A construction method to prevent cracking of silt-based fluidized solidified soil

Abstract

This application discloses a construction method for preventing cracking of silt-based fluidized solidified soil. The method involves mixing silt and a modified solidifying agent to prepare silt-based fluidized solidified soil, which, after pouring and solidification, yields crack-free fluidized solidified soil with a permeability coefficient meeting requirements. The modified solidifying agent, based on 150 parts by weight of dry silt, comprises the following components in parts by weight: 30-52 parts granulated blast furnace slag, 22-38 parts fly ash, 12-22 parts gypsum, 4-12 parts alkaline activator, 2-5 parts core-shell structure latex powder, 8-22 parts recycled fine aggregate from construction waste, and 0.2-0.5 parts toughening fiber. The core-shell structure latex powder has a shell layer of vinyl acetate-ethylene copolymer with a Tg not exceeding 0℃ and a core layer of acrylate polymer with a Tg of 20-30℃, ensuring excellent volume stability and crack resistance of the fluidized solidified soil from early to long-term conditions, thus broadening the prospects for large-scale safe application of silt-based fluidized solidified soil.

Description

Technical Field

[0001] This application relates to backfill engineering, and in particular to a construction method for preventing cracking of silt-based fluidized solidified soil. Background Technology

[0002] Large-scale engineering projects in coastal areas, including dredging and waterway improvement, have generated massive amounts of marine silt. This silt is characterized by high water content, high porosity, low strength, and high salinity (in geotechnical engineering and materials, water content is defined as the ratio of water mass to the mass of absolutely dry solid particles in the soil, usually expressed as a percentage). Traditional disposal methods, such as stockpiling or dumping, not only occupy large amounts of land but may also cause environmental pollution. Utilizing this silt as a resource, preparing it into fluidized solidified soil for roadbed backfilling, site leveling, and other projects, is an effective way to achieve "zero-waste cities" and green development.

[0003] However, due to the extremely fine particles and huge specific surface area of ​​silt, the amount of water used must be greatly increased in order to meet the fluidity required for pumping and pouring, resulting in the water content of the solidified soil often being more than twice the liquid limit (the liquid limit is the boundary water content at which soil transitions from a plastic state to a fluid state; the water content here is defined as the ratio of the mass of water to the mass of the solid particles in absolutely dry soil).

[0004] Under high moisture content conditions, as water evaporates during curing, enormous capillary tension is generated within the soil, leading to drastic volume shrinkage and subsequent severe drying shrinkage cracking. This cracking not only compromises the structural integrity and affects its load-bearing capacity but also creates seepage channels, reducing durability. Summary of the Invention

[0005] To broaden the prospects for large-scale safe application of silt-based fluidized solidified soil, a construction method for preventing cracking of silt-based fluidized solidified soil is provided.

[0006] The first inventive objective of this invention is achieved through the following technical solution: A construction method for preventing cracking of silt-based fluidized solidified soil includes the following steps: S1: Mix the silt and modified solidifying agent according to the design formula to make silt-based fluid solidified soil, and pour it into the target area; S2: After the initial setting time of the silt-based fluidized solidified soil, pour non-cracking fluidized solidified soil with a permeability coefficient that meets the requirements onto its surface; The improved curing agent, based on 150 parts by weight of dry sludge, comprises the following components in parts by weight: Granulated blast furnace slag, 30-52 parts. 22-38 parts fly ash 12-22 parts plaster 4-12 parts of alkaline activator 2-5 parts of core-shell structured latex powder 8-22 parts of recycled fine aggregate from construction waste. 0.2-0.5 parts of toughening fiber; The shell polymer of the core-shell structured latex powder is a vinyl acetate-ethylene copolymer, and the core polymer is an acrylate polymer. The glass transition temperature (Tg) of the shell polymer is not higher than 0°C, and the glass transition temperature (Tg) of the core polymer is 20-30°C.

[0007] By adopting the above technical solution, the mixture of the improved curing agent and sludge is combined to form a multi-component synergistic composite system: In the initial stage of stirring and hydration, the alkaline activator rapidly creates an alkaline environment, activating the potential activity of slag and fly ash, and initiating the formation of CSH gel that provides basic strength; gypsum reacts with the active aluminum source in the system to generate needle-like ettringite crystals, and the moderate volume expansion generated in this process effectively offsets the original shrinkage trend caused by the high water content D; the low Tg shell of the core-shell structure latex powder dissolves and is distributed in the pores, which not only improves workability, but also lays the foundation for the later film formation to form a flexible network and improve toughness; As the hardening process progresses from the mid to late stages, free water begins to evaporate, and drying shrinkage stress becomes apparent. At this point, the high Tg core polymer of the latex powder begins to form a film, which intertwines with the three-dimensional physical network formed by the toughening fibers to create a composite structure. This structure can effectively bridge and disperse shrinkage stress, inhibiting the initiation and propagation of microcracks. Meanwhile, the recycled fine aggregate from construction waste acts as a physical skeleton, optimizing the particle size distribution and reducing the overall shrinkage potential. Ultimately, by leveraging the physicochemical properties of each component and combining the core-shell differences of latex powder to form a specific reaction sequence, a multi-layered, synergistic defense system was constructed, encompassing early-stage chemical compensation and mid-stage stress dissipation. This system compensates for shrinkage and enhances toughness, ensuring that the fluidized solidified soil possesses excellent volume stability and crack resistance from the early to the long term, thus broadening the prospects for large-scale safe application of silt-based fluidized solidified soil.

[0008] Preferably, the toughening fiber is a polypropylene fiber, 12-16 mm long and 20-30 μm in diameter.

[0009] By adopting the above technical solution, the type and geometric dimensions of the toughening fiber are specifically defined: polypropylene fiber is selected, which has natural hydrophobicity and excellent chemical corrosion resistance, effectively resisting the erosion of the high-salt environment in marine silt, ensuring the durability of the fiber during long-term use; the fiber length is limited to 12-16mm and the diameter is limited to 20-30μm. This size range has been carefully optimized to give it the best aspect ratio. This length ensures that the fiber is sufficient to effectively cross the initial microcracks and form a reliable physical bridge; this combination of diameter and length ensures that the fiber has sufficient flexibility and tensile cross-section, and makes it easy to disperse in the fluid mixture, avoiding the mutual entanglement and clumping caused by excessively long or thick fibers, or the insufficient bridging effect caused by excessively short or thin fibers. Fibers of this size can be evenly distributed in the matrix to build a uniform three-dimensional network skeleton, laying the physical foundation for the subsequent efficient toughening effect.

[0010] Preferably, the polypropylene fiber has a tensile strength of 480-520 MPa and an elastic modulus of 4-5.2 GPa.

[0011] By adopting the above technical solution, the core mechanical performance indicators of polypropylene fibers are precisely defined: a tensile strength of 480-520 MPa ensures that a single fiber has sufficiently high load-bearing capacity. When microcracks propagate and stress is transferred to the fiber, the fiber can provide strong tensile resistance and is not easily broken. The elastic modulus range of 4-5.2 GPa makes it well matched with the mechanical properties of silt-based fluidized solidified soil matrix. Compared with rigid fibers (such as steel fibers), this fiber with a medium elastic modulus will not generate excessive rigid constraints when the matrix shrinks, thus avoiding damage to the matrix with low early strength. When subjected to shrinkage stress in the middle and late stages of matrix hardening, the fiber with this modulus can coordinate the deformation of the matrix through appropriate deformation, efficiently absorb and dissipate energy, and disperse the concentrated shrinkage stress to a wider area, thereby significantly inhibiting the initiation and propagation of cracks. This "combination of rigidity and flexibility" characteristic maximizes the fiber reinforcement effect and significantly improves the toughness and crack resistance of the material.

[0012] Preferably, the surface of the toughened fiber is functionalized with γ-glycidoxypropyltrimethoxysilane.

[0013] By employing the above technical solution, the surface of the toughening fiber is functionalized using γ-glycidoxypropyltrimethoxysilane. One end of the γ-glycidoxypropyltrimethoxysilane is firmly connected to the fiber surface through chemical bonds, while the other end reacts chemically with the inorganic cementitious phase (mainly CSH gel), thereby establishing a strong chemical bridge between the fiber and the inorganic hydration products. This enhances the mechanical interlocking between the toughening fiber and the "composite formed by the hydration products of inorganic cementitious materials and sludge particles" to a strong chemical bond. When the material is under stress and microcracks propagate to the fiber interface, it can ensure that the stress is effectively transferred from the matrix to the fiber, forcing the fiber to fully utilize its high tensile strength to resist damage, thereby absorbing a large amount of energy and significantly improving toughness.

[0014] Preferably, the polypropylene fibers and recycled fine aggregates from construction waste are premixed before mixing, so that the fibers partially wrap around or adhere to the surface of the recycled fine aggregates from construction waste.

[0015] By adopting the above technical solution, in the premixing step before mixing, dry polypropylene fibers with large surface area and easy static electricity are dry mixed with coarse-particle recycled construction waste aggregate under mechanical force. Under the collision, friction and shearing action of aggregate particles, toughening fibers are physically wrapped or attached to the surface of aggregate to form individual "fiber-aggregate" composite units. Subsequently, when the composite unit is added and mixed with silt, water, and other modified solidifying agent components, the aggregate particles act as the carrier and dispersion medium for the fibers. Since the aggregate itself is easy to distribute evenly in the fluid mixture, the fibers carried by it are also uniformly dispersed in three-dimensional space, avoiding the phenomenon of fibers clumping due to mutual entanglement. This solves the problem of the difficulty in uniformly dispersing fiber-reinforced materials in fluid mixtures. It achieves uniform fiber distribution, ensuring that each fiber can independently and effectively play its bridging and toughening role, thereby maximizing the crack resistance of the material with extremely low dosage and improving the quality homogeneity and reliability of the final silt-based fluidized solidified soil.

[0016] Preferably, the improved curing agent further comprises 0.5-2 parts of banyan aerial root fiber, wherein the banyan aerial root fiber is a porous hollow fiber that has been crushed.

[0017] By adopting the above technical solution, the porous wall and hollow cavity of the banyan aerial root fiber can quickly absorb and store a portion of the mixing water during the stirring process. When the silt-based fluidized solidified soil enters the hardening stage after pouring, the internal humidity decreases due to hydration reaction and surface evaporation. The water stored inside the fibers is slowly released into the surrounding matrix. This internal-to-external water supply provides a stable water source for the continuous hydration of cementitious materials (especially post-active materials such as fly ash), effectively reducing self-shrinkage and drying shrinkage caused by uneven or missing moisture. At the same time, the fibers themselves are randomly distributed in the matrix, and their fiber morphology can bridge microcracks, playing a slight reinforcing role and further enhancing toughness. Therefore, a common and underutilized local natural waste is transformed into an engineering material with active intelligent response function. By combining local resources to treat waste with waste, the synergy of internal curing and micro-reinforcement is achieved, which improves the stability of the internal microenvironment of silt-based fluidized solidified soil, inhibits the generation of shrinkage cracks, and further reduces the possibility of cracking of silt-based fluidized solidified soil.

[0018] Preferably, the modified curing agent also contains 0.8-2.2 parts of sodium polyacrylate.

[0019] By adopting the above technical solution, the three-dimensional network structure of sodium polyacrylate rapidly absorbs a large amount of free water in the initial stage of stirring, and the volume expands. This process directly reduces the effective free water content used to form fluidity, which is equivalent to reducing the final total amount of evaporable water and water-gel ratio of the system while ensuring workability, thereby reducing the potential energy of drying shrinkage from the source. During the hardening period after pouring, as cement, slag and other cementitious materials continue to hydrate and consume water, the internal humidity of the system begins to decrease. At this time, under the action of capillary tension difference, sodium polyacrylate slowly and continuously releases the stored water into the surrounding cementitious material matrix, forming an "internal curing" effect. This ensures that the deep cementitious materials (especially the later active components such as fly ash) can be fully hydrated, generating more hydration products to fill the capillary pores, making the microstructure more compact, and significantly reducing the self-shrinkage and drying shrinkage stress caused by uneven internal humidity gradient. It enables proactive intervention and optimization of the hydration reaction process, achieving precise moisture control throughout the entire cycle from stirring to long-term hardening, ensuring fluidity while maximizing volume stability and crack resistance.

[0020] Preferably, the specific steps of mixing to prepare fluidized solidified soil in step S1 include: The recycled fine aggregate from construction waste is premixed with toughening fibers to form the first premixed composite material; Granulated blast furnace slag, fly ash, gypsum, and alkaline activator are premixed to prepare a second premixed composite. The second premixed complex is first added to the sludge base material and stirred evenly to form a slurry; Then, the first premixed composite, core-shell structured latex powder, and other remaining modified curing agent components are added to the slurry in sequence and stirred until uniform to form a fluidized solidified soil.

[0021] By adopting the above technical solution, two premixing processes are performed before mixing: the first premixing physically entangles or adheres the toughening fibers and recycled fine aggregates from construction waste in a dry-mixing state, forming a "fiber-aggregate" composite unit, effectively preventing the fibers from clumping during subsequent wet mixing; the second premixing ensures that all powdered cementitious materials (such as slag, fly ash, etc.) and activators are evenly distributed, providing a synergistic basis for the hydration reaction. During formal mixing, the second premixed composite is first added and mixed with the sludge base material, allowing the cementitious materials to preferentially hydrate and form a rigid skeleton; then the first premixed composite and other polymeric components (such as core-shell latex powder) are added, using the already formed slurry substrate as a carrier to ensure that the fibers and polymeric materials are evenly dispersed without being damaged. This step-by-step feeding sequence optimizes the release and synergistic effect of each functional component: the cementitious materials build a strong skeleton in advance, while the fibers and polymers are embedded in the later stage to form a flexible network, thus achieving a "rigid and flexible" microstructure. This method systematically solves the problems of fiber dispersion, polymer functional failure, and asynchronous gelation and hydration in fluidized solidified soil, significantly improving the uniformity, workability, and crack resistance of the material, ultimately enabling fluidized solidified soil to maintain low shrinkage and high durability under high fluidity.

[0022] In summary, this application has at least the following beneficial effects: 1. A full-cycle, multi-level crack-resistant defense system was constructed. Through the synergistic effect of core-shell structure latex powder, toughening fiber three-dimensional network, gypsum expansion compensation and internal curing materials, a full-process, multi-mechanism crack-resistant protection was achieved from chemical compensation shrinkage in the early hydration stage to stress dissipation in the middle of hardening, and finally to long-term volume stability. This effectively inhibited the initiation and propagation of microcracks and significantly improved the volume stability and crack resistance of the material. 2. The improved curing agent makes extensive use of industrial solid wastes such as granulated blast furnace slag, fly ash, and recycled fine aggregates from construction waste, combined with natural wastes such as banyan tree aerial root fibers. This not only reduces material costs but also achieves the goal of treating waste with waste and being green and environmentally friendly, thus broadening the prospects for large-scale safe application of silt-based fluidized solidified soil. 3. The construction process and material performance reliability have been optimized. By using a step-by-step premixing and specific feeding sequence construction method, the reinforcement failure caused by uneven fiber dispersion and polymer functional failure is effectively reduced, ensuring the uniformity of material composition and the reliability of performance, thus providing a guarantee for the quality of engineering applications. Detailed Implementation

[0023] Definition of specific parameters Moisture content (silt, soil, rock and soil) / Moisture content D: In geotechnical engineering and materials science, moisture content is defined as the ratio of the mass of water to the mass of solid particles in an absolutely dry soil mass, usually expressed as a percentage. For ease of identification and distinction, this application will refer to the moisture content of silt, soil, rock and soil as moisture content D.

[0024] Plastic limit: The water content at which soil transitions from a semi-solid state to a plastic state, defined here as the water content D mentioned above.

[0025] Liquid limit: is the water content at which soil transitions from a plastic state to a fluid state. Here, the water content is defined as the water content D mentioned above.

[0026] raw material Methyl methacrylate, a commercially available product from Mitsubishi Chemical, polymer grade, purity 99.8 wt%, moisture content ≤0.05 wt%.

[0027] Butyl acrylate, a commercially available product from BASF, polymer grade, purity 99.8 wt%, moisture content ≤0.05 wt%.

[0028] Ethylene glycol dimethacrylate, a commercially available product of Sasol, with a functionality of 2 and a purity of 98.5 wt%.

[0029] Sodium dodecyl sulfate, a commercially available product from Sinopharm Reagent, with a purity of 98.5 wt%.

[0030] Vinyl acetate, a commercially available product from Sinopharm Reagent, with a purity of 99.8 wt%, moisture content ≤0.05 wt%, and aldehyde content ≤0.01 wt%.

[0031] 2-Ethylhexyl acrylate, a commercially available product from BASF, with a purity of 99.5 wt% and a moisture content of ≤0.05 wt%.

[0032] Alkylphenol polyoxyethylene ether (OP-10), a commercially available product from BASF, with an HLB value of 13.5 and a pH of 6.5 (1 wt% aqueous solution).

[0033] Polyvinyl alcohol, a commercially available product from Japanese synthetic chemical company, has a degree of alcoholysis of 88 mol% and a degree of polymerization of 1700 ± 50.

[0034] Ammonium persulfate, a commercially available product from Sinopharm Reagent, with a purity of 98.5 wt% and an active oxygen content of 7.5 wt%.

[0035] Ethylene, Zhenhai Refining & Chemical, purity 99.5 wt%.

[0036] Fumed silica, a commercially available product from Evonik, with a particle size of 10 nm and a specific surface area of ​​200±25 m² / g.

[0037] Raw polypropylene fiber, a product sold in Jiangsu Bote City, available in multiple specifications. See below for specific usage specifications.

[0038] γ-glycidyl etheroxypropyltrimethoxysilane, a commercially available product from Momentive, with a purity of 99.5 wt% and an epoxy value of 0.46 mol / 100g.

[0039] Anhydrous ethanol and acetic acid, commercially available analytical instruments.

[0040] Granulated blast furnace slag, commercially available product, with a specific surface area of ​​420 m² / kg and an activity index (7d) of 78%.

[0041] Fly ash, commercially available Grade II fly ash, fineness (45μm square hole sieve residue): ≤12%, loss on ignition 2.5wt%, SO3 content: 2.2wt%, free calcium oxide content: 0.32wt%.

[0042] Gypsum, a commercially available product, contains 87.5% calcium sulfate dihydrate and 3% water.

[0043] Quicklime, a commercially available product, has an effective calcium oxide content of 88% and an MgO content of ≤5%.

[0044] Solid water glass powder, commercially available product, modulus 2.3, soluble solids content 98.2 wt%.

[0045] Recycled fine aggregate from construction waste; resource-based reuse of construction waste; particle size distribution 2-5mm, D50=4mm, water absorption rate 4.5%, mud content ≤0.5wt%. The aerial root fibers of banyan trees are 10 mm long and have a fiber diameter (main trunk) of 0.8 ± 0.2 mm. After mechanical crushing, they retain a distinct hollow tubular structure with a rough surface and natural pores.

[0046] The silt was taken from the Oujiang Estuary in Wenzhou. The initial moisture content D was measured to be 65%, the liquid limit was 48% and the plastic limit was 25%. The chloride ion content was 0.3 wt% of the dry soil mass.

[0047] Preparation Example 1 A core-shell structured latex powder, wherein the shell polymer is a vinyl acetate-ethylene copolymer and the core polymer is an acrylate polymer, and its preparation process is as follows.

[0048] Preparation of core layer monomer preemulsion: Weigh 70 kg of methyl methacrylate and 30 kg of butyl acrylate and place them in a premixing tank. Add 0.5 kg of crosslinking agent ethylene glycol dimethacrylate and stir at 250 rpm for 20 min to obtain a core-layer mixed monomer. Inject the core-layer mixed monomer into 150 kg of 1 wt% sodium dodecyl sulfate aqueous solution and emulsify at 3500 rpm for 40 min to obtain a uniform milky white core-layer monomer preemulsion. 2. Preparation of shell monomer emulsion: 80 kg of vinyl acetate, 20 kg of 2-ethylhexyl acrylate and 1.0 kg of emulsifier alkylphenol polyoxyethylene ether (OP-10) were mixed and dispersed by stirring at 400 rpm for 40 min to obtain a shell monomer emulsion. 3. Core-shell polymerization: Add 15% of the total mass of core layer monomer preemulsion to the high-pressure reactor, and add 45 kg of 10 wt% polyvinyl alcohol aqueous solution. After heating to 78°C, add 4 kg of 5 wt% ammonium persulfate aqueous solution and keep the reaction at this temperature for 20 min until the solution turns milky white with a blue light. The remaining core layer monomer preemulsion was added dropwise at a rate of 1.2 kg / min, while 16 kg of 5 wt% ammonium persulfate aqueous solution was added dropwise at the same rate of 1.2 kg / min. During the dropwise addition process, the reactor temperature was maintained at 78℃ and the stirring rate was controlled at 200 rpm. After the dropwise addition was completed, the reactor was kept at 78℃ for 90 min to mature. 4. Shell polymerization reaction: Keep the reaction system at 78°C, continuously introduce ethylene gas into the reactor until the pressure stabilizes at 1.6 MPa, add shell monomer emulsion dropwise at a rate of 0.9 kg / min, and simultaneously add 200 kg of 0.5 wt% ammonium persulfate aqueous solution dropwise at a rate of 1.1 kg / min, while maintaining the stirring speed at 200 rpm. After the addition was complete, the temperature was raised to 85°C and kept warm for 120 minutes. Then the temperature was lowered to 36°C, and the pH of the system was adjusted to 7.5 with ammonia. The product was then discharged to obtain a core-shell structured polymer emulsion.

[0049] 5. Spray drying: The obtained emulsion was fed into a centrifugal spray drying tower for drying. The inlet air temperature was controlled at 160℃ and the outlet temperature at 65℃. The speed of the centrifugal atomizer was adjusted to control the D50 particle size of the finished powder at 45μm. At the outlet of the drying tower, 1.5% of fumed silica by mass of the powder was uniformly added to the powder as an anti-caking agent, and finally a white core-shell structure latex powder was obtained.

[0050] The sampling and testing results are as follows: Particle size distribution: 40-50 μm, D50 = 45 μm; Glass transition temperature (DSC): core Tg = 25℃, shell Tg = -2℃.

[0051] Preparation Example 2 A single-layer latex powder has the same polymer composition as the core polymer in Preparation Example 1, which is an acrylate polymer. It does not have a core-shell structure and has a particle size D50 = 45 μm. Its preparation process is as follows.

[0052] 1. Preparation of monomer preemulsion: Accurately weigh 70 kg of methyl methacrylate and 30 kg of butyl acrylate and place them in a premixing tank. Add 0.5 kg of crosslinking agent ethylene glycol dimethacrylate and stir at 250 rpm for 20 min to obtain a mixed monomer. Inject the mixed monomer into 150 kg of 1 wt% sodium dodecyl sulfate aqueous solution and emulsify at 3500 rpm for 40 min to obtain a uniform milky white monomer preemulsion. 2. Polymerization reaction: Add 15% of the total mass of monomer pre-emulsion to the high-pressure reactor, and add 45 kg of 10 wt% polyvinyl alcohol aqueous solution. After heating to 78°C, add 4 kg of 5 wt% ammonium persulfate aqueous solution and keep the reaction at this temperature for 20 min until the solution turns milky white with a blue tint. The remaining monomer preemulsion was added dropwise at a rate of 1.2 kg / min, while simultaneously adding 16 kg of 5 wt% ammonium persulfate aqueous solution. The reactor temperature was maintained at 78°C and the stirring rate at 200 rpm throughout the entire addition process. After the addition was complete, the reactor was kept at 78°C for 90 min to mature. After the heat preservation and curing are completed, the reaction system is heated to 85°C and cured for another 60 minutes to ensure complete reaction. Then the temperature is lowered to 36°C, the pH of the system is adjusted to 7.5 with ammonia, and the material is discharged to obtain a single-layer polymer emulsion. The obtained emulsion was fed into a centrifugal spray drying tower for drying. The inlet air temperature was controlled at 160℃ and the outlet temperature at 65℃. The speed of the centrifugal atomizer was adjusted to control the D50 particle size of the finished powder at 45μm. At the outlet of the drying tower, 1.5% of fumed silica by mass of the powder was uniformly added to the powder as an anti-caking agent, and finally a white, single-layer latex powder was obtained.

[0053] Preparation Example 3 A single-layer latex powder has the same polymer composition as the shell polymer in Preparation Example 1, which is a vinyl acetate-ethylene copolymer. It does not have a core-shell structure and has a particle size D50 = 45 μm. The preparation process is as follows.

[0054] 1. Monomer emulsion preparation: Mix 80 kg of vinyl acetate, 20 kg of 2-ethylhexyl acrylate and 1.0 kg of emulsifier alkylphenol polyoxyethylene ether (OP-10), and stir and disperse at 400 rpm for 40 min to obtain a monomer emulsion.

[0055] 2. Polymerization reaction: Add 45 kg of 10 wt% polyvinyl alcohol aqueous solution and 50 kg of deionized water to the high-pressure reactor. After heating to 78°C, add 4 kg of 5 wt% ammonium persulfate aqueous solution.

[0056] Ethylene gas was continuously introduced into the reactor until the pressure stabilized at 1.6 MPa. The monomer emulsion was added dropwise at a rate of 0.9 kg / min, while 16 kg of 5 wt% ammonium persulfate aqueous solution was added dropwise simultaneously. The stirring rate was maintained at 200 rpm. 3. Post-treatment and spray drying: After the addition was complete, the temperature was raised to 85℃ and kept warm for 120 minutes. Then the temperature was lowered to 36℃, and the pH of the system was adjusted to 7.5 with ammonia. The product was then discharged to obtain a single-layer vinyl acetate-ethylene copolymer emulsion. The obtained emulsion was fed into a centrifugal spray drying tower for drying. The inlet air temperature was controlled at 160℃ and the outlet temperature at 65℃. The speed of the centrifugal atomizer was adjusted to control the D50 particle size of the finished powder at 45μm. At the outlet of the drying tower, 1.5% of fumed silica by mass of the powder was uniformly added to the powder as an anti-caking agent, and finally a white, single-layer structure emulsion powder was obtained.

[0057] Preparation Example 4 A core-shell structured latex powder, wherein the shell polymer is a vinyl acetate-ethylene copolymer and the core polymer is an acrylate polymer, differing from preparation example 1 in that the glass transition temperature of the core polymer is 45°C.

[0058] The difference between this preparation process and that of Preparation Example 1 lies in the preparation of the core layer monomer pre-emulsion, as detailed below: Accurately weigh 90 kg of methyl methacrylate and 10 kg of butyl acrylate and place them in a premixing tank. Add 0.6 kg of crosslinking agent ethylene glycol dimethacrylate and stir at 250 rpm for 20 min to obtain a core-layer mixed monomer. Inject the core-layer mixed monomer into 150 kg of 1 wt% sodium dodecyl sulfate aqueous solution and emulsify at 3500 rpm for 40 min to obtain a uniform milky white core-layer monomer preemulsion.

[0059] Preparation Example 5 A core-shell structured latex powder, wherein the shell polymer is a vinyl acetate-ethylene copolymer and the core polymer is an acrylate polymer, differing from Preparation Example 1 in that the glass transition temperature of the core polymer is 10°C.

[0060] The difference between this preparation process and that of Preparation Example 1 lies in the preparation of the core layer monomer pre-emulsion, as detailed below: Accurately weigh 50 kg of methyl methacrylate and 50 kg of butyl acrylate and place them in a premixing tank. Add 0.4 kg of crosslinking agent ethylene glycol dimethacrylate and stir at 250 rpm for 20 min to obtain a core-layer mixed monomer. Inject the mixed monomer into 150 kg of 1 wt% sodium dodecyl sulfate aqueous solution and emulsify at 3500 rpm for 40 min to obtain a uniform milky white core-layer monomer preemulsion.

[0061] Preparation Example 6 Polypropylene fibers with surface functionalization by γ-glycidoxypropyltrimethoxysilane were obtained by modifying original polypropylene fibers. The original polypropylene fibers had a length of 15 mm, a diameter of 25 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa.

[0062] The preparation process is as follows: 1. Fiber pretreatment 10 kg of raw polypropylene fiber was evenly spread on a corrosion-resistant screen. Under 50 Pa air pressure and 45 oxygen partial pressure, the radio frequency power supply was turned on and the power was set to 300 W to perform low-temperature oxygen plasma treatment on the polypropylene fiber for 5 minutes to obtain the treated polypropylene fiber. 2. Preparation of silane hydrolysate 150g of γ-glycidyl oxypropyltrimethoxysilane and 3kg of anhydrous ethanol were mixed by stirring at 300rpm. While stirring, a mixed solution of 7.5kg of deionized water and 7.5kg of anhydrous ethanol was added dropwise over a period of 10min. After the addition is complete, adjust the pH to 4.5 with a 10wt% acetic acid aqueous solution, and continue stirring for 60 min to allow the Γ-glycidoxypropyltrimethoxysilane to be fully hydrolyzed, resulting in a clear and transparent silane hydrolysate. 3. Surface functionalization modification reaction Mix the silane hydrolysate with 20 kg of ethanol, then completely immerse the treated polypropylene fiber in the mixture to ensure that the fiber is fully wetted. Place the mixture in a constant temperature water bath shaker and react for 120 min at a temperature of 60 ± 2 °C and an oscillation frequency of 60 times / min. 4. Post-treatment and drying After the reaction was completed, the fiber was taken out and rinsed repeatedly with a large amount of deionized water until the filtrate was neutral to remove the physically adsorbed silane. The washed fiber was placed in a forced-air drying oven and vacuum dried at 60°C for 120 min to obtain functionalized modified polypropylene fiber.

[0063] Preparation Example 7 Polypropylene fibers with surface functionalization by γ-glycidyl oxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 25 μm, a tensile strength of 400 MPa, and an elastic modulus of 3.3 GPa.

[0064] Preparation Example 8 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 25 μm, a tensile strength of 480 MPa, and an elastic modulus of 4 GPa.

[0065] Preparation Example 9 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 25 μm, a tensile strength of 520 MPa, and an elastic modulus of 5.2 GPa.

[0066] Preparation Example 10 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 25 μm, a tensile strength of 580 MPa, and an elastic modulus of 6 GPa.

[0067] Preparation Example 11 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 10 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa.

[0068] Preparation Example 12 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 20 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa.

[0069] Preparation Example 13 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 30 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa.

[0070] Preparation Example 14 Polypropylene fibers with surface functionalization by γ-glycidyl etheroxypropyltrimethoxysilane were obtained by modifying the original polypropylene fibers. The difference between the original polypropylene fibers and those in Preparation Example 6 is that the original polypropylene fibers have a length of 15 mm, a diameter of 45 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa.

[0071] Example 1 A construction method for preventing cracking of silt-based fluidized solidified soil involves mixing a modified curing agent with silt to prepare silt-based fluidized solidified soil and then pouring and solidifying it.

[0072] The improved curing agents include granulated blast furnace slag, fly ash, gypsum, alkaline activators, core-shell structured latex powder, recycled fine aggregate from construction waste, toughening fibers, and banyan tree aerial root fibers.

[0073] The alkaline activator is a mixture of quicklime and solid water glass powder in a mass ratio of 5:3.

[0074] The core-shell structured latex powder was prepared in Preparation Example 1.

[0075] The toughening fiber is the functionalized modified polypropylene fiber prepared in Example 6.

[0076] Taking 1500kg of dry sludge as an example, the specific steps are as follows: S1 silt moisture content adjustment The current moisture content of the silt was tested, and silt was weighed at a dry basis of 1500 kg. Water was added and stirred to adjust the moisture content to D=100% to obtain silt base material. S2 fluidized solidified soil mixing 100 kg of recycled fine aggregate from construction waste and 3 kg of toughening fiber were put into a mixer and dry-mixed for 3 minutes to make the first premixed composite. Add 400 kg of slag, 250 kg of fly ash, 150 kg of gypsum, and 80 kg of alkaline activator to a mixer and dry mix for 5 minutes until uniform to obtain the second premixed composite. Add the second premixed compound to the sludge base material and stir evenly to obtain a slurry; The first premixed compound, 15 kg of banyan aerial root fiber, and 40 kg of core-shell structure latex powder were added to the slurry in sequence, and the mixture was stirred evenly to obtain fluidized solidified soil. The fluidity of the sample was measured to be 208 mm, which is in line with 200 ± 10 mm. S3 Pouring and Sealing Curing The fluidized solidified soil is poured into the target area and naturally leveled by its own fluidity. After the surface has initially set, it is covered with a plastic film and sealed for curing for 14 days. The film is then removed and curing continues for 28 days or longer as required by the construction schedule.

[0077] In this embodiment, 1500 kg of dry sludge was used for construction, and the moisture content of the sludge was adjusted to D=100%. The dosage of the modified curing agent is as follows: Granulated blast furnace slag 400kg, fly ash 250kg, gypsum 150kg, alkaline activator 80kg, core-shell structure latex powder 40kg, recycled fine aggregate from construction waste 100kg, toughening fiber 3kg, banyan tree aerial root fiber 15kg.

[0078] Comparative Example 1 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the modified solidifying agent does not contain core-shell structure latex powder, that is, the amount of core-shell structure latex powder added is 0 kg, while the rest are the same.

[0079] Comparative Example 2 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the core-shell structure latex powder is the latex powder prepared in Example 2.

[0080] Comparative Example 3 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the core-shell structure latex powder is the latex powder prepared in Example 3.

[0081] Comparative Example 4 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the core-shell structure latex powder is the latex powder prepared in Example 4.

[0082] Comparative Example 5 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the core-shell structure latex powder is the latex powder prepared in Example 5.

[0083] Comparative Example 6 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the modified solidifying agent does not contain an alkaline activator, i.e., the amount of alkaline activator added is 0 kg, while the rest are the same.

[0084] Comparative Example 7 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the modified solidifying agent does not contain toughening fibers, i.e., the amount of toughening fibers added is 0 kg, while the rest are the same.

[0085] Example 2 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Example 7, while the rest are the same.

[0086] Example 3 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Example 8, while the rest are the same.

[0087] Example 4 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Example 9, while the rest are the same.

[0088] Example 5 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Preparation Example 10, but the rest are the same.

[0089] Example 6 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Example 11, while the rest are the same.

[0090] Example 7 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Example 12, while the rest are the same.

[0091] Example 8 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Preparation Example 13, while the rest are the same.

[0092] Example 9 A construction method for preventing cracking of silt-based fluidized solidified soil is different from Example 1 in that the toughening fiber is prepared in Preparation Example 14, while the rest are the same.

[0093] Example 10 A construction method for preventing cracking of silt-based fluidized solidified soil differs from Example 1 in that the toughening fiber is virgin polypropylene fiber with a length of 15 mm, a diameter of 25 μm, a tensile strength of 500 MPa, and an elastic modulus of 4.8 GPa; all other aspects are the same.

[0094] Example 11 A construction method for preventing cracking of silt-based fluidized solidified soil differs from Example 1 in step S2, as follows: S2 fluidized solidified soil mixing Add 400 kg of slag, 250 kg of fly ash, 150 kg of gypsum, and 80 kg of alkaline activator to a mixer and dry mix for 5 minutes until uniform to obtain the second premixed composite. Add the second premixed compound to the sludge base material and stir evenly to obtain a slurry; Add 100kg of recycled fine aggregate from construction waste, 3kg of toughening fiber, 15kg of banyan tree aerial root fiber, and 40kg of core-shell structure latex powder to the slurry in sequence, and continue to stir evenly to obtain fluidized solidified soil.

[0095] Example 12 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that the modified solidifying agent does not contain banyan aerial root fiber, that is, the amount of banyan aerial root fiber added is 0 kg, while the rest are the same.

[0096] Example 13 A construction method for silt-based fluidized solidified soil, which differs from Example 1 in that it uses an equal mass of water-absorbing resin instead of banyan tree aerial root fibers, while the rest is the same.

[0097] Example 14 A construction method for preventing cracking of silt-based fluidized solidified soil, differing in the dosage of different components of the amendment, is as follows: Construction was carried out using 1500 kg of dry sludge with an adjusted moisture content of D=100%, along with 300 kg of granulated blast furnace slag, 220 kg of fly ash, 120 kg of gypsum, 120 kg of alkaline activator, 50 kg of core-shell structure latex powder, 80 kg of recycled fine aggregate from construction waste, 5 kg of toughening fiber, and 20 kg of banyan tree aerial root fiber.

[0098] Example 15 A construction method for preventing cracking of silt-based fluidized solidified soil, differing in the dosage of different components of the amendment, is as follows: Construction was carried out using 1500 kg of dry sludge with an adjusted moisture content of D=100%, along with 520 kg of granulated blast furnace slag, 380 kg of fly ash, 220 kg of gypsum, 40 kg of alkaline activator, 20 kg of core-shell structure latex powder, 220 kg of recycled fine aggregate from construction waste, 2 kg of toughening fiber, and 15 kg of banyan tree aerial root fiber.

[0099] The following tests were performed on the solidified soils obtained in Examples 1-15 and Comparative Examples 1-7.

[0100] 1. Flowability Refer to GB / T 2419, "Method for Determination of Flowability of Cement Mortar". Place the truncated cone mold in the center of the table, and pour the prepared fluidized solidified soil mixture into the mold in two layers, tamping each layer 20 times with a tamping rod. Scrape off the excess slurry, lift the round mold vertically upwards, start the jumping table, and complete 25 jumps within 25 seconds at a frequency of once per second; The results are expressed as the average value of the fluidity—the diffusion diameter at the bottom of the mixture (unit: mm).

[0101] 2. Unconfined compressive strength The tests were conducted in accordance with the "Standard for Geotechnical Testing Methods" GB / T 50123.

[0102] The mixed fluidized solidified soil was poured into a standard test mold (a cylinder with a diameter of 100 mm and a height of 100 mm) and sealed and cured for 28 days under standard curing conditions (temperature 20±2°C, humidity ≥95%). Remove the specimen and place it in the center of the pressure plate of the compression testing machine. Apply axial pressure to the specimen at a constant loading rate (1 mm / min) until the specimen fails. Record the maximum pressure value P when the specimen fails, take the average value of a group of multiple specimens, and calculate the unconfined compressive strength qu (MPa), qu=P / A, where A is the initial cross-sectional area of ​​the specimen.

[0103] 3. Drying shrinkage rate The test method for drying shrinkage (drying shrinkage) is based on the "Standard for Test Methods of Basic Performance of Building Mortar" JGJ / T 70.

[0104] Prismatic specimens (40mm×40mm×160mm) were used. After curing the specimens under standard curing conditions for 7 days, they were removed and their initial length L0 was measured. The specimen was moved into a constant temperature and humidity drying room (temperature 20±2°C, relative humidity 60±5%). After 28 days (including 7 days of curing), the specimen was taken out and brought to the same temperature as the measurement environment. The length Lt of the specimen was then measured. Calculate the drying shrinkage rate εt, εt=(L0-Lt) / L×100%, where L is the reference length of the specimen, 160mm.

[0105] 4. Permeability coefficient Referring to the standard GB / T 50123 "Geotechnical Testing Methods", the test results for the variable head permeability test are expressed as permeability coefficient (cm / s).

[0106] The test results are shown in the table below.

[0107] Table 1. Detection results of Examples 1-15 and Comparative Examples 1-7

[0108] Comparative Example 1 and Comparative Examples 1-7: Firstly, the fluidity of Example 1 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil. Furthermore, the 28-day compressive strength of Example 1 is significantly greater than that of Comparative Examples 1-7, the shrinkage and drying rate of Example 1 is significantly less than that of Comparative Examples 1-7, and the permeability coefficient of Example 1 is significantly less than that of Comparative Examples 1-7. Therefore, it can be seen that the modified curing agent and sludge in this application are mixed to form a multi-component synergistic composite system. The physicochemical properties of each component, combined with the core-shell differences of the latex powder, form a specific reaction sequence: In the initial stage of stirring and hydration, the alkaline activator rapidly creates an alkaline environment, activating the potential activity of slag and fly ash, and initiating the formation of CSH gel that provides basic strength; gypsum reacts with the active aluminum source in the system to generate needle-like ettringite crystals, and the moderate volume expansion generated in this process effectively offsets the original shrinkage trend caused by the high water content D; the low Tg shell of the core-shell structure latex powder dissolves and is distributed in the pores, which not only improves workability, but also lays the foundation for the formation of a flexible network and improved toughness in the later film formation. As the hardening process progresses from the mid to late stages, free water begins to evaporate, and drying shrinkage stress becomes apparent. At this point, the high Tg core polymer of the latex powder begins to form a film, which intertwines with the three-dimensional physical network formed by the toughening fibers to create a composite structure. This structure can effectively bridge and disperse shrinkage stress, inhibiting the initiation and propagation of microcracks. Meanwhile, the recycled fine aggregate from construction waste acts as a physical skeleton, optimizing the particle size distribution and reducing the overall shrinkage potential. This has led to the construction of a multi-layered, collaborative defense system that covers the entire lifecycle from early chemical compensation to mid-term stress dissipation. This system compensates for shrinkage and enhances toughness, ensuring that the fluidized solidified soil possesses excellent volume stability and crack resistance from the early to the long term, thus broadening the prospects for large-scale safe application of silt-based fluidized solidified soil.

[0109] Comparative Examples 1 and 2-5: The fluidity of Examples 2-5 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil; Furthermore, in Examples 2, 3, 1, 4, and 5, the strength of the toughening fiber is progressively advanced, and the compressive strength of the resulting silt-based fluidized solidified soil at 28 days also progressively increases. Among them, the increase in compressive strength at 28 days is significantly slower in Examples 3, 1, 4, and 5, and all are above 0.8 MPa, which meets the requirements of most backfill soil projects. The drying shrinkage rates of Examples 3, 1, and 4 are less than those of Examples 2 and 5; The permeability coefficients of Examples 3, 1, and 4 are smaller than those of Examples 2 and 5; Therefore, the tensile strength of the toughening fiber in this application, 480-520 MPa, and the elastic modulus, 4-5.2 GPa, are preferred. This ensures that a single fiber has a sufficiently high load-bearing capacity. When microcracks propagate and stress is transferred to the fiber, the fiber can provide strong tensile resistance and is not easily broken. At the same time, it forms a good match with the mechanical properties of the silt-based fluidized solidified soil matrix. The constant elastic modulus will not generate excessive rigid constraints when the matrix shrinks, thus avoiding damage to the matrix with low early strength. When the matrix is ​​subjected to shrinkage stress in the middle and late stages of hardening, the fiber with this modulus can coordinate the deformation of the matrix through appropriate deformation, efficiently absorb and dissipate energy, and disperse the concentrated shrinkage stress to a wider area, thereby significantly inhibiting the initiation and propagation of cracks. This "combination of rigidity and flexibility" characteristic maximizes the fiber reinforcement effect and significantly improves the toughness and crack resistance of the material.

[0110] Comparative Examples 1 and 6-9: The fluidity of Examples 6-9 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil; The 28-day compressive strength of Examples 1, 8, and 7 is greater than that of Examples 6 and 9; The drying shrinkage rate and permeability coefficient of Examples 1, 8, and 7 are less than those of Examples 6 and 9; Therefore, in this application, the toughening fiber with a length of 12-16 mm and a diameter of 20-30 μm is preferred. Its length ensures that the fiber is sufficient to effectively cross the initial microcracks and form a reliable physical bridge. This combination of diameter and length ensures that the fiber has sufficient flexibility and tensile cross-section, and makes it easy to disperse in the fluid mixture. This avoids the entanglement and clumping caused by excessively long or thick fibers, or the insufficient bridging effect caused by excessively short or thin fibers. Fibers of this size can be evenly distributed in the matrix to build a uniform three-dimensional network skeleton, laying a physical foundation for the subsequent efficient toughening effect.

[0111] Comparing Example 1 and Example 10: The fluidity of Example 10 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil. The 28-day compressive strength of Example 1 is greater than that of Example 10, and the drying shrinkage and permeability coefficient of Example 1 are less than those of Example 10. Therefore, in this application, γ-glycidyl etheroxypropyltrimethoxysilane is used to functionalize the surface of the toughening fiber. One end of the γ-glycidyl etheroxypropyltrimethoxysilane is firmly connected to the fiber surface by chemical bonds, while the other end reacts chemically with the inorganic cementitious phase (mainly CSH gel) (such as ionic bonding of Ca²⁺ or condensation with Si-OH on the gel surface), thereby establishing a strong chemical bridge between the fiber and the inorganic hydration products. This enhances the mechanical interlocking between the toughening fiber and the "composite formed by the hydration products of inorganic cementitious materials and sludge particles, etc." to a strong chemical bond. When the material is under stress and microcracks extend to the fiber interface, it can ensure that the stress is effectively transferred from the matrix to the fiber, forcing the fiber to fully exert its high tensile strength to resist failure, thereby absorbing a large amount of energy and significantly improving toughness.

[0112] Comparing Example 1 and Example 11: The fluidity of Example 11 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil; The 28-day compressive strength of Example 1 is greater than that of Example 11, while the drying shrinkage and permeability coefficient of Example 1 are less than those of Example 11.

[0113] Therefore, in this application, the dry polypropylene fibers with a large surface area and easy static electricity are premixed with coarse-grained recycled construction waste aggregate under mechanical force before mixing, which can improve the performance of silt-based fluidized solidified soil. The reason is that during premixing, the iron toughening fibers are physically wrapped or attached to the surface of the aggregate under the collision, friction and shearing action of the aggregate particles, forming individual "fiber-aggregate" composite units; Subsequently, when the composite unit is added and mixed with silt, water, and other modified solidifying agent components, the aggregate particles act as the carrier and dispersion medium for the fibers. Since the aggregate itself is easy to distribute evenly in the fluid mixture, the fibers carried by it are also uniformly dispersed in three-dimensional space, avoiding the phenomenon of fibers clumping due to mutual entanglement. This solves the problem of the difficulty in uniformly dispersing fiber-reinforced materials in fluid mixtures. It achieves uniform fiber distribution, ensuring that each fiber can independently and effectively play its bridging and toughening role, thereby maximizing the crack resistance of the material with extremely low dosage and improving the quality homogeneity and reliability of the final silt-based fluidized solidified soil.

[0114] Comparative Examples 1 and 12-13: The fluidity of Examples 12-13 is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil; The 28-day compressive strength of Example 1 is greater than that of Example 13, and the 28-day compressive strength of Example 13 is greater than that of Example 12; The drying shrinkage rate of Example 1 is less than that of Example 13, and the drying shrinkage rate of Example 13 is less than that of Example 12; The permeability coefficient of Example 1 is less than that of Example 13, and the number of carburizing systems in Example 13 is less than that in Example 12.

[0115] The reason is that banyan aerial root fibers were added in Example 1, and sodium polyacrylate was added in Example 13.

[0116] The porous walls and hollow cavities of banyan tree aerial root fibers can rapidly absorb and store some of the mixing water during the mixing process. When the silt-based fluidized solidified soil enters the hardening stage after pouring, the internal humidity decreases due to hydration reactions and surface evaporation. The water stored inside the fibers is then slowly released into the surrounding matrix. This internal-to-external water supply provides a stable water source for the continuous hydration of cementitious materials (especially later-stage active materials such as fly ash), effectively reducing self-shrinkage and drying shrinkage caused by uneven or missing moisture. At the same time, the fibers themselves are randomly distributed in the matrix, and their morphology can bridge microcracks, achieving synergy between internal curing and micro-reinforcement. This enhances the stability of the internal microenvironment of the silt-based fluidized solidified soil, inhibits the generation of shrinkage cracks, and further reduces the possibility of cracking in the silt-based fluidized solidified soil.

[0117] The three-dimensional network structure of sodium polyacrylate rapidly absorbs a large amount of free water during the initial mixing stage, causing volume expansion. This process directly reduces the effective free water content used to form fluidity, which is equivalent to reducing the total evaporable water and water-cement ratio of the system while ensuring workability, thus reducing the potential energy of drying shrinkage from the source. During the hardening period after casting, as cement, slag and other cementitious materials continue to hydrate and consume water, the internal humidity of the system begins to decrease. At this time, under the action of capillary tension difference, sodium polyacrylate slowly and continuously releases its stored water into the surrounding cementitious material matrix, forming an "internal curing" effect. This ensures that the deep cementitious materials (especially later active components such as fly ash) can be fully hydrated, generating more hydration products to fill the capillary pores, making the microstructure more compact. At the same time, it significantly reduces the self-shrinkage and drying shrinkage stress caused by uneven internal humidity gradient. It realizes active intervention and optimization of the hydration reaction process, achieving precise moisture control throughout the entire cycle from mixing to long-term hardening, ensuring fluidity while maximizing volume stability and crack resistance.

[0118] Furthermore, compared to sodium polyacrylate, banyan aerial root fiber transforms a common, underutilized local natural waste into an engineering material with proactive and intelligent response capabilities, combining local resources to treat waste with waste, making it more green and environmentally friendly.

[0119] There are other preferred rates in this application, such as in Examples 14 and 15, where the flowability is within 200±15mm, which meets the pumping requirements of silt-based fluidized solidified soil. Furthermore, the 28-day compressive strength of Examples 14 and 15 was significantly greater than that of Comparative Examples 1-7, while the drying shrinkage and permeability coefficient of Examples 14 and 15 were less than those of Comparative Examples 1-7. Therefore, in this application, based on 150 parts by weight of dry sludge, the amount of modified solidifying agent is preferably controlled to include the following components in parts by weight: 30-52 parts of granulated blast furnace slag, 22-38 parts of fly ash, 12-22 parts of gypsum, 4-12 parts of alkaline activator, 2-5 parts of core-shell structure latex powder, 8-22 parts of recycled fine aggregate from construction waste, and 0.2-0.5 parts of toughening fiber.

[0120] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A construction method for preventing cracking of a slurry-based flowable solidified soil, characterized by, The method comprises the following steps, S1: stirring the silt and the modified curing agent according to a design formula to prepare a silt-based fluidified solidified soil, and pouring the silt-based fluidified solidified soil into a target area; S2: after the initial setting time of the silt-based fluidified solidified soil, pouring the non-cracking fluidified solidified soil with a required permeability coefficient on the surface of the silt-based fluidified solidified soil; The modified curing agent contains the following components in parts by weight based on 150 parts by weight of dry silt: granulated blast furnace slag 30-52 parts, fly ash 22-38 parts, gypsum 12-22 parts, alkaline activator 4-12 parts, core-shell structure latex powder 2-5 parts, construction waste recycled fine aggregate 8-22 parts, toughening fiber 0.2-0.5 parts. The shell polymer of the core-shell structure latex powder is a vinyl acetate-ethylene copolymer, and the core polymer is an acrylate polymer, the glass transition temperature Tg of the shell polymer is not higher than 0℃, and the glass transition temperature Tg of the core polymer is 20-30℃.

2. The construction method for preventing cracking of a sludge-based flow state solidified soil according to claim 1, characterized in that, The toughening fiber is a polypropylene fiber with a length of 12-16 mm and a diameter of 20-30 μm.

3. The construction method for preventing cracking of a slurry-based flowable solidified soil according to claim 2, characterized in that, The tensile strength of the polypropylene fiber is 480-520 MPa, and the elastic modulus is 4-5.2 GPa.

4. The construction method for preventing cracking of a sludge-based flow state solidified soil according to claim 2, characterized in that, The surface of the toughening fiber is functionally modified by γ-glycidyl ether propyltrimethoxysilane.

5. The construction method for preventing cracking of a slurry-based flowable solidified soil according to claim 4, characterized in that, The polypropylene fiber and the construction waste recycled fine aggregate are pre-mixed before stirring, so that part of the fiber is wrapped or attached to the surface of the construction waste recycled fine aggregate.

6. The construction method for preventing cracking of a slurry-based flowable solidified soil according to claim 1, characterized in that, The modified curing agent further contains 0.5-2 parts of banyan aereal root fiber, which is a porous hollow fiber after crushing treatment.

7. The construction method for preventing cracking of a slurry-based flowable solidified soil according to claim 1, characterized in that, The modified curing agent further contains 0.8-2.2 parts of polyacrylic acid sodium salt.

8. The construction method for preventing cracking of a slurry-based flowable solidified soil according to claim 1, characterized in that, The specific steps of preparing the fluidified solidified soil in step S1 include: pre-mixing the construction waste recycled fine aggregate and the toughening fiber to prepare a first pre-mixed compound; pre-mixing the granulated blast furnace slag, fly ash, gypsum, and alkaline activator to prepare a second pre-mixed compound; adding the second pre-mixed compound to the silt base first, and stirring uniformly to form a slurry; then adding the first pre-mixed compound, the core-shell structure latex powder, and the remaining other modified curing agent components to the slurry in sequence, and stirring uniformly to prepare the fluidified solidified soil.

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