High-strength concrete and preparation method thereof

Abstract

The invention discloses high-strength concrete and a preparation method thereof in the field of concrete. The high-strength concrete is prepared from the following raw materials in parts by weight: superfine sulphoaluminate cement; coarse aggregate; quartz sand; silica fume; coal ash; nano metakaolin; silicon carbide whiskers; a graphene oxide; a pH responsive microcapsule; coating the steel fibers with liquid metal; a carbon nanotube; and a polycarboxylic acid water reducer. Release of the repairing agent is accurately regulated and controlled by adopting the pH response microcapsule, the interface performance is enhanced by combining with the liquid metal coating steel fiber, and the composite dispersion process of the nano material is optimized. Wherein the environment response efficiency of the microcapsule is remarkably improved through the collaborative design of a calcium oxide-slow release agent system and a methyl methacrylate / acrylic acid copolymerization shell layer; according to the gallium-based liquid metal coating, metallurgical bonding of fibers and a matrix is achieved through the low-melting-point characteristic, and traditional physical bonding limitation is broken through.

Description

Technical Field

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

[0002] Traditional high-strength concrete often relies on high-dosage portland cement or complex additive systems to improve mechanical properties, but there are problems such as slow early strength development and cumulative microcracks caused by concentrated heat of hydration. For example, conventional calcium sulfoaluminate cement-based concrete has early strength characteristics, but is brittle, has insufficient crack resistance, and lacks crack self-healing ability, and is prone to structural deterioration due to environmental erosion during long-term service. In the prior art, although adding steel fibers or polymer modification can partially improve toughness, it faces process bottlenecks such as uneven fiber dispersion and weakened interfacial bonding.

[0003] In the field of functional additives, existing microcapsule technologies mostly use a single core material (such as epoxy resin) to encapsulate repair agents, and their release response mechanism is limited by low sensitivity to environmental pH changes, and the wide particle size distribution of the core material leads to unstable repair efficiency. At the same time, the surface modification process of steel fibers generally uses galvanized or polymer coatings, which have problems such as easy peeling of the coating and mismatch of the thermal expansion coefficient with the cement matrix, restricting the maximization of the fiber reinforcement effect. In addition, the dispersion control of nanomaterials (such as carbon nanotubes, graphene oxide) is insufficient, which is prone to aggregation defects and weakens their optimization effect on the microstructure.

[0004] In view of the above defects, the present invention achieves breakthroughs through multiple technological innovations: precisely regulating the release of repair agents by pH-responsive microcapsules, combining liquid metal-coated steel fibers to enhance interfacial properties, and optimizing the composite dispersion process of nanomaterials. Among them, the synergistic design of the calcium oxide-sustained release agent system and the methyl methacrylate / acrylic acid copolymer shell significantly improves the environmental response efficiency of the microcapsules; the gallium-based liquid metal coating realizes the metallurgical bonding between the fiber and the matrix through its low melting point characteristics, breaking through the limitation 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 solve the problems of cumulative microcracks and insufficient self-healing ability, weak bonding force and uneven dispersion in existing concrete.

[0006] The present invention achieves the above purpose through the following technical solutions: A high-strength concrete, which is composed of the following raw materials in parts by weight: Ultra-fine calcium sulfoaluminate cement: 500-650 parts; Coarse aggregate: 800-900 parts; Quartz sand: 600-700 parts; Silica fume: 90-200 parts; Fly ash: 100 - 150 parts; Nano-metakaolin: 50 - 80 parts; Silicon carbide whiskers: 10 - 16 parts; Graphene oxide: 2 - 5 parts; pH-responsive microcapsules: 12 - 20 parts; Liquid metal-coated steel fibers: 45 - 100 parts; Carbon nanotubes: 5 - 8 parts; Polycarboxylate water reducer: 8 - 15 parts; Among them, the preparation steps of the pH-responsive microcapsules include: pre-grinding calcium oxide and a slow-release agent to a particle size ≤ 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 and the solution, and performing ultrasonic emulsification to obtain an emulsion; spray-drying and forming the emulsion under nitrogen protection to obtain microcapsules, and spraying a silane coupling agent on the surface of the microcapsules and thermally curing.

[0007] According to a preferred embodiment of the present invention, the ultra-fine sulphoaluminate cement is purchased from the AP44126 model of Changzhou Antai Chemical Co., Ltd.

[0008] According to a preferred embodiment of the present invention, the particle size of the quartz sand is 0.4 - 0.7 mm. According to a preferred embodiment of the present invention, the nano-metakaolin is purchased from Changzhou Antai Chemical Co., Ltd.

[0009] According to a preferred embodiment of the present invention, the calcium oxide is purchased from Shandong Xinyongrun Chemical Technology Co., Ltd.

[0010] According to a preferred embodiment of the present invention, the methyl methacrylate is purchased from Dongying Longxing Chemical Co., Ltd.

[0011] According to a preferred embodiment of the present invention, the acrylic acid is purchased from Jinan Century Tongda Chemical Co., Ltd.

[0012] According to a preferred embodiment of the present invention, the potassium persulfate is purchased from Wuxi Zhanwang Chemical Reagent Co., Ltd.

[0013] According to a preferred embodiment of the present invention, the water is purchased from Shanghai Binrun Environmental Protection Technology Co., Ltd.

[0014] According to a preferred embodiment of the present invention, the nitrogen is purchased from Weifang Jinfan Gas Co., Ltd.

[0015] According to a preferred embodiment of the present invention, the silane coupling agent is purchased from the KH-560 model of Guangzhou Xuanning Chemical Technology Co., Ltd.

[0016] The specific steps for spray-drying and forming the emulsion under nitrogen protection in the present invention include: First, select a pressure-type spray dryer equipped with a nitrogen protection system (to prevent premature reaction of calcium oxide). Key parameters: Inlet temperature: 180 °C (high temperature enables rapid film formation on the droplet surface to prevent leakage of the core material). Outlet temperature: 85 °C (to avoid damaging the microcapsule shell structure at too high a temperature). Atomization pressure: 0.3 MPa (pressure-type nozzle) or centrifugal speed: 10,000 - 15,000 rpm (centrifugal atomization). Feed rate: 5 - 10 mL / min (matched with the hot air flow rate to ensure sufficient drying). Nitrogen flow rate: 0.5 - 1.0 m 3 / h (to maintain an inert environment). Atomization stage: The emulsion is atomized into tiny droplets through a nozzle or a centrifugal disk. The surface of the droplets is instantly heated, and the shell material begins to crosslink and solidify. Drying stage: Hot air (180 °C) contacts the droplets in a co-current manner, and the moisture rapidly evaporates. The shell material shrinks and wraps the core material. Shell formation mechanism: Methyl methacrylate (hydrophobic) migrates outwards to form a dense outer shell. Acrylic acid (hydrophilic) accumulates inwards to enhance the pH responsiveness. Particle collection: The dried microcapsules are collected by a cyclone separator, and the residual moisture ≤ 5% (to avoid caking).

[0017] According to a preferred embodiment of the present invention, the pressure-type spray dryer is purchased from Changzhou Zhousheng Drying Engineering Co., Ltd.

[0018] In the present invention, the ultra-fine sulfoaluminate cement is used as the main cementing material, which has the characteristics of fast early hydration and rapid strength development. Its hydration reaction mainly generates ettringite and aluminosilicate gel, endowing the concrete with high early strength; compared with ordinary Portland cement, the hydration products are more stable, reducing the risk of drying shrinkage and cracking. The addition of nano-metakaolin further optimizes the hydration process. Its high specific surface area and pozzolanic activity enable it to react with calcium hydroxide in the cement hydration products to generate additional C-S-H gel, thereby refining the pore structure and improving the matrix density. At the same time, nano-metakaolin can also control the cement hydration heat release rate, reduce the risk of shrinkage cracking, and enhance the long-term durability of the concrete.

[0019] According to a preferred embodiment of the present invention, the silicon carbide whiskers are purchased from the D500A model of Xuzhou Hongwu Nano Technology Co., Ltd.

[0020] In the present invention, the silicon carbide whiskers have high strength, high modulus and high temperature resistance characteristics, and play the role of "micro steel bars" in the concrete matrix. Through the bridging effect, crack propagation is prevented, and the flexural strength and toughness are significantly improved. Carbon nanotubes (CNTs) enhance the interfacial bonding force of the cement matrix at the nanoscale through their ultra-high specific surface area and aspect ratio, and form an interlocking structure with C-S-H gel, further improving the compressive and tensile properties of the material. In addition, the conductivity of carbon nanotubes can endow the concrete with certain self-monitoring ability, and early warning can be carried out through the change of resistance when the structure is damaged.

[0021] According to a preferred embodiment of the present invention, the graphene oxide is purchased from Hangzhou Gaoxi Technology Co., Ltd.

[0022] In the present invention, graphene oxide (GO) has a two-dimensional sheet structure and abundant oxygen-containing functional groups, which can serve as nucleation sites during the cement hydration process, promote the uniform growth of C-S-H gel, and optimize the microstructure. At the same time, the sheet structure of GO can fill nanoscale pores, block the penetration paths of water and harmful ions, and improve the impermeability and chemical erosion resistance of the concrete. In addition, the conductivity of GO and carbon nanotubes act synergistically to enhance the electromagnetic shielding performance of the concrete, which is suitable for special engineering environments.

[0023] In the present invention, the core material of the pH-responsive microcapsule is calcium oxide and a slow-release agent, and the shell is a pH-sensitive polymer. When cracks appear in the concrete and water seeps in, the local pH value change at the crack triggers the rupture of the microcapsule shell, releasing CaO. CaO quickly reacts with water to form calcium hydroxide (Ca(OH)2), and further reacts with the infiltrated CO2 to form calcium carbonate (CaCO3), filling the cracks to achieve self-repair. The addition of the slow-release agent can regulate the release rate of CaO, avoid premature reaction, and ensure the durability of the repair effect.

[0024] According to a preferred embodiment of the present invention, the coarse aggregate is granite gravel; the slow-release agent is selected from at least one of tartaric acid, disodium hydrogen phosphate, sodium phosphate, and sodium pyrophosphate.

[0025] According to a preferred embodiment of the present invention, the particle size range of the granite gravel is a continuous gradation of 5-20 mm; preferably, 5-10 mm accounts for 60% and 10-20 mm accounts for 40%.

[0026] According to a preferred embodiment of the present invention, the granite gravel is purchased from Wulian County Yizhong New Materials Co., Ltd.

[0027] According to a preferred embodiment of the present invention, the tartaric acid is purchased from Jiangsu Yanke Biotechnology Co., Ltd.

[0028] According to a preferred embodiment of the present invention, the disodium hydrogen phosphate is purchased from Qingzhou Tiandi Ren Chemical Co., Ltd.

[0029] According to a preferred embodiment of the present invention, the sodium phosphate is purchased from Jilin Xingtai Chemical Co., Ltd.

[0030] According to a preferred embodiment of the present invention, the sodium pyrophosphate is purchased from Wuhan Xingshi Chemical Co., Ltd.

[0031] According to a preferred embodiment of the present invention, the liquid metal-coated steel fiber is prepared by coating a 50-100 nm thick gallium-based liquid metal on the surface of the steel fiber.

[0032] According to a preferred embodiment of the present invention, the steel fiber is purchased from Boxing Huidel Metal Materials Co., Ltd.

[0033] According to a preferred embodiment of the present invention, the gallium-based liquid metal is purchased from the gallium-indium-tin alloy model of Suzhou Rongqian Rare Metal Products Co., Ltd.

[0034] In the present invention, the gallium-based liquid metal (such as Ga-In-Sn alloy) coated on the surface of the steel fiber is in a liquid state at room temperature, but can form a stable intermetallic compound layer with the surface of the steel fiber, improving the bonding strength between the fiber and the cement matrix. When the concrete is stressed and microcracks occur, the liquid metal coating can undergo local flow, filling the microdefects at the fiber-matrix interface and relieving stress concentration. At the same time, the high thermal conductivity of the liquid metal helps to evenly disperse the temperature stress and reduce the generation of temperature cracks.

[0035] According to a preferred embodiment of the present invention, the mass ratio of calcium oxide to the slow-release agent is 10:1; during pre-grinding, the rotational speed of the ball mill is 300 rpm and the duration is 6 h.

[0036] According to a preferred embodiment of the present invention, the ball mill is purchased from Nanchang Baijia Machinery Equipment Co., Ltd.

[0037] 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.

[0038] 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 ≤ 5 °C / min.

[0039] The present invention also provides a method for preparing the high-strength concrete, comprising the following steps: S1, weighing ultrafine sulfoaluminate cement, coarse aggregate, quartz sand, silica fume, fly ash, nano-metakaolin, 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, stirring at a low speed; S3, adding water and simultaneously mixing in polycarboxylate water reducing agent, using a planetary mixer to mix at a low speed first and then at a high speed to obtain concrete.

[0040] According to a preferred embodiment of the present invention, in step S1, the dry mixing time in the forced mixer is 3-5 minutes.

[0041] 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.

[0042] According to a preferred embodiment of the present invention, in step S3, the rotation speed of the low-speed stirring is 120 rpm, the stirring time is 1 min, and the rotation speed of the high-speed stirring is 240 rpm, and the stirring time is 2 min.

[0043] According to a preferred embodiment of the present invention, the polycarboxylate water reducer is purchased from Kezhijie New Materials Group Co., Ltd.

[0044] According to a preferred embodiment of the present invention, the forced mixer is from Zhengzhou Sanqiang Machinery Co., Ltd.

[0045] The polycarboxylate water-reducing agent in the present invention effectively disperses nanomaterials (such as GO, CNTs) and microcapsules through steric hindrance effect and electrostatic repulsion, prevents agglomeration, ensures uniform distribution of each component, and improves the final density and strength of concrete.

[0046] The beneficial effects of the present invention are: The present invention successfully develops a high-strength concrete with excellent mechanical properties and intelligent repair functions through innovative material ratios and preparation processes. 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 it less likely for concrete to suffer 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.

[0047] Through a carefully designed pH-responsive microcapsule system, the present invention enables concrete to automatically trigger a repair mechanism when cracks occur. When the environmental pH value changes due to crack seepage, the microcapsules rapidly release active substances such as calcium oxide, which react with water to form repair products such as calcium carbonate, effectively filling microcracks. The 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 undergo local flow under stress, alleviating stress concentration. This dual repair mechanism significantly extends the service life of concrete structures, reduces maintenance costs, and is particularly suitable for infrastructure projects in extreme environments.

[0048] In addition, the preparation process of the present invention optimizes the incorporation sequence and mixing parameters of each component, ensuring the uniform dispersion of nanomaterials and high-performance fibers in the matrix. The rational use of polycarboxylate superplasticizer enables good workability to be obtained even under low water-binder ratio conditions, thereby further improving the final density and strength of the concrete. The microcapsules prepared by spray drying have an ideal shell thickness and thermal stability, remaining intact during the concrete mixing and hardening processes until the release of the repair agent is required. 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 implementation manners

[0049] The following detailed implementation manners are only used to further illustrate the present application and should not be construed as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0050] Example 1

[0051] Each component was accurately weighed as follows: 550.0 g of ultra-fine sulfoaluminate cement (specific surface area 650 m² / kg), 850.0 g of granite gravel, 620.0 g of quartz sand, 95.0 parts of silica fume; 120.0 parts of fly ash; 50.0 g of nano-metakaolin (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 fibers, 8.6 g of polycarboxylate superplasticizer, and 150.0 g of water.

[0052] Preparation of pH-responsive microcapsules: The preparation of microcapsules needs to be carried out 24 h in advance. First, 90.0 g of calcium oxide and 9.0 g of tartaric acid are intermittently ground in a planetary ball mill at 300 rpm for 7.5 h (including cooling time), and particles ≤5 μm are collected after passing through a 325-mesh sieve and vacuum-dried at 60 °C for 12 h. The shell material solution is prepared from 72.0 g of methyl methacrylate, 18.0 g of acrylic acid, 1.8 g of potassium persulfate and 300 ml of water under nitrogen protection, and after mixing with the core material, it is emulsified step by step by an ultrasonic cell disruptor (pulse mode 5 min + continuous mode 15 min) to obtain an emulsion with D50 = 3.2 μm. The spray drying parameters are set as inlet air temperature 180 °C, outlet air temperature 85 °C, atomization pressure 0.3 MPa, and nitrogen flow rate 0.8 m³ / h. The microcapsules are sprayed with 1.5% KH-560 ethanol solution (0.135 g of silane + 9 ml of ethanol) in a fluidized bed and then cured by programmed temperature rise (5 °C / min to 80 °C → 1 °C / min to 110 °C and held for 45 min).

[0053] Preparation of liquid metal-coated steel fibers: The steel fibers are successively ultrasonically cleaned with acetone for 15 min, pickled with 5% hydrochloric acid for 30 s, rinsed with water until neutral, dried at 100 °C, and then coated with gallium indium tin alloy (Ga:In:Sn = 68:22:10, melted at 150 °C) by electrophoretic deposition. The process parameters are 12 V voltage, 90 s deposition time, and 50 mm electrode spacing, and the final coating thickness is 82 ± 6 nm.

[0054] Concrete mixing process: Ultra-fine sulphoaluminate cement, granite gravel, quartz sand, silica fume, fly ash, nano-metakaolin, silicon carbide whiskers, and graphene oxide are dry-mixed in a forced mixer; Parameters: The dry-mixing time in the forced mixer is 5 min. The pH-responsive microcapsules, liquid metal-coated steel fibers, and carbon nanotubes are added in sequence; Parameters: The dry-mixing stirring speed is 60 rpm and the time is 2 min. Water is added, and a polycarboxylate water reducer is synchronously incorporated; Staged stirring: Low-speed stage: Stir at 120 rpm for 1 min. High-speed stage: Stir at 240 rpm for 2 min.

[0055] Molding and curing: The test mold (40×40×160 mm) is pre-coated with a release agent and poured in two layers, with each layer tamped 25 times and compacted on a vibrating table (50 Hz, 0.5 mm amplitude, 15 s). After initial setting, it is covered with a PE film, demolded after 24 h and transferred to a standard curing box (20 ± 0.5 °C, RH≥98%), and performance testing starts after 3 d.

[0056] Example 2 The specific implementation method is the same as that of Example 1, except that the ultrafine sulphoaluminate cement (specific surface area 650 m² / kg) is 520.0 g, the granite gravel is 900.0 g, the quartz sand is 600.0 g, silica fume: 105.0 parts; fly ash: 100.0 parts; nano-metakaolin (average particle size 80 nm) is 70.0 g, silicon carbide whiskers are 12.0 g, carbon nanotubes are 6.0 g, graphene oxide is 4 g, pH-responsive microcapsules are 15.0 g, gallium-based liquid metal-coated steel fibres are 55.0 g, polycarboxylate superplasticizer is 10.2 g, and water is 150.0 g. In step S1, the dry mixing time in the forced mixer is 3 min.

[0057] Example 3 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 rotation speed of the low-speed stirring is 50 rpm.

[0058] Comparative Example 1 The specific implementation method is the same as that of Example 1, except that the pH-responsive microcapsules are cancelled (replaced with an equal amount of cement); preparation method: directly skip the microcapsule addition step.

[0059] Comparative Example 2 The specific implementation method is the same as that of Example 1, except that the liquid metal-coated steel fibres are replaced with ordinary copper-plated steel fibres of 45 g; no special treatment is required on the fibre surface.

[0060] Performance test 1. Mechanical property test Compressive strength test: Test standard: GB / T 17671-2021; test equipment: YES-300 type microcomputer-controlled pressure testing machine (range 300 kN, accuracy ±0.5%); specimen preparation: 40×40×160 mm prismatic specimens; 6 parallel specimens in each group; the two ends of the specimens are levelled with sulphur mortar; test procedure: the specimens are placed centrally on the centre of the pressure machine platen; pre-loaded to 5 kN and maintained for 30 s; continuously loaded at a rate of 2.4±0.2 kN / s until failure; record the peak load (accurate to 0.1 kN); data processing: compressive strength = maximum load / compressive area (1600 mm²); take the average of 6 specimens (exclude data with deviation >10%).

[0061] 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 indenter radius 5mm; Support roller radius 2.5mm; Loading rate 50±5N / s; Test steps: Place the specimen with the long side facing up; Align the indenter with the center line of the specimen; Continuously and uniformly 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 width and height of the specimen.

[0062] Elastic modulus test: Test standard: GB / T 50081-2019; Test system: Microcomputer-controlled electro-hydraulic servo pressure testing machine; Double-sided electronic extensometer (gage length 100mm, accuracy 0.001mm); Test process: Preload three times (0.5-1.0MPa); Formally load to 40% of the ultimate load; Read the data after holding the load for 60s; Repeat three times and take the average value; Data acquisition: Record the deformation value every 0.5MPa; Plot the stress-strain curve; Calculate the modulus by taking the slope of the straight line segment of the curve.

[0063] 2. Self-healing performance test Crack repair rate test: Crack prefabrication: Use an INSTRON 8802 fatigue testing machine; Prefabricate cracks with a width of 0.30±0.02mm by the three-point bending method; Monitor the crack tip with a microscope (40 times magnification); Repair environment: Immerse in water at 20±1°C; Regularly replace to maintain pH = 7.0±0.2; Observation method: Keyence VHX-6000 ultra-depth-of-field microscope; Take pictures of the crack morphology every 24h (500 times magnification); Measure the crack width with image analysis software (accuracy 0.5μm); Calculation formula: Repair rate = [(W0 - W7) / W0]×100%; W0: Initial crack width, W7: Crack width after 7d.

[0064] Strength recovery rate test: Test process: Prefabricate standard specimens of the same batch, pre-crack at 50% of the ultimate load, control the crack width within 0.25-0.35mm, and test the residual strength after 7d of water curing; Control points: Accurately control the pre-cracking load within ±2%, mark and position the crack location, and keep the same loading direction during the test after repair.

[0065] 3. Interface performance test Single fiber pull-out test: Specimen preparation: a special mold was used to fix a single fiber, the fiber embedding length was 5.0±0.1mm, the matrix mix ratio was the same as the main body, and the standard curing was 28d; Test system: MTS Landmark test machine, 100N load sensor (accuracy 0.1N), laser displacement sensor (0.1μm resolution); Test parameters: loading rate 0.5mm / min, data acquisition frequency 100Hz, test environment 23±2℃, RH50±5%; Data analysis: extracting the maximum pull-out load, calculating the interface bonding strength, analyzing the load-displacement curve characteristics, and fiber distribution CT analysis; Scanning equipment: Zeiss Xradia 520 Versa micro-CT; Scanning parameters: voltage 80kV, power 7W, pixel size 5μm, exposure time 5s, projection number 1600; Three-dimensional reconstruction: Avizo Fire software processing, gray threshold segmentation, fiber recognition algorithm; Quantitative indicators: orientation coefficient = Σcos 2 θ / N, spacing variation coefficient = σ / μ, fiber contact point statistics.

[0066] 4. Durability test Chloride ion permeability: Test standard: ASTM C1202; Test equipment: Special RCM test device, 0.3M NaOH / 3% NaCl solution, DC regulated power supply; Specimen treatment: Φ100×50mm cylinder, vacuum saturated with water for 24h, side sealing treatment; Test procedure: Apply 30V DC voltage, record initial current, test lasts for 24h, temperature controlled at 20±2℃; Data processing: Calculate chloride ion migration coefficient and convert electrical flux according to ASTM C1202.

[0067] Rapid freeze-thaw test: GB / T 50082-2009; Equipment parameters: Fully automatic concrete freeze-thaw test machine, temperature range -20~20℃, temperature control accuracy ±0.5℃; Test points: Pre-embedded thermocouple in the center of the specimen, freeze-thaw medium is water; Test every 25 cycles: mass loss (accuracy 0.01g), transverse fundamental frequency (resonance method); Termination conditions: mass loss>5%, relative dynamic elastic modulus<60%, reaching 300 cycles.

[0068] (2) Performance test results: Table 1: Performance test results of various embodiments and comparative examples

[0069] As can be seen from Table 1, through systematic analysis of the test data of Examples 1-3 and Comparative Examples 1-2, it can be clearly verified that this technical solution effectively solves the technical bottlenecks of traditional concrete in terms of microcrack control, self-healing ability, and material dispersion. In terms of mechanical properties, the example group shows significant advantages. Among them, the 28-day compressive strength of Example 1 reaches 182.3 MPa, far higher than that of Comparative Example 1 (79.4 MPa) and Comparative Example 2 (76.2 MPa). The flexural strength index shows a leapfrog increase. The value of 32.6 MPa of Example 2 far exceeds 9.8 MPa of Comparative Example 2. This comprehensive improvement in mechanical properties directly proves the effective inhibition of the multi-scale reinforcement system of silicon carbide whiskers and carbon nanotubes on microcrack propagation. The test data of the self-healing performance is more persuasive. The crack repair rate of 89.2% and strength recovery rate of 92.5% of Example 1 are in sharp contrast to the performances of only 12.3% and 18.7% of Comparative Example 1. Especially, Example 3 further increases the repair rate to 94.7% by increasing the amount of microcapsules, fully verifying the core role of pH-responsive microcapsules in crack self-repair. The breakthrough progress in interfacial bond strength is reflected in the test value of 3.8 MPa of Example 1, which is 137% higher than 1.6 MPa of the ordinary copper-plated fiber in Comparative Example 2. This leapfrog is due to the unique advantages of the liquid metal coating. In the chloride ion permeability test, the performances of Comparative Examples 1 and 2 are significantly worse than those of Examples 1-3. The significant improvement in durability indicators fully proves the important value of material system homogenization. Combining all the test data, this technology, through the synergistic effect of the intelligent repair mechanism of pH-responsive microcapsules, the interfacial strengthening effect of liquid metal coatings, and the gradient dispersion process, enables the concrete to reduce the crack density by 82% in crack control, reach a repair rate of more than 90% in self-healing efficiency, and obtain a bond strength increase of more than 140% in interfacial performance, completely overcoming the three major technical problems of traditional concrete, namely, microcrack accumulation, poor self-healing ability, and uneven material dispersion.

[0070] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A high-strength concrete, characterized in that, It consists of raw materials in the following parts by weight: Ultra-fine 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; Nano-metakaolin: 50 - 80 parts; Silicon carbide whiskers: 10 - 16 parts; Graphene oxide: 2 - 5 parts; pH-responsive microcapsules: 12 - 20 parts; Liquid metal-coated steel fibers: 45 - 100 parts; Carbon nanotubes: 5 - 8 parts; Polycarboxylate water reducer: 8 - 15 parts; Among them, the preparation steps of the pH-responsive microcapsules include: pre-grinding calcium oxide and a slow-release agent to a particle size ≤ 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 and the solution, and performing ultrasonic emulsification to obtain an emulsion; spray-drying and forming the emulsion under nitrogen protection to obtain microcapsules, and spraying a silane coupling agent on the surface of the microcapsules and performing thermal curing.

2. The high-strength concrete according to claim 1, characterized in that, The coarse aggregate is granite gravel, 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 liquid metal-coated steel fibers are prepared by coating a 50 - 100 nm thick gallium-based liquid metal on the surface of steel fibers.

4. The high-strength concrete according to claim 1, wherein, The mass ratio of the calcium oxide to the slow-release agent is 10:1; during pre-grinding, the rotation speed of the ball mill is 300 rpm and the duration is 6 h.

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

6. The high-strength concrete according to claim 1, wherein During the thermal curing, the temperature is 80 - 110 °C, the time is 30 - 60 min, and the heating rate ≤ 5 °C / min.

7. The preparation method of the high-strength concrete according to any one of claims 1-6, characterized in that, It includes the following steps: S1, weighing ultra-fine sulphoaluminate cement, coarse aggregate, quartz sand, silica fume, fly ash, nano-metakaolin, silicon carbide whiskers, and graphene oxide in proportion, and dry-mixing them in a forced mixer; S2, sequentially adding pH-responsive microcapsules, liquid metal-coated steel fibers, and carbon nanotubes, and stirring at a low speed; S3, adding water, synchronously incorporating polycarboxylate water reducer, and first mixing at a low speed and then mixing at a high speed with a planetary mixer to obtain concrete.

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

9. The preparation method according to claim 7, characterized in that, In step S2, the rotation speed of the low-speed stirring ≤ 60 rpm, and the stirring time is 2 min.

10. The preparation method according to claim 7, characterized in that, In step S3, the rotation speed of the low-speed stirring is 120 rpm, the stirring time is 1 min, the rotation speed of the high-speed stirring is 240 rpm, and the stirring time is 2 min.

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