A composite coating for concrete structures and methods of use thereof

Abstract

This invention discloses a composite coating for concrete structures, comprising a sealing primer, an intermediate coat, and a topcoat. The sealing primer is a polyurea coating with modified concrete added, the amount of modified concrete being 3%–6% of the coating weight, and the thickness of the sealing primer being 20–100 μm. The intermediate coat is a polyurethane coating with steel powder added, the amount of steel powder being 3%–6% of the coating weight, and the thickness of the intermediate coat being 80–200 μm. The topcoat is an epoxy resin coating with molybdenum disulfide powder added, the amount of molybdenum disulfide powder being 1%–4% of the coating weight, and the thickness of the topcoat being 50–100 μm. The sealing primer of this composite coating fills concrete pores and cracks, improving structural density and providing a good foundation for subsequent coatings. The intermediate coat enhances overall strength and impact resistance, while the topcoat provides excellent anti-friction properties and chemical stability, blocking external erosion. The synergistic effect of these three components significantly extends the service life of concrete structures in harsh environments.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to a composite coating for concrete structures and its application method. Background Technology

[0002] Concrete, as a widely used basic material in construction engineering, directly affects the durability and safety of buildings due to its structural stability. However, in practical applications, concrete is highly susceptible to corrosion from various factors, leading to performance degradation and even structural damage. In industrial environments, the emission of acids and alkalis and the pervasive presence of chemical gases expose concrete structures to corrosive atmospheres for extended periods, accelerating the corrosion process. In humid environments, such as underground structures and hydraulic engineering projects, concrete is subject to erosion from groundwater and rainwater. Chemical substances in the water react with the concrete components, reducing its strength and causing cracking. In humid environments, salt and microorganisms can cause severe corrosion damage to concrete structures. Once concrete is corroded, the structural safety of a building is greatly threatened. Mild corrosion may cause the concrete surface to peel and powder, affecting the building's appearance and functionality; severe corrosion can weaken the load-bearing capacity of the concrete structure, leading to partial or even complete collapse of the building, causing huge economic losses and casualties. Furthermore, frequent repairs and maintenance of corroded concrete structures also increase costs significantly. Therefore, it is crucial to do a good job in concrete corrosion prevention, which can effectively extend the service life of buildings, protect people's lives and property, and reduce economic losses caused by concrete corrosion.

[0003] Since concrete structures are typically load-bearing, they inevitably deform and even develop micro-cracks under prolonged stress. This is especially true for large, curved concrete structures like cooling towers and chimneys, which are subject to deformation. This necessitates that the anti-corrosion coating applied to their surface possess a certain degree of elasticity. Polyurea coatings are commonly used as a sealing primer for concrete surfaces. Compared to polyurethane coatings, polyurea coatings are slightly less elastic and flexible. Under prolonged micro-deformation, polyurea coatings may crack more easily, leading to a significant decrease in the overall anti-corrosion effect. Furthermore, cracked concrete allows moisture to penetrate, accelerating alkali-aggregate reaction and causing irreparable structural damage to large concrete structures.

[0004] Therefore, existing coatings cannot meet the long-term waterproofing and corrosion protection requirements of large concrete structures. Summary of the Invention

[0005] To address the problems existing in current coatings for large-scale concrete, this invention provides a composite coating for concrete structures. This composite coating consists of a sealing primer, an intermediate coat, and a topcoat. The sealing primer is a polyurea coating with modified concrete added, the amount of modified concrete being 3%–6% of the coating weight, and the thickness of the sealing primer being 20–100 μm. The intermediate coat is a polyurethane coating with steel powder added, the amount of steel powder being 3%–6% of the coating weight, and the thickness of the intermediate coat being 80–200 μm. The topcoat is an epoxy resin coating with molybdenum disulfide powder added, the amount of molybdenum disulfide powder being 1%–4% of the coating weight, and the thickness of the topcoat being 50–100 μm.

[0006] In the composite coating of this invention, the functions and components of each layer play the following roles: The sealing primer, as the bottom layer of the composite coating, first comes into direct contact with the concrete structure surface. The added modified concrete enhances the affinity and adhesion between the sealing primer and the concrete surface, allowing the coating to adhere more tightly to the concrete. The polyurea coating itself possesses good chemical corrosion resistance and abrasion resistance, initially blocking external chemical substances and physical friction from eroding the concrete. The effective components in the modified concrete fill the tiny pores and cracks on the concrete surface, further improving the density of the concrete structure and reducing the intrusion channels of moisture and corrosive substances. Simultaneously, the 3%~6% modified concrete content ensures the coating's performance without affecting the original characteristics of the polyurea coating due to excessive dosage. The 20~100μm thickness provides a good foundation for subsequent coatings without being too thick, which would increase construction difficulty and cost. The addition of steel powder to the intermediate coat of polyurethane coating plays a crucial role in bridging the gap between the primer and the underlying concrete structure. Steel powder possesses strength and toughness, which, combined with the polyurethane coating, enhances the overall strength and impact resistance of the coating. When the concrete structure undergoes minor deformation, the intermediate coat with added steel powder can disperse stress, reducing damage to the coating caused by deformation and preventing cracks. Furthermore, steel powder can improve the conductivity of the coating to some extent, helping to eliminate potential static electricity buildup in environments where it may accumulate. The 3%–6% steel powder content ensures that the intermediate coat improves performance without affecting the flexibility and elasticity of the polyurethane coating. A thickness of 80–200 μm allows the intermediate coat to fully exert its reinforcing and buffering effects, protecting both the primer and the underlying concrete structure. The topcoat contains molybdenum disulfide powder with a particle size of 0.05~0.5μm, serving as the outermost layer of the composite coating, directly exposed to the external environment. Molybdenum disulfide powder possesses excellent lubricity and wear resistance, endowing the topcoat with superior anti-friction properties and reducing the likelihood of surface damage due to friction from external objects. Simultaneously, it exhibits certain chemical stability, enhancing the coating's resistance to chemical substances. Epoxy resin itself has good water resistance and weather resistance, effectively blocking rainwater, ultraviolet radiation, and other external factors from eroding the underlying coating and concrete structure. The optimized selection of 1%~4% molybdenum disulfide powder ensures that the topcoat maintains anti-friction and chemical stability without affecting the normal film-forming properties and adhesion of the epoxy resin coating. A thickness of 50~100μm provides a robust protective barrier for the entire composite coating, extending its service life. This three-layer composite coating design, with each layer working synergistically, overcomes the shortcomings of existing coatings, better meeting the long-term waterproofing and corrosion protection requirements of large concrete structures, and providing reliable protection for concrete structures.

[0007] Furthermore, the modified concrete is made by impregnating modified concrete powder with silane. After modification with silane, the compatibility between the concrete powder and organic matter is improved, facilitating dispersion. The resulting sealing primer exhibits stronger adhesion to the concrete structure, resulting in better waterproofing. Silane can react with the hydroxyl groups in concrete to form chemical bonds, allowing the modified concrete powder to firmly adhere to the concrete surface, further strengthening the bond between the sealing primer and the concrete. Simultaneously, silane possesses excellent hydrophobic properties, effectively preventing moisture penetration and significantly enhancing the waterproofing performance of the sealing primer.

[0008] Furthermore, the steel powder contains 70wt%~95wt% iron, 2wt%~8wt% manganese, 1wt%~5wt% chromium, 0.5wt%~3wt% silicon, 0.5wt%~0.8wt% phosphorus, 0.2wt%~0.5wt% carbon, and 0.1wt%~0.3wt% boron. A process of rapid cooling after melting yields highly uniform and fine steel powder with excellent strength and toughness. Iron is the main component, providing the basic strength of the steel powder; manganese improves the strength and hardness of the steel, enhancing its wear resistance; chromium increases the corrosion resistance of the steel; silicon helps improve the strength and elasticity of the steel; phosphorus and carbon improve the hardness and strength of the steel to some extent; and boron refines the grain size, improving the hardenability and toughness of the steel. Adding this specific proportion of steel powder to a polyurethane coating can significantly improve the coating's corrosion resistance and impact resistance.

[0009] Furthermore, different colored pigments are added to the sealing primer, intermediate coat, and topcoat, accounting for 0.5% to 1.5% of the coating weight. These pigments are selected from carbon black, titanium dioxide, iron oxide red, Prussian blue, or lead chromate. Adding different colored pigments to different paint layers allows for assessment of the degree of damage based on the exposed color when the coating is damaged. Moreover, the addition of pigments can improve the coating's weather resistance to some extent: carbon black has excellent UV absorption capabilities, effectively preventing coating aging due to UV radiation; titanium dioxide has high hiding power and whiteness, improving the coating's gloss and chalking resistance; iron oxide red, Prussian blue, and lead chromate each have their own characteristics, imparting different colors and properties to the coating.

[0010] Furthermore, the sealing primer is a two-component system (A and B) with a dosage ratio of 1:(0.9~1.15). Component A includes the following substances by weight: 50~100 parts of polyaspartic resin, 20~50 parts of organic solvent a, and 0.1~0.5 parts of anti-settling agent. Component B includes the following substances by weight: 30~80 parts of diisocyanate trimer, 10~40 parts of diisocyanate-terminated polypropylene glycol, and 5~20 parts of organic solvent b. Polyaspartic resin is the main film-forming substance of third-generation polyurea, possessing advantages such as moderate reactivity, good flexibility, and strong weather resistance. Diisocyanate trimer is an important curing agent, which can chemically react with the polyaspartic resin in component A to cure the coating into a film. The isocyanate groups at both ends of the diisocyanate-terminated polypropylene glycol can participate in the reaction, introducing flexible polypropylene glycol chains into the polyurea macromolecule. By controlling the appropriate dosage, the elasticity of the coating can be increased without reducing other mechanical properties. This A / B two-component sealing primer design, when used, involves mixing components A and B in a 1:(0.9~1.15) ratio, which allows for rapid reaction and curing, forming a tightly adhered sealing coating on the concrete surface.

[0011] Specifically, in the raw materials of the polyurea coating, the polyaspartic resin is an F-series or C-series polyaspartic ester resin, the diisocyanate trimer is selected from one or more combinations of TDI trimer, HDI trimer or IPDI trimer, and the anti-settling agent is organic bentonite or polyamide wax.

[0012] Furthermore, the polyurethane coating of the intermediate coat comprises the following components by weight: 60-100 parts diisocyanate, 70-120 parts polyol, 20-40 parts blocked isocyanate, 10-20 parts organic solvent C, and 0.5-2 parts catalyst. The diisocyanate is one of HDI, MDI, IPDI, TDI, or ADI; the polyol is a polyester polyol or polyether polyol; and the catalyst is an organotin catalyst or an organobismuth catalyst. It is worth noting that the blocked isocyanate added to the intermediate coat acts as a latent curing agent. It is relatively stable at room temperature, but upon high-temperature heating, the blocked groups dissociate, releasing isocyanate groups to continue participating in the reaction, thereby achieving secondary curing of the coating and further improving its performance.

[0013] Furthermore, the epoxy resin coating of the topcoat comprises the following components by weight: 50-70 parts epoxy resin, 20-40 parts curing agent, 0-20 parts organic solvent, 5-10 parts dispersant, and 1-2 parts defoamer. The curing agent is one or a combination of ethylenediamine, p-phenylenediamine, DETDA, or MDTDA; the dispersant is BYK dispersant or polyamide dispersant; and the defoamer is an organosilicone compound or a non-silicone defoamer. Epoxy resin, as a topcoat, enhances the coating's wear resistance and impact resistance, and also exhibits good adhesion to the polyurethane coating in the intermediate coat, ensuring the integrity of the composite coating. The curing agent induces a cross-linking reaction in the epoxy resin, forming a three-dimensional network structure, thereby giving the topcoat better hardness and strength. The dispersant ensures uniform dispersion of molybdenum disulfide powder and other components in the coating, preventing agglomeration and ensuring the stability of the coating's performance. The defoamer eliminates bubbles generated during coating preparation and application, preventing bubbles from affecting the coating's appearance and performance.

[0014] The composite coating used in this invention for concrete structures is an oil-based coating. Because of the addition of inorganic particulate matter and the inherent viscosity of the organic raw materials, the appropriate addition of organic solvents can significantly increase the mixing of the components and reduce the difficulty of construction. In the four separate mixing groups of the AB two-component primer, intermediate coat, and topcoat of this invention, substances such as toluene, butyl acetate, butanol, isopropanol, DMAc, EDGA, DMSO, and PGMEA are added. Provided there are no conflicts, the organic solvents in these separate mixing groups can be the same or different.

[0015] This invention provides a method for using the above-mentioned composite coating for concrete structures, as detailed below: 1) Clean the concrete surface with compressed air and weigh the components of each coating according to their weight. 2) The A and B components of the sealing primer are sprayed onto the concrete surface to the required thickness using a spraying process, and then quickly solidified and formed. 3) Mix all components of the intermediate paint evenly and spray it evenly on the sealing primer in two layers. After the first layer of paint film is dry to the touch, roll it with a hot roller at 60℃~90℃ to set it. Then roll it with a hot roller at 120℃~150℃. Then spray the second layer of paint film to the required thickness. After it is dry to the touch, roll it with a hot roller at 60℃~90℃ to set it. 4) After mixing the components of the topcoat, spray it onto the intermediate coat according to the required thickness. After roller pressing at 40℃~70℃, continue hot roller pressing at 120℃~150℃.

[0016] In step 1), cleaning the concrete surface is necessary, but it cannot be washed with water. This is because water will leave moisture on the concrete surface, which will affect the adhesion between the sealing primer and the concrete surface, resulting in poor adhesion of the entire composite coating. Blowing with compressed air can effectively remove dust, debris and other impurities from the concrete surface, providing a clean and smooth base for the subsequent coating.

[0017] In step 2), the spraying process allows the sealing primer to be evenly applied to the concrete surface and fill the pits and micro-cracks on the concrete surface, forming a penetrating, continuous, and complete coating. The interface between the coating and the concrete is curved and fits together, with a larger contact area than a pure flat surface. The polyurea coating can elastically deform with the micro-deformation of the concrete structure, thus playing a complete sealing role on the concrete surface.

[0018] In step 3), ensuring the uniform mixing of all components of the intermediate paint is crucial for its stable performance. Uneven mixing will lead to uneven distribution of components such as steel powder, affecting the strength and impact resistance of the intermediate paint. The intermediate paint is applied in two coats, and after each coat is surface dry, it is pressed with a hot roller for shaping. Hot roller pressing at 60℃~90℃ can initially shape the intermediate paint film, enhancing the adhesion between the paint film and the underlying sealing primer, while also making the paint film denser. Hot roller pressing at 120℃~150℃ can deseal the sealing isocyanates, releasing diisocyanate groups. These diisocyanate groups can not only react with polyols to cure the coating, but also react with hydroxyl groups on the surface of the sealing primer, further enhancing the adhesion strength between the intermediate paint and the sealing primer. This transforms the interlayer bonding from a simple physical bond to a dual effect of physical and chemical bonding. Similarly, after the epoxy resin coating is sprayed in step 4), under the pressure of hot rollers at 120~150℃, the diisocyanate groups released from the second coat of intermediate paint will also react with the hydroxyl groups in the epoxy resin coating, achieving the same interface effect as the sealing primer, thus making the overall integrity of the composite coating better.

[0019] Regarding the use of hot roller pressing for curing, since the composite coating of this invention is suitable for surface coating of large concrete structures, conventional thermosetting processes suffer from drawbacks such as low efficiency and construction difficulties. However, using hot roller pressing allows for repeated heating-cooling cycles, enabling the coating to fully react and crystallize, increasing density and uniformity. Furthermore, combined with the re-reaction of the blocked isocyanates in the intermediate coat after high-temperature desealing with the blocked primer and topcoat, hot roller pressing concentrates heat to fully deseale the blocked isocyanates. Simultaneously, the pressure of the roller pressing causes deformation of the initially shaped but not fully cured coating, increasing the contact probability of the released diisocyanate groups and hydroxyl groups, and enhancing the degree of interlayer chemical reaction. Therefore, hot roller pressing is the most suitable method in this invention.

[0020] The advantages of the composite coating of this invention for concrete structures are as follows: Firstly, from a structural design perspective, the three-layer composite coating has a clear division of labor and works in concert. The sealing primer fills the pores and cracks in the concrete, improving the structural density and providing a good foundation for subsequent coatings. The intermediate coat enhances the overall strength and impact resistance, disperses stress, and eliminates static electricity hazards. The topcoat provides excellent anti-friction properties and chemical stability, blocking external erosion. This progressive structural design forms a comprehensive, multi-layered protective system that can effectively resist the damage from various external factors such as moisture, corrosive substances, friction, and ultraviolet rays, significantly extending the service life of concrete structures and meeting the long-term waterproofing and anti-corrosion requirements of large concrete structures.

[0021] Secondly, in terms of material selection and proportioning, additives such as modified concrete, steel powder, and molybdenum disulfide powder can improve the various properties of the coating without affecting the original characteristics of the coating, ensuring flexibility, elasticity, film-forming properties, and adhesion. The addition of steel powder in specific proportions and pigments of different colors further enhances the adaptability and practicality of the coating, enabling it to perform better in the face of different environments and damage.

[0022] Thirdly, from the perspective of construction technology, the combination of spraying and hot roller pressing not only enables the coating to uniformly cover and fill pits and micro-cracks, forming a good sealing effect, but also enables the layers to achieve both physical bonding and chemical bonding, enhancing the interlayer bonding force and the overall integrity of the composite coating. In addition, the hot roller pressing curing process overcomes the drawbacks of conventional thermosetting processes, improves construction efficiency, ensures the density and uniformity of the coating, and makes the entire construction process more efficient and convenient. Detailed Implementation

[0023] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Example

[0024] A composite coating for concrete structures, comprising a sealing primer, an intermediate coat, and a topcoat; The sealing primer is a polyurea coating with KH550 impregnated modified concrete and carbon black added. The amount of modified concrete is 5% of the coating weight, and the amount of carbon black is 1% of the coating weight. The thickness of the sealing primer is 60μm. The polyurea coating consists of two components, A and B, with a ratio of 1:1.05. Component A includes the following substances by weight: 80 parts of F420 polyaspartic resin, 35 parts of butyl acetate, and 0.3 parts of organobentonite. Component B includes the following substances by weight: 55 parts of TDI trimer, 25 parts of poly(propylene glycol), toluene-2,4-diisocyanate end-capping, and 12 parts of butyl acetate. The intermediate paint is a polyurethane coating with added steel powder and titanium dioxide. The amount of steel powder is 5% of the coating weight, and the amount of titanium dioxide is 1% of the coating weight. The steel powder contains 89.4 wt% iron, 5 wt% manganese, 3 wt% chromium, 1.5 wt% silicon, 0.6 wt% phosphorus, 0.3 wt% carbon, and 0.2 wt% boron. The thickness of the intermediate paint is 150 μm. The polyurethane coating includes the following substances in parts by weight: 80 parts MDI, 100 parts polyethylene adipate, 30 parts WANNATEHTBL-275MS blocked isocyanate, 15 parts EDGA, and 1.2 parts T12 catalyst. The topcoat is an epoxy resin coating containing molybdenum disulfide powder with a particle size of 0.1 μm and Prussian blue. The amount of molybdenum disulfide powder is 2.5% of the coating weight, and the amount of Prussian blue is 1% of the coating weight. The thickness of the topcoat is 70 μm. The epoxy resin coating includes the following substances in parts by weight: 60 parts of bisphenol A type epoxy resin, 35 parts of p-phenylenediamine curing agent, 20 parts of DMSO, 8 parts of BYK161 dispersant, and 1.5 parts of organosilicone complex defoamer.

[0025] The method for applying the composite coating to concrete structures in this embodiment includes the following steps: 1) Clean the concrete surface with compressed air and weigh the components of each coating according to their weight. 2) The A and B components of the sealing primer are sprayed onto the concrete surface to the required thickness using a spraying process, and then quickly solidified and formed. 3) Mix all components of the intermediate paint evenly and spray it evenly on the sealing primer in two layers. After the first layer of paint film is dry to the touch, roll it with a hot roller at 70°C to set it. Then roll it with a hot roller at 140°C and spray the second layer of paint film to the required thickness. After it is dry to the touch, roll it with a hot roller at 75°C to set it. 4) After mixing the components of the topcoat, spray it onto the intermediate coat according to the required thickness. After roller pressing at 50°C, raise the temperature to 140°C and continue hot roller pressing. Example

[0026] A composite coating for concrete structures, comprising a sealing primer, an intermediate coat, and a topcoat; The sealing primer is a polyurea coating with KH560 impregnated modified concrete and carbon black added. The amount of modified concrete is 6% of the coating weight, and the amount of carbon black is 1.5% of the coating weight. The thickness of the sealing primer is 100μm. The polyurea coating consists of two components, A and B, with a ratio of 1:1.15. Component A includes the following substances in parts by weight: 100 parts of F520 polyaspartic acid resin, 20 parts of DMSO, and 0.5 parts of polyamide wax. Component B includes the following substances in parts by weight: 80 parts of IPDI trimer, 40 parts of poly(propylene glycol), hexamethylene-1,6-diisocyanate end-capping, and 20 parts of DMSO. The intermediate varnish is a polyurethane coating with added steel powder and iron oxide red. The amount of steel powder is 3% of the coating weight, and the amount of iron oxide red is 1.5% of the coating weight. The steel powder contains 82.4 wt% iron, 8 wt% manganese, 5 wt% chromium, 3 wt% silicon, 0.8 wt% phosphorus, 0.5 wt% carbon, and 0.3 wt% boron. The thickness of the intermediate varnish is 200 μm. The polyurethane coating includes the following substances in parts by weight: 100 parts HDI, 120 parts polyether glycol, 40 parts MR-310 blocked isocyanate, 20 parts butyl acetate, and 2 parts bismuth neodecanoate. The topcoat is an epoxy resin coating with added molybdenum disulfide powder with a particle size of 0.5μm and lead chromate. The amount of molybdenum disulfide powder is 4% of the coating weight, and the amount of lead chromate is 1.5% of the coating weight. The thickness of the topcoat is 100μm. The epoxy resin coating includes the following substances in parts by weight: 70 parts of bisphenol F type epoxy resin, 40 parts of p-phenylenediamine curing agent, 10 parts of BYK-2013 dispersant, and 2 parts of non-silicone defoamer.

[0027] The method for applying the composite coating to concrete structures in this embodiment includes the following steps: 1) Clean the concrete surface with compressed air and weigh the components of each coating according to their weight. 2) The A and B components of the sealing primer are sprayed onto the concrete surface to the required thickness using a spraying process, and then quickly solidified and formed. 3) Mix all components of the intermediate paint evenly and spray it evenly on the sealing primer in two layers. After the first layer of paint film is dry to the touch, roll it with a hot roller at 90°C to set it. Then roll it with a hot roller at 150°C and spray the second layer of paint film to the required thickness. After it is dry to the touch, roll it with a hot roller at 90°C to set it. 4) After mixing the components of the topcoat, spray it onto the intermediate coat according to the required thickness. After roller pressing at 70°C, raise the temperature to 150°C and continue hot roller pressing. Example

[0028] A composite coating for concrete structures, comprising a sealing primer, an intermediate coat, and a topcoat; The sealing primer is a polyurea coating with KH570 impregnated modified concrete and carbon black added. The amount of modified concrete is 3% of the coating weight, and the amount of carbon black is 0.5% of the coating weight. The thickness of the sealing primer is 20μm. The polyurea coating consists of two components, A and B, in a ratio of 1:0.9. Component A includes the following substances in parts by weight: 50 parts of C1420 polyaspartic acid resin, 25 parts of PGMEA, and 0.1 parts of organobentonite. Component B includes the following substances in parts by weight: 35 parts of HDI trimer, 10 parts of diphenylmethane-4,4'-diisocyanate end-capping, and 5 parts of PGMEA. The intermediate varnish is a polyurethane coating with added steel powder and Prussian blue. The amount of steel powder is 3% of the coating weight, and the amount of Prussian blue is 0.5% of the coating weight. The steel powder contains 95.7 wt% iron, 2 wt% manganese, 1 wt% chromium, 0.5 wt% silicon, 0.5 wt% phosphorus, 0.2 wt% carbon, and 0.1 wt% boron. The thickness of the intermediate varnish is 80 μm. The polyurethane coating includes the following substances in parts by weight: 60 parts TDI, 70 parts polycaprolactone polyol, 20 parts Desmodur BL3370 blocked isocyanate, 10 parts DMAc, and 0.5 parts T12 catalyst. The topcoat is an epoxy resin coating with added molybdenum disulfide powder and titanium dioxide with a particle size of 0.05μm. The amount of molybdenum disulfide powder is 1% of the coating weight, and the amount of titanium dioxide is 0.5% of the coating weight. The thickness of the topcoat is 50μm. The epoxy resin coating includes the following substances in parts by weight: 50 parts of epoxy resin H type, 20 parts of MDTDA curing agent, 10 parts of butyl acetate, 5 parts of BYK-110 dispersant, and 1 part of organosilicone complex defoamer.

[0029] The method for applying the composite coating to concrete structures in this embodiment includes the following steps: 1) Clean the concrete surface with compressed air and weigh the components of each coating according to their weight. 2) The A and B components of the sealing primer are sprayed onto the concrete surface to the required thickness using a spraying process, and then quickly solidified and formed. 3) Mix all components of the intermediate paint evenly and spray it evenly on the sealing primer in two layers. After the first layer of paint film is dry to the touch, roll it with a hot roller at 60°C to set it. Then roll it with a hot roller at 120°C and spray the second layer of paint film to the required thickness. After it is dry to the touch, roll it with a hot roller at 60°C to set it. 4) After mixing the components of the topcoat, spray it onto the intermediate coat according to the required thickness. After roller pressing at 40°C, raise the temperature to 120°C and continue hot roller pressing.

[0030] The composite coatings of Examples 1-3 were tested according to the items listed in Table 1. As can be seen from the data in Table 1, the composite coatings of the present invention exhibit excellent performance in key performance indicators such as adhesion, hardness, abrasion resistance, and corrosion resistance. In the adhesion test, the composite coatings of Examples 1-3 showed strong adhesion to the concrete surface, all reaching a high level. This is attributed to the good sealing and penetration effect of the sealing primer on the concrete surface, and the physical and chemical bonding between the subsequent coating and the primer achieved through hot roller pressing. Regarding hardness, the hardness of the coatings in each example meets the requirements of actual use. The steel powder and other components added to the intermediate paint effectively enhance the hardness and impact resistance of the coating. In the abrasion resistance test, the composite coatings exhibited excellent abrasion resistance characteristics. The molybdenum disulfide powder added to the topcoat played a key role, forming a lubricating film on the coating surface, reducing the coefficient of friction, and decreasing the degree of wear. The corrosion resistance test results were also very satisfactory. Regardless of whether in acidic, alkaline, or salt spray environments, the composite coatings provided effective protection for the concrete structure, preventing it from being corroded by chemical substances. This is mainly because the layers of the coating are tightly bonded together, forming a continuous and complete protective barrier that prevents the intrusion of corrosive media.

[0031] Table 1. Test results of composite coating properties in Examples 1-3 detection indicators Implementation Standards Example 1 Example 2 Example 3 Adhesion / MPa ISO 4624:2023 17.3 16.5 16.1 abrasion resistance JC / T 1015 0.11 0.14 0.12 Salt spray resistance / h GB / T1771~2007 6000 6000 6000 Non-volatile content / % GB / T 1725-2007 87 88 84 Impact resistance / cm HG / T 4566-2013 50 50 50 Bending test / mm GB / T 6742-2007 2 2 2 The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite coating for concrete structures, characterized in that, The composite coating consists of a sealing primer, an intermediate coat, and a topcoat. The sealing primer is a polyurea coating with added modified concrete, wherein the amount of modified concrete is 3% to 6% of the weight of the polyurea coating, and the thickness of the sealing primer is 20 to 100 μm. The intermediate paint is a polyurethane coating with added steel powder, wherein the amount of steel powder is 3% to 6% of the weight of the polyurethane coating, and the thickness of the intermediate paint is 80 to 200 μm. The topcoat is an epoxy resin coating with added molybdenum disulfide powder, wherein the amount of molybdenum disulfide powder is 1% to 4% of the weight of the epoxy resin coating, and the thickness of the topcoat is 50 to 100 μm.

2. The composite coating for concrete structures according to claim 1, characterized in that, The modified concrete is silane-impregnated modified concrete powder; the steel powder contains 70wt%~95wt% iron, 2wt%~8wt% manganese, 1wt%~5wt% chromium, 0.5wt%~3wt% silicon, 0.5wt%~0.8wt% phosphorus, 0.2wt%~0.5wt% carbon, and 0.1wt%~0.3wt% boron; the molybdenum disulfide powder has a particle size of 0.05~0.5μm; the sealing primer, intermediate coat, and topcoat contain pigments of different colors, accounting for 0.5%~1.5% of the coating weight, and the pigments are selected from carbon black, titanium dioxide, iron oxide red, Prussian blue, or lead chromate.

3. The composite coating for concrete structures according to claim 2, characterized in that, The sealing primer is a two-component system of A and B with a dosage ratio of 1:(0.9~1.15). Component A includes the following substances in parts by weight: 50~100 parts of polyaspartic acid resin, 20~50 parts of organic solvent a, and 0.1~0.5 parts of anti-settling agent. Component B includes the following substances in parts by weight: 30~80 parts of diisocyanate trimer, 10~40 parts of diisocyanate-terminated polypropylene glycol, and 5~20 parts of organic solvent b.

4. The composite coating for concrete structures according to claim 3, characterized in that, The polyaspartic acid resin is an F-series polyaspartic acid ester resin; the diisocyanate trimer is selected from one or more combinations of TDI trimer, HDI trimer, or IPDI trimer; the anti-settling agent is organic bentonite or polyamide wax.

5. The composite coating for concrete structures according to claim 3, characterized in that, The polyurethane coating comprises the following components by weight: 60-100 parts diisocyanate, 70-120 parts polyol, 20-40 parts blocked isocyanate, 10-20 parts organic solvent C, and 0.5-2 parts catalyst.

6. The composite coating for concrete structures according to claim 5, characterized in that, The diisocyanate is one of HDI, MDI, IPDI, TDI or ADI; the polyol is a polyester polyol or a polyether polyol; and the catalyst is an organotin catalyst or an organobismuth catalyst.

7. The composite coating for concrete structures according to claim 5, characterized in that, The epoxy resin coating comprises the following components in parts by weight: 50-70 parts epoxy resin, 20-40 parts curing agent, 0-20 parts organic solvent, 5-10 parts dispersant, and 1-2 parts defoamer.

8. The composite coating for concrete structures according to claim 7, characterized in that, The curing agent is one or a combination of ethylenediamine, p-phenylenediamine, DETDA, or MDTDA; the dispersant is a BYK dispersant or a polyamide dispersant; and the defoamer is an organosilicone complex or a non-silicone defoamer.

9. The composite coating for concrete structures according to any one of claims 3, 5, or 7, characterized in that, The organic solvents a, b, c, and d are independently selected from one or more combinations of toluene, butyl acetate, butanol, isopropanol, DMAc, EDGA, DMSO, and PGMEA.

10. A method of applying the composite coating for concrete structures as described in claim 9, characterized in that, Includes the following steps: 1) Clean the concrete surface with compressed air and weigh the components of each coating according to their weight. 2) The A and B components of the sealing primer are sprayed onto the concrete surface to the required thickness using a spraying process, and then quickly solidified and formed. 3) Mix all components of the intermediate paint evenly and spray it evenly on the sealing primer in two layers. After the first layer of paint film is dry to the touch, roll it with a hot roller at 60℃~90℃ to set it. Then roll it with a hot roller at 120℃~150℃. Then spray the second layer of paint film to the required thickness. After it is dry to the touch, roll it with a hot roller at 60℃~90℃ to set it. 4) After mixing the components of the topcoat, spray it onto the intermediate coat according to the required thickness. After roller pressing at 40℃~70℃, continue hot roller pressing at 120℃~150℃.