Hydrophobic sustained-release capsule and rheology-modified high-performance accelerator

Abstract

The application provides a hydrophobic slow-release capsule and a rheology-adjusted high-performance accelerator, wherein the hydrophobic slow-release capsule can release hydrophobic components in time sequence under the dual response of pH / time, solves the problems of the existing shotcrete technology, such as contradiction between the accelerating function and the hydrophobic function, high rebound rate, large late strength loss, poor anti-permeation and anti-corrosion capacity, and has good application effect in wet shotcrete construction.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a hydrophobic slow-release capsule and a rheology-modifying high-performance accelerator. Background Technology

[0002] Shotcrete, with its advantages of being support-free, rapid setting, and highly adaptable, is widely used in tunnel excavation, underground engineering support, and emergency rescue. Its core requirements are "rapid setting and hardening for immediate support" and "long-term durable protection against environmental erosion." However, in traditional shotcrete technology, there is a significant conflict between the quick-setting and hydrophobic functions: quick-setting agents need to participate in cement hydration quickly to shorten the setting time, while the early intervention of hydrophobic components such as silanes can hinder the cement hydration process, leading to delayed strength development. At the same time, traditional shotcrete generally suffers from high rebound rate (usually 20-30%), large late-stage strength loss, and poor impermeability and corrosion resistance, which seriously affect project quality and economy. Summary of the Invention

[0003] The purpose of this invention is to provide a hydrophobic slow-release capsule and a rheology-modified high-performance quick-setting agent. The hydrophobic slow-release capsule has a dual pH / time response, enabling the time-sequential release of its hydrophobic contents. In the rheology-modified high-performance quick-setting agent, it synergistically combines quick-setting and rheology-modifying functions, eliminating the contradiction between quick-setting and hydrophobic functions in traditional shotcrete technology, and overcoming the defects of traditional shotcrete such as high rebound rate, large later strength loss, and poor impermeability and corrosion resistance.

[0004] To achieve the above objectives, one aspect of the present invention provides a hydrophobic sustained-release capsule comprising a shell and hydrophobic contents enclosed by the shell; the shell is a mixture of polyvinyl butyral, hydroxypropyl methylcellulose and borax, and the hydrophobic contents are a mixture of isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol.

[0005] According to the present invention, the mass of the shell is 100%, wherein the mass of the polyvinyl butyral is 65 wt% to 80 wt%, the mass of the hydroxypropyl methylcellulose is 15 wt% to 30 wt%, and the mass of the borax is 1 wt% to 5 wt%.

[0006] According to the present invention, the mass of the hydrophobic contents is 100%, wherein the mass of isobutyltriethoxysilane is 83 to 83.5 wt%, the mass of octadecyltrimethoxysilane is 9 to 9.5 wt%, and the mass of the first low-carbon monohydric alcohol is 7 to 7.5 wt%.

[0007] According to the present invention, the polyvinyl butyral is type B-30 polyvinyl butyral; and / or The hydroxypropyl methylcellulose is E5 type hydroxypropyl methylcellulose; and / or The first low-carbon monohydric alcohol is ethanol.

[0008] According to the present invention, the hydrophobic sustained-release capsule satisfies the following conditions: particle size D50 is 20±5 μm; and / or The load factor is 60% to 70%.

[0009] The second invention provides a method for preparing hydrophobic sustained-release capsules as described in the first invention, comprising the following steps: A shell material solution is obtained by mixing polyvinyl butyral, hydroxypropyl methylcellulose, borax and organic solvent; and a hydrophobic contents are obtained by mixing isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol. The hydrophobic contents are dropped into the shell material solution and emulsified to obtain an O / W type emulsion; The O / W emulsion is stirred at a first temperature to evaporate the organic solvent, and then spray-dried to obtain the hydrophobic sustained-release capsule.

[0010] According to the present invention, the organic solvent is a mixture of dichloromethane and ethyl acetate.

[0011] According to the present invention, the emulsification is carried out under stirring conditions for a duration of 30-60 min; and / or The first temperature is 40°C to 60°C; and / or The inlet air temperature of the spray drying process is 120°C to 150°C, and the outlet air temperature is 60°C to 80°C.

[0012] According to the present invention, the encapsulation efficiency achieved by the method for preparing the hydrophobic sustained-release capsule is not less than 85%.

[0013] The third invention provides a quick-setting agent powder, including an alkali-free quick-setting agent, a hydrophobic slow-release capsule, a rheology modifier, an early strength agent, and a moisture-proof agent; The hydrophobic sustained-release capsule is a hydrophobic sustained-release capsule according to one of the present inventions or a hydrophobic sustained-release capsule prepared by the method described in another of the present inventions.

[0014] According to the present invention, based on the total mass of the quick-setting agent powder as 100%, the alkali-free quick-setting agent accounts for 50wt% to 60wt%, the hydrophobic sustained-release capsule accounts for 25wt% to 30wt%, the rheology modifier accounts for 8wt% to 12wt%, the early strength agent accounts for 2wt% to 8wt%, and the moisture-proof agent accounts for 1wt% to 3wt%. Preferably, based on the total mass of the quick-setting agent powder as 100%, the mass of the alkali-free quick-setting agent is 55wt%, the mass of the hydrophobic sustained-release capsule is 28wt%, the mass of the rheology modifier is 10wt%, the mass of the early strength agent is 5wt%, and the mass of the moisture-proof agent is 2wt%.

[0015] According to the present invention, the alkali-free quick-setting agent is obtained by compounding aluminum sulfate, diethanolamine, sodium fluorosilicate and anhydrous calcium sulfate; and / or The rheology modifier is a compound of anti-mud polycarboxylate superplasticizer, hydrophobically associating hydroxyethyl cellulose, and Brunei gum; and / or The early strength agent is calcium formate; and / or the moisture-proof agent is fumed silica.

[0016] According to the present invention, the mass of the alkali-free quick-setting agent is 100%, wherein the mass of aluminum sulfate is 72wt% to 80wt%, the mass of diethanolamine is 5wt% to 10wt%, the mass of sodium fluorosilicate is 5wt% to 8wt%, and the mass of anhydrous calcium sulfate is 5wt% to 10wt%.

[0017] According to the present invention, in the rheology modifier, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose and the Brunei gum is (4 to 6):(3 to 4):(1 to 3); Preferably, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose, and the Brunei gum is 5:3:2.

[0018] According to the present invention, the particle size of the quick-setting agent powder is 60 to 80 mesh.

[0019] The fourth invention provides a liquid quick-setting agent, which is obtained by compounding quick-setting agent powder, dispersant stabilizer, low carbon diol, second low carbon monool and water; The quick-setting agent powder is the quick-setting agent powder described in Part III of this invention.

[0020] According to the present invention, based on the total mass of the liquid quick-setting agent as 100%, the quick-setting agent powder accounts for 65wt% to 70wt%, the dispersing stabilizer accounts for 1wt% to 2wt%, the low-carbon diol accounts for 2wt% to 3wt%, the second low-carbon monool accounts for 3wt% to 5wt%, and the water accounts for 20wt% to 25wt%.

[0021] According to the present invention, the dispersing stabilizer is a compound of xanthan gum and sodium alginate; and / or The low-carbon diol is propylene glycol; and / or The second low-carbon monohydric alcohol is ethanol.

[0022] The fifth invention provides a method for preparing a liquid quick-setting agent as described in the fourth invention, comprising the following steps: The dispersant stabilizer, low-carbon diol, second low-carbon monool and water are stirred and mixed at a second temperature, and the quick-setting agent powder is added. The mixture is then homogenized, refined, dispersed and sieved to obtain the liquid quick-setting agent.

[0023] According to the present invention, the second temperature is 55°C to 65°C; and / or The homogenization and refining dispersion includes emulsification, grinding to an average particle size of no more than 3 μm, ultrasonic dispersion; and / or The sieving process involves passing the material through a 100-150 mesh sieve.

[0024] The application of any one of the following in shotcrete: the hydrophobic slow-release capsule according to one of the present inventions, the hydrophobic slow-release capsule prepared by the method according to another of the present inventions, the quick-setting agent powder according to another of the present inventions, the liquid quick-setting agent according to another of the present inventions, and the liquid quick-setting agent prepared by the method according to another of the present inventions. The dosage of the liquid accelerator is 5 wt% to 7 wt% of the mass of the cementitious material in the shotcrete.

[0025] The beneficial effects of this invention are: To address the problems of existing shotcrete technology, such as the contradiction between rapid setting and hydrophobic properties, high rebound rate, large strength loss in the later stage, and poor impermeability and corrosion resistance, this invention provides a hydrophobic slow-release capsule and a rheology-modified high-performance rapid setting agent.

[0026] Compared with the prior art, the present invention has at least the following advantages: (1) The hydrophobic slow-release capsule provided by the present invention uses a compound of polyvinyl butyral, hydroxypropyl methylcellulose and borax as the shell. Polyvinyl butyral provides basic slow-release performance by slowly hydrolyzing after being stably present in the alkaline environment of cement (pH=12-13.5) for a period of time. Hydroxypropyl methylcellulose and borax further achieve the control of the slow-release precision of the hydrophobic contents by optimizing the film-forming and shell-forming properties and establishing a three-dimensional cross-linked network in the shell. Ultimately, the shell achieves the time-sequential release of the hydrophobic contents under the dual response of pH and time. This can delay the release time of the hydrophobic components and avoid the large release of hydrophobic components in the early rapid setting stage, which would prolong cement hydration and affect the normal development of early strength. This achieves both rapid setting and slow release. The water function is decoupled in sequence: the early-stage quick-setting component shortens the cement hydration time and promotes quick setting to ensure construction efficiency; in the later stage, the shell of the hydrophobic slow-release capsule is completely hydrolyzed to release the hydrophobic contents, which are obtained by compounding isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol. Isobutyltriethoxysilane and octadecyltrimethoxysilane constitute a two-component highly active hydrophobic system, and the first low-carbon monohydric alcohol gives the hydrophobic contents good fluidity, which facilitates the migration of the highly active hydrophobic system. In the highly active hydrophobic system, isobutyltriethoxysilane provides a basic hydrophobic layer, and octadecyltrimethoxysilane enhances the hydrophobic durability, achieving long-term hydrophobic protection and overcoming the problem that quick-setting function and hydrophobic function cannot be achieved simultaneously in the prior art.

[0027] (2) The quick-setting powder and liquid quick-setting agent provided by the present invention are compounded with anti-mud polycarboxylate superplasticizer, hydrophobic associative hydroxyethyl cellulose and Brunei gum to obtain a ternary composite synergistic rheology modifier. The anti-mud polycarboxylate superplasticizer, hydrophobic associative hydroxyethyl cellulose and Brunei gum achieve synergistic rheology regulation by dispersing cement particles to enhance compatibility with mud-containing aggregates, forming a three-dimensional network to improve plastic viscosity, and maintaining excellent water retention and thixotropy. It has been verified that the ternary composite synergistic rheology modifier can significantly improve the yield stress and thixotropy of concrete slurry, making its rebound rate ≤10% (the rebound rate is reduced by more than 50% compared with the existing traditional sprayed concrete slurry), and the thickness of a single spraying reaches 100-150mm, which is beneficial to improving the efficiency and quality of wet spraying construction.

[0028] (3) The quick-setting powder and liquid quick-setting agent provided by the present invention provide an alkali-free quick-setting agent with aluminum sulfate as the main body, synergistic compound of diethanolamine, sodium fluorosilicate and anhydrous calcium sulfate, and an early strength agent calcium formate. In this case, sodium fluorosilicate slowly releases fluorosilicate ions to promote cement hydration, and diethanolamine regulates the cement hydration rate to avoid flash setting. Aluminum sulfate accelerates setting by reacting rapidly with calcium hydroxide, a cement hydration product, to generate ettringite, thus forming an early hardening network. Anhydrous calcium sulfate provides sulfate ions to enhance early strength. The above-mentioned alkali-free quick-setting agent and early strength agent work together to ensure the strength development of shotcrete from the wet spraying construction stage. It has been verified that the concrete compressive strength reaches 18-20 MPa in 1 day, which meets the requirements of rapid support while avoiding alkali-aggregate reaction. The strength retention rate in 28 days is ≥98%, ensuring long-term structural safety.

[0029] (4) In the quick-setting powder and liquid quick-setting agent provided by the present invention, it has been verified that the permanent hydrophobic network formed after the hydrophobic slow-release capsule completely releases the hydrophobic contents can reduce the water absorption rate of concrete by more than 87%, reduce the chloride ion diffusion coefficient by more than 85%, and increase the water contact angle to ≥130°, thereby significantly extending the service life of concrete.

[0030] (5) The quick-setting agent powder provided by the present invention can be prepared by simply mixing the components according to the existing mature dry powder mixing process, without the need for specially designed new special equipment; and the dosage of the liquid quick-setting agent provided by the present invention is only 5-7 wt% of the mass of cementitious materials in shotcrete, which is compatible with the existing shotcrete construction process, has strong versatility, and is suitable for promotion and use in wet shotcrete. Attached Figure Description

[0031] Figure 1 This is a physical image of the liquid quick-setting agent provided by the present invention.

[0032] Figure 2 This is a schematic diagram of the application of the liquid quick-setting agent provided by the present invention.

[0033] Figure 3 The results show the sulfate resistance test results of the liquid accelerator prepared in Example 4 and the ordinary accelerator prepared in Comparative Example 10. Detailed Implementation

[0034] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0035] Shotcrete is used in various scenarios, including tunnel excavation, underground engineering support, and emergency rescue. It offers advantages such as requiring no support, rapid setting, and high adaptability. Its key features lie in "rapid setting and hardening for immediate support" and "long-term durable protection against environmental erosion." However, traditional shotcrete technology faces a contradiction: achieving both rapid setting and hydrophobic properties simultaneously is difficult. Accelerators shorten setting time by quickly participating in cement hydration, while the early intervention of hydrophobic components, such as silanes, hinders cement hydration and delays strength development. Furthermore, traditional shotcrete commonly suffers from high rebound rates (typically 20-30%), significant later-stage strength loss, and poor impermeability and corrosion resistance. In response to this, although adding alkali-free quick-setting agents to shotcrete can avoid the risk of alkali-aggregate reaction, it is difficult to balance early strength and later strength; hydrophobic admixtures are mostly added directly, which can easily cause antagonistic effects with quick-setting components; rheology modifiers are mostly added during concrete mixing, which leads to increased pumping pressure and is very likely to cause pipe blockage, thus failing to meet the precise control requirements of shotcrete for yield stress and thixotropy.

[0036] To address the aforementioned problems in existing shotcrete technology, the first aspect of this invention provides a hydrophobic slow-release capsule comprising a shell and hydrophobic contents enclosed by the shell; the shell is a mixture of polyvinyl butyral, hydroxypropyl methylcellulose, and borax, and the hydrophobic contents are a mixture of isobutyltriethoxysilane, octadecyltrimethoxysilane, and a first low-carbon monohydric alcohol.

[0037] In the hydrophobic sustained-release capsule provided by the present invention: On one hand, a compound of polyvinyl butyral, hydroxypropyl methylcellulose, and borax is used as the shell material. The polyvinyl butyral is stable in the strongly alkaline environment of cement for 1 to 6 hours before gradually hydrolyzing, releasing the hydrophobic contents. Furthermore, the hydroxypropyl methylcellulose is used to further optimize the film-forming and shell-forming properties of the polyvinyl butyral, as well as the precision of its slow-release of the hydrophobic contents. The addition of borax acts as a crosslinking agent, constructing a three-dimensional crosslinked network within the shell, further regulating the hydrolysis rate of the shell material and thus improving the precision of its slow-release of the hydrophobic contents. The shell, composed of polyvinyl butyral, hydroxypropyl methylcellulose, and borax, achieves a dual response to pH and time, enabling the time-sequential release of the encapsulated hydrophobic contents. On the other hand, the hydrophobic contents of the hydrophobic sustained-release capsule contain a highly active hydrophobic system composed of isobutyltriethoxysilane and octadecyltrimethoxysilane. Isobutyltriethoxysilane has high reactivity and can react quickly to form a basic hydrophobic layer, while octadecyltrimethoxysilane provides long-chain alkyl groups to further enhance the hydrophobic durability. In addition, a first low-carbon monohydric alcohol is added as a diffusion carrier to reduce the viscosity of the hydrophobic contents, improve its fluidity, and enhance the migration efficiency of the above-mentioned highly active hydrophobic system after release. In summary, the hydrophobic slow-release capsule provided by this invention can achieve time-sequential release of hydrophobic contents under dual pH / time response. The released hydrophobic contents have the advantages of strong hydrophobicity, good persistence, and high flow migration efficiency, laying the foundation for solving the inherent contradiction between the rapid setting function and hydrophobic function in shotcrete.

[0038] In this invention, the proportion of polyvinyl butyral, hydroxypropyl methylcellulose, and borax in the shell of the hydrophobic sustained-release capsule affects its pH / time dual response performance, as well as the film-forming and hydrolytic sustained-release properties of the shell; the proportion of isobutyltriethoxysilane and octadecyltrimethoxysilane in the hydrophobic contents of the hydrophobic sustained-release capsule affects the hydrophobic and durable properties of the hydrophobic contents, while the proportion of the first low-carbon monohydric alcohol affects the flowability of the hydrophobic contents and thus its migration after release. The following embodiments are provided for this purpose.

[0039] In one specific embodiment of the present invention, the mass of the shell is taken as 100%, wherein the mass of polyvinyl butyral is 65wt% to 80wt%, the mass of hydroxypropyl methylcellulose is 15wt% to 30wt%, and the mass of borax is 1wt% to 5wt%.

[0040] In one specific embodiment of the present invention, the mass of the hydrophobic contents is 100%, wherein the mass of isobutyltriethoxysilane is 83 to 83.5 wt%, the mass of octadecyltrimethoxysilane is 9 to 9.5 wt%, and the mass of the first low-carbon monohydric alcohol is 7 to 7.5 wt%.

[0041] In a preferred embodiment of the invention, the polyvinyl butyral is type B-30 polyvinyl butyral; and / or The hydroxypropyl methylcellulose is E5 type hydroxypropyl methylcellulose; and / or The first low-carbon monohydric alcohol is ethanol.

[0042] In one specific embodiment of the present invention, the hydrophobic sustained-release capsules satisfy the following conditions: particle size D50 is 20±5μm; and / or loading rate is 60% to 70%.

[0043] A second aspect of the present invention provides a method for preparing hydrophobic sustained-release capsules as described in the first aspect of the present invention, comprising the following steps: A shell material solution is obtained by mixing polyvinyl butyral, hydroxypropyl methylcellulose, borax and organic solvent; and a hydrophobic contents are obtained by mixing isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol. The hydrophobic contents are dropped into the shell material solution and emulsified to obtain an O / W type emulsion; The O / W emulsion is stirred at a first temperature to evaporate the organic solvent, and then spray-dried to obtain the hydrophobic sustained-release capsule.

[0044] It should be noted that in this invention, "O / W type emulsion" refers to "oil-in-water emulsion", specifically an emulsion formed by the shell material solution encapsulating droplets of the hydrophobic contents.

[0045] In one specific embodiment of the present invention, polyvinyl butyral, hydroxypropyl methylcellulose and borax are added to the organic solvent in the proportion of "65wt% to 80wt% polyvinyl butyral, 15wt% to 30wt% hydroxypropyl methylcellulose and 1wt% to 5wt% borax, based on the total mass of the three as 100%", and stirred until completely dissolved to obtain the shell material solution.

[0046] In one specific embodiment of the present invention, the organic solvent is a mixture of dichloromethane and ethyl acetate; The mass ratio of dichloromethane to ethyl acetate is 1:1.

[0047] In one specific embodiment of the present invention, isobutyltriethoxysilane, octadecyltrimethoxysilane and the first low-carbon monohydric alcohol are mixed in a ratio of 83 to 83.5 wt% isobutyltriethoxysilane, 9 to 9.5 wt% isodecyltrimethoxysilane and 7 to 7.5 wt% isobutyltriethoxysilane, and the first low-carbon monohydric alcohol is stirred evenly to obtain the hydrophobic contents.

[0048] In one specific embodiment of the present invention, the emulsification is carried out under stirring conditions for 30-60 minutes. Specifically, the shell material solution is stirred at a speed of 1000 to 3000 rpm, during which the hydrophobic contents are slowly dripped into the shell material solution, followed by continuous stirring and emulsification for 30-60 minutes to obtain a stable O / W type emulsion.

[0049] In one specific embodiment of the present invention, the organic solvent in the O / W emulsion is evaporated by heating and stirring, wherein the first temperature is 40°C to 60°C. Specifically, the O / W emulsion is placed in an environment of 40°C to 60°C and stirred until the organic solvent therein is completely evaporated.

[0050] In one specific embodiment of the present invention, the inlet air temperature of the spray drying process is 120°C to 150°C, and the outlet air temperature is 60°C to 80°C. Specifically, the spray drying process is performed by setting the inlet air temperature of the spray dryer to 120°C to 150°C and the outlet air temperature to 60°C to 80°C.

[0051] The method for preparing the hydrophobic sustained-release capsules provided by this invention, by combining multiphase emulsification, solvent evaporation and spray drying processes, can prepare hydrophobic sustained-release capsules with a particle size D50 of 20±5μm and a loading rate of 60% to 70%. This ensures that the hydrophobic sustained-release capsules are uniformly dispersed in concrete without damaging the concrete slurry structure. The method can also achieve an encapsulation rate of not less than 85%, enabling efficient utilization of the hydrophobic contents and saving the manufacturing cost of the hydrophobic sustained-release capsules.

[0052] A third aspect of the present invention provides a quick-setting agent powder, comprising an alkali-free quick-setting agent, a hydrophobic slow-release capsule, a rheology modifier, an early strength agent, and a moisture-proof agent; The hydrophobic sustained-release capsule is the hydrophobic sustained-release capsule described in the first aspect of the present invention or the hydrophobic sustained-release capsule prepared by the method described in the second aspect of the present invention.

[0053] In one specific embodiment of the present invention, the alkali-free quick-setting agent is a compound of aluminum sulfate, diethanolamine, sodium fluorosilicate and anhydrous calcium sulfate.

[0054] In one specific embodiment of the present invention, the mass of the alkali-free quick-setting agent is 100%, wherein the mass of aluminum sulfate is 72wt% to 80wt%, the mass of diethanolamine is 5wt% to 10wt%, the mass of sodium fluorosilicate is 5wt% to 8wt%, and the mass of anhydrous calcium sulfate is 5wt% to 10wt%.

[0055] In this invention, sodium fluorosilicate promotes cement hydration by slowly releasing fluorosilicate ions in the alkali-free quick-setting agent; the main component, aluminum sulfate, has high reactivity and can quickly react with cement hydration products (i.e., calcium hydroxide) to generate ettringite, accelerating cement setting; the alkali-free quick-setting agent also contains diethanolamine and anhydrous calcium sulfate, wherein diethanolamine can regulate the cement hydration rate and prevent flash setting of cement due to the rapid reaction of its hydration products with aluminum sulfate; and anhydrous calcium sulfate can replenish sulfate ions in the reaction system and improve the early strength of cement.

[0056] In one specific embodiment of the present invention, the rheology modifier is obtained by compounding an anti-mud polycarboxylate superplasticizer, a hydrophobic associative hydroxyethyl cellulose and Brunei gum.

[0057] In one specific embodiment of the present invention, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose and the Brunei gum in the rheology modifier is (4 to 6):(3 to 4):(1 to 3).

[0058] In a preferred embodiment of the present invention, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose, and the Brunei gum is 5:3:2.

[0059] In a preferred embodiment of the present invention, the molecular weight of the anti-mud polycarboxylate superplasticizer is 20,000 to 50,000.

[0060] In the rheology modifier constructed in this invention, the anti-mud polycarboxylate superplasticizer can disperse cement particles based on electrostatic repulsion and steric hindrance, resisting the intercalation and adsorption of mud-containing aggregates, maintaining good water-reducing performance, and exhibiting high compatibility with mud-containing aggregates; the hydrophobic associating hydroxyethyl cellulose can form a three-dimensional network in the cement paste to improve plastic viscosity; and the Brunei gum can impart excellent water retention properties and good thixotropy to the cement paste. In this rheology modifier, the anti-mud polycarboxylate superplasticizer, hydrophobic associating hydroxyethyl cellulose, and Brunei gum work synergistically to increase the yield stress of the cement paste and shorten its thixotropic recovery time. Specifically, it can increase the yield stress of the cement paste by more than 40% and shorten the thixotropic recovery time by at least 30%, ultimately reducing the resilience of the cement paste.

[0061] In one specific embodiment of the present invention, the early strength agent is calcium formate, which can accelerate cement hydration and improve its 1-day compressive strength.

[0062] In one specific embodiment of the present invention, the desiccant is fumed silica, which can effectively adsorb free moisture in the system, prevent the quick-setting agent powder from absorbing moisture and clumping during storage, and help ensure the storage stability of the quick-setting agent powder.

[0063] In one specific embodiment of the present invention, based on the total mass of the quick-setting agent powder as 100%, the mass of the alkali-free quick-setting agent accounts for 50wt% to 60wt%, the mass of the hydrophobic sustained-release capsule accounts for 25wt% to 30wt%, the mass of the rheology modifier accounts for 8wt% to 12wt%, the mass of the early strength agent accounts for 2wt% to 8wt%, and the mass of the moisture-proof agent accounts for 1wt% to 3wt%.

[0064] In a preferred embodiment of the present invention, based on the total mass of the quick-setting agent powder as 100%, the mass of the alkali-free quick-setting agent is 55wt%, the mass of the hydrophobic sustained-release capsule is 28wt%, the mass of the rheology modifier is 10wt%, the mass of the early strength agent is 5wt%, and the mass of the moisture-proof agent is 2wt%.

[0065] In a more preferred embodiment of the present invention, based on the total mass of the quick-setting agent powder as 100%, the mass of the alkali-free quick-setting agent accounts for 55 wt%, the mass of the hydrophobic slow-release capsule accounts for 28 wt%, the mass of the rheology modifier (wherein the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose and the Brunei gum is 5:3:2) accounts for 10 wt%, the mass of the early strength agent calcium formate accounts for 5 wt%, and the mass of the moisture-proof agent fumed silica accounts for 2 wt%.

[0066] A fourth aspect of the present invention provides a method for preparing the accelerator powder as described in the third aspect of the present invention, comprising the following steps: The alkali-free quick-setting agent, the hydrophobic slow-release capsule, the rheology modifier, the early strength agent and the moisture-proof agent are mixed, stirred and then passed through a 60 to 80 mesh sieve to obtain the quick-setting agent powder.

[0067] In one specific embodiment of the present invention, the alkali-free quick-setting agent is prepared according to the following steps: Aluminum sulfate, diethanolamine, sodium fluorosilicate, and anhydrous calcium sulfate are added to a dry powder mixer in the following proportions: aluminum sulfate 72wt% to 80wt%, diethanolamine 5wt% to 10wt%, sodium fluorosilicate 5wt% to 8wt%, and anhydrous calcium sulfate 5wt% to 10wt%, with the total mass of the four components being 100%. The mixture is stirred until all components are evenly mixed and then passed through an 80-100 mesh sieve to obtain the alkali-free quick-setting agent.

[0068] In one specific embodiment of the present invention, in order to ensure that aluminum sulfate, diethanolamine, sodium fluorosilicate and anhydrous calcium sulfate are thoroughly mixed, the stirring speed of the four components in the dry powder mixer is 50-100 rpm and the stirring time is 30-60 min.

[0069] In one specific embodiment of the present invention, the rheology modifier is prepared according to the following steps: The anti-mud polycarboxylate superplasticizer, the hydrophobic associating hydroxyethyl cellulose, and the Brunei gum are added to a high-speed mixer in a ratio of "the anti-mud polycarboxylate superplasticizer, the hydrophobic associating hydroxyethyl cellulose, and the Brunei gum by mass (4 to 6):(3 to 4):(1 to 3)" (preferably in a ratio of "the anti-mud polycarboxylate superplasticizer, the hydrophobic associating hydroxyethyl cellulose, and the Brunei gum by mass 5:3:2"), and stirred until all components are uniformly mixed to obtain the rheology modifier.

[0070] In one specific embodiment of the present invention, in order to fully mix the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose and the Brunei gum, the three are stirred in a high-speed mixer at a speed of 1000-2000 rpm for a duration of 15-30 min.

[0071] In one specific embodiment of the present invention, in order to prevent the prepared rheology modifier from absorbing moisture during storage, the humidity of its storage environment should be controlled to be no higher than 60%.

[0072] In one specific embodiment of the present invention, the alkali-free quick-setting agent, the hydrophobic slow-release capsule, the rheology modifier, the early strength agent, and the moisture-proof agent are added to a double-helix conical mixer in the following proportions: "50wt% to 60wt% of the alkali-free quick-setting agent, 25wt% to 30wt% of the hydrophobic slow-release capsule, 8wt% to 12wt% of the rheology modifier, 2wt% to 8wt% of the early strength agent, and 1wt% to 3wt% of the moisture-proof agent, based on 100% of the total mass of the quick-setting agent powder" (preferably in the following proportions: "55wt% of the alkali-free quick-setting agent, 28wt% of the hydrophobic slow-release capsule, 10wt% of the rheology modifier, 5wt% of the early strength agent, and 2wt% of the moisture-proof agent, based on 100% of the total mass of the quick-setting agent powder"). The mixture is stirred until all components are evenly mixed and then passed through a 60 to 80 mesh sieve to obtain the quick-setting agent powder.

[0073] In one specific embodiment of the present invention, in order to fully mix the alkali-free quick-setting agent, the hydrophobic slow-release capsule, the rheology modifier, the early strength agent and the moisture-proof agent, the five components are stirred at a speed of 30-50 rpm for 60-90 minutes.

[0074] In one specific embodiment of the present invention, the obtained quick-setting agent powder is packaged under nitrogen protection.

[0075] To adapt to the wet spraying construction method of shotcrete, the fifth aspect of the present invention also provides a liquid accelerator, which is obtained by compounding accelerator powder, dispersant stabilizer, low carbon diol, second low carbon monool and water. The accelerator powder is the accelerator powder described in the third aspect of the present invention or the accelerator powder prepared by the method described in the fourth aspect of the present invention.

[0076] In one specific embodiment of the present invention, based on the total mass of the liquid quick-setting agent as 100%, the quick-setting agent powder accounts for 65wt% to 70wt%, the dispersing stabilizer accounts for 1wt% to 2wt%, the low-carbon diol accounts for 2wt% to 3wt%, the second low-carbon monool accounts for 3wt% to 5wt%, and the water accounts for 20wt% to 25wt%.

[0077] In a preferred embodiment of the present invention, based on the total mass of the liquid quick-setting agent as 100%, the quick-setting agent powder accounts for 67.5 wt%, the dispersant stabilizer accounts for 1.5 wt%, the low-carbon diol accounts for 2.5 wt%, the second low-carbon monool accounts for 4 wt%, and the water accounts for 24.5 wt%.

[0078] In one specific embodiment of the present invention, the dispersing stabilizer is a compound of xanthan gum and sodium alginate; The preferred mass ratio of xanthan gum and sodium alginate is 1:1.

[0079] In one specific embodiment of the present invention, the low-carbon diol is propylene glycol; and / or The second low-carbon monohydric alcohol is ethanol.

[0080] A sixth aspect of the present invention provides a method for preparing a liquid accelerator as described in the fifth aspect of the present invention, comprising the following steps: The dispersant stabilizer, low-carbon diol, second low-carbon monool and water are stirred and mixed at a second temperature, and the quick-setting agent powder is added. The mixture is then homogenized, refined, dispersed and sieved to obtain the liquid quick-setting agent.

[0081] In one specific embodiment of the present invention, the homogenization and refining dispersion includes emulsification, grinding to an average particle size of no more than 3 μm, and ultrasonic dispersion.

[0082] In one specific embodiment of the present invention, the sieving process is to pass through a 100-150 mesh sieve.

[0083] In one specific embodiment of the present invention, the dispersing stabilizer, the low-carbon diol, and the second low-carbon monohydric alcohol are added to water according to the following proportions (preferably according to the following proportions): "1 wt% to 2 wt% of the dispersing stabilizer, 2 wt% to 3 wt% of the low-carbon diol, 3 wt% to 5 wt% of the second low-carbon monohydric alcohol, 20 wt% to 25 wt% of water, based on 100% of the total mass of the liquid quick-setting agent"; and stirred at the second temperature until completely dissolved to obtain a dispersion matrix. The accelerator powder is added to the dispersion matrix at a ratio of 65wt% to 70wt% of the accelerator powder, based on 100% of the total mass of the liquid accelerator (preferably 67.5wt% of the accelerator powder, based on 100% of the total mass of the liquid accelerator). The mixture is stirred and emulsified to ensure uniform mixing of the accelerator powder and the dispersion matrix. Then, the mixture is fined by particle size reduction using a colloid mill, ultrasonically dispersed, and passed through a 100-150 mesh sieve to obtain the liquid accelerator, the physical form of which is shown below. Figure 1 As shown.

[0084] In one specific embodiment of the present invention, the second temperature is 55°C to 65°C; and / or During the preparation of the dispersion matrix, the stirring time shall not be less than 30 minutes in order to ensure that the dispersion stabilizer, the low carbon diol and the second low carbon monool are fully dissolved in water.

[0085] In one specific embodiment of the present invention, in order to fully mix the quick-setting agent powder with the dispersion matrix, the stirring and emulsification speed is 800-1000 rpm and the duration is 40-60 min.

[0086] In one specific embodiment of the present invention, the particle size of the colloid abrasive is refined to no more than 3 μm.

[0087] In one specific embodiment of the present invention, in order to obtain a uniform and stable liquid quick-setting agent, the ultrasonic dispersion time is 15-20 min.

[0088] In one specific embodiment of the present invention, the prepared liquid quick-setting agent is sealed and stored, and then shaken well before use.

[0089] The application of any one of the following in shotcrete: the hydrophobic slow-release capsule according to the first aspect of the present invention, the hydrophobic slow-release capsule prepared by the method according to the second aspect of the present invention, the accelerator powder according to the third aspect of the present invention, the accelerator powder prepared by the method according to the fourth aspect of the present invention, the liquid accelerator according to the fifth aspect of the present invention, and the liquid accelerator prepared by the method according to the sixth aspect of the present invention. The liquid accelerator is added at a rate of 5 wt% to 7 wt% of the mass of the cementitious material in the shotcrete, preferably 6 wt%. As is known to those skilled in the art, the "cementitious material" mentioned herein includes materials added to the shotcrete that possess the ability to bind and hydrate upon contact with water, such as cement, silica fume, and fly ash.

[0090] In one specific embodiment of the invention, in the application, the liquid quick-setting agent is mixed evenly with the sprayed concrete pumped thereto at the nozzle of the wet spraying trolley, and then spraying is performed at the target location, for example... Figure 2 The application scenarios shown.

[0091] In the wet spraying of shotcrete, the accelerator powder (or liquid accelerator) provided by this invention achieves performance breakthroughs at each stage of action through temporal synergy and functional coupling, ultimately improving both the efficiency and quality of wet spraying of shotcrete. The specific mechanism is as follows: During the 0-30 minute spraying stage: the alkali-free quick-setting agent dissolves rapidly. With the dual protection of sodium fluorosilicate releasing fluorosilicate ions to promote hydration and diethanolamine regulating the hydration rate to avoid flash setting, aluminum sulfate reacts with calcium hydroxide, a cement hydration product, to form ettringite, creating an initial hardening network. During this period, the rheology modifier simultaneously plays a rheology regulating role, the anti-mud polycarboxylate superplasticizer disperses cement particles, and the hydrophobic associative HEC (i.e., hydrophobic associative hydroxyethyl cellulose) and Brunei gum construct a three-dimensional network, improving the slurry yield stress and thixotropy, ensuring good cohesion and non-flow during spraying, and reducing the wet spray rebound rate (≤10%). At this time, the shell of the hydrophobic slow-release capsule remains intact in the alkaline environment of the cement, shielding the hydrophobic contents without interfering with the slurry setting and subsequent early strength development.

[0092] In the early stage of strength development (1-24 hours): as cement hydration continues, the alkalinity of the slurry pore liquid gradually increases, and the shell of the hydrophobic slow-release capsule begins to hydrolyze gradually at the designed rate under the dual regulation of pH and time; at the same time, the early strength agent calcium formate accelerates the hydration process, and the anhydrous calcium sulfate in the alkali-free quick-setting agent replenishes sulfate ions to enhance early strength, so that the compressive strength of concrete reaches 18-20 MPa in 1 day, meeting the requirements of rapid support.

[0093] During the 1-7 day functional formation period: the shell of the hydrophobic sustained-release capsule is completely hydrolyzed, releasing the hydrophobic contents. Under the action of low-carbon monohydric alcohol, the hydrophobic contents have good fluidity and migrate to the pores and interfaces inside the concrete under capillary action. A basic hydrophobic film is formed by the chemical reaction between isobutyltriethoxysilane and the silanols of the pore walls. The long-chain alkyl group of octadecyltrimethoxysilane is used to further densify the hydrophobic layer and build a permanent hydrophobic network.

[0094] During the long-term service life of 28 days and beyond: the concrete retains ≥98% of its strength after 28 days, while also exhibiting excellent durability, with a 24-hour volumetric water absorption rate ≤0.8% and a chloride ion diffusion coefficient ≤1.2×10⁻⁶. -12 m 2 / s, with a contact angle ≥130°, effectively resisting the intrusion of harmful media such as moisture and chloride ions.

[0095] The following provides several embodiments and comparative examples, along with performance tests, to further detail the technical solution and the technical effects achieved by the present invention.

[0096] The following anti-mud polycarboxylate superplasticizer is used: Wuhan Huaxuan High-Tech Co., Ltd., model KH-6.

[0097] The hydrophobic associative hydroxyethyl cellulose used below is: Natrosol Plus 330, manufactured by Aqualon, USA.

[0098] The following cement was used: Jinyu Group P.O42.5 type cement.

[0099] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0100] Preparation of hydrophobic sustained-release capsules.

[0101] Example 1: This embodiment provides a hydrophobic sustained-release capsule, which includes a shell and hydrophobic contents enclosed by the shell; The shell is composed of "70wt% of B-30 type polyvinyl butyral (hereinafter referred to as PVB), 25wt% of E5 type hydroxypropyl methylcellulose (hereinafter referred to as HPMC), and 5wt% of borax, with the total mass of the shell being 100%". The hydrophobic contents consist of "83.36 wt% isobutyltriethoxysilane, 9.24 wt% octadecyltrimethoxysilane, and 7.40 wt% ethanol, based on the total mass of the hydrophobic contents being 100%"; The hydrophobic sustained-release capsule has a particle size D50 of 20 μm and a loading rate of 65%.

[0102] The hydrophobic sustained-release capsules provided in this embodiment are prepared according to the following steps: 1) Add 7 kg of PVB, 2.5 kg of HPMC, and 0.5 kg of borax to 50 kg of organic solvent (i.e., a mixture of dichloromethane and ethyl acetate in a mass ratio of 1:1), and stir until dissolved to obtain a shell material solution; 17.23 kg of isobutyltriethoxysilane, 1.91 kg of octadecyltrimethoxysilane, and 1.53 kg of ethanol were mixed evenly to obtain a hydrophobic contents. 2) While stirring the shell material solution at 2000 rpm, the hydrophobic contents were added dropwise to the shell material solution. After the addition was completed, the mixture was stirred at 2000 rpm for 40 minutes to emulsify. Then the temperature was raised to 45°C and stirred at this temperature until the organic solvent was completely evaporated. The mixture was then sent to a spray dryer and spray dried under the conditions of "inlet air 130°C and outlet air 70°C". 27.98 kg of hydrophobic sustained-release capsules were collected.

[0103] According to the test and calculation, the encapsulation rate achieved by preparing the hydrophobic sustained-release capsule in this embodiment is 88%.

[0104] Example 2: This embodiment provides a hydrophobic sustained-release capsule, which includes a shell and hydrophobic contents enclosed by the shell; The shell is composed of "65wt% of B-30 type polyvinyl butyral (hereinafter referred to as PVB), 30wt% of E5 type hydroxypropyl methylcellulose (hereinafter referred to as HPMC), and 5wt% of borax, with the total mass of the shell being 100%". The hydrophobic contents consist of "83.33 wt% isobutyltriethoxysilane, 9.26 wt% octadecyltrimethoxysilane, and 7.41 wt% ethanol, based on the total mass of the hydrophobic contents being 100%"; The hydrophobic sustained-release capsule has a particle size D50 of 18 μm and a loading rate of 64%.

[0105] The hydrophobic sustained-release capsules provided in this embodiment are prepared according to the following steps: 1) Add 6.5 kg of PVB, 3 kg of HPMC, and 0.5 kg of borax to 50 kg of organic solvent (i.e., a mixed solvent of dichloromethane and ethyl acetate in a mass ratio of 1:1), and stir until dissolved to obtain a shell material solution; 17.09 kg of isobutyltriethoxysilane, 1.90 kg of octadecyltrimethoxysilane, and 1.52 kg of ethanol were mixed evenly to obtain a hydrophobic contents. 2) While stirring the shell material solution at 2000 rpm, the hydrophobic contents were added dropwise to the shell material solution. After the addition was completed, the mixture was stirred at 2000 rpm for 40 minutes to emulsify. Then the temperature was raised to 45°C and stirred at this temperature until the organic solvent was completely evaporated. The mixture was then sent to a spray dryer and spray dried under the conditions of "inlet air 130°C and outlet air 70°C". 27.24 kg of hydrophobic sustained-release capsules were collected.

[0106] According to the test and calculation, the encapsulation rate achieved by preparing the hydrophobic sustained-release capsule in this embodiment is 85%.

[0107] Example 3: This embodiment provides a hydrophobic sustained-release capsule, which includes a shell and hydrophobic contents enclosed by the shell; The shell is composed of "80wt% of B-30 type polyvinyl butyral (hereinafter referred to as PVB), 15wt% of E5 type hydroxypropyl methylcellulose (hereinafter referred to as HPMC), and 5wt% of borax, with the total mass of the shell being 100%". The hydrophobic contents consist of "83.33 wt% isobutyltriethoxysilane, 9.27 wt% octadecyltrimethoxysilane, and 7.40 wt% ethanol, based on the total mass of the hydrophobic contents being 100%"; The hydrophobic sustained-release capsule has a particle size D50 of 22 μm and a loading rate of 70%.

[0108] The hydrophobic sustained-release capsules provided in this embodiment are prepared according to the following steps: 1) Add 8 kg of PVB, 1.5 kg of HPMC, and 0.5 kg of borax to 50 kg of organic solvent (i.e., a mixed solvent of dichloromethane and ethyl acetate in a mass ratio of 1:1), and stir until dissolved to obtain a shell material solution; 18.15 kg of isobutyltriethoxysilane, 2.02 kg of octadecyltrimethoxysilane, and 1.61 kg of ethanol were mixed evenly to obtain a hydrophobic contents. 2) While stirring the shell material solution at 2000 rpm, the hydrophobic contents were added dropwise to the shell material solution. After the addition was completed, the mixture was stirred at 2000 rpm for 40 minutes to emulsify. Then the temperature was raised to 45°C and stirred at this temperature until the organic solvent was completely evaporated. The mixture was then sent to a spray dryer and spray dried under the conditions of "inlet air 130°C and outlet air 70°C". 28.00 kg of hydrophobic sustained-release capsules were collected.

[0109] According to the test and calculation, the encapsulation rate achieved by preparing the hydrophobic sustained-release capsule in this embodiment is 90%.

[0110] Comparative Example 1: This comparative example provides a hydrophobic sustained-release capsule, which includes a shell and hydrophobic contents enclosed by the shell; The shell is made of a single type B-30 polyvinyl butyral (hereinafter referred to as PVB); The formulation of the hydrophobic contents is the same as that of the hydrophobic contents in Example 1; The hydrophobic sustained-release capsule has a particle size D50 of 20 μm and a loading rate of 60%.

[0111] The hydrophobic sustained-release capsules provided in this comparative example were prepared according to the steps in Example 1, with the only difference being that: 10 kg of PVB was added to 50 kg of organic solvent (i.e., a mixed solvent of dichloromethane and ethyl acetate in a mass ratio of 1:1), and stirred until dissolved to obtain a shell material solution. Everything else was the same as in Example 1, and a total of 24.21 kg of hydrophobic sustained-release capsules were finally obtained.

[0112] According to the test and calculation, the encapsulation rate achieved by the hydrophobic sustained-release capsule prepared in this comparative example is 70%.

[0113] Comparative Example 2: This comparative example provides a hydrophobic sustained-release capsule, which includes a shell and hydrophobic contents enclosed by the shell; The shell formulation is the same as that in Example 1; The hydrophobic contents consist of "92.60 wt% isobutyltriethoxysilane and 7.40 wt% ethanol, based on the total mass of the hydrophobic contents being 100%"; The hydrophobic sustained-release capsule has a particle size D50 of 20 μm and a loading rate of 66%.

[0114] The hydrophobic sustained-release capsules provided in this comparative example were prepared according to the steps in Example 1, with the only difference being that 19.14 kg of isobutyltriethoxysilane and 1.53 kg of ethanol were mixed evenly to obtain the hydrophobic contents. Everything else was the same as in Example 1, and a total of 27.87 kg of hydrophobic sustained-release capsules were finally obtained.

[0115] According to the test and calculation, the encapsulation rate achieved by the hydrophobic sustained-release capsule prepared in this comparative example is 89%.

[0116] Performance testing of hydrophobic sustained-release capsules.

[0117] The basic physical properties, pH response and sustained-release performance, and hydrophobic efficacy of the hydrophobic sustained-release capsules prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested.

[0118] (1) Basic physical property test.

[0119] Loading rate test: The percentage of mass loss of the hydrophobic sustained-release capsules prepared in any example (or comparative example) within the temperature range of 50-400℃ was determined by thermogravimetric analysis (TGA). Specifically, it is the percentage of the mass of the hydrophobic contents that volatilize and / or decompose in the hydrophobic sustained-release capsule during the test relative to the initial mass of the hydrophobic sustained-release capsule, thus obtaining the loading rate of the hydrophobic sustained-release capsules prepared in any example (or comparative example).

[0120] Encapsulation efficiency test: The percentage of the total mass of hydrophobic contents effectively encapsulated in the shell of all hydrophobic sustained-release capsules prepared in any example (or comparative example) is determined by solvent extraction-gas chromatography, relative to the total mass of hydrophobic contents fed into the capsule during the preparation of the hydrophobic sustained-release capsule in that example (or comparative example), thus obtaining the encapsulation efficiency achieved by the preparation of the hydrophobic sustained-release capsule in that example (or comparative example).

[0121] Particle size D50 test: The particle size D50 of the prepared hydrophobic sustained-release capsules was determined using a laser diffraction particle size analyzer.

[0122] (2) pH response and sustained release performance test.

[0123] At room temperature (25℃), the hydrophobic sustained-release capsules were immersed in simulated cement pore liquid (a mixture of 500g cement and 200g water) with a pH of 12.5. The amount of hydrophobic sustained-release capsules added was 1.134wt% (based on the mass of 500g cement as 100%). Samples were taken at 2h and 12h time points, and the total mass of silane substances (i.e., isobutyltriethoxysilane and / or octadecyltrimethoxysilane, the same below) released by the hydrophobic sustained-release capsules was determined by gas chromatography (GC). The release rates at 2h and 12h were calculated. The specific test steps are as follows.

[0124] 1) Establishing a standard curve: Before the test begins, a gas chromatograph is used to detect a mixed standard solution of isobutyltriethoxysilane and octadecyltrimethoxysilane at known concentrations, and a standard curve of "chromatographic peak area - concentration of silane" is plotted.

[0125] 2) Conduct immersion release experiment: At room temperature (25℃), accurately weigh 1.000g of hydrophobic sustained-release capsules and put them into 100.0mL of the above simulated cement pore liquid. Stir to obtain a uniform immersion system, start timing and keep the temperature constant (i.e., keep it at 25℃). When the soaking time reaches the set time, a certain volume of the soaking system sample is quickly taken out and the solid and liquid are separated by filtration or centrifugation to obtain 5.00 mL of silane solution sample; The silane solution sample was injected into a gas chromatograph for analysis. The GC identified the chromatographic peaks of isobutyltriethoxysilane and / or octadecyltrimethoxysilane based on their retention times, and the peak areas were obtained by integration.

[0126] 3) Calculate the concentration of silanes: Substitute the peak area obtained in 2) into the standard curve obtained in 1) to calculate the concentration C' of isobutyltriethoxysilane and / or octadecyltrimethoxysilane in the silane solution sample (unit: µg / mL or mg / L); assuming a homogeneous soaking system is obtained in 2), the concentration C' of isobutyltriethoxysilane and / or octadecyltrimethoxysilane in the silane solution sample is the concentration of isobutyltriethoxysilane and / or octadecyltrimethoxysilane dissolved in the simulated cement pore liquid in the entire soaking system.

[0127] 4) Calculate the release rate: By combining the obtained concentration C' with the volume of 100.0 mL of simulated cement pore liquid, the total mass of isobutyltriethoxysilane and / or octadecyltrimethoxysilane dissolved in the simulated cement pore liquid in the entire soaking system was calculated, which is the total mass m of isobutyltriethoxysilane and / or octadecyltrimethoxysilane released by 1.000 g of hydrophobic sustained-release capsules. 释放 ; Based on the loading rate of the hydrophobic sustained-release capsule and the formulation of the hydrophobic contents, the total mass m of isobutyltriethoxysilane and / or octadecyltrimethoxysilane loaded in 1.000g of the hydrophobic sustained-release capsule was calculated. 负载 ; Release rate = m 释放 / m 负载 ×100%.

[0128] The release rates at 2 hours and 12 hours were tested and calculated according to the above methods and steps, which are the release rates when the set duration is 2 hours and 12 hours, respectively, as described in 2).

[0129] (3) Hydrophobic performance test.

[0130] 1) Sample preparation: Weigh 500g of cement and add it to 200g of water, stir evenly, then add 1.134wt% (based on the mass of 500g of cement as 100%) of hydrophobic slow-release capsules, then pour the resulting mixture into a mold and cure it for 7 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain cement test blocks containing capsules. Weigh 500g of cement and add it to 200g of water, stir well, then pour the resulting mixture into a mold of the same size and cure it for 7 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain blank cement test blocks.

[0131] 2) Water contact angle test: Test the surface water contact angle of the cement specimen containing capsules obtained in 1) in accordance with the provisions of GB / T 31520-2015.

[0132] 3) Water absorption rate reduction test: Under the condition of 20±2℃, test the 24h water absorption rate of the cement block with capsule and the blank cement block obtained in 1), and calculate the percentage reduction of the 24h water absorption rate of the cement block with capsule relative to the blank cement block. The percentage decrease in water absorption rate over 24 hours = (24-hour water absorption rate of blank cement block - 24-hour water absorption rate of cement block containing capsule) / 24-hour water absorption rate of blank cement block × 100%.

[0133] The hydrophobic sustained-release capsules prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to the tests described in (1) to (3) above, and the results are shown in Table 1.

[0134] Table 1. Performance test results of hydrophobic sustained-release capsules: .

[0135] Based on the formulations of the hydrophobic sustained-release capsules provided in Examples 1 to 3 and Comparative Examples 1 to 2, and the test results in Table 1, it can be concluded that: Regarding the shell of the hydrophobic sustained-release capsules, Examples 1 to 3 used a compound of polyvinyl butyral, hydroxypropyl methylcellulose, and borax as the shell. The prepared hydrophobic sustained-release capsules had a particle size D50 in the range of 20±5 μm, a loading rate of 60% to 70%, and an encapsulation efficiency of not less than 85%, exhibiting suitable particle size, high loading rate, and encapsulation efficiency. More importantly, in the pH response and sustained-release performance test under a simulated high-alkalinity cement environment (pH=12.5), the hydrophobic sustained-release capsules prepared in Examples 1 to 3 all showed excellent "pH / time dual response" characteristics: the initial (2h) release rate of silane substances was less than 10% (Example 1: 4.8%, Example 2: 1.9%, Example 3: 8.1%), which could effectively shield the hydrophobic components from interfering with the early hydration of cement; subsequently, the hydrophobic contents were released at the designed rate, achieving the time-release of the hydrophobic contents within 12 to 24 hours. The release of hydrophobic contents can be further controlled by adjusting the ratio of polyvinyl butyral to hydroxypropyl methylcellulose in the shell (e.g., the proportion of hydroxypropyl methylcellulose is increased to 30 wt% in Example 2), thereby slowing down the release of the hydrophobic contents (e.g., the 12-hour release rate in Example 2 is reduced to 38.7%). This indicates that the shell of the hydrophobic sustained-release capsule "polyvinyl butyral, hydroxypropyl methylcellulose and borax" ternary compound system provided by the present invention has good designability and can adapt to different construction and strength development cycle requirements.

[0136] In contrast, Comparative Example 1, using a single polyvinyl butyral shell material, exhibited significantly lower loading rates (60%) and encapsulation rates (70%) compared to Example 1. This demonstrates that the lack of film-forming optimization from hydroxypropyl methylcellulose and cross-linking stabilization from borax in the shell resulted in a porous shell structure and low encapsulation efficiency for hydrophobic contents. Crucially, in pH response and release performance tests conducted in a high-alkaline cement environment (pH=12.5), the hydrophobic slow-release capsules provided in Comparative Example 1 showed a silane release rate as high as 32.5% after 2 hours and nearly complete release (95%) after 12 hours, completely losing their slow-release and initial shielding functions. This inevitably leads to the premature and excessive release of hydrophobic components from the capsules in concrete, severely hindering the normal setting and early strength development of the cement paste.

[0137] The above comparison results between Comparative Example 1 and Example 1 strongly confirm that in the shell of the hydrophobic sustained-release capsule provided by the present invention, polyvinyl butyral, hydroxypropyl methylcellulose and borax have a significant synergistic effect in ensuring the structural integrity of the hydrophobic sustained-release capsule and achieving precise pH / time response. They are essential for constructing a hydrophobic sustained-release capsule with a complete structure and precise pH / time response capability.

[0138] Regarding the hydrophobic contents of the hydrophobic sustained-release capsules, the hydrophobic sustained-release capsules provided in Examples 1 to 3 use hydrophobic contents composed of isobutyltriethoxysilane, octadecyltrimethoxysilane, and ethanol. In the hydrophobic performance test, they exhibited excellent synergistic hydrophobic effects: the surface water contact angle of the cement test blocks containing the hydrophobic sustained-release capsules prepared in Examples 1 to 3 was greater than 130° (specifically 132° to 135°), and the 24-hour water absorption rate was reduced by more than 85% compared with the blank cement test block without the addition of the hydrophobic sustained-release capsules. This indicates that the hydrophobic sustained-release capsules provided by the present invention achieve immediate and long-lasting hydrophobic protection.

[0139] In contrast, compared with Example 1, the hydrophobic sustained-release capsule prepared in Comparative Example 2 contained only isobutyltriethoxysilane and ethanol as its hydrophobic contents. Although the physical encapsulation effect (loading rate 66%, encapsulation rate 89%) and initial release behavior (2h release rate 5.2%) of the hydrophobic sustained-release capsule were similar to those of Example 1, it ultimately showed a significant deficiency in hydrophobic performance. Specifically, the surface water contact angle of the cement block containing the capsule prepared in Comparative Example 2 was only 118°, and the water absorption rate after 24 hours was only 70.1% lower than that of the blank cement block, which could not achieve immediate and long-term hydrophobic protection.

[0140] The comparison results between Comparative Example 2 and Example 1 demonstrate that the long-chain alkyl group of octadecyltrimethoxysilane is crucial for the formation of a dense, robust, and durable hydrophobic layer in cement by the hydrophobic sustained-release capsule. While the absence of octadecyltrimethoxysilane in the hydrophobic contents of the hydrophobic sustained-release capsule can achieve a certain degree of early hydrophobicity, it cannot achieve the long-lasting, high impermeability hydrophobic protection level sought by this invention, and thus fails to meet the durability requirements under harsh environments. Furthermore, not only octadecyltrimethoxysilane, but the absence of any component in the hydrophobic contents will adversely affect the hydrophobic protective efficacy of the hydrophobic sustained-release capsule.

[0141] Preparation of quick-setting agent powder and liquid quick-setting agent.

[0142] Example 4: This embodiment provides a quick-setting agent powder, comprising 55wt% alkali-free quick-setting agent, 28wt% hydrophobic slow-release capsules, 10wt% rheology modifier, 5wt% calcium formate, and 2wt% fumed silica, with the total mass of the quick-setting agent powder being 100%. The alkali-free quick-setting agent is composed of "76wt% aluminum sulfate, 8wt% diethanolamine, 6wt% sodium fluorosilicate, and 10wt% anhydrous calcium sulfate, with the total mass of the alkali-free quick-setting agent being 100%". The hydrophobic sustained-release capsules are from Example 1; The rheology modifier is obtained by mixing an anti-mud polycarboxylate superplasticizer with a molecular weight of 30,000, hydrophobic associating HEC (i.e., hydrophobic associating hydroxyethyl cellulose), and Brunei gum in a mass ratio of 5:3:2.

[0143] In this embodiment, the above-mentioned accelerator powder is prepared according to the following steps, and the accelerator powder is further prepared into a liquid accelerator: (1) Preparation of alkali-free quick-setting agent: Add 41.8 kg of aluminum sulfate, 4.4 kg of diethanolamine, 3.3 kg of sodium fluorosilicate and 5.5 kg of anhydrous calcium sulfate to a dry powder mixer, stir at 80 rpm for 45 min, pass through a 100 mesh sieve and set aside; (2) Preparation of rheology modifier: Add 5 kg of anti-mud polycarboxylate superplasticizer (molecular weight 30,000), 3 kg of hydrophobic associative HEC, and 2 kg of Brunei gum to a high-speed mixer and stir at 1500 rpm for 20 min for later use; (3) Add 55 kg of the above-mentioned alkali-free quick-setting agent, 28 kg of hydrophobic slow-release capsules, 10 kg of rheology modifier, 5 kg of calcium formate, and 2 kg of fumed silica to a double-helix conical mixer, stir at 40 rpm for 75 min, pass through an 80-mesh sieve, and package with nitrogen to obtain the quick-setting agent powder product.

[0144] (4) The above-mentioned quick-setting agent powder product is compounded to prepare a liquid quick-setting agent (denoted as quick-setting agent S4): Preparation of the dispersion base: 2.22 kg of dispersion stabilizer (a mixture of xanthan gum and sodium alginate in a mass ratio of 1:1), 3.7 kg of propylene glycol, and 5.926 kg of ethanol were added to 36.3 kg of deionized water and stirred at 60°C for 30 min until completely dissolved; Emulsification and dispersion: Add 100kg of the finished quick-setting agent powder and emulsify at 900rpm for 50min to ensure uniform mixing; Refining and stabilizing: The particles were refined to a particle size ≤3μm by colloid milling, ultrasonically dispersed for 20min, and then passed through a 100-mesh sieve; Sealed packaging, shake well before use, compatible with existing wet spraying application processes.

[0145] Example 5: This embodiment provides a quick-setting agent powder, comprising 54wt% alkali-free quick-setting agent, 29wt% hydrophobic slow-release capsules, 12wt% rheology modifier, 3wt% calcium formate, and 2wt% fumed silica, with the total mass of the quick-setting agent powder being 100%. The alkali-free quick-setting agent is composed of "72 wt% aluminum sulfate, 10 wt% diethanolamine, 8 wt% sodium fluorosilicate, and 10 wt% anhydrous calcium sulfate, with the total mass of the alkali-free quick-setting agent being 100%". The hydrophobic sustained-release capsule is from Example 2; The rheology modifier is a compound of three components in a mass ratio of 5:3:2:3 ...

[0146] In this embodiment, the above-mentioned accelerator powder is prepared according to the following steps, and the accelerator powder is further prepared into a liquid accelerator: (1) Preparation of alkali-free quick-setting agent: Add 72 kg of aluminum sulfate, 10 kg of diethanolamine, 8 kg of sodium fluorosilicate and 10 kg of anhydrous calcium sulfate to a dry powder mixer, stir at 80 rpm for 45 min, pass through a 100-mesh sieve and set aside. (2) Preparation of rheology modifier: 6 kg of anti-mud polycarboxylate superplasticizer (molecular weight 30,000), 3.6 kg of hydrophobic associative HEC, and 2.4 kg of Brunei gum were added to a high-speed mixer and stirred at 1500 rpm for 20 min for later use; (3) Add 54 kg of the above-mentioned alkali-free quick-setting agent, 29 kg of hydrophobic slow-release capsules, 12 kg of rheology modifier, 3 kg of calcium formate, and 2 kg of fumed silica to a double-helix conical mixer, stir at 40 rpm for 75 min, pass through an 80-mesh sieve, and package with nitrogen to obtain the quick-setting agent powder product.

[0147] (4) The above-mentioned quick-setting agent powder product is compounded to prepare a liquid quick-setting agent (denoted as quick-setting agent S5): Preparation of the dispersion base: 2.22 kg of dispersion stabilizer (a mixture of xanthan gum and sodium alginate in a mass ratio of 1:1), 3.7 kg of propylene glycol, and 5.926 kg of ethanol were added to 36.3 kg of deionized water and stirred at 60°C for 30 min until completely dissolved; Emulsification and dispersion: Add 100kg of the finished quick-setting agent powder and emulsify at 900rpm for 50min to ensure uniform mixing; Refining and stabilizing: The particles were refined to a particle size ≤3μm by colloid milling, ultrasonically dispersed for 20min, and then passed through a 100-mesh sieve; Sealed packaging, shake well before use, compatible with existing wet spraying application processes.

[0148] Example 6: This embodiment provides a quick-setting agent powder, comprising 60wt% alkali-free quick-setting agent, 25wt% hydrophobic slow-release capsules, 8wt% rheology modifier, 5wt% calcium formate, and 2wt% fumed silica, with the total mass of the quick-setting agent powder being 100%. The alkali-free quick-setting agent is composed of "80wt% aluminum sulfate, 5wt% diethanolamine, 5wt% sodium fluorosilicate, and 10wt% anhydrous calcium sulfate, with the total mass of the alkali-free quick-setting agent being 100%". The hydrophobic sustained-release capsule is from Example 3; The rheology modifier is a compound of three components in a mass ratio of 4:3:1 ...

[0149] In this embodiment, the above-mentioned accelerator powder is prepared according to the following steps, and the accelerator powder is further prepared into a liquid accelerator: (1) Preparation of alkali-free quick-setting agent: Add 80 kg of aluminum sulfate, 5 kg of diethanolamine, 5 kg of sodium fluorosilicate and 10 kg of anhydrous calcium sulfate to a dry powder mixer, stir at 80 rpm for 45 min, pass through a 100-mesh sieve and set aside. (2) Preparation of rheology modifier: Add 4 kg of anti-mud polycarboxylate superplasticizer (molecular weight 30,000), 3 kg of hydrophobic associative HEC, and 1 kg of Brunei gum to a high-speed mixer and stir at 1500 rpm for 20 min for later use; (3) Add 60 kg of the above-mentioned alkali-free quick-setting agent, 25 kg of hydrophobic slow-release capsules, 8 kg of rheology modifier, 5 kg of calcium formate, and 2 kg of fumed silica to a double-helix conical mixer, stir at 40 rpm for 75 min, pass through an 80-mesh sieve, and package with nitrogen to obtain the quick-setting agent powder product.

[0150] (4) The above-mentioned quick-setting agent powder product is compounded to prepare a liquid quick-setting agent (denoted as quick-setting agent S6): Preparation of the dispersion base: 2.22 kg of dispersion stabilizer (a mixture of xanthan gum and sodium alginate in a mass ratio of 1:1), 3.7 kg of propylene glycol, and 5.926 kg of ethanol were added to 36.3 kg of deionized water and stirred at 60°C for 30 min until completely dissolved; Emulsification and dispersion: Add 100kg of the finished quick-setting agent powder and emulsify at 900rpm for 50min to ensure uniform mixing; Refining and stabilizing: The particles were refined to a particle size ≤3μm by colloid milling, ultrasonically dispersed for 20min, and then passed through a 100-mesh sieve; Sealed packaging, shake well before use, compatible with existing wet spraying application processes.

[0151] Comparative Example 3: This comparative example provides a quick-setting agent powder, which is further formulated into a liquid quick-setting agent (denoted as quick-setting agent D3). The only difference from Example 4 is that the hydrophobic sustained-release capsules prepared in Example 1 used in Example 4 are replaced with an equal mass of the hydrophobic sustained-release capsules prepared in Comparative Example 1. Everything else is the same as in Example 4.

[0152] Comparative Example 4: This comparative example provides a quick-setting agent powder, which is further formulated into a liquid quick-setting agent (denoted as quick-setting agent D4). The only difference from Example 4 is that the hydrophobic sustained-release capsules prepared in Example 1 used in Example 4 are replaced with an equal mass of the hydrophobic sustained-release capsules prepared in Comparative Example 2. Everything else is the same as in Example 4.

[0153] Comparative Example 5: This comparative example provides a conventional alkali-free quick-setting agent (denoted as quick-setting agent D5), which consists of 55 wt% powder and 45 wt% deionized water, based on the total mass of the conventional alkali-free quick-setting agent as 100%; wherein, the powder consists of "80 wt% aluminum sulfate, 10 wt% diethanolamine, and 10 wt% sodium fluorosilicate, based on the total mass of the powder as 100%".

[0154] Comparative Example 6: This comparative example provides a composite accelerator (denoted as accelerator D6), which consists of "55wt% alkali-free accelerator, 28wt% isobutyltriethoxysilane, 10wt% rheology modifier, 5wt% calcium formate, and 2wt% fumed silica, based on the total mass of the composite accelerator being 100%". The alkali-free quick-setting agent is composed of "76wt% aluminum sulfate, 8wt% diethanolamine, 6wt% sodium fluorosilicate, and 10wt% anhydrous calcium sulfate, with the total mass of the alkali-free quick-setting agent being 100%". The rheology modifier is obtained by mixing a 30,000-molecular-weight anti-mud polycarboxylate superplasticizer, hydrophobic associative HEC (i.e., hydrophobic associative hydroxyethyl cellulose), and Brunei gum in a mass ratio of 5:3:2.

[0155] Comparative Example 7: This comparative example provides a composite quick-setting agent (denoted as quick-setting agent D7), which is composed of "55wt% alkali-free quick-setting agent, 28wt% hydrophobic slow-release capsules, 10wt% anti-mud polycarboxylate superplasticizer, 5wt% calcium formate, and 2wt% fumed silica, based on the total mass of the composite quick-setting agent being 100%"; wherein, the alkali-free quick-setting agent is composed of "76wt% aluminum sulfate, 8wt% diethanolamine, 6wt% sodium fluorosilicate, and 10wt% anhydrous calcium sulfate, based on the total mass of the alkali-free quick-setting agent being 100%".

[0156] Comparative Example 8: This comparative example provides a quick-setting agent powder, which is further formulated into a liquid quick-setting agent (denoted as quick-setting agent D8). The only difference from Example 4 is that the "Brunei gum" in the rheology modifier used in Example 4 is replaced with an equal mass of "anti-mud polycarboxylate superplasticizer with a molecular weight of 30,000". Everything else is the same as in Example 4.

[0157] Comparative Example 9: This comparative example provides a quick-setting agent powder, which is further formulated into a liquid quick-setting agent (denoted as quick-setting agent D9). The only difference from Example 4 is that the dosage of each component in the quick-setting agent powder provided in Example 4 is adjusted to "65wt% alkali-free quick-setting agent, 20wt% hydrophobic slow-release capsule, 8wt% rheology modifier, 4wt% calcium formate, and 3wt% fumed silica, based on the total mass of the quick-setting agent powder as 100%". Everything else is the same as in Example 4.

[0158] Comparative Example 10: This comparative example provides a common accelerator (denoted as accelerator D10), which consists of "30.4 wt% aluminum sulfate, 4 wt% diethanolamine, 2.6 wt% sodium fluorosilicate, 2 wt% anhydrous calcium sulfate, 1 wt% fumed silica and 60 wt% water, based on the total mass of the common accelerator being 100%".

[0159] Performance testing of accelerators.

[0160] Cement slurry samples, concrete specimens, and fresh concrete were prepared using the accelerators S4 to S6 provided in Examples 4 to 6 and the accelerators D3 to D9 provided in Comparative Examples 3 to 9. The initial setting and final setting times of the cement slurry samples were then tested. The 1-day compressive strength, 28-day compressive strength, 24-hour volumetric water absorption rate (hereinafter referred to as 24-hour water absorption rate), chloride ion diffusion coefficient, and contact angle of the concrete specimens were tested. The wet spray rebound rate and single spray thickness of the fresh concrete were tested. The performance of each accelerator was comprehensively evaluated.

[0161] 1. Preparation of cement slurry samples and testing of initial and final setting times.

[0162] Weigh 500g of cement and add it to 200g of water, stir evenly, and then add 6wt% of the quick-setting agent S4 prepared in Example 4 (i.e., add 6wt% quick-setting agent S4 based on the total mass of 500g of cement and 200g of water as 100%), stir evenly, and obtain a cement slurry sample. Cement slurry samples were prepared using the accelerators S5 and S6 prepared in Examples 5 and 6, and the accelerators D3 to D9 prepared in Comparative Examples 3 to 9, respectively, following the steps described above. Following the steps for setting time testing specified in GBT1346-2024 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", the initial setting time and final setting time of each prepared cement slurry sample were tested (test environment: temperature 20℃±2℃, relative humidity not less than 50%). The results are shown in Table 2 below.

[0163] 2. Concrete sample preparation, fresh concrete mix design, and related performance testing.

[0164] Part 1: Preparation of fresh concrete mix, concrete sample preparation and reference sample preparation.

[0165] Preparation of fresh concrete: Weigh out each raw material according to the formula "485 kg cement, 850 kg sand, 850 kg aggregate, 29.1 kg quick-setting agent (specifically, any one of the quick-setting agents S4 to S6 provided in Examples 4 to 6 or any one of the quick-setting agents D3 to D9 provided in Comparative Examples 3 to 9), 194 kg water, and 4.85 kg water-reducing agent", mix them evenly to obtain fresh concrete; wherein, the water-reducing agent is KZJ-101, which comes from Kezhijie New Materials Group Co., Ltd. Fresh concrete was prepared by using the accelerators S4, S5, and S6 prepared in Examples 4 to 6, and the accelerators D3 to D9 prepared in Comparative Examples 3 to 9, respectively, according to the above formula.

[0166] Concrete sample preparation: Each freshly mixed concrete was placed into a mold and cured under standard curing conditions of "temperature 20±2℃ and relative humidity ≥95%" to obtain concrete samples with various quick-setting agents added.

[0167] Preparation of reference samples: According to the formula "485 kg of cement, 850 kg of sand, 850 kg of stone, 29.1 kg of quick-setting agent D5 (i.e., the traditional alkali-free quick-setting agent provided in Comparative Example 5), 194 kg of water, and 4.85 kg of water-reducing agent", each raw material was weighed, mixed evenly, and then placed into a mold. The sample was cured under standard curing conditions "temperature 20±2℃, relative humidity ≥95%". The water-reducing agent was KZJ-101, which was from Kezhijie New Materials Group Co., Ltd.

[0168] Part Two: Performance Testing.

[0169] (1) In accordance with the provisions of GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete", the 1-day compressive strength and 28-day compressive strength of each concrete sample obtained in Part 1 were tested, and the 28-day compressive strength of the reference sample was tested. The percentage of the 28-day compressive strength of each concrete sample to the 28-day compressive strength of the reference sample was calculated, which is the 28-day strength retention rate of the concrete sample.

[0170] (2) Under the standard curing conditions of "temperature 20±2℃ and relative humidity ≥95%", the concrete samples obtained in Part 1 were cured for 28 days and the initial volume was recorded. Then, they were immersed in water for 24 hours at a temperature of 20±2℃ and then taken out. The mass of each concrete sample after immersion was measured and the volume of water absorbed in each concrete sample was calculated. Combined with the initial volume of each concrete sample, the water absorption rate after 24 hours was calculated.

[0171] (3) After curing each concrete sample obtained in Part 1 for 28 days under the standard curing conditions of "temperature 20±2℃ and relative humidity ≥95%", the chloride ion diffusion coefficient was tested in accordance with the provisions of GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete".

[0172] (4) After curing each concrete sample obtained in Part 1 for 28 days under standard curing conditions of "temperature 20±2℃ and relative humidity ≥95%", the surface water contact angle was measured in accordance with the provisions of ASTM D7334.

[0173] (5) In accordance with the provisions of GB 50086-2015 "Technical Specification for Rock and Soil Anchors and Shotcrete Support Engineering", wet spraying construction, wet spraying rebound rate determination and single spraying thickness determination were carried out on each freshly mixed concrete obtained in Part 1.

[0174] The test results for (1) to (5) above are shown in Table 2 below.

[0175] Table 2. Performance test results of accelerators: .

[0176] Based on the formulations of each embodiment and comparative example, as well as the test results in Table 2, it can be concluded that: The liquid accelerator formulations provided in Examples 4 to 6 exhibit excellent performance in all aspects within the scope defined in this application: the initial setting time and final setting time are within the optimal construction range of 3 to 4 minutes and 6 to 8 minutes, respectively; the strength development is excellent, with a 1-day compressive strength of not less than 18.5 MPa and a 28-day strength retention rate of not less than 98%; the hydrophobic properties are good, with a 24-hour water absorption rate of less than 0.8% and contact angles all above 130°; the impermeability is good, with a chloride ion diffusion coefficient not exceeding 1.2 × 10⁻⁶. -12 m 2 / s; good compatibility with wet spraying, with a wet spraying rebound rate of no more than 10%, and a single spray thickness of approximately 120mm. Among them, the liquid accelerator provided in Example 4 achieves optimal balance among various properties without exhibiting any performance shortcomings; the liquid accelerator provided in Example 5 has a slightly higher proportion of hydrophobic slow-release capsules and a slightly higher amount of rheology modifier, resulting in a slightly longer setting time, but still meeting the usage requirements; the liquid accelerator provided in Example 6 has a slightly higher proportion of alkali-free accelerator, resulting in a slightly shorter setting time, but still meeting the usage requirements. This indicates that the liquid accelerator provided by this invention has excellent and balanced performance in all aspects, possessing superior comprehensive performance.

[0177] Compared to Example 4, the liquid accelerator provided in Comparative Example 3 used a hydrophobic slow-release capsule prepared in Comparative Example 1 with a shell consisting only of B-30 type polyvinyl butyral. Because this capsule shell lacked hydroxypropyl methylcellulose and borax, the encapsulation efficiency and loading rate of the hydrophobic slow-release capsule decreased, while the 2-hour and 12-hour release rates were high. The hydrophobic contents were released prematurely, resulting in a decrease in the 1-day compressive strength and 28-day strength retention of the concrete samples containing the liquid accelerator prepared in Comparative Example 3, a 24-hour water absorption rate as high as 1.8%, and a chloride ion diffusion coefficient as high as 2.5 × 10⁻⁶. -12 m 2 With a water contact angle of only 105°, the fresh concrete prepared with the liquid accelerator prepared in Comparative Example 3 exhibited a wet spraying rebound rate as high as 13% and a single spraying thickness of only 90 mm during wet spraying. This indicates that the premature release of the hydrophobic contents of the hydrophobic slow-release capsules in the liquid accelerator interferes with cement hydration in the early stages, affecting normal strength development. Furthermore, insufficient release of the hydrophobic contents in the later stages also affects the hydrophobic properties, resulting in poor overall performance and reduced compatibility with wet spraying.

[0178] Compared to Example 4, the liquid accelerator provided in Comparative Example 4, which used the hydrophobic contents prepared in Comparative Example 2, lacked the hydrophobic sustained-release capsule of octadecyltrimethoxysilane. Although this hydrophobic sustained-release capsule had a decent early hydrophobic effect, its long-term hydrophobicity was poor. This was evident in the concrete sample with the liquid accelerator prepared in Comparative Example 4 showing a 24-hour water absorption rate as high as 1.5% and a chloride ion diffusion coefficient as high as 2.1 × 10⁻⁶. -12 m 2 With a contact angle of only 115°, the fresh concrete mixed with the liquid accelerator prepared in Comparative Example 4, when sprayed with the liquid accelerator, achieved a single spray thickness of only 110 mm in wet spraying. This indicates that the absence of octadecyltrimethoxysilane in the hydrophobic slow-release capsules of the liquid accelerator prevents it from exerting a densifying effect through long-chain alkyl groups, resulting in a significant decrease in long-term hydrophobic properties and resistance to chloride ion penetration. This also negatively impacts its compatibility with wet spraying.

[0179] Comparative Example 5 provides a traditional alkali-free quick-setting agent; Comparative Example 6 provides a composite quick-setting agent with direct addition of isobutyltriethoxysilane, a hydrophobic component, without encapsulation; and Comparative Example 7 provides a composite quick-setting agent using only an anti-mud polycarboxylate superplasticizer as a rheology modifier. Compared with Examples 4 to 6, all three examples lack key raw materials or key formulation components or key methods. Specifically, the traditional alkali-free quick-setting agent in Comparative Example 5 has prolonged initial and final setting times (initial setting time over 4 minutes, final setting time over 9 minutes), reduced 1-day compressive strength (below 16 MPa), and lost hydrophobicity and chloride ion penetration resistance (24-hour water absorption rate reaches over 6%, water contact angle is less than 90°, chloride ion diffusion coefficient reaches 7.5 × 10⁻⁶). -12 m 2 The wet-sprayed rebound rate increased significantly (up to 22%). The composite accelerator provided in Comparative Example 6 had the longest initial / final setting time (initial setting time exceeding 8.5 min, and final setting time exceeding 15 min), the lowest 1-day compressive strength (below 8.5 MPa) and 28-day strength retention rate (only 75%), high 24-hour water absorption rate (above 1%), and high wet-sprayed rebound rate (up to 18%). The composite accelerator provided in Comparative Example 7 had a significantly higher wet-sprayed rebound rate (reaching 16%) and poor rheological regulation performance. It can be seen that the overall performance of the traditional alkali-free accelerator provided in Comparative Example 5 and the composite accelerators provided in Comparative Examples 6 and 7 is significantly worse than that of Examples 4 to 6.

[0180] Compared with Example 4, the liquid quick-setting agent provided in Comparative Example 8 lacked the Brunei gum component in its rheology modifier, which disrupted the synergy of the components in the rheology modifier, resulting in poor water retention and thixotropy. This manifested as a significant increase in wet spray rebound rate (reaching 14%) and a deterioration in rheology regulation performance.

[0181] Compared to Example 4, the dosage of each component in the liquid quick-setting agent provided in Comparative Example 9 exceeded the dosage range defined by this invention, disrupting the synergy between the components and resulting in an overall performance imbalance. This manifested as a significant reduction in initial / final setting time (initial setting time less than 3 minutes, final setting time less than 6 minutes), and reduced strength development (28-day strength retention rate of only 90%), hydrophobic properties (24-hour water absorption rate reaching 1.2%, water contact angle less than 125°), and resistance to chloride ion penetration (chloride ion penetration coefficient reaching 2.0 × 10⁻⁶). - 12 m 2 The compatibility with wet spraying (wet spraying rebound rate is above 10%, and the thickness of a single spray is less than 90mm) has deteriorated significantly.

[0182] 3. Test on resistance to sulfate attack.

[0183] The liquid accelerator prepared in Example 4 and the ordinary accelerator prepared in Comparative Example 10 were prepared into several concrete samples of the same specifications according to the same method described in "2. Concrete Sample Preparation, Fresh Concrete Mixing and Related Performance Testing" above, and cured for 28 days under standard curing conditions of "temperature 20±2℃, relative humidity ≥95%". Then, at 20±2℃, each concrete sample was completely immersed in a sodium sulfate aqueous solution (sodium sulfate accounts for 5wt% of the total mass of the sodium sulfate aqueous solution, and the total mass of the sodium sulfate aqueous solution is 100%), left to stand, and the sulfate resistance test was carried out. The sulfate resistance of each concrete sample was characterized by the mass loss of each sample at different erosion ages (erosion age is understood as the time after the concrete sample is immersed in sodium sulfate aqueous solution and left to stand).

[0184] The results are as follows Figure 3 As shown, the mass loss rate is calculated with the initial mass of each concrete sample before the sulfate resistance test as 100%.

[0185] Figure 3 The results of sulfate attack resistance tests are shown for concrete samples with the liquid accelerator prepared in Example 4 and concrete samples with the ordinary accelerator prepared in Comparative Example 10. Figure 3It can be seen that although the mass loss rate of the concrete sample with the liquid retarder prepared in Example 4 increased with the extension of the erosion age, its overall mass loss rate was low, with a mass loss rate of less than 7.5% after 300 days of erosion, indicating good resistance to sulfate attack. In contrast, the mass loss of the concrete sample with the ordinary quick-setting agent prepared in Comparative Example 10 increased rapidly with the extension of the erosion age, reaching more than 7.5% at 150 days of erosion, and nearly 35% at 300 days of erosion, which is about 5 times the mass loss rate of the concrete sample with the liquid retarder prepared in Example 4 at the same erosion age, indicating significantly worse resistance to sulfate attack.

[0186] Figure 3 The comparative results show that the liquid quick-setting agent provided by the present invention, when added to concrete, can significantly improve the concrete's resistance to sulfate attack.

[0187] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. A hydrophobic sustained-release capsule comprising a shell and hydrophobic contents enclosed by the shell; wherein the shell is a mixture of polyvinyl butyral, hydroxypropyl methylcellulose and borax, and the hydrophobic contents are a mixture of isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol.

2. The hydrophobic sustained-release capsule according to claim 1, characterized in that, The mass of the shell is taken as 100%, wherein the mass of polyvinyl butyral is 65 wt% to 80 wt%, the mass of hydroxypropyl methylcellulose is 15 wt% to 30 wt%, and the mass of borax is 1 wt% to 5 wt%.

3. The hydrophobic sustained-release capsule according to claim 1, characterized in that, The mass of the hydrophobic contents is 100%, wherein the mass of isobutyltriethoxysilane is 83 to 83.5 wt%, the mass of octadecyltrimethoxysilane is 9 to 9.5 wt%, and the mass of the first low-carbon monohydric alcohol is 7 to 7.5 wt%.

4. The hydrophobic sustained-release capsule according to claim 1, characterized in that, The polyvinyl butyral is type B-30 polyvinyl butyral; and / or The hydroxypropyl methylcellulose is E5 type hydroxypropyl methylcellulose; and / or The first low-carbon monohydric alcohol is ethanol.

5. The hydrophobic sustained-release capsule according to any one of claims 1 to 4, characterized in that, The hydrophobic sustained-release capsules meet the following requirements: particle size D50 of 20±5μm; and / or loading rate of 60% to 70%.

6. A method for preparing a hydrophobic sustained-release capsule as described in any one of claims 1 to 5, comprising the following steps: A shell material solution is obtained by mixing polyvinyl butyral, hydroxypropyl methylcellulose, borax and organic solvent; and a hydrophobic contents are obtained by mixing isobutyltriethoxysilane, octadecyltrimethoxysilane and a first low-carbon monohydric alcohol. The hydrophobic contents are dropped into the shell material solution and emulsified to obtain an O / W type emulsion; The O / W emulsion is stirred at a first temperature to evaporate the organic solvent, and then spray-dried to obtain the hydrophobic sustained-release capsule.

7. The method according to claim 6, characterized in that, The organic solvent is a mixture of dichloromethane and ethyl acetate.

8. The method according to claim 6, characterized in that, The emulsification is carried out under stirring conditions for 30-60 minutes; and / or The first temperature is 40°C to 60°C; and / or The inlet air temperature of the spray drying process is 120°C to 150°C, and the outlet air temperature is 60°C to 80°C.

9. The method according to any one of claims 6 to 8, characterized in that, The encapsulation efficiency achieved by the method in preparing the hydrophobic sustained-release capsule is not less than 85%.

10. A quick-setting agent powder, comprising an alkali-free quick-setting agent, a hydrophobic sustained-release capsule, a rheology modifier, an early-strength agent, and a moisture-proof agent; The hydrophobic sustained-release capsule is a hydrophobic sustained-release capsule according to any one of claims 1 to 5 or a hydrophobic sustained-release capsule prepared by the method according to any one of claims 6 to 9.

11. The quick-setting agent powder according to claim 10, characterized in that, Based on the total mass of the quick-setting agent powder as 100%, the alkali-free quick-setting agent accounts for 50wt% to 60wt%, the hydrophobic sustained-release capsule accounts for 25wt% to 30wt%, the rheology modifier accounts for 8wt% to 12wt%, the early strength agent accounts for 2wt% to 8wt%, and the moisture-proof agent accounts for 1wt% to 3wt%. Preferably, based on the total mass of the quick-setting agent powder as 100%, the mass of the alkali-free quick-setting agent is 55wt%, the mass of the hydrophobic sustained-release capsule is 28wt%, the mass of the rheology modifier is 10wt%, the mass of the early strength agent is 5wt%, and the mass of the moisture-proof agent is 2wt%.

12. The accelerator powder according to claim 10, characterized in that, The alkali-free quick-setting agent is obtained by compounding aluminum sulfate, diethanolamine, sodium fluorosilicate, and anhydrous calcium sulfate; and / or The rheology modifier is a compound of anti-mud polycarboxylate superplasticizer, hydrophobically associating hydroxyethyl cellulose, and Brunei gum; and / or The early strength agent is calcium formate; and / or the moisture-proof agent is fumed silica.

13. The accelerator powder according to claim 12, characterized in that, The mass of the alkali-free quick-setting agent is 100%, wherein the mass of aluminum sulfate is 72wt% to 80wt%, the mass of diethanolamine is 5wt% to 10wt%, the mass of sodium fluorosilicate is 5wt% to 8wt%, and the mass of anhydrous calcium sulfate is 5wt% to 10wt%.

14. The accelerator powder according to claim 12, characterized in that, In the rheology modifier, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose, and the Brunei gum is (4 to 6):(3 to 4):(1 to 3); Preferably, the mass ratio of the anti-mud polycarboxylate superplasticizer, the hydrophobic associative hydroxyethyl cellulose, and the Brunei gum is 5:3:

2.

15. The accelerator powder according to any one of claims 10 to 14, characterized in that, The particle size of the quick-setting agent powder is 60 to 80 mesh.

16. A liquid accelerator, which is obtained by compounding accelerator powder, dispersant stabilizer, low carbon diol, second low carbon monool and water; The accelerator powder is the accelerator powder according to any one of claims 10 to 15.

17. The liquid quick-setting agent according to claim 16, characterized in that, Based on the total mass of the liquid quick-setting agent as 100%, the quick-setting agent powder accounts for 65wt% to 70wt%, the dispersant stabilizer accounts for 1wt% to 2wt%, the low-carbon diol accounts for 2wt% to 3wt%, the second low-carbon monool accounts for 3wt% to 5wt%, and the water accounts for 20wt% to 25wt%.

18. The liquid quick-setting agent according to claim 16, characterized in that, The dispersant stabilizer is a compound of xanthan gum and sodium alginate; and / or The low-carbon diol is propylene glycol; and / or The second low-carbon monohydric alcohol is ethanol.

19. A method for preparing a liquid accelerator as described in any one of claims 16 to 18, comprising the following steps: The dispersant stabilizer, low-carbon diol, second low-carbon monool and water are stirred and mixed at a second temperature, and the quick-setting agent powder is added. The mixture is then homogenized, refined, dispersed and sieved to obtain the liquid quick-setting agent.

20. The method according to claim 19, characterized in that, The second temperature is 55°C to 65°C; and / or The homogenization and refining dispersion includes emulsification, grinding to an average particle size of no more than 3 μm, and ultrasonic dispersion. and / or The sieving process involves passing the material through a 100-150 mesh sieve.

21. The application of any one of the following in shotcrete: the hydrophobic slow-release capsule according to any one of claims 1 to 5, the hydrophobic slow-release capsule prepared by the method according to any one of claims 6 to 9, the accelerator powder according to any one of claims 10 to 15, the liquid accelerator according to any one of claims 16 to 18, and the liquid accelerator prepared by the method according to claim 19 or 20; in, The dosage of the liquid accelerator is 5 wt% to 7 wt% of the mass of the cementitious material in the sprayed concrete.

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