A SiO2 aerogel solution, thermal insulation aggregate, and preparation method

Abstract

The application belongs to the technical field of thermal insulation materials, and discloses a SiO2 aerogel solution, a thermal insulation aggregate and a preparation method, wherein anhydrous ethanol and distilled water are uniformly mixed to obtain an alcohol solution; a bonding agent is added to the alcohol solution and uniformly mixed to obtain a viscous alcohol solution; SiO2 aerogel powder is added to the viscous alcohol solution, and stirring is carried out at a stirring rate of 100-500 r / min for 120-240 s to prepare the SiO2 aerogel solution; wherein the addition amount of the anhydrous ethanol is 40%-45% of the total mass of the SiO2 aerogel solution, the addition amount of the distilled water is 14%-19% of the total mass of the SiO2 aerogel solution, the addition amount of the bonding agent is 8%-20% of the total mass of the SiO2 aerogel solution, and the addition amount of the SiO2 aerogel powder is 24%-28% of the total mass of the SiO2 aerogel solution. The SiO2 aerogel solution developed by the application has good cohesiveness, a long stable time and a high SiO2 aerogel content, and the SiO2 aerogel modified aggregate prepared by using the SiO2 aerogel solution and the aggregate has excellent thermal insulation.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation materials technology, specifically relating to a SiO2 aerogel solution, thermal insulation aggregate, and preparation method. Background Technology

[0002] The region spans multiple climate zones, which presents numerous environmental challenges to the operation of asphalt pavements. For example, the hot and humid weather in the south can easily cause the asphalt pavement to soften and flow, leading to rutting problems that are difficult to repair. In the north, the large temperature difference between day and night and the sudden drop in temperature can easily cause low-temperature cracking or freezing cracking of asphalt pavements, resulting in problems such as short service life, frequent maintenance and high costs for asphalt pavements.

[0003] The application of heat-insulating asphalt pavement materials to the surface layer of the road can reduce the temperature of the middle and lower asphalt surface layers during the high temperatures of summer, thereby reducing rutting disease of asphalt pavement. In winter, it can maintain the heat of the middle and lower asphalt surface layers, reducing cracking disease caused by sudden temperature drops and low temperature invasion. At the same time, it can also alleviate the problem of temperature-induced fatigue cracking, thereby improving the service performance and service life of asphalt pavement and reducing the total life cycle cost.

[0004] Aggregates account for over 90% of the mass of insulating asphalt mixtures, therefore, the thermal conductivity of the aggregates significantly impacts their heat transfer performance. Currently, some researchers have explored using high-porosity insulating aggregates such as ceramics, ceramsite, ceramsite sand, refractory crushed stone, calcined bauxite, and expanded vermiculite to replace some natural aggregates and improve the insulating properties of asphalt mixtures. However, these types of aggregates mostly achieve insulating properties at the expense of the mechanical or road performance of the asphalt mixture; large-scale substitution is not practical, and therefore the resulting insulating performance is relatively weak.

[0005] SiO2 aerogel has a thermal conductivity as low as 0.018 W / (m·K), only 0.7 times that of air. If used to treat aggregates, it can enhance their thermal insulation properties without reducing their mechanical properties. However, SiO2 aerogel is characterized by low density, high porosity, and brittleness, and it lacks adhesiveness, making it unsuitable for direct aggregate treatment or as a substitute for aggregates. How to bond SiO2 aerogel to aggregates while preserving its excellent thermal insulation properties has become a key technical challenge hindering the development of SiO2 aerogel-based insulating asphalt mixtures.

[0006] In summary, developing SiO2 aerogel solution formulation technology and exploring methods and processes for treating aggregates with SiO2 aerogel solution are key approaches to preparing SiO2 aerogel-modified aggregates with excellent thermal insulation properties. This lays a solid foundation for preparing SiO2 aerogel asphalt mixtures with excellent thermal insulation properties, effectively alleviating the problem of rutting deformation of asphalt pavements at high temperatures, reducing thermal shrinkage cracking and fatigue cracking caused by low-temperature changes, and avoiding the problems of porous aggregates significantly reducing pavement performance and conventional heat-insulating aggregates having poor thermal insulation effects. This has significant engineering, economic, and environmental implications. Summary of the Invention

[0007] To address the challenges of existing technologies, the present invention aims to provide a SiO2 aerogel solution, insulating aggregate, and preparation method. The SiO2 aerogel solution of the present invention contains a large amount of SiO2 aerogel powder to ensure thermal insulation, and has an initial settling time of over 90 minutes (the time at which sedimentation begins to occur) to facilitate construction. It also has good viscosity to ensure the adhesion between the SiO2 aerogel powder and the aggregate. The SiO2 aerogel-modified aggregate has excellent thermal insulation properties.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a SiO2 aerogel solution includes the following steps: Anhydrous ethanol and distilled water are mixed thoroughly to obtain an alcohol solution; Add a binder to the alcohol solution and mix well to obtain a viscous alcohol solution; Add SiO2 aerogel powder to the viscous alcohol solution and stir at a stirring rate of 100~500 r / min for 120~240 s to prepare the SiO2 aerogel solution. The amount of anhydrous ethanol added is 40% to 45% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 14% to 19% of the total mass of the SiO2 aerogel solution, the amount of binder added is 8% to 20% of the total mass of the SiO2 aerogel solution, and the amount of SiO2 aerogel powder added is 24% to 28% of the total mass of the SiO2 aerogel solution.

[0009] Preferably, SiO2 aerogel powder is added to the viscous alcohol solution, and the mixture is stirred at a stirring rate of 100~500 r / min for 120~240 s to prepare the SiO2 aerogel solution. When preparing the SiO2 aerogel solution, variable speed stirring is performed, and the stirring rate is switched repeatedly within the range of 100~500 r / min, with the variable speed of the stirring rate being 18-22 r / s.

[0010] Preferably, the particle size of the SiO2 aerogel powder is less than 1 μm. In this case, the amount of anhydrous ethanol added is 40%-41% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 14%-15% of the total mass of the SiO2 aerogel solution, the amount of binder added is 19%-20% of the total mass of the SiO2 aerogel solution, and the remainder is SiO2 aerogel powder.

[0011] Preferably, the particle size of the SiO2 aerogel powder is less than 10 μm, wherein the SiO2 aerogel powder with a particle size of 1-10 μm accounts for more than 95% of the total mass of the SiO2 aerogel powder. In this case, the amount of anhydrous ethanol added is 44%-45% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 18%-19% of the total mass of the SiO2 aerogel solution, the amount of binder added is 8%-9% of the total mass of the SiO2 aerogel solution, and the remainder is SiO2 aerogel powder.

[0012] Preferably, the particle size of the SiO2 aerogel powder is less than 50 μm, wherein the SiO2 aerogel powder with a particle size of 10-50 μm accounts for more than 95% of the total mass of the SiO2 aerogel powder. In this case, the amount of anhydrous ethanol added is 42%-43% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 16%-17% of the total mass of the SiO2 aerogel solution, the amount of binder added is 17%-18% of the total mass of the SiO2 aerogel solution, and the remainder is SiO2 aerogel powder.

[0013] Preferably, the adhesive is polyvinyl alcohol glue.

[0014] The present invention also provides a SiO2 aerogel solution, which is prepared by the preparation method of the present invention as described above.

[0015] The present invention also provides a method for preparing thermally insulating aggregate, comprising the following steps: The SiO2 aerogel solution of the present invention as described above is mixed with the aggregate and then dried to obtain the heat-insulating aggregate, wherein the SiO2 aerogel solution accounts for 10% to 20% of the mass of the aggregate.

[0016] Preferably, the aggregate is RAP material or natural aggregate; When mixing the SiO2 aerogel solution with the aggregate: pour the SiO2 aerogel solution into the aggregate and then let it stand; or spray the SiO2 aerogel solution onto the surface of the RAP material while stirring, and then let it stand. During the settling process, the mixture is stirred every 25-35 minutes, with the stirring rate controlled at 20-40 r / min and the stirring time controlled at 3-5 minutes each time; the total settling time is controlled at 120-140 minutes. During drying, the drying temperature is 105℃~120℃. Take it out and stir it every 55-65 minutes. The stirring rate is controlled at 10~30 r / min each time, and the stirring time is controlled at 5~10 minutes until it is completely dried.

[0017] The present invention also provides a heat-insulating aggregate, which is prepared by the heat-insulating aggregate preparation method of the present invention as described above.

[0018] The present invention has the following beneficial effects: The method for preparing SiO2 aerogel solution provided by this invention involves first mixing anhydrous ethanol and distilled water to form an alcohol solution, then adding a binder to obtain a viscous alcohol solution, and finally adding SiO2 aerogel powder and stirring at a stirring rate of 100-500 r / min for 120-240 s. This method, combined with a specific ratio of anhydrous ethanol (40%-45% by mass), distilled water (14%-19%), binder (8%-20%), and SiO2 aerogel powder (24%-28%), synergistically addresses key issues in the preparation of SiO2 aerogel solution from both system composition and process perspectives. Based on the experimental results of the embodiments and comparative examples of this invention, the specific principle of this invention is as follows: This specific alcohol-water ratio can prevent the binder from agglomerating due to excessive ethanol content. The process involves gelation, preventing the SiO2 aerogel powder from floating and stratifying due to excessive moisture content, and ensuring uniform dispersion of the binder in the solution. The sequence of preparing an aqueous ethanol solution before adding the aerogel powder avoids direct contact between the SiO2 aerogel and high-concentration anhydrous ethanol, preventing alcoholysis and effectively protecting its microporous structure while preserving its excellent thermal insulation properties. Specific stirring rates and times ensure thorough wetting and uniform dispersion of the SiO2 aerogel powder, preventing clumping, adhesion to walls, or floating, thus increasing the effective aerogel content and system stability. A reasonable amount of binder provides the solution with suitable viscosity, solving the problem of pure SiO2 aerogel's lack of adhesiveness and difficulty in binding with aggregates, and also preventing clumping and adhesion between aggregates during mixing, providing a stable and usable treatment solution for subsequent aggregate modification. The entire preparation process can be completed simply by stirring at room temperature. The process conditions are mild, the parameters are clear, and the controllability is strong. It can stably prepare SiO2 aerogel solutions with uniform dispersion, good stability, suitable adhesion, and high solid content, providing a reliable preparation method for the engineering application of SiO2 aerogel in the thermal insulation modification of asphalt pavement aggregates. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the steps required in the preparation process are briefly described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a diagram illustrating the preparation method steps of an embodiment of the present invention.

[0020] Figure 2 This is a photograph of the SiO2 aerogel solution prepared according to the preferred embodiment 3 of the present invention.

[0021] Figure 3 This is a photograph showing the layering phenomenon of SiO2 aerogel powder covering the surface of the viscous alcohol solution during the experiment when the ratio of anhydrous ethanol to distilled water in Comparative Example 1 of this invention reaches 1:1.

[0022] Figure 4 This is a photograph of the phenomenon where, when the ratio of anhydrous ethanol to distilled water in Comparative Example 2 of the present invention reaches 4:1, the binder agglomerates into a gel-like solid after being dripped in during the experiment.

[0023] Figure 5 The photo shows a small amount of SiO2 aerogel powder floating on the solution and exhibiting clumping and sticking to the wall due to insufficient stirring time after adding SiO2 aerogel powder in Comparative Example 7 of this invention.

[0024] Figure 6 These are photographs of the morphology of the natural aggregate in Comparative Example 8 and the SiO2 aerogel-modified natural aggregate in Example 4 of this invention.

[0025] Figure 7 This is a photograph showing the temperature distribution of the top surface of the natural aggregate in Comparative Example 8 of this invention at different heating times within 60 minutes on a constant-temperature copper plate at 55°C.

[0026] Figure 8 This is a photograph showing the temperature distribution of the top surface of the SiO2 aerogel-modified natural aggregate in Example 4 of the present invention on a 55°C constant-temperature hot copper plate at different heating times within 60 minutes.

[0027] Figure 9 These are photographs comparing the time-varying temperature paths of the top surface of the natural aggregate in Comparative Example 8 and the SiO2 aerogel-modified natural aggregate in Example 4 on a 55°C constant-temperature hot copper plate over 60 minutes.

[0028] Figure 10 These are photographs of the morphology of the untreated RAP material in Comparative Example 9 and the SiO2 aerogel-modified RAP material in Example 5 of this invention.

[0029] Figure 11 This is a photograph showing the temperature distribution of the top surface of the RAP material of Comparative Example 9 of this invention on a 55°C constant-temperature hot copper plate at different heating times within 60 minutes.

[0030] Figure 12 This is a photograph showing the temperature distribution of the top surface of the SiO2 aerogel modified RAP material of Example 5 of the present invention at different heating times within 60 minutes on a constant-temperature copper plate at 55°C.

[0031] Figure 13 These are photographs comparing the time-varying temperature paths of the top surface of the RAP material in Comparative Example 9 and the SiO2 aerogel-modified RAP material in Example 5 on a 55°C constant-temperature hot copper plate over 60 minutes.

[0032] Figure 14 These are photographs of some Marshall specimens prepared according to Examples 6-7 and Comparative Examples 11-12 of the present invention.

[0033] Figure 15 These are photographs of some rut plate specimens prepared according to Examples 6-7 and Comparative Examples 11-12 of the present invention.

[0034] Figure 16 These are photographs showing the outdoor thermal insulation test results of some rutted slab specimens prepared according to Examples 6-7 and Comparative Examples 11-12 of the present invention. Detailed Implementation

[0035] This invention discloses a method for preparing SiO2 aerogel solution and enhancing the thermal insulation properties of aggregates. Those skilled in the art can draw upon this content and make modifications or appropriate changes and combinations to the methods and process parameters described herein without departing from the scope, spirit, and intent of this invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within this invention.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0037] This invention provides a SiO2 aerogel solution, insulating aggregate, and a preparation method. The SiO2 aerogel solution is obtained from SiO2 aerogel powder, a binder, distilled water, and anhydrous ethanol. The insulating aggregate is composed of the SiO2 aerogel solution and aggregate (including natural aggregate and / or RAP material) modified by this invention. The SiO2 aerogel solution prepared by this invention has good adhesion, a long stability time, and a high SiO2 aerogel content. The SiO2 aerogel-modified aggregate has excellent thermal insulation properties without reducing the mechanical properties of the aggregate, and its overall performance meets road application requirements. This invention endows the aggregate with thermal insulation properties, effectively alleviating rutting problems in asphalt pavements in high-temperature areas and low-temperature cracking problems in cold areas. The preparation is simple, the production equipment is simple, the process conditions are mild, and the production efficiency is high.

[0038] Specifically, the method for preparing the SiO2 aerogel solution of the present invention includes the following steps: First, add anhydrous ethanol to distilled water and stir until homogeneous to obtain an alcohol solution. Then, add the binder to the alcohol solution and stir until homogeneous to obtain a viscous alcohol solution. Subsequently, add SiO2 aerogel powder to the viscous alcohol solution and continue stirring until homogeneous to obtain a viscous SiO2 aerogel solution.

[0039] This invention creatively discovers that the order of addition of components and stirring time affect the final preparation result when preparing SiO2 aerogel solutions. For example, adding the binder directly to anhydrous ethanol or to a solution with a high anhydrous ethanol content will cause the binder to precipitate. Directly mixing SiO2 aerogel powder with anhydrous ethanol will induce alcoholysis, and drying will damage the pore structure of the SiO2 aerogel. When mixed with distilled water, stratification will occur. Adding SiO2 aerogel powder to a solvent will also cause stratification if the water content is too high or the stirring time is too short. After the SiO2 aerogel solution is prepared, prolonged standing will produce obvious precipitation. The initial sedimentation time can reflect the compatibility of the components in the SiO2 aerogel solution, and the transmittance can indirectly test and evaluate the SiO2 aerogel content in the solution.

[0040] In the above-mentioned scheme of the present invention, the amount of anhydrous ethanol added is 40% to 45% of the total mass of SiO2 aerogel solution, the amount of distilled water added is 14% to 19% of the total mass of SiO2 aerogel solution, the amount of binder added is 8% to 20% of the total mass of SiO2 aerogel solution, and the amount of SiO2 aerogel powder added is 24% to 28% of the total mass of SiO2 aerogel solution.

[0041] When mixing anhydrous ethanol and distilled water, the stirring rate should be 50-100 r / min, and the stirring time should be 10-30 s. When mixing binder and alcohol solution, the stirring rate should be 50-100 r / min, and the stirring time should be 30-100 s. When mixing SiO2 aerogel powder and viscous alcohol solution, the stirring rate should be 100-500 r / min, and the stirring time should be 120-240 s. When mixing SiO2 aerogel powder with viscous alcohol solution, it is best to use variable speed stirring. Specifically, the stirring speed should be switched repeatedly within the range of 100~500 r / min. That is, you can start stirring at a stirring speed of 100 r / min, then gradually increase the speed to 500 r / min, then gradually decrease the speed from 500 r / min to 100 r / min, and then start stirring at a stirring speed of 100 r / min again. Repeat this process until the preset stirring time is reached. The speed variation of the stirring speed is 18-22 r / s. Using variable-speed stirring can effectively prevent problems such as powder scattering, floating, and sticking to the walls caused by continuous high-speed stirring, while ensuring that the SiO2 aerogel powder and the viscous alcohol solution are fully and uniformly mixed. The low-speed stage helps the aerogel powder to be stably wetted and initially dispersed, avoiding the dry powder being directly thrown up by high-speed impact. The high-speed stage can improve the overall uniformity of the solution and eliminate local agglomeration. The reciprocating variable speed takes into account both the dispersion effect and the powder stability, so that the powder is gradually coated by the slurry. This ensures that the mixing is sufficient and the system is uniform, while significantly reducing powder scattering loss, improving raw material utilization and preparation safety, and finally obtaining a SiO2 aerogel solution with better stability and more uniform dispersion.

[0042] In the above-mentioned scheme of the present invention, hydrophobic SiO2 aerogel powder with a particle size of less than 1 μm can be used. Through experiments, it is further preferred that the amount of anhydrous ethanol added is 40%-41% of the total mass of SiO2 aerogel solution, the amount of distilled water added is 14%-15% of the total mass of SiO2 aerogel solution, the amount of binder added is 19%-20% of the total mass of SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

[0043] In the above-mentioned scheme of the present invention, hydrophobic SiO2 aerogel powder with a particle size of less than 10 μm (of which, SiO2 aerogel powder with a particle size of 1-10 μm accounts for more than 95% of the total mass of SiO2 aerogel powder) can be used. Through experiments, it is further preferred that the amount of anhydrous ethanol added is 44%-45% of the total mass of SiO2 aerogel solution, the amount of distilled water added is 18%-19% of the total mass of SiO2 aerogel solution, the amount of binder added is 8%-9% of the total mass of SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

[0044] In the above-mentioned scheme of the present invention, hydrophobic SiO2 aerogel powder with a particle size of less than 50 μm (of which, SiO2 aerogel powder with a particle size of 10-50 μm accounts for more than 95% of the total mass of SiO2 aerogel powder) can be used. Through experiments, it is further preferred that the amount of anhydrous ethanol added is 42%-43% of the total mass of SiO2 aerogel solution, the amount of distilled water added is 16%-17% of the total mass of SiO2 aerogel solution, the amount of binder added is 17%-18% of the total mass of SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

[0045] This invention modifies aggregates (such as RAP materials or natural aggregates) using the above-mentioned SiO2 aerogel solution to obtain the thermally insulating aggregate of this invention. Specifically, the preparation method of the thermally insulating aggregate of this invention includes the following processes: For natural aggregates, SiO2 aerogel solution is poured into the aggregates, left to stand, and stirred intermittently until the mixture is uniform. Then, it is placed in an oven to dry, and stirred until uniformly dried to obtain SiO2 aerogel solution modified natural aggregates.

[0046] For RAP materials, SiO2 aerogel solution is put into a spray bottle and sprayed onto the surface of the RAP material while stirring. After the SiO2 aerogel solution is sprayed, it is left to stand and stirred intermittently until it is evenly mixed. Then it is placed in an oven to dry and stirred until it is evenly dried to obtain SiO2 aerogel solution modified RAP material.

[0047] In the above scheme, the amount of SiO2 aerogel solution should be 10% to 20% of the mass of natural aggregate or RAP material.

[0048] In the above scheme, after the SiO2 aerogel solution is mixed with the aggregate (natural aggregate or RAP material), the standing time is generally 120-140 minutes. During this process, it is stirred every 25-35 minutes, with a stirring rate of 20-40 r / min and an interval of 3-5 minutes. The material of the part of the stirring tool that comes into contact with the material should be a hard material that does not chemically react with the SiO2 aerogel solution, such as stainless steel or a wooden stick. This invention uses a method of first standing and then stirring to mix the SiO2 aerogel solution with the aggregate. The purpose is to ensure that the SiO2 aerogel solution fully wets the aggregate while achieving a uniform distribution of the SiO2 aerogel solution components on the surface and in the internal gaps of the aggregate. A longer settling time allows sufficient time for the SiO2 aerogel solution to penetrate, enabling it to slowly enter the pores, cracks, and interparticle spaces on the aggregate surface through its own fluidity. This prevents the solution from being carried away from the aggregate surface before it can penetrate due to continuous stirring, thus ensuring effective adhesion and filling of the aggregate's internal structure with aerogel, improving the uniformity of modification and the integrity of the insulation layer. Combined with low-speed intermittent stirring, this breaks up any potential localized solution accumulation or surface film formation, ensuring full contact between all parts of the aggregate and the aerogel solution. The gentle stirring speed and controllable time prevent disruption of the established wetting and penetration state, and avoid the shedding, delamination, or scattering of SiO2 aerogel powder. This combination of settling and low-speed intermittent stirring achieves both thorough filling and coating of the aggregate with the SiO2 aerogel solution, while ensuring a uniform and robust modified layer. This provides a reliable guarantee for the subsequent preparation of aerogel-modified aggregates with stable thermal insulation performance and reliable road application performance.

[0049] In the above scheme, after standing and stirring, the SiO2 aerogel solution and aggregate mixture are placed in an oven at a temperature of 105℃~120℃. The mixture is taken out and stirred once every 55-65 minutes. The stirring rate should be 10~30 r / min each time, and the stirring time should be 5~10 minutes.

[0050] The raw material information used in the following embodiments and comparative examples of this invention is as follows: Adhesive (polyvinyl alcohol glue), supplier: Jiangming Desai Chemical Trading Co., Ltd.; 1 SiO2 aerogel powder with particle size ZE, supplier: Langfang Zhuoer Insulation Materials Co., Ltd.; 10 SiO2 aerogel powder with particle size KM, supplier: Suzhou Kangmai New Materials Co., Ltd.; In this SiO2 aerogel powder, the particle size of 1-10μm accounts for more than 95% of the mass. 50 ZN SiO2 aerogel powder with particle size of 10-50μm, supplier: Shenzhen Zhongning Technology Co., Ltd.; in this SiO2 aerogel powder, the mass of the particle size is more than 95%; Anhydrous ethanol, supplier: Tianjin Tianli Chemical Reagent Co., Ltd. Distilled water, homemade in the lab; Natural aggregate (limestone crushed stone), supplier: Shaanxi Ankang Tianlong Mining Engineering Construction Co., Ltd.; RAP material, supplier: Shaanxi Sanqin Road & Bridge Co., Ltd.

[0051] Example 1 The preparation method of SiO2 aerogel solution in this embodiment includes the following steps: 40.3% anhydrous ethanol and 14.8% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 19.8% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 25.1% ZE type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was then taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0052] Example 2 The preparation method of SiO2 aerogel solution in this embodiment includes the following steps: 45.0% anhydrous ethanol and 19% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 7.9% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then, 28.1% KM type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was then taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0053] Example 3 The preparation method of SiO2 aerogel solution in this embodiment includes the following steps: 42.5% anhydrous ethanol and 15.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 17.9% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 24% Zn-type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was then taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0054] Example 4 The method for preparing the thermal insulation aggregate in this embodiment includes the following steps: 1500g of natural aggregate with a particle size of 5-10mm was dried in an oven at 105℃ and cooled to room temperature in a drying oven. The ZN-type SiO2 aerogel solution prepared in Example 3 was taken and poured into the natural aggregate, wherein the ZN-type SiO2 aerogel solution accounted for 15% of the mass of the natural aggregate. The mixture was left to stand for 120min, and stirred with a stainless steel rod at a stirring rate of 30 r / min for 5min every 30min. Then the mixture of SiO2 aerogel solution and aggregate was placed in an oven at 120℃. It was taken out every 60min and stirred once at a stirring rate of 10 r / min for 5min each time until it was completely dried, thus obtaining SiO2 aerogel modified natural aggregate. SiO2 aerogel-modified natural aggregate was placed between two layers of dry clay sheets, and its overall thermal conductivity was tested using a flat plate thermal conductivity meter. A 4cm thick insulation trough was constructed using polystyrene foam board, with an open size of 10cm×10cm×10cm. The SiO2 aerogel-modified natural aggregate was densely packed into the trough to a height of 90mm and heated under an iodine-tungsten lamp. The temperature difference between the top and bottom surfaces of the SiO2 aerogel-modified natural aggregate was measured, and its thermal insulation coefficient (the temperature difference per unit thickness per unit time before the temperature difference between the top and bottom surfaces of the heat-insulating material stabilizes within 120 minutes of external radiation) was calculated. Based on the solid content of each component in the SiO2 aerogel solution and the mass change of the aggregate before and after modification, the adhesion coefficient of the natural aggregate after modification with the SiO2 aerogel solution was calculated. The SiO2 aerogel-modified natural aggregate was filled to a size of... An open stainless steel box measuring 135mm × 18.3mm was placed on a hot copper plate at a constant temperature of 55℃. The temperature distribution on the top surface of the aggregate was measured using an infrared thermal imager over a period of 60 minutes. The experimental results are shown in Table 2.

[0055] Example 5 The method for preparing the thermal insulation aggregate in this embodiment includes the following steps: 1500g of RAP material with a particle size of 5-10mm was dried in an oven at 105℃ and cooled to room temperature in a drying oven. The ZN-type SiO2 aerogel solution prepared in Example 3 was taken and put into a spray bottle and sprayed onto the surface of the RAP material while stirring. It was left to stand for 120min and stirred for 5min every 30min with a stainless steel rod at a stirring rate of 30 r / min. The amount of ZN-type SiO2 aerogel solution sprayed was 15% of the mass of the RAP material. Then the mixture of SiO2 aerogel solution and RAP material was placed in an oven at 120℃. It was taken out every 60min and stirred once at a stirring rate of 10 r / min for 5min each time until it was completely dried to obtain SiO2 aerogel modified RAP material. SiO2 aerogel-modified RAP material was placed between two layers of dry modeling clay sheets, and its overall thermal conductivity was measured using a flat plate thermal conductivity meter. A 4cm thick insulation tank was constructed using polystyrene foam board, with an opening size of 10cm×10cm×10cm. The SiO2 aerogel-modified RAP material was densely packed into the insulation tank to a height of 90mm, and heated under an iodine-tungsten lamp. The temperature difference between the top and bottom surfaces of the SiO2 aerogel-modified RAP material was measured, and its thermal insulation coefficient was calculated. Based on the solid content of each component in the SiO2 aerogel solution and the mass change of the RAP material before and after modification, the adhesion coefficient of the RAP material after modification with the SiO2 aerogel solution was calculated. The SiO2 aerogel-modified RAP material was then filled to a size of... An open stainless steel box measuring 135mm × 18.3mm was placed on a 55℃ constant-temperature hot copper plate, and the temperature distribution on the top surface of the RAP material was measured using an infrared thermal imager over 60 minutes. The experimental results are shown in Table 2.

[0056] Example 6 This embodiment includes the following process: Based on the aggregate gradation curve of SMA-13 ​​in JTG F40-2004, natural aggregates were blended. ZN-type SiO2 aerogel solution was prepared according to the method in Example 3. Then, SiO2 aerogel-modified natural aggregates were prepared according to the method in Example 4. SiO2 aerogel-modified SMA-13 ​​mixtures were prepared using the SMA design method in JTG F40-2004. The corresponding Marshall specimen SA-SMA-M was prepared using the method in JTGE20-2011. The asphalt type used was SBS modified asphalt, with a dosage of 5.66%. Rutting slabs SA-SMA-R were prepared using the method in JTG E20-2011. The thermal conductivity of the Marshall specimen SA-SMA-M was tested using a thermal conductivity meter. Based on the dimensions of the rutted slab (30cm×30cm×5cm), a 5cm thick insulation groove was constructed using polystyrene foam board and tightly fitted to the rutted slab. Temperature sensors were attached to the top and bottom surfaces. At 13:00 noon on a sunny summer day with an ambient temperature of 35℃, the rutted slab specimen SA-SMA-R was placed under sunlight on an outdoor road surface to measure the temperature difference and calculate the thermal insulation coefficient. Based on the JTG E20-2011 standard test method and corresponding instruments, the high-temperature stability (dynamic stability), low-temperature crack resistance (maximum flexural tensile failure strain), and water stability (marshall residual stability after immersion) of the SiO2 aerogel-modified SMA-13 ​​mixture were tested. The experimental results are shown in Table 3.

[0057] Example 7 This embodiment includes the following process: Replacing 30% of the natural aggregate with RAP material, the natural aggregate and RAP material were adjusted based on the aggregate gradation curve of SMA-13 ​​in JTG F40-2004 standard, aiming to be as close to the middle line as possible. ZN-type SiO2 aerogel solution was prepared according to the method in Example 3, and SiO2 aerogel modified RAP material was prepared according to the method in Example 4. SiO2 aerogel modified SMA-13 ​​recycled mixture was prepared using the SMA design method in JTG F40-2004 standard, and the corresponding recycled Marshall specimen SA-SMA-MR was prepared using the method in JTG E20-2011 standard. The asphalt type used was SBS modified asphalt, with a dosage of 4.52%. Recycled rutting slab SA-SMA-RR was prepared using the method in JTG E20-2011 standard. The thermal conductivity of the recycled Marshall specimen SA-SMA-MR was tested using a thermal conductivity meter. Based on the dimensions of the rutted slab (30cm×30cm×5cm), a 5cm thick insulation groove was constructed using polystyrene foam board and tightly fitted to the recycled rutted slab. Temperature sensors were attached to the top and bottom surfaces. At 13:00 on a sunny summer day with an ambient temperature of 35℃, the recycled rutted slab specimen SA-SMA-RR was placed under sunlight on an outdoor road surface to measure the temperature difference and calculate the thermal insulation coefficient. Based on the JTG E20-2011 standard test method and corresponding instruments, the high-temperature stability (dynamic stability), low-temperature crack resistance (maximum flexural tensile failure strain), and water stability (marshall residual stability after immersion) of the SiO2 aerogel-modified SMA-13 ​​recycled mixture were tested. The experimental results are shown in Table 3.

[0058] Comparative Example 1 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 40% anhydrous ethanol and 40% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 10% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then, 10% Zn-type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded with a stopwatch (initial precipitation time). The middle solution was taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0059] Comparative Example 2 The preparation method of this comparative example includes the following steps: Mix 40% anhydrous ethanol and 10% distilled water in a beaker, stir with a glass rod at 60 r / min for 10 s to obtain an alcohol solution, add 20% binder to the alcohol solution, and observe and record whether there is agglomeration or gelation.

[0060] Comparative Example 3 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 44.4% anhydrous ethanol and 29.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 18.5% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. The time when obvious precipitation first appeared (initial precipitation time) was observed and recorded. The middle solution was taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0061] Comparative Example 4 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 44.4% anhydrous ethanol and 29.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 18.5% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 7.5% ZE type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was then taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0062] Comparative Example 5 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 44.4% anhydrous ethanol and 29.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 18.5% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 7.5% KM type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded with a stopwatch (initial precipitation time). The middle solution was taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0063] Comparative Example 6 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 44.4% anhydrous ethanol and 29.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 18.5% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 7.5% Zn-type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 120 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0064] Comparative Example 7 The preparation method of this comparative SiO2 aerogel solution includes the following steps: 42.5% anhydrous ethanol and 15.6% distilled water were mixed in a beaker and stirred with a glass rod at 60 r / min for 10 s to obtain an alcohol solution. 17.9% binder was added to the alcohol solution and stirred with a glass rod at 60 r / min for 30 s to obtain a viscous alcohol solution. Then 24% Zn-type SiO2 aerogel powder was added and stirred with a glass rod at 60 r / min for 60 s to obtain a SiO2 aerogel solution. The time when obvious precipitation first appeared was observed and recorded using a stopwatch (initial precipitation time). The middle solution was then taken with a dropper and placed in a spectrophotometer to test its transmittance. The experimental results are shown in Table 1.

[0065] Comparative Example 8 The process of aggregate modification in this comparative example includes: 1500g of natural aggregate with a particle size of 5-10mm was selected, dried in an oven at 105℃, and then cooled to room temperature in the drying oven. It was then placed between two layers of dried modeling clay sheets, and its overall thermal conductivity was tested using a flat plate thermal conductivity meter. A 4cm thick insulation trough was constructed using polystyrene foam board, with an open size of 10cm×10cm×10cm. The natural aggregate was densely packed into the insulation trough to a height of 90mm, and heated under an iodine-tungsten lamp. The temperature difference between the top and bottom surfaces of the SiO2 aerogel-modified natural aggregate was measured, and its thermal insulation coefficient was calculated. The natural aggregate was then used to fill the trough with materials of various sizes. An open stainless steel box measuring 135mm × 18.3mm was placed on a hot copper plate at a constant temperature of 55℃. The temperature distribution on the top surface of the aggregate was measured using an infrared thermal imager over a period of 60 minutes. The experimental results are shown in Table 2.

[0066] Comparative Example 9 The process of aggregate modification in this comparative example includes: 1500g of RAP material with a particle size of 5-10mm was selected, dried in an oven at 105℃, and then cooled to room temperature in the drying oven. It was then placed between two layers of dried modeling clay sheets, and its overall thermal conductivity was tested using a flatbed thermal conductivity meter. A 4cm thick insulation groove was constructed using polystyrene foam board, with an opening size of 10cm×10cm×10cm. The RAP material was densely packed into the insulation groove to a height of 90mm, and heated under an iodine-tungsten lamp. The temperature difference between the top and bottom surfaces of the RAP material was measured, and its thermal insulation coefficient was calculated. The RAP material was then used to fill the groove to a depth of... An open stainless steel box measuring 135mm × 18.3mm was placed on a 55℃ constant-temperature hot copper plate. The temperature distribution on the top surface of the RAP material was measured using an infrared thermal imager over 60 minutes. The experimental results are shown in Table 2.

[0067] Comparative Example 10 The process of aggregate modification in this comparative example includes: 1500g of RAP material with a particle size of 5~10mm was dried in an oven at 105℃ and cooled to room temperature in a drying oven. ZN-type SiO2 aerogel solution was prepared according to the method in Example 3. 5% of the mass of the RAP material was taken into a spray bottle and sprayed onto the surface of the RAP material while stirring. The mixture was left to stand for 120min, and stirred for 5min at a stirring rate of 30 r / min with a stainless steel rod every 30min. Then, the mixture of SiO2 aerogel solution and RAP material was placed in an oven at 120℃. It was taken out every 60min and stirred once at a stirring rate of 10 r / min for 5min each time until it was completely dried, thus obtaining SiO2 aerogel modified RAP material. The SiO2 aerogel-modified RAP material was placed between two layers of dry clay sheets, and its overall thermal conductivity was tested using a flat plate thermal conductivity meter. A 4cm thick insulation tank was made using polystyrene foam board, with an opening size of 10cm×10cm×10cm. The SiO2 aerogel-modified RAP material was densely packed into the insulation tank to a height of 90mm, and heated under an iodine-tungsten lamp. The temperature difference between the top and bottom surfaces of the SiO2 aerogel-modified RAP material was measured, and its thermal insulation coefficient was calculated. Based on the solid content of each component in the SiO2 aerogel solution and the mass change of the RAP material before and after modification, the adhesion coefficient of the RAP material after modification with SiO2 aerogel solution was calculated. The experimental results are shown in Table 2.

[0068] Comparative Example 11 The process of aggregate modification in this comparative example includes: Based on the aggregate gradation curve of SMA-13 ​​in JTG F40-2004 specification, natural aggregates were blended, and SMA-13 ​​mixtures were prepared using the SMA design method in JTG F40-2004 specification. The corresponding Marshall specimen SMA-M was prepared using the method in JTG E20-2011 specification. The asphalt type used was SBS modified asphalt, and the dosage was 5.66%. Rutting slabs SMA-R were prepared using the method in JTG E20-2011 specification. The thermal conductivity of the Marshall specimen SMA-M was tested using a thermal conductivity meter. Based on the dimensions of the rutted slab (30cm×30cm×5cm), a 5cm thick insulation groove was constructed using polystyrene foam board and tightly fitted to the rutted slab. Temperature sensors were attached to the top and bottom surfaces. At 13:00 noon on a sunny summer day with an ambient temperature of 35℃, the rutted slab specimen SMA-R was placed under sunlight on an outdoor road surface to test its temperature difference and calculate the thermal insulation coefficient. Based on the JTG E20-2011 standard test method and corresponding instruments, the high-temperature stability (dynamic stability), low-temperature crack resistance (maximum flexural tensile failure strain), and water stability (marshall residual stability after immersion) of the SMA-13 ​​mixture were tested. The experimental results are shown in Table 3.

[0069] Comparative Example 12 The process of aggregate modification in this comparative example includes: Replacing 30% of the natural aggregate with RAP material, the natural aggregate and RAP material were adjusted based on the aggregate gradation curve of SMA-13 ​​in JTG F40-2004 specification, aiming to be as close to the middle line as possible. SMA-13 ​​recycled mixture was prepared using the SMA design method in JTG F40-2004 specification, and the corresponding recycled Marshall specimen SMA-MR was prepared using the method in JTG E20-2011 specification. The asphalt type used was SBS modified asphalt, with a dosage of 4.52%. Recycled rutting slab SMA-RR was prepared using the method in JTG E20-2011 specification. The thermal conductivity of the recycled Marshall specimen SMA-MR was tested using a thermal conductivity meter. Based on the dimensions of the rutted slab (30cm×30cm×5cm), a 5cm thick insulation groove was constructed using polystyrene foam board and tightly fitted to the recycled rutted slab. Temperature sensors were attached to the top and bottom surfaces. At 13:00 on a sunny summer day with an ambient temperature of 35℃, the recycled rutted slab specimen SMA-RR was placed under sunlight on an outdoor road surface to measure the temperature difference and calculate the thermal insulation coefficient. Based on the JTG E20-2011 standard test method and corresponding instruments, the high-temperature stability (dynamic stability), low-temperature crack resistance (maximum flexural tensile failure strain), and water stability (marshall residual stability after immersion) of the SMA-13 ​​recycled mixture were tested. The experimental results are shown in Table 3.

[0070] The test results of the above embodiments and comparative examples are compared as follows: The initial sedimentation time and transmittance of the SiO2 aerogel solutions prepared in Examples 1-3 and Comparative Examples 3-7 are shown in Table 1. Sedimentation times exceeding 120 min are represented as 120 min; the test results are representative values ​​from multiple parallel tests.

[0071] Table 1

[0072] As can be seen from Table 1, the initial settling times of the SiO2 aerogel solutions prepared in Examples 1 to 3 are all longer than those in Comparative Examples 4 to 7, while their transmittance is lower than that in Comparative Examples 3 to 7. This indicates that the SiO2 aerogel solutions prepared according to the methods in Examples 1 to 3 have better suspension stability (see Table 1). Figure 2 This makes construction easier, and the high SiO2 aerogel content in the solution helps to exert its heat insulation properties.

[0073] The different initial settling times in Examples 1, 2, and 3 indicate that different types of SiO2 aerogels have significant differences in suspension stability in solution. However, an initial settling time exceeding 90 minutes is sufficient to meet construction requirements. The difference in light transmittance is due to the different compatibility between SiO2 aerogels and solutions. Example 2 has the lowest light transmittance, indicating that the amount of SiO2 aerogel suspended in solution is the highest.

[0074] In Comparative Example 1, the ratio of anhydrous ethanol to distilled water was 1:1. During the experiment, it was found that after stirring, a large amount of SiO2 aerogel powder still covered the surface of the viscous alcohol solution (see...). Figure 3 This indicates that excessive distilled water content will prevent SiO2 aerogel powder from suspending in the viscous alcohol solution.

[0075] In Comparative Example 2, the ratio of anhydrous ethanol to distilled water was 4:1. During the experiment, it was observed that as soon as the adhesive was added to the alcohol solution, it agglomerated into a gel-like solid (see...). Figure 4 This indicates that excessive anhydrous ethanol content can lead to the coagulation of the binder.

[0076] The longer initial settling time and higher light transmittance of Comparative Example 3 are due to the absence of SiO2 aerogel powder and the presence of only binder, which also indirectly demonstrates the excellent construction stability of Example 3.

[0077] Both Example 1 and Comparative Example 4 used ZE-type SiO2 aerogel powder. However, the SiO2 aerogel solution formulation in Comparative Example 4 was outside the recommended range of this invention, with an initial settling time of only 20 minutes, making on-site construction difficult. Furthermore, its light transmittance was 2.58 times that of Example 1, indicating that the content of suspended SiO2 aerogel powder was significantly lower than in Example 1. Both Example 2 and Comparative Example 5 used KM-type SiO2 aerogel powder. Comparative Example 5 had an initial settling time of only 25 minutes, making on-site construction difficult, and its light transmittance was 17% higher than in Example 2, indicating that the content of suspended SiO2 aerogel powder was also relatively low. Both Example 3 and Comparative Example 6 used ZN-type SiO2 aerogel powder. Comparative Example 6 had an initial settling time of 78 minutes, still exhibiting insufficient construction stability, and its light transmittance was 2.16 times that of Example 3, indicating that the content of suspended SiO2 aerogel powder was significantly lower than in Example 3. These examples demonstrate that SiO2 aerogel solutions prepared according to the present invention have better construction stability and higher SiO2 aerogel powder content.

[0078] The main difference between Comparative Examples 4, 5 and 6 is the type of SiO2 aerogel. The ZE, KM and ZN types of SiO2 aerogels have the greatest difference in particle size. This indicates that the solution formulations for SiO2 aerogels with different particle sizes are also quite different. Therefore, the optimal solution formulations used for different types of SiO2 aerogels in Examples 1 to 3 are not uniform.

[0079] Compared to Comparative Example 7, the stirring time for Comparative Example 7 after adding SiO2 aerogel powder was halved. During the experiment, a small amount of SiO2 aerogel powder was observed floating on the solution, and clumping and adhesion to the walls were observed (see...). Figure 5 The results indicate that the mixing was insufficient. The stirring time is crucial to the uniformity of the SiO2 aerogel solution. The experimental results show that Comparative Example 7 has a shorter initial settling time and higher light transmittance, which further confirms that the stirring time affects the construction stability of the SiO2 aerogel solution and the suspended content of SiO2 aerogel powder in the solution.

[0080] Aggregates were prepared according to Examples 4-5 and Comparative Examples 8-10, and their comprehensive thermal conductivity, temperature difference, thermal insulation coefficient, and adhesion coefficient are shown in Table 2. The test results are representative values ​​from multiple parallel tests.

[0081] Table 2

[0082] As shown in Table 2, the overall thermal conductivity of the SiO2 aerogel-modified natural aggregate and SiO2 aerogel-modified RAP material prepared in Examples 4 and 5 is 20% and 8.9% lower than that of Comparative Example 8 (untreated natural aggregate) and Comparative Example 9 (untreated RAP material), respectively. This indicates that the thermal conductivity of the natural aggregate and RAP material is reduced after SiO2 aerogel solution modification treatment.

[0083] In Examples 4 and 5, the temperature difference between SiO2 aerogel-modified natural aggregate and SiO2 aerogel-modified RAP material was 0.3℃ and 1.4℃ higher than that of Comparative Examples 8 and 9, respectively. This indicates that the temperature at the bottom of the aggregate can be reduced to some extent after modification with SiO2 aerogel solution. However, the reason why the cooling effect is not very significant is the difference in ambient temperature during the test.

[0084] In Examples 4 and 5, the thermal insulation coefficients of SiO2 aerogel-modified natural aggregate and SiO2 aerogel-modified RAP material were 36.3% and 4.7% higher than those of Comparative Examples 8 and 9, respectively. This indicates that the time required for the aggregate to reach a temperature equilibrium state is extended after SiO2 aerogel solution modification. The slight increase in the thermal insulation coefficient of SiO2 aerogel-modified RAP material may be due to the shedding of old asphalt with SiO2 aerogel adhering to it during the SiO2 aerogel solution modification process. This reasoning can be confirmed by the adhesion coefficient.

[0085] In Example 5, the thermal conductivity of the SiO2 aerogel-modified RAP material was lower than that of Comparative Example 10, while the temperature difference between the top and bottom surfaces and the thermal insulation coefficient were higher than those of Comparative Example 10. This indicates that the 5% SiO2 aerogel modification solution dosage is not the optimal dosage to enhance the thermal insulation of the RAP material. The adhesion coefficient of Example 5 was 28.1% lower than that of Comparative Example 10, indicating that a 5% SiO2 aerogel modification solution dosage can achieve better SiO2 aerogel utilization. However, considering its overall thermal insulation performance, the SiO2 aerogel modification solution dosage range recommended by this invention is still better.

[0086] The morphologies of the natural aggregate in Comparative Example 8 and the SiO2 aerogel-modified natural aggregate in Example 4 are shown below. Figure 6 The temperature distribution on the top surface of the copper plate at a constant temperature of 55℃ over 60 minutes is shown in the attached figure. Figures 7-8 See the appendix for a comparison of temperature time-varying paths. Figure 9 .

[0087] Depend on Figures 7-9The comparison shows that the highest temperature of the top surface of the SiO2 aerogel-modified natural aggregate in Example 4 is 1.8°C lower than that of the natural aggregate in Comparative Example 8, while the lowest temperature of its top surface is 1.3°C lower. During the heating process over 60 minutes, although the initial temperature of the SiO2 aerogel-modified natural aggregate in Example 4 was higher, the final equilibrium highest and lowest temperatures of its top surface were both lower than those of the natural aggregate in Comparative Example 8. Since the sample thickness is only 1.8 cm and it is in a loose state, the difference in thermal insulation effect between the two is relatively limited.

[0088] The morphologies of the natural aggregate in Comparative Example 9 and the SiO2 aerogel-modified natural aggregate in Example 5 are shown below. Figure 10 The temperature distribution on the top surface of a copper plate heated to a constant temperature of 55℃ over 60 minutes is shown in the figure. Figures 11-12 For a comparison of temperature time-varying paths, see [link to relevant documentation]. Figure 13 .

[0089] Depend on Figures 11-13 The comparison shows that the average temperature of the top surface of the SiO2 aerogel-modified RAP material in Example 5 is 1.3℃ lower than that of the RAP material in Comparative Example 9, while its lowest temperature is 2.6℃ lower. During the 60-minute heating process, although the initial temperature of the SiO2 aerogel-modified natural aggregate in Example 5 was 1.0℃ higher than that in Comparative Example 9, the final equilibrium average and lowest temperatures of the top surface were both lower than those of the RAP material in Comparative Example 9. Furthermore, from 10 minutes to 60 minutes of heating, the average and lowest temperatures of the top surface of the SiO2 aerogel-modified RAP material in Example 5 were consistently lower than those of the RAP material in Comparative Example 9. Since the sample thickness is only 1.8 cm and it is in a loose state, the difference in thermal insulation effect between the two is relatively limited.

[0090] Some Marshall specimens and rut plate specimens from Examples 6-7 and Comparative Examples 11-12 are shown below. Figures 14-15 Outdoor thermal insulation test see Figure 16 Its thermal conductivity, temperature difference and insulation coefficient are shown in Table 3.

[0091] Table 3

[0092] As shown in Table 3, the thermal conductivity of Example 6 is 9.8% lower than that of Comparative Example 11, the temperature difference is 3.2℃ higher, and the thermal insulation coefficient is 45.2% higher than that of Comparative Example 11. Similarly, the thermal conductivity of Example 7 is 6.9% lower than that of Comparative Example 12, the temperature difference is 2.8℃ higher, and the thermal insulation coefficient is 1.76 times higher than that of Comparative Example 11. This indicates that asphalt mixtures prepared using SiO2 aerogel solution-modified natural aggregates and SiO2 aerogel solution-modified RAP materials both have better thermal insulation effects than asphalt mixtures prepared using natural aggregates and RAP materials.

[0093] The thermal conductivity of Example 6 is lower than that of Example 7, and the temperature difference and thermal insulation coefficient are also smaller than those of Example 7. This indicates that simply improving the thermal insulation of RAP material that replaces 30% of natural aggregate is not enough to significantly improve the thermal insulation performance of recycled asphalt mixture. Only by comprehensively enhancing the thermal insulation of aggregate can we obtain asphalt mixture with better thermal insulation performance.

[0094] The dynamic stability, maximum flexural failure strain, and water immersion Marshall residual stability test results of the asphalt mixtures prepared according to Examples 6-7 and Comparative Examples 11-12 are shown in Table 4.

[0095] Table 4

[0096] As shown in Table 4, the dynamic stability of Example 6 is 7.4% higher than that of Comparative Example 11, while the maximum flexural strain and residual stability after immersion in water are 4.3% and 2.5% lower, respectively. The dynamic stability of Example 7 is 9.5% higher than that of Comparative Example 12, while the maximum flexural strain and residual stability after immersion in water are 5.8% and 2.9% lower, respectively. This indicates that asphalt mixtures prepared using SiO2 aerogel solution-modified natural aggregates and SiO2 aerogel solution-modified RAP materials both exhibit higher high-temperature stability than asphalt mixtures prepared using natural aggregates and RAP materials, but their low-temperature crack resistance and water stability are slightly reduced.

[0097] Example 6 exhibits weaker high-temperature stability than Example 7, but better low-temperature crack resistance and water stability. This is mainly because the asphalt in the RAP material has a high degree of aging and greater hardness, but its poor ductility and water stability also affect the road performance of the mixture.

[0098] The asphalt mixtures prepared according to Examples 6-7 and Comparative Examples 11-12 all meet the specifications for high-temperature stability, low-temperature crack resistance and water stability, indicating that the asphalt mixtures prepared by modifying aggregates with SiO2 aerogel solution can be used in asphalt pavement construction, and the SiO2 aerogel solution gives the aggregates and the corresponding asphalt mixtures good thermal insulation properties.

[0099] In summary, the SiO2 aerogel solution developed in this invention exhibits good adhesion, a long stability time, and a high SiO2 aerogel content. Furthermore, the SiO2 aerogel-modified aggregate prepared using the SiO2 aerogel solution and aggregates demonstrates excellent thermal insulation properties. This invention endows aggregates with thermal insulation properties, effectively alleviating rutting problems in high-temperature regions and low-temperature cracking problems in cold regions. Moreover, the preparation process is simple, requiring minimal equipment, with mild process conditions, and achieving high production efficiency.

[0100] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a SiO2 aerogel solution, characterized in that, The process includes the following: Anhydrous ethanol and distilled water are mixed thoroughly to obtain an alcohol solution; Add a binder to the alcohol solution and mix well to obtain a viscous alcohol solution; Add SiO2 aerogel powder to the viscous alcohol solution and stir at a stirring rate of 100~500 r / min for 120~240 s to prepare the SiO2 aerogel solution. The amount of anhydrous ethanol added is 40% to 45% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 14% to 19% of the total mass of the SiO2 aerogel solution, the amount of binder added is 8% to 20% of the total mass of the SiO2 aerogel solution, and the amount of SiO2 aerogel powder added is 24% to 28% of the total mass of the SiO2 aerogel solution.

2. The method for preparing a SiO2 aerogel solution according to claim 1, characterized in that, SiO2 aerogel powder is added to the viscous alcohol solution and stirred at a stirring rate of 100~500 r / min for 120~240 s to prepare the SiO2 aerogel solution. When preparing the SiO2 aerogel solution, the stirring is carried out at a variable speed, and the stirring rate is switched repeatedly within the range of 100~500 r / min. The speed of the stirring is 18-22 r / s.

3. The method for preparing a SiO2 aerogel solution according to claim 1, characterized in that, The particle size of the SiO2 aerogel powder is less than 1 μm. At this time, the amount of anhydrous ethanol added is 40%-41% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 14%-15% of the total mass of the SiO2 aerogel solution, the amount of binder added is 19%-20% of the total mass of the SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

4. The method for preparing a SiO2 aerogel solution according to claim 1, characterized in that, The particle size of the SiO2 aerogel powder is less than 10 μm, wherein the SiO2 aerogel powder with a particle size of 1-10 μm accounts for more than 95% of the total mass of the SiO2 aerogel powder. At this time, the amount of anhydrous ethanol added is 44%-45% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 18%-19% of the total mass of the SiO2 aerogel solution, the amount of binder added is 8%-9% of the total mass of the SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

5. The method for preparing a SiO2 aerogel solution according to claim 1, characterized in that, The particle size of the SiO2 aerogel powder is less than 50 μm, wherein the SiO2 aerogel powder with a particle size of 10-50 μm accounts for more than 95% of the total mass of the SiO2 aerogel powder. At this time, the amount of anhydrous ethanol added is 42%-43% of the total mass of the SiO2 aerogel solution, the amount of distilled water added is 16%-17% of the total mass of the SiO2 aerogel solution, the amount of binder added is 17%-18% of the total mass of the SiO2 aerogel solution, and the balance is SiO2 aerogel powder.

6. The method for preparing a SiO2 aerogel solution according to claim 1, characterized in that, The adhesive used is polyvinyl alcohol glue.

7. A SiO2 aerogel solution, characterized in that, The SiO2 aerogel solution is prepared by the preparation method according to any one of claims 1-6.

8. A method for preparing thermally insulating aggregate, characterized in that, The process includes the following: The SiO2 aerogel solution of claim 7 is mixed with the aggregate and then dried to obtain the heat-insulating aggregate, wherein the SiO2 aerogel solution accounts for 10% to 20% of the mass of the aggregate.

9. The method for preparing a heat-insulating aggregate according to claim 8, characterized in that, The aggregate is either RAP material or natural aggregate; When mixing the SiO2 aerogel solution with the aggregate: pour the SiO2 aerogel solution into the aggregate and then let it stand; or spray the SiO2 aerogel solution onto the surface of the RAP material while stirring, and then let it stand. During the settling process, the mixture is stirred every 25-35 minutes, with the stirring rate controlled at 20-40 r / min and the stirring time controlled at 3-5 minutes each time; the total settling time is controlled at 120-140 minutes. During drying, the drying temperature is 105℃~120℃. Take it out and stir it every 55-65 minutes. The stirring rate is controlled at 10~30 r / min each time, and the stirring time is controlled at 5~10 minutes until it is completely dried.

10. A thermally insulating aggregate, characterized in that, The insulating aggregate is prepared by the preparation method described in claim 8 or 9.

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