Phase change-repair microcapsule with core-shell composite structure as well as preparation method and application of phase change-repair microcapsule

Abstract

The invention relates to the technical field of intelligent concrete functional materials, in particular to a core-shell composite structure phase change-repair microcapsule and a preparation method and application thereof. The core-shell composite structure phase change-repair microcapsule provided by the invention sequentially comprises an inner core, an inner shell layer and an outer shell layer from inside to outside. Wherein the inner core comprises a normal-temperature phase-change material and can absorb early hydration heat of concrete; the inner shell layer is a macromolecular coating layer and wraps the outer side of the inner core, so that the stability of the inner core can be guaranteed; the shell layer comprises a composite functional layer formed by a high-temperature phase change material, a self-repairing agent and an alkali-resistant shell material, and later-stage high-temperature response temperature control and crack self-repairing can be achieved. Through functional material integration and a multi-stage response structure, the limitation of a traditional single-function microcapsule is broken through, the microcapsule is particularly suitable for complex scenes such as concrete serving in a low-temperature environment, and the crack resistance and durability of the concrete can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent concrete functional materials technology, and in particular to a core-shell composite phase change-repair microcapsule, its preparation method, and its application. Background Technology

[0002] Concrete, as a commonly used engineering material, has a wide range of applications, such as dams, buildings, bridges, and roads. Overall, concrete faces a very complex environment, with temperature having a significant impact on its performance. For example, in cold regions, concrete is subject to extreme diurnal temperature variations, making it prone to freeze-thaw cycles and other forms of degradation. This can lead to reduced strength, cracking, and even complete loss of function.

[0003] Later, researchers discovered that self-healing concrete is an effective method for addressing concrete deterioration, with microcapsule-filled concrete attracting widespread attention. Microcapsule self-healing involves pre-inserting microcapsules containing a repair agent into the concrete. When external forces damage the concrete, the microcapsules rupture, releasing the repair material to fill and repair cracks, thus achieving self-healing of the concrete.

[0004] However, existing microcapsules only have temperature control or self-healing functions, which cannot fully meet the complex needs of concrete in low-temperature environments. Furthermore, these microcapsules have poor stability in low-temperature alkaline environments, and the temperature control and repair timeliness are mismatched. Summary of the Invention

[0005] In view of this, the present invention provides a core-shell composite phase change-repair microcapsule, its preparation method and application. The core-shell composite phase change-repair microcapsule provided by the present invention has good stability, adaptability and functional effectiveness in low temperature environment, filling the technical gap of intelligent concrete functional materials for low temperature environment service.

[0006] This invention provides a core-shell composite phase change-repair microcapsule, comprising, from the inside out, a core, an inner shell layer, and an outer shell layer; the core comprises a room-temperature phase change material with a phase change temperature of 12~40℃; the inner shell layer comprises a polymer coating layer; the outer shell layer comprises a composite functional layer comprising a high-temperature phase change material, a self-healing agent, and an alkali-resistant shell material; the high-temperature phase change material has a phase change temperature of 45~80℃. Preferably, the latent heat of the room-temperature phase change material is 120~200 J / g; the room-temperature phase change material includes one or more of paraffin, decane, tetradecyl alcohol and diethylene glycol monoethyl ether stearate.

[0007] Preferably, the polymer material of the inner shell layer includes one or more of urea-formaldehyde resin, polyurethane, and polymethyl methacrylate.

[0008] Preferably, the latent heat of the high-temperature phase change material is 80~150J / g; the high-temperature phase change material includes one or more of high-melting-point paraffin wax, stearic acid, butyl stearate and palmitic acid; the phase change temperature of the high-melting-point paraffin wax is 52~70℃.

[0009] Preferably, the self-healing agent includes one or more of the following: Bacillus pasteurellii spores, urease spores, carbonic anhydrase, urea, sulfate-reducing spores, and calcium phosphate crystallizer.

[0010] Preferably, the mass ratio of the high-temperature phase change material to the self-healing agent is 3~5:1; the mass of the self-healing agent accounts for 5~15% of the total mass of the outer shell layer.

[0011] Preferably, the alkali-resistant shell material includes one or more of silica sol, epoxy-modified silica sol, epoxy resin, and cement-based composite materials; the epoxy resin is bisphenol A type epoxy resin; the bisphenol A type epoxy resin includes one or more of bisphenol A type epoxy resin E-44, bisphenol A type epoxy resin E-51, and modified epoxy resin.

[0012] Preferably, the preparation method of the modified epoxy resin includes the following steps: mixing bisphenol A type epoxy resin, acetate buffer and deionized water to obtain a microcapsule dispersion; mixing an aminosilane coupling agent and ethanol to obtain a modifier; and adding the modifier dropwise to the microcapsule dispersion for hydrolysis and grafting reaction.

[0013] This invention also provides a method for preparing the core-shell composite phase transition-repair microcapsules described above, comprising the following steps: (1) The room temperature phase change material is mixed with emulsifier and water to emulsify and obtain an emulsion. The emulsion is then mixed with an initiator to carry out a first polymerization reaction to obtain core microcapsules. Alternatively, a room-temperature phase change material and an organic solvent are mixed to obtain an oil phase, an emulsifier and water are mixed to obtain an aqueous phase, the oil phase and the aqueous phase are mixed and emulsified to obtain a water-in-oil emulsion, and the water-in-oil emulsion is mixed with an interfacial initiator to carry out an interfacial polymerization reaction to obtain core microcapsules; (2) The core microcapsule is mixed with a polymer prepolymer, a catalyst and water to carry out a second polymerization reaction to obtain a core-inner shell microcapsule; (3) The core-inner shell microcapsule is mixed with molten high-temperature phase change material, self-healing agent and alkali-resistant shell material precursor to carry out surface in-situ polymerization reaction to obtain the core-shell composite phase change-repair microcapsule.

[0014] The present invention also provides the application of the core-shell composite phase change-repair microcapsules described in the above-described scheme or the core-shell composite phase change-repair microcapsules prepared by the above-described scheme in concrete products.

[0015] This invention provides a core-shell composite phase change-repair microcapsule. The core-shell composite phase change-repair microcapsule provided by this invention, through a specific hierarchical structure and specific functional materials, achieves a synergistic function of "early temperature control and crack prevention + late-stage response repair," ensuring that the core-shell composite phase change-repair microcapsule possesses good stability, adaptability, and functional effectiveness in low-temperature environments. This fills the technological gap in intelligent concrete functional materials for low-temperature environments, reduces the maintenance costs of concrete serving in low-temperature environments, and extends its service life. Specifically: The core-shell composite phase transition-repair microcapsule provided by this invention comprises, from the inside out, a core, an inner shell layer, and an outer shell layer (e.g., ...). Figure 1 (As shown). The core comprises a room-temperature phase change material capable of absorbing the early hydration heat of concrete; the inner shell is a polymer coating layer encapsulating the core to ensure its stability; the outer shell comprises a composite functional layer formed by a high-temperature phase change material, a self-healing agent, and an alkali-resistant shell material, enabling later-stage high-temperature response temperature control and crack self-healing. This invention, through the integration of functional materials and a multi-level response structure, overcomes the limitations of traditional single-function microcapsules, making it particularly suitable for complex scenarios such as concrete operating in low-temperature environments, and can significantly improve the crack resistance and durability of concrete.

[0016] This invention also provides a method for preparing the core-shell composite phase transition-repair microcapsules described above. The preparation method provided by this invention is simple in steps, convenient to operate, safe and controllable, and has good repeatability.

[0017] This invention also provides the application of the core-shell composite phase change-repair microcapsules described in the above-described scheme or the core-shell composite phase change-repair microcapsules prepared by the above-described scheme in concrete products. The core-shell composite phase change-repair microcapsules provided by this invention, by controlling the type and ratio of phase change materials (room temperature phase change materials and high temperature phase change materials), can be used in various types and structures of concrete. They are particularly well-suited for precisely matching the performance requirements of concrete serving in low-temperature environments, and are especially suitable for low-temperature environments such as underground engineering in cold regions, low-temperature roads, or buildings in permafrost regions. They can integrate the temperature regulation function and crack self-repair function of concrete, improving the durability and safety of concrete serving in low-temperature environments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of this invention, the accompanying drawings used in the embodiments of this invention or in the prior art are briefly described below. For those skilled in the art, other drawings can be derived from the following drawings without creative effort, and all such drawings are within the protection scope of this invention.

[0019] Figure 1This is a schematic diagram of the core-shell composite phase change-repair microcapsule provided by the present invention; wherein, 1 is the core, 2 is the inner shell layer, and 3 is the outer shell layer; Figure 2 Particle size distribution curve of the core-shell composite phase change-repair microcapsule provided by the present invention; Figure 3 The figure shows the compressive strength test results of concrete cubes with doped and undoped core-shell composite phase transition-repair microcapsules of the present invention. Detailed Implementation

[0020] This invention provides a core-shell composite phase change-repair microcapsule, comprising, from the inside out, a core, an inner shell layer, and an outer shell layer; the core comprises a room-temperature phase change material with a phase change temperature of 12~40℃; the inner shell layer comprises a polymer coating layer; the outer shell layer comprises a composite functional layer comprising a high-temperature phase change material, a self-healing agent, and an alkali-resistant shell material; the high-temperature phase change material has a phase change temperature of 45~80℃. The core-shell composite phase change-repair microcapsule provided by the present invention includes a core; the latent heat of the room temperature phase change material is preferably 120~200 J / g; the room temperature phase change material preferably includes one or more of paraffin, decane, tetradecyl alcohol and diethylene glycol monoethyl ether stearate.

[0021] In this invention, the paraffin wax is preferably C18~C22 paraffin wax, the phase transition temperature is preferably 30~35℃, and the latent heat is preferably 180J / g; the phase transition temperature of the diethylene glycol monoethyl ether stearate is preferably 10~20℃, more preferably 12~15℃, and the latent heat is preferably 170J / g.

[0022] The core-shell composite phase change-repair microcapsule provided by the present invention includes an inner shell layer; the polymer material of the inner shell layer preferably includes one or more of urea-formaldehyde resin, polyurethane and polymethyl methacrylate (PMMA).

[0023] In this invention, the porosity of the inner shell layer is preferably ≤5%.

[0024] In this invention, the ratio of the diameter of the core to the thickness of the inner shell is preferably (5~8):1~2, and more preferably (5~7):1.

[0025] The core-shell composite phase change-repair microcapsule provided by the present invention includes an outer shell layer; the latent heat of the high-temperature phase change material is preferably 80~150J / g; the high-temperature phase change material preferably includes one or more of high-melting-point paraffin wax, stearic acid, butyl stearate and palmitic acid.

[0026] In this invention, the phase transition temperature of the high melting point paraffin is preferably 52~70℃; the high melting point paraffin is preferably C24~C28 paraffin.

[0027] In this invention, the phase transition temperature of the stearic acid is preferably 69~70℃.

[0028] In this invention, the phase change temperature of the butyl stearate is preferably 45-50°C, and the latent heat is preferably 105 J / g. For concrete used in low-temperature environments, replacing the room-temperature phase change material with diethylene glycol monoethyl ether stearate and the high-temperature phase change material with butyl stearate helps to improve the low-temperature temperature control effect.

[0029] In this invention, the phase transition temperature of the palmitic acid is preferably 62~64℃.

[0030] In this invention, the self-healing agent preferably includes one or more of the following: Bacillus pasteurellii spores, urease-producing bacteria spores, carbonic anhydrase (CA), urea, sulfate-reducing bacteria spores, and calcium phosphate crystallizer; the urease-producing bacteria spores are preferably low-temperature resistant urease-producing bacteria spore powder; the low-temperature resistant urease-producing bacteria spore powder preferably has a tolerance temperature of -10 to 80°C, a particle size of 2 to 3 μm, and an activity of ≥10. 9 CFU / g; the low-temperature urease-resistant bacterial spore powder is preferably Bacillus pasteurellii spore powder. For sulfate-eroded environments, the self-healing agent can be a combination of sulfate-reducing bacterial spores and calcium phosphate crystallizing agent to enhance resistance to sulfate erosion.

[0031] In this invention, the particle size of the self-healing agent is preferably 1~5μm, more preferably 2~4μm.

[0032] In this invention, the mass ratio of the high-temperature phase change material to the self-healing agent is preferably 3 to 5:1, and more preferably 4:1.

[0033] In this invention, the mass of the self-healing agent preferably accounts for 5-15% of the total mass of the outer shell layer, more preferably 8-12%.

[0034] In this invention, the alkali-resistant shell material preferably includes one or more of silica sol, epoxy-modified silica sol, epoxy resin, and cement-based composite materials. When the concrete is in a high-salt marine environment, the alkali-resistant shell material can be epoxy-modified silica sol, with graphene added to improve corrosion resistance; the graphene preferably accounts for 5-8% of the total mass of the alkali-resistant shell material, more preferably 6-7%.

[0035] In this invention, the SiO2 content of the silica sol is preferably 28%.

[0036] In this invention, the SiO2 content of the epoxy-modified silica sol is preferably 30%. In a specific embodiment of this invention, the epoxy-modified silica sol is the KHZCM-30 type epoxy-modified silica sol from Kehan ​​Silicon Products Co., Ltd.

[0037] In this invention, the epoxy resin is preferably a bisphenol A type epoxy resin; the bisphenol A type epoxy resin preferably includes one or more of bisphenol A type epoxy resin E-44, bisphenol A type epoxy resin E-51, and modified epoxy resin; the modified epoxy resin preferably includes one or more of aminosilane coupling agent modified bisphenol A type epoxy resin E-44 and aminosilane coupling agent modified bisphenol A type epoxy resin E-51; the grafting amount of the modified epoxy resin is preferably 1~2% (based on 100% of the mass of the alkali-resistant shell material of the outer shell layer). This invention improves the interfacial bonding strength between the core-shell composite structure phase change-repair microcapsules and the concrete matrix by grafting silane coupling agents onto the surface of the outer shell layer, thereby increasing the interfacial bonding strength by more than 30%.

[0038] In this invention, the preferred method for preparing the modified epoxy resin includes the following steps: mixing bisphenol A type epoxy resin, acetate buffer and deionized water to obtain a microcapsule dispersion; mixing an aminosilane coupling agent and ethanol to obtain a modifier; and adding the modifier dropwise to the microcapsule dispersion for hydrolysis and grafting reaction.

[0039] In this invention, the pH value of the microcapsule dispersion is preferably 4.0 to 5.0.

[0040] In this invention, the aminosilane coupling agent is preferably KH-550.

[0041] In this invention, the hydrolysis and grafting reactions are preferably carried out under stirring conditions; the temperature of the hydrolysis and grafting reactions is preferably 20-25°C, and the holding time is preferably 1-2 hours, more preferably 1.5 hours. This invention, by controlling the pH value and temperature, avoids the self-polymerization or uncontrolled hydrolysis of the coupling agent, ensuring grafting uniformity and the integrity of the microcapsule structure.

[0042] In this invention, the hydrolysis and grafting reactions preferably further include centrifugation, removal of unreacted coupling agent, and drying of the resulting product; the removal of unreacted coupling agent is preferably washing; the washing is preferably performed 2 to 3 times; the drying is preferably vacuum drying or spray drying; the vacuum drying temperature is preferably 45 to 65°C, and the vacuum degree is preferably -0.08 to -0.1 MPa. This invention, by using spray drying instead of vacuum drying, can improve production efficiency by more than 5 times.

[0043] In this invention, the cement-based composite material is preferably a tricalcium silicate-silica fume-polyvinyl alcohol fiber composite material.

[0044] In this invention, the preparation method of the tricalcium silicate-silica fume-polyvinyl alcohol fiber composite material preferably includes the following steps: mixing tricalcium silicate, silica fume, polyvinyl alcohol (PVA) fiber, water reducing agent and water (denoted as mixture B) and then sequentially molding, curing and grinding.

[0045] In this invention, the preferred mass ratio of tricalcium silicate to silica fume is 14:3.

[0046] In this invention, the mass ratio of tricalcium silicate to polyvinyl alcohol fiber is preferably 14:1.

[0047] In this invention, the water-reducing agent preferably includes a polycarboxylate-based high-efficiency water-reducing agent; the solid content of the polycarboxylate-based high-efficiency water-reducing agent is preferably 38-40%; the polycarboxylate-based high-efficiency water-reducing agent is preferably a low-temperature compatible polycarboxylate-based high-efficiency water-reducing agent; in a specific embodiment of this invention, the water-reducing agent can be a polycarboxylate high-performance water-reducing agent (manufacturer: Weike Building Materials Sales Center, product model: HLX, standard type, solid content 38.3%, low-temperature compatible type). This invention uses the above-mentioned water-reducing agent, which not only meets the dispersion requirements of cement-based materials but also adapts to low-temperature engineering scenarios, avoiding slurry clumping and insufficient fluidity at low temperatures.

[0048] In this invention, the mass ratio of tricalcium silicate to water-reducing agent is preferably 140:1.

[0049] In this invention, the water is preferably deionized water.

[0050] In this invention, the preferred mass ratio of the water-reducing agent to water is 1:20.

[0051] In this invention, the mixture B preferably includes the following steps: stirring and mixing tricalcium silicate and silica fume (referred to as the first stirring and mixing) to obtain a premixed powder; ultrasonically stirring and mixing polyvinyl alcohol fiber, water reducing agent and deionized water to obtain a fiber dispersion; and stirring and mixing the fiber dispersion and the premixed powder (referred to as the second stirring and mixing).

[0052] In this invention, the first mixing device is preferably a planetary mixer; the first mixing time is preferably 5 minutes.

[0053] In this invention, the ultrasonic stirring and mixing preferably includes the following steps: ultrasonically dispersing polyvinyl alcohol fibers and water, and then adding a water-reducing agent to the resulting dispersion and stirring and mixing.

[0054] In this invention, the ultrasonic dispersion power is preferably 300W, and the ultrasonic dispersion time is preferably 10 minutes.

[0055] In this invention, the stirring speed of the second mixing is preferably 500 rpm, and the mixing time is preferably 15 minutes.

[0056] In this invention, the molding preferably includes the following steps: pouring the slurry obtained by mixing B into a mold and vibrating it to compact it.

[0057] In this invention, the vibration frequency is preferably 50~60Hz, the amplitude is preferably 0.5~1.0mm, and the duration is preferably 2~3min.

[0058] In this invention, the curing is preferably carried out in a standard curing room; the curing preferably includes pre-demolding curing and post-demolding curing performed sequentially; the temperature of the pre-demolding curing is preferably 18-20 degrees Celsius, the humidity is preferably not less than 95%, and the curing time is preferably 24 hours; the temperature of the post-demolding curing is preferably 18-20 degrees Celsius, the humidity is preferably not less than 95%, and the curing time is preferably 7 days.

[0059] In this invention, the grinding is preferably ball milling; the ball milling is preferably wet ball milling; the medium for wet ball milling is preferably anhydrous ethanol; and the ball milling time is preferably 2 hours.

[0060] In this invention, the grinding process preferably includes sieving the resulting product; the sieve used for sieving preferably has a mesh size of 200 mesh (74~75 micrometers).

[0061] In this invention, the porosity of the outer shell layer is preferably 8-12%, more preferably 9-10%.

[0062] In this invention, the thickness ratio of the inner shell layer to the outer shell layer is preferably 1~2:1~3, more preferably 1.5:2.

[0063] In this invention, the particle size of the core-shell composite phase change-repair microcapsules is preferably 50~200μm, more preferably 100~150μm.

[0064] This invention also provides a method for preparing the core-shell composite phase transition-repair microcapsules described above, comprising the following steps: (1) The room temperature phase change material is mixed with emulsifier and water to emulsify and obtain an emulsion. The emulsion is then mixed with an initiator to carry out a first polymerization reaction to obtain core microcapsules. Alternatively, a room-temperature phase change material and an organic solvent are mixed to obtain an oil phase, an emulsifier and water are mixed to obtain an aqueous phase, the oil phase and the aqueous phase are mixed and emulsified to obtain a water-in-oil emulsion, and the water-in-oil emulsion is mixed with an interfacial initiator to carry out an interfacial polymerization reaction to obtain core microcapsules; (2) The core microcapsule is mixed with a polymer prepolymer, a catalyst and water to carry out a second polymerization reaction to obtain a core-inner shell microcapsule; (3) The core-inner shell microcapsule is mixed with molten high-temperature phase change material, self-healing agent and alkali-resistant shell material precursor to carry out surface in-situ polymerization reaction to obtain the core-shell composite phase change-repair microcapsule.

[0065] This invention involves emulsifying a room-temperature phase change material with an emulsifier and water (referred to as the first water) to obtain an emulsion. The emulsion is then mixed with an initiator to undergo a first polymerization reaction, yielding core microcapsules. In this invention, the emulsifier preferably includes one or more of sodium dodecylbenzenesulfonate and Tween-80.

[0066] In this invention, the mass ratio of the room-temperature phase change material to the emulsifier is preferably 10~20:1, more preferably 15~17:1.

[0067] In this invention, the first water is preferably deionized water.

[0068] In this invention, the mass ratio of the first water to the room-temperature phase change material is preferably 3 to 5:1, and more preferably 4:1.

[0069] In this invention, the first mixing is preferably stirring; the stirring speed is preferably 300~500 r / min, more preferably 350 r / min, and the mixing time is preferably 20~40 minutes, more preferably 35 minutes.

[0070] In this invention, the initiator preferably includes one or more of ammonium persulfate and azobisisobutyronitrile.

[0071] In this invention, the mass ratio of the initiator to the room-temperature phase change material is preferably 0.5~2:100, more preferably 1~1.5:100.

[0072] In this invention, the temperature of the first polymerization reaction is preferably 60~70℃, more preferably 65℃, and the holding time is preferably 2~4 hours, more preferably 3 hours.

[0073] In this invention, the first polymerization reaction preferably includes cooling the resulting product system and then separating the solid and liquid phases; the final cooling temperature is preferably room temperature; and the solid-liquid separation is preferably centrifugation.

[0074] Alternatively, the present invention mixes a room-temperature phase change material and an organic solvent to obtain an oil phase, mixes an emulsifier and water to obtain an aqueous phase, mixes the oil phase and the aqueous phase (denoted as mixture A) and emulsifies them to obtain a water-in-oil emulsion, and mixes the water-in-oil emulsion with an interfacial initiator to carry out an interfacial polymerization reaction to obtain core microcapsules.

[0075] In this invention, the organic solvent is preferably an aromatic solvent; the aromatic solvent is preferably toluene.

[0076] In this invention, the preferred mass ratio of the room-temperature phase change material to the organic solvent is 3:1.

[0077] In this invention, the mass ratio of the emulsifier to water is preferably 1:40.

[0078] In this invention, the volume ratio of the oil phase to the water phase is preferably 1:3.

[0079] In this invention, the mixing A is preferably stirred; the stirring speed is preferably 400 r / min, and the mixing time is preferably 30 min.

[0080] In this invention, the interface initiator is preferably hydrochloric acid; the mass ratio of the interface initiator to the emulsifier is preferably 2:5.

[0081] In this invention, the preferred temperature for the interfacial polymerization reaction is 50°C, and the preferred holding time is 1.5 hours. By controlling the reaction conditions, this invention increases the core coating rate to over 95%.

[0082] In this invention, the interfacial polymerization reaction preferably further includes cooling and centrifuging the resulting product.

[0083] In order to control the uniformity of stirring and the stability of reaction temperature during large-scale production, this invention preferably uses continuous polymerization equipment to ensure the consistency of product performance.

[0084] After obtaining the core, the present invention mixes the core microcapsule with a polymer prepolymer, a catalyst, and water (denoted as the second water) to carry out a second polymerization reaction to obtain a core-inner shell microcapsule. In the present invention, the polymer prepolymer preferably includes one or more of urea-formaldehyde resin prepolymer, polyurethane prepolymer, and PMMA prepolymer.

[0085] In this invention, the weight-average molecular weight of the urea-formaldehyde resin prepolymer is preferably 200-500 Da, more preferably 300-400 Da.

[0086] In this invention, the solid content of the polyurethane prepolymer is preferably 65%, and the weight-average molecular weight is preferably 1000~3000 Da, more preferably 2000 Da.

[0087] In this invention, the weight-average molecular weight of the PMMA prepolymer is preferably 10,000 to 100,000 Da.

[0088] In this invention, the catalyst is preferably hydrochloric acid or oxalic acid.

[0089] In this invention, the mass ratio of the catalyst to the polymer prepolymer is preferably 1 to 3:100, more preferably 2:100.

[0090] In this invention, the second water is preferably deionized water.

[0091] In this invention, the mass ratio of the second water to the core microcapsule is preferably 5~8:1, more preferably 6~7:1.

[0092] In this invention, the second mixing preferably includes the following steps: dispersing the core microcapsules in deionized water to obtain a pre-dispersion, and then adding a polymer prepolymer and a catalyst to the pre-dispersion.

[0093] In this invention, the pH of the system is preferably adjusted to 4-6 before the second polymerization reaction; the reagent used to adjust the pH of the system is preferably hydrochloric acid or acetic acid; the concentration of hydrochloric acid is preferably 1-2 mol / L; and the concentration of acetic acid is preferably 2-3 mol / L.

[0094] In this invention, the second polymerization reaction is preferably carried out under stirring conditions; the stirring speed is preferably 200~300 r / min; the temperature of the second polymerization reaction is preferably 50~60℃, more preferably 55℃, and the holding time is preferably 3~5 hours, more preferably 4 hours.

[0095] In this invention, the second polymerization reaction preferably includes washing the resulting product and then separating the solid and liquid phases; the washing is preferably water washing; the water used for washing is preferably deionized water; the number of washings is preferably three or more; and the solid-liquid separation is preferably centrifugation.

[0096] After obtaining the core-inner shell microcapsules, the present invention mixes the core-inner shell microcapsules with molten high-temperature phase change material, self-healing agent and alkali-resistant shell material precursor (referred to as the third mixture) and carries out an in-situ surface polymerization reaction to obtain the core-shell composite phase change-repair microcapsules.

[0097] In this invention, the melting temperature is preferably 70~90℃, more preferably 80℃, and the holding time is preferably 10~20 minutes, more preferably 15 minutes.

[0098] In this invention, the alkali-resistant shell material precursor preferably includes one or more of tetraethyl orthosilicate, epoxy-modified silica sol, epoxy resin, and cement-based composite materials.

[0099] In this invention, the third mixing preferably includes the following steps: melting a high-temperature phase change material and mixing it with a self-healing agent to obtain a composite functional slurry; ultrasonically mixing the core-inner shell microcapsules and the composite functional slurry to obtain a premix; and then mixing the premix with an alkali-resistant shell material precursor.

[0100] In this invention, the ultrasonic mixing time is preferably 15 to 25 minutes, more preferably 20 minutes.

[0101] In this invention, the surface in-situ polymerization reaction preferably includes adjusting the pH of the system to 7-9 beforehand; the reagent used to adjust the pH of the system is preferably ammonia or triethanolamine; the concentration of the ammonia is preferably 2-5 mol / L, more preferably 3 mol / L.

[0102] In this invention, the surface in-situ polymerization reaction is preferably carried out at room temperature, and the reaction time is preferably 1 to 2 hours, more preferably 1.5 hours.

[0103] In this invention, the surface in-situ polymerization reaction preferably further includes drying and sieving the resulting product sequentially; the drying temperature is preferably 60-80°C, and the holding time is preferably 8-12 hours; the target particle size for sieving is preferably 50-200 μm, more preferably 100-150 μm. This invention avoids damaging the activity of the low-temperature resistant self-healing agent through low-temperature drying.

[0104] The present invention also provides the application of the core-shell composite phase change-repair microcapsules described in the above-described scheme or the core-shell composite phase change-repair microcapsules prepared by the above-described scheme in concrete products.

[0105] In this invention, the preferred method of application includes the following steps: mixing the core-shell composite phase change-repair microcapsules and concrete mixture, followed by sequential pouring and curing; the concrete mixture includes cement.

[0106] In this invention, the cement is preferably P·O 42.5 early-strength cement.

[0107] In this invention, the mass ratio of the core-shell composite phase change-repair microcapsule to cement is preferably 2~5:100, more preferably 4:100. For high-strength concrete (design strength grade ≥ C60), the dosage of the core-shell composite phase change-repair microcapsule is preferably 2~3%; for ordinary concrete (C30~C50), the dosage is preferably 3~5%.

[0108] In this invention, when the mass ratio of the core-shell composite phase change-repair microcapsules to cement is greater than 5:100, it is preferable to increase the dosage of water-reducing agent in the concrete: based on 5 wt%, for every 1 wt% increase in the core-shell composite phase change-repair microcapsules, the dosage of water-reducing agent increases by 0.1 wt%. Excessive dosage of the core-shell composite phase change-repair microcapsules may lead to a decrease in the fluidity of the concrete. By increasing the dosage of water-reducing agent, it is possible to ensure that the slump of the concrete meets the construction requirements (≥160 mm).

[0109] In this invention, the water-cement ratio of the concrete mixture is preferably 0.4 to 0.6, and the sand ratio is preferably 35 to 45%.

[0110] In this invention, the curing is preferably performed at room temperature or at low temperature; the room temperature curing temperature is preferably 25~40℃, more preferably 30~35℃, and the heat preservation time is preferably 1~7 days. After curing with this invention, when the ambient temperature is ≥50℃ or cracks with a width ≥0.1mm appear in the concrete, the outer shell layer responds by releasing functional components (high-temperature phase change material and self-healing agent), achieving a synergistic effect of temperature control and repair. In this invention, the low-temperature curing preferably includes the following steps: curing at 25-40℃ for the first 1-3 days, and then curing at 18-22℃ and relative humidity ≥95% for the 4th-28th days.

[0111] The core-shell composite phase change-repair microcapsules provided by this invention are suitable for concrete structures in underwater, underground or marine engineering. They can improve the crack resistance and durability of concrete, with a 28-day compressive strength retention rate of ≥90% and a crack self-repair rate of ≥60% (when the crack width is ≤0.3mm).

[0112] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments.

[0113] Example 1 This embodiment prepared core-shell composite phase transition-repair microcapsules adapted to low-temperature environments. The specific steps are as follows: 1) Material Preparation: The room-temperature phase change material uses diethylene glycol monoethyl ether stearate (phase change temperature 12~15℃, latent heat 170J / g), suitable for early hydration heat control of concrete in low-temperature environments; the high-temperature phase change material uses butyl stearate (phase change temperature 45~50℃, latent heat 105J / g), suitable for later temperature fluctuation response in low-temperature environments; the inner shell layer uses polyurethane prepolymer (65% solid content, weight-average molecular weight 2000Da), improving shell flexibility in low-temperature environments; the alkali-resistant shell material of the outer shell layer uses epoxy-modified silica sol (Kehan ​​Silicon Products Co., Ltd., KHZCM-30, SiO2 content 30%), enhancing stability in low-temperature alkaline environments; the self-healing agent uses low-temperature resistant urease-resistant spore powder (particle size distribution 2~3μm, activity ≥10). 9 (CFU / g, with a temperature tolerance of -10~80℃); among the auxiliary materials, the emulsifier is Tween-80, the initiator is azobisisobutyronitrile, the catalyst is oxalic acid, and the water is deionized water.

[0114] 2) The preparation formula (by mass) is shown in Table 1: Table 1. Preparation formula of this embodiment

[0115] 3) Preparation steps: S1. Core preparation: 16g of diethylene glycol monoethyl ether stearate and 1.2g of Tween-80 were added to 55g of deionized water and emulsified at 350r / min for 35min to obtain a uniform oil phase emulsion; 0.24g of azobisisobutyronitrile was added to the obtained oil phase emulsion, the temperature was raised to 65℃, and the polymerization reaction was carried out at a constant temperature for 3.5h; after the reaction was completed, the mixture was cooled to room temperature and centrifuged at 8000r / min for 10min. The supernatant was discarded to obtain the core microcapsules.

[0116] S2. Inner shell coating: The core microcapsules obtained in step S1 were dispersed in 35g of deionized water, 22g of polyurethane prepolymer and 0.44g of oxalic acid were added, the pH of the system was adjusted to 5.5 with dilute acetic acid, and a secondary polymerization reaction was carried out at 50℃ for 4.5h with a stirring speed of 250r / min. After the reaction was completed, the microcapsules were washed three times with deionized water and centrifuged to obtain the core-inner shell microcapsules.

[0117] S3. Outer shell layer composite: 9g of butyl stearate was heated to 55℃ to melt, and 2.25g of low-temperature resistant urease-resistant spore powder was added. The mixture was stirred at 300r / min until homogeneous to obtain a composite functional slurry. The core-inner shell microcapsules were added to the composite functional slurry and ultrasonically dispersed for 20min (power 200W). Then, 13g of epoxy-modified silica sol was added, and the pH of the system was adjusted to 8.5 with ammonia. The mixture was stirred at room temperature for 1.5h.

[0118] S4. Drying and sieving: The product obtained in step S3 is placed in a vacuum drying oven and dried at 65°C for 12 hours. It is then sieved through a standard sieve to obtain core-shell composite phase change-repair microcapsules with a particle size of 50~200μm. The thickness ratio of the core, inner shell, and outer shell is 6:1.5:2.5.

[0119] Example 2 In this embodiment, the core-shell composite phase change-repair microcapsules prepared in Example 1 are applied to concrete, and the prepared concrete is used for underground engineering in cold regions.

[0120] 1) The concrete mix proportions (by mass) in this embodiment are shown in Table 2: Table 2 Concrete mix proportions for this embodiment

[0121] 2) Application steps: 1) Pour cement, river sand and gravel into a concrete mixer and dry mix for 2 minutes until evenly mixed; 2) Add the water-reducing agent to water and stir to dissolve it, thus obtaining an aqueous solution of the water-reducing agent; spray the aqueous solution of the water-reducing agent evenly into the mixer and mix for 3 minutes. 3) Add 12 kg of core-shell composite phase change-repair microcapsules to a mixer and continue stirring for 2 minutes until well mixed; 4) Pour the concrete into the mold (100mm×100mm×100mm), vibrate it to make it dense, and then use a low temperature curing process: place it in a 25~40℃ heat preservation shed for 1~3 days after pouring, and then transfer it to a standard curing room (temperature 20±2℃, relative humidity ≥95%) for 28 days to continue curing, which is suitable for the construction and curing conditions of underground engineering in cold regions.

[0122] Example 3 This embodiment uses interfacial polymerization to prepare core-shell composite phase change-repair microcapsules. The specific steps are as follows: 1) Material preparation: The room temperature phase change material is paraffin wax (C18~C22 paraffin wax, phase change temperature 30~35℃, latent heat of 180J / g); the inner shell layer is urea-formaldehyde resin prepolymer (molecular weight 400Da); the high temperature phase change material is C24~C28 high melting point paraffin wax (phase change temperature 55~65℃, latent heat of 120J / g); the alkali-resistant shell material in the outer shell layer is bisphenol A type epoxy resin E-44 modified with aminosilane coupling agent KH-550; the self-healing agent is Bacillus pasteurellii spore powder (particle size distribution of 3~4μm); among the auxiliary materials, the emulsifier is sodium dodecylbenzenesulfonate, the oil phase solvent is toluene, the catalyst is hydrochloric acid, and the water is deionized water. 2) Preparation formula (by mass): 15g paraffin wax, 5g toluene, 1g sodium dodecylbenzenesulfonate, 20g urea-formaldehyde resin prepolymer, 0.4g hydrochloric acid, 8g C24~C28 high-melting-point paraffin wax, 2g Bacillus pasteurellii spore powder, 12g aminosilane coupling agent KH-550 modified bisphenol A type epoxy resin E-44, and 80g deionized water. 3) Preparation steps (interfacial polymerization method): S1. Core preparation: 15g of paraffin was dissolved in 5g of toluene to obtain the oil phase; 1g of sodium dodecylbenzenesulfonate was dissolved in 40g of deionized water to obtain the aqueous phase; the oil phase and aqueous phase were mixed at a volume ratio of 1:3 and emulsified at a stirring speed of 400r / min for 30min to obtain a water-in-oil emulsion; 0.4g of hydrochloric acid was added, the temperature was raised to 50℃, and the interfacial polymerization reaction was carried out for 1.5h; after cooling, the core microcapsules were obtained by centrifugation (encapsulation rate 96%). S2. Inner shell coating: Disperse the core microcapsules in 20g of deionized water (water to core mass ratio 6:1), add 20g of urea-formaldehyde resin prepolymer, adjust the pH to 5 with hydrochloric acid, and perform secondary polymerization at 250r / min and 55℃ for 4h; wash and centrifuge to obtain core-inner shell microcapsules.

[0123] S3. Shell Layer Composite: Bisphenol A type epoxy resin E-44, acetate buffer, and deionized water were mixed to obtain a microcapsule dispersion with a pH of 4.5; aminosilane coupling agent KH-550 and ethanol were mixed to obtain a modifier, which was added dropwise to the microcapsule dispersion. Hydrolysis and grafting reactions were carried out at 23°C for 1.5 hours under stirring conditions. After centrifugation, unreacted coupling agent was washed to remove it, and the mixture was spray-dried to obtain the aminosilane coupling agent KH-550 modified bisphenol A type epoxy resin E-44 precursor.

[0124] 8g of C24~C28 high melting point paraffin was heated to 80℃ and melted. 2g of Bacillus pasteurellii spore powder was added and stirred evenly to obtain a composite functional slurry. Core-inner shell microcapsules were added and ultrasonically dispersed for 20min. Then, 12g of aminosilane coupling agent KH-550 modified bisphenol A type epoxy resin E-44 precursor was added. The pH value was adjusted to 8 with triethanolamine and the reaction was stirred at room temperature for 1.5h.

[0125] S4: Drying and sieving: Vacuum drying at 70℃ (maintained within the range of -0.08~-0.1MPa) for 10h, followed by sieving to obtain core-shell composite phase change-repair microcapsules with a particle size of 60~180μm (the thickness ratio of the inner core: inner shell: outer shell is 7:1:2.5).

[0126] Example 4 This embodiment prepared core-shell composite phase change-repair microcapsules adapted to high-salt marine environments. The preparation method was the same as in Example 1, except that the alkali-resistant shell material of the outer shell layer used 13g of epoxy-modified silica sol and 0.65g of graphene to improve corrosion resistance. Accordingly, in step S3, 13g of epoxy-modified silica sol and 0.65g of graphene were mixed and then added to the composite functional slurry. The core-shell composite phase change-repair microcapsules prepared in this embodiment are used in marine engineering concrete. The application steps are the same as in Example 2, except that the dosage of the core-shell composite phase change-repair microcapsules is 4%, and the temperature during the first to third days of curing is 25 to 35°C.

[0127] Testing showed that, in a seawater environment, the concrete with doped core-shell composite phase change-repair microcapsules prepared in this embodiment exhibited a crack self-repair rate of ≥62% (when the crack width was ≤0.3mm). Example 5 This embodiment prepared core-shell composite phase change-repair microcapsules adapted to sulfate-erosion environments. The preparation method was the same as in Example 1, except that the self-healing agent was a mixture of sulfate-reducing bacterial spores and calcium phosphate crystallizing agent (mass ratio 1:1), and the alkali-resistant shell material in the outer shell layer was a tricalcium silicate-silica fume-polyvinyl alcohol fiber composite material. Accordingly, in step S3, 2.25g of low-temperature resistant urease-resistant bacterial spore powder was replaced with 1g of sulfate-reducing bacterial spores and 1g of calcium phosphate crystallizing agent, and the epoxy-modified silica sol was replaced with 15g of tricalcium silicate-silica fume-polyvinyl alcohol fiber composite material.

[0128] The preparation method of the tricalcium silicate-silica ash-polyvinyl alcohol fiber composite material in this embodiment is as follows: 1) Powder premixing: Put 14kg of tricalcium silicate powder and 3kg of silica fume into a planetary mixer and dry mix for 5 minutes until the mixture is uniform to obtain premixed powder; 2) Fiber dispersion: Add 1 kg of PVA fiber to 2 kg of deionized water and ultrasonically disperse for 10 min at 300 W. Add 0.1 kg of polycarboxylate high-performance water-reducing agent (manufacturer: Weike Building Materials Sales Center, product model: HLX, standard type, solid content 38.3%, low temperature adaptable type) and stir until dissolved to obtain fiber dispersion. 3) Slurry mixing: Pour the fiber dispersion into the premixed powder and stir at 500 r / min for 15 min to form a uniform slurry; 4) Molding and curing: Pour the obtained slurry into the mold and vibrate it at a vibration frequency of 55Hz and an amplitude of 1.0mm for 2 minutes to compact it. Then place it in a standard curing room (20±2℃, RH≥95%) for curing for 24 hours. After demolding, continue curing for 7 days. 5) Powder preparation: The cured block was placed in a ball mill and ball-milled for 2 hours with anhydrous ethanol as the medium. The mixture was then passed through a 200-mesh sieve to obtain tricalcium silicate-silica fume-polyvinyl alcohol fiber composite material.

[0129] The core-shell composite phase change-repair microcapsules prepared in this embodiment are used in sulfate-eroded concrete environments, and the application steps are the same as in Example 2.

[0130] Tests showed that, under sulfate attack conditions, the concrete prepared in this embodiment retained ≥92% of its 28-day compressive strength and had a self-healing rate of ≥63% for cracks.

[0131] Test Example 1 1) Performance testing of core-shell composite phase transition-repair microcapsules: 1.1) Particle size distribution test: Testing instrument: Laser particle size analyzer (model: Malvern Mastersizer 3000).

[0132] Test method: 0.1 g of the core-shell composite phase change-repair microcapsules prepared in Example 1 was dispersed in 50 mL of deionized water and ultrasonically dispersed for 5 min. The particle size distribution was tested using a dry method. The test results are as follows: Figure 2 As shown.

[0133] according to Figure 2 It can be seen that the average particle size of the core-shell composite phase change-repair microcapsules is 106 μm, the particle size distribution range is 40~180 μm, and the distribution uniformity is good (coefficient of variation ≤15%).

[0134] 2) Concrete performance testing: 2.1) Mechanical property testing: Test methods: The compressive strength of concrete at 7 days and 28 days was tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Concrete without core-shell composite phase change-repair microcapsules (standard curing: 20±2℃, RH≥95%) was used as Comparative Example 1; concrete without core-shell composite phase change-repair microcapsules (cured at -5℃ for 7 days) was used as Comparative Example 2; Example 6 was prepared by adjusting the curing conditions of Example 2 to -5℃ for 7 days; Example 7 was prepared by adjusting the curing conditions of Example 2 to standard curing (20±2℃, RH≥95%); Example 8 was prepared by adjusting the curing conditions of Example 4 to seawater curing (20±2℃); Example 9 was prepared by adjusting the curing conditions of Example 5 to sulfate attack (5% Na2SO4 solution, 20±2℃); the test results are as follows: Figure 3 As shown in Table 3.

[0135] Table 3. Test results of concrete in Examples 6-9 and Comparative Examples 1-2

[0136] according to Figure 3 As shown in Table 3, the concrete doped with core-shell composite phase change-repair microcapsules has a 7-day compressive strength of 31.8 MPa and a 28-day compressive strength of 47.5 MPa; the concrete in Comparative Example 2 has a 7-day compressive strength of 28.2 MPa and a 28-day compressive strength of 45.1 MPa. After doping with core-shell composite phase change-repair microcapsules, the early strength of the concrete is increased by 12.8%, and the 28-day strength retention rate is ≥90%, which not only meets the requirements of low-temperature curing, but also has no adverse effect on mechanical properties.

[0137] 2.2) Self-healing effect test: Test method: A three-point bending test was used to pre-cast cracks with a width of 0.2 mm on concrete specimens, which were then cured in a standard curing room for 28 days. The change in ultrasonic wave velocity before and after crack repair was tested using the ultrasonic method, and the repair rate was calculated using the following formula: Repair rate = (wave velocity after repair - wave velocity before repair) / (wave velocity of uncracked specimen - wave velocity before repair) × 100%.

[0138] Table 4. Self-healing test results of Examples 6-9 and Comparative Example 2

[0139] As can be seen from Table 4, the concrete doped with core-shell composite phase change-repair microcapsules of the present invention has a repair rate of over 62%, which is much higher than that of the comparative example.

[0140] 2.3) Low-temperature environment repair test: Cracks with a width of 0.2 mm were precast at -5℃ and cured for 28 days using a low-temperature curing process. Test results showed that the crack repair rate of the concrete doped with core-shell composite phase change-repair microcapsules was 65%, while the crack repair rate of Comparative Example 2 was only 12%. Under standard curing conditions, the crack repair rate of the concrete doped with core-shell composite phase change-repair microcapsules was 68%, indicating that it still possesses significant self-healing effects even at low temperatures.

[0141] 2.4) Long-term performance verification: To verify the long-term service performance of concrete, referring to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" and GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the compressive strength test method was used to conduct 50 freeze-thaw cycle strength tests on the concrete of Comparative Examples 1-2, Examples 6-7 (low-temperature adapted microcapsules), Example 7 (marine adapted microcapsules), and Example 8 (sulfate adapted microcapsules). The specific test items, standards, and results are shown in Table 5. Table 5 Test Items, Standards, and Results

[0142] As can be seen from Table 5, the core-shell composite phase change-repair microcapsules provided by this invention can effectively improve the strength retention rate of materials and have better long-term service performance.

[0143] The embodiments of the present invention have been described above; however, these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the above embodiments of the present invention without inventive effort are within the protection scope of the present invention.

Claims

1. A core-shell composite phase transition-repair microcapsule, characterized in that, From the inside out, it consists of a core, an inner shell, and an outer shell. The core comprises a room-temperature phase change material; The phase transition temperature of the room temperature phase change material is 12~40℃; The inner shell layer includes a polymer coating layer; The outer shell layer includes a composite functional layer, which includes a high-temperature phase change material, a self-healing agent, and an alkali-resistant shell material. The phase transition temperature of the high-temperature phase change material is 45~80℃.

2. The core-shell composite phase transition-repair microcapsule according to claim 1, characterized in that, The latent heat of the room-temperature phase change material is 120~200J / g; The room-temperature phase change material includes one or more of paraffin, decane, tetradecyl alcohol, and diethylene glycol monoethyl ether stearate.

3. The core-shell composite phase transition-repair microcapsule according to claim 1, characterized in that, The polymer material of the inner shell includes one or more of urea-formaldehyde resin, polyurethane, and polymethyl methacrylate.

4. The core-shell composite phase transition-repair microcapsule according to claim 1, characterized in that, The latent heat of the high-temperature phase change material is 80~150J / g; The high-temperature phase change material includes one or more of high-melting-point paraffin, stearic acid, butyl stearate, and palmitic acid; The phase transition temperature of the high-melting-point paraffin is 52~70℃.

5. The core-shell composite phase transition-repair microcapsule according to claim 1 or 4, characterized in that, The self-healing agent includes one or more of the following: Bacillus pasteurellii spores, urease spores, carbonic anhydrase, urea, sulfate-reducing spores, and calcium phosphate crystallizer.

6. The core-shell composite phase transition-repair microcapsule according to claim 1 or 4, characterized in that, The mass ratio of the high-temperature phase change material to the self-healing agent is 3~5:1; The self-healing agent accounts for 5-15% of the total mass of the outer shell.

7. The core-shell composite phase transition-repair microcapsule according to claim 1, characterized in that, The alkali-resistant shell material includes one or more of silica sol, epoxy-modified silica sol, epoxy resin, and cement-based composite materials; The epoxy resin is a bisphenol A type epoxy resin; The bisphenol A type epoxy resin includes one or more of bisphenol A type epoxy resin E-44, bisphenol A type epoxy resin E-51, and modified epoxy resin.

8. The core-shell composite phase transition-repair microcapsule according to claim 7, characterized in that, The preparation method of the modified epoxy resin includes the following steps: Bisphenol A type epoxy resin, acetate buffer and deionized water were mixed to obtain microcapsule dispersion; An aminosilane coupling agent and ethanol are mixed to obtain a modifier, which is then added dropwise to a microcapsule dispersion for hydrolysis and grafting reactions.

9. A method for preparing the core-shell composite phase change-repair microcapsules according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) The room temperature phase change material is mixed with emulsifier and water to emulsify and obtain an emulsion. The emulsion is then mixed with an initiator to carry out a first polymerization reaction to obtain core microcapsules. Alternatively, a room-temperature phase change material and an organic solvent are mixed to obtain an oil phase, an emulsifier and water are mixed to obtain an aqueous phase, the oil phase and the aqueous phase are mixed and emulsified to obtain a water-in-oil emulsion, and the water-in-oil emulsion is mixed with an interfacial initiator to carry out an interfacial polymerization reaction to obtain core microcapsules; (2) The core microcapsule is mixed with a polymer prepolymer, a catalyst and water to carry out a second polymerization reaction to obtain a core-inner shell microcapsule; (3) The core-inner shell microcapsule is mixed with molten high-temperature phase change material, self-healing agent and alkali-resistant shell material precursor to carry out surface in-situ polymerization reaction to obtain the core-shell composite phase change-repair microcapsule.

10. The application of the core-shell composite phase change-repair microcapsule according to any one of claims 1 to 8 or the core-shell composite phase change-repair microcapsule obtained by the preparation method according to claim 9 in concrete products.

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