Barrier material for inhibiting migration of subgrade soil salt to pavement and preparation method thereof

Abstract

The invention discloses a barrier material for inhibiting subgrade soil salt from migrating to a road surface and a preparation method thereof. The barrier material comprises the following components in percentage by mass: 20-40% of a surface hydrophobically reinforced nano SiO2 / ZnO composite material, 10-20% of a filler, 10-30% of a filler and 10-30% of a filler, 10%-25% of a functionalized carbon nanotube with the surface grafted with a silane coupling agent; and 35%-60% of polyvinyl alcohol-based hydrogel. Through the synergistic effect of the hydrophobic nano barrier, the carbon tube conductive network and hydrogel adsorption, efficient dispersion of the nano material and multi-scale pore sealing are realized, and migration of subgrade soil salt to the pavement is continuously inhibited. The invention realizes breakthrough improvement of sulfate corrosion resistance, and is suitable for harsh environments such as saline land and the like.

Description

Technical Field

[0001] This invention relates to the field of road engineering, specifically to a barrier material and its preparation method for inhibiting the migration of salts from subgrade soil to the pavement. Background Technology

[0002] Cement-based materials, as core foundation materials in modern construction engineering, have long faced serious durability problems in sulfate-rich environments such as saline-alkali land infrastructure. Sulfate ions (SO4²⁻) - The chemical reaction between Na2SO4 and cement hydration products produces gypsum (CaSO4·2H2O) and ettringite (AFt), leading to expansion stress within the material and subsequently causing structural damage such as cracking and spalling. Studies have shown that in an environment where ordinary silicate cement-based materials are immersed in a 5% Na2SO4 solution, the compressive strength loss rate after 180 days can reach more than 35%, and the volume expansion rate exceeds 0.6%, seriously threatening the service life of roads.

[0003] Existing technologies for improving the sulfate resistance of cement-based materials include: First, mineral admixture modification. This involves incorporating volcanic ash materials such as slag and fly ash to reduce erosion reactants by consuming Ca(OH)2. However, this method suffers from slow early strength development and limited porosity reduction (only from 18% to about 15%), making it difficult to cope with high-concentration sulfate environments (>3%). Second, organic protective coatings. Epoxy resins and other coatings are used for surface sealing. However, the coefficient of thermal expansion of the coating does not match the substrate, making it prone to peeling under temperature cycling. Third, fiber reinforcement technology. This involves incorporating steel fibers or polypropylene fibers to improve crack resistance. However, fiber materials are expensive (increasing costs by about 30%), and uneven dispersion can lead to localized stress concentration.

[0004] In recent years, nanomaterial modification technology has provided a new direction for improving the performance of cement-based materials. The method of modifying cement-based materials with nano-CaCO3 mainly targets chloride ion attack protection, but its inhibitory effect on sulfate attack is limited (the compressive strength loss rate still reaches 18%). Furthermore, while the incorporation of single-layer nano-SiO2 on the surface can refine the pore structure, excessive addition (>4%) can induce agglomeration, thus reducing the material's density.

[0005] Therefore, a barrier material and its preparation method for inhibiting the migration of salt from subgrade soil to the pavement are provided. Summary of the Invention

[0006] The purpose of this invention is to provide a barrier material and preparation method for inhibiting the migration of salt from subgrade soil to the road surface. This material can achieve efficient dispersion of nanomaterials, multi-scale pore closure, and continuous inhibition of the migration of salt from subgrade soil to the road surface. This overcomes the shortcomings of existing technologies, which mainly target chloride ion corrosion protection and have limited inhibitory effects on sulfate corrosion. Furthermore, excessive addition of single nano-SiO2 can cause agglomeration and reduce the density of the material.

[0007] To achieve the above objectives, the present invention provides the following technical solutions: In a first aspect, the present invention provides a barrier material for inhibiting the migration of salts from subgrade soil to the pavement, comprising the following components by mass percentage: Hydrophobically reinforced nano-SiO2 / ZnO composite material: 20%~40%; Functionalized carbon nanotubes with surface-grafted silane coupling agents: 10%~25%; Polyvinyl alcohol-based hydrogel: 35%~60%.

[0008] Furthermore, in the nano-SiO2 / ZnO composite material, the mass ratio of the surface-hydrophobically reinforced nano-SiO2 to nano-ZnO is 1:1 to 1:2.

[0009] Furthermore, the amount of silane coupling agent grafted into the functionalized carbon nanotubes grafted with the surface-grafted silane coupling agent is 5% to 15% of the mass of the carbon nanotubes.

[0010] Furthermore, the polyvinyl alcohol-based hydrogel is prepared by crosslinking polyvinyl alcohol, maleic acid, and acrylamide in a mass ratio of 3:1:1 to 5:2:1, and the degree of crosslinking of the polyvinyl alcohol-based hydrogel is 60% to 85%, with a swelling ratio ≤3.

[0011] Secondly, the present invention also provides a method for preparing a barrier material for inhibiting the migration of subgrade soil salts to the pavement, comprising the following steps: Prepare surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials; Preparation of functionalized carbon nanotubes with surface-grafted silane coupling agents; Preparation of polyvinyl alcohol-based hydrogels; The nano-framework was obtained by mixing surface-hydrophobic reinforced nano-SiO2 / ZnO composite material with functionalized carbon nanotubes in a certain proportion, adding 0.1%~0.5% sodium dodecyl sulfate, and grinding. Microencapsulated composite powder was prepared by mixing polyvinyl alcohol-based hydrogel with a nanoframework and then using a spray drying method. The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

[0012] Furthermore, the materials are graded according to the salt content of the subgrade soil, and different distribution ratios are selected accordingly: When the salt content of the subgrade soil is ≤1.5%, the composition is 20%~30% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 10%~15% of functionalized carbon nanotubes, and 55%~60% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is 1.5%~3%, the composition is 30%~35% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 15%~20% of functionalized carbon nanotubes, and 45%~55% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is ≥3%, the composition is 35%~40% of the surface hydrophobic reinforced nano-SiO2 / ZnO composite material, 20%~25% of the functionalized carbon nanotubes, and 35%~45% of the polyvinyl alcohol-based hydrogel.

[0013] Furthermore, the preparation process of the surface-hydrophobically reinforced nano-SiO2 / ZnO composite material is specifically as follows: Nano-SiO2 was dispersed in an ethanol solution, zinc nitrate precursor was added, the pH was controlled at 8-10, the reaction temperature was 60-80℃, and the hydrothermal reaction was carried out for 6-12 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in a 5%~10% ethanol solution of silane coupling agent, ultrasonically treated for 1~2 hours, and dried to obtain a surface-hydrophobically reinforced nano SiO2 / ZnO composite material.

[0014] Furthermore, the preparation process of the functionalized carbon nanotubes with surface-grafted silane coupling agents is as follows: Carbon nanotubes were placed in a mixed acid at a reaction temperature of 80°C and refluxed for 3 hours. The carbon nanotubes were then centrifuged and washed until neutral. Add silane coupling agent to an acetate buffer solution at pH 4, and perform an ultrasonic-assisted reaction for 2 hours at a temperature of 40°C. Then, add silane coupling agent to bring the total grafting amount to 10%–15%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

[0015] Furthermore, the preparation process of the polyvinyl alcohol-based hydrogel is as follows: Polyvinyl alcohol was dissolved in deionized water at 90°C to form a 5%~10% wt% solution, and the solution was cooled to 50°C. Maleic acid, acrylamide monomer and ammonium persulfate initiator are added to the solution and nitrogen gas is purged for protection. The crosslinking reaction is carried out at a temperature of 60-70℃ for 2-4 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution was soaked in deionized water to obtain a polyvinyl alcohol-based hydrogel.

[0016] Furthermore, in the preparation of microencapsulated composite powder by spray drying, the inlet temperature of the spray is 150~180℃ and the outlet temperature is 80~100℃. The microencapsulated composite powder obtained has a particle size range of 10~100μm; The reaction was carried out at a temperature of 50°C and for 2 hours while immersed in an ethanol solution.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a barrier material for inhibiting the migration of salts from subgrade soil to the road surface. Through the synergistic effect of hydrophobic nanobarriers, carbon nanotube conductive networks, and hydrogel adsorption, this invention achieves efficient dispersion of nanomaterials, multi-scale pore sealing, and continuous inhibition of salt migration from subgrade soil to the road surface. This invention achieves a breakthrough improvement in sulfate resistance, making it suitable for harsh environments such as saline swamps. The barrier material of this invention utilizes the efficient dispersion and multi-scale pore sealing mechanism of nanomaterials to continuously inhibit the migration of salts from subgrade soil to the road surface, while significantly improving sulfate resistance. This material is not only suitable for harsh environments such as saline swamps but also has a low environmental impact, meets the standards of green building materials, and has good sustainability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2 in Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram showing the salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2 in Embodiment 2 of the present invention.

[0020] Figure 3 This is a schematic diagram showing the salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2 in Embodiment 3 of the present invention. Detailed Implementation

[0021] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0027] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0029] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. The raw materials involved in this invention are all conventional commercially available products, and the specific operating methods and testing methods involved, unless otherwise specified, are under conventional conditions.

[0030] This invention provides a barrier material for inhibiting the migration of salts from subgrade soil to the pavement, comprising the following components by mass percentage: Hydrophobically reinforced nano-SiO2 / ZnO composite material: 20%~40%; Functionalized carbon nanotubes with surface-grafted silane coupling agents: 10%~25%; Polyvinyl alcohol-based hydrogel: 35%~60%.

[0031] In the surface-hydrophobically reinforced nano-SiO2 / ZnO composite material, the mass ratio of nano-SiO2 to nano-ZnO is 1:1 to 1:2; in the functionalized carbon nanotubes grafted with silane coupling agent, the amount of silane coupling agent grafted is 5% to 15% of the mass of the carbon nanotubes; the polyvinyl alcohol-based hydrogel is prepared by crosslinking polyvinyl alcohol, maleic acid, and acrylamide in a mass ratio of 3:1:1 to 5:2:1, and the degree of crosslinking of the polyvinyl alcohol-based hydrogel is 60% to 85%, and the swelling ratio is ≤3.

[0032] In another embodiment of the present invention, a method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement is also provided, comprising the following steps: Prepare surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials; The specific preparation process of the surface-hydrophobically reinforced nano-SiO2 / ZnO composite material is as follows: Nano-SiO2 was dispersed in an ethanol solution using the sol-gel method, zinc nitrate precursor was added, the pH was controlled at 8-10, the reaction temperature was 60-80℃, and the hydrothermal reaction was carried out for 6-12 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in an ethanol solution of 5%~10% by mass of silane coupling agent (KH-570), ultrasonically treated for 1~2 hours, and dried to obtain a nano-SiO2 / ZnO composite material with hydrophobic reinforcement.

[0033] Preparation of functionalized carbon nanotubes with surface-grafted silane coupling agents; The specific preparation process of functionalized carbon nanotubes with surface-grafted silane coupling agents is as follows: Carbon nanotubes were placed in a mixed acid (concentrated HNO3:H2SO4=3:1), the reaction temperature was 80℃, the reflux time was 3 hours, and the carbon nanotubes were centrifuged and washed until neutral to achieve carbon nanotube pre-oxidation treatment. Add 5% (by weight of carbon nanotubes) of silane coupling agent (KH-550) to an acetate buffer solution at pH 4. After ultrasonic-assisted reaction for 2 hours at 40°C, add more silane coupling agent (KH-550) to bring the total grafting amount to 10%–15%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

[0034] Preparation of polyvinyl alcohol-based hydrogels; The specific preparation process of polyvinyl alcohol-based hydrogel is as follows: polyvinyl alcohol is dissolved in deionized water at a temperature of 90°C to form a 5%~10% wt% solution, and the solution is cooled to 50°C; Maleic acid, acrylamide monomer and ammonium persulfate initiator are added to the solution and nitrogen gas is purged for protection. The crosslinking reaction is carried out at a temperature of 60-70℃ for 2-4 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution is soaked in deionized water. The deionized water is changed 3-5 times over 24 hours until no residual monomer is found, thus obtaining a polyvinyl alcohol-based hydrogel.

[0035] The nano-framework was obtained by mixing surface-hydrophobic reinforced nano-SiO2 / ZnO composite material with functionalized carbon nanotubes in a certain proportion, adding 0.1%~0.5% sodium dodecyl sulfate, and grinding. Different mix ratios are selected to address varying salt contents in subgrade soils. Specifically: When the salt content of the subgrade soil is ≤1.5%, the composition is 20%~30% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 10%~15% of functionalized carbon nanotubes, and 55%~60% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is 1.5%~3%, the composition is 30%~35% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 15%~20% of functionalized carbon nanotubes, and 45%~55% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is ≥3%, the composition is 35%~40% of the surface hydrophobic reinforced nano-SiO2 / ZnO composite material, 20%~25% of the functionalized carbon nanotubes, and 35%~45% of the polyvinyl alcohol-based hydrogel.

[0036] Polyvinyl alcohol-based hydrogels were mixed with nanoframeworks and microencapsulated composite powders were prepared by spray drying. The inlet temperature of the spray was 150-180℃ and the outlet temperature was 80-100℃. The particle size range of the prepared microencapsulated composite powders was 10-100μm. The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

[0037] Example 1 For low-salt environments with a roadbed soil salt content of ≤1.5%, a sample structure was adopted with an upper layer of cement-stabilized crushed stone (15cm thick, 5% cement content) and a lower layer of graded crushed stone (30cm thick), as shown in Table 1. The test group added 3% of the barrier material prepared in this invention to the lower layer of graded crushed stone.

[0038] In preparing surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials Nano-SiO2 was dispersed in an ethanol solution, zinc nitrate precursor was added, the pH was controlled at 8-10, the reaction temperature was 60℃, and the hydrothermal reaction was carried out for 6 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in a 10% (w / w) silane coupling agent ethanol solution, ultrasonically treated for 2 hours, and dried to obtain a surface-hydrophobically reinforced nano-SiO2 / ZnO composite material.

[0039] In this embodiment, the mass ratio of nano-SiO2 to nano-ZnO is 1:1.

[0040] In the process of preparing functionalized carbon nanotubes with surface-grafted silane coupling agents: Carbon nanotubes were placed in a mixed acid at a reaction temperature of 80°C and refluxed for 3 hours. The carbon nanotubes were then centrifuged and washed until neutral. Add silane coupling agent to an acetate buffer solution at pH 4, and perform an ultrasonic-assisted reaction for 2 hours at a temperature of 40°C. Then, add silane coupling agent to bring the total grafting amount to 10%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

[0041] In this embodiment, the amount of silane coupling agent grafted into the functionalized carbon nanotubes with surface-grafted silane coupling agent is 5% of the mass of the carbon nanotubes.

[0042] In the preparation of polyvinyl alcohol-based hydrogels, polyvinyl alcohol is dissolved in deionized water at 90°C to form a 5% wt% solution, and the solution is cooled to 50°C. Maleic acid, acrylamide monomer and ammonium persulfate initiator were added to the solution and nitrogen gas was purged. The crosslinking reaction was carried out at 70°C for 4 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution was soaked in deionized water to obtain a polyvinyl alcohol-based hydrogel.

[0043] The composition consists of 20% surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 10% functionalized carbon nanotubes, and 60% polyvinyl alcohol-based hydrogel. A nano-SiO2 / ZnO composite material with surface hydrophobic reinforcement was mixed with functionalized carbon nanotubes in a certain proportion, and 0.1% sodium dodecyl sulfate was added and ground to obtain a nano-framework. Polyvinyl alcohol-based hydrogel was mixed with the nano-framework, and microencapsulated composite powder was prepared by spray drying. In the preparation of microencapsulated composite powder by spray drying, the inlet temperature of the spray was 150~180℃, the outlet temperature was 80~100℃, the water-cement ratio of the graded crushed stone layer was 0.35, the wet ball milling parameters were 400 rpm for 3 hours, and 0.3% SDS dispersant was added.

[0044] The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

[0045] Table 1

[0046] Experimental procedure: The experiment employed a water-salt migration device. The structures of the control and experimental groups are shown in Table 1. After compaction, the specimens underwent standard curing for 7 days, followed by immersion in a 3% sodium sulfate solution for 30 days, with the solution replaced every 7 days. The temperature control system was controlled by a temperature guide plate, the moisture replenishment system consisted of a Marshall bottle and a perforated plate, and the data monitoring system used a CR1000X data acquisition unit. The temperature setting range for the top temperature guide plate was -5℃ to 50℃, with a temperature cycle of 96 hours, including 48 hours of freezing (at -5℃) and 48 hours of thawing (at 50℃). The water-salt migration monitoring time was approximately 300 hours. The asphalt pavement gradation used was AC-16, with an optimal asphalt-aggregate ratio of 4.4% and a porosity of 5%. The technical indicators of coarse and fine aggregates and mineral powder met the requirements. The subgrade saline soil was taken from an area in Kashgar region prone to arching, and the compaction degree of the pavement structure met the specifications.

[0047] Experimental results: See Figure 1 The values ​​represent the salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2, derived from... Figure 1 It can be seen that as the number of temperature cycles increases, the salt content inside the subgrade soil shows a trend of gradually increasing and then gradually decreasing along the height direction. Structure 1 without a barrier layer shows a salt-rich zone (5.1% salt content) at a depth of 25cm, while in structure 2 with a graded gravel barrier layer, the salt accumulation depth shifts upwards to 20cm and the concentration decreases to 2.54%. The barrier layer, through its large pore structure, blocks the capillary migration of liquid water but allows the diffusion of gaseous water, forming a condensation-gravity settling cycle, leading to salt accumulation at the bottom of the barrier layer.

[0048] After immersion for 30 days, the salt content of the experimental group decreased by 50.8% compared with the control group, and no base layer cracking caused by salt crystallization occurred, proving the synergistic strengthening effect of nanoframework and carbon nanotubes in a medium-salt environment.

[0049] Example 2 For medium-salt environments with a roadbed soil salt content of 1.5% to 3%, a sample structure was adopted with an upper layer of cement-stabilized crushed stone (15cm thick, 5% cement content) and a lower layer of graded crushed stone (30cm thick), as shown in Table 2. The test group added 4% of the barrier material prepared in this invention to the lower layer of graded crushed stone.

[0050] Table 2

[0051] In preparing surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials Nano-SiO2 was dispersed in an ethanol solution, zinc nitrate precursor was added, the pH was controlled at 9, the reaction temperature was 60℃, and the hydrothermal reaction was carried out for 6 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in a 10% (w / w) silane coupling agent ethanol solution, ultrasonically treated for 2 hours, and dried to obtain a surface-hydrophobically reinforced nano-SiO2 / ZnO composite material.

[0052] In this embodiment, the mass ratio of nano-SiO2 to nano-ZnO is 1:2.

[0053] In the process of preparing functionalized carbon nanotubes with surface-grafted silane coupling agents: Carbon nanotubes were placed in a mixed acid at a reaction temperature of 80°C and refluxed for 3 hours. The carbon nanotubes were then centrifuged and washed until neutral. Add silane coupling agent to an acetate buffer solution at pH 4, and perform an ultrasonic-assisted reaction for 2 hours at a temperature of 40°C. Then, add silane coupling agent to bring the total grafting amount to 15%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

[0054] In this embodiment, the amount of silane coupling agent grafted into the functionalized carbon nanotubes with surface-grafted silane coupling agent is 8% of the mass of the carbon nanotubes.

[0055] In the preparation of polyvinyl alcohol-based hydrogels, polyvinyl alcohol is dissolved in deionized water at 90°C to form a 10%wt% solution, and the solution is cooled to 50°C. Maleic acid, acrylamide monomer and ammonium persulfate initiator were added to the solution and nitrogen gas was purged. The crosslinking reaction was carried out at 60°C for 2 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution was soaked in deionized water to obtain a polyvinyl alcohol-based hydrogel.

[0056] The composition consists of 30% surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 15% functionalized carbon nanotubes, and 55% polyvinyl alcohol-based hydrogel. A nano-SiO2 / ZnO composite material with surface hydrophobic reinforcement was mixed with functionalized carbon nanotubes in a certain proportion, and then 0.3% sodium dodecyl sulfate was added and ground to obtain a nano-framework. Polyvinyl alcohol-based hydrogel was mixed with the nano-framework, and microencapsulated composite powder was prepared by spray drying. In the preparation of microencapsulated composite powder by spray drying, the inlet temperature of the spray was 150~180℃, the outlet temperature was 80~100℃, and the particle size of the microencapsulated powder was ≤50μm to improve dispersibility.

[0057] The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

[0058] Experimental procedure: Same as the experimental procedure in Example 1.

[0059] Experimental results: like Figure 2 The figures show the salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2. Figure 2 It can be seen that as the number of temperature cycles increases, the salt content inside the subgrade soil shows a trend of gradually increasing and then gradually decreasing along the height direction. Structure 1 without a barrier layer shows a salt-rich zone (5.51% salt content) at a depth of 25cm, while in structure 2 with a graded gravel barrier layer, the salt accumulation depth shifts upwards to 20cm and the concentration decreases to 2.79%. The barrier layer, through its large pore structure, blocks the capillary migration of liquid water but allows the diffusion of gaseous water, forming a condensation-gravity settling cycle, leading to salt accumulation at the bottom of the barrier layer.

[0060] After immersion for 30 days, the salt content of the experimental group decreased by 49.4% compared with the control group, and no cracking of the base layer caused by salt crystallization occurred, proving the synergistic strengthening effect of nanoframework and carbon nanotubes in a medium-salt environment.

[0061] Example 3 For high-salt environments with a soil salt content ≥3%, a sample structure was adopted with cement-stabilized crushed stone (15cm thick, 5% cement content) on top and graded crushed stone (30cm thick) on the bottom, as shown in Table 3. The test group added 5% of the barrier material prepared in this invention to the graded crushed stone in the bottom layer and added 0.2% polycarboxylate superplasticizer to improve the mixing and dispersibility.

[0062] Table 3

[0063] In preparing surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials Nano-SiO2 was dispersed in an ethanol solution, zinc nitrate precursor was added, the pH was controlled at 10, the reaction temperature was 80℃, and the hydrothermal reaction was carried out for 12 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in a 10% (w / w) silane coupling agent ethanol solution, ultrasonically treated for 1 hour, and dried to obtain a surface-hydrophobic reinforced nano-SiO2 / ZnO composite material.

[0064] In this embodiment, the mass ratio of nano-SiO2 to nano-ZnO is 1:2.

[0065] In the process of preparing functionalized carbon nanotubes with surface-grafted silane coupling agents: Carbon nanotubes were placed in a mixed acid at a reaction temperature of 80°C and refluxed for 3 hours. The carbon nanotubes were then centrifuged and washed until neutral. Add silane coupling agent to an acetate buffer solution at pH 4, and perform an ultrasonic-assisted reaction for 2 hours at a temperature of 40°C. Then, add silane coupling agent to bring the total grafting amount to 15%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

[0066] In this embodiment, the amount of silane coupling agent grafted into the functionalized carbon nanotubes with surface-grafted silane coupling agent is 8% of the mass of the carbon nanotubes.

[0067] In the preparation of polyvinyl alcohol-based hydrogels, polyvinyl alcohol is dissolved in deionized water at 90°C to form a 15% wt% solution, and the solution is cooled to 50°C. Maleic acid, acrylamide monomer and ammonium persulfate initiator were added to the solution and nitrogen gas was purged. The crosslinking reaction was carried out at 60°C for 2 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution was soaked in deionized water to obtain a polyvinyl alcohol-based hydrogel.

[0068] The composition consists of 30% surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 15% functionalized carbon nanotubes, and 55% polyvinyl alcohol-based hydrogel. A nano-SiO2 / ZnO composite material with surface hydrophobic reinforcement was mixed with functionalized carbon nanotubes in a certain proportion, and 0.5% sodium dodecyl sulfate was added and ground to obtain a nano-framework. Polyvinyl alcohol-based hydrogel was mixed with the nano-framework, and microencapsulated composite powder was prepared by spray drying. In the preparation of microencapsulated composite powder by spray drying, the inlet temperature of the spray was 150~180℃, the outlet temperature was 80~100℃, and the particle size of the microencapsulated powder was ≤50μm to improve dispersibility.

[0069] The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

[0070] Experimental procedure: The experimental procedure is the same as that in Example 1.

[0071] Experimental results: Figure 3 The salt content monitoring values ​​at different depths of the roadbed in test structures 1 and 2 are obtained from... Figure 3It can be seen that as the number of temperature cycles increases, the salt content inside the subgrade soil shows a trend of gradually increasing and then gradually decreasing along the height direction. Structure 1 without a barrier layer shows a salt-rich zone (5.83% salt content) at a depth of 25cm, while in structure 2 with a graded gravel barrier layer, the salt accumulation depth shifts upwards to 20cm and the concentration decreases to 2.86%. The barrier layer, through its large pore structure, blocks the capillary migration of liquid water but allows the diffusion of gaseous water, forming a condensation-gravity settling cycle, leading to salt accumulation at the bottom of the barrier layer.

[0072] After the specimens were soaked for 30 days, the salt content of the experimental group decreased by 50.9% compared with the control group, and no cracking of the base layer caused by salt crystallization was observed, which proves the synergistic strengthening effect of nanoframework and carbon nanotubes in a medium-salt environment.

[0073] In summary, the salt barrier performance of this invention is significantly enhanced: through the synergistic effect of hydrophobic nanobarriers, carbon nanotube conductive networks, and hydrogel adsorption, the salt migration inhibition rate is ≥95%, which is more than 50% higher than that of traditional single materials; component classification reduces consumption: the component ratio is dynamically adjusted according to the salt content of the subgrade soil (low / medium / high), reducing the amount of high-cost nanomaterials by 20%~30%, achieving a 15%~25% reduction in raw material costs for the same effect; process economy is optimized: by adopting efficient processes such as sol-gel in-situ coating and ultrasonic-assisted grafting, the production cycle is shortened by 40%, energy consumption is reduced by 35%, and the overall production cost is reduced by 20%.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A barrier material for inhibiting the migration of salts from subgrade soil to the pavement, characterized in that, It includes the following components by mass percentage: Hydrophobically reinforced nano-SiO2 / ZnO composite material: 20%~40%; Functionalized carbon nanotubes with surface-grafted silane coupling agents: 10%~25%; Polyvinyl alcohol-based hydrogel: 35%~60%.

2. The barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 1, characterized in that, In the surface hydrophobically reinforced nano-SiO2 / ZnO composite material, the mass ratio of nano-SiO2 to nano-ZnO is 1:1 to 1:

2.

3. The barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 1, characterized in that, The amount of silane coupling agent grafted into the functionalized carbon nanotubes with surface-grafted silane coupling agent is 5% to 15% of the mass of the carbon nanotubes.

4. The barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 1, characterized in that, The polyvinyl alcohol-based hydrogel is prepared by crosslinking polyvinyl alcohol, maleic acid, and acrylamide in a mass ratio of 3:1:1 to 5:2:

1. The degree of crosslinking of the polyvinyl alcohol-based hydrogel is 60% to 85%, and the swelling ratio is ≤3.

5. A method for preparing a barrier material to inhibit the migration of salt from subgrade soil to the pavement, characterized in that, Includes the following steps: Prepare surface-hydrophobically reinforced nano-SiO2 / ZnO composite materials; Preparation of functionalized carbon nanotubes with surface-grafted silane coupling agents; Preparation of polyvinyl alcohol-based hydrogels; The nano-framework was obtained by mixing surface-hydrophobic reinforced nano-SiO2 / ZnO composite material with functionalized carbon nanotubes in a certain proportion, adding 0.1%~0.5% sodium dodecyl sulfate, and grinding. Microencapsulated composite powder was prepared by mixing polyvinyl alcohol-based hydrogel with a nanoframework and then using a spray drying method. The microencapsulated composite powder is impregnated in an ethanol solution containing 1% to 3% perfluorooctyltriethoxysilane, and then dried after the reaction to obtain the barrier material.

6. A method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 5, characterized in that, The materials are graded according to the salt content of the subgrade soil, and different distribution ratios are selected: When the salt content of the subgrade soil is ≤1.5%, the composition is 20%~30% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 10%~15% of functionalized carbon nanotubes, and 55%~60% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is 1.5%~3%, the composition is 30%~35% of surface-hydrophobic reinforced nano-SiO2 / ZnO composite material, 15%~20% of functionalized carbon nanotubes, and 45%~55% of polyvinyl alcohol-based hydrogel; When the salt content of the subgrade soil is ≥3%, the composition is 35%~40% of the surface hydrophobic reinforced nano-SiO2 / ZnO composite material, 20%~25% of the functionalized carbon nanotubes, and 35%~45% of the polyvinyl alcohol-based hydrogel.

7. A method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 6, characterized in that, The specific preparation process of the surface-hydrophobic reinforced nano-SiO2 / ZnO composite material is as follows: Nano-SiO2 was dispersed in an ethanol solution, zinc nitrate precursor was added, the pH was controlled at 8-10, the reaction temperature was 60-80℃, and the hydrothermal reaction was carried out for 6-12 hours to obtain SiO2 / ZnO composite material. The SiO2 / ZnO composite material was impregnated in a 5%~10% ethanol solution of silane coupling agent, ultrasonically treated for 1~2 hours, and dried to obtain a surface-hydrophobically reinforced nano SiO2 / ZnO composite material.

8. A method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 6, characterized in that, The preparation process of the functionalized carbon nanotubes with surface-grafted silane coupling agents is as follows: Carbon nanotubes were placed in a mixed acid at a reaction temperature of 80°C and refluxed for 3 hours. The carbon nanotubes were then centrifuged and washed until neutral. Add silane coupling agent to an acetate buffer solution at pH 4, and perform an ultrasonic-assisted reaction for 2 hours at a temperature of 40°C. Then, add silane coupling agent to bring the total grafting amount to 10%–15%, and add 0.1% Fe³⁺. + Catalysis was performed, and the mixture was stirred and reacted at 80°C for 4 hours to obtain the first product. The first product, after being dried with CO2, yielded functionalized carbon nanotubes with a surface-grafted silane coupling agent and a specific surface area ≥250 m² / g.

9. A method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 6, characterized in that, The preparation process of the polyvinyl alcohol-based hydrogel is as follows: Polyvinyl alcohol is dissolved in deionized water at 90°C to form a 5%~10%wt% solution, and the solution is cooled to 50°C. Maleic acid, acrylamide monomer and ammonium persulfate initiator are added to the solution and nitrogen gas is purged for protection. The crosslinking reaction is carried out at a temperature of 60-70℃ for 2-4 hours to obtain a mixed solution. After adding the crosslinking agent N,N'-methylenebisacrylamide to the mixed solution, the solution was soaked in deionized water to obtain a polyvinyl alcohol-based hydrogel.

10. A method for preparing a barrier material for inhibiting the migration of salt from subgrade soil to the pavement according to claim 6, characterized in that, In the preparation of microencapsulated composite powder by spray drying, the inlet temperature of the spray is 150~180℃ and the outlet temperature is 80~100℃. The microencapsulated composite powder obtained has a particle size range of 10~100μm; The reaction was carried out at a temperature of 50°C and for 2 hours while immersed in an ethanol solution.

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