A scalable and stable process for converting incineration bottom ash into usable aggregates

Abstract

Disclosed is an aggregate comprising a cement comprising ordinary Portland cement, ground granulated blast furnace slag, and bottom ash, where the cement is hydrated in the presence of the ground granulated blast furnace slag to form calcium silicate hydrate or a derivative thereof that encapsulates the bottom ash. Also disclosed herein is a method of producing the aggregate, the method comprising mixing the cement and ground granulated blast furnace slag with the bottom ash in the presence of water to form a precoated bottom ash, and granulating the precoated bottom ash.

Description

Detailed Description of the Invention

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Singapore Patent Application No. 10202108358Q, filed on July 30, 2021, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0002] Technical Field The present disclosure relates to an aggregate. The present disclosure also relates to a method for producing the aggregate and uses of the aggregate.

[0003] background The generation rate of municipal solid waste (MSW) may be increasing proportionately with the increase in the world population, possibly due to anthropogenic activities, urbanization, economic development, and industrialization. Sump and incineration may be considered as the two main MSW treatment / disposal approaches worldwide. Thus, the increase in MSW may inevitably raise the pressure to have more landfill sites to dispose of incineration residues. Referring to Singapore as an example, it was estimated that about 7.2 million tonnes of MSW was generated in 2019 alone, of which 58% was estimated to be recycled, 39% was estimated to be incinerated, and 3% was estimated to be landfilled. Although 90% of the waste volume can be reduced by incineration, it is still not the final stage of waste treatment at the end of incineration. This is because residuals such as incineration bottom ash (IBA) and incineration fly ash (IFA) still need to be disposed of after incineration via landfill, and Singapore only has one landfill site, the Semakau landfill (SL). Unfortunately, the lifespan of SL is expected to be less than 20 years, up to 2035 at most. Therefore, countries such as Singapore may have to make careful plans to fully utilize incineration ash (IA), especially incineration bottom ash which accounts for 85%-95% of the total weight of ash after MSW incineration, which appears to be the only way to extend the lifespan of SL due to the limited availability of landfill sites.

[0004] To reduce incineration bottom ash for landfill disposal, the use of incineration bottom ash has been considered. However, the toxic heavy metal and chloride content in incineration bottom ash appears to significantly hinder its utilization in many applications. Therefore, even before incineration bottom ash can be utilized, it must be treated. Many existing treatment methods, such as separation processes for metal recovery, solidification / stabilization to fix harmful contents in incineration bottom ash, heat treatment, and alkali treatment, may improve the quality of incineration bottom ash and reduce its environmental impact. Despite this, such treatment processes tend to be time-consuming, costly, or difficult in practice. For example, using chemicals and recirculating the same water to wash IBA often increases the amount of heavy metals dissolved in the water, which can reach concentrations that exceed regulatory limits in the effluent.

[0005] In order to utilize incineration bottom ash while minimizing or avoiding the aforementioned processing, we considered the use of MSW incineration bottom ash as a substitute for coarse or fine aggregate in concrete, considering that the sources of non-renewable natural aggregates are rapidly depleting as the global demand continues to increase. In general, incineration bottom ash may contain metal, ceramic, stone, glass fragments and unburned organic matter, possibly with a particle size distribution ranging from 0.1 mm to 100 mm. Stone fragments made from incineration bottom ash are one of the most sought-after alternative aggregate materials. This may be because incineration bottom ash stone fragments may be similar to aggregates and the large incineration bottom ash volume generated by waste-to-energy plants makes incineration bottom ash stone fragments a convenient alternative to bridge the aggregate supply-demand gap. That said, incineration bottom ash stone fragments tend to contain high concentrations of toxic heavy metals that may be easily leached and have relatively weaker strength properties like untreated incineration bottom ash compared to treated incineration bottom ash. Therefore, the use of untreated IBA as an aggregate replacement in concrete remains a challenge.

[0006] Therefore, there is a need for scalable, sustainable and cost-effective processing methods to convert IBA into usable materials such as coarse or fine aggregates in the production of ready-mix concrete.

[0007] overview In a first embodiment, there is provided an aggregate comprising: Cement containing ordinary Portland cement; pulverized granulated blast furnace slag; Including the main ash, An aggregate is provided in which the cement is hydrated in the presence of the ground granulated blast furnace slag to form calcium silicate hydrate or a derivative thereof which encapsulates the bottom ash.

[0008] In another aspect, there is provided a method of producing an aggregate as described in various embodiments of the first aspect, the method comprising: mixing cement and ground granulated blast furnace slag with bottom ash in the presence of water to form a precoated bottom ash; granulating the precoated bottom ash; Includes.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS The drawings are not necessarily to scale, emphasis instead being placed upon illustrating generally the principles of the present disclosure.In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which: [Brief description of the drawings]

[0010] [Figure 1A]FIG. 1A shows a cross-section of one of the GGBS-OPC coated IBA aggregates (which may be referred to herein as GGBS-coated IBA aggregates) of the present disclosure (see the left image, which is an optical image obtained by optical microscopy). The aggregate was cut at its center. The average size of the aggregate is 2418.78 μm. This aggregate is based on a GGBS-OPC:IBA weight ratio of 2:1. The average thickness of the encapsulation layer surrounding the IBA core is 448.31 μm, which is derived from at least 18 points (e.g., 18 or 20 points) measured along the encapsulation layer as shown in the table (see the right image). The average size of the aggregate may range from 2000 μm to 4000 μm, from 2418 μm to 2523 μm, etc. The average thickness of the encapsulation layer surrounding the IBA core may range from 295 μm to 449 μm, from 319 μm to 449 μm, etc. [Figure 1B] FIG. 1B shows a cross-section of another one of the GGBS-OPC coated IBA aggregates of the present disclosure (see left image, which is an optical image obtained by optical microscopy). The aggregate was cut at its center. The average size of the aggregate is 2523.072 μm. This aggregate is based on a 1:1 GGBS-OPC:IBA weight ratio. The average thickness of the encapsulation layer surrounding the IBA core is 319.118 μm, which is derived from 20 points measured along the encapsulation layer as shown in the table (see right image). The average size of the aggregate can range from 2000 μm to 4000 μm, 2418 μm to 2523 μm, etc. The average thickness of the encapsulation layer surrounding the IBA core can range from 295 μm to 449 μm, 319 μm to 449 μm, etc. [Diagram 2]FIG. 2 is a schematic diagram of the disclosed method. In the illustrated method, IBA (which may have a size of 0.3 mm to 2 mm, 1.12 mm to 2 mm, etc.) is first wetted with water by spraying water on the IBA particles. A powder mixture including ground granulated blast-furnace slag (GGBS) and ordinary Portland cement (OPC) is then mixed with the wet IBA particles, which are then granulated to form the GGBS-OPC coated IBA aggregate. As seen in FIG. 2, the GGBS-OPC coated IBA aggregate is shown in the form of a core-shell aggregate. The shell includes GGBS-OPC, which may be completely or substantially converted to calcium silicate hydrate (CSH). The core includes IBA with heavy metals and toxic substances trapped inside and prevented from leaching by the shell layer. [Figure 3A] Figure 3A is a table showing the results of batch leaching tests based on the standard EN12457-1:2002 (mg / kg) for samples designated CS0 to CS15. The batch leaching tests detect certain toxic elements and compounds, including heavy metals as well as chemical oxygen demand (COD). The aggregates in this sample are based on a 2:1 GGBS-OPC:IBA weight ratio. [Figure 3B] FIG. 3B is a table showing the results of a batch leaching test based on the standard EN12457-1:2002 (mg / kg) for the sample designated CS11-R. The batch leaching test detects certain toxic elements and compounds, including heavy metals and chemical oxygen demand (COD). The aggregates in this sample are based on a 1:1 GGBS-OPC:IBA weight ratio. 14D and 7D indicate the number of days of curing the sample underwent (14 days and 7 days, respectively). [Figure 4] FIG. 4 is a table showing the results of leaching tests of various volatile organic components (mg / kg) for samples CS0-CS15. [Diagram 5]5 shows a flow chart of one embodiment of the method of the present disclosure. In particular, in this embodiment, the raw IBA may undergo a sieving and / or size reduction step. The IBA may then be wetted with water before mixing with GGBS and OPC to form a GGBS-OPC coated IBA aggregate. The GGBS-OPC coated IBA aggregate may undergo hardening. [Figure 6] Figure 6 shows a flow chart of another embodiment of the method of the present disclosure, which differs from that shown in Figure 5 in that GGBS and OPC are mixed with water to form a cement slurry, and then the cement slurry containing GGBS and OPC is mixed with IBA.

[0011] Detailed Description The following detailed description refers to the accompanying drawings, which show, by way of illustration, specific details and embodiments in which the disclosure may be practiced.

[0012] Features described in the context of one embodiment may be applicable to the same or similar features of other embodiments. Features described in the context of an embodiment may be applicable to other embodiments even if they are not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives to features described in the context of an embodiment may be applicable to the same or similar features of the other embodiments.

[0013] The present disclosure relates to aggregates. The aggregates of the present disclosure may be referred to herein as "manufactured aggregates", including reference to aggregates that can be used in concrete, where the aggregate is a granular material, and the granular material may be a composite (i.e., a mixture of materials). The aggregates of the present invention may be used in a variety of applications, including, but not limited to, as building and / or construction materials, coastal applications, support materials, and the like.

[0014] The aggregates can be incorporated into concrete as an environmentally friendly alternative to conventional aggregates. The aggregates of the present invention are advantageous in that they are derived from waste materials. Thus, the aggregates of the present invention are not only cost effective but also reduce the amount of waste that must be disposed of. For example, the aggregates of the present invention can be formed from bottom ash, such as incineration bottom ash (IBA), which is traditionally disposed of in landfills. In countries with limited land, such as Singapore, this is a concern. Thus, by utilizing incineration bottom ash, the amount of landfilled material is reduced, thereby preserving the life of the landfill. The aggregates of the present invention can also be formed using granulated blast-furnace slag (GBS), which is an undesirable by-product from the manufacture of steel. Thus, the aggregates are environmentally advantageous in reducing IBA waste disposal and recycling unwanted GBS by-products.

[0015] As mentioned above, the aggregates of the present invention can be used in a variety of applications including, but not limited to, construction and / or building materials, coastal applications, support materials, etc., even though the aggregates of the present invention contain IBA, which may contain heavy metals and toxic substances that are harmful to the environment. This is because the aggregates of the present invention have a core-shell structure, where the shell encapsulates the IBA in the core, and the shell traps the heavy metals and toxic substances in the core and prevents them from leaching out.

[0016] The present disclosure also relates to a method for producing the aforementioned aggregate. The method of the present invention is simpler than the conventional methods for producing concrete aggregates and does not require prior chemical treatment of IBA. The method of the present invention may include crushing raw IBA to reduce its original size and granulating the IBA with a powder binder (i.e., powder mixture) formed from ground granulated blast-furnace slag (GGBS) and ordinary Portland cement (OPC), i.e., GGBS-OPC (also abbreviated as OPC-GGBS). Ground granulated blast-furnace slag refers to ground granulated blast-furnace slag.

[0017] Details of various embodiments of the aggregates and methods of the present invention, as well as advantages associated with various embodiments, are described below. Where embodiments and advantages are further described in the Examples section below, they will not be repeated for the sake of brevity.

[0018] In various embodiments, the aggregate can include cement, ground granulated blast furnace slag, and bottom ash. The cement can include ordinary Portland cement. The ground granulated blast furnace slag can include micro-fine ground granulated blast furnace slag. The cement and ground granulated blast furnace slag can include calcium silicate hydrate or a derivative thereof that encapsulates the bottom ash. In other words, the cement can be hydrated in the presence of the ground granulated blast furnace slag to form calcium silicate hydrate or a derivative thereof that encapsulates the bottom ash.

[0019] The term "cement" refers to a component of concrete, and cement can act as a binder, a substance used in construction that sets, hardens, and / or adheres other materials (sand, gravel, etc.) to bind them together. The cement of the present disclosure can include or consist of hydraulic cement.

[0020] In various embodiments, the cement may be a hydraulic cement. Hydraulic cement refers to a cement that becomes an adhesive and hardens due to a chemical reaction between (i) the dry ingredients used in the cement and / or concrete and (ii) water. The chemical reaction results in mineral hydrates that are fairly insoluble in water, which impart durability in water and resistance to chemical attack. Hydraulic cements can also set wet or in water, further protecting the hardened material from chemical attack. Non-limiting examples of hydraulic cements include or can be Portland cement.

[0021] The terms "Portland cement" and "ordinary Portland cement" are used interchangeably herein. Ordinary Portland cement is abbreviated as OPC in this disclosure. The term "Portland cement" is not a brand name, but a general term for a type of cement, just as stainless steel is a type of steel. Portland cement is a type of cement that is made up of, but not limited to, tricalcium silicate (3CaO SiO 2 ), dicalcium silicate (2CaO SiO 2 ), tricalcium aluminate (3CaO·Al 2 O 3 ), and / or tetracalcium aluminoferrite (4CaO·Al 2 O 3 Fe 2 O 3 ).

[0022] In various embodiments, ordinary Portland cement may include microfine ordinary Portland cement. In various embodiments, ordinary Portland cement is a composite of lime (CaO), silica (SiO 2 ), Alumina (Al 2 O 3 ), iron(III) oxide (Fe 2 O 3 ), and / or magnesia (MgO). In various embodiments, the microfine ordinary Portland cement may contain lime (CaO), silica (SiO 2), Alumina (Al 2 O 3 ), iron(III) oxide (Fe 2 O 3 ), and / or magnesia (MgO).

[0023] In various embodiments, ordinary Portland cement and / or microfine ordinary Portland cement may include lime and silica present in an amount of at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, etc.

[0024] In various embodiments, the ground granulated blast furnace slag contains CaO, SiO 2 In various embodiments, the microfine ground granulated blast furnace slag may contain CaO, SiO 2 , and / or MgO.

[0025] In various embodiments, the ground granular blast furnace slag and / or the micro-fine ground granular blast furnace slag may include CaO present in an amount ranging from 30-50 wt%, 30-40 wt%, 40-50 wt%, etc. In various embodiments, the ground granular blast furnace slag and / or the micro-fine ground granular blast furnace slag may include SiO present in an amount ranging from 28-38 wt%, 28-35 wt%, 28-30 wt%, 30-38 wt%, 35-38 wt%, etc. 2 In various embodiments, the ground granulated blast furnace slag and / or the micro-fine ground granulated blast furnace slag may include MgO present in an amount of 1-18% by weight, 5-18% by weight, 10-18% by weight, 15-18% by weight, 1-5% by weight, 5-10% by weight, 10-15% by weight, etc.

[0026] In various embodiments, the ground granulated blast furnace slag and / or the microfine ground granulated blast furnace slag comprises Al 2 O 3 may contain Al 2 O 3may be present in an amount ranging from 8-24% by weight, 10-24% by weight, 15-24% by weight, 20-24% by weight, 8-10% by weight, 8-15% by weight, 8-20% by weight, 10-20% by weight, etc.

[0027] In various embodiments, the bottom ash may include bottom ash from any power plant and / or any incineration facility. Bottom ash herein refers to the form of ash (i.e., non-combustible residue) generated from any power plant and / or any incineration facility. Power plants may include municipal solid waste (MSW) incineration plants, power plants, coal power plants, biomass power plants, etc. Incineration facilities may include MSW incinerators, etc. In various embodiments, the bottom ash may be incineration bottom ash.

[0028] In various embodiments, the bottom ash may contain heavy metals, halides, and / or volatile organic compounds.

[0029] In various embodiments, the ordinary Portland cement may include microfine ordinary Portland cement, or the ground granulated blast furnace slag may include microfine ground granulated blast furnace slag, or the ordinary Portland cement may include microfine ordinary Portland cement and the ground granulated blast furnace slag may include microfine ground granulated blast furnace slag.

[0030] In various embodiments, the microfine ordinary Portland cement is 750 m 2 / kg or more, 800m 2 / kg or more, 850m 2 / kg or more, 900m 2 / kg or more, 950m 2 In various embodiments, the microfine ground granulated blast furnace slag has a specific surface area of ​​750 m 2 / kg or more, 800m 2 / kg or more, 850m 2 / kg or more, 900m 2 / kg or more, 950m 2 / kg or more.

[0031] The term "microfine" in the context of this disclosure means 750 mm 2 / kg or more. Higher specific surface areas naturally refer to finer materials. Ultrafine and nanofine materials are materials with specific surface areas of 1,000 m 2 / kg or more. Ultrafine and nanofine materials are finer (i.e., have a higher specific surface area than microfine materials). The terms "ultrafine" and "nanofine" in the context of this disclosure differ in that "ultrafine" refers to particles that may have a size greater than 0.5 μm, and "nanofine" refers to particles that may have a size less than 100 nm. In other words, ultrafine particles are particles that are greater than 0.5 μm in size and have a specific surface area greater than 1,000 m 2 / kg or more, and nanofine particles have a size of less than 100 nm and a specific surface area of ​​1,000 m 2 / kg or more. In various cases, ordinary Portland cement, microfine ordinary Portland cement, ground granulated blast furnace slag, and microfine ground granulated blast furnace slag can include ultrafine and / or nanofine versions thereof.

[0032] In various embodiments, the specific surface area of ​​ordinary Portland cement is, for example, 315 m 2 / kg~375m 2 / kg, 315m 2 / kg~345m 2 In various embodiments, the specific surface area of ​​the ground granulated blast furnace slag may range from 420 to 460 m 2 In contrast, as noted above, the specific surface area of ​​microfine ordinary Portland cement and microfine ground granulated blast furnace slag can be in the range of 750 m 2 / kg or more.

[0033] In various embodiments, the aggregate may include at least about 40% by weight ordinary Portland cement (and / or microfine ordinary Portland cement). In various embodiments, the aggregate may include at least about 10% by weight ground granulated blast furnace slag (and / or microfine ground granulated blast furnace slag).

[0034] In various embodiments, the calcium silicate hydrate or derivatives thereof encapsulating the bottom ash can have an average thickness ranging from 200 μm to 700 μm, 300 μm to 700 μm, 400 μm to 700 μm, 500 μm to 700 μm, 600 μm to 700 μm, etc. In specific non-limiting examples, the calcium silicate hydrate can have an average thickness of about 448 μm or about 319 μm.

[0035] In various embodiments, the aggregate may have an average diameter of 0.8 mm or more, 0.9 mm or more, 1 mm or more. The terms "diameter" and "size" are used interchangeably herein. The diameter is measured from one point on the perimeter of the aggregate via a line through the center of the aggregate to another point on the perimeter.

[0036] In various embodiments, the aggregate may further include additives. The additives may include bentonite, clay, carbon nanofiber, biochar, fly ash, and / or silica fume. As mentioned above, the aggregate of the present disclosure may include one or more additives. Besides bentonite and silica fume, other additives may be included. Some examples of other additives are described above. In one example, adding 2% to 5% by weight of bentonite to a microfine GGBS-OPC mixture demonstrated positive results of encapsulation of IBA, with the weight percentages being based on GGBS and OPC. A GGBS content of about 50-60% may also show better results of encapsulation, with the weight percentages being based on GGBS and OPC.

[0037] A binder solution with a higher viscosity showed better encapsulation due to improved adhesion of the binder solution coat to the IBA, however, if the binder solution is too viscous, it may be difficult to spread the GGBS-OPC mixture onto the IBA.

[0038] The aggregate as described above may be a core-shell aggregate in various embodiments. The shell may include hydraulic cement and ground granular blast furnace slag. The shell may include calcium silicate hydrate or a derivative thereof. The hydraulic cement and ground granular blast furnace slag may include calcium silicate hydrate or a derivative thereof. The cement may be hydrated in the presence of ground granular blast furnace slag such that calcium silicate hydrate or a derivative thereof is formed. The cement may be fully or substantially converted to calcium silicate hydrate or a derivative thereof in the presence of ground granular blast furnace slag. In other words, the hydraulic cement, ground granular blast furnace slag, and / or calcium silicate hydrate may form a shell that encapsulates the core. The core may include bottom ash. The hydraulic cement and ground granular blast furnace slag may include calcium silicate hydrate or a derivative thereof that encapsulates the bottom ash. The hydraulic cement may be or may include microfine ordinary Portland cement. The ground granular blast furnace slag may be or may include micro-fine ground granular blast furnace slag.

[0039] The present disclosure also relates to a method for producing aggregates. The embodiments and advantages described for the aggregates of the present invention in the various embodiments of the first aspect may be equally valid for the methods of the present invention described later herein, and vice versa. Where various embodiments and advantages have already been described above and exemplified herein, they should not be repeated for the sake of brevity.

[0040] The method of producing the aggregate may include mixing cement and ground granulated blast furnace slag with bottom ash in the presence of water to form a precoated bottom ash, and granulating the precoated bottom ash. Two non-limiting embodiments of the method of the present invention are shown in Figures 5 and 6.

[0041] In various embodiments, prior to mixing the cement and ground granulated blast furnace slag with the bottom ash, the bottom ash may be subjected to a size reduction process, such as grinding, to reduce the original size of the raw bottom ash.

[0042] In certain non-limiting embodiments, the method may further include contacting the bottom ash with water prior to mixing the cement and ground granulated blast furnace slag with the bottom ash (such non-limiting embodiments are shown throughout FIG. 5). Contacting the bottom ash with water may include spraying the bottom ash with water.

[0043] In certain non-limiting embodiments, granulating the precoated bottom ash may be performed for a duration of at least 3 minutes. In certain non-limiting embodiments, granulating the precoated bottom ash may be performed for a duration of at least 3 minutes, and granulating the precoated bottom ash may include granulating the precoated bottom ash in a granulator drum rotating at a speed of at least 100 revolutions per minute (rpm).

[0044] In certain non-limiting embodiments, the method may further include mixing the cement and ground granulated blast furnace slag with water to form a slurry prior to mixing the cement and ground granulated blast furnace slag with the bottom ash (such an embodiment is shown via FIG. 6). In such non-limiting examples, granulating the precoated bottom ash may include adding additional cement to the precoated bottom ash. In such non-limiting examples, the method may further include pelletizing the precoated bottom ash after granulating the precoated bottom ash. Pelletizing the precoated bottom ash may occur in a disc pelletizer.

[0045] In certain non-limiting embodiments, ordinary Portland cement (and / or microfine ordinary Portland cement) and ground granular blast furnace slag (and / or microfine ground granular blast furnace slag) can be used in combination with the grout to provide a low permeability grout that acts as a diffusion barrier, (ii) the use of microfine slag can increase the CSH (calcium silicate hydrate) content since the CSH has a high surface area that allows for the adsorption of ions into its crystal structure, and (iii) can be in the form of a liquid binder (e.g., at the start of mixing or during mixing) to aid in the immobilization of heavy metals through a faster setting time compared to slag.

[0046] In various embodiments, the method may further include hardening the aggregate. Hardening the aggregate may include heat treating the aggregate in a humidity chamber and conditioning the aggregate in water.

[0047] In various embodiments, hardening the aggregate may further include steam treating the aggregate in a humidity chamber.

[0048] As mentioned above, the method may include hardening the aggregate. Hardening the aggregate may include heat treating the aggregate in a humidity chamber and steam hardening the aggregate. Heat treating and steam hardening the aggregate in the chamber helps to strengthen the binders (e.g., GGBS and OPC) in the aggregate, i.e., the shell of the aggregate becomes more cohesive. When the shell becomes more cohesive, it can pack more tightly, gain mechanical strength, and trap the bottom ash within the shell (preventing leaching).

[0049] The heat treatment may include heating the aggregate in a humidity chamber. The humidity in the humidity chamber may be at least 85%, 90%, etc. The heat treatment may be carried out for at least 12 hours, 24 hours, etc. The heat treatment also serves to reduce the duration of conditioning the aggregate in water from 28 days to 14 days or less.

[0050] Steam curing may involve passing steam through a steam curing chamber at atmospheric pressure. Steam curing may be carried out for at least one hour. Steam curing also serves to reduce the duration of conditioning the aggregate under water from 28 days to seven days or less.

[0051] Following the steps above, the treated aggregate may be placed in a water bath containing water as a final step in the curing process. The aggregate may be left in the water for at least three days.

[0052] Sufficient time may be allowed for the binder coat to cure for 1 day, 3 days, 7 days and 28 days. Accelerated curing may be relied upon by placing the coated IBA in a water bath at a temperature of 40°C for 2 days.

[0053] In summary, the aggregate and method of the present invention includes encapsulation as described above. Ordinary Portland cement and ground granular blast furnace slag may be commercially available, but this is not true for microfine ordinary Portland cement and microfine ground granular blast furnace slag. In various non-limiting embodiments of the present disclosure, when microfine OPC and microfine GGBS are used, microfine ground granular blast furnace slag and microfine ordinary Portland cement are produced to form the aggregate of the present invention. Ample availability of starting raw materials makes the production of microfine ordinary Portland cement and microfine ground granular blast furnace slag, and thus the aggregate and method of the present invention, economically viable. When encapsulating bottom ash in combination with the powder coating mixture (e.g., GGBS-OPC) and granulation process of the present invention, the aggregate and method of the present invention advantageously meets stringent leaching requirements. Here, the combination of ordinary Portland cement and ground granular blast furnace slag to encapsulate bottom ash does not result in undesirable agglomeration of the encapsulated IBA to form concrete or aggregate-free slag. In comparison, conventional encapsulation methods tend not to develop aggregates of the size and advantages achieved herein using conventional materials. The desired encapsulation results are achieved by utilizing the powder coating mixture (e.g., GGBS-OPC) and granulation process / methodology of the present invention.

[0054] The term "substantially" may refer to a component being present in an amount of at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99%, 99.5%, 99.9%, etc. by weight of the composite. If desired, the word "substantially" may be omitted from the definition of this disclosure.

[0055] In the context of various embodiments, the articles "a," "an," and "the" used in reference to features or elements include a reference to one or more of the feature or element.

[0056] In the context of various embodiments, the term "about" or "approximately" applied to a numerical value encompasses the exact value and a reasonable variance.

[0057] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0058] Unless otherwise specified, the terms "comprising" and "comprises," and grammatical variations thereof, are intended to express "open" or "inclusive" language, such as to include the recited elements, but also permit the inclusion of additional, unrecited elements. EXAMPLES

[0059] Working Example The present disclosure relates to aggregates, their production methods and uses.

[0060] The aggregates of the present invention include bottom ash, such as incineration bottom ash (IBA). The bottom ash may or may not be chemically treated. The method of making the aggregates of the present invention may include direct processing of the bottom ash to form the aggregate, and advantageously, the bottom ash does not need to be chemically treated prior to use of the bottom ash.

[0061] The method of the invention may meet the requirements of the British Standard Institute for disposal waste to landfill, e.g. BS EN12457-1:2002 (Characterisation of waste leaching. Suitability tests for leaching of granular waste materials and sludges. For materials with high solids content and particle size less than 4mm (with or without size reduction), one stage batch test at 2L / kg liquid to solids ratio, standard from European Standards adopted by the UK). The aggregates of the invention formed from the method of the invention will meet the same requirements if the method of the invention meets such criteria.

[0062] Further advantageously, the aggregates and methods of the present invention are economically viable because they are based on the use of readily available materials, which reduces the risk of including untested materials that would complicate the reliability of the aggregates and methods of the present invention.

[0063] The aggregates of the present invention, their production and use are described in further detail as set forth below, by way of non-limiting examples.

[0064] Example 1: Introduction to aggregates and methods

[0065] The method of the present disclosure has been developed based on a granulation process (i.e., includes a granulation step) involving a mixture of ground granulated blast furnace slag and ordinary Portland cement (also referred to herein as "ground granulated blast furnace slag-ordinary Portland cement (GGBS-OPC)") to produce coated incineration bottom ash that can be used as at least an aggregate, e.g., a concrete aggregate. As the method of the present invention involves coating of incineration bottom ash, the method of the present invention is referred to herein as a "coating method". The method and aggregate of the present invention can be performed with any bottom ash produced by a power plant, such as a municipal solid waste (MWS) incineration power plant, a coal power plant, a biomass power plant, and / or any other power plant.

[0066] At least 13 formulations were tested. The formulations tested include GGBS-OPC powder (also referred to herein as powder binder), which can include a mixture of OPC and GGBS, where OPC and GGBS can range from 40 weight percent to 100 weight percent (wt%) and 10-50 wt% (or even 10-60 wt%), respectively. That is, in one of the samples tested, no GGBS was used, i.e., only 100 wt% OPC was used in the powder (see Figure 3A and CS1 in Figure 4). The wt% is based on the mixture of GGBS and OPC. The powder forms a coating that encapsulates the incineration bottom ash, forming an IBA aggregate. The coating that encapsulates the incineration bottom ash prevents leaching of heavy metals and toxic substances from the encapsulated incineration bottom ash.

[0067] The OPC and GGBS may be or may include microfine OPC (MFOPC) and microfine GGBS, respectively, i.e., the microfine OPC and microfine GGBS may range from 40% to 100% by weight and 10 to 50% by weight (or even 10 to 60% by weight), respectively, the weight percentages being based on the GGBS and OPC mixture.

[0068] Among the formulations tested, one formulation containing ordinary Portland cement, microfine ordinary Portland cement, and ground granular blast furnace, referred to herein as "OPC:MFOPC:GGBS" (for brevity, referred to as CS11), was observed to be the most desirable (although other formulations could be used). This is because CS11 showed the least leaching, i.e. the lowest amount of heavy metals and toxic substances detected compared to the raw IBA. It was discovered that the CS11 formulation is able to significantly reduce chloride leaching, i.e. from 9800 mg / kg of raw IBA to 27 mg / kg. This achievement does not seem to be achievable by conventional coating methods. From the formulations tested, it can be seen that the powder coating (with OPC and GGBS, even with microfine OPC and GGBS) is able to effectively trap and immobilize the toxic heavy metals present in the IBA. More precisely, a core-shell aggregate is produced using the method of the present invention, which includes granulation. Each of the core-shell aggregates, i.e., the aggregates of the present invention, has a shell formed from a powder coating (OPC, GGBS and / or their microfine versions) that encapsulates IBA in the core. It has also been observed that the GGBS-OPC coated IBA aggregates can also be utilized as a suitable replacement for fine aggregates in producing ready-mix concrete. Based on all the formulations tested, all the resulting aggregates were successfully constructed from coated IBA, with the GGBS-OPC formulation acting as a powder binder that coats the IBA and prevents the leaching of toxic heavy metals from the IBA. Thus, the GGBS-OPC coated IBA aggregates can be used as an alternative aggregate for incorporation into concrete matrix without environmental concerns.

[0069] Using the granulation process described in this disclosure, the production of GGBS-OPC coated IBA can be scaled up and replicated into industrial scale operations for commercialization. The formulated GGBS-OPC powder binder is robust (i.e. imparts longer shelf life and durability to the shell and therefore the aggregate), the process is simple, and in the absence of chemical processing of IBA, it can be further configured to achieve cost savings in the resulting aggregate product and the overall manufacturing process from raw material use to the final product.

[0070] One or more examples of the present disclosure show a powder coating method with granulation. Prior to granulation, a grinding capability was also developed to aid in the production of GGBS-OPC coated IBA particles (i.e., aggregates of the present invention) with sizes ranging from about 0.8 mm to about 4 mm, about 2 mm to about 4 mm, etc. The GGBS-OPC coated IBA particles can be used as a fine aggregate replacement in fresh concrete. During granulation, the IBA particles can be wetted with GGBS-OPC powder (which can act as a binder for IBA).

[0071] More specifically, a powder coating method by granulation was developed. Before granulation, a grinding capability (i.e., grinding process) was developed to produce IBA with an average particle size in the range of about 0.075 mm to about 6.3 mm. In one example, the average size fraction of IBA used in the method of the present invention was about 1.12 mm to 2 mm. During granulation, the particle size of the IBA particles was increased due to the coating of GGBS-OPC powder binder on the IBA particles. After granulation, the average particle size of the OPC-GGBS coated IBA aggregate is about 0.8 mm to about 4 mm, about 2 mm to about 4 mm. The selection of this range of GGBS-OPC coated IBA size helps to meet the international leaching test requirements (i.e., EN12457-1:2002, Compliance Test Leaching of Granular Waste and Sludge. One-stage batch test at 2 L / kg liquid to solid ratio for materials with high solids content and particle size less than 4 mm (with or without size reduction)). Thus, the resulting GGBS-OPC coated IBA particles have great potential to be used as fine aggregate replacement in the ready mixed concrete industry. The resulting aggregates may have an average diameter of 25 mm, 20 mm, etc. The resulting aggregates may have an average diameter of 0.8 mm or more. Granulation involves forming a layer of coating on the IBA particles (e.g., on each of the IBA particles). The coating layer traps heavy metals and any toxic substances therein (i.e., leaching is prevented even when the resulting aggregate is used in harsh environments). The layer of coating can be considered as a shell that encapsulates one or more IBA particles. Granulation can include, as non-limiting examples, any one of agglomeration, pelleting, briquetting, spray drying agglomeration. In spray drying agglomeration, a slurry may be sprayed into a column containing the particles. The slurry may include materials for forming the layer of coating (e.g., OPC, GGBS and / or their microfine versions) and the particles may include IBA particles. Granulation may be carried out using a drum granulator, a tumbling (pan) granulator, or a mixer granulator, which includes a combination of a drum and a tumbling granulator.

[0072] Entrapment and / or immobilization of heavy metals within the aggregate core can be achieved by one or more of the following: (1) high alkalinity binder mixtures (i.e., GGBS-OPC mixtures), which completely or substantially reduce leaching of heavy metals; (2) calcium silicate hydrate (CSH) gels have a high surface area that allows for adsorption of heavy metal ions (slag-blend cement mixtures produce a higher percentage of CSH, which increases sorption capacity); and / or (3) the low permeability of the hardened shell acts as a diffusion barrier to heavy metal leaching.

[0073] The CSH gel described above may result, for example, when slag (GGBS) is blended with cement (e.g., OPC) during the formation of the GGBS-OPC coating. The cement (e.g., OPC) is hydrated in the presence of GGBS to form calcium silicate hydrate or its derivatives within the shell (i.e., encapsulation layer). In the early stages of forming the encapsulation layer, the calcium silicate hydrate (or its derivatives) may be present in gel form. In other words, the CSH gel may form in the shell during the early stages of forming the encapsulation layer around the IBA. However, the CSH gel hardens into a solid as the CSH gel hardens. Thus, in the resulting aggregate, the CSH gel forms a solid calcium silicate hydrate layer. The calcium silicate hydrate layer may be present in the shell. In a specific, non-limiting example, the calcium silicate hydrate layer may form around the shell away from the IBA core. In such a non-limiting example, the CSH serves as an additional coating of the encapsulation in addition to the GGBS-OPC coating the IBA. In such a non-limiting example, the CSH layer may form a periphery of the GGBS-OPC layer, and the GGBS-OPC may in certain non-limiting examples be completely converted to CSH, with the CSH then functioning as the only encapsulation layer for the IBA core.

[0074] In addition to GGBS-OPC and CSH, the concrete matrix into which the aggregate is incorporated when the aggregate is utilized as a concrete aggregate provides a "double defense" encapsulation to hinder and / or prevent leaching of heavy metals for use in concrete applications. In other words, when GGBS-OPC coated IBA is used as an aggregate substitute in general concrete production, the concrete can form another protective layer outside of the CSH and / or GGBS-OPC coated IBA, which is referred to herein as "double defense", i.e., the first defense refers to the encapsulation layer of CSH and / or GGBS-OPC coated on IBA, and the second defense refers to the concrete matrix into which the aggregate is incorporated. As can be understood from the above, granulation is easy to encapsulate IBA in GGBS-OPC, and therefore is easily scaled up to cost-effective and commercially valuable granulation.

[0075] Example 2: Advantages of the aggregates and methods of the present invention over conventional methods

[0076] The method of the present invention results in higher specific gravity and stronger compressive strength of the IBA aggregate of the present invention. Conventionally, alkali-activated materials as liquid binders may be used in the granulation process of IBA aggregate. However, such conventional approaches tend to suffer from certain limitations such as high operating costs, use of chemicals, and ineffective immobilization of heavy metals. In contrast, the method of the present invention involves blending GGBS with OPC to obtain a GGBS-OPC powder binder for producing IBA aggregate by the aforementioned granulation. The aggregate of the present invention may be referred to herein as a "waste resource" aggregate since the method of the present invention converts waste materials such as IBA into resources such as aggregates useful for concrete materials. Besides IBA, which is a waste material, GGBS was also derived from waste materials. In the method of the present invention, GGBS was produced in-house by grinding granulated blast furnace slag (an industrial by-product of steelworks pig iron production in blast furnaces, where pig iron refers to crude iron). Being a by-product, granulated blast furnace slag tends to be undesirable and therefore is readily available. Thus, granulated blast furnace slag is abundant and GGBS is available in abundance, making it a cost-effective material (compared to OPC).

[0077] In certain non-limiting examples, high shear granulation processes may be preferred as they may allow for the spreading of viscous liquids, the handling of viscous materials, and the production of more compact and spherical granules than low shear granulation processes. In general, granulation may be initiated, for example, by the addition of pre-coated IBA to a granulation drum. During granulation, IBA particles are wetted with water, mixed with GGBS-OPC powder binder, and subsequently collided and adhered to each other as part of the particle expansion process. Hydration of the GGBS-OPC powder binder also results in a liquid binder that results in the formation of a calcium silicate hydrate (CSH) gel (or a derivative thereof) on the surface of the IBA particles. As the CSH gel hardens (cures), the IBA particles are incorporated into the crystalline structure of the CSH matrix, resulting in a rigid mass with improved physical and chemical properties. It is expected that the CSH gel layer formed starting from the hydration of OPC in the presence of GGBS and water that hardens into a solid can function as a first or primary encapsulation layer of protection against potential leaching of heavy metals. From there, the resulting coated IBA can be used as an aggregate in concrete. In other words, the coated IBA as an aggregate is encapsulated in the matrix of the concrete, with the concrete acting as a second layer of encapsulation of the IBA. Thus, because of the unique advantage of the method of the present invention of immobilizing heavy metals via the CSH matrix created during the encapsulation process, and considering the advantage of the ultimate use of the encapsulated aggregate as an aggregate in the concrete matrix, the aggregate and method of the present invention provide an opportunity to utilize solid waste IBA as an inert coarse or fine aggregate in concrete. In other words, the concrete matrix acts as a second encapsulating layer of defense to mitigate potential leaching of toxic heavy metals. This double encapsulation, arising from the CSH matrix (and / or even the GGBS-OPC) and binding the coated IBA aggregate within the green concrete, endows the resulting IBA aggregate with a "double defense" that prevents and / or mitigates leaching of heavy metals and toxic contents from the concrete.

[0078] Example 3: Technical Considerations of the Aggregates and Methods of the Invention

[0079] The summary of the aggregate and method of the present invention is that waste-source IBA aggregate is produced by blending GGBS with OPC to form a GGBS-OPC powder binder for encapsulating IBA by granulation. The formed core-shell granules were then investigated for use as GGBS-OPC coated IBA green aggregate.

[0080] In particular, the aggregates and methods of the present invention may involve the hydration of GGBS-OPC, which forms calcium silicate hydrate (CSH) in the gel phase during the process and then converts to a crystalline phase in the resulting aggregate. Furthermore, GGBS can reduce the pore structure of the OPC (i.e., reduce porosity) and reduce toxic metal diffusion from the shell. Thus, the GGBS-OPC powder binder promotes the formation of a CSH gel (and thus a solid CSH encapsulation layer) on the surface of the IBA particles during granulation. Immobilization may also be due to sorption of ions by forming CSH, precipitation of insoluble hydroxides, and intralattice intercalation into crystalline components in the GGBS-OPC matrix (see, for example, FIG. 1).

[0081] Granulation may include the steps of: (1) spraying water onto the IBA particles; (2) pre-coating the IBA with a blend of GGBS-OPC powder binder; (3) feeding the pre-coated IBA into a granulator drum; (4) commencing granulation at normal speed for a period of time (e.g., granulation in the granulator rotating drum at a speed of at least 100 rpm for at least 3 minutes); and (5) spraying water during granulation until all the weighted GGBS-OPC powder binder has been fused with the IBA. (5) repeating the process of adding GGBS-OPC powder binder to the granular IBA; (6) drying the GGBS-OPC coated IBA, for example in a humidity chamber providing an environment of at least 85% humidity at at least 25° C. for a minimum of 12 hours (e.g., 24 hours); (7) allowing the GGBS-OPC coated IBA to harden for 14 days; and (8) sieving and grading the resulting GGBS-OPC coated IBA aggregate.

[0082] The green IBA aggregate produced was then subjected to a leaching test according to BS EN12457-1, a single stage batch test at a liquid to solid ratio of 10L / kg. The pH of the resulting leachate was measured using a pH meter. Anions in the leachate solution were identified and determined using ionic chromatography (IC) and cations in the leachate by inductively coupled plasma (ICP) spectrometry. The total organic carbon content of the leachate was determined using a total organic carbon (TOC) analyzer. The total dissolved solids (TDS) and dissolved organic carbon (DOC) of the leachate were also measured.

[0083] Figures 3A, 3B and 4 show the batch leaching test results EN12457-1:2002 and volatile organic composition leaching tests of GGBS-OPC coated IBA with various formulations (see, for example, Figures 3A and 3B). The leaching results are shown in Table 3. The leaching results are shown in Table 3. The leaching results are shown in Table 3. The leaching results are shown in Table 3. The leaching results are shown in Table 3. The leaching results are shown in Table 3. 4The leaching of chromium (VI), indicated as total nitrogen and total organic carbon (TOC), significantly exceeds the limit value for the raw IBA sample (herein denoted as R1). In addition, leaching of phenol and mineral oil (C10-C36) was also detected. Heavy metals tend to raise more concerns than volatile organic compounds due to their higher potential for leaching and contamination. Therefore, heavy metals (Figure 3) are given more attention in this study. The results showed that heavy metals such as Cr, Mo, Ni and Zn in GGBS-OPC coated IBA (CS0 and CS2-CS12) are successfully immobilized in the matrix of GGBS-OPC, as they are not detected or are below the limit value in the leachate. Furthermore, the heavy metal of Cu, for example, was significantly reduced below the limit value for leaching in samples CS9, CS10, CS11 and CS14 compared to the raw IBA. Leaching of Pb is not detected for all GGBS-OPC coated IBA samples except for samples CS1, CS2, CS3 and S12 which are 0.27mg / kg, 0.36mg / kg, 0.028mg / kg and 0.034mg / kg respectively compared to the limit value of 0.02mg / kg. This may be due to Pb not being fully encapsulated in calcium silicate hydrate or GGBS-OPC matrix. Ettringite is found to have strong fixation with heavy metals such as Pb which is strongly encapsulated in calcium silicate matrix by replacing Ca in GGBS-OPC. However, ettringite from OPC (CS1) or GGBS-OPC (CS2 and CS3) is not significantly improved for leaching of Pb. Metal specific factors such as redox potential on Cr, organic ligands in case of Cu, and mineral precipitation and sorption rate on Pb may significantly affect their mobility. Thus, leaching of one or more of the metals Cr, Cu and Pb may be detected. The GGBS-OPC coated IBA showed detectable Al in leaching tests. However, the Al leaching is not from the IBA since no Al was detected in the raw IBA. Therefore, the detected Al leaching is not a concern or relevant indicator of leaching in this context. Rather, the Al is present in the chemical composition as a 2 O3 It may be from GGBS and OPC containing

[0084] The results showed that compared to the original raw IBA, the leaching of sodium (Na), chloride, bromide, sulfate, and ammonia was reduced by approximately 20, 250, 300, 70, and more than 7 times, respectively. Furthermore, for all GGBS-OPC coated IBA aggregate samples, the leaching of Na, SO 4 The leaching of Na, SO and ammonia was below the permissible limit. The possibility of coating IBA using GGBS-OPC powder binder is observably advantageous. The efficiency of the GGBS-OPC matrix was improved by reducing the leaching of Na, SO and CO from IBA. 4 and ammonia have been demonstrated. Samples CS9, CS10, and CS11 showed the most favorable results of all the GGBS-OPC coated IBA aggregate samples based on below the limit of chloride detected (less than 40mg / kg). The results clearly show that the GGBS-OPC matrix was remarkably successful in reducing chloride leaching from the IBA. Vanadium and bromide were detected in CS9 and CS11, but they are very close to the limit and the instrument detection limit, so the values ​​are negligible. Microfine ordinary Portland Cement (MFOPC) is a cement that is more stable than Ordinary Portland Cement (OPC), e.g., about 331m 2 / kg (±5%), compared to a high specific surface area of ​​about 800 m 2 / kg (±5%). This finding indicated that the high specific surface area likely enhanced the capture efficacy due to its effectiveness in immobilizing toxic metals and preventing them from leaching from the IBA. To demonstrate this, samples CS10 and CS11 were formulated, which showed the advantage of being able to maximize the utilization of IBA in addition to the promising opportunity to make IBA beneficial as a raw material as a partial replacement for fine aggregate for use in concrete, a global challenge. The conversion of waste to fine aggregate substitutes and the production cost savings (e.g., avoiding the high water usage and high energy costs required by conventional methods) could allow countries using current aggregates and methods to obtain significant environmental benefits.

[0085] Example 4: Commercial and Potential Applications

[0086] The aggregates of the present disclosure are sometimes referred to herein as "green" IBA aggregates, since they are derived from waste materials as described above, particularly IBA.

[0087] The aggregate is produced by encapsulating the blended GGBS-OPC powder binder onto IBA by granulation. The aggregate and method of the present invention can be scaled up and is economically viable for commercialization. The aggregate and method of the present invention allows solid waste IBA to be deployed as a green aggregate for application in ready mixed and precast concrete. The global consumption of construction aggregates is likely to reach 62.9 billion metric tons by the end of 2024 from 43.3 billion metric tons in 2016. The value of construction aggregates is therefore estimated to be 3.2-3.8 billion metric tons from 2016-2024. The high demand for aggregates is mainly due to economic growth and increasing construction activity. The aggregate and method of the present invention will help significantly reduce Singapore's annual waste disposal handling volume, which is about 500,000 to 600,000 metric tons of IBA per year, and will significantly extend the life of the Semakau landfill site.

[0088] Although the present disclosure has been particularly shown and described with reference to certain embodiments, it should be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims. Accordingly, the scope of the present disclosure is defined by the appended claims, and it is intended to include all modifications within the meaning and scope of the claims.

Claims

1. An aggregate, comprising: a cement containing ordinary Portland cement; ground granulated blast furnace slag; and main ash, wherein the cement is hydrated in the presence of the ground granulated blast furnace slag to form calcium silicate hydrate or a derivative thereof that encapsulates the main ash.

2. The ordinary Portland cement contains lime (CaO), silica (SiO ２ ), alumina (Al ２ O ３ ), iron(III) oxide (Fe ２ O ３ ), and / or magnesia (MgO). The aggregate according to claim 1.

3. The aggregate according to claim 1, wherein the ordinary Portland cement contains lime and silica present in an amount of at least 50% by weight.

4. The pulverized granular blast furnace slag contains CaO, SiO ２ , and / or MgO, and the aggregate according to claim 1.

5. The ground granulated blast furnace slag contains: CaO present in an amount in the range of 30 to 50% by weight; and SiO present in an amount in the range of 28 to 38% by weight ２ and MgO present in an amount of 1 to 18% by weight. The aggregate according to claim 1.

6. The aggregate according to claim 1, wherein the main ash contains main ash from any power plant and / or any incineration facility.

7. The aggregate according to claim 1, wherein the main ash contains heavy metals, halides, and / or volatile organic compounds.

8. The ordinary Portland cement contains microfine ordinary Portland cement, or the ground granulated blast furnace slag contains microfine ground granulated blast furnace slag, or the ordinary Portland cement contains microfine ordinary Portland cement and the ground granulated blast furnace slag contains microfine ground granulated blast furnace slag. The aggregate according to claim 1.

9. The fine ordinary Portland cement has a specific surface area of 750 m ２ / kg or more, and the aggregate according to claim 8.

10. The micro-finely pulverized granulated blast furnace slag has a specific surface area of 750 m ２ / kg or more, and the aggregate according to claim 8.

11. The aggregate according to claim 1, wherein the aggregate contains at least about 40% by weight of the ordinary Portland cement.

12. The aggregate according to claim 1, wherein the aggregate contains at least about 10% by weight of the ground granulated blast furnace slag.

13. The aggregate according to claim 1, wherein the calcium silicate hydrate or a derivative thereof that encapsulates the main ash has an average thickness in the range of 200 μm to 700 μm.

14. The aggregate according to claim 1, wherein the aggregate has an average diameter of 0.8 mm or more.

15. The aggregate according to claim 1, further comprising an additive, wherein the additive contains bentonite, clay, carbon nanofiber, biochar, fly ash, and / or silica fume.

16. Mixing the cement and the ground granulated blast furnace slag with the main ash in the presence of water to form a pre-coated main ash; and Granulating the pre-coated main ash. A method for manufacturing the aggregate according to claim 1.

17. Before mixing the cement and the ground granulated blast-furnace slag with the main ash, contacting the main ash with water, or Before mixing the cement and the ground granulated blast-furnace slag with the main ash, contacting the main ash with water, wherein contacting the main ash with water includes spraying water on the main ash, and further includes contacting the main ash with water before mixing the cement and the ground granulated blast-furnace slag with the main ash, the method according to claim 16.

18. Granulating the precoat main ash is carried out over a duration of at least 3 minutes, or Granulating the precoat main ash is carried out over a duration of at least 3 minutes, and granulating the precoat main ash includes granulating the precoat main ash in a granulator drum rotating at a speed of at least 100 rpm. The method according to claim 16.

19. Before mixing the cement and the ground granulated blast-furnace slag with the main ash, further including mixing the cement and the ground granulated blast-furnace slag with water to form a slurry, the method according to claim 16.

20. Granulating the precoat main ash includes adding additional cement to the precoat main ash, the method according to claim 19.

21. After granulating the precoat main ash, further including pelletizing the precoat main ash, the method according to claim 19.

22. Further including curing the aggregate, and curing the aggregate is Heat-treating the aggregate in a humidity chamber, and Conditioning the aggregate in water, The method according to claim 16.

23. Curing the aggregate further includes steam-treating the aggregate in the humidity chamber, the method according to claim 22.

Images