A soil solidifying agent, its preparation method and application

Abstract

The present application relates to a kind of soil solidifying agent and its preparation method and application, the soil solidifying agent includes phosphoric acid modified steel slag, phosphoric acid modified steel slag includes calcium phosphate phase.It can still have better reaction adaptability in high water content, salt and contaminated soil, to speed up the formation of solidified structure and improve the early strength of soil.Thereby simultaneously improving the solidification effect of three kinds of special soil of high water content soil, heavy metal pollution and saline soil.

Description

Technical Field

[0001] This application relates to civil engineering materials technology, and more particularly to a soil solidification agent, its preparation method, and its application. Background Technology

[0002] In engineering practice, high-moisture-content silt (moisture content ≥ 80%), coastal saline soil, and soft soil contaminated with heavy metals are common engineering challenges. For example, in roadbed construction, the insufficient bearing capacity of high-moisture-content silt can lead to foundation settlement; in coastal areas, chloride ion erosion of saline soil can accelerate the deterioration of concrete structures; and in sites contaminated with heavy metals, untreated soil may cause secondary pollution of groundwater through rainwater migration. Therefore, it is necessary to use solidifying agents to solidify and stabilize high-moisture-content silt, coastal saline soil, and soft soil contaminated with heavy metals.

[0003] Traditional solidification and stabilization methods often use cement for solidification. However, traditional cement-based solidifiers have significant limitations in treating the aforementioned special soil types. They have limited effectiveness in solidifying soils with high water content, heavy metal contamination, and saline soils, resulting in the solidified soil still being prone to problems such as slow strength development, insufficient durability, and leaching of heavy metal ions.

[0004] Therefore, how to develop a curing agent that can simultaneously improve the curing effect of three special soil types—high moisture content soil, heavy metal contaminated soil, and saline soil—to meet the engineering needs of special soil treatment is an urgent problem to be solved in the field of civil engineering for the curing treatment of special soil types. Summary of the Invention

[0005] This invention provides a low-carbon soil solidifier that exhibits good reactivity in high-moisture, saline, and contaminated soils, thereby accelerating the formation of solidified structures and improving the early strength of the soil. This simultaneously enhances the solidification effect on three special soil types: high-moisture soils, heavy metal-contaminated soils, and saline soils.

[0006] This invention provides a method for preparing a low-carbon soil solidification agent, which can efficiently and cost-effectively prepare the low-carbon soil solidification agent to improve the soil solidification effect.

[0007] This invention provides a solidification method that can improve the solidification effect on three special soil types: soil with high water content, soil contaminated with heavy metals, and saline soil.

[0008] The first aspect of this invention provides a low-carbon soil solidification agent, comprising phosphoric acid modified steel slag, wherein the phosphoric acid modified steel slag comprises a calcium phosphate phase.

[0009] The soil low-carbon solidification agent described above, wherein the calcium phosphate phase is CaHPO4·2H2O; and / or,

[0010] The content of calcium phosphate phase in phosphoric acid modified steel slag is 8-15%; and / or,

[0011] The specific surface area of ​​phosphoric acid modified steel slag is ≥550m². 2 / kg.

[0012] The soil low-carbon solidification agent described above further includes slag and a composite alkali activator, wherein the composite alkali activator comprises rice husk ash extract and sodium carbonate in a mass ratio of 1:(2-4), and the rice husk ash extract contains amorphous SiO2; and / or,

[0013] It also includes auxiliary functional components, which include a polycarboxylate superplasticizer and sodium alginate in a mass ratio of (3-5):1.

[0014] The soil low-carbon solidification agent described above contains rice husk ash extract with an active SiO2 content of ≥40% on a dry basis, and amorphous SiO2 accounts for ≥85% of the active SiO2.

[0015] The soil low-carbon solidification agent described above, wherein the phosphoric acid modified steel slag is prepared by a method comprising the following steps: mixing steel slag with a phosphoric acid solution, stirring and reacting at 65-75°C for 3-4 hours, and filtering to obtain phosphoric acid modified steel slag; and / or,

[0016] Rice husk ash extract was prepared by a method comprising the following steps: hydrothermal extraction of amorphous SiO2 content exceeding 90% of rice husk ash at 85-95℃ for 4-5 hours, followed by filtration and concentration to a solid content of not less than 35%, thereby obtaining the rice husk ash extract; and / or,

[0017] The water reduction rate of polycarboxylate superplasticizers is ≥30%; and / or,

[0018] Sodium alginate has a viscosity-average molecular weight of 180,000-220,000.

[0019] The soil low-carbon solidifier described above, wherein the soil solidifier comprises, by mass percentage:

[0020] Slag 45-54%, phosphoric acid modified steel slag 25-32%, desulfurized gypsum 9-12%, composite alkali activator 5-9%, auxiliary functional components 1.5-3%; and / or,

[0021] The mass concentration of the phosphoric acid solution is 8-12%, and the mass ratio of steel slag to phosphoric acid solution is 1:(2-3).

[0022] A second aspect of the present invention provides a method for preparing a soil solidification agent as described above, comprising the following steps:

[0023] Phosphoric acid modified steel slag is mixed with other raw material components, including at least one of slag, phosphoric acid modified steel slag, desulfurized gypsum, composite alkali activator and auxiliary functional components, to obtain a soil solidification agent.

[0024] The preparation method described above, wherein the mixing process includes the following steps:

[0025] First, premix the slag with the compound alkali activator for 10-15 minutes;

[0026] Then add phosphoric acid modified steel slag, desulfurized gypsum and auxiliary functional components, mix for 40-50 minutes, and control the material temperature ≤40℃ during the mixing process to obtain soil solidification agent.

[0027] A third aspect of the present invention provides a curing method, comprising the step of curing soil using a soil curing agent including the soil curing agent provided above.

[0028] The solidification method described above, wherein the soil includes at least one of high water content soil, heavy metal contaminated soil and saline soil, wherein the water content of the high water content soil is ≥80%, the heavy metal contaminated soil contains Pb content ≥500mg / kg, Cr content ≥300mg / kg and Cd content ≥20mg / kg, and the saline soil contains chloride ion content ≥0.5%.

[0029] The low-carbon soil solidification agent provided by this invention comprises a calcium phosphate phase in phosphoric acid-modified steel slag. The calcium phosphate phase itself possesses hydraulic properties and participates in the cementation reaction, maintaining good early cementation and strength development even in soils with high water content, thereby improving the solidification effect on high water content soils. Simultaneously, the calcium phosphate phase provides abundant chemical adsorption and ion exchange sites for Pb. 2+ Cr 3+ Cr 6+ Cd 2+ Heavy metal ions possess strong complexing and immobilization capabilities, forming insoluble phosphate precipitates, thus exhibiting highly efficient solidification and stabilization effects on heavily polluted soils; the calcium phosphate phase provides ion exchange sites, facilitating the formation of Cl- precipitates. - It possesses adsorption and fixation properties, with a high chloride ion fixation rate, thereby achieving corrosion prevention and salt swelling prevention in coastal saline soil solidification projects, and enhancing the long-term effectiveness of these projects. The aforementioned phosphoric acid-modified steel slag can improve the reactivity and solidification effect of steel slag-based materials in special soils, promote the formation of a more stable and dense solidified structure, and enhance the stabilization capacity for heavy metal ions and durability under chloride ion environments. This results in a synergistic improvement in solidification efficiency, environmental stability, and durability in special soils. Attached Figure Description

[0030] Figure 1The XRD pattern of the product of step (1) in Embodiment 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] With the large-scale development of infrastructure construction, river dredging, and coastal engineering in my country, a large amount of high-moisture-content silt, heavy metal-contaminated soil, and saline soil has been generated. These soils have low strength, poor bearing capacity, and are prone to pollutant migration. Direct discharge or dumping not only occupies land but also causes environmental pollution. Traditional treatment methods often use cement solidification, but cement production is energy-intensive and generates large carbon emissions. Furthermore, cement has limited effectiveness in solidifying high-moisture-content soil, heavy metal-contaminated soil, and saline soil, often resulting in slow strength development, insufficient durability, and heavy metal ion leaching.

[0033] In order to overcome the aforementioned defects of cement-solidified soil with high water content, heavy metal contaminated soil and saline soil, the inventors analyzed the special soil solidification treatment method. Existing special soil treatment methods mostly use cement-based solidifying agents or alkali-activated solid waste cementitious materials. After being mixed with the soil, they undergo hydration or activation reactions to form cementitious products, thereby improving soil strength, reducing compressibility and improving stability.

[0034] However, after analysis, the inventors found that existing solidification methods are insufficient in adapting to complex environmental factors: on the one hand, high-water-content sludge is prone to problems such as low solidification efficiency and slow formation of early bearing capacity; on the other hand, the ionic effects in saline environments weaken the durability of the solidified structure, while lacking stable and effective fixation capabilities for heavy metal ions in contaminated soil. Therefore, while existing methods have certain effects in general soil treatment, under conditions of high water content, salinity, or contamination, the solidification reaction is often incomplete due to insufficient activity of raw materials and low reaction rates, resulting in a relatively loose solidified structure. This not only affects the foundation treatment effect but may also lead to long-term performance degradation and increased environmental risks, making it difficult to simultaneously meet the requirements of engineering performance, environmental safety, and low-carbon applications.

[0035] Based on this, the first aspect of the present invention provides a soil solidification agent, comprising phosphoric acid modified steel slag, wherein the phosphoric acid modified steel slag comprises a calcium phosphate phase.

[0036] The calcium phosphate phase itself possesses hydraulic properties and participates in the cementation reaction. When this soil solidifier is applied to high-water-content silt, the phosphate modification disrupts the relatively inert passivation layer on the surface of the original steel slag particles, making it easier for reactive components in the steel slag to dissolve and participate in subsequent cementation reactions. The activated surface sites of the phosphate-modified steel slag can quickly contact pore water. Water in the soil provides a medium for ion migration and reaction. The active components such as calcium, silicon, and aluminum released from the phosphate-modified steel slag can further form cementation products, encapsulating, bridging, and filling soil particles. The calcium phosphate phase, as a pre-existing stable phase after modification, can provide additional crystal nuclei or interface sites at the microscopic level, resulting in a more uniform cementation structure. Based on the above analysis, the solidifier of this invention, through the synergistic effect of the surface activation effect of phosphate modification and the calcium phosphate phase, improves the reaction initiation efficiency and structure formation rate, thereby enabling the solidified body to establish a continuous framework earlier. This allows the solidifier to maintain good early cementation and strength development in high-water-content soils, thus improving the solidification effect on high-water-content soils.

[0037] When this soil stabilizer is applied to saline soil, common chlorides, sulfates, and other soluble salts in the soil can alter the ionic strength of the pore fluid and interfere with the hydration balance in conventional stabilization systems. However, the calcium phosphate phase formed in phosphoric acid-modified steel slag exhibits good chemical stability, and its composite structure with the surface of the phosphoric acid-modified steel slag can mitigate some of the adverse effects of salts on the stabilization framework. Simultaneously, the calcium phosphate phase provides ion exchange sites, which are beneficial for Cl-. - It has an adsorption and fixation function with a high chloride ion fixation rate, thereby achieving corrosion prevention and salt swelling prevention in coastal saline soil solidification projects, and improving the integrity and durability of coastal saline soil.

[0038] When this soil stabilizer is applied to soil contaminated with heavy metals, the role of the calcium phosphate phase is further manifested in the adsorption, complexation, and precipitation fixation of heavy metal ions. This is achieved through the interaction of phosphate ions with Pb in the soil. 2+ Cr 3+ Cr 6+ Cd 2+ The chemical interaction between heavy metal ions can promote the conversion of some heavy metals into phosphorus-containing stabilized products with lower solubility. At the same time, the porous active interface formed on the surface of phosphoric acid-modified steel slag also provides conditions for ion exchange and surface adsorption, thus having a highly efficient solidification and stabilization effect on heavily polluted soil.

[0039] The aforementioned phosphoric acid-modified steel slag can improve the reactivity and solidification effect of steel slag-based materials in three special soil types: high-moisture-content silt, heavy metal contaminated soil, and saline soil. It promotes the formation of a more stable and dense solidified structure, and improves the stabilization capacity of heavy metal ions and the durability adaptability under chloride ion environment. In this way, it achieves a synergistic improvement in solidification efficiency, environmental stability, and durability of special soil types.

[0040] Furthermore, the calcium phosphate phase is CaHPO4·2H2O.

[0041] Furthermore, the content of the calcium phosphate phase in the phosphoric acid modified steel slag is 8-15%. By controlling the calcium phosphate phase in the phosphoric acid modified steel slag within the range of 8%, 10%, 13%, 15%, or any combination thereof, the surface activation of the steel slag can be further effectively promoted and an appropriate calcium phosphate phase can be obtained. This further improves the reactivity and solidification effect of steel slag-based materials in three special soil types: high-moisture-content silt, heavy metal contaminated soil, and saline soil.

[0042] Furthermore, the specific surface area of ​​phosphoric acid modified steel slag is ≥550 m². 2 / kg. The specific surface area of ​​the phosphoric acid-modified steel slag is controlled to be ≥550m². 2 / kg, preferably 550-650m 2 / kg, which can significantly increase the contact interface between the material and soil particles, moisture and activating components, and enhance ion migration and the nucleation rate of cement products.

[0043] Furthermore, it also includes slag and a composite alkali activator, the composite alkali activator comprising rice husk ash extract and sodium carbonate in a mass ratio of 1:(2-4), the rice husk ash extract containing amorphous SiO2.

[0044] Slag and phosphoric acid-modified steel slag together form the main cementitious framework, and the potential hydraulic properties of slag can be utilized to improve early reaction activity and later strength. In the composite alkali activator, rice husk ash extract provides a soluble active silicon source, and its contained amorphous SiO2 is more easily dissolved and participates in the polymerization reaction. Sodium carbonate provides a moderately alkaline environment, promoting the release of active components in slag and steel slag and the formation of a dense gel. Controlling the ratio of rice husk ash extract to sodium carbonate to 1:2, 1:3, 1:4, or any combination thereof within this temperature range avoids silicon source activity loss due to high temperature, while ensuring the effective concentration of active ingredients when subsequently compounded with sodium carbonate, thereby enhancing the activation intensity of the composite alkali activator.

[0045] Furthermore, it also includes auxiliary functional components, which include a polycarboxylate superplasticizer and sodium alginate in a mass ratio of (3-5):1.

[0046] Polycarboxylate superplasticizers and sodium alginate, when blended in ratios of 3:1, 4:1, 5:1, or any combination thereof, can simultaneously improve dispersibility, water retention, and formability. The polycarboxylate superplasticizer reduces water demand and inhibits agglomeration, while sodium alginate forms a network-like water-retaining structure and mitigates shrinkage stress. Combining the two in the aforementioned ratios achieves a balance between water reduction and water retention, resulting in more uniform slurry flow, more stable mixing, and improved curing durability of the hardener on the soil.

[0047] Furthermore, the active SiO2 content in the rice husk ash extract is ≥40% on a dry basis, and amorphous SiO2 accounts for ≥85% of the active SiO2. Active SiO2 is a functional concept, referring to soluble silicon components that can participate in polymerization reactions under alkaline activation conditions; amorphous SiO2 is a phase structure concept, referring to amorphous (non-crystalline) SiO2. Most amorphous SiO2 is reactive (i.e., soluble in alkaline solutions), but active SiO2 also includes some soluble silicon from silicate minerals with low crystallinity; amorphous SiO2 may also contain portions that are not easily dissolved due to surface densification. This invention simultaneously limits both types of SiO2 to ensure that the silicon source has both high reactivity and is predominantly amorphous, thereby guaranteeing the rate and sufficiency of the alkaline activation reaction.

[0048] Furthermore, phosphoric acid modified steel slag is prepared by a method including the following process: mixing steel slag with phosphoric acid solution, stirring and reacting at 65-75℃ for 3-4 hours, and then filtering to obtain a soil solidification agent.

[0049] Steel slag can be mixed with phosphoric acid solution and reacted to allow the phosphoric acid to react with free calcium oxide and other calcium-containing active components in the steel slag. For example, phosphoric acid reacts with f-CaO: 2H3PO4 + 3CaO → Ca3(PO4)2 + 3H2O; phosphoric acid reacts with C2S to form dicalcium phosphate (CaHPO4·2H2O). After the above treatment, the phosphoric acid treatment destroys the passivation layer on the surface of the steel slag, increases the number of surface active sites, increases the specific surface area, and generates a calcium phosphate phase, making it easier for the slag to participate in subsequent reactions after being mixed with soil.

[0050] Furthermore, the stirring speed for the reaction is 150-250 rpm.

[0051] Further, after the stirring reaction is completed, the reaction slurry is vacuum filtered and washed with deionized water until the pH of the filtrate is close to neutral in order to remove excess phosphate ions and soluble impurities; the filter cake is placed in an oven at 105℃ and dried for 20-30 hours, then crushed and sieved to obtain powder with a water content of ≤1%, thus obtaining phosphoric acid modified steel slag.

[0052] Furthermore, the steel slag is taken from converter steel slag, and undergoes magnetic separation to remove iron, crushing, and grinding to a specific surface area of ​​approximately 450 m². 2 / kg, its main mineral composition is 35-45% dicalcium silicate (C2S), 15-25% calcium ferrite, and a small amount of free calcium oxide (f-CaO) 3-8% and periclase (f-MgO) 2-5%.

[0053] Furthermore, the rice husk ash extract was prepared by a method comprising the following steps: rice husk ash with an amorphous SiO2 content exceeding 90% was hydrothermally extracted at 85-95℃ for 4-5 hours, filtered, and concentrated to a solid content of not less than 35%, thus obtaining the rice husk ash extract. This process achieves efficient dissolution and enrichment of amorphous silicon, and controlling the solid content to not less than 35% helps ensure the effective concentration of active ingredients when subsequently compounded with sodium carbonate, thereby enhancing the activation intensity of the composite alkali activator.

[0054] Further, rice husk ash with an amorphous SiO2 content of over 90% is mixed with deionized water at a mass ratio of 1:(5-7), placed in a water bath at 85-95℃, and mechanically stirred for 4-5 hours at a stirring speed of 100-200 rpm.

[0055] Further, after hydrothermal extraction, the solution is filtered while still hot using a Buchner funnel and a 0.45 μm microporous membrane to obtain a clear filtrate. The filtrate is then concentrated by rotary evaporation at 60-80 °C until the solid content of the concentrate reaches 35-40% (by weight), yielding the rice husk ash extract. This temperature range avoids the loss of silicon source activity caused by high temperatures, while ensuring the effective concentration of active ingredients when subsequently compounded with sodium carbonate, thereby enhancing the activation intensity of the composite alkali activator.

[0056] Furthermore, polycarboxylate superplasticizers have a water reduction rate of ≥30%, strong dispersion and water reduction capabilities, and can maintain system fluidity and reduce porosity under low water-cement ratio conditions.

[0057] Furthermore, the polycarboxylate superplasticizer has a solid content of 40%.

[0058] Furthermore, sodium alginate has a viscosity-average molecular weight of 180,000-220,000 (Ubbelohde viscometer method, 25℃, 0.1 mol / L NaCl solution), which can form a moderate molecular entanglement and water-retaining network in the system, balancing workability and molding stability.

[0059] Furthermore, the soil stabilizer, by mass percentage, includes:

[0060] The composition includes 45-54% slag, 25-32% phosphoric acid modified steel slag, 9-12% desulfurized gypsum, 5-9% composite alkali activator, and 1.5-3% auxiliary functional components.

[0061] This soil solidification agent uses slag as the main cementing material. When the content is controlled within the range of 45%, 50%, 54%, or any two of these, it ensures that the system has sufficient potential active silica-alumina sources. Subsequently, under the action of a composite alkali activator, a dense gel skeleton is formed, thereby improving the later strength of the soil. Phosphoric acid-modified steel slag, controlled within the range of 25%, 28%, 30%, 32%, or any two of these, generates a calcium phosphate phase on its surface after phosphoric acid treatment, increasing its specific surface area. This enhances its interfacial reaction capacity with soil particles and provides fixation sites for heavy metal ions, making the solidified body more stable in heavy metal contaminated soil. Desulfurized gypsum, controlled within the range of 9%, 10%, 11%, 12%, or any two of these, is used to continuously supply sulfate ions, promoting the formation of early products such as ettringite, which can accelerate structural formation and improve early bearing capacity. The composite alkali activator, controlled within the range of 5%, 7%, 9%, or any two of these components, provides suitable alkalinity and promotes the activation of slag and phosphoric acid-modified steel slag. Furthermore, the synergistic effect of rice husk ash extract and sodium carbonate balances the replenishment of active silicon source with a mild reaction, preventing structural embrittlement caused by excessive alkali corrosion. The auxiliary functional components, controlled within the range of 1.5%, 2%, 2.5%, 3%, or any two of these components, regulate the dynamics of the mixture through water reduction, water retention, and thickening, making it more suitable for construction in high-water-content silt and soft soil, thereby improving uniformity and molding quality.

[0062] Furthermore, the slag is granulated blast furnace slag, using S95 grade product conforming to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete" standard, with its specific surface area controlled at 420±20 m². 2 / kg, density is 2.85-2.95g / cm³ 3 The mass ratio (basicity coefficient) of CaO to SiO2+Al2O3 in the chemical composition is approximately 1.05.

[0063] Furthermore, the slag is pretreated before use. The pretreatment involves drying the slag in an oven at 105±5℃ to constant weight (moisture content <0.5%) and passing it through an 80μm square mesh sieve to remove coarse particles.

[0064] Furthermore, the desulfurized gypsum is calcined desulfurized gypsum, in which the content of hemihydrate gypsum is 68%, the content of anhydrous gypsum III is about 30%, and the remainder is a small amount of unconverted dihydrate gypsum.

[0065] Furthermore, the preparation method of desulfurized gypsum is as follows: the desulfurized gypsum raw material is calcined at a constant temperature of 280℃ in a calcining furnace for 2.2 hours. This temperature range ensures that calcium sulfate dihydrate (CaSO4·2H2O) is gradually dehydrated into hemihydrate gypsum (CaSO4·0.5H2O) and a small amount of anhydrous gypsum III (CaSO4Ⅲ), avoiding excessive dehydration caused by high temperature (such as the formation of anhydrous gypsum II), thereby ensuring the early strength performance and micro-expansion compensation ability of the calcined desulfurized gypsum.

[0066] Furthermore, the desulfurization gypsum raw material comes from the by-product of wet desulfurization in power plants, and its main component is calcium sulfate dihydrate (CaSO4·2H2O) with a purity of ≥92%.

[0067] Furthermore, the desulfurized gypsum is ground before use, with a specific surface area controlled at 350-400 m² / kg and a sieve residue of ≤10% on an 80 μm square hole sieve, to ensure uniform dispersion and appropriate dissolution rate in the system.

[0068] Furthermore, the mass concentration of the phosphoric acid solution is 8-12%, and the mass ratio of steel slag to phosphoric acid solution is 1:(2-3). Controlling the concentration of the phosphoric acid solution to a range of 8%, 10%, 12%, or any combination thereof, can further ensure sufficient acidification modification of the steel slag surface. When the steel slag and phosphoric acid solution are mixed in a 1:(2-3) ratio, this ratio is determined based on the content of free CaO in the steel slag (3-8%) and the acid-base equivalent ratio of phosphoric acid (the molar ratio of H3PO4 to CaO is 2:1). This ratio allows the phosphoric acid to fully react with the free CaO in the steel slag to generate a calcium phosphate phase (such as CaHPO4·2H2O), while avoiding excessive dissolution of other active components in the steel slag (such as C2S), thereby maintaining the reactivity and structural stability of the steel slag.

[0069] A second aspect of this invention provides a method for preparing a soil solidification agent, comprising the following steps:

[0070] Phosphoric acid modified steel slag is mixed with other raw material components, including at least one of slag, phosphoric acid modified steel slag, desulfurized gypsum, composite alkali activator and auxiliary functional components, to obtain a soil solidification agent.

[0071] Phosphoric acid-modified steel slag, combined with slag, desulfurized gypsum, composite alkali activator, and auxiliary functional components, can work together to form a cementitious structure in subsequent applications, thereby improving the soil consolidation effect.

[0072] Furthermore, the mixing process includes the following steps:

[0073] First, premix the slag with the compound alkali activator for 10-15 minutes;

[0074] Then add phosphoric acid modified steel slag, desulfurized gypsum and auxiliary functional components, mix for 40-50 minutes, and control the material temperature ≤40℃ during the mixing process to obtain soil solidification agent.

[0075] Premix for 10-15 minutes to ensure the activator is evenly coated on the surface of the slag particles, guaranteeing sufficient contact between the activator and the slag. The slag then forms an activated dissolution environment under the action of the composite alkali activator. Next, add phosphoric acid-modified steel slag to prevent premature contact and reaction between the phosphate-modified steel slag and the activator, ensuring uniform dispersion of all components. The phosphoric acid-modified steel slag provides a solid-phase reaction source containing the calcium phosphate phase, and the desulfurized gypsum provides calcium and sulfur components. After thorough mixing, all three can participate in the formation of gelling products during subsequent use. The polycarboxylate superplasticizer and sodium alginate in the auxiliary functional components synergistically disperse the particles and maintain system homogeneity, ensuring a relatively uniform spatial distribution of the active components during the mixing stage. Control the material temperature to ≤40℃ during mixing to prevent premature deactivation of the composite alkali activator due to frictional heating, ensuring the reactivity during on-site mixing.

[0076] By combining premixing, primary mixing, and temperature control, the raw materials can form a stable composite curing system, thereby ensuring that the resulting soil curing agent is consistent with the chemical product of this application, and making the reaction basis more uniform and reliable when used in special soils.

[0077] Furthermore, the mixing process specifically includes the following steps:

[0078] Add the slag and composite alkali activator together into a laboratory high-efficiency three-dimensional motion mixer of model V-10. Start the mixer and premix at a speed of 20-40 rpm for 10-15 minutes to make the activator evenly adhere to the surface of the mineral powder.

[0079] Add phosphoric acid modified steel slag, desulfurized gypsum, polycarboxylate superplasticizer and sodium alginate in sequence, increase the mixing speed to 40-50 rpm, and continue mixing for 40-50 minutes;

[0080] The temperature of the material was consistently maintained at ≤40℃ during the mixing process, as monitored by an infrared thermometer.

[0081] A third aspect of the present invention provides a curing method, comprising the step of curing soil using a soil curing agent including the soil curing agent provided above.

[0082] When soil is solidified using a solidifying agent including the aforementioned soil solidifier, the phosphoric acid-modified steel slag in the solidifier can interact with moisture, active components, and the ionic environment in the soil to promote cementation and structural reconstruction. Because the phosphoric acid-modified steel slag contains a calcium phosphate phase, it maintains good reactivity in high-moisture, saline, and contaminated soils, thereby accelerating the formation of the solidified structure and improving the early strength of the soil. Simultaneously, the calcium phosphate phase helps enhance the density and stability of the solidified framework, reducing salt interference and improving the pore structure, thus improving durability and deformation resistance. For heavy metal ions in contaminated soil, the chemical fixation and structural containment of the solidification system can reduce their migration risk, thus achieving a balance between engineering reinforcement effects, environmental safety, and long-term service stability.

[0083] Furthermore, the soil includes at least one of high moisture content soil, heavy metal contaminated soil, and saline soil. The moisture content of the high moisture content soil is ≥80%. The heavy metal contaminated soil contains Pb content ≥500mg / kg, Cr content ≥300mg / kg, and Cd content ≥20mg / kg. The saline soil contains chloride ion content ≥0.5% (on a dry basis).

[0084] By limiting the soil type to at least one of high water content soil, heavy metal contaminated soil, and saline soil, the scope of application of the solidifying agent of this invention covers soil types that are weak, contaminated, and saline in nature, or exist alone. For high water content soil (≥80%), which is rich in pore water and has a loose structure, the use of the solidifying agent facilitates the formation of a more stable solidification framework in a high-water environment, thereby improving early strength and bearing capacity. For contaminated soil containing heavy metal ions, structural enhancement and stabilization of harmful ions can be achieved simultaneously during the solidification process, thus balancing engineering performance and environmental safety requirements. For saline soil containing chloride ions, the agent can reduce the adverse effects of salt on the integrity of the solidified structure, thereby improving the durability and long-term stability of the solidified soil. Therefore, it is suitable for engineering scenarios such as roadbeds, soft soil foundations, and dredged soil backfill, where strength, stability, and environmental risk control are all required.

[0085] Furthermore, the dosage of the soil stabilizer is 10-20% of the dry weight of the soil. Within this range, the slag, phosphoric acid-modified steel slag, and desulfurized gypsum in the stabilizer can fully react with the soil to generate a multiphase cementitious network containing CSH gel, ettringite, and calcium phosphate phases. This enables the stabilized soil to achieve significant and balanced compressive strength, water stability, and volume stability, while also improving chloride ion fixation rate and resistance to salt erosion. It is suitable for the reinforcement of difficult soils such as high water content soils and coastal saline soils.

[0086] Furthermore, the amount of curing agent added is 10-20% of the dry mass of the soil.

[0087] Furthermore, the preferred amount of solidifier in high moisture content soil is 12-18%, the preferred amount of solidifier in heavy metal contaminated soil is 15-20%, and the preferred amount of solidifier in saline soil is 10-15%.

[0088] Furthermore, it includes the following steps:

[0089] Soil pretreatment: The soil to be solidified is crushed and screened to remove stones and debris with a particle size greater than 50mm; the natural moisture content, pH value, organic matter content and pollution indicators (heavy metal concentration / salt content) of the soil are measured, and the amount of solidifying agent is adjusted accordingly;

[0090] Use a forced mixer or road mixer for mixing: First, spread the soil to be solidified to the designed thickness (20-30cm / layer), and evenly sprinkle or spray the solidifying agent powder; mix at least twice, and the mixing depth should exceed the designed layer thickness by 2-3cm to ensure no soil interlayer; during the mixing process, add an appropriate amount of water according to the soil moisture content, so that the moisture content of the mixture is controlled within the range of optimum moisture content ±2%;

[0091] Molding and curing: After mixing, the paving, compaction or casting should be completed within 2 hours;

[0092] Subgrade / site consolidation: Layered compaction using a road roller, with a compaction degree ≥93% (heavy compaction standard);

[0093] Solidified soil blocks / precast components: Vibrate to form after pouring, and demold after standing for 24 hours;

[0094] After molding, the material is cured by sprinkling water at a temperature of 20±2℃ and a relative humidity of ≥90% for at least 7 days. The design strength can be achieved in 28 days.

[0095] The present invention will be further described below through specific embodiments.

[0096] Example 1:

[0097] The method for preparing the soil solidification agent in this embodiment includes the following steps:

[0098] (1) Preparation of phosphoric acid modified steel slag:

[0099] Take 1 kg of the above steel slag and place it in a reactor equipped with stirring and temperature control. Add 2.5 kg of 10% phosphoric acid (H3PO4) solution, i.e., the mass ratio of steel slag to phosphoric acid solution is 1:2.5. Turn on the stirring and the stirring speed is 200 rpm.

[0100] The system was heated to 72°C and kept constant for 3.5 hours. After the reaction was completed, the slurry was washed with deionized water under vacuum until the pH of the filtrate was close to neutral in order to remove excess phosphate ions and soluble impurities.

[0101] The filter cake was dried in an oven at 105℃ for 24 hours, then crushed and sieved to obtain powder with a moisture content of ≤1%, which is the phosphoric acid modified steel slag.

[0102] (2) Preparation of rice husk ash extract:

[0103] Rice husk ash with an amorphous SiO2 content of over 90% was mixed with deionized water at a mass ratio of 1:6 and placed in a 90℃ water bath for mechanical stirring extraction for 4.5 hours at a stirring speed of 150 rpm.

[0104] While still hot, filter the solution using a Buchner funnel and a 0.45 μm microporous membrane to obtain a clear filtrate. Concentrate the filtrate by rotary evaporation at 70 °C until the solid content of the concentrate reaches 38% (by weight), thus obtaining the rice husk ash extract.

[0105] The obtained rice husk ash extract and anhydrous sodium carbonate were stirred and mixed evenly at room temperature to form a paste-like composite alkali activator for later use.

[0106] (3) Raw material preparation:

[0107] Weigh the dried raw materials precisely by weight percentage:

[0108] Granulated blast furnace slag 53%, phosphoric acid modified steel slag 28%, calcined desulfurized gypsum 11%, composite alkali activator 6%, auxiliary functional components 2%.

[0109] The compound alkali activator contains 13.75g of rice husk ash extract and 41.25g of sodium carbonate, meaning the mass ratio of rice husk ash extract to sodium carbonate is 1:3.

[0110] Among the auxiliary functional components, there are 14.4g of polycarboxylate superplasticizer and 3.6g of sodium alginate, that is, the mass ratio of polycarboxylate superplasticizer to sodium alginate is 4:1.

[0111] (4) Mixing and homogenization:

[0112] Granulated blast furnace slag and composite alkali activator were added together into a laboratory high-efficiency three-dimensional motion mixer of model V-10. The mixer was started and premixed at a speed of 30 rpm for 12 minutes to ensure that the activator was evenly attached to the surface of the mineral powder.

[0113] Phosphoric acid-modified steel slag, desulfurized gypsum, polycarboxylate superplasticizer, and sodium alginate powder were added sequentially. The mixing speed was increased to 45 rpm, and mixing continued for 45 minutes. The material temperature was maintained at 35-38℃ throughout the mixing process, as monitored by an infrared thermometer.

[0114] After mixing, the material is discharged to obtain a light gray, uniform, and free-flowing powdered curing agent product, which is the soil curing agent.

[0115] Example 2:

[0116] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that: in step (3), the dried raw materials are accurately weighed by weight percentage:

[0117] Granulated blast furnace slag 46%, phosphoric acid modified steel slag 32%, calcined desulfurized gypsum 10%, composite alkali activator 9%, auxiliary functional components 3%.

[0118] In the compound alkali activator, the mass ratio of rice husk ash extract to sodium carbonate is 1:4.

[0119] Among the auxiliary functional components, the mass ratio of polycarboxylate superplasticizer to sodium alginate is 5:1.

[0120] Example 3:

[0121] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that: in step (3), the dried raw materials are accurately weighed by weight percentage:

[0122] Granulated blast furnace slag 52%, phosphoric acid modified steel slag 25%, calcined desulfurized gypsum 12%, composite alkali activator 9%, auxiliary functional components 2%.

[0123] In the compound alkali activator, the mass ratio of rice husk ash extract to sodium carbonate is 1:2.

[0124] Among the auxiliary functional components, the mass ratio of polycarboxylate superplasticizer to sodium alginate is 3:1.

[0125] Example 4:

[0126] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that: in step (3), the dried raw materials are accurately weighed by weight percentage:

[0127] Granulated blast furnace slag 48%, phosphoric acid modified steel slag 35%, calcined desulfurized gypsum 9%, composite alkali activator 5%, auxiliary functional components 3%.

[0128] In the compound alkali activator, the mass ratio of rice husk ash extract to sodium carbonate is 1:5; in the auxiliary functional components, the mass ratio of polycarboxylate water-reducing agent to sodium alginate is 6:1.

[0129] Example 5:

[0130] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that the mass ratio of steel slag and phosphoric acid solution in step (1) is 1:2.

[0131] Example 6:

[0132] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that the mass ratio of steel slag and phosphoric acid solution in step (1) is 1:3.

[0133] Example 7:

[0134] The method for preparing the soil solidification agent in this embodiment differs from that in Example 1 in that the mass ratio of steel slag and phosphoric acid solution in step (1) is 1:4.

[0135] Comparative Example 1:

[0136] The preparation method of the soil solidification agent in this comparative example differs from that in Example 1 in that: in step (3), the phosphoric acid modified steel slag is replaced by an equal amount of unmodified undisturbed steel slag.

[0137] Comparative Example 2:

[0138] The preparation method of the soil solidification agent in this comparative example differs from that in Example 1 in that: in step (3), the rice husk ash extract in the composite alkali activator is replaced with an equal amount of sodium carbonate.

[0139] Comparative Example 3:

[0140] The preparation method of the soil stabilizer in this comparative example differs from that in Example 1 in that: in step (3), sodium carbonate in the composite alkali activator is replaced with rice husk ash extract in equal amounts.

[0141] Comparative Example 4:

[0142] The preparation method of the soil stabilizer in this comparative example differs from that in Example 1 in that: in step (3), sodium alginate in the auxiliary functional component is replaced with polycarboxylate superplasticizer in equal amounts.

[0143] Comparative Example 5:

[0144] The preparation method of the soil stabilizer in this comparative example differs from that in Example 1 in that: in step (1), the 10% phosphoric acid solution is replaced by an equal amount of 20% phosphoric acid solution.

[0145] Comparative Example 6:

[0146] A commercially available alkali-activated slag-based curing agent for soft soil solidification was selected. Its main components are slag, cement clinker, sodium sulfate, etc., and it meets the general product technical indicators in the JG / T575-2020 standard "Soft Soil Curing Agent".

[0147] Experimental example:

[0148] 1. Structural characterization

[0149] (1) The product (powder with water content ≤1%) of step (1) in Examples 1-7 was tested by a laser particle size analyzer to test its specific surface area. The test results are shown in Table 1.

[0150] (2) The product (powder with a water content ≤1%) from step (1) of Example 1 was subjected to X-ray diffraction (XRD) testing. The X-ray diffraction (XRD) analysis showed (see Figure 1 The product of step (1) shows obvious characteristic diffraction peaks of calcium phosphate at 20.9° (2θ), indicating that the product of step (1) in Example 1 includes the calcium phosphate phase.

[0151] (3) The products of step (1) in Examples 1-7 were tested by X-ray diffraction (XRD) and then quantitatively analyzed by Rietveld full spectrum fitting to determine the content of calcium phosphate phase (mainly CaHPO4·2H2O). The results are shown in Table 1.

[0152] (4) The product from step (2) of Example 1 was analyzed by the silicomolybdenum blue spectrophotometric method. The results showed that the content of active SiO2 in the extract was 45%, and the content was further determined by... 29 Si NMR analysis confirmed that more than 85% of the silicon in the above-mentioned active SiO2 exists in the form of highly active Q3 and Q4 units.

[0153] Table 1:

[0154]

[0155] As can be seen from Examples 1-7 and Table 1, the specific surface area of ​​the soil stabilizer prepared in Examples 1-7 and the content of calcium phosphate phase in phosphoric acid modified steel slag are both within the limits specified in this application.

[0156] 2. Performance Testing:

[0157] (1) Unconfined compressive strength (UCS): The test was conducted according to method T0805-1994 in JTGE51-2009 "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering". The curing agent was mixed with the soil to be cured (silt or saline soil) in a certain proportion, compacted and formed into cylindrical specimens with a diameter of Φ50mm×H50mm. The specimens were then cured under standard curing conditions (temperature 20±2°C, humidity ≥95%) until the specified age before testing.

[0158] (2) Heavy metal leaching toxicity: The leachate was prepared according to HJ / T299-2007 "Leaching Toxicity of Solid Waste Leaching Method Sulfuric Acid Nitric Acid Method", and the concentrations of Pb, Cr, Cd and other ions were determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0159] (3) Chloride ion fixation rate: Refer to the relevant methods in JTS / T 236-2019 "Technical Specification for Testing and Inspection of Concrete in Water Transport Engineering" to determine the acid-soluble chloride ion content before and after solidification of saline soil and in the solidified body, and calculate the fixation rate.

[0160] (4) Salt-freezing cycle test: Refer to the rapid freezing method in GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", but replace the water medium with 5% NaCl solution. The UCS of the 28-day standard cured specimen is used as the initial strength. After a certain number of cycles (e.g., 5 times), the remaining strength is tested until the strength loss rate reaches 25% or the number of cycles reaches the set upper limit. Record the number of cycles and the strength loss rate after 30 salt-freezing cycles.

[0161] A. The curing agents of Examples 1-7 and Comparative Examples 1-6 were applied to the first soil sample, with the curing agent dosage being 15% of the dry soil mass of the first soil sample. The first soil sample was taken from a river dredging project, with an initial moisture content of 85%, an organic matter content of 5.2%, a Pb content of 860 mg / kg, a Cr content of 420 mg / kg, and a Cd content of 35 mg / kg. The unconfined compressive strength and heavy metal leaching toxicity were tested using the above-mentioned unconfined compressive strength and heavy metal leaching toxicity test methods, and the test results are shown in Table 2.

[0162] B. The curing agents of Examples 1-7 and Comparative Examples 1-6 were applied to the second soil mass, with the curing agent dosage being 18% of the dry weight of the second soil mass. Cl in the second soil mass - The content was 1.2% (dry basis). The unconfined compressive strength, chloride ion fixation rate, and salt-freezing cycle test methods described above were used for determination. The appearance of the soil under cyclic salt-freezing conditions was also observed. The results of the determination and observation are shown in Table 3.

[0163] Table 2:

[0164]

[0165] In conjunction with Example 1 and Comparative Example 6, the soil stabilizer prepared in Example 1 was used to treat the first soil (i.e., soil with high water content and heavy metal contamination), while Comparative Example 6 used a commercially available conventional stabilizer to treat the first soil. Table 2 shows that the unconfined compressive strength of the first soil treated with the soil stabilizer of Example 1 was significantly higher than that of Comparative Example 6, and the concentrations of Pb, Cr, and Cd ions in the first soil were significantly lower than those in Comparative Example 6. This indicates that the soil stabilizer of the present invention exhibits good reactivity in high water content and contaminated soil, improves the stabilization ability of heavy metal ions, and enhances the early strength of the soil.

[0166] Compared to Example 1, the content of phosphoric acid-modified steel slag, the mass ratio of rice husk ash extract to sodium carbonate, and the mass ratio of polycarboxylate-based water-reducing agent to sodium alginate in the soil solidification agents of Examples 2-3 are the upper and lower limits set by this invention, respectively. The content of phosphoric acid-modified steel slag, the mass ratio of rice husk ash extract to sodium carbonate, and the mass ratio of polycarboxylate-based water-reducing agent to sodium alginate in Example 4 are outside the range set by this invention. As shown in Table 2, the lateral confined compressive strength and the concentrations of Pb, Cr, and Cd ions in the first soil treated in Examples 2-3 are comparable to those in Example 1 and significantly better than those in Comparative Example 6. However, the lateral confined compressive strength of the first soil treated in Example 4 is significantly lower than that in Example 1, and the concentrations of Pb, Cr, and Cd ions are significantly higher than those in Example 1. This demonstrates that limiting the content of phosphoric acid-modified steel slag, the mass ratio of rice husk ash extract to sodium carbonate, and the mass ratio of polycarboxylate-based water-reducing agent to sodium alginate in the soil stabilizer within the range set by this invention enables the soil stabilizer to maintain good reactivity in high-moisture and contaminated soils, improves its stabilization ability for heavy metal ions, and enhances the early strength of the soil.

[0167] Compared to Example 1, the mass ratio of steel slag to phosphoric acid solution in the soil stabilizer of Examples 5-6 is the upper and lower limit set by this invention, respectively. The mass ratio of steel slag to phosphoric acid solution in Example 7 is outside the range set by this invention. As shown in Table 2, the lateral confined compressive strength and the concentrations of Pb, Cr, and Cd ions in the first soil treated in Examples 5-6 are comparable to those in Example 1 and significantly better than those in Comparative Example 6. However, the lateral confined compressive strength of the first soil treated in Example 7 is significantly lower than that in Example 1, and the concentrations of Pb, Cr, and Cd ions are significantly higher than those in Example 1. This indicates that limiting the mass ratio of steel slag to phosphoric acid solution in the soil stabilizer to the range set by this invention allows the soil stabilizer to maintain good reactivity in high-moisture and contaminated soils, improves its stabilization ability for heavy metal ions, and enhances the early strength of the soil.

[0168] Compared to Example 1, Comparative Example 1 replaced the phosphoric acid-modified steel slag with an equal amount of unmodified undisturbed steel slag. Table 2 shows that the unconfined compressive strength of the first soil sample treated with the soil stabilizer in Comparative Example 1 was significantly lower than that in Example 1, and the concentrations of Pb, Cr, and Cd ions in the first soil sample were significantly higher than those in Example 1. This indicates that the soil stabilizer prepared using phosphoric acid-modified steel slag exhibits good reactivity in high-moisture and contaminated soils, improves the stabilization capacity for heavy metal ions, and enhances the early strength of the soil.

[0169] Compared to Example 1, Comparative Example 2 replaced the rice husk ash extract in the composite alkali activator with an equal amount of sodium carbonate, and Comparative Example 3 replaced the sodium carbonate in the composite alkali activator with an equal amount of rice husk ash extract. Table 2 shows that the unconfined compressive strength of the first soil sample treated with the soil stabilizer in Comparative Examples 2-3 was significantly lower than that in Example 1, and the concentrations of Pb, Cr, and Cd ions in the first soil sample were significantly higher than those in Example 1. This indicates that the soil stabilizer prepared by combining sodium carbonate and rice husk ash extract still exhibits good reactivity in high-moisture and contaminated soils, improves the stabilization ability of heavy metal ions, and enhances the early strength of the soil.

[0170] Compared to Example 1, Comparative Example 4 replaced sodium alginate in the auxiliary functional component with an equal amount of polycarboxylate superplasticizer. Table 2 shows that the unconfined compressive strength of the first soil sample treated with the soil stabilizer in Comparative Example 4 was significantly lower than that in Example 1, and the concentrations of Pb, Cr, and Cd ions in the first soil sample were significantly higher than those in Example 1. This indicates that the soil stabilizer prepared by combining sodium alginate and polycarboxylate superplasticizer exhibits good reactivity in high-moisture and contaminated soils, improves the stabilization capacity for heavy metal ions, and enhances the early strength of the soil.

[0171] Table 3:

[0172]

[0173] Based on Example 1, Comparative Example 6, and Table 3, it can be seen that the unconfined compressive strength, chloride ion solidification rate, and number of salt-freezing cycles of the second soil (i.e., saline soil) treated with the soil solidifier of Example 1 are significantly higher than those of Comparative Example 6, and the salt-freezing strength loss rate is significantly lower than that of Comparative Example 6. This indicates that the soil solidifier of the present invention can still maintain good reactivity in saline soil, improve durability under chloride ion conditions, and enhance the early strength of the soil.

[0174] Based on Examples 2-4 and Table 3, it can be seen that the unconfined compressive strength, chloride ion solidification rate, salt-freezing cycle count, and salt-freezing strength loss rate of the soil treated in Examples 2-3 are comparable to or slightly lower than those of Example 1, and significantly better than Comparative Example 6. However, the lateral confined compressive strength, chloride ion solidification rate, and salt-freezing cycle count of the second soil treated in Example 4 are significantly lower than those of Example 1, and the salt-freezing strength loss rate is significantly higher than that of Example 1. This indicates that limiting the content of phosphoric acid-modified steel slag, the mass ratio of rice husk ash extract to sodium carbonate, and the mass ratio of polycarboxylate-based water-reducing agent to sodium alginate in the soil solidifier to the range set by this invention allows the soil solidifier to maintain good reactivity in saline soil, improves durability under chloride ion conditions, and enhances the early strength of the soil.

[0175] Based on Examples 5-7 and Table 3, it can be seen that the unconfined compressive strength, chloride ion solidification rate, number of salt-freezing cycles, and salt-freezing strength loss rate of the second soil treated in Examples 5-6 are comparable to those of Example 1 and significantly better than those of Comparative Example 6. However, the unconfined compressive strength, chloride ion solidification rate, and number of salt-freezing cycles of the second soil treated in Example 7 are significantly lower than those of Example 1, and the salt-freezing strength loss rate is significantly higher than that of Example 1. This indicates that limiting the mass ratio of steel slag and phosphoric acid solution in the soil solidifier to the range set by this invention allows the soil solidifier to maintain good reactivity in saline soil, improves durability under chloride ion conditions, and enhances the early strength of the soil.

[0176] Based on Comparative Example 1 and Table 3, it can be seen that the unconfined compressive strength, chloride ion solidification rate, and number of salt-freezing cycles of the second soil treated with the soil solidifier in Comparative Example 1 are significantly lower than those in Example 1, while the salt-freezing strength loss rate is significantly higher than that in Example 1. This indicates that the soil solidifier prepared using phosphoric acid-modified steel slag can still exhibit good reactivity in saline soil, improve durability under chloride ion conditions, and enhance the early strength of the soil.

[0177] Based on Comparative Examples 2-3 and Table 3, it can be seen that the unconfined compressive strength, chloride ion solidification rate, and number of salt-freezing cycles of the second soil treated with the soil stabilizer in Comparative Examples 2-3 were significantly lower than those in Example 1, while the salt-freezing strength loss rate was significantly higher than that in Example 1. This indicates that the soil stabilizer prepared by compounding sodium carbonate and rice husk ash extract can still exhibit good reactivity in saline soil, improve durability under chloride ion conditions, and enhance the early strength of the soil.

[0178] Based on Comparative Example 4 and Table 3, it can be seen that the unconfined compressive strength, chloride ion curing rate, and number of salt-freezing cycles of the second soil treated with the soil stabilizer in Comparative Example 4 are significantly lower than those in Example 1, while the salt-freezing strength loss rate is significantly higher than that in Example 1. This indicates that the soil stabilizer prepared by compounding sodium alginate and polycarboxylate superplasticizer can still exhibit good reactivity in saline soil, improve durability under chloride ion conditions, and enhance the early strength of the soil.

[0179] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A soil stabilizing agent, characterized in that: It includes phosphoric acid modified steel slag, wherein the phosphoric acid modified steel slag includes a calcium phosphate phase.

2. The soil solidification agent according to claim 1, characterized in that: The calcium phosphate phase is CaHPO4·2H2O; and / or, The calcium phosphate phase in the phosphoric acid-modified steel slag contains 8-15%; and / or, The specific surface area of ​​the phosphoric acid modified steel slag is ≥550 m². 2 / kg.

3. The soil stabilizing agent according to claim 1 or 2, characterized in that: It also includes slag and a composite alkali activator, wherein the composite alkali activator comprises rice husk ash extract and sodium carbonate in a mass ratio of 1:(2-4), wherein the rice husk ash extract contains amorphous SiO2; and / or, It also includes auxiliary functional components, which include a polycarboxylate superplasticizer and sodium alginate in a mass ratio of (3-5):

1.

4. The soil solidification agent according to claim 3, characterized in that: The active SiO2 content in the rice husk ash extract is ≥40% on a dry basis, and the proportion of amorphous SiO2 to active SiO2 is ≥85%.

5. The soil solidification agent according to claim 3, characterized in that: The phosphoric acid-modified steel slag is prepared by a method comprising the following steps: mixing steel slag with a phosphoric acid solution, stirring and reacting at 65-75°C for 3-4 hours, and filtering to obtain phosphoric acid-modified steel slag; and / or, The rice husk ash extract is prepared by a method comprising the following steps: hydrothermal extraction of rice husk ash with an amorphous SiO2 content exceeding 90% at 85-95℃ for 4-5 hours, followed by filtration and concentration to a solid content of not less than 35%, thereby obtaining the rice husk ash extract; and / or, The water reduction rate of the polycarboxylate superplasticizer is ≥30%; and / or, The viscosity-average molecular weight of the sodium alginate is 180,000-220,000.

6. The soil solidification agent according to claim 5, characterized in that, According to the percentage content by mass, it includes: Slag 45-54%, phosphoric acid modified steel slag 25-32%, desulfurized gypsum 9-12%, composite alkali activator 5-9%, auxiliary functional components 1.5-3%; and / or, The phosphoric acid solution has a mass concentration of 8-12%, and the mass ratio of the steel slag to the phosphoric acid solution is 1:(2-3).

7. A method for preparing a soil consolidation agent as described in any one of claims 3-6, characterized in that, Includes the following steps: The phosphoric acid-modified steel slag is mixed with other raw material components, including at least one of slag, desulfurized gypsum, composite alkali activator, and auxiliary functional components, to obtain the soil solidification agent.

8. The preparation method according to claim 7, characterized in that, The mixing process includes the following steps: First, premix the slag with the composite alkali activator for 10-15 minutes; Then add the phosphoric acid modified steel slag, desulfurized gypsum and auxiliary functional components, mix for 40-50 minutes, and control the material temperature ≤40℃ during the mixing process to obtain the soil solidification agent.

9. A curing method, characterized in that: The step includes using the soil solidifying agent according to any one of claims 1-6 as a solidifying agent to solidify the soil.

10. The curing method according to claim 9, characterized in that: The soil includes at least one of high water content soil, heavy metal contaminated soil and saline soil. The water content of high water content soil is ≥80%. The heavy metal contaminated soil contains Pb content ≥500mg / kg, Cr content ≥300mg / kg and Cd content ≥20mg / kg. The chloride ion content of saline soil is ≥0.5%.

Images