Asphalt mixture high-modulus agent containing modified RAP (Reactive Asphalt Polymer) fine powder and preparation method of asphalt mixture high-modulus agent

Abstract

The invention provides an asphalt mixture high-modulus agent containing modified RAP ground powder, belongs to the technical field of asphalt mixture high-modulus agents containing modified RAP ground powder, and particularly relates to the asphalt mixture high-modulus agent containing modified RAP ground powder. Through the treatment scheme provided by the invention, the asphalt mixture high modulus agent containing the modified RAP ground powder is improved.

Description

Technical Field

[0001] This application relates to the field of road engineering materials technology, and in particular to a high modulus agent for asphalt mixtures containing modified RAP fine powder and its preparation method. Background Technology

[0002] With the continuous advancement of transportation infrastructure construction, asphalt pavements are entering their maintenance and repair phase. Road reconstruction, expansion, and maintenance projects are gradually increasing, resulting in a large amount of waste asphalt pavement (RAP). Improper handling of these waste materials not only leads to significant resource waste but also causes serious environmental pollution. The effective recycling and utilization of RAP has become a key issue for the industry. Reusing RAP in asphalt mixture production can significantly alleviate resource pressure on raw material supplies such as asphalt and aggregates, effectively reduce project costs, and is of great significance for ecological environmental protection, aligning with the strategic requirements of sustainable development.

[0003] Currently, to achieve high recycling rates for RAP (Rich Asphalt Acrylic Acid), engineering practices often involve crushing and separating RAP into multiple grades, which are then recycled according to the designed gradation. However, this approach fails to realize the high-value utilization of RAP. RAP fine powder, as a component of the separation products, has potential value in improving the modulus of asphalt mixtures due to its high content of aged asphalt and is frequently considered for application in the preparation of high-modulus asphalt mixtures. In existing technologies, to address the mixing problem between RAP fine powder and new asphalt, the common approach is to extend the mixing time and increase the mixing intensity in the mixing equipment. This aims to uniformly disperse the RAP fine powder in the new asphalt, hoping to promote full integration and form a stable asphalt binder, thereby improving the overall performance of the asphalt mixture.

[0004] However, although extending the mixing time and increasing the mixing intensity helps with mixing to some extent, the uniformity of the mixture between RAP fine powder and new asphalt is still unsatisfactory. Due to its inherent particle characteristics, RAP fine powder is prone to agglomeration during mixing, making it difficult to distribute uniformly in the new asphalt as single particles. This results in some areas of the asphalt mixture having excessively high RAP fine powder concentrations while others have excessively low concentrations, leading to significant differences in the properties of the asphalt binder. This inhomogeneity causes inconsistencies in the pavement's performance, such as fluctuations in key performance indicators like high-temperature stability, affecting the overall quality and service life of the pavement and increasing subsequent road maintenance costs. Summary of the Invention

[0005] In view of this, this application provides a high modulus agent for asphalt mixtures containing modified RAP fine powder, which solves the problem that new and old asphalt cannot be uniformly fused after direct mixing in the prior art, and improves the high-temperature stability of asphalt pavement.

[0006] The technical solution provided in this application for a high modulus agent for asphalt mixtures containing modified RAP fine powder and its preparation method is as follows:

[0007] A high modulus agent for asphalt mixtures containing modified RAP fine powder comprises the following raw materials in parts by weight:

[0008] 60-80 parts of modified RAP fine powder;

[0009] 15-30 parts of polyethylene;

[0010] 5-10 parts of star-shaped SBS elastomer;

[0011] 2-6 parts of short-cut basalt fibers;

[0012] Stabilizer 1-3 parts;

[0013] 0.5-2 parts of regenerant;

[0014] The modified RAP fine powder is a RAP fine powder grafted with MOF, where MOF is a metal-organic framework.

[0015] By employing the above technical solutions, metal-organic frameworks (MOFs) construct multi-level channels on the surface of RAP fine powder through aluminum-oxygen cluster coordination bonds, precisely matching the size of asphaltene to selectively adsorb polar molecules and eliminate the polarity difference between new and old asphalt interfaces. Long-chain alkyl groups grafted onto MOFs generate entropy-driven van der Waals forces with non-polar new asphalt, forming a molecularly compatible transition layer, effectively solving the two-phase separation caused by RAP agglomeration. Polyethylene melts and entangles to form a three-dimensional rigid network, providing anti-rutting skeleton support for the system. The styrene blocks of star-shaped SBS elastomer are compatible with polyethylene to form a continuous phase, while the butadiene blocks separate into elastic islands that absorb stress energy, compensating for the low-temperature brittleness of high-modulus agents. The necessity of this component combination lies in balancing rigidity and toughness. Short-cut basalt fibers bridge the aggregate gaps and block crack propagation through silanol-carboxyl hydrogen bonds, effectively suppressing micro-stress concentration. Stabilizer metal ions bind to unsaturated coordination sites of MOFs, inhibiting high-temperature agglomeration and ensuring uniform dispersion. Regenerator small-molecule alkane permeates aged asphalt, replacing polar bonds, reversing aging brittleness, and restoring rheological properties. The components work synergistically to simultaneously improve rutting resistance, crack resistance, and water stability under high RAP dosage.

[0016] Optionally, the preparation of the modified RAP fine powder includes the following steps:

[0017] Step 1: Aluminum nitrate hexahydrate and terephthalic acid were hydrothermally synthesized in N,N-dimethylformamide for 18-24 hours to generate a MOF crystalline framework;

[0018] Step 2: The MOF crystalline framework obtained in Step 1 is reacted with long-chain alkanols in a mass ratio of (5-8):1 under the action of a catalyst to produce an intermediate with alkyl grafts on its surface.

[0019] Step 3: The intermediate obtained in step 2 is mixed with RAP fine powder and stirred at 60°C for 10 minutes to obtain modified RAP fine powder.

[0020] By adopting the above technical solution, aluminum nitrate hexahydrate hydrolyzes to form [AlO4(OH)2] octahedral clusters, which self-assemble with terephthalic acid carboxyl groups via μ2-O bridging bonds to form a one-dimensional rhombic channel MOF, accurately capturing asphaltenes aggregates and effectively targeting and adsorbing polar molecules. The exposed uncoordinated carboxyl groups esterify with long-chain alkanols to form alkyl ester covalent bonds, constructing a low-energy nonpolar interface and eliminating the surface polarity of the MOF. The alkylated MOF penetrates into the RAP microcracks through capillary action, and the inner surface of the channel forms hydrogen bonds with carbonyl oxygen to fix polar molecules, effectively enhancing the modification efficiency.

[0021] Optionally, in the third step, a reducing agent, tetraethylthiuram disulfide, needs to be added.

[0022] By adopting the above technical solution, the lone pair electrons of the sulfur atom of tetraethylthiuram disulfide can fill the empty orbitals of the aluminum ion in MOF to form a Lewis adduct, which homolytically cleaves to generate sulfur free radicals to activate the reaction; the free radical attacks the sulfoxide group (S=O) to abstract oxygen to generate a low polarity sulfide, eliminating the strong dipole moment; the released oxygen free radical reduces the carbonyl group to methylene through a chain reaction, disintegrating the polar hierarchy.

[0023] Optionally, the long-chain alkanoic acid in the second step is octadecanoic acid.

[0024] By adopting the above technical solution, octadecane alcohol straight-chain alkyl groups are esterified by acid catalysis to form a hydrocarbon barrier, completely blocking the interaction of polar molecules; the octadecane alcohol chain length can generate a significant entropy driving force, promoting the spontaneous dispersion of MOF-RAP.

[0025] In a first aspect, this application provides a method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, optionally including the following preparation steps:

[0026] S1: Melt-blend polyethylene and star-shaped SBS elastomer in a 160-170℃ internal mixer for 10-15 minutes;

[0027] S2: Preheat the regenerant to 60℃, add the modified RAP fine powder and soak for 5-10 minutes;

[0028] S3: Add the mixture obtained in step 2 to the molten matrix in step 1, heat it to 165-170℃ in a high-speed disperser, and shear mix at 500-800 rpm for 15-20 minutes.

[0029] S4: Add chopped basalt fiber and stabilizer, mix at low speed at 140-145℃ until homogeneous to obtain a high modulus agent for asphalt mixtures containing modified RAP fine powder.

[0030] By adopting the above technical solutions, the internal mixer melt blends to form a polyethylene / SBS elastomer interpenetrating network, and a rigid-tough balanced matrix is ​​constructed through physical cross-linking; the preheated regenerator can effectively enhance the microporous permeability of RAP; high-speed shear exfoliation of MOF is a nanosheet reinforced coating, which effectively overcomes the interlayer van der Waals forces; when the temperature is >150℃, it is easy to cause the silicon-oxygen bond to break, so low-temperature mixing is required to retain the fiber strength.

[0031] Optionally, the stabilizer added in S4 is zinc stearate.

[0032] By adopting the above technical solution, the zinc stearate carboxylate group can form a coordination bond with MOF aluminum ions, and the zinc ions can simultaneously hybridize with pitch carboxyl groups to construct a double-bridged structure.

[0033] Optionally, the speed of the internal mixer in step S1 is controlled to be 300-500 rpm.

[0034] By adopting the above technical solution, medium-speed shearing causes the polyethylene molecular chains to align in an oriented manner, and the SBS elastic arms to stretch and entangle to form a uniform island phase, thereby optimizing the matrix continuity and dispersion stability and eliminating local performance differences.

[0035] Optionally, in step S2, the preheating temperature of the regenerant is 55-65℃, and the impregnation process is carried out in a closed mixing tank with a stirring rate of 200-400 rpm.

[0036] By adopting the above technical solutions, the sealed environment isolates oxygen to prevent oxidation, the vortex stirring negative pressure promotes the penetration of the regenerator into the micropores, the preheating reduces viscosity, preserves the active ingredients, and achieves full-area regeneration.

[0037] Optionally, the regenerator in S2 is furfural oil.

[0038] By adopting the above technical solution, the saturated small molecule alkanes of furfural oil dilute the concentration of colloids, and the large π bonds of aromatics and the π-π stacking of polar groups dissolve flocculants, thus synergistically restoring fluidity and eliminating phase separation.

[0039] Optionally, the rotor linear velocity of the shear mixing in step S3 is ≥15m / s.

[0040] By adopting the above technical solutions, the high linear velocity rotor shear force overcomes the interlayer force of MOF sheets, enabling them to be nanoscaled. The turbulent cavitation effect breaks up RAP agglomerates, increases the specific surface area to enhance modification, and ensures microscopic uniformity.

[0041] In summary, this application includes the following beneficial technical effects: Interface modification of RAP fine powder via metal-organic frameworks (MOFs): Aluminum-based MOFs synthesized from aluminum nitrate hexahydrate and terephthalic acid utilize multi-level nanopores to selectively adsorb polar molecules in aged asphalt, eliminating the polarity difference between new and old asphalt interfaces; furthermore, long-chain alkyl groups are grafted onto the MOF surface via octadecanoyl esterification, generating entropy-driven forces with non-polar new asphalt to form a molecularly compatible layer, thoroughly inhibiting RAP aggregation; combined with the synergistic effect of multiple components—polyethylene... A fused structure is constructed to create a rigid skeleton resistant to rutting. The styrene blocks of star-shaped SBS form a continuous phase with polyethylene, while the butadiene blocks separate into "elastic islands" to absorb stress and compensate for low-temperature brittleness. Short-cut basalt fibers bridge the gaps between aggregates through silanol-carboxyl hydrogen bonds, blocking crack propagation. Furfural oil permeates and replaces the polar bonds of aged asphalt to restore rheological properties. Zinc stearate and MOF aluminum ions coordinate to inhibit high-temperature agglomeration—achieving efficient utilization of high-dosage RAP and simultaneously improving the high-temperature rutting resistance, low-temperature crack resistance, and water stability of asphalt mixtures. Detailed Implementation

[0042] The embodiments of this application are described in detail below.

[0043] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0045] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0046] This application provides a high modulus agent for asphalt mixtures containing modified RAP fine powder.

[0047] Preparation Example

[0048] Preparation Example 1:

[0049] Step 1: Take 6g of aluminum nitrate hexahydrate and 4g of terephthalic acid, add 50mL of N,N-dimethylformamide, and perform hydrothermal synthesis at 120℃ for 22h to generate MOF crystalline framework;

[0050] Step 2: Take 10g of the MOF crystalline framework obtained in Step 1, mix it with 2g of octadecyl alcohol (mass ratio 5:1), add 0.3g of tetrabutyl titanate catalyst, and heat at 140℃ for 3h to prepare an intermediate with alkyl grafts on the surface.

[0051] Step 3: Take 100g of RAP fine powder, add 15g of the intermediate obtained in step 2, and then add 0.5g of reducing agent tetraethylthiuram disulfide. Stir at 300rpm for 10min at 60℃ to obtain modified RAP fine powder.

[0052] Preparation Example 2:

[0053] Step 1: Take 5g of aluminum nitrate hexahydrate and 3g of terephthalic acid, add 40mL of N,N-dimethylformamide, and perform hydrothermal synthesis at 110℃ for 18h to generate MOF crystalline framework;

[0054] Step 2: Take 8g of the MOF crystalline framework obtained in Step 1, mix it with 1g of octadecyl alcohol (mass ratio 8:1), add 0.2g of tetrabutyl titanate catalyst, and heat at 130℃ for 2.5h to prepare an intermediate with alkyl grafts on the surface.

[0055] Step 3: Take 100g of RAP fine powder, add 12g of the intermediate obtained in step 2, and then add 0.3g of reducing agent tetraethylthiuram disulfide. Stir at 250rpm for 10min at 60℃ to obtain modified RAP fine powder.

[0056] Preparation Example 3

[0057] Step 1: Take 7g of aluminum nitrate hexahydrate and 5g of terephthalic acid, add 60mL of N,N-dimethylformamide, and perform hydrothermal synthesis at 130℃ for 24h to generate MOF crystalline framework;

[0058] Step 2: Take 12g of the MOF crystalline framework obtained in Step 1, mix it with 2g of octadecyl alcohol (mass ratio 6:1), add 0.4g of tetrabutyl titanate catalyst, and heat at 150℃ for 3.5h to prepare an intermediate with alkyl grafts on the surface.

[0059] Step 3: Take 100g of RAP fine powder, add 18g of the intermediate obtained in step 2, without adding the reducing agent tetraethyl thiuram disulfide, and stir at 350rpm for 10min at 60℃ to obtain modified RAP fine powder.

[0060] Preparation Example 4

[0061] Step 1: Take 6g of aluminum nitrate hexahydrate and 4g of terephthalic acid, add 50mL of N,N-dimethylformamide, and perform hydrothermal synthesis at 120℃ for 20h to generate MOF crystalline framework;

[0062] Step 2: Take 10g of the MOF crystalline framework obtained in Step 1, mix it with 1.5g of hexadecyl alcohol (mass ratio 6.7:1), add 0.3g of tetrabutyl titanate catalyst, and heat at 140℃ for 3h to prepare an intermediate with alkyl grafts on the surface.

[0063] Step 3: Take 100g of RAP fine powder, add 15g of the intermediate obtained in step 2, and then add 0.5g of reducing agent tetraethylthiuram disulfide. Stir at 300rpm for 10min at 60℃ to obtain modified RAP fine powder.

[0064] Table 1

[0065] Performance Comparison Analysis

[0066]

[0067]

[0068] Example

[0069] Example 1

[0070] S1: Add 22g of polyethylene and 8g of star-shaped SBS elastomer to a mixer, control the temperature at 165℃ and the speed at 400rpm, and melt-blend for 12 minutes.

[0071] S2: Preheat 1.2g of regenerator furfural oil to 60℃, add 70g of modified RAP fine powder, and stir and soak in a sealed mixing tank at 300rpm for 8 minutes.

[0072] S3: Add the mixture obtained from S2 to the molten matrix of S1, transfer it to a high-speed disperser, heat it to 168°C, and shear and mix it at 650 rpm (rotor linear speed 18 m / s) for 18 minutes.

[0073] S4: Add 4g of short-cut basalt fiber and 2g of stabilizer zinc stearate, control the temperature at 142℃, and stir at low speed for 15 minutes until homogeneous to obtain a high modulus agent.

[0074] In this embodiment, the modified RAP fine powder is the modified RAP fine powder prepared in Preparation Example 1.

[0075] Table 2

[0076] Raw materials / Example (g) Example 1 Example 2 Example 3 Modified RAP fine powder 70 60 80 polyethylene 22 15 30 Star-shaped SBS elastomer 8 5 10 Short-cut basalt fibers 4 2 6 stabilizer zinc stearate 2 1 3 Regenerator furfural oil 1.2 0.5 2

[0077] In Examples 2 and 3, the modified RAP fine powder was the modified RAP fine powder prepared in Example 1.

[0078] Example 4

[0079] A method for preparing a high modulus agent for asphalt mixtures containing RAP fine powder, which differs from Example 1 in that it uses the modified RAP fine powder prepared in Preparation Example 2.

[0080] Example 5

[0081] A method for preparing a high modulus agent for asphalt mixtures containing RAP fine powder, which differs from Example 1 in that the modified RAP fine powder prepared in Preparation Example 3 is used.

[0082] Example 6

[0083] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that the modified RAP fine powder prepared in Preparation Example 4 is used.

[0084] Example 7

[0085] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, differing from Example 1 in that the regenerator is replaced with epoxidized soybean oil.

[0086] Example 8

[0087] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that the stabilizer is replaced with calcium stearate.

[0088] Example 9

[0089] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that short-cut basalt fibers are replaced with short-cut glass fibers.

[0090] Comparative Example 1

[0091] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that no star-shaped SBS elastomer is added.

[0092] Comparative Example 2

[0093] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that short-cut basalt fibers are not added.

[0094] Comparative Example 3

[0095] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that the stabilizer zinc stearate is not added.

[0096] Comparative Example 4

[0097] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that the modified RAP fine powder is replaced with unmodified RAP fine powder.

[0098] Comparative Example 5

[0099] A method for preparing a high modulus agent for asphalt mixtures containing modified RAP fine powder, which differs from Example 1 in that the regenerating agent furfural oil is not added.

[0100] Performance testing

[0101] Test items and standards

[0102] The dynamic modulus was tested according to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0103] The dynamic stability of the rutting test was tested according to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0104] The low-temperature bending failure strain was tested according to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0105] Water stability was tested according to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0106] Dispersion uniformity: Observed by fluorescence microscopy and rated according to grade.

[0107] Table 3

[0108]

[0109]

[0110] According to Example 1 and Table 3, Example 1 uses the modified RAP fine powder prepared in Example 1. This fine powder is modified by MOF grafting. The MOF crystalline framework formed by aluminum nitrate hexahydrate and terephthalic acid has multi-level nanopores, which can accurately adsorb polar molecules in aged asphalt and eliminate the polarity difference between the new and old asphalt interfaces. At the same time, the octadecyl alcohol long-chain alkyl grafted on the MOF surface generates entropy-driven van der Waals forces with the non-polar new asphalt, forming a molecular-level compatible transition layer, which completely solves the problem of RAP agglomeration. From the perspective of component synergy, after melting, polyethylene entangles to form a three-dimensional rigid network, providing a rutting-resistant skeleton support for the system; the styrene blocks of the star-shaped SBS elastomer are compatible with polyethylene to form a continuous phase, while the butadiene blocks separate into "elastic islands" that can absorb stress energy under low-temperature conditions and compensate for the low-temperature brittleness of the high-modulus agent; short-cut basalt fibers form hydrogen bonds with asphalt carboxyl groups through surface silanol groups, bridging aggregate gaps and blocking crack propagation, thus inhibiting micro-stress concentration; the carboxyl groups of the stabilizer zinc stearate form coordination bonds with MOF aluminum ions, preventing MOF agglomeration at high temperatures and ensuring the uniformity of system dispersion; the saturated small-molecule alkanes of the regenerator furfural oil can dilute the concentration of aged asphalt resin, while the large π bonds of the aromatic components form π-π stacks with polar groups, dissolving asphalt flocs and restoring the rheological properties of aged asphalt. The above components form a synergistic effect from three dimensions: interfacial compatibility, structural support, and performance balance, ultimately enabling Example 1 to achieve the "optimal performance combination".

[0111] According to Examples 1, 7, 8, and 9, and in conjunction with Table 3, the core function of furfural oil is to restore the properties of aged asphalt through three steps: penetration, displacement, and dissolution. Its saturated small-molecule alkanes can quickly penetrate into the interior of RAP fine powder, displacing the polar bonds in the aged asphalt, while the aromatics dissolve the asphalt flocs. In contrast, the saturated content of epoxidized soybean oil is only 65%-70% of that of furfural oil, with a low penetration rate and a lack of π-π stacking effect of aromatics, which makes it unable to fully dissolve the asphalt flocs. This results in incomplete restoration of the rheological properties of aged asphalt, a decrease in the interfacial bonding strength between new and old asphalt, and ultimately, weakened rutting resistance and water stability. In Example 1, the zinc stearate has a +2 valence and a small ionic radius, resulting in a high coordination bond energy with unsaturated coordination sites in the MOF, which effectively inhibits MOF lamellar aggregation at high temperatures. In contrast, in Example 8, the calcium stearate has a +2 valence and a large ionic radius, resulting in a low coordination bond energy with the MOF and weaker coordination. At high temperatures, some MOFs aggregate, leading to uneven local component concentrations, decreased rigidity of the skeleton, and reduced dynamic modulus and dynamic stability. However, because the SBS elastomer remains unchanged, the low-temperature bending strain is less affected. In Example 1, the chopped basalt fibers have a high silanol content on their surface, which can form strong hydrogen bonds with carboxyl groups in the asphalt. After bridging the aggregate gaps, this effectively transfers stress and blocks crack propagation. In Example 9, the chopped glass fibers have a low silanol content on their surface, resulting in fewer hydrogen bonds, decreased interfacial bonding strength, and easier crack propagation at the fiber-asphalt interface, leading to weakened overall rigidity and water resistance.

[0112] Based on Example 1 and Comparative Example 4, and referring to Table 3, it can be seen that after MOF grafting modification, the modified RAP fine powder of Example 1 exhibits selective adsorption of polar molecules in aged asphalt through the multi-level nanopores of MOF. Simultaneously, the octadecyl alcohol long-chain alkyl groups grafted onto the surface reduce the surface polarity of the RAP fine powder, essentially matching the polarity of the new asphalt and eliminating the polarity difference at the interface between the old and new asphalt. In contrast, the unmodified RAP fine powder of Comparative Example 4 has high surface polarity, showing a significant difference from the polarity of the new asphalt. During stirring, it cannot be uniformly dispersed due to polarity repulsion, forming a two-phase separation structure. Furthermore, the modified RAP fine powder synergistically interacts with the regenerator furfural oil. The small-molecule alkanes of furfural oil penetrate into the interior of the RAP fine powder, replacing the polar bonds in the aged asphalt and restoring its rheological properties. Simultaneously, the MOF pores can fix the active ingredients, preventing the loss of the regenerator. In contrast, the unmodified RAP fine powder of Comparative Example 4 exhibits high surface polarity, significantly different from the polarity of the new asphalt. In Example 4, the polar bonds of the aged asphalt were not replaced, and it remained in a rigid and brittle state. After mixing with new asphalt, it could not form a continuous binder network, resulting in a decrease in binder strength. In Example 1, the modified RAP fine powder could be uniformly dispersed in a polyethylene / SBS elastomer matrix and synergistically constructed a three-dimensional structure of "rigid skeleton-elastic filler-fiber reinforcement" with chopped basalt fibers, with a dynamic modulus as high as 21980 MPa. However, the unmodified RAP fine powder in Comparative Example 4 had agglomerates with a size of 50-100 μm, forming "stress-weak areas" in the matrix. Under external forces, stress concentration was easily generated, resulting in a dynamic modulus of only 10420 MPa. The dynamic stability also dropped to 3250 kPa due to the fracture of the rigid skeleton. This fully demonstrates that MOF grafting modification is a key technical means to realize the high-value utilization of RAP fine powder.

[0113] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high modulus agent for asphalt mixtures containing a modified RAP fine powder, characterized in that, The raw materials include the following weight parts: Modified RAP fine powder 60-80 parts; Polyethylene 15-30 parts; Star SBS elastomer 5-10 parts; Chopped basalt fiber 2-6 parts; Stabilizer 1-3 parts; Regeneration agent 0.5-2 parts; The modified RAP fine powder is RAP fine powder grafted with MOF, and the MOF is a metal organic framework.

2. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 1, characterized in that, The preparation of the modified RAP fine powder includes the following steps: First step: hydrothermal synthesis of aluminum nitrate hexahydrate and terephthalic acid in N,N-dimethylformamide for 18-24 hours to generate a MOF crystalline framework; Second step: heating reaction of the MOF crystalline framework prepared in the first step and long-chain alkanol in a mass ratio of (5-8):1 under the action of a catalyst to prepare an intermediate grafted with alkyl on the surface; Third step: blending the intermediate prepared in the second step and RAP fine powder, stirring at 60°C for 10 minutes to prepare the modified RAP fine powder.

3. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 2, characterized in that, A reducing aid, tetraethylthiuram disulfide, is also added in the third step.

4. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 2, characterized in that, The long-chain alkanol in the second step is octadecanol.

5. Process for the preparation of asphalt mixtures high modulus agents containing modified RAP mill-fines according to any one of claims 1-4, characterized in that, The preparation includes the following steps: S1: melt blending polyethylene and star SBS elastomer in a 160-170°C internal mixer for 10-15 minutes; S2: preheating the regeneration agent to 60°C, adding the modified RAP fine powder and soaking for 5-10 minutes; S3: adding the mixture obtained in step two to the melt matrix of step one, heating to 165-170°C in a high-speed disperser, and shearing mixing at 500-800 rpm for 15-20 minutes; S4: adding chopped basalt fiber and stabilizer, and mixing at 140-145°C at low speed until homogeneous to prepare an asphalt mixture high modulus agent containing modified RAP fine powder.

6. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 5, characterized in that, The stabilizer added in S4 is zinc stearate.

7. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 5, characterized in that, The rotation speed of the internal mixer in step S1 is controlled to be 300-500 rpm.

8. The asphalt mixture high modulus agent containing modified RAP mill fines according to claim 5, characterized in that, The preheating temperature of the regeneration agent in step S2 is 55-65°C, and the soaking process is carried out in a sealed stirring tank at a stirring rate of 200-400 rpm.

9. The asphalt mixture high modulus agent containing modified RAP mill fines of claim 5, wherein, The regeneration agent in S2 is furfural oil.

10. The asphalt mixture high modulus agent containing modified RAP mill fines of claim 5, wherein, The rotor linear speed of shearing mixing in step S3 is ≥15 m / s.

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