Method for manufacturing hydrated and solidified steel slag

Abstract

To provide a method for producing steel slag hydrated matrix that can ensure appropriate fluidity of a mixture of water and a material that contains powdery steel slag.SOLUTION: A method for producing steel slag hydrated matrix includes: a mixing step in which a mixture is produced by mixing water with a material that contains steel slag containing CaO, SiO2, and P2O5, and a binder that contains fine powders of blast furnace slag; and a hardening step in which the mixture is hardened. The steel slag has a mass ratio of CaO / SiO2 of 1.4 or more and a P2O5 content of 0.3 mass% or less. In the mixing step, the water, the blast furnace slag, and the binder are added so as to satisfy the following relation. Volume of water / (Volume of binder+volume of steel slag)=0.60-0.90.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a hydrated and solidified steel slag body, which is generated by hardening a mixture of a material containing steelmaking slag and water. [Background technology]

[0002] Some steelmaking slags generated in reductive refining, such as secondary refining slag and molten reduction slag, have a lower P2O5 content than other steelmaking slags. Steelmaking slags with high basicity, indicated by CaO / SiO2, contain dicalcium silicate as their main mineral phase. In steelmaking slags with low P2O5 content, dicalcium silicate undergoes a phase transformation from α' to γ ​​during the solidification process.

[0003] Steelmaking slag with a basicity of 1.4 or higher and a P2O5 content of 0.3% by mass or less tends to pulverize due to the aforementioned phase transformation. Slag that satisfies the above conditions of basicity and P2O5 mass% will be hereinafter referred to as powdered steelmaking slag.

[0004] Powdered steelmaking slag is unsuitable as aggregate for hydrated solidified bodies due to its fine particle size. Attempts are being made to utilize such powdered steelmaking slag as a hydrated solidified body. For example, Patent Document 1 describes a method for producing a slag hardened body in which water is added to a mixture containing powdered steelmaking slag and an SiO2-containing substance having latent hydraulic properties, and then the mixture is molded under a predetermined pressure.

[0005] Incidentally, steelmaking slag is also used as a roadbed material. For example, Patent Document 2 describes the use of a steel slag-containing composition, obtained by compacting a composition containing steelmaking slag, blast furnace slag fine powder, and water, as a pavement. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-114547 [Patent Document 2] Japanese Patent Publication No. 2015-196631 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, when using the manufacturing method described in Patent Document 1, there is a problem in that the workability deteriorates due to the poor fluidity of the powdered steelmaking slag. For this reason, the manufacturing method in Patent Document 1 involves forming the material under a predetermined pressure. Consequently, it is necessary to install new dedicated equipment for this forming process, and improvements are needed in terms of introduction costs. Furthermore, the operation of this equipment is complicated, and improvements are needed in terms of work efficiency.

[0008] Furthermore, when a steel slag-containing composition is manufactured using powdered steel slag according to the description in Patent Document 2, the fluidity of the mixture containing powdered steel slag and water is extremely low, which presents a problem in that it is difficult to manufacture the steel slag-containing composition.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a hydrated and solidified steel slag body that can easily ensure appropriate fluidity of a mixture of a material containing powdered steelmaking slag and water. [Means for solving the problem]

[0010] To solve the above problems, the present invention has the following features. [1] CaO, SiO 2、 A mixing step to produce a mixture by mixing a material containing steelmaking slag containing P2O5 and a binder containing blast furnace slag fine powder with water, The process includes a curing step of curing the mixture, The steelmaking slag has a CaO / SiO2 mass ratio of 1.4 or more, and a P2O5 content of 0.3% by mass or less. In the mixing step, a method for producing a steel slag hydrated solid, wherein the water, the steelmaking slag, and the binder are added so as to satisfy the following relationship. Volume of water / (Volume of binder + Volume of steelmaking slag) = 0.60 to 0.90 [2] The content of the steelmaking slag in the mixture is 370 kg or less per 1 m 3 .[1] The method for producing a steel slag hydrated solid according to [1]. [3] The method for producing a steel slag hydrated solid according to [1] or [2], wherein the maximum particle size of the steelmaking slag is 15 mm or less.

Effect of the Invention

[0011] According to the method for producing a steel slag hydrated solid of the present invention, in the mixing step of mixing the material and water to form a mixture, each component is added in an amount that satisfies the above relational expression, so that appropriate fluidity of the mixture can be ensured.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described. The method for producing a steel slag hydrated solid includes a mixing step of mixing a material containing steelmaking slag and a binder with water to form a mixture, and a curing step of curing the mixture.

[0013] The steelmaking slag is not particularly limited, but contains CaO, SiO 2、 P2O5. The steelmaking slag has a mass ratio of CaO / SiO2 of 1.4 or more and a P2O5 content of 0.3 mass% or less. Here, the P2O5 content of 0.3 mass% or less may be a content less than the detection limit of the device for detecting P2O5. In other words, for P2O5, it is sufficient that it may be contained in the steelmaking slag, and it may be a trace amount that is not actually detected by the detection device. In general, ordinary steelmaking slag contains P2O5, and the probability that its content exceeds 0.3 mass% is very high.

[0014] As such steelmaking slag, slag with a CaO / SiO2 ratio of 2.0 or higher is preferred because it produces a large amount of dicalcium silicate. For example, secondary refining slag generated when molten steel is secondary refined in a vacuum degassing unit, or molten reduction refining slag generated when the mother molten metal is directly melted with Cr ore before the production of stainless steel, can be used.

[0015] Steelmaking slag with this composition precipitates a dicalcium silicate phase during cooling. Furthermore, because the P2O5 content of the steelmaking slag is low, the dicalcium silicate transforms into a γ phase, causing the steelmaking slag to pulverize. Therefore, steelmaking slag with this composition will henceforth be referred to as powdered steelmaking slag.

[0016] The maximum particle size of the powdered steelmaking slag should preferably be 15 mm or less, more preferably 10 mm or less, and more preferably 5 mm or less. By setting the maximum particle size of the powdered steelmaking slag to 15 mm or less, the expansion due to hydration of the hydrated solidified steel slag, which is formed by hardening a mixture of the material and water, can be reduced. In other words, it becomes possible to improve the expansion stability of the hydrated solidified steel slag.

[0017] Furthermore, the maximum particle size of powdered steelmaking slag is expressed as the particle size at the smallest mesh opening of the sieve through which all of the powdered steelmaking slag can pass. The mesh size of the sieve used for sieve analysis is not particularly limited, but for example, those specified in JIS Z 8801 can be used. Specifically, if the maximum particle size of the powdered steelmaking slag is 15 mm or less, a sieve with a nominal size of 15 mm has a mesh opening of 16 mm, so it is preferable to use powdered steelmaking slag that can pass through a sieve with a mesh opening of 16 mm in its entirety.

[0018] Furthermore, the materials may include steelmaking slag that does not meet the requirements for powdered steelmaking slag as described above.

[0019] The binder contains blast furnace slag fine powder. For example, pulverized blast furnace slag can be used as the blast furnace slag fine powder. For example, blast furnace slag fine powder used in JIS R 5211 2009 "Blast Furnace Cement" or blast furnace slag fine powder conforming to JIS A 6206 2013 "Blast Furnace Slag for Concrete" can be used.

[0020] The specific surface area of ​​blast furnace slag fine powder produced by the Blaine process is approximately 3000 cm². 2 It is preferable that the amount be 1 / g or more. Furthermore, the specific surface area of ​​the blast furnace slag fine powder produced by the Blaine method is 4000 cm². 2 A value of 1 / g or higher is preferable because it increases the activity index, which is an indicator of hydraulic hardness.

[0021] Furthermore, the binder is not particularly limited, and in addition to alkali stimulants, silica-containing substances with pozzolanic reactivity can be used. As alkali stimulants, slaked lime and ordinary Portland cement as specified in JIS R 5210 2019 can be used. As silica-containing substances with pozzolanic reactivity, fly ash and silica fume can be used.

[0022] Examples of silica-containing materials include those conforming to JIS R 5210 2009 "Portland cement," JIS R 5211 2009 "Blast furnace cement," and JIS A 6201 2015 "Fly ash for concrete."

[0023] The material may contain a water-reducing agent. The inclusion of a water-reducing agent in the material allows for a reduction in the amount of water added to the mixture and improves the dispersibility of the material. Reducing the amount of water added to the mixture increases the strength of the hydrated and solidified steel slag.

[0024] As a water-reducing agent, for example, a polycarboxylic acid-based water-reducing agent can be used. The amount of water-reducing agent used is preferably 0.3 to 0.5% by mass of the unit binder amount.3 It is the mass of the binder contained in

[0025] In the mixing step, materials including water, powdered steel slag, and a binder are added so as to satisfy the following relationship. Volume of water / (Volume of binder + Volume of powdered steel slag) = 0.60 to 0.90 Also, the volume ratio is preferably 0.65 to 0.85, more preferably 0.65 to 0.80, and even more preferably 0.70 to 0.75.

[0026] By setting the ratio of the volume of water to the volume of powdered steel slag and the binder (hereinafter also referred to as the main material) to 0.60 or more, appropriate fluidity can be imparted to the mixture of the material and moisture.

[0027] Also, as the ratio of the volume of water to the volume of the main material increases, that is, as the volume of water in the mixture increases, the strength of the steel slag hydrated solid tends to decrease. Also, as the volume of the main material becomes smaller than the volume of water, the addition amount of powdered steel slag decreases, and the utilization amount of powdered steel slag decreases. Therefore, the ratio of the volume of water to the volume of the main material in the mixture is preferably 0.90 or less.

[0028] The amount of powdered steel slag per unit of the steel slag hydrated solid is preferably 370 kg / m 3 or less. In other words, the content of powdered steel slag in the mixture is preferably 370 kg or less per 1 m 3 and is preferably 70 to 370 kg, more preferably 80 to 350 kg, and even more preferably 90 to 350 kg.

[0029] By setting the content of powdered steel slag in the mixture to 370 kg or less per 1 m 3 the amounts of free CaO and free MgO in the mixture are suppressed. As a result, sufficient expansion stability can be ensured when the mixture is made into a steel slag hydrated solid.

[0030] Furthermore, the powdered steelmaking slag content of the mixture is 1 m 3 When the amount exceeds 370 kg per unit area, the fluidity of the mixture tends to decrease. From this perspective, the unit amount of powdered steelmaking slag should be 370 kg / m³. 3 The following is preferable: The content of powdered steelmaking slag in the mixture should be 1 m 3 Setting the amount to 70 kg or more per unit is preferable because it increases the amount of powdered steelmaking slag that can be added, thereby promoting its utilization.

[0031] The mixing in the mixing step is not particularly limited, but for example, it can be done using a concrete mixer at room temperature.

[0032] In the hardening step, which involves curing the mixture, hardening methods used in the cement and concrete fields can be employed. For example, the mixture can be hardened by curing it in water at 20°C. The processing time for the hardening step should be adjusted as appropriate according to temperature, humidity, etc. [Examples]

[0033] (Example Test 1: Liquidity Assessment) A mixture was prepared by mixing powdered steelmaking slag, a binder-containing material, and water. By changing the proportions of the materials used in the production of the hydrated and solidified steel slag, Invention Examples 1 to 6 and Comparative Examples 1 to 2 were prepared, and the fluidity of each mixture was evaluated.

[0034] (material) The mixture was composed of powdered steelmaking slag, steelmaking slag (hereinafter also referred to as slag A), a binder, and a water-reducing agent.

[0035] Two types of secondary refining slag with the compositions shown in Table 1 were used as powdered steelmaking slag. The detection limit of the detection device used for P2O5 detection was 0.05 mass%. In Table 1, the P2O5 content of powdered steelmaking slag 2 is expressed as <0.05 mass% because, although it may contain P2O5, the content is below the detection limit of the detection device. Also, the units of the values ​​listed in Table 1 are mass% except for the "CaO / SiO2" item.

[0036] [Table 1]

[0037] Slag A is an aggregate. Slag A is not limited to slag; crushed stone and other materials can also be used. In this embodiment, steelmaking slag with a maximum particle size of 40 mm or less is used as slag A. When using steelmaking slag as slag A, it is preferable that the P2O5 content is higher than 0.3% by mass and that it is not pulverized.

[0038] As binders, blast furnace slag powder and ordinary Portland cement as specified in JIS R 5210 2019 were used. The densities of blast furnace slag powder, ordinary Portland cement, and powdered steelmaking slag are shown in Table 2. In subsequent test examples, the case in which blast furnace slag powder, ordinary Portland cement, and powdered steelmaking slag were used as the main materials will be described.

[0039] [Table 2]

[0040] As a water-reducing agent, a polycarboxylic acid-based high-performance water-reducing agent (Tupol, manufactured by Takemoto Oil Co., Ltd.) was used.

[0041] The mixtures of Invention Examples 1-6 and Comparative Examples 1-2 were prepared using the formulations shown in Table 3.

[0042] (Evaluation of fluidity and strength) The material and water were mixed to prepare a mixture, which was then cast. The mixture was allowed to harden at room temperature, and the formwork was removed the following day. The hardened mixture was cured in water at 20°C for 7 days to produce a hydrated and solidified steel slag body.

[0043] The fluidity of the mixture was evaluated in relation to the fluidity of the mixture when producing the hydrated solidified steel slag. The slump value during mixing (refer to JIS A 1101, Method for testing slump of concrete) was measured. The target slump value was set to 3.0 cm to 20.0 cm, considering slipform construction or manual construction. Furthermore, the strength of the hydrated solidified steel slag was evaluated using the method described below.

[0044] The strength of the hydrated and solidified steel slag was evaluated by measuring the flexural strength at 7 days of age according to JIS A 1108 2018. The flexural strength was evaluated using the nominal strength of 4.5 N / mm² listed in JIS A 5308 2019 "Ready-Mixed Concrete" for paving concrete. 2 The above were deemed acceptable. Table 3 shows the bending strength evaluations for Invention Examples 1-6 and Comparative Examples 1-2. In the following tables, the strength evaluation is given as 7-day bending strength (N / mm²). 2 ) should be written as follows.

[0045] [Table 3]

[0046] In Invention Examples 1 to 6, where the volume ratio of water to the volume of the main material was 0.60 to 0.90, appropriate fluidity of the mixture was obtained. Furthermore, appropriate flexural strength was obtained in the hydrated and solidified steel slag bodies obtained by hardening Invention Examples 1 to 6.

[0047] In contrast, in Comparative Example 1, where the water volume / main material volume ratio was less than 0.60, the fluidity of the mixture was lower than that of Invention Examples 1-6, making placement difficult. Furthermore, in Comparative Example 2, where the water volume / main material volume ratio exceeded 0.90, the fluidity was too high, making it unsuitable as paving concrete. In addition, the strength of the hydrated and solidified steel slag bodies in Comparative Examples 1 and 2 was lower than that of Invention Examples 1-6, and appropriate strength could not be obtained.

[0048] By the way, the paving concrete has a bending strength of 4.5 N / mm² on the 28th. 2 It is stipulated that, for Invention Examples 1 to 6, a strength exceeding the specified value can be obtained within 7 days after placement. Therefore, if the hydrated and solidified steel slag bodies of Invention Examples 1 to 6 are used as a substitute for pavement concrete, traffic can be reopened at an earlier stage.

[0049] (Test Example 2: Expansion evaluation of hydrated and solidified steel slag) By changing the composition of the mixture used to produce the hydrated and solidified steel slag, Invention Examples 7-10 and Comparative Example 3 were prepared, and the fluidity and expansion properties of each mixture were evaluated. The mixtures of Invention Examples 7-10 and Comparative Example 3 were prepared with the proportions shown in Table 4. The mixtures of Invention Examples 1-3 and 6, which were tested in Test Example 1, were also subjected to the tests in Test Example 2.

[0050] The mixtures of Invention Examples 7-10 and Comparative Example 3 were prepared in the same manner as in Test Example 1. The fluidity was also evaluated in the same manner as in Test Example 1. The mixtures of Invention Examples 7-10 and Comparative Example 3 were prepared using the proportions shown in Table 4. The mixtures of Invention Examples 1-3 and 6, which were tested in Test Example 1, were also used in the tests of Test Example 2.

[0051] Specifically, for Invention Examples 6 to 10, the powdered steelmaking slag content of the mixture is 1 m 3 The mixture was manufactured to satisfy the conditions of having a volume of 370 kg or less per unit area and a water volume / main material volume ratio of 0.60 to 0.90. In Invention Examples 2 and 3, the powdered steelmaking slag content of the mixture was 1 m³. 3 The weight per unit is 370 kg or less, and the ratio of water volume to main material volume is 0.60 to 0.90.

[0052] Furthermore, in Comparative Example 3, the powdered steelmaking slag content of the mixture was 1 m 3 We created a product that did not meet either of the following conditions: weighing less than 370 kg per unit area, or having a water volume / main material volume ratio of 0.60 to 0.90.

[0053] (Expansion evaluation) The material and water were mixed to prepare a mixture, which was then cast. The mixture was allowed to harden at room temperature, and the formwork was removed the following day. The hardened mixture was cured in water at 20°C for 7 days to produce a hydrated and solidified steel slag body. Subsequently, an expansion test was performed on the hydrated and solidified steel slag body.

[0054] After immersing the hydrated and solidified steel slag in 80°C water for 10 consecutive days, the appearance of the hydrated and solidified steel slag was observed to check for the presence of large cracks. Those without visible cracks were evaluated as "pass," while those with visible cracks were evaluated as "fail." Furthermore, for mixes with poor fluidity that could not be cast, both the 7-day bending strength and expansion resistance evaluations were evaluated as "unmeasurable."

[0055] [Table 4]

[0056] Invention Example 1 satisfies the condition that the volume ratio of water to the volume of the main material is 0.60 to 0.90. Invention Examples 2 to 3 and 6 to 10 have a powdered steelmaking slag content of 1 m³ in the mixture. 3 The weight per unit is 370 kg or less, and the ratio of water volume to main material volume satisfies the condition of 0.60 to 0.90.

[0057] The mixtures of Invention Examples 1-3 and 6-10 had slump values ​​in the range of 3.5-20.0 and possessed appropriate fluidity. The flexural strength of the hydrated solidified steel slag bodies obtained by curing the mixtures of Invention Examples 1-3 and 6-10 was 4.5 N / mm² in all cases. 2 That was all.

[0058] As mentioned above, the paving concrete has a 28-day flexural strength of 4.5 N / mm². 2 It is stipulated that, for Invention Examples 1-3 and 6-10, strength exceeding the specified value can be obtained within 7 days after placement. Therefore, if the hydrated and solidified steel slag of Invention Examples 1-3 and 6-10 is used as a substitute for pavement concrete, traffic can be opened to traffic at an early stage. Furthermore, no cracks were observed in the hydrated and solidified steel slag of Invention Examples 2-3 and 6-10 during the expansion performance evaluation. Therefore, the hydrated and solidified steel slag of Invention Examples 2-3 and 6-10 can also be used as roadbed material.

[0059] In Comparative Example 3, the mixture had low fluidity, making placement difficult. Therefore, it was impossible to measure the expansion properties in Comparative Example 3. Furthermore, the powdered steelmaking slag content of the mixture was 1 m³. 3 In Invention Example 1, which exceeded 370 kg per unit area, cracking was observed during the expansion performance evaluation.

[0060] (Test Example 3: Evaluation of the physical properties of particle size of powdered steelmaking slag) By changing the formulation used in the production of hydrated and solidified steel slag, Invention Examples 11 and 8 and Comparative Examples 1 and 2 were prepared, and the fluidity and swellability of each mixture were evaluated.

[0061] The mixtures of Invention Examples 11 and 8 and Comparative Examples 1 and 2 were prepared in the same manner as in Test Example 1. The fluidity was also evaluated in the same manner as in Test Example 1. The mixtures of Invention Examples 11 and 8 and Comparative Examples 1 and 2 were prepared using the formulations shown in Table 5.

[0062] Specifically, for Invention Example 11, powdered steelmaking slag, which has been classified to a maximum particle size of 10 mm or less using a sieve, was used as the material, and the product was manufactured to satisfy the condition that the volume ratio of water to the volume of the main material is 0.60 to 0.90. In Table 5, this powdered steelmaking slag is listed as Powdered Steelmaking Slag 1 (0-10 mm). Furthermore, the composition of Invention Example 11 is the same as that of Invention Example 5, except that the maximum particle size of the powdered steelmaking slag is different.

[0063] Furthermore, in Table 5, the powdered steelmaking slag in Invention Example 8 is labeled as "Powdered Steelmaking Slag 1 (0-40mm)" to make the difference from the maximum particle size of the powdered steelmaking slag in Invention Example 11 clearer.

[0064] Comparative Examples 1 and 2 are identical to Test Example 1, so their explanation will be omitted.

[0065] (Expansion evaluation) The appearance of the hydrated and solidified steel slag was observed to check for the presence of large cracks (cracks that may affect the structural strength). In the observation, samples without large cracks were marked "◎", samples without large cracks but with small cracks (cracks that do not affect the structural strength) or pop-outs (a phenomenon in which the surface peels off like a cone) were marked "〇", and samples with large cracks were marked "×". The expansiveness evaluations for Invention Examples 11 and 8 and Comparative Examples 1 and 2 are shown in Table 5.

[0066] [Table 5]

[0067] The mixture of Invention Example 11 had a slump value in the range of 3.5 to 20.0 and possessed appropriate fluidity. No cracks were observed in Invention Example 11. The mixture of Invention Example 8 also possessed appropriate fluidity. Although there was some small pop-out in Invention Example 8, no cracks were observed. As described above, Comparative Example 1 had low fluidity and was difficult to place. Comparative Example 2 had excessively high fluidity and was not suitable as paving concrete. Comparative Examples 1 and 2 had a unit powdered steelmaking slag content of 370 kg / m³. 3 The above results show that large cracks were observed after immersion at 80°C for 10 days. Furthermore, the 7-day bending strength was 4.5 N / mm². 2 The results were as follows:

[0068] As described above, when it is required to satisfy the fluidity of the mixture, the strength of the hydrated and solidified steel slag, and the expansion stability of the hydrated and solidified steel slag at a high level, it has been confirmed that it is preferable to produce the hydrated and solidified steel slag using powdered steelmaking slag with a maximum particle size of 10 mm or less.

Claims

1. CaO, SiO ２ , P ２ O ５ A mixing step to produce a mixture by mixing a material containing steelmaking slag and a binder containing blast furnace slag fine powder with water, The process includes a curing step of curing the mixture, The aforementioned steelmaking slag is CaO / SiO ２ The mass ratio of is 1.4 or more, and P ２ O ５ The content is 0.3% by mass or less. In the mixing step, the water, the steelmaking slag, and the binder are added in such a way that the following relationship is satisfied: A method for producing a hydrated and solidified steel slag body, wherein the steelmaking slag content of the mixture is 370 kg or less per 1 m³. Volume of water / (Volume of binder + Volume of steelmaking slag) = 0.60 to 0.90

2. The method for producing a hydrated and solidified steel slag body according to claim 1, wherein the maximum particle size of the steelmaking slag is 15 mm or less.

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