Phosphogypsum highway subgrade construction method based on novel waterproof and anti-freezing material

Abstract

The invention discloses a phosphogypsum highway subgrade construction method based on a novel waterproof and anti-freezing material. The phosphogypsum highway subgrade construction method comprises the steps of S1, highway subgrade pretreatment and cohesive soil paving; s2, a road foundation waterproof and anti-freezing layer is arranged, specifically, 6.0-9.0 kg / m < 2 > of a waterproof and anti-freezing material is sprayed, the film forming thickness is not smaller than 0.6 mm, and the waterproof and anti-freezing material is composed of calcium chloride, water glass and SBR modified emulsified asphalt according to the mass ratio of 1: 1: 10-15; s3, laying and rolling of an ardealite mixture, wherein the ardealite mixture is obtained by doping 3%-7% of quick lime into ardealite; s4, finishing and compacting the ardealite highway subgrade; s5, after the upper surface and the two side surfaces of the ardealite highway subgrade are dried, a waterproof and anti-freezing material is sprayed in time, and the film forming thickness is not smaller than 0.6 mm; and S6, protective engineering construction. According to the method, the ardealite can be consumed in a large scale, so that the ardealite highway roadbed can meet the requirements of bearing capacity and stability, and environmental pollution caused by the ardealite can be prevented.

Description

Technical Field

[0001] The invention relates to the fields of highway transportation and phosphorus chemical industry, and in particular to a phosphogypsum highway subgrade construction method based on a new waterproof and antifreeze material, so that the phosphogypsum highway subgrade can meet the requirements of bearing capacity and stability and prevent environmental pollution caused by phosphogypsum. Background Art

[0002] Phosphogypsum is a byproduct of phosphate fertilizer and wet phosphoric acid production. Its main components include calcium sulfate, a small amount of undecomposed phosphate rock powder, free phosphoric acid, iron phosphate, aluminum phosphate, and impurities such as calcium hydrogen phosphate and fluorosilicate eutectic with gypsum, especially a small amount of heavy metal harmful substances. my country's phosphate fertilizer production is large, and hundreds of millions of tons of phosphogypsum are produced every year, which not only occupies a large amount of land resources, but also causes serious environmental pollution.

[0003] In the existing technology, the treatment of phosphogypsum is still mainly based on on-site stacking and mine landfill, which poses a great risk of environmental pollution. At present, the comprehensive utilization rate of phosphogypsum is only about 20%, and there is an urgent need to develop new ways to utilize phosphogypsum solid waste materials in large quantities. On the other hand, highway construction is large-scale, requiring hundreds of millions of cubic meters of road construction materials every year. The external soil sources for highway construction are limited, and there is an urgent need to explore new ways to use highway construction materials. The use of phosphogypsum industrial solid waste materials can not only solve the problem of limited highway construction materials, but also effectively reduce the pollution caused by phosphogypsum to the natural environment. However, as a highway subgrade construction material, phosphogypsum has the technical difficulties of heavy metals and other harmful components escaping to cause environmental pollution and phosphogypsum highway subgrade surface frost heave cracking damage or rain erosion damage, and there is an urgent need for effective technical means. Summary of the invention

[0004] The purpose of the present invention is to provide a phosphogypsum highway subgrade construction method to address the problems of phosphogypsum highway subgrade diseases and environmental pollution caused by water damage or frost heave damage that may occur when phosphogypsum is used as a highway subgrade construction material.

[0005] To achieve the above object, the present invention adopts the following technical solution: A phosphogypsum highway subgrade construction method based on a novel waterproof and antifreeze material comprises the following steps: Step S1, pretreatment of highway foundation and paving of clay soil: the foundation within the scope of the highway foundation to be constructed is pre-cleaned of debris, weeds and silt (including the removal of silty soil, humus and soil containing perishable materials such as tree roots and turf), and then paved with clay soil material with a thickness of not less than 30 cm, compacted by rolling, and a compaction degree of not less than 92%, so that it not only meets the requirements of roadbed bearing capacity and stability, but also has a certain function of blocking the rise of capillary water.

[0006] Step S2: Setting of waterproof and antifreeze layer for highway foundation: spraying waterproof and antifreeze material on the compacted clay soil, with a spreading amount of 6.0-9.0 kg / m 2 , so that the film thickness of the waterproof and antifreeze layer is not less than 0.6mm, so as to prevent groundwater from penetrating into the phosphogypsum highway subgrade; the waterproof and antifreeze material is composed of calcium chloride, water glass, and SBR modified emulsified asphalt diluent, the mass ratio of calcium chloride, water glass, and SBR modified emulsified asphalt is 1:1:10-15, and the solid content of the SBR modified emulsified asphalt is 30%-50%; Step S3, laying and rolling of phosphogypsum mixture: the phosphogypsum mixture is obtained by mixing 3% to 7% quicklime into phosphogypsum and stirring evenly. The compaction degree of the laid phosphogypsum mixture after rolling is required to reach more than 96%, so that its compressive strength after curing for 27 days and soaking in water for 1 day reaches more than 3MPa, which not only meets the roadbed bearing capacity and stability requirements, but also has a certain effect of preventing harmful substances in phosphogypsum from escaping; Table 1 shows the water quality test results (mg / L) of phosphogypsum mixture specimens with a quicklime content of 3% after crushing and soaking in water. The specimens with a quicklime content of less than 3% are difficult to meet the strength requirements, and the cost is too high when it is higher than 7%, and the practicality and economy are poor.

[0007] Table 1 Note: Implement the "Comprehensive Wastewater Discharge Standard" GB8978-1996. Discharge into Class III surface water (mainly applicable to secondary protection areas of centralized drinking water surface water sources, fish and shrimp wintering grounds, migration channels, aquaculture areas and other fishery waters and swimming areas) implement the first-level standard; discharge into Class IV surface water (mainly applicable to general industrial water areas and recreational water areas that are not directly in contact with the human body), Class V is mainly applicable to agricultural water areas and general landscape water areas to implement the second-level standard; discharge into sewage treatment plants to implement the third-level standard.

[0008] Step S4, roadbed finishing and compaction: When the phosphogypsum roadbed is constructed, its width should be 10-20 cm wider than the design width. After the phosphogypsum roadbed construction reaches the design elevation, the slope is trimmed in time, and the loose layer on the surface is removed and compacted by a slope compaction machine or manually tamped to make the surface flat and dense; Step S5: Waterproof and antifreeze setting on the upper layer and both sides of the roadbed: After the upper surface and both sides of the phosphogypsum roadbed are dry, spray the waterproof and antifreeze material described in step S2 in time, with a spraying amount of 6.0~9.0kg / m 2, so that the film thickness reaches more than 0.6mm, and the micropores and microcracks on the surface of the phosphogypsum roadbed are sealed. The two sides and the upper surface are fully sealed, and the roadbed drainage and protection system is strengthened to prevent the phosphogypsum roadbed from being damaged by rainwater and thus improve the stability of the phosphogypsum roadbed. It effectively blocks rainwater or groundwater from penetrating into the phosphogypsum roadbed, and prevents the phosphogypsum roadbed from being damaged by frost heave or polluting the environment.

[0009] Further optimization, in S2, the preparation method of the waterproof and antifreeze material is: 1) Dilute the SBR modified asphalt stock solution to a solid content of 30% to 50% and stir evenly; 2) Grind the calcium chloride block into powder, and select the powder with a particle size of less than 1.5 mm through a 1.5 mm round hole sieve for later use; 3) Prepare a mixture of water glass and calcium chloride in a weight ratio of 1:1. First, add water glass into a plastic container, then slowly add calcium chloride powder, stirring while adding until the two are evenly mixed; 4) Place the diluted SBR modified emulsified asphalt in step 1) in a container and stir it evenly, then add the water glass and calcium chloride mixture obtained in step 3) in a prescribed proportion, stirring while adding until it is evenly mixed.

[0010] The waterproof and antifreeze material of the present invention uses modified emulsified asphalt with a solid content of 30% to 50% as a basic material, uses calcium chloride as an antifreeze agent to reduce the freezing temperature of the phosphogypsum roadbed, and adds water glass to improve its permeability in the phosphogypsum roadbed, so that it can penetrate into the phosphogypsum roadbed to a certain depth, effectively seal the micropores and microcracks on the surface of the phosphogypsum roadbed, and achieve the purpose of water sealing when the film thickness of the waterproof and antifreeze material is not less than 0.6 mm.

[0011] Further optimization, in S3: before paving, the phosphogypsum mixture is spread with a thickness of not less than 1 cm to prevent the transportation equipment from damaging the waterproof and antifreeze layer.

[0012] Further optimization, in S3: a base mixer is used to mix the lime-stabilized phosphogypsum mixture. For areas with frequent rainfall, the preferred lime blending ratio is 5%~7%, and the 28d compressive strength reaches above 3.0MPa, which can solidify the harmful components in the phosphogypsum and ensure the bearing capacity and stability of the phosphogypsum highway subgrade.

[0013] In further optimization, in S5, the spraying amount per square meter of the waterproof and antifreeze material on both sides of the phosphogypsum highway subgrade is greater than the spraying amount per square meter of the waterproof and antifreeze material on the upper surface of the phosphogypsum highway subgrade.

[0014] Further optimization includes steps S2 and S5: after the waterproof and antifreeze material penetrates and forms a film, the film thickness should be sampled and tested. If the film thickness is found to be insufficient or there are blank spots, it should be replenished in time to ensure that the requirements are met.

[0015] Further optimization also includes step S6: after the phosphogypsum roadbed waterproof and antifreeze new material is dried and formed into a film, it is advisable to promptly construct the phosphogypsum roadbed protection project, drainage project and greening project to effectively protect the phosphogypsum roadbed and the waterproof and antifreeze layer. If the phosphogypsum roadbed waterproof and antifreeze layer is damaged during the construction process, the phosphogypsum roadbed waterproof and antifreeze new material can be promptly sprayed to repair the waterproof and antifreeze layer, and the spraying amount should be taken to the upper limit.

[0016] Furthermore, the protection project includes setting frame beams on the slope of the phosphogypsum highway roadbed, the frame beams divide the roadbed into blocks, the maximum width of which does not exceed 8m, and the frame beams are filled with clay planting soil, the thickness of which reaches more than 30cm.

[0017] Furthermore, the greening project includes planting slope plants in the sticky planting soil, and the slope plants are preferably selected from grass species with developed root systems, a soil depth of not less than 10 cm, drought resistance and high natural growth density, so as to alleviate rainwater erosion of the roadbed slope and protect the project.

[0018] The main function of using frame beam + sticky planting soil + greening project is to improve the stability of the roadbed; select grass species with developed root system, soil penetration depth of not less than 10cm, dense growth, drought resistance and high natural growth density, such as high wool, whose main function is to alleviate the impact of raindrops on the roadbed slope, improve the stability of phosphogypsum roadbed and protection projects, and beautify the natural environment. The frame beam structure is adopted, and its maximum width does not exceed 8m. By dividing the roadbed into blocks, the shrinkage and cracking of the roadbed soil slope can be effectively controlled, thereby improving the stability of the roadbed. The sticky planting soil is specially selected, which is not only conducive to plant growth, but also has a certain waterproof effect.

[0019] The beneficial effects of the phosphogypsum highway subgrade construction method provided by the present invention are as follows: The method of the present invention can consume phosphogypsum in large quantities, ensuring that the phosphogypsum highway subgrade can meet the requirements of bearing capacity and stability, and can also play an important role in preventing environmental pollution caused by phosphogypsum.

[0020] The invention discloses a construction method of a phosphogypsum highway subgrade. Based on a new antifreeze material, the method can prevent moisture from penetrating into the phosphogypsum highway subgrade to cause the escape of harmful components, and can also prevent the phosphogypsum highway subgrade from being damaged by frost heave at low temperatures of -20°C to 0°C, thereby achieving the purpose of ensuring the bearing capacity and stability of the phosphogypsum highway subgrade and protecting the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is the design drawing for the phosphogypsum highway subgrade project. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention clearer, a detailed description will be given in combination with the design and construction method of the phosphogypsum highway subgrade and its waterproof and antifreeze layer.

[0023] Example 1 A new secondary road in a certain county requires a large amount of construction materials. It is difficult to borrow soil from outside, the transportation distance is long, and the cost is high. There is a phosphogypsum storage site 2km away from the secondary road, covering an area of ​​nearly 50 acres, which has a certain impact on the surrounding environment. Therefore, the road construction unit decided to use phosphogypsum to build the road. The specific procedures and methods are as follows: Step S1, pretreatment of highway foundation and laying of clay soil: pre-clean the foundation within the scope of the highway foundation to be constructed, including desilting ponds and farmland, removing silt and humus. Then lay clay soil material to fill the roadbed leveling layer, with a thickness of not less than 30cm, until it is more than 30cm higher than the original foundation, and compact it with a compaction degree of not less than 92%, so that it can meet the roadbed bearing capacity and stability requirements, and have a certain function of blocking the rise of capillary water.

[0024] Step S2: Setting of waterproof and antifreeze layer for highway foundation: After the leveling layer is accepted, spray waterproof and antifreeze material at a rate of 7.0 kg / m 2 , so that the film thickness of the waterproof and antifreeze layer is not less than 0.6mm, to prevent groundwater from penetrating into the phosphogypsum highway subgrade; the waterproof and antifreeze material is composed of calcium chloride, water glass, and SBR modified emulsified asphalt diluent, the mass ratio of calcium chloride, water glass, and SBR modified emulsified asphalt is 1:1:12, and the solid content of the SBR modified emulsified asphalt is 40%; Waterproof and antifreeze material preparation process: 1) Dilute the SBR modified asphalt stock solution to a solid content of 40% and stir evenly; 2) Grind the calcium chloride block into powder, and select the powder with a particle size of less than 1.5 mm through a 1.5 mm round hole sieve for later use; 3) Prepare a mixture of water glass and calcium chloride in a weight ratio of 1:1. First, add water glass into a plastic container, then slowly add calcium chloride powder, stirring while adding until the two are evenly mixed; 4) Place the diluted SBR modified emulsified asphalt in step 1) in a container and stir it evenly, then add the water glass and calcium chloride mixture obtained in step 3) in a prescribed proportion, stirring while adding until it is evenly mixed.

[0025] Step S3, laying and rolling of phosphogypsum mixture: the phosphogypsum mixture is obtained by adding 5% quicklime to phosphogypsum and stirring evenly, and the stirring time is not less than 60s. The compaction degree of the laid phosphogypsum mixture after rolling is required to reach more than 96%, and the compressive strength after curing for 27 days and soaking in water for 1 day is required to reach more than 3MPa, which not only meets the roadbed bearing capacity and stability requirements, but also has a certain effect of preventing the escape of harmful substances in the phosphogypsum.

[0026] Before paving, spread the phosphogypsum mixture with a thickness of not less than 1 cm to prevent the transportation equipment from damaging the waterproof and antifreeze layer.

[0027] The phosphogypsum mixture is spread by a paver with a thickness of 30cm. The paver should spread at a uniform speed of 3~5km / h, and start the vibration tamping to make the loose paving compaction reach more than 82%; first use a light steel wheel roller to statically press the phosphogypsum mixture, and then use a light double steel wheel roller to vibrate and compact it once, so as to improve the compaction of the lime-stabilized phosphogypsum highway subgrade, so that it has the bearing capacity of an 11-ton heavy steel wheel roller. Use a heavy roller to roll 3~5 times, and the procedure is to statically press once at a rolling speed of 3~5km / h, and then vibrate and roll 2~4 times until the compaction reaches more than 96%. Use a heavy roller to statically press 1~3 times again until the surface displacement cracks of the phosphogypsum highway subgrade are eliminated.

[0028] Step S4, roadbed finishing and compaction: When the phosphogypsum roadbed is constructed, its width should be 10-20 cm wider than the design width. After the phosphogypsum roadbed construction reaches the design elevation, the slope is trimmed in time, and the loose layer on the surface is removed and compacted using a slope compaction machine or manually tamped to make the surface smooth and dense.

[0029] Step S5: Waterproof and antifreeze setting on the upper layer and both sides of the roadbed: After the upper surface and both sides of the phosphogypsum roadbed are dry, spray the waterproof and antifreeze material in time, with a spraying amount of 7.0 kg / m 2 , so that the film thickness reaches more than 0.6mm, closing the micropores and microcracks on the surface of the phosphogypsum roadbed. Effectively blocking rainwater or groundwater from penetrating into the phosphogypsum roadbed, preventing the phosphogypsum roadbed from frost heaving and damage or polluting the environment.

[0030] In this embodiment, calcium chloride: water glass: modified emulsified asphalt = 1:1:12. The ratio of lime to phosphogypsum is 5%. The waterproof and antifreeze material can withstand a low temperature of -19°C on the surface of the phosphogypsum mixture specimen, and does not crack under the condition of a film thickness of 0.6mm, indicating that it has a certain ductility; and the water permeability coefficient is 0, indicating that it does not seep water. The data is measured according to the test method specified in the T0605-2011 Asphalt Ductility Test Procedure in the "Test Procedure for Asphalt and Asphalt Mixture" (JTG E20-2011).

[0031] After the waterproof and antifreeze materials penetrate and form a film in steps S2 and S5, the film thickness should be sampled and tested. If there is white exposure or insufficient local spreading amount, it should be re-sprayed in time to make the film thickness reach more than 0.6mm to prevent rainwater from penetrating into the phosphogypsum highway subgrade.

[0032] Step S6, after the construction of the phosphogypsum highway subgrade is completed and its strength reaches 0.7MPa or above (about 3 days), the construction of supporting projects such as pavement engineering, protection engineering, greening engineering and drainage engineering should be carried out in time to effectively protect the phosphogypsum highway subgrade. The protection engineering includes setting frame beams on the slope of the phosphogypsum highway subgrade, and filling the frame beams with sticky planting soil, and the thickness of the sticky planting soil reaches more than 30cm. The greening engineering includes planting slope plants in the sticky planting soil, and the slope plants should be selected from grass species with well-developed root systems, a soil depth of not less than 10cm, drought resistance and high natural growth density.

[0033] Construction of phosphogypsum highway subgrade protection, drainage and greening projects: frame beam structure (such as Figure 1 As shown in the figure, vertical reinforced concrete beams are set up at a maximum spacing of no more than 8m. If the fill height is greater than 6m, a transverse reinforced concrete beam is set up in the middle; then, clay planting soil is filled in the frame, and grass seeds with well-developed root systems, a depth of no less than 10cm, and dense growth are spread, and artificial leveling and compaction are achieved to beautify the environment and prevent the slope from being washed away and damaged by rainwater. A drainage ditch is set up every 30~50m for the roadbed drainage project to drain rainwater from the road surface in a timely manner.

[0034] Example 2 A new first-class highway was built in a certain city. The road has four lanes in both directions and the designed road surface width is 22m. One section passes through a hilly area and is a half-filled and half-cut section. The maximum fill height on one side is 5.0m, and the fill height on the other side is 0.5m. In order to save land, a flaked concrete retaining wall is designed on the side with high fill, with a width of 50cm at the top and 100cm at the bottom. There is a phosphogypsum storage site 300m away from the road, which stores about 3.2 million m 3 Phosphogypsum has a certain impact on the surrounding environment. Therefore, the road construction unit decided to use phosphogypsum to build the road to reduce environmental pressure and solve the common quality problem of highway engineering that the uneven thickness of fill may cause uneven settlement of the roadbed. The specific procedures and methods are as follows: Step S1, pretreatment of highway foundation and paving of clay soil: pre-clean the foundation within the scope of the highway subgrade land to be constructed with debris, weeds, trees and silt. Moreover, dig steps and construction access roads according to the height difference of 30cm, and build a flaked stone concrete retaining wall on the side with large fill height. After the curing of cement concrete of the flaked stone concrete retaining wall is completed, clay soil can be used as the lower layer filler of the phosphogypsum subgrade. When its width reaches more than 2m and its thickness is not less than 30cm, it is compacted and compacted with a compaction degree of not less than 92%, so that it can meet the requirements of subgrade bearing capacity and stability, and have a certain function of blocking the rise of capillary water.

[0035] Step S2: Setting of waterproof and antifreeze layer for highway foundation: spraying waterproof and antifreeze material with a spraying amount of 7.0 kg / m 2 , so that the film thickness of the waterproof and antifreeze layer is not less than 0.6mm, preventing groundwater from penetrating into the phosphogypsum highway subgrade; the waterproof and antifreeze material is composed of calcium chloride, water glass, and SBR modified emulsified asphalt diluent, the mass ratio of calcium chloride, water glass, and SBR modified emulsified asphalt is 1:1:14, and the solid content of the SBR modified emulsified asphalt is 40%; the preparation method is the same as Example 1.

[0036] Step S3, laying and rolling of phosphogypsum mixture: the phosphogypsum mixture is obtained by adding 6% quicklime to phosphogypsum and stirring evenly, and the stirring time is not less than 60s. The compaction degree of the laid phosphogypsum mixture after rolling is required to reach more than 96%, and the compressive strength after curing for 27 days and soaking in water for 1 day is required to reach more than 3MPa, which not only meets the roadbed bearing capacity and stability requirements, but also has a certain effect of preventing the escape of harmful substances in the phosphogypsum.

[0037] For the smaller width of the lower part of the roadbed, the lime-stabilized phosphogypsum mixture can be spread manually, with a loose paving thickness of no more than 20cm. Use a small roller or vibrating rammer to roll the lime-stabilized phosphogypsum mixture. When the compaction degree reaches more than 85% and the width is greater than 2m, a heavy roller of 9t or more can be used for rolling. First, use a light steel wheel roller to statically press the lime-stabilized phosphogypsum mixture once, and then use a heavy double steel wheel roller to statically press once to improve the compaction degree of the lime-stabilized phosphogypsum highway roadbed, so that it has the bearing capacity of an 11-ton heavy steel wheel roller. Use a heavy roller to roll 3 to 5 times, and the procedure is to statically press once at a rolling speed of 3 to 5km / h, and then vibrate and roll 2 to 4 times until the compaction degree reaches more than 96%. Finally, use a heavy roller to statically press 1 to 2 times until the surface displacement cracks of the phosphogypsum highway roadbed are eliminated.

[0038] S4. Roadbed finishing and compaction: When constructing the phosphogypsum roadbed, its width should be 10~20cm wider than the design width. After the phosphogypsum roadbed construction reaches the design elevation, the slope should be trimmed in time. After removing the loose layer on the surface, the slope should be compacted by slope compaction equipment or manually tamped to make the surface smooth and dense. S5. Waterproof and antifreeze setting on the upper layer and both sides of the highway subgrade: After the upper surface and both sides of the phosphogypsum highway subgrade are dry, spray the waterproof and antifreeze material in time, with a spraying amount of 7.0kg / m 2 , so that the film thickness reaches more than 0.6mm, and the micropores and microcracks on the surface of the phosphogypsum roadbed are sealed. It effectively blocks rainwater or groundwater from penetrating into the interior of the phosphogypsum roadbed, and prevents the phosphogypsum roadbed from frost heaving and damage or environmental pollution. During construction, the waterproof antifreeze can be used less on the upper surface, and more on the two sides.

[0039] After the waterproof and antifreeze material of the phosphogypsum highway subgrade has penetrated and formed a film, sampling should be carried out to test the film thickness. If there is white exposure or insufficient local spreading amount, it should be supplemented in time to make the film thickness reach more than 0.6mm to prevent rainwater from penetrating into the phosphogypsum highway subgrade.

[0040] After the construction of the phosphogypsum highway subgrade is completed, when its strength reaches above 3MPa, the base layer and asphalt surface layer should be constructed in time to effectively seal and protect the phosphogypsum highway subgrade.

[0041] The above-mentioned embodiments are only partial embodiments of the present invention and cannot cover the whole of the present invention. Based on the above-mentioned embodiments and drawings, technical personnel in this field can obtain more implementation methods without paying creative work. Therefore, these implementation methods obtained without paying creative work should be included in the protection scope of the present invention.

Claims

1. A phosphogypsum highway subgrade construction method based on a new waterproof and antifreeze material, characterized in that: Step S1, pretreatment of highway foundation and paving of clay soil: pre-clean the foundation within the scope of the highway foundation to be constructed from debris, weeds and silt, then pave the clay soil material with a thickness of not less than 30 cm, compact it with rolling, and the compaction degree is not less than 92%; Step S2: Setting of waterproof and antifreeze layer for highway foundation: spraying waterproof and antifreeze material on the compacted clay soil, with a spreading amount of 6.0-9.0 kg / m 2 , so that the film thickness of the waterproof and antifreeze layer is not less than 0.6mm; the waterproof and antifreeze material is composed of calcium chloride, water glass, and SBR modified emulsified asphalt, the mass ratio of calcium chloride, water glass, and SBR modified emulsified asphalt is 1:1:10-15, and the solid content of the SBR modified emulsified asphalt is 30%-50%; Step S3, laying and rolling the phosphogypsum mixture: the phosphogypsum mixture is obtained by mixing 3% to 7% of quicklime into phosphogypsum and stirring evenly, and the compaction degree of the laid phosphogypsum mixture after rolling reaches more than 96%; Step S4, roadbed finishing and compaction: After the phosphogypsum roadbed construction reaches the designed elevation, slope finishing is performed by using a slope compaction machine or manual tamping; Step S5: Waterproof and antifreeze setting on the upper layer and both sides of the roadbed: After the upper surface and both sides of the phosphogypsum roadbed are dry, spray the waterproof and antifreeze material with a spraying amount of 6.0-9.0 kg / m 2 , so that its film thickness reaches more than 0.6mm, sealing the micropores and microcracks on the surface of the phosphogypsum highway subgrade.

2. A phosphogypsum highway subgrade construction method according to claim 1, characterized in that: In step S2, the preparation of the waterproof and antifreeze material comprises the following steps: 1) Dilute the SBR modified asphalt stock solution to a solid content of 30% to 50% and stir evenly; 2) Grind the calcium chloride block into powder, and select the powder with a particle size of less than 1.5 mm through a 1.5 mm round hole sieve for later use; 3) Prepare a mixture of water glass and calcium chloride in a mass ratio of 1:

1. First, add water glass into a plastic container, then slowly add calcium chloride powder, stirring while adding until the two are evenly mixed; 4) Place the diluted SBR modified emulsified asphalt in step 1) in a container and stir it evenly, then add the water glass and calcium chloride mixture obtained in step 3) in a prescribed proportion, stirring while adding until it is evenly mixed.

3. A phosphogypsum highway subgrade construction method according to claim 1, characterized in that: In step S3: before paving, the phosphogypsum mixture is spread with a thickness of not less than 1 cm to prevent the transportation equipment from damaging the waterproof and antifreeze layer.

4. A phosphogypsum highway subgrade construction method according to claim 1, characterized in that: In S3: the phosphogypsum mixture is obtained by adding 5% to 7% quicklime into phosphogypsum and stirring evenly.

5. A phosphogypsum highway subgrade construction method according to claim 1, characterized in that: In S5, the spraying amount per square meter of the waterproof and antifreeze material on both sides of the phosphogypsum highway subgrade is greater than the spraying amount per square meter of the waterproof and antifreeze material on the upper surface of the phosphogypsum highway subgrade.

6. A phosphogypsum highway subgrade construction method according to claim 1, characterized in that: The method also includes step S6: after the phosphogypsum roadbed waterproof and antifreeze material is completely dried and formed into a film, protective engineering, drainage engineering and greening engineering are implemented to protect the phosphogypsum roadbed.

7. A phosphogypsum highway subgrade construction method according to claim 6, characterized in that: The protection project includes setting up a frame beam structure on the slope of the phosphogypsum highway subgrade. The frame beam divides the subgrade into blocks with a maximum width of no more than 8m. The frame beam is filled with clay planting soil with a thickness of more than 30cm.

8. A phosphogypsum highway subgrade construction method according to claim 7, characterized in that: The greening project includes planting slope plants in sticky planting soil, and the slope plants are selected from grass species with developed root systems, a soil penetration depth of not less than 10 cm, drought resistance and a large natural growth density.

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