Production method of green building material recycled concrete

Abstract

The application relates to the technical field of building materials, and particularly discloses a production method of green building material recycled concrete, which comprises the following steps: vacuum impregnation treatment is carried out on recycled coarse aggregate to obtain functional recycled aggregate; the functional recycled aggregate is mixed with cementitious material, fine aggregate, a pressure response type slow-release pH regulator and water, the concrete preform is placed and maintained for 18-24 hours under the condition that the temperature is 25-30 DEG C and the humidity is greater than or equal to 90%, the treated preform is placed in a closed maintenance equipment, and variable pressure maintenance including pressure increase-steady pressure-pressure release circulation is carried out. In the application, microorganisms and reaction ions are preloaded in the recycled aggregate by vacuum impregnation, and a pressure response type slow-release pH regulator is introduced in the concrete mixing stage, which can drive the microorganism mineralization reaction and the CO2 carbonization reaction to occur in the recycled aggregate-new mortar interface transition zone, and the obtained concrete component has better overall performance and carbon fixation capacity.

Description

Technical Field

[0001] This application relates to the field of building materials technology, and more specifically, it relates to a method for producing recycled concrete, a green building material. Background Technology

[0002] With increasing global emphasis on sustainable development and the recycling of building resources, processing demolition waste into recycled aggregates and using them to prepare new concrete has become an important development direction in the field of green building materials. The application of recycled concrete can not only effectively dispose of construction waste and reduce the mining of natural sand and gravel resources, but also reduce carbon emissions caused by cement production, thus having significant environmental and social benefits.

[0003] Currently, the production of recycled concrete typically involves crushing, screening, and removing basic impurities from waste concrete to obtain recycled aggregates. These recycled aggregates then partially or completely replace natural aggregates, and the mix design is based on the proportions of ordinary concrete. Finally, the finished product is obtained through mixing, molding, and natural or steam curing. However, when using atmospheric or low constant pressure CO2 curing to carbonize and strengthen recycled concrete, CO2 gas cannot effectively penetrate into the interior of the concrete and the interface transition zone that encapsulates the recycled aggregates. This results in the carbonization reaction mainly remaining on the surface, making it difficult to improve the overall performance of the material. Summary of the Invention

[0004] To address the problem that existing recycled concrete production methods struggle to improve overall material performance, this application provides a method for producing recycled concrete as a green building material.

[0005] This application provides a method for producing recycled concrete, a green building material, using the following technical solution: A method for producing recycled concrete, a green building material, includes the following steps: S1. Vacuum impregnation of recycled coarse aggregate is performed, and a composite liquid containing microorganisms and reactive ions is loaded to obtain functional recycled aggregate. S2. The functional recycled aggregate is mixed with cementitious materials, fine aggregate, pressure-responsive slow-release pH adjuster and water, and then poured into molds to obtain precast concrete bodies. S3. The precast concrete body is left to stand for 18-24 hours under conditions of 25-30℃ and ≥90% humidity to form a treated precast body; S4. Place the precast body in a closed curing equipment, introduce CO2-containing gas, and carry out variable pressure curing including pressure increase-pressure stabilization-pressure decompression cycle to form concrete components. The peak pressure in the variable pressure curing is 1.6-2.0 MPa, the total duration of each cycle is 65-120 minutes, and the curing temperature is 25-35℃. S5. Reduce the pressure inside the sealed curing equipment to normal pressure, and remove the concrete components for standard curing.

[0006] By adopting the above technical solution, the preloading of microorganisms and reactive ions into the recycled aggregate through vacuum impregnation, and the introduction of a pressure-responsive slow-release pH adjuster during the concrete mixing stage, the subsequent static activation and dynamic pressure-variable CO2 curing processes can drive the synergistic occurrence of microbial mineralization and CO2 carbonization reactions in the transition zone between the recycled aggregate and new mortar. This, through a specific pressurization-stabilization-depressurization cycle, enhances the transport and exchange of CO2 and reaction products, achieving in-situ and deep strengthening of weak points within the concrete. The resulting concrete components exhibit superior overall performance and carbon fixation capacity, solving the problem that existing recycled concrete production struggles to improve the overall material performance.

[0007] Preferably, in step S1, the composite solution comprises urea with a concentration of 1.0-1.5 mol / L, a calcium salt solution with a concentration of 0.5-1.0 mol / L, and a concentrated suspension of Bacillus pasteurellii with an OD600 value of 0.8-1.2. The vacuum degree of the vacuum impregnation treatment is -0.09 MPa to -0.085 MPa, and the impregnation time is not less than 30 minutes.

[0008] By adopting the above technical solution, and by defining a composite liquid formulation containing a specific concentration of urea, calcium salt, and highly active bacterial suspension, and by combining optimized vacuum impregnation process parameters, it is possible to ensure that microorganisms and reactive ions are efficiently and uniformly loaded into the pore network of the recycled aggregate.

[0009] Preferably, in step S2, the pressure-responsive sustained-release pH adjuster is a microcapsule coated with a pH-adjusting substance, with a particle size of 75-150 μm, and the amount of the microcapsule added is 0.5%-1.5% of the total mass of the gelling material.

[0010] By adopting the above technical solution, the pressure-responsive slow-release pH adjuster is limited to microcapsules with a specific particle size range, and its addition amount is controlled based on the quality of the cementitious material. This ensures that the functional component is appropriately and uniformly dispersed in the concrete matrix, enabling it to achieve a precise and controllable response to changes in internal pressure and chemical environment during subsequent dynamic pressure curing. In this way, it buffers drastic pH fluctuations throughout the reaction system, creating and maintaining a stable microenvironment for microbial activity and orderly precipitation of calcium carbonate.

[0011] Preferably, the wall material of the microcapsule is a gelatin-gum arabic composite, and the core material is citric acid.

[0012] By adopting the above technical solution, the use of gelatin-gum arabic as a composite wall material to coat the citric acid core material endows the microcapsules with good biocompatibility and specific responsive release characteristics under pressure and chemical environmental changes. This enables them to adapt to the complex conditions in the concrete mixing and curing process, ensuring reliable triggering of the slow-release function and synergistic regulation of the reaction process.

[0013] Preferably, in step S2, the water-cement ratio of the concrete mixture formed by mixing is 0.35-0.40.

[0014] By adopting the above technical solution, by controlling the water-cement ratio within 0.35-0.40, a denser paste microstructure can be formed while ensuring the necessary workability of the concrete mixture. This is beneficial for guiding reactants such as CO2 and calcium ions and pH changes to react more concentratedly in the aggregate interface area during subsequent curing, rather than being consumed disorderly in the matrix, thereby improving the targeting and efficiency of the interface strengthening effect.

[0015] Preferably, in step S4, the transformer maintenance is performed for 3-5 cycles.

[0016] By adopting the above technical solution, since the number of cycles of variable pressure maintenance is limited to 3-5 times, a balance can be achieved between ensuring the sufficiency and depth of the reaction. This allows the forced CO2 infiltration, interfacial mineralization reaction, and by-product removal processes to be repeated multiple times, thereby achieving layer-by-layer and cumulative strengthening of the interfacial structure.

[0017] Preferably, the cycle includes linearly increasing the pressure from the reference pressure to the peak pressure within 15-30 minutes, maintaining the peak pressure for 10-20 minutes, and then uniformly decreasing the pressure to the reference pressure within 40-70 minutes.

[0018] By adopting the above technical solution, a pulsed pressure field with specific dynamics is constructed by limiting the duration of the three stages of pressurization, stabilization and depressurization in each pressure cycle. This not only forces CO2 to penetrate into the micropores, but also ensures sufficient reaction time through the stabilization stage, and promotes the exchange and renewal of reaction products by utilizing the pumping effect generated by the slow depressurization stage, thereby optimizing the mass transfer and reaction kinetics of the entire synergistic mineralization reaction.

[0019] Preferably, the reference pressure is 1.0-1.2 MPa.

[0020] By adopting the above technical solution, the reference pressure is limited to 1.0-1.2 MPa and matched with the peak pressure of 1.6-2.0 MPa, thus providing sufficient driving force for the deep transport of reactants.

[0021] Preferably, in step S4, the CO2-containing gas is pure CO2 or a mixed gas with a CO2 volume fraction of not less than 30%.

[0022] By adopting the above technical solution, the use of pure CO2 or a mixed gas with a CO2 volume fraction of not less than 30% ensures a sufficiently high CO2 partial pressure in the maintenance environment, thereby driving CO2 to effectively dissolve, diffuse and participate in carbonization reactions and synergistic microbial mineralization reactions, thus enabling deep carbonization and improving CO2 fixation rate.

[0023] Preferably, in step S5, the process of reducing the pressure to normal takes no less than 120 minutes, and the standard curing involves placing the concrete component in an environment with a temperature of 18-22°C and a relative humidity of >95%.

[0024] By adopting the above technical solution, since the depressurization process must be carried out slowly and then standard curing is carried out under specific temperature and humidity conditions, damage to the internal microstructure of concrete caused by sudden pressure drop can be avoided, and the unreacted cementitious materials can continue to hydrate and develop later strength, thereby ensuring and optimizing the final macroscopic performance and long-term durability of concrete components.

[0025] In summary, this application has the following beneficial effects: 1. Because this application uses vacuum impregnation to preload microorganisms and reactive ions into the recycled aggregate, and introduces a pressure-responsive slow-release pH adjuster during the concrete mixing stage, the subsequent static activation and dynamic pressure-variable CO2 curing processes can drive the microbial mineralization reaction and CO2 carbonization reaction to occur synergistically in the transition zone between the recycled aggregate and the new mortar interface. By utilizing a specific pressurization-stabilization-depressurization cycle, the transport and exchange of CO2 and reaction products are enhanced, achieving in-situ and deep strengthening of weak points inside the concrete. The resulting concrete components have better overall performance and carbon fixation capacity, overcoming the problem that existing recycled concrete production cannot improve the overall performance of materials.

[0026] 2. By combining the concentrations of urea, calcium salt, and microbial inoculum in the composite solution with vacuum impregnation process parameters, this application can ensure that microorganisms and reactive ions are loaded efficiently, uniformly, and in sufficient quantities within the pores of the recycled aggregate. This provides sufficient raw material reserves and active sites for the continuous and stable bio-chemical synergistic mineralization reaction in the interface transition zone, thereby improving the effect and uniformity of interface strengthening.

[0027] 3. This application combines a pressure-responsive slow-release pH adjuster with a cementitious material to achieve uniform dispersion in the concrete matrix and to achieve responsive and controllable release according to changes in pressure and chemical environment during dynamic pressure curing. This effectively buffers the drastic pH fluctuations caused by the combined effects of microbial metabolism and CO2 dissolution in the interfacial transition zone, creating and maintaining a suitable microchemical environment for the orderly and efficient precipitation of calcium carbonate.

[0028] 4. This application constructs a pressure field with optimized dynamic characteristics by coordinating the number of cycles, duration of each stage, peak pressure and reference pressure of variable pressure curing. This not only forces CO2 to overcome capillary resistance and penetrate into the micropores of concrete, but also ensures the full reaction through periodic pressure stabilization. Furthermore, it utilizes the pumping effect generated by slow pressure relief to promote the discharge of by-products and the replenishment of fresh reactants, thereby achieving layer-by-layer and cumulative strengthening of the interface transition zone and deep fixation of CO2. Attached Figure Description

[0029] Figure 1 This is a flowchart of a production method for recycled concrete, a green building material, provided in this application. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Technical Concept: Recycled concrete refers to concrete materials made by partially or completely replacing natural aggregates with recycled aggregates obtained from the crushing and screening of demolition waste. The current conventional production method of recycled concrete usually involves crushing, screening and removing impurities from waste concrete to obtain recycled aggregates, which are then mixed with cement, sand and gravel according to the mix proportion, and then molded and naturally cured or steam cured to make concrete products. However, in the recycled concrete prepared by this method, the interface transition zone formed between the old mortar layer attached to the surface of the recycled aggregate and the freshly mixed cement paste has a loose structure and high porosity, which has become the main weak link restricting the mechanical properties and durability of the material.

[0032] To address the aforementioned technical problems, this application discovers that the interconnected pore network within recycled aggregates has the potential to serve as an in-situ reaction site, and that microbial-induced calcium carbonate precipitation and carbon dioxide carbonation reactions can produce a synergistic mineralization effect under suitable microenvironmental conditions. Based on this discovery, this application organically combines three technical means: vacuum impregnation with loaded microorganisms and reactive ions, introduction of pressure-responsive slow-release pH adjusters, and dynamic pressure-switching carbon dioxide curing. By transforming aggregate pores into in-situ microreactors, constructing a stable reaction microenvironment in the interfacial region, and utilizing pulsed pressure fluctuations to enhance the mass transfer process, this application achieves in-situ, synergistic, and continuous microbial mineralization and carbonation reactions in the interfacial transition zone, solving the problem that existing recycled concrete production struggles to improve the overall material performance.

[0033] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0034] Preparation Example 1: Preparation of a Pressure-Response Sustained-Release pH Adjuster Dissolve 10g of gelatin and 5g of gum arabic in 500mL of deionized water at 50℃ to prepare a 3% (w / w) composite wall material solution. The gelatin is type B with a Bloom value of 200. Dissolve 15g of citric acid monohydrate in 50mL of deionized water to prepare the core material solution. While stirring at 400 rpm, the core material solution was slowly added dropwise to the wall material solution. After the addition was complete, the pH of the system was adjusted to 4.1 with 1.0 mol / L glacial acetic acid solution. Continue stirring the reaction at 45°C for 60 minutes. Cool the reaction system to below 10°C, add 1 mL of glutaraldehyde solution, and allow the crosslinking reaction to proceed for 2 hours. After the reaction was completed, the solid product was filtered, washed three times with deionized water, dried under vacuum at 38°C for 12 hours, sieved, and the microcapsule product with a particle size of 75-150 μm was collected.

[0035] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0036] The following is a further description with reference to the embodiments: Example 1: Please refer to the appendix Figure 1 A method for producing recycled concrete, a green building material, includes the following steps: S1. Vacuum impregnation of recycled coarse aggregate is performed, and a composite liquid containing microorganisms and reactive ions is loaded to obtain functional recycled aggregate. S2. The functional recycled aggregate is mixed with cementitious materials, fine aggregate, pressure-responsive slow-release pH adjuster and water, and then poured into molds to obtain precast concrete bodies. S3. The precast concrete body is left to cure statically for 18-24 hours at a temperature of 27.5℃ and a humidity of ≥90% to form a treated precast body; S4. Place the precast body in a closed curing equipment, introduce CO2-containing gas, and carry out variable pressure curing including pressure increase-pressure stabilization-pressure decompression cycle to form concrete components. The peak pressure during variable pressure curing is 1.8MPa, the total duration of each cycle is 92.5 minutes, and the curing temperature is 30℃. S5. Reduce the pressure inside the sealed curing equipment to normal pressure, and remove the concrete components for standard curing.

[0037] In step S1, the composite liquid contains urea at a concentration of 1.25 mol / L, calcium salt solution at a concentration of 0.75 mol / L, and concentrated Bacillus pasteurellium suspension with an OD600 value of 1. The vacuum degree of the vacuum impregnation treatment is -0.0875 MPa, the impregnation time is not less than 30 minutes, the recycled coarse aggregate has a particle size of 5-20 mm and an apparent density of 2450 kg / m³, and the loading is as follows: the recycled aggregate is placed in a vacuum impregnation tank, the vacuum is drawn to an absolute pressure of 13 kPa and maintained for 25 minutes, the vacuum is maintained, the composite liquid is injected to completely immerse the recycled aggregate, it is allowed to stand for 30 minutes, then the pressure is restored to normal and drained.

[0038] In step S2, the pressure-responsive slow-release pH adjuster is a microcapsule coated with a pH-adjusting substance, with a particle size of 112.5 μm. The amount of microcapsule added is 1% of the total mass of the cementitious material. The cementitious material is, per cubic meter of concrete, weighed as follows: 200 kg of P·O42.5 ordinary Portland cement, 200 kg of S95 grade granulated blast furnace slag powder, 600 kg of fine aggregate (fineness modulus 2.5) of natural river sand, and 150 kg of water.

[0039] The wall material of the microcapsules is a gelatin-gum arabic composite, and the core material is citric acid.

[0040] In step S2, the water-cement ratio of the concrete mixture is 0.375.

[0041] In step S4, transformer maintenance is performed in 4 cycles.

[0042] The cycle involves linearly increasing the pressure from the reference pressure to the peak pressure over 22.5 minutes, holding the peak pressure for 15 minutes, and then uniformly decreasing the pressure back to the reference pressure over 55 minutes.

[0043] The reference pressure is 1.1 MPa.

[0044] In step S4, the gas containing CO2 is pure CO2 or a mixed gas with a CO2 volume fraction of not less than 30%.

[0045] In step S5, the process of reducing the pressure to normal takes no less than 120 minutes, and the standard curing is to place the concrete component in an environment with a temperature of 20°C and a relative humidity of >95%.

[0046] Example 2: This example differs from Example 1 above in that: A method for producing recycled concrete, a green building material, includes the following steps: S1. Vacuum impregnation of recycled coarse aggregate is performed, and a composite liquid containing microorganisms and reactive ions is loaded to obtain functional recycled aggregate. S2. The functional recycled aggregate is mixed with cementitious materials, fine aggregate, pressure-responsive slow-release pH adjuster and water, and then poured into molds to obtain precast concrete bodies. S3. The precast concrete body is left to cure statically for 18 hours at a temperature of 25℃ and a humidity of ≥90% to form a treated precast body. S4. Place the precast body in a closed curing equipment, introduce CO2-containing gas, and carry out variable pressure curing including pressure increase-pressure stabilization-pressure decompression cycle to form concrete components. The peak pressure during variable pressure curing is 1.6MPa, the total duration of each cycle is 65 minutes, and the curing temperature is 25℃. S5. Reduce the pressure inside the sealed curing equipment to normal pressure, and remove the concrete components for standard curing.

[0047] Example 3: This example differs from Example 1 above in that: A method for producing recycled concrete, a green building material, includes the following steps: S1. Vacuum impregnation of recycled coarse aggregate is performed, and a composite liquid containing microorganisms and reactive ions is loaded to obtain functional recycled aggregate. S2. The functional recycled aggregate is mixed with cementitious materials, fine aggregate, pressure-responsive slow-release pH adjuster and water, and then poured into molds to obtain precast concrete bodies. S3. The precast concrete body is left to cure statically for 24 hours at a temperature of 30℃ and a humidity of ≥90% to form a treated precast body; S4. Place the precast body in a closed curing equipment, introduce CO2-containing gas, and carry out variable pressure curing including pressure increase-pressure stabilization-pressure decompression cycle to form concrete components. The peak pressure in variable pressure curing is 2.0 MPa, the total duration of each cycle is 120 minutes, and the curing temperature is 35℃. S5. Reduce the pressure inside the sealed curing equipment to normal pressure, and remove the concrete components for standard curing.

[0048] Comparative Example 1: A method for producing recycled concrete, comprising the following steps: Construction waste is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. Based on the amount of concrete per cubic meter, the following should be weighed: 400kg of P·O 42.5 cement, 850kg of recycled coarse aggregate, 600kg of natural river sand, and 150kg of water. After the raw materials are mixed evenly, they are poured into molds and cured in a standard curing room for 28 days.

[0049] Comparative Example 2: This comparative example differs from Example 1 above in that: In step S2, no pressure-responsive sustained-release pH adjuster is added; Everything else is exactly the same as in Example 1.

[0050] Comparative Example 3: This comparative example differs from Example 1 above in that: In step S4, CO2-containing gas is introduced, the pressure is directly increased to 1.8 MPa, and the gas is kept under constant pressure for 6.2 hours. Everything else is exactly the same as in Example 1.

[0051] Comparative Example 4: This comparative example differs from Example 1 above in that: In step S1, vacuum impregnation and loading are not performed; only recycled coarse aggregate is used in step S2. Everything else is exactly the same as in Example 1.

[0052] Performance testing: Compressive strength: The cube compressive strength was tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete"; Microhardness of the interface transition zone: After the test block is sliced ​​and polished, the Vickers microhardness tester is used to test the hardness value in a 50μm wide area near the interface between aggregate and mortar at 10μm intervals. The average value is taken as the microhardness characterization of the interface transition zone. Chloride ion diffusion coefficient: The chloride ion diffusion coefficient is tested according to the electric flux method in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The lower the value, the better the impermeability and durability. CO2 fixation rate: Thermogravimetric analysis was used to determine the CaCO3 content of the powder sample decomposed at high temperature, and the CO2 fixation rate relative to the mass of cementitious material was calculated.

[0053] Table 1 As can be seen from Examples 1 to 3 and Comparative Example 1, and in conjunction with Table 1, the synergistic process provided in this application, which includes the preparation of functional recycled aggregates, the introduction of pressure-responsive slow-release agents, and dynamic pressure-variable CO2 curing, can improve the overall performance of concrete. Through the close connection and functional complementarity of each step, effective carbon sequestration is achieved while strengthening the structure of the interface transition zone.

[0054] As can be seen from Example 1 and Comparative Example 2, and Table 1, the pressure-responsive slow-release pH adjuster can ensure the stability of the interfacial microenvironment during dynamic pressure curing. This adjuster can be released responsively under pressure conditions, neutralize reaction byproducts, and maintain the pH value of the interfacial region within a range conducive to the orderly precipitation of calcium carbonate, thereby ensuring the synergistic efficiency of microbial mineralization and CO2 carbonation reactions. The lack of this component will lead to insufficient interfacial strengthening, affecting the compactness and durability of concrete.

[0055] As can be seen from Example 1 and Comparative Example 3 and Table 1, the pulse-type variable pressure curing mode, which includes pressure increase, pressure stabilization and pressure release stages, can achieve deep and uniform synergistic mineralization. The pumping effect generated by pressure circulation promotes the transmission and exchange of CO2 and reaction products in the micropores of concrete, avoiding the problem of premature closure of reaction channels that may be caused by constant pressure curing, thereby more effectively strengthening the internal interface and improving the CO2 fixation rate.

[0056] As can be seen from Example 1 and Comparative Example 4, and Table 1, preloading recycled aggregate with microorganisms and reactive ions can transform recycled aggregate into in-situ microreactors, providing local biocatalysts and high-concentration reactive ion reserves for subsequent curing processes. However, unfunctionalized aggregate cannot initiate efficient interfacial directional mineralization reactions, resulting in limited performance improvement of the final product.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for producing recycled concrete, a green building material, characterized in that, Includes the following steps: S1. Vacuum impregnation of recycled coarse aggregate is performed, and a composite liquid containing microorganisms and reactive ions is loaded to obtain functional recycled aggregate. S2. The functional recycled aggregate is mixed with cementitious materials, fine aggregate, pressure-responsive slow-release pH adjuster and water, and then poured into molds to obtain precast concrete bodies. S3. The precast concrete body is left to stand for 18-24 hours under conditions of 25-30℃ and ≥90% humidity to form a treated precast body; S4. Place the precast body in a closed curing equipment, introduce CO2-containing gas, and carry out variable pressure curing including pressure increase-pressure stabilization-pressure decompression cycle to form concrete components. The peak pressure in the variable pressure curing is 1.6-2.0 MPa, the total duration of each cycle is 65-120 minutes, and the curing temperature is 25-35℃. S5. Reduce the pressure inside the sealed curing equipment to normal pressure, and remove the concrete components for standard curing.

2. The method for producing recycled concrete, a green building material, according to claim 1, is characterized in that: In step S1, the composite solution contains urea with a concentration of 1.0-1.5 mol / L, calcium salt solution with a concentration of 0.5-1.0 mol / L, and concentrated Bacillus pasteurellium suspension with an OD600 value of 0.8-1.

2. The vacuum degree of the vacuum impregnation treatment is -0.09 MPa to -0.085 MPa, and the impregnation time is not less than 30 minutes.

3. The method for producing recycled concrete, a green building material, according to claim 1, is characterized in that: In step S2, the pressure-responsive sustained-release pH adjuster is a microcapsule coated with a pH-adjusting substance, with a particle size of 75-150 μm, and the amount of the microcapsule added is 0.5%-1.5% of the total mass of the gelling material.

4. The method for producing recycled concrete, a green building material, according to claim 3, is characterized in that: The wall material of the microcapsules is a gelatin-gum arabic composite, and the core material is citric acid.

5. The method for producing recycled concrete, a green building material, according to claim 1, is characterized in that: In step S2, the water-cement ratio of the concrete mixture formed by mixing is 0.35-0.

40.

6. The method for producing recycled concrete, a green building material, according to claim 1, is characterized in that: In step S4, the transformer maintenance is performed in 3-5 cycles.

7. The method for producing recycled concrete, a green building material, according to claim 6, is characterized in that: The cycle includes linearly increasing the pressure from the reference pressure to the peak pressure over 15-30 minutes, maintaining the peak pressure for 10-20 minutes, and then uniformly decreasing the pressure back to the reference pressure over 40-70 minutes.

8. The method for producing recycled concrete, a green building material, according to claim 7, is characterized in that: The reference pressure is 1.0-1.2 MPa.

9. The method for producing recycled concrete, a green building material, according to claim 1, is characterized in that: In step S4, the CO2-containing gas is pure CO2 or a mixed gas with a CO2 volume fraction of not less than 30%.

10. A method for producing recycled concrete, a green building material, according to claim 1, characterized in that: In step S5, the process of reducing the pressure to normal takes no less than 120 minutes, and the standard curing involves placing the concrete component in an environment with a temperature of 18-22℃ and a relative humidity of >95%.

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