Recycled aggregate and method for producing the same

Abstract

The application discloses a kind of recycled aggregate and preparation method thereof, belong to building material technical field, including the following mass parts of raw materials are made: 40-50 parts of tailings, 2-5 parts of coal gangue, building phosphogypsum 5-10 parts, strong electrolyte solvent 10-15 parts, weak electrolyte solvent 4-6 parts, steel slag 20-25 parts, carbide slag 5-8 parts, 1-3 parts of waste mud, carbon fiber 0.1-0.5 parts, steel fiber 2-4 parts, water reducing agent 0.5-1 part.By controlling particle size distribution to realize precision packing, reduce harmful pore content;And add micro fine cementitious material particles, reduce the total specific surface area of material, reduce water consumption;In addition, limestone waste mud is used to supplement micro fine pores, limestone has certain water reducing effect, can further increase the compactness of system, reduce water-cement ratio, reduce harmful pore content.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a recycled aggregate and its preparation method. Background Technology

[0002] Recycled aggregate is a material made by crushing, screening, and mixing construction waste in a certain proportion. It can be used to replace natural aggregate in the preparation of concrete with different properties and application requirements. However, the numerous pores on the surface of recycled aggregate lead to a large number of microcracks in the interface transition zone (ITZ) between the aggregate and cement paste. Furthermore, the crushing and screening process of waste concrete results in recycled aggregate having many irregular edges and uneven particle size distributions. For these reasons, the quality and overall performance of recycled aggregate are far inferior to those of natural aggregate. Therefore, exploring methods to improve the performance of recycled aggregate has become an urgent research topic for scholars both domestically and internationally.

[0003] Since the main factors affecting the performance of recycled aggregates are the cement mortar adhering to the surface and the transition zone between the recycled and old aggregates, methods for strengthening recycled aggregates are mainly divided into three categories: removing old mortar, reinforcing old mortar, and improving the mixing process of recycled concrete. Methods for removing old mortar mainly include mechanical grinding, heated grinding, and acid treatment. Mechanical grinding utilizes the shear stress generated between the wall of a high-speed rotating eccentric gear and the surface of the recycled aggregate to remove the adhering mortar. Heated grinding involves pre-treating the recycled aggregate at high temperature to weaken the old mortar layer on its surface, followed by mechanical grinding to better remove the old mortar. Acid treatment involves immersing the recycled aggregate in an acid solution to dissolve the old mortar on the aggregate surface, thereby modifying the recycled aggregate. Methods for reinforcing old mortar mainly include pozzolanic slurry immersion, polymer emulsion immersion, and carbonation treatment. The volcanic ash slurry soaking method involves adding volcanic ash mineral admixtures (such as fly ash, silica fume, and slag) to pure cement slurry to prepare volcanic ash slurry. This slurry can fill the pores and microcracks on the surface of recycled aggregates and react with the attached mortar, thereby strengthening the recycled aggregates. The polymer emulsion soaking method involves preparing a modified solution of polymer emulsion in a certain proportion and soaking the recycled aggregates in a vacuum pump. A commonly used polymer emulsion is polyvinyl alcohol (PVA) emulsion, which has gelling properties and can quickly solidify and fill the pores and microcracks on the surface of the attached old mortar, significantly reducing the water absorption rate and other properties of the recycled aggregates. The carbonation treatment method uses CO2 to accelerate the carbonation of the old mortar on the surface of the recycled aggregates, generating calcium carbonate and silica gel, effectively filling the internal pores and microcracks. Although the above methods improve the quality and overall performance of recycled aggregates to some extent, they still have limitations such as complex processes, high energy consumption, and unsatisfactory results. Therefore, scholars both at home and abroad have sought a modification technology that is simple to implement, cost-effective, and highly efficient. Summary of the Invention

[0004] This invention aims to solve the problems existing in the prior art and provides a recycled aggregate and its preparation method. By controlling the particle size distribution to achieve precise packing and reduce the content of harmful pores, fine cementitious material particles are added to reduce the total specific surface area of ​​the material and reduce water consumption. In addition, limestone-containing waste mud is used to supplement the micropores. Limestone has a certain water-reducing effect, which can further increase the compactness of the system, reduce the water-cement ratio, and reduce the content of harmful pores.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A recycled aggregate is made from the following raw materials in parts by weight: 40-50 parts tailings, 2-5 parts coal gangue, 5-10 parts building phosphogypsum, 10-15 parts strong electrolyte solvent, 4-6 parts weak electrolyte solvent, 20-25 parts steel slag, 5-8 parts calcium carbide slag, 1-3 parts waste mud, 0.1-0.5 parts carbon fiber, 2-4 parts steel fiber, and 0.5-1 parts water-reducing agent.

[0007] Preferably, the tailings are one or more of iron tailings, graphite tailings, and copper tailings; the resistivity of the tailings is less than 1000 ohms, the fineness modulus of the tailings is 2.5-3.0, and the silicon content of the tailings is greater than 60%.

[0008] Preferably, the coal gangue is solid waste discharged during the coal mining and coal washing processes, and the coal gangue has a particle size of 0.1-2 mm and a fineness modulus of 3.3-3.5.

[0009] Preferably, the building phosphogypsum is obtained by heating and dehydrating solid waste phosphogypsum generated during the phosphoric acid production process, and its hemihydrate gypsum content is greater than 80%, and the residue on an 80μm sieve is less than 10%.

[0010] Preferably, the strong electrolyte solvent is one or more of the following: ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the strong electrolyte solvent is 20-35 wt%.

[0011] Preferably, the weak electrolyte solvent is one or more of the following: ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the weak electrolyte solvent is 2-5 wt%.

[0012] Preferably, the steel slag has a calcium content greater than 50% and a specific surface area of ​​350-400 m². 2 / kg.

[0013] Preferably, the calcium carbide slag is the main solid waste generated from the hydrolysis of calcium carbide to produce acetylene gas, and the calcium content of the calcium carbide slag is greater than 80%, with a specific surface area of ​​350-400 m². 2 / kg.

[0014] Preferably, the waste sludge is settling solid waste from the washing and dust removal process during limestone manufactured sand production, with a moisture content of less than 20% and a specific surface area of ​​400-450 m². 2 / kg, the calcium content of the waste sludge is greater than 40%.

[0015] Preferably, the carbon fiber has an aspect ratio of 100-400:1 and a length of 1-3 cm; the steel fiber has an aspect ratio of 80-100:1 and a length of 0.5-1.5 cm.

[0016] Preferably, the water-reducing agent is a UHPC-specific water-reducing agent with a water reduction rate greater than 45%.

[0017] A method for preparing recycled aggregate includes the following steps:

[0018] Step 1: Weigh out the tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber according to the mass fractions, mix them thoroughly, soak for 24-36 hours, filter and dry.

[0019] Step 2: Weigh out the construction phosphogypsum, steel slag and carbide slag according to the mass fractions, mix them thoroughly, and then remove the fine powder by air separation;

[0020] Step 3: After thoroughly mixing the dried tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber with the de-dusted building phosphogypsum, steel slag and carbide slag, add the weak electrolyte and water-reducing agent weighed according to the mass fraction, mix evenly and then put into the granulator for granulation.

[0021] Step 4: Place the granulated particles into an autoclave and autoclave at 175-785℃ for 7-10 hours to obtain recycled aggregate.

[0022] Preferably, in step two, the content of fine powder after the building phosphogypsum, steel slag and carbide slag are thoroughly mixed and then air-classified is 1-2%.

[0023] Preferably, in step three, the particle size obtained by granulation in the granulator is 25-35mm.

[0024] The beneficial effects of this technical solution are as follows:

[0025] I. The present invention provides a recycled aggregate that achieves precise packing by controlling particle size distribution, thereby reducing the content of harmful pores; and uses fine cementitious material particles to reduce the total specific surface area of ​​the material and reduce water consumption; in addition, it uses limestone-containing waste mud to supplement the micropores, and limestone has a certain water-reducing effect, which can further increase the compactness of the system, reduce the water-cement ratio, and reduce the content of harmful pores.

[0026] II. The present invention provides a recycled aggregate incorporating abundant carbon fiber and steel fiber. The addition of these high-performance fibers not only significantly improves the strength of the aggregate itself, but also greatly enhances the connectivity with the surrounding interface by extending the fibers to the surface of the aggregate, thereby further enhancing the overall structural strength of the concrete prepared from this aggregate, exhibiting excellent performance and broad application potential. The waste sludge contains a large amount of polyacrylamide, which can effectively assist in the dispersion of fibers, further increasing the tensile strength of the fiber web. The pores in the coal gangue provide a point of application for the fibers inside the aggregate, strengthening the friction between the fibers and the aggregate, and enhancing the performance of the recycled aggregate.

[0027] III. The present invention provides a recycled aggregate containing a large amount of polar materials, such as iron tailings, chalcopyrite tailings, and strong electrolyte solvents. In particular, coal gangue contains a large number of large pores, allowing strong electrolyte solvents to penetrate and adhere to it. During the molding process, the cementitious material further fills the internal voids of the coal gangue, effectively preventing the escape of electrolyte solutes. The prepared recycled aggregate has good polarity, while cement and river sand in concrete are non-polar materials. When heated by microwave, only the aggregate, being a polar material, is heated and expands, causing the mortar in the concrete to dissociate along the interface, thus achieving aggregate recycling. Moreover, there is no old mortar on the surface. The internal pores brought by the coal gangue also enhance the aggregate's ability to absorb waves, improving the aggregate's thermal performance.

[0028] IV. The present invention provides a recycled aggregate containing a large amount of conductive materials. The conductive properties are enhanced by carbon fiber and steel fiber, and the aggregate frame is made conductive by overlapping with other aggregates. Cement and river sand in concrete are insulating materials. When voltage is applied to the concrete, ions or electrons migrate in the aggregate frame to form current and generate heat. Only the aggregate expands due to heat, and the mortar in the concrete at the interface dissociates, thus realizing the recycling of aggregate, and there is no old mortar on the surface.

[0029] V. The recycled aggregate provided by this invention exhibits excellent solid waste utilization rate while significantly reducing production costs. It possesses high strength and particularly outstanding bonding ability with concrete mortar. Even more commendable is that this aggregate can be easily recycled through electric or microwave heating, demonstrating extremely high practical value and environmental benefits.

[0030] VI. This invention provides a recycled aggregate where a strong electrolyte solvent enhances the polarity and conductivity of materials such as coal gangue and tailings. If only a weak electrolyte solvent is used to enhance the overall polarity and conductivity of the aggregate, excessive electrolyte solute can lead to excessive air content in the cementitious components, corrosion of reinforcing steel, and damage to internal crystallization, thus affecting concrete performance. Therefore, the final amount of electrolyte solute added is strictly controlled during aggregate preparation. Furthermore, the substances mixed with the strong electrolyte solution are all ionicly conductive or poorly polar non-cementing substances. Contact with the strong electrolyte does not affect the performance of the cementitious materials and can enhance conductivity and polarity, balancing the internal conductivity and polarity of the aggregate materials. The recycled aggregate obtained by this invention has a soundness of less than 1.2%, a strength greater than 120 MPa, a crushing index of less than 2.6%, a water absorption rate of less than 0.15%, and a microwave heating efficiency greater than 80℃, meeting the requirements for aggregate use.

[0031] VII. The present invention provides a method for preparing recycled aggregate. During the granulation process, the building phosphogypsum is rapidly hydrated, which can make the particles form according to the design scheme. Sodium sulfate, potassium hydroxide, sodium hydroxide, ferric sulfate and other substances in the electrolyte solution of the system have certain early strength effects, which can help improve early strength. In addition, steel slag, carbide slag and other substances can also be rapidly hydrated under the combined action of alkali activation and sulfate activation, and together with the building phosphogypsum, form early strength and complete the shaping.

[0032] 8. The present invention provides a method for preparing recycled aggregate, the main materials of which are calcium or silicon, and the calcium-silicon ratio is controlled by the material composition; after shaping and autoclaving, the resulting aggregate has excellent compressive strength, easily exceeding 150MPa, and exhibits excellent mechanical properties, providing a reliable material basis for various high-strength applications. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the present invention;

[0034] Figure 2 This is an actual diagram of the present invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0036] Example

[0037] A recycled aggregate is made from the following raw materials in parts by weight: 40-50 parts tailings, 2-5 parts coal gangue, 5-10 parts building phosphogypsum, 10-15 parts strong electrolyte solvent, 4-6 parts weak electrolyte solvent, 20-25 parts steel slag, 5-8 parts calcium carbide slag, 1-3 parts waste mud, 0.1-0.5 parts carbon fiber, 2-4 parts steel fiber, and 0.5-1 parts water-reducing agent.

[0038] Preferably, the tailings are one or more of iron tailings, graphite tailings, and copper tailings; the resistivity of the tailings is less than 1000 ohms, the fineness modulus of the tailings is 2.5-3.0, and the silicon content of the tailings is greater than 60%.

[0039] Preferably, the coal gangue is solid waste discharged during the coal mining and coal washing processes, and the coal gangue has a particle size of 0.1-2 mm and a fineness modulus of 3.3-3.5.

[0040] Preferably, the building phosphogypsum is obtained by heating and dehydrating solid waste phosphogypsum generated during the phosphoric acid production process, and its hemihydrate gypsum content is greater than 80%, and the residue on an 80μm sieve is less than 10%.

[0041] Preferably, the strong electrolyte solvent is one or more of the following: ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the strong electrolyte solvent is 20-35 wt%.

[0042] Preferably, the weak electrolyte solvent is one or more of the following: ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the weak electrolyte solvent is 2-5 wt%.

[0043] Preferably, the steel slag has a calcium content greater than 50% and a specific surface area of ​​350-400 m². 2 / kg.

[0044] Preferably, the calcium carbide slag is the main solid waste generated from the hydrolysis of calcium carbide to produce acetylene gas, and the calcium content of the calcium carbide slag is greater than 80%, with a specific surface area of ​​350-400 m². 2 / kg.

[0045] Preferably, the waste sludge is settling solid waste from the washing and dust removal process during limestone manufactured sand production, with a moisture content of less than 20% and a specific surface area of ​​400-450 m². 2 / kg, the calcium content of the waste sludge is greater than 40%.

[0046] Preferably, the carbon fiber has an aspect ratio of 100-400:1 and a length of 1-3 cm; the steel fiber has an aspect ratio of 80-100:1 and a length of 0.5-1.5 cm.

[0047] Preferably, the water-reducing agent is a UHPC-specific water-reducing agent with a water reduction rate greater than 45%.

[0048] A method for preparing recycled aggregate includes the following steps:

[0049] Step 1: Weigh out the tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber according to the mass fractions, mix them thoroughly, soak for 24-36 hours, filter and dry.

[0050] Step 2: Weigh out the construction phosphogypsum, steel slag and carbide slag according to the mass fractions, mix them thoroughly, and then remove the fine powder by air separation;

[0051] Step 3: After thoroughly mixing the dried tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber with the de-dusted building phosphogypsum, steel slag and carbide slag, add the weak electrolyte and water-reducing agent weighed according to the mass fraction, mix evenly and then put into the granulator for granulation.

[0052] Step 4: Place the granulated particles into an autoclave and autoclave at 175-785℃ for 7-10 hours to obtain recycled aggregate (e.g. Figure 1 and Figure 2 (As shown).

[0053] The proportions of recycled aggregate in each embodiment are shown in Table 1:

[0054] Table 1. Recycled Aggregate Raw Materials for Each Embodiment

[0055]

[0056]

[0057] The parameter requirements for each raw material in the recycled aggregate of each embodiment are shown in Table 2:

[0058] Table 2. Parameter requirements for each raw material in the recycled aggregate of each embodiment.

[0059]

[0060]

[0061] The methods for preparing recycled aggregates in each embodiment are shown in Table 3.

[0062] Table 3. Parameter requirements for the recycled aggregate preparation methods in each embodiment.

[0063]

[0064]

[0065] The recycled aggregates prepared in the above examples were tested for relevant properties in accordance with the national standard GB / T 14685-2022 "Construction Gravel and Crushed Stone". The aggregates were spread evenly in a 100*100*100mm non-polar abrasive mold, and the mold was placed in a KQ6000 adjustable industrial box-type microwave heating device with a power of 20kW and a frequency of 2.45GHz. After heating for ten minutes, the temperature was recorded, and the microwave heating efficiency was tested. The results are shown in Table 4.

[0066] Table 4 Performance parameters of recycled aggregates in each embodiment

[0067]

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 is that the tailings are 35g; the recycled aggregate prepared has a soundness of 0.9%, a strength of 117MPa, a crushing index of 2.6%, a water absorption rate of 0.13%, and a microwave heating efficiency of 101.3℃.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that the tailings are 55g; the recycled aggregate prepared has a soundness of 1.3%, a strength of 125MPa, a crushing index of 2.3%, a water absorption rate of 0.08%, and a microwave heating efficiency of 95.1℃.

[0072] Comparative Example 3

[0073] The difference between this comparative example and Example 1 is that the resistivity of the tailings is 1050 ohms; the recycled aggregate prepared has a soundness of 1.1%, a strength of 122 MPa, a crushing index of 2.5%, a water absorption rate of 0.1%, and a microwave heating efficiency of 96.8°C.

[0074] Comparative Example 4

[0075] The difference between this comparative example and Example 1 is that the fineness modulus of the tailings is 3.0; the recycled aggregate prepared has a soundness of 1.3%, a strength of 105 MPa, a crushing index of 2.8%, a water absorption rate of 0.15%, and a microwave heating efficiency of 103.2℃.

[0076] Comparative Example 5

[0077] The difference between this comparative example and Example 1 is that the silicon content of the tailings is 75%; the recycled aggregate prepared has a soundness of 1.8%, a strength of 98.6 MPa, a crushing index of 2.9%, a water absorption rate of 0.18%, and a microwave heating efficiency of 101.6°C.

[0078] Comparative Example 6

[0079] The difference between this comparative example and Example 1 is that: no strong electrolyte solvent is used; recycled aggregate is prepared with a soundness of 1.2%, a strength of 112 MPa, a crushing index of 2.7%, a water absorption rate of 0.13%, and a microwave heating efficiency of 94.9°C.

[0080] Comparative Example 7

[0081] The difference between this comparative example and Example 1 is that the calcium content of the steel slag is 45%, and the specific surface area is 320 m². 2 / kg; the recycled aggregate was prepared with a soundness of 1.9%, a strength of 93.4 MPa, a crushing index of 3.0%, a water absorption rate of 0.2%, and a microwave heating efficiency of 101.8℃.

[0082] Comparative Example 8

[0083] The difference between this comparative example and Example 1 is that the specific surface area of ​​the steel slag is 420 m². 2 / kg; the recycled aggregate was prepared with a soundness of 2.6%, a strength of 81.3 MPa, a crushing index of 3.5%, a water absorption rate of 0.29%, and a microwave heating efficiency of 99.1℃.

[0084] Comparative Example 9

[0085] The difference between this comparative example and Example 1 is that the calcium content of the carbide slag is 75%, and the specific surface area is 320 m². 2 / kg; the recycled aggregate was prepared with a soundness of 1.8%, a strength of 97.1 MPa, a crushing index of 2.9%, a water absorption rate of 0.18%, and a microwave heating efficiency of 100.2℃.

[0086] Comparative Example 10

[0087] The difference between this comparative example and Example 1 is that the specific surface area of ​​the carbide slag is 420 m². 2 / kg; the recycled aggregate was prepared with a soundness of 2.3%, a strength of 93.4 MPa, a crushing index of 2.8%, a water absorption rate of 0.16%, and a microwave heating efficiency of 99.4℃.

[0088] Comparative Example 11

[0089] The difference between this comparative example and Example 1 is that carbon fiber is not used; a recycled aggregate is prepared, which has a strength of 1.2%, a strength of 115 MPa, a crushing index of 2.6%, a water absorption rate of 0.11%, and a microwave heating efficiency of 94.7°C.

[0090] Comparative Example 12

[0091] The difference between this comparative example and Example 1 is that steel fibers are not used; recycled aggregate is prepared with a soundness of 1.1%, a strength of 109 MPa, a crushing index of 2.8%, a water absorption rate of 0.12%, and a microwave heating efficiency of 95.1°C.

[0092] Comparative Example 13

[0093] The difference between this comparative example and Example 1 is that: no weak electrolyte solvent is used, the robustness of this recycled aggregate is 1.5%, the strength is 97 MPa, the crushing index is 2.8%, the water absorption rate is 0.15%, and the microwave heating efficiency is 61.1°C.

[0094] Comparative Example 14

[0095] The difference between this comparative example and Example 1 is that the content of fine powder is 0.5%, the robustness of the recycled aggregate is 1.8%, the strength is 76 MPa, the crushing index is 3.1%, the water absorption rate is 0.19%, and the microwave heating efficiency is 95.7°C.

[0096] Comparative Example 15

[0097] The difference between this comparative example and Example 1 is that the content of fine powder is 2.5%, the robustness of the recycled aggregate is 2.3%, the strength is 51 MPa, the crushing index is 3.6%, the water absorption rate is 0.24%, and the microwave heating efficiency is 91.8°C.

[0098] Comparative Example 16

[0099] The difference between this comparative example and Example 1 is that the particle size obtained by granulation is 20 mm, the soundness of the recycled aggregate is 1.3%, the strength is 98 MPa, the crushing index is 2.8%, the water absorption rate is 0.13%, and the microwave heating efficiency is 106.3 °C.

[0100] Comparative Example 17

[0101] The difference between this comparative example and Example 1 is that the particle size obtained by granulation is 40 mm, the soundness of the recycled aggregate is 0.8%, the strength is 133 MPa, the crushing index is 2.2%, the water absorption rate is 0.9%, and the microwave heating efficiency is 79.2°C.

[0102] As can be seen from the above, compared with Example 1, the strength and crushing index of Comparative Example 1 are significantly reduced when the tailings content is too low; compared with Example 1, the soundness of Comparative Example 2 is reduced when the tailings content is too high; compared with Example 1, the soundness, strength, and crushing index of Comparative Example 4 are significantly reduced when the fineness modulus of the tailings is too low; compared with Example 1, the soundness, strength, crushing index, and water absorption of Comparative Example 5 are significantly reduced when the silicon content of the tailings is too low; compared with Example 1, the soundness, strength, and crushing index of Comparative Example 6 are significantly reduced when only the local cutoff solvent is used; compared with Example 1, the soundness, strength, crushing index, and water absorption of Comparative Example 7 are significantly reduced when the calcium content and specific surface area of ​​the steel slag are too low; compared with Example 1, the soundness, strength, crushing index, and water absorption of Comparative Example 8 are significantly reduced when the specific surface area of ​​the steel slag is too high; compared with Example 1, the soundness, strength, crushing index, and water absorption of Comparative Example 9 are significantly reduced when the calcium content and specific surface area of ​​the carbide slag are too low; compared with Example 10, the soundness, strength, crushing index, and water absorption of Comparative Example 9 are significantly reduced when the calcium content and specific surface area of ​​the carbide slag are too low; and the soundness, strength, crushing index, and water absorption of Comparative Example 10 are significantly reduced when the specific surface area of ​​the carbide slag is too high. Compared to Example 1, when the specific surface area of ​​the carbide slag is too high, the robustness, strength, crushing index, and water absorption rate are significantly reduced. Compared to Example 1, when carbon fiber is not used in Comparative Example 11, the robustness, strength, and crushing index are significantly reduced. Compared to Example 1, when steel fiber is not used in Comparative Example 12, the strength and crushing index are significantly reduced. Compared to Example 1, when a weak electrolyte solvent is not used in Comparative Example 13, the robustness, strength, crushing index, water absorption rate, and microwave heating efficiency are significantly reduced. Compared to Example 1, when the content of fine powder is too low in Comparative Example 14, the robustness, strength, crushing index, and water absorption rate are significantly reduced. Compared to Example 1, when the content of fine powder is too high in Comparative Example 15, the robustness, strength, crushing index, and water absorption rate are significantly reduced. Compared to Example 1, when the particle size obtained by granulation is too small in Comparative Example 16, the robustness, strength, and crushing index are significantly reduced. Compared to Example 1, when the particle size obtained by granulation is too large in Comparative Example 17, the microwave heating efficiency is significantly reduced.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A recycled aggregate, characterized in that, The material is made from the following raw materials in parts by weight: 40-50 parts tailings, 2-5 parts coal gangue, 5-10 parts phosphogypsum, 10-15 parts strong electrolyte solvent, 4-6 parts weak electrolyte solvent, 20-25 parts steel slag, 5-8 parts calcium carbide slag, 1-3 parts waste sludge, 0.1-0.5 parts carbon fiber, 2-4 parts steel fiber, and 0.5-1 parts water-reducing agent; the strong electrolyte solvent is one or more of ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the strong electrolyte solvent is 20-35 wt%; the weak electrolyte solvent is one or more of ferric sulfate aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution; the mass fraction of the weak electrolyte solvent is 2-5 wt%; the waste sludge is the settling solid waste from the washing and dust removal process during the production of limestone manufactured sand, and the recycled aggregate has a soundness of less than 1.2%, a strength greater than 120 MPa, a crushing index of less than 2.6%, a water absorption rate of less than 0.15%, and a microwave heating efficiency greater than 80℃.

2. The recycled aggregate according to claim 1, characterized in that: The tailings are one or more of iron tailings, graphite tailings, and copper tailings; the resistivity of the tailings is less than 1000 ohms, the fineness modulus of the tailings is 2.5-3.0, and the silicon content of the tailings is greater than 60%.

3. The recycled aggregate according to claim 1, characterized in that: The coal gangue is a solid waste discharged during the coal mining and washing process. The particle size of the coal gangue is 0.1-2 mm, and the fineness modulus of the coal gangue is 3.3-3.

5.

4. The recycled aggregate according to claim 1, characterized in that: The building phosphogypsum is obtained by heating and dehydrating solid waste phosphogypsum generated during the phosphoric acid production process, and its hemihydrate gypsum content is greater than 80%, and the residue on an 80um sieve is less than 10%.

5. A recycled aggregate according to claim 1, characterized in that: The steel slag has a calcium content greater than 50% and a specific surface area of ​​350-400 m² / kg.

6. A recycled aggregate according to claim 1, characterized in that: The calcium carbide slag is the main solid waste produced by the hydrolysis of calcium carbide to produce acetylene gas. The calcium content of the calcium carbide slag is greater than 80%, and the specific surface area of ​​the calcium carbide slag is 350-400 m2 / kg.

7. The recycled aggregate according to claim 1, characterized in that: The sludge has a moisture content of less than 20%, a specific surface area of ​​400-450 m² / kg, and a calcium content of more than 40%.

8. A recycled aggregate according to claim 1, characterized in that: The carbon fiber has an aspect ratio of 100-400:1 and a length of 1-3 cm; the steel fiber has an aspect ratio of 80-100:1 and a length of 0.5-1.5 cm.

9. A recycled aggregate according to claim 1, characterized in that: The water-reducing agent is a UHPC-specific water-reducing agent with a water reduction rate greater than 45%.

10. A method for preparing recycled aggregate according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Weigh out the tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber according to the mass fractions, mix them thoroughly, soak for 24-36 hours, filter and dry. Step 2: Weigh out the construction phosphogypsum, steel slag and carbide slag according to the mass fractions, mix them thoroughly, and then remove the fine powder by air separation; Step 3: After thoroughly mixing the dried tailings, coal gangue, strong electrolyte, waste sludge, carbon fiber and steel fiber with the de-dusted building phosphogypsum, steel slag and carbide slag, add the weak electrolyte and water-reducing agent weighed according to the mass fraction, mix evenly and then put into the granulator for granulation. Step 4: Place the granulated particles into an autoclave and autoclave at 175-785℃ for 7-10 hours to obtain recycled aggregate.

11. The method for preparing recycled aggregate according to claim 10, characterized in that: In step two, the fine powder content of the building phosphogypsum, steel slag and carbide slag after being thoroughly mixed and then air-classified is 1-2%.

12. The method for preparing recycled aggregate according to claim 11, characterized in that: In step three, the particle size obtained by granulation in the granulator is 25-35mm.

Images