A paste filling material

Abstract

The application relates to a paste filling material, raw material components of the paste filling material comprising: a red mud-based active material, a first red mud, a pumping agent and a stabilizer; wherein the red mud-based active material is obtained by sintering of dealkalization red mud and industrial by-product gypsum, raw material components of the dealkalization red mud comprising a second red mud and calcium oxide-rich slag. The application converts the red mud into the paste filling material through two-stage utilization, has the advantages of simple process and low cost, and has excellent performances such as good fluidity, high mechanical strength and slight expansion, reaches the performance requirements of the mine filling material, and realizes high-content utilization of the red mud in the filling material field.

Description

Technical Field

[0001] This application relates to the field of comprehensive utilization technology of industrial solid waste, and in particular to a paste filling material. Background Technology

[0002] Red mud is a solid waste generated during the alumina production process. Due to its strong alkalinity, fine particle size, high viscosity, and complex composition, red mud is difficult to utilize as a resource. Red mud stockpiling not only occupies large amounts of land but also easily causes environmental pollution and poses safety hazards. Currently, using red mud to prepare mine backfill materials can significantly reduce backfilling costs and improve economic efficiency.

[0003] However, the amount of red mud added is small, and cement needs to be used as a binder. At the same time, a large amount of solid waste such as fly ash and coal gangue are used. Summary of the Invention

[0004] This application provides a paste-filling material to address the technical problem of low utilization rate of existing red mud.

[0005] In a first aspect, this application provides a paste-filling material, wherein the raw material components of the paste-filling material include:

[0006] Red mud-based active materials, first red mud, pumping agents, and stabilizers; among which...

[0007] The red mud-based active material is obtained by sintering dealkalized red mud with industrial by-product gypsum.

[0008] The raw material components of the dealkalized red mud include second red mud and slag rich in calcium oxide.

[0009] Optionally, the industrial by-product gypsum includes at least one of the following: desulfurized gypsum, phosphogypsum, and citric acid gypsum.

[0010] Optionally, the pumping agent includes at least one of the following: naphthalene-based water-reducing agent, lignin sulfonate water-reducing agent, and aminosulfonate water-reducing agent.

[0011] Optionally, the stabilizer includes at least one of the following: aluminum silicate, sodium silicate, magnesium silicate, and magnesium aluminum silicate.

[0012] Optionally, the weight ratio of the red mud-based active material to the first red mud is (1-2):(8-9).

[0013] Optionally, relative to 1 total part by weight of the red mud-based active material and the first red mud, the pumping agent is 0.005 parts by weight to 0.01 parts by weight, and the stabilizer is 0.005 parts by weight to 0.015 parts by weight.

[0014] Optionally, the weight ratio of the dealkalized red mud to the industrial by-product gypsum is 1:(0.1-0.2).

[0015] Optionally, the calcium oxide-rich slag material includes at least one of the following: lime or carbide slag.

[0016] Optionally, the weight ratio of the second red mud to the calcium oxide-rich slag is 1:(0.2 to 0.4).

[0017] Optionally, the sintering process parameters include: a temperature of 1100℃~1250℃ and a time of 0.5h~2.5h.

[0018] The technical solutions provided in this application have the following advantages compared with the prior art:

[0019] The paste-like filling material provided in this application embodiment comprises dealkalized red mud with raw material components including calcium oxide-rich slag and industrial by-product gypsum containing a large amount of calcium sulfate. The dealkalized red mud and industrial by-product gypsum are sintered to generate red mud-based active material. This red mud-based active material contains various composite cementitious mineral phases, including dicalcium silicate, calcium sulfoaluminate, calcium aluminoferrite, calcium aluminosilicate, and calcium aluminate. Simultaneously, the red mud-based active material contains amorphous active alumina and silica components. These beneficial components are further mixed with the red mud, promoting the formation of multi-component cementitious bodies. Furthermore, the sodium oxide in the red mud further activates the amorphous active alumina and silica, forming a stable sodium-containing zeolite structure, thus solidifying and sealing sodium ions in the red mud. The red mud-based active material and red mud form a multi-component composite cementitious mineral phase with a dense network structure, improving the mechanical strength of the filling material and giving it excellent high strength and micro-expansion properties. It also effectively solidifies and seals heavy metal ions in the red mud. Meanwhile, the pumping agent gives the paste filling material a certain degree of fluidity, and the stabilizer ensures that the particles of the paste filling material are in full contact and react, thereby improving the mechanical strength, durability and erosion resistance of the paste filling material. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the preparation process of a paste filling material provided in an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0025] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] Firstly, this application provides a paste-like filling material, please refer to [link to relevant documentation]. Figure 1 The raw material components of the paste filling material include:

[0028] Red mud-based active materials, first red mud, pumping agents, and stabilizers; among which...

[0029] The red mud-based active material is obtained by sintering dealkalized red mud with industrial by-product gypsum.

[0030] The raw material components of the dealkalized red mud include second red mud and slag rich in calcium oxide.

[0031] In some embodiments, the industrial by-product gypsum includes at least one of the following: desulfurized gypsum, phosphogypsum, and citric acid gypsum.

[0032] In the embodiments of this application, desulfurized gypsum, phosphogypsum, and citric acid gypsum contain a large amount of calcium sulfate, which sinters with dealkali-treated red mud to generate red mud-based active materials.

[0033] In some embodiments, the pumping agent includes at least one of the following: naphthalene-based water-reducing agent, lignin sulfonate water-reducing agent, and aminosulfonate water-reducing agent.

[0034] In the embodiments of this application, the above-mentioned pumping agents are all anionic, which have dispersing, air-entraining and initial hydration-inhibiting effects, and lubrication between particles. They can effectively improve the fluidity of paste filling materials and improve pumping effect.

[0035] In some embodiments, the stabilizer includes at least one of the following: aluminum silicate, sodium silicate, magnesium silicate, and magnesium aluminum silicate.

[0036] In the embodiments of this application, the stabilizer can be uniformly dispersed and filled in the pores of the filling material to form a stable grid structure, which can enhance the curing and sealing effect of heavy metal ions and fluoride ions, effectively reduce the shrinkage and cracking of the filling material, improve the later strength of the filling material, and improve the compactness, durability and crack resistance of the filling material.

[0037] In some embodiments, the weight ratio of the red mud-based active material to the first red mud is (1-2):(8-9).

[0038] In this embodiment, while meeting the requirements for mechanical strength and other indicators of the red mud-based paste filling, the amount of red mud-based active material used is minimized to reduce the cost of the paste filling material. If the amount of the first red mud is too high or the amount of the red mud-based active material is too low, the mechanical strength of the filling material may be poor; conversely, if the amount of the first red mud is too low or the amount of the red mud-based active material is too high, the cost of the filling material may increase. Specifically, the weight ratio of the red mud-based active material to the first red mud is 1:9, 2:8, 1.5:8.5, etc. Furthermore, generally, the moisture content of the red mud-based active material is controlled to be <3%; the moisture content of the red mud produced by pressure filtration is around 30%, and the above-mentioned red mud usage is calculated on an absolute dry basis.

[0039] In some embodiments, the pumping agent is 0.005 to 0.01 parts by weight relative to 1 total part by weight of the red mud-based active material and the first red mud, and the stabilizer is 0.005 to 0.015 parts by weight.

[0040] In this embodiment, the pumping agent improves the flowability of the paste filling material, ensuring the pumping effect during the filling process. Excessive use of the pumping agent may lead to higher costs, and although the flowability is significantly improved, the compressive strength may decrease considerably in the later stages; insufficient use of the pumping agent may result in poor flowability. The stabilizer improves the suspension and dispersion of particles in the slurry, ensuring sufficient contact and reaction between the paste filling material particles, thereby improving the mechanical strength, durability, and erosion resistance of the paste filling material. Excessive use of the stabilizer may lead to higher costs; insufficient use of the stabilizer may result in unstable compressive strength and large fluctuations in the later stages. Specifically, the pumping agent can be 0.005 parts by weight, 0.006 parts by weight, 0.007 parts by weight, 0.008 parts by weight, 0.009 parts by weight, 0.01 parts by weight, etc., and the pumping agent can be 0.005 parts by weight, 0.007 parts by weight, 0.009 parts by weight, 0.011 parts by weight, 0.013 parts by weight, 0.015 parts by weight, etc.

[0041] In some embodiments, the weight ratio of the dealkalized red mud to the industrial by-product gypsum is 1:(0.1-0.2).

[0042] In this embodiment, the addition of desulfurized gypsum mainly regulates the formation of a stable calcium sulfoaluminate (3CaO·3Al2O3·CaSO4) mineral phase by reacting calcium sulfate with alumina and calcium oxide. Excessive use of this industrial by-product gypsum can lead to a large surplus of calcium sulfate, delaying the setting time of the red mud-based active material. Conversely, insufficient use can result in a low amount of calcium sulfoaluminate mineral phase, negatively impacting the early strength of the paste filling material. Specifically, the weight ratio of the dealkalized red mud to the industrial by-product gypsum can be 1:0.1, 1:0.2, 1:0.15, etc.

[0043] In some embodiments, the calcium oxide-rich slag material includes at least one of the following: lime or carbide slag.

[0044] In the embodiments of this application, lime and carbide slag are rich in calcium oxide, providing a calcium source.

[0045] In some embodiments, the weight ratio of the second red mud to the calcium oxide-rich slag is 1:(0.2 to 0.4).

[0046] In this embodiment, while ensuring sufficient dealkali removal of the second red mud, it is also ensured that the mineral phase of the calcined red mud-based active powder material is stable and the compressive strength of the paste filling material meets the requirements. If the amount of the calcium oxide-rich slag is too large, it will, to some extent, change the mineral phase composition of dicalcium silicate, calcium sulfoaluminate, calcium aluminoferrite, calcium aluminosilicate, and calcium aluminate in the red mud-based active material. In addition, a large amount of unreacted calcium oxide will exist in the red mud-based active material, resulting in a decrease in the compressive strength of the paste filling material. If the amount of the calcium oxide-rich slag is too small, it will, to some extent, lead to incomplete dealkali removal of the red mud, making it difficult to form the mineral phase composition of dicalcium silicate, calcium sulfoaluminate, calcium aluminoferrite, calcium aluminosilicate, and calcium aluminate in the red mud-based active material, thus failing to achieve good cementing properties. Specifically, the weight ratio of the second red mud to the calcium oxide-rich slag can be 1:0.2, 1:0.3, 1:0.4, etc.

[0047] In some embodiments, the sintering process parameters include: a temperature of 1100℃~1250℃ and a time of 0.5h~2.5h.

[0048] In the embodiments of this application, a suitable sintering process is beneficial to the formation of composite cementitious mineral phases in red mud-based active materials. If the sintering temperature is too low or the time is too short, the amount of composite cementitious mineral phases formed in the red mud-based active materials may be reduced, resulting in incomplete sintering. If the sintering temperature is too high or the time is too long, the clinker may become molten, the material may become sticky and hard, making it difficult to discharge and grind, thus increasing production energy consumption. Specifically, the temperature can be 1100℃, 1150℃, 1200℃, 1250℃, etc., and the time can be 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, etc.

[0049] Furthermore, both the first and second red mud can be Bayer process red mud or sintering process red mud. The particle size of the dealkali-treated red mud, industrial by-product gypsum, and red mud-based active materials is <80µm. Excessively large particle size may reduce the specific surface area of ​​the active powder, hindering its hydration reaction and affecting the strength of the paste filling material. Generally, the moisture content of the aforementioned dealkali-treated red mud is controlled at <5%, and the moisture content of the aforementioned desulfurized gypsum is controlled at <5%. The aforementioned paste filling material also contains water, with a mass concentration of 55%–65%. During the hydration process, this paste filling material produces hydration products such as hydrated calcium silicate (CSH), hydrated calcium aluminosilicate (CASH), ettringite (AFt), hydrated calcium aluminoferrite (CAFH), and hydrated calcium aluminate (CAH), which improve the strength of the paste filling material and ensure its strength and fluidity.

[0050] In the embodiments of this application, the initial flowability of the above-mentioned paste-like backfill material reaches over 300 mm, the flowability is maintained at over 280 mm after 30 minutes, the 3-day compressive strength is greater than 2.0 MPa, the 7-day compressive strength is greater than 3.0 MPa, and the 28-day compressive strength reaches over 3.5 MPa. The concentrations of heavy metals and fluorides in the leachate of the paste-like backfill material are far lower than the Class III water index of the "Groundwater Quality Standard" (GB14848-2017). This paste-like backfill material not only meets the performance and mechanical strength requirements of mine backfilling operations, but also complies with environmental leaching index requirements, solving the problem of low red mud usage in current mine backfilling and realizing high-volume utilization of red mud in mine backfilling materials.

[0051] The above-mentioned paste filling material does not require additional cement or other cementing materials, nor does it require the addition of large amounts of fly ash, slag, coal gangue, or other solid waste. Through two-stage utilization, red mud is converted into paste filling material, which has the advantages of simple process and low cost, as well as excellent properties such as good fluidity, high mechanical strength, and micro-expansion. It meets the performance requirements of mine filling materials and realizes high-volume utilization of red mud in the field of filling materials, with the comprehensive utilization of red mud reaching more than 85%.

[0052] In addition, please see Figure 1The method for preparing the paste filling material shown includes: S1, dealkalizing the first red mud with calcium oxide-containing slag to obtain dealkalized red mud;

[0053] Specifically, the red mud slurry is heated and stirred to remove alkali by adding slag rich in calcium oxide, and then dewatered by pressure filtration to obtain dealkali-removed red mud;

[0054] Adding calcium oxide-rich slag enhances the exchange capacity of Ca. 2+ Displaces some exchangeable Na + This process involves adding lime to convert the lime into soluble sodium, thus achieving dealkalization. For example, the alkali in red mud is mainly in the form of bound alkali existing as sodium silicate slag. Adding lime under hydrothermal conditions can convert the sodium silicate slag in the red mud into calcium silicate slag, allowing the Na₂O in the sodium silicate slag to enter the solution, achieving dealkalization. This step is to account for the need to add calcium oxide as a calcium source for the clinker later, so adding it in advance also helps with dealkalization and avoids the high alkali content in the red mud affecting the performance of the red mud-based active powder. The temperature for the above stirring and heating dealkalization is 80℃~95℃, and the time is 2h~10h, so that heating promotes the dissolution of lime and improves the dealkalization efficiency.

[0055] S2. The dealkalized red mud is sintered with industrial by-product gypsum to obtain red mud-based active material;

[0056] Specifically, dealkali-treated red mud is mixed and ground with industrial by-product gypsum. The ground and mixed raw material is then sintered at high temperature. The sintered high-temperature clinker is cooled and then ground to obtain red mud-based active material.

[0057] Red mud contains silicon dioxide, aluminum oxide, and iron oxide. The addition of calcium oxide-rich slag in the early stage, and the subsequent addition of industrial by-product gypsum, supplements the calcium oxide and calcium sulfate components. When compounded with dealkalized red mud and sintered at high temperature, it generates a variety of composite cementitious mineral phases, including dicalcium silicate, calcium sulfoaluminate, calcium aluminoferrite, calcium aluminosilicate, and calcium aluminate. These mineral phases have cementing properties and can contribute to the strength of paste filling materials.

[0058] S3. The red mud-based active material is mixed with the second red mud, pumping agent and stabilizer to form a paste filling material.

[0059] Specifically, the second red mud is mixed with red mud-based active materials, pumping agents and stabilizers according to the specified ratio, and water is added and stirred evenly to form a paste filling material.

[0060] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0061] Example 1

[0062] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, naphthalene-based water-reducing agent and magnesium aluminum silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0063] Preparation of paste filling material: Lime at 38% of the solid mass of Bayer process red mud was added to the Bayer process red mud slurry (mass concentration 50%), and then stirred and heated at 85℃ for 2 hours. The stirred dealkali-treated red mud slurry was then dehydrated by pressure filtration and dried to obtain dried dealkali-treated red mud. Dried desulfurized gypsum at 17% of the mass of the dried dealkali-treated red mud was mixed and ground to a particle size <80μm. The ground mixture was added to a rotary kiln for high-temperature sintering at 1180℃ for 1.5 hours. After cooling, the sintered high-temperature clinker was ground to a particle size <80μm to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, naphthalene-based water-reducing agent, and magnesium aluminum silicate were mixed with water in a ratio of 85:15:0.5:1.5 to form a slurry with a mass concentration of 58%, thus obtaining red mud-based filling paste material.

[0064] Comparative Example 1

[0065] The amount of lime added in Example 1 was changed to 15%, and the rest was the same as in Example 1.

[0066] Example 2

[0067] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, aminosulfonate water-reducing agent and aluminum silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0068] Preparation of paste filling material: Lime at 20% of the weight of Bayer process red mud solids was added to the Bayer process red mud slurry (weight concentration 50%), and then stirred and heated at 95℃ for 4 hours. The stirred dealkali-treated red mud slurry was then dehydrated by pressure filtration and dried to obtain dried dealkali-treated red mud. 20% of the weight of the dried dealkali-treated red mud was mixed with dried desulfurized gypsum and ground to a particle size <80μm. The ground mixture was added to a rotary kiln for high-temperature sintering at 1250℃ for 0.5 hours. After cooling, the sintered high-temperature clinker was ground to a particle size <80μm to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, aminosulfonate water-reducing agent, and aluminum silicate were mixed with water in a ratio of 80:20:0.7:1.2 to form a slurry with a mass concentration of 54%, thus obtaining red mud-based filling paste material.

[0069] Comparative Example 2

[0070] The amount of desulfurized gypsum added in Example 2 was changed to 25%, and the rest was the same as in Example 2.

[0071] Example 3

[0072] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, lignin sulfonate water-reducing agent and magnesium silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0073] Preparation of paste filling material: Lime at 26% of the solid mass of Bayer process red mud was added to the Bayer process red mud slurry (mass concentration 50%), and then stirred and heated at 90℃ for 5 hours. The stirred dealkali-treated red mud slurry was then dehydrated by pressure filtration and dried to obtain dried dealkali-treated red mud. Dried desulfurized gypsum at 19% of the mass of the dried dealkali-treated red mud was mixed and ground to a particle size <80μm. The ground mixture was added to a rotary kiln for high-temperature sintering at 1230℃ for 1 hour. After cooling, the sintered high-temperature clinker was ground to a particle size <80μm to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, lignin sulfonate water-reducing agent, and magnesium silicate were mixed with water in a ratio of 90:10:1:0.8 to form a slurry with a mass concentration of 50%, thus obtaining red mud-based filling paste material.

[0074] Comparative Example 3

[0075] In Example 2, the ratio of Bayer red mud to red mud-based active gelling powder, lignin sulfonate water-reducing agent, and magnesium silicate was changed to 95:5:1:0.8, while the rest remained the same as in Example 3.

[0076] Example 4

[0077] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, naphthalene-based water-reducing agent, lignin sulfonate water-reducing agent, sodium silicate, and magnesium aluminum silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0078] Preparation of paste filling material: Lime at 40% (by weight of the solids in Bayer process red mud) is added to the Bayer process red mud slurry (50% by weight concentration). The mixture is then stirred and heated at 88°C for 10 hours. The resulting dealkali-treated red mud slurry is dewatered by pressure filtration and then dried to obtain dried dealkali-treated red mud. Dried desulfurized gypsum at 15% (by weight of the dried dealkali-treated red mud) is mixed with the dried dealkali-treated red mud and ground to a particle size <80 μm. The ground mixture is then added to a rotary kiln for high-temperature sintering. The temperature was 1100℃, the sintering time was 2.5h, and the sintered high-temperature clinker was cooled and then ground to a particle size of <80um to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, naphthalene-based water-reducing agent, lignin sulfonate water-reducing agent, sodium silicate, and magnesium aluminum silicate were mixed with water in a ratio of 86:14:0.45:0.45:0.25:0.25 to form a slurry with a mass concentration of 53% to obtain red mud-based filling paste material.

[0079] Comparative Example 4

[0080] The difference from Example 4 is that no pumping agent is added; otherwise, it is the same as Example 4.

[0081] Example 5

[0082] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, naphthalene-based water-reducing agent and magnesium aluminum silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0083] Preparation of paste filling material: Lime at 30% of the weight of Bayer process red mud solids was added to the Bayer process red mud slurry (weight concentration 50%), and then stirred and heated at 80℃ for 7 hours. The stirred dealkali-treated red mud slurry was then dehydrated by pressure filtration and dried to obtain dried dealkali-treated red mud. 10% of the weight of the dried dealkali-treated red mud was mixed with dried desulfurized gypsum and ground to a particle size <80μm. The ground mixture was added to a rotary kiln for high-temperature sintering at 1150℃ for 2 hours. After cooling, the sintered high-temperature clinker was ground to a particle size <80μm to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, naphthalene-based water-reducing agent, and magnesium aluminum silicate were mixed with water in a ratio of 82:18:0.6:1 to form a slurry with a mass concentration of 65%, thus obtaining red mud-based filling paste material.

[0084] Comparative Example 5

[0085] The difference from Example 5 is that no stabilizer is added; otherwise, it is the same as Example 5.

[0086] Example 6

[0087] The raw material components of the paste filling material are: red mud-based active material, first Bayer process red mud, naphthalene-based water-reducing agent and magnesium aluminum silicate; wherein, the above-mentioned red mud-based active material is obtained by sintering dealkalized red mud and desulfurized gypsum, and the raw material components of the above-mentioned dealkalized red mud include second Bayer process red mud and lime.

[0088] Preparation of paste filling material: Lime at 32% of the solid mass of Bayer process red mud was added to the Bayer process red mud slurry (mass concentration 50%), and then stirred and heated at 83℃ for 8 hours. The stirred dealkali-treated red mud slurry was then dehydrated by pressure filtration and dried to obtain dried dealkali-treated red mud. 13% of the dry dealkali-treated red mud mass of dried desulfurized gypsum was mixed with the dried dealkali-treated red mud and ground to a particle size <80μm. The ground mixture was added to a rotary kiln for high-temperature sintering at 1200℃ for 1 hour. After cooling, the sintered high-temperature clinker was ground to a particle size <80μm to obtain red mud-based active gelling powder. Bayer process red mud, red mud-based active gelling powder, naphthalene-based water-reducing agent, and magnesium aluminum silicate were mixed with water in a ratio of 88:12:0.8:0.9 to form a slurry with a mass concentration of 62%, thus obtaining red mud-based filling paste material.

[0089] The performance of the red mud-based filling paste prepared according to the above embodiments was tested. The fluidity was tested using a fluidity tester according to the "Test Method for Performance of Ordinary Concrete Mixtures" (GB / T50080-2016); the vertical expansion rate was determined according to the method for vertical expansion rate of grouting expansive mortar in Appendix C of the "Technical Specification for Application of Concrete Admixtures" (GB50119-2013).

[0090] The filling paste slurry was poured into a standard triple mold (70.7mm × 70.7mm × 70.7mm) to prepare test blocks. The test blocks were placed at room temperature (20±2℃) for 24 hours before demolding and placed in a standard cement curing chamber (temperature set at 20℃, relative humidity at 90%) for curing to the specified age for compressive strength testing. The toxicity leachate was prepared from the 28-day-cured test blocks according to the requirements of "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJT299-2007). The heavy metal concentration in the leachate was detected using inductively coupled plasma mass spectrometry (ICP-MS) as described in "Determination of Metal Elements in Solid Waste" (HJ766-2015). Specifically, please refer to Table 1 for the performance test results of the red mud-based paste filling material, and Table 2 for the results.

[0091] The results of the test for harmful factors in the leachate of the red mud-based paste filling material are shown.

[0092] Table 1 Performance test results of red mud-based paste filling materials

[0093]

[0094] Table 2. Test results of harmful factors in leachate of red mud-based paste filling materials.

[0095]

[0096] The test results above show that the red mud-based backfill paste material prepared in this application embodiment has an initial flowability of over 300 mm and retains a flowability of over 280 mm after 30 minutes, meeting the flowability requirements for mine backfilling operations. The 3-day compressive strength of the paste backfill material is greater than 2 MPa, the 7-day compressive strength is greater than 3 MPa, and the 28-day compressive strength is greater than 3.5 MPa, fully meeting the strength requirements for backfilling goaf areas in mines. Furthermore, the paste backfill material in this application embodiment has a micro-expansion characteristic, which can improve the automatic roof support capability of the backfill material and improve the backfilling effect. The concentrations of heavy metals and fluorides in the leachate of the red mud-based paste backfill material in this application embodiment are far lower than the Class III water index of the "Groundwater Quality Standard" (GB14848-2017), meeting the environmental protection indicators for backfilling goaf areas in mines. The method for preparing red mud-based backfill paste material in this application not only realizes the large-scale disposal and utilization of red mud solid waste and solves the ecological and environmental hazards caused by red mud, but also solves the problem that mine backfilling requires the consumption of a large amount of cementing materials and solid waste, and realizes the economical and rational large-scale utilization of solid waste resources.

[0097] Comparative Example 1 showed that due to the reduction in lime content, the compressive strength of the filling paste material at different ages was significantly reduced, with a 3-day compressive strength of only 1.39 MPa, a 7-day compressive strength of 1.58 MPa, and a 28-day compressive strength of 1.69 MPa. The concentrations of heavy metal ions and fluoride ions in the leachate of the filling paste material increased.

[0098] Comparative Example 2 increased the amount of desulfurized gypsum, which led to a significant decrease in the compressive strength of the filling paste material at different ages. The 3-day compressive strength was only 1.52 MPa, the 7-day compressive strength was 1.76 MPa, and the 28-day compressive strength was 1.85 MPa. The concentration of heavy metal ions and fluoride ions in the leachate of the filling paste material increased.

[0099] Comparative Example 3 reduced the amount of red mud-based active gelling powder, resulting in a significant decrease in the compressive strength of the filling paste material at different ages. The 3-day compressive strength was only 1.81 MPa, the 7-day compressive strength was 1.92 MPa, and the 28-day compressive strength was 2.06 MPa. The concentrations of heavy metal ions and fluoride ions in the leachate of the filling paste material increased.

[0100] Comparative Example 4 omitted the addition of pumping agent, resulting in an initial flowability of only 255 mm and a 30-minute flowability of only 232 mm for the filling paste material, which could not meet the requirements for pumping filling in mines.

[0101] Comparative Example 5 omitted the addition of stabilizers, resulting in a smaller increase in the compressive strength of the filling paste material from 7 days to 28 days, and also a significant increase in the concentration of heavy metal ions and fluoride ions in the leachate of the filling paste material.

[0102] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A paste-like filling material, characterized in that, The raw material components of the paste filling material include: Red mud-based active materials, first red mud, pumping agents, and stabilizers; among which... The red mud-based active material is obtained by sintering dealkalized red mud with industrial by-product gypsum at a temperature of 1100℃~1250℃ for 0.5h~2.5h. The dealkali-removed red mud is obtained by adding calcium oxide-rich slag to the second red mud slurry, heating and stirring to remove alkali, and then dewatering by pressure filtration. The dealkali removal temperature is 80℃~95℃ and the time is 2h~10h. The weight ratio of the red mud-based active material to the first red mud is (1~2):(8~9); Relative to 1 total part by weight of the red mud-based active material and the first red mud, the pumping agent is 0.005 parts by weight to 0.01 parts by weight, and the stabilizer is 0.005 parts by weight to 0.015 parts by weight; The weight ratio of the dealkalized red mud to the industrial by-product gypsum is 1:(0.1~0.2); The weight ratio of the second red mud slurry to the calcium oxide-rich slag is 1:(0.2~0.4); The particle size of the dealkalized red mud, industrial by-product gypsum, and red mud-based active materials is <80µm. The paste filling material does not contain cement as a binder.

2. The paste-filling material according to claim 1, characterized in that, The industrial by-product gypsum includes at least one of the following: desulfurized gypsum, phosphogypsum, and citric acid gypsum.

3. The paste-filling material according to claim 1, characterized in that, The pumping agent includes at least one of the following: naphthalene-based water-reducing agent, lignin sulfonate water-reducing agent, and aminosulfonate water-reducing agent.

4. The paste-filling material according to claim 1, characterized in that, The stabilizer includes at least one of the following: aluminum silicate, sodium silicate, magnesium silicate, and magnesium aluminum silicate.

5. The paste-filling material according to claim 1, characterized in that, The calcium oxide-rich slag material includes at least one of the following: lime and carbide slag.

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