EP-4735399-A1 - METHOD FOR MANUFACTURING COMPOSITE CEMENT

Abstract

Composite cement comprising Portland cement, a calcium carbonate and a mechanochemically activated clay obtained by grinding a clay raw material which was mined from one or more natural clay deposits in a ball mill or roller mill at a temperature below 150 °C until the absorbance units of the OH peak at 3600 to 3700 cm -1 and the SiO 2 peak at 900 to 1000 cm -1 in an FTIR spectrum decrease by at least 20 %, as well as method for manufacturing the composite cement by blending Portland cement, calcium carbonate and the mechanochemically activated clay.

Inventors

• Schade, Tim
• SKOCEK, Jan
• BOLTE, GERD
• PATO, Nicolas
• HANAFI, Ahmed
• MULLER, Arnaud

Assignees

• Heidelberg Materials AG

Dates

Publication Date

20260506

Application Date

20240625

Claims (16)

1. 1 . Composite cement comprising Portland cement, a calcium carbonate and a mechanochemically activated clay, wherein a clay raw material was obtained by mining one or more natural clay deposits and activated by grinding in a ball mill or roller mill at a temperature < 150 °C until the absorbance units of the OH peak at 3600 to 3700 cm -1 and the SiO2 peak at 900 to 1000 cm -1 in an FTIR spectrum decrease by at least 20 % to provide the mechanochemically activated clay.
2. 2. Composite cement according to claim 1 , wherein the composite cement comprises - at least 45 wt.-% Portland cement, preferably at least 50 wt.-%, most preferred at least 65 wt.-% - from 3 to 34 wt.-% calcium carbonate(s), preferably from 6 to 20 wt.-% - from 1 to 40 wt.-% activated clay, preferably from 5 to 30 wt.-%.
3. 3. Composite cement according to claim 1 or 2, wherein the calcium carbonate is limestone, dolomite, precipitated calcium carbonate, carbonated recycled concrete paste, or a mixture of two or all of them, especially limestone, and/or the CaCOs content of the calcium carbonate is at least 40 wt.-%, preferably at least 60 wt.-%, more preferred at least 75 wt.-%, and most preferred at least 90 wt.-%.
4. 4. Composite cement according to any one of claims 1 to 3, wherein the clay raw material comprises at least 10 wt.-% clay minerals, preferably at least 15 wt.-%, more preferred at least 20 wt.-%, most preferred at least 30 wt.-%, and/or up to 90 wt.-%, preferably up to 85 wt.-%, more preferred up to 80 wt.-%, most preferred up to 70 wt.-%, clay minerals with respect to the total clay raw material weight.
5. 5. Composite cement according to any one of claims 1 to 4, wherein the composite cement comprises one or more additional supplementary cementitious materials, preferably selected from ground granulated blast furnace slag and other latent-hydraulic or pozzolanic slags, fly ashes both calcium rich and lean ones, burnt oil shale, natural pozzolans like volcanic ash and ground volcanic glass, artificial pozzolans, recycled concrete paste, process dusts from cement clinker manufacturing like cement kiln dust, and mixtures thereof and/or the composite cement or a hydraulically hardening building material made from it contains admixtures and/or additives.
6. 6. Method for manufacturing a composite cement comprising the steps - providing Portland cement, - providing a calcium carbonate, - manufacturing activated clay by grinding a clay raw material obtained by mining one or more natural clay deposits in a ball mill or roller mill at a temperature < 150 °C until the absorbance units of the OH peak at 3600 to 3700 cm’ 1 and the SiO2 peak at 900 to 1000 cm’ 1 in an FTIR spectrum decrease by at least 20 %, - blending the Portland cement with the calcium carbonate and the activated clay.
7. 7. Method according to claim 6, wherein the clay raw material is ground until the absorbance units of the OH peak and the SiO2 peak decrease by at least 25 %, preferably by at least 30 %.
8. 8. Method according to claim 6 or 7, wherein the temperature during grinding remains below 130 °C, preferably below 110 °C and/or grinding takes place in air.
9. 9. Method according to any one of claims 6 to 8, wherein the mill is not additionally heated during grinding and/or the mill is not cooled during grinding.
10. 10. Method according to any one of claims 6 to 8, wherein the clay raw material is dried to a free water content of 4 wt.%, preferably less than 2 wt.-%, most preferred less than 1 wt.-%, before grinding or during grinding.
11. 11 . Method according to claim 10, wherein the clay raw material is dried during grinding by introducing a hot gas, preferably an exhaust gas, most preferred an exhaust gas from cement manufacturing, into the mill, wherein the temperature of the clay raw material in the mill remains below 150 °C.
12. 12. Method according to any one of claims 6 to 11 , wherein a clay raw material comprising one or more of kaolinite, dickite, halloysite, nacrite, montmorillonite, nontronite, beidellite, saponite, illite, palygorskite, and/or sepiolite is used.
13. 13. Method according to any one of claims 6 to 12, wherein the clay raw material is partially calcined before grinding, preferably at a temperature from 400 to 1000 °C, either for 10 to 120 minutes in a kiln or for 1 to 30 seconds in a flash calciner, so that of clay minerals contained in the clay raw material at least 5 wt.-%, preferably at least 10 wt.-% and most preferred at least 15 wt.-% remain non-calcined in the calcined clay raw material.
14. 14. Method according to claim 13, wherein the clay raw material and the calcination conditions are selected so that the activated clay does not contain more than 3 wt.-%, preferably not more than 1 wt.-% free lime.
15. 15. Method according to any one of claims 6 to 14, wherein providing the Portland cement comprises grinding a Portland cement clinker and/or a sulfate carrier and mixing them.
16. 16. Method according to claim 15, wherein blending Portland cement, calcium carbonate and mechanochemically activated clay is combined with grinding Portland cement clinker or sulfate carrier or both or blending is combined with grinding the Portland cement and/or the calcium carbonate.

Description

Method for manufacturing composite cement [0001] The present invention relates to a method for manufacturing composite cement comprising Portland cement, calcium carbonate, and an activated clay as well as to the composite cement obtainable thereby. [0002] The cement industry is struggling with high CO2 emissions related to the production of cement clinker. Since the demand for cement is increasing worldwide, the emission will further increase. Consequently, there is a demand for further reduction of the emission associated with cement production. The easiest way to limit this environmental footprint is to produce composite cements or to increase the usage of supplementary cementitious material (abbreviated SCM) during the concrete production. Unfortunately, the increase of the proportion of the composite cements in the product portfolio is limited by the availability of high quality supplementary cementitious material, i.e. , reactive materials resulting in appreciable strength evolution. The most often used ones are (ground) granulated blast furnace slag (abbreviated GBFS or GGBFS) and fly ash. Since they are industrial by-products from quality iron production and coal combustion, respectively, as a consequence of the decarbonation of the industry a declining availability is expected. Alternatives are needed. [0003] Another material which may be used as SCM is calcined clay. This material is already described in cement and concrete standards like EN 197-1 or ASTM C618. To obtain good quality SCM a high-quality raw clay should be used as starting material for calcination. High-quality raw clays consisting of a few or only one clay mineral are rare in actual practice and, therefore, are too expensive because of the competition with other industry branches. With mixtures of clay minerals, it is difficult to set an optimum calcination temperature, or to put it another way, the different optimum temperatures for different clay minerals make it impossible to activate the entire raw clay. If the temperature is too low, insufficient volumes will be activated. At somewhat higher temperatures, only those minerals that react at these lower temperatures will be activated. In most cases, this fraction is still too low. Although a sufficient fraction will generally be activated at medium temperatures, some fractions of the raw clay will have already formed crystalline and therefore inert phases. Although (nearly) all fractions of the raw clay will be activated at high temperatures, most fractions will already have formed inert crystalline phases. The various clay minerals have the following optimum calcination temperatures: - Serpentinite 400 - 500°C, - Palygorskite 600 - 800°C, - Kaolinite 600 - 800°C, - Halloysite 600 - 800°C, - Pyrophyllite 750 - 950°C, - Montmorillonite 800 - 950°C, - Illite 800 - 1000°C, - Mica 650 - 1000°C. Non-converted clay minerals have an especially high water demand and therefore must be avoided as much as possible. Further, non-converted clays would not contribute actively to the strength development in blends with Ordinary Portland cement (abbreviated OPC), composite cements would have low compressive strengths. Many raw clays are also low in AI2O3 content, considerable amounts of SiO2 and other constituents such as Fe2O3, CaO, MgO, Na2O and K2O are present. For these reasons, many raw clays, which may fulfill minimum technical requirements, cannot be used economically and in certain circumstances claycontaining or clay-rich materials therefore have to be dumped. [0004] To solve the problem of deviating optimal calcination temperatures, proposals for replacing calcination by mechanochemical activation have been made. For example, EP 3 909 682 A1 discloses a method and device for activating clay mixtures by grinding in a temperature range from 300 to 1000 °C in a roller mill. Suitable conditions for mechanochemical activation were examined by I. Tole, "Mechanical activation of clay - a novel route to sustainable cementitious binders", Licentiate Thesis, Lulea University of Technology, 2019. The Swedish clay tested therein was best activated in a ball mill with a rotational speed of 500 rpm, a balls/material ratio of 25, and grinding times of 20 minutes. While these proposals allow to activate clay without the problem of different calcination temperatures, composite cements may still show insufficient reactivity. This restricts useful replacement levels and the potential of reducing CO2 emissions. It is also suggested in WO 2022/010425 A1 to activate a mixture of clay-based material and calcium-based material by thermal or by mechanical treatment until 70 - 95 wt.-% of the calcium-based material is activated. No details on mechanical treatment are provided, the examples solely illustrate thermal treatment. [0005] Thus, there is still a need for providing composite cements with adequate strength development both at early ages (1 or 2 days) and later (at 28 days) so that the carbon dioxide