A curing material for ground pile grouting, its preparation method, and grouting construction method thereof.

Abstract

This application provides a curing material for grouting of ground piles, its preparation method, and grouting construction method. The curing material comprises the following components in parts by weight: 48-52 parts of volcanic ash ultrafine powder, 22-26 parts of calcined diatomaceous earth, 14-17 parts of modified metakaolin, 1.8-2.5 parts of composite retarder stabilizer, 3.8-5.0 parts of nano-silica sol, 1.0-1.4 parts of lignin sulfonate modified dispersant, and 0.2-0.35 parts of trace coagulant accelerator. The chemical composition of the volcanic ash ultrafine powder, by mass percentage, is: SiO2 64%-67%, Al2O3 21%-25%, Fe2O3 5%-6%, CaO 3%-4%, MgO 1%-2%. The modified metakaolin is obtained by surface modification of metakaolin with aluminum dihydrogen phosphate solution. The trace coagulant accelerator is a compound of nano-zinc oxide and lithium carbonate in a mass ratio of 5:1. This invention significantly slows down the hydration reaction rate.

Description

Technical Field

[0001] This application belongs to the field of curing agent technology, specifically relating to a curing material for ground pile grouting and its preparation method and grouting construction method. Background Technology

[0002] Current grouting and solidification materials for ground piles are mostly prepared with cement and blast furnace slag as the core components, combined with conventional dispersants, which has many drawbacks. Traditional cement-based materials have high heat of hydration, which can easily cause thermal expansion and cracking of the soil around the pile, affecting the stability of the pile. Although blast furnace slag-based materials have lower heat of hydration, particle settling is severe, and bleeding and segregation are likely to occur after grouting, with a high risk of pipe blockage. Existing dispersants have poor compatibility, mostly targeting single cement or slag systems. In composite systems, uneven dispersion and subsequent strength reduction are likely to occur. In addition, existing materials have weak erosion resistance in water-rich strata, are easily diluted and lost by groundwater after grouting, have insufficient solidified body strength, and have not optimized particle size distribution for the porosity characteristics of different geological conditions, resulting in poor grouting penetration. They are unable to meet the long-term stability requirements of pile foundations under complex geological conditions, and have shortcomings in construction adaptability and durability. Summary of the Invention

[0003] This application provides a solidification material for grouting of ground piles, its preparation method, and grouting construction method. The invention aims to solve four core problems of existing ground pile grouting solidification materials: First, excessive heat of hydration leads to cracking of the surrounding soil and uneven stress on the pile; second, poor material suspension stability results in easy settling and high bleeding rate, causing easy blockage of grouting pipes and low construction efficiency; third, weak erosion resistance in water-rich strata leads to easy loss of the solidified body and difficulty in achieving the required strength; fourth, unreasonable particle size distribution results in poor compatibility with geological porosity, insufficient penetration depth, poor uniformity of the solidified body, and weak durability. Simultaneously, it is necessary to avoid the core technical elements of existing patents such as blast furnace slag, graded cement, and acrylic dispersants, and develop a new type of grouting solidification material with wide adaptability, low heat of hydration, strong stability, and excellent erosion resistance to meet the long-term stability requirements of grouting construction in complex geological conditions such as soft soil and gravel layers, thereby reducing construction risks and subsequent maintenance costs.

[0004] On one hand, embodiments of the present invention provide a curing material for grouting of ground piles, comprising the following components in parts by weight: 48-52 parts of volcanic ash ultrafine powder, 22-26 parts of calcined diatomaceous earth, 14-17 parts of modified metakaolin, 1.8-2.5 parts of composite retarder stabilizer, 3.8-5.0 parts of nano silica sol, 1.0-1.4 parts of lignin sulfonate modified dispersant, and 0.2-0.35 parts of trace coagulation accelerator; The particle size of the volcanic ash ultrafine powder is 0.9-4.8μm, and the specific surface area is 9000-11000cm² / g. Its chemical composition by mass percentage is: SiO2 64%-67%, Al2O3 21%-25%, Fe2O3 5%-6%, CaO 3%-4%, MgO 1%-2%. The particle size of calcined diatomaceous earth is 1.5μm-6.0μm, the specific surface area is 7500cm² / g-9000cm² / g, the porosity is 68%-72%, and the organic matter content is ≤1.5%. Modified metakaolin is prepared by surface modification of metakaolin with aluminum dihydrogen phosphate solution, and the particle size after modification is ≤5μm. The trace coagulant is a compound of nano zinc oxide and lithium carbonate in a mass ratio of 5:1.

[0005] In one optional embodiment, the lignin sulfonate modified dispersant is prepared by pyrolysis modification of sodium lignin sulfonate at 122-128°C for 32-38 minutes, with nitrogen gas purging during the pyrolysis process.

[0006] In one optional embodiment, the composite retarding stabilizer is prepared by compounding trisodium citrate, sodium gluconate, and anhydrous borax in a mass ratio of (2.8-3.2):(1.0-1.2):(0.8-1.0).

[0007] In one optional embodiment, the nano-silica sol is an alkaline silica sol with a solid content of 30wt%-33wt%, a particle size of 20nm-25nm, a pH value of 8.8-9.2, and a viscosity of 5mPa·s-8mPa·s.

[0008] In another aspect, a method for preparing a low-heat-of-hydration, high-stability curing material for ground pile grouting, as described in any of the above claims, is provided, characterized by comprising the following steps: S1. Raw material pretreatment: Volcanic ash ultrafine powder and calcined diatomaceous earth are passed through a 160-200 mesh sieve, and modified metakaolin, composite retarder stabilizer, lignin sulfonate modified dispersant and trace amount of coagulation aid are passed through a 180-220 mesh sieve; nano silica sol is sealed and stored. S2. Dry material premixing: Weigh each pretreated solid raw material according to the ratio, put them into a dry powder mixer, and mix them at a speed of 40-50 r / min for a total mixing time of 16-20 min; S3. Adding wet materials and high-speed stirring: Transfer the dry material mixture into a high-speed stirring vessel and stir at a speed of 80-90 r / min. At the same time, add nano-silica sol dropwise at a rate of 0.8-1.2 L / min. After the dropwise addition is completed, continue stirring for 10-14 min and control the temperature inside the vessel to ≤35℃. S4. Finished product screening and packaging: The well-stirred slurry is screened through a 100-140 mesh vibrating screen. After screening, the finished product is allowed to cool naturally to room temperature and then sealed in a moisture-proof composite film.

[0009] In one optional embodiment, in step S2, the stirring method is as follows: first, premix at 35-45 r / min for 4-6 min, and then increase the speed to 45-55 r / min and stir for 11-15 min.

[0010] In one optional embodiment, in step S4, the storage conditions after packaging the finished product are: temperature 15-30℃, humidity ≤50%, finished product moisture content 1.8-2.2%, and loose density 0.75-0.85g / cm³.

[0011] Furthermore, a grouting construction method using any of the aforementioned curing materials is provided, comprising the following steps: Adjust the water-material ratio according to the porosity of the geological conditions: the water-material ratio is 0.9-1.1 for soft soil, 1.3-1.7 for sand and gravel layers, and 1.0-1.2 for ordinary silty soil. Mix the solidification material with water, first stirring at a low speed of 30-40 r / min for 2-3 min, then stirring at a high speed of 70-80 r / min for 5-7 min to obtain the grouting slurry. Grouting is carried out using grouting equipment, with the grouting pressure controlled at 0.4-0.7MPa and the grouting speed controlled at 25-35L / min. The grouting pipe is lifted uniformly from the bottom of the pile to the top of the pile at a speed of 0.5-1.0m / min.

[0012] In one alternative embodiment, when the pile diameter is ≤800mm, the grouting pressure is 0.4MPa-0.5MPa and the grouting speed is 25L / min-30L / min; when the pile diameter is >800mm, the grouting pressure is 0.5MPa-0.7MPa and the grouting speed is 30L / min-35L / min.

[0013] In one optional embodiment, the prepared grout has a bleeding rate of ≤1.0% after standing for 50-70 minutes, and a funnel viscosity of 25-35s. After grouting is completed, allow it to stand for 7-14 days to cure at a temperature of 15-30℃. The compressive strength of the cured body after 28 days is 9.0-11.0 MPa. The permeability coefficient of the cured body at 28 days is ≤8×10 -8 cm / s, erosion resistance ≤4%.

[0014] The curing material of the present invention achieves the following significant effects: First, the curing material of this invention uses low-calcium volcanic ash ultrafine powder (CaO only 3-4%) as the main cementitious component, replacing the high-calcium minerals (CaO about 60-65%) in traditional cement, significantly slowing down the hydration reaction rate. Simultaneously, the geopolymerization reaction of modified metakaolin is a condensation reaction, with an exothermic heat release only 1 / 3 to 1 / 2 of that of silicate cement hydration. The combined effect of these two factors results in the peak hydration heat of the curing material of this invention being approximately 40% lower than that of 42.5 grade ordinary silicate cement, with a maximum temperature rise not exceeding 45°C. This characteristic effectively avoids the risk of cracking of the soil around the pile due to thermal expansion after grouting, ensuring the integrity of the pile-soil interface and the stable performance of side friction resistance. Second, the high porosity (68-72%) of the calcined diatomaceous earth in the curing material of this invention locks in free water through capillary adsorption, physically inhibiting water seepage; the lignin sulfonate modified dispersant adsorbs onto the particle surface to form a hydration film, preventing particle sedimentation from a colloidal chemical perspective; and nano-silica sol fills submicron-level pores, reducing the space for free particle movement. The synergistic effect of these three factors ensures that the bleeding rate of the grout after 60 minutes of settling is controlled to within 1.0%, far lower than the 5-8% of traditional cement grout. This not only prevents blockage of the grouting pipes but also ensures the uniformity of the solidified body along the height of the pile after grouting, avoiding the problems of excessive water-cement ratio and low strength in the upper grout caused by settlement. Third, the rigid micro-framework of calcined diatomaceous earth in the solidification material of this invention plays a role similar to crushed stone reinforcement in the solidified body. When subjected to groundwater erosion, these particles can resist the shear force generated by the water flow, preventing the gel matrix from being peeled off. At the same time, the geopolymer gel generated by modified metakaolinite forms a strong interfacial bond with the diatomaceous earth particles through chemical bonding, rather than simple physical encapsulation. It is particularly suitable for pile foundation engineering in water-rich sandy gravel layers. Fourth, the nano-silica sol in the solidification material of this invention fills the voids between micron-sized particles, giving the grout a high bulk density before solidification. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the low-carbon solidification method for soft soil provided in this application. Detailed Implementation

[0016] The present application will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0017] The following detailed descriptions are exemplary and intended to provide further detailed explanation of this application. Unless otherwise specified, all technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application.

[0018] This invention provides a curing material for grouting of ground piles, comprising the following components in parts by weight: 48-52 parts of volcanic ash ultrafine powder, 22-26 parts of calcined diatomaceous earth, 14-17 parts of modified metakaolin, 1.8-2.5 parts of composite retarder stabilizer, 3.8-5.0 parts of nano-silica sol, 1.0-1.4 parts of lignin sulfonate modified dispersant, and 0.2-0.35 parts of trace coagulation accelerator; The particle size of the volcanic ash ultrafine powder is 0.9-4.8μm, the specific surface area is 9000-11000cm² / g, and its chemical composition by mass percentage is: SiO2 64%-67%, Al2O3 21%-25%, Fe2O3 5%-6%, CaO 3%-4%, MgO 1%-2%; The particle size of calcined diatomaceous earth is 1.5μm-6.0μm, the specific surface area is 7500cm² / g-9000cm² / g, the porosity is 68%-72%, and the organic matter content is ≤1.5%. Modified metakaolin is prepared by surface modification of metakaolin with aluminum dihydrogen phosphate solution, and the particle size after modification is ≤5μm. The trace coagulant is a compound of nano zinc oxide and lithium carbonate in a mass ratio of 5:1.

[0019] The solidification material described in this application is specifically designed for grouting of ground piles in geotechnical engineering, particularly for pile foundation reinforcement and water-stopping construction under complex geological conditions such as soft soil, gravel layers, and silty clay. During construction, the material is mixed with water to form a slurry, which is then pumped into the pores of the soil surrounding the pile. The slurry gradually solidifies to form a dense, low-permeability solidified body, thereby increasing the pile's side friction resistance, reducing the permeability of the foundation, and preventing erosion damage to the soil around the pile under the action of water flow.

[0020] This application controls the particle size of ultrafine volcanic ash powder to 0.9-4.8 μm, with a specific surface area of ​​9000-11000 cm² / g. These extremely fine particles possess a large number of unsaturated surface active sites. The combined content of SiO₂ and Al₂O₂ in its chemical composition exceeds 80%, while the CaO content is only 3-4%, classifying it as a low-calcium volcanic ash material. When mixed with water, under alkaline conditions (pH 8.8-9.2 provided by nano-silica sol), these active silica-alumina components slowly dissolve, reacting with the small amount of Ca²⁺ they carry. + The silanol provided by the nano-silica sol reacts to generate hydrated calcium silicate (CSH) and hydrated calcium aluminate with a low calcium-to-silica ratio. Due to the low calcium content, the hydration reaction rate is slow, and the exothermic process is mild and long-lasting, avoiding the drastic temperature rise caused by the rapid hydration of high-calcium minerals (C3S, C2S) in traditional silicate cement.

[0021] Calcined diatomaceous earth has a particle size of 1.5-6.0 μm, a specific surface area of ​​7500-9000 cm² / g, and a porosity of 68-72%. These microporous structures can lock excess free water in the slurry within the pores through capillary adsorption, thus significantly reducing the bleeding rate. Simultaneously, the diatomaceous earth particles themselves are chemically inert and do not participate in early rapid hydration. Instead, they act as a rigid microskeleton, uniformly distributed in the slurry. This hinders the settling of other cementing particles and increases the overall erosion resistance after solidification. When impacted by groundwater flow, these rigid particles can resist the shear force of the water flow, preventing the surface of the solidified body from peeling off.

[0022] Modified metakaolin is produced by calcining kaolin and then surface-modifying it with aluminum dihydrogen phosphate solution. While ordinary metakaolin possesses high pozzolanic activity, its uneven surface charge distribution makes it prone to localized agglomeration in composite systems. After aluminum dihydrogen phosphate modification, an aluminum phosphate coordination compound layer forms on the surface of the metakaolin particles. This layer not only prevents particle agglomeration through steric hindrance but also undergoes slow hydrolysis in the early stages of hydration, continuously releasing Al³⁺. + and PO4³ - Al³ + Reacting with silicate ions dissolved from volcanic ash, a three-dimensional network structure of aluminosilicate geopolymer is generated. This gel has high chemical bond energy and a dense structure, capable of filling micron-sized pores and reducing the permeability coefficient to 10. -8 On the order of cm / s.

[0023] The trace coagulation accelerator is a mixture of nano-zinc oxide and lithium carbonate in a 5:1 mass ratio. The nano-zinc oxide, with a particle size of 60-90 nm, acts as heterogeneous nuclei, providing nucleation sites for hydration products and accelerating early strength development. Lithium carbonate, on the other hand, disrupts the network structure of silicon-oxygen and aluminum-oxygen bonds, promoting the dissolution of the active components. The synergistic effect of these two components, even at extremely low dosages (only 0.2-0.35 parts), can shorten the initial coagulation time from over 10 hours under natural conditions to 5-7 hours, without generating additional heat of hydration. This is because the catalysis targets the already existing mild hydration reaction, rather than introducing a highly exothermic reaction.

[0024] Lignosulfonate-modified dispersant, composite retarder stabilizer, and nano-silica sol work synergistically to maintain the homogeneity and fluidity of the slurry. The dispersant adsorbs onto the particle surface to form a hydration film, preventing agglomeration; the trisodium citrate in the composite retarder stabilizer complexes with Ca²⁺. + The initial setting time is controlled, sodium gluconate enhances the stability of the hydration film, and anhydrous borax prolongs the final setting time and improves durability; nano-silica sol fills the gaps between particles, optimizes the gradation, and participates in the gelation reaction.

[0025] The curing material of the present invention achieves the following significant effects: First, the curing material of this invention uses low-calcium volcanic ash ultrafine powder (CaO only 3-4%) as the main cementitious component, replacing the high-calcium minerals (CaO about 60-65%) in traditional cement, significantly slowing down the hydration reaction rate. Simultaneously, the geopolymerization reaction of modified metakaolin is a condensation reaction, with an exothermic heat release only 1 / 3 to 1 / 2 of that of silicate cement hydration. The combined effect of these two factors results in the peak hydration heat of the curing material of this invention being approximately 40% lower than that of 42.5 grade ordinary silicate cement, with a maximum temperature rise not exceeding 45°C. This characteristic effectively avoids the risk of cracking of the soil around the pile due to thermal expansion after grouting, ensuring the integrity of the pile-soil interface and the stable performance of side friction resistance. Second, the high porosity (68-72%) of the calcined diatomaceous earth in the curing material of this invention locks in free water through capillary adsorption, physically inhibiting water seepage; the lignin sulfonate modified dispersant adsorbs onto the particle surface to form a hydration film, preventing particle sedimentation from a colloidal chemical perspective; and nano-silica sol fills submicron-level pores, reducing the space for free particle movement. The synergistic effect of these three factors ensures that the bleeding rate of the grout after 60 minutes of settling is controlled to within 1.0%, far lower than the 5-8% of traditional cement grout. This not only prevents blockage of the grouting pipes but also ensures the uniformity of the solidified body along the height of the pile after grouting, avoiding the problems of excessive water-cement ratio and low strength in the upper grout caused by settlement. Third, the rigid micro-framework of calcined diatomaceous earth in the solidification material of this invention plays a role similar to crushed stone reinforcement in the solidified body. When subjected to groundwater erosion, these particles can resist the shear force of the water flow and prevent the gel matrix from being peeled off. At the same time, the geopolymer gel generated by the modified metakaolinite forms a strong interfacial bond with the diatomaceous earth particles through chemical bonding, rather than a simple physical encapsulation. It is particularly suitable for pile foundation engineering in water-rich sandy gravel layers. Fourth, the nano-silica sol in the solidification material of this invention fills the voids between micron-sized particles, giving the grout a high bulk density before solidification.

[0026] For example, the mass fraction of volcanic ash ultrafine powder can be 48, 49, 50, 51, or 52; calcined diatomaceous earth can be 22, 23, 24, 25, or 26; modified metakaolin can be 14, 15, 16, or 17; composite retarder stabilizer can be 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5; nano silica sol can be 3.8, 4.0, 4.2, 4.5, 4.8, or 5.0; lignin sulfonate modified dispersant can be 1.0, 1.1, 1.2, 1.3, or 1.4; and trace amount of coagulating aid can be 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, or 0.35.

[0027] The particle size of the volcanic ash ultrafine powder can be 0.9, 1.5, 2.0, 3.0, 4.0, or 4.8 μm; the specific surface area can be 9000, 9500, 10000, 10500, or 11000 cm² / g; the SiO₂ content can be 64%, 65%, 66%, or 67%; the Al₂O₃ content can be 21%, 22%, 23%, 24%, or 25%; the Fe₂O₃ content can be 5%, 5.5%, or 6%; the CaO content can be 3%, 3.5%, or 4%; and the MgO content can be 1%, 1.5%, or 2%.

[0028] The particle size of calcined diatomaceous earth can be 1.5, 2.0, 3.0, 4.0, 5.0, or 6.0 μm; the specific surface area can be 7500, 8000, 8500, or 9000 cm² / g; the porosity can be 68%, 69%, 70%, 71%, or 72%; and the organic matter content can be 0.5%, 1.0%, or 1.5%.

[0029] The particle size of modified metakaolin can be 1, 2, 3, 4, or 5 μm.

[0030] The mass ratio of nano zinc oxide to lithium carbonate in trace coagulant is strictly 5:1, for example, 5g:1g, 10g:2g, 15g:3g, etc.

[0031] In one optional embodiment, the lignin sulfonate modified dispersant is prepared by pyrolysis modification of sodium lignin sulfonate at 122-128°C for 32-38 minutes, with nitrogen gas purging during the pyrolysis process.

[0032] After the curing material is mixed with water, the dispersant needs to be rapidly adsorbed onto particles with different surface properties (volcanic ash, diatomaceous earth, metakaolin, etc.) to prevent them from agglomerating and settling due to gravity or Brownian motion. Ordinary sodium lignosulfonate has a low molecular weight and insufficient branching, resulting in limited dispersion in composite cementitious systems and a tendency for later bleeding and stratification. Therefore, its molecular structure needs to be appropriately modified.

[0033] Sodium lignosulfonate is a natural high-molecular-weight anionic surfactant. Its molecule consists of a hydrophobic aromatic ring backbone and hydrophilic sulfonate, phenolic hydroxyl, and alcoholic hydroxyl groups. Under intermediate temperature conditions of 122-128℃, some of the ether bonds (COC) in the molecule break, generating free radicals. These free radicals do not react with oxygen under nitrogen protection, but instead couple with each other to form longer-chain polymers. At the same time, pyrolysis causes the molecular conformation to gradually unfold from its original tightly coiled state, exposing the hydrophilic groups that were originally enclosed inside to the molecular surface.

[0034] The modified dispersant has more adsorption sites (sulfonate groups, phenolic hydroxyl groups) and longer molecular chains. When added to a slurry, sulfonate groups are adsorbed onto the surface of positively charged cementitious particles (such as Ca²⁺ in volcanic ash) via electrostatic interactions. + Site, Al³ in metakaolin + The long-chain hydrophobic framework extends into the aqueous phase, forming a three-dimensional hydration layer approximately 3-5 nm thick around the particles. Strong spatial repulsion forces are generated between the hydration layers of adjacent particles, effectively preventing particles from approaching and agglomerating.

[0035] The key role of nitrogen protection is that the aromatic rings in lignin are easily oxidized at high temperatures to form quinone-based colored substances. This not only darkens the color of the dispersant but also consumes phenolic hydroxyl groups, reducing its adsorption capacity for particles. Introducing nitrogen removes oxygen, ensuring the activity and appearance of the modified product.

[0036] Embodiments of the present invention After the above-described pyrolysis modification, the dispersant exhibits excellent compatibility in the composite gelling system of this invention: the initial fluidity is increased by more than 20% compared to the unmodified form, and the funnel viscosity is stable at 25-35 s; after standing for 2 hours, the particle settling rate in the slurry is less than 5%, while the control sample using the unmodified dispersant has a settling rate of more than 20% in the same time period. Simultaneously, this dispersant shows good compatibility with trisodium citrate and sodium gluconate in the composite retarder stabilizer, and will not fail due to calcium ion complexation like polycarboxylate dispersants, nor will it cause excessive adsorption on the metakaolin surface leading to abnormal retarding like acrylic dispersants. Furthermore, the pyrolysis process does not use toxic catalysts or organic solvents, making it environmentally friendly and cost-effective.

[0037] As an example, the pyrolysis temperature can be 122, 123, 124, 125, 126, 127, or 128°C; the pyrolysis time can be 32, 33, 34, 35, 36, 37, or 38 minutes. The nitrogen protection gas flow rate can be adjusted according to the reactor volume, for example, 0.5, 1.0, or 1.5 L / min.

[0038] In one optional embodiment, the composite retarding stabilizer is prepared by compounding trisodium citrate, sodium gluconate, and anhydrous borax in a mass ratio of (2.8-3.2):(1.0-1.2):(0.8-1.0).

[0039] During grouting, it often takes several hours for the grout to be injected into the pile hole after mixing, and the residence time of the grout in the pipeline varies depending on the grouting depth. If the grout sets too quickly (e.g., initial setting <3h), it may clog the pipeline or result in incomplete grouting; if the grout sets too slowly (e.g., initial setting >12h), the grout that has not yet solidified is easily washed away by water flow in strata rich in groundwater. Therefore, a compound retarder stabilizer is needed that can precisely control the setting time while maintaining the suspension stability of the grout.

[0040] Trisodium citrate (C6H5Na3O7·2H2O) is a potent complexing agent; its three carboxylate groups can react with Ca²⁺. + Forming a stable five-membered ring chelate, Ca²⁺ + It is locked in the solution, preventing it from combining with silicate and aluminate to form gelling products. This effect mainly influences the nucleation stage of the hydration reaction, thus having the most significant effect on prolonging the initial setting time. However, when trisodium citrate is used alone, the slurry is prone to stratification and sedimentation because Ca²⁺… + After being chelated, the electrostatic repulsion between particles is weakened.

[0041] Sodium gluconate (C6H) 11 Sodium gluconate (NaO7) molecules contain multiple hydroxyl groups and one carboxyl group. It primarily functions by adsorbing onto the particle surface. On one hand, the adsorbed layer increases steric hindrance between particles, inhibiting sedimentation; on the other hand, its hydroxyl groups can form hydrogen bonds with water molecules, thickening the hydration film on the particle surface and improving the water retention of the slurry. Sodium gluconate has a significant effect on Ca²⁺. + Its complexing ability is very weak, so its effect on the initial setting time is much smaller than that of trisodium citrate, but its role in stabilizing the slurry is indispensable.

[0042] Anhydrous borax (Na2B4O7) dissolves in water to form boric acid (H3BO3) and borate ions (B4O7²). - ). Borate and Ca² + The formation of insoluble calcium metaborate (CaB2O4) precipitate, covering the surface of unhydrated particles, further delays the final setting time. Furthermore, in an alkaline environment, boron can participate in the network construction of aluminosilicate gels in the form of borate ions, forming BO-Si or BO-Al bonds, thereby increasing the crosslinking density and long-term durability of the gel (such as resistance to sulfate attack and carbonization).

[0043] When the three components are blended in a ratio of (2.8-3.2):(1.0-1.2):(0.8-1.0), trisodium citrate dominates, controlling the initial setting time to 5-7 hours; sodium gluconate assists in stabilizing the slurry, reducing the bleeding rate to below 1.0% at 60 minutes; and anhydrous borax extends the final setting time to 10-12 hours and enhances the later-stage durability of the solidified body. The optimized ratio of the three components avoids the problems of slurry stratification when using trisodium citrate alone, insufficient retarding when using sodium gluconate alone, and excessively short initial setting time when using borax alone.

[0044] The embodiments of this invention employ the aforementioned compounding ratio, allowing for precise adjustment of the initial setting time of the grout to 5-7 hours and the final setting time to 10-12 hours, fully adapting to different grouting depths and construction rhythms. After standing for 3 hours, the bleeding rate remains below 0.5%, and the grout maintains a uniform suspension state throughout. After 180 days of water curing, the compressive strength of the cured body still increases by 5-8% compared to 28 days, while the control sample using single-component trisodium citrate retarder showed a 10-15% decrease in strength after 180 days. This demonstrates that the addition of anhydrous borax significantly improves long-term durability.

[0045] As an example, the mass ratio of trisodium citrate:sodium gluconate:anhydrous borax can be 2.8:1.0:0.8, 2.9:1.05:0.85, 3.0:1.1:0.9, 3.1:1.15:0.95, or 3.2:1.2:1.0. The total mass fraction of the composite retarder stabilizer in the cured material can be 1.8, 2.0, 2.2, 2.5, etc.

[0046] In one optional embodiment, the nano-silica sol is an alkaline silica sol with a solid content of 30wt%-33wt%, a particle size of 20nm-25nm, a pH value of 8.8-9.2, and a viscosity of 5mPa·s-8mPa·s.

[0047] In grouting materials, optimizing particle size distribution is crucial for grout permeability and solidified density. Volcanic ash ultrafine powder (0.9-4.8 μm) and calcined diatomaceous earth (1.5-6.0 μm) have micron-level particle sizes, while the interparticle voids range from tens to hundreds of nanometers, which cannot be filled by micron-sized particles. Nano-silica sol, with a particle size of 20-25 nm, can effectively fill these submicron-level pores, thereby improving the grout's bulk density and post-solution impermeability.

[0048] In alkaline nano-silica sol, SiO2 particles exist in an amorphous state with numerous silanol groups (Si-OH) on their surface. Under alkaline conditions (pH 8.8-9.2), some of these silanol groups ionize into Si-O. -This causes the particles to carry a negative charge on their surface, resulting in mutual repulsion and a stable dispersed state, preventing them from agglomerating. The low viscosity of 5-8 mPa·s ensures that the silica sol can diffuse rapidly in the slurry during the dropping process, without causing excessively high local concentrations.

[0049] When silica sol is mixed with cementing materials, the nanoparticles first diffuse into the gaps between the micron-sized particles through Brownian motion, acting as a physical filler and increasing the packing density of the particle system from approximately 0.65 in natural packing to over 0.75. Subsequently, Si-O... - With Ca² in the slurry + (From volcanic ash) The reaction produces hydrated calcium silicate gel with a low calcium-to-silica ratio (C / S molar ratio 0.8-1.0). This low-calcium gel has better chemical stability than the high-calcium CSH (C / S 1.5-2.0) produced by ordinary cement hydration, and is less prone to calcium dissolution and structural damage in water-rich environments.

[0050] In addition, nano-silica sol can also be adsorbed on the surface of modified metakaolin particles. The silanol on its surface undergoes a condensation reaction with the aluminum hydroxyl on the surface of metakaolin to form Si-O-Al bonds, which helps to promote the polymerization reaction and make the gel network more compact.

[0051] In this embodiment of the invention, after adding nano-silica sol, the 28-day permeability coefficient of the cured body never exceeded 10. -6 The speed decreased to the order of 8 × 10 cm / s -8 The flow rate is below cm / s, and the impermeability grade reaches P12 or above. After grouting in water-rich strata, the erosion resistance of the solidified body is ≤4%, while the mass loss of the control sample without nano-silica sol exceeds 15% under the same erosion conditions. In addition, the filling effect of silica sol and the formation of low-calcium gel reduce the drying shrinkage rate of the solidified body by more than 30%, effectively reducing microcracks caused by shrinkage.

[0052] As an example, the solid content of the nano-silica sol can be 30, 31, 32, or 33 wt%; the particle size can be 20, 21, 22, 23, 24, or 25 nm; the pH value can be 8.8, 8.9, 9.0, 9.1, or 9.2; and the viscosity (at 25°C) can be 5, 6, 7, or 8 mPa·s. The mass fraction in the cured material can be 3.8, 4.0, 4.2, 4.5, 4.8, or 5.0.

[0053] Please see Figure 1 On the other hand, the present invention provides a method for preparing a solidification material for ground pile grouting with low heat of hydration and high stability, characterized by comprising the following steps: Step S1. Raw material pretreatment: Volcanic ash ultrafine powder and calcined diatomaceous earth are passed through a 160-200 mesh sieve, and modified metakaolin, composite retarder stabilizer, lignin sulfonate modified dispersant and trace amount of coagulation aid are passed through a 180-220 mesh sieve; nano silica sol is sealed and stored.

[0054] Step S2. Dry material premixing: Weigh each pretreated solid raw material according to the ratio, put them into a dry powder mixer, and mix them at a speed of 40-50 r / min for a total mixing time of 16-20 min.

[0055] Step S3. Adding wet materials and high-speed stirring: Transfer the dry material mixture into a high-speed stirring vessel and stir at a speed of 80-90 r / min. At the same time, add nano-silica sol dropwise at a rate of 0.8-1.2 L / min. After the dropwise addition is complete, continue stirring for 10-14 min and control the temperature inside the vessel to ≤35℃.

[0056] Step S4. Finished product screening and packaging: The well-stirred slurry is screened through a 100-140 mesh vibrating screen. After screening, the finished product is allowed to cool naturally to room temperature and then sealed in a moisture-proof composite film.

[0057] The purpose of step S1, the sieving step, in this invention is to remove agglomerated particles formed during the transportation and storage of raw materials due to moisture absorption or static electricity. Volcanic ash ultrafine powder and calcined diatomaceous earth are sieved through a 160-200 mesh (approximately 75-100 μm) sieve, while finer components such as modified metakaolin are sieved through a 180-220 mesh (approximately 65-85 μm) sieve. This ensures that all particles entering the mixing process are in a monodisperse or micro-agglomerated state, preventing large particles from becoming the seeds for uneven mixing later. The nano-silica sol is stored in a sealed container to prevent it from absorbing CO2 from the air and lowering the pH value, as CO2 can cause the silica sol to gel.

[0058] In step S2, the rotation speed of 40-50 r / min and the total time of 16-20 min for dry material premixing are optimized parameters. If the rotation speed is too low or the time is too short, powders with large density differences cannot be fully mixed; if the rotation speed is too high or the time is too long, lightweight diatomaceous earth may be thrown against the cylinder wall due to centrifugal force, causing separation. The rotation speed and time range of this invention can ensure uniform mixing without stratification.

[0059] In step S3, when adding the wet material, the nano-silica sol is slowly added dropwise at a rate of 0.8-1.2 L / min, while maintaining stirring during the addition process. This is because the nano-silica sol has high surface activity; if added all at once or added too quickly, a high concentration will form in localized areas, causing colloidal particles to aggregate into macroscopic gel clusters due to collisions. Once these gel clusters form, they are difficult to disperse again, which can clog the grouting pipes or reduce the strength of the cured body. After the addition is complete, continue stirring for 10-14 minutes to allow the silica sol to fully diffuse and adsorb onto the surface of the solid particles. Controlling the reactor temperature to ≤35℃ is to prevent premature hydration triggered by heat generated from mechanical stirring or excessively high ambient temperatures, which would lead to an abnormal increase in slurry viscosity.

[0060] In step S4, passing the product through a 100-140 mesh (approximately 105-150 μm) vibrating sieve removes trace amounts of soft agglomerates that may form during stirring (usually caused by static electricity or weak adsorption), ensuring a fine, granule-free finished product. Natural cooling to room temperature before packaging prevents condensation and clumping inside the heat-sealed packaging. A moisture-proof composite film (such as aluminum-plastic film) effectively isolates water vapor, ensuring the product remains dry throughout its shelf life.

[0061] The cured material produced by the method of this invention exhibits a component content deviation of ≤±1.5% in random sampling tests, and its mixing uniformity is significantly higher than that of ordinary dry powder mixing equipment (typically with a deviation of ±5%). The finished product has a moisture content controlled between 1.8-2.2% and a loose density of 0.75-0.85 g / cm³, and even after 6 months of storage, its activity decay does not exceed 5%. In field use, the initial funnel viscosity of the grout fluctuates between batches by no more than ±2 seconds, demonstrating high construction stability.

[0062] As an example, in step S1, the sieve mesh size for volcanic ash and diatomaceous earth can be 160, 170, 180, 190, or 200 mesh; the sieve mesh size for other solids can be 180, 190, 200, 210, or 220 mesh. In step S2, the rotation speed can be 40, 42, 45, 48, or 50 r / min; the stirring time can be 16, 17, 18, 19, or 20 min. In step S3, the stirring speed can be 80, 85, or 90 r / min; the dropping rate can be 0.8, 0.9, 1.0, 1.1, or 1.2 L / min; the stirring time after dropping can be 10, 11, 12, 13, or 14 min; and the temperature inside the vessel can be controlled at 30, 32, or 35℃. In step S4, the sieve mesh size can be 100, 110, 120, 130, or 140 mesh.

[0063] In one optional embodiment, in step S2, the stirring method is as follows: first, premix at 35-45 r / min for 4-6 min, and then increase the speed to 45-55 r / min and stir for 11-15 min.

[0064] During the dry premixing stage, because the bulk density of calcined diatomaceous earth is much lower than that of other components, if the same rotation speed is used throughout the process, stratification can easily occur, with lighter components floating and heavier components sinking. Therefore, a two-stage mixing method is required: first, a lower rotation speed is used to allow powders of different densities to fully convect and contact each other, forming a preliminary core-shell encapsulation structure; then, a higher rotation speed is used to break up any soft agglomerates that may exist, ensuring that the dispersant and retarder adhere evenly.

[0065] For the first 4-6 minutes, the stirring speed is 35-45 r / min, primarily for convective mixing. At this stage, the linear velocity of the stirring paddle is low, and the powder tumbles as a whole with the paddle, but the relative speed between particles is not high. The lightweight diatomaceous earth is not thrown towards the cylinder wall due to centrifugal force, but is gradually lifted and enveloped from below by the heavier volcanic ash particles, forming composite particles with volcanic ash as the core and diatomaceous earth as the shell. Once this structure is formed, the diatomaceous earth loses the possibility of floating independently. For the next 11-15 minutes, the speed is increased to 45-55 r / min, significantly enhancing the shear force. The main tasks in this stage are: first, to break up any soft agglomerates that may exist due to electrostatic or weak adsorption; second, to ensure that the lignin sulfonate modified dispersant and composite retarder stabilizer are evenly coated on the surface of each particle; and third, to further strengthen the stability of the core-shell structure. The total duration is controlled at 15-21 minutes (4-6 plus 11-15), matching the 16-20 minute range in weight 5.

[0066] In this embodiment of the invention, the two-stage mixing method achieves a mixing uniformity qualification rate (component content deviation ≤ ±1.5%) of over 98%, while the qualification rate of the comparative process using constant-speed mixing throughout is only around 85%. Furthermore, due to the longer proportion of the low-speed stage, the total energy consumption is reduced by approximately 10-15% compared to constant-speed mixing. During storage, the finished product will not exhibit quality stratification due to uneven mixing (i.e., higher volcanic ash content at the bottom of the packaging bag and higher diatomaceous earth content at the top), ensuring product consistency and reliability.

[0067] As an example, the premixing speed can be 35, 40, or 45 r / min; the premixing time can be 4, 5, or 6 min; the subsequent stirring speed can be 45, 50, or 55 r / min; and the subsequent stirring time can be 11, 12, 13, 14, or 15 min.

[0068] In one optional embodiment, in step S4, the storage conditions after packaging the finished product are: temperature 15-30℃, humidity ≤50%, finished product moisture content 1.8-2.2%, and loose density 0.75-0.85g / cm³.

[0069] After leaving the factory, cured materials need to undergo transportation and on-site storage, which may expose them to varying temperature and humidity environments. Improper storage can cause the material to absorb moisture and clump together, or prematurely undergo hydration reactions, leading to decreased activity or even rendering it unusable. Therefore, it is essential to clearly define the quality indicators of the finished product and establish a suitable storage environment.

[0070] It should be noted that when the finished product moisture content is below 1.8%, the water film on the particle surface is too thin, and electrostatic attraction dominates, making it easy for particles to agglomerate due to electrostatic adsorption. When the moisture content is above 2.2%, some cementing components (especially modified metakaolin) may begin to undergo a slow hydration reaction with the adsorbed water, generating a small amount of cementing products that bind the particles together, also leading to agglomeration. A loose density of 0.75-0.85 g / cm³ reflects the rationality of the particle size distribution: too low a density indicates that the gaps between particles are too large, allowing air humidity to easily penetrate; too high a density indicates that the grinding is too fine or the gradation is unreasonable, resulting in an abnormally high water demand.

[0071] At storage temperatures below 15°C, hydration is slower, but condensation may occur; above 30°C, even without additional water, adsorbed water on the particle surface may slow down hydration. Humidity ≤50% is maintained to prevent water vapor in the air from condensing into liquid water on the particle surface. Once a liquid water film forms, the hydration reaction begins.

[0072] Under the aforementioned storage conditions, the shelf life of the cured material in this invention can reach 6 months. After 6 months of storage, when it is pulped at the same water-to-material ratio, the key indicators such as initial setting time, 28-day compressive strength, and bleeding rate show no change of more than 5% compared to the freshly manufactured product. This means that engineering units can purchase and prepare materials in advance without worrying about the materials deteriorating in the warehouse. Furthermore, these storage conditions can be met in conventional industrial warehouses, eliminating the need to build temperature- and humidity-controlled warehouses and reducing operating costs.

[0073] As an example, the storage temperature can be 15, 20, 25, or 30°C; the humidity can be 30%, 40%, or 50%; the finished product moisture content can be 1.8%, 1.9%, 2.0%, 2.1%, or 2.2%; and the loose density can be 0.75, 0.78, 0.80, 0.82, or 0.85 g / cm³.

[0074] On the other hand, embodiments of the present invention also provide a grouting construction method using any of the above-mentioned curing materials, comprising the following steps: Adjust the water-material ratio according to the porosity of the geological conditions: the water-material ratio is 0.9-1.1 for soft soil, 1.3-1.7 for sand and gravel layers, and 1.0-1.2 for ordinary silty soil. Mix the solidification material with water, first stirring at a low speed of 30-40 r / min for 2-3 min, then stirring at a high speed of 70-80 r / min for 5-7 min to obtain the grouting slurry. Grouting is carried out using grouting equipment, with the grouting pressure controlled at 0.4-0.7MPa and the grouting speed controlled at 25-35L / min. The grouting pipe is lifted uniformly from the bottom of the pile to the top of the pile at a speed of 0.5-1.0m / min.

[0075] Soft soil (porosity 40-50%) has high water content and poor permeability. If the water-to-material ratio is too high, the slurry will be too thin and easily mix with free water in the soil after injection, leading to further dilution and a significant decrease in strength. If the water-to-material ratio is too low, the slurry will be too thick and difficult to diffuse in low-permeability soil layers. Therefore, a relatively low water-to-material ratio of 0.9-1.1 is chosen. Gravel and sand layers (porosity 50-60%) have large pores and good permeability, requiring a higher water-to-material ratio (1.3-1.7) to ensure sufficient fluidity of the slurry to fill the large pores and achieve a sufficient diffusion radius. Ordinary silty clay (porosity 35-40%) falls between these two categories, and a water-to-material ratio of 1.0-1.2 is sufficient.

[0076] The stirring process is divided into two stages: low speed and high speed. Low speed (30-40 r / min) stirring for 2-3 minutes primarily allows the dry powder to initially contact with water, forming a basic slurry without lumps. Excessive stirring speed during this stage will generate a large number of bubbles. High speed (70-80 r / min) stirring for 5-7 minutes provides sufficient shear force to fully expand the molecular chains of the dispersant, resulting in uniform dispersion of the nano-silica sol and optimal particle size distribution. Experiments show that when the high-speed stirring time is less than 5 minutes, the initial fluidity of the slurry is low; exceeding 7 minutes may damage the hydration film structure due to excessive shear.

[0077] Grouting pressures of 0.4-0.7 MPa fall under the category of low-pressure grouting. Below 0.4 MPa, the grout struggles to overcome lateral soil pressure and pipe friction, resulting in excessively slow grouting speeds. Above 0.7 MPa, fracturing can easily occur in soft soil, forming irregular grout veins rather than uniform penetration reinforcement. A grouting speed of 25-35 L / min, matched to the pressure, ensures continuous and stable grout injection. The grouting pipe is lifted uniformly from the pile bottom to the pile top at a speed of 0.5-1.0 m / min, ensuring the grout gradually fills from the bottom upwards, preventing voids or pile breaks.

[0078] The method provided in this invention ensures that, after the slurry is stirred and allowed to stand for 50-70 minutes, the bleeding rate remains below 1.0%, and the funnel viscosity is 25-35s, fully meeting the time window requirements for on-site construction. After grouting, the solidified body exhibits a 28-day compressive strength of 9.0-11.0 MPa and a 28-day permeability coefficient ≤8×10⁻⁶. -8 cm / s, erosion resistance ≤4%. Field comparative tests show that the ultimate bearing capacity of pile foundations grouted using this method is 40-60% higher than that of ungrouted piles and 15-20% higher than that of traditional cement grouted piles.

[0079] For example, the water-to-material ratio for soft soil can be 0.9, 1.0, or 1.1; for sand and gravel layers, it can be 1.3, 1.4, 1.5, 1.6, or 1.7; and for silty clay, it can be 1.0, 1.1, or 1.2. The low-speed mixing speed can be 30, 35, or 40 r / min, with a duration of 2, 2.5, or 3 min; the high-speed mixing speed can be 70, 75, or 80 r / min, with a duration of 5, 6, or 7 min. The grouting pressure can be 0.4, 0.5, 0.6, or 0.7 MPa; the grouting speed can be 25, 28, 30, 32, or 35 L / min; and the lifting speed can be 0.5, 0.7, 0.8, or 1.0 m / min.

[0080] In one alternative embodiment, when the pile diameter is ≤800mm, the grouting pressure is 0.4MPa-0.5MPa and the grouting speed is 25L / min-30L / min; when the pile diameter is >800mm, the grouting pressure is 0.5MPa-0.7MPa and the grouting speed is 30L / min-35L / min.

[0081] In pile foundation engineering, pile diameters vary greatly. Small piles (such as support piles with a diameter of 300-600mm) and large piles (such as bridge pier piles with a diameter of 1000-2000mm) have different requirements for grouting parameters. Small piles have a small volume of soil around them, and excessively high grouting pressure can easily cause soil heave or pile uplift. Large piles, on the other hand, require higher pressure and speed to ensure that the grout fully fills the large space on the pile side and at the pile bottom.

[0082] When the pile diameter is ≤800mm, the grouting volume of a single pile is usually no more than 2m³, and the grout diffusion radius is limited (generally 0.5-1.0m). Using a low pressure of 0.4-0.5MPa is sufficient to evenly squeeze the grout out of the pile side without causing splitting risk to the soft soil foundation; the grouting speed of 25-30L / min makes the grouting process stable and controllable, avoiding the grout from flowing out concentratedly along a weak point in the pile body due to excessive speed, resulting in insufficient filling in other areas.

[0083] When the pile diameter is greater than 800mm, the grouting volume can reach 5-10m³ or even more, and the grout needs to spread over a greater distance (1.5-2.5m) to form an effective reinforcement ring. In this case, the grouting pressure needs to be increased to 0.5-0.7MPa to overcome the resistance of the grout during long-distance seepage; simultaneously, the grouting speed should be increased to 30-35L / min to ensure that the entire grouting volume is completed before the grout initially sets (5-7 hours). The upper limit of 35L / min for the grouting speed is based on the rated capacity of conventional grouting pumps and consideration of pipeline wear; exceeding this speed may accelerate the wear and tear on the pump and pipeline.

[0084] After classifying and controlling parameters according to pile diameter, the soil heave during grouting of small piles was controlled within 2mm, and the pile body uplift did not exceed 0.5‰ of the pile diameter, meeting the specifications. After grouting of large piles, core sampling inspection showed that the solidified body on the pile side was continuous and full, without broken piles or honeycomb defects, and the pile body filling coefficient (the ratio of actual grouting volume to theoretical calculation volume) reached 1.05-1.10. In contrast, in the comparison project without graded control, small piles experienced pile body uplift due to excessive pressure, while large piles experienced blank grouting areas at the pile bottom due to insufficient pressure.

[0085] For example, when the pile diameter is ≤800mm, the grouting pressure can be 0.4, 0.45, or 0.5MPa; the grouting speed can be 25, 28, or 30L / min. When the pile diameter is >800mm, the grouting pressure can be 0.5, 0.6, or 0.7MPa; the grouting speed can be 30, 32, or 35L / min.

[0086] In one alternative embodiment, the prepared grout has a bleeding rate of ≤1.0% after standing for 50-70 minutes, and a funnel viscosity of 25-35s.

[0087] At the grouting construction site, there is often a certain amount of time between the completion of grout mixing and its actual injection into the pile hole. For example, when one grouting pump serves multiple piles simultaneously, grouting needs to be done sequentially, and the mixed grout may need to wait in the storage tank for 30-60 minutes. If significant bleeding or settling occurs in the grout during this period, it will lead to uneven grout injection into the pile hole, or even blockage of the grouting pipe. Therefore, it is necessary to limit the performance indicators of the grout after a certain settling time.

[0088] Bleeding rate refers to the percentage of free water precipitated on the surface of the slurry after it has settled. A bleeding rate ≤1.0% means that only a very small amount of free water precipitates during a settling period of 50-70 minutes, with the vast majority of water still adsorbed or bound by the cementitious particles in the micropores of the calcined diatomaceous earth. This indicator is the result of the synergistic effect of the high porosity (68-72%) of the calcined diatomaceous earth physically adsorbing water, the sodium gluconate-enhanced hydration film in the composite retarder stabilizer, and the filling of voids by nano-silica sol.

[0089] Funnel viscosity is an indicator of slurry flowability, measured using a standard cement mortar funnel (150mm upper diameter, 10mm lower diameter, 200mm cone height). A flow time of 25-35 seconds corresponds to a Marsh funnel viscosity of approximately 20-28 seconds, indicating medium flowability. Too low a viscosity (<25s) means the slurry is too thin and easily flows away after injection; too high a viscosity (>35s) results in high pumping resistance and difficulty in penetrating fine pores. This viscosity range matches the aforementioned water-to-material ratio range, ensuring smooth pumping of the slurry while maintaining good filling properties within the formation.

[0090] This invention avoids the problem of workers adding water to dilute the grout based on experience, which could lead to an uncontrolled water-to-material ratio and reduced strength. Secondly, it avoids inconsistencies in composition between the first and second injected grouts due to settling. In actual construction, even in high-temperature environments (30-35℃) during summer, the grout remains in a uniform suspension state after standing for 60 minutes, and the strength difference between the upper and lower parts of the solidified grout after injection does not exceed 5%.

[0091] For example, the settling time can be 50, 55, 60, 65, or 70 minutes; the water exudation rate can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, or 1.0%; and the funnel viscosity can be 25, 26, 28, 30, 32, 34, or 35 seconds.

[0092] After grouting is completed, allow it to stand for 7-14 days to cure at a temperature of 15-30℃. The compressive strength of the cured body after 28 days is 9.0-11.0 MPa.

[0093] After grouting is completed, the solidified body needs a certain curing time to reach the design strength. Since a standard curing room (20±1℃, humidity ≥95%) cannot be provided on-site, it is necessary to determine the minimum number of curing days and the suitable temperature range under natural conditions.

[0094] For example, the curing days can be 7, 8, 9, 10, 11, 12, 13, or 14 days; the curing temperature can be 15, 20, 25, or 30℃; and the 28-day compressive strength can be 9.0, 9.5, 10.0, 10.5, or 11.0 MPa.

[0095] The permeability coefficient of the cured body at 28 days is ≤8×10 -8 cm / s, erosion resistance ≤4%.

[0096] For example, the 28-day permeability coefficient can be 8 × 10⁻⁶. -8 7×10 -8 6×10 -8 5×10 -8 4×10 -8cm / s; erosion resistance can be 4%, 3.5%, 3%, 2.5%, or 2%.

Claims

1. A curing material for grouting ground piles, characterized in that, The composition includes the following components in parts by weight: 48-52 parts of volcanic ash ultrafine powder, 22-26 parts of calcined diatomaceous earth, 14-17 parts of modified metakaolin, 1.8-2.5 parts of composite retarder and stabilizer, 3.8-5.0 parts of nano-silica sol, 1.0-1.4 parts of lignin sulfonate modified dispersant, and 0.2-0.35 parts of trace coagulation accelerator. The volcanic ash ultrafine powder has a particle size of 0.9-4.8 μm and a specific surface area of ​​9000-11000 cm² / g. Its chemical composition, by mass percentage, is: SiO₂ 64%-67%, Al₂O₃ 21%-25%, Fe₂O₃ 5%-6%, CaO 3%-4%, MgO 1%-2%. The calcined diatomaceous earth has a particle size of 1.5μm-6.0μm, a specific surface area of ​​7500cm² / g-9000cm² / g, a porosity of 68%-72%, and an organic matter content of ≤1.5%. The modified metakaolin was prepared by surface modification of metakaolin with aluminum dihydrogen phosphate solution, and the particle size after modification was ≤5μm. The trace coagulation aid is composed of nano zinc oxide and lithium carbonate in a mass ratio of 5:

1.

2. The curing material for ground pile grouting according to claim 1, characterized in that, The lignin sulfonate modified dispersant is prepared by pyrolysis modification of sodium lignin sulfonate at 122-128℃ for 32-38 minutes, with nitrogen gas introduced for protection during the pyrolysis process.

3. The curing material for ground pile grouting according to claim 1, characterized in that, The composite retarding stabilizer is composed of trisodium citrate, sodium gluconate, and anhydrous borax in a mass ratio of (2.8-3.2):(1.0-1.2):(0.8-1.0).

4. The curing material for ground pile grouting according to claim 1, characterized in that, The nano-silica sol is an alkaline silica sol with a solid content of 30wt%-33wt%, a particle size of 20nm-25nm, a pH value of 8.8-9.2, and a viscosity of 5mPa·s-8mPa·s.

5. A method for preparing a curing material for ground pile grouting as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Raw material pretreatment: Volcanic ash ultrafine powder and calcined diatomaceous earth are passed through a 160-200 mesh sieve, and modified metakaolin, composite retarder stabilizer, lignin sulfonate modified dispersant and trace amount of coagulation aid are passed through a 180-220 mesh sieve; nano silica sol is sealed and stored. S2. Dry material premixing: Weigh each pretreated solid raw material according to the ratio, put them into a dry powder mixer, and mix them at a speed of 40-50 r / min for a total mixing time of 16-20 min; S3. Adding wet materials and high-speed stirring: Transfer the dry material mixture into a high-speed stirring vessel and stir at a speed of 80-90 r / min. At the same time, add nano-silica sol dropwise at a rate of 0.8-1.2 L / min. After the dropwise addition is completed, continue stirring for 10-14 min and control the temperature inside the vessel to ≤35℃. S4. Finished product screening and packaging: The well-stirred slurry is screened through a 100-140 mesh vibrating screen. After screening, the finished product is allowed to cool naturally to room temperature and then sealed in a moisture-proof composite film.

6. The preparation method according to claim 5, characterized in that, In step S2, the stirring method is as follows: first, premix at 35-45 r / min for 4-6 min, then increase the speed to 45-55 r / min and stir for 11-15 min.

7. The preparation method according to claim 5, characterized in that, In step S4, the storage conditions after packaging the finished product are: temperature 15-30℃, humidity ≤50%, finished product moisture content 1.8-2.2%, and loose density 0.75-0.85g / cm³.

8. A grouting construction method using the curing material according to any one of claims 1-4, characterized in that, Includes the following steps: Adjust the water-material ratio according to the porosity of the geological conditions: the water-material ratio is 0.9-1.1 for soft soil, 1.3-1.7 for sand and gravel layers, and 1.0-1.2 for ordinary silty soil. Mix the solidification material with water, first stirring at a low speed of 30-40 r / min for 2-3 min, then stirring at a high speed of 70-80 r / min for 5-7 min to obtain the grouting slurry. Grouting is carried out using grouting equipment, with the grouting pressure controlled at 0.4-0.7MPa and the grouting speed controlled at 25-35L / min. The grouting pipe is lifted uniformly from the bottom of the pile to the top of the pile at a speed of 0.5-1.0m / min.

9. The grouting construction method according to claim 8, characterized in that, When the pile diameter is ≤800mm, the grouting pressure is 0.4MPa-0.5MPa and the grouting speed is 25L / min-30L / min; when the pile diameter is >800mm, the grouting pressure is 0.5MPa-0.7MPa and the grouting speed is 30L / min-35L / min.

10. The grouting construction method according to claim 8, characterized in that, The prepared grouting slurry has a bleeding rate of ≤1.0% after standing for 50-70 minutes, and a funnel viscosity of 25-35s. After grouting is completed, allow it to stand for 7-14 days to cure at a temperature of 15-30℃. The compressive strength of the cured body after 28 days is 9.0-11.0 MPa. The permeability coefficient of the solidified body at 28 days is ≤8×10⁻⁶. -8 cm / s, erosion resistance ≤4%.

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