High-strength sludge solidified soil and preparation method thereof

Abstract

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

Description

Technical Field

[0001] The 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, and is mainly composed of fine sand, silt, clay, and organic matter. Due to its high water content, low strength, and high compressibility, silt is considered a poor soil in engineering construction and is 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 a large amount of silt, and the stacking and treatment of this silt has become an environmental problem that needs to be solved urgently.

[0003] Traditional sludge treatment methods mainly include the following: drainage consolidation, natural drying, mechanical dehydration, heating treatment, chemical solidification, etc. With the rapid development of economic construction, the increasing level of urbanization, the increasing number of engineering project activities in my country, the demand for engineering soil is also increasing. Chemical solidification treatment converts dredged sludge into engineering soil, which has good 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 a 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 document CN111410498A discloses a low chloride ion content environmentally friendly alkaline residue sludge composite solidified soil, the invention uses 201X7 strong basic anion resin as anion exchanger, diammonium phosphate and diatomite as encapsulation agent, and alkaline residue as the alkali activator of curing agent, and in the case of having a certain unconfined compressive strength, an environmentally friendly solidified soil with low chloride ion content is prepared, and the dissolved chloride ion content is lower than that of the original beach mud, and the problem of high environmental pollution caused by the dissolved chloride ion concentration in the alkaline residue is solved, and the resource utilization of the alkaline residue is realized, and environmental pollution is reduced, and the economic, social and environmental benefits are obvious. However, the invention mainly focuses on reducing the chloride ion content, but the mechanical properties and impermeability of the solidified soil prepared by it are still to be improved, and for engineering applications, impermeability and durability are the key performance indicators of solidified soil, especially in water environment or freeze-thaw environment, impermeability is insufficient and can cause the performance of solidified soil to deteriorate rapidly. Summary of the invention

[0006] The main purpose of the 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-mentioned purpose, the present invention provides a high-strength silt-solidified 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, wherein the water glass reacts with silicate ions ionized in water to generate calcium silicate precipitation and silicate gelling material, so that the soil body is bonded and the strength of the solidified body is improved; the cement and calcium oxide can undergo hydrolysis and hydration reaction with water and soil particles in the sludge to generate hydrated calcium silicate wrapped on the surface of the soil body, so that the structure of the soil body is compacted, and at the same time, the Ca in the hydration product thereof 2+ It can react with acidic oxides in sludge to generate water-insoluble crystals to fill voids and bond with soil particles to form a soil skeleton. Calcium oxide can also activate potential active ingredients in slag and react with it 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. It also helps to evenly distribute the curing agent in the soil and avoid the problem of insufficient local strength. The composite curing agent can maximize the curing performance of each curing agent through a series of physical and chemical reactions to improve 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 and then immersing it in a sodium hydroxide aqueous solution, adding γ-glycidyloxypropyltrimethoxysilane, heating and stirring to react, taking out and drying to obtain epoxidized flax fiber;

[0015] 2) adding zinc nitrate and 2-aminoterephthalic acid to N,N-dimethylformamide, mixing evenly, then adding zeolite powder, dispersing evenly and heating to react, after the reaction is completed, filtering, washing and drying 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 the 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, thereby forming a composite reinforcing agent. The reinforcing agent can form an "island effect" in the solidified soil, and through dispersion and filling effects, the structure of the solidified soil is made denser, and its water absorption and chloride ion permeability are significantly reduced, 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-solidified soil, comprising the following steps:

[0022] The water glass, cement, reinforcing agent, calcium oxide, sodium lignin sulfonate and slag are evenly mixed to obtain a composite curing agent, and 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 and solidified 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 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 environmental pollution caused by silt stacking, 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 present invention has a simple preparation process and low construction cost, and at the same time realizes the efficient utilization of silt, 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 of the zeolite powder with 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 improve the elastic modulus in the solidified soil, making the solidified soil show 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 dried and cured for 36 hours to obtain the high-strength silt-solidified soil.

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

[0035] 1) 18 g of flax fiber was treated with plasma and then immersed in 200 mL of 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was to evacuate the plasma instrument and then introduce oxygen, the power was set to 180 W, and the treatment time was 8 min; 4.2 g of γ-glycidyloxypropyltrimethoxysilane was added, heated and stirred at 50° C. for 4 h, and then taken out and dried to obtain epoxidized flax fiber;

[0036] 2) adding 7.8 g of zinc nitrate hexahydrate and 5 g of 2-aminoterephthalic acid to 150 mL of N,N-dimethylformamide, mixing evenly, then adding 17.8 g of zeolite powder, dispersing evenly, heating at 130° C. for reaction for 4 h, and after the reaction is completed, filtering, washing, and drying to obtain a zeolite-based composite material;

[0037] 3) 6.8 g of epoxidized flax fiber and 5.1 g of zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, filtered, and the solid was separated and 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 evenly mixed 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 the high-strength silt-solidified soil is obtained by demolding.

[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 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was to evacuate the plasma instrument and then introduce oxygen, the power was set to 180 W, and the treatment time was 8 min; 3 g of γ-glycidyloxypropyltrimethoxysilane was added, heated and stirred at 50° C. for 4 h, and then taken out and dried to obtain epoxidized flax fiber;

[0043] 2) adding 6 g of zinc nitrate hexahydrate and 4 g of 2-aminoterephthalic acid to 150 mL of N,N-dimethylformamide, mixing evenly, then adding 15 g of zeolite powder, dispersing evenly, heating at 120° C. for reaction for 6 h, and after the reaction is completed, filtering, washing, and drying to obtain a zeolite-based composite material;

[0044] 3) 5 g of epoxidized flax fiber and 4 g of zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, filtered, and the solid was separated and 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 1 mol / L sodium hydroxide aqueous solution. The plasma treatment process was to evacuate the plasma instrument and then introduce oxygen, the power was set to 180 W, and the treatment time was 8 min; 5 g of γ-glycidyloxypropyltrimethoxysilane was added, heated and stirred at 60° C. for 3 h, and then taken out and dried to obtain epoxidized flax fiber;

[0050] 2) adding 10 g of zinc nitrate hexahydrate and 6 g of 2-aminoterephthalic acid to 150 mL of N,N-dimethylformamide, mixing evenly, then adding 20 g of zeolite powder, dispersing evenly, heating at 150° C. for reaction for 3 h, and after the reaction is completed, filtering, washing, and drying to obtain a zeolite-based composite material;

[0051] 3) 8 g of epoxidized flax fiber and 6 g of zeolite-based composite material were added to 200 mL of xylene, heated and stirred at 50° C. for 2 h, filtered, and the solid was separated and 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 the high-strength silt-solidified soil is obtained by demolding.

[0055] Comparative Example 2

[0056] A method for preparing high-strength silt-solidified soil is similar to that of Example 1, except that the reinforcing agent is a zeolite-based composite material, and 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 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 the high-strength silt-solidified soil is obtained by demolding.

[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 and dispersed evenly, and heated at 130° C. for reaction for 4 h. After the reaction was completed, the zeolite-based composite material was obtained by filtering, washing and drying, which was the reinforcing agent.

[0060] Performance Testing

[0061] Test of 28d unconfined compressive strength: 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 Geotechnical Test Code", and the average value of the unconfined compressive strength 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 reduction, and ensure the long-term stability of the project.

[0066] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A high-strength silt solidification soil, characterized in that: The invention comprises 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.

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 preparation method of the enhancer is as follows: 1) treating flax fiber with plasma and then immersing it in a sodium hydroxide aqueous solution, adding γ-glycidyloxypropyltrimethoxysilane, heating and stirring to react, taking out and drying to obtain epoxidized flax fiber; 2) adding zinc nitrate and 2-aminoterephthalic acid to N,N-dimethylformamide, mixing evenly, then adding zeolite powder, dispersing evenly and heating to react, 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.

6. The silt-stabilized soil according to claim 5, 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.

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

8. The silt-stabilized soil according to claim 5, characterized in that: In the step 2), the mass ratio of zinc nitrate, 2-aminoterephthalic acid and zeolite powder is 6-10:4-6:15-20.

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

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

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