A bio-based-solid waste-based-fiber synergistically improved silt subgrade material and a preparation method thereof

Abstract

The application provides a kind of bio-based-solid waste-based-fiber synergistic improved silt subgrade material and preparation method, belongs to road engineering technical field.The raw material of the subgrade material includes: silt, biopolymer, solid waste-based curing agent, fiber;With the mass of silt as benchmark, the amount of biopolymer is 1%-2% of the mass of silt, the amount of solid waste-based curing agent is 8%-10% of the mass of silt, and the amount of fiber is 2%-4% of the mass of silt.The application uses specific proportion of biopolymer, solid waste-based curing agent and fiber to synergistically improve the strength, toughness and durability of silt, and obtains a high-performance, eco-friendly, widely practical, highly compatible and durable subgrade material.The 28d compressive strength of the subgrade material is as high as 3.48 Mpa, the 28d splitting strength is as high as 0.69 Mpa, the dry-wet cycle compressive strength loss rate is as low as 15.3%, the freeze-thaw cycle compressive strength loss rate is as low as 18.6%, and it has good application prospect in road engineering.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to a bio-based-solid waste-based-fiber synergistic improvement material for silty sand roadbed and its preparation method. Background Technology

[0002] The Yellow River basin in my country is rich in silty soil, with numerous alluvial plains. However, road construction in these plains often faces challenges, including difficulties in obtaining soil for roadbed filling and a shortage of base course aggregate. Using silty soil as a road construction filler can effectively alleviate the growing demand for highways in the plains and the shortage of filler material. However, silty soil generally suffers from poor cohesion, poor gradation, low plasticity index, low strength, and low long-term durability, making it difficult to guarantee project quality when used directly as a road construction material. To improve the feasibility of using silty soil as a road construction material, it needs to be improved before use in road construction projects.

[0003] Traditional silty soil improvement techniques mainly employ the addition of inorganic materials as solidifying agents, such as cement, lime, and fly ash. While using inorganic materials to solidify silty soil can improve its mechanical properties and stability, it also has drawbacks such as requiring large dosages, long construction periods, and causing severe environmental pollution.

[0004] In recent years, bio-based soil improvement technology has gradually become a research hotspot. Microbial induced calcium carbonate deposition (MICP) technology is an emerging soil improvement technology. Its principle is to introduce specific microorganisms (such as urease bacteria) and reactants (such as nutrient solution) into the soil, thereby generating calcium carbonate precipitate on the soil surface to achieve the purpose of soil solidification. However, MIP technology has problems such as uneven reaction, great susceptibility to environmental interference, poor economic efficiency, and difficulty in field application, making it difficult to promote and apply in actual engineering.

[0005] Biopolymers are environmentally friendly materials and a novel type of bio-based soil amendment. They are composed of high-molecular-weight polysaccharide polymers. Biopolymers exhibit good stability, low sensitivity to environmental factors such as temperature, pH, and humidity, and can effectively improve soil rigidity, bearing capacity, and durability. Existing technologies report the effective improvement of loess, clay, silt, and expansive soils, but their application in improving silty sand subgrades is rarely reported. Furthermore, it should be noted that biopolymers are natural polysaccharides and are biodegradable; their long-term performance improvement effects on soil require further investigation and verification. Therefore, simply using biopolymers to improve silty sand carries risks to long-term durability and may not guarantee the required service life of subgrade materials.

[0006] Solid waste-based solidification materials possess potential cementitious activity. Their application in soil solidification can significantly enhance the physical and mechanical properties of the soil and effectively reduce the environmental impact of solid waste, aligning with ecological environmental protection principles. Solid waste-based solidification materials primarily achieve soil solidification through hydration, pozzolanic reaction, and carbonization. As the soil curing age increases, these reactions become more complete, resulting in excellent long-term solidification effects. During the improvement and solidification process of silty sand subgrades, while soil strength and other properties significantly improve, brittleness also gradually increases, impacting the safety of the subgrade structure. Adding fibers during silty sand improvement can effectively reduce the brittleness of the solidified silty sand and improve the toughness and durability of the silty sand subgrade. Currently, there are no known bio-based, solid waste-based, and fiber-based synergistic improvement materials or preparation methods for silty sand subgrades. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a roadbed material for the synergistic improvement of silty sand by bio-based, solid waste-based, and fiber-based materials, and its preparation method.

[0008] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides a roadbed material for the synergistic improvement of silty soil by bio-based, solid waste-based, and fiber, the raw materials of which include: silty soil, biopolymer, solid waste-based solidifying agent, and fiber; based on the mass of silty soil, the amount of biopolymer is 1%-2% of the mass of silty soil, the amount of solid waste-based solidifying agent is 8%-10% of the mass of silty soil, and the amount of fiber is 2%-4% of the mass of silty soil.

[0010] Furthermore, the biopolymer comprises xanthan gum and guar gum in a mass ratio of 1:(0.8-1.2).

[0011] Further, by weight, the solid waste-based solidifying agent comprises: 20-30 parts cement, 30-50 parts carbide slag, 20-30 parts fly ash, and 2-4 parts activator.

[0012] Furthermore, the cement is ordinary Portland cement with a strength grade of not less than 42.5.

[0013] Furthermore, the activator is sodium sulfate (Na2SO4).

[0014] Furthermore, the length of the fiber is 3-5 mm.

[0015] Furthermore, the fiber includes at least one of basalt fiber and lignin fiber; the basalt fiber has a diameter of 10-20 μm, and the lignin fiber has a diameter of 15-25 μm.

[0016] Secondly, the present invention provides a method for preparing the bio-based-solid waste-based-fiber synergistically improved silty soil subgrade material, comprising the following steps:

[0017] The amount of water required to prepare the subgrade material is determined based on the optimum moisture content of the silty soil.

[0018] Add silt, biopolymer, solid waste-based solidifier and fiber to a mixer in proportion, mix at low speed for 2-3 minutes, then add 1 / 3 of the total water and continue mixing at low speed for 5-8 minutes; add the remaining 2 / 3 of the total water and continue mixing at low speed for 5-8 minutes until the raw materials are mixed evenly to obtain a mixture.

[0019] The mixture is removed and left to stand for 24-36 hours to obtain a roadbed material for bio-based, solid waste-based, and fiber-synergistic improvement of silty soil.

[0020] Furthermore, the optimum moisture content of the silty soil was determined according to the compaction test (T0131-2019) in the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020).

[0021] Furthermore, the low-speed stirring rate is 50-80 r / min.

[0022] Thirdly, the present invention provides the application of the bio-based-solid waste-based-fiber synergistic modified silty soil subgrade material in road engineering.

[0023] This invention addresses the problems existing in current silty soil subgrade improvement technologies. Using silty soil as the base material, it employs a specific ratio of biopolymers, solid waste-based solidifying agents, and fibers to synergistically improve the strength, toughness, and durability of silty soil. This results in a high-performance, eco-friendly, widely applicable, highly compatible, and durable bio-based-solid waste-based-fiber synergistically improved silty soil subgrade material. The biopolymer is a composite of xanthan gum and guar gum in a specific ratio, which enhances the cohesiveness of silty soil and improves soil density and strength. Xanthan gum has good stability, reducing the environmental sensitivity of the biopolymer, while guar gum contains a large number of special hydroxyl groups, which can improve the early mechanical properties and stability of the soil. The solid waste-based solidifying agent differs from the hydration reaction system in existing technologies; it is a compound of cement, carbide slag, fly ash, and sodium sulfate in a specific ratio, which can rapidly improve the early strength and long-term durability of the soil, and has a high solid waste utilization rate. The fibers are basalt fibers or lignin fibers. Basalt fibers have higher strength than polymer fibers and have better reinforcement and toughening effects. At the same time, their surface is rich in hydroxyl groups, which can combine with silt to form stronger interfacial strength. Lignin fibers have good dispersibility and high compatibility with silt.

[0024] The core of this invention lies in the synergistic effect of bio-based, solid waste-based, and fiber-based materials in a silty soil system, rather than a simple functional superposition. Biopolymers contribute to the formation of the initial bonding network, providing a more uniform matrix for subsequent hydration reactions; the hydration products and pozzolanic reaction products of the solid waste-based solidifier form an organic-inorganic composite three-dimensional cementing system, improving the material's density and early and long-term strength; the fiber acts as a "micro-reinforcement," overcoming the increased brittleness of silty soil after solidification. No simple combination of any two materials can achieve the comprehensive technical effect of a three-component system that balances early strength, long-term durability, and high toughness.

[0025] Furthermore, this invention also specifically designs a method for preparing roadbed materials for the bio-based, solid waste-based, and fiber-coordinated system of synergistic improvement of silty soil. This method, through a specific process combination of "stepwise water addition + low-speed stirring + curing treatment," aims to meet the different physicochemical reaction requirements of the three components: bio-based polymer, solid waste-based solidifying agent, and fiber. Stepwise water addition provides sufficient water environment and hydration time for the biopolymer, ensuring the formation of a stable initial gel network. Simultaneously, the entire process uses a temperature below 80°C. Low-speed stirring at r / min effectively avoids the breakage of biopolymer molecular chains, thus preserving its core functions of thickening, film formation, and cross-linking. The uniformly distributed moisture also provides a sufficient hydration environment for the hydration reactions of cement, carbide slag, and fly ash, as well as the volcanic ash reaction. The subsequent curing process ensures reaction time, allowing the solid waste-based solidifier to fully react and generate sufficient cementitious products to improve material strength. The mixing sequence of dry mixing followed by stepwise wet mixing is conducive to the uniform dispersion of basalt fibers or lignin fibers in the system and their penetration into the organic-inorganic composite cementing system, forming an effective three-dimensional network "micro-reinforced material" structure.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] 1. Immediate Modification and Bridging Effect of Biopolymers: The bio-based modification material in this invention uses a composite of xanthan gum and guar gum in a specific ratio. The rigid rod-like helical structure of xanthan gum has good stability, reducing the sensitivity of the composite to factors such as ambient temperature and pH. Guar gum contains a large number of special hydroxyl groups, which can combine with soil particles to form a hydrogel network, improving the early mechanical properties and stability of the soil. At the same time, the particle size of the composite powder is smaller than that of silt, and it has high viscosity after hydration. It can not only effectively fill the gaps between silt particles, reduce the number of macropores in silt, promote the compaction of silt particles, and weaken the capillary action in silt, but also enhance the bonding strength between soil particles, improve the overall density and strength of the soil, and thus significantly improve the silt subgrade material.

[0028] 2. Contribution of solid waste-based solidifying agent to early and long-term strength: The solid waste-based solidifying agent in this invention is a composite of cement, carbide slag, fly ash, and activator in a specific ratio. Each component material improves the strength of silty soil by cementing silty sand particles and filling soil pores. The early strength of the improved silty sand subgrade is mainly generated by the cementing and filling of cement hydration products. Among them, carbide slag and activator can effectively improve the alkaline environment in the system and increase the hydration reaction rate. The cement hydration reaction products effectively cement soil particles and fill soil pores, thereby improving the early strength of the soil. Fly ash undergoes a pozzolanic reaction in an alkaline environment to generate long-term cementing products, which continuously fill pores and significantly improve the later strength and durability of the material.

[0029] 3. Toughening and Crack Resistance Effect of Fibers: The fiber materials in this invention are basalt fibers or lignin fibers, both of which have good dispersibility and mechanical properties. They are easy to mix evenly with silty soil. Basalt fibers or lignin fibers can be uniformly adsorbed on the surface of silty soil particles and, under the action of cementing materials, cement with soil particles to form a three-dimensional network structure. This forms a supporting and connecting effect inside the soil, effectively dispersing and weakening stress concentration under stress, improving the overall mechanical properties of the material, and effectively reducing the brittleness of the solidified silty soil material, thus enhancing its toughness and crack resistance.

[0030] 4. Synergistic Effect of Three Components, Achieving Complementary and Leapfrog Performance: The core of this invention lies in the significant synergistic effect generated between the bio-based, solid waste-based, and fiber components in the silty soil system, rather than a simple functional superposition. In this invention, there is a significant synergistic enhancement effect among the biopolymer, solid waste-based solidifying agent, and fiber.

[0031] Synergistic effects of biopolymers and solid waste base: Biopolymers can rapidly encapsulate soil particles, forming an initial organic bonding network that more tightly binds silt particles and solid waste base particles together. This provides a larger contact area and a more stable reaction space for the inorganic hydration reaction, while preventing excessive moisture loss, thus accelerating and optimizing the hydration process. Furthermore, the hydration products and volcanic ash reaction products of the solid waste base solidifier not only fill the network space composed of biopolymers and silt particles but also intertwine with them to form an organic-inorganic composite three-dimensional cementing system, greatly improving the density and early and long-term strength of the subgrade material.

[0032] Synergistic effect of fiber and cementing system: The fiber runs through the above-mentioned organic-inorganic composite three-dimensional cementing system, playing the role of "micro reinforcement", effectively transferring and dispersing stress, inhibiting the generation and propagation of cracks, and effectively overcoming the defect of increased brittleness after solidification of silty soil.

[0033] Synergistic improvement effect of bio-based, solid waste-based and fiber: The silty sand roadbed material improved by the synergistic effect of the three has the advantages of excellent early strength, continuous long-term strength, and high toughness and crack resistance that traditional solidification materials do not have, thus achieving a qualitative improvement in comprehensive road performance.

[0034] 5. The modified materials incorporated into the silty sand roadbed material in this invention are all natural and environmentally friendly materials. They have good compatibility with the silty sand matrix material, produce no secondary pollution, are ecological and environmentally friendly, and can absorb a certain amount of solid waste, realizing the resource utilization of solid waste. They have high application value and significant environmental and economic benefits. Attached Figure Description

[0035] Figure 1 This is a flowchart of a method for preparing a bio-based, solid waste-based, and fiber-synergistically improved silty soil subgrade material according to the present invention. Detailed Implementation

[0036] To enable those skilled in the art to clearly and completely understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art. Obviously, the embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a roadbed material for the synergistic improvement of silty soil using a bio-based, solid waste-based, and fiber method. The raw materials include: silty soil, biopolymer, solid waste-based solidifying agent, and fiber. Based on the mass of the silty soil, the amount of biopolymer is 1%-2% of the mass of the silty soil, the amount of solid waste-based solidifying agent is 8%-10% of the mass of the silty soil, and the amount of fiber is 2%-4% of the mass of the silty soil.

[0038] In some examples, the biopolymer comprises xanthan gum and guar gum in a mass ratio of 1:(0.8-1.2).

[0039] In some examples, the solid waste-based solidifying agent comprises, by weight, 20-30 parts cement, 30-50 parts calcium carbide slag, 20-30 parts fly ash, and 2-4 parts activator.

[0040] In some examples, the cement is ordinary Portland cement with a strength grade of not less than 42.5.

[0041] In some examples, the fiber is 3-5 mm long and includes at least one of basalt fiber and lignin fiber; the basalt fiber has a diameter of 10-20 μm and the lignin fiber has a diameter of 15-25 μm.

[0042] The preparation method of the bio-based-solid waste-based-fiber synergistic improvement of silty soil subgrade material is as follows: Figure 1 As shown, it includes the following steps:

[0043] The optimum moisture content of the silty soil was determined according to the compaction test (T0131-2019) in the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020), and the amount of water required to prepare the subgrade material was determined based on the optimum moisture content of the silty soil.

[0044] Add silt, biopolymer, solid waste-based solidifier, and fiber to a mixer in the specified proportions. Mix at a low speed of 50-80 r / min for 2-3 minutes. Then add 1 / 3 of the total water and continue mixing at a low speed of 50-80 r / min for 5-8 minutes. Add the remaining 2 / 3 of the total water and continue mixing at a low speed of 50-80 r / min for 5-8 minutes until the raw materials are mixed evenly to obtain a mixture.

[0045] The mixture is removed and left to stand for 24-36 hours to obtain a roadbed material for bio-based, solid waste-based, and fiber-synergistic improvement of silty soil.

[0046] In the following specific embodiments, the silty soil was collected from the Kaifeng section of the Yellow River. The biopolymer is a composite of xanthan gum and guar gum in a mass ratio of 1:1; both xanthan gum and guar gum are commonly used biopolymers in engineering, purchased from Hebei Hongtao Bioengineering Co., Ltd., both are slightly yellow in appearance, in powder form, odorless, non-toxic and harmless, and easily soluble in water. By mass, the solid waste-based solidifying agent includes: 30 parts cement, 40 parts carbide slag, 28 parts fly ash, and 2 parts activator; the cement is P.O42.5 cement, purchased from Jiyuan Zhonglian Cement Co., Ltd., the carbide slag is from Anyang Xinhai Metallurgical Co., Ltd., the activator is sodium sulfate, and the fly ash and sodium sulfate are from Xinxiang Shenglong Building Materials Co., Ltd. The basalt fiber has a length of 3 mm, a diameter of 15 μm, and a density of 2.64 g·cm³. -3 The tensile strength is 3500 MPa, the elastic modulus is 102 GPa, the melting point is 1500℃, and the breaking strength is 0.69 N·tex. -1 It exhibits strong resistance to acids and alkalis and was purchased from Haining Anjie Composite Materials Co., Ltd.; the lignin fibers have a length of 3 mm, a diameter of 20 μm, and a density of 1.5 g·cm³. -3It has a melting point of 260℃, a pH value of 7.5, and strong resistance to acids and alkalis. It was purchased from Haining Anjie Composite Materials Co., Ltd.

[0047] Example 1

[0048] A bio-based, solid waste-based, and fiber-synergistic modified silty soil subgrade material, comprising silty soil, biopolymer, solid waste-based solidifying agent, and basalt fiber, wherein the biopolymer accounts for 2% of the silty soil mass, the solid waste-based solidifying agent accounts for 10% of the silty soil mass, and the basalt fiber accounts for 3% of the silty soil mass;

[0049] The preparation steps of the bio-based-solid waste-based-fiber synergistic modified silty soil subgrade material are as follows:

[0050] S1: Determine the optimum moisture content of the silty soil according to the compaction test (T0131-2019) in the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020), and determine the required water content accordingly;

[0051] S2: Add silty sand, biopolymer, solid waste-based solidifier and basalt fiber to the mixer in proportion, and mix at a low speed of 70r / min for 3 minutes;

[0052] S3: Slowly add 1 / 3 of the total water volume to the mixture from step S2, and continue stirring at a low speed of 70 r / min for 8 minutes.

[0053] S4: Add the remaining 2 / 3 of the total water volume and continue stirring at a low speed of 70 r / min for 8 minutes until the mixture is homogeneous and a mixture is obtained.

[0054] S5: Remove the mixture and let it stand for 24 hours to obtain the bio-based-solid waste-based-fiber synergistic improved silty sand roadbed material.

[0055] Example 2

[0056] A bio-based, solid waste-based, and fiber-based synergistic improvement material for silty soil subgrade includes silty soil, biopolymer, solid waste-based solidifying agent, and lignin fiber as raw materials. Based on the mass of silty soil, the biopolymer is used at 1% of the silty soil mass, the solid waste-based solidifying agent is used at 8% of the silty soil mass, and the lignin fiber is used at 3% of the silty soil mass.

[0057] The preparation steps of the bio-based-solid waste-based-fiber synergistic modified silty soil subgrade material are as follows:

[0058] S1: Determine the optimum moisture content of the silty soil according to the compaction test (T0131-2019) in the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020), and determine the required water content accordingly;

[0059] S2: Add silty sand, biopolymer, solid waste-based solidifier and lignin fiber to the mixer in proportion, and mix at a low speed of 70r / min for 3 minutes;

[0060] S3: Slowly add 1 / 3 of the total water volume to the mixture from step S2, and continue stirring at a low speed of 70 r / min for 8 minutes.

[0061] S4: Add the remaining 2 / 3 of the total water volume and continue stirring at a low speed of 70 r / min for 8 minutes until the mixture is homogeneous and a mixture is obtained.

[0062] S5: Remove the mixture and let it stand for 24 hours to obtain the bio-based-solid waste-based-fiber synergistic improved silty sand roadbed material.

[0063] Comparative Example 1

[0064] The difference between the roadbed material in this comparative example and that in Example 1 is that the raw materials do not include biopolymers, but all other aspects are the same.

[0065] Comparative Example 2

[0066] The difference between the roadbed material in this comparative example and that in Example 1 is that the raw materials do not include solid waste-based curing agents; all other aspects are the same.

[0067] Comparative Example 3

[0068] The difference between the roadbed material in this comparative example and that in Example 1 is that the raw materials do not include basalt fiber, but all other aspects are the same.

[0069] Comparative Example 4

[0070] The difference between the roadbed material in this comparative example and that in Example 1 is that the raw material is silty sand, while all other aspects are the same.

[0071] Comparative Example 5

[0072] The difference between the roadbed material in this comparative example and that in Example 1 is that the biopolymer used is only xanthan gum, while all other components are the same.

[0073] Comparative Example 6

[0074] The difference between the roadbed material in this comparative example and that in Example 1 is that the biopolymer used is only guar gum, while all other aspects are the same.

[0075] Comparative Example 7

[0076] The difference between the roadbed material in this comparative example and that in Example 1 is that the mass ratio of xanthan gum to guar gum is 3:1, while all other aspects are the same.

[0077] Comparative Example 8

[0078] The difference between the roadbed material in this comparative example and that in Example 1 is that an equal amount of quicklime is used to replace carbide slag, while all other aspects are the same.

[0079] Comparative Example 9

[0080] The difference between the roadbed material in this comparative example and that in Example 1 is that an equal amount of polypropylene fiber is used instead of basalt fiber; all other aspects are the same.

[0081] To compare the bearing capacity and mechanical properties of soils from different embodiments and comparative examples, specimens for CBR, unconfined compressive strength, and splitting tensile strength tests were prepared for Examples 1-2 and Comparative Examples 1-9 according to the "Specifications for Testing Geotechnical Engineering for Highways" (JTG 3430—2020) and the "Specifications for Testing Inorganic Binder Stabilized Materials for Highway Engineering" (JTG 3441—2024). The CBR, 7-day, and 28-day compressive strength and splitting tensile strength of the specimens were tested according to the test specifications T0134-2019, T0805-2024, and T0806-2024, respectively. Furthermore, to compare the durability of soils from different embodiments and comparative examples, the compressive strength of different specimens after wet-dry cycles and freeze-thaw cycles was tested. The wet-dry cycle test method involved immersing the cured specimens in still water for 12 hours, draining them after immersion, and then drying them in an oven for 12 hours, thus completing one wet-dry cycle. The number of wet-dry cycles was set to 10. The freeze-thaw cycle test method involves placing the cured specimens in a -10℃ environmental chamber for 12 hours, followed by thawing at 15℃ for 12 hours, thus completing one freeze-thaw cycle. The number of freeze-thaw cycles was set to 10. The test results are shown in Table 1.

[0082] Table 1: Experimental Results of Examples 1-2 and Comparative Examples 1-9

[0083]

[0084] As shown in Table 1, Example 1 exhibits the highest CBR, 7-day, and 28-day compressive strength and splitting tensile strength, and the lowest compressive strength loss rate after wet-dry and freeze-thaw cycles, indicating that it has the best load-bearing capacity, mechanical properties, and durability. Example 2 is the second best, demonstrating that the biopolymer, solid waste-based curing agent, and fiber in this invention can produce a good synergistic reinforcement effect in the silt system. Specifically, the biopolymer contributes to the formation of the initial bonding network, improves the early strength of the material, and provides a more uniform matrix for subsequent hydration reactions. The hydration products and pozzolanic reaction products of the solid waste-based curing agent form an organic-inorganic composite three-dimensional cementing system, improving the material's density, early and long-term strength, and durability. The fiber acts as a "micro-reinforcing material," overcoming the increased brittleness of silt after curing, effectively inhibiting crack generation and development, and playing a crucial auxiliary role in improving the material's durability. Furthermore, the results of Comparative Examples 1-3 show that a simple combination of any two materials cannot achieve the comprehensive technical effect of a three-component system that balances early strength, long-term durability, and high toughness. As can be seen from the results of Comparative Example 4, the unmodified silty sand has the worst performance in all indicators and cannot meet the requirements of engineering construction.

[0085] Furthermore, changes in the composition or proportion of biopolymers, such as in Comparative Examples 5-7, lead to a decrease in the material's load-bearing capacity, mechanical properties, and durability. All performance indicators of Comparative Examples 5-7 are significantly lower than those of Example 1. Specifically, Comparative Example 5 exhibits the worst performance indicators, Comparative Example 6 shows better performance indicators, and Comparative Example 7's performance indicators fall between those of Comparative Examples 6 and 5. Comparing Example 1 and Comparative Examples 5-7, it is evident that a well-designed biopolymer blend system is superior to a single system, and guar gum demonstrates a better improvement effect on silty soil than xanthan gum. When biopolymers are used alone, Comparative Example 6 outperforms Comparative Example 5. This is mainly because guar gum has a long-chain molecular structure and contains a large number of hydroxyl groups, allowing it to better bind with soil particles to form a hydrogel network. Xanthan gum, as an anionic polysaccharide, mainly binds with soil particles through physical coating, resulting in a weaker effect on improving soil strength. When xanthan gum and guar gum are combined, the ordered helical structure of xanthan gum endows the composite material with thermal stability and acid and alkali resistance, while the long-chain molecules of guar gum form a better network system with the soil through multi-point hydrogen bonds, thus achieving a better synergistic improvement effect. It is worth noting that when compounding biopolymers, a reasonable ratio (1:0.8-1.2) must be maintained. If the ratio is unbalanced, as in Comparative Example 7, the improvement effect will be reduced.

[0086] When the composition of solid waste-based solidifying agents changes, as in Comparative Example 8, it can lead to a significant reduction in the load-bearing capacity, mechanical properties, and durability of soil materials. Compared to the quicklime in Comparative Example 8, carbide slag particles are finer, have a larger specific surface area, and contain a higher proportion of active ingredients. This not only allows for more uniform coating of soil particles but also results in a faster and more uniform hydration reaction, producing more cementitious products. This can better improve the compactness of the soil and enhance its mechanical and durability properties.

[0087] When basalt fiber or lignin fiber is replaced with other fibers, such as in Comparative Example 9, the bearing capacity, mechanical properties, and durability of the soil material decrease. This is mainly due to the significant differences in the physical and mechanical properties, surface properties, and interfacial bonding ability of different fibers with the matrix, leading to differences in the toughening effectiveness of different types of fibers in the three-dimensional synergistic system. Comparing Examples 1, 2, and Comparative Example 9, it was found that basalt fiber had the best improvement effect in the three-dimensional synergistic system, followed by lignin fiber, while polymer fiber was relatively poor. This is because basalt fiber has the best mechanical properties, with its tensile strength and elastic modulus significantly higher than those of lignin fiber and polymer fiber. Furthermore, basalt fiber has more active groups on its surface, exhibiting better synergy with biopolymers and solid waste matrix, thus resulting in a superior improvement effect. Polypropylene fiber has slightly worse mechanical properties than lignin fiber and possesses a certain degree of chemical inertness, limiting its synergistic effect with biopolymers and solid waste matrix, thus its toughening effect on soil materials is weaker.

[0088] In summary, this invention utilizes a specific ratio of biopolymers, solid waste-based solidifying agents, and fibers to synergistically improve the strength, toughness, and durability of silty soil, resulting in a high-performance, eco-friendly, widely applicable, highly compatible, and durable roadbed material. The roadbed material exhibits a CBR value of 85.2%-87.6%, a 28-day compressive strength as high as 3.48 MPa, a 28-day splitting strength as high as 0.69 MPa, a low dry-wet cycle compressive strength loss rate of 15.3%, and a low freeze-thaw cycle compressive strength loss rate of 18.6%, demonstrating promising application prospects in road engineering.

[0089] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A roadbed material for synergistic improvement of silty sand using bio-based, solid waste-based, and fiber methods, characterized in that, The raw materials include: silt, biopolymer, solid waste-based solidifying agent, and fiber; based on the mass of silt, the amount of biopolymer is 1%-2% of the mass of silt, the amount of solid waste-based solidifying agent is 8%-10% of the mass of silt, and the amount of fiber is 2%-4% of the mass of silt.

2. The roadbed material for synergistic improvement of silty soil based on bio-based, solid waste-based, and fiber as described in claim 1, characterized in that, The biopolymer comprises xanthan gum and guar gum in a mass ratio of 1:(0.8-1.2).

3. The roadbed material for synergistic improvement of silty sand based on bio-based, solid waste-based, and fiber as described in claim 1, characterized in that, By weight, the solid waste-based solidifying agent comprises: 20-30 parts cement, 30-50 parts calcium carbide slag, 20-30 parts fly ash, and 2-4 parts activator.

4. The roadbed material for synergistic improvement of silty soil based on bio-based, solid waste-based, and fiber as described in claim 3, is characterized in that... The cement is ordinary Portland cement with a strength grade of not less than 42.

5.

5. The roadbed material for synergistic improvement of silty sand based on bio-based, solid waste-based, and fiber as described in claim 3, is characterized in that... The activator is sodium sulfate.

6. The roadbed material for synergistic improvement of silty sand based on bio-based, solid waste-based, and fiber as described in claim 1, characterized in that, The fiber is 3-5 mm in length.

7. The roadbed material for synergistic improvement of silty sand based on bio-based, solid waste-based, and fiber as described in claim 6, characterized in that, The fiber includes at least one of basalt fiber and lignin fiber.

8. The method for preparing the bio-based-solid waste-based-fiber synergistic improvement material for silty soil as described in any one of claims 1-7, characterized in that, Includes the following steps: The amount of water required to prepare the subgrade material is determined based on the optimum moisture content of the silty soil. Add silty sand, biopolymer, solid waste-based solidifier, and fiber to a mixer in proportion, mix at low speed for 2-3 minutes, then add 1 / 3 of the total water and continue mixing at low speed for 5-8 minutes; add the remaining 2 / 3 of the total water and continue mixing at low speed for 5-8 minutes to obtain a mixture; remove the mixture and let it stand for curing treatment to obtain a roadbed material for silty sand synergistic improvement by bio-based, solid waste-based, and fiber.

9. The method for preparing the roadbed material of bio-based-solid waste-based-fiber synergistic improvement of silty soil according to claim 8, characterized in that, The low-speed stirring rate is 50-80 r / min.

10. The application of the bio-based-solid waste-based-fiber synergistic modified silty soil subgrade material according to any one of claims 1-7 in road engineering.

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