Cement composition and manufacturing method of hydraulic composition

Abstract

To provide a cement composition including a cement admixture, thereby enabling reduction of amount of use of a cement clinker and nonetheless enabling suppression of propagation of neutralization.SOLUTION: A cement composition is provided which includes a clinker ground product, gypsum, a cement admixture, and a neutralization retardant. In the cement composition, the neutralization retardant is at least one of amines and a thickener and a content of a clinker ground product in the cement composition is 90 mass% or under. A hydraulic composition is also provided which includes the cement composition, water, and an aggregate. A manufacturing method of the hydraulic composition is also provided, the manufacturing method includes: a powder type blend product preparation step of blending a clinker ground product, gypsum, and a cement admixture, thereby obtaining a powder type blend product; and a hydraulic composition preparation step of blending the powder type blend product, a neutralization retardant, water, and an aggregate, thereby preparing a hydraulic composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement composition and a method for producing a hydraulic composition containing the cement composition. [Background technology]

[0002] Currently, measures to combat global warming are calling for a significant reduction in carbon dioxide emissions, even in the cement manufacturing industry. Most of the carbon dioxide emissions in the cement manufacturing industry are generated during the production of cement clinker, and in order to reduce carbon dioxide emissions, there is a need to reduce the amount of cement clinker produced. Blended cement, which has a lower cement clinker ratio, is known as a cement that can reduce the amount of cement clinker used. Blended cement has a lower CO2 emission intensity during production, making it more environmentally friendly than Portland cement. As an example of a mixed cement using a reduced amount of cement clinker, Patent Document 1 describes a powdery mixed cement composition containing cement clinker powder, gypsum, ground granulated blast furnace slag, and limestone powder, characterized in that, relative to a total amount of 100% by mass of the cement clinker powder, ground granulated blast furnace slag, and limestone powder, the proportion of the cement clinker powder is 42 to 59% by mass, the proportion of the ground granulated blast furnace slag powder is 27 to 55% by mass, and the proportion of the limestone powder is 2 to 26% by mass, and the mass ratio of the ground granulated blast furnace slag powder to the limestone powder (ground granulated blast furnace slag / limestone powder) is 1.4 to 25.0. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-155004 Summary of the Invention [Problem to be solved by the invention]

[0004] Cement compositions containing cement admixtures have a problem in that they are prone to carbonation, and therefore concrete and the like using cement compositions containing cement admixtures has a high risk of rebar corrosion. An object of the present invention is to provide a cement composition that contains a cement admixture, thereby reducing the amount of cement clinker used and suppressing the progress of carbonation. [Means for solving the problem]

[0005] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by a cement composition containing ground clinker, gypsum, a cement admixture, and a carbonation inhibitor which is at least one of an amine and a thickener, and in which the ground clinker content is 90 mass% or less, and have completed the present invention. That is, the present invention provides the following [1] to [8]. [1] A cement composition comprising ground clinker, gypsum, a cement admixture, and a carbonation inhibitor, wherein the carbonation inhibitor is at least one of an amine and a thickener, and the content of the ground clinker in the cement composition is 90 mass% or less. [2] The cement composition according to [1], wherein the cement admixture is one or more selected from ground granulated blast furnace slag, silica admixture, fly ash, limestone fine powder, and calcined clay, and the amount of the cement admixture is 5 parts by mass or more per 100 parts by mass of the total amount of the ground clinker and the gypsum. [3] The cement composition according to [2], wherein the cement admixture is limestone fine powder and calcined clay, and the amount of the cement admixture is 5 to 240 parts by mass per 100 parts by mass of the total amount of the ground clinker and the gypsum. [4] The cement composition according to any one of [1] to [3], wherein the amount of the carbonation inhibitor is 0.1 to 10 parts by mass per 100 parts by mass of the total amount of the clinker pulverized material, the gypsum, and the cement admixture.

[0006] [5] The cement composition according to any one of [1] to [4], wherein the amines are water-soluble amines and the thickener is a glycol-based thickener. [6] The cement composition according to [5], wherein the amine is at least one of methyldiethanolamine and hydroxyethylpiperazine, and the thickener is polyethylene glycol. [7] A hydraulic composition comprising the cement composition according to any one of [1] to [6] above, water, and an aggregate. [8] A method for producing the hydraulic composition according to [7] above, comprising: a powdered mixture preparation step of mixing the clinker pulverized material, the gypsum, and the cement admixture to obtain a powdered mixture; and a hydraulic composition preparation step of mixing the powdered mixture, the carbonation inhibitor, the water, and the aggregate to prepare the hydraulic composition. [Effects of the Invention]

[0007] According to the cement composition of the present invention, by including a cement admixture, the amount of cement clinker used can be reduced, and the amount of cement clinker produced can be reduced, thereby reducing carbon dioxide emissions in cement production. Furthermore, the cement composition of the present invention can suppress the progress of carbonation despite containing a cement admixture. DETAILED DESCRIPTION OF THE INVENTION

[0008] The cement composition of the present invention is a cement composition comprising ground clinker, gypsum, a cement admixture, and a carbonation inhibitor, wherein the carbonation inhibitor is at least one of an amine and a thickener, and the content of ground clinker in the cement composition is 90 mass% or less. A detailed explanation is provided below. [Clinker crushing material] The ground clinker used in the present invention is obtained by grinding cement clinker, which is the main raw material for cement. The cement clinker is not particularly limited, and examples thereof include Portland cement clinker used in various Portland cements such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement, and cement clinker used in mixed cements such as blast-furnace cement, fly ash cement, and silica cement.

[0009] The content of the ground clinker in the cement composition is 90% by mass or less, preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and particularly preferably 45 to 65% by mass. If the content exceeds 90% by mass, the object of the present invention of reducing carbon dioxide emissions in cement production by reducing the amount of cement clinker used and the amount of cement clinker produced cannot be achieved. In addition, since the neutralization of hydraulic compositions containing the cement composition is unlikely to progress, there is little need to consider the inhibition of carbonation. If the content is 30% by mass or more, the strength development of the cement composition can be further improved. The Blaine specific surface area of ​​the ground clinker is preferably 2,500 to 6,000 cm 2 / g, more preferably 2,800 to 5,500 cm 2 / g, particularly preferably 3,000 to 5,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,500 cm 2 / g or more, the strength development of the cement composition is further improved. 2 / g or less, the labor required to produce ground clinker will not be excessive. In this specification, the Blaine specific surface area can be measured by a method in accordance with "JIS R 5201 (Physical testing methods for cement)".

[0010] [plaster] The type of gypsum used in the present invention is not particularly limited, and examples thereof include natural gypsum dihydrate, flue gas desulfurization gypsum (flue gas desulfurization gypsum), phosphate gypsum, titanic gypsum, and hydrofluoric gypsum. These may be used alone or in combination of two or more. Examples of the form of gypsum (whether hydrated or not) include gypsum dihydrate, gypsum hemihydrate, and anhydrous gypsum. These may consist of only one form, or may include two or more forms. The amount of gypsum is such that the gypsum content in the cement composition (calculated as SO3) is preferably 0.2 to 5.0 mass%, more preferably 0.5 to 4.0 mass%, and particularly preferably 1.0 to 3.5 mass%. If the content is 0.2 mass% or more, the usable time before hardening (the time during which good fluidity can be maintained) of concrete containing the cement composition is extended. If the content is 5.0 mass% or less, the strength development of the cement composition is improved.

[0011] Gypsum is usually in powder form. When a powder mixture preparation step is performed in which ground clinker, gypsum, and a cement admixture are mixed to obtain a powder mixture, it is preferable to prepare the gypsum in advance so that the Blaine specific surface area falls within a specific numerical range. The preferred Blaine specific surface area of ​​the gypsum is preferably 2,500 to 6,000 cm 2 / g, more preferably 2,800 to 5,500 cm 2 / g, particularly preferably 3,000 to 5,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,500 cm 2 / g or more, the strength development of the cement composition is further improved. 2 / g or less, the labor required to crush the gypsum is not excessive. When the coarsely crushed cement clinker and uncrushed gypsum are crushed simultaneously in the powdery mixture preparation step, the Blaine specific surface area of ​​the powdery mixture only needs to be within a suitable numerical range described below, and the Blaine specific surface area of ​​the gypsum does not necessarily need to be within the above numerical range. In the present invention, the ground clinker and gypsum may be any of the above-mentioned various Portland cements and blended cements. In addition, gypsum other than that contained in cement may be used for the purpose of adjusting the gypsum content in the cement composition.

[0012] [Cement mixture] The cement admixture used in the present invention is one or more selected from ground granulated blast furnace slag, siliceous admixture, fly ash, limestone fine powder, and calcined clay. Among them, ground granulated blast furnace slag is preferred from the viewpoint of carbonation inhibition and strength development. Furthermore, at least one of limestone fine powder and calcined clay may be used as the cement admixture. Cement compositions containing at least one of limestone fine powder and calcined clay (for example, limestone-calcined clay cement) have low fluidity, so it is usually necessary to take measures such as increasing the amount of water blended. When the amount of water blended is increased, bleeding tends to occur more easily. However, according to the cement composition of the present invention, bleeding can be suppressed even in cement compositions containing at least one of limestone and calcined clay. Furthermore, it is more preferable to use both limestone fine powder and calcined clay from the viewpoint of improving the strength development of the cement composition in addition to the above reasons. The cement mixture is usually in a powder form. The Blaine specific surface area of ​​the cement mixture (when the cement mixture is made of a plurality of types of raw materials, the mixture obtained by mixing the plurality of types of raw materials) is preferably 2,500 to 30,000 cm 2 / g, more preferably 3,000 to 25,000 cm 2 / g, particularly preferably 4,000 to 10,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,500 cm 2 / g or more, the strength development of the cement composition is further improved. 2 If the saturation is 0.05 to 0.15 g / g or less, the labor required to grind the cement mixture will not be excessive.

[0013] Examples of finely ground blast furnace slag include granulated slag, which is obtained by rapidly cooling molten slag, a by-product of pig iron production in a blast furnace, with water and then crushing it, and slowly cooled slag, which is obtained by slowly cooling the molten slag and then crushing it. The Blaine specific surface area of ​​the ground granulated blast furnace slag is preferably 2,500 to 10,000 cm 2 / g, more preferably 3,500 to 9,000 cm 2 / g, particularly preferably 4,000 to 8,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,500 cm 2 / g or more, the strength development of the cement composition is further improved. 2 If the slag content is 0.1g or less, the labor required to crush the blast furnace slag will not be excessive. Examples of siliceous admixtures include those containing silicon dioxide in a proportion of preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more. Specific examples include silica fume, silica dust, and volcanic glass fine powder. Among these, silica fume is preferred from the viewpoint of ease of availability. The BET specific surface area of ​​the silica admixture is preferably 15 to 35 m from the viewpoint of availability. 2 / g. If the BET specific surface area is within the above range, the strength development of the cement composition is further improved. The BET specific surface area can be measured, for example, by a method in accordance with "JIS Z 8830 (Method for measuring the specific surface area of ​​powder (solid) by gas adsorption)".

[0014] The Blaine specific surface area of ​​fly ash is set to 2,000 to 10,000 cm from the viewpoint of ease of availability. 2 / g, more preferably 2,500 to 8,000 cm 2 / g, and particularly preferably 3,000 to 6,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,000 cm 2 / g or more, the strength development of the cement composition is further improved. The Blaine specific surface area of ​​the limestone fine powder is preferably 2,500 to 10,000 cm 2 / g, more preferably 3,000 to 8,000 cm 2 / g, and particularly preferably 4,000 to 6,000 cm 2 / g. The specific surface area of ​​the above Blaine is 2,500 cm 2 / g or more, the strength development of the cement composition is further improved. 2 If the amount is less than 1 / g, the labor required to crush the limestone will not be excessive.

[0015] Calcined clay is clay that has been calcined. Examples of calcined clay include clay minerals such as kaolin, montmorillonite, allophane, illite, smectite, imogolite, glauconite, chlorite, talc, and zeolite. Among these, from the viewpoint of high activity, kaolin and montmorillonite are preferred as clay minerals, and kaolin is more preferred. These may be contained alone or in combination of two or more. The Blaine specific surface area of ​​the fired clay is preferably 5,000 to 30,000 cm 2 / g, more preferably 8,000 to 28,000 cm 2 / g, particularly preferably 10,000 to 26,0000 cm 2 / g. The specific surface area of ​​the above Blaine is 5,000 cm 2 / g or more, the strength development of the cement composition is further improved. 2 If the particle size is 1 / g or less, the labor required to crush the fired clay will not be excessive.

[0016] The amount of cement admixture is preferably 5 parts by mass or more, more preferably 10 to 240 parts by mass, even more preferably 15 to 150 parts by mass, even more preferably 20 to 100 parts by mass, and particularly preferably 30 to 80 parts by mass, relative to 100 parts by mass of the total amount of the ground clinker and gypsum. If the amount is 5 parts by mass or more, the amount of ground clinker can be relatively reduced, and carbon dioxide emissions in cement production can be further reduced. If the amount is 240 parts by mass or less, the strength development of the cement composition can be further improved. Furthermore, the content of the cement admixture in the cement composition is preferably 10% by mass or more, more preferably 15 to 80% by mass, more preferably 20 to 60% by mass, even more preferably 30 to 50% by mass, and particularly preferably 35 to 45% by mass. If the content is 10% by mass or more, the amount of ground clinker can be relatively reduced, and carbon dioxide emissions in cement production can be further reduced. If the amount is 80% by mass or less, the strength development of the cement composition can be further improved. When two or more cement admixtures are used, the above amount and content are the total of the two or more cement admixtures.

[0017] [Powder mixture] The powder mixture obtained by mixing the clinker pulverized material, gypsum, and cement admixture (hereinafter also referred to as "powder mixture") preferably has a Blaine specific surface area of ​​2,000 to 20,000 cm 2 / g, more preferably 2,500 to 15,000 cm 2 / g, particularly preferably 3,000 to 12,000 cm 2 / g. The value is 2,000 cm 2 / g or more, the strength development of the cement composition is further improved. 2 / g or less, the fluidity of the cement composition is further improved, and the labor required for pulverization to obtain a powder having such a particle size is reduced.

[0018] The carbonation inhibitor used in the present invention is at least one of an amine and a thickener. By using the carbonation inhibitor, the progress of carbonation of concrete containing the cement composition can be suppressed. As the amines, water-soluble amines are preferred from the viewpoint of dispersibility during mixing. Examples of water-soluble amines include methyldiethanolamine (MDEA), hydroxyethylpiperazine (HEPZ), monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diglycolamine (DGA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), etc. These may be used alone or in combination of two or more. Among these, methyldiethanolamine and hydroxyethylpiperazine are more preferred from the viewpoint of being able to further suppress neutralization, and methyldiethanolamine is particularly preferred from the viewpoint of being able to suppress neutralization with a smaller amount. Amines are compounds that have an amino group in the molecule. When they have a hydrophilic group such as a hydroxyl group, they are often water-soluble.

[0019] Examples of thickeners include glycol-based thickeners such as polyethylene glycol; cellulose-based thickeners such as methylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose; acrylic-based thickeners such as acrylamide homopolymers and acrylamide copolymers; polyvinyl compounds such as polyvinyl alcohol; biopolymer-based thickeners such as galactomannan, alginic acid, β-1,3 glucan, pullulan, welan gum, xanthan gum, guar gum, carrageenan, and pectin; amino acid-based thickeners, etc. These may be used alone or in combination of two or more. Among these, glycol-based thickeners are preferred, and polyethylene glycol is more preferred, from the viewpoint of being able to further suppress neutralization, etc. The molecular weight of polyethylene glycol is preferably 5,000 to 15,000, more preferably 8,000 to 12,000, from the viewpoint of easy availability and suppressing neutralization.

[0020] The amount of at least one of the amines and the thickener varies depending on the type of amine and the thickener, but is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, even more preferably 0.3 to 6 parts by mass, even more preferably 0.5 to 5 parts by mass, even more preferably 0.6 to 2.5 parts by mass, and particularly preferably 0.8 to 1.2 parts by mass, relative to 100 parts by mass of the total amount of ground clinker, gypsum, and cement admixture. By keeping the amount within the above numerical range, carbonation of concrete containing the cement composition can be further suppressed. Furthermore, if the amount is 10 parts by mass or less, the cost of the carbonation inhibitor can be reduced.

[0021] The hydraulic compositions of paste, mortar and concrete containing the above-mentioned cement composition are excellent in carbonation inhibition properties. [Hydraulic composition] The hydraulic composition of the present invention contains the above-mentioned cement composition, water, and aggregate. The water is not particularly limited, and examples thereof include tap water and recycled water as specified in "JIS A 5308:2019 (Ready-mixed concrete)". The amount of water to be added may be adjusted as appropriate depending on the desired fluidity and the type of cement admixture. For example, the amount is such that the mass ratio of water to powdery mixture (water / powdery mixture) is preferably 0.2 to 0.6, and more preferably 0.3 to 0.55. Furthermore, when the cement admixture is at least one of limestone and calcined clay, in order to ensure fluidity, the amount of water to be added is an amount such that the mass ratio of water to the powdered mixture (water / powdered mixture) is preferably 0.45 to 0.65, more preferably 0.47 to 0.53.

[0022] The aggregate may be fine aggregate alone or a combination of fine and coarse aggregate. Natural aggregate, artificial aggregate, or recycled aggregate may all be used. The fine aggregate is not particularly limited, and examples thereof include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, limestone aggregate, slag fine aggregate, lightweight fine aggregate, clinker fine aggregate, and CCU fine aggregate (fine aggregate in which carbon dioxide is fixed in one or more selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag), etc. These may be used alone or in combination of two or more.

[0023] The coarse aggregate is not particularly limited, and examples thereof include river gravel, mountain gravel, land gravel, sea gravel, crushed stone, limestone aggregate, slag coarse aggregate, lightweight coarse aggregate, clinker coarse aggregate, and CCU coarse aggregate (coarse aggregate in which carbon dioxide is fixed in one or more selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag), etc. These may be used alone or in combination of two or more. When the hydraulic composition contains coarse aggregate, the fine aggregate ratio (s / a) is preferably 5 to 70%, more preferably 10 to 60%, and particularly preferably 20 to 50%. If the fine aggregate ratio is within the above range, the workability and ease of molding of mortar or concrete are improved. The content of aggregate in the hydraulic composition (the total amount when fine aggregate and coarse aggregate are used in combination) is preferably 200 to 750 parts by mass, more preferably 250 to 600 parts by mass, per 100 parts by mass of the powdery mixture. If the content is within the above range, the strength of the set body of the hydraulic composition will be greater and the shrinkage rate of the set body will be smaller. Furthermore, the hydraulic composition may contain various admixtures, such as a water-reducing agent, an air-entraining water-reducing agent, a high-performance water-reducing agent, a high-performance air-entraining water-reducing agent, a cement dispersant such as a superplasticizer, an air-entraining agent, and a shrinkage-reducing agent, as needed.

[0024] [Method for producing hydraulic composition] An example of a method for producing the above-mentioned hydraulic composition includes a powdery mixture preparation step of mixing pulverized clinker, gypsum, and a cement admixture to obtain a powdery mixture, and a hydraulic composition preparation step of mixing the powdery mixture, a carbonation inhibitor, water, and aggregate to prepare a hydraulic composition. In the powdery mixture preparation step, the coarsely crushed cement clinker, uncrushed gypsum, and uncrushed cement admixture (e.g., granulated blast furnace slag) or cement admixture may be simultaneously crushed and mixed to prepare the powdery mixture. In addition, in the hydraulic composition preparation process, the carbonation inhibitor is usually mixed with water in advance, and then the resulting liquid mixture is mixed with other materials such as a powder mixture.

[0025] Another example of the method for producing the hydraulic composition described above includes a method including a cement composition preparation step of simultaneously grinding and mixing coarsely crushed cement clinker, uncrushed gypsum, and an uncrushed cement admixture (e.g., granules of blast furnace slag) or a cement admixture and a carbonation inhibitor to prepare a cement composition, and a hydraulic composition preparation step of mixing the cement composition, water, and aggregate to prepare a hydraulic composition. In this method, the carbonation inhibitor can also serve as a grinding aid.

[0026] The cement composition of the present invention includes not only a mixture obtained by mixing ground clinker, gypsum, a cement admixture, and a carbonation inhibitor, but also a combination of a powdery mixture (premix) of ground clinker, gypsum, and a cement admixture with a carbonation inhibitor, in which the powdery mixture (premix) and the carbonation inhibitor are mixed when preparing a hydraulic composition such as concrete. [Example]

[0027] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Portland cement: Taiheiyo Cement Corporation, ordinary Portland cement (gypsum content (SO3 equivalent): 1.50 mass%), Blaine specific surface area: 3,260 cm 2 / g (2) Blast furnace cement (powder mixture A); manufactured by Taiheiyo Cement Corporation, blast furnace cement type B (granulated blast furnace slag content: 42.5% by mass, gypsum content (SO3 equivalent): 1.315% by mass), Blaine specific surface area: 3,760 cm 2 / g (3) Cement mixture A: limestone fine powder (shown as "limestone" in Table 1), Blaine specific surface area: 4,950 cm 2 / g (4) Cement mixture B: Calcined clay A (gypsum content (SO3 equivalent): 6.64 mass%), Blaine specific surface area: 20,910 cm 2 / g, calcined kaolin (5) Cement mixture C; calcined clay B (not containing gypsum), Blaine specific surface area: 25,290 cm 2 / g, calcined kaolin (6) Neutralization inhibitor A (amines): hydroxyethylpiperazine (referred to as “HEPZ” in Tables 2 and 3). (7) Neutralization inhibitor B (amines): methyldiethanolamine (referred to as “MDEA” in Tables 2 and 3). (8) Neutralization inhibitor C (thickener): polyethylene glycol (referred to as “PEG” in Tables 2 and 3), average molecular weight: 10,000 (9) Fine aggregate: Standard sand for cement strength test table

[0028] [Production of Powdered Mixture B] Ordinary Portland cement, limestone powder, calcined clay A, and calcined clay B were mixed in the amounts shown in Table 1 to prepare powder mixture B (clinker pulverized material content: 56% by mass, gypsum content (SO3 equivalent): 0.93% by mass, cement admixture content: 37% by mass, Blaine specific surface area: 8,710 cm). 2 / g) was produced.

[0029] [Table 1]

[0030] [Examples 1 to 12] A hydraulic composition (mortar) was prepared in accordance with JIS R 5201:2015 (Physical Testing Methods for Cement) using the types and amounts of materials shown in Table 2. Specifically, a liquid mixture prepared by mixing water and a carbonation inhibitor in advance and a powder mixture were charged into a mixer, and then the mixture was mixed at low speed for 30 seconds. Next, while mixing at low speed, fine aggregate was charged over 30 seconds, and after charging, the mixture was mixed at high speed for 30 seconds. After that, mixing was paused for 90 seconds, and the mixture adhering to the inner wall of the mixer was scraped off within the first 30 seconds of the pause. After the pause, the mixture was further mixed at high speed for 60 seconds to prepare the hydraulic composition. The resulting hydraulic composition was poured into a rectangular formwork with internal dimensions of 4 x 4 x 16 cm, subjected to moist air curing for 24 hours, and then demolded to obtain a test specimen. After demolding, the specimen was subjected to carbonation curing in an environment of 20°C, 60% relative humidity, and 5% by volume of carbon dioxide. After casting, the carbonation depth at 7, 14 and 28 days, as well as the compressive strength and flexural strength at 28 days, were measured according to the following methods.

[0031] [Measurement of neutralization depth] The carbonation depth of the specimen was measured as follows: The specimen was broken at half its longitudinal length, and a phenolphthalein solution was sprayed onto the fractured surface of one specimen. The carbonation depth of the specimen was measured as the average length from the four sides (top, bottom, left, and right) of the specimen in the vertical direction to the reddish-purple colored area inside the fractured surface. If the specimen was completely carbonated, the carbonation depth would be 20.0 mm. [Compression strength measurement] The compressive strength of the fractured specimens used to measure the carbonation depth was measured in accordance with JIS R 5201:2015 (Physical testing methods for cement). [Bending strength measurement] The bending strength of the fractured specimens used to measure the carbonation depth was measured in accordance with JIS R 5201:2015 (Physical testing methods for cement).

[0032] [Comparative Examples 1 to 2] A test specimen was prepared in the same manner as in Example 1 except that no carbonation inhibitor was used, and the carbonation depth and other parameters were measured. [Reference example 1] Test specimens were prepared in the same manner as in Example 1, except that ordinary Portland cement was used as the cement composition, and the carbonation depth and other parameters were measured. The results are shown in Table 2.

[0033] [Table 2]

[0034] From Table 2, it can be seen that the carbonation depths of Examples 1 to 6 at 7 and 14 days of age (7 days of age: 3.9 to 9.4 mm, 14 days of age: 5.2 to 13.2 mm) are smaller than the carbonation depths of Comparative Example 1 at 7 and 14 days of age (7 days of age: 9.7 mm, 14 days of age: 15.3 mm). In addition, the carbonation depths of Examples 1 to 2 and 5 to 6 at 28 days of age (7.8 to 11.8 mm) are smaller than the carbonation depth of Comparative Example 1 at 28 days of age (20.0 mm), and it can be seen that carbonation is suppressed in the specimens of Examples 1 to 6 compared to Comparative Example 1. It can also be seen that the carbonation depth (7.3 to 10.4 mm) of Examples 7 to 12 at an age of 7 days is smaller than the carbonation depth (12.5 mm) of Comparative Example 2 at an age of 7 days. It can also be seen that the carbonation depth (13.1 to 17.4 mm) of Examples 7 to 10 and 12 at an age of 14 days is smaller than the carbonation depth (20.0 mm) of Comparative Example 2 at an age of 14 days, and it can be seen that carbonation is suppressed in the specimens of Examples 7 to 10 and 12 compared to Comparative Example 2.

[0035] [Examples 13 to 17] A hydraulic composition (paste) was prepared using the types and amounts of materials shown in Table 3. Specifically, a liquid mixture prepared by previously mixing water and a carbonation inhibitor and a powder mixture were added, and then the mixture was kneaded at low speed for 60 seconds and at high speed for 30 seconds. After that, mixing was paused for 90 seconds, and the kneaded material adhering to the inner wall of the mixer was scraped off within the first 30 seconds of the pause. After the pause, the mixture was kneaded at high speed for an additional 60 seconds to prepare the hydraulic composition. The final bleeding rate of the obtained hydraulic composition was measured in accordance with "JSCE-F522." The final bleeding rate was calculated using the following formula. The lower the final bleeding rate, the less likely the material is to bleed. Final bleeding rate (%) = (B´ / V) x 100 (In the formula, B' is the amount of water (mL) due to bleeding after 20 hours or more have elapsed, and V is the volume of the mortar (mL).) Comparative Example 3 A hydraulic composition (paste) was prepared in the same manner as in Example 13 except that no carbonation inhibitor was used, and then the final bleeding rate was measured in accordance with "JSCE-F522". The results of the measured bleeding rates are shown in Table 3.

[0036] [Table 3]

[0037] From Table 3, it can be seen that the final bleeding rates of Examples 13 to 15 were smaller than that of Comparative Example 3, and that bleeding was suppressed in the specimens of Examples 13 to 15 compared to Comparative Example 3. Furthermore, the final bleeding rates of Examples 16 and 17 were smaller than that of Comparative Example 4, and that bleeding was suppressed in the specimens of Examples 16 and 17 compared to Comparative Example 4.

Claims

1. A cement composition comprising ground clinker, gypsum, a cement admixture, and a carbonation inhibitor, the neutralization inhibitor is at least one of an amine and a thickener, A cement composition characterized in that the content of the ground clinker in the cement composition is 90 mass % or less.

2. 2. The cement composition according to claim 1, wherein the cement admixture is one or more selected from the group consisting of ground granulated blast furnace slag, siliceous admixture, fly ash, limestone fine powder, and burnt clay, and the amount of the cement admixture is 5 parts by mass or more per 100 parts by mass of the total amount of the ground clinker and the gypsum.

3. The cement admixture is limestone fine powder and calcined clay, and the amount of the cement admixture is 5 to 240 parts by mass per 100 parts by mass of the total amount of the clinker pulverized material and the gypsum. The cement composition according to claim 2.

4. The cement composition according to claim 1, wherein the amount of the carbonation inhibitor is 0.1 to 10 parts by mass per 100 parts by mass of the total amount of the clinker pulverized material, the gypsum, and the cement admixture.

5. 2. The cement composition according to claim 1, wherein the amines are water-soluble amines and the thickener is a glycol-based thickener.

6. 6. The cement composition according to claim 5, wherein the amine is at least one of methyldiethanolamine and hydroxyethylpiperazine, and the thickener is polyethylene glycol.

7. A hydraulic composition comprising the cement composition according to any one of claims 1 to 6, water, and aggregate.

8. A method for producing the hydraulic composition according to claim 7, comprising: a powdery mixture preparation step of mixing the ground clinker, the gypsum, and the cement admixture to obtain a powdery mixture; a hydraulic composition preparation step of mixing the powdery mixture, the carbonation inhibitor, the water, and the aggregate to prepare the hydraulic composition; A method for producing a hydraulic composition comprising the steps of:

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