JP2022040900A - Hydraulic composition, method of producing hydraulic composition, molding, hardened material, and method of producing hardened material - Google Patents

Abstract

To provide a hydraulic composition capable of improving compression strength of a hardened material.SOLUTION: The hydraulic composition comprises cement and at least one carbonate selected from the group consisting of a carbonic acid salt and a carbonic acid ester, with the carbonic acid salt being a salt of a monovalent cation and a carbonate ion or a bicarbonate ion.SELECTED DRAWING: None

Description

The present invention relates to a hydraulic composition, a method for producing a hydraulic composition, a molded product, a cured product, and a method for producing a cured product.

Various techniques have been developed in the field of improving the durability of structural materials or structures. In Patent Document 1, the base material for forming a structure and the solubility in water at the temperature of the environment existing inside or on the surface of the base material and in which the base material is arranged are equal to or less than the first value. A structural material characterized by comprising an ion supply source for supplying at least one of a cation and an anion constituting a sparingly soluble salt has been proposed. Further, Non-Patent Document 1 describes the principle of Patent Document 1.

In addition, various techniques have been developed to stop water from minute cracks. Patent Document 2 describes a grout solution which is composed of a first aqueous solution rich in calcium ions and a second aqueous solution containing carbonate ions, and calcium carbonate is precipitated by mixing the two solutions.

International Publication No. 2020/040243 Japanese Unexamined Patent Publication No. 2006-249294

Hidekazu Yoshida et al. , Scientific Reports volume 5, Article number: 14123 (2015)

Patent Document 1 describes that the mechanism of forming spherical lumps called concretions related to tusk shells is to be applied to fields such as cement-based structural materials. However, Patent Document 1 does not actually describe an experimental example using a composition containing cement, a specific composition, or the like. Therefore, even a person skilled in the art who has come into contact with Patent Document 1 cannot read what composition, structure, physical properties, etc. are appropriate when concretion is applied to a composition containing cement. In addition, it is not possible to read an appropriate manufacturing method for a composition containing cement, a structural material, or the like.

In addition, Patent Document 1 and Non-Patent Document 1 are patent applications and academic papers mainly composed of the same researcher, respectively. According to Patent Document 1 and Non-Patent Document 1, calcium ions (Ca ²⁺ ) derived from seawater and carbonate species derived from fatty acid decomposition of tsunogai rapidly react at a reaction front where the pH changes to form carbonic acid. It has been described that calcium (CaCO ₃ ) is rapidly precipitated and the horn mussels form concretions. The reaction front is a boundary between the pH of seawater of about 8.6 and the pH of the inside of the tusk shell of about 4 to 5.

On the other hand, for example, cement and concrete are usually alkaline, and the environment is significantly different from the experimental example of Non-Patent Document 1. Therefore, even those skilled in the art cannot understand that a reaction front is formed in the same manner as the acidic tusk shell. The abundance ratio of carbon dioxide (CO ₂ ), bicarbonate ion ( ^HCO _3- ^, also referred to as hydrogen carbonate ion), and carbonate ion (CO _3-2- ) changes depending on the pH. Carbon dioxide increases in the low pH range such as pH 7 or less. Bicarbonate ions increase in the medium pH range such as pH 7 to 11. Carbonate ions increase in a high pH range such as pH 11 or higher. Non-Patent Document 1 describes that fatty acids of Tsunogai are decomposed, carbon dioxide is released in an acidic environment, and carbon dioxide becomes bicarbonate ion at the reaction front. As a result, bicarbonate ion and calcium ion react with each other to form a concretion. For example, the molecular size of carbon dioxide is smaller than the ion size of carbonate ions. It is presumed that this affects the diffusion rate of carbonic acid species to the reaction front and changes the morphology and physical properties of calcium carbonate formed, but the effect is not described in Patent Document 1.

Therefore, the present inventor has studied the composition, structure, physical properties, manufacturing method, etc. that are effective for forming concretions, and by diligently studying them, to develop a water-hardening composition that is effective for improving compressive strength. I arrived. That is, an object of the present invention is to provide a hydraulic composition capable of improving the compressive strength of a cured product. The present invention also provides a method for producing a water-hard composition capable of improving the compressive strength of the cured product, and a method for producing a cured product, a molded product, and a cured product of such a water-hard composition. With the goal.

The water-hard composition of the present invention comprises cement and at least one carbonate selected from the group consisting of carbonates and carbonates, wherein the carbonate is a monovalent cation and a carbonate ion or a bicarbonate ion. It is a salt of carbonic acid and has a solubility of 1 g or more in 100 ml of water at 20 ° C.

It is preferable that the carbonate is at least one selected from the group consisting of lithium carbonate, sodium carbonate, and potassium carbonate.

（式（Ｉ）中、Ｒ^１及びＲ^２はそれぞれ独立に１～４個の炭素原子を含む一価の炭化水素基（当該一価の炭化水素基は、ハロゲン原子、水酸基、又は１～３個の炭素原子を有するアルコキシ基により置換されていてもよい。）であり、式（ＩＩ）中、Ｒ^３は２～４個の炭素原子を含む二価の炭化水素基（当該二価の炭化水素基は、ハロゲン原子、水酸基、又は１～３個の炭素原子を有するアルコキシ基により置換されていてもよい。）である。） The carbonic acid ester is preferably at least one of a compound represented by the following formula (I) and a compound represented by the following formula (II).

(In the formula (I), R ¹ and R ² each independently contain a monovalent hydrocarbon group containing 1 to 4 carbon atoms (the monovalent hydrocarbon group is a halogen atom, a hydroxyl group, or 1 to 3). It may be substituted with an alkoxy group having 1 carbon atom), and in formula (II), R ³ is a divalent hydrocarbon group containing 2 to 4 carbon atoms (the divalent hydrocarbon). The hydrogen group may be substituted with a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 3 carbon atoms.))

The carbonic acid ester is preferably at least one of ethylene carbonate, propylene carbonate, and glycerol 1,2-carbonic acid.

The content of the carbonate is preferably 3 parts by mass or more with respect to 100 parts by mass of cement.

The content of the carbonate is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the cement.

The method for producing a water-hard composition of the present invention includes a step of preparing a mixture containing cement and at least one carbonic acid selected from the group consisting of carbonates and carbonic acids, and a step of adding water to the mixture. , The carbonate is a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and the solubility in 100 ml of water at 20 ° C. is 1 g or more.

Further, the method for producing a water-hard composition of the present invention comprises a step of adding an aqueous solution or an aqueous dispersion containing at least one kind of carbonic acid selected from the group consisting of a carbonate and a carbonic acid ester to the cement, and the carbonate is contained. It may be a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and may have a solubility of 1 g or more in 100 ml of water at 20 ° C.

The molded product of the present invention is a molded product of the above hydraulic composition and has a dent on the surface.

The cured product of the present invention is the cured product of the hydraulic composition or the molded product.

The cured product of the present invention is a cured product formed from the above-mentioned water-hardening composition or molded product, and is formed in a cement cured product formed by hardening cement and in a recess on the surface of the cement cured product. Includes deposits and deposits.

It is preferable that the deposit contains calcium carbonate.

The method for producing a cured product of the present invention comprises a step of curing the water-hardening composition or a molded product to obtain a cement cured product having a compressive strength of 5 N / mm ² or more, and using the cement cured product as a carbonate ion. Includes a step of contacting with an aqueous solution containing cations that form an insoluble salt.

According to the present invention, it is possible to provide a hydraulic composition capable of improving the compressive strength of a cured product. Further, according to the present invention, there is provided a method for producing a water-hard composition capable of improving the compressive strength of a cured product, and a method for producing a cured product, a molded product, and a cured product of such a water-hard composition. can do.

It is a photograph of the cured product of Example 2. It is a photograph of the cured product of Example 3. It is a photograph of the cured product of Example 4.

<Hydraulic composition>
The water-hard composition of the present embodiment contains cement and at least one carbonate selected from the group consisting of carbonates and carbonates, wherein the carbonate is a monovalent cation and a carbonate ion or a bicarbonate ion. It is a salt of carbonic acid and has a solubility of 1 g or more in 100 ml of water at 20 ° C. In addition, in this specification, a carbonate is a concept including both a carbonate and a carbonic acid ester.

Since the hydraulic composition of the present embodiment contains cement, it can be said that it is a cement composition. The hydraulic compound of this embodiment contains a carbonate as well as cement. If the carbonate is a carbonate, it is decomposed in water to release carbonate ions. Further, if the carbonic acid is a carbonic acid ester, it is considered that it reacts with a component of cement which is basic and is hydrolyzed to release carbonic acid ions. Therefore, the water-hard composition of the present embodiment can be cured by the water-hard reaction of cement at the time of use, and the water-hard compound after or during curing is further released from the water-hard composition. By placing it in an environment where carbonate ions form an insoluble carbonate (for example, in seawater), the insoluble carbonate is precipitated on the surface (that is, by forming a concret) and has improved strength. A cured product (that is, a composite material) can be obtained.
The above-mentioned carbonate ion changes to bicarbonate ion or carbon dioxide depending on the pH of water.

Further, the insoluble carbonate is formed on the surface of the cured product by diffusing the carbonate ions released from the surface of the water-hard composition from the surface. Therefore, the water-hardening composition of the present embodiment has a property that even if cracks, cracks, etc. occur on the surface during curing, the formed insoluble carbonate fills and repairs the cracks, etc. (that is, self-repairing). Has repairability). Further, even if a gap is formed between the surrounding structure and the surrounding structure due to curing shrinkage or the like, the gap can be filled by the self-repairing property, and the adhesion with the surrounding structure can be achieved. Can be suppressed. Further, due to these properties, the hydraulic composition of the present embodiment is also useful as an injectable agent.

The cement is not particularly limited, and ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement and other Portland cement; blast furnace cement, fly ash cement, silica. Mixed cement such as cement; one or more types can be selected and used from other cements such as eco-cement, ultrafast hard cement, alumina cement, phosphoric acid cement, and air-hardening cement, and these cements can be used. Further added calcium aluminate, plaster, etc. can also be used as cement.

The carbonate may be either a normal salt or a hydrogen carbonate, but it is more preferable that the carbonate is a normal salt that does not release hydrogen ions to generate an acidic compound. Examples of the carbonate as a normal salt include alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate, and ammonium carbonate ((NH ₄ ) ₂ CO ₃ ). Examples of the hydrogen carbonate include alkali metal hydrogen carbonates such as lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, rubidium hydrogen carbonate, and cesium hydrogen carbonate, and ammonium hydrogen carbonate (NH ₄ HCO ₃ ).

Only one type of carbonate may be used, or two or more types may be used in combination. The carbonate is preferably at least one selected from the group consisting of lithium carbonate, sodium carbonate, and potassium carbonate.

The carbonic acid ester is not particularly limited. The molecular weight of the carbonic acid ester is preferably 200 or less, more preferably 170 or less, and even more preferably 150 or less. More specifically, a carbonic acid ester represented by the following formula (I) and a carbonic acid ester represented by the formula (II) can be mentioned.

（式（Ｉ）中、Ｒ^１及びＲ^２はそれぞれ独立に１～４個の炭素原子を含む一価の炭化水素基（当該一価の炭化水素基は、ハロゲン原子、水酸基、又は１～３個の炭素原子を有するアルコキシ基により置換されていてもよい。）であり、式（ＩＩ）中、Ｒ^３は２～４個の炭素原子を含む二価の炭化水素基（当該二価の炭化水素基は、ハロゲン原子、水酸基、又は１～３個の炭素原子を有するアルコキシ基により置換されていてもよい。）である。）

(In the formula (I), R ¹ and R ² each independently contain a monovalent hydrocarbon group containing 1 to 4 carbon atoms (the monovalent hydrocarbon group is a halogen atom, a hydroxyl group, or 1 to 3). It may be substituted with an alkoxy group having 1 carbon atom), and in formula (II), R ³ is a divalent hydrocarbon group containing 2 to 4 carbon atoms (the divalent hydrocarbon). The hydrogen group may be substituted with a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 3 carbon atoms.))

The monovalent hydrocarbon group may be an alkyl group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group and an n-butyl group. When R ¹ and R ² have substituents, the number of substituents may be 1 or 2, and may be 1. Examples of the substituent include a halogen atom such as a fluorine atom and a chlorine atom, and an alkoxy group such as a hydroxyl group and a methoxy group.

Examples of the carbonic acid ester represented by the formula (I) include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylmethyl carbonate, allylmethyl carbonate, allylcarbonate, 1-chloroethylethyl carbonate, chloromethylisopropylcarbonate and 1-chloroethylisopropylcarbonate. And so on.

The divalent hydrocarbon group may be an alkylene group, and examples thereof include an ethylene group, an n-propylene group, an isopropylene group, and an n-butylene group. When R ³ has a substituent, the number of substituents may be 1 or 2, and may be 1. Examples of the substituent include a halogen atom such as a fluorine atom and a chlorine atom, and an alkoxy group such as a hydroxyl group and a methoxy group.

Examples of the carbonic acid ester represented by the formula (II) include ethylene carbonate, propylene carbonate, 1,3-dioxane-2-one, 4-fluoro-1,3-dioxolane-2-one, 4-chloro-1,3. -Dioxolane-2-one, 4-vinyl-1,3-dioxolane-2-one, 4-methoxy-1,3-dioxolane-2-one, glycerol 1,2-carbonate, vinylene carbonate and the like can be mentioned.

Only one type of carbonic acid ester may be used, or two or more types may be used in combination. The carbonic acid ester preferably contains at least one of ethylene carbonate, propylene carbonate, and glycerol 1,2-carbonate.

The content of carbonate in the water-hard composition increases, for example, the content of cement 100 from the viewpoint of increasing the amount of concrete formed and improving the strength of the cured product, the volume of the injection material, the self-healing property of the cured product, and the like. With respect to parts by mass, it is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 20 parts by mass or more, and 30 parts by mass or more. Is even more preferable, 40 parts by mass or more is more preferable, and 50 parts by mass or more is particularly preferable. Further, such a range is preferable from the viewpoint of economic efficiency.
Further, the content of carbonate in the hydraulic composition is, for example, 200 parts by mass or less with respect to 100 parts by mass of cement content from the viewpoint of maintaining a balance between the strength of cement and the strength of concretion. It is more preferably 150 parts by mass or less, further preferably 120 parts by mass or less, further preferably 110 parts by mass or less, and particularly preferably 100 parts by mass or less.
The upper and lower limits of the carbonate content in the hydraulic composition may be arbitrarily combined. The content of carbonate in the hydraulic composition is, for example, preferably 3 to 200 parts by mass, and more preferably 10 to 200 parts by mass with respect to 100 parts by mass of cement.

Further, the content of carbonate is, for example, 100 parts by mass of the water-hardening composition from the viewpoint of increasing the amount of concretion formation and improving the strength of the cured product, the volume of the injection material, the self-healing property of the cured product, and the like. On the other hand, it is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, further preferably 7 parts by mass or more, further preferably 8 parts by mass or more, and 9 parts by mass or more. Is particularly preferable.
Further, the content of carbonate is preferably 30 parts by mass or less, preferably 25 parts by mass, with respect to 100 parts by mass of the hydraulic composition, for example, from the viewpoint of maintaining a balance between the strength of cement and the strength of concretion. It is more preferably parts or less, more preferably 20 parts by mass or less, and even more preferably 18 parts by mass or less.
The upper and lower limits of the carbonate content in the hydraulic composition may be arbitrarily combined. The content of carbonate in the hydraulic composition is preferably, for example, 5 to 30 parts by mass with respect to 100 parts by mass of the hydraulic composition.

The hydraulic composition can appropriately contain cement and other materials other than the carbonic acid source, depending on the intended use.
Specific examples of other materials include aggregates and mixed materials.

The aggregate used in the hydraulic composition of the present embodiment is not limited.
Specific examples of the aggregate include natural fine aggregates such as river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, and natural emery sand; slag fine aggregate, and fired fine bone made by firing fly ash. One or more can be selected and used from materials, artificial fine aggregates such as coarsely crushed carbides such as artificial emery sand, alumina, silicon carbide and boron carbide, fine aggregates of limestone or coarse aggregates. can. The content of the aggregate is preferably 100 to 800 parts by mass, more preferably 200 to 600 parts by mass with respect to 100 parts by mass of cement.

The hydraulic composition of the present embodiment may appropriately contain an admixture material depending on desired physical properties and uses.
Specific examples of the admixture material include shrinkage reducing agents, AE agents, AE water reducing agents, high-performance AE water reducing agents, fluidizing agents, water reducing agents, high-performance water reducing agents, underwater concrete admixtures, thickeners, and retarding agents. , Hydration heat inhibitor, waterproofing agent, rust preventive, hydration accelerator, quick-setting agent, antifreeze, antifoaming agent, limestone, fly ash, silica fume, pozzolan, blast furnace slag, metal fiber silicic acid fine powder , Swelling agent, high-strength admixture, polymer admixture, colorant, mineral fine powder and the like. The admixture material may include one or more of the above-mentioned materials.
As the admixture, for example, an underwater concrete admixture or a thickener is preferable.

The hydraulic composition of the present embodiment may be a dry composition to which water is not added, or a wet composition to which water is added. In the present specification, even if the carbonic acid ester contained as carbonic acid is a liquid, if water is not added to the hydraulic composition, it is a dry composition. Further, the hydraulic composition may be any of various compositions such as a mortar composition, a concrete composition and a grout composition.

When the hydraulic composition contains water, the W / C (mass ratio of water to cement (%)) in the hydraulic composition is preferably 30 to 150% from the viewpoint of further improving the strength of the cured product. , 40 to 120% is more preferable, and 50 to 100% is further preferable. The mass ratio (%) of carbonate to water in the hydraulic composition is preferably 30 to 150%, more preferably 50 to 120%.

<Manufacturing method of hydraulic composition>
Hereinafter, a method for producing the hydraulic composition of the present embodiment will be described.
The method for producing a hydraulic composition of the present embodiment is any method that can prepare a hydraulic composition by mixing cement, carbonate and other materials such as aggregates and admixtures which are optional components, and optionally water. There are no particular restrictions. As such a production method, for example, the following two methods (post-addition method and pre-addition method) in which the timing of adding carbonate and water to the cement are different can be mentioned.
(1) The above-mentioned carbonic acid comprises a step of preparing a mixture containing cement and at least one kind of carbonic acid selected from the group consisting of a carbonate and a carbonic acid ester, and a step of adding water to the mixture. A production method (post-addition method), which is a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and has a solubility in 100 ml of water at 20 ° C. of 1 g or more.
(2) Including a step of adding an aqueous solution or an aqueous dispersion containing at least one kind of carbonic acid selected from the group consisting of carbonates and carbonates to cement, the above-mentioned carbonates are monovalent cations and carbonate ions or heavy. A production method (pre-addition method), which is a salt with carbonate ion and has a solubility in 100 ml of water at 20 ° C. of 1 g or more.

In the post-addition method, first, cement, carbonate, and optionally other components are mixed to obtain a desired blending ratio to prepare a mixture. The method for preparing the mixture is not particularly limited, and examples thereof include pulverization and mixing with a mixer, a ball mill, or the like. Water is then added to the prepared mixture to prepare a hydraulic composition. The water and the mixture may be mixed by a mixer, a ball mill or the like. As described above, the other components may be added to the mixture before the addition of water, may be added to the mixture after the addition of water, or may be added to the mixture together with water. It may be combined. When an aggregate is used as another component, it may be pulverized in advance and then mixed with cement and carbonate, or it may be mixed with cement and carbonate and pulverized and mixed together, or these may be combined (these may be combined). For example, a part of the aggregate may be pulverized and mixed with a mixture containing cement and carbonate, and then the remaining aggregate may be pulverized separately and added to the mixture).

In the pre-addition method, an aqueous solution or an aqueous dispersion containing a carbonate prepared in advance is added to the cement. The aqueous dispersion is a dispersion system containing an aqueous solution of carbonate and a solid (powder or the like) carbonate that remains undissolved, and may be, for example, a suspension. Other materials may be added to the cement before the aqueous solution or the aqueous dispersion is added to the cement, or may be added together with the aqueous solution or the aqueous dispersion or after the aqueous solution or the aqueous dispersion is added. When an aggregate is used as another component, it may be pulverized in advance and then mixed with cement before or after the addition of the aqueous solution or the aqueous dispersion, or it may be pulverized and mixed together with the cement. They may be combined (eg, a portion of the aggregate may be ground and mixed with a mixture containing cement and carbonate, then the remaining aggregate may be separately ground and added to the mixture). The cement, the aqueous solution containing carbonate or the aqueous dispersion, and other materials as optional components may be mixed by a mixer, a ball mill, or the like.

The produced hydraulic composition may be a kneaded composition obtained by kneading water, cement, carbonate, and other components. That is, the hydraulic composition of the present embodiment may be a kneaded composition containing water, cement, and carbonate.

As a method for producing the hydraulic composition, for example, it is preferable to use a post-addition method. As a result, the strength of the cured product forming the concretion can be improved. Although the detailed mechanism is not clear, it is presumed that the dispersibility of the carbonate source in the hydraulic composition is improved and the concretion formation rate becomes uniform.

<Molded body>
The molded product of the present embodiment is a product obtained by molding the hydraulic composition containing water into a predetermined shape (that is, a cement-based molded product). The molded product refers to a molded product before curing.

The method for obtaining the molded product is not particularly limited, and the molded product can be obtained by casting by a known method. For example, a method of pouring a hydraulic composition into a formwork for placing concrete and molding the hydraulic composition in the formwork can be mentioned. When reinforced concrete, steel-framed concrete, or the like is obtained, a core material such as reinforced concrete may be placed at a predetermined position in the formwork before placing.

The molded product of the present embodiment may have one or more dents on its surface.

<Curing product>
A cured product can be obtained by curing the hydraulic composition or the above-mentioned molded product. The cured product includes a cement cured product formed by a water-hardening reaction and a deposit formed by concretion on at least a part of the surface of the cement cured product. That is, the cured product is a composite material containing a cement cured product and deposits. The hardened cement may be a solidified cement or a partially hardened cement in which the cement is only incompletely hardened (not yet solidified).

The deposit may contain an insoluble carbonate and may contain some of the components of the hardened cement or surrounding substances (soil, etc.) that are present when the effect is performed.

The insoluble carbonate is a salt that is sparingly soluble or insoluble in water. The solubility of the insoluble carbonate is less than 1 g, preferably 0.1 g or less, more preferably 0.05 g or less, still more preferably 0.01 g or less, relative to 100 ml of water at 20 ° C. .. Examples of the insoluble carbonate include alkaline earth metal carbonates such as magnesium carbonate, barium carbonate, calcium carbonate and strontium carbonate, and transition metal carbonates, and calcium carbonate is preferable from the viewpoint of strength.

<Manufacturing method of cured product>
The method for producing the cured product is not particularly limited, and may be any method including a hydraulic reaction for curing cement in a hydraulic composition or a molded product and forming a concretion. .. As such a method, for example, a step (curing step) of curing the above-mentioned water-hardening composition or molded product by a water-hardening reaction to obtain a cement cured product having a compressive strength of 5 N / mm ² or more, and the cement. Examples thereof include a production method including a step of contacting the cured product with an aqueous solution containing a cation containing a cation forming an insoluble salt with a carbonate ion (precipitation step).

In the above-mentioned production method, for example, first, the hydraulic composition or the molded product is cured to obtain a hardened cement product. The curing method is not particularly limited, and various curing processes such as underwater curing and sealing curing can be performed. As described above, the hardened cement body is a hardened body obtained by a water-hardening reaction of cement. The curing step is carried out until the compressive strength of the hardened cement becomes 5 N / mm ² or more. The compressive strength of the hardened cement obtained in the curing step may be 6 N / mm ² or more, or 7 N / mm ² or more. Further, the compressive strength of the hardened cement body may be, for example, 100 N / mm ² or less. The compressive strength can be measured, for example, by the method described in JIS A 1108-2006 “Concrete compression test method”.

In the precipitation step, the hardened cement obtained in the curing step is brought into contact with an aqueous solution containing cations forming an insoluble salt with carbonate ions. Examples of such cations include alkaline earth metal ions such as magnesium ion, barium ion, calcium ion and strontium ion, transition metal ions such as copper ion (I) and iron ion (III), and cured products. Calcium ions are preferable from the viewpoint of further improving the strength of the above.

An aqueous solution containing a cation that forms an insoluble salt with a carbonate ion can be prepared by adding a water-soluble salt containing such a cation to water. Examples of the water-soluble salt include calcium chloride and the like. The aqueous solution containing cations forming an insoluble salt with carbonate ions may be a natural aqueous solution such as seawater, groundwater, and leachate that exists in an environment in which a water-hard composition or a molded product is used.

In the precipitation step, carbonate ions released from the surface of the hardened cement form form insoluble salts with cations contained in the surrounding aqueous solution and are deposited (fixed) on the surface of the hardened cement. The strength of the hardened material (composite material) is further increased by the deposits fixed on the surface of the hardened cement body. A part of the surface of the hardened cement may be brought into contact with an aqueous solution containing cations that form insoluble salts with carbonate ions, and the entire surface of the hardened cement contains cations that form insoluble salts with carbonate ions. It may be brought into contact with an aqueous solution (for example, soaked).

In particular, when the hardened cement body is a cured product of the above-mentioned molded body having dents on the surface, dents are also present on the surface of the hardened cement body. In the precipitation step, the concentration of carbonate ions released from the surface of the space inside the depression tends to increase, and the formation of insoluble carbonate tends to occur. Therefore, a large amount of insoluble carbonate is likely to precipitate in the dents of the hardened cement body, and a part or all of the dents existing on the surface are buried by the deposit. This makes it possible to more reliably improve the strength of the cured product. The size of the recess of the hardened cement is preferably 0.1 mm to 5.0 mm in diameter (opening diameter) and 0.1 mm to 2.0 mm in depth.

In the method for producing a cured product of the present embodiment, it is easy to obtain a cured product having higher strength. Although the detailed mechanism is not clear, it is speculated that the diffusion rate of carbonate ions can be slowed down and the diffusion rate appropriate for concretion formation can be achieved by increasing the compressive strength and then placing it in seawater. As a result, the formed CaCO ₃ is not easily diffused, the strength of the cured product is improved, and the formed CaCO 3 can serve as an injection material (see FIG. 2).

The precipitation reaction can be carried out until the water-hardening reaction of the hardened cement progresses and the hardened cement solidifies. Further, after the precipitation step, curing for solidifying the hardened cement body may be performed separately. The cured product may be a cement-based structure such as a concrete structure or a mortar structure having a predetermined shape. Examples of the cement-based structure include a wave-dissipating block, various building materials, and the like.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

<Measurement of structure strength>
(Example 1)
The amounts of ordinary Portland cement, limestone, potassium carbonate, and water shown in Table 1 were prepared. In the following Example 1 and Comparative Example 1, tap water was used as water.
First, ordinary Portland cement and limestone were mixed using a mixer to prepare a mixture. Then, an aqueous solution in which potassium carbonate (K ₂ CO ₃ ) was dissolved in water was prepared. This aqueous solution was added to the above mixture to prepare a hydraulic composition. The hydraulic composition was quickly poured into a 10 mm × 10 mm × 60 mm mold. The hydraulic composition is surface-finished between the beginning and the end, demolded when a compressive strength of about 1 N / mm ² is obtained, sealed and cured, and sufficiently cured to react in Example 1. A cement hardened body was obtained.

(Comparative Example 1)
The amounts of ordinary Portland cement, limestone, and water shown in Table 1 were prepared.
First, ordinary Portland cement and limestone were mixed using a mixer to prepare a mixture. Water was then added to the mixture to prepare a hydraulic composition. Then, the cement cured product of Comparative Example 1 was obtained by the same method as in Examples 1 and 2.

(Preparation of cured product)
The cured products of Example 1 and Comparative Example 1 were placed in simulated seawater in which 50 g of calcium chloride was added to 3000 g of seawater to prepare a specimen of the structure. In the specimen of Example 1, a white deposit (precipitate) was formed on the surface, and it was confirmed by wide-angle X-ray diffraction measurement that the deposit was calcium carbonate.

(Compressive strength)
The compressive strength was measured by the following procedure.
The compressive strength of the cured products of Example 1 and Comparative Example was tested. The compressive strength test was performed on the 3rd, 7th, and 28th days after the cured product specimen was placed in the simulated seawater.
The compressive strength test method was in accordance with the method described in JIS A 1108-2006 “Concrete compression test method”.
The test results are shown in Table 1 below.

As shown in Table 1, it was found that Example 1 had improved compressive strength as compared with Comparative Example 1.
Further, in Example 1, it was confirmed that a white solid was adhered to the surface of the cured product. It is considered to be CaCO ₃ , and it can be seen that it exerts a role as an injection material and self-healing property.

<Relationship between the strength of the cured product and concretion>
Next, the relationship between the strength of the hardened cement before being placed in seawater and the concretion was evaluated.

(Example 2)
A hydraulic composition was prepared in the same manner as in Example 1. The hydraulic composition was immediately poured into a sphere-forming mold having a diameter of 4 mm after preparation, and was subjected to initial curing. A surface finish was applied to the hydraulic composition from the start to the end of the initial curing. When the curable composition was cured to some extent in the mold, the mold was removed to obtain a molded product. The obtained molded product was further sealed and cured for one day to obtain a cement cured product having a compressive strength of 1 N / mm ² .
Next, pseudo seawater was prepared by adding 50 g of calcium chloride to 3000 g of seawater. The cement cured product was submerged in the prepared pseudo-seawater for one day to form a concretion to obtain a cured product. A photograph of the obtained cured product is shown in FIG. As shown in FIG. 1, the hardened cement was fixed by a pedestal made of wire so that the entire surface was in contact with the pseudo seawater.

(Example 3)
A cement cured product was produced in the same manner as in Example 2 except that the cement cured product having a compressive strength of 7 N / mm ² was obtained by performing sealing curing for 7 days. The cement cured product was submerged in simulated seawater for 7 days to form a concretion to obtain a cured product. A photograph of the obtained cured product is shown in FIG. Note that FIG. 2 is a photograph taken after submerging the hardened cement body in pseudo-seawater for 7 days, and concretion was formed to the extent that it was almost the same as that in FIG. 2 after 1 day.

As shown in FIGS. 1 and 2, in any of the cured products of Examples 2 and 3, white deposits were formed on the surface of the hardened cement body. It was confirmed by wide-angle X-ray diffraction measurement that the deposit was calcium carbonate in any of the cured products.
As shown in FIG. 1, the deposit in the cured product of Example 2 was frost-like and slightly soft. This is because the degree of hardening of the hardened cement body was not so advanced when it was brought into contact with pseudo-seawater (that is, the compressive strength was not so high yet), so carbon dioxide from the surface of the hardened cement body was obtained. It is considered that this is because the diffusion rate of ions is high and the concretion is formed rapidly. As in Example 2, the hardened cement in a state where the compressive strength has not been increased so much is considered to be suitable as an injection material because the formation rate of the deposit is high.

As shown in FIG. 2, the deposit in the cured product of Example 3 firmly adhered to the surface of the cement cured product and was considerably hard. This is because the degree of hardening of the hardened cement body was sufficiently advanced when it was brought into contact with the simulated seawater (that is, the state where the compressive strength was increased), so that carbon dioxide ions were released from the surface of the hardened cement body. It is considered that this is because the speed was low and the concretion was formed slowly. The cured product produced in Example 3 has a very high compressive strength, and is therefore considered to be suitable for injection materials, various building materials, and the like.

<Relationship between the shape of the cured product and concretion>
(Example 4)
The amount of the hydraulic composition of Example 1 poured into the mold was adjusted to prepare a molded product having a dent on the surface. A cured product was prepared in the same manner as in Example 3 except that a molded product having a dent on the surface was used.
FIG. 3 is a photograph of the cured product of Example 4 taken after being taken out of the simulated seawater and washed with water. According to this, it was confirmed that concretion was formed intensively in the depression.
The size of the depression was 0.45 to 3.3 mm in diameter and 1.0 mm in depth.

Claims (13)

With cement,
Containing at least one carbonate selected from the group consisting of carbonates and carbonates,
A water-hard composition in which the carbonate is a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and the solubility in 100 ml of water at 20 ° C. is 1 g or more. The water-hard composition according to claim 1, wherein the carbonate is at least one selected from the group consisting of lithium carbonate, sodium carbonate, and potassium carbonate. The hydraulic composition according to claim 1 or 2, wherein the carbonic acid ester is at least one of a compound represented by the following formula (I) and a compound represented by the following formula (II).

(In the formula (I), R ¹ and R ² each independently contain a monovalent hydrocarbon group containing 1 to 4 carbon atoms (the monovalent hydrocarbon group is a halogen atom, a hydroxyl group, or 1 to 3). It may be substituted with an alkoxy group having 1 carbon atom), and in formula (II), R ³ is a divalent hydrocarbon group containing 2 to 4 carbon atoms (the divalent hydrocarbon). The hydrogen group may be substituted with a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 3 carbon atoms.)) The hydraulic composition according to any one of claims 1 to 3, wherein the carbonic acid ester is at least one of ethylene carbonate, propylene carbonate and glycerol 1,2-carbonic acid. The hydraulic composition according to any one of claims 1 to 4, wherein the content of the carbonate is 3 parts by mass or more with respect to 100 parts by mass of the cement. The hydraulic composition according to any one of claims 1 to 5, wherein the content of the carbonate is 10 to 200 parts by mass with respect to 100 parts by mass of the cement. A step of preparing a mixture containing cement and at least one carbonic acid selected from the group consisting of carbonates and carbonates.
Including the step of adding water to the mixture.
A method for producing a water-hard composition, wherein the carbonate is a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and the solubility in 100 ml of water at 20 ° C. is 1 g or more. It comprises the step of adding an aqueous solution or an aqueous dispersion containing at least one carbonic acid selected from the group consisting of carbonates and carbonates to cement.
A method for producing a water-hard composition, wherein the carbonate is a salt of a monovalent cation and a carbonate ion or a bicarbonate ion, and the solubility in 100 ml of water at 20 ° C. is 1 g or more. The molded product of the hydraulic composition according to any one of claims 1 to 6, which has a dent on the surface. A cured product which is the hydraulic composition according to any one of claims 1 to 6 or a cured product of the molded product according to claim 9. The hydraulic composition according to any one of claims 1 to 6, or a cured product formed from the molded product according to claim 9.
A hardened product containing a hardened cement formed by hardening the cement and a deposit formed in a depression on the surface of the hardened cement. The cured product according to claim 11, wherein the deposit contains calcium carbonate. It is a method for manufacturing a cured product.
A step of curing the water-hardening composition according to any one of claims 1 to 6 or the molded product according to claim 9 to obtain a cement cured product having a compressive strength of 5 N / mm ² or more.
A method for producing a cured product, which comprises a step of contacting the cement cured product with an aqueous solution containing cations forming an insoluble salt with carbonate ions.

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