Preparation method of carbonized modified steel slag with improved hydration activity, modified steel slag and active admixture for cement-based cementitious materials

Abstract

The present invention relates to a preparation method of carbonization-modified steel slag with improved hydration activity, modified steel slag and an active admixture for cementitious materials. The preparation method of the present invention includes: dissolving acidic amino acids to obtain an amino acid solution and heating it to the reaction temperature; adding steel slag into the stirring amino acid solution to produce a steel slag suspension, and then introducing CO2 gas into the steel slag suspension to start the reaction; after the reaction is completed, separating the solid from the system, and adding ethanol to the obtained solid, and drying to obtain steel slag. The preparation method of the present invention breaks the inherent view of the prior art, realizes the simultaneous improvement of the soundness and hydration activity of steel slag, and even can improve the hydration activity by extending the reaction time. The operation of the present invention is simple and has strong practicability. In addition, the acidic amino acid additive used belongs to a bio-friendly material and is non-toxic and harmless.

Description

Technical Field

[0001] The present invention relates to a preparation method of carbonized modified steel slag with improved hydration activity, modified steel slag, and an active admixture for cement-based cementitious materials. In particular, the modified steel slag of the present invention can be used to prepare a high-strength steel slag cement composite cementitious material. Background Art

[0002] Steel slag is an industrial by-product generated during the steelmaking process. In recent years, with the rapid development of the steelmaking industry in China, China's steel production has ranked first in the world for many years. At the same time, a large amount of steel slag has been generated, and its waste stockpile is increasing year by year. According to the latest statistics, China's crude steel output reached 1.033 billion tons in 2021, and about 150 million tons of steel slag was generated at the same time. The waste stockpile of steel slag will cause serious pollution to the atmosphere, water resources, and soil, damage the surrounding ecological environment, and occupy a large amount of land resources. Improving the comprehensive utilization rate of steel slag can not only improve the resource utilization rate but also reduce pollutant emissions, contributing to the realization of the national energy conservation and emission reduction goals, which is of great significance to the sustainable development of China and even the world.

[0003] Steel slag can generally be divided into three types: converter slag, open-hearth slag, and electric furnace slag. Due to fluctuations in the raw material composition and different steelmaking processes in steel mills, the composition of steel slag from different steel mills and at different times will have certain fluctuations, but its main chemical components remain unchanged, mainly including CaO, SiO2, Al2O3, Fe2O3, FeO, MgO, and P2O5. The main mineral phase composition of steel slag is C3S, C2S, RO phase, C4AF, C2F, and a small amount of f-CaO, f-MgO, etc., which is similar to Portland cement clinker. Therefore, steel slag has the potential to be used as an active admixture for cement-based cementitious materials.

[0004] However, the silicate content and activity in steel slag are lower than those in cement clinker, and the iron and phosphorus contents are relatively high, resulting in insufficient mechanical strength of the cementitious material using steel slag. On the other hand, f-CaO and f-MgO in steel slag will slowly hydrate, causing volume expansion and ultimately leading to cracking of the cementitious material, that is, the soundness of steel slag is also insufficient.

[0005] To solve the problem of the application of steel slag in cement-based cementitious materials, the key is to improve its soundness, hydration activity, and thus the strength of the cementitious material obtained from it. Carbonation is an important method of continuously introducing CO2 gas into steel slag at a certain temperature and pressure to eliminate free CaO and free MgO, generate stable calcium and magnesium carbonates, and improve the soundness of steel slag. Non-patent document 1 reported that wet carbonation was used to modify steel slag, and then the carbonated steel slag was compounded with cement to prepare a cementitious material. It was found that when the carbonation time was 1 h, the 28-day strength of the cementitious material reached the maximum value. When the carbonation time exceeded 1 h, the strength value decreased with the prolongation of the carbonation time. This is because this method consumes mineral phases such as calcium silicate in steel slag. Although the generated carbonate will play a filling role and promote hydration as the crystal nucleus of the hydration reaction, the overall effect is still inferior to the original silicate phase; in addition, with the prolongation of the carbonation time, more carbonates will replace the originally low-content silicate, further weakening the hydration activity of steel slag.

[0006] It can be seen that there is a need for technologies in the prior art that can simultaneously improve the soundness and hydration activity of steel slag.

[0007] Existing literature:

[0008] Non-patent document 1: Chen Z, Li R, Liu J. Preparation and properties of carbonated steel slag used in cement cementitious materials[J]. Construction and Building Materials, 2021, 283(2): 122667. Summary of the invention

[0009] The purpose of the present invention is to provide a preparation method of modified steel slag that can easily improve the soundness and hydration activity of steel slag simultaneously.

[0010] The purpose of the present invention is to provide a modified steel slag that can improve the soundness and hydration activity simultaneously and an active admixture of cement-based cementitious material using the same.

[0011] According to the in-depth research of the inventors, the following technical solutions can achieve the above purposes of the present invention:

[0012] The preparation method of carbonated modified steel slag with improved hydration activity of the present invention includes:

[0013] Dissolve acidic amino acids to obtain an amino acid solution, and raise the temperature to the reaction temperature;

[0014] Add the steel slag sample to the amino acid solution that is being stirred to produce a steel slag suspension, and then introduce CO2 gas into the steel slag suspension to start the reaction;

[0015] After the reaction ends, separate the solid from the system, and add ethanol to the obtained solid, and dry it to obtain steel slag.

[0016] The present inventors surprisingly found that applying amino acids to the carbonization of steel slag can improve the soundness of steel slag while controlling the transformation of carbonization products into metastable calcium carbonate such as vaterite, thereby optimizing the wet carbonization process of steel slag and improving the hydration activity of steel slag. Therefore, the cement mortar sample obtained by using the modified steel slag of the present invention has higher mechanical strength.

[0017] Furthermore, from the viewpoint of improving the modification efficiency of the present invention, the reaction temperature is preferably 50 to 70 °C, more preferably 55 to 65 °C.

[0018] Furthermore, from the viewpoint of better realizing the effects of the present invention, the acidic amino acid is at least one of L-aspartic acid and L-glutamic acid.

[0019] Furthermore, from the viewpoint of more easily treating steel slag with amino acids, the concentration of the acidic amino acid in the amino acid solution is preferably 0.05 to 0.15 mol / L, more preferably 0.08 to 0.12 mol / L.

[0020] In addition, the solvent for dissolving the acidic amino acid is a solvent containing water. In addition to water, it may optionally contain an organic solvent that can dissolve the acidic amino acid and is miscible with water. Particularly preferably, only water is used to dissolve the acidic amino acid.

[0021] Furthermore, from the viewpoint of more easily treating steel slag with amino acids, the solid-liquid mass ratio of steel slag to amino acid solution in the steel slag suspension is 1:(25 to 35), more preferably 1:(28 to 32).

[0022] Furthermore, from the viewpoint of better simultaneously performing carbonization and controlling the transformation of carbonization products into metastable calcium carbonate, for every 10 g of steel slag, the CO2 gas flow rate is preferably 80 to 100 mL / min.

[0023] Furthermore, although there is no particular limitation on the reaction time of the carbonization reaction of the present invention, from the viewpoint of more effectively realizing the technical effects of the present invention, the reaction time is preferably 0.2 to 5 h, more preferably 0.5 to 4.5 h.

[0024] The modified steel slag of the present invention is obtained by the above preparation method of the present invention. Therefore, the modified steel slag of the present invention improves both soundness and hydration activity.

[0025] The active admixture of the cementitious material of the present invention includes the above-mentioned modified steel slag of the present invention. Therefore, the active admixture of the cementitious material of the present invention simultaneously exhibits excellent soundness and mechanical strength.

[0026] The advantages of the technical solution of the present invention are as follows:

[0027] The preparation method of the present invention breaks the inherent view of the prior art, realizes the simultaneous improvement of the soundness and hydration activity of steel slag, and even can improve the hydration activity by extending the reaction time (as shown in the examples, manifested as the improvement of the mechanical strength of the cement mortar sample).

[0028] The operation of the present invention is simple and highly practical. In addition, the acidic amino acid additive used belongs to a bio-friendly material and is non-toxic and harmless. Description of the Drawings

[0029] Figure 1 It is the SEM image of vaterite on the surface of the carbonized steel slag sample prepared in Example 1. Detailed Embodiments

[0030] The specific implementation steps of the method of the present invention are as follows:

[0031] (1) Add deionized water to the reaction vessel, stir and preheat to 55 - 65 °C.

[0032] (2) Add the acidic amino acid sample to the reaction vessel, keep the reaction temperature constant and stir to dissolve the amino acid to form an amino acid solution (0.05 - 0.15 mol / L). When the pH of the solution drops to about 2 - 4, it can be considered completely dissolved.

[0033] (3) Add the steel slag sample to the amino acid solution (the solid-liquid mass ratio of steel slag to dispersion medium is 1:(25 - 35)) to form a steel slag suspension. At the same time, introduce CO2 gas into the suspension, and control the CO2 flow rate at 80 - 100 mL / min for every 10 g of steel slag.

[0034] (4) After a reaction time of 0.2 - 5 h, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the obtained solid to terminate hydration, and centrifuge after 36 - 72 h. Put the centrifuged solid sample into a vacuum drying oven and dry it at 60 - 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0035] The present invention will be described in more detail below by listing some specific examples.

[0036] Comparative Example 1: Measure 300 mL of deionized water, add it to a reaction vessel, stir and preheat to 60 °C; weigh 10 g of steel slag sample, add it to the vessel to form a steel slag suspension, and simultaneously introduce CO2 gas with a flow rate of 80 mL / min; after a reaction time of 0.5 h, stop the reaction. Centrifuge the suspension to separate the solid and liquid, add anhydrous ethanol to the solid to terminate the hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry it at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0037] Mix the carbonized steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), with a water-binder ratio of 0.5, and prepare a mortar sample according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 40.69 MPa.

[0038] Comparative Example 2: Measure 300 mL of deionized water, add it to a reaction vessel, stir and preheat to 60 °C; weigh 10 g of steel slag sample, add it to the vessel to form a steel slag suspension, and simultaneously introduce CO2 gas with a flow rate of 80 mL / min; after a reaction time of 4 h, stop the reaction. Centrifuge the suspension to separate the solid and liquid, add anhydrous ethanol to the solid to terminate the hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry it at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0039] Mix the carbonized steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), with a water-binder ratio of 0.5, and prepare a mortar sample according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 32.26 MPa.

[0040] Example 1: Measure 300 mL of deionized water, add it to a reaction vessel, stir and preheat to 60 °C; weigh 3.99 g of L-aspartic acid, add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved; weigh 10 g of steel slag sample, add it to the vessel to form a steel slag suspension, and simultaneously introduce CO2 gas with a flow rate of 80 mL / min; after a reaction time of 0.5 h, stop the reaction. Centrifuge the suspension to separate the solid and liquid, add anhydrous ethanol to the solid to terminate the hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry it at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0041] Mix the carbonated steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), and prepare a mortar sample with a water-binder ratio of 0.5 according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 41.59 MPa.

[0042] Example 2: Measure 300 mL of deionized water, add it to the reaction vessel, stir and preheat to 60 °C; weigh 3.99 g of L-aspartic acid, add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved; weigh 10 g of the steel slag sample, add it to the vessel to form a steel slag suspension, and at the same time introduce CO2 gas with a flow rate of 80 mL / min; after 4 h of reaction time, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the solid to terminate hydration, and centrifuge for 48 h. Put the centrifuged solid sample into a vacuum drying oven and dry it at 75 °C for more than 12 h. The obtained powder sample is the carbonated steel slag sample.

[0043] Mix the carbonated steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), and prepare a mortar sample with a water-binder ratio of 0.5 according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 42.38 MPa.

[0044] Example 3: Measure 300 mL of deionized water, add it to the reaction vessel, stir and preheat to 60 °C; weigh 3.99 g of L-aspartic acid, add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved; weigh 12 g of the steel slag sample, add it to the vessel to form a steel slag suspension, and at the same time introduce CO2 gas with a flow rate of 100 mL / min; after 4 h of reaction time, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the solid to terminate hydration, and centrifuge for 48 h. Put the centrifuged solid sample into a vacuum drying oven and dry it at 75 °C for more than 12 h. The obtained powder sample is the carbonated steel slag sample.

[0045] Mix the carbonated steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), and prepare a mortar sample with a water-binder ratio of 0.5 according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 42.71 MPa.

[0046] Example 4: Measure 300 mL of deionized water and add it to a reaction vessel. Stir and preheat to 60 °C. Weigh 4.41 g of L-glutamic acid and add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved. Weigh 10 g of the steel slag sample and add it to the vessel to form a steel slag suspension. At the same time, introduce CO2 gas with a flow rate of 80 mL / min. After a reaction time of 0.5 h, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the solid to terminate hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0047] Mix the carbonized steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), and prepare a mortar sample with a water-binder ratio of 0.5 according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 43.13 MPa.

[0048] Example 5: Measure 300 mL of deionized water and add it to a reaction vessel. Stir and preheat to 60 °C. Weigh 4.41 g of L-glutamic acid and add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved. Weigh 10 g of the steel slag sample and add it to the vessel to form a steel slag suspension. At the same time, introduce CO2 gas with a flow rate of 80 mL / min. After a reaction time of 4 h, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the solid to terminate hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0049] Mix the carbonized steel slag sample with cement and standard sand (the mass fraction of steel slag in the cementitious material is 10%), and prepare a mortar sample with a water-binder ratio of 0.5 according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 43.95 MPa.

[0050] Example 6: Measure 300 mL of deionized water and add it to a reaction vessel. Stir and preheat to 60 °C. Weigh 4.41 g of L-glutamic acid and add it to the vessel to dissolve and form an amino acid solution. When the pH of the solution drops to about 3, it can be considered completely dissolved. Weigh 12 g of the steel slag sample and add it to the vessel to form a steel slag suspension. At the same time, introduce CO2 gas with a flow rate of 100 mL / min. After a reaction time of 4 h, stop the reaction. Centrifuge the suspension for solid-liquid separation, add anhydrous ethanol to the solid to terminate hydration, and centrifuge for 48 h. Place the centrifuged solid sample in a vacuum drying oven and dry at 75 °C for more than 12 h. The obtained powder sample is the carbonized steel slag sample.

[0051] Mix the carbonized steel slag sample with cement and standard sand (the mass fraction of steel slag in the binder is 10%), with a water-binder ratio of 0.5, and prepare the mortar sample according to GB / T 17671-1999. The 28-day compressive strength of the obtained mortar sample is 44.10 MPa.

Claims

1. A preparation method of carbonized modified steel slag with improved hydration activity, characterized in that, It includes: Dissolve acidic amino acids to obtain an amino acid solution, and raise the temperature to the reaction temperature. The solvent used to dissolve acidic amino acids is only water, and the acidic amino acid is L-glutamic acid. The concentration of acidic amino acids in the amino acid solution is 0.05 - 0.15 mol / L; Add steel slag to the stirring amino acid solution to produce a steel slag suspension, and then only introduce CO2 gas into the steel slag suspension. For every 10 g of steel slag, the CO2 gas flow rate is 80 - 100 mL / min, start the reaction, and the reaction time is 4 - 5 h. The solid-liquid mass ratio of steel slag to amino acid solution is 1:(25 - 35); After the reaction is completed, separate the solid from the system, and add ethanol to the obtained solid, and dry to obtain steel slag.

2. The preparation method according to claim 1, wherein The reaction temperature is 50 - 70 °C.

3. The preparation method according to claim 1, characterized in that, The concentration of acidic amino acids in the amino acid solution is 0.08 - 0.12 mol / L.

4. The preparation method according to claim 1, characterized in that, In the steel slag suspension, the solid-liquid mass ratio of steel slag to amino acid solution is 1:(28 - 32).

5. The preparation method according to claim 1, characterized in that, The reaction time is 4 - 4.5 h.

6. A modified steel slag, characterized in that: Obtained by the preparation method according to any one of claims 1 - 5.

7. A cement-based gelling material active admixture, characterized in that: It includes: The modified steel slag according to claim 6.

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