Mixed cement composition

Abstract

To provide a mixed cement composition that contributes to CO2 reduction and exhibits excellent initial compressive strength. [Solution] The mixed cement composition comprises Portland cement, blast furnace slag, and carbonate ester. The carbonate ester may contain cyclic carbonates.

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] For example, Patent Document 1 describes an attempt to activate the hydration reaction of blast furnace slag fine powder by adding nitrite as a hardening accelerator to a cement-based hydraulic composition in which a portion of the cement is replaced with blast furnace slag fine powder. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-076203 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in blast furnace cement with a high mixing ratio of blast furnace slag or the like, as described above, even if a hardening accelerator such as nitrite is added, the initial strength may not be improved.

[0007] An object of the present disclosure is to provide a blended cement composition that contributes to CO2 reduction and has excellent initial compressive strength.

Means for Solving the Problems

[0008] One aspect of the present disclosure provides a blended cement composition comprising Portland cement, blast furnace slag, and a carbonate ester.

[0009] Since the above blended cement composition contains blast furnace slag and a carbonate ester, it contributes to CO2 reduction and has excellent initial compressive strength.

[0010] The mechanism by which the above effects are obtained is not clear, but the present inventors推测 as follows. 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 progresses. Then, the pH of the cement composition increases, and the dissolution of aluminum in the blast furnace slag is promoted. As a result, the formation of cement hydrates by the hydration reaction of alite progresses, and it is considered that the compressive strength is improved. Note that the mechanism by which the above effects are obtained is not limited to this.

[0011] A hardened body containing the hardened product of the above blended cement composition contributes to CO2 reduction and has excellent initial compressive strength.

Effects of the Invention

[0012] According to the present disclosure, a blended cement composition that contributes to CO2 reduction and has excellent initial compressive strength can be provided.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments for implementing the present disclosure (hereinafter referred to as "the present embodiments") will be described in detail. The present disclosure is not limited to the following embodiments.

[0014] In this specification, in the numerical range indicated by using "~", the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. Also, in the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0015] The materials exemplified in this specification can be used singly or in combination of two or more unless otherwise specified. 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.

[0016] [Mixed Cement Composition] A mixed cement composition according to an embodiment includes Portland cement, blast furnace slag, and carbonate ester.

[0017] (Portland Cement) The Portland cement may be any Portland cement defined in JIS R 5210:2009 "Portland Cement". Examples of the Portland cement include ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, medium-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and the like. The Portland cement can be used singly or in combination of two or more.

[0018] 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.

[0019] 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".

[0020] 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 initial 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.

[0021] (Blast furnace slag) Blast furnace slag may be commercially available, for example, or a slag equivalent to blast furnace slag may be prepared.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Blast furnace slag may also contain other components such as NaO2 (sodium oxide), K2O (potassium oxide), and TiO2 (titanium oxide).

[0028] 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".

[0029] The basicity calculated from the following formula (1) based on the chemical composition of the blast furnace slag may be 1.50 or higher, 1.55 or higher, or 1.60 or higher, and may be 1.90 or lower, 1.87 or lower, 1.80 or lower, 1.75 or lower, or 1.70 or lower. 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.]

[0030] The basicity calculated from formula (1) above is the basicity calculated by the method described in JIS R 5211:2019 "Blast Furnace Cement".

[0031] The specific surface area of ​​blast furnace slag is, for example, 2500 cm². 2 / g or more, 3000cm 2 / g or more, 4000 cm 2 / g or more, 4100 cm 2 / g or more, or 4200 cm 2 / g or more may be acceptable. By setting the lower limit value 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 acceptable. By setting the upper limit value 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 when manufacturing 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) The carbonate is not particularly limited and may include chain carbonates or may include cyclic carbonates. Only one type of carbonate 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] [[ID=and=39]]

[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 allows for superior compressive strength when the mixed cement composition is hardened.

[0046] The mixed cement composition according to this embodiment may contain other components besides Portland cement, blast furnace slag, and carbonate ester. Examples of other components include water, sand, gypsum, aggregate, and water-reducing agents.

[0047] The gypsum content in the mixed cement composition may be 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, based on the total amount of Portland cement, blast furnace slag, and gypsum, in terms of SO3. This ensures that a sufficient amount of gypsum is included in the cement composition, allowing for improved initial compressive strength while maintaining sufficiently high thermal crack resistance. The gypsum content in the mixed cement composition may be 4.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less, based on the total amount of Portland cement, blast furnace slag, and gypsum, in terms of SO3.

[0048] Examples of water-reducing agents include nitrohumic acid salts, lignin sulfonates, citric acid, polycarboxylic acids, and naphthalene.

[0049] 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.

[0050] A method for producing a mixed cement composition according to one embodiment comprises 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. The mixing method is not particularly limited.

[0051] The mixed cement composition obtained by the above mixing process contributes to CO2 reduction and exhibits excellent initial compressive strength.

[0052] The above-described embodiment includes the following: [1] A mixed cement composition comprising Portland cement, blast furnace slag, and carbonate ester. [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 containing 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 and blast furnace slag. [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 and the blast furnace slag. [7] The mixed cement composition according to [2] or [3], wherein the cyclic carbonate comprises 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. Table 1 shows the chemical composition, ignition loss, C / S ratio (CaO / SiO2 ratio (mass ratio)), basicity, basicity calculated from the above formula (1), and Blaine specific surface area of ​​slag A and slag B.

[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] (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)

[0060] [Table 1]

[0061] (Examples 1-17 and Comparative Examples 1-6) Mixed cement compositions of Examples 1-17 and Comparative Examples 1-6 were prepared by mixing Portland cement (OPC), blast furnace slag, and carbonate ester. The type 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 of OPC and slag (mass%) are based on the total proportions of OPC and slag, 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 and slag.

[0062] [Measurement of compressive strength] For each mixed cement composition prepared in Examples 1-17 and Comparative Examples 1-6, 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.

[0063] 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").

[0064] 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 body was cured in water for 7 days (7 days old) in a constant temperature chamber at 20°C. The hardened mortar body after water curing was used as a test specimen, and the compressive strength of the hardened mortar body at 7 days old (7d) was measured. For the hardened mortars obtained from the mixed cement compositions of Examples 1-5, 15-17 and Comparative Examples 1-6, underwater curing was also performed in a constant temperature chamber at 20°C for 28 days (28 days of age), and the compressive strength of the hardened mortars at 28 days (28d) was also measured.

[0065] 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 mixed 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 ratio of Example 1 is a relative value when the compressive strength of Comparative Example 1 is set to 100, and the compressive strength ratios of Examples 3 to 5 are relative values ​​when the compressive strength of Comparative Example 3 is set to 100.

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] As shown in Tables 2 to 4, the initial compressive strength (at 7 days of age) of the mixed cement compositions in each example containing carbonate ester was higher than that of the mixed cement compositions in each comparative example that did not contain carbonate ester.

Claims

1. A mixed cement composition comprising Portland cement, blast furnace slag, and carbonate ester.

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 (It is a divalent hydrocarbon group containing 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 and blast furnace slag.

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 and the blast furnace slag.

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

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