Water-resistant all-solid waste phosphogypsum road building material and preparation method thereof

Abstract

The invention discloses a water-resistant all-solid-waste ardealite road building material and a preparation method thereof. A production raw material formula comprises the following components in parts by mass: 100 parts of ardealite, 3-18 parts of functional solid waste, 0.06-0.15 part of a dispersing agent and 0.12-0.28 part of an adsorbent, the functional solid waste is prepared from the following components in parts by weight: 78 parts of blast furnace mineral powder, 0.1-12 parts of waste concrete powder, 3-8 parts of alkaline residue powder and 5-16 parts of magnesium residue powder; the dispersing agent comprises potassium sodium tartrate; the adsorbent is prepared from polyaluminum sulfate and activated aluminum oxide according to the mass ratio of 1: (0.8-1.3). The method has the advantages that 1) the water resistance of the phosphogypsum road building material is obviously improved; the phosphogypsum road building material has the advantages of simple preparation process, realization of curing and sealing of phosphogypsum pollutants, realization of dual effects of physical sealing and chemical bonding, safe and reliable environmental protection performance, substantial reduction of carbon emission and material cost, and solving of the contradiction between a high phosphogypsum use amount and a low comprehensive cost performance of a large-dosage phosphogypsum road building material.

Description

TECHNICAL FIELD

[0001] The application relates to a building material production technology, in particular to a phosphogypsum road building material production method. BACKGROUND

[0002] Phosphogypsum is an industrial by-product of the wet-process phosphoric acid leaching process, is acidic, has many internal impurity elements, and has a high difficulty in large-scale disposal, especially the excessive soluble phosphorus and fluorine dissolution concentration limits its large-scale resource utilization, but long-term stacking still causes pollution to the surrounding soil, water quality, and atmosphere. At present, the resource utilization of phosphogypsum is mainly concentrated in the fields of building materials and agricultural materials, but the disposal scale is limited, and the comprehensive utilization rate is not high, and the road field as an application scenario capable of absorbing a large amount of phosphogypsum is concerned.

[0003] Cement is commonly used as the most commonly used cementitious material to prepare road water-stable materials, modified solidified soil and the like, but the cement cementation solidification of phosphogypsum used as road building material has the following practical application problems: first, when the application proportion of phosphogypsum is low, the purpose of large-scale utilization of phosphogypsum cannot be achieved, and the relatively high cement dosage will significantly increase the material cost, and there is a risk of poor long-term volume stability and excessive pollution dissolution concentration; second, when the application proportion of phosphogypsum is high, the strength of the road building material is too low to meet the road requirements and control the pollution dissolution effect. That is, the comprehensive contradiction between high phosphogypsum dosage and good road performance, low material cost, and environmental safety standard seriously hinders the large-scale resource utilization of phosphogypsum in the road field.

[0004] Patent document CN118459164A discloses an anti-water environment-friendly high-dosage phosphogypsum base material and a preparation method and application thereof, the cement content is 10% to 20%, and the unconfined compressive strength of the material after 7d standard curing and then soaking in water for 28d is lower than that after 28d direct standard curing, indicating that the material does not have water resistance. If the reaction system of phosphogypsum can be improved, the pollutants in phosphogypsum can be effectively solidified, stabilized and stored, and the water resistance can be improved, so that the durability of the high-dosage phosphogypsum road building material is more stable and reliable, and the full-solid waste road building not only can reduce the road construction cost, but also can promote environmental protection, and has great economic benefits and ecological construction effect. Therefore, it is of urgent practical significance to develop an anti-water high-dosage phosphogypsum base full-solid waste road building material to solve the above problems. SUMMARY

[0005] In order to solve the contradiction between high phosphogypsum dosage and low comprehensive performance price of the cement-bonded phosphogypsum for preparing road materials, and the poor water resistance of the road material with large amount of phosphogypsum after long-term soaking, and optimize the volume stability in the later period to realize the effective solidification, stabilization and storage of phosphogypsum pollutants, and achieve the purpose of large-scale resource utilization of phosphogypsum, the application provides an anti-water type full-solid waste phosphogypsum road material and a preparation method thereof.

[0006] The technical scheme adopted by the application is: a preparation method of the anti-water type full-solid waste phosphogypsum road material, characterized by that: the production raw material formula comprises the following components in the mass fraction: 100 parts of phosphogypsum, 3-18 parts of functional solid waste, 0.06-0.15 parts of dispersant, and 0.12-0.28 parts of adsorbent; the functional solid waste is composed of the following components in the weight fraction: 78 parts of blast furnace slag, 0.1-12 parts of waste concrete powder, 3-8 parts of alkali slag powder, and 5-16 parts of magnesium slag powder; the dispersant comprises potassium sodium tartrate; and the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:0.8-1.3.

[0007] Part of the component description:

[0008] The "blast furnace slag" in the application refers to a solid waste powder obtained by grinding a molten material with silicate and silico-aluminate as main components after quenching and granulating during blast furnace smelting of pig iron.

[0009] The "waste concrete powder" in the application refers to a solid waste powder formed by crushing and grinding of waste concrete with original C30 and above strength grade.

[0010] The "alkali slag powder" in the application refers to a solid waste powder obtained by grinding of alkali slag with main components of calcium carbonate and calcium sulfate discharged during the ammonia-soda process.

[0011] The "magnesium slag powder" in the application refers to a solid waste powder obtained by grinding of magnesium slag with silicate minerals as main components during industrial smelting of metallic magnesium.

[0012] The poor water resistance of the large-dosage phosphogypsum-based road material leads to unqualified strength and environmental protection, and the micro mechanism mainly has three points: 1, the fundamental reason is that the phosphogypsum is slightly soluble in water, and the surface crystals are easy to dissolve to form Ca 2+ and SO4 2-1. Ions enter the aqueous solution. 2. The internal reason is that phosphogypsum crystals are irregularly shaped, such as needle-like or plate-like, resulting in numerous pores between phosphogypsum particles. Furthermore, the irregular shapes of the crystals overlap and connect, exacerbating the aggregation of phosphogypsum particles, leading to poor particle dispersion and more free water molecules trapped within the pores. When the ambient humidity changes, the water in the phosphogypsum evaporates or migrates. At this time, the ions dissolved in the water may not recrystallize in situ, but rather recrystallize in the pores or on the material surface. The growth of new crystals generates enormous crystallization pressure, which forces the original crystal structure apart from the inside, causing microcracks, surface powdering, and flaking. Each change in moisture, like a wet-dry cycle, exacerbates this damage, repeating until the structure completely collapses. 3. The external reason is that phosphogypsum contains impurities such as phosphorus and fluorine, which are adsorbed and coated on the particle surface, making the water film adhering to the phosphogypsum particle surface acidic. Under acidic conditions, the solubility of calcium sulfate dihydrate is significantly increased, thereby accelerating the above-mentioned dissolution-recrystallization process, greatly increasing the dissolution rate of gypsum, and thus accelerating the destruction process many times over.

[0013] As a further improvement of the present invention, the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:1.5 to 2.7.

[0014] This invention can be implemented according to the following steps:

[0015] S1. Take the required quantities of each raw material according to the production raw material formula, and calculate the total amount of water to be added;

[0016] S2. Dissolve the dispersant in water at 20-30% of the total amount of water to obtain a dispersant solution. Then, uniformly add the dispersant solution to the phosphogypsum and stir at a stirring rate of 250-350 r / min for 6-8 min. Then, seal the material at room temperature for 6-8 h to obtain pretreated phosphogypsum.

[0017] S3. Add water at 20-30% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum. Stir at a stirring rate of 250-350 r / min for 3-5 min, and then seal and let it sit at room temperature for 12-18 h to obtain modified phosphogypsum.

[0018] S4. Grind the functional solid waste for 2-3 minutes to obtain a solid waste mixture;

[0019] S5. After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1200-1300 r / min for 5-10 min to obtain a wet mixture.

[0020] S6. After pressing the wet mixture into shape as needed, cure it at 15-30℃ for at least 5 days to obtain water-resistant solid waste phosphogypsum road construction material.

[0021] As will be understood by those skilled in the art, the "total water added" mentioned in the above scheme refers to the total water added after deducting the water content of wet phosphogypsum, calculated according to the compaction test method of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTG 3441-2024 standard. If this procedure is revised, the revised procedure will naturally be followed.

[0022] As a further improvement of the present invention, the phosphogypsum meets the following requirements: calcium sulfate dihydrate (CaSO4·2H2O) content ≥90%, aging time greater than 6 months, particle size ≤1.18mm, attached water content ≤10%, and pH ≥4.5.

[0023] It should be noted that the blast furnace ore powder used in this invention should meet the following requirements: specific surface area 500-600 m² / kg, 28-day activity index ≥105%. Waste concrete powder should meet the following requirements: Na₂O content 5%-8%, specific surface area 800-1000 m² / kg. Alkali slag powder should meet the following requirements: easily soluble salt content ≤5%, particle size concentration ≥90% between 0.005 and 0.05 mm. Magnesium slag powder should meet the following requirements: specific surface area 600-800 m² / kg, MgO content 3%-7%, CaO content ≥65%.

[0024] As a further improvement of the present invention, the basicity of the polyaluminum sulfate is 55% to 60%; the particle size of the activated alumina is 1 to 300 nm, and the Al2O3 content is ≥95%; the polycarboxylate superplasticizer is a hyperbranched polycarboxylate superplasticizer with a water reduction rate ≥38% and an adsorption capacity ≥8 mg / g.

[0025] The present invention also discloses a water-resistant solid waste phosphogypsum road construction material, which is prepared by the preparation method of the water-resistant solid waste phosphogypsum road construction material of the present invention.

[0026] The beneficial effects of this invention are:

[0027] (1) The present invention disperses phosphogypsum particles through a pretreatment process and releases free water and its soluble pollutants such as phosphorus and fluorine to stabilize them. Then, combined with the synergistic effect of the components of functional solid waste, a water-resistant all-solid waste phosphogypsum road construction material is formed. This allows the road construction material to continuously and stably increase its compressive strength during long-term immersion in water, without decreasing due to prolonged immersion time, thus demonstrating excellent water resistance.

[0028] (2) This invention utilizes an adsorbent to adsorb, complex, and precipitate soluble phosphorus and fluorine in phosphogypsum, thereby achieving its stabilization treatment. Combined with the cementing and solidification effect of hydration products, it further achieves the solidification and sealing of phosphogypsum pollutants, achieving the dual effects of physical solidification and chemical bonding. The environmental performance is safe and reliable.

[0029] (3) This invention uses solid waste materials to formulate road construction materials with a large amount of phosphogypsum, which significantly reduces carbon emissions and material costs compared with cement-stabilized crushed stone materials. It solves the engineering application problem and environmental protection problem of the contradiction between the high amount of phosphogypsum and the low overall cost performance of road construction materials with a large amount of phosphogypsum, and achieves the goal of large-scale resource utilization of phosphogypsum. It has good environmental and economic benefits. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments.

[0031] All materials used in the following examples and comparative examples were from the same batch and met the following parameters:

[0032] Phosphogypsum: Calcium sulfate dihydrate (CaSO4·2H2O) content 96.4%, aging time 10 months, particle size ≤1.03mm, attached water content 5.3%, pH 4.9.

[0033] Blast furnace ore powder: specific surface area 568m² / kg, 28d activity index 107%.

[0034] Waste concrete powder: solid waste powder formed by crushing and grinding waste concrete of original C30 strength grade, with Na2O content of 6.9% and specific surface area of ​​935m² / kg.

[0035] Alkali residue powder: soluble salt content 3.4%, particle size concentration between 0.005 and 0.05 mm is 96.9%.

[0036] Magnesium slag powder: specific surface area 706 m² / kg, MgO content 5.7%, CaO content 78.1%.

[0037] Aluminum polysulfate: basicity 59.1%;

[0038] Activated alumina: particle size D50=43nm, Al2O3 content ≥98.2%;

[0039] The polycarboxylate superplasticizer is a hyperbranched polycarboxylate superplasticizer with a water reduction rate of 41.5% and an adsorption capacity of 9.6 mg / g.

[0040] Example 1:

[0041] Prepare road construction materials according to the following steps:

[0042] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste, 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 12 parts of waste concrete powder, 8 parts of alkali slag powder and 16 parts of magnesium slag powder; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0043] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0044] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0045] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0046] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0047] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain water-resistant solid waste phosphogypsum road construction material.

[0048] Example 2:

[0049] Prepare road construction materials according to the following steps:

[0050] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 4 parts of functional solid waste, 0.06 parts of dispersant, and 0.12 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 2 parts of waste concrete powder, 3 parts of alkali slag powder and 7 parts of magnesium slag powder; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2.5; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.2.

[0051] (2) Dissolve the dispersant in water at 20% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 250 r / min for 7 min. Then, seal the material at room temperature for 6 h to obtain pretreated phosphogypsum.

[0052] (3) Add water at 20% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 250 r / min for 4 min. Then seal and let it sit at room temperature for 15 h to obtain modified phosphogypsum.

[0053] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0054] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1250 r / min for 8 min to obtain a wet mixture;

[0055] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 58 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 22℃ and a relative humidity of 95% for 6 days to obtain water-resistant solid waste phosphogypsum road construction material.

[0056] Example 3:

[0057] Prepare road construction materials according to the following steps:

[0058] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 10 parts of functional solid waste, 0.12 parts of dispersant, and 0.13 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 15 parts of waste concrete powder, 10 parts of alkali slag powder and 18 parts of magnesium slag powder; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:1.8; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:0.8.

[0059] (2) Dissolve the dispersant in water at 30% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 200 r / min for 5 min. Then, seal and let it sit at room temperature for 6 h to obtain pretreated phosphogypsum.

[0060] (3) Add water at 30% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 200 r / min for 3 min. Then seal and let it sit at room temperature for 14 h to obtain modified phosphogypsum.

[0061] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0062] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1200 r / min for 8 min to obtain a wet mixture;

[0063] (6) The wet mixture is loaded into a mold with a diameter of 50 mm and pressed into a cylindrical test block of ϕ50 mm×50 mm under a pressure of 62 MPa. The test block is then placed in a standard curing room with a temperature of 18℃ and a relative humidity of 95% for 6 days to obtain water-resistant solid waste phosphogypsum road construction material.

[0064] Comparative Example 1:

[0065] This comparative example is a control experiment of Example 1, using the commonly used method of preparing road construction materials with phosphogypsum and cement, as follows:

[0066] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum and 15 parts of cement.

[0067] (2) The phosphogypsum, cement and water are mixed and stirred at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0068] (3) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0069] Comparative Example 2:

[0070] This comparative example is a control experiment of Example 1, carried out according to the same steps and conditions as Example 1, except that: no material curing treatment was performed in steps (2) and (3), and the specific scheme is as follows:

[0071] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste, 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 12 parts of waste concrete powder, 8 parts of alkali slag powder and 16 parts of magnesium slag powder; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0072] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution, and then uniformly add the dispersant solution to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min to obtain pretreated phosphogypsum.

[0073] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min to obtain modified phosphogypsum.

[0074] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0075] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0076] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0077] Comparative Example 3:

[0078] This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions as Example 1, except that only polycarboxylate superplasticizer is used as the dispersant, without potassium sodium tartrate. The specific scheme is as follows:

[0079] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste, 0.06 parts of dispersant (polycarboxylate superplasticizer) (minus sodium potassium tartrate), and 0.20 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 12 parts of waste concrete powder, 8 parts of alkali slag powder and 16 parts of magnesium slag powder; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0080] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0081] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0082] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0083] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0084] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0085] Comparative Example 4:

[0086] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, except that the waste concrete powder was replaced with cement of equal mass and equivalent specific surface area. The specific scheme is as follows:

[0087] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste, 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the functional solid waste is composed of the following components in the following weight proportions: 78 parts of blast furnace ore powder, 12 parts of cement (specific surface area of ​​941 m² / kg), 8 parts of alkali slag powder and 16 parts of magnesium slag powder; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0088] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0089] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0090] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0091] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0092] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0093] Comparative Example 5:

[0094] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, with the difference that all functional solid waste is blast furnace ore powder, and the total amount of functional solid waste used remains unchanged. The specific scheme is as follows:

[0095] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste (blast furnace ore powder), 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0096] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0097] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0098] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0099] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0100] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0101] Comparative Example 6:

[0102] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, with the difference that all functional solid waste is waste concrete powder, and the total amount of functional solid waste used remains unchanged. The specific scheme is as follows:

[0103] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste (waste concrete powder), 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0104] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0105] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0106] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0107] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0108] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0109] Comparative Example 7:

[0110] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, with the difference that all functional solid waste is alkaline slag powder, and the total amount of functional solid waste used remains unchanged. The specific scheme is as follows:

[0111] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste (alkali slag powder), 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate water-reducing agent in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0112] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0113] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0114] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0115] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0116] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0117] Comparative Example 8:

[0118] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, with the difference that all functional solid waste is magnesium slag powder, and the total amount of functional solid waste used remains unchanged. The specific scheme is as follows:

[0119] (1) Take the raw materials according to the following production raw material formula and calculate the total amount of water to be added according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024: 100 parts of phosphogypsum, 15 parts of functional solid waste (magnesium slag powder), 0.09 parts of dispersant, and 0.20 parts of adsorbent; wherein the dispersant is composed of potassium sodium tartrate and polycarboxylate water-reducing agent in a mass ratio of 1:2; wherein the adsorbent is composed of polyaluminum sulfate and activated alumina in a mass ratio of 1:1.

[0120] (2) Dissolve the dispersant in water at 25% of the total amount of water to obtain a dispersant solution. Then, add the dispersant solution evenly to the phosphogypsum and stir at a stirring rate of 300 r / min for 8 min. Then, seal and let it sit at room temperature for 8 h to obtain pretreated phosphogypsum.

[0121] (3) Add water at 25% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum and stir at a stirring rate of 300 r / min for 5 min. Then seal and let it sit at room temperature for 18 h to obtain modified phosphogypsum.

[0122] (4) Grind the functional solid waste for 3 minutes to obtain a solid waste mixture;

[0123] (5) After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1300 r / min for 10 min to obtain a wet mixture;

[0124] (6) The wet mixture is loaded into a mold with a diameter of 50 mm, and the pressure is controlled at 60 MPa to press it into a cylindrical test block of ϕ50 mm × 50 mm. Then, it is placed in a standard curing room with a temperature of 20 °C and a relative humidity of 96% for 6 days to obtain phosphogypsum road construction material.

[0125] Comparative experiment on the water resistance of phosphogypsum road construction materials:

[0126] According to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTG 3441-2024, the standard unconfined compressive strength and the unconfined compressive strength after soaking in water of the phosphogypsum-based road construction materials in the examples and comparative examples were determined to reflect their water resistance performance. The test results are shown in Table 1.

[0127] Table 1. Comparison of Water Resistance Properties of Phosphogypsum Road Building Materials (Characterized by Representative Values ​​of Unconfined Compressive Strength)

[0128] Standard curing 14d (MPa) Standard curing 6d + water curing 8d (MPa) Standard curing 28d (MPa) Standard curing 6d + water curing 22d (MPa) Example 1 6.36 8.56 11.32 11.81 Example 2 4.93 6.60 8.35 8.83 Example 3 6.02 7.83 9.87 10.32 Comparative Example 1 (Prior Art) 3.52 2.87 4.98 3.36 Comparative Example 2 (No Curing) 5.79 6.27 8.32 8.02 Comparative Example 3 (No Potassium Sodium Tartrate) 6.39 6.32 11.27 10.55 Comparative Example 4 (Cement Replaced by Concrete Powder) 3.12 2.68 4.32 3.27 Comparative Example 5 (Single Blast Furnace Slag) 1.19 0 (Disintegrated) 1.61 0 (Disintegrated) Comparative Example 6 (Single Waste Concrete Powder) 1.04 0 (Disintegrated) 1.56 0 (Disintegrated) Comparative Example 7 (Single Alkaline Slag) 0.98 0 (Disintegrated) 1.07 0 (Disintegrated) Comparative Example 8 (Single Magnesium Slag) 0.85 0 (Disintegrated) 1.02 0 (Disintegrated)

[0129] As can be seen from the test results of Examples 1 to 3 in Table 1, the strength of the water-resistant phosphogypsum-based solid waste road construction material samples prepared by the method of the present invention after soaking in water is higher than that of the samples of the same age that have not been soaked in water. Moreover, the strength of the samples still increases slightly with the extension of the soaking time, showing excellent water resistance.

[0130] As can be seen from the comparison of the test results of Example 1 and Comparative Example 2 in Table 1, although the strength of the specimen in Comparative Example 2 did not decrease significantly after short-term immersion in water, the strength began to decrease after the immersion time was extended, which proves that the immersion method adopted in this invention can improve the water resistance of phosphogypsum road construction materials to a certain extent.

[0131] As can be seen from the comparison of the test results of Example 1 and Comparative Example 3 in Table 1, if potassium sodium tartrate is not used in the curing process, the short-term and long-term water resistance of the specimens are affected to a certain extent and show a downward trend. This indicates that in this invention, potassium sodium tartrate has a positive effect on the water resistance of phosphogypsum road construction materials. The inventors believe that the reason is that potassium sodium tartrate can selectively form directional adsorption on specific crystal faces of phosphogypsum crystals, causing the phosphogypsum particles to separate due to the electrostatic repulsion of potassium / sodium carboxylate groups (-COO-) and the steric hindrance effect of hyperbranched polycarboxylate superplasticizer, releasing the encapsulated free water, and achieving full contact between functional solid waste and phosphogypsum particles. Hydration forms needle-like AFt that fills the gaps between phosphogypsum particles, and C(-A)-SH gel encapsulates and cements phosphogypsum particles and ettringite crystals to form a dense structure, thereby reducing the porosity caused by subsequent water evaporation.

[0132] As can be seen from the comparison of the test results of Example 1 and Comparative Example 4 in Table 1, when the waste concrete powder in Example 1 was replaced with cement, the long-term standard curing strength and short-term and long-term water resistance of the specimens both decreased significantly, indicating that the waste concrete powder used in this invention cannot be replaced with cement.

[0133] As can be seen from the comparison of Examples 1, 5, 6, 7 and 8 in Table 1, when blast furnace ore powder, waste concrete powder, alkali slag powder or magnesium slag powder are added individually as functional solid waste, under the premise of the same usage, the compressive strength of the phosphogypsum road construction material is significantly reduced compared with Example 1. Moreover, the unconfined compressive strength in both short-term and long-term water immersion test results is significantly lower than that of the un-water-immersed sample, leading to collapse. However, the composite functional solid waste composed of blast furnace ore powder, waste concrete powder, alkali slag powder and magnesium slag powder in Example 1 shows a significant increase in the compressive strength of the sample, and the strength after water immersion is higher than that of the un-water-immersed sample of the same age. This indicates that blast furnace ore powder, waste concrete powder, alkali slag powder and magnesium slag powder have a significant synergistic effect in improving the water resistance of phosphogypsum road construction material in this invention. The inventors believe that the reason is that when blast furnace ore powder, waste concrete powder, alkali slag powder and magnesium slag powder are used in combination, they can play a synergistic regulatory role on the hydration reaction process, so that the entire phosphogypsum material mixing system is transformed from an air-hardening material system to a hydraulic material system, which changes the degree to which each component in the system participates in the hydration reaction, thereby achieving a fundamental improvement in water resistance.

Claims

1. A method for preparing water-resistant all-solid waste phosphogypsum road construction material, characterized in that: The raw material formula includes the following components in the following mass fraction ratios: 100 parts phosphogypsum, 3-18 parts functional solid waste, 0.06-0.15 parts dispersant, and 0.12-0.28 parts adsorbent; the functional solid waste is composed of the following components in the following weight fraction ratios: 78 parts blast furnace ore powder, 0.1-12 parts waste concrete powder, 3-8 parts alkaline slag powder, and 5-16 parts magnesium slag powder; the dispersant includes potassium sodium tartrate; the adsorbent is composed of aluminum polysulfate and activated alumina in a mass ratio of 1:0.8-1.

3.

2. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 1, characterized in that: The dispersant is composed of potassium sodium tartrate and polycarboxylate superplasticizer in a mass ratio of 1:1.5 to 2.

7.

3. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 2, characterized in that, Includes the following steps: S1. Take the required quantities of each raw material according to the production raw material formula, and calculate the total amount of water to be added; S2. Dissolve the dispersant in water at 20-30% of the total amount of water to obtain a dispersant solution. Then, uniformly add the dispersant solution to the phosphogypsum and stir at a stirring rate of 250-350 r / min for 6-8 min. Then, seal and let it sit at room temperature for 6-8 h to obtain pretreated phosphogypsum. S3. Add water at 20-30% of the total amount of water to fully disperse the adsorbent, and then immediately add it to the pretreated phosphogypsum. Stir at a stirring rate of 250-350 r / min for 3-5 min, and then seal and let it sit at room temperature for 12-18 h to obtain modified phosphogypsum. S4. Grind the functional solid waste for 2-3 minutes to obtain a solid waste mixture; S5. After mixing the modified phosphogypsum with the solid waste mixture, add the remaining water equal to the total amount of water added, and stir at a stirring rate of 1200-1300 r / min for 5-10 min to obtain a wet mixture. S6. After pressing the wet mixture into shape according to process requirements, cure it at 15-30℃ for at least 5 days to obtain water-resistant solid waste phosphogypsum road construction material.

4. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The phosphogypsum meets the following requirements: calcium sulfate dihydrate content ≥90%, aging time greater than 6 months, particle size ≤1.18mm, attached water content ≤10%, and pH ≥4.

5.

5. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The blast furnace ore powder meets the following requirements: specific surface area 500-600 m² / kg, 28-day activity index ≥105%.

6. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The waste concrete powder meets the following requirements: Na2O content 5%–8%, specific surface area 800–1000 m² / kg.

7. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The alkaline residue powder meets the following requirements: soluble salt content ≤ 5%, and particle size concentration between 0.005 and 0.05 mm ≥ 90%.

8. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The magnesium slag powder meets the following requirements: specific surface area of ​​600-800 m² / kg, MgO content of 3%-7%, and CaO content of ≥65%.

9. The preparation method of the water-resistant all-solid waste phosphogypsum road construction material according to claim 3, characterized in that: The basicity of the polyaluminum sulfate is 55%–60%; the particle size of the activated alumina is 1–300 nm, and the Al2O3 content is ≥95%; the polycarboxylate superplasticizer is a hyperbranched polycarboxylate superplasticizer with a water reduction rate ≥38% and an adsorption capacity ≥8 mg / g.

10. A water-resistant phosphogypsum road construction material prepared by the method described in any one of claims 1 to 9.