High-dosage RAP low-temperature hot mix plant recycled SMA-13 asphalt mixture and preparation process thereof

Abstract

The invention belongs to the technical field of asphalt mixtures, and relates to a high-dosage RAP low-temperature hot mix plant recycled SMA-13 asphalt mixture and a preparation process thereof, and the low-temperature hot mix plant recycled SMA-13 asphalt mixture comprises the following components by weight: 50-60 parts of an asphalt mixture reclaimed material; 30-40 parts of modified steel slag aggregate; 3-5 parts of SBS modified asphalt; 0.02 to 0.06 part of a low-temperature asphalt modifier; 3-8 parts of superfine slag powder; 0.2 to 0.5 part of lignin fiber; and 1-2 parts of a self-made asphalt regenerant. The limitation of the traditional RAP doping amount is broken through, the highest doping amount reaches 70%, the steel slag recycled aggregate replaces natural aggregate, the consumption of raw materials and the emission of waste are remarkably reduced, and the steel slag recycled aggregate meets the target requirements of the new era of dual-carbon strategy and sustainable development; and the method is particularly suitable for winter construction, heavy traffic roads and green road construction in iron and steel industry areas, and has technical advancement and engineering practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of asphalt mixtures and relates to a high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture and a preparation process thereof. Background Art

[0002] As the country pays more attention to energy conservation, emission reduction and recycled materials, recycled asphalt pavement (RAP) has been increasingly used as an increasingly important recycled material in the transportation industry.

[0003] Research shows that compared with asphalt pavement paved with new materials, when recycled pavement is used, when the RAP content reaches 20% to 50%, the total project cost can be reduced by 14% to 50%; at present, domestic research on recycled materials of low-RAP plant-mixed hot asphalt mixtures is relatively comprehensive, and has been put into practice in many engineering projects. The utilization rate is generally less than 30%, and the utilization rate of old materials is low; and for the application of recycled materials of plant-mixed hot asphalt mixtures with a RAP content greater than 30%, it is found that the conventional regeneration temperature requires 160 to 180°C, which has high energy consumption and further aggravates aging; the interface between new and old materials is poorly integrated, and water damage and fatigue cracking are prone to occur, especially when the content of recycled materials in the asphalt mixture is too high, which will lead to a decrease in the low-temperature crack resistance and water damage resistance of the mixture; and if the content is too low, the old asphalt pavement material cannot be fully utilized, which increases maintenance costs.

[0004] At the same time, steel slag is a by-product of the metallurgical industry. It has high hardness and high compressive strength (usually higher than natural stone), which can significantly improve the rutting resistance of asphalt mixtures and is particularly suitable for heavy-load traffic roads. Steel slag particles are angular and rough on the surface, and have strong adhesion to asphalt, which can enhance the internal friction and shear resistance of the mixture and reduce the risk of aggregate stripping. In addition, as an aggregate, it can reduce the mining of natural stone, reduce environmental damage, and conform to the concept of a circular economy. Therefore, the purpose of this study was to study the regeneration effect of recycled materials in hot asphalt mixtures mixed at high RAP dosages. The determination of the reasonable dosage and road performance of recycled materials and steel slag aggregates in asphalt mixtures is of great significance for optimizing the mix design of recycled materials in low-temperature hot asphalt mixtures mixed at low temperatures and improving the quality of road maintenance. Summary of the Invention

[0005] In response to the deficiencies in the above-mentioned prior art, the present invention provides a high-volume RAP low-temperature plant-mixed hot-recycled SMA-13 asphalt mixture and a preparation process thereof. The present invention can fully utilize the properties of recycled asphalt mixture (RAP) and steel slag aggregate to improve the comprehensive performance of plant-mixed hot-recycled SMA-13 (Stone Mastic Asphalt or Stone Matrix Asphalt, with a maximum nominal particle size of 13 mm) asphalt mixture. The specific technical solution is as follows:

[0006] The first object of the present invention is to provide a high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture, comprising the following components in parts by weight:

[0007] 50-60 parts of recycled asphalt mixture (RAP); 30-40 parts of modified steel slag aggregate; 3-5 parts of SBS modified asphalt; 0.02-0.06 parts of low-temperature asphalt modifier; 3-8 parts of slag powder; 0.2-0.5 parts of lignin fiber; 1-2 parts of homemade asphalt regeneration agent;

[0008] The modified steel slag aggregate is prepared by soaking the steel slag aggregate in a phosphoric acid solution and spraying a silane coupling agent after the surface is dried;

[0009] The self-made asphalt regeneration agent comprises the following components in parts by weight:

[0010] 52-60 parts of naphthenic oil; 10-20 parts of SBS rubber powder; 3-8 parts of tall oil fatty acid; 2-7 parts of silane coupling agent; 1-3 parts of antioxidant; 0.3-0.5 parts of anti-stripping agent; 10-15 parts of plasticizer; 4-7 parts of silica sol.

[0011] The present invention uses SMA-13 asphalt mixture recycled material with no less than 50% recycled asphalt mixture, and as the amount of recycled asphalt mixture increases, the high-temperature performance of the SMA-13 asphalt mixture recycled material improves. This is because the aged asphalt film in the RAP wraps around the aggregate, providing a certain initial strength. After the asphalt ages, the internal molecular structure changes, the light components evaporate, the heavy components increase, and the asphalt becomes brittle and hard. At the same time, the asphalt mixture recycled material has good angularity. When the aged asphalt in the asphalt mixture recycled material is mixed and recycled with new modified steel slag aggregate, this aggregate combination increases the stiffness modulus of the asphalt mixture recycled material. Therefore, increasing the amount of recycled asphalt mixture recycled material significantly improves the high-temperature rutting resistance of the asphalt mixture recycled material, making it more suitable for use in the high-temperature regions of southern my country.

[0012] The present invention adopts modified steel slag recycled aggregate. The steel slag aggregate not only has excellent angularity, but also has better rutting resistance than natural aggregate. The high hardness of the steel slag aggregate (crushing value ≤ 15%) makes up for the defect that the roughness decreases with the increase of RAP particle size and dosage. The porosity of the surface has good adsorption properties for asphalt. Moreover, the modified steel slag solves the contradiction that the steel slag aggregate is easy to expand when it comes into contact with water. The silane coupling agent sprayed on the surface further enhances the bonding effect between the steel slag and the asphalt, and the adsorption capacity and coating capacity are stronger.

[0013] The present invention adopts a composite modification of a low-temperature asphalt modifier and an SBS modified asphalt, and cooperates with the light oil and plasticizer in the homemade asphalt regeneration agent to further improve the low-temperature plastic penetration of the mixture into the aged asphalt, restore the colloidal structure, and further improve the road performance of the asphalt mixture recycling material. It also reduces the mixing and compaction temperature of the recycled mixture, and reduces the construction temperature to 120-135°C, which is above 160°C compared to the conventional hot regeneration mixing temperature, thereby reducing energy consumption, reducing pollution emissions, and the risk of accelerated aging of asphalt. The present invention uses SBS modified asphalt to achieve a balance of high and low temperature performance of the asphalt mixture recycling material. This is because the SBS elastic network can not only improve the crack resistance of the asphalt mixture recycling material (-20°C bending strain ≥ 2500με), but also improve the rutting resistance of the asphalt mixture recycling material (dynamic stability ≥ 4000 times / mm); in addition, the low-temperature SBS modified asphalt has enhanced adhesion, further improving its chemical bonding with the surface modification layer of the steel slag aggregate.

[0014] The present invention utilizes a self-made asphalt regeneration agent, which is compounded and synergistically modified with low-temperature SBS modified asphalt to improve the high-temperature and low-temperature performance, water stability, and freeze-thaw resistance of the recycled asphalt mixture. The naphthenic oil incorporated into the self-made asphalt regeneration agent has strong solubility, penetrating aged asphalt and restoring its rheological properties. Simultaneously, the polymer synergistically modifies the SBS rubber powder, providing elasticity and enhancing crack resistance. The plasticizer, in conjunction with the naphthenic oil and SBS rubber powder, lowers the mixture's low-temperature brittle point (below -20°C). Meanwhile, the nanosilica in the silica sol enhances high-temperature stability, specifically anti-rutting performance, achieving a balance between low-temperature and long-lasting properties. Tall oil fatty acids and silane coupling agents strengthen the low-temperature SBS composite modified asphalt coating, improving the adhesion between steel slag and asphalt and significantly reducing water damage.

[0015] Furthermore, the high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0016] 55 parts of recycled asphalt mixture (RAP); 35 parts of modified steel slag aggregate; 3.5 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.16 parts of homemade asphalt regeneration agent.

[0017] Furthermore, the recycled asphalt mixture (RAP) comprises the following components in parts by weight:

[0018] 55-65 parts of recycled asphalt mixture with a particle size of 5mm-10mm; 10-20 parts of recycled asphalt mixture with a particle size of 3mm-5mm; 20-30 parts of recycled asphalt mixture with a particle size less than 3mm.

[0019] The recycled asphalt mixture (RAP) is crushed and screened by physical collision using oilstone separation technology, and the particle sizes are selected into three grades: 5mm-10mm, 3mm-5mm, and 0mm-3mm.

[0020] Regarding the particle size range of each level of 5mm-10mm, 3mm-5mm, and 0mm-3mm, the minimum end value is not included in the range, and the maximum end value is included in the range.

[0021] Furthermore, the preparation method of the modified steel slag aggregate comprises the following steps:

[0022] A1: The steel slag aggregate after magnetic separation is further crushed and sieved to target particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm.

[0023] A2: Soak steel slag aggregates with particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm in 3%-6% phosphoric acid solution for 20-30 hours respectively;

[0024] A3: After soaking, the ingredients with four particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm are dried naturally or in a forced air drying oven until surface dry;

[0025] A4: Dilute the surface-dried particles of four grades (10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm) with a silane coupling agent at a ratio of 0.5%-1.5% and spray them onto the surface of the steel slag. The total amount of the silane coupling agent accounts for 3-5% of the weight of the steel slag. After turning and spraying 2-3 times, the modified steel slag aggregate is obtained.

[0026] Furthermore, the steel slag aggregate in A2 comprises the following components in parts by weight:

[0027] 50-60 parts of steel slag aggregate with a particle size of 10mm-15mm; 15-25 parts of steel slag aggregate with a particle size of 5mm-10mm; 10-20 parts of steel slag aggregate with a particle size of 3mm-5mm; 10-20 parts of steel slag aggregate with a particle size of 0mm-3mm.

[0028] Regarding the particle size range of each level of 10mm~16mm, 5mm~10mm, 3mm~5mm, and 0mm~3mm, the minimum end value is not included in the range, and the maximum end value is included in the range.

[0029] Furthermore, the preparation method of the homemade asphalt regeneration agent comprises the following steps:

[0030] B1: SBS rubber powder is passed through a 40-mesh sieve to remove impurities and preheated to 50-70°C. The pH value of the silica sol is adjusted to 8-10 with aqueous ammonia. The naphthenic oil is dehydrated to a moisture content of ≤0.1%, which is achieved by heating to 105°C ± 5°C using a modified asphalt mixing plant and stirring for 20-50 minutes.

[0031] B2: Add cyclohexane oil to a reactor containing an inert gas shielding atmosphere and heat to 80-90°C; slowly add SBS rubber powder, maintain the temperature at 90-100°C, and stir for 1-2 hours until the particles are completely dissolved to form a homogeneous solution.

[0032] B3: Cool solution 1 to 70-80°C, add tall oil fatty acid and silane coupling agent in sequence, and stir for 15-30 minutes; then add antioxidant and anti-stripping agent, and stir for 30-50 minutes to obtain solution 2;

[0033] B4: Cool the second solution to 50-60°C, slowly add silica sol and plasticizer, and stir at a speed of 3000-5000 rpm for 20-30 minutes until uniformly dispersed to obtain the homemade asphalt regeneration agent; seal it in a dark glass bottle for later use.

[0034] The prepared homemade asphalt regeneration agent has the following characteristics: viscosity 200-500 mPa·s (25°C, Brookfield viscometer); flash point: ≥180°C (Cleveland open cup method); softening point difference after mixing with aged asphalt is ≤2.5°C (ring and ball method).

[0035] Furthermore, the inert gas shielding gas is one or more of nitrogen, argon or helium.

[0036] Furthermore, the silane coupling agent is one or more of KH-550, KH-560 or KH-570.

[0037] Furthermore, the antioxidant is one or both of octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate or pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; the anti-stripping agent is the SA-3 asphalt anti-stripping agent produced by Jiangsu Subote New Materials Co., Ltd.; and the plasticizer is dioctyl phthalate (DOP).

[0038] Furthermore, the SBS modified asphalt can be commercially available.

[0039] Furthermore, the density of the low-temperature asphalt modifier is 0.94-0.98 g / mm 3 , flash point 180 ~ 220 ℃, ash content <1.0; such as the USP-H low temperature asphalt modifier produced by Shandong Road Star New Materials Co., Ltd.

[0040] Furthermore, the specific surface area of the slag powder is 400 to 500 m 2 / kg, such as the S95 or above grade blast furnace slag powder produced by Shandong LuBi Building Materials Co., Ltd.

[0041] Furthermore, the density of the lignin fiber is 1.5 g·cm -3 The oil absorption ratio is 5 to 9 times the fiber mass, and the ash content is 18±5, such as the loose flocculent wood fiber produced by Jiangsu Sheyang Siding Fiber Manufacturing Co., Ltd.

[0042] The second object of the present invention is to provide a process for preparing the above-mentioned high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture, comprising the following steps:

[0043] S1: Mixing dried recycled asphalt mixture (RAP), modified steel slag aggregate, and slag powder at a temperature of 120-130°C for 15-20 seconds until the aggregates are uniform and free of lumps to obtain a mixture;

[0044] S2: Heat the homemade asphalt regeneration agent to 60-70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 10-15 seconds;

[0045] S3: adding low-temperature SBS modified asphalt, stirring at a temperature of not less than 120°C, stirring for 20 to 30 seconds to ensure that the asphalt completely covers the aggregate; the preparation method of the low-temperature SBS modified asphalt is to premix the low-temperature modifier with the SBS modified asphalt, stirring at a temperature of 140 to 150°C, stirring for not less than 30 minutes, until the mixture is uniform, to obtain the low-temperature SBS modified asphalt;

[0046] S4: Add lignin fibers slowly and dispersedly to avoid clumping. The stirring temperature should not be lower than 120℃. Stir for 15 to 20 seconds until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain a large-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture.

[0047] Beneficial effects of the present invention:

[0048] The present invention provides a low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture recycled material with a RAP content of ≥50%. After testing, the following characteristics are achieved: the Marshall stability is up to 17.3 kN, the water-immersion Marshall residual stability is ≥90%, the dynamic stability (DS) is ≥5000 times / mm, and the highest reaches 8500 times / mm, the low-temperature bending strain is ≥3000 με, and the freeze-thaw splitting strength ratio (TSR) is ≥90%. The relevant indicators far exceed the corresponding technical requirements of SBS modified asphalt mixture in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0049] This invention breaks through the limitations of traditional RAP dosage (usually ≤30%), with the maximum dosage reaching 70%. Combined with steel slag recycled aggregate, it completely replaces natural aggregate, significantly reducing virgin material consumption and waste emissions, and is in line with the dual carbon strategy and sustainable development goals of the new era. It is particularly suitable for winter construction, heavy-load traffic roads and green road construction in steel industry areas, and has both technological advancement and engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a photo of the Marshall compaction specimen of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0052] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0053] Low-temperature asphalt modifier: USP-H low-temperature asphalt modifier produced by Shandong Road Star New Materials Co., Ltd., with a density of 0.94-0.98g / mm 3 , flash point 180~220℃, ash content <1.0.

[0054] Slag powder: Shandong Lubi Building Materials Co., Ltd. produces blast furnace slag powder of grade S95 or above, with a specific surface area of 400-500m 2 / kg.

[0055] Lignin fiber: loose flocculent wood fiber produced by Jiangsu Sheyang Siding Fiber Manufacturing Co., Ltd., with a density of 1.5g cm -3 The oil absorption rate is 5 to 9 times of the fiber mass, and the ash content is 18±5.

[0056] Anti-stripping agent: SA-3 asphalt anti-stripping agent produced by Jiangsu Subote New Materials Co., Ltd.;

[0057] Recycled Asphalt Mixture (RAP): Utilizing oilstone separation technology, the material is crushed and screened by physical collision, with particle sizes of 5mm-10mm, 3mm-5mm, and 0mm-3mm being selected. It includes the following components in parts by weight:

[0058] 60 parts of recycled asphalt mixture with a particle size of 5mm to 10mm; 15 parts of recycled asphalt mixture with a particle size of 3mm to 5mm; 25 parts of recycled asphalt mixture with a particle size of 0mm to 3mm.

[0059] The preparation method of modified steel slag aggregate comprises the following steps:

[0060] A1: The steel slag after magnetic separation is further crushed and sieved to target particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm for batching;

[0061] A2: Soak four grades of aggregate with particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm in 4% phosphoric acid solution for 24 hours to form a stable calcium phosphate or magnesium phosphate reinforced surface layer to block the expansion path; among them, 55 parts of steel slag aggregate with a particle size of 10mm-15mm; 20 parts of steel slag aggregate with a particle size of 5mm-10mm; 15 parts of steel slag aggregate with a particle size of 3mm-5mm; and 15 parts of steel slag aggregate with a particle size of 0mm-3mm.

[0062] A3: After soaking, the ingredients with four particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm are naturally air-dried until surface dry;

[0063] A4: Four grades of surface-dried steel slag with particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm are spread out separately. Silane coupling agent KH-550 is diluted by 1% and then sprayed on the surface of the steel slag. The total amount of silane coupling agent KH-550 accounts for 4% of the weight of the steel slag. After three turns and spraying, the modified steel slag aggregate is obtained.

[0064] The homemade asphalt regeneration agent includes the following components in parts by weight:

[0065] 57 parts of naphthenic oil; 15 parts of SBS rubber powder; 5 parts of tall oil fatty acid; 4 parts of silane coupling agent KH-550; 1.8 parts of Irganox 1010 hindered phenol antioxidant; 0.4 parts of anti-stripping agent; 12 parts of plasticizer dioctyl phthalate DOP; 4.8 parts of silica sol;

[0066] The preparation method of the self-made asphalt regeneration agent comprises the following steps:

[0067] B1: Raw material preparation:

[0068] ① Pass the SBS rubber powder through a 40-mesh sieve to remove impurities and preheat to 60°C;

[0069] ② Adjust the pH value of silica sol to 9 with ammonia water;

[0070] ③ Dehydrate the purchased naphthenic oil, heat it to 105°C using modified asphalt mixing equipment, and stir for 30 minutes until the moisture content is ≤0.1%;

[0071] B2: Add cyclohexane oil to a reactor containing an inert gas shielding atmosphere and heat to 85°C. Slowly add SBS rubber powder, maintain the temperature at 100°C, and stir at 200 rpm for 2 hours until the particles are completely dissolved to form a homogeneous solution.

[0072] B3: Cool solution 1 to 70°C, add tall oil fatty acid and silane coupling agent KH-550 in sequence, and stir for 20 minutes; then add antioxidant and anti-stripping agent, and stir for 40 minutes to obtain solution 2;

[0073] B4: Cool the second solution to 60°C, slowly add silica sol and plasticizer, and stir with a high-speed shearing machine at a speed of 3500 rpm for 30 minutes until uniformly dispersed to obtain the homemade asphalt regeneration agent;

[0074] After testing, the homemade asphalt regeneration agent meets the following indicators: viscosity 300mPa·s (25℃, Brookfield viscometer); flash point: ≥180℃ (Cleveland open cup method); softening point difference after mixing with aged asphalt ≤2.5℃ (ring and ball method); sealed in dark glass bottles for use.

[0075] The above substances were used in the following examples or comparative examples.

[0076] Example 1:

[0077] A high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0078] 55 parts of recycled asphalt mixture (RAP); 35 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.16 parts of homemade asphalt regeneration agent.

[0079] The preparation process of the high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following steps:

[0080] S1: Add dry RAP, modified steel slag aggregate, and slag powder into an asphalt mixture mixer and stir at a temperature of 120°C for 15 seconds until the aggregates are uniform and free of lumps to obtain a mixture;

[0081] S2: Heat the homemade asphalt regeneration agent to 70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 15 seconds;

[0082] S3: adding low-temperature SBS modified asphalt, stirring at a temperature of 125°C for 30 seconds to ensure that the asphalt completely covers the aggregate; the preparation method of the low-temperature SBS modified asphalt is to premix the low-temperature modifier with the SBS modified asphalt, stirring for 50 minutes at a stirring temperature of 145°C until the mixture is uniform, thereby obtaining the low-temperature SBS modified asphalt;

[0083] S4: Add lignin fibers slowly and dispersedly to avoid clumping. The stirring temperature is 125℃ and stirring is carried out for 20s until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain a large amount of RAP low-temperature factory-mixed hot recycled SMA-13 asphalt mixture.

[0084] The method for preparing a Marshall compaction specimen of a low-temperature plant-mixed hot-recycled SMA-13 asphalt mixture comprises the following steps:

[0085] G1: Mold preparation: Heat the Marshall test mold (φ101.6mm×63.5mm) and the hammer to 110℃ and apply a small amount of glycerin release agent;

[0086] G2: Loading: Load the mixture in two batches, taking about 750g of the mixture each time, and tamping the mixture 15 times along the periphery and 10 times in the middle with a spatula to remove air bubbles;

[0087] G3: Compaction: Use double-sided compaction method, compacting 50 times on each side (standard Marshall compaction number, hammer weight 4.53kg, drop height 457mm); the height of the specimen after compaction should be 63.5mm±1.3mm, otherwise adjust the material amount;

[0088] G4: Demolding: After compaction, use a demoulder to push out the specimen while it is still hot to avoid deformation;

[0089] G5: Specimen curing and storage: The specimens should be left at room temperature for 24 hours, out of direct sunlight, and cooled to room temperature; the specimen number, mix ratio and molding date should be marked.

[0090] The RAP content of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture prepared in this embodiment is 55%, and the Marshall compaction specimens prepared are as follows: Figure 1 As shown; after testing, its Marshall stability is 15.7kN, the immersion Marshall residual stability is 92.5%, the dynamic stability (DS) is 7500 times / mm, the low-temperature bending strain is 3455με, and the freeze-thaw splitting strength ratio (TSR) is 92.3%. The relevant indicators all exceed the corresponding technical requirements of SBS modified asphalt mixture in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0091] Example 2:

[0092] A high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0093] 60 parts of recycled asphalt mixture (RAP); 30 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.16 parts of homemade asphalt regeneration agent.

[0094] The preparation method of the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture and the preparation method of the Marshall compaction specimen are the same as those in Example 1 and will not be repeated here.

[0095] Compared to Example 1, this example uses the same total aggregate content, but increases the amount of recycled asphalt mixture (RAP) to 60 parts, reduces the amount of modified steel slag aggregate to 30 parts, and maintains the remaining components and their mass fractions. Testing of the above mixture specimens revealed a Marshall stability of 15.3 kN, a water-immersion Marshall residual stability of 87.5%, a dynamic stability (DS) of 5500 times / mm, a low-temperature bending strain of 3010 με, and a freeze-thaw splitting strength ratio (TSR) of 90.3%. These indicators still exceed the corresponding technical requirements for SBS-modified asphalt mixtures in the "Technical Specification for Highway Asphalt Pavement Construction" (JTGF40-2004). This indicates that even at a high RAP utilization rate of 60%, the specification requirements are still met, demonstrating that the addition of low-temperature SBS-modified asphalt and a regeneration agent can effectively restore the performance of aged asphalt.

[0096] Example 3:

[0097] A high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0098] 50 parts of recycled asphalt mixture (RAP); 36 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 8 parts of slag powder; 0.3 parts of lignin fiber; 1.66 parts of homemade asphalt regeneration agent.

[0099] The preparation method of the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture and the preparation method of the Marshall compaction specimen are the same as those in Example 1 and will not be repeated here.

[0100] Compared to Example 1, this example reduced the amount of recycled asphalt mixture (RAP) to 50 parts, increased the amount of modified steel slag aggregate to 36 parts, and increased the amount of slag powder to 8 parts, appropriately increasing the dosage of the homemade asphalt regeneration agent. Testing of the above mixture specimens revealed a Marshall stability of 17.3 kN, a water-immersion Marshall residual stability of 94.0%, a dynamic stability (DS) of 8500 times / mm, a low-temperature bending strain of 3100 με, and a freeze-thaw splitting strength ratio (TSR) of 95.0%. These indicators all exceed the corresponding technical requirements for SBS modified asphalt mixtures in the "Technical Specification for Highway Asphalt Pavement Construction" (JTGF40-2004). It can be seen that at a RAP utilization rate of 50%, the slag powder filling effect improves density, with a Marshall stability of 17.3 kN and a record dynamic stability of 8500 times / mm. Low-temperature performance is slightly reduced, but still meets the requirements of the specification. Therefore, the high and low temperature requirements should be balanced according to the material properties and road load level.

[0101] Example 4:

[0102] A high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0103] 55 parts of recycled asphalt mixture (RAP); 35 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 0.06 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.64 parts of homemade asphalt regeneration agent.

[0104] The stirring temperature in S4 of the method for preparing the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture is 120°C.

[0105] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0106] Compared to Example 1, this example increased the low-temperature asphalt modifier to 0.06 parts, and appropriately reduced the dosage of the homemade asphalt rejuvenator. The stirring temperature in S4 was lowered to 120°C. Testing of the above mixture specimens revealed a Marshall stability of 16.1 kN, a water-immersion Marshall residual stability of 90.9%, a dynamic stability (DS) of 5300 times / mm, a low-temperature bending strain of 3560 με, and a freeze-thaw splitting strength ratio (TSR) of 91.5%. These indicators all exceeded the corresponding technical requirements for SBS-modified asphalt mixtures in the "Technical Specification for Highway Asphalt Pavement Construction" (JTGF40-2004). This example demonstrates the feasibility of low-temperature construction, namely, mixing at 120°C still met all the requirements.

[0107] Example 5:

[0108] A high-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture comprises the following components in parts by weight:

[0109] 55 parts of recycled asphalt mixture (RAP); 36 parts of modified steel slag aggregate; 3.0 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4 parts of slag micropowder; 0.3 parts of lignin fiber; 1.66 parts of homemade asphalt regeneration agent.

[0110] The preparation method of the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture and the preparation method of the Marshall compaction specimen are the same as those in Example 1 and will not be repeated here.

[0111] Compared to Example 1, this example reduced the amount of SBS modified asphalt to 3 parts, the amount of slag powder to 4 parts, and the amount of modified steel slag aggregate to 36 parts. Testing of the above mixture specimens revealed a Marshall stability of 15.1 kN, a water-immersion Marshall residual stability of 91.2%, a dynamic stability (DS) of 5500 times / mm, a low-temperature bending strain of 3100 με, and a freeze-thaw splitting strength ratio (TSR) of 92.7%. These indicators all exceed the technical requirements for SBS modified asphalt mixtures in the Technical Specifications for Highway Asphalt Pavement Construction (JTGF40-2004). This example demonstrates that the elastic network of SBS modified asphalt plays a crucial role in improving the mechanical properties of recycled asphalt mixtures.

[0112] Comparative Example 1:

[0113] A low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following components in parts by weight:

[0114] 55 parts of recycled asphalt mixture (RAP); 35 parts of basalt aggregate; 4 parts of SBS modified asphalt; 4.5 parts of slag powder; 0.3 parts of lignin fiber; 1.2 parts of homemade asphalt regeneration agent;

[0115] The basalt aggregate comprises the following components in parts by weight: 18.3 parts of basalt aggregate with a particle size of 10mm to 15mm; 6.7 parts of basalt aggregate with a particle size of 5mm to 10mm; 5 parts of basalt aggregate with a particle size of 3mm to 5mm; and 5 parts of basalt aggregate with a particle size of 0mm to 3mm.

[0116] The preparation process of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following steps:

[0117] S1: Add dry RAP, basalt aggregate, and slag powder into an asphalt mixture mixer and stir at a temperature of 173°C for 15 seconds until the aggregates are uniform and free of lumps to obtain a mixture;

[0118] S2: Heat the homemade asphalt regeneration agent to 70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 15 seconds;

[0119] S3: Add SBS modified asphalt, stirring at 168°C for 30 seconds to ensure that the asphalt completely covers the aggregate;

[0120] S4: Add lignin fibers slowly and dispersedly to avoid clumping. Stir at 168°C for 20 seconds until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture.

[0121] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0122] This comparative example is a low-temperature, factory-mixed, hot-recycled SMA-13 asphalt mixture commonly used on the market. Compared to Example 1, the modified steel slag aggregate is replaced with natural basalt aggregate, with the corresponding mass fractions remaining unchanged. No low-temperature asphalt modifier is added, and the remaining components and mass fractions remain unchanged. The mixing temperature of this comparative asphalt mixture is 173°C. Testing of the above mixture specimens showed a Marshall stability of 13.2 kN, a water-immersion Marshall residual stability of 79.3%, a dynamic stability (DS) of 3500 times / mm, a low-temperature bending strain of 3200 με, and a freeze-thaw splitting strength ratio (TSR) of 73.9%. Compared with Example 1, the RAP asphalt exhibits significant secondary aging due to high-temperature mixing, resulting in significant performance degradation, especially a significant decrease in the freeze-thaw splitting strength ratio (TSR).

[0123] Comparative Example 2:

[0124] A low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following components in parts by weight:

[0125] 55 parts of recycled asphalt mixture (RAP); 35 parts of unmodified steel slag aggregate; 4 parts of SBS modified asphalt; 4.5 parts of slag powder; 0.04 parts of low-temperature asphalt modifier; 0.3 parts of lignin fiber; 1.2 parts of asphalt regeneration agent (HR-R series produced by Shandong Hi-Speed Huarui Road Materials Technology Co., Ltd.).

[0126] The unmodified steel slag aggregate comprises the following components in parts by weight: 55 parts of steel slag aggregate with a particle size of 10 mm to 15 mm; 20 parts of steel slag aggregate with a particle size of 5 mm to 10 mm; 15 parts of steel slag aggregate with a particle size of 3 mm to 5 mm; and 15 parts of steel slag aggregate with a particle size of 0 mm to 3 mm.

[0127] The preparation process of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following steps:

[0128] S1: Add dry RAP, unmodified steel slag aggregate, and slag powder into an asphalt mixture mixer and stir at a temperature of 173°C for 15 seconds until the aggregates are uniform and free of lumps to obtain a mixture;

[0129] S2: Heat the asphalt regeneration agent to 70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 15 seconds;

[0130] S3: adding low-temperature SBS modified asphalt, stirring at a temperature of 168°C for 20 to 30 seconds to ensure that the asphalt completely covers the aggregate; the preparation method of the low-temperature SBS modified asphalt is to premix the low-temperature modifier with the SBS modified asphalt, stirring for not less than 30 minutes at a stirring temperature of 145°C until the mixture is uniform, thereby obtaining the low-temperature SBS modified asphalt;

[0131] S4: Add lignin fibers slowly and dispersedly to avoid clumping. Stir at 168°C for 20 seconds until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture.

[0132] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0133] Compared to Example 1, this comparative example replaced the modified steel slag aggregate with unmodified steel slag aggregate, while retaining the remaining components, mass fractions, and processing techniques. Testing of the mixture specimens revealed a Marshall stability of 12.5 kN, a water-immersion Marshall residual stability of 82%, a dynamic stability (DS) of 4500 times / mm, a low-temperature bending strain of 2600 με, and a freeze-thaw splitting strength ratio (TSR) of 81.5%. Compared to Example 1, the unmodified steel slag aggregate exhibited poor adhesion to asphalt. When the RAP content was too high, the unmodified steel slag powder was unable to compensate for weak interfacial areas, resulting in insufficient water stability.

[0134] Comparative Example 3:

[0135] A low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following components in parts by weight:

[0136] 55 parts of recycled asphalt mixture (RAP); 35 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.16 parts of asphalt regeneration agent (HR-R series produced by Shandong Hi-Speed Huarui Road Materials Technology Co., Ltd.).

[0137] The preparation process of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following steps:

[0138] S1: Add dry RAP, modified steel slag aggregate, and slag powder into an asphalt mixture mixer and stir at a temperature of 175°C for 15 seconds until the aggregates are uniform and free of lumps to obtain a mixture;

[0139] S2: Heat the asphalt regeneration agent to 70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 15 seconds;

[0140] S3: Add SBS modified asphalt, stirring at 170°C for 30 seconds to ensure that the asphalt completely covers the aggregate;

[0141] S4: Add lignin fibers slowly and dispersedly to avoid clumping. Stir at 170°C for 20 seconds until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture.

[0142] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0143] Compared to Example 1, this comparative example omitted the addition of a low-temperature asphalt modifier and replaced the homemade asphalt rejuvenator with a commercially available asphalt rejuvenator. All other components and weight fractions remained unchanged. The asphalt mixture in this comparative example was mixed at a temperature of 175°C. Testing of the mixture specimens revealed a Marshall stability of 12.6 kN, a water-immersion Marshall residual stability of 77.6%, a dynamic stability (DS) of 3400 times / mm, a low-temperature bending strain of 2800 με, and a freeze-thaw splitting strength ratio (TSR) of 72.1%. Compared to Example 1, secondary aging of the RAP asphalt caused by high-temperature mixing, coupled with performance differences in the corresponding commercially available asphalt rejuvenator, resulted in an overall decline in the performance of the asphalt mixture specimens in this comparative example, with the Marshall stability, in particular, failing to meet regulatory requirements.

[0144] Comparative Example 4:

[0145] A low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following components in parts by weight:

[0146] 55 parts of recycled asphalt mixture (RAP); 33.66 parts of modified steel slag aggregate; 4 parts of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 2.5 parts of homemade asphalt regeneration agent.

[0147] The stirring temperature in S1 of the method for preparing the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture is 125°C.

[0148] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0149] Compared with Example 1, this comparative example increased the amount of the homemade asphalt regeneration agent to 2.5 parts, correspondingly reducing the amount of modified steel slag aggregate. The remaining components and mass fractions remained unchanged. The mixing temperature of the asphalt mixture in this comparative example was 125°C. Testing of the above mixture specimens revealed a Marshall stability of 11.2 kN, a water-immersion Marshall residual stability of 73.2%, a dynamic stability (DS) of 2800 times / mm, a low-temperature bending strain of 3260 με, and a freeze-thaw splitting strength ratio (TSR) of 62.1%. Compared with Example 1, the excessive amount of homemade regeneration agent (containing aromatic oil + activator) in Control 1 resulted in decreased high-temperature stability, and the Marshall stability also failed to meet regulatory requirements.

[0150] Comparative Example 5:

[0151] A low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture comprises the following components in parts by weight:

[0152] 55 parts of recycled asphalt mixture (RAP); 37.5 parts of modified steel slag aggregate; 1 part of SBS modified asphalt; 0.04 parts of low-temperature asphalt modifier; 4.5 parts of slag micropowder; 0.3 parts of lignin fiber; 1.66 parts of homemade asphalt regeneration agent.

[0153] The stirring temperature in S1 of the method for preparing the high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture is reduced to 125°C.

[0154] The preparation method of the Marshall compaction specimen is the same as that in Example 1 and will not be repeated here.

[0155] Compared to Example 1, this comparative example reduced the SBS modified asphalt content to 1 part, and increased the modified steel slag aggregate content accordingly. The remaining components and mass fractions remained unchanged. The mixing temperature of the comparative example asphalt mixture was 125°C. Testing of the above mixture specimens revealed a Marshall stability of 7.5 kN, a water-immersion Marshall residual stability of 53.1%, a dynamic stability (DS) of 2100 times / mm, a low-temperature flexural strain of 1360 με, and a freeze-thaw splitting strength ratio (TSR) of 45.2%. Compared to Example 1, Control 1, due to its insufficient SBS asphalt content, lacked a balanced high- and low-temperature performance. Furthermore, the high-temperature rutting resistance was insufficient when the SBS asphalt content was too low, and the remaining performance indicators also failed to meet regulatory requirements. This demonstrates that the amount of SBS modified asphalt should be appropriately controlled.

[0156] The performance test of the low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture of the present invention is based on the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011), and other indicators are tested and evaluated based on the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0157] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture, characterized by: It comprises the following components in parts by weight: 50-60 parts of recycled asphalt mixture; 30-40 parts of modified steel slag aggregate; 3-5 parts of SBS modified asphalt; 0.02-0.06 parts of low-temperature asphalt modifier; 3-8 parts of slag powder; 0.2-0.5 parts of lignin fiber; 1-2 parts of homemade asphalt regeneration agent; The modified steel slag aggregate is prepared by soaking the steel slag aggregate in a phosphoric acid solution and spraying a silane coupling agent after the surface is dried; The self-made asphalt regeneration agent comprises the following components in parts by weight: 52-60 parts of naphthenic oil; 10-20 parts of SBS rubber powder; 3-8 parts of tall oil fatty acid; 2-7 parts of silane coupling agent; 1-3 parts of antioxidant; 0.3-0.5 parts of anti-stripping agent; 10-15 parts of plasticizer; 4-7 parts of silica sol.

2. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The asphalt mixture recycled material comprises the following components in parts by weight: 55-65 parts of recycled asphalt mixture with a particle size of 5mm-10mm; 10-20 parts of recycled asphalt mixture with a particle size of 3mm-5mm; 20-30 parts of recycled asphalt mixture with a particle size less than 3mm.

3. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The preparation method of the modified steel slag aggregate comprises the following steps: A1: The steel slag aggregate after magnetic separation is further crushed and sieved to target particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm. A2: Soak steel slag aggregates with particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm in 3%-6% phosphoric acid solution for 20-30 hours respectively; A3: After soaking, the ingredients with four particle sizes of 10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm are dried naturally or in a forced air drying oven until surface dry; A4: Dilute the surface-dried particles of four grades (10mm-16mm, 5mm-10mm, 3mm-5mm, and 0mm-3mm) with a silane coupling agent at a ratio of 0.5%-1.5% and spray them onto the surface of the steel slag. The total amount of the silane coupling agent accounts for 3-5% of the weight of the steel slag. After 2-3 times of turning and spraying, the modified steel slag aggregate is obtained.

4. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 3 is characterized in that: The steel slag aggregate in A2 comprises the following components in parts by weight: 50-60 parts of steel slag aggregate with a particle size of 10mm-15mm; 15-25 parts of steel slag aggregate with a particle size of 5mm-10mm; 10-20 parts of steel slag aggregate with a particle size of 3mm-5mm; 10-20 parts of steel slag aggregate with a particle size of 0mm-3mm.

5. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The preparation method of the self-made asphalt regeneration agent comprises the following steps: B1: SBS rubber powder is passed through a 40-mesh sieve to remove impurities and preheated to 50-70°C; the pH value of the silica sol is adjusted to 8-10 with aqueous ammonia; and the naphthenic oil is dehydrated to a moisture content of ≤0.1%. B2: Add cyclohexane oil to a reactor containing an inert gas shielding atmosphere and heat to 80-90°C; slowly add SBS rubber powder, maintain the temperature at 90-100°C, and stir for 1-2 hours until the particles are completely dissolved to form a homogeneous solution. B3: Cool solution 1 to 70-80°C, add tall oil fatty acid and silane coupling agent in sequence, and stir for 15-30 minutes; then add antioxidant and anti-stripping agent, and stir for 30-50 minutes to obtain solution 2; B4: Cool the second solution to 50-60°C, slowly add silica sol and plasticizer, and stir at a speed of 3000-5000 rpm for 20-30 minutes until uniformly dispersed to obtain the homemade asphalt regeneration agent; seal it in a dark glass bottle for later use.

6. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 5 is characterized in that: The inert gas shielding gas is one or more of nitrogen, argon or helium.

7. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The silane coupling agent is one or more of KH-550, KH-560 or KH-570.

8. The high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The antioxidant is one or both of octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; the anti-stripping agent is the SA-3 asphalt anti-stripping agent produced by Jiangsu Subote New Materials Co., Ltd.; and the plasticizer is dioctyl phthalate.

9. The high-volume RAP low-temperature factory-mixed hot-regenerated SMA-13 asphalt mixture according to claim 1 is characterized in that: The density of the low-temperature asphalt modifier is 0.94-0.98 g / mm 3 , flash point 180~220℃, ash content <1.0; the specific surface area of the slag powder is 400~500m 2 / kg; the density of the lignin fiber is 1.5g·cm -3 The oil absorption rate is 5 to 9 times of the fiber mass, and the ash content is 18±5.

10. A process for preparing a high-volume RAP low-temperature plant-mixed hot-regenerated SMA-13 asphalt mixture according to any one of claims 1 to 9, characterized in that: The steps include: S1: Mix the dried asphalt mixture recycled material, modified steel slag aggregate, and slag powder at a temperature of 120-130°C for 15-20 seconds until the aggregate is uniform and free of lumps, thereby obtaining a mixture; S2: Heat the homemade asphalt regeneration agent to 60-70°C, spray it evenly into the mixture through an atomizing nozzle, and stir for 10-15 seconds; S3: adding low-temperature SBS modified asphalt, stirring at a temperature of not less than 120°C, stirring for 20 to 30 seconds to ensure that the asphalt completely covers the aggregate; the preparation method of the low-temperature SBS modified asphalt is to premix the low-temperature modifier with the SBS modified asphalt, stirring for not less than 30 minutes until the mixture is uniform, and stirring at a temperature of 140°C to 150°C to obtain the low-temperature SBS modified asphalt; S4: Add lignin fibers slowly and dispersedly to avoid clumping. The stirring temperature should not be lower than 120℃. Stir for 15 to 20 seconds until the fibers are evenly dispersed, the asphalt film is uniform, and there is no white material. This is to obtain a large-volume RAP low-temperature factory-mixed hot-recycled SMA-13 asphalt mixture.

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