A palm oil-based recycled asphalt mixture and a method of preparing the same

Abstract

The present application belongs to the technical field of recycled asphalt mixture, and particularly relates to a palm oil-based recycled asphalt mixture and a preparation method thereof. Palm oil is used as a raw material to prepare a recycling agent, and then the recycling agent is added in the preparation process of the recycled asphalt mixture, so that the effect of toughening the asphalt mixture is achieved. The bio-based modifier recycled asphalt mixture prepared by the present application can restore the high-temperature stability and low-temperature crack resistance of aged asphalt, has good mechanical properties and water stability, and can guarantee the safety of the recycled asphalt mixture and the green and low-carbon production process.

Description

Technical Field

[0001] This invention belongs to the field of recycled asphalt mixture technology, specifically relating to a palm oil-based recycled asphalt mixture and its preparation method. Background Technology

[0002] Adding an appropriate amount of reclaimed asphalt pavement (RAP) with a rejuvenator can effectively improve its low-temperature crack resistance and fatigue performance. Currently, commonly used rejuvenators on the market are mixtures of lubricating oil, mineral oil, and asphalt, with the base oils mostly being petroleum-based products. To reduce the consumption of petroleum-based products and achieve the goal of "carbon reduction," the development of novel non-petroleum-based asphalt rejuvenators has become a hot topic. The rejuvenator is dispersed in droplet form on the surface of the reclaimed asphalt particles through mechanical mixing and adheres to the asphalt. Under external force, it forms a rejuvenator film encapsulating the reclaimed asphalt, then moves into the interior of the reclaimed asphalt through diffusion and mixes with it, thereby restoring the performance of the reclaimed asphalt. Vegetable oils contain both polar ester groups and non-polar straight-chain alkanes. Using them as base oil raw materials to prepare asphalt rejuvenators results in rejuvenators with an amphiphilic structure, capable of both adsorbing asphaltenes and fusing with them through non-polar straight-chain alkanes. Related studies have shown that vegetable oil can restore the softening point, penetration and ductility of aged asphalt, and improve the fatigue performance and low-temperature crack resistance of aged asphalt, but will reduce its high-temperature rutting resistance.

[0003] This invention uses palm oil-based resin as a regenerator for old asphalt. As a vegetable oil-based regenerator, palm oil-based resin can restore the high-temperature performance and crack resistance of aged asphalt, while ensuring the safety of the recycled asphalt mixture. Furthermore, the production process is green and environmentally friendly, featuring low cost, easy processing, renewability, and abundant raw material resources. The palm oil molecule mainly consists of three fatty acid chains linked by glycerol. The ester group, as the active functional group in the triglyceride molecule, is converted into a low-molecular-weight, low-viscosity monoglyceride through an alcohol-ester transesterification reaction. The palm oil-based resin synthesized via this route exhibits high activity and can dissolve aged asphalt, restoring its mechanical properties, processing properties, and the road performance of its mixture. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing asphalt recycling agents by providing a palm oil-based recycled asphalt mixture and its preparation method. The modified recycled asphalt mixture prepared by this invention can restore the high-temperature performance and crack resistance of aged asphalt, while ensuring the safety of the recycled asphalt mixture. Furthermore, the production process is green and environmentally friendly, and it possesses excellent mechanical properties, high-temperature stability, low-temperature crack resistance, and water stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The palm oil-based recycled asphalt mixture comprises old asphalt mixture, new asphalt, basalt aggregate, mineral powder, and palm oil-based recycler. The asphalt mixture gradation type is AC-20, where the old asphalt mixture (RAP) accounts for 30% to 90% of the total mass of the recycled asphalt mixture. The RAP is categorized into three sizes: 9.5–20 mm, 4.75–9.5 mm, and 0–4.75 mm. The basalt aggregate is categorized into four sizes: 10–20 mm, 5–10 mm, 3–5 mm, and 0–3 mm. The old asphalt mixtures of various grades, basalt aggregates, and mineral powder are mixed in the following mass ratios (9.5~20mm : 9.5~4.75mm : 4.75~0mm : 10~20mm : 5~10mm : 3~5mm : 0~3mm : mineral powder = 24 : 14 : 7 : 15 : 10 : 7 : 20 : 3) to form the target gradation (gradation curve as shown). Figure 1 (As shown). The amount of new asphalt used accounts for 4.0% to 5.5% of the total mass of the old asphalt mixture, basalt aggregate, and mineral powder used; the amount of recycling agent POFA-EA is 3% to 15% of the mass of asphalt contained in the old material.

[0007] The preparation process of the regenerator POFA-EA is based on patent CN111533843A: A high-performance bio-based resin and its preparation method and application, including the following steps:

[0008] (1) Take 150g (0.32mol) of palm oil and 150mL of tetrahydrofuran respectively, place them in a 500mL three-necked round-bottom flask, and stir magnetically for 2min until they are mixed evenly;

[0009] (2) Add N 115 g (1.0 mol) of 2-(2-hydroxyethyl)acrylamide (HEAA) was added, followed by the addition of 0.3 g of 2,6-dimethylphenol as a polymerization inhibitor;

[0010] (3) The reaction was carried out at 40°C, and NaOH (5g) powder was slowly added as a catalyst during the reaction.

[0011] (4) The reaction proceeded until the solution was completely homogeneous (about 16 h); the reaction product was diluted with dichloromethane and purified with brine, and then dried under vacuum to obtain a white solid POFA-EA with a yield of 93.4% (205 g).

[0012] The preparation process of modified recycled asphalt mixture includes the following steps:

[0013] (1) RAP material is divided into three grades according to particle size: 9.5~20mm, 4.75~9.5mm and 0~4.75mm. The aggregate of each grade is weighed separately using an electronic scale according to the mass ratio (9.5~20mm : 9.5~4.75mm : 4.75~0mm = 24 : 14 : 7). The three grades of RAP material are placed on the same tray and preheated in an oven at 130℃ for 2 hours.

[0014] (2) Basalt aggregates are divided into four grades according to particle size: 10~20mm, 5~10mm, 3~5mm and 0~3mm. Basalt aggregates and mineral powder of each grade are weighed separately using an electronic scale in the ratio (10~20mm : 5~10mm : 3~5mm : 0~3mm : mineral powder = 15 : 10 : 7 : 20 : 3). Basalt aggregates of each grade are placed on the same tray, and mineral powder is placed on another tray. Then, basalt aggregates and mineral powder are placed in an oven and preheated at 180℃ for 4 hours.

[0015] (3) Weigh out POFA-EA, the amount of which is 3% to 15% of the mass of asphalt contained in the old material;

[0016] (4) Put the RAP material and the preheated basalt aggregate mixture into the mixing pot and mix at 180°C for 60 seconds.

[0017] (5) POFA-EA and new asphalt are mixed at 150°C and the asphalt is mixed evenly by high-speed rotational shearing method at a shearing rate of 1000 r / min for 10 min.

[0018] (6) Add a mixture of new asphalt (the amount of new asphalt accounts for 4.0%~5.5% of the total mass of RAP material, new aggregate and mineral powder used) and recycling agent POFA-EA to the mixing pot and mix for 60s;

[0019] (7) Add the preheated mineral powder to the mixing pot and mix for 60 seconds;

[0020] (8) After the mixture is well mixed, take it out immediately, put it into the mold, compact it into shape, let it cool naturally for 12 hours, and then demold it for testing.

[0021] The beneficial effects of this invention are as follows:

[0022] 1) Compared with existing technologies, the most significant difference of this invention lies in the fact that palm oil-based resin, as a vegetable oil regenerator, can restore the high-temperature performance and crack resistance of aged asphalt, while ensuring the safety of recycled asphalt mixtures. Furthermore, its production process is green and environmentally friendly, featuring low cost, easy processing, renewability, and abundant raw material resources. The palm oil molecule mainly consists of three fatty acid chains linked by glycerol. The ester group, as an active functional group in the triglyceride molecule, can be converted into low-molecular-weight, low-viscosity monoglycerides through transesterification of alcohols and ester groups. The palm oil-based resin synthesized via this route exhibits high activity and can dissolve aged asphalt, restoring its mechanical properties, processing properties, and the road performance of its mixtures. Its synthesis mechanism is as follows: under the catalysis of sodium hydroxide… N -(2-hydroxyethyl)acrylamide (HEAA) undergoes a transesterification reaction with palm oil triglycerides to yield palm oil vinyl monoglyceride (POFA-EA) containing an active double bond, such as... Figure 2 As shown, POFA-EA exhibits high reactivity and can rapidly undergo free radical polymerization. The palm oil-based monomers converted through this pathway have small molecular weights and low viscosity, exhibiting excellent compatibility with asphalt and the ability to wet the surface of recycled aggregates. Furthermore, during the mixing process between palm oil vinyl monomers and aged asphalt, weak intermolecular interactions, such as van der Waals forces and hydrogen bonding, can occur. These interactions help enhance the compatibility between the two phases, forming a three-dimensional network structure that strengthens and toughens the asphalt.

[0023] 2) Infrared spectra of palm oil, HEAA, and POFA-EA ( Figure 3 As can be seen, POFA-EA exhibits characteristic peaks typical of palm oil molecules, namely the stretching vibrations of ‒CH2‒ and ‒CH3 on the fatty acid chain (2924 cm⁻¹). −1 and 2857cm −1 ) and bending vibration (1458cm) −1 Due to the transesterification reaction between palm oil and HEAA, the stretching vibration peaks of the C=O and C‒O‒C groups on palm oil triglycerides increased from 1751 cm⁻¹. −1 and 1164cm −1 Redshifted to 1733cm −1 And up to 1175 cm −1 This confirmed the transesterification reaction between the two. No characteristic ‒OH peak (located at 3283 cm⁻¹) from HEAA was found in the POFA-EA spectrum. −1 and 1060cm −1 (stretching and bending vibrations at the point), but the POFA-EA spectrum retains N-H bonds from HEAA in the 3122~3588 cm⁻¹ range. −1 and 1556cm −1The stretching and bending vibration peaks at 1659 cm⁻¹ and 1659 cm⁻¹ −1 The peak of C=O stretching vibration of the amide group was observed; in addition, the C=C bond of HEAA was observed (1621 cm⁻¹) in the POFA-EA spectrum. −1 The stretching vibration peaks of POFA-EA were observed. These results further confirmed the successful synthesis of the transesterification reaction and POFA-EA.

[0024] 3) POFA-EA 1 H spectrum Figure 4 As shown, the main characteristic peaks (unit: ppm) and their corresponding covalent bonds are: 0.84 (‒CH3‒), 1.21 (‒CH2‒), 1.57 (‒O‒CO‒CH2‒CH2‒), 1.96 (‒CH2‒CH=CH‒CH2‒), 2.26~2.31 (‒O‒CO‒CH2‒), 3.50~3.56 (‒NH‒CH2‒), 4.13~4.17 (‒CO‒O‒CH2‒), 5.26~5.34 (‒CH=CH‒), 5.56~5.62 and 6.10~6.15 (‒CH=CH2), 6.17 (‒NH‒). 6.19~6.24(‒CH=CH2). POFA-EA 13 C spectrum Figure 5 As shown, the main characteristic peaks (unit: ppm) and their corresponding covalent bonds are: 13.98 (CH3), 22.45~31.98 (CH2), 34.02 (OCOC), 38.77 (NHC), 62.87 (COOC), 126.67 (CH2=C), 129.73~130.23 (C=C), 130.42 (CH2=C), 166.73 (NHCO), 173.86 (COO).

[0025] 4) Differential scanning calorimetry analysis of the recycling agent and its asphalt mixture ( Figure 6 As can be seen, both the curves of the regenerator and its asphalt mixture show a distinct curing exothermic peak, indicating that the resin system has high reactivity. The exothermic peak temperatures of the regenerator POFA-EA and its asphalt mixture are 141.4℃ and 161.2℃, respectively. The reactivity of the regenerator POFA-EA is higher than that of the asphalt mixture, and the incorporation of asphalt has a delaying effect on the curing of the regenerator POFA-EA.

[0026] 5) The modified recycled asphalt mixture prepared by this invention can restore the high-temperature stability and low-temperature crack resistance of aged asphalt, and can also ensure the safety of the recycled asphalt mixture. Moreover, the production process is green and environmentally friendly, and it has excellent mechanical properties and water stability.

[0027] 6) The recycled asphalt mixture prepared by this invention helps reduce the use of petroleum-based products, contributes to the development of a low-carbon economy, protects the environment, and makes full use of waste materials (waste aggregates, aged asphalt, etc.). Palm oil-based recyclers have the characteristics of low cost, easy processing, renewability, and abundant raw material resources. Compared with conventional commercial recyclers, the recycled asphalt mixture prepared by this invention has a low cost. Attached Figure Description

[0028] Figure 1 This is the AC-20 gradation curve diagram;

[0029] Figure 2 This is the synthetic route diagram for POFA-EA;

[0030] Figure 3 These are Fourier transform infrared spectra of palm oil, HEAA, and POFA-EA;

[0031] Figure 4 It is the POFA-EA nuclear magnetic resonance. 1 H spectrum;

[0032] Figure 5 It is POFA-EA nuclear magnetic resonance imaging. 13 C spectrum;

[0033] Figure 6 It is a differential scanning calorimetry (DSC) graph of the recycling agent and its asphalt mixture;

[0034] Figure 7 This refers to the Marshall stability of modified recycled asphalt mixtures. The horizontal lines above and below the rectangular bars in the graph represent the standard deviation of the data mean. The absence of identical letters above the bars indicates a significant difference between the means of the two sets of data; otherwise, the difference is not significant. P >0.05); control group (97% basalt aggregate, 3% mineral powder), old material group (45% old material, 52% basalt aggregate, 3% mineral powder), recycled group (45% old material, 52% basalt aggregate, 3% mineral powder, 9% regenerator).

[0035] Figure 8 It is the indirect tensile property of recycled asphalt mixture;

[0036] Figure 9 It is the high-temperature stability of recycled asphalt mixtures;

[0037] Figure 10 It refers to the low-temperature flexural properties of recycled asphalt mixtures. Detailed Implementation

[0038] To further disclose, and not limit, the present invention, the invention will be further described in detail below with reference to examples.

[0039] The raw material composition of recycled asphalt mixture: the amount of recycling agent POFA-EA is 9% of the mass of asphalt contained in the old material; the ratio of the total mass of new petroleum asphalt to the total mass of new and old aggregates (old asphalt mixture + basalt aggregate + mineral powder) (oil-aggregate ratio) is 4.26%, and the mixture is of AC-20 type gradation.

[0040] The specific preparation steps for recycled asphalt mixture are as follows:

[0041] Step 1: Weigh out the recycling agent POFA-EA (the amount of recycling agent accounts for 9% of the mass of asphalt in the old material) and melt and mix it with the new asphalt in an oil bath at 150°C. Use high-speed rotary shearing to mix the new asphalt and recycling agent evenly. The shearing rate is 1000 r / min. Stir for 10 min and set aside.

[0042] Step 2: The old asphalt mixture (RAP) is divided into three grades according to particle size: 9.5~20mm, 4.75~9.5mm, and 0~4.75mm. The aggregates of each grade are weighed separately using an electronic scale according to the mass ratio (9.5~20mm : 9.5~4.75mm : 4.75~0mm = 24 : 14 : 7) (310.0g of 9.5~20mm aggregate, 183.8g of 9.5~4.75mm aggregate, and 90.4g of 4.75~0mm aggregate). The three grades of old asphalt mixture are placed on the same tray and preheated in an oven at 130℃ for 2 hours. Basalt aggregates are categorized into four grades based on particle size: 10-20mm, 5-10mm, 3-5mm, and 0-3mm. Each grade of basalt aggregate and mineral powder is weighed separately using an electronic scale according to the mass ratio (10-20mm : 5-10mm : 3-5mm : 0-3mm : mineral powder = 15 : 10 : 7 : 20 : 3). The weights are 187.5g for 10-20mm aggregate, 125g for 5-10mm aggregate, 87.5g for 3-5mm aggregate, 250g for 0-3mm aggregate, and 37.5g for mineral powder. The basalt aggregates are placed on one tray, and the mineral powder on another. The basalt aggregates and mineral powder are preheated in an oven at 180℃ for 4 hours. The preheated aggregates are then placed together in a mixing pot and mixed at 180℃ for 60 minutes. 54.0g of petroleum asphalt (the amount of new asphalt accounts for 4.26% of the total mass of the old asphalt mixture, basalt aggregate and mineral powder) and POFA-EA (1.68g, the amount of POFA-EA is 9% of the mass of the old asphalt) were mixed at 150℃, and the asphalt and the recycling agent were mixed evenly by high-speed rotary shearing method at a shearing rate of 1000r / min for 10min; the mixture of new asphalt and recycling agent was poured into a mixing pot and mixed for 60s; preheated mineral powder was added to the mixing pot and mixed for 60s; after the mixture was well mixed, it was immediately taken out, put into a mold, compacted and shaped, and allowed to cool naturally for 12h before demolding for testing.

[0043] Raw materials: Used asphalt mixture, sourced from milled material from the Zhangzhou section of the Xiamen-Chengdu Expressway; basalt aggregate purchased from Zhangzhou, Fujian; mineral powder, white powdered limestone; petroleum asphalt (Grade A, No. 70; penetration 7.08mm (25℃); softening point 47.6℃), purchased from Xiamen Huatai Group Co., Ltd.; palm oil (melting point 18℃; acid value 0.16 mg KOH / g), purchased from Shanghai Dingfen Chemical Co., Ltd. N -(2-hydroxyethyl)acrylamide (HEAA, >98%) and 4-dimethylaminopyridine (DMAP, >99%) were purchased from Aladdin Company (Shanghai). Sodium chloride (NaCl, ≥99.5%), dichloromethane (CH2Cl2, ≥99.5%), sodium hydroxide (NaOH, ≥96%), and tetrahydrofuran (THF, ≥99.5%) were purchased from Sinopharm Group (Shanghai).

[0044] Example 1 (Control Group)

[0045] The preparation process of Marshall samples for the control group asphalt mixture was as follows: basalt aggregate was divided into four grades according to particle size: 10~20mm, 5~10mm, 3~5mm, and 0~3mm. The basalt aggregate and mineral powder of each grade were mixed in the following mass ratio (10~20mm : 5~10mm : 3~5mm : 0~3mm : mineral powder = 33 : 20 : 18 : 25 : 4) Weigh the following using an electronic scale (the total mass of aggregate for one Marshall specimen is 1250g, of which 412.5g is 10-20mm aggregate, 250g is 5-10mm aggregate, 225g is 3-5mm aggregate, 312.5g is 0-3mm aggregate, and 37.5g is mineral powder). Place the basalt aggregates of each grade on the same tray and the mineral powder on another tray. Preheat the basalt aggregates and mineral powder separately in an oven at 180℃ for 4 hours. Put the preheated basalt aggregates into a mixing pot and mix at 180℃ for 60 seconds. Add 47.5g of petroleum asphalt to the mixing pot (the amount of asphalt accounts for 3.8% of the total mass of basalt aggregates and mineral powder used) and mix for 60 seconds. Add the preheated mineral powder to the mixing pot and mix for 60 seconds. After the mixture is well mixed, immediately remove it, put it into a mold, compact it, and let it cool naturally for 12 hours before demolding.

[0046] Example 2 (used materials, without recycling agent)

[0047] The preparation process of RAP asphalt mixture composite material is as follows: RAP material is divided into three grades according to particle size: 9.5~20mm, 4.75~9.5mm and 0~4.75mm. The aggregates of each grade are weighed separately using an electronic scale according to the mass ratio (9.5~20mm : 9.5~4.75mm : 4.75~0mm = 24 : 14 : 7) (310.0g of 9.5~20mm aggregate, 183.8g of 9.5~4.75mm aggregate, and 90.4g of 4.75~0mm aggregate). The three grades of RAP material are placed on the same tray and preheated in an oven at 130℃ for 2 hours. Basalt aggregate is classified into four grades according to particle size: 10-20mm, 5-10mm, 3-5mm, and 0-3mm. The mass ratio of basalt aggregate to mineral powder for each grade is (10-20mm : 5-10mm : 3-5mm : 0-3mm : mineral powder = 15 : 10 : 7 : 20 : 3) Weigh the following materials using an electronic scale: 187.5g for 10-20mm aggregate, 125g for 5-10mm aggregate, 87.5g for 3-5mm aggregate, 250g for 0-3mm aggregate, and 37.5g for mineral powder. Place the basalt aggregates of each grade on one tray and the mineral powder on another tray. Preheat the basalt aggregates and mineral powder separately in an oven at 180℃ for 4 hours. Place the preheated new and old aggregates together in a mixing pot and mix at 180℃ for 60 seconds. Add 55.7g of petroleum asphalt to the mixing pot (the amount of new asphalt accounts for 4.39% of the total mass of the old asphalt mixture, basalt aggregate, and mineral powder used), and mix for 60 seconds. Add the preheated mineral powder to the mixing pot and mix for 60 seconds. After the mixture is well mixed, immediately remove it, put it into a mold, compact it, and let it cool naturally for 12 hours before demolding.

[0048] Example 3 (Regeneration Group, with Added Regenerant)

[0049] The specific steps for preparing recycled asphalt mixtures are as follows:

[0050] (1) Weigh out POFA-EA (1.68g, the amount of POFA-EA is 9% of the mass of asphalt contained in the old material);

[0051] (2) The RAP material is divided into three grades according to the particle size: 9.5~20mm, 4.75~9.5mm and 0~4.75mm. The aggregates of each grade are weighed separately using an electronic scale according to the mass ratio (9.5~20mm : 9.5~4.75mm : 4.75~0mm = 24 : 14 : 7) (310.0g of 9.5~20mm aggregate, 183.8g of 9.5~4.75mm aggregate, and 90.4g of 4.75~0mm aggregate). The three grades of RAP material are placed on the same tray and preheated in an oven at 130℃ for 2 hours. Basalt aggregates were divided into four grades according to particle size: 10-20mm, 5-10mm, 3-5mm, and 0-3mm. Basalt aggregates and mineral powder of each grade were weighed separately using an electronic scale according to the mass ratio (10-20mm: 5-10mm: 3-5mm: 0-3mm: mineral powder = 15:10: 7: 20: 3). The weights were 187.5g for 10-20mm aggregates, 125g for 5-10mm aggregates, 87.5g for 3-5mm aggregates, 250g for 0-3mm aggregates, and 37.5g for mineral powder. The basalt aggregates of each grade were placed on one tray, and the mineral powder on another. The basalt aggregates and mineral powder were preheated in an oven at 180℃ for 4 hours. The preheated new and old aggregates were then placed together in a mixing pot and mixed at 180℃ for 60 seconds. Add a mixture of petroleum asphalt (54.0g, the amount of new asphalt accounts for 4.26% of the total mass of the old asphalt mixture, basalt aggregate and mineral powder) and recycling agent POFA-EA (1.68g, the amount of POFA-EA is 9% of the mass of asphalt contained in the old material) to the mixing pot and mix for 60s; add preheated mineral powder to the mixing pot and mix for 60s; after the mixture is well mixed, immediately remove it, put it into the mold, compact it into shape, and let it cool naturally for 12 hours before demolding.

[0052] Asphalt mixture performance testing:

[0053] The Marshall stability, indirect tensile strength, and water stability tests of asphalt mixtures were conducted using standard Marshall specimens (101.6 mm in diameter, 63.5 mm in height). High-temperature stability tests were conducted using rutted slab specimens (300 mm long, 300 mm wide, 50 mm high). Low-temperature crack resistance tests were conducted using small beam specimens (250 mm long, 30 mm wide, 35 mm high). The preparation methods for Marshall specimens, small beam specimens, and rutted slab specimens were the same, differing only in size. The mixture gradation type adopted is fixed gradation AC-20. The control group is basalt asphalt mixture without RAP (97% basalt aggregate, 3% mineral powder). According to the preliminary test results, the optimal asphalt-aggregate ratio of the control group is 3.8%. The optimal asphalt-aggregate ratio of both the old material group (45% RAP, 52% basalt aggregate, 3% mineral powder) and the recycled group (45% RAP, 52% basalt aggregate, 3% mineral powder, 9% recycling agent POFA-EA) is 5.95%.

[0054] Tables 1-2 and Figures 7-10 The results are from tests conducted in accordance with the requirements of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" JTG E20-2011.

[0055] Marshall stability of recycled asphalt mixture

[0056] Depend on Figure 7 The Marshall stability was 9.13 kN for the control group, 8.78 kN for the recycled material group, and 9.42 kN for the regenerated group. The Marshall stability of the recycled material group was significantly lower than that of the control group, while the Marshall stability of the regenerated group was slightly higher than that of the control group. The Marshall stability of the regenerated group was 3.18% and 7.29% higher than that of the control group and the recycled material group, respectively.

[0057] Indirect tensile properties of recycled asphalt mixtures

[0058] Depend on Figure 8 It is known that the indirect tensile strength of the control group was 1827 kPa, the indirect tensile strength of the recycled material group was 1568 kPa, and the indirect tensile strength of the recycled group was 1775 kPa. The indirect tensile strength of the recycled group was 13.2% higher than that of the recycled material group, but there was no significant difference compared with the control group.

[0059] High-temperature stability of recycled asphalt mixtures

[0060] Depend on Figure 9 The dynamic stability of the control group was 915 cycles / mm, the old material group was 2113 cycles / mm, and the recycled group was 1456 cycles / mm. The control group had the lowest dynamic stability, while the old material group had the highest. The aged asphalt in the RAP mix had a higher viscosity, resulting in greater overall hardness and better high-temperature stability. The dynamic stability of the asphalt mixture after adding the recycling agent POFA-EA decreased by 31.1% compared to the old material group, but increased by 59.1% compared to the control group.

[0061] Low-temperature flexural properties of recycled asphalt mixtures

[0062] Depend on Figure 10 It is known that the bending tensile strain of the control group was 2311 με, the bending tensile strain of the old material group was 3703 με, and the bending tensile strain of the recycled group was 4557 με. The bending tensile strain values ​​were all greater than 2000 με, which met the reliability requirements for the use of asphalt mixtures. Among them, the bending tensile strain of the recycled group was the largest, which was 97.2% and 23.1% higher than that of the control group and the old material group, respectively, indicating that the low-temperature crack resistance of the recycled group was significantly improved.

[0063] Water stability properties of recycled asphalt mixtures

[0064] The main indicators characterizing water stability are residual stability and freeze-thaw splitting strength. As shown in Table 1, the stability of the specimens after immersion in water was lower than that of the conventional stability. The residual stability of the regenerated group was lower than that of the control group, but both were significantly higher than the standard requirements.

[0065] Table 1 Residual Stability

[0066]

[0067] As shown in Table 2, the conventional splitting strength and freeze-thaw splitting strength of the mixed specimens with added regenerator were both improved. Among them, the splitting strength ratio (the ratio of freeze-thaw splitting strength to conventional splitting strength) of the regenerated group was the highest, indicating that the regenerated group with added regenerator POFA-EA has good freeze-thaw resistance.

[0068] Table 2 Freeze-thaw splitting test data

[0069]

[0070] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A palm oil-based recycled bitumen mixture, characterized in that: The asphalt mixture consists of recycled asphalt, new asphalt, basalt aggregate, mineral powder, and recycling agent. The asphalt mixture gradation type is AC-20, with recycled asphalt accounting for 44% of the total mass of the recycled asphalt mixture. The basalt aggregate is divided into four grades based on particle size: 10-20mm, 5-10mm, 3-5mm, and 0-3mm. The recycled asphalt aggregate is divided into three grades based on particle size: 9.5-20mm, 4.75-9.5mm, and 0-4.75mm. The mass ratio of each grade of recycled asphalt mixture, basalt aggregate, and mineral powder is 9.5-20mm : 9.5-4.75mm : 4.75-0mm : 10-20mm : 5-10mm : 3-5mm : 0-3mm : mineral powder = 24 : 14 : 7 : 15 : 10 : 7 : 20 :

3. The target gradation is prepared; the amount of new asphalt accounts for 4.25% of the total mass of the old asphalt mixture, basalt aggregate and mineral powder used; the recycling agent is palm oil fatty acid acrylamide ethyl ester POFA-EA.

2. The palm oil-based recycled bitumen mixture according to claim 1, characterized in that: The recycling agent POFA-EA is used at a rate of 3% to 15% of the mass of old asphalt in the old asphalt mixture.

3. The method for preparing palm oil-based recycled bitumen mixture according to claim 1, characterized in that: Includes the following steps: (1) Weigh out three grades of old asphalt mixture with particle sizes of 9.5~20mm, 4.75~9.5mm and 0~4.75mm respectively. Place the three grades of aggregates on the same tray, and then put the tray and aggregates into an oven to preheat at 130℃ for 2 hours. (2) Weigh out basalt aggregates and mineral powder of four grades with particle sizes of 10~20mm, 5~10mm, 3~5mm and 0~3mm respectively. Place the basalt aggregates of each grade on the same tray and the mineral powder on another tray. Then put the basalt aggregates and mineral powder into an oven and preheat at 180℃ for 4 hours. (3) Put the old asphalt mixture and basalt aggregate into the mixing pot and mix at 180°C for 60 seconds; (4) Mix the new asphalt and the recycling agent POFA-EA and stir evenly, then pour into the mixing pot and stir for 60 seconds; (5) Add the preheated mineral powder to the mixing pot and mix for 60 seconds; (6) After the mixture is well mixed, take it out immediately, put it into the mold, compact it into shape, and let it cool naturally for 12 hours before demolding and testing.

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