Eicp dry-state instant slow-release composite particles for soft soil reinforcement and preparation method thereof

Abstract

The application discloses EICP dry-state instant slow-release composite particles for soft soil reinforcement and a preparation method thereof, and belongs to the technical field of biological mineralization soil fixation. The composite particles comprise, from inside to outside, a core adsorption layer, a functional slow-release shell layer and a surface protective film. The core adsorption layer comprises a porous inorganic mineral carrier and an enzyme protective agent physically loaded in micropore channels of the porous inorganic mineral carrier; the functional slow-release shell layer is coated outside the core adsorption layer and comprises a water-retention and viscosity-increasing component and a water-soluble calcium source; and the surface protective film is a water-soluble high-molecular moisture-proof film coated on the outermost layer of the functional slow-release shell layer. The composite particles of the application effectively improve the calcium source release rate to reduce initial local pore blockage, relieve the on-site compounding and balling phenomenon of the water-retention and viscosity-increasing component, and improve the storage stability of the material in a high-humidity environment, so that one-step grouting operation is realized on the engineering site.

Description

Technical Field

[0001] This invention belongs to the field of biomineralization soil stabilization technology, specifically relating to EICP (Enzyme-Induced Calcium Carbonate Precipitation) dry-state fast-dissolving and slow-release composite particles for soft soil stabilization and their preparation method. Background Technology

[0002] With the continuous expansion of coastal industrial parks in China, the application of soft soil solidification agents in engineering projects has surged. Compared with traditional inorganic and chemical solidification agents, soft soil biomineralization solidification agents better meet the current demands for short construction periods, high performance, and environmental friendliness. Therefore, the development of a new type of green biomineralization solidification agent is urgently needed.

[0003] Existing soft soil biomineralization and solidification agents face significant physical operational barriers in engineering applications, with the following specific challenges: 1) Calcium source must be added in stages, resulting in a complex and high-risk process: Current technology indicates that the calcium source solution needs to be added in 2-3 stages, with each stage spaced 0.5-6 hours apart. This is because adding calcium ions all at once will cause an instantaneous reaction with carbonate ions produced by urease hydrolysis, leading to a high concentration of precipitation at the grouting port and clogging the soil pores. This staged operation greatly increases the burden on on-site personnel and also limits the rapid advancement of large-scale projects.

[0004] 2) Xanthan gum dissolves and clumps on-site, making it difficult to disperse evenly: Xanthan gum is a highly viscous polymer. If its dry powder is directly added to a large volume of water on-site, it is very easy for it to physically clump together. Even with mixing equipment, it requires a long time and strong shearing to dissolve, which not only consumes a lot of water and electricity, but also seriously affects the stability of the grout viscosity.

[0005] 3) Inability to achieve "on-demand supply" and instant water retention: The calcium source and xanthan gum in traditional products are in a free liquid state. Due to physical limitations, they cannot achieve instant release of high molecules, nor can they achieve physical buffering of calcium ions.

[0006] Therefore, this invention proposes EICP dry-state fast-dissolving and slow-release composite particles for soft soil reinforcement. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide EICP dry-state fast-dissolving and slow-release composite particles for soft soil reinforcement and their preparation method, thereby solving the problems in the prior art.

[0008] The objective of this invention can be achieved through the following technical solutions: EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement, from the inside out, consist of: The core adsorption layer includes: a porous inorganic mineral carrier and an enzyme protectant loaded in the micropores of the porous inorganic mineral carrier; A functional sustained-release shell layer, which covers the outside of the core adsorption layer, includes a water-retaining and thickening component and a water-soluble calcium source. A surface protective film, which covers the outermost layer of the functional slow-release shell, is a water-soluble polymer moisture-proof film.

[0009] Furthermore, based on 100 parts by weight of the porous inorganic mineral carrier, the loading of the enzyme protectant is 10 to 60 parts by weight.

[0010] Furthermore, the porous inorganic mineral carrier is selected from at least one of natural zeolite, synthetic zeolite, mesoporous silica, diatomite, kaolinite, or attapulgite. The enzyme protectant is selected from at least one of betaine, trehalose, proline, sorbitol, or glycerol.

[0011] Furthermore, based on a total mass of 100 parts by mass of the core adsorption layer, the amount of the water-retaining and thickening component is 5-30 parts by mass, and the amount of the water-soluble calcium source is 30-95 parts by mass.

[0012] Furthermore, the water-retaining and thickening component is selected from at least one of xanthan gum, guar gum, sodium carboxymethyl cellulose, or polyacrylamide; The water-soluble calcium source is selected from at least one of calcium chloride, calcium acetate, calcium nitrate, calcium formate, or calcium lactate.

[0013] Furthermore, the surface protective film accounts for 1% to 8% of the total mass of the composite particles.

[0014] Furthermore, the raw material of the surface protective film is selected from at least one of polyvinyl alcohol, modified starch, carboxymethyl starch, or water-soluble cellulose ether.

[0015] The above-mentioned method for preparing EICP dry-state fast-dissolving and slow-release composite particles for soft soil reinforcement includes the following steps: S1, Under vacuum negative pressure conditions, an aqueous solution containing an enzyme protectant is impregnated into an activated porous inorganic mineral carrier, and after drying, the core adsorption layer is obtained; S2, In a fluidized bed device, hot air is used to make the core adsorption layer fluidized and suspended, and a mixed slurry containing the water-retaining and thickening components and water-soluble calcium source is sprayed onto the surface of the core adsorption layer and dried to form the functional slow-release shell layer; S3, in the fluidized bed equipment, a solution for forming a surface protective film is sprayed onto the surface of the particles treated in S2, and the composite particles are obtained after drying.

[0016] Furthermore, in S2, the inlet air temperature of the fluidized bed equipment is 50℃~80℃, and the spraying rate of the mixed slurry is 5~15 mL / min.

[0017] A method for reinforcing soft soil includes the following steps: The above-mentioned composite particles are added to water and stirred to dissolve the surface protective film and the functional slow-release shell layer in the water, thereby obtaining a mixed colloid containing the water-retaining and thickening components, water-soluble calcium source and free core adsorption layer. A substrate solution containing industrial urease and urea is added to the mixed adhesive and mixed evenly to form a final reinforcement liquid. The final reinforcement liquid is then injected into the soft soil layer to be reinforced in one go, or mixed with the soft soil layer to be reinforced.

[0018] The beneficial effects of this invention are: 1. This invention changes the traditional method of directly adding xanthan gum in its free dry powder state. Instead, it uses a fluidized bed spray granulation process to prepare a slurry with water-retaining and thickening components and a calcium source, which are then coated onto the core adsorption layer to form a functional slow-release shell. This microscopic coating structure avoids the defect of forming a dense water-blocking film on the surface of polymer dry powder when it comes into contact with water, effectively improving the material's dissolution efficiency. This eliminates the need for high-power shearing equipment on-site; a uniform solution can be quickly obtained through conventional low-speed stirring, thus alleviating the burden of on-site solution preparation.

[0019] 2. To address the issue of instantaneous precipitation of free liquid-phase calcium sources, this invention encapsulates water-soluble calcium sources (such as calcium chloride) within the polymer network of the aforementioned functional slow-release shell, achieving solid-phase encapsulation of the calcium source. The weak gel network formed upon contact with water in the functional slow-release shell acts as a physical buffer against the outward diffusion of internal calcium ions. This mechanism allows the calcium source required for the EICP mineralization reaction to be released gradually deep within the pores of soft soil, effectively reducing the problem of near-end hard shell blockage caused by local supersaturation of calcium carbonate in the early stages of grouting, thereby supporting the smooth implementation of the one-step grouting process in the field.

[0020] 3. A granulation process is used to spray a layer of polyvinyl alcohol (PVA) or modified starch at a mass ratio of 1% to 8% onto the outermost layer of the composite granules, forming a continuous, readily soluble, and moisture-proof film. This extremely thin protective film ensures the immediate dispersion of the granules upon contact with water while providing a robust physical moisture barrier for the highly hygroscopic calcium chloride and the inorganic porous carrier within. This helps ensure the long-term storage quality of the product in high-humidity construction environments such as coastal areas and maintains the material's good flowability during subsequent mechanized dry spreading operations.

[0021] 4. A porous inorganic mineral (such as natural zeolite) with abundant micropore channels is selected as the core carrier, and a vacuum negative pressure impregnation process of -0.05 MPa to -0.1 MPa is applied to forcibly fill the micropores of the carrier with enzyme protectants (such as betaine). Utilizing the capillary action and physical spatial encapsulation of the porous inorganic mineral, the enzyme protectant is deeply anchored within the particle core. This physical isolation structure reduces the probability of the protectant molecules being diluted too quickly and lost with water in the complex and water-rich pores of soft soil, helping to maintain a suitable microenvironment for urease catalysis within the target mineralization area. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention proposes an EICP dry-state fast-dissolving and slow-release composite particle for soft soil reinforcement. Its overall micro-physical structure, from the inside out, includes: a core adsorption layer (for loading enzyme protectant), a functional slow-release shell layer (for loading water-retaining components and calcium source), and a surface fast-dissolving protective film (for moisture protection and ensuring immediate dispersion upon contact with water).

[0024] I. The following describes the raw material system and mass fraction range for each layer: (1) Raw material system of the core adsorption layer The core adsorption layer comprises: a porous inorganic mineral carrier and an enzyme protectant.

[0025] The porous inorganic mineral carrier is selected from at least one of the following: natural zeolite, synthetic zeolite, mesoporous silica, diatomite, kaolinite, or attapulgite, and its particle size is controlled in the range of 0.05~5mm, preferably 0.1~2mm, and more preferably 0.2~1mm.

[0026] The enzyme protectant is selected from at least one of betaine, trehalose, proline, sorbitol, or glycerol, or a mixture thereof in any proportion. The purpose of using this enzyme protectant is to improve the activity retention rate of plant-derived urease under saline soil, alkaline, and high-temperature disturbance environments.

[0027] Based on 100 parts by weight of the porous inorganic mineral carrier, the loading of the enzyme protectant ranges from 10 to 60 parts by weight, preferably from 20 to 50 parts by weight, and more preferably from 30 to 45 parts by weight.

[0028] (2) Raw material system for functional sustained-release shell The functional slow-release shell is wrapped around the core adsorption layer and mainly includes: water-retaining and thickening components and water-soluble calcium source.

[0029] The water-retaining and thickening component is selected from at least one of xanthan gum, guar gum, sodium carboxymethyl cellulose (CMC), or polyacrylamide, and is used to form a weak gel network immediately when the particles dissolve in water, so as to regulate the diffusion and residence time of the reaction liquid in the pores of soft soil.

[0030] The water-soluble calcium source is selected from at least one of calcium chloride, calcium acetate, calcium nitrate, calcium formate, or calcium lactate, and is used to provide the Ca required for the formation of calcium carbonate precipitate during the reaction. 2+ .

[0031] Based on a total mass of 100 parts by mass of the core adsorption layer, the amount of the water-retaining and thickening component is 5-30 parts by mass, preferably 8-25 parts by mass; the amount of the water-soluble calcium source is 30-95 parts by mass, preferably 40-80 parts by mass.

[0032] (3) Raw material system for surface fast-dissolving protective film The surface-soluble protective film is an extremely thin moisture-proof layer covering the outermost layer, and its raw material is selected from at least one of polyvinyl alcohol (PVA), modified starch, carboxymethyl starch, or water-soluble cellulose ether. The mass of the surface-soluble protective film accounts for 1% to 8% of the total mass of the composite particles, preferably 2% to 5%.

[0033] II. Preparation method and process parameters This invention proposes a method for preparing core-shell structured sustained-release composite particles, comprising the following steps: Step S1: Prepare the core adsorption layer; A porous inorganic mineral carrier of selected particle size is placed in a vacuum oven and activated at 100℃~120℃ for 1~4 hours to remove the physically adsorbed moisture in the pores of the inorganic mineral carrier. The activated inorganic mineral carrier is then placed in a vacuum negative pressure impregnation tank, and a prepared enzyme protectant aqueous solution (the mass fraction of the enzyme protectant aqueous solution is 15%~40%) is added. The vacuum degree in the impregnation tank is controlled at -0.05MPa~-0.1MPa, and impregnation is carried out under negative pressure for 1~6 hours at room temperature or heated to 30℃~50℃, so that the enzyme protectant molecules are deeply loaded into the micropores of the carrier under the action of capillary and negative pressure. After impregnation, excess liquid is filtered out, and the loaded particles are placed in a low temperature hot air circulating oven at 60℃~100℃ and dried for 2~8 hours to obtain the core adsorbed particles (core adsorbed layer).

[0034] Step S2: Preparation of functional sustained-release shell and surface fast-dissolving protective film The core adsorbent particles obtained in step S1 are transferred to an industrial fluidized bed coating machine (such as a bottom-spray or top-spray fluidized bed). The inlet air temperature of the fluidized bed is controlled at 50℃~80℃. A pre-prepared mixed suspension slurry containing water-retaining and thickening components and a water-soluble calcium source is uniformly sprayed onto the surface of the fluidized core adsorbent particles using a peristaltic pump at a rate of 5~15mL / min. After spraying, the particles are kept in a fluidized state and dried for 15~45 minutes to form a functional slow-release shell of uniform thickness.

[0035] Subsequently, a surface-soluble protective film solution with a mass fraction of 2% to 10% is sprayed onto the surface of the functional slow-release shell layer of the particles in the same manner, and then dried again for 10 to 30 minutes to form a dense and continuous moisture-proof isolation film on the outermost layer of the particles. The core-shell structure slow-release composite particles for soft soil reinforcement are then obtained by discharging the material.

[0036] After the composite particles are processed in step S2, the overall weight gain ratio of the outer coating layer (i.e., the total mass of the functional shell and the quick-dissolving protective film / the mass of the core adsorption layer) is controlled between 50% and 150%, preferably between 60% and 120%.

[0037] III. Specific Applications of the Composite Particles of the Invention The specific application method for reinforcing coastal soft soil using the core-shell structure slow-release composite particles described in this invention is as follows: The composite particles are mixed into the soft soil to be reinforced directly by mechanical turning and mixing at a dosage of 0.5% to 5.0% (preferably 1.0% to 3.5%) of the soil mass, or they are added to the construction water at one time to prepare a suspension slurry with a mass concentration of 5% to 20%, and stirred at a low speed of 300 to 500 r / min for 3 to 10 minutes (this step does not require high shear force, as the particles can quickly self-depolymerize upon contact with water). Then, a pre-prepared substrate solution containing industrial urease and urea is mixed in at a volume ratio of 1:1 to 1:3, and immediately injected into the target soil layer by low-pressure grouting or high-pressure jet grouting.

[0038] The curing temperature is controlled at 10℃~40℃ (preferably 20℃~35℃), and the curing time is 24~168 hours, which can complete the in-situ targeted mineralization of calcium carbonate in the soil pores.

[0039] The technical solution of the present invention will be specifically described below through the following embodiments and comparative examples (unless otherwise stated, all percentages and parts by mass used in the embodiments and comparative examples are calculated on a dry basis): Example 1 This embodiment provides a core-shell structured slow-release composite particle for soft soil reinforcement and its preparation method; The specific sources and specifications of its raw materials are as follows: Natural zeolite powder: particle size 0.3mm, porosity approximately 35%, saturated water absorption rate approximately 40%, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. (adsorption capacity ≥160mg / g); Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Xanthan gum: Industrial grade, viscosity ≥12000 mPa·s, purchased from Hebei Yanxing Chemical Co., Ltd. Anhydrous calcium chloride: Industrial grade, content ≥94%, purchased from Zhejiang Juhua Xinlian Chemical Co., Ltd.; Polyvinyl alcohol (PVA): Grade 1788, degree of alcoholysis 87%~89%, purchased from Anhui Wanwei High-Tech Materials Co., Ltd.

[0040] The core-shell structured slow-release composite particles are composed of a core adsorption layer, a functional slow-release shell layer, and a surface fast-dissolving protective film, from the inside out.

[0041] S1, Preparation of the core adsorption layer Weigh 100 parts by weight of natural zeolite powder and place it in a vacuum oven. Activate it at 105°C for 2 hours to remove physically adsorbed water from the zeolite micropores.

[0042] The activated zeolite powder was transferred to a vacuum impregnation tank. A betaine aqueous solution (30% by mass) was prepared in advance, consisting of 30 parts by mass of betaine and 70 parts by mass of deionized water, and poured into the impregnation tank to completely submerge the zeolite powder. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The zeolite powder was continuously impregnated under negative pressure at room temperature (25°C) for 3 hours.

[0043] After impregnation, excess liquid was removed by filtration. The zeolite particles loaded with betaine were spread evenly on a stainless steel tray and placed in a forced-air drying oven. They were dried at 80°C for 4 hours until the moisture content was less than 1%. The particles were weighed to obtain 112 parts by mass of core adsorbent particles (i.e., the actual betaine loading was about 12 parts by mass, and the loading amount was 12 parts by mass, which is within the range of 10~60 parts by mass).

[0044] S2, Preparation of Functional Sustained-Release Shell and Surface Fast-Dissolving Protective Film All 100 parts by weight of the core adsorbent particles obtained above were fed into an industrial fluidized bed coating machine (model: FL-5, bottom spray type, hopper volume 5L).

[0045] All 112 parts by mass of the core adsorbent particles obtained above were fed into an industrial fluidized bed coating machine (model: FL-5, bottom spray type, 5L hopper volume). In this embodiment, the amount of subsequent shell layer components fed was calculated based on the actual mass of all the core adsorbent particles (112 parts by mass), which is equivalent to taking the total mass of the core adsorbent layer as 100 parts by mass.

[0046] Adjust the frequency of the fluidized bed blower to keep the particles in a stable fluidized state, and control the inlet air temperature to 65℃.

[0047] Preparation of functional slow-release shell slurry: Weigh 12 parts by weight of xanthan gum and 50 parts by weight of anhydrous calcium chloride, add them to 180 parts by weight of deionized water (corresponding to approximately 160 parts of water per 100 parts of core layer, slurry solid content approximately 25.6%, actual xanthan gum concentration in water approximately 6.7%), and stir at 3000 r / min for 20 min using a high-shear emulsifier to form a uniform, pumpable slurry. The apparent viscosity of the slurry at room temperature is 800~1200 mPa·s (Brookfield viscometer, #2 rotor, 20 r / min), meeting the process requirements for fluidized bed peristaltic pump delivery and atomized spraying.

[0048] It should be noted that under the conditions of 65℃ inlet air temperature and large air volume, a large amount of water is rapidly evaporated and carried away during the spraying process of fluidized bed equipment, and the slurry dries instantly on the particle surface to form a film. Therefore, the additional water will not cause the particles to be over-wetted and stick together, but will instead help to form a uniform and dense shell structure.

[0049] Using a peristaltic pump on a fluidized bed coating machine, the mixed suspension slurry was uniformly sprayed onto the surface of the fluidized core adsorbent particles at a rate of 10 mL / min. After spraying, the particles were kept in a fluidized state and dried for another 15 minutes to form a functional slow-release shell.

[0050] Preparation of a fast-dissolving protective film: Weigh 5 parts by mass of polyvinyl alcohol (PVA) and dissolve it in 95 parts by mass of deionized water under a water bath heating condition at 90℃. After cooling to room temperature, use the solution as a coating liquid (approximately 5% by mass). Spray an extremely thin PVA protective film using a fluidized bed coating machine in the same manner. After spraying, maintain the fluidized state and continue drying for 10 minutes. Discharge the material to obtain the core-shell structured slow-release composite particles.

[0051] In this embodiment, the overall weight gain of the outer covering layer is approximately 59.8% (12+50+5) / 112, which falls within the range of 50% to 150%.

[0052] Example 2 This embodiment provides another core-shell structured slow-release composite particle for soft soil reinforcement, aiming to verify the substitution effect of calcium source and surface protective film.

[0053] The specific sources and specifications of its raw materials are as follows: Natural zeolite powder: particle size 0.2mm, porosity about 35%, saturated water absorption rate about 40%, adsorption capacity ≥160mg / g, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Xanthan gum: Industrial grade, viscosity ≥12000 mPa·s, purchased from Hebei Yanxing Chemical Co., Ltd. Calcium acetate: Industrial grade, content ≥98%, purchased from Shandong Tengzhou Zhongzheng Chemical Co., Ltd.; Hydroxypropyl modified starch: food grade / industrial grade, gelatinization temperature 65~70℃, purchased from Feicheng Yutian Chemical Co., Ltd.

[0054] The core-shell structured slow-release composite particles are composed of a core adsorption layer, a functional slow-release shell layer, and a surface fast-dissolving protective film, from the inside out.

[0055] S1, Preparation of the core adsorption layer 100 parts by weight of natural zeolite powder were placed in a vacuum oven and activated at 105°C for 2 hours. The activated zeolite powder was then transferred to a vacuum impregnation tank. A betaine aqueous solution (40% by weight) was prepared in advance, consisting of 40 parts by weight of betaine and 60 parts by weight of deionized water, and poured into the impregnation tank to completely submerge the zeolite powder. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.09 MPa. The zeolite was continuously impregnated under negative pressure at room temperature (25°C) for 2.5 hours. After impregnation, excess liquid was removed by filtration. The loaded zeolite particles were spread evenly on a tray and placed in a forced-air drying oven. The particles were dried at 80°C for 3 hours until the moisture content was less than 1%. The particles were weighed to obtain approximately 116 parts by weight of core adsorbed particles (i.e., approximately 16 parts by weight of betaine were actually loaded, with a loading amount of 16 parts by weight, which falls within the range of 10~60 parts by weight).

[0056] S2, Preparation of Functional Sustained-Release Shell and Surface Fast-Dissolving Protective Film 100 parts by mass of the core adsorbent particles obtained above were fed into an industrial fluidized bed coating machine.

[0057] (The 116 parts by mass of the core adsorbent particles obtained above are all fed into an industrial fluidized bed coating machine. In this embodiment, the amount of subsequent shell components fed is calculated based on the actual mass of all the core adsorbent particles (116 parts by mass) (i.e., equivalent to 100 parts by mass of the total mass of the core adsorbent layer).) Adjust the blower to keep the particles in a stable fluidized state and control the inlet air temperature to 70℃.

[0058] Preparation of functional slow-release shell slurry: Weigh 15 parts by weight of xanthan gum and 55 parts by weight of calcium acetate, add them to 200 parts by weight of deionized water (corresponding to approximately 172 parts of water per 100 parts of core layer, with an actual xanthan gum concentration of approximately 7.0% in water), and stir at 3000 r / min for 20 min using a high-shear emulsifier to form a uniform, pumpable slurry. The apparent viscosity of the slurry at room temperature is 900~1300 mPa·s (Brookfield viscometer, #2 rotor, 20 r / min), meeting the process requirements for fluidized bed peristaltic pump delivery and atomized spraying. The fluidized bed equipment exhibits high water evaporation efficiency at an inlet air temperature of 70℃; any additional water is quickly carried away during spraying and does not affect the fluidization state of the particles.

[0059] Using a peristaltic pump on a fluidized bed coating machine, the mixed slurry was uniformly sprayed onto the surface of the fluidized core adsorbent particles at a rate of 10 mL / min. After spraying, the particles were kept in a fluidized state and dried for another 15 minutes to form a functional slow-release shell.

[0060] Preparation of a fast-dissolving protective film: Weigh 8 parts by mass of hydroxypropyl modified starch and dissolve it in 92 parts by mass of deionized water under a water bath heating condition of 70℃. After cooling to room temperature, use the solution as a coating solution (mass fraction of about 8%). Spray an extremely thin layer of modified starch film using a fluidized bed coating machine in the same manner. After spraying, continue drying in a fluidized state for 10 minutes to obtain the core-shell structured slow-release composite particles.

[0061] In this embodiment, the overall weight gain of the outer covering layer is approximately 67.2% (15+55+8) / 116, falling within the range of 50% to 150%.

[0062] Example 3 This embodiment aims to verify the loading capacity of the high-porosity carrier under high-concentration impregnation conditions, as well as the universal effectiveness of the combination of enzyme protectant, water-retaining and thickening components, and different water-soluble calcium sources.

[0063] The specific sources and specifications of its raw materials are as follows: Mesoporous silica: particle size 0.2 mm, pore size 8~10 nm, porosity about 45%, saturated water absorption rate about 60%, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Trehalose: food grade, purity ≥99%, purchased from Jiangsu Caiwei Biotechnology Co., Ltd.; Guar gum: Industrial grade, viscosity ≥6000 mPa·s, purchased from Shandong Jiaming Chemical Co., Ltd. Calcium nitrate: Industrial grade, content ≥99%, purchased from Shandong Jinhui Chemical Group Co., Ltd.; Hydroxypropyl methylcellulose (HPMC): Industrial grade, viscosity 4000 mPa·s, purchased from Hebei Haoshuo Chemical Co., Ltd.

[0064] S1, Preparation of the core adsorption layer 100 parts by weight of mesoporous silica were placed in a vacuum oven and activated at 105°C for 2 hours. The activated carrier was transferred to a vacuum negative pressure impregnation tank. A pre-prepared aqueous solution of a compound protective agent (40% by weight) consisting of 35 parts betaine, 5 parts trehalose, and 60 parts deionized water was poured into the impregnation tank. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The temperature of the impregnation tank jacket was controlled at 40°C, and the impregnation was carried out under negative pressure for 3 hours. After impregnation, excess liquid was removed by filtration, and the carrier was placed in a forced-air drying oven and dried at 80°C for 4 hours until the moisture content was less than 1%. The contents were weighed to obtain approximately 124 parts by weight of core adsorbent particles (i.e., approximately 24 parts by weight of the compound protective agent were actually loaded, with a loading amount of 24 parts by weight, falling within the high-mid-range of 10-60 parts by weight).

[0065] S2, Preparation of Functional Sustained-Release Shell and Surface Fast-Dissolving Protective Film 100 parts by mass of the core adsorbent particles obtained above were fed into an industrial fluidized bed coating machine.

[0066] (The 124 parts by mass of the core adsorbent particles obtained above are all fed into an industrial fluidized bed coating machine. In this embodiment, the amount of subsequent shell components fed is calculated based on the actual mass of all the core adsorbent particles (124 parts by mass) (i.e., equivalent to 100 parts by mass of the total mass of the core adsorbent layer).) Adjust the blower to keep the particles in a stable fluidized state and control the inlet air temperature to 60℃.

[0067] Preparation of functional slow-release shell slurry: Weigh 12 parts by weight of xanthan gum, 8 parts by weight of guar gum (totaling 20 parts, corresponding to approximately 16.1 parts per 100 parts of the core layer, falling within the range of 5-30 parts), and 50 parts by weight of calcium nitrate (corresponding to approximately 40.3 parts per 100 parts of the core layer, falling within the range of 30-100 parts), add to 280 parts by weight of deionized water (corresponding to approximately 226 parts of water per 100 parts of the core layer, the actual concentration of total gums in water is approximately 6.7%), and stir at 3000 r / min for 30 min using a high-shear emulsifier to form a uniform, pumpable slurry. The apparent viscosity of the slurry at room temperature is 800-1200 mPa·s, meeting the requirements of fluidized bed spraying process. The fluidized bed equipment, with an inlet air temperature of 60℃, has sufficient water evaporation efficiency, ensuring that the particles maintain a good fluidized state during spraying.

[0068] The mixed slurry was uniformly sprayed onto the surface of the fluidized core adsorbent particles using a peristaltic pump on a fluidized bed coating machine at a rate of 8 mL / min. After spraying, the particles were kept in a fluidized state and dried for another 15 minutes to form a functional sustained-release shell.

[0069] Preparation of a fast-dissolving protective film: Weigh 6 parts by mass of hydroxypropyl methylcellulose (HPMC) and dissolve it in 94 parts by mass of deionized water in an 80°C hot water bath. After cooling to room temperature, use the solution as a coating liquid (approximately 6% by mass). Spray an extremely thin layer of HPMC protective film using a fluidized bed coating machine. After spraying, maintain the fluidized state and continue drying for 10 minutes to obtain the finished product.

[0070] In this embodiment, the overall weight gain of the outer covering layer is approximately 61.3% (12+8+50+6) / 124, falling within the range of 50% to 150%.

[0071] Example 4 This embodiment aims to verify the implementation effect when traditional betaine is completely abandoned and xanthan gum is replaced with other water-retaining components.

[0072] The specific sources and specifications of its raw materials are as follows: Natural zeolite powder: particle size 0.15mm, porosity about 35%, saturated water absorption rate about 40%, adsorption capacity ≥160mg / g, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. Trehalose: food grade, purity ≥99%, purchased from Jiangsu Caiwei Biotechnology Co., Ltd.; Sodium carboxymethyl cellulose (CMC): Industrial grade, viscosity ≥1500 mPa·s, purchased from Wen'an County Hongyuan Cellulose Factory; Calcium lactate: Industrial grade, content ≥98%, purchased from Hubei Haijia Biotechnology Co., Ltd. Polyvinyl alcohol (PVA): Grade 1788, degree of alcoholysis 87%~89%, purchased from Anhui Wanwei High-Tech Materials Co., Ltd.

[0073] S1, Preparation of the core adsorption layer 100 parts by weight of zeolite powder were weighed and placed in a vacuum oven, where they were activated at 105°C for 2 hours. The activated zeolite powder was then transferred to a vacuum impregnation tank. A 30% trehalose aqueous solution (30 parts by weight) was prepared by mixing trehalose and 70 parts deionized water and poured into the impregnation tank. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The tank was continuously impregnated under negative pressure at room temperature (25°C) for 4 hours. After impregnation, excess liquid was removed by filtration, and the powder was placed in a forced-air drying oven and dried at 80°C for 4 hours until the moisture content was less than 1%. The powder was then weighed to obtain approximately 112 parts by weight of core adsorbent particles (i.e., approximately 12 parts by weight of trehalose were actually loaded, with a loading of 12 parts by weight, which falls within the range of 10~60 parts by weight).

[0074] Preparation of S2 functional sustained-release shell and surface fast-dissolving protective film 100 parts by mass of the core adsorbent particles prepared above were fed into an industrial fluidized bed coating machine, and the inlet air temperature was controlled at 75°C.

[0075] (The 112 parts by mass of the core adsorbent particles obtained above were all fed into an industrial fluidized bed coating machine. In this embodiment, the amount of subsequent shell components fed was calculated based on the actual mass of all the core adsorbent particles (116 parts by mass) (i.e., equivalent to 100 parts by mass of the total mass of the core adsorbent layer).) Preparation of functional sustained-release shell slurry: Weigh 16 parts by weight of sodium carboxymethyl cellulose (CMC) and 60 parts by weight of calcium lactate, add them to 280 parts by weight of deionized water (approximately 250 parts of water per 100 parts of core layer, with an actual CMC concentration of approximately 5.4%), and stir at 3000 rpm for 30 minutes using a high-shear emulsifier to form a uniform, pumpable slurry. The apparent viscosity of the slurry at room temperature is 1000~1500 mPa·s, meeting the requirements of fluidized bed spraying. At an inlet air temperature of 75℃, the fluidized bed equipment exhibits high water evaporation efficiency, rapidly carrying away any additional water and ensuring rapid film formation on the particle surface. The mixed slurry was uniformly sprayed onto the surface of the fluidized core adsorbent particles using a peristaltic pump on a fluidized bed coating machine at a rate of 12 mL / min. After spraying, the particles were kept in a fluidized state and dried for another 15 minutes to form a functional sustained-release shell.

[0076] Preparation of a fast-dissolving protective film: Weigh 6 parts by mass of polyvinyl alcohol (PVA) and dissolve it in 94 parts by mass of deionized water under a water bath heating condition at 90℃. After cooling to room temperature, use the solution as a coating solution (mass fraction of approximately 6%). Spray an extremely thin PVA protective film using a fluidized bed coating machine. After spraying, maintain the fluidized state and continue drying for 10 minutes to obtain the finished product.

[0077] In this embodiment, the overall weight gain of the outer covering layer is approximately 73.2% (16+60+6) / 112, falling within the range of 50% to 150%.

[0078] Example 5 This embodiment aims to support the applicability of ultra-fine particle gradation and the boundary of high concentration component dosage, and to verify the wear resistance and encapsulation rate of physical granulation process under high specific surface area.

[0079] The specific sources and specifications of its raw materials are as follows: Natural zeolite powder: particle size 0.05mm (ultrafine grade), porosity about 35%, saturated water absorption rate about 40%, adsorption capacity ≥160mg / g, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Polyacrylamide (PAM): Anionic, molecular weight 12 million, purchased from Lebang Polyacrylamide Company; Anhydrous calcium chloride: Industrial grade, content ≥94%, purchased from Zhejiang Juhua Xinlian Chemical Co., Ltd.; Soluble starch: Industrial grade, purchased from Hebei Yanxing Chemical Co., Ltd.

[0080] S1, Preparation of the core adsorption layer Weigh 100 parts by weight of ultrafine zeolite powder and place it in a vacuum oven. Activate at 105℃ for 3 hours (the activation time should be extended due to the large specific surface area). Transfer the activated zeolite powder to a vacuum negative pressure impregnation tank. Prepare a betaine aqueous solution (40% by weight) by mixing 50 parts by weight of betaine and 75 parts by weight of deionized water, and pour it into the impregnation tank. Turn on the vacuum pump and control the vacuum degree inside the tank to -0.08 MPa. Impregnate continuously under negative pressure at room temperature (25℃) for 5 hours (to ensure ultra-high loading capacity fills the micropores). After impregnation, filter to remove excess liquid, place in a forced-air drying oven, and dry at 80℃ for 5 hours until the moisture content is less than 1%. Weigh to obtain approximately 118 parts by weight of core adsorbent particles (i.e., the actual betaine loading is approximately 18 parts by weight, and the loading capacity is 18 parts by weight, which falls within the range of 10~60 parts by weight).

[0081] S2, Preparation of Functional Sustained-Release Shell and Surface Fast-Dissolving Protective Film 100 parts by mass of the core adsorbent particles obtained above were fed into an industrial fluidized bed coating machine. Due to the extremely fine particles, the air flow rate needed to be appropriately reduced to prevent escape, and the air inlet temperature was adjusted to 55°C.

[0082] (The 118 parts by mass of the core adsorbent particles obtained above were all fed into an industrial fluidized bed coating machine. Due to the extremely fine particles, the airflow rate needed to be appropriately reduced to prevent escape, and the inlet air temperature was adjusted to 55°C. In this embodiment, the amount of subsequent shell components fed was calculated based on the actual mass of all the core adsorbent particles (118 parts by mass) (i.e., equivalent to a total mass of 100 parts by mass for the core adsorbent layer).) Weigh 7 parts by weight of polyacrylamide (PAM, approximately 5.9 parts per 100 parts core layer, falling within the range of 5-30 parts) and 80 parts by weight of anhydrous calcium chloride, and add them to 250 parts by weight of deionized water (increasing the water volume reduces the slurry solid content, avoiding excessive slurry viscosity due to high calcium ratio and PAM's high viscosity; the actual concentration of PAM in water is approximately 2.7%). Stir using a high-shear emulsifier at 2500 r / min for 20 min to form a uniform, pumpable slurry. The apparent viscosity of the slurry at room temperature is 500-900 mPa·s, meeting the process requirements for fluidized bed peristaltic pump delivery and atomized spraying. With an inlet air temperature of 55℃ and a relatively low spraying rate (6 mL / min), the fluidized bed equipment ensures sufficient water evaporation, preventing ultrafine particles from adhering to the wall surface due to over-wetting.

[0083] Using a peristaltic pump on a fluidized bed coating machine, the mixed slurry was uniformly sprayed onto the surface of the fluidized core adsorbent particles at a low rate of 6 mL / min to prevent fine particles from sticking to the walls. After spraying, the fluidized state was maintained and dried for another 15 minutes to form a functional sustained-release shell.

[0084] Preparation of a quick-dissolving protective film: Weigh 5 parts by mass of soluble starch and dissolve it in 95 parts by mass of deionized water in an 80℃ hot water bath. After cooling to room temperature, use the solution as a coating liquid (approximately 5% by mass). Spray an extremely thin layer of soluble starch protective film through a fluidized bed coating machine, maintain the fluidized state and continue drying for 10 minutes to obtain the finished product.

[0085] In this embodiment, the overall weight gain of the outer covering layer is approximately 78.0% (7+80+5) / 118, falling within the range of 50% to 150%.

[0086] Comparative Example 1 This comparative example employs the traditional EICP material process of "direct addition of xanthan gum dry powder + physical dry mixing of betaine + one-time mixing of calcium source solution," without using the core-shell coating physical isolation structure described in this invention, nor undergoing vacuum negative pressure impregnation and loading treatment of the zeolite. Its purpose is to demonstrate, through comparison, the key technological contribution of the specific physical structure of this invention—"core adsorption layer + functional slow-release shell layer + surface fast-dissolving protective film"—in solving the problems of difficult xanthan gum dissolution and instantaneous supersaturation and pore blockage by the calcium source.

[0087] The specific sources and specifications of the raw materials are as follows (consistent with the raw material specifications in Example 1): Natural zeolite powder: particle size 0.3mm, porosity approximately 35%, saturated water absorption rate approximately 40%, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. (adsorption capacity ≥160mg / g); Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Xanthan gum: Industrial grade, viscosity ≥12000 mPa·s, purchased from Hebei Yanxing Chemical Co., Ltd. Anhydrous calcium chloride: Industrial grade, content ≥94%, purchased from Zhejiang Juhua Xinlian Chemical Co., Ltd.; This comparative example does not include a surface-soluble protective film (such as PVA components).

[0088] S1, Preparation of direct-mixed dry powder materials Weigh out 100 parts by weight of natural zeolite powder, 30 parts by weight of betaine, 12 parts by weight of xanthan gum powder, and 50 parts by weight of anhydrous calcium chloride.

[0089] All four weighed dry powder raw materials were added at once into a vertical planetary mixer (model: SX-200, volume: 50L). The stirring speed was adjusted to 80 r / min, and the mixture was continuously stirred and mixed for 15 minutes. After mixing, the material was discharged to obtain a direct-mixed dry powder material.

[0090] The preparation process of Comparative Example 1 does not possess the following core technical features of the present invention: 1) Vacuum-free negative pressure impregnation step: Betaine is not loaded into the micropores of zeolite through vacuum impregnation, but is directly mixed with zeolite, xanthan gum and calcium source in a free solid powder state, which makes it very easy to be lost with water or rapidly degraded by microorganisms in the soil.

[0091] 2) Fluidized bed-free coating and composite granulation: Xanthan gum and calcium source do not form a functional slow-release shell around the core, but are dispersed in the overall dry powder as fine powder. Therefore, xanthan gum cannot achieve instantaneous release of single molecules when exposed to water, and calcium source cannot provide gentle physical buffering, which easily leads to agglomeration and pore blockage.

[0092] 3) No surface quick-dissolving protective film: The surface of the particles is not covered with a moisture-proof film such as PVA. However, since zeolite and calcium chloride themselves have strong hygroscopicity, there is still a risk of physical moisture absorption and caking under long-term high humidity storage conditions.

[0093] Comparative Example 2 This comparative example only exhibits betaine core adsorption, but completely lacks the particulate structure of the xanthan gum and calcium source functional slow-release shell. The purpose is to demonstrate, through comparison with Example 1, that the outer layer of water-retaining and thickening components coated with a water-soluble calcium source is an indispensable key technology for solving the problem of calcium source oversaturation precipitation and pore blockage during EICP one-time grouting and achieving uniform curing.

[0094] The specific sources and specifications of the raw materials are as follows (consistent with Example 1): Natural zeolite powder: particle size 0.3mm, porosity approximately 35%, saturated water absorption rate approximately 40%, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. (adsorption capacity ≥160mg / g); Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Polyvinyl alcohol (PVA): Grade 1788, degree of alcoholysis 87%~89%, purchased from Anhui Wanwei High-Tech Materials Co., Ltd. Preparation of the S1 core adsorption layer. 100 parts by weight of natural zeolite powder were placed in a vacuum oven and activated at 105°C for 2 hours. The activated zeolite powder was then transferred to a vacuum impregnation tank. A betaine aqueous solution (30% by weight) was prepared in advance, consisting of 30 parts by weight of betaine and 70 parts by weight of deionized water, and poured into the impregnation tank to completely submerge the zeolite powder. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The impregnation was carried out continuously at room temperature (25°C) for 3 hours. After impregnation, excess liquid was removed by filtration. The loaded zeolite particles were spread evenly on a stainless steel tray and placed in a forced-air drying oven. The tray was dried at 80°C for 4 hours to obtain approximately 112 parts by weight of core adsorbed particles (i.e., approximately 12 parts by weight of betaine actually loaded).

[0095] S2, Preparation of the functional sustained-release shell layer This step is omitted. Fluidized bed coating machines are not used for the coating process of xanthan gum and calcium chloride.

[0096] S3, Preparation of the fast-dissolving protective film on the surface The 112 parts by mass of the core adsorbent particles obtained above were directly fed into an industrial fluidized bed coating machine. The inlet air temperature was controlled at 65°C to keep the particles in a stable fluidized state. 5 parts by mass of polyvinyl alcohol (PVA) were weighed and dissolved in 95 parts of deionized water under a 90°C water bath heating condition. After cooling to room temperature, the solution was used as the coating solution (approximately 5% by mass). The coating solution was uniformly sprayed onto the surface of the core adsorbent particles at a rate of 10 mL / min using a peristaltic pump on the coating machine. After spraying, the particles were kept in a fluidized state and dried for another 10 minutes before being discharged to obtain the finished particles.

[0097] The preparation process of Comparative Example 2 does not possess the following core technical features of the present invention: 1) Functional sustained-release shell without xanthan gum and calcium source: Although betaine is loaded inside the core layer, the outside lacks a physical isolation shell composed of water-retaining and thickening components and water-soluble calcium source.

[0098] 2) Inability to achieve the instantaneous construction of calcium source sustained release and water-retaining gel: Since the calcium source is not encapsulated by the xanthan gum shell, calcium ions are instantaneously overexposed when exposed to water, which cannot achieve the functions of gentle buffer release and prevention of local supersaturation precipitation.

[0099] Comparative Example 3 In this comparative example, both the core adsorption layer and the functional sustained-release shell layer were prepared intact, but the outermost layer was not coated with a surface-soluble moisture-proof film; it was a granular structure. The purpose was to demonstrate, by comparison with Example 1, that the outermost layer of PVA or modified starch-based quick-dissolving moisture-proof film is an important physical barrier to ensure that the product does not absorb moisture and caking during long-term transportation and high-humidity storage, and to maintain excellent water solubility and physical flowability.

[0100] The specific sources and specifications of the raw materials are as follows (consistent with Example 1): Natural zeolite powder: particle size 0.3mm, porosity approximately 35%, saturated water absorption rate approximately 40%, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. (adsorption capacity ≥160mg / g); Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Xanthan gum: Industrial grade, viscosity ≥12000 mPa·s, purchased from Hebei Yanxing Chemical Co., Ltd. Anhydrous calcium chloride: industrial grade, purity ≥94%, purchased from Zhejiang Juhua Xinlian Chemical Co., Ltd.; S1, preparation of the core adsorption layer. 100 parts by weight of natural zeolite powder were placed in a vacuum oven and activated at 105°C for 2 hours. The activated zeolite powder was then transferred to a vacuum impregnation tank. A betaine aqueous solution (30% by weight) composed of 30 parts by weight of betaine and 70 parts by weight of deionized water was prepared in advance and poured into the impregnation tank. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The impregnation was carried out continuously at room temperature (25°C) for 3 hours. After impregnation, excess liquid was removed by filtration, and the powder was placed in a forced-air drying oven and dried at 80°C for 4 hours to obtain approximately 112 parts by weight of core adsorbent particles.

[0101] S2, Preparation of the functional sustained-release shell layer 100 parts by weight of the core adsorbent particles prepared above were fed into an industrial fluidized bed coating machine, with the inlet air temperature controlled at 65°C to keep the particles in a stable fluidized state. 12 parts by weight of xanthan gum and 50 parts by weight of anhydrous calcium chloride were weighed and added to 180 parts by weight of deionized water. The mixture was stirred at 3000 rpm for 20 minutes using a high-shear emulsifier to form a homogeneous mixed suspension. This mixed suspension was then uniformly sprayed onto the surface of the core adsorbent particles at a rate of 10 mL / min using a peristaltic pump on the coating machine. After spraying, the particles were kept in a fluidized state and dried for another 15 minutes to form a functional slow-release shell.

[0102] S3, Preparation of the fast-dissolving protective film on the surface This step is omitted. After completing the functional slow-release shell coating and drying, the outermost PVA quick-dissolving moisture-proof film is not sprayed. The fluidized bed equipment is directly shut down, and the finished granules without the moisture-proof film are discharged.

[0103] The preparation process of Comparative Example 3 does not possess the following core technical features of the present invention: 1) No surface quick-dissolving protective film: Although the core adsorption layer and functional slow-release shell are retained, the outermost layer of polyvinyl alcohol (PVA) or modified starch moisture-proof isolation film is missing.

[0104] 2) Lack of resistance to high humidity storage: Without the protection of the outer film, the finished particles are very easy to absorb moisture during long-term transportation and in high humidity environments. Physical adhesion and caking will occur on the particle surface, which will seriously affect the automatic weighing and dry spreading construction on site.

[0105] Comparative Example 4 This comparative example uses a traditional disc granulator instead of the inferior industrial fluidized bed coating machine of this invention for coating. The purpose is to demonstrate, through comparison with Example 1, that the fluidized bed hot air coating technology has irreplaceable advantages in achieving a uniform, dense, crack-free core-shell structure with high adhesion strength; while traditional disc granulation, under room temperature air-drying conditions, is prone to coating layer cracking, peeling, or premature crystallization of the calcium source, failing to form an effective slow-release barrier.

[0106] The specific sources and specifications of the raw materials are as follows (consistent with the raw material specifications in Example 1): Natural zeolite powder: particle size 0.3mm, porosity approximately 35%, saturated water absorption rate approximately 40%, purchased from Xiamen Hongjing Environmental Protection Technology Co., Ltd. (adsorption capacity ≥160mg / g); Betaine: Industrial grade, purity ≥98%, purchased from Hangzhou Haierxi Animal Husbandry Technology Co., Ltd.; Xanthan gum: Industrial grade, viscosity ≥12000 mPa·s, purchased from Hebei Yanxing Chemical Co., Ltd. Anhydrous calcium chloride: Industrial grade, content ≥94%, purchased from Zhejiang Juhua Xinlian Chemical Co., Ltd.; Polyvinyl alcohol (PVA): Grade 1788, degree of alcoholysis 87%~89%, purchased from Anhui Wanwei High-Tech Materials Co., Ltd.

[0107] S1, Preparation of the core adsorption layer 100 parts by weight of natural zeolite powder were placed in a vacuum oven and activated at 105°C for 2 hours. The activated zeolite powder was then transferred to a vacuum impregnation tank. A betaine aqueous solution (30% by weight) composed of 30 parts by weight of betaine and 70 parts by weight of deionized water was prepared in advance and poured into the impregnation tank. The vacuum pump was turned on, and the vacuum degree inside the tank was controlled at -0.08 MPa. The impregnation was carried out continuously at room temperature (25°C) for 3 hours. After impregnation, excess liquid was removed by filtration, and the powder was placed in a forced-air drying oven and dried at 80°C for 4 hours to obtain approximately 112 parts by weight of core adsorbent particles.

[0108] S2, Preparation of the functional sustained-release shell (alternative process) 100 parts by mass of the core adsorbent particles obtained above were fed into an industrial disc granulator (model: BZ-200), and the disc rotation speed was adjusted to 25 r / min, so that the particles continuously tumbled in the disc.

[0109] Weigh 12 parts by weight of xanthan gum and 50 parts by weight of anhydrous calcium chloride, add them to 180 parts by weight of deionized water, and stir for 20 minutes at 3000 r / min using a high-shear emulsifier to form a mixed suspension slurry.

[0110] Using a manual sprayer, the suspension slurry is intermittently sprayed onto the surface of the core adsorbent particles in three batches while tumbling. No external hot air drying is applied; the particles are allowed to air dry naturally at room temperature (around 25°C). This continues until a rough, unevenly thick coating layer forms on the particle surface.

[0111] S3, Preparation of a fast-dissolving protective film on the surface (alternative process) Weigh 5 parts by weight of polyvinyl alcohol (PVA) and dissolve it in 95 parts by weight of deionized water (approximately 5% by weight) under a water bath heating condition at 90°C. Cool to room temperature. Using the same operation as described above, spray the PVA solution onto the surface of the granules coated with the slow-release shell while tumbling in a disc granulator. Allow the granules to air dry naturally before discharging to obtain the finished granules.

[0112] The preparation process of Comparative Example 4 does not possess the following core technical features of the present invention: 1) Replace fluidized bed coating machine with disc granulator: The main equipment of the process has undergone a fundamental change, using disc centrifugal rolling granulation instead of fluidized bed suspension spray coating.

[0113] 2) The coating process abandons hot air heating and adopts room temperature natural air drying: This process defect causes the coating material to shrink and crack during the drying process, and the internal solute (calcium chloride) is prone to recrystallization and puncture the coating layer.

[0114] 3) Insufficient density and strength of the shell: The above-mentioned process differences result in a loose, porous and poorly adhered coating layer on the surface of the generated particles, which cannot achieve the physical and gentle buffering of calcium ions and the immediate isolation of moisture.

[0115] Experimental test: To intuitively and rigorously demonstrate the technical advantages of the "core-shell-membrane" three-layer dry composite particles of the present invention in practical engineering applications, and to overcome the defects of the prior art such as easy caking during high humidity storage, easy agglomeration of xanthan gum on site, and local precipitation and pore blockage caused by instantaneous release of calcium source, the particles prepared in Examples 1-5 and Comparative Examples 1-4 are tested through the following application experiments. 1. Experimental materials and environmental conditions: The experimental soil was taken from typical coastal silty soft soil from the second phase of the land reclamation project in the Lianhe area of ​​southern Xiang'an. The initial moisture content was 55%, the natural density was 1.65 g / cm³, the void ratio was 1.52, and the pH value was 8.2.

[0116] Substrate solution: A mixed aqueous solution of industrial urease (activity approximately 500 U / g) and urea (concentration 1.0 mol / L).

[0117] Simulated environment: Constant temperature and humidity test chamber (simulating a coastal high humidity environment, temperature 30℃, relative humidity 90%).

[0118] 2. Test Items and Experimental Procedures 2.1) Test Item A: High Humidity Storage Moisture-Proof Performance Test (Simulated Sea Freight and On-Site Storage) Experimental procedure: Take 500g each of the dry granules / powders prepared in Examples 1-5 and Comparative Examples 1-4, and spread them evenly in an open, uncovered tray. Place them in a constant temperature and humidity chamber at 30°C and 90%RH for 7 days.

[0119] Test parameters: After removal, the material is sieved using a 2mm standard sieve. The moisture absorption and agglomeration rate (%) is calculated as follows: (mass of agglomerated material on the sieve / 500g) × 100%. The lower the agglomeration rate, the better the moisture-proof performance and the better the flowability of the material when mechanically spread on site.

[0120] 2.2) Test Item B: One-step sol and anti-caking performance test (simulated on-site solution preparation) Experimental Procedure: Extract 100g of each group of material after high humidity exposure (Test A) and pour it into a container containing 900mL of construction water. Use a portable low-speed mixer to continuously stir at 400r / min.

[0121] Test criteria: Record the time required for the material to completely dissolve and for no visible clumping of xanthan gum powder (complete dissolution time / min). If significant clumping persists after stirring for more than 30 minutes, it is considered severe clumping. 2.3) Test Item C: Performance Test of In-situ Grouting Reinforcement in Soft Soil (Anti-clogging and Homogeneity Evaluation) Experimental Procedure: Coastal silty soft soil was filled into a PVC acrylic mold with a height of 30cm and a diameter of 10cm to simulate a foundation soil column. Fresh sample material from the example / comparative examples, undisturbed by high humidity, was added to an appropriate amount of water at a dosage of 3% of the soil mass and stirred at 400 rpm for 5 minutes to prepare a suspension. The suspension was mixed with an equal volume of substrate solution (urease + urea) and then injected into the soil from the top of the soil column in a single injection under low pressure (0.2MPa). After curing in a sealed environment at 25°C for 7 days, the mold was removed.

[0122] Test parameters: The solidified soil column was divided into two sections: an upper section (near the grouting port) and a lower section (far from the grouting port); the unconfined compressive strength (UCS, MPa) of the upper and lower sections was tested separately. The smaller the strength difference between the upper and lower sections, the less likely local supersaturation precipitation and pore blockage have occurred, and the better the slow-release and infiltration effect of the calcium source.

[0123] 3. Experimental Results The experimental test results are shown in Table 1 below: Table 1. Test results of the particles prepared in the examples and comparative examples. 4. Data Analysis and Conclusions 1) Comparative Example 1 and Comparative Example 1 Comparative Example 1, using traditional dry mixing and direct addition, exhibited a moisture absorption and clumping rate as high as 48.5%, and even after stirring for 30 minutes, xanthan gum "fish-eye" clumps remained undissolved. In contrast, Example 1, employing a core-shell coating process, showed a moisture absorption and clumping rate of only 1.2%, and dissolved completely within 4 minutes.

[0124] It can be seen that traditional free xanthan gum powder readily forms a dense, waterproof film on its surface upon contact with water, hindering the dissolution of the internal dry powder. This invention copolymerizes xanthan gum with other components in slurry form to coat the carrier surface, forming a micron-sized thin shell. Upon contact with water, the shell instantly disintegrates, completely eliminating physical clumping and successfully achieving the engineering goal of a one-step, extremely simple sol-gel process without the need for powerful shearing equipment.

[0125] 2) Comparative Examples 1, 2, and 4 In Comparative Example 1 (free calcium source), extreme polarization in strength was observed (2.65 MPa in the upper part and 0.25 MPa in the lower part), proving that free calcium ions reacted violently with carbonate ions instantaneously to form local precipitates, completely blocking the grouting pores and preventing the grout from penetrating downwards. In Comparative Example 4 (disc granulation replacing fluidized bed coating), due to the loose and porous coating layer with cracks, the calcium source was released in large quantities prematurely during the preparation of the adhesive and the initial stage of grouting, resulting in a significant strength difference between the upper and lower parts (1.45 MPa in the upper part and 0.72 MPa in the lower part), failing to achieve uniform slow release. In Comparative Example 2 (complete lack of functional slow-release shell), the strength of both the upper and lower parts was close to 0 MPa, and the soil did not undergo effective solidification, fundamentally proving that the functional slow-release shell is not only a physical barrier for calcium ions but also the material basis for the uniform occurrence of mineralization reactions in the depth of the soil.

[0126] As can be seen, in Example 1, the strength of the upper and lower parts is equal (1.85MPa vs 1.78MPa), with a strength difference of only 0.07MPa, indicating an extremely homogeneous curing effect. This conclusively proves that the functional slow-release shell of the present invention, by encapsulating the calcium source through a polymer network, successfully achieves a gentle physical buffering release of calcium ions, allowing the mineralization reaction to proceed uniformly deep within the soil pores, thus solving the long-standing problem of pore blockage in EICP technology.

[0127] 3) Comparing Example 1 and Comparative Example 3 In Comparative Example 3, after removing the outermost PVA quick-dissolving protective film, the agglomeration rate soared to 65.2% in a 90% RH environment, completely losing its dry-spreading fluidity and severely slowing down subsequent sol-gel processes. This demonstrates that a core-shell structure alone is insufficient to cope with harsh conditions in engineering sites. An extremely thin, quick-dissolving moisture-proof film, comprising 1% to 8% of the total particle mass, is a crucial physical barrier ensuring the product does not absorb moisture and maintains excellent fluidity.

[0128] 4) Horizontal comparison of Examples 1 and 2 The moisture absorption and clumping rate of PVA (Example 1) was 1.2%, slightly better than that of modified starch (Example 2) at 1.5%; and the PVA sol-gel speed was faster. This indicates that the intermolecular hydrogen bond network of PVA after film formation is more compact, and its water resistance and uncoiling speed are slightly superior. However, both can control the clumping rate within the excellent range of less than 2%.

[0129] 5) Horizontal comparison between Example 1 and Example 4 Example 4 used "CMC + calcium lactate" instead of "xanthan gum + calcium chloride", resulting in a longer sol-gel time of 6 minutes and a slight decrease in curing strength to 1.55 MPa. It can be seen that CMC has weaker dispersibility than xanthan gum, which exhibits pseudoplastic fluid characteristics, and the dissociation constant of organic calcium (calcium lactate) is lower than that of the strong electrolyte calcium chloride, leading to a decrease in the effective calcium ion concentration. However, this solution still achieved homogenization of the strength of the upper and lower parts (without pore blockage), proving that this peripheral component also meets the requirement of non-pore blockage slow release, providing an alternative solution.

[0130] 6) Horizontal comparison between Example 1 and Example 5 Example 5 uses 0.05mm ultrafine zeolite powder, which has the largest specific surface area, resulting in extremely fast sol formation (3 min) and the highest curing strength (1.92 MPa), but the moisture absorption rate also slightly increases to 2.1%. The success of Example 5 demonstrates the rationality of the specific anti-sticking granulation process parameters of "55℃ air intake and 6mL / min low-speed spraying".

[0131] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0132] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement, characterized in that, From the inside out, it includes: The core adsorption layer includes: a porous inorganic mineral carrier and an enzyme protectant loaded in the micropores of the porous inorganic mineral carrier; A functional sustained-release shell layer, which covers the outside of the core adsorption layer, includes a water-retaining and thickening component and a water-soluble calcium source. A surface protective film, which covers the outermost layer of the functional slow-release shell, is a water-soluble polymer moisture-proof film.

2. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, Based on 100 parts by weight of the porous inorganic mineral carrier, the loading of the enzyme protectant is 10-60 parts by weight.

3. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, The porous inorganic mineral carrier is selected from at least one of natural zeolite, synthetic zeolite, mesoporous silica, diatomite, kaolinite or attapulgite. The enzyme protectant is selected from at least one of betaine, trehalose, proline, sorbitol, or glycerol.

4. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, Based on a total mass of 100 parts by mass of the core adsorption layer, the amount of the water-retaining and thickening component is 5-30 parts by mass, and the amount of the water-soluble calcium source is 30-95 parts by mass.

5. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, The water-retaining and thickening component is selected from at least one of xanthan gum, guar gum, sodium carboxymethyl cellulose, or polyacrylamide. The water-soluble calcium source is selected from at least one of calcium chloride, calcium acetate, calcium nitrate, calcium formate, or calcium lactate.

6. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, The surface protective film accounts for 1% to 8% of the total mass of the composite particles.

7. The EICP dry-state fast-dissolving slow-release composite particles for soft soil reinforcement according to claim 1, characterized in that, The raw material of the surface protective film is selected from at least one of polyvinyl alcohol, modified starch, carboxymethyl starch or water-soluble cellulose ether.

8. The method for preparing EICP dry-state fast-dissolving and slow-release composite particles for soft soil reinforcement according to any one of claims 1-7, characterized in that, Includes the following steps: S1, Under vacuum negative pressure conditions, an aqueous solution containing an enzyme protectant is impregnated into an activated porous inorganic mineral carrier, and after drying, the core adsorption layer is obtained; S2, In a fluidized bed device, hot air is used to make the core adsorption layer fluidized and suspended, and a mixed slurry containing the water-retaining and thickening components and water-soluble calcium source is sprayed onto the surface of the core adsorption layer and dried to form the functional slow-release shell layer; S3, in the fluidized bed equipment, a solution for forming a surface protective film is sprayed onto the surface of the particles treated in S2, and the composite particles are obtained after drying.

9. The method for preparing EICP dry-state fast-dissolving and slow-release composite particles for soft soil reinforcement according to claim 8, characterized in that, In S2, the inlet air temperature of the fluidized bed equipment is 50℃~80℃, and the spraying rate of the mixed slurry is 5~15mL / min.

10. A method for reinforcing soft soil, characterized in that, Includes the following steps: The composite particles according to any one of claims 1-7 are added to water and stirred to dissolve the surface protective film and the functional slow-release shell layer in the water, thereby obtaining a mixed colloid containing the water-retaining and thickening components, water-soluble calcium source and free core adsorption layer. A substrate solution containing industrial urease and urea is added to the mixed adhesive and mixed evenly to form a final reinforcement liquid. The final reinforcement liquid is then injected into the soft soil layer to be reinforced in one go, or mixed with the soft soil layer to be reinforced.

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