Cement composition, and method of producing cement composition

Abstract

To provide a cement composition capable of obtaining mortar or concrete excellent in compression strength in a short-term material age, even when synthetic calcium carbonate is used as an admixture, and a method of producing the cement composition.SOLUTION: The cement composition according to the present invention includes cement clinker and synthetic calcium carbonate, wherein a content of the synthetic calcium carbonate is more than 5 mass% and 15 mass% or less relative to the cement composition, the synthetic calcium carbonate has an n value of 2.5 or more in a particle size distribution represented by Rosin-Rammler distribution, and a particle diameter (D50) at a cumulative frequency of 50% in a volume-based particle size distribution by a laser diffraction scattering particle size distribution measurement method is 10.0 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a cement composition and a method for producing the same.

Background Art

[0002] Conventionally, from the viewpoint of improving fluidity, limestone fine powder mainly composed of calcium carbonate may be mixed as an admixture in a cement composition (for example, Patent Document 1). As the limestone fine powder, a material obtained by pulverizing natural limestone with a pulverizer and then classifying it is used.

[0003] So far, artificially synthesized calcium carbonate (hereinafter also referred to as "synthetic calcium carbonate") has not been used as an admixture in a cement composition. However, since calcium carbonate can be synthesized using, for example, carbon dioxide in exhaust gas, the application of synthetic calcium carbonate as an admixture has been studied from the viewpoint of reducing the amount of carbon dioxide released into the atmosphere.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Various commercially available synthetic calcium carbonates are in circulation. However, even when commercially available synthetic calcium carbonate is used as an admixture, sufficient compressive strength at a short age of mortar or concrete may not be obtained.

[0006] In view of such circumstances, an object of the present invention is to provide a cement composition capable of obtaining mortar or concrete excellent in compressive strength at an early age even when synthetic calcium carbonate is used as an admixture, and a method for producing the cement composition.

Means for Solving the Problems

[0007] The cement composition according to the present invention includes a cement clinker and synthetic calcium carbonate, the content of the synthetic calcium carbonate is more than 5% by mass and 15% by mass or less with respect to the cement composition, and the synthetic calcium carbonate has an n value of the particle size distribution represented by the Rosin-Rammler distribution of 2.5 or more, and the particle diameter (D50) at the cumulative frequency of 50% in the volume-based particle size distribution by the laser diffraction / scattering particle size distribution measurement method is 10.0 μm or less.

[0008] With such a configuration, the cement composition can obtain mortar or concrete excellent in compressive strength at an early age even when synthetic calcium carbonate is used as an admixture.

[0009] In the cement composition according to the present invention, the n value may be 2.5 or more and 5.0 or less.

[0010] With such a configuration, the cement composition can obtain mortar or concrete having even better compressive strength at an early age.

[0011] In the cement composition according to the present invention, the D50 may be 2.0 μm or more and 10.0 μm or less.

[0012] With such a configuration, the cement composition can obtain mortar or concrete having even better compressive strength at an early age.

[0013] The method for manufacturing a cement composition according to the present invention is the above-described method for manufacturing a cement composition, and includes a mixing step of mixing cement and synthetic calcium carbonate so that the content of synthetic calcium carbonate in the cement composition exceeds 5% by mass and is 15% by mass or less.

[0014] With such a configuration, the cement composition can obtain mortar or concrete excellent in compressive strength at a short age even when synthetic calcium carbonate is used as an admixture.

Effects of the Invention

[0015] According to the present invention, it is possible to provide a cement composition capable of obtaining mortar or concrete excellent in compressive strength at a short age even when synthetic calcium carbonate is used as an admixture, and a method for manufacturing the cement composition.

Brief Description of the Drawings

[0016]

Figure 1

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the cement composition according to the present embodiment and the method for manufacturing the cement composition will be described.

[0018] <Cement Composition> The cement composition according to the present embodiment includes a cement clinker and synthetic calcium carbonate.

[0019] (Cement Clinker) Examples of cement clinker include Portland cements such as ordinary Portland cement, rapid hardening Portland cement, super rapid hardening Portland cement, moderate heat Portland cement, low heat Portland cement, sulfate resistant Portland cement, and white Portland cement defined in JIS R 5210, cements for ultra-high early strength cement, alumina cement, etc., and clinkers for such cements. Note that the cement clinker may be used alone or in combination of two or more kinds.

[0020] The content of the cement clinker can be, for example, 89% by mass or more and 91% by mass or less with respect to the cement composition. When two or more kinds of cement clinkers are included, the content is the total content of the cement clinkers.

[0021] (Synthetic calcium carbonate) The synthetic calcium carbonate has an n value of the particle size distribution represented by the Rosin-Rammler distribution of 2.5 or more, preferably 2.5 or more and 5.0 or less, and more preferably 2.5 or more and 4.0 or less. The n value can be adjusted, for example, by controlling the reaction time, reaction process, etc. when synthesizing calcium carbonate.

[0022] Note that the Rosin-Rammler distribution is a particle size distribution represented by the following formula (1). The n value is a constant indicating the spread of the distribution. The larger the n value, the narrower the distribution, meaning that the particle diameters are more uniform.

[0023] [Number] In the formula, R(x) is the cumulative mass distribution by sieving, x is the particle diameter, and b and n represent constants.

[0024] The n value is determined using the least squares method from the particle size distribution.

[0025] The synthetic calcium carbonate has a particle size (D50) at a cumulative frequency of 50% in the volume-based particle size distribution measured by the laser diffraction scattering method of 10.0 μm or less, preferably 2.0 μm or more and 10.0 μm or less, and more preferably 2.0 μm or more and 8.0 μm or less. The D50 can be adjusted, for example, by controlling the reaction rate or the like when synthesizing calcium carbonate.

[0026] The content of the synthetic calcium carbonate is more than 5% by mass and 15% by mass or less, preferably 5% by mass or more and 10% by mass or less, and more preferably 5% by mass or more and 7% by mass or less, based on the cement composition. When two or more types of synthetic calcium carbonate are included, the content is the total content of the synthetic calcium carbonate.

[0027] The synthetic calcium carbonate is artificially synthesized calcium carbonate. The method for synthesizing the synthetic calcium carbonate is not particularly limited. The synthetic calcium carbonate can be synthesized, for example, by adding carbon dioxide while heating in contact a cement hydrate-containing material and superheated steam. Further, the synthetic calcium carbonate can be synthesized, for example, by bringing a solution containing an alkali metal hydroxide into contact with a gas containing carbon dioxide and then further bringing a gypsum-containing material into contact therewith. Furthermore, the synthetic calcium carbonate can be synthesized by adding hydrochloric acid water to a calcium-containing waste to produce an aqueous solution containing calcium ions and then adding an aqueous solution containing potassium carbonate and / or sodium carbonate.

[0028] The cement composition according to this embodiment may further contain other admixtures other than synthetic calcium carbonate. Examples of other admixtures include inorganic fine powders such as fly ash, cement kiln dust, blast furnace fume, ground granulated blast furnace slag, ground blast furnace slag after cooling, ground converter slag, hemihydrate gypsum, expansive agent, fine limestone powder, quicklime fine powder, dolomite fine powder, etc., sodium-type bentonite, calcium-type bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu (volcanic ash), shirasu balloon, kaolinite, metakaolin (calcined clay), synthetic zeolite, artificial zeolite, man-made zeolite, mordenite, clinoptilolite, and other inorganic fillers. These other admixtures may be used alone or in combination of two or more kinds.

[0029] The content of other admixtures can be, for example, 5% by mass or more and 30% by mass or less based on the cement composition. When two or more kinds of other admixtures are contained, the content is the total content of the other admixtures.

[0030] The cement composition according to this embodiment contains cement clinker and synthetic calcium carbonate, and the content of the synthetic calcium carbonate is more than 5% by mass and 15% by mass or less based on the cement composition. The synthetic calcium carbonate has an n value of the particle size distribution represented by the Rosin-Rammler distribution of 2.5 or more, and the particle diameter (D50) at the cumulative frequency of 50% in the volume-based particle size distribution measured by the laser diffraction scattering method is 10.0 μm or less. Thus, even when synthetic calcium carbonate is used as an admixture, mortar or concrete excellent in compressive strength at an early age can be obtained.

[0031] When the n value of the cement composition according to this embodiment is 2.5 or more and 5.0 or less, mortar or concrete having more excellent compressive strength at an early age can be obtained.

[0032] The cement composition according to this embodiment can obtain mortar or concrete with excellent compressive strength at a short age because the D50 is 2.0 μm or more and 10.0 μm or less.

[0033] <Manufacturing method of cement composition> The manufacturing method of the cement composition according to this embodiment includes a mixing step of mixing cement clinker and synthetic calcium carbonate so that the content of synthetic calcium carbonate in the cement composition exceeds 5% by mass and is 15% by mass or less. As a method of mixing each material, it is not particularly limited, and a conventionally known method can be used.

[0034] The temperature in the mixing step is not particularly limited, and for example, it can be carried out at 5°C or more and 35°C or less.

[0035] The manufacturing method of the cement composition according to this embodiment is the above-described manufacturing method of the cement composition, and includes a mixing step of mixing cement and synthetic calcium carbonate so that the content of synthetic calcium carbonate in the cement composition exceeds 5% by mass and is 15% by mass or less. By using synthetic calcium carbonate as an admixture, mortar or concrete with excellent compressive strength at a short age can be obtained.

Examples

[0036] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0037] <Preparation of cement composition> After weighing so that calcium carbonate is 10 parts by mass with respect to 90 parts by mass of ordinary Portland cement, it was sufficiently mixed with a mixer until it became homogeneous, and the cement compositions of each example and each comparative example shown in Table 1 were obtained.

[0038] Details of each component are shown below. Ordinary Portland cement: Manufactured by Sumitomo Osaka Cement Co., Ltd. Synthetic calcium carbonate 1: Manufactured by Kojima Chemical Co., Ltd. Synthetic calcium carbonate 2: manufactured by Kinoshita Chemical Co., Ltd. Synthetic calcium carbonate 3: manufactured by Yahashi Kogyo Co., Ltd. Natural limestone: manufactured by Joetsu Mining Co., Ltd.

[0039] <Measurement of D50 and calculation of constants in the Rosin-Rammler distribution> Using a laser diffraction / scattering particle size distribution measuring device MT3000 manufactured by Microtrac Bell Corporation, the particle size at a cumulative frequency of 50% in the volume-based particle size distribution and the n value in the Rosin-Rammler distribution were determined. The results are shown in Table 1.

[0040]

Table 1

[0041] <Measurement of mortar compressive strength> For the cement compositions of each example and each comparative example, specimens were formed in accordance with the "Physical Test Methods for Cement" of JIS R 5201:2015, and a mortar compressive strength test was conducted. The results are shown in Table 2 and Figure 1.

[0042]

Table 2

[0043] As can be seen from the results of Tables 1 and 2, the cement compositions of each example that satisfy all the constituent requirements of the present invention can obtain specimens with excellent compressive strength at short-term ages, particularly at ages of 3 days and 7 days, even when using synthetic calcium carbonate as an admixture.

Claims

1. A cement composition comprising cement clinker and synthetic calcium carbonate, wherein the content of the synthetic calcium carbonate is more than 5% by mass and 15% by mass or less with respect to the cement composition, wherein the synthetic calcium carbonate has an n value of the particle size distribution represented by the Rosin-Rammler distribution of 2.5 or more, and a particle diameter (D50) at a cumulative frequency of 50% in the volume-based particle size distribution by the laser diffraction / scattering particle size distribution measurement method of 10.0 μm or less.

2. The cement composition according to claim 1, wherein the n value is 2.5 or more and 5.0 or less.

3. The cement composition according to claim 1 or 2, wherein the D50 is 2.0 μm or more and 10.0 μm or less.

4. A method for producing the cement composition according to claim 1 or 2, comprising a mixing step of mixing cement clinker and synthetic calcium carbonate so that the content of synthetic calcium carbonate with respect to the cement composition is more than 5% by mass and 15% by mass or less.

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