A composite concrete waterproofing agent, its preparation method and application

Abstract

This invention provides a composite concrete waterproofing agent, its preparation method, and its application. Using nano-hexagonal boron nitride (nano-h-BN) and acrylic redispersible latex powder as core raw materials, the nano-h-BN is hydroxylated and modified with KH-570 silane coupling agent. Then, it is in-situ grafted copolymerized with acrylic redispersible latex powder and acrylic monomers through a redox initiation system. Finally, the powdered composite waterproofing agent is obtained by spray drying. This invention solves the technical problems of poor dispersibility and weak interfacial bonding of inorganic nanomaterials in organic acrylic systems. Combining the layered barrier effect of nano-h-BN with the rigid film-forming, alkali-resistant, and weather-resistant properties of acrylic latex powder, it achieves a dual waterproofing effect, significantly improving the concrete's resistance to water penetration, chloride ion penetration, freeze-thaw cycles, and early cracking, while also improving shrinkage characteristics. The preparation process is mild and controllable, the raw materials are readily available, and it can be industrially scaled up.

Description

Technical Field

[0001] This invention belongs to the field of concrete waterproofing agent preparation technology, specifically relating to a composite concrete waterproofing agent, its preparation method, and its application. Background Technology

[0002] Concrete, as the core building material in civil engineering, is prone to water seepage and chloride ion intrusion due to its porous structure, leading to steel corrosion, structural cracking, and significantly reducing the durability and service life of concrete structures. Concrete waterproofing agents are key materials for improving the waterproofing and seepage resistance of concrete. Among them, acrylic waterproofing agents, due to their good film-forming properties and excellent alkali and weather resistance, have become the most widely used organic waterproofing agents in engineering projects.

[0003] Existing acrylic concrete waterproofing agents are mostly prepared using physical blending processes, such as simply mixing inorganic nanomaterials, waste adhesive powder, etc. with acrylic emulsion. This has two major technical defects: First, inorganic nanomaterials have poor dispersibility in organic acrylic systems and are prone to agglomeration, resulting in weak interfacial bonding and failing to fully exert the filling and barrier effects of nanomaterials. Second, there are no chemical bonds between the components of physical blending, which can easily lead to phase separation in the alkaline environment of concrete and during long-term service, resulting in insufficient waterproofing durability.

[0004] Meanwhile, existing technologies also include using inorganic nanomaterials alone for concrete crack resistance and seepage prevention, or grafting VAE latex powder with inorganic materials to prepare waterproofing agents. However, the former only improves the density of concrete without forming a waterproof film, resulting in a single function; the latter's VAE system has poor weather resistance and water immersion resistance, and the overall performance of the grafted product is insufficient to meet the waterproofing requirements of harsh scenarios. In addition, although some acrylic grafting technologies have been applied in fields such as pharmaceutical excipients, the process parameters and raw material systems of such technologies are completely incompatible with the field of concrete waterproofing agents and cannot be directly transplanted and applied.

[0005] Therefore, developing a composite concrete waterproofing agent that can achieve covalent bonding between inorganic nanomaterials and acrylic latex powder, good dispersibility, strong interfacial bonding, and has both layered barrier and rigid film-forming dual waterproofing effects has become the key to solving the pain points of existing technologies. Summary of the Invention

[0006] In view of this, the present invention provides a composite concrete waterproofing agent, its preparation method, and its application. The present invention achieves molecular-level bonding between inorganic nano-hexagonal boron nitride and organic acrylic latex powder through a covalent graft copolymerization process, solving the problem of nanomaterial agglomeration. Combining the performance advantages of both materials achieves dual waterproofing, significantly improving the waterproofing, crack resistance, freeze-thaw resistance, and chloride ion penetration resistance of concrete. Furthermore, the process is mild and controllable, the raw materials are readily available, and it can be industrially scaled up.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A composite concrete waterproofing agent, comprising the following components: modified nano-hexagonal boron nitride, acrylic redispersible latex powder, acrylic monomer, and emulsion; Among them, the modified nano-hexagonal boron nitride is obtained by reacting a silane coupling agent with hydroxylated nano-hexagonal boron nitride; The amount of modified nano-hexagonal boron nitride added is 1% to 2% of the mass of the composite concrete waterproofing agent; The amount of silane coupling agent used is 10% to 15% of the mass of nano-hexagonal boron nitride; The mass ratio of acrylic redispersible latex powder to nano-hexagonal boron nitride is (8~12):1; The mass ratio of acrylic monomer to nano-hexagonal boron nitride is (4~6):1; The emulsion is prepared by mixing water, emulsifier and buffer, and the volume-to-mass ratio of the emulsion to nano-hexagonal boron nitride is (65~75):1.

[0008] Furthermore, the modified nano-hexagonal boron nitride is prepared as follows: S11. Add nano-hexagonal boron nitride to hydrogen peroxide, sonicate, and then transfer to a hydrothermal reactor. After the reaction is complete, cool to room temperature, centrifuge, wash the precipitate until the pH of the filtrate is 6.5~7.5, dry, and grind to obtain hydroxylated nano-hexagonal boron nitride. S12. Prepare an ethanol-deionized water solvent and adjust the pH to 4-5. Add hydroxylated nano-hexagonal boron nitride to the solvent, disperse it by ultrasonication, slowly add silane coupling agent and stir, heat and reflux the reaction. After the reaction is completed, centrifuge, wash the precipitate with anhydrous ethanol and dry it to obtain modified nano-hexagonal boron nitride.

[0009] Preferably, in step S11, the mass-to-volume ratio of nano-hexagonal boron nitride to hydrogen peroxide is 1:(55~65). Hydrothermal reaction conditions: temperature 85~95℃, time 5~7 h; Centrifugation conditions: speed 7000~9000 r / min, time 8~12 min; Drying conditions: Dry at 55~65℃ under vacuum for 10~14 h; The hydrogen peroxide concentration was 30%, and the ultrasound was performed in an ice bath.

[0010] Preferably, in step S12, the volume ratio of ethanol to deionized water in the ethanol-deionized water solvent is (7~9):(3~1), and hydroxylated nano-hexagonal boron nitride is added at a material-to-liquid ratio of 1:(75~85). Reflux reaction conditions: temperature 55~60℃, time 2.5~3.5 h; Centrifugation conditions: speed 7000~9000 r / min, time 8~12 min; Drying conditions: Dry at 45~55℃ under vacuum for 7~9 h.

[0011] The silane coupling agent used is KH-570 silane coupling agent. The pH is adjusted using glacial acetic acid, and the ultrasound is performed in an ice bath.

[0012] Furthermore, the glass transition temperature of the acrylic redispersible latex powder is 20~30℃; The acrylic monomer is obtained by mixing methyl methacrylate and butyl acrylate in a mass ratio of 1:1.

[0013] Furthermore, the volume-to-mass ratio of water, emulsifier, and buffer in the emulsion is (500~600):(2~3):1; The emulsifier is obtained by mixing sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 5:3. The buffer is sodium bicarbonate.

[0014] A method for preparing the above-mentioned composite concrete waterproofing agent, the preparation method comprising the following steps: S21. Add modified nano-hexagonal boron nitride to the emulsion, disperse it ultrasonically, add acrylic redispersible latex powder, stir and disperse; then add acrylic monomer, stir evenly to obtain a mixed system; S22. Heat the mixed system and add part of the redox initiation system to initiate prepolymerization. Then, add the remaining redox initiation system dropwise at a uniform rate while maintaining a constant temperature and stirring. After the reaction is complete, heat the system to mature, cool it to room temperature, and filter it to obtain a modified nano-hexagonal boron nitride-acrylic grafted composite emulsion. Spray dry or freeze dry the modified nano-hexagonal boron nitride-acrylic grafted composite emulsion to obtain a white powdery composite concrete waterproofing agent.

[0015] Preferably, the redox reaction conditions in step S22 are: temperature 50~55℃, initiation prepolymerization reaction time 10~20min, and constant temperature reaction time 2~3h; Curing conditions: temperature 60~65℃, time 20~40 min; The redox initiation system is composed of potassium persulfate and sodium bisulfite mixed in a mass ratio of 5:2, and the mass ratio of the redox initiation system to nano-hexagonal boron nitride is (7~8):1. Half the mass of the redox initiation system is added during prepolymerization, and the remaining half is added during the isothermal reaction.

[0016] Preferably, the spray drying conditions in step S22 are: inlet air temperature 160~180℃, outlet air temperature 75~85℃, and feed rate 10 mL / min.

[0017] A waterproof concrete, wherein the waterproof concrete is prepared by adding the above-mentioned composite concrete waterproofing agent at 0.5 to 1.5% of the cement mass.

[0018] The graft copolymerization reaction of this invention achieves active site construction and covalent bonding in three steps, the specific mechanism of which is as follows: 1. After hydrogen peroxide hydroxylation, hydroxyl groups (-OH) are introduced on the surface of nano-h-BN, providing active sites for subsequent modification; 2. After hydrolysis, KH-570 silane coupling agent undergoes a condensation reaction with hydroxyl groups, and can be grafted onto the surface of nano-h-BN to polymerize vinyl groups (C=C). 3. The redox initiation system initiates the free radical copolymerization of vinyl groups with acrylic latex powder and acrylic monomers, achieving covalent bonding between nano-h-BN and acrylic latex powder, forming h-BN-g-acrylic acid graft copolymer.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Structural innovation to solve core technical problems: This invention achieves covalent bonding between nano-hexagonal boron nitride and acrylic redispersible latex powder through in-situ graft copolymerization, breaking through the technical bottleneck of existing physical blending, and solving the problems of poor dispersibility and weak interfacial bonding of inorganic nanomaterials in organic acrylic system. Nano-hexagonal boron nitride achieves molecular-level dispersion in the system without agglomeration.

[0020] (2) Synergistic performance to achieve dual waterproofing effect: Combining the layered barrier effect of nano-hexagonal boron nitride (filling concrete pores to form a dense physical barrier layer to prevent water and chloride ions from penetrating) with the rigid film-forming effect of acrylic latex powder (forming a continuous organic film inside the concrete to improve waterproofing and sealing), it also has excellent alkali resistance, weather resistance and water immersion resistance, and its waterproofing durability far exceeds that of traditional VAE-based waterproofing agents and physically blended waterproofing agents.

[0021] (3) Excellent comprehensive performance and improved concrete multi-dimensional characteristics: When the composite waterproofing agent of the present invention is added to concrete, it not only significantly improves the concrete’s resistance to water penetration (28d resistance grade ≥ P20), resistance to chloride ion penetration (electric flux ≤ 500C), and resistance to freeze-thaw cycles (freeze-thaw cycles ≥ 300 times), but also effectively improves the early crack resistance (crack width ≤ 0.05mm) and shrinkage characteristics (28d shrinkage rate ≤ 90%). All performances meet the requirements of relevant national standards.

[0022] (4) The process is mild and easy to scale up to industrial scale: The preparation process adopts low-temperature oxidation-reduction initiation (grafting temperature 50~55℃), which avoids the thermal decomposition of acrylic latex powder and the agglomeration of nano-hexagonal boron nitride, resulting in a high grafting rate; all raw materials are conventional products on the market, and the equipment is conventional equipment for laboratory and industrial production (ultrasonic cleaner, hydrothermal reactor, spray dryer, etc.). The process is highly repeatable, and the performance of laboratory small-scale tests and industrial pilot tests is consistent, making it easy to mass-produce in industrial scale.

[0023] (5) Wide range of applications and suitable for harsh scenarios: The product is in powder form, which is convenient for storage, transportation and compounding in concrete engineering. It is suitable for internal waterproofing in various concrete engineering projects, especially for harsh service scenarios such as outdoor, long-term water immersion, chloride ion erosion (such as coastal projects and municipal water supply and drainage projects), and freeze-thaw cycles (such as projects in cold northern regions). Compared with existing waste adhesive powder modified acrylic waterproofing agents, it does not rely on waste raw materials and has more stable performance. Compared with single inorganic nano crack-resistant materials, it has both waterproof and crack-resistant functions and is applicable to a wider range of scenarios. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and all reagents and consumables are commercially available products.

[0025] Example 1 This embodiment provides a composite concrete waterproofing agent, the preparation method of which is as follows: 1.1 Hydroxylation Modification 1 g of nano-hexagonal boron nitride (h-BN, particle size 50~200 nm) was added to 60 mL of 30% hydrogen peroxide and sonicated in an ice bath for 40 min. Then, it was transferred to a hydrothermal reactor and reacted at 90 °C for 6 h. After the reaction was completed, it was cooled and centrifuged at 8000 r / min for 10 min. The product was washed with deionized water until the pH of the filtrate was 7.0. The product was vacuum dried at 60 °C for 12 h to obtain hydroxylated nano-hexagonal boron nitride (nano-h-BN-OH).

[0026] 1.2 Modification of Silane Coupling Agents Prepare 80 mL of ethanol-deionized water mixed solvent (ethanol to deionized water volume ratio of 8:2), adjust pH to 4.5 using glacial acetic acid, add the prepared nano-h-BN-OH and sonicate for 30 min in an ice bath; then add 0.12 g of silane coupling agent (KH-570), stir at room temperature for 10 min, and reflux at 58 °C for 3 h; after the reaction is complete, centrifuge at 8000 r / min for 10 min, wash twice with anhydrous ethanol, and dry the product under vacuum at 50 °C for 8 h to obtain modified nano-hexagonal boron nitride (nano-h-BN-KH570).

[0027] 1.3 In-situ graft copolymerization Add 0.2g sodium dodecyl sulfate (SDS), 0.12g octylphenol polyoxyethylene ether (OP-10), and 0.12g NaHCO3 to 70g deionized water and stir at 300r / min until dissolved to obtain an emulsion. Add 1g nano-h-BN-KH570 to the emulsion and sonicate for 45min in an ice bath. Then add 10g acrylic redispersible latex powder and stir for 20min. Add 5g acrylic monomer (obtained by compounding methyl methacrylate (MMA) and butyl acrylate (BA) in a mass ratio of 1:1) and stir for 10min. Then raise the temperature to 53℃ and add 1 / 2 mass of the redox initiation system (obtained by mixing 0.1g potassium persulfate and 0.04g sodium bisulfite) for prepolymerization for 15min. Finally, add the remaining redox initiation system and react at a constant temperature of 53℃ for 2.5h. Finally, raise the temperature to 63℃ for 30min, cool and filter to obtain the modified nano-hexagonal boron nitride-acrylic acid grafted composite emulsion.

[0028] 1.4 Spray drying The modified nano-hexagonal boron nitride-acrylic acid grafted composite emulsion was fed into a spray dryer with an inlet air temperature of 170℃, an outlet air temperature of 80℃, and a feed rate of 10mL / min. After drying, a white powdery nano-hexagonal boron nitride-grafted acrylic latex powder composite concrete waterproofing agent was obtained and stored in a sealed container.

[0029] Example 2 This embodiment provides a composite concrete waterproofing agent, the preparation method of which is basically the same as that of Embodiment 1, except that the amount of nano-h-BN-KH570 added in step 1.3 is changed to 2g, while the rest remain unchanged.

[0030] Comparative Example 1 This embodiment provides a composite concrete waterproofing agent, the preparation method of which is basically the same as that of Embodiment 1, except that the amount of nano-h-BN-KH570 added in step 1.3 is changed to 3g, while the rest remain unchanged.

[0031] Comparative Example 2 This comparative example provides a concrete waterproofing agent, which uses only acrylic emulsion as the waterproofing agent.

[0032] Comparative Example 3 This comparative example provides a concrete waterproofing agent, the preparation method of which is as follows: Take 1.0g of unmodified nano-h-BN and mix it evenly with 15g of acrylic emulsion to obtain a concrete waterproofing agent.

[0033] Comparative Example 4 This comparative example provides a composite concrete waterproofing agent, the preparation method of which is basically the same as that of Example 1, except that: the acrylic redispersible latex powder is replaced by an equal amount of VAE redispersible latex powder, and the rest remain unchanged.

[0034] Furthermore, in order to understand the performance of the concrete waterproofing agents prepared in the above embodiments and comparative examples, the following tests were also conducted: Each prepared concrete waterproofing agent was added to concrete at a dosage of 1% of the cement mass. The standard concrete mix proportion was: 400 parts cement, 740 parts sand, 1100 parts aggregate, 160 parts water, and an appropriate amount of water-reducing agent. Standard specimens were prepared and their performance tested according to the following national standards: (1) GB / T 50082-2024 Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete: Water permeability resistance (permeability grade), freeze-thaw resistance (rapid freezing method), chloride ion permeability resistance (electric flux method), early crack resistance; (2) JC474-2008 "Waterproofing Agents for Mortar and Concrete": Shrinkage ratio; (3) JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering": to assist in verifying various performance indicators.

[0035] The performance test results are shown in Table 1: Table 1. Test results of concrete performance in each experimental group

[0036] As shown in Table 1, the products prepared in Examples 1 and 2 are both of excellent quality. Among them, the composite waterproofing agent in Example 2 has the best performance. The concrete has a 28-day impermeability grade of P20, a freeze-thaw cycle of F300, a chloride ion flux as low as 382C, an early crack resistance of 0 (no visible cracks), and a 28-day shrinkage rate of only 90%. All of its properties are significantly better than those of other experimental groups.

[0037] In Comparative Example 1, a higher addition of modified nano-h-BN may lead to agglomeration, which could reduce the waterproofing and crack resistance of concrete. Therefore, its mass fraction is preferably 1% to 2.5%. Meanwhile, Examples 1 and 2 showed performance far superior to pure acrylic waterproofing agent (Comparative Example 2), physically blended product (Comparative Example 3), and VAE-based grafted product (Comparative Example 4), demonstrating that covalent graft copolymerization can achieve synergistic performance between nano-h-BN and acrylic latex powder, solving the core pain points of existing technologies.

[0038] In addition, a 10kg pilot-scale experiment was conducted to understand the adaptability of the product and its preparation method. The results showed that the prepared product was basically the same as that prepared in the laboratory, and there was no significant difference in concrete modification performance, proving that the process can be directly scaled up to industrial mass production.

[0039] The following precautions were also observed during actual use: 1. Anti-agglomeration of nano-h-BN: Ice bath ultrasonic dispersion is used throughout the process. The amount of KH-570 is strictly controlled at 10%~15% of the mass of nano-h-BN to avoid self-agglomeration caused by excessive dosage. The dispersion effect of the system can be observed through a microscope during the process. 2. Raw material selection: For acrylic redispersible latex powder, the general type with Tg=20~30℃ should be preferred to avoid products with high Tg (>40℃) which may cause insufficient flexibility and easy cracking of concrete; 3. Temperature control: The grafting reaction temperature is strictly controlled at 50~55℃, and the curing temperature is ≤65℃ to avoid excessive temperature from causing thermal decomposition of acrylic latex powder and volatilization of monomers, which would reduce the grafting rate. 4. Product storage: The prepared powdered composite waterproofing agent should be sealed and stored in a dry, cool environment to avoid moisture absorption and clumping. Shelf life is ≥6 months. 5. Dosage for engineering projects: The dosage is adjusted according to the service scenarios of concrete projects. The dosage for normal scenarios is 1% of the cement mass, and the dosage for harsh scenarios (coastal, cold regions) is 1.5%~2%. No additional waterproofing agents are required. It has good compatibility with concrete water-reducing agents, fly ash and other admixtures.

[0040] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite concrete waterproofing agent, characterized in that, The composite concrete waterproofing agent comprises the following components: modified nano-hexagonal boron nitride, acrylic redispersible latex powder, acrylic monomer, and emulsion; Among them, the modified nano-hexagonal boron nitride is obtained by reacting a silane coupling agent with hydroxylated nano-hexagonal boron nitride; The amount of modified nano-hexagonal boron nitride added is 1% to 2.5% of the mass of the composite concrete waterproofing agent; The amount of silane coupling agent used is 10% to 15% of the mass of nano-hexagonal boron nitride; The mass ratio of acrylic redispersible latex powder to nano-hexagonal boron nitride is (8~12):1; The mass ratio of acrylic monomer to nano-hexagonal boron nitride is (4~6):1; The emulsion is prepared by mixing water, emulsifier and buffer, and the volume-to-mass ratio of the emulsion to nano-hexagonal boron nitride is (65~75):

1.

2. The composite concrete waterproofing agent according to claim 1, characterized in that, The modified nano-hexagonal boron nitride was prepared as follows: S11. Add nano-hexagonal boron nitride to hydrogen peroxide, sonicate, and then transfer to a hydrothermal reactor. After the reaction is complete, cool to room temperature, centrifuge, wash the precipitate until the pH of the filtrate is 6.5~7.5, dry, and grind to obtain hydroxylated nano-hexagonal boron nitride. S12. Prepare an ethanol-deionized water solvent and adjust the pH to 4-5. Add hydroxylated nano-hexagonal boron nitride to the solvent, disperse it by ultrasonication, slowly add silane coupling agent and stir, heat and reflux the reaction. After the reaction is completed, centrifuge, wash the precipitate with anhydrous ethanol and dry it to obtain modified nano-hexagonal boron nitride.

3. The composite concrete waterproofing agent according to claim 2, characterized in that, In step S11, the mass-to-volume ratio of nano-hexagonal boron nitride to hydrogen peroxide is 1:(55~65). Hydrothermal reaction conditions: temperature 85~95℃, time 5~7 h; Centrifugation conditions: speed 7000~9000 r / min, time 8~12 min; Drying conditions: Dry at 55~65℃ under vacuum for 10~14 h; The hydrogen peroxide concentration was 30%, and the ultrasound was performed in an ice bath.

4. The composite concrete waterproofing agent according to claim 2, characterized in that, In step S12, the volume ratio of ethanol to deionized water in the ethanol-deionized water solvent is (7~9):(3~1), and hydroxylated nano-hexagonal boron nitride is added at a material-to-liquid ratio of 1:(75~85). Reflux reaction conditions: temperature 55~60℃, time 2.5~3.5 h; Centrifugation conditions: speed 7000~9000 r / min, time 8~12 min; Drying conditions: Dry at 45~55℃ under vacuum for 7~9 h. The silane coupling agent used is KH-570 silane coupling agent. The pH is adjusted using glacial acetic acid, and the ultrasound is performed in an ice bath.

5. The composite concrete waterproofing agent according to claim 1, characterized in that, The glass transition temperature of the acrylic redispersible latex powder is 20~30℃; The acrylic monomer is obtained by mixing methyl methacrylate and butyl acrylate in a mass ratio of 1:

1.

6. The composite concrete waterproofing agent according to claim 1, characterized in that, The volume-to-mass ratio of water, emulsifier, and buffer in the emulsion is (500~600):(2~3):1; The emulsifier is obtained by mixing sodium dodecyl sulfate and octylphenol polyoxyethylene ether in a mass ratio of 5:

3. The buffer is sodium bicarbonate.

7. A method for preparing the composite concrete waterproofing agent according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: S21. Add modified nano-hexagonal boron nitride to the emulsion, disperse it ultrasonically, add acrylic redispersible latex powder, stir and disperse; then add acrylic monomer, stir evenly to obtain a mixed system; S22. Heat the mixed system and add part of the redox initiation system to initiate prepolymerization. Then, add the remaining redox initiation system dropwise at a uniform rate while maintaining a constant temperature and stirring. After the reaction is complete, heat the system to mature, cool it to room temperature, and filter it to obtain a modified nano-hexagonal boron nitride-acrylic grafted composite emulsion. Spray dry or freeze dry the modified nano-hexagonal boron nitride-acrylic grafted composite emulsion to obtain a white powdery composite concrete waterproofing agent.

8. The preparation method according to claim 7, characterized in that, The redox reaction conditions in step S22 are: temperature 50~55℃, initiation prepolymerization reaction time 10~20min, and constant temperature reaction time 2~3h; Curing conditions: temperature 60~65℃, time 20~40 min; The redox initiation system is composed of potassium persulfate and sodium bisulfite mixed in a mass ratio of 5:2, and the mass ratio of the redox initiation system to nano-hexagonal boron nitride is (7~8):

1. Half the mass of the redox initiation system is added during prepolymerization, and the remaining half is added during the isothermal reaction.

9. The preparation method according to claim 7, characterized in that, The spray drying conditions in step S22 are: inlet air temperature 160~180℃, outlet air temperature 75~85℃, and feed rate 10 mL / min.

10. A waterproof concrete, characterized in that, The waterproof concrete is prepared by adding the composite concrete waterproofing agent described in any one of claims 1-6 at 0.5-1.5% of the cement mass.

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