Method for manufacturing cured body, and cured body

Abstract

Provided is a method for manufacturing a cured body that has a rapid curing property and that makes it possible to suppress expansion due to delayed generation of ettringite.　The method for manufacturing a cured body comprises: a mixing step for mixing steelmaking slag, a binder containing a blast furnace slag fine powder, and water to form a mixture; and a curing step for curing the mixture. The mixture satisfies relational expression (1).　(1): 2.5 ≤ (the mass of sulfur in terms of SO3 per 1 m3 of the cured body × 100) / (the mass of the blast furnace slag fine powder per 1 m3 of the cured body) ≤ 9.0

Description

Method for producing hardened body and hardened body

[0001] The present invention relates to a method for producing a hardened body that has rapid hardening properties and can suppress expansion due to delayed ettringite formation, and the hardened body.

[0002] One of the slag products made from steelmaking slag, a by-product of steelworks, is hydrated steel slag.Hydrated steel slag is primarily made from steelmaking slag and ground granulated blast furnace slag, and can be manufactured using mixing equipment similar to concrete.

[0003] However, because steel slag hydrated hardened compacts use a large amount of ground granulated blast furnace slag, they develop strength more slowly than regular concrete, and require a long time, from pouring after mixing to removing the form and curing, before they attain sufficient strength for use as a product. For this reason, an efficient and inexpensive manufacturing process for steel slag hydrated hardened compacts is needed.

[0004] To address this issue, Patent Document 1 discloses a process for manufacturing a hydrated hardened steel slag body using an immediate demolding method. When steelmaking slag containing free CaO is used as the material for the hydrated hardened steel slag body, cracks may occur in the hydrated hardened steel slag body due to volume expansion caused by the hydration reaction of the free CaO. To address this issue, Patent Document 2 discloses a process for manufacturing a hydrated hardened steel slag body using a slag containing free CaO and SiO ２ A method for producing a hardened slag body by hydrating and hardening a mixture containing substances has been disclosed. According to Patent Document 2, by adding 0.5 mass % or more of CaS and / or S in terms of S, a hardened slag body having high strength and suppressing hydration expansion of free CaO can be produced.

[0005] JP 2016-132578 A JP 2001-153567 A

[0006] The method disclosed in Patent Document 1, which aims to establish an efficient and inexpensive manufacturing process for hydrated hardened steel slag bodies, requires a large capital investment because it requires vibration-pressure compaction molding equipment. Since the mold used is fixed, there are limitations on the dimensions of the hardened bodies that can be manufactured, making it difficult to apply the method to all of the various shapes required for hydrated hardened steel slag bodies.

[0007] When an attempt was made to manufacture a hardened body using the method for manufacturing a slag hardened body disclosed in Patent Document 2, the hardened body produced had a problem in that cracks that were thought to be due to delayed ettringite formation occurred. The present invention was made in consideration of these problems of the prior art, and its object is to provide a method for manufacturing a hardened body that has rapid hardening properties and can suppress expansion due to delayed ettringite formation, and a hardened body.

[0008] The means for solving the above problems are as follows: [1] A method for producing a hardened body, comprising a mixing step of mixing steelmaking slag, a binder containing ground granulated blast furnace slag, and water to form a mixture, and a hardening step of hardening the mixture, wherein the mixture satisfies the following formula (1): 2.5≦1m of hardened body ３ Winning SO ３ Converted mass of sulfur x 100 / 1 m of hardened material ３ [2] The method for producing a hardened body according to [1], wherein the steelmaking slag contains a sulfur component. [3] The amount of the SO ３ [4] The method for producing a hardened body according to [2], wherein the converted sulfur component concentration is 0.25 mass% or more. [4] The method for producing a hardened body according to [2] or [3], wherein the number of days that have passed since the steelmaking slag was discharged is 30 days or more. [5] The method for producing a hardened body according to any one of [1] to [4], wherein the steelmaking slag is carbonated steelmaking slag. [6] A hardened body comprising steelmaking slag, a binder containing ground granulated blast furnace slag, and water, and satisfying the following formula (1): 2.5≦1m of hardened body ３ Winning SO ３ Converted mass of sulfur x 100 / 1 m of hardened material ３ Mass of the ground granulated blast furnace slag per 1000g≦9.0g (1) [7] The hardened body according to [6], wherein the steelmaking slag is carbonated steelmaking slag.

[0009] By carrying out the method for producing a hardened body according to the present invention, it is possible to produce a hardened body that has rapid hardening properties and in which expansion due to delayed formation of ettringite is suppressed.

[0010] The inventors used a material containing a sulfur component as the material for the hardened body, and optimized the weight balance between the sulfur component contained in the material and ground granulated blast furnace slag. As a result, they found that while suppressing expansion due to delayed formation of ettringite, the development of the latent hydraulic properties of the ground granulated blast furnace slag is promoted by sulfate ions, thereby increasing the rapid hardening property of the hardened body and shortening the curing period compared to conventional methods, and thus completed the present invention.

[0011] The present invention will be described in detail below through embodiments of the present invention. In the following embodiments, an example of producing a hardened body using steelmaking slag containing a sulfur component will be described. However, this embodiment shows a preferred example of the present invention, and the present invention is not limited to this embodiment.

[0012] The method for producing a hardened body according to this embodiment includes a mixing step of mixing a sulfur-containing steelmaking slag, a binder containing ground granulated blast furnace slag, and water to produce a mixture, and a hardening step of hardening the mixture. The sulfur-containing steelmaking slag is preferably used as the steelmaking slag. The sulfur-containing steelmaking slag refers to steelmaking slag that contains sulfur or a sulfur compound.

[0013] By using steelmaking slag containing sulfur components, the hardened body according to this embodiment can be produced without adding sulfur separately to the mixture. Steelmaking slag containing sulfur components is prone to powdering and is difficult to use for roadbed materials, etc. Therefore, by using steelmaking slag containing sulfur components to produce the hardened body, it is possible to effectively utilize slag that is difficult to use for roadbed materials, etc., and it is also possible to reduce waste.

[0014] SO of steelmaking slag used in the production of hardened bodies ３The sulfur concentration in the steelmaking slag is preferably 0.25% by mass or more. The use of such steelmaking slag not only allows for the effective use of the slag, but also promotes the elution of sulfate ions from the steelmaking slag in the mixing step, further enhancing the rapid hardening of the hardened body in the hardening step. The method for measuring the sulfur concentration in the steelmaking slag is not particularly limited. For example, the sulfur concentration can be measured by a combustion ion chromatography method, in which the sulfur components are converted into sulfate ions by a combustion method, an aqueous solution is prepared, and then the sulfate ions in the aqueous solution are quantified using ion chromatography.

[0015] Examples of sulfur-containing steelmaking slag that can be used include secondary refining slag produced in a vacuum degassing system, smelting reduction refining slag produced by directly refining molten iron with Cr ore before the production of stainless steel, and desulfurization slag produced in the desulfurization treatment of hot metal. The steelmaking slag preferably has a particle size of 5 mm or less. A particle size of 5 mm or less means a particle size that can be sieved through a sieve with 5 mm openings.

[0016] When using steelmaking slag containing sulfur components, it is preferable to use steelmaking slag that has been discharged for 30 days or more. In the steelmaking process, sulfur-containing slag is often generated in refining processes in a reducing atmosphere. For this reason, it is thought that the sulfur contained in steelmaking slag is mainly in the form of sulfide ions. On the other hand, sulfide ions contained in steelmaking slag that has been discharged for 30 days or more are oxidized to sulfate ions upon contact with oxygen in the air during storage. These sulfate ions promote the development of the latent hydraulic properties of the ground blast furnace slag, so using steelmaking slag that has been discharged for 30 days or more can further enhance the rapid hardening properties of the hardened body.

[0017] It is preferable to use carbonated steelmaking slag as the steelmaking slag. In carbonated steelmaking slag, the calcium oxide and calcium hydroxide contained in the steelmaking slag are converted to calcium carbonate, which suppresses an increase in pH when the slag comes into contact with seawater. Therefore, a hardened body produced using steelmaking slag that has been carbonated as the steelmaking slag has the effect of increasing biocompatibility when used in marine areas. There are no particular limitations on the method for carbonating steelmaking slag. For example, the carbonation method can be carried out by adding CO ２ The steelmaking slag can be carbonated by contacting it with a gas containing

[0018] The binder contains ground granulated blast furnace slag. As the ground granulated blast furnace slag, ground granulated blast furnace slag conforming to JIS A 6206:2013 "Blast furnace slag for concrete" may be used. The specific surface area of ​​the ground granulated blast furnace slag contained in the binder is 3000 cm. ２ / g or more. ２ / g or more, the activity index, which is an index of hydraulic properties, is high. Therefore, the specific surface area of ​​the ground granulated blast furnace slag contained in the binder is 4000 cm ２ / g or more is more preferable.

[0019] The binder may contain, in addition to an alkali activator, a silica-containing substance having pozzolanic activity. Examples of the alkali activator include slaked lime, ordinary Portland cement as specified in JIS R 5210:2019, and blast furnace cement as specified in JIS R 5211:2019. Examples of the silica-containing substance having pozzolanic activity include fly ash, silica fume, and fly ash for concrete as specified in JIS A 6201:2015.

[0020] The water may be, for example, tap water, river water, lake water, well water, groundwater, industrial water, recycled water, or the like that meets the quality requirements of JIS A 5308: 2019. Seawater or hot spring water containing sulfate ions or thiosulfate ions may also be used.

[0021] In the mixing step, in addition to the sulfur-containing steelmaking slag, binder, and water, a chemical admixture such as a high-performance water reducer may be mixed. By mixing a chemical admixture, the amount of water to be mixed can be reduced and the dispersibility of the material can be increased. By reducing the amount of water to be mixed into the mixture, the strength of the hardened body can be increased. For example, a polycarboxylic acid-based high-performance water reducer can be used as the chemical admixture. The amount of the high-performance water reducer to be mixed is preferably 0.3% by mass or more and 0.5% by mass or less of the unit binder amount. The unit binder amount is 0.3% by mass or more and 0.5% by mass or less of the unit binder amount per 1 m of hardened body. ３ is the mass of binder contained in

[0022] In the mixing step, the steelmaking slag containing sulfur components and the ground granulated blast furnace slag are mixed so as to satisfy the following formula (1). ３ Winning SO ３ The converted mass of sulfur is "SO ３ Mass" is written as "mass". 1 m of hardened body ３ Winning SO ３ Converted mass of sulfur x 100 / 1 m of hardened material ３ The percentage of the mass of ground granulated blast furnace slag per unit mass is expressed as "SO ３ / BFS".

[0023] 2.5≦cured body 1m ３ Winning SO ３ Converted mass of sulfur (kg) x 100 / 1 m of hardened body ３ Mass of ground granulated blast furnace slag per unit (kg) ≦ 9.0 ... (1)

[0024] SO ３ Mass: 1 m of hardened body ３ The mass (kg) of the material containing sulfur components used per unit and the sulfur content of the material are expressed as SO ３ When materials containing multiple types of sulfur components are used in the production of a hardened body, the sulfur content of each material is calculated by multiplying the converted value (mass%) by the amount of sulfur. ３ The converted masses are calculated and the calculation results are added together.

[0025] SO ３By making the / BFS 2.5 or more, sulfate ions are eluted, which promotes the development of the latent hydraulic properties of the ground granulated blast furnace slag, thereby increasing the rapid hardening property of the hardened body in the hardening step. ３ If the BFS / BFS exceeds 9.0, the sulfate ions become excessive, and cracks occur in the hardened body due to expansion caused by delayed formation of ettringite. ３ / BFS must be 2.5 or more and 9.0 or less. ３ / BFS is preferably 3.0 or more and 8.5 or less, more preferably 4.0 or more and 8.0 or less, and most preferably 4.5 or more and 7.5 or less.

[0026] The mixing of the materials in the mixing step is not particularly limited, but may be performed, for example, using a concrete mixer to mix the materials at room temperature. The mixing step is preferably performed in an environment of 30°C or less. This suppresses a temperature rise in the mixture obtained by mixing the materials, and reduces the risk of expansion of the hardened body due to delayed ettringite formation. The mixing step is more preferably performed in an environment of 25°C or less. This further suppresses a temperature rise in the mixture, and further reduces the risk of expansion of the hardened body due to delayed ettringite formation.

[0027] The materials for the hardened body are not limited to sulfur-containing steelmaking slag, a binder containing ground granulated blast furnace slag, and water, but may also contain other materials. For example, the aggregate may be electric furnace slag, slag generated in non-ferrous metal smelting, crushed stone, crushed sand, natural aggregate, sulfur-free steelmaking slag, etc.

[0028] In the hardening step, the mixture produced in the mixing step is hardened. The method of hardening the mixture can be carried out using a method used in the cement and concrete fields. In the hardening step, for example, the mixture poured into a formwork is removed the next day and cured in water at 20°C. This hardens the mixture, producing a hardened body.

[0029] As described above, in the method for producing a hardened body according to this embodiment, by satisfying the above formula (1), it is possible to produce a hardened body that has rapid hardening properties and in which expansion due to delayed ettringite formation is suppressed. The hardened body produced in this manner contains steelmaking slag, a binder containing ground granulated blast furnace slag, and water, and satisfies the above formula (1). By satisfying the above formula (1), the hardened body according to this embodiment has rapid hardening properties and in which expansion due to delayed ettringite formation is suppressed.

[0030] Although this embodiment has been described using an example in which steelmaking slag containing sulfur components is used as the material for the hardened body, this is not limiting. Steelmaking slag not containing sulfur components may also be used as the material for the hardened body. In this case, it is sufficient to mix another material containing sulfur components that satisfies the above formula (1) into the mixture. This makes it possible to produce a hardened body that has rapid hardening properties and in which expansion due to delayed ettringite formation is suppressed.

[0031] Example 1 Next, an example will be described in which a hardened body was produced by using steelmaking slag, ground granulated blast furnace slag as a binder, ordinary Portland cement, water, and a high-performance water-reducing agent, and adjusting the mixing ratio of these. ３ Three types of steelmaking slag A to C with different converted sulfur component concentrations were used. ３ The converted sulfur component concentrations are shown in Table 1 below.

[0032]

[0033] Steelmaking slag A and steelmaking slag B are steelmaking slags containing sulfur components, while slag C is a steelmaking slag that does not contain sulfur components. ３ The converted sulfur component concentration was less than 0.05 mass%, so SO ３ In the calculation of / BFS, the mass of elemental sulfur in slag C was set to 0. Steelmaking slag A and steelmaking slag B were steelmaking slags that had been discharged for more than 30 days. These steelmaking slags were crushed to a particle size of 5 mm or less and used to produce the hardened bodies.

[0034] The binders used were ground granulated blast furnace slag and ordinary Portland cement as specified in JIS R 5210:2019. ３ The converted sulfur component concentration is 2.0 mass%, which is the same as the SO of ordinary Portland cement. ３ The converted sulfur component concentration was 2.1% by mass. In Example 1, a polycarboxylic acid-based high-performance water-reducing agent (Tupol manufactured by Takemoto Yushi Co., Ltd.) was also used as a chemical admixture.

[0035] These materials were mixed in a concrete mixer to form a mixture, which was then poured into a cylindrical formwork measuring φ100 × 200 mm. After sealed and curing at 20°C until the next day, the formwork was removed and the mixture was cured in water at 20°C until the specified age, producing a hardened body for strength evaluation.

[0036] <Strength evaluation> The strength of the hardened body was evaluated by measuring the compressive strength in accordance with JIS A 1108:2018. At the age of 1 day, the compressive strength of the hardened body was 5 N / mm, which is a guideline for the strength at which the hardened body can be removed from the frame and handled after 1 day of curing. ２ At the age of 7 days, the compressive strength of the hardened body was 18 N / mm, which corresponds to the strength of ordinary concrete at 28 days. ２ If the result was above this, it was evaluated as passing.

[0037] <Evaluation of Expansion Stability> The expansion stability of the hardened body was evaluated by curing the material in water at 20°C for up to 7 days, then immersing the cylindrical hardened body in a water tank maintained at 60°C for 21 days, and evaluating the expansion stability mainly based on the expansion due to delayed ettringite formation of the hardened body from the appearance of the hardened body after immersion. The evaluation criteria are as follows.

[0038] ◯: No cracks occurred in the hardened body, and no large pop-outs occurred on the surface of the hardened body. Δ: No cracks occurred in the hardened body, and large pop-outs occurred on the surface of the hardened body. ×: Cracks occurred in the hardened body.

[0039] <Seawater immersion evaluation> A mixture of materials and water kneaded in a concrete mixer was poured into a cylindrical formwork of φ100 x 200 mm. After sealing and curing at 20°C until the next day, the formwork was removed, and sealing and curing was continued at 20°C until the material reached an age of 7 days, producing a hardened body for seawater immersion evaluation. For the seawater immersion evaluation, the hardened body was immersed in artificial seawater with a volume (mL) 10 times the mass (g) of the hardened body, and shaken at about 200 times per minute with a shaker for 6 hours while measuring the pH, and the highest pH value during shaking was recorded. The composition of the materials for the hardened body, SO ３ The results of the / BFS value, strength evaluation, expansion stability evaluation and seawater immersion evaluation are shown in Table 2 below.

[0040]

[0041] In Table 2, the 1-day strength indicates the compressive strength of the hardened material at 1 day old, and the 7-day strength indicates the compressive strength of the hardened material at 7 days old. ３ In the hardened bodies of Examples 1 to 8, in which the BFS was adjusted to 2.5 or more and 9.0 or less, the compressive strength at 1 day of age was 5 N / mm ２ The compressive strength at 7 days is 18N / mm ２ In the expansion stability evaluation, no harmful cracks or large pop-outs were observed, and the evaluation was ○.

[0042] On the other hand, SO ３ In Comparative Examples 1 to 4, where the BFS was less than 2.5, the strength of the hardened body after one day was 5 N / mm ２ The 7-day strength was less than 18 N / mm ２ The results were less than 100%, and the test was not successful. In particular, in Comparative Example 3, the hardened body did not have enough strength to be removed from the frame, and it was not possible to carry out the strength evaluation and expansion stability evaluation. For this reason, in Table 1, the 1-day strength of Comparative Example 3 was rated as x, the 7-day strength was rated as x, the expansion stability was rated as -, and the seawater immersion resistance was rated -. SO ３ In Comparative Example 5, in which the / BFS was greater than 9.0, cracks occurred in the cured product in the expansion stability evaluation, and the expansion stability was evaluated as x.

[0043] <Example 2> Next, Example 2 will be described in which a hardened body was produced using steelmaking slags A' and B', which are the same as steelmaking slags A and B shown in Table 1, but which had been discharged less than 30 days ago. In Example 2, a hardened body was produced under the same conditions as Example 1, except that steelmaking slags A' and B', which had been discharged less than 30 days ago, were used, and strength evaluation, expansion stability evaluation, and seawater immersion evaluation were performed. The composition of the materials for the hardened body, SO ３ The results of the / BFS value, strength evaluation, expansion stability evaluation and seawater immersion evaluation are shown in Table 3 below.

[0044]

[0045] In Table 3, Example 9 corresponds to Example 2 in Table 1, Example 10 corresponds to Example 6 in Table 1, and Example 11 corresponds to Example 8 in Table 1.

[0046] As shown in Table 3, even for the hardened bodies of Examples 9 to 11, which used steelmaking slags A' and B' that had been discharged for less than 30 days, the strength evaluations at ages of 1 day and 7 days passed, and the expansion stability was also evaluated as ○. From these results, it can be seen that even when steelmaking slags A' and B' that had been discharged for less than 30 days were used, SO ３ It was confirmed that if the / BFS was 2.5 or more and 9.0 or less, the strength evaluation was passed and the expansion stability evaluation was good.

[0047] On the other hand, when compared with Inventive Examples 2, 6, and 8 corresponding to Inventive Examples 9 to 11, Inventive Examples 9 to 11 had lower compressive strengths at both 1-day and 7-day ages. In the expansion stability evaluation, Inventive Example 11 showed no cracks in the hardened body, but significant pop-out was observed, resulting in a fair rating. These results confirm that when using steelmaking slag containing sulfur components, it is preferable to use steelmaking slag that has been discharged 30 days or more since its disposal.

[0048] Example 3 Next, Example 3 will be described in which hardened bodies were produced using carbonated steelmaking slags A", B", and C", which are the same steelmaking slags as steelmaking slags A, B, and C shown in Table 1, but which were obtained by carbonated treatment of these slags. The carbonation treatment of the steelmaking slag was carried out by pouring CO ２ In Example 3, hardened bodies were produced under the same conditions as in Example 1, except that carbonated steelmaking slags A", B", and C" were used, and strength evaluation, expansion stability evaluation, and seawater immersion evaluation were carried out. ３ The results of the / BFS value, strength evaluation, expansion stability evaluation and seawater immersion evaluation are shown in Table 4 below.

[0049]

[0050] In Table 4, Example 12 corresponds to Example 2 in Table 1, and Example 13 corresponds to Example 6 in Table 1.

[0051] As shown in Table 4, the hardened bodies of Examples 12 and 13, which used carbonated steelmaking slags A", B", and C", passed the strength evaluation at ages of 1 day and 7 days, and the expansion stability was also evaluated as ○. From these results, it can be seen that the use of carbonated steelmaking slags A", B", and C" did not affect the SO ３ It was confirmed that if the / BFS was 2.5 or more and 9.0 or less, the strength evaluation was passed and the expansion stability evaluation was good.

[0052] On the other hand, in Examples 2 and 6, which used non-carbonated steelmaking slag, the pH of the artificial seawater in which the hardened bodies were immersed rose to 8.5 or higher, as shown in Table 2. In contrast, in Examples 12 and 13, which used carbonated steelmaking slag A", B", and C", the pH of the artificial seawater in which the hardened bodies were immersed fell below 8.5, as shown in Table 4. These results confirm that hardened bodies manufactured using and containing carbonated steelmaking slag hardly increase the pH of the surrounding seawater even when used in marine areas, and that these hardened bodies have high biocompatibility in those marine areas.

Claims

1. A mixing step involves mixing steelmaking slag, a binder containing blast furnace slag fine powder, and water to form a mixture. A curing step of curing the mixture, It has, A method for producing a cured body, wherein the mixture satisfies the following formula (1). 2.5≦cured body 1m ３ Winning SO ３ Converted mass of sulfur × 100 / 1 m of hardened body ３ The mass of the blast furnace slag fine powder per unit is ≤ 9.0 ... (1)

2. The method for producing a hardened body according to claim 1, wherein the steelmaking slag contains a sulfur component.

3. The aforementioned steelmaking slag SO ３ The method for producing a cured body according to claim 2, wherein the converted sulfur component concentration is 0.25% by mass or more.

4. The method for manufacturing a hardened body according to claim 2 or 3, wherein the steelmaking slag has been discharged for 30 days or more.

5. The method for producing a hardened body according to any one of claims 1 to 3, wherein the steelmaking slag is carbonated steelmaking slag.

6. The method for producing a hardened body according to claim 4, wherein the steelmaking slag is carbonated steelmaking slag.

7. It contains steelmaking slag, a binder containing blast furnace slag fine powder, and water. A hardened body that satisfies the following equation (1). 2.5≦cured body 1m ３ Winning SO ３ Converted mass of sulfur × 100 / 1 m of hardened body ３ The mass of the blast furnace slag fine powder per unit is ≤ 9.0 ... (1)

8. The hardened body according to claim 7, wherein the steelmaking slag is carbonated steelmaking slag.