Chitosan modified perlite-based self-melting snow asphalt mixture and preparation method thereof

Abstract

This invention discloses a chitosan-modified perlite-based self-melting asphalt mixture and its preparation method, relating to the field of asphalt pavement technology. The mixture includes asphalt, aggregates, fillers, and a self-melting additive; the self-melting additive is perlite particles coated with chitosan and internally loaded with chloride salts, with an dosage of 5%~10% of the total mass of the mixture. In preparation, the perlite particles are first dried and vacuum pretreated, then impregnated under vacuum pressure to adsorb chloride salts into the pores, obtaining a perlite-chloride core material; subsequently, the perlite-chloride core material is mixed with chitosan, allowing chitosan to coat the surface of the perlite-chloride core material, obtaining the self-melting additive; finally, the self-melting additive, asphalt, aggregates, and fillers are mixed and stirred to obtain the chitosan-modified perlite-based self-melting asphalt mixture. This method not only achieves the persistence and controllability of the self-melting function but also actively improves the key road performance of the asphalt mixture.

Description

Technical Field

[0001] This invention belongs to the field of asphalt pavement technology, specifically relating to a chitosan-modified perlite-based self-melting snow asphalt mixture and its preparation method. Background Technology

[0002] In the field of road engineering, especially for asphalt pavements in cold and snowy regions, the accumulation of ice and snow in winter poses a serious threat to driving safety. Traditional manual or mechanical snow removal methods are not only costly in terms of manpower and resources, but also often have a delay. To improve the active safety performance of road surfaces in winter, self-melting asphalt pavement technology has emerged. The core idea of ​​this technology is to pre-integrate snow-melting components with the ability to lower the freezing point into the pavement material, enabling it to function automatically in icy and snowy weather. International research in this area started earlier. For example, Germany explored loading chloride salts into porous materials in the early stages, while Switzerland developed V-260 and V-175 materials with specific freezing point inhibition effects. Japan launched the well-known Mafilon product through technological cooperation. my country began to pay attention to and introduce this type of technology around 2008, and while digesting and absorbing it, it also developed its own domestic products such as ICB and IGD. These technologies achieve the slow release of snow-melting components to prevent icing by storing salt inside the pavement, thus reducing the dependence on external snow removal operations to a certain extent.

[0003] Despite the proven value of self-melting pavement technology, its practical application still faces a series of challenges. The most prominent issue is the irreconcilable conflict between the salts added to achieve snow melting and the core requirement of ensuring long-term pavement durability. Salts, especially commonly used chlorides, are hygroscopic, which not only inconveniences the storage and transportation of asphalt mixtures containing such materials, but more importantly, during pavement use, the salts dissolve in water to form an electrolyte solution. This solution erodes the bonding interface between asphalt and aggregate, weakening their bond and leading to a series of performance degradations. For example, it makes the pavement more prone to rutting under repeated traffic loads, increases brittleness and cracking at low temperatures, and is more susceptible to water damage such as peeling and potholes under moisture erosion.

[0004] In existing technologies, "oil-coated salt compounds" are commonly used to reduce the erosion of asphalt mixtures by salt. This method involves loading salt onto a porous carrier and then coating it with coupling agents and hydrophobic agents to form a protective film that controls salt release. However, this method has significant limitations: the added chemical coating materials may have poor compatibility with the asphalt system, and the coating layer lacks long-term stability under complex road conditions; furthermore, the high proportion of fillers added to achieve effective snow melting often interferes with the asphalt mastic structure, leading to a decrease in the high-temperature rutting resistance and low-temperature crack resistance of the mixture, making it difficult to simultaneously achieve snow melting function and pavement durability. Summary of the Invention

[0005] In order to overcome the shortcomings of existing self-melting asphalt mixtures in that it is difficult to balance snow melting function and road surface durability, this invention provides a chitosan-modified perlite-based self-melting asphalt mixture and its preparation method.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a chitosan-modified perlite-based self-melting snow asphalt mixture, comprising asphalt, aggregate, filler and self-melting snow additive; The self-melting snow additive is perlite particles with chitosan coated on the surface and chloride salt loaded inside. Based on the total mass of the asphalt mixture, the dosage of the self-melting snow additive is 5% to 10%.

[0007] A further improvement of the present invention is that the perlite particles have a particle size of 70-90 mesh.

[0008] A further improvement of the present invention is that the chloride salt is potassium chloride.

[0009] A further improvement of the present invention is that the degree of deacetylation of the chitosan is 86% to 90%.

[0010] Secondly, the present invention also provides a method for preparing chitosan-modified perlite-based self-melting snow asphalt mixture, comprising the following steps: S1. Dry and vacuum pretreat the perlite particles; S2. The pretreated perlite particles are immersed in a saturated chloride solution and impregnated under vacuum conditions to allow the chloride to be adsorbed into the pores of the perlite, thus obtaining perlite-salt core material. S3. Mix the perlite-salt core material with chitosan, so that the chitosan coats the surface of the perlite-salt core material to obtain a self-melting snow additive. S4. Mix and stir the self-melting snow additive, asphalt, aggregate and filler to obtain the chitosan-modified perlite-based self-melting snow asphalt mixture.

[0011] A further improvement of the present invention is that, in step S1, the drying is performed at 100~110℃ for 20~24h; and the vacuum pretreatment is performed by evacuating to a pressure of -0.01MPa and maintaining it for 1~1.5h.

[0012] A further improvement of the present invention is that, in step S2, the impregnation time is 6-10 hours; and the impregnation under vacuum conditions specifically involves: drawing a vacuum and maintaining pressure for 20-40 minutes.

[0013] A further improvement of the present invention is that, in step S3, after the perlite-salt core material is mixed with chitosan, a drying step is also included, wherein the drying is performed at 100~110℃ for 20~24h.

[0014] A further improvement of the present invention is that, in step S4, the self-melting snow additive is added at a ratio of 5% to 10% of the total mass of the asphalt mixture.

[0015] A further improvement of the present invention is that, in step S2, after the pressure impregnation and before step S3, the following steps are also included: verifying the chloride ion slow-release effect of the impregnated perlite particles, and proceeding with subsequent steps only after confirming that the adsorption meets the standard.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a chitosan-modified perlite-based self-melting asphalt mixture. By using perlite particles coated with chitosan and internally loaded with chloride salts as a self-melting additive, and incorporating them at a specific proportion of 5% to 10% of the total asphalt mixture mass, a synergistic improvement in snow-melting function and core pavement performance is achieved. This dosage range ensures that sufficient salt content is effectively loaded to achieve sustained slow-release snow melting while avoiding significant weakening of the asphalt mastic structure due to excessive additives, thus maintaining the overall mechanical integrity of the mixture. In this additive, the porous structure of perlite provides a stable and substantial storage space for chlorides, while the chitosan coating plays a crucial dual role: First, the active groups such as amino and hydroxyl groups on its molecular chains can form strong hydrogen bonds with asphalt molecules, significantly enhancing the bonding strength and cohesion of the asphalt binder, thereby directly improving the mixture's resistance to cracking and loosening, and enhancing pavement durability. Second, this coating forms an intelligent slow-release barrier on the surface of the perlite-salt core material, effectively regulating the release rate of salts triggered by moisture. While ensuring continuous snow melting, it significantly reduces the opportunity for salts to directly and rapidly contact and erode the asphalt phase, thus mitigating the accelerating effect of salts on the asphalt aging process. Furthermore, both the perlite and chitosan used in this mixture are natural, biodegradable, and environmentally friendly materials, reducing the potential pollution risks to the surrounding ecological environment from the source of traditional snow melting technologies, aligning with the development direction of green building materials.

[0017] This invention also provides a method for preparing a chitosan-modified perlite-based self-melting asphalt mixture. First, perlite particles are dried and pretreated under vacuum to fully open and empty the perlite's pore structure, laying a physical foundation for efficient salt loading. Second, under vacuum pressure impregnation, the saturated chloride solution is deeply penetrated and stably adsorbed into the perlite using negative pressure, forming a perlite-salt core material with stable salt storage and slow-release potential. Then, chitosan is introduced for surface coating. This step not only utilizes the molecular properties of chitosan to form a controllable slow-release barrier on the core material surface, regulating the salt release rate to extend the snow-melting cycle, but also improves the interfacial compatibility between the core material and the organic asphalt matrix through its active groups. Finally, mixing and stirring ensure the uniform dispersion of functional additives in the asphalt mixture. The entire process works synergistically, achieving long-lasting self-melting snow-melting functionality while fundamentally improving the bonding quality between additives and the asphalt matrix, and demonstrating the characteristics of green production due to the use of natural and environmentally friendly raw materials. Attached Figure Description

[0018] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0019] Figure 1 This is a flowchart illustrating the preparation method of the chitosan-modified perlite-based self-melting snow asphalt mixture of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] This invention provides a chitosan-modified perlite-based self-melting snow asphalt mixture, comprising asphalt, aggregate, filler, and self-melting snow additive; The self-melting snow additive is perlite particles with chitosan coated on the surface and chloride salt loaded inside. Based on the total mass of the asphalt mixture, the dosage of the self-melting snow additive is 5% to 10%.

[0026] As a preferred embodiment, the chloride salt is potassium chloride. As a preferred embodiment, the degree of deacetylation of the chitosan is 86% to 90%.

[0027] like Figure 1 As shown, the present invention also provides a method for preparing chitosan-modified perlite-based self-melting snow asphalt mixture, comprising the following steps: S1. Perlite pretreatment: Place the purchased 70-90 mesh perlite particles at 100-110℃ and dry for 20-24 hours to fully remove the surface moisture. After drying, transfer the perlite to a vacuum device, evacuate to a pressure of -0.01MPa, and maintain this pressure for 1-1.5 hours to ensure that the air in the pores of the perlite is completely expelled, providing a channel for subsequent salt solution penetration.

[0028] S2. Chloride loading and adsorption verification: Perlite particles pretreated in S1 were immersed in a saturated chloride solution, stirred thoroughly, and allowed to stand for 22-24 hours. Subsequently, the system was subjected to vacuum suction treatment and pressure was maintained for 20-40 minutes. The vacuum negative pressure environment promoted the full penetration of the salt solution into the internal pores of the perlite, achieving saturated adsorption of chloride ions by the perlite, thus obtaining perlite-salt core material.

[0029] Optionally, this step may also include verification of the adsorption effect: a portion of the impregnated perlite particles may be dried and their chloride ion slow-release performance may be measured to confirm that the adsorption meets the standard before proceeding with subsequent steps.

[0030] S3. Chitosan Coating Modification: The perlite-salt core material obtained in S2 is filtered to obtain a salt-saturated core material. Subsequently, it is mixed with chitosan to coat the surface of the perlite-salt core material, and then dried at 100~110℃ for 20~24h to obtain the self-melting snow additive.

[0031] S4. Asphalt mixture mixing: According to the engineering design requirements, the self-melting snow additive is added to the mixing equipment along with asphalt, aggregate and filler at a ratio of 5% to 10% of the total mass of the asphalt mixture. A high-speed mixer is used to mix the additive thoroughly to ensure that the additive and the asphalt mixture are mixed evenly, and finally the chitosan modified perlite-based self-melting snow asphalt mixture is obtained.

[0032] In step S1, perlite particles of 70-90 mesh are selected. This particle size range ensures that the material possesses sufficient specific surface area and a well-developed interconnected pore structure, which is the physical basis for achieving efficient adsorption and slow release functions. Drying at 100-110℃ for 20-24 hours is based on the desorption kinetics of water adsorption in porous materials, which can thoroughly remove free water from the surface and shallow pores, preventing it from occupying the effective space for salt solution loading. The subsequent vacuum pretreatment (maintaining at -0.01MPa for 1-1.5 hours) utilizes the pressure difference driving principle to forcibly expel trapped air in deep pores, creating the necessary conditions for unobstructed, full-channel permeation of the subsequent salt solution. This series of pretreatments is not a simple washing and drying process, but rather an activation process for the porous structure of perlite, which is a prerequisite for achieving a high loading rate in this method.

[0033] Step S2 involves immersing the activated perlite in a saturated chloride solution for 22–24 hours to ensure sufficient contact between the salt and the pore surface via diffusion. The subsequent vacuum-pressure impregnation (20–40 minutes) is a crucial strengthening step. The negative pressure generated by the vacuum significantly reduces the resistance to the solution entering the micropores, driving the salt solution to rapidly fill the nanoscale channels, achieving deep and saturated adsorption of chloride ions within the carrier. The abundant silanol (-SiOH) functional groups on the perlite surface can interact with chloride ions (such as K+)... + Cl - This structure generates weak chemical bonds and physical adsorption, enhancing the stability of the load. During road service, salt can only slowly diffuse to the surface through the pore channels under the induction of moisture, thus achieving a long-lasting and controllable snow melting function and avoiding the problems of sudden release or premature loss of salt in traditional technologies.

[0034] The introduction of chitosan for coating modification in step S3 is an innovative aspect of this invention. The amino (-NH2) and hydroxyl (-OH) functional groups abundant in the chitosan molecular chain have a dual function: firstly, they form strong hydrogen bonds with polar components in the asphalt matrix, significantly enhancing the adhesion and cohesion of the asphalt mastic; secondly, they interact with functional groups on the perlite surface, improving the interfacial bonding between the perlite core and the asphalt matrix, and enhancing the compatibility between inorganic fillers and the organic asphalt matrix. Simultaneously, the thin coating layer formed by chitosan on the core surface allows for slow water penetration to trigger salt leaching, but effectively slows the direct diffusion rate of salt into the asphalt phase, thereby significantly reducing the aging erosion and structural damage caused by salts to the asphalt, resolving the core contradiction of balancing snow melting function and road durability.

[0035] In step S4, the self-melting snow additive is incorporated at 5% to 10% of the total mass of the asphalt mixture. This range is an optimized window derived from extensive experiments and engineering simulations. The lower limit of 5% ensures effective initial snow melting capacity and durability under general snow and ice conditions; the upper limit of 10% meets the high-intensity snow melting requirements of frigid regions while avoiding problems such as imbalance in the asphalt binder ratio, excessive increase in mixture stiffness, and increased risk of low-temperature brittleness caused by excessive filler. A high-speed mixing process ensures that the surface-modified perlite core material is uniformly dispersed in the hot asphalt, avoiding uneven performance caused by localized aggregation.

[0036] In summary, this method not only achieves the persistence and controllability of self-melting snow function, but also actively improves the key road performance of asphalt mixtures. The reinforcing effect of chitosan helps improve the high-temperature rutting resistance, low-temperature crack resistance, and water stability of the mixture. Both the perlite and chitosan used are abundant, renewable, and environmentally friendly materials. The entire preparation process produces no toxic or harmful emissions, and the slow-release properties of the core material greatly reduce the instantaneous pollution load of salt on the surrounding soil and water bodies, achieving a balance between functionality, durability, and environmental protection, aligning with the development direction of green and low-carbon road construction. This method has a clear process chain, strong compatibility with existing asphalt concrete production equipment, and good prospects for large-scale application.

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0039] Example 1 This embodiment provides a method for preparing a snow-melting and salt-storage overlay material (i.e., chitosan-modified perlite-based self-melting asphalt mixture) suitable for the cold regions of Northeast China, including the following steps: Step S1: Place 5 portions of 90-mesh perlite granules (96% purity) in an oven at 105°C and dry for 24 hours to thoroughly remove moisture. Then transfer them to a vacuum device, evacuate to a pressure of -0.01 MPa and maintain for 1 hour to remove air from the internal pores.

[0040] Step S2: Immerse the pretreated perlite particles in a saturated solution prepared with 3 parts potassium chloride for 24 hours. Subsequently, vacuum the impregnation system and maintain the pressure for 30 minutes (pressure -0.01 MPa) to promote deep penetration of the salt solution and obtain perlite-potassium chloride core material.

[0041] Step S3: The perlite-potassium chloride core material obtained in step S2 is uniformly mixed with 0.5 parts of chitosan powder with a degree of deacetylation of 88% to coat the surface of the core material with chitosan. Then, this mixture is dried at 105°C for 24 hours to obtain the self-melting snow additive (i.e., modified perlite core material).

[0042] Step S4: Place the self-melting snow additive obtained in step S3, 50 parts of 70# road petroleum asphalt (heated to a fluid state), 100 parts of basalt aggregate and 10 parts of limestone powder into a mixer, and stir at high speed at 160°C for 90 seconds until all components are evenly mixed. After subsequent rolling and molding processes, the snow-melting salt storage overlay material (i.e., chitosan-modified perlite-based self-melting snow asphalt mixture) is obtained.

[0043] The snow-melting salt-storage overlay material prepared in this embodiment is suitable for highways with winter temperatures ranging from -20°C to -5°C and annual snowfall ≥100cm. This material maintains stable snow-melting performance even in low-temperature environments, effectively preventing snow and ice formation on the road surface, improving highway traffic safety in winter, and its core material has good compatibility with the asphalt matrix, without affecting the pavement structural strength.

[0044] Example 2 This embodiment provides a method for preparing a snow-melting road paving material (i.e., chitosan-modified perlite-based self-melting asphalt mixture) suitable for southern North China, including the following steps: Step S1: Place two portions of 70-mesh perlite granules (95% purity) in an oven at 110°C and dry for 20 hours to thoroughly remove moisture. Then transfer them to a vacuum device, evacuate to a pressure of -0.01 MPa and maintain for 1.5 hours to remove air from the internal pores.

[0045] Step S2: Immerse the pretreated perlite particles in a saturated solution prepared with 1.8 parts potassium chloride for 22 hours. Subsequently, vacuum suction and pressure holding are applied to the impregnation system for 40 minutes (pressure -0.01 MPa) to promote deep penetration of the salt solution, thereby obtaining perlite-potassium chloride core material.

[0046] Step S3: The perlite-potassium chloride core material obtained in step S2 is uniformly mixed with 0.3 parts of chitosan powder with a deacetylation degree of 86% to coat the surface of the core material with chitosan. Then, this mixture is dried at 110°C for 20 hours to obtain the self-melting snow additive (i.e., modified perlite core material).

[0047] Step S4: Place the self-melting snow additive obtained in step S3, 60 parts of 90# road petroleum asphalt (heated to a fluid state), 100 parts of basalt aggregate and 15 parts of limestone powder into a mixing machine, and stir at high speed at 160°C for 90 seconds until all components are evenly mixed. After subsequent rolling and molding processes, the snow-melting road paving material (i.e., chitosan-modified perlite-based self-melting snow asphalt mixture) is obtained.

[0048] The snow-melting road paving material prepared in this embodiment is suitable for county and township roads with winter temperatures of -5℃ to 5℃ and annual snowfall ≤50cm. Considering the climate characteristics of southern North China, which has low winter snowfall and short durations of low temperatures, this material adopts a low core material content design. While ensuring the basic snow-melting and anti-skid effect, it minimizes preparation costs, meets the construction and usage needs of county and township roads, and possesses good wear resistance and anti-aging properties.

[0049] Example 3 This embodiment provides a perlite-based self-melting snow asphalt mixture without chitosan modification to verify the key role of chitosan in improving overall performance. Its preparation method includes the following steps: Step S1: Place 5 portions of 90-mesh perlite particles (96% purity) in an oven at 105°C and dry for 24 hours, then pre-treat them under a vacuum of -0.01 MPa for 1 hour.

[0050] Step S2: Immerse the pretreated perlite particles in a saturated solution of 3 parts potassium chloride for 24 hours, then perform vacuum suction and pressure holding for 30 minutes (pressure -0.01MPa) to obtain perlite-potassium chloride core material.

[0051] Step S3: The perlite-potassium chloride core material obtained in step S2 is directly dried at 105°C for 24 hours to obtain a self-melting snow additive without chitosan coating.

[0052] Step S4: The self-melting snow additive obtained in step S3, 50 parts of 70# road petroleum asphalt, 100 parts of basalt aggregate and 10 parts of limestone powder are mixed at high speed at 160℃ for 90 seconds. After being mixed evenly, an asphalt mixture is obtained.

[0053] Comparative Example 1 This comparative example provides a standard asphalt mixture without any self-melting snow additives as a benchmark control group for performance evaluation. Its preparation method is a conventional hot-mix asphalt mixture process: 50 parts of 70# road petroleum asphalt (heated to a fluid state), 100 parts of basalt aggregate and 10 parts of limestone powder were placed in a mixing machine and stirred at high speed at 160℃ for 90 seconds until all components were mixed evenly. The mixture was then rolled into ordinary asphalt mixture specimens.

[0054] Comparative Example 2 This comparative example provides an asphalt mixture using traditional porous material activated carbon as a salt carrier, to compare the effects of different carrier materials. Its preparation method includes the following steps: Step S1: Place 5 portions of activated carbon particles with a particle size equivalent to 90-mesh perlite in an oven at 105°C and dry for 24 hours, then pre-treat them under a vacuum of -0.01 MPa for 1 hour.

[0055] Step S2: Immerse the pretreated activated carbon particles in a saturated solution prepared with 3 parts potassium chloride for 24 hours, then perform vacuum suction and maintain pressure for 30 minutes (pressure -0.01MPa) to obtain activated carbon-potassium chloride core material.

[0056] Step S3: Dry the activated carbon-potassium chloride core material at 105°C for 24 hours to obtain the self-melting snow additive (without chitosan coating).

[0057] Step S4: The prepared additive, 50 parts of 70# road petroleum asphalt, 100 parts of basalt aggregate and 10 parts of limestone powder are stirred at high speed at 160℃ for 90 seconds. After being mixed evenly, the activated carbon core material asphalt mixture is obtained.

[0058] The snow melting and de-icing effects of the above embodiments and comparative examples were tested. The concentration of chloride ions in the core material was measured using a fully automatic chloride ion analyzer, and the melting efficiency was determined by measuring the volume of ice layer on the rutted surface. The test results are shown in Table 1 below.

[0059] Table 1. Comparison of snow melting and de-icing effects between the embodiments and comparative examples of the present invention.

[0060] As shown in Table 1, Example 1 exhibits the best snow melting and de-icing effect, demonstrating its efficient and long-lasting snow melting capability. In contrast, Example 3 performs the worst. The main reason for this difference is that Example 3 is the control group without chitosan modification. Its self-melting additive was not coated with chitosan, which may lead to faster and more uncontrolled salt release, or poor bonding with the asphalt matrix, thus affecting the slow-release effect and overall snow melting efficiency. The intelligent slow-release barrier formed by the chitosan coating layer on the perlite-salt core material surface can effectively regulate the release rate of salt under moisture triggering, significantly reducing the opportunity for salt to directly and rapidly contact and erode the asphalt phase while ensuring continuous snow melting effect. Because Example 3 lacks this crucial coating, its slow-release performance and snow melting effect are significantly weaker than those of the fully modified Examples 1 and 2. Furthermore, all snow melting indicators of Comparative Example 1 are 0, indicating that it does not possess any self-melting function. Although the indicators of Comparative Example 2 were higher than those of Comparative Example 1, they were all significantly lower than those of Example 1. Furthermore, the sustained-release performance and snow-melting effect decreased significantly over time, failing to achieve long-term stable snow melting. Therefore, the solution using perlite as a carrier combined with chitosan modification is more advantageous.

[0061] The mechanical property data of asphalt mixtures used in road performance tests based on the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" are shown in Table 2 below.

[0062] Table 2 Comparison of mechanical properties of embodiments and comparative examples of the present invention

[0063] As shown in Table 2, Example 1 exhibits the best overall mechanical properties, maintaining relatively optimal resistance to deformation and high-temperature stability. Example 3 and Comparative Example 2 show poorer mechanical properties. The main reason for this difference is the presence or absence of a chitosan coating layer. The self-melting snow additives in Examples 1 and 2 underwent chitosan coating modification, while Examples 3 and Comparative Example 2 are control groups without chitosan modification. The amino and hydroxyl groups on the chitosan molecular chain can form strong hydrogen bonds with asphalt molecules, significantly enhancing the bonding strength and cohesion of the asphalt binder, thereby directly improving the mixture's resistance to cracking and loosening. Examples 3 and Comparative Example 2 lack this crucial interfacial reinforcement and slow-release barrier, resulting in a significant decrease in their mechanical properties, especially rutting resistance. The optimal mechanical properties of Comparative Example 1 highlight that the filler added to achieve the self-melting snow function does indeed affect the pure mechanical properties of the asphalt mixture. This invention, through chitosan modification, introduces functionality while maximizing the maintenance of road performance.

[0064] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A chitosan-modified perlite-based self-melting snow asphalt mixture, characterized in that, Includes asphalt, aggregates, fillers, and self-melting snow additives; The self-melting snow additive is perlite particles with chitosan coated on the surface and chloride salt loaded inside. Based on the total mass of the asphalt mixture, the dosage of the self-melting snow additive is 5% to 10%.

2. The chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 1, characterized in that, The perlite particles have a particle size of 70-90 mesh.

3. The chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 1, characterized in that, The chloride salt is potassium chloride.

4. The chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 1, characterized in that, The degree of deacetylation of the chitosan is 86%~90%.

5. A method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Dry and vacuum pretreat the perlite particles; S2. The pretreated perlite particles are immersed in a saturated chloride solution and impregnated under vacuum conditions to allow the chloride to be adsorbed into the pores of the perlite, thus obtaining perlite-salt core material. S3. Mix the perlite-salt core material with chitosan, so that the chitosan coats the surface of the perlite-salt core material to obtain a self-melting snow additive. S4. Mix and stir the self-melting snow additive, asphalt, aggregate and filler to obtain the chitosan-modified perlite-based self-melting snow asphalt mixture.

6. The method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 5, characterized in that, In step S1, the drying is performed at 100~110℃ for 20~24h; the vacuum pretreatment is performed by evacuating to a pressure of -0.01MPa and maintaining it for 1~1.5h.

7. The method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 5, characterized in that, In step S2, the impregnation time is 22-24 hours; the impregnation under vacuum conditions specifically involves: drawing a vacuum and maintaining pressure for 20-40 minutes.

8. The method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 5, characterized in that, In step S3, after the perlite-salt core material is mixed with chitosan, a drying step is also included, wherein the drying is performed at 100~110℃ for 20~24h.

9. The method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 5, characterized in that, In step S4, the self-melting snow additive is added at a ratio of 5% to 10% of the total mass of the asphalt mixture.

10. The method for preparing a chitosan-modified perlite-based self-melting snow asphalt mixture according to claim 5, characterized in that, In step S2, after the pressure impregnation and before step S3, the following steps are also included: verifying the chloride ion slow-release effect of the impregnated perlite particles, and proceeding with subsequent steps only after confirming that the adsorption meets the standard.

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