Concrete for modular building as well as preparation method and application of concrete

Abstract

The invention relates to concrete for a modular building as well as a preparation method and application of the concrete. Comprising the following components in parts by weight: 280 to 320 parts of cement, 150 to 200 parts of slag powder, 50 to 70 parts of fly ash, 5 to 15 parts of rice hull ash, 800 to 880 parts of recycled coarse aggregate, 700 to 890 parts of recycled fine aggregate, 7 to 14 parts of a water reducing agent, 0.3 to 0.8 part of an isopropylacrylamide-polyethylene glycol copolymer, 2 to 5 parts of rice hull derived biological nanofiber and 130 to 160 parts of water. High-performance and low-carbon concrete is constructed by using industrial by-products such as slag powder and fly ash and agricultural wastes such as rice hull ash as admixtures to partially replace cement and optimizing the overall proportion, and the implicit carbon emission and production cost of the admixtures are far lower than those of the cement, so that the concrete has a good application prospect. Therefore, the carbon emission and raw material cost of the concrete per unit volume are obviously reduced, and the concrete is green, environment-friendly and low in cost.

Description

Technical Field

[0001] This invention relates to the field of building concrete technology, and in particular to a type of concrete for modular buildings, its preparation method, and its application. Background Technology

[0002] With the continuous expansion of my country's construction industry, it has become a key area of ​​energy consumption and carbon emissions. The production and use of concrete materials contribute significantly to carbon emissions throughout the building lifecycle. In recent years, modular construction, as an important technological approach for green and low-carbon transformation in the construction sector, can effectively reduce energy consumption and material waste on construction sites through factory prefabrication, standardized production, and efficient construction, providing a new solution for achieving the carbon reduction goals of the construction industry.

[0003] Traditional concrete, as a core structural material, has a carbon emission intensity as high as 0.9 kg CO2 / kg of cement. my country's annual cement production accounts for approximately 50% of the global total, resulting in annual carbon emissions exceeding 1.5 billion tons from the construction industry. Current concrete preparation technologies use silicate cement as a binder, and the calcination process of cement clinker generates significant process carbon emissions. Simultaneously, the high price of cement leads to high production costs, resulting in substantial cement consumption and carbon emissions. Summary of the Invention

[0004] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a concrete for modular buildings, its preparation method and application, which solves the technical problems of large cement consumption, heavy pollution, high carbon emissions and high cost in traditional concrete technology.

[0005] (II) Technical Solution To achieve the above objectives, the main technical solutions adopted by the present invention include: In a first aspect, embodiments of the present invention provide a concrete for modular construction, comprising, by weight: 280-320 parts cement, 150-200 parts slag powder, 50-70 parts fly ash, 5-15 parts rice husk ash, 800-880 parts recycled coarse aggregate, 700-890 parts recycled fine aggregate, 7-14 parts water-reducing agent, 0.3-0.8 parts isopropylacrylamide-polyethylene glycol copolymer, 2-5 parts rice husk-derived bio-nanofibers, and 130-160 parts water.

[0006] In a preferred embodiment of the present invention, the critical dissolution temperature of the isopropylacrylamide-polyethylene glycol copolymer is 25-30°C. When the ambient temperature is below the critical dissolution temperature, the isopropylacrylamide-polyethylene glycol copolymer remains in a liquid state, and when the temperature is above the critical dissolution temperature, the isopropylacrylamide-polyethylene glycol copolymer forms a gel structure. The rice husk-derived bio-nanofibers have an average diameter of 50-200 nm, an average length of 10-50 μm, and a crystallinity of 65-75%; the rice husk-derived bio-nanofibers are cellulose nanofibers extracted from rice husks by TEMPO oxidation.

[0007] Preferably, the isopropylacrylamide-polyethylene glycol copolymer is 0.4-0.7 parts, and the rice husk-derived bio-nanofiber is 2.5-4 parts.

[0008] In a preferred embodiment of the present invention, the cement is grade 52.5 cement; the specific surface area of ​​the slag powder is 350-450 m². 2 / kg, and the calcium aluminosilicate content >20%; the specific surface area of ​​the fly ash is 2400-2600 m² / kg. 2 / kg; the SiO2 content in the rice husk ash is ≥90%.

[0009] In a preferred embodiment of the present invention, the particle size of the recycled coarse aggregate is 5-20 mm; the particle size of the recycled fine aggregate is 1.6-3.0 mm. The water-reducing agent accounts for 1.0%-2.27% of the total weight of the cement, slag powder, fly ash and rice husk ash.

[0010] In a preferred embodiment of the present invention, the recycled coarse aggregate is at least one of crushed concrete from building demolition and steel slag; the recycled fine aggregate is at least one of manufactured sand, tailings sand and ceramic waste.

[0011] In a preferred embodiment of the present invention, the recycled coarse aggregate is composed of a first recycled coarse aggregate with a particle size of 5-10 mm and a second recycled coarse aggregate with a particle size of 15-20 mm; the weight ratio of the first recycled coarse aggregate to the second recycled coarse aggregate is 1.5-2.5:1.

[0012] In a preferred embodiment of the present invention, the water-reducing agent is at least one of polycarboxylate-based water-reducing agents, aminosulfonic acid-based water-reducing agents, and naphthalene-based water-reducing agents; The water-reducing agent has a water reduction rate of ≥25%.

[0013] Preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0014] Secondly, embodiments of the present invention provide a method for preparing concrete for modular buildings, comprising the following steps: S1. Preparation of rice husk-derived bio-nanofibers: Rice husks were oxidized with TEMPO to obtain rice husk-derived bio-nanofibers. S2. Dry mixing: After the recycled coarse aggregate is put into the mixing equipment and mixed, cement, slag powder, fly ash, rice husk ash and recycled fine aggregate are added in sequence to dry mix and obtain dry mix. S3, Preparation of mixing water: Isopropylacrylamide-polyethylene glycol copolymer, water-reducing agent and rice husk-derived bio-nanofibers from S1 are mixed with water to prepare mixing water; S4. Slurry preparation: Add the mixing water from S3 to the dry mix in S2 in batches and stir until a uniform concrete slurry is obtained. S5. Curing: After pouring the S4 concrete slurry into the mold and compacting it, cure it under the conditions of temperature 20±2℃ and humidity ≥95%.

[0015] In a preferred embodiment of the present invention, in S1, the preparation of the rice husk-derived bio-nanofibers includes: S11. Washing and drying: After rinsing the rice husks to remove impurities, dry them at 80-120℃ until the moisture content is ≤5%; S12, TEMPO oxidation treatment: Dry rice husks are mixed with TEMPO oxidant at a mass ratio of 1:0.5-1 and oxidized under ultrasonic assistance to obtain rice husk fibers. S13. High-pressure homogenization dispersion: The oxidized rice husk fibers are homogenized and dispersed under a pressure of 20-35 MPa to obtain rice husk-derived bio-nanofibers.

[0016] In a preferred embodiment of the present invention, the stirring temperature in steps S3 and S4 is below 25°C.

[0017] Thirdly, embodiments of the present invention provide the application of concrete in the preparation of modular building components.

[0018] (III) Beneficial Effects The beneficial effects of this invention are as follows: This invention provides a type of concrete for modular construction. By partially replacing cement with a high proportion of industrial byproducts such as slag powder and fly ash, as well as agricultural waste such as rice husk ash, and optimizing the overall mix proportions, a high-performance, low-carbon concrete is constructed. The efficient utilization of slag powder, fly ash, and rice husk ash significantly reduces cement usage. The implicit carbon emissions and production costs of these admixtures are far lower than those of cement, thus significantly reducing carbon emissions and raw material costs per unit volume of concrete, making it green, environmentally friendly, and low-cost. Simultaneously, the addition of slag powder and other admixtures effectively optimizes the rheological properties of concrete, reduces yield stress, improves workability, and reduces bleeding and segregation, thereby obtaining concrete with stable performance that is easy to pump and pour. Through the synergistic effect of the components, the necessary early and long-term strength of the concrete is guaranteed, effectively overcoming the problems of heavy pollution, high carbon emissions, concentrated heat of hydration, and easy shrinkage cracking inherent in traditional high-cement-content concrete. It is particularly suitable for the comprehensive requirements of modular construction regarding material performance, construction efficiency, and sustainability.

[0019] Among them, isopropylacrylamide-polyethylene glycol copolymer, as a temperature-sensitive smart component, can maintain good workability when stirred at room temperature, and the concrete maintains optimal construction performance at ambient temperatures of 10-40℃. Through natural temperature difference or active temperature control, the copolymer's setting-promoting effect can be triggered after pouring, thereby significantly shortening the time required for concrete demolding, thus improving the mold turnover rate and increasing the efficiency of the modular precast production line.

[0020] Rice husk-derived bio-nanofibers form a three-dimensional network reinforcement in a cement matrix, effectively bridging microcracks, preventing their propagation, and significantly improving the material's crack resistance, impact toughness, and fracture energy. Furthermore, rice husk-derived bio-nanofibers are homologous to rice husk ash, resulting in good synergy within the material system.

[0021] By using high-strength Grade 52.5 cement, a strong and rapid initial hydration driving force is provided for the entire cementitious system, ensuring that the concrete achieves high early strength. The high specific surface area of ​​slag powder enables its rapid reaction speed, and the high calcium aluminosilicate content in slag powder allows it to work synergistically with cement, ensuring continuous and stable strength development from early to late stages.

[0022] Ultrafine fly ash effectively lubricates particles, reduces internal friction, and significantly improves the fluidity of concrete, making it more suitable for pumping and pouring. Simultaneously, the ultrafine particles efficiently fill the micro-voids between cement and slag powder. Rice husk ash, primarily composed of highly active amorphous silica, has an extremely fine particle size that further fills the smallest pores not yet filled by the ultrafine fly ash. The gradient composite filling effect of fly ash and rice husk ash, combined with chemical activity, greatly enhances the density of concrete.

[0023] Both coarse and fine aggregates are recycled aggregates, replacing natural aggregates in existing technologies, significantly reducing the mining of natural sand and gravel, and protecting the natural environment and river ecosystem. Precise control of the recycled aggregate particle size ensures good continuous gradation. This forms a dense skeletal structure, effectively compensating for any potential strength deficiencies in the recycled aggregate itself, and guaranteeing excellent workability of the concrete.

[0024] Because recycled aggregates have rough surfaces, many pores, and high water absorption, limiting the proportion of water-reducing agent to ≤2.27% can meet the higher water demand of recycled aggregates while fully dispersing the cementitious materials, so that the concrete can obtain the required fluidity and cohesiveness.

[0025] By precisely dividing and blending recycled coarse aggregates into two grades, the skeleton structure of concrete is optimized, resulting in less frictional resistance between aggregate particles during mixing and pumping of fresh concrete. This effectively improves workability and fluidity, making it more suitable for the industrial production of precast components.

[0026] This invention also provides a method for preparing concrete, directly converting agricultural waste rice husks into high-performance nanofibers, achieving internal circulation of raw material systems and reducing dependence on and costs associated with purchased materials. By employing a process of adding granules first, then powders, and then drying before wetting, with water added in stages, the problem of uneven mixing caused by differences in material density and particle size is solved. Adding water and water-reducing agents in stages prevents the water-reducing agent from being locally adsorbed and becoming ineffective, and allows for more precise control of the water-cement ratio and the rheological state of the concrete, effectively preventing clumping.

[0027] The concrete of this invention can be used in modular building components, such as wall components, floor slab components, beam-column joint components, etc. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for preparing concrete for modular buildings in an embodiment of the present invention; Figure 2 This refers to the concrete prepared in Example 2 of the present invention. Detailed Implementation

[0029] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0031] Example 1

[0032] This embodiment provides a method for preparing rice husk-derived bio-nanofibers, including the following steps: Step 1, Washing and Drying: After rinsing the rice husks to remove impurities, dry them at 100℃ until the moisture content is ≤5%; Step 2, TEMPO oxidation treatment: Dry rice husks and TEMPO oxidant are mixed at a mass ratio of 1:1 and oxidized under ultrasonic assistance to obtain rice husk fibers; Step 3, High-pressure homogenization and dispersion: The oxidized rice husk fibers are homogenized and dispersed under a pressure of 30 MPa to obtain rice husk-derived bio-nanofibers.

[0033] Example 2

[0034] This embodiment provides a method for preparing concrete for modular buildings, including the following steps: (1) Preparation of materials: Prepare the following by weight: 300 parts of cement (52.5 grade Conch silicate cement), 180 parts of slag powder (S110 grade), 60 parts of fly ash, 10 parts of rice husk ash (calcined at 600-800℃, with SiO2 content ≥90%), 840 parts of recycled coarse aggregate (of which 560 parts of the first recycled coarse aggregate and 280 parts of the second recycled coarse aggregate), 780 parts of recycled fine aggregate, 9 parts of water-reducing agent (WS-PC type polycarboxylate water-reducing agent, manufacturer: Shenzhen Wushan New Materials Co., Ltd.), 0.5 parts of isopropylacrylamide-polyethylene glycol copolymer (manufacturer: Xi'an Qiyue Biotechnology Co., Ltd.), 3 parts of rice husk-derived bio-nanofiber (prepared in Example 1), and 145 parts of water; The recycled coarse aggregate is made from crushed concrete from building demolition, and the recycled fine aggregate is tailings sand.

[0035] (2) Pretreatment: Aggregate moisture content correction: If the moisture content (MC, mass fraction %) of recycled coarse or fine aggregate is not zero, the actual amount of water added shall be corrected according to the following formula: ; in, This refers to the actual amount of water added. This is the theoretical amount of water to be added. and These are the mass fractions and moisture content of each aggregate; Water-reducing agent pretreatment: Mix the water-reducing agent with 50% of the total water volume in advance, stir evenly, and let stand for later use.

[0036] (3) Dry mixing: The recycled coarse aggregate is put into the mixing equipment and mixed at low speed for 20s to eliminate agglomeration. Then, cement, slag powder, fly ash, rice husk ash and recycled fine aggregate are added in sequence for dry mixing. The mixing time is continued for 120s to obtain dry mix. Ensure that the dry mix is ​​premixed evenly and that the fine aggregate fully fills the aggregate voids.

[0037] (4) Preparation of mixing water: Isopropylacrylamide-polyethylene glycol copolymer, water-reducing agent and rice husk-derived bio-nanofiber are mixed with water to prepare mixing water. The stirring temperature is below 25℃.

[0038] (5) Preparation of slurry: Add mixing water to the dry mix in batches and stir until a uniform concrete slurry is obtained. The stirring temperature is below 25℃. Specifically, add 60% of the total water to the dry mix and stir at low speed for 60 seconds to fully wet and initially disperse the powder; then add the remaining water in 2-3 batches and stir at high speed for 90 seconds until the concrete mixture is in a uniform flow state; stop stirring and let it stand for 60 seconds to allow air bubbles inside the concrete mixture to escape; stir at high speed again for 60 seconds to ensure that there is no obvious residual dry powder in the concrete mixture and that the slump is controlled between 80-200mm.

[0039] (6) Curing: After the concrete slurry is poured into the mold and vibrated to compact it, it is cured under the conditions of temperature 20±2℃ and humidity ≥95%.

[0040] Specifically, the concrete slurry is poured into the mold under normal pressure, and the vibration molding time is 60 seconds with a vibration pressure of about 0.3 MPa. Then, the molded component is placed in an environment with a temperature of 20±2℃ and a humidity of ≥95% for 24 hours before demolding. After demolding, it continues to be cured under the same temperature and humidity conditions until 28 days of age.

[0041] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0042] Example 3

[0043] This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is as follows: Step (1) Material preparation: Prepare the following by weight: 280 parts of cement, 200 parts of slag powder, 70 parts of fly ash, 15 parts of rice husk ash, 860 parts of recycled coarse aggregate (of which 573 parts are the first recycled aggregate and 287 parts are the second recycled aggregate), 800 parts of recycled fine aggregate, 12 parts of water-reducing agent (WS-PC type polycarboxylate water-reducing agent, manufacturer: Shenzhen Wushan New Materials Co., Ltd.), 0.5 parts of isopropylacrylamide-polyethylene glycol copolymer, 3 parts of rice husk-derived bio-nanofiber, and 150 parts of water; The remaining steps are the same.

[0044] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0045] Example 4

[0046] This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is as follows: Step (1) Material preparation: Prepare the following by weight: 320 parts cement, 150 parts slag powder, 50 parts fly ash, 8 parts rice husk ash, 850 parts recycled coarse aggregate (of which 573 parts are first recycled aggregate and 287 parts are second recycled aggregate), 720 parts recycled fine aggregate, 9 parts water-reducing agent (aminosulfonic acid water-reducing agent), 0.4 parts isopropylacrylamide-polyethylene glycol copolymer, 2.5 parts rice husk-derived bio-nanofibers, and 130 parts water; the remaining steps are the same.

[0047] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0048] Example 5

[0049] This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is as follows: Step (1) Material preparation: Prepare the following by weight: 320 parts cement, 150 parts slag powder, 50 parts fly ash, 8 parts rice husk ash, 850 parts recycled coarse aggregate, 720 parts recycled fine aggregate, 9 parts water-reducing agent (WS-PC type polycarboxylate water-reducing agent, manufacturer: Shenzhen Wushan New Materials Co., Ltd.), 0.7 parts isopropylacrylamide-polyethylene glycol copolymer, 4 parts rice husk-derived bio-nanofiber and 130 parts water; The remaining steps are the same.

[0050] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0051] Comparative Example 1 This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is that: Step (1) Material preparation: Prepare the following by weight: 550 parts of cement, 870 parts of coarse aggregate (of which, the coarse aggregate is natural coarse aggregate), 820 parts of fine aggregate, 9 parts of water-reducing agent (WS-PC type polycarboxylate water-reducing agent, manufacturer: Shenzhen Wushan New Materials Co., Ltd.) and 171 parts of water; The remaining steps are the same.

[0052] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0053] Comparative Example 2 This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is as follows: Step (1) Material preparation: Prepare the following by weight: 530 parts of cement, 840 parts of recycled coarse aggregate (of which 560 parts of the first recycled aggregate and 280 parts of the second recycled aggregate), 746 parts of recycled fine aggregate, 11 parts of water-reducing agent (WS-PC type polycarboxylate water-reducing agent, manufacturer: Shenzhen Wushan New Materials Co., Ltd.), 0.3 parts of isopropylacrylamide-polyethylene glycol copolymer, 2 parts of rice husk-derived bio-nanofibers and 159 parts of water; Comparative Example 3 This embodiment provides a method for preparing concrete for modular buildings. The difference between this embodiment and embodiment 2 is that: Step (1) Material preparation: 280 parts cement, 200 parts slag powder, 70 parts fly ash, 15 parts rice husk ash, 860 parts recycled coarse aggregate, 800 parts recycled fine aggregate, 12 parts water-reducing agent, 0.5 parts isopropylacrylamide-polyethylene glycol copolymer and 150 parts water; Application Example 1 The concrete prepared in Examples 2-5 can be used for modular building components, such as wall components, floor slab components, beam-column joint components, etc.

[0054] The density, maximum bearing capacity and compressive strength of the prepared concrete were tested, and the test results are detailed in Table 1.

[0055] Table 1 Performance indicators of concrete prepared in different embodiments and comparative examples

[0056] Based on the performance test results in Table 1, the following analytical conclusions can be drawn: Examples 2 and 3 are preferred embodiments. The concrete prepared from solid waste materials for modular construction has a 28-day compressive strength of over 76 MPa and a 28-day maximum bearing capacity of 740 kg / m³. 3The carbon emissions per cubic meter of concrete are below 263 kg CO2e. This ensures continuous and stable growth in strength over time, and its final load-bearing capacity fully meets the structural safety requirements of high-rise modular buildings, while also reducing carbon emissions.

[0057] Compared to Comparative Examples 1-3, the concrete prepared for modular buildings in all embodiments also showed significantly improved overall performance.

[0058] Comparing Examples 2-5 with Comparative Example 2, it can be seen that, with similar recycled aggregate content, the embodiments of the present invention have advantages in workability and strength, overcome the performance degradation problem caused by the inherent defects of recycled aggregate, provide a high-performance solution for the resource utilization of construction waste, and achieve a unity of environmental protection and high performance.

[0059] Comparing Example 2 with Comparative Example 1, it can be seen that, with the same total amount of cementitious materials, the present invention achieves higher later-stage strength by introducing slag powder, fly ash, and rice husk ash, while significantly reducing the amount of cement used alone. This not only directly reduces material costs but also reduces the high carbon emissions from cement production at the source.

[0060] Comparing Example 2 and Comparative Example 3, it can be seen that removing rice husk-derived bio-nanofibers directly leads to a decrease in 28-day compressive strength and load-bearing capacity. As a microscopic reinforcing agent, bio-nanofibers play a bridging and crack-preventing role in the hardening process of concrete. Their three-dimensional network structure effectively transfers and disperses the load, enhancing the toughness and final load-bearing capacity of the matrix.

[0061] In summary, the test data demonstrates that the concrete mix design and preparation method provided by this invention, through the synergistic optimization of active admixtures and recycled aggregates, successfully produces a concrete material that combines high early strength, high final strength, excellent workability, and significant environmental benefits. Its overall technical performance far surpasses that of traditional formulations, making it particularly suitable for modular construction applications with stringent requirements for material performance, construction efficiency, and environmental friendliness. This technology efficiently utilizes industrial solid waste, enhances the green sustainability of modular buildings, and effectively overcomes the problems of high cement consumption, heavy pollution, high carbon emissions, and high costs associated with traditional concrete technologies.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of concrete for modular construction, characterized in that, It includes, by weight: 280-320 parts cement, 150-200 parts slag powder, 50-70 parts fly ash, 5-15 parts rice husk ash, 800-880 parts recycled coarse aggregate, 700-890 parts recycled fine aggregate, 7-14 parts water-reducing agent, 0.3-0.8 parts isopropylacrylamide-polyethylene glycol copolymer, 2-5 parts rice husk-derived bio-nanofibers, and 130-160 parts water.

2. The concrete for modular construction as described in claim 1, characterized in that: The critical dissolution temperature of the isopropylacrylamide-polyethylene glycol copolymer is 25-30℃. When the ambient temperature is below the critical dissolution temperature, the isopropylacrylamide-polyethylene glycol copolymer remains in a liquid state, and when the temperature is above the critical dissolution temperature, the isopropylacrylamide-polyethylene glycol copolymer forms a gel structure. The rice husk-derived bio-nanofibers have an average diameter of 50-200 nm, an average length of 10-50 μm, and a crystallinity of 65-75%; the rice husk-derived bio-nanofibers are cellulose nanofibers extracted from rice husks by TEMPO oxidation.

3. The concrete for modular construction as described in claim 1, characterized in that: The cement is grade 52.5 cement; the specific surface area of ​​the slag powder is 350-450 m². 2 / kg, and the calcium aluminosilicate content >20%; the specific surface area of ​​the fly ash is 2400-2600 m² / kg. 2 / kg; the SiO2 content in the rice husk ash is ≥90%.

4. The concrete for modular construction as described in claim 1, characterized in that: The recycled coarse aggregate has a particle size of 5-20 mm; the recycled fine aggregate has a particle size of 1.6-3.0 mm. The water-reducing agent accounts for 1.0%-2.27% of the total weight of the cement, slag powder, fly ash and rice husk ash.

5. The concrete for modular construction as described in claim 4, characterized in that: The recycled coarse aggregate is at least one of the following: crushed concrete from building demolition and steel slag; the recycled fine aggregate is at least one of the following: manufactured sand, tailings sand, and ceramic waste.

6. The concrete for modular construction as described in claim 5, characterized in that: The recycled coarse aggregate is composed of a first recycled coarse aggregate with a particle size of 5-10 mm and a second recycled coarse aggregate with a particle size of 15-20 mm; the weight ratio of the first recycled coarse aggregate to the second recycled coarse aggregate is 1.5-2.5:

1.

7. The concrete for modular construction as described in claim 1, characterized in that: The water-reducing agent is at least one of polycarboxylate-based water-reducing agents, aminosulfonic acid-based water-reducing agents, and naphthalene-based water-reducing agents; The water-reducing agent has a water reduction rate of ≥25%.

8. A method for preparing concrete for modular buildings as claimed in any one of claims 1-7, characterized in that, Includes the following steps: S1. Preparation of rice husk-derived bio-nanofibers: Rice husks were oxidized with TEMPO to obtain rice husk-derived bio-nanofibers. S2. Dry mixing: After the recycled coarse aggregate is put into the mixing equipment and mixed, cement, slag powder, fly ash, rice husk ash and recycled fine aggregate are added in sequence to dry mix and obtain dry mix. S3, Preparation of mixing water: Isopropylacrylamide-polyethylene glycol copolymer, water-reducing agent and rice husk-derived bio-nanofibers from S1 are mixed with water to prepare mixing water; S4. Slurry preparation: Add the mixing water from S3 to the dry mix in S2 in batches and stir until a uniform concrete slurry is obtained. S5. Curing: After pouring the S4 concrete slurry into the mold and compacting it, cure it under the conditions of temperature 20±2℃ and humidity ≥95%.

9. The preparation method according to claim 8, characterized in that, In S1, the preparation of the rice husk-derived bio-nanofibers includes: S11. Washing and drying: After rinsing the rice husks to remove impurities, dry them at 80-120℃ until the moisture content is ≤5%; S12, TEMPO oxidation treatment: Dry rice husks are mixed with TEMPO oxidant at a mass ratio of 1:0.5-1 and oxidized under ultrasonic assistance to obtain rice husk fibers. S13. High-pressure homogenization dispersion: The oxidized rice husk fibers are homogenized and dispersed under a pressure of 20-35 MPa to obtain rice husk-derived bio-nanofibers.

10. The use of concrete as described in any one of claims 1-9 in the preparation of modular building components.

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