Asphalt mixture based on waste tire rubber powder and waste tire fiber composite modification and preparation method

Abstract

The invention discloses an asphalt mixture based on composite modification of waste tire rubber powder and waste tire fibers and a preparation method of the asphalt mixture. The asphalt mixture comprises the following substances in percentage by weight: 76-85wt% of aggregate, 5-11wt% of mineral powder, 5.5-6.5 wt% of composite modified asphalt, 4-7wt% of an asphalt adsorption material and 0.3-0.8 wt% of a reinforcing material. The preparation method comprises the following steps: preparing composite modified asphalt; a mixing pot is preheated to a preset temperature, the aggregate and the reinforcing material are put into the mixing pot to be mixed, and the reinforcing material is evenly dispersed; adding composite modified asphalt for mixing, so that the composite modified asphalt is uniformly coated on the surface of the solid material; adding an asphalt adsorption material for mixing so as to stabilize the internal structure of the system; and adding the mineral powder for mixing, and uniformly mixing the substances, thereby obtaining the asphalt mixture based on the composite modification of the waste tire rubber powder and the waste tire fibers. According to the invention, the compatibility problem of the waste tire rubber powder and the waste tire fibers can be fundamentally solved, and the prepared asphalt mixture has excellent comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of road engineering material design and preparation technology, specifically relating to an asphalt mixture based on waste tire rubber powder and waste tire fiber composite modification and its preparation method. Background Technology

[0002] Asphalt mixtures, as the main paving material in modern road engineering, are widely used in the paving of various transportation routes such as highways, urban arterial roads, and rural roads due to their good adhesion, smoothness, and ease of construction. Their comprehensive performance directly determines the service life and driving safety of the pavement. However, in actual service, traditional asphalt mixtures, limited by their inherent material properties, are prone to pavement distress such as high-temperature rutting, low-temperature cracking, fatigue damage, and water damage under the combined effects of repeated high-load traffic, extreme weather conditions, and long-term environmental erosion. To improve the road performance of traditional asphalt mixtures, the industry has developed various modification technologies, mainly by adding various modifiers to modify the asphalt, or by optimizing the mixture gradation design and improving construction processes to enhance the mixture's own structure.

[0003] The generation of waste tires has also increased significantly, leading to a surge in demand for their recycling and utilization. As solid waste, waste tires are traditionally disposed of mainly through landfilling and stockpiling, which not only occupies a large amount of land but also poses risks of spontaneous combustion and long-term environmental pollution. Therefore, promoting the high-value-added resource utilization of waste tires has become an inevitable requirement for practicing low-carbon, environmentally friendly, and sustainable development.

[0004] Waste tires, through deep processing, can yield various recycled materials such as rubber, carbon black, steel wire, and fibers, with fibers accounting for approximately 10%. In the field of road engineering, current recycling of waste tires mainly focuses on components like rubber, carbon black, and steel wire, while the recycling of fibers remains largely unexplored. Using waste tire rubber powder and waste tire fibers synergistically as modifiers for asphalt or asphalt mixtures not only allows for large-scale disposal of waste tires but also significantly improves the overall performance of road materials, representing a highly promising technological approach.

[0005] Existing technologies regarding the application of waste tire rubber powder and / or waste tire fibers in asphalt mixtures face the following technical bottlenecks: First, the modification effect of a single component is limited. While adding waste tire rubber powder can improve the elastic recovery of asphalt and enhance the fatigue resistance of the mixture, it also leads to a decrease in the stiffness of the mixture and a limited improvement in high-temperature rutting resistance. In addition, if the interfacial compatibility between the asphalt mastic and waste tire rubber powder is not properly treated, it can also affect the long-term stability of the mixture. Although adding waste tire fiber can play a role in reinforcing, toughening, and stabilizing asphalt, its modification function is relatively singular and it is difficult to synergistically improve the high-temperature rutting resistance, elastic recovery, and fatigue resistance of the mixture. Furthermore, the uneven dispersion and weak interfacial bonding of waste tire fiber in asphalt can lead to debonding and peeling of the asphalt mastic during long-term service.

[0006] Secondly, while theoretically, combining waste tire rubber powder and waste tire fibers could produce highly elastic, tough, crack-resistant, and durable asphalt mixtures, achieving a synergistic improvement in overall performance, in practical applications, they are difficult to directly modify asphalt mixtures through simple blending. Due to significant differences in their physicochemical properties, waste tire rubber powder and waste tire fibers struggle to form a uniform and stable three-phase composite mastic structure in asphalt systems. Simple blending easily leads to component segregation and uneven dispersion, creating stress-weak zones at the interfaces, which in turn induce cracks and weaken the modification effect. Without targeted design in material proportions and process parameters, waste tire rubber powder hinders the effective formation of the waste tire fiber network, while the structure of the waste tire fibers limits the full utilization of the elasticity of the waste tire rubber powder.

[0007] Thirdly, for SMA asphalt mixtures, the amount of coarse aggregate is relatively large, resulting in a smaller specific surface area and thus a larger average film thickness of the asphalt binder. In the absence of internal stabilizing or adsorbing components, this thick asphalt film system is prone to migration, flow, and even leakage of asphalt under high temperatures or long-term loads. This not only causes uneven asphalt distribution but also leads to a decrease in the effective asphalt content within the mixture, severely damaging the structural strength and durability of the pavement.

[0008] Fourth, for SMA asphalt mixtures, the skeleton structure of the mixture mainly relies on the point contact and interlocking action between coarse aggregates. If the skeleton structure lacks internal constraints, such as the spatial winding and reinforcement of reinforcing materials, the interlocking and frictional constraint force between coarse aggregates is insufficient. Under repeated loads, aggregate displacement and skeleton reconstruction are likely to occur, resulting in overall deformation of the mixture and affecting structural stability.

[0009] Therefore, there is an urgent need to develop an asphalt mixture and preparation method based on the composite modification of waste tire rubber powder and waste tire fiber to solve the problems existing in the current technology. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides an asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber. The mass percentage of each substance in the asphalt mixture is as follows: aggregate 76-85 wt%, mineral powder 5-11 wt%, composite modified asphalt 5.5-6.5 wt%, asphalt adsorbent 4-7 wt%, and reinforcing material 0.3-0.8 wt%, with the sum of the contents of all substances being 100 wt%. Both the composite modified asphalt and the asphalt adsorbent contain waste tire rubber powder and waste tire fiber.

[0011] Preferably, the aggregate includes seven particle size grades, and each particle size grade accounts for the following percentages by mass: 4.75mm ≤ particle size < 9.5mm 15-20wt%, 2.36mm ≤ particle size < 4.75mm 25-30wt%, 1.18mm ≤ particle size < 2.36mm 35-40wt%, 0.6mm ≤ particle size < 1.18mm 5-8wt%, 0.3mm ≤ particle size < 0.6mm 3-5wt%, 0.15mm ≤ particle size < 0.3mm 3-5wt%, and 0.075mm ≤ particle size < 0.15mm 3-5wt%.

[0012] Alternatively, the aggregate may comprise eight particle size grades, with each grade representing a percentage of the aggregate's mass as follows: 9.5mm ≤ particle size < 13.2mm 10-15 wt%, 4.75mm ≤ particle size < 9.5mm 25-30 wt%, 2.36mm ≤ particle size < 4.75mm 32-38 wt%, 1.18mm ≤ particle size < 2.36mm 8-10 wt%, 0.6mm ≤ particle size < 1.18mm 3-5 wt%, 0.3mm ≤ particle size < 0.6mm 3-5 wt%, 0.15mm ≤ particle size < 0.3mm 3-5 wt%, and 0.075mm ≤ particle size < 0.15mm 3-5 wt%.

[0013] Alternatively, the aggregate may comprise nine particle size grades, with each grade representing a percentage of the aggregate's mass as follows: 13.2mm ≤ particle size < 16mm 5-10 wt%, 9.5mm ≤ particle size < 13.2mm 25-30 wt%, 4.75mm ≤ particle size < 9.5mm 30-35 wt%, 2.36mm ≤ particle size < 4.75mm 10-15 wt%, 1.18mm ≤ particle size < 2.36mm 3-5 wt%, 0.6mm ≤ particle size < 1.18mm 3-5 wt%, 0.3mm ≤ particle size < 0.6mm 3-5 wt%, 0.15mm ≤ particle size < 0.3mm 3-5 wt%, and 0.075mm ≤ particle size < 0.15mm 3-5 wt%.

[0014] The aggregate is basalt or diabase; the mineral powder is limestone with a particle size of less than 0.075 mm.

[0015] In any of the above embodiments, it is preferred that the mass percentage of each substance in the composite modified asphalt is 72-78 wt% of base asphalt, 17-24 wt% of composite modifier, and 3-6 wt% of SBS modifier, with the sum of the contents of each substance being 100 wt%. The base asphalt is No. 70 or No. 90 base asphalt, and the SBS modifier is a linear SBS modifier.

[0016] In any of the above embodiments, it is preferred that the mass percentage of each substance in the composite modifier is as follows: 55-60 wt% waste tire rubber powder, 25-30 wt% waste tire fiber, 2.5-3.5 wt% rubber powder pretreatment agent, 1.5-2.5 wt% fiber pretreatment agent, 5-8 wt% interfacial solvent, and 2-3 wt% auxiliary additives, with the sum of the contents of each substance being 100 wt%.

[0017] The waste tire rubber powder comprises three particle size grades, with each grade accounting for the following percentages by mass: 0.6mm ≤ particle size ≤ 0.85mm 45-55wt%, 0.25mm ≤ particle size < 0.6mm 30-38wt%, and 0.18mm ≤ particle size < 0.25mm 12-20wt%. The diameter of the waste tire fibers is controlled within the range of 8-20μm, and the length is controlled within the range of 6-12mm. The three particle size grades of the waste tire rubber powder can be used individually, but more preferably, all three particle size grades can be used simultaneously.

[0018] In any of the above embodiments, it is preferred that the mass percentage of each substance in the rubber powder pretreatment agent is as follows: polyethylene polyamine 12-18 wt%, dibenzothiazole disulfide 1.8-3.8 wt%, alkylphenol disulfide 2-4 wt%, stearic acid 2.5-4.5 wt%, silane coupling agent 20-28 wt%, and epoxidized soybean oil 48-55 wt%, with the sum of the contents of each substance being 100 wt%; the type of silane coupling agent is KH-590.

[0019] In any of the above embodiments, it is preferred that the mass percentage of each substance in the fiber pretreatment agent is 65-80 wt% liquid polybutadiene, 10-20 wt% silane coupling agent, 2-5 wt% tetramethylthiuram disulfide, and 5-15 wt% nano-calcium carbonate, with the sum of the contents of each substance being 100 wt%; the type of silane coupling agent is KH-590.

[0020] In any of the above embodiments, it is preferred that the mass percentage of each substance in the interfacial solvent is 60-72 wt% polypropylene grafted with maleic anhydride and 28-40 wt% chlorinated polypropylene; the auxiliary additive is composed of zinc stearate and antioxidant 1010, and the mass ratio of zinc stearate to antioxidant 1010 is 1.2-1.8:1.

[0021] In any of the above embodiments, preferably, the mass percentage of each substance in the asphalt adsorbent material is as follows: 38-45 wt% waste tire rubber powder, 8-12 wt% waste tire fiber, 10-15 wt% activated carbon, and 30-38 wt% zeolite powder, with the sum of the contents of each substance being 100 wt%; the particle size of the waste tire rubber powder is controlled within the range of 0.25-0.6 mm, the diameter of the waste tire fiber is controlled within the range of 8-20 μm, and the length is controlled within the range of 6-12 mm, the particle size of the activated carbon is not greater than 75 μm, and the particle size of the zeolite powder is not greater than 38 μm.

[0022] In any of the above embodiments, it is preferred that the mass percentage of each substance in the reinforcing material is 60-70 wt% waste tire fiber and 30-40 wt% calcium carbonate whiskers; the diameter of the waste tire fiber is controlled within the range of 8-20 μm and the length is controlled within the range of 6-12 mm, and the diameter of the calcium carbonate whiskers is controlled within the range of 0.5-1 μm and the length is controlled within the range of 0.8-1.5 mm.

[0023] This invention also provides a method for preparing asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber, the preparation method comprising the following steps in sequence: Step 1: Prepare composite modified asphalt in advance and keep it warm for later use; Step 2: Place the aggregates and mineral powder of each particle size into an oven for drying and keep them warm for later use; Step 3: Preheat the mixing pot to the preset temperature, put the dried aggregates of various particle sizes, as well as the waste tire fibers and calcium carbonate whiskers in the reinforcing material into the mixing pot for mixing, so that the aggregates of various particle sizes are mixed evenly, and the waste tire fibers and calcium carbonate whiskers are evenly dispersed in the aggregates. Step 4: Put the pre-prepared composite modified asphalt into the mixing pot and mix it to make the composite modified asphalt evenly coat the surface of the solid material. Step 5: Add the waste tire rubber powder, waste tire fiber, activated carbon and zeolite powder from the asphalt adsorbent material into the mixing pot and mix them to increase the viscosity of the asphalt and stabilize the internal structure of the system. Step Six: Place the dried mineral powder into a mixing pot and mix it to ensure that all substances are evenly mixed, thus obtaining the asphalt mixture based on the composite modification of waste tire rubber powder and waste tire fiber.

[0024] Preferably, in step one, the preparation of the composite modified asphalt includes the following steps in a specific order: Step 1.1: Place the base asphalt in an oven for heat treatment at a temperature of 140-150℃ for 2-3 hours to bring the base asphalt into a fluid state. Step 1.2: Place the mixing container containing the base asphalt into an oil bath and stir. The stirring temperature is 150-160℃, the stirring speed is 200-300 rpm, and the stirring time is 2-5 min. Step 1.3: Increase the stirring temperature to 165-175℃ and the stirring speed to 4000-5000 rpm. Put the SBS modifier into the stirring container and perform high-speed shear stirring for 25-35 minutes to ensure that all substances are mixed evenly. Step 1.4: Keep the stirring temperature and stirring speed constant, put the pre-prepared composite modifier into the mixing container and perform high-speed shear stirring for 25-35 minutes to ensure that all substances are mixed evenly, thus obtaining the composite modified asphalt.

[0025] In any of the above embodiments, it is preferred that the preparation of the composite modifier includes the following steps in a specific order: Step (1): Pre-treat waste tire rubber powder. Specific operation: First, put epoxidized soybean oil into a reaction vessel and heat it while stirring at a speed of 100-200 rpm. After the temperature rises to 60-80℃, add dibenzothiazole disulfide, alkylphenol disulfide, and stearic acid into the reaction vessel and continue stirring for 10-15 minutes to disperse them evenly. Then, add the silane coupling agent into the reaction vessel and continue stirring for 5-10 minutes to mix them evenly. Subsequently, cool down while stirring. After the temperature drops to 40-50℃, add polyethylene polyamine into the reaction vessel and continue stirring for 20-30 minutes. A rubber powder pretreatment agent is prepared. Then, waste tire rubber powder of various particle sizes is placed into a mixer, and the temperature is increased while stirring. The stirring speed is 100-200 rpm. After the temperature rises to 60-80℃, stirring is continued for 3-5 minutes to ensure that the waste tire rubber powder of various particle sizes is evenly mixed. Then, the rubber powder pretreatment agent is added to the mixer and stirring is continued for 3-5 minutes to ensure that the material is evenly mixed. Finally, the stirring temperature is increased to 115-125℃, and the stirring speed is increased to 800-1000 rpm to stir the material in the mixer for 40-50 minutes to ensure that the material is evenly dispersed. Step (2): Pre-treat the waste tire fibers. Specific steps: First, place liquid polybutadiene into another reactor and heat it while stirring at 300-500 rpm. Once the temperature reaches 60-80℃, increase the stirring speed to 1000-1500 rpm. Add nano-calcium carbonate to the reactor and stir for 10-15 minutes to ensure uniform dispersion. Then, cool the reactor while stirring until the temperature drops to 40-50℃. Add the silane coupling agent to the reactor and continue stirring for 5-10 minutes. Mix the materials thoroughly, then add tetramethylthiuram disulfide to the reactor and continue stirring for 10-15 minutes to ensure uniform dispersion, thus obtaining the fiber pretreatment agent. Next, place the waste tire fibers and fiber pretreatment agent into another mixer, stirring and heating simultaneously at a speed of 300-500 rpm. Once the temperature reaches 60-80℃, continue stirring for 5-8 minutes to ensure uniform mixing. Finally, increase the stirring temperature to 95-115℃ and stir the materials in the mixer for 30-40 minutes to ensure uniform dispersion. Step (3): Put the pretreated waste tire rubber powder and the pretreated waste tire fiber into the same mixer and mix them. The mixing temperature is 120-130℃, the mixing speed is 1000-1500rpm, and the mixing time is 3-5min to make the materials evenly mixed. Step (4): Increase the stirring temperature to 150-160℃, keep the stirring speed constant, put the polypropylene grafted with maleic anhydride and chlorinated polypropylene in the interface solvent and the zinc stearate and antioxidant 1010 in the auxiliary additives into the mixer and continue stirring for 5-10 minutes to make the materials evenly mixed. Step (5): Use granulation equipment to granulate the uniformly mixed material to obtain the composite modifier. The particle size is controlled within the range of 3-8mm and the length is controlled within the range of 0.5-1.5cm.

[0026] In any of the above schemes, it is preferred that in step two, the drying temperature of aggregates and mineral powder of each particle size is 170-190℃ and the drying time is 2.5-3h.

[0027] In any of the above schemes, it is preferred that, in step three, the preheating temperature of the mixing pot is 170-185℃, the mixing speed of aggregates and reinforcing materials of various particle sizes is 100-300 rpm, and the mixing time is 2-3 min.

[0028] In any of the above schemes, it is preferred that, in step four, after adding the composite modified asphalt, the mixing speed is 100-300 rpm and the mixing time is 90-120 s.

[0029] In any of the above schemes, it is preferred that, in step five, after adding the asphalt adsorbent, the mixing speed is 100-300 rpm and the mixing time is 90-120 s.

[0030] In any of the above schemes, it is preferred that, in step six, after adding the mineral powder, the mixing speed is 100-300 rpm and the mixing time is 90-120 s.

[0031] The ovens, mixing pots, oil baths, reaction vessels, mixers (including ordinary mixers and high-speed shear mixers), and granulation equipment (suitable for melt granulation) used in this invention are all traditional equipment, and there are no special requirements for the equipment models. Some components of each piece of equipment can be slightly adjusted or modified according to actual usage without affecting the overall performance. The operating methods for each piece of equipment should follow existing technologies, as long as the aforementioned process parameters meet the requirements of this invention. The waste tire rubber powder and waste tire fibers used in this invention can be purchased directly; there are no special requirements for their chemical composition and separation process, as long as the particle size of the waste tire rubber powder and the size of the waste tire fibers meet the requirements of this invention.

[0032] The particle size ranges of the aggregates in this invention include: 13.2mm ≤ particle size < 16mm, 9.5mm ≤ particle size < 13.2mm, 4.75mm ≤ particle size < 9.5mm, 2.36mm ≤ particle size < 4.75mm, 1.18mm ≤ particle size < 2.36mm, 0.6mm ≤ particle size < 1.18mm, 0.3mm ≤ particle size < 0.6mm, 0.15mm ≤ particle size < 0.3mm, and 0.075mm ≤ particle size < 0.15mm. For each particle size range, the material is obtained by passing it through two sieves, one above the other, with a particle size between the two sieve openings. For example, 1.18mm ≤ particle size < 2.36mm means the material is obtained by passing it through a 2.36mm sieve and a 1.18mm sieve, with a particle size between 1.18mm and 2.36mm.

[0033] This invention innovatively uses waste tire rubber powder and waste tire fiber in combination to prepare asphalt mixture. Waste tire rubber powder and / or waste tire fiber are used multiple times in the entire asphalt mixture preparation process, and the two substances play different roles at different process stages.

[0034] In the preparation stage of the composite modifier, waste tire rubber powder and waste tire fibers are pretreated and then melt-blended under the action of an interfacial solvent, enabling chemical coupling and compatibility between the two substances at the microscopic interface. Waste tire rubber powder, as an elastic component, is embedded into the system through interfacial reaction, while waste tire fibers form a reinforcing skeleton and network support. The two substances form a stable composite structure at the microscale, fundamentally improving the elastic recovery and damage resistance of asphalt.

[0035] In the asphalt mixture preparation stage, waste tire rubber powder and waste tire fibers are used synergistically again, but the mechanism of action changes to physical synergy. Waste tire rubber powder adsorbs asphalt and swells moderately due to its porous properties, while waste tire fibers form a spatial network structure through their high specific surface area. Together, they optimize asphalt distribution, adsorb and stabilize asphalt, and prevent asphalt bleeding or migration during construction and service, ensuring uniform and stable asphalt film thickness.

[0036] Furthermore, during the asphalt mixture preparation stage, waste tire fibers, acting as a reinforcing material, work synergistically with calcium carbonate whiskers to strengthen and toughen the mixture. The waste tire fibers and calcium carbonate whiskers are uniformly dispersed within the aggregate skeleton to form a reinforcing network, effectively bridging microcracks, dispersing stress concentration, significantly improving the crack resistance of the asphalt mixture, and preventing deformation.

[0037] This invention relates to an asphalt mixture modified from waste tire rubber powder and waste tire fiber, and its preparation method, which has the following beneficial effects: (1) This invention achieves synergistic modification of waste tire rubber powder and waste tire fiber through material proportioning and process design, overcoming the limitations of single-component modification. The waste tire rubber powder fully utilizes its high elasticity and fatigue resistance in the system, while the reinforcing network of waste tire fiber effectively compensates for the stiffness loss caused by the waste tire rubber powder. In addition, it can ensure that each component is uniformly dispersed in the asphalt mortar and that the interface is firmly bonded, solving the problems of asphalt mortar debonding and peeling caused by poor compatibility, and ensuring the long-term service stability of the asphalt mixture.

[0038] (2) In this invention, waste tire rubber powder and waste tire fibers are pretreated, and an interfacial solvent is introduced to melt-blend the pretreated waste tire rubber powder and waste tire fibers, establishing a coupling connection within the system. The waste tire rubber powder and waste tire fibers form a stable composite structure that is uniformly dispersed and mutually supportive in the asphalt matrix. The two are synergistically coupled, solving the problems of component segregation and interfacial stress concentration caused by simple blending, thereby preparing a composite modified asphalt with high elasticity, high toughness, crack resistance, and durability.

[0039] (3) The waste tire rubber powder and waste tire fiber added in this invention are not simple physical filler materials, but are transformed into a composite modifier with complementary functions and interface compatibility through specific pretreatment, material ratio and process design. This composite modifier can form a synergistic and stable system with asphalt and aggregates, fundamentally solving the compatibility problem, thereby preparing asphalt mixtures with excellent high-temperature stability, low-temperature crack resistance, fatigue resistance and durability.

[0040] (4) This invention addresses the technical problem of the thick asphalt film in SMA asphalt mixtures being prone to flow migration. It utilizes the adsorption and swelling characteristics of waste tire rubber powder and the spatial network effect of waste tire fibers to introduce an internal stabilization mechanism into the asphalt system, which significantly improves the stability of the thick asphalt film under high temperature and load. This fundamentally inhibits the leakage and uneven migration of asphalt, ensuring the long-term stability and uniform distribution of the effective asphalt content inside the asphalt mixture.

[0041] (5) This invention addresses the technical problem that SMA asphalt mixtures are prone to aggregate displacement and structural instability due to insufficient skeleton constraint. It uses waste tire fiber as a key reinforcing component, which is uniformly dispersed in the aggregate and forms a spatial winding network. This generates internal reinforcement and constraint on the aggregates in point contact, significantly enhancing the interlocking friction and integrity of the aggregates, and greatly improving the deformation capacity of asphalt mixtures under repeated loads.

[0042] (6) This invention transforms waste tire rubber powder and waste tire fiber, which are difficult to process, into high-performance asphalt mixture, realizing the resource utilization of solid waste. It has advantages such as low carbon and environmental protection, low cost and resource recycling, and provides a practical and feasible technical path for the green and low carbon development of road engineering construction. Attached Figure Description

[0043] Figure 1 A photograph of waste tire rubber powder in a preferred embodiment of the asphalt mixture modified by waste tire rubber powder and waste tire fiber according to the present invention and the preparation method thereof; Figure 2 for Figure 1 A photograph of the waste tire fibers shown in the embodiment; Figure 3 for Figure 1 A photograph of the composite modifier prepared in the illustrated embodiment; Figure 4 for Figure 1 A photograph of the composite modified asphalt prepared in the illustrated embodiment; Figure 5 for Figure 1 Fluorescent images of the composite modified bitumen prepared in the illustrated embodiment; Figure 6 for Figure 1 Photograph of SMA asphalt mixture containing waste tire rubber powder and waste tire fiber prepared in the example shown; Figure 7 for Figure 1 The diagram shows the asphalt leakage state of the SMA asphalt mixture containing waste tire rubber powder and waste tire fiber prepared in the example shown. Figure 8 Fluorescence images of ordinary SBS-modified bitumen used for comparison; Figure 9 The diagram shows the state of asphalt leakage in a standard SMA asphalt mixture prepared for comparison. Detailed Implementation

[0044] To further understand the invention, the following detailed description of the invention will be provided in conjunction with specific embodiments.

[0045] Example 1: According to a preferred embodiment of the present invention, the asphalt mixture based on the composite modification of waste tire rubber powder and waste tire fiber comprises the following mass percentages: aggregate 80wt%, mineral powder 8wt%, composite modified asphalt 6wt%, asphalt adsorbent 5.5wt%, and reinforcing material 0.5wt%; both the composite modified asphalt and the asphalt adsorbent contain waste tire rubber powder and waste tire fiber.

[0046] This embodiment is an SMA asphalt mixture, the aggregate includes seven particle size grades, and the mass percentage of each particle size grade in the aggregate is as follows: 4.75mm ≤ particle size < 9.5mm accounts for 17wt%, 2.36mm ≤ particle size < 4.75mm accounts for 27wt%, 1.18mm ≤ particle size < 2.36mm accounts for 37wt%, 0.6mm ≤ particle size < 1.18mm accounts for 7wt%, 0.3mm ≤ particle size < 0.6mm accounts for 4wt%, 0.15mm ≤ particle size < 0.3mm accounts for 4wt%, and 0.075mm ≤ particle size < 0.15mm accounts for 4wt%.

[0047] Alternatively, the aggregate may include eight particle size categories, with each category accounting for the following percentages by mass: 9.5mm ≤ particle size < 13.2mm 13wt%, 4.75mm ≤ particle size < 9.5mm 27wt%, 2.36mm ≤ particle size < 4.75mm 35wt%, 1.18mm ≤ particle size < 2.36mm 9wt%, 0.6mm ≤ particle size < 1.18mm 4wt%, 0.3mm ≤ particle size < 0.6mm 4wt%, 0.15mm ≤ particle size < 0.3mm 4wt%, and 0.075mm ≤ particle size < 0.15mm 4wt%.

[0048] Alternatively, the aggregate comprises nine particle size grades, with each grade accounting for the following percentages by mass: 13.2mm ≤ particle size < 16mm (8 wt%), 9.5mm ≤ particle size < 13.2mm (27 wt%), 4.75mm ≤ particle size < 9.5mm (32 wt%), 2.36mm ≤ particle size < 4.75mm (13 wt%), 1.18mm ≤ particle size < 2.36mm (4 wt%), 0.6mm ≤ particle size < 1.18mm (4 wt%), 0.3mm ≤ particle size < 0.6mm (4 wt%), 0.15mm ≤ particle size < 0.3mm (4 wt%), and 0.075mm ≤ particle size < 0.15mm (4 wt%). The aggregate is basalt or diabase; the mineral powder is limestone with a particle size less than 0.075mm.

[0049] The composite modified asphalt comprises the following mass percentages: base asphalt 75 wt%, composite modifier 21 wt%, and SBS modifier 4 wt%. The base asphalt is No. 70 base asphalt, and the SBS modifier is a linear SBS modifier.

[0050] The mass percentages of each substance in the composite modifier are as follows: 58 wt% waste tire rubber powder, 28 wt% waste tire fiber, 3 wt% rubber powder pretreatment agent, 2 wt% fiber pretreatment agent, 6.5 wt% interface solvent, and 2.5 wt% auxiliary additives.

[0051] The waste tire rubber powder comprises three particle size grades, with each grade accounting for the following percentages by mass: 0.6mm ≤ particle size ≤ 0.85mm 50wt%, 0.25mm ≤ particle size < 0.6mm 34wt%, and 0.18mm ≤ particle size < 0.25mm 16wt%. The diameter of the waste tire fibers is controlled within the range of 8-20μm, and the length is controlled within the range of 6-12mm.

[0052] The mass percentages of each substance in the rubber powder pretreatment agent are as follows: polyethylene polyamine 15.7 wt%, dibenzothiazole disulfide 2.8 wt%, alkylphenol disulfide 3 wt%, stearic acid 3.5 wt%, silane coupling agent 24 wt%, and epoxidized soybean oil 51 wt%; the silane coupling agent is model KH-590.

[0053] The mass percentages of each substance in the fiber pretreatment agent are as follows: 68 wt% liquid polybutadiene, 16 wt% silane coupling agent, 4 wt% tetramethylthiuram disulfide, and 12 wt% nano-calcium carbonate; the silane coupling agent is of type KH-590.

[0054] The mass percentage of each substance in the interfacial solvent is 66 wt% polypropylene grafted with maleic anhydride and 34 wt% chlorinated polypropylene; the auxiliary additive is composed of zinc stearate and antioxidant 1010, and the mass ratio of zinc stearate to antioxidant 1010 is 1.5:1.

[0055] The mass percentages of each substance in the asphalt adsorbent material are as follows: 43 wt% waste tire rubber powder, 10 wt% waste tire fiber, 13 wt% activated carbon, and 34 wt% zeolite powder. The particle size of the waste tire rubber powder is controlled within the range of 0.25-0.6 mm, the diameter of the waste tire fiber is controlled within the range of 8-20 μm, and the length is controlled within the range of 6-12 mm. The particle size of the activated carbon is not greater than 75 μm, and the particle size of the zeolite powder is not greater than 38 μm.

[0056] The mass percentage of each substance in the reinforcing material is 65wt% waste tire fiber and 35wt% calcium carbonate whiskers; the diameter of the waste tire fiber is controlled within the range of 8-20μm and the length is controlled within the range of 6-12mm, and the diameter of the calcium carbonate whiskers is controlled within the range of 0.5-1μm and the length is controlled within the range of 0.8-1.5mm.

[0057] This embodiment also provides a method for preparing asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber, the preparation method including the following steps in sequence: Step 1: Prepare composite modified asphalt in advance and keep it warm for later use; Step 2: Place the aggregates and mineral powder of each particle size into an oven for drying and keep them warm for later use; Step 3: Preheat the mixing pot to the preset temperature, put the dried aggregates of various particle sizes, as well as the waste tire fibers and calcium carbonate whiskers in the reinforcing material into the mixing pot for mixing, so that the aggregates of various particle sizes are mixed evenly, and the waste tire fibers and calcium carbonate whiskers are evenly dispersed in the aggregates. Step 4: Put the pre-prepared composite modified asphalt into the mixing pot and mix it to make the composite modified asphalt evenly coat the surface of the solid material. Step 5: Add the waste tire rubber powder, waste tire fiber, activated carbon and zeolite powder from the asphalt adsorbent material into the mixing pot and mix them to increase the viscosity of the asphalt and stabilize the internal structure of the system. Step Six: Place the dried mineral powder into a mixing pot and mix it to ensure that all substances are evenly mixed, thus obtaining the asphalt mixture based on the composite modification of waste tire rubber powder and waste tire fiber.

[0058] In step one, the preparation of the composite modified asphalt includes the following steps in sequence: Step 1.1: Place the base asphalt in an oven for heat treatment at a temperature of 145℃ for 2.5 hours to bring the base asphalt into a fluid state. Step 1.2: Place the mixing container containing the base asphalt into an oil bath and stir. The stirring temperature is 155℃, the stirring speed is 250 rpm, and the stirring time is 3.5 min. Step 1.3: Increase the stirring temperature to 170℃ and the stirring speed to 4500 rpm. Put the SBS modifier into the stirring container and perform high-speed shear stirring for 30 minutes to ensure that all substances are mixed evenly. Step 1.4: Keep the stirring temperature and stirring speed constant, put the pre-prepared composite modifier into the mixing container and perform high-speed shear stirring for 30 minutes to ensure that all substances are mixed evenly, thus obtaining the composite modified asphalt.

[0059] The preparation of the composite modifier includes the following steps in sequence: Step (1): Pre-treatment of waste tire rubber powder. Specific operation: First, epoxidized soybean oil is placed in a reaction vessel, and the temperature is increased while stirring at 150 rpm. After the temperature reaches 70℃, dibenzothiazole disulfide, alkylphenol disulfide, and stearic acid are added to the reaction vessel and stirred for 12.5 minutes to ensure uniform dispersion. Then, silane coupling agent is added to the reaction vessel and stirred for 7.5 minutes to ensure uniform mixing. Subsequently, the temperature is decreased while stirring. After the temperature drops to 45℃, polyethylene polyamine is added to the reaction vessel and stirred for 2 minutes. After 5 minutes, a rubber powder pretreatment agent is prepared. Then, waste tire rubber powder of various particle sizes is placed into a mixer, and the temperature is increased while stirring. The stirring speed is 150 rpm. After the temperature rises to 70℃, stirring continues for 4 minutes to ensure that the waste tire rubber powder of various particle sizes is evenly mixed. Then, the rubber powder pretreatment agent is added to the mixer and stirred for another 4 minutes to ensure that the material is evenly mixed. Finally, the stirring temperature is increased to 120℃ and the stirring speed is increased to 900 rpm to stir the material in the mixer for 45 minutes to ensure that the material is evenly dispersed. Step (2): Pretreatment of waste tire fibers. Specific operation: First, liquid polybutadiene is placed in another reactor and heated while stirring at a speed of 400 rpm. After the temperature rises to 70℃, the stirring speed is increased to 1250 rpm. Nano-calcium carbonate is added to the reactor and stirred for 12.5 min to ensure uniform dispersion. Then, the temperature is lowered while stirring until it drops to 45℃. Silane coupling agent is added to the reactor and stirred for 7.5 min to ensure uniform mixing. Tetramethylthiuram disulfide is then added to the reactor and stirred for another 12.5 min to ensure uniform dispersion, thus obtaining the fiber pretreatment agent. Next, waste tire fibers and the fiber pretreatment agent are placed in another mixer and heated while stirring at a speed of 400 rpm. After the temperature rises to 70℃, stirring is continued for 6.5 min to ensure uniform mixing. Finally, the stirring temperature is increased to 105℃, and the materials in the mixer are stirred for 35 min to ensure uniform dispersion. Step (3): Put the pretreated waste tire rubber powder and the pretreated waste tire fiber into the same mixer and mix them. The mixing temperature is 125℃, the mixing speed is 1250rpm, and the mixing time is 4min to make the materials evenly mixed. Step (4): Increase the stirring temperature to 155℃, keep the stirring speed constant, put the polypropylene grafted with maleic anhydride and chlorinated polypropylene in the interfacial solvent and the zinc stearate and antioxidant 1010 in the auxiliary additives into the mixer and continue stirring for 7.5 minutes to make the materials evenly mixed. Step (5): Use granulation equipment to granulate the uniformly mixed material to obtain the composite modifier. The particle size is controlled within the range of 3-8mm and the length is controlled within the range of 0.5-1.5cm.

[0060] In step two, the drying temperature for aggregates and mineral powder of all particle sizes is 180℃, and the drying time is 2.8h.

[0061] In step three, the preheating temperature of the mixing pot is 178℃, the mixing speed of aggregates and reinforcing materials of each particle size is 200 rpm, and the mixing time is 2.5 min.

[0062] In step four, after adding the composite modified asphalt, the mixing speed is 200 rpm and the mixing time is 105 s.

[0063] In step five, after adding the asphalt adsorbent, the mixing speed is 200 rpm and the mixing time is 105 s.

[0064] In step six, after adding the mineral powder, the mixing speed is 200 rpm and the mixing time is 105 s.

[0065] The waste tire rubber powder and waste tire fibers used in this embodiment are respectively as follows: Figure 1 and Figure 2 As shown, the prepared composite modifier is as follows: Figure 3 As shown, the prepared composite modified asphalt is as follows: Figure 4 As shown, the fluorescence image of the composite modified asphalt is as follows: Figure 5 As shown, the prepared SMA asphalt mixture containing waste tire rubber powder and waste tire fiber is as follows: Figure 6 As shown, the asphalt mixture exhibits asphalt leakage as follows: Figure 7 As shown.

[0066] from Figure 5 It can be seen that the composite modifier is uniformly dispersed in the base asphalt, and the two have good compatibility, forming a continuous network structure with high molecular cross-linking density. This structure can effectively improve the performance of asphalt.

[0067] from Figure 7 It can be seen that only a small amount of asphalt precipitated in the asphalt mixture, which indicates that under high temperature and high load conditions, the asphalt film inside the asphalt mixture remained stable and did not undergo significant flow or migration.

[0068] This embodiment has the following beneficial effects: (1) Through material ratio and process design, the synergistic modification effect of waste tire rubber powder and waste tire fiber is realized, overcoming the limitations of single component modification. (2) Waste tire rubber powder and waste tire fiber are pretreated in advance, and an interfacial solvent is introduced to melt-blend the pretreated waste tire rubber powder and waste tire fiber, establishing a coupling connection in the system. (3) In response to the technical problem of easy flow migration of thick asphalt film in SMA asphalt mixture, the adsorption and swelling characteristics of waste tire rubber powder and the spatial network effect of waste tire fiber are used to introduce an internal stabilization mechanism in the asphalt system, significantly improving the stability of thick asphalt film under high temperature and load. (4) In response to the technical problem of easy aggregate displacement and structural instability in SMA asphalt mixture due to insufficient skeleton constraint, waste tire fiber is used as a key reinforcing component, which is uniformly dispersed in the aggregate and forms a spatial winding network, generating internal reinforcement and constraint effect on the point contact aggregate, improving the deformation capacity of asphalt mixture under repeated load.

[0069] Example 2: According to another preferred embodiment of the present invention, the asphalt mixture modified by waste tire rubber powder and waste tire fiber and its preparation method are basically the same as those in Embodiment 1, except that: The asphalt mixture comprises the following components: 76.2 wt% aggregate, 11 wt% mineral powder, 5.5 wt% composite modified asphalt, 7 wt% asphalt adsorbent, and 0.3 wt% reinforcing material.

[0070] The aggregate includes seven particle size categories, with the following percentages: 4.75mm ≤ particle size < 9.5mm (16 wt%), 2.36mm ≤ particle size < 4.75mm (30 wt%), 1.18mm ≤ particle size < 2.36mm (35 wt%), 0.6mm ≤ particle size < 1.18mm (8 wt%), 0.3mm ≤ particle size < 0.6mm (3 wt%), 0.15mm ≤ particle size < 0.3mm (5 wt%), and 0.075mm ≤ particle size < 0.15mm (3 wt%).

[0071] Alternatively, the aggregate may include eight particle size categories, with the following percentages: 9.5mm ≤ particle size < 13.2mm 11wt%, 4.75mm ≤ particle size < 9.5mm 30wt%, 2.36mm ≤ particle size < 4.75mm 33wt%, 1.18mm ≤ particle size < 2.36mm 10wt%, 0.6mm ≤ particle size < 1.18mm 3wt%, 0.3mm ≤ particle size < 0.6mm 5wt%, 0.15mm ≤ particle size < 0.3mm 3wt%, and 0.075mm ≤ particle size < 0.15mm 5wt%.

[0072] Alternatively, the aggregate may comprise nine particle size grades, with the following percentages: 13.2mm ≤ particle size < 16mm accounting for 6 wt%, 9.5mm ≤ particle size < 13.2mm accounting for 30 wt%, 4.75mm ≤ particle size < 9.5mm accounting for 30 wt%, 2.36mm ≤ particle size < 4.75mm accounting for 15 wt%, 1.18mm ≤ particle size < 2.36mm accounting for 3 wt%, 0.6mm ≤ particle size < 1.18mm accounting for 5 wt%, 0.3mm ≤ particle size < 0.6mm accounting for 3 wt%, 0.15mm ≤ particle size < 0.3mm accounting for 5 wt%, and 0.075mm ≤ particle size < 0.15mm accounting for 3 wt%.

[0073] The composite modified asphalt comprises, in proportions of 73 wt% base asphalt, 24 wt% composite modifier, and 3 wt% SBS modifier. The composite modifier comprises, in proportions of 55 wt% waste tire rubber powder, 30 wt% waste tire fiber, 2.5 wt% rubber powder pretreatment agent, 2.5 wt% fiber pretreatment agent, 8 wt% interfacial solvent, and 2 wt% auxiliary additives.

[0074] The waste tire rubber powder includes three particle size categories, with the following proportions: 0.6mm ≤ particle size ≤ 0.85mm accounting for 45wt%, 0.25mm ≤ particle size < 0.6mm accounting for 36wt%, and 0.18mm ≤ particle size < 0.25mm accounting for 19wt%.

[0075] The proportions of each substance in the rubber powder pretreatment agent are as follows: 12.7 wt% polyethylene polyamine, 1.8 wt% dibenzothiazole disulfide, 2 wt% dialkylphenol disulfide, 2.5 wt% stearic acid, 28 wt% silane coupling agent, and 53 wt% epoxidized soybean oil.

[0076] The fiber pretreatment agent comprises the following components in the following proportions: 65 wt% liquid polybutadiene, 20 wt% silane coupling agent, 5 wt% tetramethylthiuram disulfide, and 10 wt% nano-calcium carbonate.

[0077] The proportions of each substance in the interface solvent are 60 wt% polypropylene grafted with maleic anhydride and 40 wt% chlorinated polypropylene. The mass ratio of zinc stearate to antioxidant 1010 in the auxiliary additives is 1.2:1.

[0078] The asphalt adsorbent material comprises 40 wt% waste tire rubber powder, 12 wt% waste tire fiber, 10 wt% activated carbon, and 38 wt% zeolite powder. The reinforcing material comprises 60 wt% waste tire fiber and 40 wt% calcium carbonate whiskers.

[0079] In step one, the preparation of the composite modified asphalt includes the following main parameters: heating the base asphalt at 140℃ for 3 hours; placing the mixing container containing the base asphalt into an oil bath and stirring at 150℃, 200 rpm for 5 minutes; increasing the stirring temperature to 165℃ and the stirring speed to 4000 rpm, adding the SBS modifier and performing high-speed shear mixing for 35 minutes; maintaining the stirring temperature and speed constant, adding the pre-prepared composite modifier and continuing mixing for 35 minutes to obtain the composite modified asphalt.

[0080] The preparation of the composite modifier includes the following main parameters: Step (1): Pre-treat waste tire rubber powder. First, put epoxidized soybean oil into a reaction vessel and stir at 100 rpm. After the temperature rises to 60°C, add dibenzothiazole disulfide, alkylphenol disulfide, and stearic acid and continue stirring for 15 min. Then add silane coupling agent and continue stirring for 10 min. After the temperature drops to 40°C, add polyethylene polyamine and continue stirring for 30 min to obtain rubber powder pretreatment agent. Then, put waste tire rubber powder of various particle sizes into a mixer and stir at 100 rpm. After the temperature rises to 60°C, continue stirring for 5 min. Then add rubber powder pretreatment agent and continue stirring for 5 min. Finally, increase the stirring temperature to 120°C and the stirring speed to 800 rpm, and stir the material for 50 min. Step (2): Pre-treat the waste tire fibers. First, put liquid polybutadiene into another reactor and stir at a speed of 300 rpm. After the temperature rises to 60°C, increase the stirring speed to 1000 rpm, add nano-calcium carbonate and stir for 15 min. After the temperature drops to 40°C, add silane coupling agent and continue stirring for 10 min. Then add tetramethylthiuram disulfide and continue stirring for 15 min to obtain the fiber pretreatment agent. Then, put the waste tire fibers and fiber pretreatment agent into another mixer and stir at a speed of 300 rpm. After the temperature rises to 60°C, continue stirring for 8 min. Finally, increase the stirring temperature to 95°C and stir the material for 40 min. Step (3): Put the pretreated waste tire rubber powder and the pretreated waste tire fiber into the same mixer and mix them. The mixing temperature is 120℃, the mixing speed is 1000rpm, and the mixing time is 5min. Step (4): Increase the stirring temperature to 150°C, keep the stirring speed constant, add the interfacial solvent and auxiliary additives and continue stirring for 10 minutes; Step (5): Use granulation equipment to granulate the uniformly mixed material to obtain the composite modifier. The particle size is controlled within the range of 3-8mm and the length is controlled within the range of 0.5-1.5cm.

[0081] In step two, the drying temperature for aggregates and mineral powder of all particle sizes is 170℃, and the drying time is 3 hours.

[0082] In step three, the preheating temperature of the mixing pot is 170℃, the mixing speed of aggregates and reinforcing materials of each particle size is 100 rpm, and the mixing time is 3 min.

[0083] In step four, after adding the composite modified asphalt, the mixing speed is 100 rpm and the mixing time is 120 s.

[0084] In step five, after adding the asphalt adsorbent, the mixing speed is 100 rpm and the mixing time is 120 s.

[0085] In step six, after adding the mineral powder, the mixing speed is 100 rpm and the mixing time is 120 seconds.

[0086] Example 3: According to another preferred embodiment of the present invention, the asphalt mixture modified by waste tire rubber powder and waste tire fiber and its preparation method are basically the same as those in Embodiment 1, except that: The asphalt mixture comprises the following components: 83.7 wt% aggregate, 5 wt% mineral powder, 6.5 wt% composite modified asphalt, 4 wt% asphalt adsorbent, and 0.8 wt% reinforcing material.

[0087] The aggregate includes seven particle size categories, with the following percentages: 4.75mm ≤ particle size < 9.5mm (20 wt%), 2.36mm ≤ particle size < 4.75mm (25 wt%), 1.18mm ≤ particle size < 2.36mm (40 wt%), 0.6mm ≤ particle size < 1.18mm (5 wt%), 0.3mm ≤ particle size < 0.6mm (3 wt%), 0.15mm ≤ particle size < 0.3mm (3 wt%), and 0.075mm ≤ particle size < 0.15mm (4 wt%).

[0088] Alternatively, the aggregate may include eight particle size categories, with the following percentages: 9.5mm ≤ particle size < 13.2mm 15wt%, 4.75mm ≤ particle size < 9.5mm 25wt%, 2.36mm ≤ particle size < 4.75mm 38wt%, 1.18mm ≤ particle size < 2.36mm 8wt%, 0.6mm ≤ particle size < 1.18mm 4wt%, 0.3mm ≤ particle size < 0.6mm 3wt%, 0.15mm ≤ particle size < 0.3mm 4wt%, and 0.075mm ≤ particle size < 0.15mm 3wt%.

[0089] Alternatively, the aggregate may comprise nine particle size grades, with the following percentages: 13.2mm ≤ particle size < 16mm 10wt%, 9.5mm ≤ particle size < 13.2mm 25wt%, 4.75mm ≤ particle size < 9.5mm 35wt%, 2.36mm ≤ particle size < 4.75mm 10wt%, 1.18mm ≤ particle size < 2.36mm 5wt%, 0.6mm ≤ particle size < 1.18mm 3wt%, 0.3mm ≤ particle size < 0.6mm 5wt%, 0.15mm ≤ particle size < 0.3mm 3wt%, and 0.075mm ≤ particle size < 0.15mm 4wt%.

[0090] The composite modified asphalt comprises, in proportions of 78 wt% base asphalt, 17 wt% composite modifier, and 5 wt% SBS modifier. The composite modifier comprises, in proportions of 60 wt% waste tire rubber powder, 27 wt% waste tire fiber, 3.5 wt% rubber powder pretreatment agent, 1.5 wt% fiber pretreatment agent, 5 wt% interfacial solvent, and 3 wt% auxiliary additives.

[0091] The waste tire rubber powder includes three particle size categories, with the following proportions: 0.6mm ≤ particle size ≤ 0.85mm accounting for 55wt%, 0.25mm ≤ particle size < 0.6mm accounting for 32wt%, and 0.18mm ≤ particle size < 0.25mm accounting for 13wt%.

[0092] The proportions of each substance in the rubber powder pretreatment agent are as follows: 18 wt% polyethylene polyamine, 3.8 wt% dibenzothiazole disulfide, 4 wt% alkylphenol disulfide, 4.5 wt% stearic acid, 21.7 wt% silane coupling agent, and 48 wt% epoxidized soybean oil.

[0093] The fiber pretreatment agent comprises the following components in the following proportions: 74 wt% liquid polybutadiene, 10 wt% silane coupling agent, 2 wt% tetramethylthiuram disulfide, and 14 wt% nano-calcium carbonate.

[0094] The proportions of each substance in the interface solvent are 72 wt% polypropylene grafted with maleic anhydride and 28 wt% chlorinated polypropylene. The mass ratio of zinc stearate to antioxidant 1010 in the auxiliary additives is 1.8:1.

[0095] The asphalt adsorbent material comprises 45 wt% waste tire rubber powder, 9 wt% waste tire fiber, 15 wt% activated carbon, and 31 wt% zeolite powder. The reinforcing material comprises 70 wt% waste tire fiber and 30 wt% calcium carbonate whiskers.

[0096] In step one, the preparation of the composite modified asphalt includes the following main parameters: heating the base asphalt at 150°C for 2 hours; placing the mixing container containing the base asphalt into an oil bath and stirring at 160°C, 300 rpm for 2 minutes; increasing the stirring temperature to 175°C and the stirring speed to 5000 rpm, adding the SBS modifier and performing high-speed shear mixing for 25 minutes; maintaining the stirring temperature and speed constant, adding the pre-prepared composite modifier and continuing to stir for 25 minutes to obtain the composite modified asphalt.

[0097] The preparation of the composite modifier includes the following main parameters: Step (1): Pre-treat waste tire rubber powder. First, put epoxidized soybean oil into a reaction vessel and stir at a stirring speed of 200 rpm. After the temperature rises to 80°C, add dibenzothiazole disulfide, alkylphenol disulfide, and stearic acid and continue stirring for 10 min. Then add silane coupling agent and continue stirring for 5 min. After the temperature drops to 50°C, add polyethylene polyamine and continue stirring for 20 min to obtain rubber powder pretreatment agent. Then, put waste tire rubber powder of various particle sizes into a mixer and stir at a stirring speed of 200 rpm. After the temperature rises to 80°C, continue stirring for 3 min. Then add rubber powder pretreatment agent and continue stirring for 3 min. Finally, increase the stirring temperature to 125°C and the stirring speed to 1000 rpm, and stir the material for 40 min. Step (2): Pre-treat the waste tire fibers. First, put liquid polybutadiene into another reactor and stir at a speed of 500 rpm. After the temperature rises to 80°C, increase the stirring speed to 1500 rpm, add nano-calcium carbonate and stir for 10 min. After the temperature drops to 50°C, add silane coupling agent and continue stirring for 5 min. Then add tetramethylthiuram disulfide and continue stirring for 10 min to obtain the fiber pretreatment agent. Then, put the waste tire fibers and fiber pretreatment agent into another mixer and stir at a speed of 500 rpm. After the temperature rises to 80°C, continue stirring for 5 min. Finally, increase the stirring temperature to 115°C and stir the material for 30 min. Step (3): Put the pretreated waste tire rubber powder and the pretreated waste tire fiber into the same mixer and mix them. The mixing temperature is 130℃, the mixing speed is 1500rpm, and the mixing time is 3min. Step (4): Increase the stirring temperature to 160℃, keep the stirring speed constant, add the interfacial solvent and auxiliary additives and continue stirring for 5 minutes; Step (5): Use granulation equipment to granulate the uniformly mixed material to obtain the composite modifier. The particle size is controlled within the range of 3-8mm and the length is controlled within the range of 0.5-1.5cm.

[0098] In step two, the drying temperature for aggregates and mineral powder of all particle sizes is 190℃, and the drying time is 2.5h.

[0099] In step three, the preheating temperature of the mixing pot is 185℃, the mixing speed of aggregates and reinforcing materials of each particle size is 300 rpm, and the mixing time is 2 min.

[0100] In step four, after adding the composite modified asphalt, the mixing speed is 300 rpm and the mixing time is 90 s.

[0101] In step five, after adding the asphalt adsorbent, the mixing speed is 300 rpm and the mixing time is 90 seconds.

[0102] In step six, after adding the mineral powder, the mixing speed is 300 rpm and the mixing time is 90 seconds.

[0103] Comparative example: This comparative example is a standard SMA asphalt mixture, with the following proportions: aggregate 85 wt%, mineral powder 8.5 wt%, and SBS modified asphalt 6.5 wt%. The preparation method for this asphalt mixture is as follows: the aggregate and mineral powder are dried; the SBS modified asphalt is heated; first, the dried aggregate is placed in a mixing pot and stirred; then, the heated SBS modified asphalt is placed in the mixing pot and stirred; finally, the dried mineral powder is placed in the mixing pot and stirred. The aggregate gradation and process parameters are basically the same as in Example 1. Neither the modified asphalt nor the asphalt mixture in this comparative example contains waste tire rubber powder or waste tire fiber, nor does it contain any added asphalt adsorbent material (containing waste tire rubber powder and waste tire fiber) or reinforcing material (containing waste tire fiber).

[0104] The fluorescence image of the ordinary SBS modified bitumen used in this comparative example is as follows: Figure 8 As shown, the asphalt leakage of the prepared ordinary SMA asphalt mixture is as follows: Figure 9 As shown. From Figure 8 It can be seen that a clear SBS modifier molecular network structure is visible in the base asphalt, but the intermolecular cross-linking is not dense enough, the network structure is isolated, and the compatibility with the base asphalt is poor; from Figure 9 It can be seen that a large amount of asphalt was released from the asphalt mixture, which indicates that the asphalt film flowed and migrated under high temperature and high load conditions.

[0105] According to relevant testing standards and specifications, the asphalt mixtures prepared in the above embodiments and comparative examples were subjected to road performance tests. The testing environment, conditions, and equipment were all the same, and the test results are shown in Table 1. The road performance test results show that the SMA asphalt mixtures prepared in the three embodiments exhibit excellent high-temperature stability, low-temperature crack resistance, and water stability. This demonstrates that by introducing waste tire rubber powder and waste tire fibers, and by optimizing the material ratio and process design, the compatibility issue was resolved, thereby improving the overall performance of the asphalt mixture.

[0106] The various raw materials used in the above embodiments and comparative examples were purchased from Beijing Construction Engineering Group Co., Ltd., Beijing Municipal Road and Bridge Building Materials Group Co., Ltd., Aladdin Reagent Co., Ltd., and Sinopharm Chemical Reagent Co., Ltd., or can be purchased from other regular manufacturers on the market.

[0107] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant progress of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive experimentation. For each parameter and the combinations thereof, the inventors have recorded a large amount of experimental data; however, due to space limitations, the specific experimental data is not disclosed here.

[0108] It will be readily understood by those skilled in the art that this invention includes any combination of the inventive description and specific embodiments outlined in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An asphalt mixture modified from waste tire rubber powder and waste tire fiber, characterized in that, The mass percentages of each substance in the asphalt mixture are as follows: aggregate 76-85 wt%, mineral powder 5-11 wt%, composite modified asphalt 5.5-6.5 wt%, asphalt adsorbent 4-7 wt%, and reinforcing material 0.3-0.8 wt%, with the total content of each substance being 100 wt%. Both the composite modified asphalt and the asphalt adsorbent contain waste tire rubber powder and waste tire fiber.

2. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 1, characterized in that, The aggregate comprises seven particle size grades, with each grade accounting for the following percentages by mass: 4.75mm ≤ particle size < 9.5mm 15-20wt%, 2.36mm ≤ particle size < 4.75mm 25-30wt%, 1.18mm ≤ particle size < 2.36mm 35-40wt%, 0.6mm ≤ particle size < 1.18mm 5-8wt%, 0.3mm ≤ particle size < 0.6mm 3-5wt%, 0.15mm ≤ particle size < 0.3mm 3-5wt%, and 0.075mm ≤ particle size < 0.15mm 3-5wt%. Alternatively, the aggregate may comprise eight particle size grades, with each grade representing a percentage of the aggregate's mass as follows: 9.5mm ≤ particle size < 13.2mm 10-15 wt%, 4.75mm ≤ particle size < 9.5mm 25-30 wt%, 2.36mm ≤ particle size < 4.75mm 32-38 wt%, 1.18mm ≤ particle size < 2.36mm 8-10 wt%, 0.6mm ≤ particle size < 1.18mm 3-5 wt%, 0.3mm ≤ particle size < 0.6mm 3-5 wt%, 0.15mm ≤ particle size < 0.3mm 3-5 wt%, and 0.075mm ≤ particle size < 0.15mm 3-5 wt%. Alternatively, the aggregate may comprise nine particle size grades, with each grade representing a percentage of the aggregate's mass as follows: 13.2mm ≤ particle size < 16mm 5-10 wt%, 9.5mm ≤ particle size < 13.2mm 25-30 wt%, 4.75mm ≤ particle size < 9.5mm 30-35 wt%, 2.36mm ≤ particle size < 4.75mm 10-15 wt%, 1.18mm ≤ particle size < 2.36mm 3-5 wt%, 0.6mm ≤ particle size < 1.18mm 3-5 wt%, 0.3mm ≤ particle size < 0.6mm 3-5 wt%, 0.15mm ≤ particle size < 0.3mm 3-5 wt%, and 0.075mm ≤ particle size < 0.15mm 3-5 wt%. The aggregate is basalt or diabase; the mineral powder is limestone with a particle size of less than 0.075 mm.

3. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 2, characterized in that, The mass percentage of each substance in the composite modified asphalt is 72-78 wt% of base asphalt, 17-24 wt% of composite modifier, and 3-6 wt% of SBS modifier, with the sum of the contents of each substance being 100 wt%.

4. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 3, characterized in that, The mass percentage of each substance in the composite modifier is as follows: waste tire rubber powder 55-60 wt%, waste tire fiber 25-30 wt%, rubber powder pretreatment agent 2.5-3.5 wt%, fiber pretreatment agent 1.5-2.5 wt%, interface solvent 5-8 wt%, auxiliary additives 2-3 wt%, and the sum of the contents of each substance is 100 wt%.

5. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 4, characterized in that, The waste tire rubber powder includes three particle size grades, with each grade accounting for the following percentages by mass: 0.6mm ≤ particle size ≤ 0.85mm 45-55wt%, 0.25mm ≤ particle size < 0.6mm 30-38wt%, and 0.18mm ≤ particle size < 0.25mm 12-20wt%. The diameter of the waste tire fibers is controlled within the range of 8-20μm, and the length is controlled within the range of 6-12mm. The mass percentages of each substance in the rubber powder pretreatment agent are as follows: polyethylene polyamine 12-18 wt%, dibenzothiazole disulfide 1.8-3.8 wt%, alkylphenol disulfide 2-4 wt%, stearic acid 2.5-4.5 wt%, silane coupling agent 20-28 wt%, and epoxidized soybean oil 48-55 wt%, with a total content of 100 wt%; the silane coupling agent is designated as KH-590. The fiber pretreatment agent comprises the following components by mass percentage: 65-80 wt% liquid polybutadiene, 10-20 wt% silane coupling agent, 2-5 wt% tetramethylthiuram disulfide, and 5-15 wt% nano-calcium carbonate, with a total content of 100 wt%; the silane coupling agent is designated as KH-590. The mass percentage of each substance in the interfacial solvent is 60-72 wt% polypropylene grafted with maleic anhydride and 28-40 wt% chlorinated polypropylene; the auxiliary additive is composed of zinc stearate and antioxidant 1010, and the mass ratio of zinc stearate to antioxidant 1010 is 1.2-1.8:

1.

6. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 5, characterized in that, The mass percentages of each substance in the asphalt adsorbent material are as follows: waste tire rubber powder 38-45 wt%, waste tire fiber 8-12 wt%, activated carbon 10-15 wt%, and zeolite powder 30-38 wt%, with a total content of 100 wt%. The particle size of the waste tire rubber powder is controlled within the range of 0.25-0.6 mm, the diameter of the waste tire fiber is controlled within the range of 8-20 μm, and the length is controlled within the range of 6-12 mm. The particle size of the activated carbon is not greater than 75 μm, and the particle size of the zeolite powder is not greater than 38 μm.

7. The asphalt mixture modified by composite of waste tire rubber powder and waste tire fiber according to claim 6, characterized in that, The mass percentage of each substance in the reinforcing material is 60-70 wt% waste tire fiber and 30-40 wt% calcium carbonate whiskers; the diameter of the waste tire fiber is controlled within the range of 8-20 μm and the length is controlled within the range of 6-12 mm, and the diameter of the calcium carbonate whiskers is controlled within the range of 0.5-1 μm and the length is controlled within the range of 0.8-1.5 mm.

8. A method for preparing asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber according to any one of claims 1-7, characterized in that, The preparation method includes the following steps in sequence: Step 1: Prepare composite modified asphalt in advance and keep it warm for later use; Step 2: Place the aggregates and mineral powder of each particle size into an oven for drying and keep them warm for later use; Step 3: Preheat the mixing pot to the preset temperature, put the dried aggregates of various particle sizes, as well as the waste tire fibers and calcium carbonate whiskers in the reinforcing material into the mixing pot for mixing, so that the aggregates of various particle sizes are mixed evenly, and the waste tire fibers and calcium carbonate whiskers are evenly dispersed in the aggregates. Step 4: Put the pre-prepared composite modified asphalt into the mixing pot and mix it to make the composite modified asphalt evenly coat the surface of the solid material. Step 5: Add the waste tire rubber powder, waste tire fiber, activated carbon and zeolite powder from the asphalt adsorbent material into the mixing pot and mix them to increase the viscosity of the asphalt and stabilize the internal structure of the system. Step Six: Place the dried mineral powder into a mixing pot and mix it to ensure that all substances are evenly mixed, thus obtaining the asphalt mixture based on the composite modification of waste tire rubber powder and waste tire fiber.

9. The method for preparing asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber according to claim 8, characterized in that, In step one, the preparation of the composite modified asphalt includes the following steps in sequence: Step 1.1: Place the base asphalt in an oven for heat treatment at a temperature of 140-150℃ for 2-3 hours to bring the base asphalt into a fluid state. Step 1.2: Place the mixing container containing the base asphalt into an oil bath and stir. The stirring temperature is 150-160℃, the stirring speed is 200-300 rpm, and the stirring time is 2-5 min. Step 1.3: Increase the stirring temperature to 165-175℃ and the stirring speed to 4000-5000 rpm. Put the SBS modifier into the stirring container and perform high-speed shear stirring for 25-35 minutes to ensure that all substances are mixed evenly. Step 1.4: Keep the stirring temperature and stirring speed constant, put the pre-prepared composite modifier into the mixing container and perform high-speed shear stirring for 25-35 minutes to make the substances evenly mixed, thus obtaining the composite modified asphalt. The preparation of the composite modifier includes the following steps in sequence: Step (1): Pre-treat waste tire rubber powder. Specific operation: First, put epoxidized soybean oil into a reaction vessel and heat it while stirring at a speed of 100-200 rpm. After the temperature rises to 60-80℃, add dibenzothiazole disulfide, alkylphenol disulfide, and stearic acid into the reaction vessel and continue stirring for 10-15 minutes to disperse them evenly. Then, add the silane coupling agent into the reaction vessel and continue stirring for 5-10 minutes to mix them evenly. Subsequently, cool down while stirring. After the temperature drops to 40-50℃, add polyethylene polyamine into the reaction vessel and continue stirring for 20-30 minutes. A rubber powder pretreatment agent is prepared. Then, waste tire rubber powder of various particle sizes is placed into a mixer, and the temperature is increased while stirring. The stirring speed is 100-200 rpm. After the temperature rises to 60-80℃, stirring is continued for 3-5 minutes to ensure that the waste tire rubber powder of various particle sizes is evenly mixed. Then, the rubber powder pretreatment agent is added to the mixer and stirring is continued for 3-5 minutes to ensure that the material is evenly mixed. Finally, the stirring temperature is increased to 115-125℃, and the stirring speed is increased to 800-1000 rpm to stir the material in the mixer for 40-50 minutes to ensure that the material is evenly dispersed. Step (2): Pre-treat the waste tire fibers. Specific steps: First, place liquid polybutadiene into another reactor and heat it while stirring at 300-500 rpm. Once the temperature reaches 60-80℃, increase the stirring speed to 1000-1500 rpm. Add nano-calcium carbonate to the reactor and stir for 10-15 minutes to ensure uniform dispersion. Then, cool the reactor while stirring until the temperature drops to 40-50℃. Add the silane coupling agent to the reactor and continue stirring for 5-10 minutes. Mix the materials thoroughly, then add tetramethylthiuram disulfide to the reactor and continue stirring for 10-15 minutes to ensure uniform dispersion, thus obtaining the fiber pretreatment agent. Next, place the waste tire fibers and fiber pretreatment agent into another mixer, stirring and heating simultaneously at a speed of 300-500 rpm. Once the temperature reaches 60-80℃, continue stirring for 5-8 minutes to ensure uniform mixing. Finally, increase the stirring temperature to 95-115℃ and stir the materials in the mixer for 30-40 minutes to ensure uniform dispersion. Step (3): Put the pretreated waste tire rubber powder and the pretreated waste tire fiber into the same mixer and mix them. The mixing temperature is 120-130℃, the mixing speed is 1000-1500rpm, and the mixing time is 3-5min to make the materials evenly mixed. Step (4): Increase the stirring temperature to 150-160℃, keep the stirring speed constant, put the polypropylene grafted with maleic anhydride and chlorinated polypropylene in the interface solvent and the zinc stearate and antioxidant 1010 in the auxiliary additives into the mixer and continue stirring for 5-10 minutes to make the materials evenly mixed. Step (5): Use granulation equipment to granulate the uniformly mixed material to obtain the composite modifier. The particle size is controlled within the range of 3-8mm and the length is controlled within the range of 0.5-1.5cm.

10. The method for preparing asphalt mixture based on composite modification of waste tire rubber powder and waste tire fiber according to claim 9, characterized in that, In step two, the drying temperature for aggregates and mineral powder of all particle sizes is 170-190℃, and the drying time is 2.5-3h. In step three, the preheating temperature of the mixing pot is 170-185℃, the mixing speed of aggregates and reinforcing materials of each particle size is 100-300 rpm, and the mixing time is 2-3 min. In step four, after adding the composite modified asphalt, the mixing speed is 100-300 rpm and the mixing time is 90-120 s; In step five, after adding the asphalt adsorbent, the mixing speed is 100-300 rpm and the mixing time is 90-120 seconds. In step six, after adding the mineral powder, the mixing speed is 100-300 rpm and the mixing time is 90-120 seconds.

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