A solid waste-based concrete material, its preparation method and application

Abstract

This invention discloses a solid waste-based concrete material, its preparation method, and its application, belonging to the field of solid waste comprehensive utilization technology. It comprises the following raw material components by weight: 62-87 parts mixed micro-powder, 8-15 parts cement, 5-11 parts slag micro-powder, 10-12 parts lime, 18-36 parts mixing water, and 0.4-1.25 parts water-reducing agent. The mixed micro-powder includes the following components: wet sand-making tailings, decommissioned wind turbine blades, and converter steel slag. The wet sand-making tailings are dried or air-dried and aged, then crushed together with the wind turbine blades, and finally mixed with the converter steel slag and roller-milled. This invention creatively achieves large-scale synergistic utilization of wet sand-making tailings and decommissioned wind turbine blades. The prepared and hardened solid waste-based concrete can be used for roadbed backfilling in rock mining areas and manufactured sand production enterprises to improve road bearing capacity; or for support and backfilling of rock mining goaf areas to prevent goaf collapse and realize on-site utilization of solid waste resources.

Description

Technical Field

[0001] This invention belongs to the field of solid waste comprehensive utilization technology, specifically relating to a solid waste-based concrete material and a method for preparing concrete material using wet sand-making tailings and waste wind turbine blades. Background Technology

[0002] In recent years, the market size of the sand and gravel aggregate industry has shown a steady growth trend. With increased investment in green building materials industrial parks and rising industry standards for resource utilization and environmental protection, the market size of sand and gravel aggregate will continue to expand. Compared to natural sand, manufactured sand has advantages in product quality and production cost, and can meet various customer needs by adjusting parameters. Therefore, the development momentum of manufactured sand has been extremely rapid in recent years.

[0003] The production processes for manufactured sand are mainly divided into wet and dry methods. In the wet sand-making process, after the mine rocks are crushed, screened, and subjected to multi-stage washing, solid waste formed by the agglomeration of mud and stone powder is separated, which is called tailings. Due to its strong adsorption and high impurity content, tailings are difficult to utilize in large quantities and efficiently. Currently, its treatment mainly involves pressure filtration to obtain blocky tailings filter cakes with a moisture content of about 20%, which are then transported and stockpiled or randomly landfilled. This treatment method not only increases transportation costs and occupies a large amount of land resources, but also poses many safety and environmental hazards, such as triggering debris flows and causing ecological damage.

[0004] Wind turbine blades are composite structures, made by combining glass fiber as reinforcement and synthetic resin as the matrix. As wind power facilities continue to operate, early-installed wind turbines gradually reach their designed service life, and retired wind turbine blades have become large-scale solid waste requiring urgent disposal. Currently, the mainstream disposal methods for retired wind turbine blades are landfill and incineration.

[0005] Due to the unique material and structure of wind turbine blades, they are difficult to degrade under natural conditions, and incineration releases large amounts of harmful gases. Existing landfill and incineration methods not only waste resources but also cause serious environmental pollution, making it difficult to achieve resource recycling and reuse of retired wind turbine blades. Therefore, how to rationally dispose of waste wind turbine blades has become a pressing technical challenge in this field.

[0006] Currently, some patents have been used to conduct research on the resource utilization of manufactured sand tailings. For example, CN118619579A discloses a cement-based material admixture based on manufactured sand tailings and its preparation method. The method uses chemical activation to improve the chemical reactivity of manufactured sand tailings. However, from the implementation path of this method, the invention does not take into account that most manufactured sand production enterprises are located in remote mountainous areas, and the cement-based material admixtures they produce need to consider the problem of transportation, which makes it impossible to realize the on-site disposal of tailings solid waste resources. At the same time, the fluctuation of demand in the building materials field may also make it difficult to achieve large-scale disposal of cement-based material admixtures produced by this method. Furthermore, the addition of ultrasonic treatment will further complicate the already cumbersome pretreatment process of manufactured sand tailings, and additional sites and storage containers are required to implement this method.

[0007] Therefore, developing an efficient disposal method for tailings from wet sand production lines that meets the requirements of large-scale consumption and has broad applicability is an important measure for the sand and gravel aggregate industry to reduce existing solid waste and increase new production capacity. Summary of the Invention

[0008] The purpose of this invention is to propose a method for the large-scale disposal of tailings solid waste from wet sand production lines and the co-processing of decommissioned wind turbine blades, using a lower processing cost. This method enables large-scale on-site disposal of bulk industrial solid waste from mining, reduces the environmental impact of long-term tailings stockpiling on mining areas, alleviates the environmental pressure on enterprises operating on a "waste-driven production" basis, and increases the overall production capacity of sand and gravel enterprises. Simultaneously, it can alleviate the pressure on the recycling and utilization of new energy solid waste resources to some extent.

[0009] The first objective of this invention is to provide a method for the large-scale disposal of wet-process sand-making tailings and decommissioned wind turbine blades, and for the preparation of solid waste-based concrete materials using these materials, comprising the following preparation steps: Step 1) Spread the wet sand-making tailings filter cake out in an open space to dry or place it in a greenhouse under the sun for natural air drying and aging. Step 2) The dried / aged tailings filter cake and retired wind turbine blades are crushed together by an impact crusher, and the two materials are evenly mixed by a mixer. Step 3) Add the dried mixed crushed material and converter steel slag together into a dry roller mill to make mixed micro powder; Step 4) Add cement, slag powder or lime and other inorganic binders to the mixed powder and mix. Then add water-reducing agent and appropriate amount of water and mix until uniform to make a mixed slurry. Step 5) The mixed slurry is foamed and expanded to obtain solid waste foamed slurry; Step 6) Pour the solid waste foaming slurry into the prepared mold, and then transfer the mold together to a hydrothermal environment for rapid curing to obtain a hardened green body; Step 7) Separate the hardened billet from the mold, and then transfer the billet to an environment filled with saturated water vapor for curing to obtain solid waste-based concrete material.

[0010] Furthermore, the initial moisture content of the filter cake from the wet sand-making line tailings in step 1) is 20-28%; the drying should be carried out in sunny weather, and the environmental conditions required for aging are a temperature of 20-30℃ and humidity of less than 70%. Furthermore, in step 1), the overall moisture content of the tailings is reduced to below 5% after sun-drying or air-drying and aging.

[0011] Furthermore, the impact crusher mentioned in step 2) is preferably of model CI1313 or HD1315, and the particle size of the crushed material is in the range of 10~54mm.

[0012] Furthermore, the mass ratio of tailings to wind turbine blades used in step 2) is 6.5~9:1~3.5.

[0013] Furthermore, in step 2), the mixer speed is between 15 and 60 rpm, and the material mixing time is ≥40 min.

[0014] Furthermore, in step 3), the mass of converter steel slag accounts for 1 / 5 to 2 / 3 of the mixed crushed material.

[0015] Furthermore, the grinding time described in step 3) is controlled to be 1~4 hours.

[0016] Furthermore, the stirring speed of the slurry in step 4) is 600~1200 rpm.

[0017] Further, the foaming and expansion treatment method described in step 5) is one of physical foaming or chemical foaming; the physical foaming method is nitrogen filling or foam particle filling, and the chemical foaming method is polyurethane foaming agent or aluminum powder foaming agent.

[0018] Furthermore, the volume of the solid waste mixture slurry described in step 5) expands by 0.3 to 0.8 times; Furthermore, in step 6), the hydrothermal environment temperature is controlled at 45~65℃, the humidity is controlled at 80~95%, and the hardening time is controlled at 1.2~4.5h; Further, the curing environment conditions described in step 7) are: temperature range 165~195℃, saturated steam pressure range 0.7~1.4MPa, and curing time 4~8h; The second objective of this invention is to provide a formula for preparing solid waste-based concrete material using wet sand-making tailings and decommissioned wind turbine blades as main raw materials: The solid waste-based concrete material comprises the following raw material components in parts by weight: 62-87 parts of mixed powder, 8-15 parts of cement, 5-11 parts of slag powder, 10-12 parts of lime, 18-36 parts of mixing water, and 0.4-1.25 parts of water-reducing agent.

[0019] The solid waste-based concrete material described above includes the following components: wet sand-making tailings, decommissioned wind turbine blades, and converter steel slag. The wet sand-making tailings are dried or air-dried and aged, then crushed together with the wind turbine blades, and then mixed with the converter steel slag and roller-milled.

[0020] In the solid waste-based concrete material described above, the SiO2 content in the wet sand-making tailings is ≥60%, and the CaO content is ≤5%.

[0021] In the solid waste-based concrete material described above, the volume content of glass fiber in the decommissioned wind turbine blades is 64-74%, and the volume content of resin matrix is ​​26-36%.

[0022] The solid waste-based concrete material as described above, wherein the cement is one or more of silicate cement, fly ash silicate cement, and slag silicate cement; the lime is calcareous lime that meets the requirements of CL85 grade or above in JC / T 479-2013, wherein the total effective calcium oxide and magnesium oxide content of the CL85 grade lime is not less than 85%.

[0023] The solid waste-based concrete material described above uses a melamine-based or polycarboxylate-based water-reducing agent as the water-reducing agent.

[0024] The third objective of this invention is to provide an application method for the above-mentioned solid waste-based concrete material, including: using the prepared and hardened solid waste-based concrete for roadbed backfilling in rock mining areas and manufactured sand production enterprises to improve the road bearing capacity; and cutting the hardened solid waste-based concrete to specific specifications for support and backfilling in rock mining goaf areas to prevent the collapse of goaf areas and realize the on-site utilization of solid waste resources.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention creatively integrates the large-scale co-processing of wet sand-making tailings solid waste with decommissioned wind turbine blades. By co-grinding the tailings filter cake and wind turbine blade fragments, the abrasion resistance of the dried tailings is used to create physical defects in the wind turbine blade fibers, improving the tight contact between the subsequent hardening materials and the wind turbine blade fibers. The subsequent high-temperature and high-pressure curing process further creates cracking defects in the wind turbine blade fibers, increasing the contact sites on the fiber surface and further improving the mechanical properties of the solid waste-based concrete material, which is conducive to the stable application of subsequent roadbed and other supporting materials.

[0026] The method provided by this invention can dispose of tailings on a large scale, greatly reducing the pressure on manufactured sand production enterprises to stockpile and dispose of tailings filter cake; the developed application method has wide applicability and is easy to replicate, and is suitable for most manufactured sand production enterprises to dispose of by-product solid waste resources on-site, saving the recycling cost of solid waste raw materials and achieving the goal of resource-based green development of mining solid waste. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The compositional analysis results of the wet sand-making tailings used in the embodiments of this application are shown in the following table. Table 1. Chemical composition analysis results of tailings from wet sand making line

[0029] Retired wind turbine blades are disassembled, and the blade body is retained, which is the main body of the blade made of fiberglass and synthetic resin.

[0030] Example 1 The method for preparing concrete materials using wet sand-making tailings and discarded wind turbine blades comprises the following steps: Step 1) Spread the tailings filter cake from the wet sand making line out to dry in an open area, and control the moisture content of the tailings filter cake to 5% or lower. Step 2) The dried tailings filter cake and retired wind turbine blades are crushed to a particle size range of 30~45mm by CI1313 impact crusher. The two solid waste materials are mixed at a ratio of tailings filter cake: retired wind turbine blades = 8:2. The mixer is started with the following parameters: mixer speed 30rpm, material mixing time 1h. Step 3) Add the dried mixed crushed material and converter steel slag together into a dry roller mill. The steel slag accounts for 2 / 5 of the mass of the mixed crushed material. The roller mill grinding time is 1 hour to make it into mixed micro powder. Step 4) Add 10 parts cement, 7 parts slag powder, and 12 parts lime to 70 parts solid waste mixed powder and mix. Then add 0.8 parts water-reducing agent and 29 parts water and mix until uniform to prepare solid waste mixed slurry. The water-reducing agent is polycarboxylate copolymer PCE, the lime is calcareous lime, CL85 grade in JC / T 479-2013, and the cement is ordinary Portland cement (P·O). Step 4) Add polyurethane foaming agent to the solid waste mixture slurry to expand the slurry by 0.6 times, and obtain solid waste foamed slurry; Step 5) Pour the solid waste foaming slurry into the prepared mold, and place the mold together in a curing environment at 55°C and 95% humidity for 2 hours to obtain a hardened green body; Step 6) Separate the hardened billet from the mold, and then transfer the billet to an environment filled with saturated water vapor at a temperature of 195°C and a saturated steam pressure of 1.4 MPa for 4.5 hours to obtain solid waste-based concrete material.

[0031] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 720 kg / m³. 3 It has a compressive strength of 4.2 MPa and a flexural strength of 1.6 MPa, which meets the requirements of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2019) for cement-stabilized base courses of Class II and below highways with heavy traffic, which have an unconfined compressive strength of 3.0~5.0 MPa at 7 days. It can be used as a substitute material for Class II highway base courses.

[0032] Example 2 The method for preparing concrete materials using wet sand-making tailings and discarded wind turbine blades comprises the following steps: Step 1) Spread the tailings filter cake from the wet sand making line out to dry in an open area, and control the moisture content of the tailings filter cake to 4% or lower. Step 2) The dried tailings filter cake and retired wind turbine blades are crushed to a particle size range of 15~28mm by CI1313 impact crusher. The two materials are mixed in a ratio of tailings filter cake: retired wind turbine blades = 7.5:2.5. The mixer is started with the following parameters: mixer speed 15rpm, material mixing time 50min. Step 3) Add the dried mixed crushed material and converter steel slag together into a dry roller mill. The steel slag accounts for 1 / 5 of the mass of the mixed crushed material. The roller mill grinding time is 1 hour to make it into mixed micro powder. Step 4) Add 12 parts cement, 6 parts slag powder, and 10 parts lime to 80 parts solid waste mixed powder and mix. Then add 0.5 parts water-reducing agent and 32 parts water and mix until uniform to make solid waste mixed slurry. The water-reducing agent is polycarboxylate copolymer PCE, the lime is calcareous lime, CL85 grade in JC / T 479-2013, and the cement is fly ash silicate cement. Step 5) Add foam particles to the solid waste mixture slurry to expand the slurry volume by 0.6 times, and obtain solid waste foamed slurry; Step 6) Pour the solid waste foaming slurry into the prepared mold, and place the mold together in a curing environment with a temperature of 47°C and a humidity of 85% for 2.5 hours to obtain a hardened green body; Step 7) Separate the hardened blank from the mold, and then transfer the blank to an environment filled with saturated water vapor at a temperature of 175°C and a saturated steam pressure of 0.89 MPa for 7 hours to obtain solid waste-based concrete material.

[0033] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 735 kg / m³. 3 It has a compressive strength of 4.4 MPa and a flexural strength of 1.3 MPa, which meets the requirements of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2019) for cement-stabilized base courses of Class II and below highways with heavy traffic, which have an unconfined compressive strength of 3.0~5.0 MPa at 7 days. It can be used as a substitute material for Class II highway base courses.

[0034] Example 3 The method for preparing concrete materials using wet sand-making tailings and discarded wind turbine blades comprises the following steps: Step 1) Spread the tailings filter cake from the wet sand making line out to dry in an open area, and control the moisture content of the tailings filter cake to 5% or lower. Step 2) The dried tailings filter cake and retired wind turbine blades are crushed to a particle size range of 24~30mm by CI1313 impact crusher. The two materials are then mixed in a ratio of tailings filter cake: retired wind turbine blades = 8.5:1.5. The mixer is started with the following parameters: mixer speed 45rpm, material mixing time 1h. Step 3) Add the dried mixed crushed material and converter steel slag together into a dry roller mill. The steel slag accounts for 1 / 2 of the mass of the mixed crushed material. The roller mill grinding time is 2.5 hours to make it into mixed micro powder. Step 4) Add 8 parts cement, 9 parts slag powder, and 12 parts lime to 75 parts solid waste mixed powder and mix. Then add 0.8 parts water-reducing agent and 34 parts water and mix until uniform to make solid waste mixed slurry. The water-reducing agent is sulfonated melamine formaldehyde condensate (SMF), the lime is calcareous lime, CL90 grade in JC / T 479-2013, and the cement is slag silicate cement. Step 5) Add polyurethane foaming agent to the solid waste mixture slurry to expand the slurry by 0.5 times to obtain solid waste foamed slurry; Step 6) Pour the solid waste foaming slurry into the prepared mold, and place the mold together in a curing environment with a temperature of 60°C and a humidity of 85% for 2 hours to obtain a hardened green body; Step 7) Separate the hardened blank from the mold, and then transfer the blank to an environment filled with saturated water vapor at a temperature of 180°C and a saturated steam pressure of 1.0 MPa for 4.5 hours to obtain solid waste-based concrete material.

[0035] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 725 kg / m³. 3 It has a compressive strength of 3.9 MPa and a flexural strength of 1.5 MPa, which meets the requirements of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2019) for cement-stabilized base courses of Class II and below highways with heavy traffic, which have an unconfined compressive strength of 3.0~5.0 MPa at 7 days. It can be used as a substitute material for Class II highway base courses.

[0036] Example 4 The method for preparing concrete materials using wet sand-making tailings and discarded wind turbine blades comprises the following steps: Step 1) Spread the tailings filter cake from the wet sand making line out to dry in an open area, extend the drying / aging time, and control the moisture content of the tailings filter cake to 2% or lower. Step 2) The dried tailings filter cake and retired wind turbine blades are crushed to a particle size range of 24~30mm by CI1313 impact crusher. The two materials are then mixed in a ratio of tailings filter cake: retired wind turbine blades = 8:2. The mixer is started with the following parameters: mixer speed 20rpm, material mixing time 1.5h. Step 3) Add the dried mixed crushed material and converter steel slag together into a dry roller mill. The steel slag accounts for 1 / 3 of the mass of the mixed crushed material. The roller mill grinding time is 2 hours to make it into mixed micro powder. Step 4) Add 9 parts cement, 12 parts slag powder, and 10 parts lime to 78 parts solid waste mixed powder and mix. Then add 1.1 parts water-reducing agent and 33 parts water and mix until uniform to make solid waste mixed slurry. The water-reducing agent is sulfonated melamine formaldehyde condensate (SMF), the lime is calcareous lime, CL90 grade in JC / T 479-2013, and the cement is ordinary Portland cement. Step 5) Add foam particles to the solid waste mixture slurry to expand the slurry volume by 0.4 times, and obtain solid waste foamed slurry; Step 6) Pour the solid waste foaming slurry into the prepared mold, and place the mold together in a curing environment with a temperature of 65°C and a humidity of 90% for 2.5 hours to obtain a hardened green body; Step 7) Separate the hardened blank from the mold, and then transfer the blank to an environment filled with saturated water vapor at a temperature of 180°C and a saturated steam pressure of 1.0 MPa for 5.5 hours to obtain solid waste-based concrete material.

[0037] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 769 kg / m³. 3It has a compressive strength of 4.2 MPa and a flexural strength of 1.4 MPa, which meets the requirements of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2019) for cement-stabilized base courses of Class II and below highways with heavy traffic, which have an unconfined compressive strength of 3.0~5.0 MPa at 7 days. It can be used as a substitute material for Class II highway base courses.

[0038] Comparative Example 1 The methods used in this comparative example and Example 1 are basically the same, except that no decommissioned wind turbine blades are added in step 2.

[0039] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 708 kg / m³. 3 The compressive strength is 0.8 MPa and the flexural strength is 0.3 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / T F20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0040] Comparative Example 2 The methods in this comparative example and Example 1 are basically the same, except that in step 2, the dried tailings and decommissioned wind turbine blades are crushed separately, and in step 3, the tailings, decommissioned wind turbine blades and converter steel slag are ground separately.

[0041] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 720 kg / m³. 3 The compressive strength is 1.2 MPa and the flexural strength is 0.5 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / T F20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0042] Comparative Example 3 The methods used in this comparative example and Example 1 are basically the same, except that step 6 is omitted and the process proceeds directly from step 5 to step 7.

[0043] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 785 kg / m³. 3The compressive strength is 0.8 MPa and the flexural strength is 0.3 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / T F20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0044] Comparative Example 4 The methods in this comparative example and Example 1 are basically the same, except that in step 2, ordinary glass fiber is used to replace the retired wind turbine blades in an equal amount.

[0045] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 713 kg / m³. 3 The compressive strength is 1.13 MPa and the flexural strength is 0.4 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / TF20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0046] Comparative Example 5 The methods in this comparative example and Example 1 are basically the same, except that the high-temperature and high-pressure curing conditions in step 7 are changed to a normal-pressure hydrothermal environment with a temperature of 90°C.

[0047] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 694 kg / m³. 3 The compressive strength is 1.18 MPa and the flexural strength is 0.3 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / TF20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0048] Comparative Example 6 The methods in this comparative example and Example 2 are basically the same, except that converter steel slag powder is not added in step 3.

[0049] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 734 kg / m³. 3The compressive strength is 1.1 MPa and the flexural strength is 0.4 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / T F20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0050] Comparative Example 7 The methods in this comparative example and Example 3 are basically the same, except that step 5 is not performed, i.e., no foaming and expansion treatment is performed, and no decommissioned wind turbine blades are added in step 2.

[0051] Mechanical property tests were conducted on the solid waste-based concrete obtained from the above steps. The results showed that the bulk density was 798 kg / m³. 3 The compressive strength is 0.9 MPa and the flexural strength is 0.32 MPa, which does not meet the requirement of 3.0~5.0 MPa unconfined compressive strength at 7 days for cement-stabilized materials for heavy traffic base courses of Class II and below highways as stipulated in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / TF20-2019). Therefore, it cannot be used as a substitute material for Class II highway base courses.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing concrete materials using wet-process sand-making tailings and discarded wind turbine blades, characterized in that... Includes the following steps: Step S1: Sun-dry or air-dry the filter cake from the wet sand-making process. Step S2: Crush and mix the tailings treated in Step S1 and the decommissioned wind turbine blades together to obtain mixed crushed material. Step S3: After drying the mixed crushed materials, they are mixed with converter steel slag to form mixed micro powder; Step S4: Add cement, slag powder and lime to the mixed powder and mix. Then add water-reducing agent and appropriate amount of water and mix until uniform to make a mixed slurry. Step S5: The mixed slurry is foamed and expanded to obtain solid waste foamed slurry; Step S6: Pour the solid waste foaming slurry into the prepared mold, and then transfer it together with the mold to a hydrothermal environment for rapid curing to obtain a hardened green body; Step S7: Separate the hardened billet from the mold, and transfer the billet to an environment filled with saturated water vapor for curing to obtain solid waste-based concrete material.

2. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: In step S1, the tailings from the wet sand making line have a SiO2 content of ≥60%, a CaO content of ≤5%, and a moisture content of ≤5%.

3. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: In step S2, the volume content of glass fiber in the decommissioned wind turbine blades is 64-74%, the volume content of resin matrix is ​​26-36%, the mass ratio of tailings to wind turbine blades is 6.5-9:1-3.5, and the particle size of the mixed crushed material is 10-54 mm.

4. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: In step S3, the mass of converter steel slag accounts for 1 / 5 to 2 / 3 of the mixed crushed material.

5. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: In step S5, the foaming and expansion treatment method is either physical foaming or chemical foaming; physical foaming is nitrogen filling or foam microparticle filling, and chemical foaming is adding polyurethane foaming agent or aluminum powder foaming agent; the volume of the mixed slurry expands by 0.3 to 0.8 times.

6. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: In step S6, the hydrothermal environment temperature is controlled at 45~65℃, the humidity is controlled at 80~95%, and the hardening time is controlled at 1.2~4.5h.

7. The method for preparing concrete materials using wet sand-making tailings and waste wind turbine blades according to claim 1, characterized in that: The curing environment conditions in step S7 are: temperature range 165~195℃, saturated steam pressure range 0.7~1.4MPa, and curing time 4~8h.

8. A solid waste-based concrete material, characterized in that: The raw material components include the following parts by weight: 62-87 parts of mixed micro powder, 8-15 parts of cement, 5-11 parts of slag micro powder, 10-12 parts of lime, 18-36 parts of mixing water, and 0.4-1.25 parts of water-reducing agent; prepared by the preparation method described in any one of claims 1-7.

9. A solid waste-based concrete material according to claim 8, characterized in that: The cement is selected from one or more combinations of silicate cement, fly ash silicate cement, and slag silicate cement; the lime is calcareous lime, meeting the requirements of CL85 grade and above in JC / T479-2013; the water-reducing agent is selected from melamine-based water-reducing agents or polycarboxylate-based water-reducing agents.

10. The application of the solid waste-based concrete material according to claim 9, characterized in that: Hardened solid waste-based concrete material is used for roadbed backfilling and mining subsidence support filling.

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