Method for preparing solidified soil based on iron ore tail mud

Abstract

The invention provides a method for preparing solidified soil based on iron ore tail mud, which comprises the following steps: adding a curing agent slurry consisting of phosphate cement, high-alumina cement, a thermosensitive active agent, an expanding agent, sodium silicate, modified superfine slag powder, a water reducing agent and a plasticizer, uniformly mixing, vibrating, exhausting, adjusting the pH value, and condensing at normal temperature to form the solidified soil. According to the method, through the pozzolanic activity of the modified superfine slag powder, the ion release of the thermosensitive active agent and the micro-expansion effect of the expanding agent, the compactness and the mechanical property of the material are remarkably enhanced. Under the high-temperature condition, the hydration reaction is further promoted to generate more gelatinization products, and the compressive strength and the durability are improved. The high-performance solidified soil can be prepared by effectively utilizing the iron ore tailing mud, the environmental problem caused by tailing mud stockpiling is solved, and the method is suitable for the fields of mine backfill, foundation reinforcement and the like.

Description

Technical Field

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

[0002] Iron ore tailings are fine-grained wastes generated during the mining and beneficiation of iron ore. Their storage 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 accumulation of iron ore tailings is increasing. How to effectively utilize and dispose of these tailings has become an engineering and environmental problem that needs to be solved urgently. At present, solidified soil technology is widely used in the field of converting industrial waste into engineering materials. By adding a curing agent, wastes such as tailings are formed into solid materials with certain strength and stability, which are used for road foundations, foundation reinforcement and mine backfilling. However, in the process of preparing solidified soil using iron ore tailings, low strength is a prominent problem. The main reason is that the chemical activity of iron ore tailings is low and it is difficult to fully react with the curing agent, resulting in unsatisfactory strength of the solidified soil at both room temperature and high temperature.

[0003] In view of the above-mentioned deficiencies in the prior art, we have invented a method for preparing solidified soil based on iron ore tailings. Summary of the invention

[0004] To solve the technical problems existing in the prior art, the present application provides a preparation method for solidified soil based on iron ore tailings, comprising the following steps: step S1. putting phosphate cement, high alumina cement, heat-sensitive active agent and expansion agent into a mixer, dry mixing for 5 minutes, adding sodium silicate solution, and continuing stirring to fully mix, and finally adding modified slag powder, water reducer and plasticizer, stirring evenly to form a curing agent slurry; step S2. mixing the iron ore tailings and the curing agent in a mass ratio of 70:30, adding an appropriate amount of water to the mixer, stirring for 5 to 8 minutes to form a uniform slurry, and adjusting the pH of the slurry to 5.0 to 6.0, pouring the slurry into a mold, and slightly vibrating to remove bubbles; step S3. standing at room temperature for 2 to 4 hours to complete coagulation.

[0005] It should be noted that in the preparation of the curing agent, phosphate cement and high alumina cement are used as the main cementing materials. Phosphate cement has the characteristics of rapid hardening and high early strength, while high alumina cement has excellent high temperature resistance and sulfate erosion resistance. The combination of the two can significantly enhance the mechanical properties and environmental adaptability of the cured soil. The addition of heat-sensitive activators (such as aluminum oxide or magnesium oxide) is relatively stable at room temperature, but is activated under high temperature and acidic conditions, releasing active ions (such as Al 3+ and Mg 2+), promoting the hydration reaction of silicates and aluminates, thereby accelerating the coagulation and hardening process. Expansion agents (such as calcium sulfoaluminate) produce a micro-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, SiO in the sodium silicate solution 3 2- Ca generated by hydration reaction 2+ Reaction to form calcium silicate hydrate (CSH), further enhancing the strength and durability of the material. The modified slag powder improves the volcanic ash activity through surface modification, forms a strong interface bond with the cement matrix, and generates additional cementitious products, thereby optimizing the microstructure of the material. The introduction of water reducer and plasticizer improves the fluidity and uniformity of the slurry, reduces the porosity, and improves the construction performance and mechanical properties of the material. As a fine-grained waste, iron ore tailings have low chemical activity and are difficult to react alone to form a high-strength structure. It is mixed with the curing agent in a mass ratio of 70:30, and through the introduction of an appropriate amount of water and sufficient stirring, it is ensured that the tailings particles are fully in contact and react with the curing agent to form a uniform slurry. The pH value of the slurry is adjusted to 5.0 to 6.0, a range that helps to stimulate the activity of the heat-sensitive active agent and maintain the optimal conditions for the hydration reaction of silicates and aluminates. The slurry is slightly vibrated to eliminate bubbles, further reduce pores, improve the density and uniformity after molding, and lay the foundation for subsequent coagulation and strength improvement.

[0006] During the 2-4 hours of standing at room temperature, the hydration reaction of cement-based materials begins to proceed, generating preliminary cementitious products (such as CSH and CAH) and forming the preliminary skeleton structure of the solidified soil. At this stage, phosphate cement provides early strength, the high temperature resistance and chemical corrosion resistance of high-aluminum cement gradually play a role, and the activation of heat-sensitive activators in an acidic environment promotes the depth of the hydration reaction. Through the uniform dispersion of the slurry and the elimination of pores, the density of the material is further improved, ensuring the structural strength and stability after solidification.

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

[0008] It should be noted that by controlling the water-to-solid ratio at 0.25-0.35, the slurry is ensured to have appropriate fluidity and viscosity, which promotes the full mixing and reaction of the curing agent and the iron ore tailings, thereby improving the uniformity and mechanical properties of the cured soil.

[0009] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the thermosensitive activator is aluminum oxide or magnesium oxide.

[0010] It should be noted that by adding aluminum oxide and magnesium oxide as heat-sensitive activators to the curing agent, the properties of aluminum oxide and magnesium oxide being activated under high temperature and acidic conditions are utilized to release aluminum oxide and magnesium oxide. 3+ and Mg 2+ Active ions such as silicates and aluminates promote the hydration reaction of silicates. This process accelerates coagulation and hardening, generates more and more stable cementitious products, and optimizes the microstructure of the material. Ultimately, the prepared solidified soil has higher strength, density and durability, meeting special engineering requirements in high temperature environments.

[0011] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the expansion agent is calcium sulphoaluminate.

[0012] It should be noted that by adding calcium sulfoaluminate as an expansion agent to the solidified soil, its hydration reaction under high temperature conditions is used to generate expansive products such as calcium aluminate, which produces a crystallization expansion effect, fills and compacts the pores and microcracks inside the material, and improves the microstructure. This expansion effect not only compensates for the shrinkage and thermal stress during the hardening process of the material and prevents cracking, but also improves the compressive strength and durability of the material.

[0013] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the water reducer is sodium salt of β-naphthalenesulfonic acid formaldehyde condensate.

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

[0015] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the plasticizer is calcium lignin sulfonate.

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

[0017] As a preferred technical solution for a preparation method of solidified soil based on iron ore tailings, in step S1, the solidifying agent slurry includes, in parts by mass: 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 thermosensitive activator, 5 to 10 parts of expansion agent, 3 to 5 parts of modified slag powder, 0.5 to 1 part of water reducer, and 0.5 to 1 part of plasticizer.

[0018] It should be noted that, through the precise control of the contents of the above-mentioned components and their organic combination, the curing agent slurry of the present invention achieves an optimal balance in performance, meets the special needs of preparing cured soil under high temperature environments, and embodies innovation and practicality.

[0019] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the preparation steps of the modified slag powder include:

[0020] Slowly add the dried nano-scale slag powder into anhydrous ethanol, mix it with ultrasonic equipment, weigh an appropriate amount of organosilane coupling agent, slowly add it into the dispersion, keep stirring, control the reaction temperature at 40 to 80°C, and continue stirring for 1-2 hours, filter the reaction liquid through a vacuum filter, retain the modified slag powder, wash the slag powder with anhydrous ethanol solvent, remove the residual organosilane and by-products. Repeat washing 3-5 times, put the washed slag powder into an oven, and dry it at 80-100°C for 12-24 hours.

[0021] It should be noted that modified slag powder significantly enhances the stability and durability of the material in high temperature environments by improving its own chemical reaction activity and optimizing the microstructure of the solidified soil, meeting the special requirements of high temperature construction environments for the performance of solidified soil.

[0022] As a preferred technical solution for a method for preparing solidified soil based on iron ore tailings, the organosilane coupling agent is 3-aminopropyltriethoxysilane, 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 by using 3-aminopropyltriethoxysilane (APTES) to modify the surface of nano-slag powder, the modified slag powder has better dispersibility, compatibility and thermal stability. It can form a strong interface bond with the matrix material in the solidified soil, thereby improving the density and mechanical properties of the material. 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 environments. Finally, the introduction of modified slag powder significantly improves the performance of the solidified soil under high temperature conditions, meeting the needs of special engineering environments.

[0024] The present invention has significant beneficial effects. First, by adopting modified slag micropowder and optimized formula design, the solidified soil of the present invention 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 environments. Secondly, the density of the solidified soil is improved and the porosity is reduced, which effectively improves the anti-penetration performance of the material and extends the service life of the material. In addition, the addition of the thermosensitive active agent accelerates the hydration reaction under high temperature environment, further improving the curing efficiency and strength of the material. By using a water reducer and a plasticizer, the fluidity and plasticity of the material are improved, which not only improves the construction efficiency, but also ensures the molding quality. In summary, the present invention has good adaptability in a high-temperature construction environment, and significantly improves the strength, durability and construction performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a fracture electron microscope image of the performance test of the solidified soil column prepared in Example 1 at room temperature;

[0026] Figure 2 This is a fracture electron microscope image of the solidified soil column prepared in Example 1, which was subjected to a performance test at 100° C. for 5 hours;

[0027] Figure 3 This is a data chart showing the performance test of the solidified soil column prepared in Example 5 at room temperature;

[0028] Figure 4 This is a data chart showing the performance test of the solidified soil column prepared in Example 5 at 100° C. for 5 hours; DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0033] Preparation example of modified slag powder

[0034] The following is an explanation of the preparation example 1.

[0035] The preparation steps of the modified slag powder in this preparation example include: slowly adding the dried nano-scale slag powder to anhydrous ethanol, mixing it with an ultrasonic device, weighing 3-aminopropyl triethoxysilane according to 1wt% of the mass of the nano-scale slag powder, slowly adding it to the dispersion, while keeping stirring, controlling the reaction temperature at 60°C, and stirring for 1 hour, filtering the reaction solution through a vacuum filtration device, retaining the modified slag powder, washing the slag powder with anhydrous ethanol solvent, and removing residual organosilane and by-products. Repeat the washing 3 times, put the washed slag powder into an oven, and dry it at 100°C for 24 hours.

[0036] Example

[0037] Example 1

[0038] The curing agent used for curing the soil includes the following parts by mass: 30 parts of phosphate cement, 25 parts of high alumina cement, 10 parts of sodium silicate, 12 parts of thermosensitive activator, 5 parts of expansion agent, 5 parts of modified slag powder, 0.8 parts of water reducer and 0.6 parts of plasticizer.

[0039] The method for preparing solidified soil based on iron ore tailings comprises the following steps:

[0040] Step S1. Put phosphate cement, high alumina cement, alumina and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, sodium salt of β-naphthalenesulfonic acid formaldehyde condensate and calcium lignin sulfonate, stir evenly to form a curing agent slurry;

[0041] Step S2. The iron ore tailings and the curing agent are mixed in a mass ratio of 70:30, and an appropriate amount of water is added to the mixer, with a water-to-solid ratio of 0.25, and stirred for 8 minutes to form a uniform slurry, and the pH of the slurry is adjusted to 6.5, and the slurry is slightly vibrated to remove bubbles, to obtain a solidified soil slurry based on the iron ore tailings;

[0042] Step S3. Pour the prepared solidified soil slurry into a 40 mm × 40 mm × 160 mm column mold and let it stand at room temperature for 4 hours to complete solidification.

[0043] Example 2

[0044] The curing agent used for curing the soil includes the following parts by mass: 25 parts of phosphate cement, 15 parts of high alumina cement, 15 parts of sodium silicate, 10 parts of thermosensitive activator, 10 parts of expansion agent, 4 parts of modified slag powder, 0.6 parts of water reducer, and 0.5 parts of plasticizer.

[0045] The method for preparing solidified soil based on iron ore tailings comprises the following steps:

[0046] Step S1. Put phosphate cement, high alumina cement, magnesium oxide and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, sodium salt of β-naphthalenesulfonic acid formaldehyde condensate and calcium lignin sulfonate, stir evenly to form a curing agent slurry;

[0047] Step S2. The iron ore tailings and the curing agent are mixed in a mass ratio of 70:30, and an appropriate amount of water is added to the mixer, with a water-to-material ratio of 0.35, and stirred for 5 minutes to form a uniform slurry, and the pH of the slurry is adjusted to 6.0, and the slurry is slightly vibrated to remove bubbles to obtain a solidified soil slurry based on the iron ore tailings;

[0048] Step S3. Pour the prepared solidified soil slurry into a 40 mm × 40 mm × 160 mm column mold and let it stand at room temperature for 2 hours to complete solidification.

[0049] Example 3

[0050] The curing agent used for curing the soil includes the following parts by mass: 35 parts of phosphate cement, 20 parts of high alumina cement, 12 parts of sodium silicate, 15 parts of thermosensitive activator, 8 parts of expansion agent, 3 parts of modified slag powder, 1 part of water reducing agent, and 1 part of plasticizer.

[0051] The method for preparing solidified soil based on iron ore tailings comprises the following steps:

[0052] Step S1. Put phosphate cement, high alumina cement, magnesium oxide and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, sodium salt of β-naphthalenesulfonic acid formaldehyde condensate and calcium lignin sulfonate, stir evenly to form a curing agent slurry;

[0053] Step S2. The iron ore tailings and the curing agent are mixed in a mass ratio of 70:30, and an appropriate amount of water is added to the mixer, with a water-to-material ratio of 0.30, and stirred for 6 minutes to form a uniform slurry, and the pH of the slurry is adjusted to 5.0, and the slurry is slightly vibrated to remove bubbles, to obtain a solidified soil slurry based on the iron ore tailings;

[0054] Step S3. Pour the prepared solidified soil slurry into a 40 mm × 40 mm × 160 mm column mold and let it stand at room temperature for 2 hours to complete solidification.

[0055] Example 4

[0056] The curing agent used for curing the soil includes the following parts by mass: 25 parts of phosphate cement, 15 parts of high alumina cement, 14 parts of sodium silicate, 10 parts of thermosensitive activator, 5 parts of expansion agent, 3 parts of modified slag powder, 0.5 parts of water reducer, and 0.5 parts of plasticizer.

[0057] The method for preparing solidified soil based on iron ore tailings comprises the following steps:

[0058] Step S1. Put phosphate cement, high alumina cement, alumina and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, sodium salt of β-naphthalenesulfonic acid formaldehyde condensate and calcium lignin sulfonate, stir evenly to form a curing agent slurry;

[0059] Step S2. The iron ore tailings and the curing agent are mixed in a mass ratio of 70:30, and an appropriate amount of water is added to the mixer, with a water-to-material ratio of 0.32, and stirred for 8 minutes to form a uniform slurry, and the pH of the slurry is adjusted to 5.5, and the slurry is slightly vibrated to remove bubbles, to obtain a solidified soil slurry based on the iron ore tailings;

[0060] Step S3. Pour the prepared solidified soil slurry into a 40 mm × 40 mm × 160 mm column mold and let it stand at room temperature for 2 hours to complete solidification.

[0061] Example 5

[0062] The curing agent used for curing the soil includes the following parts by mass: 31 parts of phosphate cement, 24 parts of high alumina cement, 10 parts of sodium silicate, 12 parts of thermosensitive activator, 5 parts of expansion agent, 5 parts of modified slag powder, 0.9 parts of water reducer and 0.6 parts of plasticizer.

[0063] The method for preparing solidified soil based on iron ore tailings comprises the following steps:

[0064] Step S1. Put phosphate cement, high alumina cement, alumina and calcium sulfoaluminate into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, sodium salt of β-naphthalenesulfonic acid formaldehyde condensate and calcium lignin sulfonate, stir evenly to form a curing agent slurry;

[0065] Step S2. The iron ore tailings and the curing agent are mixed in a mass ratio of 70:30, an appropriate amount of water is added to the mixer, the water-to-material ratio is 0.32, and the mixture is stirred for 8 minutes to form a uniform slurry, and the pH of the slurry is adjusted to (3, 4, 5, 6, 7, 8, 9), and the slurry is slightly vibrated to remove bubbles, so as to obtain a solidified soil slurry based on the iron ore tailings;

[0066] Step S3. Pour the prepared solidified soil slurry into a 40 mm × 40 mm × 160 mm column mold and let it stand at room temperature for 4 hours to complete solidification.

[0067] Comparative Example 1

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

[0069] Comparative Example 2

[0070] The difference between this control example and implementation 1 is that no thermosensitive active agent is added in step S1.

[0071] Comparative Example 3

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

[0073] Comparative Example 4

[0074] The difference between this control example and implementation 1 is that no water reducing agent is added in step S1.

[0075] Comparative Example 5

[0076] The difference between this control example and implementation 1 is that no plasticizer is added in step S1.

[0077] Performance Testing Methods

[0078] Column specimens with a size of 40 mm × 40 mm × 160 mm were prepared and tested for compressive strength and flexural strength at room temperature and at 100 °C for 5 h.

[0079] Table 2

[0080]

[0081] Combined with Example 1 and Figure 1 and 2 It can be seen that Figure 1 The microstructure in the Figure 2 The microstructure in the sample is denser and has almost no pores. The microstructure of the solidified soil shows higher density under high temperature conditions, the porosity inside the sample is low, and the particles are evenly distributed, indicating that bubbles and voids have been effectively eliminated through reasonable formula and process optimization. This dense structure significantly improves the compressive strength and flexural strength of the material.

[0082] Combining Examples 1 to 4 and Table 2, it can be seen that in Examples 1 to 4, the compressive strength of the solidified soil at room temperature ranges from 48.79 MPa to 60.45 MPa, and the flexural strength ranges from 6.89 MPa to 8.14 MPa. The compressive strength of the solidified soil at 100°C for 5 h ranges from 68.81 MPa to 85.73 MPa, and the flexural strength ranges from 8.59 MPa to 10.56 MPa. The solidified samples are placed in a drying oven at 100°C for 5 h. h. Under high temperature conditions, the thermosensitive active agent is activated and releases active ions, which significantly accelerates the hydration reaction of cement-based materials, generates more CSH gel and calcium aluminate hydrate (CAH) and other gelling products, and improves the strength and durability of the material. At the same time, high temperature promotes the decomposition of the expansion agent, produces a micro-expansion effect, fills the micro-cracks inside the material, reduces the porosity, and enhances the density and impermeability. In addition, the modified slag powder is activated under high temperature conditions, and its volcanic ash activity is stimulated, and reacts with Ca(OH) 2 Secondary reactions occur to generate additional gelling products, further improving the mechanical properties of the material.

[0083] Combining Example 1, Control Example 1 and Table 2, it can be seen that under the conditions of room temperature and 100°C insulation for 5 hours, the compressive strength and flexural strength of Example 1 are significantly higher than those of Control Example 1. Specifically, at room temperature, the compressive strength of Example 1 is 55.21MPa, and the flexural strength is 7.54MPa, while the compressive strength of Control Example 1 is only 32.45MPa, and the flexural strength is 5.48MPa; under 100°C insulation for 5 hours, the compressive strength of Example 1 is 78.54MPa, and the flexural strength is 9.52MPa, while the compressive strength of Control Example 1 is only 42.18MPa, and the flexural strength is 6.24MPa. This difference is mainly attributed to the significant improvement of material properties by the addition of modified slag powder. The active sites of the modified slag powder can interact with Ca in cement-based materials. 2+ The reaction occurs to generate more cementitious products such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH). These products fill the pores inside the material, optimize the microstructure and enhance the density. In addition, the coupling groups formed by the surface modification of the modified slag powder improve the interface bonding ability with the matrix material and reduce the microcracks and interface defects inside the material, thereby improving the mechanical properties of the material at room temperature and high temperature.

[0084] Combining Example 1, Comparative Example 2 and Table 2, it can be seen that at room temperature, the compressive strength and flexural strength of Example 1 are not much different from those of Comparative Example 2. Under the condition of 100°C insulation for 5 hours, the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 2; at room temperature, in Example 1, the compressive strength is 55.21MPa, the flexural strength is 7.54MPa, the compressive strength of Comparative Example 2 is 54.67MPa, the flexural strength is 7.18MPa, and under the condition of 100°C insulation for 5 hours, in Example 1, the compressive strength is 78.54MPa, the flexural strength is 6.52MPa, the compressive strength of Comparative Example 2 is 29.56MPa, and the flexural strength is only 4.56MPa. Under room temperature conditions, the hydration reaction of the material mainly depends on the hydration process of components such as phosphate cement and high alumina cement, and the solidified structure formed by the generated hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH) gelled products provides a certain strength. However, under high temperature conditions, the hydration reaction failed to be significantly accelerated due to the lack of activation by thermosensitive activators and the lack of additional active ions (such as Al 3+ ) to promote the deep reaction of silicates and aluminates. The stability of the cured material under high temperature environment depends on the quantity and quality of the gelled products formed. In Control Example 2, less gelled products are generated, the porosity inside the material is higher, and the density is poor, resulting in the inability to effectively improve the strength. In addition, high temperature conditions may cause thermal expansion and loose structure of unreacted components in the material, further weakening its mechanical properties. Therefore, the reason why the strength of Control Example 2 is significantly reduced under high temperature conditions is that the lack of the introduction of heat-sensitive active agents leads to the failure to effectively carry out the release of active ions and deep hydration reactions in high temperature environments, and the density and structural stability of the materials cannot be improved, which ultimately manifests as a significant decrease in strength. This shows that the role of heat-sensitive active agents in high temperature environments is crucial, and can significantly improve the performance of materials by activating the generation of gelled products and improving the microstructure.

[0085] Combining Example 1, Control Example 3 and Table 2, it can be seen that at room temperature, the compressive strength and flexural strength of Example 1 are not much different from those of Control Example 3. Under the condition of insulation at 100°C for 5 hours, the compressive strength and flexural strength of Example 1 are significantly higher than those of Control Example 3. At room temperature, in Example 1, the compressive strength is 55.21 MPa and the flexural strength is 7.54 MPa, and the compressive strength of Control Example 3 is 53.69 MPa and the flexural strength is 7.45 MPa. Under the condition of insulation at 100°C for 5 hours, in Example 1, the compressive strength is 78.54 MPa and the flexural strength is 6.52 MPa, and the compressive strength of Control Example 3 is 35.69 MPa and the flexural strength is 5.48 MPa. At room temperature, the hydration reaction rate of cement-based materials is low, and it mainly relies on the basic hydration process of phosphate cement and high-alumina cement to generate cementitious products such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH); these products provide the material with a preliminary solidification structure and fill part of the pores, thereby giving the material basic compressive and flexural strength; under high temperature conditions of 100°C for 5 hours, the pH value of the slurry in Example 1 is adjusted to an acidic range (5.0-6.0), which effectively stimulates the activity of the heat-sensitive activator (such as alumina or magnesium oxide) and releases more Al 3+ These ions promote the hydration reaction of silicates and aluminates, significantly accelerating the formation of CSH and CAH gel products. In contrast, the pH value of the slurry in Control Example 3 was adjusted to neutral (7.0), which failed to stimulate the activity of the thermosensitive active agent, resulting in a lower hydration reaction rate under high temperature conditions and a significant reduction in the number of gel products generated.

[0086] Combining Example 1, Comparative Example 4 and Table 2, it can be seen that the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 4 at room temperature and 100°C for 5 hours. At room temperature, the compressive strength of Example 1 is 55.21MPa, and the flexural strength is 7.54MPa, while the compressive strength of Comparative Example 4 is only 35.68MPa, and the flexural strength is 5.72MPa. Under 100°C for 5 hours, the compressive strength of Example 1 is 78.54MPa, and the flexural strength is 9.52MPa, while the compressive strength of Comparative Example 4 is only 43.57MPa, and the flexural strength is 6.19MPa; this performance difference is mainly attributed to the introduction of a water reducer. In Example 1, a water reducer (such as sodium salt of β-naphthalenesulfonic acid formaldehyde condensate) significantly improves the fluidity and uniformity of the slurry by dispersing cement particles and reducing the amount of free water in the mixture, thereby promoting the full mixing and reaction of the curing agent and the iron ore tailings. This effect not only reduces the porosity of the material and significantly improves its density, but also generates more cementitious products such as calcium silicate hydrate (CSH), which improves the mechanical properties of the material under both normal and high temperature conditions. In contrast, the control example 3 lacks a water reducer, and the fluidity and dispersibility of the slurry are poor, resulting in uneven mixing of the curing agent and the iron ore tailings, insufficient reaction in some areas, less cementitious products generated, and a loose internal structure and high porosity of the material. This not only leads to lower mechanical properties under normal temperature conditions, but also in high temperature environments, due to the presence of microcracks and pores inside the material, the thermal expansion effect is aggravated, further weakening the overall strength and durability of the material.

[0087] Combining Example 1, Comparative Example 5 and Table 2, it can be seen that the compressive strength and flexural strength of Example 1 are significantly higher than those of Comparative Example 5 at room temperature and 100°C for 5 hours. At room temperature, the compressive strength of Example 1 is 55.21MPa and the flexural strength is 7.54MPa, while the compressive strength of Comparative Example 5 is only 38.97MPa and the flexural strength is 6.12MPa. Under 100°C for 5 hours, the compressive strength of Example 1 is 78.54MPa and the flexural strength is 9.52MPa, while the compressive strength of Comparative Example 5 is only 41.25MPa and the flexural strength is 5.98MPa. This performance difference is mainly attributed to the introduction of plasticizer in Example 1. Plasticizers (such as calcium lignin sulfonate) improve the construction performance and mixing uniformity of the material by reducing the viscosity of the mixture and improving the fluidity of the slurry. In Example 1, the effect of the plasticizer enables the slurry to be evenly dispersed under a lower water-to-material ratio, and the curing agent and the iron ore tailings are fully contacted and reacted to generate more calcium silicate hydrate (CSH) and other gelled products. These products fill the pores inside the material, significantly improve the density, reduce microcracks, and thus improve the mechanical properties under normal and high temperature conditions. In contrast, no plasticizer was added to the control example 5, and the slurry viscosity was high, resulting in poor dispersibility and fluidity in the mixture, resulting in insufficient reaction in local areas, and more pores and microcracks were formed in the internal structure. Under high temperature conditions, these pores and cracks may be further expanded due to thermal expansion, significantly weakening the material's compressive and flexural properties. In addition, the lack of lubrication of the plasticizer makes it difficult for the uniformity and density of the slurry to reach the optimal state during mixing.

[0088] Combined with Example 5 and Figure 3It can be seen that under acidic conditions (pH < 7), the flexural strength and compressive strength are low, mainly because the hydration reaction of cement-based materials is significantly restricted. The acidic environment inhibits the hydration reaction of silicates and aluminates, resulting in less production of cementitious products (such as CSH and CAH), which makes the internal structure of the material loose, the porosity high, and the compressive and flexural properties poor. In addition, the strong acidic environment may have a corrosive effect on the mineral components of the material, destroy its microstructure, and further weaken the mechanical properties of the material. When the pH value gradually increases to neutral conditions (pH = 7), the flexural strength and compressive strength of the material reach the maximum value. In a neutral environment, the hydration reaction rate is significantly increased, and a large amount of calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) are generated. These products effectively fill the pores inside the material and significantly enhance the density and mechanical properties of the material. However, when the pH value exceeds 7 and enters an alkaline environment, the flexural strength and compressive strength gradually decrease. This is because alkaline conditions may cause a passivation layer to form on the surface of some mineral components (such as silicates), inhibiting subsequent chemical reactions and reducing the formation of gelled products. At the same time, the inhomogeneity of the reaction in an alkaline environment will increase the porosity inside the material and microcracks will not be effectively repaired.

[0089] Combined with Example 5 and Figure 4 It can be seen that under strong acidic conditions (pH 3-4), the flexural strength and compressive strength of the material are 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 significantly insufficient amount of hydration products (such as hydrated calcium silicate CSH and hydrated calcium aluminate CAH). These gelled products are not enough to fill the internal pores of the material, resulting in a loose structure and poor density. In addition, the strong acidic environment will aggravate the corrosion effect on mineral components (such as phosphates and silicates), further weaken the microstructural stability of the material, and reduce the mechanical properties; under weak acidic conditions (pH 5-6), the flexural strength and compressive strength of the material reach the maximum value, and the weak acidic environment can fully activate the thermosensitive active agent and release a large number 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 strength and compressive strength of the material gradually decrease, which is mainly due to the passivation effect of the chemical reaction. In an alkaline environment, a passivation layer may form on the surface of silicates and aluminates, hindering further hydration reactions and resulting in a reduction in the amount of generated gelled products.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing solidified soil based on iron ore tailings, characterized in that: The steps include: Step S1. Put phosphate cement, high alumina cement, heat-sensitive active agent and expansion agent into a mixer, dry mix for 5 minutes, add sodium silicate solution, continue stirring to mix thoroughly, finally add modified slag powder, water reducer and plasticizer, stir evenly to form curing agent slurry; Step S2. The iron ore tailings and the curing agent slurry are mixed in a mass ratio of 70:30, an appropriate amount of water is added to a mixer, and stirred for 5 to 8 minutes to form a uniform slurry, and the pH of the slurry is adjusted to 5.0 to 6.0, and the slurry is slightly vibrated to remove bubbles, so as to obtain a solidified soil slurry based on the iron ore tailings; Step S3: standing at room temperature for 2 to 4 hours to complete condensation.

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 0.25-0.

35.

3. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that: The heat-sensitive active agent is aluminum oxide or magnesium oxide.

4. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that: The expansion agent is calcium sulphoaluminate.

5. 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.

6. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that: The plasticizer is calcium lignin sulfonate.

7. The method for preparing solidified soil based on iron ore tailings according to claim 1, characterized in that: In step S1, the curing agent slurry includes, in parts by mass: 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 thermosensitive activator, 5 to 10 parts of expansion agent, 3 to 5 parts of modified slag powder, 0.5 to 1 part of water reducer, and 0.5 to 1 part of plasticizer.

8. 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: Slowly add the dried nano-scale slag powder into anhydrous ethanol, mix it using ultrasonic equipment, weigh an appropriate amount of organosilane coupling agent, slowly add it into the dispersion, and keep stirring. The reaction temperature is controlled at 40 to 80°C, and stirring is continued for 1-2 hours. Filter the reaction solution through a vacuum filtration device, retain the modified slag powder, wash the slag powder with anhydrous ethanol solvent, remove residual organosilane and by-products, and wash repeatedly for 3-5 times. Put the washed slag powder into an oven and dry it at 80-100°C for 12-24 hours.

9. The method for preparing solidified soil based on iron ore tailings according to claim 8, characterized in that: The organosilane coupling agent is 3-aminopropyltriethoxysilane, and the organosilane coupling agent accounts for 1wt% to 3wt% of the mass of the nano-scale slag powder.

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