Road base material based on phosphogypsum and preparation method thereof

Abstract

The invention relates to the technical field of road base materials, and discloses an ardealite-based road base material and a preparation method thereof, the ardealite-based road base material comprises 35-55 parts of ardealite, 8-18 parts of a composite gel activator, 35-55 parts of graded aggregate, 0.3-0.8 part of a composite functional additive, 0.05-0.2 part of a water content regulator, 0.1-0.3 part of an interface enhancer, 0.2-0.5 part of an anti-crack modifier, and 7-11 parts of water. The road base material based on phosphogypsum has excellent mechanical properties through the components such as the composite gelling activator and the graded aggregate, the stability and durability of the material are improved by adding the components such as the moisture content regulator, the construction process is simple and convenient, and production is convenient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road base materials, in particular to a phosphogypsum-based road base material and a preparation method thereof. BACKGROUND

[0002] Phosphogypsum is a large amount of industrial solid waste generated in the production process of wet-process phosphoric acid, and its main component is calcium sulfate dihydrate. About 4.5-5 tons of phosphogypsum are generated per ton of phosphoric acid produced. At present, the stock of phosphogypsum in China has exceeded hundreds of millions of tons, and the annual new production is huge. A large amount of phosphogypsum accumulation not only occupies land resources, but also may pollute the soil and water bodies due to the presence of soluble phosphorus, fluorine and acidic substances, which has become a major environmental problem restricting the sustainable development of the phosphorus chemical industry.

[0003] At present, the resource utilization approaches of phosphogypsum mainly include: being used as a cement retarder, producing gypsum building materials (such as gypsum board, gypsum block), soil conditioner and filling mine, etc. However, these utilization methods have limited consumption capacity, and have certain requirements for the purity of phosphogypsum. Using phosphogypsum in road engineering, especially in road base, is considered to be one of the most effective ways to scale and high-value consumption of phosphogypsum.

[0004] There have been attempts to use phosphogypsum in road base in the prior art, but generally face the following technical bottlenecks: Insufficient strength and water resistance, the hydration product of phosphogypsum itself has low strength, and the soluble impurities contained therein will affect the long-term water stability of the material, which is easy to soften and the strength to drop sharply when encountering water, and is difficult to meet the mechanical properties and durability requirements of road base. Poor volume stability, phosphogypsum may shrink or swell under the alternating action of dry and humid environments, resulting in cracking or deformation of the base. The setting time is difficult to control, the setting and hardening characteristics of phosphogypsum are different from those of conventional cement stabilized materials, and the workability and compaction time window are difficult to grasp.

[0005] Environmental risk, direct use of untreated phosphogypsum may have leaching risk of harmful substances (such as radioactive nuclides and heavy metals).

[0006] Therefore, it is of great significance to provide a phosphogypsum-based road base material with excellent mechanical properties, strong water resistance, volume stability and environmental safety. SUMMARY

[0007] In view of this, the present application provides a phosphogypsum-based road base material and a preparation method thereof, aiming to solve at least one of the problems in the current background technology.

[0008] The present application provides a phosphogypsum-based road base material, which comprises the following components in mass fraction: 35-55 parts phosphogypsum, 8-18 parts composite cementitious activator, 35-55 parts graded aggregate, 0.3-0.8 parts composite functional admixture, 0.05-0.2 parts moisture content regulator, 0.1-0.3 parts interface reinforcing agent, 0.2-0.5 parts crack-resistant modifier, and 7-11 parts water.

[0009] Preferably, the phosphogypsum is aged phosphogypsum or calcined phosphogypsum. When the phosphogypsum is aged phosphogypsum, the mass fraction is 35-45 parts, and when the phosphogypsum is calcined phosphogypsum, the mass fraction is 35-55 parts.

[0010] Preferably, the composite gelling activator comprises an alkaline activator, a silica-alumina active component, and a sulfate source, with a mass ratio of 1.5-3:2-4:0.5-1.5.

[0011] Preferably, the alkaline activator is one or more of quicklime, carbide slag, and silicate cement clinker; the siliceous aluminous active component is one or more of granulated blast furnace slag powder, fly ash, and metakaolin; and the sulfate source is one or more of gypsum dihydrate, desulfurized gypsum, and sodium sulfate.

[0012] Preferably, the graded aggregate includes coarse aggregate, medium aggregate and fine aggregate, and the mass ratio of coarse aggregate, medium aggregate and fine aggregate is 4~5:3~4:1~3; the particle size of the coarse aggregate is 10-31.5mm, the particle size of the medium aggregate is 5~10mm, and the particle size of the fine aggregate is 2~5mm.

[0013] Preferably, the composite functional admixture includes a water-reducing agent, a waterproofing agent, and a retarder, wherein the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, the waterproofing agent is an organosilane-based waterproofing agent, and the retarder is sodium gluconate or citric acid.

[0014] Preferably, the moisture content regulator is one or more of bentonite, diatomaceous earth, and calcium oxide, the interface reinforcing agent is methyltrimethoxysilane, and the crack-resistant modifier is polypropylene fiber or lignin fiber.

[0015] The present invention also provides a method for preparing the phosphogypsum-based road base material described in the above technical solution, comprising the following steps: The phosphogypsum is crushed and the aggregate raw materials are graded to obtain graded aggregates containing coarse aggregates, medium aggregates and fine aggregates. Phosphogypsum, composite cementitious activator, graded aggregate and crack-resistant modifier are mixed and stirred to obtain premix; Water is added to the premix and stirred to obtain a mixture. Water, composite functional additives, moisture content regulators, and interface enhancers are added to the mixture, and the mixture is stirred to obtain the phosphogypsum-based road base material.

[0016] Preferably, the stirring rate is 300~400 r / min and the stirring time is 5~8 minutes.

[0017] Preferably, the phosphogypsum, after being crushed, has an average particle size ≤20mm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly improved mechanical properties: This invention utilizes the synergistic mechanism of alkaline activation by composite cementitious activator, silica-alumina reaction, and sulfate catalysis to efficiently activate the potential activity of phosphogypsum and generate dense cementitious products such as hydrated calcium silicate and hydrated calcium sulfoaluminate. Combined with the skeleton interlocking effect of graded aggregate and the bonding and strengthening effect of interface reinforcing agent, it meets the mechanical performance requirements of road base course and solves the technical problem of insufficient strength of traditional phosphogypsum-based materials.

[0019] (2) Excellent stability and durability: The moisture content regulator of the present invention has the functions of moisture adsorption and slow release. Combined with the three-dimensional network constraint of the anti-cracking modifier, it effectively inhibits drying shrinkage and cracking. The organosilane waterproofing agent forms a hydrophobic film on the particle surface. Combined with the dense microstructure, it can adapt to complex service environments such as humidity and freezing, and solves the problems of poor water resistance and easy softening of phosphogypsum-based materials.

[0020] (3) Strong construction adaptability: The water-reducing agent in the composite functional admixture of the present invention improves the workability of the mixture, and the retarder prolongs the initial setting time. Combined with the segmented mixing process, the workability of the mixture is stable for ≥4h, which is suitable for construction in environments from -5℃ to 35℃. The average particle size of the phosphogypsum after crushing is ≤20mm. The graded aggregate is matched in a precise ratio to ensure smooth paving and compaction processes, and the compaction degree meets the standards, thus reducing the difficulty of construction operations. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0022] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] This invention proposes a road base material based on phosphogypsum, comprising the following components in parts by weight: 35-55 parts phosphogypsum, 8-18 parts composite cementitious activator, 35-55 parts graded aggregate, 0.3-0.8 parts composite functional admixture, 0.05-0.2 parts moisture content regulator, 0.1-0.3 parts interface reinforcing agent, 0.2-0.5 parts crack-resistant modifier, and 7-11 parts water.

[0027] In this invention, the preferred proportions of the raw materials in the phosphogypsum-based road base material are: 40-50 parts phosphogypsum, 10-14 parts composite cementitious activator, 40-50 parts graded aggregate, 0.3-0.5 parts composite functional admixture, 0.05-0.1 parts moisture content regulator, 0.1-0.2 parts interface reinforcing agent, 0.2-0.3 parts crack-resistant modifier, and 7-9 parts water.

[0028] In this invention, the phosphogypsum is preferably aged phosphogypsum or calcined phosphogypsum. When the phosphogypsum is aged phosphogypsum, the mass fraction is preferably 35-40 parts. When the phosphogypsum is preferably calcined phosphogypsum, the mass fraction is 35-50 parts.

[0029] This invention uses phosphogypsum and graded aggregates to form a dense skeleton structure, fill the gaps between aggregates, reduce the porosity of the mixture, improve the compaction of the structure after compaction, and provide physical support for the strength of the material.

[0030] It complements the graded aggregate, optimizes the gradation curve of the mixture, enhances the interlocking effect between particles, and improves the load-bearing capacity and deformation resistance of the base material.

[0031] In this invention, the composite gelling activator preferably includes an alkaline activator, a silica-alumina active component, and a sulfate source, with a preferred mass ratio of 1.5-3:2-4:0.5-1.5.

[0032] In this invention, the alkaline activator is preferably one or more of quicklime, carbide slag, and silicate cement clinker; the siliceous aluminous active component is preferably one or more of granulated blast furnace slag powder, fly ash, and metakaolin; and the sulfate source is preferably one or more of gypsum dihydrate, desulfurized gypsum, and sodium sulfate.

[0033] In this invention, the alkaline activator is obtained by mixing quicklime and silicate cement clinker at a mass ratio of 1:2, balancing strong alkalinity with early strength contribution. The silica-alumina active component is obtained by compounding granulated blast furnace slag powder and metakaolin at a mass ratio of 3:1. The granulated blast furnace slag powder provides long-term strength, while the metakaolin enhances early activity activation. In addition, fly ash can be used to replace part of the granulated blast furnace slag powder, improving the workability of the mixture. The sulfate source is desulfurized gypsum, which has a stable crystal morphology and a mild hydration rate, avoiding excessive use that could lead to strength reduction.

[0034] The composite gelling activator of this invention provides a strongly alkaline environment through an alkaline activator, dissolving the passivation film (formed by soluble phosphorus and fluorine impurities) on the surface of phosphogypsum, releasing calcium ions and sulfate ions, creating conditions for the hydration reaction. A sulfate source provides additional sulfate ions, which, synergistically with the calcium sulfate in the phosphogypsum itself, accelerate the hydration reaction of the aluminosilicate active components, generating gelling products such as hydrated calcium silicate (CSH) and hydrated calcium sulfoaluminate. These products fill the gaps in the skeleton, significantly improving the compressive strength and bonding strength of the material. This composite gelling activator solves the technical problem that a single activator cannot simultaneously address activity activation, strength development, and durability through a synergistic mechanism of alkaline activation, aluminosilicate reaction, and sulfate catalysis. The aluminosilicate active components provide strength support, and the sulfate source accelerates the reaction process; the combination of these three factors simultaneously improves the mechanical properties, durability, and volume stability of phosphogypsum-based materials.

[0035] In this invention, the graded aggregate includes coarse aggregate, medium aggregate, and fine aggregate, and the mass ratio of the coarse aggregate, medium aggregate, and fine aggregate is 4~5:3~4:1~3; the particle size of the coarse aggregate is 10-31.5mm, the particle size of the medium aggregate is 5~10mm, and the particle size of the fine aggregate is 2~5mm.

[0036] In this invention, the coarse aggregate is selected from limestone crushed stone, the medium aggregate is selected from graded crushed stone, and the fine aggregate is selected from river sand or manufactured sand. This invention divides the graded aggregate into three types: coarse, medium, and fine. The coarse aggregate serves as the core skeleton unit, forming a stable structure through interlocking and bonding between particles. It bears the main load of the road base layer (such as vehicle rolling stress), improves the compressive strength and deformation resistance of the material, and prevents excessive settlement or slippage of the base layer. The medium and fine aggregates gradually fill the gaps between the coarse aggregate, making the gradation curve closer to the ideal continuous gradation, reducing the porosity of the mixture, and further improving the load-bearing stability. The presence of fine and medium aggregates improves the particle size distribution of the mixture, reduces dry material agglomeration, and improves mixing uniformity; at the same time, it reduces the water demand of the mixture. Combined with composite functional admixtures, it maintains a suitable slump in the mixture, facilitating paving and compaction operations.

[0037] Furthermore, the aggregate itself exhibits strong chemical stability and does not participate in the hydration reaction, thus inhibiting potential volume deformation during phosphogypsum hydration. This physical constraint reduces the risk of base layer cracking, resulting in a material shrinkage rate of ≤0.06%. The dense skeletal structure reduces the intrusion of moisture and harmful substances (such as sulfate solutions) into the material, lowers capillary porosity, and enhances impermeability and freeze-thaw resistance, preventing the base layer from softening upon contact with water and cracking due to frost heave. The high thermal conductivity of the aggregate disperses the heat generated by the hydration reaction, preventing thermal expansion cracking caused by excessively high local temperatures; simultaneously, it reduces the amount of cementitious materials used, lowering costs while further improving the material's volume stability.

[0038] In this invention, the composite functional admixture includes a water-reducing agent, a waterproofing agent, and a retarder. The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, the waterproofing agent is an organosilane-based waterproofing agent, and the retarder is sodium gluconate or citric acid.

[0039] This invention does not specifically limit the types of water-reducing agents and waterproofing agents. Polycarboxylate-based high-efficiency water-reducing agents and organosilane-based waterproofing agents, well-known to those skilled in the art, can be used. The water-reducing agent used in this invention reduces the water demand of the mixture through molecular adsorption-dispersion effects, improving the lubricity between particles and solving the problems of high water demand and easy agglomeration in phosphogypsum-based materials, thus facilitating paving and compaction. Furthermore, it can reduce the capillary porosity inside the mixture, improve structural density, indirectly enhance compressive strength and impermeability, and simultaneously reduce the release of heat of hydration, avoiding cracking caused by excessively high local temperatures.

[0040] This invention utilizes an organosilane-based waterproofing agent that reacts with hydration products to generate a hydrophobic siloxane film. This film covers the surface of particles and fills capillary pores, significantly reducing the material's water absorption rate and improving its impermeability. It also blocks the contact channels between water and soluble impurities, reducing structural damage caused by impurity leaching. Simultaneously, it enhances the material's freeze-thaw resistance and sulfate corrosion resistance, making it suitable for road base courses in humid and saline-alkali areas.

[0041] The retarder of the present invention inhibits the reaction rate of calcium ions and sulfate ions by adsorbing onto the surface of hydration product crystals, prolongs the initial setting time of the mixture, and avoids problems such as insufficient compaction and surface sanding caused by excessively rapid setting during construction.

[0042] In this invention, the moisture content regulator is preferably one or more of bentonite, diatomaceous earth, and calcium oxide, the interface enhancer is preferably methyltrimethoxysilane, and the crack-resistant modifier is preferably polypropylene fiber or lignin fiber.

[0043] This invention regulates moisture content and improves material volume stability through a moisture content regulator. Specifically, bentonite and diatomaceous earth, with their high specific surface area and strong adsorption properties, can adsorb free moisture in the mixture and release it slowly, ensuring uniform moisture distribution and preventing localized over-drying or over-wetting. Calcium oxide reacts with water to form calcium hydroxide, which both consumes excess moisture and replenishes the alkaline environment, making it suitable for high-humidity raw material scenarios. Through this moisture adsorption-slow release mechanism, surface dehydration and cracking under high-temperature drying conditions are prevented, as well as strength reduction and compaction difficulties caused by excessive moisture under high humidity conditions. Furthermore, it reduces shrinkage deformation caused by differences in moisture evaporation rates, and, in conjunction with crack-resistant modifiers, lowers the risk of base layer cracking. The hydration reaction of calcium oxide can compensate for some volume shrinkage, further optimizing stability.

[0044] This invention enhances interfacial bonding strength and improves durability through an interface reinforcing agent. Specifically, the siloxy group at one end of the methyltrimethoxysilane molecule reacts chemically with the hydroxyl groups on the surface of aggregates and phosphogypsum to form covalent bonds; the organic group at the other end interacts with gelation hydration products (CSH gel, etc.), eliminating interfacial voids between different components, improving interfacial bonding strength, and increasing the 28-day splitting tensile strength. The resulting siloxane film covers the particle surface, filling interfacial capillary pores, reducing water intrusion channels, improving the material's impermeability, and simultaneously reducing water absorption. It can also block the migration and dissolution of soluble impurities (phosphorus, fluorine) at the interface, reducing the damage of impurities to interfacial bonding; and simultaneously enhance the material's resistance to freeze-thaw cycles and sulfate attack.

[0045] This invention inhibits crack initiation and propagation through a crack-resistant modifier, improving the material's toughness and impact resistance. Specifically, fibers are randomly dispersed within the mixture, forming a three-dimensional support network that prevents the initiation of shrinkage cracks and temperature cracks. When cracks appear, the fibers transfer stress through bridging, preventing further crack propagation and enhancing crack resistance. Furthermore, the polypropylene fibers have a tensile strength ≥350MPa, and the lignin fibers have an oil absorption rate ≥5 times, both enhancing the material's deformation capacity, improving the base layer's impact resistance and fatigue resistance to vehicle loads, and extending road service life. The fibers can also absorb some moisture, slowing down the evaporation rate, and further improving water retention when combined with a moisture content regulator; simultaneously, they reduce segregation and bleeding during the mixing process, improving uniformity.

[0046] The present invention also provides a method for preparing the phosphogypsum-based road base material described in the above technical solution, preferably comprising the following steps: The phosphogypsum is crushed and the aggregate raw materials are graded to obtain graded aggregates containing coarse aggregates, medium aggregates and fine aggregates. Phosphogypsum, composite cementitious activator, graded aggregate and crack-resistant modifier are mixed and stirred to obtain premix; Water is added to the premix and stirred to obtain a mixture. Water, composite functional additives, moisture content regulators, and interface enhancers are added to the mixture, and the mixture is stirred to obtain the phosphogypsum-based road base material.

[0047] In this invention, the stirring rate is preferably 300-400 r / min, and the stirring time is preferably 5-8 minutes.

[0048] In this invention, the phosphogypsum, after being crushed, has an average particle size of ≤20mm.

[0049] Example 1 (1) Raw material preparation (mass quantity) 40 parts of phosphogypsum (aged phosphogypsum, aged for 30 days) Composite cementitious activator: 12 parts (alkaline activator: silica-alumina active component: sulfate source = 2:3:1; wherein the alkaline activator is obtained by mixing quicklime and silicate cement clinker at a mass ratio of 1:2, the silica-alumina active component is obtained by mixing granulated blast furnace slag powder and metakaolin at a mass ratio of 3:1, and the sulfate source is desulfurized gypsum) Graded aggregate: 45 parts (of which, the mass ratio of coarse aggregate, medium aggregate, and fine aggregate is 4:3:2; the coarse aggregate is limestone crushed stone with a particle size of 10-31.5mm; the medium aggregate is graded crushed stone with a particle size of 5-10mm; and the fine aggregate is river sand with a particle size of 2-5mm). Composite functional admixture: 0.4 parts (wherein, the mass ratio of water-reducing agent, waterproofing agent, and retarder is 65:30:5; the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, the waterproofing agent is an organosilane-based waterproofing agent, and the retarder is sodium gluconate) Moisture content regulator: 0.1 parts (bentonite) Interface enhancer: 0.15 parts (methyltrimethoxysilane) Crack-resistant modifier: 0.25 parts (polypropylene fiber, 6 mm in length) Water: 8 parts (2) Preparation process Pretreatment: Phosphogypsum is crushed to an average particle size of ≤15mm, and aggregate raw materials are graded and screened to obtain corresponding graded aggregates, which are then dried to a moisture content of ≤3%.

[0050] Dry mixing: Add phosphogypsum, composite cementitious activator, graded aggregate and crack-resistant modifier in proportion, and stir at 350 r / min for 2 minutes to obtain premix.

[0051] Pre-wetting mixing: Add 5.6 parts water (70% of the total water volume) to the premix and stir at a speed of 350 r / min for 1.5 minutes to obtain the mixture.

[0052] Final mixing: Add the remaining 2.4 parts of water, composite functional admixture, moisture content regulator and interface reinforcing agent diluted with ethanol (volume ratio 1:10), stir at 350 r / min for 2 minutes, and the total stirring time is 5.5 minutes to obtain the road base material.

[0053] Example 2 (1) Raw material preparation (mass quantity) Phosphogypsum: 50 parts (calcined phosphogypsum, calcination temperature 500℃, calcination time 2.5 hours) Composite cementitious activator: 16 parts (wherein, the mass ratio of alkaline activator, silica-alumina active component, and sulfate source is 2.5:3.5:1.2; wherein the alkaline activator is obtained by mixing quicklime and carbide slag at a mass ratio of 1:1, the silica-alumina active component is obtained by mixing granulated blast furnace slag powder, fly ash, and metakaolin at a mass ratio of 2:1:1, and the sulfate source is gypsum dihydrate) Graded aggregate: 40 parts (of which, the mass ratio of coarse aggregate, medium aggregate, and fine aggregate is 5:3:2; the coarse aggregate is limestone crushed stone with a particle size of 10-31.5mm; the medium aggregate is graded crushed stone with a particle size of 5-10mm; and the fine aggregate is manufactured sand with a particle size of 2-5mm). Composite functional admixture: 0.6 parts (wherein, the mass ratio of water-reducing agent, waterproofing agent and retarder is 60:35:5; wherein, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, the waterproofing agent is an organosilane waterproofing agent, and the retarder is citric acid) Moisture content regulator: 0.15 parts (obtained by mixing diatomaceous earth and calcium oxide in a mass ratio of 2:1) Interface enhancer: 0.2 parts (methyltrimethoxysilane) Crack-resistant modifier: 0.3 parts (lignin fiber) Water: 9 parts (2) Preparation process Pretreatment: Phosphogypsum is crushed to an average particle size of ≤12mm, and aggregate raw materials are graded and screened to obtain corresponding graded aggregates, which are then dried to a moisture content of ≤3%.

[0054] Dry mixing: Add phosphogypsum, composite cementitious activator, graded aggregate and crack-resistant modifier in proportion, and stir at 380 r / min for 2.5 minutes to obtain premix.

[0055] Pre-wetting mixing: Add 6.3 parts water (70% of the total water volume) to the premix and stir at 380 r / min for 2 minutes to obtain the mixture.

[0056] Final mixing: Add the remaining 2.7 parts of water, composite functional admixture, moisture content regulator and interface reinforcing agent diluted with ethanol (volume ratio 1:10), stir at 380 r / min for 2.5 minutes, and the total stirring time is 7 minutes to obtain the road base material.

[0057] Performance testing (1) Mechanical property test: According to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG E51-2009), the compressive strength of the materials obtained in Example 1 and Example 2 at 3d, 7d and 28d was tested; (2) Volume stability: According to the "Test Method for Drying Shrinkage of Cement-based Composite Materials" (GB / T 29407-2012), the 28-day drying shrinkage rate of the materials obtained in Example 1 and Example 2 was tested; (3) Durability: The water absorption rate (weighing method) of the materials obtained in Example 1 and Example 2 after 24 hours and the strength loss rate after 25 freeze-thaw cycles (-15℃ freezing for 4 hours / 20℃ thawing for 4 hours) were tested. (4) Environmental performance: According to the "Leaching Toxicity of Solid Waste - Horizontal Oscillation Method" (HJ / T 299-2007), the soluble phosphorus and fluorine content in the leachate of the materials obtained in Example 1 and Example 2 was tested.

[0058] The test results are shown in Table 1. Table 1 Test Results

[0059] Based on the above, the 3d compressive strength, 7d compressive strength and 28d compressive strength of Examples 1 and 2 all far exceed the basic mechanical requirements of road base materials. Moreover, Example 2 has better mechanical properties because it uses calcined phosphogypsum with higher activity. This proves that the composite cementitious activator and graded aggregate of the present invention can work synergistically to effectively activate the activity of phosphogypsum and significantly improve the strength of the material.

[0060] The 28-day shrinkage rates of Examples 1 and 2 were only 0.05% and 0.04%, respectively, which are far lower than those of traditional phosphogypsum-based materials. This indicates that the synergistic effect of the moisture content regulator and crack-resistant modifier in this invention successfully suppressed the material's shrinkage deformation, avoided the risk of base layer cracking, and ensured the structural stability of the material during long-term service.

[0061] The 24-hour water absorption rates of Examples 1 and 2 were 7.2% and 6.5%, respectively, and the strength loss rates after 25 freeze-thaw cycles were only 12.3% and 10.5%, respectively. This demonstrates the synergistic water-resistant and freeze-resistant effects of organosilane waterproofing agents and dense microstructures, enabling the material to adapt to complex service environments such as dampness and freezing, and solving the technical problems of poor water resistance and easy softening of traditional phosphogypsum-based materials.

[0062] In the leachates of Examples 1 and 2, the soluble phosphorus content was 0.03 mg / L and 0.02 mg / L, respectively, and the fluorine content was 0.3 mg / L and 0.2 mg / L, respectively, both far below the environmental protection standard limits. This proves that the present invention effectively inhibits the leaching of harmful impurities through raw material pretreatment and synergistic effect of components, and realizes the environmentally friendly resource utilization of phosphogypsum.

[0063] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A road base material based on phosphogypsum, characterized in that, The components include the following parts by mass: 35-55 parts phosphogypsum, 8-18 parts composite cementitious activator, 35-55 parts graded aggregate, 0.3-0.8 parts composite functional admixture, 0.05-0.2 parts moisture content regulator, 0.1-0.3 parts interface reinforcing agent, 0.2-0.5 parts crack-resistant modifier, and 7-11 parts water.

2. The phosphogypsum-based road base material according to claim 1, characterized in that, The phosphogypsum is aged phosphogypsum or calcined phosphogypsum. When the phosphogypsum is aged phosphogypsum, the mass fraction is 35-45 parts. When the phosphogypsum is calcined phosphogypsum, the mass fraction is 35-55 parts.

3. The phosphogypsum-based road base material according to claim 1, characterized in that, The composite gelling activator comprises an alkaline activator, a silica-alumina active component, and a sulfate source, with a mass ratio of 1.5-3:2-4:0.5-1.

5.

4. The phosphogypsum-based road base material according to claim 3, characterized in that, The alkaline activator is one or more of quicklime, carbide slag, and silicate cement clinker; the siliceous aluminous active component is one or more of granulated blast furnace slag powder, fly ash, and metakaolin; and the sulfate source is one or more of gypsum dihydrate, desulfurized gypsum, and sodium sulfate.

5. The phosphogypsum-based road base material according to claim 1, characterized in that, The graded aggregate includes coarse aggregate, medium aggregate, and fine aggregate, with a mass ratio of 4~5:3~4:1~3. The coarse aggregate has a particle size of 10-31.5 mm, the medium aggregate has a particle size of 5-10 mm, and the fine aggregate has a particle size of 2-5 mm.

6. The phosphogypsum-based road base material according to claim 1, characterized in that, The composite functional admixture includes a water-reducing agent, a waterproofing agent, and a retarder. The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, the waterproofing agent is an organosilane-based waterproofing agent, and the retarder is sodium gluconate or citric acid.

7. The phosphogypsum-based road base material according to claim 1, characterized in that, The moisture content regulator is one or more of bentonite, diatomaceous earth, and calcium oxide; the interface reinforcing agent is methyltrimethoxysilane; and the crack-resistant modifier is polypropylene fiber or lignin fiber.

8. A method for preparing a road base material based on phosphogypsum according to any one of claims 1 to 7, characterized in that, Includes the following steps: The phosphogypsum is crushed and the aggregate raw materials are graded to obtain graded aggregates containing coarse aggregates, medium aggregates and fine aggregates. Phosphogypsum, composite cementitious activator, graded aggregate and crack-resistant modifier are mixed and stirred to obtain premix; Water is added to the premix and stirred to obtain a mixture. Water, composite functional additives, moisture content regulators, and interface enhancers are added to the mixture, and the mixture is stirred to obtain the phosphogypsum-based road base material.

9. The method for preparing road base material based on phosphogypsum according to claim 8, characterized in that, The stirring rate is 300~400 r / min, and the stirring time is 5~8 minutes.

10. The method for preparing road base material based on phosphogypsum according to claim 8, characterized in that, After being crushed, the average particle size of the phosphogypsum is ≤20mm.

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