Bio-asphalt synergistic recycling agent modified asphalt recycling fine aggregate and preparation method thereof

Abstract

The application discloses a kind of bio-asphalt synergistic modifier modified asphalt recycled fine aggregate and preparation method thereof.The modified asphalt recycled fine aggregate includes: 50-70% of recycled asphalt mixture after screening coarse aggregate;5-15% of new asphalt;1-3% of bio-asphalt;0.5-2.5% of multi-component recycling agent;15-25% of new fine aggregate;3-8% of mineral powder;when preparing, first, recycled asphalt mixture after screening coarse aggregate is mixed with bio-asphalt to carry out pre-coating, then mixed with other raw materials, and then stirred at 110-130 DEG C to obtain;Multi-component recycling agent is composed of tackifying resin 50-70%, viscosity reducer 10-20%, and anti-aging agent 20-40%.The preparation method of the application combines bio-asphalt low viscosity and low temperature mixing process, and cooperates with multi-component recycling agent through pre-coating technology, with the advantages of high regeneration efficiency, environmental protection, low carbon, stable fine aggregate grading and controllable cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of road engineering materials, and particularly relates to a bio-asphalt and synergistic recycling agent modified asphalt recycling fine aggregate and a preparation method thereof. BACKGROUND

[0002] Asphalt pavement recycling is a key technology for realizing the "double carbon" goal and resource recycling. Plant-mixed hot recycling has become the mainstream because it can efficiently utilize 30%-70% of recycled asphalt mixture (RAP). However, the traditional process faces multiple bottlenecks. The recycling agent (petroleum-based aromatic hydrocarbons) has poor compatibility (compatibility index ≤0.6) with aged asphalt due to high viscosity (135℃ viscosity 800 mPa·s-1200 mPa·s), and can only penetrate the surface layer (≤100 μm) of old materials, failing to repair the internal aging structure. High-temperature mixing at 150℃-170℃ aggravates the secondary aging of asphalt (penetration ratio ≤65%), and has high energy consumption (12 kg-15 kg of standard coal per ton of material), large VOCs emissions (120 mg / m 3 -200 mg / m 3 ), and poor water stability (immersed Marshall residual stability ≤75%) of fine aggregate (≤4.75 mm) due to high specific surface area "oil competition" leading to grading segregation (CV ≥8%). Although bio-asphalt (plant oil / animal fat / microbial oil) has the advantages of being renewable and having low viscosity (200 mPa·s-500 mPa·s), existing technologies have not developed the "carrier-supporting" synergistic mechanism of bio-asphalt and multi-component recycling agents, nor have they optimized the penetration and grading control for fine aggregate recycling. Under the background of "double carbon" policy driving (recycling utilization rate ≥70%, energy consumption reduction 20%) and upgrading of heavy traffic demand, it is urgent to break through the bottlenecks of traditional technology and develop new low-carbon and efficient fine aggregate recycling technology.

[0003] The asphalt pavement recycling technology mainly restores the performance of aged asphalt by adding a recycling agent. The Chinese patent application with publication number CN108976826A discloses a hot recycling composite recycling agent for asphalt pavement, which comprises 10-50% of palm oil, 5-10% of soybean oil, 5-10% of wood fiber, 5-15% of SBS particles and 10-80% of asphalt. The recycling agent can restore the aged asphalt to the original four-component ratio, and increase the fluidity and low-temperature crack resistance of the aged asphalt. The Chinese patent with publication number CN113698139B proposes a high-mixing RAP plant-mixed hot recycling modified asphalt mixture, which improves the utilization value and utilization rate of RAP through the dual performance improvement of aged asphalt and recycled modified asphalt mixture. The Chinese patent with publication number CN111518404B discloses an environmentally friendly warm-mixed asphalt recycling agent, which restores the performance of aged asphalt by using effective components such as bio-asphalt, and realizes the warm-mixed production of recycled asphalt mixture by enhancing the diffusion effect through epoxy soybean oil. The Chinese patent application with publication number CN118063973A proposes an environmentally friendly asphalt recycling agent, which comprises environmentally friendly aromatic oil, plasticizer, tackifier and other components, and has good recycling performance, and can be used for preparing recycled SBS modified asphalt and recycled SBS modified asphalt mixture. The Chinese patent application with publication number CN118562305A introduces a recycling agent for plant-mixed hot recycling, which comprises base oil, tackifier, anti-aging agent, easy-melting thermoplastic elastomer, etc., and can be compounded according to the road performance requirements of different road grades and different application layers. However, these existing technologies still have one or more of the following defects: (1) the recycling agents used are mostly petroleum-based aromatic hydrocarbons, which are easy to volatilize at high temperatures and produce a large amount of volatile organic compounds (VOCs), causing environmental pollution and having poor compatibility with aged asphalt, which is difficult to deeply penetrate and repair the microstructure of old materials; (2) in the process of plant-mixed hot recycling, fine aggregate (≤4.75mm) is easy to have the phenomenon of "competing for oil" with new asphalt due to its large specific surface area and strong adsorption, resulting in segregation of recycled mixture gradation and decrease of water stability, which affects the pavement performance; (3) in order to ensure the penetration of the recycling agent and the uniformity of the mixture, the traditional process usually needs to be mixed at a high temperature of 150℃-170℃, which not only has high energy consumption, but also easily causes secondary aging of asphalt, further reducing the durability of the mixture. Therefore, it is of great significance to develop a kind of asphalt recycling material that can overcome the above-mentioned defects of the existing technologies. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the deficiencies of the prior art, and to provide a bio-asphalt synergistic recycling agent modified asphalt recycling fine aggregate with environmental protection and low carbon, stable fine aggregate gradation and excellent road performance, and a preparation method thereof.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A kind of bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, raw material composition includes by mass percent: 50%~70% of recycled asphalt mixture after screening coarse aggregate;5%~15% of new asphalt;1%~3% of bio-asphalt;0.5%~2.5% of multi-component recycling agent;15~25% of new fine aggregate;3%~8% of mineral powder;When preparing, first mix the recycled asphalt mixture after screening coarse aggregate with bio-asphalt and mix pre-wrap, then mix with other raw materials and get after mixing at 110~130 DEG C;The multi-component recycling agent is composed of tackifying resin 50%~70%, viscosity reducer 10%~20%, anti-aging agent 20%~40%;The bio-asphalt is prepared by physical modification or chemical modification using renewable biomass resources as raw material, and the renewable biomass resources are at least one of vegetable oil, animal fat and microbial fermentation products.

[0007] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, the raw material composition further includes light stabilizer 0.1%~0.5%.

[0008] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, when the penetration of the recycled asphalt mixture after screening coarse aggregate is ≤20dmm, the amount of bio-asphalt is increased;When the penetration of the recycled asphalt mixture after screening coarse aggregate is ≥40dmm, the amount of bio-asphalt is reduced.

[0009] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, the tackifying resin uses at least one of C5 petroleum resin, C9 petroleum resin, rosin modified resin, coumarone-indene resin and terpene resin.

[0010] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, the viscosity reducer is naphthenic oil or vegetable oil-based mineral oil, and the vegetable oil-based mineral oil is a modified oil obtained by chemical modification of vegetable oil.

[0011] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, the anti-aging agent is 2,6-di-tert-butyl-p-cresol, thioester anti-aging agent or composite anti-aging agent, and the composite anti-aging agent is composed of hindered phenol and thioester.

[0012] The bio-asphalt cooperates with recycling agent modified asphalt recycled fine aggregate, preferably, the new fine aggregate is at least one of basalt stone chips, machine-made sand and stone chips;The mineral powder is limestone powder;The light stabilizer is hindered amine light stabilizer.

[0013] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the number average molecular weight of the C5 petroleum resin and the C9 petroleum resin is 500-1000.

[0014] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the rosin modified resin is esterified rosin resin, and contains ester groups and hydroxyl groups in the molecular structure, and the content of the ester groups is greater than or equal to 30%.

[0015] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the number average molecular weight of the coumarone-indene resin is 800-1500, the molecular chain contains double bonds, can react with the oxidation products of aged asphalt to form chemical bonds, and the compatibility index with gum and asphaltene of aged asphalt is greater than or equal to 0.85.

[0016] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the terpene resin takes alpha-pinene and / or beta-pinene as the main polymerization monomer, the content of alpha-pinene is greater than or equal to 60%, and the iodine value is 20 g-60 g I2 / 100 g.

[0017] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the content of naphthenes in the naphthenic oil is greater than or equal to 70%, the total content of saturated hydrocarbons is greater than or equal to 95%, the content of aromatic hydrocarbons is less than or equal to 3%, and the content of mechanical impurities is less than or equal to 0.01%.

[0018] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the molecule of the hindered phenol contains monophenol hydroxyl groups, at least one tert-butyl group is substituted at the ortho position of the phenol hydroxyl group, and the purity is greater than or equal to 98%; the thioester is a dithioester compound or a thio propionate compound, the purity is greater than or equal to 98%, and the mass percentage content of sulfur is 8%-15%.

[0019] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the thermal weight loss rate of the hindered amine light stabilizer is less than or equal to 3% at 140 ℃ for 2 h, the compatibility index with asphalt is greater than or equal to 0.8, the asphalt penetration retention rate after 300 h of ultraviolet irradiation is greater than or equal to 75%, the melting point is 60 ℃-100 ℃, the VOCs emission amount at 140 ℃ is less than or equal to 5 mg / m 3 , and the migration rate at 25 ℃ for 120 d is less than or equal to 0.01 mm / d.

[0020] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the recycled asphalt mixture after screening out coarse aggregate is a recycled fine aggregate in which coarse aggregate with a particle size greater than 4.75 mm is screened out, and only the fine aggregate and the aged asphalt are retained.

[0021] The bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the vegetable fat is waste vegetable fat, and the animal fat is waste animal fat.

[0022] As a general technical concept, the present application also provides a preparation method of the above-mentioned bio-asphalt and synergistic recycling agent modified asphalt recycling fine aggregate, comprising the following steps:

[0023] (1) The vegetable fat, animal fat or microbial fermentation product is dehydrated, degummed, rectified, and modified by oxidation to obtain bio-asphalt;

[0024] (2) The tackifying resin, viscosity reducer and anti-aging agent are mixed and heated and stirred to obtain a multi-component recycling agent;

[0025] (3) The recycling asphalt mixture after screening out coarse aggregate is mixed with bio-asphalt for pre-wrapping to obtain pre-wrapped recycling asphalt mixture;

[0026] (4) The pre-wrapped recycling asphalt mixture, new asphalt, multi-component recycling agent, new fine aggregate and mineral powder are pre-mixed at a cold temperature and then heated and mixed, and the temperature of the heated and mixed step is 110-130°C.

[0027] In the above-mentioned preparation method of bio-asphalt and synergistic recycling agent modified asphalt recycling fine aggregate, preferably, in step (1), the dehydration is performed until the water content is ≤0.05%, the degumming is performed using phosphoric acid, the rectification is performed to collect a fraction at 180-350°C, and the oxidation modification is performed by adding an oxidizing agent and reacting at 60-70°C for 2-4 hours; the amount of phosphoric acid used is 0.3-0.5% of the mass of the vegetable fat, animal fat or microbial fermentation product, and the amount of oxidizing agent used is 6-10% of the mass of the vegetable fat, animal fat or microbial fermentation product.

[0028] In the above-mentioned preparation method of bio-asphalt and synergistic recycling agent modified asphalt recycling fine aggregate, preferably, in step (2), the temperature of the heated and stirred step is 80-100°C, and in step (3), the temperature of the pre-wrapping step is 80-100°C.

[0029] In the above-mentioned preparation method of bio-asphalt and synergistic recycling agent modified asphalt recycling fine aggregate, preferably, in step (2), the rotation speed of the heated and stirred step is 30-60 r / min, and the time of the heated and stirred step is 25-35 min; in step (3), the pre-wrapping is achieved by stirring at a rotation speed of 40-70 r / min for 3-5 min; in step (4), the rotation speed of the cold temperature pre-mixing step is 25-35 r / min, and the time of the cold temperature pre-mixing step is 1-2 min; and the rotation speed of the heated and mixed step is 80-85 r / min, and the time of the heated and mixed step is 8-10 min.

[0030] The preparation method of the above-mentioned bio-asphalt and recycling agent modified asphalt recycled fine aggregate, preferably, the bio-asphalt is a vegetable oil based bio-asphalt or an animal fat based bio-asphalt, the animal fat based bio-asphalt is prepared by using animal fat (such as beef tallow, lard, fish oil) as raw material and being modified by oxidation (such as air blowing or catalyst oxidation). The characteristics of the animal fat based bio-asphalt are highly similar to those of the vegetable oil based bio-asphalt, and the animal fat based bio-asphalt can replace the vegetable oil based bio-asphalt as a carrier to realize directional penetration of the recycling agent, and the animal fat based bio-asphalt has a wide source (such as slaughterhouse waste oil), so that the cost can be further reduced.

[0031] In the present application, the terpene resin (alpha-pinene polymerization) molecular chain contains double bonds and a large number of aromatic ring structures, can occur addition reaction with the oxidation products of aged asphalt to form chemical bonding, and enhance the repair effect. The compatibility index with the gum and asphaltene of aged asphalt is greater than or equal to 0.85, which can more efficiently fill the intermolecular gaps.

[0032] Compared with the prior art, the present application has the following advantages:

[0033] (1) In view of the problems of high volatility of the recycling agent, the "oil competition" phenomenon of the fine aggregate, high energy consumption and secondary aging of asphalt caused by high temperature mixing in the traditional asphalt recycling technology, the present application provides a bio-asphalt and recycling agent modified asphalt recycled fine aggregate, which has the technical advantages of high synergistic recycling efficiency, environmental protection and low carbon, stable fine aggregate grading, and controllable cost.

[0034] (1.1) High synergistic recycling efficiency: the present application first uses bio-asphalt (vegetable oil based / animal fat based / microbial fermentation products) as an active carrier, and uses its low viscosity (135℃ viscosity 200mPa·s~500mPa·s), high polarity (containing carboxyl / hydroxyl functional groups after oxidation modification), and high surface activity (reducing interfacial energy) three characteristics to replace the single penetration mode of traditional petroleum based recycling agent. The low viscosity and strong penetration of the bio-asphalt can carry multi-component recycling agent into the internal pores of the old material, so that the multi-component recycling agent can be deeply and directionally penetrated into the old material (penetration depth greater than or equal to 200μm, and the penetration depth of the traditional process is less than or equal to 100μm), which solves the problem that the traditional recycling agent can only repair the defects of the surface layer of the old material, realizes deep penetration and repair of the aged asphalt, and makes the residual stability of the recycled mixture greater than or equal to 85% (the residual stability of the traditional process is less than or equal to 75%), and the freeze-thaw splitting strength ratio is greater than or equal to 80% (the freeze-thaw splitting strength ratio of the traditional process is less than or equal to 70%), which significantly improves the performance of the recycled mixture.

[0035] (1.2) Environmental protection and low carbon: the present application uses a low temperature mixing process (110℃~130℃), which reduces the energy consumption by 25%~35% compared with the traditional process (150℃~170℃), and the bio-asphalt and multi-component recycling agent do not contain harmful ingredients such as benzene series, and the VOCs emission is reduced by more than 60%, which meets the green environmental protection requirements.

[0036] (1.3) Stable fine aggregate gradation: By pre-coating the recycled asphalt mixture after the coarse aggregate is removed with bio-asphalt, the phenomenon of "competing for oil" between recycled fine aggregate and new asphalt is effectively reduced, and the gradation variation coefficient of the mixture is ≤5% (the traditional process can only reach ≤8%), which improves the overall performance and durability of the recycled mixture.

[0037] (1.4) The multi-component recycling agent is one of the core materials in this invention that solves the bottleneck of traditional plant-mixed hot recycling technology. Through the functional synergistic design of "tackifying resin + viscosity reducer + anti-aging agent", it specifically repairs the aging structure of old material, optimizes the gradation stability of fine aggregate, and inhibits secondary aging. It is a key support for the effectiveness of bio-asphalt "active carrier". This invention proposes a quantitative compounding scheme of tackifying resin (50%~70%), viscosity reducer (10%~20%), and anti-aging agent (20%~40%). Through the synergistic effect of "repairing the binder network (tackifying resin) - reducing the oil competition of fine aggregate (viscosity reducer) - inhibiting secondary aging (anti-aging agent)", it simultaneously solves the problems of gradation segregation, poor water stability and high-temperature aging of recycled fine aggregate, and breaks through the limitations of simple compounding of traditional recycling agents. Specifically, the core function of viscosity reducers is to lower the viscosity of the asphalt-recycling agent system, making the asphalt more fluid and more evenly coating the recycled fine aggregate, thus avoiding an imbalance of localized "oil grabbing" and localized "oil shortage"; bio-asphalt itself has low viscosity (200-500 mPa). (s) Characteristics: Viscosity reducers can further optimize the flowability of bio-asphalt, allowing it to coat the surface of recycled fine aggregates more quickly and evenly during the pretreatment stage, forming a complete bio-asphalt film. This film can isolate the recycled fine aggregates from direct contact with new asphalt, reducing the "oil competition" dynamic from the source. Furthermore, viscosity reducers do not cause excessively low system viscosity leading to asphalt loss because 50%–70% of the tackifying resin in the multi-component recycling agent provides cohesive strength. The three components work synergistically to achieve the goals of "good flowability (viscosity reducer) + uniform coating (bio-asphalt) + structural stability (tackifying resin)," completely resolving the gradation segregation caused by "oil competition."

[0038] (1.5) This invention utilizes waste biomass resources to prepare bio-asphalt, reducing raw material costs by 15%–20% compared to petroleum-based asphalt. Furthermore, the regenerant compounding process is simple, suitable for large-scale industrial production, and offers significant economic benefits. The bio-asphalt used in this invention is an asphalt-like material prepared from renewable biomass resources such as vegetable oils, animal fats, and microbial fermentation products through physical or chemical modification. Its core characteristics are low carbon and renewability. Through functional modification, it can possess bonding properties similar to petroleum-based asphalt, making it an important alternative material in the road engineering field to address the "dual carbon" target.

[0039] (1.6) The light stabilizer is a preferred functional component designed in this invention to address the photoaging problem of asphalt mixtures exposed to sunlight for extended periods. It significantly improves the durability of recycled mixtures by inhibiting the oxidative degradation reaction induced by ultraviolet (UV) radiation. In traditional plant-mixed hot recycling technology, photoaging is often overlooked (relying solely on antioxidants). However, in this invention, the light stabilizer works synergistically with bio-asphalt and multi-component recycling agents to form a full-chain protection system of "antioxidant-anti-light-repair," which is a key supplement to improve the long-term performance of the mixture.

[0040] (2) The preparation method of the present invention combines the low viscosity characteristics of bio-asphalt and develops a low temperature mixing process of 110-130℃ (20-40℃ lower than the traditional process). By screening out the coarse aggregate and pre-coating the recycled asphalt mixture with bio-asphalt, a bio-asphalt film is formed on the surface of the old material, reducing the direct contact between fine aggregate and new asphalt, achieving a gradation variation coefficient of ≤5% (traditional process ≤8%), while reducing energy consumption (unit energy consumption ≤8.5kg standard coal / ton of material) and VOCs emissions (≤50mg / m³). Detailed Implementation

[0041] The present invention will be further described below in conjunction with the specification and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0042] Example 1 (Proportion of bio-asphalt + intermediate mixing temperature)

[0043] This invention discloses a bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, which is composed of the following components by mass percentage: 60% recycled asphalt mixture (RAP) after screening to remove coarse aggregate; 12% new asphalt (70#, penetration 65 (0.1mm), softening point 48℃); 2% bio-asphalt; 1% multi-component regenerator; 20% new fine aggregate (0-4.75mm, crushing value 18%); 4.8% limestone powder (hydrophilicity coefficient 0.8); and 0.2% hindered amine light stabilizer.

[0044] The multi-component regenerator consists of 60% C9 petroleum resin (tackifying resin), 15% naphthenic oil (thickness reducer) and 25% 2,6-di-tert-butyl-p-cresol (anti-aging agent).

[0045] The hindered amine light stabilizer specifically used is light stabilizer 770, namely bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, manufactured by Zhejiang Dier Chemical Co., Ltd., and model number HALS-770.

[0046] The C9 petroleum resin was purchased from Lanzhou Petrochemical Company of China National Petroleum Corporation, and its model is C9-110.

[0047] The naphthenic oil was purchased from China National Petroleum Corporation's Karamay Petrochemical Branch, and its model number is KN4006.

[0048] This embodiment describes a method for preparing bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, comprising the following steps:

[0049] (1) Preparation of bio-asphalt: Waste soybean oil is used as raw material. First, it is dehydrated to a moisture content of ≤0.05%, then 0.5% phosphoric acid is added for degumming treatment. Then, the fraction at 180℃~350℃ is collected by distillation. Finally, 8% H2O2 is added as an oxidant and the reaction is carried out at 65℃ for 3h to complete the oxidation modification and obtain bio-asphalt.

[0050] (2) Multi-component regenerator compounding: Mix the tackifying resin, tack reducer and anti-aging agent in the above proportions, and stir at 40 r / min for 30 min at 90℃ to obtain a multi-component regenerator.

[0051] (3) Pretreatment of old material: The RAP after screening out coarse aggregate is mixed with bio-asphalt and stirred at 90℃ and 50r / min for 4min to achieve pre-coating, so that the bio-asphalt is evenly distributed on the RAP surface.

[0052] (4) Low temperature mixing: The pre-coated RAP, new asphalt, multi-component recycling agent, new fine aggregate, mineral powder and light stabilizer are put into the mixer in proportion. First, the cold material is pre-mixed at a speed of 30r / min for 2min, and then the temperature is raised to 120℃ and the mixture is stirred at a speed of 80r / min for 9min to obtain the asphalt recycled fine aggregate product.

[0053] The performance of the recycled asphalt fine aggregate product in this embodiment was tested to ensure that the indicators met the standards.

[0054] Testing revealed that the Marshall stability of this recycled asphalt fine aggregate product was 9.3 kN, meeting the specification requirement of ≥8.2 kN, demonstrating the improvement in structural strength brought about by the synergistic system of bio-asphalt and multi-component recycling agent. The freeze-thaw splitting strength ratio was 84%, higher than the specification standard of ≥75%, indicating that the combination of bio-asphalt and anti-aging agent optimized water stability. The gradation variation coefficient was only 4.2%, far below the specification upper limit of ≤8%, verifying the effective solution of the "oil competition" problem for fine aggregates by the pre-coating process. Mixing energy consumption was reduced by 30% compared to traditional processes, and VOC emissions were reduced by 65%, highlighting the advantages of low-temperature processes and environmentally friendly raw materials.

[0055] Example 2 (High proportion of bio-asphalt + optimized type of rejuvenator resin)

[0056] This invention discloses a bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, composed of the following components by mass percentage: RAP after screening to remove coarse aggregate, accounting for 60%; new asphalt (70#, penetration 65 (0.1mm), softening point 48℃), accounting for 11.5%; bio-asphalt 2.5%; multi-component regenerator 1%; new fine aggregate (0-4.75mm, crushing value 18%), accounting for 20%; limestone powder (hydrophilicity coefficient 0.8), accounting for 4.7%; and hindered amine light stabilizer, accounting for 0.3%.

[0057] The multi-component regenerator consists of 70% rosin-modified resin (tackifying resin), 10% vegetable oil-based mineral oil (thickness reducer), and 20% thioester anti-aging agent.

[0058] The rosin-modified resin was purchased from Guangdong Kemao Forestry Chemical Co., Ltd., model KM-G80.

[0059] Vegetable oil-based mineral oil is a modified oil obtained by chemical modification of vegetable oil, such as hydrogenation and esterification. It has the dual characteristics of renewable raw materials (vegetable oil-based) and stable performance (mineral oil-like). In this embodiment, the vegetable oil-based mineral oil is hydrogenated rapeseed oil, purchased from Jiangsu Kerun Industrial Media Co., Ltd., model HVO-30.

[0060] The thioester anti-aging agent specifically uses distearate dithiopropionate (DSTP).

[0061] This embodiment describes a method for preparing bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, comprising the following steps:

[0062] (1) Preparation of bio-asphalt: Waste rapeseed oil is used as raw material, dehydrated to a moisture content of ≤0.03%, and then 0.3% phosphoric acid is added for degumming treatment. Then, the fraction at 180℃~350℃ is collected by distillation. Finally, 10% H2O2 is added as an oxidant and reacted at 70℃ for 2.5h to complete the oxidation modification and obtain bio-asphalt.

[0063] (2) Multi-component regenerator compound: The tackifying resin, tack reducer and anti-aging agent are mixed in the above proportion and stirred at 85°C for 30 minutes to form the compound.

[0064] (3) Pretreatment of old material: Mix the RAP after screening out coarse aggregate with bio-asphalt, and pre-coat it at 85°C for 3 minutes to make the bio-asphalt evenly distributed on the RAP surface.

[0065] (4) Low temperature mixing: The pre-coated RAP, new asphalt, multi-component recycling agent, fine aggregate, mineral powder and light stabilizer are put into the mixer in proportion. First, the cold material is pre-mixed at a speed of 30r / min for 2min, and then the temperature is raised to 110℃ and the mixture is stirred at a speed of 80r / min for 10min to obtain the asphalt recycled fine aggregate product.

[0066] The performance of the recycled asphalt fine aggregate product in this embodiment was tested to ensure that the indicators met the standards.

[0067] Testing revealed that the Marshall stability of this recycled asphalt fine aggregate product was 8.9 kN, meeting the specifications. This demonstrates the synergistic effect of the multi-component recycling system of bio-asphalt and rosin-modified resin on improving structural strength and enhancing the cohesiveness of the recycled asphalt fine aggregate. The freeze-thaw splitting strength ratio reached 85%, indicating that increasing the proportion of bio-asphalt enhances its permeability to aged asphalt and further optimizes water stability. The gradation variation coefficient was 3.8%, demonstrating a significant pre-coating effect. Compared to traditional processes, mixing energy consumption was reduced by 35%, and VOC emissions were reduced by 70%, indicating that increasing the proportion of bio-asphalt strengthens environmental benefits.

[0068] Example 3 (Low proportion of bio-asphalt + upper limit of mixing temperature)

[0069] This invention discloses a bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, which is composed of the following components by mass percentage: RAP after screening to remove coarse aggregate, accounting for 60%; new asphalt (70#, penetration 65 (0.1mm), softening point 48℃), accounting for 12%; bio-asphalt 1.5%; multi-component regenerator 0.5%; new fine aggregate (0-4.75mm, crushing value 18%), accounting for 21%; limestone powder (hydrophilicity coefficient 0.8), accounting for 4.8%; and hindered amine light stabilizer, accounting for 0.2%.

[0070] The multi-component regenerator consists of 55% C5 petroleum resin (tackifying resin), 20% naphthenic oil (thickness reducer) and 25% complex anti-aging agent (hindered phenol and thioester compounded in a 1:1 mass ratio).

[0071] The C5 petroleum resin was purchased from Lanzhou Petrochemical, and the model is Lanzhou Petrochemical Ordinary C5.

[0072] Hindered phenol, specifically chemically named pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], commonly traded as Antioxidant 1010.

[0073] Thioesters, specifically chemically known as distearate thiodipropionate, are commonly traded under the name DSTDP.

[0074] This embodiment describes a method for preparing bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate, comprising the following steps:

[0075] (1) Preparation of bioasphalt: Using microbial fermentation products as raw materials, the product is first dehydrated to a moisture content of ≤0.02%, then 0.4% phosphoric acid is added for degumming treatment, followed by distillation to collect the fraction at 180℃~350℃, and finally 6% H2O2 is added as an oxidant. The product is oxidized and modified at 60℃ for 4h to obtain bioasphalt.

[0076] (2) Multi-component regenerator compounding: Mix the tackifying resin, tack reducer and anti-aging agent in the above proportions and stir at 100°C for 30 minutes to obtain a multi-component regenerator.

[0077] (3) Pretreatment of old material: Mix the RAP after screening out coarse aggregate with bio-asphalt, and pre-coat it at 100°C for 5 minutes to make the bio-asphalt evenly distributed on the RAP surface.

[0078] (4) Low temperature mixing: The pre-coated RAP is added to the mixer along with new asphalt, multi-component recycling agent, new fine aggregate, mineral powder and light stabilizer in proportion. First, the cold material is pre-mixed at a speed of 30r / min for 2min, and then the temperature is raised to 130℃ and the mixture is stirred at a speed of 85r / min for 8min to obtain the asphalt recycled fine aggregate product.

[0079] The performance of the recycled asphalt fine aggregate product in this embodiment was tested to ensure that the indicators met the standards.

[0080] Tests showed that the mixture had a Marshall stability of 9.1 kN, meeting the specifications, indicating that low-proportion bio-asphalt can still form an effective synergy with multi-component recycling agents; the freeze-thaw splitting strength ratio was 82%, indicating that the anti-aging agent composite system played a good role; the gradation variation coefficient was 4.5%, indicating that the pre-coating process is suitable for scenarios with low bio-asphalt usage; mixing energy consumption was reduced by 25%, which is still better than traditional processes even at the upper temperature limit; VOC emissions were reduced by 62%, indicating that the performance of asphalt recycled fine aggregate products made with bio-asphalt is significantly better than that made with petroleum-based asphalt.

[0081] Comparative Example 1 (non-bio-based bitumen + single-component recycling agent + conventional high-temperature mixing)

[0082] A regenerator-modified asphalt recycled fine aggregate has a composition that is basically the same as that of Example 1. The main difference is that it does not contain bio-asphalt and uses a single-component naphthenic oil regenerator instead of a multi-component regenerator, accounting for 1%; the remaining components and parameters are the same as those of Example 1.

[0083] In this comparative example, the preparation steps of bio-asphalt are omitted, pure naphthenic oil is used directly as the regenerator, no RAP pre-coating treatment is performed, the mixing temperature is increased to 160℃ (the temperature of the traditional process), and the remaining steps are the same as in Example 1, to obtain regenerator-modified asphalt recycled fine aggregate.

[0084] The recycled asphalt fine aggregate modified with the recycling agent in this comparative example was tested according to the testing method in Example 1. The test results showed that the Marshall stability of the recycled asphalt fine aggregate was only 7.5 kN, which did not meet the specification requirements. The reason is that it lacks the synergistic effect of bio-asphalt, and the single-component recycling agent has a single function and cannot effectively restore the performance of aged asphalt. The freeze-thaw splitting strength ratio was only 68%, which is lower than the specification standard. Because the recycling agent does not contain anti-aging agents, the water stability of the mixture is poor. The gradation variation coefficient was 9.2%, which far exceeded the upper limit of the specification. The lack of pre-coating led to a serious "oil competition" phenomenon in the fine aggregate. The mixing energy consumption was not reduced, the high-temperature process returned to a high-energy consumption state, the VOCs emission was high, the petroleum-based recycling agent volatilized seriously at high temperatures, and the environmental protection was lacking.

[0085] Comparative Example 2 (with bio-asphalt, but without pre-coating process)

[0086] A bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate has the same composition as in Example 1, including all components such as bio-asphalt and a multi-component regenerator in a specific ratio.

[0087] The preparation method of bio-asphalt synergistic regenerator modified asphalt fine aggregate in this comparative example is basically the same as that in Example 1. The main difference is that step (3) is omitted, namely the pretreatment of old material. RAP, bio-asphalt and all other components after screening out coarse aggregate are directly put into the mixer. The remaining steps and parameters are consistent with those in Example 1.

[0088] The recycled asphalt fine aggregate of this comparative example was tested according to the testing method in Example 1. The test results showed that the Marshall stability of the recycled asphalt fine aggregate dropped to 8.0 kN, close to the lower limit of the specification. Due to the lack of pre-coating, the fine aggregate competed for oil, resulting in uneven distribution of asphalt in the mixture and a decrease in structural strength. The freeze-thaw splitting strength ratio was 73%, which did not meet the specification requirements. Gradation segregation directly reduced water stability. The gradation variation coefficient was 8.8%, far exceeding the 4.2% of Example 1. Excessive adsorption of new asphalt by the fine aggregate caused serious gradation problems. Although the energy consumption was still reduced by 30% and the VOCs emission was reduced by 65% ​​compared with the high-temperature mixing process, and the advantages of low temperature and environmentally friendly raw materials were retained, the core road performance did not meet the standards, highlighting the necessity of the pre-coating process.

[0089] Comparative Example 3 (with a synergistic system but using traditional high-temperature mixing)

[0090] A bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate has the same composition as in Example 2, including a high proportion of bio-asphalt and all components such as an optimized multi-component regenerator.

[0091] The preparation method of bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate in this comparative example is basically the same as that in Example 2. The main difference is that the mixing temperature in step (4) is increased from 110℃ to 160℃. The other steps (bio-asphalt preparation, regenerator compounding, RAP pre-coating, etc.) are the same.

[0092] The recycled asphalt fine aggregate of this comparative example was tested according to the testing method in Example 1. The test results showed that the Marshall stability of the recycled asphalt fine aggregate was 8.3 kN, just reaching the lower limit of the specification. This is because the high temperature caused secondary aging of the asphalt, which offset the performance gain of the synergistic system. The freeze-thaw splitting strength ratio was 76%, slightly higher than the lower limit of the specification but much lower than 85% in Example 2, indicating that secondary aging significantly reduced the durability of the mixture. The gradation variation coefficient was 4.0%, which is because the pre-coating process still played a role and the gradation control was good, but the performance loss caused by the high temperature could not be compensated. The mixing energy consumption was not reduced, and the energy-saving advantage of the high-temperature process disappeared. The VOC emissions were reduced by only 30%, which is much lower than 70% in Example 2. The high temperature caused some of the bio-asphalt to volatilize, greatly reducing the environmental benefits.

[0093] Comparative Example 4 (Adjustment of Bio-asphalt + Multi-component Recycling Agent Formulation)

[0094] A bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate has the same composition as Example 2, except that the multi-component regenerator ratio is adjusted to: 40% tackifying resin, 30% tack reducer, and 10% anti-aging agent, which deviates from the ratio range required by this invention; the remaining components and parameters are the same as in Example 2.

[0095] The preparation method of bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate in this comparative example is exactly the same as that in Example 2.

[0096] The recycled asphalt fine aggregate of this comparative example was tested according to the testing method in Example 1. The test results showed that the Marshall stability of the recycled asphalt fine aggregate was 7.8 kN, which did not meet the specification requirements. Due to insufficient proportion of tackifying resin, the cohesiveness of the mixture was poor. The freeze-thaw splitting strength ratio was 72%, which was lower than the specification standard. The amount of anti-aging agent was too small, which could not effectively inhibit oxidative aging. The gradation variation coefficient was 5.0%. The pre-coating process was still effective, but the imbalance of the recycling agent ratio caused the synergistic effect to fail. Although the mixing energy consumption was reduced by 35% and the VOCs emission was reduced by 70%, the environmental protection and energy-saving advantages were retained. However, the core road performance did not meet the engineering requirements, which proved that the specific ratio of the recycling agent was the key to achieving the performance standard.

[0097] The performance test data of the recycled fine aggregates prepared in the various embodiments and comparative examples of the present invention are shown in Table 1 below.

[0098] Table 1 - Performance test data of Examples 1-3 and Comparative Examples 1-4 of the present invention

[0099]

[0100] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A bio-based asphalt synergistic regenerator modified asphalt recycled fine aggregate, characterized in that, By weight percentage, the raw material composition includes: 50%–70% recycled asphalt mixture after screening out coarse aggregates; 5%–15% new asphalt; 1%–3% bio-asphalt; 0.5%–2.5% multi-component recycling agent; 15%–25% new fine aggregates; and 3%–8% mineral powder. The preparation process involves first mixing and pre-coating the recycled asphalt mixture after removing coarse aggregates with bio-asphalt, then mixing it with other raw materials and stirring at 110℃~130℃; the pre-coating temperature is 80℃~100℃. The multi-component regenerator is composed of 50%–70% tackifying resin, 10%–20% viscosity reducer, and 20%–40% anti-aging agent; The bio-asphalt is prepared from renewable biomass resources through physical or chemical modification. The renewable biomass resources are at least one of vegetable oils, animal oils, and microbial fermentation products. Specifically, the process involves dehydrating, degumming, distilling, and oxidizing the vegetable oil, animal oil, or microbial fermentation product to obtain bioasphalt. The dehydration is carried out until the moisture content is ≤0.05%, and the degumming is performed using phosphoric acid. The distillation collects the fraction at 180℃–350℃. The oxidizing modification involves adding an oxidant and reacting at 60℃–70℃ for 2–4 hours. The amount of phosphoric acid used is 0.3%–0.5% of the mass of the vegetable oil, animal oil, or microbial fermentation product. The amount of the oxidant used is 6%–10% of the mass of the vegetable oil, animal oil, or microbial fermentation product. When the penetration of the recycled asphalt mixture after removing coarse aggregate is ≤20dmm, the amount of bio-asphalt should be increased; when the penetration of the recycled asphalt mixture after removing coarse aggregate is ≥40dmm, the amount of bio-asphalt should be reduced. The recycled asphalt mixture after removing coarse aggregate is a mixture in which coarse aggregate with a particle size > 4.75 mm is removed, and only fine aggregate and aged asphalt are retained as recycled fine aggregate.

2. The bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to claim 1, characterized in that, The raw material composition also includes 0.1% to 0.5% light stabilizer.

3. The bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to claim 2, characterized in that, The tackifying resin is at least one of C5 petroleum resin, C9 petroleum resin, rosin-modified resin, coumarone-indene resin, and terpene resin. The viscosity reducer is a naphthenic oil or a vegetable oil-based mineral oil, wherein the vegetable oil-based mineral oil is a modified oil obtained by chemical modification of vegetable oil as raw material; The anti-aging agent is 2,6-di-tert-butyl-p-cresol, a thioester anti-aging agent, or a composite anti-aging agent, wherein the composite anti-aging agent is composed of hindered phenol and thioester. The new fine aggregate is at least one of basalt rock chips, manufactured sand, and stone chips; The mineral powder is limestone powder; The light stabilizer is a hindered amine light stabilizer.

4. The bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to claim 3, characterized in that, The number average molecular weight of the C5 and C9 petroleum resins is 500 to 1000. The rosin-modified resin is an esterified rosin resin, which contains ester and hydroxyl groups in its molecular structure, with an ester group content of ≥30%. The coumarone-indene resin has a number-average molecular weight of 800-1500, and its molecular chain contains double bonds. It can undergo an addition reaction with the oxidation products of aged asphalt to form chemical bonds, and its compatibility index with the gum and asphaltenes of aged asphalt is ≥0.

85. The terpene resin uses α-pinene and / or β-pinene as the main polymer monomers, with an α-pinene content ≥60% and an iodine value of 20g~60g I2 / 100g; The naphthenic oil contains ≥70% naphthenic hydrocarbons, ≥95% total saturated hydrocarbons, ≤3% aromatic hydrocarbons, and ≤0.01% mechanical impurities. The hindered phenol molecule contains a monophenolic hydroxyl group, with at least one tert-butyl group substituted at the ortho position of the phenolic hydroxyl group, and has a purity ≥98%; the thioester is a dithioester compound or a thiopropionate compound, with a purity ≥98%, and a sulfur mass percentage of 8%–15%. The hindered amine light stabilizer exhibits a thermal weight loss rate of ≤3% after 2 hours at 140℃, a compatibility index with asphalt of ≥0.8, an asphalt penetration retention rate of ≥75% after 300 hours of UV irradiation, a melting point of 60℃~100℃, and VOC emissions of ≤5mg / m³ at 140℃. 3 The migration rate at 25℃ for 120 days is ≤0.01mm / d.

5. The bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to any one of claims 1 to 4, characterized in that, The vegetable oil is waste vegetable oil, and the animal oil is waste animal oil.

6. A method for preparing bio-asphalt synergistic regenerator modified asphalt fine aggregate as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) The vegetable oil, animal oil or microbial fermentation product is dehydrated, degummed, distilled and oxidized to obtain bioasphalt; (2) Mix the thickening resin, viscosity reducer, and anti-aging agent, heat and stir to obtain a multi-component regenerator; (3) The recycled asphalt mixture after the coarse aggregate has been removed is mixed with bio-asphalt and pre-coated to obtain a pre-coated recycled asphalt mixture; (4) The pre-coated recycled asphalt mixture, new asphalt, multi-component recycling agent, new fine aggregate and mineral powder are first cold-mixed and then heated and mixed. The temperature of the heating and mixing is 110℃~130℃.

7. The method for preparing bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to claim 6, characterized in that, In step (2), the temperature of heating and stirring is 80℃~100℃.

8. The method for preparing bio-asphalt synergistic regenerator modified asphalt recycled fine aggregate according to claim 7, characterized in that, In step (2), the heating and stirring speed is 30 r / min to 60 r / min, and the heating and stirring time is 25 min to 35 min; in step (3), the pre-coating is achieved by stirring at a speed of 40 r / min to 70 r / min for 3 min to 5 min; in step (4), the cold material premixing speed is 25 r / min to 35 r / min, and the cold material premixing time is 1 min to 2 min; the heating and stirring speed is 80 r / min to 85 r / min, and the heating and stirring time is 8 min to 10 min.

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