Manufacturing method for hydrated iron and steel slag solidified body

Abstract

To provide a producing method of a hydrated and solidified steel slag product having excellent expansion stability.SOLUTION: The producing method of the hydrated and solidified steel slag product according to the present embodiment includes a preparation step of preparing electric furnace slag with a MgO content of more than 8.5 mass%, and a kneading step of kneading 1000 to 2000 kg of steelmaking slag, 300 to 400 kg of binder, 150 to 250 kg of water, and 0 to 700 kg of blast furnace slag per 1 m3. Regarding the steelmaking slag at the kneading step, a blending ratio of the electric furnace slag is more than 25 to 100 mass%, and a blending ratio of low Mg-containing steelmaking slag with a MgO content of 8.5 mass% or less is 0 to less than 75 mass%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a hydrated iron and steel slag body. [Background technology]

[0002] In the steel production process, steel slag is generated as a by-product. As one of the environmental measures in the steel industry, development is being carried out to recycle steel slag and use it in road materials, concrete materials, building materials, etc.

[0003] Iron and steel slag is classified into blast furnace slag obtained in the ironmaking process and steelmaking slag obtained in the steelmaking process. Blast furnace slag is further classified into slowly cooled blast furnace slag, granulated blast furnace slag, and ground granulated blast furnace slag. Ground granulated blast furnace slag is formed by further pulverizing granulated blast furnace slag.

[0004] Steelmaking slag is further classified into converter slag, electric furnace slag, and reduction furnace slag. Converter slag is slag produced in the refining process using a converter. Converter slag also includes hot metal pretreatment slag. Hot metal pretreatment slag is slag produced in the refining process using an electric furnace. Reduction furnace slag is slag produced in the refining process in a reduction furnace in the production of special steel, etc. Examples of reduction furnaces include AOD furnaces and VOD furnaces.

[0005] When steel slag is used as a recycled material for the above-mentioned purposes, a hydrated steel slag is produced using the steel slag as a raw material. The hydrated steel slag is produced by the following method. Steelmaking slag, a binder, and water are prepared as raw materials for the hydrated steel slag. The steelmaking slag is used as aggregate. These raw materials are then kneaded together. At this time, the kneaded raw materials solidify through a hydration reaction, producing a hydrated steel slag.

[0006] However, some steelmaking slag may expand over time. If such steelmaking slag that has the potential to expand is used as aggregate in a steel slag hydrated body, the steel slag hydrated body may deform over time, potentially causing cracks. Therefore, in order to prevent cracks in the steel slag hydrated body, the steelmaking slag used as aggregate is required to have the property of being resistant to expansion over time. In this specification, the property of being resistant to expansion over time is referred to as "expansion stability."

[0007] Research has been conducted into how to prevent cracks from occurring over time in hydrated steel slag compacts. It is believed that cracks in hydrated steel slag occur over time through the following mechanism: Steelmaking slag, the raw material for hydrated steel slag compacts, may contain free MgO. Free MgO is magnesium oxide (MgO) that remains as a single substance within the slag without undergoing a hydration reaction with other compounds.

[0008] When steelmaking slag containing free MgO is used as a raw material to produce steel slag hydrates, free MgO remains within the produced steel slag hydrates. Over time, the free MgO in the steel slag hydrates reacts with water (hydrates) and changes to Mg(OH)2. As the free MgO changes to Mg(OH)2, its volume expands. The hydration reaction rate of free MgO is slow. Therefore, the expansion continues over a long period of time. It is believed that due to the above mechanism, the steel slag hydrates expand and deform, resulting in cracks.

[0009] As mentioned above, free MgO is one of the factors that cause cracks in steel slag hydrated compacts. Therefore, to prevent cracks and deformation in steel slag hydrated compacts, it is preferable that the raw materials for steel slag hydrated compacts contain less free MgO. For this reason, "Appendix 1: Steelmaking Slag for Steel Slag Hydrated Compacts" (Non-Patent Document 1) of the "Technical Manual for Steel Slag Hydrated Compacts (Revised Edition)" recommends using steelmaking slag with an MgO content of 8.5% by mass or less, as determined in accordance with JIS M 8205:2000, as the raw material for steel slag hydrated compacts.

[0010] Techniques for suppressing cracking in steel slag hydrated bodies are proposed in Japanese Patent Laid-Open Nos. 2001-323403 (Patent Document 1) and 2002-308662 (Patent Document 2). In Patent Document 1, a steel slag hydrated body is produced using hot metal pretreatment slag, which is a type of steelmaking slag. In Patent Document 2, a steel slag hydrated body is produced using converter slag, which is a type of steelmaking slag. The hot metal pretreatment slag and converter slag have an MgO content of 8.5% or less, as required in accordance with the above-mentioned JIS standard. In Patent Documents 1 and 2, steelmaking slag with a low MgO content is used to suppress expansion of the steel slag hydrated body and suppress cracking due to deformation. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-323403 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-308662 [Non-patent literature]

[0012] [Non-Patent Document 1] Coastal Technology Research Institute (ed.) (February 2008) "Technical Manual for Steel Slag Hydrated Solidification (Revised Edition)" Coastal Technology Research Institute Summary of the Invention [Problem to be solved by the invention]

[0013] The iron and steel slag hydrated solidified bodies disclosed in Patent Documents 1 and 2 can suppress the occurrence of cracks due to deformation. However, it may also be possible to suppress expansion in the iron and steel slag hydrated solidified bodies and suppress the occurrence of cracks due to deformation by means other than those proposed in Patent Documents 1 and 2.

[0014] An object of the present disclosure is to provide a method for producing hydrated iron and steel slag bodies that can suppress expansion and the occurrence of cracks due to deformation. [Means for solving the problem]

[0015] The method for producing a hydrated iron and steel slag according to the present disclosure includes the steps of: preparing electric furnace slag having an MgO content of more than 8.5% by mass; 3 and a mixing step of mixing 1000 to 2000 kg of steelmaking slag, 300 to 400 kg of binder, 150 to 250 kg of water, and 0 to 700 kg of blast furnace slag per slag. In the mixing step, the blending ratio of electric furnace slag in the steelmaking slag is greater than 25% to 100% by mass, and the blending ratio of low-Mg steelmaking slag, which is steelmaking slag with an MgO content of 8.5% or less by mass, is 0 to less than 75% by mass. [Effects of the Invention]

[0016] The method for producing hydrated iron and steel slag compacts of the present disclosure can produce hydrated iron and steel slag compacts that are capable of suppressing expansion and cracking due to deformation. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the MgO content of each steelmaking slag and the expansion rate as a function of the number of days elapsed obtained in a water immersion expansion test. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present inventors have investigated a manufacturing method for a hydrated iron and steel slag product that can suppress expansion and the occurrence of cracks due to deformation, and have obtained the following findings.

[0019] As mentioned above, it was previously believed that steelmaking slag with an MgO content of over 8.5% had poor expansion stability. Therefore, it was thought that hydrated steelmaking slag produced using steelmaking slag with an MgO content of over 8.5% as aggregate was prone to expansion and cracking due to deformation.

[0020] Meanwhile, in the refining process using an electric furnace, there is a demand for increasing the crude steel production rate. Increasing the crude steel production rate can result in an increase in the MgO content in the slag. In this case, the MgO content in the electric furnace slag exceeds 8.5%. For this reason, electric furnace slag has traditionally been considered to have poor expansion stability. As a result, as disclosed in the above-mentioned Patent Documents 1 and 2, hot metal pretreatment slag and converter slag, which have an MgO content of 8.5% or less, have typically been used as aggregate for steel slag hydrates, and the use of electric furnace slag has been avoided.

[0021] However, the present inventors have considered that electric furnace slag, which has been thought to have poor expansion stability, may actually have excellent expansion stability. Therefore, the inventors conducted the following tests to investigate the expansion stability of steelmaking slags such as converter slag, electric furnace slag, and reducing furnace slag.

[0022] Converter slag, electric furnace slag, reduction furnace slag A, and reduction furnace slag B were prepared. Reduction furnace slag A was produced in a different reduction furnace than reduction furnace slag B. The following tests were conducted on each of the prepared steelmaking slags, following the water immersion expansion test method specified in Appendix B of JIS A 5015:2013.

[0023] Each steelmaking slag was compacted into a mold with an inner diameter of 150 mm and a height of 125 mm. The mold containing the compacted steelmaking slag was immersed in hot water at 80°C, and the amount of expansion was measured using a dial gauge. The JIS standard requires immersion in 80°C hot water for six hours, followed by cooling and measurement of the amount of expansion using a dial gauge, and this procedure is repeated once a day for 10 days. However, in this test, the amount of expansion was measured using a dial gauge while the sample was kept immersed in 80°C hot water. Based on the results obtained, a graph was created showing the relationship between the number of days elapsed and the expansion rate.

[0024] Furthermore, the MgO content of each steelmaking slag was determined in accordance with JIS M 8205:2000.

[0025] The results are shown in Figure 1. Referring to Figure 1, the MgO content in converter furnace slag was 5.0% by mass, which was less than 8.5%. On the other hand, the MgO content in electric furnace slag, reduction furnace slag A, and reduction furnace slag B exceeded 8.5% by mass.

[0026] However, the results of the water immersion expansion test showed results that differed from conventional knowledge. Specifically, referring to the graph in Figure 1 showing the relationship between the number of days elapsed and the expansion rate, the expansion rate of both reduction furnace slag A and reduction furnace slag B increased significantly with increasing number of days elapsed, indicating poor expansion stability. On the other hand, although the MgO content of electric furnace slag was significantly higher than 8.5%, the increase in the expansion rate with increasing number of days was significantly suppressed compared to reduction furnace slag A and reduction furnace slag B, indicating superior expansion stability compared to reduction furnace slag. Electric furnace slag also had superior expansion stability compared to converter furnace slag.

[0027] Based on the above results, the present inventors concluded as follows: The MgO content determined in accordance with JIS M 8205:2000 is a value calculated by converting the quantitative Mg value, assuming that all Mg in steelmaking slag is present as MgO. Therefore, the MgO content determined by this method may differ from the content of free MgO actually present in the steelmaking slag. Based on the results of Figure 1, the present inventors concluded that even if the MgO content determined by the above method exceeds 8.5%, the Mg in actual electric furnace slag is not necessarily present as free MgO.

[0028] Therefore, the present inventors performed X-ray diffraction analysis of compounds in electric furnace slag. X-ray diffraction analysis makes it possible to identify compounds in slag. As a result of the X-ray diffraction analysis, the compounds containing Mg in electric furnace slag were mainly mineral phases containing Mg (Mg-containing mineral phases). Furthermore, it was found that free MgO was hardly detected in the X-ray diffraction analysis.

[0029] Based on the above findings, the present inventors have hypothesized that electric furnace slag, which has traditionally been avoided as an aggregate for steel slag hydrates, may actually be suitable for use as an aggregate for steel slag hydrates. Therefore, they investigated the expansion stability of steel slag hydrates using electric furnace slag as an aggregate. As a result, they found that steel slag hydrates containing electric furnace slag with an MgO content of more than 8.5% are less likely to expand and deform over time, thereby suppressing the occurrence of cracks. Therefore, the present inventors have discovered for the first time that electric furnace slag with an MgO content of more than 8.5% is suitable as an aggregate for steel slag hydrates.

[0030] The method for producing a hydrated iron and steel slag product of this embodiment, which was completed based on the above findings, includes the following steps.

[0031] [1] a preparation step of preparing electric furnace slag having an MgO content of more than 8.5% by mass; 1m 3 Around 1000-2000 kg of steelmaking slag, 300-400 kg of binder, 150-250 kg of water, a mixing process of mixing the slag with 0 to 700 kg of blast furnace slag; Including, In the kneading step, In the steelmaking slag, the blending ratio of the electric furnace slag is more than 25 to 100% by mass, and the blending ratio of low-Mg steelmaking slag, which is steelmaking slag having an MgO content of 8.5% or less by mass, is 0 to less than 75% by mass. A method for manufacturing hydrated iron and steel slag solidified bodies.

[0032] [2] [1] A method for producing a hydrated iron and steel slag solidified body, The Mg-containing compound in the electric furnace slag is a Mg-containing mineral phase that is a mineral phase that mainly contains Mg. A method for manufacturing hydrated iron and steel slag solidified bodies.

[0033] [3] [2] A method for producing a hydrated iron and steel slag solidified body, The Mg-containing mineral phase One or more selected from the group consisting of akermanite, diopside, monticellite and spinel A method for manufacturing hydrated iron and steel slag solidified bodies.

[0034] [4] [2] or [3], the manufacturing method of the iron and steel slag hydrated solidified body, Among the compounds containing Mg in the electric furnace slag, the content of the Mg-containing mineral phase is 50% by mass or more. A method for manufacturing hydrated iron and steel slag solidified bodies.

[0035] [5] [4] A method for producing a hydrated iron and steel slag solidified body according to the present invention, Among the compounds containing Mg in the electric furnace slag, the content of free MgO is 5% by mass or less. A method for manufacturing hydrated iron and steel slag solidified bodies.

[0036] The method for producing a hydrated iron and steel slag product of this embodiment will be described in detail below. The method for producing a hydrated iron and steel slag product of this embodiment includes the following steps. (Process 1) Preparation process (Process 2) Kneading process Each step will be described below.

[0037] [(Process 1) Preparation process] First, electric furnace slag with an MgO content exceeding 8.5% by mass is prepared. In this specification, the "MgO content" is a value calculated by converting the quantitative Mg value, assuming that all Mg in the steelmaking slag is present as MgO.

[0038] [About electric furnace slag] Electric furnace slag is slag produced when steel is smelted in an electric furnace. As mentioned above, in electric furnace refining, increasing the crude steel production rate can result in an increased MgO content in the slag. As a result, the MgO content of electric furnace slag can exceed 8.5% by mass.

[0039] However, as mentioned above, most of the Mg in electric furnace slag is not present as free MgO but is contained in the mineral phase. In other words, electric furnace slag contains almost no free MgO. As a result, contrary to conventional knowledge, electric furnace slag has excellent expansion stability, as shown in Figure 1. Therefore, electric furnace slag with an MgO content of more than 8.5% is suitable as a raw material for aggregate in steel slag hydrated compacts.

[0040] [How to calculate MgO content] The MgO content (mass%) in electric furnace slag is determined using the following method: A sample is collected from the electric furnace slag. The collected sample is subjected to X-ray fluorescence analysis in accordance with JIS M 8205:2000 "Iron ore - X-ray fluorescence analysis method" to quantify the amount of Mg in the sample. Based on the obtained quantitative value of Mg, and assuming that all of the Mg in the sample is present as MgO, the content converted to MgO is taken as the MgO content (%) in mass%.

[0041] [Mg-containing mineral phases in Mg compounds in electric furnace slag] In this specification, compounds containing Mg are referred to as “Mg compounds.” The Mg compounds in electric furnace slag are mainly Mg-containing mineral phases.

[0042] The Mg-containing mineral phase may be one or more selected from the group consisting of akermanite (Ca2(Mg,Al)(Si,Al)2O7), diopside (Ca(Mg,Al)(Si,Al)2O6), monticellite (CaMgSiO4), and spinel (Mg(Al,Cr)2O4).

[0043] Preferably, the content of the Mg-containing mineral phase among the Mg compounds in the electric furnace slag is 50% by mass or more. In other words, when the total mass of the Mg compounds in the electric furnace slag is taken as 100%, the content of the Mg-containing mineral phase is 50% or more. A more preferred lower limit of the content of the Mg-containing mineral phase is 55%, even more preferably 60%, and even more preferably 70%.

[0044] [How to determine the content of Mg-containing mineral phases] The mass% content of the Mg-containing mineral phase in electric furnace slag is determined using X-ray diffraction (XRD) analysis as follows: A sample is collected from the electric furnace slag. A diffraction profile is obtained using the collected sample by X-ray diffraction (XRD). The XRD diffraction analysis uses a Cu tube, a tube voltage of 40 kV, a tube current of 200 mA, a diffraction angle (2θ) of 5 to 90°, a step of 0.02°, a scan speed of 4° / min, a divergence / scattering slit of 1 / 2 deg, and a receiving slit of 0.3 mm. Mg compounds and Mg-containing mineral phases are identified based on the diffraction angle and peak intensity in the obtained diffraction profile.

[0045] The mass % content of the Mg-containing mineral phase among the identified Mg compounds is determined as follows: In the obtained diffraction profile, the peak area of ​​each identified Mg compound is determined. The ratio of the sum of the peak areas of all Mg-containing mineral phases to the sum of the peak areas of all Mg compounds is defined as the mass % content of the Mg-containing mineral phase.

[0046] [Free MgO in Mg compounds in electric furnace slag] As mentioned above, the magnesium compounds in electric furnace slag are mainly magnesium-containing mineral phases, and there is almost no free magnesium oxide. The content of free magnesium oxide in the magnesium compounds in electric furnace slag is 5% by mass or less.

[0047] [(Step 2) Kneading process] In the kneading step, the following raw materials 1 to 3 are kneaded in the blending amounts shown below. (Raw material 1) Steelmaking slag: 1m 3 1000-2000kg per (Raw material 2) Binding material: 1m 3 300-400kg per (Raw material 3) Water: 1m 3 150-250kg per Each raw material will be described below.

[0048] [(Raw material 1) Steelmaking slag: 1m 3 1000-2000 kg per Electric furnace slag, which is produced by oxidation treatment (smelting) in an electric furnace, is used as aggregate for hydrated steel slag. 3 Mix 1000 to 2000 kg per batch.

[0049] In this embodiment, the blending ratio of electric furnace slag in the steelmaking slag is greater than 25% and less than 100% by mass. The blending ratio of low-Mg steelmaking slag, which has an MgO content of 8.5% or less by mass, is 0% to less than 75% by mass. Here, low-Mg steelmaking slag refers to steelmaking slag with an MgO content of 8.5% or less, as determined in accordance with JIS M 8205:2000. Low-Mg steelmaking slag is any raw material. The low-Mg steelmaking slag is, for example, converter slag.

[0050] The particle size of the electric furnace slag is not particularly limited and may be any known particle size. For example, the particle size of the electric furnace slag is 40 mm or less. A particle size of 40 mm or less improves the efficiency of the aging treatment of the electric furnace slag in the aging treatment step described below. A preferred particle size of the electric furnace slag is 25 mm or less.

[0051] The preferred lower limit of the blending ratio of electric furnace slag in steelmaking slag is 30%, more preferably 35%, and even more preferably 40%. The preferred upper limit of the blending ratio of low Mg content steelmaking slag is 70%, more preferably 65%, and even more preferably 60%. 3 The preferred lower limit of the amount per 1 m of steelmaking slag is 1100 kg, and more preferably 1150 kg. 3 A preferred upper limit of the amount per unit is 1900 kg, more preferably 1800 kg.

[0052] [(Raw material 2) Binding material: 1m 3 300-400 kg per In this embodiment, the bonding material is 1 m 3The binder is a silica-containing material and a material having porosity reactivity. The binder is, for example, one or more selected from the group consisting of ground granulated blast furnace slag, blast furnace cement, and Portland cement. 3 The preferred lower limit of the amount per m of binder is 310 kg, more preferably 320 kg. 3 A preferred upper limit of the amount per unit is 380 kg, more preferably 360 kg, and even more preferably 350 kg.

[0053] Ground granulated blast furnace slag is a powder obtained by pulverizing granulated blast furnace slag. As specified in JIS A 6206:2013 (ground granulated blast furnace slag for concrete), there are three types of ground granulated blast furnace slag, 4000, 6000, and 8000, depending on the fineness. In this embodiment, one or more of the three types of ground granulated blast furnace slag may be used as a binder.

[0054] [(Raw material 3) Water: 1m 3 150-250 kg per In this embodiment, the water is 1 m 3 The water used as a raw material is, for example, ordinary industrial water. 3 The preferred lower limit of the amount per 1 m of water is 155 kg, more preferably 160 kg. 3 A preferred upper limit for the amount per unit is 245 kg, more preferably 240 kg.

[0055] [About mixing] In the kneading process, the above-mentioned raw materials 1 to 3 are kneaded in the above-mentioned proportions. At this time, a hydration reaction occurs, and the mixture of raw materials 1 to 3 solidifies. Through the above processes, the steel slag hydrated compact of this embodiment is produced. In the method for producing a hydrated compact of this embodiment, electric furnace slag is used as aggregate to produce the steel slag hydrated compact. The produced hydrated compact does not easily expand over time. Therefore, the occurrence of cracks due to deformation is suppressed.

[0056] [Regarding any ingredients other than ingredients 1 to 3] In addition to raw materials 1 to 3, the following raw material 4 may be optionally blended and kneaded together with raw materials 1 to 3. (Raw material 4) Blast furnace slag: 1m 3 0-700kg per

[0057] Blast furnace slag is an optional ingredient. In other words, it does not have to be mixed. If mixed, blast furnace slag should be 1m 3 The amount of blast furnace slag to be mixed is 700 kg or less per 1 m 3 It is preferable to mix 100 kg or more per 1 m of blast furnace slag, and more preferably 300 kg or more. 3 A preferred upper limit per unit weight is 680 kg, and more preferably 660 kg.

[0058] The blast furnace slag may be, for example, granulated blast furnace slag. Preferably, the granulated blast furnace slag complies with JIS A 5011-1 "Slag aggregate for concrete - Part 1: blast furnace slag aggregate." The particle size of the granulated blast furnace slag is such that 100% by mass passes through a sieve with a nominal mesh size of 5 mm. The granulated blast furnace slag may be used as fine aggregate.

[0059] [Regarding any ingredients other than ingredient 4] The raw materials for the steel slag hydrated solidified body of this embodiment may include raw materials other than the above-mentioned raw materials 1 to 4. Examples of raw materials other than raw materials 1 to 4 include known fly ash conforming to JIS A 6201:2015, known alkaline activators, known air-entraining agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, and resin fibers conforming to JIS A 6204:2011.

[0060] [Optional manufacturing process: Aging treatment process] As described above, in the method for producing a steel slag hydrated body of this embodiment, the aging treatment step may be performed as an optional step after the preparation step and before the kneading step. In other words, the aging treatment step is an optional step.

[0061] Aging is a process that promotes the hydration reaction of steelmaking slag. When carrying out the aging process, steam is supplied to the prepared electric furnace slag at atmospheric pressure or higher for at least five days. In other words, the electric furnace slag is kept in a humid atmosphere at atmospheric pressure or higher for at least five days.

[0062] There is no particular upper limit to the period for which the aging treatment is carried out, and the aging treatment may be carried out, for example, at atmospheric pressure or higher for 5 to 20 days.

[0063] Steam may be supplied to the electric furnace slag by supplying steam to the surface of the electric furnace slag. Alternatively, as described in JP 2009-280445 A, the electric furnace slag may be placed in a container and steam may be supplied to the steelmaking slag in the container through a steam pipe. In this case, the container containing the electric furnace slag may be a pressure-resistant container, and steam may be supplied at a pressure higher than atmospheric pressure. In this case, the aging treatment may be carried out for, for example, 1 hour to 24 hours. [Example]

[0064] The effects of the method for producing hydrated iron and steel slag products of this embodiment will be explained in more detail below using examples. The conditions in the following examples are examples adopted to confirm the feasibility and effects of the method for producing hydrated iron and steel slag products of this embodiment. Therefore, the production method of this embodiment is not limited to these examples.

[0065] Steelmaking slag was prepared with the raw material numbers shown in Table 1. For each steelmaking slag with a raw material number, the MgO content (mass%) was determined in accordance with JIS M 8205:2000 "Iron ore - X-ray fluorescence analysis method."

[0066] [Table 1]

[0067] [Aging process] Of the steelmaking slags shown in Table 1, the steelmaking slags from converter A and converter B were subjected to the following aging treatment. The steelmaking slags from converter A and converter B were placed outdoors. The steelmaking slags were heated to 100°C while being sprayed with steam. After heating, the steelmaking slags were held at 100°C for five days. After holding for five days, the temperature was lowered to room temperature over one day.

[0068] Furthermore, the following aging treatment was carried out on the steelmaking slag from the electric furnace and the reducing furnace among the steelmaking slags shown in Table 1. The steelmaking slag from the electric furnace and the reducing furnace was placed outdoors. The temperature of each steelmaking slag was raised to 100°C while spraying steam onto it. After the temperature was raised, the steelmaking slag was held at 100°C for 12 days. After holding for 12 days, the temperature was lowered to room temperature over one day.

[0069] [Kneading process] In the mixing step, the following raw materials were prepared: (Raw material 1) Steelmaking slag As the steelmaking slag, the steelmaking slags shown in Table 1 were prepared. (Raw material 2) Binding material As a binder, commercially available blast furnace cement type B manufactured by Taiheiyo Cement Corporation was prepared. (Raw material 3) Water As the water, industrial water was prepared. (Raw material 4) Blast furnace slag Granulated blast furnace slag was prepared as the blast furnace slag. The particle size of the granulated blast furnace slag was 5 mm or less. In addition to the above, other raw materials prepared were a high-performance AE water-reducing agent (trade name: Chupol EX60) manufactured by Takemoto Yushi Co., Ltd. and polypropylene fiber (trade name: Ballink) manufactured by Hagiwara Kogyo Co., Ltd.

[0070] The above raw materials were mixed in the proportions (kg / m) shown in Table 2. 3 ), and then placed in a mold to produce a hydrated steel slag (hereinafter referred to as a test specimen). Note that the "blending ratio (%)" in Table 2 indicates the ratio (mass %) of the mass of electric furnace slag to the total mass of low-Mg steelmaking slag (converter A and converter B) and electric furnace slag.

[0071] [Table 2]

[0072] Specifically, specimens with each test number were manufactured in accordance with JIS A 1132:2020. The formwork was removed 48 hours after casting. Using the above manufacturing process, specimens with each test number shown in Table 2 were manufactured.

[0073] [Evaluation test] The following evaluation tests were carried out on the manufactured test specimens (steel slag hydrated solidified bodies). (Test 1) Compression strength evaluation test (Test 2) Expansion stability evaluation test Each test will be explained below.

[0074] [(Test 1) Compression strength evaluation test] The specimens were cured at a temperature of 20±3°C, and after removing the formwork, they were left to wet cure for 7 days and 28 days, respectively. The compressive strength (N / mm 2 ) was determined. The obtained compressive strengths are shown in Table 3. As shown in Table 3, in test number 8, the steelmaking slag was reduction furnace slag, so the compressive strength was low. In contrast, in test numbers 1 to 7 and 9, sufficient compressive strength was obtained.

[0075] [Table 3]

[0076] [(Test 2) Expansion Stability Evaluation Test] The following expansion stability evaluation test was conducted on the 10 specimens of each test number, following the water immersion expansion test method specified in Appendix B of JIS A 5015:2013.

[0077] 48 hours after casting, the formwork was removed and each specimen was immersed in a curing device that stored water. At this time, the water level in the curing device was set to be at least 15 mm higher than the top surface of the specimen. After each specimen was immersed in the water in the curing device, the water temperature in the device was raised to 80°C. Once the water temperature reached 80±3°C, it was maintained. At the schedules shown in Table 4, the specimens were removed from the curing device and allowed to cool to room temperature. The appearance of the specimens was then visually inspected to check for cracks. Cracking was evaluated as follows: ○: No cracks were observed ×: Cracks with a width of 0.3 mm or more and a depth of 4 mm or more can be confirmed. The appearance of the specimens was visually observed on the 5th, 10th, and 15th days after the water temperature was maintained at 80±3°C. After visual observation, the specimens were again immersed in the curing device with the water temperature maintained at 80±3°C. The test results are shown in Table 4.

[0078] [Table 4]

[0079] Referring to Tables 1 to 4, in the specimens with test numbers 1 to 5, electric furnace slag was blended as the steelmaking slag, and the blending ratio was over 25%. Therefore, in the specimens with these test numbers, similar to test numbers 6, 7, and 9, no cracks with a width of 0.3 mm or more and a depth of 4 mm or more were observed by the 15th day (equivalent to "○" in the above evaluation). In other words, despite containing a large amount of electric furnace slag, the steel slag hydrated compacts of the present invention were able to suppress cracks due to expansion at a level equivalent to that of conventional steel slag hydrated compacts.

[0080] On the other hand, in test number 8, in which reduction furnace slag was used as the steelmaking slag, cracks with a width of 0.3 mm or more and a depth of 4 mm or more (equivalent to "x" in the above evaluation) were confirmed by the 10th day.

[0081] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

Claims

1. A preparation step of preparing electric furnace slag having an MgO content of more than 8.5% by mass; 1 m ３ Around 1,000 to 2,000 kg of steelmaking slag; 300-400 kg of binder; 150 to 250 kg of water, a mixing step of mixing the slag with 0 to 700 kg of blast furnace slag; Including, In the kneading step, In the steelmaking slag, the blending ratio of the electric furnace slag is more than 25 to 100% by mass, and the blending ratio of low-Mg steelmaking slag, which is steelmaking slag having an MgO content of 8.5% or less by mass, is 0 to less than 75% by mass. A method for manufacturing hydrated iron and steel slag solidified bodies.

2. The method for producing a hydrated iron and steel slag solidified body according to claim 1, The compound containing Mg in the electric furnace slag is a Mg-containing mineral phase that is a mineral phase that mainly contains Mg. A method for manufacturing hydrated iron and steel slag solidified bodies.

3. The method for producing a hydrated iron and steel slag solidified body according to claim 2, The Mg-containing mineral phase is One or more selected from the group consisting of akermanite, diopside, monticellite and spinel A method for manufacturing hydrated iron and steel slag solidified bodies.

4. The method for producing a hydrated iron and steel slag solidified body according to claim 2 or 3, Among the compounds containing Mg in the electric furnace slag, the content of the Mg-containing mineral phase is 50% by mass or more. A method for manufacturing hydrated iron and steel slag solidified bodies.

5. The method for producing a hydrated iron and steel slag solidified body according to claim 4, Among the compounds containing Mg in the electric furnace slag, the content of free MgO is 5% by mass or less. A method for manufacturing hydrated iron and steel slag solidified bodies.

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