Patent Description:
Concrete is a composite material, comprising a matrix of aggregate (typically a rocky material) and a binder (typically Portland cement or asphalt), which holds the matrix together. Concrete is one of the most frequently used building materials and is said to be the second most widely used material on earth, after water.

In order to reduce the cost of concrete and the CO<NUM> emissions generated by global cement production, much research effort has been dedicated to identifying cheap material which can be used as a filler or alternative binder to replace the binder component without (detrimentally) affecting the properties of concrete. Such secondary cementitious materials are an area of broad industry interest.

An example of a widely employed cement filler is limestone. A comprehensive overview of fillers in cementitious materials can be found in <NPL>.

The production of Portland cement contributes to about <NUM>% of world carbon dioxide emissions. According to Vanderley et al. the traditional mitigation strategies for CO<NUM> emissions in the cement industry are not sufficient to ensure the necessary mitigation in a scenario of increasing cement demand. Currently, cement production is increasing due to a combination of increasing urbanization and replacement of old infrastructure. Therefore, the adoption of expensive and environmentally risky carbon capture and storage (CCS) has been considered an unavoidable solution by cement industry leaders.

Hence, there remains a need to develop affordable filler technology which can combine both the CO<NUM> emission reduction achieved by reduced cement production and the CO<NUM> emission reduction achieved by carbon capture technology and which does not detrimentally affect the properties of concrete.

<CIT> describes reduction of CO<NUM> emission of concrete by partly replacing cement with a supplementary cementitious material comprising a calcined clay and a ground carbonate material.

It is an object of the present invention to provide improved fillers for cement, geopolymer or asphalt binder.

It is a further object of the present invention to provide improved fillers for cement, geopolymer or asphalt binder which are cheap to produce.

It is a further object of the present invention to provide improved fillers for cement, geopolymer or asphalt binder which are produced using CO<NUM> capture technology.

It is a further object of the present invention to provide improved fillers for cement, geopolymer or asphalt binder which improve the properties of the resulting concrete, such as the compressive strength, the strength activity index and/or the water demand.

In a first aspect the present invention provides a mechanochemically carbonated clay which has a specific surface area of less than <NUM><NUM>/g.

In another aspect, the invention provides a method for producing a mechanochemically carbonated clay, said method comprising the steps of:.

This method can be applied to various types of clay precursors, advantageously resulting in unique mechanochemically carbonated clay.

In another aspect, the invention provides a mechanochemically carbonated clay obtainable by the method for producing the mechanochemically carbonated clay described herein.

As will be shown in the appended examples, it was found that when such mechanochemically carbonated clays described herein are used as a filler in cement the compressive strength of the resulting concrete is surprisingly increased beyond the values obtained for non-carbonated clay and in particular well beyond the values of pure Portland cement. In particular, the set time for the strength development is strongly improved (shortened) compared to when non-mechanochemically carbonated clay is used as a filler. Furthermore, a much higher amount of this mechanochemically carbonated clay can be used as a filler while still resulting in acceptable or even improved concrete properties.

It was furthermore found that the durability of the concrete produced using said mechanochemically carbonated clay is considerably increased. Without wishing to be bound by any theory, the present inventors believe that this is due to enhanced micro and sub-microscale hydration, a reduced chloride permeability, reduced porosity of the concrete and/or passivation of free lime. Moreover, the increased oxygen content as compared to untreated precursors or feedstock may result in better dispersion in polar solvents, and better compatibility with materials that have epoxy or carboxyl functional groups.

Furthermore, as is shown in the appended examples, the water demand is decreased compared to pure cement, as well as compared to cement filled with non-carbonated clay. This is particularly surprising in view of the reduced particle size of the mechanochemically carbonated clay compared to the non-carbonated clay. A reduced particle size is generally associated with an increased water demand. The reduced water demand as compared to untreated feedstocks or pure cement may contribute to improved properties such as workability, compressive strength, permeability, watertightness, durability, weathering resistance, drying shrinkage and potential for cracking. For these reasons, limiting and controlling the amount of water in concrete is important for both constructability and service life. Thus, the present invention allows to have better control over the water demand. Without wishing to be bound by any theory, it is believed that the mechanochemical process of the invention may result in an increase in amorphous content when analyzed by XRD wherein at least some crystalline domains which may be present in a feedstock are maintained via an internal architecture in the form of microcrystallinity, which persists in a more generalized disordered structure. This disordered macro structure, thus, promotes higher reactivity and improves cement hydration.

Additionally, the production of the mechanochemically carbonated clay relies on a cheap CO<NUM> capture technology platform capable of operating on dilute CO<NUM> streams, such as directly on a point source emissions of a combustion plant, such that a filler is provided which can be produced in an economically viable manner and which combines both the CO<NUM> emission reduction achieved by reduced cement production and the CO<NUM> emission reduction achieved by CO<NUM> sequestration. Thus, the mechanochemically carbonated clay of the present invention, in particular the mechanochemically carbonated clay of the invention, constitutes an excellent filler for many applications, combining distinct mechanical properties with a cost-efficient CO<NUM> capture technology.

In another aspect, the invention provides a composition comprising a mechanochemically carbonated clay as described herein and a further material selected from the group consisting of asphalt, geopolymers, cement, polymers and combinations thereof.

In another aspect, the invention provides a method for preparing a composition as described herein, said method comprising the following steps:.

In another aspect, the invention provides a method for preparing concrete or mortar, said method comprising the following steps:.

In another aspect, the invention provides concrete or mortar obtainable by a method for preparing concrete described herein.

In another aspect the invention provides the use of a mechanochemically carbonated clay as described herein:.

The expression "comprise" and variations thereof, such as, "comprises" and "comprising" as used herein should be construed in an open, inclusive sense, meaning that the embodiment described includes the recited features, but that it does not exclude the presence of other features, as long as they do not render the embodiment unworkable.

The expressions "one embodiment", "a particular embodiment", "an embodiment" etc. as used herein should be construed to mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such expressions in various places throughout this specification do not necessarily all refer to the same embodiment. For example, certain features of the disclosure which are described herein in the context of separate embodiments are also explicitly envisaged in combination in a single embodiment.

The singular forms "a," "an," and "the" as used herein should be construed to include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its broadest sense, that is as meaning "and/or" unless the content clearly dictates otherwise.

Whenever reference is made throughout this document to a compound which is a salt, this should be construed to include the anhydrous form as well as any solvates (in particular hydrates) of this compound.

The terms "clay precursor" and "clay" as used herein should be construed as a solid material comprising at least <NUM> wt. % of hydrous aluminium phyllosilicates, preferably at least <NUM> wt. % of hydrous aluminium phyllosilicates, more preferably at least <NUM> wt. % of hydrous aluminium phyllosilicates. The hydrous aluminium phyllosilicates are preferably selected from the kaolin group, the smectite group, the vermiculite group, or mixtures thereof. The clay may be calcined or non-calcined.

The term "mechanochemically carbonated clay" is used herein to refer to a clay obtainable by the mechanochemical carbonation method of the present invention.

In accordance with the invention, the BET surface area as referred to herein is determined at a temperature of <NUM> using a sample mass of <NUM>-<NUM>. The BET surface area as referred to herein is determined using nitrogen. A preferred analysis method to determine the BET surface area comprises heating samples to <NUM> for a desorption cycle prior to surface area analysis. A suitable and thus preferred analysis apparatus for determining the BET surface area is a Micromeritics Gemini VII <NUM> Surface Analyzer preferably equipped with a Micromeritics FlowPrep <NUM> flowing-gas degassing unit.

TGA as used herein refers to Thermogravimetric Analysis, a technique known to the person skilled in the art. A preferred TGA setup to determine the CO<NUM> content of the feedstocks and carbonated materials in the context of the present invention is a Setaram TAG <NUM> TGA/DSC dual chamber balance employing a <NUM>-<NUM> sample. In accordance with the invention, the TGA is performed under an inert atmosphere, such as nitrogen or argon.

In accordance with the invention, the particle size distribution characteristics referred to herein such as D10, D50 and D90 as well as the specific surface area (unless explicitly mentioned to be BET surface area) are determined by measuring with a laser light scattering particle size analyzer utilizing the Fraunhofer theory of light scattering, such as the Brookhaven laser particle sizer, Model Microbrook 2000LD or another instrument of equal or better sensitivity and reporting the data using a volume equivalent sphere model. As is known to the skilled person, the D50 is the mass median diameter, i.e. the diameter at which <NUM>% of a sample's mass is comprised of smaller particles. Similarly, the D10 and D90 represent the diameter at which <NUM> or <NUM>% of a sample's mass is comprised of smaller particles.

The Total Carbon (TC) content referred to herein is preferably determined in accordance with the method described on <NPL> and further, incorporated herein by reference. The Total Carbon (TC) content is always expressed herein as wt. % based on the total weight of the composition being measured, i.e. based on the total weight of the clay precursor, or based on the total weight of the carbonated clay.

In accordance with the invention, the compressive strength, strength-activity index and water demand as referred to herein is determined in accordance with ASTM C311/C311 M-<NUM>. As will be evident to the skilled person, in performing these tests, the clay precursor or the carbonated clay of the present invention was used instead of the "fly ash or natural pozzolan" specified by the standard.

For the purposes of the present disclosure, ideal gas law is assumed such that the vol% of a gas is considered as equal to the mol%.

In a first aspect the invention provides a mechanochemically carbonated clays which has a specific surface area of less than <NUM><NUM>/g. The mechanochemically carbonated clay preferably has a CO<NUM> content of more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), preferably more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), more preferably more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), wherein the CO<NUM> content is determined as the mass loss above <NUM> measured by TGA employing a temperature trajectory wherein the temperature was increased from room temperature to <NUM> at a rate of <NUM>/min.

In preferred embodiments the mechanochemically carbonated clay meets the strength requirements set out in ASTM C618-12a (<NUM>).

In preferred embodiments of the invention, the mechanochemically carbonated clay has a specific surface area of at least <NUM><NUM>/g, preferably at least <NUM><NUM>/g, more preferably at least <NUM><NUM>/g.

In preferred embodiments of the invention, the mechanochemically carbonated clay has a specific surface area of less than <NUM><NUM>/g, preferably less than <NUM><NUM>/g, more preferably less than <NUM><NUM>/g. For example, the mechanochemically carbonated clay has a specific surface area of at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, etc..

In highly preferred embodiments of the invention, the mechanochemically carbonated clay has a specific surface area of less than <NUM><NUM>/g, preferably less than <NUM><NUM>/g, more preferably less than <NUM><NUM>/g. For example, the mechanochemically carbonated clay has a specific surface area of less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, etc..

The inventors have observed that a mechanochemically carbonated clay having a specific surface area within the ranges specified herein have particular properties when considering performance, handling, etc. in comparison to untreated precursors or even carbonated materials with other surface areas. Hence, in accordance with highly preferred embodiments of the invention, the mechanochemically carbonated clay has a specific surface area in a region defined according to the upper and lower bounds described herein, such as a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g.

In embodiments of the invention, the mechanochemically carbonated clay has one, two, or three, preferably three, of the following characteristics:.

In embodiments of the invention, the mechanochemically carbonated clay has a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. The inventors have observed that a mechanochemically carbonated clay having a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, provided even better results. Hence, in preferred embodiments, mechanochemically carbonated clay has a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, provided even better results.

Without wishing to be bound by any theory, the present inventors believe that the specific surface area increase effected by the dry mechanochemical carbonation method of another aspect of the invention (which is described herein elsewhere) is associated with the beneficial properties observed (such as the excellent strength activity index, and reduced water demand). Hence, in embodiments of the invention, the mechanochemically carbonated clay described herein is provided which is obtainable by concomitant carbonation and specific surface area increase of a clay precursor wherein the ratio of the specific surface area of the mechanochemically carbonated clay to the specific surface area of the clay precursor is at least <NUM>:<NUM>, preferably at least <NUM>:<NUM>, more preferably at least <NUM>:<NUM>.

Without wishing to be bound by any theory, the present inventors believe that the BET surface area increase effected by the dry mechanochemical carbonation method of another aspect of the invention (which is described herein elsewhere) is associated with the beneficial properties observed (such as the excellent strength activity index, and reduced water demand). Hence, in embodiments of the invention, the mechanochemically carbonated clay described herein is provided which is obtainable by concomitant carbonation and BET surface area increase of a clay precursor wherein the ratio of the BET surface area of the mechanochemically carbonated clay to the BET surface area of the clay precursor is at least <NUM>:<NUM>, preferably at least <NUM>:<NUM>, more preferably at least <NUM>:<NUM>.

Without wishing to be bound by any theory, the present inventors believe that the BET surface area increase effected by the dry mechanochemical carbonation method of another aspect of the invention (which is described herein elsewhere) may largely be attributed to an increase in the number of pores, observed by a decrease in the average pore width and an increase in the total pore surface area. Hence, in embodiments of the invention, the mechanochemically carbonated clay is provided which is obtainable by concomitant carbonation and BET surface area increase of a clay precursor wherein the BJH desorption cumulative surface area of pores of the mechanochemically carbonated clay is at least <NUM>%, preferably at least <NUM>%, more preferably at least <NUM>%, of the BJH desorption cumulative surface area of pores of the clay precursor and the desorption average pore width (4V/A by BET) of the mechanochemically carbonated clay is no more than <NUM>%, preferably no more than <NUM>%, more preferably no more than <NUM>%, of the desorption average pore width (4V/A by BET) of the clay precursor.

In accordance with the invention, the mechanochemically carbonated clay typically has a strength activity index (SAI) at day <NUM> which is at least <NUM>%, preferably at least <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having excellent day <NUM> SAI. Hence, in preferred embodiments the mechanochemically carbonated clay has a SAI at day <NUM> of at least <NUM>%, preferably at least <NUM>%, even more preferably at least <NUM>%.

In embodiments of the invention, the mechanochemically carbonated clay has a strength activity index (SAI) at day <NUM> which is at least <NUM>%, preferably at least <NUM>%, more preferably at least <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having excellent day <NUM> SAI. Hence, in preferred embodiments the mechanochemically carbonated clay has a SAI at day <NUM> of at least <NUM>%, preferably at least <NUM>%, even more preferably at least <NUM>%.

In embodiments of the invention, the mechanochemically carbonated clay has a water demand which is less than <NUM>%, preferably less than <NUM>%, more preferably less than <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having an extremely low water demand. Hence, in preferred embodiments the mechanochemically carbonated clay has a water demand which is less than <NUM>%, preferably less than <NUM>%.

Without wishing to be bound by any theory, the present inventors believe that the dry mechanochemical carbonation method of the present invention imparts unique and desirable properties to the carbonated clay obtainable by this method. For example, it is believed that the unique surface area and pore properties effected by the dry mechanochemical carbonation method of the present invention is important to achieve the surprising performance of the materials in e.g. concrete.

In a further aspect, the invention provides a method for producing a mechanochemically carbonated clay, said method comprising the following steps:.

The term "feedstock" is to be interpreted as a material consisting of or comprising a clay precursor. The clay may be mixed with other materials to form the feedstock (e.g. as is the case when shale is used as a feedstock) or it may consist essentially of clay. The term "precursor" is used to designate the clay before it is submitted to the mechanochemical carbonation of the invention. However, preferably, the feedstock consists essentially of a clay precursor as this allows optimisation of process conditions to achieve the desired carbonated clay properties without having to take into account the properties of other materials present in the feedstock.

It is within the capacity of one skilled in the art, in light of the guidance provided in the present disclosure, to adapt the relevant process parameters such that a mechanochemically carbonated clay is obtained which has the properties recited herein.

The gas provided in step (b) may be any gas stream comprising CO<NUM>, such as regular air, a waste gas stream having a low CO<NUM> concentration, or concentrated CO<NUM> streams.

In embodiments of the method described herein the gas provided in step (b) is regular air.

In highly preferred embodiments of the method described herein the gas provided in step (b) is a combustion flue gas, in particular a flue gas from fossil fuel combustion, wood pellet combustion, biomass combustion or municipal waste combustion. Fossil fuel combustion may be coal, petroleum coke, petroleum, natural gas, shale oil, bitumens, tar sand oil, or heavy oils combustion, or any combination thereof. The combustion flue gas may optionally have been treated to reduce the water content, the SO<NUM> content, and/or the NOx content.

The CO<NUM> concentration in the gas provided in step (b) is preferably at least <NUM> vol%, more preferably at least <NUM> vol%. Typical CO<NUM> concentrations for combustion flue gas are in the range of <NUM>-<NUM> vol%, such as <NUM>-<NUM> vol%, such that it is preferred that the gas provided in step (b) has a CO<NUM> concentration in the range of <NUM>-<NUM> vol%, such as <NUM>-<NUM> vol%. In alternative embodiments of the invention, the gas provided in step (b) comprises at least <NUM> vol% CO<NUM>, preferably at least <NUM> vol% CO<NUM>. In some embodiments of the invention, the gas provided in step (b) comprises at least <NUM> vol% CO<NUM>, preferably at least <NUM> vol% CO<NUM> and less than <NUM> ppm (v/v) H<NUM>O, preferably less than <NUM> ppm (v/v) H<NUM>O. In some embodiments, the gas provided in step (b) comprises CO<NUM> in at least <NUM> vol% and H<NUM>O in the range of <NUM>-<NUM> vol%. For example, in case of flue gas, the gas provided in step (b) preferably comprises CO<NUM> in the range of <NUM>-<NUM> vol%, such as <NUM>-<NUM> vol% and H<NUM>O in the range of <NUM>-<NUM> vol%, such as <NUM>-<NUM> vol%. The gas is typically not in a supercritical state as this is not necessary for the mild mechanochemical carbonation process of the present invention. Hence in any embodiment of the invention, it is highly preferred that the gas is not in a supercritical state.

In some embodiments of the invention, the method described herein is provided with the provision that the temperature and pressure during step (d) are such that the pressure is lower than the saturated vapour pressure of water at the temperature in the mechanical agitation unit.

The expression "in the presence of said gas" in step (d) should be construed to mean that the atmosphere inside the mechanical agitation unit consists essentially of the gas provided in step (b) when step (d) is initiated. It will be understood by the skilled person that the composition of the gas will change as the reaction progresses unless the reactor (the mechanical agitation unit) is continuously purged or replenished.

In general, step (d) can be performed at atmospheric pressure, below atmospheric pressure or above atmospheric pressure. In general it is preferred that step (d) is performed at or above atmospheric pressure. Hence, it is preferred that step (d) is performed at a pressure of at least about <NUM> kPa (e.g. at least <NUM> kPa). In preferred embodiments of the invention, step (d) is performed at a pressure of more than around <NUM> kPa (e.g., <NUM> kPa), preferably more than around <NUM> kPa (e.g., <NUM> kPa). In alternative embodiments of the invention, step (d) is performed at pressures of less than around <NUM> kPa (e.g. at least <NUM> kPa), such as less than <NUM> kPa or less than <NUM> kPa. It will be understood by the skilled person that (if not actively maintained) the pressure of the gas will change as the reaction progresses. In these embodiments it should be understood that the pressure inside the mechanical agitation unit is as specified herein when step (d) is initiated. In some embodiments the pressure inside the mechanical agitation unit is as specified herein throughout step (d).

In highly preferred embodiments of the method described herein, in order to stimulate carbonation, step (d) is performed at a temperature of less than <NUM>, preferably less than <NUM>, preferably less than <NUM>, more preferably less than <NUM>, most preferably less than <NUM>. In highly preferred embodiments of the invention, step (d) is performed at a temperature within the range of <NUM>-<NUM>, preferably <NUM>-<NUM>. In preferred embodiments of the invention, no active heating is applied and any increase in temperature is attributed to friction resulting from the mechanical agitation or to exothermic reactions taking place during the mechanochemical carbonation. The temperature is preferably determined on the solid material in the reactor (i.e. the mechanical agitation unit) during processing.

The low temperature requirement of the present process means that no fossil fuels are required, and electric heating means (or low caloric value green fuel sources) can realistically be used to supply heat in case friction caused by the mechanical agitation is insufficient to reach the desired temperature, such as more than <NUM>. In this way, fossil fuels can be avoided throughout the whole production chain.

As with any chemical process, the appropriate reaction time is highly dependent on the extent of carbonation desired, the surface area desired, as well as the pressure, temperature and mechanochemical agitation applied and can easily be determined by sampling material on a regular basis and monitoring reaction progress e.g. via BET analysis, particle size analysis and Total Carbon determination as explained herein.

The present inventors have furthermore found that the mechanochemical carbonation methods described herein may advantageously be performed without employing additional oxidizing agents such as acids. Hence, the mechanochemical carbonation methods described herein are preferably performed without employing a strong acid, preferably without employing any further oxidizing agent other than the gas provided in step (b).

In preferred embodiments of the invention, the mechanical agitation operation of step (d) comprises grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication, preferably grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), or ultrasonication. The present inventors have found that the mechanochemical carbonation process is facilitated if the mechanochemical agitation operation of step (d) the mechanochemical agitation operation of step (d) is performed in the presence of grinding or milling media, preferably balls or beads. A preferred material is stainless steel or aluminium oxide. In such highly preferred embodiments of the invention, the mechanical agitation operation may be simply rotating the mechanical agitation unit containing the solid feedstock, the grinding or milling media, and the gas. For example, grinding or milling media can be made from steel (e.g. AISI H13, modified H10), chrome white cast irons (e.g. ASTM A532), molybdenum steel (e.g. AISI M2, M4, M-<NUM>), chromium-based steels (e.g. H11, H12, H13 CPM V9, ZDP-<NUM>) or other media with a target HRC hardness of <NUM>. Such grinding media can be utilized with or without surface treatments such as nitriding and carburizing. This can conveniently be performed in a rotating drum. It will be understood that the product obtainable by the process of the invention when performed in a rotating drum, may also be obtainable using alternative grinding or milling techniques known to the skilled person.

In preferred embodiments of the invention, step (d) is performed in the presence of a catalyst, preferably a metal oxide catalyst, such as a transition metal oxide catalyst. Examples of suitable catalysts are selected from the group consisting of iron oxides, cobalt oxides, ruthenium oxides, titanium oxides, nickel oxides, aluminium oxides and combinations thereof.

Hence, as will be understood from the above, in highly preferred embodiments of the invention, step (d) comprises grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), shaking, blending, pulverizing, powderizing, crushing, crumbling, a fluidized bed or ultrasonication, preferably grinding, milling, mixing, stirring (such as low-speed stirring or high-speed stirring), shearing (such as high-torque shearing), or ultrasonication, in the presence of grinding or milling media and a metal oxide catalyst.

The present inventors have found that it is advantageous with a view to the efficiency of the mechanochemical carbonation (e.g. reaction time, CO<NUM> absorption and particle size reduction) to employ media as described herein before coated with said metal oxide catalyst and/or to employ a mechanical agitation unit (or parts thereof) which are coated with said metal oxide catalyst. As explained herein elsewhere, the mechanical agitation operation may be simply rotating the mechanical agitation unit containing the feedstock or the clay precursor for mechanochemical carbonation, the grinding or milling media, the metal oxide catalyst and the gas. This can conveniently be performed in a rotating drum.

As will be clear from the present description, step (d) is a substantially dry process. While some moisture may be present, step (d) is not performed on an aqueous solution or slurry. The present inventors have found that this greatly improves energy efficiency (as no water has to be removed afterwards) and imparts unique properties on the resulting mechanochemically carbonated clays, yielding materials which are substantially different from e.g. aqueous carbonation materials. This is also reflected in their distinct properties, e.g. when used as a filler in concrete. In embodiments of the invention, the solid feedstock preferably has a moisture content of less than <NUM> wt. % (by total weight of the solid feedstock), preferably less than <NUM> wt.

In particular, the present inventors have found that it is important that step (d) is carried out such that certain extents of carbonation, size reduction and/or surface area increase are effect during step (d), i.e. during the combined carbonation and mechanical agitation. This results in markedly different materials from materials which were e.g. milled and subsequently carbonated.

Thus, in highly preferred embodiments of the invention, the method of the invention is provided wherein carbonation, size reduction and/or surface area increase are effected during step (d) such that the method has one, two, or all three, preferably all three, of the following characteristics.

As is shown in the examples, certain materials have additional improved strength and/or water demand characteristics. Hence, in some particularly preferred embodiments of the invention, the method of the invention is provided wherein carbonation, size reduction and/or surface area increase are effected during step (d) such that the method has one, two, or all three, preferably all three, of the following characteristics.

The inventors have observed that the method of the invention is preferably provided wherein carbonation is effected during step (d) such that the ratio of the total carbon content of the mechanochemically carbonated clay obtained in step (d) to the total carbon content of the clay precursor of step (a) is at least <NUM>:<NUM>, more preferably at least <NUM>:<NUM>. The inventors have observed that methods wherein said ratio is at least <NUM>:<NUM>, preferably at least <NUM>:<NUM>, more preferably at least <NUM>:<NUM>, provided even better results such that these are preferred.

Without wishing to be bound by any theory, the present inventors believe that the BET surface area increase effected by the dry mechanochemical carbonation method is associated with the beneficial properties observed (such as the excellent strength activity index, and reduced water demand). Hence, in highly preferred embodiments of the invention, the method of the invention is provided wherein carbonation and BET surface area increase are effected during step (d) such that the ratio of the BET surface area of the mechanochemically carbonated clay to the BET surface area of the clay precursor is at least <NUM>:<NUM>, preferably at least <NUM>:<NUM>, more preferably at least <NUM>:<NUM>.

The skilled person will understand that, as the material of step (a) is fed to step (d), this means that the carbonation, size reduction and/or surface area specified above is effected during step (d).

In particularly preferred embodiments of the method of the invention, the BJH desorption cumulative surface area of pores of the mechanochemically carbonated clay obtained in step (d) is at least <NUM>%, preferably at least <NUM>%, more preferably at least <NUM>%, of the BJH desorption cumulative surface area of pores of the clay precursor and the desorption average pore width (4V/A by BET) of the mechanochemically carbonated clay obtained in step (d) is no more than <NUM>%, preferably no more than <NUM>%, more preferably no more than <NUM>%, of the desorption average pore width (4V/A by BET) of the clay precursor.

In preferred embodiments of the method described herein, the clay precursor is a particulate solid material which has a specific surface area of less than <NUM><NUM>/g, preferably less than <NUM><NUM>/g, more preferably less than <NUM><NUM>/g.

In highly preferred embodiments of the invention, the clay precursor has one, two, or three, preferably three, of the following characteristics:.

In preferred embodiments of the method for producing a carbonated clay described herein, the carbonated clay obtained in step (d) a specific surface area of less than <NUM><NUM>/g. The mechanochemically carbonated clay obtained in step (d) preferably has a CO<NUM> content of more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), preferably more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), more preferably more than <NUM> wt. % (by total weight of the mechanochemically carbonated clay), wherein the CO<NUM> content is determined as the mass loss above <NUM> measured by TGA employing a temperature trajectory wherein the temperature was increased from room temperature to <NUM> at a rate of <NUM>/min.

In preferred embodiments the mechanochemically carbonated clay obtained in step (d) meets the strength requirements set out in ASTM C618-12a (<NUM>).

In preferred embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a specifoc surface area of at least <NUM><NUM>/g, preferably at least <NUM><NUM>/g, more preferably at least <NUM><NUM>/g.

In preferred embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a specific surface area of less than <NUM><NUM>/g, preferably less than <NUM><NUM>/g, more preferably less than <NUM><NUM>/g. For example, the mechanochemically carbonated clay obtained in step (d) has a specific surface area of at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, at most <NUM><NUM>/g, etc..

In highly preferred embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a specific surface area of less than <NUM><NUM>/g, preferably less than <NUM><NUM>/g, more preferably less than <NUM><NUM>/g. For example, the mechanochemically carbonated clay has a specific surface area of less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, less than <NUM><NUM>/g, etc..

The inventors have observed that a mechanochemically carbonated clay having a specific surface area within the ranges specified herein have particular properties when considering performance, handling, etc. in comparison to untreated precursors or even carbonated materials with other surface areas. Hence, in accordance with highly preferred embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a specific surface area in a region defined according to the upper and lower bounds described herein, such as a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g; a specific surface area in the range of <NUM>-<NUM><NUM>/g, preferably <NUM>-<NUM><NUM>/g, more preferably <NUM>-<NUM><NUM>/g.

In embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has one, two, or three, preferably three, of the following characteristics:.

In embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. The inventors have observed that a mechanochemically carbonated clay having a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, provided even better results. Hence, in preferred embodiments, mechanochemically carbonated clay obtained in step (d) has a total carbon content of at least <NUM> wt. %, preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, provided even better results.

In accordance with the invention, the mechanochemically carbonated clay obtained in step (d) typically has a strength activity index (SAI) at day <NUM> which is at least <NUM>%, preferably at least <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having excellent day <NUM> SAI. Hence, in preferred embodiments the mechanochemically carbonated clay obtained in step (d) has a SAI at day <NUM> of at least <NUM>%, preferably at least <NUM>%, even more preferably at least <NUM>%.

In embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a strength activity index (SAI) at day <NUM> which is at least <NUM>%, preferably at least <NUM>%, more preferably at least <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having excellent day <NUM> SAI. Hence, in preferred embodiments the mechanochemically carbonated clay obtained in step (d) has a SAI at day <NUM> of at least <NUM>%, preferably at least <NUM>%, even more preferably at least <NUM>%.

In embodiments of the invention, the mechanochemically carbonated clay obtained in step (d) has a water demand which is less than <NUM>%, preferably less than <NUM>%, more preferably less than <NUM>%. The inventors have observed that the mechanochemical process of the present invention allows obtaining carbonated clay having an extremely low water demand. Hence, in preferred embodiments the mechanochemically carbonated clay obtained in step (d) has a water demand which is less than <NUM>%, preferably less than <NUM>%.

The present inventors have found that the mechanochemical carbonation described herein imparts unique properties on the resulting mechanochemically carbonated clays, yielding materials which are substantially different from e.g. aqueous carbonation materials. This is also reflected in their distinct properties, e.g. when used as a filler in concrete. In particular, the present inventors have found that it is important that step (d) is carried out such that certain extents of carbonation, size reduction and/or surface area increase are effect during step (d), i.e. during the combined carbonation and mechanical agitation. This results in markedly different materials from materials which were e.g. carbonated in an aqueous environment, or even materials which were milled and subsequently carbonated.

Hence, in another aspect the invention provides the mechanochemically carbonated clay obtainable by the method for producing mechanochemically carbonated clay described herein.

As will be understood by the skilled person in light of the present disclosure, the mechanochemically carbonated clay of the present invention constitutes an excellent filler for many applications, combining distinct mechanical properties with a cost-efficient CO<NUM> sequestration approach.

Hence, in another aspect the invention provides a composition comprising a mechanochemically carbonated clay as described herein and a further material selected from the group consisting of asphalt, cement, geopolymers, polymers, and combinations thereof, preferably cement, more preferably Portland cement.

In embodiments of the invention, the further material is a polymer selected from thermoplastic polymers and thermosetting polymers. In preferred embodiments of the invention, the further component is a polymer selected from the group consisting of epoxide resin, phenol-formaldehyde resin, polyalkylene terephthalate (preferably polyethylene terephthalate), polalkylene adipate terephthalate (preferably polybutylene adipate terephthalate), polyalkylene isosorbide terephthalate (preferably polyethylene isosorbide terephthalate), polyalkylene aromatic polyamide (preferably polyethylene aromatic polyamide), polyacrylonitrile, polyacetal, polyimide, aromatic polyester, polyisoprene (preferably cis-<NUM>,<NUM>-polyisoprene), polyethylene, polypropylene, polyurethane, polyisocyanurate, polyamide, polyether, polyester, polyhydroxyalkanoate, polylactic acid, poly lactic-co-glycolic acid, polyvinylidene fluoride, polyvinyl acetate, polyvinyl chloride, polystyrene, polytetrafluoroethylene, acrylonitrile-butadiene-styrene, nitrile rubber, styrenebutadiene, ethylene-vinyl acetate, copolymers thereof and combinations thereof, more preferably a polyolefin, such as polypropylene, polyethylene, copolymers thereof and combinations thereof. The term "polymer" as used herein includes copolymers, such as block copolymers.

In highly preferred embodiments the further material is selected from cement, asphalt, geopolymers or combinations thereof.

In accordance with the invention, the cement may be a hydraulic or non-hydraulic cement. In preferred embodiments of the invention, the cement is a hydraulic cement, such as Portland cement. In highly preferred embodiments of the invention, the cement is one of the cements defined in EN197-<NUM> (<NUM>), preferably Portland cement as defined in EN197-<NUM> (<NUM>).

In embodiments of the invention, the composition comprises at least <NUM> wt. % (by total weight of the composition), preferably at least <NUM> wt. %, more preferably more than <NUM> wt. % of the mechanochemically carbonated clay and/or at least <NUM> wt. % (by total weight of the composition), preferably more than <NUM> wt. %, more preferably more than <NUM> wt. % of the further material.

In embodiments of the invention, the composition comprises less than <NUM> wt. % (by total weight of the composition), preferably less than <NUM> wt. %, more preferably less than <NUM> wt. % of the mechanochemically carbonated clay and/or less than <NUM> wt. % (by total weight of the composition), preferably less than <NUM> wt. %, more preferably less than <NUM> wt. % of the further material.

In embodiments of the invention, the composition is provided wherein the weight:weight ratio of the mechanochemically carbonated clay to the further material is within the range of <NUM>:<NUM> to <NUM>:<NUM>, preferably within the range of <NUM>:<NUM> to <NUM>:<NUM>, more preferably within the range of <NUM>:<NUM> to <NUM>:<NUM>.

In embodiments of the invention, the composition comprises <NUM>-<NUM> wt. % (by total weight of the composition), preferably <NUM>-<NUM> wt. %, more preferably <NUM>-<NUM> wt. % of the mechanochemically carbonated clay and <NUM>-<NUM> wt. % (by total weight of the composition), preferably <NUM>-<NUM> wt. %, preferably <NUM>-<NUM> wt. % of the further material.

In embodiments of the invention, the composition comprises less than <NUM> wt. % (by total weight of the composition water, preferably less than <NUM> wt. %, more preferably less than <NUM> wt. The amount of water can suitably be determined as the mass loss up to <NUM> measured by TGAMS employing a temperature trajectory wherein the temperature was increased from room temperature to <NUM> at a rate of <NUM>/min.

In embodiments of the invention, the composition consists of the mechanochemically carbonated clay and the further material.

In another aspect the invention provides a method for preparing a composition as described herein, said method comprising the following steps:.

Hence, in another aspect the invention provides a method for preparing concrete or mortar, said method comprising the following steps:.

In another aspect the invention provides a concrete or mortar obtainable by the method for preparing concrete as described herein.

In preferred embodiments of the invention, step (iii) further comprises contacting, preferably mixing the mechanochemically carbonated clay and the further material of step (i) with the construction aggregate of step (ii) and water. In accordance with the invention, the mechanochemically carbonated clay and the further material of step (i), the construction aggregate of step (ii) and the water may be contacted, preferably mixed at substantially the same time, or in a step-wise manner wherein the composition of step (i) is first contacted, preferably mixed with water, before being contacted, preferably mixed with the construction aggregate of step (ii).

The BET surface area (SSA), the BJH desorption cumulative surface area of pores and the desorption average pore width (4V/A by BET) were determined at a temperature of <NUM> using a sample mass of <NUM>-<NUM> wherein samples were heated to <NUM> for a desorption cycle prior to surface area analysis.

Particle Size Distribution and specific surface area measurements were carried out on a Brookhaven laser particle sizer, Model Microbrook 2000LD using utilizing the Fraunhofer theory of light scattering and reporting the data using a volume equivalent sphere model.

Compressive strength, strength activity index and water demand was measured in accordance with ASTM C311/C311M-<NUM>. As will be evident to the skilled person, in performing these tests, the clay precursor or the carbonated clay of the present invention was used instead of the "fly ash or natural pozzolan" specified by the standard.

The CO<NUM> content was determined as the mass loss above <NUM> as measured by TGA employing a temperature trajectory wherein the temperature was increased from room temperature to <NUM> at a rate of <NUM>/min. A Setaram TAG <NUM> TGA/DSC dual chamber balance employing a <NUM>-<NUM> sample under an inert nitrogen atmosphere was used.

Mechanochemically carbonated clay was produced by inserting <NUM> of clay precursor (non-calcined clay) into a pressure cell with <NUM> of first milling media (stainless steel ball bearing(s) of <NUM> size) and with <NUM> of second milling media (stainless steel ball bearing(s) of <NUM> size). The cell is pressurized with concentrated CO<NUM> gas and rotated on rollers at <NUM> RPM for <NUM> days to obtain mechanochemically carbonated clay. The clay precursor was used as received. The reaction was initiated at room temperature and no heating or cooling was applied. The properties of the clay precursor (A1) and the obtained mechanochemically carbonated clay (A2) are shown in the below table.

Mechanochemically carbonated clay was produced by inserting <NUM> of clay precursor (calcined clay, different origin from sample A) into a pressure cell with <NUM> of milling media (ceramic bearings of <NUM> size). The cell is pressurized with flue gas (CO<NUM>: <NUM>-<NUM> vol%; H<NUM>O: <NUM>-<NUM> vol%; O<NUM>: <NUM>-<NUM> vol%; N<NUM>: <NUM>-<NUM> vol%) to an initial pressure of <NUM> kPa, and rotated on rollers at <NUM> RPM for <NUM> days to obtain mechanochemically carbonated clay. The clay precursor was used as received. The reaction was initiated at room temperature and no heating or cooling was applied. The ceramic bearings have an Al<NUM>O<NUM> content of <NUM> wt. % such that they also served as catalyst. The properties of the clay precursor (B1) and the obtained mechanochemically carbonated clay (B2) are shown in the below table.

Mechanochemically carbonated clay was produced by inserting <NUM> of clay precursor (calcined clay, different origin from sample A or B) into a pressure cell with <NUM> of milling media (ceramic bearings of <NUM> size). The cell is pressurized with flue gas (CO<NUM>: <NUM>-<NUM> vol%; H<NUM>O: <NUM>-<NUM> vol%; O<NUM>: <NUM>-<NUM> vol%; N<NUM>: <NUM>-<NUM> vol%) to an initial pressure of <NUM> kPa, and rotated on rollers at <NUM> RPM for <NUM> days to obtain mechanochemically carbonated clay. The clay precursor was used as received. The reaction was initiated at room temperature and no heating or cooling was applied. The ceramic bearings have an Al<NUM>O<NUM> content of <NUM> wt. % such that they also served as catalyst. A portion of the clay precursor was subjected to regular milling to serve as a comparative example. The properties of the milled clay precursor (C1) and the obtained mechanochemically carbonated clay (C2) are shown in the below table.

Mechanochemically carbonated clay was produced by inserting <NUM> of clay precursor (non-calcined clay, same origin from sample C) into a pressure cell with <NUM> of milling media (ceramic bearings of <NUM> size). The cell is pressurized with flue gas (CO<NUM>: <NUM>-<NUM> vol%; H<NUM>O: <NUM>-<NUM> vol%; O<NUM>: <NUM>-<NUM> vol%; N<NUM>: <NUM>-<NUM> vol%) to an initial pressure of <NUM> kPa, and rotated on rollers at <NUM> RPM for <NUM> days to obtain mechanochemically carbonated clay. The clay precursor was used as received. The reaction was initiated at room temperature and no heating or cooling was applied. The ceramic bearings have an Al<NUM>O<NUM> content of <NUM> wt. % such that they also served as catalyst. A portion of the clay precursor was subjected to regular milling to serve as a comparative example. The properties of the milled clay precursor (D1) and the obtained mechanochemically carbonated clay (D2) are shown in the below table.

Mechanochemically carbonated clay was produced by inserting <NUM> of clay precursor (shale feedstock, non-calcined) which was pretreated by calcining (<NUM>) and conventional milling into a pressure cell with <NUM> of milling media (ceramic bearings of <NUM> size). The cell is pressurized with flue gas (CO<NUM>: <NUM>-<NUM> vol%; H<NUM>O: <NUM>-<NUM> vol%; O<NUM>: <NUM>-<NUM> vol%; N<NUM>: <NUM>-<NUM> vol%) to an initial pressure of <NUM> kPa, and rotated on rollers at <NUM> RPM for <NUM> days to obtain mechanochemically carbonated clay. The reaction was initiated at room temperature and no heating or cooling was applied. The ceramic bearings have an Al<NUM>O<NUM> content of <NUM> wt. % such that they also served as catalyst. The properties of the milled and calcined clay precursor (E1) and the obtained mechanochemically carbonated clay (E2) are shown in the below table.

For sample A, the BET surface area of the precursor and the carbonated material was determined as <NUM><NUM>/g and <NUM><NUM>/g respectively, showing that a large part of the surface area increase effected by the method of the present invention can be attributed to changes in the pore surface area.

Claim 1:
A mechanochemically carbonated clay which has a specific surface area of less than <NUM><NUM>/g and having a strength activity index, SAI, at day <NUM> determined according to ASTM C311/C311M-<NUM> which is at least <NUM>% and having a strength activity index, SAI, at day <NUM> determined according to ASTM C311/C311M-<NUM> which is at least <NUM>%.