Quality improvement method for recycled coarse aggregate from waste concrete using composite stimulating materials

Abstract

To provide a quality improvement method for a waste concrete recycle coarse aggregate by a composite stimulus material.SOLUTION: In step 1, an alkaline solution is prepared; in step 2, a composite precursor powder is prepared; in step 3, a recycled coarse aggregate is manufactured; in step 4, a high-pressure airless spray device is turned on, and the alkaline solution prepared in step 1 is sprayed to the recycled coarse aggregate obtained in step 3; in step 5, a powder ejection device is turned on, and the composite precursor powder prepared in step 2 is uniformly sprayed to the surface of the recycled coarse aggregate whose surface has been uniformly sprayed with the alkaline solution; in step 6, the alkaline solution prepared in step 1 is uniformly sprayed to the surface of the recycled coarse aggregate whose surface has been uniformly sprayed with the composite precursor powder; and in step 7, the strengthened recycled coarse aggregate is left in a shaded place for curing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to the technical field of coarse aggregate recycled from waste concrete, and in particular to a method for improving the quality of coarse aggregate recycled from waste concrete by using composite stimulating materials. [Background technology]

[0002] In current construction work, natural coarse aggregate mixed with concrete is used in large quantities as a non-renewable resource, and at the same time, a large number of dilapidated buildings are demolished, generating a large amount of waste concrete, which takes up space and causes environmental problems.Waste concrete can be processed into recycled coarse aggregate as a substitute for natural coarse aggregate.

[0003] Compared to natural coarse aggregate, recycled coarse aggregate has many corners, is unevenly coated with mortar on its surface, and has unevenly distributed microcracks, which results in high water absorption, a high porosity, and a high crushing value. Concrete directly mixed with recycled coarse aggregate has poor workability and low strength, limiting the applications of recycled concrete coarse aggregate (hereinafter referred to as recycled coarse aggregate). Therefore, in order to expand the application scope of recycled coarse aggregate concrete, reduce the consumption of natural aggregate, and improve the utilization rate of waste concrete, it is necessary to improve the quality of recycled coarse aggregate.

[0004] Conventional methods for upgrading recycled coarse aggregate include physical, chemical, and microbial enrichment. Physical enrichment consumes a lot of energy, causes significant damage to the recycled aggregate, and reduces resource utilization. Chemical enrichment results in significant material loss and is expensive. Microbial enrichment is slow and inefficient. Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of this application is to provide a method for improving the quality of recycled coarse aggregate from waste concrete using composite stimulating materials, so as to solve the technical problems of the conventional recycled coarse aggregate strengthening technology, such as high cost and low efficiency. [Means for solving the problem]

[0006] To achieve the above objectives, the present application adopts the following technical solutions.

[0007] The method for improving the quality of waste concrete recycled coarse aggregate by composite stimulating materials includes the following steps:

[0008] In step 1, an alkaline solution is prepared, and the composition, by mass, is 20 to 30 parts of NaOH or KOH solid particles, 10 to 15 parts of fast-dissolving sodium silicate fine powder, and 100 parts of water. The water, NaOH or KOH solid particles, and fast-dissolving sodium silicate fine powder are mixed and stirred until the solid particles are completely dissolved.

[0009] In step 2, a composite precursor powder is prepared, and the powder is mixed in a powder mixer in a proportion of 100 parts of solid waste-based activating material and 15-20 parts of sulfate, by mass, and mixed uniformly.

[0010] In step 3, the waste concrete is crushed, sieved, washed, and dried so that 95% or more of the aggregate has a particle size of 5 to 20 mm, to obtain recycled coarse aggregate.

[0011] In step 4, the high-pressure airless spray device, which includes a first vibrating screen machine and a high-pressure airless spray machine used in combination, is turned on, the recycled coarse aggregate obtained in step 3 is fed into the inlet of the high-pressure airless spray device, the alkaline solution prepared in step 1 is sprayed uniformly onto the surface of the recycled coarse aggregate, and the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface is discharged from the outlet of the high-pressure airless spray device.

[0012] In step 5, a powder spraying device including a second vibrating screen machine and an electrostatic powder sprayer used in combination is turned on, the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface obtained in step 4 is fed into the inlet of the powder spraying device, the composite precursor powder prepared in step 2 is uniformly sprayed on the surface of the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface, and the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface is discharged from the outlet of the powder spraying device.

[0013] In step 6, the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface obtained in step 5 is left to stand for 30 to 60 minutes, and after the composite precursor powder on the surface of the recycled coarse aggregate has basically solidified, it is fed into the inlet of a high-pressure airless sprayer. The first vibrating screen and high-pressure airless sprayer are turned on, and the alkaline solution prepared in step 1 is uniformly sprayed on the surface of the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface. The reinforced recycled coarse aggregate is discharged from the outlet of the high-pressure airless sprayer, and the reinforced layer thickness of the reinforced recycled coarse aggregate is controlled to be 0.8 mm to 1.5 mm.

[0014] In step 7, the reinforced recycled coarse aggregate obtained in step 6 is left in the shade for 24 hours, and then placed in a standard curing chamber for curing for 7 days.

[0015] Furthermore, the first vibrating screen is a linear vibrating screen, the screen openings are 4 mesh size and square holes, the screen width is 1 to 1.2 m, the aspect ratio of the screen surface is 2:1 to 3:1, the inclination angle α of the screen surface is 3 to 5°, the vibration direction angle δ is 45°, the amplitude A is 4 to 6 mm, and the frequency ω is 800 to 900 r / min. A high-pressure airless spray machine is used in combination with the first vibrating screen, and two rows of high-pressure airless spray nozzles are arranged above and below the screen surface, perpendicular to the screen surface and 0.5 m away from the screen surface, with the spray pressure greater than 5 MPa and the flow rate of a single nozzle greater than 3 L / min.

[0016] Furthermore, the second vibrating screen is a linear vibrating screen, the sieve has a size of 4 mesh and square holes, the sieve width is 1 to 1.2 m, the aspect ratio of the sieve surface is 2:1 to 3:1, and the inclination angle α of the sieve surface is 3 to 5°; The vibration direction angle δ is 45°, the amplitude A is 4-6 mm, and the frequency ω is 800-900 r / min. The electrostatic powder sprayer is used in combination with a second vibrating sieve machine, with two rows of powder spray nozzles arranged above and below the sieve surface, perpendicular to the sieve surface, and 0.5 m away from the sieve surface. The spray pressure is greater than 0.5 MPa, and the powder output of a single nozzle is greater than 500 g / min.

[0017] Furthermore, the solid waste-based activated material is one or more of a combination of granulated blast furnace slag, fly ash, finely divided refuse incineration bottom slag, and finely divided calcined refuse.

[0018] Furthermore, the sulfate is phosphogypsum or desulfurized gypsum.

[0019] Furthermore, the granulated blast furnace slag is S105-grade granulated blast furnace slag powder, the fly ash is Class 2 fly ash, the finely divided waste incineration bottom slag powder is a residue obtained by recovering metals from bottom slag produced at a waste incineration facility, then aging, drying, and pulverizing the slag in an open-air environment and passing it through a 200-mesh sieve, and the calcined waste fine powder is a residue obtained by calcining waste at 800 to 1000°C, pulverizing the slag, and passing it through a 200-mesh sieve.

[0020] Furthermore, the phosphate gypsum or desulfurized gypsum is metaphosphate gypsum or desulfurized gypsum, and is 200 mesh or less.

[0021] Compared with the prior art, the present application has the following characteristics and beneficial effects:

[0022] This application discloses a method for improving the quality of recycled coarse aggregate from waste concrete using a composite stimulating material. By using industrial solid waste as the basic raw material and modifying existing equipment to form a reinforced layer with a certain thickness on the recycled coarse aggregate through spraying, powder spraying, and further spraying, the quality of recycled coarse aggregate from waste concrete can be effectively improved, and the method has the characteristics of safety and high applicability, and has high value for popularization and practical use. If it is widely popularized and applied, it will achieve good economic benefits. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic flow chart of the present application. [Figure 2] 1 is a structural schematic diagram of a high-pressure airless spray device according to the present application. [Figure 3] 1 is a structural schematic diagram of a powder ejection device according to the present application. DETAILED DESCRIPTION OF THE INVENTION

[0024] In the following, the present application will be further described in order to make the technical means realized by the present application, creative features, objectives and effects achieved by the present application more comprehensible.

[0025] The examples described herein are specific embodiments of the present application used to explain the concept of the present application, and are all explanatory and exemplary, and should not be construed as limitations on the embodiments and the scope of the present application. In addition to the examples described herein, a person skilled in the art may further adopt other obvious technical solutions based on the claims and the contents disclosed in the specification of the present application, and these technical solutions include technical solutions adopting any obvious substitutions and modifications made to the embodiments described herein.

[0026] The present application discloses a method for upgrading waste concrete recycled coarse aggregate with composite stimulating materials, which includes the following steps:

[0027] In step 1, an alkaline solution is prepared, and the composition, by mass, is 20 to 30 parts of NaOH or KOH solid particles, 10 to 15 parts of fast-dissolving sodium silicate fine powder, and 100 parts of water. The water, NaOH or KOH solid particles, and fast-dissolving sodium silicate fine powder are mixed and stirred until the solid particles are completely dissolved.

[0028] In step 2, a composite precursor powder is prepared and mixed with 100 parts by mass of a solid waste-based activating material, which is a combination of one or more of granulated blast furnace slag, fly ash, finely ground waste incineration bottom slag, and finely ground calcined refuse, and 15 to 20 parts by mass of sulfate, and the mixture is proportionately placed in a powder mixer and uniformly mixed.

[0029] The sulfate is phosphate gypsum or desulfurized gypsum. The granulated blast furnace slag is commercially available S105-grade granulated blast furnace slag powder. The fly ash is commercially available Class 2 fly ash. The finely ground waste incineration bottom slag is the residue obtained after metals are recovered from bottom slag generated at a waste incineration facility, which is then aged, dried, and crushed in an open-air environment and passed through a 200-mesh sieve. The finely ground calcined waste is the residue obtained after calcining waste at 800-1000°C, crushing it, and passing it through a 200-mesh sieve. The phosphate gypsum or desulfurized gypsum is commercially available metaphosphate gypsum or desulfurized gypsum, 200 mesh or smaller.

[0030] In step 3, the waste concrete is crushed, sieved, washed, and dried so that 95% or more of the aggregate has a particle size of 5 to 20 mm, to obtain recycled coarse aggregate.

[0031] In step 4, the high-pressure airless spray device, which includes a first vibrating screen machine and a high-pressure airless spray machine used in combination, is turned on, the recycled coarse aggregate obtained in step 3 is fed into the inlet of the high-pressure airless spray device, the alkaline solution prepared in step 1 is sprayed uniformly onto the surface of the recycled coarse aggregate, and the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface is discharged from the outlet of the high-pressure airless spray device.

[0032] The first vibrating screen machine is a linear vibrating screen, the sieve mesh size is 4 mesh, the holes are square, the sieve width is 1 to 1.2 m, the aspect ratio of the sieve surface is 2:1 to 3:1, the inclination angle α of the sieve surface is 3 to 5°, the vibration direction angle δ is 45°, the amplitude A is 4 to 6 mm, and the frequency ω is 800 to 900 r / min. A high-pressure airless spray machine is used in combination with the first vibrating screen machine, and two rows of high-pressure airless spray nozzles are arranged above and below the sieve surface, perpendicular to the sieve surface and 0.5 m away from the sieve surface, with the spray pressure greater than 5 MPa and the flow rate of a single nozzle greater than 3 L / min.

[0033] In step 5, a powder spraying device including a second vibrating screen machine and an electrostatic powder sprayer used in combination is turned on, the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface obtained in step 4 is fed into the inlet of the powder spraying device, the composite precursor powder prepared in step 2 is uniformly sprayed on the surface of the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface, and the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface is discharged from the outlet of the powder spraying device.

[0034] The second vibrating screen is a linear vibrating screen, the sieve mesh size is 4 mesh, the holes are square, the sieve width is 1 to 1.2 m, the aspect ratio of the sieve surface is 2:1 to 3:1, the inclination angle α of the sieve surface is 3 to 5°, the vibration direction angle δ is 45°, the amplitude A is 4 to 6 mm, and the frequency ω is 800 to 900 r / min. An electrostatic powder sprayer is used in combination with the second vibrating screen, with two rows of powder spray nozzles arranged above and below the sieve surface, perpendicular to the sieve surface and 0.5 m away from the sieve surface, the spray pressure is greater than 0.5 MPa, and the powder discharge rate of a single nozzle is greater than 500 g / min.

[0035] In step 6, the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface obtained in step 5 is left to stand for 30 to 60 minutes, and after the composite precursor powder on the surface of the recycled coarse aggregate has basically solidified, it is fed into the inlet of a high-pressure airless sprayer. The first vibrating screen and high-pressure airless sprayer are turned on, and the alkaline solution prepared in step 1 is uniformly sprayed on the surface of the recycled coarse aggregate with the composite precursor powder uniformly sprayed on its surface. The reinforced recycled coarse aggregate is discharged from the outlet of the high-pressure airless sprayer, and the reinforced layer thickness of the reinforced recycled coarse aggregate is controlled to be 0.8 mm to 1.5 mm.

[0036] In step 7, the reinforced recycled coarse aggregate obtained in step 6 is left in the shade for 24 hours, and then placed in a standard curing chamber for curing for 7 days.

[0037] Example 1. This example provides a method for upgrading recycled concrete coarse aggregate using a composite stimulating material. The raw material contains a solid waste-based activating material, sulfate, and alkaline solution. The mass ratio of each component in the raw material is shown in Table 1 by the raw material and its corresponding mass part for each component in the row of Example 1. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1 mm.

[0038] Example 2. This example provides a method for upgrading waste concrete recycled coarse aggregate using a different composite stimulating material. The raw materials include a solid waste-based activating material, sulfate, and alkaline solution. The mass blending ratio of each component in the raw materials is shown in Table 1 by the raw materials and their corresponding mass parts for each component in the row of Example 2. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1 mm.

[0039] Example 3. This example provides a method for upgrading waste concrete recycled coarse aggregate using another composite stimulating material. The raw material includes a solid waste-based activating material, sulfate, and alkaline solution. The mass blending ratio of each component in the raw material is shown in Table 1 by the raw material and its corresponding mass part for each component in the row of Example 3. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1 mm.

[0040] Example 4. This example provides a method for upgrading waste concrete recycled coarse aggregate using another composite stimulating material. The raw materials include a solid waste-based activating material, sulfate, and alkaline solution. The mass blending ratio of each component in the raw materials is shown in Table 1 by the raw materials and their corresponding mass parts for each component in the row of Example 4. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1.5 mm.

[0041] Example 5. This example provides a method for upgrading waste concrete recycled coarse aggregate using another composite stimulating material. The raw materials include a solid waste-based activating material, sulfate, and alkaline solution. The mass blending ratio of each component in the raw materials is shown in Table 1 by the raw materials and their corresponding mass parts for each component in the row of Example 5. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1.5 mm.

[0042] Example 6. This example provides a method for upgrading waste concrete recycled coarse aggregate using another composite stimulating material. The raw material includes a solid waste-based activating material, sulfate, and alkaline solution. The mass blending ratio of each component in the raw material is shown in Table 1 by the raw material and its corresponding mass part for each component in the row of Example 6. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 1.5 mm.

[0043] Comparative Example 1. As a comparative example to Example 1, the components and mass blending ratios in the raw materials are shown by the raw materials and their corresponding mass parts for each component in the row of Comparative Example 1 in Table 1. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibrating sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and sets the thickness of the reinforced layer to 0.8 mm.

[0044] Comparative Example 2. As a comparative example for Example 5, the components and mass blending ratios in the raw materials are shown in Table 1 by the raw materials and their corresponding mass parts for each component in the row for Comparative Example 2. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibration sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and the thickness of the reinforced layer is set to 0.8 mm.

[0045] Comparative Example 3. As a comparative example to Example 6, the components and mass blending ratios in the raw materials are shown in Table 1 by the raw materials and their corresponding mass parts for each component in the row of Comparative Example 3. The manufacturing method uses steps 1 to 7 to control the thickness of the reinforced layer by controlling the linear vibration sieve frequency ω, the spray pressure of the high-pressure airless sprayer, the flow rate of the single nozzle, the spray pressure of the electrostatic powder sprayer, and the powder discharge amount of the single nozzle, and the thickness of the reinforced layer is set to 0.8 mm.

[0046] Comparative Example 4: This comparative example is a comparative example to Examples 1 to 6, and is a recycled waste concrete coarse aggregate that has not been subjected to a strengthening treatment.

[0047] Performance Test: Performance tests were conducted on the performance of the reinforced recycled coarse aggregates produced in Examples 1 to 6 and Comparative Examples 1 to 3, and the recycled coarse aggregate from waste concrete in Comparative Example 4. The performance of the reinforced recycled coarse aggregate from waste concrete provided by the present application was tested in accordance with "Construction boulders and crushed stones" (GB / T 14685-2022) and "Recycled coarse aggregate for concrete" (GB / T 25177-2010). After curing for 28 days, the specific test results are shown in Table 2.

[0048] As can be seen from Table 2, the method for improving the quality of recycled coarse aggregate from waste concrete using composite stimulating materials provided by the present application can effectively improve the quality of recycled coarse aggregate from waste concrete, with the following characteristics: Crushing value decreased by 27.1% to 37.3%, reaching or approaching the standard for Class I recycled coarse aggregate; Water absorption decreased by 38.4% to 44.4%, reaching the standard for Class II recycled coarse aggregate; Apparent density increased by 12.1 to 16.7%, reaching or approaching the standard for Class II recycled coarse aggregate; Bulk density increased by 10.3% to 14.1%, a significant increase. Table 1. Ingredients of each component of the reinforcing material and the corresponding parts by mass JPEG0007806374000001.jpg73102 Table 2. Performance test results for aggregate performance JPEG0007806374000002.jpg45102

[0049] Compared with the prior art, the method for improving the quality of recycled coarse aggregate from waste concrete using composite stimulating materials provided by the present application has the following advantages:

[0050] The material provided by the present application for improving the quality of coarse aggregate recycled from waste concrete does not use cement in its production, but rather stimulates the mineral activity of industrial solid waste such as granulated blast furnace slag, fly ash, waste incineration bottom slag, slag, phosphogypsum, or desulfurized gypsum, thereby improving the quality of coarse aggregate recycled from waste concrete, "strengthening waste with waste," reducing costs, saving energy and protecting the environment, and providing a new direction for the application of industrial solid waste as a resource.

[0051] The method for improving the quality of recycled coarse aggregate from waste concrete using composite stimulating materials provided by this application involves modifying existing equipment and forming a reinforcing layer on the surface of recycled coarse aggregate by spraying, powder spraying, or spraying instead of the traditional immersion method, thereby saving materials, eliminating the need for wastewater treatment, simplifying the process, and reducing the cost of reinforcing the recycled coarse aggregate.

[0052] In view of the above, the method for improving the quality of recycled coarse aggregate from waste concrete using composite stimulating materials provided by this application can effectively improve the quality of recycled coarse aggregate from waste concrete, ``strengthen waste with waste'', make full use of industrial solid waste, open up new fields for the resource utilization of industrial solid waste, improve the utilization rate and utilization quality of industrial solid waste, save water and materials, simplify the process, and reduce the strengthening processing costs of recycled coarse aggregate.

[0053] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application. [Explanation of symbols]

[0054] 1 sieve box 2. Sieve 3. Vibration damping spring 4 Inlet 5 Outlet 6 High-pressure airless spray nozzles 7. Vibration Electrical Equipment 8 Electrostatic Powder Sprayer Nozzles

Claims

1. A method for improving the quality of recycled coarse aggregate from waste concrete using a composite stimulating material, comprising: Step 1 of preparing an alkaline solution, the alkaline solution comprising, by mass, 20 to 30 parts of NaOH or KOH solid particles, 10 to 15 parts of fast-dissolving sodium silicate fine powder, and 100 parts of water, the water, the NaOH or KOH solid particles, and the fast-dissolving sodium silicate fine powder being mixed and stirred until the solid particles are completely dissolved; Step 2 of preparing a composite precursor powder, which comprises, by mass, 100 parts of a solid waste-based activated material, which is one or more combinations of granulated blast furnace slag, fly ash, finely ground waste incineration bottom slag, and finely ground calcined refuse, and 15 to 20 parts of gypsum, and the resulting mixture is proportionately placed in a powder mixer and uniformly stirred; A step 3 for producing recycled coarse aggregate includes crushing, sieving, washing, and drying the waste concrete so that aggregate having a particle size of 5 to 20 mm accounts for 95% or more of the recycled coarse aggregate; Step 4: turning on a high-pressure airless spray device including a first vibrating screen machine and a high-pressure airless spray machine used in combination, feeding the recycled coarse aggregate obtained in step 3 into an inlet of the high-pressure airless spray device, uniformly spraying the alkaline solution prepared in step 1 onto the surface of the recycled coarse aggregate, and discharging the recycled coarse aggregate with the alkaline solution uniformly sprayed on its surface from an outlet of the high-pressure airless spray device; Step 5: turning on a powder spraying device including a second vibrating screen machine and an electrostatic powder spraying device used in combination; feeding the recycled coarse aggregate obtained in step 4, the surface of which has been uniformly sprayed with the alkaline solution, into an inlet of the powder spraying device; uniformly spraying the composite precursor powder prepared in step 2 onto the surface of the recycled coarse aggregate, the surface of which has been uniformly sprayed with the alkaline solution; and discharging the recycled coarse aggregate, the surface of which has been uniformly sprayed with the composite precursor powder, from an outlet of the powder spraying device. Step 6: leaving the recycled coarse aggregate, the surface of which has been uniformly sprayed with the composite precursor powder obtained in step 5, to stand for 30 to 60 minutes; after the composite precursor powder on the surface of the recycled coarse aggregate has essentially solidified, feeding the recycled coarse aggregate into the inlet of the high-pressure airless sprayer; turning on the first vibrating screen and the high-pressure airless sprayer; uniformly spraying the alkaline solution prepared in step 1 onto the surface of the recycled coarse aggregate, the surface of which has been uniformly sprayed with the composite precursor powder; and discharging the reinforced recycled coarse aggregate from the outlet of the high-pressure airless sprayer, controlling the thickness of the reinforced layer of the reinforced recycled coarse aggregate to be 1.0 mm to 1.5 mm; Step 7: leaving the reinforced recycled coarse aggregate obtained in step 6 in the shade for 24 hours, and then placing it in a standard curing chamber and curing it for 7 days; A method for improving the quality of recycled coarse aggregate from waste concrete using a composite stimulating material, comprising:

2. The first vibrating screen is a linear vibrating screen, the sieve openings are 4 meshes in size and have square holes, the sieve width is 1-1.2 m, the aspect ratio of the sieve surface is 2:1-3:1, the inclination angle α of the sieve surface is 3-5°, the vibration direction angle δ is 45°, the amplitude A is 4-6 mm, and the frequency ω is 800-900 r / min. The high-pressure airless sprayer is used in combination with the first vibrating screen, and two rows of high-pressure airless spray nozzles are arranged above and below the sieve surface, perpendicular to the sieve surface and 0.5 m away from the sieve surface, with a spray pressure greater than 5 MPa and a flow rate of a single nozzle greater than 3 L / min. The method for improving the quality of recycled coarse aggregate from waste concrete using the composite stimulating material according to claim 1.

3. The second vibrating screen is a linear vibrating screen, the sieve openings are 4 meshes in size and have square holes, the sieve width is 1-1.2 m, the aspect ratio of the sieve surface is 2:1-3:1, the inclination angle α of the sieve surface is 3-5°, the vibration direction angle δ is 45°, the amplitude A is 4-6 mm, and the frequency ω is 800-900 r / min. The electrostatic powder sprayer is used in combination with the second vibrating screen, and two rows of powder injection nozzles are arranged above and below the sieve surface, perpendicular to the sieve surface, and 0.5 m away from the sieve surface, with an injection pressure greater than 0.5 MPa and a powder output rate of a single nozzle greater than 500 g / min. The method for improving the quality of recycled coarse aggregate from waste concrete using the composite stimulating material according to claim 2.

4. The gypsum is phosphogypsum or desulfurized gypsum. The method for improving the quality of recycled coarse aggregate from waste concrete using the composite stimulating material according to claim 1.

5. The granulated blast furnace slag is S105-grade granulated blast furnace slag powder, the fly ash is second-grade fly ash, the finely divided waste incineration bottom slag powder is a residue obtained by recovering metals from bottom slag generated in a waste incineration facility, aging, drying, and pulverizing the slag in an open-air environment, and passing it through a 200-mesh sieve, and the finely divided calcined waste powder is a residue obtained by calcining waste at 800 to 1000°C, pulverizing the slag, and passing it through a 200-mesh sieve. The method for improving the quality of recycled coarse aggregate from waste concrete using the composite stimulating material according to claim 1.

6. The phosphogypsum is metaphosphogypsum. The method for improving the quality of recycled coarse aggregate from waste concrete using the composite stimulating material according to claim 4.

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