A carbon dioxide-cured seawater concrete and a method for producing the same

Abstract

The application belongs to the technical field of building materials, and particularly relates to a seawater concrete for carbon dioxide fixation and a preparation method thereof. The preparation method of the seawater concrete for carbon dioxide fixation provided by the application comprises the following steps: (1) mixing seawater after pretreatment and a water reducing agent uniformly, then adding coarse aggregate, fine aggregate, cementitious material and a rust inhibitor, and introducing CO2 to perform carbonation reaction to obtain concrete slurry; (2) performing hierarchical curing treatment on the concrete slurry obtained in the step (1) after molding to obtain concrete, wherein the hierarchical curing treatment comprises first stage curing and second stage curing, the first stage curing is performed in a CO2 environment with a concentration of 15-25%vol, and the second stage curing is performed in a CO2 environment with a concentration of 3-8%vol.

Description

Technical Field

[0001] This invention belongs to the technical field of building materials, specifically relating to a seawater concrete that solidifies carbon dioxide and its preparation method. Background Technology

[0002] With the rapid development of marine engineering and coastal infrastructure construction, the scale of marine projects such as cross-sea bridges, port terminals, offshore wind power foundations, and coastal protection dikes continues to expand, leading to a surge in the consumption of concrete as a core construction material. Traditional marine concrete is prepared using freshwater mixing, but coastal areas generally suffer from a scarcity of freshwater resources. Long-distance transportation of freshwater not only significantly increases construction costs but also consumes large quantities of high-quality freshwater resources, contradicting the industry's development philosophy of green infrastructure and water and energy conservation. To overcome these drawbacks, the industry is gradually adopting seawater as a substitute for freshwater in concrete preparation. Seawater is abundant, readily available locally, and can effectively conserve freshwater resources and reduce construction costs in coastal projects, demonstrating significant economic value and promising engineering application prospects.

[0003] However, existing seawater concrete preparation technologies still have many inherent defects, severely restricting their large-scale engineering applications. On the one hand, seawater is rich in highly corrosive ions such as chloride and sulfate. When used directly in concrete mixing, it easily induces internal reinforcement corrosion, leading to structural defects such as steel expansion, concrete matrix cracking, and surface spalling. This significantly reduces the mechanical and durability properties of the concrete, making it unsuitable for the harsh service environment of the ocean—high salinity, high humidity, and wet-dry cycles—and drastically shortening its overall service life. On the other hand, existing seawater concrete technologies only replace mixing water resources and do not meet the low-carbon development needs of the construction industry. Traditional concrete production relies on large amounts of cement, and the cement preparation process generates huge amounts of carbon dioxide, resulting in a high overall carbon emission level, which cannot meet the core requirements of the low-carbon transformation of the construction sector under the current "dual-carbon" strategy.

[0004] Currently, the industry's methods for modifying seawater concrete are relatively limited, with conventional solutions mainly involving the simple addition of rust inhibitors, optimization of aggregate gradation, and thickening of the structural protective layer. However, thickening the protective layer can easily lead to shrinkage cracking of the concrete matrix, creating corrosive ion penetration channels and exacerbating structural corrosion damage. Modification methods that solely add rust inhibitors or auxiliary cementitious materials suffer from limited improvement effects and insufficient long-term stability, failing to fundamentally solve the dual technical challenges of poor corrosion resistance and high carbon emissions in seawater concrete. Furthermore, existing technologies cannot achieve the resource-based solidification and utilization of carbon dioxide during concrete preparation, resulting in a waste of greenhouse gas resources.

[0005] In addition, Friedel salt (3CaO·Al2O3·CaCl2·10H2O), which is commonly found in seawater concrete, is extremely sensitive to environmental pH. Traditional seawater concrete generally uses a single curing process after molding, which can lead to a sharp drop in pH, causing Friedel salt to decompose and release a large amount of Cl. - This accelerates steel corrosion, makes it unsuitable for the special hydration reaction characteristics of seawater mixing systems, and fails to meet the process requirements of carbonation modification. It easily leads to problems such as uneven early strength development of concrete, insufficient structural stability in the later stages, and high matrix porosity, further accelerating the penetration rate of salt corrosion ions. Ultimately, this results in a short service life of concrete structures and high maintenance costs in the later stages, seriously affecting the safety and reliability of marine engineering structures.

[0006] In summary, existing seawater concrete technologies generally suffer from technical bottlenecks such as unreasonable utilization of freshwater resources, poor corrosion resistance and durability, high carbon emissions, and an inability to simultaneously achieve both mechanical and environmental performance. Therefore, developing a method for preparing seawater concrete that can efficiently solidify carbon dioxide, possesses excellent corrosion resistance and stable mechanical properties, and is low-carbon and environmentally friendly, thereby overcoming the many shortcomings of existing technologies, is a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing seawater concrete that solidifies carbon dioxide.

[0008] The method for preparing solidified carbon dioxide seawater concrete according to an embodiment of the present invention includes the following steps:

[0009] (1) After pretreatment of seawater, it is mixed evenly with water-reducing agent, and then coarse aggregate, fine aggregate, cementitious material and rust inhibitor are added and CO2 is introduced to carry out carbonation reaction to obtain concrete slurry; (2) After the concrete slurry obtained in step (1) is formed, it is subjected to graded curing treatment to obtain concrete; the graded curing treatment includes a first stage curing and a second stage curing. The first stage curing is carried out in a CO2 environment with a concentration of 15~25%vol, and the second stage curing is carried out in a CO2 environment with a concentration of 3~8%vol.

[0010] The advantages and technical effects of the method for preparing carbon dioxide-cured seawater concrete according to embodiments of the present invention are as follows: 1. The method of the present invention adds a water-reducing agent to the concrete slurry. The water-reducing agent can significantly reduce water consumption and improve the rheology and durability of seawater concrete. Furthermore, by adsorbing the surface of cement particles, it disperses aggregates and reduces the water-cement ratio, thereby improving rheology and reducing the water-cement ratio, thus reducing the concentration and permeability of chloride ions in seawater, improving the overall quality of concrete while reducing steel corrosion; 2. The method of the present invention generates carbonates during the carbonation reaction, which can block the capillary pores in seawater concrete, forming a double barrier with the densifying effect of the water-reducing agent, significantly reducing the diffusion rate of chloride ions; 3. The method of the present invention adopts a graded curing treatment scheme. The first stage is carried out in a high-concentration CO2 environment, which can induce the generation of a large number of "calcite" nanocrystals on the surface. These crystals not only fill the capillary pores but also form a structure targeting chloride ions through charge adsorption. - The "chemiluminescent layer," a layered structure, acts like a trap to capture free Cl- in seawater attempting to invade. - The first stage involves fixing the carbonized material in the surface layer, effectively preventing it from penetrating to the surface of the reinforcing steel. The second stage is carried out in a low-concentration CO2 environment. The low-concentration environment can avoid shrinkage cracks caused by excessive carbonization of the surface layer, while guiding the continuous mineralization of calcium hydroxide inside, further optimizing the micropore structure of seawater concrete, reducing the chloride ion diffusion coefficient by more than 40%, and maintaining the pH value of the pore liquid above 12.0 to ensure the chemical stability of the internal Friedel salt, thus realizing the ion regulation strategy of "internal stability and external closure".

[0011] In some embodiments, the pretreatment in step (1) includes filtration and precipitation.

[0012] In some embodiments, in step (1), the cementing material is a composite material containing calcium carbonate and magnesium hydroxide obtained by calcining calcium magnesium waste residue, the calcination temperature is 700~850℃, and the mass ratio of calcium carbonate to magnesium hydroxide in the composite material is 1:(0.5~1.5).

[0013] In some embodiments, in step (1), the amount of cementitious material added is such that the water-cement ratio of the concrete slurry is less than 0.3, where the water-cement ratio is the ratio of the mass of seawater to the mass of cementitious material.

[0014] In some embodiments, in step (1), the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent, and the content of the water-reducing agent is 0.8~1.5 wt% of the cementitious material. And / or, in step (1), the rust inhibitor includes at least one of nitrite rust inhibitor or amine compound rust inhibitor, and the content of the rust inhibitor is 1 to 3 wt% of the cementitious material.

[0015] In some embodiments, in step (1), the coarse aggregate comprises basalt with a particle size of 5-20 mm; And / or, in step (1), the fine aggregate includes at least one of sea sand or stone powder, with a particle size of 0.15~4.75 mm; And / or, in step (1), the mass ratio of coarse aggregate to fine aggregate is (1.5~4):1, and the mass ratio of the total mass of coarse aggregate and fine aggregate to the mass of gel material is (3~4):1.

[0016] In some embodiments, in step (1), the amount of CO2 introduced is such that the system pressure reaches 0.2~0.4MPa; And / or, in step (1), the temperature of the carbonation reaction is 20~50 ℃ and the time of the carbonation reaction is 0.5~2 h.

[0017] In some embodiments, in step (2), the graded maintenance treatment is carried out at 20~30℃; the first stage of maintenance lasts for 4~8 hours, and the second stage of maintenance lasts for 14~28 days.

[0018] In some embodiments, in step (2), the graded curing treatment is carried out in a sealed curing chamber or a reactor. The amount of CO2 with a concentration of 15~25%vol introduced in the first stage of curing is such that the pressure in the sealed curing chamber or reactor is ≥0.15MPa. After the first stage of curing is completed, the pressure is released and the second stage of curing is carried out at atmospheric pressure.

[0019] This invention also provides a seawater concrete that solidifies carbon dioxide, prepared using the above-described preparation method. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process for preparing solidified carbon dioxide seawater concrete in an embodiment of the present invention; Figure 2 This is a diagram of the injection system and pressure feedback mechanism in an embodiment of the present invention; Figure 3 This is a flowchart of the micro-positive pressure closed-loop control logic in an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] like Figure 1 As shown, the method for preparing seawater concrete with solidified carbon dioxide according to an embodiment of the present invention includes the following steps: (1) After pretreatment of seawater, it is mixed evenly with water-reducing agent, and then coarse aggregate, fine aggregate, cementitious material and rust inhibitor are added and CO2 is introduced to carry out carbonation reaction to obtain concrete slurry; (2) After the concrete slurry obtained in step (1) is formed, it is subjected to graded curing treatment to obtain concrete; the graded curing treatment includes a first stage curing and a second stage curing. The first stage curing is carried out in a CO2 environment with a concentration of 15~25%vol, and the second stage curing is carried out in a CO2 environment with a concentration of 3~8%vol.

[0023] The method for preparing carbon dioxide-cured seawater concrete according to embodiments of the present invention involves adding a water-reducing agent to the concrete slurry. This water-reducing agent significantly reduces water consumption and improves the rheology and durability of the seawater concrete. Furthermore, by adsorbing onto the surface of cement particles, it disperses aggregates and reduces the water-cement ratio, thereby improving rheology and reducing the water-cement ratio, thus lowering the concentration and permeability of chloride ions in seawater, improving the overall quality of the concrete while reducing steel corrosion. In the method of this embodiment, the carbonates generated during the carbonation reaction can block the capillary pores in the seawater concrete, forming a double barrier with the densifying effect of the water-reducing agent, significantly reducing the diffusion rate of chloride ions. The method of this embodiment employs a graded curing treatment scheme. The first stage is carried out in a high-concentration CO2 environment, which induces the formation of a large number of calcite nanocrystals on the surface. These crystals not only fill the capillary pores but also form a structure targeting chloride ions through charge adsorption. - The "chemiluminescent layer," a layered structure, acts like a trap to capture free Cl- in seawater attempting to invade. - The first stage involves fixing the carbonized material in the surface layer, effectively preventing it from penetrating to the surface of the reinforcing steel. The second stage is carried out in a low-concentration CO2 environment. The low-concentration environment can avoid shrinkage cracks caused by excessive carbonization of the surface layer, while guiding the continuous mineralization of calcium hydroxide inside, further optimizing the micropore structure of seawater concrete, reducing the chloride ion diffusion coefficient by more than 40%, and maintaining the pH value of the pore liquid above 12.0 to ensure the chemical stability of the internal Friedel salt, thus realizing the ion regulation strategy of "internal stability and external closure".

[0024] In the embodiments of the present invention, the gas used is obtained by treating industrial waste gas, and the remaining part is mainly nitrogen, with a small amount of oxygen and water vapor.

[0025] In some embodiments, preferably, the pretreatment in step (1) includes filtration and sedimentation. Suspended solids and organic impurities in seawater are removed through simple filtration and sedimentation processes, avoiding negative impacts on concrete performance.

[0026] In some embodiments, preferably, in step (1), the cementing material is a composite material containing calcium carbonate and magnesium hydroxide obtained by calcining calcium-magnesium waste residue. The calcination temperature is 700~850℃, and the mass ratio of calcium carbonate to magnesium hydroxide in the composite material is 1:(0.5~1.5), for example, 1:0.5, 1:1, or 1:1.5. In this embodiment of the invention, the calcium carbonate and magnesium hydroxide composite material is obtained by treating calcium-magnesium waste residue in a calcination furnace. The calcination temperature can be matched with the waste heat level of the industrial kiln. Compared with directly purchasing commercial expansion agents, the carbon footprint is reduced by more than 60%. The calcium carbonate and magnesium hydroxide composite material is selected as the cementing material to enhance carbon dioxide absorption. The generated carbonate crystals are micron-sized or nano-sized. These crystals are "anchored" in the micropores of sea sand, improving the overall curing strength.

[0027] In some embodiments, preferably, in step (1), the amount of cementitious material added is such that the water-cement ratio of the concrete slurry is less than 0.3, where the water-cement ratio is the ratio of the mass of seawater to the mass of cementitious material. Since the water-cement ratio of 0.3 is extremely low, conventional mixing cannot achieve the desired consistency. The seawater must be mixed with the water-reducing agent first, and the dispersing effect of the water-reducing agent is used to achieve the flow of the slurry with such a small amount of seawater. In the process of calculating the water-cement ratio, the mineralization reaction after the introduction of CO2 needs to be considered. This reaction mainly affects the content of free water and the volume of the solid phase. The generated CaCO3 nanocrystals have a volume compensation effect of "replacing water with carbon". The amount of free water consumed should be deducted in the calculation, and the contribution of the structural densification brought about by the formation of calcium carbonate to the bulk modulus should be considered. This means that with an extremely low amount of seawater, the density of the structure is improved by carbonation. The low water-cement ratio directly limits the total amount of chloride ions per unit volume (because the amount of seawater is less), thereby reducing the risk of corrosion to the steel reinforcement from the source.

[0028] In some embodiments, preferably, in step (1), the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent, and the content of the water-reducing agent is 0.8~1.5 wt% of the cementitious material. The high-performance water-reducing agent controls the water-cement ratio to below 0.30, providing a compact initial spatial template for subsequent mineralization reactions.

[0029] In some embodiments, preferably, in step (1), the rust inhibitor includes at least one of nitrite-based rust inhibitors or amine-based rust inhibitors, and the content of the rust inhibitor is 1-3 wt% of the cementitious material. Such a rust remover can reduce potential environmental pollution.

[0030] In some embodiments, preferably, in step (1), the coarse aggregate comprises basalt with a particle size of 5~20mm; And / or, in step (1), the fine aggregate includes at least one of sea sand or stone powder, with a particle size of 0.15~4.75 mm; And / or, in step (1), the mass ratio of coarse aggregate to fine aggregate is (1.5~4):1, and the mass ratio of the total mass of coarse aggregate and fine aggregate to the mass of gel material is (3~4):1.

[0031] In this embodiment of the invention, basalt is used as coarse aggregate. Basalt is resistant to salt corrosion, which can avoid the problem of reduced strength caused by salt erosion of ordinary sand and gravel.

[0032] In some embodiments, preferably, in step (1), the amount of CO2 introduced is such that the system pressure reaches 0.2~0.4 MPa; And / or, in step (1), the carbonation reaction is carried out at a temperature of 20-50°C for 0.5-2 hours. The chemical reaction involves CO2 reacting with Ca in seawater. 2+ / Mg 2+ Carbonation of ions: Ca 2+ +CO2+2OH →CaCO3↓+H2O. This ensures that carbon dioxide reacts fully with the calcium and magnesium components in the slurry to generate nanonuclei, without affecting workability.

[0033] In this embodiment of the invention, CO2 in industrial waste gas is preferentially utilized to achieve resource recycling through carbon capture technology. In this process, the carbon dioxide that is not completely absorbed is reintroduced into the cycle for carbon dioxide atmosphere maintenance.

[0034] In some embodiments, preferably, in step (2), the graded maintenance treatment is carried out at 20~30℃; the first stage of maintenance lasts for 4~8 hours, and the second stage of maintenance lasts for 14~28 days.

[0035] In some embodiments, preferably, in step (2), the graded curing treatment is carried out in a sealed curing chamber or a reactor. In the first stage of curing, the amount of CO2 with a concentration of 15~25%vol introduced is such that the pressure of the sealed curing chamber or reactor is ≥0.15MPa. After the first stage of curing is completed, the pressure is released and the second stage of curing is carried out at atmospheric pressure.

[0036] like Figure 2 As shown in this embodiment of the invention, graded curing is performed in a closed environment. The demolded concrete components are placed in a sealed curing chamber or reactor with pressure-bearing capacity. High-concentration CO2 from a carbon capture system is injected into the sealed curing chamber or carbonation reactor using a pumping device. The system needs to be equipped with a CO2 gas injection device, with its output pressure set at 0.2~0.4 MPa. Automated sensors are introduced to monitor the CO2 concentration and pressure inside the chamber in real time to ensure P CO2 With an pressure of ≥0.15MPa, the first stage of micro-positive pressure curing is achieved. The pressure difference drives CO2 to react rapidly with Ca(OH)2 within 5mm of the surface layer within 2 hours, compressing the porosity from 18.2% to below 5.5%. This measure aims to establish the first "chlorine-proof barrier".

[0037] like Figure 3 As shown, the four specific steps to achieve micro-positive pressure are not a one-time inflation process, but a dynamic physicochemical process: Step 1: Initial Displacement and Pressure Boost In the initial stage of molding (t=0~6h), CO2 with a concentration of 15%~25% is injected into the sealed chamber. Gas is continuously introduced using an air pump until the internal pressure reaches a slightly positive pressure state of more than 0.15 MPa.

[0038] Step 2: Pressure gradient-driven diffusion Using the pressure difference formed inside and outside the reactor as the driving force, CO2 molecules are forced to overcome the resistance of the concrete pores and rapidly penetrate into the surface layer to a depth of 5mm in a short time (about 2 hours).

[0039] Step 3: In-situ mineralization and consumption compensation As CO2 reacts with the surface Ca(OH)2 to form CaCO3, the gas inside the chamber is consumed, causing a pressure drop. At this point, the intelligent control system automatically replenishes gas based on feedback from the pressure sensor to maintain a constant micro-positive pressure of ≥0.15MPa.

[0040] Step 4: Phased blood pressure reduction and regulation After completing the first stage of surface densification, the system will actively reduce the pressure and concentration (to 3%~8%) and switch to the second stage of deep equilibrium curing to avoid excessive carbonization of the surface and the resulting cracks.

[0041] This invention also provides a seawater concrete that solidifies carbon dioxide, prepared using the above-described preparation method.

[0042] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1 (1) Mix 160 kg of seawater after filtration and sedimentation with 5.5 kg of polycarboxylate-based high-performance water-reducing agent and add it to the reactor. (2) Calcium and magnesium waste residue is calcined in a calcining furnace at a temperature of 800℃ to obtain calcium carbonate and magnesium hydroxide composite material, wherein the mass ratio of calcium carbonate and magnesium hydroxide is 1:1; 550 kg of composite material, 1250 kg of basalt with a particle size of 10~15 mm, 680 kg of sea sand with a particle size of 1~2.5 mm, and 11 kg of sodium nitrite rust inhibitor are added to the reactor, and CO2 is introduced at the same time to carry out carbonation reaction at 30℃ for 1 h. The amount of CO2 introduced is based on the pressure of the reactor reaching 0.3 MPa to obtain concrete slurry; (3) After the concrete slurry is formed, it is demolded and placed in a sealed curing chamber. It is cured at 25°C. High concentration CO2 with a concentration of 20%vol is injected into the curing chamber through a pumping device. The pressure in the curing chamber is measured to be 0.15MPa. The first stage of curing is carried out. After 6 hours of curing, the pressure is released so that the pressure in the curing chamber reaches normal pressure. Low concentration CO2 with a concentration of 5%vol is introduced for the second stage of curing. The curing lasts for 20 days.

[0044] Example 2 The preparation method of this embodiment is the same as that of embodiment 1, except that in step (2), the pressure of the first stage of curing is 0.4 MPa and the curing time is 4 h.

[0045] Example 3 The preparation method of this embodiment is the same as that of Example 1, except that in step (1), the amount of polycarboxylate superplasticizer used is 8.25 kg; In step (2), the amount of basalt used is 1200 kg, and the amount of fine aggregate sea sand used is 800 kg.

[0046] Example 4 The preparation method of this embodiment is the same as that of Example 1, except that in step (2), the second stage uses CO2 with a concentration of 3%vol for 28 days.

[0047] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that in step (2), the molded specimen is placed in an environment with a temperature of 20±2℃ and a relative humidity of more than 95%, and is cured by continuous atomized spraying.

[0048] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that in step (2), a first-stage curing treatment is adopted, specifically: after the concrete slurry is molded, it is demolded and placed in a sealed curing chamber, and cured at 25°C. A high concentration of CO2 with a concentration of 20%vol is injected into the curing chamber through a pumping device. The pressure in the curing chamber is detected to be 0.15MPa. The first stage of curing is carried out for 6 hours.

[0049] The properties of the concrete prepared in Examples 1-4 and Comparative Examples 1-2 were tested, and the results are shown in Table 1: Table 1

[0050] Note: Cl - Migration depth: Cl was measured using the RCM (Rapid Chloride Migration) method or spontaneous potential titration. - The migration depth is determined by the following procedure: A cylindrical specimen with a diameter of 100 × 50 mm is placed in a 3.0 wt% NaCl solution, removed and split at a specified age. A 0.1 mol / L AgNO3 solution is sprayed onto the split surface, and the average thickness of the colored (white precipitate) area is measured; this is the chloride ion migration depth.

[0051] Friedel salt stability was tested using XRD coupled with TG-DTG. Powder from the 10-20 mm depth within the concrete was collected, and the amount of Friedel salt formed was quantitatively analyzed by XRD diffraction peak intensity. Subsequently, the temperature was increased to 1000℃ at 10℃ / min under nitrogen atmosphere, and the decomposition rate of Friedel salt was calculated by measuring the mass loss in the 300-400℃ range, thus assessing its chemical stability under strongly alkaline conditions.

[0052] Aggregate / matrix interfacial energy: The matrix refers to the continuous hardened slurry formed by the reaction of cementitious materials (mineralized products of calcium-magnesium waste), seawater, water-reducing agents, and rust inhibitors. Nanoindentation testing was used, with scanning electron microscopy to locate the interfacial transition zone between the aggregate and the hardened slurry. Indentation tests were performed at 5 μm intervals from the aggregate edge towards the matrix. The changes in hardness and elastic modulus were recorded. An increase in interfacial energy is manifested as a reduction in the ITZ width and a smoothing of the hardness gradient.

[0053] pH gradient variation: Powder was collected in layers every 2 mm along the concrete carbonation direction. The powder was mixed with deionized water at a 1:1 mass ratio, shaken for 24 hours, and the pH value of the supernatant was measured. The pH gradient from the surface (low-concentration CO2 curing zone) to the core (high-pressure mineralization zone) was observed by fitting a curve. This invention requires the internal pH to be maintained above 12.0 to ensure the passivation protection capability for the reinforcing steel.

[0054] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing seawater concrete that solidifies carbon dioxide, characterized in that, Includes the following steps: (1) After pretreatment of seawater, it is mixed evenly with water-reducing agent, and then coarse aggregate, fine aggregate, cementitious material and rust inhibitor are added and CO2 is introduced to carry out carbonation reaction to obtain concrete slurry; (2) After the concrete slurry obtained in step (1) is formed, it is subjected to graded curing treatment to obtain concrete; the graded curing treatment includes a first stage curing and a second stage curing. The first stage curing is carried out in a CO2 environment with a concentration of 15~25%vol, and the second stage curing is carried out in a CO2 environment with a concentration of 3~8%vol.

2. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (1), the pretreatment includes filtration and sedimentation.

3. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (1), the cementitious material is a composite material containing calcium carbonate and magnesium hydroxide obtained by calcining calcium magnesium waste residue. The calcination temperature is 700~850℃, and the mass ratio of calcium carbonate to magnesium hydroxide in the composite material is 1:(0.5~1.5).

4. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1 or 3, characterized in that, In step (1), the amount of cementitious material added is such that the water-cement ratio of the concrete slurry is less than 0.3, where the water-cement ratio is the ratio of the mass of seawater to the mass of cementitious material.

5. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (1), the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent, and the content of the water-reducing agent is 0.8~1.5 wt% of the cementitious material; And / or, in step (1), the rust inhibitor includes at least one of nitrite rust inhibitor or amine compound rust inhibitor, and the content of the rust inhibitor is 1 to 3 wt% of the cementitious material.

6. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (1), the coarse aggregate includes basalt with a particle size of 5~20 mm; And / or, in step (1), the fine aggregate includes at least one of sea sand or stone powder, with a particle size of 0.15~4.75mm; And / or, in step (1), the mass ratio of coarse aggregate to fine aggregate is (1.5~4):1, and the mass ratio of the total mass of coarse aggregate and fine aggregate to the mass of gel material is (3~4):

1.

7. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (1), the amount of CO2 introduced is such that the system pressure reaches 0.2~0.4 MPa; And / or, in step (1), the temperature of the carbonation reaction is 20~50℃ and the time of the carbonation reaction is 0.5~2h.

8. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1, characterized in that, In step (2), the graded maintenance treatment is carried out at 20~30℃; the first stage of maintenance lasts for 4~8 hours, and the second stage of maintenance lasts for 14~28 days.

9. The method for preparing seawater concrete with solidified carbon dioxide according to claim 1 or 8, characterized in that, In step (2), the graded curing treatment is carried out in a sealed curing chamber or a reactor. In the first stage of curing, the amount of CO2 with a concentration of 15~25%vol is introduced so that the pressure in the sealed curing chamber or reactor is ≥0.15MPa. After the first stage of curing is completed, the pressure is released and the second stage of curing is carried out under normal pressure.

10. A type of seawater concrete that solidifies carbon dioxide, characterized in that, It is prepared by any one of claims 1 to 9.

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