Mixed cement composition

Abstract

To provide a mixed cement composition that exhibits excellent compressive strength while using blast furnace slag, which has a low basicity. [Solution] The mixed cement composition contains Portland cement, blast furnace slag, and carbonate ester. The basicity calculated from formula (1) below based on the chemical composition of the blast furnace slag is 1.79 or less, and the gypsum content is 4.0% by mass or less in terms of SO3, based on the total amount of Portland cement, blast furnace slag, and gypsum. Basicity = (CaO + MgO + Al2O3) / SiO2 ... Equation (1) [In formula (1), CaO represents the content (mass%) of calcium oxide in the blast furnace slag, MgO represents the content (mass%) of magnesium oxide in the blast furnace slag, Al2O3 represents the content (mass%) of aluminum oxide in the blast furnace slag, and SiO2 represents the content (mass%) of silicon dioxide in the blast furnace slag.]

Description

[Technical Field]

[0001] This disclosure relates to a mixed cement composition. [Background technology]

[0002] In recent years, with increasing demands for measures against global warming, there is a need to reduce CO2 emissions in cement production. As a method to reduce CO2 emissions, a method of replacing a portion of cement clinker, which has a large CO2 emission rate during preparation, with admixtures is being widely investigated. Among the admixtures, steel slag such as blast furnace granulated slag (BFS) is expected to enhance the long-term strength of concrete and improve its salt shielding effect. Therefore, research is underway on cement that uses steel slag as an admixture and increases its mixing ratio.

[0003] However, blast furnace cement with a higher proportion of granulated blast furnace slag tends to have lower initial strength during hardening compared to ordinary Portland cement (OPC) used alone. Therefore, various methods are being investigated to achieve a strength comparable to that of OPC alone, even in the case of blast furnace cement.

[0004] On the other hand, in Japan, granulated blast furnace slag used as a cement additive is selected and used if it has a high basicity, which is considered advantageous for strength development. Such granulated blast furnace slag generally has a basicity of 1.85 or higher as defined by JIS (hereinafter also referred to as "JIS basicity"). For example, Patent Document 1 discloses a cement composition in which CO2 emissions are reduced by adding granulated blast furnace slag with a JIS basicity of 1.85 to 1.91. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-285302 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] While the use of blast furnace cement is being expanded, it may become difficult to obtain blast furnace slag with high JIS basicity in the future. Therefore, it is believed that CO2 emissions can be further reduced if blast furnace slag with low JIS basicity can be effectively utilized. However, blast furnace cement made using low-basicity blast furnace slag (blast furnace slag with JIS basicity of 1.84 or less) tends to have lower strength compared to blast furnace cement made using high-basicity blast furnace slag.

[0007] This disclosure has been made in view of the above-mentioned problems, and aims to provide a mixed cement composition that has excellent compressive strength while using blast furnace slag with low basicity. [Means for solving the problem]

[0008] One aspect of this disclosure is a mixed cement composition comprising Portland cement, blast furnace slag, and carbonate ester, wherein the basicity calculated from the following formula (1) based on the chemical composition of the blast furnace slag is 1.79 or less, and the gypsum content is 4.0% by mass or less in terms of SO3, based on the total amount of Portland cement, blast furnace slag, and gypsum. Basicity = (CaO + MgO + Al2O3) / SiO2 ... Equation (1) [In formula (1), CaO represents the content (mass%) of calcium oxide in the blast furnace slag, MgO represents the content (mass%) of magnesium oxide in the blast furnace slag, Al2O3 represents the content (mass%) of aluminum oxide in the blast furnace slag, and SiO2 represents the content (mass%) of silicon dioxide in the blast furnace slag.]

[0009] The above-mentioned mixed cement composition contains blast furnace slag and carbonate ester, and because the blast furnace slag has a specific range of basicity and the gypsum content is within a specific range in terms of SO3, it is possible to improve compressive strength even while using blast furnace slag, which has a low basicity.

[0010] Although the mechanism by which the above effects are obtained is not clear, the inventors of the present invention have the following speculation. When a carbonate ester comes into contact with water, it hydrolyzes to generate carbonate ions. These carbonate ions react with calcium ions to form calcium carbonate. As a result, the calcium ion concentration in the cement composition decreases, and the dissolution of slaked lime proceeds. Then, the pH of the cement composition increases, and the dissolution of aluminum in the blast furnace slag is promoted. As a result, it is considered that the formation of cement hydrates due to the hydration reaction of alite proceeds and the compressive strength is improved. Note that the mechanism by which the above effects are obtained is not limited to this.

[0011] A cured body containing the cured product of the above mixed cement composition is excellent in compressive strength while using blast furnace slag with a low basicity.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide a mixed cement composition that is excellent in compressive strength while using blast furnace slag with a low basicity.

Brief Description of the Drawings

[0013] [Figure 1] It is a graph summarizing the relationship between the amount of SO3 and the compressive strength ratio for Examples 1, 5 to 7 and Comparative Examples 1 to 4.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present disclosure (hereinafter referred to as "the present embodiment") will be described in detail. The present disclosure is not limited to the following embodiments.

[0015] In this specification, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. Furthermore, in numerical ranges described in stages in this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples.

[0016] Unless otherwise specified, the materials exemplified herein may be used individually or in combination of two or more. The content of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.

[0017] [Mixed cement composition] A mixed cement composition according to one embodiment comprises Portland cement, blast furnace slag, and carbonate ester, and has a basicity of 1.79 or less calculated from the following formula (1) based on the chemical composition of blast furnace slag, and the gypsum content is 4.0% by mass or less in terms of SO3, based on the total amount of Portland cement, blast furnace slag, and gypsum. Basicity = (CaO + MgO + Al2O3) / SiO2 ... Equation (1) [In formula (1), CaO represents the content (mass%) of calcium oxide in the blast furnace slag, MgO represents the content (mass%) of magnesium oxide in the blast furnace slag, Al2O3 represents the content (mass%) of aluminum oxide in the blast furnace slag, and SiO2 represents the content (mass%) of silicon dioxide in the blast furnace slag.]

[0018] The basicity calculated from formula (1) above is the basicity calculated by the method described in JIS R 5211:2019 "Blast Furnace Cement". The basicity calculated from formula (1) above may be 1.50 or higher, 1.55 or higher, or 1.60 or higher, and may be less than 1.79, 1.75 or lower, or 1.70 or lower.

[0019] (Portland cement) Portland cement may be any type of Portland cement specified in JIS R 5210:2009 "Portland Cement". Examples of Portland cement include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. Portland cement can be used individually or in combination of two or more types.

[0020] When a mixed cement composition contains ordinary Portland cement, the change in the fluidity of the mixed cement composition over time can be significantly reduced. This allows for highly uniform application of the mixed cement composition, even during large-scale concrete placement. Furthermore, the inclusion of ordinary Portland cement reduces the manufacturing cost of the mixed cement composition.

[0021] The Blaine specific surface area of ​​Portland cement is, for example, 2500 cm². 2 / g or more, or 3000cm 2 It may be 10,000 cm² or more. By increasing the Blaine specific surface area of ​​Portland cement, the strength development of the mixed cement composition is improved and the setting time can be shortened. In addition, the amount of bleeding can be reduced. The Blaine specific surface area of ​​Portland cement is, for example, 10,000 cm². 2 / g or less, 8000cm 2 / g or less, or 5000cm 2 It may be less than or equal to / g. By reducing the Blaine specific surface area of ​​Portland cement, it is possible to further reduce CO2 emissions during Portland cement production while lowering manufacturing costs. In this specification, the Blaine specific surface area is measured in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement".

[0022] The Portland cement content may be 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total amount of Portland cement and blast furnace slag, from the viewpoint of sufficiently increasing the compressive strength of the hardened body including the hardened material of the mixed cement composition, and 95% by mass or less, 85% by mass or less, or 70% by mass or less, from the viewpoint of sufficiently reducing CO2 emissions when manufacturing the mixed cement composition. From the above viewpoint, the Portland cement content may be 30-95% by mass, 30-85% by mass or 30-70% by mass, based on the total amount of Portland cement and blast furnace slag.

[0023] (Blast furnace slag) Blast furnace slag may be commercially available, for example, or a slag equivalent to blast furnace slag may be prepared.

[0024] The SO3 equivalent gypsum content in blast furnace slag may be 0.01% by mass or more, 0.02% by mass or more, or 0.03% by mass or more. This allows for improved initial compressive strength while maintaining sufficiently high thermal crack resistance. The SO3 equivalent gypsum content in blast furnace slag may be 3.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, or 0.3% by mass or less.

[0025] The Al2O3 (aluminum oxide) content in the blast furnace slag may be, for example, 14.5% by mass or less, 14.0% by mass or less, or 13.5% by mass or less. This can sufficiently suppress the decrease in long-term strength development when the mixed cement composition hardens. The Al2O3 content in the blast furnace slag may be, for example, 8.0% by mass or more, 10.0% by mass or more, or 12.0% by mass or more. This allows the latent hydraulic properties of the blast furnace slag to be more fully exhibited.

[0026] The SiO2 (silicon dioxide) content in blast furnace slag may be, for example, 30.0% by mass or more, 31.0% by mass or more, or 32.0% by mass or more. This further suppresses the decrease in initial and long-term strength development. The SiO2 content in blast furnace slag may be, for example, 40.0% by mass or less, 39.0% by mass or less, 38.0% by mass or less, or 37.0% by mass or less. This further suppresses the decrease in initial strength development.

[0027] The CaO (calcium oxide) content in blast furnace slag may be, for example, 38.0% by mass or more, 40.0% by mass or more, or 42.0% by mass or more. This can further improve the initial strength development. The CaO content in blast furnace slag may be, for example, 50.0% by mass or less, 48.0% by mass or less, or 46.0% by mass or less. This can further suppress the long-term decline in strength development.

[0028] The MgO (magnesium oxide) content in the blast furnace slag may be, for example, 3.0% by mass or more, 4.0% by mass or more, or 4.5% by mass or more. This further suppresses the decrease in initial and long-term strength development when the mixed cement composition is hardened. The MgO content in the blast furnace slag may be, for example, 10.0% by mass or less, 9.0% by mass or less, or 8.0% by mass or less. This further suppresses the decrease in initial strength development when the mixed cement composition is hardened.

[0029] Blast furnace slag may also contain other components such as NaO2 (sodium oxide), K2O (potassium oxide), and TiO2 (titanium oxide).

[0030] In this specification, the chemical composition is measured in accordance with the methods described in JIS R 5202:2015 "Methods for chemical analysis of cement" or JIS R 5204:2019 "Methods for X-ray fluorescence analysis of cement".

[0031] The specific surface area of ​​blast furnace slag is, for example, 2500 cm². 2 / g or more, 3000cm2 above / g, 4000 cm 2 above / g, 4100 cm 2 above / g, or 4200 cm 2 above / g may be sufficient. By setting the lower limit of the Blaine specific surface area of the pulverized blast furnace slag within such a range, the compressive strength can be increased. The Blaine specific surface area of the blast furnace slag is, for example, 20000 cm 2 / g or less, 10000 cm 2 / g or less, 8000 cm 2 / g or less, 6000 cm 2 / g or less, or 5000 cm 2 / g or less may be sufficient. By setting the upper limit of the Blaine specific surface area of the blast furnace slag within such a range, a decrease in fluidity and handling properties can be suppressed.

[0032] From the perspective of sufficiently reducing the CO₂ emissions during the production of the blended cement composition, the content of blast furnace slag may be 5% by mass or more, 15% by mass or more, or 30% by mass or more, based on the total amount of Portland cement and blast furnace slag. From the perspective of sufficiently increasing the compressive strength of the hardened body including the hardened product of the blended cement composition, it may be 70% by mass or less, 60% by mass or less, or 50% by mass or less. From the above perspectives, the content of blast furnace slag may be 5 - 70% by mass, 15 - 70% by mass, or 30 - 70% by mass, based on the total amount of Portland cement and blast furnace slag.

[0033] In the blended cement composition according to this embodiment, granulated blast furnace slag may be used as the blast furnace slag.

[0034] (Carbonate ester) The carbonate ester is not particularly limited and may include a chain carbonate and may include a cyclic carbonate. Only one type of carbonate ester may be used, or two or more types may be used in combination.

[0035] The chain carbonate may include a compound represented by the following formula (I). [Chemical formula]

[0036] In formula (I), R 1 and R 2 Each of these is an independent monovalent hydrocarbon group containing 1 to 4 carbon atoms. At least one of the hydrogen atoms in the monovalent hydrocarbon group may be substituted with a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 3 carbon atoms.

[0037] R 1 and R 2 Each of these may independently be an alkyl group, and examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, etc. 1 and R 2 If the compound has substituents, the number of substituents may be one, two, or one. Examples of substituents include halogen atoms such as fluorine atoms and chlorine atoms, and alkoxy groups such as hydroxyl groups and methoxy groups.

[0038] Examples of compounds represented by formula (I) include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylmethyl carbonate, allylmethyl carbonate, allylethyl carbonate, 1-chloroethylethyl carbonate, chloromethylisopropyl carbonate, and 1-chloroethylisopropyl carbonate.

[0039] Cyclic carbonates may include compounds represented by the following formula (II). [ka]

[0040] In formula (II), R 3 This is a divalent hydrocarbon group containing 2 to 6 carbon atoms. At least one of the hydrogen atoms in this divalent hydrocarbon group may be substituted with a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 3 carbon atoms.

[0041] R 3R may be an alkylene group, and examples of alkylene groups include ethylene, n-propylene, isopropylene, and n-butylene groups. 3 If the compound has substituents, the number of substituents may be one, two, or one. Examples of substituents include halogen atoms such as fluorine atoms and chlorine atoms, and alkoxy groups such as hydroxyl groups and methoxy groups.

[0042] Compounds represented by formula (II) include ethylene carbonate, propylene carbonate, 1,3-dioxan-2-one, 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4-vinyl-1,3-dioxolan-2-one, 4-methoxy-1,3-dioxolan-2-one, glycerol-1,2-carbonate, vinylene carbonate, and the like.

[0043] The cyclic carbonate preferably contains at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol-1,2-carbonate.

[0044] The carbonate ester content may be 0.01 to 1 part by mass, 0.02 to 1 part by mass, or 0.03 to 1 part by mass per 100 parts by mass of blast furnace slag. This allows for a higher compressive strength when the mixed cement composition is hardened.

[0045] The carbonate ester content may be 0.02 to 2 parts by mass, 0.05 to 1.5 parts by mass, or 0.1 to 1 part by mass per 100 parts by mass of the total of Portland cement and blast furnace slag. This makes it possible to increase the compressive strength when the mixed cement composition is hardened.

[0046] (plaster) The gypsum may be gypsum that has been pre-added to the Portland cement and blast furnace slag, or it may be gypsum that is added separately to the Portland cement and blast furnace slag. Examples of separately added gypsum include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. One type of gypsum may be used alone, or multiple types may be used in combination.

[0047] The gypsum content in the mixed cement composition is 4.0% by mass or less in terms of SO3, based on the total amount of Portland cement, blast furnace slag, and gypsum, and may be 0.5-3.5% by mass, 0.7-3.0% by mass, or 1.0-2.5% by mass. This allows for a higher compressive strength when the mixed cement composition is hardened. When gypsum is added separately, the above gypsum content is the sum of the gypsum originally contained in the Portland cement and blast furnace slag and the separately added gypsum.

[0048] The mixed cement composition according to this embodiment may contain other components besides Portland cement, blast furnace slag, and carbonate ester. Other components include water, sand, aggregate, water-reducing agents, etc.

[0049] Examples of water-reducing agents include nitrohumic acid salts, lignin sulfonates, citric acid, polycarboxylic acids, and naphthalene.

[0050] The Blaine specific surface area of ​​the mixed cement composition is, for example, 3000 cm². 2 / g or more, 3200cm 2 / g or more, 3300cm 2 / g or more, or 3450cm 2 It may be 1 / g or more. Having the lower limit of the Blaine specific surface area of ​​the mixed cement composition within this range allows for increased compressive strength and enhances the long-term strength development effect when a small amount of low-basicity blast furnace slag is added. For example, the Blaine specific surface area of ​​the mixed cement composition may be 6000 cm². 2 / g or less, 5000cm 2 / g or less, 4200cm 2 / g or less, or 3850cm 2 It may be less than or equal to / g. Having the upper limit of the Blaine specific surface area of ​​the mixed cement composition within this range helps to suppress a decrease in fluidity and handling properties. The Blaine specific surface area of ​​the mixed cement composition may be adjusted within the above range, for example, 3450 to 3850 cm². 2 / g is acceptable.

[0051] A method for producing a mixed cement composition according to one embodiment includes a mixing step of preparing a mixed cement composition by mixing Portland cement, blast furnace slag, and carbonate ester. If raw materials other than Portland cement, blast furnace slag, and carbonate ester are used, they are mixed together in the mixing step.

[0052] The above-described embodiment includes the following: [1] A mixed cement composition comprising Portland cement, blast furnace slag, and carbonate ester, wherein the basicity calculated from the following formula (1) based on the chemical composition of the blast furnace slag is 1.79 or less, and the gypsum content is 4.0% by mass or less in terms of SO3, based on the total amount of Portland cement, blast furnace slag, and gypsum. Basicity = (CaO + MgO + Al2O3) / SiO2 ... Equation (1) [In formula (1), CaO represents the content (mass%) of calcium oxide in the blast furnace slag, MgO represents the content (mass%) of magnesium oxide in the blast furnace slag, Al2O3 represents the content (mass%) of aluminum oxide in the blast furnace slag, and SiO2 represents the content (mass%) of silicon dioxide in the blast furnace slag.] [2] The mixed cement composition according to [1], wherein the carbonate ester comprises a cyclic carbonate. [3] The mixed cement composition according to [2], wherein the cyclic carbonate comprises a compound represented by the following formula (II). [ka] (In formula (II), R 3 (It is a divalent hydrocarbon group having 2 to 6 carbon atoms.) [4] The mixed cement composition according to any one of [1] to [3], wherein the content of the carbonate ester is 0.01 to 1 part by mass per 100 parts by mass of the blast furnace slag. [5] The mixed cement composition according to any one of [1] to [4], wherein the blast furnace slag content is 5 to 70% by mass, based on the total amount of Portland cement, blast furnace slag, and gypsum. [6] The mixed cement composition according to any one of [1] to [5], wherein the content of the carbonate ester is 0.02 to 2 parts by mass with respect to 100 parts by mass of the total of the Portland cement, the blast furnace slag, and the gypsum. [7] The mixed cement composition according to [2] or [3], wherein the cyclic carbonate is at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol-1,2-carbonate.

[0053] The embodiments described above are examples of this disclosure, and various other configurations can be adopted. [Examples]

[0054] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to these examples.

[0055] [Preparation of mixed cement composition] The following materials were used as raw materials for the mixed cement composition.

[0056] (Portland cement) For the Portland cement used, ordinary Portland cement (OPC, manufactured by UBE Mitsubishi Cement Corporation) was employed. The chemical composition, ignition loss, and Blaine specific surface area of ​​OPC are shown in Table 1.

[0057] (Blast furnace slag) As blast furnace slags, slag A and slag B, having the chemical composition and properties shown in Table 1 below, were used. The chemical composition, ignition loss, C / S ratio (CaO / SiO2 ratio (mass ratio)), basicity calculated from the above formula (1), and Blaine specific surface area of ​​slag A and slag B are shown in Table 1.

[0058] For Portland cement, the chemical composition was measured in accordance with JIS R 5204:2019 "X-ray fluorescence analysis method for cement," and the loss on ignition was measured in accordance with JIS R 5202:2010. For blast furnace slag, the chemical composition excluding SO3 was measured in accordance with JIS R 5204:2019 "X-ray fluorescence analysis method for cement," and SO3 and loss on ignition were measured in accordance with JIS R 5202:2010.

[0059] (plaster) Natural anhydrous gypsum was used as the gypsum material.

[0060] (Carbonate ester) The following compounds were used as carbonate esters. • Dimethyl carbonate (DMC, manufactured by UBE Corporation) • Ethylene carbonate (EC, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Glycerol-1,2-carbonate (GC, manufactured by UBE Corporation)

[0061] [Table 1]

[0062] (Examples 1-9, Comparative Examples 1-6, and Reference Examples 1-10) Mixed cement compositions for Examples 1-9, Comparative Examples 1-6, and Reference Examples 1-10 were prepared by mixing Portland cement (OPC), blast furnace slag, anhydrous gypsum, and carbonate ester. The types of slag used, the proportions of OPC and slag, and the amount of carbonate ester added are shown in Tables 2-4. In Tables 2-4, the proportions (mass%) of OPC and slag A and B are based on the total proportions of OPC, slag A and B, and anhydrous gypsum, and the amount of carbonate ester added (parts by mass) is the amount added relative to 100 parts by mass of the total amount of OPC, slag A and B, and anhydrous gypsum.

[0063] [Measurement of compressive strength] For each mixed cement composition prepared in Examples 1-9, Comparative Examples 1-6, and Reference Examples 1-10, the compressive strength (N / mm²) was tested in accordance with the description in JIS R 5201:2015 "Physical Testing Methods for Cement". 2 ) was measured.

[0064] Specifically, a mortar composition for evaluation was prepared by mixing 100 parts by mass of the above-mentioned mixed cement composition with 300 parts by mass of sand (standard sand / manufactured by the Cement Association) as fine aggregate and 50 parts by mass of water. The above mixture was adjusted so that the ratio of mixed cement composition:sand:water was 100:300:50 (by mass, in accordance with the description in JIS R 5201:2015 "Physical Test Methods for Cement").

[0065] Mortar hardened bodies were prepared using each of the obtained mortar compositions. First, the above mortar compositions were mixed as mortar in a constant temperature chamber at 20°C and filled into a 4cm × 4cm × 16cm mold (prepared in accordance with the description in JIS R 5201:2015 "Physical Test Methods for Cement"). The mold was stored in a humidity chamber and cured for 24 hours under conditions of 20°C and 60%RH. After 24 hours of curing, the mold was removed to obtain a hardened mortar body. The obtained hardened mortar bodies were cured in water for 7 days (age 7 days) in a constant temperature chamber at 20°C. The hardened mortar bodies after water curing were used as test specimens, and the compressive strength of the hardened mortar bodies at age 7 days (7d) was measured. In addition, each hardened mortar body was also cured in water for 28 days (age 28 days) in a constant temperature chamber at 20°C, and the compressive strength of the hardened mortar bodies at age 28 days (28d) was also measured.

[0066] The compressive strength was measured in accordance with JIS R 5201:1992 "Physical Testing Methods for Cement". The compressive strength ratio (%) was calculated from the measured compressive strength. The results are shown in Tables 2 to 4. Note that the compressive strength ratios in Tables 2 to 4 are relative values ​​when the compressive strength of the hardened mixture of cement compositions, where the type and amount of OPC and blast furnace slag are the same and no carbonate ester is added, is set to 100. Specifically, for example, the compressive strength ratios of Examples 1 to 4 are relative values ​​when the compressive strength of Comparative Example 1 is set to 100, and the compressive strength ratio of Example 5 is relative values ​​when the compressive strength of Comparative Example 2 is set to 100.

[0067] [Table 2]

[0068] [Table 3]

[0069] [Table 4]

[0070] As shown in Tables 2 to 4, the mixed cement compositions of each example exhibited excellent compressive strength (at 7 days and 28 days of age) despite using blast furnace slag (slag B), which has a low basicity. Figure 1 is a graph summarizing the relationship between SO3 content (SO3 content in gypsum equivalent) and compressive strength ratio for Examples 1, 5 to 7 and Comparative Examples 1 to 4. In Figure 1, the % notation for GC corresponds to the mass % relative to the total of OPC, slag, and anhydrous gypsum. As shown in Figure 1, it was confirmed that adding carbonate ester in the range of SO3 content of 4 mass% or less increased the compressive strength at both 7 and 28 days of age.

Claims

1. It contains Portland cement, blast furnace slag, and carbonate esters. The basicity calculated from the following formula (1) based on the chemical composition of the blast furnace slag is 1.79 or less, The gypsum content is based on the total amount of Portland cement, blast furnace slag, and gypsum, SO ３ A mixed cement composition having a composition of 4.0% by mass or less. Basicity = (CaO + MgO + Al ２ O ３ ) / SiO ２ ... Formula (1) [In formula (1), CaO represents the content (mass%) of calcium oxide in blast furnace slag, MgO represents the content (mass%) of magnesium oxide in blast furnace slag, and Al ２ O ３ This indicates the aluminum oxide content (mass%) in blast furnace slag, and SiO ２ This indicates the silicon dioxide content (mass%) in blast furnace slag.

2. The mixed cement composition according to claim 1, wherein the carbonate ester comprises a cyclic carbonate.

3. The mixed cement composition according to claim 2, wherein the cyclic carbonate comprises a compound represented by the following formula (II). 【Chemistry 1】 (In formula (II), R ３ (This is a divalent hydrocarbon group having 2 to 6 carbon atoms.)

4. The mixed cement composition according to any one of claims 1 to 3, wherein the content of the carbonate ester is 0.01 to 1 part by mass per 100 parts by mass of the blast furnace slag.

5. The mixed cement composition according to any one of claims 1 to 3, wherein the blast furnace slag content is 5 to 70% by mass, based on the total amount of Portland cement, blast furnace slag, and gypsum.

6. The mixed cement composition according to any one of claims 1 to 3, wherein the content of the carbonate ester is 0.02 to 2 parts by mass with respect to 100 parts by mass of the total of the Portland cement, the blast furnace slag, and the gypsum.

7. The mixed cement composition according to claim 2, wherein the cyclic carbonate is at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol-1,2-carbonate.

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