High-content phosphogypsum pavement base material and preparation method thereof

Abstract

The invention discloses a high-content phosphogypsum pavement base material and a preparation method thereof, and belongs to the field of pavement base materials. The material is prepared from the following components in parts by weight: 7 to 9 parts of binding material, 30 to 45 parts of ardealite artificial fine aggregate, 45 to 60 parts of ardealite artificial coarse aggregate and 0.05 to 0.1 part of water glass, wherein the binding material is prepared by mixing 3.5 to 4.5 parts of phosphogypsum, 3 to 3.5 parts of slag powder, 0.3 to 0.7 part of cement and 0.2 to 0.3 part of phosphorus slag powder. The ardealite artificial aggregate is prepared by mixing ardealite, slag powder, cement, a performance regulator, water and a water reducing agent, pouring, curing, crushing, shaping and screening. The preparation method of the material comprises the following three steps: pretreating the aggregate, mixing the materials and forming and curing. According to the invention, high-dosage utilization of the phosphogypsum is realized, the technical problems that the utilization rate and pavement performance of the phosphogypsum in the existing phosphogypsum pavement base material cannot be considered at the same time and the construction convenience is poor are solved, and the obtained material has good pavement performance.

Description

TECHNICAL FIELD

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

[0002] With the development of industrial production, phosphogypsum, as an industrial by-product produced in the production process of phosphate fertilizer, phosphoric acid and its derivatives, its stockpiling volume increases year by year, not only occupies a large amount of land resources, but also may cause environmental pollution. Applying phosphogypsum to road base material is one of the important ways to realize its resource utilization. At present, there have been more researches on the application of phosphogypsum in road base at home and abroad, and certain progress has been made.

[0003] Phosphogypsum pavement base materials can be divided into three types: powder type, aggregate type and flowable type according to raw material composition and material form. The powder type phosphogypsum pavement base material is used for pavement base after mixing phosphogypsum with cementing materials, curing agents and other auxiliary materials, etc. For example, patent CN114804773A proposes a composite solid waste pavement base binder, which is made of pretreated alkaline phosphogypsum powder mixed with fly ash, slag powder and cement, which can improve the strength of pavement base, reduce the shrinkage and cracking of pavement base, and at the same time reduce the cement consumption and cost. Patent CN119430836A discloses a phosphogypsum road base material, which comprises phosphogypsum 850-900 parts, quicklime 5-15 parts, cement 40-60 parts, composite curing agent 55-85 parts and curing activator 8.5-13 parts. Through modification and treatment of phosphogypsum, the soluble phosphorus and fluorine in phosphogypsum are cured, and the strength and stability of the base material are improved.

[0004] The aggregate type phosphogypsum pavement base material is prepared by mixing phosphogypsum, cementing materials, curing agents and auxiliary materials with aggregate. The aggregate is natural aggregate or phosphogypsum aggregate prepared by centrifugal rolling, extrusion and other methods using phosphogypsum as the main raw material. For example, CN119638356A discloses a high-dosage phosphogypsum-cement stabilized macadam mixture, which comprises graded macadam 100-120 parts, phosphogypsum 60-80 parts, cement 5-10 parts, curing agent 1-3 parts and water 5-15 parts by weight. The activity of raw phosphogypsum is activated by using cement and curing agent, and the macadam is stabilized by adding water, which solves the problem of poor engineering performance of phosphogypsum. In the paper “Application Research of Modified Phosphogypsum Lightweight Aggregate in Roadbed Material” (published in Concrete and Cement Products, 2022, No. 6, pp. 82-86), it is proposed that phosphogypsum lightweight aggregate is prepared by granulating and screening phosphogypsum into balls, and then part of the phosphogypsum lightweight aggregate is used to replace macadam for the preparation of road stabilized layer. When the phosphogypsum dosage in the phosphogypsum lightweight aggregate is 88%, the 7d unconfined compressive strength of the stabilized layer is ≥3MPa.

[0005] Flowable phosphogypsum pavement base material is a base mixture with certain fluidity formed by mixing phosphogypsum, cementitious material, aggregate and the like, adding water and admixture and stirring, and then pouring and forming on site. For example, CN119191800A proposes a self-compacting phosphogypsum road base material, the components of which include phosphogypsum 40-55%, cementitious material 4-13%, aggregate 35-50%, and admixture 0.2-0.7% by mass percentage. The base material has a slump spread index reaching SF1 level (550-655 mm), an expansion time T 500 reaching VS1 level (≥2 s), a low cement dosage, a high phosphogypsum utilization rate, and can effectively overcome or avoid the occurrence of early diseases of road base.

[0006] However, although phosphogypsum is used for pavement base at present, it has broad prospects, but due to limitations in utilization methods and the like, it is difficult to give consideration to phosphogypsum utilization rate, road performance of base material, construction convenience and practicality and the like, which limits the large-scale application of phosphogypsum in pavement base. The following problems exist in particular: Firstly, in powder-type phosphogypsum pavement base material, phosphogypsum is not easy to mix uniformly with the binder, multiple types of road rollers need to be used for multiple times of rolling, the construction is complicated, the compaction degree is difficult to reach the standard requirement, the road performance is poor, and diseases are prone to occur after the pavement is put into use.

[0007] Secondly, in aggregate-type phosphogypsum pavement base material, the addition of ordinary aggregate reduces the utilization rate of phosphogypsum. Due to the low strength and the mostly circular shape of the phosphogypsum aggregate, the mutual embedding and extruding effect between the aggregates is not good, which affects the performance of the base material.

[0008] Finally, flowable phosphogypsum pavement base material increases the construction process, needs to install a formwork and perform joint cutting and filling, has poor practicality, and is difficult to use in road sections with large longitudinal and transverse slopes.

[0009] Therefore, it is urgent to develop a high-phosphogypsum-content pavement base material which can not only improve the utilization rate of phosphogypsum but also ensure the road performance of pavement base material, and has good construction convenience and practicality. SUMMARY

[0010] In order to solve the problems of the existing phosphogypsum pavement base material in utilization rate, road performance, construction convenience and practicality and the like, the present application provides a high-phosphogypsum-content pavement base material and a preparation method thereof.

[0011] The technical solution adopted by the present application to solve the technical problems is as follows: Firstly, the application provides a high-doped phosphogypsum pavement base material, which comprises the following raw materials in parts by weight: 7-9 parts of binder, 30-45 parts of phosphogypsum artificial fine aggregate, 45-60 parts of phosphogypsum artificial coarse aggregate, and 0.05-0.1 parts of water glass.

[0012] Preferably, the binder is mixed by the following components in parts by weight: 3.5-4.5 parts of phosphogypsum, 3-3.5 parts of slag powder, 0.3-0.7 parts of cement, and 0.2-0.3 parts of phosphorus slag powder.

[0013] Preferably, the phosphogypsum artificial fine aggregate and the phosphogypsum artificial coarse aggregate are prepared by the following process: 45-55 parts of phosphogypsum, 25-37 parts of slag powder, 0-5 parts of cement, and 5-8 parts of performance adjusting agent are added into water with a total solid mass of 0.23-0.24 times and 0.02-0.025 times of polycarboxylate superplasticizer, and then mixed and stirred, poured, maintained, mechanically broken, shaped, and sieved to form particles with required gradation and particle shape.

[0014] Preferably, the performance adjusting agent is mixed by the following components in parts by weight after drying: 2-3 parts of fly ash, 1.5-2.5 parts of metakaolin, 1-1.5 parts of silica fume, and 0.5-1 parts of steel slag powder.

[0015] The performance adjusting agent can shorten the setting time of the phosphogypsum artificial aggregate mother material, accelerate the strength growth, improve the strength, and improve the volume stability.

[0016] Preferably, the modulus of the water glass is 1.5-2.5. The low-modulus water glass has a high content of free sodium oxide and strong alkalinity, can quickly stimulate the activity of slag powder, accelerate hydration, and improve early strength, but excessive alkalinity can lead to loose structure of later hydration products, affecting the later strength growth and the performance of the base material. The high-modulus water glass is opposite, has weak early stimulating effect, slow strength development, but the structure of the hydration products is more compact, and the later strength development is stable. The application has been verified by tests that the phosphogypsum pavement base material has good early strength and road performance when the modulus of the water glass is in the range.

[0017] Preferably, the phosphogypsum is the original phosphogypsum with a particle size less than 2.36 mm after crushing. Since the original phosphogypsum is mostly in a water-containing state, crushing through a 2.36 mm sieve is more practical and can ensure the quality of the phosphogypsum aggregate and the performance of the base material.

[0018] Preferably, the cement is P·042.5 cement, the slag powder is S95 grade granulated blast furnace slag powder, and the polycarboxylate superplasticizer has a solid content of 8-12% and a water-reducing rate of ≥25%.

[0019] Preferably, the phosphogypsum artificial coarse aggregate is a mixture of nominal particle size 4.75-9.5 mm and 9.5-26.5 mm, the ratio of which is 1:6-9, and meets the following specifications: nominal particle size 4.75-9.5 mm, mass percentage passing 13.2 sieve hole is 100%, mass percentage passing 9.5 sieve hole is 90-100%, mass percentage passing 4.75 sieve hole is 0-10%, mass percentage passing 2.36 sieve hole is 0-5%; nominal particle size 9.5-26.5 mm, mass percentage passing 31.5 sieve hole is 100%, mass percentage passing 26.5 sieve hole is 90-100%, mass percentage passing 9.5 sieve hole is 0-10%, mass percentage passing 4.75 sieve hole is 0-5%. The phosphogypsum artificial fine aggregate meets the specification of nominal particle size 0-4.75 mm, mass percentage passing 9.5 sieve hole is 100%, mass percentage passing 4.75 sieve hole is 90-100%, mass percentage passing 0.075 sieve hole is 0-15%.

[0020] The application also provides a preparation method of the high-content phosphogypsum pavement base material, which comprises the following steps: (1) Preprocessing aggregate: add water with 2-3% higher than the saturated surface dry water absorption of the phosphogypsum artificial fine aggregate, stir uniformly, and then stew the material for 24-48 h; immerse the phosphogypsum artificial coarse aggregate in water for more than 24 h, and then drain the water until no water is left; (2) Mixing material: mix the binder, the pretreated phosphogypsum artificial coarse and fine aggregate uniformly; dissolve the water glass in water, and then add to the mixture and stir uniformly; (3) Molding and curing: mold the mixture, and then cure to obtain the base material.

[0021] The preprocessing process of "stewing and saturating water + saturating and draining" in the preparation method can solve the influence of high water absorption of the phosphogypsum aggregate on the construction state of the base material, and ensure the construction performance of the base material.

[0022] Preferably, the material is sealed in step (1); and the water glass is completely dissolved in water before being added to the mixture in step (3).

[0023] Preferably, the amount of the pretreated coarse and fine aggregate in step (2) is calculated according to the actual water content, and the actual amount of aggregate = dry mass of aggregate × (1+water content after saturation).

[0024] Preferably, the amount of water in step (2) = total water amount - dry mass of aggregate × (water content after saturation - saturated surface dry water absorption), and the total water amount is determined by the compaction test.

[0025] The application has the following beneficial effects: 1. Compared with the powder type phosphogypsum pavement base material, the base material mixture of the application has good uniformity, the construction can refer to the traditional water stable material, the compaction degree can reach similar to the traditional water stable material, the process is mature, and the road performance is good.

[0026] 2. Compared with the aggregate type phosphogypsum pavement base material, the base material phosphogypsum artificial aggregate of the application has high strength, can completely replace ordinary aggregate, the particles are tightly embedded and extruded, the phosphogypsum utilization rate is high, and the road performance is good.

[0027] 3. Compared with the flowable type phosphogypsum pavement base material, the base material of the application has strong universality, is suitable for construction of the whole road section, and the construction process is mature and simple.

[0028] 4. The application reduces the application of cement and ordinary aggregate in highway base construction, most of the raw materials are solid waste, saves resources and energy, and effectively relieves the ecological environment pressure.

[0029] 5. The 7d unconfined compressive strength of the high-dosage phosphogypsum pavement base material of the application can reach 5.6Mpa, and the 28d unconfined compressive strength can reach 7.2Mpa, which is suitable for base and bottom base of expressway and first-class highway. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application, and should not be regarded as specific limitation on the application.

[0031] The process, conditions, reagents, experimental methods and the like for implementing the application are the general knowledge and common sense in the art, and the application has no special limitation. The experimental methods not specified in the embodiments are usually performed according to the conventional conditions or the conditions specified in the relevant standard procedures.

[0032] Unless otherwise specified, the meanings of all professional terms and scientific terms used in the specification are the same as those generally understood by the skilled person in the technical field to which the application belongs. However, if there is a conflict, the specification containing the definition shall prevail.

[0033] Example 1 The high-dosage phosphogypsum pavement base material of the application comprises the following raw materials in parts by weight: 8 parts of binder, 38 parts of phosphogypsum artificial fine aggregate, 52 parts of phosphogypsum artificial coarse aggregate, and 0.07 parts of water glass.

[0034] The binder is mixed by 4 parts by weight of phosphogypsum, 3.3 parts by weight of slag powder, 0.5 parts by weight of cement, and 0.2 parts by weight of phosphorus slag powder.

[0035] The phosphogypsum artificial coarse and fine aggregate is prepared by mixing and stirring 50 parts of phosphogypsum, 31 parts of slag powder, 2.5 parts of cement, 6.5 parts of performance adjusting agent, 21.15 parts of water and 2.25 parts of polycarboxylic acid water reducing agent, pouring into a mold, curing for 7 days, and then mechanically crushing, shaping and screening.

[0036] The modulus of the water glass is 2.0.

[0037] The phosphogypsum has a particle size less than 2.36 mm, the cement is P·O 42.5 cement, and the slag powder is S95 grade granulated blast furnace slag powder.

[0038] The performance adjusting agent is prepared by mixing and stirring 2.5 parts of fly ash, 2 parts of metakaolin, 1.3 parts of silica fume and 0.7 parts of steel slag powder after drying.

[0039] The polycarboxylic acid water reducing agent has a solid content of 10% and a water reducing rate of 27%.

[0040] The phosphogypsum artificial coarse and fine aggregate has the following specifications: The phosphogypsum artificial coarse aggregate has a nominal particle size of 4.75-9.5 mm and 9.5-26.5 mm, and the ratio of the two is 1:7.5, and the specifications are shown in Table 1.

[0041] The phosphogypsum artificial fine aggregate has a nominal particle size of 0-4.75 mm, and the specific specifications are shown in Table 2.

[0042] Table 2 Specifications of the phosphogypsum artificial fine aggregate in the embodiment

[0043] The preparation method of the phosphogypsum-based pavement base material specifically includes the following steps: Step one: it is determined that the saturated surface dry water absorption rate of the phosphogypsum artificial coarse aggregate is 5.7%, the initial moisture content of the phosphogypsum artificial fine aggregate is 4.5%, and the saturated surface dry water absorption rate is 12.5%. 10% of water (the amount of water added exceeds the surface saturated surface dry water absorption rate by 2%) of the mass of the phosphogypsum artificial fine aggregate is added and stirred uniformly, and the mixture is sealed and stewed for 24 hours. The phosphogypsum coarse aggregate is saturated with water and soaked for 24 hours, then taken out and drained until no clear water flows out. The water content of the phosphogypsum coarse and fine aggregate after saturation is determined, wherein the coarse aggregate is 6.1%, and the fine aggregate is 13.8%; Step two: the components are weighed, the actual mass of the phosphogypsum coarse and fine aggregate is the dry mass of the phosphogypsum coarse and fine aggregate multiplied by (1+water content after saturation), and the actual mass of water is the total amount of water minus the dry mass of the phosphogypsum coarse and fine aggregate multiplied by (water content after saturation-saturated surface dry water absorption rate). The total amount of water is determined to be 5.7 parts by the compaction test; the specific amount is shown in Table 3.

[0044] Table 3 Theoretical and actual proportioning of each material in the preparation of the embodiment

[0045] Step three: the combined material and phosphogypsum artificial coarse and fine aggregate are mixed uniformly to obtain a mixture, and the water glass is dissolved in water, and then mixed and poured into the mixture to obtain a base material mixture; Step four: the mixture is poured into a mold for shaping and curing, and the high-mixing phosphogypsum pavement base material is obtained.

[0046] Embodiment 2 The high-mixing phosphogypsum pavement base material comprises the following raw materials in parts by weight: 7 parts of binder, 30 parts of phosphogypsum artificial fine aggregate, 45 parts of phosphogypsum artificial coarse aggregate, and 0.05 parts of water glass.

[0047] The binder is mixed by 3.5 parts of phosphogypsum, 3 parts of slag powder, 0.3 parts of cement, and 0.2 parts of phosphorus slag powder. The phosphogypsum artificial coarse and fine aggregate is mixed by 45 parts of phosphogypsum, 25 parts of slag powder, and 5 parts of performance adjusting agent, and then mixed and stirred with 17.25 parts of water and 1.5 parts of polycarboxylic acid water reducing agent. After pouring and shaping, it is cured for 7 days, and then mechanically crushed, shaped, and sieved to obtain the phosphogypsum artificial coarse and fine aggregate.

[0048] The modulus of the water glass is 2.5.

[0049] The particle size of the phosphogypsum is less than 2.36 mm, the cement is P·042.5 cement, and the slag powder is S95 grade granulated blast furnace slag powder.

[0050] The performance adjusting agent is mixed by 2 parts of fly ash, 1.5 parts of metakaolin, 1 part of silica fume, and 0.5 parts of steel slag powder after drying.

[0051] The solid content of the polycarboxylic acid water reducing agent is 10%, and the water reducing rate is 27%.

[0052] The phosphogypsum artificial coarse and fine aggregate has the following specifications: Phosphogypsum artificial coarse aggregate: a mixture of nominal particle sizes of 4.75-9.5 mm and 9.5-26.5 mm at a ratio of 1:6, and the specifications are shown in Table 4. Table 4 Specifications of phosphogypsum artificial coarse aggregate in the embodiment

[0053] Phosphogypsum artificial fine aggregate: the nominal particle size is 0-4.75 mm, and the specific specifications are shown in Table 5. Table 5 Specifications of phosphogypsum artificial fine aggregate in the embodiment

[0054] The application further provides a preparation method of the phosphogypsum-based pavement base material, and specifically comprises the following steps: Step one: according to the measurement, the saturated surface dry water absorption rate of the phosphogypsum artificial coarse aggregate is 6.1%, the initial moisture content of the phosphogypsum artificial fine aggregate is 3.4%, and the saturated surface dry water absorption rate is 12.9%. 11.5% of water (the amount of water added is 2% more than the surface saturated surface dry water absorption rate) of the mass of the phosphogypsum artificial fine aggregate is added and stirred uniformly, and the material is sealed and stewed for 36 hours. The phosphogypsum coarse aggregate is saturated with water for 24 hours, and then taken out and drained until no clear water flows out. The water content of the phosphogypsum coarse and fine aggregates after saturation is measured, wherein the water content of the coarse aggregate is 6.5%, and the water content of the fine aggregate is 14.3%. Step two: the components are weighed, the actual mass of the phosphogypsum coarse and fine aggregates is the dry mass of the phosphogypsum coarse and fine aggregates multiplied by (1+the water content after saturation), and the actual mass of water is the water amount minus the dry mass of the phosphogypsum coarse and fine aggregates multiplied by (the water content after saturation minus the saturated surface dry water absorption rate). The water amount is determined to be 5.7 parts by the compaction test. The specific amount is shown in Table 6.

[0055] Table 6 Theoretical and actual proportioning of each material in the preparation of the embodiment

[0056] Step three: the binder and the phosphogypsum artificial coarse and fine aggregates after weighing are mixed uniformly to obtain a mixture, the water glass is dissolved in water, and then the mixture is poured into the uniformly mixed mixture to obtain a base material mixture. Step four: the mixture is poured into a mold for shaping and curing, and a high-mixing phosphogypsum pavement base material is obtained.

[0057] Embodiment 3 The high-mixing phosphogypsum pavement base material comprises the following raw materials in parts by weight: 9 parts of binder, 45 parts of phosphogypsum artificial fine aggregate, 60 parts of phosphogypsum artificial coarse aggregate, and 0.1 part of water glass.

[0058] The binder is composed of 4.5 parts by weight of phosphogypsum, 3.5 parts by weight of slag powder, 0.7 parts by weight of cement, and 0.3 parts by weight of phosphorus slag powder. The phosphogypsum artificial coarse and fine aggregates are composed of 55 parts by weight of phosphogypsum, 37 parts by weight of slag powder, 5 parts by weight of cement, and 8 parts by weight of performance regulator. After mixing, 25.2 parts by weight of water and 2.625 parts by weight of polycarboxylic acid water reducer are added and stirred, and then the mixture is poured into a mold for shaping and curing for 7 days. After mechanical crushing, shaping and screening, the phosphogypsum artificial coarse and fine aggregates are obtained.

[0059] The modulus of the water glass is 1.5.

[0060] The particle size of the phosphogypsum is less than 2.36 mm, the cement is P·042.5 cement, and the slag powder is S95 grade granulated blast furnace slag powder.

[0061] The performance regulator is prepared by mixing 3 parts of fly ash, 2.5 parts of metakaolin, 1.5 parts of silica fume and 1 part of steel slag powder after drying.

[0062] The polycarboxylic acid water reducing agent has a solid content of 10% and a water reducing rate of 27%.

[0063] The phosphogypsum artificial coarse and fine aggregate has the following specifications: The phosphogypsum artificial coarse aggregate has a nominal particle size of 4.75-9.5 mm and 9.5-26.5 mm, and the ratio of the two is 1:9, and the specifications are shown in Table 7.

[0064] The phosphogypsum artificial fine aggregate has a nominal particle size of 0-4.75 mm, and the specific specifications are shown in Table 8.

[0065] The application also provides a preparation method of the phosphogypsum-based pavement base material, which specifically comprises the following steps: Step one: according to the measurement, the saturated surface dry water absorption rate of the phosphogypsum artificial coarse aggregate is 5.5%, the initial moisture content of the phosphogypsum artificial fine aggregate is 4.0%, and the saturated surface dry water absorption rate is 12.2%. 11.2% of water (the amount of water added exceeds the surface saturated surface dry water absorption rate by 3%) is added to the phosphogypsum artificial fine aggregate and stirred uniformly, and the material is sealed and stewed for 48 h. The phosphogypsum coarse aggregate is saturated with water for 24 h and then taken out for water drainage until no clear water flows out. The water content of the phosphogypsum coarse and fine aggregate after saturation is measured, and the coarse aggregate is 6.0%. The fine aggregate is 13.1%; Step two: the actual mass of the phosphogypsum coarse and fine aggregate is measured, and the actual mass of the phosphogypsum coarse and fine aggregate is the dry mass of the phosphogypsum coarse and fine aggregate multiplied by (1+water content after saturation). The actual mass of water is the water amount minus the dry mass of the phosphogypsum coarse and fine aggregate multiplied by (water content after saturation-saturated surface dry water absorption rate). The water amount is determined to be 5.7 parts by the compaction test. The specific amount is shown in Table 9.

[0066] Table 9 Theoretical and actual proportioning of each material in the preparation of the embodiment

[0067] Step three: the binder and the phosphogypsum artificial coarse and fine aggregate are mixed uniformly to obtain a mixture, the water glass is dissolved in water, and then the mixture is poured into the uniformly mixed mixture, and the base material mixture is obtained after mixing. Step four: the mixture is poured into a mold for shaping and curing, and a high-mixing phosphogypsum pavement base material is obtained.

[0068] Comparative Example 1 differs from Example 1 in that the performance adjusting agent is not contained in the raw material for preparing the phosphogypsum artificial aggregate, and the rest is the same as Example 1.

[0069] Comparative Example 2 differs from Example 1 in that the modulus of the water glass is 3.0, and the rest is the same as Example 1.

[0070] Comparative Example 3 differs from Example 1 in that the modulus of the water glass is 1.0, and the rest is the same as Example 1.

[0071] Comparative Example 4 differs from Example 1 in that the phosphogypsum artificial fine aggregate is not subjected to the saturation water pretreatment by stewing, the phosphogypsum artificial coarse aggregate is not subjected to the saturation water leaching treatment, the dry density of the base material is determined by the compaction test after the mixing of the base material is completed, and the test piece is formed at the dry density. Due to the influence of the water absorption of the phosphogypsum, the actual water content of the base material at this time is lower than the optimum water content, and the dry density is smaller than the maximum dry density in Example 1, and the rest is the same as Example 1.

[0072] Comparative Example 5 differs from Example 1 in that the phosphogypsum artificial fine aggregate is not subjected to the saturation water pretreatment by stewing, the phosphogypsum artificial coarse aggregate is not subjected to the saturation water leaching treatment, the water consumption is different, the water consumption = the water consumption of Example 1 + the water absorption of the saturated surface of the phosphogypsum aggregate in Example 1, the dry density of the base material is determined by the compaction test after the mixing of the base material is completed, and the test piece is formed at the dry density. Due to the influence of the water absorption and the water absorption rate of the phosphogypsum aggregate, the actual water content of the base material at this time is higher than the optimum water content, and the dry density is smaller than the maximum dry density in Example 1, and the rest is the same as Example 1.

[0073] The properties of the base materials prepared in Examples 1-3 and Comparative Examples 1-5 are detected according to the “Highway Engineering Inorganic Binder Stabilized Material Test Regulations”, and the results are shown in Table 10.

[0074] Table 10 Properties of base materials of examples and comparative examples

[0075] The results of Examples 1-3 show that the 7d unconfined compressive strength of the high-dosage phosphogypsum pavement base material can reach 5.1-5.6Mpa, and the 28d unconfined compressive strength can reach 6.5-7.2Mpa, which is suitable for the base and subbase of expressways and first-class highways. The ordinary aggregate can be completely replaced, the particles are tightly embedded and extruded, the utilization rate of phosphogypsum is high, and the road performance is good.

[0076] Comparative Example 1 compared with Example 1 shows that the performance adjusting agent has an important influence on the properties of the base material, the performance adjusting agent can improve the strength of the phosphogypsum aggregate and the volume stability, and indirectly improve the properties of the base material.

[0077] Compared with Example 1, the comparative example 2-3 shows that the modulus of water glass has an important influence on the strength, and the excessive modulus weakens the activation of the mineral powder, affecting the strength growth of the base material; the excessive low modulus can effectively improve the early strength, but will lead to loose structure of the late hydration product of the base material, affecting the late strength growth and the performance of the base material.

[0078] Compared with Example 1, the comparative example 4-5 shows that the pretreatment of the phosphogypsum aggregate has an important role, and the process of “braising and saturating + saturating and draining” can solve the influence of the high water absorption of the phosphogypsum aggregate on the construction state of the base material. The base material prepared by the phosphogypsum aggregate without saturation will continuously absorb water during mixing and after mixing, which leads to the uncertainty of the best water content of the base material during molding, and the actual water content usually deviates greatly from the best water content, thereby affecting the compactness of the base material and reducing the performance of the base material.

[0079] The applicant declares that the above is only a few embodiments of the application, and does not limit the application in any form. Although the application discloses the above preferred embodiments, it does not limit the application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical scheme of the application, which is equivalent to the equivalent embodiment, and belongs to the scope of the technical scheme.

Claims

1. A high-content phosphogypsum pavement base material, characterized in that: The invention comprises the following raw materials in parts by weight: 7 to 9 parts of binder, 30 to 45 parts of phosphogypsum artificial fine aggregate, 45 to 60 parts of phosphogypsum artificial coarse aggregate, and 0.05 to 0.1 parts of water glass; wherein the binder is mixed by the following components in parts by weight: 3.5 to 4.5 parts of phosphogypsum, 3 to 3.5 parts of slag powder, 0.3 to 0.7 parts of cement, and 0.2 to 0.3 parts of phosphate slag powder.

2. The high-content phosphogypsum pavement base material according to claim 1, characterized in that: The phosphogypsum artificial fine aggregate and the phosphogypsum artificial coarse aggregate are prepared by the following process: 45-55 parts of phosphogypsum, 25-37 parts of slag powder, 0-5 parts of cement, and 5-8 parts of a performance regulator are added with 0.23-0.24 times the total mass of water and 0.02-0.025 times the total mass of a polycarboxylate water reducer, mixed and stirred, and then poured, cured, mechanically crushed, shaped, and screened to form particles with gradation and particle shape meeting the requirements.

3. The high-content phosphogypsum pavement base material according to claim 2, characterized in that: The performance regulator is prepared by drying and mixing the following components in parts by weight: 2-3 parts of fly ash, 1.5-2.5 parts of metakaolin, 1-1.5 parts of silica fume, and 0.5-1 part of steel slag powder.

4. The high-content phosphogypsum pavement base material according to claim 2, characterized in that: The phosphogypsum artificial coarse aggregate is a mixture of materials with nominal particle sizes of 4.75-9.5 mm and 9.5-26.5 mm, with a ratio of 1:6-9. The phosphogypsum artificial fine aggregate has a nominal particle size of 0-4.75 mm.

5. The high-content phosphogypsum pavement base material according to claim 2, characterized in that: The polycarboxylate water reducer has a solid content of 8-12% and a water reduction rate of ≥25%.

6. The high-content phosphogypsum pavement base material according to claim 1, characterized in that: The modulus of the water glass is 1.5 to 2.

5.

7. The high-content phosphogypsum pavement base material according to claim 1 or 2, characterized in that The phosphogypsum is original phosphogypsum with a particle size of less than 2.36 mm after crushing; the cement is P·042.5 cement, and the slag powder is S95 grade granulated blast furnace slag powder.

8. A method for preparing a high-content phosphogypsum pavement base material according to any one of claims 1 to 6 or claim 7, characterized in that: The following steps are involved: (1) Aggregate pretreatment: Add water 2-3% higher than the saturated surface dry water absorption rate to the fine aggregate, stir evenly, and simmer for 24-48 hours; soak the coarse aggregate in water for more than 24 hours, and drain until there is no visible water; (2) Mixing materials: Mix the binder, pre-treated phosphogypsum artificial fine aggregate and phosphogypsum artificial coarse aggregate evenly; dissolve water glass in water, add the dissolved water glass into the mixture and mix evenly; (3) Molding and curing: The mixture is molded and cured to obtain the base material.

9. The preparation method according to claim 8, characterized in that The amount of pretreated phosphogypsum artificial fine aggregate and phosphogypsum artificial coarse aggregate in step (2) is calculated based on the actual moisture content. The amount of pretreated aggregate = dry mass of aggregate × (1 + moisture content after saturation).

10. The preparation method according to claim 8, characterized in that The amount of water used in step (2) = total water consumption - dry mass of aggregate × (moisture content after saturation - saturated surface dry water absorption rate). The total water consumption is determined according to the compaction test.

Images