Green low-carbon concrete prepared based on recycled aggregate and preparation method of green low-carbon concrete

Abstract

The invention relates to the field of concrete preparation, and particularly discloses green low-carbon concrete prepared based on recycled aggregate and a preparation method of the green low-carbon concrete. The green low-carbon concrete is prepared from the following raw materials in parts by weight: 10-12 parts of fly ash, 20-30 parts of slag, 80-100 parts of modified recycled aggregate, 5-8 parts of an exciting agent, 15-20 parts of cement, 10-20 parts of water, 1-3 parts of sodium gluconate and 0.5-1.5 parts of a water reducing agent, and the modified recycled aggregate is recycled aggregate subjected to surface activation treatment; the preparation method comprises the following steps: sequentially adding and mixing the fly ash, the slag and the modified recycled aggregate, carrying out dry mixing at a rotating speed of 30-50r / min for 2-3min, adding the exciting agent, the water and the water reducing agent, and uniformly stirring to form a uniform concrete mixture; and curing to obtain the product. The composition can be used for engineering construction and has the advantages of being green, low in carbon and high in compressive strength.

Description

Technical Field

[0001] The present application relates to the field of concrete preparation, and more specifically, to a green low-carbon concrete prepared based on recycled aggregate and a preparation method thereof. Background Art

[0002] With the acceleration of urbanization and the continuous advancement of infrastructure construction, the demand for concrete, one of the most important building materials, is increasing day by day. However, there are many problems in the traditional concrete production process, which puts tremendous pressure on resources and the environment.

[0003] On the one hand, traditional concrete uses a large amount of natural aggregates, such as river sand and pebbles. The mining of these natural aggregates not only damages the natural ecological environment, leading to a series of ecological problems such as riverbed incision, soil erosion, and vegetation destruction, but also natural aggregates are non-renewable resources. With continuous mining, their reserves are decreasing and their prices are constantly rising. This poses a serious challenge to the sustainable development of the concrete industry.

[0004] On the other hand, the generation of construction waste is increasing rapidly, with discarded concrete comprising a significant proportion. This waste concrete is typically disposed of in landfills, which not only consumes significant land resources but also generates pollutants such as leachate during the landfill process, posing a potential threat to the soil and groundwater environment. Furthermore, a significant amount of aggregate from discarded concrete remains unused, resulting in significant waste.

[0005] To address these issues, the use of recycled aggregates has gradually gained attention. Recycled aggregate refers to aggregate obtained by crushing, cleaning, and screening waste concrete. Using recycled aggregate to make concrete not only reduces reliance on natural aggregates and protects the natural ecological environment, but also enables the resource utilization of construction waste and reduces environmental pollution, thus having significant green and low-carbon significance.

[0006] However, concrete made from recycled aggregates currently faces several challenges in practical application. Recycled aggregates, due to the numerous microcracks produced during the crushing process, have a rough surface and are laden with old cement mortar, resulting in high water absorption, high porosity, and low strength. These characteristics result in a significant gap in strength performance between recycled aggregate concrete and natural aggregate concrete, limiting its widespread application in engineering projects. Therefore, effectively improving the performance of recycled aggregates and producing high-performance, green, low-carbon concrete has become a key issue that needs to be addressed in the current concrete industry. Summary of the Invention

[0007] In order to improve the strength of recycled aggregate concrete, the present application provides a green low-carbon concrete prepared based on recycled aggregate and a preparation method thereof.

[0008] In the first aspect, the present application provides a green low-carbon concrete prepared based on recycled aggregate, which adopts the following technical solution: A green low-carbon concrete prepared based on recycled aggregate, comprising the following raw materials in parts by weight: 10-12 parts of fly ash, 20-30 parts of slag, 80-100 parts of modified recycled aggregate, 5-8 parts of activator, 15-20 parts of cement, 10-20 parts of water, 1-3 parts of sodium gluconate, and 0.5-1.5 parts of water reducer, wherein the modified recycled aggregate is recycled aggregate that has undergone surface activation treatment.

[0009] By adopting the above-mentioned technical solution, a large amount of recycled aggregate is used, effectively reducing the mining of natural aggregates, realizing the resource utilization of construction waste, reducing dependence on natural resources, conforming to the concept of sustainable development, and promoting the green transformation of the construction industry. In terms of performance, the modified recycled aggregate undergoes surface activation treatment, significantly improving its bonding properties with cementitious materials, thereby enhancing the strength and durability of concrete; at the same time, the addition of steel fiber further improves the crack resistance and toughness of concrete, enabling it to better withstand various complex stresses and extend the service life of concrete structures. In addition, the use of activators effectively activates fly ash and slag, improving the utilization rate of these industrial wastes, reducing solid waste emissions, and reducing environmental pollution risks.

[0010] Optionally, the modified recycled aggregate is recycled aggregate that has undergone surface activation treatment, and its preparation includes the following steps: (1) Barium titanate nanoparticles are dispersed in a 2 wt% 3-aminopropyltriethoxysilane ethanol solution and ultrasonically treated for 20-30 min. The solution is heated to 75-85° C. and refluxed for 110-130 min under nitrogen protection. The solution is washed with ethanol and dried. After that, ethanol is added and mixed uniformly to obtain an amino-barium titanate nanoparticle ethanol suspension for use. (2) activating Bacillus pasteurianus and inoculating it into a nutrient medium, shaking the culture to induce spore formation, preparing a spore suspension, mixing it with dopamine hydrochloride in a tris-hydroxymethylaminomethane buffer, ultrasonically dispersing it at 24-26 kHz and 20-30 W for 8-12 minutes, and stirring it at room temperature for 22-24 hours to form a microcapsule suspension containing Bacillus pasteurianus; (3) After the recycled aggregate is vacuumed to -0.08 MPa, an ethanol suspension of amino-barium titanate nanoparticles is added, and the pressure is increased to 0.2-0.4 MPa for reaction for 1.5-2.5 hours, and then the pressure is released. The mixture is treated at 50-60° C. under normal pressure for 3-5 hours, and the microcapsule suspension is sprayed by atomization, solidified, and dried to obtain the modified recycled aggregate.

[0011] By adopting the above technical solution, barium titanate nanoparticles are aminated and then loaded onto recycled aggregate, which enhances the active sites on the aggregate surface and improves the bonding ability between the aggregate and the cementitious material, thereby improving the overall strength and stability of the concrete. In addition, barium titanate, as a piezoelectric material, can generate surface charge under mechanical stress. Secondly, the self-polymerization properties of dopamine are utilized to encapsulate Bacillus pasteurianus into microcapsules and load them onto the aggregate. When the internal environment of concrete is suitable, Bacillus pasteurianus can induce the precipitation of calcium carbonate, filling the tiny pores between the aggregate and the cementitious material, improving the structure of the interfacial transition zone, and further enhancing the density and durability of the concrete. At the same time, the microcapsule structure can protect the activity of the bacteria and prolong its effect time. In addition, the vacuum and pressure treatment process allows the aminated barium titanate nanoparticles to fully penetrate the pores of the aggregate, improving the activation effect inside and on the surface of the aggregate, while the atomized spraying method of the microcapsule suspension ensures the uniform distribution of the microcapsules on the aggregate surface. These process optimization measures jointly improve the performance of the modified recycled aggregate, providing high-quality raw materials for the preparation of high-performance green and low-carbon concrete, and improving the strength and stability of concrete.

[0012] Optionally, the weight ratio of the barium titanate nanoparticles to the 3-aminopropyltriethoxysilane ethanol solution is 1:45-55; The weight ratio of the dopamine hydrochloride, tris buffer and spore suspension is 0.4-0.6:10:10; The spraying amount of the microcapsule suspension is 5-10% of the added amount of the recycled aggregate.

[0013] By adopting the above technical solution, when the microcapsule loading is within this range, it can ensure that a sufficient number of Bacillus pasteurianus can play a role inside the concrete, effectively fill the pores by inducing the production of calcium carbonate precipitation, improve the interface structure, and enhance the density and durability of the concrete. At the same time, the microcapsules will not accumulate on the surface of the aggregate or in the pores due to excessive loading, affecting the bonding performance of the aggregate with other materials and the working performance of the concrete. The mixing of barium titanate nanoparticles and 3-aminopropyltriethoxysilane ethanol solution in this proportion can make the barium titanate nanoparticles fully and evenly aminated, forming a stable and effective chemical bond in the subsequent bonding process with the aggregate, significantly enhancing the activity of the aggregate surface, thereby improving the bonding strength between the aggregate and the cementitious material, ensuring the stable performance of the overall mechanical properties of the concrete, and ultimately preparing recycled aggregate concrete with excellent performance and green and low carbon.

[0014] Optionally, the recycled aggregate is obtained by mixing particles having particle sizes of 0.025-5 mm and 10-20 mm in a weight ratio of 2-3:5.

[0015] By adopting this technical solution, 0.025-5mm fine aggregate can fill the gaps between 10-20mm coarse aggregate, forming a tightly packed structure. This effectively reduces the porosity within the concrete, making the overall structure more compact and improving the density and strength of the concrete. Furthermore, this mixing method of different particle size gradations allows the coarse aggregate to serve as a skeleton support in the concrete, while the fine aggregate fills the gaps between the coarse aggregate, enhancing the stability of the skeleton and enabling the concrete to better transfer stress when subjected to force. This significantly improves the concrete's mechanical properties, such as compressive and flexural strength, making the concrete structure more solid and durable.

[0016] Optionally, the activator is a mixture of sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:2-4, and the modulus of water glass is 2.2-3.0.

[0017] By adopting the above technical solution, the mixed activator of sodium hydroxide and water glass can provide an alkaline environment to stimulate the active silica and aluminum components in fly ash and slag. The appropriate mass ratio ensures that the alkaline environment is neither too strong to cause negative effects such as "alkali-aggregate reaction" nor too weak to effectively stimulate activity. The water glass modulus is within the range of 2.5-3.5, and its sodium silicate molecular structure is rational, providing a suitable silicon source for activation. Working synergistically with sodium hydroxide, it fully participates in the reaction of the active silica and aluminum components in fly ash and slag, generating more gel products such as hydrated calcium silicate, significantly improving the strength of concrete.

[0018] Optionally, 1-2 parts of epoxy resin emulsion are also added to the raw materials.

[0019] By adopting the above technical solution, the epoxy resin emulsion forms a flexible transition layer on the surface of the aggregate, which not only fills the pores between the aggregates and reduces the stress concentration effect, thereby improving the strength of the concrete, but also significantly improves the bonding strength of the interface bonding area between the aggregate and the cementitious material, further improving the strength and stability of the concrete.

[0020] Optionally, 0.5-1.5 parts of silica aerogel powder with a particle size of 10-50 nm is further added to the raw materials.

[0021] By adopting the above technical solution, nano-scale silica aerogel powder can fill the tiny pores and cracks inside the concrete, enhance the bonding strength of the interface transition zone between the recycled aggregate and the cementitious material, reduce stress concentration, and enhance the strength and durability of the concrete. At the same time, when the microorganisms in the microcapsules generate calcium carbonate, the three-dimensional nano-network of the aerogel can act as a template to guide the directional growth of calcite whiskers, forming an "aerogel skeleton-calcium carbonate whisker" interpenetrating reinforcement structure, further improving the strength of the concrete.

[0022] In a second aspect, the present application provides a method for preparing green low-carbon concrete based on recycled aggregate, which adopts the following technical solution: A method for preparing green low-carbon concrete based on recycled aggregate comprises the following steps: (1) Fly ash, slag, and modified recycled aggregate are added and mixed in sequence, and dry-mixed at a speed of 30-50 r / min for 2-3 min. An activator, water, and a water reducer are added and stirred to form a uniform concrete mixture; (2) pouring the concrete mixture into a mold, vibrating it to make it dense, demoulding it after curing it at room temperature for 24 hours, and then curing it to a specified age at a temperature of 20±2°C and a relative humidity of not less than 95%, thereby obtaining the green low-carbon concrete prepared based on recycled aggregate.

[0023] In summary, this application has the following beneficial effects: 1. This application makes extensive use of recycled aggregates that have undergone surface activation treatment, effectively reducing the mining of natural aggregates, realizing the resource utilization of construction waste, reducing dependence on natural resources, complying with the concept of sustainable development, and promoting the green transformation of the construction industry.

[0024] 2. The modified recycled aggregate in this application undergoes surface activation treatment, and the barium titanate nanoparticles are amino-treated and then loaded onto the recycled aggregate, which enhances the active sites on the aggregate surface and improves the bonding ability between the aggregate and the cementitious material. The dopamine self-polymerization property is used to encapsulate Bacillus pasteurianus into microcapsules and load them into the aggregate. When the internal environment of the concrete is suitable, Bacillus pasteurianus can induce the production of calcium carbonate precipitation, filling the tiny pores between the aggregate and the cementitious material, improving the structure of the interface transition zone, and further enhancing the density and durability of the concrete. In addition, the epoxy resin emulsion forms a flexible transition layer on the surface of the aggregate, filling the pores between the aggregates, reducing the stress concentration effect, and improving the bonding strength of the interface bonding area between the aggregate and the cementitious material. The nano-scale silica aerogel powder can fill the tiny pores and cracks inside the concrete, enhancing the bonding strength of the interface transition zone between the recycled aggregate and the cementitious material, reducing stress concentration. The synergistic effect of multiple aspects significantly improves the strength and durability of the concrete.

[0025] 3. The method of the present application, through the preparation process of modified recycled aggregate, especially the loading of Bacillus pasteurianus microcapsules, induces the formation of calcium carbonate precipitation to fill the pores when the internal environment of the concrete is suitable, thereby improving the interface structure. At the same time, the microcapsule structure protects the activity of bacteria and prolongs their function time. Combined with the synergistic effect of other raw materials, it improves the crack resistance and toughness of concrete, enables it to better withstand various complex stresses, and extends the service life of the concrete structure. DETAILED DESCRIPTION

[0026] The present application is further described in detail below with reference to the embodiments.

[0027] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0028] The cement was silicate cement purchased from Lingshou County Qianfu Mineral Products Processing Plant, with a strength grade of 42.5; the water glass solution was purchased from Zhengzhou Longfan Chemical Co., Ltd.; the first-grade fly ash was purchased from Lingshou County Shuangshi Mineral Products Processing Plant, with a density of 2.65 g / cm 3 ; Slag S95 was purchased from Lingshou County Changwang Mineral Products Processing Plant, item number A201902; recycled aggregate was obtained from waste concrete after crushing, screening and washing; epoxy resin emulsion was purchased from Langfang Nanze Anticorrosion Materials Co., Ltd., brand E-44; the water reducer was polycarboxylic acid water reducer, model SPF-300.

[0029] Preparation examples of raw materials and / or intermediates Preparation Example 1 A modified recycled aggregate, the preparation of which comprises the following steps: (1) 2 kg of barium titanate nanoparticles were dispersed in 90 kg of a 2 wt% 3-aminopropyltriethoxysilane ethanol solution, ultrasonicated at 40 kHz for 25 min, heated to 75-85° C. under nitrogen protection and refluxed for 120 min, washed with ethanol three times, and then vacuum dried. 100 kg of ethanol was added and mixed uniformly to obtain an amino-barium titanate nanoparticle ethanol suspension for later use; (2) After activation, Bacillus pasteurianus was inoculated into a nutrient-poor medium containing 0.1% MnSO4 and cultured at 45°C for 48 h to induce spore formation. 8 CFU / mL spore suspension; 0.5 kg dopamine hydrochloride was dissolved in 10 kg Tris buffer (pH 8.5), mixed with 10 kg spore suspension, ultrasonically dispersed at 25 kHz and 25 W for 10 min, and stirred at room temperature for 23 h to form a microcapsule suspension containing Bacillus pasteurianus; (3) After evacuating 100 kg of recycled aggregate to -0.08 MPa and maintaining it for 30 minutes, 100 kg of an ethanol suspension of amino-modified barium titanate nanoparticles was added, pressurized to 0.3 MPa, reacted for 2 hours, and then released. The mixture was treated at 54°C under normal pressure for 4 hours, sprayed with 5 kg of a microcapsule suspension, and cured and dried to obtain the modified recycled aggregate. The recycled aggregate was graded in a weight ratio of 2:5, with a particle size of 0.025-5 mm and a particle size of 10-20 mm.

[0030] Preparation Example 2 A modified recycled aggregate, the preparation of which comprises the following steps: (1) 2 kg of barium titanate nanoparticles were dispersed in 100 kg of a 2 wt% 3-aminopropyltriethoxysilane ethanol solution and ultrasonicated at 40 kHz for 30 min. The solution was heated to 85° C. and refluxed for 130 min under nitrogen protection. The solution was washed with ethanol three times and then dried under vacuum. 100 kg of ethanol was added and mixed uniformly to obtain an amino-barium titanate nanoparticle ethanol suspension for later use. (2) After activation, Bacillus pasteurianus was inoculated into a nutrient-poor medium containing 0.1% MnSO4 and cultured at 45°C for 48 h to induce spore formation. 8 CFU / mL spore suspension; 0.4 kg dopamine hydrochloride was dissolved in 10 kg Tris buffer (pH 8.5), mixed with 10 kg spore suspension, ultrasonically dispersed at 24 kHz and 20 W for 12 min, and stirred at room temperature for 22 h to form a microcapsule suspension containing Bacillus pasteurianus; (3) After evacuating 100 kg of recycled aggregate to -0.08 MPa and maintaining it for 30 minutes, 100 kg of an ethanol suspension of amino-modified barium titanate nanoparticles was added, pressurized to 0.4 MPa, reacted for 1.5 hours, and then released. The mixture was treated at 58°C under normal pressure for 3 hours, and atomized and sprayed with 10 kg of a microcapsule suspension. The mixture was cured and dried to obtain the modified recycled aggregate. The recycled aggregate was graded in a weight ratio of 3:5, with the sizes of 0.025-5 mm and 10-20 mm.

[0031] Preparation Example 3 A modified recycled aggregate, the preparation of which comprises the following steps: (1) 2 kg of barium titanate nanoparticles were dispersed in 110 kg of a 2 wt% 3-aminopropyltriethoxysilane ethanol solution, ultrasonicated at 40 kHz for 20-30 min, heated to 75° C. under nitrogen protection and refluxed for 110 min, washed with ethanol three times, and then vacuum dried. 100 kg of ethanol was added and mixed uniformly to obtain an amino-barium titanate nanoparticle ethanol suspension for later use; (2) After activation, Bacillus pasteurianus was inoculated into a nutrient-poor medium containing 0.1% MnSO4 and cultured at 45°C for 48 h to induce spore formation. 8 CFU / mL spore suspension; 0.6 kg dopamine hydrochloride was dissolved in 10 kg Tris buffer (pH 8.5), mixed with 10 kg spore suspension, ultrasonically dispersed at 24 kHz and 30 W for 8 min, and stirred at room temperature for 24 h to form a microcapsule suspension containing Bacillus pasteurianus; (3) After evacuating 100 kg of recycled aggregate to -0.08 MPa and maintaining it for 30 minutes, 100 kg of an ethanol suspension of amino-modified barium titanate nanoparticles was added, pressurized to 0.2 MPa, reacted for 2.5 hours, and then released. The mixture was treated at 50°C and atmospheric pressure for 5 hours, and 7.5 kg of a microcapsule suspension was sprayed on the mixture by atomization, cured, and dried to obtain the modified recycled aggregate. The recycled aggregate was graded in a weight ratio of 2:5, with a particle size of 0.025-5 mm and a particle size of 10-20 mm.

[0032] Preparation Example 4 A modified recycled aggregate, which is different from Preparation Example 1 in that the preparation in this Preparation Example includes the following steps: (1) Dispersing 2 kg of barium titanate nanoparticles in 100 kg of ethanol and mixing them uniformly to obtain a barium titanate nanoparticle ethanol suspension for later use; (2) After activation, Bacillus pasteurianus was inoculated into a nutrient-poor medium containing 0.1% MnSO4 and cultured at 45°C for 48 h to induce spore formation. 8 CFU / mL spore suspension; 0.5 kg dopamine hydrochloride was dissolved in 10 kg Tris buffer (pH 8.5), mixed with 10 kg spore suspension, ultrasonically dispersed at 25 kHz and 25 W for 10 min, and stirred at room temperature for 23 h to form a microcapsule suspension containing Bacillus pasteurianus; (3) After evacuating 100 kg of recycled aggregate to -0.08 MPa and maintaining it for 30 minutes, 100 kg of an ethanol suspension of amino-modified barium titanate nanoparticles was added, pressurized to 0.3 MPa, reacted for 2 hours, and then released. The mixture was treated at 54°C under normal pressure for 4 hours, sprayed with 5 kg of a microcapsule suspension, and cured and dried to obtain the modified recycled aggregate. The recycled aggregate was graded in a weight ratio of 2:5, with a particle size of 0.025-5 mm and a particle size of 10-20 mm. Example

[0033] Example 1 A green low-carbon concrete prepared based on recycled aggregate, the preparation comprising the following steps: (1) 11 kg of fly ash, 25 kg of slag, 15 kg of cement, and 90 kg of the modified recycled aggregate prepared in Preparation Example 1 were added and mixed in sequence, and dry-mixed at a speed of 40 r / min for 2 min. 5 kg of activator, 2 kg of sodium gluconate, 15 kg of water, and 1 kg of polycarboxylate water reducer were added and stirred evenly to form a uniform concrete mixture; the activator was obtained by mixing sodium hydroxide and water glass in a mass ratio of 1:2, and the water glass modulus was 2.5; (2) pouring the concrete mixture into a mold, vibrating it to make it dense, and demoulding it after curing it at room temperature for 24 hours. Then, curing it at a temperature of 20° C. and a relative humidity of not less than 95% to a specified age to obtain the green low-carbon concrete prepared based on recycled aggregate.

[0034] Example 2 A green low-carbon concrete prepared based on recycled aggregate, the preparation comprising the following steps: (1) 10 kg of fly ash, 20 kg of slag, 20 kg of cement, and 80 kg of the modified recycled aggregate prepared in Preparation Example 2 were added and mixed in sequence, and dry-mixed at a speed of 30 r / min for 3 min. 6.5 kg of activator, 1 kg of sodium gluconate, 10 kg of water, and 1.5 kg of polycarboxylate water reducer were added and stirred evenly to form a uniform concrete mixture; the activator was obtained by mixing sodium hydroxide and water glass in a mass ratio of 1:3, and the water glass modulus was 3.0; (2) pouring the concrete mixture into a mold, vibrating it to make it dense, and demolding it after curing it at room temperature for 24 hours. Then, curing it at a temperature of 22° C. and a relative humidity of not less than 95% to a specified age to obtain the green low-carbon concrete prepared based on recycled aggregate.

[0035] Example 3 A green low-carbon concrete prepared based on recycled aggregate, the preparation comprising the following steps: (1) 12 kg of fly ash, 30 kg of slag, 17.5 kg of cement, and 100 kg of the modified recycled aggregate prepared in Preparation Example 3 were added and mixed in sequence, and dry-mixed at a speed of 50 r / min for 2 min. 8 kg of activator, 3 kg of sodium gluconate, 20 kg of water, and 0.5 kg of polycarboxylate water reducer were added and stirred to form a uniform concrete mixture; the activator was obtained by mixing sodium hydroxide and water glass in a mass ratio of 1:2, and the water glass modulus was 2.5; (2) pouring the concrete mixture into a mold, vibrating it to make it dense, and demoulding it after curing it at room temperature for 24 hours. Then, curing it at a temperature of 18° C. and a relative humidity of not less than 95% to a specified age to obtain the green low-carbon concrete prepared based on recycled aggregate.

[0036] Example 4 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that sodium hydroxide is used as an activator in this example.

[0037] Example 5 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that water glass is used as an activator in this embodiment.

[0038] Example 6 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that in this embodiment, 100 kg of the amino-barium titanate nanoparticle ethanol suspension prepared in step (1) of Preparation Example 1 and 5 kg of the microcapsule suspension prepared in step (2) are directly added, specifically comprising the following steps: (1) 11 kg of fly ash, 25 kg of slag, 15 kg of cement, and 90 kg of recycled aggregate were added and mixed in sequence, and dry-mixed at a speed of 40 r / min for 2 min. 5 kg of activator, 2 kg of sodium gluconate, 15 kg of water, and 1 kg of polycarboxylate water reducer were added and stirred evenly. Then, 100 kg of amino-barium titanate nanoparticle ethanol suspension prepared in step (1) of Preparation Example 1 and 5 kg of microcapsule suspension prepared in step (2) were added and heated and stirred at low temperature until the ethanol was completely volatilized to form a uniform concrete mixture; the activator was obtained by mixing sodium hydroxide and water glass in a mass ratio of 1:2, and the water glass modulus was 2.5; the remaining steps were the same as in Example 1.

[0039] Example 7 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that 1 kg of epoxy resin emulsion is added after the water reducer is added in this embodiment.

[0040] Example 8 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that 2 kg of epoxy resin emulsion is added after the water reducer is added in this embodiment.

[0041] Example 9 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that 0.5 kg of silica aerogel powder with a particle size of 10-50 nm is added after adding the recycled aggregate in this example.

[0042] Example 10 A green low-carbon concrete prepared based on recycled aggregate is different from Example 1 in that 1.5 kg of silica aerogel powder with a particle size of 10-50 nm is added after the recycled aggregate is added in this example.

[0043] Comparative Example Comparative Example 1 A green low-carbon concrete prepared based on recycled aggregate, which is different from Example 1 in that the recycled aggregate is not modified in this comparative example.

[0044] Comparative Example 2 A green low-carbon concrete prepared based on recycled aggregate, which is different from Example 1 in that the modified recycled aggregate prepared in Preparation Example 4 is used in this comparative example.

[0045] Performance testing Self-healing effect evaluation: Prefabricate a 0.2 mm wide crack and apply a 0.5 Hz dynamic load (stress 2 MPa) for 56 days. The compressive strength of the concrete before and after repair is measured, and the self-healing capacity ratio (%) of the concrete is calculated. For details, see T / CECS 913-2021 "Standard for Test Methods for Self-Healing Properties of Cement Concrete"; Compressive strength: The 7d compressive strength of concrete was tested in accordance with the test method of the national standard GB / T50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test specimens were formed using a 100mm×100mm×100mm mold.

[0046] Table 1 Test data Self-repair ability ratio (%) Compressive strength / MPa Example 1 90.25 54.9 Example 2 87.6 53.8 Example 3 89.5 54.35 Example 4 85.3 45.2 Example 5 83.45 43.15 Example 6 71.2 42.5 Example 7 92.8 58.6 Example 8 93.35 61.25 Example 9 93.4 62.7 Example 10 93.15 62.83 Comparative Example 1 / 32.2 Comparative Example 2 55 41.35 Combining Examples 1-3 and Comparative Example 1 and Table 1, it can be seen that the test data of Examples 1-3 are better than those of Comparative Example 1, indicating that the modification of recycled aggregate using the method of the present application can significantly improve the self-repair effect and compressive strength of concrete.

[0047] Combining Examples 1-3 and Comparative Example 2 and Table 1, it can be seen that the various test data of Examples 1-3 are better than those of Comparative Example 2, indicating that the introduction of amino barium titanate nanoparticles plays an important role in improving the performance of concrete prepared from modified recycled aggregate. In Preparation Example 4, the barium titanate nanoparticles were not subjected to amination treatment, resulting in a decrease in the performance of the modified recycled aggregate, thereby affecting the performance of the concrete; and combined with Example 6, it can be seen that the amino barium titanate nanoparticle ethanol suspension and the microcapsule suspension are directly added to the concrete mixture without first modifying the recycled aggregate. The various properties of the concrete are not as good as those of Example 1, indicating that the recycled aggregate is modified before being used in concrete preparation, which can better play the role of each component and improve the performance of the concrete.

[0048] Combining Example 1 with Examples 4-5 and Table 1, it can be seen that the various test data of Example 1 are better than those of Examples 4-5, indicating that the activator composed of sodium hydroxide and water glass has a better stimulating effect on the raw materials, and can better promote the reaction of the various components in the concrete, thereby improving the self-repair effect and compressive strength of the concrete.

[0049] Combining Example 1 with Examples 7-8 and Table 1, it can be seen that the test data of Examples 7-8 are better than those of Example 1, indicating that the addition of epoxy resin emulsion can improve the density and integrity of concrete, enhance the compressive strength of concrete, and at the same time have a certain auxiliary effect on the self-repair process, thereby improving the self-repair effect of concrete.

[0050] Combining Example 1 with Examples 9-10 and Table 1, it can be seen that the test data of Examples 9-10 are better than those of Example 1, indicating that the addition of silica aerogel powder can improve the microstructure of concrete, increase the porosity and density of concrete, and thus enhance the compressive strength of concrete. At the same time, when the microorganisms in the microcapsules generate calcium carbonate, the three-dimensional nanonetwork of the aerogel can serve as a template to guide the directional growth of calcite whiskers, further improving the compressive strength of the concrete.

[0051] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A green low-carbon concrete prepared based on recycled aggregate, characterized in that: It includes the following raw materials in parts by weight: 10-12 parts of fly ash, 20-30 parts of slag, 80-100 parts of modified recycled aggregate, 5-8 parts of activator, 15-20 parts of cement, 10-20 parts of water, 1-3 parts of sodium gluconate, and 0.5-1.5 parts of water reducer, wherein the modified recycled aggregate is recycled aggregate that has undergone surface activation treatment.

2. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: The modified recycled aggregate is recycled aggregate that has been surface activated, and its preparation includes the following steps: (1) Barium titanate nanoparticles are dispersed in a 2 wt% 3-aminopropyltriethoxysilane ethanol solution and ultrasonically treated for 20-30 min. The solution is heated to 75-85°C under nitrogen and refluxed for 110-130 min. After washing and drying with ethanol, ethanol is added and mixed evenly to obtain an amino-barium titanate nanoparticle ethanol suspension for use. (2) Activating Bacillus pasteurianus and inoculating it into a nutrient medium, shaking the culture to induce spore formation, preparing a spore suspension, mixing it with dopamine hydrochloride in a tris-hydroxymethylaminomethane buffer, ultrasonically dispersing it at 24-26 kHz and 20-30 W for 8-12 minutes, and stirring it at room temperature for 22-24 hours to form a microcapsule suspension containing Bacillus pasteurianus; (3) After the recycled aggregate is evacuated to -0.08 MPa, an ethanol suspension of amino-barium titanate nanoparticles is added, and the pressure is increased to 0.2-0.4 MPa and the reaction is carried out for 1.5-2.5 hours. The pressure is then released and the aggregate is treated at 50-60°C under normal pressure for 3-5 hours. The microcapsule suspension is sprayed by atomization, solidified, and dried to obtain the modified recycled aggregate.

3. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: The weight ratio of the barium titanate nanoparticles to the 3-aminopropyltriethoxysilane ethanol solution is 1:45-55; The weight ratio of the dopamine hydrochloride, tris buffer and spore suspension is 0.4-0.6:10:10; The spraying amount of the microcapsule suspension is 5-10% of the added amount of the recycled aggregate.

4. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: The recycled aggregate is obtained by mixing particle sizes of 0.025-5 mm and 10-20 mm in a weight ratio of 2-3:

5.

5. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: The activator is a mixture of sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:2-4, and the modulus of water glass is 2.2-3.

0.

6. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: 1-2 parts of epoxy resin emulsion are also added to the raw materials.

7. The green low-carbon concrete prepared based on recycled aggregate according to claim 1, characterized in that: 0.5-1.5 parts of silicon dioxide aerogel powder with a particle size of 10-50 nm is also added to the raw materials.

8. A method for preparing green low-carbon concrete based on recycled aggregate according to any one of claims 1 to 7, characterized in that: The steps include: (1) Fly ash, slag, and modified recycled aggregate are added and mixed in sequence, and dry-mixed at a speed of 30-50 r / min for 2-3 minutes. Then, activator, water, and water reducer are added and stirred evenly to form a uniform concrete mixture; (2) pouring the concrete mixture into a mold, vibrating it to make it dense, and demoulding it after curing it at room temperature for 24 hours. Then, curing it at a temperature of 20±2°C and a relative humidity of not less than 95% to a specified age to obtain the green low-carbon concrete prepared based on recycled aggregate.