A method for preparing concrete based on desert sand and recycled glass fibers from decommissioned wind turbine blades

Abstract

The application provides a method for preparing concrete based on desert sand and recycled glass fiber of retired wind power blades, comprising the following steps: performing mechanical cutting on the main beam and skin parts of the retired wind power blades, and processing the main beam and skin parts into block materials; the block materials are subjected to crushing, grinding and screening treatment to obtain recycled glass fiber; the recycled glass fiber, coarse aggregate and fine aggregate are uniformly dry-mixed according to a preset mixing ratio, and then cementing material and mixing water are added, and low-speed dispersion stirring is performed to obtain concrete; the application breaks through the limitation that the desert sand and the recycled glass fiber are independently applied in the prior art, and combines the two for the first time to prepare high-performance concrete, solves the industry blank that the high-substitution-rate desert sand concrete has insufficient performance and the recycled glass fiber is only suitable for river sand, and builds an integrated technical path of "solid waste resourceization + high-performance material".

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and concrete building materials technology, and in particular to a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades. Background Technology

[0002] As the global energy structure shifts towards clean energy, wind power, as a crucial component of renewable energy, has achieved large-scale development. However, this is accompanied by the gradual retirement of early-operated wind turbine blades, generating a large amount of wind turbine blade waste. Statistics show that the number of retired wind turbine blades globally each year is increasing rapidly, and their harmless treatment and resource utilization have become a key bottleneck restricting the sustainable development of the wind power industry.

[0003] The core material of wind turbine blades is glass fiber reinforced polymer (GFRP), a composite material made of glass fiber and a resin matrix. It possesses excellent properties such as lightweight, high strength, and corrosion resistance. Currently, the industry's recycling technologies for retired wind turbine blades include: mechanically crushing the blades into granular or powdered fillers for use as raw materials in concrete preparation, thus producing recycled glass fiber reinforced concrete. However, this single recycling method has significant shortcomings. The crushed mixed particles lack targeted treatment, and when used as fillers, they not only fail to improve concrete performance but may also lead to a decrease in concrete strength due to poor interfacial bonding.

[0004] Currently, research and application of recycled glass fiber are mainly limited to ordinary cement concrete systems using river sand as fine aggregate. However, when extending this technology to scenarios such as wind farm construction in desert areas, this traditional approach faces significant economic and technological challenges. Purchasing and transporting river sand from non-desert regions using existing technologies would lead to a sharp increase in raw material costs, completely offsetting the economic benefits of recycled glass fiber as a reinforcing material, making the commercial application of this technology in desert environments extremely difficult. Summary of the Invention

[0005] In response to the problems existing in the background technology, the present invention provides a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades. This method not only makes full use of the abundant desert sand resources in the local wind farm area and realizes "turning waste into treasure", but also effectively alleviates the increasingly scarce construction sand resources in my country, and provides a new, economical and environmentally friendly aggregate solution for infrastructure construction in desert areas.

[0006] The specific details of the invention are as follows: This invention provides a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades, the method comprising: The main beam and skin of the retired wind turbine blades are mechanically cut and processed into blocks; The block material is crushed, ground, and sieved to obtain recycled glass fiber; The recycled glass fiber is dry-mixed with coarse and fine aggregates according to the preset mixing ratio, and then cementitious materials and mixing water are added. After low-speed dispersion and mixing, concrete is obtained. The fine aggregate comprises natural sand and desert sand, with desert sand accounting for 10% to 80%. The amount of recycled glass fiber in the concrete is 0.5-2%.

[0007] Optionally, the length of the recycled glass fiber is 0.5 mm to 15 mm, and the aspect ratio is 300-400.

[0008] Optionally, before using the desert sand to prepare fine aggregate, the method further includes: washing and desliming the desert sand before using it for preparing fine aggregate.

[0009] Optionally, before the desert sand is used to prepare fine aggregate, the method further includes: The particle size distribution curve of the desert sand was determined experimentally. The obtained particle size distribution curve is compared with the standard curves for zones I, II, and III specified in GB / T 14684-2022, and the proportion of desert sand in the fine aggregate is determined based on the comparison results.

[0010] Optionally, determining the proportion of desert sand in the fine aggregate based on the comparison results includes: When the particle size distribution curve is below the Zone III standard curve specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 25%.

[0011] Optionally, determining the proportion of desert sand in the fine aggregate based on the comparison results includes: When the particle size distribution curve partially falls within the range of the Zone III standard curve specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 40%.

[0012] Optionally, determining the proportion of desert sand in the fine aggregate based on the comparison results includes: When the particle size distribution curve is close to the range of the standard curve in Zone II specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 50%.

[0013] Optionally, the method further includes: The Andreasen & Andersen close packing model was used to optimize the gradation of fine aggregates, including desert sand and natural sand. Formula I; in: P(d): Cumulative volume percentage of fine aggregate with a particle size less than d, expressed as a percentage (%). d: A specific particle size of the aggregate, expressed in millimeters (mm); D max : Maximum particle size of aggregate, in millimeters (mm); q: Distribution coefficient, with a value range of 0.23 to 0.45, used to adjust the shape of the gradation curve to obtain the best packing effect.

[0014] Optionally, the particle size of the block material is 50mm to 200mm.

[0015] Optionally, the block material undergoes crushing, grinding, and sieving processes, including: After being mechanically crushed, the block material undergoes coarse crushing and medium crushing processes in sequence to obtain crushed products of different sizes. The crushed product is fed into a ball mill or vertical mill for grinding, and then subjected to multi-stage screening and purification through a vibrating screen, air classifier or water classifier to remove resin powder, light impurities and residual metal fragments, and finally obtain the recycled glass fiber.

[0016] Optionally, the concrete material is poured using a high-frequency wall-mounted vibrator.

[0017] This invention provides a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades. The method includes: mechanically cutting the main beam and skin of decommissioned wind turbine blades into blocks; crushing, grinding, and sieving the blocks to obtain recycled glass fiber; dry-mixing the recycled glass fiber with coarse and fine aggregates according to a preset mix ratio, then adding cementitious materials and mixing water, and dispersing and stirring at low speed to obtain concrete; wherein the fine aggregates consist of natural sand and desert sand, with the desert sand accounting for 10% to 80%; and the recycled glass fiber content in the concrete is 0.5% to 2%.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention breaks through the limitations of the independent application of desert sand and recycled glass fiber in the prior art. For the first time, the two are combined for the preparation of high-performance concrete, which solves the industry problems of insufficient performance of high-substitution desert sand concrete and the fact that recycled glass fiber is only suitable for river sand. It constructs an integrated technical path of "solid waste resource utilization + high-performance materials".

[0019] 2. To address the wind farm needs in desert areas, we have developed a process model that utilizes locally sourced materials and prepares concrete on-site, avoiding the pain points of long-distance transportation of recycled glass fiber and off-site allocation of river sand. This enables the scenario-based adaptation of resource utilization and engineering applications, filling the technological gap in the on-site preparation of high-performance concrete in desert areas.

[0020] 3. This invention uses desert sand and decommissioned wind turbine blades together in concrete formulation. Through the adaptation design of the two, it solves the problems of poor gradation of desert sand and poor dispersion of recycled glass fiber, and achieves a dual improvement in matrix performance and reinforcement effect. It breaks through the bottleneck of low strength and unstable reinforcement of traditional desert sand concrete and achieves high-performance concrete indicators. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart of a method for preparing concrete from desert sand and recycled glass fiber from decommissioned wind turbine blades, provided by an embodiment of the present invention, is shown. Detailed Implementation

[0023] 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by anyone under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0024] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0025] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] The current applications of recycled glass fiber and desert sand in concrete preparation technology each have their own limitations. Desert sand concrete primarily suffers from poor gradation, large specific surface area, and an imbalance between workability and strength. Due to the excessively fine particles, uniform gradation, and smooth surface of desert sand, high replacement rates (60%–80%) result in concrete with high water demand, viscous paste, and a tendency to segregate and bleed. Weak aggregate bonding leads to decreased compressive / tensile strength, increased risk of shrinkage cracking, and difficulty in achieving high-performance indicators. Furthermore, using desert sand in concrete preparation requires increased cement and high-efficiency water-reducing agent dosages to encapsulate the ultra-fine desert sand particles, resulting in high cementitious material usage, reduced economic efficiency and environmental friendliness, and increased carbon emissions, contradicting the principles of green building materials. Meanwhile, research and application of recycled glass fiber are mainly limited to ordinary cement concrete systems using river sand as fine aggregate. The preparation process suffers from the challenge of off-site river sand sourcing, leading to a sharp increase in raw material costs, completely offsetting the economic benefits of recycled glass fiber as a reinforcing material, making the commercial application of this technology in desert environments extremely difficult.

[0028] Based on the goal of achieving the synergistic utilization of recycled glass fiber and desert sand, and overcoming the limitations of existing technologies that apply desert sand and recycled glass fiber independently, this invention provides a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades. Figure 1 A flowchart illustrating the method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades, as provided in an embodiment of the present invention, is shown. Figure 1 As shown, the method includes: S1. Mechanically cut the main beam and skin of the retired wind turbine blades and process them into blocks; S2. The block material is crushed, ground and sieved to obtain recycled glass fiber; S3. The recycled glass fiber is dry-mixed with coarse aggregate and fine aggregate according to the preset mixing ratio, and then cementitious materials and mixing water are added. After low-speed dispersion and mixing, concrete is obtained. The fine aggregate comprises natural sand and desert sand, with desert sand accounting for 10% to 80%. The amount of recycled glass fiber in the concrete is 0.5-2%.

[0029] This embodiment addresses the wind farm requirements in desert regions by developing a process mode that utilizes locally sourced materials and prepares the concrete locally. This avoids the pain points of long-distance transportation of recycled glass fiber and off-site allocation of river sand, achieving scenario-based adaptation of resource utilization and engineering applications. It fills the technological gap in the local preparation of high-performance concrete in desert regions. Through the adaptive design of the two, it solves the respective shortcomings of poor gradation of desert sand and poor dispersion of recycled glass fiber, breaking through the bottlenecks of low strength and unstable reinforcement of traditional desert sand concrete, and achieving high-performance concrete indicators.

[0030] In practice, after disassembling the retired wind turbine blades, they are cut and separated according to the structure of different parts of the blades. The blades are then processed according to their main components, sequentially disassembling the skin, main beam, web, core filler, and metal fasteners. Finally, the main beam and skin components containing fiber-reinforced composite materials are cut into blocks with a particle size of 50mm to 200mm. These blocks of composite material from the retired wind turbine blades are fed into a crushing device. By adjusting the crushing intensity and changing different types of blades, the blades undergo coarse and medium crushing processes to obtain crushed products of different sizes, such as recycled glass fiber and resin particles. The crushed products are then fed into a ball mill or vertical mill for grinding. After multi-stage screening and purification using a vibrating screen, air classifier, or water classifier, resin powder, light impurities, and residual metal fragments are removed, ultimately yielding the recycled glass fiber.

[0031] In practice, local desert sand from the area where decommissioned wind farms are located is collected. The desert sand is tested for particle size distribution, mud content, moisture content, water absorption, crushing index, organic matter, and harmful substance content to ensure it meets the basic requirements for fine aggregates used in concrete. Through single-factor comparative experiments, the influence of the desert sand substitution rate on the workability of concrete mixtures, such as slump, spread, and setting time, as well as mechanical properties such as compressive strength, splitting tensile strength, and flexural strength, is systematically studied. Combined with durability test results, the optimal desert sand substitution rate for overall performance is determined. In the composition of concrete raw materials, desert sand of equal quality is used to replace natural building sand, with the substitution rate controlled between 20% and 80%.

[0032] In practice, a step-by-step mixing process is adopted. First, the coarse and fine aggregates are dry-mixed evenly. Then, the cementitious material is added and dry-mixed again. Finally, the recycled glass fiber is added and dispersed and mixed at a low speed to avoid fiber clumping, agglomeration, and uneven distribution, ensuring that the recycled glass fiber is evenly dispersed in the concrete matrix.

[0033] In one specific implementation, multiple sets of mix proportion comparison tests can be conducted to study the effects of recycled glass fiber content and fiber length on the workability, hardened mechanical properties, and durability of concrete mixtures, thereby determining the optimal recycled glass fiber content and mixing process parameters. This will allow for the evaluation of the prepared desert sand. High-performance recycled glass fiber reinforced concrete underwent multiple performance tests, including compressive strength, splitting tensile strength, flexural strength, axial compressive strength, modulus of elasticity, drying shrinkage, chloride ion penetration resistance, freeze-thaw resistance, and carbonation resistance, to comprehensively evaluate its structural application feasibility. Finally, the optimal mix proportion scheme synergistically combining workability, mechanical properties, and durability was determined. The preferred content of recycled glass fiber in the concrete is 0.5-2%. The preferred length of the recycled glass fiber is 0.5 mm to 15 mm, and the preferred aspect ratio is 300-400.

[0034] In one specific implementation, the desert sand has a high mud content. The high mud content will coat the surface of the aggregate, blocking the effective bonding between the cement stone and the aggregate, resulting in a comprehensive deterioration of durability properties such as impermeability, frost resistance, and chloride ion penetration resistance. Therefore, before the desert sand is used to prepare fine aggregate, the method further includes: washing and removing mud from the desert sand before using it to prepare fine aggregate.

[0035] In one specific implementation, the fine aggregate is configured as follows: the particle size distribution curve of the desert sand is determined experimentally; that is, based on GB / T 14684-2022, a standard sieve test (0.075 / 0.15 / 0.3 / 0.6 / 1.18 / 2.36 / 4.75mm full set of sieves) is performed on the desert sand, and the cumulative passing rate corresponding to each particle size is calculated, and the measured particle size distribution curve of the desert sand is plotted.

[0036] Furthermore, the obtained measured particle size distribution curve is compared with the standard curves for zones I, II, and III specified in GB / T 14684-2022, and the proportion of desert sand in the fine aggregate is determined based on the comparison results.

[0037] Specifically, determining the proportion of desert sand in the fine aggregate based on the comparison results includes: When the particle size distribution curve is below the standard curve for Zone III (fine sand) specified in GB / T 14684-2022, it indicates that the desert sand particles are severely fine, have a large specific surface area, require a large amount of water, and are prone to shrinkage and cracking. It can only be used in small quantities. In order to ensure the performance requirements of concrete, the proportion of desert sand in the fine aggregate needs to be controlled to no more than 25%.

[0038] Furthermore, when the particle size distribution curve partially falls within the range of the Zone III standard curve specified in GB / T 14684-2022, it indicates that desert sand mainly consists of fine sand particles with a large specific surface area, high water demand, and is prone to shrinkage and cracking. It can only be used in small quantities. To ensure the performance requirements of concrete, the proportion of desert sand in the fine aggregate needs to be controlled to no more than 40%.

[0039] Furthermore, when the particle size distribution curve is close to the range of the standard curve in Zone II specified in GB / T 14684-2022, it indicates that the desert sand has a good particle size distribution, and the substitution rate of natural sand can be appropriately increased. The proportion of desert sand in the fine aggregate can be controlled within 50%.

[0040] Furthermore, for fine aggregates composed of desert sand and natural sand, the Andreasen & Andersen close packing model can be used to optimize the gradation of fine aggregates including desert sand and natural sand. Formula I; in: P(d): Cumulative volume percentage of fine aggregate with a particle size less than d, expressed as a percentage (%). d: A specific particle size of the aggregate, expressed in millimeters (mm); D max : Maximum particle size of aggregate, in millimeters (mm); q: Distribution coefficient, with a value range of 0.23 to 0.45, used to adjust the shape of the gradation curve to obtain the best packing effect.

[0041] This invention is based on the high-value utilization of desert sand and recycled glass fiber from decommissioned wind turbine blades in the concrete field. The core improvements revolve around "localization, high value, and large-scale production," specifically addressing the shortcomings of existing technologies, as detailed below: 1. Improved Scene Adaptability for Efficient On-Site Resource Utilization: Leveraging the unique location characteristics of wind farms, this approach breaks through the limitations of existing recycled glass fiber, which is only compatible with river sand and requires long-distance transportation. Desert sand from the surrounding wind farms is used locally as fine aggregate in concrete, allowing for the local consumption of composite materials from retired wind turbine blades. This enables the local sourcing and utilization of building materials. This not only reduces the environmental pressure and costs associated with natural sand and gravel mining and long-distance transportation, lowering carbon emissions and project costs, and avoiding resource waste, but also achieves efficient synergistic utilization of recycled materials from retired wind turbine blades and desert sand resources in new energy bases, balancing environmental, economic, and social benefits.

[0042] 2. Improved Application of Desert Sand for Large-Scale High-Value Utilization: Addressing the performance imbalance of existing high-replacement-rate desert sand concrete, this study optimizes the gradation and removes impurities from local desert sand used in wind farms, replacing natural construction sand in concrete at a replacement rate of 10%–80% using equal mass or volume methods. Through systematic mechanical and workability tests, the study investigates the impact of the desert sand replacement rate on concrete strength, flowability, and density, determining the optimal replacement rate parameters for comprehensive performance. This approach fully utilizes the abundant desert sand resources in wind farms, turning waste into treasure, while effectively alleviating the growing shortage of construction sand resources in my country, providing a new, economical, and environmentally friendly aggregate solution for infrastructure construction in desert regions.

[0043] 3. Improved Recycled Glass Fiber Preparation for Enhanced Reinforcement Stability: Addressing the issues of low purity, uneven length, poor dispersibility, and incompatibility with desert sand matrices in existing recycled glass fibers, a multi-stage separation process combining coarse, medium, and fine crushing with air, water, and magnetic separation was employed. This effectively removed resin matrix, metallic impurities, and lightweight dust, resulting in high-purity recycled glass fibers with controllable length, good dispersibility, and compatibility with concrete preparation. Through systematic mix proportion experiments, the effects of recycled glass fiber dosage and length on the mechanical properties, toughness, and durability of concrete were studied. Optimal dosage parameters were determined, ultimately yielding high-strength, high-toughness, and excellent crack-resistant recycled glass fiber reinforced desert sand concrete, overcoming the performance bottlenecks of traditional processes.

[0044] To enable those skilled in the art to more clearly understand the present invention, the following embodiments are provided to illustrate in detail a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades.

[0045] Example 1 (1) Raw material preparation Cementitious material: P O 52.5 ordinary Portland cement, Grade II fly ash, S95 mineral powder, silica fume; Aggregates: 5~25 mm continuously graded crushed stone, natural river sand (GB / T 14684-2022 Zone II gradation), desert sand (in-situ sand from a desert wind farm, pre-treated by washing and removing mud); Reinforcing material: Recycled glass fiber from decommissioned wind turbine blades (self-made); Admixture: Polycarboxylate superplasticizer (water reduction rate 28%); Mixing water: ordinary drinking water, meeting the requirements of the "Standard for Water Used in Concrete" GB / T 14684-2011.

[0046] Recycled wind turbine blades Main beam section: Select glass fiber reinforced composite (GFRP) wind turbine blades that have been retired after 15 years of service. Separate the main beam and web / skin sections, and process them into block-shaped coarse fiber particles through precision mechanical cutting. The size is controlled to be 60 mm (length) × 3.0 mm (width) × 0.9 mm (thickness), with no obvious breakage or lumps.

[0047] (2) Mixed fine aggregate configuration 1) Determination of desert sand gradation curve Local desert sand was collected from the wind farm, air-dried / oven-dried (at 105±5℃ to constant weight), and mud and impurities were removed. The sample was reduced to a fraction using the quartering method, and 500 g of sample was taken (accurately weighed and recorded as m). 0= 500.0g), stack standard sieves in descending order of aperture (4.75mm on top, 0.075mm on the bottom), pour 500g of desert sand sample into the top sieve, cover the sieve, place it in a shaking sieve machine, and sieve for 10 minutes; after removing, gently tap the sieve manually to ensure no particles remain; weigh the residue on each sieve (m1~m7) and the residue on the bottom sieve (m8) in sequence. Total mass verification: =498.6g, error 0.28% < 1%, the test is valid.

[0048] Calculate three core indicators (see Table 1): % of screen residue, % of cumulative screen residue, and % of cumulative pass rate; where % of screen residue is a. i = (Mass of residue on a certain sieve / Total mass of sample) × 100%; Cumulative sieve residue A i =The sum of the residues of the sieve and all the sieves above; Cumulative pass rate P i =100% Cumulative sieve residue A i (The gradation curve uses the pass rate).

[0049] Table 1 Calculation results of desert sand gradation data

[0050] Based on the gradation data calculated in Table 1 above, a gradation curve was plotted and compared with the standard curves of GB / T 14684-2022 Zone I / II / III. It was found that the measured curve was completely below the standard curve of GB / T 14684-2022 Zone III. This indicates that the desert sand particles are severely fine, have a large specific surface area, require a large amount of water, and are prone to shrinkage and cracking. Therefore, it can only be used in small quantities. To ensure the performance requirements of concrete, the desert sand content in the fine aggregate should not exceed 25%. In this embodiment, 25% is used.

[0051] 2) Determination of the gradation of mixed fine aggregates In this embodiment, the proportion of desert sand in the fine aggregate is 25%. By adjusting the mixing of natural sand (the measured gradation of natural sand is shown in Table 2) and desert sand, the gradation of the fine aggregate is further optimized. First, the cumulative passing rate of each particle size of the mixed fine aggregate is calculated using the weighted average method (see Table 2). P 混合(d) =P 天然砂(d) 75%+P 沙漠砂(d) 25%; Table 2 Calculation results of natural sand gradation data

[0052] Furthermore, the Andreasen & Andersen close-packed model was used to calculate the gradation of the mixed fine aggregate containing 25% desert sand and 75% natural sand, where D max =4.75 mm, q=0.3; ; Theoretical cumulative pass rate calculated per particle size: P(4.75) = (4.75 / 4.75) 0.30 ×100%=100%; P(2.36)=(2.36 / 4.75) 0.30 ×100%≈81.5%; P(1.18) = (1.18 / 4.75) 0.30 ×100%≈66.2%; P(0.6) = (0.6 / 4.75) 0.30 ×100%≈54.1%; P(0.3) = (0.3 / 4.75) 0.30 ×100%≈42.3%; P(0.15) = (0.15 / 4.75) 0.30 ×100%≈32.8%; P(0.075) = (0.075 / 4.75) 0.30 ×100%≈25.1%.

[0053] The mean square error (MSE) was used to determine the fit between the mixed fine aggregate and the theoretical curve (see Table 3). The calculated MSE value was 2.36, which is less than 3, indicating that the mixed fine aggregate has reached a state of close packing and low porosity.

[0054] Table 3. Goodness-of-fit evaluation

[0055] Furthermore, the cumulative passing rate of the mixed fine aggregate through a 0.6 mm sieve is 59.72%, which falls within Zone II of GB / T 14684-2022, and the full-size gradation curve falls in the lower part of Zone II, indicating that it belongs to the high-quality medium sand gradation.

[0056] (3) Concrete preparation process (total mixing volume 1 m³) 3 ) According to the C60 high-performance concrete mix design shown in Table 4, first mix recycled glass fiber, crushed stone, and mixed fine aggregate and dry mix for 30 seconds until uniform. Then add cement, fly ash, mineral powder, and silica fume, and continue to dry mix for 30 seconds. After adding cement, fly ash, mineral powder, and silica fume, continue to dry mix for 30 seconds. The concrete mixture should have no segregation, no bleeding, and uniform fiber dispersion.

[0057] Table 4 Concrete Mix Proportions

[0058] 3) Pouring and Vibration Process Mold preparation: Use 100mm×100mm×400mm prism molds (for bending and tensile tests), 150mm×150mm×150mm cube molds (for compressive tests), and Φ100mm×200mm cylinder molds (for durability tests). Apply release agent to the inner wall of the molds.

[0059] Pouring: The concrete mixture is poured into the test mold in two layers, with each layer being about 1 / 2 the height of the test mold. Aggregate accumulation should be avoided during the pouring process.

[0060] Vibration: A high-frequency wall-mounted vibrator (vibration frequency 120Hz, amplitude 0.8mm) was used and fixed to the outside of the test mold. The vibration time was extended by 40% compared with the conventional method (60 seconds per layer, total vibration time 120 seconds) until the concrete surface showed slurry and no obvious air bubbles overflowed.

[0061] Smoothing and curing: After vibration, smooth the surface of the test mold in time and place it in a standard curing room with a temperature of 20±2℃ and a relative humidity of ≥95% for 28 days.

[0062] 4) Comparison group settings A baseline control group (C60 conventional concrete) was set up according to the baseline concrete mix proportion. The mixing process and curing conditions were completely consistent with those in this embodiment. Three parallel test blocks were prepared for each test item, and the average value was taken as the test result.

[0063] (3) Implementation process for effect verification 1) Test Content Slump test: Before pouring, take concrete mix and fill it into a slump cone in layers according to the standard method. After compaction, lift the cone and measure the slump height of the mix. At the same time, observe the cohesiveness and water retention.

[0064] Mechanical property testing: Take out the test block after 28 days of curing, wipe off the surface moisture, place it on the testing machine, and load it according to the standard loading rate (compressive 0.5 MPa / s, tensile 0.05 MPa / s, bending 0.05 MPa / s), record the failure load, and calculate the corresponding strength.

[0065] The test results are shown in Table 5: Table 5 Performance Test Results

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0067] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0068] The above provides a detailed description of a method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades, characterized in that, The method includes: The main beam and skin of the retired wind turbine blades are mechanically cut and processed into blocks; The block material is crushed, ground, and sieved to obtain recycled glass fiber; The recycled glass fiber is dry-mixed with coarse and fine aggregates according to the preset mixing ratio, and then cementitious materials and mixing water are added. After low-speed dispersion and mixing, concrete is obtained. The fine aggregate comprises natural sand and desert sand, with desert sand accounting for 10% to 80%. The amount of recycled glass fiber in the concrete is 0.5-2%.

2. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, The length of the recycled glass fiber is 0.5 mm to 15 mm, and the aspect ratio is 300-400.

3. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, Before the desert sand is used to prepare fine aggregate, the method further includes: washing and removing mud from the desert sand before using it to prepare fine aggregate.

4. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, Before the desert sand is used to prepare fine aggregate, the method further includes: The particle size distribution curve of the desert sand was determined experimentally. The obtained particle size distribution curve is compared with the standard curves for zones I, II, and III specified in GB / T 14684-2022, and the proportion of desert sand in the fine aggregate is determined based on the comparison results.

5. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 4, characterized in that, Determining the proportion of desert sand in the fine aggregate based on comparison results includes: When the particle size distribution curve is below the Zone III standard curve specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 25%.

6. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 4, characterized in that, The proportion of desert sand in the fine aggregate was determined based on the comparison results, including: When the particle size distribution curve partially falls within the range of the Zone III standard curve specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 40%.

7. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 4, characterized in that, The proportion of desert sand in the fine aggregate was determined based on the comparison results, including: When the particle size distribution curve falls within the range of the standard curve in Zone II specified in GB / T 14684-2022, the proportion of desert sand in the fine aggregate shall not exceed 50%.

8. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to any one of claims 1-7, characterized in that, The method further includes: The Andreasen & Andersen close packing model was used to optimize the gradation of fine aggregates, including desert sand and natural sand. Formula I; in: P(d): Cumulative volume percentage of fine aggregate with a particle size less than d, expressed as a percentage (%). d: A specific particle size of the aggregate, expressed in millimeters (mm); D max : Maximum particle size of aggregate, in millimeters (mm); q: Distribution coefficient, with a value range of 0.23 to 0.45, used to adjust the shape of the gradation curve to obtain the best packing effect.

9. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, The particle size of the block material is 50mm to 200mm.

10. The method for preparing concrete based on desert sand and recycled glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, The block material undergoes crushing, grinding, and sieving processes, including: After being mechanically crushed, the block material undergoes coarse crushing and medium crushing processes in sequence to obtain crushed products of different sizes. The crushed product is fed into a ball mill or vertical mill for grinding, and then subjected to multi-stage screening and purification through a vibrating screen, air classifier or water classifier to remove resin powder, light impurities and residual metal fragments, and finally obtain the recycled glass fiber.

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