A recycled rubber powder modified asphalt based on a renewable composite activator and a preparation method and application thereof

Abstract

The application belongs to the composition of high molecular compound, and relates to a renewable rubber powder modified asphalt based on renewable composite activator and a preparation method and application thereof, the renewable rubber powder modified asphalt comprises matrix asphalt and activated rubber powder with a mass ratio of 1: (0.2-0.3), the activated rubber powder comprises waste tire rubber powder and a composite activator with a mass ratio of 10: (0.8-1.5), the composite activator comprises an organic phase and an inorganic phase with a mass ratio of (1.5-3):1, the organic phase is chitosan-amino acid derivative, and the inorganic phase is layered double hydroxide. Compared with the prior art, the prepared rubber powder modified asphalt has good high-temperature storage stability and interface structure integrity, and exhibits excellent anti-aging performance and high-temperature anti-rutting performance in a long-term service process.

Description

Technical Field

[0001] This invention belongs to the field of polymer compound composition technology, and relates to a regenerated rubber powder modified asphalt based on a renewable composite activator, its preparation method and application. Background Technology

[0002] Waste tires, as a typical recalcitrant solid waste, pose a serious challenge to the ecological environment and resource management. Crushing waste tires into rubber powder and using it for asphalt modification is one of the important pathways to achieve resource recycling and environmental pollution control. Asphalt modified with recycled rubber powder not only possesses good high-temperature rutting resistance and a certain degree of crack resistance, but also significantly extends the service life of roads, and has been widely applied in road engineering projects in many countries and regions. However, due to the inherent microstructural characteristics of waste rubber powder, its engineering application still faces significant technical bottlenecks. Rubber powder has a highly cross-linked three-dimensional network structure, low molecular polarity, and a lack of active functional groups on its surface, leading to uneven dispersion and poor interfacial bonding in the matrix asphalt. This makes it prone to agglomeration, sedimentation, and stratification during storage or construction. This not only affects the uniformity of mixing and processing stability but also significantly weakens the modification effect and storage performance, becoming a key issue restricting the engineering application of this type of material.

[0003] Therefore, researchers proposed using external activators to pretreat the surface of rubber powder to improve its interfacial compatibility with asphalt. Currently used organic additives such as aromatic oils, phenolic resins, and petroleum resins can soften rubber powder and enhance wettability to a certain extent, but they also have obvious defects: (1) most of them are derived from non-renewable petrochemical resources and lack environmental friendliness; (2) they are prone to volatilization, oxidation, or even degradation under high temperature conditions, affecting the thermal stability and safety of materials; (3) they mainly rely on physical adsorption mechanisms, and their regulatory effect is short-lived and lacks synergy. Therefore, traditional single-component organic activator systems have room for improvement in terms of green performance, interfacial stability, and multifunctional regulation. More importantly, during the service of roads, modified asphalt also needs to withstand multiple environmental effects such as heat and oxygen, water loss, and ultraviolet radiation for a long time, and the aging problem is becoming increasingly prominent. Studies have shown that rubber powder modified systems with insufficient interfacial treatment are more prone to delamination and stress concentration in the weak interfacial area, accelerating the occurrence of aging cracks and the degradation of structural performance, thereby affecting the overall durability of the pavement. Therefore, improving the interfacial bonding stability and anti-aging ability of recycled rubber powder modified asphalt has become a core issue for the long-term performance optimization of this type of material system. Summary of the Invention

[0004] The purpose of this invention is to overcome the key technical problems of existing waste rubber powder in asphalt, such as poor dispersibility, weak interfacial compatibility, poor storage stability and insufficient anti-aging performance. The invention proposes a method for preparing recycled rubber powder modified asphalt based on a renewable composite activator and its application.

[0005] The objective of this invention can be achieved through the following technical solutions: One of the technical solutions of this invention is to provide a recycled rubber powder modified asphalt based on a renewable composite activator, comprising base asphalt and activated rubber powder in a mass ratio of 1:(0.2~0.3). The activated rubber powder comprises waste tire rubber powder and a composite activator in a mass ratio of 10:(0.8~1.5). The composite activator comprises an organic phase and an inorganic phase in a mass ratio of (1.5~3):1. The organic phase is a chitosan-amino acid derivative, and the inorganic phase is a layered bimetallic hydroxide.

[0006] In some specific embodiments, the chitosan-amino acid derivative is a product generated by the reaction of chitosan and amino acids in an aqueous solution, wherein the amino acid is selected from any one or more combinations of glutamic acid, aspartic acid, and arginine.

[0007] More preferably, the chitosan-amino acid derivative is a product generated by the reaction of chitosan and glutamic acid in an aqueous solution, which can be used to introduce polar functional groups and enhance the polarity regulation ability of the composite activator and the interfacial affinity of the powder surface.

[0008] In some specific embodiments, the mass ratio of chitosan to amino acids is 1:(0.8~1.5).

[0009] In some specific embodiments, the layered bimetallic hydroxide is selected from any one of magnesium-aluminum layered bimetallic hydroxide (Mg-Al-LDH), zinc-aluminum layered bimetallic hydroxide (Zn-Al-LDH), and calcium-aluminum layered bimetallic hydroxide (Ca-Al-LDH).

[0010] More preferably, the layered bimetallic hydroxide is magnesium-aluminum layered bimetallic hydroxide (Mg-Al-LDH), which, as an inorganic phase component, endows the composite system with good structural stability and storage performance under thermal conditions.

[0011] This invention relates to a composite activator composed of an organic phase of chitosan-amino acid derivatives and an inorganic phase of layered double hydroxide (LDH), possessing dual functions of interfacial polarity regulation and structural stabilization. Applying this activator to the surface treatment of waste tire rubber powder can improve its surface polarity and reactivity, enhance the dispersibility and interfacial compatibility of the rubber powder in the matrix asphalt, and reduce sedimentation and stratification under high-temperature conditions, thereby improving the storage stability and homogeneity of the modified asphalt.

[0012] The second technical solution of the present invention provides a method for preparing recycled rubber powder modified asphalt based on a renewable composite activator as described in one of the above technical solutions, comprising the following steps: S1, Composite Activator: Chitosan and amino acids are mixed in acetic acid water and reacted to obtain a chitosan-amino acid derivative solution; Layered bimetallic hydroxides were prepared by precipitation method; Chitosan-amino acid derivative solution and layered bimetallic hydroxide are mixed to form a milky white and uniform composite activator slurry; S2. Surface activation treatment of waste rubber powder: The waste rubber powder and the composite activator slurry obtained in step S1 are reacted with the mixture at high temperature to obtain activated rubber powder. S3, Recycled Rubber Powder Modified Asphalt: The base asphalt is heated, and the activated rubber powder obtained in step S2 is added under stirring conditions. The reaction is carried out at high temperature and high shear to obtain recycled rubber powder modified asphalt.

[0013] In some specific embodiments, in step S1, the amino acid is composed of glutamic acid and aspartic acid in a mass ratio of 1:1. The mass ratio of chitosan to amino acids is 1:(0.8~1.5). The layered bimetallic hydroxide is Mg-Al-LDH; The reaction temperature is 50~70℃ and the time is 1~3 h.

[0014] In some specific embodiments, in step S2, the mass ratio of waste adhesive powder to composite activator slurry is 10:(0.8~1.5). The high-temperature stirring reaction is carried out at a temperature of 75~85℃ for 20~40 min.

[0015] In some specific embodiments, step S3 involves heating the base asphalt to a temperature of 150~160°C. The mass ratio of base asphalt to activated adhesive powder is 1:(0.2~0.3). The high-temperature, high-shear reaction was carried out at a temperature of 160-180℃, a shear rate of 4500-6000 rpm, and a time of 45-70 min.

[0016] The third technical solution of the present invention is to provide an application of recycled rubber powder modified asphalt based on a renewable composite activator in highway paving, as described in one of the above technical solutions.

[0017] In some specific embodiments, the recycled rubber powder modified asphalt is used in the paving of heavy-duty traffic roads.

[0018] Compared with the prior art, the present invention has the following advantages: (1) The composite activation system proposed in this invention is composed of bio-based chitosan-amino acid derivatives and inorganic layered double metal hydroxide (LDH), which has clear polarity regulation and structural support functions, realizing efficient interface modification of waste rubber powder and filling the application gap of green activators in this field.

[0019] (2) Through synergistic activation treatment, the surface polarity of waste rubber powder is significantly enhanced, which improves its wettability and reactivity in the matrix asphalt, effectively improves the interfacial bonding strength, and has better compatibility, which is conducive to the formation of a structurally continuous and homogeneous composite system.

[0020] (3) The rubber powder modified asphalt prepared by the present invention has good high-temperature storage stability and interface structure integrity, and exhibits excellent anti-aging performance and high-temperature anti-rutting performance during long-term service.

[0021] (4) The method of the present invention has strong adaptability and is compatible with the existing hot-mix asphalt mixture production process. It has the technological foundation required for promotion and can improve the high-value utilization efficiency of waste tire rubber, thus having both engineering and environmental benefits. Attached Figure Description

[0022] Figure 1 This is a diagram illustrating the mechanism of action of the composite activator.

[0023] Figure 2 A comparison chart of rutting factor results for modified asphalt under different temperature conditions.

[0024] Figure 3 This is a comparison chart showing the irreversible creep compliance results of modified asphalt after short-term aging. J nr 0.1 represents the non-recoverable creep compliance under a stress of 0.1 kPa. J nr 3.2 represents the non-recoverable creep compliance under a stress of 3.2 kPa.

[0025] Figure 4 This is a comparison chart of the elastic recovery rate results of modified asphalt after short-term aging. R 0.1 represents the elastic recovery rate under a stress of 0.1 kPa. R 3.2 represents the elastic recovery rate under a stress of 3.2 kPa.

[0026] Figure 5 The figures show the Han curve analysis of rubber-modified asphalt under different aging states. (a) is the Han curve of the control group S1 under different aging states, and (b) is the Han curve of the experimental group S5 under different aging states. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0029] Unless otherwise specified, the materials and processes described in the following embodiments or examples are conventional materials and processes used in the art to achieve the corresponding functions.

[0030] Example 1 This embodiment provides a recycled rubber powder modified asphalt based on a renewable composite activator, and its preparation method is as follows: Figure 1 As shown, it includes the following steps: 1. Preparation of composite activators (1) Weigh 5 g of chitosan and dissolve it in 100 mL of 2% acetic acid aqueous solution. Add a mixture of glutamic acid and aspartic acid (0.5 g each) with a molar ratio of about 1:1. Stir the mixture at 60°C for 2 hours to obtain a chitosan-amino acid derivative solution (organic phase).

[0031] (2) Preparation of Mg-Al-LDH by precipitation method: Dissolve 0.3 mol Mg(NO3)2·6H2O and 0.1 mol Al(NO3)3·9H2O in 100 mL of deionized water, and add 1 mol / L NaOH solution dropwise to the solution to adjust the pH to 10. Aging at room temperature for 24 hours, filter, dry and grind to fine powder to obtain inorganic phase Mg-Al-LDH.

[0032] (3) Mix the organic phase and the inorganic phase at a mass ratio of 1.5:1 and mechanically stir for 45 minutes to form a milky white and uniform composite activator slurry for later use.

[0033] 2. Surface activation treatment of waste rubber powder Weigh 100 g of 60-mesh waste tire rubber powder, add 10 g of the prepared composite activator, and place it in an 80℃ water bath environment for mechanical stirring for 30 minutes. The surface of the activated rubber powder is slightly wetted and has a uniform structure, showing good interfacial affinity.

[0034] 3. Preparation of modified asphalt using recycled rubber powder The base asphalt (PG 64-22) was heated to 160°C, and the activated rubber powder of a predetermined mass fraction was slowly added under stirring conditions. Maintaining a shear rate of 5000 rpm, the temperature was increased to 180°C, and continuous shearing and stirring was performed for 60 minutes to fully disperse the rubber powder and melt it into the asphalt, thus obtaining recycled rubber powder modified asphalt.

[0035] Test case To verify the actual effect of the composite activator proposed in this invention on improving the performance of rubber powder modified asphalt, a systematic comparative test and performance evaluation were carried out.

[0036] The modified asphalt samples prepared in this invention were compared with conventional rubber powder modified asphalt samples without composite activation treatment. Short-term aging (Rolling Thin Film Oven Test, RTFOT) and long-term aging (Pressure Aging Vessel, PAV) treatments were carried out according to the standard method of "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" JTG 3410-2025 to evaluate the changes in the system compatibility of the modified asphalt before and after aging.

[0037] Control group (traditional modified asphalt): S1 (unactivated rubber powder + base asphalt, rubber powder content R1); S2 (unactivated rubber powder + base asphalt, rubber powder content R2); Experimental group (asphalt modified with rubber powder of this invention): S3 (organic activator-treated rubber powder + asphalt of the same matrix, rubber powder parameter R1); S4 (Inorganic activator-treated rubber powder + same matrix asphalt, rubber powder parameter R1); S5 (composite activator treated rubber powder + same matrix asphalt, rubber powder parameter R1); S6 (composite activator treated rubber powder + same matrix asphalt, rubber powder parameter R2); R1 refers to the proportion of rubber powder to the mass of base asphalt, which is 25%; R2 refers to the proportion of rubber powder to the mass of base asphalt, which is 20%.

[0038] Indicator 1: Storage stability The settling behavior of waste rubber powder in asphalt matrix can be estimated based on Stokes' settling theory. The formula for calculating the settling velocity is shown in equation (1) below. This formula indicates that reducing the particle size of the rubber powder, increasing the matrix viscosity, or reducing the density difference can all help to suppress the settling behavior of the rubber powder, thereby improving storage stability.

[0039] (1) in: Vis the settling velocity of the rubber powder in asphalt (m / s); r Where is the radius of the adhesive powder particles (m); ρ p Density of adhesive powder (kg / m³) 3 ); ρ f The density of asphalt (kg / m³) 3 ); η ρ represents the apparent viscosity of asphalt under shear conditions (Pa·s). g The acceleration due to gravity (9.81 m / s²) 2 ).

[0040] Index 2: Effect of rubber powder reinforcement on the complex shear modulus of asphalt Considering the contribution of rubber powder as a reinforcing phase in asphalt, its complex shear modulus can be predicted using an improved mixing model, as shown in equation (2) below. This model shows that, under a certain reinforcement coefficient, the higher the volume fraction of rubber powder, the more significant the effect on improving the asphalt shear modulus, reflecting the rigid skeleton reinforcement effect of rubber powder.

[0041] (2) in: G * The shear modulus (Pa) of the modified asphalt. G m The shear modulus of the base bitumen (Pa); φ This represents the volume fraction of the adhesive powder. α It is the reinforcing coefficient of the adhesive powder (related to particle size and interfacial bonding).

[0042] Indicator 3: Complex Shear Modulus and Rutting Factor Analysis The high-temperature properties of modified bitumen can be characterized by complex shear modulus and phase angle.

[0043] (3) (4) in: G ′ represents the energy storage modulus; G " is the loss modulus; G * G* is the complex shear modulus; G* / sinδ is the rutting factor, which is used to determine the ability of a material to resist plastic flow at high temperatures.

[0044] Index 4: Han curve compatibility and anti-aging performance analysis The Han curve is analyzed based on the relationship between complex modulus and phase angle, and is plotted accordingly. G ′ - GThe Han curve reflects the physical blending state of modified asphalt. In an ideal blending system, the Han curve exhibits good overlap at different frequencies or temperatures; if phase separation occurs in the system, the curve will deviate and bifurcate. Therefore, the Han curve can be used to determine the interfacial compatibility and structural stability of rubber powder and asphalt, and is an important tool for analyzing changes in the microstructure of composite materials.

[0045] To verify the enhancing effect of the composite activator of this invention on the performance of reclaimed rubber powder modified asphalt, rheometer performance tests were conducted on samples S1-S6, including complex shear modulus, phase angle, irreversible creep compliance, elastic recovery rate, Han curve overlap analysis, and 48-h softening point difference. The performance changes before and after aging were evaluated in conjunction with RTFOT and PAV.

[0046] Table 1 Comparison of Asphalt Performance between Examples and Comparative Examples

[0047] Experimental results show that, compared with conventional rubber powder modified asphalt that is untreated or only physically mixed, the asphalt treated with the composite activator composed of chitosan-amino acids and LDH in this invention exhibits the following advantages: (1) Based on the 48-hour softening point difference in Table 1 and Figure 5 The Han curve compatibility and anti-aging performance analysis showed that the interfacial bonding between the rubber powder and the asphalt matrix was significantly enhanced, the material dispersion was better, and the overall system structure was more uniform and stable.

[0048] (2) such as Figure 2 As shown, the rutting factor G* / sinδ (test temperature: 64℃) of the composite activated rubber powder modified asphalt is not less than 4500 Pa, which is more than 25% higher than that of the unactivated rubber powder modified asphalt. This indicates that the rutting resistance is significantly enhanced, and it has good high-temperature rutting resistance performance, meeting the rutting resistance performance requirements of heavy traffic roads.

[0049] (3) such as Figure 3 As shown, irreversible creep compliance J nr It is an indicator characterizing the residual strain of asphalt after creep-recovery cycles. J nr The smaller the value, the better the asphalt's resistance to permanent deformation. The composite activated rubber powder modified asphalt... J nr The stress (3.2 kPa, test temperature 64℃) is less than 2.0×10⁻³ Pa⁻¹, which is significantly lower than that of unactivated rubber powder modified asphalt, indicating that its resistance to permanent deformation is improved.

[0050] (4) such as Figure 4As shown, the elastic recovery rate R is an index of asphalt elasticity; the higher the R, the better the elastic recovery ability. Composite activated rubber powder modified asphalt... R The values ​​(test temperature: 64℃) are all above 80%, indicating excellent elastic recovery performance.

[0051] (5) such as Figure 5 As shown, the Han curves of the composite activated rubber powder modified asphalt S5 maintained good overlap at different temperatures and frequencies, without bifurcation or shift (see Figure (b)), while the control group S1 showed bifurcation (see the dashed box in Figure (a)). S5 has better modification stability and compatibility than S1, indicating that the interface structure of the composite activated rubber powder and matrix asphalt is stable under different aging states, with no obvious phase separation phenomenon, indicating that the material has good resistance to thermo-oxidative aging and long-term service performance.

[0052] The above performance enhancement mechanism stems from the synergistic interfacial effect of the composite activator: chitosan-amino acid derivatives are rich in polar functional groups, which can effectively regulate the surface polarity of the rubber powder and enhance wettability and compatibility; layered bimetallic hydroxide (Mg-Al-LDH) possesses thermal stability and physical support capabilities, which can inhibit structural delamination and thermal stress damage. The synergistic effect of the two not only improves the interfacial activity of the rubber powder but also enhances the overall stability of the modified asphalt system.

[0053] In summary, the composite activator proposed in this invention exhibits significant advantages in improving the high-temperature performance, aging durability, and interface uniformity of rubber-modified asphalt. It has strong engineering applicability and promotion value, and is suitable for high-grade road structural layers and recycling applications.

[0054] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A type of regenerated rubber powder modified asphalt based on a renewable composite activator, characterized in that, It includes base asphalt and activated binder powder in a mass ratio of 1:(0.2~0.3). The activated rubber powder comprises waste tire rubber powder and a composite activator in a mass ratio of 10:(0.8~1.5). The composite activator comprises an organic phase and an inorganic phase in a mass ratio of (1.5~3):

1. The organic phase is a chitosan-amino acid derivative, and the inorganic phase is a layered bimetallic hydroxide. The chitosan-amino acid derivative is a product generated by reacting chitosan and amino acids in an aqueous acetic acid solution, wherein the amino acid is selected from any one or more combinations of glutamic acid, aspartic acid, and arginine.

2. The regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 1, characterized in that, The mass ratio of chitosan to amino acids is 1:(0.8~1.5).

3. The regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 1, characterized in that, The layered bimetallic hydroxide is selected from any one of magnesium-aluminum layered bimetallic hydroxide, zinc-aluminum layered bimetallic hydroxide, and calcium-aluminum layered bimetallic hydroxide.

4. A method for preparing regenerated rubber powder modified asphalt based on a renewable composite activator as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1, Composite Activator: Chitosan and amino acids are mixed in an aqueous acetic acid solution and reacted to obtain a chitosan-amino acid derivative solution; Layered bimetallic hydroxides were prepared by precipitation method; Chitosan-amino acid derivative solution and layered bimetallic hydroxide are mixed to form a milky white and uniform composite activator slurry; S2. Surface activation treatment of waste rubber powder: The waste rubber powder and the composite activator slurry obtained in step S1 are reacted with the mixture at high temperature to obtain activated rubber powder; wherein, the temperature of the high temperature reaction is (75~85)℃. S3. Recycled rubber powder modified asphalt: The base asphalt is heated, and the activated rubber powder obtained in step S2 is added under stirring conditions. The reaction is carried out at high temperature and high shear to obtain recycled rubber powder modified asphalt. The temperature of the high temperature and high shear reaction is (160~180)℃, and the shear rate is (4500~6000) rpm.

5. The method for preparing regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 4, characterized in that, In step S1, the amino acid is composed of glutamic acid and aspartic acid in a mass ratio of 1:1, and the mass ratio of chitosan to amino acids is 1:(0.8~1.5). The layered bimetallic hydroxide is Mg-Al-LDH; The reaction temperature is (50~70)℃ and the time is (1~3) h.

6. The method for preparing regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 4, characterized in that, In step S2, the mass ratio of waste adhesive powder to composite activator slurry is 10:(0.8~1.5). The high-temperature stirring reaction time is (20~40) min.

7. The method for preparing regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 4, characterized in that, Step S3 involves heating the base asphalt to a temperature of (150~160)℃. The mass ratio of base asphalt to activated adhesive powder is 1:(0.2~0.3). The high-temperature, high-shear reaction time is (45~70) min.

8. The application of recycled rubber powder modified asphalt based on a renewable composite activator as described in any one of claims 1 to 3 in highway paving.

9. The application of regenerated rubber powder modified asphalt based on a renewable composite activator according to claim 8, characterized in that, The application of recycled rubber powder modified asphalt in the paving of heavy-duty traffic roads.

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