Solid waste phosphogypsum subgrade soil improvement agent and preparation method thereof

Abstract

The present application relates to the technical field of soil solidifying agent, and more particularly to a solid waste phosphogypsum subgrade improved soil solidifying agent and a preparation method thereof.The solidifying agent comprises the following raw materials in percentage by mass: a solidifying material is formed by proportioning a solidifying mixture and a stabilizer; the solidifying mixture comprises cement 7%, lime 2%, calcined phosphogypsum 10%, and phosphogypsum 81%; the stabilizer comprises sodium silicate, sodium metaaluminate, and calcium chloride; and the proportion of the solidifying material to soil is proportioned adaptively.Through the above, the early performance and water stability of the solidified soil are improved, the internal structure of the sample is more compact, and therefore the strength is greatly improved.The preparation method is used for preparing the above solid waste phosphogypsum subgrade improved soil solidifying agent.

Description

Technical Field

[0001] This invention relates to the field of soil stabilizer technology, and in particular to a solid waste phosphogypsum roadbed soil stabilizer and its preparation method. Background Technology

[0002] Regarding the application of phosphogypsum in road engineering base materials, Chinese invention patent CN114804675A provides a composite alkali-activated cementitious material and its application method. The prepared composite alkali-activated cementitious material not only has advantages such as low energy consumption, high strength, and good durability, but also meets the requirements of different soil types, significantly improving its mechanical properties. Another example is Chinese invention patent CN115893966A, which provides a cement-stabilized phosphogypsum-based aggregate for road bases and its preparation method. This cement-stabilized phosphogypsum-based aggregate for road bases simultaneously expands the resource utilization of aggregate and phosphogypsum, completely replaces natural fine aggregates, and reduces cement production resource consumption, protecting the environment while conserving resources. Finally, Chinese invention patent CN115974515A provides a fluidized solidified soil based on cohesive soil and its preparation method. This invention realizes the preparation of a fluidized solidified soil based on cohesive soil, which is an efficient, economical, and stable cohesive soil fluidized solidified soil.

[0003] In light of the above, the feasibility of adding phosphogypsum for roadbed construction has been proven, and its use in soil stabilization is another approach. However, due to the hydrophilic nature of phosphogypsum, previous studies have shown that the dosage was too low, failing to achieve the goal of large-scale phosphogypsum consumption. Alternatively, too many types of admixtures need to be added, complicating the application process and increasing costs. Therefore, it is necessary to provide a stabilization material that can both absorb large quantities of phosphogypsum and meet strength requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a solid waste phosphogypsum roadbed soil stabilizer and its preparation method in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A solid waste phosphogypsum roadbed soil stabilizer comprises the following raw materials by mass percentage: the stabilizing material is composed of a stabilizing mixture and a stabilizer; the stabilizing mixture comprises 7% cement, 2% lime, 10% calcined phosphogypsum, and 81% phosphogypsum; the stabilizer comprises sodium silicate, sodium aluminate, and calcium chloride; and the ratio of the stabilizing material to the soil is adaptively proportioned.

[0007] Preferably, the ratio of the solidified mixture to the stabilizer is 98%:2%, and the stabilizer includes 100% sodium silicate; wherein, the ratio of the solidified material to the soil is 20%-30% solidified material and 70%-80% soil.

[0008] Preferably, the ratio of the solidification material to the soil is 25%:75%.

[0009] Preferably, the ratio of the solidified mixture to the stabilizer is 97.8%:2.2%, and the stabilizer includes 90% sodium silicate and 10% sodium aluminate. The ratio of the solidified material to the soil is 20%-30% solidified material and 70%-80% soil.

[0010] Preferably, the ratio of the solidification material to the soil is 25%:75%.

[0011] Preferably, the ratio of the solidified mixture to the stabilizer is 97.5%:2.5%, and the stabilizer includes 80% sodium silicate and 20% calcium chloride. The ratio of the solidified material to the soil is 20%-30% solidified material and 70%-80% soil.

[0012] Preferably, the ratio of the solidification material to the soil is 25%:75%.

[0013] Preferably, calcined phosphogypsum is prepared by calcining phosphogypsum in an oven at 150°C for 2 hours to dehydrate it.

[0014] A method for preparing a solid waste phosphogypsum roadbed soil conditioner and stabilizer, the method comprising the following steps:

[0015] S1. Dry the soil thoroughly in an oven at 105℃ for more than 12 hours; then grind the dried soil sample and pass it through a 2mm sieve to obtain a uniform powdery soil sample, which is then placed in a dry and sealed environment for later use.

[0016] S2. Add lime and phosphogypsum to the powdery soil sample in S1 in the correct proportions and mix well.

[0017] S3. Weigh out a certain amount of water and add the stabilizer to the water according to the ratio, and mix well so that the stabilizer is completely dissolved in the water.

[0018] S4. Mix the stabilizer solution in S3 with the medium-mixed soil in S2 evenly.

[0019] S5. Add cement and calcined phosphogypsum to the soil mixture in S4 in the correct proportions and mix thoroughly.

[0020] S6. Use static pressing to statically press the soil mixture in S5 into a cylindrical specimen with a diameter of 5cm and a height of 5cm.

[0021] S7. After demolding the specimen from S6, place it in a sealed bag and cure it under standard curing conditions until the required age to obtain phosphogypsum composite solidified soil.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] In this invention, calcined phosphogypsum undergoes a hydration reaction upon contact with water to form phosphogypsum. The gypsum grains interconnect to form a stable structure, and its inherent cohesive force helps maintain the material's stability and improve its strength. Phosphogypsum contains P2O5 and is acidic, but this has a negative impact when phosphogypsum composites are used to solidify soil. Therefore, adding lime helps inhibit the leaching of water-soluble phosphorus and fluorine from the phosphogypsum, neutralizes the acidity of the phosphogypsum, and provides a favorable alkaline environment for the hydration reaction to form gel and ettringite, thus improving early strength. Phosphogypsum reacts with cement hydration products to form ettringite, while a pozzolanic reaction also occurs between cement and lime; this process is prolonged and slow.

[0024] The introduction of sodium silicate promotes cement hydration. Soil particles are coated with hydrated calcium silicate cement and fill the pores, forming a stable aggregate structure. A small amount of short columnar ettringite is locally generated. Sodium silicate and cement hydration products overlap and are distributed in a network, making the solidified soil particle structure more compact. This better improves the early performance and water stability of the solidified soil.

[0025] Sodium aluminate, upon dissolving in water, readily precipitates aluminum hydroxide. Because it does not react with alkalis, it makes the solution slightly alkaline. Erythrite, a fine needle-like crystal, intersperses between hydrated calcium silicate and unhydrated phases, enhancing the interparticle bonding and thus increasing strength. Al in solution... 3+ S04 2- It is beneficial to the formation of ettringite and improve strength. On the one hand, the addition of sodium silicate and sodium aluminate can promote the formation of gel. A large amount of hydrated calcium silicate causes soil particles to clump together and form a whole, which improves the strength. On the other hand, sodium silicate and sodium aluminate react to generate aluminum hydroxide, which fills the small gaps and makes the internal structure of the sample more compact, thus greatly improving the strength.

[0026] When calcium chloride and sodium silicate are added together, the sodium silicate reacts with the calcium chloride to immediately form silica gel. The reaction formula is: Na₂O·nSiO₂ + CaCl₂ + mH₂O → nSiO₂·(m⁻¹)H₂O + Ca(OH)₂ + 2NaCl. The cementing material can encapsulate soil particles, cementing them together and filling pores. Under standard curing conditions, this increases strength. During the later stages of hydration, various crystals cross-crystallize and form dense layers. However, the presence of ettringite crystals within the cementitious material produced by the reaction of calcium chloride and sodium silicate enhances the overall structural integrity, thus significantly increasing strength. Attached Figure Description

[0027] Figure 1 A schematic diagram of phosphogypsum sampling and processing;

[0028] Figure 2 A schematic diagram of the microstructure of phosphogypsum;

[0029] Figure 3 This is a schematic diagram of the XRD pattern of phosphogypsum provided by the present invention according to an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the particle size distribution curve of phosphogypsum provided by the present invention according to an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the phosphogypsum compaction curve provided by the present invention according to an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of calcined phosphogypsum;

[0033] Figure 7 A schematic diagram of the microstructure of CPG;

[0034] Figure 8 This is a schematic diagram of the particle size distribution curve of loess provided by the present invention according to an embodiment of the present invention.

[0035] Figure 9 This is a schematic diagram of the XRD pattern of the phosphogypsum composite material solidified soil provided by the present invention according to an embodiment of the present invention;

[0036] Figure 10 This is an electron microscopy scan image of the cured soil of the phosphogypsum composite material of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 1-10 The present invention provides a technical solution:

[0039] A solid waste phosphogypsum roadbed soil stabilizer comprises the following raw materials by mass percentage: the stabilizing material is composed of a stabilizing mixture and a stabilizer; the stabilizing mixture comprises 7% cement, 2% lime, 10% calcined phosphogypsum, and 81% phosphogypsum; the stabilizer comprises sodium silicate, sodium aluminate, and calcium chloride; and the ratio of the stabilizing material to the soil is adaptively proportioned.

[0040] Example 1

[0041] The ratio of the solidified mixture to the stabilizer is 98%:2%, and the stabilizer includes 100% sodium silicate; the ratio of the solidified material to the soil is 20% solidified material and 80% soil.

[0042] Example 2

[0043] The ratio of the solidified mixture to the stabilizer is 98%:2%, and the stabilizer includes 100% sodium silicate; the ratio of the solidified material to the soil is 25% solidified material and 75% soil.

[0044] Example 3

[0045] The ratio of the solidified mixture to the stabilizer is 98%:2%, and the stabilizer includes 100% sodium silicate; the ratio of the solidified material to the soil is 30% solidified material and 70% soil.

[0046] Example 4

[0047] The ratio of the solidified mixture to the stabilizer is 97.8%:2.2%. The stabilizer includes 90% sodium silicate and 10% sodium aluminate. The ratio of the solidified material to the soil is 20% solidified material and 80% soil.

[0048] Example 5

[0049] The ratio of the solidified mixture to the stabilizer is 97.8%:2.2%. The stabilizer includes 90% sodium silicate and 10% sodium aluminate. The solidified material accounts for 25% and the soil accounts for 75%.

[0050] Example 6

[0051] The ratio of the solidified mixture to the stabilizer is 97.8%:2.2%. The stabilizer includes 90% sodium silicate and 10% sodium aluminate. The solidified material accounts for 30% and the soil accounts for 70%.

[0052] Example 7

[0053] The ratio of the solidified mixture to the stabilizer is 97.5%:2.5%. The stabilizer includes 80% sodium silicate and 20% calcium chloride. The solidified material accounts for 20% and the soil accounts for 80%.

[0054] Example 8

[0055] The ratio of the solidified mixture to the stabilizer is 97.5%:2.5%. The stabilizer includes 80% sodium silicate and 20% calcium chloride. The solidified material accounts for 25% and the soil accounts for 75%.

[0056] Example 9

[0057] The ratio of the solidified mixture to the stabilizer is 97.5%:2.5%. The stabilizer includes 80% sodium silicate and 20% calcium chloride. The solidified material accounts for 30% and the soil accounts for 70%.

[0058] Control group: Soil 100%.

[0059] Among them, calcined phosphogypsum is produced by calcining phosphogypsum in an oven at 150°C for 2 hours to dehydrate it.

[0060] In the above embodiments, calcined phosphogypsum undergoes a hydration reaction upon contact with water to form phosphogypsum. The gypsum grains interconnect to form a stable structure, and its inherent cohesive force helps maintain the stability of the material and improve its strength. Phosphogypsum contains P2O5 and is acidic, but this has a negative impact when phosphogypsum composites are used to solidify soil. Therefore, adding lime helps to inhibit the leaching of water-soluble phosphorus and fluorine from phosphogypsum, neutralizes the acidity of the phosphogypsum, and provides a favorable alkaline environment for the hydration reaction to form gel and ettringite, thus improving early strength. Phosphogypsum reacts with cement hydration products to form ettringite, while a pozzolanic reaction also occurs between cement and lime; this process is persistent and slow.

[0061] The introduction of sodium silicate promotes cement hydration. Soil particles are coated with hydrated calcium silicate cement and fill the pores, forming a stable aggregate structure. A small amount of short columnar ettringite is locally generated. Sodium silicate and cement hydration products overlap and are distributed in a network, making the solidified soil particle structure more compact. This better improves the early performance and water stability of the solidified soil.

[0062] Sodium aluminate, upon dissolving in water, readily precipitates aluminum hydroxide. Because it does not react with alkalis, it makes the solution slightly alkaline. Erythrite, a fine needle-like crystal, intersperses between hydrated calcium silicate and unhydrated phases, enhancing the interparticle bonding and thus increasing strength. Al in solution... 3+ S04 2- It is beneficial to the formation of ettringite and improve strength. On the one hand, the addition of sodium silicate and sodium aluminate can promote the formation of gel. A large amount of hydrated calcium silicate causes soil particles to clump together and form a whole, which improves the strength. On the other hand, sodium silicate and sodium aluminate react to generate aluminum hydroxide, which fills the small gaps and makes the internal structure of the sample more compact, thus greatly improving the strength.

[0063] When calcium chloride and sodium silicate are added together, the sodium silicate reacts with the calcium chloride to immediately form silica gel. The reaction formula is: Na₂O·nSiO₂ + CaCl₂ + mH₂O → nSiO₂·(m⁻¹)H₂O + Ca(OH)₂ + 2NaCl. The cementing material can encapsulate soil particles, cementing them together and filling pores. Under standard curing conditions, this increases strength. During the later stages of hydration, various crystals cross-crystallize and form dense layers. However, the presence of ettringite crystals within the cementitious material produced by the reaction of calcium chloride and sodium silicate enhances the overall structural integrity, thus significantly increasing strength.

[0064] Furthermore, phosphogypsum: in this scheme Figure 1 (a) Photograph taken at the sampling site of phosphogypsum. Before drying, it is dark gray in color, mostly in powder form, with many lumps, pH 4.96, and a moisture content as high as 16.34%. Figure 1 (b) The phosphogypsum was dried at 55°C, cooled, and then sieved through a 2mm sieve. Figure 1 (c). The results of scanning electron microscopy observation of its microstructure are as follows: Figure 2 As shown, phosphogypsum is mainly in the form of plate-like crystals, with fine particles adhering to the surface. The chemical composition of the phosphogypsum experimental material, determined by X-ray fluorescence spectrometry, is shown in Table 1. According to... Figure 3 The XRD pattern of phosphogypsum shows that its main component is calcium sulfate dihydrate (CaSO4·2H2O), and it contains small amounts of other impurities such as P2O2. The particle size distribution of the sieved phosphogypsum is between 4 μm and 300 μm, and the particle size distribution curve is shown below. Figure 4 As shown. The optimum moisture content is 12.1%, the maximum dry density is 1.575 g / cm³, and the compaction curve is as follows. Figure 5 As shown;

[0065] Table 1. Main chemical components of phosphogypsum (mass percentage)

[0066]

[0067] Calcined phosphogypsum: Calcination of phosphogypsum (PG) in an oven at 150℃ for 2 hours causes rapid heat absorption, resulting in the instantaneous loss of 1.5 H2O from PG (CaSO4·2H2O), forming hemihydrate gypsum (CaSO4·2H2O), thus obtaining the calcined phosphogypsum (CPG) used in this experiment. The calcined phosphogypsum used in this experiment was processed by a chemical plant; it is grayish-white in appearance and powdery. Figure 6 As shown in Table 2, the chemical composition of the calcined phosphogypsum experimental material was determined by X-ray fluorescence spectrometry. Its microstructure is shown in... Figure 7 As shown. Compared to phosphogypsum, CPG exhibits smaller, rhomboid, plate-like particles, a more uneven surface, and more powdery material.

[0068] Table 1. Main chemical components of calcined phosphogypsum (mass percentage %)

[0069]

[0070] Cement and lime: P·O 42.5 ordinary Portland cement and commercially available quicklime were used in this experiment. The chemical composition of the test materials was tested by X-ray fluorescence spectrometry and is shown in Table 3.

[0071] Table 2. Main chemical components of cement and lime (mass percentage)

[0072]

[0073] Stabilizers: Sodium silicate (Na2SiO3·5H2O), produced by Tianjin Zhiyuan Chemical Reagent Co., Ltd., AR analytical grade, white granules or powder; Sodium aluminate (NaAl O2), produced by Tianjin Damao Chemical Reagent Factory, AR analytical grade, white powder; Anhydrous calcium chloride (CaCl2), produced by Xilong Chemical Co., Ltd., AR analytical grade, spherical granules.

[0074] Loess: The soil samples for this experiment were taken directly from a construction site on a university campus. The primary characteristics of the soil samples were: predominantly yellowish-brown in color, mixed with a small amount of grayish-brown soil, and containing relatively few impurities such as stones or plant matter. The soil samples were placed in an oven at 105℃ for 24 hours. After cooling to room temperature, the dried soil was ground in a ball mill. Particle size analysis was performed on the ball-milled loess using a laser particle size analyzer. The particle size distribution of the ball-milled loess ranged from 1μm to 70μm, as shown in the particle size distribution curve. Figure 8 As shown. The main components of this soil are loess and fine sand. This scheme uses this soil for curing tests of phosphogypsum composite materials.

[0075] Mixing ratio: The main curing materials include 7% cement, 2% lime, 10% calcined phosphogypsum, and 81% phosphogypsum. The stabilizer is one or more of sodium silicate, sodium aluminate, and calcium chloride.

[0076] Furthermore, three phosphogypsum composite material formulations were selected and mixed with test soil to prepare solid waste solidification test soil (hereinafter referred to as solidified soil). The phosphogypsum composite solidification material was added at amounts of 20%, 25%, and 30%, respectively. The solidified soil mix proportions are shown in Table 4.

[0077] Table 4. Mix proportions of cured clay specimens made from paste composite materials.

[0078]

[0079]

[0080] I. Unconfined compressive strength test, i.e., the unconfined compressive strength results are shown in Table 5 below:

[0081] Table 5. Unconfined compressive strength results

[0082]

[0083]

[0084] Table 5 above shows the 7-day, 14-day, and 28-day unconfined compressive strength test results of three types of stabilized soil mixes. As can be seen from the table, the unconfined compressive strength of the stabilized soil increased with the increase in curing age and the amount of phosphogypsum composite material. The addition of stabilizers significantly improved the early strength, with the main strength source being the hydration reaction of the phosphogypsum composite material. More and more ettringite, hydrated calcium silicate, and hydrated calcium aluminosilicate are generated in the stabilized soil, providing strength. On the other hand, after cement is mixed with soil, the minerals on the surface of the cement particles undergo a hydration reaction with water in the soil, forming various hydrates in the soil. These hydrates continue to harden, forming cement stone aggregate. The calcium hydroxide in the hydration products of cement and lime can continue to react with CO2 in the air to form CaCO3, but this process is relatively slow, thus still showing a trend of strength increase at 28 days. Soil has high porosity, with many micropores and cracks inside. The addition of dispersed phosphogypsum can increase the overall density and improve the bonding force between the matrix.

[0085] It is worth noting that the control group without added solidifying material dispersed upon immersion in water, and this strength represents the strength without immersion. The strength varies at different ages, indicating that the raw soil itself does not have the capacity to increase in strength with age, and that the strength of the raw soil is not high. In contrast, the specimens with added phosphogypsum composite material maintained their integrity after immersion in water. This is because hydration products such as calcium silicate hydrate are insoluble mineral crystals that, while cementing soil particles, do not disintegrate upon contact with water. The hydration products fill the pores of the soil particles, reducing the porosity and permeability of the solidified soil, thereby improving its water resistance and stability. This is the result of the combined effects of the filling and cementing effects, leading to improved water stability of the solidified soil.

[0086] II. Drying shrinkage and crack resistance test results, namely the mass loss rate and drying shrinkage strain of the phosphogypsum composite solidified soil, are shown in Table 6 below:

[0087] Table 6. Mass loss rate and drying shrinkage strain of phosphogypsum composite solidified soil.

[0088] Test number Quality loss rate (%) Drying shrinkage strain (%) Example 1 9.91 0.77 Example 2 9.42 0.67 Example 3 9.41 0.55 Example 4 10.02 0.81 Example 5 9.75 0.59 Example 6 9.17 0.45 Example 7 9.73 0.768 Example 8 9.18 0.55 Example 9 8.97 0.53 control group 13.42 1.05

[0089] The table above shows the mass loss rate and drying shrinkage strain results of the phosphogypsum composite solidified soil. Both the mass loss rate and drying shrinkage strain of the phosphogypsum composite solidified soil decrease with increasing solidification material content. This is partly because the addition of stabilizers generates cementitious substances and helps fill pores and increase the material's density, thus reducing water loss and lowering the water loss rate. Another possibility is that when the mixture reacts with water, the resulting expansive crystals, such as ettringite, expand under water-rich conditions. However, since there are abundant pores between soil particles, the expansion of the crystals largely fills these pores, thereby increasing the strength of the solidified soil structure and reducing the drying shrinkage strain of the sample. During the chemical reaction within the solidified soil, some water is consumed, mostly converted into crystal water in the generated compounds, making water loss less likely and thus reducing the sample's mass loss rate.

[0090] III. XRD Spectrum Analysis

[0091] like Figure 10 The XRD spectra of Examples 3, 6, and 9 after a curing period of 28 days are shown. The figures reveal partial ettringite peaks, which are formed by the combination of phosphate ions from phosphogypsum with the gel generated during cement hydration under an alkaline environment. SO4 2- It not only promotes cement hydration but also activates phosphogypsum, improving early and later strength; OH - This will accelerate the dissolution of active minerals and form hydrated calcium silicate and hydrated calcium aluminate; in addition, SO4 2- It also reacts with the aluminum phase in the soil to form ettringite. These crystals increase the volume of the material, filling the voids between soil particles and connecting them to form a network structure, making the solidified soil denser and effectively enhancing its strength and stability. Simultaneously, the diffraction peak of calcium sulfate dihydrate was still present and very high in the specimens, indicating that much of the added phosphogypsum did not participate in the reaction. The continued hydration reaction leads to a tighter structure between different hydration products, further improving the compressive strength and durability of the solidified soil. Therefore, sufficient curing time is crucial for improving the performance of phosphogypsum composite solidified soil.

[0092] like Figure 6Electron microscopy images of the solidified soil from the phosphogypsum composite materials in Examples 3, 6, and 9 show a large number of needle-like ettringite crystals in their hydration products. The higher the strength of the hydration product, the greater the number of ettringite crystals. Furthermore, platy, flocculent, or network-like hydrated calcium silicate (CSH) products can be observed. These hydration products are interwoven between soil particles, forming an overall framework and connecting the soil particles, giving the solidified phosphogypsum composite material good mechanical strength. Besides ettringite, some unreacted platy phosphogypsum crystals and a small amount of gel are also visible, indicating that cement hydration in this system is incomplete. The ettringite crystals in Example 3 are more numerous and the crystal growth state is relatively three-dimensional. CSH gel encapsulates and coexists with the ettringite. In contrast, the ettringite in Example 9 is almost entirely interlocked, with almost no CSH gel present, indicating that cement hydration is more complete. The comparison of the microstructures of the three formulations clearly demonstrates that the strength of the phosphogypsum composite solidified soil is mainly provided by the final product, ettringite. An alkaline environment significantly promotes the activation of mineral activity in cement and soil. Notably, the figure shows more columnar ettringite. Acicular ettringite is a metastable crystal and will continue to react with calcium aluminate hydrate in the presence of surrounding calcium aluminate hydrate, forming columnar monosulfide calcium aluminate hydrate (3CaO·Al₂O₃·CaSO₄·12H₂O) which eventually reaches a stable state. During the growth process, columnar ettringite has a larger interfacial area and is more intertwined, resulting in greater frictional resistance to relative displacement under stress. Columnar crystals more fully fill structural spaces, leading to greater stability. While ettringite has high strength, it contains a large amount of water of crystallization; under water-rich conditions, its solid volume can increase by approximately 1.5 times, which is the main reason for the good drying shrinkage performance due to sample expansion.

[0093] The present invention also provides a technical solution:

[0094] A method for preparing a solid waste phosphogypsum roadbed soil conditioner and stabilizer, the method comprising the following steps:

[0095] S1. Dry the soil thoroughly in an oven at 105℃ for more than 12 hours; then grind the dried soil sample and pass it through a 2mm sieve to obtain a uniform powdery soil sample, which is then placed in a dry and sealed environment for later use.

[0096] S2. Add lime and phosphogypsum to the powdery soil sample in S1 in the correct proportions and mix well.

[0097] S3. Weigh out a certain amount of water and add the stabilizer to the water according to the ratio, and mix well so that the stabilizer is completely dissolved in the water.

[0098] S4. Mix the stabilizer solution in S3 with the medium-mixed soil in S2 evenly.

[0099] S5. Add cement and calcined phosphogypsum to the soil mixture in S4 in the correct proportions and mix thoroughly.

[0100] S6. Use static pressing to statically press the soil mixture in S5 into a cylindrical specimen with a diameter of 5cm and a height of 5cm.

[0101] S7. After demolding the specimen from S6, place it in a sealed bag and cure it under standard curing conditions until the required age to obtain phosphogypsum composite solidified soil.

[0102] The above description of the embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing stabilized soil using solid waste phosphogypsum as a roadbed soil conditioner, comprising a stabilizer, the stabilizer being composed of a solidification mixture and a stabilizer, wherein the solidification mixture comprises 7% cement, 2% lime, 10% calcined phosphogypsum, and 81% phosphogypsum; the stabilizer comprises sodium silicate, sodium aluminate, and calcium chloride; wherein, The ratio of the curing agent to the soil is 20%-30% curing agent and 70%-80% soil; its characteristic is that it includes the following steps: S1. Dry the soil thoroughly in an oven at 105℃ for more than 12 hours; then grind the dried soil sample and pass it through a 2mm sieve to obtain a uniform powdery soil sample, which is then placed in a dry and sealed environment for later use. S2. Add lime and phosphogypsum to the powdery soil sample in S1 in the correct proportions and mix well. S3. Weigh out a certain amount of water and add the stabilizer to the water according to the ratio, and mix well so that the stabilizer is completely dissolved in the water. S4. Mix the stabilizer solution in S3 with the mixing soil in S2 evenly. S5. Add cement and calcined phosphogypsum to the soil mixture in S4 in the correct proportions and mix thoroughly. S6. Use static pressing to statically press the soil mixture in S5 into a cylindrical specimen with a diameter of 5cm and a height of 5cm. S7. After demolding the specimen from S6, place it in a sealed bag and cure it under standard curing conditions until the required age to obtain phosphogypsum composite solidified soil.

2. The method for preparing solidified soil using solid waste phosphogypsum as a roadbed soil conditioner according to claim 1, characterized in that: The ratio of the solidified mixture to the stabilizer is 98%:2%, and the stabilizer includes 100% sodium silicate; the ratio of the solidifier to the soil is 25%:75%.

3. The method for preparing solidified soil using solid waste phosphogypsum as a roadbed soil conditioner according to claim 1, characterized in that: The ratio of the solidified mixture to the stabilizer is 97.8%:2.2%, and the stabilizer includes 90% sodium silicate and 10% sodium aluminate.

4. The method for preparing solidified soil using solid waste phosphogypsum roadbed soil stabilizer according to claim 1, characterized in that: The ratio of the solidified mixture to the stabilizer is 97.5%:2.5%, and the stabilizer includes 80% sodium silicate and 20% calcium chloride.

5. The method for preparing solidified soil using solid waste phosphogypsum roadbed soil stabilizer according to claim 1, characterized in that: Calcined phosphogypsum is produced by calcining phosphogypsum in an oven at 150°C for 2 hours to dehydrate it.

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