Anticorrosion coating material, anticorrosion coating layer, and anticorrosion method for concrete structures

Abstract

To provide an anti-corrosion coating material that is easy to repair a concrete structure that has been deteriorated by sulfuric acid, etc., and has excellent durability, an anti-corrosion coating layer using the anti-corrosion coating material, and a method for protecting the concrete structure using the anti-corrosion coating material.SOLUTION: An anti-corrosion coating material of this invention comprises a (meth)acrylate monomer and a hydrophobic silica, wherein an average particle diameter of the hydrophobic silica is 1 to 100 nm. An anti-corrosion coating layer of the present invention includes: a surface preparation layer comprising a hardened body of an alumina cement composition containing an alumina cement, a pozzolan substance, and aggregate; and an anti-corrosion coating layer comprising a hardened body of the anti-corrosion coating material of the present invention on the surface preparation layer. A method of the present invention for protecting the concrete structure from corrosion includes the following steps: assembling a formwork; pouring the alumina cement composition containing the alumina cement, the pozzolan substance, and the aggregate into the formwork to form a surface preparation layer; removing the formwork; and applying the anti-corrosion coating material of the present invention to form an anti-corrosion coating layer on the surface preparation layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a corrosion-protective coating material, a corrosion-protective coating layer, and a method for protecting a concrete structure from corrosion. [Background technology]

[0002] In sewers and hot spring areas, hydrogen sulfide is generated by the influence of microorganisms and volcanic gases, and when water is present, sulfuric acid is produced. In such places, corrosion of concrete structures becomes a problem. When hardened cement such as concrete comes into contact with sulfuric acid, it reacts with the calcium hydroxide in the concrete to produce gypsum dihydrate, which in turn produces ettringite, causing the concrete to expand and deteriorate. A common repair method for areas damaged by sulfuric acid involves removing the damaged area with a water jet, repairing the cross section or smoothing the unevenness, and then applying a resin lining. Repair materials used for this include a material made by blending polymer with granulated blast furnace slag (Patent Document 1), a material made of alumina cement (Patent Documents 2 and 3), and cement mortar containing a large amount of fine powder such as granulated blast furnace slag or silica fume (Patent Document 4). Other proposed materials include a material made of alumina cement and ground granulated blast furnace slag, containing 25% by weight or less of alumina cement particles of 5 μm or less and containing a lithium salt (Patent Document 5), and a material containing 0.5 to 4 parts by weight of a water-soluble organic compound having an alkali metal salt of sulfonic acid as a substituent per 100 parts by weight of cement (Patent Document 6).

[0003] In addition, known resin components used in resin linings include epoxy resins, bisphenol-based unsaturated polyester resins, HET acid-based unsaturated polyester resins, bisphenol-based vinyl ester resins, novolac-based vinyl ester resins, brominated bisphenol-based vinyl ester resins, silicone resins, polyurethane resins, polyurea resins, and acrylic resins (Non-Patent Document 1).

[0004] When repairing concrete with cementitious materials and then lining it with resin, it is common to apply multiple layers of resin lining, such as applying a primer, intermediate coat, and top coat. Depending on the type of resin, there are cases where the intermediate coat and top coat are applied twice, and many processes are required to form the final resin layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 03-290348 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-89565 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-292245 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-128618 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-293603 [Patent Document 6] Japanese Patent Application Laid-Open No. 2003-292362 [Non-patent literature]

[0006] [Non-Patent Document 1] "Manual for Corrosion Prevention and Corrosion Control Techniques for Sewerage Concrete Structures," edited by the Japan Sewage Works Agency, a local joint corporation, published by the Sewerage Works Management Center, pages 68-69, December 2017 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a corrosion-resistant coating material that is easy to repair concrete structures deteriorated by sulfuric acid or the like and that has excellent durability, a corrosion-resistant coating layer using the corrosion-resistant coating material, and a corrosion protection method for concrete structures using the corrosion-resistant coating material. [Means for solving the problem]

[0008] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by a corrosion-protective coating material containing a (meth)acrylate monomer and hydrophobic silica having a predetermined average particle size, and have thus completed the present invention. [1] (meth)acrylate monomer and hydrophobic silica, The anticorrosion coating material, wherein the hydrophobic silica has an average particle size of 1 to 100 nm. [2] The corrosion-protective coating material according to the above [1], wherein the hydrophobic silica is at least one of silica hydrophobized with an organosilane represented by the following general formula (1) and silica hydrophobized with an organosilane represented by the following general formula (2): R 1 x SiCl y H 4-x-y (1) In general formula (1), R 1 represents an alkyl group, x represents an integer of 1 to 3, y represents an integer of 0 to 3, and x+y≦4. (R 2 z H 3-z Si)2NR 3 (2) In general formula (2), R 2 represents hydrogen, an alkyl group, an alkenyl group, or a halogenated alkyl group; R 3 represents hydrogen, an alkyl group, or an alkali metal element; z represents an integer of 1 to 3. [3] The hydrophobic silica includes silica hydrophobized with a first organosilane represented by the general formula (1) and silica hydrophobized with a second organosilane represented by the general formula (1) that is different from the first organosilane; In the general formula (1), R of the first organosilane 1 is an alkyl group represented by the following general formula (3), and R of the second organosilane 1 3. The corrosion-protective coating material according to claim 2, wherein is an alkyl group represented by the following general formula (4): C s H 2s+1 (3) In the general formula (3), s represents an integer of 1 to 5. C t H 2t+1 (4) In the general formula (4), t represents an integer of 6 to 12. [4] The corrosion-protective coating material according to any one of the above [1] to [3], wherein the (meth)acrylate monomer includes a di(meth)acrylate having a bisphenol A skeleton. [5] The corrosion-protective coating material according to the above [4], wherein the di(meth)acrylate monomer having a bisphenol A skeleton is a di(meth)acrylate having a bisphenol A skeleton represented by the following general formula (5): [ka] In general formula (5), R 4 and R 4 ' represents hydrogen or a methyl group, and R 5 and R 5 ' represents an alkylene group which may have a substituent, and m and n represent integers of 1 to 20. [6] The corrosion-protective coating material according to any one of the above items [1] to [5], which is a two-component type comprising a first corrosion-protective coating material containing a polymerization initiator, the (meth)acrylate monomer, and the hydrophobic silica, and a second corrosion-protective coating material containing a decomposition accelerator that accelerates decomposition of the polymerization initiator, the (meth)acrylate monomer, and the hydrophobic silica. [7] The corrosion-protective coating material according to any one of the above [1] to [6], which has a viscosity at 25°C of 1700 to 15000 mPa·s and a thixotropy index at 25°C of 3.0 or more. [8] The corrosion-protective coating material according to any one of the above [1] to [7], which has a viscosity of 1700 to 15000 mPa·s in the range of 0 to 25°C and a thixotropy index of 3.0 or more in the range of 0 to 25°C. [9] A corrosion-resistant coating layer comprising: a surface adjustment layer made of a hardened alumina cement composition containing alumina cement, a pozzolanic substance, and an aggregate; and a corrosion-resistant coating layer made of a hardened corrosion-resistant coating material according to any one of [1] to [8] above, on the surface adjustment layer.

[10] The corrosion-protective coating layer according to the above [9], further comprising a primer formed of a cured product of a primer composition containing a (meth)acrylate monomer, disposed between the surface adjustment layer and the corrosion-protective coating layer.

[11] The corrosion-protective coating layer according to the above

[10] , wherein the (meth)acrylate monomer contained in the primer composition includes a di(meth)acrylate having a bisphenol A skeleton.

[12] The corrosion-protective coating layer according to the above

[11] , wherein the di(meth)acrylate having a bisphenol A skeleton contained in the primer composition is a di(meth)acrylate having a bisphenol A skeleton represented by the following general formula (5): [ka] In general formula (5), R 4 and R 4 ' represents hydrogen or a methyl group, and R 5 and R 5 ' represents an alkylene group which may have a substituent, and m and n represent integers of 1 to 20.

[13] The corrosion-resistant coating layer according to any one of the above

[10] to

[12] , wherein the porosity of the surface adjustment layer is 5 to 40 volume %, and in the region of the surface adjustment layer near the primer, the voids of the surface adjustment layer are filled with a cured product of the primer composition.

[14] A method for protecting a concrete structure from corrosion, comprising the steps of assembling a formwork, pouring an alumina cement composition containing alumina cement, a pozzolanic substance, and aggregate into the formwork to form a surface adjustment layer, removing the formwork, and applying the corrosion-resistant coating material described in any one of [1] to [8] above to form a corrosion-resistant coating material layer on the surface adjustment layer.

[15] The corrosion protection method for a concrete structure according to

[14] above, further comprising the step of applying a primer composition containing a (meth)acrylate monomer to the surface adjustment layer to form a primer, and the corrosion-protective coating material is applied to the primer. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a corrosion-resistant coating material that is easy to repair concrete structures deteriorated by sulfuric acid or the like and that has excellent durability, a corrosion-resistant coating layer using the corrosion-resistant coating material, and a corrosion protection method for concrete structures using the corrosion-resistant coating material. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Anti-corrosion coating material] The corrosion-protective coating material of the present invention contains a (meth)acrylate monomer and hydrophobic silica having an average particle size of 1 to 100 nm. The hydrophobic silica is silica whose surface has been hydrophobized using a treatment agent. By hydrophobizing the silica surface, it becomes easier to disperse the silica in the corrosion-protective coating material, thereby enhancing the thickening and thixotropic effects of the silica. As a result, it becomes easier to apply the corrosion-protective coating material thick. The corrosion-protective coating material of the present invention can be applied to a thickness of 400 μm or more in a single application using, for example, a roller. The use of a (meth)acrylate monomer in the corrosion-protective coating material can improve the sulfuric acid resistance and durability of the corrosion-protective coating material. It also becomes easier to form thick films of the corrosion-protective coating material.

[0011] (hydrophobic silica) The average particle size of the hydrophobic silica in the corrosion-protective coating material of the present invention is 1 to 100 nm. If the average particle size of the hydrophobic silica is less than 1 nm, it may be difficult to disperse the hydrophobic silica in the corrosion-protective coating material. If the average particle size of the hydrophobic silica is greater than 100 nm, the surface area of the hydrophobic silica decreases, weakening the thickening effect and thixotropy-imparting effect of the hydrophobic silica, making it difficult to apply a thick corrosion-protective coating material with a low viscosity. This increases the effort required to repair deteriorated concrete structures. From this perspective, the average particle size of the hydrophobic silica is preferably 2 to 80 nm, more preferably 3 to 60 nm, and even more preferably 5 to 50 nm. The average particle size of hydrophobic silica can be determined, for example, by measuring the particle size distribution of the hydrophobic silica using a laser diffraction / scattering particle size distribution analyzer (LS-13 320) manufactured by Beckman Coulter, Inc., and determining the particle size at which the cumulative frequency is 50% by volume as the average particle size of the hydrophobic silica; or by observing the particles with a transmission electron microscope, directly counting the particle size and number of particles, and determining the particle size at which the cumulative frequency is 50% by number as the average particle size of the hydrophobic silica.

[0012] The hydrophobic silica in the corrosion-protective coating material of the present invention is preferably at least one of silica hydrophobized with an organosilane represented by the following general formula (1) and silica hydrophobized with an organosilane represented by the following general formula (2). This further enhances the thickening and thixotropy-imparting effects of the hydrophobic silica, making it easier to apply the corrosion-protective coating material thicker. As a result, repair of concrete structures becomes easier. It is believed that silanol groups present on the surface of hydrophobic silica interact with silanol groups present on the surface of other hydrophobic silica through hydrogen bonding, forming a three-dimensional network structure of the hydrophobic silica, thereby increasing the viscosity and thixotropy of the corrosion-protective coating material. Furthermore, by hydrophobizing silica with an organosilane represented by the following general formula (1) and an organosilane represented by the following general formula (2), the hydrophobic silica can be sufficiently dispersed in the corrosion-protective coating material. This well-dispersed hydrophobic silica forms a three-dimensional network structure, which is believed to enhance the thickening and thixotropy-imparting effects of the hydrophobic silica.

[0013] R 1 x SiCl y H 4-x-y (1) In general formula (1), R 1 represents an alkyl group, x represents an integer of 1 to 3, y represents an integer of 0 to 3, and x+y≦4. (R 2 z H 3-z Si)2NR 3 (2) In general formula (2), R 2 represents hydrogen, an alkyl group, an alkenyl group, or a halogenated alkyl group; R 3 represents hydrogen, an alkyl group, or an alkali metal element; z represents an integer of 1 to 3.

[0014] When the hydrophobic silica is silica hydrophobized with an organosilane represented by the general formula (1), the viscosity and thixotropy of the corrosion-protective coating material are imparted to the corrosion-protective coating material, which facilitates thick application of the corrosion-protective coating material. 1The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 10, and even more preferably 1 to 8. When the hydrophobic silica is silica hydrophobized with an organosilane represented by the general formula (2), from the viewpoint of imparting viscosity and thixotropy to the corrosion-protective coating material, which facilitates thick application of the corrosion-protective coating material, R 2 is preferably hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkenyl group, or a halogenated alkyl group having 1 to 3 carbon atoms, more preferably hydrogen, or an alkyl group having 1 to 3 carbon atoms, and even more preferably hydrogen or a methyl group. 3 is preferably hydrogen, an alkyl group having 1 to 3 carbon atoms, or an alkali metal element, more preferably hydrogen or an alkyl group having 1 to 3 carbon atoms, and even more preferably hydrogen.

[0015] Although hydrophobic silica can be used alone, it is preferable to combine two or more types of hydrophobic silica to impart viscosity and thixotropy to the corrosion-protective coating material, which facilitates thick application of a low-viscosity corrosion-protective coating material. In this case, the hydrophobic silica preferably contains silica hydrophobized with a first organosilane represented by the above general formula (1) and silica hydrophobized with a second organosilane represented by the above general formula (1) that is different from the first organosilane. In the general formula (1), R of the first organosilane 1 is an alkyl group represented by the following general formula (3), and R of the second organosilane 1 is an alkyl group represented by the following general formula (4). C s H 2s+1 (3) In the general formula (3), s represents an integer of 1 to 5. C t H 2t+1 (4) In the general formula (4), t represents an integer of 6 to 12.

[0016] From the viewpoint of imparting viscosity and thixotropy to the corrosion-protective coating material, which facilitates thick application of the corrosion-protective coating material, preferably, in general formula (3), s is an integer of 1 to 3, and in general formula (4), t is an integer of 7 to 10; more preferably, in general formula (3), s is an integer of 1 to 2, and in general formula (4), t is an integer of 8 to 9.

[0017] The mass ratio of the silica hydrophobized with the first organosilane to the silica hydrophobized with the second organosilane is not particularly limited as long as it can impart viscosity and thixotropy that facilitate thick application of the corrosion-protective coating material. The mass ratio of the silica hydrophobized with the first organosilane to the silica hydrophobized with the second organosilane is, for example, 5:95 to 95:5, preferably 30:70 to 90:10, and more preferably 50:50 to 85:15.

[0018] From the viewpoint of imparting viscosity and thixotropy to the corrosion-protective coating material, which facilitates thick application of the corrosion-protective coating material, the content of hydrophobic silica in the corrosion-protective coating material is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 2 to 7 parts by mass, relative to 100 parts by mass of the (meth)acrylate monomer.

[0019] ((Meth)acrylate Monomer) The (meth)acrylate monomer of the corrosion-protective coating material of the present invention is preferably a di(meth)acrylate having a bisphenol A skeleton. The di(meth)acrylate having a bisphenol A skeleton is preferably a di(meth)acrylate having a bisphenol A skeleton represented by the following general formula (5) (hereinafter, sometimes referred to as (meth)acrylate monomer (A)). This can further improve the sulfuric acid resistance and durability of the corrosion-protective coating material. [ka] In general formula (5), R 4 and R 4 ' represents hydrogen or a methyl group, and R 5and R 5 R' represents an alkylene group which may have a substituent, and m and n represent integers of 1 to 20. 4 and R 4 ' may be the same or different. 5 and R 5 ' may be the same or different.

[0020] From the viewpoint of further improving the sulfuric acid resistance and durability of corrosion protection coating materials, 5 and R 5 is preferably an alkylene group having 1 to 12 carbon atoms which may have a substituent, more preferably an alkylene group having 2 to 4 carbon atoms which may have a substituent, and even more preferably an n-propylene group having an ethylene group and a 2-hydroxyl group (—CHCH(OH)CH—), and preferably m+n=2 to 10, more preferably m+n=2 to 4.

[0021] Examples of the (meth)acrylate monomer (A) include bisphenol A-type EO2-modified di(meth)acrylate, bisphenol A-type EO (ethylene oxide)4-modified di(meth)acrylate, bisphenol A-type EO10-modified di(meth)acrylate, bisphenol A-type PO-modified di(meth)acrylate, bisphenol A diglycidyl ether (meth)acrylic acid adduct, etc. These (meth)acrylate monomers (A) can be used alone or in combination of two or more.

[0022] Examples of commercially available (meth)acrylate monomers (A) include Miramer M-241 (manufactured by Miwon Specialty Chemical Co., Ltd.), Miramer M-2101 (manufactured by Miwon Specialty Chemical Co., Ltd.), Miramer PE210 (manufactured by Miwon Specialty Chemical Co., Ltd.), NK Ester BPE-100 (manufactured by Shin-Nakamura Chemical Co., Ltd.), NK Ester BPE-200 (manufactured by Shin-Nakamura Chemical Co., Ltd.), NK Ester BPE-500 (manufactured by Shin-Nakamura Chemical Co., Ltd.), NK Ester BPE-1300 (manufactured by Shin-Nakamura Chemical Co., Ltd.), Light Ester BP-2EMBR-MA (Kyoeisha Chemical Co., Ltd.), Fancryl FA-321M (manufactured by Hitachi Chemical Co., Ltd.), and Fancryl FA-324A (manufactured by Hitachi Chemical Co., Ltd.).

[0023] The corrosion-protective coating material of the present invention preferably contains, as the (meth)acrylate monomer, a (meth)acrylate having a dicyclopentenyl skeleton (hereinafter, sometimes referred to as (meth)acrylate monomer (B)) in addition to the (meth)acrylate monomer (A). The (meth)acrylate having a dicyclopentenyl skeleton is preferably a dicyclopentenyloxyalkylene (meth)acrylate represented by the following general formula (6). This can further improve the sulfuric acid resistance and durability of the corrosion-protective coating material. In addition, the (meth)acrylate monomer (B) also has the effect of acting as a reactive diluent. [ka] In general formula (6), R 6 represents hydrogen or a methyl group, and R 7 represents an alkylene group, and p represents an integer of 1 to 20.

[0024] From the viewpoint of sulfuric acid resistance and durability of corrosion protection coating material, R 6 is preferably a methyl group. 7is preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 4 carbon atoms, and even more preferably an ethylene group; p is preferably an integer of 1 to 3, and more preferably 1.

[0025] Examples of the (meth)acrylate monomer (B) include dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxydiethylene glycol (meth)acrylate, dicyclopentenyloxytriethylene glycol (meth)acrylate, and dicyclopentenyloxypropylene glycol (meth)acrylate. These (meth)acrylate monomers (B) can be used alone or in combination of two or more. Among these, dicyclopentenyloxyethyl (meth)acrylate is preferred from the viewpoints of sulfuric acid resistance and durability of the corrosion-protective coating material.

[0026] The corrosion-protective coating material of the present invention preferably contains, as the (meth)acrylate monomer, a hydroxyalkyl (meth)acrylate (hereinafter sometimes referred to as (meth)acrylate monomer (C)) in addition to the (meth)acrylate monomer (A) and the (meth)acrylate monomer (B), which can further improve the sulfuric acid resistance and durability of the corrosion-protective coating material.

[0027] Examples of the (meth)acrylate monomer (C) include 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and glycerol mono(meth)acrylate. These (meth)acrylate monomers (C) can be used alone or in combination of two or more. Among these, from the viewpoint of the adhesiveness of the corrosion-protective coating material, 2-hydroxyalkyl (meth)acrylates represented by the following general formula (7) are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

[0028] [ka] In general formula (7), R 8 represents hydrogen or a methyl group, and R 9 represents hydrogen or an alkyl group.

[0029] From the viewpoint of adhesion of anticorrosion coating material, R 8 is preferably a methyl group, and R 9 is preferably hydrogen or an alkyl group having 1 to 12 carbon atoms, more preferably hydrogen or an alkyl group having 1 to 5 carbon atoms, and even more preferably hydrogen.

[0030] From the viewpoint of the sulfuric acid resistance and durability of the corrosion-protective coating material, the content of the (meth)acrylate monomer (A) in the corrosion-protective coating material is preferably 20 to 80 parts by mass, more preferably 40 to 70 parts by mass, per 100 parts by mass of the total of the (meth)acrylate monomer (A), the (meth)acrylate monomer (B), and the (meth)acrylate monomer (C). On the other hand, from the viewpoint of the sulfuric acid resistance and durability of the corrosion-protective coating material, the content of the (meth)acrylate monomer (B) in the corrosion-protective coating material is preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, per 100 parts by mass of the total of the (meth)acrylate monomer (A), the (meth)acrylate monomer (B), and the (meth)acrylate monomer (C). From the viewpoint of the sulfuric acid resistance and durability of the corrosion-protective coating material, the content of the (meth)acrylate monomer (C) in the corrosion-protective coating material is preferably 5 to 35 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the total of the (meth)acrylate monomer (A), the (meth)acrylate monomer (B), and the (meth)acrylate monomer (C).

[0031] The (meth)acrylate monomer of the corrosion-protective coating material of the present invention may contain a (meth)acrylate monomer other than the (meth)acrylate monomer (A), the (meth)acrylate monomer (B), and the (meth)acrylate monomer (C), provided that the effects of the present invention are not impaired. From the viewpoint of sulfuric acid resistance and durability of the corrosion-protective coating material, the total content of the (meth)acrylate monomer (A), the (meth)acrylate monomer (B), and the (meth)acrylate monomer (C) in the (meth)acrylate monomer of the corrosion-protective coating material is preferably 80 to 100 mass%, more preferably 90 to 100 mass%, and even more preferably 95 to 100 mass%.

[0032] (Polymerization initiator) The corrosion-protective coating material of the present invention preferably contains a polymerization initiator to promote curing of the (meth)acrylate monomer. The polymerization initiator generates free radicals to initiate polymerization of the (meth)acrylate monomer. Examples of the polymerization initiator include the following organic peroxides.

[0033] (1) Ketone peroxides: methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, methylacetoacetate peroxide, acetylacetone peroxide, and the like. (2) Peroxyketals: 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)octane, n-butyl-4,4-bis(tert-butylperoxy)valerate, 2,2-bis(tert-butylperoxy)butane, and the like. (3) Hydroperoxides: tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and the like. (4) Dialkyl peroxides: di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(tert-butylperoxy-meta-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, and the like. (5) Diacyl peroxides: acetyl peroxide, isobutyl peroxide, octanoyl peroxide, decanoyl peroxide, laurinoyl peroxide, 3,3,5-trimethylhexanoyl peroxide, succinic acid peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, meta-toluoyl peroxide, and the like. (6) Peroxydicarbonates: diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-normal propyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, diallyl peroxydicarbonate, and the like. (7) Peroxyesters: tert-butyl peroxyacetate, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, tert-butyl peroxyneodecanoate, cumyl peroxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,3,5-trimethylhexanoate, tert-butyl peroxylaurate, tert-butyl peroxybenzoate, di-tert-butyl butyl peroxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl peroxymaleic acid, tert-butyl peroxyisopropyl carbonate, cumyl peroxyoctoate, tert-hexyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxyneohexanoate, tert-hexyl peroxyneohexanoate, and cumyl peroxyneohexanoate. (8) Other organic peroxides: acetylcyclohexylsulfonyl peroxide, tertiary butyl peroxy allyl carbonate, etc.

[0034] These polymerization initiators can be used alone or in combination of two or more. Among these polymerization initiators, organic peroxides are preferred in terms of adhesiveness and curability. Among organic peroxides, hydroperoxides are preferred. Among hydroperoxides, cumene hydroperoxide is preferred.

[0035] The content of the polymerization initiator in the corrosion-protective coating material is preferably 0.5 to 10 parts by mass, and more preferably 0.7 to 5 parts by mass, relative to 100 parts by mass of the total content of the (meth)acrylate monomers.

[0036] (Decomposition accelerator) The corrosion-protective coating material of the present invention preferably contains a decomposition accelerator in addition to the polymerization initiator. The decomposition accelerator accelerates the decomposition of the polymerization initiator to promote the generation of free radicals, thereby accelerating the curing reaction of the corrosion-protective coating material. This allows the corrosion-protective coating material to be cured more reliably at room temperature. Examples of decomposition accelerators include the following: (1) Thiourea derivatives: diethylthiourea, dibutylthiourea, ethylenethiourea, tetramethylthiourea, mercaptobenzimidazole, benzoylthiourea, and the like. (2) Amines: N,N-diethyl-p-toluidine, N,N-dimethyl-p-toluidine, N,N-diisopropanol-p-toluidine, N,N-di(2-hydroxyethyl)-p-toluidine, triethylamine, tripropylamine, ethyldiethanolamine, N,N-dimethylaniline, ethylenediamine, triethanolamine, and the like. (3) Metal salts of organic acids: cobalt naphthenate, copper naphthenate, zinc naphthenate, cobalt octoate, iron octoate, etc. (4) Organic metal chelate compounds: copper acetylacetonate, titanium acetylacetonate, manganese acetylacetonate, chromium acetylacetonate, iron acetylacetonate, vanadyl acetylacetonate, cobalt acetylacetonate, and the like. Other examples of the decomposition accelerator include condensation products of aldehydes and amines. These decomposition accelerators can be used alone or in combination of two or more. Among these, metal salts of organic acids are preferred from the viewpoint of curability. Among metal salts of organic acids, cobalt octylate is preferred. A combination of an amine and a metal salt of an organic acid is also preferred as the decomposition accelerator. When an amine and a metal salt of an organic acid are used in combination, the mass ratio of the amine to the metal salt of the organic acid is preferably 1-45:55-99, more preferably 5-15:85-95, per 100 parts by mass of the total of the amine and the metal salt of the organic acid.

[0037] The content of the decomposition accelerator in the corrosion-protective coating material is preferably 0.5 to 10 parts by mass, and more preferably 1.0 to 5 parts by mass, relative to 100 parts by mass of the total content of the (meth)acrylate monomers.

[0038] (Silane coupling agent) The corrosion-protective coating material of the present invention can contain a silane coupling agent to improve adhesion. Examples of silane coupling agents include γ-chloropropyltrimethoxysilane, vinyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris(β-methoxyethoxy)silane, γ-(meth)acryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and γ-ureidopropyltriethoxysilane. Among these, γ-(meth)acryloxypropyltrimethoxysilane is preferred in terms of adhesion. The amount of the silane coupling agent used is preferably 0.01 to 20 parts by mass, and more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the total content of the (meth)acrylate monomers.

[0039] (Other ingredients) The corrosion-protective coating material of the present invention may also contain components other than those mentioned above.

[0040] The content of the other components in the corrosion-protective coating material is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the total content of (meth)acrylate monomers.

[0041] (2-dose form) The corrosion-protective coating material of the present invention may be a one-component type, but is preferably a two-component type consisting of a first corrosion-protective coating material containing the polymerization initiator, the (meth)acrylate monomer, and the hydrophobic silica, and a second corrosion-protective coating material containing the decomposition accelerator, the (meth)acrylate monomer, and the hydrophobic silica. However, the amine is preferably contained in the first corrosion-protective coating material, and the thiourea derivative, the metal salt of an organic acid, or the organometallic chelate compound is preferably contained in the second corrosion-protective coating material. By using a two-component corrosion-protective coating material of the present invention, the workability of the corrosion-protective coating material of the present invention is further improved. Furthermore, by making the first and second corrosion-protective coating materials substantially similar in composition, the tolerance for the blending ratio is broadened, allowing the corrosion-protective coating material to be used in workplaces where blending at a strict blending ratio is difficult. Therefore, it is preferable that the compositions of the first and second corrosion-protective coating materials be substantially similar, except for the polymerization initiator and the decomposition accelerator. Specifically, it is preferred that the first and second corrosion-protective coating materials each contain the same hydrophobic silica, (meth)acrylate monomer (A), (meth)acrylate monomer (B), and (meth)acrylate monomer (C), and that the contents of the hydrophobic silica per 100 parts by mass of the (meth)acrylate monomer, and the contents of the (meth)acrylate monomer (A), (meth)acrylate monomer (B), and (meth)acrylate monomer (C) per 100 parts by mass of the total of the (meth)acrylate monomer (A), (meth)acrylate monomer (B), and (C) are the same. Furthermore, in corrosion protection work for concrete structures, materials are usually delivered, then blended and kneaded to prepare a corrosion-protective coating material. Therefore, by making the corrosion-protective coating material of the present invention a two-component type, the first corrosion-protective coating material and the second corrosion-protective coating material can be mixed easily, and the corrosion-protective coating material can be produced efficiently.

[0042] (viscosity) The viscosity of the corrosion-protective coating material of the present invention at 25°C is preferably 1700 to 15,000 mPa·s. When the viscosity of the corrosion-protective coating material at 25°C is 1700 mPa·s or more, the corrosion-protective coating material can be easily applied thickly. When the viscosity of the corrosion-protective coating material at 25°C is 15,000 mPa·s or less, the corrosion-protective coating material can be easily applied. From this perspective, the viscosity of the corrosion-protective coating material at 25°C is more preferably 2,000 to 15,000 mPa·s, and even more preferably 2,500 to 10,000 mPa·s. When the corrosion-protective coating material of the present invention is a two-component type consisting of a first corrosion-protective coating material and a second corrosion-protective coating material, the viscosity of the corrosion-protective coating material of the present invention is the viscosity of the corrosion-protective coating material obtained by mixing the first corrosion-protective coating material and the second corrosion-protective coating material. The viscosity of the corrosion-protective coating material can be measured by the method described in the Examples below.

[0043] The viscosity of the corrosion-protective coating material of the present invention in the temperature range of 0 to 25°C is preferably 1700 to 15000 mPa·s. When the viscosity of the corrosion-protective coating material in the temperature range of 0 to 25°C is 1700 mPa·s or more, the corrosion-protective coating material can be easily applied thickly even at low temperatures. When the viscosity of the corrosion-protective coating material in the temperature range of 0 to 25°C is 15000 mPa·s or less, the corrosion-protective coating material can be easily applied even at low temperatures. From this perspective, the viscosity of the corrosion-protective coating material in the temperature range of 0 to 25°C is more preferably 2000 to 15000 mPa·s, and even more preferably 2500 to 10000 mPa·s.

[0044] (thixotropy index) The thixotropy index of the corrosion-protective coating material of the present invention at 25°C is preferably 3.0 or more. When the thixotropy index of the corrosion-protective coating material at 25°C is 3.0 or more, the viscosity of the corrosion-protective coating material is reduced during application, making the corrosion-protective coating material easier to apply, and the viscosity of the corrosion-protective coating material after application is increased, making it possible to suppress sagging of the corrosion-protective coating material. As a result, it becomes easier to apply the corrosion-protective coating material thickly. From this perspective, the thixotropy index of the corrosion-protective coating material at 25°C is more preferably 3.3 or more, and even more preferably 3.5 or more. The upper limit of the thixotropy index of the corrosion-protective coating material at 25°C is not particularly limited, but is, for example, 10.0 or less. When the corrosion-protective coating material of the present invention is a two-component type consisting of a first corrosion-protective coating material and a second corrosion-protective coating material, the thixotropy index of the corrosion-protective coating material of the present invention is the thixotropy index of the corrosion-protective coating material obtained by mixing the first corrosion-protective coating material and the second corrosion-protective coating material. The thixotropy index of the corrosion-protective coating material can be measured by the method described in the examples below.

[0045] The corrosion-protective coating material of the present invention preferably has a thixotropy index of 3.0 or more in the temperature range of 0 to 25°C. When the corrosion-protective coating material has a thixotropy index of 3.0 or more in the temperature range of 0 to 25°C, the viscosity of the corrosion-protective coating material is reduced during application, even at low temperatures, making the corrosion-protective coating material easier to apply. The viscosity of the corrosion-protective coating material after application is increased, preventing sagging of the corrosion-protective coating material. As a result, the corrosion-protective coating material can be easily applied thickly even at low temperatures. From this perspective, the thixotropy index of the corrosion-protective coating material at 25°C is more preferably 4.0 or more, and even more preferably 5.0 or more. The upper limit of the thixotropy index of the corrosion-protective coating material in the temperature range of 0 to 25°C is not particularly limited, but is, for example, 10.0 or less.

[0046] (Pot life) From the viewpoint of workability of the corrosion-protective coating material of the present invention, the pot life of the corrosion-protective coating material of the present invention is preferably 15 to 75 minutes, more preferably 30 to 50 minutes. The pot life of the corrosion-protective coating material can be measured by the method described in the examples below.

[0047] (Curing time) From the viewpoint of workability of the corrosion-protective coating material of the present invention, the curing time of the corrosion-protective coating material of the present invention is preferably 30 to 120 minutes, more preferably 50 to 80 minutes. The curing time of the corrosion-protective coating material can be measured by the method described in the examples below.

[0048] (tensile shear adhesive strength) From the viewpoint of durability of the corrosion-protective coating material of the present invention, the tensile shear adhesive strength of the corrosion-protective coating material of the present invention is preferably 5 to 35 N / mm 2 and more preferably 10 to 30 N / mm 2 The tensile shear adhesive strength of the corrosion-protective coating material can be measured by the method described in the Examples below.

[0049] [Corrosion-resistant coating layer] The corrosion-protective coating layer of the present invention includes a surface adjustment layer made of a hardened alumina cement composition containing alumina cement, a pozzolanic substance, and an aggregate, and a corrosion-protective coating layer made of a hardened corrosion-protective coating material of the present invention on the surface adjustment layer. This makes it possible to easily repair concrete structures deteriorated by sulfuric acid or the like, and to obtain a corrosion-protective coating layer that is excellent in sulfuric acid resistance and durability.

[0050] (Tensile adhesive strength) From the viewpoint of durability of the corrosion-protective coating layer of the present invention, the tensile adhesive strength of the corrosion-protective coating layer of the present invention is preferably 1.0 to 4.0 N / mm 2 and more preferably 1.5 to 4.0 N / mm 2 The tensile adhesive strength of the corrosion-protective coating layer of the present invention can be measured by the method described in the Examples below.

[0051] (sulfuric acid penetration depth) In view of the sulfuric acid resistance of the corrosion-protective coating layer of the present invention, the sulfuric acid penetration depth of the corrosion-protective coating layer of the present invention is preferably less than 0.3 mm, more preferably less than 0.1 mm. The sulfuric acid penetration depth of the corrosion-protective coating layer of the present invention can be measured by the method described in the examples below.

[0052] (Anti-corrosion coating layer) The corrosion-protective coating layer in the corrosion-protective coating layer of the present invention is made of a cured product of the corrosion-protective coating material of the present invention. Therefore, a thick corrosion-protective coating layer can be easily formed. This facilitates repair of concrete structures deteriorated by sulfuric acid or the like. Furthermore, the corrosion-protective coating layer can be made to have excellent sulfuric acid resistance and durability. This also results in excellent sulfuric acid resistance and durability of the corrosion-protective coating layer of the present invention.

[0053] <Thickness> From the viewpoint of sulfuric acid resistance and durability of the corrosion-protective coating layer, the thickness of the corrosion-protective coating layer in the corrosion-protective coating layer of the present invention is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably 0.8 mm or more. Furthermore, by not making the corrosion-protective coating layer thicker than necessary, the corrosion-protective coating material is not wasted and the effort required for repairing the concrete structure is reduced, so the thickness of the corrosion-protective coating layer is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less.

[0054] (Surface adjustment layer) The surface conditioning layer of the corrosion-protective coating layer of the present invention is made of a hardened alumina cement composition. This further improves the sulfuric acid resistance and durability of the corrosion-protective coating layer. The alumina cement composition contains alumina cement, a pozzolanic substance, and an aggregate.

[0055] <Alumina cement> The alumina cement in the alumina cement composition used in the surface adjustment layer of the corrosion-protective coating layer of the present invention differs from Portland cement in that it forms a hardened body without producing slaked lime as a hydration product, and therefore has excellent sulfuric acid resistance. Alumina cement is obtained from ground clinker containing monocalcium aluminate as the main mineral, and examples that can be used include Alumina Cement No. 1 and Alumina Cement No. 2.

[0056] The fineness of alumina cement is 2000-8000 cm Specific surface area. 2 / g is preferred in terms of hydration activity.

[0057] <Pozzolanic substance> The pozzolanic substance in the alumina cement composition used in the surface adjustment layer of the corrosion-protective coating layer of the present invention is a substance that exhibits pozzolanic activity when stimulated by alkali. When used in combination with alumina cement, the pozzolanic substance can suppress strength reduction due to hydrate phase transition and improve the sagging resistance of the alumina cement composition during application. Examples of pozzolanic substances include granulated blast furnace slag, slowly cooled blast furnace slag, converter slag, silica fume, and fly ash. These pozzolanic substances can be used alone or in combination of two or more.

[0058] The fineness of the pozzolanic material is determined by the hydration activity and the specific surface area of the Blaine powder (3000 cm). 2 / g or more is preferred. The amount of the pozzolanic substance used is usually preferably 60 to 200 parts by mass, more preferably 80 to 150 parts by mass, per 100 parts by mass of alumina cement. The amount of silica fume used is preferably 1 to 20 parts by mass per 100 parts by mass of alumina cement.

[0059] <Aggregate> The aggregate in the alumina cement composition used in the surface adjustment layer of the corrosion-resistant coating layer of the present invention is not particularly limited and may be a commonly available aggregate. Examples include silica sand aggregate, silica stone aggregate, limestone aggregate, heavy aggregate, and lightweight aggregate. These aggregates may be used alone or in combination of two or more. In terms of acid resistance, it is preferable to use aggregates other than limestone aggregate. Among aggregates other than limestone aggregate, silica sand is preferred. By including an aggregate in the alumina cement composition, the strength of the surface adjustment layer can be improved.

[0060] The amount of aggregate used is not particularly limited as long as it is used within a range that does not affect acid resistance or fluidity, but is preferably 100 to 400 parts by mass per 100 parts by mass of the total of the alumina cement and pozzolanic substance.

[0061] <Portland cement> The alumina cement composition may further contain Portland cement to further enhance the hardening properties of the pozzolanic substance contained in the alumina cement composition. This can improve the strength of the surface adjustment layer. The amount of Portland cement used is not particularly limited as long as it is used within a range that does not affect acid resistance or fluidity, but is preferably 25 to 70 parts by mass per 100 parts by mass of alumina cement. Furthermore, when the alumina cement composition contains Portland cement, the alumina cement composition may further contain gypsum to enhance the strength of the surface adjustment layer. The amount of gypsum used is not particularly limited as long as it is used within a range that does not affect acid resistance or fluidity, but is preferably 50 to 150 parts by mass per 100 parts by mass of Portland cement. Furthermore, when the alumina cement composition contains Portland cement, the alumina cement composition may further contain slaked lime to accelerate the hardening of the alumina cement composition. The amount of slaked lime used is not particularly limited as long as it is used within a range that does not affect acid resistance or fluidity, but is preferably 5 to 50 parts by mass per 100 parts by mass of Portland cement.

[0062] <Additives> The alumina cement composition used in the surface adjustment layer of the corrosion-resistant coating layer of the present invention can contain various additives to the extent that they do not adversely affect the quality of the surface adjustment layer. It is preferable not to use higher fatty acid admixtures intended for waterproofing or crack prevention, as they may deteriorate the adhesion between the concrete and the surface adjustment layer. It is also preferable not to use concrete curing agents containing waxes, resins, chlorinated rubbers, etc. dissolved in solvents, as they may also deteriorate the adhesion between the concrete and the surface adjustment layer.

[0063] <Porosity> The porosity of the surface adjusting layer is preferably 5 to 40% by volume. When the porosity of the surface adjusting layer is 5% by volume or more, the corrosion-resistant coating material or the primer composition described below can be sufficiently penetrated into the surface adjusting layer, further preventing the corrosion-resistant coating material layer or the primer from peeling off from the surface adjusting layer. As a result, the sulfuric acid resistance and durability of the corrosion-resistant coating layer are further improved. Furthermore, when the porosity of the surface adjusting layer is 40% by volume or less, the corrosion-resistant coating material or the primer composition described below can be prevented from excessively penetrating into the surface adjusting layer. Note that excessive penetration of the corrosion-resistant coating material or the primer composition described below into the surface adjusting layer significantly increases the amount of corrosion-resistant coating material or the primer composition required to form a corrosion-resistant coating material layer or primer of the desired thickness. From this perspective, the porosity of the surface adjusting layer is more preferably 5 to 30% by volume. Furthermore, when the surface adjustment layer has the above-mentioned porosity, the voids in the surface adjustment layer in the region near the corrosion-protective coating layer or in the region near the primer are filled with a cured product of the corrosion-protective coating material or a cured product of the primer composition. The region of the surface adjustment layer near the corrosion-protective coating layer is within 0.5 mm from the interface between the surface adjustment layer and the corrosion-protective coating layer. The region of the surface adjustment layer near the primer is within 2 mm from the interface between the surface adjustment layer and the primer.

[0064] <Thickness> From the viewpoint of the sulfuric acid resistance and durability of the corrosion-protective coating layer, the thickness of the surface adjustment layer in the corrosion-protective coating layer of the present invention is preferably 10 mm or more, more preferably 15 mm or more, and even more preferably 20 mm or more. Furthermore, by not making the surface adjustment layer thicker than necessary, the alumina cement composition is not wasted and the repair of the concrete structure is not laborious, so the thickness of the surface adjustment layer is preferably 70 mm or less, more preferably 60 mm or less, and even more preferably 50 mm or less.

[0065] <Compression strength> From the viewpoint of durability of the corrosion-protective coating layer, the compressive strength of the alumina cement composition used in the surface adjustment layer of the corrosion-protective coating layer of the present invention is preferably 30 to 90 N / mm 2 and more preferably 40 to 80 N / mm 2 The compressive strength of the alumina cement composition can be measured by the method described in the Examples below.

[0066] (Primer) The corrosion-protective coating layer of the present invention preferably includes a primer disposed between the surface adjustment layer and the corrosion-protective coating layer. This prevents the corrosion-protective coating layer from peeling off from the surface adjustment layer. As a result, the sulfuric acid resistance and durability of the corrosion-protective coating layer are further improved. The primer is made of a cured product of a primer composition containing a (meth)acrylate monomer.

[0067] The (meth)acrylate monomer contained in the primer composition is preferably the same as the (meth)acrylate monomer used in the above-mentioned corrosion-protective coating material. This further strengthens the adhesion between the primer and the corrosion-protective coating layer. As a result, the sulfuric acid resistance and durability of the corrosion-protective coating layer are further improved. Similarly to the (meth)acrylate monomer used in the above-mentioned corrosion-protective coating material, the primer composition also preferably contains a polymerization initiator and a decomposition accelerator. Similarly to the (meth)acrylate monomer used in the above-mentioned corrosion-protective coating material, the primer composition may also contain the other components described above. Similarly to the (meth)acrylate monomer used in the above-mentioned corrosion-protective coating material, the primer composition is preferably a two-part type consisting of a first primer composition containing the polymerization initiator and the (meth)acrylate monomer, and a second primer composition containing the decomposition accelerator and the (meth)acrylate monomer.

[0068] The (meth)acrylate monomer, polymerization initiator, and decomposition accelerator contained in the primer composition are the same as the (meth)acrylate monomer, polymerization initiator, and decomposition accelerator used in the corrosion-protective coating material described above, and therefore a description of the (meth)acrylate monomer, polymerization initiator, and decomposition accelerator contained in the primer composition will be omitted. The (meth)acrylate monomer, polymerization initiator, and decomposition accelerator contained in the primer composition are preferably the same as the (meth)acrylate monomer, polymerization initiator, and decomposition accelerator used in the corrosion-protective coating material of the corrosion-protective coating material layer provided adjacent to the primer.

[0069] <Thickness> From the viewpoint of preventing the corrosion-resistant coating layer from peeling off from the surface adjustment layer, the thickness of the primer is preferably 50 to 250 μm, more preferably 80 to 200 μm, and even more preferably 100 to 150 μm.

[0070] <Viscosity> From the viewpoint of workability of the primer composition, the viscosity of the primer composition at 25° C. is preferably 50 to 1000 mPa s, and more preferably 100 to 500 mPa s. The viscosity of the primer composition at 25° C. can be measured by the method described in the Examples below.

[0071] (Pot life) From the viewpoint of workability of the primer composition, the pot life of the primer composition is preferably 10 to 50 minutes, more preferably 20 to 30 minutes. The pot life of the primer composition can be measured by the method described in the examples below.

[0072] (Curing time) From the viewpoint of workability of the primer composition, the curing time of the primer composition is preferably 15 to 85 minutes, more preferably 30 to 50 minutes. The curing time of the primer composition can be measured by the method described in the examples below.

[0073] (Construction period) Factors that adversely affect the quality of a corrosion-protective coating layer include application periods such as rainy seasons, high temperatures, and low temperatures. Low temperatures are particularly undesirable as application periods because they adversely affect the curing and performance of the resin. However, the corrosion-protective coating layer of the present invention can maintain high quality even in low temperatures (for example, in an application environment with a temperature of 0 to 15°C), and therefore the corrosion-protective coating layer can be applied even in low temperatures.

[0074] [Corrosion prevention methods for concrete structures] The corrosion protection method for concrete structures of the present invention includes the steps of (A) assembling formwork, (B) pouring the above-mentioned alumina cement composition into the formwork to form a surface adjustment layer, (C) removing the formwork, and (D) applying the corrosion-protective coating material of the present invention to form a corrosion-protective coating layer on the surface adjustment layer. This makes it easy to form a corrosion-protective coating layer that has excellent sulfuric acid resistance and durability, and facilitates the repair of concrete structures deteriorated by sulfuric acid or the like.

[0075] (Process (A)) In step (A), a formwork is assembled. By using the formwork, corrosion protection can be performed on concrete structures that have severe damage to rebars and require relatively large-scale repair. For example, when protecting the inner wall surface of a manhole from corrosion, the cylindrical formwork described in JP 2015-71939 A can be used.

[0076] (Process (B)) In step (B), the alumina cement composition is poured into a formwork to form a surface adjustment layer. For example, when protecting the inner wall surface of a manhole from corrosion, the alumina cement composition is poured into the gap between the cylindrical formwork and the inner wall surface of the manhole and hardened to form a surface adjustment layer. The alumina cement composition must be poured in such a way as to minimize material separation and to avoid the formation of construction defects in the poured surface adjustment layer. After pouring the alumina cement composition, compaction may be performed using a vibrator. This allows the formation of a dense surface adjustment layer with few air bubbles or voids. Furthermore, the alumina cement composition can be thoroughly spread around the reinforcing bars and throughout the formwork.

[0077] (Process (C)) In step (C), the formwork is removed. The formwork must be removed after the surface adjustment layer has reached the strength required to support its own weight and the loads applied during construction. To determine when the surface adjustment layer has reached the required strength, for example, the compressive strength of a standard specimen cured under the same conditions as the surface adjustment layer may be measured. It is preferable to first remove the parts of the formwork that are relatively unloaded, followed by the removal of the remaining important parts. For example, it is preferable to remove the horizontal parts of the formwork later than the vertical parts.

[0078] (Process (D)) In step (D), the corrosion-resistant coating material of the present invention is applied to form a corrosion-resistant coating layer on the surface conditioning layer. To ensure sulfuric acid resistance throughout the entire corrosion-resistant coating layer, it is important to ensure a uniform application thickness and the absence of pinholes. Therefore, the corrosion-resistant coating material is preferably applied carefully using a roller, trowel, dedicated applicator, or the like. The corrosion-resistant coating material of the present invention can be applied thickly even at low viscosity, thereby achieving a uniform coating thickness and suppressing the occurrence of pinholes. The applied corrosion-resistant coating material must have the required layer thickness. Because the corrosion-resistant coating material of the present invention can be easily applied thickly, it is easy to ensure the required layer thickness of the corrosion-resistant coating material. To ensure the durability of the corrosion-resistant coating layer, it is preferable to perform appropriate curing after application of the corrosion-resistant coating material to prevent damage to the corrosion-resistant coating layer until it is in a usable condition. The curing period for the corrosion-resistant coating layer is, for example, 1 to 7 days.

[0079] (Process (E)) The corrosion protection method for concrete structures of the present invention may further include step (E) of applying a primer composition containing a (meth)acrylate monomer to a surface adjustment layer to form a primer. In this case, step (D) involves applying a corrosion-resistant coating material to the primer. This allows the primer to be formed between the surface adjustment layer and the corrosion-resistant coating material layer. The primer composition is applied to the surface adjustment layer using, for example, a brush or roller. The primer composition is preferably applied to a dried surface adjustment layer. For example, the surface moisture content of the surface adjustment layer to which the primer composition is applied is preferably 7% or less.

[0080] (Steps inside a manhole) The steps (footrests) inside the manhole may be corroded by corrosive gases such as hydrogen sulfide. For this reason, it is preferable to replace the steps inside the manhole when applying corrosion protection to the inner wall surface of the manhole. From this perspective, the corrosion protection method for a concrete structure of the present invention may include a step of removing the old steps before step (A) and a step of installing new steps after step (D). The old steps can be removed, for example, by cutting them. The new steps can also be installed, for example, by the twin drill method recommended by the Twin Drill Method Association.

[0081] (Process to remove corroded parts) The corrosion prevention method for a concrete structure of the present invention may include a step of removing corroded portions of the concrete structure prior to step (A). For example, the corroded portions may be removed by ultra-high pressure water treatment until a sound concrete surface is exposed. The water pressure used in the ultra-high pressure water treatment is, for example, 150 to 200 MPa. Whether a sound concrete surface has been exposed can be determined, for example, by the phenolphthalein method.

[0082] (Rebar processing) In the corrosion prevention method for a concrete structure of the present invention, before step (A), the corroded portion of the concrete structure may be removed, and then the reinforcing steel bars in the concrete structure may be treated. For example, in treating the reinforcing steel bars, loose rust may be removed using sandblasting, power tools, etc., and the reinforcing steel bars may be cleaned using air blasting or high-pressure water, and then a rust inhibitor may be applied to the reinforcing steel bars.

[0083] (Cross-section repair) If defects such as cracks are present in the cross section of the concrete that appears after removing the corroded portion of the concrete structure, these defects can cause defects in the corrosion-protective coating layer. For this reason, it is preferable to repair the cross section of the concrete prior to step (A). For example, a V-cut is made along the crack in the concrete using a grinder or the like. A primer may then be applied to the V-cut area, after which a sealant may be filled in. Alternatively, the sealant may be filled in after the construction of the corrosion-protective coating layer.

[0084] [Application] The present invention is suitable for corrosion inhibition and corrosion prevention technologies for sewer concrete structures. The present invention can extend the service life of sewer concrete structures as long as possible. Sewerage facilities include, for example, sewer pipes, pumping stations, and treatment plants. Among these facilities, the present invention is particularly suitable for corrosion inhibition and corrosion prevention technologies for sewer pipe concrete structures, which have limited working space, because the concrete structures can be easily repaired. It is even more suitable for corrosion inhibition and corrosion prevention technologies for sewer pipe manholes. The corrosive environment in sewer pipe manholes generally has an annual average hydrogen sulfide gas concentration of 10 ppm or more and less than 50 ppm, a corrosive environment in which concrete corrosion is prominent (Corrosive Environment Classification: Type II, described on page 47 of Non-Patent Document 1). If left unattended, this corrosive environment is expected to cause concrete corrosion within several years (an average annual corrosion rate of approximately 4 mm / year), with the corrosion reaching the reinforcing steel. However, the present invention can extend the service life of sewer concrete structures as long as possible, even in such a severe corrosive environment. [Example]

[0085] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0086] The corrosion-protective coating materials of the examples and comparative examples were evaluated as follows. (Viscosity / thixotropy index) The viscosity of the corrosion-protective coating material was measured using a Brookfield viscometer (rotor No. 5) at a spindle rotation speed of 20 rpm in the temperature range of 0 to 35°C. In addition, the viscosity was measured at spindle rotation speeds of 2 rpm and 20 rpm, and then the thixotropy index was calculated based on the following formula. <Calculation formula for thixotropy index> Thixotropy index = viscosity at 2 rpm ÷ viscosity at 20 rpm The viscosity of the primer composition used as the primer for the corrosion-protective coating layer in the examples and comparative examples was also measured in the same manner.

[0087] (Curing time, pot life) 25g of corrosion-resistant coating material A and 25g of B were weighed and mixed to prepare a mixed solution, and the temperature of the mixed solution was measured using a thermocouple. The time when the temperature reached its highest was taken as the curing time. The pot life was calculated using the following formula. <Pot life calculation formula> Pot life = curing time x 0.6 The curing time and working life of the primer compositions used as primers for the corrosion-protective coating layers in the Examples and Comparative Examples were also measured in the same manner.

[0088] (tensile shear adhesive strength) The tensile shear adhesive strength of the corrosion-resistant coating material was measured in accordance with JIS K6850. Specifically, two SS400 steel plates (100 mm × 25 mm × 1.6 mm thick) whose surfaces had been sandblasted and degreased with acetone were prepared. The corrosion-resistant coating material was applied to one of the SS400 steel plates within 12.5 mm from the longitudinal end. The two SS400 steel plates were bonded together (adhesion area 3.125 cm) so that the area of one SS400 steel plate coated with the corrosion-resistant coating material overlapped only the area of the other SS400 steel plate within 12.5 mm from the longitudinal end. 2), and tensile shear bond strength test pieces were prepared. The corrosion-resistant coating material of the tensile shear bond strength test pieces was then cured for one day at a temperature of 23°C and a humidity of 50%. The non-overlapping side of the two SS400 steel plates in the tensile shear bond strength test piece was the gripping part of the tensile tester. The tensile shear bond strength of the prepared test pieces was measured using a tensile tester at a temperature of 23°C, a humidity of 50%, and a tensile speed of 10 mm / min.

[0089] (Coatability) A mold form measuring 140 mm x 195 mm x 20 mm was attached to a concrete slab, and the alumina cement composition was poured into it to prepare a test specimen. After removing the formwork, the test specimen was immediately placed upright and cured for one day at a temperature of 20°C and humidity of 60%. After curing, a primer composition was applied to the surface of the test specimen in an amount of 150 g / m. 2 The primer was applied to the surface of the test specimen at a rate of 500 g / m2 and then cured for 30 minutes. 2 The coating was applied at 100°C. The coating was then cured for one day at a temperature of 20°C and a humidity of 60%. The appearance of the cured coating was evaluated visually, and the thickness of the coating was measured using a wet gauge. A coating was judged as good if it was able to form a coating film at least 0.4 mm thick without dripping and had no wrinkles, unevenness, or peeling on the exterior. On the other hand, if there was dripping, if a coating film at least 0.4 mm thick could not be formed, or if the exterior had at least one of the defects of wrinkles, unevenness, or peeling, it was judged as poor.

[0090] The alumina cement compositions used in the surface adjustment layers of the corrosion-protective coating layers of the Examples and Comparative Examples were evaluated as follows. (compressive strength, porosity) The compressive strength of the alumina cement composition was measured according to JIS R5201. Specifically, the alumina cement composition was poured into a 40 mm × 40 mm × 160 mm mold formwork to prepare a test specimen. After demolding the next day, the test specimen was cured in water at 20°C for 27 days, and the compressive strength of the test specimen after 28 days was measured. The porosity of the test specimen was also measured according to ASTM-C-642.

[0091] The corrosion-protective coating layers of the examples and comparative examples were evaluated as follows. (Average particle size) The particle size distribution of the hydrophobic silica was measured using a laser diffraction scattering particle size distribution analyzer (LS-13 320) manufactured by Beckman Coulter, Inc., and the particle size at which the cumulative frequency was 50% by volume was taken as the average particle size of the hydrophobic silica. (Blaine specific surface area) Measurement was carried out in accordance with JIS R5201. (Adhesiveness) The adhesion of the corrosion-resistant coating layer was measured according to JIS A7502-2:2015 "Concrete Corrosion Prevention Technology for Sewerage Structures - Part 2: Corrosion Prevention Design Standard, Appendix L (Regulations) Tensile Test (Sheet Lining Method and Mortar Lining Method)." Specifically, a 280mm x 280mm x 20mm mold formwork was attached to a concrete slab (300mm x 300mm x 60mm), and an alumina cement composition was poured to form a surface adjustment layer. After demolding the next day, the surface adjustment layer was cured in water at 20°C for 27 days. After curing, a primer composition was applied to the surface of the surface adjustment layer at a rate of 150g / m. 2 The primer was formed on the surface of the surface adjustment layer by applying a corrosion prevention coating material at a rate of 500 g / m2. 2 The coating was applied to the concrete slab using a 40 mm x 40 mm incision, which reached the concrete slab, using a concrete cutter. A steel upper tension jig was attached to the surface of the corrosion-resistant coating using an adhesive (Denka Hardlock II acrylic resin mortar Dyna N, manufactured by Denka Co., Ltd.). The maximum tensile load was measured using a Construction Research Institute adhesion tester at 23°C and 50% humidity, and the tensile bond strength was calculated using the following formula. The fracture surface of the test specimen was also observed to identify the fracture location. <Tensile adhesive strength> σ t =T / 1600 σ t : Tensile adhesive strength (N / mm 2 ) T: Maximum tensile load (N)

[0092] (Sulfuric acid resistance test) A sulfuric acid resistance test was carried out in accordance with JIS A7502 "Immersion test of corrosion-protective coating layer c) In the case of mortar lining method." Specifically, the alumina cement composition was poured into a 75 mmφ × 150 mm mold formwork, demolded the next day, and then cured in water at 20°C for 27 days to produce an alumina cement hardened body. A primer composition was applied to the entire surface of the alumina cement hardened body at a rate of 100 g / m. 2 The primer was applied to the surface of the hardened alumina cement body at a rate of 500 g / m2 and then cured for 30 minutes to form a primer. 2 The primer was applied to the surface of the primer at a temperature of 25°C and a humidity of 50%, and then cured for one day to form a corrosion-resistant coating layer on the primer surface, preparing specimens for sulfuric acid resistance tests. The prepared specimens were immersed in a test solution (5% aqueous sulfuric acid solution). The test solution was replaced every 7 days for the first 4 weeks, and then every 4 weeks thereafter. The specimens were removed after 112 days of immersion. The specimens were then rinsed with water and their appearance was visually evaluated. Those without wrinkles, unevenness, peeling, or cracks were judged to be good. On the other hand, those with at least one of the defects of wrinkles, unevenness, peeling, or cracks were judged to be poor.

[0093] (sulfuric acid penetration depth) The sulfuric acid penetration depth was measured according to JIS A7502, "Method for measuring sulfuric acid penetration depth of corrosion-protective coating layers (mortar lining method)." Specifically, after the sulfuric acid resistance test described above, the test specimen was cut in half perpendicular to the axial direction of the cylinder. A 1% solution of phenolphthalein was sprayed onto the circular cut surface. The diameter of the red-colored part of the test specimen was measured at five points with a vernier caliper, and the average value was subtracted from the initial value (75 mm) to calculate half of this value, which was used as the sulfuric acid penetration depth. Note that the pH value of the test specimen decreases in the areas where sulfuric acid has penetrated, so the areas where sulfuric acid has penetrated do not turn color with phenolphthalein.

[0094] An anticorrosion coating material, an alumina cement composition and a primer composition were prepared as follows. (Anti-corrosion coating material) Anticorrosion coating materials were prepared using the materials shown in Tables 1 and 2, and their physical properties were measured. The results are shown in Tables 1 and 2.

[0095] (Alumina cement composition) Alumina cement compositions were prepared using the materials shown in Table 3, and their physical properties were measured. The results are shown in Table 3.

[0096] (Primer composition) Primer compositions were prepared using the materials shown in Table 4, and their physical properties were measured. The results are shown in Table 4.

[0097] (Anti-corrosion coating layer) The corrosion-protective coating layer was formed using the above-mentioned corrosion-protective coating material, alumina cement composition, and primer composition, and the physical properties were measured. The results are shown in Table 5.

[0098] (Materials used) ((Meth)acrylate Monomer) M-241: Bisphenol A type EO4 modified dimethacrylate: In the general formula (5), R 4 and R 4 ' is a methyl group, and R 5 and R 5 ' is an ethylene group, and m+n is approximately 4. Manufactured by Miwon Specialty Chemical Co., Ltd. PE210: Bisphenol A glycidyl ether acrylic acid adduct: In general formula (5), R 4 and R 4 ' is hydrogen and R 5 and R 5 ' is an n-propylene group having a 2-hydroxyl group, and m and n are 1. Manufactured by Miwon Specialty Chemical Co., Ltd. Fancryl FA512M: dicyclopentenyloxyethyl methacrylate, in general formula (6), R 6 is a methyl group, and R 7 is an ethylene group, and p is approximately 1. 2HEMA: 2-hydroxyethyl methacrylate, in general formula (7), R 8 is a methyl group, and R 9 is hydrogen. : Manufactured by Mitsubishi Chemical Corporation (silica) Aerosil R-972: dimethyldichlorosilane (in general formula (1), R 1 is a methyl group, x is 2, and y is 2. Hydrophobized silica: average particle size 16 nm, manufactured by Evonik Japan Co., Ltd. Aerosil R-805: octylsilane (in general formula (1), R 1 is an octyl group (carbon number 8), x is 1, and y is 0. Hydrophobized silica: average particle size 12 nm, manufactured by Evonik Japan Co., Ltd. Aerosil R-812: hexamethyldisilazane (in general formula (2), R 2 is a methyl group, and R 3 is hydrogen, and z is 3.) Hydrophobized silica: average particle size 7 nm, manufactured by Evonik Japan Co., Ltd. Aerosil RX-50: hexamethyldisilazane (in general formula (2), R 2 is a methyl group, and R 3 is hydrogen, and z is 3.) Hydrophobized silica: average particle size 40 nm, manufactured by Evonik Japan Co., Ltd. FB-5D: Fused silica, average particle size 5 μm, manufactured by Denka Co., Ltd. Aerosil 380: Hydrophilic fumed silica, average particle size 7 nm, manufactured by Evonik Japan Co., Ltd. (inorganic thixotropic agent) Esben WX: Organic bentonite with quaternary ammonium cations modified on the crystal surface of montmorillonite, manufactured by Hojun Co., Ltd. (Polymerization initiator) Kayakumen H: Cumene hydroperoxide, manufactured by Kayaku Nouryon Co., Ltd. (Decomposition accelerator) Co-12E: Cobalt octylate, manufactured by Tokyo Fine Chemical Co., Ltd. (Silane coupling agent) SILQUEST A-174: γ-Methacryloxypropyltrimethoxysilane, manufactured by Momentive Performance Materials Japan, LLC (curing accelerator) PT-2HE: N,N-di(2-hydroxyethyl)-p-toluidine, manufactured by Morin Chemical Industry Co., Ltd. (alumina cement) Alumina cement No. 1: Alumina cement, Blaine specific surface area 4800 cm 2 / g, manufactured by Denka Co., Ltd. (Portland cement) Ordinary cement: Portland cement, manufactured by Denka Co., Ltd. (pozzolanic substances) Blast furnace slag: Granulated blast furnace slag, commercially available, Blaine specific surface area 6100 cm 2 / g Silica fume, commercially available (others) Gypsum: commercially available Slaked lime, commercially available Silica sand, commercially available

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] [Table 4]

[0103] [Table 5]

[0104] The corrosion-protective coating materials of Examples 1 to 5, which contained (meth)acrylate monomers and hydrophobic silica with an average particle size of 1 to 100 nm, exhibited good coatability. On the other hand, the corrosion-protective coating material of Comparative Example 1, in which the silica was not hydrophobized and the average particle size of the silica was greater than 100 nm, could not be applied thickly. The corrosion-protective coating material of Comparative Example 2, in which the silica was not hydrophobized, failed to uniformly disperse the silica, resulting in unevenness. Furthermore, the corrosion-protective coating material of Comparative Example 3, which did not contain hydrophobic silica, exhibited dripping and could not be applied thickly. The corrosion-protective coating material of Comparative Example 4, in which organic bentonite, a type of inorganic thixotropic agent, was blended in place of hydrophobic silica, exhibited little effect in increasing viscosity and imparting thixotropy, resulting in dripping and making it impossible to apply the corrosion-protective coating material thick. The primer compositions of Examples 6 to 11 could be applied to a thickness of 100 μm without dripping.

[0105] The corrosion-resistant coating layers of Examples 6 to 11, which included a surface conditioning layer made of a hardened product of an alumina cement composition containing alumina cement, a pozzolanic substance, and an aggregate, and a corrosion-resistant coating layer made of a hardened product of the corrosion-resistant coating material of the present invention on the surface conditioning layer, were found to have excellent sulfuric acid resistance. Furthermore, since the tensile bond strength (tensile adhesive strength) was also high in addition to excellent sulfuric acid resistance, the corrosion-resistant coating layers of Examples 6 to 11 were found to have excellent durability. Furthermore, a comparison of the corrosion-resistant coating layer of Example 6 with the corrosion-resistant coating layer of Example 10 revealed that the provision of a primer improved sulfuric acid resistance, thereby further improving durability. Furthermore, compared with the corrosion-resistant coating layer of Example 7, it was found that the corrosion-resistant coating layer of the present invention can be applied as an excellent corrosion-resistant coating even in low-temperature periods. On the other hand, the corrosion-resistant coating layers of Comparative Examples 5 to 8, which did not include a corrosion-resistant coating layer made of a hardened product of the corrosion-resistant coating material of the present invention, exhibited poor sulfuric acid resistance. Furthermore, the corrosion-resistant coating layers of Comparative Examples 9 and 10, which did not include a corrosion-resistant coating layer, exhibited poor sulfuric acid resistance. Furthermore, although the anticorrosion coating layers of Comparative Examples 5 to 8 have high tensile bond strength, they are inferior in sulfuric acid resistance, and therefore it is clear that the anticorrosion coating layers of Comparative Examples 5 to 8 have poor durability.

Claims

1. (meth)acrylate monomers and hydrophobic silica, The average particle size of the hydrophobic silica is 1 to 100 nm, The hydrophobic silica is at least one of silica hydrophobized with an organosilane represented by the following general formula (1) and silica hydrophobized with an organosilane represented by the following general formula (2), When the hydrophobic silica is silica hydrophobized with an organosilane represented by the following general formula (1), the hydrophobic silica includes silica hydrophobized with a first organosilane represented by the general formula (1) and silica hydrophobized with a second organosilane represented by the general formula (1) that is different from the first organosilane, In the general formula (1), R of the first organosilane １ is an alkyl group represented by the following general formula (3), and R of the second organosilane １ is an alkyl group represented by the following general formula (4). R １ ｘ SiCS ｙ H ４－ｘ－ｙ (1) In general formula (1), R １ represents an alkyl group, x represents an integer of 1 to 3, y represents an integer of 0 to 3, and x+y≦4. (R) ２ ｚ H ３－ｚ Yes) ２ NR ３ (2) In general formula (2), R ２ represents hydrogen, an alkyl group, an alkenyl group, or a halogenated alkyl group; R ３ represents hydrogen, an alkyl group or an alkali metal element; z represents an integer of 1 to 3; C ｓ H ２ｓ＋１ (3) In the general formula (3), s represents an integer of 1 to 5. C ｔ H ２ｔ＋１ (4) In the general formula (4), t represents an integer of 6 to 12.

2. The corrosion-protective coating material according to claim 1 , wherein the (meth)acrylate monomer comprises a di(meth)acrylate having a bisphenol A skeleton.

3. 3. The corrosion-protective coating material according to claim 2, wherein the di(meth)acrylate monomer having a bisphenol A skeleton is a di(meth)acrylate having a bisphenol A skeleton represented by the following general formula (5): 【Chemical 1】 In general formula (5), R ４ and R ４ ' represents hydrogen or a methyl group, and R ５ and R ５ "'" represents an alkylene group which may have a substituent, and m and n represent integers of 1 to 20.

4. 4. The corrosion-protective coating material according to claim 1, which is a two-component type comprising: a first corrosion-protective coating material containing a polymerization initiator, the (meth)acrylate monomer, and the hydrophobic silica; and a second corrosion-protective coating material containing a decomposition accelerator that accelerates decomposition of the polymerization initiator, the (meth)acrylate monomer, and the hydrophobic silica.

5. The viscosity at 25°C is 1700 to 15000 mPa s, The corrosion-protective coating material according to any one of claims 1 to 4, which has a thixotropy index at 25°C of 3.0 or more.

6. The viscosity in the range of 0 to 25°C is 1700 to 15000 mPa s, The corrosion-protective coating material according to any one of claims 1 to 5, which has a thixotropy index in the range of 0 to 25°C of 3.0 or more.

7. A corrosion-resistant coating layer comprising: a surface adjustment layer made of a hardened body of an alumina cement composition containing alumina cement, a pozzolanic substance, and an aggregate; and a corrosion-resistant coating layer made of a hardened body of the corrosion-resistant coating material according to any one of claims 1 to 6 on the surface adjustment layer.

8. The process of assembling the formwork, A step of casting an alumina cement composition containing alumina cement, a pozzolanic substance, and an aggregate into the formwork to form a base adjustment layer; removing the formwork; and A corrosion prevention method for a concrete structure, comprising the step of applying the corrosion-preventive coating material according to any one of claims 1 to 6 to form a corrosion-preventive coating layer on the surface adjustment layer.

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