A method for preparing a solidified soil based on iron ore tailings

Abstract

The application provides a method for preparing solidified soil based on iron ore tailings, which comprises adding a solidifying agent slurry composed of phosphate cement, high-alumina cement, heat-sensitive active agent, expanding agent, sodium silicate, modified slag powder, water reducing agent and plasticizer, uniformly mixing, vibrating and exhausting and adjusting pH value, and then coagulating at room temperature to form solidified soil. The method significantly enhances the compactness and mechanical properties of the material through the pozzolanic activity of the modified slag powder, the ion release of the heat-sensitive active agent and the micro-expansion effect of the expanding agent. Under high temperature conditions, the method further promotes the hydration reaction to generate more cementitious products, thereby improving the compressive strength and durability. The application can effectively utilize iron ore tailings to prepare high-performance solidified soil, solve the environmental problems caused by tailings storage, and is suitable for mine backfilling, foundation reinforcement and other fields.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method for preparing solidified soil based on iron ore tailings, and belongs to the technical field of solidified soil. BACKGROUND

[0002] Iron ore tailings are fine-grained waste produced in the process of iron ore mining and beneficiation. The storage of the tailings not only occupies a large amount of land resources, but also may cause environmental pollution and safety hazards. With the rapid development of the mining industry, the cumulative amount of iron ore tailings is increasing. How to effectively utilize and dispose of the tailings has become an urgent engineering and environmental problem. At present, the solidified soil technology is widely used in the field of converting industrial waste into engineering materials. By adding a solidifying agent, the tailings and other waste can be formed into solid materials with certain strength and stability, which are used for road foundation, ground reinforcement and mine backfilling and the like. However, in the process of preparing solidified soil based on iron ore tailings, the low strength is a prominent problem. The main reason is that the chemical activity of the iron ore tailings is low, and it is difficult to fully react with the solidifying agent, resulting in that the strength of the solidified soil at room temperature and high temperature is not ideal.

[0003] In view of the deficiencies of the prior art, the application provides a preparation method for preparing solidified soil based on iron ore tailings. SUMMARY

[0004] To solve the technical problems existing in the prior art, the application provides a preparation method for preparing solidified soil based on iron ore tailings, which comprises the following steps: step S1. Put phosphate cement, high-alumina cement, heat-sensitive active agent and expanding agent into a mixer, dry mix for 5 minutes, add sodium silicate solution, and continue to stir at the same time to make them fully mixed, finally add modified slag powder, water reducing agent and plasticizer, stir uniformly to form a solidifying agent slurry; step S2. Mix the iron ore tailings and the solidifying agent according to a mass ratio of 70:30, add an appropriate amount of water in a stirrer, stir for 5-8 minutes to form a uniform slurry, and adjust the pH of the slurry to 5.0-6.0, pour the slurry into a mold and slightly vibrate to remove air bubbles; step S3. Stand at room temperature for 2-4 hours to complete setting.

[0005] It should be noted that, in the preparation of the solidifying agent, phosphate cement and high-alumina cement are used as main cementitious materials. The phosphate cement has the characteristics of rapid hardening and high early strength, and the high-alumina cement has excellent high-temperature resistance and sulfuric acid resistance. The combination of the two can significantly enhance the mechanical properties and environmental adaptability of the solidified soil. The addition of the heat-sensitive active agent (such as alumina or magnesium oxide) is relatively stable at room temperature, but is activated under high temperature and acidic conditions to release active ions (such as Al 3+ and Mg 2+), promote the hydration reaction of silicate and aluminate, thereby accelerating the setting and hardening process. Expanding agent (such as calcium sulphoaluminate) produces a slight expansion effect through hydration reaction under high temperature conditions, filling the pores and microcracks inside the material, improving the density and crack resistance. In addition, the SiO3 2- reacts with the Ca 2+ generated by the hydration reaction to form calcium silicate hydrate (C-S-H), further enhancing the strength and durability of the material. The modified slag powder improves the pozzolanic activity through surface modification, forms a firm interfacial bond with the cement matrix, and generates additional cementitious products, thereby optimizing the microstructure of the material. The introduction of water reducing agent and plasticizer improves the fluidity and uniformity of the paste, reduces the porosity, and improves the construction performance and mechanical properties of the material. Iron ore tailings, as fine waste, have low chemical activity and are difficult to react alone to form high-strength structures. Mixing it with the curing agent at a mass ratio of 70:30 and introducing an appropriate amount of water and stirring thoroughly ensures that the tailings particles are in full contact with the curing agent and react to form a uniform paste. The pH value of the slurry is adjusted to 5.0 to 6.0, which helps to activate the heat-sensitive active agent and maintain the optimal conditions for the hydration reaction of silicates and aluminates. The paste is slightly vibrated to remove air bubbles, further reducing porosity and improving the density and uniformity after molding, laying a foundation for subsequent setting and strength improvement.

[0006] During the 2-4 hours of normal temperature standing, the hydration reaction of the cement-based material begins, generating preliminary cementitious products (such as C-S-H and C-A-H) and forming the initial skeletal structure of the solidified soil. In this stage, the phosphate cement provides early strength, the high-alumina cement gradually exhibits high-temperature resistance and chemical corrosion resistance, and the activation of the heat-sensitive active agent in the acidic environment promotes the in-depth progress of the hydration reaction. Through uniform dispersion of the paste and porosity elimination, the material's density is further improved, ensuring the structural strength and stability after setting.

[0007] As a preferred technical solution of the preparation method of the solidified soil based on iron ore tailings, in step S2, the water-to-material ratio in the blender is 0.25-0.35.

[0008] It should be noted that by controlling the water-to-material ratio to 0.25-0.35, the paste has appropriate fluidity and viscosity, promoting the thorough mixing and reaction of the curing agent with the iron ore tailings, thereby improving the uniformity and mechanical properties of the solidified soil.

[0009] As a preferred technical solution of the preparation method of the solidified soil based on iron ore tailings, the heat-sensitive active agent is aluminum oxide or magnesium oxide.

[0010] It should be noted that by adding alumina and magnesia as heat-sensitive activators in the curing agent, taking advantage of their activated characteristics under high temperature and acidic conditions, Al 3+ and Mg 2+ and other active ions, promote the hydration reaction of silicate and aluminate, which accelerates the setting and hardening process, generates more and more stable cementitious products, optimizes the microstructure of the material, and finally, the prepared solidified soil has higher strength, density and durability, which meets the special engineering requirements in high temperature environment.

[0011] As a preferred technical solution of the preparation method of the solidified soil prepared from iron ore tailings, the expanding agent is calcium sulphoaluminate.

[0012] It should be noted that by adding calcium sulphoaluminate as an expanding agent in the solidified soil, taking advantage of its hydration reaction under high temperature conditions to generate ettringite and other expansive products, a crystalline expansion effect is produced, which fills and compacts the pores and micro-cracks inside the material, improving the microstructure. This expansion effect not only compensates for the dry shrinkage and thermal stress during the hardening process of the material, preventing cracking, but also improves the compressive strength and durability of the material.

[0013] As a preferred technical solution of the preparation method of the solidified soil prepared from iron ore tailings, the water reducing agent is β-naphthalenesulfonic acid formaldehyde condensate sodium salt.

[0014] It should be noted that β-naphthalenesulfonic acid formaldehyde condensate sodium salt as a water reducing agent, by dispersing particles, reducing water consumption, improving the fluidity and density of the slurry, significantly improving the mechanical properties and durability of the solidified soil.

[0015] As a preferred technical solution of the preparation method of the solidified soil prepared from iron ore tailings, the plasticizer is calcium lignosulfonate.

[0016] It should be noted that by adding calcium lignosulfonate as a plasticizer in the preparation of solidified soil, taking advantage of its dispersing, lubricating and viscosity-reducing effects, the fluidity and plasticity of the mixture are improved, so that the construction requirements can still be met at a lower water-cement ratio, improving the mechanical properties and durability of the solidified soil.

[0017] As a preferred technical solution of the preparation method of the solidified soil prepared from iron ore tailings, in step S1, the curing agent slurry comprises, by mass fraction: 25 to 35 parts of phosphate cement, 15 to 25 parts of high-alumina cement, 10 to 15 parts of sodium silicate, 10 to 15 parts of heat-sensitive activator, 5 to 10 parts of expanding agent, 3 to 5 parts of modified slag powder, 0.5 to 1 part of water reducing agent, and 0.5 to 1 part of plasticizer.

[0018] It should be noted that through the precise control of the above ingredient content and the organic combination, the curing agent slurry of the application achieves an optimal balance in performance, meets the special needs of curing soil preparation under high temperature environment, and embodies innovation and practicality.

[0019] As a preferred technical solution of the preparation method of the curing soil based on iron mine tailings, the preparation step of the modified slag powder includes:

[0020] The dried nano-scale slag powder is slowly added to anhydrous ethanol, and an ultrasonic device is used for mixing. An appropriate amount of organosilane coupling agent is weighed and slowly added to the dispersion liquid while stirring. The reaction temperature is controlled at 40-80°C, and the stirring is continued for 1-2 hours. The reaction liquid is filtered through a vacuum filtration device, and the modified slag powder is retained. The slag powder is washed with anhydrous ethanol solvent to remove residual organosilane and by-products. The washed slag powder is placed in an oven and dried at 80-100°C for 12-24 hours.

[0021] It should be noted that the modified slag powder significantly enhances the stability and durability of the material in a high-temperature environment by improving its chemical reactivity and optimizing the microstructure of the curing soil, meeting the special requirements of high-temperature construction environment on the performance of curing soil.

[0022] As a preferred technical solution of the preparation method of the curing soil based on iron mine tailings, the organosilane coupling agent is 3-aminopropyl triethoxysilane, and the organosilane coupling agent accounts for 1wt% to 3wt% of the mass of the nano-scale slag powder.

[0023] It should be noted that the nano-scale slag powder is surface modified by using 3-aminopropyl triethoxysilane (APTES), and the modified slag powder has better dispersibility, compatibility and thermal stability. It can form a firm interface bond with the matrix material in the curing soil, improve the density and mechanical properties of the material, and at the same time, APTES modification gives the material higher high-temperature resistance and dimensional stability, preventing structural damage and performance degradation in high-temperature environment. Finally, the introduction of modified slag powder significantly improves the performance of curing soil under high-temperature conditions, meeting the needs of special engineering environment.

[0024] The present application has significant beneficial effects. First, by using modified slag powder and optimized formula design, the solidified soil of the present application exhibits excellent mechanical properties under high temperature conditions, especially the compressive strength and flexural strength are significantly improved, which is suitable for engineering needs in high temperature environment. Second, the compactness of the solidified soil is improved, and the porosity is reduced, effectively improving the permeability resistance of the material and prolonging the service life of the material. In addition, the addition of heat-sensitive active agent accelerates the hydration reaction in high temperature environment, further improving the solidification efficiency and strength of the material. By using water reducing agent and plasticizer, the fluidity and plasticity of the material are improved, which not only improves the construction efficiency, but also ensures the forming quality. In summary, the present application has good adaptability in high temperature construction environment, and significantly improves the strength, durability and construction performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a fracture electron micrograph of the solidified soil column prepared in Example 1 for performance testing at room temperature;

[0026] Figure 2 is a fracture electron micrograph of the solidified soil column prepared in Example 1 for performance testing at 100℃ for 5h;

[0027] Figure 3 is a data graph of the solidified soil column prepared in Example 5 for performance testing at room temperature;

[0028] Figure 4 is a data graph of the solidified soil column prepared in Example 5 for performance testing at 100℃ for 5h; DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below in combination with the description examples.

[0030] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific embodiments disclosed below.

[0031] Secondly, "one embodiment" or "embodiment" referred to herein means that specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is separate or alternative to other embodiments.

[0032] The present application will be further described in detail below in combination with examples, preparation examples and comparative examples, and the raw materials involved in the present application can be obtained by market purchase.

[0033] Preparation example of modified slag powder

[0034] The following is described taking preparation example 1 as an example

[0035] The preparation steps of the modified slag powder in this preparation example include: slowly adding the dried nanoscale slag powder into anhydrous ethanol, mixing uniformly using an ultrasonic device, weighing 3-aminopropyl triethoxysilane accounting for 1wt% of the mass of the nanoscale slag powder, slowly adding into the dispersion liquid while maintaining stirring, controlling the reaction temperature at 60℃, and continuously stirring for 1 hour, filtering the reaction liquid through a vacuum filtering device, retaining the modified slag powder, washing the slag powder with anhydrous ethanol solvent to remove residual organosilane and by-products. Repeat the washing for 3 times, and place the washed slag powder into an oven for drying at 100℃ for 24 hours.

[0036] Example

[0037] Example 1

[0038] The solidifying agent for solidifying soil includes, in mass parts: phosphate cement 30 parts, high-alumina cement 25 parts, sodium silicate 10 parts, heat-sensitive activator 12 parts, expanding agent 5 parts, modified slag powder 5 parts, water reducing agent 0.8 parts, and plasticizer 0.6 parts.

[0039] The preparation method of the solidifying soil based on iron mine tailings includes the following steps:

[0040] Step S1. Put the phosphate cement, high-alumina cement, aluminum oxide, and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution while continuing to stir, so as to fully mix, and finally add modified slag powder, β-naphthalene sulfonate formaldehyde condensate sodium salt, and calcium lignosulfonate, stir uniformly to form a solidifying agent slurry;

[0041] Step S2. Mix the iron mine tailings with the solidifying agent according to a mass ratio of 70:30, add an appropriate amount of water in a blender, the water-material ratio is 0.25, stir for 8 minutes to form a uniform slurry, and adjust the pH of the slurry to 6.5, slightly vibrate the slurry to remove air bubbles, to obtain a solidifying soil slurry based on iron mine tailings;

[0042] Step S3. Put the prepared solidifying soil slurry into a column mold of 40mm x 40mm x 160mm, stand at room temperature for 4 hours to complete the coagulation.

[0043] Example 2

[0044] The solidifying agent for solidifying soil comprises, in parts by mass: phosphate cement 25 parts, high-alumina cement 15 parts, sodium silicate 15 parts, heat-sensitive active agent 10 parts, expanding agent 10 parts, modified slag powder 4 parts, water reducing agent 0.6 parts, and plasticizer 0.5 parts.

[0045] The preparation method of the solidified soil based on iron mine tailings comprises the following steps:

[0046] Step S1. Put the phosphate cement, high-alumina cement, magnesium oxide and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution while continuing to stir, mix thoroughly, finally add modified slag powder, β-naphthalenesulfonic acid formaldehyde condensate sodium salt and calcium lignosulfonate, stir uniformly to form a solidifying agent slurry;

[0047] Step S2. Mix the iron mine tailings and the solidifying agent at a mass ratio of 70:30, add an appropriate amount of water in a blender, the water-material ratio is 0.35, stir for 5 minutes to form a uniform slurry, adjust the pH of the slurry to 6.0, slightly vibrate the slurry to remove air bubbles, and obtain a solidified soil slurry based on iron mine tailings;

[0048] Step S3. Put the solidified soil slurry into a 40mm*40mm*160mm column mold, stand at room temperature for 2 hours, and complete coagulation.

[0049] Example 3

[0050] The solidifying agent for solidifying soil comprises, in parts by mass: phosphate cement 35 parts, high-alumina cement 20 parts, sodium silicate 12 parts, heat-sensitive active agent 15 parts, expanding agent 8 parts, modified slag powder 3 parts, water reducing agent 1 part, and plasticizer 1 part.

[0051] The preparation method of the solidified soil based on iron mine tailings comprises the following steps:

[0052] Step S1. Put the phosphate cement, high-alumina cement, magnesium oxide and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution while continuing to stir, mix thoroughly, finally add modified slag powder, β-naphthalenesulfonic acid formaldehyde condensate sodium salt and calcium lignosulfonate, stir uniformly to form a solidifying agent slurry;

[0053] Step S2. Mix the iron mine tailings and the solidifying agent at a mass ratio of 70:30, add an appropriate amount of water in a blender, the water-material ratio is 0.30, stir for 6 minutes to form a uniform slurry, adjust the pH of the slurry to 5.0, slightly vibrate the slurry to remove air bubbles, and obtain a solidified soil slurry based on iron mine tailings;

[0054] Step S3. Put the solidified soil slurry into a 40mm*40mm*160mm column mold, stand at room temperature for 2 hours, and complete coagulation.

[0055] Example 4

[0056] The solidifying agent for solidifying soil comprises, in mass parts: phosphate cement 25 parts, high-alumina cement 15 parts, sodium silicate 14 parts, heat-sensitive active agent 10 parts, expanding agent 5 parts, modified slag powder 3 parts, water reducing agent 0.5 parts, and plasticizer 0.5 parts.

[0057] The preparation method for preparing solidifying soil based on iron mine tailings comprises the following steps:

[0058] Step S1. Put phosphate cement, high-alumina cement, aluminum oxide, and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution while continuing to stir, mix thoroughly, finally add modified slag powder, beta-naphthalene sulfonate formaldehyde condensate sodium salt, and calcium lignosulfonate, stir uniformly to form a solidifying agent slurry;

[0059] Step S2. Mix the iron mine tailings with the solidifying agent at a mass ratio of 70:30, add an appropriate amount of water in a blender, the water-to-material ratio is 0.32, stir for 8 minutes to form a uniform slurry, adjust the pH of the slurry to 5.5, slightly vibrate the slurry to remove air bubbles, and obtain a solidifying soil slurry prepared based on iron mine tailings;

[0060] Step S3. Pour the solidifying soil slurry into a 40mm x 40mm x 160mm column mold, and let it stand at room temperature for 2 hours to complete the coagulation.

[0061] Example 5

[0062] The solidifying agent for solidifying soil comprises, in mass parts: phosphate cement 31 parts, high-alumina cement 24 parts, sodium silicate 10 parts, heat-sensitive active agent 12 parts, expanding agent 5 parts, modified slag powder 5 parts, water reducing agent 0.9 parts, and plasticizer 0.6 parts.

[0063] The preparation method for preparing solidifying soil based on iron mine tailings comprises the following steps:

[0064] Step S1. Put phosphate cement, high-alumina cement, aluminum oxide, and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution while continuing to stir, mix thoroughly, finally add modified slag powder, beta-naphthalene sulfonate formaldehyde condensate sodium salt, and calcium lignosulfonate, stir uniformly to form a solidifying agent slurry;

[0065] Step S2. Mix the iron mine tailings with the solidifying agent at a mass ratio of 70:30, add an appropriate amount of water in a blender, the water-to-material ratio is 0.32, stir for 8 minutes to form a uniform slurry, adjust the pH of the slurry to (3, 4, 5, 6, 7, 8, 9), slightly vibrate the slurry to remove air bubbles, and obtain a solidifying soil slurry prepared based on iron mine tailings;

[0066] Step S3. The prepared solidified soil slurry was poured into a 40 mm x 40 mm x 160 mm column mold, and left to stand at room temperature for 4 hours to complete coagulation.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that an equal amount of nanoscale slag powder is used to replace the modified slag powder.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 1 is that no heat-sensitive active agent is added in Step S1.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that the pH of the slurry is adjusted to 7.0.

[0073] Comparative Example 4

[0074] The difference between this comparative example and Example 1 is that no water reducing agent is added in Step S1.

[0075] Comparative Example 5

[0076] The difference between this comparative example and Example 1 is that no plasticizer is added in Step S1.

[0077] Performance Test Method

[0078] Column samples with a size of 40 mm x 40 mm x 160 mm were prepared, and compressive strength and flexural strength tests were performed at room temperature and 100°C for 5 hours, respectively.

[0079] Table 2

[0080]

[0081] In combination with Example 1 and Figure 1 and 2 It can be seen that, Figure 1 The microstructure in Example 1 shows that there are obvious pores and voids, in contrast, Figure 2 The microstructure in Example 1 is more dense, with almost no pores, and the microstructure of the solidified soil exhibits high density under high temperature conditions, the porosity inside the sample is low, and the particle distribution is uniform, indicating that through reasonable formulation and process optimization, bubbles and voids are effectively excluded, and this dense structure makes the compressive strength and flexural strength of the material exhibit significant improvement.

[0082] It can be seen from Examples 1 to 4 and Table 2 that in Examples 1 to 4, the compressive strength of the cured soil at room temperature ranges from 48.79 MPa to 60.45 MPa, the flexural strength ranges from 6.89 MPa to 8.14 MPa, the compressive strength of the cured soil at 100°C for 5h ranges from 68.81 MPa to 85.73 MPa, and the flexural strength ranges from 8.59 MPa to 10.56 MPa; the sample after setting is placed in a drying oven at a temperature of 100°C for 5h, under high temperature conditions, the heat-sensitive active agent is activated, active ions are released, and the hydration reaction of the cement-based material is significantly accelerated, generating more C-S-H gel and hydrated calcium aluminate (C-A-H) and other cementitious products, improving the strength and durability of the material, at the same time, high temperature promotes the decomposition of the expansive agent, producing a micro-expansion effect, filling the micro-cracks inside the material, reducing porosity, enhancing compactness and impermeability, in addition, the modified slag powder is activated under high temperature conditions, its pozzolanic activity is stimulated, and a secondary reaction with Ca(OH)2 occurs, generating additional cementitious products, further improving the mechanical properties of the material.

[0083] It can be seen from Example 1, Comparative Example 1 and Table 2 that under the conditions of room temperature and 100°C for 5h, the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 1. Specifically, at room temperature, the compressive strength of Example 1 is 55.21 MPa, and the flexural strength is 7.54 MPa, while the compressive strength of Comparative Example 1 is only 32.45 MPa, and the flexural strength is 5.48 MPa; at 100°C for 5h, the compressive strength of Example 1 is 78.54 MPa, and the flexural strength is 9.52 MPa, while the compressive strength of Comparative Example 1 is only 42.18 MPa, and the flexural strength is 6.24 MPa. This difference is mainly due to the significant improvement of the modified slag powder on the performance of the material, the active sites of the modified slag powder can react with the Ca 2+ OH)2 in the cement-based material to generate more hydrated calcium silicate (C-S-H) and hydrated calcium aluminate (C-A-H) and other cementitious products, which fill the pores inside the material, optimize the microstructure, and enhance the compactness, in addition, the coupling groups formed by surface modification of the modified slag powder improve the interfacial bonding ability with the matrix material, reduce the micro-cracks and interface defects inside the material, thereby improving the mechanical properties of the material at room temperature and high temperature.

[0084] It can be seen from Example 1, Comparative Example 2 and Table 2 that at room temperature, the compressive strength and flexural strength of Example 1 are not much different from those of Comparative Example 2, and under the condition of 100°C for 5 hours, the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 2; at room temperature, the compressive strength of Example 1 is 55.21 MPa, and the flexural strength is 7.54 MPa, the compressive strength of Comparative Example 2 is 54.67 MPa, and the flexural strength is 7.18 MPa, under the condition of 100°C for 5 hours, the compressive strength of Example 1 is 78.54 MPa, and the flexural strength is 6.52 MPa, the compressive strength of Comparative Example 2 is 29.56 MPa, and the flexural strength is only 4.56 MPa. At room temperature, the hydration reaction of the material mainly depends on the hydration process of components such as phosphate cement and high-alumina cement, and the solidification structure formed by the generated hydration calcium silicate (C-S-H) and hydration calcium aluminate (C-A-H) cementitious products provides a certain strength. However, under high temperature conditions, due to the lack of activation of the heat-sensitive active agent, the hydration reaction cannot be significantly accelerated, and there is a lack of additional active ions (such as Al 3+ ) to promote the deep reaction of silicates and aluminates. The stability of the solidified material under high temperature conditions depends on the quantity and quality of the generated cementitious products. In Comparative Example 2, the generated cementitious products are less, the porosity in the material is higher, and the compactness is poor, resulting in that the strength cannot be effectively improved. In addition, high temperature conditions can cause thermal expansion and loose structure of unreacted components in the material, further weakening its mechanical properties. Therefore, the reason why the strength of Comparative Example 2 significantly decreases under high temperature conditions is that the introduction of the heat-sensitive active agent leads to the release of active ions and the deep hydration reaction under high temperature conditions cannot be effectively carried out, and the compactness and structural stability of the material cannot be improved, finally showing a large decrease in strength. This shows that the heat-sensitive active agent is crucial in high temperature environment, which can significantly improve the performance of the material by activating the generation of cementitious products and improving the microstructure.

[0085] It can be seen from Example 1, Comparative Example 3 and Table 2 that at room temperature, the compressive strength and flexural strength of Example 1 are not much different from those of Comparative Example 3, and under the condition of 100°C for 5 hours, the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 3; at room temperature, the compressive strength of Example 1 is 55.21 MPa, and the flexural strength is 7.54 MPa, while the compressive strength of Comparative Example 3 is 53.69 MPa, and the flexural strength is 7.45 MPa, and under the condition of 100°C for 5 hours, the compressive strength of Example 1 is 78.54 MPa, and the flexural strength is 6.52 MPa, while the compressive strength of Comparative Example 3 is 35.69 MPa, and the flexural strength is 5.48 MPa. At room temperature, the hydration reaction rate of the cement-based material is low, mainly relying on the basic hydration process of the phosphate cement and the high-alumina cement to generate cementitious products such as hydrated calcium silicate (C-S-H) and hydrated calcium aluminate (C-A-H); these products provide the material with a preliminary solidification structure and fill part of the pores, thereby endowing the material with basic compressive and flexural strength; under the high-temperature condition of 100°C for 5 hours, the pH value of the slurry in Example 1 is adjusted to the acidic range (5.0-6.0), which effectively stimulates the activity of the heat-sensitive active agent (such as aluminum oxide or magnesium oxide) and releases more Al 3+ active ions. These ions promote the hydration reaction of silicates and aluminates and significantly accelerate the generation of C-S-H and C-A-H cementitious products, in contrast, the pH value of the slurry in Comparative Example 3 is adjusted to neutral (7.0), which fails to stimulate the activity of the heat-sensitive active agent, resulting in a low hydration reaction rate under high-temperature conditions and a significant reduction in the amount of generated cementitious products.

[0086] It can be seen from Example 1, Comparative Example 4 and Table 2 that the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 4 at room temperature and at 100°C for 5 hours. At room temperature, the compressive strength of Example 1 is 55.21 MPa, and the flexural strength is 7.54 MPa. The compressive strength of Comparative Example 4 is only 35.68 MPa, and the flexural strength is 5.72 MPa. At 100°C for 5 hours, the compressive strength of Example 1 is 78.54 MPa, and the flexural strength is 9.52 MPa. The compressive strength of Comparative Example 4 is only 43.57 MPa, and the flexural strength is 6.19 MPa. The performance difference is mainly due to the introduction of the water reducing agent. In Example 1, the water reducing agent (such as β-naphthalene sulfonate formaldehyde condensate sodium salt) significantly improves the fluidity and uniformity of the slurry by dispersing the cement particles and reducing the amount of free water in the mixture, thereby promoting the full mixing and reaction of the solidifying agent and the iron ore tailings. This action not only reduces the porosity of the material and significantly improves its density, but also generates more cementitious products such as calcium silicate hydrate (C-S-H), which improves the mechanical properties of the material at room temperature and high temperature. In contrast, Comparative Example 3 lacks a water reducing agent, and the fluidity and dispersibility of the slurry are poor, which leads to uneven mixing of the solidifying agent and the iron ore tailings, insufficient reaction in some areas, and the generation of fewer cementitious products. The internal structure of the material is loose, and the porosity is high. This not only leads to lower mechanical properties at room temperature, but also exacerbates the thermal expansion effect in a high-temperature environment due to the presence of microcracks and pores in the material, further weakening the overall strength and durability of the material.

[0087] It can be seen from Example 1, Comparative Example 5 and Table 2 that the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 5 at room temperature and at 100°C for 5 hours. At room temperature, the compressive strength of Example 1 is 55.21 MPa, and the flexural strength is 7.54 MPa. The compressive strength of Comparative Example 5 is only 38.97 MPa, and the flexural strength is 6.12 MPa. At 100°C for 5 hours, the compressive strength of Example 1 is 78.54 MPa, and the flexural strength is 9.52 MPa. The compressive strength of Comparative Example 5 is only 41.25 MPa, and the flexural strength is 5.98 MPa. The performance difference is mainly due to the introduction of plasticizer in Example 1. Plasticizer (such as calcium lignosulfonate) improves the workability and mixing uniformity of the material by reducing the viscosity of the mixture and improving the fluidity of the paste. In Example 1, the role of plasticizer enables the paste to be uniformly dispersed at a lower water-to-binder ratio, so that the solidifying agent can fully contact and react with the iron ore tailings, thereby generating more hydrated calcium silicate (C-S-H) and other cementitious products. These products fill the pores inside the material, significantly improve the density, reduce microcracks, and thus improve the mechanical properties at room temperature and high temperature. In contrast, no plasticizer is added in Comparative Example 5, and the paste has high viscosity, resulting in poor dispersion and flowability of the mixture, so that the local area is insufficiently reacted, and the internal structure forms more pores and microcracks. Under high temperature conditions, these pores and cracks can further expand due to thermal expansion, significantly weakening the compressive and flexural properties of the material. In addition, the absence of the lubricating effect of the plasticizer makes it difficult to achieve the best uniformity and density of the paste during mixing.

[0088] In combination with Example 5 and Figure 3It can be seen that under acidic conditions (pH < 7), the flexural and compressive strengths are relatively low, mainly due to the significant inhibition of the hydration reaction of the cement-based material. The acidic environment inhibits the hydration of silicates and aluminates, resulting in a lower amount of cementitious products (such as C-S-H and C-A-H) being generated, which leads to a loose internal structure, high porosity, and poor compressive and flexural performance. In addition, the strongly acidic environment can have a corrosive effect on the mineral components of the material, damaging its microstructure and further weakening the mechanical properties of the material. As the pH gradually increases to neutral conditions (pH = 7), the flexural and compressive strengths of the material reach a maximum value. Under neutral conditions, the hydration reaction rate significantly increases, generating a large amount of hydrated calcium silicate (C-S-H) and hydrated calcium aluminate (C-A-H), which effectively fill the internal pores of the material, significantly enhancing the material's density and mechanical properties. However, when the pH value exceeds 7 and enters the alkaline environment, the flexural and compressive strengths gradually decrease. This is because the alkaline conditions can cause the formation of a passivation layer on the surface of some mineral components (such as silicates), inhibiting subsequent chemical reactions and reducing the generation of cementitious products. At the same time, the inhomogeneous reaction in the alkaline environment can lead to an increase in the internal porosity of the material, and microcracks are not effectively repaired.

[0089] In combination with Example 5 and Figure 4 It can be seen that under strongly acidic conditions (pH 3-4), the flexural and compressive strengths of the material are relatively low, mainly due to the significant inhibition of the hydration reaction. The acidic environment destroys the surface chemical stability of silicates and aluminates, resulting in a significant lack of hydration products (such as hydrated calcium silicate C-S-H and hydrated calcium aluminate C-A-H). These cementitious products are insufficient to fill the internal pores of the material, leading to a loose structure and poor density. In addition, the strongly acidic environment can exacerbate the corrosion effect on mineral components (such as phosphates, silicates), further weakening the microstructure stability of the material and reducing the mechanical properties; under weakly acidic conditions (pH 5-6), the flexural and compressive strengths of the material reach a maximum value, and the weakly acidic environment can fully activate the heat-sensitive active agent, releasing a large amount of active ions (such as Al 3+ and Mg 2+ ), further accelerating the hydration reaction and significantly enhancing the mechanical properties of the material; under alkaline conditions (pH ≥ 7), the flexural and compressive strengths of the material gradually decrease, mainly due to the passivation effect of the chemical reaction. In the alkaline environment, a passivation layer may form on the surface of silicates and aluminates, hindering further hydration reactions and resulting in a decrease in the amount of cementitious products generated.

[0090] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing solidified soil based on iron ore tailings, characterized in that, Includes the following steps: Step S1. Place 25 to 35 parts of phosphate cement, 15 to 25 parts of high-alumina cement, 10 to 15 parts of thermosensitive activator and 5 to 10 parts of expansion agent into a mixer and dry mix for 5 minutes. Add 10 to 15 parts of sodium silicate solution and continue stirring to mix thoroughly. Finally, add 3 to 5 parts of slag powder modified with 3-aminopropyltriethoxysilane, 0.5 to 1 part of water-reducing agent and 0.5 to 1 part of plasticizer and stir evenly to form a curing agent slurry. Step S2. Mix iron ore tailings and solidifying agent slurry at a mass ratio of 70:

30. Add an appropriate amount of water to the mixer and stir for 5 to 8 minutes to form a uniform slurry. Adjust the pH of the slurry to 5.0 to 6.

0. Vibrate the slurry slightly to remove air bubbles and obtain solidified soil slurry based on iron ore tailings. Step S3. Let stand at room temperature for 2-4 hours to complete condensation; The thermosensitive activator is aluminum oxide or magnesium oxide.

2. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that, In step S2, the water-to-material ratio in the mixer is 0.25 to 0.

35.

3. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that, The expanding agent is calcium sulfoaluminate.

4. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that, The water-reducing agent is sodium salt of β-naphthalenesulfonic acid formaldehyde condensate.

5. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that, The plasticizer is calcium lignosulfonate.

6. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that, The preparation steps of the modified slag powder include: The dried nano-sized slag powder was slowly added to anhydrous ethanol and mixed using an ultrasonic device. An appropriate amount of organosilane coupling agent was weighed and slowly added to the dispersion while stirring. The reaction temperature was controlled at 40 to 80°C and stirring was continued for 1-2 hours. The reaction solution was filtered through a vacuum filter to retain the modified slag powder. The slag powder was washed with anhydrous ethanol solvent to remove residual organosilane and byproducts. The washing was repeated 3-5 times. The washed slag powder was placed in an oven and dried at 80-100°C for 12-24 hours.

7. The method for preparing solidified soil based on iron ore tailings as described in claim 6, characterized in that, The 3-aminopropyltriethoxysilane accounts for 1 wt% to 3 wt% of the mass of the nano-sized slag powder.

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