Modified regenerated PET fiber reinforced regenerated aggregate asphalt mixture and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a modified regenerated PET fiber reinforced regenerated aggregate asphalt mixture and a preparation method thereof. According to the mixture, recycled aggregate obtained by crushing and screening waste concrete is used for partially replacing natural aggregate, and recycled PET fibers prepared from waste plastic bottles are used for reinforcement; in order to solve the problem of poor double-interface bonding performance of recycled aggregate / asphalt and PET fiber / asphalt in the application of the mixture, gamma-aminopropyltriethoxysilane (KH550) is adopted to modify the recycled aggregate, and gamma-aminopropylmethyldiethoxysilane (KH902) is adopted to modify the recycled PET fiber. Through the double-interface modification technology, the asphalt mixture which is excellent in pavement performance, green and low in carbon is prepared, the resource utilization rate of solid waste can be remarkably increased, and remarkable economic and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building materials, in particular to a modified recycled PET fiber reinforced recycled aggregate asphalt mixture and a preparation method thereof. BACKGROUND

[0002] The total amount of building waste in China has reached about 20 billion tons, and the average resource utilization rate is less than 10% per year. On the other hand, the coastal areas of Fujian are facing a shortage of sand and stone resources due to the expansion of construction scale. The use of recycled aggregate (RCA) prepared by recycling, crushing and grading of waste concrete to replace natural sand and stone to prepare asphalt mixture can effectively alleviate the shortage of resources, reduce landfill occupation and cost, and reduce carbon emissions in road construction. Studies have shown that the residual mortar attached to the surface of RCA can enhance the friction with the asphalt matrix, improve the high-temperature stability and fatigue resistance of the mixture, and prolong the service life of the pavement. However, RCA has defects such as high porosity, strong water absorption and large crushing value, which can easily lead to a decrease in the low-temperature crack resistance and water stability of the asphalt mixture. Therefore, improving the water stability and low-temperature crack resistance of the recycled aggregate asphalt mixture is crucial to its engineering application.

[0003] Adding fibers to recycled aggregate asphalt mixture is an effective solution. Fibers in asphalt mixture can play the roles of adsorption, reinforcement and thickening, etc., and can significantly improve the high-temperature stability, low-temperature crack resistance and water stability of the asphalt mixture, and can also delay the reflection cracks of the pavement, which is beneficial to solve the early disease problems of asphalt pavement. At present, the fibers applied in pavement engineering are mainly basalt fibers, glass fibers and lignin fibers, etc., but the preparation of these fibers consumes a large amount of natural resources. Recycled polyethylene terephthalate (PET) fiber is obtained by recycling, crushing and re-preparing waste plastic bottles, and has good mechanical properties, thermal stability, chemical corrosion resistance, low price and plastic reduction, etc., which provides a sustainable solution for pavement engineering. However, there are double-interface defect problems in the application of recycled PET fiber reinforced recycled aggregate asphalt mixture. On the one hand, the RCA / asphalt interface is prone to water erosion and reduces the durability of the mixture due to the high porosity and strong water absorption of the aggregate, which makes it difficult for asphalt to fully infiltrate and adhere; on the other hand, the recycled PET / asphalt interface is prone to fiber pullout or debonding due to the smooth surface of the fiber and the polarity difference between the fiber and the asphalt, which affects the overall mechanical properties of the mixture. Patent CN114772969B uses recycled PET fiber to reinforce asphalt mixture, which improves the road performance of the mixture to a certain extent, but does not solve the interface defect problem.

[0004] To solve the above problems, the application proposes a double-interface synergistic modification strategy: using gamma-aminopropyl triethoxysilane (KH550) to modify RCA, forming Si-O-Si bonds and penetrating into pores to strengthen the aggregate structure and simultaneously build a hydrophobic barrier; using gamma-aminopropyl methyl diethoxysilane (KH902) to modify recycled PET fibers, using active groups to graft and build a chemical bonding interface, and inducing nanometer roughening of the fiber surface to enhance the mechanical interlocking effect. The organic chain structure of the two types of silanes drives the interface energy to approach, prompting the asphalt to form a multi-level interlocking continuous bonding network between the modified aggregate and the fibers, synergistically improving the high-temperature deformation resistance, low-temperature crack resistance and water stability of the mixture, realizing high-value resource utilization of solid waste, and promoting the green and sustainable development of road engineering. SUMMARY

[0005] To solve the above problems, the application proposes a double-interface synergistic modification strategy: using gamma-aminopropyl triethoxysilane (KH550) to modify RCA, forming Si-O-Si bonds and penetrating into pores to strengthen the aggregate structure and simultaneously build a hydrophobic barrier; using gamma-aminopropyl methyl diethoxysilane (KH902) to modify recycled PET fibers, using active groups to graft and build a chemical bonding interface, and inducing nanometer roughening of the fiber surface to enhance the mechanical interlocking effect. The organic chain structure of the two types of silanes drives the interface energy to approach, prompting the asphalt to form a multi-level interlocking continuous bonding network between the modified aggregate and the fibers, synergistically improving the high-temperature deformation resistance, low-temperature crack resistance and water stability of the mixture, realizing high-value resource utilization of solid waste, and promoting the green and sustainable development of road engineering.

[0006] To achieve the above purposes, the application is implemented by the following technical solutions:

[0007] A modified recycled PET fiber reinforced recycled aggregate asphalt mixture mainly consists of natural aggregate, modified RCA, mineral powder, base asphalt and modified recycled PET fiber components; the components specifically include:

[0008] 10-20mm limestone aggregate, 5-10mm limestone aggregate, 3-5mm limestone aggregate, 0-3mm limestone aggregate, 4.75-9.5mm modified RCA, 9.5-13.2mm modified RCA, 13.2-16mm modified RCA, 16-19mm modified RCA, mineral powder, base asphalt and modified recycled PET fiber.

[0009] As a possible implementation, further, the natural aggregate, modified RCA and mineral powder each component includes, by weight parts: 10-20mm limestone aggregate 8 parts, 5-10mm limestone aggregate 10 parts, 3-5mm limestone aggregate 10 parts, 0-3mm limestone aggregate 40 parts, 4.75-9.5mm modified RCA 6 parts, 9.5-13.2mm modified RCA 11 parts, 13.2-16mm modified RCA 9 parts, 16-19mm modified RCA 4 parts and mineral powder 2 parts.

[0010] As a possible implementation, further, the mass of the matrix asphalt accounts for 5.4% of the total mass of the natural aggregate, the modified RCA and the mineral powder, and the mass of the modified recycled PET fiber accounts for 0.2%-0.6% of the mass of the matrix asphalt.

[0011] As a possible implementation, further, the RCA is obtained by recycling, crushing and grading the waste concrete, has a particle size of 4.75-16 mm, a crushing index of 13.6%, a water absorption of 4.5%, and an apparent density of 2590.0 kg / m 3 3 .

[0012] As a possible implementation, further, the RCA is modified by a modifier γ-aminopropyl triethoxysilane (KH550, chemical formula: H2N(CH2)3Si(OC2H5)3) to obtain the modified RCA.

[0013] As a possible implementation, further, the preparation method of the modified RCA comprises:

[0014] 1) sandpaper polishing of the RCA to reduce the surface roughness, ultrasonic cleaning with deionized water for 10 minutes to remove impurities, and drying in a 105°C oven for 2 hours to a water content <0.5%;

[0015] 2) preparation of a treatment solution containing 1.5wt% γ-aminopropyl triethoxysilane (KH550) + 0.1wt% acetic acid + 98.4wt% deionized water, magnetic stirring for 30 minutes (pH=4.5);

[0016] 3) immersion of the dried RCA in the treatment solution at a solid-liquid ratio of 1:1.5, constant temperature oscillation at 40°C for 40 minutes; after taking out, rapid washing with deionized water for 3 seconds, then placing in a 105°C oven for drying for 1 hour to complete the curing at the same time, and sealing and storing after cooling.

[0017] As a possible implementation, further, the recycled PET fiber is obtained by recycling, crushing and re-preparing the waste plastic bottles, and has physical performance indexes of: length: 6 mm, diameter: 15.6 μm, strength retention rate: 93.2%, tensile strength: 700 MPa, elongation at break: 16.5%, and melting point: 255°C.

[0018] As a possible implementation, further, the recycled PET fiber is modified by γ-aminopropyl methyl diethoxysilane (KH902, chemical formula: H2N(CH2)3Si(CH3)(OC2H5)2) to obtain the modified recycled PET fiber.

[0019] ​As a possible implementation, further, the preparation method of the modified recycled PET fiber comprises the following steps:

[0020] a) take water 50 parts, gamma-aminopropyl methyl diethoxysilane (KH902) modifier 50 parts and anhydrous ethanol 1000 parts into a beaker, stir for 30 min with a magnetic stirrer to obtain a modified solution;

[0021] b) take the open processed recycled PET fiber 100 parts and soak in the above modified solution, place in a 25℃ environment for 2h, then filter, and then put the treated recycled PET fiber into an oven at 60℃ and dry to constant weight;

[0022] c) take the dried recycled PET fiber and open it again and place it in a sealed bag for use.

[0023] As a possible implementation, further, the preparation method of the modified recycled PET fiber reinforced recycled aggregate asphalt mixture comprises the following steps:

[0024] S1: place the natural aggregate, modified RCA and mineral powder in an oven at 180℃ and heat for more than 4 hours;

[0025] S2: slowly add the modified recycled PET fiber to the base asphalt in a 170℃ oil bath, stir at a speed of 1000r / min for 15min to ensure uniform dispersion of the fiber;

[0026] S3: put the preheated aggregate and modified RCA together into a 170℃ mixing pot and mix for 60s;

[0027] S4: add the fiber asphalt in step S2 to the mixing pot and mix for 60s;

[0028] S5: add the preheated mineral powder to the mixing pot and mix for 60s; after stirring, the modified recycled PET fiber reinforced recycled aggregate asphalt mixture is obtained.

[0029] The beneficial effects of the present application are as follows:

[0030] 1. Compared with the prior art, the difference of the present application is that RCA partially replaces natural aggregate, which alleviates the problem of shortage of natural aggregate; at the same time, the residual mortar on the surface of RCA increases the friction performance of aggregate and asphalt, thereby improving the high temperature stability and fatigue resistance of asphalt mixture. In addition, the PET fiber regenerated from waste mineral water bottles is introduced as a reinforcing material, which has high elastic modulus, large specific surface area, excellent tensile strength, chemical corrosion resistance and high temperature stability, which can further improve the mechanical and road performance of recycled aggregate asphalt mixture. The present application promotes the low-carbon transformation of road engineering through the collaborative high-value utilization of construction solid waste and plastic waste.

[0031] 2、Compared with the prior art, the regenerated PET fiber is modified by KH902 silane coupling agent. KH902 is a single amino silane, which has significant dual reactivity and can simultaneously react with the fiber and asphalt (the mechanism is shown in Figure 1 ). The amino group of KH902 can react with the hydroxyl group on the surface of the regenerated PET fiber to form a chemical bond, and at the same time, the silane group can react with the organic components such as aromatic compounds and polar asphaltene in the asphalt to further enhance the interfacial adhesion between the fiber and the asphalt. This unique dual functional structure not only significantly improves the chemical bonding strength and compatibility between the fiber and the asphalt, but also effectively maintains the flexibility of the fiber and inhibits stress cracking, thereby effectively improving the overall performance of the asphalt mixture.

[0032] 3、Compared with the prior art, the RCA is modified by impregnation with KH550 silane coupling agent. On the one hand, the short-chain amino propyl group of KH550 synchronously bonds the polar components of asphalt, enhancing the adhesion between asphalt and aggregate interface. On the other hand, silane penetrates into the residual mortar pores on the surface of RCA, strengthening the inorganic interface of aggregate through Si-O-Si covalent bond, and improving the strength and modulus of RCA. In addition, silane treatment makes RCA change from hydrophilic to hydrophobic, and the surface energy is close to that of asphalt, which reduces the contact angle of asphalt on the surface of modified material, accelerates the infiltration speed, forms a more uniform and thicker asphalt film, and reduces water adsorption, further improving the water stability of the mixture.

[0033] 4、Compared with the prior art, the dual-interface modification strategy provided by the present application has a synergistic effect. The surface pores of RCA are filled with silane to form microconvexities after KH550 treatment, and the surface roughness of PET fiber is increased after KH902 treatment. When the two are in contact, the rough surfaces bite each other to form physical anchoring points, and the asphalt penetrates into the pores to form a "barb" structure after solidification, enhancing the anti-slippage ability under high-temperature shear stress. In addition, the organic chain structure of the two types of homologous silanes drives the interface energy to approach, prompting the asphalt to form a multi-level interlocking continuous bonding network between the modified RCA and the fiber, and synergistically improving the high-temperature deformation resistance, low-temperature cracking resistance and water stability of the mixture. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0035] Figure 1 is a hydrolysis mechanism diagram of KH902.

[0036] Figure 2 are the cross-section scanning electron microscope (SEM) images of the recycled PET fiber reinforced asphalt mortar; wherein, figures a-c are the cross-section of the asphalt binder mixed with unmodified recycled PET fiber, and figures d-h are the cross-section of the asphalt binder mixed with modified recycled PET fiber.

[0037] Figure 3 are the contact angle images of the recycled PET fiber before and after modification.

[0038] Figure 4 are the Marshall stability comparison charts of the asphalt mixtures of each embodiment and the comparative example.

[0039] Figure 5 are the wheel rut dynamic stability comparison charts of the asphalt mixtures of each embodiment and the comparative example.

[0040] Figure 6 are the low-temperature bending strength comparison charts of the asphalt mixtures of each embodiment and the comparative example.

[0041] Figure 7 are the residual stability comparison charts of the asphalt mixtures of each embodiment and the comparative example.

[0042] Figure 8 are the freeze-thaw splitting test strength ratio comparison charts of the asphalt mixtures of each embodiment and the comparative example. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application,

[0044] The present application provides a modified recycled PET fiber reinforced recycled aggregate asphalt mixture and a preparation method thereof. The raw material composition of the modified recycled PET fiber reinforced recycled aggregate asphalt mixture comprises natural aggregate, modified RCA, mineral powder, base asphalt and modified recycled PET fiber.

[0045] The components in the natural aggregate, modified RCA and mineral powder by weight parts include: 10-20 mm limestone aggregate 8 parts, 5-10 mm limestone aggregate 10 parts, 3-5 mm limestone aggregate 10 parts, 0-3 mm limestone aggregate 40 parts, 4.75-9.5 mm modified RCA 6 parts, 9.5-13.2 mm modified RCA 11 parts, 13.2-16 mm modified RCA 9 parts, 16-19 mm modified RCA 4 parts and mineral powder 2 parts. The mass of the base asphalt accounts for 5.4% of the total mass of the natural aggregate, modified RCA and mineral powder, and the mass of the modified recycled PET fiber accounts for 0.2%-0.6% of the mass of the base asphalt.

[0046] Wherein, the RCA is modified by modifier γ-aminopropyl triethoxysilane (KH550, chemical formula: H2N(CH2)3Si(OC2H5)3) to obtain modified RCA; the recycled PET fiber is modified by γ-aminopropyl methyl diethoxysilane (KH902, chemical formula: H2N(CH2)3Si(CH3)(OC2H5)2) to obtain modified recycled PET fiber. The RCA is obtained by recycling, crushing and grading of waste concrete, and has a particle size of 4.75-16 mm, a crushing index of 13.6%, a water absorption of 4.5%, and an apparent density of 2590.0 kg / m 3 , a bulk density of 1285.0 kg / m 3 ; the recycled PET fiber is obtained by recycling, crushing and re-preparing of waste plastic bottles, and has physical performance indexes of: length: 6 mm, diameter: 15.6 μm, strength retention rate: 93.2%, tensile strength: 700 MPa, elongation at break: 16.5%, and melting point: 255℃.

[0047] The specific preparation steps of the modified recycled PET fiber reinforced RCA asphalt mixture are as follows:

[0048] 1) The natural aggregate, modified RCA and mineral powder are placed in an oven at 180℃ for heating for more than 4 hours;

[0049] 2) The 70# base asphalt is weighed, and the modified recycled PET fiber is slowly added to the base asphalt in the 170℃ oil bath, and stirred at a speed of 1000 r / min for 15 min to ensure uniform dispersion of the fiber;

[0050] 3) The preheated aggregate of each size is put into the 170℃ mixing kettle together and mixed for 60 s;

[0051] 4) The fiber asphalt in step 2) is added to the mixing kettle and mixed for 60 s;

[0052] 5) The preheated mineral powder is added to the mixing kettle and mixed for 60 s; after stirring, the required modified recycled PET fiber reinforced recycled aggregate asphalt mixture is obtained.

[0053] The present solution is further illustrated in technical details in connection with a plurality of embodiments and comparative examples as follows:

[0054] Embodiment 1

[0055] The present embodiment provides a modified recycled PET fiber reinforced recycled aggregate asphalt mixture, which is mainly composed of the following components: natural aggregate, modified RCA, mineral powder, base asphalt and modified recycled PET fiber.

[0056] Among them, the components in the natural aggregate, modified RCA and mineral powder are calculated by weight parts, including: 10-20mm limestone aggregate 8 parts, 5-10mm limestone aggregate 10 parts, 3-5mm limestone aggregate 10 parts, 0-3mm limestone aggregate 40 parts, 4.75-9.5mm modified RCA 6 parts, 9.5-13.2mm modified RCA 11 parts, 13.2-16mm modified RCA 9 parts, 16-19mm modified RCA 4 parts and mineral powder 2 parts; the mass of base asphalt accounts for 5.4% of the total mass of natural aggregate, modified RCA and mineral powder, and the mass of modified recycled PET fiber accounts for 0.2% of the mass of base asphalt.

[0057] The preparation method of the modified recycled PET fiber reinforced recycled aggregate asphalt mixture is as follows:

[0058] 1) RCA modification process: first, sandpaper polishing is performed on RCA to reduce surface roughness, ultrasonic cleaning is performed with deionized water for 10 minutes to remove impurities, and drying is performed in a 105℃ oven for 2 hours to a water content <0.5%; second, a treatment solution containing 1.5wt% γ-aminopropyl triethoxysilane (KH550) + 0.1wt% acetic acid + 98.4wt% deionized water is prepared, and magnetic stirring is performed for 30 minutes (pH = 4.5); then, the dried aggregate is immersed in the treatment solution at a solid-liquid ratio of 1:1.5, and constant temperature oscillation is performed at 40℃ for 40 minutes; after taking out, it is quickly rinsed with deionized water for 3 seconds, and drying is performed in a 105℃ oven for 1 hour to complete curing simultaneously, and after cooling, it is sealed and stored.

[0059] Among them, the RCA is obtained by recycling, crushing and grading of waste concrete, and its particle size is 4.75-16mm, the crushing index is 13.6%, the water absorption rate is 4.5%, and the apparent density is 2590.0kg / m 3 , the bulk density is 1285.0kg / m 3 .

[0060] 2) The modification process of the recycled PET fiber: The recycled PET fiber was dried to constant weight in an oven at 60°C and then used. The mixed modifier of water, KH902 and anhydrous ethanol was prepared according to the mass ratio of 1:1:20. The mass ratio of the mixed modifier to the recycled PET fiber was 10:1. The opened recycled PET fiber was soaked in the prepared mixed modifier and dipped for 2 hours in an environment at 25°C. Then the fiber was filtered and taken out and placed in an oven at 60°C for drying to constant weight. After the dried recycled PET fiber was opened again, it was placed in a sealed bag for use.

[0061] The recycled PET fiber was recycled, crushed and re-prepared from waste plastic bottles, and its physical performance index was: length: 6 mm, diameter: 15.6 μm, strength retention rate: 93.2%, tensile strength: 700 MPa, elongation at break: 16.5%, melting point: 255°C.

[0062] 3) Preparation of modified recycled PET fiber reinforced recycled aggregate asphalt mixture and test block: The test block was prepared according to the provisions of the People's Republic of China Industry Standard "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" (JTG E20-2011). First, the natural aggregate, modified RCA and mineral powder were heated in an oven at 180°C for more than 4 hours. Then, the heated aggregate was placed in an asphalt mixture stirring pot and dry mixed for 60 seconds. Next, the weighed modified recycled PET fiber asphalt (preparation method: according to the above component allocation ratio, the modified recycled PET fiber was weighed and added to 70# base asphalt, placed in an oil bath environment at 170°C, and stirred with a high shear stirrer at 1000 r / min for 15 minutes to ensure uniform dispersion of the fiber in the asphalt.) was added to the stirring pot and stirred for 60 seconds. Finally, the mineral powder was added to the stirring pot and stirred for 60 seconds. After stirring, the mixture was loaded into a Marshall test mold (or a rutting plate mold), and a Marshall electric compaction instrument (or a rutting plate forming instrument) was used to prepare the test piece. The test piece was demolded after standing at room temperature for 16 hours to obtain the modified recycled PET fiber reinforced recycled aggregate asphalt mixture test block, which was placed in a well-ventilated place for use in subsequent tests.

[0063] Example 2

[0064] The embodiment provides a modified recycled PET fiber reinforced recycled aggregate asphalt mixture which mainly comprises the following components: natural aggregate, modified RCA, mineral powder, matrix asphalt and modified recycled PET fiber. Wherein, the components in the natural aggregate, the modified RCA and the mineral powder are calculated by weight parts, and the components comprise the following: 8 parts of 10-20mm limestone aggregate, 10 parts of 5-10mm limestone aggregate, 10 parts of 3-5mm limestone aggregate, 40 parts of 0-3mm limestone aggregate, 6 parts of 4.75-9.5mm modified RCA, 11 parts of 9.5-13.2mm modified RCA, 9 parts of 13.2-16mm modified RCA, 4 parts of 16-19mm modified RCA and 2 parts of mineral powder; the mass of the matrix asphalt accounts for 5.4% of the total mass of the natural aggregate, the modified RCA and the mineral powder, and the mass of the modified recycled PET fiber accounts for 0.4% of the mass of the matrix asphalt.

[0065] The preparation of the modified recycled PET fiber reinforced recycled aggregate asphalt mixture and the test block in the embodiment is same as that in the embodiment 1, and details are not described herein.

[0066] Example 3

[0067] The embodiment provides a modified recycled PET fiber reinforced recycled aggregate asphalt mixture which mainly comprises the following components: natural aggregate, modified RCA, mineral powder, matrix asphalt and modified recycled PET fiber. Wherein, the components in the natural aggregate, the modified RCA and the mineral powder are calculated by weight parts, and the components comprise the following: 8 parts of 10-20mm limestone aggregate, 10 parts of 5-10mm limestone aggregate, 10 parts of 3-5mm limestone aggregate, 40 parts of 0-3mm limestone aggregate, 6 parts of 4.75-9.5mm modified RCA, 11 parts of 9.5-13.2mm modified RCA, 9 parts of 13.2-16mm modified RCA, 4 parts of 16-19mm modified RCA and 2 parts of mineral powder; the mass of the matrix asphalt accounts for 5.4% of the total mass of the natural aggregate, the modified RCA and the mineral powder, and the mass of the modified recycled PET fiber accounts for 0.6% of the mass of the matrix asphalt.

[0068] The preparation of the modified recycled PET fiber reinforced recycled aggregate asphalt mixture and the test block in the embodiment is same as that in the embodiment 1, and details are not described herein.

[0069] Comparative Example 1

[0070] The comparative example 1 is basically same as the embodiment 1, and the difference lies in that the RCA and the recycled PET fiber are not modified in the comparative example.

[0071] The comparative example is a recycled PET fiber reinforced recycled aggregate asphalt mixture which mainly comprises the following components: natural aggregate, RCA, mineral powder, matrix asphalt and recycled PET fiber.

[0072] The components in the natural aggregate, RCA, and mineral powder by weight parts include: 8 parts of 10-20 mm limestone aggregate, 10 parts of 5-10 mm limestone aggregate, 10 parts of 3-5 mm limestone aggregate, 40 parts of 0-3 mm limestone aggregate, 6 parts of 4.75-9.5 mm RCA, 11 parts of 9.5-13.2 mm RCA, 9 parts of 13.2-16 mm RCA, 4 parts of 16-19 mm RCA, and 2 parts of mineral powder. The mass of the base asphalt accounts for 5.4% of the total mass of the natural aggregate, RCA, and mineral powder, and the mass of the recycled PET fiber accounts for 0.2% of the mass of the base asphalt.

[0073] The preparation of the recycled PET fiber reinforced recycled aggregate asphalt mixture includes the following specific steps:

[0074] The preparation of the recycled PET fiber reinforced recycled aggregate asphalt mixture and test block is performed according to the provisions of the People's Republic of China Industry Standard “Highway Engineering Asphalt and Asphalt Mixture Test Procedures” (JTG E20-2011). First, the natural aggregate, RCA, and mineral powder are heated in an oven at 180°C for more than 4 hours, and the asphalt is heated in an oven at 170°C for more than 2 hours. Then, the heated aggregate is placed in an asphalt mixture stirring pot and dry-mixed for 60 seconds. Next, the weighed recycled PET fiber asphalt (preparation method: according to the above component allocation ratio, the recycled PET fiber is weighed and added to 70# base asphalt, placed in an oil bath environment at 170°C, and stirred at 1000 r / min for 15 minutes using a high-shear stirrer to ensure uniform dispersion of the fiber in the asphalt.) is added to the stirring pot and stirred for 60 seconds. After stirring is completed, the mixture is loaded into a Marshall test mold (or a rutting plate mold), and a Marshall electric compaction instrument (or a rutting plate forming instrument) is used to prepare the test piece. After the test piece is left to stand at room temperature for 16 hours, it is demolded to obtain a recycled PET fiber reinforced recycled aggregate asphalt mixture test block, which is placed in a well-ventilated area for later use.

[0075] Comparative test

[0076] In order to facilitate performance testing and comparison of the asphalt mixtures prepared in the examples and comparative examples and the test pieces prepared therefrom, the following tests are mainly used for comparison, and the specific items and parameters are as follows:

[0077] (1) Scanning electron microscope test: This test is performed using a Talos F200i field emission transmission electron microscope produced by Thermo Fisher Scientific Company, USA. The acceleration voltage is 3 kV during morphology shooting, and gold spraying treatment is performed using an Oxford Quorum SC7620 sputtering coater with a platinum target.

[0078] (2) Contact angle test: This test is performed using a Germany The DSA 30 contact angle measuring instrument (measurement range 0-180°) produced by the company was used to test and analyze the surface properties of the fibers to measure the contact angle CA.

[0079] (3) Marshall stability test: According to the "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" (JTG E20-2011), the Marshall stability was tested using a standard size Φ101.6mm×63.5mm cylindrical specimen, and after the Marshall stability test was completed, the flow value of the specimen was measured simultaneously, the test temperature was 60°C, the holding time was 30-40 minutes, and the DF type Marshall stability tester was used for testing.

[0080] (4) Rutting test: According to the "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" (JTG E20-2011), the rutting test used a plate-shaped specimen with dimensions of 300mm×300mm×50mm, the test temperature was 60°C, the wheel pressure was 0.7MPa, the test wheel speed was 42 times / minute (one way), the standard test duration was 60 minutes (total 2520 times), and the SYD-0719C type rutting tester was used to measure the dynamic stability (DS, unit: times / mm).

[0081] (5) Low temperature beam bending test: According to the "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" (JTG E20-2011), the low temperature beam bending test used a prism-shaped specimen with dimensions of 250mm×30mm×35mm for testing, the test temperature was -10°C, the loading rate was 50mm / min, and the Instron 5567 type universal material testing machine was used to measure the failure strain, bending stiffness modulus and failure stress.

[0082] (6) Immersion Marshall test: According to the "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" (JTG E20-2011), the immersion Marshall test used a standard size Φ101.6mm×63.5mm cylindrical specimen, the specimen was kept in a 60°C constant temperature water tank for 30-40min, then the Marshall stability (MS1) was measured, and then the stability was measured again after being immersed for 48h (or 24h) (MS2), the residual stability was calculated (MS0=MS2 / MS1×100%), and the DF type Marshall stability tester was used for testing.

[0083] (7) Freeze-thaw splitting test: refer to "Standard Test Methods of Bituminous Pavement Materials" (JTG E20-2011), the freeze-thaw splitting test uses a standard size of Φ101.6mm x 63.5mm cylindrical test piece, the test piece is vacuum saturated, then frozen at -18℃ for 16h, then melted in a 60℃ water bath for 24h to complete one freeze-thaw cycle, then the splitting test is carried out, the splitting strength ratio (TSR) before and after freezing and thawing is measured, and a DF type Marshall test instrument is used for testing.

[0084] Test result comparison

[0085] The asphalt mixtures or test blocks prepared from Examples 1, 2, 3 and Comparative Examples are tested by the aforementioned comparative tests (1) to (6), and the results are as follows:

[0086] (1) From Figure 2 a, b, c, it can be seen that there are gaps between the unmodified recycled PET fibers and the asphalt matrix, and the fiber surface is smooth, so the combination is not good, and therefore the reinforcing effect is limited. After modification of the recycled PET fibers, the fibers present a three-dimensional distribution in the asphalt matrix (d, e, f, g, h), the gap between the fibers and the asphalt matrix is small and the combination is tight, and the transition zone structure is dense, so the combination between the modified recycled PET fibers and the matrix is significantly improved, and the reinforcing effect on the asphalt mortar is more significant. Figure 2 d, e, f, g, h), the gap between the fibers and the asphalt matrix is small and the combination is tight, and the transition zone structure is dense, so the combination between the modified recycled PET fibers and the matrix is significantly improved, and the reinforcing effect on the asphalt mortar is more significant.

[0087] (2) From Figure 3 It can be seen that the contact angle of the modified recycled PET fibers is reduced, which can be attributed to the chemical reaction between the coupling agent and the fiber surface during the modification process. KH902 not only increases the roughness and polarity of the fiber surface, but also enhances the physical entanglement with the asphalt by forming new chemical bonds (such as C-O or N-O bonds), thereby improving the interfacial bonding force between the fiber and the asphalt. In addition, according to the calculation of the adhesion work, the adhesion work between the unmodified recycled PET fibers and the asphalt is 12.75mJ / m 2 , the adhesion work between the modified recycled PET fibers and the asphalt is 14.74mJ / m 2 , which is 1.16 times that of the unmodified recycled PET fibers. This further confirms that the modification process significantly enhances the interfacial bonding force between the fiber and the asphalt, which helps to improve the overall mechanical properties and durability of the asphalt mixture.

[0088] (3) Combined Figure 4From the comparison of Marshall stability of the mixtures, it can be seen that the average Marshall stability of Examples 1, 2 and 3 is 11.74 kN, 12.38 kN and 11.91 kN respectively, which is higher than 10.07 kN of the comparative example, indicating that the modified mixture has higher shear strength and overall stability. RCA treated by KH550 fills the pores by silane curing and forms a micro-convex structure, which produces stronger physical anchoring with asphalt, while RCA treated by KH902 increases the surface roughness and forms micro-mechanical interlocking with asphalt, which collectively enhances the skeleton structure of the mixture, reduces deformation at high temperature, and thus improves the Marshall stability. At the same time, the increase of fiber content can further improve the shear strength of the mixture, but too high fiber content may cause the flexibility of the mixture to decrease, affecting the overall performance, so the Marshall stability of Example 3 is slightly lower than that of Example 2.

[0089] (4) Combination Figure 5 From the comparison of dynamic stability of the mixtures, it can be seen that the average rutting dynamic stability of Examples 1, 2 and 3 is 1589.12 times / mm, 1729.62 times / mm and 1827.37 times / mm respectively, which is significantly higher than 1374.24 times / mm of the comparative example. KH550 coupling agent enhances the compactness and strength of RCA and strengthens its bonding force with asphalt through Si-O-Si or Si-O-Al covalent bond. KH902 coupling agent forms a flexible three-dimensional reinforced net by improving the compatibility and adhesion of RCA with asphalt. These modified materials work together to promote the uniform spreading and bonding of asphalt on the surface of fibers and aggregates, and improve the stress transfer efficiency. Although the fiber content increases to 0.6% (Example 3) may cause local aggregation and affect the skeleton density, but the overall stability is still high.

[0090] (5) Combination Figure 6 From the comparison of low-temperature bending strength of the mixtures, it can be seen that the average bending strength of Examples 1, 2 and 3 is 10.20 MPa, 11.39 MPa and 10.85 MPa respectively, which is higher than 9.22 MPa of the comparative example. This indicates that the double-interface modification strategy significantly improves the low-temperature bending resistance of asphalt mixture. KH550 modification enhances the compactness and strength of aggregates, and improves the low-temperature bonding performance. KH902 modified fiber further improves the low-temperature bending resistance by promoting the interaction between fiber and asphalt. However, when the fiber content increases to 0.6%, it may cause local aggregation and form stress concentration points, resulting in slightly lower bending strength than Example 2.

[0091] (6) Combination Figure 7Compared with the residual stability of the mixtures in Table 1, it can be seen that the residual stability of Example 2 is the highest, reaching 89.77%, followed by Example 3 and Example 1, which are 88.19% and 87.26% respectively, all higher than 86.79% of Comparative Example 1. The aggregate modified by KH550 enhances the bonding force with asphalt by forming stable covalent bonds and forms a hydrophobic surface, effectively preventing the intrusion of moisture. At the same time, the modified recycled PET fiber enhances the interaction between the fiber and asphalt, further improving the structural stability of the mixture and reducing the structural damage caused by moisture. The synergistic effect of the two materials helps to form a more uniform and thicker asphalt film, thereby improving the water damage resistance of the asphalt mixture. However, when the fiber content increases to 0.6% (Example 3), it may cause local agglomeration and form stress concentration points, resulting in a slightly lower residual stability than Example 2.

[0092] Table 1 Results of immersion Marshall test

[0093]

[0094] (7) Combination Figure 8 Compared with the freeze-thaw splitting strength ratio of the mixtures in Table 2, according to the freeze-thaw splitting test results in Table 2, the splitting strength ratios of Examples 1, 2 and 3 are 89.82%, 92.49% and 90.70% respectively, all higher than 87.75% of Comparative Example 1. The aggregate modified by KH550 forms a hydrophobic surface, effectively preventing the intrusion of moisture. The use of modified recycled PET fiber improves the adhesion between the fiber and asphalt, further improving the freeze-thaw splitting strength ratio of the mixture. This interaction helps to maintain the structural integrity of the asphalt matrix during freeze-thaw cycles, reducing the intrusion of moisture and splitting damage. However, when the fiber content reaches 0.6% (Example 3), the freeze-thaw splitting strength ratio is slightly lower than that of Example 2, which may be due to the local weakening of the matrix structure caused by the excessive incorporation of fiber.

[0095] Table 2 Results of freeze-thaw splitting test

[0096]

[0097] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A modified recycled PET fiber reinforced recycled aggregate asphalt mixture, characterized in that: It is mainly composed of natural aggregate, modified recycled aggregate, mineral powder, matrix asphalt and modified recycled PET fiber components; its components specifically include: 10-20mm limestone aggregate, 5-10mm limestone aggregate, 3-5mm limestone aggregate, 0-3mm limestone aggregate, 4.75-9.5mm modified recycled aggregate, 9.5-13.2mm modified recycled aggregate, 13.2-16mm modified recycled aggregate, 16-19mm modified recycled aggregate, mineral powder, matrix asphalt and modified recycled PET fiber.

2. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 1, characterized in that: The components of the natural aggregate, modified recycled aggregate and mineral powder, calculated by weight, include: 8 parts of 10-20 mm limestone aggregate, 10 parts of 5-10 mm limestone aggregate, 10 parts of 3-5 mm limestone aggregate, 40 parts of 0-3 mm limestone aggregate, 6 parts of 4.75-9.5 mm modified recycled aggregate, 11 parts of 9.5-13.2 mm modified recycled aggregate, 9 parts of 13.2-16 mm modified recycled aggregate, 4 parts of 16-19 mm modified recycled aggregate and 2 parts of mineral powder.

3. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 2, characterized in that: The mass of the matrix asphalt accounts for 5.4% of the total mass of natural aggregate, modified recycled aggregate and mineral powder, and the mass of the modified recycled PET fiber accounts for 0.2% to 0.6% of the mass of the matrix asphalt.

4. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 1, characterized in that: The recycled aggregate is obtained by recycling, crushing and grading waste concrete. Its particle size is 4.75-16mm, the crushing index is 13.6%, the water absorption rate is 4.5%, and the apparent density is 2590.0kg / m 3 , the bulk density is 1285.0kg / m 3 .

5. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 4, characterized in that: The recycled aggregate is modified by using a modifier, gamma-aminopropyltriethoxysilane, to obtain modified recycled aggregate.

6. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 1, characterized in that: The preparation method of the modified recycled aggregate comprises: 1) The recycled aggregate was sanded to reduce the surface roughness, ultrasonically cleaned with deionized water for 10 minutes to remove impurities, and dried in an oven at 105°C for 2 hours to a moisture content of <0.5%; 2) preparing a treatment solution containing 1.5 wt% KH550 + 0.1 wt% acetic acid + 98.4 wt% deionized water and magnetically stirring for 30 minutes; 3) Immerse the dried recycled aggregate in the treatment solution at a solid-liquid ratio of 1:1.5, and shake at a constant temperature of 40°C for 40 minutes; after taking it out, quickly rinse it with deionized water, then place it in a 105°C oven to dry for 1 hour to complete the curing simultaneously, and seal it for storage after cooling.

7. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 1, characterized in that: Recycled PET fiber is obtained by recycling, crushing and re-preparing discarded plastic bottles. Its physical properties are as follows: length: 6mm, diameter: 15.6μm, strength retention rate: 93.2%, tensile strength: 700MPa, elongation at break: 16.5%, melting point: 255℃.

8. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 7, characterized in that: The regenerated PET fiber is modified by using gamma-aminopropylmethyldiethoxysilane to obtain modified regenerated PET fiber.

9. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to claim 1, characterized in that: The preparation method of the modified regenerated PET fiber comprises: a) Add 50 parts of water, 50 parts of KH902 modifier and 1000 parts of anhydrous ethanol into a beaker and stir with a magnetic stirrer for 30 minutes to obtain a modified solution; b) taking 100 parts of the opened regenerated PET fibers and immersing them in the above-mentioned modification solution, placing them in an environment at 25° C. for 2 hours, then filtering them, and then drying the treated regenerated PET fibers in an oven at 60° C. to constant weight; c) The dried regenerated PET fibers are opened again and placed in a sealed bag for later use.

10. The modified recycled PET fiber reinforced recycled aggregate asphalt mixture according to any one of claims 1 to 9, characterized in that: The method for preparing the modified recycled PET fiber reinforced recycled aggregate asphalt mixture comprises the following steps: S1: Heat the natural aggregate, modified recycled aggregate and mineral powder in an oven at 180°C for more than 4 hours; S2: Slowly add the modified recycled PET fiber into the matrix asphalt in a 170°C oil bath and stir at 1000 rpm for 15 min to ensure uniform dispersion of the fiber; S3: Place the preheated aggregates of each grade and modified recycled aggregate into a mixing pot at 170°C and mix for 60 seconds; S4: Add the fiber pitch in step S2 into the mixing pot and mix for 60 seconds; S5: adding the preheated mineral powder into the mixing pot and stirring for 60 seconds; after the stirring is completed, the modified recycled PET fiber reinforced recycled aggregate asphalt mixture is obtained.

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