Filling cementitious material containing fine tailings and process for its preparation

Abstract

The present application relates to the field of resource comprehensive utilization and the field of mining technology, and particularly relates to a filling cementing material containing fine tailings and a preparation process thereof. The preparation process of the filling cementing material containing fine tailings comprises the following steps: preparing an internal curing agent; preparing a water hyacinth extract and a cactus extract; activating the fine tailings; and preparing the filling cementing material. In the present application, methacrylic acid is neutralized to weak acidity, then mixed with a montmorillonite suspension and a hydroxypropyl methylcellulose solution, and polyaspartic acid is added, N,N'-methylene bisacrylamide is used as a crosslinking agent, and a polymerization reaction is carried out under the initiation of an initiator, so as to form a three-dimensional network structure, and the dispersed montmorillonite nanosheet layers are embedded into the polymer network through electrostatic interaction and hydrogen bonding to obtain the internal curing agent. After the internal curing agent is added into the filling cementing material, the shrinkage stress caused by capillary negative pressure can be reduced, and then the drying shrinkage of the filling cementing material can be inhibited.

Description

Technical Field

[0001] This invention relates to the fields of comprehensive resource utilization and mining technology, specifically to a backfill cementitious material containing fine tailings and its preparation process. Background Technology

[0002] Mine backfilling technology is one of the core technologies for achieving green mining of mineral resources, controlling goaf subsidence, and solving the problem of solid waste storage in mines. The performance and cost of backfill cementitious materials directly determine mining efficiency and environmental benefits. Fine tailings, as a major solid waste generated during the beneficiation of both metallic and non-metallic minerals, not only occupy large amounts of land but also easily lead to ecological risks such as tailings dam failure and dust pollution. Therefore, utilizing fine tailings resources for backfill cementitious materials has become a key path to balance mining safety and solid waste reduction.

[0003] However, fine tailings have a large specific surface area and high surface inertia, resulting in poor compatibility with cement, quicklime, and other cementing materials. This necessitates the addition of large amounts of cementing materials to ensure strength, leading to high backfilling costs. Furthermore, the amount of fine tailings can be limited, resulting in low solid waste resource utilization. In addition, fine tailings easily absorb moisture, and the surface moisture evaporates quickly, causing the system to experience "volume shrinkage stress" due to water shortage. This results in low early strength and high shrinkage rate of the backfill, as well as insufficient compressive strength and crack resistance. Under deep high-stress or mine water erosion environments, cracking and strength decay are likely to occur, making it unable to meet long-term service requirements.

[0004] Therefore, there is a need for a filling cementitious material containing fine tailings that can suppress early shrinkage cracking, has high compressive strength and good crack resistance, and its preparation process. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a backfill cementitious material containing fine tailings and its preparation process.

[0006] This invention provides a process for preparing a backfill cementitious material containing fine tailings, comprising the following steps:

[0007] S1: Preparation of internal maintenance agent

[0008] S1.1: Add montmorillonite to deionized water at a ratio of 1g:(20-30)mL, disperse ultrasonically at 60-70℃ for 1-2h, and after cooling, obtain a montmorillonite suspension;

[0009] S1.2: Add hydroxypropyl methylcellulose to hot water at 60-80℃ at a ratio of 1g:(25-30)mL while stirring. After uniform dispersion, add cold water at 6-8℃ and continue stirring until completely dissolved. After cooling, a hydroxypropyl methylcellulose solution is obtained. The amount of cold water added is 50% of the volume of hot water.

[0010] S1.3: Under water bath conditions of 1-3℃, add sodium hydroxide solution with a mass concentration of 20% to methacrylic acid while stirring, adjust the pH to 5, and obtain a neutralized methacrylic acid solution;

[0011] S1.4: Thoroughly mix the above montmorillonite suspension, hydroxypropyl methylcellulose solution and methacrylic acid neutralization solution, then add polyaspartic acid, N,N'-methylenebisacrylamide and initiator solution. Under nitrogen protection, heat and stir the mixture at 60-65℃ for 2-4 hours. After cooling, soak the mixture in deionized water for 24 hours, then vacuum dry, pulverize and sieve to obtain the internal curing agent.

[0012] S2: Preparation of water hyacinth extract and cactus extract

[0013] Extracts were extracted from water hyacinth and cactus respectively to obtain water hyacinth extract and cactus extract;

[0014] S3: Activated fine tailings

[0015] After the fine tailings are activated with an alkaline activating solution, an aqueous solution of sulfobetaine is added for surface modification. Then, it is mixed with styrene and benzoyl peroxide is added to react and obtain an activated fine tailings mixture.

[0016] S4: Preparation of filling cementitious materials

[0017] The activated fine tailings mixture, quicklime, desulfurized gypsum, sodium sulfate, and the above-mentioned internal curing agent are stirred and mixed evenly. Then, water-reducing agent, water hyacinth extract, cactus extract, and water are added for wet mixing, pouring, vibration molding, and room temperature curing to obtain the filling cementitious material.

[0018] Furthermore, S2 specifically includes the following steps:

[0019] S2.1: After washing, drying and crushing the water hyacinth, add it to the mixed solvent at a solid-liquid ratio of 1g:(15-25)mL, and extract with ultrasonic assistance at 300-400W power and 50-60℃ for 40-60min. After filtration, collect the filtrate to obtain the water hyacinth extract.

[0020] S2.2: Remove the thorns and epidermis from fresh, unrotten cactus stem segments, then wash, dry and crush them. Add water at a ratio of 1g:(15-20)mL, heat and stir at 50-60℃ for 2-3 hours, cool, centrifuge and filter, collect the filtrate to obtain cactus extract.

[0021] Furthermore, S3 specifically includes the following steps:

[0022] S3.1: After drying the fine tailings, crush them and pass them through a 200-mesh sieve. Then, ball mill them for 30-40 minutes, add alkaline activation solution, stir for 10-20 minutes, and then cure them at a constant temperature of 60-80℃ for 24-30 hours. After cooling, filter and wash until the pH of the filtrate is 10, and then dry and grind them to obtain alkaline activated fine tailings.

[0023] S3.2: Immerse the above-mentioned alkali-activated fine tailings in a 0.1% sulfobetaine aqueous solution at a ratio of 1g:(5-6)mL, stir at 50-60℃ for 30-40min, and then filter and dry to obtain surface-modified fine tailings.

[0024] S3.3: Mix the above-mentioned surface-modified fine tailings with styrene at a mass ratio of 1:(0.3-0.5), then add benzoyl peroxide, and heat the mixture at 70-80℃ for 2-4 hours under nitrogen protection. After cooling, the activated fine tailings mixture is obtained.

[0025] Furthermore, the amount of montmorillonite added is 10-15% of the mass of methacrylic acid in the methacrylic acid neutralization solution, the amount of hydroxypropyl methylcellulose added to the hydroxypropyl methylcellulose solution is 5-10% of the mass of methacrylic acid in the methacrylic acid neutralization solution, and the amount of polyaspartic acid added is 3-5% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

[0026] Furthermore, the amount of N,N'-methylenebisacrylamide added is 0.1-0.2% of the mass of methacrylic acid in the methacrylic acid neutralization solution, the initiator solution is a 10% ammonium persulfate solution, and the amount of initiator added is 0.4-0.6% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

[0027] Furthermore, the mixed solvent is prepared by mixing a 60-70% ethanol solution and a 4-6% sodium hydroxide solution at a volume ratio of (3-5):1.

[0028] Furthermore, the alkaline activating solution is prepared by mixing a 20% sodium hydroxide solution and a 30% sodium silicate solution in a volume ratio of (1-3):1.

[0029] Furthermore, the amount of benzoyl peroxide added is 0.5-1% of the mass of styrene.

[0030] Furthermore, by weight, the raw material composition of the filling cementitious material is as follows: 90-100 parts activated fine tailings mixture, 10-20 parts quicklime, 10-20 parts desulfurized gypsum, 3-5 parts sodium sulfate, 1-3 parts internal curing agent, 1-2 parts water-reducing agent, 3-5 parts water hyacinth extract, 3-5 parts cactus extract, and 40-50 parts water, wherein the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0031] A backfill cementitious material containing fine tailings, which is prepared by the preparation process of a backfill cementitious material containing fine tailings as described in any one of the above claims.

[0032] The present invention has the following advantages:

[0033] 1. In this invention, methacrylic acid is neutralized to a weakly acidic state, then mixed with montmorillonite suspension and hydroxypropyl methylcellulose solution, and polyaspartic acid is added. N,N'-methylenebisacrylamide is used as a crosslinking agent, and a polymerization reaction is initiated by an initiator to form a three-dimensional network structure. Montmorillonite is embedded into the polymer network through electrostatic interaction and hydrogen bonding to obtain an internal curing agent. When this agent is added to the filling cementitious material, the montmorillonite interlayers in the internal curing agent adsorb a large amount of water through hydrogen bonding, and the material is encapsulated by the polymer network. When the cementitious material hydrates and consumes water, osmotic pressure is formed inside the system, and water is slowly released from the montmorillonite interlayers, continuously providing a "water source" for hydration and reducing the shrinkage stress caused by capillary negative pressure. Simultaneously, the carboxyl groups in the internal curing agent can react with the Ca produced during cement hydration. 2 ⁺ Combining to form a stable calcium ion-carboxylic acid complex fills the gaps in the CSH gel. Furthermore, the hydroxypropyl methylcellulose molecular chains bind to the CSH gel through hydrogen bonds, enhancing the continuity of the gel structure. This synergistic effect makes the microstructure of the filling more compact, improves its resistance to shrinkage stress, and ultimately inhibits the drying shrinkage of the filling gel material.

[0034] 2. In this invention, by adding water hyacinth extract and cactus extract to the filling gelling material, the water hyacinth extract can react with Ca... 2 The complexation promotes CSH gel formation and refines Ca(OH)2 crystals, avoiding structural defects caused by oriented crystal arrangement. Meanwhile, cactus extract acts as an active precipitation site for CSH gel, guiding the gel to precipitate uniformly on the surface of activated fine tailings, reducing localized loose areas. The combined use of these two ingredients can increase the polymerization degree of CSH gel, making the hydration products denser and more uniformly distributed, thereby synergistically improving the compressive strength of the filling cementitious material. Furthermore, water hyacinth extract can form a three-dimensional network structure in the system, consuming energy through "pull-out and fracture" when cracks initiate. Cactus extract can form a flexible film, providing a flexible buffer and generating slight deformation at the crack tip to absorb some shrinkage stress. The combination of these two ingredients synergistically prevents crack propagation and improves the crack resistance of the filling cementitious material.

[0035] 3. In this invention, an alkaline activating solution is first used to break the Si-O and Al-O bonds of the inert SiO2 and Al2O3 on the surface of fine tailings, generating soluble sodium silicate, sodium aluminate, and other active substances, which then react with the Ca produced by the hydration of the cementitious material. 2The reaction generates more CSH and CASH gels. Sulfobetaine is then used to modify the surface of the fine tailings, binding with the hydroxyl groups on the tailings surface and providing "anchor points" for subsequent styrene grafting. This reduces tailings particle agglomeration and ensures uniform mixing with the cementitious matrix. Finally, benzoyl peroxide is used to initiate the polymerization of styrene on the tailings surface, forming a thin and dense polystyrene coating. This coating binds to the organic components and inorganic hydration products in the cementitious material through van der Waals forces and hydrogen bonds, improving the interfacial bonding strength between the tailings and the cementitious matrix. This enhances the compressive strength of the filling cementitious material. Furthermore, the activation of the tailings increases its activity and compatibility, allowing for increased dosage in the filling cementitious material. This increases tailings consumption, reduces tailings dam accumulation, and mitigates environmental risks such as tailings dam failure and dust pollution. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the preparation process of the backfill cementitious material containing fine tailings used in an embodiment of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0038] Example 1: A preparation process for a backfill cementitious material containing fine tailings, such as... Figure 1 As shown, it includes the following steps:

[0039] S1: Preparation of internal maintenance agent

[0040] S1.1: Add montmorillonite to deionized water at a ratio of 1g:20mL, disperse ultrasonically at 60℃ for 1h, and after cooling, obtain a montmorillonite suspension;

[0041] S1.2: Add hydroxypropyl methylcellulose to hot water at 60°C at a ratio of 1g:25mL while stirring. After uniform dispersion, add cold water at 6°C and continue stirring until completely dissolved. After cooling, a hydroxypropyl methylcellulose solution is obtained. The amount of cold water added is 50% of the volume of hot water.

[0042] S1.3: Under 1℃ water bath conditions, a 20% sodium hydroxide solution was added to methacrylic acid while stirring to adjust the pH to 5, thus obtaining a neutralized methacrylic acid solution.

[0043] S1.4: The above montmorillonite suspension, hydroxypropyl methylcellulose solution, and methacrylic acid neutralization solution are thoroughly mixed. Then, polyaspartic acid, N,N'-methylenebisacrylamide, and initiator solution are added. Under nitrogen protection, the mixture is heated and stirred at 60°C for 2 hours. After cooling, it is soaked in deionized water for 24 hours. Then, it is vacuum dried, pulverized, and sieved to obtain the internal curing agent. The amount of montmorillonite added to the montmorillonite suspension is 10% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of hydroxypropyl methylcellulose added to the hydroxypropyl methylcellulose solution is 5% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of polyaspartic acid added is 3% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of N,N'-methylenebisacrylamide added is 0.1% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The initiator solution is a 10% ammonium persulfate solution, and the amount of initiator added is 0.4% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

[0044] S2: Preparation of water hyacinth extract and cactus extract

[0045] S2.1: After washing, drying and crushing the water hyacinth, add it to the mixed solvent at a solid-liquid ratio of 1g:15mL, and extract with ultrasonic assistance at 300W and 50℃ for 40min. After filtration, collect the filtrate to obtain the water hyacinth extract. The mixed solvent is prepared by mixing 60% ethanol solution and 4% sodium hydroxide solution at a volume ratio of 3:1.

[0046] S2.2: Remove the thorns and epidermis from fresh, unrotten cactus stem segments, then wash, dry and crush them. Add them to water at a ratio of 1g:15mL, heat and stir at 50℃ for 2 hours, cool, centrifuge and filter, collect the filtrate to obtain cactus extract.

[0047] S3: Activated fine tailings

[0048] S3.1: After drying the fine tailings, crush them and pass them through a 200-mesh sieve. Then, ball mill them for 30 minutes, add alkaline activation solution, stir for 10 minutes, and then cure them at a constant temperature of 60℃ for 24 hours. After cooling, filter and wash until the pH of the filtrate is 10. Then dry and grind them to obtain alkaline activated fine tailings. The alkaline activation solution is prepared by mixing a 20% sodium hydroxide solution and a 30% sodium silicate solution in a volume ratio of 1:1.

[0049] S3.2: Immerse the above-mentioned alkali-activated fine tailings in a 0.1% sulfobetaine aqueous solution at a ratio of 1g:5mL, stir at 50℃ for 30min, and then filter and dry to obtain surface-modified fine tailings.

[0050] S3.3: Mix the above-mentioned surface-modified fine tailings with styrene at a mass ratio of 1:0.3, then add benzoyl peroxide, and heat at 70°C for 2 hours under nitrogen protection. After cooling, an activated fine tailings mixture is obtained, wherein the amount of benzoyl peroxide added is 0.5% of the mass of styrene.

[0051] S4: Preparation of filling cementitious materials

[0052] Mix 90 parts by weight of the above activated fine tailings mixture, 10 parts by weight of quicklime, 10 parts by weight of desulfurized gypsum, 3 parts by weight of sodium sulfate, and 1 part by weight of the above internal curing agent evenly. Then add 1 part by weight of polycarboxylate superplasticizer, 3 parts by weight of the above water hyacinth extract, 3 parts by weight of the above cactus extract, and 40 parts by weight of water. Perform wet mixing, pouring, vibration molding, and room temperature curing to obtain the filling cementitious material.

[0053] Example 2: A preparation process for a backfill cementitious material containing fine tailings, as follows: Figure 1 As shown, it includes the following steps:

[0054] S1: Preparation of internal maintenance agent

[0055] S1.1: Add montmorillonite to deionized water at a ratio of 1g:25mL, disperse ultrasonically at 65℃ for 1.5h, and after cooling, obtain a montmorillonite suspension;

[0056] S1.2: Add hydroxypropyl methylcellulose to hot water at 70°C at a ratio of 1g:27.5mL while stirring. After uniform dispersion, add cold water at 7°C and continue stirring until completely dissolved. After cooling, a hydroxypropyl methylcellulose solution is obtained. The amount of cold water added is 50% of the volume of hot water.

[0057] S1.3: Under 2℃ water bath conditions, while stirring, add a 20% sodium hydroxide solution to methacrylic acid to adjust the pH to 5, and obtain a neutralized methacrylic acid solution;

[0058] S1.4: The above montmorillonite suspension, hydroxypropyl methylcellulose solution, and methacrylic acid neutralization solution are thoroughly mixed. Then, polyaspartic acid, N,N'-methylenebisacrylamide, and initiator solution are added. Under nitrogen protection, the mixture is heated and stirred at 62.5°C for 3 hours. After cooling, it is soaked in deionized water for 24 hours. Then, it is vacuum dried, pulverized, and sieved to obtain the internal curing agent. The amount of montmorillonite added to the montmorillonite suspension is 12.5% ​​of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of hydroxypropyl methylcellulose added to the hydroxypropyl methylcellulose solution is 7.5% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of polyaspartic acid added is 4% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of N,N'-methylenebisacrylamide added is 0.15% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The initiator solution is a 10% ammonium persulfate solution, and the amount of initiator added is 0.5% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

[0059] S2: Preparation of water hyacinth extract and cactus extract

[0060] S2.1: After washing, drying and crushing the water hyacinth, add it to the mixed solvent at a solid-liquid ratio of 1g:20mL, and extract with ultrasonic assistance at 350W and 55℃ for 50min. After filtration, collect the filtrate to obtain the water hyacinth extract. The mixed solvent is prepared by mixing 65% ethanol solution and 5% sodium hydroxide solution at a volume ratio of 4:1.

[0061] S2.2: Remove the thorns and epidermis from fresh, unrotten cactus stem segments, then wash, dry and crush them. Add water at a ratio of 1g:17.5mL, heat and stir at 55℃ for 2.5h, cool, centrifuge and filter, collect the filtrate to obtain cactus extract.

[0062] S3: Activated fine tailings

[0063] S3.1: After drying the fine tailings, crush them and pass them through a 200-mesh sieve. Then, ball mill them for 35 minutes, add alkaline activation solution, stir for 15 minutes, and then cure them at a constant temperature of 70℃ for 27 hours. After cooling, filter and wash until the pH of the filtrate is 10. Then dry and grind them to obtain alkaline activated fine tailings. The alkaline activation solution is prepared by mixing a 20% sodium hydroxide solution and a 30% sodium silicate solution in a volume ratio of 2:1.

[0064] S3.2: Immerse the above-mentioned alkali-activated fine tailings in a 0.1% sulfobetaine aqueous solution at a ratio of 1g:5.5mL, stir at 55℃ for 35min, and then filter and dry to obtain surface-modified fine tailings.

[0065] S3.3: Mix the above-mentioned surface-modified fine tailings with styrene at a mass ratio of 1:0.4, then add benzoyl peroxide, and heat at 75°C for 3 hours under nitrogen protection. After cooling, an activated fine tailings mixture is obtained, wherein the amount of benzoyl peroxide added is 0.75% of the mass of styrene.

[0066] S4: Preparation of filling cementitious materials

[0067] Mix 95 parts by weight of the above activated fine tailings mixture, 15 parts by weight of quicklime, 15 parts by weight of desulfurized gypsum, 4 parts by weight of sodium sulfate, and 2 parts by weight of the above internal curing agent evenly. Then add 1.5 parts by weight of polycarboxylate superplasticizer, 4 parts by weight of the above water hyacinth extract, 4 parts by weight of the above cactus extract, and 45 parts by weight of water for wet mixing, pouring, vibration molding, and room temperature curing to obtain the filling cementitious material.

[0068] Example 3: A preparation process for a backfill cementitious material containing fine tailings, as follows: Figure 1 As shown, it includes the following steps:

[0069] S1: Preparation of internal maintenance agent

[0070] S1.1: Add montmorillonite to deionized water at a ratio of 1g:30mL, disperse ultrasonically at 70℃ for 2h, and after cooling, obtain a montmorillonite suspension;

[0071] S1.2: Add hydroxypropyl methylcellulose to hot water at 80℃ at a ratio of 1g:30mL while stirring. After uniform dispersion, add cold water at 8℃ and continue stirring until completely dissolved. After cooling, a hydroxypropyl methylcellulose solution is obtained. The amount of cold water added is 50% of the volume of hot water.

[0072] S1.3: Under 3℃ water bath conditions, a 20% sodium hydroxide solution was added to methacrylic acid while stirring to adjust the pH to 5, thus obtaining a neutralized methacrylic acid solution.

[0073] S1.4: The above montmorillonite suspension, hydroxypropyl methylcellulose solution, and methacrylic acid neutralization solution are thoroughly mixed. Then, polyaspartic acid, N,N'-methylenebisacrylamide, and initiator solution are added. Under nitrogen protection, the mixture is heated and stirred at 65°C for 4 hours. After cooling, it is soaked in deionized water for 24 hours. Then, it is vacuum dried, pulverized, and sieved to obtain the internal curing agent. The amount of montmorillonite added to the montmorillonite suspension is 15% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of hydroxypropyl methylcellulose added to the hydroxypropyl methylcellulose solution is 10% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of polyaspartic acid added is 5% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The amount of N,N'-methylenebisacrylamide added is 0.2% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The initiator solution is a 10% ammonium persulfate solution, and the amount of initiator added is 0.6% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

[0074] S2: Preparation of water hyacinth extract and cactus extract

[0075] S2.1: After washing, drying and crushing the water hyacinth, add it to the mixed solvent at a solid-liquid ratio of 1g:25mL, and extract with ultrasonic assistance at 400W and 60℃ for 60min. After filtration, collect the filtrate to obtain the water hyacinth extract. The mixed solvent is prepared by mixing 70% ethanol solution and 6% sodium hydroxide solution at a volume ratio of 5:1.

[0076] S2.2: Remove the thorns and epidermis from fresh, unrotten cactus stem segments, then wash, dry and crush them. Add water at a ratio of 1g:20mL, heat and stir at 60℃ for 3 hours, cool, centrifuge and filter, collect the filtrate to obtain cactus extract.

[0077] S3: Activated fine tailings

[0078] S3.1: After drying the fine tailings, crush them and pass them through a 200-mesh sieve. Then, ball mill them for 40 minutes, add alkaline activation solution, stir for 20 minutes, and then cure them at a constant temperature of 80℃ for 30 hours. After cooling, filter and wash until the pH of the filtrate is 10. Then dry and grind them to obtain alkaline activated fine tailings. The alkaline activation solution is prepared by mixing a 20% sodium hydroxide solution and a 30% sodium silicate solution in a volume ratio of 3:1.

[0079] S3.2: Immerse the above-mentioned alkali-activated fine tailings in a 0.1% sulfobetaine aqueous solution at a ratio of 1g:6mL, stir at 60℃ for 40min, and then filter and dry to obtain surface-modified fine tailings.

[0080] S3.3: Mix the above-mentioned surface-modified fine tailings with styrene at a mass ratio of 1:0.5, then add benzoyl peroxide, and heat at 80°C for 4 hours under nitrogen protection. After cooling, an activated fine tailings mixture is obtained, wherein the amount of benzoyl peroxide added is 1% of the mass of styrene.

[0081] S4: Preparation of filling cementitious materials

[0082] Mix 100 parts by weight of the above activated fine tailings mixture, 20 parts by weight of quicklime, 20 parts by weight of desulfurized gypsum, 5 parts by weight of sodium sulfate, and 3 parts by weight of the above internal curing agent evenly. Then add 2 parts by weight of polycarboxylate superplasticizer, 5 parts by weight of the above water hyacinth extract, 5 parts by weight of the above cactus extract, and 50 parts by weight of water for wet mixing, pouring, vibration molding, and room temperature curing to obtain the filling cementitious material.

[0083] Comparative Example 1 differs from Example 1 in that the internal curing agent in step S4 is removed.

[0084] Comparative Example 2 differs from Example 1 in that the water hyacinth extract and cactus extract in step S4 are removed.

[0085] Comparative Example 3 differs from Example 1 in that the water hyacinth extract in step S4 is replaced with an equal amount of cactus extract.

[0086] Comparative Example 4 differs from Example 1 in that the cactus extract in step S4 is replaced with an equal amount of water hyacinth extract.

[0087] Comparative Example 5 differs from Example 1 in that steps S3.2 and S3.3 are removed, and the activated fine tailings in step S4 are replaced with an equal amount of alkali-activated fine tailings.

[0088] Test example:

[0089] Test 1: The 90-day drying shrinkage of the filling cementitious materials prepared in Examples 1-3 and Comparative Example 1 was tested according to the test method of JC / T603-2004. The test was repeated three times and the average value was taken. The results are shown in Table 1.

[0090] Table 1: Results of Drying Shrinkage Test

[0091] <![CDATA[90d drying shrinkage (×10 -4 )]]> Example 1 9.6 Example 2 9.2 Example 3 8.7 Comparative Example 1 19.3

[0092] As shown in Table 1 above, the 90-day drying shrinkage of the filling gel material prepared in Comparative Example 1 without the addition of an internal curing agent was significantly higher than that in Example 1. This indicates that by neutralizing methacrylic acid to a weakly acidic state, mixing it with montmorillonite suspension and hydroxypropyl methylcellulose solution, and adding polyaspartic acid, using N,N'-methylenebisacrylamide as a crosslinking agent, and initiating a polymerization reaction under the initiation of an initiator, a three-dimensional network structure is formed. Montmorillonite is embedded into the polymer network through electrostatic interaction and hydrogen bonding to obtain an internal curing agent. When this internal curing agent is added to the filling gel material, it can inhibit the drying shrinkage of the filling gel material.

[0093] Test 2: Referring to the test method of GB / T51450-2022, the 7-day and 28-day compressive strength of the filling cementitious materials prepared in Examples 1-3 and Comparative Examples 2-5 were tested respectively. The tests were repeated three times and the average value was taken. The results are shown in Table 2.

[0094] Table 2: Compressive Strength Test Results

[0095] 7-day compressive strength (MPa) 28-day compressive strength (MPa) Example 1 29.25 57.39 Example 2 29.28 57.46 Example 3 29.32 57.52 Comparative Example 2 18.86 42.65 Comparative Example 3 25.08 48.99 Comparative Example 4 26.12 50.07 Comparative Example 5 15.56 38.47

[0096] As shown in Table 2 above, in Comparative Example 2, without the addition of water hyacinth extract and cactus extract, the 7-day and 28-day compressive strengths of the prepared filling gelling material were both lower than those of Example 1. In Comparative Examples 3 and 4, when only one of cactus extract or water hyacinth extract was added, the 7-day and 28-day compressive strengths of the prepared filling gelling material were higher than those of Comparative Example 2, but both were lower than those of Example 1. This indicates that by adding water hyacinth extract and cactus extract to the filling gelling material, the water hyacinth extract can react with Ca... 2 The complexation promotes CSH gel formation and refines Ca(OH)2 crystals, avoiding structural defects caused by crystal orientation. Cactus extract can serve as a precipitation active site for CSH gel, guiding the gel to precipitate evenly on the surface of activated fine tailings and reducing local loose areas. The combined use of the two can improve the polymerization degree of CSH gel, making the hydration products more compact and evenly distributed, thereby synergistically improving the compressive strength of the filling cementitious material.

[0097] Furthermore, in Comparative Example 5, when the fine tailings were activated by alkaline activation liquid without subsequent sulfobetaine modification and styrene polymerization, the 7-day and 28-day compressive strengths of the resulting filling cementitious material were lower than those in Example 1. This shows that by using sulfobetaine to modify the surface of the fine tailings and then using benzoyl peroxide to initiate the polymerization of styrene on the surface of the fine tailings to form a thin and dense polystyrene coating, the interfacial bonding strength between the fine tailings and the cementitious matrix can be improved, thereby enhancing the compressive strength of the filling cementitious material.

[0098] Test 3: The splitting tensile strength of the filling cementitious materials prepared in Examples 1-3 and Comparative Examples 2-4 were tested according to the test method of GB / T50081-2019. The test was repeated three times and the average value was taken. The results are shown in Table 3.

[0099] Table 3: Results of Splitting Tensile Strength Test

[0100] 28-day splitting tensile strength (MPa) Example 1 3.5 Example 2 3.6 Example 3 3.8 Comparative Example 2 2.2 Comparative Example 3 2.9 Comparative Example 4 3.1

[0101] As shown in Table 3, when neither water hyacinth extract nor cactus extract was added in Comparative Example 2, the 28-day splitting tensile strength of the prepared filling cementitious material was lower than that of Example 1. Furthermore, when only one of cactus extract or water hyacinth extract was added in Comparative Examples 3 and 4, the 28-day splitting tensile strength of the prepared filling cementitious material was also lower than that of Example 1. This indicates that water hyacinth extract and cactus extract can synergistically prevent crack propagation and improve the crack resistance of the filling cementitious material.

[0102] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A preparation process for a backfill cementitious material containing fine tailings, characterized in that, Includes the following steps: S1: Preparation of internal maintenance agent S1.1: Add montmorillonite to deionized water at a ratio of 1g:(20-30)mL, disperse ultrasonically at 60-70℃ for 1-2h, and after cooling, obtain a montmorillonite suspension; S1.2: Add hydroxypropyl methylcellulose to hot water at 60-80℃ at a ratio of 1g:(25-30)mL while stirring. After uniform dispersion, add cold water at 6-8℃ and continue stirring until completely dissolved. After cooling, a hydroxypropyl methylcellulose solution is obtained. The amount of cold water added is 50% of the volume of hot water. S1.3: Under water bath conditions of 1-3℃, add sodium hydroxide solution with a mass concentration of 20% to methacrylic acid while stirring, adjust the pH to 5, and obtain a neutralized methacrylic acid solution; S1.4: Thoroughly mix the above montmorillonite suspension, hydroxypropyl methylcellulose solution and methacrylic acid neutralization solution, then add polyaspartic acid, N,N'-methylenebisacrylamide and initiator solution. Under nitrogen protection, heat and stir the mixture at 60-65℃ for 2-4 hours. After cooling, soak the mixture in deionized water for 24 hours, then vacuum dry, pulverize and sieve to obtain the internal curing agent. S2: Preparation of water hyacinth extract and cactus extract Extracts were extracted from water hyacinth and cactus respectively to obtain water hyacinth extract and cactus extract; S3: Activated fine tailings After the fine tailings are activated with an alkaline activating solution, an aqueous solution of sulfobetaine is added for surface modification. Then, it is mixed with styrene and benzoyl peroxide is added to react and obtain an activated fine tailings mixture. S4: Preparation of filling cementitious materials The activated fine tailings mixture, quicklime, desulfurized gypsum, sodium sulfate, and the above-mentioned internal curing agent are stirred and mixed evenly. Then, water-reducing agent, water hyacinth extract, cactus extract, and water are added for wet mixing, pouring, vibration molding, and room temperature curing to obtain the filling cementitious material.

2. The preparation process of a backfill cementitious material containing fine tailings according to claim 1, characterized in that, S2 specifically includes the following steps: S2.1: After washing, drying and crushing the water hyacinth, add it to the mixed solvent at a solid-liquid ratio of 1g:(15-25)mL, and extract with ultrasonic assistance at 300-400W power and 50-60℃ for 40-60min. After filtration, collect the filtrate to obtain the water hyacinth extract. S2.2: Remove the thorns and epidermis from fresh, unrotten cactus stem segments, then wash, dry and crush them. Add water at a ratio of 1g:(15-20)mL, heat and stir at 50-60℃ for 2-3 hours, cool, centrifuge and filter, collect the filtrate to obtain cactus extract.

3. The preparation process of a backfill cementitious material containing fine tailings according to claim 2, characterized in that, S3 specifically includes the following steps: S3.1: After drying the fine tailings, crush them and pass them through a 200-mesh sieve. Then, ball mill them for 30-40 minutes, add alkaline activation solution, stir for 10-20 minutes, and then cure them at a constant temperature of 60-80℃ for 24-30 hours. After cooling, filter and wash until the pH of the filtrate is 10, and then dry and grind them to obtain alkaline activated fine tailings. S3.2: Immerse the above-mentioned alkali-activated fine tailings in a 0.1% sulfobetaine aqueous solution at a ratio of 1g:(5-6)mL, stir at 50-60℃ for 30-40min, and then filter and dry to obtain surface-modified fine tailings. S3.3: Mix the above-mentioned surface-modified fine tailings with styrene at a mass ratio of 1:(0.3-0.5), then add benzoyl peroxide, and heat the mixture at 70-80℃ for 2-4 hours under nitrogen protection. After cooling, the activated fine tailings mixture is obtained.

4. The preparation process of a backfill cementitious material containing fine tailings according to claim 1, characterized in that, In step S1.4, the amount of montmorillonite added is 10-15% of the mass of methacrylic acid in the methacrylic acid neutralization solution, the amount of hydroxypropyl methylcellulose added to the hydroxypropyl methylcellulose solution is 5-10% of the mass of methacrylic acid in the methacrylic acid neutralization solution, and the amount of polyaspartic acid added is 3-5% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

5. The preparation process of a backfill cementitious material containing fine tailings according to claim 1, characterized in that, The amount of N,N'-methylenebisacrylamide added is 0.1-0.2% of the mass of methacrylic acid in the methacrylic acid neutralization solution. The initiator solution is a 10% ammonium persulfate solution, and the amount of initiator added is 0.4-0.6% of the mass of methacrylic acid in the methacrylic acid neutralization solution.

6. The preparation process of a backfill cementitious material containing fine tailings according to claim 2, characterized in that, The mixed solvent is prepared by mixing 60-70% ethanol solution and 4-6% sodium hydroxide solution at a volume ratio of (3-5):

1.

7. The preparation process of a backfill cementitious material containing fine tailings according to claim 3, characterized in that, The alkaline activating solution is prepared by mixing a 20% sodium hydroxide solution and a 30% sodium silicate solution in a volume ratio of (1-3):

1.

8. The preparation process of a backfill cementitious material containing fine tailings according to claim 3, characterized in that, The amount of benzoyl peroxide added is 0.5-1% of the mass of styrene.

9. The preparation process of a backfill cementitious material containing fine tailings according to claim 1, characterized in that, By weight, the raw material composition of the filling cementitious material is as follows: 90-100 parts activated fine tailings mixture, 10-20 parts quicklime, 10-20 parts desulfurized gypsum, 3-5 parts sodium sulfate, 1-3 parts internal curing agent, 1-2 parts water-reducing agent, 3-5 parts water hyacinth extract, 3-5 parts cactus extract, and 40-50 parts water, wherein the water-reducing agent is a polycarboxylate-based water-reducing agent.

10. A backfill cementitious material containing fine tailings, characterized in that, It is prepared by the preparation process of a filling cementitious material containing fine tailings as described in any one of claims 1-9.

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