Mechanochemically carboxylated fly ash, its production method and use

Abstract

The present invention is based on a BET surface area of ​​50 m 2 The present invention relates to a mechanochemically carboxylated fly ash having a carbon dioxide content of less than 1% by weight and a CO2 content of greater than 1% by weight. The present invention further relates to methods of preparation and uses, for example, as a filler. The present invention also relates to a composition comprising the mechanochemically carboxylated fly ash and a material selected from the group consisting of asphalt, cement, polymers, and combinations thereof, and a method of preparation thereof.

Description

[Technical Field]

[0001] The present invention relates to mechanochemically carboxylated fly ash. The invention also relates to a method for preparing and using the same, for example as a filler. The invention also relates to a composition comprising the mechanochemically carboxylated fly ash and a material selected from the group consisting of asphalt, cement, polymers, and combinations thereof, and a method for preparing the same. [Background technology]

[0002] Concrete is a composite material containing a matrix of aggregate (usually rock-based) and a binder (usually Portland cement or asphalt) that binds the matrix. Concrete is one of the most frequently used building materials and is said to be the second most widely used substance on Earth after water.

[0003] In order to reduce the cost of concrete and the CO2 emissions generated by cement production worldwide, much research effort is being devoted to identifying inexpensive materials that can be used as fillers to replace or as new binder components without (harmful) affecting the properties of concrete. Such secondary cementitious materials are an area of ​​widespread interest in industry.

[0004] An example of a widely adopted cement filler is limestone. A comprehensive overview of fillers in cement-based materials can be found in [1].

[0005] Portland cement production accounts for approximately 10% of global carbon dioxide emissions. According to Vanderley et al., traditional strategies for reducing CO2 emissions in the cement industry are insufficient to ensure the necessary reductions in the face of growing cement demand. Therefore, the adoption of carbon capture and storage (CCS), which is expensive and carries significant environmental risks, has been considered a compelling solution by cement industry leaders. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] John,Vanderley M.,et al.'Fillers in cementitious materials-Experience, recent advances and future potential.'Cement and Concrete Research 114(2018):65-78 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need to develop an inexpensive filler technology that can reduce CO2 emissions by reducing cement production and CO2 emissions through carbon capture technology, without impairing the properties of concrete.

[0008] It is an object of the present invention to provide an improved filler for use in cement or asphalt binders.

[0009] It is a further object of the present invention to provide an improved filler for use in cement or asphalt binders that is inexpensive to produce.

[0010] It is a further object of the present invention to provide an improved filler for use in binders for cement or asphalt produced using CO2 storage technology.

[0011] It is a further object of the present invention to provide an improved filler for use in cement or asphalt binders which improves properties, such as compressive strength, of the resulting concrete. [Means for solving the problem]

[0012] In a first aspect, the present invention provides a crystalline silica having a BET surface area of ​​50 m 2 / g and a CO2 content greater than 1 wt. %, wherein the CO2 content is determined from the mass loss at or above 120°C measured by TGA-MS following a temperature curve from room temperature to 800°C at 10°C / min and then cooling to room temperature at 15°C / min.

[0013] As shown in the Examples below, the use of such mechanochemically carboxylated fly ash as a filler in cement has been found to surprisingly increase the compressive strength of the resulting concrete over that achieved with pure cement. Furthermore, the time required for strength development is shortened. Furthermore, the mechanochemically carboxylated fly ash can be used in very large amounts as a dispersant while still achieving acceptable concrete properties.

[0014] Furthermore, the production of the mechanochemically carboxylated fly ash relies on an inexpensive CO2 capture technology platform, providing a filler that can be produced in an economically sustainable manner and combines the CO2 emission reductions of reduced cement production with those of carbon capture technology.

[0015] Furthermore, the inventors have found that the durability of concrete obtained using the mechanochemical fly ash filler is significantly improved. While not wishing to be bound by any particular theory, they believe this is due to accelerated hydration at the micro- and sub-microscale, resulting in reduced chloride permeability and / or reduced concrete porosity. Finally, the increased oxygen content compared to the untreated raw material is believed to improve dispersibility in polar solvents and compatibility with materials containing epoxy and carboxyl groups.

[0016] In a further aspect, the present invention provides a method for producing a mechanochemically carboxylated fly ash, preferably a mechanochemically carboxylated fly ash as described herein, comprising the steps of: a) providing a solid feedstock comprising or consisting of fly ash, said solid feedstock having a BET surface area of ​​0.01 m 2 / g and the particulate matter has a D50 value in the range of 0.1 to 5000 μm; b) providing an oxidizing gas comprising CO2; c) feeding the solid raw material and the oxidizing gas into a mechanical stirring device; and d) placing the solid raw material in the mechanical stirring device and subjecting it to mechanical stirring in the presence of the oxidizing gas at an oxidizing gas pressure of more than 1 atm to obtain mechanochemically carboxylated fly ash.

[0017] In another aspect, the present invention provides a mechanochemically carboxylated fly ash obtainable by the method for producing a mechanochemically carboxylated fly ash described herein.

[0018] In another aspect, the present invention provides a composition comprising the mechanochemically carboxylated fly ash described herein and an additional material selected from the group consisting of asphalt, cement, polymers, and combinations thereof.

[0019] In another aspect, the present invention provides a method for obtaining the compositions described herein, such method comprising the steps of: (i) providing a mechanochemically carboxylated fly ash as described herein; (ii) providing a further material selected from the group consisting of asphalt, cement, polymers, and combinations thereof; (iii) combining the mechanochemically carboxylated fly ash of step (i) with the material of step (ii).

[0020] In another aspect, the present invention provides a method for obtaining concrete, said method comprising the steps of: (i) providing a composition as described herein, wherein the additional material is asphalt or concrete; (ii) preparing construction aggregate; and (iii) contacting, preferably mixing, the composition of step (i) with the construction aggregate of step (ii).

[0021] In another aspect, the present invention provides a concrete obtainable by the method for obtaining a concrete described herein.

[0022] In another aspect, the present invention provides the use of the chemically carboxylated fly ash described herein, wherein the use comprises: Use as a filler, preferably as a filler in one material selected from the group consisting of asphalt, cement, polymers and combinations thereof; Use as a partial replacement for asphalt or cement in concrete; Use to increase the compressive strength of concrete; Use to improve the durability of concrete; or Use to improve the durability of concrete by reducing chloride permeability and / or porosity. DETAILED DESCRIPTION OF THE INVENTION

[0023] The first aspect of the present invention is a method for producing a cellulose ester having a BET surface area of ​​50 m 2 / g and a CO2 content greater than 1 wt.%, where the CO2 content is determined from the mass loss at or above 120°C measured by TGA-MS following a temperature curve from room temperature to 800°C at 10°C / min and then cooling to room temperature at 15°C / min.

[0024] According to the present invention, the BET surface area, BJH desorption cumulative pore surface area, and desorption average pore diameter (4V / A by BET) are determined using a sample having a mass of 0.5 to 1 g at a temperature of 77 K. A preferred analytical method for determining the BET surface area, BJH desorption cumulative pore surface area, and desorption average pore diameter (4V / A by BET) involves heating the sample to 400° C. during the desorption cycle prior to performing the surface area analysis.

[0025] As used herein, TGA-MS refers to a thermogravimetric analyzer coupled to a mass spectrometer, a technique known to those skilled in the art. In the context of the present invention, a preferred TGA-MS setup for determining the CO content of raw and mechanochemically carboxylated materials is a dual-chamber TGA / DSC instrument, Setaram TAG 16, coupled to an Ametek Dycor Proline MS, using 0.1-2 mg samples.

[0026] In a preferred embodiment, the mechanochemically carboxylated fly ash satisfies one, two or three, preferably three, of the following properties: · SiO2 content less than 50 wt.% (relative to the total weight of mechanochemically carboxylated fly ash); · Al2O3 content less than 20 wt.% (relative to the total weight of mechanochemically carboxylated fly ash); Fe2O3 content greater than 10% by weight (based on the total weight of mechanochemically carboxylated fly ash).

[0027] In a preferred embodiment, the mechanochemically carboxylated fly ash satisfies one, two or three, preferably three, of the following properties: an SiO2 content (relative to the total weight of the mechanochemically carboxylated fly ash) of more than 30% by weight, preferably more than 40% by weight; an Al2O3 content (relative to the total weight of the mechanochemically carboxylated fly ash) of more than 10 wt.%, preferably more than 15 wt.%; Fe2O3 content (relative to the total weight of the mechanochemically carboxylated fly ash) is less than 40% by weight, preferably less than 30% by weight.

[0028] In a highly preferred embodiment, the mechanochemically carboxylated fly ash meets one, two or three, preferably three, of the following properties: · SiO2 content of 30-50 wt.% (based on the total weight of mechanochemically carboxylated fly ash); · Al2O3 content of 10-20 wt% (relative to the total weight of mechanochemically carboxylated fly ash); Fe2O3 content of 10-40 wt% (based on the total weight of mechanochemically carboxylated fly ash).

[0029] The content of inorganic components such as SiO2, Al2O3, Fe2O3 or CaO is determined by X-ray fluorescence spectroscopy, preferably using a Bruker Tracer 5G. As will be appreciated by those skilled in the art, the content of SiO2, Al2O3, Fe2O3 and CaO in both the raw material and the mechanochemically carboxylated fly ash herein is preferably determined by X-ray fluorescence spectroscopy as described herein.

[0030] In an embodiment of the present invention, the particle size distribution of the mechanochemically carboxylated fly ash satisfies one, two, three or all, preferably all, of the following characteristics: the D10 value is in the range of 0.005 to 5 μm, preferably 0.01 to 1 μm, most preferably 0.1 to 0.5 μm; the D50 value is in the range of 0.5 to 50 μm, preferably 1 to 25 μm, most preferably 1 to 10 μm; the D90 value is in the range of 5 to 200 μm, preferably 20 to 100 μm, most preferably 30 to 50 μm; The value of D(4:3) is in the range of 1 to 100 μm, preferably 10 to 25 μm.

[0031] According to the present invention, particle size distribution characteristics such as D10, D50, D90, and D(4:3) are determined by measuring with a laser light scattering particle size analyzer utilizing the Fraunhofer theory of light scattering, such as a Fritsch Analysette 22 Nanotec or other instruments of comparable or greater sensitivity, and recording the data using a volume-equivalent sphere model. As known to those skilled in the art, D50 represents the mass median diameter, i.e., the diameter at which 50% of the sample's mass is made up of smaller particles. Similarly, D10 and D90 represent the diameters at which 10% and 90% of the sample's mass is made up of smaller particles. As known to those skilled in the art, D(4:3) is the volume mean diameter.

[0032] In an embodiment of the present invention, the density of the mechanochemically carboxylated fly ash is 2.5 g / cm 3 more than 2.7 g / cm 3 More preferably, it is greater than 3 g / cm 3 It's super.

[0033] In a preferred embodiment of the present invention, the mechanochemically carboxylated fly ash has a density of 2.5 g / cm 3 greater than 1 μm, D10 less than 1 μm, D50 less than 10 μm, and D90 less than 50 μm.

[0034] In a further aspect, the present invention provides a method for obtaining a mechanochemically carboxylated fly ash, preferably a mechanochemically carboxylated fly ash as described herein, comprising the steps of: a) providing a solid feedstock comprising or consisting of fly ash, said solid feedstock having a BET surface area of ​​0.01 m 2 / g and the particulate matter has a D50 value in the range of 0.1 to 5000 μm; b) providing an oxidizing gas comprising CO2; c) feeding the solid raw material and the oxidizing gas into a mechanical stirring device; and d) placing the solid raw material in the mechanical stirring device and subjecting it to mechanical stirring in the presence of the oxidizing gas at an oxidizing gas pressure of more than 1 atm to obtain mechanochemically carboxylated fly ash.

[0035] In light of the guidance provided in this disclosure, it is within the ability of one skilled in the art to appropriately modify the relevant process parameters to obtain a mechanochemically carboxylated fly ash having the properties described herein.

[0036] In a preferred embodiment of the present invention, the BET surface area of ​​the mechanochemically carboxylated fly ash is at least 110%, preferably at least 120%, and more preferably at least 150% of the BET surface area of ​​the solid raw material.

[0037] While not wishing to be bound by any particular theory, the inventors believe that the increase in BET surface area observed upon mechanochemical carboxylation of fly ash is largely due to the decrease in average pore size and the increase in the number of pores resulting from the increase in total pore surface area. Therefore, in this embodiment, the BJH desorption integrated surface area of ​​the pores of the mechanochemically carboxylated fly ash is at least 110%, preferably at least 120%, and more preferably at least 150% of the BJH desorption integrated surface area of ​​the pores of the solid feedstock. Furthermore, the desorption average pore size (BET 4V / A) of the mechanochemically carboxylated fly ash is 90% or less, preferably 85% or less, and more preferably 80% or less of the desorption average pore size (BET 4V / A) of the solid feedstock.

[0038] In a preferred embodiment of the present invention, the Fe2O3 content of the mechanochemically carboxylated fly ash is at least 150%, preferably at least 200%, and most preferably at least 250%, relative to the Fe2O3 content of the solid raw material.

[0039] In a preferred embodiment of the present invention, the CO content of the mechanochemically carboxylated fly ash is greater than 2 wt. %, preferably greater than 5 wt. %, and most preferably greater than 7 wt. % (based on the total weight of the mechanochemically carboxylated fly ash), as determined from the mass loss above 120° C. measured by TGA-MS following a temperature curve from room temperature to 800° C. at 10° C. / min, followed by a temperature decrease to room temperature at 15° C. / min.

[0040] In an even more preferred embodiment of the invention, the CO content of the solid feedstock is less than 0.5 wt. % (based on the total weight of the solid feedstock), preferably less than 0.2 wt. %, and most preferably less than 0.1 wt. %, as determined from the mass loss above 120° C. measured by TGA-MS following a temperature curve ramping from room temperature to 800° C. at 10° C. / min, then ramping down to room temperature at 15° C. / min.

[0041] As used herein, the term "fly ash" refers to any type of fly ash, including coal fly ash and petroleum fly ash. Without wishing to be bound by any particular theory, the inventors have found that performance improves when the solid feedstock is low in carbonaceous fly ash. Carbonaceous fly ash is a particularly distinctive type of fly ash that makes up a large proportion of petroleum fly ash.

[0042] Thus, in preferred embodiments, the fly ash is coal fly ash, such as lignite fly ash, subbituminous coal fly ash, anthracite fly ash, bituminous coal fly ash, and combinations thereof. In highly preferred embodiments of the present invention, the solid feedstock comprises or consists of fly ash that meets the requirements of ASTM C618(2019), preferably Class C of ASTM C618(2019).

[0043] In an embodiment, the solid feedstock has a combined SiO2, Al2O3, and Fe2O3 content of greater than 60 wt. %, preferably greater than 70 wt. %, and more preferably greater than 75 wt. % (based on the total weight of the solid feedstock).

[0044] Without wishing to be bound by any particular theory, the inventors have found that improved mechanochemical carboxylation and filler performance results when the feedstock contains at least some CaO. Thus, in this embodiment, the solid feedstock contains more than 0.5 wt. %, preferably more than 1 wt. %, and more preferably more than 3 wt. % CaO (based on the total weight of the solid feedstock). In more preferred embodiments of the invention, the solid feedstock contains more than 5 wt. % or more than 8 wt. % CaO (based on the total weight of the solid feedstock).

[0045] In an embodiment of the present invention, the particle size distribution of the solid feedstock has one, two, three or all, preferably all, of the following characteristics: the D10 value is in the range of 0.1 to 50 μm, preferably 0.5 to 20 μm, most preferably 1 to 10 μm; the D50 value is in the range of 1 to 200 μm, preferably 5 to 100 μm, most preferably 10 to 50 μm; the D90 value is in the range of 50 to 700 μm, preferably 5 to 500 μm, most preferably 60 to 400 μm; The value of D(4:3) is in the range of 10 to 200 μm, preferably 20 to 130 μm.

[0046] In an embodiment of the invention, the oxidizing gas provided in step (b) comprises more than 80 mol% CO, preferably more than 95 mol% CO. In a preferred embodiment of the invention, the oxidizing gas provided in step (b) comprises more than 80 mol% CO, preferably more than 95 mol% CO, and less than 1000 ppm (v / v) HO, preferably less than 100 ppm (v / v) HO.

[0047] In an embodiment of the present invention, step (d) is carried out at a pressure greater than 3 atm, preferably greater than 6 atm. In an embodiment of the present invention, step (d) is carried out at a temperature less than 100°C, preferably less than 60°C, more preferably less than 30°C. In an embodiment of the present invention, step (d) is carried out for at least 1 hour, preferably at least 4 hours, more preferably at least 8 hours. In a preferred embodiment of the present invention, step (d) is carried out at a pressure greater than 3 atm, preferably greater than 6 atm; at a temperature less than 100°C, preferably less than 60°C, more preferably less than 30°C; and for at least 1 hour, preferably at least 4 hours, more preferably at least 8 hours.

[0048] The inventors have further found that the mechanochemical carboxylation processes described herein can be carried out without providing an additional oxidizing agent, such as an acid. Thus, the mechanochemical carboxylation processes described herein are preferably carried out without the use of a strong acid, and preferably without the use of any additional oxidizing agent other than the oxidizing gas provided in step (b).

[0049] In a preferred embodiment of the present invention, the mechanochemical stirring operation in step (d) comprises grinding, milling, mixing, stirring (low or high speed stirring), shearing (high torque shear), shaking, blending, fluidized bed, or ultrasonic treatment, and is preferably grinding, milling, mixing, stirring (low or high speed stirring), shearing (high torque shear), or ultrasonic treatment. The inventors have found that the mechanochemical carboxylation process is facilitated when the mechanochemical stirring operation in step (d) is carried out in the presence of an inert grinding or milling medium, preferably inert balls or beads. A preferred inert material is stainless steel.

[0050] In a preferred embodiment of the present invention, step (d) is carried out in the presence of a catalyst, preferably a transition metal oxide catalyst, more preferably a transition metal dioxide catalyst, most preferably a transition metal dioxide catalyst selected from the group consisting of iron oxide, cobalt oxide, ruthenium oxide, titanium oxide, and combinations thereof.

[0051] Thus, as can be seen from the above, in a highly preferred embodiment of the present invention, step (d) comprises a mechanical agitation operation, preferably grinding, milling, mixing, stirring (low or high speed), shearing (high torque shear), shaking, blending, fluidized bed, or ultrasonic treatment, in the presence of an inert grinding or milling medium and a transition metal oxide catalyst. The inventors have found that the use of an inert medium as described herein prior to coating with the transition metal oxide catalyst is beneficial in terms of the efficiency of the mechanochemical carboxylation (e.g., reaction time, CO2 uptake, and particle size reduction).

[0052] In another embodiment, the present invention provides a mechanochemically carboxylated fly ash obtained by the method for obtaining a mechanochemically carboxylated fly ash described herein.

[0053] As will be appreciated by those skilled in the art in light of the present disclosure, the mechanochemically carboxylated fly ash of the present invention combines excellent mechanical properties with cost-effective CO2 capture technology, making it an excellent filler for many applications.

[0054] Thus, in another aspect, the present invention provides a composition comprising the mechanochemically carboxylated fly ash described herein and an additional material selected from the group consisting of asphalt, cement, polymers, and combinations thereof.

[0055] In this embodiment, the additional material is a polymer selected from thermoplastic polymers and thermosetting polymers. In a preferred embodiment, the additional material is a polymer selected from the group consisting of epoxy resin, phenol-formaldehyde resin, polyethylene terephthalate, aromatic polyamide, polyacrylonitrile, polyimide, aromatic polyester, polyethylene, polypropylene, polyurethane, polyisocyanurate, polyamide, polyether, polyester, polyhydroxyalkanoate, polylactic acid, polyvinylidene fluoride, polyvinyl acetate, polyvinyl chloride, polystyrene, polytetrafluoroethylene, acrylonitrile-butadiene-styrene, nitrile rubber, styrene-butadiene, ethylene-vinyl acetate, and combinations thereof. As used herein, the term 'polymer' includes copolymers such as block copolymers.

[0056] In a highly preferred embodiment, the additional material is selected from cement, asphalt, and combinations thereof.

[0057] According to the present invention, the cement may be a hydraulic cement or a non-hydraulic cement. In a preferred embodiment, the cement is a hydraulic cement such as Portland cement. In a more preferred embodiment of this embodiment, the cement is one of the cements defined in EN 197-1 (2011), and even more preferably, Portland cement as defined in EN 197-1 (2011).

[0058] In an embodiment of the invention, the composition comprises more than 0.1 wt. %, preferably more than 1 wt. %, more preferably more than 5 wt. % of mechanochemically carboxylated fly ash (relative to the total weight of the composition) and / or more than 0.1 wt. %, preferably more than 1 wt. %, more preferably more than 20 wt. % of further material (relative to the total weight of the composition).

[0059] In an embodiment of the invention, the composition comprises less than 60 wt. %, preferably less than 50 wt. %, more preferably less than 45 wt. % of mechanochemically carboxylated fly ash (based on the total weight of the composition) and / or less than 95 wt. %, preferably less than 90 wt. %, more preferably less than 80 wt. % of additional materials (based on the total weight of the composition).

[0060] In an embodiment of the present invention, there is provided a composition in which the ratio of mechanochemically carboxylated fly ash to the further material, expressed in weight:weight, is in the range of 1:9 to 2:1, preferably 1:8 to 1:1, more preferably 1:6 to 5:6.

[0061] In an embodiment of the present invention, the composition comprises 5 to 70 wt. %, preferably 10 to 60 wt. %, more preferably 20 to 50 wt. % of mechanochemically carboxylated fly ash (based on the total weight of the composition) and 30 to 95 wt. %, preferably 40 to 90 wt. %, more preferably 50 to 80 wt. % of further material (based on the total weight of the composition).

[0062] In an embodiment of the invention, the composition contains less than 5 wt. % water (based on the total weight of the composition), preferably less than 1 wt. %, more preferably less than 0.1 wt. %. The water content is suitably determined from the mass loss up to 120°C measured by TGA-MS following a temperature curve from room temperature to 800°C at 10°C / min.

[0063] In an embodiment of the present invention, the composition comprises mechanochemically carboxylated fly ash and an additional material.

[0064] In another aspect, the present invention provides a method for obtaining the compositions described herein, such method comprising the steps of: (i) providing a mechanochemically carboxylated fly ash as described herein; (ii) providing a further material selected from the group consisting of asphalt, cement, polymers, and combinations thereof; and (iii) combining the mechanochemically carboxylated fly ash of step (i) above with the further material of step (ii) above.

[0065] In another aspect, the present invention provides a method for obtaining concrete, said method comprising the steps of: (i) providing a composition as described herein, wherein the additional material is asphalt or cement; (ii) preparing construction aggregates; (iii) contacting, preferably mixing, the composition of step (i) above with the construction aggregate of step (ii) above.

[0066] In another aspect, the present invention provides a concrete obtainable by the method for obtaining a concrete described herein.

[0067] In an embodiment of the present invention, the construction aggregate is selected from the group consisting of sand, gravel, crushed stone, slag, recycled concrete, clay, pumice, perlite, vermiculite, and combinations thereof. In a preferred embodiment, the construction aggregate is an aggregate defined in EN 13043 (2002), EN 13383 (2019), EN 12620 (2013), or EN 13242 (2013), preferably an aggregate defined in EN 12620 (2013).

[0068] In a preferred embodiment of the present invention, step (iii) further comprises contacting, preferably mixing, the composition of step (i) with the construction aggregate of step (ii) and water. According to the present invention, the composition of step (i), the construction aggregate of step (ii), and the water may be contacted, preferably mixed, substantially simultaneously, or may be contacted, preferably mixed, in stages, with the composition of step (i) first contacted, preferably mixed, with the water and then contacted, preferably mixed, with the construction aggregate of step (ii).

[0069] In another aspect of the present invention, there is provided the use of the mechanochemically carboxylated fly ash described herein. Use as a filler, preferably as a filler in materials selected from the group consisting of asphalt, cement, polymers and combinations thereof; Use as a partial replacement of asphalt or cement in concrete; · Use to increase the compressive strength of concrete; Use to improve the durability of concrete; or ·Use to improve the durability of concrete by reducing chloride permeability and / or porosity.

[0070] It will be understood by those skilled in the art that the embodiments of the invention described herein, with respect to the features of the compositions, in particular the mechanochemically carboxylated fly ash, or with respect to the features of the further materials, are applicable to the methods for obtaining said mechanochemically carboxylated fly ash or compositions described herein, to the methods for obtaining the concrete described herein, and to the uses of the mechanochemically carboxylated fly ash described herein. [Example]

[0071] The BET surface area, BJH desorption cumulative pore surface area, and desorption average pore diameter (4V / A by BET) were determined at a temperature of 77 K using samples weighing 0.5–1 g that had been heated to 400 °C during the desorption cycle prior to surface area analysis.

[0072] Particle size distribution measurements were performed using a Fritsch Analysette 22 Nanotec using the Fraunhofer theory.

[0073] The inorganic (SiO2, Al2O3, Fe2O3 and CaO) contents were determined by X-ray fluorescence spectroscopy using a Bruker Tracer 5G.

[0074] The CO2 content was determined from the mass loss above 120°C measured by TGA-MS using a Setaram TAG 16 TGA / DSC dual chamber balance coupled with an Ametek Dycor Proline MS. Samples of 0.1–2 g were heated from room temperature to 800°C at 10°C / min, then cooled to room temperature at 15°C / min.

[0075] Compressive strength was tested in accordance with ISO1920:2005 Part 4.

[0076] Example 1 Mechanochemically carboxylated fly ash was prepared by placing a 10 g sample of fly ash in a pressure cell along with 500 g of titanium dioxide-coated inert media (stainless steel balls). The cell was pressurized to 1 MPa (9.87 atm) and placed in a high-energy ball mill, rotating at 5000 rpm for 48 hours. The reaction was initiated at room temperature and was not heated or cooled.

[0077] Example 2 Two raw fly ash samples, Samples A and B, were mechanochemically carboxylated (treated) as in Example 1, with variations in mechanical agitation and CO pressure to yield products with the properties shown in the table below. Raw Sample A was obtained from a coal plant in Genesee, Alberta (Canada) and meets the requirements of Class F of ASTM C618 (2019). Raw Sample B was obtained from a coal plant in Civitavecchia (Italy). Raw Sample C was obtained from a coal plant in Cordomé (France). The raw fly ash samples B and C are generally poor quality fly ash and are unsuitable for use as concrete fillers at concentrations greater than 10% by weight.

[0078] [Table 1]

[0079] Mechanochemically carboxylated fly ash A and B were mixed with Portland cement in a weight:weight ratio of 1:5 (filler:cement) and used as fillers.

[0080] The resulting mixture of mechanochemically carboxylated fly ash and Portland cement was mixed with fine gravel and water (the same ratio was used for all samples) to obtain concrete slurries. The compressive strength of the resulting concrete was measured after 2, 7, and 28 days.

[0081] For comparison, similar concrete slurries were prepared using raw fly ash samples A and B and pure Portland cement.

[0082] [Table 2]

[0083] As can be seen from compressive strength measurements, the mechanochemically carboxylated inorganic fillers of the present invention provide unexpectedly large performance improvements compared to untreated materials (such as fly ash). Even more surprisingly, the mechanochemically carboxylated inorganic fillers of the present invention have been found to even outperform pure cement blends.

Claims

1. BET surface area is 50m ２ / g or less, CO ２ The content is more than 1% by weight, The CO ２ The content is determined from the mass loss above 120°C measured by TGA-MS following a temperature curve ramping from room temperature to 800°C at 10°C / min, then ramping down to room temperature at 15°C / min; Mechanochemically carboxylated fly ash having a D90 in the range of 20 to 100 μm and / or a D50 in the range of 0.5 to 50 μm.

2. 2. The mechanochemically carboxylated fly ash of claim 1, which satisfies one, two, or three of the following characteristics: SiO (based on the total weight of mechanochemically carboxylated fly ash) ２ The content is in the range of 30 to 50% by weight; Al (based on the total weight of mechanochemically carboxylated fly ash) ２ O ３ The content is in the range of 10 to 20% by weight; Fe (based on the total weight of mechanochemically carboxylated fly ash) ２ O ３ The content is in the range of 10 to 40% by weight.

3. 3. The mechanochemically carboxylated fly ash of claim 1 or 2, which satisfies one, two, three or all of the following characteristics: - D10 value is in the range of 0.005 to 5 μm; - D50 value is in the range of 1 to 25 μm; - D90 value is in the range of 30-50 μm; The value of D(4:3) is within the range of 1 to 100 μm.

4. A method for producing the mechanochemically carboxylated fly ash according to any one of claims 1 to 3, comprising the steps of: a) providing a solid feedstock comprising or consisting of fly ash, said solid feedstock having a BET surface area of ​​0.01 m ２ / g and a D50 value in the range of 0.1 to 5000 μm; b) CO ２ providing an oxidizing gas comprising: c) feeding the solid source material and the oxidizing gas into a mechanical stirring device; and d) placing the solid raw material in the mechanical stirring device and subjecting it to a mechanical stirring operation in the presence of the oxidizing gas at an oxidizing gas pressure of more than 1 atm to obtain a mechanochemically carboxylated fly ash, wherein the mechanical stirring operation includes grinding or milling.

5. The solid raw material, SiO ２ , Al ２ O ３ and Fe ２ O ３ The method according to claim 4, wherein the total content of the solid raw materials is more than 60% by weight (based on the total weight of the solid raw materials).

6. 6. The method of claim 4 or 5, wherein the solid feedstock comprises or consists of fly ash meeting the requirements of ASTM C618.

7. The method according to any one of claims 4 to 6, wherein the oxidizing gas provided in step (b) comprises more than 90 mol% CO2.

8. Step (d) carried out at pressures above 3 atm; carried out at a temperature below 100°C; and / or It will last at least an hour, The method according to any one of claims 4 to 7.

9. 9. The process of claim 8, wherein step (d) is carried out for at least 1 hour.

10. 9. The process of claim 8, wherein step (d) is carried out for at least 8 hours.

11. A composition comprising the mechanochemically carboxylated fly ash of any one of claims 1 to 3 and one additional material selected from the group consisting of asphalt, cement, and combinations thereof.

12. 12. The composition of claim 11, wherein the weight:weight ratio of the mechanochemically carboxylated fly ash to the additional material is in the range of 1:9 to 2:

1.

13. A concrete obtained by a method for producing concrete comprising the following steps: (i) providing a composition according to claim 11 or 12, wherein the further material is asphalt or concrete; (ii) preparing construction aggregate; (iii) mixing said composition of step (i) with said construction aggregate of step (ii) and water.

14. Use of the mechanochemically carboxylated fly ash according to any one of claims 1 to 3, Use as a filler; Use as a partial replacement for asphalt or cement in concrete; Use to increase the compressive strength of concrete; Use to improve the durability of concrete; or Use to improve the durability of concrete by reducing chloride permeability and / or porosity.

Images