Pasty solidified soil for foundation treatment as well as preparation method and application of pasty solidified soil

Abstract

The invention relates to the technical field of solidified soil, in particular to pasty solidified soil for foundation treatment and a preparation method and application of the pasty solidified soil. The preparation method of the pasty solidified soil comprises the following steps: firstly, carrying out organosilane modification on polycarboxylic acid; then mixing the curing agent, the modified polycarboxylic acid and the water together, and then adding the soil material for multiple times and stirring. Meanwhile, the modified polycarboxylic acid is further modified by polyurethane and inorganic nanoparticles, so that the compressive strength and permeability resistance of the pasty solidified soil are improved. In addition, the curing agent contains solid wastes, so that the resource utilization rate of the solid wastes is improved, and the pollution of the solid wastes to the environment is reduced. The pasty solidified soil can be applied to the foundation treatment process, is directly poured into a storage bin of a pile driver, is pumped into a pile hole, rapidly fills the pile hole and is tightly combined with foundation soil, and cavities and defects are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of solidified soil, and in particular to a paste-like solidified soil for foundation treatment, and a preparation method and application thereof. Background Art

[0002] With the accelerated advancement of industry and urbanization, the emission of construction waste has increased year by year, especially the slag generated by construction projects, most of which is regarded as abandoned soil and directly piled up and landfilled, which not only occupies land resources, but also brings serious environmental pollution problems during the landfill process. Therefore, how to make resource utilization of these construction wastes is an issue that we need to solve urgently.

[0003] In recent years, the most studied resource utilization of construction waste is to use construction slag as the main raw material, supplemented by cementitious materials as a curing agent, and add appropriate amounts of additives and water to make fluidized solidified soil, which is used for filling foundation trenches, holes, pits, etc. of buildings, pipeline corridors, rail transit, etc., or foundation treatment of roads, buildings, etc. Before solidification, the fluidized solidified soil has the characteristics of high fluidity and self-compacting. It basically does not require vibration during construction. After a certain period of solidification, it forms a new type of geotechnical engineering material with certain strength, low permeability, water stability, and long-term stability. Through the fluidized solidified soil technology, not only the performance of backfill soil is improved, which plays an important role in foundation reinforcement, but also meets the resource utilization of construction waste, achieving dual benefits.

[0004] When fluidized solidified soil is used for foundation treatment, the fluidized solidified soil needs to have high compressive strength and excellent low permeability after solidification, so that the foundation has a high bearing capacity, and can effectively reduce the penetration of water and protect the foundation from being eroded by water. The application document with publication number CN118048897A discloses a vibration stirring fluidized solidified soil pile construction method for foundation treatment. The method uses loess as a soil source sample and a composition of cement, fly ash, and slag powder as a curing agent. The vibration stirring technology is applied to the field of solidified soil mixing, and an economical and environmentally friendly fluidized solidified soil slurry is obtained. The pile driver hole forming and in-hole pumping process are then used to make a vibration stirring fluidized solidified soil pile. The method has certain advantages in foundation treatment, but the compressive strength of the solidified soil is low, and there is a lack of evaluation of the permeability of the solidified soil. Summary of the invention

[0005] In order to obtain paste-like solidified soil with high strength and low permeability, the present application provides a paste-like solidified soil for foundation treatment, a preparation method and application thereof.

[0006] A method for preparing paste-like solidified soil comprises the following steps: S1: dissolving the initiator in water to prepare solution A, dissolving acrylic acid monomer and 2-acrylamide-2-methylpropane sulfonic acid in water to prepare solution B; uniformly mixing allyl alcohol polyoxyethylene ether, maleic anhydride and organosilane, heating to 75-90° C., adding solution A and solution B, keeping the temperature for 1-3 hours, cooling to 30-50° C., adjusting the pH value, and drying to obtain modified polycarboxylic acid; S2: Stir the curing agent, modified polycarboxylic acid and water, add the soil material in 4-5 times, add water and stir after adding the soil material.

[0007] In the above technical scheme, polycarboxylic acid is an excellent water reducer. When added to the solidified soil, the amount of water added can be reduced, and the fluidity, water stability and early strength of the solidified soil can be improved. In order to further improve the performance of the paste-like solidified soil, the polycarboxylic acid is modified using organic siloxane. On the one hand, hydrophobic groups are introduced into the polycarboxylic acid molecular chain. When encountering a humid environment, the hydrophobic groups can squeeze water molecules out of the pores, reducing the damage of water to the performance of the paste-like solidified soil. On the other hand, in a humid environment, the organic siloxane groups are hydrolyzed to form a gel, which can increase the density of the paste-like solidified soil, increase the solidification speed of the paste-like solidified soil, and can also further enhance the strength and anti-permeability of the paste-like solidified soil.

[0008] In addition, when mixing, the curing agent and modified polycarboxylic acid are first added with water and stirred to make them fully mixed. The soil material is added in multiple times, once every 20-30 seconds, so that the soil material is fully in contact with the curing agent and water, which is conducive to the hydration reaction and makes the cured soil stronger.

[0009] Preferably, in step S1, the organosilane is one or more of vinyltrimethoxysilane, vinyltriethoxysilane and 3-butenetriethoxysilane.

[0010] Preferably, in step S1, the molar ratio of the acrylic acid monomer, 2-acrylamide-2-methylpropane sulfonic acid, maleic anhydride and organosilane is 1:(0.1-0.3):(2-3):(0.3-0.8).

[0011] Further preferably, the modified polycarboxylic acid is further modified by a method comprising the following steps: Mix diisocyanate and ethyl acetate evenly to prepare mixed solution I; disperse modified polycarboxylic acid in water to obtain mixed solution II; dissolve 1,4-butanediol in water to obtain solution III; mix mixed solution I with mixed solution II, heat to 60-85°C, add solution III, stir to react for 1-3h, filter, wash and dry.

[0012] In the above technical scheme, polyurethane is used as the capsule wall to embed the modified polycarboxylic acid. When the solidified soil is mixed, after stirring, part of the capsule wall breaks and the modified polycarboxylic acid is released. The modified polycarboxylic acid is adsorbed on the surface of the soil particles, which improves the dispersibility of the soil particles and thus improves the fluidity of the paste-like solidified soil. Moreover, the organic siloxane groups in the released modified polycarboxylic acid are hydrolyzed to form a gel, which improves the solidification rate and early strength of the paste-like solidified soil. With the extension of time, in a humid environment, the polyurethane swells and slowly releases the modified polycarboxylic acid, thereby enhancing the mid- and late-stage strength of the paste-like solidified soil. In addition, polyurethane can form more hydrogen bonds. Therefore, when the paste-like solidified soil is affected by the outside world and cracks occur, the hydrogen bonds can be rebuilt to partially repair the cracks, which will also increase the strength of the paste-like solidified soil.

[0013] Preferably, the diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate, and the mass ratio of the diisocyanate, 1,4-butanediol, and modified polycarboxylic acid is 10:(5-10):(2-5).

[0014] Further preferably, inorganic nanoparticles are added during the preparation of mixed solution II, wherein the inorganic nanoparticles are nano-calcium carbonate or nano-silicon dioxide, and the mass ratio of the inorganic nanoparticles to the modified polycarboxylic acid is 1:(1-5).

[0015] By adopting the above technical scheme, the inorganic nanoparticles added during the preparation of mixed solution II have strong surface activity and can act as a dispersant to effectively prevent particle agglomeration. As the modified polycarboxylic acid is embedded, the inorganic nanoparticles dispersed in the water may also be doped into the capsule wall, thereby increasing the roughness and structural stability of the capsule wall surface, thereby increasing the strength of the paste-like solidified soil.

[0016] Preferably, in step S2, the curing agent comprises the following components in parts by weight: 40-60 parts of cement; 20-30 parts of blast furnace slag powder, 10-25 parts of fly ash, and 2-5 parts of carbide slag.

[0017] In the above technical scheme, blast furnace slag powder and fly ash contain more calcium oxide, silicon dioxide, aluminum oxide, etc., which are similar to cement and can also undergo hydration reaction to form cementitious materials. Carbide slag mainly contains calcium hydroxide, which not only provides more calcium ions, but also provides an alkaline environment, which can destroy the glass network structure in slag and fly ash, release more calcium ions and silicon (aluminum) oxygen tetrahedrons, and continuously form gel, thereby improving the solidification rate and strength of the solidified soil.

[0018] Preferably, in step S2, the mass ratio of the soil material, the curing agent, water, and the modified polycarboxylic acid is 100:(7.2-12):(35-45):(0.5-1).

[0019] A paste-like solidified soil is prepared by the above-mentioned preparation method.

[0020] In the above technical scheme, on the one hand, the paste-like solidified soil contains polycarboxylic acid modified by organosilane, which can not only reduce the amount of water added and increase the solidification rate of the solidified soil, but also reduce the erosion of the foundation by water during foundation treatment; on the second hand, after the modified polycarboxylic acid in the paste-like solidified soil is further modified, polyurethane is used as the capsule wall and the modified polycarboxylic acid is used as the capsule core, which can not only slowly release the modified polycarboxylic acid and improve the mid- and late-stage strength of the paste-like solidified soil, but also repair the microcracks generated by the paste-like solidified soil during long-term use through the self-repairing effect of hydrogen bonds, thereby further improving the strength of the foundation; in addition, the curing agent used in the preparation process of the paste-like solidified soil contains blast furnace slag, fly ash and carbide slag, which improves the resource utilization rate of solid waste and reduces the pollution of solid waste to the environment.

[0021] An application of a paste-like solidified soil, wherein the paste-like solidified soil is used in foundation treatment, and the specific method is as follows: Use a pile driver to drill a pile hole, pour the paste-like solidified soil into the pile driver's storage bin, pump it into the pile hole through a delivery pump, and let it solidify.

[0022] In the above technical solution, the paste-like solidified soil has good fluidity and can be directly poured into the storage bin of the pile driver and pumped into the pile hole, eliminating the need for special paste-like solidified soil transport tankers and pumping trucks. In addition, the paste-like solidified soil can quickly fill the pile hole and combine closely with the foundation soil to quickly generate cementitious materials, further increasing the bonding strength between the pile body and the foundation and reducing the generation of voids and defects.

[0023] The above technical solution of the present application includes at least the following beneficial effects: 1. The present application modifies polycarboxylic acid to improve the fluidity, water resistance and compressive strength of paste-like solidified soil.

[0024] 2. The present application uses polyurethane to embed modified polycarboxylic acid, thereby improving the early strength and mid- to late-stage strength of the paste-like solidified soil and reducing the permeability.

[0025] 3. This application uses solid waste as part of the curing agent, which improves the resource utilization rate of solid waste and reduces the pollution of solid waste to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the 28d unconfined compressive strength and 28d permeability of paste-like solidified soil; Figure 2 It is the flow extension of paste-like solidified soil; Figure 3It is the setting time of paste-like solidified soil. DETAILED DESCRIPTION

[0027] The present application is further described in detail below in conjunction with embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0029] In the following examples and comparative examples, the soil material is loess, the cement is ordinary Portland cement, the blast furnace slag is S95 grade slag, and the fly ash is Class F Grade I fly ash.

[0030] Example Example 1 The method for preparing the paste-like solidified soil of this embodiment comprises the following steps: S1: Weigh 0.14 g of potassium persulfate and dissolve it in 50 mL of deionized water to prepare solution A; weigh 7.2 g of acrylic acid and 2.1 g of 2-acrylamide-2-methylpropane sulfonic acid and dissolve them in 500 mL of deionized water to prepare solution B; weigh 192 g of allyl alcohol polyoxyethylene ether with a relative molecular mass of 2400, 19.6 g of maleic anhydride and 5.7 g of vinyl triethoxysilane, place them in a four-necked flask equipped with a stirrer, heat to 75°C, then use a peristaltic pump to evenly add solution A and solution B, keep warm for 3 hours after the addition is completed, then cool to 30°C, add sodium hydroxide to adjust the pH value to 7, and after drying, obtain a modified polycarboxylic acid; S2: Add 4kg of cement, 2kg of blast furnace slag powder, 1kg of fly ash, 0.2kg of calcium carbide slag, 0.5kg of modified polycarboxylic acid and 20kg of water into a mixer, stir for 5 minutes, add soil materials in 5 times, add once every 20 seconds, add 20kg each time, add 15kg of water after adding soil materials, stir for 5 minutes, and obtain; The specific method of applying the paste-like solidified soil in this embodiment to foundation treatment is as follows: Use a pile driver to drill a pile hole, pour the paste-like solidified soil into the pile driver's storage bin, pump it into the pile hole through a delivery pump, and let it solidify.

[0031] Example 2 The method for preparing the paste-like solidified soil of this embodiment comprises the following steps: S1: Weigh 0.22 g of ammonium persulfate and dissolve it in 50 mL of deionized water to prepare solution A, weigh 7.2 g of acrylic acid and 6.2 g of 2-acrylamide-2-methylpropane sulfonic acid and dissolve them in 500 mL of deionized water to prepare solution B; weigh 360 g of allyl alcohol polyoxyethylene ether with a relative molecular mass of 2400, 29.4 g of maleic anhydride and 11.85 g of vinyl trimethoxysilane, place them in a four-necked flask equipped with a stirrer, heat to 90°C, then use a peristaltic pump to evenly add solution A and solution B, keep warm for 1 hour after the addition is completed, then cool to 50°C, add sodium hydroxide to adjust the pH value to 7, and after drying, obtain a modified polycarboxylic acid; S2: Add 4kg of cement, 2kg of blast furnace slag powder, 1kg of fly ash, 0.2kg of calcium carbide slag, 0.5kg of modified polycarboxylic acid and 20kg of water into a mixer, stir for 5min, add soil material in 4 times, add once every 30s, add 25kg each time, add 15kg of water after adding soil material, stir for 5min, and obtain; In this embodiment, the modified polycarboxylic acid is modified by a method comprising the following steps: Weigh 10 g of isophorone diisocyanate and 10 mL of ethyl acetate and stir and mix them evenly to prepare mixed solution I; disperse 2 g of modified polycarboxylic acid in 100 g of deionized water to obtain mixed solution II; dissolve 5 g of 1,4-butanediol in 100 g of deionized water to obtain solution III; add mixed solution I to mixed solution II, stir for 5 min, heat to 60°C, slowly add solution III with a peristaltic pump, react for 3 h, filter, wash and dry; The specific method of applying the paste-like solidified soil in this embodiment to foundation treatment is the same as that in Embodiment 1.

[0032] Example 3 The method for preparing the paste-like solidified soil of this embodiment comprises the following steps: S1: Weigh 0.17 g of ammonium persulfate and dissolve it in 50 mL of deionized water to prepare solution A; weigh 7.2 g of acrylic acid and 4.1 g of 2-acrylamide-2-methylpropane sulfonic acid and dissolve them in 500 mL of deionized water to prepare solution B; weigh 240 g of allyl alcohol polyoxyethylene ether with a relative molecular mass of 2400, 24.5 g of maleic anhydride and 10.9 g of 3-butylene triethoxysilane, place them in a four-necked flask equipped with a stirrer, heat to 80°C, then use a peristaltic pump to evenly add solution A and solution B, keep warm for 2 hours after the addition is completed, then cool to 40°C, add sodium hydroxide to adjust the pH value to 7, and after drying, obtain a modified polycarboxylic acid; S2: Add 4kg of cement, 2kg of blast furnace slag powder, 1kg of fly ash, 0.2kg of calcium carbide slag, 0.5kg of modified polycarboxylic acid and 20kg of water into a mixer, stir for 5 minutes, add soil materials in 5 times, add once every 30 seconds, add 20kg each time, add 15kg of water after adding soil materials, stir for 5 minutes, and obtain; In this embodiment, the modified polycarboxylic acid is modified by a method comprising the following steps: Weigh 10 g of hexamethylene diisocyanate and 10 mL of ethyl acetate and stir and mix them evenly to prepare a mixed solution I; disperse 5 g of modified polycarboxylic acid and 1 g of nano calcium carbonate in 100 g of deionized water to obtain a mixed solution II; dissolve 10 g of 1,4-butanediol in 100 g of deionized water to obtain a solution III; add the mixed solution I to the mixed solution II, stir for 10 min, heat to 85 ° C, slowly add the solution III with a peristaltic pump, react for 1 h, filter, wash and dry; The specific method of applying the paste-like solidified soil in this embodiment to foundation treatment is the same as that in Embodiment 1.

[0033] Example 4 The preparation method of the paste-like solidified soil in this embodiment is different from that in Embodiment 3 in that: S3: Add 6kg of cement, 3kg of blast furnace slag powder, 2.5kg of fly ash, 0.5kg of calcium carbide slag, 0.5kg of modified polycarboxylic acid and 30kg of water into a mixer, stir for 5 minutes, add soil materials in 5 times, add once every 30 seconds, add 20kg each time, add 15kg of water after adding soil materials, stir for 5 minutes, and obtain; The remaining steps are the same as those in Example 3; The specific method of applying the paste-like solidified soil in this embodiment to foundation treatment is the same as that in Embodiment 1.

[0034] Example 5 The preparation method of the paste-like solidified soil in this embodiment is different from that in Embodiment 3 in that: S3: Add 6kg of cement, 3kg of blast furnace slag powder, 2.5kg of fly ash, 0.5kg of calcium carbide slag, 1kg of modified polycarboxylic acid and 30kg of water into a mixer, stir for 5 minutes, add soil materials in 5 times, add once every 30 seconds, add 20kg each time, add 15kg of water after adding soil materials, stir for 5 minutes, and obtain; The remaining steps are the same as those in Example 3; The specific method of applying the paste-like solidified soil in this embodiment to foundation treatment is the same as that in Embodiment 1.

[0035] Comparative Example Comparative Example 1 The preparation method of the paste-like solidified soil of this comparative example comprises the following steps: Add 4kg of cement, 2kg of blast furnace slag powder, 1kg of fly ash, 0.2kg of carbide slag and 20kg of water into a mixer, stir for 5 minutes, add soil materials in 5 times, add once every 30 seconds, add 20kg each time, add 15kg of water after adding soil materials, stir for 5 minutes, and you have it. The specific method of applying the paste-like solidified soil in this comparative example to foundation treatment is the same as that in Example 1.

[0036] Comparative Example 2 The preparation method of the paste-like solidified soil of this comparative example comprises the following steps: Add 4kg of cement, 2kg of blast furnace slag powder, 1kg of fly ash, 0.2kg of calcium carbide slag, 0.5kg of polyacrylate water reducer and 20kg of water into a mixer, stir for 5 minutes, add soil material in 5 times, add once every 30 seconds, add 20kg each time, add 15kg of water after adding soil material, stir for 5 minutes, and you have it. The specific method of applying the paste-like solidified soil in this comparative example to foundation treatment is the same as that in Example 1.

[0037] Performance testing 1. Unconfined compressive strength test According to JGJ / T233-2011 "Cement-Soil Mix Design Code", the 28-day unconfined compressive strength test results are as follows: Figure 1 shown.

[0038] 2. Penetration test According to GB / T50123-2019 Geotechnical Test Method Standard, the permeability of the paste-like solidified soil was tested after 28 days of standard curing. The results are as follows: Figure 1 shown.

[0039] 3. Flow expansion test Referring to DBJ51T188-2022 "Technical Standard for Engineering Application of Premixed Fluidized Solidified Soil", the fluidity of paste-like solidified soil was tested. The results are as follows: Figure 2 shown.

[0040] 4. Setting time test Refer to GB / T1346 "Test Methods for Water Consumption, Setting Time and Stability of Cement Standard Consistency" to conduct setting time test. The results are as follows: Figure 3 shown.

[0041] Results Analysis from Figure 1It can be seen from the data that compared with comparative examples 1-2, the 28d unconfined compressive strength of the paste-like solidified soil in the embodiment is higher, which may be because with the increase in the amount of curing agent added and the addition of modified polycarboxylic acid, the solidification rate of the paste-like solidified soil is accelerated, thereby improving the compressive strength. At the same time, the permeability gradually decreases, which may be because the faster solidification rate and compressive strength make the paste-like solidified soil denser and the permeability smaller. In addition, a certain degree of self-repair and water resistance of modified polycarboxylic acid may also be the reason for the reduced permeability.

[0042] from Figure 2 It can be seen from the data that the flow expansion of the paste-like solidified soil obtained by the preparation method of the embodiment is greater than 160 mm, which meets the requirement of 120-180 mm for the flow expansion of fluidized solidified soil for foundation treatment in the DBJ51T188-2022 standard, indicating that the paste-like solidified soil of the embodiment meets the requirements of foundation treatment application.

[0043] from Figure 3 It can be seen from the data that the initial setting time of the paste-like solidified soil in the embodiment and the comparative example is 12-25h, and the final setting time is 34-56h. Compared with the comparative example, the initial setting time and the final setting time of the paste-like solidified soil in the embodiment are shorter, indicating that compared with the comparative example, the solidification rate of the paste-like solidified soil in the embodiment is faster, and the solidification rate is accelerated by increasing the amount of curing agent and modified polycarboxylic acid added.

[0044] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A method for preparing paste-like solidified soil, characterized in that: The steps include: S1: dissolving the initiator in water to prepare solution A, dissolving acrylic acid monomer and 2-acrylamide-2-methylpropane sulfonic acid in water to prepare solution B; uniformly mixing allyl alcohol polyoxyethylene ether, maleic anhydride and organosilane, heating to 75-90° C., adding solution A and solution B, keeping the temperature for 1-3 hours, cooling to 30-50° C., adjusting the pH value, and drying to obtain modified polycarboxylic acid; S2: Stir the curing agent, modified polycarboxylic acid and water, add the soil material in 4-5 times, add water and stir after adding the soil material.

2. The method for preparing paste-like solidified soil according to claim 1, characterized in that: In step S1, the organosilane is one or more of vinyltrimethoxysilane, vinyltriethoxysilane and 3-butenetriethoxysilane.

3. The method for preparing the paste-like solidified soil according to claim 1, characterized in that: In step S1, the molar ratio of the acrylic acid monomer, 2-acrylamide-2-methylpropane sulfonic acid, maleic anhydride and organosilane is 1:(0.1-0.3):(2-3):(0.3-0.8).

4. The method for preparing the paste-like solidified soil according to claim 1, characterized in that: The modified polycarboxylic acid is further modified by a method comprising the following steps: Mix diisocyanate and ethyl acetate evenly to prepare mixed solution I; disperse modified polycarboxylic acid in water to obtain mixed solution II; dissolve 1,4-butanediol in water to obtain solution III; mix mixed solution I with mixed solution II, heat to 60-85°C, add solution III, stir to react for 1-3h, filter, wash and dry.

5. The method for preparing the paste-like solidified soil according to claim 4, characterized in that: The diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate, and the mass ratio of the diisocyanate, 1,4-butanediol and modified polycarboxylic acid is 10:(5-10):(2-5).

6. The method for preparing paste-like solidified soil according to claim 4, characterized in that: In the process of preparing the mixed solution II, inorganic nanoparticles are also added. The inorganic nanoparticles are nano-calcium carbonate or nano-silicon dioxide. The mass ratio of the inorganic nanoparticles to the modified polycarboxylic acid is 1:(1-5).

7. The method for preparing paste-like solidified soil according to claim 1, characterized in that: In step S2, the curing agent comprises the following components in parts by weight: 40-60 parts of cement; 20-30 parts of blast furnace slag powder, 10-25 parts of fly ash, and 2-5 parts of calcium carbide slag.

8. The method for preparing paste-like solidified soil according to claim 1, characterized in that: In step S2, the mass ratio of the soil material, the curing agent, water, and the modified polycarboxylic acid is 100:(7.2-12):(35-45):(0.5-1).

9. A paste-like solidified soil, characterized in that: The paste-like solidified soil is prepared by the preparation method described in any one of claims 1-8.

10. An application of paste-like solidified soil, characterized in that: The paste-like solidified soil is used in foundation treatment, and the specific method is as follows: Use a pile driver to drill a pile hole, pour the paste-like solidified soil into the pile driver's storage bin, pump it into the pile hole through a delivery pump, and let it solidify.

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