High-strength concrete and preparation method thereof

Abstract

The present invention discloses a high-strength concrete and its preparation method, which is based on the following raw materials in parts by weight: ultrafine sulfoaluminate cement; coarse aggregate; quartz sand; silica fume; fly ash; nanometakaolin; silicon carbide whiskers; graphene oxide; pH-responsive microcapsules; liquid metal-coated steel fibers; carbon nanotubes; and polycarboxylate superplasticizers. The present invention utilizes pH-responsive microcapsules to precisely control the release of a repair agent, combines liquid metal-coated steel fibers to enhance interfacial properties, and optimizes the nanomaterial composite dispersion process. The synergistic design of the calcium oxide-sustained release agent system and the methyl methacrylate / acrylic acid copolymer shell significantly enhances the environmental response efficiency of the microcapsules. The gallium-based liquid metal coating, through its low melting point, achieves metallurgical bonding between the fiber and the substrate, breaking through the limitations of traditional physical bonding.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to high-strength concrete and a preparation method thereof. Background Art

[0002] Traditional high-strength concrete often relies on high amounts of Portland cement or complex additive systems to achieve improved mechanical properties, but it suffers from problems such as slow early strength development and the accumulation of microcracks caused by concentrated hydration heat. For example, while conventional sulfoaluminate cement-based concrete exhibits early strength properties, it is brittle, lacks crack resistance, and lacks the ability to self-repair cracks. This makes it susceptible to structural degradation due to environmental erosion during long-term service. While existing technologies can partially improve toughness by adding steel fibers or polymer modifications, they face process bottlenecks such as uneven fiber dispersion and weakened interfacial bonding.

[0003] In the field of functional additives, existing microencapsulation technologies often use a single core material (such as epoxy resin) to encapsulate the repair agent. This release response mechanism is limited by low sensitivity to changes in environmental pH, and the wide particle size distribution of the core material leads to unstable repair efficiency. Furthermore, steel fiber surface modification processes commonly use galvanizing or polymer coatings, which pose challenges such as easy coating flaking and thermal expansion coefficient mismatch with the cement matrix, limiting the maximization of fiber reinforcement. Furthermore, insufficient dispersion control of nanomaterials (such as carbon nanotubes and graphene oxide) can easily lead to agglomeration defects, weakening their ability to optimize the microstructure.

[0004] To address these shortcomings, the present invention achieves breakthroughs through multiple technological innovations: using pH-responsive microcapsules to precisely control the release of the repair agent, combining liquid metal-coated steel fibers to enhance interfacial properties, and optimizing the nanomaterial composite dispersion process. The synergistic design of the calcium oxide-sustained-release agent system and the methyl methacrylate / acrylic acid copolymer shell significantly enhances the environmental response efficiency of the microcapsules. The gallium-based liquid metal coating, through its low melting point, achieves a metallurgical bond between the fiber and the substrate, overcoming the limitations of traditional physical bonding. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength concrete and a preparation method thereof, which solves the problems of microcrack accumulation and insufficient self-repairing ability, weak bonding strength and uneven dispersion of existing concrete.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A high-strength concrete, which is composed of the following raw materials in parts by weight:

[0008] Ultrafine sulphoaluminate cement: 500-650 parts;

[0009] Coarse aggregate: 800-900 parts;

[0010] Quartz sand: 600-700 parts;

[0011] Silica fume: 90-200 parts;

[0012] Fly ash: 100-150 parts;

[0013] Nanometakaolin: 50-80 parts;

[0014] Silicon carbide whiskers: 10-16 parts;

[0015] Graphene oxide: 2-5 parts;

[0016] pH responsive microcapsules: 12-20 copies;

[0017] Liquid metal coated steel fiber: 45-100 parts;

[0018] Carbon nanotubes: 5-8 parts;

[0019] Polycarboxylate water reducer: 8-15 parts;

[0020] The pH-responsive microcapsule preparation steps include: pre-grinding calcium oxide and a sustained-release agent to a particle size of ≤5 μm, and vacuum drying at 60° C. to obtain a pretreated core material; mixing methyl methacrylate and acrylic acid in a mass ratio of 4:1, adding potassium persulfate, and dissolving in water to form a solution; mixing the pretreated core material with the solution, and ultrasonically emulsifying to obtain an emulsion; spray-drying the emulsion under nitrogen protection to obtain microcapsules, spraying a silane coupling agent on the surface of the microcapsules, and thermally curing.

[0021] According to a preferred embodiment of the present invention, the ultrafine sulphoaluminate cement is purchased from Changzhou Antai Chemical Co., Ltd. as model AP44126.

[0022] According to a preferred embodiment of the present invention, the particle size of the quartz sand is 0.4-0.7 mm.

[0023] According to a preferred embodiment of the present invention, the nano-metakaolin is purchased from Changzhou Antai Chemical Co., Ltd.

[0024] According to a preferred embodiment of the present invention, the calcium oxide is purchased from Shandong Xinyongrun Chemical Technology Co., Ltd.

[0025] According to a preferred embodiment of the present invention, the methyl methacrylate is purchased from Dongying Longxing Chemical Co., Ltd.

[0026] According to a preferred embodiment of the present invention, the acrylic acid is purchased from Jinan Century Tongda Chemical Co., Ltd.

[0027] According to a preferred embodiment of the present invention, the potassium persulfate is purchased from Wuxi Zhanwang Chemical Reagent Co., Ltd.

[0028] According to a preferred embodiment of the present invention, the water is purchased from Shanghai Binrun Environmental Protection Technology Co., Ltd.

[0029] According to a preferred embodiment of the present invention, the nitrogen is purchased from Weifang Jinfan Gas Co., Ltd.

[0030] According to a preferred embodiment of the present invention, the silane coupling agent is purchased from Guangzhou Xuanning Chemical Technology Co., Ltd. as model KH-560.

[0031] The specific steps of spray drying and forming the emulsion under nitrogen protection in the present invention include: first, selecting a pressure spray dryer equipped with a nitrogen protection system (to prevent premature reaction of calcium oxide). Key parameters: Inlet temperature: 180°C (high temperature allows rapid film formation on the surface of the droplets to prevent core material leakage). Outlet temperature: 85°C (to avoid excessive temperature from damaging the microcapsule shell structure). Atomization pressure: 0.3MPa (pressure nozzle) or centrifugal speed: 10,000-15,000rpm (centrifugal atomization). Feed rate: 5-10mL / min (matched with the hot air flow rate to ensure sufficient drying). Nitrogen flow rate: 0.5-1.0m 3 / h (maintain an inert environment). Atomization stage: The emulsion is atomized into tiny droplets through a nozzle or centrifugal disk. The surface of the droplets is instantly heated, and the shell material begins to cross-link and solidify. Drying stage: Hot air (180°C) contacts the droplets downstream, the water evaporates rapidly, and the shell material shrinks and wraps around the core material. Shell formation mechanism: Methyl methacrylate (hydrophobic) migrates outward to form a dense shell. Acrylic acid (hydrophilic) is enriched inward to enhance pH responsiveness. Particle collection: The dried microcapsules are collected by a cyclone separator, and the residual moisture is ≤5% (to avoid agglomeration).

[0032] According to a preferred embodiment of the present invention, the pressure spray dryer is purchased from Changzhou Zhousheng Drying Engineering Co., Ltd.

[0033] The ultrafine sulphoaluminate cement used in the present invention serves as the primary cementitious material, characterized by rapid early hydration and rapid strength development. Its hydration reaction primarily produces calcium aluminoferrite and alumina gel, imparting high early strength to the concrete. Compared to ordinary Portland cement, the hydration products are more stable, reducing the risk of drying shrinkage and cracking. The addition of nanometakaolin further optimizes the hydration process. Its high specific surface area and volcanic ash activity allow it to undergo a secondary reaction with the calcium hydroxide in the cement hydration products, generating additional CSH gel, thereby refining the pore structure and improving the matrix density. At the same time, nanometakaolin can also regulate the rate of heat release during cement hydration, reducing the risk of shrinkage and cracking, and enhancing the long-term durability of concrete.

[0034] According to a preferred embodiment of the present invention, the silicon carbide whiskers are purchased from Xuzhou Hongwu Nanotechnology Co., Ltd. Model D500A.

[0035] The silicon carbide whiskers in this invention possess high strength, high modulus, and high-temperature resistance. They act like "micro-rebars" within the concrete matrix, preventing crack propagation through a bridging effect and significantly improving flexural strength and toughness. Carbon nanotubes (CNTs), with their ultra-high surface area and aspect ratio, enhance the interfacial bonding within the cement matrix at the nanoscale and form an interlocking structure with the CSH gel, further enhancing the material's compressive and tensile properties. Furthermore, the conductivity of CNTs imparts a degree of self-monitoring capability to concrete, providing early warning of structural damage through changes in resistance.

[0036] According to a preferred embodiment of the present invention, the graphene oxide is purchased from Hangzhou Gaoxun Technology Co., Ltd.

[0037] The graphene oxide (GO) in this invention has a two-dimensional lamellar structure and abundant oxygen-containing functional groups. It serves as a nucleation site during cement hydration, promoting the uniform growth of CSH gel and optimizing its microstructure. Furthermore, GO's lamellar structure fills nanoscale pores, blocking the permeation pathways for water and harmful ions, thereby improving the concrete's impermeability and resistance to chemical attack. Furthermore, GO's electrical conductivity synergizes with carbon nanotubes to enhance the concrete's electromagnetic shielding properties, making it suitable for specialized engineering environments.

[0038] The pH-responsive microcapsules in this invention have a core composed of calcium oxide and a slow-release agent, and a shell composed of a pH-sensitive polymer. When cracks appear in concrete and water infiltrates, the local pH change at the crack triggers the microcapsule shell to rupture, releasing CaO. The CaO rapidly reacts with water to form calcium hydroxide (Ca(OH)₂), which further reacts with the infiltrating CO₂ to form calcium carbonate (CaCO₃), filling the cracks and achieving self-healing. The addition of a slow-release agent regulates the CaO release rate, preventing premature reaction and ensuring a long-lasting repair effect.

[0039] According to a preferred embodiment of the present invention, the coarse aggregate is granite crushed stone; and the slow-release agent is selected from at least one of tartaric acid, disodium hydrogen phosphate, sodium phosphate, and sodium pyrophosphate.

[0040] According to a preferred embodiment of the present invention, the particle size range of the granite crushed stones is continuously graded from 5 to 20 mm; preferably, 5 to 10 mm accounts for 60% and 10 to 20 mm accounts for 40%.

[0041] According to a preferred embodiment of the present invention, the granite crushed stones are purchased from Wulian County Yizhong New Materials Co., Ltd.

[0042] According to a preferred embodiment of the present invention, the tartaric acid is purchased from Jiangsu Yanke Bioengineering Co., Ltd.

[0043] According to a preferred embodiment of the present invention, the disodium hydrogen phosphate is purchased from Qingzhou Tiandiren Chemical Co., Ltd.

[0044] According to a preferred embodiment of the present invention, the sodium phosphate is purchased from Jilin Xingtai Chemical Co., Ltd.

[0045] According to a preferred embodiment of the present invention, the sodium pyrophosphate is purchased from Wuhan Awakening Lion Chemicals Co., Ltd.

[0046] According to a preferred embodiment of the present invention, the liquid metal coated steel fiber is prepared by coating a gallium-based liquid metal with a thickness of 50-100 nm on the surface of the steel fiber.

[0047] According to a preferred embodiment of the present invention, the steel fiber is purchased from Boxing Huideli Metal Materials Co., Ltd.

[0048] According to a preferred embodiment of the present invention, the gallium-based liquid metal is a gallium-indium-tin alloy model purchased from Suzhou Rongqian Rare Metal Products Co., Ltd.

[0049] The gallium-based liquid metal (such as a Ga-In-Sn alloy) coated on the steel fiber surface in this invention is liquid at room temperature but forms a stable intermetallic compound layer with the steel fiber surface, enhancing the bond strength between the fiber and the cement matrix. When microcracks form in concrete under stress, the liquid metal coating can flow locally, filling microdefects at the fiber-matrix interface and alleviating stress concentration. Furthermore, the high thermal conductivity of the liquid metal helps evenly distribute thermal stresses, reducing the occurrence of thermal cracks.

[0050] According to a preferred embodiment of the present invention, the mass ratio of calcium oxide to sustained-release agent is 10:1; during pre-grinding, the ball mill speed is 300 rpm and the time is 6 hours.

[0051] According to a preferred embodiment of the present invention, the ball mill is purchased from Nanchang Baijia Machinery Equipment Co., Ltd.

[0052] According to a preferred embodiment of the present invention, during spray drying, the inlet and outlet temperatures are set to 180° C. and 85° C., respectively, and the atomization pressure is 0.3 MPa.

[0053] According to a preferred embodiment of the present invention, the temperature during thermal curing is 80-110°C, the time is 30-60 min, and the heating rate is ≤5°C / min.

[0054] The present invention also provides a method for preparing the high-strength concrete, comprising the following steps:

[0055] S1, weighing ultrafine sulphoaluminate cement, coarse aggregate, quartz sand, silica fume, fly ash, nanometakaolin, silicon carbide whiskers, and graphene oxide in proportion, and dry mixing them in a forced mixer;

[0056] S2, adding pH-responsive microcapsules, liquid metal-coated steel fibers, and carbon nanotubes in sequence with low-speed stirring;

[0057] S3, add water and polycarboxylate water reducer simultaneously, use planetary mixer to mix at low speed first and then at high speed to obtain concrete.

[0058] According to a preferred embodiment of the present invention, in step S1, the dry mixing time in the forced mixer is 3-5 minutes.

[0059] According to a preferred embodiment of the present invention, in step S2, the rotation speed of the low-speed stirring is ≤60 rpm, and the stirring time is 2 min.

[0060] According to a preferred embodiment of the present invention, in step S3, the rotation speed of the low-speed stirring is 120 rpm, and the stirring time is 1 min; the rotation speed of the high-speed stirring is 240 rpm, and the stirring time is 2 min.

[0061] According to a preferred embodiment of the present invention, the polycarboxylate water reducer is purchased from Kezhijie New Materials Group Co., Ltd.

[0062] According to a preferred embodiment of the present invention, the forced mixer is from Zhengzhou Sanqiang Machinery Co., Ltd.

[0063] The polycarboxylate superplasticizer in the present invention effectively disperses nanomaterials (such as GO, CNTs) and microcapsules through steric hindrance and electrostatic repulsion, prevents agglomeration, ensures uniform distribution of various components, and improves the final density and strength of concrete.

[0064] The beneficial effects of the present invention are:

[0065] The present invention successfully developed a high-strength concrete with excellent mechanical properties and intelligent repair functions through innovative material proportioning and preparation technology. The concrete shows significant advantages in compressive strength, flexural strength and durability. Ultrafine sulphoaluminate cement is used as the main cementitious material. Its high activity characteristics enable the early strength of concrete to develop rapidly. At the same time, the addition of nano-metakaolin further optimizes the microstructure of the cement matrix, forming a dense network structure, which greatly improves the overall mechanical properties of the material. The synergistic effect of silicon carbide whiskers and carbon nanotubes effectively enhances the toughness and crack resistance of the matrix, making the concrete less prone to brittle failure when subjected to high loads. The introduction of graphene oxide strengthens the interface transition zone between cement stone and aggregate at the nanoscale.

[0066] The present invention uses a carefully designed pH-responsive microcapsule system to automatically trigger a repair mechanism when cracks appear in concrete. When the environmental pH changes due to water seepage through the cracks, the microcapsules rapidly release active substances such as calcium oxide, which, upon contact with water, generate repair products such as calcium carbonate, effectively filling microcracks. Liquid metal-coated steel fibers not only enhance the bonding performance between the fibers and the matrix, but their unique liquid metal layer can also flow locally under stress, alleviating stress concentration. This dual repair mechanism significantly extends the service life of concrete structures and reduces maintenance costs, making it particularly suitable for infrastructure projects in extreme environments.

[0067] In addition, the preparation process of the present invention ensures the uniform dispersion of nanomaterials and high-performance fibers in the matrix by optimizing the order of incorporation of each component and the stirring parameters. The rational use of polycarboxylic acid water-reducing agent enables good working performance to be obtained under low water-cement ratio conditions, thereby further improving the final density and strength of the concrete. The microcapsules prepared by the spray drying method have an ideal shell thickness and thermal stability, and remain intact during the concrete mixing and hardening process until the repair agent is released when needed. Overall, this high-strength concrete has achieved breakthrough progress in mechanical properties, durability and intelligent functions, providing a new technical direction for the development of modern civil engineering materials. DETAILED DESCRIPTION

[0068] The following specific implementation methods are only used to further illustrate the present application and should not be understood as limiting the scope of protection of the present application. Technicians in this field may make some non-essential improvements and adjustments to the present application based on the above application content.

[0069] Example 1

[0070] The components were accurately weighed as follows: 550.0 g of ultrafine sulphoaluminate cement (specific surface area 650 m² / kg), 850.0 g of granite crushed stone, 620.0 g of quartz sand, 95.0 parts of silica fume, 120.0 parts of fly ash, 50.0 g of nanometakaolin (average particle size 80 nm), 10.5 g of silicon carbide whiskers, 5.0 g of carbon nanotubes, 3 g of graphene oxide, 12.0 g of pH-responsive microcapsules, 45.0 g of gallium-based liquid metal-coated steel fiber, 8.6 g of polycarboxylate water reducer, and 150.0 g of water.

[0071] Preparation of pH-responsive microcapsules: Microcapsules were prepared 24 hours in advance. First, 90.0 g of calcium oxide and 9.0 g of tartaric acid were intermittently ground in a planetary ball mill at 300 rpm for 7.5 hours (including cooling time). Particles ≤5 μm were filtered through a 325-mesh sieve and dried in a vacuum at 60°C for 12 hours. A shell material solution was prepared under nitrogen from 72.0 g of methyl methacrylate, 18.0 g of acrylic acid, 1.8 g of potassium persulfate, and 300 ml of water. The shell material was mixed with the core material and then emulsified in an ultrasonic cell disruptor in a stepwise manner (pulse mode for 5 minutes followed by continuous mode for 15 minutes) to obtain an emulsion with a D50 of 3.2 μm. Spray drying parameters were set as an inlet air temperature of 180°C, an outlet air temperature of 85°C, an atomization pressure of 0.3 MPa, and a nitrogen flow rate of 0.8 m³ / h. The microcapsules were sprayed with 1.5% KH-560 ethanol solution (0.135 g silane + 9 ml ethanol) in a fluidized bed and then programmed temperature curing (5°C / min to 80°C → 1°C / min to 110°C and maintained for 45 min).

[0072] Preparation of liquid metal-coated steel fibers: The steel fibers were ultrasonically cleaned with acetone for 15 min, pickled with 5% hydrochloric acid for 30 s, and rinsed with water until neutral. After drying at 100°C, they were coated with gallium-indium-tin alloy (Ga:In:Sn=68:22:10, melted at 150°C) by electrophoretic deposition. The process parameters were 12 V voltage, 90 s deposition time, and 50 mm electrode spacing. The final coating thickness was 82 ± 6 nm.

[0073] Concrete Mixing Process: Ultrafine sulfoaluminate cement, granite crushed stone, quartz sand, silica fume, fly ash, nanometakaolin, silicon carbide whiskers, and graphene oxide were dry-mixed in a forced mixer. Dry-mixing time in the forced mixer was 5 minutes. pH-responsive microcapsules, liquid metal-coated steel fibers, and carbon nanotubes were added sequentially. Dry-mixing speed was 60 rpm for 2 minutes. Water was added, along with a polycarboxylate superplasticizer. Mixing was performed in stages: low-speed stage: 120 rpm for 1 minute. High-speed stage: 240 rpm for 2 minutes.

[0074] Molding and Curing: A test mold (40×40×160mm) was pre-coated with release agent and cast in two layers. Each layer was rammed 25 times and compacted on a vibrating table (50Hz, 0.5mm amplitude, 15s). After initial setting, the mold was covered with PE film, removed after 24 hours, and placed in a standard curing chamber (20±0.5°C, RH≥98%). Performance testing began 3 days later.

[0075] Example 2

[0076] The specific implementation method is the same as that of Example 1, except that 520.0 g of ultrafine sulfoaluminate cement (specific surface area 650 m² / kg), 900.0 g of granite crushed stone, 600.0 g of quartz sand, 105.0 parts of silica fume, 100.0 parts of fly ash, 70.0 g of nanometakaolin (average particle size 80 nm), 12.0 g of silicon carbide whiskers, 6.0 g of carbon nanotubes, 4 g of graphene oxide, 15.0 g of pH-responsive microcapsules, 55.0 g of gallium-based liquid metal-coated steel fibers, 10.2 g of a polycarboxylate superplasticizer, and 150.0 g of water are used. In step S1, the dry mixing time in the forced mixer is 3 minutes.

[0077] Example 3

[0078] The specific implementation method is the same as that of Example 1, except that: graphene oxide: 4.05; pH-responsive microcapsules: 20 g; in step S2, the low-speed stirring speed is 50 rpm.

[0079] Comparative Example 1

[0080] The specific implementation method is the same as that of Example 1, except that the pH-responsive microcapsules are eliminated (12 g is replaced by an equal amount of cement); the preparation method is to directly skip the microcapsule addition step.

[0081] Comparative Example 2

[0082] The specific implementation method is the same as that of Example 1, except that the liquid metal coated steel fiber is replaced with 45g of ordinary copper-plated steel fiber; no special treatment is required for the fiber surface.

[0083] Performance test 1. Mechanical properties test

[0084] Compressive strength test: Test standard: GB / T 17671-2021; Test equipment: YES-300 microcomputer-controlled pressure testing machine (range 300kN, accuracy ±0.5%); Specimen preparation: 40×40×160mm prismatic specimen; 6 parallel specimens per group; Both ends of the specimen are leveled with sulfur mortar; Test procedure: The specimen is centered on the center of the press platen; Preload to 5kN and hold for 30s; Continuously load at a rate of 2.4±0.2kN / s until failure; Record peak load (accurate to 0.1kN); Data processing: Compressive strength = maximum load / compressed area (1600mm²); Take the average value of 6 specimens (eliminate data with deviation >10%).

[0085] Flexural Strength Test: Test standard: GB / T 17671-2021; Equipment: WDW-100 electronic universal testing machine (equipped with a three-point bending fixture); Test parameters: Span 100±0.5mm; Loading head radius 5mm; Support roller radius 2.5mm; Loading rate 50±5N / s; Test steps: Place the specimen with its long side facing up; Align the indenter with the specimen centerline; Apply continuous and uniform load until fracture; Calculation formula: Flexural strength = 3FL / (2bh²); where F is the failure load, L is the span, and b and h are the specimen width and height.

[0086] Elastic modulus test: Test standard: GB / T 50081-2019; Test system: Microcomputer-controlled electro-hydraulic servo pressure testing machine; Double-sided electronic extensometer (gauge length 100mm, accuracy 0.001mm); Test procedure: Preload three times (0.5-1.0MPa); Formal load to 40% of the ultimate load; Read after holding the load for 60 seconds; Repeat three times and take the average; Data acquisition: Record deformation value every 0.5MPa; Plot stress-strain curve; Calculate modulus by taking the slope of the straight line segment of the curve.

[0087] 2. Self-repair performance test

[0088] Crack repair rate test: Crack prefabrication: Using an INSTRON 8802 fatigue testing machine; prefabricate a 0.30±0.02mm crack using the three-point bending method; monitor the crack tip with a microscope (40x magnification); Repair environment: immersion in water at 20±1°C;

[0089] The pH was maintained at 7.0 ± 0.2 using a Keyence VHX-6000 ultra-depth microscope. Crack morphology was photographed every 24 h (500x magnification). Crack width was measured using image analysis software (accuracy 0.5 μm). The calculation formula was: repair rate = [(W0-W7) / W0] × 100%; W0: initial crack width, W7: crack width after 7 days.

[0090] Strength recovery rate test: Test process: prefabricate standard specimens from the same batch, pre-crack at 50% of the ultimate load, control the crack width to 0.25-0.35mm, and test the residual strength after 7 days of water curing; control points: accurately control the pre-crack load to ±2%, mark and locate the crack position, and maintain the same loading direction during the test after repair.

[0091] 3. Interface performance test

[0092] Single-fiber pullout test: Specimen preparation: A single fiber was fixed in a custom mold with a fiber embedment length of 5.0 ± 0.1 mm. The matrix mix ratio was the same as that of the main body, and standard curing was performed for 28 days. Testing system: MTS Landmark testing machine, 100 N load cell (0.1 N accuracy), laser displacement sensor (0.1 μm resolution). Test parameters: loading rate 0.5 mm / min, data acquisition frequency 100 Hz, test environment 23 ± 2°C, RH 50 ± 5%. Data analysis: extraction of maximum pullout load, calculation of interfacial bond strength, analysis of load-displacement curve characteristics, and CT analysis of fiber distribution were performed. Scanning equipment: Zeiss Xradia 520 Versa microCT. Scanning parameters: voltage 80 kV, power 7 W, pixel size 5 μm, exposure time 5 s, number of projections 1600. 3D reconstruction: Avizo Fire software, grayscale threshold segmentation, fiber identification algorithm. Quantitative indicator: orientation coefficient = Σcos 2 θ / N, spacing variation coefficient = σ / μ, fiber contact point statistics.

[0093] 4. Durability test

[0094] Chloride Ion Permeability: Test Standard: ASTM C1202; Test Equipment: Dedicated RCM test device, 0.3M NaOH / 3% NaCl solution, DC regulated power supply; Specimen Preparation: Φ100×50mm cylinder, vacuum saturated with water for 24 hours, and side sealing treatment; Test Procedure: Apply 30V DC voltage, record initial current, test for 24 hours, temperature controlled at 20±2°C; Data Processing: Calculate chloride ion migration coefficient and convert electrical flux according to ASTM C1202.

[0095] Rapid freeze-thaw test: GB / T 50082-2009; Equipment parameters: Fully automatic concrete freeze-thaw testing machine, temperature range -20 to 20°C, temperature control accuracy ±0.5°C; Test key points: A thermocouple is embedded in the center of the specimen, and the freeze-thaw medium is water; Every 25 cycles, the following tests are performed: mass loss (accuracy 0.01g) and transverse fundamental frequency (resonance method); Termination conditions: Mass loss > 5%, relative dynamic elastic modulus < 60%, and 300 cycles are achieved.

[0096] (2) Performance test results:

[0097] Table 1: Performance test results of various embodiments and comparative examples

[0098]

[0099] As can be seen in Table 1, a systematic analysis of the test data from Examples 1-3 and Comparative Examples 1-2 clearly demonstrates that this technical solution effectively addresses the technical bottlenecks of conventional concrete in terms of microcrack control, self-healing ability, and material dispersibility. In terms of mechanical properties, the Example group exhibits significant advantages. The 28-day compressive strength of Example 1 reaches 182.3 MPa, significantly higher than that of Comparative Example 1 (79.4 MPa) and Comparative Example 2 (76.2 MPa). The flexural strength index also shows a significant increase, with Example 2's value of 32.6 MPa far exceeding the 9.8 MPa of Comparative Example 2. This comprehensive improvement in mechanical properties directly confirms the effective suppression of microcrack propagation by the multi-scale reinforcement system of silicon carbide whiskers and carbon nanotubes. The test data of self-repair performance is more convincing. The crack repair rate of 89.2% and the strength recovery rate of 92.5% in Example 1 are in sharp contrast to the performance of only 12.3% and 18.7% in Comparative Example 1. In particular, Example 3 further improves the repair rate to 94.7% by increasing the amount of microcapsules, which fully verifies the core role of pH-responsive microcapsules in autonomous crack repair. The breakthrough in interfacial bonding strength is reflected in the 3.8MPa test value of Example 1, which is 137% higher than the 1.6MPa of ordinary copper-plated fiber in Comparative Example 2. This leap is due to the unique advantages of liquid metal coatings. In the chloride ion permeability test, the performance of Comparative Examples 1 and 2 is significantly worse than that of Examples 1-3. The significant improvement in durability indicators fully demonstrates the important value of homogenization of the material system. Based on all the test data, this technology achieves an 82% reduction in crack density in concrete crack control, a repair rate of more than 90% in self-repair efficiency, and an improvement in bond strength of more than 140% in interface performance through the synergistic effect of the intelligent repair mechanism of pH-responsive microcapsules, the interface strengthening effect of liquid metal coating, and the gradient dispersion process. This completely overcomes the three major technical difficulties of traditional concrete: accumulation of microcracks, poor self-repairing ability, and uneven material dispersion.

[0100] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A high-strength concrete, characterized in that: It is composed of the following raw materials in parts by weight: Ultrafine sulphoaluminate cement: 500-650 parts; Coarse aggregate: 800-900 parts; Quartz sand: 600-700 parts; Silica fume: 90-200 parts; Fly ash: 100-150 parts; Nanometakaolin: 50-80 parts; Silicon carbide whiskers: 10-16 parts; Graphene oxide: 2-5 parts; pH responsive microcapsules: 12-20 copies; Liquid metal coated steel fiber: 45-100 parts; Carbon nanotubes: 5-8 parts; Polycarboxylate water reducer: 8-15 parts; The pH-responsive microcapsule preparation steps include: pre-grinding calcium oxide and a sustained-release agent to a particle size of ≤5 μm, and vacuum drying at 60° C. to obtain a pretreated core material; mixing methyl methacrylate and acrylic acid in a mass ratio of 4:1, adding potassium persulfate, and dissolving in water to form a solution; mixing the pretreated core material with the solution, and ultrasonically emulsifying to obtain an emulsion; spray-drying the emulsion under nitrogen protection to obtain microcapsules, spraying a silane coupling agent on the surface of the microcapsules, and thermally curing; The liquid metal coated steel fiber is prepared by coating a gallium-based liquid metal with a thickness of 50-100 nm on the surface of the steel fiber.

2. The high-strength concrete according to claim 1, characterized in that The coarse aggregate is granite crushed stone, and the slow-release agent is selected from at least one of tartaric acid, disodium hydrogen phosphate, sodium phosphate, and sodium pyrophosphate.

3. The high-strength concrete according to claim 1, characterized in that The mass ratio of the calcium oxide to the sustained-release agent is 10:1; during pre-grinding, the ball mill speed is 300 rpm and the time is 6 hours.

4. The high-strength concrete according to claim 1, characterized in that During spray drying, the inlet and outlet temperatures were set at 180°C and 85°C, respectively, and the atomization pressure was 0.3 MPa.

5. The high-strength concrete according to claim 1, characterized in that The temperature during the thermal curing is 80-110°C, the time is 30-60 minutes, and the heating rate is ≤5°C / min.

6. The method for preparing high-strength concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, weighing ultrafine sulphoaluminate cement, coarse aggregate, quartz sand, silica fume, fly ash, nanometakaolin, silicon carbide whiskers, and graphene oxide in proportion, and dry mixing them in a forced mixer; S2, adding pH-responsive microcapsules, liquid metal-coated steel fibers, and carbon nanotubes in sequence with low-speed stirring; S3, add water and polycarboxylate water reducer simultaneously, use planetary mixer to mix at low speed first and then at high speed to obtain concrete.

7. The preparation method according to claim 6, characterized in that In step S1, the dry mixing time in the forced mixer is 3-5 minutes.

8. The preparation method according to claim 6, characterized in that In step S2, the rotation speed of the low-speed stirring is ≤60 rpm, and the stirring time is 2 min.

9. The preparation method according to claim 6, characterized in that In step S3, the rotation speed of the low-speed stirring is 120 rpm, and the stirring time is 1 min. The rotation speed of the high-speed stirring is 240 rpm, and the stirring time is 2 min.

Images