A method for preparing ultra-high performance concrete based on recycled fiber-reinforced sulfoaluminate cement from decommissioned wind turbine blades.

Abstract

This invention belongs to the field of building materials and electromagnetic shielding technology, specifically disclosing a recycled fiber-reinforced sulfoaluminate cement-based ultra-high performance concrete for retired wind turbine blades and its preparation method. This ultra-high performance concrete comprises sulfoaluminate cement, rice husk ash, silica fume, quartz powder, fine aggregate, retarder, dispersant, polycarboxylate superplasticizer, modified recycled carbon fiber, modified recycled glass fiber, and water. The modified recycled carbon fiber and modified recycled glass fiber are respectively obtained by surface magnetization, in-situ growth of conductive nanonetworks, and silane modification of the recycled fibers. This invention achieves high-value closed-loop resource utilization of waste wind turbine blades, not only avoiding environmental pollution from landfill and incineration, but also providing the wind power industry with a circular economy model of "blade-concrete-wind power facility," which can be directly used in structural parts such as wind turbine towers and nacelle covers.

Description

Technical Field

[0001] This invention belongs to the field of building materials and electromagnetic shielding technology, specifically relating to a regenerated fiber-reinforced sulfoaluminate cement-based ultra-high performance concrete for decommissioned wind turbine blades and its preparation method. Background Technology

[0002] With the rapid development of the global wind power industry, wind turbine blades are typically designed for a lifespan of 15-20 years, and a large number of early-installed wind turbines are gradually entering their retirement period. The main components of retired wind turbine blades are glass fiber reinforced composite materials and carbon fiber reinforced composite materials. These blades are bulky and difficult to biodegrade naturally; traditional landfill or incineration methods cause serious environmental pollution and resource waste. How to achieve efficient recycling and resource reuse of high-value fibers from retired wind turbine blades has become a key bottleneck restricting the green and sustainable development of the wind power industry. This is especially true in the offshore wind power sector, where the requirements for full life-cycle green certification are even more stringent. The high-value-added closed-loop utilization of retired blades has significant industry demonstration value.

[0003] Offshore wind turbines integrate numerous sensitive electronic devices, including converters, SCADA monitoring systems, 5G wireless communication modules, various sensors, and control cabinets. These devices are sensitive to external electromagnetic interference (such as lightning electromagnetic pulses, marine weather radar signals, and electromagnetic radiation from nearby turbines), and they also generate their own electromagnetic radiation, potentially interfering with the normal operation of other precision instruments within the tower. Especially with the widespread deployment of 5G communication technology in smart wind farms, electromagnetic interference in the 3.94–5.99 GHz frequency band is becoming increasingly prominent. Therefore, critical locations within the offshore wind turbine tower (such as control cabinet bases, cable penetration holes, and sensor mounting bases) require components with electromagnetic shielding capabilities to ensure the reliable operation of the electronic systems.

[0004] Currently, small shielding components inside offshore wind turbine towers are mostly made of metal (such as galvanized steel plate bases and copper shielding sleeves) or metal-plastic composites. These solutions have the following drawbacks: metal components are prone to electrochemical corrosion in the high humidity and high salt spray environment of the ocean, requiring regular painting and maintenance or the use of expensive corrosion-resistant alloys; metal-plastic composites suffer from interface aging and shielding effectiveness degradation. Furthermore, these traditional solutions cannot be synergistically integrated with the resource utilization of solid waste from retired wind turbine blades.

[0005] Therefore, developing an ultra-high performance concrete material that can fully utilize the recycled fibers of retired wind turbine blades, possesses good electromagnetic shielding performance, resists seawater corrosion, and has a feasible preparation process, and applying it to small shielding components on offshore wind turbine tower platforms, is of great significance for promoting the development of a circular economy in the wind power industry, reducing the maintenance cost of offshore wind turbines throughout their entire life cycle, and improving the electromagnetic protection capabilities of key equipment. Summary of the Invention

[0006] To address the problems existing in the aforementioned background technology, this invention provides an ultra-high performance concrete based on recycled fiber-reinforced sulfoaluminate cement from decommissioned wind turbine blades for use in offshore wind turbine shielding components, and its preparation method. Sulfoaluminate cement is characterized by low alkalinity (pH < 10.5), high early strength, and excellent resistance to sulfate attack, making it highly suitable for marine environments. While its low-alkalinity environment effectively alleviates the alkali corrosion problem of recycled glass fibers, excessively rapid setting time (initial setting often less than 30 min) leads to uneven fiber dispersion and molding difficulties. By introducing a retarder, the problem of uneven fiber dispersion caused by excessively rapid setting is solved, allowing the fibers to be uniformly distributed in the slurry. The entire preparation process of this invention's ultra-high performance concrete does not involve high temperature, high pressure, or organic solvents, making it environmentally friendly and easy to industrialize.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A type of ultra-high performance concrete based on sulfoaluminate cement and recycled fiber reinforced for retired wind turbine blades comprises sulfoaluminate cement, rice husk ash, silica fume, quartz powder, fine aggregate, retarder, dispersant, polycarboxylate superplasticizer, modified recycled carbon fiber, modified recycled glass fiber, and water. The weight proportions of each component are as follows: 100-140 parts of sulfoaluminate cement 20-30 parts rice husk ash 20-30 parts silica fume 15-30 parts quartz powder 100-150 parts fine aggregate, 0.5-2.0 parts of retarder. Dispersant 0.1~0.5 parts, Polycarboxylate superplasticizer, 0.8~2.0 parts. 25-40 parts water; Furthermore, the volume replacement rate of modified recycled carbon fiber in each cubic meter of concrete is 1.5 vol.%, and the volume replacement rate of modified recycled glass fiber is 0.5 vol.%. The sulfoaluminate cement is 52.5 sulfoaluminate cement; further, the sulfoaluminate cement is rapid-hardening sulfoaluminate cement or low-alkalinity sulfoaluminate cement, with an alkalinity pH value <10.5. The water reduction rate of the polycarboxylate superplasticizer is 22%~25%, and the solid content is 20%. The modified recycled carbon fiber is obtained by modifying the surface of recycled carbon fiber with silane using a silane coupling agent, and the modified recycled glass fiber is obtained by modifying the surface of recycled glass fiber with silane using a silane coupling agent, in order to improve the interfacial bonding performance between the fiber and the cement matrix. The method includes: placing the recycled carbon fiber and recycled glass fiber in an oven to dry them to remove surface moisture, then subjecting the recycled carbon fiber to surface magnetization treatment and in-situ growth of conductive nanonetwork treatment, and the recycled glass fiber to in-situ growth of conductive nanonetwork treatment, and finally modifying the surfaces of the two types of recycled fibers after the above treatment with a silane coupling agent. The oven temperature was set to 60~80℃ and the drying time was 12~24h. The preferred silane coupling agent is KH550. The two types of regenerated fibers are surface modified using an immersion method. Specifically, the silane coupling agent and anhydrous ethanol are mixed at a mass ratio of 1:8-12 to prepare a treatment solution. The dried regenerated carbon fiber and regenerated glass fiber are then completely immersed in the treatment solution. The solid-liquid ratio of fiber mass (g) to treatment solution volume (mL) is controlled at 1:8-15, and the immersion time is 30-60 minutes. After immersion, the two types of regenerated fibers are removed, excess liquid is drained, and they are dried in an oven at 60-80℃ for 2-4 hours, thus completing the surface modification of the regenerated fibers. The recycled carbon fiber and recycled glass fiber are both obtained from decommissioned wind turbine blades through cutting, crushing, and chemical recycling processes. The specific recycling process is as follows: (1) The main structure of the decommissioned wind turbine blade after the removal of metal accessories is classified and processed. Specifically, the collected decommissioned wind turbine blades made of carbon fiber composite material and decommissioned wind turbine blades made of glass fiber composite material are operated separately as follows: the two types of fiber composite material decommissioned wind turbine blades are cut into block materials by high pressure water jet cutting machine, and then the block materials are fed into jaw crusher for coarse crushing and then into hammer crusher for fine crushing. The output particle size is controlled to be less than 20mm, and fragments containing glass fiber reinforced composite material and fragments containing carbon fiber reinforced composite material are obtained respectively. The size of the block material mentioned in step (1) is 300 mm × 300 mm; (2) The two types of fragments obtained in step (1) are respectively put into a high-speed vortex pulverizer for pulverization. The processing time is 5~8 min. The high-speed rotating blades in the high-speed vortex pulverizer apply shearing and impact force to the composite material fragments, so that the fibers in the composite material and the cured epoxy resin matrix are initially separated, and the primary mixture of carbon fiber and resin powder I and the primary mixture of glass fiber and resin powder II are obtained respectively. The blade tip linear velocity of the high-speed eddy current pulverizer rotor in step (2) is 35~50m / s; (3) The two primary mixtures obtained in step (2) are fed into an air classifier and separated by the difference in suspension velocity of the two fibers and resin powder in the airflow. The specific separation method is as follows: the fan speed in the airflow separator is controlled by the frequency converter, and the airflow velocity in the airflow separator is controlled within the range of 1.0~2.5m / s. Under this wind speed, the light fibers overcome gravity and are enriched with the airflow and enter the collector, while the heavy resin powder settles due to its lower suspension velocity, thereby achieving separation. The fiber-enriched part is collected to obtain carbon fiber containing residual resin and glass fiber containing residual resin, respectively. (4) The two types of fibers containing residual resin obtained in step (3) are immersed in a chemical depolymerization solution and stirred continuously. The synergistic effect of acidic medium and oxidant causes the residual epoxy resin matrix on the fiber surface to swell, oxidize and depolymerize, thereby completely peeling the resin off the fiber surface. At the same time, the reaction temperature and time are controlled to avoid excessive etching of the fiber itself. After the stirring reaction is completed, the fiber is filtered out and repeatedly washed with deionized water until the washing solution is neutral. Then the washed fiber is placed in a vacuum drying oven to dry, and recycled carbon fiber and recycled glass fiber with clean surface are obtained respectively. The chemical depolymerization solution described in step (4) is prepared by mixing nitric acid and hydrogen peroxide in a volume ratio of 1:3~5; The solid-liquid ratio of the carbon fiber containing residual resin, the glass fiber containing residual resin, and the chemical depolymerization solution is controlled to be 1:15~25. The stirring reaction temperature was set to 60~80℃, and the continuous stirring reaction time was set to 4~8h. The temperature of the vacuum drying ovens was set to 60~80℃ and the drying time was set to 8~12h. The recycled carbon fiber has a length of 3-15 mm, an average diameter of 5-10 μm, and an apparent density of 1650-1950 kg / m³, while the recycled glass fiber has a length of 12-20 mm, an average diameter of 10-20 μm, and an apparent density of 1500-1800 kg / m³.

[0008] Furthermore, the total volume replacement rate of the modified recycled carbon fiber and the modified recycled glass fiber described in this invention is preferably 2% to avoid the adverse effects of fiber agglomeration on concrete performance.

[0009] Furthermore, the silica fume of the present invention has an average particle size of 0.1~0.2μm and a specific surface area of ​​18000~20000m². 2 / kg.

[0010] Furthermore, the quartz powder of the present invention has a particle size of 200-400 mesh.

[0011] Furthermore, the fine aggregate described in this invention is river sand or quartz sand with a particle size of 40-140 mesh.

[0012] Furthermore, the rice husk ash described in this invention is ultrafine rice husk ash with an average particle size of 1-3 μm, an active silica content greater than 98%, and is a neutral material. This ultrafine rice husk ash is obtained from agricultural waste rice husks through controlled-temperature incineration followed by further grinding and grading. Its ultrafine particle size gives it excellent micro-aggregate filling effect, effectively filling the micropores between cement particles and quartz powder, significantly improving the density of the matrix and the uniformity of the interface transition zone. The active silica content exceeding 98% endows the rice husk ash with extremely high pozzolanic activity, enabling it to rapidly react with calcium hydroxide produced during the hydration of sulfoaluminate cement to generate additional hydrated calcium silicate gel. This not only further densifies the microstructure but also consumes free calcium hydroxide in the system, reducing the matrix alkalinity, thereby providing a milder chemical environment for recycled glass fibers and suppressing potential alkali corrosion risks. Furthermore, the rice husk ash is a neutral material (pH value approximately 6.8~7.2), which can buffer local alkalinity fluctuations during the initial hydration of sulfoaluminate cement, providing additional protection for recycled glass fibers sensitive to alkaline environments. Simultaneously, the high specific surface area and abundant silanol functional groups on the surface of the ultrafine rice husk ash enable it to exhibit good physicochemical adsorption with dispersants, retarders, and the modified layer on the fiber surface, contributing to improved fiber dispersion uniformity in the slurry and the fiber-matrix interfacial bonding strength.

[0013] Furthermore, the retarder described in this invention is selected from any one or more of boric acid, borax, citric acid, and sodium gluconate to ensure that the initial setting time of sulfoaluminate cement is adjusted to 45-90 min and the final setting time is controlled accordingly to 70-120 min.

[0014] Furthermore, the dispersant of the present invention is selected from any one or a mixture of more than one of hydroxypropyl methylcellulose, polyethylene glycol, sodium dodecyl sulfate, and sodium carboxymethyl cellulose, and is used to promote the uniform dispersion of regenerated fibers in the slurry.

[0015] This invention also provides a method for preparing the above-mentioned recycled fiber-reinforced sulfoaluminate cement-based ultra-high performance concrete for decommissioned wind turbine blades, specifically including the following steps: (1) Fiber pretreatment: Regenerated carbon fiber and regenerated glass fiber are respectively modified by surface silane by silane coupling agent to obtain modified regenerated carbon fiber and modified regenerated glass fiber. As a further improvement to the technical solution of this invention, in order to maximize the axial reinforcement and conductivity of the fiber, the recycled carbon fiber in step (1) is subjected to surface magnetization treatment before silane modification in the pretreatment stage. Specifically, nano-Fe3O4 particles are deposited on the surface of the recycled carbon fiber using a chemical co-precipitation method, with the particle size controlled at 10~30nm. This treatment not only imparts weak magnetism to the fiber to respond to the applied magnetic field, but also the Fe3O4 particles themselves have good wave absorption characteristics, which can synergistically enhance the electromagnetic shielding effectiveness with the carbon fiber. Furthermore, the surface magnetization treatment step of the recycled carbon fiber is specifically as follows: the dried recycled carbon fiber is dispersed in a solution containing Fe2O3. + / Fe³ + In an alkaline salt solution, under nitrogen protection, the reaction is continuously stirred at 50-80℃ for 30-60 min to deposit nano-Fe3O4 particles on the fiber surface. After the reaction, the regenerated carbon fibers are repeatedly washed with deionized water until the solution is neutral. Then, the regenerated carbon fibers are dried in a vacuum drying oven at 60-80℃ for 6-12 h to obtain regenerated carbon fibers with magnetic response characteristics. + / Fe³ + The salt is a mixture of FeCl2·4H2O and FeCl3·6H2O, Fe² + Fe³ + The molar ratio of the two is 1:1.5~2, the alkaline solution is a 0.5~1.0 mol / L NaOH solution, and the pH of the alkaline reaction system is maintained at 10~11; recycled carbon fiber and Fe² + / Fe³ + The solid-liquid ratio of an alkaline salt solution is 1:50~100; As a further improvement to the technical solution of this invention, to further enhance the fiber-matrix interfacial bonding strength and construct a multi-scale conductive network, the regenerated carbon fibers and regenerated glass fibers undergo in-situ surface growth of conductive nanonetworks before silane modification in the pretreatment stage. Specifically, for regenerated carbon fibers, carbon nanotubes are grown using chemical vapor deposition; for regenerated glass fibers, a polypyrrole conductive layer is coated using in-situ polymerization. The above-mentioned conductive nanonetwork growth step can be performed before or after silane coupling agent modification, preferably before silane coupling agent modification to obtain better interfacial bonding. The surface of untreated regenerated carbon fibers / glass fibers contains more hydroxyl, carboxyl, or defect sites, making it easier for catalyst precursors or pyrrole monomers to be directly adsorbed and anchored onto the original fiber surface, thereby forming a conductive nanonetwork with higher bonding strength and more uniform coverage.

[0016] For recycled carbon fibers, carbon nanotubes (CNTs) are grown in situ on their surface using chemical vapor deposition: The dried recycled carbon fibers with magnetic response properties are completely immersed in a solution containing a nickel or iron catalyst. After impregnation, the fibers are filtered out and dried to constant weight. Then, they are placed in a tube furnace and heated to 600-800°C under an inert atmosphere. Acetylene, the carbon source gas, is introduced to carry out the reaction, resulting in the uniform growth of carbon nanotubes with a length of 1-5 μm and a diameter of 10-30 nm on the fiber surface. After the reaction, ... Cool to room temperature in an inert atmosphere; specifically, the solution containing nickel or iron catalyst is preferably an aqueous solution of nickel nitrate or ferric nitrate, each with a concentration of 0.05~0.2 mol / L; during impregnation, the solid-liquid ratio (the ratio of the mass of recycled carbon fiber in g to the volume of catalyst solution in mL) is controlled at 1:10~20, and the impregnation time is 30~60 min to ensure that the catalyst precursor is fully adsorbed on the fiber surface; after impregnation, the drying temperature is 80~100℃; the acetylene gas flow rate is controlled at 50~200 mL / min, and the reaction time is 5~20 min.

[0017] For recycled glass fiber, an in-situ polymerization method is used to coat its surface with a conductive polymer layer: the recycled glass fiber is immersed in a mixed aqueous solution containing pyrrole monomer and oxidant FeCl3, and the reaction is continuously stirred at room temperature to form a uniform polypyrrole conductive coating on the fiber surface. After the reaction is completed, the fiber is removed, repeatedly washed with deionized water to remove unreacted monomers and homopolymers, and then vacuum dried to constant weight. The concentration of pyrrole monomer in the mixed aqueous solution is 0.1~0.5 mol / L, the concentration of FeCl3 is 0.2~1.0 mol / L, and the molar ratio of pyrrole monomer to FeCl3 is preferably 1:2~1:3. The solid-liquid ratio of recycled glass fiber to the mixed aqueous solution is 1:15~25, the immersion time is 1~4 hours, and the vacuum drying temperature is 60℃. The above two treatments (in-situ growth of conductive nanonetworks on the surface of recycled carbon fiber and recycled glass fiber) can be implemented alone or in combination. When implemented in combination, the carbon nanotubes on the surface of recycled carbon fiber and the conductive polymer coating on the surface of recycled glass fiber overlap to form a hierarchical conductive network across different fiber types, transforming the "point contact" between fibers into a highly efficient "line-surface composite contact". (2) Dry material mixing: Weigh out sulfoaluminate cement, silica fume, rice husk ash, quartz powder and fine aggregate according to the proportion, put them into a forced mixer and dry mix for 4~6 minutes to make the powder and aggregate evenly mixed to obtain mixed dry material; (3) Fiber dispersion: The pretreated modified recycled carbon fiber and modified recycled glass fiber are premixed with a dispersant accounting for 1 / 3 to 1 / 2 of the total amount of dispersant, so that the dispersant is uniformly attached to the fiber surface. Then the fiber mixture is slowly added to the dry mixture in step (2) and dry mixing is continued for 2 to 4 minutes to allow the fiber to be initially dispersed in the powder, thus obtaining a fiber-dry mixture. (4) Liquid preparation: Dissolve the retarder, remaining dispersant, and polycarboxylate superplasticizer in all the water and stir to form a uniform mixed solution; (5) Slurry mixing: Slowly add the mixed solution to the fiber-dry material mixture, first stir at low speed for 1-2 minutes, then switch to high speed for 2-4 minutes until a uniform, fluid slurry is formed; The low-speed stirring speed is 50~80 r / min; The high-speed stirring speed is 120~180 r / min; (6) Molding and curing: Pour the slurry mixed in step (5) into the mold and vibrate it on the vibrating table for 1 to 2 minutes to remove air bubbles; cover the outside of the mold with plastic film and cure it for 24 hours at 20±2℃ and relative humidity ≥95%. After demolding, continue to cure it in a standard curing room (20±2℃, relative humidity ≥95%) for 28 days to obtain the ultra-high performance concrete of the present invention.

[0018] Furthermore, in the fiber pretreatment stage in step (1), the recycled carbon fiber is also subjected to surface magnetization treatment, that is, step (6) also includes arranging electromagnetic coils around the mold covered with plastic film to generate a directional magnetic field with an intensity of 0.1~0.5T. The direction of the magnetic field is set according to the target requirements to be perpendicular to the electromagnetic wave incident direction (to maximize the electromagnetic shielding effectiveness) or parallel to the principal stress direction of the component (to maximize the mechanical reinforcement effect). The magnetic field is maintained for 5~15 minutes until the slurry initially solidifies and sets, thereby inducing the recycled carbon fiber with magnetic response to be oriented along the magnetic field direction.

[0019] When used for large components such as wind turbine towers or nacelle covers, the casting process in step (6) of the preparation method is replaced by vacuum-assisted grouting or pressure grouting to improve fiber orientation and density.

[0020] Compared with the prior art, the present invention has the following advantages: (1) This invention is the first to realize the hybrid synergistic utilization of recycled carbon fiber and recycled glass fiber in sulfoaluminate cement-based ultra-high performance concrete. By hybrid designing two recycled fibers with the same source but complementary functions, recycled carbon fiber provides excellent conductive path and electromagnetic shielding function, while recycled glass fiber provides high elastic modulus and reinforcement and toughening effect. Together, they construct a "conductive-mechanical" dual network structure, overcoming the shortcomings of single fiber in performance.

[0021] (2) The present invention cleverly utilizes the low-alkali environment of sulfoaluminate cement to solve the problem that recycled glass fibers are prone to alkali-silica reaction in high-alkali cement. This low-alkali environment can effectively inhibit the alkali corrosion on the surface of recycled glass fibers, maintain the original strength and long-term durability of the fibers, and at the same time, by introducing a retarder, the initial setting time of sulfoaluminate cement is adjusted to 45~90 min, which solves the problem of uneven fiber dispersion caused by excessively fast setting, so that the fibers can be evenly distributed in the slurry.

[0022] (3) The present invention constructs an efficient electromagnetic shielding network. Recycled carbon fibers overlap in the cement matrix to form a three-dimensional conductive network. Combined with the isolation and dielectric regulation effect of recycled glass fiber, especially in the 3.94~5.99GHz frequency band faced by the widespread deployment of 5G communication in smart wind farms, the average shielding efficiency can reach more than 35dB. It can effectively resist the interference of lightning electromagnetic pulse, weather radar and broadcast communication signals, and meet the general industrial and civil electromagnetic protection requirements.

[0023] (4) By further introducing the technology of in-situ growth of carbon nanotubes or conductive polymer layers on the fiber surface, the present invention constructs a multi-scale hierarchical conductive network on the fiber surface, transforming the “point contact” between fibers into “line-surface composite contact”, increasing the number of conductive pathways by 1 to 2 orders of magnitude, and further improving the electromagnetic shielding effectiveness to 50 to 70 dB. At the same time, the interfacial bonding strength between the fiber and the cement matrix is ​​increased by more than 40%.

[0024] (5) By introducing magnetic field-assisted orientation arrangement technology, the present invention enables the regenerated carbon fibers with magnetic response to be oriented in a specific direction. The electromagnetic shielding efficiency perpendicular to the fiber orientation direction can be improved by 50% to 100%, while the flexural strength along the fiber orientation direction is increased by more than 30%, truly realizing "on-demand orientation reinforcement" and opening up a new dimension for structural and functional integration.

[0025] (6) This invention realizes the high-value closed-loop resource utilization of waste wind turbine blades, which not only avoids environmental pollution caused by landfill and incineration, but also provides a circular economy model of "blade-concrete-wind power facility" for the wind power industry. The material itself has ultra-high performance (compressive strength ≥150MPa, flexural strength ≥30MPa) and can be directly used in structural parts such as wind turbine towers and nacelle covers.

[0026] (7) The preparation process of the present invention is flexible and controllable. All regenerated fibers do not require complex sorting and secondary cutting. The above-mentioned surface modification and directional arrangement technologies can be embedded in the existing mixing-casting process. The fast hardening and early strength characteristics of sulfoaluminate cement enable the components to be demolded quickly and improve production efficiency. The entire preparation process does not involve high temperature, high pressure or organic solvents, is green and environmentally friendly, and is easy to promote industrially. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] A type of ultra-high performance concrete based on sulfoaluminate cement and recycled fiber reinforced for retired wind turbine blades comprises sulfoaluminate cement, rice husk ash, silica fume, quartz powder, fine aggregate, retarder, dispersant, polycarboxylate superplasticizer, modified recycled carbon fiber, modified recycled glass fiber, and water. The weight proportions of each component are as follows: 100-140 parts of sulfoaluminate cement 20-30 parts rice husk ash 20-30 parts silica fume 15-30 parts quartz powder 100-150 parts fine aggregate, 0.5-2.0 parts of retarder. Dispersant 0.1~0.5 parts, Polycarboxylate superplasticizer, 0.8~2.0 parts. 25-40 parts water; Furthermore, the volume replacement rate of modified recycled carbon fiber in each cubic meter of concrete is 1.5 vol.%, and the volume replacement rate of modified recycled glass fiber is 0.5 vol.%. The sulfoaluminate cement is 52.5 sulfoaluminate cement; further, the sulfoaluminate cement is rapid-hardening sulfoaluminate cement or low-alkalinity sulfoaluminate cement, with an alkalinity pH value <10.5. The water reduction rate of the polycarboxylate superplasticizer is 22%~25%, and the solid content is 20%. The modified recycled carbon fiber is obtained by modifying the surface of recycled carbon fiber with silane using a silane coupling agent, and the modified recycled glass fiber is obtained by modifying the surface of recycled glass fiber with a silane coupling agent. The method includes: placing the recycled carbon fiber and recycled glass fiber separately in an oven to dry to remove surface moisture; then, the recycled carbon fiber undergoes surface magnetization treatment and in-situ growth of a conductive nanonetwork; the recycled glass fiber undergoes in-situ growth of a conductive nanonetwork; finally, the surfaces of the two types of recycled fibers treated above are modified with a silane coupling agent to obtain the modified recycled carbon fiber. To improve the interfacial bonding performance between fibers and cement matrix, the oven temperature is set to 60-80℃, and the drying time is 12-24h. The preferred silane coupling agent is KH550. The two types of recycled fibers are surface modified using an immersion method. Specifically, the silane coupling agent and anhydrous ethanol are mixed at a mass ratio of 1:8-12 to prepare a treatment solution. The dried recycled carbon fibers and recycled glass fibers are then completely immersed in the treatment solution. The solid-liquid ratio of fiber mass (g) to treatment solution volume (mL) is controlled at 1:8-15, and the immersion time is 30-60 min. After immersion, the two types of recycled fibers are removed, excess liquid is drained, and they are dried in an oven at 60-80℃ for 2-4 hours to complete the surface modification of the recycled fibers. The recycled carbon fiber and recycled glass fiber are both obtained from decommissioned wind turbine blades through cutting, crushing, and chemical recycling processes. The specific recycling process is as follows: (1) The main structure of the decommissioned wind turbine blade after the removal of metal accessories is classified and processed. Specifically, the collected decommissioned wind turbine blades made of carbon fiber composite material and decommissioned wind turbine blades made of glass fiber composite material are operated separately as follows: the two types of fiber composite material decommissioned wind turbine blades are cut into block materials by high pressure water jet cutting machine, and then the block materials are fed into jaw crusher for coarse crushing and then into hammer crusher for fine crushing. The output particle size is controlled to be less than 20mm, and fragments containing glass fiber reinforced composite material and fragments containing carbon fiber reinforced composite material are obtained respectively. The size of the block material is 300 mm × 300 mm; (2) The two types of fragments obtained in step (1) are respectively fed into a high-speed vortex pulverizer for pulverization. The processing time is 5 to 8 minutes. The high-speed rotating blades in the high-speed vortex pulverizer apply shearing and impact forces to the composite material fragments, so that the fibers in the composite material and the cured epoxy resin matrix are initially separated, and primary mixture I of carbon fiber and resin powder and primary mixture II of glass fiber and resin powder are obtained respectively; the blade tip linear velocity of the rotor of the high-speed vortex pulverizer is 35 to 50 m / s; (3) The two primary mixtures obtained in step (2) are fed into an air classifier and separated by the difference in suspension velocity of the two fibers and resin powder in the airflow. The specific separation method is as follows: the fan speed in the air classifier is controlled by the frequency converter, and the airflow velocity in the air classifier is controlled within the range of 1.0~2.5m / s. At this wind speed, the light fibers overcome gravity and are enriched by the airflow and enter the collector, while the heavy resin powder settles due to the lower suspension velocity, thereby achieving separation. The fiber enriched part is collected to obtain carbon fiber containing residual resin and glass fiber containing residual resin respectively. (4) The two types of fibers containing residual resin obtained in step (3) were immersed in a chemical depolymerization solution and continuously stirred. The synergistic effect of the acidic medium and the oxidant caused the residual epoxy resin matrix on the fiber surface to swell, oxidize and degrade, and chemically depolymerize, thereby completely peeling the resin off the fiber surface. At the same time, the reaction temperature and time were controlled to avoid excessive etching of the fiber itself. After the stirring reaction was completed, the fiber was filtered out and repeatedly washed with deionized water until the washing solution was neutral. Then the washed fiber was placed in a vacuum drying oven to dry, and clean recycled carbon fibers were obtained respectively. Recycled glass fiber; the chemical depolymerization solution is prepared by mixing nitric acid and hydrogen peroxide at a volume ratio of 1:3~5; the solid-liquid ratio of the carbon fiber containing residual resin, the glass fiber containing residual resin, and the chemical depolymerization solution is controlled at 1:15~25; the stirring reaction temperature is set to 60~80℃, and the continuous stirring reaction time is set to 4~8h; the vacuum drying oven temperature is set to 60~80℃, and the drying time is set to 8~12h; the length of the recycled carbon fiber is 3~15mm, the average diameter is 5~10μm, and the apparent density is 1650~1950 kg / m³, and the length of the recycled glass fiber is 12~20mm, the average diameter is 10~20μm, and the apparent density is 1500~1800 kg / m³.

[0029] The silica fume described in this invention has an average particle size of 0.1~0.2μm and a specific surface area of ​​18000~20000m². 2 / kg.

[0030] The quartz powder of this invention has a particle size of 200-400 mesh.

[0031] The fine aggregate described in this invention is river sand or quartz sand with a particle size of 40-140 mesh.

[0032] The rice husk ash described in this invention is ultrafine rice husk ash with an average particle size of 1~3μm, an active silica content of more than 98%, and is a neutral material.

[0033] The retarder described in this invention is selected from any one or more of boric acid, borax, citric acid, and sodium gluconate to ensure that the initial setting time of sulfoaluminate cement is adjusted to 45-90 min and the final setting time is controlled accordingly to 70-120 min.

[0034] The dispersant described in this invention is selected from any one or a mixture of more than one of hydroxypropyl methylcellulose, polyethylene glycol, sodium dodecyl sulfate, and sodium carboxymethyl cellulose, and is used to promote the uniform dispersion of regenerated fibers in the slurry.

[0035] This invention also provides a method for preparing the above-mentioned ultra-high performance concrete, specifically including the following steps: (1) Fiber pretreatment: Regenerated carbon fiber and regenerated glass fiber are respectively modified by surface silane by silane coupling agent to obtain modified regenerated carbon fiber and modified regenerated glass fiber. Furthermore, the recycled carbon fiber described in step (1) underwent surface magnetization treatment before silane modification during the pretreatment stage. Specifically, nano-sized iron tetroxide (Fe3O4) particles were deposited on the surface of the recycled carbon fiber using a chemical co-precipitation method, with the particle size controlled at 10~30nm; the surface magnetization treatment step of the recycled carbon fiber specifically involved dispersing the dried recycled carbon fiber in a solution containing Fe2O4. + / Fe³ + In an alkaline salt solution, under nitrogen protection, the reaction is continuously stirred at 50-80℃ for 30-60 min to deposit nano-Fe3O4 particles on the fiber surface. After the reaction, the regenerated carbon fibers are repeatedly washed with deionized water until the solution is neutral. Then, the regenerated carbon fibers are dried in a vacuum drying oven at 60-80℃ for 6-12 h to obtain regenerated carbon fibers with magnetic response characteristics. + / Fe³ + The salt is a mixture of FeCl2·4H2O and FeCl3·6H2O, Fe² + Fe³ + The molar ratio of the two is 1:1.5~2, the alkaline solution is a 0.5~1.0 mol / L NaOH solution, and the pH of the alkaline reaction system is maintained at 10~11; recycled carbon fiber and Fe² + / Fe³ + The solid-liquid ratio of an alkaline salt solution is 1:50~100; Furthermore, before silane modification in the pretreatment stage, the regenerated carbon fibers and regenerated glass fibers undergo in-situ surface growth of conductive nanonetworks. Specifically, for regenerated carbon fibers, carbon nanotubes are grown using chemical vapor deposition; for regenerated glass fibers, a polypyrrole conductive layer is coated using in-situ polymerization. Specifically, for regenerated carbon fibers, carbon nanotubes (CNTs) are grown in-situ on their surface using chemical vapor deposition: the dried regenerated carbon fibers with magnetic response characteristics are completely immersed in a solution containing a nickel or iron catalyst for impregnation. After impregnation, the fibers are filtered out and dried to constant weight, then placed in a tube furnace and heated to 600-800°C under an inert atmosphere. Acetylene, the carbon source gas, is introduced to react, resulting in the uniform growth of carbon nanotubes with a length of 1-5 μm and a diameter of 10-30 nm on the fiber surface. After the reaction, ... Cool to room temperature in an inert atmosphere; specifically, the solution containing nickel or iron catalyst is preferably an aqueous solution of nickel nitrate or ferric nitrate, each with a concentration of 0.05~0.2 mol / L; during impregnation, the solid-liquid ratio (the ratio of the mass of recycled carbon fiber in g to the volume of the catalyst solution in mL) is controlled at 1:10~20, and the impregnation time is 30~60 min to ensure that the catalyst precursor is fully adsorbed on the fiber surface; after impregnation, the drying temperature is 80~100℃; the acetylene gas flow rate is controlled at 50~200 mL / min, and the reaction time is 5~20 min. For recycled glass fiber, an in-situ polymerization method is used to coat its surface with a conductive polymer layer: the recycled glass fiber is immersed in a mixed aqueous solution containing pyrrole monomer and oxidant FeCl3, and the reaction is continuously stirred at room temperature to form a uniform polypyrrole conductive coating on the fiber surface. After the reaction is completed, the fiber is removed, repeatedly washed with deionized water to remove unreacted monomers and homopolymers, and then vacuum dried to constant weight. The concentration of pyrrole monomer in the mixed aqueous solution is 0.1~0.5 mol / L, the concentration of FeCl3 is 0.2~1.0 mol / L, and the molar ratio of pyrrole monomer to FeCl3 is preferably 1:2~1:3. The solid-liquid ratio of recycled glass fiber to the mixed aqueous solution is 1:15~25, the immersion time is 1~4 hours, and the vacuum drying temperature is 60℃. (2) Dry material mixing: Weigh out sulfoaluminate cement, silica fume, rice husk ash, quartz powder and fine aggregate according to the proportion, put them into a forced mixer and dry mix for 4~6 minutes to make the powder and aggregate evenly mixed to obtain mixed dry material; (3) Fiber dispersion: The pretreated modified recycled carbon fiber and modified recycled glass fiber are premixed with a dispersant accounting for 1 / 3 to 1 / 2 of the total amount of dispersant, so that the dispersant is uniformly attached to the fiber surface. Then the fiber mixture is slowly added to the dry mixture in step (2) and dry mixing is continued for 2 to 4 minutes to allow the fiber to be initially dispersed in the powder, thus obtaining a fiber-dry mixture. (4) Liquid preparation: Dissolve the retarder, remaining dispersant, and polycarboxylate superplasticizer in all the water and stir to form a uniform mixed solution; (5) Slurry mixing: The mixed solution is slowly added to the fiber-dry material mixture. First, it is stirred at a low speed for 1 to 2 minutes, and then stirred at a high speed for 2 to 4 minutes until a uniform and fluid slurry is formed. The low speed stirring speed is 50 to 80 r / min; the high speed stirring speed is 120 to 180 r / min. (6) Molding and curing: Pour the slurry mixed in step (5) into the mold and vibrate it on the vibrating table for 1 to 2 minutes to remove air bubbles; cover the outside of the mold with plastic film and cure it for 24 hours at 20±2℃ and relative humidity ≥95%. After demolding, continue to cure it in a standard curing room (20±2℃, relative humidity ≥95%) for 28 days to obtain the ultra-high performance concrete of the present invention.

[0036] In the fiber pretreatment stage of step (1), the recycled carbon fiber is also subjected to surface magnetization treatment, that is, in step (6), electromagnetic coils are arranged around the mold covered with plastic film to generate a directional magnetic field with an intensity of 0.1~0.5T. The direction of the magnetic field is set to be perpendicular to the electromagnetic wave incident direction (to maximize the electromagnetic shielding effectiveness) or parallel to the principal stress direction of the component (to maximize the mechanical reinforcement effect) according to the target requirements. The magnetic field is maintained for 5~15 minutes until the slurry is initially solidified and shaped, thereby inducing the recycled carbon fiber with magnetic response to be oriented along the magnetic field direction.

[0037] When used for large components such as wind turbine towers or nacelle covers, the casting process in step (6) of the preparation method is replaced by vacuum-assisted grouting or pressure grouting to improve fiber orientation and density.

[0038] Example 1 A type of ultra-high performance concrete based on sulfoaluminate cement and recycled fiber reinforced for retired wind turbine blades is formulated from the following raw materials in parts by weight: 120 parts of 52.5 sulfoaluminate cement, 25 parts of rice husk ash, 25 parts of silica fume, 22 parts of 300-mesh quartz powder, 120 parts of 40-70 mesh quartz sand, with a total volume replacement rate of 2% for modified recycled fibers, of which the volume replacement rate of modified recycled carbon fiber is 1.5%, the volume replacement rate of modified recycled glass fiber is 0.5%, boric acid is 1.5 parts, hydroxypropyl methylcellulose is 0.3 parts, polycarboxylate superplasticizer is 1.5 parts, and water is 30 parts; the modified recycled carbon fiber is obtained by pretreatment of recycled carbon fiber, and the modified recycled glass fiber is obtained by pretreatment of recycled glass fiber. The recycled carbon fiber has a length of 8 mm, an average diameter of 7 μm, and an apparent density of 1800 kg / m³; the recycled glass fiber has a length of 15 mm, an average diameter of 15 μm, and an apparent density of 1680 kg / m³; the rice husk ash is ultrafine rice husk ash with an average particle size of 2 μm, an active silica content of 98.5%, and a pH value of 7.0; the sulfoaluminate cement is rapid-hardening sulfoaluminate cement with a pH value of 10.2; the retarder is boric acid; and the dispersant is hydroxypropyl methylcellulose.

[0039] Specifically, the preparation steps of the aforementioned ultra-high performance concrete are as follows: (1) Fiber pretreatment: The recycled carbon fibers and recycled glass fibers were dried in an 80℃ oven for 12 hours to remove surface moisture; then the following steps were performed: ① In-situ growth of carbon nanotubes on the surface of recycled carbon fibers: The dried recycled carbon fibers were immersed in a solution containing nickel nitrate catalyst (0.1 mol / L), the solid-liquid ratio was controlled at 1:15 during the immersion process, and after soaking for 30 min, they were taken out and dried at 80℃; then the recycled carbon fibers loaded with catalyst were placed in a tube furnace, heated to 700℃ under Ar / H2 atmosphere protection, and acetylene gas (flow rate 100 mL / min) was introduced to react for 10 min, so that carbon nanotubes with a length of 1~5 μm and a diameter of 10~30 nm were uniformly grown on the fiber surface; after the reaction, they were cooled to room temperature in Ar atmosphere; ② In-situ polymerization of conductive polymer layer on the surface of recycled glass fibers: The dried recycled glass fibers were immersed in a solution containing pyrrole monomer (0.2 mol / L) and oxidant FeCl3 (0.5 mol / L). In a mixed aqueous solution containing Fe²⁺ (mol / L), the solid-liquid ratio of recycled glass fiber to the mixed aqueous solution is 1:20. The mixture is stirred at room temperature for 2 hours to form a uniform polypyrrole conductive coating on the fiber surface. After the reaction, the fiber is removed and repeatedly washed with deionized water to remove unreacted monomers and homopolymers, and then vacuum dried at 60℃. ③ Surface magnetization treatment: The recycled carbon fibers with grown carbon nanotubes are dispersed in a solution containing Fe²⁺. + / Fe³ + In an alkaline solution of salt (made of FeCl2·4H2O and FeCl3·6H2O in a molar ratio of Fe²⁺), + :Fe³ += 1:2 mixture, total iron concentration 0.3 mol / L, and pH adjusted to 10.5 with NaOH solution), add recycled carbon fiber to the mixed solution at a solid-liquid ratio of 1:75, react at 60℃ for 45 min under nitrogen protection to further deposit nano Fe3O4 particles (particle size 10~30 nm) on the fiber surface; after the reaction, repeatedly wash the fiber with deionized water until the washing solution is neutral, and then dry at 80℃ for 9 hours; ④ Silane coupling agent modification: prepare a treatment solution by mixing silane coupling agent and anhydrous ethanol at a mass ratio of 1:10, and then immerse the two types of dried fibers in the treatment solution respectively, with the fiber mass (g) to treatment solution volume (mL) controlled at 1:8, and the immersion time is 45 min; after immersion, take out the fiber, drain the excess liquid, and place it in an 80℃ oven to dry for 3 hours to complete the surface modification. It should be noted that in this embodiment, the conductive nanonetwork growth step is carried out before the silane coupling agent modification to obtain a better interfacial bonding effect, so that the carbon nanotubes and polypyrrole layers can be directly and firmly bonded to the fiber surface. Subsequently, the silane coupling agent further improves the compatibility between the fiber and the cement matrix.

[0040] (2) Dry material mixing: Weigh out sulfoaluminate cement, rice husk ash, silica fume, quartz powder and quartz sand according to the proportion, put them into a forced mixer, and dry mix at 60 r / min for 5 min to make the powder and aggregates evenly mixed. (3) Fiber dispersion: The pretreated modified recycled carbon fiber and modified recycled glass fiber are premixed with hydroxypropyl methylcellulose accounting for 1 / 2 of the total amount of dispersant, so that the dispersant is uniformly attached to the fiber surface. Then the fiber mixture is slowly added to the dry material and dry-mixed at 60 r / min for 3 min to initially disperse the fiber in the powder. (4) Liquid preparation: Dissolve boric acid, the remaining hydroxypropyl methylcellulose and polycarboxylate superplasticizer in all water, and stir at 200 r / min for 2 min to form a uniform mixed solution; (5) Slurry mixing: Slowly add the mixed solution to the fiber-dry material mixture, first stir at a low speed of 50 r / min for 1.5 min, then stir at a high speed of 120 r / min for 3 min, until a uniform and fluid slurry is formed; (6) Molding and curing: The mixed slurry is poured into the mold to be tested, and then vibrated on the vibrating table for 1.5 min to remove air bubbles; electromagnetic coils are arranged around the mold, and a direct current is passed through to generate a directional magnetic field with an intensity of 0.3T. The direction of the magnetic field is set to be perpendicular to the surface of the plate specimen (i.e., perpendicular to the direction of electromagnetic wave incident). The magnetic field is maintained for 10 min until the slurry initially sets and solidifies; then, it is covered with plastic film and cured for 24 hours at 20±2℃ and relative humidity ≥95%. After demolding, it is continued to be cured in a standard curing room (20±2℃, relative humidity ≥95%) for 28 days to obtain the sulfoaluminate cement-based ultra-high performance concrete with electromagnetic shielding function.

[0041] Example 2 The difference compared to Example 1 is as follows: The fiber pretreatment process is as follows: Recycled carbon fibers and recycled glass fibers are dried in a 60℃ oven for 24 hours to remove surface moisture. Then, the following steps are performed: ① In-situ growth of carbon nanotubes on the surface of recycled carbon fibers: The dried recycled carbon fibers are immersed in a solution containing ferric nitrate catalyst (0.2 mol / L), with the solid-liquid ratio controlled at 1:10 during immersion. After immersion for 60 min, they are removed and dried at 100℃. Then, the catalyst-loaded recycled carbon fibers are placed in a tube furnace and heated to 800℃ under an Ar / H2 atmosphere. Acetylene gas is introduced (flow rate 200 mL / min) and reacted for 5 min, allowing uniform growth of nanotubes with a length of 1~5 μm and a diameter of 10~30 μm on the fiber surface. ① Carbon nanotubes of nm; after the reaction, cool to room temperature in Ar atmosphere; ② In-situ polymerization of conductive polymer layer on the surface of recycled glass fiber: immerse the dried recycled glass fiber in a mixed aqueous solution containing pyrrole monomer (0.1 mol / L) and oxidant FeCl3 (0.2 mol / L), with a solid-liquid ratio of 1:15 between the recycled glass fiber and the mixed aqueous solution, and stir at room temperature for 4 hours to form a uniform polypyrrole conductive coating on the fiber surface; after the reaction, remove the fiber, wash repeatedly with deionized water to remove unreacted monomers and homopolymers, and vacuum dry at 60℃; ③ Surface magnetization treatment: disperse the recycled carbon fiber with grown carbon nanotubes in a solution containing Fe²⁺. + / Fe³ + In an alkaline solution of salt (made of FeCl2·4H2O and FeCl3·6H2O in a molar ratio of Fe²⁺), + :Fe³ += 1:1.8 mixture, total iron concentration 0.3 mol / L, and pH adjusted to 10.5 with NaOH solution), add recycled carbon fiber to the mixed solution at a solid-liquid ratio of 1:50, react at 80℃ for 30 min under nitrogen protection to further deposit nano Fe3O4 particles (particle size 10~30 nm) on the fiber surface; after the reaction, repeatedly wash the fiber with deionized water until the washing solution is neutral, and then dry at 70℃ for 6 hours; ④ Silane coupling agent modification: prepare a treatment solution by mixing silane coupling agent and anhydrous ethanol at a mass ratio of 1:8, and then immerse the two types of dried fibers in the treatment solution respectively, with the fiber mass (g) to treatment solution volume (mL) controlled at 1:12, and the immersion time is 60 min; after immersion, take out the fiber, drain the excess liquid, and place it in a 60℃ oven to dry for 4 hours to complete the surface modification. It should be noted that in this embodiment, the conductive nanonetwork growth step is carried out before the silane coupling agent modification to obtain a better interfacial bonding effect, so that the carbon nanotubes and polypyrrole layers can be directly and firmly bonded to the fiber surface. Subsequently, the silane coupling agent further improves the compatibility between the fiber and the cement matrix.

[0042] In step (6) of the method for preparing ultra-high performance concrete, a directional magnetic field with a strength of 0.1T is used, and the magnetic field is applied for 15 minutes. The boric acid retarder was changed to borax retarder, and the hydroxypropyl methylcellulose dispersant was changed to polyethylene glycol (molecular weight 4000) dispersant.

[0043] Example 3 The difference compared to Example 1 is as follows: The fiber pretreatment process is as follows: Recycled carbon fibers and recycled glass fibers are dried in a 70℃ oven for 20 hours to remove surface moisture. Then, the following steps are performed: ① In-situ growth of carbon nanotubes on the surface of recycled carbon fibers: The dried recycled carbon fibers are immersed in a solution containing a nickel nitrate catalyst (0.05 mol / L), with a solid-liquid ratio controlled at 1:20 during immersion. After immersion for 45 minutes, the fibers are removed and dried at 90℃. Then, the catalyst-loaded recycled carbon fibers are placed in a tube furnace and heated to 600℃ under an Ar / H2 atmosphere. Acetylene gas is introduced (flow rate 50 mL / min) and reacted for 20 minutes, allowing uniform growth of nanotubes with a length of 1~5 μm and a diameter of 10~30 μm on the fiber surface. ① Carbon nanotubes of nm; after the reaction, cool to room temperature in Ar atmosphere; ② In-situ polymerization of conductive polymer layer on the surface of recycled glass fiber: immerse the dried recycled glass fiber in a mixed aqueous solution containing pyrrole monomer (0.5 mol / L) and oxidant FeCl3 (1 mol / L), with a solid-liquid ratio of 1:25 between the recycled glass fiber and the mixed aqueous solution, and stir at room temperature for 1 hour to form a uniform polypyrrole conductive coating on the fiber surface; after the reaction, remove the fiber, wash repeatedly with deionized water to remove unreacted monomers and homopolymers, and vacuum dry at 60℃; ③ Surface magnetization treatment: disperse the recycled carbon fiber with grown carbon nanotubes in a solution containing Fe²⁺. + / Fe³ + In an alkaline solution of salt (made of FeCl2·4H2O and FeCl3·6H2O in a molar ratio of Fe²⁺), + :Fe³ + = 1:2 mixture, total iron concentration 0.3 mol / L, and pH adjusted to 10.5 with NaOH solution), recycled carbon fibers are added to the mixed solution at a solid-liquid ratio of 1:75, and reacted at 50℃ for 60 min under nitrogen protection to further deposit nano-Fe3O4 particles (particle size 10~30 nm) on the fiber surface; after the reaction, the fibers are repeatedly washed with deionized water until the washing solution is neutral, and then dried at 60℃ for 12 hours; ④ The silane coupling agent modification method is the same. It should be noted that in this embodiment, the conductive nanonetwork growth step is carried out before the silane coupling agent modification to obtain a better interfacial bonding effect, so that the carbon nanotubes and polypyrrole layers can be directly and firmly bonded to the fiber surface. Subsequently, the silane coupling agent further improves the compatibility between the fiber and the cement matrix.

[0044] In step (6) of the method for preparing ultra-high performance concrete, a directional magnetic field with a strength of 0.5 T is used, and the magnetic field is applied for 5 minutes. The hydroxypropyl methylcellulose dispersant was changed to sodium dodecyl sulfate dispersant.

[0045] Comparative Example 1 Compared with Example 1, the difference is that 52.5 sulfoaluminate cement is replaced with 52.5 ordinary silicate cement.

[0046] Comparative Example 2 Compared with Example 1, the difference is that rice husk ash is replaced with fly ash of the same particle size and dosage.

[0047] Comparative Example 3 Compared with Example 1, the difference is that the addition of the retarder boric acid is omitted.

[0048] Comparative Example 4 Compared with Example 1, the difference is that the dispersant hydroxypropyl methylcellulose was omitted.

[0049] Comparative Example 5 Compared with Example 1, the difference is that the use of silane coupling agent KH550 is omitted, that is, silane modification is not carried out in the pretreatment stage of recycled carbon fiber and recycled glass fiber.

[0050] Comparative Example 6 Compared with Example 1, the difference is that the addition of modified recycled fibers (including modified recycled carbon fibers and modified recycled glass fibers) is omitted.

[0051] Comparative Example 7 Compared with Example 1, the difference is that the volume substitution rate of modified recycled carbon fiber is adjusted to 2 vol.%, and modified recycled glass fiber is not used.

[0052] Comparative Example 8 Compared with Example 1, the difference is that the volume substitution rate of modified recycled glass fiber is adjusted to 2 vol.%, and modified recycled carbon fiber is not used.

[0053] Comparative Example 9 The difference compared to Example 1 is that no directional magnetic field is applied during the molding and curing process.

[0054] Comparative Example 10 Compared with Example 1, the difference is that the modified recycled carbon fiber is replaced with commercially available ordinary carbon fiber, and the modified recycled glass fiber is replaced with commercially available ordinary glass fiber.

[0055] Comparative Example 11 Compared with Example 1, the difference is that the surface magnetization treatment of recycled carbon fibers is omitted, and the original recycled carbon fibers are used directly. Furthermore, the ultra-high performance concrete based on recycled wind turbine blade fiber-reinforced sulfoaluminate cement is composed of the following raw materials in parts by weight: 100 parts of 52.5 sulfoaluminate cement, 20 parts of rice husk ash, 20 parts of silica fume, 15 parts of 200-mesh quartz powder, 100 parts of 40-70 mesh river sand, a total volume replacement rate of 2% for modified recycled fibers, of which the volume replacement rate of modified recycled carbon fibers is 1.5%, the volume replacement rate of modified recycled glass fibers is 0.5%, boric acid is 0.5 parts, hydroxypropyl methylcellulose is 0.1 parts, polycarboxylate superplasticizer is 0.8 parts, and water is 25 parts.

[0056] Comparative Example 12 Compared with Example 1, the difference lies in the omission of the steps of in-situ growth of carbon nanotubes on the surface of recycled carbon fibers and in-situ polymerization of conductive polymer layers on the surface of recycled glass fibers during fiber pretreatment, and the omission of magnetization of the surface of recycled carbon fibers. Furthermore, the ultra-high performance concrete based on recycled wind turbine blade fiber-reinforced sulfoaluminate cement is composed of the following raw materials in parts by weight: 140 parts of 52.5 sulfoaluminate cement, 30 parts of rice husk ash, 30 parts of silica fume, 30 parts of 400-mesh quartz powder, 150 parts of 40-70 mesh quartz sand, a total volume replacement rate of 2% for modified recycled fibers, of which the volume replacement rate of modified recycled carbon fibers is 1.5%, the volume replacement rate of modified recycled glass fibers is 0.5%, 1.5 parts of borax, 0.3 parts of hydroxypropyl methylcellulose, 1.5 parts of polycarboxylate superplasticizer, and 30 parts of water.

[0057] Comparative Example 13 Compared with Example 1, the differences are as follows: the volume substitution rate of modified recycled carbon fiber and the volume substitution rate of modified recycled glass fiber are adjusted to 1 vol.% and 1 vol.%, respectively; the retarder is changed from boric acid to citric acid; the mass ratio of silane coupling agent to anhydrous ethanol in the fiber pretreatment process is changed from 1:10 to 1:12; and the ratio of fiber mass to treatment liquid volume is adjusted from 1:8 to 1:15. In addition, the ultra-high performance concrete based on fiber-reinforced sulfoaluminate cement for recycled wind turbine blades is composed of the following raw materials in parts by weight: 120 parts of 52.5 sulfoaluminate cement, 25 parts of rice husk ash, 25 parts of silica fume, 30 parts of 400-mesh quartz powder, 150 parts of 40-70 mesh river sand, a total volume replacement rate of 2% for modified recycled fibers, of which the volume replacement rate of modified recycled carbon fiber is 1.5%, the volume replacement rate of modified recycled glass fiber is 0.5%, 2.0 parts of borax, 0.5 parts of hydroxypropyl methylcellulose, 2.0 parts of polycarboxylate superplasticizer, and 40 parts of water.

[0058] Comparative Example 14 Compared with Example 1, the difference is that the volume substitution rate of the modified recycled glass fiber was adjusted to 1.5 vol.%, while the volume substitution rate of the modified recycled carbon fiber was adjusted to 0.5 vol.%. Furthermore, during the magnetization treatment of the recycled carbon fiber surface, the recycled carbon fiber with grown carbon nanotubes was dispersed in an alkaline solution containing Fe²⁺ / Fe³⁺ salt (a mixture of FeCl₂·4H₂O and FeCl₃·6H₂O in a molar ratio of Fe²⁺:Fe³⁺ = 1:1.5, with a total iron concentration of 0.3 mol / L, and the pH adjusted to 11 with NaOH solution). The recycled carbon fiber was added to this mixed solution at a solid-liquid ratio of 1:100, and reacted at 60°C for 45 min under nitrogen protection, further depositing nano-Fe₃O₄ particles (particle size 10~30 nm) on the fiber surface.

[0059] The solidification time, electromagnetic shielding performance, compressive strength, flexural strength, resistance to sulfate corrosion and resistance to chloride corrosion of the above component samples were evaluated, and the test and evaluation results are shown in Table 1.

[0060] Setting time test: The setting time of cement paste was determined by the Vicat method according to GB / T 1346-2011. During the test, the cement paste was mixed under standard consistency water conditions, and the specimens were cured in a standard curing chamber at a temperature of 20±1℃ and a relative humidity of not less than 90%. The initial setting time and the final setting time were recorded as the test results.

[0061] Electromagnetic performance testing: The main range of the 5G band is 3~6GHz. Using an E5071C microwave vector network analyzer, the electromagnetic parameters of the SF-SAC solid rectangular sample in the 3.94~5.99 GHz frequency range were tested using the waveguide method. The waveguide type was WR-187, and the field source emission power was 2.54 mW.

[0062] Mechanical property testing: According to GB / T 50081-2019, the compressive strength test was carried out on a cubic specimen with dimensions of 100 mm × 100 mm × 100 mm. The curing period of the specimen was 28 days, and the average value of the three results was taken as the experimental value of compressive strength.

[0063] Flexural strength test: According to GB / T 50081-2019, the flexural strength test was carried out on prism specimens with dimensions of 150 mm × 150 mm × 600 mm. The curing period of the specimens was 28 days, and the average value of the three results was taken as the experimental value of flexural strength.

[0064] Sulfate erosion resistance test: According to GB / T 749-2008 "Test Method for Sulfate Erosion Resistance of Cement", the immersion method was used to determine the sulfate erosion resistance coefficient of the specimens. Prismatic specimens with dimensions of 40 mm × 40 mm × 160 mm were cured under standard conditions for 28 days, then immersed in clean water and a 5% Na₂SO₄ solution for 90 days respectively. The flexural strength of both was tested. The sulfate erosion resistance of the material was evaluated using the erosion coefficient K (the ratio of the flexural strength of the specimen immersed in Na₂SO₄ solution to that of the specimen immersed in clean water). The closer the K value is to 1, the better the erosion resistance.

[0065] Chloride erosion resistance test: According to the rapid chloride ion migration coefficient method (RCM method) in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", the chloride ion diffusion coefficient of the specimen after 28 days of curing was tested (unit: ×10). - (¹² m² / s). The specimen is a cylinder with dimensions of Φ100 mm × 50 mm. A DC voltage of 30 V is applied, and after 24 hours of operation, the chloride ion penetration depth is measured, and the chloride ion diffusion coefficient is calculated. The smaller the diffusion coefficient, the better the resistance to chloride salt corrosion.

[0066] Table 1. Test results of the comprehensive performance of ultra-high performance concrete prepared in each embodiment and comparative example.

[0067] As can be seen from the test results in Table 1, Example 1 achieved the highest performance in all three indicators: electromagnetic shielding effectiveness (62 dB), compressive strength (152 MPa), and flexural strength (32 MPa). Simultaneously, it achieved a sulfate resistance coefficient of 0.96 and a chloride ion diffusion coefficient as low as 0.8 × 10⁻⁶. - The ¹² m² / s indicates that it not only has excellent mechanical and shielding properties, but also exhibits outstanding long-term durability in high-humidity and high-salt-spray marine environments. Regarding setting time, Example 1 has an initial setting time of 50 min, falling precisely within the 45-90 min initial setting window required by this invention, and a moderate final setting time (95 min), ensuring sufficient construction time without affecting demolding efficiency due to slow setting. In contrast, other examples with added retarders (Examples 2-3 and Comparative Examples 2, 4, 5, 11-14) generally have initial setting times between 38 and 48 min. Although significantly longer than Comparative Example 3 (20 min) without retarders, these times are still slightly below the ideal lower limit of 45 min, indicating a relatively tight construction window. While Comparative Example 1 has a longer initial setting time (60 min), its final setting time is as long as 150 min, which is detrimental to rapid demolding and production efficiency. Therefore, Example 1 achieves the most balanced and excellent setting performance while ensuring sufficient construction time and production efficiency.

[0068] Comparative Examples 11 and 12 show that magnetization and conductive nanonetwork growth each have their own focus but are both indispensable. Comparative Example 11 omitted magnetization, resulting in the carbon fibers failing to orient themselves in a magnetic field. This reduced the shielding effectiveness to 50 dB and the flexural strength to 29 MPa. Simultaneously, the sulfate resistance coefficient slightly decreased to 0.94, while the chloride ion diffusion coefficient increased to 1.1 × 10⁻¹² m² / s. This is because the lack of oriented carbon fiber arrangement led to a slight decrease in matrix density and an increase in ion penetration channels. Its initial setting time (38 min) was significantly shorter than that of Example 1. This is because the unmagnetized carbon fiber surface lacked an Fe₃O₄ particle layer, weakening the physical resistance to cement hydration and resulting in a slightly poorer retarding effect. Comparative Example 12 omitted the conductive nanonetwork, allowing only "point contact" between fibers, further reducing the shielding effectiveness to 40 dB. However, its magnetization orientation still resulted in a slightly higher flexural strength (30 MPa) than Comparative Example 11, while its durability index (K=0.93, diffusion coefficient 1.2×10⁻¹² m² / s) was slightly inferior to Example 1. Its initial setting time of 40 min was also lower than Example 1. This indicates that the conductive nanonetwork contributes more to the shielding effectiveness, while the magnetization orientation contributes more significantly to the mechanical properties and durability; both must be present simultaneously to achieve the best effect.

[0069] Comparing the fiber blending ratios, Comparative Example 13 adjusted the volume substitution ratio of recycled carbon fiber to recycled glass fiber to 1:1, resulting in a relatively lower carbon fiber ratio. This led to a decrease in conductive network density and a reduction in shielding effectiveness to 56 dB. Simultaneously, the increased glass fiber content produced a certain "isolation-dilution" effect, with limited improvement in mechanical properties; compressive strength decreased to 140 MPa and flexural strength to 28 MPa. Its sulfate resistance coefficient decreased to 0.91, while its chloride ion diffusion coefficient increased to 1.5 × 10⁻¹² m² / s, indicating that the imbalance in fiber ratio led to an increase in internal matrix defects and a significant decrease in durability. Its initial setting time was 42 min, lower than Example 1, possibly due to the reduced carbon fiber content, which weakened the overall physical adsorption of moisture by the fibers and the retarding effect of the surface modification layer on cement hydration. Comparative Example 14 further adjusted the ratio of recycled carbon fiber to recycled glass fiber to 0.5:1.5. The carbon fiber ratio was significantly too low, resulting in a sparse conductive network and a shielding effectiveness reduced to 50 dB. Excess glass fiber did not provide the expected reinforcement effect; the compressive strength was 144 MPa, the flexural strength was 28 MPa, and the mechanical properties were not improved. Its durability indicators (K=0.92, diffusion coefficient 1.3×10⁻¹² m² / s) were also lower than in Example 1, with an initial setting time of 44 min. These two examples fully demonstrate that 1.5:0.5 is the optimal mixing ratio of recycled carbon fiber to recycled glass fiber in this invention, achieving the best synergistic effect of the "conductive-mechanical" dual-network structure.

[0070] In Example 2, the retarder was replaced with borax instead of boric acid. The shielding effectiveness decreased to 58 dB, compressive strength decreased to 146 MPa, flexural strength decreased to 29 MPa, sulfate resistance decreased to 0.93, and chloride ion diffusion coefficient increased to 1.1 × 10⁻¹² m² / s. The initial setting time was 46 min, shorter than in Example 1, indicating that boric acid is not only more precise and effective in controlling setting time, but also superior to borax in its auxiliary effect on fiber dispersion and improvement of matrix density. In Example 3, the dispersant was replaced with sodium dodecyl sulfate instead of hydroxypropyl methylcellulose. The shielding effectiveness decreased to 59 dB, compressive strength was 150 MPa, and flexural strength was 30 MPa, still at a high level. However, the sulfate resistance decreased to 0.95, and the chloride ion diffusion coefficient increased to 1.0 × 10⁻¹² m² / s. The initial setting time was 48 min, slightly shorter than in Example 1. This indicates that the anionic dispersant sodium dodecyl sulfate has a less effective effect on retarding cement hydration and on steric hindrance of fibers than the nonionic hydroxypropyl methylcellulose, resulting in a slight decrease in the density of the matrix microstructure and lower durability than in Example 1. In conclusion, boric acid and hydroxypropyl methylcellulose are the optimal combination after screening, and their synergistic effect on fiber dispersion, matrix density, and setting time control is the best overall result.

[0071] In Comparative Example 1, replacing sulfoaluminate cement with ordinary silicate cement resulted in severe corrosion of the glass fibers due to the high-alkali environment. The flexural strength plummeted from 32 MPa to 18 MPa, the shielding effectiveness dropped to 32 dB, the sulfate attack resistance coefficient became as low as 0.72, and the chloride ion diffusion coefficient reached as high as 3.8 × 10⁻⁶. - The ¹² m² / s ratio demonstrates the protective effect of low-alkali sulfoaluminate cement on recycled glass fibers, while also indicating that the durability of ordinary silicate cement matrix in marine environments is far inferior to that of sulfoaluminate cement systems. Its initial setting time is 60 min, and its final setting time is 150 min. Although the initial setting time is within the range of 45-90 min, the excessively long final setting time is due to the inherent hydration characteristics of ordinary silicate cement, and not an ideal result of retarder regulation.

[0072] Comparative Example 2, when rice husk ash was replaced with fly ash, resulted in the complete loss of pozzolanic activity, micro-aggregate filling, and surface adsorption functions. Shielding effectiveness decreased to 30 dB, compressive strength decreased to 130 MPa, flexural strength decreased to 22 MPa, sulfate resistance decreased to 0.85, and chloride ion diffusion coefficient increased to 2.5 × 10⁻⁶. - The ¹² m² / s indicates that rice husk ash is a key auxiliary cementitious material, and its absence significantly reduces the matrix density and erosion resistance. Its initial setting time was 40 min, lower than in Example 1, because fly ash has a weaker retarding effect than ultrafine rice husk ash, while the high specific surface area and silanol functional groups of rice husk ash help adsorb retarders, thereby prolonging the setting time.

[0073] Comparative Examples 3, 4, and 5, which omitted the retarder, dispersant, and silane coupling agent respectively, showed severe deterioration in fiber dispersion and interfacial adhesion, resulting in a comprehensive decline in performance. Comparative Example 3, without a retarder, had an initial setting time of only 20 min and a final setting time of 70 min. This rapid setting prevented uniform fiber dispersion, resulting in a shielding effectiveness of only 22 dB and a flexural strength of 22 MPa. Comparative Example 4, without a dispersant, had an initial setting time of 42 min and a final setting time of 85 min. Although this was longer than without a retarder, severe fiber agglomeration still resulted in poor performance (21 dB, 22 MPa). Comparative Example 5, without a silane coupling agent, had an initial setting time of 44 min and a final setting time of 86 min. Debonding occurred at the fiber-matrix interface, resulting in a flexural strength of only 16 MPa and a shielding effectiveness of only 16 dB. These three examples demonstrate that the retarder, dispersant, and silane coupling agent are all indispensable; otherwise, the fibers cannot be uniformly dispersed, and the interfacial adhesion is weak, allowing corrosive media to easily penetrate along the fiber-matrix interface.

[0074] Comparative Example 6, without any added fibers, has a shielding effectiveness of only 3 dB, a compressive strength of 110 MPa, a flexural strength of 15 MPa, a sulfate resistance coefficient of 0.88, and a chloride ion diffusion coefficient of 2.0 × 10⁻⁶. - ¹² m² / s provides a benchmark for matrix performance and demonstrates that the introduction of fibers is not only key to achieving electromagnetic shielding and ultra-high performance, but also improves the crack resistance and impermeability of the matrix through the bridging and filling effects of fibers. Its initial setting time is 35 min, and its final setting time is 60 min, which is relatively short because the hydration of cement paste without fibers is not affected by the fiber surface modification layer, and there is no fiber adsorption of water, thus setting faster.

[0075] Comparative Example 7 used pure recycled carbon fiber (volume replacement rate of 2%) without adding recycled glass fiber. The shielding effectiveness reached 55 dB, but due to the complete lack of the toughening effect and dielectric modulation capability of glass fiber, the compressive strength decreased to 138 MPa, the flexural strength decreased to 26 MPa, the sulfate resistance coefficient was only 0.90, and the chloride ion diffusion coefficient increased to 1.8 × 10⁻⁶. - ¹² m² / s, resulting in significant deterioration in durability. Its initial setting time was 40 min, shorter than that of Example 1, reflecting the insufficient retarding effect of the single carbon fiber system on cement hydration.

[0076] Comparative Example 8 used pure recycled glass fiber without adding recycled carbon fiber. Its shielding effectiveness plummeted to 22 dB, providing almost no electromagnetic protection. Its compressive strength was 132 MPa, and its flexural strength was 26 MPa, with mechanical properties also far lower than Example 1. Its initial setting time was 46 min; despite the longer setting time, it exhibited the worst durability (K=0.89, diffusion coefficient 1.7×10⁻⁶). -(¹²m² / s), because the interfacial bonding between pure glass fiber and the cement matrix is ​​weak, and the interface is prone to becoming a channel for rapid penetration of corrosive media during long-term service. Comparative Examples 7 and 8 fully demonstrate that a single fiber cannot construct a "conductive-mechanical" dual-network synergistic structure, and hybrid fiber design is a necessary prerequisite for achieving structural-functional integration.

[0077] Comparative Example 9, which eliminated the directional magnetic field induction process, saw its shielding effectiveness plummet from 62 dB to 42 dB, a decrease of 32%. Its flexural strength also dropped from 32 MPa to 30 MPa, directly verifying the outstanding technical effect of magnetic field-assisted orientation technology, which can improve shielding effectiveness perpendicular to the fiber orientation direction by more than 50%. Simultaneously, without magnetic field orientation, the sulfate resistance coefficient slightly decreased from 0.96 to 0.94, and the chloride ion diffusion coefficient decreased from 0.8 × 10⁻⁶. - ¹² m² / s increased to 1.0 × 10⁻⁶ - The ¹² m² / s further demonstrates that the directional arrangement of carbon fibers not only enhances mechanical and shielding properties but also improves the matrix's impermeability by optimizing fiber spatial distribution. Its initial setting time of 48 min is similar to that of Example 1, indicating that the magnetic field itself has no significant impact on the slurry's chemical process.

[0078] Comparative Example 10 used commercially available ordinary carbon fiber and glass fiber to replace the recycled fiber of the present invention in equal amounts. The shielding effectiveness was 50 dB, the compressive strength was 146 MPa, the flexural strength was 30 MPa, and the durability index (K=0.94, diffusion coefficient 1.2×10) was [not specified]. - While the efficiency (¹² m² / s) is slightly lower than that of Example 1, the overall performance remains at a high level. This precisely highlights the core advantage of the present invention: under the premise of realizing high-value utilization of solid waste from retired wind turbine blades and significantly reducing environmental impact, the key performance indicators of the material have reached a level comparable to or even better than those using virgin fibers. This is due to the rough surface and rich functional groups of the regenerated fibers, which are more conducive to the construction of conductive networks, truly embodying the circular economy concept of "turning waste into treasure without sacrificing performance".

[0079] In summary, Example 1 is optimal because it simultaneously integrates a cementing system of low-alkali sulfoaluminate cement and ultrafine rice husk ash, carbon nanotube growth and magnetized deposition on the carbon fiber surface, polypyrrole coating on the glass fiber surface, an optimal fiber mixing ratio of 1.5:0.5, and 0.3 T directional magnetic field-induced arrangement. The absence or alteration of any of these technical features would lead to a significant decrease in shielding effectiveness, mechanical properties, or durability, fully demonstrating that the technical solution represented by Example 1 possesses outstanding substantive characteristics and significant progress.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A retired wind turbine blade recycled fiber reinforced sulphoaluminate cementitious ultra-high performance concrete, characterized in that, include: The components are sulfoaluminate cement, rice husk ash, silica fume, quartz powder, fine aggregate, retarder, dispersant, polycarboxylate superplasticizer, modified recycled carbon fiber, modified recycled glass fiber, and water. The weight parts of each component are as follows: 100-140 parts of sulfoaluminate cement 20-30 parts rice husk ash 20-30 parts silica fume 15-30 parts quartz powder 100-150 parts fine aggregate, 0.5-2.0 parts of retarder. Dispersant 0.1~0.5 parts, Polycarboxylate superplasticizer, 0.8~2.0 parts. 25-40 parts water Furthermore, in each cubic meter of ultra-high performance concrete, the volume replacement rate of modified recycled carbon fiber is 1.5 vol.%, and the volume replacement rate of modified recycled glass fiber is 0.5 vol.%. The sulfoaluminate cement is 52.5 sulfoaluminate cement; The water reduction rate of the polycarboxylate superplasticizer is 22%~25%, and the solid content is 20%. The preparation method of the modified recycled carbon fiber and modified recycled glass fiber includes: placing the recycled carbon fiber and recycled glass fiber in an oven to dry them to remove surface moisture; then, the recycled carbon fiber is subjected to surface magnetization treatment and in-situ growth of conductive nanonetwork treatment; the recycled glass fiber is subjected to in-situ growth of conductive nanonetwork treatment; and finally, the two types of recycled fibers treated with the above methods are surface modified with a silane coupling agent. The oven temperature is set to 60~80℃ and the drying time is 12~24h. Both the recycled carbon fiber and recycled glass fiber are obtained from decommissioned wind turbine blades through cutting, crushing, and chemical recycling processes.

2. The retired wind turbine blade recycled fiber reinforced sulphoaluminate cementitious ultra high performance concrete according to claim 1, characterized in that, The specific recycling process for the recycled carbon fiber and recycled glass fiber is as follows: (1) The main structure of the decommissioned wind turbine blade after the removal of metal accessories is classified and processed. Specifically, the collected decommissioned wind turbine blades made of carbon fiber composite material and decommissioned wind turbine blades made of glass fiber composite material are operated separately as follows: the two types of fiber composite material decommissioned wind turbine blades are cut into block materials by high pressure water jet cutting machine, and then the block materials are fed into jaw crusher for coarse crushing and then into hammer crusher for fine crushing. The output particle size is controlled to be less than 20mm, and fragments containing glass fiber reinforced composite material and fragments containing carbon fiber reinforced composite material are obtained respectively. (2) The two fragments obtained in step (1) are respectively put into a high-speed vortex pulverizer for pulverization. The processing time is 5~8 min, and primary mixture I of carbon fiber and resin powder and primary mixture II of glass fiber and resin powder are obtained respectively. (3) The two primary mixtures obtained in step (2) are fed into an air classifier and separated by the difference in suspension velocity of the two fibers and resin powder in the airflow to obtain two fibers containing residual resin. (4) The two types of fibers containing residual resin obtained in step (3) are immersed in the chemical depolymerization solution and stirred continuously. After the stirring reaction is completed, the fibers are filtered out and washed repeatedly with deionized water until the washing solution is neutral. Then the washed fibers are placed in a vacuum drying oven to dry, and recycled carbon fiber and recycled glass fiber with clean surface are obtained respectively. The chemical depolymerization solution is prepared by mixing nitric acid and hydrogen peroxide in a volume ratio of 1:3~5. The preparation method of the modified recycled carbon fiber and modified recycled glass fiber using silane coupling agent modification specifically includes: preparing a treatment solution by mixing silane coupling agent and anhydrous ethanol at a mass ratio of 1:8~12; then completely immersing the dried recycled carbon fiber and recycled glass fiber in the treatment solution, with the solid-liquid ratio of fiber mass (g) to treatment solution volume (mL) controlled at 1:8~15, and the immersion time being 30~60 min; after immersion, removing the two types of recycled fibers, draining excess liquid, and drying them in an oven at 60~80℃ for 2~4 hours to complete the surface modification of the recycled fibers; the silane coupling agent is KH550.

3. The retired wind turbine blade recycled fiber reinforced sulphoaluminate cementitious ultra high performance concrete according to claim 2, characterized in that, In the recycling process of the recycled carbon fiber and recycled glass fiber, the size of the block material in step (1) is 300 mm × 300 mm; The blade tip linear velocity of the high-speed eddy current pulverizer rotor in step (2) is 35~50m / s; The specific separation method in step (3) is as follows: the fan speed in the airflow separator is controlled by the frequency converter, and the airflow speed in the airflow separator is controlled within the range of 1.0~2.5m / s. Under this wind speed, the light fibers are enriched with the airflow and enter the collector, while the heavy resin powder settles, and carbon fibers containing residual resin and glass fibers containing residual resin are obtained respectively. In step (4), the solid-liquid ratio of the carbon fiber containing residual resin, the glass fiber containing residual resin, and the chemical depolymerization solution is controlled to be 1:15~25; the stirring reaction temperature is set to 60~80℃, and the continuous stirring reaction time is set to 4~8h; the vacuum drying oven temperature is set to 60~80℃, and the drying time is set to 8~12h. The recycled carbon fiber has a length of 3-15 mm, an average diameter of 5-10 μm, and an apparent density of 1650-1950 kg / m³, while the recycled glass fiber has a length of 12-20 mm, an average diameter of 10-20 μm, and an apparent density of 1500-1800 kg / m³.

4. The ultra-high performance concrete based on recycled fiber-reinforced sulfoaluminate cement as described in claim 1, characterized in that, The sulfoaluminate cement is rapid-hardening sulfoaluminate cement or low-alkalinity sulfoaluminate cement with an alkalinity pH value < 10.

5. The average particle size of the silica fume is 0.1-0.2 μm, and the specific surface area is 18000-20000 m 2 / kg; The quartz powder has a particle size of 200-400 mesh; The fine aggregate is river sand or quartz sand with a particle size of 40-140 mesh; The rice husk ash is ultrafine rice husk ash with an average particle size of 1~3μm, an active silica content of more than 98%, and is a neutral material; The retarder is selected from any one or more of boric acid, borax, citric acid, and sodium gluconate to ensure that the initial setting time of sulfoaluminate cement is adjusted to 45-90 min and the final setting time is controlled accordingly to 70-120 min. The dispersant is selected from any one or a mixture of more than one of hydroxypropyl methylcellulose, polyethylene glycol, sodium dodecyl sulfate, and sodium carboxymethyl cellulose.

5. A method for preparing recycled fiber-reinforced sulfoaluminate cement-based ultra-high performance concrete for decommissioned wind turbine blades as described in any one of claims 1 to 4, characterized in that, Specifically, the following steps are included: (1) Fiber pretreatment: Regenerated carbon fiber is subjected to surface magnetization treatment and surface in-situ growth of conductive nano-network treatment in sequence, and regenerated glass fiber is subjected to surface in-situ growth of conductive nano-network treatment. Then, silane coupling agent is used to modify the surface of the two types of regenerated fibers after the above treatment to obtain modified regenerated carbon fiber and modified regenerated glass fiber. (2) Dry material mixing: Weigh out sulfoaluminate cement, silica fume, rice husk ash, quartz powder and fine aggregate according to the proportion, put them into a forced mixer and dry mix for 4~6 minutes to make the powder and aggregate evenly mixed to obtain mixed dry material; (3) Fiber dispersion: The pretreated modified recycled carbon fiber and modified recycled glass fiber are premixed with a dispersant accounting for 1 / 3 to 1 / 2 of the total amount of dispersant, so that the dispersant is uniformly attached to the fiber surface. Then the fiber mixture is slowly added to the dry mixture in step (2) and dry mixing is continued for 2 to 4 minutes to allow the fiber to be initially dispersed in the powder, thus obtaining a fiber-dry mixture. (4) Liquid preparation: Dissolve the retarder, remaining dispersant, and polycarboxylate superplasticizer in all the water and stir to form a uniform mixed solution; (5) Slurry mixing: Slowly add the mixed solution to the fiber-dry material mixture, first stir at low speed for 1-2 minutes, then switch to high speed for 2-4 minutes until a uniform, fluid slurry is formed; The low-speed stirring speed is 50~80 r / min; The high-speed stirring speed is 120~180 r / min; (6) Molding and curing: Pour the slurry mixed in step (5) into the mold and vibrate it on the vibrating table for 1 to 2 minutes to remove air bubbles; cover the outside of the mold with plastic film and cure it for 24 hours at 20±2℃ and relative humidity ≥95%. After demolding, continue to cure it in the standard curing room for 28 days to obtain the ultra-high performance concrete; the temperature in the standard curing room is 20±2℃ and the relative humidity is ≥95%.

6. The preparation method according to claim 5, characterized in that, Before the silane modification in the pretreatment stage, the recycled carbon fiber described in step (1) was also subjected to surface magnetization treatment, that is, nano-iron oxide particles were deposited on the surface of the recycled carbon fiber by chemical co-precipitation method, and the particle size was controlled at 10~30nm. Before the silane modification in the pretreatment stage, the recycled carbon fiber and recycled glass fiber in step (1) are subjected to in-situ surface growth of conductive nano-network. Specifically, for the recycled carbon fiber, carbon nanotubes are grown by chemical vapor deposition; for the recycled glass fiber, a polypyrrole conductive layer is coated by in-situ polymerization.

7. The preparation method according to claim 6, characterized in that, The specific steps for surface magnetization treatment of the recycled carbon fiber are as follows: The dried regenerated carbon fiber is dispersed in a solution containing Fe 2+ / Fe 3+ The surface of the fiber is deposited with nano Fe3O4 particles under nitrogen protection at 50-80°C for 30-60 min under continuous stirring; after the reaction is completed, the regenerated carbon fiber is repeatedly washed with deionized water until the solution is neutral, and then the regenerated carbon fiber is dried in a vacuum drying box at 60-80°C for 6-12 h to obtain regenerated carbon fiber with magnetic response characteristics. The Fe 2+ / Fe 3+ The salt is a mixture of FeCl2·4H2O and FeCl3·6H2O, Fe 2+ : Fe 3+ The molar ratio of the two is 1:1.5~2, the alkaline solution is a NaOH solution with a concentration of 0.5~1.0 mol / L, the pH value of the alkaline reaction system is maintained at 10~11; the solid-liquid ratio of the regenerated carbon fiber and the alkaline solution of the Fe 2+ / Fe 3+ salt is 1:50~100.

8. The preparation method according to claim 6, characterized in that, The in-situ growth of conductive nanonetworks on the surface of the recycled carbon fiber specifically includes: completely immersing the dried recycled carbon fiber with magnetic response characteristics in a solution containing a nickel or iron catalyst for impregnation; after impregnation, filtering out the fiber and drying it to constant weight; then placing it in a tube furnace and heating it to 600-800℃ under an inert atmosphere, introducing acetylene as the carbon source gas to carry out the reaction, so that carbon nanotubes with a length of 1-5 μm and a diameter of 10-30 nm are uniformly grown on the fiber surface; after the reaction, cooling it to room temperature under an inert atmosphere; the solution containing the nickel or iron catalyst is an aqueous solution of nickel nitrate or iron nitrate, each with a concentration of 0.05-0.2 mol / L; during the impregnation process, the solid-liquid ratio of the mass (g) of the recycled carbon fiber to the volume (mL) of the catalyst solution is controlled at 1:10-20, and the impregnation time is 30-60 min; after impregnation, the drying temperature is 80-100℃; the flow rate of the acetylene gas is controlled at 50-200 mL / min, and the reaction time is 5-20 min. The in-situ growth of conductive nanonetworks on the surface of the recycled glass fiber specifically includes: immersing the recycled glass fiber in a mixed aqueous solution containing pyrrole monomer and oxidant FeCl3, continuously stirring at room temperature to form a uniform polypyrrole conductive coating on the fiber surface; after the reaction, removing the fiber, repeatedly washing it with deionized water to remove unreacted monomers and homopolymers, and vacuum drying to constant weight; the concentration of pyrrole monomer in the mixed aqueous solution is 0.1~0.5 mol / L, the concentration of FeCl3 is 0.2~1.0 mol / L, and the molar ratio of pyrrole monomer to FeCl3 is 1:2~1:3; the solid-liquid ratio of the recycled glass fiber to the mixed aqueous solution is 1:15~25; the immersion time is 1~4 hours; and the vacuum drying temperature is 60℃.

9. The preparation method according to claim 6, characterized in that, Step (6) also includes arranging electromagnetic coils around the mold covered with plastic film to generate a directional magnetic field with an intensity of 0.1~0.5T. The direction of the magnetic field is set to be perpendicular to the electromagnetic wave incident direction or parallel to the principal stress direction of the component according to the target requirements. The magnetic field is maintained for 5~15 minutes until the slurry initially solidifies and sets, thereby inducing the regenerated carbon fibers with magnetic response to be oriented along the direction of the magnetic field.

10. The preparation method according to claim 5, characterized in that, When the ultra-high performance concrete is used for large components such as wind turbine towers or nacelle covers, the pouring process in step (6) of the preparation method is replaced by vacuum-assisted grouting or pressure grouting.

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