A method for preparing structural synergistically reinforced high-performance modified asphalt by using plant shell and the modified asphalt

Abstract

The application discloses a method for preparing high-performance modified asphalt with structural synergistic reinforcement by using plant shells and the modified asphalt, and relates to the technical field of asphalt preparation for road engineering. The method comprises the following steps: drying, pre-pulverizing and sieving the plant shells; performing degreasing by immersing the plant shells in a degreasing agent; performing extraction by heating a neutral detergent buffer solution and performing ice-bath extraction; performing secondary refinement by using a wet grinding method; performing ultrasonic-assisted surface activation modification on the plant shells by using a pre-hydrolyzed silane coupling agent solution; drying and solidifying the plant shell fine powder to be used as a modified asphalt agent; adding the modified asphalt agent into base asphalt according to 3-10 wt% of the weight of the base asphalt; performing high-speed shearing mixing and uniform dispersion; and performing vacuum degassing to obtain the modified asphalt. On the basis of the synergistic modification effect of the symbiotic forms of lignin-cellulose-phenols and the like in the original structure of the plant shells, the application further proposes a three-step synergistic process path of "degreasing treatment, surface activation and high-speed shearing", which can solve the key problems of the natural plant shell powder modified material, such as poor dispersibility, unstable interface and low aging performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of asphalt materials for road engineering, in particular to a method for preparing high-performance modified asphalt with structural synergistic reinforcement using plant shells and modified asphalt, especially to a method for preparing high-performance modified asphalt with structural synergistic reinforcement by using plant shells as raw materials through a dry-pre-pulverization-degreasing-neutral washing-wet planetary ball milling cascade process and modified asphalt. BACKGROUND

[0002] Asphalt is a widely used binding material in road engineering. In order to improve its high-temperature stability, low-temperature crack resistance, and durability, modification techniques are usually used to enhance the performance of base asphalt. Existing modification techniques can be mainly divided into two categories: one is to use synthetic polymer materials such as SBS (styrene-butadiene-styrene), PE (polyethylene), EVA (ethylene-vinyl acetate), etc. This type of modifier has a significant effect on improving the performance of asphalt, but it has problems such as high price, non-renewable, high energy consumption in preparation, and resource dependence on the petrochemical industry. The other is an environmentally friendly modifier based on renewable or natural materials, such as waste tire rubber powder, mineral cellulose, and plant powder. In recent years, agricultural and forestry waste such as coconut shell powder, corn cob, and rice husk has been explored for asphalt modification in order to obtain renewable and low-carbon green road materials. Among them, plant shells have attracted attention due to their stable biological structure, strong adsorption capacity, and abundant sources, becoming a potential low-cost modification material.

[0003] Existing plant shell modification materials mainly use a simple method of "physical pulverization + mechanical stirring" to add them to asphalt. For example, Chinese patent document CN118879090A discloses a low-carbon high-performance modified asphalt and asphalt concrete and a preparation method thereof. In this scheme, waste camellia shell is pulverized into camellia shell powder, which is then directly added to base asphalt at a mass fraction of 4-16 wt%. After modification by mixing, a modified asphalt material with excellent high-temperature performance and good creep performance is obtained. However, this method of adding plant shell modification materials to asphalt by "physical pulverization + mechanical stirring" has the following disadvantages:

[0004] (1) Existing plant shell modification materials have large particle sizes and poor dispersibility, leading to insufficient compatibility of asphalt. Existing plant shells are mostly coarse powders, which are simply physically mixed into asphalt. Due to the lack of particle size control and surface polarity matching treatment, they are unevenly distributed, agglomerated, or severely settled in asphalt, making it difficult to form a stable spatial framework structure and affecting the uniformity and mechanical stability of the material.

[0005] (2) Plant fiber surface inert, lack of intermolecular interface with asphalt. Natural plant shell powder is mostly hydrophobic inert surface, lack of active groups, difficult to react with the polar molecules or resin components in asphalt or form a stable interface layer, thereby reducing the modification efficiency, leading to the increase of the performance of limited dosage.

[0006] (3) The existing natural plant shell modification material has weak anti-aging ability in asphalt, and it is difficult to inhibit thermal oxidation and ultraviolet degradation. The existing natural plant shell modification material lacks shielding ability for thermal aging and ultraviolet aging, especially under high temperature or sunlight conditions, asphalt is prone to hardening, brittle cracking and other failure problems, which affects the service life of the pavement.

[0007] (4) The existing modification method is mostly single physical mixing, lacking of composite activation and high-efficiency dispersion means. The plant shell modified asphalt on the market mostly uses mechanical stirring for direct addition, without chemical modification or microstructure regulation, which leads to limited modification effect, poor process stability, and is not conducive to industrialization promotion.

[0008] It can be seen that the existing adding modification method of "physical crushing + mechanical stirring" cannot solve the core technical problems such as powder particle size, dispersion uniformity, interface compatibility and chemical inertness, which leads to limited modification efficiency and insufficient performance improvement, hindering the engineering application and promotion of this kind of green modification technology. Therefore, it is urgent to develop a method for preparing modified asphalt using plant shell as raw material to solve the above technical problems. SUMMARY

[0009] The technical problem to be solved by the present application is to provide a method for preparing structure synergistically enhanced high-performance modified asphalt using plant shell and modified asphalt. The purpose is to utilize the synergistic modification effect of lignin-cellulose-phenolic symbiotic form in the original structure of plant shell; adopt the cascade process of "dry pre-crushing-degreasing-neutral washing, ice bath extraction-wet planetary ball milling secondary refinement", and propose the three-step synergistic process path of "degreasing treatment, surface activation, high-speed shearing", so as to synergistically improve the powder particle size, functional group exposure and interface adhesion, in order to solve the key problems of natural plant shell powder modification material such as poor dispersion, unstable interface and low aging performance.

[0010] In order to solve the above technical problems, the following technical solutions are adopted in the present application:

[0011] In a first aspect, the present application provides a method for preparing structure synergistically enhanced high-performance modified asphalt using plant shell, which comprises the following steps:

[0012] S1, crushing treatment: dry the plant shell, pre-crush and sieve to obtain plant shell particles;

[0013] S2, defatting treatment: the plant shell particles obtained in S1 are immersed with a defatting agent to remove lipid-soluble substances in the cytoplasm to obtain defatted particles; before the defatting treatment, sodium sulfite is added to the plant shell particles to avoid oxidation of phenols;

[0014] S3, washing extraction: the defatted particles of S2 are placed in a neutral detergent buffer solution and heated for extraction for 45-60 min, then washed with distilled water for 2-3 times, and the temperature is maintained at 70-80°C during the operation; before the washing extraction, sodium sulfite is added to the defatted particles to avoid oxidation of phenols; finally, acetone or anhydrous ethanol is used for ice-bath extraction for 2-3 times at 3-5°C, and the purpose of ice-bath extraction is to reduce the solubility of phenols in ethanol and acetone to ensure the retention of free phenols;

[0015] S4, particle refinement: the material obtained in S3 is refined by wet grinding for the second time, dried, and sieved to obtain pretreated plant shell fine powder with a particle size of ≥500;

[0016] S5, surface activation: the pretreated plant shell fine powder obtained in S4 is mixed with a pre-hydrolyzed silane coupling agent solution at a mass ratio of 1:15-1:20, and surface modification treatment is performed at 60-80°C for 1-2 hours under ultrasonic conditions;

[0017] S6, drying and curing: the material obtained in S5 is placed at a temperature of 105°C for 1-2 hours to obtain plant shell fine powder;

[0018] S7, high-speed shearing mixing: the plant shell fine powder obtained in S6 is added to base asphalt as an asphalt modifier at a weight percentage of 3-10 wt% based on the weight of the base asphalt, and high-speed shearing mixing and uniform dispersion are performed;

[0019] S8, vacuum degassing: the mixture treated in S7 is vacuum degassed under negative pressure to obtain the high-performance modified asphalt with structural synergistic reinforcement.

[0020] Further, the plant shell is a natural plant shell, including one or a mixture of two or more of natural plant shells such as litchi shell, oil tea shell, and grain shell (such as rice hull).

[0021] Preferably, the plant shell is litchi shell, and the litchi shell includes the following main components in the following weight percentage:

[0022] Lignin: 34%-36%; cellulose: 25%-30%; hemicellulose: 18%-22%; phenols / tannins: 11%-13%; water-soluble ash: 4%-5%; and the sum of the weight percentages of the main components is not greater than 100%.

[0023] Further, the defatting agent in step S3 is petroleum ether or n-hexane.

[0024] Further, the solid-liquid ratio of the plant shell particles to the degreasing agent in step S3 is 1:5-1:10 g / mL, and the time for stirring and leaching degreasing is 45-60 min.

[0025] Further, the neutral detergent buffer solution in step S4 is composed of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA and 0.05 M sodium borate buffer solution, or composed of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA and 0.05 M disodium hydrogen phosphate buffer solution.

[0026] Further, the solid-liquid ratio of the degreased particles to the neutral detergent buffer solution is 1:30-1:50 g / mL.

[0027] Further, 0.5% by weight of sodium sulfite is added to the plant shell particles in step S3, and 0.5% by weight of sodium sulfite is added to the degreased particles in step S4.

[0028] Further, the silane coupling agent in step S6 is any one of KH550 and KH570.

[0029] Further, the pre-hydrolyzed silane coupling agent solution is prepared by the following method: first, a solution with a mass ratio of anhydrous ethanol to deionized water of 90:10 is prepared, then ice acetic acid is used to adjust the pH of the solution to 2 to serve as a hydrolysis solution, and then a pre-hydrolyzed silane coupling agent solution is prepared by ultrasonic oscillation at 90°C for 15 min according to a mass ratio of the silane coupling agent to the hydrolysis solution of 1:160. Preferably, the ultrasonic oscillation power is 200 w.

[0030] Further, in step S8, the matrix asphalt is first preheated to 130-140°C to melt it, and the high-speed shearing conditions are as follows: a shearing mixing speed of 3000-5000 rpm for 15-30 min, and a preparation temperature of 150-160°C, to ensure that the plant shell fine powder is uniformly dispersed in the matrix asphalt.

[0031] Further, in step S9, the vacuum degree is controlled to be-0.08--0.1 MP.

[0032] In a second aspect, the present application provides a high-performance modified asphalt with structural synergistic reinforcement prepared by the above method.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] The method provided by the application comprises the following steps: drying treatment of plant shell, pre-pulverization and screening; defatting by soaking in a defatting agent; extraction by heating in a neutral detergent buffer solution, and extraction by ice bath; secondary refinement by wet grinding and drying and screening; ultrasonic-assisted surface activation modification by using a pre-hydrolyzed silane coupling agent solution; and drying and solidification of the plant shell fine powder as a bitumen modifier, adding the modifier into base bitumen, high-speed shearing mixing and uniform dispersion; and vacuum degassing to obtain modified bitumen. Firstly, by using a cascade process of "drying, pre-pulverization, defatting, neutral washing and secondary refinement by wet planetary ball milling", the particle size of the plant shell (for example, litchi shell) powder is stably controlled at about 20-30 microns, and free lipids, ash and waxes are removed, so as to avoid the shielding of polar groups and the weakening of interfacial adhesion caused by oil and wax coating. Subsequently, under the condition of 60-80 DEG C, the powder surface is modified in situ by using ultrasonic-assisted silane coupling agent, so that the hydroxyl groups on the powder surface are condensed with the coupling agent to generate polar functional groups with hydrogen bonding and covalent double coupling capacity, and the crosslinking strength of the powder and the polar sites such as phenolic hydroxyl, carbonyl and sulfoxide in bitumen is significantly improved. Then, the activated powder is added into base bitumen at about 160 DEG C at a proportion of 3-10 wt%, and the powder is rapidly dispersed and the coating gas and volatile light components are removed under the condition of high-speed shearing at greater than or equal to 3000 rpm and vacuum degassing at greater than or equal to-0.08 to-0.1 MPa, and at the same time, micro-bubbles formed in the high-speed shearing process are removed. The bubbles further induce local micro-flow in the bitumen during the process of floating and discharging, so as to promote the penetration of the bitumen into the space structure constructed by the cascade process of "drying, pre-pulverization, defatting, neutral washing and secondary refinement by wet planetary ball milling". Thus, a "skeleton-matrix" interpenetrating network is formed at the micro-nano scale, so that the natural antioxidant and ultraviolet-resistant active components can be fully utilized. The process realizes the synergistic enhancement of particle size optimization, interfacial activation and uniform dispersion, and thus the high-temperature rutting resistance, thermal-oxidative and ultraviolet aging resistance and storage stability of the material are simultaneously improved.

[0035] The preparation method of the application can effectively improve the anti-aging performance, low-temperature ductility, adhesion and water stability of the modified bitumen, and has good industrial application prospect.

[0036] The wet ball milling (planetary ball mill) is used in the plant shell powder refinement step, so that the plant shell powder can be further refined to about 20-30 microns, and the specific surface area and reactivity can be significantly improved; and the step lays a foundation for subsequent dispersion. In the subsequent silane coupling agent modification stage, the pre-hydrolyzed silane coupling agent solution is used for ultrasonic-assisted surface activation modification, the ultrasonic wave provides high-frequency mechanical disturbance, promotes the penetration of the coupling agent and activates the powder surface, and realizes the synergistic effect of "particle size optimization-interfacial activation-uniform dispersion". The powder treated in this way can be quickly and uniformly distributed in the bitumen system during high-speed shearing, and the natural antioxidant and ultraviolet-resistant components can be fully released, so that the high-temperature stability, anti-aging ability and storage stability of the modified bitumen are significantly improved.

[0037] The silane coupling agent (such as KH550, KH570) is used for surface modification of plant shell powder in the application, and in the modification process of the plant shell powder, one end of the silane coupling agent molecule will react with the hydroxyl group on the surface of the plant shell, and in the further modification process of the asphalt, the other end of the silane coupling agent molecule will form a hydrogen bond or a chemical bond with the polar functional group in the asphalt, thereby constructing a stable interface connecting layer. This interface enhancement mechanism can significantly improve the bonding strength between the powder and the asphalt matrix, and is a key step to ensure the stability and performance durability of the material. The specific principle is as follows.

[0038] Taking KH550 (gamma-aminopropyl triethoxysilane) as an example, the hydrolysis reaction mechanism formula of the pre-hydrolyzed silane coupling agent in S6 of the application is as follows formula (1).

[0039]

[0040] Formula (1)

[0041] Further, the reaction mechanism formula of surface activation of the pretreated plant shell fine powder by the silane coupling agent in S6 of the application is as follows formula (2).

[0042]

[0043] Formula (2)

[0044] Further, the reaction mechanism formula of using the plant shell fine powder prepared by S6 and S7 as an asphalt modifier to prepare high-performance modified asphalt with structural synergistic enhancement in S8 of the application is as follows formula (3) and formula (4).

[0045]

[0046] Formula (3)

[0047]

[0048] Formula (4)

[0049] The high shear mixing in the preparation method of the application can provide strong mechanical shear force, so that the modified powder can be quickly dispersed in the asphalt and form a uniform network structure. Further, vacuum degassing can effectively remove the micro-bubbles and low molecular residues introduced during the mixing process, improve the compactness and thermal stability of the system, and further enhance the storage stability and construction performance of the asphalt.

[0050] The multi-step treatment in the preparation method of the application is not performed independently, but forms a progressive enhancement mechanism of "structure activation-particle size optimization-interface construction-uniform distribution-system stability". Each step supports each other, and together improves the action efficiency of the modifier in the asphalt, realizes the multi-scale synergistic effect from microstructure regulation to macro performance improvement.

[0051] The modified asphalt prepared by the method of this invention has a significantly improved softening point compared with petroleum-based asphalt and the comparative scheme described in this invention, a significantly enhanced shear modulus, and more stable penetration loss after TFOT (asphalt film heating test) and UV aging compared with the comparative example, exhibiting excellent high-temperature stability and aging durability.

[0052] In summary, the method provided by this invention is suitable for further optimizing the performance of natural plant shells as asphalt modifiers. It fully utilizes low-cost natural plant shells as raw materials, achieving comprehensive resource utilization of these materials. Furthermore, it overcomes the technical bottlenecks of traditional plant shell modifiers in terms of dispersibility, interfacial compatibility, and anti-aging capabilities, significantly improving the dispersion uniformity and structural stability of plant shell modifiers in asphalt. Moreover, this method is mild, highly adaptable to equipment, and utilizes widely available and low-cost plant shells, making it green, low-carbon, and environmentally friendly. It achieves comprehensive resource utilization of plant shells and has good industrialization prospects and promotional value. Attached Figure Description

[0053] Figure 1 This is a schematic flowchart illustrating a method for preparing high-performance modified asphalt with synergistic structural reinforcement using lychee shells as raw materials, as an embodiment of the present invention. Detailed Implementation

[0054] As used in this article:

[0055] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0056] When a parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1~5” is disclosed, the described range should be interpreted as including the ranges “1~4”, “1~3”, “1~2”, “1~2 and 4~5”, “1~3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0057] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0058] For the purposes of this disclosure, reference will be made to the accompanying drawings which form a part of the disclosure. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the application. The embodiments of the application illustrated herein are by way of example only and various modifications can be made thereto without departing from the spirit of the application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise noted, conventional methods of mass spectroscopy, molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry, and immunology were used, unless otherwise indicated. The reagents used in the examples were obtained from commercial suppliers unless otherwise noted.

[0060] The present application provides a method for preparing a high-performance modified asphalt with structural synergistic reinforcement using plant shells. The plant shells defined in the present application refer to natural plant shell materials whose main components are lignin, cellulose, and phenolic substances (mainly tannin substances). The lignin-cellulose forms a three-dimensional skeleton, which can enhance high-temperature stability and low-temperature flexibility; the phenolic substances (tannins) provide antioxidant and anti-ultraviolet aging functions. The plant shells in the present application include one or a mixture of two or more of litchi shells, oil tea shells, and grain shells (such as rice husks). The specific embodiments of the present application are exemplified by natural plant shells, litchi shells. The preparation method specifically includes the following steps:

[0061] S1, crushing treatment: first, dry the litchi shells. Specifically, wash and chop the litchi shells, and then naturally air dry or low-temperature dry at 40-50°C. The natural drying or low-temperature drying time is 48-60h. Generally, the litchi shells include the following main components with the following weight percentage contents: lignin: 34%-36%; cellulose: 25%-30%; hemicellulose: 18%-22%; phenolic substances (tannins): 11%-13%; water-soluble ash: 4%-5%; the sum of the weight percentages of the main components is not greater than 100%. After drying treatment, the litchi shells are pre-pulverized and sieved through a 40-60 mesh screen to obtain litchi shell particles.

[0062] S2, defatting treatment: add 0.5% sodium sulfite by weight of the litchi shell particles to the litchi shell particles obtained in S1 to prevent phenolic oxidation, and then use a defatting agent for leaching to remove lipid-soluble substances in the cytoplasm to obtain defatted particles. The defatting agent is petroleum ether or n-hexane, and the solid-liquid ratio of the litchi shell particles to the defatting agent is 1:5-1:10 g / mL. The stirring leaching time for defatting is 45-60 min.

[0063] S3, washing extraction: add 0.5% sodium sulfite to the defatted particles of S2 to prevent phenolic oxidation, then place them in a neutral detergent buffer solution for heating extraction for 45-60 min, then wash and extract 2-3 times with distilled water, and the temperature is maintained at 70-80°C during the operation; finally, extract 2-3 times with acetone or anhydrous ethanol in an ice bath at 3-5°C; the purpose of ice bath extraction is to reduce the solubility of phenols in ethanol and acetone to ensure the retention of free phenols.

[0064] The neutral detergent buffer solution is composed of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA, and 0.05 M sodium borate buffer, or composed of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA, and 0.05 M disodium hydrogen phosphate buffer. The solid-liquid ratio of defatted particles to neutral detergent buffer solution is 1:30-1:50 g / mL.

[0065] S4, particle refinement: the material obtained in S3 is refined by wet milling method for the second time, dried, and sieved to obtain pretreated litchi shell fine powder with a particle size of ≥500 mesh. The wet milling method for the second time is carried out in a planetary ball mill.

[0066] S5, surface activation: mix the pretreated litchi shell fine powder obtained by S4 with a pre-hydrolyzed silane coupling agent solution at a mass ratio of 1:15-1:20, and perform surface modification treatment at 60-80°C for 1-2 hours. The silane coupling agent is any one of KH550 and KH570. The pre-hydrolyzed silane coupling agent solution is prepared by the following method: first, prepare a solution of anhydrous ethanol and deionized water at a mass ratio of 90:10, then use glacial acetic acid to adjust the solution pH to 2 as a hydrolysis solution, then prepare the pre-hydrolyzed silane coupling agent solution according to the mass ratio of silane coupling agent to hydrolysis solution of 1:160, at 90°C, with an ultrasonic shaking power of 200w, and ultrasonic shaking for 15 min.

[0067] S6, drying and curing: place the material obtained in S5 in a 105°C temperature drying oven for 1-2 hours to obtain litchi shell fine powder.

[0068] S7, high-speed shearing mixing: preheat the base asphalt to 130-140°C to melt it, add the litchi shell fine powder obtained in S6 as an asphalt modifier at 3-10 wt% of the base asphalt weight to the base asphalt, control the high-speed shearing rotation speed to 3000-5000 rpm, high-speed shearing mixing and uniform dispersion, shearing mixing for 15-30 minutes, and the preparation temperature is 150-160°C to ensure uniform dispersion of the plant shell fine powder in the base asphalt.

[0069] S8, vacuum degassing: vacuum degassing the mixture treated in S7 under negative pressure condition, the vacuum degree is controlled at -0.08~ -0.1 MP, thereby obtaining the high-performance modified asphalt with structural synergistic reinforcement.

[0070] The following is further illustrated by specific examples:

[0071] Example 1

[0072] This example provides a method for preparing high-performance green modified asphalt with structural synergistic reinforcement using litchi shell as raw material. The litchi shell raw material used in this example is sourced from a litchi processing plant in a certain region of Guangdong. The component contents are measured according to standards ASTM D1107, ASTM D1106-96 (2013), ASTM D1104-56 (Reapproved 2013), ASTM D1102-84 (2013), and NREL / TP-510-42618, as shown in Table 1 below.

[0073]

[0074] In the natural composite structure of litchi shell, lignin-cellulose forms a three-dimensional skeleton, enhancing high-temperature stability and low-temperature flexibility; phenolics / tannins provide antioxidant and anti-UV aging functions; and its natural porous structure can improve the interfacial bonding force with asphalt.

[0075] As a preferred embodiment, the preparation method of this example specifically includes the following steps:

[0076] S1, crushing treatment: wash and cut the litchi shell, then dry it at 50°C for 48h; after drying treatment, use a crusher to pre-crush the litchi shell, and sieve to obtain litchi shell particles with a particle size of 60 mesh.

[0077] S2, defatting treatment: add 0.5% sodium sulfite based on the weight of the litchi shell particles to the litchi shell particles obtained in S1 to prevent phenolic oxidation, then add the litchi shell particles to n-hexane according to a solid-liquid ratio of 1:5 g / mL, stir and leach for 45min to remove lipid-soluble substances in the cytoplasm, and obtain defatted particles.

[0078] S3, washing extraction: the defatted particles obtained in S2 were added with 0.5% sodium sulfite by weight of the defatted particles to avoid phenolic oxidation, and then the defatted particles were placed in a neutral detergent buffer solution at a solid-liquid ratio of 1:50 g / mL, heated and extracted for 60 min, washed and extracted twice with distilled water, and the temperature was maintained at 70°C during the operation; finally, the defatted particles were rinsed and extracted twice with anhydrous ethanol in an ice bath at 4°C; the purpose of ice bath extraction was to reduce the solubility of phenols in ethanol and acetone to ensure the retention of free phenols. The neutral detergent buffer solution in this example was composed of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA, and 0.05 M sodium phosphate dibasic buffer.

[0079] S4, particle refinement: the material obtained in S3 was refined twice by wet milling using a planetary ball mill, and the pretreated lychee shell powder with a particle size of ≥500 μm was obtained by drying and sieving.

[0080] S5, surface activation: the pretreated plant shell powder obtained in S4 was mixed with a pre-hydrolyzed silane coupling agent solution at a mass ratio of 1:20, and surface modification treatment was performed at 70°C for 1.5 hours under ultrasonic conditions.

[0081] The silane coupling agent used in this example was KH550, and the pre-hydrolyzed silane coupling agent solution was prepared by the following method: first, a solution with a mass ratio of anhydrous ethanol to deionized water of 90:10 was prepared, then ice acetic acid was used to adjust the solution pH to 2 as a hydrolysis solution, and then the pre-hydrolyzed silane coupling agent solution was prepared by mixing the silane coupling agent KH550 with the hydrolysis solution at a mass ratio of 1:160 under the conditions of 90°C, ultrasonic shaking power of 200 w, and ultrasonic shaking for 15 min.

[0082] S6, drying and curing: the material obtained in S5 was placed in a blast oven and dried at 105°C for 2 hours to obtain dried lychee shell powder.

[0083] S7, high-speed shearing mixing: the base asphalt (double dragon 70# base asphalt was used in this example) was first preheated to 140°C to melt it, then the lychee shell powder obtained in S6 was added as a bitumen modifier at a weight of 5% of the base asphalt, and high-speed shearing mixing and uniform dispersion were performed; the high-speed shearing conditions were controlled as follows: 3500 rpm rotation speed, shearing mixing for 30 minutes, and the preparation temperature was 160°C to ensure uniform dispersion of the lychee shell powder in the asphalt.

[0084] S8, vacuum degassing: the mixture treated in S7 was vacuum degassed under negative pressure conditions at a vacuum degree of about -0.08 MPa for 10 min to obtain the high-performance green modified asphalt with structural synergistic reinforcement.

[0085] Example 2

[0086] The difference between this embodiment and embodiment 1 is that the proportion of litchi shell fine powder added to the base pitch in step S7 is 3%.

[0087] Embodiment 3

[0088] The difference between this embodiment and embodiment 1 is that the proportion of litchi shell fine powder added to the base pitch in step S7 is 7%.

[0089] Embodiment 4

[0090] The difference between this embodiment and embodiment 1 is that the proportion of litchi shell fine powder added to the base pitch in step S7 is 10%.

[0091] In order to verify the overall technical effects of the scheme of the present application and the mutual coordination between the steps, the following comparative examples are provided:

[0092] Comparative Example 1: Single Component Control - Lignin

[0093] Commercially available industrial lignin powder is selected as one of the main natural components in litchi shells (corresponding to about 35% of the mass of litchi shells in embodiment 1). The difference from embodiment 1 is that the lignin powder is not pretreated, and is added to the base pitch according to the method of steps S7 and S8 of embodiment 1 at 5 wt% (relative to the mass percentage of pitch), to prepare a modified pitch. This is to verify the effect of a single component on the modification of pitch without treatment.

[0094] Comparative Example 2: Artificial Component Physical Mixing Simulating Litchi Shell

[0095] An artificial "composite modifier" is prepared by mixing the following three industrial raw materials according to the mass ratio: lignin (simulating the lignin component in litchi shells, set to 35 wt%), cellulose (simulating the cellulose component, set to 28 wt%), and gallic acid (a natural polyphenolic organic acid containing multiple phenolic hydroxyl groups, widely present in plant fruits and tree bark, with good antioxidant performance, commonly used to simulate phenolic active components in plants, used to simulate phenolic / tannin components, set to 12 wt%), corresponding to the mass percentage content of each component in embodiment 1.

[0096] The difference from embodiment 1 is that only the components are physically mixed, without any chemical or interfacial treatment, and are directly incorporated into the base pitch according to the method of steps S7 and S8 of embodiment 1 (the total amount of the composite modifier is 5 wt%), to prepare a modified pitch.

[0097] Comparative Example 3: Untreated Natural Litchi Shell Powder

[0098] The same source of dried litchi shell as in Example 1 was directly pulverized to a particle size of about 80 pm. The difference from Example 1 is that the steps of S2-S6 were skipped, and the modified asphalt was prepared by adding the litchi shell powder to the base asphalt at a proportion of 5 wt% according to the method of steps S7 and S8 of Example 1, to test the improvement effect of the litchi shell on the performance of the asphalt in the original state. The effect of the natural litchi shell material without activated structure as an asphalt modifier was verified.

[0099] Comparative Example 4: Litchi shell powder only subjected to defatting washing (without surface modification)

[0100] The difference between this comparative example and Example 1 is that the surface modification of S5 and S6 was skipped in the plant shell modified asphalt preparation step, and the modified asphalt was prepared by adding the litchi shell to the base asphalt at a proportion of 5 wt% according to the method of steps S7 and S8 of Example 1, to verify the influence of the three-step treatment without one on the comprehensive performance.

[0101] Comparative Example 5: Litchi shell defatting washing without free phenol retention and protection treatment

[0102] The difference between this comparative example and Example 1 is that no sodium sulfite was added in the plant shell modified asphalt preparation steps S2 and S3, and the “finally extracted twice with anhydrous ethanol at 25°C” in S3 was changed to “finally extracted twice with anhydrous ethanol at 25°C”. The influence of sodium sulfite and ice bath extraction on the formation of “dry pre-pulverization-defatting-neutral washing-wet planetary ball milling twice” cascade process and “lignin-cellulose-phenolic etc. symbiotic modification” and the performance of the final product modified asphalt was verified.

[0103] Comparative Example 6: Litchi shell powder without defatting washing (only surface modification)

[0104] The difference between this comparative example and Example 1 is that the defatting extraction of S2 and S3 was skipped in the natural litchi shell modified asphalt preparation step, and the particle refinement and surface activation in the original scheme S4 and S5 steps were directly entered, and the modified asphalt was prepared by adding the litchi shell to the base asphalt at a proportion of 5 wt% according to the method of steps S7 and S8 of Example 1, to verify the influence of the defatting extraction treatment on the performance of the final product modified asphalt.

[0105] Comparative Example 7: Artificial three-step treatment + component recombination simulation

[0106] The difference from Comparative Example 2 is that the lignin, cellulose, and gallic acid in Comparative Example 2 were treated according to the surface treatment process of steps S4-S6 of Example 1, and then physically mixed according to the natural component proportion of litchi shell (corresponding to the proportion of each component in Example 1 being 35:28:12) to form an “artificial simulated composite powder”.

[0107] The "artificial simulation composite powder" is incorporated into the base asphalt at a proportion of 5 wt% according to the method of steps S7 and S8 of Example 1, to verify whether the synergistic structural effect of natural lychee shells can be replicated by artificial construction under the condition that the component proportion and processing method are consistent.

[0108] The modified asphalts prepared in the above examples and comparative examples are subjected to performance testing, and the testing methods of the performance testing are referred to the "Standard Test Methods for Asphalt and Asphalt Mixtures for Highway Engineering"; the testing results are shown in Table 2.

[0109]

[0110] According to the data in Table 2, combined with the specific performance of the comparative samples and the samples of the embodiments of the present application in the key indicators such as softening point, penetration, shear modulus, aging performance, low temperature performance and storage stability, the analysis is as follows:

[0111] (1) From the data of the softening point, the softening point of the modified asphalt prepared by the embodiment scheme of the present application ranges from 53.3°C to 62.7°C, which is overall higher than that of the comparative examples. The highest softening point of comparative example 5 (54.5°C) is also lower than that of the corresponding example 1. Under the same addition proportion (5%), the improvement range reaches 5% to 13%. In addition, the complex shear modulus of the modified asphalt sample prepared by the embodiment scheme of the present application at 60°C is significantly enhanced, reaching a maximum of 8173 Pa, which is significantly better than all the comparative examples (maximum 4917 Pa), indicating that the material can significantly improve the high-temperature anti-rutting performance of petroleum asphalt.

[0112] (2) After TFOT (thin film oven test) treatment, the penetration retention ratio of the modified asphalt prepared by the embodiment scheme of the present application is between 79.4% and 84.7%, which is significantly better than 73.1% to 77.3% of comparative examples 1 to 4. After ultraviolet aging (UV) treatment, the penetration retention ratio is 54.7% to 61.1%, which is overall 3% to 11% higher than that of the comparative examples. This shows that the modified asphalt material prepared by the embodiment scheme of the present application has stronger structural stability and anti-aging ability in dealing with thermal oxidation and ultraviolet aging, and is a good material that can be applied to long-term service environment.

[0113] (3) Although the modified asphalt prepared by the comparative example 5 and the embodiment of the present application use the same component ratio and similar processing method, the modified asphalt prepared by the embodiment of the present application can significantly improve the modification effect of asphalt because of the adoption of natural lychee shell and the unique intercalated porous structure and the interface reaction characteristics after the activation treatment. The softening point, modulus and stability of the comparative example 5 are obviously worse than those of the modified asphalt prepared by the embodiment of the present application, which also shows the irreplaceability of the natural intercalated structure in forming the synergistic enhanced interface.

[0114] (4) As can be seen from the data comparison of the comparative examples 3 and 4, although both of them use natural lychee shell material, the surface of the comparative example 4 is also subjected to degreasing washing treatment, but it fails to form a stable bonding interface due to the lack of effective interface activation, resulting in unsatisfactory modification effect. The embodiment of the present application can enhance the compatibility and interface stability of the modifier and the asphalt matrix by specific interface modification means and process optimization, and realize the whole process coupling of interface reaction-structure synergy-performance enhancement.

[0115] (5) As can be seen from the data of the embodiment 1 and the comparative example 5, both of them are subjected to degreasing extraction and surface activation pretreatment, but the comparative example 5 fails to effectively retain the free polyphenol contained therein. Therefore, there is a significant difference in performance between the two: the low temperature ductility and anti-aging performance of the embodiment 1 are better than those of the comparative example 5. Compared with the comparative example 5, the modification effect of the free polyphenol on the performance of the matrix asphalt is lacking, the low temperature rheological performance is decreased, but the high temperature performance is slightly improved. More importantly, due to the lack of the adsorption capacity of polyphenol to free radicals under the action of heat and oxygen and ultraviolet, the anti-aging performance of the comparative example 5 is significantly weakened. This result fully verifies the necessity of the measures such as "sodium sulfite to avoid phenolic oxidation" and "ice bath extraction" emphasized in the steps S3 and S4 in the original scheme.

[0116] (6) From the data of Example 1 and Comparative Example 6, the performance of the latter is worse than that of the former, especially in high temperature and storage stability. The performance difference is due to the fact that the natural litchi shell powder in Comparative Example 6 is not subjected to defatting extraction treatment to remove free lipids, resulting in the internal polar groups being covered and shielded and the interfacial adhesion being enhanced, so that the silane coupling agent surface activation treatment is weakened compared with Example 1. In the scheme of Example 1, the plant shell is subjected to defatting treatment, which may be based on the fact that the internal polar groups of the main components of the plant shell powder can be exposed by removing the lipids, thereby preparing for subsequent silane coupling agent surface activation treatment. The exposed polar groups can react with silane coupling agent molecules to form hydrogen bonds or chemical bonds to construct a stable interfacial connection layer. The low temperature rheological property, high temperature property and anti-aging property of Comparative Example 6 are all significantly lower than those of Example 1, which fully verifies the necessity of defatting treatment in the original scheme.

[0117] (7) The softening point difference of the modified asphalt prepared by the scheme of the present application is only 1.1℃~2.3℃, which is lower than that of the comparative example group. The minimum softening point difference of Comparative Example 5 (1.4℃) in the comparative example group is also higher than that of Example 1 (1.1℃) under the same addition ratio (5%), indicating that the modified agent has good dispersibility and high compatibility in asphalt, effectively solving the problem of phase separation of traditional modified agents. This characteristic is of great significance to ensure the quality consistency and construction adaptability of the material during production, storage and transportation.

[0118] In summary, the scheme of the present application uses natural plant shell (such as litchi shell) as a kind of natural structure synergistic composite material. On the basis of utilizing the synergistic modification effect of lignin-cellulose-phenolic etc. symbiotic form in the original structure of plant shell; a cascade process of “dry pre-pulverization-defatting-neutral washing, ice bath extraction-wet planetary ball milling secondary refinement” is adopted, and a three-step synergistic process path of “defatting treatment, surface activation, high-speed shearing” is proposed, which synergistically improves the powder particle size, functional group exposure and interfacial adhesion, solves the key problems of natural plant shell powder modified material such as poor dispersibility, unstable interface and low aging performance, significantly improves the dispersibility and structural stability of plant shell modifier in asphalt, and further improves the anti-aging performance, low temperature ductility, adhesion and water stability of modified asphalt, which has good industrial application prospect.

[0119] Based on the same inventive concept, the asphalt concrete prepared by mixing the high-performance green modified asphalt with structural synergistic enhancement effect provided by the scheme of the present application with mineral aggregate has the same technical effects as the modified asphalt of the present application. Furthermore, it should also be within the protection scope of the present application.

[0120] The above merely describes some of the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells, characterized in that, The method includes the following steps: S1. Crushing process: After drying the plant shells, pre-crush and sieve them to obtain plant shell particles; S2, Degreasing treatment: The plant shell particles from S1 are soaked in a degreasing agent to remove fat-soluble substances from the cytoplasm and obtain degreased particles; sodium sulfite is added to the plant shell particles before degreasing treatment to prevent phenol oxidation; the degreasing agent is petroleum ether or n-hexane; S3. Washing and Extraction: Place the defatted particles from S2 into a neutral detergent buffer and heat for 45-60 min. Then wash and extract 2-3 times with distilled water, maintaining the temperature at 70-80℃ throughout the process. Before washing and extraction, add sodium sulfite to the defatted particles to prevent phenol oxidation. Finally, extract 2-3 times with acetone or anhydrous ethanol in an ice bath at 3-5℃. The neutral detergent buffer consists of 0.5% sodium dodecyl sulfate, 20 mM disodium EDTA, and 0.05 M sodium borate buffer or disodium hydrogen phosphate buffer. The solid-liquid ratio of defatted particles to neutral detergent buffer is 1:30-1:50 g / mL. S4. Particle refinement: The material obtained in S3 is further refined by wet milling, dried and sieved to obtain pretreated plant shell fine powder with a particle size ≥500 mesh. S5. Surface activation: The pretreated plant shell powder obtained from S4 treatment is mixed with the pre-hydrolyzed silane coupling agent solution at a mass ratio of 1:15 to 1:20, and the surface is modified by ultrasonic treatment at 60 to 80°C for 1 to 2 hours. S6. Drying and curing: The material obtained in S5 is dried at 105°C for 1-2 hours to obtain fine plant shell powder; S7. High-speed shear mixing: The plant shell powder obtained in S6 is used as an asphalt modifier and added to the base asphalt at 3-10 wt% of the base asphalt weight. The mixture is then subjected to high-speed shear mixing and uniform dispersion. S8. Vacuum degassing: The mixture treated by S7 is vacuum degassed under negative pressure to obtain high-performance modified asphalt with synergistic structural reinforcement.

2. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, The plant shell is a natural plant shell, including one or a mixture of two or more of the following: lychee shell, camellia shell, and grain shell.

3. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 2, characterized in that, The plant shell is a lychee shell, and the lychee shell contains the following main components in weight percentage: Lignin: 34%~36%; Cellulose: 25%~30%; Hemicellulose: 18%~22%; Phenolics / Tannins: 11%~13%; Water-soluble ash: 4%~5%; The sum of the weight percentages of the main components shall not exceed 100%.

4. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, In step S2, the solid-liquid ratio of plant shell particles to degreasing agent is 1:5~1:10 g / mL, and the stirring and soaking degreasing time is 45~60 min.

5. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, In step S2, 0.5% by weight of sodium sulfite granules of plant shells are added; in step S3, 0.5% by weight of sodium sulfite granules of defatted granules are added.

6. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, The silane coupling agent used in step S5 is either KH550 or KH570; The pre-hydrolyzed silane coupling agent solution was prepared as follows: First, a solution of anhydrous ethanol and deionized water in a mass ratio of 90:10 was prepared. Then, the pH of the solution was adjusted to 2 with glacial acetic acid to serve as the hydrolysate. Finally, the pre-hydrolyzed silane coupling agent solution was prepared by ultrasonic vibration at 90°C for 15 minutes at a mass ratio of 1:

160.

7. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, In step S7, the base asphalt is preheated to 130~140℃ to melt it. The high-speed shearing conditions are: shearing and mixing at 3000~5000 rpm for 15~30 minutes, and the preparation temperature is 150~160℃ to ensure that the plant shell powder is evenly dispersed in the base asphalt.

8. The method for preparing high-performance modified asphalt with synergistic structural reinforcement using plant shells according to claim 1, characterized in that, In step S8, the vacuum level is controlled between -0.08 and -0.1 MPa.

9. High-performance modified asphalt with synergistic structural enhancement prepared by the method of any one of claims 1 to 8.

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