Composite modified asphalt and method for preparing the same

Abstract

This invention proposes a composite modified asphalt and its preparation method. The raw materials for the composite modified asphalt include base asphalt, waste tire rubber powder, and modified graphene oxide. The modified graphene oxide has a core-shell structure, comprising graphene oxide and polydopamine from the inside out. Through multiple physicochemical synergistic mechanisms among its components, the composite modified asphalt achieves simultaneous and significant improvements in high-temperature rutting resistance, low-temperature crack resistance, workability, storage stability, and anti-aging properties. Its overall road performance is significantly improved compared to traditional rubber powder modified asphalt and simple physically blended graphene oxide / rubber powder composite asphalt, thus extending the service life of the pavement.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, and in particular to a composite modified asphalt and its preparation method. Background Technology

[0002] Waste tire rubber powder modified asphalt is currently the most widely used environmentally friendly road modification material. It can realize the resource utilization of solid waste, significantly improve the low-temperature crack resistance, fatigue resistance, and aging resistance of asphalt, and extend the service life of the pavement. However, traditional rubber powder modified asphalt has many insurmountable industry pain points: First, the compatibility between rubber powder and asphalt matrix is ​​poor, and long-term storage at high temperatures can easily lead to stratification and segregation, resulting in poor storage stability; second, when the rubber powder content is high, the asphalt viscosity increases sharply, the workability deteriorates, and the difficulty of paving and compaction increases; third, the improvement in high-temperature rutting resistance is limited, making it difficult to meet the needs of heavy traffic and high-temperature areas, thus limiting its application scenarios.

[0003] Graphene oxide, as a two-dimensional nanomaterial, possesses an ultra-large specific surface area, excellent mechanical properties, and thermal stability. Adding even a small amount can significantly improve the high-temperature stability, anti-aging properties, and structural density of asphalt, making it commonly used in asphalt modification. However, when graphene oxide is compounded with rubber powder to modify asphalt, significant technical shortcomings remain: graphene oxide has a high surface energy, making it prone to agglomeration in asphalt systems and difficult to disperse uniformly; the interfacial bonding between graphene oxide, rubber powder, and the asphalt matrix is ​​weak, hindering the full realization of synergistic modification effects; and simple physical addition not only results in low modification efficiency but also further exacerbates the problem of increased asphalt viscosity, leading to even worse workability.

[0004] Most existing technologies employ simple physical blending methods without specific optimization for dispersion processes, interfacial compatibility, and viscosity control. This results in either excessively high graphene oxide content leading to soaring costs, or minimal performance improvements and significant construction difficulties, making it challenging to balance environmental friendliness, road performance, and ease of construction. Therefore, developing a composite modified asphalt with low dosage, uniform dispersion, good compatibility, and moderate viscosity, capable of achieving synergistic performance between graphene oxide and rubber powder, is a current research hotspot in the field of road materials and an urgent need to solve practical engineering problems. Summary of the Invention

[0005] In view of this, and addressing the technical shortcomings of traditional rubber powder modified asphalt and graphene oxide / rubber powder composite systems, such as easy agglomeration of graphene oxide, weak interfacial bonding, poor synergistic modification effect, and high construction viscosity, this invention proposes a composite modified asphalt and its preparation method. The composite modified asphalt comprises polydopamine-coated graphene oxide and modified nano-silica. Through a multi-faceted physicochemical synergistic mechanism, the components achieve simultaneous and significant improvements in high-temperature rutting resistance, low-temperature crack resistance, workability, storage stability, and anti-aging properties. The overall road performance is significantly improved compared to traditional rubber powder modified asphalt and simple physically blended graphene oxide / rubber powder composite asphalt, extending the service life of the pavement.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a composite modified asphalt, the raw materials of which include base asphalt, waste tire rubber powder, and modified graphene oxide. The modified graphene oxide has a core-shell structure, comprising graphene oxide and polydopamine from the inside out.

[0007] This invention first employs polydopamine to coat the surface of graphene oxide, forming a core-shell structure (denoted as GO@PDA) with graphene oxide as the core and polydopamine as the shell. This structure addresses the issues of easy agglomeration of graphene oxide in asphalt, weak interfacial bonding, poor synergistic modification effect, and high application viscosity in the following three aspects: (1) Suppressing aggregation and achieving nanoscale dispersion The surface of graphene oxide is rich in polar functional groups such as carboxyl and hydroxyl groups, and the layers easily aggregate irreversibly through hydrogen bonding and π-π stacking. After being covered with a polydopamine shell, adjacent layers are physically isolated through steric hindrance; on the other hand, the amine groups on the polydopamine molecular chain can be partially protonated in the weakly polar environment of asphalt, generating electrostatic repulsion. The synergistic effect of these two factors improves the dispersion uniformity of graphene oxide in asphalt.

[0008] (2) Enhance interfacial bonding through chemical action. Polydopamine contains abundant catechol groups (-OH) and amino groups (-NH2). Catechol can form strong hydrogen bonds with the carboxyl and sulfonic acid groups in asphalt; the amino groups can undergo amidation reactions with the carboxyl groups on the surface of waste tire rubber powder to form covalent bonds. Simultaneously, the aromatic rings of polydopamine interact with the aromatic components in asphalt through π-π stacking. Through these triple interactions of hydrogen bonding, covalent bonding, and π-π stacking, GO@PDA establishes a chemical network with asphalt matrix and waste tire rubber powder, significantly enhancing the interfacial bonding strength.

[0009] (3) Adjusting viscosity to improve construction difficulty The polydopamine shell has a certain degree of flexibility, which can reduce the interfacial frictional resistance between the rigid graphene oxide sheets and the matrix bitumen, thereby offsetting the viscosity increase effect caused by the graphene oxide itself. Combined with a compatibilizer, the viscosity of the system is further reduced.

[0010] Based on the above technical solution, the preparation method of the modified graphene oxide further includes: dispersing graphene oxide in a buffer solution, adding dopamine hydrochloride, reacting, and then adding glutaraldehyde to obtain the modified graphene oxide.

[0011] Based on the above technical solution, further, after the reaction to produce polydopamine, glutaraldehyde is added, and the reaction temperature is 25~60℃, and the time is 12~24h.

[0012] The present invention further employs glutaraldehyde to chemically crosslink the polydopamine shell. The aldehyde groups of glutaraldehyde react with the amino groups of polydopamine to form a covalent network, thereby improving the thermal stability and structural stability of polydopamine.

[0013] Based on the above technical solution, the mass ratio of glutaraldehyde to dopamine hydrochloride is further 0.05~0.15:1.

[0014] Based on the above technical solution, the mass ratio of graphene oxide to dopamine hydrochloride is further 1:(0.8~1.5).

[0015] If the amount of dopamine hydrochloride is too small, the polydopamine shell will be incomplete, failing to effectively inhibit the aggregation of graphene oxide, and the improvement in dispersion uniformity and interfacial bonding ability will be limited. If the amount of dopamine hydrochloride is too large, the polydopamine shell will be too thick, not only increasing costs but also reducing the high-temperature rutting resistance due to excessive lubrication of the shell. Therefore, this invention controls the mass ratio of graphene oxide to dopamine hydrochloride at 1:(0.8~1.5), balancing dispersion effect, mechanical properties, and economy.

[0016] Based on the above technical solution, the raw materials further include the following components in parts by weight: 80-120 parts base asphalt, 15-25 parts waste tire rubber powder, and 0.2-0.5 parts modified graphene oxide.

[0017] Based on the above technical solution, the raw materials further include modified nano-SiO2, which is obtained by modifying nano-SiO2 with a silane coupling agent.

[0018] This invention further incorporates modified nano-silica with a silane coupling agent surface modification. In terms of mechanical properties, the synergistic effect of GO@PDA and modified nano-SiO2 significantly enhances the high-temperature rutting resistance of asphalt.

[0019] Regarding anti-aging properties, although polydopamine has free radical scavenging capabilities, it is prone to photo-oxidative degradation under ultraviolet light irradiation. Modified nano-SiO2 can effectively absorb ultraviolet light, significantly reducing the light intensity reaching the polydopamine shell on the GO@PDA surface; while the small amount of free radicals generated by ultraviolet light that is not completely shielded can still be captured by polydopamine.

[0020] Regarding interfacial bonding, the modified nano-SiO2 surface possesses active functional groups such as amino or epoxy groups, which can chemically bond or hydrogen bond with the polar components of asphalt, the carboxyl groups on the surface of waste tire rubber powder, and the phenolic hydroxyl groups of polydopamine, thus connecting GO@PDA, waste tire rubber powder, and asphalt into a continuous chemical cross-linked network. This network effectively inhibits the migration of components during high-temperature storage, significantly improving storage stability.

[0021] Based on the above technical solution, the preparation method of the modified nano-SiO2 further includes: dispersing nano-SiO2 in anhydrous ethanol, adding a silane coupling agent, reacting, and obtaining the modified nano-SiO2.

[0022] Based on the above technical solution, the mass ratio of the nano-SiO2 to the silane coupling agent is further 1:(0.05~0.2).

[0023] Based on the above technical solution, the raw materials further include compatibilizers and dispersants. The compatibilizers include one or more of maleic anhydride-grafted SBS, aromatic rubber oil, and petroleum resin, and the dispersants include stearates.

[0024] Based on the above technical solutions, furthermore, when using it, maleic anhydride-grafted SBS and aromatic rubber oil can be compounded as compatibilizers, or aromatic rubber oil and petroleum resin can be compounded as compatibilizers.

[0025] Based on the above technical solution, the raw materials further include 1-3 parts modified nano-SiO2, 0.5-1.5 parts compatibilizer, and 0.3-0.8 parts dispersant.

[0026] Secondly, the present invention also provides a method for preparing composite modified asphalt, comprising the following steps: S1, mixing modified graphene oxide, modified nano-SiO2, compatibilizer and dispersant to obtain a mixture, and dispersing it to obtain a dispersion; S2. After melting the base asphalt, add waste tire rubber powder and mix well to obtain a rubber powder asphalt system. S3. Add the dispersion prepared in step S1 to the rubber powder asphalt system, mix well, disperse while heating, and obtain the composite modified asphalt after shear development.

[0027] Based on the above technical solution, further, the dispersion in step S1 includes dispersing the mixture in an ultrasonic disperser with an ultrasonic power of 200~400W and an ultrasonic time of 10~20min.

[0028] Based on the above technical solution, the melting temperature in step S2 is further 140~150℃.

[0029] Based on the above technical solution, further, in step S2, the mixing speed is 300~400 r / min and the time is 15~25 min.

[0030] Based on the above technical solution, the heating temperature in step S3 is further 170~180℃.

[0031] Based on the above technical solution, further, the dispersion in step S3 includes shearing and ultrasonication, wherein the shearing rotation speed is 3000~5000r / min, the time is 30~60min, and the ultrasonic power is 100~200W.

[0032] Based on the above technical solution, in step S3, the development temperature is 160~170℃, the shearing speed is 300~500r / min, the development time is 2~4h, and the composite modified asphalt is obtained after development is completed, and a casting sample is tested.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved dispersibility and interfacial bonding strength: This invention uses polydopamine to coat and modify graphene oxide, forming a core-shell structure with graphene oxide as the core and polydopamine as the shell. The polydopamine layer contains abundant catechol hydroxyl and amino functional groups. On the one hand, it effectively inhibits the stacking and aggregation between graphene oxide sheets through steric hindrance. On the other hand, its phenolic hydroxyl and amino groups can form hydrogen bonds with polar components such as carboxyl groups and gums in asphalt, and at the same time, it undergoes an amidation reaction with the carboxyl groups on the surface of rubber powder to form multi-point chemical anchoring, which significantly improves the dispersion uniformity and interfacial bonding strength.

[0034] (2) Synergistic enhancement of high-temperature rutting resistance and low-temperature crack resistance: Graphene oxide itself has an ultra-high elastic modulus and a two-dimensional sheet structure, which can serve as a rigid skeleton to significantly improve the high-temperature deformation resistance of asphalt; the polydopamine shell has a certain degree of flexibility after cross-linking, which can buffer low-temperature shrinkage stress; waste tire rubber powder provides elastic toughening. The synergistic effect of the three enables asphalt to simultaneously obtain excellent high-temperature rutting resistance and low-temperature crack resistance.

[0035] (3) Significantly improved workability: In response to the problem of the sharp increase in viscosity of traditional graphene oxide / rubber powder composite system, this invention introduces compatibilizer and dispersant. At the same time, the chain segments of polydopamine shell can be oriented in the shear flow field, reducing the interfacial friction resistance and solving the problems of viscous construction and difficult paving and compaction.

[0036] (4) Excellent storage stability: In this invention, the chemical bonding network formed between the polydopamine shell and the asphalt and rubber powder "anchors" the modified graphene oxide in the system. At the same time, the uniform dispersion of modified nano-SiO2 further enhances the overall stability of the system, meeting the needs of long-distance transportation and long-term storage at construction sites.

[0037] (5) Significantly improved anti-aging performance: This invention constructs multiple anti-aging barriers: the graphene oxide sheets physically block oxygen and ultraviolet rays; the catechol groups in polydopamine can capture peroxy free radicals generated by thermo-oxidative aging and terminate the chain reaction; the modified nano-SiO2 can absorb and scatter ultraviolet rays, reducing the photo-oxidative degradation of polydopamine and asphalt. The three mechanisms work synergistically to significantly extend the service life of the pavement.

[0038] (6) Green and environmentally friendly, high-value utilization of solid waste: This invention uses waste tire rubber powder as one of the main modified raw materials to realize the resource utilization of waste tires and reduce black pollution; the preparation process uses water or ethanol as the dispersion medium and there is no emission of toxic and harmful substances; the modified graphene oxide dosage is small, the cost is controllable, it is suitable for large-scale engineering applications, and it is in line with the development direction of green and low-carbon road construction. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] In the following specific embodiments, the base asphalt used is 70# Grade A road petroleum asphalt; the waste tire rubber powder is 40~80 mesh room temperature ground rubber powder with a rubber hydrocarbon content ≥60%; the graphene oxide has a sheet structure with a sheet diameter of 10~50μm, 1~5 layers, and an oxygen content ≥30%; unless otherwise specified, all other reagents are commercially available analytical grade.

[0041] In the following specific implementation, the aromatic rubber oil was purchased from Wuhan Kangrun Petrochemical Co., Ltd., the maleic anhydride-grafted SBS was purchased from Dongguan Shenghao Plastic Raw Materials Co., Ltd. (item number 5541254), the petroleum resin was purchased from Zibo Xinle Chemical Co., Ltd. (item number 68131-77-1), and the nano silica was purchased from Hangzhou Jiupeng New Materials Co., Ltd. (item number 131).

[0042] In the following specific implementation, 1 part by weight is 1 kg.

[0043] Example 1 This embodiment provides a composite modified asphalt and its preparation method. The raw materials are as follows by weight: 100 parts of base asphalt, 20 parts of waste tire rubber powder, 0.3 parts of modified graphene oxide (GO@PDA), 2 parts of modified nano-SiO2, 1 part of compatibilizer (aromatic rubber oil), and 0.5 parts of dispersant (zinc stearate). 1 part by weight is 1 kg.

[0044] The preparation method of GO@PDA includes: a1. Dispersing 0.3 parts of graphene oxide in 200 mL of Tris buffer (pH=8.5) and ultrasonically dispersing for 30 min (power 300W) to obtain GO dispersion; a2. Add 0.3 parts of dopamine hydrochloride to the above GO dispersion and stir at room temperature for 18 hours to allow dopamine to self-polymerize and form a polydopamine coating layer; a3. Add 0.03 parts of glutaraldehyde, stir for 2 hours, centrifuge, wash and dry with deionized water and anhydrous ethanol respectively to obtain GO@PDA, 1 part by weight is 1 kg.

[0045] The preparation method of modified nano-SiO2 includes: dispersing 2.0 parts of nano-silica in 80 mL of anhydrous ethanol, adding 0.2 parts of silane coupling agent KH550, adjusting the pH to 4.5, and stirring in a water bath at 60 °C for 6 h. After centrifugation, washing, and drying, modified nano-SiO2 is obtained, with 1 part by weight equaling 1 kg.

[0046] The preparation method of composite modified asphalt includes the following steps: S1. Mix modified graphene oxide, modified nano-SiO2, compatibilizer, and dispersant, add 500 mL of anhydrous ethanol to form a paste, stir for 15 min to obtain a dispersion.

[0047] S2. Heat the base asphalt to 145℃ to melt it, add waste tire rubber powder, and stir at 350r / min for 20min to obtain a rubber powder asphalt system.

[0048] S3. Add the dispersion from step S1 to the rubber powder asphalt system from step S2, mix well, heat to 170℃, shear at 4000r / min for 45min, and develop at 165℃ for 3h at a rotation speed of 400r / min to obtain the composite modified asphalt.

[0049] Example 2 This embodiment provides a composite modified asphalt and its preparation method. The raw materials are as follows by weight: 80 parts of base asphalt, 15 parts of waste tire rubber powder, 0.2 parts of modified graphene oxide (GO@PDA), 1 part of modified nano-SiO2, 1 part of compatibilizer (1 part of aromatic rubber oil, 0.5 parts of maleic anhydride grafted SBS), and 0.3 parts of dispersant (calcium stearate). 1 part by weight is 1 kg.

[0050] The preparation method of GO@PDA includes: a1. Dispersing 0.2 parts of graphene oxide in 150 mL of Tris buffer (pH=8.5) and ultrasonically dispersing for 30 min (power 300W) to obtain GO dispersion; a2. Add 0.16 parts of dopamine hydrochloride to the above GO dispersion and stir at room temperature for 18 hours to allow dopamine to self-polymerize and form a polydopamine coating layer; a3. Add 0.008 parts of glutaraldehyde, stir for 2 hours, centrifuge, wash with deionized water and anhydrous ethanol respectively, and dry to obtain GO@PDA, 1 part by weight is 1 kg.

[0051] The preparation method of modified nano-SiO2 includes: dispersing 1 part of nano-silica in 40 mL of anhydrous ethanol, adding 0.1 part of silane coupling agent KH550, adjusting the pH to 4.5, and stirring in a water bath at 60 °C for 6 h. After centrifugation, washing, and drying, modified nano-SiO2 is obtained, with 1 part by weight equaling 1 kg.

[0052] The preparation method of composite modified asphalt includes the following steps: S1. Mix modified graphene oxide, modified nano-SiO2, compatibilizer, and dispersant, add 500 mL of anhydrous ethanol to form a paste, stir for 15 min to obtain a dispersion.

[0053] S2. Heat the base asphalt to 140℃ to melt it, add waste tire rubber powder, and stir at 350r / min for 15min to obtain a rubber powder asphalt system.

[0054] S3. Add the dispersion from step S1 to the rubber powder asphalt system from step S2, mix well, heat to 160℃, shear at 3000 r / min for 30 min, and develop at 160℃ for 2 h at a rotation speed of 300 r / min to obtain the composite modified asphalt.

[0055] Example 3 This embodiment provides a composite modified asphalt and its preparation method. The raw materials are as follows by weight: 120 parts of base asphalt, 25 parts of waste tire rubber powder, 0.5 parts of modified graphene oxide (GO@PDA), 3 parts of modified nano-SiO2, compatibilizer (0.5 parts of petroleum resin + 1 part of aromatic rubber oil), and 0.8 parts of dispersant (magnesium stearate). 1 part by weight is 1 kg.

[0056] The preparation method of GO@PDA includes: a1. Dispersing 0.5 parts of graphene oxide in 150 mL of Tris buffer (pH=8.5) and ultrasonically dispersing for 30 min (power 300W) to obtain GO dispersion; a2. Add 0.75 parts of dopamine hydrochloride to the above GO dispersion and stir at room temperature for 18 hours to allow dopamine to self-polymerize and form a polydopamine coating layer; a3. Add 0.09 parts of glutaraldehyde, stir for 2 hours, centrifuge, wash with deionized water and anhydrous ethanol respectively, and dry to obtain GO@PDA, 1 part by weight is 1 kg.

[0057] The preparation method of modified nano-SiO2 includes: dispersing 3 parts of nano-silica in 120 mL of anhydrous ethanol, adding 0.3 parts of silane coupling agent KH550, adjusting the pH to 4.5, and stirring in a water bath at 70 °C for 8 h. After centrifugation, washing, and drying, modified nano-SiO2 is obtained, with 1 part by weight equaling 1 kg.

[0058] The preparation method of composite modified asphalt includes the following steps: S1. Mix modified graphene oxide, modified nano-SiO2, compatibilizer, and dispersant, add 500 mL of anhydrous ethanol to form a paste, stir for 15 min to obtain a dispersion.

[0059] S2. Heat the base asphalt to 150℃ to melt it, add waste tire rubber powder, and stir at 350r / min for 25min to obtain a rubber powder asphalt system.

[0060] S3. Add the dispersion from step S1 dropwise to the rubber powder asphalt system from step S2, mix well, heat to 180℃, shear at 5000r / min for 60min, and develop at 170℃ for 4h at a rotation speed of 500r / min to obtain the composite modified asphalt.

[0061] Comparative Example 1 The difference between this comparative example and Example 1 is that graphene oxide is used instead of modified graphene oxide.

[0062] Comparative Example 2 The difference between this comparative example and Example 2 is that nano-SiO2 is used instead of modified nano-SiO2.

[0063] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not contain glutaraldehyde.

[0064] Comparative Example 4 The difference between this comparative example and Example 1 is that: there is too little dopamine hydrochloride, and the mass ratio of graphene oxide to dopamine hydrochloride is 1:0.5.

[0065] Comparative Example 5 The difference between this comparative example and Example 1 is that: there is too much dopamine hydrochloride, and the mass ratio of graphene oxide to dopamine hydrochloride is 1:2.

[0066] Performance testing Examples 1-3 and Comparative Examples 1-5 were tested according to the JTG E20-2011 standard, and the results are shown in Table 1 below.

[0067] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-5

[0068] As can be seen from the performance comparison data of Examples 1-3 and Comparative Examples 1-5 above, the composite modified asphalt prepared by the present invention is significantly better than each comparative example in terms of softening point, dynamic stability, storage stability and anti-aging performance.

[0069] Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 directly uses graphene oxide and nano-silica. Due to its high surface energy and rich polar functional groups, GO severely agglomerates in asphalt, forming micron-sized aggregates, which cannot play the role of a rigid framework for the nanosheets. At the same time, the agglomerated GO sheets hinder the flow of asphalt molecules, resulting in a sharp increase in viscosity. Nano-SiO2 also has poor compatibility with asphalt due to its hydrophilic and oleophobic properties, and is prone to sedimentation and segregation.

[0070] As can be seen from the comparison between Example 1 and Comparative Example 2, Comparative Example 2 did not add modified nano-SiO2. Although GO@PDA itself already possesses good dispersibility and interfacial bonding ability, it lacks the rigid pinning points provided by nano-SiO2. Under high temperature and heavy load, although the cross-linked PDA shell is harder than the uncross-linked one, it still has the potential for slight creep. Nano-SiO2 can form a three-dimensional point-like constraint network in the asphalt matrix, interpenetrating with the two-dimensional GO@PDA sheets, significantly improving the modulus and resistance to permanent deformation of the composite system. In addition, the ultraviolet shielding effect of SiO2 further delays the photoaging of PDA and asphalt, resulting in better anti-aging performance.

[0071] As can be seen from the comparison between Example 1 and Comparative Example 3, the GO@PDA in Comparative Example 3 was not cross-linked with glutaraldehyde, and the polydopamine shell was in a flexible chain state. Although this flexible layer can reduce viscosity through orientation, molecular chain slippage is prone to occur at high temperatures, resulting in a significant decrease in high-temperature rutting resistance.

[0072] As can be seen from the comparison between Example 1 and Comparative Example 4, the amount of dopamine hydrochloride in Comparative Example 4 was only half that of GO, resulting in an incomplete polydopamine shell and partial exposure of GO sheets. The exposed GO will still aggregate through hydrogen bonds and π-π stacking, leading to decreased dispersion uniformity and the formation of localized stress concentration points. Simultaneously, the insufficient number of functional groups in the shell reduces the number of chemical bonding sites with asphalt and rubber powder, lowering the interfacial bonding strength and resulting in poorer storage stability and decreased anti-aging properties. The incompletely coated rigid GO sheets directly contacting the asphalt further exacerbate the viscosity increase.

[0073] As can be seen from the comparison between Example 1 and Comparative Example 5, the amount of dopamine hydrochloride in Comparative Example 5 was twice that of GO, resulting in an excessively thick polydopamine shell. Although the thick shell provided abundant functional groups and good interfacial compatibility, its excessive flexible components, and even after glutaraldehyde crosslinking, weakened the contribution of the GO rigid skeleton due to the excessively high proportion of polymer layers, leading to a decrease in high-temperature modulus and rutting resistance instead of an increase. In addition, the excessive PDA increased the viscoelastic resistance of the system, which is detrimental to construction.

[0074] In summary, addressing the technical shortcomings of traditional rubber powder modified asphalt and graphene oxide / rubber powder composite systems, such as easy agglomeration of graphene oxide, weak interfacial bonding, poor synergistic modification effect, and high construction viscosity, this invention proposes a composite modified asphalt comprising polydopamine-coated graphene oxide and modified nano-silica. Through a multi-faceted physicochemical synergistic mechanism, the components achieve simultaneous and significant improvements in high-temperature rutting resistance, low-temperature crack resistance, workability, storage stability, and anti-aging properties. The overall road performance is significantly improved compared to traditional rubber powder modified asphalt and simple physically blended graphene oxide / rubber powder composite asphalt, extending pavement service life.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite modified asphalt, characterized in that, Its raw materials include base asphalt, waste tire rubber powder, modified nano-SiO2, and modified graphene oxide. The modified graphene oxide has a core-shell structure, comprising graphene oxide and polydopamine from the inside out. The method for preparing the modified graphene oxide includes: dispersing graphene oxide in a buffer solution, adding dopamine hydrochloride, reacting, and then adding glutaraldehyde to obtain the modified graphene oxide. The mass ratio of graphene oxide to dopamine hydrochloride is 1:(0.8~1.5). The modified nano-SiO2 is obtained by modifying nano-SiO2 with a silane coupling agent.

2. The composite modified asphalt as described in claim 1, characterized in that, Its raw materials include the following components in parts by weight: 80-120 parts base asphalt, 15-25 parts waste tire rubber powder, and 0.2-0.5 parts modified graphene oxide.

3. The composite modified asphalt as described in claim 1, characterized in that, The method for preparing the modified nano-SiO2 includes: dispersing nano-SiO2 in anhydrous ethanol, adding a silane coupling agent, reacting, and obtaining the modified nano-SiO2.

4. The composite modified asphalt as described in claim 3, characterized in that, The mass ratio of nano-SiO2 to silane coupling agent is 1:(0.05~0.2).

5. The composite modified asphalt as described in claim 1, characterized in that, Its raw materials also include glutaraldehyde, compatibilizer, and dispersant. The compatibilizer includes one or more of maleic anhydride-grafted SBS, aromatic rubber oil, and petroleum resin. The dispersant includes stearate.

6. The composite modified asphalt as described in claim 5, characterized in that, Its raw materials also include 1-3 parts modified nano-SiO2, 0.5-1.5 parts compatibilizer, and 0.3-0.8 parts dispersant.

7. The method for preparing composite modified asphalt according to any one of claims 1 to 6, characterized in that, The process includes the following steps: S1, mixing modified graphene oxide, modified nano-SiO2, compatibilizer, and dispersant to obtain a mixture, and then dispersing it to obtain a dispersion; S2. After melting the base asphalt, add waste tire rubber powder and mix well to obtain a rubber powder asphalt system. S3. Add the dispersion prepared in step S1 to the rubber powder asphalt system, mix well, disperse while heating, and obtain the composite modified asphalt after shear development.

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