Cement composition and method for manufacturing the same

Abstract

To provide a low-carbon cement composition with excellent strength development properties. [Solution] A cement composition is provided comprising Portland cement and crushed inorganic minerals, wherein the crushed material has a smaller BET specific surface area than before crushing, and the crushed material content is 10 to 50% by mass, and the Portland cement content is 50 to 90% by mass.

Description

[Technical Field]

[0001] This disclosure relates to cement compositions and methods for producing the same. [Background technology]

[0002] As part of efforts to promote decarbonization, cement compositions are being used in which a portion of the cement clinker, which has a high CO2 emission during manufacturing, is replaced with admixtures. Limestone is widely used as an admixture added to cement because it is readily available and inexpensive.

[0003] Currently, the amount of admixture added to ordinary Portland cement is set at 5% by mass or less according to JIS R 5210:2009. On the other hand, from the perspective of preventing global warming and reducing carbon emissions, it is desirable to further increase the proportion of cement clinker replaced by admixture in order to reduce the amount of cement clinker used, thereby creating a lower-carbon cement. However, simply adding limestone in amounts exceeding the current 5% by mass results in a decrease in strength compared to current ordinary Portland cement (for example, Non-Patent Literature 1).

[0004] Regarding the types of mixed materials, JIS standards specify that, in addition to limestone, fly ash, blast furnace slag, and silica fume should be used as small-amount mixed components. In recent years, other promising mixed materials have been explored. For example, it is known that adding metakaolin, which is produced by calcining kaolin, a natural material, to cement yields good strength development (Non-Patent Literature 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Ayaka Nakaguchi et al., "Quality Evaluation of Cement with Increased Amount of Small Mixed Components," Abstracts of Presentations at the Cement Technology Conference, 2018, pp. 270-271. [Non-Patent Document 2] Karen Scrivener et al.: Calcined clay limestone cements (LC3), Cement and Concrete Research,Vol.114,pp.49-56 (2018)

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, for kaolin, which is the raw material of metakaolin cited in Non-Patent Document 2, the regions and countries where it is produced are limited. Therefore, if there are materials that can be used as admixtures other than kaolin, it is extremely useful for the development of low-carbon cement.

[0007] <​​​​​​​​​​​​​​​The above cement composition contains pulverized inorganic minerals whose BET specific surface area is smaller than that before pulverization. Such inorganic minerals have fine pores before pulverization, and because they adsorb nitrogen in these pores, they have a large BET specific surface area. When such inorganic minerals are pulverized, the microstructure that forms the pores is destroyed, so the BET specific surface area decreases. When such microstructure is destroyed, the hydration reaction of the cement proceeds more easily, which contributes to the development of strength in the cement composition. The above cement composition contains a predetermined amount of such pulverized inorganic minerals together with Portland cement. For this reason, it is a low-carbon type while having excellent strength development properties. In this specification, a low-carbon type cement composition means a cement composition in which CO2 emissions during the manufacture of the cement composition can be reduced by replacing a portion of the cement clinker contained in Portland cement with an admixture.

[0010] One aspect of this disclosure is a cement composition comprising Portland cement and crushed inorganic minerals, The inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite. The present invention provides a cement composition having a crushed material content of 10 to 50% by mass and a Portland cement content of 50 to 90% by mass.

[0011] The above cement composition contains pulverized inorganic minerals, including at least one selected from the group consisting of allophane, halloysite, and imogolite. Inorganic minerals containing allophane, halloysite, or imogolite have a microstructure that forms minute pores. When such pulverized inorganic minerals are pulverized, the microstructure that forms minute pores is destroyed, which facilitates the hydration reaction of the cement and contributes to the development of the strength of the cement composition. The above cement composition contains a predetermined amount of such pulverized inorganic minerals together with Portland cement. For this reason, it has excellent strength development properties while being a low-carbon type.

[0012] One aspect of the present disclosure includes a pulverization step of pulverizing an inorganic mineral to obtain a pulverized product having a BET specific surface area smaller than that of the inorganic mineral, and a mixing step of mixing Portland cement and the pulverized product. There is provided a method for producing a cement composition, in which the content of the pulverized product is 10 to 50% by mass and the content of the Portland cement is 50 to 90% by mass.

[0013] In the method for producing the cement composition, the inorganic mineral is pulverized in the pulverization step to obtain a pulverized product having a BET specific surface area smaller than that of the inorganic mineral before pulverization. Since such a pulverized product is obtained by destroying the fine structure forming the pores of the inorganic mineral, the hydration reaction of the cement proceeds easily and contributes to the strength development of the cement composition. By mixing Portland cement and the above-mentioned pulverized product, a cement composition in which the content of the pulverized product and the content of Portland cement are in a predetermined ratio can be obtained. In this way, a cement composition having excellent strength development properties while being low-carbon can be obtained.

Effects of the Invention

[0014] The present disclosure can provide a low-carbon cement composition having excellent strength development properties and a method for producing the same.

Modes for Carrying Out the Invention

[0017] The Blaine specific surface area of the cement composition is 3000 cm 2 / g or more, 3150 cm 2 / g or more, 3300 cm 2 / g or more, 3500 cm 2 / g or more, or 3700 cm 2 / g or more. The Blaine specific surface area of the cement composition is 20000 cm 2 / g or less, 18000 cm 2 / g or less, or 16000 cm 2 / g or less. When the Blaine specific surface area of the cement composition is within the above range, the inorganic mineral is appropriately pulverized, and it is possible to sufficiently balance strength development and heat generation suppression at a high level while sufficiently reducing the pulverization cost and CO2 emissions. An example of the range of the Blaine specific surface area of the cement composition may be, for example, 3000 - 20000 cm 2 / g. The Blaine specific surface area of the cement composition can be measured based on the description in JIS R 5201:2015 "Physical Testing Methods for Cement".

[0018] Examples of Portland cement include various Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, medium-heat Portland cement, low-heat Portland cement, oil well Portland cement, and sulfate-resistant Portland cement. The Portland cement may contain cement clinker, gypsum, and carbonate.

[0019] The cement clinker may be a Portland cement clinker used to prepare various Portland cements as specified in JIS R 5210:2009 "Portland Cement". Examples of Portland cement clinkers include ordinary Portland cement clinker, rapid-hardening Portland cement clinker, ultra-rapid-hardening Portland cement clinker, moderate-heat Portland cement clinker, low-heat Portland cement clinker, oil well Portland cement clinker, and sulfate-resistant Portland cement clinker. The cement clinker may also contain C3S, C2S, C3A, and C4AF as its mineral composition.

[0020] The Portland cement content, based on the total amount of the cement composition, is 50 to 90% by mass. Having a Portland cement content within this range allows for a reduction in cement clinker content, resulting in a low-carbon cement composition that reduces CO2 emissions during manufacturing. From the viewpoint of further improving the strength development of the cement composition, the Portland cement content may be 60% by mass or more. From the viewpoint of further reducing the cement clinker content in the cement composition and further reducing CO2 emissions during manufacturing, the Portland cement content may be 80% by mass or less, or 70% by mass or less. From the viewpoint of reducing CO2 emissions during manufacturing and maintaining high levels of strength development, examples of the above range for the Portland cement content include, for example, 50 to 80% by mass, 50 to 70% by mass, or 60 to 80% by mass.

[0021] The cement composition contains crushed inorganic minerals. The inorganic minerals may be minerals produced by the weathering of volcanic ejecta, i.e., minerals derived from volcanic ejecta. Examples of volcanic ejecta include volcanic ash, volcanic lapilli, pumice, and pyroclastic flow deposits. The inorganic minerals may also be minerals produced by the weathering of igneous rocks. Examples of igneous rocks include granite. Allophane is produced by the weathering of volcanic ejecta or igneous rocks, halloysite is produced by further weathering of allophane, and kaolin or kaolinite is produced by further weathering of halloysite. Kaolin, kaolinite, allophane, and halloysite are clay minerals.

[0022] The inorganic mineral may include at least one selected from the group consisting of allophane, halloysite, and imogolite. Imogolite is a mineral derived from volcanic ejecta similar to allophane or halloysite. From the viewpoint of increasing reactivity with cement clinker, the inorganic mineral may include at least one selected from the group consisting of allophane and halloysite, and may also include allophane. Allophane is an amorphous inorganic mineral. Halloysite is a crystalline inorganic mineral. Examples of inorganic minerals containing allophane include Kanuma soil and Secard P1 (trade name, manufactured by Shinagawa General Co., Ltd.). Examples of inorganic minerals containing halloysite include dragonite (trade name, manufactured by Applied Minerals).

[0023] Inorganic minerals have a reduced BET specific surface area upon pulverization. That is, pulverized inorganic minerals have a smaller BET specific surface area than those before pulverization. In this specification, "pulverized material" refers to pulverized inorganic minerals obtained by pulverizing various forms such as lumps, granules, aggregates, and granulated materials using a pulverizer such as a disc mill. When the inorganic mineral is allophane, the microstructure, such as the layered structure of SiO2 and Al2O3 that constitutes the pores, is destroyed by pulverization. When the inorganic mineral is halloysite, the microstructure, such as the crystalline structure of SiO2 and Al2O3 that constitutes the pores, is destroyed by pulverization. In addition, the coordination number of Al atoms changes from six coordination to four coordination, and the bonding state of the atoms also changes. It is believed that these changes in microstructure and molecular structure facilitate the hydration reaction of cement, thereby improving the strength development of the cement composition.

[0024] The content of crushed inorganic minerals, based on the total amount of the cement composition, is 10 to 50% by mass. Having the crushed inorganic mineral content within this range reduces the cement clinker content, resulting in a low-carbon cement composition that reduces CO2 emissions during manufacturing. From the viewpoint of further reducing the cement clinker content and CO2 emissions, the crushed inorganic mineral content may be 20% by mass or more, or 30% by mass or more. From the viewpoint of improving mixability and further improving the compressive strength of the hardened body, the crushed inorganic mineral content may be 40% by mass or less. From the viewpoint of reducing CO2 emissions during manufacturing, maintaining high levels of mixability and the compressive strength of the hardened body, examples of the range for the crushed inorganic mineral content may be, for example, 20 to 50% by mass, 30 to 50% by mass, or 20 to 40% by mass.

[0025] The BET specific surface area of ​​inorganic minerals before crushing is 30-300 m². 2 / g, or 50-280m 2 It may also be / g. The BET specific surface area in this specification is a value obtained from a BET plot in the relative pressure range of 0.05 to 0.35 by a BET multipoint method using nitrogen gas.

[0026] The BET specific surface area of ​​pulverized inorganic minerals is 180 m², from the viewpoint of improving mixability. 2 / g or less, 160m 2 / g or less, 140m 2 / g or less, or 120m 2 It may be less than / g. The BET specific surface area of ​​the crushed material should be 30m² from the viewpoint of improving the strength development of the cement composition. 2 / g or more, 40m 2 / g or more, or 50m 2 It may be more than / g. An example of the range of the BET specific surface area of ​​the pulverized material is, for example, 30 to 180 m². 2 / g is also acceptable.

[0027] The ratio α of the BET specific surface area of ​​the crushed inorganic mineral to the BET specific surface area of ​​the inorganic mineral before crushing may be 0.10 to 0.90. The BET specific surface area ratio α may be 0.20 or higher, or 0.30 or higher. An example of the range of the BET specific surface area ratio α is 0.20 to 0.90, or 0.30 to 0.90. By having the BET specific surface area ratio α within the above range, it is possible to further improve the strength development of the cement composition while reducing crushing costs and the time required for crushing.

[0028] When the inorganic mineral contains allophane, the ratio α of the BET specific surface area of ​​the pulverized inorganic mineral to the BET specific surface area of ​​the inorganic mineral before pulverization may be 0.10 to 0.50 or 0.12 to 0.40. When the inorganic mineral contains halloysite, the ratio α of the BET specific surface area of ​​the pulverized inorganic mineral to the BET specific surface area of ​​the inorganic mineral before pulverization may be 0.50 to 0.90 or 0.70 to 0.90. By setting the BET specific surface area of ​​the pulverized material within the above ranges depending on the type of inorganic mineral, it is possible to further improve the strength development of the cement composition while reducing pulverization costs and the time required for pulverization.

[0029] The Blaine specific surface area of ​​inorganic minerals before pulverization is 8000 cm². 2 / g or more, 10000cm 2 / g or more, or 11,000 cm 2It may be 1 / g or more. This can further improve the strength development of the cement composition. The Blaine specific surface area of ​​the inorganic mineral is, for example, 30,000 cm². 2 / g or less, 28000cm 2 / g or less, or 26,000 cm 2 It may be less than / g. This can reduce grinding costs. An example of the range of Blaine specific surface area for inorganic minerals is, for example, 8000 to 30000 cm². 2 It may also be expressed as / g. The Blaine specific surface area of ​​inorganic minerals can be measured according to the description in JIS R 5201:2015.

[0030] The Blaine specific surface area of ​​the pulverized inorganic mineral does not have to change from before pulverization, but may also increase compared to before pulverization. The Blaine specific surface area of ​​the pulverized inorganic mineral is 8000 cm². 2 / g or more, 10000cm 2 / g or more, or 11,000 cm 2 It may be 1 / g or more. This can further improve the strength development of the cement composition. The Blaine specific surface area of ​​the inorganic mineral is, for example, 30,000 cm². 2 / g or less, 28000cm 2 / g or less, or 26,000 cm 2 It may be less than / g. This can reduce grinding costs. An example of the range of Blaine specific surface area for inorganic minerals is, for example, 8000 to 30000 cm². 2 It may also be / g. By setting the Blaine specific surface area of ​​the pulverized material within the above range, it is possible to further improve the strength development of the cement composition while reducing pulverization costs and the time required for pulverization.

[0031] The ratio β of the Blaine specific surface area of ​​the pulverized material to the Blaine specific surface area of ​​the inorganic mineral before pulverization may be 1.00 to 1.50. A Blaine specific surface area ratio β of 1.00 or higher can further enhance the strength development of the cement composition. The Blaine specific surface area ratio β may also be 1.40 or less, 1.30 or less, or 1.20 or less. This can reduce pulverization costs and the time required for pulverization. An example of the range for the Blaine specific surface area ratio β is, for example, 1.00 to 1.40 or 1.00 to 1.30. Having the Blaine specific surface area ratio β within the above range allows for further enhancement of the strength development of the cement composition while reducing pulverization costs and the time required for pulverization.

[0032] Inorganic minerals, when crushed, have a Blaine specific surface area of ​​500 cm². 2 / g or more, or 1000cm 2 The amount may increase by more than / g. By including such pulverized material, the compressive strength of the hardened body can be made sufficiently high. The pulverized inorganic mineral has a Blaine specific surface area of ​​2000 cm². 2 The increase may be less than or equal to / g. The increase in Blaine specific surface area due to the grinding of inorganic minerals is, for example, 500 to 2000 cm². 2 / g is also acceptable.

[0033] The insoluble residue of inorganic minerals and their pulverized products, as measured by the hydrochloric acid-sodium carbonate method specified in JIS R 5202:2010, may be 1-50% by mass, 5-40% by mass, or 10-33% by mass. Having an insoluble residue of 50% by mass or less enhances the reactivity of the inorganic mineral pulverized product, further improving the strength development of the cement composition. Furthermore, from the viewpoint of reducing the labor and cost required to remove impurities that constitute the insoluble residue, the inorganic minerals or their pulverized products may contain 1% by mass or more of insoluble residue.

[0034] The SiO2 content of the inorganic mineral and its pulverized material may be 15-55% by mass, 20-45% by mass, or 25-35% by mass, from the viewpoint of reactivity with Portland cement clinker. The Al2O3 content of the inorganic mineral and its pulverized material may be 15-55% by mass, 20-45% by mass, or 30-40% by mass, from the viewpoint of reactivity with Portland cement clinker.

[0035] In a cement composition, the gypsum content relative to the total amount of the cement composition may be 0.5 to 3.5% by mass, 0.7 to 3.0% by mass, or 0.8 to 2.5% by mass in terms of SO3. Examples of gypsum include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. The gypsum may consist of one type from dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum alone, or a combination of several types. The inclusion of gypsum in the cement composition can adjust the rate of the hydration reaction. The gypsum content can be determined, for example, by determining the sulfur content from chemical analysis using the fundamental parameter method of X-ray fluorescence, based on JIS R 5202:2010 "Chemical Analysis Method of Cement," and then converting the obtained sulfur content to the SO3 content.

[0036] The cement composition may further contain carbonates. The carbonates may be present in the Portland cement from the start, or they may be added from the outside during the preparation of the cement composition. The carbonates can promote the hydration reaction between the Portland cement clinker and inorganic minerals. Examples of carbonates include alkali metal carbonates, alkaline earth metal carbonates, and their hydrates. Specifically, examples include sodium carbonate, sodium carbonate decahydrate (Na2CO3·10H2O), potassium carbonate (K2CO3), calcium carbonate (limestone), and magnesium carbonate. The carbonate may also include sodium sesquicarbonate dihydrate (Na3H(CO3)2·NaHCO3·2H2O).

[0037] As limestone, for example, commercially available limestone powder, granite powder, or other powders mainly composed of calcium carbonate can be used. Preferably, the limestone contains those that conform to the small amount of mixed components described in JIS R 5210:2009 "Portland cement".

[0038] The carbonate content based on the total amount of the cement composition may be 1.0% by mass or more, 2.0% by mass or more, 4.0% by mass or more, or 5.0% by mass or more, from the viewpoint of improving fluidity. The carbonate content in the cement composition may be 14.5% by mass or less, 14.0% by mass or less, 13.0% by mass or less, 11.5% by mass or less, or 9.5% by mass or less, from the viewpoint of sufficiently increasing the compressive strength of the hardened body. An example of the range of carbonate content based on the total amount of the cement composition is, for example, 1.0 to 14.5% by mass.

[0039] The cement composition may contain other components such as inorganic fine powder, calcium hydroxide, calcium-containing powders other than calcium hydroxide, concrete water-reducing agents, accelerators, and retarders (excluding gypsum, carbonates, and inorganic minerals). The inclusion of inorganic fine powder in the cement composition further improves its compressive strength. The content of other components may be 10% by mass or less, 8% by mass or less, or 6% by mass or less, based on the total amount of the cement composition. Examples of inorganic fine powder include powdered materials such as silica and crushed stone. The inorganic fine powder content in the cement composition may be greater than 0% by mass or 5% by mass or more from the viewpoint of fluidity, and 10% by mass or less, 8% by mass or less, or 6% by mass or less from the viewpoint of compressive strength, based on the total amount of the cement composition.

[0040] A hardened body can be prepared by adding water to the above cement composition and allowing it to harden. The hardened body may be a paste containing the above cement composition and water that has been hardened, or it may be mortar or concrete prepared by mixing water and aggregate and allowing it to harden. The hardening conditions are not particularly limited. The hardened body can be prepared in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement". Alternatively, the hardened body can be prepared by the procedure described in the examples.

[0041] From the viewpoint of improving fluidity, the amount of water in the paste may be 25 parts by mass or more, or 40 parts by mass or more, per 100 parts by mass of the total cement composition. From the viewpoint of making it easier to densen the void structure of the hardened body, the amount of water in the paste may be 80 parts by mass or less, or 70 parts by mass or less, per 100 parts by mass of the total cement composition. From the viewpoint of improving fluidity while making it easier to densen the void structure of the hardened body, the water content per 100 parts by mass of the total cement composition may be 25 to 80 parts by mass, or 40 to 70 parts by mass.

[0042] <Method for manufacturing cement composition> A method for producing a cement composition according to one embodiment comprises a grinding step of grinding an inorganic mineral to obtain a pulverized material having a BET specific surface area smaller than that of the inorganic mineral, and a mixing step of mixing Portland cement and the pulverized material, thereby obtaining a cement composition having a pulverized material content of 10 to 50% by mass and a Portland cement content of 50 to 90% by mass.

[0043] In the grinding process, inorganic minerals are ground to obtain a pulverized material having a BET specific surface area smaller than that of the inorganic minerals. In the grinding process, the BET specific surface area of ​​the pulverized material is 180 m². 2 Inorganic minerals may be crushed to a value of less than / g. In the crushing process, from the viewpoint of improving the kneadability, the BET specific surface area of ​​the crushed material should be 160m². 2 / g or less, 140m 2 / g or less, or 120m 2Inorganic minerals may be crushed to a value of less than / g. In the crushing process, from the viewpoint of improving the strength development of the cement composition, the BET specific surface area of ​​the crushed material should be 30 m². 2 / g or more, 40m 2 / g or more, or 50m 2 Inorganic minerals may be crushed to a value of 1 / g or more. In the crushing process, the BET specific surface area of ​​the crushed material is, for example, in the range of 30 to 180 m². 2 Inorganic minerals may be crushed to a value of / g.

[0044] In the grinding process, the inorganic minerals may be ground so that the ratio α of the BET specific surface area of ​​the ground inorganic minerals to the BET specific surface area of ​​the inorganic minerals before grinding is 0.10 to 0.90. By grinding the inorganic minerals so that the ratio α of the BET specific surface area is 0.90 or less, the strength development of the cement composition can be further improved. The inorganic minerals may also be ground so that the ratio α of the BET specific surface area is 0.20 or more, or 0.30 or more. This can reduce grinding costs and the time required for grinding. The inorganic minerals may also be ground so that the range of the BET specific surface area ratio α is, for example, 0.20 to 0.90, or 0.30 to 0.90. By grinding the inorganic minerals so that the ratio α of the BET specific surface area is within the above range, the strength development of the cement composition can be further improved while reducing grinding costs and the time required for grinding.

[0045] In the grinding process, the inorganic minerals may be ground so that the ratio β of the Blaine specific surface area of ​​the ground material to the Blaine specific surface area of ​​the inorganic minerals before grinding is 1.00 to 1.50. By grinding the inorganic minerals so that the ratio β of the Blaine specific surface area is 1.00 or higher, the strength development of the cement composition can be further improved. The inorganic minerals may also be ground so that the ratio β of the Blaine specific surface area is 1.40 or less, 1.30 or less, or 1.20 or less. This can reduce the grinding cost and the time required for grinding. The inorganic minerals may also be ground so that the range of the ratio β of the Blaine specific surface area is, for example, 1.00 to 1.40, or 1.00 to 1.30. By grinding the inorganic minerals so that the ratio β of the Blaine specific surface area is within the above range, the strength development of the cement composition can be further improved while reducing the grinding cost and the time required for grinding.

[0046] In the grinding process, the Blaine specific surface area of ​​the ground material is 500 cm² higher than that of the inorganic mineral before grinding. 2 Inorganic minerals may be crushed to increase the amount by more than 1 / g. The crushing process increases the Blaine specific surface area to 500 cm². 2 / g or more, or 1000cm 2 The amount may increase by more than / g. By including such pulverized material, the compressive strength of the hardened body can be sufficiently increased. The pulverization of the inorganic mineral increases the Blaine specific surface area to 2000 cm². 2 The material may be ground to increase by 500 to 2000 cm² compared to the inorganic mineral before grinding. 2 Inorganic minerals may be crushed to increase the amount per gram.

[0047] Grinding may be carried out using a grinder. Examples of grinders include standard mills, disc mills, vertical roller mills, and roller presses. By adjusting the grinding time, the BET specific surface area, Blaine specific surface area, ratio α, and ratio β of the ground material can be adjusted. From the viewpoint of sufficiently lowering the BET specific surface area of ​​the inorganic mineral and destroying the microstructure to promote the hydration reaction and further enhance the strength development of the cement composition, the grinding time may be 3 minutes or more, or 5 minutes or more. From the viewpoint of suppressing the destruction of reaction sites due to excessive grinding and promoting the hydration reaction to further enhance the strength development of the cement composition, the grinding time may be 20 minutes or less, or 15 minutes or less. The range of grinding time may be, for example, 3 to 20 minutes.

[0048] In the mixing process, Portland cement is mixed with the pulverized material obtained in the grinding process. The mixing process may be carried out using a mixer such as a pan mixer, a tilting drum mixer, or a ribbon mixer. The Portland cement may be a commercially available product, or it may be obtained in a separate process from the grinding process by grinding cement clinker and gypsum.

[0049] In a method for producing a cement composition, in addition to the grinding and mixing steps, any other steps may be included. For example, a sorting step may be included before or after the grinding step. In the sorting step, in order to select inorganic minerals with high strength development, impurities such as sand and scrap iron with large insoluble residues and low reactivity are adjusted in particle size and composition of the inorganic minerals by methods such as sieving, specific gravity sorting, air classification, and magnetic separation. At that time, the sorting may be performed so that the insoluble residue of the inorganic minerals, as measured by the hydrochloric acid-sodium carbonate method specified in JIS R 5202:2010, is 50% by mass or less.

[0050] The description of the above-mentioned embodiment of the <cement composition> also applies to the manufacturing method of this embodiment. Therefore, redundant explanations are omitted.

[0051] The above-described embodiment includes the following:

[0052] [1] A cement composition comprising Portland cement and crushed inorganic minerals, The aforementioned pulverized material has a smaller BET specific surface area than before pulverization. A cement composition having a content of 10 to 50% by mass of the pulverized material and a content of 50 to 90% by mass of the Portland cement. [2] The cement composition according to [1], wherein the inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite. [3] A cement composition comprising Portland cement and crushed inorganic minerals, The inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite. A cement composition having a content of 10 to 50% by mass of the pulverized material and a content of 50 to 90% by mass of the Portland cement. [4] The BET specific surface area of ​​the pulverized material is 180 m². 2 It is less than / g The ratio of the BET specific surface area of ​​the pulverized material to the BET specific surface area of ​​the pulverized material before pulverization is 0.10 to 0.90. The Brain specific surface area is 3000 cm². 2 A cement composition according to any one of [1] to [3], wherein the amount is 1 / g or more. [5] A cement composition according to any one of [1] to [4], wherein the gypsum content is 0.5 to 3.5% by mass in terms of SO3. [6] A cement composition according to any one of [1] to [5], further comprising a carbonate. [7] A grinding step of grinding an inorganic mineral to obtain a pulverized material having a BET specific surface area smaller than that of the inorganic mineral, The process includes a mixing step of mixing Portland cement and the crushed material, The content of the pulverized material is 10-50% by mass, and the content of the Portland cement is 50-90% by mass, and the Blaine specific surface area is 3000 cm². 2 A method for producing a cement composition, which yields a cement composition of 1g or more. [8] Braine specific surface area of ​​3000 cm² 2 A method for producing the cement composition according to [7], to obtain the cement composition of 1 / g or more. [9] A method for producing a cement composition according to [7] or [8], wherein the inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite.

[10] In the grinding process, the BET specific surface area of ​​the ground material is 180 m². 2 A method for producing a cement composition according to any one of [7] to [9], comprising crushing the inorganic mineral to a value of less than or equal to / g.

[11] A method for producing a cement composition according to any one of [7] to

[10] , wherein the inorganic mineral is crushed in the crushing step such that the ratio of the BET specific surface area of ​​the crushed product to the BET specific surface area of ​​the inorganic mineral before crushing is 0.10 to 0.90.

[12] In the grinding process, the Blaine specific surface area of ​​the pulverized material is 500 cm² greater than that of the inorganic mineral before grinding. 2 A method for producing a cement composition according to any one of [7] to

[11] , comprising grinding the inorganic mineral so that the amount increases by more than / g.

[0053] Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above. [Examples]

[0054] The contents of this disclosure will be described in more detail below with reference to examples, comparative examples, and reference examples. However, this disclosure is not limited to the examples described below.

[0055] [Raw materials for cement composition] Ordinary Portland cement (OPC, UBE Mitsubishi Cement Co., Ltd.) was prepared as the Portland cement. The chemical components contained in ordinary Portland cement were determined by chemical analysis using the fundamental parameter method of X-ray fluorescence, as specified in JIS R 5202:2010 "Chemical Analysis Methods for Cement" (equipment used: Rigaku ZSX-100e). In addition, the ignition loss (Ig. loss) was measured according to JIS R 5202:2010, and the Blaine specific surface area was measured according to JIS R 5201:2015 "Physical Testing Methods for Cement". The results are shown in Table 1.

[0056] As inorganic minerals, we prepared clay minerals such as kaolinite, halloysite, or inorganic minerals containing allophane. For the inorganic mineral containing kaolinite, we used kaolin (trade name, manufactured by Nacalai Tesque Co., Ltd.). For the inorganic mineral containing allophane, we used Secard P1 (trade name, manufactured by Shinagawa General Co., Ltd.). For the inorganic mineral containing halloysite, we used dragonite (trade name, manufactured by Applied Minerals).

[0057] The insoluble residue, ignition loss (Ig. loss), and chemical composition of Secard P1 were measured. Ig. loss was measured according to the method of JIS R 5202:2010, and the insoluble residue was measured by the hydrochloric acid-sodium carbonate method. The chemical composition was determined according to JIS R 5202:2010, similar to the chemical composition contained in ordinary Portland cement. The results are shown in Table 2.

[0058] [Table 1]

[0059] [Table 2]

[0060] Each of the inorganic minerals mentioned above was ground for 5 minutes or 15 minutes using a disc mill "GYRO P-6200" (product name, manufactured by Ito Seisakusho Co., Ltd.) to prepare pulverized inorganic minerals. 25g of inorganic mineral was fed into the disc mill, and grinding was performed at room temperature (approximately 25°C). In Tables 3 to 5, A-1, B-1, and C-1 represent unground inorganic minerals, A-2, B-2, and C-2 represent inorganic minerals ground for 5 minutes, and A-3, B-3, and C-3 represent inorganic minerals ground for 15 minutes.

[0061] The density, BET specific surface area, and Blaine specific surface area of ​​the inorganic minerals before and after grinding were determined. Density was determined using an automatic densimeter (instrument: MAT-7000, Seishin Corporation). BET specific surface area was calculated using a BET multipoint method with nitrogen gas using a BELSORP MINI (product name) manufactured by Microtrac-Bel, based on the measurement results of nitrogen gas adsorption in the relative pressure range of 0.05 to 0.35. Blaine specific surface area was measured in accordance with the description in JIS R 5201:2015. From the obtained BET specific surface area and Blaine specific surface area values ​​of the inorganic minerals before and after grinding, the ratio α of the BET specific surface area of ​​the ground material to the BET specific surface area of ​​the inorganic minerals before grinding, and the ratio β of the Blaine specific surface area of ​​the ground material to the Blaine specific surface area of ​​the inorganic minerals before grinding were determined. The BET specific surface area and Blaine specific surface area of ​​the inorganic minerals before and after grinding (ground material) are shown in Table 3.

[0062] [Table 3]

[0063] As shown in Table 3, both Secard P1 and dragonite showed a decrease in BET specific surface area upon grinding. Furthermore, the Blaine specific surface area of ​​both inorganic minerals either remained unchanged or increased compared to before grinding. Therefore, it was confirmed that while grinding of Secard P1 and dragonite resulted in finer particles, it also destroyed the microstructure within the powder. On the other hand, when kaolin was ground under the same conditions as Secard P1 and dragonite, its BET specific surface area increased upon grinding.

[0064] [Preparation of cement composition] To the ordinary Portland cement shown in Table 1, inorganic minerals (before or after grinding) were added and mixed according to the formulations shown in Table 4 to prepare the cement compositions of Examples 1-10, Comparative Examples 1-5, and Reference Examples 1-10. Examples 1-10 are cement compositions containing ground inorganic minerals including allophane or halloysite. Comparative Examples 1-5 are cement compositions containing inorganic minerals before grinding, including allophane or halloysite. Reference Example 1 is a cement composition that does not contain inorganic minerals. Reference Examples 2-10 are cement compositions containing kaolinite.

[0065] [Preparation of hardened material] To the prepared cement composition, sand (No. 6 sand) was mixed as fine aggregate in a mass ratio of 1:2. Furthermore, water was added to 100 parts by mass of the cement composition in an amount of 65 parts by mass. After mixing with a hand mixer for 1 minute, the mixture was packed into a mold measuring 1 cm x 1 cm x 6 cm (length x width x height). The mixture was cured in water in a constant temperature chamber at 20°C for 7, 28, or 91 days, and after the predetermined curing period, the mold was removed to prepare the hardened body.

[0066] [Measurement of Compression Strength Ratio] In accordance with JIS R 5201:2015, the compressive strengths of the hardened bodies described above were measured at 7, 28, and 91 days of age. The results are shown in Table 4. Two types of compressive strength ratios were calculated: the ratio of the compressive strength to the hardened body in Reference Example 1, which does not contain inorganic minerals, and the ratio of the compressive strength to the hardened body of the comparative example containing inorganic minerals before pulverization. The results are shown in Table 5.

[0067] [Measurement of Braine specific surface area] The density and Blaine specific surface area of ​​the cement compositions of Examples 5, 6, 9, and 10, and Comparative Examples 3 and 5 were determined. Density was determined using an automatic densimeter (equipment: MAT-7000, Seishin Corporation). Blaine specific surface area was determined in accordance with the description in JIS R 5201:2015. In addition, the Blaine specific surface area of ​​the cement compositions of Examples 1 to 10 and Comparative Examples 1 to 5 was calculated using the following formula (1). The results are shown in Table 6. (Blaine specific surface area of ​​cement composition) = (Blaine specific surface area of ​​ordinary Portland cement) × (content of ordinary Portland cement) + (Blaine specific surface area of ​​inorganic mineral) × (content of inorganic mineral) (1)

[0068] [Table 4]

[0069] [Table 5]

[0070] [Table 6]

[0071] Comparative Examples 2, 3, 5, and Reference Example 8, shown in shaded areas in Tables 4 and 5, solidified rapidly when water was added to the cement composition, making mixing impossible and preventing the preparation of a hardened body. However, even with the same formulation, when the inorganic mineral was added to the cement composition as a pulverized material, a hardened body could be prepared in all examples. Furthermore, it was confirmed that all hardened bodies exhibited excellent strength development. It was confirmed that cement compositions containing pulverized inorganic minerals, which have a smaller BET specific surface area after pulverization than before pulverization, exhibit excellent strength development comparable to cement compositions containing kaolinite. Therefore, cement compositions containing pulverized inorganic minerals, which have a smaller BET specific surface area after pulverization, have compressive strength equivalent to hardened bodies containing kaolinite, resulting in a low-carbon hardened body with reduced cement clinker content.

Claims

1. A cement composition comprising Portland cement and crushed inorganic minerals, The aforementioned pulverized material has a smaller BET specific surface area than before pulverization. A cement composition having a content of 10 to 50% by mass of the pulverized material and a content of 50 to 90% by mass of the Portland cement.

2. The cement composition according to claim 1, wherein the inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite.

3. A cement composition comprising Portland cement and crushed inorganic minerals, The inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite. A cement composition having a content of 10 to 50% by mass of the pulverized material and a content of 50 to 90% by mass of the Portland cement.

4. The BET specific surface area of ​​the aforementioned pulverized material is 180 m². ２ / g or less, The ratio of the BET specific surface area of ​​the pulverized material to the BET specific surface area of ​​the pulverized material before pulverization is 0.10 to 0.

90. Brain specific surface area is 3000 cm² ２ A cement composition according to any one of claims 1 to 3, wherein the amount is 1 / g or more.

5. The gypsum content is SO ３ A cement composition according to any one of claims 1 to 3, wherein the amount is 0.5 to 3.5% by mass when converted.

6. The cement composition according to any one of claims 1 to 3, further comprising a carbonate.

7. A grinding step of grinding an inorganic mineral to obtain a pulverized material having a BET specific surface area smaller than that of the inorganic mineral, The process includes a mixing step of mixing Portland cement and the crushed material, A method for producing a cement composition, wherein the content of the pulverized material is 10 to 50% by mass, and the content of the Portland cement is 50 to 90% by mass.

8. Brain specific surface area is 3000 cm² ２ A method for producing the cement composition according to claim 7, which yields the cement composition of 1g or more.

9. A method for producing a cement composition according to claim 7 or 8, wherein the inorganic mineral comprises at least one selected from the group consisting of allophane, halloysite, and imogolite.

10. In the aforementioned grinding process, the BET specific surface area of ​​the ground material is 180 m². ２ A method for producing a cement composition according to claim 7 or 8, wherein the inorganic mineral is crushed to a value of less than or equal to / g.

11. The method for producing a cement composition according to claim 7 or 8, wherein in the grinding step, the inorganic mineral is ground so that the ratio of the BET specific surface area of ​​the ground product to the BET specific surface area of ​​the inorganic mineral before grinding is 0.10 to 0.

90.

12. In the aforementioned grinding process, the Blaine specific surface area of ​​the pulverized material is 500 cm² higher than that of the inorganic mineral before grinding. ２ A method for producing a cement composition according to claim 7 or 8, wherein the inorganic mineral is crushed so that the amount increases by 1 / g or more.

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