High-temperature-resistant large-dosage RAP recycled asphalt mixture and gradient activation preparation method thereof

Abstract

The invention relates to the technical field of recycled asphalt, and particularly discloses a high-temperature-resistant large-dosage RAP recycled asphalt mixture and a gradient activation preparation method thereof, and the recycled asphalt mixture comprises the following components in parts by weight: 70-90 parts of an RAP material, 5-26 parts of a new aggregate, 4-5 parts of SBS modified asphalt and 0.04-0.05 part of a composite regenerant. The composite regenerant and the bio-oil-based regenerant provided by the invention can recover the flexibility of the aged asphalt; after the silane coupling agent is hydrolyzed, silicon hydroxyl (Si-OH) formed by the silane coupling agent and the bio-oil-based regenerant can be bonded with hydroxyl (Si-O-Si bond) on the surface of the aggregate to form a bonded network, so that the interface adhesion strength is improved, the interface slippage is reduced, the skeleton of the mixture is more stable, the stripping resistance of the interface is enhanced, the dynamic stability and the water stability are improved, and the service life of the mixture is prolonged. And after the recycling agent recovers the flexibility of the asphalt, a bonding network formed by the silane coupling agent endows the recycled asphalt mixture with a high-elasticity characteristic, and the risk of fatigue cracking is reduced.

Description

Technical Field

[0001] This invention relates to the field of recycled asphalt technology, specifically to high-temperature resistant, high-volume RAP recycled asphalt mixtures and their gradient activation preparation method. Background Technology

[0002] Asphalt mixture recycling technology is a resource recovery technology that reuses waste asphalt pavement material (RAP) in road construction after physical or chemical treatment, and it is a core direction of green road engineering. This technology reduces the consumption of new materials and carbon emissions by recycling asphalt and aggregates from old materials, aligning with the concept of sustainable development.

[0003] Existing asphalt mixture recycling technologies have the following technical problems: 1) Performance degradation with high RAP content: When the RAP content is >30%, the high temperature stability of the mixture decreases sharply (rutting depth increases by 2-3 times) and the low temperature crack resistance is insufficient (bending strain <3000με at -10℃). 2) Limitations of recycling agents: Ordinary recycling agents only restore the penetration of aged asphalt and cannot solve the problems of delamination at the interface between new and old materials and low elastic recovery rate; 3) Limitations of process and gradation: Traditional single-stage mixing results in excessive temperature difference between new and old materials, and shallow penetration of regenerator; interference from RAP fine particles causes the skeleton to become loose and the low-temperature crack resistance to be insufficient. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a high-temperature resistant, high-volume RAP recycled asphalt mixture and its gradient activation preparation method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a high-temperature resistant, high-volume RAP recycled asphalt mixture, comprising the following components by weight: 70-90 parts RAP material, 5-26 parts new aggregate, 4-5 parts SBS modified asphalt and 0.04-0.05 parts composite recycling agent.

[0006] Furthermore, the RAP material has a particle size of no more than 9.5 mm and an oil content of 4.0-5.0%.

[0007] Furthermore, in the RAP material, the fine particles with a particle size of 0-3mm are less than 15 parts.

[0008] Furthermore, the new aggregate is made of diabase with a particle size of 9.5-16 mm and an apparent density ≥2.50 g / cm³. 3 Water absorption rate ≤2.0%.

[0009] Furthermore, the SBS modified bitumen is of type ID.

[0010] Furthermore, the composite regenerator is a combination of a highly permeable bio-oil-based regenerator and a silane coupling agent in a 6:1 ratio.

[0011] Furthermore, the highly permeable bio-oil-based regenerator is modified from soybean oil residue through transesterification reaction, and 5-8% epoxidized soybean oil and 3-5% petroleum resin are added.

[0012] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0013] A gradient activation preparation method for high-temperature resistant, high-volume RAP recycled asphalt mixtures, used to prepare the aforementioned high-temperature resistant, high-volume RAP recycled asphalt mixtures, includes the following steps: S1. Install 2-4 symmetrically arranged nozzles on the top of the mixing chamber, and simultaneously atomize the high-penetration bio-oil-based regenerator and coupling agent into the RAP material in proportion, and mix at low speed at 100-110℃ for 90-145s. S2. Once the RAP material is evenly spread in the mixing bin, heat it to 130-140℃. S3. Apply pressure to the RAP material in three intermittent stages, with a 2-minute interval between each application, and increase the pressure in steps from 0.4 to 0.8 MPa. S4. Heat to 170-180℃, add new aggregate and SBS modified asphalt, and mix at high speed for 60-90 seconds.

[0014] Furthermore, the low speed in S1 is 30 r / min for revolution and 50 r / min for rotation; The high speed in S4 is 50 r / min for revolution and 90 r / min for rotation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The composite regenerator provided in this invention, the bio-oil-based regenerator can restore the flexibility of aged asphalt; the silane coupling agent, after hydrolysis, forms silanol groups (Si–OH) with the bio-oil-based regenerator, which can bond with the hydroxyl groups on the aggregate surface (Si–O–Si bonds) to form a bonding network, improving the interfacial adhesion strength, reducing interfacial slippage, making the mixture skeleton more stable, and strengthening the interface's anti-peeling ability, improving dynamic stability and water stability performance. Moreover, after the regenerator restores the flexibility of asphalt, the bonding network formed by the silane coupling agent endows the recycled asphalt mixture with high elasticity, reducing the risk of fatigue cracking. 2. This invention adopts a skeleton-elastic gradation design to replace continuous gradation. The new aggregate uses 9.5-16mm diabase to form a rigid skeleton through directional interlocking to bear most of the load. The RAP material is crushed to a particle size of less than 9.5mm, and the fine particles of 0-2mm are controlled to be less than 15 parts through fine screening to form an elastic transition layer. This layer fills the gaps in the rigid skeleton while providing flexible support, avoiding the softening of fine particles at high temperatures and causing skeleton instability. This provides a "rigid-flexible" structure. Under high temperature conditions, the load is resisted by the rigid skeleton, and under low temperature shrinkage, it is absorbed by the elastic transition layer. Even when the RAP content is as high as 90%, it can still take into account both rutting resistance and crack resistance. 3. This invention provides a three-stage thermal gradient activation process to ensure full activation of RAP material and reduce the skeleton gap ratio; Low-temperature bonding stage: The RAP material is heated to 100-110℃ to avoid the volatilization of the regenerator caused by high temperature and to keep the silane coupling agent active and prevent it from becoming ineffective. The regenerator and silane coupling agent are atomized and sprayed evenly through a dual-fluid nozzle. The regenerator softens the old bitumen in the RAP material, and the alkoxy groups (–Si–OR) in the silane coupling agent are hydrolyzed to generate active silanols (–Si–OH). The silanols can undergo a condensation reaction with the hydroxyl groups (–OH) on the RAP surface, thereby achieving initial bonding. Medium-temperature compaction and penetration stage: The RAP material is kept at 130-140℃ for 10-15 minutes, and the material layer is compacted three times using a hydraulic plate. The compaction increases the diffusion rate of the recycling agent, and the mechanical force drives the silane coupling agent to penetrate deep into the RAP material, thereby ensuring that the old asphalt in the RAP material is fully activated. High-temperature centrifugal fusion stage: The temperature is raised to 170-180℃. At high temperature, the fluidity of SBS modified asphalt is enhanced. The silane coupling agent bonds the SBS modified asphalt with the old asphalt in the RAP material to the molecular distance. The centrifugal mixer is stirred at high speed for 60-90s. The centrifugal force helps the new aggregate to be oriented and the gap ratio between the skeleton is reduced. 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 This is a comparison image of the rutting marks of recycled asphalt prepared in this application and recycled asphalt prepared by conventional continuous gradation.

[0017] In the figure: the upper left is a schematic diagram of the rut marks of the recycled asphalt prepared in Example 1; The bottom left is a schematic diagram of the rut marks of recycled asphalt prepared in Example 2; The upper right corner shows a schematic diagram of the ruts of recycled asphalt prepared in Comparative Example 1. The bottom right is a schematic diagram of the ruts of recycled asphalt prepared in Comparative Example 2. Detailed Implementation

[0018] 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.

[0019] Please see Figure 1 .

[0020] Example 1: The high-temperature resistant, high-volume RAP recycled asphalt mixture comprises the following components by weight: 70 parts RAP material, 26 parts new aggregate, 4 parts SBS modified asphalt, and 0.04 parts composite recycling agent.

[0021] Preferably, the RAP material has a particle size of no more than 9.5 mm, an oil content of 4.0-5.0%, and less than 15 parts of fine material with a particle size of 0-3 mm.

[0022] Preferably, the new aggregate is diabase with a particle size of 9.5-16 mm and an apparent density ≥2.50 g / cm³. 3 Water absorption rate ≤2.0%.

[0023] Preferably, the SBS modified asphalt is of type ID, and its technical indicators are as follows: penetration at 25℃, 100g, and 5s is 40-600.1mm, softening point ≥75℃, ductility (5cm / min, 5℃) ≥20cm, flash point ≥230℃, segregation softening point difference ≤2.5℃ at 48h, elastic recovery (25℃, 10cm) ≥75%, viscosity at 60℃ ≥3000Pa·s, kinematic viscosity at 135℃ ≤3Pa·s, and adhesion to coarse aggregate is grade 5.

[0024] Preferably, the composite regenerator is a combination of a highly permeable bio-oil-based regenerator and a silane coupling agent in a 6:1 ratio.

[0025] Preferably, the high-permeability bio-oil-based regenerator is modified from soybean oil residue via transesterification, with the addition of 5-8% epoxidized soybean oil and 3-5% petroleum resin. Key performance indicators: kinematic viscosity at 25°C 80-120 mmHg. 2 / s, penetration increment ≥30 (0.1mm), penetration depth ≥5mm (25℃, 24h), compatibility with aged asphalt ≥95%. It can quickly soften aged asphalt, restore its ductility and flexibility, and reduce asphalt brittleness.

[0026] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane with a purity ≥98%. The molecule contains an amino group (-NH2) and a triethoxysilyl group (-Si(OC2H5)3). The amino group reacts with the polar functional group carboxyl group in the asphalt to form hydrogen bonds, improving the compatibility of the coupling agent with the asphalt. The triethoxysilyl group hydrolyzes to generate silanol groups (-Si-OH), which can undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of the RAP material to form strong Si–O–Si covalent bonds, bridging the interface between new and old materials and improving adhesion strength and peel resistance.

[0027] A gradient activation preparation method for high-temperature resistant, high-volume RAP recycled asphalt mixtures, used to prepare the aforementioned high-temperature resistant, high-volume RAP recycled asphalt mixtures, includes the following steps: S1. Install 2-4 symmetrically arranged nozzles on the top of the mixing chamber, and simultaneously atomize the high-penetration bio-oil-based regenerator and coupling agent into the RAP material in proportion. Control the droplet size to 50~100μm, mix at low speed at 100-110℃ for 90-145s, with a revolution of 30r / min and a rotation of 50r / min. S2. Once the RAP material is evenly spread in the mixing bin, heat it to 130-140℃. S3. Apply pressure to the RAP material in three intermittent stages, with a 2-minute interval between each application, and increase the pressure in steps from 0.4 to 0.8 MPa. S4. Heat to 170-180℃, add new aggregate and SBS modified asphalt, mix at high speed for 60-90s, with a revolution speed of 50r / min and a rotation speed of 90r / min.

[0028] Example 2: The difference between this embodiment and Embodiment 1 is that the high-temperature resistant, high-volume RAP recycled asphalt mixture comprises the following components by weight: 90 parts RAP material, 5 parts new aggregate, 5 parts SBS modified asphalt, and 0.05 parts composite recycling agent.

[0029] Comparative Example 1: The difference between this comparative example and Example 1 is that the skeleton-elastic gradation design of this application is not adopted, and the gradation type uses the AC-13 continuous type gradation design in the specification.

[0030] Comparative Example 2: The difference between this comparative example and comparative example 2 is that the skeleton-flexible gradation design of this application is not adopted, and the gradation type uses the AC-13 continuous type gradation design in the specification.

[0031] Comparative Example 3: The difference between this comparative example and Example 2 is that no composite regenerator is used; only a highly permeable bio-oil-based regenerator is employed.

[0032] Comparative Example 4: The difference between this comparative example and Example 2 is that the three-stage thermal gradient activation process of this application is not used; instead, a traditional thermal regeneration mixing method is used.

[0033] The performance of the recycled asphalt mixtures prepared in Examples 1-2 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1 below.

[0034] Table 1 Performance test results of recycled asphalt mixtures in each embodiment and comparative example

[0035] As shown in Table 1: 1. In conjunction with Examples 1 and 2, the high-temperature resistant, high-content RAP surface layer recycled asphalt mixture obtained by adopting the technical solution of the present invention meets the specifications for all road performance indicators at a RAP content of 70%-90%, thus meeting the performance requirements of recycled asphalt mixture. 2. Combining Example 1 and Comparative Example 1, with 70% RAP content, the same type of regenerator and preparation method, the skeleton-elastic gradation design of the present invention was used to replace the existing AC-13 gradation type, which resulted in an increase of 4.19 percentage points and 16.74 percentage points in residual stability and freeze-thaw splitting strength ratio, respectively, an increase of 3263 cycles / mm in dynamic stability, and an increase of 2042 με in bending tensile failure strain; Combining Example 2 and Comparative Example 2, with 90% RAP content, the same regenerator type and preparation method, the skeleton-elastic gradation design of the present invention replaces the existing AC-13 gradation type, resulting in an increase of 5.95 percentage points in residual stability and 12.19 percentage points in freeze-thaw splitting strength ratio, an increase of 3676 cycles / mm in dynamic stability, and an increase of 4599 με in bending tensile failure strain. That is, the skeleton-elastic gradation design replaces the existing AC-13 gradation type, providing a "rigid and flexible" structure. Under high temperature conditions, the load is resisted by the rigid skeleton, and under low temperature shrinkage, it is absorbed by the elastic transition layer. Even when the RAP content is as high as 90%, it can still take into account both rutting resistance and crack resistance. 3. Combining Example 2 and Comparative Example 3, under the same RAP dosage, gradation type and preparation method, the regenerator of this invention - silane coupling agent was used to replace the existing regenerator without silane coupling agent, which resulted in an increase in residual stability of 19.89 percentage points, a freeze-thaw splitting strength ratio that remained basically unchanged, an increase in dynamic stability of 9912 cycles / mm, and an increase in bending tensile failure strain of 3408 με. That is, the existing regenerator without silane coupling agent is replaced by a regenerator-silane coupling agent. After the silane coupling agent is hydrolyzed, the silanol groups (Si–OH) formed with the bio-oil-based regenerator can bond with the hydroxyl groups on the aggregate surface (Si–O–Si bonds) to form a bonding network, which improves the interfacial adhesion strength. After the regenerator restores the flexibility of asphalt, the bonding network formed by the silane coupling agent endows the recycled asphalt mixture with high elasticity and reduces the risk of fatigue cracking. 4. Combining Example 2 and Comparative Example 4, under the same RAP dosage, gradation type and regenerator type, the three-stage thermal gradient activation process of the present invention is used to replace the existing traditional thermal regeneration preparation method, which improves the residual stability and freeze-thaw splitting strength ratio by 10.1 percentage points and 2.72 percentage points, respectively, while the freeze-thaw splitting strength ratio remains basically unchanged. The dynamic stability is improved by 6648 cycles / mm, and the bending tensile failure strain is improved by 3287με. That is, by adopting the three-stage thermal gradient activation process of the present invention, the synergistic effect of coupling agent and recycling agent can be better stimulated, which can improve the performance of the mixture to a certain extent, ensure that the RAP material is fully activated, reduce the skeleton gap ratio, and improve the overall performance of recycled asphalt mixture.

[0036] 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-temperature resistant, high-volume RAP recycled asphalt mixture, characterized in that, The composition by weight is as follows: 70-90 parts RAP material, 5-26 parts new aggregate, 4-5 parts SBS modified bitumen and 0.04-0.05 parts composite recycling agent.

2. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 1, characterized in that, The RAP material has a particle size of no more than 9.5 mm and an oil content of 4.0-5.0%.

3. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 2, characterized in that, In the RAP material, the fine particles with a particle size of 0-3mm are less than 15 parts.

4. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 1, characterized in that, The new aggregate is made of diabase with a particle size of 9.5-16 mm and an apparent density ≥2.50 g / cm³. 3 Water absorption rate ≤2.0%.

5. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 1, characterized in that, The SBS modified asphalt is of type ID.

6. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 1, characterized in that, The composite regenerant is a combination of a highly permeable bio-oil-based regenerant and a silane coupling agent in a 6:1 ratio.

7. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 6, characterized in that, The highly permeable bio-oil-based regenerator is modified from soybean oil residue through transesterification reaction, and contains 5-8% epoxidized soybean oil and 3-5% petroleum resin.

8. The high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 6, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane.

9. A gradient activation preparation method for high-temperature resistant, high-volume RAP recycled asphalt mixtures, characterized in that, The method for preparing high-temperature resistant, high-volume RAP recycled asphalt mixtures as described in any one of claims 1-8 comprises the following steps: S1. Install 2-4 symmetrically arranged nozzles on the top of the mixing chamber, and simultaneously atomize the high-penetration bio-oil-based regenerator and coupling agent into the RAP material in proportion, and mix at low speed at 100-110℃ for 90-145s. S2. Once the RAP material is evenly spread in the mixing bin, heat it to 130-140℃. S3. Apply pressure to the RAP material in three intermittent stages, with a 2-minute interval between each application, and increase the pressure in steps from 0.4 to 0.8 MPa. S4. Heat to 170-180℃, add new aggregate and SBS modified asphalt, and mix at high speed for 60-90 seconds.

10. The gradient activation preparation method for high-temperature resistant, high-volume RAP recycled asphalt mixture according to claim 9, characterized in that, The low speed in S1 is 30 r / min for revolution and 50 r / min for rotation; The high speed in S4 is 50 r / min for revolution and 90 r / min for rotation.

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