Blended cement composition, and method for producing the same

Abstract

To provide a mixed cement composition that contributes to CO2 reduction by increasing the amount of admixture used and that contributes to the effective use of low-basicity blast furnace slag. [Solution] One aspect of the present disclosure provides a mixed cement composition comprising cement clinker, gypsum, limestone, and blast furnace slag having an Al2O3 content within a predetermined range, wherein the blast furnace slag has a basicity Bu(7d) and a basicity Bu(28d) based on its chemical composition that are equal to or less than predetermined values, and an activity index A50(7d) and an activity index A50(28d) that are within predetermined ranges, the contents of limestone and blast furnace slag being within predetermined ranges, and the content of blast furnace slag being within a predetermined range based on the total amount of limestone and blast furnace slag. Bu(7d)=(CaO+0.43MgO+0.28Al2O3) / SiO2-0.46TiO2-0.27MnO...Formula (1) Bu(28d) = (CaO + 0.42MgO + 0.16Al2O3) / SiO2 - 0.60TiO2 - 0.14MnO...Equation (2)

Description

Technical Field

[0001] The present disclosure relates to a blended cement composition and a method for manufacturing the same.

Background Art

[0002] In recent years, as the demand for countermeasures against global warming has increased, a reduction in the amount of CO2 generated in cement production has been demanded. Cement clinker, which occupies a high proportion as a cement raw material, has a large amount of CO2 emissions in its manufacturing process, and from the perspective of preventing global warming, it is desirable to increase the amount of admixture used instead of cement clinker. As an admixture to replace cement clinker, in addition to limestone, which is a natural resource, by using industrial by-products, etc., it becomes possible to reduce the environmental load associated with cement production.

[0003] One of the indexes for judging the activity of blast furnace slag is basicity. In JIS R 5211:2019 "Blast Furnace Cement", it is stipulated that blast furnace slag with a basicity (hereinafter also referred to as JIS basicity) calculated by the following formula (A) of 1.60 or more is used for blast furnace cement. Basicity = (CaO + Al2O3 + MgO) / SiO2... Formula (A)

[0004] However, as blast furnace slag used for cement addition in Japan, high-basicity blast furnace slag, which is advantageous for strength development, is selected and used. As such blast furnace slag, those with a JIS basicity of generally 1.85 or more are often used. Blast furnace slag with a low basicity, even if its JIS basicity is 1.60 or more, is generally considered to have low strength development properties, and in Japan, it has been less likely to be used as blast furnace slag for cement addition. For example, Patent Document 1 discloses a cement composition in which the amount of CO2 emissions is reduced by adding a large amount of blast furnace slag, but the blast furnace slag used has a high JIS basicity of 1.85 to 1.91.

[0005] On the one hand, blast furnace slag for cement addition is used not only in the production of cement compositions containing a large amount of blast furnace slag known as blast furnace cements of types A, B, and C, but also as a minor admixture in ordinary Portland cement with a large production volume. In recent years, as an attempt to promote carbon reduction, the case of increasing the amount of minor admixture in ordinary Portland cement with a large production volume has been assumed, and studies have been conducted on formulations with more than 5% by mass of admixture added. For example, in Non-Patent Document 1, blast furnace slag with a JIS basicity of 1.85 is used as a minor admixture.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In order to reduce the CO2 emissions associated with cement production, when increasing the amount of minor admixture as a substitute for cement clinker, there is a concern that the strength may decrease compared to the current ordinary Portland cement. Furthermore, if the use of a large amount of blast furnace slag as considered in Patent Document 1 increases, it may become difficult to obtain blast furnace slag with a high JIS basicity that has been conventionally used, and it becomes necessary to effectively utilize blast furnace slag with a low JIS basicity.

[0009] However, when using blast furnace slag with a low basicity (blast furnace slag with a JIS basicity of less than 1.85), there is a concern that the strength may decrease compared to when using blast furnace slag with a high basicity. Also, in the case of adding a small amount of blast furnace slag assumed to be used as a minor mixing component, sufficient consideration has not been given to the use of blast furnace slag with a low basicity.

[0010] An object of the present disclosure is to provide a blended cement composition that contributes to CO2 reduction by increasing the amount of admixture used compared to conventional ordinary Portland cement and that facilitates the effective use of blast furnace slag with a low basicity.

Means for Solving the Problems

[0011] One aspect of the present disclosure provides a blended cement composition including cement clinker, gypsum, limestone, and blast furnace slag with an Al2O3 content of 12.7 mass% or more. The blast furnace slag has a basicity Bu(7d) calculated from the following formula (1) based on the chemical composition of the blast furnace slag of 1.20 or less, and a basicity Bu(28d) calculated from the following formula (2) of 1.00 or less. The activity index A50(7d) of the blast furnace slag at the age of 7 days is 63.5 to 96.5%, and the activity index A50(28d) of the blast furnace slag at the age of 28 days is 86.5 to 111.0%. The total content of the limestone and the blast furnace slag is more than 5.0 mass% and 10.0 mass% or less, and the content of the blast furnace slag is 1 to 90 mass% based on the total amount of the limestone and the blast furnace slag. Bu(7d)=(CaO + 0.43×MgO + 0.28×Al2O3) / SiO2 - 0.46×TiO2 - 0.27×MnO … Formula (1) Bu(28d)=(CaO + 0.42×MgO + 0.16×Al2O3) / SiO2 - 0.60×TiO2 - 0.14×MnO … Formula (2)

[0012] In the above formula (1) and the above formula (2), CaO represents the content rate (mass%) of calcium oxide in blast furnace slag, MgO represents the content rate (mass%) of magnesium oxide in blast furnace slag, Al2O3 represents the content rate (mass%) of aluminum oxide in blast furnace slag, SiO2 represents the content rate (mass%) of silicon dioxide in blast furnace slag, TiO2 represents the content rate (mass%) of titanium oxide in blast furnace slag, and MnO represents the content rate (mass%) of manganese oxide in blast furnace slag. However, when the TiO2 content rate is 0.8 mass% or more, TiO2 is taken as 0.8 mass%.

[0013] Since the above mixed cement composition contains a predetermined amount of blast furnace slag that satisfies predetermined conditions, it contributes to CO2 reduction and contributes to the effective utilization of blast furnace slag having a low basicity.

[0014] The content of the above blast furnace slag may be 0.1 to 5.0 mass%.

[0015] The JIS basicity calculated from the following formula (3) based on the chemical composition of the above blast furnace slag may be 1.65 or more and less than 1.85. JIS basicity = (CaO + MgO + Al2O3) / SiO2… Formula (3)

[0016] In the above formula (3), CaO represents the content rate (mass%) of calcium oxide in blast furnace slag, MgO represents the content rate (mass%) of magnesium oxide in blast furnace slag, Al2O3 represents the content rate (mass%) of aluminum oxide in blast furnace slag, and SiO2 represents the content rate (mass%) of silicon dioxide in blast furnace slag.

[0017] The Blaine specific surface area may be 3000 cm 2 / g or more.

[0018] The amount of MnO in the above blast furnace slag may be 0.15 mass% or more.

[0019] The blast furnace slag may be a mixture of a blast furnace slag having a JIS basicity calculated from the following formula (3) based on the chemical composition of less than 1.65 and a blast furnace slag having a JIS basicity calculated from the following formula (3) based on the chemical composition of 1.65 or more. JIS basicity = (CaO + MgO + Al2O3) / SiO2 … formula (3)

[0020] In the above formula (3), CaO represents the content rate (mass%) of calcium oxide in the blast furnace slag, MgO represents the content rate (mass%) of magnesium oxide in the blast furnace slag, Al2O3 represents the content rate (mass%) of aluminum oxide in the blast furnace slag, and SiO2 represents the content rate (mass%) of silicon dioxide in the blast furnace slag.

[0021] One aspect of the present disclosure has a sorting step of sorting blast furnace slag having a basicity Bu(7d) calculated from the following formula (1) based on the chemical composition of the blast furnace slag of 1.20 or less, a basicity Bu(28d) calculated from the following formula (2) of 1.00 or less, an activity index A50(7d) at an age of 7 days of 63.5 to 96.5%, and an activity index A50(28d) at an age of 28 days of 86.5 to 111.0%, and an Al2O3 amount of 12.7 mass% or more, and a mixing step of mixing raw materials including cement clinker, gypsum, limestone, and the above blast furnace slag, wherein the total content of the limestone and the blast furnace slag is more than 5.0 mass% and 10.0 mass% or less, and the content of the blast furnace slag is 1 to 90 mass% based on the total amount of the limestone and the blast furnace slag, and provides a method for producing a blended cement composition. Bu(7d) = (CaO + 0.43×MgO + 0.28×Al2O3) / SiO2 - 0.46×TiO2 - 0.27×MnO … formula (1) Bu(28d) = (CaO + 0.42×MgO + 0.16×Al2O3) / SiO2 - 0.60×TiO2 - 0.14×MnO … formula (2)

[0022] In the above formulas (1) and (2), CaO represents the content rate (% by mass) of calcium oxide in blast furnace slag, MgO represents the content rate (% by mass) of magnesium oxide in blast furnace slag, Al2O3 represents the content rate (% by mass) of aluminum oxide in blast furnace slag, SiO2 represents the content rate (% by mass) of silicon dioxide in blast furnace slag, TiO2 represents the content rate (% by mass) of titanium oxide in blast furnace slag, and MnO represents the content rate (% by mass) of manganese oxide in blast furnace slag. However, when the TiO2 content rate is 0.8% by mass or more, TiO2 is taken as 0.8% by mass.

[0023] Since the method for producing the above mixed cement composition includes a step of selecting blast furnace slag that satisfies predetermined conditions and a step of blending the selected blast furnace slag in a predetermined amount, it is possible to produce a mixed cement composition that contributes to CO2 reduction as described above and contributes to the effective utilization of blast furnace slag having a low basicity.

[0024] The step of selecting the blast furnace slag further includes a step of separating it into a first fraction in which the basicity Bu(7d) calculated from the above formula (1) is 1.20 or less and the basicity Bu(28d) calculated from the above formula (2) is 1.00 or less based on the chemical composition of the blast furnace slag, and a second fraction of the others. The above mixing step is a step of mixing cement clinker, gypsum, limestone, and a raw material containing the first fraction, or a step of mixing cement clinker, gypsum, limestone, and a raw material containing the second fraction. The blending amount of the first fraction may be 10% by mass or less, and the blending amount of the second fraction may be more than 30% by mass and less than 60% by mass.

[0025] The above blast furnace slag may be prepared by mixing blast furnace slag having a JIS basicity of less than 1.65 calculated from the following formula (3) based on the chemical composition and blast furnace slag having a JIS basicity of 1.65 or more calculated from the following formula (3) based on the chemical composition so that it is less than 85 based on the chemical composition. JIS basicity = (CaO + MgO + Al2O3) / SiO2 … formula (3)

[0026] In the above formula (3), CaO represents the content (% by mass) of calcium oxide in blast furnace slag, MgO represents the content (% by mass) of magnesium oxide in blast furnace slag, Al2O3 represents the content (% by mass) of aluminum oxide in blast furnace slag, and SiO2 represents the content (% by mass) of silicon dioxide in blast furnace slag.

Advantages of the Invention

[0027] According to the present disclosure, it is possible to provide a cement composition that contributes to CO2 reduction by increasing the amount of admixture used compared to conventional ordinary Portland cement and that contributes to the effective utilization of blast furnace slag with a low basicity.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0029] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. In the following description, when described as "X to Y" (X and Y are arbitrary numbers), it means "X or more and Y or less" unless otherwise specified.

[0030] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0031] One embodiment of the blended cement composition includes cement clinker, gypsum, limestone, and blast furnace slag having an Al2O3 content of 12.7 mass% or more.

[0032] Examples of the cement clinker include ordinary cement clinker, early-strength cement clinker, medium-heat cement clinker, low-heat cement clinker, and oil well cement clinker. Among these, considering the strength characteristics and availability, ordinary cement clinker and early-strength cement clinker can be preferably used.

[0033] The cement clinker contains C3S, C2S, C3A, and C4AF, and their respective contents can be calculated by the Bogue formula. The Bogue formula is a widely used formula for calculating the content ratio of the main minerals in cement clinker from the content ratio of the chemical composition. By using the Bogue formula shown below, the content of tricalcium silicate (3CaO·SiO 2、 denoted as C3S), dicalcium silicate (2CaO·SiO 2、 denoted as C2S), tricalcium aluminate (3CaO·Al2O3, denoted as C3A), and tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3, denoted as C4AF) in the cement clinker can be calculated. The chemical formula represents the content ratio (mass%) of each compound shown by the chemical analysis value according to JIS R 5204 "Fluorescent X-ray Analysis Method for Cement".

[0034] <Bogue formula> C3S [mass%] = (4.07 × CaO [mass%]) - (7.60 × SiO2 [mass%]) - (6.72 × Al2O3 [mass%]) - (1.43 × Fe2O3 [mass%]) - (2.85 × SO3 [mass%]) C2S [mass%] = (2.87 × SiO2 [mass%]) - (0.754 × C3S [mass%]) C3A [mass%] = (2.65 × Al2O3 [mass%]) - (1.69 × Fe2O3 [mass%]) C4AF [mass%] = 3.04 × Fe2O3 [mass%]

[0035] The amount of C3S in the cement clinker is preferably 30.0 to 70.0% by mass, more preferably 45.0 to 66.0% by mass, still more preferably 50.0 to 63.0% by mass, even more preferably 55.0 to 61.5% by mass, and particularly preferably 58.0 to 60.0% by mass. By setting the lower limit value of the C3S amount within the above range, the initial strength in the hardening of the cement composition can be further improved. Also, by setting the upper limit value of the C3S amount within the above range, the heat generation during the hardening of the cement composition can be further suppressed.

[0036] The amount of C2S in the cement clinker is preferably 5.0 to 65.0% by mass, more preferably 10.0 to 55.0% by mass, still more preferably 12.0 to 30.0% by mass, even more preferably 15.0 to 25.0% by mass, and particularly preferably 17.0 to 20.0% by mass. By setting the lower limit value of the C2S amount within the above range, the long-term strength in the hardening of the cement composition can be further improved. Also, by setting the upper limit value of the C2S amount within the above range, the initial strength in the hardening of the cement composition can be further improved.

[0037] The lower limit of the C3A content in cement clinker is preferably 7.0% by mass or more, more preferably 8.0% by mass or more, still more preferably 8.5% by mass or more, even more preferably 9.0% by mass or more, and particularly preferably 9.3% by mass or more. By setting the lower limit of the C3A content within the above range, it is possible to produce a cement composition with an increased amount of waste and by-products such as fly ash used as cement clinker raw materials. The upper limit of the C3A content in cement clinker is preferably 13.0% by mass or less, more preferably 12.0% by mass or less, still more preferably 11.0% by mass or less, even more preferably 10.0% by mass, and particularly preferably 9.7% by mass or less. By setting the upper limit of the C3A content within the above range, the regeneration of ettringite (a compound represented by 3CaO·Al2O3·3CaSO4·32H2O) can be suppressed, and the increase in the adiabatic temperature rise during the hardening of the cement composition can be further reduced.

[0038] The lower limit of the C4AF content in cement clinker is preferably 7.0% by mass or more, more preferably 8.0% by mass or more, still more preferably 9.0% by mass or more, even more preferably 9.5% by mass or more, and particularly preferably 10.0% by mass or more. By setting the lower limit of the C4AF content within the above range, it is possible to produce a cement composition with an increased amount of waste and by-products such as fly ash used as cement clinker raw materials. The upper limit of the C4AF content in cement clinker is preferably 14.0% by mass or less, more preferably 13.0% by mass or less, still more preferably 12.0% by mass or less, even more preferably 11.0% by mass, and particularly preferably 10.5% by mass or less. By setting the upper limit of the C4AF content within the above range, the increase in the adiabatic temperature rise during the hardening of the cement composition can be further reduced.

[0039] As the gypsum, for example, dihydrate gypsum, hemihydrate gypsum, anhydrous gypsum, etc. can be used. The gypsum may be used alone or in combination of two or more. The content of gypsum in the cement composition may be equivalent to that in ordinary Portland cement.

[0040] The content of gypsum in the blended cement composition, in terms of SO3 conversion, may be, for example, 0.5 to 3.5% by mass, 0.7 to 3.0% by mass, or 1.0 to 2.5% by mass, with the total amount of the blended cement being 100% by mass.

[0041] As the limestone, for example, generally sold limestone and limestone powder, and powders mainly composed of calcium carbonate such as picromerite powder can be used. The limestone preferably includes those conforming to the minor blending components described in JIS R 5210 "Portland Cement".

[0042] The content of aluminum oxide in blast furnace slag (also expressed as the amount of Al2O3) is 12.7% by mass or more. The lower limit value of the Al2O3 amount in blast furnace slag may be, for example, 12.8% by mass or more, 12.9% by mass or more, or 13.0% by mass or more. By the lower limit value of the Al2O3 amount in blast furnace slag being within the above range, the early strength development property can be further improved. The upper limit value of the Al2O3 amount in blast furnace slag may be, for example, 14.0% by mass or less, 13.9% by mass or less, 13.8% by mass or less, or 13.7% by mass or less. By the upper limit value of the Al2O3 amount in blast furnace slag being within the above range, a decrease in the long-term strength development property can be suppressed. The Al2O3 amount in blast furnace slag may be adjusted within the above range and may be, for example, 12.7 to 14.0% by mass.

[0043] The lower limit of the calcium oxide content (also denoted as CaO content) in blast furnace slag may be, for example, 35.0 mass% or more, 38.5 mass% or more, or 40.0 mass% or more. By the lower limit of the CaO content of the blast furnace slag being within the above range, the initial strength development property can be further improved. The upper limit of the CaO content of the blast furnace slag may be, for example, 45.0 mass% or less, 43.5 mass% or less, 43.0 mass% or less, 42.5 mass% or less, 42.0 mass% or less, or 41.5 mass% or less. By the upper limit of the CaO content of the blast furnace slag being within the above range, it is possible to suppress a decrease in the long-term strength development property. The CaO content of the blast furnace slag may be adjusted within the above range, and may be, for example, 38.5 to 45.0 mass%.

[0044] The lower limit of the silicon dioxide content (also denoted as SiO2 content) in blast furnace slag may be, for example, 30.0 mass% or more, 34.0 mass% or more, 34.5 mass% or more, or 35.0 mass% or more. By the lower limit of the SiO2 content of the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial and long-term strength development properties. The upper limit of the SiO2 content of the blast furnace slag may be, for example, 40.0 mass% or less, 38.0 mass% or less, 36.5 mass% or less, or 35.5 mass% or less. By the upper limit of the SiO2 content of the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial strength development property. The SiO2 content of the blast furnace slag may be adjusted within the above range, and may be, for example, 34.5 to 40.0 mass%.

[0045] The lower limit of the content of iron(III) oxide (also denoted as the amount of Fe2O3) in blast furnace slag may be, for example, 0.1 mass% or more, 0.2 mass% or more, or 0.3 mass% or more. By the lower limit of the Fe2O3 amount in the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial strength development property. The upper limit of the Fe2O3 amount in the blast furnace slag may be, for example, 4.0 mass% or less, 2.5 mass% or less, 2.0 mass% or less, 1.5 mass% or less, or 1.0 mass% or less. By the upper limit of the Fe2O3 amount in the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial and long-term strength development properties. The Fe2O3 amount in the blast furnace slag may be adjusted within the above range and may be, for example, 0.1 to 4.0 mass%.

[0046] The lower limit of the content of magnesium oxide (also denoted as the amount of MgO) in blast furnace slag may be, for example, 4.0 mass% or more, 5.5 mass% or more, 6.0 mass% or more, 7.0 mass% or more, or 7.2 mass% or more. By the lower limit of the MgO amount in the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial and long-term strength development properties. The upper limit of the MgO amount in the blast furnace slag may be, for example, 10.0 mass% or less, 9.0 mass% or less, less than 7.5 mass%, or less than 7.4 mass%. By the upper limit of the MgO amount in the blast furnace slag being within the above range, it is possible to suppress a decrease in the initial strength development property. The MgO amount in the blast furnace slag may be adjusted within the above range and may be, for example, 4.0 to 10.0 mass%.

[0047] The lower limit of the manganese oxide content (also expressed as the amount of MnO) in blast furnace slag may be, for example, 0.15% by mass or more, 0.40% by mass or more, 0.70% by mass or more, or 0.85% by mass or more. When the lower limit of the amount of MnO is within such a range, the basicity Bu(7d) and Bu(28d) become small, making it suitable for small additions. The upper limit of the amount of MnO in blast furnace slag may be, for example, 3.00% by mass or less, 2.00% by mass or less, 1.50% by mass or less, or 1.20% by mass or less. When the upper limit of the amount of MnO is within such a range, the strength development property can be improved. The amount of MnO in blast furnace slag may be adjusted within the above-mentioned range, for example, it may be 0.15 to 3.00% by mass.

[0048] The chemical composition of the blast furnace slag in this specification means the value measured in accordance with the description in JIS R 5202:2015 "Methods of Chemical Analysis of Cement".

[0049] The blast furnace slag has a basicity calculated from the following formulas (1) and (2) based on the chemical composition of the blast furnace slag within a predetermined range. Specifically, the basicity Bu(7d) calculated from the following formula (1) is 1.20 or less, and the basicity Bu(28d) calculated from the following formula (2) is 1.00 or less. Bu(7d) = (CaO + 0.43×MgO + 0.28×Al2O3) / SiO2 - 0.46×TiO2 - 0.27×MnO... Formula (1) Bu(28d) = (CaO + 0.42×MgO + 0.16×Al2O3) / SiO2 - 0.60×TiO2 - 0.14×MnO... Formula (2)

[0050] In the above formula (1) and the above formula (2), CaO represents the content rate (mass %) of calcium oxide in blast furnace slag, MgO represents the content rate (mass %) of magnesium oxide in blast furnace slag, Al2O3 represents the content rate (mass %) of aluminum oxide in blast furnace slag, SiO2 represents the content rate (mass %) of silicon dioxide in blast furnace slag, TiO2 represents the content rate (mass %) of titanium oxide in blast furnace slag, and MnO represents the content rate (mass %) of manganese oxide in blast furnace slag. However, when the TiO2 content rate is 0.8 mass % or more, TiO2 is taken as 0.8 mass %.

[0051] The upper limit value of the basicity Bu(7d) calculated from formula (1) based on the chemical composition of blast furnace slag may be, for example, 1.20 or less, 1.15 or less, 1.05 or less, 0.95 or less, or 0.85 or less. When the upper limit value of the basicity Bu(7d) is within the above range, even when the content of blast furnace slag is low, the decrease in strength development property can be more suppressed. The lower limit value of the basicity Bu(7d) calculated from formula (1) of blast furnace slag may be, for example, 0.00 or more, 0.20 or more, 0.40 or more, 0.55 or more, or 0.70 or more. When the lower limit value of the basicity Bu(7d) is within the above range, the decrease in the reactivity of blast furnace slag can be more suppressed.

[0052] The upper limit value of the basicity Bu(28d) calculated from formula (2) based on the chemical composition of blast furnace slag may be, for example, 1.00 or less, 0.95 or less, 0.85 or less, 0.75 or less, or 0.70 or less. When the upper limit value of the basicity Bu(28d) is within the above range, even when the content of blast furnace slag is low, the decrease in strength development property can be more suppressed. The lower limit value of the basicity Bu(28d) calculated from formula (2) of blast furnace slag may be, for example, 0.00 or more, 0.20 or more, 0.40 or more, 0.55 or more, or 0.60 or more. When the lower limit value of the basicity Bu(28d) is within the above range, the decrease in the reactivity of blast furnace slag can be more suppressed.

[0053] The basicity Bu(7d) and basicity Bu(28d) of blast furnace slag in this specification mean the values calculated based on Formula (1) and Formula (2) respectively, using the values obtained by the method described in JIS A 6206:2013.

[0054] The upper limit value of the JIS basicity (hereinafter, also simply referred to as JIS basicity) calculated from the following Formula (3) based on the chemical composition of blast furnace slag may be, for example, less than 1.85, 1.80 or less, 1.78 or less, 1.76 or less, or 1.74 or less. The lower limit value of the JIS basicity of blast furnace slag may be, for example, 1.65 or more, 1.68 or more, or 1.70 or more. The JIS basicity of blast furnace slag may be adjusted within the above range, for example, 1.65 or more and less than 1.85, or 1.65 or more and 1.78 or less. JIS basicity = (CaO + MgO + Al2O3) / SiO2 … Formula (3)

[0055] In the above Formula (3), CaO represents the content rate (mass%) of calcium oxide in blast furnace slag, MgO represents the content rate (mass%) of magnesium oxide in blast furnace slag, Al2O3 represents the content rate (mass%) of aluminum oxide in blast furnace slag, and SiO2 represents the content rate (mass%) of silicon dioxide in blast furnace slag.

[0056] Blast furnace slag may be a mixture. For example, it may be a mixture of slag with a low JIS basicity and slag with a high JIS basicity. Blast furnace slag may be, for example, a mixture of blast furnace slag with a JIS basicity of less than 1.65 (low basicity slag) and blast furnace slag with a JIS basicity of 1.65 or more (high basicity slag). By using such a mixture, the utilization of blast furnace slag with a low JIS basicity that has not been conventionally utilized can be promoted, contributing to the reduction of environmental load.

[0057] The lower limit of the JIS basicity of blast furnace slag with a low JIS basicity (low basicity slag) may be, for example, 1.30 or more, 1.40 or more, 1.50 or more, or 1.60 or more. The upper limit of the JIS basicity of blast furnace slag with a high JIS basicity (high basicity slag) may be, for example, 2.20 or less, 2.00 or less, 1.90 or less, or less than 1.85.

[0058] When the blast furnace slag is a mixture of slag with a low JIS basicity and slag with a high JIS basicity, the JIS basicity of the mixture preferably satisfies the requirements for the JIS basicity of the blast furnace slag described above, and the blending amounts of the slag with a low JIS basicity and the slag with a high JIS basicity may be adjusted from the viewpoint of satisfying the requirements for the JIS basicity.

[0059] As the form of the blast furnace slag, it may be granular or powdery. The blended cement may be produced by mixing and pulverizing granular blast furnace slag with cement clinker, gypsum, etc., or by mixing separately pulverized fine powder of blast furnace slag with each separately pulverized raw material. Note that the fine powder of blast furnace slag may sometimes indicate a mixture with additives such as gypsum, but the JIS basicity, basicity Bu(7d) and Bu(28d) of the blast furnace slag in this specification mean the values calculated from the chemical composition of the blast furnace slag without adding a mixture such as gypsum.

[0060] The blast furnace slag has activity indices at the age of 7 days and 28 days within a predetermined range. Specifically, the activity index A50(7d) at the age of 7 days is 63.5 - 96.5%, and the activity index A50(28d) of the blast furnace slag at the age of 28 days is 86.5 - 111.0%.

[0061] The lower limit of the activity index A50(7d) of the blast furnace slag at the age of 7 days may be, for example, 63.5% or more, 65.0% or more, 66.5% or more, or 68.0% or more. The upper limit of the activity index A50(7d) of the blast furnace slag at the age of 7 days may be, for example, 96.5% or less, 95.0% or less, 93.0% or less, 90.0% or less, 80.0% or less, 74.0% or less, or 70.0% or less.

[0062] The lower limit of the activity index A50(28d) of blast furnace slag at 28 days of age may be, for example, 86.5% or more, 87.5% or more, 88.5% or more, or 90.0% or more. The upper limit of the activity index A50(28d) of blast furnace slag at 28 days of age may be, for example, 111.0% or less, 106.0% or less, 101.0% or less, or 96.0% or less. Blast furnace slag with a low activity index has a large decrease in compressive strength when added in a large amount and tends to be difficult to use for cement addition. However, by using blast furnace slag with such an activity index in a small amount, sufficient reactivity of blast furnace slag and improvement in strength when added in a small amount can be obtained, contributing to the effective utilization of blast furnace slag.

[0063] The lower limit of the content of blast furnace slag may be, for example, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1.5% by mass or more, or 2.5% by mass or more based on the total amount of the blended cement composition. By setting the lower limit of the content of blast furnace slag within such a range, the compressive strength can be increased. The upper limit of the content of blast furnace slag may be, for example, 5.0% by mass or less, 4.5% by mass or less, 3.5% by mass or less, or 3.0% by mass or less based on the total amount of the blended cement composition. By setting the upper limit of the content of blast furnace slag within such a range, the increase in adiabatic temperature can be reduced. The content of blast furnace slag may be adjusted within the above range and may be, for example, 0.1 to 5.0% by mass based on the total amount of the blended cement composition.

[0064] The total content of the above limestone and the above blast furnace slag is more than 5.0% by mass and 10.0% by mass or less. The lower limit value of the total content of the above limestone and the above blast furnace slag may be, for example, more than 5.0% by mass, 5.5% by mass or more, 6.5% by mass or more, or 7.5% by mass or more. When the lower limit value of the total content of the above limestone and the above blast furnace slag is within such a range, it can contribute to the low-carbonization of cement. The upper limit value of the total content of the above limestone and the above blast furnace slag may be, for example, 10.0% by mass or less, 9.6% by mass or less, 9.3% by mass or less, or 9.0% by mass or less. When the upper limit value of the total content of the above limestone and the above blast furnace slag is within such a range, the compressive strength can be increased.

[0065] The content of the above blast furnace slag is 1 to 90% by mass based on the total amount of the above limestone and the above blast furnace slag. The upper limit value of the content of the above blast furnace slag may be, for example, 90% by mass or less, 80% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less based on the total amount of the above limestone and the above blast furnace slag. When the upper limit value of the content of the above blast furnace slag is within such a range, the increase in adiabatic temperature can be reduced. The lower limit value of the content of the above blast furnace slag may be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, or 20% by mass or more based on the total amount of the above limestone and the above blast furnace slag. When the lower limit value of the content of the above blast furnace slag is within such a range, the compressive strength can be increased.

[0066] The lower limit value of the Blaine specific surface area of the pulverized product of blast furnace slag is, for example, 2500 cm 2 / g or more, 3000 cm 2 / g or more, 4000 cm 2 / g or more, 4200 cm 2 / g or more, or 4400 cm 2 / g or more. When the lower limit value of the Blaine specific surface area of the pulverized product of blast furnace slag is within such a range, the compressive strength can be increased. The upper limit value of the Blaine specific surface area of blast furnace slag is, for example, 20000 cm 2 / g or less, 10000 cm 2 / g or less, 8000 cm2 / g or less, 6000 cm 2 / g or less, or 5000 cm 2 / g or less. By having the upper limit value of the Blaine specific surface area of the blast furnace slag within such a range, it is possible to suppress a decrease in fluidity and handleability.

[0067] The lower limit value of the Blaine specific surface area of the blended cement composition is, for example, 3000 cm 2 / g or more, 3200 cm 2 / g or more, 3300 cm 2 / g or more, or 3450 cm 2 / g or more. By having the lower limit value of the Blaine specific surface area of the blended cement composition within such a range, it is possible to increase the compressive strength and enhance the long-term strength development effect when a small amount of low basicity blast furnace slag is added. The upper limit value of the Blaine specific surface area of the blended cement composition is, for example, 6000 cm 2 / g or less, 5000 cm 2 / g or less, 4200 cm 2 / g or less, or 3850 cm 2 / g or less. The Blaine specific surface area of the blended cement composition may be adjusted within the above-mentioned range, for example, 3450 - 3850 cm 2 / g. By having the upper limit value of the Blaine specific surface area of the blended cement composition within such a range, it is possible to suppress a decrease in fluidity and handleability.

[0068] The "Blaine specific surface area" in this specification means a value measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement".

[0069] The blended cement may contain other components within the scope not impairing the gist of the present disclosure, in addition to cement clinker, gypsum, limestone, and blast furnace slag with an Al2O3 content of 12.7 mass% or more. Examples of the other components include fly ash, silica fume, calcium hydroxide, silica powder, other inorganic powders containing calcium (excluding gypsum and limestone), water reducing agents for concrete, accelerators, retarders, and the like. The content of the above other components may be, for example, 10 mass% or less based on 100 parts by mass of the total amount of the blended cement composition.

[0070] The above-described blended cement composition can be produced, for example, by the following method. One embodiment of the method for producing a blended cement composition has a selection step of selecting blast furnace slag with a basicity Bu(7d) calculated from the above formula (1) of 1.20 or less, a basicity Bu(28d) calculated from the above formula (2) of 1.00 or less, an activity index A50(7d) at an age of 7 days of 63.5 to 96.5%, and an activity index A50(28d) at an age of 28 days of 86.5 to 111.0%, and an Al2O3 content of 12.7 mass% or more, and a mixing step of mixing raw materials including cement clinker, gypsum, limestone, and the above blast furnace slag. The total content of the above limestone and the above blast furnace slag is more than 5.0 mass% and 10.0 mass% or less, and the content of the above blast furnace slag is 1 to 90 mass% based on the total amount of the above limestone and the above blast furnace slag.

[0071] In the sorting process, blast furnace slag is sorted from blast furnace slag in which the basicity Bu(7d) calculated from the above formula (1) is 1.20 or less, the basicity Bu(28d) calculated from the above formula (2) is 1.00 or less, the activity index A50(7d) at the age of 7 days is 63.5 to 96.5%, and the activity index A50(28d) at the age of 28 days is 86.5 to 111.0%, and the amount of Al2O3 is 12.7% by mass or more. As the blast furnace slag before sorting, generally available ones may be used. For each lot of the obtained blast furnace slag, the basicity Bu(7d), the basicity Bu(28d), the activity index A50(7d), and the activity index A50(28d) are measured, and sorted into lots that meet the above requirements and lots that do not meet them.

[0072] The blast furnace slag that meets the above requirements may be prepared by mixing blast furnace slag with a JIS basicity of less than 1.65 and blast furnace slag with a JIS basicity of 1.65 or more so that the JIS basicity is 1.65 to 1.85.

[0073] The mixing process is a process of mixing raw materials including cement clinker, gypsum, limestone, and the above blast furnace slag so that the total content of the above limestone and the above blast furnace slag is more than 5.0% by mass and 10.0% by mass or less, and the content of the above blast furnace slag is 1 to 90% by mass based on the total amount of the above limestone and the above blast furnace slag.

[0074] In the mixing process, in addition to mixing the main components, the main components may be crushed, and the order of mixing and crushing is not particularly limited. That is, crushing may be performed after mixing the main components, mixing may be performed after crushing the main components, or mixing and crushing of the main components may be performed simultaneously. The mixing of the main components in the mixing process may be performed using a mixer such as a pan-type mixer, a tilting drum mixer, a ribbon mixer, etc., and may be mixed and crushed using a pulverizer such as a ball mill or a vertical roller mill, and a roller press, or may be mixed using a mixer such as a mechanical mixer after crushing each of the main components.

[0075] The above manufacturing method may include other steps such as a sorting step and a mixing step.

[0076] The above manufacturing method may further include a step of sorting the above blast furnace slag (the blast furnace slag sorted by the sorting step) into a first fraction in which the basicity Bu(7d) calculated from the above formula (1) is 1.20 or less and the basicity Bu(28d) calculated from the above formula (2) is 1.00 or less based on the chemical composition, and another second fraction. In this case, the above mixing step can be a step of mixing cement clinker, gypsum, limestone, and raw materials including the above first fraction, and the blending amount of the above first fraction may be 10% by mass or less. Since the above first fraction of the blast furnace slag has low Bu(7d) and Bu(28d), a relatively small activity index, and a relatively large compressive strength ratio when added in a small amount, it is suitable as a small mixing component of ordinary Portland cement. Therefore, it is suitable for the production of a blended cement composition used as a small mixing (for example, 10% by mass or less, or 5% by mass or less).

[0077] The above manufacturing method may further include a step of sorting the above blast furnace slag (the blast furnace slag sorted by the sorting step) into a first fraction in which the basicity Bu(7d) calculated from the following formula (1) is 1.20 or less and the basicity Bu(28d) calculated from the above formula (2) is 1.00 or less based on the chemical composition, and another second fraction. In this case, the above mixing step can be a step of mixing cement clinker, gypsum, limestone, and raw materials including the above second fraction, and the blending amount of the above second fraction may be more than 30% by mass and less than 60% by mass. Since the above second fraction of the blast furnace slag has large Bu(7d) and Bu(28d), a relatively large activity index, and a relatively small compressive strength ratio when added in a small amount, it is suitable as the blast furnace slag when producing blast furnace cement type B. That is, the blended cement composition obtained by the production method using the second fraction in the mixing step can be used as blast furnace cement type B.

[0078] The blended cement composition produced by the above manufacturing method may be mixed with fine aggregate, coarse aggregate, water, admixture, etc. and used as mortar.

[0079] Fine aggregates can use fine aggregates and the like specified in JIS A 5005:2020 "Crushed Stone and Crushed Sand for Concrete". Examples of fine aggregates include river sand, land sand, sea sand, crushed sand, silica sand, copper slag fine aggregates, and electric furnace oxidized slag fine aggregates. When using fine aggregates, the amount of fine aggregates used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass with respect to 100 parts by mass of the above-mentioned blended cement composition.

[0080] Coarse aggregates can use coarse aggregates and the like specified in JIS A 5005:2020 "Crushed Stone and Crushed Sand for Concrete". Examples of coarse aggregates include gravel and crushed stone. When using coarse aggregates, the amount of coarse aggregates used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass with respect to 100 parts by mass of the above-mentioned blended cement composition.

[0081] Fine aggregates and coarse aggregates can also be used in combination. In this case, the total amount of fine aggregates and coarse aggregates used may be 100 to 300 parts by mass, or 200 to 250 parts by mass with respect to 100 parts by mass of the above-mentioned blended cement composition.

[0082] Examples of water include tap water, distilled water, and deionized water. The amount of water used may be 20 to 100 parts by mass, or 40 to 70 parts by mass with respect to 100 parts by mass of the above-mentioned blended cement composition.

[0083] Examples of admixtures include AE agents, water reducers, AE water reducers, high-performance water reducers, high-performance AE water reducers, fluidizing agents, defoaming agents, shrinkage reducing agents, setting accelerators, setting retarders, and thickening agents. The amount of admixtures used may be, for example, 0.01 to 2 parts by mass with respect to 100 parts by mass of the above-mentioned blended cement composition.

[0084] As described above, several embodiments have been explained, but the present disclosure is not limited to the above embodiments at all. Also, the description contents of the above-described embodiments can be applied to each other.

Example

[0085] Hereinafter, the content of the present disclosure will be described in more detail with reference to Examples, Comparative Examples, and Reference Examples. However, the present disclosure is not limited to the following examples.

[0086] [Raw materials of the blended cement composition] The following materials were used as the raw materials of the blended cement composition.

[0087] (Cement clinker) As the cement clinker, ordinary Portland cement clinker with a mineral composition according to the Bogue formula as described in Table 1 below was used.

[0088]

Table 1

[0089] (Gypsum) As the gypsum, gypsum satisfying the requirements described in JIS R 9151:2009 "Natural Gypsum for Cement" was used.

[0090] (Limestone) As the limestone, limestone satisfying the requirements of the minor mixing components described in JIS R 5210:2009 "Portland Cement" was used.

[0091] (Blast furnace slag) For BS1, BS4 - BS6, commercially available granulated blast furnace slag without gypsum was used. BS2 was prepared by mixing BS1 and BS4 at a mass ratio of 1:3, and BS3 was prepared by mixing BS1 and BS4 at a mass ratio of 1:1. The chemical compositions measured in accordance with the description in JIS R 5202:2015 "Chemical Analysis Methods for Cement" for each of the blast furnace slags are shown in Table 2. Also, the activity index A50 of the blast furnace slag was measured by the following method.

[0092] [Measurement of the activity index of blast furnace slag] The evaluation of the activity index of blast furnace slag complied with the "Test Method for Activity Index and Flow Value Ratio of Blast Furnace Slag Micropowder by Mortar" described in the appendix of JIS A 6206:2013 "Blast Furnace Slag Micropowder for Concrete", and the values at the ages of 7 days and 28 days were measured.

[0093]

Table 2

[0094] (Examples 1 to 14, Comparative Examples 1 to 6, and Reference Example 1) A blended cement composition was prepared by mixing and crushing cement clinker, gypsum, limestone, and blast furnace slag at the blending ratios (parts by mass) shown in Tables 3 and 4. Specifically, first, the cement composition of Reference Example 1 was prepared by mixing and grinding cement clinker, gypsum, and limestone in a ball mill. Then, the cement compositions of the Examples and Comparative Examples were obtained by mixing the cement composition of Reference Example 1 with separately ground blast furnace slag micropowder and limestone micropowder at a predetermined ratio.

[0095] <Measurement of Compressive Strength> Using each of the blended cement compositions prepared in Examples 1 to 14, Comparative Examples 1 to 6, and Reference Example 1, the compressive strength ratio was measured in accordance with the description of JIS R 5201:2015 "Physical Test Methods for Cement".

[0096] Specifically, first, for 100 parts by mass of the above blended cement composition, 300 parts by mass of standard sand for cement strength test obtained from the Cement Association and 50 parts by mass of water were mixed as fine aggregate to prepare a mortar composition. The mortar composition was kneaded in a constant temperature room at 20°C, molded, and the mold was stored in a humidity box for 24 hours of curing. After 24 hours of curing, the mold was removed to obtain a hardened mortar body. The obtained hardened mortar body was cured in water in a constant temperature room at 20°C until the ages of 7 days and 28 days, and then the compressive strength was measured.

[0097] The ratio of the compressive strength of the mortar hardened body to be measured to the compressive strength of the reference mortar hardened body was defined as the compressive strength ratio Am. The reference mortar hardened body was prepared in the same manner as the preparation of the mortar hardened body for measuring the activity index described above, using the cement composition of Reference Example 1 (equivalent to the current ordinary Portland cement with a small amount of mixed components of 5% by mass or less). After demolding at 20°C, the mortar hardened body was cured in water until the age of 7 days and 28 days. The compressive strength of the reference mortar hardened body was measured in the same manner, and the compressive strength ratio Am of each mortar hardened body was calculated using the obtained value. The results are shown in Tables 3 and 4.

[0098] <Evaluation of the relationship between the compressive strength ratio and the activity index of blast furnace slag> The relationship between the compressive strength ratio obtained by the above evaluation for the mortar compositions using the mixed cement compositions prepared in Examples 1 to 14, Comparative Examples 1 to 6, and Reference Example 1, and the activity index A50 and basicity Bu of the blast furnace slag used in the preparation of the mixed cement as its raw material was evaluated. Specifically, the relationship between the value obtained by dividing the compressive strength ratio by the activity index A50 (Am / A50) and the basicity Bu was used as an index. The larger the value of Am / A50, the more advantageous it is from the perspective of strength development when a small amount of blast furnace slag is added, and it can be said that the blast furnace slag used in the evaluation is suitable for applications with a small amount of addition. The results are shown in Tables 3 and 4, and Figures 1 and 2.

[0099] <Measurement of adiabatic temperature> Using the mixed cement compositions prepared in Examples 5, 6, 10, 11 and Comparative Example 4, the adiabatic temperature was measured according to the method described below.

[0100] Specifically, first, 318 parts by mass of crushed sand (produced in Miyano, Yamaguchi Prefecture) as fine aggregate and 55 parts by mass of water were mixed with 100 parts by mass of the above-described blended cement composition to prepare a mortar composition. The mortar composition was kneaded, filled into a 20 mL measuring container in a predetermined amount, a thermocouple was inserted, and the heat generation amount was measured using a heat flow calorimeter for small samples (manufactured by Tokyo Institute of Technology Co., Ltd., product name: ATR-6L). The measurement time was set to the time until the adiabatic temperature rise ended (2 to 3 days). In the measurement of the heat generation amount, the temperature of the mortar composition was measured by a thermocouple, and the temperature of the tank in which the measuring container was installed was controlled so that the temperature around the measuring container was the same as the temperature measured by the thermocouple, thereby approximating the adiabatic condition. Then, the final temperature rise amount (°C) was evaluated as the temperature rise amount in the adiabatic state. The adiabatic temperature rise rate was evaluated by applying the measurement results to the adiabatic temperature rise regression formula proposed by the Concrete Engineering Society (formula (4) below). Q(t)=Q∞(1-exp(-γ(t-t0))) … formula (4)

[0101] In the above formula (4), Q(t) represents the adiabatic temperature rise amount (°C), Q∞ represents the final adiabatic temperature rise amount (°C), t represents the age (days), t0 represents the age at the start of heat generation (days), and γ is a constant related to the temperature rise rate.

[0102] However, in the apparatus of the heat flow calorimeter for small samples used in this measurement, even in an approximate adiabatic condition, there is heat loss from the apparatus. Therefore, in accordance with the method described in Non-Patent Document 2, the heat loss from the apparatus was corrected to obtain the adiabatic temperature rise amount. The results are shown in Tables 3 and 4.

[0103]

Table 3

[0104]

Table 4

[0105] Figures 1 and 2 are graphs showing the relationship between the basicity of blast furnace slag and the value obtained by dividing the compressive strength ratio of the mortar composition using the slag by the activity index A50 of the slag (Am / A50) in hardened mortars at 7 days and 28 days of age. As shown in Figures 1 and 2, it can be confirmed that the smaller the basicity Bu, the more the value of the above Am / A50 tends to increase.

[0106] Table 3 shows the evaluation results of cement compositions with a Blaine specific surface area of 3300 ± 100 cm 2 / g. When comparing cement compositions with similar Blaine specific surface areas and blast furnace slag blending amounts, it is found that the smaller Bu(7d) and Bu(28d) are, the more the value of Am / A50 tends to increase.

[0107] From the comparison between Comparative Example 1 and Examples 1 to 3, and the comparison between Comparative Example 3 and Examples 4 to 6, in the cement compositions (Comparative Examples 1 and 3) using blast furnace slag BS1 with small Bu and A50, the compressive strength ratio Am at low addition amounts is small. In particular, the compressive strength ratio Am at 7 days of age is smaller than that of any corresponding Example for each Comparative Example. It was confirmed that by using blast furnace slag with an activity index A50 of a certain level or more, such as BS3 to BS5, a good compressive strength ratio Am can be obtained even when added in small amounts.

[0108] On the other hand, from the comparison between Comparative Example 2 and Examples 1 to 3, and the comparison between Comparative Example 4 and Examples 4 to 6, the compressive strength ratios Am of Comparative Examples 2 and 4 containing blast furnace slag BS6 with a high JIS basicity, which is considered to have excellent strength development according to conventional technical common sense, are lower than those of any corresponding Example. Therefore, it can be said that for low addition applications, it is more preferable to use blast furnace slag with small basicity Bu(7d) and Bu(28d), such as BS3 to BS5.

[0109] Table 4 shows the evaluation results of cement compositions with a Blaine specific surface area of 3600 ± 50 cm 2It shows the evaluation results of the cement composition with / g. When comparing cement compositions with similar Blaine specific surface area and blast furnace slag content, generally, the smaller the Bu(7d) and Bu(28d), the more the value of Am / A50 tends to increase. However, in Comparative Examples 5 and 6 using BS1, which is a blast furnace slag with a small A50, although the value of Am / A50 is high, the compressive strength ratio Am at 7 days of age is small, resulting in insufficient compressive strength.

[0110] Example 5 and Comparative Example 4, Example 10 and Example 11 are cement compositions with the same Blaine specific surface area and mixing ratio respectively, but different blast furnace slags used. In the cement compositions (Examples 5 and 10) using blast furnace slags with low Bu(7d) and Bu(28d), a tendency for the increase in adiabatic temperature to decrease was confirmed. Also, Example 8 and Example 11 are cement compositions using the same blast furnace slag with different addition amounts of blast furnace slag. The smaller the addition amount of blast furnace slag, the lower the increase in adiabatic temperature.

[0111] As shown in Tables 3 and 4, even for blast furnace slags with a JIS basicity of less than 1.85 (low basicity blast furnace slags), by using blast furnace slags that meet the requirements of the blast furnace slags of the present disclosure in the blending amounts of the present disclosure, for example, it was confirmed that a sufficient compressive strength ratio can be exhibited. That is, by using it in the above-mentioned applications, blast furnace slags with low basicity can be effectively utilized.

[0112] Also, when comparing BS1, BS3, and BS4 that can be compared with the Blaine specific surface area, as shown in Table 3, in the mixed cement compositions with a low Blaine specific surface area (Examples 1, 2, 3, 5, Comparative Examples 1, 3), when blending blast furnace slags with a high JIS basicity and basicity Bu(28d) as a whole, the compressive strength ratio at 28 days of age also tends to increase. On the other hand, in the cement compositions with a high Blaine specific surface area shown in Table 4 (Examples 8, 9, 11, 12, Comparative Examples 5, 6), when using blast furnace slags with a low JIS basicity and basicity Bu(28d), a tendency for the compressive strength ratio at 28 days of age to increase can be seen.

[0113] Conventionally, in blast furnace cement, it has been considered advantageous to use blast furnace slag with a high JIS basicity for the development of excellent compressive strength. However, the above results of the present disclosure show that when a small amount of blast furnace slag is added to form a cement composition with a large Blaine specific surface area, instead of using blast furnace slag with a higher JIS basicity, rather, by using blast furnace slag with a somewhat lower JIS basicity and basicity Bu(28d), it can be said that stable long-term compressive strength can be exhibited.

Industrial Applicability

[0114] According to the present disclosure, it is possible to provide a cement composition that contributes to CO2 reduction by increasing the amount of admixture used compared to conventional ordinary Portland cement and that contributes to the effective use of blast furnace slag with a low basicity.

Claims

1. Cement clinker, gypsum, limestone, and blast furnace slag with an Al ２ O ３ content of 12.7% by mass or more, and The blast furnace slag has a basicity Bu(7d) calculated from the following formula (1) based on the chemical composition of the blast furnace slag of 0.55 or more and 1.20 or less, and a basicity Bu(28d) calculated from the following formula (2) of 0.55 or more and 1.00 or less. The activity index A50(7d) of the blast furnace slag at the age of 7 days is 63.5 to 96.5%, and the activity index A50(28d) of the blast furnace slag at the age of 28 days is 86.5 to 111.0%. The total content of the limestone and the blast furnace slag is more than 5.0% by mass and 10.0% by mass or less. The content of the blast furnace slag is 5.0% by mass or less. A mixed cement composition in which the content of the blast furnace slag is 1 to 60% by mass based on the total amount of the limestone and the blast furnace slag. Bu(7d) = (CaO + 0.43×MgO + 0.28×Al ２ O ３ ) / SiO ２ - 0.46×TiO ２ - 0.27×MnO … Equation (1) Bu(28d) = (CaO + 0.42×MgO + 0.16×Al ２ O ３ ) / SiO ２ - 0.60×TiO ２ - 0.14×MnO … Equation (2) In Formula (1) and Formula (2), CaO represents the content rate (mass %) of calcium oxide in blast furnace slag, MgO represents the content rate (mass %) of magnesium oxide in blast furnace slag, Al ２ O ３ represents the content rate (mass %) of aluminum oxide in blast furnace slag, SiO ２ represents the content rate (mass %) of silicon dioxide in blast furnace slag, TiO ２ represents the content rate (mass %) of titanium oxide in blast furnace slag, and MnO represents the content rate (mass %) of manganese oxide in blast furnace slag. However, when the content rate of TiO ２ is 0.8 mass % or more, TiO ２ is set to 0.8 mass %.

2. The mixed cement composition according to Claim 1, wherein the content of the blast furnace slag is 0.1 to 4.5% by mass.

3. The mixed cement composition according to Claim 1 or 2, wherein the JIS basicity calculated from the following formula (3) based on the chemical composition of the blast furnace slag is 1.65 or more and less than 1.

85. JIS basicity = (CaO + MgO + Al ２ O ３ ) / SiO ２ … Equation (3) In formula (3), CaO represents the content rate (mass%) of calcium oxide in blast furnace slag, MgO represents the content rate (mass%) of magnesium oxide in blast furnace slag, and Al ２ O ３ represents the content rate (mass%) of aluminum oxide in blast furnace slag, and SiO ２ represents the content rate (mass%) of silicon dioxide in blast furnace slag.]

4. The brain specific surface area is 3000 cm ２ / g or more, and the blended cement composition according to any one of claims 1 to 3.

5. The mixed cement composition according to any one of Claims 1 to 4, wherein the amount of MnO in the blast furnace slag is 0.15% by mass or more.

6. The blast furnace slag is a blast furnace slag having a JIS basicity calculated from the following formula (3) based on the chemical composition of less than 1.65, and a blast furnace slag having a basicity calculated from the following formula (3) based on the chemical composition of 1.65 or more, and is a mixture thereof. The mixed cement composition according to any one of Claims 1 to 5. JIS basicity = (CaO + MgO + Al ２ O ３ ) / SiO ２ … Equation (3) In formula (3), CaO represents the content rate (mass %) of calcium oxide in blast furnace slag, MgO represents the content rate (mass %) of magnesium oxide in blast furnace slag, and Al ２ O ３ represents the content rate (mass %) of aluminum oxide in blast furnace slag, and SiO ２ represents the content rate (mass %) of silicon dioxide in blast furnace slag.

7. The basicity Bu(7d) calculated from the following formula (1) based on the chemical composition is 0.55 or more and 1.20 or less, the basicity Bu(28d) calculated from the following formula (2) is 0.55 or more and 1.00 or less, the activity index A50(7d) at the age of 7 days is 63.5 to 96.5%, and the activity index A50(28d) at the age of 28 days is 86.5 to 111.0%, and Al ２ O ３ a sorting step of sorting blast furnace slag with an Al content of 12.7% by mass or more; It has a mixing step of mixing raw materials including cement clinker, gypsum, limestone, and the blast furnace slag, the total content of the limestone and the blast furnace slag is more than 5.0% by mass and 10.0% by mass or less, the content of the blast furnace slag is 5.0% by mass or less, A method for producing a mixed cement composition in which the content of the blast furnace slag is 1 to 60% by mass based on the total amount of the limestone and the blast furnace slag. Bu(7d) = (CaO + 0.43×MgO + 0.28×Al ２ O ３ ) / SiO ２ - 0.46×TiO ２ - 0.27×MnO … Equation (1) Bu(28d) = (CaO + 0.42×MgO + 0.16×Al ２ O ３ ) / SiO ２ - 0.60×TiO ２ - 0.14×MnO … Equation (2) In Formula (1) and Formula (2), CaO represents the content rate (mass %) of calcium oxide in blast furnace slag, MgO represents the content rate (mass %) of magnesium oxide in blast furnace slag, Al ２ O ３ represents the content rate (mass %) of aluminum oxide in blast furnace slag, SiO ２ represents the content rate (mass %) of silicon dioxide in blast furnace slag, TiO ２ represents the content rate (mass %) of titanium oxide in blast furnace slag, and MnO represents the content rate (mass %) of manganese oxide in blast furnace slag. However, when the content rate of TiO ２ is 0.8 mass % or more, TiO ２ is taken as 0.8 mass %. **Claim 8**: A sorting step of sorting blast furnace slag in which the basicity Bu(7d) calculated from the following formula (1) based on the chemical composition is 0.55 or more and 1.20 or less, the basicity Bu(28d) calculated from the following formula (2) is 0.55 or more and 1.00 or less, the activity index A50(7d) at the age of 7 days is 63.5 to 96.5%, and the activity index A50(28d) at the age of 28 days is 86.5 to 111.0%, and the amount of Al₂O₃ is 12.7% by mass or more, a mixing step of mixing raw materials including cement clinker, gypsum, limestone, and the blast furnace slag, wherein the total content of the limestone and the blast furnace slag is more than 5.0% by mass and 10.0% by mass or less, the content of the blast furnace slag is 1 to 60% by mass based on the total amount of the limestone and the blast furnace slag, the method further includes a step of sorting the blast furnace slag into a first fraction in which the basicity Bu(7d) calculated from the formula (1) based on the chemical composition is 1.20 or less and the basicity Bu(28d) calculated from the formula (2) is 1.00 or less, and another second fraction, the mixing step is a step of mixing raw materials including cement clinker, gypsum, limestone, and the first fraction, or a step of mixing raw materials including cement clinker, gypsum, limestone, and the second fraction, a method for producing a blended cement composition, wherein the blending amount of the first fraction is 10% by mass or less, and the blending amount of the second fraction is more than 30% by mass and less than 60% by mass. Bu(7d) = (CaO + 0.43×MgO + 0.28×Al₂O₃) / SiO₂ - 0.46×TiO₂ - 0.27×MnO... Formula (1) Bu(28d) = (CaO + 0.42×MgO + 0.16×Al₂O₃) / SiO₂ - 0.60×TiO₂ - 0.14×MnO... Formula (2) In Formula (1) and Formula (2), CaO represents the content rate (% by mass) of calcium oxide in blast furnace slag, MgO represents the content rate (% by mass) of magnesium oxide in blast furnace slag, Al₂O₃ represents the content rate (% by mass) of aluminum oxide in blast furnace slag, SiO₂ represents the content rate (% by mass) of silicon dioxide in blast furnace slag, TiO₂ represents the content rate (% by mass) of titanium oxide in blast furnace slag, and MnO represents the content rate (% by mass) of manganese oxide in blast furnace slag. However, when the TiO₂ content rate is 0.8% by mass or more, TiO₂ is taken as 0.8% by mass.

9. The manufacturing method according to Claim 7 or 8, wherein the blast furnace slag is prepared by mixing blast furnace slag having a JIS basicity calculated from the following formula (3) based on the chemical composition of less than 1.65 and blast furnace slag having a JIS basicity calculated from the following formula (3) based on the chemical composition of 1.65 or more so that the JIS basicity calculated from the following formula (3) based on the chemical composition is 1.65 or more and less than 1.

85. JIS basicity = (CaO + MgO + Al ２ O ３ ) / SiO ２ … Equation (3) In formula (3), CaO represents the content rate (mass %) of calcium oxide in blast furnace slag, MgO represents the content rate (mass %) of magnesium oxide in blast furnace slag, Al ２ O ３ represents the content rate (mass %) of aluminum oxide in blast furnace slag, and SiO ２ represents the content rate (mass %) of silicon dioxide in blast furnace slag.]

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