Preparation method of cement-based high-efficiency carbon sequestration based on nanotechnology

Abstract

A method for preparing high-efficiency carbon-fixing cement-based materials based on nanotechnology includes the following steps: 1) ultrasonically dispersing nano-calcium oxide and nano-magnesium oxide in water; 2) using a nanobubble generator to disperse carbon dioxide gas into nano-carbon dioxide bubbles with an average particle size of 50–300 nm, obtaining mixing water containing CO2 nanobubbles that is stable at 20℃–30℃ for at least 24 h; 3) dry-mixing cement, auxiliary cementitious materials, aggregates, and admixtures according to a set mass ratio to form a uniform dry mixture; 4) adding the mixing water obtained in step 1) to the dry mixture and stirring at 40–60 rpm for 5–15 min to obtain a uniform cement-based mixture; 5) molding, compacting, and curing the obtained mixture to obtain a carbon-fixing reinforced cement-based material. This invention can obtain cement-based materials with high carbon fixation content, high density, and high durability.

Description

Technical Field

[0001] This invention belongs to the field of cement-based materials technology, specifically relating to a method for preparing efficient cement-based carbon fixation based on nanotechnology. Background Technology

[0002] To address global warming and achieve the "dual carbon goals," carbon dioxide capture, utilization, and storage (CCDS) technology is considered one of the most promising technological routes. Among these, carbon dioxide mineralization of cementitious materials can permanently seal carbon dioxide while improving various properties of concrete products, thereby effectively reducing cement usage. Generally, carbon dioxide can undergo a carbonation reaction with hydrated calcium silicate gel and calcium hydroxide in cementitious materials, generating dense calcium carbonate and gel, filling microscopic pores and improving the performance of cementitious materials to a certain extent. This technology can also be deeply coupled with industrial solid waste to achieve resource utilization of solid waste, with significant potential for comprehensive emission reduction. In recent years, most existing technologies involve injecting carbon dioxide gas into the mixer during concrete preparation, utilizing the continuous stirring process of the concrete to achieve full contact with carbon dioxide and thus achieve carbon sequestration. However, the following key issues remain to be addressed in existing technologies: 1) Insufficient carbon dioxide concentration during stirring. Using sealed stirring equipment or pressurization can improve carbon fixation efficiency to some extent, but the cost of modification and new construction is too high.

[0003] 2) Existing carbon fixation technology can easily lead to a decline in the performance of cement-based materials, thus restricting their industrial application.

[0004] 3) Existing carbon fixation technologies suffer from low carbon dioxide absorption rates during the carbon mixing process, and carbon adsorption aids or other additives are unlikely to significantly improve the carbon fixation capacity of cement-based materials.

[0005] Chinese invention patent document (publication number: CN120698719A) discloses a hollow fiber-mediated bio-concrete carbon fiber, which provides a diffusion channel for CO2 through a hollow structure (sisal / polypropylene fiber) and loads Bacillus mucilaginosus to promote CO2 mineralization. While increasing the carbon fixation amount, it also enhances the fiber-matrix interface bonding. However, maintaining the long-term activity of microorganisms in a high-alkali concrete environment is challenging, and the fiber pretreatment and loading process is relatively complex. Controlling the fiber dispersion uniformity and microbial survival rate in large-scale production is difficult. Chinese invention patent document (publication number: CN120554061A) discloses a sodium carboxylate-reinforced carbon-fixing concrete. Sodium carboxylate is used as a carbon fixation aid. Its carboxylate group complexes calcium ions to promote the mineralization of CO2 into calcium carbonate. It also improves the density and mechanical properties of concrete by optimizing the pore structure. However, the optimal dosage of sodium carboxylate needs to be strictly controlled (1-5% of the mass of cementitious materials). Excessive dosage may affect the setting time and early strength development. In addition, CO2 needs to be introduced into the mixing process in a special closed equipment, which results in high process costs. The long-term carbonation durability still needs to be verified by engineering. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for preparing high-efficiency carbon fixation in cement based on nanotechnology. By introducing nano-carbon dioxide bubbles, nano-calcium oxide, and nano-magnesium oxide, the rapid transfer, deep mineralization, and stable storage of CO2 in the cement-based system are achieved. At the same time, nano-calcium oxide is used to supplement calcium hydroxide to maintain the alkalinity of the system, and the micro-expansion properties of nano-magnesium oxide are used to fill the pores introduced by the bubbles, thereby obtaining a cement-based material with high carbon fixation, high density, and high durability.

[0007] The technical solution adopted by this invention to solve its technical problem is: A method for preparing efficient cement-based carbon fixation based on nanotechnology includes the following steps: Nano-calcium oxide and nano-magnesium oxide were added to water and ultrasonically dispersed to obtain a nanomaterial dispersion. Carbon dioxide gas was introduced into the nanomaterial dispersion using a nanobubble generator to generate nano-carbon dioxide bubbles with an average particle size of 50–300 nm, resulting in mixing water containing CO2 nanobubbles and nanomaterials that remained stable at 20°C–30°C for at least 24 h. Cement, auxiliary cementitious materials, aggregates, and admixtures are dry-mixed according to a predetermined mass ratio to form a homogeneous dry mix. Cement and auxiliary cementitious materials together constitute the cementitious material. Add the mixing water prepared in step 2) to the dry mixture and stir at 40-60 rpm for 5-15 minutes to obtain a uniform cement-based mixture; The resulting mixture is shaped, compacted, and cured to obtain a carbon-fixed reinforced cementitious material.

[0008] Further, in step 1), the nanomaterials are nano-calcium oxide and nano-magnesium oxide, wherein the nano-calcium oxide has a particle size of 20~100 nm and a specific surface area ≥50 m². 2 / g; the nano-magnesium oxide has a particle size of 50~100 nm and a specific surface area of ​​80~120 m². 2 / g.

[0009] In the third step, the mass ratio of cement, auxiliary cementitious material, aggregate and admixture is (650~750):(250~350):(280~320):(7~9).

[0010] In step 3), the cement is P·O 42.5 ordinary Portland cement.

[0011] More preferably, in step 3), the auxiliary cementing material is one or a mixture of two or more of fly ash, silica fume, steel slag powder, and slag. The auxiliary cementing material provides active SiO2 and fine particle filling, which can further improve the density of the system and the stability of the carbon fixation products.

[0012] The nano-calcium oxide hydrates in the cement-based system to generate calcium hydroxide, replenishing the calcium hydroxide consumed by the carbon dioxide mineralization reaction, maintaining the alkaline environment of the system, and preventing the risk of pH reduction due to excessive carbonization of cement-based materials; at the same time, the high reactivity of nano-calcium oxide can promote the generation of hydration products and act as a nucleation site to accelerate CSH gel deposition and improve the density of the matrix.

[0013] The nano-magnesium oxide exhibits excellent micro-expansion characteristics and carbonation activity in cement-based systems. The generation of its hydration product Mg(OH)2 can compensate for shrinkage during cement hardening and fill some of the pores introduced into the concrete by nano-carbon dioxide bubble water. At the same time, Mg(OH)2 can react with carbon dioxide to generate dense and stable MgCO3 crystals, which further fill the pores of the cement matrix and form a composite carbonate structure together with the generated CaCO3, making the carbonate phase distribution inside the hardened body more continuous and uniform, thereby improving the mechanical strength, impermeability and overall durability of the material.

[0014] The nano-carbon dioxide bubbles used in this invention possess high specific surface area, high interfacial energy, and high gas-dissolving capacity, enabling uniform dispersion of CO2 in the slurry during the mixing stage. This allows CO2 to participate in the reaction from the early stages of cement hydration. The nano-sized bubbles significantly improve the mass transfer rate of CO2, reduce escape losses, and allow it to directly penetrate the slurry interior to undergo mineralization reactions with Ca(OH)2 and Mg(OH)2, promoting the formation and deposition of CaCO3 and MgCO3, thereby significantly improving carbon sequestration efficiency.

[0015] Furthermore, in 3), the aggregate includes fine aggregate with a particle size of 1~4.75 mm that is continuously graded and coarse aggregate with a particle size of 5~25 mm that is well graded, and the mass ratio of fine aggregate to coarse aggregate is 120:180.

[0016] In step 5), the maintenance conditions are: 28 days of maintenance under the conditions of temperature 20±2℃ and humidity ≥95%.

[0017] This invention utilizes electrochemical and cavitation methods to prepare a solution containing carbon dioxide nanobubbles. These nanobubbles, with a diameter of 50-300 nm, possess advantages such as large specific surface area, high interfacial zeta potential, high mass transfer efficiency, and the generation of hydroxyl radicals. They can remain stable in water for tens of hours. Based on the prepared carbon dioxide nanobubbles, this invention adds them simultaneously with water during the mixing process of cement-based materials. This ensures that the carbon dioxide is fully mixed with the cement matrix and reacts rapidly, achieving efficient carbon fixation.

[0018] This invention has the advantages of high carbon fixation efficiency, good internal density of the material, significant improvement in compressive strength and durability, simple preparation process and easy engineering application, which is of great significance for realizing carbon emission reduction and green development in the cement industry.

[0019] The beneficial effects of this invention are mainly reflected in: 1) Compared with traditional cement-based carbon fixation technology, the present invention is significantly less sensitive to water-cement ratio and curing environment.

[0020] 2) This invention has advantages such as low cost and strong applicability. Furthermore, due to the in-situ formation of calcium carbonate, its carbonation products can be evenly distributed inside the cement-based matrix, effectively filling the microstructure.

[0021] 3) The carbon dioxide concentration used in the mixing process described in this invention is high and the dosage is controllable. The nano-sized carbon dioxide bubbles can improve the fluidity of cement-based slurry and the freeze-thaw resistance of the hardened matrix. Detailed Implementation

[0022] The present invention will now be described in further detail.

[0023] A method for preparing efficient cement-based carbon fixation based on nanotechnology includes the following steps: 1) Add nanomaterials to water and ultrasonically disperse them evenly to obtain a nanomaterial dispersion; then use a nanobubble generator to introduce carbon dioxide gas into the nanomaterial dispersion to generate nano carbon dioxide bubbles with an average particle size of 50-300 nm, and obtain a mixing water containing CO2 nanobubbles, nano calcium oxide, and nano magnesium oxide that is stable at 20℃-30℃ for at least 24 h. 2) Dry mix cement, auxiliary cementitious materials, aggregates and admixtures in a mass ratio of (650~750):(250~350):(280~320):(7~9) to form a uniform dry mix; The nano-calcium oxide has a particle size of 20~100 nm and a specific surface area ≥50 m². 2 / g; the nano-magnesium oxide has a particle size of 50~100 nm and a specific surface area of ​​80~120 m². 2 / g.

[0024] The nano-calcium oxide hydrates in the cement-based system to generate calcium hydroxide, replenishing the calcium hydroxide consumed by the carbon dioxide mineralization reaction, maintaining the alkaline environment of the system, and preventing the risk of pH reduction due to excessive carbonization of cement-based materials; at the same time, the high reactivity of nano-calcium oxide can promote the generation of hydration products and act as a nucleation site to accelerate CSH gel deposition and improve the density of the matrix.

[0025] The nano-magnesium oxide exhibits excellent micro-expansion characteristics and carbonation activity in cement-based systems. The generation of its hydration product Mg(OH)2 can compensate for shrinkage during cement hardening and fill some of the pores introduced into the concrete by nano-carbon dioxide bubble water. At the same time, Mg(OH)2 can react with carbon dioxide to generate dense and stable MgCO3 crystals, which further fill the pores of the cement matrix and form a composite carbonate structure together with the generated CaCO3, making the carbonate phase distribution inside the hardened body more continuous and uniform, thereby improving the mechanical strength, impermeability and overall durability of the material.

[0026] The cement is preferably P·O 42.5 ordinary Portland cement. The auxiliary cementitious material is one or a mixture of two or more of fly ash, silica fume, steel slag powder, and blast furnace slag. The auxiliary cementitious material provides active SiO2 and fine particle filling effect, which can further improve the density of the system and the stability of carbon fixation products.

[0027] The nano-carbon dioxide bubbles used in this invention possess high specific surface area, high interfacial energy, and high gas-dissolving capacity, enabling uniform dispersion of CO2 in the slurry during the mixing stage. This allows CO2 to participate in the reaction from the early stages of cement hydration. The nano-sized bubbles significantly improve the mass transfer rate of CO2, reduce escape losses, and allow it to directly penetrate the slurry interior to undergo mineralization reactions with Ca(OH)2 and Mg(OH)2, promoting the formation and deposition of CaCO3 and MgCO3, thereby significantly improving carbon sequestration efficiency.

[0028] The aggregates include fine aggregates with a particle size of 1 to 4.75 mm that are continuously graded and coarse aggregates with a particle size of 5 to 25 mm that are well graded. The mass ratio of fine aggregates to coarse aggregates is 120:180.

[0029] 3) Add the nano CO2 bubble mixing water to the dry mixture and stir at 40-60 rpm for 5-15 min to obtain a uniform cement-based mixture; 4) The resulting mixture is shaped, vibrated, and cured to obtain a carbon-fixed reinforced cementitious material.

[0030] Example 1 This embodiment provides a method for preparing efficient cement-based carbon fixation based on nanotechnology, with the following mass ratio of each component: Cement (PO 42.5): 700 g; Fly ash (Grade II): 270 g; Silica fume: 30 g; Nano calcium oxide: 10 g; Nano magnesium oxide: 10 g; Aggregates: Machine-made sand (fine aggregate): 120 g (sand ratio 0.4); Crushed stone (coarse aggregate): 180 g; Mixing water: 400 g of nano carbon dioxide bubble water (water-to-binder ratio 0.4); Admixture: Polycarboxylate superplasticizer: 8 g (0.8% of the mass of cementitious material); This embodiment also provides a method for preparing the above-mentioned concrete, including the following steps: 1. Add nano-calcium oxide and nano-magnesium oxide to 400 g of water and ultrasonically disperse for 15 min to obtain a nanomaterial dispersion; then use a pressurized cavitation nanobubble generator to pass carbon dioxide gas into deionized water at a flow rate of 200 mL / min for 15 min to obtain mixing water containing nano-carbon dioxide bubbles, nano-calcium oxide, and nano-magnesium oxide, with an average nanobubble particle size of about 300 nm. 2. Add cement, fly ash, silica fume, manufactured sand, crushed stone, and water-reducing agent to the mixer and dry mix for 3 minutes; 3. Add the above-mentioned mixing water to the dry mixture and stir at 50 rpm for 6 minutes to obtain a uniform cement-based mixture; 4. After compacting the mixture in the mold and allowing it to stand for 24 hours, demold it and then cure it for 28 days at 20±2 ℃ and relative humidity ≥95%.

[0031] Example 2 This embodiment provides a method for preparing efficient carbon fixation of cement-based materials, with the following mass ratio of each component: Cement (PO 42.5): 650 g; Fly ash (Grade II): 315 g; Silica fume: 35 g; Nano calcium oxide: 7 g; Nano magnesium oxide: 8 g; Aggregates: manufactured sand (fine aggregate): 112 g (sand ratio 0.4); crushed stone (coarse aggregate): 168 g; Mixing water: 400 g of nano carbon dioxide bubble water (water-to-binder ratio 0.4); Admixture: Polycarboxylate superplasticizer: 7 g (0.7% of the mass of cementitious material); This embodiment also provides a method for preparing the above-mentioned concrete, including the following steps: 1. Add nano-calcium oxide and nano-magnesium oxide to 400 g of water and ultrasonically disperse for 15 min to obtain a nanomaterial dispersion; then use a pressurized cavitation nanobubble generator to pass carbon dioxide gas into deionized water at a flow rate of 300 mL / min for 15 min to obtain mixing water containing nano-carbon dioxide bubbles, nano-calcium oxide, and nano-magnesium oxide, with an average nanobubble particle size of about 180 nm. 2. Add cement, fly ash, silica fume, manufactured sand, crushed stone, and water-reducing agent to the mixer and dry mix for 3 minutes; 3. Add the above-mentioned mixing water to the dry mixture and stir at 50 rpm for 6 minutes to obtain a uniform cement-based mixture; 4. After compacting the mixture in the mold and allowing it to stand for 24 hours, demold it and then cure it for 28 days at 20±2 ℃ and relative humidity ≥95%.

[0032] Example 3 This embodiment provides a method for preparing efficient carbon fixation of cement-based materials. Based on a total mass of 1000 g of cementitious materials, the mass ratio of each component is as follows: Cement (PO 42.5): 750 g; Fly ash (Grade II): 225 g; Silica fume: 25 g; Nano calcium oxide: 13 g; Nano magnesium oxide: 12 g; Aggregates: Manufactured sand (fine aggregate): 128 g (sand ratio 0.4); Crushed stone (coarse aggregate): 192 g; Mixing water: 400 g of nano carbon dioxide bubble water (water-to-binder ratio 0.4); Admixture: Polycarboxylate superplasticizer: 9 g (0.9% of the mass of cementitious material); This embodiment also provides a method for preparing the above-mentioned concrete, including the following steps: 1. Add nano-calcium oxide and nano-magnesium oxide to 400 g of water and ultrasonically disperse for 15 min to obtain a nanomaterial dispersion; then use a pressurized cavitation nanobubble generator to pass carbon dioxide gas into deionized water at a flow rate of 400 mL / min for 15 min to obtain mixing water containing nano-carbon dioxide bubbles, with an average nanobubble particle size of about 50 nm. 2. Add cement, fly ash, silica fume, manufactured sand, crushed stone, and water-reducing agent to the mixer and dry mix for 3 minutes; 3. Add the above-mentioned nano-carbon dioxide bubble water to the dry mixture and stir at 50 rpm for 6 min to obtain a uniform cement-based mixture; 4. After compacting the mixture in the mold and allowing it to stand for 24 hours, demold it and then cure it for 28 days at 20±2 ℃ and relative humidity ≥95%.

[0033] Comparative Example This embodiment provides a method for preparing ordinary cement-based materials. Based on a total cementitious material mass of 1000 g, the mass ratio of each component is as follows: Cement (PO 42.5): 700 g; Fly ash (Grade II): 270 g; Silica fume: 30 g; Nano SiO2: 10 g; Nano MgO: 10 g; Aggregates: Machine-made sand (fine aggregate): 120 g (sand ratio 0.4); Crushed stone (coarse aggregate): 180 g; Mixing water: Municipal tap water: 400 g (water-cement ratio 0.4); Admixture: Polycarboxylate superplasticizer: 8 g (0.8% of the mass of cementitious material); This embodiment also provides a method for preparing the above-mentioned concrete, including the following steps: 1. Add cement, fly ash, silica fume, nano silica, nano magnesium oxide, manufactured sand, crushed stone and water-reducing agent to the mixer and dry mix for 3 minutes; 2. Add municipal tap water to the dry mix and stir at 50 rpm for 6 minutes to obtain a uniform cement-based mixture; 3. After compacting the mixture in the mold and allowing it to stand for 24 hours, demold it and then cure it for 28 days at 20±2 ℃ and relative humidity ≥95%.

[0034] Therefore, the only difference between the preparation method provided in this comparative example and the preparation method in the embodiment is that this comparative example does not use ultrasonic dispersion and nanobubble treatment, the nanomaterials are directly dry mixed, and the mixing water is ordinary tap water.

[0035] Performance testing: 1. Mechanical property testing: The 28-day compressive strength of each group of specimens was tested according to GB / T 17671—2021 "Test Method for Strength of Cement Mortar (ISO Method)". The test results are shown in Table 1.

[0036] 2. Quantitative analysis of carbonation products: Thermogravimetric-differential thermal analysis (TG-DTG) was used to test the 28-day-old specimens in each group. The equivalent calcium carbonate production was calculated by the mass loss rate in the 600–800 °C range to quantify the mineralization and sequestration effect of carbon dioxide. The test results are shown in Table 1.

[0037] 3. Pore structure analysis: The pore structure of the 28-day-old specimens in each group was tested using the mercury intrusion porosimetry (MIP) method to obtain the total porosity and critical pore size, in order to evaluate the degree of matrix densification. The test results are shown in Table 1.

[0038] Table 1 shows the performance test results of the samples prepared in the examples and comparative examples; As shown in Table 1, the cement-based materials prepared using the method of this invention in Examples 1-3 are significantly superior to the comparative examples in terms of mechanical properties, carbon fixation capacity, and microstructure densification. By introducing nano-carbon dioxide bubble water during the mixing stage, CO2 is uniformly dispersed at the nanoscale within the cement-based system, significantly improving the mass transfer efficiency and reactivity of carbon dioxide in the early stages of hydration, promoting the conversion of Ca(OH)2 and Mg(OH)2 to CaCO3 and MgCO3, thereby achieving an overall carbon fixation effect "from the inside out". As the nano-bubble particle size decreases (Examples 1 to 3), the 28-day compressive strength of the samples increases from 50.9 MPa to 58.2 MPa, while the equivalent CaCO3 formation continues to increase, and the total porosity and critical pore size decrease significantly. This indicates that nano-CO2 bubbles, in conjunction with nano-calcium oxide and nano-magnesium oxide, can effectively fill capillary pores and micropores, significantly improving the density and load-bearing capacity of the matrix. Compared to the control group without the introduction of nano-carbon dioxide bubbles, the compressive strength, carbon mineralization and sequestration, and pore structure of the water are significantly inferior, which fully verifies the significant advantages of the technical route of this invention in efficient carbon fixation and synergistic performance improvement.

[0039] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for preparing cement-based high-efficiency carbon fixation based on nanotechnology, characterized in that, The method includes the following steps: 1) Add the nanomaterials to water and disperse them evenly by ultrasonication to obtain a nanomaterial dispersion; 2) Carbon dioxide gas is introduced into the nanomaterial dispersion using a nanobubble generator to generate nano-carbon dioxide bubbles with an average particle size of 50-300 nm, and CO2-containing nanobubbles and nanomaterial mixing water that are stable at 20℃-30℃ for at least 24 h are obtained. 3) Dry-mix cement, auxiliary cementitious materials, aggregates, and admixtures according to the set mass ratio to form a uniform dry mix. Cement and auxiliary cementitious materials together constitute the cementitious material. 4) Add the mixing water prepared in step 2) to the dry mixture and stir at 40-60 rpm for 5-15 minutes to obtain a uniform cement-based mixture; 5) The resulting mixture is shaped, vibrated, and cured to obtain a carbon-fixed reinforced cementitious material.

2. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 1, characterized in that, In the third step, the mass ratio of cement, auxiliary cementitious material, aggregate and admixture is (650~750):(250~350):(280~320):(7~9).

3. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 1, characterized in that, In step 1), the nanomaterials are nano-calcium oxide and nano-magnesium oxide, wherein the nano-calcium oxide has a particle size of 20~100nm and a specific surface area ≥50 m². 2 / g; the nano-magnesium oxide has a particle size of 50~100 nm and a specific surface area of ​​80~120 m². 2 / g.

4. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 1, characterized in that, The cement is P·O 42.5 ordinary Portland cement.

5. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 1, characterized in that, In step 3), the auxiliary cementing material is one or a mixture of two or more of fly ash, silica fume, steel slag powder and slag.

6. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 3, characterized in that, The nano-calcium oxide hydrates in the cement-based system to generate calcium hydroxide, replenishing the calcium hydroxide consumed by the carbon dioxide mineralization reaction, maintaining the alkaline environment of the system, and preventing the risk of pH reduction due to excessive carbonization of cement-based materials; at the same time, the high reactivity of nano-calcium oxide can promote the generation of hydration products and act as a nucleation site to accelerate CSH gel deposition and improve the density of the matrix.

7. The method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in claim 3, characterized in that, The nano-magnesium oxide exhibits excellent micro-expansion characteristics and carbonation activity in cement-based systems. The generation of its hydration product Mg(OH)2 can compensate for shrinkage during cement hardening and fill some of the pores introduced into the concrete by nano-carbon dioxide bubble water. At the same time, Mg(OH)2 can react with carbon dioxide to generate dense and stable MgCO3 crystals, which further fill the pores of the cement matrix and form a composite carbonate structure together with the generated CaCO3, making the carbonate phase distribution inside the hardened body more continuous and uniform, thereby improving the mechanical strength, impermeability and overall durability of the material.

8. A method for preparing high-efficiency cement-based carbon fixation based on nanotechnology as described in any one of claims 1 to 7, characterized in that, In step 3), the aggregate includes fine aggregate with a particle size of 1~4.75 mm that is continuously graded and coarse aggregate with a particle size of 5~25 mm that is well graded, and the mass ratio of fine aggregate to coarse aggregate is 120:

180.

9. A method for preparing cement-based high-efficiency carbon fixation based on nanotechnology as described in any one of claims 1 to 7, characterized in that, In step 5), the curing conditions are: 28 days of curing under a temperature of 20±2℃ and a humidity of ≥95%.

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