In-situ solidified microcapsule for concrete self-repair and preparation method thereof, and self-repairing concrete

Abstract

The application discloses in-situ solidification microcapsules for concrete self-repairing and a preparation method thereof and self-repairing concrete. The in-situ solidification microcapsules for concrete self-repairing comprise a composite capsule wall composed of an inner wall and an outer wall. The outer wall is loaded with a solidification agent inside the wall and the solidification agent is attached outside the wall. The inner wall is free of the solidification agent. The composite capsule wall is loaded with a repairing agent, the repairing agent is separated from the solidification agent through the inner wall, the composite capsule wall is damaged, and the repairing agent is combined with the solidification agent in situ. The problem that the existing self-repairing microcapsules cannot effectively repair concrete cracks due to the fact that the adhesive and the solidification agent cannot be fully contacted, resulting in incomplete solidification of the adhesive, is effectively solved. In addition, the self-repairing concrete can further improve the mechanical properties such as compressive strength and flexural strength after self-repairing of concrete microcracks.

Description

Technical Field

[0001] This disclosure relates to the field of UV-curable materials, and more particularly to a UV-curable hydrophobic and antiscaling composite resin and its preparation method. Background Technology

[0002] Due to prolonged use and environmental stress, many in-service concrete structures develop microcracks and localized damage. With changes in load and the passage of time, these internal cracks gradually expand into fissures or even fractures, leading to concrete damage. Current self-healing methods for concrete include shape memory alloy self-healing, hollow fiber self-healing, microbial self-healing, and microcapsule self-healing.

[0003] The self-healing microcapsule method involves uniformly dispersing microcapsules in concrete. When microcracks appear in the concrete due to external forces, the microcapsule walls at the microcracks rupture, releasing the repair agent as the core material to seal the microcracks and achieve self-repair. For example, invention patents such as EP 2239242B1, US 8552092B2, and CN115010440A all utilize microcapsules encapsulating an adhesive (an adhesive resin, i.e., the repair agent) and then using it in conjunction with a curing agent. The curing agent can be added in several ways: directly mixing the solid curing agent into the cement when adding the microcapsules; preparing microcapsules to coat the curing agent and adding it to the concrete along with the microcapsule-encapsulated adhesive; or preparing a double-shell microcapsule where the inner shell is coated with adhesive and the space between the inner and outer shells is coated with curing agent, etc. The principle behind these methods is that after the microcapsule walls rupture, the fluidity of the adhesive penetrates deep into the cracks and cures, achieving self-repair. However, the above methods have many shortcomings. Directly mixing the curing agent with cementitious materials significantly affects the properties of the cement itself, and from an engineering perspective, it is undesirable to alter the process. Furthermore, using microcapsules to separately encapsulate the adhesive and curing agent cannot guarantee that the released adhesive and curing agent will bond promptly when the microcapsules rupture. If the adhesive does not cure sufficiently, the self-healing process cannot be effectively completed, resulting in a low repair rate. Even with external pressure to assist in microcapsule rupture repair, the problem of insufficient contact between the repair agent and curing agent cannot be fundamentally solved, leading to incomplete curing of the repair agent and an inability to effectively repair cracked concrete. Therefore, the application of microcapsules for concrete crack repair is limited. Summary of the Invention

[0004] In view of this, this disclosure provides in-situ curing microcapsules for self-healing concrete and their preparation method, as well as self-healing concrete, which solves the problem that current self-healing microcapsules for concrete microcracks cannot effectively repair concrete cracks because the adhesive and curing agent cannot fully contact each other, resulting in incomplete curing of the adhesive.

[0005] The design concept of the in-situ curing microcapsules for self-healing concrete disclosed herein is as follows:

[0006] The microcapsules utilize a composite capsule wall composed of an inner and outer wall. The outer wall contains a curing agent both internally and externally, while the inner wall material does not contain a curing agent. The repair agent is encapsulated within the microcapsule by the inner wall but does not come into contact with the curing agent loaded within or adhering to the outer wall surface. Thus, when the cement-based material is in normal service, the microcapsules are in a dormant state. When the cement-based material develops microcracks or pores due to external forces, the capsule walls of the microcapsules, uniformly dispersed within the cement, rupture, releasing the repair agent. Since the curing agent of the repair agent is attached to or dispersed on the microcapsule wall, once released, it can immediately combine with the curing agent, achieving in-situ curing of the resin and thus better completing the self-repair process.

[0007] Based on the above design concept, the technical solution provided in this disclosure can be summarized as follows:

[0008] The inner and outer walls of the composite capsule are made of the same resin raw material, except that a curing agent is added to the resin raw material of the outer wall. Then, the inner wall prepolymer and the outer wall prepolymer are made separately, and the repair agent is formulated into an emulsion. The emulsion is first reacted with the inner wall prepolymer to obtain a suspension containing the capsule. Then, the outer wall prepolymer is added to the suspension containing the capsule to continue the reaction, and finally the in-situ cured microcapsule of the present invention is obtained.

[0009] Based on the above technical solution, in order to achieve the purpose of this invention, in a first aspect, the in-situ curing microcapsules for self-healing concrete provided in this disclosure include:

[0010] A complex capsule wall consisting of an inner wall and an outer wall;

[0011] The outer wall has a curing agent loaded inside and the curing agent attached to the outside; the inner wall does not contain a curing agent inside.

[0012] The composite capsule wall contains a repair agent, which is separated from the curing agent by the inner wall. When the composite capsule wall is damaged, the repair agent and the curing agent bond in situ.

[0013] In this disclosure and possible embodiments, the composite capsule wall is made of one of polyurethane, acrylonitrile resin, urea-formaldehyde resin, melamine resin, or phenolic resin; and / or,

[0014] The repair agent is epoxy resin, and the curing agent is one or more of diethylenetriamine, dicyandiamide, phthalic anhydride, 2-ethylimidazole, or 2-methylimidazole; and / or,

[0015] The microcapsules are spherical with a particle size of 5μm to 150μm.

[0016] Secondly, the method for preparing the in-situ curing microcapsules for self-healing concrete provided in this disclosure includes:

[0017] Prepare the resin raw materials for synthesizing the composite capsule wall according to the set ratio, divide the resin raw materials into two parts, react one part to generate an inner wall prepolymer, and add a set amount of curing agent to the other part to react and generate an outer wall prepolymer.

[0018] The repair agent is formulated into an emulsion, and the emulsion reacts with the inner wall prepolymer to generate a first suspension; the first suspension reacts with the outer wall prepolymer to generate a second suspension.

[0019] The filter material from the second suspension is washed and dried to obtain the in-situ solidified microcapsules.

[0020] In this disclosure and possible embodiments, the resin raw material is one or more of urea, phenol, melamine, formaldehyde, isocyanate, polyester polyol or acrylonitrile, the resin raw material is formulated into a mixed solution, and the mixed solution is divided into a first mixed solution and a second mixed solution;

[0021] The pH of the first mixed solution is adjusted to 7.5~10.0, and the mixed system reacts at a temperature of 50~80℃ to generate the inner wall prepolymer;

[0022] The curing agent is added to the second mixed solution and the pH is adjusted to 7.5~10.0. At a temperature of 50~80°C, the mixed system reacts to generate the outer wall prepolymer.

[0023] In this disclosure and possible embodiments, the method for generating the first suspension is to add the inner wall prepolymer to the emulsion, heat the system to 55°C to 95°C, add a pH adjuster to adjust the pH value to 1.0 to 3.5, and react under stirring to generate the first suspension.

[0024] The method for generating the second suspension is to add the outer wall prepolymer regulator to the first suspension, adjust the pH of the system to 1.0~3.5, and react at a temperature of 55℃~95℃ under stirring to generate the second suspension.

[0025] In this disclosure and possible embodiments, the method of formulating the repair agent into an emulsion includes:

[0026] The repair agent, emulsifier, auxiliary agent and deionized water are mixed evenly to form an emulsion system. Under stirring and a temperature of 50~65°C, the emulsion system reacts to obtain the emulsion.

[0027] In this disclosure and possible embodiments, the repair agent is one of bisphenol A epoxy resin (E-55, E-51, E-44, E42, E35), bisphenol F epoxy resin, or bisphenol S epoxy resin; and / or,

[0028] The emulsifier is one or more of polyvinyl alcohol, sodium dodecylbenzene sulfonate, or Tween 80; and / or

[0029] The adjuvant is one or more of resorcinol, hydroquinone, or ammonium chloride; and / or.

[0030] In this disclosure and possible embodiments, the system is adjusted to a pH of 1.0 to 3.5 using one or more of sulfuric acid, acetic acid, and citric acid;

[0031] The curing agent is sieved through a mesh size of 100-1000.

[0032] Thirdly, the self-healing concrete provided in this disclosure includes:

[0033] The in-situ solidified microcapsules described in the first aspect.

[0034] In this disclosure and possible embodiments, the amount of in-situ solidified microcapsules added is 0.5-30% according to the external doping method.

[0035] This disclosure has the following beneficial effects:

[0036] The in-situ curing microcapsules of this invention, because the curing agent of the repair agent is attached to the surface of the microcapsule wall or loaded on the outer wall of the composite capsule, allow the repair agent to react rapidly with the curing agent for in-situ curing. This enables the generated insoluble substances to promptly plug micro-cracks, achieving self-repair of the concrete. Furthermore, the curing of the repair agent is more thorough and complete, effectively solving the problem of incomplete curing of the adhesive and ineffective repair of concrete cracks caused by insufficient contact between the adhesive and curing agent in existing self-healing microcapsules. In addition, the self-healing concrete of this invention exhibits improved compressive strength. Therefore, in the long term, the in-situ curing microcapsules of this invention, after repairing micro-cracks in concrete, can extend the service life of the concrete material and further improve its mechanical properties such as compressive strength and flexural strength. Attached Figure Description

[0037] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0038] Figure 1 This is a schematic diagram of the structure of the microcapsules prepared in Example 1;

[0039] Figure 2-1SEM image of phenolic shell coated with epoxy;

[0040] Figure 2-2 Here is a scanning electron microscope image of the microcapsules prepared in Example 1;

[0041] Figure 3 This is the infrared spectrum of the microcapsules prepared in Example 2;

[0042] Figure 4 Here is a scanning electron microscope image of the microcapsules prepared in Example 3;

[0043] Figure 5 An optical microscope image of the self-healing microcapsules prepared in Example 4 within a concrete specimen. Detailed Implementation

[0044] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0045] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description is provided with reference to the accompanying drawings and examples, specifically using epoxy resin as the repair agent. In each embodiment, the preparation method of the in-situ curing microcapsules for self-healing concrete of this invention specifically includes the following steps:

[0047] Step 1: Preparation of the composite capsule wall prepolymer for microcapsules:

[0048] Add 2.5-30 parts by weight of urea, phenol, melamine, isocyanate or acrylonitrile to 3-50 parts by weight of 37% formaldehyde aqueous solution or polyester polyol and mix well. Divide the mixture into two parts, a and b. Add a pH adjuster to part a to adjust the pH to 7.5-10.0. Then, allow the system to react at a temperature of 50-80℃ for 1-3 hours to generate a resin prepolymer, which is used as the inner wall prepolymer. Then, cool it to room temperature for later use.

[0049] Add 0.2 to 20 parts by weight of the ground and sieved curing agent to part b and stir evenly. Similarly, add a pH adjuster to adjust the pH to 7.5 to 10.0. Similarly, allow the system to react at a temperature of 50 to 80°C to form a prepolymer of resin and curing agent. Use this as the outer wall prepolymer and then cool it to room temperature for later use.

[0050] In this step, the pH adjuster is preferably one or more of triethanolamine, ammonia, and sodium bicarbonate; the curing agent is sieved through a mesh size of 100-1000 mesh; the curing agent is one or more of diethylenetriamine, dicyandiamide, phthalic anhydride, 2-ethylimidazole, and 2-methylimidazole.

[0051] Step 2: Prepare the emulsion of the repair agent:

[0052] Mix 0.5-40 parts by weight of epoxy resin, 0.2-10 parts by weight of emulsifier, 0.01-5.95 parts by weight of additives and 20-500 parts by weight of deionized water evenly. Under stirring and at a temperature of 50-65°C, the system reacts to obtain an emulsion.

[0053] In this step, the epoxy resin is preferably one of bisphenol A epoxy resin (E-55, E-51, E-44, E42, E35), bisphenol F epoxy resin, or bisphenol S epoxy resin. The emulsifier is one or more of polyvinyl alcohol, sodium dodecylbenzene sulfonate, and Tween 80; the additive is one or more of resorcinol, hydroquinone, and ammonium chloride.

[0054] Step 3: Preparation of microcapsules:

[0055] The cooled inner wall prepolymer was added to the emulsion, the system was heated to 55-95°C, a pH adjuster was added to adjust the pH to 1.0-3.5, and the system was stirred to react, obtaining a first suspension containing capsules; the cooled outer wall prepolymer was added to the first suspension, and a pH adjuster was added to adjust the pH to 1.0-3.5, and the system was stirred to react, obtaining a second suspension containing self-healing microcapsules.

[0056] In this step, the pH adjuster is preferably one or more of sulfuric acid, acetic acid, and citric acid; the stirring speed is 300-2000 rpm.

[0057] Step 4: Post-processing of microcapsules:

[0058] The second suspension containing the self-healing microcapsules was cooled to room temperature and filtered. After washing with distilled water and ethanol respectively, it was dried in an oven to obtain in-situ cured microcapsules for self-healing of microcracks in concrete.

[0059] In this step, it is preferable to wash with distilled water and ethanol 3 to 5 times.

[0060] The following embodiments are merely some preferred implementation methods and do not limit the scope and technical means of the invention in any way.

[0061] All raw materials involved in the embodiments of this disclosure are conventional products that can be purchased commercially, and all reagents used are domestically produced industrial-grade reagents. Example 1

[0062] This embodiment 1 provides a method for preparing in-situ curing microcapsules for self-healing concrete that can repair microcracks, including the following steps:

[0063] (1) Mix 2g of phenol and 10g of 37% formaldehyde aqueous solution evenly, divide into two parts a and b. Add triethanolamine to part a, adjust the pH of the system to 7.5~10.0, and react the system at 50℃ to form an inner wall prepolymer. Then cool to room temperature for later use. Add 1.5g of 2-ethylimidazole that has been ground and sieved through a 200-mesh sieve to part b, stir evenly, add triethanolamine, adjust the pH of the system to 7.5~10.0, and react the system at 50℃ to form an outer wall prepolymer. Then cool to room temperature for later use.

[0064] (2) Mix 7.5g E-55 epoxy resin, 0.5g Tween 80, 0.05g resorcinol and 100g deionized water evenly, and react the system under stirring and temperature of 55℃ to obtain an emulsion.

[0065] (3) Add the cooled inner wall prepolymer to the emulsion, heat the system to 60°C, add hydrochloric acid, adjust the pH to 1.5, and let the system react under stirring at 300 r / min to obtain the first suspension containing the capsule. Continue to add the cooled outer wall prepolymer, add hydrochloric acid, adjust the pH of the system to 1.0~3.5, and let the system react under stirring at 300 r / min to obtain the second suspension of the self-healing microcapsules.

[0066] (4) Cool the second suspension of the self-healing microcapsule to room temperature and filter it. Wash it with distilled water and ethanol respectively and then dry it in an oven to obtain the in-situ curing microcapsule for self-healing concrete in Example 1.

[0067] Figure 1 This is a schematic diagram of the structure of the in-situ solidified microcapsules prepared in Example 1. Figure 1As can be seen, the epoxy resin inside the microcapsule is encapsulated by a resin shell, which consists of an inner wall and an outer wall, forming the composite capsule wall of the microcapsule. The outer wall is a resin layer loaded with curing agent, and particles are also attached to its outer surface. The inner wall does not contain curing agent. In other words, the inner wall can separate the repair agent from the curing agent loaded in the outer wall and attached to its surface. Thus, when the cement-based material is in normal service, the microcapsule is in a dormant state. Only when the cement-based material develops tiny cracks or pores due to external forces will the capsule wall of the microcapsule, which is uniformly dispersed in the cement, rupture. The repair agent will then precipitate out and combine with the curing agent in time, allowing the resin to cure in situ and completing the self-repair process of the concrete.

[0068] Figure 2-1 The image shows a SEM image of the microcapsules obtained by adding only the inner wall prepolymer in step (3) of this embodiment 1. The surface is relatively intact and smooth. Figure 2-2 This is a SEM image of the microcapsules prepared in Example 1, compared to... Figure 2-1 The surface is rougher because it is based on Figure 2-1 The microcapsule continues to form a new layer of phenolic resin shell (this new layer of resin shell is the outer wall of the composite capsule) loaded with 2-ethylimidazole curing agent, and the surface is also covered with a lot of particulate matter. Since the curing agent and resin are only physically mixed and no chemical reaction occurs, these particles are 2-ethylimidazole curing agent. Example 2

[0069] This embodiment 2 provides a method for preparing in-situ curing microcapsules for self-healing concrete that can repair microcracks, including the following steps:

[0070] (1) Mix 8g of urea and 30g of 37% formaldehyde aqueous solution evenly and divide into two parts, a and b. Add sodium bicarbonate to part a and adjust the pH of the system to 7.5~10.0. React the system at 70℃ to form an inner wall prepolymer and then cool it to room temperature for later use. Add 3g of 2-methylimidazole that has been ground and sieved through a 600-mesh sieve to part b and stir evenly. Add sodium bicarbonate and adjust the pH of the system to 7.5~10.0. React the system at 70℃ to form a prepolymer of resin and curing agent. Use this as the outer wall prepolymer and then cool it to room temperature for later use.

[0071] (2) Mix 10g of repair agent E-44 epoxy resin, 0.8g of sodium dodecylbenzenesulfonate, 0.5g of hydroquinone and 100g of deionized water evenly, and react the system under stirring and temperature of 60℃ to obtain an emulsion.

[0072] (3) Add the cooled inner wall prepolymer to the emulsion, heat the system to 70°C, add anhydrous citric acid, adjust the pH to 3.0, and let the system react under stirring at 800 r / min to obtain the first suspension containing the capsule. Continue to add the cooled outer wall prepolymer, add anhydrous citric acid, adjust the pH of the system to 1.0~3.5, and let the system react under stirring at 800 r / min to obtain the second suspension of the self-healing microcapsules.

[0073] (4) Cool the second suspension of the self-healing microcapsules to room temperature and filter it. Wash it with distilled water and ethanol respectively and then dry it in an oven to obtain the in-situ curing microcapsules for self-healing concrete in Example 2.

[0074] Figure 3 The image shows the infrared spectrum of the in-situ solidified microcapsules prepared in Example 2. Figure 3 The infrared spectrum shows that the peak at 829 cm⁻¹ is the stretching vibration peak of the epoxy group, which is a characteristic absorption peak of epoxy resin, indicating that the epoxy resin was successfully coated; the peaks at 1182 cm⁻¹ and 778 cm⁻¹ correspond to the bending vibration of the imidazole ring; the peak at 1556 cm⁻¹ corresponds to the stretching vibration of the C=N bond; and the peak at 2927 cm⁻¹ corresponds to the CH stretching vibration of the aromatic heterocycle, all of which prove that the urea-formaldehyde resin shell contains a 2-methylimidazolium curing agent. Example

[0075] This embodiment 3 provides a method for preparing in-situ curing microcapsules for self-healing concrete that can repair microcracks, including the following steps:

[0076] (1) Mix 15g isocyanate and 40g polyester polyol evenly, divide into two parts a and b. Add ammonia to part a, adjust the pH of the system to 7.5~10.0, and react the system at 80℃ to form an inner wall prepolymer. Then cool to room temperature for later use. Add 5g of ground and sieved 1000 mesh dicyandiamide to part b, stir evenly, add ammonia, adjust the pH of the system to 7.5~10.0, and react the system at 70℃ to form a prepolymer of resin and curing agent, which serves as the outer wall prepolymer. Then cool to room temperature for later use.

[0077] (2) Mix 20g of repair agent bisphenol S type epoxy resin, 2.0g of polyvinyl alcohol, 1.5g of ammonium chloride and 100g of deionized water evenly, and let the system react under stirring and temperature of 65℃ to obtain an emulsion.

[0078] (3) Add the cooled inner wall prepolymer to the emulsion, heat the system to 90°C, add acetic acid, adjust the pH to 2.0, and let the system react under stirring at 1500 r / min to obtain the first suspension containing the capsule. Continue to add the cooled outer wall prepolymer, add acetic acid, adjust the pH of the system to 1.0~3.5, and let the system react under stirring at 1500 r / min to obtain the second suspension of the self-healing microcapsules.

[0079] (4) Cool the second suspension of the self-healing microcapsules to room temperature and filter it. Wash it with distilled water and ethanol respectively and then dry it in an oven to obtain the in-situ curing microcapsules for self-healing concrete in Example 3.

[0080] Figure 4 The scanning electron microscope image of the microcapsule prepared in Example 3 shows the spherical shape of the microcapsule. The repair agent is tightly wrapped by the outer capsule wall and is evenly distributed without adhesion. This indicates that the preparation of the microcapsule for self-repair of concrete microcracks has achieved the expected effect, and the size of the microcapsule is between 5 and 150 micrometers. Example 3

[0081] In this embodiment, self-healing concrete is prepared using microcapsules prepared in Examples 1, 2, and 3. The preparation method includes the following steps:

[0082] (1) Weigh 320 parts by weight of cement, 80 parts by weight of fly ash, 736 parts by weight of river sand, and 1104 parts by weight of gravel with a particle size of 5~10mm, and stir until uniform.

[0083] (2) Add 168 parts by weight of water, 6 parts by weight of polycarboxylate superplasticizer, and 0, 0.5%, 2%, 10% and 30% by weight of cement admixture microcapsules from Examples 1, 2 and 3, and stir until evenly dispersed.

[0084] (3) The specimen was cast into a cube with dimensions of 50mm×50mm×50mm. After curing in a constant temperature and humidity chamber at 50℃ and 95% humidity for 24 hours, it was demolded and cured in the constant temperature and humidity chamber for 7 days. After pre-compression of the specimen, it was cured in the constant temperature and humidity chamber for another 7 days and its compressive strength was tested.

[0085] The compressive strength was tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". Compared with concrete without microcapsules, the compressive strength of concrete with microcapsules was improved. Different dosages of microcapsules have different effects. When the dosage is too high, it will damage the concrete structure itself, reduce compactness, and thus cause a decrease in compressive strength.

[0086] Combination Figure 5 The optical microscope images of the prepared microcapsules in concrete specimens show that the addition of microcapsules has a significant repair effect on cracks.

[0087] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. An in-situ solidified microcapsule for concrete self-repair, characterized by, Comprise: A composite capsule wall composed of an inner wall and an outer wall; The outer wall is loaded with a curing agent inside the wall, and the curing agent is attached outside the wall; the inner wall does not contain a curing agent inside the wall; The composite capsule wall contains a repair agent, which is separated from the curing agent by the inner wall, and the repair agent combines with the curing agent in situ when the composite capsule wall is damaged.

2. The in-situ curing microcapsule according to claim 1, wherein: The material of the composite capsule wall is one or more of polyurethane, acrylonitrile resin, urea-formaldehyde resin, melamine resin or phenolic resin.

3. The in-situ curing microcapsule according to claim 1, wherein: The repair agent is epoxy resin, and the curing agent is one or more of diethylene triamine, dicyandiamide, phthalic anhydride, 2-ethyl imidazole or 2-methyl imidazole.

4. The in-situ curing microcapsule according to claim 1, wherein: The microcapsule is spherical with a particle size of 5 μm to 150 μm.

5. Process for the preparation of in-situ solidified microcapsules for self- healing concrete according to any of claims 1 to 4, characterized in that, Comprise: Prepare resin raw materials for synthesizing the composite capsule wall in a set ratio, divide the resin raw materials into two parts, and react one part to generate an inner wall prepolymer, and add a set amount of curing agent to the other part to react to generate an outer wall prepolymer; Prepare the repair agent into an emulsion, react the emulsion with the inner wall prepolymer to generate a first suspension, and react the first suspension with the outer wall prepolymer to generate a second suspension; After filtering, washing and drying the second suspension, the in-situ curing microcapsule is obtained.

6. The preparation method of the in-situ curing microcapsule according to claim 5, wherein: The resin raw materials are one or more of urea, phenol, melamine, formaldehyde, isocyanate, polyester polyol or acrylonitrile, and the resin raw materials are prepared into a mixed solution, which is divided into a first mixed solution and a second mixed solution; Adjust the pH of the first mixed solution to 7.5-10.0, and the mixed system reacts at a temperature of 50-80°C to generate the inner wall prepolymer; Add the curing agent to the second mixed solution and adjust the pH to 8-10, and the mixed system reacts at a temperature of 50-80°C to generate the outer wall prepolymer.

7. The preparation method of the in-situ curing microcapsule according to claim 5 or 6, wherein: The method for generating the first suspension is to add the inner wall prepolymer to the emulsion, warm the system to 55-95°C, add a pH adjuster, adjust the pH to 1.0-3.5, and react under stirring to generate the first suspension; The method for generating the second suspension is to add the outer wall prepolymer adjuster to the first suspension, adjust the pH of the system to 1.0-3.5, and react under stirring at a temperature of 55-95°C to generate the second suspension.

8. The process for the production of in-situ cured microcapsules according to claim 7, characterized in that, The method for preparing the repair agent into an emulsion comprises: Mix the repair agent, emulsifier, auxiliary agent and deionized water uniformly to form an emulsion system, and the emulsion system reacts under stirring and at a temperature of 50-65°C to obtain the emulsion.

9. The method of claim 8, wherein the repair agent is one of E-55, E-51, E-44, E42, E35 bisphenol A epoxy resin, bisphenol F epoxy resin or bisphenol S epoxy resin.

10. The method of claim 8, wherein the emulsifier is one or more of polyvinyl alcohol, sodium dodecyl benzene sulfonate or Tween 80.

11. The method of claim 8, wherein the auxiliary agent is one or more of resorcinol, hydroquinone or ammonium chloride.

12. The method of claim 6, wherein the system is adjusted to a pH value of 1.0-3.5 using one or more of sulfuric acid, acetic acid and citric acid; and the curing agent is sieved to a mesh size of 100-1000 mesh.

13. The self-repairing concrete of claim 1, wherein the in-situ cured microcapsules are added in an amount of 0.5-30% by weight.

14. The self-repairing concrete of claim 13, wherein the in-situ cured microcapsules are added in an amount of 0.5-30% by weight. ​ ​ ​ 13. A self-healing concrete, characterized in that ​ ​ ​ ​

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