A hydraulic foam concrete protective coating material and a preparation method thereof

Abstract

This invention relates to the field of hydraulic coating technology, specifically disclosing a protective coating material for hydraulic foamed concrete and its preparation method. The protective coating material for hydraulic foamed concrete of this invention comprises 30-40 parts epoxy resin, 10-20 parts cement, 5-12 parts water, 18-25 parts modified bainite-silica mixture, and 25-35 parts styrene-butadiene emulsion. Through the synergistic effect of the modified bainite-silica mixture, epoxy resin, and styrene-butadiene emulsion, this protective coating material simultaneously possesses mechanical properties, waterproof properties, and thermal insulation properties, significantly reducing surface damage to foamed concrete and extending its service life.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic coating technology, specifically relating to a protective coating material for hydraulic foamed concrete and its preparation method. Background Technology

[0002] Foamed concrete, as a lightweight and environmentally friendly cement-based porous material, boasts advantages such as simple production and construction processes, convenient mix proportion adjustment, and low overall cost. Furthermore, it possesses numerous beneficial properties, including thermal insulation and energy absorption. It not only provides adequate insulation but also exhibits superior interfacial bonding performance due to its homologous composition with hydraulic concrete. Currently, foamed concrete has gradually developed into a new type of protective and functional material in the hydraulic engineering field, and has been successfully applied in projects such as water pipeline insulation and cold-region canal insulation. In the future, it is expected to completely replace organic insulation materials, becoming an important protective insulation material in concrete dam projects.

[0003] In existing and relatively mature foamed concrete preparation technologies, it typically contains only a small amount of aggregate or even none, and a large number of artificial air bubbles. These factors create a relatively complex pore structure in foamed concrete, while also giving it a certain water absorption capacity. In water-prone and cold regions, the likelihood of foamed concrete undergoing saturated freeze-thaw cycles increases significantly, posing a serious challenge to its stability. During saturated freeze-thaw cycles, the expansion stress generated inside the foamed concrete becomes more pronounced, and the destructive effect on its mechanical and thermal properties becomes more severe. Applying a hydraulic waterproof coating to the surface of foamed concrete can extend its service life.

[0004] However, existing hydraulic waterproofing coating materials can be broadly categorized into organic, inorganic, and organic-inorganic composite waterproofing coating materials. Firstly, organic waterproofing coating materials are primarily composed of carbon-containing organic compounds, such as organosilicon, polystyrene, polyurethane coatings, and acrylic polymers. They typically possess excellent elasticity and flexibility and do not react with cement. Secondly, inorganic waterproofing coating materials are mainly composed of inorganic compounds, such as cement-based penetrating crystalline waterproofing coatings and polymer-cement-based waterproofing coatings. These coating materials usually react chemically with cement and exhibit excellent impermeability, abrasion resistance, and weather resistance. Thirdly, organic-inorganic composite waterproofing coating materials possess excellent adaptability and stability, effectively coping with changing environmental conditions. They maintain the good performance of concrete and extend its service life under adverse factors such as water pressure, water erosion, and climate change.

[0005] However, none of the above materials can guarantee complete waterproofing, especially under long-term immersion and freeze-thaw conditions. Hydraulic structures or materials still face the risk of freeze-thaw cycle erosion and damage. Shell powder and diatomaceous earth, as derivatives of marine organisms, are often used in whitening architectural coatings, but their application in hydraulic waterproofing coatings, especially in the field of thermal insulation, remains somewhat lacking.

[0006] Chinese patent CN117210116A discloses a polyurethane waterproof coating and its preparation method. The coating raw materials include polyurethane, modified nano-silica, hydrogen-containing silicone oil, chloroplatinic acid, and various additives. The additives include viscosity reducers, talc, latent curing agents, dehydrating agents, defoamers, coupling agents, ultraviolet light absorbers, anti-aging agents, pigments, and activators. The polyurethane waterproof coating has good waterproof properties, tensile strength, and flame retardancy.

[0007] Invention patent CN108102473A discloses a method for preparing an inorganic thermal insulation and waterproof coating for building exterior walls. The coating raw materials include wollastonite fiber, hydrated magnesium silicate ultrafine powder, sepiolite powder, aluminum sulfate, sodium silicate, styrene-acrylic emulsion, thickener, and citric acid, etc. The inorganic thermal insulation and waterproof coating has excellent thermal insulation and waterproof performance.

[0008] For hydraulic engineering waterproof coating materials, mechanical properties, waterproofing properties, and thermal insulation properties are all indispensable. Mechanical properties primarily reduce the damage caused by floating debris impacting the surface of hydraulic structures in reservoir water, thus protecting the structures themselves. Waterproofing properties primarily reduce the intrusion of moisture into the hydraulic materials, mitigating the adverse effects of environmental changes or chemical components in the water. Thermal insulation properties primarily reduce freeze-thaw damage to hydraulic structures or materials caused by freeze-thaw cycles, extending the service life of the hydraulic structures. However, current waterproof coatings on the market cannot simultaneously meet all these requirements, and they utilize a large number of raw materials, making the research and development process quite complex, posing a significant challenge to the development of hydraulic engineering waterproof and thermal insulation coatings. Summary of the Invention

[0009] To address the shortcomings and problems of current hydraulic waterproof and thermal insulation coatings in protecting foamed concrete, which cannot simultaneously meet the requirements of mechanical properties, waterproofing, and thermal insulation, this invention provides a hydraulic foamed concrete protective coating material and its preparation method.

[0010] The protective coating material for hydraulic foam concrete provided by this invention comprises the following raw materials in parts by weight: 30-40 parts epoxy resin, 10-20 parts cement, 5-12 parts water, 18-25 parts modified bainite-silica mixture, and 25-35 parts styrene-butadiene emulsion.

[0011] The preparation method of the shale-silica mixture in the above-mentioned hydraulic foam concrete protective coating material is as follows: (1) The shell powder is wet-milled to a particle size D50 of 5-25 μm and its diameter-to-thickness ratio is controlled to be >20. Then it is soaked in dilute acid for 5-15 min and dried to obtain flake shell powder. (2) Disperse the flake-shaped shell powder prepared in step (1) in an aqueous solution containing rare earth ions, stir and react at 60-80℃ for 2-4 hours, and then take it out and dry it; (3) The porous diatomaceous earth is mixed with the flake shell powder treated in step (2) to obtain a modified shell-silicon mixture.

[0012] The above-mentioned protective coating material for hydraulic foam concrete is characterized in that: the dilute acid solution is a 0.1-0.5 mol / L hydrochloric acid or nitric acid solution.

[0013] In the above-mentioned protective coating material for hydraulic foam concrete, the particle size of the shell powder is 50-80μm; and the particle size of the diatomaceous earth is 30-45μm.

[0014] In the above-mentioned protective coating material for hydraulic foam concrete, the aqueous solution containing rare earth ions is an aqueous solution of lanthanum nitrate hexahydrate or cerium nitrate hexahydrate (III) with a mass concentration of 2%-4%.

[0015] The aforementioned protective coating material for hydraulic foam concrete contains a styrene-butadiene emulsion, which is a mixture of butadiene and styrene as the main components.

[0016] The cement used in the aforementioned hydraulic foam concrete protective coating material is ordinary Portland cement.

[0017] The application of the hydraulic foam concrete protective coating material described in any of the above items in the protection of hydraulic foam concrete.

[0018] The preparation method of any of the above-mentioned hydraulic foam concrete protective coating materials includes the following steps: S1. Mix the modified bainite-silica mixture and cement evenly; S2. Disperse waterborne epoxy resin, water and one-third styrene-butadiene emulsion evenly to form a matrix liquid; S3. The modified bainite-silica mixture from step S1 and cement are gradually added to the matrix liquid and dispersed by high-speed shearing to form a uniform slurry; then the remaining styrene-butadiene emulsion is added and stirred at low speed until uniform to obtain the finished coating.

[0019] The above-mentioned protective coating material for hydraulic foam concrete further includes step S3 by adding 0.01-0.03% ethylenediamine by volume of the slurry at the end of the slurry preparation stage.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention uses flaky seashell powder as a rigid reinforcement after surface hydroxylation and rare earth ion loading, and styrene-butadiene emulsion and part of epoxy resin as a flexible matrix. During the preparation of the epoxy resin, cross-linking and curing begins to form the first rigid network. During the film formation process, the styrene-butadiene emulsion particles fuse with each other and interpenetrate with the incompletely cross-linked epoxy segments to form a flexible network. The two networks interpenetrate to form the matrix of the coating. Combined with the coordination bond effect at the interface between the two, it can ensure the overall strength and have stronger flexible deformation ability. At the same time, the pore structure formed by the uniformly dispersed diatomaceous earth and its own pores, as well as the micro-interfacial pores formed between the flexible network and the rigid filler, reduces the thermal conductivity and effectively improves the thermal insulation performance of the coating.

[0021] This invention increases the density of surface-active hydroxyl groups by hydroxylating the sheet-like shell powder. After treatment with an aqueous solution containing rare earth ions, the rare earth ions coordinate with the hydroxyl groups on the shell powder surface, thereby loading the shell powder surface with active rare earth ions. The addition of porous diatomaceous earth increases the porosity of the coating and improves its thermal insulation performance. When the shell-silica mixture is added to the matrix liquid formed by epoxy resin and styrene-butadiene emulsion, it can be encapsulated by the polymer. At the same time, the epoxy resin begins to cross-link and cure to form the first rigid network. During the film formation process, the styrene-butadiene emulsion particles fuse with each other and interpenetrate with the incompletely cross-linked epoxy segments to form the second flexible network. The two networks interpenetrate each other and constitute the matrix of the coating, which can effectively improve the compressive strength and freeze resistance of the coating, significantly reduce surface damage to foamed concrete, and extend the service life of foamed concrete. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments.

[0023] Materials and Methods: Cement: PO 42.5 grade ordinary Portland cement; Shell powder: Jiayuan Mineral Products Processing Plant, Lingshou County, Shijiazhuang City, Hebei Province. Particle size is 50-80μm. Chemical composition is shown in Table 1 below.

[0024]

[0025] Diatomite: Jilin Yuantong Mining Co., Ltd., Jilin City, Jilin Province. Particle size is 30-45μm. Chemical composition is shown in Table 2 below.

[0026]

[0027] Waterborne epoxy resin: Produced by Shenzhen Mingde Chemical Co., Ltd., Guangdong Province, it is made by mixing epoxy resin adhesive, waterborne curing agent, diluent, toughening agent and other solvents in proportion.

[0028] Styrene-butadiene emulsion: Produced by Shenzhen Yoshida Chemical Co., Ltd., Guangdong Province. Its main components are butadiene and styrene, with a solid content of 54.5% and a pH value of 6.5.

[0029] Example 1: This example provides a water-based waterproof coating material with thermal insulation function, comprising the following raw materials: 40 parts of water-based epoxy resin emulsion, 15 parts of cement, 10 parts of water, 20 parts of modified bainite-silica mixture, and 30 parts of styrene-butadiene emulsion.

[0030] Its preparation method is as follows: S1. Preparation of modified shell-silica mixture: Shell powder is wet-milled to a particle size D50 of 5-25 μm and its aspect ratio is controlled to be >20. Then, it is soaked in 0.5 mol / L hydrochloric acid solution for 5-15 min and dried to obtain flake shell powder. The prepared flake shell powder is then dispersed in 3% cerium nitrate hexahydrate (III) aqueous solution and stirred at 60-80℃ for 2-4 hours. After drying, porous diatomaceous earth is mixed with the treated flake shell powder at a ratio of 1:2 to obtain modified shell-silica mixture. S2. Mix the modified bainite-silica mixture and cement evenly to obtain a dry powder system; S3. Disperse waterborne epoxy resin, water and one-third styrene-butadiene emulsion evenly to form a matrix liquid; S4. Gradually add the modified bainite-silica mixture from step S1 and cement to the matrix liquid and disperse them at high speed to form a uniform slurry; then add the remaining styrene-butadiene emulsion and stir at low speed until uniform to obtain the finished coating.

[0031] Example 2: The similarities between this example and Example 1 will not be repeated. The difference is that the water-based waterproof coating material in this example includes the following raw materials: 35 parts water-based epoxy resin, 10 parts cement, 12 parts water, 25 parts modified bainite-silica mixture, and 30 parts styrene-butadiene emulsion.

[0032] Example 3: The similarities between this example and Example 1 will not be repeated. The difference is that the water-based waterproof coating material in this example includes the following raw materials: 40 parts of water-based epoxy resin, 10 parts of cement, 10 parts of water, 18 parts of modified bainite-silica mixture, and 25 parts of styrene-butadiene emulsion.

[0033] Example 4: This example provides a water-based waterproof coating material with thermal insulation function, comprising the following raw materials: 40 parts of water-based epoxy resin emulsion, 15 parts of cement, 10 parts of water, 20 parts of modified bainite-silica mixture, and 30 parts of styrene-butadiene emulsion.

[0034] Its preparation method is as follows: S1. Preparation of modified shell-silica mixture: Shell powder is wet-milled to a particle size D50 of 5-25 μm and its aspect ratio is controlled to be >20. Then, it is soaked in 0.5 mol / L hydrochloric acid solution for 5-15 min and dried to obtain flake shell powder. The prepared flake shell powder is then dispersed in 3% cerium nitrate hexahydrate (III) aqueous solution and stirred at 60-80℃ for 2-4 hours. After drying, porous diatomaceous earth is mixed with the treated flake shell powder at a ratio of 1:2 to obtain modified shell-silica mixture. S2. Mix the modified bainite-silica mixture and cement evenly to obtain a dry powder system; S3. Disperse waterborne epoxy resin, water and one-third styrene-butadiene emulsion evenly to form a matrix liquid; S4. Gradually add the modified bainite-silica mixture from step S1 and cement to the matrix liquid and disperse them evenly by high-speed shearing. Then add 0.02% of the slurry volume of ethylenediamine to form a uniform slurry. Then add the remaining styrene-butadiene emulsion and stir evenly at low speed to obtain the finished coating.

[0035] Comparative Example 1: The water-resistant waterproof coating material provided in this comparative example is the same as that in Example 1, and will not be repeated here. The difference is that it includes the following raw materials: 40 parts epoxy resin, 15 parts cement, 10 parts water, 20 parts bacon-silica mixture, and 30 parts styrene-butadiene emulsion.

[0036] Preparation method: S1. Mix shell powder and diatomaceous earth evenly, add silane coupling agent and mix evenly to obtain a mixture. The mass ratio of silane coupling agent, shell powder and diatomaceous earth is 1:40:30. Place the mixture in an electric heating drying oven and dry it at a temperature of 95~100℃ for 1.5~2 hours. After cooling, a shell-silicon mixture is obtained. S2. Pour cement and water into a mixer in sequence and mix. Add basil-silicon mixture and styrene-butadiene emulsion and continue mixing. After mixing evenly, add water-based epoxy resin and mix thoroughly to form a slurry to obtain the finished coating.

[0037] Comparative Example 2: The water-resistant waterproof coating material provided in this comparative example is the same as that in Example 1, and will not be repeated here. The difference is that it includes the following raw materials: 40 parts epoxy resin, 20 parts cement, 10 parts water, 15 parts diatomaceous earth, 5 parts shell powder, and 30 parts styrene-butadiene emulsion.

[0038] The preparation method is as follows: S1. Mix diatomaceous earth, shell powder and cement evenly to obtain a dry powder system; S3. Disperse waterborne epoxy resin, water and one-third styrene-butadiene emulsion evenly to form a matrix liquid; S4. Gradually add the dry powder from step S1 to the base liquid and disperse it at high speed to form a uniform slurry; then add the remaining styrene-butadiene emulsion and stir at low speed until uniform to obtain the finished coating.

[0039] Comparative Example 3: The water-based waterproof coating material provided in this comparative example is the same as that in Example 1, and will not be repeated here. The difference is that it includes the following raw materials: 40 parts of water-based epoxy resin emulsion, 15 parts of cement, 10 parts of water, 20 parts of modified bainite-silica mixture, and 20 parts of styrene-butadiene emulsion.

[0040] Comparative Example 4: The water-resistant waterproof coating material provided in this comparative example is the same as that in Example 1, and will not be repeated here. The difference is that it includes the following raw materials: 25 parts epoxy resin, 15 parts cement, 10 parts water, 20 parts modified bainite-silica mixture, and 30 parts styrene-butadiene emulsion.

[0041] Test Example: Performance Testing Preparation of specimens: After mixing cement and aggregate evenly, add water and water-reducing agent and continue mixing to obtain a mixture. Pour the mixture into a mold and vibrate to form it. After demolding, place it in a curing box for 28 days. The precast mold is a cuboid with dimensions of 120×80×30mm.

[0042] (1) Measurement of compressive strength, thermal conductivity and contact angle In accordance with the requirements of the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081-2019), "Temperature Test Method for Thermal Conductivity and Thermal Diffusion Coefficient of Building Materials under Transient Plane Heat Source" (GB / T 32064-2015), and "Standard Test Method for Determination of Wetness and Absorbency of Covering Material Surface using Automatic Contact Angle Tester" (ASTM 5725), the compressive strength, thermal conductivity, and contact angle of the waterproof coating materials prepared in Examples 1-4 and Comparative Examples 1-4 of this invention were measured respectively, and the results are shown in Table 3 below.

[0043]

[0044] As shown in Table 3, the protective coating material prepared by this invention has a low thermal conductivity and high compressive strength and contact angle. The low thermal conductivity effectively reduces the destructive impact of low temperatures on foamed concrete, lowering temperature stress and reducing coating cracking and peeling. The high compressive strength provides effective load-bearing and protective layers for foamed concrete, effectively resisting external damage. Simultaneously, the high contact angle indicates that the coating material of this invention has good hydrophobic properties, reducing water intrusion and lowering the water absorption rate of foamed concrete, which is beneficial for maintaining long-term coating stability. Furthermore, the use of styrene-butadiene emulsion gives the coating material both high strength and good toughness, achieving a rigid yet non-brittle effect.

[0045] Experimental Example 2: The Influence of Waterproof Coating on the Water Absorption Rate of Foamed Concrete To verify the effect of waterproof coating materials on the water absorption rate of foamed concrete, this experiment selected the coating materials of Example 1 and Comparative Example 1, respectively, and measured the water absorption rate of different thicknesses of waterproof coatings applied to the surfaces of three types of foamed concrete (F1, F2, and F3). F1, F2, and F3 were all foamed concrete, and the raw materials used were: Cement: P·O 42.5 ordinary Portland cement produced by Anhui Conch Group Co., Ltd. of China, conforming to the national standard "General Portland Cement" GB175-2023.

[0046] Water: Tap water, conforming to the industry standard "Standard for Water Used in Concrete" JGJ 63-2006.

[0047] Foaming agent: AES polymer composite cement foaming agent produced by Weihai ZhongSheng New Building Materials Co., Ltd., China. Specific parameters are shown in Table 4.

[0048]

[0049] Mix proportions and preparation process of F1, F2, and F3 foamed concrete: The dry density method was used to prepare foamed concrete of three density grades. The specific mix proportions are shown in Table 5.

[0050]

[0051] Before the experiment, the foam bleeding and settling distance were tested. The foaming agent and water were diluted according to the specified ratio to prepare a foaming agent aqueous solution. Air was uniformly dispersed into the foaming agent aqueous solution using a foaming machine, and foam was produced by stirring and pressurizing. The produced foam was placed in a 200ml graduated cylinder and allowed to stand for 1 hour. The bleeding and settling distance were measured and compared with the specifications in the standard until a foam meeting the requirements was prepared. Based on the calculated foam concrete mix proportion, the required mass of water and cement was weighed and placed in a forced mixer to produce cement slurry. The qualified foam was added to the cement slurry and stirring continued until the foam and cement slurry were uniformly mixed. A layer of plastic film was covered on the surface of the poured foam concrete to prevent moisture evaporation. After curing at room temperature for 24 hours, the concrete was demolded and then placed in sealed plastic bags in a standard curing room for 28 days.

[0052] Before the test, the foamed concrete was placed in an electric heating drying oven and dried to constant weight at (105±5)℃. The weighing error of each group of foamed concrete should be less than 0.2%, and the weighing time interval was 4 hours. The water absorption test results are shown in Table 6 below.

[0053]

[0054] As shown in Table 6, compared with the uncoated waterproof coating material, applying a waterproof coating material to the surface of foamed concrete can reduce the water absorption rate of foamed concrete. The comparison shows that the decrease in water absorption rate of foamed concrete coated with the coating material of Example 1 is much greater than that of foamed concrete coated with the coating material of Comparative Example 1. This indicates that the waterproof coating material prepared in this invention can effectively prevent water from penetrating the foamed concrete and has strong waterproof and seepage-proof capabilities. By comparing the water absorption rates of different coating thicknesses, it can be seen that the water absorption rate of foamed concrete decreases with the increase of the waterproof coating thickness, but the decreasing trend gradually flattens out.

[0055] Test Example 3: Freeze Resistance Test In accordance with the requirements of the "Test Procedure for Hydraulic Concrete" (SL / T 352-2020), the hydraulic waterproof coating materials prepared in Examples 1-3 and Comparative Examples 1-4 were used to coat foamed concrete F2 with a coating thickness of 3 mm. Foamed concrete without waterproof coating was used as a blank control. After 50 freeze-thaw cycles, the peeling depth and peeling area of ​​the foamed concrete coatings in different treatment groups were measured. The test results are detailed in Table 7.

[0056]

[0057] As shown in Table 7, after 50 freeze-thaw cycles, compared with the uncoated group, applying a waterproof coating to the surface of foamed concrete significantly reduced the surface peeling depth and area, indicating that applying a waterproof coating to the surface of foamed concrete can significantly reduce surface damage caused by freeze-thaw cycles. Compared with the coating material in the control group, the protective coating material of this invention exhibits significantly smaller surface peeling depth and area. This may be due to the overlapping effect of the flake shell powder in the coating, forming an effective physical barrier, and the multiple synergistic effects of the epoxy resin and styrene-butadiene emulsion interpenetrating network, which weakens the stress at the interface between the coating and the substrate, reducing brittle fracture of the interfacial bond, allowing the coating to adhere firmly to the substrate without large-area peeling. The coating in Example 4 exhibits even less peeling, possibly because a small amount of the small-molecule organic compound ethylenediamine is added at the end of the slurry preparation stage. This allows for stronger coordination with the rare earth ions loaded on the surface of the flake shell powder. Under external force, these coordination bonds break before the chemical bonds, effectively reducing stress damage.

[0058] Test Example 4: Salt Tolerance Test According to the "Standard for Durability Design of Concrete Structures" (GB / T50476-2019), the coating materials prepared in Examples 1, 4, and Comparative Examples 1-4 were applied to hydraulic concrete specimens. After stabilization, the specimens were immersed in a 3.5% NaCl solution for 0 days, 30 days, and 90 days. The coating condition was observed, and the compressive strength of the hydraulic concrete after immersion was measured. The results are shown in Table 8 below.

[0059]

[0060] As shown in Table 8, with the increase of soaking time, the compressive strength of the concrete specimens coated with the coatings in Examples 1 and 4 and Comparative Examples 1-4 all decreased to varying degrees. However, the decrease in compressive strength of the concrete specimens coated with the coatings in Examples 1 and 4 was smaller, and no obvious bubbles, mottled spots, or peeling appeared on the coating surface after soaking for 90 days. In contrast, the decrease in compressive strength of the concrete specimens coated with the coatings in Comparative Examples 1-4 was significantly larger, and all of them showed varying degrees of blistering and peeling.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A protective coating material for hydraulic foamed concrete, characterized in that: The raw materials include the following parts by weight: 30-40 parts epoxy resin, 10-20 parts cement, 5-12 parts water, 18-25 parts modified bainite-silica mixture, and 25-35 parts styrene-butadiene emulsion.

2. The protective coating material for hydraulic foamed concrete according to claim 1, characterized in that: The preparation method of the silica-silica mixture is as follows: (1) The shell powder is wet-milled to a particle size D50 of 5-25 μm and its diameter-to-thickness ratio is controlled to be >20. Then it is soaked in dilute acid for 5-15 min and dried to obtain flake shell powder. (2) Disperse the flake-shaped shell powder prepared in step (1) in an aqueous solution containing rare earth ions, stir and react at 60-80℃ for 2-4 hours, and then take it out and dry it; (3) The porous diatomaceous earth is mixed with the flake shell powder treated in step (2) to obtain a modified shell-silicon mixture.

3. The protective coating material for hydraulic foamed concrete according to claim 2, characterized in that: The dilute acid solution is a 0.1-0.5 mol / L hydrochloric acid or nitric acid solution.

4. The protective coating material for hydraulic foamed concrete according to claim 2, characterized in that: The shell powder has a particle size of 50-80 μm; the diatomaceous earth has a particle size of 30-45 μm.

5. The protective coating material for hydraulic foamed concrete according to claim 2, characterized in that: The aqueous solution containing rare earth ions is a 2%-4% (w / w) aqueous solution of lanthanum nitrate hexahydrate or cerium nitrate hexahydrate (III).

6. The protective coating material for hydraulic foamed concrete according to claim 1, characterized in that: The styrene-butadiene emulsion is a mixture of butadiene and styrene as the main components.

7. The protective coating material for hydraulic foamed concrete according to claim 1, characterized in that: The cement is ordinary Portland cement.

8. The hydraulic foam concrete protective coating material according to any one of claims 1-7, characterized in that: This coating material is applied to hydraulic foamed concrete.

9. The hydraulic foam concrete protective coating material according to any one of claims 1-7, characterized in that: Its preparation method includes the following steps: S1. Mix the modified bainite-silica mixture and cement evenly; S2. Disperse waterborne epoxy resin, water and one-third styrene-butadiene emulsion evenly to form a matrix liquid; S3. The modified bainite-silica mixture from step S1 and cement are gradually added to the matrix liquid and dispersed by high-speed shearing to form a uniform slurry; then the remaining styrene-butadiene emulsion is added and stirred at low speed until uniform to obtain the finished coating.

10. The hydraulic foam concrete protective coating material as described in claim 9, characterized in that: Step S3 also includes adding 0.01-0.03% of ethylenediamine by volume of the slurry at the end of the slurry preparation stage.

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