Fan blade regenerated fiber-based high-solid-waste low-carbon concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to fan blade regenerated fiber-based high-solid-waste low-carbon concrete and a preparation method thereof, and the fan blade regenerated fiber-based high-solid-waste low-carbon concrete comprises the following raw materials by weight: 0.9-1.1 parts of an alkali-activated active precursor; 0.4 to 0.8 part of iron tailing sand; 0 to 1.1 parts of natural sand; 1.9 to 2.4 parts of recycled aggregate; 0.15 to 0.20 part of a composite alkali activator; 0.015 to 0.020 part of fan blade regenerated glass fiber; 0.001 to 0.003 part of a retarder; 0.35 to 0.45 part of water; wherein the alkali-activated active precursor is granulated blast furnace slag powder. The obtained concrete mixture is good in workability, the 28-day compressive strength reaches 40 MPa or above, the drying shrinkage rate is reduced by 30%-50% compared with that of traditional alkali-activated concrete, additional curing measures are not needed, the concrete mixture is particularly suitable for prefabricated parts such as curbs, sleepers and manhole covers, and a feasible technical path is provided for high-valued and large-scale utilization of bulk industrial solid waste.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-solids-waste low-carbon concrete based on recycled fiber for wind turbine blades and its preparation method. Background Technology

[0002] With the deepening of the "dual-carbon" strategy, the construction industry, as a key area of ​​resource consumption and carbon emissions, urgently needs to develop low-carbon or even zero-carbon cementitious material systems. Alkali-activated cementitious materials are considered an ideal alternative to traditional silicate cement because they do not require calcination and can fully utilize industrial solid waste (such as granulated blast furnace slag). However, existing alkali-activated concrete still faces two major bottlenecks in engineering applications: First, poor volume stability, as the strong alkali activation reaction leads to significant chemical shrinkage and drying shrinkage, which easily causes early cracking and seriously affects structural durability; second, the solid waste utilization pathway is singular and the dosage is limited, with most studies still relying on natural sand and gravel as aggregates, failing to achieve a complete solid waste substitution chain from cementitious materials to aggregates.

[0003] In recent years, iron tailings, as a typical bulk industrial solid waste, have generated huge annual emissions. Theoretically, their physicochemical properties (rich in SiO2, CaO, and a certain amount of Fe2O3) suggest they have the potential to be used as fine aggregates and even as potential active components. However, due to poor particle size distribution, rough surfaces, and potential expansion risks, their direct use in concrete can easily lead to decreased workability and volume instability. Meanwhile, the harmless disposal of decommissioned wind turbine blades (mainly composed of epoxy resin-based glass fiber composites) has become an emerging environmental challenge. Although the recycled glass fibers possess advantages such as high strength and high modulus, their surface inertness and tendency to agglomerate make them difficult to effectively disperse and exert a reinforcing and toughening effect in cement-based or alkali-activated matrices.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a high-solids-waste low-carbon concrete based on iron tailings sand and recycled glass fiber from wind turbine blades, and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A type of recycled fiber-based high-solids-waste low-carbon concrete for wind turbine blades is composed of the following raw materials in parts by weight:

[0008] Alkali-activated active precursor: 0.9-1.1 parts;

[0009] Iron tailings: 0.4-0.8 parts;

[0010] Natural sand: 0-1.1 parts;

[0011] Recycled aggregate: 1.9-2.4 parts;

[0012] Compound alkali activator: 0.15-0.20 parts;

[0013] Recycled glass fiber for wind turbine blades: 0.015-0.020 parts;

[0014] Retarder: 0.001-0.003 parts;

[0015] Water: 0.35-0.45 parts;

[0016] The alkali-activated precursor is granulated blast furnace slag powder; the composite alkali activator consists of a main activating component and an auxiliary activating component. The main activating component is a mixture of sodium silicate solution and solid sodium hydroxide with a modulus of 0.9-1.1, and the auxiliary activating component is a soluble aluminum salt, the amount of which accounts for 1.5%-3.0% of the total mass of the composite alkali activator.

[0017] The amount of natural sand used is 0 parts, meaning that the fine aggregate of the concrete is entirely composed of iron tailings sand.

[0018] The granulated blast furnace slag powder has a specific surface area of ​​390–420 m² / kg and an activity index of not less than 95%.

[0019] The chemical composition by mass percentage of the granulated blast furnace slag powder is as follows: CaO: 35-55 wt%, SiO2: 35-45%, Al2O3: 3-15%, MgO: 1-10%, SO3: 0.2-2.5%; Fe2O3: 0.2-0.7%, TiO2: 0-0.8%, K2O: 0.2-0.5%, Na2O: 0-0.7%, with the remainder being impurities.

[0020] The fineness modulus of the iron tailings sand is 2.6-3.0, and the apparent density is 2800-2900 kg / m³. 3 The bulk density is 1600-1650 kg / m³ 3 .

[0021] The chemical composition of the iron tailings sand includes 35-40 wt% SiO2, 12-18 wt% CaO and 6-10 wt% TFe.

[0022] The recycled glass fibers used in the wind turbine blades are 12-25 mm in length and 10-15 μm in diameter, and are treated with a surface coupling agent; their tensile strength is 1700-2500 MPa; their elastic modulus is 65-72 GPa; and their apparent density is 2400-2600 kg / m³. 3 .

[0023] The molar ratio of Na2O to SiO2 in the sodium silicate solution is 2.0; the solid sodium hydroxide is chemically pure sodium hydroxide with a purity of 98% or higher.

[0024] The soluble aluminum salt is aluminum sulfate, sodium aluminate, or aluminum nitrate.

[0025] A method for preparing recycled fiber-based high-solid-waste low-carbon concrete for wind turbine blades includes the following steps:

[0026] (1) Preparation of composite activator: Dissolve solid sodium hydroxide in part of the mixing water, cool to room temperature, add sodium silicate solution, then add soluble aluminum salt, stir until completely dissolved, seal and age for 12-24 hours to obtain composite alkali activator;

[0027] (2) Dry mixing: Add granulated blast furnace slag powder, iron tailings sand, recycled aggregate and natural sand into a mixer and dry mix for 2-3 minutes until uniform.

[0028] (3) Wet mixing: Add the composite alkali activator prepared in step (1) and the remaining mixing water to the dry mixture, and stir for 3-4 minutes until uniform.

[0029] (4) Fiber incorporation: Under stirring conditions, the recycled glass fiber of the wind turbine blades is evenly sprinkled in 2-3 batches, and stirring is continued for 1-2 minutes until the fiber is evenly dispersed and there are no clumps, thus obtaining the high solid waste alkali activated concrete mixture.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) Achieving truly high solid waste / all solid waste concrete: This application uses granulated blast furnace slag powder as the only cementitious precursor, combined with iron tailings sand, natural sand (iron tailings sand can completely replace natural sand), recycled aggregate and recycled fiber. The whole system does not contain any cement clinker, and the total amount of solid waste (by mass) can reach more than 95%, which greatly reduces carbon footprint and resource consumption.

[0032] (2) Establishing an "alkali-aluminum composite activation" mechanism to actively compensate for shrinkage: Based on the traditional NaOH / water glass main activation system, 1.5%-3.0% of soluble aluminum salts (such as aluminum sulfate, sodium aluminate, or aluminum nitrate) are introduced as auxiliary activation components. This design not only promotes the deep depolymerization of silicon and aluminum components in slag, generating a denser and more stable CASH gel, but more importantly, the aluminum salt reacts with Ca in the system. 2+ (CaO derived from slag and iron tailings) and SO4 2- (Derived from slag or aluminum salts themselves) In-situ reaction, controllable generation of trace amounts of ettringite phase, producing a micro-expansion effect of 0.01%-0.03%, precisely compensating for the chemical shrinkage during the alkali activation process, fundamentally inhibiting early cracking.

[0033] (3) Synergistic effect of iron tailings sand and recycled fiber: The appropriate amount of CaO and Fe2O3 in iron tailings sand not only participates in the alkali-activated reaction, but its micro-aggregate filling effect also improves the matrix density; the recycled glass fiber of the wind turbine blade treated with coupling agent achieves uniform dispersion under the optimized batch addition process, forming a three-dimensional network crack-resistant structure, which together with the chemical compensation mechanism constitutes a dual crack-resistant system of "chemical self-healing + physical crack resistance", significantly improving the crack resistance and toughness of concrete;

[0034] (4) Excellent comprehensive performance and practical engineering application: The resulting concrete mixture has good workability, with a 28-day compressive strength of over 40 MPa. The drying shrinkage rate is 30%-50% lower than that of traditional alkali-activated concrete, and no additional curing measures are required. It is particularly suitable for precast components such as curbs, sleepers, and manhole covers, providing a practical and feasible technical path for the high-value and large-scale utilization of bulk industrial solid waste. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] A type of recycled fiber-based high-solids-waste low-carbon concrete for wind turbine blades is composed of the following raw materials in parts by weight:

[0037] Alkali-activated active precursor: 0.9-1.1 parts;

[0038] Iron tailings: 0.4-0.8 parts;

[0039] Natural sand: 0-1.1 parts;

[0040] Recycled aggregate (recycled aggregate generally uses stones recovered from construction waste, with a particle size of 5-15mm; or uses continuously graded basalt with a particle size of 5-20mm): 1.9-2.4 parts;

[0041] Compound alkali activator: 0.15-0.20 parts;

[0042] Recycled glass fiber for wind turbine blades: 0.015-0.020 parts;

[0043] Retarder: 0.001-0.003 parts;

[0044] Water: 0.35-0.45 parts;

[0045] The alkali-activated precursor is granulated blast furnace slag powder; the composite alkali activator consists of a main activating component and an auxiliary activating component. The main activating component is a mixture of sodium silicate solution and solid sodium hydroxide with a modulus of 0.9-1.1, and the auxiliary activating component is a soluble aluminum salt, which accounts for 1.5%-3.0% of the total mass of the composite alkali activator (the addition of soluble aluminum salt promotes the in-situ generation of micro-expanded ettringite phase during the hardening process of concrete, and its volume expansion rate is controlled at 0.01%-0.03%, which is used to compensate for the chemical shrinkage caused by the alkali activation reaction).

[0046] The amount of natural sand used is 0 parts, meaning that all the fine aggregate in the concrete is made up of iron tailings sand. The preferred option of "all solid waste fine aggregate" is selected, which maximizes the utilization of solid waste and enhances the advanced nature and environmental value of the solution.

[0047] The specific surface area of ​​granulated blast furnace slag powder is 390-420 m² / kg, and its activity index is not less than 95%. The chemical composition of the granulated blast furnace slag powder by mass percentage is as follows: CaO: 35-55 wt%, SiO2: 35-45%, Al2O3: 3-15%, MgO: 1-10%, SO3: 0.2-2.5%; Fe2O3: 0.2-0.7%, TiO2: 0-0.8%, K2O: 0.2-0.5%, Na2O: 0-0.7%, with the remainder being impurities.

[0048] The fineness modulus of iron tailings sand is 2.6-3.0, and the apparent density is 2800-2900 kg / m³. 3 The bulk density is 1600-1650 kg / m³ 3 The chemical composition of iron tailings sand includes 35-40 wt% SiO2, 12-18 wt% CaO and 6-10 wt% TFe.

[0049] The recycled glass fibers used in wind turbine blades are 12-25 mm in length and 10-15 μm in diameter, treated with a surface coupling agent; their tensile strength is 1700-2500 MPa; their elastic modulus is 65-72 GPa; and their apparent density is 2400-2600 kg / m³. 3 .

[0050] The molar ratio of Na2O to SiO2 in the sodium silicate solution is 2.0; the solid sodium hydroxide is chemically pure sodium hydroxide with a purity of 98% or higher; the soluble aluminum salt is aluminum sulfate, sodium aluminate, or aluminum nitrate.

[0051] A method for preparing recycled fiber-based high-solid-waste low-carbon concrete for wind turbine blades includes the following steps:

[0052] (1) Preparation of composite activator: Dissolve solid sodium hydroxide in part of the mixing water, cool to room temperature, add sodium silicate solution, then add soluble aluminum salt, stir until completely dissolved, seal and age for 12-24 hours to obtain composite alkali activator;

[0053] (2) Dry mixing: Put granulated blast furnace slag powder, iron tailings sand, recycled aggregate and natural sand (if any) into a mixer and dry mix for 2-3 minutes until uniform;

[0054] (3) Wet mixing: Add the composite alkali activator prepared in step (1) and the remaining mixing water to the dry mixture, and stir for 3-4 minutes until uniform.

[0055] (4) Fiber incorporation: Under stirring conditions, the recycled glass fiber of the wind turbine blades is evenly sprinkled in 2-3 batches, and stirring is continued for 1-2 minutes until the fiber is evenly dispersed and there are no clumps, thus obtaining the high solid waste alkali activated concrete mixture.

[0056] Raw material description:

[0057] Granulated blast furnace slag powder: specific surface area 405 m² / kg, activity index 98%, chemical composition (wt%): CaO 48.2%, SiO2 39.5%, Al2O3 8.7%, MgO 2.1%, SO3 1.3%, Fe2O3 0.5%, balance being trace impurities.

[0058] Iron tailings sand: fineness modulus 2.8, apparent density 2850 kg / m³, bulk density 1620 kg / m³, chemical composition (wt%): SiO2 37.3%, CaO 15.1%, TFe 8.1%.

[0059] Recycled aggregate: Stones recovered from construction waste with a particle size of 5-15 mm.

[0060] Wind turbine blade recycled glass fiber: 18 mm in length, 12 μm in diameter, surface treated with KH-550 silane coupling agent, tensile strength 2100 MPa, elastic modulus 68 GPa.

[0061] Composite alkali activator: The main activating component is prepared by mixing sodium silicate solution with modulus 1.0 (Na2O:SiO2 molar ratio = 2.0) with chemically pure NaOH (≥98%); the auxiliary activating component is aluminum sulfate octadecylhydrate [Al2(SO4)3·18H2O].

[0062] Retarder: Sodium gluconate.

[0063] Natural sand: River sand, fineness modulus 2.7.

[0064] All raw material units in the following examples and comparative examples are in kg / m³.

[0065] Example 1 (Total Solid Waste System):

[0066] Slag powder: 450

[0067] Iron tailings sand: 720 (natural sand: 0)

[0068] Recycled aggregate: 1150

[0069] Composite alkaline activator: 90 (of which NaOH 30, sodium silicate solution 55, and aluminum sulfate 2.7 (accounting for 3.0% of the total mass of the activator))

[0070] Recycled glass fiber: 8.1

[0071] Retarder: 0.45

[0072] Water: 180

[0073] Preparation method: The concrete was prepared according to the above-mentioned method for preparing high-solids waste alkali-activated concrete, including the preparation of composite activator, dry mixing, wet mixing, and fiber incorporation. The composite activator was aged for 24 hours; the fibers were added in three batches, with a total mixing time of 6 minutes.

[0074] Example 2 (High solid waste system, containing a small amount of natural sand):

[0075] Slag powder: 450

[0076] Iron tailings sand: 360, natural sand: 360

[0077] Recycled aggregate: 1150

[0078] Compound alkali activator: 90 (aluminum sulfate dosage 2.25%, accounting for 2.5%)

[0079] Recycled glass fiber: 8.1

[0080] Retarder: 0.45

[0081] Water: 180

[0082] The preparation method is the same as in Example 1.

[0083] Example 3 (Preferred parameter combination)

[0084] Slag powder: 450

[0085] Iron tailings: 720

[0086] Recycled aggregate: 1150

[0087] Compound alkali activator: 90 (aluminum sulfate dosage 1.8, accounting for 2.0%)

[0088] Recycled glass fiber: 8.1

[0089] Retarder: 0.45

[0090] Water: 180

[0091] The preparation method is the same as in Example 1.

[0092] Comparative Example 1 (aluminum salt-free, otherwise the same as Example 1):

[0093] The formulation is exactly the same as in Example 1, but the composite alkali activator does not contain aluminum sulfate, that is, the activator is only NaOH + sodium silicate solution (90 kg).

[0094] Comparative Example 2 (including cement clinker):

[0095] P·O 42.5 cement: 36 (8% of cementitious materials)

[0096] Slag powder: 414

[0097] Iron tailings: 720

[0098] Recycled aggregate: 1150

[0099] NaOH + sodium silicate activator: 90 (aluminum-free)

[0100] Recycled glass fiber: 8.1

[0101] Retarder: 0.45

[0102] Water: 180

[0103] The preparation method is the same as in Example 1.

[0104] Performance testing and results analysis:

[0105] After all specimens have been cured to the specified age according to standard, the following properties are tested (drying shrinkage is tested according to GB / T 50082; plate cracking test is conducted according to ASTM C1581, with dimensions of 600×600×50 mm, and fan-assisted evaporation):

[0106] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 28-day compressive strength (MPa) 43.2 41.8 45.6 38.5 40.1 <![CDATA[56d drying shrinkage rate (×10 -6 )]]> 420 450 390 680 610 Plate cracking test (number of cracks / total area in 24 hours) 0 strips / 0 mm² 1 strip / 12 mm² 0 strips / 0 mm² 5 strips / 86 mm² 3 strips / 45 mm² 28-day compressive strength (MPa) 43.2 41.8 45.6 38.5 40.1 <![CDATA[56d drying shrinkage rate (×10 -6 )]]> 420 450 390 680 610 Plate cracking test (number of cracks / total area in 24 hours) 0 strips / 0 mm² 1 strip / 12 mm² 0 strips / 0 mm² 5 strips / 86 mm² 3 strips / 45 mm²

[0107] In summary, the following comparisons and conclusions can be drawn:

[0108] Compressive strength: The strength of Examples 1-3 was higher than that of Comparative Examples 1 and 2, indicating that the introduction of aluminum salt not only did not weaken the strength, but also improved the mechanical properties by promoting the reaction and densifying the microstructure. Example 3 had the highest strength due to the optimized amount of aluminum salt.

[0109] Volume stability: The drying shrinkage rates of Examples 1-3 were significantly lower than those of Comparative Example 1 (reduced by approximately 38-43%) and Comparative Example 2 (reduced by approximately 36-41%), which directly proves that the micro-expanded ettringite induced by soluble aluminum salts effectively compensates for shrinkage and solves the inherent defects of alkali-activated materials.

[0110] Crack resistance: In the stringent plate cracking test, Examples 1 and 3 showed no cracks at all, while Comparative Example 1 showed multiple through cracks and Comparative Example 2 also showed obvious cracking. This fully demonstrates the synergistic crack resistance advantage of the dual mechanism of "chemical compensation + physical crack resistance" in this application.

[0111] Solid waste utilization value: Example 1 achieved zero cement and all solid waste aggregate, while Comparative Example 2 still relied on 8% cement, which violated the original intention of low carbon; Although Comparative Example 1 had no cement, its performance deteriorated due to uncontrolled shrinkage, resulting in poor engineering applicability.

[0112] Therefore, this application, through the innovative combination of composite alkali activator (containing aluminum salt) + iron tailings sand + wind turbine blade recycled fiber, achieves ultra-high solid waste content while significantly improving the volume stability and crack resistance of alkali-activated concrete, with technical effects far exceeding those of existing technologies.

[0113] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A type of recycled fiber-based high-solids-waste low-carbon concrete for wind turbine blades, characterized in that... Composed of the following raw materials in parts by weight: Alkali-activated active precursor: 0.9-1.1 parts; Iron tailings: 0.4-0.8 parts; Natural sand: 0-1.1 parts; Recycled aggregate: 1.9-2.4 parts; Compound alkali activator: 0.15-0.20 parts; Recycled glass fiber for wind turbine blades: 0.015-0.020 parts; Retarder: 0.001-0.003 parts; Water: 0.35-0.45 parts; The alkali-activated precursor is granulated blast furnace slag powder; the composite alkali activator consists of a main activating component and an auxiliary activating component. The main activating component is a mixture of sodium silicate solution and solid sodium hydroxide with a modulus of 0.9-1.1, and the auxiliary activating component is a soluble aluminum salt, the amount of which accounts for 1.5%-3.0% of the total mass of the composite alkali activator.

2. The high-solids waste alkali-activated concrete as described in claim 1, characterized in that: The amount of natural sand used is 0 parts, meaning that the fine aggregate of the concrete is entirely composed of iron tailings sand.

3. The high-solids waste alkali-activated concrete according to claim 1, characterized in that: The granulated blast furnace slag powder has a specific surface area of ​​390–420 m² / kg and an activity index of not less than 95%.

4. The wind turbine blade recycled fiber-based high-solids-waste low-carbon concrete according to claim 1, characterized in that: The chemical composition by mass percentage of the granulated blast furnace slag powder is as follows: CaO: 35-55 wt%, SiO2: 35-45%, Al2O3: 3-15%, MgO: 1-10%, SO3: 0.2-2.5%; Fe2O3: 0.2-0.7%, TiO2: 0-0.8%, K2O: 0.2-0.5%, Na2O: 0-0.7%, with the remainder being impurities.

5. The wind turbine blade recycled fiber-based high-solids-waste low-carbon concrete according to claim 1, characterized in that: The fineness modulus of the iron tailings sand is 2.6-3.0, and the apparent density is 2800-2900 kg / m³. 3 The bulk density is 1600-1650 kg / m³ 3 .

6. The wind turbine blade recycled fiber-based high-solids-waste low-carbon concrete according to claim 5, characterized in that: The chemical composition of the iron tailings sand includes 35-40 wt% SiO2, 12-18 wt% CaO and 6-10 wt% TFe.

7. The wind turbine blade recycled fiber-based high-solids-waste low-carbon concrete according to claim 1, characterized in that, The recycled glass fibers used in the wind turbine blades are 12-25 mm in length and 10-15 μm in diameter, and are treated with a surface coupling agent; their tensile strength is 1700-2500 MPa; their elastic modulus is 65-72 GPa; and their apparent density is 2400-2600 kg / m³. 3 .

8. The wind turbine blade recycled fiber-based high-solid-waste low-carbon concrete according to claim 1, characterized in that, The molar ratio of Na2O to SiO2 in the sodium silicate solution is 2.0; the solid sodium hydroxide is chemically pure sodium hydroxide with a purity of 98% or higher.

9. The wind turbine blade recycled fiber-based high-solids-waste low-carbon concrete according to claim 1, characterized in that, The soluble aluminum salt is aluminum sulfate, sodium aluminate, or aluminum nitrate.

10. A method for preparing recycled fiber-based high-solid-waste low-carbon concrete for wind turbine blades as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of composite activator: Dissolve solid sodium hydroxide in part of the mixing water, cool to room temperature, add sodium silicate solution, then add soluble aluminum salt, stir until completely dissolved, seal and age for 12-24 hours to obtain composite alkali activator; (2) Dry mixing: Add granulated blast furnace slag powder, iron tailings sand, recycled aggregate and natural sand into a mixer and dry mix for 2-3 minutes until uniform. (3) Wet mixing: Add the composite alkali activator prepared in step (1) and the remaining mixing water to the dry mixture, and stir for 3-4 minutes until uniform. (4) Fiber incorporation: Under stirring conditions, the recycled glass fiber of the wind turbine blades is evenly sprinkled in 2-3 batches, and stirring is continued for 1-2 minutes until the fiber is evenly dispersed and there are no clumps, thus obtaining the high solid waste alkali activated concrete mixture.