Carbonation promoter for hydraulic composition and production method for hydraulic composition hardened product

Abstract

Provided is a carbonation promoter for a hydraulic composition, said promoter being capable of promoting the carbonation of a hydraulic composition when added to the hydraulic composition. Specifically provided is a carbonation promoter for a hydraulic composition, said promoter being characterized by containing 10-100 mass% of an anionic surfactant which is a compound containing an organic acid ion having 6-50 hydrophobic groups per molecule.

Description

Carbonation accelerator for hydraulic composition and method for producing hardened hydraulic composition

[0001] The present invention relates to a carbonation accelerator for hydraulic compositions and a method for producing a hardened product of the hydraulic composition. More specifically, the present invention relates to a carbonation accelerator for hydraulic compositions that can accelerate the carbonation of a hydraulic composition by adding it to the hydraulic composition, and a method for producing a hardened product of the hydraulic composition.

[0002] In recent years, efforts to achieve a carbon-neutral or carbon-negative society have been accelerating around the world. For example, Japan declared in 2020 that it would achieve carbon neutrality by 2050, and in 2021 set a target of reducing greenhouse gas emissions by 46% by fiscal 2030 (compared to fiscal 2013 levels).

[0003] For example, the construction industry is also working to reduce carbon dioxide (CO2) emissions.

[0004] Specifically, concrete is a material that emits a large amount of carbon dioxide during its production, using cement that emits a large amount of carbon dioxide. Therefore, in order to reduce carbon dioxide emissions, low-carbon cement and low-carbon concrete, which use industrial by-products such as ground granulated blast furnace slag and fly ash to reduce the amount of cement used, are known.

[0005] Precast concrete is also known, which is made by hardening a concrete mixture containing powdered steelmaking slag and Portland cement to which γ-CS has been added, and then carbonation curing the concrete after demolding (see, for example, Patent Document 1). This precast concrete is made using a technology in which carbonation progresses on the surface of the concrete due to the absorption of carbon dioxide, resulting in densification in those areas and achieving high durability. γ-CS is γ-2CaO.SiO (sometimes called "γ-belite").

[0006] In Patent Document 1, carbonation curing is performed to densify concrete and improve its durability. However, this technology involves the fixation and absorption of carbon dioxide by concrete. In other words, it can be said that the amount of carbon dioxide emissions is reduced throughout the concrete manufacturing process by the amount of carbon dioxide fixed and absorbed by the concrete through carbonation curing. In this way, γ-CS (γ-2CaO.SiO) is sometimes used as a technology for reducing, fixing, absorbing, etc. carbon dioxide (CO2).

[0007] Similarly, as one of the efforts to reduce greenhouse gases, a carbonation promoter that promotes the carbonation of alkaline earth metal compounds has also been reported (see Patent Document 2).

[0008] JP 2006-182583 A JP 2023-103807 A

[0009] However, there is still room for improvement in the amount and rate of carbon dioxide absorption. Therefore, there is a need for the development of a carbonation accelerator that can further increase the amount of carbon dioxide absorbed and fixed by concrete, improve the rate of carbon dioxide absorption, or both. Increasing the amount of carbon dioxide absorbed by concrete at a given age shortens the time it takes to absorb a certain amount of carbon dioxide, which in turn shortens the carbonation curing period (shortening the production time of concrete products).

[0010] In view of the above circumstances, an object of the present invention is to provide a carbonation accelerator for hydraulic compositions, which, when added to a hydraulic composition, can accelerate the carbonation of the hydraulic composition and reduce the carbon dioxide balance of the hydraulic composition, and a method for producing a hardened hydraulic composition. The carbon dioxide balance is the amount of carbon dioxide calculated by the formula: "amount of carbon dioxide derived from the raw materials constituting the concrete (i.e., the amount of carbon dioxide generated during the production of the raw materials)" - "amount of carbon dioxide absorbed and fixed by carbonation curing, etc." "Reducing the carbon dioxide balance" means increasing the amount of carbon dioxide reduction, which means reducing the value of the amount of carbon dioxide calculated by the formula.

[0011] As a result of intensive research aimed at solving the above problems, the present inventors have found that the above problems can be solved by including a specific anionic surfactant. According to the present invention, the following carbonation accelerator for a hydraulic composition and a method for producing a hardened hydraulic composition are provided.

[0012] [1] A carbonation accelerator for a hydraulic composition, comprising an anionic surfactant in a proportion of 10 to 100 mass %, wherein the anionic surfactant is a compound containing an organic acid ion having a hydrophobic group having 6 to 50 carbon atoms in the molecule.

[0013] [2] The carbonation accelerator for a hydraulic composition according to [1], wherein the anionic surfactant is at least one compound selected from compounds represented by the following general formula (1):

[0014] (In general formula (1), R 1 is an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, an aryl group having 8 to 20 carbon atoms, a residue obtained by removing a carboxylic acid from rosin, or a residue obtained by removing a hydrogen atom from a compound obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a total ratio of 1 to 10 moles per mole of an aliphatic alcohol having 1 to 24 carbon atoms. X is represented by the following general formulas (a) to (f):

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] (In general formulas (a) to (f), R 2 and R 3 are each independently a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 1 to 24 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a ratio of 1 to 10 moles in total to 1 mole of an aliphatic alcohol having 1 to 24 carbon atoms.1 ~M 8 are each independently an alkali metal, an alkaline earth metal, ammonium, or an organic amine; and n is an integer of 2 or 3.

[0021] [3] The carbonation accelerator for a hydraulic composition according to [1], wherein the anionic surfactant is at least one selected from the compounds represented by the following general formulas (1-1) to (1-5):

[0022] (In general formula (1-1), R 4 is an alkyl group having 6 to 20 carbon atoms, an alkenyl group having 6 to 20 carbon atoms, or an acyl residue of rosin. 9 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.

[0023] (In the general formula (1-2), R 5 is an alkyl group having 6 to 20 carbon atoms, an alkenyl group having 6 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. 10 ~M 11 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.

[0024] (In the general formula (1-3), R 6 is a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a ratio of 1 to 10 moles in total to 1 mole of an aliphatic alcohol having 6 to 20 carbon atoms. 12 , M 13 are each independently hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.

[0025] (In the general formula (1-4), R 7 , R 8 are each independently a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a compound obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a ratio of 1 to 10 moles in total to 1 mole of an aliphatic alcohol having 6 to 20 carbon atoms.14 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.

[0026] (In the general formula (1-5), R 9 , R 10 are each independently a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a ratio of 1 to 10 moles in total to 1 mole of an aliphatic alcohol having 6 to 20 carbon atoms. 15 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine; and m is an integer of 2 or 3.

[0027] [4] The carbonation accelerator for a hydraulic composition according to [3], wherein the compound represented by the general formula (1-1) is a compound represented by the following general formula (1-1a), and the anionic surfactant is a mixture containing the compound represented by the general formula (1-1a) and at least one selected from the compounds represented by the general formulas (1-2) to (1-5).

[0028] (In the general formula (1-1a), R 11 is an alkyl group having 6 to 20 carbon atoms or an alkenyl group having 6 to 20 carbon atoms. 16 is hydrogen, an alkali metal, an alkaline earth metal, or an organic amine.

[0029] [5] The carbonation accelerator for hydraulic compositions according to any one of [1] to [4], which is added to a hydraulic composition that has undergone a carbonation curing process, which is a process of curing in an environment with a volume concentration of carbon dioxide of 5% or more, and that has become a hardened hydraulic composition.

[0030] [6] The carbonation accelerator for hydraulic compositions according to any one of [1] to [4], which is added to a hydraulic composition containing a binder containing 40 to 99 mass% of ground granulated blast furnace slag, water, and aggregate.

[0031] [7] The carbonation accelerator for hydraulic compositions according to any one of [1] to [4], wherein the hydraulic composition contains γ-2CaO.SiO2.

[0032] [8] The carbonation accelerator for hydraulic compositions according to any one of [1] to [4], wherein the hydraulic composition contains at least one selected from the following CO2-fixing fine powder and the following CO2-fixing modified recycled fine aggregate. CO2-fixing fine powder: Modified concrete powder having a 50% particle size of 50 μm or less, which is a reaction product of recycled concrete powder and carbon dioxide, and the modified concrete powder contains calcium carbonate and silicates. The content of the CO2-fixing fine powder in the hydraulic composition is in the range of 1 to 100% by mass, relative to 100% by mass of the binder. CO2-fixing modified recycled fine aggregate: Modified recycled fine aggregate, which is a dry or wet reaction product of recycled fine aggregate, all particles of which have a particle size of 10 mm or less, 85% or more of which are 5 mm or less, and which has a water absorption rate of more than 3.0% and 10% or less, and carbon dioxide, and the modified recycled fine aggregate contains calcium carbonate and silicon dioxide. However, the content of the CO2 fixation modified recycled fine aggregate in the hydraulic composition is in the range of 10 to 100% by volume with respect to the total aggregate volume.

[0033] [9] A method for producing a hydraulic composition hardened body, comprising: a preparation step of preparing a hydraulic composition containing the carbonation accelerator for hydraulic compositions according to any one of [1] to [4] above, a binder containing 40 to 99 mass% of ground granulated blast furnace slag, and water; a hardening step of hardening the obtained hydraulic composition to obtain a hydraulic composition hardened body; and a carbonation curing step of curing the obtained hydraulic composition hardened body in an environment with a volume concentration of carbon dioxide of 5% or more, thereby absorbing and immobilizing carbon dioxide in the hydraulic composition hardened body.

[0034] The carbonation accelerator for hydraulic compositions of the present invention, when added to a hydraulic composition, promotes the carbonation of the hydraulic composition and has the effect of reducing the carbon dioxide balance of the hydraulic composition.

[0035] According to the method for producing a hydraulic composition hardened product of the present invention, the amount of carbon dioxide reduced in the production process is increased because the hydraulic composition containing the carbonation accelerator for hydraulic compositions of the present invention is used.

[0036] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate changes, modifications, etc. can be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. In the following examples, % means % by mass, and parts means parts by mass, unless otherwise specified.

[0037] (1) Carbonation Accelerator for Hydraulic Composition: The carbonation accelerator for hydraulic composition of the present invention contains an anionic surfactant in a proportion of 10 to 100% by mass, and this anionic surfactant is a compound containing an organic acid ion having a hydrophobic group having 6 to 50 carbon atoms in the molecule.

[0038] When added to a hydraulic composition, such a carbonation accelerator for hydraulic compositions can accelerate the carbonation of the hydraulic composition and increase the amount of carbon dioxide absorbed by the hydraulic composition (i.e., the amount of carbon dioxide reduction). In other words, the carbon dioxide balance of the hydraulic composition can be reduced. Note that calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) are produced by the hydration of cement. Furthermore, the hydraulic composition contains calcium oxide (CaO) and the like as its raw material. These compounds are carbonated (react with carbon dioxide), allowing carbon dioxide to be absorbed and fixed in the hydraulic composition (the hardened product of the hydraulic composition).

[0039] For example, thermal power plants emit carbon dioxide into the atmosphere as exhaust gas. This carbon dioxide is considered to be one of the causes of global warming, but by supplying the carbon dioxide in the exhaust gas to the carbonation curing process, the carbon dioxide can be absorbed into the hydraulic composition, thereby reducing carbon dioxide emissions. Note that the hardened hydraulic composition can be used not only in the carbonation curing process, but also after the process, by being placed in a predetermined location, where it can fix carbon dioxide in the atmosphere for a long period of time.

[0040] (1-1) Anionic surfactant: The content of the anionic surfactant is 10 to 100% by mass, preferably 15 to 100% by mass, and more preferably 20 to 100% by mass. By setting the content within the above range, the carbon dioxide balance of the hydraulic composition can be reduced.

[0041] The content ratio of "components other than anionic surfactants" is reduced for the following reasons. First, when the "components other than anionic surfactants" are other than water, it is possible to avoid adding too much of the "components other than anionic surfactants" when adding the carbonation accelerator for hydraulic compositions to the hydraulic composition. As a result, it is possible to reduce the risk of the "components other than anionic surfactants" affecting various physical properties of the hydraulic composition. Furthermore, when the "components other than anionic surfactants" are water (i.e., when the carbonation accelerator for hydraulic compositions is an aqueous anionic surfactant solution), the above content ratio makes it easier to maintain the product stability of the carbonation accelerator for hydraulic compositions. In other words, an excessively high water content can easily cause spoilage and other problems.

[0042] An anionic surfactant is a compound containing an organic acid ion having a hydrophobic group with 6 to 50 carbon atoms in the molecule, and by containing this specific organic acid ion, the amount of carbon dioxide absorbed by the set body of the hydraulic composition can be increased.

[0043] The inclusion of the above-mentioned specific anionic surfactant in the carbonation accelerator for hydraulic compositions is presumed to have the following effect. That is, fine bubbles can be uniformly entrained within the hydraulic composition containing the carbonation accelerator for hydraulic compositions. This improves the material permeability of the hydraulic composition when it is hardened, and effectively forms flow paths through which gas (carbon dioxide) flows from the outer surface toward the center. Furthermore, the formation of these flow paths makes it easier for carbon dioxide to flow into the center of the hardened body of the hydraulic composition during carbonation curing, further accelerating carbonation.

[0044] (1-1-1) Compound represented by general formula (1): The anionic surfactant is not particularly limited as long as it satisfies the above conditions, but is preferably, for example, at least one compound selected from compounds represented by the following general formula (1). That is, the anionic surfactant may be one type of compound represented by general formula (1), or two or more types of compounds represented by general formula (1) may be present.

[0045] (In general formula (1), R 1 is an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, an aryl group having 8 to 20 carbon atoms, a residue obtained by removing a carboxylic acid from rosin, or a residue obtained by removing a hydrogen atom from a compound obtained by adding an alkylene oxide having 2 to 3 carbon atoms in a total ratio of 1 to 10 moles per mole of an aliphatic alcohol having 1 to 24 carbon atoms. X is one represented by the above-mentioned general formulas (a) to (f).

[0046] Rosin contains diterpene acid compounds known as resin acids (rosin acids). The resin acids contained in rosin are primarily abietic acid, but other resin acids include neoabietic acid, dehydroabietic acid, tetrahydroabietic acid, palustric acid, pimaric acid, isopimaric acid, sandaracopimaric acid, and levopimaric acid.

[0047] R in general formula (1) 1The "residue obtained by removing a carboxylic acid from rosin" refers to a residue obtained by removing a carboxylic acid from a resin acid that constitutes rosin. That is, for example, it includes a residue obtained by removing a carboxylic acid from abietic acid and a residue obtained by removing a carboxylic acid from palustric acid. For this reason, the "residue obtained by removing a carboxylic acid from rosin" usually includes two or more types of "residue obtained by removing a carboxylic acid from rosin," but it may also be a residue of one type (for example, a residue obtained by removing a carboxylic acid from abietic acid).

[0048] In addition, R in the general formula (1-1) 4 The same applies to the rosin of the acyl residue of rosin in the above, and "acyl residue of rosin" refers to the acyl residue of a carboxylic acid such as a resin acid that constitutes rosin.

[0049] (1-1-2) Compounds represented by general formulas (1-1) to (1-5): The anionic surfactant is preferably at least one selected from the compounds represented by general formula (1), more specifically, the compounds represented by the above-mentioned general formulas (1-1) to (1-5). By containing these compounds, the amount of carbon dioxide absorbed by the set body of the hydraulic composition can be further increased.

[0050] The compounds represented by the general formulas (1-3) to (1-5) can be used as a mixture to form an anionic surfactant. The composition ratio of these compounds can be determined by measuring the P NMR integral ratio.

[0051] The method for measuring the P nuclear NMR integral ratio is as follows. First, excess KOH is added to a mixture of compounds (phosphate esters) represented by general formulas (1-3) to (1-5) to adjust the pH to 12 or higher. Next, under these conditions (i.e., conditions after alkaline over-neutralization pretreatment with KOH), 31 P-NMR measurement is performed, and the P nuclear NMR integral ratio can be calculated using the obtained measurement value based on the following formulas (a) to (c). 31 Specifically, the P-NMR is a MERCURY plus NMR Spectrometer System (300 MHz) manufactured by VALIAN. 31The solvent used in the P-NMR measurement may be a mixed solvent of heavy water / tetrahydrofuran=8 / 2 (volume ratio).

[0052]

[0053]

[0054]

[0055] In the above formulas (a) to (c), P-1, P-2, and P-3 are as follows: P-1: P-nucleus NMR integral value assigned to the compound represented by general formula (1-3) (phosphate ester); P-2: P-nucleus NMR integral value assigned to the compound represented by general formula (1-4) (phosphate ester); P-3: P-nucleus NMR integral value assigned to the compound represented by general formula (1-5) (phosphate ester).

[0056] The term "alkaline overneutralization pretreatment" refers to a pretreatment in which an excess amount of alkali is added relative to the amount of phosphate ester. 31 In the P-NMR measurement, when this "alkaline overneutralization pretreatment" is performed, the peaks attributed to the phosphate esters can be clearly separated, and it becomes possible to calculate the P nuclear NMR integral ratios attributed to each compound according to the above formulas (a) to (c).

[0057] (1-1-3) Compound represented by general formula (1-1a): The compound represented by general formula (1-1) is preferably a compound represented by the following general formula (1-1a). In the present invention, the anionic surfactant is preferably a mixture containing a compound represented by the following general formula (1-1a) and at least one selected from the compounds represented by general formulas (1-2) to (1-5). By containing these compounds, the amount of carbon dioxide absorbed by the set body of the hydraulic composition can be further increased.

[0058] (In the general formula (1-1a), R 11 is an alkyl group having 6 to 20 carbon atoms or an alkenyl group having 6 to 20 carbon atoms. 16 is hydrogen, an alkali metal, an alkaline earth metal, or an organic amine.

[0059] R in general formula (1-1a) 11 represents an alkyl group having 6 to 20 carbon atoms or an alkenyl group having 6 to 20 carbon atoms.

[0060] M in general formula (1-1a) 16 is hydrogen, an alkali metal, an alkaline earth metal, or an organic amine.

[0061] (1-2) Other Components: The carbonation accelerator for hydraulic compositions of the present invention can contain other components in addition to the anionic surfactants described above, within the range that does not impair the effects.

[0062] As the other components, for example, water and additives added to conventionally known hydraulic compositions can be appropriately selected and used.

[0063] The other components may be used alone or in combination of two or more.

[0064] The carbonation accelerator for hydraulic compositions of the present invention is preferably one that is added to the hydraulic compositions described below.

[0065] (2) Hydraulic composition: The carbonation accelerator for a hydraulic composition of the present invention can be added to a hydraulic composition. This hydraulic composition can contain a binder (hydraulic binder), water, and aggregate (fine aggregate, coarse aggregate) in the same manner as conventionally known hydraulic compositions.

[0066] The content of the carbonation accelerator for hydraulic compositions of the present invention in the hydraulic composition is not particularly limited and can be set appropriately. For example, the content of the carbonation accelerator for hydraulic compositions of the present invention can be 0.0005 to 2 mass% relative to 100 mass% of the binder.

[0067] Examples of binders include various types of Portland cement such as ordinary Portland cement, moderate-heat Portland cement, low-heat Portland cement, high-early-strength Portland cement, and sulfate-resistant Portland cement, as well as various types of cement such as blast-furnace cement, fly ash cement, and silica fume cement.

[0068] Furthermore, various admixtures such as fly ash, ground granulated blast furnace slag, ground limestone, stone powder, silica fume, expanding agent, anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum may be used in combination with the various cements mentioned above.

[0069] The binder preferably contains 40 to 99% by mass of ground granulated blast furnace slag. In other words, the hydraulic composition to which the carbonation accelerator for hydraulic compositions of the present invention is added preferably contains a binder containing 40 to 99% by mass of ground granulated blast furnace slag, water, and aggregate. The content of ground granulated blast furnace slag is preferably 50 to 99% by mass, and more preferably 60 to 99% by mass. In this way, the carbon dioxide balance of the hydraulic composition can be further reduced.

[0070] Examples of aggregates include fine aggregates and coarse aggregates.

[0071] Examples of fine aggregates include river sand, mountain sand, land sand, sea sand, silica sand, crushed sand, various slag fine aggregates, and various recycled fine aggregates, but they may also contain fine particles such as clay.

[0072] Examples of coarse aggregate include river gravel, mountain gravel, land gravel, crushed stone, various slag coarse aggregates, lightweight aggregates, and various recycled coarse aggregates.

[0073] The hydraulic composition preferably contains γ-2CaO·SiO2. In other words, the carbonation accelerator for hydraulic compositions of the present invention is preferably added to a hydraulic composition containing γ-2CaO·SiO2. In this way, γ-2CaO·SiO2 exhibits the function of immobilizing carbon dioxide, thereby further increasing the amount of carbon dioxide absorbed by the set body of the hydraulic composition (i.e., the amount of carbon dioxide reduction). As a result, the carbon dioxide balance of the hydraulic composition can be further reduced. This γ-2CaO·SiO2 is a material that hardens by carbonation. Note that γ-2CaO·SiO2 may be added to a hydraulic composition containing a binder containing 40 to 99 mass% ground granulated blast furnace slag, water, and aggregate, or to a hydraulic composition that does not contain these binders.

[0074] The content of γ-2CaO·SiO2 is not particularly limited, but can be, for example, a proportion corresponding to 1 to 30 mass % relative to 100 mass % of the binder.

[0075] The hydraulic composition preferably contains at least one selected from the CO2-fixing fine powder and the CO2-fixing modified recycled fine aggregate described below. This further reduces the carbon dioxide balance of the hydraulic composition. Carbon capture and utilization (CCU) materials, such as CO2-fixing fine powder and CO2-fixing modified recycled aggregate (including CO2-fixing modified recycled fine aggregate), are powders or aggregates produced by reacting CO2 with calcium derived from waste materials such as waste concrete. These CCU materials are sometimes used in carbon-neutral or carbon-negative concrete. The hydraulic composition may further contain CO2-fixing modified recycled coarse aggregate in addition to the CO2-fixing modified recycled fine aggregate, or CO2-fixing modified recycled coarse aggregate may be used instead of the CO2-fixing modified recycled fine aggregate.

[0076] (CO2-fixing fine powder) The CO2-fixing fine powder has a 50% particle size of 50 μm or less and includes modified concrete powder, which is a reaction product of recycled concrete powder and carbon dioxide, and this modified concrete powder contains calcium carbonate and silicate. The content of the CO2-fixing fine powder is in the range of 1 to 100% by mass relative to 100% by mass of the binder.

[0077] CO2-fixing fine powder can be produced as follows. First, concrete blocks are crushed or ground to recover recycled concrete fine powder with a median diameter of 100 μm or less. The method for this crushing or grinding is not particularly limited, and known crushing or grinding devices, such as shot-blasting crushers, impact crushers, and grinding devices using mechanical grinding without heating, can be used. Next, the recovered recycled concrete fine powder is reacted with carbon dioxide at a volume concentration of 5% or more to fix CO2 to the cement-derived components contained in the recycled concrete fine powder. The reaction with carbon dioxide can be carried out either by a dry method in which gaseous carbon dioxide is brought into contact with the recycled concrete fine powder, or by a wet method in which the recycled concrete fine powder is immersed in a solution such as water and then carbon dioxide is blown into the liquid (dispersion) to contact the recycled concrete fine powder. In this manner, CO2-fixing fine powder can be produced.

[0078] (CO2-fixed modified recycled aggregate) CO2-fixed modified recycled aggregate is an aggregate produced by reacting CO2 in advance with calcium derived from waste materials such as waste concrete. Examples include CO2-fixed modified recycled fine aggregate and CO2-fixed modified recycled coarse aggregate. Among these, it is preferable to use CO2-fixed modified recycled fine aggregate. This is because CO2-fixed modified recycled fine aggregate contains more calcium derived from cement, fixes a larger amount of CO2 during the production of CO2-fixed modified recycled aggregate (i.e., the "emission of carbon dioxide derived from materials" is smaller), and is highly effective in reducing the carbon dioxide balance when applied to hydraulic compositions.

[0079] (CO2 fixation modified recycled fine aggregate) The CO2 fixation modified recycled fine aggregate includes recycled fine aggregate in which all particles have a particle size of 10 mm or less, with at least 85% of those particles being 5 mm or less, and which has a water absorption rate of more than 3.0% and not more than 10%, and modified recycled fine aggregate which is a dry or wet reaction product with carbon dioxide. The modified recycled fine aggregate contains calcium carbonate and silicon dioxide. The content of the CO2 fixation modified recycled fine aggregate is in the range of 10 to 100 volume % of the total aggregate volume.

[0080] CO2 fixation and modified recycled fine aggregate can be produced as follows. Specifically, concrete blocks are first crushed or ground to obtain recycled fine aggregate. There are no particular limitations on the method of crushing or grinding, and known crushing or grinding devices, such as shot-blasting crushers, impact crushers, and grinding devices using mechanical grinding without heating, can be used. Subsequently, particles with a particle size of 10 mm or less are classified, and particles with a water absorption rate of more than 3% and less than 10% are used as recycled fine aggregate. Next, the recycled fine aggregate is reacted with carbon dioxide at a volume concentration of 5% or more to obtain CO2 fixation and modified recycled fine aggregate containing calcium carbonate and silicon dioxide. The reaction between the recycled fine aggregate and carbon dioxide can be performed using either a dry method or a wet method. In this manner, CO2 fixation and modified recycled fine aggregate can be produced.

[0081] The content of the CO2-fixing fine powder is 1 to 100% by mass, preferably 10 to 90% by mass, and more preferably 30 to 80% by mass, relative to 100% by mass of the binder, as described above.

[0082] The content of the CO2 fixation modified recycled fine aggregate is 10 to 100% by volume, preferably 20 to 100% by volume, and more preferably 30 to 100% by volume, of the total aggregate volume (more specifically, the aggregate volume when the original natural aggregate is used), as described above.

[0083] Here, the term "original mix" refers to a mix that does not use CO2 fixation modified recycled fine aggregate. Furthermore, "natural aggregate" refers to aggregate that has not been subjected to CO2 fixation treatment. Examples of natural aggregate include fine aggregates such as river sand, mountain sand, land sand, sea sand, silica sand, crushed sand, and various slag fine aggregates, and coarse aggregates such as river gravel, mountain gravel, land gravel, crushed stone, various slag coarse aggregates, and lightweight aggregates. In other words, "relative to the aggregate volume using natural aggregate in the original mix" refers to the volume of natural aggregate such as river sand as in the past. In other words, CO2 fixation modified recycled fine aggregate may be used in place of the aggregate conventionally used (100% by volume), or it may be used by replacing approximately 1 / 5 (i.e., 20% by volume).

[0084] The hydraulic composition may further contain other components as appropriate within the range that does not impair the effect. Examples of such other components include setting retarders such as sugars and oxycarboxylates, dispersing components such as sodium lignin sulfonate, antifoaming agents such as oxyalkylene compounds, hardening accelerators such as alkanolamines, shrinkage reducers such as polyoxyalkylene alkyl ethers, thickeners such as cellulose ether compounds, preservatives such as isothiazolinone compounds, and rust inhibitors such as nitrites.

[0085] The content of the other constituent components can be, for example, 0 to 5% by mass relative to 100% by mass of the binder.

[0086] The ratio of water to binder in the hydraulic composition (water / binder ratio) can be suitably selected from conventionally known ratios, and can be, for example, 25 to 70 mass %.

[0087] The hydraulic composition can be hardened to form a hydraulic composition hardened product (specifically, mortar or concrete). When obtaining such a hardened hydraulic composition, it is preferable to subject the hydraulic composition to a carbonation curing process, which is a process of curing in an environment with a volume concentration of carbon dioxide of 5% or more. By subjecting the hydraulic composition to such a carbonation curing process, a large amount of carbon dioxide can be absorbed and fixed in the hydraulic composition (hardened hydraulic composition).

[0088] The volume concentration of carbon dioxide in the carbonation curing step is not particularly limited, but can usually be set to 5 to 100%.

[0089] (3) Manufacturing method for hardened hydraulic composition: The manufacturing method for hardened hydraulic composition of the present invention comprises the steps of: preparing a hydraulic composition containing at least the carbonation accelerator for hydraulic compositions of the present invention, a binder containing 40 to 99% by mass of ground granulated blast furnace slag, and water; hardening the obtained hydraulic composition to obtain a hardened hydraulic composition; and curing the obtained hardened hydraulic composition in an environment with a carbon dioxide volume concentration of 5% or more to absorb and fix carbon dioxide in the hardened hydraulic composition. According to this manufacturing method for hardened hydraulic composition, the amount of carbon dioxide reduced in the manufacturing process is increased because a hydraulic composition containing the carbonation accelerator for hydraulic compositions of the present invention is used.

[0090] (3-1) Preparation step: The preparation step is a step of preparing a hydraulic composition containing at least the carbonation accelerator for hydraulic compositions of the present invention, a binder containing 40 to 99 mass% of ground granulated blast furnace slag, and water.

[0091] As described above, the ground granulated blast furnace slag is contained in an amount of 40 to 99 mass%, preferably 50 to 99 mass%, and more preferably 60 to 99 mass%. By setting the content to the above ratio, the amount of carbon dioxide reduced in the process of producing the hydraulic composition hardened body increases.

[0092] (3-2) Curing Step: The curing step is a step of curing the hydraulic composition obtained in the preparation step to obtain a hydraulic composition cured product. As a method for curing the hydraulic composition, a conventionally known method can be appropriately adopted.

[0093] (3-3) Carbonation Curing Step: The carbonation curing step is a step in which the hardened hydraulic composition obtained in the hardening step is cured (carbonation curing) in an environment with a volume concentration of carbon dioxide of 5% or more, thereby absorbing and immobilizing carbon dioxide in the hardened hydraulic composition.

[0094] In this step, carbon dioxide in the atmosphere is absorbed into the hardened hydraulic composition, carbonated, and fixed. The use of the carbonation accelerator for hydraulic compositions of the present invention is presumed to result in the following: Fine bubbles are uniformly entrained within the hydraulic composition. As a result, flow paths through which gas (carbon dioxide) flows from the outer surface toward the center of the hardened hydraulic composition are well formed. The formation of these flow paths makes it easier for carbon dioxide to flow to the center of the hardened hydraulic composition, allowing more carbon dioxide to be absorbed and fixed in the hydraulic composition (hardened hydraulic composition).

[0095] The volume concentration of carbon dioxide is not particularly limited, but can usually be set to 5 to 100%.

[0096] If the volume concentration of carbon dioxide is less than 5%, the amount of carbon dioxide absorbed will be too small, and the carbonation curing period required to achieve a predetermined fixed amount of carbon dioxide may be prolonged.

[0097] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0098] (Examples 1 to 48, Comparative Examples 1 to 12) (1) Carbonation accelerator for hydraulic composition: First, carbonation accelerators A-1 to A-16 and RA-1 to RA-2 for hydraulic compositions of Examples and Comparative Examples were prepared according to the formulations shown in Table 1 below.

[0099]

[0100] Next, Table 2 below shows specific details of the essential components (anionic surfactants a-1 to a-18) and other components (b-1 to b-5) shown in Table 1. b-5 is "Squish 21B" (special polycarboxylic acid surfactant), a product name manufactured by Kao Corporation.

[0101]

[0102] The method for producing each of the anionic surfactants (a-1 to a-18) will be specifically described below.

[0103] The anionic surfactant (a-1) used was oleic acid from Tokyo Chemical Industry Co., Ltd. The anionic surfactant (a-13) used branched-chain sodium dodecylbenzenesulfonate from Tokyo Chemical Industry Co., Ltd. The anionic surfactant (a-14) used linear sodium dodecylbenzenesulfonate from Tokyo Chemical Industry Co., Ltd. The anionic surfactant (a-15) used sodium decyl sulfate from Kao Corporation. The anionic surfactant (a-16) used sodium higher alcohol ethoxy sulfate from Teika Corporation. The anionic surfactant (a-17) used sodium tetradecenesulfonate (sodium α-olefinsulfonate) from Lion Specialty Chemicals. The anionic surfactant (a-18) used sodium sec-alkyl (C14-17) sulfonate from Clariant.

[0104] The anionic surfactants (a-1 to a-12) can be classified as compounds represented by general formulas (1-1) to (1-5) as follows: Anionic surfactants a-1 to a-4 and a-12 are compounds represented by general formula (1-1), and anionic surfactants a-10 to a-11 are compounds represented by general formula (1-2). Anionic surfactants a-5 to a-9 are mixtures of compounds represented by general formulas (1-3) to (1-5). Anionic surfactants a-13 to a-18 are compounds containing organic acid ions having a hydrophobic group with 6 to 50 carbon atoms in the molecule.

[0105] Anionic surfactant a-2: 437.91 g of ion-exchanged water and 18.17 g of 48% aqueous potassium hydroxide solution were placed in a reaction vessel and heated to 40°C. 43.92 g of oleic acid (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) was added thereto with stirring. After thorough stirring, the mixture was aged for 1 hour. In this way, a 10% aqueous solution of potassium oleate (anionic surfactant a-2) was obtained.

[0106] Anionic surfactants a-3 and a-4: Anionic surfactants a-3 and a-4 were synthesized in the same manner as anionic surfactant a-2, except that the types and charging ratios of the compounds used (raw material fatty acid and alkali used for neutralization) were changed.

[0107] Anionic surfactant a-5: 221.44 g of 1-octanol (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in a reaction vessel and subjected to dehydration treatment for 2 hours under conditions of 120°C and 0.05 MPa. The pressure was then returned to atmospheric pressure, and 78.56 g of diphosphorus pentoxide was added over 0.5 hours at 60±5°C with stirring. The mixture was aged for 3 hours at 80°C, and then 200.00 g of ion-exchanged water was added and aged for 0.5 hours to obtain a 60% aqueous solution of phosphate ester (a-5), which is anionic surfactant a-5.

[0108] Anionic surfactant a-6-1: 407.11 g of ion-exchanged water and 71.29 g of a 60% aqueous solution of phosphate ester (a-5) were placed in a reaction vessel, and the mixture was heated to 50° C. 21.61 g of a 48% aqueous solution of potassium hydroxide was added dropwise to the mixture to neutralize it, thereby obtaining a 10% aqueous solution of phosphate ester (a-6-1), which is anionic surfactant a-6-1.

[0109] Anionic surfactant a-6-2: A reaction vessel was charged with 136.53 g of 1-octanol (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was dehydrated for 2 hours under conditions of 120°C and 0.05 MPa. The pressure was then returned to atmospheric pressure, and 86.93 g of diphosphorus pentoxide was added over 0.5 hours at 60±5°C with stirring. After aging for 3 hours at 80°C, 47.74 g of ion-exchanged water was added and the mixture was aged for 0.5 hours. 228.81 g of a 48% aqueous potassium hydroxide solution was added dropwise at 50°C to neutralize the mixture, thereby obtaining a 60% aqueous solution of phosphate ester (a-6-2). The solution was then adjusted to 10% with ion-exchanged water, obtaining a 10% aqueous solution of anionic surfactant a-6-2.

[0110] Anionic surfactant a-7: Anionic surfactant a-7 was synthesized in the same manner as anionic surfactant a-5, except that the type of compound (raw material alcohol) used and the charging ratio of raw material alcohol to diphosphorus pentoxide were changed.

[0111] Anionic surfactant a-8: (Synthesis of poly(5 mol)oxyethylene octyl ether) 371.58 g of 1-octanol (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) and 1.0 g of potassium hydroxide were charged into a pressure vessel equipped with a stirrer, a pressure gauge, and a thermometer. Subsequently, while maintaining the reaction system at 150±5°C, 628.42 g of ethylene oxide was added at a gauge pressure of 0.4 MPa over 4 hours, and the temperature was maintained at 150±5°C for 1 hour to terminate the reaction. Thereafter, neutralization was carried out using Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.), and filtration was carried out to obtain poly(5 mol)oxyethylene octyl ether.

[0112] (Phosphorylation) Next, 210.96 g of the obtained poly(5 mol)oxyethylene octyl ether was charged into another reaction vessel, and dehydration treatment was performed at 120 ° C. for 2 hours under conditions of 0.05 MPa or less. After returning to atmospheric pressure, 47.35 g of diphosphorus pentoxide was added over 0.5 hours at 60 ± 5 ° C. with stirring. After aging for 3 hours at 80 ° C., 117.06 g of ion-exchanged water was added and aged for 0.5 hours. To this was added dropwise 124.63 g of 48% aqueous potassium hydroxide solution at 50 ° C. for neutralization, to obtain a 60% aqueous solution of phosphate ester (a-8). Thereafter, the solution was adjusted to 10% with ion-exchanged water to obtain a 10% aqueous solution of anionic surfactant a-8.

[0113] Anionic surfactant a-9: Anionic surfactant a-9 was synthesized in the same manner as anionic surfactant a-6-1, except that the type of compound (raw material alcohol) used and the charging ratio of raw material alcohol to diphosphorus pentoxide were changed.

[0114] Anionic surfactant a-10: 298.6 g of ion-exchanged water and 90.3 g of a 48% aqueous potassium hydroxide solution were charged into a reaction vessel and uniformly dissolved with stirring, and then the temperature of the reaction system was maintained at 40°C in a warm water bath. Next, 111.1 g of dodecenyl succinic anhydride (reagent, manufactured by Tokyo Chemical Industry Co., Ltd., branched chain isomer mixture) was added dropwise over 1 hour to neutralize, and then the mixture was stirred at 45°C for 2 hours. After the neutralization reaction, 913.09 g of ion-exchanged water was added and the mixture was thoroughly stirred. In this way, a 10% aqueous solution of anionic surfactant a-10 was obtained.

[0115] Anionic surfactant a-11: Anionic surfactant a-11 was synthesized in the same manner as anionic surfactant a-10, except for the changes shown in Table 1.

[0116] Anionic surfactant a-12: 701.7 g of ion-exchanged water and 76.3 g of a 48% aqueous potassium hydroxide solution were placed in a reaction vessel and heated to 90° C. 222.0 g of rosin (reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added thereto with stirring. After the addition, the mixture was aged for 1 hour to obtain a 25% aqueous solution of rosin potassium salt, which is anionic surfactant a-12.

[0117] (Weight-average molecular weight) The weight-average molecular weight of each anionic surfactant (a-1 to a-18) is shown in the "Molecular weight" column in Table 2. The weight-average molecular weight was measured using gel permeation chromatography (GPC) under the following conditions. <Measurement conditions> Apparatus: Shodex GPC-101 (Showa Denko K.K.) Column: OHpak SB-G + SB-804M HQ + SB-802.5M HQ (Showa Denko K.K.) Detector: Differential refractometer (RI) Eluent: 50 mM aqueous sodium nitrate solution Flow rate: 0.7 mL / min Column temperature: 40°C Sample concentration: Eluent solution with a sample concentration of 0.5% by mass Standard substance: PEG / PEO (Agilent Technologies)

[0118] (P NMR Integral Ratio) Each of the anionic surfactants a-5 to a-9 shown in Table 2 is a mixture of compounds represented by general formulas (1-3) to (1-5). Therefore, the P NMR integral ratio attributable to each of the compounds represented by general formulas (1-3) to (1-5) was measured. The results are shown in Table 2. In the "P NMR Integral Ratio" column in Table 2, "mono" indicates the P NMR integral ratio attributable to the compound represented by general formula (1-3), "di" indicates the P NMR integral ratio attributable to the compound represented by general formula (1-4), and "poly" indicates the P NMR integral ratio attributable to the compound represented by general formula (1-5).

[0119] The P nuclear NMR integral ratio was determined by first adding excess KOH to each prepared phosphate ester (organophosphate ester) to adjust the pH to 12 or higher. Next, under these conditions (i.e., conditions after alkaline over-neutralization pretreatment with KOH), 31 P-NMR measurement was carried out, and the P nuclear NMR integral ratio was calculated using the obtained measurement values ​​based on the following formulas (a) to (c). 31 Specifically, the P-NMR is a MERCURY plus NMR Spectrometer System (300 MHz) manufactured by VALIAN. 31 The solvent used in the P-NMR measurement was a mixed solvent of heavy water / tetrahydrofuran = 8 / 2 (volume ratio).

[0120]

[0121]

[0122]

[0123] In the above formulas (a) to (c), P-1, P-2, and P-3 are as follows: P-1: P-nucleus NMR integral value assigned to the compound represented by general formula (1-3) (phosphate ester); P-2: P-nucleus NMR integral value assigned to the compound represented by general formula (1-4) (phosphate ester); P-3: P-nucleus NMR integral value assigned to the compound represented by general formula (1-5) (phosphate ester).

[0124] (2) Hydraulic Compositions: Next, hydraulic compositions (mortars) were prepared using formulations C-1 to C-3 shown in Table 3.

[0125] Specifically, ordinary Portland cement, ground granulated blast furnace slag #4000, LEAF carbonation admixture mainly composed of γ-2CaO·SiO2, fine aggregate, carbon dioxide (CO2) fixation fine powder (CCU fine powder), and carbon dioxide (CO2) fixation modified recycled aggregate (CCU recycled fine aggregate) were first sequentially added to a mixer specified in JIS R5201 in the formulations C-1 to C-3 (mortar formulations) shown in Table 3, and then dry-mixed for 10 seconds. Note that ordinary Portland cement, ground granulated blast furnace slag, and carbonation admixture were considered as binders. Ordinary Portland cement has a density of 3.16 g / cm3.3 (manufactured by Taiheiyo Cement Corporation). Ground granulated blast furnace slag #4000 has a density of 2.89 g / cm 3 (Manufactured by Esment Chubu Co., Ltd.) LEAF, a carbonated admixture whose main component is γ-2CaO SiO2, has a density of 3.09 g / cm 3 (manufactured by Denka Co., Ltd.) The fine aggregate has a density of 2.58 g / cm 3 (Oi River water system land sand). Carbon dioxide (CO2) fixed fine powder has a density of 2.51 g / cm 3 The carbon dioxide (CO2) fixed and modified recycled aggregate has a density of 2.42 g / cm 3 is.

[0126] The CO2 fixation fine powder and CO2 fixation modified recycled aggregate are specifically shown below.

[0127] The CO2 fixation fine powder has a 50% particle size of 50 μm or less, includes modified concrete powder which is a reaction product of recycled concrete powder and carbon dioxide, and contains calcium carbonate and silicate.

[0128] Specifically, this CO2-fixing fine powder was produced as follows: concrete blocks were crushed and ground using a known crusher to obtain recycled concrete fine powder with a median diameter of 100 μm or less. 3 1,800 kg of water and 200 kg of the resulting recycled concrete fine powder were sequentially added to the container and stirred. Carbon dioxide gas was then injected from the bottom of the container at a rate of 150 L / min to react the recycled concrete fine powder with CO2. The reaction process was continued until the pH of the dispersion reached 6.8 or less, after which a reaction product of recycled concrete fine powder and CO2 was obtained. After the reaction was completed, the resulting reaction product was removed, excess water was removed using a polypropylene twill filter, and the mixture was air-dried to obtain CO2-fixed fine powder.

[0129] The CO2 fixation modified recycled aggregate (specifically, CO2 fixation modified recycled fine aggregate) includes modified recycled fine aggregate, which is a dry or wet reaction product of recycled fine aggregate with a water absorption rate of more than 3.0% and not more than 10% and carbon dioxide, and contains calcium carbonate, silicon dioxide, and gypsum.

[0130] Specifically, this CO2 fixation and modified recycled aggregate was produced as follows: concrete blocks were crushed and ground using a known crusher, and then classified using a sieve so that all particles had a particle size of 10 mm or less. Among these, particles with a water absorption rate of more than 3% and less than 10% were obtained as recycled fine aggregate. 3 1,800 kg of water and 200 kg of the resulting recycled fine aggregate were sequentially added to the container and stirred. Carbon dioxide gas was then injected from the bottom of the container at a rate of 150 L / min to react the recycled fine aggregate with CO2. The reaction process was continued until the pH of the dispersion reached 6.8 or less, after which a reaction product of the recycled fine aggregate and CO2 was obtained. After the reaction was completed, the resulting reaction product was removed, excess water was removed using a polypropylene twill filter, and the mixture was air-dried to obtain a CO2-immobilized and modified recycled fine aggregate.

[0131] Next, the carbonation accelerator for hydraulic compositions shown in Table 1, a water-reducing agent (high-performance water-reducing agent Chupol NV-80 (trade name) manufactured by Takemoto Yushi Co., Ltd.), and an antifoaming agent (AFK-2 (trade name) manufactured by Takemoto Yushi Co., Ltd.) were added to the mixing water. However, the carbonation accelerator, water-reducing agent, and antifoaming agent were considered to be part of the mixing water. Thereafter, this mixing water was charged into a mixer and mixed for 180 seconds to obtain a hydraulic composition (mortar).

[0132] The antifoaming agent was added in an amount of 0.0005% by mass relative to the binder (however, no antifoaming agent was added in Comparative Examples 2, 5, and 8). The carbonation accelerator for hydraulic compositions was added in an amount within the range of 0.001 to 0.05% by mass relative to the binder, as shown in Tables 4 to 6, so that the air content of the mixed mortar would be within 4.5±0.5%. However, in Comparative Examples 2, 5, and 8, the mixer was stirred at high speed when mixing the mortar, so that the air content of the mixed mortar would be 4.5±0.5%.

[0133] In addition, the amount of water-reducing agent added was such that the mortar flow was within 200±5 mm in mixes C-1 and C-2, and such that the mortar flow was within 275±5 mm in mix C-3.

[0134]

[0135] The following relationships exist between mixes C-1 to C-3. Specifically, no carbonation admixture was used in mixes C-1, while carbonation admixture was used in mixes C-2 and C-3. This carbonation admixture accounts for 30% by mass of the binder. Mix C-3 contains CCU fine powder, which replaces the fine aggregate at 50% by mass of the binder. Mix C-3 also contains recycled CCU fine aggregate, which replaces 100% of the fine aggregate.

[0136] In Table 3, "Amount of carbon dioxide emitted from materials (α)" was calculated based on the amount of carbon dioxide emitted during the production of each component. That is, the carbon dioxide emission amount for ordinary Portland is 764.3 kg / t, and that for ground granulated blast furnace slag is 26.5 kg / t. The carbon dioxide emission amount for carbonated admixture is 124.5 kg / t, that for recycled CCU fine aggregate is -26.9 kg / t, and that for fine CCU powder is -83.8 kg / t.

[0137] Tables 4 to 6 show the test results (mortar flow (mm), air content (%)) and carbon dioxide balance results for the mortars prepared using each of the blends C-1 to C-3. The values ​​in the "Amount of carbon dioxide emitted from materials (α)" column in Tables 4 to 6 refer to the "Amount of carbon dioxide emitted from materials (α)" shown in Table 3.

[0138] In addition, in Examples 1 to 16 and Comparative Examples 1 and 2 shown in Table 4, the carbon dioxide balance of Comparative Example 3 was used as the standard, and the difference between the carbon dioxide balance in each Example and Comparative Example was calculated to determine the "amount of carbon dioxide reduction" by the carbonation accelerator for hydraulic compositions. In Examples 17 to 32 and Comparative Examples 5 and 6 shown in Table 5, the carbon dioxide balance of Comparative Example 7 was used as the standard, and the difference between the carbon dioxide balance in each Example and Comparative Example was calculated to determine the "amount of carbon dioxide reduction" by the carbonation accelerator for hydraulic compositions. In Examples 33 to 48 and Comparative Examples 9 and 10 shown in Table 6, the carbon dioxide balance of Comparative Example 11 was used as the standard, and the difference between the carbon dioxide balance in each Example and Comparative Example was calculated to determine the "amount of carbon dioxide reduction" by the carbonation accelerator for hydraulic compositions.

[0139] Here, in Comparative Examples 3, 7, and 11, no carbonation accelerator for hydraulic compositions was used, and only a water-reducing agent was used. In Comparative Examples 3, 7, and 11, air was intentionally entrained in the hydraulic compositions by stirring them at high speed. However, the entrained air was coarser than when a carbonation accelerator for hydraulic compositions was used. Note that the carbon dioxide balances of Comparative Examples 4, 8, and 12 were greater than those of Comparative Examples 3, 7, and 11, respectively, and therefore the "amount of carbon dioxide reduction" was not calculated.

[0140] The methods for measuring the mortar flow (mm) and air content (%) of the hydraulic composition are as follows.

[0141] (Mortar Flow) The hydraulic composition immediately after mixing was measured in accordance with JIS R5201 without dropping.

[0142] (Air Content (Volume %)) The air content of the hydraulic composition immediately after mixing was measured in accordance with JIS A1116 using a mortar container.

[0143] (3) Manufacturing Method of Hardened Hydraulic Composition: (Mortar Hardening Step) First, a cylindrical tin mold for forming a concrete specimen (trade name "Summit Mold", manufactured by Sumitomo Cement Corporation, mold bottom diameter 50 mm, mold height 100 mm) was prepared, and the prepared hydraulic composition (mortar) was filled into this mold using a two-layer filling method.

[0144] Next, the mortar was cured in air (20°C) in a room at 20°C. Two hours after the preparation of the mortar, the surface of the filled mortar was smoothed, and polyethylene wrap was placed over it to prevent evaporation of water, and sealed curing was carried out until the material reached an age of two days. Then, a test specimen (hardened mortar) was obtained.

[0145] (Carbonation curing process of hardened mortar (hardened hydraulic composition)) After sealed curing, the test specimen (hardened mortar) was removed from the formwork and subjected to carbonation curing (curing conditions: 20°C, 60% RH, volume concentration of carbon dioxide 60%) in a high-concentration accelerated carbonation curing tank (manufactured by Marui Co., Ltd.) capable of controlling temperature, humidity, and carbon dioxide concentration until the material was 7 days old. At this time, the test specimen was not covered, and carbonation was carried out from the entire surface of the test specimen. In this way, a hardened hydraulic composition was produced.

[0146] (Measurement of Amount of Fixed Carbon Dioxide) The amount of fixed carbon dioxide in the produced hardened hydraulic composition was measured as follows.

[0147] (Method of preparing analytical samples) After carbonation curing, the test specimens (hardened hydraulic composition bodies) were removed from the curing tank and promptly transferred to a furnace at 105° C. for drying treatment for two days. After drying, the test specimens were all crushed and further pulverized in a ball mill to particles of 150 μm or less, and these were used as analytical samples.

[0148] (Method for measuring total carbon amount, method for calculating amount of CO2 fixed by carbonation curing) To confirm the amount of carbon dioxide fixed by carbonation curing (amount of CO2 fixed), the total carbon amount (C (%)) in the analytical sample was measured using a total organic carbon meter ("TOC-L" and solid sample combustion apparatus "SSM-5000A" manufactured by Shimadzu Corporation). The measurement conditions were a sample amount of 50 mg and a combustion temperature of 900°C.

[0149] The amount of CO2 fixed (%) in the analytical sample was calculated from the obtained total carbon amount using the following formula, and the amount of carbon dioxide fixed by carbonation curing (kg-CO2 / m 3 ) was calculated using the formula: CO2 (%) = C (%) × 44 / 12

[0150] The amount of CO2 fixation is the percentage of the sample weight after heat treatment at 900°C. The amount of CO2 fixation due to carbonation curing was calculated after subtracting the amount of carbon detected from the materials used in the mortar and the added components (water-reducing agent, antifoaming agent, carbonation accelerator for hydraulic compositions). The "materials used in the mortar" mentioned above are cement, ground granulated blast furnace slag, carbonation accelerator, CO2-fixed fine powder, fine aggregate, and CO2-fixed modified recycled aggregate (CO2-fixed modified recycled fine aggregate).

[0151] In Tables 4 to 6, "carbon dioxide balance (α - β)" is a value calculated by the formula: carbon dioxide emission amount derived from materials (α) - carbon dioxide fixation amount by carbonation curing (β). Also, "carbon dioxide reduction amount" is a value calculated by the formula: |"carbon dioxide balance" of each Example - "carbon dioxide balance" of Comparative Examples 3, 7, and 11|. Note that the results of this "carbon dioxide reduction amount" show that each Example has a superior carbon dioxide absorption effect compared to the benchmarks of Comparative Examples 3, 7, and 11. In other words, in each Example, the carbonation of the hydraulic composition is promoted by the carbonation accelerator for hydraulic compositions.

[0152]

[0153] In Table 4, the evaluation of "carbon dioxide reduction amount" was based on the following evaluation criteria: S: Carbon dioxide reduction amount (kg-CO2 / m 3 ) is 30 kg-CO2 / m 3 A: Carbon dioxide reduction (kg-CO2 / m 3 ) is 20 kg-CO2 / m 3 30 kg-CO2 / m 3 If it is less than B: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 More than 20 kg-CO2 / m 3 If less than C: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 If it is less than

[0154]

[0155] In Table 5, the evaluation of "carbon dioxide reduction amount" was based on the following evaluation criteria: S: Carbon dioxide reduction amount (kg-CO2 / m 3 ) is 30 kg-CO2 / m 3 A: Carbon dioxide reduction (kg-CO2 / m 3 ) is 20 kg-CO2 / m 3 30 kg-CO2 / m 3 If it is less than B: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 More than 20 kg-CO2 / m 3 If less than C: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 If it is less than

[0156]

[0157] In Table 6, the evaluation of "carbon dioxide reduction amount" was based on the following evaluation criteria: S: Carbon dioxide reduction amount (kg-CO2 / m 3 ) is 25 kg-CO2 / m 3 A: Carbon dioxide reduction (kg-CO2 / m 3 ) is 20 kg-CO2 / m 3 More than 25 kg CO2 / m 3 If it is less than B: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 More than 20 kg-CO2 / m 3 If less than C: Carbon dioxide reduction (kg-CO2 / m 3 ) is 10 kg-CO2 / m 3 If it is less than

[0158] (Results) As shown in Tables 4 to 6, it can be seen that the addition of the carbonation accelerator for hydraulic compositions of this Example accelerates the carbonation of the hydraulic composition, thereby increasing the amount of carbon dioxide reduction by the hydraulic composition (hardened hydraulic composition). Furthermore, according to the method for producing a hardened hydraulic composition of this Example, it can be seen that the use of the carbonation accelerator for hydraulic compositions of this Example as a raw material accelerates the carbonation of the hydraulic composition, thereby increasing the amount of carbon dioxide absorbed by the hardened hydraulic composition produced (reduced carbon dioxide).

[0159] The carbonation accelerator for hydraulic compositions of the present invention can be used as a raw material for producing a hardened hydraulic composition that reduces carbon dioxide by adding it to the hydraulic composition. The method for producing a hardened hydraulic composition of the present invention can be employed as a method for producing a hardened hydraulic composition that absorbs carbon dioxide.

Claims

1. A carbonation accelerator for a hydraulic composition, which contains an anionic surfactant at a ratio of 10 to 100% by mass, and the anionic surfactant is a compound containing an organic acid ion having a hydrophobic group with 6 to 50 carbon atoms in the molecule.

2. The carbonation accelerator for a hydraulic composition according to claim 1, wherein the anionic surfactant is at least one compound selected from the compounds represented by the following general formula (1). (In general formula (1), R 1 is an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, an aryl group having 8 to 20 carbon atoms, a residue obtained by removing carboxylic acid from rosin, or a residue obtained by removing hydrogen from a product obtained by adding a total of 1 to 10 moles of alkylene oxide having 2 to 3 carbon atoms per mole of an aliphatic alcohol having 1 to 24 carbon atoms. X is represented by the following general formulas (a) to (f).) (In general formulas (a) to (f), R 2 and R 3 are each independently a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 1 to 24 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding a total of 1 to 10 moles of alkylene oxide having 2 to 3 carbon atoms per mole of an aliphatic alcohol having 1 to 24 carbon atoms. M 1 to M 8 are each independently an alkali metal, an alkaline earth metal, ammonium, or an organic amine. n is an integer of 2 or 3.) 3. The carbonation accelerator for the hydraulic composition according to claim 1, wherein the anionic surfactant is at least one selected from the compounds represented by the following general formulas (1-1) to (1-5). (In general formula (1-1), R 4 is an alkyl group having 6 to 20 carbon atoms, an alkenyl group having 6 to 20 carbon atoms, or an acyl residue of rosin. M 9 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.) (In general formula (1-2), R 5 is an alkyl group having 6 to 20 carbon atoms, an alkenyl group having 6 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. M 10 to M 11 is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or an organic amine.) (In general formula (1-3), R 6 is a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding a total of 1 to 10 moles of an alkylene oxide having 2 to 3 carbon atoms per mole of an aliphatic alcohol having 6 to 20 carbon atoms. M 12 , M 13 are each independently hydrogen, an alkali metal, an alkaline earth metal, ammonium or an organic amine.) (In general formula (1-4), R 7 , R 8 are each independently a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding a total of 1 to 10 moles of an alkylene oxide having 2 to 3 carbon atoms per mole of an aliphatic alcohol having 6 to 20 carbon atoms. M 14 is hydrogen, an alkali metal, an alkaline earth metal, ammonium or an organic amine.) (In general formula (1-5), R 9 , R 10 is, independently of each other, a residue obtained by removing a hydroxyl group from an aliphatic alcohol having 6 to 20 carbon atoms, or a residue obtained by removing a hydroxyl group from a product obtained by adding 1 to 10 moles in total of an alkylene oxide having 2 to 3 carbon atoms per mole of an aliphatic alcohol having 6 to 20 carbon atoms. M 15 is hydrogen, an alkali metal, an alkaline earth metal, ammonium or an organic amine. m is an integer of 2 or 3.) 4. The carbonation accelerator for a hydraulic composition according to claim 3, wherein the anionic surfactant is a mixture containing a compound represented by the general formula (1-1a) and at least one compound selected from the compounds represented by the general formulas (1-2) to (1-5). (In the general formula (1-1a), R 11 is an alkyl group having 6 to 20 carbon atoms or an alkenyl group having 6 to 20 carbon atoms. M 16 is hydrogen, an alkali metal, an alkaline earth metal, or an organic amine.) 5. The carbonation accelerator for a hydraulic composition according to any one of claims 1 to 4, which is added to a hydraulic composition that becomes a hardened body of the hydraulic composition through a carbonation curing process, which is a curing process carried out in an environment with a volume concentration of carbon dioxide of 5% or more.

6. The carbonation accelerator for a hydraulic composition according to any one of claims 1 to 4, which is added to a hydraulic composition containing a binder containing 40 to 99% by mass of blast furnace slag fine powder, water, and aggregates.

7. The carbonation accelerator for a hydraulic composition according to any one of claims 1 to 4, wherein the hydraulic composition contains γ-2CaO·SiO2.

8. The carbonation accelerator for a hydraulic composition according to any one of claims 1 to 4, wherein the hydraulic composition contains at least one selected from the following CO2-fixing fine powder and the following CO2-fixing modified recycled fine aggregate. CO2-fixing fine powder: The 50% particle size is 50 μm or less, and it includes a modified concrete powder that is a reaction product of recycled concrete powder and carbon dioxide gas. The modified concrete powder contains calcium carbonate and silicate. However, the content ratio of the CO2-fixing fine powder in the hydraulic composition is in the range of 1 to 100% by mass with respect to 100% by mass of the binder. CO2-fixing modified recycled fine aggregate: The particle size of all particles is 10 mm or less, and 85% or more of them are 5 mm or less. It includes a modified recycled fine aggregate that is a dry or wet reaction product of a recycled fine aggregate with a water absorption rate exceeding 3.0% and not exceeding 10% and carbon dioxide gas. The modified recycled fine aggregate contains calcium carbonate and silicon dioxide. However, the content ratio of the CO2-fixing modified recycled fine aggregate in the hydraulic composition is in the range of 10 to 100% by volume with respect to the total aggregate volume.

9. A preparation step of preparing a hydraulic composition containing a carbonation accelerator for a hydraulic composition according to any one of claims 1 to 4, a binder containing 40 to 99% by mass of fine blast furnace slag powder, and water; a curing step of curing the obtained hydraulic composition to obtain a cured body of the hydraulic composition; and a carbonation curing step of curing the obtained cured body of the hydraulic composition in an environment with a volume concentration of carbon dioxide of 5% or more to absorb and immobilize carbon dioxide in the cured body of the hydraulic composition. A method for producing a cured body of a hydraulic composition, characterized by comprising the steps.

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