Anti-erosion multi-element solid waste synergistic red mud-based filling material and preparation method thereof

Abstract

The invention discloses an anti-erosion multi-element solid waste synergistic red mud-based filling material and a preparation method thereof. The filling material is prepared from the following components in parts by weight: 60 to 80 parts of red mud, 18 to 30 parts of fly ash, 3 to 9 parts of desulfurized gypsum, 3 parts of cement, 0.3 to 0.7 part of water reducing agent, 0.3 to 0.9 part of fiber and 27 to 30 parts of water. Red mud is used for supporting a framework, an alkaline environment is provided, and Si-O and Al-O bond fracture is promoted. The fly ash provides active Al2O3 and SiO2 to promote the generation of C-(A)-S-H gel, so that the material has better mechanical properties. The desulfurized gypsum is used as sulfate solid waste, and Ca < 2 + > and SO4 < 2-> are provided to promote the formation of ettringite and fill internal pores. In addition, a small amount of admixture is used, the early strength of the material is remarkably improved through doping of cement, the doping amount of water is reduced through doping of a water reducing agent, the compactness of the material is improved, generation of microcracks is inhibited through the bridging effect of fibers, and the durability of the material is remarkably improved. The filling material provided by the invention is low in cost, good in compressive strength, strong in erosion resistance and excellent in environmental protection performance, and resource utilization and large-scale consumption of solid wastes such as red mud are favorably realized.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of solid waste and filling materials, and in particular to an anti-corrosion multi-solid waste synergistic red mud-based filling material and a preparation method thereof. Background Art

[0002] Red mud is a highly alkaline solid waste generated during the production of alumina. The storage of red mud not only occupies a large amount of land resources, but also causes a series of environmental problems such as alkaline dust, soil salinization and water pollution.

[0003] The area of ​​goaf formed by mining in my country exceeds 120 square kilometers every year, and geological disasters such as surface collapse and landslides caused by this frequently occur, causing huge economic losses. Backfilling technology is an effective means to solve the above problems. The existing backfilling materials are mainly cement, which is not only expensive, accounting for about 20% of the mining cost, but also the cement production emits a large amount of CO2, which affects the atmospheric environment.

[0004] Using red mud as a raw material for filling has significant environmental benefits and economic value, and is in line with the circular economy concept of "using waste to treat harm". It not only utilizes a large amount of solid waste to reduce the environmental pressure caused by red mud storage, but also reduces the amount of traditional cement used and reduces carbon emissions during the filling process, and has great application potential.

[0005] However, the complex environmental conditions in mines include sulfate erosion, alternating dry and wet conditions, and freeze-thaw cycles. If the filling material has poor corrosion resistance, it will increase maintenance costs. In addition, whether the filling material with solid waste as the main raw material can stabilize heavy metals and alkaline anions to avoid groundwater pollution needs to be solved urgently. Summary of the invention

[0006] One of the purposes of the present invention is to provide an anti-corrosion multi-solid waste synergistic red mud-based filling material. By adding fly ash, desulfurized gypsum, cement, water reducer, fiber and other raw materials, the compressive strength and corrosion resistance of the filling material are enhanced, the leaching toxicity of heavy metals is reduced, and at the same time, the large-scale disposal of solid waste is achieved, and the carbon emissions of filling materials and filling costs are reduced.

[0007] A second object of the present invention is to provide a method for preparing the red mud-based filling material.

[0008] The present invention provides an anti-corrosion multi-solid waste synergistic red mud-based filling material. The raw materials of the multi-solid waste synergistic red mud-based filling material include the following components by weight: 60-80 parts of red mud, 18-30 parts of fly ash, 3-9 parts of desulfurized gypsum, 3 parts of cement, 0.3-0.7 parts of water reducer, 0.3-0.9 parts of fiber, and 27-30 parts of water.

[0009] Preferably, the raw materials of the multi-solid waste collaborative red mud-based filling material include the following components by weight: 60-80 parts of red mud, 18-23 parts of fly ash, 4-7 parts of desulfurized gypsum, 3 parts of cement, 0.3-0.7 parts of water reducing agent, 0.3-0.9 parts of fiber, and 27-29 parts of water.

[0010] Preferably, the red mud is Bayer process red mud.

[0011] The main purpose of adding red mud to the raw materials is to create an alkaline environment and provide appropriate amounts of SiO2 and Al2O3.

[0012] Preferably, the fly ash is Class F secondary fly ash.

[0013] The main role of adding fly ash to the raw materials is to provide reactive SiO2 and Al2O3 to form C-S-H gel.

[0014] Preferably, the content of calcium sulfate dihydrate in the desulfurized gypsum is greater than 80%.

[0015] The main role of adding desulfurized gypsum to the raw materials is to act as a sulfate activator to provide Ca 2+ and SO4 2- to react with reactive Al2O3 to form ettringite, making the pores in the material more dense.

[0016] The cement is 42.5 Portland cement.

[0017] The main role of adding cement to the raw materials is to enhance the early strength of the material.

[0018] The water reducing agent is a polycarboxylate water reducing agent.

[0019] The purpose of adding a water reducing agent to the raw materials is to reduce the water content and increase the density of the material.

[0020] The fiber is polypropylene fiber.

[0021] The role of adding fiber to the raw materials is to enhance the erosion resistance of the material.

[0022] Furthermore, the fiber length is 6 mm - 12 mm.

[0023] Furthermore, the particle sizes of the fly ash and desulfurized gypsum are not greater than 0.18 mm; the particle size of the red mud is not greater than 1 mm.

[0024] Preferably, the particle sizes of the fly ash and desulfurized gypsum are not greater than 0.15 mm; the particle size of the red mud is not greater than 0.8 mm.

[0025] The present invention also provides a preparation method of the multi-solid waste collaborative red mud-based filling material, including the following steps:

[0026] S1. Weigh the raw materials according to the weight ratio of the raw materials, put the fly ash, desulfurized gypsum, and cement among them into a stirring pot and stir for 5 - 10 minutes;

[0027] S2. Add the weighed red mud into the stirring pot and stir for 10 - 15 minutes;

[0028] S3. Add the weighed water reducing agent and fiber into the stirring pot and stir for 5 - 10 minutes;

[0029] S4. Add the weighed water into the stirring pot and stir for 5 - 10 minutes to obtain the multi - solid waste collaborative red mud - based filling material.

[0030] The compressive strength of the multi - solid waste collaborative red mud - based filling material after 7 - day curing > 2.5MPa; the compressive strength after 28 - day curing > 4MPa; the compressive strength of the samples obtained by soaking the samples of the multi - solid waste collaborative red mud - based filling material after 28 - day curing in Na2SO4 solution, undergoing wet - dry alternation, and freeze - thaw cycle is all > 3MPa.

[0031] The multi - solid waste collaborative red mud - based filling material inhibits the dissolution of heavy metals, making the leaching toxicity of various heavy metals reach the Class III water standard in GB / T 14848 - 2017, and the pH of the soaking solution < 8.5 after soaking in 5% Na2SO4 solution for 180 days and 20 cycles of wet - dry alternation.

[0032] The specific curing method is: put the samples of the multi - solid waste collaborative red mud - based filling material into a curing box with a temperature of 20 ± 1°C and a humidity of 95 ± 1% for curing;

[0033] The specific Na2SO4 solution soaking is: put the samples of the multi - solid waste collaborative red mud - based filling material after 28 - day curing into 5% Na2SO4 solution and soak for 180 days;

[0034] The specific wet - dry alternation is: put the samples of the multi - solid waste collaborative red mud - based filling material after 28 - day curing into 5% Na2SO4 solution and soak for 12 hours, then put them into an oven at 50°C for 12h. This is taken as 1 cycle and lasts for 20 cycles in total;

[0035] The specific freeze - thaw cycle is: after soaking the samples of the multi - solid waste collaborative red mud - based filling material after 28 - day curing in water, put them into a refrigerator at - 20°C for freezing for 12 hours, and then put them into a curing box at 20°C for 12 hours. This is taken as 1 cycle and lasts for 30 cycles in total.

[0036] The principle of the present invention:

[0037] The present invention uses red mud as the main raw material, which is used to support the skeleton and create an alkaline environment to promote the breaking of Al-O bonds and Si-O bonds in active Al2O3 and SiO2 in fly ash; fly ash and gypsum are used as the main cementitious raw materials. Fly ash is used to provide active Al2O3 and SiO2 to promote the formation of C-(A)-S-H and provide strength for the material. The addition of an appropriate amount of desulfurized gypsum can react with active Al2O3, promote the formation of ettringite, fill the large pores in the material, reduce the porosity, and is beneficial to enhancing the compressive strength of the material. Cement, water reducer, and fiber are used as admixtures to enhance the engineering properties of the material. Among them, the addition of cement can enhance the early strength of the material, the addition of water reducer increases the density and workability of the material, and the addition of fiber reduces the generation of microcracks through bridging effect, significantly increases the compressive strength and durability of the material, and reduces the maintenance cost.

[0038] Advantages of the present invention:

[0039] (1) The multi-solid waste collaborative red mud-based filling material provided by the present invention uses red mud as the main raw material, and multiple solid wastes are collaboratively used to prepare the filling material. The content of red mud in the solid phase is ≥60%, and the content of solid waste in the solid phase is >95%. Only appropriate grinding treatment is required, with low cost and good compressive strength, which is beneficial to increasing the comprehensive utilization rate of solid waste;

[0040] (2) The multi-solid waste collaborative red mud-based filling material provided by the present invention has good environmental effects, reduces the environmental risks of solid waste stacking, reduces carbon emissions, and the leaching toxicity of multiple heavy metals in the prepared filling material reaches the Class III water standard in GB / T 14848-2017. After soaking in 5% Na2SO4 solution for 180 days and undergoing 20 cycles of wet-dry alternation, the pH of the soaking solution is <8.5;

[0041] (3) The multi-solid waste collaborative red mud-based filling material provided by the present invention incorporates an appropriate amount of fiber, which not only increases the compressive strength but also increases the erosion resistance of the material, and is beneficial to reducing the maintenance cost of the filling material;

[0042] (4) The multi-solid waste collaborative red mud-based filling material provided by the present invention reduces the water content by adding a high-performance water reducer, increases the density of the material, and is beneficial to increasing the workability and erosion resistance of the material. Description of the drawings

[0043] Figure 1 It is the composition diagram of red mud, fly ash, and desulfurized gypsum used in the embodiments of the present invention;

[0044] Figure 2 It is the XRD diagram of red mud in the embodiments of the present invention;

[0045] Figure 3 It is the XRD diagram of fly ash in the embodiments of the present invention;

[0046] Figure 4 XRD pattern of desulfurized gypsum in the embodiment of the present invention;

[0047] Figure 5 XRD pattern of the filling materials obtained in Example 4 and Example 5 of the present invention;

[0048] Figure 6 NMR pattern of the filling materials obtained in Example 4 and Example 5 of the present invention;

[0049] Figure 7 SEM pattern of the filling material obtained in Example 4 of the present invention. Detailed implementation mode

[0050] The main component compositions of the red mud, fly ash and desulfurized gypsum used in the embodiments of the present invention are as Figure 1 shown.

[0051] Among them, the XRD pattern of the red mud is as Figure 2 shown, the XRD pattern of the fly ash is as Figure 3 shown, and the XRD pattern of the desulfurized gypsum is as Figure 4 shown.

[0052] Example 1

[0053] Weigh 21 parts of fly ash, 6 parts of desulfurized gypsum, and 3 parts of cement and put them into a mixing pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the mixing pot and stir for 15 minutes. Then weigh 0.5 part of water reducer and 0.6 part of fiber and stir in the mixing pot for 10 minutes. Then weigh 28 parts of water and pour it into the mixing pot and stir for 10 minutes to obtain the filling slurry.

[0054] Pour the filling slurry into a Φ50×100mm cylindrical mold coated with silicone oil, place it on a vibrating table and oscillate for 30 seconds, put it into a curing box at a temperature of 20±1°C and a humidity of 95±1% for curing. Demold after 1 day of curing, measure the compressive strength and leaching toxicity at 7 days of curing. The remaining specimens are cured to 28 days and the compressive strength is tested. Part of the remaining specimens are soaked in 5% Na2SO4 solution for 180 days and then the compressive strength and pH value of the soaking solution are tested. Part of the remaining specimens are soaked in 5% Na2SO4 solution for 12 hours, then put into an oven at a temperature of 50°C for 12 hours. This is taken as 1 cycle and lasts for 20 cycles in total, and then the compressive strength and pH value of the soaking solution are tested. Part of them are soaked in water and then put into a -20°C refrigerator for 12 hours, and then put into a 20°C curing box for 12 hours. This is taken as 1 cycle and lasts for 30 cycles in total, and then the compressive strength is tested.

[0055] Example 2

[0056] Weigh 14 parts of fly ash, 3 parts of desulfurized gypsum, and 3 parts of cement and put them into a stirring pot and stir for 6 minutes. Then weigh 80 parts of red mud and put it into the stirring pot and stir for 15 minutes. Then weigh 0.5 part of water reducer and 0.6 part of fiber and stir in the stirring pot for 10 minutes. Then weigh 27 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0057] Example 3

[0058] Weigh 30 parts of fly ash, 7 parts of desulfurized gypsum, and 3 parts of cement and put them into a stirring pot and stir for 10 minutes. Then weigh 60 parts of red mud and put it into the stirring pot and stir for 10 minutes. Then weigh 0.5 part of water reducer and 0.6 part of fiber and stir in the stirring pot for 10 minutes. Then weigh 29 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0059] Example 4

[0060] Weigh 23 parts of fly ash, 4 parts of desulfurized gypsum, and 3 parts of cement and put them into a stirring pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.5 part of water reducer and 0.6 part of fiber and stir in the stirring pot for 12 minutes. Then weigh 28 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0061] Example 5

[0062] Weigh 18 parts of fly ash, 9 parts of desulfurized gypsum, and 3 parts of cement and put them into a stirring pot and stir for 5 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.5 part of water reducer and 0.6 part of fiber and stir in the stirring pot for 10 minutes. Then weigh 28 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0063] Example 6

[0064] Weigh 21 parts of fly ash, 6 parts of desulfurized gypsum, and 3 parts of cement and put them into a stirring pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.3 part of water reducer and 0.6 part of fiber and stir in the stirring pot for 8 minutes. Then weigh 30 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0065] Example 7

[0066] Weigh 21 parts of fly ash, 6 parts of desulfurized gypsum, and 3 parts of cement, and put them into a stirring pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.7 part of water reducing agent and 0.6 part of fiber and stir in the stirring pot for 6 minutes. Then weigh 27 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0067] Example 8

[0068] Weigh 21 parts of fly ash, 6 parts of desulfurized gypsum, and 3 parts of cement, and put them into a stirring pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.5 part of water reducing agent and 0.3 part of fiber and stir in the stirring pot for 5 minutes. Then weigh 28 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0069] Example 9

[0070] Weigh 21 parts of fly ash, 6 parts of desulfurized gypsum, and 3 parts of cement, and put them into a stirring pot and stir for 8 minutes. Then weigh 70 parts of red mud and put it into the stirring pot and stir for 12 minutes. Then weigh 0.5 part of water reducing agent and 0.9 part of fiber and stir in the stirring pot for 10 minutes. Then weigh 28 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0071] Comparative Example 1

[0072] Weigh 14 parts of fly ash, 3 parts of desulfurized gypsum, and 3 parts of cement, and put them into a stirring pot and stir for 6 minutes. Then weigh 80 parts of red mud and put it into the stirring pot and stir for 15 minutes. Then weigh 0.5 part of water reducing agent and stir in the stirring pot for 10 minutes. Then weigh 27 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0073] Comparative Example 2

[0074] Weigh 14 parts of fly ash, 3 parts of desulfurized gypsum, and 3 parts of cement, and put them into a stirring pot and stir for 6 minutes. Then weigh 80 parts of red mud and put it into the stirring pot and stir for 15 minutes. Then weigh 0.6 part of fiber and stir in the stirring pot for 10 minutes. Then weigh 33 parts of water and pour it into the stirring pot and stir for 10 minutes to obtain a filling slurry. The subsequent operations are the same as those in Example 1.

[0075] The XRD patterns of the filling materials obtained in Example 4 and Example 5 are as Figure 5 shown, and the NMR patterns are as Figure 6 shown.

[0076] The SEM image of the filling material obtained in Example 4 is as Figure 7 shown.

[0077] The uniaxial compressive strength was tested using a universal testing machine with a loading rate of 1 mm / min. The fluidity was determined according to GB / T 2419-2005 "Test Method for Fluidity of Cement Mortar". The test results of the compressive strength and fluidity of the filling materials obtained in Examples 1-8 and Comparative Examples 1-2 at 7 days and 28 days are shown in Table 1. The anti-corrosion performance and pH of the leaching solution of the filling materials obtained in Examples 1-8 and Comparative Examples 1-2 are shown in Table 2. The leaching toxicity was determined according to the national standard "Horizontal Oscillation Method for Leaching Toxicity of Solid Wastes" (HJ 557-2010), and the results are shown in Table 3.

[0078] Table 1 Test Table of Compressive Strength and Fluidity of Filling Materials in Each Example and Comparative Example

[0079] Group 7-day compressive strength (MPa) 28-day compressive strength (MPa) Flowability (cm) Example 1 2.97 4.64 23.8 Example 2 2.51 4.02 24.9 Example 3 3.27 5.08 23.1 Example 4 2.72 4.39 24.1 Example 5 2.79 4.23 24.2 Example 6 2.91 4.19 24.1 Example 7 3.03 4.36 23.9 Example 8 2.93 4.64 23.6 Example 9 2.86 4.48 23.9 Comparative Example 1 2.03 3.26 23.5 Comparative Example 2 1.84 3.39 23.9

[0080] Table 2 Test Table of Anti-corrosion Performance and pH of Leaching Solution of Filling Materials in Each Example and Comparative Example

[0081]

[0082] Table 3 Test Table of Leaching Toxicity of Filling Materials in Each Example and Comparative Example

[0083]

[0084]

[0085] As can be seen from Tables 1-3, the 7-day compressive strength of the red mud-based multi-solid waste filling material of the present invention > 2.5 MPa, and the 28-day compressive strength > 4 MPa, which can meet the strength requirements of mine filling materials. After being soaked in 5% Na2SO4 solution, subjected to 20 cycles of wet-dry alternation and 30 cycles of freeze-thaw cycling, the compressive strength > 3 MPa, and the anti-corrosion performance is good.

[0086] The leaching toxicity of various heavy metals in the red mud-based multi-solid waste filling material of the present invention is lower than the Class III water standard in GB / T14848-2017. After being soaked in 5% Na2SO4 solution and subjected to 20 cycles of wet-dry alternation, the pH value of the soaking solution is lower than 8.5, and the environmental protection performance is excellent.

[0087] Compared with the water reducer, the fiber has a better effect on enhancing the mechanical properties and anti-corrosion performance of the material. However, the water reducer effectively reduces the water content, increases the density of the specimen, and is beneficial to the disposal of more solid waste.

[0088] Compared with the comparative examples without adding water reducing agents or fibers, the compressive strength of the materials in the examples increased significantly. Especially after being soaked in 5% Na2SO4 solution, undergoing 20 cycles of wet-dry alternation and 30 cycles of freeze-thaw cycles, they had better compressive strength. At the same time, the leaching toxicity of various heavy metals decreased, and the environmental protection performance was better.

[0089] The above examples are only the preferred embodiments of the present invention. For those skilled in the art of this technology, without departing from the spirit or scope of this application, some technical solutions in the present invention can be modified or some technical features can be replaced, and these modifications and replacements should also be regarded as the protection scope of the present invention.

Claims

1. A multi-solid waste collaborative red mud-based filling material resistant to erosion, characterized in that, The raw materials of the multi-solid waste collaborative red mud-based filling material include the following components by weight: 60-80 parts of red mud, 18-30 parts of fly ash, 3-9 parts of desulfurized gypsum, 3 parts of cement, 0.3-0.7 parts of water reducing agent, 0.3-0.9 parts of fiber, and 27-30 parts of water.

2. The erosion-resistant multi-solid waste collaborative red mud-based filling material according to claim 1, characterized in that, The raw materials of the multi-solid waste collaborative red mud-based filling material include the following components by weight: 60-80 parts of red mud, 18-23 parts of fly ash, 4-7 parts of desulfurized gypsum, 3 parts of cement, 0.3-0.7 parts of water reducing agent, 0.3-0.9 parts of fiber, and 27-29 parts of water.

3. The erosion-resistant multi-solid waste synergistic red mud-based filling material according to claim 1, characterized in that The red mud is Bayer process red mud; the fly ash is Class F secondary fly ash; the cement is 42.5 Portland cement; the water reducing agent is polycarboxylate water reducing agent; the fiber is polypropylene fiber.

4. The anti-erosion multi-solid waste collaborative red mud-based filling material according to claim 1, characterized in that, The content of calcium sulfate dihydrate in the desulfurized gypsum is greater than 80%.

5. The erosion-resistant multi-solid waste synergistic red mud-based filling material according to claim 1, characterized in that, The fiber length is 6mm-12mm.

6. The anti-erosion multi-solid waste collaborative red mud-based filling material according to claim 1, characterized in that The particle sizes of the fly ash and desulfurized gypsum are not greater than 0.18mm; the initially proposed particle size is not greater than 1mm.

7. The erosion-resistant multi-solid waste synergistic red mud-based filling material according to claim 6, wherein The particle sizes of the fly ash and desulfurized gypsum are not greater than 0.15mm; the initially proposed particle size is not greater than 0.8mm.

8. A method for preparing the erosion-resistant multi-solid waste synergistic red mud-based filling material according to any one of claims 1 to 7, characterized in that, It includes the following steps: S1. Weigh the raw materials according to the weight ratio of the raw materials, and put the fly ash, desulfurized gypsum, and cement among them into a mixing pot and stir for 5-10 minutes. S2. Add the weighed red mud into the mixing pot and stir for 10-15 minutes. S3. Add the weighed water reducing agent and fiber into the mixing pot and stir for 5-10 minutes. S4. Add the weighed water into the mixing pot and stir for 5-10 minutes to obtain the multi-solid waste collaborative red mud-based filling material.

9. The preparation method according to claim 8, wherein, The compressive strength of the multi-solid waste collaborative red mud-based filling material after 7 days of curing > 2.5MPa; the compressive strength after 28 days of curing > 4MPa; the samples of the multi-solid waste collaborative red mud-based filling material after 28 days of curing are respectively soaked in Na2SO4 solution, subjected to wet-dry alternation, and freeze-thaw cycle, and the compressive strength of the obtained samples is > 3MPa, and the pH of the soaking solution of the samples obtained by soaking in Na2SO4 solution and wet-dry alternation is < 8.

5.

10. The preparation method according to claim 9, characterized in that, The specific curing method is: put the samples of the multi-solid waste collaborative red mud-based filling material into a curing box at a temperature of 20±1°C and a humidity of 95±1% for curing. The specific soaking in Na2SO4 solution is: put the samples of the multi-solid waste collaborative red mud-based filling material after 28 days of curing into 5% Na2SO4 solution and soak for 180 days. The specific wet-dry alternation is: put the samples of the multi-solid waste collaborative red mud-based filling material after 28 days of curing into 5% Na2SO4 solution and soak for 12 hours, then put them into an oven at a temperature of 50°C for 12h. This is taken as one cycle and lasts for 20 cycles in total. The specific freeze-thaw cycle is: after soaking the samples of the multi-solid waste collaborative red mud-based filling material after 28 days of curing in water, put them into a refrigerator at -20°C and freeze for 12 hours, and then put them into a curing box at 20°C for 12 hours. This is taken as one cycle and lasts for 30 cycles in total.

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