Graphene snow-melting deicing conductive concrete and preparation method thereof

Abstract

This application relates to the field of building materials technology, specifically disclosing a graphene-based snow-melting and de-icing conductive concrete and its preparation method. The graphene-based snow-melting and de-icing conductive concrete comprises the following raw materials in parts by weight: 90-110 parts cement, 15-25 parts microencapsulated phase change material, 1-3 parts conductive filler, 150-200 parts aggregate, 20-40 parts admixture, 0.5-2 parts water-reducing agent, and 30-45 parts water. The core material of the microencapsulated phase change material is paraffin wax with a phase change temperature of 3-5℃, and the outer shell is hydroxymethylated melamine. The graphene-based snow-melting and de-icing conductive concrete of this application can be used in winter for transportation infrastructure such as roads, bridges, and airport runways. It has the advantages of high-efficiency and energy-saving de-icing, intelligent and active de-icing, excellent durability, and no damage to basic mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a graphene-based conductive concrete for snow melting and de-icing, and its preparation method. Background Technology

[0002] Snow and ice accumulation on roads, bridges, and airport runways during winter pose a serious threat to driving safety and traffic efficiency. Traditional physical de-icing methods (such as mechanical scraping) are energy-intensive, inefficient, and prone to damaging road surfaces; chemical de-icing (such as applying chloride salts) corrodes steel structures, damages concrete durability, and pollutes the water and soil environment. In recent years, conductive concrete based on electrothermal conversion has become a research hotspot for intelligent de-icing. It incorporates conductive materials (such as carbon fiber, steel fiber, and graphite) to generate Joule heat when electricity is applied, thus melting the ice and snow. However, existing technologies generally suffer from the following bottlenecks: First, conventional conductive fillers have poor dispersibility and are prone to agglomeration, leading to uneven conductivity and high resistivity in concrete. This necessitates higher voltages to generate sufficient heat, resulting in high energy consumption and safety hazards. Second, relying solely on electrothermal heating leads to a delayed system response, making it ineffective for prevention and buffering during the initial stages of snow and ice or under sustained low temperatures. Third, some studies have attempted to incorporate phase change materials to impart temperature-regulating properties to concrete, but ordinary phase change materials are prone to leakage during concrete mixing and use, exhibit poor compatibility with the cement matrix, leading to performance degradation and damage to the mechanical properties of concrete. Furthermore, achieving efficient dispersion and stable networking of conductive fillers, and ensuring the long-term synergistic stability of functional components within the complex concrete system, remain key challenges restricting their engineering application. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a graphene-based conductive concrete for snow melting and de-icing, and its preparation method.

[0004] In a first aspect, this application provides a graphene-based conductive concrete for snow melting and de-icing, employing the following technical solution: A graphene-based conductive concrete for snow melting and de-icing comprises the following raw materials in parts by weight: 90-110 parts cement, 15-25 parts microencapsulated phase change material, 1-3 parts conductive filler, 150-200 parts aggregate, 20-40 parts admixture, 0.5-2 parts water-reducing agent, and 30-45 parts water; wherein the core material of the microencapsulated phase change material is paraffin wax with a phase change temperature of 3-5℃, and the outer shell is hydroxymethylated melamine.

[0005] By employing the above technical solution, the conductive filler generates Joule heat when energized, directly heating the concrete surface to rapidly melt snow and ice. Simultaneously, the microencapsulated phase change material undergoes a phase change when the ambient temperature approaches its freezing point, absorbing or releasing latent heat, effectively buffering temperature fluctuations and delaying or preventing ice formation. The synergistic effect of these two components achieves efficient and low-energy snow and ice removal, significantly improving road safety and maintenance efficiency in winter. Furthermore, the microencapsulation structure protects the phase change material from leakage, ensuring the long-term durability of the concrete, while the hydroxymethylated melamine shell enhances compatibility with the cement matrix, optimizing the overall mechanical properties of the concrete.

[0006] Optionally, the conductive filler is composed of graphene nanosheets and chopped carbon fibers in a weight ratio of 1:0.5-1.2.

[0007] By employing the aforementioned technical solution, graphene nanosheets and chopped carbon fibers are composited in a specific ratio, synergistically constructing a highly efficient and stable three-dimensional conductive network within a concrete matrix. The high specific surface area and high conductivity of the graphene nanosheets, acting as planar units, form dense charge conduction paths, significantly reducing the overall resistance of the system. Meanwhile, the high aspect ratio and relatively stiff chopped carbon fibers act as linear bridges, interspersed between the nanosheets, effectively preventing agglomeration and connecting isolated conductive points, thus greatly enhancing the network's connectivity and structural stability. This multi-scale, multi-morphological synergistic effect allows the composite material to achieve excellent conductivity even at low dosages, resulting in more rapid and uniform Joule heating during energization, thereby significantly improving the response speed and energy efficiency of snow melting and de-icing. Simultaneously, the addition of carbon fibers enhances the mechanical properties and crack resistance of the concrete, further ensuring the durability of the conductive network under long-term freeze-thaw cycles and load conditions.

[0008] Optionally, the thickness of the graphene nanosheets is 5-10 nm; the length of the chopped carbon fibers is 6-12 mm.

[0009] By employing the above-mentioned technical solutions, ultrathin graphene nanosheets possess extremely high specific surface area and excellent flexibility, enabling them to more fully coat and tightly adhere to cement particles. This forms a dense two-dimensional conductive layer with low contact resistance at the microscale, providing an efficient substrate for charge transport and Joule heating. Short-cut carbon fibers of specific lengths, much larger than nanomaterials, act as "load-bearing beams" and "connecting bridges" at both the macro and micro scales. On the one hand, they effectively penetrate and anchor within the cement paste, inhibiting microcrack propagation and enhancing the toughness of the composite material. On the other hand, the long fibers can reliably connect graphene conductive regions separated by cement hydration products across relatively long distances, significantly improving the overall connectivity and structural robustness of the three-dimensional conductive network. This precise dimensional design allows the nanosheets and carbon fibers to function and synergize at their most effective scales, ensuring the conductive network remains stable even under the complex environment and stress of concrete, thereby achieving rapid, uniform, and long-lasting electrothermal conversion and excellent snow melting and de-icing performance.

[0010] Optionally, the microencapsulated phase change material is prepared by the following steps: Paraffin wax and hydroxymethylated melamine are emulsified with an emulsifier to form a stable O / W emulsion. Subsequently, a polymer shell is formed on the surface of the core material droplets through in-situ polymerization. After solid-liquid separation, washing, and drying, microencapsulated phase change material is obtained.

[0011] By employing the above technical solution, a stable water-in-oil emulsion is first formed under the action of an emulsifier, uniformly dispersing liquid paraffin into micron-sized droplets. This lays the foundation for the subsequent formation of uniformly sized and well-dispersed microcapsules. The crucial in-situ polymerization step allows the hydroxymethylated melamine prepolymer to polymerize and solidify directly on the surface of the paraffin droplets, forming a dense, robust, and reactive polymer shell around the core material. This shell not only completely encapsulates the paraffin, effectively preventing leakage and interaction with other concrete components during the phase change process, but also allows its surface active groups, such as hydroxymethyl groups, to chemically bond with cement hydration products, significantly enhancing the interfacial bonding between the microcapsules and the cement matrix. This strong interfacial bonding ensures the long-term stability of the phase change material in concrete, allowing its heat storage and temperature regulation functions to be sustained. The final microcapsule structure obtained by the entire process is intact and has good thermal stability, enabling it to efficiently regulate surface temperature and delay freezing in concrete without compromising the mechanical properties and durability of the concrete.

[0012] Optionally, the microencapsulated phase change material includes 60-80 parts by weight of paraffin, 20-40 parts by weight of an aqueous solution of hydroxymethylated melamine, 1-5 parts by weight of an emulsifier, and 90-100 parts by weight of deionized water.

[0013] By adopting the above technical solution, the high paraffin content ensures that the microcapsules possess sufficient latent heat storage capacity for phase change, thereby absorbing or releasing a large amount of heat near the critical temperature. This effectively delays the sudden drop or rise in concrete surface temperature, providing valuable buffer time and an energy-saving basis for active electrothermal de-icing. Simultaneously, the matched amount of hydroxymethylated melamine aqueous solution is sufficient to polymerize on the surface of the core material droplets to form a continuous, dense shell with sufficient mechanical strength. This shell completely seals the paraffin, preventing leakage during phase change cycles or concrete mixing, ensuring the long-term reliability of the material. An appropriate amount of emulsifier ensures that the paraffin can form highly stable, uniformly sized fine droplets in the aqueous phase, a prerequisite for obtaining monodisperse, high-performance microcapsules; while sufficient deionized water provides a suitable fluid environment for emulsification and in-situ polymerization reactions, ensuring the uniformity and controllability of the reaction. The optimized proportions ultimately work synergistically to produce microencapsulated phase change materials that possess high heat storage density, excellent structural stability, and good compatibility with cementitious matrices, thus enabling them to perform intelligent temperature regulation functions in concrete in a long-lasting and stable manner.

[0014] Optionally, the chopped carbon fiber is a modified chopped carbon fiber with a graphene-modified silane coupling agent layer coated on its surface, and the coating thickness is 0.1-0.3 μm.

[0015] By employing the above technical solutions, the fiber-cement matrix interface is fundamentally optimized and the conductive network is strengthened. The silane coupling agent in the coating is chemically bonded to the carbon fiber surface at one end, while the other end forms a stable chemical bond with cement hydration products (such as CSH gel). This creates a strong and tough interfacial transition zone between the fiber and concrete, significantly improving interfacial bond strength and load transfer efficiency, and substantially enhancing the mechanical properties and crack resistance of the concrete. Simultaneously, the graphene nanosheets uniformly incorporated into the coating form a highly conductive continuous film on the fiber surface. This film not only significantly reduces the fiber's own contact resistance but, more importantly, establishes a highly efficient electronic "highway" between the fiber and the surrounding dispersed graphene nanosheets and other conductive fillers. This facilitates smoother electron migration between point, line, and surface conductive units, thereby significantly reducing the interfacial resistance of the overall conductive network and improving conductivity uniformity and electrothermal conversion efficiency. Furthermore, this dense coating effectively protects the carbon fiber from the alkaline environment of concrete, ensuring the long-term stability of its conductivity and reinforcing functions. This surface modification strategy, through the synergy of chemical bonding and physical conduction, enables carbon fibers to transform from "passive filling" to "active functionalization," thereby comprehensively improving the overall performance of concrete.

[0016] Optionally, the modified chopped carbon fibers are prepared by the following steps: Graphene oxide was dispersed in a mixed solvent of ethanol and water and ultrasonically treated to obtain a uniform dispersion. A silane coupling agent was added, the pH was adjusted to 4-5 with acid, and the mixture was stirred at 60-80℃ for 4-8 hours to obtain a graphene-modified silane coupling agent dispersion. The short-cut carbon fibers are immersed in the dispersion obtained in step A, ultrasonically dispersed for 10-30 minutes, then removed, dried, and heat-treated at 115-125℃ for 1.5-2.5 hours. After cooling to room temperature, short-cut carbon fibers with a graphene-modified silane coupling agent layer on the surface are obtained.

[0017] By employing the above technical solution, synergistic bonding and uniform coating of graphene and silane coupling agent on the carbon fiber surface were achieved, thereby constructing a strong and highly conductive interfacial transition layer at the molecular level. First, under acidic conditions, the silane coupling agent undergoes hydrolysis and reacts with oxygen-containing functional groups on the graphene oxide sheet, forming a composite functional dispersion that combines silanol active end groups with the conductive network structure of graphene. Subsequently, under ultrasonic assistance, this dispersion can fully wet and uniformly adhere to the carbon fiber surface. The subsequent heat treatment process is crucial, as it promotes the condensation reaction between the silanol groups and the active sites on the carbon fiber surface, forming strong chemical bonds (Si-OC bonds). Simultaneously, it partially thermally reduces the graphene oxide, restoring its excellent intrinsic conductivity, and further cross-links and cures the coating, forming a dense, stable, and firmly bonded composite functional coating. This process ensures that graphene and coupling agent molecules are uniformly and firmly anchored on the fiber surface, ultimately enabling the modified fiber to simultaneously achieve excellent chemical bonding with the cement matrix (through silane end groups) and extremely low interfacial contact resistance (through the graphene conductive layer), thereby achieving simultaneous optimization of enhancement and conductivity.

[0018] Optionally, the modified chopped carbon fiber comprises the following raw materials in parts by weight: 0.5-2 parts graphene oxide, 20-30 parts deionized water, 80-100 parts anhydrous ethanol, 3-10 parts silane coupling agent, and 10-20 parts chopped carbon fiber.

[0019] By employing the above technical solution, an appropriate amount of graphene oxide ensures the construction of a continuous, dense, and highly conductive network on the fiber surface. Too little graphene oxide leads to an incoherent coating, while too much easily causes agglomeration. A specific ratio of silane coupling agent is sufficient to react fully with graphene oxide to form a functional complex, and also provides ample active anchoring sites on the fiber surface, ensuring the chemical bonding strength of the coating. The mixed solvent system of deionized water and anhydrous ethanol creates an ideal reaction environment. Water promotes the hydrolysis of the silane coupling agent, while ethanol helps disperse graphene oxide and improves the wettability of the solution on the carbon fibers. The combination of these two factors ensures reaction uniformity and dispersion stability. The amount of chopped carbon fibers fed, matched to the volume of the dispersion liquid, ensures that each fiber is fully coated by the functional dispersion liquid during processing, resulting in a modified coating with uniform thickness and consistent performance. This optimized formulation works synergistically to ultimately prepare modified fibers with both excellent interfacial bonding strength and extremely low contact resistance in a highly efficient and reliable manner, laying the foundation for the stability and efficiency of the concrete conductive network.

[0020] Secondly, this application provides a method for preparing graphene-based conductive concrete for snow melting and de-icing, employing the following technical solution: A method for preparing graphene-based conductive concrete for snow melting and de-icing includes the following steps: S1. Dry mixing: Mix cement, admixtures, aggregates, and conductive fillers evenly; S2. Wet mixing: Add water-reducing agent and water to the dry mixture from step S1 and stir to form a uniform slurry; S3. Add phase change material: Add microencapsulated phase change material to the slurry in step S2, and stir at low speed using vacuum stirring technology until uniform to obtain concrete mixture; S4. Casting and molding: Pour the mixture into the mold, vibrate to compact it, and cure according to standard.

[0021] By adopting the above technical solution, and through a carefully designed feeding sequence and special process, the integrity, uniform dispersion, and synergy with the cement matrix of key functional components (conductive filler and phase change microcapsules) in concrete are ensured to the greatest extent. First, dry mixing is performed to ensure the conductive filler is fully and uniformly dispersed in the dry powder particles of cement, admixtures, and aggregates, laying the physical foundation for the subsequent formation of a continuous three-dimensional conductive network. Then, water-reducing agents and water are added in the wet mixing stage, achieving good workability while preventing the conductive filler from agglomerating due to premature water contact. The most crucial step is the low-speed incorporation of the microencapsulated phase change material using vacuum mixing technology. The vacuum environment effectively eliminates air bubbles introduced during mixing, ensuring the compactness of the concrete; while the low-speed mixing greatly reduces the mechanical shear force on the microcapsule shell, preventing damage and core material leakage, thus perfectly preserving its phase change temperature-regulating function. The entire process flow ensures efficient construction of the conductive network, complete functionality of the phase change material, and dense concrete matrix, ultimately enabling the concrete to simultaneously achieve rapid and uniform electrothermal melting and intelligent temperature buffering after hardening, and possessing excellent long-term durability.

[0022] In summary, this application has the following beneficial effects: 1. Because this application uses graphene nanosheets and short-cut carbon fibers to form a multi-scale composite conductive filler, and prioritizes dry mixing during preparation, the conductive filler constructs a uniform, interconnected and stable three-dimensional conductive network in the concrete matrix. This structure significantly reduces the overall and interfacial resistance of the system, thereby enabling the concrete to achieve a rapid and uniform Joule heating effect when energized. This results in the final technical effect of rapidly starting ice melting under low voltage and uniform heat distribution, thus significantly reducing the energy consumption of the snow melting and de-icing system and improving the response speed.

[0023] 2. In this application, microcapsules of phase change paraffin are preferably encapsulated with hydroxymethylated melamine as the outer shell, and introduced into concrete through a vacuum low-speed stirring process. This outer shell not only completely seals the core material to prevent leakage, but its surface-active groups can also form chemical bonds with cement hydration products. At the same time, the gentle stirring process protects the integrity of the microcapsule structure, thus achieving the technical effect of enabling concrete to have intelligent temperature buffering capacity (absorbing / releasing latent heat near the freezing point to delay freezing), and the phase change functional components remain stable during concrete mixing and long-term service, without impairing the mechanical properties and durability of concrete.

[0024] 3. The method of this application involves treating short-cut carbon fibers with a graphene-modified silane coupling agent surface coating and optimizing the coating preparation and composite process. This coating establishes a strong chemical bonding interface between the fiber and the cement matrix and significantly improves the electrical connectivity between the fiber and the conductive network. Combined with the overall orderly mixing process, this achieves the final technical effect of simultaneously and significantly improving the mechanical strength, crack resistance, and durability of the conductive network of the concrete, ensuring its long-term stable electrothermal de-icing performance under freeze-thaw cycles and loads. Detailed Implementation

[0025] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0026] The cement is PO 42.5 ordinary Portland cement; the aggregate is a continuously graded crushed stone with a particle size of 5-20mm and medium sand with a fineness modulus of 2.3-2.6, with a sand ratio of 40%. Preparation examples of microencapsulated phase change materials Preparation Example 1 A microencapsulated phase change material is prepared by the following steps: 70 kg of paraffin and 2 kg of sodium dodecyl sulfate (emulsifier) ​​were added to 100 kg of deionized water. The mixture was heated to 65°C in a water bath and emulsified at a high-speed shear rate of 8000 rpm for 10 minutes to form a preliminary O / W type emulsion. The preliminary emulsion was transferred to a high-pressure homogenizer and homogenized three times at 65°C and 45 MPa to obtain a milky white, uniform, and stable paraffin / O / W pre-emulsion. The average droplet size of the emulsion was controlled at 1-5 μm. 30 kg of 50% hydroxymethylated melamine aqueous solution was slowly added to the emulsion, and then the pH of the reaction system was slowly adjusted to 4.0-4.5 with 10% citric acid aqueous solution. The reaction was continued for 3.5 hours under stirring at 65°C and 350 rpm for in-situ polymerization. After the reaction was completed, the reaction system was naturally cooled to room temperature. The pH of the emulsion was adjusted to 7-8 with 10% sodium hydroxide aqueous solution to terminate the reaction. The reaction product was centrifuged at 3000 rpm for 10 min and washed with anhydrous ethanol and deionized water alternately 3-5 times. The washed product was placed in a vacuum drying oven at 45°C and dried for 12 h until constant weight was obtained to obtain the microencapsulated phase change material.

[0027] Preparation Example 2 A microencapsulated phase change material is prepared by the following steps: Add 60 kg of paraffin wax and 1 kg of sodium dodecyl sulfate (emulsifier) ​​to 90 kg of deionized water, heat the mixture in a water bath to 65°C, and emulsify it at a high speed of 8000 rpm for 10 minutes to form a preliminary O / W type emulsion. The preliminary emulsion was transferred to a high-pressure homogenizer and homogenized three times at 65°C and 40 MPa to obtain a milky white, uniform, and stable paraffin / O / W pre-emulsion. The average droplet size of the emulsion was controlled at 1-5 μm. 40 kg of 50% hydroxymethylated melamine aqueous solution was slowly added to the emulsion, and then the pH of the reaction system was slowly adjusted to 4.0-4.5 with 10% citric acid aqueous solution. The reaction was continued for 3 hours under stirring at 65°C and 400 rpm for in-situ polymerization. After the reaction was completed, the reaction system was naturally cooled to room temperature. The pH of the emulsion was adjusted to 7-8 with 10% sodium hydroxide aqueous solution to terminate the reaction. The reaction product was centrifuged at 3000 rpm for 10 min and washed with anhydrous ethanol and deionized water alternately 3-5 times. The washed product was placed in a vacuum drying oven at 40°C and dried for 12 h until constant weight was obtained to obtain the microencapsulated phase change material.

[0028] Preparation Example 3 A microencapsulated phase change material is prepared by the following steps: Add 80 kg of paraffin wax and 5 kg of sodium dodecyl sulfate (emulsifier) ​​to 95 kg of deionized water. Heat the mixture in a water bath to 65°C and emulsify it at a high-speed shear rate of 8000 rpm for 10 minutes to form a preliminary O / W type emulsion. The preliminary emulsion was transferred to a high-pressure homogenizer and homogenized three times at 65°C and 50 MPa to obtain a milky white, uniform, and stable paraffin / O / W pre-emulsion. The average droplet size of the emulsion was controlled at 1-5 μm. 20 kg of 50% hydroxymethylated melamine aqueous solution was slowly added to the emulsion, and then the pH of the reaction system was slowly adjusted to 4.0-4.5 with 10% citric acid aqueous solution. The reaction was continued for 4 hours under stirring at 65°C and 300 rpm for in-situ polymerization. After the reaction was completed, the reaction system was naturally cooled to room temperature. The pH of the emulsion was adjusted to 7-8 with 10% sodium hydroxide aqueous solution to terminate the reaction. The reaction product was centrifuged at 3000 rpm for 10 min and washed with anhydrous ethanol and deionized water alternately 3-5 times. The washed product was placed in a vacuum drying oven at 50°C and dried for 12 h until constant weight was obtained to obtain the microencapsulated phase change material.

[0029] Preparation example of modified short-cut carbon fibers Preparation Example 4 A modified chopped carbon fiber, prepared by the following steps: 1 kg of graphene oxide was added to 90 kg of water and ultrasonically treated at 400 W for 45 min to obtain a preliminary dispersed aqueous dispersion of graphene oxide. Then, 25 kg of anhydrous ethanol was added and stirred evenly at room temperature. 7 kg of silane coupling agent was added and stirred continuously to mix evenly. During stirring, 10% citric acid aqueous solution was added to adjust the pH of the reaction system to 4.0-5.0. The reaction was stirred at 70 °C for 6 hours to obtain a graphene-modified silane coupling agent dispersion. 15 kg of chopped carbon fibers were immersed in a dispersion solution, ultrasonically treated at 55°C and 200 W for 15 minutes, then removed and pre-dried at 70°C for 1.5 h, followed by heat treatment at 120°C for 2 h, and then cooled to room temperature to obtain chopped carbon fibers with a graphene-modified silane coupling agent layer on the surface; the length of the chopped carbon fibers was 6-12 mm.

[0030] Preparation Example 5 A modified chopped carbon fiber, prepared by the following steps: 0.5 kg of graphene oxide was added to 100 kg of water and ultrasonically treated at 300 W for 60 min to obtain a preliminary dispersed aqueous dispersion of graphene oxide. Then, 20 kg of anhydrous ethanol was added and stirred evenly at room temperature. 3 kg of silane coupling agent was added and stirred continuously to mix evenly. During stirring, 10% citric acid aqueous solution was added to adjust the pH of the reaction system to 4.0-5.0. The reaction was stirred at 60 °C for 8 hours to obtain a graphene-modified silane coupling agent dispersion. 10 kg of chopped carbon fibers were immersed in a dispersion solution, ultrasonically treated at 50°C and 300 W for 10 minutes, then removed and pre-dried at 60°C for 2 hours. The temperature was then raised to 115°C for 2.5 hours and cooled to room temperature to obtain chopped carbon fibers with a graphene-modified silane coupling agent layer on the surface. The length of the chopped carbon fibers was 6-12 mm.

[0031] Preparation Example 6 A modified chopped carbon fiber, prepared by the following steps: 2 kg of graphene oxide was added to 80 kg of water and ultrasonically treated at 500 W for 60 min to obtain a preliminary dispersed aqueous dispersion of graphene oxide. Then, 30 kg of anhydrous ethanol was added and stirred evenly at room temperature. 10 kg of silane coupling agent was added and stirred continuously to mix evenly. During stirring, 10% citric acid aqueous solution was added to adjust the pH of the reaction system to 4.0-5.0. The reaction was stirred at 80 °C for 4 hours to obtain a graphene-modified silane coupling agent dispersion. 20 kg of chopped carbon fibers were immersed in a dispersion solution, ultrasonically treated at 60°C and 200 W for 30 minutes, then removed and pre-dried at 80°C for 1 hour. The temperature was then raised to 125°C for 1.5 hours and cooled to room temperature to obtain chopped carbon fibers with a graphene-modified silane coupling agent layer on the surface. The length of the chopped carbon fibers was 6-12 mm.

[0032] Example

[0033] Example 1

[0034] A graphene-based conductive concrete for snow melting and de-icing is prepared by the following steps: S1. Dry mixing: Mix 100kg of cement, 30kg of fly ash (admixture), 175kg of aggregate, and 2kg of conductive filler evenly; the conductive filler is composed of graphene nanosheets and modified short-cut carbon fibers prepared in Preparation Example 4 at a weight ratio of 1:0.8; wherein the thickness of the graphene nanosheets is 5-10nm. S2. Wet mixing: Add 1 kg of polycarboxylate superplasticizer to 40 kg of water and stir evenly. Then slowly pour it into the dry mixture of S1 and stir until a slurry with good fluidity and uniform color is formed. S3. Add phase change material: Add 20 kg of the microencapsulated phase change material from Preparation Example 1 to the slurry from step S2, and stir at 80 rpm for 2-3 minutes under a vacuum of -0.08 MPa to obtain the concrete mixture. S4. Casting and molding: Pour the mixture into the mold, vibrate to compact it, and cure according to standard.

[0035] Example 2

[0036] A graphene-based conductive concrete for snow melting and de-icing is prepared by the following steps: S1. Dry mixing: Mix 90 kg of cement, 40 kg of fly ash (admixture), 150 kg of aggregate, and 1 kg of conductive filler evenly; the conductive filler is composed of graphene nanosheets and modified short-cut carbon fibers prepared in Preparation Example 5 in a weight ratio of 1:1.2; wherein the thickness of the graphene nanosheets is 5-10 nm. S2. Wet mixing: Add 0.5 kg of polycarboxylate superplasticizer to 45 kg of water and stir evenly. Then slowly pour it into the dry mixture of S1 and stir until a slurry with good fluidity and uniform color is formed. S3. Add phase change material: Add 15 kg of the microencapsulated phase change material from Preparation Example 2 to the slurry in step S2, and stir at 80 rpm for 2-3 minutes under a vacuum of -0.08 MPa to obtain concrete mixture; S4. Casting and molding: Pour the mixture into the mold, vibrate to compact it, and cure according to standard.

[0037] Example 3

[0038] A graphene-based conductive concrete for snow melting and de-icing is prepared by the following steps: S1. Dry mixing: Mix 110 kg of cement, 20 kg of fly ash (admixture), 200 kg of aggregate, and 3 kg of conductive filler evenly; the conductive filler is composed of graphene nanosheets and modified short-cut carbon fibers prepared in Preparation Example 6 at a weight ratio of 1:0.5; wherein the thickness of the graphene nanosheets is 5-10 nm. S2. Wet mixing: Add 2 kg of polycarboxylate superplasticizer to 30 kg of water and stir evenly. Then slowly pour it into the dry mixture of S1 and stir until a slurry with good fluidity and uniform color is formed. S3. Add phase change material: Add 25 kg of the microencapsulated phase change material of Preparation Example 3 to the slurry in step S2, and stir at 80 rpm for 2-3 minutes under a vacuum of -0.08 MPa to obtain concrete mixture; S4. Casting and molding: Pour the mixture into the mold, vibrate to compact it, and cure according to standard.

[0039] Example 4

[0040] A graphene-based conductive concrete for snow melting and de-icing differs from Example 1 in that the conductive filler in this example is composed of graphene nanosheets and unmodified ordinary short-cut carbon fibers (i.e., short-cut carbon fibers with a length of 6-12 mm that have not undergone the process of Preparation Examples 4-6) in a weight ratio of 1:0.8. The remaining raw materials and preparation steps are exactly the same as in Example 1.

[0041] Comparative Example Comparative Example 1 A graphene-based snow melting and de-icing conductive concrete differs from Example 1 in that no microencapsulated phase change material is added in this comparative example; its weight is replaced by an equal amount of admixture (fly ash), i.e., the amount of fly ash is 50 kg. The remaining raw materials and preparation steps are exactly the same as in Example 1.

[0042] Comparative Example 2 A graphene-based conductive concrete for snow melting and de-icing differs from Example 1 in that: no conductive filler was added in this comparative example (i.e., no graphene nanosheets and modified short-cut carbon fibers were added), while the remaining raw materials and preparation steps were exactly the same as in Example 1.

[0043] Comparative Example 3 A graphene-based snow-melting and ice-removing conductive concrete differs from Example 1 in that: in this comparative example, the same mass of unencapsulated ordinary paraffin is used to directly replace the "microencapsulated phase change material," while the remaining raw materials and preparation steps are exactly the same as in Example 1.

[0044] Comparative Example 4 A graphene-based snow melting and de-icing conductive concrete has the same raw material composition as Example 1, but the preparation method is different: in step S3, instead of using vacuum stirring technology, the microencapsulated phase change material is added to the slurry at a conventional speed of 300 rpm under normal pressure and stirred until uniform. The remaining steps are the same as in Example 1.

[0045] Performance testing Detection methods / test methods Compressive strength: The compressive strength of the test specimen (150mm×150mm×150mm cube) was tested according to the relevant methods in GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Electrical conductivity: The volume resistivity of the specimen was obtained by testing the specimen using the four-electrode method (four-probe method) in GB / T 34982-2017 "Test Method for Electrical Conductivity of Concrete". Electric heating and de-icing performance testing: The test was conducted in accordance with the test principle of surface working temperature and temperature uniformity in JG / T 286-2010 "Electric Heating Film for Building". The test was combined with the characteristics of concrete materials and de-icing application scenarios to test the time required to heat up to 20℃, the steady-state temperature after 60 minutes, and the surface temperature uniformity (i.e. the temperature difference between the highest and lowest points). Freeze-thaw cycle resistance: According to the "rapid freezing method" in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", the dynamic elastic modulus retention rate of the test specimen is tested after 300 freeze-thaw cycles, from +5℃ to -18℃ and then back to +5℃.

[0046] Table 1 Test Data

[0047] Combining Examples 1-3 and Comparative Example 1 with Table 1, it can be seen that the test data of Examples 1-3 are superior to those of Comparative Example 1, indicating that the introduction of microencapsulated phase change materials into concrete can significantly improve the freeze-thaw cycle durability of the material without significantly affecting its electrical and electrothermal properties. This confirms that phase change materials, through their heat storage and temperature regulation functions, effectively buffer internal temperature stress, thereby playing a crucial protective and reinforcing role in the long-term performance stability of concrete in cold environments.

[0048] Combining Examples 1-3 and Comparative Example 2 with Table 1, it can be seen that the test data of Examples 1-3 are better than those of Comparative Example 2. This indicates that the conductive filler composed of graphene nanosheets and short-cut carbon fibers is the core functional component that gives concrete the ability to conduct electricity and generate heat. The three-dimensional conductive network constructed by it is the basis for achieving a rapid and uniform electrothermal response. Without this component, the material will completely lose its active ice-melting function.

[0049] Combining Examples 1-3 and Comparative Example 3 with Table 1, it can be seen that the test data of Examples 1-3 are superior to those of Comparative Example 3. This indicates that microencapsulation of phase change paraffin with a hydroxymethylated melamine shell effectively prevents leakage of the phase change material during operation, avoiding damage to the cement matrix structure. Thus, while ensuring the phase change temperature regulation function, it significantly improves the mechanical strength and long-term durability of concrete.

[0050] Combining Examples 1-3 and Comparative Example 4 with Table 1, it can be seen that the test data of Examples 1-3 are better than those of Comparative Example 4. This indicates that the preparation process of incorporating microencapsulated phase change materials at low speed using vacuum stirring technology can effectively protect the integrity of the microcapsule structure and reduce air bubbles in the mixture, thereby optimizing the microstructure of concrete and having a positive effect on improving the electrical conductivity uniformity, electrothermal efficiency and comprehensive mechanical properties of the final product.

[0051] Combining Examples 1 and 4 with Table 1, it can be seen that the test data of Example 1 are better than those of Example 4. This indicates that surface treatment of short-cut carbon fibers with graphene-modified silane coupling agent can significantly improve the interfacial bonding between the fiber and the cement matrix and optimize its electrical connection efficiency in the conductive network, thereby effectively improving the conductivity, electrothermal response speed, mechanical properties and freeze-thaw durability of concrete.

[0052] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A graphene-based conductive concrete for snow melting and de-icing, characterized in that, The raw materials include the following parts by weight: 90-110 parts cement, 15-25 parts microencapsulated phase change material, 1-3 parts conductive filler, 150-200 parts aggregate, 20-40 parts admixture, 0.5-2 parts water-reducing agent, and 30-45 parts water; the core material of the microencapsulated phase change material is paraffin wax with a phase change temperature of 3-5℃, and the outer shell is hydroxymethylated melamine.

2. The graphene-based snow-melting and de-icing conductive concrete according to claim 1, characterized in that: The conductive filler is composed of graphene nanosheets and chopped carbon fibers in a weight ratio of 1:0.5-1.

2.

3. The graphene-based snow-melting, de-icing, and conductive concrete according to claim 1, characterized in that: The thickness of the graphene nanosheets is 5-10 nm; the length of the chopped carbon fibers is 6-12 mm.

4. The graphene-modified conductive concrete for snow melting and de-icing according to claim 1, characterized in that: The microencapsulated phase change material is prepared by the following steps: Paraffin wax and hydroxymethylated melamine are emulsified with an emulsifier to form a stable O / W emulsion. Subsequently, a polymer shell is formed on the surface of the core material droplets through in-situ polymerization. After solid-liquid separation, washing, and drying, microencapsulated phase change material is obtained.

5. The graphene-based snow-melting and de-icing conductive concrete according to claim 1, characterized in that: The microencapsulated phase change material comprises 60-80 parts by weight of paraffin, 20-40 parts by weight of an aqueous solution of hydroxymethylated melamine, 1-5 parts by weight of an emulsifier, and 90-100 parts by weight of deionized water.

6. The graphene-modified conductive concrete for snow melting and de-icing according to claim 2, characterized in that: The chopped carbon fiber is a modified chopped carbon fiber with a graphene-modified silane coupling agent layer coated on its surface, and the coating thickness is 0.1-0.3 μm.

7. The graphene-modified conductive concrete for snow melting and de-icing according to claim 6, characterized in that: The modified short-cut carbon fibers are prepared by the following steps: Graphene oxide was dispersed in a mixed solvent of ethanol and water and ultrasonically treated to obtain a uniform dispersion. A silane coupling agent was added, the pH was adjusted to 4-5 with acid, and the mixture was stirred at 60-80℃ for 4-8 hours to obtain a graphene-modified silane coupling agent dispersion. The short-cut carbon fibers are immersed in the dispersion obtained in step A, ultrasonically dispersed for 10-30 minutes, then removed, dried, and heat-treated at 115-125℃ for 1.5-2.5 hours. After cooling to room temperature, short-cut carbon fibers with a graphene-modified silane coupling agent layer on the surface are obtained.

8. The graphene-modified conductive concrete for snow melting and de-icing according to claim 7, characterized in that: The modified chopped carbon fiber comprises the following raw materials in parts by weight: 0.5-2 parts graphene oxide, 20-30 parts deionized water, 80-100 parts anhydrous ethanol, 3-10 parts silane coupling agent, and 10-20 parts chopped carbon fiber.

9. A method for preparing graphene-based snow-melting and de-icing conductive concrete according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Dry mixing: Mix cement, admixtures, aggregates, and conductive fillers evenly; S2. Wet mixing: Add water-reducing agent and water to the dry mixture from step S1 and stir to form a uniform slurry; S3. Add phase change material: Add microencapsulated phase change material to the slurry in step S2, and stir at low speed using vacuum stirring technology until uniform to obtain concrete mixture; S4. Casting and molding: Pour the mixture into the mold, vibrate to compact it, and cure according to standard.

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