Silane composite nano ettringite hydrophobic agent and preparation method and application thereof

Abstract

The application discloses a silane composite nano ettringite hydrophobic agent and a preparation method and application thereof, and belongs to the technical field of building material surface protection. The application aims to solve the problems of weak interface bonding force and poor alkali stability of a full solid waste cementitious material surface protective agent. The hydrophobic agent is composed of the following raw materials in mass parts: 10-14 parts of nano ettringite powder, 3-4 parts of organic silane, 85-90 parts of anhydrous ethanol, 0.15-0.35 parts of water and 0.02-0.05 parts of acetic acid. The organic silane is a mixture of n-octyl triethoxysilane and gamma-aminopropyl triethoxysilane, and the mass ratio of the two is (60-85):(15-40). The technical scheme is used for the surface protection of a full solid waste cementitious material, can form a stable hydrophobic layer, and has the advantages of a surface water contact angle of greater than or equal to 100 degrees, a capillary water absorption coefficient reduction of greater than or equal to 30%, and a chloride ion penetration depth reduction of greater than or equal to 50%. The preparation process is simple, the alkali stability is strong, the hydrophobic effect is durable, and the application is suitable for the long-term protection of a full solid waste cementitious material such as a steel slag powder-mineral slag powder-gypsum system.

Description

Technical Field

[0001] This invention relates to the field of surface protection technology for building materials, and in particular to a silane composite nano-calcite hydrophobic agent, its preparation method, and its application. Background Technology

[0002] Currently, all-solid-waste cementitious materials, with industrial solid wastes such as steel slag powder, blast furnace slag powder, and desulfurized gypsum as the main cementing components, are gradually becoming an important development direction in the field of cement-based materials. These materials have significant advantages in reducing carbon emissions and resource consumption, but they also have significant surface durability issues during service.

[0003] Due to their relatively loose pore structure, low Ca(OH)2 content, and the fact that the reaction products are mostly ettringite (AFt) and C-(A)-SH gel with a low calcium-to-silicon ratio, all-solid waste cementitious materials generally have weak resistance to ionic erosion. Long-term exposure to humid, hot, and salt spray environments easily leads to significant capillary water absorption, enhanced chloride ion penetration, surface weathering, and salt crystallization erosion, resulting in rapid deterioration of material properties and limiting their application in complex environments such as harbor structures, road slabs, and wind power foundations.

[0004] To improve the surface properties of solid waste-based cementitious materials, methods such as organosilane waterproofing agents, epoxy resin coatings, or polymer emulsion infiltration treatments are commonly used. However, traditional organosilane protective agents have the following shortcomings in the overall solid waste system:

[0005] (1) Weak interfacial bonding: Due to the low density of hydroxyl groups on the matrix surface, it is difficult for silanes to form stable chemical bonds with the matrix;

[0006] (2) Poor stability in alkaline environment: Some silanes are prone to self-condensation and precipitation in alkaline pore liquid, resulting in uneven hydrophobic layer;

[0007] (3) Limited penetration depth: The small size of a single organosilane molecule makes it difficult to achieve effective micro-filling and thus difficult to achieve long-lasting protection.

[0008] To address these issues, the industry has attempted to introduce inorganic nanomaterials into protective systems to improve durability and interfacial stability. For example, inorganic particles such as nano-SiO2, TiO2, or Al2O3 can improve coating density, but their surfaces are prone to aggregation, and their compatibility with silane systems is limited, making it difficult to form a stable organic-inorganic composite structure. This fails to fundamentally solve the problems of weak interfacial bonding and poor alkali stability. Summary of the Invention

[0009] The technical problem to be solved and the technical task proposed by this invention is to improve and refine existing technical solutions, and to provide a silane composite nano-calcite hydrophobic agent, its preparation method, and its application, so as to achieve efficient and long-term protection of solid waste cementitious materials. To this end, this invention adopts the following technical solution.

[0010] The first aspect of the present invention is to provide a silane composite nano-calcite hydrophobic agent, wherein the hydrophobic agent is prepared from the following raw materials in parts by weight: 10-14 parts nano-calcite powder, 3-4 parts organosilane, 85-90 parts anhydrous ethanol, 0.15-0.35 parts water, and 0.02-0.05 parts acetic acid; wherein the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane, wherein the mass ratio of n-octyltriethoxysilane to γ-aminopropyltriethoxysilane is (60-85):(15-40).

[0011] This technical solution combines nano-ettringite with a dual-silane composite system. Nano-ettringite, as the core hydration product of the solid waste cementitious material, has natural phase compatibility with the matrix, fundamentally solving the core problem of weak interfacial bonding and easy detachment between traditional silane protective agents and the solid waste matrix. A specific ratio of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane is used. n-Octyltriethoxysilane provides a long-lasting hydrophobic long-chain structure, while γ-aminopropyltriethoxysilane provides active reactive groups. The two work synergistically to achieve controllable hydrolysis and stable loading of silanes, avoiding the defects of easy self-condensation and deactivation of single silanes. Acetic acid, as a hydrolysis catalyst, can gently regulate the hydrolysis and condensation rate of silanes, preventing excessive silane condensation and ensuring the uniformity and storage stability of the hydrophobic agent system.

[0012] As a preferred technical means, the purity of the nano-calcite powder is ≥95%, and the median particle size D50 is 200-300nm.

[0013] A purity of ≥95% ensures the integrity of the ettringite crystal structure and provides sufficient surface active sites; the median particle size of 200-300nm ensures good dispersibility of nano-ettringite in the ethanol system, avoids particle agglomeration, and forms a nanoscale rough structure on the surface of the solid waste substrate, enhancing the micro-nano dual-scale effect of the hydrophobic coating and further improving the water contact angle and waterproof performance of the material surface.

[0014] As a preferred technical means: in the hydrophobic agent, an organic-inorganic composite coating layer is formed on the surface of the nano-calcite powder, and the composite coating layer contains Si-O-Al and Si-O-Ca chemical bond structures.

[0015] Organosilanes are firmly bonded to the surface of nano-ettringite via chemical bonds (Si-O-Al and Si-O-Ca), forming a stable composite coating layer. This chemical bonding method significantly enhances the organic-inorganic interface bonding force, avoiding the problem of silane detachment caused by traditional physical mixing or adsorption. Simultaneously, the Si-O-Al and Si-O-Ca bonds exhibit excellent chemical stability in the highly alkaline environment of the solid waste cementitious material, ensuring the long-term protective effect of the hydrophobic agent.

[0016] A second aspect of the present invention is to provide a method for preparing a silane composite nano-calcite hydrophobic agent, the method comprising the following steps:

[0017] Preparation of dispersion: Take 10-14 parts of nano-calcite powder according to the mass ratio, add it to 76-81 parts of anhydrous ethanol and disperse it to obtain a uniform calcite suspension.

[0018] Preparation of silane premix: Take 3-4 parts of organosilane by mass ratio, add 8-10 parts of anhydrous ethanol and stir, then add 0.02-0.05 parts of acetic acid and stir continuously and rapidly to obtain silane premix; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane, with a mass ratio of (60-85):(15-40);

[0019] Preparation of silane sol: Take 0.15-0.35 parts by mass of water and slowly add it dropwise to the silane premixed solution in multiple portions. After the addition is complete, continue stirring to obtain silane sol.

[0020] Composite reaction: Under the temperature conditions of 20-25℃, silane sol is added dropwise to ettringite suspension, and the reaction is continuously stirred after the addition is completed;

[0021] Post-processing: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5-1%, thus obtaining the silane composite nano-calcite hydrophobic agent.

[0022] This technical solution employs a stepwise preparation process. First, a ettringite suspension and a silane sol are prepared separately, followed by a composite reaction. This achieves stepwise controllable hydrolysis and composite loading of silane, effectively avoiding excessive hydrolysis and polymerization of silane and ensuring the stability of the hydrophobic agent system. Anhydrous ethanol is used in two parts: one for ettringite dispersion and the other for silane premixing. This avoids uneven dispersion and particle agglomeration problems caused by direct mixing of nano-ettringite and silane, ensuring uniform mixing and sufficient reaction of all components. Acetic acid is used as a hydrolysis regulator, achieved through stepwise dropwise addition of water. The controllable hydrolysis of silanes allows for regulation of the degree of polymerization of silane sols, avoiding gelation problems caused by excessive hydrolysis. The composite reaction is carried out at room temperature (20-25℃), eliminating the need for high-temperature and high-pressure equipment. This results in a low process threshold, low energy consumption, and suitability for continuous industrial production. By controlling the residual alcohol content of the product to 0.5-1% through depressurized deethanolination, the storage stability of the hydrophobic agent is ensured, avoiding problems such as excessive evaporation and uneven film formation caused by excessive ethanol. This also ensures the permeability of the hydrophobic agent on the substrate surface, achieving excellent protective effects.

[0023] As a preferred technical means: in the dispersion preparation step, the mass of anhydrous ethanol added to the nano-calcite powder is 90% of the total mass of anhydrous ethanol; in the silane premix preparation step, the mass of anhydrous ethanol added to the organosilane is 10% of the total mass of anhydrous ethanol; the total mass fraction of anhydrous ethanol is 85-90 parts.

[0024] In this technical solution, anhydrous ethanol is used in two parts at a ratio of 90% and 10%. 90% of the ethanol is used for ettringite dispersion, which can fully ensure the dispersion effect of nano-ettringite and avoid ettringite agglomeration caused by insufficient dispersion medium. 10% of the ethanol is used for silane premixing, which can provide a uniform reaction environment for silane hydrolysis and ensure the homogeneity of silane premix solution. This ratio can ensure that ettringite is fully dispersed and silane is fully hydrolyzed, while avoiding the problems of low solid content and insufficient hydrophobic effect caused by excessive ethanol, thus taking into account both system stability and protective effect.

[0025] As a preferred technical means: in the dispersion preparation step, after adding anhydrous ethanol to the nano-calcite powder, it is ultrasonically dispersed for 15 minutes to obtain a uniform calcite suspension; the calcite purity of the nano-calcite powder is ≥95%, and the median particle size D50 is 200-300nm; in the silane premix preparation step, after adding anhydrous ethanol to the organosilane, it is stirred for 5 minutes, and then the acetic acid is added, and it is continuously stirred rapidly at a speed of 400rpm.

[0026] This technical solution employs ultrasonic dispersion for 15 minutes, which effectively deagglomerates nano-ettringite without damaging its crystal structure, resulting in a stable suspension and preventing particle sedimentation during subsequent compounding. During silane premixing, stirring for 5 minutes before adding acetic acid ensures thorough mixing of the silane with ethanol before adding the hydrolysis catalyst, facilitating control of the hydrolysis reaction initiation rate. A stirring speed of 400 rpm ensures thorough mixing of acetic acid and silane while avoiding excessive bubbles and rapid ethanol evaporation caused by excessively high stirring speeds, thus guaranteeing the stable quality of the silane premix.

[0027] As a preferred technical means: in the silane sol preparation step, the water is slowly added to the silane premixed solution in four drops, and after the addition is completed, the mixture is stirred for 10 minutes to obtain the silane sol.

[0028] This technical solution involves adding water slowly in four stages, which allows for precise control of the degree of hydrolysis and polymerization of silane. This avoids the problems of excessively high local water content and rapid hydrolysis and polymerization of silane leading to gel formation caused by adding water all at once. After each addition, the silane undergoes partial hydrolysis, gradually forming a sol with a uniform degree of polymerization, which is beneficial for obtaining a silane sol with uniform particle size and high stability. After the addition is completed, stirring is continued for 10 minutes to ensure that the silane hydrolysis reaction proceeds fully, forming a transparent and stable silane sol system, which provides better reactivity for the subsequent composite reaction with ettringite.

[0029] As a preferred technical means: in the composite reaction step, the silane sol is slowly added dropwise to the ettringite suspension within 10-20 minutes, and the reaction is continuously stirred for 5-6 hours after the addition is completed.

[0030] This technical solution involves slowly adding silane sol dropwise into the ettringite suspension over 10-20 minutes, avoiding agglomeration or uneven coating caused by excessively high local concentrations, and ensuring uniform distribution of silane on the surface of each ettringite nanoparticle. Continuous stirring for 5-6 hours provides sufficient time for the chemical bonding between silane and the ettringite surface (forming Si-O-Al and Si-O-Ca bonds), allowing the composite reaction to proceed to completion, thereby obtaining a structurally stable and densely coated hydrophobic agent.

[0031] A third aspect of the present invention is to provide an application of a silane composite nano-calcite hydrophobic agent, wherein the aforementioned silane composite nano-calcite hydrophobic agent, or the silane composite nano-calcite hydrophobic agent obtained by the aforementioned preparation method, is uniformly applied to the surface of the solid waste cementitious material to be protected at an application rate of 200-300 g / m² after the initial setting and before the final setting of the solid waste cementitious material.

[0032] This technical solution involves applying the coating during the window period between the initial setting and final setting of the solid waste cementitious material. At this time, the substrate surface still has a certain degree of wettability and active hydroxyl groups, which is conducive to the chemical bonding between the silane in the hydrophobic agent and the substrate. At the same time, the nano-ettling stone in the hydrophobic agent can act as a crystal nucleus to induce the growth of hydration products in the matrix, achieving an integrated bond between the protective layer and the substrate. An application amount of 200-300 g / m² can form a continuous and dense hydrophobic protective layer on the substrate surface, while avoiding the waste of raw materials and surface film cracking caused by excessive application. The solid waste cementitious material treated in this way can achieve a surface water contact angle of over 100°, a 7-day capillary water absorption coefficient that is more than 30% lower than the control group, and a 28-day chloride ion penetration depth that is more than 50% lower than the control group, which can significantly improve the long-term service durability of the solid waste cementitious material.

[0033] As a preferred technical means, the all-solid waste cementitious material is an all-solid waste cementitious system composed of slag powder, gypsum, and steel slag powder.

[0034] The slag powder-gypsum-steel slag powder system is a typical representative of solid waste cementitious materials. Its hydration products contain a large amount of ettringite, which is homologous and chemically compatible with the nano-ettringite carrier in the hydrophobic agent of this invention. After application, the nano-ettringite in the hydrophobic agent can act as crystal nuclei to induce further growth of ettringite on the substrate surface, forming an integrated composite protective layer, which greatly enhances the adhesion between the coating and the substrate. At the same time, the porous solution of this system is rich in calcium and aluminum ions, which is conducive to the stable existence of Si-O-Al and Si-O-Ca bonds, thereby achieving a long-lasting protective effect.

[0035] Beneficial effects:

[0036] (1) Formation of a stable organic-inorganic composite structure: Through the amino activation of γ-aminopropyltriethoxysilane, Si-O-Al and Si-O-Ca chemical bonds are generated on the surface of ettringite, which significantly enhances the immobilization degree of silane molecules on the inorganic surface and avoids the problem of easy peeling of traditional silanes; In view of the problem of easy peeling of traditional hydrophobic coatings, the specific crystal structure of ettringite can be used as a nucleation site for the hydration products of solid waste cementitious materials, so that a strong chemical bond is formed between the coating and the substrate, which significantly improves the durability of the coating.

[0037] (2) Improve the density and durability of the protective layer: Calcium alum nanoparticles serve as a carrier to provide micro-filling and adsorption, making the hydrophobic layer more uniform and dense and forming a nano-scale rough surface on the surface, thereby improving the hydrophobicity, impermeability and salt corrosion resistance of the coating.

[0038] (3) Adaptable to the alkaline environment of the solid waste gelling system: The composite hydrophobic agent of the present invention can still maintain a stable dispersion state in a strongly alkaline environment with pH value > 12, effectively avoiding excessive condensation and precipitation of silane in the pore liquid of the solid waste gelling material, and solving the core problem of poor alkaline stability of traditional silane protective agents in the solid waste system.

[0039] (4) Significantly improved performance: The surface contact angle of the treated solid waste cementitious material exceeds 100°, and the chloride ion permeability is improved by more than 50%, which significantly improves the service life of the material in humid, hot, salt spray and marine environments.

[0040] (5) Strong green sustainability: The present invention adopts a solvent-free reaction system and a low-energy preparation process, and the protective agent is fully compatible with the solid waste-based cementitious system, which is in line with the development direction of green building materials. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating the preparation process of the silane composite nano-calcite hydrophobic agent of the present invention.

[0042] Figure 2 This is a schematic diagram of the contact angle in an embodiment of the present invention. Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] This invention relates to a silane composite nano-calcite hydrophobic agent, its preparation method, and its application. Unless otherwise stated, "parts" refers to parts by weight.

[0045] This invention provides a silane composite nano-calcite hydrophobic agent, its preparation method, and its application. The hydrophobic agent is prepared from the following raw materials in parts by weight: 10-14 parts nano-calcite powder, 3-4 parts organosilane, 85-90 parts anhydrous ethanol, 0.15-0.35 parts water, and 0.02-0.05 parts acetic acid; wherein the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane, wherein the mass ratio of n-octyltriethoxysilane to γ-aminopropyltriethoxysilane is (60-85):(15-40).

[0046] like Figure 1 As shown, the preparation method of the silane composite nano-calcite hydrophobic agent includes the following steps:

[0047] Preparation of dispersion: Take 10-14 parts of nano-calcite powder according to the mass ratio, add it to 76-81 parts of anhydrous ethanol and disperse it to obtain a uniform calcite suspension.

[0048] Preparation of silane premix: Take 3-4 parts of organosilane by mass ratio, add 8-10 parts of anhydrous ethanol and stir, then add 0.02-0.05 parts of acetic acid and stir continuously and rapidly to obtain silane premix; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane, with a mass ratio of (60-85):(15-40);

[0049] Preparation of silane sol: Take 0.15-0.35 parts by mass of water and slowly add it dropwise to the silane premixed solution in multiple portions. After the addition is complete, continue stirring to obtain silane sol.

[0050] Composite reaction: Under the temperature conditions of 20-25℃, silane sol is added dropwise to ettringite suspension, and the reaction is continuously stirred after the addition is completed;

[0051] Post-processing: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5-1%, thus obtaining the silane composite nano-calcite hydrophobic agent.

[0052] The application method is as follows: After the initial setting of the solid waste cementitious material and before the final setting, apply the composite hydrophobic agent to the surface of the material by spraying or impregnation at a rate of 200-300g / m2, and cure at room temperature for a period of time to form a dense protective layer.

[0053] In the following examples and comparative examples, the performance testing uniformly adopted the following standard method:

[0054] 1. Surface water contact angle test: The contact angle meter was used to test the deionized water drop volume by the seat drop method. The volume of the deionized water drop was 5μL. The reading was taken 5 seconds after the drop was added. At least 5 points were tested for each sample, and the average value was taken.

[0055] 2.7d capillary water absorption coefficient test: The capillary water absorption coefficient was calculated by taking the slope of the linear segment at the initial stage of water absorption, and the reduction rate compared with the untreated blank control group was calculated.

[0056] 3.28d Chloride Ion Penetration Depth Test: Referring to the RCM electromigration method in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the specimen was split after energizing, and 0.1mol / L silver nitrate solution was sprayed to develop color. The average depth of the white colored band to the chloride-exposed surface was measured at multiple points along the specimen diameter, and the reduction rate compared with the untreated blank control group was calculated.

[0057] Alkali stability test: Place the hydrophobic agent in a sodium hydroxide solution with pH=13 and let it stand at room temperature for 72 hours. Observe whether layering, precipitation, or exudation occurs to determine its alkali stability.

[0058] Example 1

[0059] The silane composite nano-calcite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 10 parts nano-calcite powder, 3 parts organosilane, 90 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 85:15; the nano-calcite powder has a calcite purity of 95% and a median particle size D50 of 300 nm.

[0060] The preparation method includes the following steps:

[0061] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0062] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0063] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0064] (4) Composite reaction: Under the temperature condition of 20°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0065] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0066] Example 2

[0067] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 12 parts nano-ettringite powder, 3.5 parts organosilane, 90 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 75:25; the nano-ettringite powder has an ettringite purity of 97.5% and a median particle size D50 of 250 nm.

[0068] The preparation method is the same as in Example 1.

[0069] Example 3

[0070] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 3.5 parts organosilane, 90 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0071] The preparation method is the same as in Example 1.

[0072] Example 4

[0073] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 4 parts organosilane, 87.5 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0074] The preparation method is the same as in Example 1.

[0075] Example 5

[0076] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 4 parts organosilane, 85 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0077] The preparation method includes the following steps:

[0078] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0079] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0080] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0081] (4) Composite reaction: Under the temperature condition of 22.5℃, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0082] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0083] Example 6

[0084] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.25 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0085] The preparation method includes the following steps:

[0086] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0087] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0088] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0089] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0090] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0091] Example 7

[0092] The silane composite nano-calcite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-calcite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-calcite powder has a calcite purity of 100% and a median particle size D50 of 200 nm.

[0093] The preparation method includes the following steps:

[0094] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0095] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0096] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0097] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension within 10 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0098] (5) Post-treatment: The product after the composite reaction is completed is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.75%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0099] Example 8

[0100] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.03 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0101] The preparation method includes the following steps:

[0102] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0103] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0104] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0105] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 15 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0106] (5) Post-treatment: The product after the composite reaction is completed is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 1%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0107] Example 9

[0108] The silane composite nano-ettringite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.02 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0109] The preparation method includes the following steps:

[0110] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0111] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0112] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0113] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 5 hours after the addition is completed;

[0114] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0115] Example 10

[0116] The silane composite nano-calcite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-calcite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-calcite powder has a calcite purity of 100% and a median particle size D50 of 200 nm.

[0117] The preparation method includes the following steps:

[0118] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0119] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0120] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0121] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 5.5 hours after the addition is completed;

[0122] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0123] Example 11

[0124] The silane composite nano-calcite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-calcite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-calcite powder has a calcite purity of 100% and a median particle size D50 of 200 nm.

[0125] The preparation method includes the following steps:

[0126] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0127] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0128] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0129] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0130] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0131] Example 12

[0132] The silane composite nano-calcite hydrophobic agent of this embodiment is prepared from the following raw materials in parts by weight: 14 parts nano-calcite powder, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.05 parts acetic acid; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 60:40; the nano-calcite powder has a calcite purity of 100% and a median particle size D50 of 200 nm.

[0133] The preparation method includes the following steps:

[0134] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0135] (2) Preparation of silane premix: According to the above ratio, take organosilane, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes, then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0136] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0137] (4) Composite reaction: Under the temperature condition of 25°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0138] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the silane composite nano-calcite hydrophobic agent of this embodiment.

[0139] The process parameters and raw material ratios for Examples 1-12 above are summarized as follows:

[0140] Table 1 Process Parameters

[0141]

[0142] Table 2. Basic Implementation Examples and Their Proportions

[0143]

[0144] Note: The spraying amount is a parameter of the application step and is not included in the preparation method. The spraying amount corresponding to Example 11 is 200g / m², the spraying amount corresponding to Example 12 is 250g / m², and the spraying amount of the other examples is 300g / m².

[0145] Comparative Example 1

[0146] The silane composite nano-ettringite hydrophobic agent of this comparative example is prepared from the following raw materials in parts by weight: 14 parts nano-ettringite powder, 3.5 parts n-octyltriethoxysilane (TOES, excluding γ-aminopropyltriethoxysilane), 90 parts anhydrous ethanol, 0.15 parts water, and 0.05 parts acetic acid; the nano-ettringite powder has an ettringite purity of 100% and a median particle size D50 of 200 nm.

[0147] The preparation method includes the following steps:

[0148] (1) Preparation of dispersion: According to the above ratio, take nano-calcite powder, add it to anhydrous ethanol accounting for 90% of the total mass of anhydrous ethanol, and ultrasonically disperse for 15 minutes to obtain a uniform calcite suspension.

[0149] (2) Preparation of silane premix: Take TOES according to the above ratio, add it to anhydrous ethanol accounting for 10% of the total mass of anhydrous ethanol and stir for 5 minutes. Then add acetic acid and stir continuously at 400 rpm to obtain silane premix.

[0150] (3) Preparation of silane sol: Take water according to the above ratio and slowly add it to the silane premix in four portions. After the addition is completed, continue stirring for 10 minutes to obtain silane sol;

[0151] (4) Composite reaction: Under the temperature condition of 20°C, the silane sol is slowly added dropwise to the ettringite suspension over 20 minutes, and the reaction is continued to be stirred for 6 hours after the addition is completed;

[0152] (5) Post-treatment: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5%, thus obtaining the hydrophobic agent of this comparative example.

[0153] The application method is the same as in Example 3, and the spraying amount is 300g / m².

[0154] Results Analysis

[0155] The effects of each embodiment are shown in Table 3.

[0156] Table 3. Results of hydrophobicity test

[0157]

[0158] Example contact angle Figure 2 As shown.

[0159] The results show that:

[0160] (1) With the increase of KH-550 ratio, the Si-O-Al bond content in the product increases, the density of the composite layer is enhanced, and the surface contact angle increases from 86° to 115°.

[0161] (2) The protective effect is optimal when the particle size of nano-calcite is about 200 nm and the silane ratio is TOES:KH-550=60:40;

[0162] (3) The resulting coating can significantly inhibit capillary water absorption and chloride ion penetration, exhibiting excellent durability and alkali resistance.

[0163] In this invention, nano-calcite serves as a multi-cation channel carrier. Its surface hydroxyl groups react with the -NH2 groups in KH-550 to form Si-O-Al and Si-O-Ca bonds, thereby inducing the ordered condensation of TOES and constructing a hydrophobic long-chain structure. The resulting composite layer combines chemical bonding with the hydrophobic organic chain arrangement effect, resulting in a micro-nano dual-scale rough structure on the surface, thus achieving durable and stable superhydrophobic properties.

[0164] Considering all performance parameters, Examples 9 and 12 showed the best results. The raw material ratio for Example 9 was: 14 parts ettringite (100% purity, D50=200nm), TOES:KH-550=60:40, 4 parts organosilane, 90 parts anhydrous ethanol, 0.35 parts water, and 0.02 parts acetic acid. The process parameters were: composite reaction temperature 25℃, dropping time 20min, composite reaction time 5h, residual ethanol content 0.5%, and spraying amount 300g / m². It achieved a contact angle of 115°, a 40% reduction in capillary water absorption coefficient, and a 60% reduction in chloride ion penetration depth. Example 12 had the same ratio as Example 9, but the composite reaction time was extended to 6h, the spraying amount was 250g / m², and the contact angle was 114°, also showing excellent performance.

[0165] The silane-based composite nano-calcite hydrophobic agent prepared under optimized conditions exhibits the following characteristics: it forms a stable sol system upon reaction at room temperature; it bonds firmly to the matrix of solid waste cementitious materials; it possesses excellent alkali stability (stable dispersion even at pH>12); its contact angle is ≥110°; and its chloride ion penetration depth decreases by ≥50% after 28 days. Therefore, this protective agent can maintain its surface protection performance for a long time under complex service environments and is suitable for solid waste cementitious material structures in marine, salt spray, and humid heat environments.

[0166] The above-described silane composite nano-calcite hydrophobic agent, its preparation method, and its application are specific embodiments of the present invention, demonstrating the substantial features and progress of the present invention. Equivalent modifications can be made to it according to actual usage needs, under the guidance of the present invention, and all such modifications are within the scope of protection of this solution.

Claims

1. A method for preparing a silane composite nano-calcite hydrophobic agent, characterized in that, Includes the following steps: Dispersion preparation: Take 10-14 parts by mass of nano-ettringite powder and add it to 76-81 parts of anhydrous ethanol to disperse it, thereby obtaining a uniform ettringite suspension; wherein the median particle size D50 of the nano-ettringite powder is 200-300 nm. Preparation of silane premix: Take 3-4 parts of organosilane by mass ratio, add 8-10 parts of anhydrous ethanol and stir, then add 0.02-0.05 parts of acetic acid and continue stirring to obtain silane premix; the organosilane is a mixture of n-octyltriethoxysilane and γ-aminopropyltriethoxysilane, with a mass ratio of (60-85):(15-40); Preparation of silane sol: Take 0.15-0.35 parts by mass of water and slowly add it dropwise to the silane premixed solution in multiple portions. After the addition is complete, continue stirring to obtain silane sol. Composite reaction: Under the temperature conditions of 20-25℃, silane sol is added dropwise to ettringite suspension, and the reaction is continuously stirred after the addition is completed; Post-processing: The product of the composite reaction is subjected to de-alcoholization under reduced pressure until the residual alcohol content in the product is 0.5-1%, thus obtaining the silane composite nano-calcite hydrophobic agent.

2. The preparation method of the silane composite nano-calcite hydrophobic agent according to claim 1, characterized in that: In the dispersion preparation step, the mass of anhydrous ethanol added to the nano-calcite powder is 90% of the total mass of anhydrous ethanol; in the silane premix preparation step, the mass of anhydrous ethanol added to the organosilane is 10% of the total mass of anhydrous ethanol; the total mass fraction of anhydrous ethanol is 85-90 parts.

3. The preparation method of the silane composite nano-calcite hydrophobic agent according to claim 2, characterized in that: In the dispersion preparation step, after adding anhydrous ethanol to the nano-calcite powder, it is ultrasonically dispersed for 15 minutes to obtain a uniform calcite suspension; the purity of the nano-calcite powder is ≥95%; in the silane premix preparation step, after adding anhydrous ethanol to the organosilane, it is stirred for 5 minutes, and then the acetic acid is added, and it is continuously stirred rapidly at a speed of 400 rpm.

4. The preparation method of the silane composite nano-calcite hydrophobic agent according to claim 1, characterized in that: In the silane sol preparation step, the water is slowly added dropwise to the silane premixed solution four times. After the addition is completed, the mixture is stirred for 10 minutes to obtain the silane sol.

5. The preparation method of the silane composite nano-calcite hydrophobic agent according to claim 1, characterized in that: In the composite reaction step, the silane sol is slowly added dropwise to the ettringite suspension over 10-20 minutes, and the reaction is continued with stirring for 5-6 hours after the addition is completed.

6. A silane composite nano-calcite hydrophobic agent, characterized in that: The silane composite nano-calcite hydrophobic agent is obtained by the preparation method of the silane composite nano-calcite hydrophobic agent according to any one of claims 1-5.

7. An application of a silane composite nano-calcite hydrophobic agent, characterized in that: The silane composite nano-calcite hydrophobic agent obtained by the preparation method according to any one of claims 1-5 is uniformly applied to the surface of the solid waste cementitious material to be protected at an application rate of 200-300 g / m² after the initial setting and before the final setting of the solid waste cementitious material.

8. The application of the silane composite nano-calcite hydrophobic agent according to claim 7, characterized in that: The solid waste cementitious material is a solid waste cementitious system composed of slag powder, gypsum, and steel slag powder.

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