Crack self-healing composite material for railway concrete and preparation method thereof

Abstract

The invention relates to a crack self-healing composite material for railway concrete and a preparation method thereof, and belongs to the technical field of civil engineering materials, the crack self-healing composite material comprises a concrete matrix and self-healing systems distributed in the concrete matrix; the self-healing system comprises: a phase change microcapsule, the core material of which is an organic phase change material with a phase change temperature of 30-40 DEG C, and the wall material of which is a polymer shell; the nanometer nucleation agent is a nanometer material which is subjected to surface modification and can promote crystallization of the organic phase change material; the bionic capillary network is formed by hollow fiber tubes filled with a repairing agent in a three-dimensional grid form; the internal curing water source is provided by super absorbent polymer particles; four bionic principles of'microcapsule rupture ', 'capillary delivery', 'nanocrystal nucleus guide 'and'internal maintenance' are integrated, so that full-scale and intelligent self-repairing from nanoscale pores to macroscopic cracks is realized, and the repairing effect is more comprehensive and more reliable.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering materials technology, specifically referring to a self-healing composite material for cracks in railway concrete and its preparation method. Background Technology

[0002] Concrete, as the most widely used material in modern civil engineering, has always posed a challenge due to its inherent brittleness and susceptibility to cracking. In railway engineering, factors such as the cyclical load of high-speed trains, diurnal temperature variations, and foundation settlement can easily lead to micro-cracks in concrete track slabs, bridges, sleepers, and other components. These cracks provide pathways for the intrusion of moisture, chloride ions, and other harmful substances, accelerating steel corrosion and concrete deterioration, seriously threatening train safety and significantly increasing subsequent maintenance costs.

[0003] To address this problem, self-healing concrete technology has emerged. Existing technologies mainly include: Microbial remediation technology involves encapsulating calcium carbonate-producing microorganisms and their nutrient sources and then incorporating them into concrete. When cracks form, moisture intrusion activates the microorganisms, and their metabolic products induce calcium carbonate deposition to fill the cracks. However, this technology suffers from drawbacks such as low microbial survival rate in the highly alkaline environment of concrete, slow repair speed, and significant temperature-dependent repair effects.

[0004] Encapsulation repair technology: Repair agents (such as epoxy resin or sodium silicate) are encapsulated in brittle capsules and dispersed in concrete. Crack propagation causes the capsules to rupture, releasing the repair agent and achieving repair. However, this technology is typically a one-time repair, and the random distribution of capsules may lead to incomplete repair. Furthermore, common repair agents crystallize slowly and randomly in the alkaline environment of concrete, resulting in repairs with low strength.

[0005] Shape memory alloy / polymer technology: This technology utilizes the shape memory effect of materials to generate restoring forces under specific conditions (such as heating), forcing cracks to close. However, this method requires external energy input, is complex, and expensive, making it difficult to widely apply in large-scale civil engineering projects.

[0006] Vascular network repair technology: Hollow fiber or three-dimensional pipe network is pre-embedded in concrete and a repair agent is injected. This technology can achieve multiple repairs, but the network is prone to blockage or damage during concrete vibration, and the delivery and triggering mechanism of the repair agent is difficult to control.

[0007] In summary, existing technologies mostly rely on a single repair mechanism, which has limitations such as low repair efficiency, uncontrollable effects, and the ability to repair only micro-cracks or require external intervention. Therefore, developing a self-healing concrete composite material that can intelligently respond, work synergistically, cover multi-scale cracks, and requires no external energy has become an urgent technological need in this field. Summary of the Invention

[0008] In order to overcome some of the problems mentioned in the background above, the present invention provides a self-healing composite material for cracks in railway concrete and a method for preparing the same, so as to at least partially solve the above problems.

[0009] According to the technical solution of the present invention, a self-healing composite material for cracks in railway concrete is provided, characterized in that it includes a concrete matrix and a self-healing system distributed in the concrete matrix; the self-healing system includes: Phase change microcapsules have an organic phase change material as the core material and a polymer shell as the wall material. The nanocrystallization nucleating agent is a surface-modified nanomaterial that can promote the crystallization of the organic phase change material. The biomimetic microvascular network is composed of hollow fiber tubes filled with repair agent in a three-dimensional mesh form; The internal water source is provided by superabsorbent polymer particles.

[0010] Preferably, the core material of the phase change microcapsule is n-eicosane, and the wall material is one of polyurea-formaldehyde, melamine-formaldehyde resin, or polymethyl methacrylate. The phase change microcapsules have a particle size of 50-150 μm and their volume content accounts for 3%-8% of the total volume of concrete cementitious materials.

[0011] Preferably, the nanocrystalline nucleating agent is silane coupling agent-modified nano-graphene oxide or surfactant-modified amorphous calcium carbonate; The dosage of the nanocrystalline nucleating agent is 0.5%-1.5% of the mass of the concrete cementitious material.

[0012] Preferably, the nanocrystalline nucleating agent contains nano-graphene oxide sheets with a diameter of 100-500 nm and a thickness of 1-3 atomic layers.

[0013] Preferably, the hollow fiber tubes in the biomimetic microvascular network are borosilicate glass fiber tubes or biodegradable polymer tubes, with an outer diameter of 1-3 mm and an inner diameter of 0.5-2 mm. The repair agent is one of low-viscosity epoxy resin, cyanoacrylate, or silicone-based sealant; the hollow fiber tubes are arranged at intervals of 5-15 cm in the concrete matrix.

[0014] Preferably, the internal curing water source is cross-linked sodium polyacrylate superabsorbent polymer particles with a particle size of 40-100μm and an admixture amount of 0.3%-1.0% of the mass of concrete cementitious materials.

[0015] On the other hand, the present invention also provides a method for preparing a self-healing composite material for cracks in railway concrete, comprising the following steps: (1) Preparation of phase change microcapsules and modified nanocrystalline nuclei; (2) Prepare and fill the biomimetic microvascular network; (3) Dry mix cement, aggregate, phase change microcapsules, nanocrystalline nucleating agent and superabsorbent polymer dry powder, and stir evenly to obtain dry mix; (4) Add mixing water to the dry mix from step (3) and stir to form a concrete mixture; (5) After pouring a layer of the concrete mixture into the mold, the biomimetic microvascular network is laid out, and then the remaining mixture is poured and tamped to form the shape.

[0016] Preferably, the phase change microcapsules in step (1) are prepared by in-situ polymerization, including the following steps: Organic phase change materials are emulsified and dispersed in an aqueous phase, and wall material monomers or prepolymers are added. The pH is adjusted to acidic and the temperature is controlled while stirring to carry out the polymerization reaction. After the reaction is completed, the microcapsule powder is obtained by washing and drying.

[0017] Preferably, the preparation of the modified nanocrystalline nucleating agent in step (1) includes the following steps: Nanoscale graphene oxide was dispersed in a solvent, a silane coupling agent was added, and surface grafting modification was carried out under heating and reflux conditions. The modified product was then obtained by centrifugation, washing and drying.

[0018] Preferably, the vibration in step (5) is performed by a low amplitude of 0.1-0.4 mm and a high frequency of 150-250 Hz, wherein the vibrating rod avoids direct contact with the deployed biomimetic microvascular network to prevent its damage.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: Synergistic effect of multiple biomimetic mechanisms: It innovatively integrates four biomimetic principles, namely "microcapsule rupture", "microvascular delivery", "nanocrystalline nucleus guidance" and "internal maintenance", to achieve full-scale, intelligent self-repair from nanoscale pores to macroscopic cracks, with more comprehensive and reliable repair effects.

[0020] Repair efficiency and quality are significantly improved: By introducing nanocrystal nucleating agents, the crystallization process of n-eicosane in hydrophobic repair agents is effectively guided and accelerated, forming a dense, interwoven network repair body, overcoming the defects of random, loose, and low-strength crystallization of traditional repair agents.

[0021] Intelligent Response and Active Repair: The material possesses intelligent characteristics of "sensing-response-repair". Phase change microcapsules respond to cracks and temperature, and microvascular networks respond directionally to wider cracks, achieving on-demand repair and reducing the ineffective consumption of repair agents.

[0022] Integrated Functions: The phase change microcapsules simultaneously serve as both a "repair agent carrier" and a "thermal buffer unit," helping to mitigate the formation of temperature cracks from the source; the internal curing water source serves both the goals of "internal curing of concrete" and "maintaining a self-healing environment," enhancing the material's basic performance and durability.

[0023] High feasibility for engineering applications: The preparation method fully considers existing concrete production processes while ensuring functionality. Key components can be prepared in advance, and the on-site pouring process requires minimal adjustments, making it easy to promote industrialization. Detailed Implementation

[0024] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0025] This invention provides a self-healing composite material for cracks in railway concrete and a method for preparing the same, in order to at least partially solve the above-mentioned problems.

[0026] According to the technical solution of the present invention, a self-healing composite material for cracks in railway concrete is provided, characterized in that it includes a concrete matrix and a self-healing system distributed in the concrete matrix; the self-healing system includes: Phase change microcapsules have an organic phase change material as the core material and a polymer shell as the wall material. The nanocrystallization nucleating agent is a surface-modified nanomaterial that can promote the crystallization of the organic phase change material. The biomimetic microvascular network is composed of hollow fiber tubes filled with repair agent in a three-dimensional mesh form; The internal water source is provided by superabsorbent polymer particles.

[0027] In a further embodiment of this example, the core material of the phase change microcapsule is n-eicosane, and the wall material is one of polyurea-formaldehyde, melamine-formaldehyde resin, or polymethyl methacrylate. The phase change microcapsules have a particle size of 50-150 μm and their volume content accounts for 3%-8% of the total volume of concrete cementitious materials.

[0028] In a further embodiment of this example, the nanocrystal nucleating agent is silane coupling agent-modified nano-graphene oxide or surfactant-modified amorphous calcium carbonate. The dosage of the nanocrystalline nucleating agent is 0.5%-1.5% of the mass of the concrete cementitious material.

[0029] In a further embodiment of this example, the nanocrystalline nucleating agent contains nano-graphene oxide sheets with a diameter of 100-500 nm and a thickness of 1-3 atomic layers.

[0030] In a further embodiment of this example, the hollow fiber tube in the biomimetic microvascular network is a borosilicate glass fiber tube or a biodegradable polymer tube, with an outer diameter of 1-3 mm and an inner diameter of 0.5-2 mm. The repair agent is one of low-viscosity epoxy resin, cyanoacrylate, or silicone-based sealant; the hollow fiber tubes are arranged at intervals of 5-15 cm in the concrete matrix.

[0031] In a further embodiment of this example, the internal curing water source is cross-linked sodium polyacrylate superabsorbent polymer particles with a particle size of 40-100μm and a dosage of 0.3%-1.0% of the mass of concrete cementitious materials.

[0032] On the other hand, embodiments of the present invention also provide a method for preparing a self-healing composite material for cracks in railway concrete, comprising the following steps: (1) Preparation of phase change microcapsules and modified nanocrystalline nuclei; (2) Prepare and fill the biomimetic microvascular network; (3) Dry mix cement, aggregate, phase change microcapsules, nanocrystalline nucleating agent and superabsorbent polymer dry powder, and stir evenly to obtain dry mix; (4) Add mixing water to the dry mix from step (3) and stir to form a concrete mixture; (5) After pouring a layer of the concrete mixture into the mold, the biomimetic microvascular network is laid out, and then the remaining mixture is poured and tamped to form the shape.

[0033] In a further embodiment of this example, the phase change microcapsules in step (1) are prepared by in-situ polymerization, including the following steps: Organic phase change materials are emulsified and dispersed in an aqueous phase, and wall material monomers or prepolymers are added. The pH is adjusted to acidic and the temperature is controlled while stirring to carry out the polymerization reaction. After the reaction is completed, the microcapsule powder is obtained by washing and drying.

[0034] In a further embodiment of this example, the preparation of the modified nanocrystalline nucleating agent in step (1) includes the following steps: Nanoscale graphene oxide was dispersed in a solvent, a silane coupling agent was added, and surface grafting modification was carried out under heating and reflux conditions. The modified product was then obtained by centrifugation, washing and drying.

[0035] In a further embodiment of this example, the vibration in step (5) is performed by a low amplitude of 0.1-0.4 mm and a high frequency of 150-250 Hz, wherein the vibrating rod avoids direct contact with the deployed biomimetic microvascular network to prevent its damage.

[0036] It should be noted that phase change microcapsules serve as the primary response mechanism for microcracks. Stress concentration at the crack tip causes the crack wall to rupture, allowing liquid n-eicosane to flow out and rapidly fill the crack space due to its excellent permeability (derived from low surface tension). Subsequently, nanocrystalline nucleating agents play a crucial role; their surfaces, being hydrophobic n-eicosane, provide numerous nucleation sites, significantly reducing the energy barrier required for crystallization. This guides the formation of a dense, interwoven network crystal structure, rather than loose, coarse crystals, thus achieving efficient and robust filling.

[0037] For wider cracks, a biomimetic microvascular network is activated. The crack causes the microvessels to rupture, and the low-viscosity epoxy resin repair agent inside is precisely and directionally delivered to the damaged area driven by the capillary effect. After the epoxy resin comes into contact with the concrete, it reacts with the latent curing agent or absorbs moisture from the air (moisture-curing type) and gradually cures into a high-strength polymer, achieving mechanical repair of the structural crack.

[0038] Throughout the process, the slowly released water from the internal curing water source (SAP) provides water for the continuous hydration of unhydrated cement particles, and the newly generated hydration products (CSH gel) can automatically seal finer pores and cracks. On the other hand, it provides the necessary moist environment for the repair interface, ensuring the smooth progress of all repair chemical reactions. Example 1

[0039] Pre-preparation of functional components: Phase change microcapsules: Add 100g of n-eicosane to 300g of deionized water, add 1g of sodium dodecyl sulfate, and emulsify at 10000rpm for 15 minutes in a 60°C water bath to form a stable emulsion.

[0040] Transfer the emulsion to a three-necked flask and slowly add a prepolymer solution prepared from 37% formaldehyde and urea in a molar ratio of 1.5:1. Adjust the pH to 3.0 with citric acid.

[0041] The reaction was carried out at 60°C with continuous stirring at 400 rpm for 4 hours.

[0042] After the reaction was completed, the mixture was filtered, washed, and dried under vacuum at 40°C for 24 hours to obtain white powdered polyurea-formaldehyde encapsulated n-eicosane phase change microcapsules with an average particle size of about 100 μm.

[0043] Nanocrystalline nucleating agent: 1g of nano-graphene oxide was dispersed in 200g of a 4:1 volume ratio ethanol / water mixed solvent and ultrasonically treated for 1 hour.

[0044] Add 0.1g of KH-560 silane coupling agent, then stir magnetically for 30 minutes. Reflux the system at 80°C for 6 hours, then centrifuge, wash with ethanol, and freeze-dry to obtain modified nano-graphene oxide powder.

[0045] Bionic microvascular network: Select a borosilicate glass fiber tube with an outer diameter of 2mm and an inner diameter of 1.5mm, cut it, and then fill it with a low-viscosity (~450cP) moisture-curing epoxy resin repair agent.

[0046] Seal both ends of the tube with hydrolyzable PLA plastic caps.

[0047] Composite material preparation and casting: Mix proportion (per 1 m³): Cementing materials: 400 kg of P.O52.5 cement and 40 kg of modified calcium carbonate powder with an average particle size of 10 μm.

[0048] Aggregates: sand, gravel, water; admixtures: polycarboxylate superplasticizer.

[0049] Functional components: Phase change microcapsules, modified nano-graphene oxide, superabsorbent polymer (SAP).

[0050] Preparation process: Cement, stone powder, aggregate, phase change microcapsules, modified nano-graphene oxide, and SAP dry powder are poured into a forced mixer and dry-mixed for 5 minutes. The volume of phase change microcapsules accounts for 5% of the total volume of concrete cementitious materials, the volume of modified nano-graphene oxide accounts for 0.8% of the total mass of concrete cementitious materials, and the volume of SAP dry powder is 0.5% of the mass of concrete cementitious materials.

[0051] Add the mixing water containing the water-reducing agent, stir at low speed for 2 minutes, then stir at high speed for 3 minutes to obtain the mixture.

[0052] Pour a mixture approximately 2 cm thick into the bottom of a 100 mm × 100 mm × 400 mm mold.

[0053] The pre-filled biomimetic microvascular network was manually laid out with a grid spacing of 10cm×10cm.

[0054] Slowly pour the remaining concrete, using a small vibrator (25mm in diameter) for gentle compaction, and strictly control the vibrator to avoid touching the capillaries.

[0055] Cover with plastic film and cure in a standard curing room (20±2°C, RH≥95%) for 28 days. Example 2

[0056] The difference from Example 1 is that the nanocrystalline nucleating agent used is amorphous calcium carbonate; The volumetric content of phase change microcapsules accounts for 5% of the total volume of concrete cementitious materials, the content of modified nano-graphene oxide accounts for 1% of the total mass of concrete cementitious materials, and the content of SAP dry powder is 0.5% of the mass of concrete cementitious materials. Example 3

[0057] The difference from Example 1 is that the biomimetic microvascular network process is omitted. Example 4

[0058] The difference from Example 1 is that the volume of phase change microcapsules accounts for 3% of the total volume of the concrete cementitious material, the modified nano-graphene oxide accounts for 0.8% of the total mass of the concrete cementitious material, and the SAP dry powder content is 0.5% of the mass of the concrete cementitious material. Example 5

[0059] The difference from Example 1 is that the volume of phase change microcapsules accounts for 8% of the total volume of the concrete cementitious material, the content of modified nano-graphene oxide accounts for 0.8% of the total mass of the concrete cementitious material, and the content of SAP dry powder is 0.5% of the mass of the concrete cementitious material. Example 6

[0060] The difference from Example 1 is that the volume of phase change microcapsules accounts for 5% of the total volume of the concrete cementitious material, the modified nano-graphene oxide accounts for 0.8% of the total mass of the concrete cementitious material, and SAP dry powder is not added.

[0061] Comparative Example 1 The difference from Example 1 is that the volumetric dosage of phase change microcapsules accounts for 3% of the total volume of concrete cementitious materials, and modified nano-graphene oxide and SAP dry powder are not doped.

[0062] Comparative Example 2 The difference from Example 1 is that the phase change microcapsules are not doped, the modified nano-graphene oxide is not doped, and the SAP dry powder content is 0.5% of the mass of the concrete cementitious material.

[0063] Comparative Example 3 Concrete without phase change microcapsules, modified nano-graphene oxide, and SAP dry powder.

[0064] The data obtained from the tests conducted on the concrete obtained in Examples 1-6 and Comparative Examples 1-3 are shown in the following tables.

[0065] Table 1 Crack width repair rate (%) Group 0.1mm crack 0.3mm crack 0.5mm crack Example 1 98.2±1.1 95.6±1.8 88.3±2.4 Example 2 96.5±1.3 92.8±2.1 85.1±2.8 Example 3 94.3±1.5 87.2±2.5 72.6±3.2 Example 4 92.1±1.7 85.3±2.7 70.8±3.4 Example 5 97.8±1.2 94.1±1.9 86.9±2.6 Example 6 90.5±1.9 83.7±2.9 68.3±3.6 Comparative Example 1 75.3±2.8 58.6±3.5 42.1±4.2 Comparative Example 2 65.2±3.2 52.3±3.8 48.7±4.1 Comparative Example 3 12.5±4.1 8.3±4.5 5.2±4.8 Table 2 Ultrasonic speed recovery rate (%) Group 0.1mm crack 0.3mm crack 0.5mm crack Example 1 96.8±1.2 93.5±1.7 89.2±2.2 Example 2 94.2±1.4 90.8±2.0 86.5±2.5 Example 3 91.5±1.6 85.3±2.4 78.9±3.0 Comparative Example 1 72.6±2.9 61.8±3.3 53.2±3.8 Comparative Example 2 68.3±3.1 63.5±3.2 59.7±3.5 Comparative Example 3 45.2±4.2 38.7±4.5 32.1±4.7 Table 3 Bending strength recovery rate (%) Group 0.1mm crack 0.3mm crack 0.5mm crack Example 1 92.5±2.1 88.3±2.8 83.7±3.2 Example 2 90.8±2.3 85.6±3.0 80.2±3.5 Example 3 87.2±2.6 80.1±3.3 72.8±3.8 Comparative Example 1 65.3±3.8 52.7±4.2 41.3±4.6 Comparative Example 2 62.8±3.9 58.3±4.1 53.6±4.3 Comparative Example 3 35.2±4.8 28.7±5.1 22.4±5.3 Table 4. Improvement rate of chloride ion permeability (28 days, %) Group Improvement rate Example 1 85.3±2.5 Example 2 82.1±2.8 Example 3 78.6±3.1 Comparative Example 1 45.2±4.3 Comparative Example 2 51.7±4.1 Comparative Example 3 15.3±5.2 Table 5 Comprehensive Performance Evaluation Group Microcrack repair (0.1mm) Repair of a medium-sized crack (0.3mm) Repair of wide cracks (0.5mm) Comprehensive evaluation Example 1 excellent excellent excellent Optimal Example 2 excellent excellent good excellent Example 3 excellent good generally good Example 4 excellent good generally good Example 5 excellent excellent good excellent Example 6 excellent good generally good Comparative Example 1 generally generally Difference generally Comparative Example 2 generally generally Difference generally Comparative Example 3 Difference Difference Difference Difference The experimental methods for the above experimental data are as follows: Crack induction: The three-point bending method was used to load the specimen on a universal testing machine until cracks of predetermined widths (0.1 mm, 0.3 mm, 0.5 mm) were generated.

[0066] Self-healing conditions: temperature 35±2°C, relative humidity 95±3%, curing time 28 days.

[0067] The test metrics and methods are shown in Table 6 below: Table 6 Test metrics Test methods Test Standards Crack width variation Digital Microscope Measurement ASTM E1853 Ultrasonic recovery rate Ultrasonic pulse velocity test ASTM C597 Strength recovery rate Three-point bending strength test ASTM C293 Permeability restoration Chloride ion permeability test ASTM C1202 In addition, the evaluation criteria in Table 5 are as follows: Excellent: Crack width repair rate ≥90%, wave velocity recovery rate ≥90%, strength recovery rate ≥85%.

[0068] Good: Crack width repair rate 70%-89%, wave velocity recovery rate 70%-89%, strength recovery rate 60%-84%.

[0069] Generally: crack width repair rate 50%-69%, wave velocity recovery rate 50%-69%, strength recovery rate 40%-59%.

[0070] Poor: Crack width repair rate <50%, wave velocity recovery rate <50%, strength recovery rate <40%.

[0071] In summary, Example 1 performed best in all test indicators, demonstrating that the synergistic effect of phase change microcapsules, nanocrystal nucleating agents, microvascular networks, and internal maintenance water sources is significantly superior to any single repair mechanism. The comparison between Example 1 and Comparative Example 1 shows that the addition of nanocrystal nucleating agents increased the crack repair rate by 25-35% and the strength recovery rate by 30-45%, proving its key role in guiding the crystallization of repair agents.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-healing composite material for railway concrete, characterized in that, The self-healing system comprises a concrete matrix and a self-healing system distributed in the concrete matrix; the self-healing system comprises: The phase change microcapsule has an organic phase change material with a phase change temperature of 30-40℃ as a core material and a polymer shell as a wall material; The nanocrystalline nucleating agent is a nanomaterial that is surface-modified and capable of promoting crystallization of the organic phase change material; The biomimetic microvascular network is formed by hollow fiber tubes filled with a repair agent in a three-dimensional grid form; The internal curing water source is provided by high water-absorbing polymer particles.

2. The self-healing composite material for railway concrete according to claim 1, characterized in that, The core material of the phase change microcapsule is n-eicosane, and the wall material is one of polyurea-formaldehyde, melamine-formaldehyde resin or polymethyl methacrylate; The particle size of the phase change microcapsule is 50-150μm, and the volume content of the phase change microcapsule accounts for 3%-8% of the total volume of the concrete binder.

3. The self-healing composite material for railway concrete according to claim 1, characterized in that, The nanocrystalline nucleating agent is nanographene oxide modified by a silane coupling agent or amorphous calcium carbonate modified by a surfactant; The content of the nanocrystalline nucleating agent accounts for 0.5%-1.5% of the mass of the concrete binder.

4. The crack self-healing composite material for railway concrete according to claim 3, characterized by, The nanographene oxide in the nanocrystalline nucleating agent has a sheet diameter of 100-500nm and a thickness of 1-3 atomic layers.

5. The self-healing composite material for railway concrete according to claim 1, wherein The hollow fiber tube in the biomimetic microvascular network is a borosilicate glass fiber tube or a degradable polymer tube, which has an outer diameter of 1-3mm and an inner diameter of 0.5-2mm; The repair agent is one of low-viscosity epoxy resin, cyanoacrylate or silicone-based sealant; and the hollow fiber tube is arranged in the concrete matrix at an interval of 5-15cm.

6. The self-healing composite material for railway concrete according to claim 1, wherein The internal curing water source is crosslinked sodium polyacrylate high water-absorbing polymer particles with a particle size of 40-100μm and a content of 0.3%-1.0% of the mass of the concrete binder.

7. A method for the production of a self-healing composite material for railway concrete according to any one of claims 1 to 6, characterized in that The method comprises the following steps: (1) preparing phase change microcapsules and modified nanocrystalline nucleating agents; (2) preparing and filling the biomimetic microvascular network; (3) dry mixing cement, aggregate, phase change microcapsules, nanocrystalline nucleating agents and high water-absorbing polymer dry powder to obtain a dry mixture; (4) adding mixing water to the dry mixture of step (3) to form a concrete mixture; (5) pouring a layer of the concrete mixture in a mold, arranging the biomimetic microvascular network, and then pouring the remaining mixture and performing tamping and vibration molding.

8. The method for preparing a self-healing composite material for railway concrete according to claim 7, characterized in that, The phase change microcapsules in step (1) are prepared by in-situ polymerization, which comprises the following steps: The organic phase change material is emulsified and dispersed in an aqueous phase, wall material monomers or prepolymers are added, the pH is adjusted to be acidic, and the temperature is controlled and stirred to perform polymerization reaction. After the reaction is completed, the microcapsule powder is obtained by washing and drying.

9. The method for preparing a self-healing composite material for railway concrete according to claim 7, characterized in that, The preparation of the modified nanocrystalline nucleating agent in step (1) comprises the following steps: Nanographene oxide is dispersed in a solvent, a silane coupling agent is added, surface grafting modification is performed under heating and reflux conditions, and then the modified product is obtained by centrifugation, washing and drying.

10. The method for preparing a self-healing composite material for railway concrete according to claim 7, characterized in that, The vibration in step (5) is performed by low amplitude with an amplitude of 0.1-0.4mm and high frequency with a frequency of 150-250Hz, wherein the vibration rod avoids direct contact with the arranged biomimetic microvascular network to prevent damage.