SBS / waste tire rubber powder composite modified asphalt mixture and preparation method thereof

Abstract

The invention relates to the field of modified asphalt mixtures, and provides an SBS / waste tire rubber powder composite modified asphalt mixture and a preparation method thereof. The SBS / waste tire rubber powder composite modified asphalt mixture comprises coarse aggregate, fine aggregate, mineral powder, an SBS modifier, modified waste tire rubber powder, a composite bio-based silane coupling agent and matrix asphalt, wherein the modified waste tire rubber powder is obtained through interface pre-modification; according to interface pre-modification, sulfur-sulfur cross-linking bonds in rubber powder are selectively broken through a regeneration activating agent; enabling the surface of the waste tire rubber powder to be self-assembled through an interface guiding agent to form a nano interface layer; the high-temperature stability, low-temperature crack resistance, water stability and aging resistance of the SBS / waste tire rubber powder composite modified asphalt provided by the invention are remarkably improved, and the SBS / waste tire rubber powder composite modified asphalt is green, environment-friendly and high in fatigue self-repairing capability.

Description

Technical Field

[0001] This invention relates to the field of modified asphalt mixture technology, and more specifically, to an SBS / waste tire rubber powder composite modified asphalt mixture and its preparation method. Background Technology

[0002] With the rapid development of my country's transportation industry, higher requirements have been placed on the high-temperature stability, low-temperature crack resistance, durability, and environmental friendliness of asphalt pavement materials. Polymer-modified asphalt is one of the key technologies for improving pavement performance. Among them, styrene-butadiene-styrene block copolymer (SBS) modified asphalt is widely used due to its excellent comprehensive performance. Meanwhile, applying waste tire rubber powder (GTR) to asphalt modification is not only an effective way to realize the resource utilization of waste tires, but also significantly improves the high-temperature performance and fatigue resistance of asphalt.

[0003] Theoretically, combining SBS with waste tire rubber powder can combine the advantages of both to produce composite modified asphalt mixtures with superior performance, lower cost, and greater environmental friendliness. However, in practical applications, SBS / waste tire rubber powder composite modification technology faces severe challenges. The core bottleneck lies in the fact that waste tire rubber powder, as an elastomer with a cross-linked network structure, has a chemically inert surface and poor compatibility with asphalt. At the same time, SBS modifier and waste tire rubber powder compete with each other in the asphalt system, resulting in weak interfacial bonding between the multi-component components.

[0004] Currently, common pretreatment methods to improve the compatibility of rubber powder and asphalt include mechanical shearing, thermal degradation, and the addition of activators or softeners (such as furfural oil and aromatic oil). However, while these methods can promote the swelling and dispersion of rubber powder to some extent, they often have limitations: mechanical and thermal degradation methods can easily over-degrade the rubber elasticity of the rubber powder, turning it from "elastic particles" into "inert fillers" and losing its modifying effect; while adding conventional softeners can improve processing fluidity, it cannot establish a strong chemical bond between the rubber powder and asphalt / SBS, resulting in limited improvement in interfacial adhesion and a tendency for phase separation and performance degradation under long-term use. This leads to existing SBS / rubber powder composite modified asphalt mixtures often exhibiting problems such as insignificant improvement in high-temperature stability, insufficient improvement in low-temperature crack resistance, and poor water stability and anti-aging properties. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the prior art, the core objective of this invention is to solve the technical problems of existing SBS / rubber powder composite modified asphalt mixtures, which have insufficient improvement in high temperature stability and low temperature crack resistance, as well as poor water stability and anti-aging performance.

[0006] This invention is achieved through the following technical solution: The first objective of this invention is to provide an SBS / waste tire rubber powder composite modified asphalt mixture, wherein the SBS / waste tire rubber powder composite modified asphalt mixture comprises the following raw materials: Coarse aggregate, fine aggregate, mineral powder, SBS modifier, modified waste tire rubber powder, composite bio-based silane coupling agent and base asphalt; The modified waste tire rubber powder is obtained through interface pre-modification. The interface pre-modification involves first using a regenerating activator to selectively break the sulfur-sulfur crosslinking bonds in the rubber powder, and then using an interface guiding agent to cause the waste tire rubber powder surface to self-assemble into a nano-interface layer.

[0007] This invention solves the problems of poor compatibility and weak interfacial adhesion between waste tire rubber powder (GTR) and SBS / asphalt multi-component systems in existing technologies through a multi-level mechanism of "targeted interface activation - dynamic nano-coupling - bio-based synergistic enhancement". It significantly improves the various properties and durability of the composite modified asphalt mixture under high and low temperature conditions. Specifically: First, this invention pre-modifies the interface of waste tire rubber powder. The purpose is that, under thermal shear conditions, the added regeneration activator (i.e., disulfide or organic amine compound) can selectively break the sulfur-sulfur (SS) crosslinking bonds on the surface of the rubber powder particles, while ensuring that the damage to the stronger carbon-carbon (CC) backbone is reduced. This process is not a traditional deep pyrolysis, but rather creates a large number of reactive "sulfur breaking points" and microporous structures on the surface of the rubber powder, realizing the transformation of waste tire rubber powder from "inert filling" to "activated state". This transformation provides key reaction sites and anchoring foundation for subsequent more refined interface modification, which is an important prerequisite for achieving deep compatibility.

[0008] Furthermore, this invention introduces a dynamic covalent interface directing agent, which is key to forming a stable nano-interface after the waste tire rubber powder is activated on the surface. This nano-interface layer realizes the transition of the modulus gradient from the rubber powder particles to the asphalt matrix, achieving the effect of effectively transferring and dispersing stress, thereby improving the performance at the interface, especially the comprehensive performance under high and low temperature conditions.

[0009] Furthermore, this invention introduces a composite bio-based silane coupling agent, which works synergistically with modified waste tire rubber powder to significantly enhance the multiphase interfacial adhesion of the entire composite material, thereby enhancing its resistance to water damage.

[0010] Preferably, based on 100 parts by weight of the base asphalt, the dosage of each component is as follows: 2.5-4 parts of SBS modifier, 10-25 parts of modified waste tire rubber powder, 0.5-1.5 parts of interface guiding agent, and 0.1-0.3 parts of composite bio-based silane coupling agent.

[0011] Preferably, the regeneration activator is a disulfide and / or an organic amine compound.

[0012] More preferably, the disulfide includes at least one of diphenyl disulfide, di(xylyl) disulfide, and tert-dodecylthiopropyl disulfide; the organic amine compound includes at least one of hexamethylenetetramine, triethylenetetramine, triethanolamine, and piperidine.

[0013] Preferably, the interface directing agent is a triblock molecule, the structure of which is composed of a dynamically covalent functional group connected by chemical bonds, a flexible linking chain, and a polycyclic aromatic hydrocarbon structure in sequence. The dynamic covalent functional group includes at least one of thiol, disulfide bond, or borate ester bond; The flexible connecting chain is a C8 to C18 alkyl chain and / or polyether chain.

[0014] In this invention, the most dynamic covalent functional groups and the "sulfur break points" on the surface of activated waste tire rubber powder form a strong and reversible bond through dynamic covalent chemical reactions (specifically, sulfur exchange reactions). This dynamic characteristic enables the interface to have a certain self-healing ability under the high temperature and shear stress of asphalt construction and use. At the same time, polycyclic aromatic hydrocarbon structures (specifically, phenanthrene, naphthalene, pyrene, etc.) generate strong intermolecular forces with the aromatic components rich in asphalt due to their strong π-π conjugation effect, thus deeply embedding themselves into the matrix asphalt. The flexible connecting chain acts as a key and flexible bridging role, which not only effectively alleviates the internal stress caused by the difference in thermal expansion coefficients between rubber powder and asphalt, but also promotes the self-assembly of the entire molecule at the rubber powder-asphalt interface to form a dense nanoscale transition layer under the drive of thermal shear. This nanoscale interface layer realizes the modulus gradient transition from rubber powder particles to asphalt matrix, effectively transfers and disperses stress, and avoids the interface becoming a performance bottleneck of the final mixture.

[0015] Preferably, the composite bio-based silane coupling agent includes a first bio-based silane coupling agent and a second bio-based silane coupling agent; wherein the mass ratio of the first bio-based silane coupling agent to the second bio-based silane coupling agent is (1:4) to (4:1).

[0016] More preferably, the first bio-based silane coupling agent comprises bio-based hexadecyltrimethoxysilane or bio-based octadecyltrimethoxysilane.

[0017] More preferably, the second bio-based silane coupling agent includes at least one of bio-based 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropylmethyldimethoxysilane.

[0018] In this invention, the composite bio-based silane coupling agent utilizes the synergistic effect of long-chain alkyl silanes (i.e., the first bio-based silane coupling agent) and mercaptosilanes (i.e., the second bio-based silane coupling agent). Specifically, the long-chain alkyl silane reacts with the hydroxyl groups on the surface of the aggregate through its silanol groups. Simultaneously, its long alkyl chains are compatible with the lightweight asphalt components, forming a hydrophobic layer at the aggregate-asphalt interface, thereby enhancing its resistance to water damage. The thiol groups (-SH) of mercaptosilane can react with the surface of activated waste tire rubber powder and interact with the unsaturated bonds in the SBS modifier, thereby establishing an additional chemical "link" between the "rubber powder-SBS-asphalt" multi-component system. This forms a network with both spatial and chemical coupling in the entire system, further enhancing the multiphase interfacial adhesion of the entire composite material.

[0019] The second objective of this invention is to provide a method for preparing the above-mentioned SBS / waste tire rubber powder composite modified asphalt mixture, comprising the following steps: S1. Waste tire rubber powder is mixed with a regeneration activator, then subjected to continuous desulfurization and regeneration treatment under normal pressure, and then subjected to hot shearing treatment to obtain activated rubber powder. S2. An interface guiding agent is added to the activated rubber powder, and then the mixture is subjected to stirring reaction and stirring development in sequence to obtain modified waste tire rubber powder. S3. Heat the base asphalt, then add the modified waste tire rubber powder, and then develop it under hot shear conditions. Then add the SBS modifier to continue development, and then add the composite bio-based silane coupling agent. After stirring and developing, the composite modified asphalt is obtained. S4. Mix the coarse aggregate, fine aggregate, mineral powder and the composite modified asphalt in proportion to obtain SBS / waste tire rubber powder composite modified asphalt mixture.

[0020] Preferably, in step S1, the parameters of the thermal shearing treatment include: a temperature of 180–220°C and a shearing speed of 4000–5000 rpm / min; in step S2, the parameters of the stirring reaction include: a temperature of 180–200°C, a speed of 2000–3000 rpm / min, and a time of 15–20 min; and the parameters of the stirring development include: a speed of 500–1000 rpm / min and a time of 10–15 min.

[0021] Preferably, in step S3, the base asphalt is heated to 160-180°C, then the modified waste tire rubber powder is added, and the mixture is sheared and developed at a speed of 4000-5000 rpm / min for 30-45 min. Then the SBS modifier is added, and the mixture is sheared and developed at the same speed for 45-60 min. Then the composite bio-based silane coupling agent is added, and the mixture is stirred and developed at 170-180°C and a speed of 500-1000 rpm / min to obtain the composite modified asphalt.

[0022] More preferably, the coarse aggregate includes No. 1 crushed stone (12-18) mm, No. 2 crushed stone (7-12) mm, and No. 3 crushed stone (4-7) mm; the fine aggregate is No. 4 manufactured sand (0-4) mm.

[0023] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: (1) This invention significantly improves the compatibility and interfacial bonding strength between waste tire rubber powder and SBS / asphalt system through a multi-level mechanism of “targeted interface activation-dynamic nano-coupling-bio-based synergistic enhancement”.

[0024] (2) The present invention has significantly improved high temperature stability, low temperature crack resistance, water stability and anti-aging performance, and is green and environmentally friendly.

[0025] (3) Compared with existing ordinary SBS modified asphalt, the present invention also has significant fatigue self-healing ability, thereby improving the applicability of the mixture and further extending its service life. Detailed Implementation

[0026] Example 1 This embodiment provides a method for preparing SBS / waste tire rubber powder composite modified asphalt mixture, including the following steps: (1) Raw material preparation: Asphalt binder component: Based on 100 parts of base asphalt, 100 parts of 70# road petroleum asphalt, 3.5 parts of SBS modifier (linear structure, YH-791), 18 parts of modified waste tire rubber powder (40 mesh waste tire rubber powder as raw material), 1.0 part of interface directing agent, and 0.2 parts of composite bio-based silane coupling agent (of which, the mass ratio of bio-based octadecyltrimethoxysilane to bio-based 3-mercaptopropyltrimethoxysilane is 1:1, i.e., 0.1 parts each).

[0027] Aggregate and mineral powder portion: AC-16C type gradation is adopted, and the unit is mass percentage. Coarse aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 1 crushed stone (12~18)mm accounts for 28%, No. 2 crushed stone (7~12)mm accounts for 26%, and No. 3 crushed stone (4~7)mm accounts for 10%; Fine aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 4 manufactured sand (0~4)mm accounts for 31%; Mineral powder (produced by Sichuan Chengzhou Yixian Construction Engineering Co., Ltd.) accounts for 5%; Optimal asphalt-aggregate ratio: 4.6% (that is, the percentage of the mass of composite modified asphalt to the total mass of mineral aggregate).

[0028] (2) Preparation of modified waste tire rubber powder: Activation: 100 parts of 40-mesh waste tire rubber powder and 2.5 parts of regeneration activator diphenyl disulfide (DPDS) are premixed evenly in a high-speed mixer. The mixture is then fed into an atmospheric pressure continuous desulfurization and regeneration equipment and treated under hot shear conditions of 190℃ and 4500rpm for 15 minutes to obtain activated rubber powder.

[0029] Interface modification: The activated rubber powder was transferred to a reactor and the temperature was maintained at 190℃. 1.0 part of an interface directing agent (the specific structure of which is: dynamic covalent functional group is a disulfide bond, flexible linking chain is a C12 alkyl chain, and polycyclic aromatic hydrocarbon structure is pyrene) was added. The mixture was stirred at 2500 rpm for 18 min to allow the interface directing agent to fully react with the surface of the activated rubber powder. Subsequently, the stirring speed was reduced to 800 rpm and stirred for 12 min to promote the self-assembly of the interface directing agent molecules on the surface of the rubber powder, forming a nano-interface layer. After further cooling, modified waste tire rubber powder was obtained.

[0030] (3) Preparation of composite modified asphalt: 100 parts of 70# base asphalt were heated to 175℃ in a heat-conducting oil pan to melt and flow. Then, 18 parts of modified waste tire rubber powder obtained in step (2) were added to the base asphalt. The mixture was sheared and developed at a high speed of 4500 rpm for 40 min to fully disperse and swell the modified rubber powder in the asphalt. While keeping the shearing speed constant, 3.5 parts of SBS modifier were added, and the mixture was sheared and developed at high speed for 50 min until the SBS was completely swollen and formed a uniform network structure. 0.1 parts of bio-based octadecyltrimethoxysilane and 0.1 parts of bio-based 3-mercaptopropyltrimethoxysilane were premixed evenly to prepare a composite bio-based silane coupling agent. The composite coupling agent was poured into the asphalt system, the temperature was adjusted to 175℃, and the speed was reduced to 800 rpm. Under these conditions, the mixture was stirred at low speed for 30 min to allow the silane coupling agent to fully play its role and obtain a homogeneous SBS / waste tire rubber powder composite modified asphalt.

[0031] (4) Mixing of asphalt mixtures: Place the coarse and fine aggregates in a mixing pot, heat to above 185°C, and then add mineral powder and dry mix for 10 seconds. Add the composite modified asphalt prepared in step (3) to the mixing pot according to the optimal asphalt-aggregate ratio, wet mix for 45 seconds, and make SBS / waste tire rubber powder composite modified asphalt mixture.

[0032] Example 2 This embodiment provides a method for preparing SBS / waste tire rubber powder composite modified asphalt mixture, including the following steps: (1) Raw material preparation: Asphalt binder component: Based on 100 parts of base asphalt, 100 parts of 70# road petroleum asphalt, 2.5 parts of SBS modifier (star structure, such as YH-801), 10 parts of modified waste tire rubber powder (60 mesh waste tire rubber powder as raw material), 0.5 parts of interface directing agent, and 0.1 parts of composite bio-based silane coupling agent (of which, the mass ratio of bio-based hexadecyltrimethoxysilane to bio-based 3-mercaptopropyltriethoxysilane is 1:4, i.e., 0.02 parts of the former and 0.08 parts of the latter).

[0033] Aggregate and mineral powder portion: AC-16C type gradation is adopted, and the unit is mass percentage. Coarse aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 1 crushed stone (12~18)mm accounts for 30%, No. 2 crushed stone (7~12)mm accounts for 28%, and No. 3 crushed stone (4~7)mm accounts for 12%; Fine aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 4 manufactured sand (0~4)mm accounts for 25%; Mineral powder (produced by Sichuan Chengzhou Yixian Construction Engineering Co., Ltd.) accounts for 5%; Optimal asphalt-aggregate ratio: 4.8%.

[0034] (2) Preparation of modified waste tire rubber powder: Activation: 100 parts of 60-mesh waste tire rubber powder and 2.0 parts of regeneration activator hexamethylenetetramine (HMTA) were premixed evenly in a high-speed mixer. The mixture was then fed into an atmospheric pressure continuous desulfurization and regeneration equipment and treated under hot shear conditions of 180℃ and 4000rpm for 20 minutes to obtain activated rubber powder.

[0035] Interface modification: The above-mentioned activated rubber powder was transferred to a reaction vessel, and the temperature was maintained at 180℃. 0.5 parts of an interface directing agent (the specific structure of which is: dynamic covalent functional group is mercapto, flexible linking chain is C8 alkyl chain, and polycyclic aromatic hydrocarbon structure is naphthyl) was added. The reaction was stirred at 2000 rpm for 20 min. Then, the speed was reduced to 500 rpm and stirred for 15 min. After further cooling, modified waste tire rubber powder was obtained.

[0036] (3) Preparation of composite modified asphalt: 100 parts of 70# base asphalt were heated to 160℃ in a heat-conducting oil pan to melt and flow. Then, 10 parts of modified waste tire rubber powder obtained in step (2) were added to the base asphalt. The mixture was sheared and developed at a high speed of 4000 rpm for 45 min. While keeping the shearing speed constant, 2.5 parts of SBS modifier were added and the mixture was sheared and developed at high speed for 60 min. 0.02 parts of bio-based hexadecyltrimethoxysilane and 0.08 parts of bio-based 3-mercaptopropyltriethoxysilane were premixed evenly to prepare a composite bio-based silane coupling agent. The composite coupling agent was poured into the asphalt system, the temperature was adjusted to 170℃, the speed was reduced to 500 rpm, and the mixture was stirred and developed at low speed for 40 min under these conditions to obtain homogeneous SBS / waste tire rubber powder composite modified asphalt.

[0037] (4) Mixing of asphalt mixtures: Place the coarse and fine aggregates in a mixing pot and heat them to above 185°C. Then add mineral powder and dry mix for 10 seconds. Heat the composite modified asphalt prepared in step (3) to 175°C and add it to the mixing pot according to the optimal asphalt-aggregate ratio. Wet mix for 45 seconds to make SBS / waste tire rubber powder composite modified asphalt mixture.

[0038] Example 3 This embodiment provides a method for preparing SBS / waste tire rubber powder composite modified asphalt mixture, including the following steps: (1) Raw material preparation: Asphalt binder component: Based on 100 parts of base asphalt, 100 parts of 70# road petroleum asphalt, 4.0 parts of SBS modifier (linear structure, such as Sinopec Baling Petrochemical 4303), 25 parts of modified waste tire rubber powder (30 mesh waste tire rubber powder as raw material), 1.5 parts of interface guiding agent, and 0.3 parts of composite bio-based silane coupling agent (of which, the mass ratio of bio-based octadecyltrimethoxysilane to bio-based 3-mercaptopropylmethyldimethoxysilane is 4:1, i.e., 0.24 parts of the former and 0.06 parts of the latter).

[0039] Aggregate and mineral powder portion: AC-16C type gradation is adopted, and the unit is mass percentage. Coarse aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 1 crushed stone (12~18)mm accounts for 31%, No. 2 crushed stone (7~12)mm accounts for 29%, and No. 3 crushed stone (4~7)mm accounts for 13%; Fine aggregate (produced by Xinjiang Iron and Steel Yamansu Mining Co., Ltd.): No. 4 manufactured sand (0~4)mm accounts for 22%; Mineral powder (produced by Sichuan Chengzhou Yixian Construction Engineering Co., Ltd.) accounts for 5%; Optimal asphalt-aggregate ratio: 4.4%.

[0040] (2) Preparation of modified waste tire rubber powder: Activation: 100 parts of 30-mesh waste tire rubber powder and 3.0 parts of regeneration activator triethylenetetramine (TETA) were premixed evenly in a high-speed mixer. The mixture was then fed into an atmospheric pressure continuous desulfurization and regeneration equipment and treated under hot shear conditions of 220℃ and 5000rpm for 12 minutes to obtain activated rubber powder.

[0041] Interface modification: The above-mentioned activated rubber powder was transferred to a reaction vessel, and the temperature was maintained at 200℃. 1.5 parts of interface directing agent (the specific structure of which is: dynamic covalent functional group is borate ester bond, flexible linking chain is C18 alkyl chain, and polycyclic aromatic hydrocarbon structure is phenanthrene group) were added. The reaction was stirred at 3000 rpm for 15 min. Then, the speed was reduced to 1000 rpm and stirred for 10 min. After further cooling, modified waste tire rubber powder was obtained.

[0042] (3) Preparation of composite modified asphalt: 100 parts of 70# base asphalt were heated to 180℃ in a heat-conducting oil pan to melt and flow. Then, 25 parts of modified waste tire rubber powder obtained in step (2) were added to the base asphalt. The mixture was sheared and developed at a high speed of 5000 rpm for 30 min. While keeping the shearing speed constant, 4.0 parts of SBS modifier were added and the mixture was sheared and developed at high speed for 45 min. 0.24 parts of bio-based octadecyltrimethoxysilane and 0.06 parts of bio-based 3-mercaptopropylmethyldimethoxysilane were premixed evenly to prepare a composite bio-based silane coupling agent. The composite coupling agent was poured into the asphalt system, the temperature was adjusted to 180℃, the speed was reduced to 1000 rpm, and the mixture was stirred and developed at low speed for 20 min under these conditions to obtain homogeneous SBS / waste tire rubber powder composite modified asphalt.

[0043] (4) Mixing of asphalt mixtures: Place the coarse and fine aggregates in a mixing pot and heat them to above 185°C. Then add mineral powder and dry mix for 10 seconds. Heat the composite modified asphalt prepared in step (3) to 175°C and add it to the mixing pot according to the optimal asphalt-aggregate ratio. Wet mix for 45 seconds to make SBS / waste tire rubber powder composite modified asphalt mixture.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that only step (2) is modified: no activation and interface modification treatment is performed, and an equal amount (18 parts) of ordinary 40-mesh waste tire rubber powder is directly used to replace the modified waste tire rubber powder.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that only step (2) is modified: activation treatment is performed (i.e., shearing treatment with diphenyl disulfide at 190°C and 4500 rpm for 15 min), but no interface guiding agent is added for subsequent interface modification, and the activated rubber powder is directly used for the preparation of composite modified asphalt in step (3).

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that only step (2) is modified: in the interface modification step, an equal amount (1.0 part) of furfural extract oil is used to replace the interface guide agent.

[0047] Comparative Example 4 The difference between this comparative example and Example 1 is that only step (3) is modified: the composite bio-based silane coupling agent is replaced with an equal amount (0.2 parts) of ordinary petroleum-based silane coupling agent KH-570 (3-methacryloyloxypropyltrimethoxysilane).

[0048] Comparative Example 5 The difference between this comparative example and Example 1 is that only steps (3) and (4) are modified: 100 parts of base asphalt at 175°C are mixed with 3.5 parts of SBS modifier and sheared at 4500 rpm for 90 minutes without adding rubber powder and silane coupling agent; the SBS modified asphalt is used to mix asphalt mixture at the same asphalt-aggregate ratio (4.6%).

[0049] Experimental Example 1 This experiment used the SBS / waste tire rubber powder composite modified asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-5 as samples to conduct multiple performance comparison tests. The specific test contents and methods are as follows: High-temperature stability test: The rutting test was adopted (according to JTGE20-2011T0719). The specimen size was 300mm×300mm×50mm, the test temperature was 60℃, and the wheel pressure was 0.7MPa. The dynamic stability (DS, cycles / mm) was used as the evaluation index. The higher the DS value, the stronger the rutting resistance and the better the high-temperature performance.

[0050] Low-temperature crack resistance test: A low-temperature small beam bending test was conducted (according to JTGE20-2011T0715). The specimen size was 250mm×30mm×35mm, the test temperature was -10℃, and the loading rate was 50mm / min. The maximum bending tensile strain (με) at failure was used as the evaluation index. The larger the strain value, the better the low-temperature deformation capacity and the better the crack resistance.

[0051] Water stability test: Immersion Marshall test (according to JTGE20-2011T0709): Calculate the residual stability (MS0) after immersion. MS0 ≥ 80% is acceptable. The higher the value, the stronger the resistance to water damage.

[0052] Freeze-thaw splitting test (according to JTGE20-2011T0729): Calculate the freeze-thaw splitting strength ratio (TSR). A TSR ≥ 75% is considered qualified. The higher the value, the stronger the resistance to freeze-thaw damage.

[0053] Preliminary durability evaluation: Short-term aging simulation (according to JTGE20-2011T0630, asphalt mixture oven aging method) was used to conduct immersion Marshall tests on the aged specimens, and the residual stability after aging (AgedMS0) was calculated to evaluate the anti-aging performance of the mixture. The test results are shown in Table 1 below: Table 1. Performance Test Results of SBS / Waste Tire Rubber Powder Modified Asphalt Mixture

[0054] Analysis of Table 1 shows that: High-temperature stability (corresponding to dynamic stability DS): The dynamic stability of all examples is significantly higher than that of the comparative examples. Among them, the high-dosage modified rubber powder and SBS in Example 3 performed best. Therefore, this indicates that the present invention can effectively improve the compatibility of rubber powder and asphalt through the "targeted interface activation-dynamic nano-coupling" mechanism, forming a stronger three-dimensional network structure, thereby greatly improving the resistance of the mixture to permanent deformation. In contrast, Comparative Example 1 uses unmodified waste tire rubber powder, which has the lowest DS value due to its poor compatibility and weak interface. Although the DS values ​​of Comparative Example 2 (without interface directing agent) and Comparative Example 3 (with furfural oil replacing the interface directing agent) are improved, they are significantly lower than those of the examples. This proves that the nano-transition layer formed by the interface directing agent is crucial for stress transfer and dispersion. The DS values ​​of Comparative Example 4 (with ordinary silane coupling agent) and Comparative Example 5 (with pure SBS modified asphalt) are lower than those of the examples, indicating that the synergistic enhancement effect of the composite bio-based silane coupling agent and modified rubber powder / SBS contributes positively to high-temperature performance.

[0055] Low-temperature crack resistance (corresponding to flexural strain): The low-temperature flexural strain of all embodiments is better than that of the comparative examples and far exceeds the technical requirements; among them, Example 1 performs the best, which shows that the modulus gradient transition interface constructed by the present invention effectively alleviates the stress concentration problem, enabling the mixture to withstand greater deformation at low temperatures without cracking; while Comparative Example 1 has the worst low-temperature performance due to weak interfacial bonding; the strain values ​​of Comparative Examples 2 and 3 show that without an effective interfacial transition layer, the rubber powder particles are still prone to becoming stress concentration points; the strain values ​​of Comparative Examples 4 and 5 are acceptable, but lower than those of the embodiments, further confirming the comprehensive effect of the multi-level action mechanism of the present invention on improving low-temperature toughness.

[0056] Water stability (corresponding to MSO and TSR): The MSO and TSR values ​​of all examples were significantly higher than the technical requirements, indicating that they have excellent resistance to water damage. This is mainly due to the dual effect of the composite bio-based silane coupling agent. Specifically, this is because the long-chain alkyl silane forms a hydrophobic layer at the aggregate-asphalt interface, and the mercapto silane establishes a chemical "bond" between the "rubber powder-SBS-asphalt", which significantly enhances the interfacial adhesion of the multiphase interface. The water stability of Comparative Example 4, which uses a common silane coupling agent, is qualified but lower than that of the examples, highlighting the synergistic advantage of bio-based long-chain alkyl and mercapto silanes. The water stability indices of Comparative Examples 1 to 3 are all close to or lower than the qualified line, further proving that the rubber powder without sufficient interface modification is prone to making the interface a weak link for water damage.

[0057] Durability (corresponding to residual stability after aging): The residual stability after aging of the example showed the smallest decrease and the highest retention rate, indicating that it has better anti-aging performance. This is due to the reversible characteristics of the dynamic covalent interface, which gives it a certain self-regulating ability during thermo-oxidative aging, further alleviating the aging embrittlement effect. In contrast, all comparative examples, especially comparative examples 1 to 3, showed more significant performance degradation after aging.

[0058] Experimental Example 2 In this experiment, the SBS / waste tire rubber powder composite modified asphalt mixture prepared in Example 1, as well as the asphalt mixtures prepared in Comparative Example 1 and Comparative Example 5, were used as samples for a four-point bending fatigue test. The test method is as follows: Initial stiffness test: Non-destructive four-point bending test was performed on all specimens, and a small load was applied to determine their initial stiffness modulus (S0); First fatigue damage: Repeated loading with controlled stress was applied to each specimen (stress level set to 0.5 MPa, loading frequency 10 Hz, temperature 15℃); Loading continued until the stiffness modulus of the specimen dropped to 50% of its initial value S0 (i.e., S1 = 0.5 × S0), at which point loading was stopped, and the number of load applications in this stage was defined as the first fatigue life (N1). At this point, microcracks had formed inside the specimen, but macroscopic fracture had not yet occurred; Repair process: The specimen after the first fatigue damage was carefully transferred to a constant temperature oven and left to stand at 80℃ for 24 hours to provide thermodynamic conditions for the breakage and recombination of dynamic covalent bonds (self-repair). Second fatigue test: After the repair period, the specimen was cooled to 15℃ and then subjected to a second four-point bending fatigue test under the same conditions as the first. Loading continued until the specimen completely failed (the stiffness modulus dropped to a certain set threshold or the specimen fractured). The number of load applications in this stage was recorded as the second fatigue life (N2). Calculation of fatigue life recovery rate (Healing Ratio, HR): HR(%) = (N2 / N1) × 100%. This value directly reflects the material's ability to recover its fatigue life after damage. The higher the HR value, the stronger the self-repair ability. The test results are shown in Table 2.

[0059] Table 2 Results of Four-Point Bending Fatigue Test

[0060] As shown in Table 2, Example 1 exhibits significant fatigue self-healing capability, with a recovery rate of nearly 50%. This indicates that after initial fatigue damage, the sample's remaining fatigue life can recover to nearly half of its initial life after thermal repair treatment. Furthermore, Comparative Example 1, with its ordinary rubber powder, shows the lowest recovery rate. This is mainly due to physical entanglement and the weak healing effect of the asphalt itself. Because of the weak adhesion between the rubber powder and the asphalt interface, severe initial damage, and lack of dynamic chemical bonds, it essentially lacks active repair capability. Comparative Example 5, with its ordinary SBS modified asphalt, shows a higher recovery rate than Comparative Example 1, but significantly lower than Example 1. This is mainly due to the thermoplastic behavior of the SBS polymer network and the healing ability of the asphalt itself, which is a physical repair with limited efficiency. Therefore, without the synergy of modified rubber powder and a dynamic interface, the self-healing effect is not significant.

Claims

1. A SBS / ground tire rubber compound modified asphalt mixture, characterized by: The SBS / waste tire rubber powder composite modified asphalt mixture comprises the following raw materials: coarse aggregate, fine aggregate, mineral powder, SBS modifier, modified waste tire rubber powder, composite bio-based silane coupling agent and matrix asphalt. The modified waste tire rubber powder is obtained by interface pre-modification; the interface pre-modification is to selectively break the sulfur-sulfur cross-linking bonds in the rubber powder by using a reactivated agent, and then to make the waste tire rubber powder surface self-assemble to form a nano interface layer by using an interface directing agent.

2. The SBS / ground tire rubber hybrid modified asphalt mixture according to claim 1, wherein: In terms of 100 parts of the mass of the matrix asphalt, the dosages of the components are as follows: 2.5-4 parts of SBS modifier, 10-25 parts of modified waste tire rubber powder, 0.5-1.5 parts of interface directing agent and 0.1-0.3 parts of composite bio-based silane coupling agent.

3. The SBS / ground tire rubber hybrid modified asphalt mixture of claim 1, wherein: The reactivated agent is a disulfide and / or an organic amine compound.

4. The SBS / ground tire rubber hybrid modified asphalt mixture of claim 1, wherein: The interface directing agent is a molecule with a triblock structure, and the molecule is composed of a dynamic covalent functional group, a flexible connecting chain and a polycyclic aromatic hydrocarbon structure connected in sequence by chemical bonds: The dynamic covalent functional group comprises at least one of a mercapto group, a disulfide bond or a borate ester bond. The flexible connecting chain is an alkyl chain and / or a polyether chain with C8-C18.

5. The SBS / ground tire rubber hybrid modified asphalt mixture of claim 1, wherein: The composite bio-based silane coupling agent comprises a first bio-based silane coupling agent and a second bio-based silane coupling agent; the mass ratio of the first bio-based silane coupling agent to the second bio-based silane coupling agent is (1:4) to (4:1).

6. The SBS / ground tire rubber hybrid modified asphalt mixture of claim 5, wherein: The first bio-based silane coupling agent comprises bio-based hexadecyl trimethoxysilane or bio-based octadecyl trimethoxysilane.

7. The SBS / ground tire rubber hybrid modified asphalt mixture of claim 1, wherein: The second bio-based silane coupling agent comprises at least one of bio-based 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane and 3-mercaptopropyl methyl dimethoxysilane.

8. A process for the preparation of SBS / ground tire rubber composite modified asphalt mixtures according to any one of claims 1 to 7, characterized by: The method comprises the following steps: S1, blending waste tire rubber powder with a reactivated agent, then performing normal-pressure continuous desulfurization regeneration treatment, and then performing heat shearing treatment to obtain activated rubber powder; S2, adding an interface directing agent to the activated rubber powder, and then sequentially performing stirring reaction and stirring development to obtain modified waste tire rubber powder; S3, heating matrix asphalt, then adding the modified waste tire rubber powder, and then developing under heat shearing conditions, then adding SBS modifier to continue development, and then adding composite bio-based silane coupling agent, and then performing stirring development to obtain composite modified asphalt; S4, mixing coarse aggregate, fine aggregate and mineral powder with the composite modified asphalt in a certain proportion to obtain SBS / waste tire rubber powder composite modified asphalt mixture.

9. The process for the preparation of SBS / ground tire rubber composite modified asphalt mixture as claimed in claim 8, wherein: In step S1, the parameters of the heat shearing treatment include a temperature of 180-220 DEG C and a shearing rotation speed of 4000-5000 rpm / min; in step S2, the parameters of the stirring reaction include a temperature of 180-200 DEG C, a rotation speed of 2000-3000 rpm / min and a time of 15-20 min; and the parameters of the stirring development include a rotation speed of 500-1000 rpm / min and a time of 10-15 min.

10. The method for preparing SBS / waste tire rubber powder composite modified asphalt mixture according to claim 8, characterized in that: In step S3, the base asphalt is heated to 160-180℃, then the modified waste tire rubber powder is added, and shearing development is carried out at a speed of 4000-5000 rpm / min for 30-45 min, then the SBS modifier is added, and shearing development is continued at the same speed for 45-60 min, then the composite bio-based silane coupling agent is added, and stirring development is carried out at 170-180℃ and a speed of 500-1000 rpm / min, to obtain the composite modified asphalt.

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