A red mud based ferrite-aluminate cement and a method of making the same

Abstract

The present application relates to a kind of red mud-based ferrite cement and its preparation method, belong to cement clinker technical field.The raw material includes the following weight parts of component: high calcium solid waste 50-60 parts, high silicon solid waste 15-25 parts, high aluminum solid waste 10-25 parts, bayer red mud 20-40 parts and high sulfur solid waste 0-10 parts.Preparation method includes the following steps: S1, after high calcium solid waste, high silicon solid waste, high aluminum solid waste and bayer red mud are mixed, after grinding, homogenization, sample preparation, calcination, cooling is made into red mud-based ferrite cement clinker;S2, red mud-based ferrite cement clinker and the remaining high calcium solid waste, high aluminum solid waste and high sulfur solid waste are mixed, and are ground together, obtain red mud-based ferrite cement.Can utilize the high alkalinity of bayer red mud to prepare ferrite cement, realizes the efficient solidification of red mud alkaline component, solves the technical problem that red mud product is easy to alkali, can be largely absorbed red mud.

Description

Technical Field

[0001] This invention belongs to the field of cement clinker technology, specifically relating to a red mud-based ferroaluminate cement and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Red mud is an industrial solid waste discharged during the extraction of alumina in the aluminum industry. Due to its high iron oxide content and appearance resembling red soil, it is also known as red mud. Currently, my country has accumulated over 1 billion tons of red mud, but the resource utilization rate is less than 10%. Long-term storage will cause serious pollution to soil and groundwater, threatening the health of residents in the region. Currently, technologies for truly industrialized applications include red mud iron ore extraction, red mud as roadbed materials, and red mud as building materials.

[0004] The red mud produced during the Bayer process for alumina production is called Bayer red mud. Bayer red mud is rich in iron and aluminum, making it a valuable secondary resource. Sodium aluminoferrite (sodium calcium) cement is a low-carbon, green cement. Compared to silicate cement, its production process does not require the consumption of natural mineral resources, has low energy consumption, and produces less carbon dioxide emissions.

[0005] Domestic and international scholars have conducted some research on the preparation of aluminoferrite cement clinker using solid waste. Patents CN101343152 B and CN101857388 A both disclose a strontium calcium sulfoaluminate cement; patent CN113277758A discloses a low-cost method for preparing solid waste-based sulfoaluminate cement; and patent CN111533473A discloses a method for preparing aluminoferrite cement clinker using Bayer process red mud. These patents have made some progress in the field of cement preparation from solid waste, but none have achieved large-scale utilization of red mud or efficient solidification of the alkaline components of red mud. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a red mud-based aluminoferrate cement and its preparation method. By utilizing the high alkalinity of Bayer process red mud to prepare aluminoferrate cement, this invention achieves efficient solidification of the alkaline components of Bayer process red mud, solves the technical problem of easy efflorescence in red mud products, and enables the large-scale disposal of red mud.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] Firstly, a red mud-based aluminoferrite cement, the raw materials of which include the following components in parts by weight:

[0009] 50-60 parts of high-calcium solid waste, 15-25 parts of high-silicon solid waste, 10-25 parts of high-alumina solid waste, 20-40 parts of Bayer process red mud, and 0-10 parts of high-sulfur solid waste;

[0010] The chemical composition satisfies the following conditions: the mass ratio of Al2O3 to Fe2O3 is 0.65 to 0.85, the mass ratio of SiO2 to (Fe2O+Al2O3) is 1.1 to 1.3, the molar ratio of CaO to Fe2O+Al2O3+Na2O is 1.98 to 2.3, and the molar ratio of SiO2 to Na2O is 4.2 to 8.

[0011] Secondly, the above-mentioned method for preparing red mud-based aluminoferrate cement includes the following steps:

[0012] S1. High-calcium solid waste, high-silicon solid waste, high-alumina solid waste and Bayer process red mud are mixed and then ground, homogenized, sampled, calcined and cooled to produce red mud-based aluminoferrate cement clinker.

[0013] S2. Mix the red mud-based ferroaluminate cement clinker with the remaining high-calcium solid waste, high-aluminum solid waste and high-sulfur solid waste, and grind them together to obtain red mud-based ferroaluminate cement.

[0014] The mineral phase composition and volume ratio of the cement clinker obtained by calcination are: 40-60% dicalcium silicate, 25-40% aluminoferrite, 5-15% tricalcium aluminate and 5-15% tricalcium silicate; the chemical formula of the aluminoferrite is 7CaO·2Al2O3·2Fe2O3·NaO.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention utilizes a specific proportion of solid waste to control the molar ratios of CaO / (Fe2O+Al2O3+Na2O) and SiO2 / Na2O within appropriate ranges. This allows for the regulation of soluble alkalis (NaHCO3 and Na2CO3) in Bayer process red mud during high-temperature calcination, transforming them into stable molten aluminoferrite phases, specifically a novel mineral phase—sodium aluminoferrite (calcium ferroaluminate), ensuring that the aluminoferrite (referring to sodium aluminoferrite (calcium ferroaluminate)) content is not less than 25%; and ensuring that the octahedral [Fe...] in the aluminoferrite phase... 0.76 Al 0.24 O6] 9- and tetrahedron [Fe 0.24 Al 0.76 O4] 5- The constructed spatial structure can seal and solidify the structural alkali in high-iron and high-alumina Bayer process red mud, thereby improving the utilization rate of red mud and reducing the cost of dealkali removal, and solving the problem of easy alkali blooming in traditional red mud-based products.

[0017] 2. This invention controls the mass ratio of Al2O3 / Fe2O3 and the mass ratio of SiO2 / (Fe2O+Al2O3) within appropriate ranges, thereby regulating the formation of aluminoferrites during the mineral phase synthesis process. A small amount of Na oxide can improve the liquid phase environment during the formation of mineral phases in red mud-based aluminoferrite cement clinker, and also act as a mineralizing agent to stabilize the coexistence of mineral phases in red mud-based calcium aluminoferrite cement clinker. Accordingly, the high-iron, high-alumina mineral phases in Bayer process red mud, together with other high-calcium, high-silica mineral phases, achieve mineral phase reconstruction during high-temperature solid-phase reaction, resulting in the directional synthesis of red mud-based aluminoferrite cement clinker, which can consume a large amount of highly alkaline red mud.

[0018] 3. This invention relates to a red mud-based aluminoferrite cement with calcium aluminoferrite (sodium aluminoferrite) and dicalcium silicate as the main minerals, exhibiting excellent erosion and scour resistance. The inert alkaline components in the Bayer process red mud further improve the erosion resistance of the red mud-based aluminoferrite cement, and the residual alkaline components synergistically activate the geopolymer mineral phase system, enhancing the cement's mechanical properties. Compared to traditional aluminoferrite cement, its mechanical properties and corrosion resistance are further improved.

[0019] 4. The raw materials used in this invention are all bulk solid waste resources. Industrial solid wastes such as Bayer red mud, coal gangue, silica fume, iron tailings, low-calcium fly ash, carbide slag, limestone tailings, blast furnace slag, high-calcium fly ash, sintered red mud, and alumina ash are used to replace traditional non-renewable resources to prepare red mud-based aluminoferrite cement. This high-performance, low-cost method promotes the resource recycling of various types of solid waste, alleviates the crisis of non-renewable resource scarcity to a certain extent, and reduces the occupation of arable land and the pollution of soil, groundwater, and other ecological environments. It reduces the production cost of traditional cement materials, ensuring the large-scale promotion and application of the material. It can utilize solid waste in large quantities, realizing the resource utilization of solid waste. Compared with ordinary aluminoferrite cement, the product obtained by this invention has the advantages of high later-stage strength, low firing temperature, low cost, and energy saving, and has significant environmental, economic, and engineering application value. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 The results are the XRD quantitative analysis results of the red mud-based ferroaluminate cement clinker of this invention;

[0022] Figure 2 This is a microstructure diagram of the clinker from the SEM-EDS analysis results of the red mud-based ferroaluminate cement clinker of this invention.

[0023] Figure 3This is a distribution diagram of clinker elements in the SEM-EDS analysis results of the red mud-based ferroaluminate cement clinker of this invention;

[0024] Figure 4 This is a total elemental distribution diagram of the clinker in the SEM-EDS analysis results of the red mud-based ferroaluminate cement clinker of this invention;

[0025] Figure 5 This is a diagram of mineral phase element composition in the clinker from the SEM-EDS analysis results of the red mud-based ferroaluminate cement clinker of this invention.

[0026] Figure 6 This is a crystal structure diagram of the iron aluminate mineral phase in the red mud-based iron aluminate cement clinker of this invention; Detailed Implementation

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] A red mud-based aluminoferrite cement, the raw materials of which include the following components in parts by weight:

[0030] 50-60 parts of high-calcium solid waste, 15-25 parts of high-silicon solid waste, 10-25 parts of high-alumina solid waste, 20-40 parts of Bayer process red mud, and 0-10 parts of high-sulfur solid waste;

[0031] The chemical composition satisfies the following conditions: the mass ratio of Al2O3 to Fe2O3 is 0.65 to 0.85, the mass ratio of SiO2 to (Fe2O+Al2O3) is 1.1 to 1.3, the molar ratio of CaO to Fe2O+Al2O3+Na2O is 1.98 to 2.3, and the molar ratio of SiO2 to Na2O is 4.2 to 8.

[0032] Bayer red mud refers to the highly alkaline solid waste generated during the Bayer process of alumina production.

[0033] Optional, high-calcium solid waste includes one or more of the following: carbide slag, limestone tailings, blast furnace slag, and high-calcium fly ash;

[0034] Among them, calcium carbide slag is the waste generated during the production of acetylene by calcium carbide hydrolysis; limestone tailings is the waste residue from limestone mining and beneficiation; blast furnace slag is the waste discharged from the blast furnace during pig iron smelting; high-calcium fly ash is a waste with a high calcium oxide content discharged from thermal power plants; and high-calcium solid waste can provide calcium oxide and / or calcium carbonate.

[0035] Optionally, the high-silica solid waste includes one or more of the following: coal gangue, silica fume, iron tailings, and low-calcium fly ash;

[0036] Among them, coal gangue is solid waste discharged during the coal mining and washing process; silica fume is an ultrafine powder produced when ferrosilicon plants smelt ferrosilicon alloys and industrial silicon; iron tailings is waste after mineral processing; low-calcium fly ash is a fine ash with low calcium oxide content collected from the flue gas after coal combustion; and high-silicon solid waste can contain silicon dioxide.

[0037] Optionally, the high-alumina solid waste includes one or more of sintered red mud and aluminum ash;

[0038] Among them, sintering red mud is a solid industrial waste residue discharged from the alkaline process for producing alumina, aluminum ash is a scum that floats on the aluminum liquid in the electrolytic cell during the aluminum electrolysis process, and high-alumina solid waste can provide alumina and / or aluminum hydroxide.

[0039] Optionally, the high-sulfur solid waste includes one or more of the following: desulfurized gypsum, phosphogypsum, fluorogypsum, and borosilicate.

[0040] Among them, desulfurization gypsum is an industrial by-product gypsum obtained by coal-fired or oil-fired industrial enterprises after treating sulfur dioxide in flue gas; phosphogypsum is an industrial by-product gypsum produced during the production of high-concentration phosphate compound fertilizer; fluoride gypsum is a by-product of producing hydrogen fluoride from sulfuric acid and fluorite; and boron gypsum is a by-product produced during the production of boric acid.

[0041] By controlling the molar ratios of CaO / (Fe2O+Al2O3+Na2O) and SiO2 / Na2O within appropriate ranges, it is possible to regulate the transformation of soluble alkalis (NaHCO3 and Na2CO3) in Bayer process red mud into a stable molten aluminoferrite phase during high-temperature calcination. Specifically, this is a novel mineral phase—calcium aluminoferrite (sodium aluminoferrite), ensuring that the aluminoferrite (referring to calcium aluminoferrite (sodium aluminoferrite)) content is not less than 25%, and that the octahedral [Fe2O3+Al2O3+Na2O] in the aluminoferrite phase is... 0.76 Al 0.24 O6] 9- and tetrahedron [Fe 0.24 Al 0.76 O4] 5-The resulting spatial structure can seal and solidify the structural alkali in the high-iron, high-alumina Bayer process red mud, consuming a large amount of the alkali in the Bayer process red mud. By controlling the mass ratio of Al2O3 / Fe2O3 and the mass ratio of SiO2 / (Fe2O+Al2O3) within appropriate ranges, the formation of aluminoferrates during the mineral phase synthesis process can be regulated. A small amount of Na oxide can improve the liquid phase environment during the formation of mineral phases in red mud-based aluminoferrate cement clinker, and can also act as a mineralizing agent to stabilize the coexistence of mineral phases in red mud-based calcium aluminoferrate cement clinker. Accordingly, the high-iron, high-alumina mineral phases in Bayer process red mud, together with other high-calcium, high-silica mineral phases, achieve mineral phase reconstruction during high-temperature solid-phase reaction, directionally synthesizing red mud-based aluminoferrate cement clinker, which can consume a large amount of highly alkaline red mud.

[0042] The above-mentioned method for preparing red mud-based aluminoferrite cement includes the following steps:

[0043] S1. High-calcium solid waste, high-silicon solid waste, high-alumina solid waste and Bayer process red mud are mixed and then ground, homogenized, sampled, calcined and cooled to produce red mud-based aluminoferrate cement clinker.

[0044] S2. Mix the red mud-based ferroaluminate cement clinker with the remaining high-alumina solid waste, high-calcium solid waste and high-sulfur solid waste, and grind them together to obtain red mud-based ferroaluminate cement.

[0045] Optionally, the mineral phase composition and volume fraction of the cement clinker obtained by calcination are: 40-60% dicalcium silicate, 25-40% aluminoferrite, 5-15% tricalcium aluminate and 5-15% tricalcium silicate; wherein the aluminoferrite has the chemical formula 7CaO·2Al2O3·2Fe2O3·NaO.

[0046] The XRD quantitative analysis results of typical red mud-based ferroaluminate cement clinker obtained are as follows: Figure 1 As shown;

[0047] The SEM-EDS results of typical red mud-based ferroaluminate cement clinker obtained are as follows: Figures 2-5 As shown;

[0048] The obtained crystal structure and cell parameters of sodium aluminoferrite phase are as follows: Figure 6 As shown.

[0049] Optionally, in S1, the sample preparation step includes: wetting the mixture and pressing it into a sample under a set pressure;

[0050] Preferably, the mixture is wetted to a moisture content of 15% and pressed into a cylindrical sample with a diameter of 5 cm and a height of 1 cm under a pressure of 1.5 MPa.

[0051] Optionally, in S1, the calcination temperature is 1220–1320℃, the holding time is 15–45 min, and the heating rate is 5–10℃ / min;

[0052] Preferably, the sample is placed in a lifting high-temperature furnace, the calcination temperature is 1260℃, the heating rate is 10℃ / min, the holding time is 30min, and the calcination atmosphere is air.

[0053] Optionally, the calcined sample can be cooled by water cooling to room temperature.

[0054] Optionally, in S2, the proportion of particles co-ground to a particle size of 150 mesh is 100%.

[0055] Optionally, sodium silicate powder additive is added to S2 to compensate for the weak activation ability of residual alkaline components in the red mud-based aluminoferrite cement system, and to synergistically activate the geopolymer mineral phase system to form clinker mineral phase-geolithic mineral phase multi-mineral phase synergistic cementation, thereby enhancing the workability of the material.

[0056] Red mud-based aluminoferrite cement, with calcium aluminoferrite (sodium aluminoferrite) and dicalcium silicate as the main minerals, exhibits good erosion and scour resistance. The erosion resistance of red mud-based aluminoferrite cement can be further improved by utilizing the inert alkaline components in Bayer process red mud, and the residual alkaline components can be used to synergistically activate the geopolymer mineral phase system, thereby enhancing the mechanical properties of the cement.

[0057] Example 1

[0058] The raw materials include the following components:

[0059] The Bayer process red mud was found to contain 36.42% Fe2O3, 27.38% Al2O3, and 12.90% Na2O by mass.

[0060] The calcium carbide slag was found to contain 92.11% CaO.

[0061] The silica fume was found to contain 95.25% SiO2.

[0062] Desulfurized gypsum;

[0063] Sintered red mud;

[0064] Blast furnace slag;

[0065] Sodium silicate.

[0066] The preparation method is as follows:

[0067] Bayer process red mud, carbide slag, and silica fume were mechanically ground and uniformly mixed to obtain a mixture with the following chemical composition: Al2O3 / Fe2O3 mass ratio of 0.81; SiO2 / (Fe2O+Al2O3) mass ratio of 1.19; CaO / (Fe2O+Al2O3+Na2O) molar ratio of 2.21; and SiO2 / Na2O molar ratio of 5.46.

[0068] The mixture was added to a ball mill for mechanical grinding and homogenization. The ball mill was filled with 40% steel balls, rotated at 35 rpm, had a ball-to-material mass ratio of 6:1, and was ground and homogenized for 10 minutes.

[0069] The homogenized mixture was wetted to a moisture content of 15%, and then pressed into a cylindrical sample with a diameter of 5 cm and a height of 1 cm under a pressure of 1.5 MPa.

[0070] The cylindrical sample was placed in a lifting high-temperature furnace, calcined at 1260℃, with a heating rate of 10℃ / min and a holding time of 30min. The calcination atmosphere was air.

[0071] The calcined sample was rapidly cooled to room temperature by water cooling and then ground to 150 mesh for sieving to obtain red mud-based ferroaluminate cement clinker powder.

[0072] The mixture will contain red mud-based ferroaluminate cement clinker powder, 8% (by mass) of desulfurized gypsum, 10% of sintered red mud, 10% of blast furnace slag and 1.2% of sodium silicate powder, and will be blended to obtain 100% red mud-based ferroaluminate cement.

[0073] The red mud-based sodium aluminate (sodium) calcium cement prepared in Example 1 was treated with an extract according to the "Analysis of Water-Soluble Salts in Forest Soils" (LY / T 1251-1999), and the cement paste with a water-cement ratio of 0.48 was soaked in water for 7 days. The content of free alkali in the extract was found to be 0, indicating a significant effect of alkali fixation. The mechanical properties of the red mud-based sodium aluminate (sodium) calcium cement mortar prepared in this example were tested according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The chloride resistance of the red mud-based sodium aluminate (sodium) calcium cement prepared in this example was tested according to JC / T1086-2008 "Test Method for Chloride Ion Diffusion Coefficient of Cement". The frost resistance and electrical conductivity of the red mud-based sodium aluminate (sodium) calcium cement prepared in this example were tested according to GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete".

[0074] Example 2

[0075] Compared with Example 1, no high-sulfur solid waste was added, and the preparation method was the same as in Example 1.

[0076] Example 3

[0077] Compared with Example 1, the mass ratio of Al2O3 / Fe2O3 was 0.65; the mass ratio of SiO2 / (Fe2O+Al2O3) was 1.10; the molar ratio of CaO / (Fe2O+Al2O3+Na2O) was 1.98; the molar ratio of SiO2 / Na2O was 4.20, and the preparation method was the same as in Example 1.

[0078] Example 4

[0079] Compared with Example 1, the mass ratio of Al2O3 / Fe2O3 was 0.85; the mass ratio of SiO2 / (Fe2O+Al2O3) was 1.30; the molar ratio of CaO / (Fe2O+Al2O3+Na2O) was 2.30; the molar ratio of SiO2 / Na2O was 8, and the preparation method was the same as in Example 1.

[0080] Example 5

[0081] Compared to Example 1, no sodium silicate powder was added.

[0082] Comparative Example 1

[0083] This comparative example uses commercially available aluminoferrite cement.

[0084] Comparative Example 2

[0085] Compared with Example 1, the molar ratio of CaO / (Fe2O+Al2O3+Na2O) in this comparative example is 1.0, which is insufficient to generate a sufficient amount of aluminoferrite phase.

[0086] Each embodiment underwent the same performance testing as in Embodiment 1, and the test results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As can be seen from Table 1, the red mud-based calcium aluminoferrite (sodium) calcium cement prepared by this invention has significantly higher erosion resistance than traditional aluminoferrite cement, and all other properties meet the requirements of the corresponding standard indicators.

[0090] Furthermore, the XRD quantitative analysis results of the red mud-based aluminoferrate cement clinker obtained in Example 1 are as follows: Figure 1 As shown, the mineral phase composition of red mud-based aluminoferrite cement clinker mainly consists of silicate phase, aluminate phase, and aluminoferrite phase. Among them, the content of tetracalcium aluminoferrite is as high as 30.27%, which is much higher than that of traditional silicate cement clinker (the content of aluminoferrite phase is 5-15%).

[0091] The SEM-EDS results of the red mud-based aluminoferrate cement clinker obtained in Example 1 are as follows: Figures 2-5 As shown, it can be seen that Figure 2 The microstructure of the mineral phases in red mud-based aluminoferrite cement clinker is shown, exhibiting platy, granular, and columnar mineral structures filling the voids in a pebble-like structure of varying sizes. Points 1 to 4 represent... Figure 5 Sampling locations for Parts 1-4; Figure 3 The distribution of mineral phase elements in red mud-based aluminoferrite cement clinker shows that Si and Ca elements are mainly distributed in the pebble-like structure region, while Fe and Al elements are distributed between the pebble-like structures, indicating that the pebble-like structure is a silicate phase, and the platy, granular, and columnar minerals in the gaps are aluminoferrite phases. Figure 4 This indicates the overall distribution of elemental content in clinker; Figure 5 The table shows the mineral phase composition in the clinker. It can be seen that the mineral phase at points 1-2 is silicate phase, and the mineral phase at points 3-4 is aluminoferrite phase.

[0092] The crystal structure of sodium aluminoferrite (sodium aluminoferrite) phase obtained in Example 1 is as follows: Figure 6 As shown, the green, red, silver-gray, purple, and brown spheres represent Na, O, Ca, Al, and Fe atoms, respectively. The unit cell parameters are shown in Table 2. It can be seen that the atomic structure of calcium aluminoferrite (sodium) obtained in Example 1 belongs to the orthorhombic crystal system space group Ibm2. One Ca atom is replaced by a Na atom. The unit cell parameters, space group symmetry, volume, and density are in very good agreement with the experimental data of calcium aluminoferrite (sodium).

[0093] Table 2

[0094]

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A red mud-based aluminoferrite cement, characterized in that, The raw materials consist of the following components in parts by weight: 50-60 parts of high-calcium solid waste, 15-25 parts of high-silicon solid waste, 10-25 parts of high-alumina solid waste, 20-40 parts of Bayer process red mud, and 0-10 parts of high-sulfur solid waste; The chemical composition satisfies the following conditions: the mass ratio of Al2O3 to Fe2O3 is 0.65 to 0.85, the mass ratio of SiO2 to (Fe2O3+Al2O3) is 1.1 to 1.3, the molar ratio of CaO to Fe2O3+Al2O3+Na2O is 1.98 to 2.3, and the molar ratio of SiO2 to Na2O is 4.2 to 8. The ferroaluminate content in red mud-based ferroaluminate cement shall not be less than 25%.

2. The red mud-based aluminoferrate cement as described in claim 1, characterized in that, The chemical composition satisfies the following conditions: the mass ratio of Al2O3 to Fe2O3 is 0.81; the mass ratio of SiO2 to (Fe2O+Al2O3) is 1.19; the molar ratio of CaO to Fe2O+Al2O3+Na2O is 2.21; and the molar ratio of SiO2 to Na2O is 5.

46.

3. The red mud-based aluminoferrate cement as described in claim 1 or 2, characterized in that, The high-calcium solid waste includes one or more of the following: carbide slag, limestone tailings, blast furnace slag, and high-calcium fly ash.

4. The red mud-based aluminoferrate cement as described in claim 1 or 2, characterized in that, The high-silica solid waste includes one or more of the following: coal gangue, silica fume, iron tailings, and low-calcium fly ash.

5. The red mud-based aluminoferrate cement as described in claim 1 or 2, characterized in that, The high-alumina solid waste includes one or more of sintered red mud and aluminum ash.

6. The red mud-based aluminoferrate cement as described in claim 1 or 2, characterized in that, The high-sulfur solid waste includes one or more of the following: desulfurized gypsum, phosphogypsum, fluorogypsum, and borosilicate.

7. A method for preparing red mud-based aluminoferrate cement as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. High-calcium solid waste, high-silicon solid waste, high-alumina solid waste and Bayer process red mud are mixed and then ground, homogenized, sampled, calcined and cooled to produce red mud-based aluminoferrate cement clinker. S2. Mix the red mud-based ferroaluminate cement clinker with the remaining high-alumina solid waste, high-calcium solid waste and high-sulfur solid waste, and grind them together to obtain red mud-based ferroaluminate cement. The mineral phase composition and volume ratio of the cement clinker obtained by calcination are: 40-60% dicalcium silicate, 25-40% aluminoferrite, 5-15% tricalcium aluminate and 5-15% tricalcium silicate; the chemical formula of the aluminoferrite is 7CaO•2Al2O3•2Fe2O3•Na2O.

8. The method for preparing red mud-based aluminoferrate cement as described in claim 7, characterized in that, In S1, the sample preparation steps include: wetting the mixture and pressing it into a sample under a set pressure.

9. The method for preparing red mud-based aluminoferrate cement as described in claim 8, characterized in that, The mixture was wetted to a moisture content of 15% and pressed into a cylindrical sample with a diameter of 5 cm and a height of 1 cm under a pressure of 1.5 MPa.

10. The method for preparing red mud-based aluminoferrate cement as described in claim 7, characterized in that, In S1, the calcination temperature is 1220~1320℃, the holding time is 15~45min, and the heating rate is 5~10℃ / min.

11. The method for preparing red mud-based aluminoferrate cement as described in claim 10, characterized in that, The sample was placed in a lifting high-temperature furnace, calcined at 1260 ℃, with a heating rate of 10 ℃ / min and a holding time of 30 min. The calcination atmosphere was air.

12. The method for preparing red mud-based aluminoferrate cement as described in claim 8, characterized in that, In S2, the proportion of particles ground to a particle size of 150 mesh is 100%. Sodium silicate powder additive is added to S2.

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