Preparation method of reducing slag treatment material, reducing slag treatment material and concrete containing reducing slag treatment material

Abstract

This invention provides a method for preparing a reducing slag treatment material using electric furnace reducing slag, wherein the reducing slag treatment material has γ-C₂S and / or magnesium silicate calcium aluminate as its main components. The method for preparing the reducing slag treatment material includes a composition adjustment step and a slow cooling step, and uses reducing slag to prepare a reducing slag treatment material with γ-C₂S and / or magnesium silicate calcium aluminate as its main components. The composition adjustment step adjusts the composition of the reducing slag discharged from the electric furnace; the slow cooling step slowly cools the composition-adjusted reducing slag. Specifically, in the composition adjustment step, the reducing slag is adjusted so that in a chemical composition where the total weight percentages of CaO, SiO₂, Al₂O₃, and MgO are 100%, the weight percentages of CaO are 40-65%, SiO₂ are 15-45%, Al₂O₃ are 1-30%, and MgO are 5-15%. Furthermore, in the slow cooling step, the composition-adjusted reducing slag is slowly cooled in a reducing atmosphere.

Description

Technical Field

[0001] This invention relates to a method for preparing reducing slag treatment materials, reducing slag treatment materials, and concrete containing reducing slag treatment materials, particularly to a method for preparing reducing slag treatment materials with γC2S (γ-2CaO·SiO2) and / or magnesium silicate calcium stone (3CaO·MgO·2SiO2) as the main components, reducing slag treatment materials, and concrete containing reducing slag treatment materials. Background Technology

[0002] Cement has long been used extensively as a raw material for concrete. Because its production process uses fossil fuels, it is a material with high carbon dioxide emissions. Therefore, as part of measures to combat global warming, it is necessary to reduce carbon dioxide emissions during concrete production.

[0003] In this process, the following invention has been proposed: using γC2S or magnesium silicate calcium stone, which is easily reactive with carbon dioxide, as an admixture, and kneading it with a small amount of water, cement and aggregate (fine and coarse) to form a concrete-like substance, and hardening it by absorbing a high concentration of carbon dioxide, thereby fixing a large amount of carbon dioxide inside the cement-based material (concrete) (see Patent Document 1, Non-Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-168436

[0005] Non-Patent Literature 1: Minoru Morioka and Koji Okuyama, “Research on Cement-Based Materials with Self-Defense Functions for Neutralization,” Civil Engineering Society, Concrete Technology Series No. 74, Summary of Reports and Seminars of the Subcommittee on the Study of Physical Property Changes and Performance of Concrete Using Blended Materials, 2007. Non-Patent Literature 2: Kenzo Watanabe, “Development and Experimental Construction of EIEN, a High-Durability Technology for Carbonated Curing Concrete,” Concrete Engineering, Vol. 45, No. 7, pp. 31-37, 2007. Summary of the Invention

[0006] Thus, γC2S and magnesium silicate calcium stone can become key materials for building a carbon-neutral or negative carbon society.

[0007] On the other hand, the preparation of γC₂S, for example, involves mixing limestone or silica, adjusting the composition, and then calcining at 1200-1400°C. This process produces a relatively expensive material, making mass production difficult. The same applies to calcium silicate.

[0008] In addition, the decarbonization and oxidation of limestone and the use of large amounts of fossil fuels are indispensable in the preparation of γC2S or magnesium silicate calcium stone. Therefore, the carbon dioxide emissions will be higher than the carbon dioxide absorption (fixation), which will lead to the problem of positive carbon.

[0009] Therefore, there is a need for a technology that can effectively obtain compositions with γC2S or magnesium silicate calcium stone as the main components, while not emitting carbon dioxide during the preparation of the compositions.

[0010] However, there is a type of electric arc furnace (EAF) reducing slag, which is a material with a chemical composition similar to γ-C₂S or magnesium silicate calcium silicate. EAF reducing slag and EAF oxidizing slag are produced in the refining process of ironmaking, where scrap iron, the main raw material, is recycled. Currently, EAF reducing slag and EAF oxidizing slag are mixed and used as low-value-added civil engineering materials.

[0011] Therefore, in the ironmaking and steelmaking and rolling industries, there is a need to effectively utilize the reducing slag discharged from electric furnaces, that is, to seek to shift towards high value-added material applications.

[0012] The present invention is based on the above-mentioned problems. The purpose of the present invention is to provide a method for preparing a reducing slag treatment material, which can effectively prepare a composition with γC2S or magnesium silicate calcium stone as the main components using electric furnace reducing slag.

[0013] In addition, another object of the present invention is to provide the above-mentioned reducing slag treatment material and concrete containing the above-mentioned reducing slag treatment material, which contains the above-mentioned reducing slag treatment material and is able to effectively fix carbon dioxide.

[0014] Through in-depth research, the inventors of this invention discovered that the conventional electric furnace reduction slag discharged from the electric furnace contains relatively little γC2S and / or magnesium silicate calcium stone. However, by adjusting the composition of the reduction slag under certain conditions and slowly cooling it, a reduction slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components can be effectively prepared.

[0015] Furthermore, this preparation method does not use fossil fuels as in the past, and can produce a cement-based material (concrete) that can effectively fix carbon dioxide, enabling a carbon-neutral (negative carbon) society, which makes this invention possible.

[0016] Therefore, the aforementioned problem is solved by the following method. According to the present invention, a method for preparing a reducing slag treatment material with γC₂S (γ-2CaO·SiO₂) and / or calcium silicate (3CaO·MgO·2SiO₂) as the main components using reducing slag discharged from an electric furnace is provided. The method includes a composition adjustment step and a slow cooling step. The composition adjustment step adjusts the composition of the reducing slag so that, in a chemical composition where the total weight percentages of CaO, SiO₂, Al₂O₃, and MgO are 100%, the weight percentages of CaO are 40-65%, SiO₂ are 15-45%, Al₂O₃ are 1-30%, and MgO are 5-15%, with the total weight percentages of all components being 100%. The slow cooling step involves slowly cooling the composition-adjusted reducing slag in a reducing atmosphere.

[0017] At this point, it is preferable to adjust the composition of the reducing slag in the composition adjustment process so that CaO and SiO2 are the main components, and in a chemical composition in which the total weight percentage of CaO, SiO2, Al2O3 and MgO is 100%, the weight percentage of CaO is 45-62%, the weight percentage of SiO2 is 20-40%, the weight percentage of Al2O3 is 2-23%, and the weight percentage of MgO is 5-15%.

[0018] In addition, it is preferable to adjust the composition of the reducing slag in the composition adjustment process so that it has the composition of the primary crystallization region of C2S in the ternary phase diagram of CaO-SiO2-Al2O3 (MgO weight percentage = 10%).

[0019] In addition, it is preferable that in the slow cooling process, the reduced residue after composition adjustment is slowly cooled in a temperature gradient of less than 20°C / minute within the range of 400-800°C.

[0020] In addition, it is preferable that, in order to obtain the γC2S contained in the reduced slag after composition adjustment, no slag pulverization inhibitor is added to prevent the conversion from αC2S and / or βC2S to γC2S.

[0021] Furthermore, the aforementioned problem is solved in the following manner. According to the present invention, a reducing slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components is provided. In a chemical composition in which the total weight percentage of CaO, SiO2, Al2O3, and MgO is 100%, the weight percentage of CaO is 40-65%, the weight percentage of SiO2 is 15-45%, the weight percentage of Al2O3 is 1-30%, and the weight percentage of MgO is 5-15%, with the total weight percentage of each component being 100%. This composition represents the primary crystallization region of C2S in the ternary phase diagram of CaO-SiO2-Al2O3 (the weight percentage of MgO is 10%).

[0022] Furthermore, the aforementioned problem is solved in the following way. According to the present invention, there is a concrete containing a reducing slag treatment material, which contains the reducing slag treatment material prepared by the above-described preparation method and fixes carbon dioxide.

[0023] According to the present invention, a method for preparing a reducing slag treatment material can be provided, which can effectively prepare a composition with γC2S and / or magnesium silicate calcium stone as the main components using electric furnace reducing slag.

[0024] In addition, it is possible to provide the above-mentioned reducing slag treatment material and concrete containing the reducing slag treatment material, which contains the above-mentioned reducing slag treatment material and can effectively fix carbon dioxide. Attached Figure Description

[0025] Figure 1 The ternary phase diagram is for CaO-SiO2-Al2O3 (MgO weight percentage = 10%).

[0026] Figure 2 A graph showing the test results of Test Example 1, which confirmed the abundance of γC2S and magnesium silicate calcium stone and the activity of carbon dioxide. Detailed Implementation

[0027] The following is for reference Figures 1-2 The embodiments of the present invention will be described.

[0028] This embodiment is an invention related to a "method for preparing reducing slag treatment materials". Its main features are: including a "composition adjustment step" for adjusting the composition of reducing slag discharged from an electric furnace and a "slow cooling step" for slowly cooling the composition-adjusted reducing slag, and using the reducing slag to prepare reducing slag treatment materials with γC2S and / or magnesium silicate calcium stone as the main components.

[0029] In addition, there are inventions related to "reduction slag treatment materials" and "concrete containing reduction slag treatment materials".

[0030] <Reducing Slag Treatment Materials>

[0031] In the steel smelting process, there are blast furnace / converter and electric furnace smelting methods. The former discharges "blast furnace slag" and "converter slag", while the latter discharges "electric furnace slag".

[0032] In an electric arc furnace, steel is produced by heating and melting scrap iron (iron scrap) from the outside, and then refining it through oxidation and reduction. The slag produced during oxidation refining is called "oxidation slag," and the slag produced during reduction refining is called "reduction slag." Both oxidation slag and reduction slag are collectively referred to as "electric arc furnace slag."

[0033] "Oxidation slag" is the slag produced during the oxidation refining process when molten steel is stirred. Oxidation slag contains about 30% iron oxides dissolved in metallic iron and slag, and is a relatively dense hard slag.

[0034] "Reduction slag" is the slag produced during the reduction refining process after oxidative refining, when the oxidized slag is discharged and quicklime or other materials are added to remove oxygen from the molten steel.

[0035] Like blast furnace slag, reducing slag is a composition primarily composed of CaO, SiO2, Al2O3, and MgO. When the C2S in the reducing slag transforms from the α or β phase to the γ phase during low-temperature phase transitions, its low density causes pulverization (grinding), making subsequent processing difficult (for example, slag with a basicity CaO / SiO2 weight ratio of approximately 1.5 or higher has the property of transforming from the α or β phase to the γ phase during its cooling process via a 2CaO / SiO2 phase transition). Therefore, fluorine-based or boron-based slag pulverization inhibitors are typically added to suppress the transformation from the α or β phase to the γ phase, maintaining the lumpy form during cooling treatment.

[0036] Reaction 1

[0037]

[0038] For example, as shown in the above reaction formula, a phase transition to the γ phase occurs within the conversion temperature range of 675℃, resulting in a volume change of approximately 1.12 times. The entire block expands and pulverizes, making it a C2S material with very poor processability. Conversely, the reducing slag discharged from the electric furnace provides an environment in which γC2S can be easily obtained.

[0039] Generally, the reducing slag discharged from the electric furnace (which is kept in block form and cooled) is mixed with the oxidizing slag, and after the unreacted components such as unreacted free lime (f-CaO) are hydrated and cured, it is used as a civil engineering material such as roadbed material.

[0040] "γC2S," also known as γ-type dicalcium silicate, is a material whose chemical composition is expressed as γ-2CaO·SiO2. Additionally, in Figure 1The ternary phase diagram of CaO-SiO2-Al2O3 (MgO weight percentage = 10%) shows the composition of the primary crystal region of "C2S".

[0041] γC2S is a carbon dioxide-active material. Although it typically lacks hydration activity, it is a highly valuable material for use as a concrete admixture. Specifically, by mixing γC2S with water, a small amount of cement, and aggregates (fine and coarse) to form a mortar / concrete mixture, and then contacting it with a high concentration (e.g., 5-20%) of carbon dioxide, a hardened mortar / concrete with normal strength can be obtained in a short time (e.g., about five days). At this point, a large amount of carbon dioxide can be fixed within the concrete.

[0042] γC₂S is generally obtained by crushing limestone and silica, followed by calcination in a converter at 1200-1400°C. At this stage, if the temperature is too low, unreacted CaO will remain; if the temperature is too high, βC₂S will undergo a high-temperature phase transition. In particular, the more oxidizing the atmosphere, the more likely βC₂S will remain.

[0043] Furthermore, limestone is used as the main raw material, and calcination requires a large amount of fossil fuels. Therefore, even if conventional preparation methods attempt to produce γC2S as a material for carbon dioxide fixation, positive carbon is already generated during the production of γC2S.

[0044] "Merwinite" is a material with a chemical composition expressed as 3CaO·MgO·2SiO2. Additionally, in... Figure 1 The ternary phase diagram shown represents the composition of the primary crystal region of "magnesium silicate calcium silicate".

[0045] Like γC2S, magnesium silicate calcium stone is a carbon dioxide-active material and is a highly valuable material for use as a concrete admixture.

[0046] The "reduction slag treatment material" of this embodiment is a composition with γC2S and / or magnesium silicate calcium stone as the main components, and the main chemical components include CaO, SiO2, Al2O3, and MgO. In addition, it may further include chemical components derived from reduction slag, and may also further include chemical components derived from additives or regulators (e.g., refining aids).

[0047] (chemical composition)

[0048] In the chemical composition of the reducing slag treatment material, where the total weight percentage of CaO, SiO2, Al2O3, and MgO is 100%, the weight percentage of CaO is 30-70%, preferably 35-70%, more preferably 40-65%, further preferably 45-62%, even more preferably 47-62%, and still more preferably 55-62%.

[0049] In addition, in the above chemical composition, the weight percentage of SiO2 is 10-50%, preferably 15-45%, more preferably 18-45%, further preferably 20-40%, and even more preferably 28-31%.

[0050] In addition, in the above chemical composition, the weight percentage of Al2O3 is 1-40%, preferably 1-30%, more preferably 2-23%, further preferably 2-15%, even more preferably 2-13%, and still more preferably 5-10%.

[0051] In addition, in the above chemical composition, the weight percentage of MgO is 1-20%, preferably 5-15%, and more preferably 5-10%.

[0052] In other words, the preferred chemical composition of the reducing slag treatment material is that CaO has a weight percentage of 55-62%, SiO2 has a weight percentage of 28-31%, Al2O3 has a weight percentage of 5-10%, MgO has a weight percentage of 5-10%, and the total weight percentage of each component is 100%.

[0053] If the chemical composition is as described above, a reduction slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components (main products) and a high content of these main components can be obtained.

[0054] At this point, by adding SiO2 and Al2O3, a reducing slag treatment material with a high content of γC2S and magnesium silicate calcium stone can be obtained.

[0055] In addition, by increasing the SiO2 content compared to the Al2O3 content, a reducing slag treatment material with a high content of γC2S and magnesium silicate calcium stone can be obtained.

[0056] In addition, by making the MgO content higher than the Al2O3 content, a reducing slag treatment material with a high magnesium silicate calcium stone content can be obtained.

[0057] (Crystallized state)

[0058] The preferred material for reducing slag treatment is... Figure 1 The ternary phase diagram of CaO-SiO2-Al2O3 (MgO weight percentage = 10%) shown is composed of either the "C2S" crystalline region or the "magnesium silicate calcium silicate" crystalline region. A more preferred composition is the primary crystallization region of "C2S".

[0059] In this way, a reduction slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components (main products) and with a high content of these main components can be obtained.

[0060] Here, the weight percentage of MgO is 10%, but it is not particularly limited. As mentioned above, the weight percentage of MgO is 1-20%, preferably 5-15%.

[0061] Furthermore, the reducing slag treatment material does not necessarily have to be composed of crystalline zones of "C2S" or "magnesia-silica-calcium stone". For example, in Figure 1 The ternary phase diagram shown can be the composition surrounding the crystalline region of "C2S" or "magnesium silicate". Alternatively, the reduction slag treatment material with the above chemical composition can be used regardless of the crystallization state. Even in this case, a reduction slag treatment material with γC2S and / or magnesium silicate as the main components can be obtained.

[0062] <Concrete containing reducing slag treatment materials>

[0063] The "concrete containing reducing slag treatment material" in this embodiment is a type of concrete that contains the aforementioned reducing slag treatment material and fixes carbon dioxide.

[0064] Specifically, water, cement, aggregates (fine and coarse) are mixed with reducing slag treatment material as an admixture to form a mortar-concrete mixture. This mixture is then cured with a high concentration (e.g., 5-20%) of carbon dioxide to obtain concrete containing reducing slag treatment material.

[0065] In the concrete containing the aforementioned reducing slag treatment material, a large amount of carbon dioxide is fixed. The more carbon dioxide is fixed, the higher the compressive strength of the concrete.

[0066] <Preparation Method of Reducing Slag Treatment Materials>

[0067] Next, the "composition adjustment step" and "slow cooling step" performed in the preparation method of this embodiment will be described in detail. In addition, other steps may appropriately employ known techniques.

[0068] In the "composition adjustment process", the chemical composition of the reducing slag CaO, SiO2, Al2O3 and MgO produced by the electric furnace is adjusted to achieve the chemical composition described above.

[0069] In detail, to suppress the increase of Al2O3 and MgO components and make CaO and SiO2 the main components, refining aids are added in the electric furnace to adjust the composition of the reducing slag. For example, Mn alloys, FeO, or steelmaking slag can be used as refining aids.

[0070] In addition to adding the aforementioned refining aids, the chemical composition of the reducing slag can also be adjusted through other methods.

[0071] Preferably, a reducing atmosphere is maintained inside the electric furnace.

[0072] In addition, the composition is adjusted in the "composition adjustment process" so that it has the composition of "C2S primary crystal region" in the ternary phase diagram of CaO-SiO2-Al2O3 (MgO weight percentage = 10%).

[0073] In detail, it is known that the reducing slag produced by the electric furnace has the same characteristics as... Figure 1 The ternary phase diagram shown approximates the chemical composition of the primary crystallization region of "C2S". Here, to make the chemical composition of the reducing slag closer to that of C2S (CaO: 65%, SiO2: 35%), raw materials such as slaked lime, dolomite, and / or silica are added to the electric furnace to adjust the composition of the reducing slag. In this way, the composition of the reducing slag can be adjusted to fall within the primary crystallization region of C2S.

[0074] Furthermore, it is necessary to supply MgO for the protection of the refractory materials of the electric furnace. By supplying MgO, in addition to γC₂S, magnesia-calcium silicate can also be obtained simultaneously.

[0075] In the "slow cooling process", the reduced slag with adjusted composition is slowly cooled in a reducing atmosphere inside the electric furnace. After being taken out of the electric furnace, it is slowly cooled at a temperature gradient of less than 20°C / minute within the range of 400-800°C.

[0076] In detail, to maintain the reducing atmosphere inside the furnace, materials such as rice husks are used to cover the furnace for insulation. Additionally, blowing cold air or spraying water is avoided as much as possible. Furthermore, other methods besides those mentioned above can also be used to maintain the reducing atmosphere.

[0077] By maintaining a reducing atmosphere in this way, metal ions such as iron are reduced to metals, which inhibits their solid dissolution in the reducing slag. This method can effectively produce reducing slag treatment materials with a high content of γC₂S and / or magnesium silicate.

[0078] Furthermore, compared to αC2S and βC2S, γC2S has a smaller solid solubility limit. Therefore, by converting the C2S contained in the reduction slag into the γ phase state of low-temperature phase transformation, its solid dissolution in the reduction slag can be further suppressed, resulting in a reduction slag treatment material with fewer impurities.

[0079] In the "slow cooling process," heating or insulation is performed near the transformation temperature from the β phase to the γ phase (approximately 675°C). By mitigating the temperature gradient, a reducing slag material with a higher γC2S content can be obtained. If the cooling rate is too fast, the βC2S content will increase, while the γC2S content will decrease.

[0080] Therefore, specifically, after being removed from the electric furnace, the material is slowly cooled with a gentle temperature gradient in the range of 650-700°C, preferably in the range of 600-750°C, more preferably in the range of 600-800°C, further preferably in the range of 500-800°C, and even more preferably in the range of 400-800°C.

[0081] In addition, within the above temperature range, slow cooling is performed at a temperature gradient of 30°C / minute or less, preferably 20°C / minute or less, more preferably 15°C / minute or less, and even more preferably 10°C / minute or less.

[0082] In addition, during the "slow cooling process", no slag pulverization inhibitors are added to promote the conversion of γC2S contained in the reduced slag after composition adjustment to αC2S and / or βC2S.

[0083] In detail, in the past, slag pulverization inhibitors such as sodium borate were added to improve the treatability of the cooled reducing slag and to suppress slag pulverization accompanying the transformation of C2S from the β phase to the γ phase. However, in this embodiment, the objective is to effectively obtain a reducing slag treatment material with a higher γC2S content. Therefore, it is preferable not to add slag pulverization inhibitors, but to slowly cool the reducing slag.

[0084] Furthermore, the slag pulverization inhibitor is not limited to sodium borate; it can be a fluorine-based or boron-based pulverization inhibitor, or other pulverization inhibitors, or it may not be added at all. Alternatively, additives or modifiers for preventing the conversion to γC2S may not be added.

[0085] Furthermore, in the "slow cooling process," the reduced slag with adjusted composition is slowly cooled in a reducing atmosphere inside the electric furnace. However, it is not necessarily slowly cooled in a reducing atmosphere after being removed from the electric furnace. That is, it can be slowly cooled in an oxidizing atmosphere outside the electric furnace.

[0086] Alternatively, conventional cooling can be performed inside the electric furnace, while slow cooling can be performed outside the furnace.

[0087] As described above, through the "composition adjustment process", "slow cooling process" and other processing steps, a reduction slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components can be prepared from the reduction slag produced by the electric furnace.

[0088] In particular, according to this preparation method, the reducing slag discharged from the electric furnace can be directly processed to obtain the reducing slag treatment material.

[0089] Example

[0090] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to these embodiments.

[0091] <Example: Reduction Slag Treatment Materials>

[0092] Based on the above-mentioned preparation method of reducing slag treatment materials, such as Figure 2 As shown, under different conditions of (1) chemical composition, (2) crystallization state, (3) cooling method, (4) whether to add pulverization prevention material, and (5) redox atmosphere, the reduction slag discharged from the electric furnace was used to prepare reduction slag treatment material.

[0093] Specifically, regarding (1) the chemical composition, the composition of the reducing slag is adjusted so that the chemical compositions of CaO, SiO2, Al2O3, and MgO are different. In addition, in the reducing slag treatment material, the total weight percentage of the chemical compositions of CaO-SiO2-Al2O3-MgO exceeds 90%, so in this embodiment, the ratio is calculated based on their total content as 100% by weight. Figure 1 The ternary phase diagram for CaO-SiO2-Al2O3 with 10% MgO by weight.

[0094] Regarding (2) the crystallization state, if it is... Figure 1 In the ternary phase diagram shown, the composition of the primary crystallization region of C2S, indicated by the thick box, is marked with "○", while compositions outside the primary crystallization region are marked with "×". Furthermore, regarding the chemical composition of the primary crystallization region of C2S in the CaO-SiO2-Al2O3-MgO system, the weight percentages are: CaO: 45-65%, SiO2: 20-40%, Al2O3: 5-23%, and MgO: 5-15%. Additionally, considering compositional variations within the electric furnace, a value of 1-30% for Al2O3 is marked with "○".

[0095] Regarding (3) the cooling method, the reducing slag is cooled by covering it with rice husks inside the furnace to maintain heat insulation. In addition, no cold air is blown or water is sprayed. At this time, the reducing slag is slowly cooled in a temperature gradient of less than 20°C / minute within the range of 400-800°C, marked with “○”, and normally cooled is marked with “×”.

[0096] Regarding (4) whether pulverization prevention materials are added, if a slag pulverization prevention agent (sodium borate) is added to inhibit the pulverization that accompanies the formation of γC2S, it is marked "○"; if not added, it is marked "×".

[0097] Regarding (5) oxidation-reduction atmosphere, the symbol “○” indicates that the reducing atmosphere will be maintained to slowly cool the reducing slag, and the symbol “×” indicates that the reducing atmosphere will not be maintained to slowly cool the reducing slag.

[0098] In this embodiment, the reduction slag treatment materials of Examples 1-18 were prepared under different conditions (1)-(5) above.

[0099] <Experimental Example 1: Evaluation Experiment>

[0100] conduct Figure 2 The preparation of the reduction slag treatment materials shown in Examples 1-18 was carried out, and tests were conducted to evaluate the abundance of γC2S and magnesium silicate calcium stone and the activity of carbon dioxide.

[0101] First, to evaluate the abundance of γC2S and calcium silicate (C3MS2) in the reduction slag treatment materials of each embodiment, powder X-ray diffraction analysis was performed on the reduction slag treatment materials using Cu-Kα radiation. That is, the presence or absence of γC2S and calcium silicate was determined by detecting the main peaks, and the abundance of γC2S and calcium silicate was calculated.

[0102] At this point, if γC2S and / or magnesium silicate are found, the highest abundance is marked with "++++", a relatively high abundance with "+++", and the presence of γC2S and / or magnesium silicate with "++" is indicated by the total abundance. Additionally, if γC2S and / or magnesium silicate are present but do not meet the above criteria ("++"-"++++"), they are marked with "+", while if they are absent, they are marked with "-".

[0103] Next, to evaluate the carbon dioxide activity of the reduction slag treatment materials in each embodiment, concrete containing the reduction slag treatment materials was prepared using the materials as admixtures, and the compressive strength of the concrete was calculated. Furthermore, the higher the amount of carbon dioxide fixed in the concrete, the higher its compressive strength.

[0104] Specifically, the reducing slag material was pulverized using a known experimental mill to achieve a Blaine surface area of ​​4000 cm². 2 / g, and adjust the powder fineness so that the pulverized slag particles are below 50μm. Then, add water (tap water), ordinary Portland cement (produced by Taiheiyo Cement Group), and fine aggregate (land sand from the Oi River in Shizuoka Prefecture, surface dry density: 2.59g / cm³). 3The cement (FM: 2.71) and reducing slag treatment material were weighed and kneaded at a mass ratio of 0.5:0.5:2.0:0.5 (water:cement:aggregate:reducing slag treatment material). Then, mortar of 4cm×4cm×16cm was prepared. One day after demolding, the mortar was wet-cure for 5 days in a curing tank with a carbon dioxide concentration of 20%, relative humidity of 100%, and temperature of 40℃. After curing, the compressive strength was measured (for the determination of compressive strength, please refer to Non-Patent Literature 2).

[0105] For the test results of concrete using the various embodiments, based on the standard of practical strength of concrete products, compressive strength above 20MPa is marked with "◎", 10-20MPa is marked with "〇", and below 10MPa is marked with "×".

[0106] (Results and research of Experiment Example 1)

[0107] The evaluation results of the abundance of γC2S and / or magnesium silicate calcium silicate and the evaluation results of carbon dioxide activity in each embodiment are summarized in Figure 2 As shown.

[0108] The test results from Example 1 show that the main products of the reduction slag treatment materials in Examples 1 and 4-16 include γC2S and / or magnesium silicate calcium stone.

[0109] It is also known that Examples 1 and 4-12 contain a corresponding amount or more of γC2S and / or magnesium silicate calcium stone.

[0110] On the other hand, for Example 2, although the chemical composition was the same as that of Example 1, the content of βC2S, which does not exhibit carbon dioxide activity, was higher due to the addition of a powdering inhibitor, and γC2S was almost absent or nonexistent. That is, it was found that the addition of the powdering inhibitor inhibited the formation of γC2S and / or calcium silicate.

[0111] For Example 3, although the chemical composition was the same as in Example 1, due to normal cooling (rapid cooling), no conversion to γC2S occurred, and it contained βC2S with almost no or no γC2S. That is, it was found that the cooling method inhibited the formation of γC2S and / or calcium silicate.

[0112] For Examples 13-16, since the crystalline state is outside the composition of the primary crystallization region of C2S, although a peak value of γC2S was detected, CaO, MgO, and feldspar were the main products. That is, it was found that the crystalline state inhibits the formation of γC2S and / or calcium silicate.

[0113] In Examples 17 and 18, since an oxidizing atmosphere was used instead of a reducing atmosphere, the formation of γC₂S was suppressed to a low level. That is, it was found that a redox atmosphere inhibits the formation of γC₂S and / or calcium silicate.

[0114] Furthermore, the test results of Example 1 show that the concrete used in Examples 1 and 4-12, which are mainly composed of γC2S and / or magnesium silicate calcium stone, has a compressive strength of over 20 MPa. That is, it has a higher carbon dioxide activity (carbon dioxide fixation).

[0115] For the concrete using Examples 13-16, the compressive strength is above 10 MPa. That is, the carbon dioxide activity is high.

[0116] On the other hand, for Examples 2, 3, 17, and 18, the compressive strength based on the above criteria was not obtained. That is, the carbon dioxide activity was low.

[0117] The above indicates that, regarding the preparation method of the above-mentioned reducing slag treatment material, by optimizing the conditions of (1) chemical composition, (2) crystallization state, (3) cooling method, (4) whether to add pulverization prevention material, and (5) redox atmosphere, it is possible to effectively prepare reducing slag treatment material with γC2S and / or magnesium silicate calcium stone as the main components, and concrete containing reducing slag treatment material.

Claims

1. A method for preparing a reducing slag treatment material, characterized by using reducing slag discharged from an electric furnace to prepare a reducing slag treatment material with γ-C2S and magnesium silicate calcium aluminate as the main components, wherein: This includes the ingredient adjustment process and the slow cooling process; The composition adjustment process adjusts the composition of the reducing slag so that, in a chemical composition where the total weight percentage of CaO, SiO2, Al2O3, and MgO is 100%, the weight percentage of CaO is 55-65%, the weight percentage of SiO2 is 28-31%, the weight percentage of Al2O3 is 2-13%, and the weight percentage of MgO is 5-10%. The slow cooling process involves slowly cooling the composition-adjusted reducing residue in a reducing atmosphere at a temperature gradient of less than 20°C / minute within a range of 400-800°C. No slag pulverization inhibitor is added during the slow cooling process; The reduction slag treatment material containing γ-C2S and magnesium silicate calcium stone as the main components is obtained.

2. The method for preparing the reducing slag treatment material according to claim 1, characterized in that: In the composition adjustment process, the composition of the reducing slag is adjusted so that it has the composition of the primary crystallization region of C2S in the ternary phase diagram of CaO-SiO2-Al2O3 with MgO weight percentage = 10%.

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