EP4479360A1 - Calcined clay - Google Patents

Abstract

The present invention relates to a clay composition, a process for calcining same, and the use of the calcined clay composition in hydraulic binders.

Description

Calcined Clay

The present invention relates to a clay composition, a method for calcining it, and the use of the calcined clay composition in hydraulic binders.

Cement is a widely used building material. By adding water, the cement hydrates and hardens. Along with aggregates like sand and gravel, cement is used to make mortar and concrete. Cement is one of the most important binders worldwide and, with a global production of around 5 billion tons, one of the most important materials.

To produce cement, limestone is ground and then heated to around 1450 °C (calcination). The cement clinker obtained is ground into the end product cement. Depending on the type of cement, the cement is modified by adding blast furnace slag, limestone, gypsum, etc. to it.

Not only the high energy consumption in calcination to produce cement, but also the sintering reaction leads to significant emissions of the greenhouse gas carbon dioxide. The cement industry is thus one of the main sources of greenhouse gases, which are blamed for global warming. The release of the carbon dioxide bound in lime during the sintering reaction alone is responsible for about 6-8% of the annual CO2 emissions: that is four times more than the CO2 emissions generated by global air traffic.

Cement and especially concrete have so far been without alternative in the construction industry due to their low price and advantageous mechanical properties. The object of the present invention is therefore to replace the proportion of cement in the usual building materials, such as concrete and mortar, if not entirely, at least with more environmentally friendly materials to substitute without the properties of the building materials being affected or affected by the usual processing methods must be deviated from.

Clay is a naturally occurring material that is plastic when it has a high water content and becomes brittle when it dries. Fired clay is referred to as ceramic and is significantly more resilient than dried clay and no longer swellable due to mineralogical-textural changes. The clay minerals are generally mixtures of layered silicates, e.g. illite, montmorillonite or kaolinite. Natural clay also contains admixtures of other minerals, such as quartz, calcite, dolomite, feldspar, metal oxides, silicic acid, which do not contribute to the plastic properties and vary depending on the mining area.

Even if marl, the main raw material for the production of cement, can also contain small admixtures of clay in addition to limestone, the proportion of clay in cement production must be kept as low as possible in order to minimize losses in quality: on the one hand, the clay does not actively participate in the Hydration and thus the chemical hardening reaction, on the other hand, the hygroscopicity of the clay causes difficulties in the processing of cement or building materials made from it, such as concrete and mortar. When mixing the building materials, the added water is largely adsorbed due to the high hygroscopicity of the clay minerals, which leads to undesirable lump formation and inhomogeneous hydration. The clay, which is inert during hydration, also leads to losses in mechanical properties, such as compressive strength.

Surprisingly, it has been shown that a specific clay composition is suitable as a starting product for a cement substitute. Neither processing difficulties nor losses in mechanical properties are observed.

A first aspect of the present invention therefore relates to a clay composition comprising

(a) SiC>2, preferably in an amount of 65-80% by weight, more preferably 70-75% by weight, based on the total dry weight;

(b) Al2O3, preferably in an amount of 7-11% by weight, more preferably 8.5-

10% by weight based on the total dry weight;

(c) Fe2Os, preferably in an amount of 2-5% by weight, more preferably 3.5-

4.5% by weight based on the total dry weight;

(d) MgO, preferably in an amount of 0.2-1.5% by weight, more preferably 1.0-

1.3% by weight based on the total dry weight; and

(e) CaO, preferably in an amount of 1-5% by weight, more preferably 2-4% by weight, based on the total dry weight.

Preferably the clay composition comprises

(a) 65-80% by weight SiO2, preferably 70-75% by weight, based on the total dry weight;

(b) Al2O3, preferably in an amount of 7-11% by weight, more preferably 8.5-

10% by weight based on the total dry weight;

(c) Fe2O3, preferably in an amount of 2-5% by weight, more preferably 3.5-

4.5% by weight based on the total dry weight;

(d) MgO, preferably in an amount of 0.2-1.5% by weight, more preferably 1.0-

1.3% by weight based on the total dry weight; and

(e) CaO, preferably in an amount of 1-5% by weight, more preferably 2-4% by weight, based on the total dry weight.

In a preferred embodiment, the clay composition may further

(f) K2O, preferably in an amount of 1.5-3% by weight, more preferably in one

Amount of 2.0-2.4% by weight based on the total dry weight and/or (g) TiC>2, preferably in an amount of 0.1-1% by weight, more preferably 0.4-0.7% by weight, based on the total dry weight.

The clay composition preferably comprises the above components in a mixture

(i) Kaolinite, preferably in an amount of 5-10% by weight, more preferably 6.5-

8.5% by weight based on the total dry weight.

(ii) Muscovite and/or lllite, preferably in an amount of 9-13% by weight, more preferably 10-13% by weight, based on the total dry weight.

(iii) Smectite and/or montmorillonite, preferably in an amount of 10-20% by weight, more preferably 14-16% by weight, based on the total dry weight.

(iv) quartz, preferably in an amount of 40-70% by weight, more preferably 45-65% by weight, based on the total dry weight and

(v) Feldspar, preferably in an amount of 4-7% by weight, more preferably 4.5-

6.5% by weight based on the total dry weight.

More preferably, the clay composition contains the above components in a mixture comprising

(i) Kaolinite, preferably in an amount of 5-10% by weight, more preferably 6.5-

8.5% by weight based on the total dry weight.

(ii) Muscovite and/or lllite, preferably in an amount of 9-13% by weight, more preferably 10-13% by weight, based on the total dry weight.

(iii) Smectite and/or montmorillonite, preferably in an amount of 10-20% by weight, more preferably 14-16% by weight, based on the total dry weight.

(iv) 45-70% by weight quartz, preferably 45-60% by weight, based on the total dry weight and

(v) Feldspar, preferably in an amount of 4-7% by weight, more preferably 4.5-

6.5% by weight based on the total dry weight. Further preferably, the clay composition comprises 30-40% by weight, more preferably 33-35% by weight, of layered silicates, based on the total dry composition.

In another aspect, the present invention relates to a method of calcining a clay composition comprising the steps

(A) providing the clay composition described above,

(B) heating the clay composition obtained in step (A) at 700-900 °C, preferably at 800-860 °C,

(C) cooling the mixture obtained after step (B) in air.

The clay composition used in step (A) preferably has a water content of 15-25%, more preferably 19-24% by weight of the total composition.

Step (B) is preferably carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft furnace.

Step (B) usually takes 25-240 minutes, preferably 40-180 minutes.

Step (B) is preferably carried out in the presence of atmospheric oxygen.

The residual moisture content of the material obtained after step (C) is <1% by weight, more preferably <0.1% by weight.

Optionally, the calcination process described above includes a further step

(D) crushing the product obtained after step (C). Step (D) can be carried out using a ball mill or roller mill. The product obtained after step (D) preferably has a particle size distribution d50 of <30 μm, preferably 0.001-25 μm.

Another aspect of the present invention relates to the calcined clay composition obtainable by the process described above.

The calcined clay composition preferably has a reactive silica content in the range 12-25% by weight, more preferably in the range 18-23% by weight. The proportion of reactive silicic acid is determined in accordance with DIN IN 196-2.

The fineness of grind of the calcined clay composition according to the invention is preferably in the range of 2000-8000 cm ² /g, more preferably in the range of 4000-6000 cm ² /g. The fineness of grinding is measured by the Blaine method, which is known to those skilled in the art.

Preferably, the calcined clay composition of the invention has a BET specific surface area in the range of 5-10 m ² /g, more preferably in the range of 5-7 m ² /g. The BET surface is determined according to DIN ISO 9277:2014-01.

The proportion of finely crystalline quartz in the calcined clay composition according to the invention is preferably in the range of 3-9% by weight, more preferably in the range of 4-6% by weight. To determine the finely crystalline quartz fraction, a corresponding sample is fractionated and dried. The fine-crystalline quartz fraction is then quantified by means of X-ray diffraction analysis (RBA/XRD) in the fraction <10 μm, preferably according to the Rietveld method. The calcined clay composition preferably has a particle size distribution of d50 < 30 pm, more preferably in the range 0.001-25 pm, measured by ISO 13320.

The calcined clay composition of the present invention can be used in hydraulic binders such as cement, concrete and mortar. The calcined clay composition according to the invention is preferably used as a substitute in hydraulic binders.

It has surprisingly been found that the calcined clay composition according to the invention can be used as a substitute for hydraulic binders, in particular for cement.

It has been shown that part of the cement composition can be replaced by the calcined clay composition according to the invention without impairing the processing properties or the mechanical properties of the cement after hardening. Preferably about 10-40%, more preferably 25-35% by weight of cement can be substituted for the calcined clay composition of the present invention. At the same time, the use of the calcined clay composition can save a significant proportion of greenhouse gas emissions compared to conventional cement. On the one hand, the calcination of the clay composition takes place at lower temperatures, so that the energy consumption is reduced compared to cement production. On the other hand, no or only small amounts of carbon dioxide are released during burning.

Therefore, another aspect of the present invention is a cement composition comprising

(1) the calcined clay composition according to the invention, preferably in an amount of 10-40% by weight based on the total dry composition and (2) Cement, preferably in an amount of 60-90% by weight based on the total dry composition.

Portland cement, Portland composite cement, blast furnace cement, pozzolan cement or composite cement is preferably used for the cement composition.

The cement composition preferably has a water requirement of 29-35% by weight, more preferably 31-33% by weight, measured according to DIN EN 196.

The cement composition preferably gives a slump of 130-170mm, more preferably 140-160mm. For this purpose, a standard mortar is prepared according to DIN EN 196-1 (1 part cement composition according to the invention, 3 parts CEN standard sand and 0.5 part water) and determined according to DIN EN 1015-3 using a flow table and slump cone.

The cement composition according to the invention preferably has an activity index after 28 days of at least 75% and after 90 days of at least 85%, more preferably after 28 days of at least 80% and after 90 days of at least 90%. The activity index is determined according to DIN EN 450-1.

The present invention is illustrated by, but not limited to, the following example.

example 1

The clay composition according to the invention

73 wt% SiO2

9.3% by weight Al2O3

3.9 wt% Fe2O3

1.1% by weight MgO

3 wt% CaO

2.1% by weight K2O

0.6 wt% TiO2 contains the following mineral components:

7.5% by weight kaolinite

11.5% by weight I Hit/ Muscovite

15% by weight smectite/montmorillonite

55% by weight quartz

5.5% by weight feldspar

The clay composition is fired at a temperature of 830 °C in a rotary kiln for 40 minutes.

The calcined clay obtained is ground with a vertical roller mill. The milled product has a Blaine mill fineness of 5500 cm ² /g. The particle size distribution has a value d50 of 20 pm.

A cement composition according to the invention consisting of 30% by weight of the calcined clay obtained above and 70% by weight of cement (CEM I 42.5 R) is provided by intensive mixing. The mortar preparation contains 1 part cement composition according to the invention or cement, 3 parts CEN standard sand and 0.5 parts water. The water requirement, the mortar slump and the compressive strength of the mixture are given in Table 1 and compared with the values for the pure cement CEM I 42.5 R.

The results show that the water requirement - an indicator of the workability of the cement compositions - is comparable for the pure cement and Example 1. This also applies to the mortar slump. The compressive strength of the cement composition according to the invention is somewhat lower than that of the pure cement in the first 7 days, but reaches the compressive strength of the pure cement composition after 28 days. Example 2 (comparative example)

A clay composition from

63.9 wt% SiO2

14.7% by weight Al2O3

5.8% by weight Fe2O3

2.5 wt% MgO

1.7 wt% CaO

1.6 wt% Na2O

4.2% by weight K2O

0.7% by weight TiO2 contains the following mineral components:

55% by weight I Hit/ Muscovite 1% by weight Quartz

15% by weight feldspar

The clay composition was fired at a temperature of 950° C. in a rotary kiln for 40 minutes and then ground in a vertical roller mill.

As in example 1, a cement composition was produced from 30% by weight of calcined clay composition and 70% by weight of cement (CEM I 42.5 R) and homogenized. The characterization was carried out as in Example 1 and is summarized in Table 1. Example 1 and Example 2 have a comparable water requirement and a comparable mortar slump. However, compressive strengths corresponding to example 1 cannot be achieved over the entire period for example 2, although the firing temperature for the illitic clay in example 2 is 120° C. higher than that of the clay composition according to the invention. A higher firing temperature usually has a positive effect on the mechanical properties. Table 1 : Properties of the substituted and pure cement

Pure cement Example 1 Example 2 100% cement CEM I 42.5 R 30% clay + 70% 30% clay + 70% cement Cement

Water requirement in M.-% 31 33 34

Mortar slump in mm 171 152 150

Compressive strength in N/mm ² / %

2d 38/100 25.1/ 66 24.0/ 63.2

7d 49/100 36.3/ 74 34.3/ 70

28d 55/100 51.6/ 93.8 45.4/82.5

In summary, it can be stated that the clay composition according to the invention or the calcined clay according to the invention proves to be ideal as a climate-friendly cement substitute without having to compromise on the mechanical properties and the processing properties.

The present invention is described by the following points:

1. Clay composition comprising

(a) SiC>2, preferably in an amount of 65-80% by weight, more preferably 70-75% by weight, based on the total dry weight;

(b) Al2O3, preferably in an amount of 7-11% by weight, more preferably 8.5-10% by weight, based on the total dry weight;

(c) Fe2O3, preferably in an amount of 2-5% by weight, more preferably 3.5-4.5% by weight, based on the total dry weight;

(d) MgO, preferably in an amount of 0.2-1.5% by weight, more preferably 1.0-1.3% by weight, based on the total dry weight; and (e) CaO, preferably in an amount of 1-5% by weight, more preferably 2-4% by weight, based on the total dry weight. Clay composition according to item 1, further comprising

(f) K2O, preferably in an amount of 1.5-3% by weight, more preferably in an amount of 2.0-2.4% by weight based on the

total dry weight and/or

(g) TiO2, preferably in an amount of 0.1-1% by weight, more preferably 0.4-0.7% by weight, based on the total dry weight. Clay composition according to any one of the preceding items, comprising

(i) Kaolinite, preferably in an amount of 5-10% by weight, more preferably 6.5-8.5% by weight, based on the total dry weight.

(ii) Muscovite and/or lllite, preferably in an amount of 9-13% by weight, more preferably 10-13% by weight, based on the total dry weight.

(iii) Smectite and/or montmorillonite, preferably in an amount of 10-20% by weight, more preferably 14-16% by weight, based on the total dry weight.

(iv) Quartz, preferably in an amount of 40-70% by weight, more preferably 45-65% by weight, based on the total dry weight and

(v) Feldspar, preferably in an amount of 4-7% by weight, more preferably 4.5-6.5% by weight, based on the total dry weight. Clay composition according to one of the preceding points, comprising 30-40% by weight, preferably 33-35% by weight, of layered silicates, based on the total dry composition. A method of calcining a clay composition comprising the steps of: (A) providing a clay composition according to any one of items 1-4,

(B) heating the clay composition obtained in step (A) at 700-900 °C, preferably 800-860 °C,

(C) cooling the mixture obtained after step (B) in air.

6. The method according to point 5, wherein the clay composition in step (A) has a residual moisture content of 15-25% by weight, preferably 19-24% by weight, based on the composition as a whole.

7. Process according to one of points 5 or 6, where step (B) is carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft furnace.

8. Calcined clay composition obtainable by a method according to any one of items 5-7.

9. Calcined clay composition according to item 8, wherein the proportion of reactive silica is in the range of 12-25% by weight, preferably in the range of 18-23% by weight.

10. Calcined clay composition according to item 8 or 9, wherein the grinding fineness is in the range of 2000-8000 cm ² /g, preferably in the range of 4000-6000 cm ² /g.

11. The calcined clay composition according to any one of items 8-10, wherein the BET specific surface area is in the range of 5-10 m ² /g, preferably in the range of 5-7 m ² /g.

12. Calcined clay composition according to one of points 8-11, wherein the proportion of finely crystalline quartz is in the range of 3-9% by weight, preferably in the range of 4-6% by weight. 13. Calcined clay composition according to any one of points 8-12, wherein the particle size distribution d50 is <30 μm, preferably in the range from 0.001-25 μm.

14. Use of the calcined clay composition according to any one of items 8-13 in hydraulic binders.

15. Use according to item 14, wherein the hydraulic binders are cement, concrete and mortar.

16. Use according to point 14 or 15 as a substitute in hydraulic binders.

17. Use according to one of points 14-16 as a substitute for hydraulic binders, in particular cement.

18. A cement composition comprising

(1) calcined clay composition according to any one of items 8-13, preferably in an amount of 10-40% by weight based on the total dry composition and

(2) Cement, preferably in an amount of 60-90% by weight based on the total dry composition.

19. Cement composition according to item 18, wherein the cement is preferably Portland cement, Portland composite cement, blast furnace cement, pozzolan cement or composite cement.

20. Cement composition according to point 18 or 19, with a water requirement of 29-35% by weight measured according to DIN EN 196.

21. Cement composition according to one of points 18-20 with a slump of 130-170 mm, preferably 140-160 mm, measured according to DIN EN 1015-3. Cement composition according to one of points 18-21, with an activity index after 28 days of at least 75% and after 90 days of at least 85%, preferably after 28 days of at least 80% and after 90 days of at least 90%, measured according to DIN EN 450 -1.

Claims

claims 1. Clay composition comprising (a) SiC>2, preferably in an amount of 65-80% by weight, more preferably 70-75% by weight, based on the total dry weight; (b) Al2O3, preferably in an amount of 7-11% by weight, more preferably 8.5-10% by weight, based on the total dry weight; (c) Fe2O3, preferably in an amount of 2-5% by weight, more preferably 3.5-4.5% by weight, based on the total dry weight; (d) MgO, preferably in an amount of 0.2-1.5% by weight, more preferably 1.0-1.3% by weight, based on the total dry weight; and (e) CaO, preferably in an amount of 1-5% by weight, more preferably 2-4% by weight, based on the total dry weight. 2. The clay composition of claim 1 further comprising (f) K2O, preferably in an amount of 1.5-3% by weight, more preferably in an amount of 2.0-2.4% by weight based on the total dry weight and/or (g) TiO2, preferably in an amount of 0.1-1% by weight, more preferably 0.4-0.7% by weight, based on the total dry weight. 3. A clay composition according to any one of the preceding claims comprising (i) Kaolinite, preferably in an amount of 5-10% by weight, more preferably 6.5-8.5% by weight, based on the total dry weight. (ii) Muscovite and/or lllite, preferably in an amount of 9-13% by weight, more preferably 10-13% by weight, based on the total dry weight. (iii) Smectite and/or montmorillonite, preferably in an amount of 10-20% by weight, more preferably 14-16% by weight, based on the total dry weight. (iv) Quartz, preferably in an amount of 40-70% by weight, more preferably 45-65% by weight, based on the total dry weight and (v) Feldspar, preferably in an amount of 4-7% by weight, more preferably 4.5-6.5% by weight, based on the total dry weight. 4. Clay composition according to any one of the preceding claims, comprising 30-40% by weight, preferably 33-35% by weight, of layered silicates, based on the total dry composition. 5. A method of calcining a clay composition comprising the steps of: (A) providing a clay composition according to any one of claims 1-4, (B) heating the clay composition obtained in step (A) at 700-900 °C, preferably 800-860 °C, (C) cooling the mixture obtained after step (B) in air. 6. The method according to claim 5, wherein step (B) is carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft furnace. 7. Calcined clay composition obtainable by a method according to any one of claims 5-6. 8. A calcined clay composition according to claim 7, wherein the proportion of reactive silica is in the range 12-25% by weight, preferably in the range 18-23% by weight. 9. A calcined clay composition according to any one of claims 7-8, wherein the proportion of finely crystalline quartz is in the range of 3-9% by weight, preferably in the range of 4-6% by weight. 10. Calcined clay composition according to any one of claims 7-9, wherein the particle size distribution d50 is <30 pm, preferably in the range of 0.001-25 pm. 11. Use of the calcined clay composition according to any one of claims 7-10 in hydraulic binders, in particular cement, concrete or mortar. 12. Use according to claim 11 as a substitute in hydraulic binders, in particular as a substitute for hydraulic binders. 13. A cement composition comprising (1) calcined clay composition according to any one of claims 7-10, preferably in an amount of 10-40 wt .-% based on the total dry composition and (2) Cement, preferably Portland cement, Portland composite cement, blast furnace cement, pozzolan cement or composite cement, more preferably in an amount of 60-90% by weight based on the total dry composition. 14. Cement composition according to claim 13, with a water requirement of 30-36% by weight measured according to DIN EN 196 and/or with a slump of 130-170 mm, preferably 140-160 mm, measured according to DIN EN 1015-3. 15. Cement composition according to one of claims 13-14, having an activity index after 28 days of at least 75% and after 90 days of at least 85%, preferably after 28 days of at least 80% and after 90 days of at least 90%, measured according to DIN EN450-1.