JPH11343184A - Prevention deterioration of wet concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a structural body by forming a specified amt. of a base coating film comprising specified proportions of epoxy resin and cement on the surface and forming a coating film of a copolymer containing alkyl(meth)acrylate units satisfying specified conditions. SOLUTION: A coating film as a base coating film containing 1 to 50 wt.% epoxy resin (bis-phenol A or the like) and 5 to 99 wt.% cement ((Portland cement or the like) and having >=40 wt.% total amt. of these based on the total solid content is applied on the surface of a wet concrete structure. Then, a coating film of a copolymer compsn. having 30 to 98 wt.% acryl (meth) acrylate unit [n-butyl(meth)acrylate or the like] having 4 to 10 carbon atoms in its alkyl group is formed on the base coating film. The upper coating film shows 50 to 2000% elongation at 20 deg.C, 10<-2> to 10<-4> mg/cm<2> .day shielding property against a salt, >=5 g/m<2> day water vapor permeability, and 100 to 5000 μm film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing deterioration of a concrete structure, and can be awarded in technical fields such as civil engineering and construction.

[0002]

2. Description of the Related Art In general, concrete structures have a pH of 12 due to the presence of calcium hydroxide, which is a hydrate of cement.
For example, in the case of a reinforced concrete structure, corrosion is suppressed by forming a passivation film on the surface of the reinforcing steel inside the concrete in order to exhibit strong alkalinity of ~ 13. However, when carbon dioxide gas enters the concrete, it reacts with calcium hydroxide, a hydrate, to produce calcium carbonate, which promotes neutralization of the concrete and chloride ions penetrate the surface of the reinforcing steel. In such a case, the passive film covering the surface of the reinforcing bar is broken, and the reinforcing bar is corroded. As the corrosion of reinforcing steel progresses, the volume expansion is about 2.5 times that before corrosion, so cracks occur in the concrete and the strength of the concrete decreases with the progress of rust. There is a problem that it is not possible to maintain the durable strength of the damaged structure. When aggregate causing an alkali-aggregate reaction is mixed in the concrete, cracks occur in the concrete due to the progress of the alkali-aggregate reaction, and the same trouble as described above occurs.

[0003] When such salt damage, neutralization, and alkali-aggregate reaction of a concrete structure occur or are concerned, repairs have conventionally been generally performed by so-called environmental isolation. That is, this is a method in which a coating film is formed on the surface of a concrete structure with a paint, a waterproof material, a polymer cement mortar, or the like, to block carbon dioxide, salt, oxygen, moisture, and the like. In this case, an acrylic resin, an epoxy resin, and a urethane resin-based paint were generally used as the paint.

[0004]

However, in the conventional method of forming a coating film such as a paint, a waterproof material and a polymer cement mortar, when the surface of the concrete structure is wet, sufficient adhesion is obtained. Therefore, it is necessary to sufficiently dry the surface of the concrete structure before coating. If the surface of the concrete structure is not sufficiently dried, blistering and peeling of the coating film have occurred. Also, even if the concrete structure surface is sufficiently dried to form a coating film, the coating film formed from the paint, the waterproofing material, and the polymer cement mortar lacks flexibility, and the concrete structure has cracks. When this occurred, the coating film could not follow this and was broken, or the coating film was blistered, peeled or peeled off due to poor water-resistant adhesiveness. Further, the coating film formed by the conventional method has a drawback that the inside of the concrete structure cannot be brought into a dry state due to poor water vapor permeability and induces an alkali-aggregate reaction, salt damage and blistering.

[0005] The present inventors have solved the above-mentioned problems, blocked the intrusion of deterioration factors into concrete structures, prevented salt damage and neutralization, and quickly removed water remaining inside the concrete structures. Releases to prevent alkali-aggregate reaction, has excellent ability to follow cracks in concrete structures, retains these properties for a long time, and adheres to the surface of concrete structures even under wet conditions They worked diligently to find a construction method with excellent properties.

[0006]

Means for Solving the Problems The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, formed on a wet concrete surface from a specific composition and having specific physical properties. The present inventors have found that a construction method for forming a layer coating film is effective and completed the present invention. Hereinafter, the present invention will be described in detail. In this specification, acrylate or methacrylate is referred to as (meth) acrylate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

-Undercoat material coating (1) In the present invention, in the undercoat material coating (1) formed on the surface of the wet concrete structure, the composition for forming the same (hereinafter referred to as composition (1)) is: It is a composition comprising an epoxy resin and cement, and is a kind of so-called polymer cement mortar. Hereinafter, each component will be described.

Epoxy resins Various epoxy resins can be used, for example, epoxy resins obtained by reacting bisphenol A or its alkylene oxide adduct with epichlorohydrin, hydrogenated bisphenol A or its alkylene oxide adduct and epichlorohydrin And a phenol novolak type epoxy resin and a cresol novolak type epoxy resin. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide. In addition, from page 372 of "Basic Synthetic Resin Chemistry (New Edition)" (Tadahiro Miwa, published by Gihodo)
Glycidyl-type epoxy resins as described on page 379 and non-glycidyl-type epoxy resins as described on pages 388 to 391 of the same book. Among these epoxy resins, a glycidyl type epoxy resin is preferable, and a liquid glycidyl type epoxy resin is more preferable. These epoxy resins are commercially available, and include, for example, Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd. The epoxy resin is preferably in the form of an emulsion. In this case, as a surfactant for dispersing the epoxy resin in water, it is preferable to use an anionic or / and nonionic surfactant having excellent stability. Examples of the nonionic surfactant include a polyethylene glycol type surfactant, and examples of the anionic surfactant include an alkali metal salt of a sulfate or a phosphate thereof. Examples of the polyethylene glycol type surfactant include those obtained by adding ethylene oxide to a compound having active hydrogen such as higher alcohol, polyhydric alcohol, oil and fat, higher fatty acid, alkylphenol and amine. Preferred surfactants include alkylphenols, or fats and oils,
Particularly, it is an ethylene oxide adduct of castor oil. The surfactants can be used alone or in combination of two or more. The amount of the surfactant used is usually preferably 1 to 15% by weight based on the solid content of the resin in the emulsion. The proportion of epoxy resin in composition (1) must be between 1 and 50% by weight, based on the total solids. Outside this range, the ability of the coating film to follow the base cracks and to adhere to wet surfaces decreases.

Cement Cement is blended with the undercoat coating film (1) for the purpose of improving toughness, water resistance, adhesion to a wet surface, and dry film formation. As the cement, a cement used in ordinary polymer cement can be used, and examples thereof include ordinary portland cement, alumina cement, and mixed portland cement such as blast furnace cement, silica cement, and fly ash cement.
Two or more cements can be used in combination. The proportion of these cements in the composition (1) needs to be from 5 to 99% by weight, preferably from 5 to 90% by weight, based on the total solids. When the amount is less than 5% by weight, the toughness of the coating film is reduced, and when it exceeds 99% by weight, the water-resistant adhesiveness with the waterproof material is reduced. Further, the total amount of the epoxy resin and the cement in the composition (1) must be 40% by weight or more based on the total solid content.
% By weight or more is preferred. If this value is less than 40% by weight, the undercoating material is difficult to dry and the adhesive strength is reduced.

Other Compounds In the composition (1) used in the present invention, in addition to the above essential components, if necessary, mono- or polyamidoamine compounds,
A higher fatty acid or a salt thereof, and an auxiliary agent such as an aggregate and a waterproofing agent can also be added.

[0011] The mono- or polyamidoamine compound is compounded to improve the strength of the coating film. Mono- or polyamidoamine compounds are compounds having two or more active hydrogen atoms in the molecule that react with the epoxy resin,
It is usually obtained by reacting an acid component such as a polymerized fatty acid and / or a fatty acid with a polyamine in excess of an amine to produce the polyamine. As the polymerized fatty acid, for example, an unsaturated fatty acid having 18 carbon atoms such as oleic acid or linoleic acid, a drying oil fatty acid,
Semi-dry oil fatty acids and those obtained by bimolecular polymerization of lower monoalcohol esters of these fatty acids are exemplified. As fatty acids, for example, stearic acid, saturated fatty acids such as 2-ethylhexane, unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid, soybean oil fatty acids, natural oils such as tall oil fatty acids and cottonseed oil fatty acids are treated. Examples of the obtained fatty acid include a hydroxyl group-containing fatty acid of castor oil fatty acid or diphenolic acid, and a fatty acid obtained by treating a natural oil or fat containing a fatty acid having 12 to 24 carbon atoms. As the polyamine, for example, ethylenediamine,
Examples include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, xylylenediamine, and metaphenylenediamine. These contents are preferably 0.5 to 70% by weight, more preferably 1 to 30% by weight, based on the epoxy resin in the composition (1).

The higher fatty acid or a salt thereof is blended to help the epoxy resin emulsion penetrate into the substrate. Specific examples of higher fatty acids include lauric acid,
Examples thereof include saturated or unsaturated fatty acids having 10 to 30 carbon atoms, such as oleic acid and stearyl acid. Examples of the salts of higher fatty acids include alkali metal salts such as sodium salts and potassium salts of these higher fatty acids, ammonium salts, and salts of amines such as lower amines and alkanolamines. These contents are preferably 0.01 to 20% by weight in the composition (1).

[0013] Examples of the auxiliary include an aggregate and a waterproofing agent. Examples of the aggregate include river sand, sea sand, silica sand, calcium carbonate, talc, bentonite, iron oxide, fly ash, alumina blast furnace water, and pigment. These are preferably blended in the composition (1) at a ratio of 300% by weight or less. Examples of the waterproofing agent include silicates such as sodium silicate and potassium silicate, SBR, NBR, E
Examples include non-reactive resin emulsions such as VA and chloroprene rubber, and water-soluble resins such as CMC and polyvinyl alcohol. These are 3 in the composition (1)
It can be blended at a ratio of 0% by weight or less.

Coating (2) In the method of the present invention, 30 to 98% by weight of an alkyl (meth) acrylate unit having an alkyl group having 4 to 10 carbon atoms is added to the surface of the undercoating material coating (1). Is a coating film formed from a composition (hereinafter referred to as composition (2)) composed of a copolymer having an elongation percentage at 20 ° C of 50 to 50%.
2000%, salt barrier 10 ^-2 to 10 ^-4 mg / cm ² · day,
Water vapor permeability of 5 g / m ² · day or more and film thickness of 100 to 50
A coating having a thickness of 00 μm is formed.

Specific examples of the alkyl (meth) acrylate having 4 to 10 carbon atoms in the alkyl group include n-butyl (meth) acrylate, iso-butyl (meth) acrylate, sec-butyl (meth) acrylate, and n-butyl (meth) acrylate. −
Amyl (meth) acrylate, iso-amyl (meth) acrylate, n-hexyl (meth) acrylate, n-hexyl (meth) acrylate, n-pentyl (meth) acrylate, oxoheptyl (meth) acrylate, n-octyl ( Examples thereof include (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, oxononyl (meth) acrylate, n-decyl (meth) acrylate, and oxodetal (meth) acrylate. An alkyl (meth) acrylate in which the alkyl group has less than 4 carbon atoms is
It is not preferable from the viewpoint of alkali resistance. On the other hand, when the number of carbon atoms exceeds 10, the cold resistance decreases. The proportion in the above-mentioned monomer needs to be 30 to 98% by weight, preferably 50 to 90% by weight. If this ratio is less than 30% by weight, the ability of the coating film to follow the cracks on the underlayer, the water resistance and the alkali resistance are reduced. On the other hand, when this ratio exceeds 98% by weight, a coating film having sufficient strength may not be obtained. The polymer in the present invention, in addition to the (meth) acrylate,
In addition, copolymers of other monomers may be used. Other monomers include styrene, acrylonitrile, (meth) acrylic acid, glycidyl (meth) acrylate, N
-Methylol acrylamide and alkyl (meth) acrylates having 1 to 3 carbon atoms. In addition, coating film (2)
Vinylidene chloride may be used as a constituent monomer in order to impart flame retardancy to the rubber.

The form of the polymer is excellent in safety, the resulting coating film is free from stickiness, and has good water resistance, chemical resistance, ultraviolet light resistance and ozone resistance. Emulsions are preferred. The proportion of the polymer in the emulsion is preferably 30 to 70% by weight.

A filler may be added to the composition (2) in order to make the resulting coating film tough, reduce the tackiness of the coating film surface, and improve the workability. The amount of the filler is preferably 30 to 300 parts by weight, more preferably about 50 to 150 parts by weight, based on 100 parts by weight of the polymer. If the amount of the filler exceeds 300 parts by weight, the adhesiveness, elongation and waterproof function of the coating film may be impaired. Specific examples of the filler include silica sand, talc, calcium carbonate, kaolin, gypsum, diatomaceous earth, titanium oxide, and various portland cements, blast furnace cements, cements such as alumina cements, and the like. it can. When compounding cement as a filler, the compounding amount is preferably up to about 50 parts by weight based on 100 parts by weight of the polymer. If necessary, up to about 5 parts by weight of a surfactant, a viscosity stabilizer, an antifoaming agent and the like can be added to 100 parts by weight of the polymer.

In order to impart flame retardancy to the coating film, a polymer of vinylidene chloride or / and a copolymer of vinylidene chloride or a compound having a triazine ring may be compounded.

The coating film (2) of the present invention has an elongation at 20 ° C. of 50 to 2000% and a salt barrier property of 10 ⁻² to 10 ⁻⁴ mg / c.
m ² · day, water vapor permeability 5 g / m ² · day or more, and film thickness 1
It is necessary that the thickness be 00 to 5000 μm.

When the elongation at 20 ° C. is less than 50%, it cannot follow cracks in concrete, cannot block water, oxygen, carbon dioxide and flying salt, and has a 2,000% reduction. If it exceeds, the coating becomes weak against abrasion and impact, and the durability of the coating film becomes insufficient. When the salt barrier property exceeds 10 ^-2 mg / cm ² · day, the barrier effect against flying salt becomes insufficient, lacks a long-term rust preventive effect, and when it is less than 10 ^-4 mg / cm ² · day. Other effects will be reduced. If the water vapor permeability is less than 5 g / m ² · day, it is difficult to release the water inside the concrete, so that the inside of the concrete cannot be dried, causing an alkali-aggregate reaction and salt damage, or coating with water. The membrane may swell. When the formed film thickness is less than 100 μm, it lacks the ability to follow concrete cracks and has poor environmental barrier properties. When the formed film thickness exceeds 5000 μm, the water vapor permeability decreases and the inside of the concrete becomes dry. Can not be
Alkali-aggregate reaction and salt damage are induced, and the coating film is easily swelled.

Coating material coating film (3) In the method of the present invention, if necessary, the purpose of improving the aesthetic appearance, the coating film (1) and the coating film (2) may be formed on the coating film (2). For the purpose of protecting the coating, a coating film of an overcoating material (3) can be formed. As the top coat (3), 20
The elongation at 50 ° C. is 50 to 500%, and the film thickness is 50 to 300.
A coating film having a thickness of μm is preferred. When the elongation at 20 ° C. of the overcoat material coating film (3) is less than 50%, the crack followability of the coating film (1) is reduced or the coating film (1)
In some cases, the coating film (3) itself may be broken without being able to follow the flexibility of the composition, and the opacity may be poor, which may be undesirable in appearance. On the other hand, if it exceeds 500%, it becomes susceptible to external contamination, which may be undesirable from the viewpoint of aesthetics. Further, since the water inside the concrete is hardly released, the inside of the concrete cannot be dried, and the alkali-aggregate reaction can be prevented. In addition, salt damage may be induced, and the coating film may be easily swollen. Various coating materials can be used as the coating material composition for forming the coating film (3), such as acrylic resin paint, acrylic urethane paint, acrylic silicone paint, fluororesin paint and epoxy resin paint. No.

The construction method The deterioration prevention method of the present invention comprises forming the undercoat material coating film (1) on the surface of a wet concrete structure and forming the coating film (2) on the surface of the coating film. . Specifically, the composition (1) and the composition (2) may be applied according to a conventional method. The composition may be applied in a usual manner, for example, by applying with a trowel, brush or roller, or by spraying with a machine such as a ricin gun or a spray gun. In particular, when applying the composition (2), it is necessary to consider the film thickness in order to impart excellent crack followability. Although the viscosity of the composition (2) varies depending on the application method, it is preferably 300 cps or more (B-type viscometer, 12 rotations, rotor No. 4, 20 ° C.) because of excellent workability, and more preferably 1 cps.
000 to 50,000 cps. 300c viscosity
When it is smaller than ps, it is difficult to apply a thick coating at a time, and when the viscosity is high, there is an advantage that the coating can be applied thickly, but there may be a difficulty in the construction.

The method of the present invention is applicable to various concrete structures in civil engineering and construction. In the present invention, the concrete structure means concrete and mortar. Further, the method of the present invention can be applied to concrete structures which have already been deteriorated or are likely to be deteriorated due to salt damage or alkali-aggregate reaction, and furthermore, those concrete surfaces are subjected to wet conditions. In some cases, it is most effective. Examples of concrete structures under wet surface conditions include piers, abutments, floor slabs, piers, dolphins, box culverts, headraces, water tanks, underground pits, walls, roofs, and the like.

[0024]

According to the method of the present invention, since the adhesion of the undercoat material coating film to the wet concrete structure surface is excellent, no blistering or peeling occurs. In addition, coating film (2)
Is a coating film having excellent crack followability, so that even if cracks occur in concrete, it is possible to follow the cracks, thereby preventing deterioration factors from invading for a long time.
In addition, since the coating film (2) is a coating film having excellent water vapor permeability, the inside of the concrete is brought into a dry state. Further, since the coating has excellent salt barrier properties, alkali-aggregate reaction, salt damage and blistering are generated. To prevent

[0025]

The present invention will be specifically described below with reference to examples and comparative examples. The “parts” and “%” shown below are
All are based on weight. Production Example 1 [Production of a composition for undercoating material] In 60 parts of a bisphenol-type epoxy resin having an epoxy equivalent of about 190, 5 parts of a nonionic surfactant nonylphenol 40 mol of ethylenoxide added at about 60 ° C. The mixture was stirred with a homomixer, and 35 parts of water was gradually added thereto to cause phase inversion, thereby obtaining 100 parts of an epoxy resin emulsion (epoxy resin content: 60%). The obtained epoxy resin emulsion and the following components were put into a mixing tank and stirred for about 5 minutes to obtain a polymer cement mortar (ratio to solid content of composition: epoxy resin 12.8).
%, Cement 85%). This is referred to as undercoat material composition P-1. Epoxy resin emulsion: 100 parts Portland cement: 400 parts Water: 200 parts Monoamide polyamine (tetraethylenepe: 40 parts Manufactured from tertamine and cottonseed oil fatty acid, amine value about 380, solid content 15%) Sodium laurate: 4 Department

The compositions P-2 to P-6 for undercoat materials were produced in the same manner as described above, except that the proportions of the epoxy resin and cement alone were changed to the proportions shown in Table 1.

[0027]

[Table 1]

Production Example 2 Production of Composition (2) Using the monomers shown in Table 2, dispersing the monomers in an aqueous medium using a surfactant, followed by heating, A radical polymerization initiator was added dropwise thereto to carry out a polymerization reaction.

[0029]

[Table 2] * 1: Polyoxyethylene nonylphenyl ether * 2: Dodecylbenzenesulfonic acid * 3: Trimethylstearyl ammonium chloride

In 100 parts of the obtained polymer emulsion,
The compositions shown in Table 3 below were added and mixed with stirring to obtain a composition (2).

[0031]

[Table 3] 1) Salt barrier property: unit is × 10 ^-4 mg / cm ² · day. However, the coating film of the composition D is mg / cm ² · day 2) Water vapor permeability: The unit is g / m ² · day

Examples 1 to 5 Concrete plate (300 mm × 300 mm × 50 mm)
Was immersed in water for one week, and then, as shown in FIG. 1, two-thirds thereof were immersed in water and left for 4 hours. The undercoat material composition (1) shown in Table 4 was evenly applied to the surface of the concrete plate soaked with water using a trowel and dried to form an undercoat material coating film (1). 2.0 kg / m ^{2 of the} composition (2) shown in Table 4 was applied using a roller, and the composition was applied at 20 ° C. and 60% RH.
H. The coating was allowed to stand for 7 days to form a coating film (2).
Using the obtained test body, evaluation was performed according to the following evaluation method. Table 4 shows the results. According to the construction method of the present invention, the adhesion between the wet concrete and the coating film was excellent, the coating film had a high ability to follow cracks, and was excellent in salt barrier properties and water vapor permeability.

○ Evaluation method (1) Wet surface base adhesion test The adhesion of the test specimen was evaluated by hand peeling (peeling test), and the adhesion was measured by a Kenken-type adhesion tester, and the broken part was determined. Recorded.

(2) Crack Followability Test The evaluation was carried out in accordance with the crack followability test described in the Japan Highway Public Corporation “Maintenance and Repair Procedures, Bridge Knitting, and Standards for Paint Materials”.

(3) Salt-Shielding Property The salt-insulating property was evaluated in accordance with the salt-tightness test described in the Japan Highway Public Corporation “Maintenance and Repair Procedures, Bridge Knitting, and Standards Test for Coating Materials”.

(4) Water Vapor Permeability JIS Z0208 “Method for testing moisture permeability of moisture-proof packaging material”
Was evaluated in accordance with

[0037]

[Table 4] 1) T-1: Formed using an acrylic urethane resin solvent type paint (Aromble Coat T-310, manufactured by Toagosei Co., Ltd.). T-2: Acrylic urethane resin solvent type paint [Allomb Coat T-300, manufactured by Toagosei Co., Ltd.] 2) A: Coating failure of coating film (2)

Comparative Examples 1 to 6 Construction was performed in the same manner as in Example except that the composition for undercoat material, composition (2) and the composition for overcoat material shown in Table 5 were used. About the obtained test body, evaluation was performed like Example. Table 5 shows the results. Comparative Example 1 is a case where a coating film (2) having an elongation at 20 ° C. of less than 50% is formed as compared with Example 1, and is inferior in crack followability and salt barrier properties. Comparative Example 2 is compared with Example 1,
Coating with elongation at 2000C of more than 2000% (2)
Is formed, and it is inferior in water vapor permeability and adhesion to a wet base. In Comparative Examples 3, 4 and 5, P-4 in which the proportion of the epoxy resin and the cement is out of the range of the undercoating material composition (1) used in the present invention, as the undercoating material composition (1). This is an example using P-5 and P-6,
In each case, the adhesive strength to the wet base was small, the result of the peeling test was poor, and the adhesion was poor. Comparative Example 6
Is a case where a coating film having a thickness of the coating film (2) less than 100 μ is formed as compared with Example 1, and is inferior in crack followability and salt barrier property.

[0039]

[Table 5] 1) Formed using an acrylic urethane resin solvent type paint (Aromble Coat T-310, manufactured by Toagosei Co., Ltd.). 2) Unit: kgf / cm ² 3) A: Coating failure of coating (2), B: Coating (1) / coating (2) interface failure of undercoating material 4) Unit: × 10 ^-4 mg / cm ² · day 5) Unit is g / m ² · day 6) *: With span

[0040]

According to the method of the present invention, since the adhesion of the primer coating film to the wet concrete surface is excellent, no blistering or peeling occurs, and the coating film (2) is formed. Because it is a coating film with excellent crack followability, it can follow even if cracks occur in concrete,
Prevents the invasion of deterioration factors for a long period of time, and the coating film with excellent water vapor permeability leads the inside of the concrete to a dry state, and also has excellent salt barrier properties, so that alkali-aggregate reaction, salt damage And prevent the occurrence of blisters.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram in which concrete boards used in each of Examples and Comparative Examples are submerged for one week, and then two-thirds are soaked in water.

[Explanation of symbols]

 1: Concrete board 2: Water

Claims (1)

[Claims] A concrete structure characterized by forming the following coating film (1) as a primer coating film on the surface of a wet concrete structure, and forming the following coating film (2) on the coating film surface. Method to prevent deterioration of objects. (1) A coating formed from a composition containing 1 to 50% by weight of an epoxy resin and 5 to 99% by weight of a cement based on the total solid content and having a total amount of 40% by weight or more. film. (2) a coating film formed from a composition comprising a copolymer having an alkyl (meth) acrylate unit having an alkyl group having 4 to 10 carbon atoms in a content of 30 to 98% by weight; Elongation at 50 to 2000%, salt barrier 10 ^-2 to 10 ^-4 mg / cm ² · day, water vapor permeability 5 g
/ M ² · day or more and a film thickness of 100 to 5000 μm.