A cast-type phosphogypsum road stable base mixture and a preparation method and construction method thereof

Abstract

The present application relates to the technical field of bulk solid waste and road, and provides a pouring type phosphogypsum road stable base mixture, a preparation method, a construction method and application thereof, wherein the high-temperature modified phosphogypsum with specific properties is used as a cementing material, and is mixed with water, an additive and the like in a large amount to form a mixture, the mixture can realize a paving and pouring type process, reduces construction operation and mechanical cost, in addition, for the area that cannot be directly operated by a road roller in the construction of a traditional road stable base, the quality defects of the area that cannot be compacted in the dead angle area or the edge area are avoided, and the obtained base structure is free of curing, can be quickly solidified, has high early strength and good quality.

Description

Technical Field

[0001] This invention relates to the field of road technology, and in particular to a cast-in-place phosphogypsum road stabilized base course mixture, its preparation method, construction method, and application. Background Technology

[0002] Phosphogypsum is the largest waste product in terms of emissions from chemical gypsum. In recent years, with the development of the national economy, the amount of phosphogypsum discharged in my country has increased rapidly. If phosphogypsum is discharged arbitrarily without treatment, it will not only occupy a large amount of land and pollute the environment, but also cause harm to the ecosystem. Although industrial solid waste phosphogypsum is a pollutant discharged from industrial phosphorus chemical industry, it also has the potential to become an inorganic cementing material. However, because industrial solid waste phosphogypsum contains strong acids, soluble phosphorus, fluorine, organic matter, and harmful substances, its direct application in engineering construction will cause secondary pollution to the environment. Traditional water washing, neutralization, and flotation processes can only remove or reduce harmful substances and cannot restore its own building material activity. At present, it is mainly used as building materials and retarders. Directly applying it to road base materials cannot effectively consolidate the water-stabilized layer, and its poor water resistance means it can only be used as an admixture. Its dosage is small, making it difficult to form a large-scale application. Therefore, its application and promotion cannot be widely formed.

[0003] For example, patent application CN103771820A discloses a fresh hemihydrate phosphogypsum-fly ash pavement base material. This material uses hemihydrate fly ash or brown fly ash as the raw material for the pavement base. Through the interlocking effect between various raw materials, and by utilizing the alkaline activation of quicklime and the sulfate activation of hemihydrate phosphogypsum to activate the pozzolanic activity of fly ash, hydration products such as CSH, CSAH, AFt, and calcium hydroxide are formed. These products constitute the early strength of the pavement base and ensure the continuous growth of later strength. This allows for the design of semi-rigid pavement base and subbase that meet the requirements of various highway grades. However, it requires the mixture to be laid and leveled under a certain loose paving coefficient, compacted according to controlled construction compaction requirements, and moisturized for curing until the specified age is reached to form the pavement base, thus completing the construction of the hemihydrate phosphogypsum-fly ash pavement base.

[0004] For example, in patent CN106517979B, a base course filler is obtained by treating a phosphogypsum mixture, curing the phosphogypsum mixture, adding water to the phosphogypsum curd, improving the crack resistance of the phosphogypsum curd, and bringing the curd in the mixed filler to the optimal moisture content. The base course filler is then loosely laid on the roadbed surface and subjected to two static compactions with an 18-21 ton vibratory roller, four vibratory compactions, and two more static compactions to achieve a base course compaction degree of ≥97% and a subbase course compaction degree of ≥95%, thus obtaining the road base course.

[0005] For example, patent application CN114804773A provides a composite solid waste road base binder. After the industrial waste phosphogypsum is pretreated with an alkaline solution (for neutralization reaction and acid treatment), it is mixed with solid wastes such as fly ash and slag, as well as cement, and used as a cementitious binder in semi-rigid base materials. However, when this binder is further used for molding with aggregates and water, static pressure molding (one of the rolling methods) must be adopted.

[0006] For example, in patent application CN116553901A, phosphogypsum, a waste of phosphoric acid, is used as a raw material. It is mixed with cement, crushed stone and water, and a cement-phosphogypsum pavement base material with interlocking aggregate is obtained through multiple paving and compaction construction methods. It can be used for the base and subbase of special, heavy traffic roads and ordinary roads.

[0007] It can be seen that when the aforementioned industrial solid waste phosphogypsum is used in road base construction, it is basically just a matter of reducing harmful substances and strong acids in the waste phosphogypsum before using it as an additive (auxiliary material) in the road base structure. Firstly, the amount added is small; secondly, the pretreatment process does not completely remove the various harmful substances and organic impurities in the phosphogypsum, resulting in a significant potential secondary risk of environmental pollution. Furthermore, the road base construction process requires paving and compaction steps, and in areas where road rollers cannot directly operate, compaction dead zones and areas where edges cannot be compacted are created, leading to frequent quality defects.

[0008] Therefore, this invention is proposed. Summary of the Invention

[0009] This invention provides a castable phosphogypsum road stabilized base course mixture, its preparation method, construction method, and application. The mixture is prepared by high-temperature calcining industrial solid waste phosphogypsum to obtain a high-temperature modified phosphogypsum with specific properties, which is then used as a cementing material. This modified phosphogypsum is mixed with water and admixtures at high dosages to form a mixture. This mixture allows for a leveling and casting process, reducing construction and machinery costs. Furthermore, it avoids quality defects in areas where road rollers cannot directly operate, such as compaction dead zones or uncompacted edges. The resulting base course structure requires no compaction or curing, can solidify rapidly, has high early strength, and is of good quality.

[0010] Specifically, in the first aspect, the present invention provides a castable phosphogypsum road stabilized base course mixture, wherein the mixture uses high-temperature modified phosphogypsum as the main cementing material, and the water-cement ratio is 25-70:100, preferably 25-55:100.

[0011] The high-temperature modified phosphogypsum has a pH value ≥7.0, a hemihydrate gypsum content ≥65%, soluble phosphorus ≤0.2%, soluble fluorine ≤0.1%, a 2-hour compressive strength ≥5.0 MPa, and a flexural strength ≥2.0 MPa.

[0012] According to the cast-in-place phosphogypsum road stabilized base mixture provided by the present invention, the mixture contains aggregate, and the mass ratio of the aggregate to the high-temperature modified phosphogypsum is ≤4:6;

[0013] Preferably, the aggregate is recycled lightweight aggregate.

[0014] According to the cast-in-place phosphogypsum road stabilized base mixture provided by the present invention, the recycled lightweight aggregate is a high-temperature recycled ceramsite aggregate generated by high-temperature fluidization reaction using one or more of the following as raw materials: construction waste soil, slag, engineering mud, urban and rural sludge, phosphogypsum waste and sludge.

[0015] The preparation method of this recycled lightweight aggregate can be obtained by referring to conventional methods.

[0016] The high-temperature recycled ceramsite aggregate obtained by high-temperature fluidization reaction has the characteristics of surface porosity and lightweight high strength, which makes it better suspended in the mixture and more uniform. At the same time, it plays a regulatory role in water storage during mixing and water release during hydration reaction, which is beneficial to the mixing and molding of high-temperature modified phosphogypsum as the main cementing material. In particular, it avoids the problem of difficult and uneven mixing of whole phosphogypsum powder.

[0017] According to the cast-in-place phosphogypsum road stabilized base mixture provided by the present invention, the recycled lightweight aggregate is obtained by mixing and kneading powdered gypsum (i.e., the above-mentioned high-temperature modified phosphogypsum) with a hemihydrate gypsum content of more than 60% and a dihydrate gypsum content of no more than 5%, a retarder, and water, and then immediately molding the gypsum hardened body after kneading. The total mixing and kneading time is 2 min to 5 min, and the amount of water added during mixing is 8% to 30% of the total mass of the powdered gypsum.

[0018] The lightweight aggregates obtained by the above method can achieve homogeneous integrated structure, make the life cycle of the structural layer raw materials more synchronized, and make recycling more efficient.

[0019] According to the cast-in-place phosphogypsum road stabilized base mixture provided by the present invention, the mixture contains one or more of stone chips, stone powder and tailings sand;

[0020] The stone chips, stone powder and tailings sand are derived from traditional sand and gravel aggregates or waste products processed by industrial and mining enterprises.

[0021] The total mass ratio of the stone chips, stone powder, and tailings sand to the mass ratio of the high-temperature modified phosphogypsum is 10-30:100.

[0022] The addition of stone chips, stone powder, and tailings sand not only achieves waste utilization but also improves the fluidity of the mixture during mixing and construction by including 50% of active powders smaller than 0.026mm. During molding, the large amount of active silicon, aluminum, and calcium in the mixture reacts with the sulfates in phosphogypsum to form cementitious structures such as CSH and CSAH, which then bond more tightly with the modified phosphogypsum, enhancing its water stability and later strength. Moreover, it is more economical and has a lower cost.

[0023] According to the castable phosphogypsum road stabilization base mixture provided by the present invention, the high-temperature modified phosphogypsum is obtained by calcining industrial solid waste phosphogypsum at a temperature above 120°C.

[0024] When the soluble phosphorus and fluorine in the industrial solid waste phosphogypsum exceed the standard, the calcination temperature is above 400℃; when the heavy metals in the industrial solid waste phosphogypsum exceed the standard, the calcination temperature is above 800℃.

[0025] Preferably, the calcination temperature of 800°C or above involves mixing the phosphogypsum premix with high-temperature ceramsite, using the residual heat of the ceramsite for combustion, and then continuing the mixing and calcination process. The coarse aggregate of the ceramsite is then separated to obtain a residue with a ceramsite powder content of ≤30wt%, which is then further processed to obtain the final product.

[0026] According to the castable phosphogypsum road stabilized base mixture provided by the present invention, the mixture contains water with a mass ratio of less than 60%; and / or, the mixture contains admixtures with a mass ratio of 0.1% to 0.3%.

[0027] Preferably, the admixture includes one or more of a retarder, a water-reducing agent, and a waterproofing agent.

[0028] More preferably, when the mass ratio of the aggregate to the high-temperature modified phosphogypsum is (2:8) to (5:5), the mixture contains water at a mass ratio of 20% to 50%.

[0029] Alternatively, when the mass ratio of the aggregate to the high-temperature modified phosphogypsum is 1:9, the mixture contains water at a mass ratio of 30% to 50%.

[0030] Alternatively, when the mass ratio of the aggregate to the high-temperature modified phosphogypsum is greater than 0 and less than 1:9, the mixture contains water with a mass ratio of 40% to 60%.

[0031] When the mixture does not contain aggregate, the mixture contains water at a mass ratio of 30-35%.

[0032] When the amount of water is too small, it is difficult to mix and pour-over construction cannot be achieved.

[0033] Secondly, the present invention also provides a method for preparing the castable phosphogypsum road stabilization base course mixture as described above, comprising: mixing the raw materials containing the high-temperature modified phosphogypsum and water.

[0034] According to the preparation method of the castable phosphogypsum road stabilized base course mixture provided by the present invention, the water is added in more than two batches during mixing, the amount of water added in the first batch is 15-18% of the mass of the high-temperature modified phosphogypsum during mixing; the time of the first mixing is within 5 minutes.

[0035] Thirdly, the present invention also provides a construction method for the cast-in-place phosphogypsum road stabilized base course mixture as described above, wherein after the mixture is laid, it is leveled manually or mechanically, smoothed and left to stand to form the base course; preferably, the laying thickness is ≥8cm, more preferably 18cm.

[0036] Fourthly, the present invention also provides a road base course, comprising the cast-in-place phosphogypsum road stabilized base course mixture as described above;

[0037] The road base layer is applied in the following manner:

[0038] (1) Used for highways, ordinary roads or municipal roads with high traffic volume;

[0039] (2) Used for the maintenance and repair of road base layers where traffic opening times are tight;

[0040] (3) Used for basic repairs, especially for small areas;

[0041] (4) It is used in irregular areas and narrow roads; it is generally not suitable for compaction operations.

[0042] This invention provides a castable phosphogypsum road stabilized base course mixture, its preparation method, and its construction method. To achieve comprehensive utilization of phosphogypsum, a major solid waste, in road base courses, this invention employs the following method:

[0043] The first step involves using phosphogypsum solid waste as raw material, which is then subjected to high-temperature calcination to render it harmless. Under the premise of meeting the current national and industry quality standards, the modified phosphogypsum powder has the following characteristics: pH value ≥ 7.0, hemihydrate gypsum content ≥ 65%, soluble phosphorus ≤ 0.2%, soluble fluorine ≤ 0.1%, 2-hour compressive strength ≥ 5.0 MPa, and flexural strength ≥ 2.0 MPa.

[0044] The second step involves using modified phosphogypsum powder as a cementing material, supplemented with traditional sand and gravel aggregates, recycled aggregates, recycled lightweight aggregates, or other tailings, slag, etc., and applying modified phosphogypsum as a cementing material in large quantities during road base construction. This results in a mixture with modified phosphogypsum as the main raw material (admixture ≥60%), which is mixed with water, admixtures, traditional sand and gravel aggregates, recycled aggregates, recycled lightweight aggregates, or other industrial tailings, slag, etc., at a rate of 5-40%, forming a highly fluid, non-segregating, and easily compacted mixture.

[0045] Applying this type of mixture to road stabilized base course can greatly improve production efficiency, change the cumbersome process of traditional road stabilized base course materials without compaction, and change the problems of edge non-compacted areas, local compacted areas, and natural defect areas during traditional compaction.

[0046] When modified phosphogypsum is used as a cementing material and as the main raw material, the structure of traditional road stabilization base materials is changed. That is, the skeleton of modified phosphogypsum cementing material with sand and gravel aggregate as auxiliary material and modified phosphogypsum as the main cementing material or modified phosphogypsum cementing material as the main material for coagulation and consolidation is formed → cementation → stabilization structure. This structure enlarges the cementing material and forms a stable structure of repeated coating → consolidation → coating → consolidation of cementing material. The coating surface is wider and it is less likely to occur in the traditional material due to the small amount of cementing material itself causing insufficient local coating.

[0047] Modified phosphogypsum is used as the main raw material in the construction of road base courses. Through material proportioning, a cast-in-place, self-compacting, non-compacting road base course structure is formed. It has advantages such as excellent structure, no need for mechanical investment, and the absence of defects left by traditional compaction machinery. It also features fast forming, high efficiency, good early strength (24-hour strength ≥ 2.5 MPa), softening coefficient ≥ 85%, no curing required, and low on-site noise.

[0048] It promotes green transportation, conserves natural resources, and in particular, changes the traditional reliance on and demand for cement in the foundation of road stabilization, resulting in energy conservation, carbon reduction, and good social and economic benefits. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0050] Figures 1-3 This is a schematic diagram of the appearance of the mixture of Embodiment 1 provided by the present invention, used in a cast-in-place manner for road stabilization base course;

[0051] Figure 4This is an internal schematic diagram of the mixture provided in Embodiment 1 of the present invention after it has been cast into a road stabilization base layer. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] The following is combined Figures 1-4 This invention describes a castable phosphogypsum road stabilized base course mixture, its preparation method, construction method, and application.

[0054] The preparation method of the high-temperature modified phosphogypsum in this invention can be achieved using existing methods. As long as the pH value is ≥7.0, the mass content of hemihydrate gypsum is ≥65%, soluble phosphorus is ≤0.2%, soluble fluorine is ≤0.1%, the 2-hour compressive strength is ≥5.0 MPa, and the flexural strength is ≥2.0 MPa, the effects of this invention can be achieved. This high-temperature modified phosphogypsum can be prepared according to the method in patent application CN116675452A. Alternatively, it can be prepared at 120–600℃ using the kiln high-temperature waste heat recovery system in patent application CN115900366A. In the following examples of this invention, the raw materials obtained in this invention are described by reference to earlier applications.

[0055] The stone chips, stone powder, and tailings sand in this invention originate from fine or ultrafine powders derived from traditional sand and gravel aggregates or industrial mineral processing. During the production process, these fine or ultrafine powders undergo repeated impact and friction, physically activating the mineral active components such as silicon, aluminum, calcium, and magnesium. After being sorted by a traditional sand and gravel aggregate screening system, a large amount of fine powder ≤0.3mm is disposed of as waste through stockpiling. Testing reveals that these fine or ultrafine powders contain 50% materials with mineral active components smaller than 0.026 μm.

[0056] Example 1 Mixture

[0057] A method for preparing a mixture, comprising mixing high-temperature modified phosphogypsum obtained in Example 1 of patent application CN116675452A, lightweight aggregate obtained in Example 1 of patent application CN116813291A, water, and a retarder; wherein the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 90:10; the amount of water is 35%, and the amount of retarder is 3%.

[0058] The water is added in two or more batches during mixing. The first batch of water is 16% of the mass of the high-temperature modified phosphogypsum during mixing. The first mixing time is 3 minutes, and water is added continuously while mixing until the target amount of water is reached.

[0059] Example 2 Mixture

[0060] It is basically the same as Example 1, except that the amount of water used is 40%.

[0061] Example 3 Mixture

[0062] It is basically the same as Example 1, except that the amount of water used is 50%.

[0063] Example 4 Mixture

[0064] It is basically the same as Example 1, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 80:20.

[0065] Example 5 Mixture

[0066] It is basically the same as Example 4, except that the amount of water used is 40%.

[0067] Example 6 Mixture

[0068] It is basically the same as Example 4, except that the amount of water used is 50%.

[0069] Example 7 Mixture

[0070] It is basically the same as Example 1, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 70:30.

[0071] Example 8 Mixture

[0072] It is basically the same as Example 7, except that the amount of water used is 40%.

[0073] Example 9 Mixture

[0074] It is basically the same as Example 7, except that the amount of water used is 50%.

[0075] Example 10 Mixture

[0076] It is basically the same as Example 1, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 60:40.

[0077] Comparative Example 1 Mixture

[0078] It is basically the same as Example 1, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 50:50.

[0079] Example 11 Mixture

[0080] It is basically the same as Example 1, except that: the lightweight aggregate is replaced by high-temperature modified phosphogypsum (i.e., it does not contain lightweight aggregate and is all high-temperature modified phosphogypsum), and the water-cement ratio is 35%.

[0081] Comparative Example 2 Mixture

[0082] It is basically the same as Example 1, except that: the lightweight aggregate is replaced by high-temperature modified phosphogypsum (i.e., it does not contain lightweight aggregate and is all high-temperature modified phosphogypsum), and the water-cement ratio is 40%.

[0083] Comparative Example 3 Mixture

[0084] It is basically the same as Example 1, except that: the lightweight aggregate is replaced by high-temperature modified phosphogypsum (i.e., it does not contain lightweight aggregate and is all high-temperature modified phosphogypsum), and the water-cement ratio is 50%.

[0085] Example 12 Mixture

[0086] It is basically the same as Example 1, except that the high-temperature modified phosphogypsum is replaced with modified phosphogypsum calcined by residual heat from the external kiln system at 200°C.

[0087] Example 13 Mixture

[0088] It is basically the same as Example 1, except that the high-temperature modified phosphogypsum is replaced with modified phosphogypsum calcined using the residual heat of the kiln external system at 400°C.

[0089] Example 14 Mixture

[0090] It is basically the same as Example 1, except that the high-temperature modified phosphogypsum is replaced with modified phosphogypsum calcined using the residual heat of the kiln external system at 600°C.

[0091] The high-temperature modified phosphogypsum obtained in Examples 12-14 meets the following requirements: pH value ≥ 7.0, hemihydrate gypsum content ≥ 65%, soluble phosphorus ≤ 0.2%, soluble fluorine ≤ 0.1%, 2-hour compressive strength ≥ 5.0 MPa, and flexural strength ≥ 2.0 MPa.

[0092] Example 15 Mixture

[0093] It is basically the same as Example 1, except that stone powder is added during mixing, and the mass ratio of the high-temperature modified phosphogypsum to the stone powder is 9:1.

[0094] The present invention, by adding stone powder to the basis of Example 1, can also meet the requirements of rapid curing and rapid opening to traffic. As the time is extended to 7 days, its strength and softening coefficient will be further improved, which is better than Example 1.

[0095] Example 16 Mixture

[0096] It is basically the same as Example 12, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 80:20.

[0097] Example 17 Mixture

[0098] It is basically the same as Example 12, except that the mass ratio of high-temperature modified phosphogypsum to lightweight aggregate is 70:30.

[0099] Application example: road stabilization base layer

[0100] A cast-in-place phosphogypsum road stabilization base course includes the following steps:

[0101] (1) Inspection and cleaning before the construction of the base layer

[0102] (2) Measurement, layout and model erection

[0103] (3) The mixture obtained in Example 1 was mixed from the first addition of water until 40 minutes before being spread, and then leveled and smoothed manually or mechanically.

[0104] (4) Allow to cure until the strength meets the specifications, and the appearance after molding is as follows: Figures 1-3 As shown, its internal structure after breakage is as follows Figure 4 As shown.

[0105] (5) Acceptance and handover, opening to traffic or construction of the underlying layer.

[0106] The mixtures obtained from other embodiments and comparative examples were applied as described above to form a base layer. The 2-hour strength and the base layer after 24 hours of curing were tested, and the test results are as follows:

[0107]

[0108]

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cast-in-place phosphogypsum road stabilization base course mixture, characterized in that, The mixture uses high-temperature modified phosphogypsum as the main cementing material, and the water-cement ratio is 25~70:

100. The pH value of the high-temperature modified phosphogypsum is ≥ 7.0, and the mass content of hemihydrate gypsum is ≥65%, soluble phosphorus ≤0.2%, soluble fluorine ≤0.1%, 2-hour compressive strength ≥5.0MPa, and flexural strength ≥2.0MPa; The preparation method of the castable phosphogypsum road stabilized base course mixture includes: mixing the raw materials containing the high-temperature modified phosphogypsum and water, wherein the water is added in two or more batches during mixing, the amount of water added in the first batch is 15-18% of the mass of the high-temperature modified phosphogypsum during mixing; the time of the first mixing is within 5 minutes. The mixture contains aggregate, which is recycled lightweight aggregate. The recycled lightweight aggregate is a high-temperature recycled ceramsite aggregate generated by high-temperature fluidization reaction using one or more of the following raw materials: construction waste soil, slag, engineering mud, phosphogypsum waste, and sludge. The porous surface and lightweight and high-strength characteristics of the high-temperature recycled ceramsite aggregate allow it to be suspended in the mixture, while also regulating the storage of water during mixing and the release of water during the hydration reaction. The mass ratio of the aggregate to the high-temperature modified phosphogypsum is ≤4:6; The mixture contains one or more of the following: stone chips, stone powder, and tailings sand. The stone chips, stone powder, or tailings sand are derived from traditional sand and gravel aggregates or waste products processed by industrial and mining enterprises. The total mass ratio of the mixture to the high-temperature modified phosphogypsum is 10~30:

100.

2. The cast-in-place phosphogypsum road stabilization base course mixture according to claim 1, characterized in that, The recycled lightweight aggregate is a hardened gypsum body obtained by mixing and grinding powdered gypsum with a hemihydrate gypsum content of more than 60% and a dihydrate gypsum content of no more than 5%, a retarder, and water, and then immediately forming it after grinding. The total mixing and grinding time is 2 min to 5 min, and the amount of water added during mixing is 8% to 30% of the total mass of the powdered gypsum.

3. The cast-in-place phosphogypsum road stabilization base course mixture according to claim 1, characterized in that, The high-temperature modified phosphogypsum is obtained by calcining industrial solid waste phosphogypsum at a temperature above 120°C. When the soluble phosphorus and fluorine in the industrial solid waste phosphogypsum exceed the standard, the calcination temperature is above 400℃; when the heavy metals in the industrial solid waste phosphogypsum exceed the standard, the calcination temperature is above 800℃.

4. The cast-in-place phosphogypsum road stabilization base course mixture according to claim 3, characterized in that, The calcination temperature of 800℃ or above involves mixing phosphogypsum premix with high-temperature ceramsite, using the residual heat of the ceramsite for combustion, and then continuing the mixing and calcination process. The coarse aggregate of the ceramsite is then separated to obtain a residue with a ceramsite powder content of ≤30wt%, which is then further processed to obtain the final product.

5. The cast-in-place phosphogypsum road stabilization base course mixture according to any one of claims 1 to 4, characterized in that, The mixture contains water at a mass ratio of less than 60%; and / or, the mixture contains an additive at a mass ratio of 0.1% to 0.3%.

6. The cast-in-place phosphogypsum road stabilization base course mixture according to claim 5, characterized in that, The admixtures include one or more of the following: retarder, water-reducing agent, and waterproofing agent.

7. The method for preparing the cast-in-place phosphogypsum road stabilized base course mixture according to any one of claims 1 to 6, characterized in that, include: The raw materials containing the high-temperature modified phosphogypsum and water are mixed together.

8. A construction method for the cast-in-place phosphogypsum road stabilized base course mixture according to any one of claims 1 to 6, characterized in that, After the mixture is spread, it is leveled, smoothed, and left to stand manually or mechanically to obtain the base layer.

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