Method for preparing high-carbon-sequestration admixture by synergistically modifying steel slag with acid-magnesium salt and application of high-carbon-sequestration admixture

Abstract

The invention relates to the technical field of low-carbon cement-based materials, in particular to a method for preparing a high-carbon-sequestration admixture through acid-magnesium salt synergistic modification of steel slag and application of the high-carbon-sequestration admixture. The method comprises the following steps: (1) adding steel slag powder and a water-soluble magnesium salt into water, then adding an organic weak acid, and carrying out a reaction under a stirring condition to obtain a pretreated steel slag suspension; and (2) introducing carbon dioxide gas into the pretreated steel slag suspension, and carrying out carbonization reaction under a stirring condition to obtain a carbonized steel slag suspension. And carrying out solid-liquid separation on the mixture, and drying the obtained solid product to obtain the high-carbon-sequestration admixture. The method provided by the invention not only can effectively improve the carbon sequestration amount of the steel slag, but also can improve the mechanical properties of the concrete / cement-based material doped with the steel slag.

Description

Technical Field

[0001] The invention relates to the technical field of low-carbon cement-based materials, and in particular to a method for preparing a high-carbon-fixing admixture by using acid-magnesium salt synergistically modified steel slag and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Steel slag is a solid waste produced during the steel smelting process. Its output is huge, and its high heavy metal content will leach and pollute the surrounding water and soil environment. Steel slag contains a large amount of calcium oxide. For example, the CaO content of converter slag is about 40%. If the CaO in the steel slag is completely carbonized into calcium carbonate, each ton of steel slag can seal about 314kg of CO2. In addition, the free calcium oxide in the steel slag can be greatly reduced after carbonization treatment ( f -CaO) content, reducing the risk of poor volume stability.

[0004] However, as carbonization proceeds, the carbides formed on the surface of the slag will gradually block the pores in the slag, making it difficult for external carbon dioxide gas to enter the slag and interact with the interior. f -CaO reaction, resulting in insufficient carbonization reaction, which not only affects the amount of carbon fixation, but also the residual f -CaO can also easily lead to poor volume stability, causing concrete / cement-based materials mixed with steel slag to crack during service and reduce their bearing capacity. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a high carbon fixation admixture by using acid-magnesium salt synergistically modified steel slag and its application, which can not only effectively increase the carbon fixation amount of steel slag, but also improve the mechanical properties of concrete / cement-based materials added with the steel slag. Specifically, the technical solution of the present invention is as follows.

[0006] First, the present invention discloses a method for preparing a high-carbon-fixing admixture by synergistically modifying steel slag with acid and magnesium salt, comprising the following steps: (1) Add steel slag powder and water-soluble magnesium salt into water, then add linear polyhydroxy organic weak acid and polycarboxylic acid water reducer and stir evenly to obtain a pretreated steel slag suspension for later use.

[0007] (2) Carbon dioxide gas is introduced into the pretreated steel slag suspension, and a carbonization reaction is carried out under stirring conditions, and a carbonized steel slag suspension is obtained after completion. After solid-liquid separation, the obtained solid product is dried to obtain the high solid carbon admixture.

[0008] Furthermore, in step (1), the mass ratio of the steel slag powder to water is 1:8-13.

[0009] Furthermore, in step (1), the steel slag powder includes at least one of converter steel slag powder, electric furnace steel slag powder, open-hearth steel slag powder, etc. Optionally, the specific surface area of ​​the steel slag is 350-550m 2 / kg. The calcium and magnesium elements in the steel slag react with carbon dioxide to form stable carbonate minerals, which play a role in solidifying carbon dioxide and also help reduce the risk of poor volume stability of steel slag admixtures.

[0010] Furthermore, in step (1), the amount of the water-soluble magnesium salt added is 1-5% of the mass of the steel slag powder. Optionally, the magnesium salt includes at least one of magnesium chloride, magnesium nitrate, and magnesium sulfate. In the present invention, the magnesium salt is used to transform the amorphous calcium carbonate formed during the carbonization process into a metastable whisker-like aragonite, providing a channel for carbon dioxide to diffuse into the steel slag, thereby significantly improving the carbonation reaction rate and the degree of carbonization reaction.

[0011] Furthermore, in step (1), the amount of the linear polyhydroxy organic weak acid added is 3-7% of the mass of the steel slag powder. Optionally, the linear polyhydroxy organic weak acid includes at least one of citric acid, gluconic acid, tartaric acid, etc. The linear polyhydroxy organic weak acid used in the present invention not only changes the pore structure of the steel slag, making the surface of the steel slag particles loose and porous, which is conducive to the entry of carbon dioxide into the interior of the steel slag particles and increasing the degree of carbonization reaction, but also utilizes the linear polyhydroxy functional groups of the linear polyhydroxy organic weak acid to promote the formation of nano-scale calcium carbonate particles during the carbonization process.

[0012] Furthermore, in step (1), the polycarboxylate water reducer is 0.3-0.6% of the mass of the steel slag powder.

[0013] Furthermore, in step (1), the stirring time is 15 to 30 minutes.

[0014] Furthermore, in step (2), the gas flow rate of the carbon dioxide is 80-120 ml / min. Preferably, the carbon dioxide is provided by industrial tail gas.

[0015] Furthermore, in step (2), the carbonization reaction time is 50-60 min, and the reaction temperature is 50-65°C.

[0016] Furthermore, in step (2), the drying temperature is 100-130° C., and the drying time is 4-6 hours.

[0017] Secondly, the present invention discloses the use of the acid-magnesium salt synergistic modified steel slag to prepare a high-carbon admixture in cement-based materials, concrete materials, etc. Optionally, the high-carbon admixture is 10-20% of the mass of the cement component.

[0018] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: As mentioned above, as carbonization proceeds, the carbides formed on the surface of the slag will gradually block the pores in the slag, resulting in insufficient carbonization reaction. To this end, the present invention places the slag in water containing magnesium salts and straight-chain polyhydroxy organic weak acids for pretreatment before carbonization. In this process, on the one hand, the straight-chain polyhydroxy organic weak acid changes the pore structure after entering the slag, making the surface of the slag particles loose and porous, which is conducive to the entry of carbon dioxide into the interior of the slag particles during the subsequent carbonization process, increasing the degree of carbonization reaction. On the other hand, the straight-chain polyhydroxy functional groups in the straight-chain polyhydroxy organic weak acids can effectively reduce the activation energy during the crystallization of calcium carbonate, accelerate the formation of crystal nuclei, and improve carbonization efficiency. At the same time, this type of functional group significantly inhibits the agglomeration tendency between crystal nuclei by stabilizing the structure of the new crystal nuclei, and ultimately leads to the generation of nano-scale calcium carbonate particles, and these nano-calcium carbonates can act as nucleation sites of CSH in the cement hydration process to promote cement hydration and improve the early strength of cement. The magnesium carbonate formed by the magnesium ions provided by the magnesium salt during the carbonization process is doped in the calcium carbonate-free calcium carbonate formed by carbonization, making the structure of calcium carbonate looser, thereby providing a channel for carbon dioxide to diffuse into the interior of the steel slag, so that the minerals inside the steel slag continue to dissolve and release more calcium ions for carbonization reaction, thereby significantly improving the carbonation reaction rate and carbonization reaction degree, ensuring the late reaction rate of the carbonization reaction, thereby sealing more carbon dioxide. On the other hand, the polycarboxylate water reducer is adsorbed on the surface of the steel slag so that the steel slag particles are more evenly dispersed in the suspension through electrostatic repulsion, so that it can be more fully contacted with carbon dioxide during carbonization, thereby improving the carbonization efficiency. At the same time, the polycarboxylate water reducer also uses its long chain to prevent the aragonite calcium carbonate formed during the carbonization process from changing to calcite, and the structure of aragonite calcium carbonate is looser, thereby inhibiting the formation of a dense calcite calcium carbonate layer on the surface of the steel slag during the carbonization process, which is conducive to the entry of carbon dioxide into the interior of the steel slag and improving the carbonization efficiency. In addition, these aragonite calcium carbonates can make the cement structure denser after spontaneously transforming into calcite structure during the hydration process of cement materials, thereby achieving later self-enhancement of material strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1This is a sample picture of the high solid carbon admixture prepared in Example 1 below.

[0021] Figure 2 : is a scanning electron microscope (SEM) image of the high solid carbon admixture prepared in Example 1 below.

[0022] Figure 3 The following is an X-ray diffraction (XRD) diagram of the high solid carbon admixture prepared in Example 1.

[0023] Figure 4 This is a compressive strength test diagram of Example 1 below. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0025] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions.

[0026] In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The technical solution of the present invention is further described in conjunction with the accompanying drawings and specific embodiments.

[0027] The main chemical components of the converter slag used in the following examples are shown in the following table: Table 1 Main chemical components of steel slag .

[0028] Example 1 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 0.9g citric acid, 0.3g magnesium chloride, 0.15g polycarboxylate water reducer, and 300g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0029] 2. Add the steel slag and magnesium chloride into deionized water, then add the citric acid and polycarboxylate water reducer, and stir with an electric stirrer for 15 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 120 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0030] 3. Separate the carbonized steel slag suspension into solid and liquid using a vacuum filter, and place the obtained solid in an oven at 105°C for 6 hours for drying. After completion, a high solid carbon admixture is obtained, such as Figure 1 shown.

[0031] Figure 2 This is a SEM image of the high solid carbon admixture prepared in this example. It can be seen that its structure is loose and porous, which provides a good channel for carbon dioxide to enter the steel slag, thereby increasing the late reaction rate of the carbonization reaction and improving the degree of the carbonization reaction.

[0032] Figure 3 This is the XRD diagram of the high solid carbon admixture prepared in this example. It can be seen that after carbonization, part of the calcium carbonate in the steel slag powder exists in the structure of aragonite, which reduces the content of calcite to a certain extent and inhibits the formation of a dense calcium carbonate layer on the surface of the steel slag structure.

[0033] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 17.82%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 15% of the cement component. Then, according to GB / T 17671 1999 "Test Method for Strength of Cement Mortar (ISO Method)", the 3d compressive strength of the test piece was 28.4 MPa, and the 28d compressive strength was 45.1 MPa. The compressive strength test is as follows: Figure 4 shown.

[0034] Example 2 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 1.5g citric acid, 0.3g magnesium sulfate, 0.09g polycarboxylate water reducer, and 240g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0035] 2. Add the steel slag and magnesium sulfate into deionized water, then add the citric acid and polycarboxylate water reducer, and stir with an electric stirrer for 20 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 80 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 65° C. After completion, a carbonized steel slag suspension is obtained.

[0036] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 105° C. and dried for 6 hours to obtain a high solid carbon admixture.

[0037] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 18.52%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 15% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 30.8 MPa, and the 28d compressive strength was 44.6 MPa.

[0038] Example 3 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 2.1g citric acid, 1.5g magnesium chloride, 0.18g polycarboxylate water reducer, and 300g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0039] 2. Add the steel slag and magnesium chloride into deionized water, then add the citric acid and polycarboxylate water reducer, and stir with an electric stirrer for 25 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 110 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0040] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 120° C. and dried for 4 hours to obtain a high-solid carbon admixture.

[0041] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 18.31%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 10% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 29.7MPa, and the 28d compressive strength was 43.5MPa.

[0042] Example 4 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 1.5g gluconic acid, 0.9g magnesium chloride, 0.12g polycarboxylate water reducer, and 360g deionized water. The specific surface area of ​​the steel slag powder is 550m 2 / kg.

[0043] 2. Add the steel slag and magnesium chloride into deionized water, then add the gluconic acid and polycarboxylate water reducer, and stir with an electric stirrer for 15 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 120 ml / min, and stir with an electric stirrer for carbonization reaction at a reaction temperature of 65°C to obtain a carbonized steel slag suspension.

[0044] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 100° C. and dried for 6 hours to obtain a high solid carbon admixture.

[0045] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 20.33%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 20% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 30.3 MPa, and the 28d compressive strength was 45.2 MPa.

[0046] Example 5 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 2.1g tartaric acid, 0.9g magnesium sulfate, 0.18g polycarboxylate water reducer, and 390g deionized water. The specific surface area of ​​the steel slag powder is 350m 2 / kg.

[0047] 2. Add the steel slag and magnesium sulfate into deionized water, then add the tartaric acid and polycarboxylate water reducer, and stir with an electric stirrer for 30 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 50 minutes at a gas flow rate of 100 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 50° C. After completion, a carbonized steel slag suspension is obtained.

[0048] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 130° C. and dried for 5 hours to obtain a high-solid carbon admixture.

[0049] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 18.43%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 16% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 30.5 MPa, and the 28d compressive strength was 45.7 MPa.

[0050] Example 6 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 1.5g citric acid, 1.5g magnesium chloride, 0.12g polycarboxylate water reducer, and 300g deionized water. The specific surface area of ​​the steel slag powder is 530m 2 / kg.

[0051] 2. Add the steel slag and magnesium chloride into deionized water, then add the citric acid and polycarboxylate water reducer, and stir with an electric stirrer for 25 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 110 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0052] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 120° C. and dried for 4 hours to obtain a high-solid carbon admixture.

[0053] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 19.02%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 20% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 28.8MPa, and the 28d compressive strength was 44.9MPa.

[0054] Example 7 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 0.9g citric acid, 0.15g polycarboxylate water reducer, and 300g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0055] 2. Add the steel slag into deionized water, then add the citric acid and polycarboxylate water reducer, and stir with an electric stirrer for 15 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 120 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0056] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 105° C. and dried for 6 hours. After completion, a high solid carbon admixture is obtained.

[0057] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 11.19%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 15% of the cement component. Then, according to GB / T 17671 1999 "Test Method for Strength of Cement Mortar (ISO Method)", the 3d compressive strength of the test piece was 27.3 MPa, and the 28d compressive strength was 41.4 MPa.

[0058] Example 8 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g of dried steel slag powder, 0.3g of magnesium sulfate, 0.09g of polycarboxylic acid water reducer, and 240g of deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0059] 2. Add the steel slag and magnesium sulfate into deionized water, then add the polycarboxylate water reducer and stir with an electric stirrer for 20 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 80 ml / min, and stir with an electric stirrer for carbonization reaction at a reaction temperature of 65°C to obtain a carbonized steel slag suspension.

[0060] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 105° C. and dried for 6 hours to obtain a high solid carbon admixture.

[0061] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 13.04%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 15% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 26.3 MPa, and the 28d compressive strength was 43.8 MPa.

[0062] Example 9 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 2.1g dilute hydrochloric acid (mass fraction 10%), 1.5g magnesium chloride, 0.18g polycarboxylate water reducer, and 300g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0063] 2. Add the steel slag and magnesium chloride into deionized water, then add the dilute hydrochloric acid and polycarboxylate water reducer, and stir with an electric stirrer for 25 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 110 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0064] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 120° C. and dried for 4 hours to obtain a high-solid carbon admixture.

[0065] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 11.25%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 10% of the cement component. Then, according to GB / T 17671 1999 "Test Method for Strength of Cement Mortar (ISO Method)", the 3d compressive strength of the test piece was 26.9MPa, and the 28d compressive strength was 41.7MPa.

[0066] Example 10 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 1.5g acetic acid, 0.3g magnesium sulfate, 0.09g polycarboxylate water reducer, and 240g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0067] 2. Add the steel slag and magnesium sulfate into deionized water, then add the acetic acid and polycarboxylate water reducer, and stir with an electric stirrer for 20 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 80 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 65° C., and a carbonized steel slag suspension is obtained after completion.

[0068] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 105° C. and dried for 6 hours to obtain a high solid carbon admixture.

[0069] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 15.23%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 15% of the cement component. Then, according to GB / T 17671 1999 "Test Method for Strength of Cement Mortar (ISO Method)", the 3d compressive strength of the test piece was 27.6MPa, and the 28d compressive strength was 42.1MPa.

[0070] Embodiment 11 A method for preparing a high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag comprises the following steps: 1. Prepare 30g dried steel slag powder, 0.9g citric acid, 0.3g magnesium chloride, and 300g deionized water. The specific surface area of ​​the steel slag powder is 480m 2 / kg.

[0071] 2. Add the steel slag and magnesium chloride into deionized water, then add the citric acid and stir with an electric stirrer for 15 minutes to obtain a pretreated steel slag suspension. Then, introduce carbon dioxide gas into the suspension for 60 minutes at a gas flow rate of 120 ml / min, and stir with an electric stirrer for carbonization reaction. The reaction temperature is set to 60° C. After completion, a carbonized steel slag suspension is obtained.

[0072] 3. The carbonized steel slag suspension is separated into solid and liquid by a vacuum filter, and the obtained solid is placed in an oven at a temperature of 105° C. and dried for 6 hours. After completion, a high solid carbon admixture is obtained.

[0073] Performance test: (1) The 1h carbon fixation rate of the high carbon fixation admixture prepared in this embodiment was measured by thermogravimetric analysis, and the result was 16.22%. (2) The high carbon fixation admixture prepared in this embodiment was added to cement mortar, and the addition amount was 10% of the cement component. Then, according to GB / T 17671 1999 "Test method for strength of cement mortar (ISO method)", the 3d compressive strength of the test piece was 25.3MPa, and the 28d compressive strength was 40.1MPa.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-carbon solid admixture by acid-magnesium salt synergistically modified steel slag, characterized in that: The steps include: (1) adding steel slag powder and water-soluble magnesium salt into water, and then adding linear polyhydroxy organic weak acid and polycarboxylic acid water reducer and stirring evenly to obtain a pretreated steel slag suspension for standby use; (2) introducing carbon dioxide gas into the pretreated steel slag suspension and performing a carbonization reaction under stirring conditions to obtain a carbonized steel slag suspension; After solid-liquid separation, the obtained solid product is dried to obtain the high solid carbon admixture.

2. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (1), the mass ratio of the steel slag powder to water is 1:8-13; Optionally, in step (1), the steel slag powder comprises: at least one of converter steel slag powder, electric furnace steel slag powder, and open-hearth steel slag powder; Optionally, the specific surface area of ​​the steel slag is 350-550m 2 / kg.

3. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (1), the amount of water-soluble magnesium salt added is 1-5% of the mass of the steel slag powder.

4. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (1), the magnesium salt includes at least one of magnesium chloride, magnesium nitrate and magnesium sulfate.

5. The method for preparing high-carbon-fixing admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (1), the amount of organic weak acid added is 3-7% of the mass of the steel slag powder; Optionally, in step (1), the organic weak acid comprises: at least one of citric acid, gluconic acid, and tartaric acid; Optionally, in step (1), the stirring time is 15 to 30 minutes.

6. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (1), the polycarboxylate water reducer is 0.3-0.6% of the mass of the steel slag powder.

7. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (2), the gas flow rate of the carbon dioxide is 80-120 ml / min; preferably, the carbon dioxide is provided by industrial tail gas.

8. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to claim 1, characterized in that: In step (2), the carbonization reaction time is 50-60 min, and the reaction temperature is 50-65°C.

9. The method for preparing high carbon solid admixture by acid-magnesium salt synergistically modified steel slag according to any one of claims 1 to 8, characterized in that: In step (2), the drying temperature is 100-130° C. and the drying time is 4-6 hours.

10. Use of a high-fixed carbon admixture prepared by the method according to any one of claims 1 to 9 in cement-based materials and / or concrete materials; optionally, the high-fixed carbon admixture accounts for 10-20% of the mass of the cement component.

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