Agent for accelerating production of calcium carbonate having vaterite-type crystal structure

Abstract

The purpose of the present invention is to provide a concrete that has sufficient strength while reducing the amount of CO2 emission. The present invention pertains to an agent for accelerating production of calcium carbonate having a vaterite-type crystal structure. The accelerating agent contains a compound having a plurality of amino groups, and is used when reacting carbon dioxide with a composition containing 5 mass% or more of calcium silicate hydrate.

Description

A promoter for the production of calcium carbonate having a vaterite-type crystal structure

[0001] The present invention relates to a production accelerator for calcium carbonate having a vaterite-type crystal structure, and more particularly to a production accelerator for calcium carbonate having a vaterite-type crystal structure that is useful for the production of calcium carbonate concrete, etc.

[0002] CO emissions from the cement industry ２ The amount is the CO emitted by all industries ２ CO emissions from the cement industry account for about 8% of the total CO emissions. ２ Reducing the amount of CO is an important issue. ２ As one of the measures to reduce emissions, ２ and recovering the recovered CO ２ Technology has been developed to produce concrete by injecting CO into cement. ２ The CO reacts with the calcium component in the cement and is fixed as calcium carbonate, and the concrete obtained in this way has excellent strength, so the amount of cement used can be reduced compared to when producing ordinary concrete. ２ As a measure to reduce emissions, waste materials such as waste concrete and concrete sludge are used as raw materials, and CO is added to the calcium in the raw materials. ２ In recent years, the technology of producing concrete by reacting these materials has also been attracting attention.

[0003] Calcium carbonate exists in one of three crystalline structures: calcite, aragonite, and vaterite. When carbon dioxide is reacted with a calcium slurry, such as a calcium hydroxide slurry or a cement slurry, calcite is usually produced as thermodynamically stable calcium carbonate. However, Non-Patent Document 1 reports that vaterite can be synthesized by adding an organic compound having an amino group or a carboxyl group to calcium hydroxide and subjecting it to a carbonation treatment in an aqueous system. Patent Document 1 also discloses a method for producing vaterite by treating a particle mixture containing calcium in the oxide and / or hydroxide form with a reaction medium containing an acid salt of an organic amine under specified conditions.

[0004] It is known that thermodynamically unstable vaterite transforms into aragonite when heated in the presence of magnesium salts. Regarding aragonite, Non-Patent Document 2 reports that the formation of aragonite in concrete improves the strength of the concrete.

[0005] Special Publication No. 05-509282

[0006] I. MATSUSHITA and four others, Journal of the Ceramic Society of Japan (Japan), 1996, Vol. 104, pp. 1081-1084; N. K. Bui and seven others, Journal of Advanced Concrete Technology (Japan), 2022, Vol. 20, pp. 691-702.

[0007] Conventionally, CO ２ To reduce emissions, there is a need for technologies to fix carbon dioxide in cement and for the expansion of the use of concrete made from recycled waste concrete, etc. At the same time, concrete that can be used as a building material is also required to have excellent strength.

[0008] The present invention has been made in view of the above-mentioned circumstances, and ２ The objective is to provide concrete that has sufficient strength while reducing emissions.

[0009] The present inventors have investigated various methods for increasing the strength of concrete obtained from raw materials such as waste concrete and carbon dioxide, and have noticed that the crystalline structure of calcium carbonate contained in concrete that has absorbed carbon dioxide affects the strength of the concrete. The present inventors have discovered that using a compound having multiple amino groups when reacting carbon dioxide with raw materials containing a predetermined amount or more of calcium silicate hydrate, such as waste concrete, results in the production of a high proportion of calcium carbonate with a vaterite crystalline structure. They have also discovered that heating this mixture converts the vaterite calcium carbonate to an aragonite structure, resulting in high-strength concrete. As mentioned above, while methods for synthesizing vaterite using calcium hydroxide or calcium oxide as raw materials are known, no reports have been published on the production of vaterite calcium carbonate using raw materials such as waste concrete. Thus, the present inventors have conceived a brilliant solution to the above-mentioned problems and have arrived at the present invention.

[0010] The present invention includes the following accelerators for the production of calcium carbonate having a vaterite type crystal structure. [1] An agent for accelerating the production of calcium carbonate having a vaterite type crystal structure, the accelerator comprising a compound having multiple amino groups, and used when reacting carbon dioxide with a composition containing 5% by mass or more of calcium silicate hydrate. [2] The accelerator for the production of calcium carbonate having a vaterite type crystal structure according to [1] above, wherein the composition comprises at least one member selected from the group consisting of concrete sludge, hydraulic hardened cement, and calcium silicate board. [3] The accelerator for the production of calcium carbonate having a vaterite type crystal structure according to [1] or [2] above, wherein the compound having multiple amino groups is ethylenediamine and / or polyethyleneimine. [4] A vaterite type calcium carbonate-containing composition comprising vaterite type calcium carbonate, a compound having multiple amino groups, and a silicon-containing compound, wherein the content of the vaterite type calcium carbonate is 3% by mass or more relative to 100% by mass of the composition. [5] A method for producing calcium carbonate having a vaterite crystal structure, the method comprising a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, wherein the content of calcium silicate hydrate in the composition is 5% by mass or more, based on 100% by mass of the composition. [6] A method for producing calcium carbonate having a vaterite crystal structure according to [5] above, wherein the carbonation step is carried out in a wet state. [7] A method for promoting the transformation of calcium carbonate to an aragonite crystal structure, the method comprising a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, and a step of heating the composition obtained in the carbonation step, wherein the content of calcium silicate hydrate in the composition used in the carbonation step is 5% by mass or more, based on 100% by mass of the composition. [8] The method for promoting the transformation of calcium carbonate into aragonite according to the above [7], wherein the carbonation step is carried out in a wet manner.[9] A method for producing calcium carbonate concrete, the method comprising: a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups; and a step of heating the composition obtained in the carbonation step, wherein the content of calcium silicate hydrate in the composition used in the carbonation step is 5% by mass or more relative to 100% by mass of the composition.

[10] A method for producing calcium carbonate concrete according to [9] above, wherein the carbonation step is carried out wet.

[11] A method for producing calcium carbonate concrete according to [9] or

[10] above, wherein the compressive strength of the concrete obtained by the method for producing calcium carbonate concrete is 1 MPa or more.

[0011] The accelerator for the production of calcium carbonate having a vaterite-type crystal structure of the present invention has the above-mentioned constitution, and when used in reacting carbon dioxide with a composition containing 5 mass % or more of calcium silicate hydrate, the accelerator for the production of calcium carbonate having a vaterite-type crystal structure is accelerated. When the vaterite-type calcium carbonate thus obtained is used as a raw material for concrete, aragonite is formed in the concrete, thereby increasing the strength of the concrete, and therefore the accelerator for the production of concrete can be suitably used.

[0012] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred embodiments of the present invention described below also falls within the scope of the present invention.

[0013] [Vaterite-Type Calcium Carbonate Production Accelerator] The accelerator for the production of calcium carbonate having a vaterite-type crystal structure of the present invention (hereinafter referred to as the vaterite-type calcium carbonate production accelerator, or simply as the accelerator) contains a compound having multiple amino groups and is characterized by being used when reacting carbon dioxide with a composition containing 5% by mass or more of calcium silicate hydrate. By using the accelerator when reacting carbon dioxide with a composition containing 5% by mass or more of calcium silicate hydrate (hereinafter referred to as CSH), it is possible to produce a high proportion of calcium carbonate having a vaterite-type crystal structure. CSH is a major hardening component of concrete and has low solubility in water, so the ability to produce a high proportion of vaterite-type calcium carbonate using calcium silicate hydrate as a raw material is an effect that would not have been predicted by those skilled in the art, and in this respect, the present invention has particularly great technical significance.

[0014] The compound having a plurality of amino groups (hereinafter also referred to as a polyamine compound) may be any compound having two or more nitrogen atom-containing groups selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and an imino group. The polyamine compound is preferably a compound represented by the following formula (1):

[0015]

[0016] In formula (1), R １ are the same or different and represent a linear alkylene group having 2 to 6 carbon atoms or a branched alkylene group having 3 to 6 carbon atoms. P is the same or different and represents a hydrogen atom or a structural unit having another amino group due to branching. a, b, and c are the same or different and represent an integer of 0 or 1 or more, and the sum of a, b, and c is 1 or more.

[0017] When P in the above formula (1) is a structural unit having another amino group, the structural unit having another amino group is preferably represented by the following formula (2), and R １’It is preferable that the alkylene group is bonded to the structure represented by formula (1) via a group. Examples of the linear alkylene group having 2 to 6 carbon atoms include an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, and an n-hexylene group. Examples of the branched alkylene group having 3 to 6 carbon atoms include an isopropylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, an isopentylene group, and a neopentylene group. １ is preferably an ethylene group, n-propylene group, n-butylene group, isopropylene group, isobutylene group, etc., more preferably an ethylene group or n-butylene group, and even more preferably an ethylene group.

[0018]

[0019] (In formula (2), a', b', c', P', R １’ are a, b, c, P, and R in formula (1), respectively. １ (Similar to the above.)

[0020] The number of amino groups in the polyamine compound is not particularly limited as long as it is 2 or more, but is preferably 2 to 60, more preferably 2 to 30, even more preferably 2 to 20, and particularly preferably 2 to 15.

[0021] Specific examples of the polyamine compound include polyalkylene polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, tetrabutylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine; polyalkylene imines such as polyethyleneimine; polyamidoamines; polyvinylamines; polyallylamine; N,N,N ’ , N ’ -Tetramethylethylenediamine, N,N,N ’ , N ’’ , N ’’and heterocyclic polyamines such as 2-methylpiperazine. More preferred polyamine compounds include polyalkylenepolyamines and polyalkyleneimines, even more preferred are polyethylenepolyamines and polyethyleneimines, and particularly preferred are ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine.

[0022] The molecular weight of the polyalkylene polyamine compound is not particularly limited, but is preferably 50 to 1,000. More preferably, it is 50 to 500, and even more preferably, it is 50 to 300. When the polyamine compound is a polyalkylene imine, it is preferable that the weight average molecular weight is 600 or more. The weight average molecular weight of the polyalkylene imine is preferably 1,000,000 or less, more preferably, 600 to 100,000, and even more preferably, 600 to 10,000. In the case of polyamidoamine, polyvinylamine, and polyallylamine, it is also preferable that the molecular weight range is the same as that of the polyalkylene imine. The weight average molecular weight of the polyalkylene imine can be measured by GPC analysis.

[0023] The content of the polyamine compound in the accelerator is not particularly limited, but is preferably 0.01 to 100% by mass, more preferably 10 to 100% by mass, even more preferably 50 to 100% by mass, particularly preferably 70 to 100% by mass, and most preferably 100% by mass, relative to 100% by mass of the accelerator.

[0024] The accelerator may contain components other than the polyamine compound. Examples of such components include, but are not limited to, polyethylene glycol derivatives. The proportion of the other components is not particularly limited, but is preferably 0 to 99% by mass relative to 100% by mass of the accelerator. It is more preferably 0 to 50% by mass, even more preferably 0 to 30% by mass, particularly preferably 0 to 10% by mass, and most preferably 0% by mass.

[0025] The accelerator is used for a composition containing 5% by mass or more of calcium silicate hydrate. The composition may contain 5% by mass or more of CSH. The CSH content is preferably 5 to 100% by mass, more preferably 10 to 80% by mass, and even more preferably 20 to 70% by mass, based on 100% by mass of the composition. Specific examples of compositions containing 5% by mass or more of CSH include concrete sludge, fresh concrete, hardened hydraulic cement, calcium silicate board, etc. A preferred embodiment of the present invention is one in which the composition contains at least one selected from the group consisting of concrete sludge, fresh concrete, hardened hydraulic cement, and calcium silicate board. Examples of the fresh concrete include fresh concrete to be discarded, such as residual concrete, residual mortar, returned concrete, and returned mortar. Examples of the hardened hydraulic cement include waste concrete and waste mortar, such as concrete rubble, concrete scrap, and waste ALC panels. Among these, concrete sludge, residual concrete, returned concrete, and waste concrete are preferred.

[0026] [Vaterite-type calcium carbonate-containing composition] The present invention also relates to a vaterite-type calcium carbonate-containing composition comprising vaterite-type calcium carbonate, a compound having multiple amino groups, and a silicon-containing compound, wherein the content of the vaterite-type calcium carbonate is 3% by mass or more relative to 100% by mass of the composition. Since the vaterite-type calcium carbonate transforms to aragonite-type calcium carbonate upon heating, a composition rich in vaterite-type calcium carbonate can be produced by heat-treating a composition rich in vaterite-type calcium carbonate. Since aragonite-type calcium carbonate contributes to improving the strength of concrete, it is useful not only as a conventional recycled aggregate but also as a concrete paste. Furthermore, vaterite-type calcium carbonate is useful as a raw material for concrete because it can be easily fluidized with cement additives such as polycarboxylic acid dispersants.

[0027] The content of vaterite calcium carbonate in the composition may be 3% by mass or more, preferably 5% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, based on 100% by mass of the composition. The content of vaterite calcium carbonate can be calculated based on the peak intensity of XRD.

[0028] The vaterite type calcium carbonate in the composition has a BET specific surface area of ​​0.1 to 500 m ２ / g, more preferably 1 to 100m ２ / g, and more preferably 10 to 70 m ２ The BET specific surface area can be measured by the method described in the Examples.

[0029] Specific examples and preferred embodiments of the compound having multiple amino groups (polyamine compound) in the composition are as described above. The content of the polyamine compound in the composition is not particularly limited, but is preferably 0.01 to 100% by mass relative to 100% by mass of vaterite calcium carbonate. It is more preferably 0.01 to 10% by mass, even more preferably 0.01 to 5% by mass, particularly preferably 0.01 to 1% by mass, and most preferably 0.01% by mass.

[0030] The content of the polyamine compound in the composition is not particularly limited, but is preferably 0.001 to 40% by mass, more preferably 0.01 to 20% by mass, even more preferably 0.05 to 10% by mass, particularly preferably 0.1 to 5% by mass, and most preferably 0.3 to 2.5% by mass, relative to 100% by mass of calcium element in the composition.

[0031] The silicon-containing compound in the composition is not particularly limited as long as it contains silicon element, and examples thereof include tricalcium silicate, dicalcium silicate, silicon dioxide, aluminum silicate, and tetracalcium aluminoferrate.

[0032] The content of the silicon-containing compound in the composition is not particularly limited, but the content of silicon element relative to 100 mol% of calcium element is preferably 0.01 to 100 mol%, more preferably 0.01 to 70 mol%, even more preferably 0.01 to 50 mol%, and particularly preferably 0.01 to 30 mol%.

[0033] [Method for producing calcium carbonate having a vaterite-type crystal structure] The present invention also relates to a method for producing calcium carbonate having a vaterite-type crystal structure, which includes a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, wherein the content of calcium silicate hydrate in the composition is 5% by mass or more relative to 100% by mass of the composition. By supplying carbon dioxide to the composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups in the carbonation step, calcium carbonate having a vaterite-type crystal structure can be produced in a high proportion.

[0034] The preferred proportion of CSH in the composition used in the carbonation step is as described above. Specific examples and preferred embodiments of the composition containing 5% by mass or more of CSH are also as described above.

[0035] Specific examples and preferred embodiments of the compound having multiple amino groups (polyamine compound) used in the carbonation step are as described above. The amount of the polyamine compound used in the carbonation step is not particularly limited, but is preferably 0.001 to 40% by mass relative to 100% by mass of calcium element in the raw material used in the carbonation step. It is more preferably 0.01 to 20% by mass, even more preferably 0.05 to 10% by mass, particularly preferably 0.1 to 5% by mass, and most preferably 0.3 to 2.5% by mass.

[0036] The amount of carbon dioxide fixed in the carbonation step is not particularly limited, but is preferably 1 to 110 mass% relative to 100 mass% of calcium element in the raw material used in the carbonation step, more preferably 10 to 110 mass%, even more preferably 30 to 110 mass%, and particularly preferably 50 to 110 mass%.

[0037] The carbonation step is preferably carried out wet. It is preferable to contact a slurry composition containing CSH with carbon dioxide gas in the presence of the polyamine compound. The amount of carbon dioxide gas passed through is not particularly limited, but is preferably 5 cc or more per minute per 1 g of solids in the composition. This further improves the amount and rate of fixation of carbon dioxide. The amount of carbon dioxide gas passed through is more preferably 10 cc or more per minute per 1 g of solids in the composition, and even more preferably 20 cc or more per minute. It is also preferable that the amount of carbon dioxide gas passed through is 100 cc or less per minute per 1 g of solids in the composition.

[0038] The time for supplying carbon dioxide in the carbonation step is not particularly limited, but is preferably 0.01 to 24 hours, more preferably 0.01 to 7 hours, and even more preferably 0.5 to 4 hours.

[0039] The supply of carbon dioxide in the carbonation step is preferably carried out until the pH of the composition becomes 10 or less. This allows the amount of carbon dioxide fixed to be further increased. Carbon dioxide is more preferably supplied until the pH becomes 9 or less, and even more preferably until the pH becomes 8 or less.

[0040] The above production method is not particularly limited as long as it includes the carbonation step, but if the CSH-containing component is in a lumpy form, it may include a step of crushing the lumps before the carbonation step. The crushing method is not particularly limited, and crushers commonly used in cement factories, etc., such as hammer crushers, roll crushers, jaw crushers, vertical mills, ball mills, rod mills, and disc mills, can be used.

[0041] [Method for Producing Calcium Carbonate Concrete] The present invention relates to a method for producing calcium carbonate concrete, comprising a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, and a heating step of the composition obtained in the carbonation step, wherein the content of calcium silicate hydrate in the composition used in the carbonation step is 5% by mass or more relative to 100% by mass of the composition. Calcium carbonate concrete refers to concrete obtained using calcium-containing components such as waste concrete and carbon dioxide as raw materials. The production method of the present invention enables concrete to be produced using only waste materials such as waste concrete, atmospheric carbon dioxide, and water as raw materials, thereby helping to resolve issues of resource depletion and waste generation. The carbonation step in the method for producing calcium carbonate concrete is the same as the carbonation step in the method for producing calcium carbonate having a vaterite crystal structure described above.

[0042] The heating step in the method for producing calcium carbonate concrete is not particularly limited as long as it heats the composition obtained in the carbonation step, but the acceleration method preferably includes a step of adding a magnesium salt and a strontium salt to the composition obtained in the carbonation step before heating the composition. The magnesium salt is not particularly limited as long as it contains magnesium element, and examples include halides, hydroxides, oxides, carbonates, nitrates, sulfates, silicates, phosphonates, and carboxylates. Halides are preferred, and chlorides are more preferred.

[0043] The concentration of the magnesium salt in the composition used in the heating step is not particularly limited, but is preferably 0 to 1 mol / L, more preferably 0.01 to 0.5 mol / L, and even more preferably 0.01 to 0.2 mol / L.

[0044] The method for producing calcium carbonate concrete preferably includes a step of adding a base to the composition obtained in the carbonation step before heating the composition. The base is not particularly limited, but examples include hydroxides and oxides of alkali metals such as lithium, sodium, and potassium, and alkaline earth metals such as calcium and magnesium. Among these, hydroxides of alkali metals are preferred, and sodium hydroxide is more preferred.

[0045] The concentration of the base in the composition used in the heating step is not particularly limited, but is preferably 0 to 1 N, more preferably 0.001 to 0.5 N, and even more preferably 0.01 to 0.3 N.

[0046] The liquid to solid ratio (liquid / solid) in the composition used in the heating step is not particularly limited, but is preferably 0.3 to 100. It is more preferably 0.5 to 50, even more preferably 0.5 to 30, and particularly preferably 0.5 to 25. In one embodiment, the ratio may be 0.5 to 10, or may be 0.5 to 3.

[0047] The method for producing calcium carbonate concrete preferably includes a step of adding a solvent such as water to the composition obtained in the carbonation step before heating the composition. The amount of the solvent is not particularly limited, but it is preferably added so that the liquid to solid ratio in the composition falls within the above-mentioned preferred range.

[0048] The method for producing calcium carbonate concrete may include a step of adding fine aggregate, coarse aggregate, a cement dispersant, and other additives to the composition obtained in the carbonation step before heating the composition.

[0049] The aggregate is not particularly limited, but examples thereof include gravel, crushed stone, granulated slag, recycled aggregate, and refractory aggregate such as silica stone, clay, zircon, high alumina, silicon carbide, graphite, chromium, chromium-magnesium, magnesia, etc. Furthermore, examples of the fine aggregate include sand, and examples of the coarse aggregate include crushed stone.

[0050] The cement dispersant (water-reducing agent) is not particularly limited, and examples thereof include (i) polyalkylarylsulfonate-based dispersants such as naphthalenesulfonic acid formaldehyde condensates; melamine formalin resin sulfonate-based dispersants such as melamine sulfonic acid formaldehyde condensates; aromatic aminosulfonate-based dispersants such as aminoarylsulfonic acid-phenol-formaldehyde condensates; lignin sulfonate-based dispersants such as lignin sulfonates and modified lignin sulfonates; polystyrene sulfonate-based dispersants; and the like. (ii) copolymers obtained from polyalkylene glycol mono(meth)acrylate monomers, (meth)acrylic acid monomers, and monomers copolymerizable with these monomers, as described in JP-B No. 59-18338 and JP-A No. 7-223852; unsaturated (poly)alkylene glycol copolymers, as described in JP-A No. 10-236858, JP-A No. 2001-220417, JP-A No. 2002-121055, and JP-A No. 2002-121056; (iii) copolymers having a (poly)oxyalkylene group and a phosphate ester group in the molecule, such as copolymers obtained from (alkoxy)polyalkylene glycol mono(meth)acrylate, phosphate monoester monomer, and phosphate diester monomer, as described in JP-A-2006-52381; Examples of the polycondensation product include a polycondensation product comprising a monomer having a (poly)oxyalkylene group and an aromatic ring group and / or a heterocyclic aromatic group, a monomer having a phosphoric acid (salt) group and / or a phosphoric acid ester group and an aromatic ring group and / or a heterocyclic aromatic group, and an aldehyde compound, as described in JP-A-2008-517080; and a dispersant having an aromatic triazine structural unit, a polyalkylene glycol structural unit, and a phosphoric acid ester structural unit, as described in JP-A-2015-508384; and various phosphoric acid-based dispersants (water-reducing agents).

[0051] The amount of the cement dispersant (water reducing agent) added is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.01 to 1.0% by mass, even more preferably 0.05 to 0.5% by mass, and particularly preferably 0.05 to 0.3% by mass, relative to 100% by mass of the vaterite-containing powder.

[0052] Examples of other additives include cement additives (materials) such as those exemplified in (1) to (12) below, cement wetting agents, thickeners, separation reducing agents, flocculants, drying shrinkage reducing agents, strength enhancing agents, self-leveling agents, rust inhibitors, colorants, and mildew inhibitors. One or more of these may be used.

[0053] (1) Water-soluble polymeric substances: nonionic cellulose ethers such as methyl cellulose, ethyl cellulose, and carboxymethyl cellulose; polysaccharides produced by microbial fermentation such as yeast glucan, xanthan gum, and β-1,3 glucans; polyacrylamide; (2) Polymer emulsions: copolymers of various vinyl monomers such as alkyl (meth)acrylate; (3) Set retarders: oxycarboxylic acids or salts thereof such as gluconic acid, glucoheptonic acid, arabinonic acid, malic acid, and citric acid; sugars and sugar alcohols; polyhydric alcohols such as glycerin; phosphonic acids and their derivatives such as aminotri(methylenephosphonic acid); (4) Early-strengthening agents and accelerators: soluble calcium salts such as calcium chloride, calcium nitrite, calcium nitrate, calcium bromide, and calcium iodide; chlorides such as iron chloride and magnesium chloride; sulfates; potassium hydroxide; sodium hydroxide; carbonates; thiosulfates; formates such as formic acid and calcium formate; alkanolamines; alumina cement; calcium aluminate silicate; (5) Oxyalkylene-based defoaming agents: polyoxyalkylene alkyl ethers such as diethylene glycol heptyl ether; polyoxyalkylene acetylene ethers; (poly)oxyalkylene fatty acid esters; polyoxyalkylene sorbitan fatty acid esters; polyoxyalkylene alkyl (aryl) ether sulfate ester salts; polyoxyalkylene alkyl phosphate esters; polyoxypropylene polyoxyethylene laurylamine (1 to 20 moles of propylene oxide added, 1 to 20 moles of ethylene oxide added, etc.), polyoxyalkylene alkylamines such as amines derived from fatty acids obtained from hardened beef tallow to which alkylene oxide has been added (1 to 20 moles of propylene oxide added, 1 to 20 moles of ethylene oxide added, etc.); polyoxyalkylene amides, etc. (6) Non-oxyalkylene-based defoaming agents: mineral oil-based, oil-based, fatty acid-based, fatty acid ester-based, alcohol-based, amide-based, phosphate ester-based, metal soap-based, silicone-based, etc. defoaming agents.

[0054] (7) Air-Entraining Agents: Resin soaps, saturated or unsaturated fatty acids, sodium hydroxystearate, lauryl sulfate, ABS (alkylbenzene sulfonic acid), alkanesulfonates, polyoxyethylene alkyl(phenyl) ethers, polyoxyethylene alkyl(phenyl) ether sulfates or their salts, polyoxyethylene alkyl(phenyl) ether phosphates or their salts, protein materials, alkenyl sulfosuccinate, α-olefin sulfonates, etc. (8) Other Surfactants: Various anionic surfactants; Various cationic surfactants such as alkyltrimethylammonium chloride; Various nonionic surfactants; Various amphoteric surfactants, etc. (9) Waterproofing Agents: Fatty acids (salts), fatty acid esters, oils and fats, silicone, paraffin, asphalt, wax, etc. (10) Rust Inhibitors: Nitrites, phosphates, zinc oxide, etc. (11) Crack Reducers: Polyoxyalkyl ethers, etc. (12) Expansive Agents: Ettringite-based, coal-based, etc.

[0055] The heating temperature of the composition in the heating step is not particularly limited, but is preferably 30 to 100°C, more preferably 40 to 95°C, and even more preferably 60 to 95°C.

[0056] The heating time in the heating step is not particularly limited, but is preferably 1 to 200 hours, more preferably 5 to 200 hours, and even more preferably 5 to 72 hours. In one embodiment, the heating time may be 1 to 20 hours, or may be 1 to 10 hours.

[0057] The method for producing calcium carbonate concrete of the present invention allows the production of concrete with high compressive strength. The compressive strength of the concrete obtained by the above production method is preferably 1 MPa or more, more preferably 5 MPa or more, and even more preferably 10 MPa or more. The compressive strength of the above concrete can be measured by the method described in the Examples.

[0058] [Method for Promoting Aragonite Transformation of Calcium Carbonate] The present invention is also a method for promoting the transformation of calcium carbonate to an aragonite crystal structure, comprising: a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having a plurality of amino groups; and a step of heating the composition obtained in the carbonation step, wherein the content of calcium silicate hydrate in the composition used in the carbonation step is 5% by mass or more relative to 100% by mass of the composition.

[0059] The carbonation step in the method for promoting the aragonite transformation of calcium carbonate is the same as the carbonation step in the method for producing calcium carbonate having a vaterite crystal structure. The heating step in the method for promoting the aragonite transformation of calcium carbonate is the same as the heating step in the method for producing calcium carbonate concrete.

[0060] [Use of a compound having multiple amino groups for promoting the aragonite transformation of calcium carbonate] The present invention also relates to use of a compound having multiple amino groups for promoting the aragonite transformation of calcium carbonate, which comprises a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, wherein the content of calcium silicate hydrate in the composition is 5% by mass or more relative to 100% by mass of the composition. The carbonation step in the above use is the same as the carbonation step in the above-mentioned method for producing calcium carbonate having a vaterite crystal structure.

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "% by mass."

[0062] The molecular weight of the following polyamine was measured as follows. (Molecular Weight Measurement (GPC Analysis)) The weight average molecular weight and number average molecular weight in the present invention can be measured by a known method using gel permeation chromatography (GPC) with pullulan as a standard substance. The following conditions are adopted as the GPC measurement conditions in the present invention. Measurement apparatus: manufactured by Shimadzu Corporation Columns used: SHODEX OHpak SB-807HQ (two columns) + SB-806M / HQ (two columns) manufactured by Showa Denko K.K. Eluent: adjusted to 0.5 mol % sodium nitrate and 0.5 mol % acetic acid Standard substance: Pullulan P-82 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Detector: differential refractometer (manufactured by Shimadzu Corporation) Flow rate: 0.4 ml / min.

[0063] (Experimental equipment and procedure) A composition was prepared by adding additives and water to concrete sludge or pulverized simulated waste concrete in a container, and carbon dioxide gas was passed through the composition for a predetermined time at room temperature. The composition was then filtered to recover a powder, which was then dried. The weight loss rate of the obtained powder was measured using a TG-DTA device (device name: STA200 (manufactured by Hitachi High-Tech Science Corporation)), and the amount of calcium carbonate produced was calculated, thereby calculating the carbonation rate. In addition, the crystal polymorphism of the calcium carbonate contained in the obtained powder was analyzed using XRD (device name: D2PHASER (manufactured by Bruker)). Details are provided below. Cement: Cement (ordinary Portland cement (OPC), manufactured by Taiheiyo Cement Corporation) Preparation of simulated crushed waste concrete: A cement paste with w / c = 0.4 was prepared (the mixing method conformed to JIS R5201), and the kneaded paste was packed into a formwork (Φ50 x 50 x 100 mm), cured in air at 20°C for 3 days, and then removed from the formwork 3 days after pouring water and cured in water for 11 days. After curing, the hardened body was crushed, and powder of 100 μm or less was collected using a sieve with 100 μm openings and used for the test. ２Injection method (for simulated waste concrete): The powder was added to ion-exchanged water at a ratio of w / b = 5 to 50 (W: additives and water, B: crushed waste concrete), and stirred at a constant speed using a stirring rod. When an additive was used, the additive was added to the ion-exchanged water. Carbon dioxide gas (manufactured by Sumitomo Seika Chemicals Co., Ltd.) was passed through the above slurry at room temperature at a flow rate of 0.3 L / min for a predetermined time, and then the filtrate was filtered. The obtained powder was washed with acetone, dried at 40°C (in a nitrogen atmosphere) for 24 hours, and subjected to TG-DTA measurement and XRD measurement. CO ２ Injection method (for concrete sludge): The powder was added to ion-exchanged water at a ratio of w / b = 0.4 (W: additives and water, B: ordinary Portland cement) and stirred at a constant speed for 4 hours using a stirring rod. After 4 hours, additional ion-exchanged water was added to achieve the desired w / b ratio. When additives were used, they were added to the additional ion-exchanged water. Carbon dioxide gas (manufactured by Sumitomo Seika Chemicals Co., Ltd.) was passed through the above slurry at room temperature at a flow rate of 0.3 L / min for a predetermined time, after which the filtrate was filtered. The obtained powder was washed with acetone, dried at 40°C (under a nitrogen atmosphere) for 24 hours, and subjected to TG-DTA and XRD measurements.

[0064] (Measurement of calcium carbonate amount) The amount of calcium carbonate was quantified using TG-DTA by the following measurement method. Conditions: Measurement was performed under a nitrogen atmosphere at a temperature rise rate of 20°C / min. Analysis: The mass loss measured by TG-DTA at around 600 to 800°C was considered to be the decarbonation of calcium carbonate, and the amount of calcium carbonate was calculated. The carbonation rate was calculated as follows, with 100% being the value when all of the calcium oxide in the cement or waste concrete had reacted with carbon dioxide. To quantify the amount of calcium oxide in the powder, the chemical composition of the ground cement or waste concrete was measured using an X-ray fluorescence analyzer (ZSX Primus II (manufactured by Rigaku Corporation)) in accordance with JIS R 5202:2015 and JIS R 5204:2019 (X-ray fluorescence analysis of cement), and the mass percentage of calcium oxide was calculated based on this. The results are shown in Table 1.

[0065] (Measurement of calcium carbonate crystal polymorphism) The crystal polymorphism of calcium carbonate was measured using XRD by the following measurement method. Conditions: Measurement was performed under the following conditions: target CuKα, tube voltage 45 kV, tube current 40 mA, scan range 5-70 deg2Θ, step width 0.02 deg. Analysis: The ratio of each crystal polymorphism was calculated by the following formula using the peak intensity Ic of the (104) plane for calcite, the peak intensity Ia of the (221) plane for aragonite, and the peak intensity Iv of the (110) plane for vaterite. Here, Xc: weight fraction of calcite, Xa: weight fraction of aragonite, and Xv: weight fraction of vaterite, and it is assumed that Xc + Xa + Xv = 1 holds. Xa = 3.175 × Ia / (Ic + 3.175 × Ia + 7.691 × Iv) Xc = Ic × Xa / (3.157 × Ia) (transition to aragonite) ２ The powder containing Vaterite obtained by the blowing operation was added to a solution of a predetermined solvent composition and heated for a predetermined time. After heating, the slurry was filtered under reduced pressure, and the obtained powder was washed with acetone, dried at room temperature (under a nitrogen atmosphere) for 24 hours, and then subjected to XRD measurement.

[0066] <Production Example 1> Production of a water-reducing agent (polycarboxylic acid copolymer α) A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, and a reflux condenser was charged with 72.26 parts of ion-exchanged water and 127.74 parts of an unsaturated alcohol prepared by adding 50 moles of ethylene oxide to 3-methyl-3-buten-1-ol. After heating to 65°C, 0.71 parts of a 30% aqueous solution of hydrogen peroxide was added, and 46.58 parts of a 40% aqueous solution of acrylic acid was added dropwise over 3 hours, 0.67 parts of 3-mercaptopropionic acid was added dropwise over 3 hours, and 12.97 parts of a 2.1% aqueous solution of L-ascorbic acid was added dropwise over 3.5 hours. The temperature was then maintained at 65°C for 60 minutes to complete the polymerization reaction. The temperature was then lowered to below 50°C and the mixture was neutralized with 76.07 parts of a 12.2% aqueous solution of sodium hydroxide to a pH of 4 to 7, yielding a polycarboxylic acid copolymer of the present invention consisting of an aqueous polymer solution having a weight-average molecular weight of 29,000. The amount of all the monomers used relative to the total amount of the raw materials used in the polymerization was 56.2% by weight.

[0067] <Paste test> Preparation of paste sample: The paste test was carried out under an environment of a temperature of 20°C ± 1°C and a relative humidity of 60% ± 15%. The mortar mix ratio was B / W = 140 / 140 (g), where: B: Example 1 (Vaterite-containing powder), Comparative Example 1 (Calcite-containing powder), W: Water-reducing agent of Production Example 1 and antifoaming agent of 0.1N NaOH and 0.1N MgCl ２ Aqueous Solution Using a mortar mixer (Hobart mixer, model number: N-50), B and W were mixed at first speed for 4 minutes.

[0068] <Measurement of compressive strength> After kneading, a compressive strength test sample was prepared, and the compressive strength after steam curing was measured under the following conditions: Specimen preparation: 50 mm x 100 mm Specimen curing: Curing was carried out for 72 hours at a temperature of 90°C and a humidity of 98% using a constant temperature and humidity oven. Compressive strength measurement: Automatic compressive strength measuring instrument (manufactured by Mayekawa Manufacturing Co., Ltd.)

[0069] (Calculation formula for carbonation rate) Symbols are in parentheses and units are in square brackets. Maximum amount of fixed carbon dioxide (A) [g] = amount of calcium oxide in 1g of powder (B) [g] x m / n m: molecular weight of carbon dioxide [g / mol] n: molecular weight of calcium oxide [g / mol] Maximum weight loss rate (C) = (A) / (1 + (A)) x 100 [%] Carbonation rate (D) = weight loss rate / (C) x 100 [%] *Weight loss rate = mass loss at around 600-800°C as determined by TG-DTA When the carbonation rate (D0) without additives is taken to be 100%, the carbonation improvement rate (E) of a sample is: (E) = carbonation rate of sample (D1) / (D0) x 100 [%]

[0070] Examples (1) to (11) and Comparative Examples (1) to (5) As shown in the following Table 2, various additives (vaterite-type calcium carbonate production accelerators) were used and the carbonation rate and the crystal polymorphism of calcium carbonate after 4 hours were measured using the above-mentioned experimental apparatus and procedures. The results are shown in Table 2.

[0071] Various conditions were investigated to transform the Vaterite-containing powder obtained in Example (1) in Table 2 into Aragonite. The results are shown in Table 3. In Table 3, L / S represents the ratio of liquid to solid (liquid / solid) in the composition.

[0072] Compressive strength test samples were prepared using the Vaterite-containing powder obtained in Example (1) or the powder of Comparative Example (1) in Table 2, and after steam curing under the above conditions, the compressive strength was measured. The results are shown in Table 4.

[0073]

Claims

1. An agent for promoting the production of calcium carbonate having a vaterite-type crystal structure, the agent comprising a compound having multiple amino groups, and used when reacting carbon dioxide with a composition containing 5% by mass or more of calcium silicate hydrate.

2. The production accelerator for calcium carbonate having a vaterite-type crystal structure according to claim 1, wherein the composition contains at least one selected from the group consisting of concrete sludge, hydraulic cement hardened body, and calcium silicate board.

3. The production accelerator for calcium carbonate having a vaterite-type crystal structure according to claim 1 or 2, wherein the compound having a plurality of amino groups is ethylenediamine and / or polyethyleneimine.

4. A vaterite-type calcium carbonate-containing composition comprising vaterite-type calcium carbonate, a compound having a plurality of amino groups, and a silicon-containing compound, wherein the content of the vaterite-type calcium carbonate is 3% by mass or more relative to 100% by mass of the composition.

5. A method for producing calcium carbonate having a vaterite-type crystal structure, comprising a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups, wherein the content of calcium silicate hydrate in the composition is 5% by mass or more relative to 100% by mass of the composition.

6. The method for producing calcium carbonate having a vaterite-type crystal structure according to claim 5, wherein the carbonation step is carried out in a wet system.

7. A method for promoting the transformation of calcium carbonate into an aragonite-type crystal structure, said method comprising: a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups; and a step of heating the composition obtained in said carbonation step, wherein the content of calcium silicate hydrate in the composition used in said carbonation step is 5% by mass or more relative to 100% by mass of the composition.

8. The method for promoting the transformation of calcium carbonate into aragonite according to claim 7, wherein the carbonation step is carried out in a wet state.

9. A method for producing calcium carbonate concrete, comprising: a carbonation step of supplying carbon dioxide to a composition containing calcium silicate hydrate in the presence of a compound having multiple amino groups; and a step of heating the composition obtained in the carbonation step, wherein the content of calcium silicate hydrate in the composition used in the carbonation step is 5% by mass or more relative to 100% by mass of the composition.

10. The method for producing calcium carbonate concrete according to claim 9, wherein the carbonation step is carried out by a wet method.

11. The method for producing calcium carbonate concrete according to claim 9 or 10, wherein the compressive strength of the concrete obtained by the method for producing calcium carbonate concrete is 1 MPa or more.

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