Cement admixture, cement composition, cement cured body, and method for producing cement admixture

Abstract

To provide a cement admixture derived from steelmaking slag, capable of suppressing pop-out caused by f-CaO, and obtaining a cement cured body having sufficient strength.SOLUTION: A cement admixture is derived from steelmaking slag, wherein the cement admixture includes f-CaO in an amount of 1.50 wt.% or less with respect to a total amount of the cement admixture, and comprises calcium silicate and calcium aluminate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cement admixture, a cement composition, a hardened cement product, and a method for producing a cement admixture. [Background technology]

[0002] Carbon dioxide is a greenhouse gas and is considered to be a factor in global warming. In recent years, climate change due to global warming has become a problem, and there is a need to reduce carbon dioxide emissions and atmospheric carbon dioxide concentrations. One effective measure to address the problem of global warming caused by carbon dioxide is the fixation of carbon dioxide. For example, a method is known in which calcium components are extracted from steelmaking slag, a calcium-containing substance, using a glycol solvent such as glycerin to produce calcium carbonate, while simultaneously fixating carbon dioxide. Furthermore, this method is known to be applicable to preventing the expansion of steelmaking slag, as it can leach unreacted lime (hereinafter simply referred to as "f-CaO") from the steelmaking slag.

[0003] On the other hand, steelmaking slag is a type of iron and steel slag, and includes converter slag, electric furnace slag, etc., which are by-produced in the steelmaking process. From the viewpoint of effective use of by-products and the conservation and preservation of natural resources, the use of such by-product steelmaking slag as a cement raw material, fine aggregate for concrete, roadbed material, civil engineering material, etc. has attracted attention.

[0004] Furthermore, there have also been reported examples of using steelmaking slag in cement admixtures, which normally use ground granulated blast furnace slag, fly ash, ground limestone, etc. As an example, Patent Document 1 describes a cement admixture made of ground granulated slag derived from steelmaking slag, which contains less than 2.0 mass% F, 33 to 53 mass% CaO, 20 to 35 mass% SiO2, 3 to 16 mass% Al2O3, and 5 to 10 mass% MgO, with a basicity (CaO / SiO2) of 1.0 to 2.1 and a specific surface area of ​​4800 to 8000 cm 2 / g of a cement admixture is described. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-222534 Summary of the Invention [Problem to be solved by the invention]

[0006] It is generally known that when steelmaking slag, a by-product, is powdered and used as a cement admixture, the volume expansion that occurs during the hydration reaction of the f-CaO contained in the steelmaking slag causes pop-out, resulting in cracks, fractures, peeling, etc. in the hardened body. Therefore, when using steelmaking slag as a cement admixture, it is necessary to remove as much f-CaO from the steelmaking slag as possible (to render it harmless) in order to prevent pop-out.

[0007] Regarding the removal of f-CaO, Patent Document 1 describes a method for separating soft components containing f-CaO, γ-2CaO SiO, etc. from the mineral phase by cooling and solidifying molten steelmaking slag under specified cooling conditions using a combination of air cooling, water spraying, etc., during the manufacturing process of cement admixture. However, cooling and solidifying steelmaking slag in this manner requires large-scale equipment, which is costly and requires complex cooling conditions. Furthermore, there is a concern that spraying water on molten steelmaking slag may cause a steam explosion.

[0008] In addition, various aging treatments that accelerate the hydration of f-CaO in steelmaking slag are known as typical methods for removing f-CaO from steelmaking slag. However, these aging treatments also promote the hydration of mineral components other than f-CaO. As a result, the hydration of mineral components with the latent hydraulic properties required for using steelmaking slag as a cement admixture also progresses.

[0009] Mineral components with latent hydraulic properties (e.g., calcium silicates such as 2CaO·SiO2) are necessary to impart sufficient strength to the hardened cement paste when the cement admixture is mixed with cement and water. In this way, it would be desirable to obtain a cement admixture that can both increase the strength of the hardened cement paste and suppress popout.

[0010] Therefore, an object of the present invention is to provide a cement admixture derived from steelmaking slag that can suppress pop-out caused by f-CaO and produce a hardened cement product with sufficient strength. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention includes the following preferred embodiments.

[0012] The cement admixture according to the first aspect of the present invention is a cement admixture derived from steelmaking slag, The cement admixture contains 1.50 mass % or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate.

[0013] A cement admixture according to a second aspect of the present invention is the cement admixture according to the first aspect, wherein the content of the calcium silicate is 40.0 mass% or more relative to the total amount of the cement admixture, and the content of the calcium aluminate is 10.0 mass% or more relative to the total amount of the cement admixture.

[0014] A cement admixture according to a third aspect of the present invention is a cement admixture according to the first or second aspect, wherein the specific surface area is 2750 cm 2 / g or more 10000cm 2 / g.

[0015] A cement composition according to a fourth aspect of the present invention contains the cement admixture according to any one of the first to third aspects and cement.

[0016] A cement composition according to a fifth aspect of the present invention is the cement composition according to the fourth aspect, wherein the content of the cement admixture is 5% by mass or more and 50% by mass or less relative to the total amount of the cement admixture and the cement, and the content of the cement is 50% by mass or more and 95% by mass or less relative to the total amount of the cement admixture and the cement.

[0017] A cement composition according to a sixth aspect of the present invention is the cement composition according to the fourth aspect, further comprising at least one of ground granulated blast furnace slag and fly ash.

[0018] A cement composition according to a seventh aspect of the present invention is the cement composition according to the sixth aspect, wherein the content of at least one of the ground granulated blast furnace slag and the fly ash is 30% by mass or more and 70% by mass or less based on the total amount of the at least one of the ground granulated blast furnace slag and the fly ash and the cement; The content of the cement is 30% by mass or more and 70% by mass or less with respect to the total amount of at least one of the ground granulated blast furnace slag and the fly ash and the cement, and The content of the cement admixture is 50 mass % or less relative to the content of at least one of the ground granulated blast furnace slag and the fly ash.

[0019] A cement composition according to an eighth aspect of the present invention is the cement composition according to the fourth or fifth aspect, further comprising 25% by mass or more and 65% by mass or less of water relative to the total amount of the cement admixture and the cement.

[0020] A cement composition according to a ninth aspect of the present invention is the cement composition according to the sixth or seventh aspect, further comprising water in an amount of 25% by mass or more and 65% by mass or less relative to the total amount of the cement admixture, at least one of the ground granulated blast furnace slag and fly ash, and the cement.

[0021] A cement composition according to a tenth aspect of the present invention is the cement composition according to any one of the fourth to ninth aspects, further comprising at least one of fine aggregate and coarse aggregate.

[0022] A hardened cement product according to an eleventh aspect of the present invention is a hardened product of the cement composition according to any one of the fourth to tenth aspects.

[0023] A method for producing a cement admixture according to a twelfth aspect of the present invention is a method for producing a cement admixture derived from steelmaking slag, The method comprises immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water, The cement admixture contains 1.50 mass % or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate.

[0024] A method for producing a cement admixture according to a thirteenth aspect of the present invention is the method for producing a cement admixture according to the twelfth aspect, wherein the content of the calcium silicate is 40.0 mass% or more relative to the total amount of the cement admixture, and the content of the calcium aluminate is 10.0 mass% or more relative to the total amount of the cement admixture.

[0025] A method for producing a cement admixture according to a fourteenth aspect of the present invention is the method for producing a cement admixture according to the twelfth or thirteenth aspect, 2 / g or more 10000cm 2 / g.

[0026] A method for preparing a cement composition according to a fifteenth aspect of the present invention includes mixing the cement composition according to any one of the fourth to tenth aspects.

[0027] A method for producing a hardened cement product according to a sixteenth aspect of the present invention includes hardening the cement composition according to any one of the fourth to tenth aspects. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a cement admixture derived from steelmaking slag that can suppress pop-out caused by f-CaO and produce a hardened cement product with sufficient strength. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a graph showing the relationship between the activity index and the content ratio of the cement admixture to the total content of the cement admixture, ground granulated blast furnace slag, and cement (total amount of cement composition). DETAILED DESCRIPTION OF THE INVENTION

[0030] The present inventors have conducted extensive research into steelmaking slag suitable for use as a cement admixture, in which f-CaO has been selectively removed while mineral components with latent hydraulic properties remain unreacted. In this research, they also analyzed the residual components of steelmaking slag with reduced f-CaO, which was ultimately obtained by a method involving extracting calcium from steelmaking slag using a glycol solvent and then immobilizing carbon dioxide, a measure to combat global warming caused by carbon dioxide. As a result, they found that steelmaking slag with reduced f-CaO content by this method retains mineral components with latent hydraulic properties largely unreacted. Based on these findings, the present inventors have investigated the relationship between the content of f-CaO relative to the total amount of cement admixture and the strength of hardened cement paste, leading to the completion of the present invention.

[0031] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0032] 1. Cement admixture The cement admixture according to this embodiment is derived from steelmaking slag. The cement admixture according to this embodiment contains 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate.

[0033] In this specification, the term "cement admixture" refers to a powdered admixture used in a composition containing cement (cement composition), such as cement paste, mortar, or concrete.

[0034] In this specification, "f-CaO" generally refers to unreacted CaO and unreacted Ca(OH)2 contained in raw steelmaking slag.

[0035] In this specification, "steelmaking slag" means steelmaking slag generally known to those skilled in the art, such as converter slag and electric furnace slag, which are by-produced in pretreatment processes, converter furnaces, secondary refining processes, etc.

[0036] [Components of cement admixtures (including mineral components)] Cement admixtures contain calcium silicate and calcium aluminate as mineral components. As used herein, "calcium silicate" refers to any mineral component classified as a calcium silicate known to those skilled in the art and capable of being contained in steelmaking slag, such as 2CaO·SiO2, CaO-SiO2, and 3CaO·SiO2. As used herein, "calcium aluminate" refers to any mineral component classified as a calcium aluminate known to those skilled in the art and capable of being contained in steelmaking slag, such as 3CaO·Al2O3, CaO·Al2O3, and 12CaO·7Al2O3.

[0037] Specifically, cement admixtures contain compounds such as f-CaO, CaO, SiO2, Al2O3, MgO, MnO, FeO, Fe2O3, Fe3O4, f-MgO, and unavoidable impurities (e.g., P2O5, TiO2, etc.), which are solidified in a mineral state as mineral components such as calcium silicates such as 2CaO·SiO2, calcium aluminates such as 3CaO·Al2O3, β-Ca2(SiO4), Ca2Fe2O5, γ-Ca2(SiO4), 2CaO·MgO·2SiO2, and 2CaO·Al2O3·SiO2.

[0038] In the cement admixture according to this embodiment, the content of f-CaO is 1.50 mass% or less relative to the total amount of the cement admixture. By including 1.50 mass% or less f-CaO in the cement admixture relative to the total amount of the cement admixture, it is possible to obtain a steelmaking slag-derived cement admixture that can produce a hardened cement product that can suppress popout caused by f-CaO.

[0039] The content of f-CaO relative to the total amount of cement admixture is preferably 1.40% by mass or less, more preferably 1.35% by mass or less, even more preferably 1.30% by mass or less, and particularly preferably 1.25% by mass or less. The content of f-CaO relative to the total amount of cement admixture is most preferably close to 0% by mass. However, since it is generally difficult to remove all of the f-CaO from the raw steelmaking slag, the lower limit of the content of f-CaO relative to the total amount of cement admixture is, for example, about 0.10% by mass.

[0040] By including calcium silicate and calcium aluminate in the cement admixture, when the cement admixture derived from steelmaking slag is mixed with cement and water, a hardened cement product having sufficient strength can be obtained.

[0041] The content of calcium silicate relative to the total amount of cement admixture is not particularly limited, but is preferably 35.0 mass% or more, more preferably 40.0 mass% or more, even more preferably 42.0 mass% or more, and particularly preferably 43.5 mass% or more. The upper limit of the content of calcium silicate relative to the total amount of cement admixture is not particularly limited, but considering the general content of calcium silicate in steelmaking slag, which is the raw material, it is, for example, about 80.0 mass% or less relative to the total amount of cement admixture.

[0042] The content of calcium aluminate relative to the total amount of the cement admixture is not particularly limited, but is preferably 3.0 mass% or more, more preferably 5.0 mass% or more, even more preferably 7.0 mass% or more, and particularly preferably 10.0 mass% or more. The upper limit of the content of calcium aluminate relative to the total amount of the cement admixture is not particularly limited, but considering the general content of calcium aluminate in steelmaking slag, which is the raw material, it is, for example, about 20.0 mass% or less relative to the total amount of the cement admixture.

[0043] In the cement admixture according to this embodiment, the calcium silicate content is preferably 40.0 mass% or more and the calcium aluminate content is preferably 10.0 mass% or more, based on the total amount of the cement admixture. When the steelmaking slag-derived cement admixture is mixed with cement and water, a hardened cement product having sufficient strength can be reliably obtained.

[0044] In this specification, the terms "calcium silicate content" and "calcium aluminate content" refer to the total content of these minerals when the cement admixture or the raw steelmaking slag described below contains two or more types of calcium silicates or two or more types of calcium aluminates, respectively.

[0045] In this specification, the components (including mineral components) of the cement admixture and the components (including mineral components) of the raw steelmaking slag described later, as well as their contents, can be measured by the same methods as those described in the Examples below. That is, values ​​can be obtained by identifying each component from a spectrum analyzed using an X-ray diffractometer and performing quantitative analysis of each component.

[0046] [Physical properties of cement admixtures] In the cement admixture according to this embodiment, the specific surface area is 2750 cm 2 / g or more 10000cm 2 / g. The specific surface area of ​​the cement admixture is preferably less than 2750 cm 2 When the specific surface area of ​​the cement admixture is 10,000 cm / g or more, the reactivity of the cement admixture when mixed with cement and water can be increased, and the strength of the hardened cement can be further improved. 2 When the slag content is less than 1 / g, the cost of crushing the raw steelmaking slag can be reduced, an excessive increase in viscosity can be suppressed, and deterioration of workability due to an increase in viscosity can be prevented.

[0047] The specific surface area of ​​cement admixture is 3000 cm 2 / g or more is more preferable, and 2 / g or more, and 2 It is particularly preferable that the specific surface area of ​​the cement admixture is 6000 cm / g or more. 2 / g or less is more preferable, and 2 / g or less is more preferable, and 2 It is particularly preferable that the saturation coefficient is 1 / g or less.

[0048] In this specification, the specific surface area of ​​a cement admixture is the average Blaine value (cm) measured by a specific surface area test in accordance with JIS R 5201:2015, as described in the Examples below. 2 / g).

[0049] The density of the cement admixture is not particularly limited, but is preferably 2.00 g / cm 3 It is preferable that the concentration is 2.50 g / cm or more. 3 More preferably, it is 3.00 g / cm or more. 3 It is more preferable that the density of the cement admixture is 5.00 g / cm or more. 3 Preferably, it is 4.40 g / cm or less. 3 More preferably, it is 3.80 g / cm or less. 3 It is even more preferable that:

[0050] In this specification, the density of the cement admixture is a value measured based on a density test in the physical testing method for cement in accordance with JIS R 5201:2015, as described in the Examples below.

[0051] [How to use cement admixtures] As will be described in later embodiments, the cement admixture according to this embodiment can suppress pop-out caused by f-CaO and produce a hardened cement product with sufficient strength by mixing cement with optionally at least one of ground granulated blast furnace slag and fly ash and water.

[0052] 2. Manufacturing method of cement admixture The method for producing a cement admixture according to this embodiment is a method for producing a cement admixture derived from steelmaking slag, and includes immersing steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water (hereinafter also referred to as the "immersion step" or "immersion treatment").

[0053] In this embodiment, various factors, such as the type of steelmaking slag used as the raw material, the shape of the steelmaking slag during the immersion treatment, the type and purity of the solvent used in the immersion process, the amount of solvent added in the immersion process, the immersion time, and the number of immersion processes, must be appropriately selected and / or adjusted so that the final steelmaking slag-derived cement admixture contains 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate. In other words, the method for producing a cement admixture according to this embodiment can produce the cement admixture according to the above-described embodiment. The contents of f-CaO, calcium silicate, and calcium aluminate in the final cement admixture can also be controlled by appropriately selecting and / or adjusting the aforementioned various factors.

[0054] First, the raw materials and ingredients used in the manufacturing method according to this embodiment will be described.

[0055] The main components (including mineral components) of the raw material steelmaking slag containing f-CaO are generally similar to the components (including mineral components) of the cement admixture according to the above-described embodiment.

[0056] The content of f-CaO relative to the total amount of raw steelmaking slag is not particularly limited, but is preferably 8.00 mass% or less, more preferably 6.00 mass% or less, even more preferably 4.00 mass% or less, and particularly preferably 3.00 mass% or less. The content of f-CaO relative to the total amount of raw steelmaking slag is most preferably close to 0 mass%. However, raw steelmaking slag generally contains f-CaO. Therefore, for example, even if the content of f-CaO is significantly low, it may be greater than 1.50 mass% relative to the total amount of raw steelmaking slag.

[0057] The calcium silicate content relative to the total amount of raw steelmaking slag is not particularly limited, but is preferably 10.0 mass% or more, more preferably 15.0 mass% or more, even more preferably 25.0 mass% or more, and particularly preferably 30.0 mass% or more. The upper limit of the calcium silicate content relative to the total amount of raw steelmaking slag is not particularly limited, but is, for example, about 80.0 mass% or less relative to the total amount of raw steelmaking slag.

[0058] The calcium aluminate content relative to the total amount of raw steelmaking slag is not particularly limited, but is preferably 3.0 mass% or more, more preferably 5.0 mass% or more, even more preferably 7.0 mass% or more, and particularly preferably 10.0 mass% or more. The upper limit of the calcium aluminate content relative to the total amount of raw steelmaking slag is not particularly limited, but is, for example, about 20.0 mass% or less relative to the total amount of raw steelmaking slag.

[0059] In this specification, the term "polyol compound" refers to an organic compound having multiple alcoholic hydroxyl groups (groups in which hydrogen atoms of aliphatic hydrocarbons are replaced with hydroxyl groups (-OH)) that can react with f-CaO in steelmaking slag.

[0060] The polyol compound preferably includes one or more selected from a diol compound and a triol compound.

[0061] Examples of diol compounds include ethylene glycol, propylene glycol, diethylene glycol, butanediol, and diethanolamine. Among these, the diol compound preferably contains one or more selected from ethylene glycol, propylene glycol, and diethylene glycol. Among these, the diol compound preferably contains ethylene glycol from the viewpoint of highly selective dissolving action on f-CaO in steelmaking slag.

[0062] From the viewpoints of high selective dissolution of f-CaO in steelmaking slag, effective utilization of industrial by-products, and ease of availability, it is preferable that the triol compound contains glycerin. Commercially available glycerin can be used. For example, a commercially available glycerin product is a reagent (density: 1.26 g / cm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 3 ) are listed.

[0063] The water used in the mixture of the polyol compound and water may be, for example, pure water.

[0064] Next, a method for producing a cement admixture according to this embodiment will be described.

[0065] In the method for producing a cement admixture according to this embodiment, it is preferable to pulverize the raw steel slag into powder before the immersion step using any device known to those skilled in the art, such as a jaw crusher, ball mill, vertical mill, roller mill, or roll breaker, or a combination of any of these devices. The powdered steel slag preferably has a coarse particle size of 40 mm or less, more preferably 10 mm or less, and even more preferably 1 mm or less.

[0066] Furthermore, even after the soaking step, any treatment known to those skilled in the art may be further included, as necessary, such as filtration, phase separation, pulverization (re-pulverization), or drying of the steelmaking slag. In the pulverization (re-pulverization) treatment after the soaking step, any device known to those skilled in the art, such as a ball mill or a vertical mill, or a combination of any of these devices, may be used to adjust the powdered steelmaking slag after the soaking step so that it has a desired specific surface area. Alternatively, the powdered steelmaking slag may be adjusted in advance to have a desired specific surface area in the pulverization treatment before the soaking step described above.

[0067] The specific method for the immersion step is not particularly limited and may be any method known to those skilled in the art. For example, immersion may be performed by placing steelmaking slag containing f-CaO pulverized to an appropriate size in a container, and then adding a polyol compound or a mixture of a polyol compound and water. The immersion step may be performed two or more times.

[0068] The immersion time is not particularly limited, but may be adjusted appropriately to obtain a cement admixture (steelmaking slag) containing 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, calcium silicate, and calcium aluminate, taking into consideration factors such as the f-CaO content in the raw steelmaking slag, the shape of the steelmaking slag during the immersion treatment, the type and purity of the solvent, the amount of solvent added, and the number of immersion steps. For example, the immersion time may be adjusted to a range of 0.1 to 24 hours.

[0069] The amount of solvent added, the type of solvent, the number of immersion steps, etc., as well as the immersion time, can be adjusted appropriately while taking other factors into consideration so that the desired cement admixture (steelmaking slag) is ultimately obtained.

[0070] Furthermore, from the viewpoint of reducing f-CaO in a shorter time during the immersion process, it is preferable to perform a shaking immersion treatment using a shaker or the like, as will be described in the Examples below. Alternatively, an agitation immersion treatment may be performed using a stirrer or the like. Alternatively, a immersion treatment may be performed in which a liquid is passed through the slag packed bed so that a flow occurs at the solid-liquid interface, or the immersion treatment may be performed in which the slag packed bed is immersed in a liquid.

[0071] In the manufacturing method according to this embodiment, a cement admixture can be manufactured using low-f-CaO steelmaking slag as a raw material, which is obtained by extracting calcium components from steelmaking slag using a glycol solvent and immobilizing the carbon dioxide, which is one of the countermeasures against global warming caused by carbon dioxide. Furthermore, although the cement admixture manufactured in this manner has reduced f-CaO, mineral components with latent hydraulic properties remain unreacted. Therefore, by mixing the admixture with cement, water, etc., it is possible to suppress popout due to f-CaO and obtain a hardened cement product with sufficient strength.

[0072] 3. Cement composition and method for preparing the cement composition The cement composition according to this embodiment contains the cement admixture according to the above embodiment and cement.

[0073] In this specification, the term "cement composition" refers to both a powdered cement composition containing a cement admixture, cement, and optionally other powdered raw materials (i.e., a premixed cement composition), and a pre-hardened cement composition in a slurry or semi-solid form containing a cement admixture, cement, optionally other powdered raw materials, and water.

[0074] The cement is not particularly limited, and any cement known in the art can be used. Examples of cement that can be used include various Portland cements such as ordinary, early strength, extra early strength, low heat, and moderate heat, blended cement (30-BB), and ecocement. Of these, the cement is preferably ordinary Portland cement as specified in JIS R 5201:2015.

[0075] When the cement composition contains a cement admixture and cement, the content of the cement admixture relative to the total amount of the cement admixture and cement is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less. When the content of the cement admixture relative to the total amount of the cement admixture and cement is 70% by mass or less, it is possible to prevent an excessive decrease in strength when a hardened cement body is formed. Furthermore, the content of the cement admixture relative to the total amount of the cement admixture and cement is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and particularly preferably 10% by mass or more. When the content of the cement admixture relative to the total amount of the cement admixture and cement is 3% by mass or more, it is possible to reduce the amount of cement, which is preferable from the viewpoint of cost reduction.

[0076] Considering the balance between ensuring the strength of the hardened body and reducing costs, it is particularly preferable that the content of the cement admixture is 5% by mass or more and 50% by mass or less based on the total amount of the cement admixture and cement, and that the content of cement is 50% by mass or more and 95% by mass or less based on the total amount of the cement admixture and cement.

[0077] When the cement composition contains a cement admixture and cement, it is preferable that the cement composition further contains 25% by mass or more and 65% by mass or less of water based on the total amount of the cement admixture and cement. By including such an amount of water, the hydraulic properties of the cement composition can be favorably exhibited. Specifically, by including 25% by mass or more of water based on the total amount of the cement admixture and cement, the mixing properties of the cement composition can be improved. Furthermore, by including 65% by mass or less of water based on the total amount of the cement admixture and cement, excessive reduction in the strength of the hardened cement body can be prevented.

[0078] When the cement composition contains a cement admixture and cement, the water content relative to the total amount of the cement admixture and cement is more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. Also, the water content relative to the total amount of the cement admixture and cement is more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less.

[0079] The cement composition according to this embodiment preferably further contains at least one of ground granulated blast furnace slag and fly ash. Specifically, by including at least one of ground granulated blast furnace slag and fly ash in addition to the cement admixture and cement according to the above-described embodiment, a hardened cement product with higher strength can be obtained.

[0080] Ground granulated blast furnace slag contains calcium oxide (CaO), silicon dioxide (SiO2), alumina (Al2O3), etc. as its main components. Any ground granulated blast furnace slag known to those skilled in the art can be used. For example, ground granulated blast furnace slag can be obtained by pulverizing granulated blast furnace slag. Granulated blast furnace slag is obtained as a by-product during iron refining in a blast furnace. Commercially available ground granulated blast furnace slag may also be used. Examples of commercially available ground granulated blast furnace slag include granulated blast furnace slag that meets the JIS A 6206:2013 standard for ground granulated blast furnace slag 4000. Examples of such commercially available ground granulated blast furnace slag include "K-MENT" sold by Kobe Steel, Ltd. and "ESMENT" manufactured by Nippon Steel Blast Furnace Cement Co., Ltd.

[0081] Fly ash contains silicon dioxide (SiO2), alumina (Al2O3), etc. as main components. Any fly ash known to those skilled in the art can be used. For example, fly ash that can be obtained by capturing it from flue gas using a dust collector may be used.

[0082] When the cement composition further contains at least one of ground granulated blast furnace slag and fly ash in addition to a cement admixture and cement, it is preferable that the content of the at least one of ground granulated blast furnace slag and fly ash is 30% by mass or more and 70% by mass or less of the total amount of the at least one of ground granulated blast furnace slag and fly ash and the cement, and that the content of cement is 30% by mass or more and 70% by mass or less of the total amount of the at least one of ground granulated blast furnace slag and fly ash and the cement.

[0083] Furthermore, when the cement composition contains at least one of ground granulated blast furnace slag and fly ash in addition to the cement admixture and cement, the content of the cement admixture is preferably 70 mass% or less, more preferably 60 mass% or less, even more preferably 55 mass% or less, and particularly preferably 50 mass% or less, relative to the content of at least one of ground granulated blast furnace slag and fly ash.

[0084] In particular, when the content of the cement admixture is 50% by mass or less relative to the content of at least one of ground granulated blast furnace slag and fly ash, it is possible to obtain a hardened cement product having significantly high strength, specifically strength equivalent to that of blast furnace cement Class B. That is, in the cement composition according to this embodiment, by adjusting the content ratio of cement to at least one of ground granulated blast furnace slag and fly ash as described above and adjusting the content of the cement admixture to 50% by mass or less relative to the content of at least one of ground granulated blast furnace slag and fly ash, the cement admixture according to the above embodiment can be used in place of ground granulated blast furnace slag in terms of the strength of the hardened cement product.

[0085] When the cement composition further contains at least one of ground granulated blast furnace slag and fly ash in addition to the cement admixture and cement, it is preferable that the cement composition further contains 25% by mass or more and 65% by mass or less of water based on the total amount of the cement admixture, the at least one of ground granulated blast furnace slag and fly ash, and the cement.

[0086] The inclusion of the above-mentioned amount of water allows the cement composition to exhibit favorable hydraulic properties. Specifically, the inclusion of 25% by mass or more of water relative to the total amount of cement, cement admixture, at least one of ground granulated blast furnace slag, and fly ash can improve the mixability of the cement composition. Furthermore, the inclusion of 65% by mass or less of water relative to the total amount of cement, cement admixture, at least one of ground granulated blast furnace slag, and fly ash can prevent excessive reduction in the strength of the hardened cement body.

[0087] Even when the cement composition further contains at least one of ground granulated blast furnace slag and fly ash in addition to the cement admixture and cement, the water content relative to the total amount of the cement admixture, at least one of ground granulated blast furnace slag, and fly ash and the cement is more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. Also, the water content relative to the total amount of the cement admixture, at least one of ground granulated blast furnace slag, and fly ash and the cement is more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less.

[0088] From the viewpoint of improving strength, the cement composition preferably further contains at least one of fine aggregate and coarse aggregate. That is, the cement composition according to this embodiment can be used as a concrete composition containing fine aggregate and coarse aggregate, or as a mortar composition containing fine aggregate but not coarse aggregate.

[0089] The fine aggregate is not particularly limited, but examples include blast furnace slag fine aggregate and fine aggregates such as general silica sand, which is a natural aggregate. Of these, it is preferable to use blast furnace slag fine aggregate. Blast furnace slag fine aggregate has latent hydraulic properties. Latent hydraulic properties are the property of increasing the strength of the hardened product due to the formation of hydrates caused by silicon dioxide (SiO2), alumina (Al2O3), etc. contained in the blast furnace slag fine aggregate. Therefore, by using blast furnace slag fine aggregate as an aggregate, the strength of the final product, the hardened cement body, can be increased.

[0090] Blast furnace slag fine aggregate is specified in JIS A 5011-1:2018. Commercially available blast furnace slag fine aggregate may also be used. Examples of commercially available blast furnace slag fine aggregate include "Shinkosand" sold by Kobe Steel, Ltd. and blast furnace slag fine aggregate manufactured by JFE Mineral Co., Ltd.

[0091] The content of the fine aggregate is not particularly limited and may be appropriately set depending on the intended use of the hardened cement body, which is the final product. The content of the fine aggregate is preferably, for example, about 100% by mass or more and 500% by mass or less relative to the content of cement.

[0092] The coarse aggregate is not particularly limited, but it is preferable to use blast furnace slag coarse aggregate made from blast furnace slag. When blast furnace slag coarse aggregate and / or the above-mentioned blast furnace slag fine aggregate are used as aggregate, industrial by-products can be effectively utilized as resources, and a cement composition with high environmental compatibility can be obtained. Furthermore, production costs can be reduced.

[0093] The content of the coarse aggregate is not particularly limited, and may be appropriately determined according to the content of the fine aggregate or according to the intended use of the hardened cement body, which is the final product.

[0094] In addition to the above components, the cement composition according to this embodiment may further contain any additive known to those skilled in the art, provided that the effects of the present invention are not impaired. Examples of known additives include water-reducing agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, antifoaming agents, thickeners, rust inhibitors, low-shrinkage agents, expanding agents, dispersants, etc.

[0095] The cement composition according to the present embodiment can be prepared (manufactured) according to any method known to those skilled in the art. Specifically, a powdered cement composition (i.e., a premixed cement composition) can be prepared (manufactured) by adding cement, optionally at least one of ground granulated blast furnace slag and fly ash, and optionally other powdered raw materials to a cement admixture and mixing them. Such a powdered cement composition (i.e., a premixed cement composition) can be mixed and kneaded with water before on-site work, construction work, etc. Furthermore, a pre-hardened cement composition in a slurry or semi-solid state can be prepared (manufactured) by adding water to the powdered cement composition (i.e., a premixed cement composition) and mixing and kneading. The mixing or kneading method is not particularly limited, and any mixing or kneading device known to those skilled in the art can be used.

[0096] By including water in the cement composition according to this embodiment, it is possible to suppress pop-out caused by f-CaO as described in the following embodiments, and to obtain a hardened cement body with sufficient strength.

[0097] 4. Hardened cement product and method for manufacturing hardened cement product The hardened cement product according to this embodiment is a hardened product of the cement composition according to the above-described embodiment. The hardened cement product has any shape that can be formed by any molding method, construction method, etc.

[0098] The hardened cement product is not particularly limited, but is preferably concrete or mortar. More specifically, the hardened cement product includes, for example, blocks for roads or revetments, blocks for storm drains or irrigation channels, tiles, bricks, sewer pipes, precast products such as piles, poles, and sleepers, cast-in-place products such as cast-in-place concrete, shotcrete, concrete repair, and dam concrete.

[0099] The method for producing a hardened cement product includes mixing the water-containing cement composition of the above-described embodiment and then curing it. Specifically, the mixed cement composition is first molded or applied using any method known to those skilled in the art, such as molding using a formwork, troweling in plastering work, spraying, or pasting. The molded or applied cement composition is then cured using any curing method known to those skilled in the art. Specific curing methods include air curing, sealed curing, and steam curing. As a result, a hardened cement product can finally be obtained.

[0100] Furthermore, when producing a hardened cement body using a formwork, it is preferable to include applying a release agent or the like to the formwork in advance. The release agent is not particularly limited as long as it is any release agent known to those skilled in the art that imparts releasability to the hardened cement body.

[0101] The hardened cement paste produced in this manner is less susceptible to cracks, breaks, peeling, etc., and has sufficient strength, since pop-out caused by f-CaO can be suppressed. [Example]

[0102] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0103] In this example, cement admixtures with various f-CaO contents were actually produced by immersing steelmaking slag containing f-CaO in a glycerin aqueous solution, and their usability as cement compositions was examined.

[0104] In this example, the density (cm) of the cement admixture or ground granulated blast furnace slag 2 / g) was measured based on the density test of the physical test method for cement in accordance with JIS R 5201:2015. The average Blaine value (cm 2 / g) was measured by a specific surface area test in the fineness test of the physical testing method for cement in accordance with JIS R 5201:2015 using a Blaine air permeability device (manufactured by Daiken Rikagaku Kikai Co., Ltd., "Blaine air permeability fineness meter").

[0105] First, a method for producing the cement admixture used in the present example, which is a raw material for the cement composition, will be described below.

[0106] [Manufacturing method of cement admixture] (Cement admixture 1) Steelmaking slag A, whose composition is shown in Table 1 below, was used as the raw material. Steelmaking slag A was crushed using a jaw crusher to reduce the particle size to 1 mm or less. The crushed slag was placed in a container, and a 40% aqueous glycerin solution prepared from water and glycerin (a reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (purity: min. 99.5% by mass)) was added, and the container was sealed. The sealed container was then shaken and immersed for an appropriate period of time using a shaker. After the shaking and immersion process, the mixed solution containing the treated slag was filtered through a filter, and the filtrate was removed from the mixed solution to obtain the treated slag. The treated slag was then pulverized using a ball mill to obtain cement admixture 1, a powder derived from steelmaking slag A. The composition of cement admixture 1 is shown in Table 2 below.

[0107] (Cement admixture 2) Except for using steelmaking slag B having the composition shown in Table 1 below as the raw steelmaking slag and for a significantly shorter shaking and immersion treatment time than in the production of cement admixture 1, the same method as in the production of cement admixture 1 was used, and finally, cement admixture 2, which is a powder derived from steelmaking slag B and has the composition shown in Table 2 below, was obtained.

[0108] (Cement admixture 3) Except for using steelmaking slag C having the composition shown in Table 1 below as the raw material steelmaking slag and for a slightly shorter shaking and immersion treatment time than in the production of cement admixture 1, the same method as in the production of cement admixture 1 was used, and finally, cement admixture 3, which is a powder derived from steelmaking slag C and has the composition shown in Table 2 below, was obtained.

[0109] Tables 1 and 2 below show the composition (mass % relative to the total amount of steelmaking slag or cement admixture) of steelmaking slag A to steelmaking slag C and cement admixture 1 to cement admixture 3, respectively. Tables 1 and 2 also show the contents of 2CaO·SiO2 and 3CaO·Al2O3, which are mineral structure components contained in steelmaking slag A to steelmaking slag C and cement admixture 1 to cement admixture 3. In addition to the components shown in Tables 1 and 2 below, steelmaking slag A to steelmaking slag C and cement admixture 1 to cement admixture 3 also contain unavoidable impurities as the balance.

[0110] [Table 1]

[0111] [Table 2]

[0112] The components of steelmaking slag A to steelmaking slag C and cement admixture 1 to cement admixture 3 in Tables 1 and 2 above were analyzed using an X-ray diffractometer. The analysis conditions are shown below. Each component was identified from the obtained spectrum and quantitatively analyzed by Rietveld analysis. The software used for Rietveld analysis was "JADE Pro" manufactured by MDI Corporation. <Analysis conditions> Analytical equipment: Horizontal X-ray diffraction equipment "SmartLab" (Rigaku Corporation) Target: Cu Monochromatization: Use a monochromator (Kα) Target output: 45kV-200mA Scanning method: θ / 2θ (concentration method) Slit: Divergence 2 / 3°, Scattering 2 / 3°, Receiving 0.6mm Monochromator receiving slit: 0.8 mm Scanning speed: 2.0° / min Sampling width: 0.02° Measurement angle (2θ): 5°~90°

[0113] In steelmaking slag A and steelmaking slag C, and in cement admixture 1 and cement admixture 3 derived from them, only 2CaO SiO2 was detected as calcium silicate, and only 3CaO Al2O3 was detected as calcium aluminate. In steelmaking slag B and cement admixture 2 derived from it, only 2CaO SiO2 was detected as calcium silicate. Furthermore, in steelmaking slag B and cement admixture 2 derived from it, calcium aluminate was not detected.

[0114] As shown in Tables 1 and 2 above, it was found that 2CaO SiO2, a calcium silicate with latent hydraulic properties, and 3CaO Al2O3, a calcium aluminate, remained almost entirely unreacted in cement admixture 1 and cement admixture 3 after immersion in a glycerin aqueous solution. On the other hand, it was found that f-CaO was selectively eluted by immersion in a glycerin aqueous solution, particularly in cement admixture 1 derived from steelmaking slag A and cement admixture 3 derived from steelmaking slag C.

[0115] Next, cement compositions for each experimental example were prepared using the cement admixture obtained by the above-mentioned method, and the presence or absence of cracks or fractures in the appearance of the hardened cement composition was confirmed. The activity index of the cement composition was also calculated. Below, the raw materials of the cement composition, the method for preparing the cement composition, the method for confirming the presence or absence of cracks or fractures, and the method for calculating the activity index are described.

[0116] [Raw materials for cement compositions] Cement admixture 1 (density: 3.45 g / cm 3 , Average Blaine value: 4000 cm 3 / g) Cement admixture 2 (density: 3.36 g / cm 3 , Average Blaine value: 4120cm 3 / g) Cement admixture 3 (density: 3.45 g / cm 3 , Average Blaine value: 4040cm 3 / g) Blast furnace slag powder A (density: 2.89 g / cm 3 , Average Blaine value: 4910 cm 3 / g) Blast furnace slag powder B (density: 2.89 g / cm 3 , Average Blaine value: 4680 cm 3 / g) Cement: A mixture of ordinary Portland cement specified in JIS R 5201:2015 from three randomly selected producers

[0117] [Method for preparing cement composition] The above raw materials were mixed in the amounts shown in Table 3 below to prepare cement compositions for each experimental example.

[0118] [Table 3]

[0119] [Method for checking the appearance of hardened cement composition for cracks or fractures] In accordance with the test method for activity index of mortar containing ground granulated blast furnace slag specified in Appendix A of JIS A 6206:2013, the cement compositions of each experiment prepared using the method described above were mixed with fine aggregate and water in the specified ratios and then underwater cured for 7 and 28 days. The mortars obtained after 7 and 28 days of underwater curing were visually inspected for cracks or fractures. The results are shown in Table 4 below. If cracks or fractures were present in either or both of the mortars after 7 and 28 days of underwater curing, the cracks or fractures were recorded as "present." If no cracks or fractures were present in either mortar, the cracks or fractures were recorded as "absent."

[0120] [Table 4]

[0121] [Method for calculating activity index of cement composition] The activity test of the cement composition was conducted in accordance with the test method for activity index of mortar containing ground granulated blast furnace slag specified in Appendix A of JIS A 6206:2013. Specifically, fine aggregate and water were mixed with the cement composition of each experimental example prepared by the above-mentioned method in a specified ratio, and the activity index was calculated after 7 and 28 days of underwater curing. In this test, the reference mortar was the mortar of the cement composition of Experimental Example 2 (a reference example containing cement and ground granulated blast furnace slag A). Furthermore, the test mortars evaluated were the mortars of the cement compositions of Experimental Example 3 (Example 1), Experimental Examples 5 and 6 (Reference Examples), Experimental Example 7 (Example 2), and Experimental Example 8 (Example 3). Because the cement composition of Experimental Example 1 (Reference Example) did not contain any components other than cement, an activity test was not conducted. Furthermore, as can be seen from Table 4 above, the cement composition of Experimental Example 4 (Comparative Example 1) also had cracks or fractures, so an activity test was not carried out.

[0122] Furthermore, if the activity index was 55% or higher after 7 days of underwater curing and 75% or higher after 28 days of underwater curing, the strength was equivalent to the strength required by the JIS R 5211:2019 standard for blast-furnace slag cement type B, and thus the hardened cement body was evaluated as having significantly greater strength. If the activity index was 35% or higher after 7 days of underwater curing and 55% or higher after 28 days of underwater curing, the hardened cement body was evaluated as having sufficient strength. If the activity index was less than 35% after 7 days of underwater curing and 55% or higher after 28 days of underwater curing, the hardened cement body was evaluated as insufficient. The results are shown in Table 5 below. Furthermore, the graph in Figure 1 shows the relationship between the activity index and the ratio of the cement admixture content to the total content of the cement admixture, ground granulated blast furnace slag, and cement (total amount of cement composition).

[0123] [Table 5]

[0124] [Consideration] As shown in Table 4 above, the mortars of Experimental Example 3 (Example 1), Experimental Example 7 (Example 2), and Experimental Example 8 (Example 3), which used cement admixture 1 or cement admixture 3 containing 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, showed no cracks or breaks. Furthermore, as shown in Table 5 above, the mortars (hardened cement products) of Experimental Example 3 (Example 1), Experimental Example 7 (Example 2), and Experimental Example 8 (Example 3), which used cement admixture 1 or cement admixture 3 in which 2CaO·SiO2, a calcium silicate with latent hydraulic properties, and 3CaO·Al2O3, a calcium aluminate, remained almost unreacted, were found to have significantly high or sufficient strength.

[0125] In particular, as can be seen from Figure 1, it was found that the mortars (cement hardened bodies) of Experimental Example 7 (Example 2) and Experimental Example 8 (Example 3), in which the ratio of the cement admixture content to the total content of the cement admixture, blast furnace slag powder, and cement (total amount of cement composition) was small, were able to obtain significantly greater strength.

[0126] On the other hand, as shown in Table 4 above, cracks and fractures occurred in the appearance of the mortar in Experimental Example 4 (Comparative Example 1), which used cement admixture 2 containing more than 1.50 mass% f-CaO relative to the total amount of the cement admixture. This is thought to be because the content of f-CaO was too high, which caused pop-out due to volume expansion that occurred during the hydration reaction of f-CaO, resulting in the cracks and fractures.

[0127] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. A cement admixture derived from steelmaking slag, The cement admixture contains 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate.

2. 2. The cement admixture according to claim 1, wherein the calcium silicate content is 40.0 mass% or more relative to the total amount of the cement admixture, and the calcium aluminate content is 10.0 mass% or more relative to the total amount of the cement admixture.

3. Specific surface area is 2750 cm ２ / g or more 10000cm ２ 2. The cement admixture of claim 1, wherein the SiO 2 content is less than 1 / g.

4. A cement composition comprising the cement admixture of claim 1 and cement.

5. The content of the cement admixture is 5% by mass or more and 50% by mass or less with respect to the total amount of the cement admixture and the cement, and the content of the cement is 50% by mass or more and 95% by mass or less with respect to the total amount of the cement admixture and the cement. The cement composition according to claim 4.

6. 5. The cement composition of claim 4, further comprising at least one of ground granulated blast furnace slag and fly ash.

7. the content of at least one of the ground granulated blast furnace slag and the fly ash is 30% by mass or more and 70% by mass or less based on the total amount of the at least one of the ground granulated blast furnace slag and the fly ash and the cement; The content of the cement is 30% by mass or more and 70% by mass or less with respect to the total amount of the cement and at least one of the ground granulated blast furnace slag and the fly ash, and 7. The cement composition according to claim 6, wherein the content of the cement admixture is 50 mass% or less relative to the content of at least one of the ground granulated blast furnace slag and fly ash.

8. The cement composition according to claim 4, further comprising 25% by mass or more and 65% by mass or less of water relative to the total amount of the cement admixture and the cement.

9. The cement composition according to claim 6, further comprising 25% by mass or more and 65% by mass or less of water based on the total amount of the cement admixture, at least one of the ground granulated blast furnace slag and fly ash, and the cement.

10. 5. The cement composition of claim 4, further comprising at least one of fine aggregate and coarse aggregate.

11. A hardened cement product, which is a hardened product of the cement composition according to any one of claims 4 to 10.

12. A method for producing a cement admixture derived from steelmaking slag, The method includes immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water; The method for producing a cement admixture, wherein the cement admixture contains 1.50 mass% or less of f-CaO relative to the total amount of the cement admixture, and also contains calcium silicate and calcium aluminate.

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