Cement-based aerogel heat preservation and heat insulation coating material for concrete and spraying construction technology of cement-based aerogel heat preservation and heat insulation coating material

Abstract

The invention discloses a cement-based aerogel heat preservation and heat insulation coating material for concrete and a spraying construction process of the cement-based aerogel heat preservation and heat insulation coating material, and belongs to the technical field of concrete materials. The coating material is prepared from powder, composite emulsion and water, and the powder is prepared by mixing superfine sand, cement, modified silicon dioxide-carbon nanotube composite aerogel powder, hollow glass beads, nanofibers, graphene nanosheets, an ultraviolet light absorber, a water reducing agent and a defoaming agent. The composite emulsion is composed of an acrylate copolymer emulsion, a polyvinyl acetate-ethylene emulsion, a temperature-sensitive polymer emulsion and a coalescing agent. Based on the multi-stage pore network and multi-component emulsion optimization design and multi-component synergistic effect, the material has good fluidity after being mixed, and has low heat conductivity coefficient, high strength and high toughness after being hardened; the construction technology of high-pressure water flushing and layered spraying is provided, and the method has the advantages of being efficient in construction, stable in quality and the like and can be applied to heat preservation and heat insulation of a concrete structure in a severe environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete materials, and relates to a cement-based aerogel thermal insulation coating material for concrete, and a high-efficiency spraying construction process adapted thereto. Background Art

[0002] Concrete, a common load-bearing and enclosure structure, is subject to complex temperature fluctuations. In particular, in harsh environments such as high temperatures and severe cold, the thermal insulation performance of concrete under repeated temperature drops and rises directly impacts the durability of the structure. Traditional insulation materials and construction techniques have numerous limitations in practical application. At the material level, although organic thermal insulation materials (such as styrene foam board, polyurethane foam, etc.) have certain thermal insulation properties, they have poor weather resistance and are prone to aging and powdering under long-term exposure to ultraviolet rays, with a short service life. At the same time, these materials are flammable and pose serious safety hazards; traditional paint-type thermal insulation coatings are mostly based on polyurethane, epoxy resin, polyimide, etc., which have limited thermal insulation effects and thermal conductivity coefficients usually between 0.1~0.3W / (m∙K). At the same time, due to the insufficient weather resistance of the base material, the coating is prone to powdering, cracking, peeling, etc. under the influence of environmental factors such as long-term ultraviolet radiation and rain erosion, resulting in a rapid decline in thermal insulation performance and a short service life; inorganic thermal insulation materials (such as expanded perlite insulation mortar, etc.) mainly rely on the porous structure of the aggregate to achieve thermal insulation. Although they have Although it has good durability, its thermal conductivity is still relatively high, generally ranging from 0.07 to 0.12 W / (m∙K). It is easy to absorb water during long-term use. Due to the high density of the material, delamination and cracking are prone to occur during construction, resulting in a significant decrease in thermal insulation performance. In addition, due to the weak bonding between lightweight aggregate and cementitious materials, the coating has poor impact resistance and is easily damaged by external mechanical action, affecting the thermal insulation effect and service life, and the maintenance cost is high. In existing relevant patents or literature, coating materials often focus on thermal insulation performance and ignore the balance between strength and elasticity. The compressive strength of insulation mortar is usually less than 15 MPa, which is easy to break in actual application. Organic thermal insulation coatings with good elasticity have problems such as low strength and poor high temperature resistance, which cannot meet the long-term use requirements of concrete structures. At the construction level, the construction process is complex and often requires professional construction personnel to operate; the traditional coating process is inefficient and cannot guarantee the uniformity and consistency of the coating; the base treatment technology is backward and cannot effectively solve the bonding problem between the coating and the concrete base (the interface bonding strength is generally less than 1.0MPa), which can easily lead to hollowing, cracking, and falling off of the coating.

[0003] As a new type of nanoporous material, aerogel has the advantages of being lightweight, resistant to high temperatures (can withstand temperatures above 600°C), and having good chemical stability due to its extremely low thermal conductivity (0.02~0.04W / (m∙K)) and high porosity. It shows great potential in the field of thermal insulation and has been used in aerospace, pipeline insulation and other fields. However, the application of aerogel in cement-based systems has fundamental defects: first, aerogel has extremely high specific surface area and surface energy, and is extremely easy to agglomerate in cement-based slurry, resulting in uneven dispersion and inability to fully exert its thermal insulation performance; second, aerogel has poor interfacial compatibility with cement-based interfaces and weak interfacial adhesion. Under the influence of external factors such as dry-wet cycles and temperature changes, it is prone to stratification and shedding, resulting in a decline in the overall performance of the coating; the loose and porous structure of the aerogel itself leads to poor mechanical properties of the coating (compressive strength is usually less than <0.5MPa), which is prone to cracks under construction or environmental stress, reducing thermal insulation performance and service life; the weather resistance is poor, and long-term exposure to humid or ultraviolet environments will significantly reduce the thermal insulation performance; in addition, problems such as complex construction technology and poor coating stability also limit the large-scale application of aerogel coating materials.

[0004] Chinese patent publication number CN104437279A discloses a doped carbon nanotube aerogel, its preparation method, and applications. The method involves mixing an aqueous dispersion of oxidized carbon nanotubes with a accelerator and subjecting it to a hydrothermal reaction to produce a carbon nanotube hydrogel. The doped carbon nanotube aerogel is then subjected to supercritical / freeze drying and high-temperature carbonization. The aerogel exhibits high specific surface area, high electrical conductivity, strong adsorption capacity for dyes and organic solvents, and excellent catalytic performance in oxygen reduction reactions. It has potential applications in fuel cell catalysts, supercapacitors, and organic pollutant treatment. However, no description of its thermal insulation properties is available.

[0005] Chinese patent publication number CN105688815A discloses a method for preparing multi-walled carbon nanotube-silica composite aerogel. During the aerogel preparation process, this invention adds multi-walled carbon nanotubes carboxylated with sulfuric acid and nitric acid. Then, under ultrasound, acidic and alkaline catalysts are used to induce reactions to prepare an aerogel "precursor." The composite aerogel is then soaked in various surface modifiers, frozen, and dried to produce the oil-absorbing material. This method leverages the carbon nanotubes' high adsorption capacity for oil phases and the aerogel's hydrophobic affinity for oil. The preparation process is complex, and no thermal conductivity test results have been obtained. The dispersibility, interfacial bonding strength, and thermal insulation performance of the aerogel in cement-based coating materials are unknown.

[0006] Chinese patent publication number CN114368741A discloses a method for preparing a graphene / carbon nanotube / silica aerogel material. This invention involves mixing graphene oxide, carbon nanotubes, water glass, silica gel, polydopamine, and urea, heating and drying them, and then performing spark plasma sintering to produce the graphene / carbon nanotube / silica aerogel material. The aerogel exhibits a thermal conductivity of 0.01–0.02 W / (m∙K) at room temperature and can withstand temperatures exceeding 500°C. However, the material is sintered using spark plasma sintering under nitrogen as a protective gas, resulting in a complex process. While the aerogel material itself has a low thermal conductivity, its effectiveness in cement-based coatings is unknown, and no surface modification, such as surface hydrophobicity enhancement or mechanical property enhancement, has been performed.

[0007] The Chinese patent with publication number CN117946554A discloses a composite aerogel thermal insulation coating and its preparation method. The invention uses a coupling agent to modify the hydrophobic aerogel particles to form an "aerogel particle-coupling agent-aqueous emulsion" bonding layer, thereby improving the compatibility between the aerogel particles and the aqueous emulsion, and by combining hollow glass microspheres of different particle sizes and using mechanical rapid dispersion, the aggregation between the aerogel particles is broken, and the hollow glass microspheres replace the interface between the aerogel particles to eliminate the problem of cracking of the thermal insulation coating caused by excessive use of aerogel particles. However, in this invention, titanium dioxide, barium sulfate, mica powder, etc. are only used as auxiliary fillers, and there are no other gelling materials, so the strength of the coating is limited; the hydrophobic aerogel is not enhanced and modified; the focus is on the crack resistance and thermal insulation effect of the coating when it is applied to the outer surface of high-temperature facilities such as pipelines, but no thermal conductivity test results are found, and the interfacial bonding strength and thermal insulation effect acting on the concrete surface are unknown.

[0008] Chinese patent publication number CN119529642A discloses a process for preparing a nanoporous aerogel thermal insulation coating. By coating the surface of silica aerogel with boron oxide, the structural stability of the silica aerogel is increased to prevent structural collapse of the silica aerogel during application. At the same time, the low thermal conductivity of boron oxide is utilized to improve the thermal insulation and mechanical properties of the aerogel thermal insulation coating. However, the silica aerogel preparation process in this invention is complex, and only the preparation method is described. There is no data to support the bonding performance and thermal insulation effect of the coating sprayed on the concrete surface, and the effect is unknown. In addition, the components do not contain cement or other cementitious materials, so the coating strength will not be high.

[0009] Chinese patent publication number CN116218274A discloses an aerogel thermal insulation putty paste and its preparation method. The putty paste is prepared using a high-density aerogel paste, filler, and emulsion. A high-Tg emulsion is used to enhance the mechanical strength of the putty paste. Different emulsions are compounded to coordinate the putty paste's flexibility, preventing cracking or powdering after curing. It is primarily used for building exterior wall insulation. Nano-calcium carbonate modification and optimized adhesion promoters are used to ensure smooth application and ease of construction. However, the thermal conductivity of the putty paste in this invention is still relatively high, at 0.03-0.07 W / (m∙K). The interfacial bonding strength is only 0.5-0.9 MPa, dropping to 0.15-0.5 MPa after immersion in water. The material's adhesion, thermal insulation properties, and durability are limited. Strength is achieved solely through emulsion bonding, resulting in low mechanical properties. Furthermore, because the finished material is a viscous paste, it can only be applied by manual scraping, which is inefficient.

[0010] The Chinese patent publication number CN115611288A discloses a closed silica aerogel microsphere and a thermal insulation coating containing the same. The use of polymer wall materials to coat and modify hydrophobic SiO2 aerogel particles facilitates the preparation of thermal insulation coatings using closed silica aerogel microspheres as a skeleton support material, thereby resolving the problem of pore collapse caused by the secondary drying process of the coating. However, the silica aerogel itself is not enhanced and modified in this invention, and its strength is only achieved through bonding with a resin emulsion, resulting in limited mechanical properties of the coating. The preparation process is complex, requiring precise control of pH, temperature, and surfactant dosage. Some raw materials, such as wall material raw materials, are tetraethoxysilane or toluene diisocyanate, which are expensive and toxic. In addition, the material can only be applied by manual scraping, which is inefficient.

[0011] Chinese patent publication number CN107858050A discloses a SiO2 aerogel thermal insulation coating. Dimethylhydroxy silicone oil is used to improve the wettability and dispersibility of the SiO2 aerogel in the coating, and hollow glass microspheres coated with titanium dioxide are introduced to synergistically enhance thermal insulation. However, the SiO2 aerogel in this invention undergoes no surface modification and is poorly compatible with the acrylic emulsion used as the base paint. Strength is achieved solely through the reaction between the base paint and the curing agent, without the presence of a cementitious material such as cement, resulting in limited mechanical properties. The thermal conductivity is still relatively high at 0.03-0.04 W / (m∙K), limiting its thermal insulation effectiveness. Furthermore, the coating's interfacial adhesion, durability, and application efficiency are unknown.

[0012] Chinese patent publication number CN113292894A discloses an aerogel coating and an aerogel coating derived from the aerogel coating. The aerogel coating is prepared by preparing SiC-SiO2 composite aerogel, modifying it with polyacrylic acid, and then compounding it with a film-forming emulsion, titanium dioxide nanoparticles, and hollow glass microspheres. The coating is then directly applied to a substrate and cured. However, this invention relies solely on the emulsion reaction to develop strength, resulting in limited mechanical properties. Only thermal insulation testing has been conducted, and its thermal conductivity, interfacial adhesion, and durability are unknown.

[0013] Chinese patent publication number CN114702867A discloses an aerogel thermal insulation decorative water-based coating and its preparation method. The coating consists of a multi-colored aerogel coating dispersed phase, a granulation liquid, and a transparent aerogel coating continuous phase. The dispersed phase provides decorative properties and basic thermal insulation, the granulation liquid stabilizes the dispersed phase morphology, and the continuous phase achieves transparent thermal insulation. This overcomes the single-function problem of traditional coatings, achieving a "multifunctional coating with a single application." It is primarily used for home decoration. However, the invention uses a variety of hydrophobic aerogels, including SiO2 aerogel, TiO2 aerogel, SiO2-TiO2 composite aerogel, Al2O3 aerogel, and ZrO2 aerogel, resulting in a complex composition and no hydrophobic surface modification. In actual use, the material preparation process is highly complex, requiring only manual scraping, resulting in low application efficiency. The interfacial bonding strength of the embodiments is low, only 0.6-0.8 MPa, and the lack of cement or other cementitious materials results in limited mechanical properties. Furthermore, the long-term stability of the coating has not been clearly verified, and its durability under long-term exposure to extreme environments such as humidity, heat, and ultraviolet light is unknown.

[0014] Chinese patent publication number CN115029035A discloses an ultra-high-performance aerogel composite thermal insulation coating and its preparation method. The coating consists of a primer, a heat-blocking and insulating midcoat, and a heat-reflecting and heat-emitting topcoat. Through layered functional integration, it achieves a triple insulation mechanism: heat blocking, heat reflection, and heat radiation. The midcoat utilizes silica aerogel and hollow glass microspheres for synergistic effect. However, the thermal conductivity of the coating in this invention is still relatively high, at 0.04-0.05 W / (m∙K), resulting in limited insulation effectiveness. In actual use, the coating requires two coats: surface cleaning, primer spraying, midcoat scraping, and topcoat spraying. This process is complex and inefficient, and the midcoat thickness must be greater than 20 mm. Thicker coatings can increase the weight of the building structure, increasing construction difficulty, construction time, and material costs. Strength is achieved solely through emulsion reaction, resulting in limited mechanical properties. Furthermore, the coating's interfacial adhesion and durability are unknown.

[0015] Chinese patent publication number CN117105614A discloses a low-thermal-conductivity aerogel slurry-modified coral sand concrete and its preparation method. By adding aerogel slurry to coral sand concrete, a composite insulation layer is formed by combining the ultra-low thermal conductivity of the aerogel with the porous structure of the coral sand. This approach addresses the poor thermal insulation performance of conventional coral sand concrete while maintaining the mechanical properties of the concrete. However, the thermal conductivity of the material in this invention is 0.05-0.6 W / (m∙K), resulting in limited insulation. The addition of aerogel slurry significantly reduces the density of the concrete, leading to a decrease in mechanical properties. In actual use, a 50mm insulation layer is required, which is difficult, time-consuming, and expensive. Furthermore, the coating's interfacial adhesion and durability are unknown, particularly regarding its insulation and aging resistance in long-term high-temperature and high-humidity environments.

[0016] Chinese patent publication number CN108610815A discloses a silica aerogel composite thermal insulation coating and its preparation method. The composite thermal insulation coating is prepared by using raw materials including silica aerogel, titanium dioxide, hollow glass microspheres, and far-infrared ceramic powder in specific proportions, and has the characteristics of barrier, reflection, and radiation. However, the thermal conductivity coefficient in the embodiment of the invention is as low as 0.08W / (m∙K), which is relatively high, and the thermal insulation effect is limited; the amount of functional components is strictly controlled, and the coating will crack if the aerogel exceeds 8wt%, and will agglomerate if the titanium dioxide exceeds 12wt% and the hollow glass microspheres exceed 10wt%, resulting in poor crack resistance and performance stability of the coating; in addition, the coating interface adhesion, mechanical properties, and anti-aging properties are unknown.

[0017] Chinese patent publication number CN120138989A discloses a carbon nanotube-aerogel-aluminum silicate superhydrophobic anti-icing material and its preparation method. Carbon nanotubes and aerogel particles are mixed to form microagglomerates, producing micro-nano composite particles with multi-level roughness. Leveraging the excellent photothermal effect of the carbon nanotubes and the excellent hydrophobicity of the aerogel particles, the composite particles are coated on the surface of an aluminum silicate fiber substrate with epoxy resin. This provides moisture-proofing, heat insulation, and photothermal deicing in high-humidity environments. However, the micro-nano composite particles have not been incorporated into cement-based materials, and their thermal insulation effect is unknown.

[0018] Chinese patent publication number CN115433730A discloses a stabilizer, a temperature-sensitive Pickering emulsion, a preparation method, and applications based on self-assembled micelles of natural macromolecules. The micelles are formed by electrostatic interactions between cationic natural macromolecules chitosan and anionic natural macromolecules. Lipase is then loaded into the hydrophobic microdomains within the micelles. A phase change material is then used as the oil phase to prepare a temperature-sensitive Pickering emulsion under high-speed homogenization. This emulsion can be used in biocatalysis, but there is no description of its performance-modulating effect on cement-based coating materials under temperature rise and fall conditions.

[0019] Chinese patent publication number CN103965421A discloses a method for preparing a thermosensitive amphiphilic block copolymer with a core-shell structure. An emulsifier, a thermosensitive hydrophilic monomer, and water are first mixed to obtain an aqueous solution of the emulsifier. A vinyl hydrophobic comonomer, a cosolvent, and an oil-soluble crosslinking monomer are then mixed and added to the aqueous solution to disperse evenly to obtain a miniemulsion. A water-soluble initiator is then added under an inert atmosphere, and polymerization is initiated at a specific temperature to obtain a product. The prepared copolymer has good stability and significant temperature sensitivity, and is widely used in controlling the loading and release of substances such as catalysts, drugs, and proteins. However, there is no description of its performance-regulating effect on coating materials.

[0020] Chinese patent publication number CN116606407A discloses a temperature-sensitive emulsifier, its preparation method, and its use in self-demulsification during emulsion polymerization. This temperature-sensitive emulsifier comprises a hydrophilic component, polyethylene glycol, and a temperature-sensitive component, poly(N-isopropylacrylamide), covalently linked. It can be used to prepare polymers during emulsion polymerization. It acts as an emulsifier at relatively high temperatures but can break emulsions at relatively low temperatures, facilitating self-demulsification during emulsion polymerization. The composition of this emulsifier is completely different from that of the present invention, and there is no description of phase transitions in the emulsion under temperature changes.

[0021] In summary, traditional concrete thermal insulation materials have many problems: high thermal conductivity, poor thermal stability, suboptimal thermal insulation performance, susceptibility to aging, cracking, poor durability, short service life, and complex construction. While aerogel materials offer excellent thermal insulation performance, they still face challenges such as poor compatibility and adhesion with the substrate, and insufficient mechanical properties. Currently, there is little research on cement-based aerogel thermal insulation coatings. To effectively address these issues, it is urgent to develop a high-performance cement-based aerogel thermal insulation coating suitable for concrete and propose an efficient spraying construction process. This will provide a technical reference for the thermal insulation of concrete structures in harsh environments, help ensure project safety, reduce operating and maintenance costs, and extend the service life of the project, with significant economic and social benefits. Summary of the Invention

[0022] Traditional concrete thermal insulation materials have problems such as high thermal conductivity, easy aging, and complex construction. Although aerogel materials have excellent thermal insulation properties, they still face challenges such as difficulty in dispersion, weak bonding with the matrix, and insufficient mechanical properties. The present invention aims to develop a cement-based aerogel thermal insulation coating material for concrete with excellent thermal insulation properties, good strength and toughness, strong interface bonding and excellent hydrophobicity, and outstanding durability through innovative modification of aerogels, microscopic structural design of materials, and efficient process optimization. The material also proposes a spraying construction process to ensure stable coating quality and efficient construction. The present invention can be effectively applied to the thermal insulation of concrete structures, ensuring project safety, reducing operating and maintenance costs, and extending the service life of the project, with significant economic and social benefits.

[0023] The cement-based aerogel thermal insulation coating material for concrete and its spraying construction process described in the present invention include the following contents: The cement-based aerogel thermal insulation coating material of the present invention is prepared from three parts of materials: powder, composite emulsion and water, wherein the mass ratio of powder, composite emulsion and water is (65-80):(16-25):(4-10).

[0024] The composite emulsion consists of 5-15 parts of acrylic copolymer emulsion, 2-10 parts of polyvinyl acetate-ethylene emulsion, 0-10 parts of temperature-sensitive polymer emulsion and 0.3-1.0 parts of film-forming aid.

[0025] Preferably, the composite emulsion is composed of 5 to 15 parts of acrylic copolymer emulsion, 2 to 10 parts of polyvinyl acetate-ethylene emulsion, 1 to 10 parts of thermosensitive polymer emulsion, and 0.3 to 1.0 part of film-forming aid.

[0026] Preferably, the composite emulsion is composed of 6 to 12 parts of acrylic copolymer emulsion, 4 to 9 parts of polyvinyl acetate-ethylene emulsion, 2 to 6 parts of thermosensitive polymer emulsion, and 0.4 to 0.6 parts of film-forming aid.

[0027] Preferably, in the composite emulsion, the acrylic copolymer emulsion, the polyvinyl acetate-ethylene emulsion, and the thermosensitive polymer emulsion are mixed in a mass ratio of (2-3):(1-2):(0-2).

[0028] More preferably, the composite emulsion consists of 9 parts of acrylic copolymer emulsion, 6 parts of polyvinyl acetate-ethylene emulsion, 6 parts of thermosensitive polymer emulsion, and 0.6 parts of film-forming aid.

[0029] The temperature-sensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate.

[0030] The mass content of each substance in the thermosensitive polymer emulsion is: 55-70 parts of butyl acrylate, 0-15 parts of lauryl acrylate, 10-20 parts of methyl methacrylate, 5-10 parts of styrene, 0-5 parts of acrylonitrile, 0-5 parts of acrylic acid, and 0-5 parts of glycidyl methacrylate.

[0031] Preferably, the mass contents of each substance in the thermosensitive polymer emulsion are: 63 parts of butyl acrylate, 10 parts of lauryl acrylate, 10 parts of methyl methacrylate, 7.5 parts of styrene, 2.5 parts of acrylonitrile, 5 parts of acrylic acid, and 2 parts of glycidyl methacrylate.

[0032] The preparation method of the thermosensitive polymer emulsion comprises the following steps: accurately weighing 55-70 parts of butyl acrylate, 0-15 parts of lauryl acrylate, 10-20 parts of methyl methacrylate, 5-10 parts of styrene, 0-5 parts of acrylonitrile, 0-5 parts of acrylic acid, and 0-5 parts of glycidyl methacrylate, adding the mixture into a container and stirring the mixture thoroughly to form a monomer mixture; preparing a solution of 2-4 wt% of sodium lauryl sulfate and 1-2 wt% of polyoxyethylene octylphenol ether, heating the mixture to 50-55° C. under nitrogen protection, slowly adding the monomer mixture after the temperature stabilizes, and continuously stirring the mixture for 20-30 minutes to form a stable pre-emulsion; then heating the pre-emulsion to 70-75° C., slowly adding a 0.5 wt% potassium persulfate solution dropwise to initiate a polymerization reaction; cooling the mixture to room temperature after sufficient reaction, and adjusting the pH value of the solution to about 7 with aqueous ammonia to finally obtain the thermosensitive polymer emulsion.

[0033] Further preferably, 63 parts of butyl acrylate, 10 parts of lauryl acrylate, 10 parts of methyl methacrylate, 7.5 parts of styrene, 2.5 parts of acrylonitrile, 5 parts of acrylic acid, and 2 parts of glycidyl methacrylate are accurately weighed and added to a container and stirred thoroughly to form a monomer mixture; 3 wt% of sodium lauryl sulfate and 1 wt% of polyoxyethylene octylphenol ether solution are prepared, and the temperature is raised to 50 ° C. under nitrogen protection. After the temperature stabilizes, the monomer mixture is slowly added and stirred for 30 minutes to form a stable pre-emulsion; the pre-emulsion is then heated to 70 ° C., and 0.5 wt% of potassium persulfate solution is slowly added dropwise to initiate the polymerization reaction; after sufficient reaction, it is cooled to room temperature, and the pH value of the solution is adjusted to about 7 with ammonia water to finally obtain a thermosensitive polymer emulsion.

[0034] Preferably, the film-forming aid is one of lauryl alcohol ester, hexadecanol ester and polyethylene glycol ether.

[0035] The addition of a thermosensitive polymer emulsion to the composite emulsion of the present invention is one of the core technologies of "multi-emulsion microstructure optimization and intelligent response". The thermosensitive polymer emulsion regulates the pore structure and thermal resistance of the coating, achieving an intelligent response of the thermal insulation performance under temperature drop and temperature rise environments. For example, a phase transition occurs during the temperature drop process, making the internal pore structure of the coating more dense, significantly improving the thermal insulation performance of the coating in low-temperature environments. The present invention designs a multi-emulsion and utilizes the different characteristics of each emulsion to optimize the microstructure, synergistically improving the thermal insulation, waterproof and mechanical properties of the coating.

[0036] The powder is prepared by mixing 15-25 parts of ultrafine sand, 20-35 parts of ordinary Portland cement, 5-15 parts of modified silica-carbon nanotube composite aerogel powder, 5-10 parts of hollow glass microspheres, 0.5-2 parts of nanofibers, 0.2-1 parts of graphene nanosheets, 0.2-1 parts of ultraviolet absorbers, 0.2-2 parts of water reducers, and 0.1-0.5 parts of defoaming agents.

[0037] Preferably, the powder is mixed by 15-20 parts of ultrafine sand, 25-35 parts of cement, 10-15 parts of modified silica-carbon nanotube composite aerogel powder, 5-10 parts of hollow glass microspheres, 1-2 parts of nanofibers, 0.5 parts of graphene nanosheets, 0.5 parts of ultraviolet absorber, 0.5-1 parts of water reducer, and 0.1-0.3 parts of defoaming agent.

[0038] The fineness modulus of the ultra-fine sand is between 0.7 and 1.5, the main particle size range is 0.05 to 0.3 mm, and the apparent density is ≥ 2600 kg / m 3 , thermal conductivity ≤ 0.2W / (m∙K); The ordinary Portland cement is of early strength type and has a strength grade of ≥42.5R; Preferably, the ordinary Portland cement is P·O 52.5R cement; The hollow vitrified microspheres have a particle size range of 0.1-0.5 mm, a wall thickness of <10 μm, and a thermal conductivity of ≤0.05 W / (m∙K); The nanofiber is one of SiO2 nanofiber, carbon nanofiber, and cellulose nanofiber, with a diameter of 50-200 nm and a length of 5-20 μm; Preferably, the nanofibers are SiO2 nanofibers; The graphene nanosheets are single-layer structures with a purity of >95%; The ultraviolet absorber is one of nano-TiO2 and nano-ZnO; The water reducer is a polycarboxylic acid high performance water reducer or a melamine high efficiency water reducer, in powder form, with a water reduction rate of not less than 25%; The defoamer is one of an amino polyether defoamer and a polyether modified silicone defoamer, and is in powder form.

[0039] The silicon dioxide-carbon nanotube composite aerogel powder is prepared through the processes of silicon dioxide sol preparation, carbon nanotube acidification, compounding and amino modification, and supercritical drying.

[0040] Preferably, the steps are as follows: S1. Preparation of silica sol: ethyl orthosilicate, anhydrous ethanol, and deionized water were mixed in a molar ratio of 1:(2-4):(1-2), stirred evenly, and then ammonia was added to adjust the pH to 8-9. The mixture was stirred at 40-60°C for 2 h to obtain silica sol. S2. Acidification of carbon nanotubes: Add carbon nanotubes to a 3 wt% nitric acid solution and sonicate at a frequency of 20-40 kHz for 1 h for acidification. Then, wash with deionized water until neutral, dry, and add to the silica sol. S3, composite and amino modification: add 2wt% of γ-aminopropyltriethoxysilane and stir at 400-500 rpm for 1-2 hours to graft amino groups into the composite system to obtain a mixed sol; S4. Supercritical drying: The mixed sol is transferred to a high-pressure reactor and dried at a temperature of 50°C and a pressure of 10 MPa using carbon dioxide as a supercritical fluid. Finally, the mixed sol is crushed and ball-milled to obtain silica-carbon nanotube composite aerogel powder with a particle size range of 2 to 20 μm.

[0041] More preferably, ethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:2.

[0042] The modified silicon dioxide-carbon nanotube composite aerogel powder is obtained by subjecting the prepared silicon dioxide-carbon nanotube composite aerogel powder to a combined modification treatment with a cationic surfactant and a nonionic surfactant.

[0043] Preferably, the cationic surfactant used in the combined modification treatment is hexadecyltrimethylammonium bromide, and the nonionic surfactant is polyethylene glycol.

[0044] More preferably, a 10% ethanol solution with a volume fraction of anhydrous ethanol and deionized water is first prepared, stirred for 10 to 20 minutes, and then silica-carbon nanotube composite aerogel powder is added at a solid-liquid mass ratio of 1:5, and stirred at a speed of 400 to 500 r / min for 20 to 30 minutes, and ultrasonic treatment is performed at a power of 500 to 800 W and a frequency of 20 to 40 kHz to form a uniform suspension; then, hexadecyltrimethylammonium bromide and polyethylene glycol are added in sequence at a rate of 1 to 3% and 2 to 5% of the mass of the composite aerogel powder, and the reaction is carried out at a temperature of 60 to 80°C and a stirring speed of 300 to 400 r / min for 2 to 3 hours; finally, the modified silica-carbon nanotube composite aerogel powder is obtained by low-temperature drying at 40°C.

[0045] The usage ratio of cetyltrimethylammonium bromide and polyethylene glycol is 1:1.5 to 1:2.5.

[0046] The cement-based aerogel thermal insulation coating material for concrete of the present invention has the following properties: ① Excellent thermal insulation performance: The thermal conductivity coefficient can be as low as below 0.025 W / (m∙K), which is 65% to 95% lower than that of traditional thermal insulation coatings, effectively reducing heat transfer to concrete structures and buffering temperature changes (such as repeated temperature rise and fall) to which concrete structures are subjected. ② Good strength, toughness, and crack resistance: The coating has a compressive strength of ≥35 MPa and a tensile strength of ≥4.0 MPa, while also having good elastic deformation capacity and an elongation at break of ≥200%, effectively preventing the coating from cracking. ③ Super strong interfacial bonding and excellent hydrophobicity: The adhesion between the coating and the concrete base surface is ≥3.5 MPa, which is more than twice that of traditional thermal insulation materials. At the same time, after hardening and film formation, the surface is hydrophobic, with a contact angle of ≥150°. ④ Outstanding durability: The coating material has excellent weather resistance, with a performance retention rate of ≥90% after 1000 hours of ultraviolet light irradiation, and no delamination or shedding occurs under the influence of long-term dry and wet conditions and temperature changes.

[0047] The method for preparing the cement-based aerogel thermal insulation coating material for concrete according to the present invention comprises the following steps: S1. Prepare a thermosensitive polymer emulsion: add butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture; prepare 2-4 wt% sodium lauryl sulfate and 1-2 wt% polyoxyethylene octylphenol ether solution, heat to 50-55°C under nitrogen protection, slowly add the monomer mixture after the temperature stabilizes, and continue stirring for 20-30 minutes to form a stable pre-emulsion; then heat the pre-emulsion to 70-75°C, slowly add 0.5 wt% potassium persulfate solution dropwise to initiate polymerization; cool to room temperature after sufficient reaction, and adjust the pH value of the solution to about 7 with ammonia water to obtain a thermosensitive polymer emulsion; S2. Preparation of modified silica-carbon nanotube composite aerogel powder: TEOS, anhydrous ethanol and deionized water were mixed in a molar ratio of 1:(2~4):(1~2), stirred evenly, and then ammonia water was added to adjust the pH to 8~9, and the mixture was stirred at 40~60°C for 2h to obtain silica sol; the carbon nanotubes were then added to a 3wt% nitric acid solution, and subjected to ultrasonic treatment at a frequency of 20~40kHz for 1h for acidification, and then washed with deionized water until neutral, dried and added to the silica sol, and 2wt% of γ-aminopropyltriethoxysilane was added at the same time, and stirred at a speed of 400~500r / min for 1~2h to graft the amino group into the composite system to obtain a mixed sol; the mixed sol was then transferred to a high-pressure reactor, and carbon dioxide was used as a supercritical fluid, and the mixture was subjected to filtration at a temperature of 50°C and a pressure of 10MPa. drying; finally, crushing and ball milling to obtain silica-carbon nanotube composite aerogel powder with a particle size range of 2~20μm; preparing an ethanol solution with a volume fraction of 10% with anhydrous ethanol and deionized water, stirring for 10~20min, and then adding silica-carbon nanotube composite aerogel powder at a solid-liquid mass ratio of 1:5, stirring at a speed of 400~500r / min for 20~30min, and simultaneously using a power of 500~800W and a frequency of 20~40kHz for ultrasonic treatment to form a uniform suspension; then adding hexadecyltrimethylammonium bromide and polyethylene glycol in a ratio of 1~3% and 2~5% of the mass of the composite aerogel powder, respectively, and reacting at a temperature of 60~80℃ and a stirring speed of 300~400r / min for 2~3h; finally, drying at a low temperature of 40℃ to obtain modified silica-carbon nanotube composite aerogel powder; S3. Preparation of composite emulsion: weighing acrylic copolymer emulsion, polyvinyl acetate-ethylene emulsion, temperature-sensitive polymer emulsion, and film-forming aid in order by mass, mixing well and setting aside; S4. Weigh the powder materials (extra fine sand, ordinary Portland cement, modified silica-carbon nanotube composite aerogel powder, hollow glass microspheres, nanofibers, graphene nanosheets, ultraviolet absorber, water reducer, and defoaming agent) in order by mass, add them into a planetary mixer, and dry mix them at a speed of 150-200 r / min for 4-5 minutes; then add water, stir at a speed of 300-500 r / min for 3-4 minutes, and finally add the composite emulsion, stir at a speed of 600-800 r / min for 2-3 minutes to obtain the coating material.

[0048] In step S4 of the preparation method of the present invention, a "multi-stage dynamic mixing" process is adopted, which is divided into three stages with different rotation speeds and stirring times.

[0049] More preferably, a planetary mixer is used to dry-mix the powder at a speed of 150 r / min for 4 minutes; then water is added and stirred at a speed of 300 r / min for 3 minutes; finally, the composite emulsion is added and stirred at a speed of 800 r / min for 2 minutes.

[0050] The "multi-stage dynamic mixing" process can ensure that the modified composite aerogel powder is fully mixed with other components, so that the modified composite aerogel particles can be evenly dispersed in the cement-based slurry, giving full play to its excellent thermal insulation properties.

[0051] The spraying construction process of the cement-based aerogel thermal insulation coating material for concrete according to the present invention comprises the following steps: 1) Use a high-pressure water gun to rinse and a wire brush to clean, with a water pressure of 3~5MPa, to remove dust, oil, loose objects and other impurities on the surface of the concrete base. When the surface is moist and there is no visible water, spray 1~2 times with nano-silicon ion impregnation crystallization solution, with a spraying amount of 200~300g / m²; 2) Weighing powder materials (extra-fine sand, ordinary Portland cement, modified silica-carbon nanotube composite aerogel powder, hollow glass microspheres, nanofibers, graphene nanosheets, ultraviolet absorber, water reducer, and defoaming agent) in order by mass, adding them to a planetary mixer, and dry mixing them at a speed of 150-200 r / min for 4-5 minutes; then adding water, stirring at a speed of 300-500 r / min for 3-4 minutes, and finally adding the composite emulsion, stirring at a speed of 600-800 r / min for 2-3 minutes to obtain a coating material; 3) Use high-pressure airless spray equipment for coating construction, with a spraying pressure of 15-20 MPa, a distance of 50-80 cm between the nozzle and the base surface, a spraying angle of 40°-60°, a spraying width of 40-50 cm, and 2-3 layers of spraying. The thickness of each layer should be controlled at 1-2 mm. The interval between layers should be adjusted according to the ambient temperature and humidity, and should be controlled between 1-3 hours. 4) After the coating is applied, cover with plastic film for 1-2 days of moisturizing maintenance. The maintenance temperature should be controlled at 15-30°C and the relative humidity should be maintained at 60-80%. During the maintenance period, the coating should be protected from mechanical damage and rain erosion.

[0052] The cement-based aerogel thermal insulation coating material for concrete and its spraying construction process described in the present invention can be applied to the thermal insulation of concrete structures in harsh environments. Its innovation lies in: ① Innovative Aerogel Modification: Drawing on design principles from aerogel composites used in the aerospace industry, silica aerogel is combined with carbon nanotubes, resulting in an aerogel that combines the ultra-low thermal conductivity of silica aerogel with the high strength and toughness of carbon nanotubes. This not only enhances the mechanical strength of the aerogel but also optimizes the thermal insulation network, resulting in a 30%-40% increase in mechanical strength and a 20%-30% improvement in thermal insulation compared to traditional aerogels. Furthermore, the incorporation of carbon nanotubes and the grafting of amino groups during the aerogel powder preparation process enhance the chemical bond between the aerogel and the cementitious paste. To address the poor dispersion and adhesion of traditional aerogels in cementitious materials, a combination of cationic and nonionic surfactants is used for modification. Cetyltrimethylammonium bromide, which ionizes in aqueous solution to produce positively charged ions, attracts negatively charged groups generated during cement hydration, imparting a positive surface charge to the aerogel particles. This electrostatic repulsion prevents agglomeration of the aerogel particles. The long polyethylene glycol chains create steric hindrance around the aerogel particles, hindering their proximity. Through the synergistic effects of electrostatic repulsion, steric hindrance, chemical bonding, etc., not only the dispersibility of aerogel in cement-based slurry is improved, but also its compatibility with cement slurry and interfacial adhesion are enhanced, giving full play to the thermal insulation advantages of aerogel.

[0053] ② Multi-level synergistic thermal insulation network design: The nanoscale pores (pore diameter 1-100nm) of the composite aerogel powder, the micron-scale closed pores (pore diameter 0.1-1mm) of the hollow vitrified microspheres, and the submicron-scale pores (pore diameter 0.1-1μm) formed by ultrafine sand filling. The modified silica-carbon nanotube composite aerogel is evenly dispersed in the cement-based slurry and overlaps with the low-thermal-conductivity ultrafine sand and hollow vitrified microspheres to form a continuous and dense multi-level pore network. This structure blocks heat transfer layer by layer from the nanometer to the micrometer scale, significantly reducing the thermal conductivity of the coating by inhibiting gas convection and heat conduction, thereby achieving stable and efficient thermal insulation under temperature rise and fall. The composite aerogel powder has a porosity of 80% to 99%, requiring multiple reflections and scattering during heat transfer, increasing the heat transfer path length. Furthermore, gas molecules are virtually unable to move freely within the nanoscale pores, significantly inhibiting convective heat transfer. Its extremely low thermal conductivity (0.010-0.025 W / (m∙K)) effectively blocks heat transfer. The interfacial bonding between the modified silica-carbon nanotube composite aerogel particles and the cement matrix also significantly reduces interfacial thermal resistance. The enclosed pores within the hollow glass microspheres form independent, microscopic thermal insulation units, further blocking the heat conduction path. Nano-inorganic fibers, with their high thermal stability and low thermal conductivity, form a three-dimensional interwoven "nanoskeleton" within the coating, effectively restricting the movement of phonons (heat transfer vectors), forcing heat transfer through more interfacial reflections and scattering. From aerogel nanopores inhibiting convection and low thermal conductivity blocking heat transfer, to glass microbeads with tiny pores blocking heat transfer paths and nanofibers restricting phonon movement paths, various materials work together to build a three-dimensional thermal insulation network.

[0054] ③ Multi-emulsion microstructure optimization and intelligent response: After the three emulsions are compounded, during the coating drying process, the acrylic copolymer emulsion forms a continuous rigid polymer membrane skeleton, interspersed with the flexible chain segments of the polyvinyl acetate-ethylene emulsion, forming a polymer membrane with both rigidity and flexibility and a nanoscale cross-linked network, which effectively fills the cement-based pores. Thermosensitive polymer emulsion is a functional emulsion material that responds to temperature changes. It can undergo phase transitions in the temperature range of 15-45°C. By regulating the pore structure and thermal resistance of the coating, it achieves intelligent response of thermal insulation performance in temperature drop and temperature rise environments. For example, a phase transition during temperature drop makes the internal pore structure of the coating denser, significantly improving the thermal insulation performance of the coating in low-temperature environments. The different characteristics of each emulsion are utilized to optimize the microstructure and synergistically improve the thermal insulation, waterproofing, and mechanical properties of the coating.

[0055] ④ The coating combines both strength and toughness: In terms of strength, 42.5R and 52.5R cements, as the primary binders, form a large number of hydration products (such as CSH gel) through hydration reactions, firmly bonding aggregates such as ultrafine sand and hollow vitrified microspheres together and imparting foundational strength to the coating. Graphene nanoplatelets possess excellent mechanical properties. Their large flake structure acts as a reinforcement and bridging agent within the cement matrix. The high specific surface area and surface activity of the nanofibers allow them to tightly bond with cement hydration products through hydrogen bonding and van der Waals forces, acting as a "bridging" and "reinforcement" agent within the cement matrix. Together, the graphene nanoplatelets and nanofibers form a three-dimensional reinforcement network, significantly enhancing the coating's tensile strength and toughness. In terms of elasticity and crack resistance, the polyvinyl acetate-ethylene emulsion and thermosensitive polymer emulsion in the composite emulsion exhibit excellent flexibility, forming a continuous polymer film within the coating, imparting a certain degree of elastic deformation capability. The acrylic copolymer emulsion enhances the coating's adhesion and cohesion, enabling it to disperse stress through its own elastic deformation when subjected to external stresses (such as temperature changes and base layer deformation), thus preventing stress concentration and cracking. Furthermore, the flexible structure of the nano-inorganic fibers and graphene nanosheets not only effectively absorbs and disperses external stress, improving the coating's toughness, but also inhibits the initiation and propagation of cracks, further enhancing the coating's crack and impact resistance.

[0056] ⑤ Coating substrate adhesion and surface hydrophobicity are balanced: Regarding substrate adhesion, the nano-silicon ion-impregnated crystallization solution sprayed during base treatment penetrates into the concrete, reacting to form hydrated calcium silicate crystals that fill the pores and microcracks on the concrete surface, strengthening the concrete substrate. It also physically entangles and chemically bonds with the emulsion components in the coating, significantly enhancing the bond between the coating and the concrete substrate. Furthermore, the acrylic copolymer emulsion and polyvinyl acetate-ethylene emulsion in the coating material composite emulsion also exhibit good adhesion to the concrete substrate, penetrating into the micropores on the surface of the substrate and forming mechanical anchors after curing, further enhancing adhesion. Regarding surface hydrophobicity, during film formation, the hydrophobic groups in the emulsion's molecular structure accumulate on the coating surface. Simultaneously, the aerogel-modified γ-aminopropyltriethoxysilane partially migrates to the coating surface, imparting a hydrophobic property to the coating surface. This not only effectively prevents water from penetrating the coating, but also reduces the adhesion of external contaminants to the coating surface, improving the coating's durability and self-cleaning ability.

[0057] ⑥ Efficient and Optimized Construction Process: During coating material preparation, a "multi-stage dynamic mixing" process is employed to ensure thorough mixing of the modified silica-carbon nanotube composite aerogel powder with other components. This allows the modified silica-carbon nanotube composite aerogel particles to be evenly dispersed in the cement-based slurry, fully leveraging their excellent thermal insulation properties. During base layer preparation, a "high-pressure water jet flushing + wire brush cleaning" process is employed. In addition to conventional cleaning and repair, a nano-silicon ion-permeable crystallization solution is sprayed. This solution penetrates the concrete and reacts to form calcium silicate hydrate crystals, filling pores and microcracks in the concrete surface and strengthening the concrete base. During coating application, a high-pressure, airless, layered spraying process is employed, increasing construction efficiency by 5-30 times compared to traditional troweling. Precise control of process parameters such as spray pressure, distance, spray angle, width, and interval time ensures coating uniformity and consistency, ensuring consistent quality.

[0058] Compared with the prior art, the present invention has the following beneficial effects: ① Aerogel has high dispersibility and strong interfacial adhesion: After carbon nanotube composite, amino grafting, cationic surfactant and non-ionic surfactant joint modification, not only the mechanical strength of aerogel is improved by 30%~40%, and it can be evenly dispersed in cement-based slurry, but also the interfacial adhesion between aerogel and cement-based slurry is significantly enhanced, and problems such as agglomeration and debonding are not prone to occur.

[0059] ② The coating has excellent thermal insulation performance: Based on the synergistic effect of the thermal resistance characteristics of multiple materials and the multi-level pore network structure, a "three-dimensional thermal insulation network" is constructed. Tests have shown that the thermal conductivity of the coating material of the present invention can be as low as 0.025W / (m∙K), which is 65% to 95% lower than that of traditional thermal insulation coatings. It can effectively reduce heat transfer to concrete structures, buffer the temperature changes of concrete structures (such as repeated temperature rise and fall), and improve the durability of concrete structures.

[0060] ③ The coating material has good strength, toughness and crack resistance: Nanofibers and graphene nanosheets are added to the material, and multi-emulsion is compounded to make the coating have high strength, the coating compressive strength ≥35MPa, and the tensile strength ≥4.0MPa. At the same time, it has good elastic deformation ability and elongation at break ≥200%, which can effectively prevent the coating from cracking and has a long service life.

[0061] ④ The coating has both super strong adhesion and excellent hydrophobic properties: through base surface repair and enhancement treatment, composite emulsion penetration and anchoring, etc., the adhesion between the coating and the concrete base surface is ≥3.5MPa, which is more than 2 times higher than that of traditional thermal insulation materials; at the same time, after the coating hardens and forms a film, the surface is hydrophobic, with a contact angle of ≥150°, which can effectively prevent the intrusion of moisture and pollutants and improve the durability of the coating.

[0062] ⑤ Outstanding durability of coating materials: Based on the material reinforcement and film-forming hydrophobic effect, the coating material has excellent weather resistance, and the performance retention rate after 1000 hours of UV lamp irradiation is ≥90%; under the influence of long-term dryness, wetness and temperature changes, there is no delamination or falling off; due to the incorporation of ultraviolet absorbers, the coating also has certain anti-UV aging properties.

[0063] ⑥ Stable efficiency of coating construction: The "multi-stage dynamic mixing" process is adopted to fully mix multiple components. The obtained coating material has low viscosity and good fluidity, which is suitable for high-pressure airless layered spraying construction technology. It has the advantages of high construction efficiency and low cost. Compared with the traditional manual coating process, the construction efficiency can be increased by 5 to 30 times, and the coating has good uniformity and stable quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Preparation of test specimens for coating material performance tests: (a) compressive strength specimen, (b) tensile strength specimen, and (c) substrate bonding strength specimen. Figure 2 Bonding performance test between cement-based aerogel thermal insulation coating material and base layer, (a) bond strength test, (b) failure mode (3d, 28d), (c) coating bond strength, (d) coating-mortar bond morphology (200×); Figure 3 Mixing and fluidity state of cement-based aerogel thermal insulation coating materials; Figure 4 On-site demonstration application of cement-based aerogel thermal insulation coating, (a) high-pressure airless sprayer, (b) spraying penetrating crystallization solution, (c) spraying thermal insulation coating material, (d) coating surface state after curing and hardening; Figure 5 It is a commercially available aerogel coating product (viscous paste). DETAILED DESCRIPTION

[0065] In order to more clearly describe the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. This embodiment is only used to better explain the content of the present invention, but does not limit the present invention. All similar embodiments listed based on the present invention should fall within the scope of protection of the present invention.

[0066] The raw materials described in the present invention can all be obtained through public channels.

[0067] The silica-carbon nanotube composite aerogel powder is prepared through the following processes: silica sol preparation, carbon nanotube acidification, compounding and amino modification, and supercritical drying. The specific process of each step is as follows: S1. Preparation of silica sol: Tetraethyl orthosilicate, anhydrous ethanol, and deionized water were mixed in a molar ratio of 1:4:2, stirred evenly, and then ammonia was added to adjust the pH to 8-9. The mixture was stirred at 50°C for 2 hours to obtain silica sol. S2, carbon nanotube acidification: carbon nanotubes were added to a 3 wt% nitric acid solution and sonicated at 30 kHz for 1 h for acidification, then washed with deionized water until neutral, dried, and added to the silica sol; S3, composite and amino modification: add 2wt% of γ-aminopropyltriethoxysilane and stir at 400-500 rpm for 1-2 hours to graft amino groups into the composite system to obtain a mixed sol; S4. Supercritical drying: The mixed sol is transferred to a high-pressure reactor and dried at a temperature of 50°C and a pressure of 10 MPa using carbon dioxide as a supercritical fluid. Finally, the mixed sol is crushed and ball-milled to obtain silica-carbon nanotube composite aerogel powder with a particle size range of 2 to 20 μm.

[0068] The coating material preparation method is as follows: S1. Weigh the acrylic copolymer emulsion, polyvinyl acetate-ethylene emulsion, temperature-sensitive polymer emulsion, and film-forming aid in order by mass, mix them evenly, and set aside; S2. Weigh the powder materials (extra fine sand, ordinary Portland cement, modified silica-carbon nanotube composite aerogel powder, hollow glass microspheres, nanofibers, graphene nanosheets, ultraviolet absorber, water reducer, and defoamer) in order by mass, add them to a planetary mixer, and dry mix at 150 r / min for 4 min. S3, add water and stir at 300r / min for 3min. S4, adding the composite emulsion mixed in S1, stirring at a speed of 800 r / min for 2 minutes to obtain a coating material.

[0069] Example 1

[0070] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three components: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 73.6:19.4:7. The powder is composed of 25 parts of ultrafine sand, 30 parts of P∙O 42.5R ordinary Portland cement, 10 parts of modified silica-carbon nanotube composite aerogel powder, 6 parts of hollow glass microspheres, 1 part of cellulose fiber, 0.5 parts of graphene nanosheets, 0.3 parts of nano-ZnO ultraviolet absorber, 0.6 parts of polycarboxylic acid-based high-performance water reducer, and 0.2 parts of amino polyether defoamer. The composite emulsion is composed of 9 parts of acrylic copolymer emulsion, 6 parts of polyvinyl acetate-ethylene emulsion, 4 parts of thermosensitive polymer emulsion, and 0.4 parts of dodecyl alcohol ester.

[0071] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 500 r / min for 20 minutes while ultrasonically treated at 800 W and 30 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, in order, at 2% and 4% by weight of the composite aerogel powder, respectively. The mixture was reacted at 60°C and 400 r / min for 3 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0072] 3) The thermosensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate. Accurately weigh 65 parts of butyl acrylate, 10 parts of lauryl acrylate, 10 parts of methyl methacrylate, 6 parts of styrene, 2 parts of acrylonitrile, 5 parts of acrylic acid, and 2 parts of glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture. A 3wt% solution of sodium lauryl sulfate and a 1wt% solution of polyoxyethylene octylphenol ether are prepared. Under nitrogen, the mixture is heated to 50°C. After the temperature stabilizes, the monomer mixture is slowly added and stirred for 30 minutes to form a stable pre-emulsion. The pre-emulsion is then heated to 70°C, and a 0.5wt% potassium persulfate solution is slowly added dropwise to initiate polymerization. After the reaction is complete, the mixture is cooled to room temperature and the pH of the solution is adjusted to approximately 7 with aqueous ammonia to obtain the thermosensitive polymer emulsion.

[0073] Example 2

[0074] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three components: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 74.3:19.6:6. The powder is composed of 20 parts of ultrafine sand, 35 parts of P∙O 52.5R ordinary Portland cement, 10 parts of modified silica-carbon nanotube composite aerogel powder, 6 parts of hollow glass microspheres, 1.5 parts of SiO2 nanofibers, 0.5 parts of graphene nanosheets, 0.5 parts of nano-TiO2 UV absorber, 0.7 parts of polycarboxylic acid-based high-performance water reducer, and 0.2 parts of amino polyether defoamer. The composite emulsion is composed of 9 parts of acrylic copolymer emulsion, 6 parts of polyvinyl acetate-ethylene emulsion, 4 parts of thermosensitive polymer emulsion, and 0.6 parts of hexadecyl alcohol ester.

[0075] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 500 r / min for 30 minutes while ultrasonically treated at 800 W and 30 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, at 2% and 4% by weight of the composite aerogel powder, respectively. The mixture was reacted at 60°C and 300 r / min for 3 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0076] 3) The thermosensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate. Accurately weigh 65 parts of butyl acrylate, 10 parts of lauryl acrylate, 10 parts of methyl methacrylate, 6 parts of styrene, 2 parts of acrylonitrile, 5 parts of acrylic acid, and 2 parts of glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture. A 3wt% solution of sodium lauryl sulfate and a 1wt% solution of polyoxyethylene octylphenol ether are prepared. Under nitrogen, the mixture is heated to 50°C. After the temperature stabilizes, the monomer mixture is slowly added and stirred for 30 minutes to form a stable pre-emulsion. The pre-emulsion is then heated to 70°C, and a 0.5wt% potassium persulfate solution is slowly added dropwise to initiate polymerization. After the reaction is complete, the mixture is cooled to room temperature and the pH of the solution is adjusted to approximately 7 with aqueous ammonia to obtain the thermosensitive polymer emulsion.

[0077] Example 3

[0078] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three components: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 73.4:21.6:5. The powder is composed of 20 parts of ultrafine sand, 33 parts of P∙O 52.5R ordinary Portland cement, 11 parts of modified silica-carbon nanotube composite aerogel powder, 6 parts of hollow glass microspheres, 1.5 parts of SiO2 nanofibers, 0.5 parts of graphene nanosheets, 0.5 parts of nano-TiO2 UV absorber, 0.7 parts of a polycarboxylic acid-based high-performance water reducer, and 0.2 parts of an amino polyether defoamer. The composite emulsion is composed of 9 parts of an acrylic copolymer emulsion, 6 parts of a polyvinyl acetate-ethylene emulsion, 6 parts of a thermosensitive polymer emulsion, and 0.6 parts of hexadecyl alcohol ester.

[0079] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 500 r / min for 30 minutes while ultrasonically treated at 800 W and 30 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, in order, at 2% and 5% by weight of the composite aerogel powder, respectively. The mixture was reacted at 60°C and 300 r / min for 3 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0080] 3) The thermosensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate. Accurately weigh 63 parts butyl acrylate, 10 parts lauryl acrylate, 10 parts methyl methacrylate, 7.5 parts styrene, 2.5 parts acrylonitrile, 5 parts acrylic acid, and 2 parts glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture. A 3wt% sodium lauryl sulfate and 1wt% polyoxyethylene octylphenol ether solution is prepared. Under nitrogen, heat the mixture to 55°C. After the temperature stabilizes, slowly add the monomer mixture and continue stirring for 20 minutes to form a stable pre-emulsion. The pre-emulsion is then heated to 70°C, and 0.5wt% potassium persulfate solution is slowly added dropwise to initiate polymerization. After the reaction is complete, cool to room temperature and adjust the pH of the solution to approximately 7 with aqueous ammonia to obtain the thermosensitive polymer emulsion.

[0081] Example 4

[0082] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three components: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 73.4:21.6:5. The powder is composed of 20 parts of ultrafine sand, 35 parts of P∙O 52.5R ordinary Portland cement, 5 parts of modified silica-carbon nanotube composite aerogel powder, 8 parts of hollow glass microspheres, 1.5 parts of SiO2 nanofibers, 0.5 parts of graphene nanosheets, 0.5 parts of nano-TiO2 UV absorber, 0.7 parts of polycarboxylic acid-based high-performance water reducer, and 0.2 parts of amino polyether defoamer. The composite emulsion is composed of 9 parts of acrylic copolymer emulsion, 6 parts of polyvinyl acetate-ethylene emulsion, 6 parts of thermosensitive polymer emulsion, and 0.6 parts of dodecyl alcohol ester.

[0083] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 400 r / min for 30 minutes while simultaneously ultrasonically treated at 500 W and 40 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, in a ratio of 3% and 5% by weight, respectively, of the composite aerogel powder. The mixture was reacted at 80°C and 300 r / min for 2 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0084] 3) The thermosensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate. Accurately weigh 56 parts of butyl acrylate, 15 parts of lauryl acrylate, 10 parts of methyl methacrylate, 9 parts of styrene, 3 parts of acrylonitrile, 5 parts of acrylic acid, and 2 parts of glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture. A 4wt% solution of sodium lauryl sulfate and a 2wt% solution of polyoxyethylene octylphenol ether are prepared. Under nitrogen, the mixture is heated to 55°C. After the temperature stabilizes, the monomer mixture is slowly added and stirred for 30 minutes to form a stable pre-emulsion. The pre-emulsion is then heated to 75°C, and a 0.5wt% potassium persulfate solution is slowly added dropwise to initiate polymerization. After the reaction is complete, the mixture is cooled to room temperature and the pH of the solution is adjusted to approximately 7 with aqueous ammonia to obtain the thermosensitive polymer emulsion.

[0085] Example 5

[0086] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three ingredients: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 73.4:21.6:5. The powder is a mixture of 20 parts ultrafine sand, 33 parts P∙O 52.5R ordinary Portland cement, 11 parts modified silica-carbon nanotube composite aerogel powder, 6 parts hollow glass microspheres, 1.5 parts SiO2 nanofibers, 0.5 parts graphene nanosheets, 0.5 parts nano-TiO2 UV absorber, 0.7 parts polycarboxylic acid-based high-performance water reducer, and 0.2 parts amino polyether defoamer. The composite emulsion is composed of 12 parts acrylic copolymer emulsion, 9 parts polyvinyl acetate-ethylene emulsion, and 0.6 parts dodecyl alcohol ester.

[0087] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 500 r / min for 30 minutes while ultrasonically treated at 500 W and 40 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, in order, at 2% and 5% by weight of the composite aerogel powder, respectively. The mixture was reacted at 80°C and 300 r / min for 2 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0088] Example 6

[0089] 1) Cement-based aerogel thermal insulation coating material for concrete is prepared from three ingredients: powder, composite emulsion, and water. The mass ratio of powder, composite emulsion, and water is 77.6:14.4:8. The powder is composed of 25 parts of ultrafine sand, 32 parts of P∙O 52.5R ordinary Portland cement, 11 parts of modified silica-carbon nanotube composite aerogel powder, 6.5 parts of hollow glass microspheres, 1.4 parts of SiO2 nanofibers, 0.5 parts of graphene nanosheets, 0.4 parts of nano-TiO2 UV absorber, 0.6 parts of polycarboxylic acid-based high-performance water reducer, and 0.2 parts of amino polyether defoamer. The composite emulsion is composed of 6 parts of acrylic copolymer emulsion, 4 parts of polyvinyl acetate-ethylene emulsion, 4 parts of thermosensitive polymer emulsion, and 0.4 parts of hexadecyl alcohol ester.

[0090] 2) Silica-carbon nanotube composite aerogel powder was modified with a combination of cationic and nonionic surfactants. A 10% ethanol solution was prepared with anhydrous ethanol and deionized water. After stirring for 20 minutes, silica-carbon nanotube composite aerogel powder was added at a solid-liquid ratio of 1:5. The mixture was stirred at 500 r / min for 30 minutes while ultrasonically treated at 800 W and 30 kHz to form a uniform suspension. Hexadecyltrimethylammonium bromide and polyethylene glycol were then added, in order, at 2% and 5% by weight of the composite aerogel powder, respectively. The mixture was reacted at 60°C and 300 r / min for 3 hours. Finally, the modified silica-carbon nanotube composite aerogel powder was obtained by drying at 40°C.

[0091] 3) The thermosensitive polymer emulsion is prepared by polymerizing monomers such as butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate. Accurately weigh 63 parts butyl acrylate, 10 parts lauryl acrylate, 10 parts methyl methacrylate, 7.5 parts styrene, 2.5 parts acrylonitrile, 5 parts acrylic acid, and 2 parts glycidyl methacrylate into a container and stir thoroughly to form a monomer mixture. A 3wt% sodium lauryl sulfate and 1wt% polyoxyethylene octylphenol ether solution is prepared. Under nitrogen, heat the mixture to 50°C. After the temperature stabilizes, slowly add the monomer mixture and continue stirring for 30 minutes to form a stable pre-emulsion. The pre-emulsion is then heated to 75°C, and 0.5wt% potassium persulfate solution is slowly added dropwise to initiate polymerization. After the reaction is complete, cool to room temperature and adjust the pH of the solution to approximately 7 with aqueous ammonia to obtain the thermosensitive polymer emulsion.

[0092] In order to facilitate comparison of the actual effects of the cement-based aerogel thermal insulation coating material for concrete in the embodiments, several groups of comparative examples are set as follows: Comparative Example 1 A commercially available expanded perlite insulation mortar product was selected, the components of which included P∙O 42.5 ordinary Portland cement, expanded perlite, dispersible latex powder, cellulose ether, anti-cracking fiber, etc. The materials were weighed and mixed evenly according to the ratio of powder to water = 1:0.6 before use.

[0093] Comparative Example 2 Choose commercially available polyurethane thermal insulation coating products, which are compounded by various water-based polymers, high-quality cement, etc. (divided into two components A and B). When using, pour components A and B into the container in a specific proportion and stir evenly.

[0094] Comparative Example 3 Select commercially available aerogel coating products (viscous paste, see Figure 5 ), the components include silica aerogel powder, acrylic emulsion, titanium dioxide, etc., and they can be stirred evenly with an electric stirrer when used.

[0095] Comparative Example 4 The types of materials and preparation methods used in this comparative example are the same as those in Example 3, except that the silica-carbon nanotube composite aerogel powder is not subjected to the combined modification treatment of the cationic surfactant and the nonionic surfactant.

[0096] Comparative Example 5 The types of materials and preparation methods used in this comparative example are the same as those in Example 3, except that the silica-carbon nanotube composite aerogel powder is modified with only a single cationic surfactant (3% hexadecyltrimethylammonium bromide).

[0097] The temperature in the laboratory was controlled at (20±2)℃ and the relative humidity was not less than 50%. The raw materials were weighed according to the material ratio and the coating material was mixed with a planetary mixer to prepare the coating test piece with a size of 300mm×300mm×20mm. The thermal conductivity of the coating material was tested in an environment with a temperature of 25℃ / 15℃ and a relative humidity of 50% according to GB / T10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - Guarded hot plate method"; the test piece with a molding size of 40mm×40mm×160mm (see Figure 1 (a)), refer to GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)", and measure the compressive strength of the cement mortar on a flexural and compressive testing machine after breaking; form an "8"-shaped specimen (see Figure 1 (b)), the tensile strength was determined according to SL / T 352-2020 "Test Procedures for Hydraulic Concrete". A dumbbell I-shaped specimen (straight section length 100 mm, width 25 mm, thickness 25 mm) was formed and, with reference to GB / T 16777-2008 "Test Methods for Building Waterproof Coatings", a strain gauge was affixed to the specimen and a tensile test was carried out on a microcomputer-controlled hydraulic servo testing machine to determine its elongation at break.

[0098] Prepare the benchmark concrete specimens with strength grade ≥ C50 in advance, grind the concrete surface to increase the roughness, and use a brush to remove the dust and powder on the end surface; then mix the coating material and apply it on the concrete surface (see Figure 1 (c) After curing to the age, the contact angle of the coating was measured using an OCA20 contact angle meter in a windless laboratory environment with a temperature of (23±2)℃ and a relative humidity of (50±5)%. Each group of samples was tested at ≥5 different positions. A 50mm diameter circular hole was drilled on the surface of the coating-concrete specimen with a drilling and milling machine and a drilling depth of 10mm. Then, a 50mm diameter pulling head was bonded to the drilled coating surface with cast steel glue. The bonding strength between the coating and the base layer was then tested using an LBY-IV pulling tester (see Figure 2 (a)~(c)), 3 samples were tested in each group, and then the coating-concrete microscopic analysis slices were prepared through cutting, grinding, polishing and other processes, and the coating interface bonding morphology characteristics were photographed using a polarizing microscope (see Figure 2 (d)); Referring to GB / T 23987-2009 "Exposure of paint and varnish coatings to fluorescent ultraviolet light and water", the coating's resistance to artificial weathering was determined by exposing the sample to UVA-340 fluorescent ultraviolet light for 1000 hours. The samples were observed for color change, surface cracking, chalking, blistering, etc. The bond strength between the coating and the base layer after treatment with the fluorescent ultraviolet light was tested using a pull-out tester, and the bond strength retention between the coating and the base layer was calculated.

[0099] The relevant test results of Examples 1 to 6 are shown in Table 1. As can be seen from the table, the cement-based aerogel thermal insulation coating materials of Examples 1 to 6 have low thermal conductivity, high strength and high toughness, high interfacial adhesion and excellent surface hydrophobicity, and excellent anti-ultraviolet aging performance.

[0100] Comparing Examples 1 to 3, it can be seen that ① compared with 42.5R cement, the cement-based aerogel thermal insulation coating material prepared with 52.5R cement has better mechanical properties and better early strength, and thanks to the carbon nanotube composite and amino modification of silica aerogel, the compressive strength of the coating is ≥35MPa and the tensile strength is ≥4.0MPa. ② Compared with cellulose fiber, the cement-based aerogel thermal insulation coating material prepared by adding an appropriate amount of SiO2 nanofiber has better crack resistance and tensile deformation performance. Combined with the good flexibility of polyvinyl acetate-ethylene emulsion and thermosensitive polymer emulsion, the elongation at break of the coating can be made ≥200%. ③ By optimizing the proportions of the three parts of powder, composite emulsion and water, as well as the preparation process of silica-carbon nanotube composite aerogel modification and thermosensitive polymer emulsion, a multi-level pore network structure can be jointly constructed, the thermal conductivity of the coating is reduced to 0.01~0.02W / (m∙K), and the coating is firmly bonded to the base concrete after hardening (see Figure 2 (d)), interface bonding strength ≥3.5MPa, the coating surface is hydrophobic, the contact angle ≥150°, the durability is good, and the performance retention rate after 1000h of UV light irradiation is ≥90%, with obvious performance advantages.

[0101] Comparing Examples 4 to 6 with Examples 2 to 3, it can be seen that ① in Example 4, 35 parts of 52.5R cement and only 5 parts of modified silica-carbon nanotube composite aerogel powder were added. Although the mechanical properties and tensile deformation properties of the coating material were comparable to those of Examples 2 to 3, the thermal conductivity increased by 84 to 173%. This indicates that when the number of modified silica-carbon nanotube composite aerogel particles is small, they cannot overlap with the ultrafine sand and glass microspheres to form an effective multi-level pore network structure, and thus cannot ensure the thermal insulation effect. ② In Example 5, the composite emulsion does not contain a thermosensitive polymer emulsion, but instead contains more acrylic copolymer emulsion and polyvinyl acetate-ethylene emulsion. The thermal conductivity of the coating material is slightly higher, reaching 0.025 W / (m∙K), and the thermal conductivity at 15°C is equivalent to that at 25°C. This indicates that the coating has poor thermal insulation performance at low temperatures and does not have intelligent regulation of thermal insulation performance under temperature drop / temperature rise environments. In addition, the coating has an elongation at break of 166%, and its tensile deformation performance is slightly worse than that of Examples 2-3. ③ In Example 6, the amount of ultrafine sand is slightly increased, and the amount of composite emulsion used is small. The thermal insulation performance of the coating material is comparable to that of Examples 2 and 3, but the mechanical properties are significantly reduced. The compressive strength decreases by 18 to 24%, the tensile strength decreases by 21 to 28%, the interfacial bonding strength decreases by 29 to 32%, the elongation at break is only 127%, and the surface contact angle is 107°. This indicates that the composite emulsion has a significant contribution to the tensile deformation properties, interfacial bonding strength, and surface hydrophobicity of the cement-based aerogel coating material. ④ The amount of powder and composite emulsion in the coating material, as well as the type and amount of composite polymer emulsion, are all matched. Low-thermal-conductivity, ultra-fine sand acts as a skeleton, hollow vitrified microspheres enhance thermal insulation, cement hydration forms strength, and nanosheets and fibers reinforce the coating for toughness and crack resistance. Polyvinyl acetate-ethylene emulsion and thermosensitive polymer emulsion impart elastic deformation capability to the coating. Acrylic copolymer emulsion and polyvinyl acetate-ethylene emulsion enhance interfacial adhesion. The thermosensitive polymer emulsion also enables the coating to adjust its thermal insulation properties under temperature fluctuations and temperature rises. Each component's amount has a reasonable range; more is not necessarily better. For example, excessive use of hollow vitrified microspheres can reduce the coating's compressive and tensile strength, while too little can increase thermal conductivity. Excessive use of thermosensitive polymer emulsion can improve elastic deformation and reduce thermal conductivity at low temperatures, but it can reduce the coating's interfacial adhesion strength. Only the synergistic effect of powder and composite emulsion components can make the coating material have the characteristics of high strength, high elasticity and toughness, strong interfacial adhesion, surface hydrophobicity, etc. after hardening, with compressive strength ≥35MPa, tensile strength ≥4.0MPa, elongation at break ≥200%, interfacial adhesion strength ≥3.5MPa, and contact angle ≥150°.⑤ The amount of silica-carbon nanotube composite aerogel used and the surfactant modification process directly affect the uniformity of the composite aerogel particles' dispersion in the cement matrix and the strength of their interfacial bond with the cement matrix, which in turn affects the thermal insulation and mechanical properties of the coating. Only through the aerogel's own reinforcement and effective dispersion can the coating achieve a thermal conductivity below 0.02 W / (m∙K). ⑥ The addition of nano-TiO2 UV absorbers imparts UV resistance to the coating. After 1000 hours of UV irradiation, the surface exhibits no noticeable color change, cracking, chalking, or blistering, and the interfacial bond strength retention rate is ≥90%, making the coating suitable for long-term exposure.

[0102] Table 1 Performance of cement-based aerogel thermal insulation coating for concrete (Example)

[0103] The test results of Comparative Examples 1 to 5 are shown in Table 2. The commercially available expanded perlite insulation mortar in Comparative Example 1 has a high thermal conductivity (≥0.085W / (m∙K)), and due to the large amount of expanded perlite lightweight aggregate used, its compressive strength, tensile strength, and bonding strength with the substrate are all low. Although it is compounded with anti-cracking fibers, its elongation at break is only 1.2%, which is an inorganic brittle material. The commercially available polyurethane coating in Comparative Example 2 is an organic material with good elastic deformation ability and surface hydrophobicity, but its thermal conductivity is as high as 0.113W / (m∙K), and its thermal insulation performance is limited. In addition, under the action of long-term ultraviolet light, it will not be easily damaged. The coating surface exhibited discoloration, powdering, and cracking, and after 1000 hours, the bond strength retention with the base layer dropped to 58%, indicating poor aging resistance. Comparative Example 3: The commercially available aerogel coating had a thermal conductivity of ≤0.045 W / (m∙K) and good thermal insulation properties, but its mechanical properties were poor, with compressive and tensile strengths both exceeding 0.5 MPa and an interfacial bonding strength of only 0.6 MPa. Furthermore, it exhibited poor weather resistance, with bubbles forming on the surface under UV light. Tests also revealed that the aerogel coating would peel off after prolonged immersion in water. This demonstrates that currently available concrete thermal insulation materials present numerous challenges, with performance in mechanical properties, interfacial bonding, and thermal insulation requiring improvement.

[0104] Compared with Example 3, the silica-carbon nanotube composite aerogel powder added in Comparative Example 4 was not modified with a cationic surfactant and a nonionic surfactant. The thermal conductivity of the prepared cement-based aerogel thermal insulation coating material was as high as 0.028~0.032W / (m∙K), which was increased by 100~155%; the mechanical properties were significantly reduced, with the compressive strength decreasing by 36%, the tensile strength decreasing by 31%, and the interfacial bonding strength decreasing by 37%. This is because the unmodified nano-aerogel particles have poor compatibility with the cement matrix, are unevenly dispersed, and are easily agglomerated, which not only leads to poor thermal insulation effect, but also increases microscopic defects, resulting in reduced strength. The silica-carbon nanotube composite aerogel powder used in Comparative Example 5 was modified with only a single cationic surfactant (cetyltrimethylammonium bromide). The thermal conductivity of the prepared cement-based aerogel thermal insulation coating material also increased by 81~136%, the compressive strength decreased by 23%, the tensile strength decreased by 19%, and the interfacial bonding strength decreased by 23%. This shows that after surface modification with cetyltrimethylammonium bromide, the surface of the aerogel particles has a positive charge, and the electrostatic repulsion can prevent the agglomeration of aerogel particles to a certain extent. However, compared with the combined modification with a cationic surfactant and a non-ionic surfactant, the dispersibility and interfacial bonding strength of the aerogel in the cement-based slurry still have room for improvement.

[0105] Table 2 Performance of cement-based aerogel thermal insulation coating for concrete (comparative example)

[0106] Example 7

[0107] A spraying construction process of cement-based aerogel thermal insulation coating material for concrete The cement-based aerogel thermal insulation coating material was prepared according to the ratio of Example 3, and the "multi-stage dynamic mixing" process was adopted to ensure that the modified silica-carbon nanotube composite aerogel powder was fully mixed with other components. The mixing and fluidity state of the prepared coating material was as follows: Figure 3 As shown. The on-site demonstration application construction process of cement-based aerogel thermal insulation coating material is as follows Figure 4 As shown, the idea of ​​"high-pressure water washing base surface + layered spraying" is adopted, which specifically includes the following steps: ① Use a high-pressure water gun with a wire brush at a water pressure of 3~5MPa to remove impurities on the surface of the concrete base. When the surface is moist and there is no visible water, spray it twice with nano-silicon ion impregnation crystallization solution (see Figure 4 (b)), the spraying amount is 300g / m²; ② Weigh the powder materials (extra fine sand, ordinary Portland cement, modified silica-carbon nanotube composite aerogel powder, hollow glass microspheres, nanofibers, graphene nanosheets, ultraviolet absorber, water reducer, and defoamer) in order by mass and add them to a planetary mixer. Dry mix them at 150 r / min for 4 min. Then, add water and stir at 300 r / min for 3 min. Finally, add the composite emulsion and stir at 800 r / min for 2 min to obtain the coating material. ③Use high pressure airless spray equipment (see Figure 4 (a)) The coating was sprayed at a pressure of 20 MPa, a distance of 80 cm between the nozzle and the substrate surface, a spray angle of 60°, and a spray width of 50 cm (see Figure 4 (c) Spray in 2 layers, with each layer thickness controlled at 1-2 mm and the interval time controlled at 1.5 h; ④ After the coating construction is completed, cover it with plastic film for moisturizing maintenance for 1~2 days.

[0108] Example 8

[0109] A spraying construction process of cement-based aerogel thermal insulation coating material for concrete A cement-based aerogel thermal insulation coating material was prepared according to the ratio of Example 3, and the construction process of "high-pressure water washing base surface + mechanical spraying" was adopted, which specifically included the following steps: ① Use a high-pressure water gun with a wire brush at a water pressure of 3~5MPa to remove impurities on the surface of the concrete base; ② Weigh the powder materials (extra fine sand, ordinary Portland cement, modified silica-carbon nanotube composite aerogel powder, hollow glass microspheres, nanofibers, graphene nanosheets, ultraviolet absorber, water reducer, and defoamer) in order by mass and add them to a planetary mixer. Dry mix them at 150 r / min for 4 min. Then, add water and stir at 300 r / min for 3 min. Finally, add the composite emulsion and stir at 800 r / min for 2 min to obtain the coating material. ③ Use high-pressure airless spray equipment for coating construction, with a spraying pressure of 20MPa, a distance of 80cm between the nozzle and the base surface, a spraying angle of 60°, a spraying width of 50cm, and two layers of spraying. The thickness of each layer is controlled at 1~2mm, and the interval time is controlled at 1.5h; ④ After the coating construction is completed, cover it with plastic film for moisturizing maintenance for 1~2 days.

[0110] According to the characteristics of different coating materials, suitable construction was selected to conduct field tests on actual projects, and the construction efficiency of the coating and the interface bonding performance after hardening were evaluated. The test results are shown in Table 3. As can be seen from the table, Example 7 uses the material ratio of Example 3, and the slurry after mixing has low viscosity and good fluidity (see Figure 3), suitable for high-pressure airless layered spraying construction technology, it is estimated that a single person and a single device can construct an area of ​​300m per hour 2 The coating has good uniformity and a bonding strength of up to 3.4MPa with the base layer. It has the advantages of high construction efficiency and stable quality. The coating thickness is 2~4mm, with low material consumption and low cost. After the coating hardens, the surface forms a film and feels smooth (see Figure 4 (d)), the surface is hydrophobic, and the durability and self-cleaning ability are excellent. Example 8 also uses the material ratio of Example 3. During construction, the base surface is not sprayed with nano-silicon ion impregnation crystallization solution after high-pressure water washing. Because one construction procedure is omitted, it is estimated that a single person and a single device can construct an area of ​​up to 350m per hour. 2 However, after the coating hardened, the bonding strength with the base layer was only 2.1 MPa, which decreased significantly. By comparison, it can be seen that spraying and soaking the crystallization solution before coating construction can strengthen the concrete base surface, which is beneficial to enhancing the bonding strength between the coating and the concrete base layer.

[0111] Compared with Examples 7-8, the commercially available expanded perlite insulation mortar, polyurethane coating, and aerogel coating in Comparative Examples 1-3 mostly require manual scraping or roller coating, and the construction area per person per hour during scraping construction is 10-15 m 2 Roller coating is slightly more efficient, but the construction area per person per hour is about 40~50m 2 ; And the three commercially available materials have generally low bonding strength with the base surface after hardening, only 0.3~0.7MPa, which is 67~91% lower than that of Examples 7~8, and the effect is poor. Among them, the commercially available aerogel coating manufacturer recommends that it can also be sprayed, but the finished product is viscous paste and relatively viscous (see Figure 5 ), the material discharge is slow and the nozzle is often clogged during spraying construction, the coating uniformity is poor, the construction thickness is about 5~8cm, and the construction area per person per hour is only about 120m 2 ; Moreover, the bonding strength between the coating and the base surface during spraying is lower than that during manual scraping, decreasing from 0.6MPa to 0.3MPa.

[0112] Table 3 Construction efficiency of thermal insulation coating for concrete

[0113] In summary, the cement-based aerogel thermal insulation coating material for concrete and its construction process described in this invention exhibit low thermal conductivity, high strength and toughness, high interfacial adhesion combined with excellent surface hydrophobicity, and excellent resistance to UV aging. Furthermore, the proposed "high-pressure water washing of the base surface followed by layered spraying" construction process offers advantages such as efficient construction and stable quality, providing a new approach to thermal insulation for concrete structures in harsh environments.

[0114] The above embodiments are only for illustrating the better performance of the present invention and do not constitute a limitation on the present invention. It should be pointed out that any form of modification made by technicians in this professional field without departing from the core concept of the present invention and the obvious changes derived therefrom fall within the scope of protection of the present invention.

Claims

1. A cement-based aerogel thermal insulation coating material for concrete, characterized by: The cement-based aerogel thermal insulation coating material is prepared from three parts of materials: powder, composite emulsion and water, wherein the mass ratio of powder, composite emulsion and water is (65-80):(16-25):(4-10); The powder is prepared by mixing 15-25 parts of ultrafine sand, 20-35 parts of ordinary Portland cement, 5-15 parts of modified silica-carbon nanotube composite aerogel powder, 5-10 parts of hollow glass microspheres, 0.5-2 parts of nanofibers, 0.2-1 parts of graphene nanosheets, 0.2-1 parts of ultraviolet absorbers, 0.2-2 parts of water reducers, and 0.1-0.5 parts of defoaming agents; The composite emulsion consists of 5-15 parts of acrylic copolymer emulsion, 2-10 parts of polyvinyl acetate-ethylene emulsion, 0-10 parts of temperature-sensitive polymer emulsion and 0.3-1.0 parts of film-forming aid.

2. The cement-based aerogel thermal insulation coating material for concrete according to claim 1, characterized in that: The modified silica-carbon nanotube composite aerogel powder is obtained by treating silica-carbon nanotube composite aerogel powder with a combined modification treatment of a cationic surfactant and a nonionic surfactant, wherein the usage ratio of the cationic surfactant to the nonionic surfactant is 1:1.5 to 1:2.

5.

3. The cement-based aerogel thermal insulation coating material for concrete according to claim 1, characterized in that: The thermosensitive polymer emulsion is prepared by polymerizing the following monomers in parts by mass: 55-70 parts of butyl acrylate, 0-15 parts of lauryl acrylate, 10-20 parts of methyl methacrylate, 5-10 parts of styrene, 0-5 parts of acrylonitrile, 0-5 parts of acrylic acid, and 0-5 parts of glycidyl methacrylate.

4. The cement-based aerogel thermal insulation coating material for concrete according to claim 1, characterized in that: The fineness modulus of the ultra-fine sand is between 0.7 and 1.5, the particle size range is 0.05 to 0.3 mm, and the apparent density is ≥ 2600 kg / m 3 , thermal conductivity ≤ 0.2W / (m∙K); the ordinary Portland cement is of early strength type and has a strength grade ≥ 42.5R; the particle size range of the hollow vitrified microspheres is 0.1~0.5mm, the wall thickness is <10μm, and the thermal conductivity ≤ 0.05W / (m∙K); the nanofiber is one of SiO2 nanofiber, carbon nanofiber, and cellulose nanofiber, with a diameter of 50~200nm and a length of 5~20μm; the graphene nanosheet is a single-layer structure with a purity > 95%; the ultraviolet absorber is one of nano-TiO2 and nano-ZnO; the water reducer is one of a polycarboxylic acid-based high-performance water reducer and a melamine-based high-efficiency water reducer, in powder form, with a water reduction rate of not less than 25%; the defoamer is one of an amino polyether defoamer and a polyether-modified silicone defoamer, in powder form.

5. The cement-based aerogel thermal insulation coating material for concrete according to claim 2, characterized in that: The cationic surfactant is cetyltrimethylammonium bromide, and the nonionic surfactant is polyethylene glycol.

6. The cement-based aerogel thermal insulation coating material for concrete according to claim 5, characterized in that: The combined modification treatment method comprises: adding silica-carbon nanotube composite aerogel powder to a 10% ethanol solution, stirring and ultrasonically treating the solution to form a uniform suspension, then sequentially adding hexadecyltrimethylammonium bromide and polyethylene glycol, reacting the solution at a temperature of 60-80°C and a stirring speed of 300-400 r / min for 2-3 hours, and low-temperature drying the solution to obtain the modified silica-carbon nanotube composite aerogel powder.

7. The cement-based aerogel thermal insulation coating material for concrete according to claim 3, characterized in that: The preparation method of the thermosensitive polymer emulsion is: 1) Weigh butyl acrylate, lauryl acrylate, methyl methacrylate, styrene, acrylonitrile, acrylic acid, and glycidyl methacrylate, add them into a container and stir thoroughly to form a monomer mixture; 2) Prepare 2-4 wt% sodium lauryl sulfate and 1-2 wt% polyoxyethylene octylphenol ether solution, heat to 50-55°C under nitrogen protection, slowly add the monomer mixture after the temperature stabilizes, and continue stirring for 20-30 minutes to form a stable pre-emulsion; 3) Heat the pre-emulsion to 70-75°C, slowly add 0.5 wt% potassium persulfate solution to initiate polymerization; after sufficient reaction, cool to room temperature, and adjust the pH value of the solution to 6-8 with ammonia water to obtain a thermosensitive polymer emulsion.

8. The cement-based aerogel thermal insulation coating material for concrete according to claim 6, characterized in that: The preparation method of the silicon dioxide-carbon nanotube composite aerogel powder is as follows: 1) Mix ethyl orthosilicate, anhydrous ethanol, and deionized water in a molar ratio of 1:(2-4):(1-2), stir evenly, add ammonia water to adjust the pH to 8-9, and stir at 40-60°C for 2 hours to prepare silica sol; 2) Add the carbon nanotubes to a 3 wt% nitric acid solution, sonicate at a frequency of 20-40 kHz for 1 hour for acidification, then wash with deionized water until neutral, dry and add to the silica sol, and simultaneously add 2 wt% γ-aminopropyltriethoxysilane, stir at a speed of 400-500 r / min for 1-2 hours to graft the amino groups into the composite system to obtain a mixed sol; 3) Transfer the mixed sol to a high-pressure reactor and dry it at a temperature of 50°C and a pressure of 10 MPa using carbon dioxide as a supercritical fluid; 4) After crushing and ball milling, silica-carbon nanotube composite aerogel powder with a particle size range of 2~20μm is obtained.

9. The method for preparing a cement-based aerogel thermal insulation coating material for concrete according to any one of claims 1 to 8, characterized in that: The powders were weighed in parts by mass and added into a planetary mixer, and dry-mixed at a speed of 150-200 r / min for 4-5 minutes; then water was added, and stirred at a speed of 300-500 r / min for 3-4 minutes; finally, the composite emulsion was added, and stirred at a speed of 600-800 r / min for 2-3 minutes to obtain a coating material.

10. The spraying construction process of the cement-based aerogel thermal insulation coating material for concrete according to any one of claims 1 to 8, characterized in that: The steps include: 1) Use a high-pressure water gun to rinse and a wire brush to clean, with a water pressure of 3~5MPa, to remove impurities on the surface of the concrete base. When the surface is moist and there is no visible water, spray 1~2 times with nano-silicon ion impregnation crystallization solution, with a spraying amount of 200~300g / m²; 2) Use high-pressure airless spray equipment for coating construction, with a spraying pressure of 15-20 MPa, a distance of 50-80 cm between the nozzle and the base surface, a spraying angle of 40°-60°, a spraying width of 40-50 cm, and 2-3 layers of spraying. The thickness of each layer should be controlled at 1-2 mm. The interval between layers should be adjusted according to the ambient temperature and humidity, and should be controlled between 1-3 hours. 3) After the coating is applied, cover with plastic film for 1-2 days of moisturizing maintenance. The maintenance temperature should be controlled at 15-30°C and the relative humidity should be maintained at 60-80%. During the maintenance period, the coating should be protected from mechanical damage and rain erosion.

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