High-strength silt solidified soil and method for preparing the same

Abstract

The application discloses high-strength silt solidified soil and a preparation method thereof, and belongs to the technical field of building materials. The high-strength silt solidified soil comprises quartz sand, silt, a composite solidifying agent and water; the composite solidifying agent comprises water glass, cement, a reinforcing agent, calcium oxide, sodium lignosulfonate and slag; the solidified soil prepared by the application has good compressive strength and good impermeability, can be applied to a humid environment or a water conservancy project, the preparation process of the application is simple, the construction cost is low, efficient utilization of silt is realized, and the application has remarkable economic benefits and social benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to high-strength silt-solidified soil and a preparation method thereof. Background Art

[0002] Silt is a fine-grained material deposited at the bottom of water bodies such as rivers, lakes, and ports. It is primarily composed of fine sand, silt, clay, and organic matter. Due to its high water content, low strength, and high compressibility, silt is considered an undesirable soil type in engineering construction, making it difficult to use directly as a foundation material or building material. With the acceleration of urbanization, activities such as river dredging and port desilting have generated large amounts of silt. The storage and disposal of this silt has become an urgent environmental issue.

[0003] Traditional sludge treatment methods include drainage consolidation, natural airing, mechanical dehydration, heat treatment, and chemical solidification. With the rapid development of my country's economy and increasing urbanization, the demand for engineering soil is increasing. Chemical solidification, which converts dredged sludge into engineering soil, offers significant economic and ecological benefits.

[0004] As a recycled backfill civil engineering material, silt stabilized soil has the advantages of high strength, low pollution, convenient construction and low cost. However, since its environment is usually in the tidal zone or other areas with frequent dry-wet cycles, the anti-permeability performance of the stabilized soil decreases under the action of multiple dry-wet cycles, which directly affects the strength of the silt stabilized soil itself.

[0005] Chinese patent literature CN111410498A discloses a kind of low chloride ion content environment-friendly alkali residue sludge composite solidified soil, this invention is with 201X7 strong basic anion resin as anion exchanger, with diammonium phosphate and diatomite as encapsulating agent, with alkali residue as the alkali activator of curing agent, when having certain unconfined compressive strength, prepared the environment-friendly solidified soil of low chloride ion content, dissolved chloride ion content is lower than original beach mud, solved the problem of high pollution environment of dissolved chloride ion concentration in alkali residue, realized the resource utilization of alkali residue, reduced environmental pollution, economic, social, environmental benefits are obvious. But this invention mainly focuses on reducing chloride ion content, but the mechanical property and the impermeability of the solidified soil prepared by it are yet to be improved, for engineering application, impermeability and durability are the key performance indicators of solidified soil, especially in water environment or freeze-thaw environment, impermeability is not enough to cause solidified soil performance to degenerate rapidly. Summary of the Invention

[0006] The main purpose of the present invention is to provide a high-strength silt solidified soil with good mechanical strength and anti-seepage performance and a preparation method thereof.

[0007] To achieve the above objectives, the present invention proposes a high-strength silt-stabilized soil, comprising quartz sand, silt, a composite curing agent and water; the composite curing agent comprises water glass, cement, a reinforcing agent, calcium oxide, sodium lignin sulfonate and slag.

[0008] Preferably, the mass ratio of the quartz sand, silt, composite curing agent and water is 4-8:10-15:5-9:16-20.

[0009] Preferably, the water content of the sludge is ≤60%.

[0010] Preferably, the mass ratio of the water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag is 3-5:3-4:2.5-3.5:0.8-1:0.3-0.5:1-5.

[0011] The composite curing agent of the present invention is composed of water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag. The water glass reacts with silicate ions ionized in water to generate calcium silicate precipitation and silicate gelling material, which makes the soil body bonded and improves the strength of the solidified body. The cement and calcium oxide can undergo hydrolysis and hydration reaction with water and soil particles in the silt to generate hydrated calcium silicate that wraps the surface of the soil body, making the structure of the soil body dense. At the same time, the Ca in the hydration product 2+ It can react with acidic oxides in silt to generate water-insoluble crystals, fill voids, and bond with soil particles to form a soil skeleton. Calcium oxide can also activate the potential active components in slag, reacting with them secondary to generate more gelling products, further enhancing the strength and impermeability of the solidified soil. Sodium lignin sulfonate can improve the fluidity of fluidized solidified soil and improve construction performance. At the same time, it helps to evenly distribute the solidifying agent in the soil, avoiding the problem of insufficient local strength. The composite solidifying agent can maximize the use of the solidification properties of each solidifying agent through a series of physical and chemical reactions, thereby improving the strength of the solidified soil.

[0012] Preferably, the cement is ordinary Portland cement.

[0013] Preferably, the preparation method of the enhancer is as follows:

[0014] 1) treating flax fiber with plasma, immersing the fiber in a sodium hydroxide aqueous solution, adding γ-glycidyloxypropyltrimethoxysilane, heating and stirring to react, and drying the fiber to obtain epoxidized flax fiber;

[0015] 2) adding zinc nitrate and 2-aminoterephthalic acid to N,N-dimethylformamide and mixing them uniformly, then adding zeolite powder, dispersing them uniformly, and heating them for reaction. After the reaction is complete, filtering, washing, and drying the mixture to obtain a zeolite-based composite material; the reinforcing agent can reduce its water absorption and chloride ion permeability, thereby improving the mechanical strength and durability of the solidified soil;

[0016] 3) adding the epoxidized flax fiber and the zeolite-based composite material into xylene, heating and stirring, filtering, separating the solid matter, and drying to obtain the reinforcing agent.

[0017] Preferably, the plasma treatment conditions in step 1) are as follows: oxygen is introduced into the plasma instrument after vacuuming, the power is set to 150-200 W, and the treatment time is 5-10 min; the mass ratio of the flax fiber and γ-glycidyloxypropyltrimethoxysilane is 15-20:3-5; the heating temperature is 40-60° C., and the heating time is 3-5 h.

[0018] Preferably, in step 2), the mass ratio of zinc nitrate, 2-aminoterephthalic acid and zeolite powder is 6-10:4-6:15-20; the heating temperature is 120-150° C., and the heating time is 3-6 hours.

[0019] Preferably, in step 3), the mass ratio of the epoxidized flax fiber to the zeolite-based composite material is 5-8:4-6.

[0020] The reinforcing agent of the present invention is formed by introducing zeolite powder loaded with zinc-based MOF material onto flax fiber through a chemical grafting method to form a composite reinforcing agent. The reinforcing agent can form an "island effect" in the solidified soil, making the structure of the solidified soil denser through dispersion and filling effects, significantly reducing its water absorption and chloride ion permeability, thereby improving the mechanical strength and durability of the solidified soil.

[0021] The present invention also provides a method for preparing the high-strength silt-stabilized soil, comprising the following steps:

[0022] Water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag are evenly mixed to obtain a composite curing agent. Then, the silt excavated from the river channel is passed through a soil dehydrator to control the moisture content and remove large particles of impurities, and then mixed evenly with quartz sand, the composite curing agent and water, and then naturally cured to obtain the high-strength silt-solidified soil.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention provides a high-strength silt-solidified soil and a preparation method thereof. By optimizing the composition of a composite solidifying agent and the preparation process of a reinforcing agent, the mechanical strength and impermeability of the solidified soil are significantly improved. The multiple components of the composite solidifying agent (water glass, cement, calcium oxide, slag, etc.) generate cementitious products such as calcium silicate through a series of physical and chemical reactions, which fill the pores of the soil and bond with the soil particles to form a dense soil skeleton structure, thereby significantly improving the compressive strength of the solidified soil; and converting river silt into high-performance engineering materials, reducing the pollution of silt stacking to the environment, and realizing the resource utilization of waste. The solidified soil prepared by the present invention has excellent compressive strength and impermeability, and can be used in humid environments or water conservancy projects. The preparation process of the present invention is simple, the construction cost is low, and the efficient utilization of silt is achieved, with significant economic and social benefits.

[0025] (2) The preparation process of the reinforcing agent of the present invention is as follows: first, flax fiber is treated with plasma to form micropores and slits on the fiber surface to provide more physical anchoring points. Subsequently, the active sites on the fiber surface are further increased by alkali treatment. Then, the fiber surface is modified by γ-glycidyloxypropyltrimethoxysilane to introduce epoxy groups to provide reaction activity for subsequent chemical grafting. On the basis of zeolite powder as a carrier, the zinc-based MOF material is loaded onto the surface of the zeolite powder by a heating synthesis method. The introduction of the zinc-based MOF material not only significantly increases the specific surface area of ​​the zeolite powder, but also enhances the compatibility between the zeolite powder and the flax fiber. At the same time, the zinc-based MOF material and the zeolite powder work synergistically to significantly improve the adsorption capacity of heavy metal ions and organic pollutants in sludge, which helps to improve the mechanical properties of the solidified soil. Finally, through a chemical grafting reaction, the amino groups on the zeolite-based composite material react with the epoxy groups on the surface of the epoxidized flax fiber to form a stable chemical bond, thereby firmly grafting the zeolite-based composite material onto the flax fiber. The grafted flax fibers can significantly increase the elastic modulus in the solidified soil, making the solidified soil exhibit higher rigidity and deformation resistance when subjected to stress. In addition, the zeolite-grafted flax fibers can form an "island effect" in the solidified soil, making the structure of the solidified soil denser through dispersion and filling, thereby improving the mechanical strength and impermeability of the solidified soil. DETAILED DESCRIPTION

[0026] To avoid redundancy, the items used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0027] The sources of some raw materials used in the present invention are as follows:

[0028] Zeolite powder, 325 mesh, SiO2 content of 88%, was purchased from Lingshou County Chenyang Mineral Products Co., Ltd.

[0029] Quartz sand, 40 mesh, SiO2 content of 80%, was purchased from Lingshou County Huixin Mining Processing Plant.

[0030] Cement, model PO 42.5 ordinary Portland cement, was purchased from Hubei Yadong Co., Ltd.

[0031] Example 1

[0032] A method for preparing high-strength silt-solidified soil comprises the following steps:

[0033] 12g of water glass, 10.5g of cement, 8.4g of reinforcing agent, 3g of calcium oxide, 1.2g of sodium lignin sulfonate, and 9g of slag are evenly mixed to obtain a composite curing agent. The silt excavated from the river channel is passed through a soil dehydrator to control the moisture content to 40% and remove large particles of impurities. 120g of the treated silt is evenly mixed with 62g of quartz sand, 68g of the composite curing agent, and 175g of water, and then naturally aired and cured for 36 hours to obtain the high-strength silt-cured soil.

[0034] The preparation method of the enhancer is as follows:

[0035] 18 g of flax fiber was treated with plasma and then immersed in 200 mL of a 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was performed by evacuating the plasma instrument and then introducing oxygen gas. The power was set to 180 W and the treatment time was 8 minutes. 4.2 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was heated and stirred at 50° C. for 4 hours. The epoxidized flax fiber was then removed and dried.

[0036] 2) 7.8 g of zinc nitrate hexahydrate and 5 g of 2-aminoterephthalic acid were added to 150 mL of N,N-dimethylformamide and mixed uniformly. 17.8 g of zeolite powder was then added and dispersed uniformly, followed by heating at 130° C. for 4 h. After the reaction was complete, the mixture was filtered, washed, and dried to obtain a zeolite-based composite material.

[0037] 3) 6.8 g of epoxidized flax fiber and 5.1 g of the zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, and then filtered to separate the solid matter, which was dried to obtain the reinforcing agent.

[0038] Example 2

[0039] A method for preparing high-strength silt-solidified soil comprises the following steps:

[0040] 9g of water glass, 9g of cement, 7.5g of reinforcing agent, 2.4g of calcium oxide, 0.9g of sodium lignin sulfonate, and 3g of slag are evenly mixed to obtain a composite curing agent. The silt excavated from the river channel is then passed through a soil dehydrator to control the moisture content to 60% and remove large particles of impurities. 100g of the treated silt is mixed evenly with 40g of quartz sand, 50g of the composite curing agent, and 160g of water, and then evenly injected into a mold with a diameter of 39.1mm and a height of 80mm. The mold is naturally cured for 28 days and demolded to obtain the high-strength silt-solidified soil.

[0041] The preparation method of the enhancer is as follows:

[0042] 1) 15 g of flax fiber was treated with plasma and then immersed in 200 mL of a 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was performed by evacuating the plasma instrument and then introducing oxygen gas. The power was set to 180 W and the treatment time was 8 minutes. 3 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was heated and stirred at 50° C. for 4 hours. The epoxidized flax fiber was then removed and dried.

[0043] 2) 6 g of zinc nitrate hexahydrate and 4 g of 2-aminoterephthalic acid were added to 150 mL of N,N-dimethylformamide and mixed uniformly. 15 g of zeolite powder was then added and dispersed uniformly, followed by heating at 120° C. for 6 h. After the reaction was complete, the mixture was filtered, washed, and dried to obtain a zeolite-based composite material.

[0044] 3) 5 g of epoxidized flax fiber and 4 g of the zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, and then filtered to separate the solid matter, which was dried to obtain the reinforcing agent.

[0045] Example 3

[0046] A method for preparing high-strength silt-solidified soil comprises the following steps:

[0047] 15g of water glass, 12g of cement, 10.5g of reinforcing agent, 3g of calcium oxide, 1.5g of sodium lignin sulfonate, and 15g of slag are evenly mixed to obtain a composite curing agent. The silt excavated from the river channel is then passed through a soil dehydrator to control the moisture content to 50% and remove large particles of impurities. 150g of the treated silt is evenly mixed with 80g of quartz sand, 90g of the composite curing agent, and 200g of water, and then evenly injected into a mold with a diameter of 39.1mm and a height of 80mm. The mold is naturally cured for 28 days, and the high-strength silt-solidified soil is obtained by demolding.

[0048] The preparation method of the enhancer is as follows:

[0049] 1) 20 g of flax fiber was treated with plasma and then immersed in 200 mL of a 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was performed by evacuating the plasma instrument and then introducing oxygen gas. The power was set to 180 W and the treatment time was 8 minutes. 5 g of γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was heated and stirred at 60° C. for 3 hours. The epoxidized flax fiber was then removed and dried to obtain the epoxidized flax fiber.

[0050] 2) 10 g of zinc nitrate hexahydrate and 6 g of 2-aminoterephthalic acid were added to 150 mL of N,N-dimethylformamide and mixed uniformly. 20 g of zeolite powder was then added, dispersed uniformly, and heated at 150° C. for 3 h. After the reaction was complete, the mixture was filtered, washed, and dried to obtain a zeolite-based composite material.

[0051] 3) 8 g of epoxidized flax fiber and 6 g of the zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, and then filtered to separate the solid matter, which was dried to obtain the reinforcing agent.

[0052] Comparative Example 1

[0053] A method for preparing high-strength silt-stabilized soil is similar to that of Example 1, except that the reinforcing agent is flax fiber, and specifically comprises the following steps:

[0054] 12g of water glass, 10.5g of cement, 8.4g of flax fiber, 3g of calcium oxide, 1.2g of sodium lignin sulfonate, and 9g of slag are evenly mixed to obtain a composite curing agent. The silt excavated from the river channel is passed through a soil dehydrator to control the moisture content to 40% and remove large particles of impurities. 120g of the treated silt is evenly mixed with 62g of quartz sand, 68g of the composite curing agent, and 175g of water, and then evenly injected into a mold with a diameter of 39.1mm and a height of 80mm. The mold is naturally cured for 28 days and demolded to obtain the high-strength silt-solidified soil.

[0055] Comparative Example 2

[0056] A method for preparing high-strength silt-stabilized soil is similar to that of Example 1, except that the reinforcing agent is a zeolite-based composite material. The method specifically comprises the following steps:

[0057] 12g of water glass, 10.5g of cement, 8.4g of zeolite-based composite material, 3g of calcium oxide, 1.2g of sodium lignin sulfonate, and 9g of slag were evenly mixed to obtain a composite curing agent. The silt excavated from the river channel was passed through a soil dehydrator to control the moisture content to 40% and remove large particles of impurities. 120g of the treated silt was mixed with 62g of quartz sand, 68g of the composite curing agent, and 175g of water, and then evenly injected into a mold with a diameter of 39.1mm and a height of 80mm. The soil was naturally cured for 28 days and demolded to obtain the high-strength silt-solidified soil.

[0058] The preparation method of the enhancer is as follows:

[0059] 7.8 g of zinc nitrate hexahydrate and 5 g of 2-aminoterephthalic acid were added to 150 mL of N,N-dimethylformamide and mixed evenly. Then, 17.8 g of zeolite powder was added, dispersed evenly, and heated at 130° C. for 4 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a zeolite-based composite material, which was the reinforcing agent.

[0060] Performance Testing

[0061] 28d unconfined compressive strength test: The high-strength silt-stabilized soil obtained in Examples 1-3 and Comparative Examples 1-2 was tested according to the unconfined compressive strength test method in JTJ051-93 "Highway Soil Engineering Test Code". The average of the unconfined compressive strengths of the three test samples was taken as the unconfined compressive strength of the stabilized soil.

[0062] Permeability coefficient test: The permeability coefficient was tested in accordance with GB / T50123-2019 "Standard for Geotechnical Test Methods". The test results are shown in Table 1:

[0063] Table 1 Test results of high-strength silt-stabilized soil performance

[0064]

[0065] It can be seen from the experimental results in Table 1 that the solidified soil prepared in the embodiment of the present invention has good mechanical strength and low permeability coefficient, can effectively prevent water from penetrating into the soil, can reduce water to avoid soil softening or strength loss, and ensure the long-term stability of the project.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. A high-strength silt-stabilized soil, characterized by: It includes quartz sand, silt, composite curing agent and water; the composite curing agent includes water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag; The preparation method of the enhancer is as follows: 1) treating flax fiber with plasma, immersing the fiber in a sodium hydroxide aqueous solution, adding γ-glycidyloxypropyltrimethoxysilane, heating and stirring to react, and drying the fiber to obtain epoxidized flax fiber; 2) adding zinc nitrate and 2-aminoterephthalic acid to N,N-dimethylformamide and mixing them evenly, then adding zeolite powder, dispersing them evenly and heating them for reaction. After the reaction is completed, filtering, washing, and drying to obtain a zeolite-based composite material; 3) adding the epoxidized flax fiber and the zeolite-based composite material into xylene, heating and stirring, filtering, separating the solid matter, and drying to obtain the reinforcing agent.

2. The silt-stabilized soil according to claim 1, characterized in that: The water content of the sludge is ≤60%.

3. The silt-stabilized soil according to claim 1, characterized in that: The mass ratio of the water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag is 3-5:3-4:2.5-3.5:0.8-1:0.3-0.5:1-5.

4. The silt-stabilized soil according to claim 1, characterized in that: The cement is ordinary Portland cement.

5. The silt-stabilized soil according to claim 1, characterized in that: The plasma treatment conditions in step 1) are as follows: the plasma instrument is evacuated and oxygen is introduced, the power is set to 150-200 W, and the treatment time is 5-10 min.

6. The silt-stabilized soil according to claim 1, characterized in that: In step 1), the mass ratio of flax fiber to γ-glycidyloxypropyltrimethoxysilane is 15-20:3-5.

7. The silt-stabilized soil according to claim 1, characterized in that: In step 2), the mass ratio of zinc nitrate, 2-aminoterephthalic acid and zeolite powder is 6-10:4-6:15-20.

8. The silt-stabilized soil according to claim 1, characterized in that: In step 3), the mass ratio of the epoxidized flax fiber to the zeolite-based composite material is 5-8:4-6.

9. A method for preparing the silt-stabilized soil according to any one of claims 1 to 8, comprising the steps of: uniformly mixing water glass, cement, a reinforcing agent, calcium oxide, sodium lignin sulfonate, and slag to obtain a composite curing agent; then, passing silt excavated from a river channel through a soil dehydrator to control the moisture content and remove large particles of impurities; and then uniformly mixing the silt with quartz sand, the composite curing agent, and water, followed by natural curing and curing to obtain the high-strength silt-stabilized soil.

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