Method for recycling, enhancing and reusing waste pavement asphalt

Abstract

The invention discloses a method for recycling, enhancing and reusing waste pavement asphalt, which comprises the following steps: crushing waste asphalt, screening, pretreating to remove moisture and impurities, adding a reinforcing agent consisting of nano silicon dioxide, graphene, rubber powder and alkali treatment modified lignin, heating, stirring and mixing, heating, modifying at high temperature, and finally cooling and molding. According to the method, the reinforcing agent and the asphalt are fully fused and reacted through specific treatment steps, the reinforcing agent is added, and the thermal activation crosslinking reaction is utilized, so that the high-temperature stability, the low-temperature crack resistance and the durability of the recycled asphalt are remarkably improved, efficient recycling of the waste asphalt is realized, and the method has good economic benefits and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of waste material recycling, and more particularly to a method for recycling and enhancing waste road asphalt. Background Art

[0002] In recent years, the scale of highway infrastructure construction has continued to expand, with over 100,000 kilometers of new highway mileage added annually. Highway maintenance and renovation and expansion projects have also entered a peak period, leading to a surge in the amount of waste pavement asphalt materials generated annually from road renovation and reconstruction. Traditionally, these materials are often disposed of in landfills or open-air dumps, which not only consumes significant land resources but also causes harmful substances such as polycyclic aromatic hydrocarbons (PAHs) in the asphalt to seep into soil and water, exacerbating ecological and environmental pressures.

[0003] Although the industry has initially established a waste asphalt recycling system, partially recycling the material through technologies such as hot and cold recycling, the performance bottleneck of recycled asphalt has remained unresolved. In actual engineering applications, recycled asphalt mixtures generally lack high-temperature stability. High summer temperatures can easily lead to excessive rutting depths on the road surface. At low temperatures, the material's crack resistance decreases, making reflective cracks more likely to appear. Furthermore, fatigue cracking and aging are significant over long-term use, shortening the service life of the road surface and seriously affecting road quality and safety.

[0004] With the improvement of green highway construction standards, traditional recycling technologies can no longer meet the stringent material performance requirements of modern road engineering. If recycled asphalt is to meet the needs of use, it must approach or even reach the standards of new asphalt in key indicators such as softening point, ductility, and needle penetration. However, recycled asphalt produced by existing processes still has significant gaps in core properties such as high-temperature viscosity and low-temperature toughness. In addition, the degree of aging and composition of waste asphalt from different sources vary greatly, resulting in a lack of universal technical solutions for the regeneration process, further restricting the large-scale development of the industry. Therefore, the development of a new recycling enhancement technology that systematically improves the performance of waste asphalt has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for recycling, enhancing and reusing waste pavement asphalt. Through specific processing steps and the addition of enhancers, the performance of waste asphalt is significantly improved, thereby achieving efficient reuse of waste pavement asphalt.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for recycling and enhancing the reuse of waste road asphalt comprises the following steps:

[0008] Step 1: Crushing the asphalt of the waste road

[0009] The collected waste road asphalt is crushed and graded and screened, and particles with a particle size of 3-5 mm and 5-10 mm are retained for later use;

[0010] Step 2: Pretreatment of waste pavement asphalt

[0011] The crushed waste asphalt is placed in a reactor for stirring and heating to remove moisture and low-boiling-point impurities in the waste asphalt;

[0012] Step 3: Mix the ingredients

[0013] Adding a reinforcing agent to the pretreated waste asphalt and heating and mixing under stirring conditions;

[0014] Step 4: High temperature modification

[0015] Continue heating the mixed material and keep it for 2-3 hours;

[0016] Step 5: Cooling and forming

[0017] The high-temperature modified asphalt material is naturally cooled to room temperature to obtain a reusable asphalt material.

[0018] Preferably, in step 1, a double-shaft shearing crusher is used for crushing, with a rotation speed of 800-1200 r / min and a time of 10-20 min.

[0019] Preferably, in step 1, a vibrating screen is used for graded screening, the vibrating screen frequency is 15-25 Hz, the amplitude is 3-5 mm, the screening time is 5-10 min, and a three-layer screen is used, with the screen hole sizes of 3 mm, 5 mm and 10 mm respectively, and the fine powder with a particle size of less than 3 mm and the particles larger than 10 mm re-enter the crusher.

[0020] In order to avoid excessive crushing and producing fine powder, a staged crushing strategy is adopted. The materials that do not meet the particle size standards can be corrected by re-entering the crusher for secondary crushing. On the one hand, the particles larger than the target particle size can be re-crushed to the qualified range. On the other hand, the fine powder that is too fine can be processed again. When the fine powder is mixed with other materials and enters the crusher, the mutual extrusion and shearing between the materials gradually agglomerate the fine powder and crush it to the ideal range. This can avoid the subsequent processing efficiency being reduced due to excessively large particles, and prevent excessive fine powder from affecting material properties, thereby ensuring the uniformity and stability of the output particle size.

[0021] Preferably, the heating temperature in step 2 is 120-150° C., the stirring speed is 100-150 r / min, and the time is 1-2 h.

[0022] This temperature range is lower than the melting point of asphalt, which can make the waste asphalt in a semi-solid or softened state. Under the action of stirring, it becomes a loose particle mixture, thereby removing moisture and some low-boiling point impurities, purifying the waste asphalt and improving the effect of subsequent enhancement treatment.

[0023] Preferably, the reinforcing agent in step three comprises the following components in parts by weight: 5-10 parts of nano-silicon dioxide, 1-3 parts of graphene, 10-20 parts of rubber powder, and 4-8 parts of alkali-treated modified lignin.

[0024] Nano-silica can fill the voids in asphalt, improving its hardness and strength; graphene has excellent mechanical and conductive properties, which can enhance the toughness and stability of asphalt; rubber powder can improve the elasticity and fatigue resistance of asphalt; alkali-treated modified lignin has good dispersibility and interfacial bonding ability, which can significantly improve the ductility and adhesion of waste asphalt, and effectively improve the asphalt's low-temperature crack resistance. At the same time, the natural polymer structure of lignin can enhance the aging resistance of asphalt and extend its service life.

[0025] Furthermore, the preparation method of the alkali-treated modified lignin in step 3 is:

[0026] The lignin is dispersed in a sodium hydroxide solution with a mass concentration of 15%, treated at 50-80° C. for 1-3 hours, filtered, washed with water, and dried.

[0027] Alkali treatment can destroy the original complex chemical bonds of lignin by demethylation, demethoxylation and other reactions, thereby exposing active groups such as carboxyl and hydroxyl groups.

[0028] Preferably, the weight ratio of the reinforcing agent to the waste asphalt in step three is 1:(5-10).

[0029] The addition of an appropriate amount of enhancer can significantly improve the high-temperature stability, fatigue resistance, elastic recovery ability and low-temperature toughness of asphalt, as well as its bonding strength with materials. However, excessive addition will cause the asphalt to become brittle, reduce its low-temperature crack resistance, affect the high-temperature viscosity and construction performance of the asphalt, and reduce its fluidity, affecting construction efficiency.

[0030] Preferably, the heating temperature in step 3 is 160-180° C., the stirring speed is 150-200 r / min, and the mixing time is 1-1.5 h, so that the reinforcing agent and the waste asphalt can be fully integrated.

[0031] Preferably, in step 4, the temperature is raised to 200-220°C.

[0032] At this temperature, the enhancer undergoes a deep chemical reaction with the waste asphalt. The macromolecular compounds in the waste asphalt undergo a heat-activated crosslinking reaction with the active groups in the enhancer, interconnecting the asphalt molecular chains to form a three-dimensional network structure. This significantly increases the asphalt's cohesion and deformation resistance, further enhancing the asphalt's performance. High temperatures accelerate the diffusion of substances in the enhancer, filling the gaps between asphalt molecules, reducing internal defects and improving the asphalt's high-temperature stability and aging resistance. The high-temperature modification process promotes the bonding between the enhancer and asphalt molecules, ultimately forming a stable composite structure.

[0033] Preferably, during the cooling process of the asphalt material after high-temperature modification in step five, a mold can be used to shape the asphalt material into a desired shape.

[0034] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a method for recycling and enhancing the reuse of waste pavement asphalt, which has the following beneficial effects:

[0035] The present invention crushes and pre-treats waste pavement asphalt to remove impurities and moisture, providing a good foundation for subsequent enhancement processing and improving the purity of the recycled asphalt. Nano-silica, graphene, rubber powder, and modified lignin are added to the enhancer. Through specific stirring and high-temperature modification steps, the enhancer and waste asphalt fully react and fuse, significantly improving the recycled asphalt's high-temperature stability, low-temperature crack resistance, elasticity, and durability, enabling it to meet the high-quality requirements of modern road construction. This invention enables the recycling and reuse of waste pavement asphalt, reduces resource waste and environmental pollution, and offers significant economic and environmental benefits. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] The preparation method of alkali-treated modified lignin in the following examples is:

[0038] The lignin was dispersed in a sodium hydroxide solution with a mass concentration of 15%, treated at 70° C. for 2 hours, filtered, washed with water, and dried.

[0039] Example 1

[0040] The collected waste road asphalt was crushed in a crusher with a speed of 800 r / min and a crushing time of 20 min. After crushing, the asphalt was sieved to obtain particles with a size of 3-5 mm and 5-10 mm.

[0041] The crushed waste asphalt was placed in a reactor and heated and stirred at 120°C and a stirring speed of 100 r / min for 2 hours to remove moisture and some low-boiling-point impurities.

[0042] Add a reinforcing agent to the pretreated waste asphalt. The reinforcing agent includes 5 parts of nano-silica, 1 part of graphene, 10 parts of rubber powder, and 4 parts of alkali-treated modified lignin. The weight ratio of the reinforcing agent to the waste asphalt is 1:5. Then, stir and mix at a temperature of 160°C and a stirring speed of 150 r / min for 1.5 hours.

[0043] The mixed asphalt material is heated to 200°C and maintained for 3 hours for high temperature modification;

[0044] The high-temperature modified asphalt material is cooled to room temperature and pressed into the desired shape through a mold.

[0045] Example 2

[0046] The collected waste road asphalt was crushed by a crusher at a speed of 1000 r / min and a crushing time of 15 min. After crushing, the asphalt was sieved to obtain particles with a size of 3-5 mm and 5-10 mm.

[0047] The crushed waste asphalt was placed in a reactor and heated and stirred at a temperature of 135°C and a stirring speed of 120 r / min for 1.5 hours to remove moisture and some low-boiling-point impurities;

[0048] Add a reinforcing agent to the pretreated waste asphalt. The reinforcing agent includes 7 parts of nano-silica, 2 parts of graphene, 15 parts of rubber powder, and 6 parts of alkali-treated modified lignin. The weight ratio of the reinforcing agent to the waste asphalt is 1:8. Then, stir and mix at a temperature of 170°C and a stirring speed of 170 r / min for 1.2 hours.

[0049] The mixed asphalt material is heated to 210°C and maintained for 2.5 hours for high temperature modification;

[0050] The high-temperature modified asphalt material is cooled to room temperature and pressed into the desired shape through a mold.

[0051] Example 3

[0052] The collected waste road asphalt was crushed in a crusher with a speed of 1200 r / min and a crushing time of 10 min. After crushing, the asphalt was sieved to obtain particles with a size of 3-5 mm and 5-10 mm.

[0053] The crushed waste asphalt was placed in a reactor and heated and stirred at a temperature of 150°C and a stirring speed of 150 r / min for 1 hour to remove moisture and some low-boiling-point impurities;

[0054] Add a reinforcing agent to the pretreated waste asphalt. The reinforcing agent includes 10 parts of nano-silica, 3 parts of graphene, 20 parts of rubber powder, and 8 parts of alkali-treated modified lignin. The weight ratio of the reinforcing agent to the waste asphalt is 1:10. Then, stir and mix at a temperature of 180°C and a stirring speed of 200 r / min for 1 hour.

[0055] The mixed asphalt material is heated to 220°C and maintained for 2 hours for high temperature modification;

[0056] The high-temperature modified asphalt material is cooled to room temperature and pressed into the desired shape through a mold.

[0057] Experimental example

[0058] 1. High temperature stability test

[0059] The softening point of the recycled asphalt materials obtained in Examples 1-3 and the untreated waste asphalt were tested according to the method in the "Testing Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The experimental data are shown in the following table:

[0060] Group Softening point (℃) Untreated waste asphalt 45 Example 1 62 Example 2 65 Example 3 68

[0061] The above results indicate that the softening point of the recycled asphalt treated by the method of the present invention is significantly increased, and the high-temperature stability is significantly improved, so that it can better adapt to the requirements of road use in high-temperature environments.

[0062] 2. Low temperature crack resistance test

[0063] The recycled asphalt materials obtained in Examples 1-3 and the untreated waste asphalt were tested for low-temperature properties using a bending beam rheometer (BBR). The test temperature was -18°C, and the creep modulus and m value of the asphalt were recorded. The experimental data are shown in the following table:

[0064] Group Creep stiffness modulus (MPa) m-value Untreated waste asphalt 300 0.25 Example 1 180 0.35 Example 2 160 0.38 Example 3 140 0.42

[0065] Experimental data show that the recycled asphalt treated by the method of the present invention is significantly better than untreated waste asphalt in terms of low-temperature crack resistance, and can effectively reduce the cracking phenomenon of roads in low-temperature environments.

[0066] 3. Durability test

[0067] The recycled asphalt materials obtained in Examples 1-3 and the untreated waste asphalt were subjected to a thin film oven aging test (TFOT) with an aging time of 5 hours and an aging temperature of 165°C. After aging, the asphalt was tested for its penetration ratio and ductility retention. The experimental data are shown in the following table:

[0068] Group Needle penetration ratio (%) Elongation retention rate (%) Untreated waste asphalt 55 40 Example 1 78 65 Example 2 82 70 Example 3 85 75

[0069] The higher the needle penetration ratio and the ductility retention rate, the better the durability of the asphalt. Experimental results show that the recycled asphalt treated by the method of the present invention has significantly improved durability, extending the service life of the asphalt material.

[0070] In summary, the method for recycling, enhancing and reusing waste pavement asphalt provided by the present invention effectively improves the performance of waste asphalt through a series of specific processing steps and the addition of enhancers, realizes the efficient reuse of waste pavement asphalt, and has good application prospects.

[0071] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling and enhancing waste road asphalt, characterized in that: The following steps are involved: Step 1: Crushing the asphalt of the waste road The collected waste road asphalt is crushed and graded and screened, and particles with a particle size of 3-5 mm and 5-10 mm are retained for later use; Step 2: Pretreatment of waste pavement asphalt The crushed waste asphalt is placed in a reactor for stirring and heating to remove moisture and low-boiling-point impurities in the waste asphalt; Step 3: Mix the ingredients Adding a reinforcing agent to the pretreated waste asphalt and heating and mixing under stirring conditions; Step 4: High temperature modification Continue heating the mixed material and keep it for 2-3 hours; Step 5: Cooling and forming The high-temperature modified asphalt material is naturally cooled to room temperature to obtain a reusable asphalt material.

2. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: In step 1, a double-shaft shearing crusher is used for crushing, with a rotation speed of 800-1200 r / min and a time of 10-20 min.

3. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: In step 1, a vibrating screen is used for graded screening. The frequency of the vibrating screen is 15-25Hz, the amplitude is 3-5mm, the screening time is 5-10min, and a three-layer screen is used. The screen hole sizes are 3mm, 5mm and 10mm respectively. Fine powder with a particle size of less than 3mm and particles larger than 10mm re-enter the crusher.

4. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: In step 2, the heating temperature is 120-150° C., the stirring speed is 100-150 r / min, and the time is 1-2 h.

5. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: The reinforcing agent in step three comprises the following components in parts by weight: 5-10 parts of nano-silicon dioxide, 1-3 parts of graphene, 10-20 parts of rubber powder, and 4-8 parts of alkali-treated modified lignin.

6. The method for recycling and enhancing waste pavement asphalt according to claim 5, characterized in that: The preparation method of the alkali-treated modified lignin in step 3 is: The lignin is dispersed in a sodium hydroxide solution with a mass concentration of 15%, treated at 50-80° C. for 1-3 hours, filtered, washed with water, and dried.

7. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: The weight ratio of the reinforcing agent to the waste asphalt in step three is 1:(5-10).

8. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: In step 3, the heating temperature is 160-180° C., the stirring speed is 150-200 r / min, and the mixing time is 1-1.5 h.

9. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: In step 4, the temperature is raised to 200-220°C.

10. The method for recycling and enhancing waste pavement asphalt according to claim 1, characterized in that: During the cooling process of the asphalt material after high-temperature modification in step 5, a mold can be used to shape the asphalt material into the desired shape.