Preparation method of modified waste concrete recycled aggregate and artificial stone prepared by the method

Abstract

The present application relates to a kind of preparation methods of modified waste concrete recycled aggregate, comprising: after crushing waste concrete, screen suitable particle size as the raw material of recycled aggregate, water washing is carried out by oscillation screen to remove part of edge and the corner that will soon fall off, using nano-silica, water-soluble silicate etc. Modification solution carries out gelation reaction, the micro-pore on the surface of concrete particle is plugged and repaired, makes its structure complete and densification, enhances the mechanical strength of aggregate, reduces porosity and water absorption, again by phenolic resin coating further reduces water absorption and enhances mechanical strength. Using the modified waste concrete recycled aggregate, mixed with cement, zeolite powder etc. And is pressed into blank, after carbonization maintenance, obtain the artificial stone with excellent mechanical properties and low water absorption rate.The method of the present application has good application prospect and environmental protection significance.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a method for preparing modified waste concrete recycled aggregate and the artificial stone prepared therefrom. Background Technology

[0002] The development of the construction industry inevitably generates construction solid waste. The accumulation of industrial solid waste not only leads to serious environmental problems but also wastes resources and hinders sustainable development. Waste cement concrete is a type of construction solid waste, accounting for a large proportion. Current treatment methods mostly involve centralized recycling and backfilling, which has low utilization value. After crushing and screening, waste cement concrete can be used as recycled aggregate, and a large amount of the powder can be directly used as a raw material for cement. Therefore, using waste cement concrete as recycled aggregate to replace natural aggregate in the preparation of artificial stone is an effective measure to solve the problem of construction solid waste accumulation and reduce pollution.

[0003] Recycled aggregates obtained from the crushing and screening of waste cement concrete have low strength, are coated with hardened cement mortar, have many sharp edges, high water absorption, and are difficult to bond. Damage to the waste cement concrete during crushing leads to internal micro-cracks, resulting in low strength and a significant disadvantage compared to natural aggregates, greatly limiting their application. With increasing carbon dioxide emissions, the atmospheric composition is gradually changing, significantly impacting air quality, affecting not only the ecological environment but also human health. If CO2 is used to cure artificial stone made from waste cement concrete, the reaction of CO2 with the green body to generate CaCO3 can improve the strength of the artificial stone compared to natural curing methods, while simultaneously achieving efficient carbon sequestration.

[0004] There are precedents for researching artificial stone in China, such as Chinese patent CN 112897956A, "Environmentally Friendly Inorganic Artificial Stone and its Preparation Method," which uses copper tailings and waste concrete to replace 100% of quartz sand. Its limitation lies in the long curing cycle, requiring steam curing followed by natural curing. Another example is Chinese patent CN 107540322A, "Inorganic Artificial Stone Containing High-Performance Ceramsite and Superabsorbent Resin and its Preparation Method," which uses microwave carbonization to cure the artificial stone, improving the surface density. However, its limitation is that it uses only natural aggregates and does not achieve the resource utilization of construction waste. Therefore, developing a high-performance artificial stone that can achieve the recycling of construction waste is essential. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for preparing modified waste concrete recycled aggregate and the artificial stone prepared therefrom. By processing the waste concrete recycled aggregate, the sharp edges of the waste concrete recycled aggregate can be reduced, the strength can be increased, the water absorption can be reduced, and the adhesion can be improved, thereby significantly increasing the mechanical properties of the artificial stone.

[0007] (II) Technical Solution

[0008] In a first aspect, the present invention provides a method for preparing modified waste concrete recycled aggregate, comprising:

[0009] S1. The waste cement concrete is crushed and sieved to obtain waste concrete particles.

[0010] S2. Place the waste concrete particles in a vibrating screen submerged in water for vibrating washing, and then dry them.

[0011] S3. Prepare a modified solution, which is composed of 3-9 parts by weight of an additive, 5-10 parts by weight of nano-silica, 15-25 parts by weight of a water-soluble silicate, and 50-60 parts by weight of water; wherein the water-soluble silicate is at least one of sodium silicate, potassium silicate, and lithium silicate; the additive is at least one of a penetrant, a preservative, and a pH adjuster; immerse the waste concrete particles treated in S2 in the modified solution for 1-6 hours, and then place them indoors to air dry naturally.

[0012] S4. Use a high-pressure water gun to rinse the waste concrete particles treated in S3, and then dry them.

[0013] S5. Prepare a phenolic resin solution containing 1-5% by mass of phenolic resin, and add a curing agent at 2-3% by mass of phenolic resin. Microwave the dried waste concrete particles from S4 for 0.5-1 hour. Spray the phenolic resin solution onto the surface of the waste concrete particles using a spraying device, stirring the waste concrete particles during the spraying process to ensure uniform spraying. The phenolic resin is cured to obtain modified waste concrete recycled aggregate.

[0014] According to a preferred embodiment of the present invention, in S1, waste cement concrete with a mesh size of 4-160 mesh is retained for subsequent preparation of recycled aggregate, and the upper portion of the 4-mesh sieve is further crushed; the lower portion of the 160-mesh sieve is ground to obtain recycled concrete powder or recycled to make cement; in S2, the mesh size of the vibrating sieve is 200 mesh, and the upper portion is retained; the mud produced in the lower portion is ground and dried to obtain recycled concrete powder.

[0015] According to a preferred embodiment of the present invention, in step S3, the pH of the modified solution is ≥11, preferably ≥12. Under alkaline conditions, the modified solution exhibits better stability and permeability. This pH also activates the waste concrete particles, enabling them to react with the modified solution and seal the fine cracks in the waste concrete particles. During the impregnation process, vacuum impregnation or ultrasonic treatment can be used to improve the impregnation effect.

[0016] According to a preferred embodiment of the present invention, in S3, the penetrant is one or more of triethanolamine, polyvinyl chloride, fatty alcohol polyoxyethylene ether, etc.; the corrosion inhibitor is a concrete-specific corrosion inhibitor mainly used to prevent corrosion by sulfate ions and chloride ions; and the pH adjuster is sodium hydroxide.

[0017] According to a preferred embodiment of the present invention, in S5, the curing agent in the phenolic resin solution is hexamethylenetetramine (HMTA) or formaldehyde; the amount of formaldehyde is 1%-2% of the mass of the phenolic resin; and the amount of HMTA is 1%-3% of the mass of the phenolic resin.

[0018] According to a preferred embodiment of the present invention, in step S5, 1-3g of phenolic resin is sprayed on every 100g of waste concrete particles.

[0019] Secondly, the present invention provides an environmentally friendly artificial stone comprising the modified waste concrete recycled aggregate prepared in any of the above embodiments.

[0020] Thirdly, the present invention provides a method for preparing environmentally friendly artificial stone, comprising:

[0021] Step 1: The modified waste concrete recycled aggregate prepared in any of the above embodiments is classified according to particle size into first-grade recycled aggregate <0.425mm, first-grade recycled aggregate 0.425mm-2.36mm and third-grade recycled aggregate 2.36mm-4.75mm.

[0022] Step 2: Mix and stir according to the following formula to obtain a uniform mixture:

[0023] First-grade recycled aggregate 10-20 wt%; Second-grade recycled aggregate 30 wt%-40 wt%; Third-grade recycled aggregate 12 wt%-20 wt%; Cement 12 wt%-15 wt%; Zeolite powder 2 wt%-4 wt%; Recycled concrete powder (a byproduct of the modified waste concrete recycled aggregate of this invention) 2 wt%-4 wt%; Metakaolin 2 wt%-5 wt%; Water-reducing agent 1 wt%-2 wt%; Styrene-butadiene emulsion 2 wt%-8 wt%; Water 2 wt%-4 wt%; Sodium pyrophosphate 1 wt%-2 wt%;

[0024] Step 3: Press the mixture into a blank, carbonize and cure it to obtain artificial stone.

[0025] According to a preferred embodiment of the present invention, the cement is phosphate cement.

[0026] According to a preferred embodiment of the present invention, metakaolin, zeolite powder, and recycled concrete powder constitute the auxiliary cementitious material; and metakaolin accounts for 30wt%-70wt% of the auxiliary cementitious material; zeolite powder accounts for 20wt%-30wt% of the auxiliary cementitious material; and recycled concrete powder accounts for 20wt%-30wt% of the auxiliary cementitious material.

[0027] The metakaolin has a particle size of less than 10 μm, preferably less than 5 μm; and a specific surface area of ​​4000-5000 cm². 2 / g; zeolite powder particle size is less than 10μm, preferably less than 5μm; specific surface area is 3000-5000 cm². 2 / g.

[0028] According to a preferred embodiment of the present invention, the water-reducing agent is at least one selected from polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, and sodium lignosulfonate. Sodium pyrophosphate acts as a retarder in the mixture, and styrene-butadiene emulsion is an organic binder (commercially available product, typically with a solid content of around 50%), improving the temperature change resistance and toughness of the artificial stone.

[0029] According to a preferred embodiment of the present invention, in step 3, the method for pressing the material into a blank is as follows: the mixture is placed into an oscillating mold frame, and a blank is obtained by static pressing. The static pressing pressure is 1.5 × 10⁻⁶. 5 N-2×10 5 N, the pressing and molding time is 20s-40s.

[0030] According to a preferred embodiment of the present invention, in step 3, the carbonization curing conditions are as follows: curing temperature 10℃-50℃, relative humidity 20%-80%, carbon dioxide concentration 10%-90%, curing time 2h-24h, and gas pressure 0.05-1MPa. The carbonization curing is completed in a carbonization chamber.

[0031] (III) Beneficial Effects

[0032] (1) In the preparation of modified waste concrete recycled aggregate, the present invention first crushes and sieves to remove particularly fine waste concrete powder, and then shakes and washes to further remove the sharp edges and floating dust of the waste concrete particles. Under the action of hydraulic and vibrating screen, the particles collide with each other to further reduce the sharp edges and loose edges of the waste concrete particles and improve the sphericity of the particles. After shaking and washing, particularly fine particles are further removed, leaving particles with a particle size greater than 200 mesh (74 μm). After drying, nano-silica and water-soluble silicates are used to penetrate the fine pits and cracks on the waste concrete particles under alkaline conditions to generate CHS (calcium silicate hydrate) gel. Water-soluble silicates (such as sodium silicate) can provide additional silicate ions in an alkaline environment to promote the formation of CSH gel, thereby sealing and repairing the micro-cracks on the waste concrete particles, thereby improving the structural integrity, density and strength of the waste concrete particles, reducing porosity and moisture absorption, and improving the sphericity of the waste concrete particles. To enhance impregnation and penetration, ultrasonic vibration can be used to assist impregnation. Next, a high-pressure water gun is used to wash away unreacted modified solution components and surface dust. Then, a phenolic resin coating is applied to obtain recycled aggregate from waste concrete. This coating process further improves the strength of the recycled aggregate and reduces its high water absorption rate, giving the prepared recycled aggregate broader application prospects. It can completely or partially replace natural quartz sand, reducing the mining of natural aggregate and possessing both economic and environmental benefits.

[0033] (2) In the environmentally friendly artificial stone prepared by the present invention, the recycled aggregate of waste concrete replaces natural quartz sand, with a replacement rate of 100%, which saves the amount of cement used, avoids the mining of natural stone, alleviates the problem of the accumulation and land occupation of construction solid waste, realizes the resource utilization of solid waste, reduces the manufacturing cost of artificial stone, and reduces the dependence of artificial stone on non-renewable natural materials and mining.

[0034] (3) The artificial stone preparation process of the present invention makes reasonable use of waste concrete recycled aggregate (and recycled concrete powder) to recycle waste concrete. At the same time, the curing method of the present invention is carbonization curing, which has a short curing time, realizes carbon fixation and reduces carbon emissions, and has good environmental protection significance.

[0035] (4) The method for preparing artificial stone of the present invention can obtain artificial stone with high strength and excellent performance. The styrene-butadiene emulsion and recycled aggregate coated with phenolic resin film added to the artificial stone can form a good bond, which is beneficial to improving the fracture toughness of the artificial stone.

[0036] In summary, this invention has the advantages of energy saving and environmental protection, carbon reduction and fixation, high economic benefits and low cost, and has good application prospects. Detailed Implementation

[0037] To better explain and facilitate understanding of the present invention, a detailed description of the invention is provided below in conjunction with specific embodiments. The phenolic resin used in all the following embodiments and comparative examples is the same, and is a commercially available product.

[0038] Example 1

[0039] This embodiment provides a method for preparing modified waste concrete recycled aggregate, which includes:

[0040] (1) Waste cement concrete is crushed and sieved to obtain waste concrete particles. The crushed waste concrete undergoes initial sieving, passing through 4-mesh and 160-mesh sieves. The undersize portion from the 4-mesh sieve is retained, while the oversize portion continues to be crushed. The oversize portion from the 160-mesh sieve is retained for preparing modified waste concrete recycled aggregate, while the undersize portion from the 160-mesh sieve is too fine and is further ground to become recycled concrete powder (RCP). RCP can be used to manufacture artificial stone or recycled for the production of new cement.

[0041] (2) The collected waste concrete particles are placed in an electric vibrating screen, which is submerged in water. The waste concrete particles are vibrated and washed for 2 hours for each batch. The mesh size of the vibrating screen is 200 mesh. The upper part of the screen is collected and dried. The mud produced from the lower part of the screen is ground and dried to obtain recycled concrete powder.

[0042] (3) Preparation of the modified solution: The modified solution is composed of 1 part by mass of the penetrant triethanolamine, 1 part by mass of the concrete-specific anti-corrosion agent, 2 parts by mass of the pH adjuster, 6 parts by mass of nano-silica, 12 parts by mass of lithium silicate, 12 parts by mass of sodium silicate, and 56 parts by mass of deionized water. The pH of the modified solution is 11.3.

[0043] (4) After drying the portion of the sieve left in step (2), immerse it in the above modified solution, soak for 3 hours, take it out, and place it indoors overnight to allow it to dry naturally.

[0044] (5) Use a high-pressure water gun to rinse the waste concrete particles processed in step (4), and then let them dry.

[0045] (6) Prepare a phenolic resin solution with a concentration of 2%, add 2% hexamethylenetetramine (HMTA) as a curing agent according to the dry weight of the phenolic resin, and stir evenly for later use.

[0046] (7) Microwave the waste concrete particles for 40 minutes to further dry their moisture content. Then, spray the waste concrete particles with a spray gun, using 100g of phenolic resin solution (containing 2g of phenolic resin) for every 100g of waste concrete particles. During the spraying process, turn the waste concrete particles over to ensure even spraying. Once the phenolic resin has cured, the modified waste concrete recycled aggregate is obtained.

[0047] Example 2

[0048] This embodiment is the same as Embodiment 1, except that the composition of the modified solution in step (3) is different. In this embodiment, the modified solution is composed of 1 part by mass of the penetrant triethanolamine, 3 parts by mass of the pH adjuster, 5 parts by mass of nano-silica, 10 parts by mass of lithium silicate, 10 parts by mass of potassium silicate, and 50 parts by mass of deionized water. The pH of this modified solution is 12.4.

[0049] Next, the portion remaining on the sieve in step (2) is dried and then immersed in the modified solution described above. Ultrasonic-assisted penetration is performed during the immersion process. After immersion for 1 hour, the sample is removed and left indoors overnight to allow for natural drying. The remaining steps are the same as in Example 1, thereby obtaining modified waste concrete recycled aggregate.

[0050] Example 3

[0051] This embodiment is the same as Embodiment 1, except that the composition of the modified solution in step (3) is different. In this embodiment, the modified solution is composed of 1 part by mass of concrete-specific anti-corrosion agent, 2 parts by mass of pH adjuster, 10 parts by mass of nano-silica, 8 parts by mass of lithium silicate, 5 parts by mass of potassium silicate, and 60 parts by mass of deionized water. The pH of this modified solution is 11.1.

[0052] Next, the portion remaining on the sieve in step (2) is dried and then immersed in the modified solution described above. The immersion process is carried out under vacuum for 1.5 hours, after which it is removed and left indoors overnight to allow for natural drying. The remaining steps are the same as in Example 1, thereby obtaining modified waste concrete recycled aggregate.

[0053] Comparative Example 1

[0054] This comparative example is made without the treatment in steps (3)-(5) of Example 1. That is, the waste concrete particles that have been washed by vibration are subjected to the phenolic resin coating treatment in steps (6)-(7) to obtain modified waste concrete recycled aggregate.

[0055] Example 4

[0056] This embodiment uses the modified waste concrete recycled aggregate prepared in Example 1 to prepare artificial stone, and the preparation method is as follows:

[0057] (1) The modified waste concrete recycled aggregate prepared in Example 1 was classified according to particle size into first-grade recycled aggregate <0.425mm, first-grade recycled aggregate 0.425mm-2.36mm and third-grade recycled aggregate 2.36mm-4.75mm.

[0058] (2) Mix and stir according to the following formula to obtain a uniform mixture.

[0059] The composition is as follows: 14 wt% primary recycled aggregate; 35 wt% secondary recycled aggregate; 19 wt% tertiary recycled aggregate; 13 wt% phosphate cement; 3 wt% zeolite powder; 3 wt% recycled concrete powder; 3 wt% metakaolin; 1 wt% polycarboxylate superplasticizer; 6 wt% styrene-butadiene emulsion (50% solids content); 2 wt% water; 1 wt% sodium pyrophosphate, totaling 100 wt%. The mass ratio of metakaolin, zeolite powder, and recycled concrete powder is 1:1:1. The specific surface area of ​​both metakaolin and zeolite powder is 4000-5000 cm². 2 / g.

[0060] (3) The mixture is placed into an oscillating mold frame and statically pressed to obtain a blank. The static pressing pressure is 1.6 × 10⁻⁶. 5 Press N for 40 seconds to obtain a green body. Place the green body in a carbonization box for curing. The temperature of the carbonization box is 30℃, the relative humidity is 50%, the air pressure is 0.05MPa, the carbon dioxide concentration is 60%, and the curing time is 12h.

[0061] Example 5

[0062] This embodiment uses the modified waste concrete recycled aggregate prepared in Example 2 to prepare artificial stone according to steps (1)-(2) of Example 4, but step (3) is changed to: filling the mixture into an oscillating mold frame and using static pressing to obtain the green body. The static pressing pressure is 1.5×10 5 Press N for 40 seconds to obtain a green body. Place the green body in a carbonization box for curing. The temperature of the carbonization box is 50℃, the relative humidity is 40%, the air pressure is 0.08MPa, the carbon dioxide concentration is 70%, and the curing time is 18h.

[0063] Example 6

[0064] This embodiment uses the modified waste concrete recycled aggregate prepared in Example 3 to prepare artificial stone according to steps (1)-(2) of Example 4, except that step (3) is changed to: filling the mixture into an oscillating mold frame and using static pressing to obtain a green body, with a static pressing pressure of 2.0 × 10⁻⁶. 5 Press N for 20 seconds to obtain a green body. Place the green body in a carbonization box for curing. The temperature of the carbonization box is 40℃, the relative humidity is 30%, the air pressure is 0.1MPa, the carbon dioxide concentration is 60%, and the curing time is 24h.

[0065] Example 7

[0066] This embodiment uses the modified waste concrete recycled aggregate prepared in Example 1 to prepare artificial stone. The only difference between this embodiment and Example 4 is the mix proportion. The mix composition in this embodiment is as follows: 14 wt% primary recycled aggregate; 35 wt% secondary recycled aggregate; 19 wt% tertiary recycled aggregate; 13 wt% phosphate cement; 2.7 wt% zeolite powder; 1.8 wt% recycled concrete powder; 4.5 wt% metakaolin; 1 wt% polycarboxylate superplasticizer; 6 wt% styrene-butadiene emulsion (50% solids content); 2 wt% water; 1 wt% sodium pyrophosphate, totaling 100 wt%. The mass ratio of metakaolin, zeolite powder, and recycled concrete powder is 5:3:2. The specific surface area of ​​both metakaolin and zeolite powder is 4000-5000 cm². 2 / g.

[0067] Comparative Example 2

[0068] This comparative example uses the modified waste concrete recycled aggregate prepared in Comparative Example 1 to prepare artificial stone according to the method of Example 4.

[0069] Comparative Example 3

[0070] This comparative example uses natural river sand and prepares artificial stone according to the gradation and method of Example 4.

[0071] Comparative Example 4

[0072] This embodiment uses the modified waste concrete recycled aggregate prepared in Example 1 to prepare artificial stone, except that the curing conditions are: the green body is naturally cured at a curing temperature of 25°C and a humidity of 30% for 7 days.

[0073] The flexural strength of the artificial stone samples prepared in Examples 4-7 and Comparative Examples 2-4 was tested according to JC / T2604-2021 "Imitation Stone Concrete Panels and Facing Bricks"; the compressive strength was tested using a press with a compression rate of 2.5 kN / s until the sample failed; the water absorption rate of the artificial stone obtained in Examples 4-7 and Comparative Examples 2-4 was tested according to GB / T4111-2013 "Test Methods for Concrete Blocks and Bricks". The test results are shown in Table 1.

[0074] Table 1: Compressive strength, flexural strength, and water absorption of artificial stone in each preparation example

[0075]

[0076]

[0077] The test results in Table 1 show that the compressive strength and flexural strength of the artificial stone prepared in Examples 4-7 are higher than those in Comparative Examples 2 and 4. Compared with the artificial stone made from natural quartz sand in Comparative Example 3, the compressive strength, flexural strength, and water absorption of the artificial stone prepared in Examples 4-7 are basically equivalent or even slightly better. In Example 7, the mass ratio of metakaolin, zeolite powder, and recycled concrete powder in the mixture was further adjusted, resulting in the best mechanical properties of the artificial stone among all examples. The recycled aggregate used in Comparative Example 2 was waste concrete particles that had not been treated with the modified solution. Although these waste concrete particles were coated with phenolic resin, the mechanical strength of the final artificial stone was still relatively poor, and the water absorption rate was also high. The composition of the artificial stone in Comparative Example 4 was the same as that in Example 1, but it was cured under natural curing conditions. Not only was the curing period longer, but the mechanical properties of the final artificial stone were also inferior to those in Example 4.

[0078] This invention uses waste concrete as recycled aggregate. After washing with water using a vibrating screen to remove some sharp edges and corners that are about to detach, a gelation reaction is carried out using nano-silica and water-soluble silicates to seal and repair the micropores on the surface of the waste concrete particles, making their structure more complete and denser, enhancing the mechanical strength of the aggregate, and reducing porosity and water absorption. A phenolic resin coating further reduces water absorption. This carbonization curing method for artificial stone not only gives it higher mechanical strength but also achieves the goal of carbon reduction and fixation. Therefore, the method of this invention has good application prospects and environmental significance.

[0079] 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 modified waste concrete recycled aggregate, characterized in that, include: S1. The waste cement concrete is crushed and sieved to obtain waste concrete particles. During crushing and sieving, the waste cement concrete with a mesh size of 4-160 mesh is retained for subsequent preparation of recycled aggregate. The upper part of the 4-mesh sieve is further crushed. The lower part of the 160-mesh sieve is ground to obtain recycled concrete powder or recycled to make cement. S2. Place the waste concrete particles in a vibrating screen submerged in water for vibrating and washing, and then dry them. The vibrating screen has a mesh size of 200, and the portion above the screen is collected. The mud produced below the screen is ground and dried to obtain recycled concrete powder. S3. Prepare a modified solution, wherein the modified solution is composed of 3-9 parts by weight of an additive, 5-10 parts by weight of nano-silica, 15-25 parts by weight of water-soluble silicate, and 50-60 parts by weight of water, and the pH of the modified solution is ≥11; wherein the water-soluble silicate is at least one of sodium silicate, potassium silicate, and lithium silicate; the additive is at least one of a penetrant, a preservative, and a pH adjuster; the waste concrete particles treated in S2 are immersed in the modified solution for 1-6 hours, and after being removed, are placed indoors to air dry naturally; S4. Use a high-pressure water gun to rinse the waste concrete particles treated in S3, and then dry them. S5. Prepare a phenolic resin solution containing 1-5% by mass of phenolic resin, and add a curing agent at 2-3% by mass of the phenolic resin. Microwave the dried waste concrete particles from S4 for 0.5-1 hour. Spray the phenolic resin solution onto the surface of the waste concrete particles using a spraying device. Stir the waste concrete particles during the spraying process to ensure uniform spraying. After the phenolic resin is cured, modified waste concrete recycled aggregate is obtained.

2. The preparation method according to claim 1, characterized in that, In S3, the penetrant is one or more of triethanolamine, polyvinyl chloride, and fatty alcohol polyoxyethylene ether; the corrosion inhibitor is a concrete-specific corrosion inhibitor used to prevent corrosion by sulfate and chloride ions; and the pH adjuster is sodium hydroxide.

3. The preparation method according to claim 1, characterized in that, In S5, the curing agent in the phenolic resin solution is hexamethylenetetramine (HMTA) or formaldehyde; the amount of formaldehyde is 2% of the mass of the phenolic resin; and the amount of HMTA is 3% of the mass of the phenolic resin.

4. The preparation method according to claim 1, characterized in that, In S5, spray 1g-3g of phenolic resin for every 100g of waste concrete particles.

5. A method for preparing environmentally friendly artificial stone, characterized in that, It includes: Step 1: The modified waste concrete recycled aggregate prepared by the preparation method according to any one of claims 1-4 is classified according to particle size into first-grade recycled aggregate <0.425mm, second-grade recycled aggregate 0.425mm-2.36mm and third-grade recycled aggregate 2.36mm-4.75mm; Step 2: Mix and stir according to the following formula to obtain a uniform mixture: First-grade recycled aggregate: 10-20 wt%; Second-grade recycled aggregate: 30 wt%-40 wt%; Third-grade recycled aggregate: 12 wt%-20 wt%; Cement: 12 wt%-15 wt%; Zeolite powder: 2 wt%-4 wt%; Recycled concrete powder: 2 wt%-4 wt%; Metakaolin: 2 wt%-5 wt%; Water-reducing agent: 1 wt%-2 wt%; Styrene-butadiene emulsion: 2 wt%-8 wt%; Water: 2 wt%-4 wt%; Sodium pyrophosphate: 1 wt%-2 wt% Step 3: Press the mixture into a blank, carbonize and cure it to obtain artificial stone.

6. The preparation method according to claim 5, characterized in that, The cement is phosphate cement; the water-reducing agent is at least one of polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, and sodium lignosulfonate.

7. The preparation method according to claim 5, characterized in that, in, The auxiliary cementitious material consists of metakaolin, zeolite powder, and recycled concrete powder; metakaolin accounts for 30wt%-70wt% of the auxiliary cementitious material; zeolite powder accounts for 20wt%-30wt% of the auxiliary cementitious material; and recycled concrete powder accounts for 20wt%-30wt% of the auxiliary cementitious material.

8. The preparation method according to claim 5, characterized in that, The method for pressing into a blank is as follows: the mixture is placed into an oscillating mold frame, and a blank is obtained by static pressing. The static pressing pressure is 1.5 × 10⁻⁶. 5 N -2×10 5 N, the pressing and molding time is 20s-40s; The conditions for carbonization curing are: curing temperature of 10℃-50℃, relative humidity of 20%-80%, carbon dioxide concentration of 10%-90%, curing time of 2h-24h, and gas pressure of 0.05-1MPa.

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