Calcined clay

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

[0001] Calcined clay

[0002] The present invention relates to a clay composition, a process for its calcination, and the use of the calcined clay composition in hydraulic binders.

[0003] Cement is a widely used building material. When water is added, it hydrates and hardens. Together with aggregates such as sand and gravel, cement is used to make mortar and concrete. Cement is one of the world's most important binding agents and, with global production of approximately 5 billion tons, one of the most important materials.

[0004] To produce cement, limestone is ground and then heated to approximately 1450 °C (calcination). The resulting cement clinker is ground into the final product, cement. Depending on the type of cement, the cement is modified by adding granulated blast furnace slag, limestone, gypsum, etc.

[0005] Not only the high energy consumption during calcination to produce cement, but also the sintering reaction leads to significant emissions of the greenhouse gas carbon dioxide. This makes the cement industry one of the main emitters of greenhouse gases blamed for global warming. The release of carbon dioxide bound in lime during the sintering reaction alone accounts for approximately 6-8% of annual CO2 emissions: four times more than the CO2 emissions generated by global aviation.

[0006] Cement, and especially concrete, have so far been the only 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 cement content in conventional building materials, such as concrete and mortar, if not entirely, with at least more environmentally friendly materials, without compromising the properties of the building materials or requiring deviations from conventional processing methods.

[0007] Clay is a naturally occurring material that is plastic at high water content and becomes brittle upon drying. Fired clay is called ceramic and, due to mineralogical and textural transformations, is significantly more resilient than dried clay and no longer swells. Clay minerals are generally mixtures of phyllosilicates, such as illite, montmorillonite, or kaolinite. Natural clay also contains admixtures of other minerals, such as quartz, calcite, dolomite, feldspar, metal oxides, and silica, which do not contribute to the plastic properties and vary depending on the mining area.

[0008] Even though marl, the main raw material for cement production, can contain small amounts of clay alongside limestone, the proportion of clay used in cement production must be kept as low as possible to minimize any loss of quality. Firstly, the clay does not actively participate in the hydration and thus the chemical hardening reaction, and secondly, the hygroscopicity of clay causes difficulties when processing cement or building materials made from it, such as concrete and mortar. When mixing the building materials, the high hygroscopicity of the clay minerals means that most of the added water is adsorbed, which leads to undesirable lump formation and inhomogeneous hydration. The clay, which is inert during hydration, also leads to a loss of mechanical properties, such as compressive strength.

[0009] Surprisingly, it has been shown that a specific clay composition is suitable as a starting material for a cement substitute. Neither processing difficulties nor impairment of mechanical properties have been observed.

[0010] A first aspect of the present invention therefore relates to a clay composition comprising

[0011] (a) SiC>2, preferably in an amount of 65-80 wt.%, more preferably 70-75 wt.% based on the total dry weight;

[0012] (b) AI2O3, preferably in an amount of 7-11 wt.%, more preferably 8.5-

[0013] 10% by weight based on the total dry weight;

[0014] (c) Fe2Os, preferably in an amount of 2-5 wt.%, more preferably 3.5-

[0015] 4.5% by weight based on the total dry weight;

[0016] (d) MgO, preferably in an amount of 0.2-1.5 wt.%, more preferably 1.0-

[0017] 1.3 wt% based on the total dry weight; and

[0018] (e) CaO, preferably in an amount of 1-5 wt.%, more preferably 2-4 wt.% based on the total dry weight.

[0019] Preferably, the clay composition comprises

[0020] (a) 65-80 wt% SiO2, preferably 70-75 wt% based on the total dry weight;

[0021] (b) AI2O3, preferably in an amount of 7-11 wt.%, more preferably 8.5-

[0022] 10% by weight based on the total dry weight;

[0023] (c) Fe2O3, preferably in an amount of 2-5 wt.%, more preferably 3.5-

[0024] 4.5% by weight based on the total dry weight;

[0025] (d) MgO, preferably in an amount of 0.2-1.5 wt.%, more preferably 1.0-

[0026] 1.3 wt% based on the total dry weight; and

[0027] (e) CaO, preferably in an amount of 1-5 wt.%, more preferably 2-4 wt.% based on the total dry weight.

[0028] In a preferred embodiment, the clay composition may further

[0029] (f) K2O, preferably in an amount of 1.5-3 wt.%, more preferably in a

[0030] Amount of 2.0-2.4 wt.% based on the total dry weight and / or (g) TiC>2, preferably in an amount of 0.1-1 wt.%, more preferably 0.4-0.7 wt.% based on the total dry weight.

[0031] The clay composition preferably contains the above-mentioned components in a mixture comprising

[0032] (i) Kaolinite, preferably in an amount of 5-10 wt.%, more preferably 6.5-

[0033] 8.5 wt% based on the total dry weight.

[0034] (ii) Muscovite and / or illite, preferably in an amount of 9-13 wt%, more preferably 10-13 wt% based on the total dry weight.

[0035] (iii) smectite and / or montmorillonite, preferably in an amount of 10-20 wt%, more preferably 14-16 wt% based on the total dry weight.

[0036] (iv) quartz, preferably in an amount of 40-70 wt%, more preferably 45-65 wt% based on the total dry weight and

[0037] (v) Feldspar, preferably in an amount of 4-7 wt.%, more preferably 4.5-

[0038] 6.5 wt% based on the total dry weight.

[0039] More preferably, the clay composition contains the above components in a mixture comprising

[0040] (i) Kaolinite, preferably in an amount of 5-10 wt.%, more preferably 6.5-

[0041] 8.5 wt% based on the total dry weight.

[0042] (ii) Muscovite and / or illite, preferably in an amount of 9-13 wt%, more preferably 10-13 wt% based on the total dry weight.

[0043] (iii) smectite and / or montmorillonite, preferably in an amount of 10-20 wt%, more preferably 14-16 wt% based on the total dry weight.

[0044] (iv) 45-70 wt% quartz, preferably 45-60 wt%, based on the total dry weight and

[0045] (v) Feldspar, preferably in an amount of 4-7 wt.%, more preferably 4.5-

[0046] 6.5 wt.% based on the total dry weight. Furthermore, the clay composition preferably comprises 30-40 wt.%, more preferably 33-35 wt.% layered silicates based on the total dry composition.

[0047] In a further aspect, the present invention relates to a process for calcining a clay composition comprising the steps

[0048] (A) Providing the clay composition described above,

[0049] (B) heating the clay composition obtained in step (A) at 700-900 °C, preferably at 800-860 °C,

[0050] (C) Cooling the mixture obtained after step (B) in air.

[0051] The clay composition used in step (A) preferably has a water content of 15-25 wt.%, more preferably 19-24 wt.%, based on the total composition.

[0052] Step (B) is preferably carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft furnace.

[0053] Step (B) usually takes 25-240 min, preferably 40-180 min.

[0054] Preferably, step (B) is carried out in the presence of atmospheric oxygen.

[0055] The residual moisture content of the material obtained after step (C) is < 1 wt.%, more preferably < 0.1 wt.%.

[0056] Optionally, the calcination process described above includes a further step

[0057] (D) Comminuting 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 pm, preferably 0.001-25 pm.

[0058] Another aspect of the present invention relates to the calcined clay composition which can be obtained by the process described above.

[0059] The calcined clay composition preferably has a reactive silica content in the range of 12-25 wt.%, more preferably in the range of 18-23 wt.%. The reactive silica content is determined according to DIN IN 196-2.

[0060] The grinding fineness 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 grinding fineness is measured according to the Blaine method, which is familiar to those skilled in the art.

[0061] Preferably, the calcined clay composition according to 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 area is determined according to DIN ISO 9277:2014-01.

[0062] The proportion of fine-crystalline quartz in the calcined clay composition according to the invention is preferably in the range of 3-9 wt.%, more preferably in the range of 4-6 wt.%. To determine the fine-crystalline quartz fraction, a corresponding sample is fractionated and dried. The fine-crystalline quartz fraction is then quantified using X-ray diffraction analysis (RBA / XRD) in the fraction <10 pm, 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 of 0.001-25 pm, measured using ISO 13320.

[0063] The calcined clay composition of the present invention can be used in hydraulic binders, such as cement, concrete, and mortar. The calcined clay composition of the present invention is preferably used as a substitute in hydraulic binders.

[0064] Surprisingly, it has been found that the calcined clay composition according to the invention can be used as a substitute for hydraulic binders, in particular for cement.

[0065] It has been shown that part of the cement composition can be replaced by the calcined clay composition according to the invention without the processing properties or the mechanical properties of the cement deteriorating after hardening. Preferably, approximately 10-40 wt. %, more preferably 25-35 wt. % of cement can be replaced with the calcined clay composition according to the invention. At the same time, the use of the calcined clay composition can save a considerable amount of greenhouse gas emissions compared to conventional cement. Firstly, the calcination of the clay composition takes place at lower temperatures, so that the energy consumption is reduced compared to that in cement production. Secondly, no or only small amounts of carbon dioxide are released during firing.

[0066] Therefore, a further aspect of the present invention is a cement composition comprising

[0067] (1) the calcined clay composition according to the invention, preferably in an amount of 10-40 wt.% based on the total dry composition and (2) cement, preferably in an amount of 60-90 wt.% based on the total dry composition.

[0068] Portland cement, Portland composite cement, blast furnace cement, pozzolanic cement or composite cement is preferably used for the cement composition.

[0069] The cement composition preferably has a water content of 29-35 wt%, more preferably 31-33 wt% measured according to DIN EN 196.

[0070] The cement composition preferably results in a slump of 130-170 mm, more preferably 140-160 mm. For this purpose, a standard mortar is prepared according to DIN EN 196-1 (1 part of the inventive cement composition, 3 parts of CEN standard sand, and 0.5 part of water) and determined according to DIN EN 1015-3 using a slump table and slump funnel.

[0071] The cement composition according to the invention preferably has an activity index of at least 75% after 28 days and at least 85% after 90 days, more preferably at least 80% after 28 days and at least 90% after 90 days. The activity index is determined according to DIN EN 450-1.

[0072] The present invention is illustrated by the following example, but is not limited thereto.

[0073] Example 1

[0074] The clay composition according to the invention from

[0075] 73 wt% SiO2

[0076] 9.3 wt% AI2O3

[0077] 3.9 wt% Fe2O3

[0078] 1.1 wt% MgO

[0079] 3 wt% CaO

[0080] 2.1 wt% K2O

[0081] 0.6 wt% TiO2 contains the following mineral components:

[0082] 7.5 wt% kaolinite

[0083] 11.5 wt.% I Hit / Muscovite

[0084] 15% by weight smectite / montmorrilonite

[0085] 55 wt% quartz

[0086] 5.5 wt% feldspar

[0087] The clay composition is fired at a temperature of 830 °C in a rotary kiln for 40 minutes.

[0088] The resulting calcined clay is ground using a roller mill. The ground product has a Blaine fineness of 5500 cm 2 / g. The particle size distribution has a d50 value of 20 pm.

[0089] A cement composition according to the invention consisting of 30 wt.% of the calcined clay obtained above and 70 wt.% cement (CEM I 42.5 R) is prepared by intensive mixing. The mortar preparation contains 1 part of the cement composition according to the invention or cement, 3 parts of CEN standard sand, and 0.5 part of water. Table 1 shows the water demand, mortar slump, and compressive strength of the mixture and compares them with the values ​​for pure cement CEM I 42.5 R.

[0090] The results show that the water demand—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 slightly 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)

[0091] A sound composition of

[0092] 63.9 wt% SiO2

[0093] 14.7 wt% AI2O3

[0094] 5.8 wt% Fe2O3

[0095] 2.5 wt% MgO

[0096] 1.7 wt% CaO

[0097] 1.6 wt% Na2O

[0098] 4.2 wt% K2O

[0099] 0.7 wt% TiO2 contains the following mineral components:

[0100] 55% by weight I Hit / Muscovite 1% by weight Quartz

[0101] 15 wt% feldspar

[0102] The clay composition was fired at a temperature of 950 °C in a rotary kiln for 40 minutes and then ground in a roller mill.

[0103] According to Example 1, a cement composition consisting of 30 wt.% calcined clay composition and 70 wt.% cement (CEM I 42.5 R) was prepared and homogenized. Characterization was carried out as in Example 1 and is summarized in Table 1. Examples 1 and Example 2 exhibit comparable water demand and mortar slump. However, compressive strengths corresponding to Example 1 could not be achieved for Example 2 over the entire period, even though the firing temperature for the illite clay in Example 2 was 120 °C higher than that of the clay composition according to the invention. Typically, a higher firing temperature has a positive effect on the mechanical properties. Table 1: Properties of the substituted and pure cement

[0104] Pure cement Example 1 Example 2 100 % cement CEM I 42.5 R 30% clay + 70 % 30% clay + 70 % cement Cement

[0105] Water demand in M% 31 33 34

[0106] Mortar spread in mm 171 152 150

[0107] Compressive strength in N / mm 2 / %

[0108] 2 d 38 / 100 25.1 / 66 24.0 / 63.2

[0109] 7 d 49 / 100 36.3 / 74 34.3 / 70

[0110] 28d 55 / 100 51.6 / 93.8 45.4 / 82.5

[0111] 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 make compromises in terms of mechanical properties and processing properties.

[0112] The present invention is described by the following points:

[0113] 1. Sound composition comprehensive

[0114] (a) SiC>2, preferably in an amount of 65-80 wt.%, more preferably 70-75 wt.% based on the total dry weight;

[0115] (b) AI2O3, preferably in an amount of 7-11 wt.%, more preferably 8.5-10 wt.% based on the total dry weight;

[0116] (c) Fe2O3, preferably in an amount of 2-5 wt.%, more preferably 3.5-4.5 wt.% based on the total dry weight;

[0117] (d) MgO, preferably in an amount of 0.2-1.5 wt.%, more preferably 1.0-1.3 wt.% based on the total dry weight; and (e) CaO, preferably in an amount of 1-5 wt.%, more preferably 2-4 wt.% based on the total dry weight. Clay composition according to item 1, further comprising

[0118] (f) K2O, preferably in an amount of 1.5-3 wt.%, more preferably in an amount of 2.0-2.4 wt.% based on the

[0119] Total dry weight and / or

[0120] (g) TiO2, preferably in an amount of 0.1-1 wt.%, more preferably 0.4-0.7 wt.% based on the total dry weight. Clay composition according to any one of the preceding points, comprising

[0121] (i) Kaolinite, preferably in an amount of 5-10 wt.%, more preferably 6.5-8.5 wt.% based on the total dry weight.

[0122] (ii) Muscovite and / or illite, preferably in an amount of 9-13 wt%, more preferably 10-13 wt% based on the total dry weight.

[0123] (iii) smectite and / or montmorillonite, preferably in an amount of 10-20 wt.%, more preferably 14-16 wt.% based on the total dry weight.

[0124] (iv) quartz, preferably in an amount of 40-70 wt%, more preferably 45-65 wt% based on the total dry weight and

[0125] (v) Feldspar, preferably in an amount of 4-7 wt.%, more preferably 4.5-6.5 wt.% based on the total dry weight. Clay composition according to any one of the preceding points, comprising 30-40 wt.%, preferably 33-35 wt.% of phyllosilicates based on the total dry weight. A process for calcining a clay composition comprising the steps: (A) providing a clay composition according to any one of points 1-4,

[0126] (B) heating the clay composition obtained in step (A) at 700-900 °C, preferably 800-860 °C,

[0127] (C)Cooling the mixture obtained after step (B) in air.

[0128] 6. The process according to item 5, wherein the clay composition in step (A) has a residual moisture content of 15-25 wt.%, preferably 19-24 wt.%, based on the total composition.

[0129] 7. Process according to one of items 5 or 6, wherein step (B) is carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft furnace.

[0130] 8. Calcined clay composition obtainable by a process according to any of items 5-7.

[0131] 9. Calcined clay composition according to item 8, wherein the proportion of reactive silica is in the range of 12-25 wt.%, preferably in the range of 18-23 wt.%.

[0132] 10. Calcined clay composition according to item 8 or 9, wherein the grinding fineness is in the range of 2,000-8,000 cm 2 / g, preferably in the range of 4,000-6,000 cm 2 / g.

[0133] 11. 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.

[0134] 12. Calcined clay composition according to any one of items 8-11, wherein the proportion of finely crystalline quartz is in the range of 3-9 wt.%, preferably in the range of 4-6 wt.%. 13. Calcined clay composition according to any one of items 8-12, wherein the particle size distribution d50 is < 30 pm, preferably in the range of 0.001-25 pm.

[0135] 14. Use of the calcined clay composition according to any of items 8-13 in hydraulic binders.

[0136] 15. Use according to point 14, where the hydraulic binders are cement, concrete and mortar.

[0137] 16. Use according to point 14 or 15 as a substitute in hydraulic binders.

[0138] 17. Use according to any of items 14-16 as a substitute for hydraulic binders, in particular cement.

[0139] 18. Cement composition comprising

[0140] (1 ) calcined clay composition according to any one of items 8-13, preferably in an amount of 10-40 wt.% based on the total dry composition and

[0141] (2) Cement, preferably in an amount of 60-90 wt.% based on the total dry composition.

[0142] 19. Cement composition according to item 18, wherein the cement is preferably Portland cement, Portland composite cement, blast furnace cement, pozzolanic cement or composite cement.

[0143] 20. Cement composition according to item 18 or 19, with a water content of 29-35 wt% measured according to DIN EN 196.

[0144] 21. Cement composition according to one of the items 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 the items 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. Comprehensive sound composition (a) S iC>2, preferably in an amount of 65-80 wt.%, more preferably 70-75 wt.% based on the total dry weight; (b) Al2O3, preferably in an amount of 7-11 wt.%, more preferably 8.5-10 wt.% based on the total dry weight; (c) Fe2O3, preferably in an amount of 2-5 wt.%, more preferably 3.5-4.5 wt.% based on the total dry weight; (d) MgO, preferably in an amount of 0.2-1.5 wt.%, more preferably 1.0-1.3 wt.% based on the total dry weight; and (e) CaO, preferably in an amount of 1-5 wt.%, more preferably 2-4 wt.% based on the total dry weight.

2. Tone composition according to claim 1, further comprising (f) K₂O, preferably in an amount of 1.5–3 wt.%, more preferably in an amount of 2.0–2.4 wt.% based on the Total dry weight and / or (g) TiÜ2, preferably in an amount of 0.1 - 1 wt.%, more preferably 0.4- 0.7 wt.% based on the total dry weight.

3. Tone composition according to one of the preceding claims, comprising (i) Kaolinite, preferably in an amount of 5-10 wt.%, more preferably 6.5-8.5 wt.% based on the total dry weight. (ii) Muscovite and / or illite, preferably in an amount of 9-13 wt.%, more preferably 10-13 wt.% based on the total dry weight. (iii) Smectite and / or montmorillonite, preferably in an amount of 10-20 wt.%, more preferably 14-16 wt.% based on the total dry weight. (iv) Quartz, preferably in an amount of 40-70 wt.%, more preferably 45-65 wt.% based on the total dry weight and (v) Feldspar, preferably in an amount of 4-7 wt.%, more preferably 4, 5-6, 5 wt.% based on the total dry weight.

4. Clay composition according to one of the preceding claims, comprising 30-40 wt.%, preferably 33-35 wt.% layered silicates based on the total dry composition.

5. Method for calcining a clay composition comprising the steps: (A) Providing a sound 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 of claim 5, wherein step (B) is carried out in a rotary kiln, flash calciner, fluidized bed reactor, entrained flow reactor or shaft kiln.

7. Calcined clay composition obtainable by a process according to one of claims 5-6.

8. Calcined clay composition according to claim 7, wherein the proportion of reactive silica is in the range of 12-25 wt.%, preferably in the range of 18-23 wt.%.

9. Calcined clay composition according to one of claims 7-8, wherein the proportion of fine-grained quartz is in the range of 3-9 wt.%, preferably in the range of 4-6 wt.%.

10. Calcined clay composition according to 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. 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, pozzolanic cement or composite cement, more preferably in an amount of 60-90 wt.% based on the total dry composition.

14. Cement composition according to claim 13, with a water content of 30-36 wt.% 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 EN 450-1.

Images