Highly viscoelastic regenerative stress absorbing layer asphalt mixture and method of making

Abstract

The present application relates to the technical field of regenerated asphalt, and particularly relates to a high viscoelastic regenerated stress absorbing layer asphalt mixture and a preparation method thereof, which comprises the following components in parts by weight: 60-80 parts of RAP material, 8-22 parts of new aggregate, 7.6-11.7 parts of composite mineral powder, 4-6 parts of high viscoelastic self-adaptive modified asphalt and 0.3-0.4 parts of composite regenerant. The present application adds the high viscoelastic self-adaptive modified asphalt, and the viscoelastic properties, high and low temperature adaptability and durability of the modified asphalt are improved through structural complementation and performance synergy of SBS and butadiene styrene rubber; the reversible cross-linking bond of the dynamic cross-linking agent-zinc dithiocarbamate breaks at high temperature to release stress, provides better anti-rutting performance, reorganizes and strengthens elasticity at low temperature to improve anti-cracking performance, so that the self-adaptive adjustment of viscoelastic properties can be realized.

Description

Technical Field

[0001] This invention relates to the field of recycled asphalt technology, specifically to a high viscoelastic recycled stress-absorbing asphalt mixture and its preparation method. Background Technology

[0002] As a core functional layer for asphalt pavement overhaul and resurfacing, the stress-absorbing layer's primary function is to absorb and disperse tensile stress in the base course or subbase, preventing reflective cracks from penetrating upwards, thereby extending the fatigue life of the multilayer pavement and improving its resistance to water damage. Current mainstream technologies face three major bottlenecks: Imbalance between viscoelastic properties and durability: Most existing high viscoelastic adaptive modified asphalt is modified with single SBS. Although it can increase viscosity, it is difficult to balance low-temperature crack resistance and aging resistance. After long-term service, it is prone to embrittlement and cracking. Limitations of single-function mineral powder: Conventional use of pure mineral powder only serves as a filler and cannot solve problems such as "weak bonding at the binder-aggregate interface, poor resistance to water damage, and insufficient resistance to spalling". The contradiction between high RAP content and performance: In existing technologies, when the RAP content exceeds 30%, the poor compatibility between aged asphalt and new asphalt and the decline in aggregate activity lead to a sharp decrease in the bond strength and crack resistance of the mixture, which cannot meet engineering requirements.

[0003] While existing technologies have achieved a certain degree of resource regeneration, they still suffer from drawbacks such as low RAP content, insufficient synergistic effect between regenerator and high viscosity agent, and poor water stability due to the single function of mineral powder. They cannot simultaneously maximize resource utilization and meet high performance requirements. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned shortcomings and provide a high viscoelastic recycled stress-absorbing asphalt mixture that constructs an adaptive modified asphalt system with "high viscoelasticity-crack resistance-aging resistance" to solve the problem of performance imbalance of single modified asphalt and enhances low-temperature toughness and long-term durability while increasing viscosity.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a high viscoelastic recycled stress-absorbing asphalt mixture, comprising by weight: 60-80 parts RAP material, 8-22 parts new aggregate, 7.6-11.7 parts composite mineral powder, 4-6 parts high viscoelastic adaptive modified asphalt and 0.3-0.4 parts composite recycling agent.

[0006] Furthermore, the RAP material is recycled asphalt pavement milling material with a particle size range of 0-6mm.

[0007] Furthermore, the new aggregate is diabase with a particle size range of 0-6 mm.

[0008] Furthermore, the composite mineral powder comprises, by mass percentage, 70%-80% S95 mineral powder, 2%-5% graphene oxide, 10%-15% sodium bentonite, 3%-8% nano-hydroxyapatite, and 1%-3% anti-stripping agent.

[0009] Furthermore, the high viscoelastic adaptive modified asphalt is based on 70# base asphalt and is composite modified with 4%-6% SBS, 2%-3% styrene-butadiene rubber and 0.5%-1% dynamic crosslinking agent by weight of the base asphalt.

[0010] Furthermore, the dynamic crosslinking agent is zinc dithiocarbamate.

[0011] Furthermore, the composite regenerator comprises 60-70 parts by weight of bio-based regenerator and 30-40 parts by weight of chemical regenerator.

[0012] Furthermore, the bio-based regenerator is a regenerator prepared from waste vegetable oil refineries.

[0013] Furthermore, the chemical regenerator comprises 60%-70% aromatic oil and 30%-40% polyester compounds by mass percentage.

[0014] A method for preparing a high viscoelastic recycled stress-absorbing asphalt mixture, comprising the following steps: S1. RAP material pretreatment: The recycled RAP material is crushed and then screened through a 6mm screen to remove impurities with a particle size greater than 6mm, so as to obtain RAP material with uniform gradation. S2. Preparation of highly viscoelastic adaptive modified asphalt: 70# base asphalt, SBS, styrene-butadiene rubber, and dynamic crosslinking agent are mixed at 160℃ for 15-20 minutes using a high-speed shear mixer at a stirring speed of 2000 r / min to obtain highly viscoelastic adaptive modified asphalt. S3. Preheating treatment: Preheat the new aggregates and composite mineral powders to 170℃, and preheat the RAP material to 140℃. S4. RAP material activation treatment: Put the pretreated RAP material into a mixing pot preheated to 180℃, add the composite regenerator and mix for 45 seconds, keep warm for 5-10 minutes to complete the activation. S5. Composite modification: Add the high viscoelastic adaptive modified asphalt prepared in S2 to the activated RAP material, mix for 45s, then add the preheated new aggregate and composite mineral powder in S3, mix for 60-90s to obtain the high viscoelastic recycled stress-absorbing asphalt mixture.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention improves the viscoelastic properties, high and low temperature adaptability, and durability of modified asphalt by adding highly viscoelastic adaptive modified asphalt. SBS and styrene-butadiene rubber complement each other in structure and synergistically enhance the properties of modified asphalt. The reversible crosslinking bonds of the dynamic crosslinking agent zinc dithiocarbamate break and release stress at high temperatures, providing better rutting resistance. At low temperatures, they recombine and strengthen elasticity, improving crack resistance, thereby enabling adaptive adjustment of viscoelastic properties. The block structure of SBS provides "skeleton support": the styrene hard segments of SBS form physical cross-linking points at low temperatures, which work together with dynamic disulfide bonds to strengthen the network; at high temperatures, the hard segments soften, providing space for network relaxation after the dynamic bonds break, thus preventing network rigidity. The random structure of SBR provides a "flexible buffer": the highly flexible molecular chains of SBR can fill the gaps in the dynamic network, reduce the rigidity of the network at low temperatures, and at the same time improve the efficiency of dynamic bond recombination, further optimizing low-temperature toughness. By using dynamic crosslinking agents to solve the problem of performance balance, the same system can actively switch crosslinking states according to temperature, achieving a wide temperature range adaptability of "high temperature rutting prevention and low temperature crack resistance". 2. This invention uses composite mineral powder and fills the interface voids with two-dimensional graphene oxide sheets to reduce interface defects; the hydroxyl groups of nano-hydroxyapatite form hydrogen bonds with the polar groups of pitch to improve the interface bonding strength; and sodium-based bentonite expands when it comes into contact with water to form a dense water-locking film to block water from penetrating the interface. Combined with an anti-stripping agent, it doubles the water resistance. 3. This invention employs a RAP material activation process, which first activates the RAP material separately to avoid interference between the high viscoelastic adaptive modified asphalt and the composite recycling agent, and then performs composite mixing to ensure that the functions of each component are fully utilized. Furthermore, it is compatible with existing mixing equipment and does not require additional special equipment. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Comparison of ductility tests of the high viscoelastic adaptive modified asphalt, SBS modified asphalt, and 70# base asphalt prepared in this invention. Detailed Implementation

[0017] 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. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: A high viscoelastic recycled stress-absorbing asphalt mixture with a RAP content of 60% comprises, by weight: 60 parts RAP material, 22 parts new aggregate, 11.7 parts composite mineral powder, 6 parts high viscoelastic adaptive modified asphalt and 0.3 parts composite recycling agent.

[0019] Preferably, the RAP material is recycled asphalt pavement milling material with a particle size range of 0-6mm, which provides skeletal support for the mixture and realizes resource recycling.

[0020] Preferably, the new aggregate is diabase with a particle size range of 0-6 mm, which supplements the RAP skeleton defects and improves the strength of the mixture.

[0021] Preferably, the composite mineral powder comprises, by weight percentage, 70%-80% S95 mineral powder, 2%-5% graphene oxide, 10%-15% sodium bentonite, 3%-8% nano-hydroxyapatite, and 1%-3% anti-stripping agent. The two-dimensional sheet structure of graphene oxide fills the interfacial pores, strengthening the bond; sodium bentonite expands upon contact with water to form a water-locking film, enhancing water resistance; nano-hydroxyapatite enhances the chemical adsorption between the mineral powder and asphalt, thereby improving the bonding strength; and the anti-stripping agent directionally improves the interfacial compatibility between the aggregate and asphalt, inhibiting water damage-induced delamination.

[0022] Preferably, the high viscoelastic adaptive modified asphalt uses 70# base asphalt as a base and is composite modified with 4%-6% SBS, 2%-3% styrene-butadiene rubber, and 0.5%-1% dynamic crosslinking agent by weight of the base asphalt. The dynamic crosslinking agent is zinc dithiocarbamate. Performance indicators: penetration (25℃, 100g, 5s) 50~60 (0.1mm), softening point (ring and ball method) ≥75℃, ductility (5cm / min, 5℃) ≥30cm, elastic recovery (25℃, 10cm) ≥85%.

[0023] Preferably, the composite regenerator comprises 60-70 parts by weight of bio-based regenerator and 30-40 parts by weight of chemical regenerator, wherein the bio-based regenerator is a regenerator prepared from waste vegetable oil refinery; and the chemical regenerator comprises 60%-70% by weight of aromatic oil and 30%-40% by weight of polyester compound. The above materials are added sequentially (addition order: first add bio-based regenerator, then add aromatic oil, and finally add molten polyester compound) to a stirred tank and stirred for 20 minutes at 80℃ and 200r / min. After stirring, the mixture is allowed to cool naturally to room temperature to obtain the composite regenerator.

[0024] Preferably, the bio-based regenerator is obtained by using waste cooking oil (waste cooking oil, rice bran oil refining residue, etc.) as raw material, which is then purified, impurity removed, and modified sequentially. Solid impurities (such as food residue) are removed by filtering through a 100-mesh filter. 5%–8% (relative to the mass of the waste cooking oil) of activated clay is added, and the mixture is stirred at 80°C for 30 minutes before filtration to achieve deacidification and decolorization. Then, 0.3% (relative to the mass of the waste cooking oil) of an alkaline catalyst (such as NaOH) is added, and the mixture is reacted at 120°C for 1 hour to reduce the oil viscosity, resulting in the bio-based regenerator (the finished product viscosity is controlled at 100–150 mPa). (s). This is existing technology, so it will not be elaborated here.

[0025] Preferably, in the chemical regenerator, the aromatic oil is selected from heavy aromatic hydrocarbon components extracted during the petroleum refining process (containing polycyclic aromatic hydrocarbons such as naphthalene and anthracene, with a content ≥70%). This component can efficiently activate the gum components in aged asphalt, without the need for additional pretreatment, and can be directly used as the activation component for later use. Selection of polyester compounds: Low molecular weight aliphatic polyesters (molecular weight 1000~3000, such as polyhexyl adipate) are preferred. This type of polyester has excellent compatibility with bio-based regenerators and aromatic oils, and can effectively play a stabilizing role. The pretreatment method is to preheat at a constant temperature of 60℃ to a completely melted state to avoid the agglomeration of solid polyester, which would lead to uneven mixing. This is existing technology, so it will not be described in detail here.

[0026] A method for preparing a high viscoelastic recycled stress-absorbing asphalt mixture, for preparing the high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, comprises the following steps: S1. RAP material pretreatment: The recycled RAP material is crushed and then screened through a 6mm screen to remove impurities with a particle size greater than 6mm, so as to obtain RAP material with uniform gradation. S2. Preparation of highly viscoelastic adaptive modified asphalt: 70# base asphalt, SBS, styrene-butadiene rubber, and dynamic crosslinking agent are mixed at 160℃ for 15 minutes using a high-speed shear machine with a stirring speed of 2000r / min to obtain highly viscoelastic adaptive modified asphalt. S3. Preheating treatment: Preheat the new aggregates and composite mineral powders to 170℃, and preheat the RAP material to 140℃. S4. RAP material activation treatment: Put the pretreated RAP material into a mixing pot preheated to 180°C, add the composite regenerator and mix for 45 seconds, then keep warm for 5 minutes to complete the activation. S5. Composite modification: Add the high viscoelastic adaptive modified asphalt prepared in S2 to the activated RAP material, mix for 45s, then add the preheated new aggregate and composite mineral powder in S3, mix for 60-90s to obtain the high viscoelastic recycled stress-absorbing asphalt mixture.

[0027] Example 2: The difference between this embodiment and Embodiment 1 is that the RAP content is 70%, which includes, by weight: 70 parts RAP material, 15 parts new aggregate, 9.65 parts composite mineral powder, 5 parts high viscoelastic adaptive modified asphalt and 0.35 parts composite recycling agent.

[0028] Example 3: The difference between this embodiment and Embodiment 1 is that the RAP content is 80%, which includes, by weight: 80 parts RAP material, 8 parts new aggregate, 7.6 parts composite mineral powder, 4 parts high viscoelastic adaptive modified asphalt and 0.4 parts composite recycling agent.

[0029] Comparative Example 1: The difference between this comparative example and Example 1 is that conventional S95 mineral powder is used instead of composite mineral powder, and single SBS modified asphalt is used instead of high viscoelastic adaptive modified asphalt.

[0030] Comparative Example 2: The difference between this comparative example and Example 1 is that conventional S95 mineral powder is used instead of composite mineral powder.

[0031] Comparative Example 3: The difference between this comparative example and Example 1 is that a single SBS modified bitumen was used instead of the high viscoelastic adaptive modified bitumen.

[0032] Comparative Example 4: The difference between this comparative example and Example 1 is that in step S4, the pretreated RAP material is put into a mixing pot preheated to 180°C, the composite regenerator is added, and after mixing for 45 seconds, step S5 is directly carried out, omitting the 5-10 minute heat preservation and activation process.

[0033] The performance of the recycled asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-4 was tested, and the results are shown in Table 1 below: Table 1 Performance test results of recycled asphalt mixture

[0034] Combination Figure 1 Analyze the performance test results: 1. In conjunction with Examples 1-3, the RAP content was increased from 60% to 80%. Due to the increased proportion of aged asphalt, the water-stabilized performance fluctuated slightly, the high-temperature performance improved, and the low-temperature performance decreased, but all of them far exceeded the technical indicators. This demonstrates the core advantage of the present invention that high-content regeneration still maintains high performance, which is in line with the technical principles of interface optimization and component synergy. 2. Combining Example 1 and Comparative Example 2, under the same RAP content, using the same high viscoelastic adaptive modified asphalt and RAP activation process, and replacing conventional S95 mineral powder with composite mineral powder, the residual stability of the prepared recycled asphalt increased by 13.02 percentage points, the freeze-thaw splitting strength ratio increased by 5.09 percentage points, the dynamic stability increased by 2670 cycles / mm, and the flexural tensile failure strain increased by 3586με. It can be seen that the use of composite mineral powder can improve water resistance and strengthen the bonding ability. Combining Comparative Example 1 and Comparative Example 3, under the same RAP content, using the same single SBS modified asphalt and RAP activation process, replacing conventional S95 mineral powder with composite mineral powder, the residual stability of the prepared recycled asphalt increased by 6.9 percentage points, the freeze-thaw splitting strength ratio increased by 25.13 percentage points, the dynamic stability increased by 671 cycles / mm, and the flexural tensile failure strain increased by 1310με, verifying its multifunctional synergistic effect; 3. Combining Example 1 and Comparative Example 3, under the same RAP content, using the same composite mineral powder and RAP activation process, the recycled asphalt prepared by replacing single SBS modified asphalt with high viscoelastic adaptive modified asphalt showed an increase in residual stability of 13.65 percentage points, an increase in freeze-thaw splitting strength ratio of 5.95 percentage points, an increase in dynamic stability of 3073 cycles / mm, and an increase in flexural tensile failure strain of 3465με, demonstrating that high viscoelastic adaptive modified asphalt has adaptive advantages in high-temperature rutting resistance and low-temperature crack resistance. Combining Comparative Example 1 and Comparative Example 2, under the same RAP content and using the same conventional S95 mineral powder and RAP activation process, replacing single SBS modified asphalt with high viscoelastic adaptive modified asphalt resulted in a 7.53 percentage point increase in residual stability, a 25.99 percentage point increase in freeze-thaw splitting strength ratio, a 1074 cycles / mm increase in dynamic stability, and a 1192 με increase in flexural tensile failure strain. This further verifies that high viscoelastic adaptive modified asphalt has excellent performance and can optimize the viscoelastic properties of the prepared recycled asphalt mixture. 4. Combining Example 1 and Comparative Example 4, under the same RAP content, the same composite mineral powder, high viscoelastic adaptive modified asphalt, and RAP activation process were used. The activation process was used to activate the pretreated RAP material. The residual stability of the prepared recycled asphalt increased by 6.97 percentage points, the freeze-thaw splitting strength ratio increased by 4.6 percentage points, and the flexural tensile failure strain increased by 3570 με. This indicates that the activation process can fully penetrate the composite recycling agent into the activated RAP material, thereby improving the performance of the recycled asphalt mixture.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A high viscoelastic recycled stress-absorbing asphalt mixture, characterized in that, By weight, it includes: 60-80 parts RAP material, 8-22 parts new aggregate, 7.6-11.7 parts composite mineral powder, 4-6 parts high viscoelastic adaptive modified bitumen, and 0.3-0.4 parts composite recycling agent.

2. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, characterized in that, The RAP material is recycled material from asphalt pavement milling, with a particle size range of 0-6mm.

3. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, characterized in that, The new aggregate is diabase with a particle size range of 0-6 mm.

4. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, characterized in that, The composite mineral powder comprises, by weight percentage, 70%-80% S95 mineral powder, 2%-5% graphene oxide, 10%-15% sodium bentonite, 3%-8% nano-hydroxyapatite, and 1%-3% anti-stripping agent.

5. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, characterized in that, The high viscoelastic adaptive modified asphalt is based on 70# base asphalt and is composite modified with 4%-6% SBS, 2%-3% styrene-butadiene rubber and 0.5%-1% dynamic crosslinking agent by weight of the base asphalt.

6. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 5, characterized in that, The dynamic crosslinking agent is zinc dithiocarbamate.

7. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 1, characterized in that, The composite regenerant comprises 60-70 parts by weight of bio-based regenerant and 30-40 parts by weight of chemical regenerant.

8. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 7, characterized in that, The bio-based regenerator is a regenerator prepared from waste vegetable oil refineries.

9. The high viscoelastic recycled stress-absorbing asphalt mixture according to claim 7, characterized in that, The chemical regenerator comprises 60%-70% aromatic oils and 30%-40% polyester compounds by mass percentage.

10. A method for preparing a high viscoelastic recycled stress-absorbing asphalt mixture, characterized in that, The method for preparing the high viscoelastic recycled stress-absorbing asphalt mixture according to any one of claims 1-9 comprises the following steps: S1. RAP material pretreatment: The recycled RAP material is crushed and then screened through a 6mm screen to remove impurities with a particle size greater than 6mm, so as to obtain RAP material with uniform gradation. S2. Preparation of highly viscoelastic adaptive modified asphalt: 70# base asphalt, SBS, styrene-butadiene rubber, and dynamic crosslinking agent are mixed at 160℃ for 15-20 minutes using a high-speed shear mixer at a stirring speed of 2000 r / min to obtain highly viscoelastic adaptive modified asphalt. S3. Preheating treatment: Preheat the new aggregates and composite mineral powders to 170℃, and preheat the RAP material to 140℃. S4. RAP material activation treatment: Put the pretreated RAP material into a mixing pot preheated to 180℃, add the composite regenerator and mix for 45 seconds, keep warm for 5-10 minutes to complete the activation. S5. Composite modification: Add the high viscoelastic adaptive modified asphalt prepared in S2 to the activated RAP material, mix for 45s, then add the preheated new aggregate and composite mineral powder in S3, mix for 60-90s to obtain the high viscoelastic recycled stress-absorbing asphalt mixture.

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