Method for preparing green carbon sequestration concrete brick by compounding industrial solid wastes

Abstract

The invention discloses a method for preparing a green carbon sequestration concrete brick by compounding industrial solid wastes, and belongs to the technical field of building materials. Firstly, steel slag particles are subjected to crushing, autoclaved heat treatment, iron separation and grinding treatment to obtain steel slag particles with different particle sizes; secondly, steel slag and carbide slag are mixed in proportion and ground to target particle size grading, CO2 industrial gas is introduced for micro-pressure carbonization, grinding and drying treatment are conducted after solid-liquid separation, and a composite active cementing material-carbonized steel slag-carbide slag is prepared; and 3, mixing the carbonized steel slag-carbide slag, cement, slag powder, aggregate, a water reducing agent and water in a concrete stirring tank, introducing CO2 industrial gas again, carrying out secondary carbonization, injecting carbonized steel slag-based concrete into a mold, and carrying out compression molding to obtain the green carbon sequestration concrete brick. The problem of poor stability of the steel slag is solved through a two-stage carbonization technology, the gelling activity of the steel slag is excited, the hydration rate and the carbonization strength of a steel slag-carbide slag system are improved, and the usage amount of cement and slag powder is greatly replaced. The green carbon sequestration concrete brick researched and developed by the project has good mechanical properties, and the curing time is shortened by 1 / 3; the preparation method is simple, convenient to operate and low in cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a method for industrially preparing green carbon sequestration concrete bricks by compounding solid wastes. Background Art

[0003] Applying industrial waste residues as mineral admixtures in concrete can significantly save resources, reduce energy consumption, and alleviate the environmental burden. On the one hand, it can reduce the cement usage and carbon emissions. On the other hand, it can reduce the cost of concrete, which is more conducive to alleviating the environmental pressure of industrial waste residues and reducing the air pollution caused by the production of the cement concrete industry, having good economic and social benefits, and being an inevitable way to achieve low-carbon concrete. In recent years, alkaline substances such as calcium- and magnesium-rich silicates and oxides can react with acidic CO2 to form solid carbonate products. This process is called mineral sequestration of CO2. Since industrial solid wastes such as steel slag and carbide slag contain a large amount of alkaline compounds, these industrial solid wastes can be used to sequester CO2 and produce valuable bulk products, including building materials, etc.

[0004] However, there are often problems such as low carbon sequestration rate, complex processes, and difficult application of the generated products in the carbon sequestration of high-calcium solid wastes. According to statistics in 2024, the utilization rate of steel slag in China is less than 30%, and the comprehensive utilization rate of carbide slag is <50%. At present, there are still many bottlenecks in the carbon sequestration and building material utilization of high-calcium industrial solid wastes (such as steel slag and carbide slag), which are mainly manifested as follows: Ø Low carbon sequestration efficiency: The insufficient CO2 absorption rate caused by reaction kinetics limitations results in poor economy; Ø Defects in product performance: The steel slag has low cementitious activity and poor volume stability, and the sulfur / phosphorus impurities in the carbide slag are likely to cause durability problems; Ø Facing the national infrastructure needs, developing an efficient and collaborative solid waste-based mineral admixture technology is the key path to break the deadlock: Ø Component optimization: Compensate for the defects of single materials through multi-component solid waste compounding (such as the steel slag-carbide slag system); Ø Low-carbon activation: Adopt mechanical-chemical combined activation to improve the activity and reduce energy consumption. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for industrially preparing green carbon sequestration concrete bricks by compounding solid wastes in view of the deficiencies existing in the prior art. The active composite cementitious material is composed of carbonated steel slag-carbide slag composite powder, which has a high carbon sequestration rate, high activity and stability, and has broad application prospects in concrete products.

[0006] To solve the technical problems proposed by the present invention, the present invention provides a method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes, comprising raw materials in the following parts by mass: 200-400 parts of steel slag, 30-100 parts of carbide slag, 10-70 parts of ordinary Portland cement, 0-50 parts of slag powder, 780-880 parts of sand, 950-1100 parts of stone, 6-10 parts of water reducing agent, and 170-180 parts of water.

[0007] In the above solution, the carbonized steel slag-carbide slag composite fine powder is obtained by carrying out a carbonization reaction on steel slag and carbide slag in a micro-pressure carbonization device according to a certain solid-liquid ratio.

[0008] In the above solution, the preparation method of the carbonized steel slag-carbide slag composite fine powder comprises the following steps: S1, subjecting the steel slag to autoclave treatment with saturated steam; performing magnetic separation to select iron on the primary coarsely crushed steel slag after autoclaving, and performing crushing and ball milling on the steel slag after iron selection until the particle size is less than 200 mesh and then performing iron selection again to obtain steel slag particles; S2, mixing the steel slag and carbide slag in proportion, grinding to the target particle size gradation, transferring to a micro-pressure carbonization device and dry mixing evenly; adding water and an admixture according to the water-binder ratio, and then introducing industrial waste gas with a CO2 concentration ≥ 15% for the first micro-pressure carbonization; after carbonization, performing solid-liquid separation, grinding and drying to prepare a composite active cementitious material: carbonized steel slag-carbide slag composite fine powder; S3, mixing the carbonized steel slag-carbide slag, cement, slag powder, aggregate, water reducing agent and water in a concrete mixing tank, and then introducing industrial gas with a CO2 concentration ≥ 90% for the second atmospheric pressure carbonization to prepare carbonized steel slag-based concrete; S4, pouring, vibrating and forming the carbonized steel slag-based concrete, statically stopping for 24 h, removing the formwork and putting it into a curing room for curing to obtain green carbon-fixing concrete bricks.

[0009] Further, in the method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes, the particle size gradation of the steel slag-carbide slag composite fine powder is D10 = 5 μm, D50 = 45 μm, and D90 = 75 μm.

[0010] Further, in the method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes, the water-binder ratio is 0.2-0.5.

[0011] Further, in the method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes, during the carbonization treatment, the carbonization pressure is 0.1-0.3 MPa; the first carbonization time is 30-90 min, and the second carbonization time is 0.5-10 min.

[0012] Further, in the method for preparing green carbon - fixing concrete bricks by compounding industrial solid wastes, the mass parts of each raw material used are as follows: 200 - 400 parts of steel slag, 30 - 100 parts of carbide slag, 10 - 70 parts of ordinary portland cement, 0 - 50 parts of slag powder, 780 - 880 parts of sand, 950 - 1100 parts of stone, 6 - 10 parts of water - reducing agent, and 170 - 180 parts of water.

[0013] Further, in the method for preparing green carbon - fixing concrete bricks by compounding industrial solid wastes, active carbonized steel slag - carbide slag composite fine powder is used to replace part of the cement to prepare concrete bricks; the replacement rate is not higher than 90%.

[0014] Further, in the method for preparing green carbon - fixing concrete bricks by compounding industrial solid wastes, the water - reducing agent includes one or several of naphthalene - based, polycarboxylate - based (PCE), and lignosulfonate, and the addition amount is 0.1 - 5% of the dosage of the cementitious material.

[0015] Further, in the method for preparing green carbon - fixing concrete bricks by compounding industrial solid wastes, the green carbon - fixing concrete mixture is poured, vibrated, formed, statically stopped for 24 h, the formwork is removed and then placed in a curing chamber for curing to obtain green carbon - fixing concrete bricks with a compressive strength of 25 ± 3 MPa and a carbonization absorption rate of 5 - 10%.

[0016] Principle of the invention: The present invention relates to a method for preparing green carbon - fixing concrete bricks by using industrial solid wastes (steel slag + carbide slag). Its core principle lies in dual carbonization activation and solid - waste synergistic modification, which are specifically divided into the following key links: 1. Pretreatment of steel slag: Eliminate the hidden danger of soundness Technical principle: Ø Autoclave treatment (150 - 233 °C, 0.5 - 3.0 MPa): Through high - temperature and high - pressure steam, promote the premature hydration of free calcium oxide (f - CaO) and magnesium oxide (f - MgO) in the steel slag to avoid the expansion and cracking of the later - stage concrete.

[0017] Ø Magnetic separation for iron extraction: Remove metallic iron in the steel slag (improve resource utilization rate) and reduce the interference with the cementitious activity.

[0018] Ø Grinding (D10 = 5 μm, D50 = 45 μm, D90 = 75 μm): Increase the specific surface area and improve the efficiency of the subsequent carbonization reaction.

[0019] 2. Composite carbonization of steel slag - carbide slag: Stimulate the cementitious activity Technical principle: Ø Component synergy: Calcium carbide slag (Ca(OH)2≥70%) provides a highly reactive calcium source and forms a reaction matrix with silicate minerals (C2S, C3S) in steel slag. Carbonated steel slag-calcium carbide slag: The role of calcium carbide slag is to adjust the calcium / silicon ratio. Some steel slags have a low calcium content. The calcium-silicon ratio of the steel slag-based cementitious material should neither be too large nor too small. Being too large will affect the stability and strength of the material, while being too small will reduce the carbon sequestration efficiency and durability. The optimal calcium-silicon ratio range is 1.5 - 2.5. In practical applications, it is necessary to optimize the calcium-silicon ratio by adding regulating materials (such as calcium carbide slag, etc.) to obtain the best cementitious properties and carbon sequestration effect.

[0020] Micro-pressure carbonation (CO2≥15%, 0 - 0.3MPa): Under a controllable pressure, CO2 rapidly reacts with Ca(OH)2 to form calcium carbonate (CaCO3), and at the same time reacts with the calcium-silicon phase in steel slag to form C-S-H gel (the cementitious core).

[0021] Ø Secondary grinding after solid-liquid separation: Optimize the particle size distribution of the carbonated products and enhance the filling effect and reaction activity.

[0022] 3. Secondary carbonation of concrete: Improve the hydration rate and strength Technical principle: Ø Component design: Carbonated steel slag-calcium carbide slag fine powder replaces cement (≤90%): As the main cementitious material, it reduces the cement consumption.

[0023] Atmospheric pressure secondary carbonation (0.5 - 10min): During the concrete mixing process, CO2 is introduced to further carbonate the unreacted Ca(OH)2 and C-S-H, forming a dense calcium carbonate network and shortening the curing time.

[0024] Ø Key effects: Carbon absorption rate of 1 - 5%: Re-sequester CO2 and reduce carbon emissions.

[0025] Compressive strength before hydrostatic pressure of 25 - 30MPa: Meet the building material standards and shorten the curing time by 1 / 3.

[0026] The present invention realizes the high-value utilization of industrial solid waste and the large-scale production of low-carbon building materials through three-level regulation of pretreatment modification → composite carbonation activation → secondary carbonation strengthening, which is in line with the development trend of green building materials.

[0027] Compared with the existing technology, the advantages of the present invention over the existing technology are as follows: 1. Synergistic mineralization and efficiency enhancement: Two solid wastes form a synergistic system under specific conditions, and its CO2 fixation efficiency is significantly higher than that of a single component (P<0.05); 2. Active regulation and optimization: After the steel slag is carbonated, the RO phase, free phase and partial C3S / C2S are decomposed, and the cementitious activity decreases; After the reaction of Ca(OH)2 in carbide slag, it still maintains high activity, and the compounding can alleviate the attenuation of the activity of steel slag (Δ activity reduction < 15%); 3. Dual benefits: While achieving a carbonation rate > 80%, improve the cementitious properties of the material, and have both waste resource utilization ("treating waste with waste") and environmental engineering application value. Specific implementation mode

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer and more definite, the following further details the present invention in combination with embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0029] A method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes mainly includes, by mass percentage: 200 - 400 parts of steel slag, 30 - 100 parts of carbide slag, 10 - 70 parts of ordinary Portland cement, 0 - 50 parts of slag powder, 780 - 880 parts of sand, 950 - 1100 parts of stone, 6 - 10 parts of water reducing agent, and 170 - 180 parts of water.

[0030] In the following examples and comparative examples, the steel slag powder is converter steel slag powder, and the following Portland cement is PO42.5 ordinary Portland cement.

[0031] Example 1, a method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes: 400 parts of cementitious materials (320 parts of steel slag, 40 parts of carbide slag, 40 parts of cement), 930 parts of recycled coarse aggregate (stone), 640 parts of recycled fine aggregate (sand), 2 parts of water reducing agent, and 153 parts of water (water-binder ratio 0.38); carbonation pressure 0.2 MPa, carbonation for 60 min for the first time to obtain carbonated steel slag-carbide slag; carbonation for 10 min under normal pressure for the second time to obtain carbonated steel slag-based concrete, pour, vibrate, form, statically stop for 24 h, remove the formwork and place it in the curing room for curing, then the green carbon-fixing concrete bricks can be obtained.

[0032] Example 2, a method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes: 400 parts of cementitious materials (270 parts of steel slag, 70 parts of carbide slag, 60 parts of cement), 930 parts of recycled coarse aggregate (stone), 640 parts of recycled fine aggregate (sand), 2 parts of water reducing agent, and 160 parts of water (water-binder ratio 0.4); carbonation pressure 0.2 MPa, carbonation for 60 min for the first time to obtain carbonated steel slag-carbide slag; carbonation for 10 min under normal pressure for the second time to obtain carbonated steel slag-based concrete, pour, vibrate, form, statically stop for 24 h, remove the formwork and place it in the curing room for curing, then the green carbon-fixing concrete bricks can be obtained.

[0033] Example 3, a method for preparing green carbon - sequestering concrete bricks by compounding industrial solid wastes: 400 parts of cementitious materials (270 parts of steel slag, 70 parts of carbide slag, 60 parts of cement), 930 parts of recycled coarse aggregate, 640 parts of recycled fine aggregate, 2 parts of water - reducing agent, and 180 parts of water (water - binder ratio 0.45); carbonization pressure 0.2 MPa, carbonize for 60 min for the first time to obtain carbonized steel slag - carbide slag; carbonize at normal pressure for 10 min for the second time to obtain carbonized steel - slag - based concrete, then carry out pouring, vibration, molding, static - stop for 24 h, remove the formwork and put it into the curing room for curing, thus obtaining green carbon - sequestering concrete bricks.

[0034] The performance parameters of the green carbon - sequestering concrete bricks prepared by compounding industrial solid wastes in the above - mentioned specific examples and comparative examples are shown in Table 1 below:

[0035] It can be seen from Table 1 that: 1. Optimization of water - binder ratio regulation. The cementitious system of the present invention adopts a water - binder ratio (mass ratio of water to cementitious materials) of 0.38 - 0.45 (Examples 1 - 3), and combines with a water - reducing agent (naphthalene - based / polycarboxylate - based) to accurately regulate fluidity: Ø Low water - binder ratio (0.38) (Example 1): Reduce the porosity and improve the early strength (1 - day compressive strength 10.4 MPa); Ø Moderate water - binder ratio (0.40) (Example 2): Balance workability and strength, 3 - day compressive strength reaches 22.9 MPa; Ø Higher water - binder ratio (0.45) (Example 3): Improve the molding density, but the strength decreases slightly (14 - day compressive strength 23.7 MPa).

[0036] 2. The cement replacement rate reaches 90%. By using carbonized steel slag - carbide slag composite fine powder to replace cement, the proportion of cement in the cementitious materials can be 10%: Ø Synergistic effect of steel slag / carbide slag: Carbide slag (Ca(OH)2≥70%) provides a calcium carbide source, and steel slag (C2S / C3S) generates C - S - H gel, jointly replacing the hydration of cement; Ø Activity optimization: After secondary carbonization, the 14 - day compressive strength of the steel - slag - based concrete reaches 24.8 - 29.9 MPa, meeting the building material standard (≥25 MPa).

[0037] Finally, it is stated that the above examples are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing green carbon - sequestering concrete bricks by compounding industrial solid wastes, characterized in that, It includes the following steps: S1. Autoclaving treatment is carried out on steel slag with saturated steam; magnetic separation is carried out on the primary coarsely crushed steel slag after autoclaving to separate iron. After iron separation, the steel slag is crushed and ball milled to a particle size less than 200 mesh and then iron is separated again to obtain steel slag particles. S2. Mix steel slag and carbide slag in proportion, grind them to the target particle size gradation, transfer them into a micro-pressure carbonization device and dry mix evenly; add water and admixtures according to the water-binder ratio, and then introduce industrial tail gas with a CO2 concentration ≥ 15% for the first micro-pressure carbonization; after carbonization, solid-liquid separation is carried out, followed by grinding and drying to produce a composite active cementitious material: carbonized steel slag-carbide slag composite fine powder. S3. After mixing carbonized steel slag-carbide slag composite fine powder, cement, slag powder, aggregate, water reducer and water in a concrete mixing tank, introduce industrial gas with a CO2 concentration ≥ 90% again for the second atmospheric pressure carbonization to produce carbonized steel slag-based concrete. S4. The carbonized steel slag-based concrete is poured, vibrated, formed, statically stopped for 24 h, the formwork is removed and it is placed in a curing room for curing to obtain green carbon-fixing concrete bricks.

2. The method for preparing green carbon sequestration concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that In the step S1, the particle size gradation of the steel slag-carbide slag composite fine powder is D10 = 5 μm, D50 = 45 μm, D90 = 75 μm.

3. The method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes according to claim 1, wherein, In the step S2, the water-binder ratio is 0.2 - 0.

5.

4. The method for preparing green carbon sequestration concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that, When carbonization treatment is carried out in the step S2, the carbonization pressure is 0.05 - 0.3 MPa; the first carbonization time is 30 - 90 min, and the second carbonization time is 0.5 - 10 min.

5. The method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that, In the step S3, the mass parts of each raw material used are: 200 - 400 parts of steel slag, 30 - 100 parts of carbide slag, 10 - 70 parts of ordinary portland cement, 0 - 50 parts of slag powder, 780 - 880 parts of sand, 950 - 1100 parts of stone, 6 - 10 parts of water reducer, and 170 - 180 parts of water.

6. The method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that, In the step S3, the active carbonized steel slag-carbide slag composite fine powder is used to replace part of the cement to prepare concrete bricks, and the replacement rate is not higher than 90%.

7. The method for preparing green carbon-fixing concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that, In the step S3, the water reducer includes one or several of naphthalene series, polycarboxylate series (PCE), and lignosulfonate, and the addition amount is 0.1 - 5% of the amount of the cementitious material.

8. The method for preparing green carbon sequestration concrete bricks by compounding industrial solid wastes according to claim 1, characterized in that, In the step S4, the green carbon-fixing concrete mixture is poured into a product mold and statically pressed into shape and cured to obtain green carbon-fixing concrete bricks with a compressive strength of 25 ± 3 MPa and a carbonization absorption rate of 5 - 10%.

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