Anti-shrinkage reinforcing agent for fluidized soil and preparation method of anti-shrinkage reinforcing agent
By constructing an alkali-resistant organic-inorganic interpenetrating network shell and a geopolymer mineralization layer, the problem of microcapsules easily failing in strongly alkaline geopolymers was solved, and the shrinkage resistance of fluidized soil was enhanced throughout its entire lifespan.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI HUASHI NANO TECH CO LTD
- Filing Date
- 2026-01-28
- Publication Date
- 2026-05-05
AI Technical Summary
Existing microencapsulation technology is prone to shell hydrolysis in strongly alkaline polymerized soils, leading to failure of internal curing and making it difficult to balance long-term volume stability and mechanical strength.
Octyltriethoxysilane and liquid paraffin were mixed and combined with modified urea-formaldehyde prepolymer to form an alkali-resistant organic-inorganic interpenetrating network shell through in-situ encapsulation. Aluminum and silicon sources were introduced into the outer layer of the microcapsule to construct a geopolymer mineralization layer and mesoporous channels.
It significantly improves the stability of microcapsules in strongly alkaline environments and their interfacial chemical healing ability, achieving full-age shrinkage enhancement of fluidized soil while taking into account both early strength and later internal curing function.
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Figure CN121974598A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of backfill material technology, specifically to an anti-shrinkage reinforcing agent for fluidized soil and its preparation method. Background Technology
[0002] With the increasing national requirements for the resource utilization of solid waste, geopolymer (alkali-activated cementitious material) fluidized soil technology, which uses industrial waste such as fly ash and slag as main raw materials, has been widely used in engineering fields such as roadbed backfilling and underground cavity filling due to its advantages of being green, low-carbon, and having early strength and rapid hardening. However, geopolymer materials have significant volume shrinkage problems during the hardening process, especially their high chemical shrinkage and drying shrinkage, which can easily lead to microcracks in the matrix, resulting in engineering hazards such as leakage, strength reduction, and decreased durability.
[0003] Currently, the main methods for solving the shrinkage problem of geopolymers include adding shrinkage-reducing agents and internal curing agents. Traditional alcohol ether-based shrinkage-reducing agents can reduce shrinkage by lowering the surface tension of the pore solution, but they often hinder the alkali-activated reaction process, significantly reducing the early strength of the material. On the other hand, internal curing materials leave macroscopic pores in the matrix after releasing moisture, severely weakening the mechanical properties and impermeability of the hardened body. In recent years, phase change microcapsule or sustained-release microcapsule technology has been introduced into this field, attempting to achieve long-term anti-shrinkage regulation by encapsulating hydrophobic components or moisture.
[0004] However, existing microencapsulation technology faces severe technical bottlenecks when directly applied to geopolymer fluidized soil systems. First, the reaction environment of geopolymers is highly alkaline (pH value is usually as high as 13-14). Traditional pure organic shells such as urea-formaldehyde resin and melamine-formaldehyde resin are prone to hydrolysis, swelling, or even rupture under this environment, causing the internal core components (such as paraffin and silane) to leak prematurely during stirring or the initial stage of solidification, thus failing to exert long-term internal curing and anti-shrinkage effects. Second, the surface of pure organic microcapsules is chemically inert, with only weak physical-mechanical interlocking with the inorganic aluminosilicate matrix, lacking chemical bonding. Under long-term dry-wet cycles or temperature change stress, this weak interfacial transition zone is prone to peeling, making the microcapsule a source of defects in the matrix. In addition, in order to improve alkali resistance, existing technologies often tend to increase the thickness or density of the shell, but this introduces a new contradiction: an overly dense shell blocks the release channels of water or modified molecules, making it impossible for the internal curing function to achieve breathable regulation, resulting in weak strength growth in the later stages.
[0005] Therefore, there is an urgent need to develop an anti-shrinkage reinforcing agent that can resist the erosion of a strongly alkaline environment and take into account both long-term volume stability and mechanical strength. Summary of the Invention
[0006] In view of this, the purpose of this invention is to propose an anti-shrinkage reinforcing agent for fluidized soil and its preparation method, so as to solve the problem that the shell of existing microcapsules in strongly alkaline geopolymers is easily hydrolyzed, leading to failure of internal curing, and it is difficult to balance long-term volume stability and mechanical strength.
[0007] To achieve the above objectives, the present invention provides a method for preparing an anti-shrinkage reinforcing agent for fluidized soil, comprising the following steps: S1: Mix n-octyltriethoxysilane and liquid paraffin, and then perform ultrasonic dispersion treatment to obtain a uniform oil phase suspension; S2: Dissolve sodium dodecylbenzenesulfonate in deionized water and stir until the solution is clear and transparent to obtain an aqueous dispersion; S3: The oil phase suspension is slowly added to the aqueous phase dispersion under high-speed shear to carry out a high-speed shear emulsification reaction, and an oil-in-water emulsion is obtained. S4: Mix urea, formaldehyde aqueous solution and gallic acid, adjust the pH of the system to 8, carry out condensation reaction under heating and stirring conditions, then add γ-aminopropyltriethoxysilane to continue the reaction, and obtain modified urea-formaldehyde prepolymer solution. S5: The modified urea-formaldehyde prepolymer solution was added dropwise to the oil-in-water emulsion, the pH of the system was adjusted to 3, and tetraethyl orthosilicate was added for in-situ coating; then γ-aminopropyltriethoxysilane was added for grafting, followed by aluminum nitrate solution for reaction, and finally tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were added to adjust the pH of the system to 9. After the reaction was completed, the wet product was obtained by separation and washing. S6: The wet product is dispersed in an aqueous solution of polyether-modified polysiloxane for impregnation treatment, and then filtered, separated and dried to obtain the shrinkage-resistant reinforcing agent for fluidized soil.
[0008] Preferably, the ratio of n-octyltriethoxysilane to liquid paraffin in step S1 is 6-10g:3.75-6.25g.
[0009] Preferably, the ultrasonic dispersion treatment in step S1 has a power of 240-360W, a frequency of 40kHz, and a treatment time of 8-12min.
[0010] Preferably, the stirring conditions in step S2 are a temperature of 25°C, a rotation speed of 800-1200 r / min, and a time of 24-36 min.
[0011] Preferably, the rotational speed of the high-speed shearing in step S3 is 8000-12000 r / min.
[0012] Preferably, the addition method in step S3 is dropwise addition, with a dropwise addition rate of 4-6 mL / min.
[0013] Preferably, the high-speed shear emulsification time in step S3 is 4-6 minutes.
[0014] Preferably, the ratio of oil phase suspension to aqueous phase dispersion in step S3 is 10-18g:150-250g.
[0015] Preferably, the pH adjustment of the system to 8 in step S4 is achieved by adding triethanolamine dropwise.
[0016] Preferably, the condensation reaction in step S4 is carried out at a temperature of 70-80°C for 1-2 hours.
[0017] Preferably, in step S4, γ-aminopropyltriethoxysilane is added and the reaction continues for 30-45 minutes.
[0018] Preferably, the ratio of urea, formaldehyde aqueous solution, gallic acid, and γ-aminopropyltriethoxysilane used in step S4 is 8-12g:21.6-32.4g:0.8-1.2g:0.8-1.2g.
[0019] Preferably, the formaldehyde aqueous solution in step S4 has a mass fraction of 37 wt%.
[0020] Preferably, the pH value is adjusted to 3 in step S5 by adding citric acid.
[0021] Preferably, the reaction temperature for in-situ coating in step S5 is 45-55°C and the reaction time is 1.5-2.5h.
[0022] Preferably, in step S5, γ-aminopropyltriethoxysilane is added and stirred for 45 min.
[0023] Preferably, in step S5, after adding the aluminum nitrate solution, the system needs to be heated to 55-65°C and kept at that temperature for 0.8-1.2 hours.
[0024] Preferably, the ratio of the modified urea-formaldehyde prepolymer solution, oil-in-water emulsion, tetraethyl orthosilicate, γ-aminopropyltriethoxysilane, aluminum nitrate solution, and hexadecyltrimethylammonium bromide in step S5 is 30-45g:150-250g:6.4-9.6g:0.8-1.2g:8-12mL:0.8-1.2g.
[0025] Preferably, the tetraethyl orthosilicate is added in two separate applications, with the ratio of the first application to the second application being 5:3.
[0026] Preferably, the aluminum nitrate solution in step S5 has a mass fraction of 2 wt%.
[0027] Preferably, the mass fraction of the polyether-modified polysiloxane aqueous solution in step S6 is 4%-5%.
[0028] Preferably, the immersion treatment time in step S6 is 25-35 minutes.
[0029] Preferably, the drying conditions in step S6 are vacuum drying at 40°C for 24 hours.
[0030] Preferably, the ratio of the wet product to the polyether-modified polysiloxane aqueous solution in step S6 is 40-50g:200mL.
[0031] Preferably, the polyether-modified polysiloxane in step S6 is BYK-349.
[0032] Furthermore, the present invention also provides a shrinkage-resistant reinforcing agent for fluidized soil.
[0033] The beneficial effects of this invention are: This invention constructs a strong alkali-resistant organic-inorganic interpenetrating network hybrid shell, solving the problem of microcapsules easily failing in geopolymers. By introducing tetraethyl orthosilicate in situ during the acidic polycondensation stage of the modified urea-formaldehyde prepolymer, the hydrolysis and condensation of the silicon source under acidic conditions are carried out simultaneously with the curing of the organic resin, forming an entangled structure between the organic resin skeleton and the inorganic silica network. This significantly improves the shell's ability to block high concentrations of hydroxide ions, effectively preventing hydrolysis and degradation in strongly alkaline geopolymer slurries, ensuring the storage stability of the internal hydrophobic and internal curing components, and avoiding component loss and matrix defects caused by early shell breakage. This invention achieves in-situ mineralization and interfacial chemical healing of geopolymer surfaces, significantly improving durability. By introducing an aluminum source into the outer layer of the microcapsule and cooperating with secondary deposition of a silicon source under alkaline conditions, a geopolymer mineralization layer rich in Si-O-Al bonds is grown in situ on the surface of the microcapsule. This mineralization layer has a natural crystal structure similarity and chemical affinity with the fly ash / slag geopolymer matrix, which can induce the directional growth of hydration products on its surface, transforming the traditional physical mechanical interlocking into a strong chemical covalent bond. Even during harsh wet and dry cycles and long-term service, the microcapsules will not peel off from the matrix, thus ensuring the long-term volume stability and impermeability of the material. This invention establishes a controllable breathing channel based on a mesoporous template, balancing early compaction with later internal curing effects. By introducing a quaternary ammonium cationic surfactant as a pore-forming template agent during shell construction, nanoscale mesoporous channels are constructed within the dense hybrid shell. These channels act as breathing valves: in the early stages, the shell remains relatively intact to support the matrix framework, providing excellent early strength; during the later drying process, the channels utilize capillary pressure differences to slowly release internally stored moisture or modified components to the surrounding matrix, maintaining continuous hydration in the interface region. This design cleverly balances the contradiction between preservation and functional release, achieving anti-shrinkage enhancement effects throughout all ages. In summary, this invention solves the problem of microcapsules' easy failure in geopolymers by constructing an organic-inorganic interpenetrating network shell resistant to strong alkalis, achieves chemical bonding with the matrix by utilizing in-situ growth of a geopolymer-like mineralization layer on the surface, significantly improving durability; and constructs nanoporous breathing channels to balance early compaction and later internal curing release, achieving full-age shrinkage enhancement of fluidized soil. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Figure 1 This is a schematic diagram of the anti-shrinkage reinforcing agent structure obtained in an embodiment of the present invention. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.
[0036] The sources or properties of the raw materials used in the embodiments and comparative examples of this invention are as follows: The formaldehyde aqueous solution has a mass fraction of 37 wt%; the citric acid solution has a mass fraction of 10 wt%; the aluminum nitrate solution has a mass fraction of 2 wt%; and the polyether-modified polysiloxane is BYK-349.
[0037] Example 1: A method for preparing an anti-shrinkage reinforcing agent for fluidized soil, the specific steps of which are as follows: (1) Weigh 6g of n-octyltriethoxysilane and 3.75g of liquid paraffin and add them to a beaker. Disperse the mixture by ultrasonication (power 240W, frequency 40kHz) for 8 minutes at room temperature to form a uniform, semi-transparent oil suspension without particle agglomeration. (2) Add 0.75g sodium dodecylbenzenesulfonate to 150mL of deionized water and stir continuously at 25℃ and 800r / min for 24min until the solution is clear and transparent and forms an aqueous dispersion. (3) Slowly add 10g of oil phase suspension to 150g of aqueous phase dispersion, start the emulsifier and set the speed to 8000r / min. Under high-speed shear, use a constant pressure dropping funnel to slowly drop the obtained oil phase suspension into the aqueous phase dispersion at a flow rate of 4mL / min. After the addition is completed, continue to maintain high-speed shear emulsification for 4min to obtain a water-in-oil emulsion with uniform particle size distribution. (4) Add 8g of urea and 21.6g of formaldehyde aqueous solution to a three-necked flask equipped with a reflux condenser, then add 0.8g of gallic acid, and add triethanolamine dropwise to adjust the pH of the system to 8. Then, place the reaction system at 70℃ and 240r / min and stir for 1h. Add 0.8g of γ-aminopropyltriethoxysilane and continue the reaction at a constant temperature for 30min to obtain a modified urea-formaldehyde prepolymer solution. (5) 30g of modified urea-formaldehyde prepolymer solution was diluted with 24mL of deionized water and then slowly added dropwise to 150g of oil-in-water emulsion at a rate of 2mL / min. After the addition was completed, the pH of the system was adjusted to 3 with citric acid solution and 4g of tetraethyl orthosilicate was added immediately. The reaction was carried out at 45℃ for 1.5h. While keeping the temperature and pH constant, 0.8g of γ-aminopropyltriethoxysilane was added to the reaction system and stirred for 45min. Then, 8mL of aluminum nitrate solution was added and the system was heated to 55℃ and kept at that temperature for 0.8h. Then, 2.4g of tetraethyl orthosilicate and 0.8g of hexadecyltrimethylammonium bromide were added to the system. Ammonia water was slowly added dropwise to adjust the pH of the system to 9 and the reaction was continued at 55℃ for 0.8h. After the reaction was completed, the product was naturally cooled to room temperature and centrifuged at 8000r / min. The precipitate was washed three times with deionized water to remove the free formaldehyde and emulsifier remaining on the surface, and the wet product was obtained.
[0038] (6) 40g of wet product was redispersed in 200mL of 4% polyether-modified polysiloxane aqueous solution and impregnated for 25min. After filtration and separation, it was dried in a vacuum drying oven at 40℃ for 24h to obtain the anti-shrinkage reinforcing agent for fluidized soil.
[0039] Example 2: A method for preparing an anti-shrinkage reinforcing agent for fluidized soil, the specific steps of which are as follows: (1) Weigh 8g of n-octyltriethoxysilane and 5g of liquid paraffin and add them to a beaker. Disperse them by ultrasound (300W power, 40kHz frequency) for 10min at room temperature to form a uniform, semi-transparent oil suspension without particle agglomeration. (2) Add 1g of sodium dodecylbenzenesulfonate to 200mL of deionized water and stir continuously at 25℃ and 1000r / min for 30min until the solution is clear and transparent and forms an aqueous dispersion. (3) Slowly add 14g of oil phase suspension to 200g of aqueous phase dispersion, start the emulsifier and set the speed to 10000r / min. Under high-speed shear, use a constant pressure dropping funnel to slowly drop the obtained oil phase suspension into the aqueous phase dispersion at a flow rate of 5mL / min. After the addition is completed, continue to maintain high-speed shear emulsification for 5min to obtain a water-in-oil emulsion with uniform particle size distribution. (4) Add 10g of urea and 27g of formaldehyde aqueous solution to a three-necked flask equipped with a reflux condenser, then add 1g of gallic acid, and add triethanolamine dropwise to adjust the pH of the system to 8. Then place the reaction system at 75℃ and 300r / min and stir for 2h. Add 1g of γ-aminopropyltriethoxysilane and continue the reaction at a constant temperature for 40min to obtain a modified urea-formaldehyde prepolymer solution. (5) 37.5g of modified urea-formaldehyde prepolymer solution was diluted with 30mL of deionized water and then slowly added dropwise to 200g of oil-in-water emulsion at a rate of 2.5mL / min. After the addition was completed, the pH of the system was adjusted to 3 with citric acid solution and 5g of tetraethyl orthosilicate was added immediately. The reaction was carried out at 50℃ for 2h. While keeping the temperature and pH constant, 1g of γ-aminopropyltriethoxysilane was added to the reaction system and stirred for 45min. Then, 10mL of aluminum nitrate solution was added and the system was heated to 60℃ and kept at 1h. Then, 3g of tetraethyl orthosilicate and 1g of hexadecyltrimethylammonium bromide were added to the system. Ammonia water was slowly added to adjust the pH of the system to 9 and the reaction was continued at 60℃ for 1h. After the reaction was completed, the product was naturally cooled to room temperature and centrifuged at 8000r / min. The precipitate was washed three times with deionized water to remove the free formaldehyde and emulsifier on the surface to obtain the wet product.
[0040] (6) 45g of wet product was redispersed in 200mL of 4.5% polyether-modified polysiloxane aqueous solution and impregnated for 30min. After filtration and separation, it was dried in a vacuum drying oven at 40℃ for 24h to obtain the anti-shrinkage reinforcing agent for fluidized soil.
[0041] Example 3: A method for preparing an anti-shrinkage reinforcing agent for fluidized soil, the specific steps of which are as follows: (1) Weigh 10g of n-octyltriethoxysilane and 6.25g of liquid paraffin and add them to a beaker. Disperse the mixture by ultrasonication (360W power, 40kHz frequency) for 12min at room temperature to form a uniform, semi-transparent oil suspension without particle agglomeration. (2) Add 1.25g sodium dodecylbenzenesulfonate to 250mL of deionized water and stir continuously at 25℃ and 1200r / min for 36min until the solution is clear and transparent and forms an aqueous dispersion. (3) Slowly add 18g of oil phase suspension to 250g of aqueous phase dispersion, start the emulsifier and set the speed to 12000r / min. Under high-speed shear, use a constant pressure dropping funnel to slowly drop the obtained oil phase suspension into the aqueous phase dispersion at a flow rate of 6mL / min. After the addition is completed, continue to maintain high-speed shear emulsification for 6min to obtain a water-in-oil emulsion with uniform particle size distribution. (4) Add 12g of urea and 32.4g of formaldehyde aqueous solution to a three-necked flask equipped with a reflux condenser, then add 1.2g of gallic acid, and add triethanolamine dropwise to adjust the pH of the system to 8. Then, place the reaction system at 80℃ and 360r / min and stir for 2h. Add 1.2g of γ-aminopropyltriethoxysilane and continue the reaction at a constant temperature for 45min to obtain a modified urea-formaldehyde prepolymer solution. (5) 45g of modified urea-formaldehyde prepolymer solution was diluted with 36mL of deionized water and then slowly added dropwise to 250g of oil-in-water emulsion at a rate of 3mL / min. After the addition was completed, the pH of the system was adjusted to 3 with citric acid solution and 6g of tetraethyl orthosilicate was added immediately. The reaction was carried out at 55℃ for 2.5h. While keeping the temperature and pH constant, 1.2g of γ-aminopropyltriethoxysilane was added to the reaction system and stirred for 45min. Then, 12mL of aluminum nitrate solution was added and the system was heated to 65℃ and kept at 1.2h. Then, 3.6g of tetraethyl orthosilicate and 1.2g of hexadecyltrimethylammonium bromide were added to the system. Ammonia water was slowly added dropwise to adjust the pH of the system to 9 and the reaction was continued at 65℃ for 1.2h. After the reaction was completed, the product was naturally cooled to room temperature and centrifuged at 8000r / min. The precipitate was washed three times with deionized water to remove the free formaldehyde and emulsifier on the surface to obtain the wet product.
[0042] (6) 50g of wet product was redispersed in 200mL of 5% polyether-modified polysiloxane aqueous solution and impregnated for 35min. After filtration and separation, it was dried in a vacuum drying oven at 40℃ for 24h to obtain the anti-shrinkage reinforcing agent for fluidized soil.
[0043] Comparative Example 1: The difference from Example 2 is that γ-aminopropyltriethoxysilane was not added in step (4), while the other conditions were the same as in Example 2.
[0044] Comparative Example 2: The difference from Example 2 is that gallic acid was not added in step (4), while the other conditions were the same as in Example 2.
[0045] Comparative Example 3: The difference from Example 2 is that aluminum nitrate solution was not added in step (5), while the other conditions were the same as in Example 2.
[0046] Comparative Example 4: The difference from Example 2 is that after adding aluminum nitrate solution in step (5), tetraethyl orthosilicate and hexadecyltrimethylammonium bromide are no longer added, while the other conditions are the same as in Example 2.
[0047] Comparative Example 5: The difference from Example 2 is that tetraethyl orthosilicate is not added before adding aluminum nitrate solution in step (5), and the other conditions are the same as in Example 2.
[0048] Comparative Example 6: The difference from Example 2 is that the process order of acid-base adjustment and shell construction in step (5) is reversed: Specifically, step (5) is modified as follows: 37.5g of modified urea-formaldehyde prepolymer solution is added to 30mL of deionized water for dilution and then slowly added dropwise to 200g of oil-in-water emulsion at a rate of 2.5mL / min. After the addition is completed, 3g of tetraethyl orthosilicate and 1g of hexadecyltrimethylammonium bromide are added to the system first, and ammonia water is slowly added to adjust the pH of the system to 9 and react at 60℃ for 1h. Then, 8g of aluminum nitrate solution is added to the system and kept warm for 1h. Finally, citric acid solution is used to adjust the pH of the system to 3, 5g of tetraethyl orthosilicate and 1g of γ-aminopropyltriethoxysilane are added, and the system is reacted at 50℃ for 2h. The remaining conditions are the same as in Example 2.
[0049] Comparative Example 7: The difference from Example 2 is that cetyltrimethylammonium bromide was not added in step (5), while the other conditions were the same as in Example 2.
[0050] Performance testing Raw material composition: 70% Class I F fly ash and 30% S95 grade granulated blast furnace slag powder as cementing material, water glass with a modulus of 1.2 and 8 mol / L sodium hydroxide solution (mass ratio 1:1) as alkali activator, and ISO standard sand as aggregate, while controlling the water-to-solid ratio at 0.55, and the amount of anti-shrinkage strengthening agent added is 2% of the total weight of cementing material; Water dissolution rate: The anti-shrinkage reinforcing agent particles (2g each) obtained in the examples and comparative examples were immersed in 200mL of deionized water, sealed and left to stand. The water was changed every 7 days. After 30 days, the particles were taken out and dried at 105℃ to constant weight. The dissolution rate was calculated. Compressive strength: The test was conducted according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar". The specimen size was 40mm×40mm×160mm. The specimens were cured under standard conditions for 7 days and 28 days. The compressive strength was determined using a pressure testing machine (loading rate 2.4kN / s). Plastic cracking test: The test was conducted according to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The specimens were 600mm×600mm×100mm plate-shaped specimens. After molding, they were first placed in an environment with a temperature of 20℃ and a relative humidity of 95% for 24 hours for initial curing in the mold to prevent surface water loss. Then, they were immediately placed in an environment with a temperature of 30℃, a relative humidity of 30% and a wind speed of 5m / s. The initial cracking time, the number of cracks within 24 hours and the maximum crack width were recorded. Drying shrinkage rate: The drying shrinkage test was conducted according to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The specimen size was 100mm×100mm×515mm prism. After the specimen was formed, it was first placed in an environment with a temperature of 20℃ and a relative humidity of 95% for 24 hours for initial curing in the mold to prevent surface water loss. Then it was transferred to a ring with a temperature of 20℃ and a relative humidity of 60%, and the shrinkage deformation rate at 3d, 14d, 28d and 90d was measured using a length comparator (accuracy 0.001mm). Wet-dry cycle shrinkage: The specimens were prisms with a size of 100mm×100mm×515mm. After molding, the specimens were first placed in an environment with a temperature of 20℃ and a relative humidity of 95% for 24 hours of initial curing in the mold to prevent surface water loss. Then, after standard curing for 28 days, wet-dry cycles were performed. The cycle regime was: immersion in saturated Ca(OH)2 solution for 48 hours, drying at 60℃ for 24 hours, and cooling at room temperature for 2 hours. Each cycle lasted for 74 hours. The shrinkage deformation was measured with a length comparator every 5 cycles, for a total of 20 cycles. The cumulative shrinkage rate after 20 cycles was recorded. The test results are shown in Table 1.
[0051]
[0052] Data Analysis: As can be seen from the data in Examples 1-3 of Table 1, the anti-shrinkage reinforcing agent for fluidized soil prepared in this invention exhibits excellent comprehensive effects in all performance indicators. These data indicate that the reinforcing agent not only effectively inhibits plastic cracking caused by rapid moisture evaporation in the early stages, but also continuously resists volume shrinkage caused by water loss or alternating environmental changes during long-term service through its stable microcapsule structure, thereby significantly improving the volume stability and durability of geopolymer fluidized soil.
[0053] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, γ-aminopropyltriethoxysilane plays a crucial chemical bridging role in the synthesis stage of modified urea-formaldehyde prepolymer. It is speculated that the introduction of γ-aminopropyltriethoxysilane effectively improves the compatibility of organic-inorganic components and the compactness of the overall structure, thereby ensuring excellent crack resistance and shrinkage resistance. When this component is missing, there may be a lack of effective chemical bonding between the organic prepolymer and the subsequently introduced inorganic silicon source, resulting in a loose hybrid shell structure and weak interfacial bonding. Under the stress of moisture erosion or alternating wet and dry conditions, this weak bonding interface is prone to peeling.
[0054] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, the introduction of gallic acid significantly improved the crosslinking density and chemical corrosion resistance of the organic shell. It is speculated that the lack of gallic acid weakens the shell's resistance to alkaline environments, making it more prone to slow degradation in the highly alkaline pore liquid of geopolymers, thereby causing the internal active substances to gradually become ineffective and weakening the long-term anti-shrinkage ability.
[0055] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, the addition of aluminum nitrate plays a decisive role in constructing a stable shell and interface structure. It is speculated that the introduction of the aluminum source may promote the in-situ formation of a geopolymer-like (Si-O-Al) structure on the surface of the microcapsules. This structure has a natural chemical affinity with the geopolymer matrix and can achieve chemical healing of the interface. When the lack of aluminum source results in only physical adsorption or weak chemical bonding on the surface of the microcapsules, it cannot resist long-term water erosion, leading to a significant increase in the shell breakage rate. Especially during the dry-wet cycle, the interface lacking chemical anchoring is prone to peeling under repeated expansion-contraction stress, becoming a weak link in the matrix, thereby seriously damaging the durability and mechanical strength of the material.
[0056] As can be seen from the data in Example 2 and Comparative Example 4 in Table 1, inner layer hybridization alone is insufficient, and the lack of outer layer mineralization weakens the overall protective performance. It is speculated that this is due to the combined effect of the outer layer tetraethyl orthosilicate and hexadecyltrimethylammonium bromide, which may have constructed a robust mineralization layer with mesoporous characteristics on the outermost layer of the microcapsule. The absence of this layer exposes the microcapsule directly to the matrix, making it susceptible to damage during stirring and hardening. In addition, the lack of outer layer mineralization results in insufficient surface roughness of the reinforcing agent and a decrease in mechanical interlocking force, which is directly reflected in the reduction of compressive strength.
[0057] As can be seen from the data in Example 2 and Comparative Example 5 in Table 1, the introduction of tetraethyl orthosilicate (TEO) under acidic conditions is crucial for constructing an organic-inorganic interpenetrating network. It is speculated that this is because TEO hydrolyzes and condenses under acidic conditions to form silica sol, which forms an interpenetrating network structure with urea-formaldehyde resin. This is the key to constructing a dense hybrid shell. Its absence results in the shell being mainly organic, which is easily hydrolyzed and destroyed in a strongly alkaline polymer environment. A large amount of internal hydrophobic components dissolve out, and the shell has insufficient strength and poor shrinkage resistance.
[0058] As can be seen from the data in Example 2 and Comparative Example 6 in Table 1, the reversal of the process sequence severely disrupted the formation of microcapsules. This is presumably because, under alkaline conditions, tetraethyl orthosilicate rapidly hydrolyzes into large silica gel particles, failing to uniformly coat the oil droplets, resulting in a discontinuous and defective shell structure. Subsequent acidic conditions may further damage the already formed structure. This incomplete shell leads to the easy dissolution of internal components, and the reinforcing agent becomes a defect point in the matrix, thereby severely reducing crack resistance and mechanical properties. As can be seen from the data in Example 2 and Comparative Example 7 in Table 1, hexadecyltrimethylammonium bromide plays a key role as a pore-forming agent in the system. It is speculated that this is because the shell formed in the absence of CTAB is too dense. Although it provides good support as a rigid filler in the early stage, it blocks the water transport channels. In addition, these mesopores can store and slowly release water, realize the internal curing effect, and promote the later continuous hydration of the interface transition zone. Therefore, the later strength is higher and the shrinkage resistance is better.
[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.
Claims
1. A method for preparing an anti-shrinkage reinforcing agent for fluidized soil, characterized in that, Includes the following steps: S1: Mix n-octyltriethoxysilane and liquid paraffin to form an oil phase suspension; S2: Dissolve sodium dodecylbenzenesulfonate in deionized water to form an aqueous dispersion; S3: The oil phase suspension is added to the aqueous phase dispersion and emulsified to form an oil-in-water emulsion; S4: Urea, formaldehyde aqueous solution and gallic acid are mixed and subjected to condensation reaction, followed by the addition of γ-aminopropyltriethoxysilane to continue the reaction, to obtain modified urea-formaldehyde prepolymer solution; S5: The modified urea-formaldehyde prepolymer solution was added dropwise to the oil-in-water emulsion, and tetraethyl orthosilicate was added for in-situ coating. Then, γ-aminopropyltriethoxysilane was added for grafting, followed by the addition of aluminum nitrate solution for reaction. Finally, tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were added, and the wet product was obtained after separation and washing. S6: The wet product is dispersed in an aqueous solution of polyether-modified polysiloxane for impregnation treatment to obtain an anti-shrinkage reinforcing agent for fluidized soil; The ratio of urea, formaldehyde aqueous solution, gallic acid, and γ-aminopropyltriethoxysilane used in step S4 is 8-12g:21.6-32.4g:0.8-1.2g:0.8-1.2g; In step S5, the ratio of the modified urea-formaldehyde prepolymer solution, oil-in-water emulsion, tetraethyl orthosilicate, γ-aminopropyltriethoxysilane, aluminum nitrate solution, and hexadecyltrimethylammonium bromide is 30-45g:150-250g:6.4-9.6g:0.8-1.2g:8-12mL:0.8-1.2g.
2. The preparation method according to claim 1, characterized in that, In step S1, the ratio of n-octyltriethoxysilane to liquid paraffin is 6-10g:3.75-6.25g.
3. The preparation method according to claim 1, characterized in that, The ratio of oil phase suspension to aqueous phase dispersion in step S3 is 10-18g:150-250g.
4. The preparation method according to claim 1, characterized in that, The addition method described in step S3 is dropwise addition, with a dropwise addition rate of 4-6 mL / min.
5. The preparation method according to claim 1, characterized in that, The condensation reaction in step S4 is carried out at a temperature of 70-80°C for 1-2 hours.
6. The preparation method according to claim 1, characterized in that, The aluminum nitrate solution in step S5 has a mass fraction of 2 wt%.
7. The preparation method according to claim 1, characterized in that, The reaction temperature for in-situ coating in step S5 is 45-55℃ and the reaction time is 1.5-2.5h.
8. The preparation method according to claim 1, characterized in that, In step S5, after adding the aluminum nitrate solution, the system needs to be heated to 55-65℃ and kept at that temperature for 0.8-1.2 hours.
9. The preparation method according to claim 1, characterized in that, In step S6, the ratio of the wet product to the polyether-modified polysiloxane aqueous solution is 40-50 g: 200 mL.
10. A shrinkage-resistant reinforcing agent for fluidized soil, characterized in that, The preparation method according to any one of claims 1-9 is obtained.