Self-repairing uhpc concrete and method for manufacturing same

Abstract

The application discloses a kind of self-repairing UHPC concrete, it includes UHPC concrete matrix and the magnetic induction microcapsule and hydrophilic modified heat-shrinkable fiber web distributed therein;Wherein magnetic induction self-repairing microcapsule includes core material and wall material, core material uses isophorone diisocyanate, wall material includes melamine formaldehyde resin and rubidium magnet;Hydrophilic modified heat-shrinkable fiber web is the woven net formed by hydrophilic modified polypropylene fiber and hydrophilic modified nylon fiber.The application introduces hydrophilic modified heat-shrinkable fiber web and electromagnetic induction self-repairing microcapsule simultaneously in UHPC concrete matrix, plays the synergistic effect crack repair, and can effectively improve the overall performance of concrete, significantly improve the toughness, crack resistance and impact resistance etc.of the obtained concrete, while realizing on-demand release of repair material in self-repairing microcapsule, improve repair agent utilization efficiency, wide applicability.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a self-healing UHPC concrete and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC) is an excellent concrete material, typically composed of a high proportion of cement, fine aggregates, and mineral admixtures (such as silica fume and fly ash), combined with chemical admixtures to enhance its performance. Notable characteristics of UHPC include high compressive strength (up to 150 MPa or more), excellent durability (resistance to water penetration, freeze-thaw cycles, and chemical attack), and improved toughness, making it suitable for harsh environments and widely used in bridges, tunnels, and high-strength building structures. However, it can still experience cracking due to factors such as temperature changes, plastic shrinkage, improper construction, and external loads.

[0003] To enhance the toughness and crack resistance of ultra-high performance concrete, fiber incorporation is an effective method. Fibers, by forming a three-dimensional network structure, effectively disperse stress, limit crack propagation, and thus delay crack formation. The incorporation of fibers not only improves the impact resistance and fatigue resistance of concrete but also enhances the overall structural reliability. To further improve the self-healing ability of concrete, microcapsules containing a repair agent can be incorporated. When cracks occur in the concrete, these capsules rupture, releasing the repair agent to automatically fill the cracks and promote healing.

[0004] Currently, while there have been some reports on the introduction of fiber mesh and self-healing microcapsule technology into concrete, many problems and shortcomings remain. These limitations prevent a comprehensive and effective solution to various issues related to the strength, durability, and self-healing properties of concrete structures. For example: 1) While fiber mesh technology can enhance the mechanical properties of concrete to some extent, its use alone often fails to effectively address crack propagation in complex environments. Furthermore, over time and under continuous external stress, fiber mesh may experience fatigue failure, failing to provide long-term stable reinforcement. Additionally, fiber mesh has limited repair capabilities for larger cracks, making it difficult to achieve the self-healing function of concrete structures. 2) Heat-shrinkable fiber methods typically employ short-cut heat-shrinkable fibers, which, although effective during cement hydration... During the exothermic process, shrinkage response occurs, which applies prestress to concrete to improve crack resistance, etc. However, the modification effect of simple heat-shrinkable fibers is limited and mainly works under specific temperature conditions. In actual engineering environments with small temperature variation ranges, their heat-shrinkable properties may not be fully utilized. In addition, the effect of short-cut heat-shrinkable fibers on improving the durability of concrete is not obvious, and they cannot effectively solve the long-term corrosion and aging problems faced by concrete. 3) Microcapsule self-healing technology can achieve a certain degree of self-healing, but it usually has problems such as uncontrollable or limited control of the release process of the repair material, which affects the self-healing effect. In addition, simple self-healing microcapsules have limited improvement on the overall mechanical properties of concrete and cannot meet the needs of some projects with high strength requirements. Summary of the Invention

[0005] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a self-healing UHPC concrete. By introducing hydrophilic modified heat-shrinkable fiber mesh and electromagnetic induction self-healing microcapsules into the UHPC concrete matrix, the high strength and toughness and excellent durability of the resulting concrete can be effectively balanced. At the same time, the controllable release of the repair material in the self-healing microcapsules can be achieved, improving the utilization efficiency of the repair agent and making it widely applicable.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A self-healing UHPC concrete includes a UHPC concrete matrix and magnetically induction self-healing microcapsules and hydrophilic modified heat-shrinkable fiber mesh distributed therein. The magnetically induction self-healing microcapsules include a core material and a wall material. The core material is isophorone diisocyanate, and the wall material includes melamine-formaldehyde resin and rubidium magnet powder. The hydrophilic modified heat-shrinkable fiber mesh is a woven mesh formed by hydrophilic modified polypropylene fibers and hydrophilic modified nylon fibers.

[0008] In the above scheme, the raw materials and their weight proportions include: 2270-2475 parts of UHPC concrete matrix raw material, 34-102 parts of electromagnetic induction self-healing microcapsules, and 60-80 parts of hydrophilic modified heat-shrinkable fiber mesh.

[0009] Furthermore, the raw materials for the UHPC concrete matrix include the following components by weight: 850 parts cement, 140-160 parts silica fume, 130-150 parts microspheres, 600-650 parts quartz sand, 220-260 parts mineral powder, 140-160 parts steel fiber, 10-15 parts water-reducing agent, and 180-220 parts water.

[0010] Furthermore, the electromagnetic induction self-healing microcapsules have an average particle size of 80–125 μm and an average capsule wall thickness of 8.0–12.5 μm.

[0011] Furthermore, the electromagnetic induction self-healing microcapsules account for 4-12% of the cement mass.

[0012] Furthermore, the preparation method of the electromagnetic induction self-healing microcapsule includes the following steps:

[0013] 1) The isophorone diisocyanate (IPDI) and polystyrene maleic anhydride copolymer (SMA) emulsion solution were mechanically stirred;

[0014] 2) Dissolve a portion of melamine-formaldehyde resin in an aqueous solution of polyvinyl alcohol to obtain a melamine-formaldehyde resin solution, and add it to the solution system obtained in step 1) to carry out a cross-linking reaction to obtain a melamine-formaldehyde resin prepolymer solution.

[0015] 3) Add rubidium magnet powder to the dispersant solution (aqueous solution), then add the remaining melamine-formaldehyde resin, mix evenly, add the resulting dispersion to the reaction product obtained in step 2), heat and stir to obtain a suspension of electromagnetic induction microcapsules;

[0016] 4) The microcapsules obtained by centrifugation are solidified and dried to obtain the electromagnetic induction self-healing microcapsules.

[0017] In the above scheme, the mass ratio of melamine-formaldehyde resin, isophorone diisocyanate, and rubidium magnet powder is (5-9):(10-18):(4-8).

[0018] In the above scheme, the mechanical stirring rate in step 1) is 300-500 r / min, and the time is 1-2 h.

[0019] In the above scheme, the emulsifier solution is prepared by adjusting the pH value of the emulsifier (using NaOH) to 10-12, and then adding water and stirring to dissolve it to a concentration of 2-4 wt%.

[0020] In the above scheme, the mass ratio of isophorone diisocyanate to polystyrene maleic anhydride copolymer is 10:(3-7).

[0021] In the above scheme, in step 2), the concentration of melamine-formaldehyde resin in the melamine-formaldehyde resin solution is 5-15 wt%; the concentration of polyvinyl alcohol is 6-10%.

[0022] In the above scheme, the amount of melamine-formaldehyde resin used in step 2) accounts for 50-60% of the mass of the IPDI core material.

[0023] In the above scheme, the crosslinking reaction stirring treatment is carried out at a temperature of 45-50℃ for 0.5-1h and a mechanical stirring rate of 400-550r / min.

[0024] In the above scheme, the dispersant can be one or more of sodium dodecyl sulfate, oleic acid, polyethylene glycol, etc.

[0025] In the above scheme, the concentration of rubidium magnet powder in the dispersion obtained in step 3) is 15-20 wt%, the concentration of melamine-formaldehyde resin is 60-70 wt%, and the concentration of dispersant is 19-25 wt%.

[0026] In the above scheme, the heating and stirring treatment is carried out at a temperature of 75-80℃ for a time of 1.5-2.5h.

[0027] In the above scheme, the curing process includes: adding oxalic acid solution dropwise to melamine-formaldehyde resin solution (same as the preparation method in step 2), stirring evenly to obtain a curing solution; adding the microcapsules obtained by centrifugation to the curing solution, stirring evenly, and carrying out a curing reaction at a temperature of 50-100℃ for 1-5 hours; taking out the microcapsules, washing them with an organic solvent (such as ethanol or acetone), and drying them (40-60℃, 2-8 hours) to obtain the cured magnetic induction self-healing microcapsules.

[0028] Furthermore, the melamine-formaldehyde resin solution is the same as the melamine-formaldehyde resin solution obtained in step 2).

[0029] In the above scheme, the concentration of the oxalic acid solution is 1-5%.

[0030] In the above scheme, the volume ratio of the oxalic acid solution to the melamine-formaldehyde resin solution is 1:(2.5-7).

[0031] In the above scheme, the hydrophilic modified heat-shrinkable fiber mesh is made by double-twisting weaving process of hydrophilic modified polypropylene fiber and hydrophilic modified nylon fiber.

[0032] Furthermore, the hydrophilic modified heat-shrinkable fiber web has a melting point of 150–220°C and will shrink under conditions of 120–180°C.

[0033] In the above scheme, the pore size of the hydrophilic modified heat-shrinkable fiber mesh is 20-30 mm.

[0034] In the above scheme, the heat shrinkage initiation temperature of the polypropylene fiber is 120-140℃, and its molecular weight is 100,000-300,000; the heat shrinkage initiation temperature of the nylon fiber is 140-180℃, and its molecular weight is 20,000-70,000; the diameter of the polypropylene fiber and the nylon fiber is 10-50μm.

[0035] In the above scheme, the hydrophilic modification step involves sequentially performing methyl ethyl cellulose coating and acrylic acid grafting modification, specifically including:

[0036] 1) Immerse polypropylene fibers or nylon fibers in ethanol to obtain pretreated fibers (pretreated polypropylene fibers or pretreated nylon fibers);

[0037] 2) Add the pretreated fiber to an ethanol solution of methyl ethyl cellulose, soak at 40-60℃ for 2-4 hours, wash, and obtain methyl ethyl cellulose coated modified fiber;

[0038] 3) Place the obtained methyl ethyl cellulose-coated modified fiber into an acrylic acid solution and perform a grafting reaction at 60-80℃ for 4-6 hours. Remove the fiber, wash it with water, and dry it to obtain hydrophilic modified polypropylene fiber or nylon fiber.

[0039] In the above scheme, the soaking treatment time in step 1) is 2 to 3 hours.

[0040] In the above scheme, the concentration of methyl ethyl cellulose in the ethanol solution is 5-10 g / mL.

[0041] In the above scheme, the introduced methyl ethyl cellulose accounts for 3 to 8% of the pretreated fiber mass.

[0042] In the above scheme, the acrylic acid introduced in step 3) accounts for 5-15% of the mass of the pretreated fiber.

[0043] In the above scheme, the concentration of the acrylic acid solution is 10-30 wt%.

[0044] In the above scheme, the blended low-melting-point heat-shrinkable fiber web has a blending ratio (mass ratio) of hydrophilic modified polypropylene fiber and hydrophilic modified nylon fiber of 1:2 to 2:1.

[0045] Preferably, the blended low-melting-point heat-shrinkable fiber mesh is woven using a double-twisted weaving process and then further indented to increase the mechanical bonding force between the fiber mesh and the concrete matrix.

[0046] Furthermore, the silicate cement is PO52.5, PO62.5 ordinary silicate cement or P·I type silicate cement.

[0047] Furthermore, the quartz sand has a particle size of 26–70 mesh.

[0048] Furthermore, the mineral powder is of grade S95 or higher.

[0049] In the above scheme, the specific surface area of ​​the silica fume is 13-30 m². 2 / g, activity index 85–120%; average microsphere size 0.5–10 μm, density 2.2–2.4 g / cm³ 3 .

[0050] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate >30%.

[0051] In the above scheme, the steel fiber is copper-plated short steel fiber with a density of 80-160 kg / m³. 3 Its nominal length is 12-17 mm and its equivalent diameter is 0.15-0.30 mm.

[0052] The above-mentioned method for preparing self-healing UHPC concrete includes the following steps:

[0053] 1) Mix 850 parts of cement, 140-160 parts of silica fume, 130-150 parts of microspheres, 600-650 parts of quartz sand, 220-260 parts of mineral powder, 140-160 parts of steel fiber and 3-6 parts of admixture evenly, then add 180-220 parts of water and 10-15 parts of water-reducing agent and mix evenly to obtain UHPC concrete matrix slurry;

[0054] 2) Place the hydrophilic modified heat-shrinkable fiber mesh in the middle of the mold;

[0055] 3) Add 34 to 102 parts of electromagnetic induction self-healing microcapsules to the UHPC concrete matrix slurry and mix evenly. Then pour the mixture into a mold with a hydrophilic modified heat-shrinkable fiber mesh, shape and cure it to obtain the self-healing UHPC concrete.

[0056] In the above scheme, the UHPC-resistant concrete is a cylindrical or block structure.

[0057] Furthermore, when preparing cylindrical UHPC concrete, the blended low-melting-point heat-shrinkable fiber mesh is in the shape of a hollow cylinder and is positioned coaxially with the cylindrical UHPC concrete at the center; when preparing block UHPC concrete, the blended low-melting-point heat-shrinkable fiber mesh is in the shape of a planar mesh structure and is positioned parallel to the surface of the UHPC concrete at the center along the thickness direction of the cylindrical UHPC concrete.

[0058] Furthermore, when preparing cylindrical UHPC concrete, during the pouring process described in step 3), the mixture is first poured into a hollow cylindrical blended low-melting-point heat-shrinkable fiber mesh. After hardening and shaping, the remaining mixture is poured until the mold is completely filled.

[0059] In the above scheme, the UHPC concrete adopts a standard curing process.

[0060] The self-healing UHPC concrete prepared according to the above scheme has a compressive strength of 183.7-263.4 MPa, an impact and abrasion resistance of 170.5-231.3 MPa, and a toughness of 2103.1-10826 J.

[0061] The principle of this invention is as follows:

[0062] This invention uses polypropylene fibers and nylon fibers, which have a heat-shrinking effect, as the main raw materials to prepare a heat-shrinkable fiber web. First, the polypropylene fibers and nylon fibers are sequentially coated with methyl ethyl cellulose and grafted with acrylic acid, which can effectively reduce the crystallinity of the fibers and form a blended low-melting-point heat-shrinkable fiber with low crystallinity and high orientation, which is beneficial to improving the heat shrinkage rate of the obtained fiber web. In addition, the modified fiber surface is hydrophilic, making the fibers easier to be wrapped and bonded by cement paste, which is beneficial to enhancing the bonding effect between the fibers and the concrete matrix.

[0063] The electromagnetic induction self-healing microcapsules of this invention can release the core material on demand, improving the utilization efficiency of the repair agent: First, the emulsifier SMA and IPDI are mechanically stirred to form a stable emulsion system. Then, MF and PVA are introduced, and a cross-linking reaction is carried out under suitable temperature and stirring conditions to optimize the cross-linking density of the wall material and initially construct a relatively stable basic structure of the wall material, providing a relatively stable framework structure for subsequent further coating of magnetocaloric particles. Then, the heating and stirring conditions of MF and magnetocaloric particles are controlled to promote the stable coating of magnetocaloric particles inside the microcapsules, ensuring a good magnetocaloric controlled release effect.

[0064] This invention combines heat-shrinkable fiber reinforcement technology with electromagnetically controlled-release microcapsule self-healing technology. Hydrophilic modified heat-shrinkable fiber mesh and electromagnetically inductive self-healing microcapsules are co-incorporated into UHPC concrete. The introduced heat-shrinkable fiber mesh forms a continuous network structure throughout the cementitious material, providing global reinforcement and significantly improving the overall performance of the concrete. The exothermic reaction of cement hydration causes the heat-shrinkable fiber mesh to shrink (primary shrinkage provides stress resistance and crack resistance), generating pre-compression stress on the surrounding hardened gel slurry, which effectively inhibits the formation or propagation of microcracks. By dispersing these stresses, it exhibits better ductility and impact resistance when subjected to impact or vibration, preventing brittle fracture. The introduced electromagnetically inductive self-healing microcapsules can controllably release the core repair agent under the action of an external magnetic field, effectively repairing cracks. Simultaneously, the released heat causes the fiber mesh to shrink secondary, applying compressive stress to the cracks and synergistically improving the crack repair effect.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0066] 1) Blended low-melting-point heat-shrinkable fiber mesh

[0067] This invention uses polypropylene fibers and nylon fibers, which have a heat-shrinking effect, as the main raw materials to prepare a heat-shrinkable fiber web. First, the polypropylene fibers and nylon fibers are coated with methyl ethyl cellulose and grafted with propionic acid, respectively. This can effectively reduce the crystallinity of the fibers and improve their orientation and surface hydrophilicity. This is beneficial to improving the heat-shrinkability of the resulting fiber web and enhancing the bonding effect between the fibers and the concrete matrix, thereby promoting the improvement of the toughness, crack resistance and impact resistance of the concrete.

[0068] 2) Electromagnetic induction microcapsules;

[0069] This invention uses melamine-formaldehyde resin, which has high mechanical strength and chemical stability and good compatibility with concrete, as the main capsule wall material, and combines it with rubidium magnet powder to give the microcapsules a strong magnetic response, which can effectively improve the controlled release performance; the introduced core material IPDI can react with moisture after release, effectively enhancing the durability of concrete; the resulting microcapsules can release the core material as needed, improving the utilization efficiency of the repair agent.

[0070] 3) This invention combines hydrophilic modified heat-shrinkable fiber mesh with electromagnetic induction self-healing microcapsules, applying them together to UHPC concrete systems. The exothermic reaction of cement hydration causes the heat-shrinkable fiber mesh to shrink, generating pre-compression stress on the surrounding hardened gel slurry, thus improving the crack resistance of the concrete. Under the action of an external magnetic field, the walls of the electromagnetic induction self-healing microcapsules rupture, and the repair agent flows into the cracks. Simultaneously, the heat-shrinkable fiber mesh is heated and induced to shrink, applying a compressive force to the cracks. The two work synergistically to repair the cracks, effectively maintaining the high precision (dimensional accuracy, shape accuracy, performance accuracy, etc.) and high durability of UHPC, especially in resisting long-term environmental erosion and internal stress changes. In addition, the reinforcing and toughening effect of the heat-shrinkable fiber mesh plays a key role when UHPC is subjected to large one-time loads, while the self-healing function of the electromagnetic controlled-release capsules plays an intermittent role during the long-term use of the UHPC structure as microcracks gradually form. The two complement each other, providing comprehensive performance assurance for UHPC concrete. Attached Figure Description

[0071] Figure 1 This is a schematic diagram of the UHPC concrete structure according to an embodiment of the present invention;

[0072] Figure 2 Comparison of the self-healing effect of UHPC concrete cracks with simultaneous incorporation of heat-shrinkable fiber mesh and electromagnetic induction microcapsules: (a) before repair; (b) after repair. Detailed Implementation

[0073] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0074] In the following embodiments, the hydrophilic modified heat-shrinkable fiber mesh is obtained by weaving hydrophilic modified polypropylene fibers and hydrophilic modified nylon fibers using a double-twisted weaving process.

[0075] The mechanical and physical properties of the polypropylene and nylon fibers used are shown in Tables 1 and 2, respectively; the characteristics of the mesh size parameters of the resulting blended low-melting-point fiber are shown in Table 3.

[0076] Table 1 Mechanical and physical properties of polypropylene fibers

[0077]

[0078] Table 2 Mechanical and physical properties of nylon fibers

[0079]

[0080] The preparation method of the hydrophilic modified heat-shrinkable fiber web includes the following steps:

[0081] 1) Place polypropylene fiber or nylon fiber into a reactor, add ethanol that can completely submerge the fiber, and soak for 2 hours to remove impurities and oil stains from the fiber surface to obtain pretreated polypropylene fiber or nylon fiber.

[0082] 2) Add methyl ethyl cellulose to ethanol at a ratio of 5 g of methyl ethyl cellulose per 100 ml of ethanol, stir well, and prepare an ethanol solution of methyl ethyl cellulose (concentration of methyl ethyl cellulose is 5 g / mL); take out the pretreated fiber, put it into the prepared ethanol solution of methyl ethyl cellulose (the introduced methyl ethyl cellulose accounts for 4% of the mass of the pretreated fiber), soak it at 40℃ for 2 h, and obtain methyl ethyl cellulose coated modified fiber; take out the fiber, rinse it with deionized water to remove the residual solution on the surface;

[0083] 3) The rinsed fibers were placed in an acrylic acid solution (concentration of 20wt%), wherein the amount of acrylic acid introduced was 5% of the fiber mass, and the grafting reaction was carried out at 60℃ for 4 hours.

[0084] 4) After the reaction is complete, the fiber is taken out and rinsed repeatedly with deionized water to remove unreacted monomers and impurities. Then the fiber is dried for 10 hours to obtain hydrophilic modified heat shrinkable fiber.

[0085] 6) The hydrophilic modified polypropylene fiber and nylon fiber are blended (blending ratio is 1:2 or 2:1) and woven into a mesh using a double twist weaving process.

[0086] Table 3. Characteristics of pore size parameters of hydrophilic modified heat-shrinkable fiber mesh

[0087]

[0088] The method for preparing the electromagnetic induction self-healing microcapsules includes the following steps:

[0089] 1) 10g of isophorone diisocyanate (IPDI) and 150mL of polystyrene maleic anhydride copolymer (SMA) emulsifier solution (SMA emulsifier hydrolysis is achieved by adding NaOH to adjust the pH to 10, and then stirring to dissolve to obtain a 2wt% SMA emulsifier solution) were mechanically stirred for 2h at a speed of 400r / min.

[0090] 2) Mix 5g of melamine-formaldehyde resin MF and 50mL of polyvinyl alcohol solution (PVA to water mass ratio of 1:10) evenly to obtain melamine-formaldehyde resin solution, and then add it to the solution obtained in step 1). Perform crosslinking reaction at 50℃ for 1h with mechanical stirring at a rate of 550r / min.

[0091] 3) Add 2g of melamine-formaldehyde resin MF and 50mL of rubidium magnet dispersion (the dispersant used is sodium dodecyl sulfate, of which 4g of rubidium magnet and 1.41g of dispersant are used) and heat and stir at 80℃ for 2h.

[0092] 4) Filter the above electromagnetically controlled release microcapsule suspension, wash the microcapsules with 75% ethanol, and filter again to obtain relatively pure microcapsules; slowly add 3% oxalic acid solution to the melamine-formaldehyde resin solution (same as in step 2), wherein the volume ratio of oxalic acid solution to melamine-formaldehyde resin solution is 1:2.5, stir evenly to obtain a curing solution; add the pretreated microcapsules to the curing solution, stir evenly, and cure the mixture at 60°C for 3 hours;

[0093] 5) After the curing reaction is complete, the microcapsules are removed from the curing solution and cleaned with 75% ethanol to remove residual curing solution and impurities on the surface; the obtained microcapsules are dried at 60°C for 8 hours to finally obtain the cured electromagnetic controlled release microcapsules.

[0094] Table 4 Performance test results of electromagnetic controlled release microcapsules

[0095]

[0096]

[0097] In the following examples, the silicate cement used is PO52.5, and the specific surface area of ​​the silica fume is 136364 cm². 2 / g, with an activity index of 120%, an average microsphere size of 0.5μm, a quartz sand particle size of 42 mesh, S95 grade mineral powder, and copper-plated short steel fibers with a density of 80kg / m³. 3 The nominal length is 12-17mm, the equivalent diameter is 0.15-0.30mm, the water-reducing agent is polycarboxylate water-reducing agent, and the water reduction rate is 35%.

[0098] Example 1

[0099] A self-healing UHPC concrete, the preparation method of which includes the following steps:

[0100] 1) Mix 850 parts cement, 150 parts silica fume, 150 parts microspheres, 600 parts quartz sand, 240 parts mineral powder, 150 parts steel fiber and 34 parts electromagnetic induction self-healing microcapsules evenly, then add 200 parts water and 10 parts water-reducing agent and mix evenly. Stir for 2 minutes to obtain UHPC concrete slurry.

[0101] 2) Place 60 parts of hydrophilic modified heat shrinkable fiber mesh (the ratio of hydrophilic modified polypropylene fiber to nylon fiber is 1:2) into a mold with a cylindrical cavity. First, fill part of the UHPC concrete slurry into the cylindrical fiber mesh. After the concrete inside has set, continue to fill the entire mold.

[0102] 3) After molding and curing, the self-healing UHPC concrete is obtained.

[0103] Comparative Example 1

[0104] A conventional UHPC concrete preparation method includes the following steps:

[0105] 1) Mix 850 parts cement, 150 parts silica fume, 150 parts microspheres, 600 parts quartz sand, 240 parts mineral powder and 150 parts steel fiber evenly, then add 200 parts water and 10 parts water-reducing agent and mix evenly to obtain UHPC concrete slurry.

[0106] 2) The obtained UHPC concrete slurry was poured and cured to obtain UHPC concrete specimens.

[0107] Comparative Example 2

[0108] A hydrophilic modified heat-shrinkable fiber mesh reinforced concrete, the preparation method of which includes the following steps:

[0109] 1) Preparation of concrete slurry: Mix 850 parts cement, 150 parts silica fume, 150 parts microspheres, 600 parts quartz sand, 240 parts mineral powder and 150 parts steel fiber evenly, then add 200 parts water and 10 parts water-reducing agent and mix evenly to obtain concrete slurry.

[0110] 2) Place 60 portions of hydrophilic modified heat-shrinkable fiber mesh (the blending ratio of hydrophilic modified polypropylene fiber and nylon fiber is 1:2, and the preparation method is the same as in Example 1) into a mold with a cylindrical cavity. First, fill part of the cylindrical fiber mesh with UHPC concrete slurry. After the concrete inside has set, continue to fill the entire mold. After molding and curing, hydrophilic modified heat-shrinkable fiber mesh reinforced concrete is obtained.

[0111] Comparative Example 3

[0112] A UHPC concrete based on electromagnetic induction self-healing microcapsules is prepared by the following steps:

[0113] 1) Mix 850 parts of cement, 150 parts of silica fume, 150 parts of microspheres, 600 parts of quartz sand, 240 parts of mineral powder, 150 parts of steel fiber and 34 parts of electromagnetic induction self-healing microcapsules (preparation method is the same as in Example 1) evenly, then add 200 parts of water and 10 parts of water-reducing agent and mix evenly. Stir for 2 minutes to obtain concrete slurry.

[0114] 2) The concrete slurry is poured and cured to obtain UHPC concrete based on electromagnetic induction microcapsules.

[0115] Comparative Example 4

[0116] A UHPC concrete based on hydrophilic modified short-cut fibers and electromagnetically inductive self-healing microcapsules is prepared by the following steps:

[0117] 1) Preparation of concrete slurry: 850 parts cement, 150 parts silica fume, 150 parts microspheres, 600 parts quartz sand, 240 parts mineral powder, 150 parts steel fiber, 60 parts hydrophilically modified polypropylene, hydrophilically modified chopped fibers (including 20 parts hydrophilically modified polypropylene and 40 parts hydrophilically modified nylon chopped fibers), and 34 parts electromagnetic induction self-healing microcapsules (preparation method as in Example 1) are mixed evenly. Then, 200 parts water and 10 parts water-reducing agent are added and mixed evenly to obtain concrete slurry. The hydrophilic modification steps for the hydrophilically modified polypropylene and nylon chopped fibers are the same as in Example 1. The average length of the hydrophilically modified polypropylene is 12 mm, and the average length of the hydrophilically modified nylon chopped fibers is 16 mm.

[0118] 3) The obtained concrete slurry is poured, and after molding and curing, UHPC concrete based on hydrophilic modified short chopped fiber and electromagnetic induction microcapsule is obtained.

[0119] Comparative Example 5

[0120] A UHPC concrete based on heat-shrinkable fiber mesh and electromagnetic induction self-healing microcapsules is prepared by the following steps:

[0121] 1) Mix 850 parts of cement, 150 parts of silica fume, 150 parts of microspheres, 600 parts of quartz sand, 240 parts of mineral powder, 150 parts of steel fiber and 34 parts of electromagnetic induction self-healing microcapsules (preparation method is the same as in Example 1) evenly, then add 200 parts of water and 10 parts of water-reducing agent and mix evenly. Stir for 2 minutes to obtain UHPC concrete slurry.

[0122] 2) Place 60 portions of heat-shrinkable fiber mesh into a mold with a cylindrical cavity. First, fill the cylindrical fiber mesh with a portion of UHPC concrete slurry. After the concrete inside has set, continue to fill the entire mold. The preparation method of the heat-shrinkable fiber mesh is roughly the same as in Example 1, except that hydrophilic modification is not performed before blending and weaving.

[0123] 3) After molding and curing, the self-healing UHPC concrete is obtained.

[0124] The concrete obtained in Example 1 and Comparative Examples 1-5 were tested for mechanical properties and durability, and the results are shown in Table 4.

[0125] Table 4. Performance test results of concrete obtained in Example 1 and Comparative Examples 1-5 after 28 days of curing.

[0126]

[0127]

[0128] In Table 4, the toughness improvement rate is the improvement rate relative to Comparative Example 1.

[0129] A self-healing experiment was conducted on the self-healing UHPC concrete obtained in Example 1. The specific steps included:

[0130] Using the splitting test method, microcracks of 0.15–0.30 mm are generated on the surface of the specimen. The specimen is then immediately removed, and the initial crack width is measured.

[0131] For the aforementioned concrete specimens, the temperature was raised to 340℃, and the crack repair was further observed under a magnetic field strength of 0.3T. Specific repair results are shown below. Figure 2 As can be seen, the concrete described in this invention can achieve self-repair of cracks with a width of 0.30 mm under a magnetic field of 300 mT.

[0132] Further experiments showed that as the magnetic field strength increased, the amount of repair material (core material) released from the microcapsules increased. At low magnetic field strength, the release was less, while at high magnetic field strength, the cracks were effectively repaired. Different magnetic field frequencies resulted in different release rates and modes. Low-frequency slow release was suitable for long-term repair, while high-frequency fast release was used for emergency treatment.

[0133] Example 2

[0134] A self-healing UHPC concrete (the specimen is in block form) comprises the following components and their respective weight percentages: 2053 parts of self-healing UHPC concrete raw materials; wherein the self-healing UHPC concrete raw materials include: 850 parts of cement, 150 parts of silica fume, 150 parts of microspheres, 600 parts of quartz sand, 240 parts of mineral powder, 150 parts of steel fiber, 200 parts of water, and 10 parts of water-reducing agent; wherein the hydrophilic modified heat-shrinkable fiber mesh is obtained by double-twisting process using hydrophilic modified polypropylene fiber and nylon fiber at different blending ratios (see Table 5); the preparation method of the self-healing UHPC concrete includes the following steps:

[0135] 1) Mix 850 parts of cement, 150 parts of silica fume, 150 parts of microspheres, 600 parts of quartz sand, 240 parts of mineral powder, 150 parts of steel fiber, and 3 parts of admixture with electromagnetic induction self-healing microcapsules of different dosages (mass percentage of cement content) (see Table 5 for details). Then add 200 parts of water and 10 parts of water-reducing agent and mix evenly. Stir for 2 minutes to obtain UHPC concrete slurry.

[0136] 2) Place 60 parts of hydrophilic modified heat shrinkable fiber mesh in the middle of the mold and pour anti-impact and abrasion concrete slurry to fill the entire mold. After molding, place it in a curing room for 28 days (temperature 25℃, humidity 95%) to obtain self-healing UHPC concrete.

[0137] Table 5. Performance test results of different fiber mesh-electromagnetic controlled release capsule systems and the resulting concrete used in Example 2.

[0138]

[0139]

[0140] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A self-healing UHPC concrete, characterized in that, It includes a UHPC concrete matrix and magnetically induction self-healing microcapsules and hydrophilic modified heat-shrinkable fiber mesh distributed within it; wherein the magnetically induction self-healing microcapsules include a core material and a wall material, the core material is isophorone diisocyanate, and the wall material includes melamine-formaldehyde resin and rubidium magnet powder; the hydrophilic modified heat-shrinkable fiber mesh is a woven mesh formed by hydrophilic modified polypropylene fibers and hydrophilic modified nylon fibers; The hydrophilic modification step involves sequentially coating with methyl ethyl cellulose and grafting with acrylic acid. The specific steps include: 1) Polypropylene fibers or nylon fibers are soaked in ethanol to obtain pretreated fibers; 2) Add the pretreated fiber to an ethanol solution of methyl ethyl cellulose, the concentration of methyl ethyl cellulose being 5~10 g / mL; soak at 40~60℃ for 2~4 h, wash, and obtain methyl ethyl cellulose coated modified fiber; 3) Place the obtained methyl ethyl cellulose-coated modified fiber into an acrylic acid solution and perform a grafting reaction at 60~80℃ for 4~6 hours. Remove the fiber, wash it with water, and dry it to obtain hydrophilic modified polypropylene fiber or nylon fiber. The raw materials for the UHPC concrete matrix include the following components by weight: 850 parts cement, 140-160 parts silica fume, 130-150 parts microspheres, 600-650 parts quartz sand, 220-260 parts mineral powder, 140-160 parts steel fiber, 10-15 parts water-reducing agent, and 180-220 parts water; the cement is ordinary Portland cement of type PO52.5 or PO62.5, or P·I type Portland cement. For the self-healing UHPC concrete, under the action of an external magnetic field, the walls of the electromagnetic induction self-healing microcapsules rupture, and the repair agent flows into the crack. At the same time, the heat-shrinkable fiber mesh is excited by heat and shrinks, applying a compressive force to the crack. The two work together to repair the crack.

2. The self-healing UHPC concrete according to claim 1, characterized in that, The raw materials and their respective weight percentages include: 2270~2475 parts of UHPC concrete matrix raw material, 34~102 parts of electromagnetic induction self-healing microcapsules, and 60~80 parts of hydrophilic modified heat-shrinkable fiber mesh.

3. The self-healing UHPC concrete according to claim 1, characterized in that, The mass ratio of melamine-formaldehyde resin, isophorone diisocyanate, and rubidium magnet powder introduced into the electromagnetic induction self-healing microcapsule is (5~9):(10~18):(4~8).

4. The self-healing UHPC concrete according to claim 1, characterized in that, The initial heat shrinkage temperature of the polypropylene fiber is 120~140℃; the initial heat shrinkage temperature of the nylon fiber is 140~180℃; and the diameter of the polypropylene fiber and the nylon fiber is 10~50μm.

5. The self-healing UHPC concrete according to claim 1, characterized in that, In the hydrophilic modified heat-shrinkable fiber web, the blending ratio of hydrophilic modified polypropylene fiber to hydrophilic modified nylon fiber is 1:2 to 2:

1.

6. The self-healing UHPC concrete according to claim 1, characterized in that, Quartz sand particle size is 26-70 mesh; mineral powder is grade S95 or higher; steel fiber is copper-plated short steel fiber, 80-160 kg / m². 3 Its nominal length is 12~17mm and its equivalent diameter is 0.15~0.30mm.

7. The self-healing UHPC concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of >30%.

8. The method for preparing self-healing UHPC concrete according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Prepare UHPC concrete matrix grout; 2) Place the hydrophilic modified heat-shrinkable fiber mesh in the middle of the mold; 3) Add the electromagnetic induction microcapsules to the UHPC concrete matrix slurry and mix evenly. Then pour the mixture into a mold equipped with a hydrophilic modified heat-shrinkable fiber mesh, shape and cure it to obtain the self-healing UHPC concrete.

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