Concrete self-healing microcapsule and ultra-high performance concrete

Abstract

The invention provides a concrete self-healing microcapsule and ultra-high performance concrete, and belongs to the technical field of building materials. The microcapsule containing the three-component composite core material provided by the invention has excellent performance of promoting self-repairing of concrete, can effectively repair concrete damage, does not generate negative effects on mechanical properties of matrix concrete, and meets industrial standard requirements. The ultra-high performance concrete prepared by adopting the self-healing microcapsule provided by the invention can be effectively repaired after being cracked, the structural integrity and durability are effectively recovered, and the service life of a wind power mixed tower structure is remarkably prolonged. From the aspect of engineering application, the self-healing concrete has important application value in severe environments such as ocean engineering and underground structures, and the maintenance cost can be greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a self-healing microcapsule for concrete and an ultra-high performance concrete. Background Technology

[0002] Ultra-High Performance Concrete (UHPC), as a new generation of cement-based composite material, has achieved breakthroughs in mechanical properties, including compressive strength exceeding 120 MPa and flexural strength exceeding 15 MPa, through optimized particle size distribution and the incorporation of steel fibers and active mineral admixtures. This has demonstrated significant advantages in bridge joints, marine engineering, and seismic structures. Its dense microstructure endows the material with excellent impermeability and durability, effectively delaying chloride ion erosion and carbonation. However, existing UHPC systems still face the problem of localized performance degradation caused by microcrack initiation during service. Traditional repair techniques rely on external intervention and are difficult to match with the properties of the matrix material, becoming a potential bottleneck restricting reliability throughout the entire life cycle.

[0003] With the rapid development of the wind power industry, the safety and durability of wind turbine hybrid towers, as a crucial structure supporting wind turbines, have become a focus of industry attention. Currently, wind turbine hybrid towers are mainly constructed using ordinary concrete or high-strength concrete. However, these materials are prone to cracking and spalling when exposed to harsh environments for extended periods, leading to a decline in structural performance and even safety hazards. In recent years, ultra-high performance concrete (UHPC) has been increasingly applied to wind turbine hybrid towers due to its superior mechanical properties and durability. However, its high cost and inability to actively repair cracks remain issues. To address the cracking problem in the concrete structure of wind turbine hybrid towers, existing technologies mainly include the following methods: first, using fiber-reinforced concrete, which improves crack resistance by adding steel fibers or synthetic fibers to the concrete; second, using waterproof coatings or sealants to prevent moisture from penetrating cracks; and third, using prestressing technology to reduce crack formation by applying prestress. However, while fiber-reinforced concrete can improve crack resistance, it cannot actively repair existing cracks; waterproof coatings and sealants are prone to aging and failure after long-term use; and prestressing technology is complex to construct and costly, making large-scale promotion difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing microcapsule for concrete and an ultra-high performance concrete, which enables concrete to be effectively repaired after cracking, and effectively restores structural integrity and durability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a self-healing concrete microcapsule, comprising a capsule shell and a core material, wherein the core material is filled inside the capsule shell; The capsule shell is made of polyurethane; The raw materials for preparing the core material include: waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent, and defoamer.

[0006] Preferably, the mass ratio of the waterborne epoxy resin, polyurethane emulsion, and acrylic emulsion is 3:0.8~1.2:0.8~1.2.

[0007] This invention also provides a method for preparing the above-mentioned self-healing concrete microcapsules, comprising the following steps: A core material solution is obtained by mixing waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent and defoamer. A polyurethane prepolymer, ethyl acetate, emulsifier, and catalyst are mixed to obtain an oil phase solution. The core material solution is injected into the oil phase solution and subjected to shear emulsification to obtain the primary emulsion; The primary emulsion was mixed and stirred with an aqueous polyvinyl alcohol solution to obtain a multiphase emulsion system; The complex emulsion system was heated to 40-60°C, and a chain extender was added to carry out the reaction to obtain the reaction product. The reaction products were cooled to below 10°C and separated into layers to obtain self-healing concrete microcapsules, including a capsule shell and a core material, wherein the core material filled the interior of the capsule shell. The capsule shell is made of polyurethane; The raw materials for preparing the core material include: waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent, and defoamer.

[0008] Preferably, the mass ratio of the polyurethane prepolymer to ethyl acetate is 7:2~4; The emulsifier is Span-80; The catalyst is dibutyltin dilaurate.

[0009] Preferably, the volume ratio of the core material solution to the oil phase solution is 1:3.5~4.5.

[0010] Preferably, the shear emulsification process is carried out at a rotation speed of 7000~9000 rpm for a time of 3~8 min; The concentration of the polyvinyl alcohol aqueous solution is 2-4 wt%; The volume ratio of the primary emulsion to the polyvinyl alcohol aqueous solution is 1:8~12; The mixing speed is 1000~1400 rpm.

[0011] Preferably, the chain extender is 1,4-butanediol, and the amount added is 10-20% of the volume of the primary emulsion. The reaction time is 3-5 hours.

[0012] Preferably, the process of obtaining the self-healing concrete microcapsules further includes washing and drying. The drying temperature is 30~50℃, and the time is 12~48h.

[0013] The present invention also provides an ultra-high performance concrete, which contains cementitious materials, aggregates, fiber materials, admixtures, water, and the above-mentioned self-healing microcapsules.

[0014] Preferably, the amount of the self-healing concrete microcapsules added is 0.5% to 1.5% of the total mass of all raw materials of the ultra-high performance concrete; The fiber material is copper-plated steel fiber; The additive is a polycarboxylate superplasticizer.

[0015] The beneficial effects of this invention are: This invention provides microcapsules containing a three-component composite core material, exhibiting excellent self-healing properties in concrete. These capsules effectively repair concrete damage without negatively impacting the mechanical properties of the matrix concrete, meeting industry standards. Ultra-high performance concrete prepared using these self-healing microcapsules effectively repairs cracks, restoring structural integrity and durability, and significantly extending the service life of wind turbine tower structures. From an engineering application perspective, this self-healing concrete has significant value in harsh environments such as marine engineering and underground structures, and can substantially reduce maintenance costs. Detailed Implementation

[0016] This invention provides a self-healing concrete microcapsule, comprising a capsule shell and a core material, wherein the core material fills the interior of the capsule shell; the capsule shell is made of polyurethane; the raw materials for preparing the core material include: aqueous epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent, and defoamer. Preferably, the mass ratio of the aqueous epoxy resin, polyurethane emulsion, and acrylic emulsion is 3:0.8~1.2:0.8~1.2.

[0017] This invention also provides a method for preparing the above-mentioned self-healing concrete microcapsules, comprising the following steps: mixing aqueous epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent and defoamer to obtain a core material solution; mixing polyurethane prepolymer, ethyl acetate, emulsifier and catalyst to obtain an oil phase solution; injecting the core material solution into the oil phase solution and performing shear emulsification treatment to obtain a primary emulsion; mixing and stirring the primary emulsion with a polyvinyl alcohol aqueous solution to obtain a multiphase emulsion system; heating the multiphase emulsion system to 40~60℃, adding a chain extender to react, and obtaining a reaction product; cooling the temperature of the reaction product to below 10℃, and obtaining self-healing concrete microcapsules after stratification, wherein the obtained self-healing concrete microcapsule structure includes a capsule shell and a core material, the core material filling the interior of the capsule shell; the capsule shell is made of polyurethane; the raw materials for preparing the core material include: aqueous epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent and defoamer.

[0018] In this invention, preferably, the mass ratio of the polyurethane prepolymer to ethyl acetate is 7:2~4; the emulsifier is Span-80; and the catalyst is dibutyltin dilaurate. Preferably, the volume ratio of the core material solution to the oil phase solution is 1:3.5~4.5. Preferably, the shear emulsification treatment speed is 7000~9000 rpm, and the time is 3~8 min; the concentration of the polyvinyl alcohol aqueous solution is 2~4 wt%; the volume ratio of the primary emulsion to the polyvinyl alcohol aqueous solution is 1:8~12; and the mixing and stirring speed is 1000~1400 rpm. Preferably, the chain extender is 1,4-butanediol, and the addition amount is 10~20 vol% of the volume of the primary emulsion; and the reaction time is 3~5 h. Preferably, after obtaining the concrete self-healing microcapsules, the process further includes washing and drying; the drying temperature is 30~50℃, and the time is 12~48 h. More preferably, the mixed resin is composed of waterborne epoxy resin, polyurethane emulsion, and acrylic emulsion in a mass ratio of 3:1:1, and homogenized by magnetic stirring at 500 rpm for 30 minutes at a constant temperature of 25°C; more preferably, the silane coupling agent is KH-550 and the addition amount is 5% of the total mass of the mixed resin, and the defoamer is BYK-024 and the addition amount is 0.5%; more preferably, in the oil phase preparation, the polyurethane prepolymer and ethyl acetate are mixed in a mass ratio of 7:3, the Span-80 emulsifier is added at 1.5% of the prepolymer mass, and the dibutyltin dilaurate catalyst is added... The addition amount is 0.3%; more preferably, the shear emulsification treatment is carried out using a high-speed homogenizer at 8000 rpm for 5 minutes, and the volume ratio of core material to oil phase is controlled at 1:4; more preferably, the polyvinyl alcohol aqueous solution is prepared with a concentration of 3wt% using PVA1788, and the primary emulsion and aqueous solution are mixed at a volume ratio of 1:10 and stirred at 1200 rpm; more preferably, the interfacial polymerization reaction is carried out by gradient heating to 50℃ at 1℃ / min, the chain extender 1,4-butanediol is added at 15% of the oil phase volume, the pH is maintained at 8.5-9.0 throughout the reaction, and 0.1wt% PVA solution is added every 30 minutes; more preferably, the post-treatment stage is carried out by rapid cooling in an ice-water bath, washing three times alternately with anhydrous ethanol and deionized water, centrifugation parameters are set at 3000 rpm × 5 min, and vacuum drying conditions are 40℃ × 24 h.

[0019] The present invention also provides an ultra-high performance concrete, which contains cementitious materials, aggregates, fiber materials, admixtures, water, and the aforementioned self-healing microcapsules. Preferably, the amount of the self-healing microcapsules added is 0.5-1.5% of the total mass of all raw materials of the ultra-high performance concrete; the fiber material is copper-plated steel fiber; and the admixture is a polycarboxylate superplasticizer.

[0020] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0021] Example 1 Preparation method of self-healing microcapsules 1. Preparation of core material solution Weigh out three materials: waterborne epoxy resin (component A), polyurethane emulsion (component B), and acrylic emulsion (component C), and mix them in a mass ratio of 3:1:1. Place the mixed resin in a thermostatic magnetic stirrer, set the temperature to 25°C, and the stirring speed to 500 rpm, and stir continuously for 30 minutes until a homogeneous mixture is formed.

[0022] Add 5 wt% of the total amount of the mixed resin of silane coupling agent KH-550, and continue stirring for 15 minutes. Then add 0.5 wt% of the total amount of the mixed resin of defoamer BYK-024 and continue stirring for 10 minutes.

[0023] II. Oil Phase Preparation The polyurethane prepolymer and ethyl acetate were mixed at a mass ratio of 7:3, and 1.5 wt% of the total amount of the prepolymer emulsifier Span-80 was added. The mixture was stirred and dissolved in a water bath at 40°C.

[0024] After complete dissolution, the temperature is lowered to 25°C, and 0.3 wt% of dibutyltin dilaurate is added as a catalyst.

[0025] III. Emulsion Preparation The core material solution was slowly injected into the oil phase solution, controlling the oil phase to core material volume ratio at 4:1. A high-speed homogenizer was used to shear and emulsify the emulsion at 8000 rpm for 5 minutes to form a W / O type primary emulsion.

[0026] The primary emulsion was transferred to an aqueous solution containing 3 wt% polyvinyl alcohol (PVA1788), with an oil-to-water volume ratio of 1:10. The stirrer speed was adjusted to 1200 rpm, and stirring was continued to form a W / O / W multiphase emulsion system.

[0027] IV. Interfacial Polymerization Reaction The temperature was slowly increased to 50°C at a rate of 1°C / min. Under nitrogen protection, 15 vol% of the total oil phase of chain extender 1,4-butanediol was added dropwise.

[0028] The pH value was controlled within the range of 8.5-9.0, and the reaction time was maintained for 4 hours. During this period, 0.1 wt% PVA solution was added every 30 minutes to maintain the stability of the system.

[0029] V. Post-processing After the reaction was completed, the temperature was immediately cooled to below 10°C using an ice-water bath. After standing and separating the layers, the microcapsules were separated using a vacuum filtration device.

[0030] Wash three times alternately with anhydrous ethanol and deionized water, centrifuging at 3000 rpm for 5 minutes after each wash.

[0031] The product was placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain spherical microcapsules with smooth surfaces.

[0032] Example 2 Preparation of self-healing ultra-high performance concrete First, the raw materials for the matrix concrete were pretreated: PO 42.5 ordinary Portland cement was sieved to remove lumps, and silica fume (specific surface area 18000±2000 m² / kg) and quartz sand (60% 0.1-0.3mm and 40% 0.3-0.5mm) were dry-mixed at a mass ratio of 1:2. Then, cementitious materials (cement:silica fume = 7:3), quartz sand, and polycarboxylate-based high-efficiency water-reducing agent (1.2%) were added to a planetary mixer and dry-mixed for 90 seconds. Then, purified water with a water-cement ratio of 0.18 was added and wet-mixed for 180 seconds to form the matrix slurry. During the low-speed mixing stage (60 rpm), 2% by volume of copper-plated steel fibers (length 15±3mm, diameter 0.25±0.05mm, tensile strength ≥2000MPa) and 1% by weight of the microcapsules prepared in Example 1 were added sequentially, controlling the mixing time to no more than 120 seconds to avoid capsule breakage. After molding, the product is steam-cured at 90℃ for 48 hours, and then transferred to a standard curing room (20±2℃, RH≥95%) for curing for 28 days.

[0033] Comparative Example 1 First, the raw materials for the matrix concrete are pretreated: PO 42.5 ordinary Portland cement is sieved to remove lumps. Silica fume (specific surface area 18000±2000 m² / kg) and quartz sand (60% 0.1-0.3mm and 40% 0.3-0.5mm) are dry-mixed at a mass ratio of 1:2 and homogenized. Then, cementitious materials (cement:silica fume = 7:3), quartz sand, and polycarboxylate-based high-efficiency water-reducing agent (1.2%) are added to a planetary mixer and dry-mixed for 90 seconds. Then, purified water with a water-cement ratio of 0.18 is added and wet-mixed for 180 seconds to form the matrix paste. During the low-speed mixing stage (60 rpm), 2% by volume of copper-plated steel fibers (length 15±3mm, diameter 0.25±0.05mm) are added sequentially. After molding, the mixture is steam-cured at 90℃ for 48 hours, and then transferred to a standard curing room (20±2℃, RH≥95%) for 28 days.

[0034] Comparative Example 2 Preparation method of self-healing microcapsules 1. Preparation of core material solution Waterborne epoxy resin was placed in a thermostatic magnetic stirrer, the temperature was set to 25℃, the stirring speed was 500rpm, and the stirring was continued for 30 minutes. Then, 5wt% of silane coupling agent KH-550 was added, and the stirring was continued for 15 minutes. Finally, 0.5wt% of defoamer BYK-024 was added, and the stirring was maintained for 10 minutes.

[0035] II. Oil Phase Preparation The polyurethane prepolymer and ethyl acetate were mixed at a mass ratio of 7:3, and 1.5 wt% of the total amount of the prepolymer emulsifier Span-80 was added. The mixture was stirred and dissolved in a water bath at 40°C.

[0036] After complete dissolution, the temperature is lowered to 25°C, and 0.3 wt% of dibutyltin dilaurate is added as a catalyst.

[0037] III. Emulsion Preparation The core material solution was slowly injected into the oil phase solution, controlling the oil phase to core material volume ratio at 4:1. A high-speed homogenizer was used to shear and emulsify the emulsion at 8000 rpm for 5 minutes to form a W / O type primary emulsion.

[0038] The primary emulsion was transferred to an aqueous solution containing 3 wt% polyvinyl alcohol (PVA1788), with an oil-to-water volume ratio of 1:10. The stirrer speed was adjusted to 1200 rpm, and stirring was continued to form a W / O / W multiphase emulsion system.

[0039] IV. Interfacial Polymerization Reaction The temperature was slowly increased to 50°C at a rate of 1°C / min. Under nitrogen protection, 15 vol% of the total oil phase of chain extender 1,4-butanediol was added dropwise.

[0040] The pH value was controlled within the range of 8.5-9.0, and the reaction time was maintained for 4 hours. During this period, 0.1 wt% PVA solution was added every 30 minutes to maintain the stability of the system.

[0041] V. Post-processing After the reaction was completed, the temperature was immediately cooled to below 10°C using an ice-water bath. After standing and separating the layers, the microcapsules were separated using a vacuum filtration device.

[0042] Wash three times alternately with anhydrous ethanol and deionized water, centrifuging at 3000 rpm for 5 minutes after each wash.

[0043] The product was placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain spherical microcapsules with smooth surfaces.

[0044] Self-healing ultra-high performance concrete was prepared according to the method described in Example 2.

[0045] Comparative Example 3 Preparation method of self-healing microcapsules 1. Preparation of core material solution The polyurethane emulsion was placed in a thermostatic magnetic stirrer, the temperature was set to 25℃, the stirring speed was 500rpm, and the stirring was continued for 30 minutes. Then, 5wt% of silane coupling agent KH-550 was added, and the stirring was continued for 15 minutes. Finally, 0.5wt% of defoamer BYK-024 was added, and the stirring was maintained for 10 minutes.

[0046] II. Oil Phase Preparation The polyurethane prepolymer and ethyl acetate were mixed at a mass ratio of 7:3, and 1.5 wt% of the total amount of the prepolymer emulsifier Span-80 was added. The mixture was stirred and dissolved in a water bath at 40°C.

[0047] After complete dissolution, the temperature is lowered to 25°C, and 0.3 wt% of dibutyltin dilaurate is added as a catalyst.

[0048] III. Emulsion Preparation The core material solution was slowly injected into the oil phase solution, controlling the oil phase to core material volume ratio at 4:1. A high-speed homogenizer was used to shear and emulsify the emulsion at 8000 rpm for 5 minutes to form a W / O type primary emulsion.

[0049] The primary emulsion was transferred to an aqueous solution containing 3 wt% polyvinyl alcohol (PVA1788), with an oil-to-water volume ratio of 1:10. The stirrer speed was adjusted to 1200 rpm, and stirring was continued to form a W / O / W multiphase emulsion system.

[0050] IV. Interfacial Polymerization Reaction The temperature was slowly increased to 50°C at a rate of 1°C / min. Under nitrogen protection, 15 vol% of the total oil phase of chain extender 1,4-butanediol was added dropwise.

[0051] The pH value was controlled within the range of 8.5-9.0, and the reaction time was maintained for 4 hours. During this period, 0.1 wt% PVA solution was added every 30 minutes to maintain the stability of the system.

[0052] V. Post-processing After the reaction was completed, the temperature was immediately cooled to below 10°C using an ice-water bath. After standing and separating the layers, the microcapsules were separated using a vacuum filtration device.

[0053] Wash three times alternately with anhydrous ethanol and deionized water, centrifuging at 3000 rpm for 5 minutes after each wash.

[0054] The product was placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain spherical microcapsules with smooth surfaces.

[0055] Self-healing ultra-high performance concrete was prepared according to the method described in Example 2.

[0056] Comparative Example 4 Preparation method of self-healing microcapsules 1. Preparation of core material solution The acrylic emulsion was placed in a thermostatic magnetic stirrer, the temperature was set to 25℃, the stirring speed was 500rpm, and the stirring was continued for 30 minutes. Then, 5wt% of silane coupling agent KH-550 was added, and the stirring was continued for 15 minutes. Finally, 0.5wt% of defoamer BYK-024 was added, and the stirring was maintained for 10 minutes.

[0057] II. Oil Phase Preparation The polyurethane prepolymer and ethyl acetate were mixed at a mass ratio of 7:3, and 1.5 wt% of the total amount of the prepolymer emulsifier Span-80 was added. The mixture was stirred and dissolved in a water bath at 40°C.

[0058] After complete dissolution, the temperature is lowered to 25°C, and 0.3 wt% of dibutyltin dilaurate is added as a catalyst.

[0059] III. Emulsion Preparation The core material solution was slowly injected into the oil phase solution, controlling the oil phase to core material volume ratio at 4:1. A high-speed homogenizer was used to shear and emulsify the emulsion at 8000 rpm for 5 minutes to form a W / O type primary emulsion.

[0060] The primary emulsion was transferred to an aqueous solution containing 3 wt% polyvinyl alcohol (PVA1788), with an oil-to-water volume ratio of 1:10. The stirrer speed was adjusted to 1200 rpm, and stirring was continued to form a W / O / W multiphase emulsion system.

[0061] IV. Interfacial Polymerization Reaction The temperature was slowly increased to 50°C at a rate of 1°C / min. Under nitrogen protection, 15 vol% of the total oil phase of chain extender 1,4-butanediol was added dropwise.

[0062] The pH value was controlled within the range of 8.5-9.0, and the reaction time was maintained for 4 hours. During this period, 0.1 wt% PVA solution was added every 30 minutes to maintain the stability of the system.

[0063] V. Post-processing After the reaction was completed, the temperature was immediately cooled to below 10°C using an ice-water bath. After standing and separating the layers, the microcapsules were separated using a vacuum filtration device.

[0064] Wash three times alternately with anhydrous ethanol and deionized water, centrifuging at 3000 rpm for 5 minutes after each wash.

[0065] The product was placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain spherical microcapsules with smooth surfaces.

[0066] Self-healing ultra-high performance concrete was prepared according to the method described in Example 2.

[0067] Experimental Example Four control groups were set up: a blank group (without microcapsules), a group containing a single core material of waterborne epoxy resin (Group A), a group containing polyurethane emulsion (Group B), or a group containing acrylic emulsion of microcapsules (Group C), with corresponding ratios of 1 to 4.

[0068] II. Performance Testing Methods Basic performance test Compressive strength was determined by preparing 100mm cube specimens according to GB / T 50081-2019, and applying a 2000kN press at a loading rate of 1.2MPa / s. Flexural strength was tested using a 40×40×160mm prism specimen, with a three-point bending test span of 100mm. The chloride ion diffusion coefficient was tested according to the electromigration method in GB / T 50082-2009, with a 30V DC current applied for 24 hours. The elastic modulus is determined by static compression tests, specifically the slope of the linear segment of the stress-strain curve. Self-repair performance test Pre-cast 0.3mm wide cracks (three-point pre-cracking method) and treated for 28 days under standard curing (20℃ / 95%RH), water immersion (20℃), and 50℃ humid heat (90%RH) environments respectively. The crack repair rate was calculated by measuring crack width changes using a digital microscope and determining the closure ratio. The strength recovery rate was assessed by applying a second load to failure and comparing the ratio of compressive strength before and after repair. Permeability restoration involved retesting the chloride ion diffusion coefficient on the repaired specimen. III. Performance Test Data Table 1. Basic performance test results (28-day period)

[0069] Note: The difference in the performance of the matrix concrete in each group was within 2.5%, indicating that the addition of microcapsules had no negative impact on the basic mechanical properties of the material and could meet the standard level.

[0070] Table 2 Self-healing performance test results (28-day repair)

[0071] Comparative experimental data shows that the microcapsules using a three-component composite core material (experimental group) exhibit significant advantages in self-healing performance. Their crack closure rate (75.73%) and strength recovery rate (72.35%) are 55.7% and 58.1% higher than the optimal single-component core material (single B group), respectively, and the chloride ion diffusion coefficient recovery rate reaches 75.82%, proving that the composite core material can produce a synergistic repair effect, and the resulting microcapsules can effectively repair concrete damage. Regarding basic mechanical properties, the differences in compressive strength and flexural strength among the groups are all less than 2.5%, indicating that the incorporation of microcapsules does not negatively affect the mechanical properties of the matrix concrete, and all groups meet industry standard requirements.

[0072] The composite repair system provided in this solution enables effective repair of cracked concrete, restoring structural integrity and durability. Compared to traditional single repair materials, this technology reduces chloride ion permeability by 75%, significantly extending the service life of wind turbine hybrid tower structures. From an engineering application perspective, this self-healing concrete has significant application value in harsh environments such as marine engineering and underground structures, and can substantially reduce maintenance costs.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-healing microcapsule for concrete, characterized in that, It includes a capsule shell and a core material, wherein the core material fills the interior of the capsule shell; The capsule shell is made of polyurethane; The raw materials for preparing the core material include: waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent, and defoamer.

2. The self-healing concrete microcapsule according to claim 1, characterized in that, The mass ratio of the waterborne epoxy resin, polyurethane emulsion, and acrylic emulsion is 3:0.8~1.2:0.8~1.

2.

3. The method for preparing the self-healing concrete microcapsules according to claim 1 or 2, characterized in that, Includes the following steps: A core material solution is obtained by mixing waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent and defoamer. A polyurethane prepolymer, ethyl acetate, emulsifier, and catalyst are mixed to obtain an oil phase solution. The core material solution is injected into the oil phase solution and subjected to shear emulsification to obtain the primary emulsion; The primary emulsion was mixed and stirred with an aqueous polyvinyl alcohol solution to obtain a multiphase emulsion system; The complex emulsion system was heated to 40-60°C, and a chain extender was added to carry out the reaction to obtain the reaction product. The reaction products were cooled to below 10°C and separated into layers to obtain self-healing concrete microcapsules, including a capsule shell and a core material, wherein the core material filled the interior of the capsule shell. The capsule shell is made of polyurethane; The raw materials for preparing the core material include: waterborne epoxy resin, polyurethane emulsion, acrylic emulsion, silane coupling agent, and defoamer.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the polyurethane prepolymer to ethyl acetate is 7:2~4; The emulsifier is Span-80; The catalyst is dibutyltin dilaurate.

5. The preparation method according to claim 3, characterized in that, The volume ratio of the core material solution to the oil phase solution is 1:3.5~4.

5.

6. The preparation method according to claim 3, characterized in that, The shear emulsification process is performed at a speed of 7000~9000 rpm for a time of 3~8 min. The concentration of the polyvinyl alcohol aqueous solution is 2-4 wt%; The volume ratio of the primary emulsion to the polyvinyl alcohol aqueous solution is 1:8~12; The mixing speed is 1000~1400 rpm.

7. The preparation method according to claim 3, characterized in that, The chain extender is 1,4-butanediol, and the amount added is 10-20% vol% of the initial emulsion volume. The reaction time is 3-5 hours.

8. The preparation method according to claim 3, characterized in that, The process of obtaining the self-healing concrete microcapsules also includes washing and drying. The drying temperature is 30~50℃, and the time is 12~48h.

9. A type of ultra-high performance concrete, characterized in that, The ultra-high performance concrete contains cementitious materials, aggregates, fiber materials, admixtures, water, and the self-healing microcapsules of concrete as described in claim 1 or 2.

10. The ultra-high performance concrete according to claim 9, characterized in that, The amount of the self-healing concrete microcapsules added is 0.5-1.5% of the total mass of all raw materials of the ultra-high performance concrete; The fiber material is copper-plated steel fiber; The additive is a polycarboxylate superplasticizer.

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