Method for producing a reconstituted mineral aggregate, reconstituted mineral aggregate and uses thereof
Patent Information
- Application Number
- EP2023837790
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-21
- Filing Date
- 2023-12-20
- Publication Date
- 2025-10-29
AI Technical Summary
Current methods lack a proven process for transforming mineral pieces and fines into usable aggregates of desired size and shape, which is essential for resource conservation and waste reduction in the building and public works sectors.
A process involving the selection of a basic mineral granular material with a large specific surface area, grinding if necessary, mixing with a binder and water, and applying pressure for shaping to create a dense, hardened aggregate of the desired size and shape.
The process effectively increases the intrinsic density and reduces porosity of the material, producing aggregates with improved properties such as low water absorption and high durability, suitable for various applications including concrete, coating, and geotechnical uses.
Abstract
Description
Process for manufacturing a reconstituted mineral aggregate, reconstituted mineral aggregate and applications of these aggregates
[0001] The present invention relates to a method for manufacturing a reconstituted mineral aggregate, to a reconstituted mineral aggregate obtainable by this method, as well as to applications of these aggregates.
[0002] In the context of current challenges of saving resources and limiting waste, circular economy solutions have been widely acclaimed in the world of construction and public works, particularly to save new aggregates. Thus, currently, crushed concrete, incineration bottom ash or crystallized slag can be used as aggregates to replace natural aggregates extracted from quarries.
[0003] However, while granular reduction techniques, such as crushing and screening, exist and make it possible to obtain usable aggregates from hard blocks, there is, conversely, no proven method for transforming mineral lumps and fines into usable-sized aggregates.
[0004] It is the objective of the present invention to satisfy this need, the method proposed for this purpose consisting of choosing at least one basic mineral granular material having a large specific surface area or grinding at least one basic mineral granular material so that it reaches such a granulometry by increasing its specific surface area, adding at least one binder and water, pressurizing the assembly and carrying out shaping to form the desired aggregate.
[0005] The present invention therefore firstly relates to a method for manufacturing a reconstituted mineral aggregate, characterized in that at least one starting particulate mineral material for aggregate is mixed with water and at least one mineral binder which can be hardened in the presence of water and / or at least one system capable of forming a hardened mineral binder in an aqueous medium, to obtain a material in the form of a wet powder which is compressed by extrusion or pressing to intimately mix the binder and / or system capable of forming the binder / starting particulate material / water and increase the intrinsic density and reduce the intrinsic porosity of the material, and to obtain, as a result of the hardening of the binder(s), a hardened, solid mass, which is in the form of the aggregate of the desired size and / or the desired shape, or is transformed into the aggregate of the desired size and / or the desired shape by cutting or crushing,immediately after compression or in a later step.,
[0006] The starting particulate mineral material may be selected from sands, such as silica sand and basalt sand; non-reactive clays; sediments, such as dredged sediments; glass; coal; crushed concrete; crushed natural aggregates; quarry fines; industrial process fines; insulating materials such as rock wool and glass wool; and mixtures thereof.
[0007] The starting particulate mineral material or the mixture of starting particulate mineral materials may advantageously have a particle size defined by: a D90 value less than or equal to 1.3 mm; a D10 value greater than or equal to 0.02 mm; and a D50 value greater than or equal to 0.1 mm and less than or equal to 1 mm,
[0008] said material or said mixture of materials having been subjected to grinding if necessary to obtain this granulometry.
[0009] By D90, D10, D50 it is meant that 90%, 10%, 50% respectively of the particles by mass must have their smallest projected surface area each time of the indicated dimension.
[0010] For the aggregate to have better properties, the mixture between the starting particulate mineral material and the binder or binder-forming system must be optimal within the composite forming this aggregate, that is to say, the material-binder / binder-forming system contact surface must be as large as possible. However, if this surface is too large, the material absorbs too much water and / or binder and therefore the composite becomes weakened. The particular values of D90, D10 and D50 indicated above are advantageous for such optimization.
[0011] The hardenable mineral binder(s) may be chosen from: hydraulically setting cement binders, such as NF EN 206 standardized cements, such as Portland cement CEM I and Portland cement CEM III; mixtures based on at least three components chosen from clinkers, metakaolins, gypsum, slags, limestone fillers, silica fume, ash, pozzolans and pozzolanic materials; mixtures of at least one binder defined in (a) and at least one component of a mixture as defined in (b).
[0012] The system(s) capable of forming a hardened mineral binder in an aqueous medium may consist of: at least one precursor for the formation of a geopolymer or an activated alkali, chosen in particular from kaolins, metakaolins, shales, clays, slags, ashes and mixtures thereof, kaolins, shales and clays which may have undergone a heat treatment such as calcination or flash treatment; and at least one activator for the formation of an activated binder chosen from soda, potash and sodium and / or potassium silicates.
[0013] At least one shaping aid chosen in particular from: petro-sourced polymers, such as polyamides, such as polyacrylamides, and concrete plasticizers and superplasticizers; bio-sourced polymers, such as corn starch or cellulose ether; and mineral plasticizers, such as bentonite and non-reactive ash.
[0014] Particularly preferably, the mixture is obtained in the form of a wet powder from:50 to 95 parts by weight, in particular 65 to 90 parts by weight, of said particulate starting material(s); and5 to 50 parts by weight, in particular 10 to 35 parts by weight, of said binder(s) and / or binder-forming system(s),
[0015] water being added at a rate of 2 to 40 parts by weight and the shaping aid(s) being able to be added up to 5 parts by weight,
[0016] all these parts by weight being given for 100 parts by weight of (A) + (B).
[0017] Water helps to harden the binder by contributing to the hydraulic setting in the case of a hardenable mineral binder or by constituting the formation medium for the geopolymer or activated alkali. Furthermore, water can help with compression by fluidifying the mass to be compressed.
[0018] The quantities of the mixture can be advantageously adjusted before compression to obtain a wet powder rheology corresponding to a concrete of class S1 to S3 according to standard NF EN 12 350-2, in particular class S1 (slump between 10 and 40 mm at the Abrams cone).
[0019] Mixing can be carried out in a paddle, plowshare, ribbon or planetary mixer for a time ranging from 3 seconds to 3 minutes.
[0020] The wet powder is advantageously compressed by extrusion in a single-screw extruder or in a twin-screw extruder or by pressing using a piston press or a vibro-compaction press to directly obtain the desired granulate or to obtain a sausage which is then cut into the desired granulate or using a compression wheel which allows the desired granulate to be obtained directly.
[0021] Compression allows several phenomena: increase in the intrinsic density of the material; intimate mixing of the binder, the material and the water; reduction of the intrinsic porosity of the material; and creation of minimal cohesion before the end of the maturation phase.
[0022] Thus without compression, the composite cannot remain in the form of aggregate while maturation takes place and at best will be filled with porosity with unactivated binder and at worst will disintegrate before its complete setting.
[0023] Either after compression, or after shaping, or after compression and after shaping, maturation can advantageously be carried out, depending on the case, on the hardened product or the aggregate in a closed enclosure for a period of 1 hour to 10 days at a temperature of 15 to 70°C.
[0024] The invention also relates to an aggregate obtained by the process as defined above, having at least one of: a water absorption according to standard NF EN 1097-6 of less than 30% by weight; a density according to standard NF EN 1097-6 of 1.5 to 3 g / cm 3 , preferably 1.6 to 2.5 g / cm 3 ; and a Los Angeles coefficient according to standard EN 1097-2 of less than 80, preferably from 10 to 70.
[0025] The aggregate as defined above advantageously has a particle size of 4 to 70 mm, preferably 4 to 31.5 mm.
[0026] The present invention also relates to the use of the aggregate manufactured by the process as defined above or of the aggregate as defined above, as aggregate for concrete (ready-mix concrete, prefabricated concrete, etc.), aggregate for asphalt, as backfill for geotechnical use, as road sub-base or as decorative aggregate, said granular material being used alone or in a mixture with other aggregates, for example with conventional aggregates such as natural aggregates, artificial aggregates or recycled aggregates based on crushed concrete in particular.
[0027] The following Examples illustrate the present invention without, however, limiting its scope.
[0028] In these examples, percentages and parts are given by weight unless otherwise indicated.
[0029] Example 1: Production of an aggregate based on a mixture of sands
[0030] A mixture of sands composed of 70% silica sand and 30% basalt sand was ground to a particle size defined by a D90 of 1.3 mm, a D10 of 0.04 mm and a D50 of 0.3 mm.
[0031] A mixture was then prepared in the form of a wet powder, having the following composition:
[0032] Ground sand mixture thus obtained74.8 partsTernary mixture of 4.25% gypsum, 80.75% clinker and 15% metakaolin (binder forming system)25.2 partsWater9.2 partsSuperplasticizer Visco crete sika Dynamon NG (MBS) (forming aid)0.88 parts
[0033] Then the mixture thus prepared was subjected to compression by passing it through a single-screw extruder, at the outlet of which the bound mixture thus shaped was cut into a sausage shape into granules with a grain size of [10; 14] mm.
[0034] This aggregate was then subjected to maturation in a closed enclosure for 7 days at 20°C.
[0035] This aggregate had: a density of 2.16 g / cm 3 ;a water absorption of 8%; and a Los Angeles coefficient of 30.
[0036] Example 2: Production of a granulate based on recycled glass
[0037] Recycled glass was crushed to a particle size defined by a D90 of 0.6 mm, a D10 of 0.06 mm and a D50 of 0.2 mm.
[0038] A mixture was then prepared in the form of a wet powder, having the following composition:
[0039] Ground glass thus obtained76.1 partsCEM III cement (binder)23.9 partsWater11.1 parts
[0040] The mixture was then subjected to compression in a piston extruder to obtain blocks of the thus shaped bonded mixture which were subjected to maturation in a closed enclosure for 3 days at 25°C.
[0041] At the end of maturation, the blocks thus obtained were crushed to obtain an aggregate with a grain size of [6; 30 mm].
[0042] This aggregate had: a density of 1.75 g / cm 3 ;a water absorption of 12%; and a Los Angeles coefficient of 45.
[0043] Example 3: Production of an aggregate based on limestone quarry fines
[0044] Limestone quarry fines were ground to a particle size defined by a D90 of 0.6 mm, a D10 of 0.02 mm and a D50 of 0.2 mm.
[0045] A mixture was then prepared in the form of a wet powder, having the following composition:
[0046] Fines60 partsActivated slag (80% slag and 20% alkali silicate (marketed by Wöllner) as activator)40 partsWater19 partsNon-reactive ash (shaping aid)1 part
[0047] Then the mixture thus prepared was subjected to compression by passing it through a single-screw extruder at the outlet of which the bound mixture thus shaped was cut into a sausage shape into granules with a grain size of 10-20 mm.
[0048] This aggregate was then subjected to maturation in a closed enclosure for 1 day at 40°C.
[0049] This aggregate had: a density of 2.2 g / cm 3 ;a water absorption of 8%; and a Los Angeles coefficient of 60.
Claims
– A method of manufacturing a reconstituted mineral aggregate, characterized in that at least one starting particulate mineral material for aggregate is mixed with water and at least one mineral binder that can be hardened in the presence of water and / or at least one system capable of forming a hardened mineral binder in an aqueous medium, to obtain a material in the form of a wet powder that is compressed by extrusion or pressing to intimately mix the binder and / or system capable of forming the binder / starting particulate material / water and increase the intrinsic density and reduce the intrinsic porosity of the material, and to obtain, as a result of the hardening of the binder(s), a hardened, solid mass, which is in the form of the aggregate of the desired size and / or shape, or is transformed into the aggregate of the desired size and / or shape by cutting or crushing,immediately after compression or in a later step., – Method according to claim 1, characterized in that the starting particulate mineral material is chosen from sands, such as silica sand and basalt sand; non-reactive clays; sediments, such as dredging sediments; glass; coal; crushed concrete; crushed aggregates; quarry fines; industrial process fines; insulating materials such as rock wool and glass wool; and mixtures thereof. – Method according to one of claims 1 and 2, characterized in that the starting particulate mineral material or the mixture of starting particulate mineral materials have a particle size defined by: a D90 value less than or equal to 1.3 mm; a D10 value greater than or equal to 0.02 mm; and a D50 value greater than or equal to 0.1 mm and less than or equal to 1 mm, said material or said mixture of materials having been subjected to grinding, if necessary, to obtain this particle size. – Method according to one of claims 1 to 3, characterized in that the hardenable mineral binder(s) are chosen from: hydraulically setting cement binders, such as NF EN 206 standardized cements, such as Portland cement CEM I and Portland cement CEM III; mixtures based on at least three components chosen from clinkers, metakaolins, gypsum, slags, limestone fillers, silica fume, ash, pozzolans and pozzolanic materials; mixtures of at least one binder defined in (a) and at least one component of a mixture as defined in (b). – Method according to one of claims 1 to 4, characterized in that the system(s) capable of forming a hardened mineral binder in an aqueous medium are constituted by: at least one precursor for the formation of a geopolymer or an activated alkali, chosen in particular from kaolins, metakaolins, shales, clays, slags, ashes and their mixtures, kaolins, shales and clays which may have undergone a heat treatment such as calcination or flash treatment; and at least one activator for the formation of an activated binder chosen from soda, potash and sodium and / or potassium silicates. – Method according to one of claims 1 to 5, characterized in that at least one shaping aid chosen in particular from: petro-sourced polymers, such as polyamides, such as polyacrylamides, and concrete plasticizers and superplasticizers; bio-sourced polymers, such as corn starch, cellulose ether; and mineral plasticizers, such as bentonite and non-reactive ash. - Method according to one of claims 1 to 6, characterized in that the mixture is obtained in the form of a wet powder from:50 to 95 parts by weight, in particular 65 to 90 parts by weight, of said particulate starting material(s); and5 to 50 parts by weight, in particular 10 to 35 parts by weight, of said binder(s) and / or binder-forming system(s),water being added in an amount of 2 to 40 parts by weight and the shaping aid(s) being able to be added up to 5 parts by weight,all these parts by weight being given per 100 parts by weight of (A) + (B). - Method according to one of claims 1 to 7, characterized in that the compression of the wet powder is carried out by extrusion in a single-screw extruder or in a twin-screw extruder or by pressing using a piston press or a vibro-compaction press to directly obtain the desired granulate or to obtain a sausage which is then cut into the desired granulate or using a compression wheel which makes it possible to directly obtain the desired granulate. - Method according to one of claims 1 to 8, characterized in that, either after compression, or after shaping, or after compression and after shaping, maturation is carried out, depending on the case, of the hardened product or of the granulate in a closed enclosure for a period of 1 hour to 10 days at a temperature of 15 to 70°C. – Aggregate obtained by the process as defined in one of claims 1 to 9, having at least one of: a water absorption according to standard NF EN 1097-6 of less than 30% by weight; a density according to standard NF EN 1097-6 of 1.5 to 3 g / cm 3 , preferably 1.6 to 2.5 g / cm 3 ; and a Los Angeles coefficient according to standard EN 1097-2 of less than 80, preferably from 10 to 70. – Aggregate according to claim 10, characterized in that it has a particle size of 4 to 70 mm, preferably 4 to 31.5 mm. - Use of the aggregate manufactured by the method according to one of claims 1 to 9 or as defined in one of claims 10 and 11, as aggregate for concrete, aggregate for asphalt, as backfill for geotechnical use, as road sub-base or as decorative aggregate, said granular material being used alone or in a mixture with other aggregates.