Composite oxide, cement admixture or blended cement containing composite oxide, and concrete

Abstract

To provide a composite oxide capable of producing concrete with reduced self-shrinkage when concrete is produced. Provided is a composite oxide containing CaO, MgO, and Al2O3, the composite oxide being characterized in that the basicity B3, which is a value obtained by dividing the sum of the mass% of CaO, the mass% of MgO, and the mass% of Al2O3 contained in the composite oxide by the mass% of SiO2 contained in the composite oxide, is 1.4-3.0, the total amount of iron contained in the composite oxide is 0.4-8.0 mass%, and the specific surface area of the composite oxide is 3000 cm2 / g or more.

Description

Complex oxides, cement admixtures containing complex oxides, or blended cements, and concrete

[0001] The present invention relates to a composite oxide, a cement admixture or blended cement containing the composite oxide, and concrete. In particular, the present invention relates to a composite oxide, a cement admixture or blended cement containing the composite oxide, and concrete that are excellent in latent hydraulic properties and can be suitably used for concrete with small autogenous shrinkage.

[0002] Ground granulated blast furnace slag is obtained by finely grinding the granulated blast furnace slag, which is produced by spraying high-pressure water onto molten blast furnace slag to rapidly cool it. Ground granulated blast furnace slag is amorphous and potentially hydraulic. For this reason, ground granulated blast furnace slag is mixed with ordinary cement and used as a raw material for blast furnace cement and as an admixture for cement.

[0003] The first advantage of using ground granulated blast furnace slag as a raw material for blast furnace cement is that ground granulated blast furnace slag generates less heat of hydration with water than ordinary Portland cement (NC). The second advantage is that concrete made using ground granulated blast furnace slag as a raw material for blast furnace cement has high long-term strength and salt resistance, and can suppress alkali-silica reaction. Furthermore, the third advantage is that the environmental impact can be reduced by reducing the amount of ordinary Portland cement (NC), which emits large amounts of carbon dioxide, used during concrete production.

[0004] On the other hand, a disadvantage of using ground granulated blast furnace slag as a raw material for blast furnace cement is that the concrete obtained using ground granulated blast furnace slag as a raw material for blast furnace cement will have a large autogenous shrinkage.

[0005] From this perspective, methods have been proposed for reducing the autogenous shrinkage of concrete using ground granulated blast furnace slag.Many methods have been proposed for reducing the autogenous shrinkage of concrete using ground granulated blast furnace slag, including the addition of expansive agents and shrinkage-reducing agents to the raw materials of blast furnace cement, and the use of blast furnace slag fine aggregate as the fine aggregate used in concrete.

[0006] A method for reducing autogenous shrinkage of concrete by adding calcium carbonate and gypsum in addition to Portland cement and blast furnace slag has been proposed (for example, Patent Document 1). That is, Patent Document 1 describes a concrete binder containing Portland cement, blast furnace slag, calcium carbonate, and gypsum, in which the blast furnace slag content is more than 5% by mass and not more than 70% by mass, the calcium carbonate content is 2% by mass or more and not more than 11% by mass, and the gypsum content, calculated as anhydrous, is 5% by mass or more and not more than 10% by mass, and the calcium carbonate content is 0.9 times or more.

[0007] Furthermore, a method has been proposed in which paraffin and nitrite are used in addition to ground granulated blast furnace slag in which 40% or more of the slag passes a 10 μm sieve and 15% or less of the slag remains on a 45 μm sieve (for example, Patent Document 2). That is, Patent Document 2 describes concrete that exhibits good early strength development in low-temperature environments, ensures resistance to freeze-thaw cycles, and exhibits little drying shrinkage, even when ground granulated blast furnace slag is used.

[0008] Furthermore, Patent Document 3 proposes a low-shrinkage AE concrete composition prepared using blast furnace cement as cement, which results in a hardened body that simultaneously has a low drying shrinkage rate, a small carbonation rate, and strong resistance to freezing and thawing. The low-shrinkage AE concrete composition described in Patent Document 3 uses blast furnace cement as cement, and adjusts the coarse particle ratio of at least a part of the fine aggregate to fall within a predetermined range, so that the concrete 1 m ３ It is produced by using 100 to 750 kg of specific fine blast furnace slag aggregate per 1000 cc, 135 to 175 kg of water, and adjusting the water / cement ratio to 30 to 60%.

[0009] JP 2016-23105 A JP 2022-89256 A JP 2011-6305 A

[0010] However, the above-mentioned conventional techniques still have the following problems to be solved. Specifically, the concrete binders described in Patent Documents 1 to 3 have the problem that additives such as expansion agents and shrinkage-reducing agents, as well as blast furnace slag fine aggregate, must be added to the blast furnace slag ground powder in order to reduce the autogenous shrinkage of concrete. Moreover, these expansion agents, additives, and blast furnace slag fine aggregate, which are necessary to produce concrete with reduced autogenous shrinkage, are a major factor in increasing the raw material costs. Furthermore, producing concrete with reduced autogenous shrinkage requires processes such as adding many additives, mixing the blast furnace slag fine aggregate, and designing the mix of concrete materials. As a result, the number of manufacturing processes required to produce concrete with reduced autogenous shrinkage increases.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a complex oxide that has excellent latent hydraulic properties and is capable of producing concrete with reduced autogenous shrinkage when produced.

[0012] Therefore, the inventors of the present invention conducted various experiments to solve the above problems, and as a result of their research into adjusting the composition of slag, they discovered that adding a modifier containing iron oxide or the like to the raw materials of concrete is extremely effective in improving the latent hydraulic properties of the raw materials and reducing the autogenous shrinkage of the resulting concrete. The present invention was made based on the above findings, and its gist is as follows.

[0013] That is, the composite oxide according to the present invention, which advantageously solves the above-mentioned problems, is composed of CaO, MgO and Al. ２ O ３ A composite oxide containing the above, wherein the mass % of the CaO, the mass % of the MgO, and the Al contained in the composite oxide are ２ O ３ The sum of the mass % of SiO contained in the composite oxide ２The basicity B3, which is the value obtained by dividing the total iron content by the mass % of the composite oxide, is 1.4 to 3.0, the total iron content of the composite oxide is 0.4 to 8.0 mass%, and the specific surface area of ​​the composite oxide is 3000 cm ２ / g or more.

[0014] Furthermore, it is believed that the complex oxide according to the present invention (a) can be obtained by adding a modifier to slag, and (b) the complex oxide has a vitrification rate of 90% or more, which may be more preferable solutions. Furthermore, the cement admixture or blended cement according to the present invention (c) is formed by containing the complex oxide. Furthermore, the concrete according to the present invention (d) is formed by containing the complex oxide.

[0015] According to the present invention, by using a cement raw material having excellent latent hydraulic properties in which a part of the cement raw material has been replaced with a composite oxide, it is possible to provide concrete with extremely reduced autogenous shrinkage.

[0016] [First embodiment] A composite oxide according to a first embodiment will be described. The composite oxide according to this embodiment is composed of CaO, MgO, and Al. ２ O ３ A composite oxide containing the above, wherein the mass % of the CaO, the mass % of the MgO, and the Al contained in the composite oxide are ２ O ３ The sum of the mass % of SiO contained in the composite oxide ２ The basicity B3, which is the value obtained by dividing the total iron content by the mass % of the composite oxide, is 1.4 to 3.0, the total iron content of the composite oxide is 0.4 to 8.0 mass%, and the specific surface area of ​​the composite oxide is 3000 cm ２ Each component contained in the composite oxide according to this embodiment will be described below.

[0017] The composite oxide according to this embodiment contains CaO, MgO, and Al as its composition components. ２ O ３ That is, the composite oxide contains CaO, MgO, and Al. ２ O ３The composite oxide may be formed by preparing and mixing materials containing these respective compositional components, or by using a material containing these compositional components as is. Also, the composite oxide may be used by adding a missing compositional component to a material containing some of these compositional components. Furthermore, the composite oxide according to this embodiment may contain SiO as a compositional component. ２ Contains:

[0018] The composite oxide contains CaO in % by mass, MgO in % by mass, and Al in % by mass. ２ O ３ The sum of the mass % of SiO contained in the composite oxide ２ The basicity B3 of the composite oxide is 1.4 or more and 3.0 or less, which is the value obtained by dividing the mass % of CaO and MgO by the mass % of Al contained in the composite oxide. By setting the basicity B3 within this range, it is possible to obtain a composite oxide that has appropriate latent hydraulic hardening properties when used as a cement admixture. In order to calculate the basicity B3 of the composite oxide, first, the mass % of CaO, the mass % of MgO, and the mass % of Al contained in the composite oxide are calculated. ２ O ３ and the mass % of the total mass of the saturation agent are calculated, and then the sum of these calculated mass % is calculated.

[0019] Next, SiO contained in the composite oxide ２ In this way, the mass % of CaO, the mass % of MgO and the mass % of Al contained in the calculated composite oxide are calculated. ２ O ３ and SiO ２ The basicity B3 of the composite oxide is calculated using the mass % of CaO, the mass % of MgO, and the mass % of Al contained in the composite oxide. ２ O ３ The sum of the mass % of SiO ２ The basicity B3 can be calculated by dividing the basicity B3 by the mass % of the total weight of the polymer. The basicity B3 may be calculated, for example, by the following relational expression (1):

[0020] In the above relational expression (1), CaO is the mass % of calcium oxide, MgO is the mass % of magnesium oxide, and Al ２ O ３is the mass % of aluminum oxide, and SiO ２ represents the mass % of silicon dioxide.

[0021] The basicity B3 calculated from each component contained in the complex oxide according to this embodiment is preferably 1.4 or more. A basicity B3 of 1.4 or more is preferable because the dissolution of the glass component contained in the complex oxide causes Ca, Si, etc. to elute, promoting the hydration reaction. A basicity B3 of 3.0 or less is preferable because it ensures appropriate latent hydraulic properties of the complex oxide and allows concrete formed containing the complex oxide to fully exhibit strength. The basicity B3 can be appropriately adjusted and set within the above range by adjusting the values ​​of each component contained in the complex oxide according to this embodiment. Specifically, to adjust the basicity B3 within the above range, the component that is lacking in the complex oxide and the amount of that component are determined. The basicity B3 can be adjusted within the above range by adding various modifiers containing the missing component to the complex oxide.

[0022] The composite oxide according to the present embodiment is characterized in that the total iron content (T.Fe) contained in the composite oxide is 0.4% by mass or more and 8.0% by mass or less. Generally, the total iron content (T.Fe) contained in blast furnace slag, a by-product of a blast furnace, is less than 0.4% by mass. Therefore, for example, even if blast furnace slag, a by-product of a blast furnace, is used as a raw material for blast furnace cement and concrete containing the blast furnace cement is produced, the autogenous shrinkage of the resulting concrete cannot be reduced. In this regard, the composite oxide according to the present embodiment has a composition in which the B3 calculated from the above relational expression (1) is an appropriate value. For example, by adding a modifier containing iron oxide to the composite oxide, the total iron content (T.Fe) of the composite oxide containing the modifier may be adjusted to 0.4% by mass or more and 8.0% by mass or less. Limiting the total iron content (T.Fe) of the composite oxide within this range ensures latent hydraulic properties and allows it to be used as a blended cement or cement admixture, and produces concrete with reduced autogenous shrinkage compared to concrete formed using ground granulated blast furnace slag.

[0023] That is, the composite oxide according to this embodiment focuses on its total iron content (T.Fe), and by increasing the total iron content (T.Fe), concrete with reduced autogenous shrinkage can be produced. A total iron content (T.Fe) of 0.4% by mass or more in the composite oxide is preferable because, when the composite oxide is used as a mixed cement, the concrete formed from the mixed cement can exhibit sufficient strength and autogenous shrinkage. A total iron content (T.Fe) of 1.0% by mass or more is more preferable, a total iron content (T.Fe) of 2.0% by mass or more is even more preferable, and a total iron content (T.Fe) of 3.0% by mass or more is particularly preferable. A total iron content (T.Fe) of 8.0% by mass or less in the composite oxide is preferable because, when the composite oxide is used as a cement admixture, its latent hydraulic property is not reduced.

[0024] The specific surface area of ​​the composite oxide is 3000 cm ２ By specifying the specific surface area of ​​the composite oxide in this way, it is possible to obtain a composite oxide having sufficient latent hydraulic property that satisfies the activity index standard specified in, for example, JIS R 6206:2013, which is preferable. That is, the composite oxide according to this embodiment has a specific surface area of ​​3000 cm ２ / g or more, the concrete containing the complex oxide can be used as a concrete product. ２ It is preferable that:

[0025] As described above, the composite oxide according to this embodiment contains blast furnace slag, and by further adding an iron oxide-containing modifier, the total iron content (T.Fe) is increased to 0.4 mass% or more compared to the total iron content (T.Fe) contained in ordinary blast furnace slag, which significantly contributes to reducing the autogenous shrinkage of concrete formed using this composite oxide.

[0026] As described above, according to the invention related to the first embodiment, it is possible to provide a complex oxide that can produce concrete with reduced autogenous shrinkage when produced.

[0027] [Second embodiment] A composite oxide according to a second embodiment will be described. The composite oxide according to this embodiment is the composite oxide according to the above embodiment, and is characterized in that it is obtained by adding a modifier to slag. Each component contained in the composite oxide according to this embodiment will be described below.

[0028] <Slag such as steel slag> The slag contained in the composite oxide according to this embodiment may be steel slag or non-ferrous metal slag produced in a metal production process, or may be waste molten slag produced in a waste thermal melting process. The steel slag is not particularly limited, and may be, for example, blast furnace slag such as granulated blast furnace slag or slowly cooled blast furnace slag, or steelmaking slag such as converter slag or electric furnace slag. It may also be slag produced as a by-product in a smelting reduction ironmaking process or a direct ironmaking process. The non-ferrous metal slag may be ferronickel slag, copper slag, or the like. The waste molten slag may be garbage molten slag, sewage sludge slag, or the like. As described above, various slags can be used as the slag contained in the composite oxide according to this embodiment. However, from the viewpoints of energy conservation, resource conservation, and carbon dioxide reduction, some of the slags that can be used in the composite oxide will be described.

[0029] (Blast Furnace Slag) The blast furnace slag contained in the composite oxide according to this embodiment is recovered as a substance with a lower density than pig iron when iron is recovered from iron ore charged into a blast furnace by adding coke, limestone, etc. to the iron ore and then reducing the iron. Approximately 290 to 300 kg of blast furnace slag is by-produced per 1.0 ton of pig iron. Granulated blast furnace slag, obtained by spraying high-pressure water onto molten blast furnace slag to rapidly cool it, has latent hydraulic properties. Granulated blast furnace slag does not harden simply by mixing with water, but in the presence of an alkali with a pH of about 12.0 or higher, the vitreous substance that constitutes the blast furnace slag decomposes, eluting Ca and Si and promoting a hydration reaction.

[0030] Blast furnace slag, a by-product of blast furnaces, is in a molten state because its temperature exceeds 1,400°C. When this molten blast furnace slag is rapidly cooled by spraying high-pressure water onto it, the molten blast furnace slag becomes granulated blast furnace slag. Granulated blast furnace slag is sandy and becomes vitreous (amorphous) because it is produced by rapidly cooling molten blast furnace slag. Granulated blast furnace slag has the ability to undergo a hydration reaction. Here, the blast furnace slag used in the production of the composite oxide according to this embodiment may be molten blast furnace slag, or may be formed from blast furnace slag that has been cooled and then re-melted.

[0031] Blast furnace slag is a by-product of the blast furnace in the blast furnace-converter process. That is, the blast furnace slag contained in the composite oxide is a by-product of the blast furnace-converter process. ２ O ３ ) is charged into a blast furnace together with coke (carbon source), which is a reducing agent, to produce molten iron with a C concentration of 4.5 to 5.0 mass %.

[0032] Furthermore, the blast furnace slag contained in the composite oxide may be a by-product of the so-called blast furnace-converter process. The composition of the blast furnace slag by-produced by the blast furnace-converter process is generally identical to the composition of the composite oxide according to this embodiment. Therefore, by simply adjusting the total iron content (T.Fe) contained in the blast furnace slag by-produced by the blast furnace-converter process, it can be used as the composite oxide according to this embodiment.

[0033] (Steelmaking slag such as electric furnace slag) In recent years, there has been an increasing demand for the expanded use of cold iron sources (scrap) in the steelmaking industry. Recycling of iron sources is essential for building a recycling-oriented society. Furthermore, increasing the use of cold iron sources (scrap) is essential in order to prevent global warming and reduce carbon dioxide emissions. Moreover, unlike iron ore, which is iron oxide, cold iron sources (scrap) do not require a reduction step in the melting process, making it possible to reduce carbon dioxide emissions. From this technical perspective, it is of great technical significance that the composite oxide according to this embodiment can utilize steelmaking slag by-produced in an electric furnace production process as the slag contained in the composite oxide. Furthermore, the steelmaking slag by-produced in an electric furnace production process has a composition that is almost identical to that contained in the composite oxide according to this embodiment. Therefore, the steelmaking slag by-produced in an electric furnace production process can be used as is, which is of even greater technical significance.

[0034] (Steelmaking Slag, Such as Smelting Reduction Furnace Slag) Furthermore, a smelting reduction ironmaking process has been proposed as a steelmaking process that does not use a blast furnace. The slag contained in the composite oxide according to this embodiment may be steelmaking slag produced by the smelting reduction ironmaking process. In the smelting reduction ironmaking process, 60 to 70 mass% of the oxygen contained in iron ore is removed in a pre-reduction furnace, and the partially oxygen-removed iron ore is then transferred to a smelting reduction furnace maintained at a temperature higher than that of the pre-reduction furnace to completely remove oxygen. In the smelting reduction ironmaking process, fine ore and powdered coal are injected into the smelting reduction furnace to remove oxygen from the iron ore, eliminating the need for sintering the iron ore. Therefore, the smelting reduction ironmaking process allows for a compact steelmaking facility, which is also beneficial from an environmental perspective. Furthermore, the smelting reduction ironmaking process offers high production flexibility and flexibility with raw materials. Compared to blast furnaces, the reaction time of iron ore is extremely short, allowing steelmaking operations to be suspended as needed. Furthermore, the smelting reduction ironmaking process significantly reduces steelmaking costs by improving capital investment efficiency. From such a technical point of view, the ability to utilize smelting reduction furnace slag produced by a smelting reduction ironmaking method in the composite oxide according to this embodiment has extremely great technical significance in terms of the environment and steelmaking costs.

[0035] <Modifiers such as iron oxide-containing modifiers> The modifiers contained in the complex oxide according to this embodiment can adjust the content of each component contained in the complex oxide. Specifically, the modifiers contained in the complex oxide contain components necessary for adjusting the basicity B3 of the complex oxide, the total iron content (T.Fe) contained in the complex oxide, and the like. Examples of modifiers contained in the complex oxide include iron oxide-containing modifiers, calcium oxide-containing modifiers, magnesium oxide-containing modifiers, aluminum oxide-containing modifiers, and silicon dioxide reagents. Below, we will explain iron oxide-containing modifiers that can adjust the total iron content (T.Fe), which is the most important compositional component contained in the complex oxide according to this embodiment.

[0036] (Iron Oxide-Containing Modifier) ​​Furthermore, the composite oxide according to this embodiment may contain an iron oxide-containing modifier as a modifier added to the slag. The iron oxide-containing modifier may contain iron oxide and increase the total iron content (T.Fe), which is a compositional component of blast furnace slag, and for example, scale or a reagent may be used. Examples of scale include iron rust and a steel oxide film, which is an iron oxide that forms on the surface of steel when the steel is exposed to air at high temperatures during the steel manufacturing process. Note that the composition of the scale varies depending on the steel components that are the base.

[0037] Examples of reagents include iron oxides such as iron(II) oxide and iron(III) oxide. Iron oxide is an oxide of iron and is found in nature as a mineral. Examples of minerals include ferrous oxide (wustite), hematite, limonite, magnetite, and maghemite. Furthermore, examples of reagents that can produce iron oxide through a dehydration reaction, such as heating, include α-iron oxyhydroxide (goethite), β-iron oxyhydroxide (akaganeite), γ-iron oxyhydroxide (lepidocrocite), δ-iron oxyhydroxide (ferroxyhite), iron(II) hydroxide, and iron(III) hydroxide.

[0038] The method of adding the modifier to the slag is not particularly limited, but the modifier may be added to molten slag, or the modifier may be added to slag that is not fully molten or in a solid state, and then the slag to which the modifier has been added may be heated to make it molten. Specifically, as a method of adding the modifier to the slag, for example, when the slag is blast furnace slag, an iron oxide-containing modifier may be added to molten blast furnace slag discharged from a blast furnace, or the blast furnace slag may be mixed with the iron oxide-containing modifier and then the blast furnace slag and the iron oxide-containing modifier may be heated to melt and make it molten.

[0039] That is, the means for obtaining the composite oxide is not particularly limited, but for example, the operating conditions for obtaining by-products of a metal refining process or a municipal waste melting process may be adjusted so as to have the composition of the composite oxide according to this embodiment. In other words, the components of such by-products may be adjusted so as to have the composition of the present invention. In particular, slag generated in a blast furnace or an electric furnace in the steel manufacturing process contains CaO, SiO ２ , Al ２ O ３ Since the slag is mainly composed of MgO, the composition of the present invention can be achieved by adding a modifier such as an iron oxide-containing modifier containing iron oxide, which is preferable. Furthermore, the composition is preferably adjusted by adding the modifier to the molten slag or by dissolving the modifier after addition. For example, the iron oxide-containing modifier may be added to the molten slag immediately before or after discharge, or the solidified blast furnace slag and the modifier may be mixed and then remelted.

[0040] A complex oxide is formed by adding a modifier to slag. The total iron content (T.Fe) of the complex oxide is 0.4% by mass or more and 8.0% by mass or less. By limiting the total iron content (T.Fe) of the complex oxide to this range, the complex oxide can be used as a raw material for blended cement, and the autogenous shrinkage of concrete and mortar formed with the blended cement can be significantly reduced. Furthermore, the complex oxide can be used as an admixture for blended cement, and the autogenous shrinkage of concrete and mortar formed with the blended cement can be significantly reduced. Note that when the complex oxide according to this embodiment is used as an admixture for blended cement or as a material for concrete or mortar formed with the blended cement, the average particle size of the complex oxide may be set to 5 to 30 μm, and the complex oxide may be pulverized to form a complex oxide fine powder. The complex oxide fine powder is produced by pulverizing steel balls and the complex oxide by collision with each other as the drum rotates in a cylindrical drum. A finishing pulverizer (finishing pulverizing mill) may be used to pulverize the complex oxide. The composite oxide powder discharged from the finishing mill may be separated into particles of different average particle diameters using a classifier such as a separator.

[0041] Furthermore, the vitrification rate of the complex oxide according to this embodiment is preferably 90% or more. The vitrification rate is an index for judging the quality of a complex oxide. By setting the vitrification rate of the complex oxide to 90% or more, it is possible to obtain a complex oxide for concrete having an activity equal to or higher than the activity of complex oxides specified in JIS R 6206:2013, for example. This is preferable. If the vitrification rate of the complex oxide is within this range, the 91-day activity index of the complex oxide contained in concrete produced using the complex oxide can be set to 100 or more. In other words, when the complex oxide according to this embodiment is used as a cement admixture, it is possible to obtain long-term strength equal to or higher than that of cement.

[0042] If the vitrification rate of the complex oxide is less than 90%, its latent hydraulic property will be reduced, and when the complex oxide is used as a blended cement, the long-term strength of the concrete produced from the cement will be lower than that of concrete made with ordinary cement, which is undesirable. The method for achieving a vitrification rate of the complex oxide of 90% or more is not particularly limited, but it is preferable, for example, to rapidly cool molten blast furnace slag by spraying water or air onto it. The vitrification rate can be measured by visually determining the ratio of glass particles to crystal particles using a polarizing microscope, or by XRD measurement.

[0043] As described above, according to the second embodiment of the invention, by adding a modifier to slag, it is possible to provide a complex oxide suitable for producing concrete with reduced autogenous shrinkage. In particular, according to the second embodiment of the invention, electric furnace slag, which is a by-product of the electric furnace manufacturing process, can be used for the complex oxide, which can promote the expansion of the use of cold iron sources (scrap) in the steelmaking industry and also meet the demand for reducing carbon dioxide emissions from the perspective of preventing global warming.

[0044] [Third embodiment] A cement admixture or a mixed cement according to a third embodiment will be described. First, the mixed cement according to this embodiment will be described. The mixed cement according to this embodiment is characterized by containing the composite oxide according to the above embodiment. That is, the mixed cement according to this embodiment contains the composite oxide and other compositional components.

[0045] Another component contained in the mixed cement according to this embodiment may be Portland cement. The mixed cement according to this embodiment is obtained by mixing at least Portland with the composite oxide according to the above embodiment. Generally, blast furnace cements are broadly classified into types A to C based on the amount of granulated blast furnace slag. Specifically, type A blast furnace cement contains more than 5% but not more than 30% of granulated blast furnace slag, type B blast furnace cement contains more than 30% but not more than 60% of granulated blast furnace slag, and type C blast furnace cement contains more than 60% but not more than 70% of granulated blast furnace slag. In other words, the mixed cement according to this embodiment is a mixed cement in which the granulated blast furnace slag contained in types A to C blast furnace cements is replaced with composite oxide fine powder. In other words, the mixed cement according to this embodiment can replace conventional types A to C blast furnace cements.

[0046] Furthermore, the Portland cement may be ordinary Portland cement. Ordinary Portland cement may contain cement clinker. Ordinary Portland cement is the most widely available cement and is readily available. The blended cement according to this embodiment contains ordinary Portland cement in a complex oxide. Therefore, the blended cement according to this embodiment has a lower heat of hydration than ordinary Portland cement, and the mixed cement can have enhanced chemical resistance after hardening. As a result, the blended cement according to this embodiment can be suitably used for civil engineering applications such as bridge piers and dams, which require strength and durability. The blended cement according to this embodiment hardens by chemical reaction with water and can be used as mortar or concrete, a construction material that supports social life.

[0047] Further, examples of other components contained in the mixed cement according to this embodiment include high-early-strength Portland cement that develops strength in a shorter period of time, moderate-heat Portland cement that has a low calorific value, and low-heat Portland cement, depending on the construction environment at the site. Other components contained in the mixed cement may also be acid-resistant cement primarily composed of calcium aluminate that is suitable for use in sulfate soils such as hot spring areas, white cement used for aesthetic purposes, ultra-rapid-hardening cement used for emergency repairs, and ecocement made from household waste such as municipal solid waste incineration residue.

[0048] The mixed cement according to this embodiment may contain the complex oxide in a mass ratio of the complex oxide to other components of 10:90 to 90:10. When the mixed cement contains the complex oxide according to the above embodiment and Portland cement, the substitution ratio of the unit amount of complex oxide (SP) to the unit amount of mixed cement (C) shown in the following relational formula (2) can be set to 0.10 to 0.90 as the complex oxide substitution ratio.

[0049] In the above relational expression (2), C represents the unit amount of cement, and SP represents the unit amount of complex oxide.

[0050] Next, the cement admixture according to this embodiment will be described. The cement admixture according to this embodiment is characterized by containing the complex oxide according to the above embodiment. The cement admixture according to this embodiment contributes to improving workability when producing concrete, and improving the slump and strength of concrete. By using the cement admixture according to this embodiment, all materials necessary for producing concrete can be easily mixed even when using a small amount of water. The amount of the cement admixture according to this embodiment can be appropriately set depending on the concrete to be produced. Furthermore, the type and amount of the complex oxide according to the above embodiment contained in the cement admixture according to this embodiment can also be appropriately set.

[0051] As described above, according to the invention of the third embodiment, after producing a cement admixture or a mixed cement using the composite oxide according to the above embodiment, it is possible to provide concrete with extremely reduced autogenous shrinkage.

[0052] [Other Embodiments] The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the technical scope of the present invention. Furthermore, systems or devices that combine separate features included in each embodiment in any way are also included in the technical scope of the present invention.

[0053] The effects of the present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

[0054] (Invention Example 1) <Production of Complex Oxide> A complex oxide according to the present invention was produced. The complex oxide can be used as ground slag for concrete. That is, the complex oxide according to the invention was produced by adding an iron oxide-containing modifier, a CaO reagent for adjusting B3, and SiO to remelted blast furnace slag. ２ Reagents, Al ２ O ３ After adding and mixing the reagent and MgO reagent, the mixture is rapidly cooled and solidified by spraying water onto it, and the specific surface area is reduced to 3000 to 5000 cm. ２ / g (specific surface area 4000±1000cm ２ That is, the composite oxide of the present invention is produced by spraying water onto molten blast furnace slag and various reagents to rapidly cool and solidify the molten slag, and then grinding the molten slag into a powder having a specific surface area of ​​4000±1000 cm. ２ In Example 1, a triiron tetroxide reagent was used as the iron oxide-containing modifier added to the blast furnace slag.

[0055] <Vitrifaction ratio of complex oxide> The vitrification ratio of complex oxide was measured. The measurement of the vitrification ratio was carried out by polarizing microscope observation. Specifically, a thin sample of the complex oxide was prepared and observed with a polarizing microscope under crossed polars to measure the vitrification ratio (%) of the complex oxide.

[0056] <Basicity B3 of Complex Oxide> The basicity B3 of the complex oxide was measured. The basicity B3 was measured by measuring the composition of each of the components contained in the complex oxide, such as CaO, SiO ２ , Al ２ O ３ The MgO content (mass %) was measured, and the basicity B3 calculated from the above relational expression (1) was 1.47.

[0057]

[0058] <Production of Concrete> Concrete was produced as a hardened concrete precursor using the composite oxide obtained in Example 1. Table 1 shows the composition of the concrete and the proportions of each component. As shown in Table 1, ordinary Portland cement, river sand as fine aggregate, and river gravel as coarse aggregate were used as the components (materials) constituting the composition other than the composite oxide obtained in Example 1.

[0059] Hardened concrete was produced according to the blending examples shown in Table 1, and the autogenous shrinkage strain of the hardened concrete at an age of 28 days was measured. The water-binder ratio, expressed by the following relational expression (3), obtained by dividing the unit amount of water by the unit amount of composite oxide and the unit amount of ordinary Portland cement, was set to 0.35. In producing the hardened concrete for measuring autogenous shrinkage strain, ordinary Portland cement (density 3.16 g / cm) was used as a material other than the composite oxide of the present invention. ３ , river sand as fine aggregate: density 2.46 g / cm ３ , river gravel as coarse aggregate: density 2.62 g / cm ３ The density of the composite oxide varies depending on the composition and total iron content, so the unit amounts of fine and coarse aggregate were adjusted as necessary.

[0060]

[0061]

[0062] The concrete composition components shown in Table 1 were mixed and then kneaded to produce concrete of Invention Example 1. The volume ratio (fine aggregate ratio) of fine aggregate (river sand) to the total volume of fine aggregate and coarse aggregate was set to 50%. Furthermore, in the concrete obtained in Invention Example 1, the substitution ratio of unit complex oxide content (SP) to unit cement content (C), which is the value calculated using the above relational formula (2), was set to 0.83.

[0063] In the above relational expression (2), W represents the unit amount of water, C represents the unit amount of cement, and SP represents the amount of complex oxide.

[0064] Furthermore, in the concrete obtained in Example 1, the water-binder ratio, which is the ratio of water to the sum of the unit cement content (C) and the unit complex oxide content (SP), calculated by the above-mentioned relational expression (3), was set to 0.35.

[0065] In the above relational expression (3), W represents the unit water content, C represents the unit cement content, and SP represents the unit composite oxide content.

[0066] <Measurement of Autogenous Shrinkage Strain of Concrete and Activity Index of Complex Oxide> A concrete precursor obtained by kneading concrete components containing complex oxides was placed in a mold, dried, and then demolded to produce a concrete specimen as a hardened body for measuring autogenous shrinkage strain.

[0067] A polycarboxylic acid-based high-performance water-reducing agent (product name "Chupol" manufactured by Takemoto Yushi Co., Ltd.) was used to prepare the hardened specimen for measuring autogenous shrinkage strain. The hardened specimen for measuring autogenous shrinkage strain was a 10 cm x 10 cm x 40 cm rectangular column, prepared with an embedded strain gauge embedded in the center. To prevent the hardened specimen from drying from the surface, the surface was covered with plastic wrap after casting and left to stand until the day after casting. The hardened specimen was then demolded, and the entire surface was covered with aluminum foil, and the entire specimen was then covered with a plastic bag for curing. The autogenous shrinkage strain was then measured at an age of 28 days.

[0068] The activity index of the composite oxide was then measured at ages of 7, 28, and 91 days. The activity index of the composite oxide at ages of 7, 28, and 91 days was measured in accordance with JIS A 6206-2:2010, "Ground granulated blast furnace slag for concrete." Specifically, the activity index is the value (%) obtained by dividing the compressive strength of a 40 mm x 40 mm x 160 mm prismatic mortar made by replacing 50% of the ordinary cement with the composite oxide by the compressive strength of a mortar made using only ordinary cement. Therefore, the compressive strength of the mortar made by replacing 50% of the cement with the composite oxide and the compressive strength of the mortar made using only cement were measured, and the activity index of the composite oxide was measured. Table 2 shows the measurement results for the composite oxide and the concrete obtained in Example 1.

[0069] (Invention Examples 2 to 41) Complex oxides were produced in the same manner as in Invention Example 1, except that the content (mass%) of each compositional component constituting the complex oxide and the content (mass%) of the total iron (T.Fe) were changed. The basicity B3 and vitrification rate (%) of the produced complex oxides were then calculated. Furthermore, using the produced complex oxides, concrete was produced as a hardened body in the same manner as in Invention Example 1, and the autogenous shrinkage strain of the concrete was measured. Thereafter, the activity index of the complex oxides was measured at ages of 7 days, 28 days, and 91 days in the same manner as in Invention Example 1. Tables 2 to 4 show the measurement results for the complex oxides and concrete obtained in Invention Examples 2 to 41.

[0070] (Comparative Examples 1 to 19) Composite oxides were produced in the same manner as in Example 1, except that the content (mass%) of each component constituting the composite oxide was changed, and the total iron (T.Fe) content (mass%) was changed to less than 0.4% (Comparative Examples 1 to 9) or more than 8.0% (Comparative Examples 10 to 19). The basicity B3 and vitrification rate (%) of the produced composite oxides were then calculated. Furthermore, using the produced composite oxides, hardened concrete was produced in the same manner as in Example 1, and the autogenous shrinkage strain of the concrete was measured. Thereafter, the activity index of the composite oxides was measured at ages of 7, 28, and 91 days in the same manner as in Example 1. Tables 4 and 5 show the measurement results of the composite oxides and concrete obtained in Comparative Examples 1 to 19.

[0071]

[0072]

[0073]

[0074]

[0075] As is clear from Tables 2 to 5, in Examples 1 to 41 in which the basicity B3 value of the composite oxide was 1.4 or more and 3.0 or less and the total iron content (T.Fe) was 0.4 mass% or more and 8.0 mass% or less, the autogenous shrinkage strain was 100 × 10 －６ In contrast, this was a smaller value than the autogenous shrinkage strain of the concrete produced using blast furnace slag shown in Comparative Example 1, and it was confirmed that the composite oxides of Invention Examples 1 to 41, when used as cement admixtures, reduce the autogenous shrinkage strain of the resulting concrete.

[0076] Furthermore, the activity index values ​​of the composite oxides of Examples 1 to 41 at ages of 7, 28, and 91 days were also equal to or greater than the reference value for ground granulated blast furnace slag 4000 specified in JIS A 6206:2013, confirming that the composite oxides of Examples 1 to 41 have sufficient latent hydraulic properties. In Comparative Examples 2 to 9, in which the total iron content (T.Fe) of the composite oxide was less than 0.4 mass%, the autogenous shrinkage strain of the concrete produced using the composite oxide was 100 x 10 －６ As a result, the effect of reducing autogenous shrinkage strain was small.

[0077] In Comparative Examples 10 to 17, in which the total iron content (T.Fe) of the complex oxide was greater than 8.0 mass%, the autogenous shrinkage strain of the concrete produced using the complex oxide was small, but the activity index of the complex oxide was below the standard value for ground granulated blast furnace slag 4000 specified in JIS A 6206: 2013, indicating reduced latent hydraulic properties. Furthermore, in Comparative Example 18, in which the complex oxide basicity B3 value was less than 1.4, and Comparative Example 19, in which the value exceeded 3.0, the activity index of the complex oxide was smaller than that of Comparative Examples 10 to 17, confirming that the complex oxide did not have sufficient latent hydraulic properties.

[0078] Furthermore, Tables 2 to 5 show that in Examples 1 to 41, in which the total iron content (T.Fe) contained in the complex oxide was 0.4 mass% or more and 8.00 mass% or less, the vitrification rate of the complex oxide was approximately 90% or more. Furthermore, it was revealed that the activity index of the complex oxides produced in Examples 1 to 41 was equal to or greater than the value that should be satisfied by ordinary ground granulated blast furnace slag as specified in JIS A 6206:2013. Therefore, it was confirmed that the complex oxides according to the present invention have latent hydraulic properties comparable to those of ordinary ground granulated blast furnace slag.

[0079] As described above, it has become clear that the complex oxide according to the present invention can ensure latent hydraulic properties by appropriately setting the basicity B3 and total iron content (T.Fe), and can also significantly reduce the autogenous shrinkage strain of concrete produced by curing a concrete precursor containing the complex oxide.

[0080] According to the present invention, by using a cement raw material in which part of the cement raw material has been replaced with a composite oxide, it is possible to provide concrete with extremely reduced autogenous shrinkage, which contributes to the development of related industries such as the steel manufacturing industry and the civil engineering and construction industry, and is extremely useful industrially.

Claims

1. CaO, MgO and Al ２ O ３ A composite oxide comprising the above, wherein the mass % of CaO, the mass % of MgO, and the mass % of Al contained in the composite oxide are ２ O ３ The sum of the mass % of SiO contained in the composite oxide is ２ The basicity B3, which is the value obtained by dividing the total iron content by the mass % of the composite oxide, is 1.4 to 3.0, the total iron content of the composite oxide is 0.4 to 8.0 mass%, and the specific surface area of ​​the composite oxide is 3000 cm ２ / g or more.

2. The composite oxide according to claim 1, which is obtained by adding a modifier to slag.

3. The complex oxide according to claim 1, characterized in that the vitrification rate of said complex oxide is 90% or more.

4. A cement admixture or mixed cement containing the complex oxide according to claim 1.

5. Concrete formed containing the complex oxide according to claim 1.

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