Cement composition and method for producing the same

Abstract

To provide a cement composition in which a part of cement is substituted with an admixture such as blast furnace slag fine powder, and which is excellent in initial strength developability as compared with the case where a part of cement is not substituted with an admixture such as blast furnace slag fine powder.SOLUTION: A cement composition comprising (A) cement, (B) an inorganic powder consisting of at least one of a blast furnace slag fine powder and fly ash, and (C) a calcium carbonate-containing material consisting of at least one of a carbonate of cement and a carbonate of cement-based waste, wherein a proportion of the component (B) is 1 to 90% by mass and a proportion of the component (C) is 1 to 50% by mass in the cement composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In order to achieve carbon neutrality, development is underway to reduce the CO2 emissions per unit of concrete. Of the constituent materials of concrete, cement has a large CO2 emission intensity, so concrete in which part of the cement is replaced with ground granulated blast furnace slag, fly ash, etc., which have relatively small CO2 emission intensity, is being considered. By using ground granulated blast furnace slag or fly ash as constituent materials, it is possible to reduce the CO2 emission intensity of concrete. For example, Patent Document 1 describes a concrete composition containing at least a binder, water, fine aggregate, coarse aggregate, and admixture, in which the following blast furnace slag composition is used as the binder, and the mass ratio of water to the blast furnace slag composition is adjusted to 30 to 60%. Blast furnace slag composition: fineness of 3000-13000 cm 2 A blast furnace slag composition containing 0.5 to 1.5 parts by mass or 5 to 45 parts by mass of an alkaline stimulant added to 100 parts by mass of a mixture containing 80 to 95% by mass of granulated blast furnace slag of 0.1g / g and 5 to 20% by mass of gypsum (total 100% by mass).

[0003] On the other hand, as an effort to fix CO2 in concrete, etc., a method has been proposed in which CO2 is fixed in cement-based raw materials using a wet carbonation method, and the cement-based raw materials with fixed CO2 are used as part of the constituent materials of concrete, etc. For example, Patent Document 2 discloses a method for producing a cement composition containing cement, aggregate, and water, which includes a cement slurry preparation step of mixing a part of the cement with a part of the water to obtain a cement slurry, a carbon dioxide gas supply step of supplying carbon dioxide gas into the cement slurry to obtain a carbon dioxide gas-containing slurry, a cement additional supply step of kneading the carbon dioxide gas-containing slurry with the remainder of the cement to obtain a high-concentration cement-containing composition, and a water additional supply step of kneading the high-concentration cement-containing composition with the remainder of the water to obtain the cement composition, and The document describes a method for producing a cement composition, characterized in that the proportion of the portion of the cement used in the cement slurry preparation step is 1 to 50 mass %, and the proportion of the remainder of the cement used in the cement supply step is 50 to 99 mass %, of the total amount of water, the proportion of the portion of the water used in the cement slurry preparation step is 50 to 99 mass %, and the proportion of the remainder of the water used in the additional water supply step is 1 to 50 mass %, and the aggregate is supplied in either or both of the cement supply step and the additional water supply step. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-285293 [Patent Document 2] Japanese Patent Application Publication No. 2023-9794 Summary of the Invention [Problem to be solved by the invention]

[0005] In hydraulic compositions such as concrete, when part of the cement is replaced with an admixture such as ground granulated blast furnace slag, the CO2 emission intensity of the hydraulic composition can be reduced compared to when no replacement is performed. On the other hand, when part of the cement is replaced with an admixture such as ground granulated blast furnace slag, there is a problem that the early strength development of the hydraulic composition is reduced. An object of the present invention is to provide a cement composition in which a portion of the cement is replaced with an admixture such as ground granulated blast furnace slag, but which has excellent early strength development properties compared to a cement composition in which a portion of the cement is not replaced with an admixture such as ground granulated blast furnace slag. [Means for solving the problem]

[0006] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned objects can be achieved by a cement composition comprising an inorganic powder made of at least one of cement, ground granulated blast furnace slag, and fly ash, and a calcium carbonate-containing material made of at least one of carbonates of cement and carbonates of cement-based waste, wherein the proportion of the inorganic powder is 1 to 90 mass % and the proportion of the calcium carbonate-containing material is 1 to 50 mass %, and have completed the present invention. That is, the present invention provides the following [1] to [7]. [1] A cement composition comprising (A) cement, (B) inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash, and (C) a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste, wherein the proportion of the (B) component in the cement composition is 1 to 90 mass % and the proportion of the (C) component is 1 to 50 mass %. [2] The BET specific surface area of ​​the above component (C) is 5 to 100 m 2 / g of the cement composition according to [1]. [3] The cement composition according to [1] or [2], wherein the component (C) is a carbonate of fresh concrete sludge. [4] A hydraulic composition comprising the cement composition according to any one of [1] to [3] above, (D) water, and (E) aggregate. [5] 1 m of the above hydraulic composition 3 The hydraulic composition according to [4], wherein the amount of the cement composition is 230 to 1,400 kg and the amount of the component (E) is 700 to 2,400 kg per unit volume.

[0007] [6] A method for producing the cement composition according to any one of [1] to [3] above, comprising: a first cementitious slurry preparation step of mixing at least one of cement and cementitious waste with water to obtain a first cementitious slurry; a first carbon dioxide gas supply step of bringing the first cementitious slurry into contact with carbon dioxide gas to obtain a first carbon dioxide fixation slurry; a solid-liquid separation step of subjecting the first carbon dioxide fixation slurry to solid-liquid separation to obtain component (C); and a cement composition preparation step of mixing component (A), component (B), and component (C) to produce the cement composition. [7] A method for producing the hydraulic composition according to [4] or [5] above, comprising: a second cementitious slurry preparation step of mixing at least one of cement and cementitious waste with a portion of the component (D) to obtain a second cementitious slurry; a second carbon dioxide gas supply step of contacting the second cementitious slurry with carbon dioxide gas to obtain a second carbon dioxide fixation slurry; and a hydraulic composition preparation step of kneading the second carbon dioxide fixation slurry, the component (A), the component (B), the remainder of the component (D), and the component (E) to obtain the hydraulic composition, wherein, based on the total amount of the component (D), the proportion of the portion of the component (D) used in the second cementitious slurry preparation step is 50 to 99 mass % and the proportion of the remainder of the component (D) used in the hydraulic composition preparation step is 1 to 50 mass %. [Effects of the Invention]

[0008] The cement composition of the present invention, in which part of the cement is replaced with an admixture such as ground granulated blast furnace slag, exhibits excellent early strength development compared to a cement composition in which part of the cement is not replaced with an admixture such as ground granulated blast furnace slag. Furthermore, according to the cement composition of the present invention, among the constituent materials of the cement composition, materials with a smaller CO2 emission intensity than cement (specifically, ground granulated blast furnace slag, fly ash, and a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste) are used, so that the CO2 emission intensity of concrete, etc. can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a carbonation apparatus for producing a calcium carbonate-containing material, which is one of the constituent materials of the cement composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The cement composition of the present invention is a cement composition containing (A) cement, (B) inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash, and (C) a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste, wherein the proportion of component (B) in the cement composition is 1 to 90 mass % and the proportion of component (C) is 1 to 50 mass %. Each component will be explained in detail below. [Component (A): Cement] The cement of component (A) is not particularly limited, and examples thereof include various types of Portland cement such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement, as well as blended cements such as blast-furnace cement and fly ash cement, and ecocement. These may be used alone or in combination of two or more. Furthermore, when blast furnace cement is used as the cement, the ground granulated blast furnace slag contained in the blast furnace cement corresponds to the "ground granulated blast furnace slag" used in the present invention. Similarly, when fly ash cement is used as the cement, the fly ash contained in the fly ash cement corresponds to the "fly ash" used in the present invention. In other words, only the cement contained in blast furnace cement (or fly ash cement) corresponds to the "cement" used in this invention. Also, the amount of ground granulated blast furnace slag (or fly ash) contained in blast furnace cement (or fly ash cement) is not included in the amount of "cement" used in this invention, but is included in the amount of "ground granulated blast furnace slag" (or "fly ash") used in this invention.

[0011] From the viewpoint of further improving the strength development of the cement composition, the proportion of cement in the cement composition is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 10 mass% or more, even more preferably 20 mass% or more, even more preferably 30 mass% or more, even more preferably 50 mass% or more, even more preferably 70 mass% or more, and particularly preferably 80 mass% or more. Furthermore, from the viewpoint that the CO2 emission intensity of the cement composition and hydraulic compositions such as concrete containing the cement composition can be reduced by relatively increasing the proportion of component (B) contained in the cement composition, the above proportion is preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[0012] [(B) Component: Inorganic powder] Component (B) is an inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash. Among these, ground granulated blast furnace slag is preferred from the viewpoint of being able to use a larger amount of inorganic powder while improving the strength development of the cement composition. The inorganic powder has a smaller CO2 emission intensity than cement, and therefore, by substituting part of the cement in a cement composition with the inorganic powder, the CO2 emission intensity of the cement composition and hydraulic compositions such as concrete containing the cement composition can be reduced compared to when only cement is used. From the viewpoint of further reducing the CO2 emission intensity of the cement composition and hydraulic compositions such as concrete containing the cement composition, the proportion of component (B) in the cement composition is 1 mass% or more, preferably 3 mass% or more, more preferably 10 mass% or more, even more preferably 30 mass% or more, still more preferably 50 mass% or more, even more preferably 60 mass% or more, still more preferably 70 mass% or more, and particularly preferably 80 mass% or more. Furthermore, from the viewpoint of further improving the strength development of the cement composition by relatively increasing the proportion of component (A) contained in the cement composition, the above proportion is 90 mass% or less, preferably 80 mass% or less, more preferably 60 mass% or less, even more preferably 50 mass% or less, even more preferably 40 mass% or less, even more preferably 30 mass% or less, even more preferably 15 mass% or less, and particularly preferably 10 mass% or less.

[0013] [(C) Ingredient: calcium carbonate-containing material] Component (C) is a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste. Of these, carbonates of cement-based waste are preferred from the viewpoints of promoting waste utilization and further reducing the CO2 emission intensity of the cement composition. Here, the carbonate of cement (or carbonate of cement-based waste) includes calcium carbonate (CaCO3) formed by a reaction between calcium contained in cement (or cement-based waste) and carbon dioxide. A calcium carbonate-containing material can be obtained by carbonating at least one of cement and cement-based waste. The term "carbonation" refers to the absorption and fixation of carbon dioxide in a substance to be carbonated. Component (C) is obtained by absorbing and fixating carbon dioxide in at least one of cement and cement-based waste. Therefore, by including component (C) in a cement composition, the CO2 emission intensity of the cement composition can be reduced. The cement used to obtain the calcium carbonate-containing material is the same as the cement used as component (A) described above.

[0014] Examples of cement wastes that can be used to obtain calcium carbonate-containing materials include (i) ready-mixed concrete sludge generated when cleaning agitator trucks or concrete manufacturing equipment, and (ii) waste concrete, waste mortar, and waste mortar generated during the manufacture of concrete products and the demolition of buildings. These may be used alone or in combination of two or more. Among these, ready-mixed concrete sludge is preferred from the viewpoints of promoting waste utilization and improving the strength development of cement compositions. Ready-mixed concrete sludge, waste concrete, and waste mortar contain coarse particles such as aggregate, so it is preferable to separate the coarse particles such as aggregate from the ready-mixed concrete sludge, etc. using a sieve or the like and turn the ready-mixed concrete sludge, etc. into a powder. From the viewpoints of ease of availability, strength development, etc., the proportion of aggregate in the ready-mixed concrete sludge, waste concrete, and waste mortar is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 0% by mass. Furthermore, the ready-mixed concrete sludge, waste concrete, waste mortar, waste mortar, etc. may be crushed, pulverized, and classified as necessary.

[0015] The proportion of component (C) in the cement composition is 1 to 50 mass%, preferably 5 to 40 mass%, more preferably 10 to 30 mass%, and particularly preferably 12 to 25 mass%. If the proportion is less than 1 mass%, the early strength development of the cement composition will be reduced. Furthermore, the amount of component (C) that has absorbed and fixed carbon dioxide will be reduced, thereby reducing the effect of reducing the CO2 emission intensity of the cement composition. If the proportion exceeds 50 mass%, the strength development of the cement composition will be reduced.

[0016] The BET specific surface area of ​​component (C) is preferably 5 to 100 m 2 / g, more preferably 20 to 95 m 2 / g, particularly preferably 60 to 90m 2 / g. The BET specific surface area is 5m 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 for pulverization can be reduced.

[0017] Furthermore, the cement composition may contain other powder materials such as limestone powder, gypsum, etc., in addition to the above-mentioned components (A) to (C), within the range that does not impair the effects of the present invention. The proportion of the other powder materials in the cement composition is not particularly limited, but is usually 10 mass % or less. The cement composition is usually in powder form.

[0018] An example of a method for producing the cement composition of the present invention includes a production method including: a first cementitious slurry preparation step of mixing at least one of cement and cementitious waste with water to obtain a first cementitious slurry; a first carbon dioxide gas supply step of supplying carbon dioxide gas into the first cementitious slurry to obtain a first carbon dioxide fixation slurry; a solid-liquid separation step of performing solid-liquid separation of the first carbon dioxide fixation slurry to obtain component (C); and a cement composition preparation step of mixing component (A), component (B), and component (C) to produce a cement composition. A detailed explanation is provided below.

[0019] [First cementitious slurry preparation step] This step is a step of mixing at least one of cement and cement-based waste with water to obtain a first cement-based slurry. In this step, the mass ratio of water to at least one of cement and cement-based waste (water / (at least one of cement and cement-based waste)) is preferably 1.0 to 5.0, more preferably 1.5 to 4.5, even more preferably 2.0 to 4.0, and particularly preferably 2.5 to 3.5. When the ratio is 1.0 or more, the fluidity of the first cement-based slurry is further improved, making it easier to uniformly supply carbon dioxide to the first cement-based slurry in the first carbon dioxide supplying step described below. When the ratio is 5.0 or less, a greater amount of carbon dioxide is immobilized in at least one of cement and cement-based waste contained in the first cement-based slurry. In this step, the method for mixing at least one of cement and cement-based waste with water is not particularly limited. For example, water may be introduced into a mixing tank, and then at least one of cement and cement-based waste may be introduced and then mixed; alternatively, water and at least one of cement and cement-based waste may be introduced into a mixing tank simultaneously and then mixed.

[0020] [First carbon dioxide gas supplying step] This step is a step of contacting the first cementitious slurry obtained in the first cementitious slurry preparation step with carbon dioxide gas to obtain a first carbon dioxide fixation slurry. Note that the carbon dioxide gas is gaseous carbon dioxide. In this step, from the viewpoint of uniformly carbonating the first cementitious slurry, it is preferable to bring the first cementitious slurry into contact with carbon dioxide gas while fluidizing it. Hereinafter, an example of a method for contacting the first cementitious slurry with carbon dioxide gas will be specifically described with reference to FIG. FIG. 1 is a diagram schematically illustrating a carbon dioxide fixation slurry production apparatus 1 including a cementitious slurry preparation tank 2 and a carbon dioxide gas contact device 3. At least one of cement and cementitious waste and water are charged into a cementitious slurry preparation tank 2, and then mixed using a mixing means (not shown) such as a hand mixer to prepare a first cementitious slurry 8 (corresponding to the first cementitious slurry preparation step described above). The first cementitious slurry 8 is fed into the carbon dioxide contactor 3 from an opening formed in the top of the carbon dioxide contactor 3 via a first slurry supply path 4 for supplying the cementitious slurry into the carbon dioxide contactor 3 using a pump 6. Carbon dioxide is supplied into the carbon dioxide contactor 3 from a carbon dioxide supply device (not shown) through a carbon dioxide supply path 9, and a gas phase containing carbon dioxide is formed. In the carbon dioxide contactor 3, the first cementitious slurry comes into contact with the gas phase, whereby the first cementitious slurry is carbonated, and a first carbon dioxide fixation slurry 7 can be obtained. The first carbon dioxide fixation slurry 7 is transferred to the cementitious slurry preparation tank 2 through the second slurry supply line 5, which is used to supply the first carbon dioxide fixation slurry 7 contained in the carbon dioxide gas contactor 3 to the cementitious slurry preparation tank 2. By circulating the slurry between the cementitious slurry preparation tank 2 and the carbon dioxide gas contactor 3 and carbonating the slurry, it is possible to obtain a sufficiently carbonated slurry.

[0021] Another example of the method for contacting the first cementitious slurry with carbon dioxide gas is a method in which a carbon dioxide gas supply means for supplying carbon dioxide gas into the first cementitious slurry is installed in a mixing tank for mixing at least one of cement and cementitious waste with water, and carbon dioxide gas is blown into the first cementitious slurry to bring the first cementitious slurry into contact with the carbon dioxide gas, thereby obtaining a first carbon dioxide fixation slurry.

[0022] Furthermore, carbon dioxide gas may be brought into contact with the first cementitious slurry as a gas consisting of carbon dioxide gas alone, but from the viewpoint of ease of availability, etc., it may also be brought into contact with the cementitious slurry as a gas containing carbon dioxide gas. The proportion of carbon dioxide gas in the carbon dioxide-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 20% by volume or more, even more preferably 50% by volume or more, still more preferably 80% by volume or more, and particularly preferably 90% by volume or more. If the proportion is 5% by volume or more, the amount of carbon dioxide immobilized in the first carbon dioxide immobilization slurry can be further increased. In addition, the time required for supplying carbon dioxide gas can be shortened. Examples of gases containing carbon dioxide include exhaust gases generated in the cement manufacturing process (carbon dioxide concentration: approximately 20% by volume), exhaust gases generated in the steelmaking process (carbon dioxide concentration: approximately 20% by volume), exhaust gases generated in thermal power generation processes (carbon dioxide concentration: approximately 10% by volume), and gases separated and recovered from these exhaust gases (carbon dioxide concentration: approximately 100% by volume).

[0023] In this step, carbon dioxide gas is supplied so that the pH of the first carbon dioxide fixation slurry is preferably within the range of 5.0 to 11.5, more preferably 5.5 to 11.0, even more preferably 6.0 to 10.0, and particularly preferably 6.5 to 9.5. When carbon dioxide gas is supplied so that the pH is 5.0 or higher, the strength development of the cement composition is further improved. In addition, the time required for supplying carbon dioxide gas can be shortened. When carbon dioxide gas is supplied so that the pH is 11.5 or lower, the amount of carbon dioxide fixed in the first carbon dioxide fixation slurry (more specifically, the amount of carbon dioxide fixed in the solid content contained in the first carbon dioxide fixation slurry) is increased. Note that the pH of the first carbon dioxide fixation slurry decreases when carbon dioxide gas is supplied. The carbon dioxide gas supply time required to fix a sufficient amount of carbon dioxide in the first carbon dioxide fixation slurry varies depending on the liquid-solid ratio of the slurry, the carbon dioxide gas supply means, the carbon dioxide gas concentration of the carbon dioxide gas-containing gas supplied using said means, etc. Therefore, in this step, it is preferable to determine the timing for ending the carbon dioxide gas supply based on the actually measured pH value of the carbon dioxide fixation slurry.

[0024] [Solid-liquid separation process] This step is a step of performing solid-liquid separation on the first carbon dioxide fixation slurry to obtain a calcium carbonate-containing material (component (C)) consisting of at least one of carbonates of cement and carbonates of cement-based waste. The solid-liquid separation method is not particularly limited as long as it is a method that can separate a liquid contained in the first carbon dioxide fixation slurry and recover a solid component (a calcium carbonate-containing component), and examples thereof include dehydration treatment using a filter press, a centrifuge, a belt filter, or the like, and sun drying. The solid matter obtained may be further dried, and after drying, may be pulverized and, if necessary, classified. The water content of the calcium carbonate-containing material varies depending on the target work efficiency, the method for preparing the hydraulic composition (described later), etc., but is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, and particularly preferably 1.0% by mass or less.

[0025] [Cement composition preparation process] This step is a step of producing a cement composition by mixing cement, an inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash, and a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste.

[0026] The hydraulic composition of the present invention comprises the above-mentioned cement composition, (D) water, and (E) aggregate. In this specification, the hydraulic composition includes the form of the hydraulic composition before and after hardening. Hydraulic composition 1m3 The amount of cement composition per unit area is preferably 230 to 1,400 kg, more preferably 250 to 1,000 kg, even more preferably 300 to 500 kg, and particularly preferably 320 to 400 kg. If the amount is 230 kg or more, the strength development of the hydraulic composition is further improved. If the amount is 1,400 kg or less, the workability when kneading the materials in producing the hydraulic composition and the workability when pouring the hydraulic composition (fluidity of the hydraulic composition) are further improved. Each component will be described in detail below.

[0027] [(D) Ingredient: Water] 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 mass ratio of water to cement composition in the hydraulic composition (water / cement composition) is preferably 0.3 to 0.65, more preferably 0.4 to 0.6. When the ratio is 0.3 or more, the workability when kneading the materials during production and the workability when casting the hydraulic composition (fluidity of the hydraulic composition) are further improved. When the ratio is 0.65 or less, the strength development of the hydraulic composition is further improved.

[0028] [Component (E): Aggregate] The aggregate used in the present invention may be fine aggregate alone or a combination of fine and coarse aggregate. In addition, any of natural aggregate, artificial aggregate, and recycled aggregate may 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, slag fine aggregate, and lightweight fine aggregate, or a mixture of two or more types selected from these. The coarse aggregate is not particularly limited, and examples thereof include river gravel, mountain gravel, land gravel, sea gravel, crushed stone, slag coarse aggregate, and lightweight coarse aggregate, or a mixture of two or more types selected from these.

[0029] Hydraulic composition 1m 3The amount of aggregate per unit area (the total amount when fine aggregate and coarse aggregate are used in combination) is preferably 700 to 2,400 kg, more preferably 1,000 to 2,200 kg, even more preferably 1,400 to 2,000 kg, and particularly preferably 1,600 to 1,800 kg. If the amount is 700 kg or more, the drying shrinkage of the hydraulic composition can be further suppressed. If the amount is 2,400 kg or less, the workability of the hydraulic composition, such as material separation resistance, can be further improved. When the hydraulic composition contains fine aggregate and coarse aggregate, the fine aggregate ratio is preferably 36 to 55%, more preferably 38 to 53%, and particularly preferably 42 to 51%. The fine aggregate ratio refers to the volume ratio of fine aggregate to the total amount of fine aggregate and coarse aggregate.

[0030] The hydraulic composition preferably contains a cement admixture from the viewpoint of further improving the air entrainment property, fluidity, etc. of the hydraulic composition. Examples of cement admixtures include cement dispersants, air-entraining agents, etc. Although these may be used alone, it is preferable to use a cement dispersant and an air-entraining agent in combination from the viewpoint of further improving the air entrainment property and fluidity of the hydraulic composition. Examples of cement dispersants include water reducing agents, air-entraining water reducing agents, high-range water reducing agents, and super-range air-entraining water reducing agents, etc. Among these, from the viewpoint of improving the fluidity of the hydraulic composition, delayed water reducing agents, air-entraining water reducing agents, and super-range air-entraining water reducing agents are preferred. These may be used alone or in combination of two or more. The hydraulic composition may also contain a retarder such as gluconic acid, citric acid, or tartaric acid in order to delay or adjust the setting of the hydraulic composition. The amount of cement admixture to be added varies depending on the air entrainment property and fluidity of the target hydraulic composition, but is preferably 0.01 to 5.0 parts by mass, more preferably 0.1 to 4.0 parts by mass, and particularly preferably 1.0 to 3.0 parts by mass, per 100 parts by mass of the cement composition.

[0031] An example of a method for producing the hydraulic composition of the present invention includes a method including: a second cementitious slurry preparation step of mixing at least one of cement and cementitious waste with a portion of water, which is component (D), to obtain a second cementitious slurry; a second carbon dioxide gas supply step of contacting the second cementitious slurry with carbon dioxide gas to obtain a second carbon dioxide fixation slurry; and a hydraulic composition preparation step of kneading the second carbon dioxide fixation slurry, component (A), component (B), the remainder of component (D), and component (E) to obtain a hydraulic composition. A detailed explanation is provided below.

[0032] [Second cementitious slurry preparation step] This step is a step of mixing at least one of cement and cement-based waste with a portion of component (D) to obtain a second cement-based slurry. In this step, a portion of the water (component (D)) contained in the hydraulic composition is mixed. In this step, the mass ratio of the part of the (D) component to at least one of the cement and cement-based waste (solid content) (part of the (D) component / (at least one of the cement and cement-based waste) is preferably 1.0 to 5.0, more preferably 1.5 to 4.5, even more preferably 2.0 to 4.0, and particularly preferably 2.5 to 3.5. When the above ratio is 1.0 or more, the fluidity of the second cement-based slurry is further improved, making it easier to uniformly supply carbon dioxide to the second cement-based slurry in the second carbon dioxide supplying step described below. When the above ratio is 5.0 or less, a greater amount of carbon dioxide is immobilized in at least one of the cement and cement-based waste contained in the second cement-based slurry.

[0033] In addition, when the cementitious waste is fresh concrete sludge or the like, and the cementitious waste contains water, the mass of at least one of the cement and cementitious waste in the above mass ratio shall be converted into solid content, and the water contained in the cementitious waste shall be calculated as the mass of "part of component (D)" in the above mass ratio. The cement and / or cement-based waste, and water used in this step can be the same as those used in the first cement-based slurry preparation step described above. The method for mixing the cement and / or cement-based waste with a portion of the component (D) (water) is not particularly limited, and the same method as that used in the first cement-based slurry preparation step described above can be used.

[0034] [Second carbon dioxide gas supplying step] This step is a step of supplying carbon dioxide gas into the second cementitious slurry to obtain a second carbon dioxide fixation slurry. This step is the same as the first carbon dioxide gas supplying step described above, except that the second cementitious slurry is used instead of the first cementitious slurry. Between the second carbon dioxide gas supplying step and the hydraulic composition preparing step, a water content adjusting step of adjusting the amount of water contained in the second carbon dioxide fixation slurry may be carried out. By adjusting the amount of water contained in the second carbon dioxide fixation slurry, the hydraulic composition can be prepared more efficiently in the hydraulic composition preparation step. The proportion of the amount of water contained in the second carbon dioxide fixation slurry relative to the total amount of water contained in the hydraulic composition (total amount of water contained in the cement composition), from the viewpoint of workability in the hydraulic composition preparation step, etc., is preferably 15 to 99 mass%, more preferably 20 to 95 mass%, even more preferably 25 to 80 mass%, and particularly preferably 30 to 70 mass%.

[0035] [Hydraulic composition preparation process] This step is a step of kneading the second carbon dioxide fixation slurry, cement as component (A), inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash as component (B), the remainder of component (D), and component (E) to obtain a hydraulic composition. In this step, the remainder of the water (component (D)) contained in the hydraulic composition is mixed. The proportion of the amount of the remainder of the water in the total amount of water contained in the hydraulic composition (total amount of water contained in the hydraulic composition) is preferably 1 to 85 mass%, more preferably 5 to 80 mass%, even more preferably 20 to 75 mass%, and particularly preferably 30 to 70 mass%. When the proportion is 1 mass% or more, the amount of air contained in the hydraulic composition increases, and the fluidity of the hydraulic composition before hardening is further improved. When the proportion is 85 mass% or less, the fluidity of the second cementitious slurry obtained in the second cementitious slurry preparation step is relatively improved, and it becomes easier to uniformly supply carbon dioxide gas to the second cementitious slurry in the second carbon dioxide gas supplying step.

[0036] The method for kneading the second carbon dioxide fixation slurry, the cement as component (A), the inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash as component (B), the remainder of the water as component (D), and the aggregate as component (E) is not particularly limited, and each component may be added simultaneously and kneaded, or components (A), (B), and (E) may be mixed in advance, and then the resulting mixture, the second carbon dioxide fixation slurry, and the remainder of the water as component (D) may be added simultaneously and kneaded.

[0037] In the second cementitious slurry preparation step and the hydraulic composition preparation step, the entire amount of water is usually used. However, a portion of the remaining water used in the hydraulic composition preparation step may be added in the second carbon dioxide gas supply step. This embodiment is also included in the present invention. In this case, the proportion of the amount of the remaining portion of water in 100% by mass of the remaining water is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less. In addition, when the hydraulic composition contains a cement admixture, the cement admixture is preferably supplied in the hydraulic composition preparation step from the viewpoint of further improving the air entrainment property and fluidity of the hydraulic composition. Another example of the method for producing the hydraulic composition of the present invention includes a method of preparing a hydraulic composition by mixing the cement composition obtained by the above-mentioned method for producing a cement composition, (D) water, and (E) aggregate. [Example]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement: Ordinary Portland cement manufactured by Taiheiyo Cement Corporation, density: 3.16 g / cm 3 (2) Cement waste: fresh concrete sludge, density: 2.30 g / cm 3 Aggregate content: 5% by mass or less (3) Ground blast furnace slag (referred to as "slag" in Table 1); Nippon Steel Blast Furnace Cement Co., Ltd., product name "ESMENT", Blaine specific surface area: 4,000 cm 2 / g, SO3 content: 1.8% by mass, density: 2.89g / cm 3 (4) Fly ash (indicated as "FA" in Table 1); fly ash type II, density: 2.36 g / cm 3 (5) Fine aggregate: mountain sand from Shizuoka Prefecture, surface dry density: 2.60 g / cm 3 (6) Coarse aggregate: Crushed hard sandstone 2005 from Ibaraki Prefecture, surface dry density: 2.64 g / cm 3 (7) Water; tap water (8) High-performance AE water reducer 1: Product name "Master Glenium SP8SV" manufactured by Pozzolith Solutions Co., Ltd. (9) High-performance AE water reducer 2: Pozzolith Solutions Co., Ltd., product name "Master Glenium SP8RV" (10) Air-entraining agent: Master Air 202, manufactured by Pozzolith Solutions Co., Ltd.

[0039] [Preparation of carbon dioxide fixation slurry containing cement carbonate] A carbon dioxide fixation slurry containing cement carbonate was prepared using the carbon dioxide fixation slurry production apparatus 1 shown in FIG. Specifically, water and ordinary Portland cement were charged into the cement-based slurry preparation tank 2 in amounts such that the mass ratio of water to ordinary Portland cement (water / ordinary Portland cement) was 3.0, and the mixture was mixed for 60 seconds using a hand mixer to obtain a mixture (cement-based slurry, temperature: 23°C) (second cement-based slurry preparation process). The mixture in the cementitious slurry preparation tank 2 was transferred through a first slurry supply line 4 to a carbon dioxide gas contactor 3 for supplying carbon dioxide gas to the mixture, and then gaseous carbon dioxide was supplied into the carbon dioxide gas contactor 3 to form a gas phase containing carbon dioxide gas. Next, the mixture was repeatedly transferred into the cementitious slurry preparation tank 2 through a second slurry supply line 5 different from the first slurry supply line 4, and circulated until the pH of the cementitious slurry reached 8.0, thereby obtaining a carbon dioxide fixation slurry containing carbonates of cement (second carbon dioxide gas supply step). Next, a portion of the water in the carbon dioxide fixation slurry containing cement carbonate was removed to adjust the liquid-solid ratio of the carbon dioxide fixation slurry containing cement carbonate (the mass ratio of water contained in the slurry to cement carbonate (water / carbonate)) to 1.1. The BET specific surface area of ​​the cement carbonate contained in the carbon dioxide fixation slurry containing cement carbonate is 41.5 m 2 / g and density is 2.58g / cm 3 It was. [Preparation of carbon dioxide fixation slurry containing carbonates from cement waste] A carbon dioxide fixation slurry containing carbonated cementitious waste with a liquid-solid ratio (mass ratio (water / carbonate) of water contained in the carbon dioxide fixation slurry containing carbonated cementitious waste to carbonated cementitious waste) of 1.1 was prepared in the same manner as in the preparation of the carbon dioxide fixation slurry containing carbonated cement described above, except that ready-mixed concrete sludge was used instead of ordinary Portland cement. The BET specific surface area of ​​the cementitious waste carbonate contained in the carbon dioxide fixation slurry containing cementitious waste carbonate is 85.7 m 2 / g and density is 2.58g / cm 3 It was.

[0040] [Examples 1 to 4, 7 to 8] Ordinary Portland cement, ground granulated blast furnace slag, fine aggregate, and coarse aggregate were dry mixed in a mixer for 15 seconds in the unit amounts shown in Table 1 to obtain a mixture. The carbon dioxide fixation slurry containing the above-mentioned cement carbonate, and a liquid mixture of the types and amounts of high-range air-entraining water-reducing agent and air-entraining agent shown in Table 2 and water (the remainder of component (D)) were charged into the mixer and mixed for 1 minute. Next, the mixed material adhering to the inner wall of the mixer was scraped off, and then the mixture was mixed for another 1 minute to obtain concrete (hydraulic cement composition) (hydraulic composition preparation step). The unit amount of water shown in Table 1 is the total amount of water contained in the carbon dioxide fixation slurry (part of component (D)) and water supplied in the additional water supply step (the remainder of component (D)).

[0041] The quality of the concrete obtained was measured according to the following method. [Slump measurement] The slump of the concrete was measured in accordance with "JIS A 1101:2020 (Concrete slump test method)". [Compression strength measurement] The compressive strength of the concrete at 1 day and 7 days of age was measured in accordance with JIS A 1108:2018 (Testing method for compressive strength of concrete). When measuring the compressive strength, the concrete was cured in water at 20°C. [Air volume measurement] The air content of the concrete was measured in accordance with JIS A 1128:2019 (Test method for air content of fresh concrete by pressure - Air chamber pressure method).

[0042] [Example 5] Concrete (hydraulic cement composition) was obtained in the same manner as in Example 1, except that the carbon dioxide fixation slurry containing the carbonates of the cement waste was used instead of the carbon dioxide fixation slurry containing the carbonates of the cement. The quality of the resulting concrete was measured in the same manner as in Example 1. [Example 6] The carbon dioxide fixation slurry containing the carbonate of the cementitious waste was subjected to solid-liquid separation and dried in a drying oven at 105°C until a constant weight was reached, thereby obtaining carbonate of the cementitious waste (powder). The density of the carbonate of the cementitious waste was 2.60 g / cm. 3 It was. Ordinary Portland cement, ground granulated blast furnace slag, carbonates of cementitious waste, fine aggregate, and coarse aggregate were dry mixed in a mixer in the unit amounts shown in Table 1 for 15 seconds to obtain a mixture. A liquid mixture prepared by previously mixing the types and amounts of high-performance air-entraining water-reducing agent and air-entraining agent shown in Table 2 with the unit amount of water shown in Table 1 was poured into the mixer and mixed for 1 minute. After scraping off the mixture adhering to the inner wall of the mixer, the mixture was mixed for another 1 minute to obtain concrete (hydraulic cement composition) (hydraulic composition preparation step). [Example 9] A concrete (hydraulic cement composition) was obtained in the same manner as in Example 1, except that fly ash was used instead of the ground granulated blast furnace slag. The quality of the resulting concrete was measured in the same manner as in Example 1.

[0043] [Comparative Examples 1 to 5] Ordinary Portland cement, ground granulated blast furnace slag, fine aggregate, and coarse aggregate were dry-mixed for 15 seconds in the unit amounts shown in Table 1 to obtain a mixture. The resulting mixture was mixed with the unit amount of water shown in Table 1 for 1 minute, and then the mixture adhering to the inner wall of the mixer was scraped off, followed by further mixing for 1 minute to obtain concrete (hydraulic cement composition). The quality of the resulting concrete was measured in the same manner as in Example 1. Comparative Example 6 Ordinary Portland cement, fly ash, fine aggregate, and coarse aggregate in the unit amounts shown in Table 1 were dry-mixed for 15 seconds to obtain a mixture. The resulting mixture was mixed with the unit amount of water shown in Table 1 for 1 minute, and then the mixture adhering to the inner wall of the mixer was scraped off, followed by further mixing for 1 minute to obtain concrete (hydraulic cement composition). The quality of the resulting concrete was measured in the same manner as in Example 1. The results are shown in Table 2.

[0044] [Table 1]

[0045] [Table 2]

[0046] From Table 2, a comparison of Example 1 (similar to Comparative Example 1 except that part of the cement is replaced with carbonate) with Comparative Example 1, a comparison of Examples 2 and 5 (similar to Comparative Example 2 except that part of the cement is replaced with carbonate) with Comparative Example 2, a comparison of Example 3 (similar to Comparative Example 3 except that part of the cement is replaced with carbonate) with Comparative Example 3, a comparison of Example 4 (similar to Comparative Example 4 except that part of the cement is replaced with carbonate) with Comparative Example 4, and a comparison of Example 9 (similar to Comparative Example 5 except that part of the cement is replaced with carbonate) with Comparative Example 5, it can be seen that the compressive strength of the Examples (especially the compressive strength at 1 day old) is greater than the compressive strength of the Comparative Examples, and that the cement compositions of the present invention have excellent early strength development. [Explanation of symbols]

[0047] 1 Carbon dioxide fixation slurry manufacturing equipment 2. Cement slurry preparation tank 3 Carbon dioxide contact device 4. First slurry supply channel 5 Second slurry supply line 6. Pump 7 Carbon dioxide fixation slurry 8. Cement-based slurry 9 Carbon dioxide supply line

Claims

1. A cement composition comprising (A) cement, (B) an inorganic powder consisting of at least one of ground granulated blast furnace slag and fly ash, and (C) a calcium carbonate-containing material consisting of at least one of carbonates of cement and carbonates of cement-based waste, A cement composition characterized in that the proportion of the component (B) is 1 to 90 mass % and the proportion of the component (C) is 1 to 50 mass % in the cement composition.

2. The BET specific surface area of ​​the component (C) is 5 to 100 m ２ The cement composition according to claim 1, wherein the hydroxyl group is 0.15 or 0.

15.

3. 3. The cement composition according to claim 1, wherein said component (C) is a carbonate of fresh concrete sludge.

4. A hydraulic composition comprising the cement composition according to claim 1 or 2, (D) water, and (E) aggregate.

5. 1 m of the above hydraulic composition ３ 5. The hydraulic composition according to claim 4, wherein the amount of the cement composition is 230 to 1,400 kg and the amount of the component (E) is 700 to 2,400 kg per 10 ...

6. 3. A method for producing the cement composition of claim 1 or 2, comprising: a first cementitious slurry preparation step of mixing at least one of cement and cementitious waste with water to obtain a first cementitious slurry; a first carbon dioxide gas supplying step of contacting the first cementitious slurry with carbon dioxide gas to obtain a first carbon dioxide fixation slurry; a solid-liquid separation step of subjecting the first carbon dioxide fixation slurry to solid-liquid separation to obtain the component (C); a cement composition preparation step of mixing the component (A), the component (B), and the component (C) to produce the cement composition; A method for producing a cement composition, comprising:

7. A method for producing the hydraulic composition according to claim 4, comprising: a second cementitious slurry preparation step of mixing at least one of cement and cementitious waste with a part of the component (D) to obtain a second cementitious slurry; a second carbon dioxide gas supplying step of contacting the second cementitious slurry with carbon dioxide gas to obtain a second carbon dioxide fixation slurry; a hydraulic composition preparation step of kneading the second carbon dioxide fixation slurry, the component (A), the component (B), the remainder of the component (D), and the component (E) to obtain the hydraulic composition, A method for producing a hydraulic composition, characterized in that, based on the total amount of the component (D), a proportion of a part of the component (D) used in the second cementitious slurry preparation step is 50 to 99 mass %, and a proportion of the remainder of the component (D) used in the hydraulic composition preparation step is 1 to 50 mass %.

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