A high-fluidity, high-strength, shrinkage-resistant fluidized soil and preparation method thereof

Abstract

The invention discloses a high-fluidity, high-strength, shrinkage-resistant fluidized soil and a preparation method thereof, and belongs to the technical field of mud solidification. The high-fluidity, high-strength, shrinkage-resistant fluidized soil of the invention comprises the following raw materials, by mass percentage: 80-95% mud, 5-20% curing agent, and 0.05-0.1% slow-release water replenishing microspheres; the curing agent comprises the following raw materials, by mass percentage: 40-70% mineral powder, 6-15% cement, 3-10% lime, 4-10% fly ash, 4-8% red mud, 5-15% glauber powder, 4-8% calcium chloride, and 0.5-3% expanded microspheres. The high-fluidity, high-strength, shrinkage-resistant fluidized soil of the invention has the advantages of high fluidity, high strength, low shrinkage, etc., overcomes the technical difficulties of large shrinkage of existing fluidized solidified soil, mismatch between fluidity and strength, and can meet the current engineering practical needs of fluidized solidified soil.

Description

Technical Field

[0001] The invention relates to the technical field of mud solidification, in particular to a high-fluidity, high-strength, shrinkage-resistant fluid soil and a preparation method thereof. Background Art

[0002] A large amount of dredged mud will be generated during the dredging of rivers and lakes. In addition, a large amount of high-water content engineering waste mud will also be generated during the construction of shield tunnels, bored piles, underground continuous walls, etc. The water content of dredged mud and engineering waste mud is mostly above 100%, with low strength and difficult to use directly. They are often directly piled or discharged, but such treatment methods will occupy a large amount of land and cause environmental pollution. Therefore, it is urgent to treat this part of high-water content mud. At present, dredged mud and engineering waste mud are mostly reduced by plate and frame filter pressing process, and then landfilled. The plate and frame filter pressing process in this method often requires the addition of some flocculants to the mud, which is not only costly but also requires the removal of water to meet the standards before it can be discharged. In addition, the landfill of the dehydrated mud also requires a large amount of land resources. Therefore, it is necessary to develop new ways to utilize dredged mud and engineering waste mud.

[0003] On the other hand, with the continuous development of urbanization, underground space development has achieved unprecedented development, and the construction of foundations, underground transportation pipelines, underground shopping malls, and underground pipelines has become increasingly widespread. After the construction of underground structures is completed, it is often necessary to backfill the surrounding voids, and the backfill area needs to be rolled multiple times to achieve a certain degree of compaction to prevent the backfill area from settling. However, when facing the backfilling of narrow spaces such as foundation pit fertilizer troughs and underground integrated pipeline corridors, large and medium-sized compaction machinery cannot be used, and only manual compaction can be used for compaction, resulting in insufficient density of backfill soil, and the quality of the project cannot be guaranteed, and even ground subsidence, landslides and other accidents. For this reason, plain concrete or lightweight foam soil is often used for backfilling narrow spaces to ensure the quality of the project. However, both plain concrete and lightweight foam soil have the problem of high prices, and a large amount of cement is required for the preparation of the above two materials, which consumes high energy. In order to solve the above problems, fluidized solidification soil technology came into being. This technology is to add a curing agent to mud with a certain fluidity, stir it evenly and then pour it. It is necessary to ensure that it has high fluidity during pouring and that it can form a certain strength after pouring is completed.

[0004] Dredged mud and engineering waste mud have a high water content and high fluidity, making them ideal materials for preparing fluidized soil. Preparing dredged mud and engineering waste mud into fluidized solidified soil can not only solve the problem of mud landfill occupying a large amount of land, but also replace plain concrete or lightweight foam soil to backfill small spaces, with outstanding environmental and economic benefits. Although dredged mud and engineering waste mud have a high water content and fluidity, the fluidity of fluidized solidified soil is often negatively correlated with strength and volume stability. High water content not only easily leads to segregation, oozing, and compaction of fluidized soil, but also inevitably reduces the strength and volume stability of fluidized soil. Therefore, how to achieve a balance between high fluidity, high strength and high volume stability is a technical problem that needs to be solved in the preparation of fluidized soil. Summary of the invention

[0005] The purpose of the present invention is to provide a high-fluidity, high-strength, shrinkage-resistant fluidized soil and a preparation method thereof to solve the problems existing in the above-mentioned prior art. The fluidized soil of the present invention has the advantages of high fluidity, high strength, low shrinkage, etc., and can overcome the technical difficulties such as large shrinkage of existing fluidized solidified soil and mismatch between fluidity and strength, and can meet the current engineering practical needs of fluidized solidified soil.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a mud curing agent, which includes the following raw materials, by mass percentage: 40-70% of mineral powder, 6-15% of cement, 3-10% of lime, 4-10% of fly ash, 4-8% of red mud, 5-15% of sodium sulfate, 4-8% of calcium chloride and 0.5-3% of expanded microspheres.

[0008] Furthermore, the mineral powder is S95 mineral powder with a specific surface area greater than 600m 2 / kg;

[0009] The cement is P.O42.5 ordinary Portland cement;

[0010] The lime is quicklime with an effective calcium oxide content greater than 75%;

[0011] The fly ash is secondary fly ash;

[0012] The particle size of the red mud is 0.1-0.2 mm, the total content of silicon dioxide and aluminum oxide in the red mud is not less than 50%, and the pH value is ≥12.

[0013] The sodium sulphate is anhydrous sodium sulfate with a purity greater than 99%;

[0014] The calcium chloride is anhydrous calcium chloride with a purity greater than 98%.

[0015] Furthermore, the expanded microspheres include the following raw materials, in percentage by mass: 60-80% montmorillonite, 10-20% cement, 10-15% gypsum, 5-10% magnesium oxide and 3-10% calcium oxide.

[0016] Furthermore, the particle size of the montmorillonite is 0.1 to 1 micron; the cement is P.O42.5 ordinary Portland cement; the gypsum is anhydrous gypsum with a calcium sulfate content greater than 85%; and the magnesium oxide is low-temperature calcined magnesium oxide with an activity index greater than 70%.

[0017] Furthermore, the method for preparing the expanded microspheres comprises the following steps:

[0018] The raw materials are added into a granulator, stirred for 2 to 3 minutes at a stirring rate of 500 to 600 r / min to obtain a mixture with a diameter of 1 to 2 mm; the mixture is loaded into a multifunctional granulating coating machine, and polyvinyl acetate phthalate slurry is sprayed into it to obtain expanded microspheres with a diameter of 2 to 3 mm and the surface of which is coated with polyvinyl acetate phthalate.

[0019] The second technical solution of the present invention: a high-fluidity, high-strength and shrinkage-resistant fluid soil, which comprises the following raw materials, by mass percentage: 80-95% mud, 5-20% of the above-mentioned mud curing agent and 0.05-0.1% slow-release water-replenishing microspheres.

[0020] Furthermore, the mud is bored pile mud with a water content of 100-200% that has not been subjected to filter pressing or flocculation dehydration, and the maximum particle size is not greater than 20 mm.

[0021] Furthermore, the slow-release moisturizing microbeads are highly absorbent resins with a mesh size of 100 to 150.

[0022] Furthermore, the slow-release water-replenishing microbeads are highly absorbent resins with a mesh size of 100 to 150, with a water absorption multiple of ≥100 times for pure water and a water absorption multiple of ≥35 times for a mud solution with a water content of 100%.

[0023] The third technical solution of the present invention is a method for preparing the above-mentioned high-fluidity, high-strength and shrinkage-resistant fluidized soil, comprising the following steps:

[0024] The mud curing agent is added into water to prepare curing agent slurry, and then the curing agent slurry and slow-release water replenishing micro beads are added into the mud and stirred evenly to obtain the high-fluidity, high-strength and shrinkage-resistant fluid soil.

[0025] Furthermore, the mass ratio of the mud curing agent to water is (0.5-1.0):1;

[0026] The stirring speed is 30-60 r / min and the stirring time is 1-2 min.

[0027] Furthermore, the preparation method of the curing agent slurry includes the following steps: mixing the raw materials of the mud curing agent, stirring for 3 to 4 minutes by mechanical stirring, and the stirring rate is 30 to 60 r / min, and then adding water and stirring evenly to obtain the curing agent slurry.

[0028] The fourth technical solution of the present invention: an application of the above-mentioned high-fluidity, high-strength and shrinkage-resistant fluidized soil in ground backfill.

[0029] Basic principles of the present invention:

[0030] (1) The high initial water content of the mud makes the fluidized soil (fluidized solidified soil) have high fluidity. Although the addition of the curing agent slurry will reduce the water content of the fluidized solidified soil to a certain extent, due to the high initial water content of the mud, the fluidized solidified soil still belongs to Bingham fluid after adding the curing agent slurry, and still has high fluidity. In addition, the fly ash particles in the mud curing agent have a good lubricating effect, which to a certain extent improves the phenomenon of reduced fluidity caused by the addition of the curing agent slurry, ensuring the high fluidity of the fluidized solidified soil.

[0031] (2) During the hardening stage of fluidized solidified soil, the alkaline environment provided by cement, lime, and red mud causes the glass in the mineral powder and fly ash to disintegrate, and the network coordination ions Ca in the glass 2+ Mg 2+ Precipitation, precipitation of Ca 2+ Mg 2+ Active SiO in the glass 2 Chemical reactions occur to generate gel products such as CSH gel; at the same time, Ca precipitated in the vitreous 2+ 、Al 3+ And the Ca provided by calcium chloride in the mud solidifier 2+ SO in Yuan Ming powder 4 2- ions form calcium sulfate; as Ca in the pore solution 2 + 、Al 3+ Gradually transformed into ettringite, Ca in the pore solution 2+ 、Al 3+ The concentration gradually decreases, and the Ca in the vitreous 2+ 、Al 3+ is continuously extracted, which makes the CaO and Al contained in the mineral powder and fly ash 2 O 3Dissolution, the vitreous network structure is continuously disintegrated, the activity in the mineral powder and fly ash is gradually stimulated, and a large amount of CSH gel and calcium aluminate are formed. While filling the pores and cementing the soil particles, part of the free water in the fluidized solidified soil is converted into mineral bound water, thereby improving the strength and density of the fluidized solidified soil. The combined use of cement, lime, red mud, and sodium sulfate ensures that the activity of mineral powder and fly ash is effectively stimulated in a weakly alkaline environment to form a cementitious product. In addition, the hydration of cement and lime will also promote the hydration reaction of red mud to form a cementitious substance, which will further fill the internal pores of the fluidized solidified soil and cement the soil particles while consuming free water, thereby improving the strength of the fluidized solidified soil.

[0032] (3) The polyvinyl acetate phthalate on the surface of the expanded microspheres blocks the contact between the montmorillonite in the expanded microspheres and water in the early stage, thus avoiding the problem of reduced fluidity caused by water absorption by the expanded soil. In the hardening stage of the fluidized solidified soil, the polyvinyl acetate phthalate on the surface of the expanded microspheres is gradually dissolved in the pore solution of the fluidized solidified soil, so that the montmorillonite in the expanded microspheres contacts with the water in the pore solution, gradually undergoing physical and chemical reactions. The montmorillonite gradually absorbs water, consumes a large amount of free water in the fluidized soil, and undergoes significant volume expansion, which gradually compacts the soil particles, improves the strength of the fluidized solidified soil, and compensates for the volume shrinkage of the fluidized solidified soil caused by water loss. At the same time, the P.O42.5 ordinary Portland cement, anhydrous gypsum, active magnesium oxide, and calcium oxide in the expanded microspheres react with water to generate CSH gel, calcium aluminate, magnesium hydroxide and other gelling products, which further fill the pores in the montmorillonite and cement the montmorillonite particles, so that the montmorillonite has a stable volume and strength after absorbing water and swelling, ensuring that the montmorillonite in the expanded microspheres still maintains good volume stability under subsequent water loss conditions, achieving the purpose of controlling shrinkage. The slow-release water-replenishing microspheres can continuously replenish free water around the expanded microspheres in the early stage of the expanded microspheres to prevent the expanded microspheres from shrinking in volume due to water loss before the strength is formed.

[0033] The present invention discloses the following technical effects:

[0034] The mud solidifying agent of the invention can improve the fluidity, strength and shrinkage resistance of the mud.

[0035] The present invention can perform fluidized solidification treatment on bored pile mud with high water content without flocculation or plate and frame filter pressing dehydration, and is significantly superior to the currently disclosed fluidized solidified soil materials. Its strength can still reach above 3.0 MPa under high water content conditions. At the same time, the shrinkage strain of the fluidized solidified soil of the present invention can be controlled below 0.74%, and can be as low as about 0.2%, which fundamentally solves the technical problem of poor shrinkage resistance of the fluidized solidified soil, and enables the fluidized solidified soil to achieve balance and unity in terms of high fluidity, high strength and low shrinkage. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0040] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0041] The contents in the specific embodiments of the present invention all refer to mass percentage.

[0042] In a specific embodiment of the present invention, the unconfined compressive strength of the prepared high-flowability, high-strength, shrinkage-resistant flowable soil is tested according to the method specified in JGJ / T 233 "Cement-Soil Mix Design Code".

[0043] In a specific embodiment of the present invention, the fluidity of the prepared high-fluidity, high-strength, shrinkage-resistant fluidized soil is tested according to the test method specified in T / CECS1175-2022 "Technical Standard for Self-compacting Solidified Soil Filling".

[0044] In a specific embodiment of the present invention, the shrinkage strain of the prepared high-flowability, high-strength and shrinkage-resistant flowable soil is tested according to the test method specified in JGJ / T 70-2009 "Standard for Test Methods for Basic Properties of Building Mortar".

[0045] In a first aspect, the present invention provides a mud curing agent, which comprises the following raw materials, measured by mass percentage: 40-70% of mineral powder, 6-15% of cement, 3-10% of lime, 4-10% of fly ash, 4-8% of red mud, 5-15% of sodium sulfate, 4-8% of calcium chloride and 0.5-3% of expanded microspheres.

[0046] The mineral powder used in the curing agent is S95 mineral powder, with a specific surface area of ​​more than 600m 2 / kg; cement is P.O42.5 ordinary Portland cement; lime is quicklime with an effective calcium oxide content greater than 75%; fly ash is secondary fly ash; the particle size of red mud is 0.1-0.2mm, the total content of silicon dioxide and aluminum oxide in the red mud is not less than 50%, and the pH value is ≥12; glauber salt is anhydrous sodium sulfate with a purity greater than 99%; calcium chloride is anhydrous calcium chloride with a purity greater than 98%.

[0047] The expanded microspheres include the following raw materials, by mass percentage: 60-80% montmorillonite, 10-20% cement, 10-15% gypsum, 5-10% magnesium oxide and 3-10% calcium oxide; preferably, the expanded microspheres include the following raw materials, by mass percentage: 60-80% montmorillonite, 10-15% cement, 10-15% gypsum, 5-10% magnesium oxide and 3-10% calcium oxide.

[0048] The particle size of the montmorillonite used in the expanded microspheres is 0.1 to 1 micron; the cement is P.O42.5 ordinary Portland cement; the gypsum is anhydrous gypsum with a calcium sulfate content greater than 85%; and the magnesium oxide is low-temperature calcined magnesium oxide with an activity index greater than 70%.

[0049] The preparation method of expanded microspheres adopted by the present invention comprises the following steps: adding raw materials into a granulator according to mass percentage, stirring for 2-3 minutes at a stirring rate of 500-600 r / min to obtain a mixture with a diameter of 1-2 mm; loading the mixture into a multifunctional granulating coating machine, spraying polyvinyl acetate phthalate slurry into the mixture, and obtaining expanded microspheres with a diameter of 2-3 mm and the surface of which is coated with polyvinyl acetate phthalate.

[0050] The second aspect of the present invention provides a high-fluidity, high-strength and shrinkage-resistant fluid soil, which comprises the following raw materials, by mass percentage: 80-95% mud, 5-20% curing agent and 0.05-0.1% slow-release water-replenishing microspheres.

[0051] The mud is bored pile mud with a water content of 100-200% that has not been filtered or flocculated and dehydrated, and the maximum particle size is not more than 20 mm.

[0052] The slow-release water-replenishing microbeads are highly absorbent resins with a mesh size of 100 to 150. The water absorption multiple of pure water is ≥100 times, and the water absorption multiple of a mud solution with a water content of 100% is ≥35 times.

[0053] The third aspect of the present invention provides a method for preparing the above-mentioned high-fluidity, high-strength and shrinkage-resistant fluidized soil, comprising the following steps:

[0054] (1) Allow the bored pile slurry to settle naturally and remove excess free water from the upper part to control its water content to 100-200%;

[0055] (2) weighing the raw materials of the curing agent according to the mass percentage, stirring for 3 to 4 minutes by mechanical stirring at a stirring rate of 30 to 60 r / min to obtain the curing agent;

[0056] (3) mixing the curing agent and water in a mass ratio of (0.5-1.0):1, stirring evenly, and obtaining a curing agent slurry;

[0057] (4) Add the curing agent slurry and slow-release water replenishing micro beads into the mud and stir mechanically (stirring rate 30-60 r / min, stirring time 1-2 min) to obtain high-flowability, high-strength and shrinkage-resistant fluidized soil.

[0058] The fourth aspect of the present invention provides an application of the above-mentioned high-fluidity, high-strength and shrinkage-resistant fluidized soil in the engineering field of fluidized solidified soil.

[0059] The application method specifically includes: pumping the high-fluidity, high-strength and shrinkage-resistant fluid soil to the backfill construction site or transporting it to the construction site by a tank truck for construction.

[0060] Example 1

[0061] A method for preparing high-fluidity, high-strength and shrinkage-resistant fluid soil:

[0062] (1) A curing agent, comprising the following raw materials in percentage by weight: 60.5% of mineral powder, 12% of cement, 3% of lime, 5% of fly ash, 4% of red mud, 8% of sodium sulfate, 5% of calcium chloride and 2.5% of expanded microspheres.

[0063] Among them, the mineral powder is S95 mineral powder with a specific surface area of ​​650m 2 / kg;

[0064] The cement is P.O42.5 ordinary Portland cement;

[0065] The lime is quicklime with an effective calcium oxide content of 78%;

[0066] The fly ash is secondary fly ash;

[0067] The particle size of red mud is 0.1-0.2 mm, the total content of silicon dioxide and aluminum oxide in red mud is 54.1% (16% silicon dioxide, 38.1% aluminum oxide), and the pH value is 13.5;

[0068] Sodium sulfate is anhydrous sodium sulfate with a purity greater than 99%;

[0069] Calcium chloride is anhydrous calcium chloride with a purity greater than 98%.

[0070] The expanded microspheres are composed of the following raw materials in percentage by mass: 63% of montmorillonite (with a particle size of 0.1 to 1 micron), 15% of cement (P.O42.5 ordinary Portland cement), 11% of anhydrous gypsum (with a calcium sulfate content of 86%), 5% of magnesium oxide (low-temperature calcined magnesium oxide with an activity index of 76.8%) and 6% of calcium oxide.

[0071] The preparation method of expanded microspheres is as follows: adding raw materials into a granulator according to mass percentage, stirring for 3 minutes at a stirring rate of 550r / min to obtain a mixture with a diameter of 1 to 2mm; loading the mixture into a multifunctional granulating coating machine, spraying polyvinyl acetate phthalate slurry, and obtaining expanded microspheres with a diameter of 2 to 3mm and the surface of which is coated with polyvinyl acetate phthalate.

[0072] (2) High-flowability, high-strength and shrinkage-resistant fluid soil, composed of the following raw materials, by mass percentage: 94.95% mud, 5% curing agent and 0.05% slow-release water-replenishing microspheres.

[0073] Among them, the slow-release water-replenishing microbeads are highly absorbent resins with a mesh size of 100 to 150. The water absorption multiple of pure water is 105 times, and the water absorption multiple of a mud solution with a water content of 100% is 38 times.

[0074] (3) Preparation method:

[0075] A. The mud taken from a bored pile construction site in Wuxi City was naturally precipitated and the excess free water on the upper part was removed to control its moisture content at 160% and the maximum particle size was no more than 20mm.

[0076] B. Weigh the raw materials of the curing agent according to the mass percentage, stir them by mechanical stirring for 4 minutes at a stirring rate of 45 r / min to obtain the curing agent.

[0077] C. Mix the curing agent and water in a mass ratio of 1:1, stir evenly, and obtain a curing agent slurry.

[0078] D. Add the curing agent slurry and slow-release water replenishing microbeads into the mud in proportion, and stir mechanically (stirring rate 45r / min, stirring time 1min) to obtain high-fluidity, high-strength and shrinkage-resistant fluid soil.

[0079] Example 2

[0080] The same as Example 1, except that the high-fluidity, high-strength, shrinkage-resistant fluid soil in step (2) is composed of the following raw materials, by mass percentage: 89.93% mud, 10% curing agent and 0.07% slow-release water-replenishing microspheres.

[0081] Example 3

[0082] The same as Example 1, except that the high-fluidity, high-strength and shrinkage-resistant fluid soil in step (2) is composed of the following raw materials by mass percentage: 84.9% mud, 15% curing agent and 0.1% slow-release water-replenishing microspheres.

[0083] The stirring time in step D of step (3) is 90 s.

[0084] Example 4

[0085] The same as Example 1, except that the high-fluidity, high-strength, shrinkage-resistant fluid soil in step (2) is composed of the following raw materials, by mass percentage: 89.93% mud, 10% curing agent and 0.07% slow-release water-replenishing microspheres.

[0086] The water content of the mud in step A of step (3) is controlled at 100%; the stirring time in step D is 120s.

[0087] Example 5

[0088] The same as Example 1, except that the high-fluidity, high-strength and shrinkage-resistant fluid soil in step (2) is composed of the following raw materials by mass percentage: 89.95% mud, 10% curing agent and 0.05% slow-release water-replenishing microspheres.

[0089] The water content of the mud in step A of step (3) is controlled at 200%.

[0090] Example 6

[0091] The same as Example 1, except that the curing agent in step (1) is composed of the following raw materials in percentage by mass: 68% mineral powder, 8% cement, 3% lime, 4% fly ash, 4% red mud, 7% sodium sulfate, 4% calcium chloride and 2% expanded microspheres.

[0092] The expanded microspheres are composed of the following raw materials in percentage by mass: 60% of montmorillonite (with a particle size of 0.1 to 1 micron), 15% of cement (P.O42.5 ordinary Portland cement), 15% of anhydrous gypsum (with a calcium sulfate content of 86%), 5% of magnesium oxide (low-temperature calcined magnesium oxide with an activity index greater than 76.8%) and 5% of calcium oxide.

[0093] The high-fluidity, high-strength, shrinkage-resistant fluid soil in step (2) is composed of the following raw materials, by mass percentage: 89.95% mud, 10% curing agent and 0.05% slow-release water-replenishing microspheres.

[0094] Example 7

[0095] The same as Example 1, except that the curing agent in step (1) is composed of the following raw materials in percentage by mass: 55% mineral powder, 13% cement, 10% lime, 6% fly ash, 5% red mud, 5% sodium sulfate, 4% calcium chloride and 2% expanded microspheres.

[0096] The expanded microspheres are composed of the following raw materials in percentage by mass: 70% of montmorillonite (with a particle size of 0.1 to 1 micron), 12% of cement (P.O42.5 ordinary Portland cement), 10% of anhydrous gypsum (with a calcium sulfate content of 91%), 5% of magnesium oxide (low-temperature calcined magnesium oxide with an activity index greater than 83.1%) and 3% of calcium oxide.

[0097] The high-fluidity, high-strength, shrinkage-resistant fluid soil in step (2) is composed of the following raw materials, by mass percentage: 89.9% mud, 10% curing agent and 0.1% slow-release water-replenishing microspheres.

[0098] Example 8

[0099] The same as Example 1, except that the curing agent in step (1) is composed of the following raw materials in percentage by mass: 48% mineral powder, 14% cement, 10% lime, 10% fly ash, 5% red mud, 6% sodium sulfate, 5% calcium chloride and 2% expanded microspheres.

[0100] The expanded microspheres are composed of the following raw materials in percentage by mass: 68% of montmorillonite (with a particle size of 0.1 to 1 micron), 12% of cement (P.O42.5 ordinary Portland cement), 12% of anhydrous gypsum (with a calcium sulfate content of 91%), 5% of magnesium oxide (low-temperature calcined magnesium oxide with an activity index greater than 83.1%) and 3% of calcium oxide.

[0101] The high-fluidity, high-strength, shrinkage-resistant fluid soil in step (2) is composed of the following raw materials, by mass percentage: 89.9% mud, 10% curing agent and 0.1% slow-release water-replenishing microspheres.

[0102] Comparative Example 1

[0103] Same as Example 2, except that the curing agent is P.O42.5 ordinary Portland cement.

[0104] Comparative Example 2

[0105] The same as Example 2, except that the curing agent in step (1) does not contain expanded microspheres. The curing agent is composed of the following raw materials in percentage by mass: 60.5% of mineral powder, 14.5% of cement, 3% of lime, 5% of fly ash, 4% of red mud, 8% of sodium sulfate and 5% of calcium chloride.

[0106] Comparative Example 3

[0107] The same as Example 2, except that the raw materials of the high-fluidity, high-strength and shrinkage-resistant fluid soil do not contain slow-release water-replenishing microbeads.

[0108] The high-fluidity, high-strength and shrinkage-resistant fluid soil is composed of the following raw materials, measured by mass percentage: 90% mud and 10% curing agent.

[0109] Comparative Example 4

[0110] The same as Example 4, except that the operations of step B and step C in step (3) are not performed, and the raw materials of the curing agent and the slow-release water-replenishing microbeads are directly added to the mud, and stirred at a stirring rate of 45 r / min for 1 min to obtain fluidized solidified soil.

[0111] Comparative Example 5

[0112] The same as Example 5, except that the step of spraying the polyvinyl acetate phthalate slurry is omitted when preparing the expanded microspheres. Specifically, the raw materials are added into a granulator according to the mass percentage, and stirred for 3 minutes at a stirring rate of 550 r / min to obtain expanded microspheres with a diameter of 2 to 3 mm.

[0113] Comparative Example 6

[0114] The same as Example 2, except that the expanded microspheres in step (1) do not contain cement. The expanded microspheres are composed of the following raw materials in percentage by mass: 80% montmorillonite (particle size of 0.1 to 1 micron), 9% anhydrous gypsum (calcium sulfate content of 86%), 5% magnesium oxide (low-temperature calcined magnesium oxide with an activity index greater than 76.8%), and 6% calcium oxide.

[0115] Comparative Example 7

[0116] The same as Example 2, except that the curing agent in step (1) does not contain red mud. The curing agent is composed of the following raw materials in percentage by mass: 64.5% of mineral powder, 12% of cement, 3% of lime, 5% of fly ash, 8% of sodium sulfate, 5% of calcium chloride and 2.5% of expanded microspheres.

[0117] Comparative Example 8

[0118] The same as Example 2, except that the curing agent in step (1) does not contain fly ash. The curing agent is composed of the following raw materials in percentage by mass: 65.5% of mineral powder, 12% of cement, 3% of lime, 4% of red mud, 8% of sodium sulfate, 5% of calcium chloride and 2.5% of expanded microspheres.

[0119] Comparative Example 9

[0120] The same as Example 2, except that the curing agent in step (1) does not contain sodium sulfate. The curing agent is composed of the following raw materials in percentage by mass: 64.5% of mineral powder, 12% of cement, 7% of lime, 5% of fly ash, 4% of red mud, 5% of calcium chloride and 2.5% of expanded microspheres.

[0121] Comparative Example 10

[0122] The same as Example 2, except that the curing agent in step (1) is composed of the following raw materials in percentage by mass: 20% mineral powder, 45% cement, 15% lime, 5% fly ash, 4% red mud, 6% sodium sulfate, 5% calcium chloride and 2.0% expanded microspheres.

[0123] The fluidity, unconfined compressive strength and 7d shrinkage rate of the fluidized soil prepared in the examples and comparative examples were tested. The results are shown in Table 1.

[0124] Table 1 Performance of fluidized soil prepared in Examples and Comparative Examples

[0125]

[0126] As can be seen from Table 1, the fluidized soil prepared by the 8 mix ratios given in Examples 1 to 8 all have high fluidity, high strength, and low shrinkage, and the fluidity is greater than 230 mm, meeting the requirement of T / CECS1175-2022 "Technical Standard for Self-compacting Solidified Soil Filling" that the fluidity of pumped fluidized solidified soil is not less than 160 mm, and the 28d unconfined compressive strength exceeds 0.83 MPa, and the highest can reach 3.15 MPa; the 7d shrinkage rate of the 8 groups of embodiments does not exceed 0.74%, and the lowest can reach 0.18%. Therefore, the fluidized soil prepared by the present invention fully meets the current engineering practical needs of fluidized solidified soil, and at the same time overcomes the technical difficulties of large shrinkage and mismatch between strength and shrinkage of existing fluidized solidified soil, which has important reference significance for promoting the practical engineering application of fluidized solidified soil.

[0127] By comparing Examples 1 to 8 with Comparative Example 1, it is found that when 100% ordinary Portland cement is used instead of the curing agent of the present invention, the 3d unconfined compressive strength is only 0.12MPa, and the 28d unconfined compressive strength is only 0.56MPa. Although the 28d unconfined compressive strength meets the minimum backfill strength requirements for fertilizer troughs, cavities, etc., the 7d drying shrinkage reaches 2.56%, and the anti-shrinkage performance is poor.

[0128] Combining Example 2 with Comparative Example 2 and Comparative Example 3, it can be seen that the expansion microspheres and the slow-release water-replenishing microspheres have little effect on the fluidity of the fluidized solidified soil, but the improvement effect of using the expansion microspheres and the slow-release water-replenishing microspheres at the same time on the shrinkage rate is better than the sum of the improvement effects produced by using the expansion microspheres alone and the slow-release water-replenishing microspheres alone, indicating that there is functional support between the expansion microspheres and the slow-release water-replenishing microspheres used in the present invention. In addition, the combined use of expansion microspheres and slow-release water-replenishing microspheres can also improve the unconfined compressive strength of fluidized soil.

[0129] By comparing Example 4 and Comparative Example 4, it is found that when the curing agent is directly added to the mud (without preparing the curing agent slurry in advance), the fluidity of Comparative Example 4 is significantly lower than that of Example 4 due to the water absorption of each component of the curing agent, and the fluidity of Comparative Example 4 is less than 160 mm, which is difficult to meet the pumping requirements. In addition, the strength of Comparative Example 4 at each age is significantly lower than that of Example 4, and the shrinkage rate is significantly higher than that of Example 4, indicating that the curing agent placement process has a significant impact on the performance of the fluidized soil.

[0130] By comparing Example 5 with Comparative Example 5, it is found that when the step of spraying the polyvinyl acetate phthalate slurry on the surface of the expanded microspheres is omitted, the performance (fluidity, unconfined compressive strength, and shrinkage rate) of the obtained fluidized soil is not as good as that of Example 5. This is mainly because when the expanded microspheres lack the polyvinyl acetate phthalate shell on the surface, the expanded microspheres will absorb water and swell during the preparation of the curing agent slurry and the stirring of the fluidized soil, resulting in reduced fluidity; and when the expanded microspheres lack the protection of the polyvinyl acetate phthalate shell, it is difficult to maintain the integrity of the expanded microspheres and they are easily dispersed in the fluidized soil. When the fluidized soil loses water, the montmorillonite component in the expanded microspheres is difficult to form a stable solidification and shrinks, resulting in poor anti-shrinkage effect.

[0131] By comparing Example 2 and Comparative Example 6, it is found that the cement component in the expanded microspheres plays an important role in the volume stability of the expanded microspheres after absorbing water. When the cement component is missing, the volume stability and strength of the montmorillonite after absorbing water and swelling are poor, and it is difficult to ensure that the montmorillonite in the expanded microspheres maintains volume stability under subsequent water loss conditions.

[0132] By comparing Example 2 with Comparative Example 7, Comparative Example 8 and Comparative Example 9, it is found that the red mud, fly ash and sodium sulfate in the curing agent of the present invention all play an important role, and the lack of any one of them will affect the strength and shrinkage resistance of the fluidized solidified soil.

[0133] By comparing Example 2 and Comparative Example 10, it is found that although the ingredients of the curing agent are the same, the content of each component in the curing agent affects the strength and shrinkage resistance of the fluidized solidified soil. The curing effect of the curing agent of the present invention is significantly better than that of the curing agent with cement and lime as the main ingredients.

[0134] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A high-fluidity, high-strength, shrinkage-resistant fluid soil, characterized in that: In terms of mass percentage, the following raw materials are included: 80-95% of mud, 5-20% of mud curing agent and 0.05-0.1% of slow-release water replenishing micro beads, and the sum of the raw material mass is 100%; The mud curing agent includes the following raw materials in terms of mass percentage: Mineral powder 40-70%, cement 6-15%, lime 3-10%, fly ash 4-10%, red mud 4-8%, sodium sulfate 5-15%, calcium chloride 4-8% and expanded microspheres 0.5-3%, the total mass of the raw materials is 100%; The expanded microspheres include the following raw materials, measured by mass percentage: 60-80% montmorillonite, 10-20% cement, 10-15% gypsum, 5-10% magnesium oxide and 3-10% calcium oxide, the sum of the raw material mass being 100%; The method for preparing the expanded microspheres comprises the following steps: The raw materials are mixed evenly and then granulated to obtain a mixture; polyvinyl acetate phthalate is coated on the surface of the mixture to obtain the expanded microspheres; The slow-release water-replenishing microbeads are highly absorbent resins with a mesh size of 100 to 150; The method for preparing the high-fluidity, high-strength and shrinkage-resistant fluidized soil comprises the following steps: The mud curing agent is added into water to prepare curing agent slurry, and then the curing agent slurry and slow-release water replenishing micro beads are added into the mud and stirred evenly to obtain the high-fluidity, high-strength and shrinkage-resistant fluid soil.

2. The high-fluidity, high-strength, shrinkage-resistant fluidized soil according to claim 1 is characterized in that: The diameter of the mixed material is 1-2 mm; the diameter of the expanded microspheres is 2-3 mm.

3. The high-fluidity, high-strength, shrinkage-resistant fluidized soil according to claim 1 is characterized in that: The water content of the mud is 100-200%, and the maximum particle size is no more than 20 mm.

4. The high-fluidity, high-strength, shrinkage-resistant fluidized soil according to claim 1, characterized in that: The mass ratio of the mud curing agent to water is (0.5-1.0):1; The stirring speed is 30-60 r / min and the stirring time is 1-2 min.

5. Use of the high-fluidity, high-strength, shrinkage-resistant fluidized soil as claimed in any one of claims 1 to 4 in ground backfilling.

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