Supersulfate negative carbon cementing material as well as preparation method and application thereof

Abstract

The invention discloses a super sulfate negative carbon cementing material and a preparation method and application thereof, and the cementing material comprises the following components in parts by mass: 38-50 parts of S95 slag, 20-30 parts of steel slag, 20-25 parts of desulfurized gypsum, 3-5 parts of charcoal, 3-5 parts of zeolite powder and 2-5 parts of Portland cement. The super-sulfate negative carbon cementing material has a remarkable carbon sequestration advantage while having relatively high mechanical properties, solves the problems that the steel slag and the desulfurized gypsum are low in utilization rate and difficult to treat due to excessive accumulation, and solidifies carbon dioxide while improving the utilization rate of solid wastes such as the slag, the steel slag and the desulfurized gypsum, so that negative carbon is realized on the raw material level; and the method is simple to operate, energy-saving, environment-friendly, good in economical efficiency and beneficial to popularization and application.

Description

Technical Field

[0001] The present invention relates to a cementitious material, in particular to a supersulfate negative carbon cementitious material, and also to a preparation method of the cementitious material and applications in the field of building materials. Background Art

[0002] The production of ordinary Portland cement (OPC) is a major source of greenhouse gas emissions, primarily due to the calcination of limestone, accounting for approximately 7-10% of global CO2 emissions. To reduce these emissions, a key strategy is to replace OPC with supplementary cementitious materials, thereby promoting the utilization of industrial solid waste in cement production and producing low-carbon or even negative-carbon cementitious materials.

[0003] Supersulfated cement, a new green cementitious material, is composed of a large amount of industrial solid waste slag, gypsum, and a small amount of Portland cement. Its production is low-carbon and energy-efficient, making it a potential alternative to OPC. However, slag, the primary raw material in traditional supersulfated cement, is already widely used in the cement industry, and its price is gradually rising. Furthermore, slag is a major source of carbon emissions from supersulfated cement, necessitating the urgent need to find new industrial solid waste alternatives to slag, thereby achieving both low cost and low carbon emissions for supersulfated cement.

[0004] Prior art discloses methods for preparing supersulfated cement using other solid wastes instead of slag. For example, patent publication number CN118545923A discloses an electrolytic manganese slag supersulfated cement. This technical solution is relatively complex in terms of electrolytic manganese slag pretreatment, which increases process energy consumption and carbon emissions, resulting in poor carbonization. Furthermore, the maximum compressive strengths at 3d and 28d are 6.83 MPa and 25.34 MPa, respectively, resulting in relatively low mechanical properties, limiting its application in practical projects. Patent publication number CN113372029A discloses a low-carbon supersulfated cement, its preparation method, and cement mortar. However, its early strength is insufficient, with a maximum 3d strength of only 7.15 MPa, limiting its application in projects requiring higher early strength. Patent publication number CN101423343A discloses steel slag supersulfated cement and its preparation method. However, CO2 emissions during the production process are still approximately 10% of those of traditional Portland cement, leaving significant room for improvement before achieving the goal of low or even negative carbon. Therefore, enhancing mechanical properties, improving solid waste utilization and solidifying carbon dioxide remain the goals of supersulfate cement development. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a super sulfate negative carbon cementitious material with strong mechanical properties, which can solidify carbon dioxide while improving the utilization rate of solid wastes such as steel slag and desulfurization gypsum, and also provide a preparation method of the above-mentioned cementitious material and its application in the field of building materials.

[0006] Technical solution: The present invention discloses a super sulfate negative carbon cementitious material, comprising the following components in parts by mass: 38 to 50 parts of S95 slag, 20 to 30 parts of steel slag, 20 to 25 parts of desulfurized gypsum, 3 to 5 parts of biochar, 3 to 5 parts of zeolite powder, and 2 to 5 parts of Portland cement.

[0007] Among them, steel slag is an industrial by-product produced during the steelmaking process and comes from the converter steelmaking process; the steel slag composition includes: 12-16% SiO2, 1-4% Al2O3, 31-38% CaO, 25-32% Fe2O3, 3-7% MgO, 0.51-1.5% TiO2, and 0.18-0.52% SO3.

[0008] Among them, desulfurization gypsum is a by-product gypsum produced after the coal-fired industry uses flue gas desulfurization technology to remove sulfur dioxide. The desulfurization gypsum composition includes: 1.5-3.2% SiO2, 0.55-0.82% Al2O3, 40-45% CaO, 0.22-0.57% Fe2O3, 0.55-1.23% K2O, 0.82-1.1% MgO, 0.012-0.055% TiO2, and 55-60% SO3.

[0009] The S95 slag has an Al2O3 content greater than 13%, a 7d activity index not less than 70%, and a 28d activity index not less than 95%.

[0010] The biochar is obtained by thermal decomposition of corn and bamboo at 800±100°C in a nitrogen atmosphere, passed through a 50-200 mesh sieve and then dried at 150±25°C, preferably obtained by thermal decomposition of corn and bamboo at 800°C in a nitrogen atmosphere, passed through a 50 mesh sieve and then dried at 150°C.

[0011] Wherein, the strength grade of the silicate cement is greater than 42.5 MPa.

[0012] The method for preparing the supersulfate negative carbon gelling material comprises the following steps:

[0013] (1) Pre-grinding the steel slag and desulfurized gypsum in a ball mill and passing through a 200-mesh standard sieve;

[0014] (2) The pretreated steel slag and desulfurized gypsum are evenly mixed with S95 slag, biochar, zeolite powder and silicate cement.

[0015] The present invention also discloses the application of the supersulfate negative carbon gelling material in carbon dioxide solidification building materials engineering.

[0016] Wherein, the solidification of carbon dioxide comprises the following steps:

[0017] (1) Mixing the cementitious material with an admixture and water to obtain a slurry, then pouring the slurry into a mold, demoulding after molding, and performing standard curing;

[0018] (2) The test block after standard curing in step (1) was dried in an oven at 60° C. for 1 day, and carbonized in a gas containing carbon dioxide to obtain a supersulfate negative carbon cementitious material product.

[0019] Wherein, in step (1), the water-cement ratio of the slurry is 0.38-0.4; the admixture is PCA-1 polycarboxylate water reducer, the dosage of which is 2‰ of the cementitious material; after the slurry is poured into the mold, it is covered with plastic wrap, and the mold is removed after 24 hours, and the standard curing age is 3-28 days.

[0020] Wherein, in step (2), the carbonization reaction temperature is 25±1° C., the relative humidity is 70%, the carbon dioxide concentration is 20±2%, and the gas pressure during the carbonization process is controlled at 0.1-1 MPa.

[0021] Principle of the Invention: This supersulfated carbon-negative cementitious material utilizes steel slag to partially replace slag, the primary raw material in supersulfated cement. Portland cement and desulfurized gypsum act as alkali activators and sulfate activators, respectively, to promote the dissolution and hydration of slag and steel slag. The dual incorporation of biochar and zeolite powder is a key enhancement mechanism. The biochar's tubular and honeycomb-like macropores facilitate the formation of carbon dioxide transport channels, while the zeolite's nanoscale pore structure and excellent surface adsorption capacity enable the adsorption and fixation of COx, achieving a combined physical and chemical carbon fixation mechanism. The multi-scale pores formed by the biochar and zeolite improve the pore structure and enhance the mechanical properties of the material. Experimental results show that the optimal mechanical properties are achieved when the mix ratio is 50 parts slag, 20 parts steel slag, 20 parts desulfurized gypsum, 3 parts biochar, 5 parts zeolite powder, and 2 parts cement. The lowest carbon emissions from the raw materials are achieved when the mix ratio is 38 parts slag, 30 parts steel slag, 20 parts desulfurized gypsum, 5 parts biochar, 5 parts zeolite powder, and 2 parts cement.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The supersulfate negative carbon cementitious material of the present invention has significant carbon fixation advantages while having high mechanical properties. After 3d and 28d of age, it can reach 29MPa and 47MPa through carbonization curing, and solves the problems of low utilization rate of steel slag and desulfurization gypsum and excessive accumulation that is difficult to handle; (2) When applied to carbon dioxide solidification building materials projects, the unit mass of carbon fixation samples prepared by the negative carbon cementitious material can absorb a maximum of 6.8wt% of carbon dioxide, and the total carbon emission of raw materials can be as low as -0.7kg CO2eq. While improving the utilization rate of solid wastes such as slag, steel slag and desulfurization gypsum, carbon dioxide is solidified, thereby achieving negative carbon at the raw material level, which plays an important role in the development of the building materials industry and the realization of the "dual carbon" goal; (3) The negative carbon cementitious material prepared according to this method can bring economic benefits of 257 to 336 yuan per ton during engineering application, and is simple to operate, has a high solid waste utilization rate, is energy-saving and environmentally friendly, has good economic efficiency, and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD diffraction patterns of some raw materials (a) slag (b) gypsum and (c) steel slag, and (d) the particle size distribution of steel slag;

[0024] Figure 2 Images of biochar properties made from bamboo and corn as raw materials (a) XRD diffraction pattern (b) pore size distribution (c) SEM image of bamboo biochar (20 kV, 1000x) (d) SEM image of corn biochar (20 kV, 1000x);

[0025] Figure 3 Images of zeolite powder related properties (a) XRD diffraction pattern (b) pore and specific surface area distribution;

[0026] Figure 4 The present invention is a simplified process flow chart for the preparation of the supersulfate negative carbon cementitious material and its carbon dioxide solidification process. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to the examples. The test materials used in the examples can all be purchased through conventional channels.

[0028] Use XRD analysis to select solid waste raw materials of different qualities, the results are as follows Figure 1 As shown in the figure, the slag contains a large amount of glass and amorphous phase, which gives the slag greater hydration activity. The main crystalline phase in desulfurization gypsum is hemihydrate gypsum. The steel slag is mainly composed of iron oxide phase and contains mineral phases with hydration activity such as C3S, β~C2S and γ~C2S.

[0029] The physical composition and pore structure of biochar are as follows: Figure 2 As shown, biochars made from bamboo and corn have similar phase compositions, with silica being the primary crystalline phase. Pore structure characterization and scanning electron microscopy images clearly demonstrate a porous structure, with most pores interconnected and pore sizes concentrated in the 5-10 nm range, indicating a large specific surface area.

[0030] The physical composition, pore size and specific surface area of ​​zeolite powder are characterized as follows: Figure 3 Zeolite powder is mainly composed of zeolite, silica and tobermorite. The pore size and specific surface area results show that its pore size is finer than that of biochar, and is concentrated in the range of 0-5 nm.

[0031] Example 1

[0032] The supersulfate negative carbon cementitious material of the present invention is measured by mass percentage as follows: 50 parts of slag, 20 parts of steel slag, 20 parts of desulfurized gypsum, 3 parts of biochar, 5 parts of zeolite powder, and 2 parts of cement; and its preparation method comprises the following steps:

[0033] (1) Pre-grinding the steel slag and desulfurized gypsum in a ball mill and passing through a 200-mesh standard sieve;

[0034] (2) The pretreated steel slag and desulfurized gypsum are evenly mixed with S95 slag, biochar, zeolite powder and silicate cement.

[0035] according to Figure 4 As shown in the flow chart, the steps for solidifying carbon dioxide are:

[0036] (1) Using a water-cement ratio of 0.4, the supersulfate negative carbon cementitious material was mixed with water and stirred using a slurry mixer. The mixture was formed into a 40x40x40 mold and cured for 24 hours before demolding. The mixture was then cured for 3 days and 27 days according to standard conditions.

[0037] (2) The standard cured sample was pre-dried at 60°C for 24 hours and then placed in a carbonization reactor for carbonization reaction. The reaction temperature was 25°C, the reaction time was 1 day and 3 days, the pressure of the carbonization reactor was atmospheric pressure, and the carbon dioxide concentration was 20%. Finally, a supersulfate negative carbon cementitious material product was obtained.

[0038] The carbonization capacity and carbonization conversion rate of the carbonized sample of Example 1 were determined using a muffle furnace. The carbonization depth and carbonization conversion rate of the supersulfate negative carbon cementitious material product of Example 1 after carbonization are shown in Table 1. The carbonization depth was measured by spraying a 1.5% phenolphthalein alcohol solution on a cross-section of the sample. The thickness of the uncolored area was measured as the carbonization depth.

[0039] The calculation formula of carbonization conversion rate of cementitious materials is as follows:

[0040] Carbonization conversion rate of cementitious material (wt%) = Δm / mass of cementitious material in the sample before carbonization

[0041] Where Δm is the mass loss during calcination at 600-900°C in a muffle furnace.

[0042] Table 1. Carbonization depth of cementitious material products and carbonization conversion rate of cementitious material in Example 1

[0043]

[0044] Example 2

[0045] The supersulfate negative carbon cementitious material of the present invention is measured by mass percentage as follows: 50 parts of slag, 20 parts of steel slag, 20 parts of desulfurized gypsum, 3 parts of biochar, 5 parts of zeolite powder, and 2 parts of cement; its preparation method and the step of solidifying carbon dioxide are the same as those in Example 1, and a supersulfate negative carbon cementitious material product is obtained.

[0046] Example 2 The carbonization depth of the supersulfate negative carbon cementitious material product after carbonization and the carbonization conversion rate of the cementitious material are shown in Table 2.

[0047] Table 2 Carbonization depth of cementitious material products and carbonization conversion rate of cementitious material in Example 2

[0048]

[0049] Example 3

[0050] The supersulfate negative carbon cementitious material of the present invention is measured by mass percentage as follows: 50 parts of slag, 30 parts of steel slag, 20 parts of desulfurized gypsum, 3 parts of biochar, 3 parts of zeolite powder, and 2 parts of cement; its preparation method and the steps of solidifying carbon dioxide are the same as those in Example 1, and a supersulfate negative carbon cementitious material product is obtained.

[0051] Example 3 The carbonization depth of the supersulfate negative carbon cementitious material product after carbonization and the carbonization conversion rate of the cementitious material are shown in Table 3.

[0052] Table 3 Carbonization depth of cementitious material products and carbonization conversion rate of cementitious material in Example 3

[0053]

[0054] Example 4

[0055] The supersulfate negative carbon cementitious material of the present invention is measured by mass percentage as follows: 38 parts of slag, 30 parts of steel slag, 20 parts of desulfurized gypsum, 5 parts of biochar, 5 parts of zeolite powder, and 2 parts of cement; its preparation method and the step of solidifying carbon dioxide are the same as those in Example 1, and a supersulfate negative carbon cementitious material product is obtained.

[0056] Example 4 The carbonization depth of the supersulfate negative carbon cementitious material product after carbonization and the carbonization conversion rate of the cementitious material are shown in Table 4.

[0057] Table 4. Carbonization depth of cementitious material products and carbonization conversion rate of cementitious material in Example 4

[0058]

[0059] According to the carbonization depths (mm) of Examples 1-4 in Tables 1-4, the carbonization depths of the samples after 28 days of standard curing were significantly lower than those after only 3 days of standard curing. This can be attributed to the longer curing time resulting in a denser matrix and thus more difficult transmission of carbon dioxide gas. Furthermore, for both 3-day and 28-day standard curing, the carbonization depth of the 3-day carbonized sample significantly exceeded that of the sample carbonized only for 1 day. The sample with the highest carbonization depth was 15.1 mm in Example 1, which was cured for 3 days after 3 days of standard curing.

[0060] The carbonization conversion rates (wt%) of the cementitious materials in Examples 1-4 were significantly greater after carbonization curing than after standard curing. The carbonization conversion rates of the samples carbonized for 1 day were significantly lower than those of the samples carbonized for 3 days. The carbonization conversion rates of the samples carbonized for 1 day were all above 5 wt%, and those of the samples carbonized for 3 days were generally above 6 wt%, with the highest reaching 6.8 wt%.

[0061] Comparative Example 1

[0062] The difference from Example 4 is that only 5 parts of biochar are added, no zeolite powder is added, and 43 parts of slag are added, and the other conditions are the same.

[0063] The carbonization depth of the cementitious material product after carbonization and the carbonization conversion rate of the cementitious material of Comparative Example 1 are shown in Table 5.

[0064] Table 5 Carbonization depth and carbonization conversion rate of the cementitious material product of Comparative Example 1

[0065]

[0066] Comparing the carbonization depth and carbonization conversion rate of the cementitious material in Example 4, if only biochar is added, the carbonization depth and carbonization conversion rate of the sample are reduced by 6.5% and 20%.

[0067] Comparative Example 2

[0068] The difference from Example 4 is that only 5 parts of zeolite powder are added alone, no biochar is added, and 43 parts of slag are added. The other conditions are the same.

[0069] The carbonization depth of the cementitious material product after carbonization and the carbonization conversion rate of the cementitious material of Comparative Example 2 are shown in Table 6.

[0070] Table 6 Carbonization depth and carbonization conversion rate of cementitious material products of Comparative Example 2

[0071]

[0072] The carbonization depth and carbonization conversion rate of the cementitious material of Example 4 were compared. If only zeolite powder was added, the carbonization depth of the sample and the carbonization conversion rate of the cementitious material decreased by 10% and 23%. Biochar has a tubular and honeycomb structure, which can form a CO2 transmission channel in the matrix and promote the carbonization reaction; zeolite powder has nano-scale pores, and its aluminosilicate skeleton can achieve physical adsorption of CO2, promoting the occurrence of carbonization reaction without affecting the structural strength. In the case of dual doping of the two, the microscopic pores of the zeolite powder provide more paths for CO2 diffusion, while the macroscopic pores of the biochar can enhance CO2 transmission. The combination of the two forms a multi-scale carbonization channel, which greatly improves the carbon fixation capacity of the supersulfate negative carbon cementitious material.

[0073] As shown in Table 7, the carbon emission standards for each raw material are as follows: slag 0.18 kg CO2 / kg, desulfurized gypsum 0.12 kg CO2 / kg, steel slag 0.019 kg CO2 / kg, biochar ~0.9 kg CO2 / kg, zeolite powder 0.012 kg CO2 / kg, and cement 0.62 kg CO2 / kg. It can be seen that the large-scale use of low-carbon emission raw material steel slag and the incorporation of negative carbon emission raw material biochar can significantly reduce the carbon emissions of cementitious materials. Furthermore, the dual incorporation of biochar and zeolite results in significantly higher carbon absorption in each example than in the control example using only single incorporation. Calculations show that the combined carbon emissions of the raw materials in Example 4 are -0.7 kg CO2eq, achieving a negative carbon level.

[0074] Table 7. Total carbon emissions of raw materials in Examples and Comparative Examples

[0075] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Slag kg 50 43 50 38 43 43 Desulfurization gypsum kg 20 20 20 20 20 20 Steel slag kg 20 30 20 30 30 30 Biochar kg 3 3 5 5 5 0 Zeolite powder kg 5 3 3 5 0 5 Cement kg 2 2 2 2 2 2 Slag carbon emissions (kg) 9.08 7.81 9.08 6.90 7.81 7.81 Desulfurization gypsum carbon emissions (kg) 2.4 2.4 2.4 2.4 2.4 2.4 Carbon emissions from steel slag (kg) 0.38 0.57 0.38 0.57 0.57 0.57 Biochar carbon emissions (kg) -2.7 -2.7 -4.5 -4.5 -4.5 0 Zeolite powder carbon emissions (kg) 0.06 0.04 0.4 0.06 0 0.06 Cement carbon emissions (kg) 1.24 1.24 1.24 1.24 1.24 1.24 Carbon absorption 6.3 6.7 6.8 6.6 5.4 5.9 <![CDATA[Total carbon emissions (kg CO2eq)]]> 41.6 26.6 22 -0.7 21.2 61.8

[0076] Compressive strength of the supersulfate negative carbon cementitious material of the test example and the cementitious material of the comparative example:

[0077] According to the requirements of the national standard "Test Method for Cement Mortar Strength" (GB / T17671-2021), the cement compressive strength test was carried out, the loading rate was set to 2.4KN / s, and the number of test blocks was 3. It can be seen from Table 8 that the compressive strength of the samples after 3 days of standard curing and then carbonization exceeded 24MPa, and the highest could reach 29.5MPa, which was significantly higher than the 19.4 and 23.2MPa of the comparative example; the compressive strength of the samples after 28 days of standard curing and then carbonization exceeded 36MPa, and the highest could reach 47.7MPa, which was significantly higher than the 33.6 and 33.1MPa of the comparative example. Compared with the comparative example, the dual addition of biochar and zeolite powder in the embodiment not only significantly improved the carbon fixation capacity of the cementitious material, but also increased the compressive strength by 5.6% to 52% under different curing systems.

[0078] Table 8. Compressive strength of supersulfate negative carbon cementitious materials of Examples and comparative examples

[0079]

[0080] The supersulfate negative carbon cementitious material prepared according to this method can bring about an economic benefit of RMB per ton during engineering application. The specific calculation steps are as follows:

[0081] 0.8A+0.8B+(0.08+0.8)C=257~336 yuan / ton

[0082] Among them: A—Production of negative carbon cementitious materials saves cement costs (170 to 220 yuan / ton)

[0083] B—Production of negative carbon cementitious materials saves the processing costs of slag, desulfurization gypsum and steel slag (50-100 yuan / ton)

[0084] C—CO2 treatment costs saved from producing negative carbon cementitious materials, including absorbed CO2 and CO2 saved during cement production (92 yuan / ton)

[0085] Therefore, the supersulfate negative carbon cementitious material of the present invention has significant carbon fixation advantages while having high mechanical properties, solving the problems of low utilization rate of steel slag and desulfurization gypsum and excessive pushing and handling difficulties. It solidifies carbon dioxide while improving the utilization rate of solid wastes such as slag, steel slag and desulfurization gypsum, thereby achieving negative carbon at the raw material level, which plays an important role in the development of the building materials industry and the realization of the "dual carbon" goals. The negative carbon cementitious material prepared according to this method can bring economic benefits of 257 to 336 yuan per ton during engineering applications, and is simple to operate, has a high solid waste utilization rate, is energy-saving and environmentally friendly, has good economy, and is conducive to promotion and application.

Claims

1. A supersulfate negative carbon cementitious material, characterized in that: The cementitious material comprises the following components in parts by mass: 38 to 50 parts of S95 slag, 20 to 30 parts of steel slag, 20 to 25 parts of desulfurized gypsum, 3 to 5 parts of biochar, 3 to 5 parts of zeolite powder, and 2 to 5 parts of Portland cement.

2. The gelling material according to claim 1, characterized in that The steel slag comprises the following components: 12-16% SiO2, 1-4% Al2O3, 31-38% CaO, 25-32% Fe2O3, 3-7% MgO, 0.51-1.5% TiO2, and 0.18-0.52% SO3.

3. The gelling material according to claim 1, characterized in that The desulfurized gypsum composition includes: 1.5-3.2% SiO2, 0.55-0.82% Al2O3, 40-45% CaO, 0.22-0.57% Fe2O3, 0.55-1.23% K2O, 0.82-1.1% MgO, 0.012-0.055% TiO2, and 55-60% SO3.

4. The gelling material according to claim 1, characterized in that The S95 slag has an Al2O3 content greater than 13%; the Portland cement has a strength grade greater than 42.5 MPa.

5. The gelling material according to claim 1, characterized in that The biochar is obtained by thermally decomposing corn and bamboo at 800±100° C. in a nitrogen atmosphere, and is passed through a 50-200 mesh sieve and then dried at 150±25° C.

6. A method for preparing the supersulfate negative carbon cementitious material according to claim 1, characterized in that: The following steps are involved: (1) Pre-grinding the steel slag and desulfurized gypsum in a ball mill and passing through a 200-mesh standard sieve; (2) The pretreated steel slag and desulfurized gypsum are evenly mixed with S95 slag, biochar, zeolite powder and silicate cement.

7. Use of the supersulfate negative carbon cementitious material according to claim 1 in a carbon dioxide solidification building materials project.

8. The use according to claim 7, characterized in that The solidification of carbon dioxide comprises the following steps: (1) Mixing the cementitious material with the admixture and water to obtain a slurry, then pouring the slurry into a mold, demoulding after molding and performing standard curing; (2) The test block after standard curing in step (1) was dried in an oven at 60° C. for 1 day, and carbonized in a gas containing carbon dioxide to obtain a supersulfate negative carbon cementitious material product.

9. The use according to claim 8, characterized in that In step (1), the water-cement ratio of the slurry is 0.38-0.4; the admixture is PCA-1 polycarboxylate water reducer, and the dosage is 2‰ of the cementitious material. After the slurry is poured into the mold, it is covered with plastic wrap and demolded after 24 hours. The standard curing age is 3-28 days.

10. The use according to claim 8, characterized in that In step (2), the carbonization reaction temperature is 25±1° C., the relative humidity is 70±20%, the carbon dioxide concentration is 20±2%, and the gas pressure during the carbonization process is controlled at 0.1-1 MPa.

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