Methods and applications for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades

Abstract

This invention belongs to the field of building materials technology, and provides a method and application for improving the interfacial bonding performance of recycled GFRP fiber-UHPC in decommissioned wind turbine blades. Addressing the problem of insufficient interfacial bonding performance between recycled epoxy resin-reinforced glass fiber and ultra-high performance concrete (UHPC) in decommissioned wind turbine blades, the method involves ultrasonically cleaning and pre-treating the fibers, preparing a mixed solution of silane hydrolysate and nano-silica, and then ultrasonically dispersing it to achieve uniform coating on the fiber surface, ultimately obtaining modified fibers with optimized interfacial performance. Single-fiber pull-out experiments show that compared to unmodified GFRP fibers, the modified GFRP fibers exhibit a 170.40% increase in peak pull-out load, a 96.80% increase in pull-out energy, and a 66.7% increase in bond strength with the UHPC matrix, significantly improving the stress transfer efficiency at the recycled GFRP fiber-UHPC matrix interface. This method is simple, low-cost, and provides an efficient and environmentally friendly treatment method for the recycling of decommissioned wind turbine blades, and also offers an effective solution for the engineering application of recycled GFRP fibers in UHPC.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to the recycling and utilization of solid waste from decommissioned wind turbine blades, surface modification technology and methods for regenerated GFRP fibers, and more specifically, a method and application for improving the interfacial bonding performance of regenerated GFRP fibers-UHPC in decommissioned wind turbine blades. Background Technology

[0002] Ultra-high performance concrete (UHVPC) has become a highly promising cement-based composite material due to its high durability, workability, and excellent mechanical properties. However, its insufficient tensile strength has led to the widespread application of steel fiber reinforced UHVPC. Although steel fibers can significantly improve the tensile strength and performance under complex loads, the large-scale incorporation of steel fibers reduces the workability of UHVPC, increases costs, and causes voids and honeycombing during pouring due to their high stiffness. Furthermore, the heavy weight of steel fibers and their tendency to settle unevenly during vibration severely limit their reinforcing effect. Given the limitations of steel fiber applications, researchers have begun to explore new fiber-reinforced materials.

[0003] Recycled GFRP fibers from decommissioned wind turbine blades possess advantages such as lightweight, high strength, corrosion resistance, and low cost, theoretically capable of compensating for the performance shortcomings of ultra-high performance concrete. However, practical applications have revealed that the epoxy resin on the surface of recycled GFRP fibers lacks reactive and hydrophilic groups, and the surface of recycled GFRP fibers after mechanical crushing exhibits severe inherent defects, resulting in weak interfacial transition zones and porosity between the fiber and the matrix. This hinders the full realization of its reinforcing effect, becoming a key bottleneck preventing its further promotion and application in ultra-high performance concrete engineering. Therefore, how to improve the inherent defects of recycled GFRP and enhance the interfacial bonding performance between the fiber and the cement matrix has become an important issue urgently needing to be addressed in the field of concrete materials. Summary of the Invention

[0004] Addressing the technical bottleneck in the field of ultra-high performance concrete (UHVPC) where insufficient bonding between recycled GFRP fiber reinforcement and the matrix hinders the improvement of overall concrete strength, this invention aims to provide a surface-modified recycled GFRP fiber and its modification method. This innovative technique enhances the interfacial bonding performance between the fiber and the matrix, effectively overcoming existing technical challenges and significantly improving the strength and overall performance of UHVPC. Single-fiber pull-out experiments show that, compared to unmodified GFRP fibers, the modified GFRP fibers exhibit a 170.40% increase in peak pull-out load, a 96.80% increase in pull-out energy, and a 66.7% increase in bond strength with the UHVPC matrix, significantly improving the stress transfer efficiency at the recycled GFRP fiber-UHVPC matrix interface. This method is simple, low-cost, and provides an efficient and environmentally friendly treatment method for the recycling of retired wind turbine blades, while also offering an effective solution for the engineering application of recycled GFRP fibers in UHVPC.

[0005] The present invention solves the problems of the prior art by adopting the following technical solution: A method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades includes the following steps: S1 Preprocessing The retired wind turbine blades were immersed in deionized water and ultrasonically cleaned at 300-1050W for 15-60 minutes, then dried at 80-120℃ for 12 hours. The cleaning and drying process was repeated three times to obtain regenerated GFRP fibers for later use. S2 preparation of composite modified liquid A mixture of anhydrous ethanol and deionized water at a mass ratio of 3:1 was prepared. 2-16 wt% of silane coupling agent was added to the mixture and hydrolyzed for 15-60 min. 0.5-1.5 wt% of nano-silica was added to the mixture for dispersion treatment to obtain a mixed modified solution of nano-silica and silane coupling agent. S3 Ultrasonic Synergistic Modification The regenerated GFRP fibers of S1 are immersed in the mixed modification solution of S2 and dispersed by ultrasonic treatment at 300-1050W for 15-60 minutes to modify the surface of the regenerated GFRP fibers by grafting nano-silica. S4 Post-processing The modified regenerated GFRP fibers were rinsed with deionized water, dried at 80-120℃ for 12 hours, and then naturally cooled to obtain regenerated GFRP fibers with silica-assisted silane coupling agent surface modification.

[0006] The method for improving the interfacial bonding performance of regenerated GFRP fibers and UHPC fibers in decommissioned wind turbine blades is used in the preparation of concrete.

[0007] The application of recycled GFRP fibers in the decommissioned wind turbine blades, wherein the concrete comprises matrix material component A and modified recycled GFRP fibers C, and matrix material component A is a cement-based composite gel material; the matrix material component A and recycled GFRP fibers C are mixed and prepared in the following weight parts: matrix material component A comprises 800-1000 parts of cement, 150-250 parts of mineral admixtures, 800-1000 parts of fine aggregate, 180-210 parts of water, and 17-21 parts of water-reducing agent; and 30-50 parts of recycled GFRP fibers C.

[0008] The application of recycled GFRP fibers in the decommissioned wind turbine blades involves concrete comprising a matrix material component A, a reinforcing material component B, and modified recycled GFRP fibers C. Matrix material component A is a cement-based composite gel material, and reinforcing material component B is copper-plated steel fiber with a copper plating on its surface. The recycled GFRP fibers are prepared by mixing the matrix material component A, reinforcing material component B, and modified recycled GFRP fibers C in the following weight proportions: matrix material component A comprises 800-1000 parts cement, 150-250 parts mineral admixtures, 800-1000 parts fine aggregate, 180-210 parts water, and 17-21 parts water-reducing agent; reinforcing material component B comprises 130-160 parts copper-plated steel fiber; and recycled GFRP fibers C comprises 30-50 parts.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses ultrasonic modification process to modify the surface of pretreated regenerated GFRP fibers. The modification time is only 15 minutes. The process is simple to operate and does not require expensive precision equipment. The silane coupling agent and nano silica used are both commonly used industrial materials, which are inexpensive and environmentally friendly. The prepared composite modification liquid can be reused and still maintain the modification effect, which significantly reduces the material cost of large-scale production and fully meets the needs of engineering batch application.

[0010] (2) This invention uses nano-silica in conjunction with a silane coupling agent to modify regenerated GFRP fibers. Compared to the relatively smooth fiber surface after modification with a single silane coupling agent, the surface of the regenerated GFRP fibers after synergistic modification forms a dotted protrusion structure. The nano-silica on the surface of the regenerated GFRP fibers can significantly improve hydrophilicity, expand the contact area between the fiber and the matrix, improve interfacial friction and stress transfer efficiency, and provide abundant adhesion sites for hydration products, thereby effectively improving the mechanical properties of ultra-high performance concrete. Single fiber pull-out test data show that, compared with unmodified fibers, the peak pull-out load of single fibers in ultra-high performance concrete increased by 170.40%, the pull-out energy increased by 96.80%, and the bond strength increased by 66.7%, and the stress transfer efficiency of the fiber-matrix interface was significantly improved. Attached Figure Description

[0011] Figure 1 Flowchart for modifying and improving GFRP fibers for decommissioned wind turbine blades; Figure 2 This is a schematic diagram of a single fiber pull-out specimen; Figure 3 This is a microscopic morphology image of the surface of the modified recycled GFRP fiber; Figure 4 A comparison of the pull-out load-displacement curves of single fibers before and after modification; Figure 5 This is a comparison of the wetting angles of the surface of recycled GFRP fibers before and after modification. Detailed Implementation

[0012] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] A method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades includes the following steps: S1 Preprocessing The retired wind turbine blades were immersed in deionized water and ultrasonically cleaned at 300-1050W for 15-60 minutes, then dried at 80-120℃ for 12 hours. The cleaning and drying process was repeated three times to obtain regenerated GFRP fibers for later use. S2 preparation of composite modified liquid A mixture of anhydrous ethanol and deionized water at a mass ratio of 3:1 was prepared. 2-16 wt% of silane coupling agent was added to the mixture and hydrolyzed for 15-60 min. 0.5-1.5 wt% of nano-silica was added to the mixture for dispersion treatment to obtain a mixed modified solution of nano-silica and silane coupling agent. S3 Ultrasonic Synergistic Modification The regenerated GFRP fibers of S1 are immersed in the mixed modification solution of S2 and dispersed by ultrasonic treatment at 300-1050W for 15-60 minutes to modify the surface of the regenerated GFRP fibers by grafting nano-silica. S4 Post-processing The modified regenerated GFRP fibers were rinsed with deionized water, dried at 80-120℃ for 12 hours, and then naturally cooled to obtain regenerated GFRP fibers with silica-assisted silane coupling agent surface modification. S1 to S4 were used to modify retired blades to generate regenerated GFRP fibers.

[0014] The silane coupling agent is γ-aminopropyltriethoxysilane; the nano silica is fumed silica powder with a particle size of 20-30 nanometers, a specific surface area of ​​183-185 m2 / g, and a silica content of 99.9%.

[0015] The ultrasonic cleaning power in S1 is 1050 W; the cleaning time is 60 min.

[0016] In step S2, 14 wt% of silane coupling agent is added and hydrolyzed for 60 min to obtain a hydrolysate; then 1 wt% of nano-silica is added for dispersion treatment.

[0017] In step S3, ultrasonic dispersion at 1050W for 15 minutes is used to prevent nanoparticle aggregation.

[0018] The drying process in S1 and S4 is carried out at a temperature of 80°C.

[0019] Application of regenerated GFRP fibers prepared by a method for improving the interfacial bonding performance of regenerated GFRP fibers and UHPC in the preparation of concrete.

[0020] The application of recycled GFRP fibers in the decommissioned wind turbine blades, wherein the concrete comprises matrix material component A and recycled GFRP fibers C, matrix material component A being a cement-based composite gel material; recycled GFRP fibers C being modified recycled GFRP fibers. The matrix material component A and recycled GFRP fibers C are mixed and formulated in the following weight proportions: matrix material component A comprising 800-1000 parts cement, 150-250 parts mineral admixtures, 800-1000 parts fine aggregate, 180-210 parts water, and 17-21 parts water-reducing agent; and 30-50 parts recycled GFRP fibers C.

[0021] The application of recycled GFRP fibers in the decommissioned wind turbine blades involves concrete comprising a matrix material component A, a reinforcing material component B, and modified recycled GFRP fibers C. Matrix material component A is a cement-based composite gel material, and reinforcing material component B is copper-plated steel fiber with a copper plating on its surface. The recycled GFRP fibers are prepared by mixing the matrix material component A, reinforcing material component B, and modified recycled GFRP fibers C in the following weight proportions: matrix material component A comprises 800-1000 parts cement, 150-250 parts mineral admixtures, 800-1000 parts fine aggregate, 180-210 parts water, and 17-21 parts water-reducing agent; reinforcing material component B comprises 130-160 parts copper-plated steel fiber; and recycled GFRP fibers C comprises 30-50 parts.

[0022] Mineral admixtures refer to powdered materials with oxides such as silicon, aluminum, and calcium as their main components, used to improve concrete performance. The use of mineral admixtures should refer to the national standard "Technical Specification for Application of Mineral Admixtures" (GB / T 51003-2014). Fine aggregate particle size is 0.15~4.75mm, and the total volume of fine and coarse aggregates typically accounts for 70%~80% of the total concrete volume. Water-reducing agents are concrete admixtures that reduce the amount of mixing water while maintaining the slump of the concrete. Matrix material component A is the concrete base material, in which recycled GFRP fiber C is added to improve concrete performance. In particular, the modified recycled GFRP fiber C has a lower surface wetting angle, resulting in better surface wettability and easier spreading and penetration. The easily modified recycled GFRP fiber C, after mixing with matrix material component A, dries and cures to form a unified whole. Modified recycled GFRP fiber C significantly improves the crack resistance of concrete through the formation of a three-dimensional network structure and chemical bonding. The modified GFRP fiber C demonstrates that the modified material promotes the hydration of calcium hydroxide in concrete, enhancing the bond between the fiber and the matrix. Compared to unmodified recycled GFRP fiber, recycled GFRP fiber C can improve the tensile, flexural, impact, and shear strength of concrete while reducing the amount of copper-plated steel fiber required.

[0023] Furthermore, the preferred silane coupling agent is γ-aminopropyltriethoxysilane; due to the amino functional group structure in the molecule, the hydrolysate is alkaline, and it can efficiently connect organic resins and inorganic materials, significantly enhancing the interfacial bonding strength, improving durability in humid environments, and is applicable to a wide range of resin types. It also has high reactivity at room temperature, simple processing, and better cost performance than similar products.

[0024] Furthermore, the nano-silica powder is fumed silica with a particle size of 20-30 nanometers and a specific surface area of ​​183-185 m². 2 / g, with a silica content of 99.9%.

[0025] This invention modifies regenerated GFRP fibers using gas-phase nano-silica in conjunction with a silane coupling agent. Experiments show that, compared to silane coupling agent-modified regenerated GFRP fibers alone, the bond strength between the regenerated GFRP fibers and ultra-high performance concrete is significantly improved under the synergistic modification of this invention. This may be because ultrasonic dispersion solves the agglomeration problem of nano-silica on the surface of the regenerated GFRP fibers, while the protrusions of silica nanoparticles on the surface of the regenerated GFRP fibers increase the friction between the regenerated GFRP fibers and the ultra-high performance concrete matrix. The addition of the silane coupling agent greatly improves the dispersion stability of nano-silica in solution. The synergistic effect of the two ultimately enhances the bond strength between the modified regenerated GFRP fibers and ultra-high performance concrete.

[0026] Applying a coating to the surface of regenerated GFRP fibers, the completeness of coating adhesion and its thickness both affect the physicochemical bond and mechanical anchoring between the regenerated GFRP fibers and the ultra-high performance concrete matrix, reducing friction during the slippage stage and preventing premature pull-out of the regenerated GFRP fibers, which is detrimental to load transfer. This invention uses a composite modification of nano-silica and a silane coupling agent to regenerate GFRP fibers. The key technical problem to be solved is how to ensure that the nano-silica is firmly and dispersedly adsorbed on the surface of the regenerated GFRP fibers. This invention first prepares a silane hydrolysate, and experiments use three modification methods—ultrasonic dispersion, electromagnetic stirring, and static settling—to modify the regenerated GFRP fibers. Experiments show that the ultrasonic modification method results in uniform and complete coverage of the nano-silica on the surface of the regenerated GFRP fibers. Figure 4 As shown, a mixed solution was obtained by mixing nano-silica and silane coupling agent hydrolysate. Then, the regenerated GFRP fibers after ultrasonic cleaning were placed in the mixed solution for ultrasonic modification. Under appropriate ratio conditions, uniform coating of nano-silica and silane coupling agent on the surface of the regenerated GFRP fibers was achieved.

[0027] Furthermore, the ultrasonic cleaning power in S1 is 1050 W. A mixture of anhydrous ethanol and deionized water is prepared at a mass ratio of 3:1. 14 wt% of a silane coupling agent is added to the mixture for hydrolysis for 60 min. The mixture is then dispersed with 1 wt% nano-silica to obtain a mixed modified solution of nano-silica and the silane coupling agent. The ultrasonic dispersion power in S3 is 1050 W; the ultrasonic dispersion time is 15 min. The drying treatment described in S1 and S4 is performed at a drying temperature of 80℃ for 12 h.

[0028] The following is an example: Example 1 This embodiment comprises four parts: first, removal of impurities from the surface of regenerated GFRP fibers; second, preparation of a mixed solution of nano-silica and silane coupling agent; third, modification of regenerated GFRP fibers; and fourth, cleaning the surface of regenerated GFRP fibers and performing thermosetting. The regenerated GFRP fibers are obtained from the mechanical crushing of retired wind turbine blades. The original surface morphology and modification process are as follows... Figure 1 As shown.

[0029] Surface modification of recycled GFRP fibers includes the following steps: S1 Regenerated GFRP Fiber Pretreatment: Select 100×4×0.3 mm 3Regenerated GFRP fibers were soaked in deionized water and then ultrasonically cleaned at 1050 W for 60 min using an ultrasonic disperser. After cleaning, they were dried in a drying oven at 80℃ for 12 h. The cleaning and drying process was repeated three times to remove impurities from the surface of the regenerated GFRP fibers.

[0030] Preparation of S2 mixed solution: Weigh out 300 g of anhydrous ethanol and mix with 100 g of deionized water, then add 14% (56 g) of silane coupling agent (γ-aminopropyltriethoxysilane). Add the silane coupling agent to a solvent prepared by mixing deionized water and anhydrous ethanol, and let it stand at room temperature for 1 h to allow the silane coupling agent to complete hydrolysis. Then add 1.0% (4 g) of nano-silica and disperse again using ultrasound for 15 min to obtain a mixed solution of nano-silica and silane coupling agent.

[0031] S3 Regenerated GFRP Fiber Surface Modification Treatment: The cleaned regenerated GFRP fibers were immersed in a mixed solution of nano-silica and silane coupling agent, and dispersed using ultrasound at 1050 W for 15 min to obtain regenerated GFRP fibers with surface grafted nano-silica and silane coupling agent.

[0032] S4 recycled GFRP fiber surface curing treatment: Regenerated GFRP fibers with surface grafted nano-silica and silane coupling agent were dried in a drying oven at 80°C for 12 h and then naturally cooled at room temperature to obtain regenerated GFRP fibers modified by nano-silica and silane coupling agent.

[0033] To verify the effectiveness, the preparation was carried out according to the table below: The application of recycled GFRP fibers in decommissioned wind turbine blades in Example 1 involves concrete comprising matrix material component A and recycled GFRP fibers C. Matrix material component A is a cement-based composite gel material; recycled GFRP fibers C are modified recycled GFRP fibers. The matrix material component A and recycled GFRP fibers C are mixed in the following weight proportions: matrix material component A comprises 800-1000 parts cement, 150-250 parts mineral admixtures, 800-1000 parts fine aggregate, 180-210 parts water, and 17-21 parts water-reducing agent; recycled GFRP fibers C comprises 30-50 parts. The required materials are added sequentially to a cement mortar mixing pot and dry-mixed for 3 minutes. Then, a uniformly mixed water-reducing agent solution is added and mixing continues for 3 minutes. The mortar is then poured into a 100×100×100 mm grout. 3 In a standard mold, regenerated GFRP fibers modified with nano-silica and silane coupling agents are inserted, such as... Figure 2As shown, it was placed in a constant temperature chamber with a humidity of 95% and a temperature of 20℃ for curing.

[0034] Comparative Example 1 The other steps are the same as in Example 1, except that step S3 is modified by using electromagnetic stirring for the composite modification. Specifically: In step S3, the cleaned regenerated GFRP fibers are immersed in a mixed solution of nano-silica and silane coupling agent, and dispersed for 15 min using electromagnetic stirring at 1000 r / min to obtain regenerated GFRP fibers with surface grafted nano-silica and silane coupling agent.

[0035] Comparative Example 2 The other steps are the same as in Example 1, except that step S3 changes the composite modification method to static modification, specifically: In step S3, the cleaned regenerated GFRP fibers are immersed in a mixed solution of nano-silica and silane coupling agent and left to stand for 15 minutes to obtain regenerated GFRP fibers with surface grafted nano-silica and silane coupling agent.

[0036] Comparative Example 3 The other steps are the same as in Example 1, except that step S2 is to modify the composite modified solution into a separate silane hydrolysate, specifically: S2 weigh 300 g of anhydrous ethanol and 100 g of deionized water, then add 14% (56 g) of silane coupling agent (γ-aminopropyltriethoxysilane). Add the silane coupling agent to a solvent composed of deionized water and anhydrous ethanol, and let it stand at room temperature for 1 h to allow the silane coupling agent to complete hydrolysis. Do not add nano-silica to obtain a silane coupling agent hydrolysis solution.

[0037] Comparative Example 4 The other steps are the same as in Example 1, except that steps S2 to S4 are omitted, and only the recycled GFRP fibers after removing surface impurities are used for the experiment.

[0038] Select the appropriate amount of raw materials according to the actual situation, as shown in Table 1 for the four material ratios: Sample preparation and curing methods: First, weigh out the required amounts of cement, mineral admixtures, and fine aggregates and add them to the mixing pot, then dry mix for 5 minutes. Add the pre-mixed water-reducing agent and water solution in three batches, mixing for 2 minutes after the first two additions and 5 minutes after the last addition. Set the fiber embedding depth in the ultra-high performance concrete matrix to 5 mm. Quickly pour the mixture into a precast mold, place the mold on a vibrating table and vibrate for 2 minutes. Then, remove excess slurry and smooth the surface. After 24 hours in an indoor environment, remove the mold and place the formed sample under standard curing conditions of 20±2℃ and relative humidity ≥95% for 28 days. Figure 2 The recycled GFRP fibers extending 50mm above the ultra-high performance concrete matrix and the cardboard are designed to facilitate subsequent mechanical experiments. In actual use, recycled GFRP fibers C are simultaneously added when fabricating the ultra-high performance concrete matrix using matrix material component A. After curing, the mixture forms an integrated structure, further enhancing the overall performance of the ultra-high performance concrete matrix. The cardboard only serves as a sample gripping point and does not alter the properties of the recycled GFRP fibers.

[0039] To prepare UHPC specimens reinforced with recycled GFRP fibers after further modification, cement, mineral admixtures, and fine aggregates were weighed and added to a mixing pot as needed, and dry-mixed for 5 minutes. The pre-mixed water-reducing agent and water solution was added in three portions, with the first two additions mixed for 2 minutes each, and the final addition mixed for 5 minutes. After the slurry exhibited good fluidity, recycled GFRP fibers with different modification methods were added. The selected size of the recycled GFRP fibers was 0.8 × 80 × 0.3 mm. 3 Finally, a well-mixed mixture is obtained. This mixture is quickly poured into a precast mold, which is then placed on a vibrating table and vibrated for 2 minutes. Excess slurry is then removed and the surface is leveled. A plastic film is gently placed on the surface. After 1 day in an indoor environment, the mold is removed, and the formed sample is placed under standard curing conditions of 20±2℃ and relative humidity ≥95% for 28 days.

[0040] After surface modification of the regenerated GFRP fiber using the above-mentioned method, the bond strength of the single fiber pull-out specimens was analyzed using a 300KN universal testing machine. The single fiber pull-out load-displacement curve of Example 1 is shown below. Figure 4 As shown, the results indicate that the bond strength of Example 1 can reach a maximum of 20.50 MPa, which is 66.7% higher than the comparative group; the pull-out energy can reach a maximum of 1.703 J, which is 133.27% higher than the comparative group. These results demonstrate that the method proposed in this invention can effectively improve the detection of the hydrophilic wetting angle of the surface of regenerated GFRP fibers. Figure 5As shown, the modified recycled GFRP fiber exhibits a reduced surface wetting angle, indicating improved surface wettability and easier spreading and penetration. This demonstrates that the modified recycled GFRP fiber significantly improves the interfacial bond strength between the recycled GFRP fiber and the ultra-high performance concrete matrix.

[0041] Table 2. Bond performance parameters of recycled GFRP fibers with different modification methods to ultra-high performance concrete. Note: Comparative Example 4 is a recycled GFRP fiber that has not undergone any modification treatment, serving as a baseline group to compare the modification effect. The data is the average of 6 parallel experiments.

[0042] Table 3 Wetting angle parameters of regenerated GFRP fibers with different modification methods This invention effectively combines nano-silica with a silane coupling agent and, in conjunction with ultrasonic modification technology, attaches nano-silica to the surface of recycled GFRP fibers. This fills the surface defects of the fibers, enhances the hydrophilicity of the recycled GFRP fiber surface, and improves the degree of secondary hydration reaction at the interface with cement. This significantly improves the bond strength between the recycled GFRP fibers and the ultra-high performance concrete matrix, thereby significantly enhancing the strength and durability of the concrete and extending its service life. It also plays a very positive role in solid waste treatment, reducing carbon dioxide emissions, and lowering the cost of ultra-high performance concrete.

[0043] Example 2 adds a reinforcing material component B to Example 1, applying recycled GFRP fibers to the decommissioned wind turbine blades. The concrete includes matrix material component A, reinforcing material component B, and recycled GFRP fibers C. Matrix material component A is a cement-based composite gel material, and reinforcing material component B is copper-plated steel fiber with a copper plating on the surface. The recycled GFRP fibers are prepared by mixing matrix material component A, reinforcing material component B, and recycled GFRP fibers C in the following weight proportions: matrix material component A includes 800-1000 parts cement, 150-250 parts mineral admixtures, 800-1000 parts fine aggregate, 180-210 parts water, and 17-21 parts water-reducing agent; reinforcing material component B includes 130-160 parts copper-plated steel fibers; and recycled GFRP fibers C includes 30-50 parts. The purpose of Example 2 is to reduce the amount of copper-plated steel fiber used by regenerated GFRP fiber C, thus utilizing waste. A certain amount of copper-plated steel fiber is added, and the matrix material component A, reinforcing material component B, and regenerated GFRP fiber C are mixed and used. Their mechanical properties are shown in Table 4. After replacing steel fiber with GFRP fiber, the material exhibits a better toughening effect, with a flexural strength increase of 27.49% and no significant decrease in compressive strength. This further demonstrates that the modified regenerated GFRP fiber significantly improves the interfacial bond strength between the regenerated GFRP fiber and the ultra-high performance concrete matrix.

[0044] Table 4 Mechanical properties of UHPC toughened with regenerated GFRP fibers Note: In the table above, "10% modified GFRP" means that 10% of the steel fiber in the concrete is replaced with an equal volume of modified recycled GFRP fiber, while "unmodified" is the same and is replaced with unmodified recycled GFRP fiber.

[0045] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades, characterized in that, Includes the following steps: S1 Preprocessing The retired wind turbine blades were immersed in deionized water and ultrasonically cleaned at 300-1050W for 15-60 minutes, then dried at 80-120℃ for 12 hours. The cleaning and drying process was repeated three times to obtain regenerated GFRP fibers for later use. S2 preparation of composite modified liquid A mixture of anhydrous ethanol and deionized water at a mass ratio of 3:1 was prepared. 2-16 wt% of silane coupling agent was added to the mixture and hydrolyzed for 15-60 min. 0.5-1.5 wt% of nano-silica was added to the mixture for dispersion treatment to obtain a mixed modified solution of nano-silica and silane coupling agent. S3 Ultrasonic Synergistic Modification The regenerated GFRP fibers of S1 are immersed in the mixed modification solution of S2 and dispersed by ultrasonic treatment at 300-1050W for 15-60 minutes to modify the surface of the regenerated GFRP fibers by grafting nano-silica. S4 Post-processing The modified regenerated GFRP fibers were rinsed with deionized water, dried at 80-120℃ for 12 hours, and then naturally cooled to obtain regenerated GFRP fibers with silica-assisted silane coupling agent surface modification.

2. The method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to claim 1, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane; the nano silica is fumed silica powder with a particle size of 20-30 nanometers, a specific surface area of ​​183-185 m2 / g, and a silica content of 99.9%.

3. The method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to claim 1, characterized in that, The ultrasonic cleaning power in S1 is 1050 W; the cleaning time is 60 min.

4. The method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to claim 1, characterized in that, In step S2, 14 wt% of silane coupling agent is added and hydrolyzed for 60 min to obtain a hydrolysate; then 1 wt% of nano-silica is added for dispersion treatment.

5. The method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to claim 1, characterized in that, In step S3, ultrasonic dispersion at 1050W for 15 minutes is used to prevent nanoparticle aggregation.

6. The method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to claim 1, characterized in that, The drying process in S1 and S4 is carried out at a temperature of 80°C.

7. The application of the regenerated GFRP fiber obtained by the method for improving the interfacial bonding performance of regenerated GFRP fiber-UHPC in decommissioned wind turbine blades according to any one of claims 1 to 6 in the preparation of concrete.

8. The application of regenerated GFRP fibers in decommissioned wind turbine blades according to claim 7, characterized in that, The concrete comprises matrix material component A and recycled GFRP fiber C. Matrix material component A is a cement-based composite gel material; recycled GFRP fiber C is the modified recycled GFRP fiber as described in any one of claims 1 to 6. The matrix material component A and recycled GFRP fiber C are mixed and prepared in the following weight proportions: matrix material component A comprises 800-1000 parts of cement, 150-250 parts of mineral admixtures, 800-1000 parts of fine aggregate, 180-210 parts of water, and 17-21 parts of water-reducing agent. Regenerated GFRP fiber C 30-50 parts.

9. The application of regenerated GFRP fibers in decommissioned wind turbine blades according to claim 7, characterized in that, The concrete comprises matrix material component A, reinforcing material component B, and recycled GFRP fiber C. Matrix material component A is a cement-based composite gel material, and reinforcing material component B is copper-plated steel fiber with a copper plating layer on the surface of the steel fiber. The recycled GFRP fiber C is the modified recycled GFRP fiber according to any one of claims 1 to 6. The matrix material component A, the reinforcing material component B, and the recycled GFRP fiber C are mixed and formulated in the following weight parts: the matrix material component A includes 800-1000 parts of cement, 150-250 parts of mineral admixtures, 800-1000 parts of fine aggregate, 180-210 parts of water, and 17-21 parts of water-reducing agent; the reinforcing material component B includes 130-160 parts of copper-plated steel fiber. Regenerated GFRP fiber C 30-50 parts.

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