Portland composite cement, for example cem ii / c-m, with mechano-chemically activated material, classified according to din en 197-1 as natural pozzolan

Abstract

The present invention relates to a method for producing a cement (60), wherein a clay mineral (10) is used as a first reactant, wherein the clay mineral (10) is selected from the group encompassing claystone, marl and sludge, more particularly harbour sludge, wherein a calcium carrier (20) is used as a second reactant, wherein the calcium carrier (20) is selected from the group encompassing limestone (40), marl, dolomite, carbonated recycled concrete fines, carbonated fly ash, shell lime, slags, wherein clinker (30) is used as a third reactant, wherein the first reactant and the second reactant are jointly activated mechano-chemically in a mill to form a first product (14), wherein the first reactant and the second reactant are mixed in a mass ratio of 1:10 to 30:1, wherein 10 to 80 wt.% of the first product (14) and 20 to 90 wt.% of the third reactant are added, wherein 0 to 30 wt.% of limestone (40) are added, wherein 0 to 10 wt.% of further reactants are added, the sum of all the components always being 100%, wherein the heat of hydration of the mechano-chemically activated first product (14) after 7 days as per the R3 test according to ASTM C1897-20 has a value of at least 100 J / g above that of a non-mechano-chemically activated mixture of the first reactant and the second reactant with the same composition.

Description

[0001] June 16, 2025

[0002] 1 / 15

[0003] Portland composite cement, for example CEM II / CM, with mechano-chemically activated material, which is classified as natural pozzolan according to DIN EN 197-1

[0004] The invention relates to a method for producing a Portland composite cement, for example of CEM II / CM, with mechano-chemically activated material.

[0005] Cement consists of several components, with clinker typically being the main component. Clinker is produced by burning limestone and clay or marl, a process that releases significant amounts of CO2. It is estimated that at least 5% of current human-caused carbon dioxide (CCD) emissions are attributable to the cement industry. Approximately 80% of these CCD emissions originate from the limestone itself, i.e., from the mineral-bound CO2. To reduce these emissions, cement substitutes are increasingly being used. These substitutes are made from materials such as clay and do not release this high proportion of CCD from mineral-bound CO2. Furthermore, natural pozzolans have been used as a raw material for concrete since antiquity, for example, in the construction of the Colosseum and the Pantheon in Rome. They impart excellent and durable properties to the concrete. Natural pozzolans are found, for example, in the Phlegraean Fields.The aim is therefore to produce pozzolans that are indistinguishable from naturally occurring ones (nature-identical) and can therefore be classified as natural pozzolans according to DIN standards.

[0006] Materials referred to as calcined clays can be used as cement clinker substitutes, preferably when the kaolinite content of the raw clays is at least 40 wt.%. It is known that the contribution to the strength development of cement mixtures containing calcined clays can be further increased by the addition of limestone in a ratio of approximately 2:1. Such cement mixtures are also known as LC3 cements and are further defined in DIN EN 197-5 as Portland composite cements CEM II / CM. It is assumed that the strength-enhancing contribution from the additional addition of limestone, which is usually considered inert, can be attributed to the fact that, during the hydration of the cements under these conditions, significant additional amounts of [unclear text] are produced.

[0007] 2 / 15

[0008] Carboaluminates are formed, which in turn results in an increased solubility of the aluminum silicates from the calcined clay minerals.

[0009] The mechanical activation of clays is known from DE 10 2023 106 210.

[0010] From EP 4 299 543 A1 a composite cement with a paste of recycled cement and calcined clay is known.

[0011] The object of the invention is to create a cement that results in an advantageous effect for the concrete from the synergistic effect of the components while simultaneously conserving natural resources or avoiding CCh emissions.

[0012] This problem is solved by the method with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0013] The process according to the invention serves to produce cement. Cement is typically a mixture, which must comply with various standardization requirements regarding composition and reactivity so that cements can be used interchangeably in construction according to their standards and static calculations can be carried out independently of the specific starting material. A clay mineral is used as the first feedstock for the production of the cement, in particular a Portland composite cement. This clay mineral is selected from the group comprising claystone, marl, and mud, especially harbor mud. The advantage of the first feedstock is that no or only minimal mineral-bound CO2 is released during its activation, making the cement more climate-friendly compared to pure clinker.A calcium carrier is used as the second starting material. This calcium carrier is selected from the group comprising limestone, marl, dolomite, carbonated reclaimed concrete particles, carbonated fly ash, shell limestone, and slag. All of these calcium carriers have properties comparable to limestone, which is therefore considered the reference system in the following. While it is generally known to add limestone to cement, for example, the combination with the first starting material and the subsequent [date missing] can lead to [unclear - possibly a change in the process].

[0014] 3 / 15

[0015] In addition to the effect described above, which is known from LC3 cements, the production process yields a further positive synergistic effect. Clinker is used as the third starting material. This is typically an important and usually mandatory component for standardized cement compositions. The first and second starting materials are mechanochemically activated together in a mill to form a first product. This mechanochemical activation is described, for example, in PCT / EP2024 / 056405, which summarizes what those skilled in the art know about mechanochemical activation. The third starting material, the clinker, is not mechanochemically activated, as it has already undergone thermal activation.

[0016] The mechanochemical activation of mineral materials, especially clay minerals, requires a higher energy input than that of conventional fine grinding, necessitating a mill with high energy density. Therefore, grinding and mechanochemical activation are preferably carried out with an energy input of at least 100 kW / m³ per grinding chamber volume. 3 In this process, grinding takes place without the addition of water; that is, not wet or in a slurry, but rather as dry grinding without added moisture, which distinguishes it from classic wet grinding methods. A typical value for a ball mill, as an example of a fine mill, is usually around 20 kW / m². 3and therefore significantly lower. Here, the grinding chamber volume refers to the volume available inside the first high-energy mill, i.e., the free volume when no material or grinding media are present. Components belonging to the mill, such as a shaft that is movably arranged inside, are therefore not included in the grinding chamber volume, as this volume cannot be occupied by material.

[0017] Mechanochemical activation, or the grinding process for mechanochemical activation, consists of three phases or stages: In the first stage, the particle size decreases (more or less linearly) with increasing energy input (Rittinger zone). Put simply, the more you grind, the finer the product becomes. However, there is a limit to this, a particle size that is almost impossible to reduce further. From this point onward, a second stage begins, in which the particle size cannot be changed further with additional energy input (activation and aggregation zone). (June 16, 2025)

[0018] 4 / 15 At this stage, crystallographic structures are destroyed by the breaking of atomic bonds; individual atoms or entire groups of atoms are replaced by other atoms or groups of other atoms. Particularly on the particle surfaces, the initial crystal structure, as well as the bond type and oxidation states of atoms, are altered due to high energy transfer and subsequent chemical reactions. For economic reasons, the transition from the first to the second stage, which is necessary for mechanochemical activation, is therefore avoided in normal milling, where only surface creation is expected. If the energy input is increased even further, a third stage can be reached in which, due to the agglomeration of nanoparticles, an increase in particle size can again be observed (agglomeration zone), which has a positive effect on the workability of activated clay cement concrete.This area is therefore much more likely to be avoided in conventional grinding, as a better result in terms of particle size distribution can be achieved with less effort.

[0019] However, it has been found that high energy inputs, i.e., in the second stage, lead to changes in the material itself. In the case of clays, for example, this activation, similar to thermal activation, results in a reactivity that enables their use as a binder (and thus as a clinker substitute). Therefore, subsequent thermal treatment can be omitted at such high energy inputs. At the same time, high temperatures are avoided during mechanochemical activation, which means that the water of crystallization from the first reactant is either not driven off or only driven off to a very small extent. This also has very positive effects on the concrete produced from the cement, as well as on its workability during concrete production.

[0020] However, it has been found that the energy requirement for purely mechanochemical activation can be higher than for thermal activation. Therefore, the inventive method initially appears to be at a disadvantage compared to conventional thermal activation. However, it has been shown that, despite the comparatively likely high energy requirement, particularly electrical energy requirement, the inventive method is advantageous, especially for activation. 16.06.2025

[0021] 5 / 15 of clays are difficult to activate thermally. Especially with complex starting materials like clays, thermal activation regularly leads to several negative effects. Firstly, it is known that substances can be released from clays in gaseous form at elevated temperatures, requiring more complex exhaust gas purification. This can be avoided with mechano-chemical activation by avoiding higher temperatures. Secondly, at elevated thermal activation temperatures, color-imparting components, such as iron compounds, are often oxidized, which, in the case of clays with a high iron content, leads to an undesirable red coloration of the product. To prevent this, either a protective gas atmosphere or subsequent chemical reduction is necessary, both of which are technically complex and expensive.While the energy requirement for the actual activation step of the process according to the invention may be increased, the exhaust gas treatment is simplified and a subsequent chemical reduction can be avoided. Furthermore, the thermal activation process still releases carbon dioxide originating from fossil fuels or waste fuels, as well as from the deacidification of carbonate minerals during calcination, which ultimately necessitates a carbon capture process. The process according to the invention requires only electrical energy, and it has been shown that the carbonate minerals are not decomposed in the mechano-chemical activation process but are retained as a partially amorphized and reactive material in the activated clay product. Thus, the entire activation process for producing a marketable binder can be efficiently simplified and decarbonized.

[0022] Furthermore, different clay minerals exhibit different optimal activation temperatures. For example, minerals of the kaolin and chlorite groups are activated at significantly lower temperatures than, for example, minerals of the mica group (muscovite, illite, and others). If the optimal activation temperature of kaolinite is selected for thermal activation of clays containing minerals of these groups, minerals such as muscovite and illite will not yet be activated. However, if the significantly higher activation temperature of muscovite and illite is selected for thermal activation, the formation of new thermodynamically stable mineral phases, especially spinels, leads to the overburning of the kaolinite, which is a 16.06.2025

[0023] 6 / 15

[0024] This results in deactivation. However, this differentiation of clay minerals with respect to the optimal activation temperature is not applicable to mechano-chemical activation.

[0025] The first and second reactants are mixed in a mass ratio of 1:10 to 30:1 and mechanochemically activated together. It has been shown that these two components, the activated clay mineral and the activated calcium carrier, together produce a very positive effect in the cement. This effect, based on surface and mechanochemistry, is independent of the hydration-based effect known from LC3 cements and leads to a further increase in the overall reactivity and, in particular, the early strength of the finished cements. Furthermore, the so-called water demand is significantly lower by up to 10 percentage points compared to calcined clays, which considerably reduces or even eliminates the need for so-called superplasticizers in the cement.Therefore, the combination of the two mechano-chemically activated products is advantageous for the finished overall product and its further processing in cement and concrete production.

[0026] The first product, consisting of the first and second reactants, both mechano-chemically activated, is added at a total weight of 10 to 80 wt.%, and the third reactant (clinker) is added at a weight of 20 to 90 wt.%. Additionally, 0 to 30 wt.% limestone is added. This refers to limestone that is conventionally ground but not mechano-chemically activated. Furthermore, 0 to 10 wt.% of other reactants are added, for example, sulfate carriers such as gypsum. Such additional reactants are known to those skilled in the art and are present in available cement compositions. The sum of all components always equals 100%.

[0027] According to the invention, the first and second reactants are jointly activated mechanochemically in a mill. The heat of hydration of the mechanochemically activated product mixture after 7 days according to the R3 test of ASTM C1897-20 is at least 100 J / g, preferably at least 150 J / g, above that of a non-mechanochemically activated mixture of the first and second reactants. 16.06.2025

[0028] 7 / 15 of the same composition. The standard ASTM C1897-20 is the standard commonly used in the cement industry for testing reactivity and setting behavior. The aim is therefore to ensure that this component also exhibits sufficient activity, allowing a higher proportion of clinker to be replaced, thus achieving improved early strength and saving as much CO2 as possible by reducing clinker.

[0029] In a further embodiment of the invention, a sulfate carrier, for example gypsum, is added as a further component. Gypsum is a very common sulfate carrier that is added to many cements to adjust their setting behavior.

[0030] In a further embodiment of the invention, the first product, consisting of the jointly mechano-chemically activated first reactant and second reactant, is added in a total amount of 20 to 50 wt.%.

[0031] In a further embodiment of the invention, the third reactant, clinker, is added at a rate of 50 to 64 wt.%.

[0032] In a further embodiment of the invention, the first reactant and the second reactant are mixed in a mass ratio of 1:3 to 10:1.

[0033] In a further embodiment of the invention, the first and second reactants are jointly mechanochemically activated in a mill. The heat of hydration of the mechanochemically activated product mixture after 7 days, as determined by the R3 test according to ASTM C1897-20, is at least 150 J / g higher than that of a non-mechanochemically activated mixture of the first and second reactants of the same composition. ASTM C1897-20 is the standard commonly used in the cement industry for investigating reactivity and setting behavior.

[0034] In a further embodiment of the invention, the first product has at least 50%, preferably at least 70%, particularly preferably at least 90% of the water of crystallization content based on the water of crystallization content of the non-mechano- 16.06.2025

[0035] 8 / 15 chemically activated mixture of the first reactant and the second reactant of the same composition. During thermal activation, the water of crystallization is mostly completely driven off, and in addition, the thermally activated clay material can even absorb additional water through cavities, which increases the water requirement for subsequent use in concrete production. The processing properties of the cement produced according to the inventive process are therefore significantly better, and it is even possible to dispense with additional additives in the cement, for example, and in particular, so-called superplasticizers.

[0036] In a further embodiment of the invention, the mechano-chemical activation takes place in a stirred ball mill. The stirred ball mill, which is preferably operated dry, is operated, for example, and preferably, at a peripheral speed of 2 m / s to 8 m / s. The mechano-chemical activation is carried out, for example, and preferably, with an energy input of at least 200 kW / m³ per grinding chamber volume. 3The following procedure is carried out. For example, a stirred ball mill with a length-to-diameter ratio of 2.5 to 5 is selected. The stirred ball mill is filled with a grinding media filling level of 50 vol.% to 95 vol.%, preferably 50 vol.% to 80 vol.%, and particularly preferably 60 vol.% to 70 vol.%. Here, the bulk volume of the grinding media is related to the grinding chamber volume of the stirred ball mill. Since the filling level is around 64% for a simple packing and only around 74% for a densest sphere packing, even with a theoretical grinding media filling level of 100%, a corresponding free space results, which can be occupied, for example, by the mineral material to be activated. However, since the filling level of a grinding media packing depends very much on the shape and uniformity of the grinding media, it is practically simpler to relate the grinding media filling level to the bulk volume and not to the actual (filled) volume.For example, mechano-chemical activation takes place at material temperatures of 100 °C to 250 °C. This elevated temperature is advantageous to prevent condensation of water and, if necessary, to allow further water to be removed.

[0037] In a further embodiment of the invention, the first product is classified as natural pozzolan (P) according to DIN EN 197-1. 16.06.2025

[0038] 9 / 15

[0039] In a further embodiment of the invention, the first product is at least 30%, preferably at least 40%, and particularly preferably at least 50% X-ray diffractometrically amorphous, based on the amount of clay minerals in the unactivated starting material. X-ray diffractometrically amorphous materials do not appear as discrete peaks, but rather as a strongly broadened background and can thus be quantified via the surface integral relative to the crystalline material. Such analyses are well known and established, for example, in the analysis of plastics, such as polyethylene.

[0040] In a further embodiment of the invention, the mechano-chemical activation is carried out with an energy density of at least 100 kW / m². 3 and a mill volume of at least 1000 m³. It has surprisingly turned out that a mill with an internal volume of at least 1 m³ 3exhibits a particularly efficient and therefore particularly economical use for activation. This difference in efficiency means that mills with an internal volume of less than 100 liters are economically inefficient, while those with an internal volume of more than 1 m³ are only economically viable. 3 exhibit economically viable efficiency. Surprisingly, pilot plant trials have shown that the ratio between achieved activation and energy input is highly dependent on the machine's size, thus defining a minimum machine size for economical operation. This means that, regardless of the desired throughput, a comparatively large mill must be selected.

[0041] In another aspect, the invention relates to a cement produced according to the inventive method.

[0042] The method according to the invention is explained in more detail below with reference to exemplary embodiments shown in the drawings.

[0043] Fig. 1 Example 16.06.2025

[0044] 10 / 15

[0045] Fig. 1 shows an example of combined mechanochemical activation. A clay mineral 10 and a calcium carrier 20 are mixed, for example, in a 1:1 ratio and activated in a combined mechanochemical activation 17 to form a first product 14. Additionally, limestone 40 is simply ground without being mechanochemically activated, i.e., in the typical comminution range where there is a linear relationship between particle size and applied grinding energy (Rittinger zone). The components of the first product, clinker, ground limestone, and gypsum are mixed, for example, in a ratio of 30:60:9:1 to produce the finished cement.

[0046] Application example 1:

[0047] The Strength Activity Index (SAI) according to EN 450-1 indicates the ratio (in %) of the compressive strengths of standardized mortar prisms tested at the same age, containing a mass fraction of 75% test cement and 25% fly ash, and standardized mortar prisms produced exclusively with test cement. Based on this standard, the SAI is also determined for other supplementary cementitious materials (SCM). Portland cement (type CEM I) of strength class 42.5 or higher according to EN 197-1 is used as the test cement. The production of the mortar prisms and the determination of the compressive strength are carried out according to EN 196-1. The activity index should be at least 75% after 28 days and at least 85% after 90 days.

[0048] In the first application example, a clay A, which in its unactivated state contains 20% kaolinite, 9% muscovite, 21% amorphous components, and <1% calcium carriers, was mechanochemically activated in a stirred ball mill. Additionally, a mixture according to the invention, consisting of 85% clay A and 15% of a limestone comprising >98% calcite, was mechanochemically activated in a stirred ball mill. The activity index of both mechanochemically activated samples was then determined after 2, 7, and 28 days. Portland cement of type CEM 142, 5R was used as the test cement.

[0049] Table 1 shows the determined SAI values. The beneficial effect of the mechanochemical activation of clay mineral and calcium carrier, especially on early strength, is clearly evident. The activity index of the activated material is [value missing] as of June 16, 2025.

[0050] 11 / 15

[0051] Despite the dilution effect (i.e., the addition of 15 wt% limestone), the SAI of the mixture was 16 percentage points higher after two days than that of the pure activated clay. Even after 28 days, the SAI of the activated mixture, at 91%, was still significantly higher than the value expected from the clay dilution (84%).

[0052] Table 1: SAI values ​​after 2, 7 and 28 days of the mechano-chemically activated clay A and the mechano-chemically activated clay A-limestone mixture

[0053] Reference sign

[0054] 10 Clay mineral

[0055] 12. First mechano-chemical activation

[0056] 14 first product

[0057] 17 common mechano-chemical activation

[0058] 20 calcium carriers

[0059] 22 second product

[0060] 24 second mechano-chemical activation

[0061] 30 clinker bricks

[0062] 40 Limestone

[0063] 42 grinding

[0064] 50 plaster

[0065] 60 cement

Claims

16. 06.2025 12 / 15 Patent claims 1. A process for producing a cement (60), wherein a clay mineral (10) is used as the first reactant, the clay mineral (10) being selected from the group comprising claystone, marl, and mud, in particular harbor mud, wherein a calcium carrier (20) is used as the second reactant, the calcium carrier (20) being selected from the group comprising limestone (40), marl, dolomite, carbonated reclaimed concrete fines, carbonated fly ash, shell limestone, and slags, wherein clinker (30) is used as the third reactant, wherein the first reactant and the second reactant are jointly mechano-chemically activated in a mill to form a first product (14), wherein the first reactant (14) and the second reactant (14) are mixed in a mass ratio of 1:10 to 30:1, the first product (14) being added at 10 to 80 wt.% and the third reactant at 20 to 90 wt.%. wherein 0 to 30 wt.% limestone (40) are added, wherein 0 to 10 wt.-% further reactants are added, the sum of all components always being 100%, the heat of hydration of the mechano-chemically activated first product (14) after 7 days according to the R3 test according to ASTM C1897-20 being at least 100 J / g above that of a non-mechano-chemically activated mixture of the first reactant and the second reactant of the same composition.

2. Method according to claim 1, characterized in that a sulfate carrier, for example gypsum (50), is added as a further component.

3. Method according to one of the preceding claims, characterized in that the first product (14) is added in a quantity of 20 to 50 wt.%.

4. Method according to one of the preceding claims, characterized in that the third reactant is added in a quantity of 50 to 64% by weight.

5. Method according to one of the preceding claims, characterized in that the first reactant () and the second reactant () are mixed in a mass ratio of 1 :3 to 10:

1. 6.2025 13 / 15 6. Method according to one of the preceding claims, characterized in that the heat of hydration of the mechano-chemically activated first product (14) after 7 days according to the R3 test according to ASTM C1897-20 has a value of at least 150 J / g above that of a non-mechano-chemically activated mixture of the first reactant and the second reactant of the same composition.

7. Method according to one of the preceding claims, characterized in that the first product (14) has at least 50%, preferably at least 70%, particularly preferably at least 90% of the water of crystallization content based on the water of crystallization content of the non-activated mixture of the first reactant and the second reactant of the same composition.

8. Method according to one of the preceding claims, characterized in that the mechano-chemical activation takes place in a stirred ball mill.

9. Method according to one of the preceding claims, characterized in that the first product (14) is classified as natural pozzolan (P) according to DIN EN 197-1.

10. Method according to one of the preceding claims, characterized in that the first product (14) is at least 30%, preferably at least 40%, particularly preferably at least 50% amorphous by x-ray diffraction, based on the clay mineral content in the unactivated mixture of the first reactant and the second reactant of the same composition.

11. Method according to one of the preceding claims, characterized in that the mechano-chemical activation is carried out with an energy density of at least 100 kW / m². 3 and is carried out with a mill volume of at least 1000 l.

12. Cement (60), produced by a process according to any of the preceding claims.

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