Cold region geopolymer hydraulic shotcrete based on multi-element solid waste and construction method

Abstract

The invention discloses a cold region geopolymer hydraulic shotcrete based on multi-element solid waste and a construction method, and belongs to the technical field of geopolymer concrete. According to the method, slag powder, decommissioned fan blade micro powder, red brick micro powder and nano silicon dioxide form a composite precursor, instant potassium silicate and sodium metasilicate pentahydrate form a composite alkali activator, rubber powder and decommissioned fan blade fibers serve as additives, polyvinyl alcohol serves as a modifier, sand, stone and stone powder serve as aggregate, and the composite alkali activator and the rubber powder serve as additives. And solidifying to form the geopolymer hydraulic shotcrete. During construction, a two-time alkali excitation mode is adopted, a mixture can be rapidly coagulated after being sprayed out, the hydraulic tunnel supporting requirement is met, instant potassium silicate serves as a first alkali activator and can effectively inhibit the common frost returning phenomenon of geopolymer concrete, meanwhile, geopolymers are modified through polyvinyl alcohol, the bonding strength can be improved, the spraying rebound rate is reduced, and the stability of the geopolymer concrete is improved. The anti-cracking performance is improved, the freeze-thaw resistance and the impermeability of the geopolymer are improved, and a powerful guarantee is provided for the safety of the hydraulic tunnel.

Description

Technical Field

[0001] This invention belongs to the field of geopolymer concrete technology, and in particular relates to geopolymer hydraulic sprayed concrete and construction method based on multi-element solid waste in cold regions. Background Technology

[0002] With rapid industrialization, my country's solid waste generation is increasing daily. Proper disposal of solid waste is essential for improving the human living environment and protecting human health. Early wind turbine equipment is nearing retirement, and current methods for treating waste blades are not mature, resulting in a large amount of new solid waste. Waste tires degrade slowly, and my country's recycling rate is low, posing a threat to human health and representing a form of solid waste that harms the natural ecosystem. Furthermore, the excavation of hydraulic tunnels generates a large amount of waste rock, which, after crushing, can be used as concrete aggregate, but also produces a large amount of stone chips, causing serious environmental pollution. The shotcrete construction for hydraulic tunnel support suffers from significant rebound, leading to increased costs, extended construction periods, and compromised construction safety. Additionally, hydraulic tunnels are subject to high-speed water flow erosion and should possess corresponding abrasion resistance. Since shotcrete projects are subject to severe freeze-thaw erosion, the shotcrete should have a certain resistance to freeze-thaw cycles; therefore, it is necessary to improve the overall performance of shotcrete. Summary of the Invention

[0003] This invention aims to replace traditional silicate cement with geopolymer concrete technology, and to make full use of the above-mentioned new solid waste. It combines recycled fibers and powders made from retired wind turbine blades, rubber powder made from waste tires, and waste stone chips into a multi-element solid waste. The composite cementitious material is then chemically reacted and solidified through alkali activation to prepare a geopolymer concrete for use in hydraulic sprayed concrete and to improve its performance indicators.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: cold region geopolymer sprayed concrete based on multi-element solid waste, the raw materials of which are composed of composite precursor, composite alkali activator, additives, modifiers and aggregates; The composite precursor includes slag powder, decommissioned wind turbine blade powder, red brick powder and nano silica; The composite alkaline activator includes fast-dissolving potassium silicate and sodium metasilicate pentahydrate; The additive is composed of rubber powder and fibers from decommissioned wind turbine blades; Fibers from decommissioned wind turbine blades can improve the impact and abrasion resistance and crack resistance of concrete.

[0005] The modifier is polyvinyl alcohol; The aggregates include sand, stone, and stone powder.

[0006] Furthermore, the raw materials, by weight, are as follows: 350-390 parts slag powder, 50-100 parts decommissioned wind turbine blade powder, 28-32 parts red brick powder, 3-5 parts nano silica, 30-50 parts readily soluble potassium silicate, 15-20 parts sodium metasilicate pentahydrate, 25-30 parts rubber powder, 1-2 parts decommissioned wind turbine blade fiber, 3-5 parts polyvinyl alcohol, 795-845 parts sand, 60-100 parts stone powder, and 685-735 parts stone; when preparing the mixture, an additional 180-200 parts by weight of water needs to be added.

[0007] Furthermore, the slag powder is of grade S95 or S105, with a specific surface area of ​​not less than 400 m². 2 / kg; the red brick powder is made by crushing and grinding waste red bricks, with a fineness of 200 mesh; the decommissioned wind turbine blade powder is made by grinding and screening decommissioned wind turbine blades, with a fineness of 200 mesh; the nano silica has a particle size of 5-100nm.

[0008] Furthermore, the readily soluble potassium silicate is an industrial-grade white powder with a modulus of 2.3-2.5; the sodium metasilicate pentahydrate is an industrial-grade white powder with a fineness of 60 mesh.

[0009] Furthermore, the rubber powder is made from crushed and ground old tires with a fineness of 150 mesh; the decommissioned wind turbine blade fiber monofilament has a diameter of 5μm and a length of 3-5mm.

[0010] Furthermore, the polyvinyl alcohol is a dry powder mixture with a fineness of 160 mesh.

[0011] Furthermore, the sand is natural sand with a fineness modulus of 2.4-2.8; the crushed stone has a particle size of 5-15mm; and the stone powder is obtained by screening waste stone chips with a particle size of no more than 0.16mm.

[0012] A construction method for hydraulic shotcrete based on multi-component solid waste in cold regions includes the following steps: Step S1: Preparation of premix; By weight, add 350-390 parts of slag powder, 50-100 parts of decommissioned wind turbine blade powder, 28-32 parts of red brick powder, 3-5 parts of nano silica, 25-30 parts of rubber powder, 1-2 parts of decommissioned wind turbine blade fiber, 3-5 parts of polyvinyl alcohol, 795-845 parts of natural sand, 60-100 parts of stone powder, and 685-735 parts of crushed stone to a mixer and use forced mixing for 3 minutes to obtain a uniform premix. Step S2: Initial alkaline activation; Dissolve 30-50 parts by weight of fast-dissolving potassium silicate in 120-140 parts by weight of water. After it is fully dissolved, put it into a mixer and continue to use forced stirring for at least 2 minutes to complete the first alkali activation. Step S3: Transportation of shotcrete; The mixture after the first alkali activation is transported to the construction site by concrete pump truck, and the spraying operation must be completed within 2 hours after the first alkali activation. Step S4: Secondary alkaline activation; Upon arrival at the spraying operation site, dissolve 15-20 parts by weight of sodium metasilicate pentahydrate in 60 parts by weight of water to prepare a secondary alkali activation solution. This secondary alkali activation solution is added to the mixture through the nozzle of the concrete spraying machine for secondary alkali activation. Step S5: Spraying operation; The shotcrete operation is carried out in sections or segments. The shotcrete is applied to the bedrock surface of the tunnel surrounding rock to be supported in the order of first the side surface and then the top surface, and from bottom to top. The thickness of the first shotcrete is controlled to be 10-30mm, and the thickness of the second shotcrete is controlled to be 20-40mm. The second shotcrete should be applied 5-10 minutes after the first shotcrete has set. Step S6: Curing of cold-region geopolymer shotcrete based on multi-element solid waste; Start water spraying for curing 2 hours after final setting, and the curing time is 7-14 days.

[0013] Through the above design scheme, the present invention can bring the following beneficial effects: This invention uses slag powder, decommissioned wind turbine blade powder, red brick powder, and nano-silica as active precursors for geopolymers. Red brick powder enhances the compressive strength of concrete, while nano-silica, due to its high specific surface area and reactivity, strengthens the density and compressive strength of the geopolymer concrete and also acts as a retarder. The composite alkali activator consists of readily soluble potassium silicate and sodium metasilicate pentahydrate. The readily soluble potassium silicate provides initial activation, which, combined with the retarding effect of nano-silica, controls the setting time to 1.5-3.5 hours, facilitating construction. A secondary activation is achieved by adding sodium metasilicate pentahydrate aqueous solution at the nozzle, accelerating setting and ensuring the mixture sets within 12 minutes, meeting the requirements for hydraulic tunnel support. Furthermore, the readily soluble potassium silicate inhibits frost formation. Polyvinyl alcohol improves workability and reduces the water-cement ratio; decommissioned wind turbine blade fibers enhance impact and crack resistance; and rubber powder and nano-silica synergistically improve impermeability and frost resistance, ensuring safe production in hydraulic tunnels. At the same time, by replacing traditional silicate cement, it effectively reduces production energy consumption and carbon emissions, while consuming a large amount of solid waste, thus solving problems such as waste disposal and environmental degradation. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a diagram showing the relationship between mechanical properties in different embodiments of the present invention; Figure 3 The curves showing the change in rebound rate during construction in different embodiments of the present invention are shown. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0016] The present invention provides a solution for cold-region geopolymer sprayed concrete based on multi-component solid waste, wherein the raw materials consist of composite precursors, composite alkali activators, additives, modifiers, and aggregates. The composite precursor includes slag powder, decommissioned wind turbine blade powder, red brick powder and nano silica; In this invention, decommissioned wind turbine blades, after being processed into micro-powder, possess a certain degree of activity, thus serving as a precursor for geopolymers. Red brick micro-powder exhibits high pozzolanic activity, and its use as a geopolymer precursor can improve the compressive strength of geopolymer concrete. Nano-silica, a material with a high specific surface area and high reactivity, can effectively enhance the density, compressive strength, and carbonation resistance of geopolymer concrete, thereby improving its durability. Furthermore, nano-silica also has a retarding effect in this composite geopolymer.

[0017] In this invention, "cold region" mainly refers to frigid areas, meaning that buildings in cold regions are subject to freeze-thaw damage during winter. Therefore, the performance of concrete in cold regions must take into account its freeze-thaw resistance.

[0018] Climate zones should be determined based on the average temperature of the coldest month as follows: ① Severe cold: average temperature of the coldest month t < -10℃. ②Cold: The average temperature of the coldest month is -10℃≤t<-3℃; ③Mild: The average temperature of the coldest month is t>-3℃.

[0019] The composite alkaline activator includes fast-dissolving potassium silicate and sodium metasilicate pentahydrate; A composite alkali activator composed of readily soluble potassium silicate and sodium metasilicate pentahydrate is used. The readily soluble potassium silicate initially activates the concrete, but due to the effect of nano-silica, the setting time is relatively long (1.5-3.5 hours), facilitating construction. A mixed aqueous solution of sodium metasilicate pentahydrate is added at the nozzle for secondary activation. At this point, the sodium metasilicate pentahydrate solution has a setting-promoting effect, allowing the mixture to set within 12 minutes after spraying, meeting the requirements for hydraulic tunnel support. As a preliminary alkali activator, readily soluble potassium silicate is more effective than alkaline sodium salt activators in suppressing the common frosting phenomenon in polymer concrete.

[0020] The additive is composed of rubber powder and fibers from decommissioned wind turbine blades; The modifier is polyvinyl alcohol; The aggregates include sand, stone, and stone powder.

[0021] Polyvinyl alcohol (PVA) can improve the workability of polymer concrete, reduce the water-cement ratio, and thus enhance the strength, freeze-thaw resistance, and impermeability of the concrete. The combined application of rubber powder and nano-silica can improve the impermeability and freeze-thaw resistance of polymer concrete. Modification of polymers with PVA can increase bond strength and reduce spray rebound rate, while also improving crack resistance, freeze-thaw resistance, and impermeability.

[0022] Furthermore, the raw materials, by weight, are as follows: 350-390 parts slag powder, 50-100 parts decommissioned wind turbine blade powder, 28-32 parts red brick powder, 3-5 parts nano silica, 30-50 parts readily soluble potassium silicate, 15-20 parts sodium metasilicate pentahydrate, 25-30 parts rubber powder, 1-2 parts decommissioned wind turbine blade fiber, 3-5 parts polyvinyl alcohol, 795-845 parts sand, 60-100 parts stone powder, and 685-735 parts stone; when preparing the mixture, an additional 180-200 parts by weight of water needs to be added.

[0023] Furthermore, the slag powder is of grade S95 or S105, with a specific surface area of ​​not less than 400 m². 2 / kg; the red brick powder is made by crushing and grinding waste red bricks, with a fineness of 200 mesh; the decommissioned wind turbine blade powder is made by grinding and screening decommissioned wind turbine blades, with a fineness of 200 mesh; the nano silica has a particle size of 5-100nm.

[0024] Furthermore, the readily soluble potassium silicate is an industrial-grade white powder with a modulus of 2.3-2.5; the sodium metasilicate pentahydrate is an industrial-grade white powder with a fineness of 60 mesh.

[0025] Furthermore, the rubber powder is made from crushed and ground old tires with a fineness of 150 mesh; the decommissioned wind turbine blade fiber monofilament has a diameter of 5μm and a length of 3-5mm.

[0026] Furthermore, the polyvinyl alcohol is a dry powder mixture with a fineness of 160 mesh.

[0027] Furthermore, the sand is natural sand with a fineness modulus of 2.4-2.8; the crushed stone has a particle size of 5-15mm; and the stone powder is obtained by screening waste stone chips with a particle size of no more than 0.16mm.

[0028] The steps for preparing fibers for decommissioned wind turbine blades are as follows: S1: After cutting the retired wind turbine blades into small pieces, put them into a toothed roller crusher to crush them into 250-1250mm filamentous primary material; S2: Put the filamentous primary material into a hammer mill and crush it again at a speed of 4000 r / min for 0.5h-1h to crush it into a mixture of fiber and powder. S3: The mixture is screened through 3mm and 5mm sieves. The material on the 5mm sieve can be further processed in a hammer mill. The powder below the 3mm sieve is the micro powder coarse material of retired fan blades. The material between the 3mm and 5mm sieve grades is the regenerated fiber of retired fan blades.

[0029] A construction method for hydraulic shotcrete based on multi-component solid waste in cold regions includes the following steps: Step S1: Preparation of premix; By weight, add 350-390 parts of slag powder, 50-100 parts of decommissioned wind turbine blade powder, 28-32 parts of red brick powder, 3-5 parts of nano silica, 25-30 parts of rubber powder, 1-2 parts of decommissioned wind turbine blade fiber, 3-5 parts of polyvinyl alcohol, 795-845 parts of natural sand, 60-100 parts of stone powder, and 685-735 parts of crushed stone to a mixer and use forced mixing for 3 minutes to obtain a uniform premix. Step S2: Initial alkaline activation; Dissolve 30-50 parts by weight of fast-dissolving potassium silicate in 120-140 parts by weight of water. After it is fully dissolved, put it into a mixer and continue to use forced stirring for at least 2 minutes to complete the first alkali activation. Step S3: Transportation of shotcrete; The mixture after the first alkali activation is transported to the construction site by concrete pump truck, and the spraying operation must be completed within 2 hours after the first alkali activation. Step S4: Secondary alkaline activation; Upon arrival at the spraying operation site, dissolve 15-20 parts by weight of sodium metasilicate pentahydrate in 60 parts by weight of water to prepare a secondary alkali activation solution. This secondary alkali activation solution is added to the mixture through the nozzle of the concrete spraying machine for secondary alkali activation. The secondary alkali activation solution is added through the nozzle of the concrete spraying machine via airflow, thus eliminating the need for mixing. The total water consumption is 180-200 parts, divided into 120-140 parts for the initial activation and 60 parts for the secondary activation.

[0030] Step S5: Spraying operation; The shotcrete operation is carried out in sections or segments. The shotcrete is applied to the bedrock surface of the tunnel surrounding rock to be supported in the order of first the side surface and then the top surface, and from bottom to top. The thickness of the first shotcrete is controlled to be 10-30mm, and the thickness of the second shotcrete is controlled to be 20-40mm. The second shotcrete should be applied 5-10 minutes after the first shotcrete has set. The final setting time for the first and second sprayings is within 12 minutes. The second spraying should be carried out 5-10 minutes after the first sprayed concrete has set. That is, at least 5-10 minutes should pass between the first and second sprayings, otherwise the concrete may fall off due to its own weight.

[0031] Step S6: Curing of cold-region geopolymer shotcrete based on multi-element solid waste; Start water spraying for curing 2 hours after final setting, and the curing time is 7-14 days.

[0032] The sprayed concrete curing process employs water spraying, using sprayers or similar tools to keep the concrete surface moist, with a relative humidity generally not lower than 90%. Insulation measures should be implemented when the temperature is below 5℃, and water spraying should only be carried out when the temperature rises above 5℃. Insulation measures are achieved by adding cotton curtain enclosures at the tunnel entrance and installing heating devices inside the tunnel when the temperature is lower than the design requirements. This improves the overall insulation effect of the space by blocking air convection, reducing heat loss, and enhancing the overall warmth of the space. Example 1

[0033] 350 parts of slag powder, 50 parts of decommissioned wind turbine blade powder, 28 parts of red brick powder, 3 parts of nano-silica, 25 parts of rubber powder, 1 part of decommissioned wind turbine blade fiber, 3 parts of polyvinyl alcohol, 845 parts of natural sand, 100 parts of stone powder, and 735 parts of crushed stone were placed in a mixer and forcibly mixed for 3 minutes. Then, 30 parts of readily soluble potassium silicate were dissolved in 120 parts of water, fully dissolved, and added to the mixer, and forcibly mixed for at least 2 minutes. At the start of the spraying operation, 15 parts of sodium metasilicate pentahydrate were dissolved in 60 parts of water, and the alkaline solution was added to the nozzle of the concrete spraying machine. Twenty-eight days after the completion of the field test section spraying, one set of core samples was drilled for compressive and bond strength tests. Bond strength was tested using the splitting method. The rebound rate was calculated based on the volume of sprayed material and the volume of rebounded material.

[0034] For the frost resistance test, a large sprayed board was used. The wooden mold of the large board had dimensions of 450×350×200mm. After spraying, it was cured under the same conditions as the construction for 28 days. The board was then cut into 400×100×100mm specimens, three in a group. For the impermeability test, six cylindrical specimens with a diameter and height of 150mm were drilled from the large board and tested for compressive strength, frost resistance, and impermeability. For the impact and abrasion resistance test, three flat cylindrical specimens (300mm in diameter and 100mm in height) were sprayed directly into the mold from bottom to top. After spraying, the specimens were cured under the same conditions as the construction for 28 days and tested using the underwater steel ball method. Example 2

[0035] 360 parts of slag powder, 62 parts of decommissioned wind turbine blade powder, 29 parts of red brick powder, 3 parts of nano-silica, 26 parts of rubber powder, 1 part of decommissioned wind turbine blade fiber, 3 parts of polyvinyl alcohol, 830 parts of natural sand, 90 parts of stone powder, and 720 parts of crushed stone were placed in a mixer and forcibly stirred for 3 minutes. Then, 35 parts of fast-dissolving potassium silicate were dissolved in 125 parts of water, and after complete dissolution, added to the mixer and forcibly stirred for at least 2 minutes. 16 parts of sodium metasilicate pentahydrate were dissolved in 60 parts of water, and the alkaline solution was added to the nozzle of the concrete spraying machine at the start of the spraying operation. Core sampling and sample preparation were the same as in Example 1. Example 3

[0036] 370 parts of slag powder, 75 parts of decommissioned wind turbine blade powder, 30 parts of red brick powder, 4 parts of nano-silica, 27 parts of rubber powder, 1 part of decommissioned wind turbine blade fiber, 4 parts of polyvinyl alcohol, 815 parts of natural sand, 80 parts of stone powder, and 705 parts of crushed stone were placed in a mixer and forcibly stirred for 3 minutes. Then, 40 parts of fast-dissolving potassium silicate were dissolved in 130 parts of water, and after complete dissolution, added to the mixer and forcibly stirred for at least 2 minutes. 17 parts of sodium metasilicate pentahydrate were dissolved in 60 parts of water, and the alkaline solution was added to the nozzle of the concrete spraying machine at the start of the spraying operation. Core sampling and sample preparation were the same as in Example 1. Example 4

[0037] 380 parts of slag powder, 88 parts of decommissioned wind turbine blade powder, 31 parts of red brick powder, 4 parts of nano-silica, 28 parts of rubber powder, 1 part of decommissioned wind turbine blade fiber, 4 parts of polyvinyl alcohol, 805 parts of natural sand, 70 parts of stone powder, and 695 parts of crushed stone were placed in a mixer and forcibly stirred for 3 minutes. Then, 45 parts of fast-dissolving potassium silicate were dissolved in 130 parts of water, and after complete dissolution, added to the mixer and forcibly stirred for at least 2 minutes. 18 parts of sodium metasilicate pentahydrate were dissolved in 60 parts of water, and the alkaline solution was added to the nozzle of the concrete spraying machine at the start of the spraying operation. Core sampling and sample preparation were the same as in Example 1. Example 5

[0038] 390 parts of slag powder, 100 parts of decommissioned wind turbine blade powder, 32 parts of red brick powder, 5 parts of nano-silica, 30 parts of rubber powder, 2 parts of decommissioned wind turbine blade fiber, 5 parts of polyvinyl alcohol, 795 parts of natural sand, 60 parts of stone powder, and 685 parts of crushed stone were placed in a mixer and forcibly stirred for 3 minutes. 50 parts of readily soluble potassium silicate were dissolved in 140 parts of water and added to the mixer after complete dissolution, and forcibly stirred for at least 2 minutes. Finally, 20 parts of sodium metasilicate pentahydrate were dissolved in 60 parts of water, and the alkaline solution was added to the nozzle of the concrete spraying machine to begin spraying. Core sampling and sample preparation were the same as in Example 1.

[0039]

[0040] The embodiments provided by this technical solution show that after adding a mixed aqueous solution of sodium metasilicate pentahydrate to the nozzle for secondary activation, the mixture solidifies within 7.5 to 11 minutes after being sprayed out. All five embodiments meet the requirement of the "Technical Specification for Anchor Spraying Support of Water Conservancy and Hydropower Projects" SL / T377 that the final setting time is no more than 12 minutes. Figure 2 The results show that the 1-day compressive strength of the five examples ranges from 23.5 MPa to 31.2 MPa, far exceeding the standard requirement of no less than 8 MPa. This is beneficial for tunnel support under complex and special conditions. The standard requires that the 28-day compressive strength of large caverns, hydraulic tunnels, and engineering support under special conditions should not be lower than C25. The 28-day compressive strength of the examples ranges from 41.6 to 52.8 MPa, meeting the standard requirements. The standard requires a 28-day bond strength of no less than 1.2 MPa for Class I and Class II surrounding rock, and no less than 0.8 MPa for Class III surrounding rock. The bond strength of the five examples ranges from 2.52 MPa to 2.85 MPa, far exceeding the standard requirements. This is extremely beneficial for tunnel support and can significantly reduce the rebound rate of shotcrete. Figure 3 The results show that the rebound rate of the five embodiments ranges from 3.8% to 8.6%, far below the standard requirement of no more than 12% for sidewalls. All five embodiments withstand more than 300 freeze-thaw cycles with relatively low mass loss and a small decrease in relative dynamic modulus. Embodiment 5 ultimately withstands over 400 freeze-thaw cycles, far exceeding the standard requirement of no less than 200 freeze-thaw cycles in cold regions. All five embodiments achieve a permeability rating of W12, higher than the standard requirement of W8. The impact and abrasion resistance of the five embodiments is 16.6 h / (kg / m²). 2 ~20.5h / (kg / m 2 ), compared to ordinary concrete 10 h / (kg / m 2 There is a significant improvement around 100%.

[0041] This invention utilizes a variety of solid waste materials through technological innovation. By using alkali activation, the composite precursor is activated twice to make it suitable for the process requirements of shotcrete. At the same time, a composite alkali activator composed of fast-dissolving potassium silicate and sodium metasilicate pentahydrate is used, which significantly inhibits the frost phenomenon of geopolymer concrete compared with a single alkaline sodium salt activator.

[0042] The test results of the embodiments show that the cold-region geopolymer shotcrete based on multi-element solid waste provided by the present invention has a setting time that meets the requirements of SL / T377 after spraying, and a significantly improved 1-day compressive strength, especially providing a safety guarantee for the early support of tunnels. It has high bond strength and effectively reduces the concrete rebound rate, reduces production costs and improves the safety of tunnel engineering quality. This new type of shotcrete has significantly improved frost resistance, impermeability and erosion resistance, providing a guarantee for the safe production of hydraulic tunnels. At the same time, because it actively consumes solid waste, it reduces energy consumption and helps to achieve the "dual carbon" goal as soon as possible.

Claims

1. A cold-region geopolymer shotcrete based on multi-element solid waste, characterized in that: The raw materials consist of composite precursors, composite alkali activators, additives, modifiers, and aggregates; The composite precursor includes slag powder, decommissioned wind turbine blade powder, red brick powder and nano silica; The composite alkaline activator includes fast-dissolving potassium silicate and sodium metasilicate pentahydrate; The additive is composed of rubber powder and fibers from decommissioned wind turbine blades; The modifier is polyvinyl alcohol; The aggregates include sand, stone, and stone powder.

2. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that, The raw materials, by weight, consist of: 350-390 parts slag powder, 50-100 parts decommissioned wind turbine blade powder, 28-32 parts red brick powder, 3-5 parts nano silica, 30-50 parts readily soluble potassium silicate, 15-20 parts sodium metasilicate pentahydrate, 25-30 parts rubber powder, 1-2 parts decommissioned wind turbine blade fiber, 3-5 parts polyvinyl alcohol, 795-845 parts sand, 60-100 parts stone powder, and 685-735 parts stone. An additional 180-200 parts by weight of water must be added during preparation.

3. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that: The slag powder is of grade S95 or S105, with a specific surface area of ​​not less than 400 m². 2 / kg; the red brick powder is made by crushing and grinding waste red bricks, with a fineness of 200 mesh; the decommissioned wind turbine blade powder is made by grinding and screening decommissioned wind turbine blades, with a fineness of 200 mesh; the nano silica has a particle size of 5-100nm.

4. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that: The fast-dissolving potassium silicate is an industrial-grade white powder with a modulus of 2.3-2.5; the sodium metasilicate pentahydrate is an industrial-grade white powder with a fineness of 60 mesh.

5. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that: The rubber powder is made from crushed and ground old tires with a fineness of 150 mesh; the fiber monofilaments of the retired wind turbine blades have a diameter of 5μm and a length of 3-5mm.

6. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that: The polyvinyl alcohol is a dry powder mixture with a fineness of 160 mesh.

7. The cold-region geopolymer shotcrete based on multi-element solid waste according to claim 1, characterized in that: The sand is natural sand with a fineness modulus of 2.4-2.8; the crushed stone has a particle size of 5-15mm; and the stone powder is obtained by screening waste stone chips with a particle size of no more than 0.16mm.

8. A construction method for cold-region geopolymer shotcrete based on multi-element solid waste, characterized in that, Includes the following steps: Step S1: Preparation of premix; By weight, add 350-390 parts of slag powder, 50-100 parts of decommissioned wind turbine blade powder, 28-32 parts of red brick powder, 3-5 parts of nano silica, 25-30 parts of rubber powder, 1-2 parts of decommissioned wind turbine blade fiber, 3-5 parts of polyvinyl alcohol, 795-845 parts of natural sand, 60-100 parts of stone powder, and 685-735 parts of crushed stone to a mixer and use forced mixing for 3 minutes to obtain a uniform premix. Step S2: Initial alkaline activation; Dissolve 30-50 parts by weight of fast-dissolving potassium silicate in 120-140 parts by weight of water. After it is fully dissolved, put it into a mixer and continue to use forced stirring for at least 2 minutes to complete the first alkali activation. Step S3: Transportation of shotcrete; The mixture after the first alkali activation is transported to the construction site by concrete pump truck, and the spraying operation must be completed within 2 hours after the first alkali activation. Step S4: Secondary alkaline activation; Upon arrival at the spraying operation site, dissolve 15-20 parts by weight of sodium metasilicate pentahydrate in 60 parts by weight of water to prepare a secondary alkali activation solution. This secondary alkali activation solution is added to the mixture through the nozzle of the concrete spraying machine for secondary alkali activation. Step S5: Spraying operation; The shotcrete operation is carried out in sections or segments. The shotcrete is applied to the bedrock surface of the tunnel surrounding rock to be supported in the order of first the side surface and then the top surface, and from bottom to top. The thickness of the first shotcrete is controlled to be 10-30mm, and the thickness of the second shotcrete is controlled to be 20-40mm. The second shotcrete should be applied 5-10 minutes after the first shotcrete has set. Step S6: Curing of cold-region geopolymer shotcrete based on multi-element solid waste; Start water spraying for curing 2 hours after final setting, and the curing time is 7-14 days.

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