Method for improving utilization rate of old asphalt mixture

Abstract

The invention discloses a method for improving the utilization rate of an old asphalt mixture, which comprises the following steps: S1, grading the old asphalt mixture, and carrying out particle size sorting on the recycled waste asphalt mixture by adopting multi-stage vibration screening equipment; s2, directional adding treatment of a regenerant and a functional modifier; s3, performing a multi-stage temperature control mixing process; s4, microstructure regulation and dynamic quality feedback; and S5, performance detection and molding of the finished asphalt mixture. According to the invention, asphalt structure components are monitored and identified in real time, and key process parameters can be dynamically fed back and adjusted; stable and consistent product quality is ensured, manual intervention is remarkably reduced, and the intelligent and automatic level is improved. The reutilization rate of the waste asphalt material is improved, the use of new aggregate and new asphalt is reduced, and natural resources are saved; rAP landfill or combustion is avoided, and carbon emission and pollution risks are reduced.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, specifically a method for improving the utilization rate of old asphalt mixtures. Background Technology

[0002] With the continuous expansion of highway construction and maintenance, a large amount of reclaimed asphalt (RAP) is generated. Currently, the reuse rate of reclaimed asphalt materials is limited by problems such as poor bonding performance of aged asphalt, insufficient high-temperature stability of recycled mixtures, and insufficient low-temperature crack resistance. Traditional recycling technologies typically replace new materials with RAP materials and use additives to improve performance, but the dosage is generally limited to 20%-40%. When using high dosages (>50%), problems such as poor mixing uniformity and poor construction stability easily occur. Therefore, there is an urgent need to develop a novel method that can significantly increase the RAP dosage while ensuring road performance. To this end, a method for improving the utilization rate of reclaimed asphalt mixtures is proposed. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a method for improving the utilization rate of old asphalt mixtures, solving the problem that: existing technologies typically replace new materials with RAP materials and use additives to improve performance, but the dosage is generally limited to 20%-40%. When using high dosages, problems such as poor mixing uniformity and poor construction stability easily occur.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the utilization rate of old asphalt mixtures, comprising the following steps.

[0007] S1, the grading treatment of old asphalt mixture, which involves sorting the recycled waste asphalt mixture by particle size using a multi-stage vibrating screen.

[0008] S2, directional addition treatment of regenerator and functional modifier;

[0009] S3, multi-stage temperature-controlled mixing process;

[0010] S4, Microstructure Regulation and Dynamic Quality Feedback;

[0011] S5, Performance testing and molding of finished asphalt mixtures.

[0012] As a further preferred embodiment of the present invention, in step S1, by setting different screen mesh sizes, the RAP is roughly divided into the following three levels: coarse aggregate portion, with a particle size greater than 13mm, mainly serving as a skeleton; medium aggregate portion with a particle size of 5-13mm, retaining part of the aged asphalt film, serving as the main body for recycling; mineral powder and fine aggregate portion, with a particle size less than 5mm, containing residual aged asphalt film, used in the blending and control of the recycling agent. For the coarse aggregate portion, further treatment is carried out to desorb the aged asphalt. Desorption is performed by a hot air rotating drum at a controlled temperature of 110°C to remove part of the aged asphalt layer on the surface and improve its adhesion to new asphalt.

[0013] As a further preferred embodiment of the present invention, in step S2, before mixing, the prepared asphalt rejuvenator is premixed with medium-sized RAP aggregate. The amount of asphalt rejuvenator accounts for 3%-5% of the total mass of the medium-sized RAP mixture. It can penetrate into the molecular structure of aged asphalt and restore its fluidity and viscoelastic properties. During premixing, RAP and rejuvenator are mixed in a special spiral stirring device at a set rate for 5-10 minutes and then left to stand for 30 minutes to allow the asphalt rejuvenator to fully penetrate into the aged asphalt, thereby achieving the purpose of initially softening the aged asphalt. Then, a functional modifier is added.

[0014] As a further preferred embodiment of the present invention, in step S2, the asphalt regenerator comprises 40-55% soybean oleate, 20-30% petroleum cracked aromatic oil, 5-10% fatty acid amide, 10-15% light-colored solvent oil, and 1-3% BHT antioxidant.

[0015] As a further preferred embodiment of the present invention, in step S2, the functional modifier is a mixture composed of styrene-butadiene-styrene, rubber powder below 40 mesh, organosilane coupling agent, graphene microplates, nano-mineral powder, and sulfur.

[0016] As a further preferred embodiment of the present invention, in step S3, the pretreated RAP mixture, new asphalt, and new aggregates are introduced into a three-stage hot-mix system and subjected to the following treatments: First stage: preliminary heating zone, the temperature in the mixing pot is set to about 120°C to heat the RAP to its softening point and activate the surface aged asphalt, with the time controlled at 3-5 minutes; Second stage: regeneration reaction zone, asphalt regenerator, functional modifier, and new asphalt are injected into the mixture, the mixing temperature is raised to 160-170°C, and a high-shear mixing device is used to vigorously stir the mixture for 58 minutes to complete the reaction and fusion of the regenerator and aged asphalt, and to restore the molecular structure; Third stage: homogenization and stabilization zone, the temperature of the mixture is adjusted to 150°C, and the mixture is homogenized by stirring for 4-6 minutes to ensure that the aggregates at all levels are fully combined with the modified asphalt, with the stirring speed controlled at 45-120 r / min.

[0017] As a further preferred embodiment of the present invention, in step S4, a microstructure regulation mechanism and a dynamic quality feedback system are introduced to realize a closed-loop system of real-time adjustment and intelligent control. A near-infrared spectrometer is installed on the asphalt mixture mixing device or conveying pipeline to collect the spectral characteristics of the asphalt binder in the mixture in real time, identifying the following key indicators: saturated components, aromatic components, resins, and asphaltenes. By comparing the collected spectral data with a standard database, it is determined in real time whether the recycling effect has reached the target indicators. A temperature monitoring module is added to monitor the temperature of the mixture at different locations in real time to ensure a uniform temperature gradient. The torque change of the mixing device is monitored to indirectly reflect the change in the consistency of the mixture. The system is connected to an industrial-grade control system or an industrial edge computing platform, and combined with a preset parameter model, the following key parameters are dynamically adjusted: the amount of recycling agent added is automatically adjusted by ±0.5%; the functional modifier and the new asphalt injection rate are linked; the mixing speed and duration are fine-tuned; the settling time is extended or a secondary mixing stage is added.

[0018] (III) Beneficial Effects

[0019] This invention provides a method for improving the utilization rate of recycled asphalt mixtures. It offers the following advantages: Through fine grading and differentiated treatment, the recycling function of materials with different particle sizes is optimized, especially the desorption treatment of coarse aggregates, which significantly improves their adhesion to new asphalt. It avoids the negative impact of aged asphalt on the overall performance of the mixture, effectively increasing the proportion of reclaimed aggregate (RAP) to 40%-70%, significantly improving resource recycling efficiency. The composite and targeted addition of recycling agents and functional modifiers improves recycling quality. Recycling agents with high permeability and flexible recovery capabilities soften and activate aged asphalt; combined with nano-functional modifiers, it significantly improves the viscoelastic properties, fatigue resistance, rutting resistance, and high-temperature stability of the recycled mixture. A multi-stage temperature-controlled process ensures reaction integrity and structural homogeneity. A three-stage temperature-controlled mixing process precisely controls the thermal conditions of the reaction process, ensuring sufficient reaction between the recycling agent and aged asphalt; a high-shear mixing device ensures full integration of the recycling agent, new asphalt, and aggregates at all levels, improving the uniformity and structural stability of the mixture. An intelligent dynamic quality control mechanism is introduced to achieve closed-loop control of the regeneration process. Near-infrared spectroscopy analysis and an industrial edge computing control system are integrated into the RAP regeneration process. This enables real-time monitoring and identification of asphalt structural components and allows for dynamic feedback adjustment of key process parameters. This ensures consistent and stable product quality, significantly reduces human intervention, and improves the level of intelligence and automation. It also increases the reuse rate of waste asphalt materials, reduces the use of new aggregates and asphalt, and conserves natural resources. Furthermore, it avoids RAP landfilling or incineration, reducing carbon emissions and pollution risks. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] Please see Figure 1 This invention provides a technical solution: a method for improving the utilization rate of old asphalt mixtures, comprising the following steps.

[0023] S1, the grading treatment of old asphalt mixture, which involves sorting the recycled waste asphalt mixture by particle size using a multi-stage vibrating screen.

[0024] S2, directional addition treatment of regenerator and functional modifier;

[0025] S3, multi-stage temperature-controlled mixing process;

[0026] S4, Microstructure Regulation and Dynamic Quality Feedback;

[0027] S5, Performance testing and molding of finished asphalt mixtures.

[0028] In step S1, by setting different screen apertures, RAP is roughly divided into the following three levels: coarse aggregate, with a particle size greater than 13mm, mainly serving as a skeleton; medium aggregate, with a particle size of 5-13mm, retaining some aged asphalt film, serving as the main body for recycling; and mineral powder and fine aggregate, with a particle size less than 5mm, containing residual aged asphalt film, used in the blending and control of the recycling agent. For the coarse aggregate, further treatment is carried out to desorb the aged asphalt. Desorption is performed by a hot air rotating drum at a controlled temperature of 110℃ to remove part of the aged asphalt layer on the surface and improve its adhesion to new asphalt.

[0029] In step S2, before mixing, the prepared asphalt rejuvenator is premixed with medium-sized RAP aggregate. The amount of asphalt rejuvenator is 3%-5% of the total mass of the medium-sized RAP mixture. It can penetrate into the molecular structure of aged asphalt and restore its fluidity and viscoelastic properties. During premixing, RAP and rejuvenator are mixed in a special spiral mixer at a set rate for 5-10 minutes and then left to stand for 30 minutes to allow the asphalt rejuvenator to fully penetrate into the aged asphalt and achieve the purpose of initially softening the aged asphalt. Then, the functional modifier is added.

[0030] In step S2, the asphalt regenerator includes 40-55% soybean oleate, 20-30% petroleum cracked aromatic oil, 5-10% fatty acid amide, 10-15% light-colored solvent oil, and 1-3% BHT antioxidant.

[0031] In step S2, the functional modifier is a mixture of styrene-butadiene-styrene, rubber powder below 40 mesh, organosilane coupling agent, graphene microplates, nano mineral powder, and sulfur.

[0032] In step S3, the pretreated RAP mixture, along with new asphalt and new aggregates, is fed into a three-stage hot-mix system and subjected to the following treatments: First stage: Initial heating zone, where the temperature in the mixing tank is set to approximately 120°C to heat the RAP to its softening point and activate the surface-aged asphalt, with a time control of 3-5 minutes; Second stage: Regeneration reaction zone, where asphalt rejuvenator, functional modifier, and new asphalt are injected into the mixture, raising the mixing temperature to 160-170°C, and simultaneously using a high-shear mixer to vigorously stir the mixture for 58 minutes to complete the reaction and fusion of the rejuvenator and aged asphalt, achieving molecular structure restoration; Third stage: Homogenization and stabilization zone, where the mixture temperature is adjusted to 150°C, and through stirring for 4-6 minutes, the mixture is homogenized, ensuring thorough bonding between aggregates at all levels and modified asphalt, with the stirring speed controlled at 45-120 r / min.

[0033] In step S4, a microstructure regulation mechanism and a dynamic quality feedback system are introduced to achieve a closed-loop system of real-time adjustment and intelligent control. A near-infrared spectroscopy analyzer is installed on the asphalt mixture mixing device or conveying pipeline to collect the spectral characteristics of the asphalt binder in the mixture in real time, identifying the following key indicators: saturated components, aromatic components, resins, and asphaltenes. By comparing the collected spectral data with a standard database, it is determined in real time whether the recycling effect has reached the target indicators. A temperature monitoring module is added to monitor the temperature of the mixture at different locations in real time to ensure a uniform temperature gradient. The torque change of the mixing device is monitored to indirectly reflect the change in the consistency of the mixture. The system is connected to an industrial-grade control system or an industrial edge computing platform, and combined with a preset parameter model, the following key parameters are dynamically adjusted: automatic adjustment of the recycling agent addition amount by ±0.5%; linkage between the functional modifier and the new asphalt injection rate; fine adjustment of the mixing speed and duration; extension of the settling time or addition of a secondary mixing stage.

[0034] To ensure that the recycled mixture meets highway construction standards and long-term performance requirements, the present invention establishes the following molding and performance testing standard procedures:

[0035] Marshall specimen molding was performed, and standard Marshall specimens (101.6 mm diameter × 63.5 mm height) were prepared by sampling. The number of compactions was 75 per side. The molding temperature was controlled at 145-155℃. After molding, the specimens were allowed to stand for 24 hours, and the stability and flow value were tested at room temperature.

[0036] The asphalt in the mixture was subjected to solvent extraction, centrifugation, and recovery, and then its following properties were tested:

[0037] Softening point (ring-sphere method);

[0038] Penetration (25℃);

[0039] Ductility (15℃);

[0040] Viscosity (135℃);

[0041] Infrared spectrum comparison (comparison with new asphalt and aged asphalt).

[0042] These results are used to determine the extent of rejuvenator action, the quality of recovery of aged asphalt, and the uniformity of mixing.

[0043] Example 1: Recycling of medium-aged RAP for municipal road maintenance projects

[0044] Raw material composition:

[0045] Recycled RAP mix particle size distribution: 45% of total mix.

[0046] New aggregate (5-10 mm graded crushed stone and manufactured sand): accounting for 40% of the total mix.

[0047] New 70# road petroleum asphalt: accounts for 10% of the total mix.

[0048] Regenerant: 5% of the mass of RAP medium-sized particles.

[0049] Functional modifier: 2% of the total mixture mass

[0050] Regenerant composition:

[0051] Soybean oleate methyl ester: 50%

[0052] Petroleum cracked aromatics oil: 25%

[0053] Fatty acid amide: 8%

[0054] Light-colored solvent oil: 13%

[0055] BHT antioxidant: 4%

[0056] Process flow:

[0057] Step S1: RAP is screened through 13 mm and 5 mm screens, and the coarse material is desorbed by a 110℃ hot air tube;

[0058] Step S2: Premix the recycling agent with 5-13 mm particle size RAP at a mass ratio of 1:20 for 10 minutes, let it stand for 30 minutes, and then add the functional modifier and new asphalt.

[0059] Step S3: Hot mixing three-stage processing:

[0060] Initial heating zone: 125℃, 4 minutes;

[0061] Regeneration reaction zone: 168℃, high shear stirring for 6 minutes;

[0062] Homogenization zone: 150℃, stir for 5 minutes at 90 rpm;

[0063] Step S4: If the near-infrared detection shows that the asphalt content is below the threshold, the recycling agent supply will be automatically reduced by 0.3%.

[0064] Step S5: Prepare a Marshall specimen and test its dynamic stability at 4200 cycles / mm and TSR at 87%.

[0065] Example 2:

[0066] Severely aged RAP regeneration, highway overlay regeneration

[0067] Raw material composition:

[0068] High-aging RAP mixtures contain significant amounts of aged binders, accounting for 50% of the total.

[0069] New aggregate, 10-20 mm graded crushed stone: 30%

[0070] New 90# petroleum asphalt: 15%

[0071] Regenerant: 6% of the medium particle size of RAP

[0072] Functional modifier: 3% of the total mixture mass

[0073] Regenerant composition:

[0074] Soybean oleate methyl ester: 45%

[0075] Petroleum cracked aromatics oil: 30%

[0076] Fatty acid amides: 10%

[0077] Light-colored solvent oil: 12%

[0078] BHT antioxidant: 3%

[0079] Process flow:

[0080] Step S1: Desorb the aged film with coarse-particle RAP for 4 minutes;

[0081] Step S2: Extend the premixing time to 15 minutes, and let it stand for 45 minutes;

[0082] Step S3:

[0083] Initial heating zone: 130℃, 4 minutes;

[0084] Regeneration reaction zone: 170℃, high shear for 7 minutes;

[0085] Homogenization stabilization zone: 155℃, 6 minutes, 100 rpm;

[0086] Step S4: If the infrared real-time detection shows that the content of aromatic components is too high, the system will automatically reduce the proportion of aromatic oil and extend the homogenization stage by 1 minute.

[0087] Step S5: The fatigue life test result is ≥120,000 cycles, and the rutting resistance reaches 5,000 cycles / mm.

[0088] The parameter table is as follows:

[0089] Performance indicators Example 1 (Moderate Aging RAP) Example 2 (Severely Aging RAP) Test methods / standards Marshall stability (kN) 11.2 12.5 JTG E20-2011 T0709 Flow value (mm) 3.1 3.5 JTG E20-2011 T0709 Stability / flow ratio (kN / mm) 3.61 3.57 Calculated value Porosity (%) 3.8 4.2 JTG E20-2011 T0711 Saturation (%) 84.3 81.6 JTG E20-2011 T0711

[0090] Example 2, under conditions of higher dosage of regenerator and functional modifier and more advanced regeneration process, exhibits the best rutting resistance and fatigue life, making it suitable for high-grade highway overlays.

[0091] Example 1 achieves a good balance in urban road regeneration, with high stability, excellent TSR, and good material economy.

[0092] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. 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 its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0093] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for improving the utilization rate of old asphalt mixtures, characterized in that: Includes the following methods and steps, S1, the grading treatment of old asphalt mixture, which involves sorting the recycled waste asphalt mixture by particle size using a multi-stage vibrating screen. S2, directional addition treatment of regenerator and functional modifier; S3, multi-stage temperature-controlled mixing process; S4, Microstructure Regulation and Dynamic Quality Feedback; S5, Performance testing and molding of finished asphalt mixtures.

2. The method for improving the utilization rate of old asphalt mixtures according to claim 1, characterized in that: In step S1, by setting different screen apertures, RAP is roughly divided into the following three levels: coarse aggregate, with a particle size greater than 13mm, mainly serving as a skeleton; medium aggregate, with a particle size of 5-13mm, retaining some aged asphalt film, serving as the main body for recycling; and mineral powder and fine aggregate, with a particle size less than 5mm, containing residual aged asphalt film, used in the blending and control of the recycling agent. For the coarse aggregate, further treatment is carried out to desorb the aged asphalt. Desorption is performed by a hot air rotating drum at a controlled temperature of 110℃ to remove part of the aged asphalt layer on the surface and improve its adhesion to new asphalt.

3. The method for improving the utilization rate of old asphalt mixtures according to claim 1, characterized in that: In step S2, before mixing, the prepared asphalt recycling agent is premixed with medium-sized RAP aggregate. The amount of asphalt recycling agent is 3%-5% of the total mass of the medium-sized RAP mixture. It can penetrate into the molecular structure of aged asphalt and restore its fluidity and viscoelastic properties. During premixing, RAP and recycling agent are mixed in a special spiral mixer at a set rate for 5-10 minutes and then left to stand for 30 minutes to allow the asphalt recycling agent to fully penetrate into the aged asphalt and achieve the purpose of initially softening the aged asphalt. Then, functional modifiers are added.

4. The method for improving the utilization rate of old asphalt mixtures according to claim 3, characterized in that: In step S2, the asphalt regenerator includes 40-55% soybean oleate, 20-30% petroleum cracked aromatic oil, 5-10% fatty acid amide, 10-15% light-colored solvent oil, and 1-3% BHT antioxidant.

5. The method for improving the utilization rate of old asphalt mixtures according to claim 4, characterized in that: In step S2, the functional modifier is a mixture of styrene-butadiene-styrene, rubber powder below 40 mesh, organosilane coupling agent, graphene microplates, nano mineral powder, and sulfur.

6. The method for improving the utilization rate of old asphalt mixtures according to claim 1, characterized in that: In step S3, the pretreated RAP mixture, along with new asphalt and new aggregates, is fed into a three-stage hot-mix system and subjected to the following treatments: First stage: Initial heating zone, where the temperature in the mixing tank is set to approximately 120°C to heat the RAP to its softening point and activate the surface-aged asphalt, with a time control of 3-5 minutes; Second stage: Regeneration reaction zone, where asphalt rejuvenator, functional modifier, and new asphalt are injected into the mixture, raising the mixing temperature to 160-170°C, and simultaneously using a high-shear mixer to vigorously stir the mixture for 58 minutes to complete the reaction and fusion of the rejuvenator and aged asphalt, achieving molecular structure restoration; Third stage: Homogenization and stabilization zone, where the mixture temperature is adjusted to 150°C, and through stirring for 4-6 minutes, the mixture is homogenized, ensuring thorough bonding between aggregates at all levels and modified asphalt, with the stirring speed controlled at 45-120 r / min.

7. The method for improving the utilization rate of old asphalt mixtures according to claim 1, characterized in that: In step S4, a microstructure regulation mechanism and a dynamic quality feedback system are introduced to achieve a closed-loop system of real-time adjustment and intelligent control. A near-infrared spectroscopy analyzer is installed on the asphalt mixture mixing device or conveying pipeline to collect the spectral characteristics of the asphalt binder in the mixture in real time, identifying the following key indicators: saturated components, aromatic components, resins, and asphaltenes. By comparing the collected spectral data with a standard database, it is determined in real time whether the recycling effect has reached the target indicators. A temperature monitoring module is added to monitor the temperature of the mixture at different locations in real time to ensure a uniform temperature gradient. The torque change of the mixing device is monitored to indirectly reflect the change in the consistency of the mixture. The system is connected to an industrial-grade control system or an industrial edge computing platform, and combined with a preset parameter model, the following key parameters are dynamically adjusted: automatic adjustment of the recycling agent addition amount by ±0.5%; linkage between the functional modifier and the new asphalt injection rate; fine adjustment of the mixing speed and duration; extension of the settling time or addition of a secondary mixing stage.

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