A warm-mix recycled asphalt sand with high RAP content and its preparation method

Abstract

This application provides a warm-mix recycled asphalt sand with high RAP content and its preparation method, relating to the field of road construction materials technology. The warm-mix recycled asphalt sand comprises: 50-70 parts of RAP fine aggregate, 0.3-0.5 parts of warm-mix recycling agent, 10-20 parts of coarse aggregate, 18-28 parts of fine aggregate, 2-3 parts of filler, and 1.4-2.6 parts of SBS modified asphalt; the RAP fine aggregate includes a first RAP fine aggregate with a particle size greater than 0 mm and less than or equal to 3 mm, and a second RAP fine aggregate with a particle size greater than 3 mm and less than or equal to 5 mm; the mass ratio of the first RAP fine aggregate to the second RAP fine aggregate is (70-78):(22-30); the warm-mix recycling agent comprises base oil, plasticizer, modifier, anti-stripping agent, and surfactant in a mass ratio of (60-65):(10-15):(2-5):(3-5):(15-20). This invention effectively solves the problems of low RAP content, easy secondary aging of asphalt, and poor finished product performance in traditional recycled asphalt sand. The road performance meets the specifications, and the project cost is reduced by 30-35%.

Description

Technical Field

[0001] This application relates to the field of road construction materials technology, and in particular to a warm-mix recycled asphalt sand with high RAP content and its preparation method. Background Technology

[0002] After decades of development, my country's highway construction has formed a vast road network. Early asphalt pavements are gradually reaching their design lifespan, and many other roads are also entering their major and medium-scale maintenance periods. During road renovation and expansion, hundreds of millions of tons of waste asphalt mixture (RAP) are generated annually. Improper disposal will not only occupy a large amount of land but also cause environmental pollution and resource waste.

[0003] Plant-mixed hot recycling technology effectively utilizes asphalt and aggregates in RAP (Rich Asphalt Pavement) while exhibiting good road performance, thus it is widely used in surface layers and flexible base courses of roads of various grades. However, due to the high variability of RAP, the proportion of plant-mixed hot recycling aggregate is generally below 30%. To improve RAP utilization, RAP is typically finely separated. The separated coarse aggregate has a low asphalt content and can be directly used as new aggregate in various structural layers of asphalt pavements. However, the fine aggregate, due to its high asphalt content and high powder content, presents challenges in heating and is prone to secondary aging during heating, severely limiting its application in traditional hot recycling technologies, resulting in a large surplus of fine RAP.

[0004] Asphalt sand has a high asphalt content and a large proportion of fine aggregates. Adding RAP fine aggregates to asphalt sand at a high proportion can fully utilize the asphalt in the RAP fine aggregates, significantly reducing the amount of new asphalt needed and substantially lowering project costs. However, existing recycled asphalt sand still uses the traditional hot-mix process, which involves high construction temperatures and still suffers from problems such as secondary aging of RAP fine aggregates, high energy consumption, and difficulty in increasing the RAP content. Therefore, the performance of recycled asphalt sand remains limited. Current technology mainly addresses these issues by adding recycling agents to transform the asphalt components and readjust their proportions. Common recycling agents on the market are modified oils or surfactants, which can improve the performance of asphalt sand, but still fall short of achieving the performance of new asphalt.

[0005] Therefore, it is necessary to provide a new type of warm-mix recycled asphalt sand with high RAP content. Summary of the Invention

[0006] The purpose of this application is to address the shortcomings of existing technologies by providing a warm-mix recycled asphalt sand with high RAP content and its preparation method. The total RAP content in the recycled asphalt sand of this application is increased to 50-70%, the construction temperature is reduced by 20-30℃, the project cost is saved by 30-35%, and the product performance is improved.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: According to one aspect of this application, a warm-mix recycled asphalt sand with high RAP content is provided, comprising the following raw materials by weight: 50-70 parts of RAP fine aggregate, 0.3-0.5 parts of warm-mix recycling agent, 10-20 parts of coarse aggregate, 18-28 parts of fine aggregate, 2-3 parts of filler, and 1.4-2.6 parts of SBS modified asphalt. The RAP fines include a first RAP fine with a particle size greater than 0 mm and less than or equal to 3 mm, and a second RAP fine with a particle size greater than 3 mm and less than or equal to 5 mm; the mass ratio of the first RAP fines to the second RAP fines is (70-78):(22-30).

[0008] Furthermore, the asphalt content of the first RAP fine aggregate is 9-11%, and the asphalt content of the second RAP fine aggregate is 2.5-3.5%.

[0009] Furthermore, the mass ratio of the first RAP fines to the second RAP fines is (70-78):(22-30), for example, it can be 70:30, 71:29, 72:28, 73:27, 74:26, 75:25, 76:24, 77:23, 78:22 or any range between them.

[0010] This application combines precisely categorized RAP fine aggregates to eliminate gradation fluctuations caused by the mixture of particle size and asphalt content in traditional RAP, achieving refined gradation control and increasing the amount of RAP added. Two types of RAP fine aggregates with different particle sizes and asphalt contents are used in combination. The first RAP fine aggregate, with a high asphalt content, acts as a filler, allowing its aged asphalt to fully integrate with new SBS modified asphalt and warm mix recycling agents, reducing the amount of new asphalt required. The second RAP fine aggregate, with a low asphalt content, constructs the mixture's skeleton structure, preventing fine aggregate concentration and localized asphalt enrichment, thus preventing problems such as bleeding and high-temperature deformation in the mixture.

[0011] Furthermore, the filler is selected from at least one of mineral powder, limestone powder, fly ash, steel slag powder, and diatomaceous earth.

[0012] Further, the warm-mix regenerator is 0.3 to 0.5 parts, for example, it can be 0.31 parts, 0.32 parts, 0.33 parts, 0.34 parts, 0.35 parts, 0.36 parts, 0.37 parts, 0.38 parts, 0.39 parts, 0.4 parts, 0.41 parts, 0.42 parts, 0.43 parts, 0.44 parts, 0.45 parts, 0.46 parts, 0.47 parts, 0.48 parts, 0.49 parts, 0.5 parts, or any range between these.

[0013] While adding warm-mix recycling agents can improve the performance of aged asphalt, excessive addition can negatively impact its high-temperature performance. Studies have shown that when the added amount of the warm-mix recycling agent in this application is in the range of 0.3–0.5 parts, it can significantly improve the low-temperature crack resistance and water stability of recycled sand. In particular, adding 0.37 parts of warm-mix recycling agent, which is approximately 7–8% of the aged asphalt content in the RAP fine aggregate, achieves even better results for the recycled asphalt sand.

[0014] Furthermore, the warm-mix regenerator comprises base oil, plasticizer, modifier, anti-stripping agent and surfactant in a mass ratio of (60-65):(10-15):(2-5):(3-5):(15-20).

[0015] Preferably, the warm-mix regenerator comprises base oil, plasticizer, modifier, anti-stripping agent and surfactant in a mass ratio of 62:15:5:3:15.

[0016] Optionally, the base oil is an aromatic oil or furfural extract oil.

[0017] Optionally, the plasticizer is selected from at least one of epoxidized soybean oil, hydrogenated castor oil, tall oil, pine tar, and diisodecyl phthalate. Preferably, the plasticizer is selected from diisodecyl phthalate and epoxidized soybean oil in a mass ratio of (60-70):(30-40).

[0018] Studies have found that selecting diisodecyl phthalate and epoxidized soybean oil as plasticizers results in a fast penetration rate, which can soften brittle asphalt in a short time and ensure that it does not migrate out during processing and after long-term use, thus guaranteeing the long-term road performance of recycled asphalt sand.

[0019] Optionally, the modifier is selected from maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin in a mass ratio of (64-70):(30-36). The addition of the modifier can form a network structure in the asphalt system, improving the adhesion between asphalt and aggregates, enhancing the high-temperature dynamic stability of the mixture, and improving the interfacial bonding between asphalt and RAP (Reclaimed Asphalt) aggregate. Simultaneously, the polar active groups of the two components can form a multi-layered interfacial protective structure with the aggregates and organic amine anti-stripping agents, synergistically improving water stability indicators such as the freeze-thaw splitting strength ratio.

[0020] Optionally, the anti-stripping agent is selected from amine anti-stripping agents, such as octadecylamine polyoxyethylene ether.

[0021] Optionally, the surfactant is selected from pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide and fatty acid glycerides in a mass ratio of (50-60):(25-33):(15-17).

[0022] Optionally, the fatty acid glyceride is selected from any one of monoglyceride, diglyceride, and triglyceride.

[0023] The surfactants selected in this application can optimize the compatibility of the system and the ductility of the asphalt. The three components work synergistically to improve the high-temperature lubrication and viscosity reduction effect, achieve temperature reduction at 20-30℃ and inhibit secondary aging of asphalt, enhance the penetration ability, improve the uniformity of the fusion of new and old asphalt, improve the low-temperature fluidity of the system, and synergistically improve the low-temperature crack resistance and water stability of the mixture.

[0024] This application uses the above-mentioned composite asphalt warm mix recycling agent, which can quickly penetrate and soften old asphalt to achieve RAP asphalt recycling; on the other hand, it reduces the viscosity and frictional resistance of asphalt mixture, realizes warm mix construction, and reduces the construction temperature by 20-30℃.

[0025] Furthermore, the coarse aggregate is limestone crushed stone with a particle size greater than 3 mm and less than or equal to 5 mm.

[0026] Furthermore, the fine aggregate is stone chips or manufactured sand with a particle size greater than 0 and less than or equal to 3 mm.

[0027] Furthermore, the warm-mix recycled asphalt sand with high RAP content in this application has a total asphalt content in the range of 6.5% to 7.5%.

[0028] According to another aspect of this application, a method for preparing the above-mentioned high RAP content warm-mix recycled asphalt sand is provided, comprising the following steps: S1. Preheat the RAP fines to 120-130°C, put them into the mixing pot, and then evenly spray the warm regenerator into the mixing pot and stir evenly. S2. After preheating the coarse and fine aggregates to 170-180℃, put them into the mixing pot and stir evenly. Then add SBS modified asphalt and mix. Finally, add mineral powder and mix. Place the mixture into a mold to form the final product.

[0029] This application prepares warm-mix recycled asphalt sand with high RAP content using the above method. The mixing temperature in the mixing pot is controlled between 145 and 155°C, and the molding temperature is controlled between 135°C and 145°C. Compared with the traditional hot-mix recycling process, the overall construction temperature is reduced by 20 to 30°C.

[0030] Compared with the prior art, the beneficial effects of this application include, but are not limited to: 1. The high RAP content warm-mix recycled asphalt sand provided in this application increases the total RAP content to 50-70% through the graded utilization of RAP fines and the combined effect of various components such as warm-mix recycling agent, thereby improving the utilization rate of RAP; the construction temperature is reduced by 20-30℃, saving 30-35% of the project cost.

[0031] 2. The combination of two types of RAP fine aggregates with different particle sizes and asphalt contents can ensure that the new and old asphalt and warm mix recycling agent are fully integrated, reducing the amount of new asphalt used. It can also avoid the concentration of fine aggregates and the local enrichment of asphalt, preventing problems such as bleeding and high-temperature deformation in the mixture.

[0032] 3. Adding maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin as modifiers to warm mix recycling agents can enhance the high-temperature dynamic stability of the mixture, improve the interfacial bonding state between asphalt and RAP old material, and synergistically improve water stability indicators such as freeze-thaw splitting strength ratio.

[0033] 4. The addition of pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide and fatty acid glycerides to the warm mix regenerator can enhance the high-temperature lubrication and viscosity reduction effect, achieve temperature reduction in the 20-30℃ warm mix, and inhibit the secondary aging of asphalt. It can also improve the penetration capacity, improve the uniformity of the fusion of new and old asphalt, and improve the low-temperature fluidity of the system, thus synergistically improving the low-temperature crack resistance and water stability of the mixture. Detailed Implementation

[0034] To more clearly illustrate the overall concept of this application, a detailed description is provided below by way of embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with the invention.

[0035] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers. Preparation methods that do not specify specific methods are generally prepared using equipment or conventional methods well known in the art.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0038] Unless otherwise specified, the "%" content in this application refers to mass content or weight content. For example, "the asphalt content of the first RAP fine material is 9-11%" means that the mass content or weight content of asphalt in the first RAP fine material is 9-11%.

[0039] Unless otherwise specified, in the following embodiments, reagents or instruments whose manufacturers are not indicated are all conventional products that can be purchased commercially.

[0040] Unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in this invention all employ conventional techniques in the fields of microbiology, biochemistry, analytical chemistry, cell culture, and related areas.

[0041] The present application will be further described below by way of specific embodiments.

[0042] Example 1 A warm-mix recycled asphalt sand with high RAP content comprises the following raw materials by weight: 50 parts RAP fines, 0.3 parts warm-mix recycling agent, 20 parts limestone crushed stone, 28 parts stone chips, 2 parts mineral powder, and 2.6 parts SBS modified asphalt. The RAP fine aggregate includes a first RAP fine aggregate with a particle size greater than 0 mm and less than or equal to 3 mm and an asphalt content of 10%, and a second RAP fine aggregate with a particle size greater than 3 mm and less than or equal to 5 mm and an asphalt content of 3.5%; the mass ratio of the first RAP fine aggregate to the second RAP fine aggregate is 78:22. The warm-mix regenerator comprises furfural extract oil, epoxidized soybean oil, modifier, octadecylamine polyoxyethylene ether, and surfactant in a mass ratio of 60:15:5:5:15; the modifier is selected from maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin in a mass ratio of 64:36; the surfactant is selected from pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide, and diglyceride fatty acid ester in a mass ratio of 50:33:17.

[0043] The above-mentioned high RAP content warm-mix recycled asphalt sand is prepared by the following method: the RAP fine aggregate is preheated to 120°C and put into the mixing pot. Then, the warm recycling agent is evenly sprayed into the mixing pot and stirred evenly. The coarse aggregate and fine aggregate are preheated to 170°C and put into the mixing pot and stirred evenly. Then, SBS modified asphalt is added and mixed. Finally, mineral powder is added and mixed. The mixing temperature is controlled at about 145°C and the molding temperature is controlled at about 135°C to obtain the high RAP content warm-mix recycled asphalt sand.

[0044] Example 2 A warm-mix recycled asphalt sand with high RAP content comprises the following raw materials by weight: 60 parts RAP fines, 0.37 parts warm-mix recycling agent, 15 parts limestone crushed stone, 23 parts stone chips, 2 parts mineral powder, and 2 parts SBS modified asphalt. The RAP fine aggregate includes a first RAP fine aggregate with a particle size greater than 0 mm and less than or equal to 3 mm and an asphalt content of 10%, and a second RAP fine aggregate with a particle size greater than 3 mm and less than or equal to 5 mm and an asphalt content of 2.5%; the mass ratio of the first RAP fine aggregate to the second RAP fine aggregate is 73:27. The warm-mix regenerator comprises furfural extract oil, diisodecyl phthalate, modifier, octadecylamine polyoxyethylene ether, and surfactant in a mass ratio of 62:15:5:3:15; the modifier is selected from maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin in a mass ratio of 70:30; the surfactant is selected from pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide, and diglyceride fatty acid ester in a mass ratio of 60:25:15.

[0045] The above-mentioned high RAP content warm-mix recycled asphalt sand is prepared by the following method: the RAP fine aggregate is preheated to 120°C and put into the mixing pot. Then, the warm recycling agent is evenly sprayed into the mixing pot and stirred evenly. The coarse aggregate and fine aggregate are preheated to 170°C and put into the mixing pot and stirred evenly. Then, SBS modified asphalt is added and mixed. Finally, mineral powder is added and mixed to obtain the high RAP content warm-mix recycled asphalt sand.

[0046] Example 3 A warm-mix recycled asphalt sand with high RAP content comprises the following raw materials by weight: 70 parts RAP fines, 0.5 parts warm-mix recycling agent, 10 parts limestone crushed stone, 18 parts stone chips, 3 parts mineral powder, and 1.4 parts SBS modified asphalt. The RAP fine aggregate includes a first RAP fine aggregate with a particle size greater than 0 mm and less than or equal to 3 mm and an asphalt content of 9%, and a second RAP fine aggregate with a particle size greater than 3 mm and less than or equal to 5 mm and an asphalt content of 3.5%; the mass ratio of the first RAP fine aggregate to the second RAP fine aggregate is 70:30. The warm-mix regenerator comprises furfural extract oil, diisodecyl phthalate, a modifier, octadecylamine polyoxyethylene ether, and a surfactant in a mass ratio of 65:10:2:3:20; the modifier is selected from maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin in a mass ratio of 64:36; the surfactant is selected from pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide, and monoglyceride fatty acid ester in a mass ratio of 60:25:15.

[0047] The above-mentioned high RAP content warm-mix recycled asphalt sand is prepared by the following method: the RAP fine aggregate is preheated to 130°C and put into the mixing pot. Then the warm recycling agent is evenly sprayed into the mixing pot and stirred evenly. The coarse aggregate and fine aggregate are preheated to 180°C and put into the mixing pot and stirred evenly. Then SBS modified asphalt is added and mixed. Finally, mineral powder is added and mixed to obtain the high RAP content warm-mix recycled asphalt sand.

[0048] Example 4 The difference from Example 1 is that the plasticizer in the warm-mix regenerator includes diisodecyl phthalate and epoxidized soybean oil in a mass ratio of 60:40, while the total amount of plasticizer remains unchanged.

[0049] Example 5 The difference from Example 1 is that the plasticizer in the warm-mix regenerator includes diisodecyl phthalate and epoxidized soybean oil in a mass ratio of 70:30, while the total amount of plasticizer remains unchanged.

[0050] Example 6 The difference from Example 1 is that the modifier in the warm-mix regenerator is only maleic anhydride-grafted ethylene-octene copolymer, and the total amount of modifier remains unchanged.

[0051] Example 7 The difference from Example 1 is that the modifier in the warm-mix recycling agent is replaced with an equal amount of styrene-butadiene rubber.

[0052] Example 8 The difference from Example 1 is that the surfactant in the warm-stir regenerator consists only of pentaerythritol stearate and diglyceride fatty acid ester.

[0053] Example 9 The difference from Example 1 is that the surfactant in the warm-stir regenerator is only PPG-2 hydroxyethyl cocoamide and fatty acid glycerides.

[0054] Example 10 The difference from Example 1 is that the surfactant in the warm-stir regenerator is replaced with undecyl glucoside, petroleum sulfonate (HAPS), alkylbenzene polyoxyethylene ether (NP-4), and triglyceride fatty acid ester in a mass ratio of 4:3:1:2.

[0055] Comparative Example 1 The difference from Example 1 is that the amount of warm-mix regenerator added is 0.6 parts.

[0056] Comparative Example 2 The difference from Example 1 is that no warm-mix regenerator is added.

[0057] Comparative Example 3 The difference from Example 1 is that the mass ratio of the first RAP fines to the second RAP fines in the RAP fines is 65:35, while the total amount of RAP fines remains unchanged.

[0058] Comparative Example 4 The difference from Example 1 is that the RAP fines are only the first RAP fines, and the total amount of RAP fines remains unchanged.

[0059] Comparative Example 5 The difference from Example 1 is that the RAP fines are only the second RAP fines, while the total amount of RAP fines remains unchanged.

[0060] Comparative Example 6 The difference from Example 1 is that the mixing temperature is controlled at 175°C and the molding temperature is controlled at 165°C.

[0061] Experimental Example 1 The properties of the warm-mix recycled asphalt sand in the above examples and comparative examples were determined according to the conventional method of "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" JTG 3410-2025. The test results are shown in Table 1 below.

[0062] Table 1. Properties of Warm-Mix Recycled Asphalt Sand

[0063] As shown in the table, the warm-mixed recycled sand prepared in Examples 1-5 exhibits excellent high-temperature stability, low-temperature crack resistance, and water stability, and all indicators meet the usage standards. In Comparative Example 6, the mixing temperature and molding temperature increased, but the performance of the resulting warm-mixed recycled sand decreased, indicating that the mixing temperature and molding temperature of the warm-mixed recycled sand in this application decreased by 20-30℃.

[0064] Compared to Example 1, no warm-mix regenerator was added in Comparative Example 2, while an excessive amount of warm-mix regenerator was added in Comparative Example 1, resulting in a decrease in various properties of the warm-mix regenerated sand. This demonstrates that the addition of warm-mix regenerator can ensure the performance of the warm-mix regenerated sand.

[0065] Compared to Example 1, the high-temperature stability of RAP fines in Comparative Examples 3-5 was significantly reduced when the ratio of the two specifications of fines was changed or only one type of fines was used. This shows that the combination of two RAP fines with specific parameters can ensure the high-temperature deformation capability of the mixture.

[0066] In addition, in Examples 6 and 7, only one modifier was used, and the freeze-thaw splitting strength ratio and other water stability indicators of the resulting warm-mixed recycled sand decreased. This indicates that the present application selects a specific modifier, which can enhance the high-temperature dynamic stability of the mixture and synergistically improve the freeze-thaw splitting strength ratio and other water stability indicators.

[0067] In Examples 8-10, the surfactant composition was changed, and the low-temperature crack resistance and water stability of the resulting warm-mixed recycled sand decreased. This shows that the addition of specific surfactants in this application can synergistically improve the low-temperature crack resistance and water stability of the mixture.

[0068] In summary, this application increases the amount of RAP by using warm-mix recycling agent and RAP fines in stages, reduces the construction temperature by 20-30℃, saves 30-35% of the project cost, and improves the high-temperature stability, low-temperature crack resistance and water stability of the product.

[0069] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, this application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope of this application should be within the protection scope of this application.

Claims

1. A warm-mix recycled asphalt sand with high RAP content, characterized in that, By weight, it includes the following raw materials: 50-70 parts of RAP fine aggregate, 0.3-0.5 parts of warm mix recycling agent, 10-20 parts of coarse aggregate, 18-28 parts of fine aggregate, 2-3 parts of filler, and 1.4-2.6 parts of SBS modified bitumen; The RAP fines include a first RAP fine with a particle size greater than 0 mm and less than or equal to 3 mm, and a second RAP fine with a particle size greater than 3 mm and less than or equal to 5 mm; the mass ratio of the first RAP fines to the second RAP fines is (70-78):(22-30). The warm-mix regenerator comprises base oil, plasticizer, modifier, anti-stripping agent and surfactant in a mass ratio of (60-65):(10-15):(2-5):(3-5):(15-20).

2. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The first RAP fine aggregate has an asphalt content of 9-11%, and the second RAP fine aggregate has an asphalt content of 2.5-3.5%.

3. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The filler is selected from at least one of mineral powder, limestone powder, fly ash, steel slag powder, and diatomaceous earth.

4. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The base oil is an aromatic oil or furfural extract oil.

5. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The plasticizer is selected from at least one of epoxidized soybean oil, hydrogenated castor oil, tall oil, pine tar, and diisodecyl phthalate. Preferably, the plasticizer is selected from diisodecyl phthalate and epoxidized soybean oil in a mass ratio of (60-70):(30-40).

6. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The modifier is selected from maleic anhydride-grafted ethylene-octene copolymer and alicyclic epoxy resin in a mass ratio of (64-70):(30-36).

7. The warm-mix recycled asphalt sand with high RAP content according to claim 1, characterized in that, The surfactant is selected from pentaerythritol stearate, PPG-2 hydroxyethyl cocoamide and fatty acid glycerides in a mass ratio of 50-60):(25-33):(15-17).

8. The warm-mix recycled asphalt sand with high RAP content according to claim 7, characterized in that, The coarse aggregate is limestone crushed stone with a particle size greater than 3 mm and less than or equal to 5 mm; the fine aggregate is stone chips or manufactured sand with a particle size greater than 0 and less than or equal to 3 mm.

9. The high RAP content warm-mix recycled asphalt sand according to any one of claims 1-8, characterized in that, The total asphalt content is in the range of 6.5% to 7.5%.

10. The method for preparing warm-mix recycled asphalt sand with high RAP content according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Preheat the RAP fines to 120-130°C, put them into the mixing pot, and then evenly spray the warm regenerator into the mixing pot and stir evenly. S2. After preheating the coarse and fine aggregates to 170-180℃, put them into the mixing pot and stir evenly. Then add SBS modified asphalt and mix. Finally, add mineral powder and mix to obtain warm-mix recycled asphalt sand with high RAP content.

Images