Preparation method of environment-safe phosphogypsum-based pavement base material

Abstract

The invention relates to the technical field of road engineering materials and industrial solid waste recycling, in particular to a preparation method of an environment-safe ardealite-based pavement base material, which comprises the following steps: a raw material pretreatment step: carrying out dehydration and particle size control treatment on ardealite, and carrying out graded material preparation on graded aggregate; a mixture preparation step: mixing and stirring the treated phosphogypsum, the graded aggregate, a cementing material, a multi-component composite activator and an environmental stabilizer to form a uniform pavement base mixture; and a compaction molding and maintenance step: paving and compacting the mixture to a predetermined compactness, and then carrying out maintenance. The complete technological process of raw material pretreatment, mixture preparation, compaction molding and maintenance is adopted, a multi-component composite activator and an environmental stabilizer are introduced into a system as key functional components, and it is ensured that the finally prepared material can synchronously achieve high pavement performance and high environmental safety from the methodological level.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials and industrial solid waste resource utilization technology, specifically to a method for preparing an environmentally safe phosphogypsum-based road base material. Background Technology

[0002] In the field of road engineering, using phosphogypsum as a base material is one of the most effective ways to achieve large-scale disposal. Although there are attempts to use phosphogypsum in road base courses, the following problems usually exist: 1. In most applications, phosphogypsum is used as an auxiliary admixture, with a low dosage, making it difficult to achieve large-scale consumption of phosphogypsum.

[0003] 2. Due to its poor water stability, presence of harmful impurities, and potential retardation effect on the cementing system, phosphogypsum often results in base materials with low early strength, poor volume stability, insufficient long-term durability, and potential environmental safety risks.

[0004] 3. In order to eliminate the adverse effects of impurities, phosphogypsum often needs to be pretreated by washing, calcining or neutralizing. This not only increases the complexity of the process and energy consumption, but also increases the application cost. Although some studies have tried to improve it by adding curing agents or using alkali activation technology, it is often difficult to balance mechanical properties and environmental safety. In particular, the long-term curing effect of harmful ions under high phosphogypsum dosage is not good, or it still relies on high-energy-consuming chemical activators. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing an environmentally safe phosphogypsum-based pavement base material. Through a complete process flow of "raw material pretreatment—mixture preparation—compacting and curing," and by introducing "multi-component composite activator" and "environmental stabilizer" as key functional components, the methodological approach ensures that the final material simultaneously achieves high road performance and high environmental safety. This design resolves the fundamental contradiction in traditional methods where performance and environmental protection are difficult to balance, providing a feasible technical path for the high-volume, high-value utilization of phosphogypsum resources.

[0006] One embodiment of the present invention provides a method for preparing an environmentally safe phosphogypsum-based pavement base material, comprising the following steps: The raw material pretreatment steps include dehydration and particle size control of phosphogypsum, and grading and preparing graded aggregates. The mixture preparation step involves mixing and stirring the treated phosphogypsum, the graded aggregate, the cementitious material, the multi-component composite activator, and the environmental stabilizer to form a uniform road base mixture. The compaction and curing steps involve spreading and compacting the mixture to a predetermined density, followed by curing.

[0007] In one embodiment, in the mixture preparation step, the amount of each material by weight is as follows: 100 to 120 parts of graded aggregate, 60 to 90 parts of phosphogypsum, 4 to 10 parts of cementitious material, 2 to 5 parts of multi-component composite activator, 1 to 3 parts of environmental stabilizer, and 8 to 15 parts of water; the cementitious material is silicate cement.

[0008] In one embodiment, the multi-component composite activator is composed of a mineral activating component, an alkali activating component, and a crystallization regulating component; wherein, the mineral activating component is composed of slag powder and silica fume in a weight ratio of 3:1 to 5:1, the alkali activating component is composed of water glass with a modulus of 1.0 to 1.3 and lithium carbonate in a weight ratio of 15:1 to 25:1, and the crystallization regulating component is composed of nano-silica with a particle size of 10 to 50 nanometers and calcium formate in a weight ratio of 1:1 to 1:3.

[0009] In one embodiment, the mineral activating component accounts for 60% to 80% of the total weight of the multi-component composite activator, the alkali activating component accounts for 15% to 30% of the total weight of the multi-component composite activator, and the crystallization regulating component accounts for 5% to 15% of the total weight of the multi-component composite activator.

[0010] In one embodiment, the environmental stabilizer includes a heavy metal stabilizing component and a pollutant blocking component; the heavy metal stabilizing component is composed of metakaolin and magnesium phosphate in a weight ratio of 2:1 to 3:1; the pollutant blocking component is composed of sodium methylsilicate and active magnesium oxide in a weight ratio of 1:1 to 2:1.

[0011] In one embodiment, the heavy metal stabilizing component accounts for 60% to 70% of the total weight of the environmental stabilizer, and the pollutant blocking component accounts for 30% to 40% of the total weight of the environmental stabilizer.

[0012] In one embodiment, in the raw material pretreatment step, phosphogypsum is dried to a moisture content of no more than 5%, and ground to a particle size of no more than 1 mm. The particles with a particle size of no more than 0.075 mm account for 20% to 30%, the particles with a particle size between 0.075 mm and 0.5 mm account for 50% to 60%, and the particles with a particle size between 0.5 mm and 1.0 mm account for 10% to 20%. The graded aggregate is graded crushed stone with a particle size range of 0 mm to 25 mm.

[0013] In one embodiment, the mixing process in the mixture preparation step adopts a high-speed forced mixing equipment, specifically including: first, putting the treated phosphogypsum, cementitious material, multi-component composite activator and environmental stabilizer into the mixer, and dry mixing at a speed of 200 to 300 revolutions per minute for three to five minutes; Then add the graded aggregate and continue dry mixing for one to two minutes; finally, add the total amount of water and linearly increase the mixer speed to 400 to 500 revolutions per minute within 30 seconds, and maintain this speed for four to six minutes.

[0014] In one embodiment, during the compaction and curing steps, a vibratory roller is used for compaction, and the compaction degree is controlled to be no less than 98% of the maximum dry density. At the same time, the moisture content of the mixture is controlled to be 5 to 10 millimeters by a moisture observation device buried in the compacted layer. After compaction, the mixture is cured for 7 to 28 days under the conditions of a temperature of 20 to 25 degrees Celsius and a relative humidity of no less than 90%.

[0015] In one embodiment, a real-time monitoring and feedback adjustment step based on material properties and environmental safety is also included: during maintenance and service, the temperature, humidity and stress-strain changes inside the base layer are continuously monitored through an embedded sensor network; core samples are periodically drilled to determine their unconfined compressive strength and softening coefficient, and the leaching concentration of heavy metal ions and phosphorus and fluoride ions is detected.

[0016] The preparation method of an environmentally safe phosphogypsum-based road base material provided by the above technical solution has the following beneficial effects: 1. Through the synergistic design of a unique multi-component composite activator and environmental stabilizer, the dosage of phosphogypsum can be significantly increased to 60-90 parts by weight (relative to 100 parts of aggregate) while ensuring excellent road performance. This dosage is much higher than the traditional phosphogypsum pavement base material dosage level of less than 10%. The multi-component composite activator effectively activates the activity of phosphogypsum and cement through the synergistic effect of mineral activation, alkali activation and crystallization regulation components, accelerates the hydration reaction rate, and promotes the formation of high-strength hydration products such as hydrated calcium sulfoaluminate (ettringite) and hydrated calcium silicate (CSH) gel. This makes the material not only have an unconfined compressive strength of more than 3.5 MPa at 7 days, but also a strength of more than 9.5 MPa at 28 days, which fully meets the strength requirements of high-grade highway base materials.

[0017] 2. By introducing crystallization-regulating components (such as nano-silica and calcium formate), the crystal form and growth of hydration products are effectively controlled, inhibiting expansion that may be caused by excessive formation of ettringite. Simultaneously, the microstructure is optimized, reducing shrinkage stress. Components such as active magnesium oxide in the environmental stabilizer can also generate micro-expansion, compensating for the material's drying shrinkage. Therefore, the 28-day drying shrinkage coefficient of the material is significantly reduced, and its volume stability is greatly improved, effectively avoiding early cracking of the base material. At the same time, the formed dense microstructure also enhances the material's resistance to water penetration and freeze-thaw cycles, ensuring its long-term durability.

[0018] 3. Through the chemical precipitation and adsorption of heavy metal stabilizing components (such as metakaolin and magnesium phosphate) and the physical barrier formed by pollutant sealing components (such as sodium methylsilicate and activated magnesium oxide), efficient and long-term immobilization of harmful components such as soluble phosphorus, fluoride, and heavy metal ions in phosphogypsum is achieved. Toxicity leaching tests show that the leaching concentration of heavy metal ions in the treated material is far below the Class III water limit of the "Groundwater Quality Standard," and the leaching concentration of fluoride is below 0.5 mg / L, thus mitigating the potential environmental risks associated with phosphogypsum in road applications.

[0019] 4. The method of this invention can directly use virgin phosphogypsum that has undergone simple drying and grinding, avoiding traditional water washing, calcination, or large-scale neutralization pretreatment, simplifying the process and reducing energy consumption and production costs. Since phosphogypsum is industrial waste, its cost is lower than traditional cement and other cementing materials; a high proportion of substitution can significantly reduce raw material costs. Furthermore, the material provided by this invention is convenient to construct, has good compatibility with conventional cement-stabilized crushed stone base construction processes, requires no special equipment, and is easy to promote. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0022] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the so-called present invention should be included in the patent scope of this case.

[0023] like Figure 1As shown, one embodiment of the present invention provides a method for preparing an environmentally safe phosphogypsum-based pavement base material, comprising the following steps: The raw material pretreatment steps include dehydration and particle size control of phosphogypsum, and grading and preparing graded aggregates. The mixture preparation step involves mixing and stirring the treated phosphogypsum, the graded aggregate, the cementitious material, the multi-component composite activator, and the environmental stabilizer to form a uniform road base mixture. The compaction and curing steps involve spreading and compacting the mixture to a predetermined density, followed by curing.

[0024] In this embodiment of the invention, a complete and synergistic technical framework is constructed. Through a complete process flow of "raw material pretreatment—mixture preparation—compaction molding and curing," and by introducing "multi-component composite activator" and "environmental stabilizer" as key functional components into the system, the methodological approach ensures that the final material can simultaneously achieve high road performance and high environmental safety. This design resolves the fundamental contradiction in traditional methods where performance and environmental protection are difficult to balance, providing a feasible technical path for the high-volume, high-value utilization of phosphogypsum resources.

[0025] In one embodiment, in the mixture preparation step, the amount of each material by weight is as follows: 100 to 120 parts of graded aggregate, 60 to 90 parts of phosphogypsum, 4 to 10 parts of cementitious material, 2 to 5 parts of multi-component composite activator, 1 to 3 parts of environmental stabilizer, and 8 to 15 parts of water; the cementitious material is silicate cement.

[0026] In this embodiment of the invention, by precisely defining the weight ratio of each component (especially 60-90 parts of phosphogypsum and 4-10 parts of cementitious material), the present claim achieves an optimal balance between high phosphogypsum content and high material performance. This ratio range is a "golden range" verified through extensive experiments, which maximizes the utilization of phosphogypsum solid waste while ensuring that the cementitious system produces sufficient hydration products, enabling the material to obtain mechanical strength that meets road application requirements. This avoids the problems of insufficient utilization due to excessively low content or strength degradation due to excessively high content.

[0027] In one embodiment, the multi-component composite activator is composed of a mineral activating component, an alkali activating component, and a crystallization regulating component; wherein, the mineral activating component is composed of slag powder and silica fume in a weight ratio of 3:1 to 5:1, the alkali activating component is composed of water glass with a modulus of 1.0 to 1.3 and lithium carbonate in a weight ratio of 15:1 to 25:1, and the crystallization regulating component is composed of nano-silica with a particle size of 10 to 50 nanometers and calcium formate in a weight ratio of 1:1 to 1:3.

[0028] In this embodiment of the invention, the activator is defined as consisting of three functional components: mineral activation, alkali activation, and crystallization regulation. This results in a significant synergistic activation effect. The mineral activation component (such as slag powder) provides long-term activity, the alkali activation component (such as water glass) breaks down impurities and accelerates early reactions, and the crystallization regulation component (such as nano-silica) optimizes the microstructure. This synergistic effect specifically overcomes the technical bottlenecks of low activity, slow hydration, and poor early strength in phosphogypsum, enabling rapid and stable strength development in the material. In one embodiment, the mineral activating component accounts for 60% to 80% of the total weight of the multi-component composite activator, the alkali activating component accounts for 15% to 30% of the total weight of the multi-component composite activator, and the crystallization regulating component accounts for 5% to 15% of the total weight of the multi-component composite activator.

[0029] In this embodiment of the invention, the weight percentages of the three components within the activator are precisely defined to ensure the high efficiency and stability of the activator system. This ratio allows each component to exert its maximum effectiveness during the reaction process, avoiding incomplete reactions or negative effects (such as over-expansion) caused by an excess or deficiency of any component. This optimizes the hydration process and improves the homogeneity and reliability of the material's final strength.

[0030] In one embodiment, the environmental stabilizer includes a heavy metal stabilizing component and a pollutant blocking component; the heavy metal stabilizing component is composed of metakaolin and magnesium phosphate in a weight ratio of 2:1 to 3:1; the pollutant blocking component is composed of sodium methylsilicate and active magnesium oxide in a weight ratio of 1:1 to 2:1.

[0031] In this embodiment of the invention, the environmental stabilizer is explicitly defined to contain two types of components: "heavy metal stabilizers" and "pollutant sealing agents," establishing a dual protection mechanism of chemical fixation and physical barriers. The heavy metal stabilizing component converts harmful ions into insoluble substances through chemical reactions; the pollutant sealing component forms a hydrophobic film on the surface of the material's pores, blocking the leaching path of water. This dual action significantly reduces the leaching risk of phosphorus, fluorine, and heavy metal ions from phosphogypsum at its source, ensuring the environmental safety of the material throughout its entire life cycle.

[0032] In one embodiment, the heavy metal stabilizing component accounts for 60% to 70% of the total weight of the environmental stabilizer, and the pollutant blocking component accounts for 30% to 40% of the total weight of the environmental stabilizer.

[0033] In this embodiment of the invention, the ratio of the two components within the stabilizer is optimized to achieve the best stabilization and sealing effect on various pollutants. A suitable ratio ensures that chemical stabilization and physical sealing functions work synergistically and persistently under complex environmental conditions, avoiding early failure or insufficient long-term protection due to imbalances, and enhancing the durability of the material's environmental safety performance.

[0034] In one embodiment, in the raw material pretreatment step, phosphogypsum is dried to a moisture content of no more than 5%, and ground to a particle size of no more than 1 mm. The particles with a particle size of no more than 0.075 mm account for 20% to 30%, the particles with a particle size between 0.075 mm and 0.5 mm account for 50% to 60%, and the particles with a particle size between 0.5 mm and 1.0 mm account for 10% to 20%. The graded aggregate is graded crushed stone with a particle size range of 0 mm to 25 mm.

[0035] In this embodiment of the invention, specific requirements are set for the moisture content, particle size, and gradation of the aggregate of phosphogypsum, thereby controlling the physical state and reactivity of the raw materials from the source. Low moisture content and fineness ensure that the phosphogypsum can fully participate in the hydration reaction; optimized aggregate gradation forms a dense skeletal structure. This lays the foundation for subsequent processes and directly contributes to the excellent density, strength, and workability of the final material.

[0036] In one embodiment, the mixing process in the mixture preparation step adopts a high-speed forced mixing equipment, specifically including: first, putting the treated phosphogypsum, cementitious material, multi-component composite activator and environmental stabilizer into the mixer, and dry mixing at a speed of 200 to 300 revolutions per minute for three to five minutes; Then add the graded aggregate and continue dry mixing for one to two minutes; finally, add the total amount of water and linearly increase the mixer speed to 400 to 500 revolutions per minute within 30 seconds, and maintain this speed for four to six minutes.

[0037] In this embodiment of the invention, the specific order of adding materials (dry-mixing the cementitious components first, then adding the aggregates, and finally adding the water) and the high-speed mixing process ensure a high degree of uniform dispersion of each component at both the macroscopic and microscopic scales. This avoids clumping or uneven distribution, allowing the activation and stabilization reactions to be more complete and thorough, significantly improving the homogeneity of the mixture and the overall performance consistency after molding, which is key to ensuring the quality of large-scale construction.

[0038] In one embodiment, during the compaction and curing steps, a vibratory roller is used for compaction, and the compaction degree is controlled to be no less than 98% of the maximum dry density. At the same time, the moisture content of the mixture is controlled to be 5 to 10 millimeters by a moisture observation device buried in the compacted layer. After compaction, the mixture is cured for 7 to 28 days under the conditions of a temperature of 20 to 25 degrees Celsius and a relative humidity of no less than 90%.

[0039] In this embodiment of the invention, precise control of compaction degree, impregnation humidity, curing temperature and humidity, and age ensures that the material can form an ideal structure and fully complete the hydration reaction during the molding period. High compaction degree results in high density; suitable impregnation humidity and curing conditions effectively inhibit shrinkage cracking and promote strength growth. These parameters work together to greatly improve the volume stability and long-term durability of the material.

[0040] In one embodiment, a real-time monitoring and feedback adjustment step based on material properties and environmental safety is also included: during maintenance and service, the temperature, humidity and stress-strain changes inside the base layer are continuously monitored through an embedded sensor network; core samples are periodically drilled to determine their unconfined compressive strength and softening coefficient, and the leaching concentration of heavy metal ions and phosphorus and fluoride ions is detected.

[0041] In this embodiment of the invention, quality control is extended from the production process to the entire service life of the road. Through real-time monitoring and regular inspections, material performance can be dynamically evaluated, potential problems can be identified in a timely manner, and early warnings or maintenance can be carried out. This not only improves the level of intelligent management of the project, but also provides valuable full life-cycle data support for the continuous optimization of the technology and its promotion and application in different regions.

[0042] Furthermore, the implementation scenarios include: 1. Prepare raw materials: Phosphogypsum: After drying to a moisture content of ≤3%, it is then ground and its particle size distribution is controlled as follows: particles with a diameter of ≤0.075mm account for 25%, particles with a diameter between 0.075mm and 0.5mm account for 55%, and particles with a diameter between 0.5mm and 1.0mm account for 20%. Graded aggregate: Graded crushed stone conforming to the specifications for base course in highway engineering is used, with a particle size range of 0-25mm; Cementitious material: P·O 42.5 grade ordinary Portland cement; Multi-component activators: Mineral activating component: slag powder and silica fume are compounded in a weight ratio of 4:1; Alkali-activated components: water glass with a modulus of 1.2 and lithium carbonate are compounded in a weight ratio of 20:1; Crystallization control component: 30nm nano-silica and calcium formate are compounded in a weight ratio of 1:2; In the final composite activator, the weight percentages of the three components are: 70% mineral activating component, 22% alkali activating component, and 8% crystallization regulating component; Environmental stabilizers: Heavy metal stabilizing component: metakaolin and magnesium phosphate are compounded in a weight ratio of 2.5:1.

[0043] Contaminant sealing component: Sodium methylsilicate and active magnesium oxide are compounded in a weight ratio of 1.5:1.

[0044] In the final environmental stabilizer, the weight percentages of the two components are: 65% heavy metal stabilizing component and 35% pollutant blocking component; 2. Ingredients (by weight): Graded aggregate: 110 parts; Processed phosphogypsum: 80 parts; Silicate cement: 7 parts; Multi-component activator: 3.5 parts; Environmental stabilizer: 2 parts; Water: 12 parts.

[0045] 3. Preparation and molding: Mixing: A high-speed forced mixer was used. First, phosphogypsum, cement, multi-component composite activator, and environmental stabilizer were added to the mixer and dry-mixed at 250 rpm for 4 minutes. Then, graded aggregates were added, and dry-mixing continued for 1.5 minutes. Finally, all water was added, and the mixer speed was linearly increased to 450 rpm within 30 seconds. This speed was maintained for 5 minutes to obtain a homogeneous mixture.

[0046] Compaction molding: The mixture is loaded into a test mold and compacted on a vibratory roller simulation device. The compaction degree is controlled to be no less than 98% of the maximum dry density, and the wettability is controlled to be 8mm by a sensor.

[0047] Curing: Immediately after compaction, place the specimens in a standard curing room with a temperature of (23±2)℃ and a relative humidity of ≥95% and cure them until the specified age.

[0048] 4. Performance Testing: Performance tests were conducted on specimens cured for 7 days and 28 days, and the results are as follows: Mechanical properties: 7-day unconfined compressive strength is 4.2 MPa, and 28-day unconfined compressive strength is 10.8 MPa.

[0049] Water stability: The softening coefficient after 28 days is 0.92, indicating that the material has excellent resistance to water damage.

[0050] Environmental safety (toxicity leaching test, refer to "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid Nitric Acid Method" HJ / T299): Lead (Pb) leaching concentration: <0.05 mg / L; Cadmium (Cd) leaching concentration: <0.003 mg / L; Fluoride (F-) leaching concentration: 0.35 mg / L; Total phosphorus (as P) leaching concentration: 0.8 mg / L; Therefore, all indicators are far below the Class III water limit of the "Groundwater Quality Standard" (GB / T 14848-2017), indicating high environmental safety.

[0051] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the paper parts and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing an environmentally safe phosphogypsum-based road base material, characterized in that, Includes the following steps: The raw material pretreatment steps include dehydration and particle size control of phosphogypsum, and grading and preparing graded aggregates. The mixture preparation step involves mixing and stirring the treated phosphogypsum, the graded aggregate, the cementitious material, the multi-component composite activator, and the environmental stabilizer to form a uniform road base mixture. The compaction and curing steps involve spreading and compacting the mixture to a predetermined density, followed by curing.

2. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 1, characterized in that, In the preparation step of the mixture, the amount of each material by weight is as follows: 100 to 120 parts of graded aggregate, 60 to 90 parts of phosphogypsum, 4 to 10 parts of cementitious material, 2 to 5 parts of multi-component activator, 1 to 3 parts of environmental stabilizer, and 8 to 15 parts of water; the cementitious material is silicate cement.

3. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 2, characterized in that, The multi-component composite activator is composed of a mineral activating component, an alkali activating component, and a crystallization regulating component. The mineral activating component is composed of slag powder and silica fume in a weight ratio of 3:1 to 5:

1. The alkali activating component is composed of water glass with a modulus of 1.0 to 1.3 and lithium carbonate in a weight ratio of 15:1 to 25:

1. The crystallization regulating component is composed of nano-silica with a particle size of 10 to 50 nanometers and calcium formate in a weight ratio of 1:1 to 1:

3.

4. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 3, characterized in that, The mineral activating component accounts for 60% to 80% of the total weight of the multi-component composite activator, the alkali activating component accounts for 15% to 30% of the total weight of the multi-component composite activator, and the crystallization regulating component accounts for 5% to 15% of the total weight of the multi-component composite activator.

5. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 2, characterized in that, The environmental stabilizer includes a heavy metal stabilizing component and a pollutant blocking component; the heavy metal stabilizing component is composed of metakaolin and magnesium phosphate in a weight ratio of 2:1 to 3:1; the pollutant blocking component is composed of sodium methylsilicate and active magnesium oxide in a weight ratio of 1:1 to 2:

1.

6. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 5, characterized in that, The heavy metal stabilizing component accounts for 60% to 70% of the total weight of the environmental stabilizer, and the pollutant blocking component accounts for 30% to 40% of the total weight of the environmental stabilizer.

7. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 1, characterized in that, In the raw material pretreatment step, phosphogypsum is dried to a moisture content of no more than 5%, and ground to a particle size of no more than 1 mm. The particles with a particle size of no more than 0.075 mm account for 20% to 30%, the particles with a particle size between 0.075 mm and 0.5 mm account for 50% to 60%, and the particles with a particle size between 0.5 mm and 1.0 mm account for 10% to 20%. The graded aggregate is graded crushed stone with a particle size range of 0 mm to 25 mm.

8. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 1, characterized in that, The mixing process in the preparation of the mixture adopts a high-speed forced mixing equipment, specifically including: first, adding the treated phosphogypsum, cementitious material, multi-component composite activator and environmental stabilizer into the mixer, and dry mixing at a speed of 200 to 300 revolutions per minute for 3 to 5 minutes; then adding graded aggregates and continuing to dry mix for 1 to 2 minutes; finally adding the total amount of water, and linearly increasing the speed of the mixer to 400 to 500 revolutions per minute within 30 seconds, maintaining this speed and mixing for 4 to 6 minutes.

9. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 1, characterized in that, In the compaction and curing steps, a vibratory roller is used for compaction, and the compaction degree is controlled to be no less than 98% of the maximum dry density. At the same time, the moisture content of the mixture is controlled to be 5 to 10 millimeters by a moisture observation device buried in the compacted layer. After compaction, the mixture is cured for 7 to 28 days under the conditions of a temperature of 20 to 25 degrees Celsius and a relative humidity of no less than 90%.

10. The method for preparing an environmentally safe phosphogypsum-based road base material according to claim 1, characterized in that, It also includes a real-time monitoring and feedback adjustment process based on material properties and environmental safety: during maintenance and service, the temperature, humidity and stress-strain changes inside the base layer are continuously monitored through an embedded sensor network; core samples are drilled periodically to determine their unconfined compressive strength and softening coefficient, and to detect the leaching concentration of heavy metal ions and phosphorus and fluoride ions.

Images