Ultra-high-performance steel fiber concrete pipe piece and preparation method thereof

Abstract

The invention belongs to the field of concrete, and provides an ultra-high-performance steel fiber concrete pipe piece and a preparation method thereof. The ultra-high-performance steel fiber concrete pipe piece adopts a composite design of functionalized steel fibers loaded with sea urchin-shaped core-shell structure particles and an ultra-high-performance concrete matrix; the sea urchin-shaped particles take separated epoxy resin and an amine curing agent microcapsule as a core material, take a polydopamine / nano SiO composite material as a shell material and form a nano-scale thorn structure, and a multi-layer structure of a silane coupling agent functional layer, an epoxy priming coat, a microcapsule loading layer and a polyurethane protective layer is arranged on the surface of the steel fiber; according to the self-repairing concrete pipe piece, excellent mechanical property, self-repairing function, interface bonding strength and durability are achieved, the technical problems that a traditional concrete pipe piece is insufficient in strength, poor in interface bonding, poor in corrosion resistance and insufficient in permeability resistance are solved, and the self-repairing concrete pipe piece has wide application value.

Description

Summary of the Invention Technical Field

[0001] The present invention relates to the field of concrete, and in particular to an ultra-high performance steel fiber concrete segment and a preparation method thereof. Background Art

[0002] With the rapid advancement of urbanization in my country and the in-depth development and utilization of underground space, the construction of major infrastructure projects such as subway tunnels, municipal pipeline corridors, and drainage systems has placed increasingly stringent performance requirements on concrete segment materials. In complex and dynamic underground environments, concrete segments must not only withstand the enormous static and dynamic loads from the strata, but also withstand the long-term effects of harsh environmental factors such as groundwater erosion, chemical corrosion, and freeze-thaw cycles. Especially in high-intensity applications, segment materials must possess excellent compressive and tensile strength to ensure the long-term stability and safety of the structure. Furthermore, in terms of corrosion resistance, the segments must effectively resist the attack of chemical media such as acids, alkalis, and salts, preventing steel corrosion and concrete deterioration. Furthermore, excellent permeability resistance is crucial to prevent groundwater seepage and maintain structural integrity. Meeting and improving these key performance indicators will not only significantly extend the service life of infrastructure and reduce maintenance costs, but also promote innovative development in underground engineering technology, providing solid technical support for sustainable urban development. Therefore, the development of new concrete segment materials with high strength, excellent corrosion resistance, and superior permeability resistance is of great practical significance and has broad application prospects.

[0003] However, the current development of concrete segment materials still faces numerous technical bottlenecks and performance deficiencies, making it difficult to fully meet the high standards required for modern engineering construction. Traditional concrete segments generally suffer from strength deficiencies, primarily due to the limited density and high internal porosity of the ordinary concrete matrix. This results in compressive and tensile strengths that fail to meet the technical specifications of ultra-high-performance concrete, and the inability to withstand the high stresses of complex geological conditions. Regarding corrosion resistance, existing segment materials are relatively weak against chemical media. This is primarily due to the alkaline environment and porous structure of the concrete matrix, which provide pathways for the penetration and diffusion of corrosive ions, accelerating the electrochemical corrosion process of the steel bars and resulting in a sharp decline in structural durability. Furthermore, insufficient permeability is a significant issue. The capillary pore structure and microcracks of traditional concrete create conditions for the penetration of moisture and harmful ions, which not only reduces the material's long-term stability but can also lead to engineering quality issues such as leakage. For example, Chinese patent publication number CN108264280A discloses a steel fiber concrete, but this suffers from uneven steel fiber dispersion and a need for improved bonding with the matrix. For example, Chinese patent publication number CN109081634A discloses a high-steel fiber concrete, but it has insufficient corrosion resistance and anti-permeability performance. SUMMARY

[0004] (1) Technical problems solved

[0005] The purpose of the present application is to provide an ultra-high performance steel fiber reinforced concrete segment and a preparation method thereof, and to solve the problems of insufficient strength, corrosion resistance and impermeability of the current concrete segment.

[0006] (2) Technical solutions

[0007] In order to achieve the above purpose, the present application provides the following technical solutions:

[0008] An ultra-high performance steel fiber reinforced concrete segment, comprising an ultra-high performance concrete matrix and steel fibers loaded with urchin-like core-shell structure particles;

[0009] The ultra-high performance concrete matrix is composed of 100 parts of Portland cement, 10-13.3 parts of silica fume, 18.8-22.2 parts of mineral admixture, 100-111 parts of quartz sand, 18-24 parts of quartz powder, 1.25-2.0 parts of polycarboxylic acid water reducer and 22.5-25.0 parts of mixing water, by weight;

[0010] The dosage of the steel fibers loaded with urchin-like core-shell structure particles is 3.5-6.5 parts;

[0011] The steel fibers are loaded with urchin-like core-shell structure particles on the surface, the urchin-like core-shell structure particles have a core material of separate epoxy resin microcapsules and amine curing agent microcapsules and a shell material of polydopamine / nano-SiO2 composite material, and the shell layer surface extends to form a nano / sub-micron spiny structure;

[0012] The steel fibers loaded with urchin-like core-shell structure particles are steel fibers with a silane coupling agent functional layer, an epoxy primer layer, a microcapsule loading layer and a polyurethane protective layer arranged on the surface in sequence.

[0013] Further, the Portland cement is P·O 52.5 grade;

[0014] The SiO2 content of the silica fume is 85%-95%;

[0015] The mineral admixture is composed of fly ash and slag powder in a mass ratio of 1:1-1:2.5;

[0016] The particle size of the quartz sand is 0.1-0.5 mm, and the SiO2 content is ≥98%;

[0017] The particle size of the quartz powder is ≤0.1 mm, and the SiO2 content is ≥99%;

[0018] The water-reducing rate of the polycarboxylic acid water reducer is ≥25%, and the solid content is 38-42%.

[0019] Furthermore, the steel fiber is a hook-end or wavy high-quality carbon steel wire with a diameter of 0.20 to 0.60 mm, a length of 13 to 35 mm, an aspect ratio of 50 to 80, and a tensile strength of 1000 to 1200 MPa;

[0020] The particle size of the sea urchin-shaped core-shell structure particle is 20-45 μm, the shell thickness is 1.0-2.5 μm, and the core material content of the sea urchin-shaped core-shell structure particle is 58-63%.

[0021] Furthermore, the specific thicknesses of each coating on the surface of the steel fiber are: the thickness of the silane coupling agent functional layer is 0.5 to 1.5 μm; the thickness of the epoxy primer layer is 15 to 25 μm; the thickness of the urchin-like core-shell structure particle loading layer is 21.0 to 45 μm; and the thickness of the polyurethane protective layer is 2 to 5 μm.

[0022] The present invention adopts a design of functionalized steel fibers loaded with sea urchin-like core-shell structure particles and a composite of ultra-high performance concrete matrix, which is mainly used to enhance the mechanical properties, durability and self-repairing properties of concrete pipe segments. In the unique morphology design of the sea urchin-like core-shell structure particles, the nano / submicron-scale thorn structure formed by the extension of the shell surface can penetrate into the microscopic pore structure of the concrete matrix, forming a three-dimensional anchoring network, significantly increasing the contact area and mechanical bite force between the steel fiber and the matrix. Polydopamine as a shell material component has excellent adhesion properties and can form strong chemical bonds with the silane coupling agent functional layer on the steel fiber surface and the concrete matrix, and the introduction of nano-SiO2 further enhances the chemical stability and mechanical strength of the interface. The multi-layer structure design on the steel fiber surface forms a complete functionalized system. The silane coupling agent functional layer provides chemical coupling, the epoxy primer ensures good adhesion and load transfer, and the polyurethane protective layer provides an outer protective barrier. The design of separate epoxy resin microcapsules and amine curing agent microcapsules implements an intelligent crack repair mechanism. When microcracks appear in concrete, stress concentration causes the urchin-like core-shell particles to rupture, releasing the epoxy resin and amine curing agent. These two react in situ at the cracks, forming a strong repair material that effectively prevents further crack expansion. The mix design of the ultra-high performance concrete matrix fully considers the synergistic effects of each component. Portland cement, the main binder, and the high SiO2 content of silica fume exert a pozzolanic effect, reacting with cement hydration products to produce more hydrated calcium silicate gel, enhancing matrix density. The appropriate proportions of fly ash and slag powder in the mineral admixtures improve workability and enhance matrix strength through latent hydraulic reactions. The grading of quartz sand and quartz powder optimizes particle packing density and reduces porosity. The use of polycarboxylate superplasticizer reduces the water-cement ratio while ensuring workability, further enhancing matrix density and strength. The multi-layered protection system on the steel fiber surface forms a complete anti-corrosion barrier. The silane coupling agent functionalized layer forms a dense silicone film on the steel fiber surface. The epoxy primer provides excellent corrosion resistance and adhesion, while the polyurethane protective layer has good chemical resistance and flexibility. This multi-layered protective structure can effectively block the intrusion of corrosive media and extend the service life of the steel fiber. The combination of functionalized steel fibers and the ultra-high performance concrete matrix produces a significant synergistic effect. The high tensile strength of the steel fibers compensates for the insufficient tensile properties of the concrete matrix, while the presence of the sea urchin-like core-shell structure particles enables the steel fibers to more effectively play a reinforcing role, achieving a simultaneous improvement in the toughness and strength of the matrix. At the same time, the introduction of self-healing functions gives the material self-healing capabilities, further enhancing the durability and reliability of the overall structure. Through this multi-element, multi-level collaborative design, the mechanical properties, durability, and self-healing properties of the concrete segments are comprehensively improved.

[0023] Further, the preparation method of the steel fiber loaded with the urchin-like core-shell structure particle comprises the following steps in sequence:

[0024] The surface pretreatment of the steel fiber is performed by sand blasting with quartz sand, followed by ultrasonic cleaning with organic solvent and acid pickling treatment. The functionalization treatment of the steel fiber surface is performed by immersing the pretreated steel fiber in a silane coupling agent solution under heating condition. The preparation of the epoxy primer layer is performed by coating the functionalized steel fiber with an epoxy primer solution and curing to form a primer layer. The particle loading is performed by immersing the steel fiber with the primer layer into a dispersion solution of the urchin-like core-shell structure particle after pretreatment with a polymer solution, and realizing the covalent bonding of the particle and the steel fiber surface through a chemical coupling agent. The preparation of the protective layer is performed by forming a polyurethane protective layer on the surface of the steel fiber loaded with the particle using a spraying process and curing.

[0025] Further, in the surface pretreatment step of the steel fiber, the sand blasting is performed with quartz sand having a mesh size of 100-200, a sand blasting pressure of 0.4-0.6 MPa, and a treatment time of 30-60 seconds. Then, the steel fiber is cleaned with acetone in an ultrasonic cleaner with a power of 50-150 W for 5-15 minutes. Then, the steel fiber is pickled with a citric acid aqueous solution with a mass fraction of 3-5% for 1-2 minutes, and finally washed with water until the pH value reaches 6.5-7.5 and dried.

[0026] In the preparation step of the epoxy primer layer, the primer solution is composed of epoxy resin E-5110 100 parts, m-phenylenediamine curing agent 15-20 parts, isophorone diamine accelerator 2-5 parts, carboxyl-terminated liquid nitrile rubber 8-12 parts, nano-SiO2 3-5 parts, silane coupling agent KH550 1-3 parts, and acetone diluent 10-15 parts by weight. The functionalized steel fiber is coated in the primer solution and cured at a temperature of 80-90°C for 90-120 minutes.

[0027] Further, in the particle loading step, the surface of the steel fiber with the primer layer is first pretreated with a polyethyleneimine phosphate buffer solution with a mass fraction of 0.5-1.0% for 20-30 minutes. The pH value of the phosphate buffer solution is 7.5-8.0. Then, the steel fiber is immersed in a deionized water dispersion solution containing urchin-like core-shell structure particles with a mass fraction of 6.0-10%. After ultrasonic dispersion for 10-15 minutes at a power of 150-200 W, EDC hydrochloride with a dosage of 30-35% of the mass of the particles and N-hydroxysuccinimide with a dosage of 15-20% of the mass of the particles are added. The reaction is performed at a temperature of 20-25°C and a stirring speed of 200-300 rpm for 4-6 hours.

[0028] Further, the preparation method of the urchin-like core-shell structure particle comprises the following steps:

[0029] A1. Preparation and emulsification of a separate core material: Epoxy resin microcapsules and amine curing agent microcapsules were prepared separately. The core material composition of the epoxy resin microcapsules was as described in claim 1, and the core material was prepared from 0.0-12.0 parts of epoxy resin E-511 and 1.0-2.0 parts of carboxyl-terminated liquid nitrile rubber. The core material composition of the amine curing agent microcapsules was as described in claim 1, and the core material was prepared from 2.0-3.0 parts of m-phenylenediamine curing agent. The two core materials were emulsified in a system of 0.5-1.0 parts of polysorbate 80, 0.1-0.3 parts of cetyltrimethylammonium bromide, and 85.0-105.0 parts of deionized water, and the mixture was stirred and emulsified at a stirring rate of 200-300 rpm for 20.0-40.0 minutes to form a stable core material emulsion.

[0030] A2. Surface modification: The prepared particles are dispersed in a 0.5-1% by mass KH560 silane coupling agent ethanol solution, modified at room temperature for 1-1.5 hours, and then spin-dried and freeze-dried to complete the functionalization of the particle surface.

[0031] Furthermore, the preparation method of the sea urchin-like core-shell structure particles includes the following steps: after the completion of step C1 and before the implementation of step C2, the preparation method of the sea urchin-like core-shell structure particles also includes a polydopamine / nano-SiO2 core-shell and thorn formation step: first, 0.2 to 0.5 parts of nano-SiO2 seed crystals with a particle size of 50 to 100 nm are added to the core material emulsion as a thorn growth template, the pH value of the core material emulsion is adjusted to 8.3 to 8.5, dopamine hydrochloride with a mass concentration of 0.5 to 1.5 g / L is added, and the reaction is carried out at a low speed with stirring at 25°C for 1 to 2 hours. The method comprises the following steps: raising the temperature to 40°C, intermittently adding a nano-SiO2 aqueous dispersion with a mass fraction of 3.0 to 5.0% in three times, with an interval of 30 minutes between each addition, and controlling the total addition time within 90 to 120 minutes. Meanwhile, the pH value is periodically adjusted between 8.5 and 7.8, and the reaction is stirred for 2 to 4 hours. Finally, the temperature is lowered to 25°C, and 0.3 to 0.8 parts of polyvinyl pyrrolidone is added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 synergistically form a nano / submicron thorn structure on the surface of the shell.

[0032] The present invention adopts a multi-step collaborative preparation process mainly for enhancing the interfacial bonding performance, corrosion resistance and self-repairing performance of steel fibers. The surface pretreatment of steel fibers is carried out through the synergistic effect of quartz sand sandblasting, acetone ultrasonic cleaning and citric acid pickling, aiming to remove the surface oxide layer and pollutants, form a clean and active surface, and provide an ideal bonding basis for subsequent functionalization treatment. The purpose of the silane coupling agent functionalization treatment is to construct a chemically bonded molecular bridge on the surface of the steel fiber to achieve an effective connection between the inorganic steel fiber and the organic functional layer. The epoxy primer is prepared by using a composite formula of epoxy resin E-51, m-phenylenediamine curing agent, isophorone diamine accelerator, terminal carboxyl liquid nitrile rubber, nano-SiO2 and silane coupling agent KH550, aiming to construct a multifunctional primer with high adhesion strength, excellent flexibility and enhanced mechanical properties. The preparation of sea urchin-like core-shell particles utilizes a separate core material design. Epoxy microcapsules composed of epoxy resin E-51 and carboxyl-terminated liquid nitrile rubber, and m-phenylenediamine curing agent microcapsules are prepared separately to prevent premature reaction of the active components and ensure controllable self-healing properties. A composite emulsification system of polysorbate 80 and cetyltrimethylammonium bromide is used to achieve a stable core material emulsion. The polydopamine / nano-SiO2 core-shell and spine formation process is precisely controlled through nano-SiO2 seed template guidance, dopamine hydrochloride polymerization, intermittent nano-SiO2 addition, and periodic pH adjustment. The goal is to create a sea urchin-like morphology with nano- / submicron-scale spines. Polyvinylpyrrolidone is added to stabilize the spine structure. The synergistic effect of polydopamine and nano-SiO2 achieves the dual goals of morphology control and performance improvement. The particle loading step uses polyethyleneimine phosphate buffer solution pretreatment to introduce amino-active groups, combined with a coupling reaction activated by EDC hydrochloride and N-hydroxysuccinimide, to achieve a strong covalent bond between the sea urchin-shaped particles and the steel fiber surface. The polyurethane protective layer spraying aims to provide an outer protective barrier for the entire functionalized system, ensuring the stability of each functional layer during long-term service. Through this targeted, hierarchical preparation process, a comprehensive upgrade of steel fibers, from basic cleaning to functional modification and protective reinforcement, is achieved, significantly enhancing their overall performance in concrete composites.

[0033] The present invention also discloses a method for preparing an ultra-high performance steel fiber concrete segment, which is characterized by comprising:

[0034] S1: Raw material preparation, including weighing Portland cement, silica fume, mineral admixtures, quartz sand, quartz powder, polycarboxylate water reducer, mixing water and steel fiber loaded with sea urchin-shaped core-shell structure particles according to the mix ratio;

[0035] S2: Ultra-high performance concrete mixing, using a capacity of 1 to 3m 3 , stirring power is 20~30kW / m 3Use a forced mixer to first stir the dry material for 2 to 4 minutes, then slowly and gradually add the steel fiber loaded with sea urchin-shaped core-shell structure particles and dry mix for 1 to 2 minutes, then add 70 to 80% of the mixing water and the water reducer solution and stir at a low speed for 4 to 6 minutes, then add the remaining mixing water and stir for 0.5 to 1.5 minutes, and finally stir for 1.5 to 2.5 minutes, ensuring a total stirring time of 12 to 17 minutes;

[0036] S3: Segment forming and curing, using a layered casting process combined with high-frequency, low-amplitude vibration. The thickness of each layer is 50-80 mm, and the casting speed is 0.5-1.0 m. 3 / h, free fall ≤50cm, vibration frequency 15000-18000 times / min, amplitude 0.5-0.8mm, vibration time at each point 15-30 seconds, vibration interval 1.3-1.7 times of the vibrator's effective radius; then adopt steam curing process, static stage 15-25℃, humidity ≥95%, lasting 24 hours; heating stage 8-12℃ / hour to 60-70℃, humidity ≥98%, lasting 4-6 hours; constant temperature stage temperature 60-70℃, humidity ≥98%, lasting 6-8 hours; cooling stage ≤15℃ / hour to ambient temperature.

[0037] The present invention adopts a staged mixing process and programmed curing to prepare ultra-high performance steel fiber concrete segments, which are mainly used to enhance the mechanical properties, molding quality and durability. The ultra-high performance concrete mixing adopts a process design of staged feeding and variable speed mixing. The dry material pre-mixing ensures the uniform dispersion of powder materials such as silicate cement, silica fume, mineral admixtures, quartz sand and quartz powder. The steel fibers loaded with sea urchin-like core-shell structure particles are slowly added in batches to avoid fiber agglomeration and ensure effective dispersion in three-dimensional space. The staged water and water reducer mixing process achieves precise control of rheological properties and workability. The initial low-speed mixing of most of the mixing water and water reducer solution ensures sufficient wetting and avoids fiber damage. The subsequent short-term mixing of the remaining mixing water adjusts the final workability. The precise control of the entire mixing time balances the concrete workability and fiber dispersion effect. The segment forming and curing process utilizes a layered pouring technique combined with high-frequency, low-amplitude vibration. Layered pouring ensures concrete density and uniformity, while controlled pouring speed prevents segregation. High-frequency, low-amplitude vibration parameters are carefully configured to ensure sufficient density while avoiding damage to the steel fiber distribution. The steam curing process optimizes the cement hydration reaction through a four-stage programmed control process: static, heating, constant temperature, and cooling. The static stage provides a stable initial hydration environment, while the slow heating stage avoids temperature stresses. High temperature and high humidity during the constant temperature stage promote full hydration and rapid strength development. Controlled cooling during the cooling stage avoids internal stresses and microcracks, while humidity control ensures water supply for the hydration reaction. The synergistic effect of the staged mixing process and programmed curing maximizes material performance. The mixing process ensures effective dispersion and interfacial bonding of the steel fibers supporting the sea urchin-like core-shell particles, while the curing process optimizes matrix strength development and interfacial properties, resulting in a comprehensive improvement in the overall performance of the ultra-high-performance steel fiber reinforced concrete segments.

[0038] (3) Beneficial technical effects

[0039] 1. The present invention achieves three-dimensional anchoring and strong chemical bonding between steel fibers and the matrix through the synergistic effect of the nano-thorn structure of sea urchin-like core-shell structure particles and the polydopamine / nano-SiO2 shell material, significantly improving the interfacial bonding strength. The separated microcapsule design gives the material intelligent self-repairing capabilities, and the multi-layer protection system extends the service life of the steel fibers. The synergistic optimization of the various components of the ultra-high-performance matrix achieves high density and strength, solving the technical problems of poor interface bonding and insufficient durability of traditional concrete pipe segments.

[0040] 2. The present invention realizes hierarchical functional modification of the steel fiber surface through a multi-step collaborative preparation process. Quartz sand sand blasting, acetone cleaning and citric acid pickling synergistically construct a clean active surface. Silane coupling agent establishes an inorganic-organic molecular bridge. The multi-component epoxy primer synergistically provides high adhesion strength and flexibility. The separated microcapsule design avoids premature reaction of active components to ensure self-repair controllability. Polydopamine and nano-SiO2 synergistically construct a sea urchin-like thorn structure to enhance interface anchoring, solving the technical problems of poor interface bonding and insufficient corrosion resistance of traditional steel fibers.

[0041] 3. The present invention optimizes the preparation of ultra-high performance steel fiber concrete segments through the synergistic effect of a staged mixing process and programmed curing. The mixing process of pre-mixing dry materials, adding fibers in batches, and adding water in stages ensures uniform dispersion of components and effective distribution of fibers. Layered pouring combined with high-frequency, low-amplitude vibration ensures molding quality. The four-stage steam curing of static stop-heating-constant temperature-cooling optimizes the hydration reaction process, solving the technical problems of fiber agglomeration, uneven molding, and insufficient strength development in traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a morphology image of the sea urchin-shaped core-shell structure particles prepared in Example 1 of the present invention;

[0043] Figure 2 This is a morphology image of the steel fiber loaded with sea urchin-shaped core-shell structure particles prepared in Example 1 of the present invention;

[0044] Figure 3 The interface between the steel fiber and the concrete matrix of the concrete segment before the self-healing test prepared in Example 1 of the present invention;

[0045] Figure 4 The interface between the steel fiber and the concrete matrix of the concrete segment after the self-healing test prepared in Example 1 of the present invention;

[0046] Figure 5 This is a morphology image of the steel fiber loaded with sea urchin-like core-shell structure particles prepared in Comparative Example 4 of the present invention;

[0047] Figure 6 This is a morphology picture of the sea urchin-shaped core-shell structure particles prepared in Comparative Example 3 of the present invention;

[0048] Figure 7 This is a morphology image of the steel fiber loaded with sea urchin-like core-shell structure particles prepared in Comparative Example 5 of the present invention;

[0049] Figure 8 A comparison chart of strength performance between the embodiment of the present invention and the comparative example;

[0050] Figure 9 A comparison chart of durability performance between the embodiment of the present invention and the comparative example;

[0051] Figure 10 2 is a comparison chart of the self-healing performance of the embodiment and the comparative example. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0053] Example 1

[0054] An ultra-high performance steel fiber concrete segment comprises an ultra-high performance concrete matrix and steel fibers loaded with sea urchin-like core-shell structure particles;

[0055] The ultra-high performance concrete matrix is ​​composed, by weight, of 100 parts of Portland cement, 11.5 parts of silica fume, 20.0 parts of mineral admixtures, 105 parts of quartz sand, 21 parts of quartz powder, 1.6 parts of polycarboxylate water reducer, and 23.5 parts of mixing water;

[0056] The content of steel fiber supporting the sea urchin-like core-shell structure particles is 4.8 parts;

[0057] The steel fiber surface is loaded with sea urchin-like core-shell structure particles, which are made of separated epoxy resin microcapsules and amine curing agent microcapsules as core materials and polydopamine / nano-SiO2 composite materials as shell materials. The shell surface extends to form nano / submicron-scale spine structures.

[0058] The steel fiber loaded with sea urchin-like core-shell structure particles is a steel fiber whose surface is sequentially provided with a silane coupling agent functional layer, an epoxy primer layer, a sea urchin-like core-shell structure particle loading layer and a polyurethane protective layer.

[0059] The Portland cement in this example is P·O 52.5 grade;

[0060] The SiO2 content of silica fume is 90%;

[0061] The mineral admixture consists of fly ash and slag powder in a mass ratio of 1:1.8;

[0062] The particle size of quartz sand is 0.3mm, and the SiO2 content is ≥98%;

[0063] Quartz powder particle size ≤ 0.1mm, SiO2 content ≥ 99%;

[0064] The water reduction rate of polycarboxylic acid water reducer is ≥25% and the solid content is 40%.

[0065] The steel fiber in this embodiment is a hook-end high-quality carbon steel wire with a diameter of 0.40 mm, a length of 24 mm, an aspect ratio of 60, and a tensile strength of 1100 MPa;

[0066] The particle size of the sea urchin-like core-shell structure particle is 32 μm, the shell thickness is 1.8 μm, and the core material content of the sea urchin-like core-shell structure particle is 60%.

[0067] The specific thicknesses of the coatings on the steel fiber surface of this embodiment are: the thickness of the silane coupling agent functional layer is 1.0 μm; the thickness of the epoxy primer layer is 20 μm; the thickness of the urchin-like core-shell structure particle loading layer is 33 μm; and the thickness of the polyurethane protective layer is 3.5 μm.

[0068] In the preparation method of the steel fiber loaded with sea urchin-shaped core-shell structure particles of this embodiment, in the surface pretreatment step of the steel fiber, quartz sand with a mesh size of 150 is used for sandblasting at a sandblasting pressure of 0.5 MPa for 45 seconds; the steel fiber is then cleaned with acetone in an ultrasonic cleaner with a power of 100 W for 10 minutes; the steel fiber is then pickled with a 4% by mass citric acid aqueous solution for 1.5 minutes, and finally rinsed with water until the pH value reaches 7.0 and dried.

[0069] In the epoxy primer preparation step, the primer liquid is composed of 100 parts of epoxy resin E-51, 17 parts of m-phenylenediamine curing agent, 3.5 parts of isophorone diamine accelerator, 10 parts of carboxyl-terminated liquid nitrile rubber, 4 parts of nano-SiO2, 2 parts of silane coupling agent KH550 and 12.5 parts of acetone diluent in parts by weight; the functionalized steel fiber is coated in the primer liquid and cured at a temperature of 85°C for 105 minutes.

[0070] In the particle loading step of this embodiment, the surface of the primer-coated steel fiber is first pretreated with a 0.75% by mass polyethyleneimine phosphate buffer solution for 25 minutes; the pH value of the phosphate buffer solution is 7.8; then the steel fiber is immersed in a deionized water dispersion containing 8.0% by mass of sea urchin-shaped core-shell structure particles, and ultrasonic dispersion is performed at a power of 175 W for 12 minutes. Then, EDC hydrochloride in an amount of 32% by mass of the particles and N-hydroxysuccinimide in an amount of 17% by mass of the particles are added, and the reaction is carried out at a temperature of 22° C. and a stirring speed of 250 rpm for 5 hours.

[0071] In the preparation method of the sea urchin-shaped core-shell structure particles of this embodiment, in the separate core material preparation and emulsification step, 1.0 parts of epoxy resin E-511 and 1.5 parts of carboxyl-terminated liquid nitrile rubber are prepared into an epoxy resin microcapsule core material, and 2.5 parts of m-phenylenediamine curing agent are separately prepared into an amine curing agent microcapsule core material. The above two core materials are separately emulsified in a system of 0.75 parts of polysorbate 80, 0.2 parts of cetyltrimethylammonium bromide and 95 parts of deionized water, and the mixture is emulsified by stirring at a stirring rate of 250 rpm for 30 minutes to form a stable core material emulsion.

[0072] In the surface modification step, the prepared particles were dispersed in a 0.75% by mass KH560 silane coupling agent ethanol solution, modified for 1.25 hours at room temperature, and then spin-dried and freeze-dried to complete the surface functionalization of the particles.

[0073] In the polydopamine / nano-SiO2 core-shell and thorn formation step of this embodiment, first, 0.35 parts of nano-SiO2 seed crystals with a particle size of 75 nm are added to the core material emulsion as a thorn growth template, the pH value of the core material emulsion is adjusted to 8.4, and dopamine hydrochloride with a mass concentration of 1.0 g / L is added. The reaction is stirred at a low speed at 25°C for 1.5 hours to form a dopamine hydrochloride prepolymer layer; then the temperature is raised to 40°C, and a nano-SiO2 aqueous dispersion with a mass fraction of 4.0% is intermittently added dropwise three times, with an interval of 30 minutes between each addition, and the total addition time is controlled within 105 minutes. At the same time, the pH value is periodically adjusted to cycle between 8.5 and 7.8, and the reaction is stirred for 3 hours. Finally, the temperature is lowered to 25°C and 0.55 parts of polyvinyl pyrrolidone is added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 synergistically form a nano / submicron thorn structure on the shell surface.

[0074] In the method for preparing ultra-high performance steel fiber concrete segments of this embodiment, step S2 uses a 2m 3 , stirring power is 25kW / m 3 Use a forced mixer to first stir the dry materials for 3 minutes, then slowly and gradually add the steel fiber loaded with sea urchin-shaped core-shell structure particles and dry mix for 1.5 minutes. Then add 75% of the mixing water and the water reducer solution and stir at a low speed for 5 minutes. Then add the remaining mixing water and stir for 1 minute. Finally, stir for 2 minutes, ensuring a total mixing time of 14.5 minutes.

[0075] Step S3 adopts a casting and molding process of layered casting combined with high-frequency and low-amplitude vibration. The thickness of each layer is 65mm and the casting speed is 0.75m. 3 / h, free fall ≤50cm, vibration frequency is 16500 times / min, amplitude is 0.65mm, vibration time at each point is 22 seconds, and vibration interval is 1.5 times of the effective radius of the vibrator; then steam curing process is adopted, with a static stage of 20℃, humidity ≥95%, and a duration of 24 hours; a heating stage of heating to 65℃ at 10℃ / hour, humidity ≥98%, and a duration of 5 hours; a constant temperature stage of 65℃, humidity ≥98%, and a duration of 7 hours; a cooling stage of naturally cooling to ambient temperature at ≤15℃ / hour.

[0076] Example 1 adopts a relatively conservative medium parameter configuration, which reflects the design concept of prioritizing process stability. In terms of matrix ratio, the content of silica fume is 11.5 parts and the content of mineral admixture is 20.0 parts, both of which are in the median value of the range. Combined with medium-sized steel fiber (diameter 0.40mm, aspect ratio 60) and a moderate dosage of 4.8 parts, the balance of the material system is ensured. The particle size of the sea urchin-shaped particles is 32μm, the shell thickness is 1.8μm, and the thickness of each functional layer tends to be stable and controllable intermediate values. The preparation process parameters such as sandblasting pressure 0.5MPa, stirring power 25kW / m 3 The 65°C curing temperature also demonstrates a balance between process safety and operability. This embodiment is suitable for conventional subway tunnel projects, municipal drainage pipelines, and the production of standardized prefabricated components, and is particularly suitable for mass production projects that require high process stability and product quality consistency.

[0077] Example 2

[0078] An ultra-high performance steel fiber concrete segment comprises an ultra-high performance concrete matrix and steel fibers loaded with sea urchin-like core-shell structure particles;

[0079] The ultra-high performance concrete matrix is ​​composed, by weight, of 100 parts of Portland cement, 13.3 parts of silica fume, 18.8 parts of mineral admixtures, 100 parts of quartz sand, 18 parts of quartz powder, 2.0 parts of polycarboxylate water reducer, and 22.5 parts of mixing water;

[0080] The content of steel fiber loaded with sea urchin-like core-shell structure particles is 6.5 parts;

[0081] The steel fiber surface is loaded with sea urchin-like core-shell structure particles, which are made of separated epoxy resin microcapsules and amine curing agent microcapsules as core materials and polydopamine / nano-SiO2 composite materials as shell materials. The shell surface extends to form nano / submicron-scale spine structures.

[0082] The steel fiber loaded with sea urchin-like core-shell structure particles is a steel fiber whose surface is sequentially provided with a silane coupling agent functional layer, an epoxy primer layer, a sea urchin-like core-shell structure particle loading layer and a polyurethane protective layer.

[0083] The Portland cement in this example is P·O 52.5 grade;

[0084] The SiO2 content of silica fume is 95%;

[0085] The mineral admixture consists of fly ash and slag powder in a mass ratio of 1:1;

[0086] The particle size of quartz sand is 0.1mm, and the SiO2 content is ≥98%;

[0087] Quartz powder particle size ≤ 0.1mm, SiO2 content ≥ 99%;

[0088] The water reduction rate of polycarboxylic acid water reducer is ≥25% and the solid content is 42%.

[0089] The steel fiber in this embodiment is a wavy high-quality carbon steel wire with a diameter of 0.20 mm, a length of 35 mm, an aspect ratio of 80, and a tensile strength of 1200 MPa;

[0090] The particle size of the sea urchin-like core-shell structure particle is 20 μm, the shell thickness is 1.0 μm, and the core material content of the sea urchin-like core-shell structure particle is 63%.

[0091] The specific thicknesses of the coatings on the steel fiber surface of this embodiment are: the thickness of the silane coupling agent functional layer is 0.5 μm; the thickness of the epoxy primer layer is 25 μm; the thickness of the urchin-like core-shell structure particle loading layer is 21 μm; and the thickness of the polyurethane protective layer is 5 μm.

[0092] In the preparation method of the steel fiber loaded with sea urchin-shaped core-shell structure particles of this embodiment, in the surface pretreatment step of the steel fiber, quartz sand with a mesh size of 200 is used for sandblasting at a sandblasting pressure of 0.6 MPa for 60 seconds; then, the steel fiber is cleaned with acetone in an ultrasonic cleaner with a power of 150 W for 15 minutes; then, the steel fiber is pickled with a 5% by mass citric acid aqueous solution for 2 minutes, and finally, it is rinsed with water until the pH value reaches 6.5 and dried.

[0093] In the epoxy primer preparation step, the primer liquid is composed of 100 parts of epoxy resin E-51, 20 parts of m-phenylenediamine curing agent, 5 parts of isophorone diamine accelerator, 12 parts of carboxyl-terminated liquid nitrile rubber, 5 parts of nano-SiO2, 3 parts of silane coupling agent KH550 and 15 parts of acetone diluent in parts by weight; the functionalized steel fiber is coated in the primer liquid and cured at a temperature of 90°C for 120 minutes.

[0094] In the particle loading step of this embodiment, the surface of the primer-coated steel fiber is first pretreated with a 1.0% by mass polyethyleneimine phosphate buffer solution for 30 minutes; the pH value of the phosphate buffer solution is 8.0; then the steel fiber is immersed in a deionized water dispersion containing 10% by mass of sea urchin-shaped core-shell structure particles, and ultrasonic dispersion is performed at a power of 200 W for 15 minutes. Then, EDC hydrochloride in an amount of 35% by mass of the particles and N-hydroxysuccinimide in an amount of 20% by mass of the particles are added, and the reaction is carried out at a temperature of 25°C and a stirring speed of 300 rpm for 6 hours.

[0095] In the preparation method of the sea urchin-shaped core-shell structure particles of this embodiment, in the separate core material preparation and emulsification step, 12.0 parts of epoxy resin E-51 and 2.0 parts of carboxyl-terminated liquid nitrile rubber are prepared into an epoxy resin microcapsule core material, and 3.0 parts of m-phenylenediamine curing agent are separately prepared into an amine curing agent microcapsule core material. The above two core materials are separately emulsified in a system of 1.0 parts of polysorbate 80, 0.3 parts of cetyltrimethylammonium bromide and 105 parts of deionized water, and the mixture is emulsified by stirring at a stirring rate of 300 rpm for 40 minutes to form a stable core material emulsion.

[0096] In the surface modification step, the prepared particles were dispersed in a 1% by mass KH560 silane coupling agent ethanol solution, modified for 1.5 hours at room temperature, and then spin-dried and freeze-dried to complete the functionalization treatment of the particle surface.

[0097] In the polydopamine / nano-SiO2 core-shell and thorn formation step of this embodiment, first, 0.5 parts of nano-SiO2 seeds with a particle size of 100 nm are added to the core material emulsion as a thorn growth template, the pH value of the core material emulsion is adjusted to 8.5, and dopamine hydrochloride with a mass concentration of 1.5 g / L is added. The mixture is stirred at a low speed at 25°C for 2 hours to form a dopamine hydrochloride prepolymer layer; then the temperature is raised to 40°C, and a nano-SiO2 aqueous dispersion with a mass fraction of 5.0% is intermittently added dropwise three times, with an interval of 30 minutes between each addition, and the total addition time is controlled within 120 minutes. At the same time, the pH value is periodically adjusted to cycle between 8.5 and 7.8, and the reaction is stirred continuously for 4 hours. Finally, the temperature is lowered to 25°C and 0.8 parts of polyvinyl pyrrolidone is added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 synergistically form a nano / submicron thorn structure on the shell surface.

[0098] In the method for preparing ultra-high performance steel fiber concrete segments of this embodiment, step S2 uses a 3m 3 , stirring power is 30kW / m 3 Use a forced mixer to first stir the dry materials for 4 minutes, then slowly and gradually add the steel fiber loaded with sea urchin-shaped core-shell structure particles and dry mix for 2 minutes, then add 80% of the mixing water and the water reducer solution and stir at a low speed for 6 minutes, then add the remaining mixing water and stir for 1.5 minutes, and finally stir for 2.5 minutes, ensuring a total mixing time of 17 minutes;

[0099] Step S3 adopts a casting and molding process of layered casting combined with high-frequency and low-amplitude vibration. The thickness of each layer is 80mm and the casting speed is 1.0m. 3 / h, free fall height ≤ 50 cm, vibration frequency 18000 times / min, vibration amplitude 0.8 mm, vibration time per point 30 seconds, vibration spacing 1.7 times the action radius of the vibrator; then a steam curing process is used, static stage 25℃, humidity ≥ 95%, duration 24 hours; temperature rising stage temperature rising to 70℃ at 12℃ / hour, humidity ≥ 98%, duration 6 hours; constant temperature stage temperature 70℃, humidity ≥ 98%, duration 8 hours; cooling stage natural cooling to ambient temperature at ≤ 15℃ / hour.

[0100] Example 2 highlights the performance orientation of high strength and high fiber content, by increasing the silica fume content to 13.3 parts and the steel fiber dosage to 6.5 parts, to maximize the mechanical properties of the material. Fine diameter high strength steel fibers (diameter 0.20 mm, tensile strength 1200 MPa, aspect ratio 80) are selected in combination with small particle size urchin-shaped particles (20 μm), as well as a relatively thick epoxy primer layer (25 μm) and protective layer (5 μm), reflecting the emphasis on interfacial bonding strength and durability. The preparation process uses a relatively aggressive combination of parameters, such as high stirring power 30 kW / m 3 , high frequency vibration 18000 times / min, high temperature curing 70℃, etc., aiming to fully exploit the synergistic effect of high performance components. This example is particularly suitable for extreme working conditions such as high-speed railway tunnels, deep long tunnels, undersea tunnels, etc., as well as important infrastructure projects with strict requirements for impact resistance and long-term durability.

[0101] Example 3

[0102] An ultra-high performance steel fiber reinforced concrete segment, comprising an ultra-high performance concrete matrix and a steel fiber loaded with urchin-shaped core-shell structure particles;

[0103] The ultra-high performance concrete matrix is composed of Portland cement 100 parts, silica fume 10 parts, mineral admixtures 22.2 parts, quartz sand 111 parts, quartz powder 24 parts, polycarboxylic acid superplasticizer 1.25 parts and mixing water 25.0 parts by weight;

[0104] The dosage of the steel fiber loaded with urchin-shaped core-shell structure particles is 3.5 parts;

[0105] The steel fiber is loaded with urchin-shaped core-shell structure particles on the surface, the urchin-shaped core-shell structure particles have a separated epoxy resin microcapsule and amine curing agent microcapsule as core material, and a polydopamine / nano-SiO2 composite material as shell material, and the shell surface extends to form a nano / sub-micron scale spine structure;

[0106] The steel fiber loaded with urchin-shaped core-shell structure particles is a steel fiber with a silane coupling agent functional layer, an epoxy primer layer, an urchin-shaped core-shell structure particle loading layer and a polyurethane protective layer sequentially arranged on the surface.

[0107] The portland cement of the embodiment is P·O 52.5 grade;

[0108] The SiO2 content of the silica fume is 85%;

[0109] The mineral admixture is composed of fly ash and slag powder in a mass ratio of 1:2.5;

[0110] The quartz sand has a particle size of 0.5 mm and a SiO2 content of ≥98%;

[0111] The quartz powder has a particle size of ≤0.1 mm and a SiO2 content of ≥99%;

[0112] The polycarboxylic acid water reducing agent has a water reducing rate of ≥25% and a solid content of 38%.

[0113] The steel fiber of the embodiment is an end-hook type high-quality carbon steel wire with a diameter of 0.60 mm, a length of 13 mm, a length-diameter ratio of 50, and a tensile strength of 1000 MPa;

[0114] The urchin-like core-shell structure particle has a particle size of 45 μm and a shell thickness of 2.5 μm, and the core material content of the urchin-like core-shell structure particle is 58%.

[0115] The specific thicknesses of the respective coating layers on the surface of the steel fiber of the embodiment are as follows: the thickness of the silane coupling agent functionalization layer is 1.5 μm; the thickness of the epoxy primer coating layer is 15 μm; the thickness of the urchin-like core-shell structure particle loading layer is 45 μm; and the thickness of the polyurethane protective layer is 2 μm.

[0116] In the surface pretreatment step of the preparation method of the urchin-like core-shell structure particle loaded steel fiber of the embodiment, the quartz sand with a mesh number of 100 is used for sandblasting treatment at a sandblasting pressure of 0.4 MPa for 30 seconds; then the functionalized steel fiber is cleaned in an ultrasonic cleaner with a power of 50 W for 5 minutes using acetone; then the functionalized steel fiber is pickled in a 3% citric acid aqueous solution for 1 minute, and finally the functionalized steel fiber is washed with water until the pH value reaches 7.5 and dried.

[0117] In the preparation step of the epoxy primer coating layer, the primer liquid is composed of 100 parts by weight of epoxy resin E-5110, 15 parts by weight of m-phenylenediamine curing agent, 2 parts by weight of isophorone diamine accelerator, 8 parts by weight of carboxyl-terminated liquid nitrile rubber, 3 parts by weight of nano-SiO2, 1 part by weight of silane coupling agent KH550, and 10 parts by weight of acetone diluent; the functionalized steel fiber is coated in the primer liquid and cured at a temperature of 80℃ for 90 minutes.

[0118] In the particle loading step of this embodiment, the surface of the primer-coated steel fiber is first pretreated with a 0.5% by mass polyethyleneimine phosphate buffer solution for 20 minutes; the pH value of the phosphate buffer solution is 7.5; then the steel fiber is immersed in a deionized water dispersion containing 6.0% by mass of sea urchin-shaped core-shell structure particles, and ultrasonic dispersion is performed at a power of 150 W for 10 minutes. Then, EDC hydrochloride in an amount of 30% by mass of the particles and N-hydroxysuccinimide in an amount of 15% by mass of the particles are added, and the reaction is carried out at a temperature of 20°C and a stirring speed of 200 rpm for 4 hours.

[0119] In the preparation method of the sea urchin-shaped core-shell structure particles of this embodiment, in the separate core material preparation and emulsification step, 10.0 parts of epoxy resin E-51 and 1.0 parts of carboxyl-terminated liquid nitrile rubber are prepared into an epoxy resin microcapsule core material, and 2.0 parts of m-phenylenediamine curing agent are separately prepared into an amine curing agent microcapsule core material. The above two core materials are separately emulsified in a system of 800.5 parts of polysorbate, 0.1 parts of cetyltrimethylammonium bromide and 85 parts of deionized water, and the mixture is emulsified by stirring at a stirring rate of 200 rpm for 20 minutes to form a stable core material emulsion.

[0120] In the surface modification step, the prepared particles were dispersed in a 0.5% by mass KH560 silane coupling agent ethanol solution, modified at room temperature for 1 hour, and then spin-dried and freeze-dried to complete the functionalization treatment of the particle surface.

[0121] In the polydopamine / nano-SiO2 core-shell and thorn formation step of this embodiment, first, 0.2 parts of nano-SiO2 seed crystals with a particle size of 50 nm are added to the core material emulsion as a thorn growth template, the pH value of the core material emulsion is adjusted to 8.3, and dopamine hydrochloride with a mass concentration of 0.5 g / L is added. The reaction is stirred at a low speed at 25°C for 1 hour to form a dopamine hydrochloride prepolymer layer; then the temperature is raised to 40°C, and a nano-SiO2 aqueous dispersion with a mass fraction of 3.0% is intermittently added dropwise three times, with an interval of 30 minutes between each addition, and the total addition time is controlled within 90 minutes. At the same time, the pH value is periodically adjusted to cycle between 8.5 and 7.8, and the reaction is stirred for 2 hours. Finally, the temperature is lowered to 25°C and 0.3 parts of polyvinyl pyrrolidone is added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 synergistically form a nano / submicron thorn structure on the shell surface.

[0122] In the method for preparing ultra-high performance steel fiber concrete segments of this embodiment, step S2 uses a 1m 3 , stirring power is 20kW / m 3Use a forced mixer to first stir the dry materials for 2 minutes, then slowly and gradually add the steel fiber loaded with sea urchin-shaped core-shell structure particles and dry mix for 1 minute, then add 70% of the mixing water and the water reducer solution and stir at a low speed for 4 minutes, then add the remaining mixing water and stir for 0.5 minutes, and finally stir for 1.5 minutes, ensuring a total stirring time of 12 minutes;

[0123] Step S3 adopts a casting and molding process of layered casting combined with high-frequency and low-amplitude vibration. The thickness of each layer is 50mm and the casting speed is 0.5m. 3 / h, free fall ≤50cm, vibration frequency is 15000 times / min, amplitude is 0.5mm, vibration time at each point is 15 seconds, and vibration interval is 1.3 times of the effective radius of the vibrator; then steam curing process is adopted, with a static stage of 15℃, humidity ≥95%, and a duration of 24 hours; a heating stage of heating to 60℃ at 8℃ / h, humidity ≥98%, and a duration of 4 hours; a constant temperature stage of 60℃, humidity ≥98%, and a duration of 6 hours; a cooling stage of naturally cooling to ambient temperature at ≤15℃ / h.

[0124] Example 3 embodies the design concept of optimizing working performance and controlling costs. By using a lower silica fume content of 10 parts, a higher mineral admixture content of 22.2 parts, and a coarser quartz sand particle size of 0.5 mm, the economy is optimized while ensuring performance. By using coarser steel fibers (diameter 0.60 mm) and a lower admixture of 3.5 parts, combined with large-sized sea urchin-shaped particles (45 μm) and a thicker particle load layer (45 μm), a parameter combination oriented towards economic applicability is formed. The preparation process parameters are relatively mild, such as a lower stirring power of 20 kW / m 3 , a low curing temperature of 60°C, etc., reflecting considerations of energy conservation, environmental protection, and process simplification. This embodiment is suitable for general sections of urban rail transit, underground pipelines in industrial plants, farmland water conservancy projects, and low- and medium-level infrastructure projects that are cost-sensitive but still require certain performance guarantees.

[0125] Example 4

[0126] An ultra-high performance steel fiber concrete segment comprises an ultra-high performance concrete matrix and steel fibers loaded with sea urchin-like core-shell structure particles;

[0127] The ultra-high performance concrete matrix is ​​composed, by weight, of 100 parts of Portland cement, 12.8 parts of silica fume, 19.5 parts of mineral admixtures, 108 parts of quartz sand, 22 parts of quartz powder, 1.8 parts of polycarboxylate water reducer, and 24.2 parts of mixing water;

[0128] The content of steel fiber loaded with sea urchin-like core-shell structure particles is 5.2 parts;

[0129] The steel fiber surface is loaded with sea urchin-like core-shell structure particles, which are made of separated epoxy resin microcapsules and amine curing agent microcapsules as core materials and polydopamine / nano-SiO2 composite materials as shell materials. The shell surface extends to form nano / submicron-scale spine structures.

[0130] The steel fiber loaded with sea urchin-like core-shell structure particles is a steel fiber whose surface is sequentially provided with a silane coupling agent functional layer, an epoxy primer layer, a sea urchin-like core-shell structure particle loading layer and a polyurethane protective layer.

[0131] The Portland cement in this example is P·O 52.5 grade;

[0132] The SiO2 content of silica fume is 88%;

[0133] The mineral admixture consists of fly ash and slag powder in a mass ratio of 1:1.5;

[0134] The particle size of quartz sand is 0.2mm, and the SiO2 content is ≥98%;

[0135] Quartz powder particle size ≤ 0.1mm, SiO2 content ≥ 99%;

[0136] The water reduction rate of polycarboxylic acid water reducer is ≥25% and the solid content is 39%.

[0137] The steel fiber in this embodiment is a wavy high-quality carbon steel wire with a diameter of 0.35 mm, a length of 28 mm, an aspect ratio of 65, and a tensile strength of 1150 MPa;

[0138] The particle size of the sea urchin-like core-shell structure particle is 38 μm, the shell thickness is 2.2 μm, and the core material content of the sea urchin-like core-shell structure particle is 61%.

[0139] The specific thicknesses of the coatings on the steel fiber surface of this embodiment are: the thickness of the silane coupling agent functional layer is 1.2 μm; the thickness of the epoxy primer layer is 18 μm; the thickness of the urchin-like core-shell structure particle loading layer is 38 μm; and the thickness of the polyurethane protective layer is 4 μm.

[0140] In the preparation method of the steel fiber loaded with sea urchin-shaped core-shell structure particles of this embodiment, in the surface pretreatment step of the steel fiber, quartz sand with a mesh size of 120 is used for sandblasting at a sandblasting pressure of 0.45 MPa for 40 seconds; the steel fiber is then cleaned with acetone in an ultrasonic cleaner with a power of 80 W for 8 minutes; the steel fiber is then pickled with a 3.5% by mass citric acid aqueous solution for 1.3 minutes, and finally rinsed with water until the pH value reaches 6.8 and dried.

[0141] In the epoxy primer preparation step, the primer liquid is composed of 100 parts of epoxy resin E-51, 18 parts of m-phenylenediamine curing agent, 4 parts of isophorone diamine accelerator, 9 parts of carboxyl-terminated liquid nitrile rubber, 4.5 parts of nano-SiO2, 2.5 parts of silane coupling agent KH550 and 13 parts of acetone diluent in parts by weight; the functionalized steel fiber is coated in the primer liquid and cured at a temperature of 87°C for 100 minutes.

[0142] In the particle loading step of this embodiment, the surface of the primer-coated steel fiber is first pretreated with a 0.8% by mass polyethyleneimine phosphate buffer solution for 28 minutes; the pH value of the phosphate buffer solution is 7.7; then the steel fiber is immersed in a deionized water dispersion containing 8.5% by mass of sea urchin-shaped core-shell structure particles, and ultrasonic dispersion is performed at a power of 180 W for 13 minutes. Then, EDC hydrochloride in an amount of 33% by mass of the particles and N-hydroxysuccinimide in an amount of 18% by mass of the particles are added, and the reaction is carried out at a temperature of 23°C and a stirring speed of 270 rpm for 5.5 hours.

[0143] In the preparation method of the sea urchin-shaped core-shell structure particles of this embodiment, in the separate core material preparation and emulsification step, 1.5 parts of epoxy resin E-511 and 1.8 parts of carboxyl-terminated liquid nitrile rubber are prepared into an epoxy resin microcapsule core material, and 2.8 parts of m-phenylenediamine curing agent are separately prepared into an amine curing agent microcapsule core material. The above two core materials are separately emulsified in a system of 0.8 parts of polysorbate 80, 0.25 parts of cetyltrimethylammonium bromide and 98 parts of deionized water, and the mixture is emulsified by stirring at a stirring rate of 280 rpm for 35 minutes to form a stable core material emulsion.

[0144] In the surface modification step, the prepared particles were dispersed in a 0.8% by mass KH560 silane coupling agent ethanol solution, subjected to modification treatment at room temperature for 1.3 hours, and then spin-dried and freeze-dried to complete the functionalization treatment of the particle surface.

[0145] In the polydopamine / nano-SiO2 core-shell and thorn formation step of this embodiment, first, 0.4 parts of nano-SiO2 seed crystals with a particle size of 85 nm are added to the core material emulsion as a thorn growth template, the pH value of the core material emulsion is adjusted to 8.45, and dopamine hydrochloride with a mass concentration of 1.2 g / L is added. The reaction is stirred at a low speed at 25°C for 1.8 hours to form a dopamine hydrochloride prepolymer layer; then the temperature is raised to 40°C, and a nano-SiO2 aqueous dispersion with a mass fraction of 4.5% is intermittently added dropwise three times, with an interval of 30 minutes between each addition, and the total addition time is controlled within 110 minutes. At the same time, the pH value is periodically adjusted to cycle between 8.5 and 7.8, and the reaction is stirred for 3.5 hours. Finally, the temperature is lowered to 25°C and 0.6 parts of polyvinyl pyrrolidone is added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 synergistically form a nano / submicron thorn structure on the shell surface.

[0146] In the method for preparing ultra-high performance steel fiber concrete segments of this embodiment, step S2 uses a 2.5m 3 , stirring power is 28kW / m 3 Use a forced mixer to first stir the dry materials for 3.5 minutes, then slowly and gradually add the steel fiber loaded with sea urchin-shaped core-shell structure particles and dry mix for 1.8 minutes. Then add 78% of the mixing water and the water reducer solution and stir at a low speed for 5.5 minutes. Then add the remaining mixing water and stir for 1.2 minutes. Finally, stir for 2.2 minutes, ensuring a total mixing time of 15.2 minutes.

[0147] Step S3 adopts a casting and molding process of layered casting combined with high-frequency and low-amplitude vibration. The thickness of each layer is 70mm and the casting speed is 0.8m. 3 / h, free fall ≤50cm, vibration frequency is 17200 times / min, amplitude is 0.7mm, vibration time at each point is 25 seconds, and vibration interval is 1.6 times of the effective radius of the vibrator; then steam curing process is adopted, with a static stage of 22℃, humidity ≥95%, and a duration of 24 hours; a heating stage of heating to 68℃ at 11℃ / hour, humidity ≥98%, and a duration of 5.5 hours; a constant temperature stage of 68℃, humidity ≥98%, and a duration of 7.5 hours; a cooling stage of naturally cooling to ambient temperature at ≤15℃ / hour.

[0148] Example 4 adopts a comprehensive and balanced parameter configuration to seek the best coordination among various indicators. Parameters such as 12.8 parts of silica fume and 5.2 parts of steel fiber in the matrix ratio are all at a relatively high level. The steel fiber specifications (diameter 0.35mm, aspect ratio 65) reflect the balance between strength and toughness. The medium particle size of the sea urchin-shaped particles is 38μm and the thickness of each functional layer is finely adjusted, as well as the selection of moderate and optimized parameters in the preparation process, such as the stirring power of 28kW / m 3, a curing temperature of 68°C, etc., demonstrating a comprehensive solution with high technical maturity. This embodiment is suitable for complex engineering environments with high requirements for mechanical properties, durability, and self-healing performance, such as urban integrated pipeline corridors, sewage treatment plant main structures, nuclear power plant auxiliary facilities, and underground pipelines in petrochemical projects, as well as critical infrastructure projects that require long-term stable operation.

[0149] Comparative Example 1: Basically the same as Example 1, except that the shell material of the sea urchin-shaped core-shell structure particles is a single polydopamine material and does not contain nano-SiO2 components. During preparation, dopamine hydrochloride with a mass concentration of 1.0 g / L is directly added to the core material emulsion, and the reaction is stirred at pH 8.4 and 25°C for 3 hours to form a polydopamine shell layer.

[0150] Comparative Example 2: Basically the same as Example 1, except that the core material of the sea urchin-shaped core-shell structure particles is a single epoxy resin E-51 microcapsule, does not contain amine curing agent microcapsules, and the core material composition is 11.0 parts of epoxy resin E-51 and 1.5 parts of terminal carboxyl liquid nitrile rubber.

[0151] Comparative Example 3: Basically the same as Example 1, except that the shell surface of the sea urchin-like core-shell structure particles is a smooth structure and no thorn structure is formed. During preparation, dopamine hydrochloride with a mass concentration of 1.0 g / L is added to the core material emulsion, and the reaction is stirred at a pH value of 8.4 and 25°C for 3 hours. No nano-SiO2 seed crystal template is added and the pH value is not periodically adjusted.

[0152] Comparative Example 4: is basically the same as Example 1, except that EDC hydrochloride and N-hydroxysuccinimide chemical coupling agents are not used in the particle loading step, and the sea urchin-shaped core-shell structure particles are loaded on the steel fiber surface only by physical adsorption.

[0153] Comparative Example 5: Basically the same as Example 1, except that the pH value in the polydopamine / nano-SiO2 core-shell and spines formation steps was kept constant at 8.4, and no periodic cycling between 8.5 and 7.8 was performed.

[0154] Comparative Example 6: basically the same as Example 1, except that dopamine hydrochloride with a mass concentration of 2.5 g / L was used in the preparation of sea urchin-shaped core-shell structure particles, and the reaction temperature was 60°C.

[0155] Comparative Example 7: basically the same as Example 1, except that the thickness of the epoxy primer layer is 5 μm.

[0156] Comparative Example 8: basically the same as Example 1, except that the thickness of the polyurethane protective layer is 8 μm.

[0157] Comparative Example 9: is basically the same as Example 1, except that the steel fiber surface pretreatment is only acetone ultrasonic cleaning for 10 minutes, and quartz sand sand blasting and citric acid pickling are not performed.

[0158] Comparative Example 10: Basically the same as Example 1, except that the epoxy primer composition does not contain a terminal carboxyl liquid nitrile rubber component, and the primer liquid is composed by weight of 1100 parts of epoxy resin E-51, 17 parts of m-phenylenediamine curing agent, 3.5 parts of isophorone diamine accelerator, 4 parts of nano-SiO2, 2 parts of silane coupling agent KH550 and 12.5 parts of acetone diluent.

[0159] Performance testing:

[0160] Test Object: Ultra-high-performance steel fiber reinforced concrete segment specimens loaded with self-healing microcapsules. Test Purpose: Evaluate the axial load-bearing capacity and compressive strength of the segment material and verify the steel fiber reinforcement effect. Test Principle: Uniaxial compression is applied until specimen failure to determine the material's maximum load-bearing capacity and stress-strain relationship. Experimental Method: Six 150mm×150mm×150mm cubic specimens and six 100mm×200mm cylindrical specimens were prepared. After curing for 28 days in a standard curing room (temperature 20±2°C, relative humidity ≥95%), the specimens were continuously and uniformly loaded using a compression testing machine at a loading rate of 0.5-0.8 MPa / s until failure. Standard Compliance: Executed in accordance with GB / T 50081-2019, "Standard for Test Methods for Physical and Mechanical Properties of Concrete." Key Parameters: Test environment temperature 20±2°C, relative humidity 45%-75%, loading rate 0.5-0.8 MPa / s, and specimen surface flatness deviation not exceeding 0.05mm. Data processing: The compressive strength is calculated according to the formula fcu=F / A, where F is the failure load and A is the pressure-bearing area of ​​the specimen. The arithmetic mean of the test results of 6 specimens is taken.

[0161] Steel Fiber Reinforced Concrete Segment Flexural Strength Test: The test subjects were beam-type specimens of ultra-high performance concrete segments containing loaded microencapsulated steel fibers. Test objective: To evaluate the flexural properties of the material and the effect of steel fibers on the toughness of concrete. Test principle: Using a three-point bending loading method, the flexural strength was determined by measuring the ultimate bearing capacity of the specimens under bending load. Experimental method: Six beam-type specimens measuring 100 mm × 100 mm × 400 mm were prepared and, after 28 days of standard curing, placed in a universal testing machine with supports spaced 300 mm apart. A concentrated load was applied at the mid-span of the specimens at a continuous loading rate of 0.05-0.08 MPa / s until failure. Standard basis: The flexural strength test method was performed in accordance with GB / T 50081-2019, "Standard for Test Methods for Physical and Mechanical Properties of Concrete." Key parameters: Test temperature 20 ± 2°C, loading rate 0.05-0.08 MPa / s, support corner radius 5 mm, loading head corner radius 10 mm, and specimen geometric dimension tolerance ± 1 mm. Data processing: Flexural strength is calculated according to the formula ff=FL / (bh 2 ), where F is the failure load, L is the support spacing, b is the specimen width, h is the specimen height, and the result is the average value of 6 specimens.

[0162] Concrete Segment Chloride Ion Permeability Test: The test object is the chloride ion diffusion performance of ultra-high performance steel fiber reinforced concrete segments. Test purpose: To evaluate the density and resistance to chloride ion penetration of the concrete matrix and verify the anti-permeability effect of the high-performance mix. Test principle: Based on Fick's second law, the anti-permeability performance is evaluated by measuring the diffusion coefficient of chloride ions in concrete. Experimental method: Preparation Six cylindrical specimens were vacuum-saturated with water after 28 days of standard curing. Using the RCM method (rapid chloride migration coefficient test), the specimens were subjected to a 30V voltage for 24 hours. The specimens were then split and sprayed with a 0.1mol / L AgNO3 solution for color development. Chloride ion penetration depth was measured. This standard was based on GB / T 50082-2009, "Test Methods for Long-term Properties and Durability of Ordinary Concrete." Key parameters included a test temperature of 20±2°C, an applied voltage of 30V, a 24-hour power-up period, a 0.1mol / L AgNO3 solution concentration, and a measurement accuracy of 0.1mm.

[0163] Freeze-thaw Cycle Performance Test of Steel Fiber Reinforced Concrete Segments: This test examines the durability of ultra-high-performance steel fiber reinforced concrete segments loaded with self-healing microcapsules under freeze-thaw conditions. Test Purpose: To evaluate the material's frost resistance and mass loss under freeze-thaw cycles. Test Principle: Repeated freeze-thaw cycles simulate the natural environment of severe cold regions, measuring the material's mass loss rate and relative dynamic elastic modulus. Experimental Method: Six 100mm×100mm×400mm prism specimens were prepared. After 28 days of standard curing and saturation with water, freeze-thaw cycle testing was performed in a rapid freeze-thaw testing machine. The freeze-thaw temperature range was -18°C to +5°C, with each cycle lasting 4 hours for 300 cycles. The specimen mass and dynamic elastic modulus were measured every 25 cycles. Standard Compliance: The rapid freeze-thaw test method specified in GB / T 50082-2009, "Standard for Test Methods for Long-term Properties and Durability of Ordinary Concrete," was used. Key parameters: Freezing temperature -18 ± 2 ° C, melting temperature 5 ± 2 ° C, freeze-thaw cycle 4 ± 0.5 h, specimen freeze-thaw in water, dynamic elastic modulus test frequency 38-42 kHz. Data processing: Mass loss rate is calculated as ΔWn = (W0-Wn) / W0 × 100%, relative dynamic elastic modulus is calculated as Pn = fn 2 / f02×100%, where W0 and f0 are initial values, and Wn and fn are values ​​measured after n cycles.

[0164] Evaluation of the Self-Healing Effect of Microcapsules in Concrete Segments: The test subjects were ultra-high-performance steel fiber reinforced concrete segments containing self-healing microcapsules. The test objective was to verify the self-healing function and repair efficiency of the epoxy resin-loaded microcapsules. The test principle was to artificially create controlled cracks, trigger the microcapsules to rupture and release the repair agent under specific conditions, and evaluate the self-healing effect. Experimental Methods: Six 100mm×100mm×100mm cubic specimens were prepared. After curing for 28 days, cracks with a width of 0.1-0.3mm were created using the wedge-cutting method. The specimens were placed in a 60°C constant temperature chamber for 24 hours to activate the self-healing process. The specimens were then cured under standard conditions for 7 days. The self-healing effect was evaluated using ultrasonic testing, dye penetration testing, and mechanical property recovery. Key parameters: crack width 0.1-0.3mm, activation temperature 60±2°C, activation time 24 hours, subsequent curing temperature 20±2°C, relative humidity ≥95%, and curing period 7 days.

[0165] Sulfate Attack Resistance Test for Steel Fiber Reinforced Concrete Segments: This test examines the chemical stability of ultra-high-performance steel fiber reinforced concrete segments in sulfate environments. Purpose: To evaluate the material's durability and resistance to chemical attack in sulfate-containing environments, such as groundwater. Principle: Through immersion in a sulfate solution, the mass change, strength change, and surface damage of the specimens are measured. Method: Twelve 70.7 mm × 70.7 mm × 70.7 mm cubic specimens are prepared. After 28 days of standard curing, the specimens are divided into a control group (pure water) and a test group (5% Na₂SO₄ solution). The specimens are continuously immersed in a 20±2°C environment. The compressive strength, mass change, and surface condition of the specimens are measured after 90, 180, and 360 days. Standard Basis: The sulfate attack resistance test method is based on the GB / T 50082-2009 "Standard for Test Methods for Long-term Properties and Durability of Ordinary Concrete." Key parameters: Na2SO4 solution concentration 5% ± 0.1%, immersion temperature 20 ± 2°C, solution replacement every 30 days, liquid-to-solid ratio ≥ 4:1, pH controlled between 6 and 8. Data processing: The sulfate corrosion resistance coefficient is calculated as Kf = fcorr / fref, where fcorr is the specimen strength in sulfate solution and fref is the comparison specimen strength in clear water. A coefficient closer to 1 indicates better corrosion resistance.

[0166] The properties of the concrete of Examples 1 to 4 and Comparative Examples 1 to 10 are summarized in Table 1. It can be seen from the table that the performance of the comparative examples is affected by a combination of various technical factors. The single polydopamine shell material (Comparative Example 1) lacks the synergistic filling effect of nano-SiO2, resulting in a decrease in shell density and a decrease in anti-permeability performance of about 71%. At the same time, the loss of the reinforcing effect of the nanoparticles weakens the mechanical properties; the single epoxy resin core material (Comparative Example 2) cannot form a complete cross-linked network due to the lack of amine curing agent, and the self-healing effect significantly deteriorates to 45.2%, and the repair efficiency is greatly reduced; the smooth shell structure (Comparative Example 3) loses the mechanical anchoring effect of the thorn structure, and the interface bonding strength decreases, but due to the complete composition of the shell material, the performance degradation is relatively mild; the physical adsorption loading method (Comparative Example 4) lacks chemical bonding force, and the particles are easy to fall off under stress, resulting in poor mechanical properties and self-healing effect. The results are doubly deteriorated; the preparation with constant pH value (Comparative Example 5) affects the polymerization morphology of polydopamine and the dispersion state of nano-SiO2, the thorn structure is not fully developed, and the interface performance is slightly reduced; although high concentration of dopamine and high temperature preparation (Comparative Example 6) may increase the polymerization rate, it is easy to cause structural defects, affecting the quality of the shell layer; too thin epoxy primer (Comparative Example 7) cannot provide sufficient interface transition and stress transfer, and the mechanical properties are significantly reduced; too thick polyurethane protective layer (Comparative Example 8) increases the number of interface layers and the risk of thermal expansion mismatch, and interlayer peeling may occur under conditions such as freeze-thaw; insufficient surface pretreatment (Comparative Example 9) directly affects the bonding quality of subsequent functional layers, becomes the weakest link, and all performances are deteriorated; the lack of terminal carboxyl liquid nitrile rubber (Comparative Example 10) causes the epoxy primer to lose its toughness modification, and brittle failure is easily generated in the stress concentration area, affecting the overall performance stability.

[0167] Table 1 Summary of the properties of concrete of Examples 1 to 4 and Comparative Examples 1 to 10

[0168]

[0169] The comprehensive experimental data and morphology analysis results fully prove the rationality and advancement of the technical solution of the present invention. Figure 1 It can be clearly observed that the sea urchin-like core-shell structure particles prepared by the present invention have a complete core-shell structure and uniformly distributed nano / submicron spines, which is different from the comparative example 3 ( Figure 6 ), which is in sharp contrast to the smooth spherical particles of the nanostructured particles, demonstrating the key roles of the polydopamine / nano-SiO2 composite shell material and the pH periodic adjustment process. Figure 2 The surface particles of the loaded particle steel fiber are evenly distributed and tightly bound, while the comparative example 4 ( Figure 5 ) and Comparative Example 5 ( Figure 7 ) showed the problems of insufficient particle loading and missing thorn structure, respectively, verifying the necessity of covalent bonding of chemical coupling agents and optimization of preparation process. More importantly, Figure 3 and Figure 4 The interface contrast clearly shows the effectiveness of the self-healing mechanism, and the interface cracks are obviously repaired after the self-healing test. The epoxy resin released by the microcapsule rupture reacts with the amine curing agent to form a continuous repair layer, effectively restoring the interface bonding strength. Figures 8 to 10 The comprehensive comparison results of the above can clearly show that the embodiments of the present application have significant advantages in the three aspects of strength performance, durability performance and self-healing performance. The compressive strength of example 2 is 158.7 MPa, and the flexural strength is 21.8 MPa, which is much higher than all the comparative examples. The chloride ion permeability coefficient of the example group is generally lower than 3.5*10 -12 m 2 / s, the freeze-thaw mass loss rate is controlled within 1.5%, the sulfate attack resistance coefficient is 0.88-0.95, showing excellent durability. Especially in the self-healing crack closure rate, the example group achieves a high efficient closure ability of 82.1%-89.7%, which is more than 10.8% higher than the highest value of the comparative examples, proving that the present application successfully realizes the organic combination of high strength and high durability through specific material combination and ratio design, and at the same time endows the material with excellent self-repairing function, providing a new technical direction for the research and development of high-performance concrete.

[0170] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that any equivalent structural transformation made within the concept of the present application, using the content of the present application specification and drawings, should be covered within the protection scope of the claims of the present application.

Claims

1. An ultra-high performance steel fiber concrete segment, characterized in that: It includes an ultra-high performance concrete matrix and steel fibers loaded with sea urchin-like core-shell structure particles; The ultra-high performance concrete matrix is ​​composed, by weight, of 100 parts of Portland cement, 10-13.3 parts of silica fume, 18.8-22.2 parts of mineral admixtures, 100-111 parts of quartz sand, 18-24 parts of quartz powder, 1.25-2.0 parts of polycarboxylate water reducer, and 22.5-25.0 parts of mixing water; The steel fiber content of the sea urchin-shaped core-shell structure particles is 3.5 to 6.5 parts; The surface of the steel fiber is loaded with sea urchin-like core-shell structure particles, which are made of separated epoxy resin microcapsules and amine curing agent microcapsules as core materials and polydopamine / nano-SiO2 composite materials as shell materials, and the shell surface extends to form nano / submicron-scale thorn structures; The steel fiber loaded with sea urchin-like core-shell structure particles is a steel fiber with a silane coupling agent functional layer, an epoxy primer layer, a sea urchin-like core-shell structure particle loading layer and a polyurethane protective layer sequentially arranged on the surface.

2. The ultra-high performance steel fiber concrete segment according to claim 1, characterized in that: The Portland cement is of P·O 52.5 grade; The SiO2 content of the silica fume is 85% to 95%; The mineral admixture is composed of fly ash and slag powder in a mass ratio of 1:1 to 1:2.5; The quartz sand has a particle size of 0.1-0.5 mm and a SiO2 content of ≥98%; The quartz powder has a particle size of ≤0.1 mm and a SiO2 content of ≥99%; The polycarboxylate water reducer has a water reduction rate of ≥25% and a solid content of 38-42%.

3. The ultra-high performance steel fiber concrete segment according to claim 1, characterized in that: The steel fiber is a hook-end or wavy high-quality carbon steel wire with a diameter of 0.20-0.60 mm, a length of 13-35 mm, an aspect ratio of 50-80, and a tensile strength of 1000-1200 MPa; The particle size of the sea urchin-like core-shell structure particles is 20-45 μm, the shell thickness is 1.0-2.5 μm, and the core material content of the sea urchin-like core-shell structure particles is 58-63%.

4. The ultra-high performance steel fiber concrete segment according to claim 1, characterized in that: The specific thicknesses of each coating on the steel fiber surface are: the thickness of the silane coupling agent functional layer is 0.5~1.5 μm; the thickness of the epoxy primer layer is 15~25 μm; the thickness of the urchin-like core-shell structure particle loading layer is 21.0~45 μm; and the thickness of the polyurethane protective layer is 2~5 μm.

5. The ultra-high performance steel fiber concrete segment according to claim 1, characterized in that: The method for preparing the steel fiber loaded with sea urchin-shaped core-shell structure particles comprises the following steps in sequence: The steel fiber surface is pretreated by sandblasting with quartz sand and then ultrasonically cleaned with an organic solvent and pickled; the pretreated steel fiber is functionalized by immersing it in a silane coupling agent solution under heating conditions for surface functionalization; the epoxy primer is prepared by coating the functionalized steel fiber with an epoxy resin primer solution and curing it to form a primer; the primer is loaded by pretreating the primer-coated steel fiber with a polymer solution and then immersing it in a dispersion of sea urchin-like core-shell structure particles, and covalent bonding of the particles to the steel fiber surface is achieved through a chemical coupling agent; the protective layer is prepared by forming a polyurethane protective layer on the surface of the particle-loaded steel fiber using a spraying process and curing it.

6. The ultra-high performance steel fiber concrete segment according to claim 5, characterized in that: The method for preparing steel fibers loaded with sea urchin-like core-shell structured particles comprises the following steps: in the surface pretreatment step, sandblasting is performed using quartz sand with a mesh size of 100-200 mesh, the sandblasting pressure is 0.4-0.6 MPa, and the treatment time is 30-60 seconds; then, the steel fibers are cleaned with acetone in an ultrasonic cleaner with a power of 50-150 W for 5-15 minutes; then, the fibers are pickled with a 3-5% by mass aqueous solution of citric acid for 1-2 minutes, and finally, the fibers are rinsed with water until the pH reaches 6.5-7.5 and dried; In the epoxy primer preparation step, the primer liquid consists of 100 parts by weight of epoxy resin E-51, 15-20 parts of m-phenylenediamine curing agent, 2-5 parts of isophorone diamine accelerator, 8-12 parts of carboxyl-terminated liquid nitrile rubber, 3-5 parts of nano-SiO2, 1-3 parts of silane coupling agent KH550, and 10-15 parts of acetone diluent; the functionalized steel fiber is coated in the primer liquid and cured at a temperature of 80-90°C for 90-120 minutes.

7. The ultra-high performance steel fiber reinforced concrete segment according to claim 1, characterized in that: In the particle loading step, the surface of the bottom-coated steel fiber is first pretreated with a polyethyleneimine phosphate buffer solution with a mass fraction of 0.5-1.0% for 20-30 minutes; the pH value of the phosphate buffer solution is 7.5-8.0; then the steel fiber is immersed in a deionized water dispersion containing a mass fraction of 6.0-10% sea urchin-shaped core-shell structure particles, and ultrasonic dispersion is performed at a power of 150-200W for 10-15 minutes. After that, EDC hydrochloride in an amount of 30-35% of the mass of the particles and N-hydroxysuccinimide in an amount of 15-20% of the mass of the particles are added, and the reaction is carried out at a temperature of 20-25°C and a stirring speed of 200-300 rpm for 4-6 hours.

8. The ultra-high performance steel fiber reinforced concrete segment according to claim 1, characterized in that: The method for preparing the sea urchin-shaped core-shell structure particles comprises the following steps: A1. Preparation and emulsification of a separate core material: Epoxy resin microcapsules and amine curing agent microcapsules were prepared separately. The core material composition of the epoxy resin microcapsules was as described in claim 1, and the core material was prepared from 10.0-12.0 parts of epoxy resin E-51 and 1.0-2.0 parts of carboxyl-terminated liquid nitrile rubber. The core material composition of the amine curing agent microcapsules was as described in claim 1, and the core material was prepared from 2.0-3.0 parts of m-phenylenediamine curing agent. The two core materials were emulsified in a system of 0.5-1.0 parts of polysorbate 80, 0.1-0.3 parts of cetyltrimethylammonium bromide, and 85.0-105.0 parts of deionized water, and the mixture was stirred at a stirring rate of 200-300 rpm for 20.0-40.0 minutes to form a stable core material emulsion. A2. Surface modification: The prepared particles were dispersed in a 0.5-1% by mass KH560 silane coupling agent ethanol solution, modified at room temperature for 1-1.5 hours, and then spin-dried and freeze-dried to complete the functionalization of the particle surface.

9. The ultra-high performance steel fiber reinforced concrete segment according to claim 8, characterized in that: The method for preparing the sea urchin-shaped core-shell structure particles comprises the following steps: The method for preparing sea urchin-shaped core-shell structure particles further comprises, after step C1 is completed and before step C2 is performed, a polydopamine / nano-SiO2 core-shell and spine formation step: first, adding 0.2 to 0.5 parts of nano-SiO2 seed crystals with a particle size of 50 to 100 nm to a core material emulsion as a spine growth template, adjusting the pH value of the core material emulsion to 8.3 to 8.5, adding dopamine hydrochloride with a mass concentration of 0.5 to 1.5 g / L, and reacting at 25° C. with low-speed stirring for 1 to 2 hours to form a dopamine hydrochloride prepolymer layer; The temperature was then raised to 40°C, and a nano-SiO2 aqueous dispersion with a mass fraction of 3.0~5.0% was intermittently added three times, with an interval of 30 minutes between each addition, and the total addition time was controlled within 90~120 minutes. At the same time, the pH value was periodically adjusted between 8.5 and 7.8, and the reaction was stirred continuously for 2~4 hours. Finally, the temperature was lowered to 25°C and 0.3~0.8 parts of polyvinylpyrrolidone were added to stabilize the thorn structure. Finally, polydopamine and nano-SiO2 worked synergistically to form a nano / submicron thorn structure on the shell surface.

10. The method for preparing an ultra-high performance steel fiber concrete segment according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Raw material preparation, including weighing Portland cement, silica fume, mineral admixtures, quartz sand, quartz powder, polycarboxylate water reducer, mixing water and steel fiber loaded with sea urchin-shaped core-shell structure particles according to the mix ratio; S2: Ultra-high performance concrete is mixed using a forced mixer with a capacity of 1-3 m³ and a mixing power of 20-30 kW / m³. First, the dry materials are stirred for 2-4 minutes. Then, the steel fibers loaded with sea urchin-shaped core-shell particles are slowly and gradually added and dry-mixed for 1-2 minutes. Next, 70-80% of the mixing water and the water-reducing agent solution are added and stirred at a low speed for 4-6 minutes. The remaining mixing water is then added and stirred for 0.5-1.5 minutes. Finally, the mixture is stirred for 1.5-2.5 minutes, ensuring a total mixing time of 12-17 minutes. S3: Segment forming and curing, using a layered casting process combined with high-frequency, low-amplitude vibration. The thickness of each layer is 50-80 mm, the casting speed is 0.5-1.0 m³ / h, the free fall is ≤50 cm, the vibration frequency is 15,000-18,000 times / min, the amplitude is 0.5-0.8 mm, the vibration time per point is 15-30 seconds, and the vibration interval is 1.3-1.7 times the vibrator's effective radius. Subsequently, a steam curing process is adopted, with a static phase of 15-25°C, humidity ≥95%, and a duration of 24 hours; a heating phase of increasing the temperature to 60-70°C at 8-12°C / hour, humidity ≥98%, and a duration of 4-6 hours; a constant temperature phase of 60-70°C, humidity ≥98%, and a duration of 6-8 hours; and a cooling phase of naturally cooling to ambient temperature at ≤15°C / hour.

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