Composite modified waste asphalt concrete recycled mixture and preparation method thereof

Abstract

The invention relates to a composite modified waste asphalt concrete recycled mixture and a preparation method thereof, and belongs to the technical field of road engineering materials. The waste asphalt concrete recycled mixture comprises the following components in parts by weight: 50-70 parts of a waste asphalt pavement material, 15-30 parts of a new aggregate, 0.5-3 parts of residual oil, 1-6 parts of waste tire rubber powder, 3-8 parts of slag powder and 3-5 parts of new asphalt. Through the activation and softening effects of residual oil and the composite plasticizing effect of tackifying and prolonging of the waste tire rubber powder, in cooperation with the micro-aggregate effect of the power plant slag powder, the mixing amount of new asphalt is reduced, efficient regeneration of the waste asphalt pavement material (RAP) is achieved, meanwhile, all the raw materials cooperate with one another to jointly construct a'regeneration-reinforcement-elasticity 'composite system, and the comprehensive performance of the pavement material is improved. The mixture can simultaneously meet the comprehensive requirements of highways on high temperature, low temperature, water stability and fatigue.

Description

Technical Field

[0001] This invention belongs to the technical field of road engineering materials, and more specifically, relates to a composite modified waste asphalt concrete recycled mixture and its preparation method. Background Technology

[0002] With the rapid development of transportation infrastructure construction in my country, a large amount of waste asphalt pavement (RAP) is being discarded, not only occupying land resources but also causing environmental pollution. At the same time, the demand for raw materials such as aggregates and asphalt in road construction is constantly increasing, putting increasing pressure on resources and the environment. Therefore, the recycling of waste asphalt pavement materials has become a research hotspot and development trend in the field of road engineering.

[0003] Currently, waste bitumen recycling technology mainly faces the following problems:

[0004] (1) Insufficient activity of aged asphalt and high cost of recycling agents: Due to the volatilization and oxidation of light components, the performance of aged asphalt is severely deteriorated, and it is necessary to add recycling agents to restore its performance. Traditional recycling agents are mostly petroleum-based products, which are expensive and have limited recycling effect.

[0005] (2) Traditional recycled asphalt mixtures have poor high-temperature rutting resistance: Due to the high RAP content, the performance of old asphalt is not fully restored, resulting in insufficient high-temperature stability and easy occurrence of rutting and other defects.

[0006] (3) Low content of waste asphalt makes it difficult to achieve high-value utilization: In the existing technology, the content of RAP is usually no more than 50%, and a large amount of waste asphalt has not been effectively utilized, resulting in low resource utilization rate. Summary of the Invention

[0007] The purpose of this invention is to provide a composite modified waste asphalt concrete recycled mixture and its preparation method, which has the characteristics of being environmentally friendly and efficient.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A composite modified recycled asphalt concrete mixture, comprising the following components by mass parts:

[0010] 50-70 portions of waste asphalt pavement material;

[0011] 15-30 portions of fresh material;

[0012] 0.5-3 parts of residual oil;

[0013] 1-6 parts of waste tire rubber powder;

[0014] 3-8 parts of slag powder; and

[0015] 3-5 parts of new asphalt.

[0016] In this technical solution, recycled asphalt pavement material (RAP) is used as the main recycled raw material. It is a valuable resource that contains high-quality, well-graded new aggregates and asphalt binders. It can reduce the consumption of new materials. Its dosage of 50-70 parts can form a complementary structure with new asphalt, enhancing the deformation resistance and high-temperature rutting resistance of concrete mixtures.

[0017] The addition of new aggregates can effectively fill the voids between RAP aggregates, forming a denser skeleton structure, thereby improving the strength and durability of the mixture.

[0018] Residual oil, as a byproduct or intermediate material of petroleum refining, is rich in light components and is an ideal asphalt rejuvenator. The addition of residual oil can improve the viscosity, rheological properties, and temperature sensitivity of asphalt, soften aged asphalt in RAP, restore its rheological properties, and thus improve the low-temperature crack resistance and workability of high-content RAP mixtures.

[0019] Waste tire rubber powder, as a toughening modifier, can significantly improve the high and low temperature performance, fatigue crack resistance, and rutting resistance of asphalt. It absorbs the lightweight components in asphalt to form a stable network structure, thereby improving the high temperature stability and low temperature crack resistance of asphalt.

[0020] Slag powder is an industrial solid waste containing active SiO2, Al2O3, CaO and other components. It has a rough and porous surface structure, which can enhance its adhesion to asphalt and fill the internal pores of the mixture, thereby improving the mixture's resistance to water damage, high-temperature stability and overall strength.

[0021] Furthermore, the new asphalt is selected from at least one of SBS modified asphalt, recycled matrix asphalt, or soft asphalt.

[0022] Among them, SBS (styrene-butadiene-styrene block copolymer) modified asphalt, as the main binder, has good elasticity, plasticity and ductility, and can effectively improve the high-temperature stability and low-temperature crack resistance of asphalt.

[0023] Recycled matrix asphalt refers to a composite binder with suitable rheological and construction properties, formed by mixing unmodified ordinary petroleum asphalt (i.e., matrix asphalt) with a chemical additive called a regenerator, which is specifically used to restore the properties of aged asphalt, in a certain proportion.

[0024] Soft asphalt can be used as a blending component in recycled mixtures to soften aged asphalt, such as AH-110 base asphalt, soft blended asphalt for recycling, or soft asphalt with a penetration >130.

[0025] The composite modification of new asphalt and waste tire rubber powder can form a more stable three-dimensional network structure, further improving the deformation resistance and durability of the mixture.

[0026] Furthermore, the particle size of the waste asphalt pavement material is ≤15mm, and the asphalt content is 3.5-4.5%.

[0027] Furthermore, the new aggregate is coarse aggregate with a particle size of 4.75-10 mm and fine aggregate with a particle size of 0.15-4.75 mm, and the mass ratio of the coarse aggregate to the fine aggregate is 1:0.8-1.5. The coarse aggregate is preferably at least one of natural crushed stone or pebbles, and the fine aggregate is preferably at least one of natural sand or manufactured sand.

[0028] As a preferred embodiment of the present invention, the new aggregate is pre-treated with a silane coupling agent, wherein the amount of the silane coupling agent is 1-3% of the mass of the new aggregate.

[0029] Furthermore, the softening point of the residual oil is 45-55℃.

[0030] As a preferred embodiment of the present invention, the waste tire rubber powder is activated by mixing it with preheated residual oil. The specific steps are as follows: the residual oil is heated to 160–170°C, and then the waste tire rubber powder is mixed with the preheated residual oil under stirring. The temperature is further increased to 190–210°C, and the mixture is heated and stirred for 1–2 hours to obtain the activated and modified rubber powder.

[0031] Furthermore, the particle size of the waste tire rubber powder is 40-80 mesh.

[0032] As a preferred embodiment of the present invention, the specific surface area of ​​the slag powder is ≥400m². 2 / kg, calcined at 700-1100℃. Calcination helps remove harmful impurities and stabilize its chemical properties.

[0033] As a preferred embodiment of the present invention, the slag powder is pre-treated with an alkaline activation solution of water glass-sodium hydroxide.

[0034] Furthermore, the modulus of the water glass-sodium hydroxide solution is 1.2-1.6; the dosage is 1.2-2.4 parts by weight; and the temperature of the alkali activation treatment is 70-80℃.

[0035] Modulus refers to a chemical property parameter of water glass (sodium silicate), specifically representing the molar ratio of silicon dioxide to sodium oxide. Adding sodium hydroxide solution lowers the modulus of water glass, making it more alkaline and stable.

[0036] Furthermore, the recycled asphalt concrete mixture further includes processing aids, which include at least one of a compatibilizer, a stabilizer, a filler, a photocatalyst, or a fiber material. Specifically, the compatibilizer comprises 0.5-1 parts by weight; the stabilizer comprises 1-1.5 parts by weight; the filler comprises 2-5 parts by weight; the photocatalyst comprises 0.1-0.5 parts by weight; and the fiber material comprises 0.2-0.5 parts by weight.

[0037] Further, the compatibilizer is furfural extract oil; the stabilizer is sulfur or phenolic resin; the filler is nano-silica, nano-calcium carbonate or nano-clay; the photocatalyst is nano-titanium dioxide; the fiber material is at least one of polymer fiber, mineral fiber or lignin fiber, wherein the polymer fiber is polyester fiber or polyacrylonitrile fiber; the mineral fiber is basalt fiber or glass fiber.

[0038] The addition of compatibilizers helps optimize the asphaltene content and improve compatibility with new asphalt. The addition of fillers helps improve the high-temperature viscosity, rutting resistance, and aging resistance of concrete. Nano-titanium dioxide has photocatalytic properties, absorbing ultraviolet light and mitigating the photo-oxidative aging of asphalt. It can also degrade pollutants such as NOx in vehicle exhaust on the road surface, achieving self-cleaning and environmental protection functions for the pavement. Fiber materials form a three-dimensional network structure in the asphalt mixture, improving the tensile strength and crack resistance of concrete, reducing the brittleness caused by the aging of waste asphalt pavement materials, and improving low-temperature crack resistance and resistance to reflective cracking.

[0039] The preparation method of the above-mentioned recycled asphalt concrete mixture includes the following steps:

[0040] S1. Heat the residual oil to 160–170℃, then mix the waste tire rubber powder with the preheated residual oil while stirring, continue to heat to 190–210℃, and heat and stir for 1–2 hours to obtain the composite recycling agent.

[0041] S2. Crush and screen the waste asphalt pavement material RAP to a particle size ≤15mm, then dehydrate, dry and preheat it; then add RAP, new aggregate and slag powder in sequence, dry mix for 1-2 minutes, and finally add composite recycling agent and new asphalt, wet mix for 1-2 minutes to obtain the finished product.

[0042] Furthermore, in step S1, the stirring speed during heating is 1000-2000 rpm.

[0043] In step S1, the light components in the residual oil can promote the surface activation of rubber powder and improve its molecular interaction with asphalt, thereby enhancing compatibility. Premixing the residual oil with waste tire rubber powder allows the rubber powder to fully swell and partially degrade in the residual oil. The polymer segments released by the swollen rubber powder work together with the residual oil to react with the aged asphalt in the RAP, achieving a more efficient synergistic regeneration effect. This not only replenishes the light components but also introduces elastic components.

[0044] Furthermore, in step S2, the temperature for dehydrating and drying the waste asphalt pavement material is 100-120℃, and the time is 40-60 minutes. Dehydration and drying of the waste asphalt pavement material helps to enhance its high-temperature stability.

[0045] Furthermore, the slag powder is pre-treated with an alkaline activation solution via water glass-sodium hydroxide solution.

[0046] Furthermore, the modulus of the water glass-sodium hydroxide solution is 1.2-1.6; the dosage is 1.2-2.4 parts by weight; and the temperature of the alkali activation treatment is 70-80℃.

[0047] Furthermore, in step S2, the composite recycling agent and the new asphalt are pre-mixed and then added to the dry-mixed mixture.

[0048] The beneficial effects of this invention are:

[0049] (1) This invention achieves high-volume and high-efficiency regeneration of waste asphalt pavement material (RAP) by combining the activation and softening effects of residual oil with the thickening and stretching effects of waste tire rubber powder, and the micro-aggregate effect of power plant slag powder.

[0050] (2) This invention incorporates a high proportion of recycled asphalt pavement material (RAP) as the main recycled raw material, which can effectively reduce the amount of new materials and thus save costs. The addition of new aggregates can supplement the insufficient aggregates in RAP, optimize the gradation, and provide skeleton structure and stability. Slag oil, as an asphalt regenerator, can soften the aged asphalt in RAP and restore its rheological properties. Waste tire rubber powder expands by absorbing the lightweight components in asphalt, forming an elastic network, which can significantly improve the deformation resistance and crack resistance of asphalt mixtures. Slag powder has pozzolanic activity and cementitious properties, which can fill voids, improve density and strength, and may participate in the cementation reaction to enhance stability. The addition of new asphalt can enhance the elasticity and toughness of asphalt, thereby improving the mixture's resistance to rutting, fatigue, and low-temperature cracking.

[0051] (3) This invention makes maximum use of various solid wastes such as waste asphalt pavement materials, slag oil, waste tires, and slag powder, reducing the consumption of original resources and environmental pollution, and has significant economic and social benefits. Detailed Implementation

[0052] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0053] Example 1

[0054] A composite modified recycled asphalt concrete mixture, comprising the following components by mass parts:

[0055] Components Remark weight Waste asphalt pavement materials Particle size ≤15mm, asphalt content 4.2% 60 gravel Coarse aggregate, particle size 4.75-10mm 14 Quartz sand Fine aggregate, particle size 0.15-4.75mm 13 residual oil Softening point 52℃ 3 Waste tire rubber powder Particle size 40-80 mesh 2 Slag powder Calcination temperature 700-1000℃ 5 New asphalt SBS modified asphalt 3

[0056] The preparation method of the above-mentioned recycled asphalt concrete mixture includes the following steps:

[0057] S1. Preparation of composite recycler: Heat the residual oil to 165±5℃, then add waste tire rubber powder under stirring and premix, then heat to 200±5℃ and shear at high speed at 1000rpm for 1 hour to obtain composite recycler.

[0058] S2. Raw material pretreatment: The waste asphalt pavement material (RAP) is crushed and screened to a particle size of ≤15mm, and then dehydrated and dried in hot air at 110℃ for 1 hour to remove surface free water.

[0059] S3. Mixing: Add the new aggregate and slag powder into the RAP container after the pretreatment in step S2 in sequence, and dry mix for 60 seconds. Then add the pre-mixed composite recycling agent and new asphalt, and wet mix for 90 seconds to obtain the waste asphalt concrete recycled mixture.

[0060] Example 2

[0061] A composite modified recycled asphalt concrete mixture, comprising the following components by mass parts:

[0062] Components Remark weight Waste asphalt pavement materials Particle size ≤15mm, asphalt content 4.2% 50 Basalt gravel Coarse aggregate, particle size 4.75-10mm 10 Manufactured sand Fine aggregate, particle size 0.15-4.75mm 10 residual oil Softening point 52℃ 2 Waste tire rubber powder Particle size 40-80 mesh 2 Slag powder Calcination temperature 700-1000℃, with prior alkali activation treatment. 8 New asphalt Recycled matrix bitumen 3 furfural extract oil compatibilizer 0.5

[0063] The preparation method in this embodiment is the same as in Example 1. The furfural extract oil is added together with the residue oil in step S1.

[0064] Example 3

[0065] A composite modified recycled asphalt concrete mixture, comprising the following components by mass parts:

[0066] Components Remark weight Waste asphalt pavement materials Particle size ≤15mm, asphalt content 4.2% 70 gravel Coarse aggregate, particle size 4.75-10mm 7 Quartz sand Fine aggregate, particle size 0.15-4.75mm 8 residual oil Softening point 52℃ 5 Waste tire rubber powder Particle size 40-80 mesh, pre-activated 3 Slag powder Calcination temperature 700-1000℃, with prior alkali activation treatment. 3 New asphalt AH-110 Base Asphalt 5 Nano silica filler 2 Polyester fiber Fiber materials 0.4

[0067] The preparation method in this embodiment is the same as in Example 1. In step S2, nano-silica and polyester fibers are added together with the slag powder.

[0068] Example 4

[0069] The difference between this embodiment and embodiment 3 is that the quartz sand in this embodiment is pre-treated with a silane coupling agent KH-550 for surface modification, wherein the amount of silane coupling agent KH-550 is 0.3 parts by weight.

[0070] Comparative Example 1

[0071] Compared with Example 1, the difference in this comparative example is that the residue oil is replaced with epoxidized soybean oil, while the other components, preparation steps and parameters are the same.

[0072] Comparative Example 2

[0073] Compared with Example 1, the difference in this comparative example is that the slag powder is omitted and the relative percentages of other components, such as waste asphalt pavement material, quartz sand, residual oil, waste tire rubber powder, and new asphalt, are exactly the same as in Example 1.

[0074] Components Remark weight Waste asphalt pavement materials Particle size ≤15mm, asphalt content 4.2% 60+5*60％＝63 gravel Coarse aggregate, particle size 4.75-10mm 14+5*14％＝14.7 Quartz sand Fine aggregate, particle size 0.15-4.75mm 13+5*13％＝13.65 residual oil Softening point 52℃ 3+5*3％＝3.15 Waste tire rubber powder Particle size 40-80 mesh 2+5*2％＝2.1 Slag powder / 0 New asphalt SBS modified asphalt 3+5*3％＝3.15

[0075] Comparative Example 3

[0076] Compared with Example 1, the difference in this comparative example is that waste tire rubber powder is omitted and the relative percentages of other components, such as waste asphalt pavement material, quartz sand, residual oil, slag powder, and new asphalt, are exactly the same as in Example 1.

[0077] Components Remark weight Waste asphalt pavement materials Particle size ≤15mm, asphalt content 4.2% 60+2*60％＝61.2 gravel Coarse aggregate, particle size 4.75-10mm 14+2*14％＝14.28 Quartz sand Fine aggregate, particle size 0.15-4.75mm 13+2*13％＝13.26 residual oil Softening point 52℃ 3+2*3％＝3.06 Waste tire rubber powder Particle size 40-80 mesh 0 Slag powder Calcination temperature 700-1000℃ 5+2*5％＝5.1 New asphalt SBS modified asphalt 3+2*3％＝3.06

[0078] The following performance tests were performed on Examples 1-4 and Comparative Examples 1-3 respectively:

[0079] Referring to JTG / T5521-2019 "Technical Specification for Recycling Asphalt Pavement of Highway", GB / T35160-2017 "Technical Specification for Warm Mix Asphalt Mixture", JTGE20-2011 "Test Procedure for Asphalt and Asphalt Mixture of Highway Engineering", and JTGF40-2004 "Technical Specification for Construction of Asphalt Pavement of Highway", samples were randomly taken from the examples and comparative examples, with each sample weighing 1200g. These samples were placed in an oven at 165±5℃ for 4-6 hours to ensure uniform heating of the mixture without localized overheating or clumping. A thin layer of release agent was then applied to the inner wall of the mold, and the heated sample was poured into the mold. The surface was leveled with a scraper and preheated in an oven at 165±5℃ for 30 minutes. An automatic compactor was used to compact each side 75 times. After compaction, wait for the specimen to cool to room temperature (about 24 hours), then use a demolding device to remove the specimen, obtaining a standard Marshall specimen with a diameter of 101.6 mm and a height of 63.5 ± 1.3 mm.

[0080] (1) Marshall stability and flow value test

[0081] The specific method is as follows: For each set of examples and comparative examples, three prepared standard Marshall specimens were placed in a constant temperature water bath at 60±0.5℃ for 45±5 minutes. The specimens must be completely submerged in water, with the water level at least 25mm from the top of the specimen. The Marshall testing apparatus was started and preheated to room temperature. The loading rate was adjusted to 50±5mm / min. The flow meter was installed on both sides of the specimen, ensuring that the measuring rod was in close contact with the specimen surface without any additional pressure. The specimen was then removed from the constant temperature water bath and quickly placed into the loading device of the Marshall testing apparatus. The loading program was started, and the specimen was loaded uniformly at a rate of 50±5mm / min until it failed. The Marshall stability (peak load) and flow value (vertical deformation value corresponding to the peak load) were recorded. The average value of the stability and flow value was taken as the final result.

[0082] (2) Residual stability test

[0083] The stability of the sample measured in (1) Marshall stability and flow value test is recorded as the conventional stability (MS0); in addition, three prepared standard Marshall specimens are taken from each set of examples and comparative examples and immersed in a constant temperature water bath at 15±0.5℃ for 24±0.5h. After the water immersion aging treatment is completed, the specimens are taken out and the stability of the specimens after water immersion aging treatment is determined according to the method of "(1) Marshall stability and flow value test". The average value is taken as the stability after water immersion (MS1). The residual stability (%) is calculated according to the ratio of conventional stability and stability after water immersion.

[0084] (3) Freeze-thaw splitting strength ratio test

[0085] Twelve prepared standard Marshall specimens were taken from each set of examples and comparative examples, and divided into two groups of six each. One group served as the freeze-thaw group, and the other as the control group. After being numbered, the specimens were dried in an oven at 105±5℃ until constant weight, and the dry weight was measured. Then, they were placed in a vacuum-saturated container, and distilled water was added until the water level was 20mm above the top of the specimen. The vacuum pump was started to bring the vacuum level inside the container to -0.098MPa and maintained for 30 minutes. The vacuum pump was then turned off, and the vacuum was slowly released, allowing the specimens to soak naturally in the water for 45±5 minutes to ensure that the specimens were fully saturated with water.

[0086] After saturating with water, the freeze-thaw test specimens were placed in sealed plastic bags, filled with an appropriate amount of distilled water to ensure complete immersion, and then sealed in a freeze-thaw cycler. The specimens were first frozen at -18±0.5℃ for 16±1 hours, then rapidly raised to 60±0.5℃ and kept at this temperature for 8±1 hours to complete one freeze-thaw cycle. After the freeze-thaw cycle, the specimens were removed, the plastic bags were opened, and the specimens were placed in a constant temperature water bath at 25±0.5℃ for 2±0.5 hours for later use. The control group specimens, after being saturated with water, were directly placed in a constant temperature water bath at 25±0.5℃ for 2±0.5 hours without freeze-thaw treatment.

[0087] Start the universal testing machine, install the splitting tensile strength test fixture, and adjust the contact position between the upper and lower arc-shaped pressure strips and the specimen to ensure that the center line of the pressure strip passes through the center of the specimen. Set the loading rate to 50±5 mm / min. Remove the specimen from the constant temperature water bath, gently wipe off the surface moisture with a dry cloth, and quickly place it into the splitting tensile strength fixture. Start the testing machine and load it uniformly at the set rate until the specimen splits and fails along the diameter direction. Record the maximum failure load (P, unit kN). Perform splitting tensile strength tests on 6 specimens from the freeze-thaw group and the control group respectively, and record the maximum failure load for each specimen in each group.

[0088] The splitting tensile strength of a single specimen was calculated using the formula R = (2P) / (πdh), where P is the maximum failure load (kN), d is the specimen diameter (m, average measured value), and h is the specimen height (m, average measured value). The freeze-thaw splitting tensile strength ratio (%) was then calculated based on the ratio of the average splitting tensile strengths of the freeze-thaw group and the control group.

[0089] (4) Dynamic stability test

[0090] Random samples were taken from the mixtures prepared in the examples and comparative examples, each weighing approximately 5000g (enough to form one 300×300×50mm specimen). These samples were placed in an oven at 165±5℃ for 4-6 hours to ensure uniform heating. A thin layer of release agent was applied to the inner wall of the rutting mold, which was then placed on the platform of a roller mill. The mold height was adjusted so that the specimen thickness after rolling reached 50±2mm. The heated mixture was poured into the mold, the surface was leveled with a scraper, and the mold was preheated in an oven at 165±5℃ for 30 minutes. The mold was then transferred to the roller mill, where a roller pressure of 0.7MPa and a rolling speed of 40 times / min were used for 25 rolling passes (one round trip counts as one pass), ensuring that the specimen density reached at least 96% of the Marshall standard density. After compaction, the specimen was allowed to cool to room temperature and then demolded to obtain a 300×300×50mm rut specimen. The surface of the specimen was free of loose material, cracks, or obvious compaction marks.

[0091] Set the temperature of the constant temperature chamber of the rutting test machine to 60±0.5℃, and place the prepared specimen in the constant temperature chamber for 5±0.5 hours. Start the rutting test machine, adjust the loading wheel pressure to 0.7±0.05MPa, and set the loading frequency N to 42 times / min (simulating the speed of a vehicle on a highway, approximately 60km / h). Install the displacement sensor at the centerline of the specimen, ensuring close contact between the sensor and the specimen surface. Remove the specimen from the constant temperature chamber after heat preservation and quickly place it on the test platform of the rutting test machine. Start the loading program and begin recording displacement data. The test lasts for 60 minutes, or stops when the specimen deformation reaches 20mm (whichever comes first). Record the displacement values ​​at different time points during the loading process, focusing on the displacement values ​​(d1 and d2) at 45 minutes (t1) and 60 minutes (t2). Calculate the dynamic stability (times / mm) using the formula DS=(t2-t1)×N / (d2-d1).

[0092] The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the test results of Examples 1-4 are significantly better than those of Comparative Examples 1-3 in terms of Marshall stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability. This indicates a synergistic effect between residual oil, slag powder, and waste tire rubber powder. The composite of residual oil and new asphalt provides a good interfacial environment for the rubber powder and slag powder. The porous structure of the slag powder adsorbs residual oil and asphalt, enhancing the dispersibility of the rubber powder. The elastic network of the rubber powder assists the slag powder in improving the skeleton stability. Together, these three components construct a "regeneration-reinforcement-elasticity" composite system, enabling the mixture to simultaneously meet the comprehensive requirements of highways for high temperature, low temperature, water stability, and fatigue. Furthermore, the cost of epoxidized soybean oil used in Comparative Example 1 is higher than that of residual oil. Therefore, the solution in this example has greater advantages in performance, cost, and environmental protection.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A composite modified recycled asphalt concrete mixture, characterized in that, By mass parts, it includes the following components: 50-70 portions of waste asphalt pavement material; 15-30 portions of fresh material; 0.5-3 parts of residual oil; 1-6 parts of waste tire rubber powder; 3-8 parts of slag powder; and 3-5 parts of new asphalt.

2. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The waste asphalt pavement material has a particle size ≤15mm and an asphalt content of 3.5-4.5%.

3. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The new aggregate consists of coarse aggregate with a particle size of 4.75-10 mm and fine aggregate with a particle size of 0.15-4.75 mm, and the mass ratio of the coarse aggregate to the fine aggregate is 1:0.8-1.

5.

4. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The waste tire rubber powder has a particle size of 40-80 mesh, and the waste tire rubber powder is activated by mixing with preheated sludge oil.

5. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The mass ratio of waste tire rubber powder to residual oil is 1:0.3-1.

6. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The slag powder was calcined at 700-1100℃ and, after treatment, has a specific surface area ≥400 m². 2 / kg of powder.

7. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The recycled asphalt concrete mixture further includes processing aids, which include at least one of compatibilizers, stabilizers, fillers, photocatalysts, or fiber materials.

8. The composite modified waste asphalt concrete recycled mixture according to claim 1, characterized in that, The new asphalt is selected from at least one of SBS modified asphalt, recycled matrix asphalt, or soft asphalt.

9. A method for preparing a composite modified waste asphalt concrete recycled mixture as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: S1. Heat the residual oil to 110-130℃, then add waste tire rubber powder for premixing to obtain a composite recycling agent; S2. Crush and screen the waste asphalt pavement material to a particle size ≤15mm, then dehydrate and dry it; then add new aggregate and slag powder in sequence, dry mix for 1-2 minutes, and finally add composite recycling agent and new asphalt, wet mix for 1-2 minutes to obtain the finished product.

10. The preparation method according to claim 9, characterized in that, In step S1, the time for premixing the residual oil and waste tire rubber powder is 20-40 minutes; the waste tire rubber powder is pre-activated, and the specific steps are as follows: the waste tire rubber powder is soaked in an activator solution, heated and stirred for 1-2 hours, then washed with water until neutral, dried and sieved to obtain activated and modified rubber powder. In step S2, the waste asphalt pavement material is dehydrated and dried at a temperature of 100-120℃ for 40-60 minutes; the slag powder is pre-treated with an alkaline activation solution of water glass-sodium hydroxide; the composite recycling agent and the new asphalt are pre-mixed and then added to the dry-mixed mixture.

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