Building solid waste recycling recycled aggregate concrete and preparation method thereof

Abstract

The invention discloses building solid waste recycled aggregate concrete and a preparation method thereof, and relates to the technical field of building materials. The recycled aggregate concrete is prepared from the following raw materials in parts by mass: 210 to 250 parts of cement, 110 to 140 parts of fly ash, 120 to 170 parts of mineral powder, 140 to 160 parts of water, 6 to 10 parts of a water reducing agent, 700 to 900 parts of modified recycled coarse aggregate, 200 to 400 parts of gravel and 600 to 800 parts of sand. According to the recycled aggregate concrete for recycling the building solid waste, CO2 diffuses into tiny pores of the recycled coarse aggregate and is dissolved in pore water to form carbonate ions in a closed vacuum environment. Calcium ions in hydrated phases and unhydrated phases in the old mortar are dissolved in pore water and react with carbonate ions to form calcium carbonate precipitates to fill tiny pores of the recycled coarse aggregate, so that the water absorption rate and the porosity performance of the recycled aggregate are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a construction solid waste recycled aggregate concrete and a preparation method thereof. Background Art

[0002] Typically, construction waste is piled up in centralized locations, occupying significant land resources and generating dust and other pollutants, significantly impacting the environment. Using construction waste to create recycled aggregate as a replacement for natural sand and gravel not only addresses the problem of waste accumulation but also alleviates natural resource constraints, playing a significant role in sustainable development and building an environmentally friendly society.

[0003] Recycled aggregate is made from crushed construction solid waste, and old cement mortar is attached to the surface, resulting in the performance disadvantages of high water absorption, low density and large porosity of the recycled aggregate. The mechanical properties and durability of the prepared recycled aggregate concrete are lower than those of ordinary concrete, which limits its large-scale and high-dosage application in engineering. In view of the shortcomings of the existing technology, the present invention provides a recycled aggregate concrete recycled from construction solid waste and a preparation method thereof to solve the above problems. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, in order to further improve the quality of recycled aggregate, improve the performance defects of recycled aggregate such as water absorption and porosity, and improve the mechanical properties and durability of recycled aggregate concrete, a recycled aggregate concrete with excellent performance is prepared. This application provides a recycled aggregate concrete recycled from construction solid waste and a preparation method thereof to solve the above problems.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A construction solid waste recycled aggregate concrete, the raw materials of which include the following components in parts by mass:

[0006] 210-250 parts of cement, 110-140 parts of fly ash, 120-170 parts of mineral powder, 140-160 parts of water, 6-10 parts of water reducer, 700-900 parts of modified recycled coarse aggregate, 200-400 parts of crushed stone, and 600-800 parts of sand;

[0007] The preparation method of the modified recycled coarse aggregate comprises the following steps:

[0008] S1, carbonization: placing the recycled coarse aggregate in a closed container, evacuating the container, and introducing 100% pure CO2 for carbonization treatment to obtain carbonized recycled coarse aggregate;

[0009] S2, microcapsule modification: the microbial microcapsules are mixed evenly with the carbonized aggregate, and the microcapsules are attached to the aggregate surface by negative pressure adsorption to obtain microcapsule regenerated coarse aggregate;

[0010] The microcapsule has a core-shell structure, the microorganism is the core material of the microcapsule, and the entire microcapsule is spherical with a smooth surface;

[0011] S3, hydrophobic isolation: immerse the microcapsule modified aggregate in a silane polymer emulsion with a mass concentration of 8%-10%, and obtain hydrophobically modified recycled coarse aggregate after drying.

[0012] Preferably, the fly ash is Class I fly ash, the mineral powder is Class S95 mineral powder, and the microbial microcapsules are Bacillus pasteurianus microcapsules.

[0013] Preferably, in the preparation method of the modified recycled coarse aggregate, the air pressure in the carbonization step is controlled to be 0.05-0.1 MPa, and the negative pressure environment pressure in the microcapsule modification step is 0.02-0.05 MPa;

[0014] The mass concentration of the silane polymer emulsion is 8%-10%.

[0015] Preferably, the modified recycled coarse aggregate replaces the natural coarse aggregate in a proportion of 70%-90%, and the water-binder ratio of the concrete is 0.35-0.45.

[0016] Preferably, the concrete has a 28-day cubic compressive strength of ≥45 MPa, a mass loss rate of ≤3.5% and a compressive strength loss rate of ≤15% after 350 freeze-thaw cycles.

[0017] Preferably, in S2, the method for preparing microbial microcapsules comprises the following steps:

[0018] S21, mixing the sodium alginate solution and the calcium chloride solution to form a sodium alginate-calcium chloride solution;

[0019] S22, adding chitosan hydrochloric acid solution dropwise to the solution in step S21, and stirring to obtain a wall material mixed solution;

[0020] S23, pouring the wall material mixture into sterile saline phosphate buffer, adding Tween-80 and glycerol, stirring, adding Bacillus pasteurianus freeze-dried powder suspension, and freeze-drying to prepare microcapsules;

[0021] The sterile saline phosphate buffer is prepared by mixing the following components in parts by mass with water: 8-10 parts of sodium chloride, 2-4 parts of disodium hydrogen phosphate, and 1-3 parts of sodium dihydrogen phosphate.

[0022] Preferably, the concentration of the sodium alginate solution is 0.9-1.2 mg / ml, the concentration of the calcium chloride solution is 0.95-1.3 mg / ml, and the concentration of the bacterial suspension prepared from the freeze-dried powder of Bacillus pasteurianus is 10-12 mg / ml.

[0023] Preferably, the mass proportions of the components of the microbial microcapsules are: 20-40 parts of sodium alginate, 15-25 parts of calcium chloride, 20-30 parts of sodium alginate-calcium chloride solution, 30-40 parts of chitosan, 70-90 parts of hydrochloric acid solution, 30-40 parts of chitosan hydrochloric acid solution, 35-55 parts of wall material mixture, 60-75 parts of sterile saline phosphate buffer, 2-3 parts of Tween-80, 1-2 parts of glycerol, and 40-60 parts of Bacillus pasteurianus freeze-dried powder.

[0024] A second aspect of the present invention discloses a method for preparing recycled aggregate concrete by recycling construction solid waste, which is characterized by comprising the following steps:

[0025] Step A1, mixing cement, fly ash and mineral powder uniformly to obtain powder;

[0026] Step A2, mixing the powder, sand and modified recycled coarse aggregate;

[0027] Step A3: adding a water reducing agent and water, stirring until uniform, to prepare concrete.

[0028] Preferably, the stirring time in step A2 is 90-120 seconds, the stirring time in step A3 is 180-240 seconds, and the stirring speed is 30-50 r / min.

[0029] The present invention discloses a construction solid waste recycled aggregate concrete and a preparation method thereof, which has the following beneficial effects:

[0030] 1. This construction waste recycling project utilizes recycled aggregate concrete to fill the micropores of the recycled coarse aggregate. The surface of the recycled coarse aggregate is clinging to old mortar, which contains substances such as calcium hydroxide (CH), hydrated calcium silicate (CSH), and partially hydrated dicalcium silicate (C2S) and tricalcium silicate (C3S). Under a sealed vacuum environment, CO2 diffuses into the micropores of the recycled coarse aggregate and dissolves in the pore water, forming carbonate ions. Calcium ions from the hydrated and unhydrated phases of the old mortar dissolve in the pore water and react with the carbonate ions to form calcium carbonate precipitates, which fill the micropores of the recycled coarse aggregate, thereby improving the water absorption and porosity of the recycled aggregate.

[0031] 2. This construction solid waste recycling method utilizes recycled aggregate concrete. The recycled coarse aggregate is modified, and microcapsules are adsorbed on the surface of the recycled coarse aggregate. The microcapsule-modified recycled coarse aggregate is then immersed in a silane polymer emulsion for hydrophobic isolation. The old mortar attached to the surface of the recycled coarse aggregate contains hydroxyl groups. When immersed in the silane polymer emulsion, the emulsion fills the tiny pores and reacts with the hydroxyl groups to form a hydrophobic film, thereby improving the basic physical properties of the recycled coarse aggregate, such as water absorption and crushing value. It also increases the adsorption of microcapsules on the surface of the recycled coarse aggregate, prevents the detachment of microcapsules, and improves the interfacial adhesion between the recycled coarse aggregate and the cement paste. When modified recycled coarse aggregate replaces natural coarse aggregate in the preparation of concrete, the adhesion in the transition zone between the recycled coarse aggregate and the cement paste is weak. When cracks form at the interface, the microbial microcapsules adsorbed on the surface of the recycled coarse aggregate rupture, releasing the microbial Bacillus pasteurianus. Bacillus pasteurianus has a negatively charged cell wall that can chelate Ca+ in the slurry and promote the reaction with Ca+ to form calcium carbonate (CaCO3) deposition through metabolic processes, thereby repairing cracks in the interface transition zone, enhancing the density and adhesion of the interface transition zone, and improving the mechanical properties and durability of concrete. Adsorbing Bacillus pasteurianus on the surface of recycled aggregate will directly fill the pores and cracks of the recycled aggregate, but has a weak ability to repair the interface transition zone of recycled concrete. Microencapsulation of Bacillus pasteurianus can delay microbial metabolism and Ca + reaction, and at the same time repair the cracks and pores in the interface transition zone of recycled concrete and recycled aggregate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Schematic diagram of the preparation method of recycled aggregate concrete of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0035] Existing technologies mainly improve the performance of recycled aggregates through physical crushing or chemical strengthening, but the effect is limited. For example, although simple carbonization treatment can fill pores, it cannot solve the problem of weak interfacial adhesion; although directly adding microorganisms can self-repair cracks, it is easy to cause repair failure due to excessive metabolism. The embodiments of the present application provide a construction solid waste recycling and recycled aggregate concrete and a preparation method thereof, which solves the performance shortcomings of the existing technology that recycled aggregates are made from crushed construction solid waste and have old cement mortar attached to the surface, resulting in high water absorption, low density, and high porosity of the recycled aggregates. The mechanical properties and durability of the prepared recycled aggregate concrete are lower than those of ordinary concrete, which limits its large-scale and high-dosage application in engineering.

[0036] Preparation example of modified recycled coarse aggregate

[0037] Preparation Example 1

[0038] Carbonization: Place the recycled coarse aggregate in a closed container, evacuate it, and introduce 100% pure CO2 for carbonization treatment to obtain carbonized recycled coarse aggregate;

[0039] Microcapsule modification: Mix microbial microcapsules with carbonized aggregate evenly, and make the microcapsules adhere to the surface of aggregate through negative pressure adsorption to obtain microcapsule regenerated coarse aggregate;

[0040] The microcapsule has a core-shell structure, the microorganism is the core material of the microcapsule, and the entire microcapsule is spherical with a smooth surface;

[0041] Hydrophobic isolation: The microcapsule-modified aggregate was immersed in a silane polymer emulsion with a mass concentration of 8%, and then dried to obtain the hydrophobically modified recycled coarse aggregate.

[0042] The method for preparing microbial microcapsules comprises the following steps:

[0043] S1. Prepare sodium alginate solution by adding 0.95 mg / ml calcium chloride solution dropwise to 0.9 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0044] S2. Dissolve 30 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix thoroughly by magnetic stirring to obtain a wall material mixture.

[0045] S3. Pour the wall solution into sterile saline phosphate buffer, add 3 parts of Tween-80 and 2 parts of glycerol, and mix well with magnetic stirring.

[0046] S4. Prepare a bacterial suspension with a concentration of 10 mg / ml using 40 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, mix evenly with magnetic stirring, place the solution in a freeze dryer, and take out to obtain microbial microcapsules.

[0047] The carboxyl groups in sodium alginate combine with the calcium ions in calcium chloride to form a cross-linked network—a three-dimensional mesh gel—transforming the liquid into a solid gel, forming the primary framework of the microcapsules. Uncross-linked carboxyl anionic groups still exist on the surface of the cross-linked sodium alginate, which bind to the amino cationic groups in chitosan through electrostatic attraction to form a polyelectrolyte composite shell.

[0048] Preparation Example 2

[0049] The difference between this preparation example and preparation example 1 is that the recycled coarse aggregate is not subjected to carbonization treatment.

[0050] Preparation Example 3

[0051] The difference between this preparation example and preparation example 1 is that the recycled coarse aggregate is not subjected to microencapsulation treatment.

[0052] Preparation Example 4

[0053] The difference between this preparation example and preparation example 1 is that the recycled coarse aggregate is not subjected to hydrophobic isolation treatment.

[0054] Preparation Example 5

[0055] The difference between this preparation example and preparation example 1 is that the recycled coarse aggregate is not modified.

[0056] Table 1 Experimental results

[0057] Test items Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Preparation Example 5 Water absorption / % 2.8 6.6 4.6 5.5 9.8 Crushing value / % 9.7 12.1 11.6 10.3 14.5 Apparent density / kg / m³ 2600 2540 2580 2550 2460

[0058] It can be seen from Table 1 that after the recycled aggregate is modified, its various performance indicators are improved.

[0059] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0060] In the recycled aggregate concrete provided in the following examples and comparative examples, the cement used is P.O42.5 ordinary Portland cement; the fly ash used is Class I fly ash; the fine aggregate used is natural sand; and the coarse aggregate used is modified recycled coarse aggregate.

[0061] The preparation method of recycled aggregate concrete using construction solid waste recycling in the following examples and comparative examples comprises the following steps:

[0062] SS1. Mix cement, fly ash and mineral powder evenly to obtain raw material powder.

[0063] SS2.Put the evenly mixed powder, sand and modified recycled coarse aggregate into a blender and mix them evenly.

[0064] SS3. Pour the water reducing agent and water into the mixture and stir it evenly with a stirrer to obtain recycled aggregate concrete made from recycled construction solid waste.

[0065] Example 1

[0066] The present embodiment provides a recycled aggregate concrete using recycled construction solid waste, the raw materials of which include: 210 parts of cement, 120 parts of fly ash, 130 parts of mineral powder, 140 parts of water, 8 parts of water reducer, 800 parts of modified recycled coarse aggregate, 200 parts of crushed stone, and 700 parts of sand.

[0067] The preparation method of modified recycled coarse aggregate comprises the following steps:

[0068] Carbonization: Place the recycled coarse aggregate into a sealed container, evacuate the container to a vacuum, introduce pure 100% CO2 to carbonize the recycled aggregate under controlled air pressure, and then take it out to obtain carbonized recycled coarse aggregate.

[0069] Microcapsule modification: 5 kg of microbial microcapsules were mixed evenly with carbonized aggregate, and placed in a vacuum adsorption device to ensure that the container was sealed, and the air pressure was reduced to form a negative pressure environment, so that the microcapsules were adsorbed on the surface of the recycled aggregate to obtain microcapsule recycled coarse aggregate.

[0070] Hydrophobic isolation: the microcapsule-modified recycled aggregate is immersed in a silane polymer emulsion with a concentration of 8%, taken out, filtered and dried to obtain a hydrophobically modified recycled coarse aggregate.

[0071] The method for preparing microbial microcapsules comprises the following steps:

[0072] S1. Prepare sodium alginate solution by adding 0.95 mg / ml calcium chloride solution dropwise to 0.9 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0073] S2. Dissolve 30 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix thoroughly by magnetic stirring to obtain a wall material mixture.

[0074] S3. Pour the wall solution into sterile saline phosphate buffer, add 3 parts of Tween-80 and 2 parts of glycerol, and mix well with magnetic stirring.

[0075] S4. Prepare a bacterial suspension with a concentration of 10 mg / ml using 40 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, mix evenly with magnetic stirring, place the solution in a freeze dryer, and take out to obtain microbial microcapsules.

[0076] The carboxyl groups in sodium alginate combine with the calcium ions in calcium chloride to form a cross-linked network—a three-dimensional mesh gel—transforming the liquid into a solid gel, forming the primary framework of the microcapsules. Uncross-linked carboxyl anionic groups still exist on the surface of the cross-linked sodium alginate, which bind to the amino cationic groups in chitosan through electrostatic attraction to form a polyelectrolyte composite shell.

[0077] Example 2

[0078] The present embodiment provides a recycled aggregate concrete using recycled construction solid waste, the raw materials of which include: 220 parts of cement, 110 parts of fly ash, 120 parts of mineral powder, 130 parts of water, 6 parts of water reducer, 800 parts of modified recycled coarse aggregate, 300 parts of crushed stone, and 600 parts of sand.

[0079] The preparation method of modified recycled coarse aggregate comprises the following steps:

[0080] Carbonization: Place the recycled coarse aggregate into a sealed container, evacuate the container to a vacuum, introduce pure 100% CO2 to carbonize the recycled aggregate under controlled air pressure, and then take it out to obtain carbonized recycled coarse aggregate.

[0081] Microcapsule modification: 8 kg of microbial microcapsules were mixed evenly with carbonized aggregate, and placed in a vacuum adsorption device to ensure that the container was sealed, and the air pressure was reduced to form a negative pressure environment, so that the microcapsules were adsorbed on the surface of the recycled aggregate to obtain microcapsule recycled coarse aggregate.

[0082] Hydrophobic isolation: the microcapsule-modified recycled aggregate is immersed in a silane polymer emulsion with a concentration of 8%, taken out, filtered and dried to obtain a hydrophobically modified recycled coarse aggregate.

[0083] The method for preparing microbial microcapsules comprises the following steps:

[0084] S1. Prepare sodium alginate solution by adding 1.0 mg / ml calcium chloride solution dropwise to 1.0 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0085] S2. Dissolve 40 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix evenly by magnetic stirring to obtain a wall material mixture.

[0086] S3. Pour the wall solution into sterile saline phosphate buffer, add 2 parts of Tween-80 and 2 parts of glycerol, and mix well by magnetic stirring.

[0087] S4. Prepare a bacterial suspension with a concentration of 10 mg / ml using 30 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, stir magnetically to mix evenly, place the solution into a freeze dryer, and take out to obtain microbial microcapsules.

[0088] Example 3

[0089] The present embodiment provides a recycled aggregate concrete using recycled construction solid waste, the raw materials of which include: 240 parts of cement, 130 parts of fly ash, 130 parts of mineral powder, 150 parts of water, 7 parts of water reducer, 700 parts of modified recycled coarse aggregate, 200 parts of crushed stone, and 700 parts of sand.

[0090] The preparation method of modified recycled coarse aggregate comprises the following steps:

[0091] Carbonization: Place the recycled coarse aggregate into a sealed container, evacuate the container to a vacuum, introduce pure 100% CO2 to carbonize the recycled aggregate under controlled air pressure, and then take it out to obtain carbonized recycled coarse aggregate.

[0092] Microcapsule modification: 6 kg of microbial microcapsules were mixed evenly with carbonized aggregate, placed in a vacuum adsorption device to ensure the container was sealed, and the air pressure was reduced to form a negative pressure environment, so that the microcapsules were adsorbed on the surface of the recycled aggregate to obtain microcapsule recycled coarse aggregate.

[0093] Hydrophobic isolation: the microcapsule-modified recycled aggregate is immersed in a 9% silane polymer emulsion, taken out, filtered, and dried to obtain a hydrophobically modified recycled coarse aggregate.

[0094] The method for preparing microbial microcapsules comprises the following steps:

[0095] S1. Prepare sodium alginate solution by adding 0.95 mg / ml calcium chloride solution dropwise to 1.2 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0096] S2. Dissolve 30 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix thoroughly by magnetic stirring to obtain a wall material mixture.

[0097] S3. Pour the wall solution into sterile saline phosphate buffer, add 2 parts of Tween-80 and 2 parts of glycerol, and mix well by magnetic stirring.

[0098] S4. Prepare a bacterial suspension with a concentration of 10 mg / ml using 50 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, mix evenly with magnetic stirring, place the solution in a freeze dryer, and take out to obtain microbial microcapsules.

[0099] Example 4

[0100] The present embodiment provides a recycled aggregate concrete made from recycled construction solid waste, the raw materials of which include: 245 parts of cement, 115 parts of fly ash, 135 parts of mineral powder, 155 parts of water, 6 parts of water reducer, 850 parts of modified recycled coarse aggregate, 250 parts of crushed stone, and 750 parts of sand.

[0101] The preparation method of modified recycled coarse aggregate comprises the following steps:

[0102] Carbonization: Place the recycled coarse aggregate into a sealed container, evacuate the container to a vacuum, introduce pure 100% CO2 to carbonize the recycled aggregate under controlled air pressure, and then take it out to obtain carbonized recycled coarse aggregate.

[0103] Microcapsule modification: 6 kg of microbial microcapsules are mixed evenly with carbonized aggregate, placed in a vacuum adsorption device to ensure that the container is sealed, and the air pressure is reduced to form a negative pressure environment, so that the microcapsules are adsorbed on the surface of the recycled aggregate to obtain microcapsule recycled coarse aggregate.

[0104] Hydrophobic isolation: the microcapsule-modified recycled aggregate is immersed in a silane polymer emulsion with a concentration of 8%, taken out, filtered and dried to obtain a hydrophobically modified recycled coarse aggregate.

[0105] The method for preparing microbial microcapsules comprises the following steps:

[0106] S1. Prepare sodium alginate solution by adding 1.2 mg / ml calcium chloride solution dropwise to 0.95 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0107] S2. Dissolve 40 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix evenly by magnetic stirring to obtain a wall material mixture.

[0108] S3. Pour the wall solution into sterile saline phosphate buffer, add 3 parts of Tween-80 and 2 parts of glycerol, and mix well with magnetic stirring.

[0109] S4. Prepare a bacterial suspension with a concentration of 11 mg / ml using 40 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, stir magnetically to mix evenly, place the solution into a freeze dryer, and take out to obtain microbial microcapsules.

[0110] Example 5

[0111] The present embodiment provides a recycled aggregate concrete obtained by recycling construction solid waste, the raw materials of which include: 233 parts of cement, 123 parts of fly ash, 143 parts of mineral powder, 155 parts of water, 7 parts of water reducer, 700 parts of modified recycled coarse aggregate, 300 parts of crushed stone, and 725 parts of sand.

[0112] The preparation method of modified recycled coarse aggregate comprises the following steps:

[0113] Carbonization: Place the recycled coarse aggregate into a sealed container, evacuate the container to a vacuum, introduce pure 100% CO2 to carbonize the recycled aggregate under controlled air pressure, and then take it out to obtain carbonized recycled coarse aggregate.

[0114] Microcapsule modification: 7 kg of microbial microcapsules were mixed evenly with carbonized aggregate, and placed in a vacuum adsorption device to ensure that the container was sealed, and the air pressure was reduced to form a negative pressure environment, so that the microcapsules were adsorbed on the surface of the recycled aggregate to obtain microcapsule recycled coarse aggregate.

[0115] Hydrophobic isolation: the microcapsule-modified recycled aggregate is immersed in a silane polymer emulsion with a concentration of 8%, taken out, filtered and dried to obtain a hydrophobically modified recycled coarse aggregate.

[0116] The method for preparing microbial microcapsules comprises the following steps:

[0117] S1. Prepare sodium alginate solution by adding 1.3 mg / ml calcium chloride solution dropwise to 0.9 mg / ml sodium alginate solution and mixing by magnetic stirring to obtain a sodium alginate - calcium chloride solution;

[0118] S2. Dissolve 35 parts of chitosan in hydrochloric acid, add the solution dropwise to the sodium alginate-calcium chloride solution, and mix thoroughly by magnetic stirring to obtain a wall material mixture.

[0119] S3. Pour the wall solution into sterile saline phosphate buffer, add 3 parts of Tween-80 and 2 parts of glycerol, and mix well by magnetic stirring.

[0120] S4. Prepare a bacterial suspension with a concentration of 12 mg / ml using 50 parts of freeze-dried Bacillus pasteurianus powder, pour it into the above solution, mix evenly using magnetic stirring, place the solution in a freeze dryer, and take out to obtain microbial microcapsules.

[0121] Example 6

[0122] The difference from Example 1 is that the concentration of the silane polymer emulsion is 9%.

[0123] Example 7

[0124] The difference from Example 2 is that the concentration of the silane polymer emulsion is 10%.

[0125] Example 8

[0126] The difference from Example 3 is that the concentration of the bacterial suspension prepared from the freeze-dried powder of Bacillus pasteurianus is 11 mg / ml.

[0127] Example 9

[0128] The difference from Example 4 is that the concentration of the bacterial suspension prepared from the freeze-dried powder of Bacillus pasteurianus is 12 mg / ml.

[0129] Example 10

[0130] The difference from Example 5 is that the concentration of the silane polymer emulsion is 10%.

[0131] Comparative Example 1

[0132] The difference from Example 1 is that the modified recycled coarse aggregate is not carbonized.

[0133] Comparative Example 2

[0134] The difference from Example 1 is that the modified recycled coarse aggregate is not modified with microcapsules.

[0135] Comparative Example 3

[0136] The difference from Example 1 is that the modified recycled coarse aggregate is not subjected to hydrophobic isolation.

[0137] Comparative Example 4

[0138] The difference from Example 1 is that after carbonization, the modified recycled coarse aggregate is first subjected to hydrophobic isolation and then to microcapsule modification.

[0139] Comparative Example 5

[0140] The difference from Example 1 is that the modified recycled coarse aggregate is first subjected to microcapsule modification and then to carbonization and hydrophobic isolation.

[0141] Comparative Example 6

[0142] The difference from Example 1 is that the modified recycled coarse aggregate is directly modified with Bacillus pasteurianus without microencapsulation of Bacillus pasteurianus.

[0143] Comparative Example 7

[0144] The difference from Example 1 is that the recycled coarse aggregate is used directly without modification.

[0145] Performance testing experiment

[0146] 1. Concrete mechanical properties test: Test the 28d cube compressive strength of concrete in accordance with the mechanical properties test method in GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0147] 2. Concrete frost resistance test: The slow freezing method in the "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete" GB / T50082-2024 is used to test the durability of concrete. The mass loss rate and compressive strength loss rate of the concrete specimens after 350 freeze-thaw cycles are tested.

[0148] Table 2 Experimental results

[0149] Test items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 28d compressive strength / MPa 42.5 45.8 43.6 44.5 46.9 44.7 47.6 44.8 46.4 Mass loss rate / % 5.78 4.25 4.89 4.78 3.89 4.72 3.22 4.71 3.59 Compressive strength loss rate% 6.26 4.55 5.16 4.99 4.16 4.89 3.52 5.03 3.98 Test items Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 28d compressive strength / MPa 48.3 36.4 38.6 40.2 39.5 37.8 35.9 32.4 Mass loss rate / % 2.89 7.57 6.46 6.19 6.33 7.11 8.89 11.1 Compressive strength loss rate% 3.12 7.98 6.97 6.66 6.72 7.83 9.92 11.9

[0150] Comparing and analyzing the data in Table 2 above, when comparative example 7 directly uses recycled aggregate without modifying it, the 28d compressive strength of the concrete is 32.4MPa, the mass loss rate after 350 freeze-thaw cycles is 11.1%, and the compressive strength loss rate is 11.9%. The concrete compressive strength is low and the frost resistance is poor. The 28d compressive strength of the recycled aggregate concrete prepared by the present invention is 48.3MPa, the mass loss rate after freeze-thaw cycles is 2.89%, and the compressive strength loss rate is 3.12%. Both the compressive strength and frost resistance are improved. When comparative examples 1-5 change the recycled aggregate modification step or directly use Bacillus pasteurianus without microencapsulation, the compressive strength and frost resistance of the concrete are better than those prepared by unmodified recycled aggregate, but the various properties of the concrete prepared by the present invention are reduced. Carbonizing recycled coarse aggregate allows CO₂ to diffuse into its micropores and dissolve in the pore water, forming carbonate ions. These react with calcium ions in both the hydrated and unhydrated phases to form calcium carbonate precipitates, filling the micropores. Microcapsules are adsorbed on the surface of the carbonized recycled coarse aggregate. The modified recycled coarse aggregate is then immersed in a silane polymer emulsion for hydrophobic isolation. The silane polymer emulsion fills the micropores and reacts with the hydroxyl groups on the surface of the recycled coarse aggregate to form a hydrophobic film, enhancing the adsorption of the microcapsules on the surface and preventing their detachment. When cracks form at the interface, the microcapsules adsorbed on the recycled coarse aggregate surface rupture, releasing Bacillus pasteurianus. Through metabolic processes, Bacillus pasteurianus reacts with Ca₂ to form calcium carbonate (CaCO₃) precipitation, thereby repairing cracks in the interfacial transition zone, enhancing the density and adhesion of the transition zone, and improving the mechanical properties and durability of recycled aggregate concrete.

[0151] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0152] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A construction solid waste recycling and recycled aggregate concrete, characterized in that: Its raw materials include the following components by mass: 210-250 parts of cement, 110-140 parts of fly ash, 120-170 parts of mineral powder, 140-160 parts of water, 6-10 parts of water reducer, 700-900 parts of modified recycled coarse aggregate, 200-400 parts of crushed stone, and 600-800 parts of sand; The preparation method of the modified recycled coarse aggregate comprises the following steps: S1, carbonization: placing the recycled coarse aggregate in a closed container, evacuating the container, and introducing 100% pure CO2 for carbonization treatment to obtain carbonized recycled coarse aggregate; S2, microcapsule modification: the microbial microcapsules are mixed evenly with the carbonized aggregate, and the microcapsules are attached to the aggregate surface by negative pressure adsorption to obtain microcapsule regenerated coarse aggregate; The microcapsule has a core-shell structure, the microorganism is the core material of the microcapsule, and the entire microcapsule is spherical with a smooth surface; S3, hydrophobic isolation: immerse the microcapsule modified aggregate in a silane polymer emulsion with a mass concentration of 8%-10%, and obtain hydrophobically modified recycled coarse aggregate after drying.

2. The recycled aggregate concrete made from construction solid waste according to claim 1, characterized in that: The fly ash is Class I fly ash, the mineral powder is Class S95 mineral powder, and the microbial microcapsules are Bacillus pasteurianus microcapsules.

3. The recycled aggregate concrete made from construction solid waste according to claim 1, characterized in that: In the preparation method of the modified recycled coarse aggregate, the air pressure in the carbonization step is controlled to be 0.05-0.1 MPa, and the negative pressure environment pressure in the microcapsule modification step is 0.02-0.05 MPa; The mass concentration of the silane polymer emulsion is 8%-10%.

4. The recycled aggregate concrete made from construction solid waste according to claim 1, characterized in that: The modified recycled coarse aggregate replaces the natural coarse aggregate in a proportion of 70%-90%, and the water-binder ratio of the concrete is 0.35-0.

45.

5. The recycled aggregate concrete made from construction solid waste according to claim 1, characterized in that: The 28-day cubic compressive strength of concrete is ≥45MPa, the mass loss rate after 350 freeze-thaw cycles is ≤3.5%, and the compressive strength loss rate is ≤15%.

6. The recycled aggregate concrete made from construction solid waste according to claim 2, characterized in that: In S2, the method for preparing microbial microcapsules comprises the following steps: S21, mixing the sodium alginate solution and the calcium chloride solution to form a sodium alginate-calcium chloride solution; S22, adding chitosan hydrochloric acid solution dropwise to the solution in step S21, and stirring to obtain a wall material mixed solution; S23, pouring the wall material mixture into sterile saline phosphate buffer, adding Tween-80 and glycerol, stirring, adding Bacillus pasteurianus freeze-dried powder suspension, and freeze-drying to prepare microcapsules; The sterile saline phosphate buffer is prepared by mixing the following components in parts by mass with water: 8-10 parts of sodium chloride, 2-4 parts of disodium hydrogen phosphate, and 1-3 parts of sodium dihydrogen phosphate.

7. The recycled aggregate concrete made from construction solid waste according to claim 6, characterized in that: The concentration of the sodium alginate solution is 0.9-1.2 mg / ml, the concentration of the calcium chloride solution is 0.95-1.3 mg / ml, and the concentration of the bacterial suspension prepared from the freeze-dried powder of Bacillus pasteurianus is 10-12 mg / ml.

8. The recycled aggregate concrete made from construction solid waste according to claim 6, characterized in that: The mass proportions of the components of the microbial microcapsules are: 20-40 parts of sodium alginate, 15-25 parts of calcium chloride, 20-30 parts of sodium alginate-calcium chloride solution, 30-40 parts of chitosan, 70-90 parts of hydrochloric acid solution, 30-40 parts of chitosan hydrochloric acid solution, 35-55 parts of wall material mixture, 60-75 parts of sterile saline phosphate buffer, 2-3 parts of Tween-80, 1-2 parts of glycerol, and 40-60 parts of Bacillus pasteurianus freeze-dried powder.

9. The method for preparing recycled aggregate concrete by recycling construction solid waste according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step A1, mixing cement, fly ash and mineral powder uniformly to obtain powder; Step A2, mixing the powder, sand and modified recycled coarse aggregate; Step A3: adding a water reducing agent and water, stirring until uniform, to prepare concrete.

10. The method for preparing recycled aggregate concrete by recycling construction solid waste according to claim 9, characterized in that: The stirring time in step A2 is 90-120 seconds, the stirring time in step A3 is 180-240 seconds, and the stirring speed is 30-50 r / min.

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