JP2016034886A - Concrete repair material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete repair material which can adsorb and fix the salt and others having entered through concrete itself and cracks of a concrete surface.SOLUTION: The present invention provides a concrete repair material which can be used for repairing concrete, the concrete repair material comprising a resin, and a layered double hydroxide represented by the chemical formula MM(OH)(A)/mHO (Mis a divalent metal, Mis a trivalent metal, and Ais an n-valent anion; 1/6<x<1/3, where m and n are natural numbers). For the layered double hydroxide, its crystallite size is made smaller so that the viscosity becomes 1000 mPa s or less.SELECTED DRAWING: None

Description

  The present invention relates to a concrete repair material.

  Reinforced concrete is a structure using both high tensile strength iron and high compressive strength concrete. Moreover, although iron is easily oxidized and rust is easily generated, a passive film is formed on the surface of the reinforcing bar by the highly alkaline cement contained in the concrete. Therefore, the iron inside the reinforced concrete does not corrode and can continue to satisfy the required performance.

  However, as the neutralization of concrete progresses, oxidation proceeds inside, and the iron inside expands due to rust, causing cracks and the like on the concrete surface. Then, a vicious cycle occurs in which oxygen, moisture, and the like enter from the cracked portion and further rust occurs.

  For this reason, in order to prevent deterioration of a reinforced concrete, the resinous coating material is apply | coated to the concrete surface (for example, refer patent document 1).

JP2014-83530

  However, the conventional coating material is only for the purpose of preventing the surface of the reinforced concrete from water and salt damage, and does not take into account the salt content or the like invading the concrete itself or cracks on the concrete surface.

  Then, an object of this invention is to provide the concrete repair material which can adsorb | suck and fix the salt etc. which penetrate | invaded from the concrete itself or the crack of the concrete surface.

In order to achieve the above object, the concrete repair material of the present invention can be used for repairing cracks in concrete, and the resin and chemical formula are M ²⁺ _1-x M ³⁺ _x (OH) ₂ ^(a _n-) layered double hydroxide represented by _{x / n · mH 2 O (} M 2+ is a divalent metal, M ³⁺ is a trivalent ^{metal, a n-represents} an anion, 1 / 6 <x <1/3, m and n are natural numbers).

  In this case, it is preferable to reduce the crystallite size of the layered double hydroxide so that the viscosity is 1000 mPa · s or less. For example, the crystallite size of the layered double hydroxide is preferably 20 nm or less. It ’s fine.

In addition, the anions carbonate ion represented by A ^n-, preferably better not hydrogen carbonate ion or a chloride ion, for example, an anion represented by A ^n-, may be nitrate ions.

Further, the layered double hydroxide, for ^example, can be used those represented by _{^{Mg 2+ 1-x Al 3+ x}} (OH) 2 (A n-) x / n · mH 2 O.

  Moreover, what consists of any one or more of an epoxy resin, an acrylic resin, and a urethane-type resin can be used for the said resin.

  According to the present invention, due to the ion exchange ability of the layered double hydroxide contained therein, it is possible to adsorb and fix the salt or the like that has entered from concrete or cracks on the concrete surface.

  Below, the concrete repair material of this invention is demonstrated. The concrete repair material of the present invention can be used for repairing concrete, and is mainly composed of a resin and a layered double hydroxide.

  The resin is a resin that can be injected into cracks in the concrete or coat the surface of the concrete, and is a curable liquid resin that can prevent moisture, chlorine, etc. from entering the concrete. Any resin that is conventionally used for concrete repair materials can be used. For example, an epoxy resin, an acrylic resin, a urethane resin, etc. are mentioned. These resins may be used alone or in combination of two or more. The resin may be a one-component resin or a two-component resin.

Examples of the epoxy resin include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, cresol novolak type epoxy resin and the like.
Examples of bisphenol A type epoxy resins that are particularly preferably used include bisphenol A diglycidyl ether, bisphenol A polypropylene oxide diglycidyl ether, bisphenol A ethylene oxide diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and hydrogenated bisphenol A propylene oxide diester. Examples thereof include polycondensation products such as bisphenol A type diglycidyl ether such as glycidyl ether. Such epoxy resins can be used alone or in combination of two or more.

  Moreover, a reactive diluent can also be added and mix | blended with an epoxy resin. Such reactive diluents are effective for reducing the viscosity of the composition. As such a reactive diluent, a compound having one epoxy group in the molecule such as phenyl glycidyl ether, butyl glycidyl ether, allyl glycidyl ether, styrene oxide, octylene oxide or the like can be preferably used. Such a reactive diluent can be blended in an amount of 45% by weight or less, preferably 25% by weight or less, based on the main agent.

  In addition, the epoxy resin may contain a compound which does not have an epoxy group but can react with a component of a curing agent (such as an amine compound) as an additive. Examples of such compounds include isocyanates such as hexamethylene diisocyanate and tolylene diisocyanate, and α, β-unsaturated carbonyl compounds that undergo a Michael addition reaction with amine compounds, such as acrylic acid esters and acrylamide derivatives. it can. Acrylic acid esters are effective in improving low-temperature curability, and acrylamide derivatives are effective in improving thixotropic properties or improving adhesiveness. Such additives can be blended in the range of preferably 30% by weight or less, more preferably 20% by weight or less per main agent.

  In addition, plasticizers, dyes, organic pigments and inorganic fillers, polymer compounds, antioxidants, ultraviolet absorbers, coupling agents, surfactants, and the like are appropriately added to the epoxy resin as other components. You can also.

As the acrylic resin, for example, a polymer of an acrylic monomer or a copolymer of an acrylic monomer and another monomer can be used. Examples of acrylic monomers include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and t-butyl (meth) acrylate. (Meth) acrylic acid C _1-10 alkyl ester such as (meth) acrylic acid hexyl, (meth) acrylic acid C _3-12 cycloalkyl ester such as cyclohexyl (meth) acrylic acid, phenyl (meth) acrylate (Meth) acrylic acid aryl esters such as benzyl (meth) acrylate and other (meth) acrylic acid aralkyl esters, 2-hydroxyethyl (meth) acrylate, and hydroxy C _2-6 alkyl such as 3-hydroxypropyl (meth) acrylate (Meth) acrylate, dimethylaminoethyl (meth) acrylate Alkylamino-alkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate and diethylaminopropyl (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, methylol (meth) acrylamide, alkoxymethyl (meth) acrylamide, etc. (Meth) acrylamide or a derivative thereof, epoxy group-containing (meth) acrylate such as glycidyl (meth) acrylate, (meth) acrylonitrile, and the like.

  Examples of the monomer copolymerized with the acrylic monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, and fatty acid vinyl monomers such as vinyl propionate, anhydrous Unsaturated polyvalent carboxylic acids such as maleic acid, maleic acid, fumaric acid and itaconic acid, or esters of unsaturated polyvalent carboxylic acid derivatives such as dimethyl maleate and diethyl fumarate, N-substituted maleimides such as N-phenylmaleimide And olefinic monomers such as ethylene and propylene. These monomers may be used alone or in combination of two or more.

  As the urethane resin, for example, a urethane prepolymer having a free isocyanate group obtained by reacting a polyol and a polyisocyanate can be suitably used.

  As the polyol, polyether polyol, polyolefin polyol, or the like can be used.

  The polyether polyol has 2 or more, preferably 2 to 6, hydroxyl groups such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, glycerin, hexanediol, hexanetriol, glycerin, trimethylolpropane, and pentaerythritol. Obtained by subjecting a polyol having 2 to 8 carbon atoms to addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran, preferably 2 to 8 carbon atoms, in the presence of an alkali catalyst or the like. It is appropriate to use polyalkylene polyols having 2 to 4 hydroxyl groups (active hydrogen groups) in the molecule.

  Examples of the polyolefin polyol include 2 to 4 molecules in a molecule obtained by addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran to a diene compound such as butadiene and isoprene. It is appropriate to use a polydiene polyol having a hydroxyl group. As the polyisocyanate, a compound having 2 or more, preferably 2 to 3 isocyanate groups in one molecule is suitable.

  Specific examples of the polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diphenyl diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, and hexamethylene. Isocyanate compounds such as diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate; Sumidur N (Sumitomo Bayer Urethane Co., Ltd.) Bullet polyisocyanate compounds such as product name); Death module IL, HL ( It can be said A.G. trade name), Coronate E. H. Polyisocyanate compounds having an isocyanate ring such as (trade name manufactured by Nippon Polyurethane Industry Co., Ltd.); Adduct polyisocyanate compounds such as Sumidur L (trade name manufactured by Sumitomo Bayer Urethane Co., Ltd.), Coronate HL (trade name manufactured by Nippon Polyurethane Industry Co., Ltd.) Can be mentioned. These polyisocyanates can be used alone or as a mixture of two or more.

The layered double hydroxide means that the chemical formula is represented by M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O. Here, M ²⁺ is a divalent metal, M ³⁺ is a trivalent ^{metal, A n-represents} an n-valent anion. X is generally a number in the range of 1/6 <x <1/3, and m and n are natural numbers. The layered double hydroxide is sometimes called a hydrotalcite-like compound.

Examples of the divalent metal include Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Zn ²⁺ , Ca ²⁺ , Li ²⁺ , Ni ²⁺ , Co ²⁺ , and Cu ²⁺ .

Examples of the trivalent metal include Al ³⁺ , Fe ³⁺ , Mn ^{3+ and the} like.

Specifically, the layered double hydroxide represented by the general formula Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O, or the general formula Zn ²⁺ Examples thereof include layered double hydroxides represented by _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O. A ⁿ⁻ is an n-valent anion and m> 0.

Further, the anion A ^n- is located between layers of the layered double hydroxide, is exchanged with higher affinity other anions and layered double hydroxides. In the anion exchange, ions having a higher charge density are more likely to be taken in. If the size is the same, ions having a higher valence are more likely to be taken in, and ions having a smaller ionic diameter are likely to be taken in if the valence is the same. Therefore, by mixing a certain amount of the layered double hydroxide with the resin, it is possible to adsorb and fix the salt or the like that has entered from the cracks on the concrete itself or the concrete surface. The ^n- interlayer anions ^A, for _{^{example, CO 3 2-, HCO 3 -}} , PO 4 3-, SO 4 2-, Cl -, NO 2 -, NO 3 - , and the like. However, carbonate ions (CO ₃ ^2-) and bicarbonate ion (HCO ₃ ^-), when released are exchanged with other anions in the cement, resulting calcium carbonate reacts with the cement, concrete There is a risk of neutralization. In addition, when chloride ions (Cl ⁻ ) are exchanged with other anions and released, iron may corrode. Accordingly, the interlayer anions A ^n- in the carbonate ion of the layered double hydroxide, it is preferable not contain bicarbonate ions or chloride ions.

  Further, it is preferable that the concrete repair material not only simply covers the concrete surface but also can be filled in the cracks. Here, the viscosity of the low-viscosity epoxy resin generally used as a crack injection material is 100 to 1000 mPa · s according to quality standards (JIS A 6024). Therefore, the viscosity of the concrete repair material is preferably 1000 mPa · s or less. However, since the viscosity of the epoxy resin increases when a general layered double hydroxide is mixed, it is necessary to reduce the amount of the layered double hydroxide in order to satisfy the quality standard. Therefore, as a result of intensive studies by the inventors of the present application, it has been found that the viscosity of the resin can be reduced by reducing the crystallite size (crystallite size) of the layered double hydroxide mixed with the resin. It was. In order to satisfy the aforementioned quality standards, the crystallite size of the layered double hydroxide is preferably 20 nm or less, more preferably 10 nm or less.

  The layered double hydroxide may be produced by a known method, but for example, it can be produced by the following method.

  First, an acidic solution containing aluminum ions and magnesium ions is prepared.

  Any aluminum source may be used as long as it generates aluminum ions in water, and is not limited to a specific substance. For example, alumina, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminum nitrate, bauxite, alumina production residue from bauxite, aluminum sludge and the like can be used. These aluminum sources may be used alone or in combination of two or more.

  The magnesium source of magnesium ions is not limited to a specific substance as long as it is a substance that generates magnesium ions in water. For example, calcite of brucite, magnesium hydroxide, magnesite, magnesite, or the like can be used. Any of these magnesium sources may be used alone or in combination of two or more.

Here, the general formula of the layered double hydroxide composed of aluminum ions and magnesium ions is Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (A ⁿ⁻ is negative) In the most common composition of highly crystalline layered double hydroxides, the molar ratio of aluminum ions to magnesium ions is known to be 1: 3 (x = 0.25). Yes. Therefore, the molar ratio of aluminum ions to magnesium ions in the acidic solution is preferably in the range of 1: 5 to 1: 2. By setting it as this range, a layered double hydroxide can be produced advantageously in terms of mass balance without wasting the aluminum source and the magnesium source.

  Further, for example, nitric acid or hydrochloric acid can be used to adjust the acidic solution to be acidic.

  Next, the acidic solution containing aluminum ions and magnesium ions is mixed with an alkaline solution containing alkali. This alkaline solution preferably has a pH of 8-11. The mixing of the acidic solution and the alkaline solution can be performed by adding the acidic solution to the alkaline solution all at once, or by dropping the acidic solution into the alkaline solution. Preferably, the acidic solution is acidic depending on the stirring ability at the time of mixing. It is better to mix an appropriate amount of solution and alkaline solution. Of course, other methods may be used as long as the acidic solution and the alkaline solution can be sufficiently stirred.

  Here, the alkali contained in the alkaline solution is not limited to a specific substance as long as the aqueous solution is alkaline. For example, sodium hydroxide or calcium hydroxide can be used. Aqueous ammonia, sodium borate, potassium borate, sodium carbonate, potassium carbonate, ammonium carbonate and the like can also be used. Any of these alkalis may be used alone or in combination of two or more.

However, since the highly crystalline layered double hydroxide is preferentially ion-exchanged with carbonate ions, if carbonate ions are contained, it cannot be efficiently ion-exchanged with the intended anions. Further, when carbonate ions (CO ₃ ²⁻ ) are exchanged with other anions and released into the cement, they react with the cement to produce calcium carbonate, which may neutralize the concrete. Further, when chloride ions (Cl ⁻ ) are exchanged with other anions and released, iron in the reinforced concrete may corrode. Therefore, it is preferable that the acidic solution and the alkaline solution do not contain carbonate ions, hydrogen carbonate ions and chloride ions.

The layered double hydroxide can be produced with a smaller crystallite size as the aging time after synthesis is shortened. Therefore, it is preferable to stop the ripening so that the crystallite size is 20 nm or less, preferably 10 nm or less. In order to stop the aging, after mixing the acidic solution and the alkaline solution in the synthesis of the layered double hydroxide, the pH of the mixed solution may be lowered to a value at which the crystal growth of the layered double hydroxide stops. For example, a layered double hydroxide represented by the general formula Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O is aged when the pH is 9 or less. Can be stopped. In addition, the layered double hydroxide represented by the general formula Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O is aged when the pH is 5 or less. Can be stopped.

The mixing method of the layered double hydroxide into the resin is not particularly limited as long as the layered double hydroxide can be uniformly mixed with the resin, and is generally known in the process of producing the resin. Can be used. For example, in a reaction kettle, mixing can be performed by using a mixer that can reasonably perform diffusion, dissolution, dispersion, and the like.
[Example 1]
The relationship between the crystallite size of the layered double hydroxide and the viscosity of the layered double hydroxide / epoxy resin blend was examined. As the layered double hydroxide, the conventional product in which the interlayer anion of the layered double hydroxide is carbonate ion (hereinafter referred to as carbonated LDH, product name DHT4A, manufactured by Kyoritsu Chemical Co., Ltd.) and the interlayer anion is carbonate ion. With a smaller crystallite size than conventional products (hereinafter referred to as carbonated NLDH, chemical formula [Mg _5.33 Al _2.67 (OH) ₁₆ ] [(CO ₃ ) _1.335 · 4H ₂ O]) An ion having a crystallite size smaller than that of a conventional product (hereinafter referred to as nitric acid type NLDH, [Mg _5.33 Al _2.67 (OH) ₁₆ ] [(NO ₃ ) _2.67 · 4H ₂ O]) was used. Moreover, as the epoxy resin, ADOX1380W (manufactured by Nippon Adox Co., Ltd., viscosity 284 mPa · s) was used. Table 1 shows the results of the layered double hydroxide / epoxy resin blend in which 20% of the layered double hydroxide is mixed with respect to the mass of the epoxy resin.

It can be seen that the smaller the crystallite size, the smaller the viscosity. In addition, conventional layered double water having a large crystallite size with respect to the viscosity quality standard (JIS A 6024: 100 to 1,000 mPa · s) of a low-viscosity epoxy resin generally used as a crack injection material It can be seen that the oxide cannot satisfy the standard, but the layered double hydroxide having a small crystallite size can satisfy the standard.
[Example 2]
The relationship between the crystallite size of the layered double hydroxide and the amount of salt adsorption was investigated. The test was conducted as follows. First, 400 ml of a 50 ppm (50 mg / L) aqueous sodium chloride solution was prepared, and the amount of chloride ions in the aqueous sodium chloride solution was measured (theoretical value: 30.3 ppm). Next, a “layered double hydroxide / epoxy resin blend” in which 20% carbonate type LDH, carbonate type NLDH or nitrate type NLDH layered double hydroxide as in Example 1 was mixed with the epoxy resin. (Concrete repair material) was prepared, 0.89 g of the mixture was infiltrated into the nonwoven fabric, and the nonwoven fabric was immersed in the prepared aqueous sodium chloride solution. After 7 days of age, the total amount of chloride ions in the aqueous sodium chloride solution was measured. In addition, the test was implemented 3 times and evaluated by the average value. The test results are shown in Table 2.

In carbonated LDH, the amount of chloride ions in the aqueous sodium chloride solution hardly changes compared to the negative control. On the other hand, it can be seen that the amount of chloride ion in the sodium chloride aqueous solution is significantly reduced in the carbonate type NLDH and the nitrate type NLDH compared to the negative control. That is, it can be seen that the adsorption amount of chloride ions increases as the crystallite size of the layered double hydroxide decreases. Furthermore, it can be seen that the adsorption amount of chloride ions is larger in the nitrate type layered double hydroxide than in the carbonate type layered double hydroxide.

Claims (7)

A concrete repair material that can be used to repair concrete,
Resin,
A layered double hydroxide represented by the chemical formula M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (M ²⁺ is a divalent metal, M ³⁺ Is a trivalent metal, A ⁿ⁻ is an n-valent anion, and 1/6 <x <1/3, m and n are natural numbers).
A concrete repair material characterized by comprising:   The concrete repair material according to claim 1, wherein the crystallite size of the layered double hydroxide is reduced so that the viscosity is 1000 mPa · s or less.   The concrete repair material according to claim 1 or 2, wherein a crystallite size of the layered double hydroxide is 20 nm or less. The anion is carbonate ion represented by A ^n-, concrete repair material according to any one of claims 1, wherein the non-bicarbonate ions or chloride ions 3. Concrete repair material according to claim 4, wherein the anion represented by the A ^n- is characterized in that it is a nitrate ion. 6. The layered double hydroxide is represented by Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O. 6. Concrete repair material as described in any one.   The concrete repair material according to any one of claims 1 to 6, wherein the resin is one or more of an epoxy resin, an acrylic resin, and a urethane resin.