Carbonized steel slag foam concrete and preparation method thereof

Abstract

The invention discloses carbonized steel slag foam concrete, which is prepared from the following raw materials in parts by weight: 30 to 40 parts of steel slag powder, 20 to 40 parts of cement, 5 to 15 parts of coal ash, 20 to 30 parts of water, 0.001 to 0.005 part of aluminum powder paste, 0.5 to 1.5 parts of anhydrous magnesium chloride and 0.005 to 0.01 part of surface dispersing agent, and the surface dispersing agent is one of tetramethylammonium hydroxide and ammonium polyacrylate; the carbonized steel slag foam concrete prepared from the components has the advantages that the carbonization time is short, the compressive strength after carbonization can reach 5.3 MPa or above only through carbonization maintenance for 5-10 h, the dry density and the compressive strength meet the A5.0 B09 level in JC / T 1062-2022 foam concrete blocks, the performance is excellent, the carbonization time is greatly shortened, and the carbonized steel slag foam concrete is suitable for industrial popularization and utilization.

Description

Technical Field

[0001] The invention belongs to the field of foam concrete, and in particular relates to carbonized steel slag foam concrete and a preparation method thereof. Background Art

[0002] Steel slag is a solid waste generated during steel production. Because steel companies are unable to dispose of it themselves, its accumulation has become an environmental problem. To recycle steel slag, it can be incorporated into concrete products as a solid waste, effectively addressing the challenges of limited slag utilization and low efficiency. Steel slag is rich in free calcium oxide and free magnesium oxide. Carbonation curing accelerates the carbonation reaction in steel slag concrete products, effectively absorbing CO₂ to form carbonates and amorphous silica, which fill micropores and create a denser internal structure. This improves mechanical properties, resulting in significant economic, environmental, and social benefits. Using steel slag as a negative carbon material not only effectively reuses solid waste resources and addresses the environmental pollution caused by unprocessed steel slag, but also effectively sequesters CO₂ through carbonation curing, mitigating the environmental pressures caused by large-scale greenhouse gas emissions. Carbonation curing can significantly improve the mechanical properties of steel slag concrete products in a short period of time, shorten curing cycles, and reduce production costs, driving the building materials industry towards green and energy-saving development.

[0003] However, steel slag currently needs to be carbonized in a carbonization chamber for 1-7 days in concrete products to ensure the final product possesses the required mechanical properties. While this fully utilizes waste generated by steel mills and solves the problem of steel slag accumulation, the prolonged carbonization time does not improve production efficiency, thus presenting production limitations. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a carbonized steel slag foam concrete and a preparation method thereof, so as to solve the problem of long carbonization time when using steel slag to prepare concrete in the prior art.

[0005] Technical solution: The carbonized steel slag foam concrete of the present invention comprises the following raw materials in parts by weight: 30-40 parts of steel slag powder, 20-40 parts of cement, 5-15 parts of fly ash, 20-30 parts of water, 0.001-0.005 parts of aluminum powder paste, 0.5-1.5 parts of anhydrous magnesium chloride, and 0.005-0.01 parts of a surface dispersant, wherein the surface dispersant is one of tetramethylammonium hydroxide and ammonium polyacrylate.

[0006] The present invention uses steel slag powder as the main negative carbon material and anhydrous magnesium chloride as a carbonization activator. Anhydrous magnesium chloride can destroy the surface structure of steel slag minerals and accelerate the dissolution of internal alkali metal ions such as calcium and magnesium, thereby providing a large amount of calcium and magnesium ions for the carbonization reaction. In the present invention, a surfactant and anhydrous magnesium chloride are used in combination. On the one hand, the surfactant can be adsorbed on the surface of anhydrous magnesium chloride particles, reducing the surface tension between anhydrous magnesium chloride particles. When the raw material is ball-milled, anhydrous magnesium chloride with ultrafine particle size and good dispersibility is obtained, thereby giving full play to its surface effect and promoting the progress of the carbonization reaction. On the other hand, the surfactant cooperates with anhydrous magnesium chloride, based on the fact that anhydrous magnesium chloride pre-destroys the surface structure of steel slag minerals, to promote the precipitation of alkaline ions such as calcium and magnesium inside the steel slag minerals, thereby promoting the progress of the carbonization reaction. The surfactant steric hindrance effect and metal ion complexing ability can also be brought into play to provide a favorable alkaline environment for promoting the carbonization reaction, thereby achieving better improvement in the mechanical properties of steel slag foam concrete after carbonization.

[0007] Specifically, in the steel slag cementitious system, the tetramethylammonium ions and hydroxide ions produced by the hydrolysis of tetramethylammonium hydroxide can enhance the ionic strength of the steel slag cementitious system, thereby reducing the electrostatic repulsion between cations such as calcium and magnesium and increasing the ion migration capacity; the hydroxide ions produced by the hydrolysis of tetramethylammonium hydroxide can effectively increase the alkalinity inside the steel slag concrete product system, generate more easily carbonizable components such as calcium hydroxide to adhere to the surface, and facilitate the carbonization reaction; the tetramethylammonium ions produced by the hydrolysis of tetramethylammonium hydroxide can also change the migration and diffusion of calcium and magnesium ions. The tetramethylammonium ions have a larger volume and occupy a larger space, and can exert their steric hindrance effect, causing the calcium and magnesium ions in the steel slag cementitious system to migrate to the external surface in large quantities under the condition of reduced electrostatic repulsion; therefore, tetramethylammonium hydroxide can increase the alkalinity of the system and at the same time increase the concentration of calcium and magnesium ions on the surface of the steel slag particles, thereby increasing the contact probability of the surface calcium and magnesium ions with carbon dioxide, thereby facilitating the carbonization reaction.

[0008] Ammonium polyacrylate has a certain alkali metal ion complexing ability. The carboxyl group of its hydrolysis product can react with metal ions such as calcium and magnesium in steel slag to form a complex reaction, accelerate the dissolution and precipitation of metal ions such as calcium and magnesium in steel slag, and form stable complexes. These complexes can fully participate in the carbonization reaction to form more carbonized products to fill the structure; its steric hindrance effect is conducive to the uniform nucleation rate and stable crystal growth of carbonized products such as calcium carbonate and magnesium carbonate in the early stage of the carbonization reaction, forming carbonized products with more uniform particle size to fill the microscopic pores, thereby increasing the reaction probability of carbon dioxide and hydroxides in the steel slag gel system, and facilitating the stable progress of the carbonization reaction in the middle and late stages.

[0009] Furthermore, the steel slag powder used in the foamed concrete of the present invention has A (CaO+MgO) ≥ 45%.

[0010] The method for preparing the carbonized steel slag foamed concrete of the present invention comprises the following steps:

[0011] (1) Grind the steel slag powder to a specific surface area of ​​≥370m 2 / kg;

[0012] (2) mixing the milled steel slag powder, cement, fly ash powder, anhydrous magnesium chloride and surface dispersant evenly, then adding warm water and mixing evenly, adding aluminum powder paste, and stirring evenly to obtain a mixed slurry;

[0013] (3) The mixture is first coated with a water-locking film and dried at a constant temperature for 10-15 hours to harden and form the steel slag foam concrete;

[0014] (4) Carbonizing and curing the steel slag foam concrete for 5-10 hours using CO2 at a concentration of 90-99% to obtain carbonized steel slag foam concrete.

[0015] Furthermore, the method for preparing the carbonized steel slag foamed concrete of the present invention comprises the following steps:

[0016] (1) mixing anhydrous magnesium chloride and a surface dispersant and performing ball milling modification to obtain modified anhydrous magnesium chloride;

[0017] (2) Grind the steel slag powder to a specific surface area of ​​≥370m 2 / kg;

[0018] (3) mixing the milled steel slag powder, cement, fly ash powder, and modified anhydrous magnesium chloride, adding warm water and mixing evenly, then adding aluminum powder paste and stirring evenly to obtain a mixed slurry;

[0019] (4) The mixture is first coated with a water-locking film, dried at a constant temperature for 10-15 hours to harden and form, and the surface is removed to obtain steel slag foam concrete;

[0020] (5) Carbonization curing of steel slag foam concrete is performed for 5-10 hours using CO2 at a concentration of 90-99% to obtain carbonized steel slag foam concrete.

[0021] Furthermore, in step (1), the mixing ball milling condition is ball milling at a rotation speed of 400-500 rpm for 5-30 minutes.

[0022] Furthermore, in step (3), the temperature of the warm water is 40-60°C.

[0023] Furthermore, in step (4), the constant temperature drying temperature is 40-60°C.

[0024] Furthermore, in step (5), the carbonization curing conditions are a temperature of 60-90° C. and a pressure of 1.0-2.0 MPa.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the carbonized steel slag foam concrete prepared by the present invention has a short carbonization time, requiring only 5-10 hours of carbonization curing, and the compressive strength after carbonization can reach more than 5.3 MPa. The dry density and compressive strength meet the A5.0B09 level in JC / T 1062-2022 "Foam Concrete Blocks". It not only has superior performance, but also greatly shortens the time required for carbonization, and is suitable for industrial promotion and utilization. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below with reference to the embodiments.

[0027] It should be noted that the raw materials used in the present invention can all be purchased commercially. The components of the steel slag powder used are shown in Table 1. Tetramethylammonium hydroxide is a colorless needle-shaped crystal that is easily soluble in water, with a content of ≥98.0%; ammonium polyacrylate is a colorless, transparent granule that is easily soluble in water, with a purity of ≥98.0%; and anhydrous magnesium chloride is a white powder with a content of ≥98%.

[0028] Table 1 Component content of steel slag powder

[0029] Chemical composition CaO <![CDATA[SiO2]]> MgO <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> Other substances content / % 29.7 24.6 17.4 8.6 11.3 margin

[0030] Example 1

[0031] The component contents of the carbonized steel slag foamed concrete of Example 1 are shown in Table 2 below.

[0032] Table 2 Component contents of steel slag foam concrete in Example 1

[0033] Components steel slag cement fly ash Anhydrous magnesium chloride Tetramethylammonium hydroxide Aluminum powder paste water Weight parts / parts 35 25 10 1 0.01 0.002 25

[0034] The method for preparing carbonized steel slag foamed concrete of Example 1 comprises the following steps:

[0035] (1) Anhydrous magnesium chloride and tetramethylammonium hydroxide were mixed and ball-milled at a rotation speed of 420 rpm for 10 min to obtain high-energy ball-milled modified anhydrous magnesium chloride.

[0036] (2) Ball mill the steel slag powder to obtain a specific surface area ≥370m 2 / kg of steel slag powder.

[0037] (3) The ground steel slag powder, cement, fly ash and high-energy ball-milled modified anhydrous magnesium chloride powder were mixed evenly according to weight proportions, warm water at 50°C was added and stirred slowly for 15 minutes, and then aluminum powder paste was added and stirred for 40 seconds to obtain a mixed slurry.

[0038] (4) Pour the obtained mixed slurry into the mold, cover it with plastic wrap, and place it in a constant temperature forced air drying oven at 50°C for 12 hours to harden and shape it.

[0039] (5) Cut off the upper surface of the mold from the hardened sample to obtain a steel slag foam concrete test block.

[0040] (6) The steel slag foam concrete specimens were carbonized and cured for 8 h at a temperature of 70°C and a pressure of 1.5 MPa using 98% CO2 to obtain carbonized steel slag foam concrete.

[0041] Example 2

[0042] The component contents of the carbonized steel slag foamed concrete of Example 2 are shown in Table 2. The preparation method of the carbonized steel slag foamed concrete of Example 2 is the same as that of Example 1.

[0043] Table 3 Component contents of steel slag foam concrete in Example 2

[0044] Components steel slag cement fly ash Anhydrous magnesium chloride Ammonium polyacrylate Aluminum powder paste water Weight parts / parts 35 25 10 1 0.01 0.002 25

[0045] Example 3

[0046] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 3 are the same as those of Example 1, except that the mixing and ball milling time is 20 minutes.

[0047] Example 4

[0048] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 4 are the same as those of Example 2, except that the mixing and ball milling time is 20 minutes.

[0049] Example 5

[0050] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 5 are the same as those of Example 1, except that the mixing and ball milling time is 30 minutes.

[0051] Example 6

[0052] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 6 are the same as those of Example 2, except that the mixing and ball milling time is 30 minutes.

[0053] Example 7

[0054] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 7 are the same as those of Example 1, except that the mixing ball mill rotation speed is 450 rpm.

[0055] Example 8

[0056] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 8 are the same as those of Example 1, except that the mixing ball milling speed is 450 rpm and the mixing ball milling time is 20 min.

[0057] Example 9

[0058] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 9 are the same as those of Example 1, except that the mixing ball milling speed is 450 rpm and the mixing ball milling time is 30 min.

[0059] Example 10

[0060] The component contents and preparation method of the carbonized steel slag foamed concrete of Example 10 are the same as those of Example 1, except that the mixing ball mill rotation speed is 480 rpm.

[0061] Example 11

[0062] The component content and preparation method of the carbonized steel slag foam concrete in Example 11 are the same as those in Example 1, except that the mixing ball milling speed is 480 rpm and the mixing ball milling time is 20 min.

[0063] Example 12

[0064] The component content and preparation method of the carbonized steel slag foam concrete of Example 12 are the same as those of Example 1, except that the mixing ball milling speed is 480 rpm and the mixing ball milling time is 30 min.

[0065] Example 13

[0066] The component contents of the carbonized steel slag foamed concrete of Example 13 are shown in Table 4 below.

[0067] Table 4 Component contents of steel slag foam concrete in Example 13

[0068] Components steel slag cement fly ash Anhydrous magnesium chloride Tetramethylammonium hydroxide Aluminum powder paste water Weight parts / parts 35 25 10 1 0.005 0.002 25

[0069] The preparation method of the carbonized steel slag foamed concrete in Example 13 is the same as that in Example 1.

[0070] Example 14

[0071] The component contents of the carbonized steel slag foamed concrete of Example 14 are shown in Table 5 below.

[0072] Table 5 Component contents of steel slag foam concrete in Example 14

[0073] Components steel slag cement fly ash Anhydrous magnesium chloride Ammonium polyacrylate Aluminum powder paste water Weight parts / parts 35 25 10 1 0.005 0.002 25

[0074] The preparation method of the carbonized steel slag foamed concrete in Example 13 is the same as that in Example 1.

[0075] Example 15

[0076] The component contents of the carbonized steel slag foamed concrete of Example 15 are shown in Table 6 below.

[0077] Table 6 Component contents of steel slag foam concrete in Example 15

[0078] Components steel slag cement fly ash Anhydrous magnesium chloride Tetramethylammonium hydroxide Aluminum powder paste water Weight parts / parts 40 40 15 1.5 0.005 0.005 30

[0079] The preparation method of the carbonized steel slag foamed concrete in Example 15 is the same as that in Example 1.

[0080] Example 16

[0081] The component contents of the carbonized steel slag foamed concrete of Example 16 are shown in Table 7 below.

[0082] Table 7 Component contents of steel slag foam concrete in Example 16

[0083] Components steel slag cement fly ash Anhydrous magnesium chloride Ammonium polyacrylate Aluminum powder paste water Weight parts / parts 40 40 15 1.5 0.005 0.005 30

[0084] The preparation method of the carbonized steel slag foamed concrete in Example 16 is the same as that in Example 1.

[0085] Example 17

[0086] The component contents of the carbonized steel slag foamed concrete of Example 17 are shown in Table 2, which are consistent with those of Example 1, except for the preparation method, which includes the following steps:

[0087] (1) Ball mill the steel slag powder to obtain a specific surface area ≥370m 2 / kg of steel slag powder.

[0088] (2) The ground steel slag powder, cement, fly ash, ball-milled anhydrous magnesium chloride, and tetramethylammonium hydroxide powders were mixed evenly according to weight proportions, and warm water at 50°C was added and stirred slowly for 15 minutes. Then, aluminum powder paste was added and stirred for 40 seconds to obtain a mixed slurry.

[0089] (4) Pour the obtained mixed slurry into the mold, cover it with plastic wrap as the water-locking film, and place it in a constant temperature blast drying oven at 50°C for 12 hours to harden and shape it.

[0090] (5) Cut off the upper surface of the mold from the hardened sample to obtain a steel slag foam concrete test block.

[0091] (6) The steel slag foam concrete specimens were carbonized and cured for 8 h at a temperature of 70°C and a pressure of 1.5 MPa using 98% CO2 to obtain carbonized steel slag foam concrete.

[0092] Comparative Example 1

[0093] The component contents of the carbonized steel slag foamed concrete of Comparative Example 1 are shown in Table 8 below.

[0094] Table 8 Component contents of steel slag foam concrete in Comparative Example 1

[0095] Components steel slag cement fly ash Anhydrous magnesium chloride Aluminum powder paste water Weight parts / parts 35 25 10 1 0.002 25

[0096] The preparation method of the carbonized steel slag foamed concrete in Comparative Example 1 is substantially the same as that in Example 1, except that no surface dispersant is used in step (1).

[0097] Performance testing

[0098] The carbonized steel slag foamed concrete prepared in Comparative Example 1 and Examples 1-17 was used to evaluate the dry density, compressive strength and other properties of the carbonized steel slag foamed concrete in accordance with JC / T1062-2022 “Foamed Concrete Blocks”. The results are shown in Table 9.

[0099] Table 9 Properties of carbonized steel slag foam concrete of Comparative Example 1 and Examples 1-17

[0100]

[0101]

[0102] As shown in Table 9, while comparative Example 1 lacks a surface dispersant and achieves the same carbonization time, its compressive strength only reaches 4.8 MPa. However, the carbonized steel slag foamed concrete prepared using the components of the present invention, with the addition of anhydrous magnesium chloride and a surface dispersant, achieves a carbonization time of only 8 hours. Furthermore, the dry density and compressive strength of the carbonized steel slag foamed concrete meet the A5.0 B09 standards in JC / T 1062-2022, "Foamed Concrete Blocks." This demonstrates that the carbonized steel slag foamed concrete prepared using the components of the present invention exhibits significantly shortened carbonization time and superior mechanical properties, making it more suitable for industrial production.

[0103] In addition, in the preparation method of carbonized steel slag foam concrete of the present invention, it can be seen from Examples 1-16 and Example 17 that the preparation method of first grinding and modifying anhydrous magnesium chloride and a surface dispersant together has a significant improvement in the mechanical properties of steel slag foam concrete, and during the grinding and modification process, the grinding time and grinding speed need to be strictly controlled to improve the uniformity of the surface dispersant on the surface of anhydrous magnesium chloride. The more uniform the surface dispersant is coated on the surface of anhydrous magnesium chloride, the better the dispersibility of sewage magnesium chloride in the system is, and the better the mechanical properties of the prepared carbonized steel slag foam concrete.

[0104] In addition to the above examples, it should be noted that the steel slag powder used in the present invention has a specific surface area of ​​≥370m 2 / kg, A (CaO + MgO) ≥ 45%; in the present invention, 30-40 parts of steel slag powder, 20-40 parts of cement, 5-15 parts of fly ash, 20-30 parts of water, 0.001-0.005 parts of aluminum powder paste, 0.5-1.5 parts of anhydrous magnesium chloride, and 0.005-0.01 parts of a surface dispersant are used; within the proportion range of the present invention, the carbonization curing time can be shortened, and at the same time, the carbonization has the effect of high compressive strength.

[0105] The technical effects claimed in the present invention can be achieved by adopting the preparation process of the present invention and the specified parameter range, and therefore no further examples are given for verification.

Claims

1. A carbonized steel slag foam concrete, characterized in that: The raw materials include the following by weight: 30-40 parts of steel slag powder, 20-40 parts of cement, 5-15 parts of fly ash, 20-30 parts of water, 0.001-0.005 parts of aluminum powder paste, 0.5-1.5 parts of anhydrous magnesium chloride, and 0.005-0.01 parts of a surface dispersant, wherein the surface dispersant is tetramethylammonium hydroxide or ammonium polyacrylate.

2. The carbonized steel slag foam concrete according to claim 1, characterized in that: A (CaO+MgO) in the steel slag powder is ≥45%.

3. A method for preparing the carbonized steel slag foamed concrete according to claim 1, characterized in that: The following steps are involved: (1) Grind the steel slag powder to a specific surface area of ​​≥370m 2 / kg; (2) mixing the milled steel slag powder, cement, fly ash powder, anhydrous magnesium chloride and surface dispersant evenly, then adding warm water and mixing evenly, adding aluminum powder paste, and stirring evenly to obtain a mixed slurry; (3) The mixture is first coated with a water-locking film and dried at a constant temperature for 10-15 hours to harden and form the steel slag foam concrete; (4) Carbonizing and curing the steel slag foam concrete for 5-10 hours using CO2 at a concentration of 90-99% to obtain carbonized steel slag foam concrete.

4. A method for preparing the carbonized steel slag foamed concrete according to claim 1, characterized in that: The following steps are involved: (1) mixing anhydrous magnesium chloride and a surface dispersant and performing ball milling modification to obtain modified anhydrous magnesium chloride; (2) Grind the steel slag powder to a specific surface area of ​​≥370m 2 / kg; (3) mixing the milled steel slag powder, cement, fly ash powder, and modified anhydrous magnesium chloride, adding warm water and mixing evenly, then adding aluminum powder paste and stirring evenly to obtain a mixed slurry; (4) The mixture is first coated with a water-locking film, dried at a constant temperature for 10-15 hours to harden and form, and the surface is removed to obtain steel slag foam concrete; (5) Carbonization curing of steel slag foam concrete is performed for 5-10 hours using CO2 at a concentration of 90-99% to obtain carbonized steel slag foam concrete.

5. The preparation method according to claim 4, characterized in that The mixed ball milling modification is performed by ball milling at a rotation speed of 400-500 rpm for 5-30 minutes.

6. The preparation method according to claim 3 or 4, characterized in that The temperature of the warm water is 40-60°C.

7. The preparation method according to claim 3 or 4, characterized in that The temperature for constant temperature drying of the mixture is 40-60℃.

8. The preparation method according to claim 3 or 4, characterized in that The carbonization curing conditions are a temperature of 60-90° C. and a pressure of 1.0-2.0 MPa.

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