorporated into the aggregate through addition of a powder.

[0076] The aspects of the methods process provided herein have several advantages over conventional aggregate production. Conventional aggregate production generates large amounts of greenhouse gases. For example, conventional aggregate production uses at least three mechanical crushing steps that are undertaken to arrive at a finalized product. The mechanical crushing processes include a primary jaw crusher, a secondary cone crusher, and a tertiary cone crusher. Each of these mechanical crushing steps 22PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE involves the use of fuels for rotary or linear motion, production of heat and greenhouse gases that are not present in the present disclosure. Conventional aggregate is first mined and then provided to a main primary jaw crusher. This step is necessary because the overall size of the aggregate obtained from nature requires crushing large portions of a rock face. This step is eliminated through the current process as the mining tailings do not need generation energy compared to natural products. Thus, the current process described is superior to conventional technologies.

[0077] Conventional technologies use a secondary cone crusher to crush medium sized pieces into more manageable sizes. Again, the current process does not use the secondary cone crusher process, saving on fuel, energy, and environmental emissions.

[0078] Conventional aggregate production does not check for the presence of toxic materials, such as heavy minerals. In the current process, any heavy metals not chemically combined during the mixing process and setting process with the lime / lye are vaporized off by the autoclave. Such toxic materials may be captured and recycled. Conventional aggregate production does not provide such environmental benefits. Conventional aggregate mining merely mechanically degrades the existing aggregate source. Thus, if the aggregate is incorporated with heavy metals in the surrounding soils, the heavy metals will continue to be present up to and after the placement of the aggregate in the final position.

[0079] Conventional aggregate production does not take a defined waste and allow the waste to be used in an environmentally friendly manner. Conventional aggregate production merely takes a naturally occurring material and uses mechanical processes to size the overall material. Such sizing and production occurs at the mine, as this is the most economical production method. 23PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0080] Conventional aggregate production activities are also eliminated by the present disclosure. For example, conventional aggregate production involves significant production of construction dust. This dust production must be treated at the source to satisfy strict environmental regulations.

[0081] In order to satisfy local, state and federal regulations, dust reduction often includes spraying down feedstock hills to minimize dust production to the local population. Aspects of the current disclosure prevents the use of dust reduction activities and use of valuable water. As will be understood, mining operations often occur at remote locations where water sources may be limited. To this end, the elimination of water usage can substantially reduce overall economic costs of aggregate production. The current disclosure provides an essentially sealed processing regime.

[0082] Due to the wetting requirements for conventional aggregate production, mining permits also require stormwater management and run-off management plans. These plans must be approved and verified by local officials. Such requirements are precluded under the disclosed process as raw materials enter the process, and only a finalized product is removed (other than emissions from the autoclave). Moreover, the emissions from the autoclave may be minimized and controlled such that greenhouse gas emissions are minimized, and toxic materials liberated by the process may be reused as feedstock for other processes and industries. To this end, the processes described herein present significant improvements over conventional aggregate production. In addition to the above, since the permits for the aggregate production are minimized or are eliminated, the cost of legal services and site maintenance are minimized.

[0083] Use of mining tailings as an aggregate is not permitted in conventional applications because of the potential for heavy metal contamination and / or generation of acids, such as sulfuric acid which can harm the environment and structures. Mining tailings may contain various element and minerals. In many applications, pyrite-based 24PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE materials may degrade, causing various toxic elements to leach into the environment. To this end, mining tailings are not used in such aggregate capacities because of the fear of contamination. Such fears of contamination are eliminated with embodiments of the disclosure. A beneficial use for mining tailings is achieved through the process by adding lime and / or lye, thereby chemically encapsulating pyrites and other materials. The chemical changes occurring throughout the process are achieved through the various steps of the process, including the use of the humidity and pressure-controlled capabilities of the autoclave.

[0084] Different mining tailings may have different chemical constituents. The methods are applied to the different chemical constituents of differing mining tailings to treat these feedstock materials such that the resultant stream of products from the method is usable under current regulatory requirements. Conventional methods do not provide such usable products.

[0085] In embodiments, the feed material is dried and screened from 35 to 500 microns. Any material larger than 35 microns will be rejected and ground down (using a ball mill) to an acceptable particle size. Screened and dry material is mixed with calcium oxide (lime) or calcium hydroxide (hydrated lime). An additional sodium hydroxide (lye) compound is added to the mix. The mix ratio of the blend is 100 percent material with 3 percent to 15 percent calcium oxide or calcium hydroxide and 1 percent to 5 percent sodium hydroxide, based on the total weight of the material. The material is thoroughly mixed, and the finished material is malleable to the touch but cannot lose shape after molding. The mixed material is transferred into a rolling press that applies a force of 5,000 pounds per square inch to 15,000 pounds per square inch to mold the green mixture into aggregate or briquette shapes. Once the green mix has been formed to the desired shape, it becomes known as a green product. Green product is transferred into a thermal curing treatment. Thermal curing is performed at 140 pounds per square inch to 350 25PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE pounds per square inch and 180 degrees Celsius to 225 degrees Celsius for 4 to 10 hours in one non-limiting embodiment.

[0086] Embodiments may include the following alternatives or features. These include performing a preparation of the feedstock into the method. In one embodiment, the mining tailings are initially subjected to a drying process to remove moisture content. Subsequently, the dried material undergoes mechanical sieves screening to achieve a particle size distribution within the range of 35 to 500 microns.

[0087] In embodiments, material particles exceeding the upper limit of 35 microns are identified and segregated for further processing, as illustrated at 112. These oversized particles are directed to a ball mill, where they undergo grinding operations until they reach the desired particle size distribution.

[0088] The material from the silos at 110 may be screened. Appropriately sized dry material is then introduced into a mixing chamber where it is blended with predetermined quantities of calcium oxide (lime) or calcium hydroxide (hydrated lime) and sodium hydroxide (lye). The proportions of these chemical compounds are adjusted to achieve the desired chemical composition and reactivity within the final product. The mixing process is carefully controlled to ensure uniform distribution of the chemical compounds throughout the material matrix.

[0089] Mixing at 122 is then performed. The blended material undergoes thorough mixing to homogenize the mixture and ensure even distribution of the chemical additives. The resulting mixture, known as the green mixed material, possesses specific physical properties, including malleability and cohesiveness, which render it suitable for subsequent forming processes. Precise control is maintained over the mixing parameters to achieve the final product's consistent quality and performance characteristics.

[0090] In embodiments, pauses in the processing of the materials may occur. For example, the dry components may be mixed and separately stored prior to addition of 26PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE water. In such embodiments, aggregate may be made to order once a customer orders material.

[0091] In embodiments, the green mixed material is then passed through a rolling press apparatus equipped with precision molds designed to impart the desired shape and dimensions to the final products. The rolling press may be hydraulically controlled to ensure a constant compaction pressure. The material is subjected to controlled compression forces ranging from 5,000 pounds per square inch to 15,000 pounds per square inch, facilitating the formation of dense, uniform aggregates or briquettes. Molds are used to ensure encapsulation of the green mixture and to allow compression.

[0092] In these embodiments, the molding process applies meticulous attention to detail to ensure the accurate replication of mold geometry and prevent defects or inconsistencies in the finished products. The mold geometry may be complex in nature to simulate natural aggregate. Finishes (rough or smooth) may be added to the aggregate.

[0093] In some embodiments, following molding, the green products are transferred to a thermal curing chamber, where they undergo a curing process to enhance their mechanical strength and durability. Thermal curing is carried out under controlled conditions, typically at temperatures ranging from 180 degrees Celsius to 225 degrees Celsius, and pressures between 140 pounds per square inch and 350 pounds per square inch, for a specified duration lasting between 4 to 10 hours. During thermal curing, chemical reactions occur within the material matrix, forming stable crystalline phases and developing interparticle bonds, thereby imparting structural integrity and dimensional stability to the final products. The thermal curing process achieves the desired performance characteristics, including compressive strength, abrasion resistance, and resistance to environmental degradation, in the finished aggregates or briquettes.

[0094] Within the autoclave, at 130, in embodiments, chemical reactions occur. The lime (calcium oxide or calcium hydroxide) and lye (sodium hydroxide) react with the other 27PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE materials in the mixture. These reactions form new compounds, such as calcium silicate hydrates and sodium alumino-silicates, through processes like pozzolanic reactions and alkali activation. In these embodiments, the high temperature and pressure conditions in the autoclave accelerate the hydration of lime and lye. Hydration reactions lead to the formation of calcium hydroxide and sodium hydroxide solutions, which act as activators for the clay minerals, promoting their dissolution and re-precipitation into stable crystalline structures.

[0095] In embodiments, under the applied pressure and temperature within the autoclave, the clay-lime-lye mixture undergoes consolidation, forming a dense, homogenous matrix. The combination of chemical reactions and compaction leads to the development of mechanical strength and structural integrity in the cured product.

[0096] In embodiments, microstructural changes occur. The thermal curing process induces changes in the microstructure of the material, including the refinement of pore size distribution and the formation of interlocking crystals or mineral phases. These changes contribute to the enhancement of mechanical properties such as compressive strength and durability.

[0097] The combination of chemical reactions and physical compaction facilitates the setting and hardening of the material. During curing in the autoclave, the clay-lime-lye mixture undergoes a transition from a plastic or malleable state to a rigid and stable form, capable of withstanding external forces and environmental conditions.

[0098] Aspects of the methods described may be performed by computer controlled equipment. As such, portions of the disclosure may be recorded onto a non-volatile memory system. For definitional purposes, a non-volatile memory system may be a memory system that does not wipe clean after the termination of electrical power to the system. Non-volatile memory systems may include compact disks, solid-state drives, and universal serial bus devices. These memory systems may be used to store program 28PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE executable method steps for a computer, server, or computing arrangement. Control of such equipment and methods under the current disclosure are contemplated.

[0099] Different descriptions of the claims are recited. These descriptions should not be considered limiting. In one example embodiment, a method to produce a mining tailings based aggregate is disclosed. The method may comprise receiving a feedstock of mining tailings. The method may further comprise separating the feedstock of mining tailings into a size of 35 microns or less to create a separated fraction of mining tailings. The method may further comprise combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of mining tailings to create a mixture. The method may further comprise dry mixing the mixture to create a mixed dry mixture. The method may further comprise adding water to the mixed dry mixture to create a green mixture. The method may further comprise roller pressing the green mixture into a green aggregate and thermally curing the green aggregate in an autoclave to form the mining tailings based aggregate.

[0100] In another example embodiment, the method may be performed wherein the combining the weighed portion of the at least one of a lye and a lime amount to the weighed portion of the separated fraction of mining tailings is performed to a mix ratio.

[0101] In another example embodiment, the method may be performed wherein the mix ratio is 3 percent to 15 percent of at least one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight.

[0102] In another example embodiment, the method may be performed wherein the thermal curing of the green aggregate is performed at a mining tailings storage area. 29PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0103] In another example embodiment, the method may be performed wherein the roller pressing is hydraulic roller pressing and the roller pressing compresses the green mixture into a mold.

[0104] In another example embodiment, the method may be performed wherein the roller pressing compresses the green mixture between 5,000 pounds per square inch and 15,000 pounds per square inch.

[0105] In another example embodiment, the method may be performed wherein the thermal curing is performed between 180 degrees Celsius to 225 degrees Celsius between 4 to 10 hours at a pressure of between 140 pounds per square inch to 350 pounds per square inch and a relative humidity over 90 percent.

[0106] In another example embodiment, the method may further comprise crushing the aggregate after the thermally curing of the green aggregate in the autoclave.

[0107] In another example embodiment, the method may be performed wherein the aggregate produced is characterized by a mineralogical crystalline phase.

[0108] In another example embodiment, the method may be performed wherein the lime is one of calcium oxide and calcium hydroxide.

[0109] In another example embodiment, the method may be performed wherein a portion of the feedstock of mining tailings over 35 microns in diameter are crushed such that the portion has a diameter of 35 microns or less after the crushing.

[0110] In another example embodiment, the method may be performed wherein the aggregate has at least one of calcium silicate hydrates and sodium alumino-silicates. 30PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0111] In another example embodiment, a method to produce a mining tailings based aggregate is disclosed. The method may comprise receiving a feedstock of mining tailings. The method may also comprise separating the feedstock of mining tailings into a size of 35 microns or less to create a separated fraction of sized mining tailings. The method may also comprise combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized mining tailings to create a mixture that has a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight. The method may also comprise mixing the mixture with water to create a green mixture. The method may also comprise roller pressing the green mixture into a pre-shaped mold to directly form a formed shape. The method may also comprise thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch and with a relative humidity over 90 percent.

[0112] In another example embodiment, the method may further comprise crushing the formed shape to an aggregate size material after the thermal curing.

[0113] In another example embodiment, the method may be performed wherein the crushing the formed shape results in a final aggregate diameter of no greater than three- fourths of an inch.

[0114] In another example embodiment, the method may be performed wherein portions of the feedstock above 35 microns size are mechanically abraded to a new size of less than 35 microns prior to adding the new sized portion to the separated fraction. 31PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE

[0115] In another example embodiment, the method may further comprise mechanically separating the crushed aggregate size material into finalized size portions.

[0116] In another example embodiment, the method may be performed wherein the thermally curing to the formed shape includes forming at least one of silicate hydrate and sodium alumino-silicates.

[0117] In another example embodiment, the method may be performed wherein the roller pressing the green mixture into a pre-shaped mold to directly form the formed shape occurs at a pressure of between 5,000 pounds per square inch and 15,000 pounds per square inch.

[0118] In another example embodiment, a construction material based upon a mining tailings material is disclosed. The material may comprise a molded formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino-silicates with incorporated mining tailings, the material having a stable crystalline structure formed into an aggregate shape.

[0119] The foregoing description of the embodiments has been provided for illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0120] While embodiments have been described herein, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments are envisioned that do not depart from the inventive scope. Accordingly, the scope of the present claims or any 32PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE subsequent claims shall not be unduly limited by the description of the embodiments described herein. 33

Claims

PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE CLAIMS What is claimed is:

1. A method to produce a mining tailings based aggregate, comprising: receiving a feedstock of mining tailings; separating the feedstock of mining tailings into a size of 35 microns or less to create a separated fraction of mining tailings; combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of mining tailings to create a mixture; dry mixing the mixture to create a mixed dry mixture; adding water to the mixed dry mixture to create a green mixture; roller pressing the green mixture into a green aggregate; and thermally curing the green aggregate in an autoclave to form the mining tailings based aggregate.

2. The method according to claim 1, wherein the combining the weighed portion of the at least one of a lye and a lime amount to the weighed portion of the separated fraction of mining tailings is performed to a mix ratio.

3. The method according to claim 2, wherein the mix ratio is 3 percent to 15 percent of at least one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight.

4. The method according to claim 1, wherein the thermal curing of the green aggregate is performed at a mining tailings storage area.

5. The method according to claim 1, wherein the roller pressing is hydraulic roller pressing and the roller pressing compresses the green mixture into a mold. 34PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE 6. The method according to claim 5, wherein the roller pressing compresses the green mixture between 5,000 pounds per square inch and 15,000 pounds per square inch.

7. The method according to claim 1, wherein the thermal curing is performed between 180 degrees Celsius to 225 degrees Celsius between 4 to 10 hours at a pressure of between 140 pounds per square inch to 350 pounds per square inch and a relative humidity over 90 percent.

8. The method according to claim 1, further comprising: crushing the aggregate after the thermally curing of the green aggregate in the autoclave.

9. The method according to claim 1, wherein the aggregate produced is characterized by a mineralogical crystalline phase.

10. The method according to claim 1, wherein the lime is one of calcium oxide and calcium hydroxide.

11. The method according to claim 1, wherein a portion of the feedstock of mining tailings over 35 microns in diameter are crushed such that the portion has a diameter of 35 microns or less after the crushing.

12. The method according to claim 1, wherein the aggregate has at least one of calcium silicate hydrates and sodium alumino-silicates.

13. A method to produce a mining tailings based aggregate, comprising: receiving a feedstock of mining tailings; 35PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE separating the feedstock of mining tailings into a size of 35 microns or less to create a separated fraction of sized mining tailings; combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized mining tailings to create a mixture that has a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight; mixing the mixture with water to create a green mixture; roller pressing the green mixture into a pre-shaped mold to directly form a formed shape; and thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch and with a relative humidity over 90 percent.

14. The method according to claim 13, further comprising: crushing the formed shape to an aggregate size material after the thermal curing.

15. The method according to claim 14, wherein the crushing the formed shape results in a final aggregate diameter of no greater than three-fourths of an inch.

16. The method according to claim 12, wherein portions of the feedstock above 35 microns size are mechanically abraded to a new size of less than 35 microns prior to adding the new sized portion to the separated fraction.

17. The method according to claim 12, further comprising: 36PATENT ATTORNEY DOCKET ECH-006 METHOD OF MAKING A MINING TAILINGS BASED AGGREGATE AND THE AGGREGATE mechanically separating the crushed aggregate size material into finalized size portions.

18. The method according to claim 12, wherein the thermally curing to the formed shape includes forming at least one of silicate hydrate and sodium alumino- silicates.

19. The method according to claim 12, wherein the roller pressing the green mixture into a pre-shaped mold to directly form the formed shape occurs at a pressure of between 5,000 pounds per square inch and 15,000 pounds per square inch.

20. A construction material based upon a mining tailings material comprising: a molded formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino-silicates with incorporated mining tailings, the material having a stable crystalline structure formed into an aggregate shape. 37

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