JP2000063757A - Water-based water-repellent paint and surface-finishing method for exposed concrete using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based water-repellent paint that gives a coating layer having excellent resistance to alkali, water and weather and is suitably useful for surface finishing of fair-faced concrete by using a water-based silicone resin or the like, silica powder, and fluorine resin powder. SOLUTION: The objective painting material includes (A) a water-based silicone resin and/or a water-based fluorine resin such as polysiloxane complex water-based emulsion or the like that has the core part of a cross-linked polymer and the shell part that cover the core part with a non-crosslinking polymer, and has polysiloxane close to the shell surface, (B) a silica powder, preferably in an amount of 5-20 pts.wt. (based on 100 pts.wt. of the solid part of the component A) and (C) a fluorine resin powder, preferably in an amount of 5-30 pts.wt. The weight ratio of the component B to the component C is 2/1-1/4. In addition, the water-based water-repellent paint preferably contains a fungicide and an algaecide and the fair-faced concrete coated with this paint preferably gives a unique feeling and high finishing quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exposed concrete.
The present invention relates to a water-based waterproof coating material capable of imparting a high finish texture to the surface of a sheet and a surface finishing method for an exposed concrete using the same.

[0002]

BACKGROUND OF THE INVENTION Exposed concrete is widely used as an outer wall material that takes advantage of the texture of the material, and its surface is usually a water repellent material or a solvent to prevent water from entering. Mold clear has been applied. This is because when the material surface is left as it is, moisture in the air causes the concrete to neutralize and the durability to decline, and mold and algae to be generated and adhere to the aesthetics to impair the aesthetic appearance and be brought from the outside. This is because if chloride penetrates into the internal reinforcing bars and corrosion progresses, the structure itself may collapse.

When conventional water-repellent materials and solvent-type clears are used individually, the water-repellent materials alone have poor sustainability of water-repellent protection, and solvent-type clears alone have a protective property but are concrete. The surface of the coating became wet and the texture of the material was impaired, and there were problems with organic solvent odor during the coating work and safety and hygiene.

In order to solve these problems, for example, Japanese Patent Publication No.
-89589, JP-A-5-124880, JP-A-9
In Japanese Patent No. 173969 and the like, a method of applying various types of water-repellent materials and solvent-type clears has been proposed, and the effect of preventing wet color is recognized. However, Tokuhei 6
In the method of No. 89895, there are many coating steps in three-layer finishing, and since a solvent type clear is used for finishing, there are problems with organic solvent odor and safety and hygiene. In addition, JP-A-5-1248
No. 80 and JP-A-9-173969, water repellency
Water resistance was still insufficient.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an aqueous silicone resin and / or an aqueous fluororesin prepared by blending a specific fine powder The present inventors have found that the clearer can not only prevent the deterioration of the concrete as a finish for the surface of the exposed concrete but also impart a unique texture and a high finished texture to the present invention.

That is, the present invention is characterized by containing (A) an aqueous silicone resin and / or an aqueous fluorine resin, (B) silica powder, and (C) a fluorine resin powder. The present invention provides a surface finish construction method for an exposed concrete, which comprises applying an undercoat material on the surface of a coating material and an exposed concrete, drying and then applying the above-mentioned water-based waterproof coating material.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The water-based silicone resin and / or water-based fluororesin (A) used in the present invention is
It is a component for forming a waterproof film, and conventionally known emulsions for waterproof paints can be used without particular limitation. Both are independent,
Alternatively, they can be used in combination. It is desirable that the aqueous silicone resin and / or the aqueous fluorine resin have excellent transparency.

As the aqueous silicone resin, for example, a polysiloxane comprising an alkoxysilane compound, an organosiloxane compound or a condensate thereof is dispersed, emulsified or dissolved in an aqueous medium, and an alkoxysilyl group-containing vinyl monomer is required. A copolymer emulsion formed by copolymerization with another vinyl monomer, an emulsion formed by complexing an organic polymer with polysiloxane, and the like are listed as specific commercial products, for example, "Polydurex" ( Asahi Kasei), "Kanebinol" (Nippon NSC), "Sanmor" (Sanyo Kasei),
Examples thereof include "KP3000S" (manufactured by JS-Al Corporation), "Zemlac" (manufactured by Kaneka Corporation).

As the above-mentioned aqueous silicone resin, from the viewpoints of film-forming property, compactness, durability, etc. of the coating film, a core part which is a cross-linked polymer and a shell part which is a non-cross-linked polymer covering the core part are provided. And a polysiloxane composite aqueous emulsion having a polysiloxane near the surface of the shell can be preferably used.

The polysiloxane composite aqueous emulsion is a polymer emulsion having polysiloxane in the vicinity of the particle surface and having an average particle size of 50 to 1000 nm. The polymer particles are emulsion polymerized in a first stage by emulsion polymerization of a monomer mixture containing 0.01 to 5% by weight of a crosslinkable monomer such as divinylbenzene, allyl methacrylate and polyvalent acrylate. As a second step in the presence of coalesced particles, a monomer mixture not containing the crosslinkable monomer is emulsion polymerized to obtain polymer particles (seed particles), and an alkoxysilane compound and / or a low molecular weight compound is obtained. It is obtained by adding the organosiloxane compound (1) and subjecting it to a condensation reaction.

Examples of the polymerizable monomer other than the crosslinkable monomer used in the first and second stages of polymerization include aromatic monovinyl compounds such as styrene and ethylvinylbenzene; methyl (meth) acrylate and ethyl. (Meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth)
Acrylate, 2-hydroxy (meth) acrylate,
(Meth) acrylic acid ester monomers such as glycidyl (meth) acrylate and N, N-dimethylaminoethyl (meth) acrylate; unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and maleic anhydride ; (Meta)
Acrylonitrile, diacetone acrylamide, diacetone methacrylamide, (meth) acrylamide,
Examples thereof include vinyltrimethoxysilane, γ- (meth) acryloyloxypropyltrimethoxysilane, and macromonomers thereof, and these may be used alone or in combination of two or more.

It is suitable that the weight ratio of the first-stage polymer to the second-stage polymer of the seed particles is within the range of 70/30 to 30/70. The glass transition temperature of the whole seed particle polymer is −
The range of 20 to 80 ° C is suitable.

Examples of the alkoxysilane compound and the low molecular weight organosiloxane compound include tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane and γ.
-Alkoxysilane compounds such as glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and dimethyldimethoxysilane, "MKC silicate MS-51" (manufactured by Mitsubishi Chemical Corporation), "ethyl silicate 48" (Tama (Manufactured by Kagaku Co., Ltd.) and the like, and the like can be used alone or in combination of two or more.

The amount of the above-mentioned alkoxysilane compound and organosiloxane compound added is 0.1 to 200 parts by weight, preferably 10 to 80 parts by weight, relative to 100 parts by weight of the seed particles.
A range of parts by weight is suitable.

The alkoxysilane compound and the organosiloxane compound are absorbed in the seed particles by adding the alkoxysilane compound and the organosiloxane compound little by little or at once to the aqueous dispersion in which the seed particles are dispersed. And stir well. It is desirable that the pH of the aqueous dispersion is adjusted to 4 to 10, preferably 6 to 8, and the temperature is 90 ° C or lower, preferably 50 ° C or lower so that the condensation of the alkoxysilane compound and the organosiloxane compound does not proceed before the absorption. The condensation reaction after absorption is controlled by the reaction temperature and pH to control the degree of polymerization of the obtained polysiloxane.

Examples of the above-mentioned aqueous fluororesins include fluoroolefins such as tetrafluoroethylene and trifluorochloroethylene, vinyl fluoride, vinylidene fluoride, hexafluoroisobutylene, perfluoro (meth) acrylic acid or alkyl esters thereof. Fluorine-containing monomers such as fluoroalkyl ester of (meth) acrylic acid, perfluorovinyl ether, and perfluoroalkyl vinyl ether, and cyclohexyl vinyl ether.
Examples thereof include those obtained by dissolving, dispersing, and emulsifying a copolymer with a ter, an alkyl vinyl ether, a hydroxyalkyl vinyl ether, an aliphatic carboxylic acid vinyl ester, a hydroxyalkyl vinyl ester and the like in an aqueous medium. Commercially available products of the aqueous fluororesin include, for example, "Cefural Coat" (manufactured by Central Glass Co., Ltd.), "Zeffle" (manufactured by Daikin Industries, Ltd.), "Fluoronet" (manufactured by Dainippon Ink and Chemicals Co., Ltd.), Lumiflon "(manufactured by Asahi Glass Co., Ltd.) can be used.

Silica powder (B) used in the present invention
Contributes to improving the matte feeling of the coated surface, and particles having a particle diameter of 1.0 to 20 μm can be usually used. Examples of the silica powder include "Sylysia" (manufactured by Fuji Silysia Chemical Ltd.), "Carplex" (manufactured by Shionogi Pharmaceutical Co., Ltd.), "Silica Flower" (manufactured by Masumi Milling Co., Ltd.), "Aerosil" (Nippon Aerosil Co., Ltd.) Commercially available products such as "made by" and "Flatting Agent" (made by Degussa) can be used.

The content of the silica powder (B) is 5 to 20 parts by weight, preferably 7 to 15 parts by weight, based on 100 parts by weight of the solid content of the component (A). When the content is less than 5 parts by weight, the matte feeling of the coated surface obtained is insufficient, while when it exceeds 20 parts by weight, the alkali resistance and water resistance of the obtained coating film are deteriorated, which is not preferable.
The silica powder can be added to the coating material by water-dispersing it with a dispersing machine such as a sand mill using a dispersing resin such as a water-soluble resin or a surfactant.

The fluorine-based resin powder (C) used in the present invention is used as a luster modifier to improve the texture of the concrete surface and is usually 1.0 to 10 μm.
Those having a particle size of m can be used. As the fluororesin powder, commercially available products such as "Shamrock" (manufactured by Shamrock Technology) and "Hostaflon" (manufactured by Hoechst Japan) can be used.

The content of the fluororesin powder (C) is 5 to 100 parts by weight of the solid content of the component (A).
30 parts by weight, preferably 7 to 20 parts by weight are suitable.
When the content is less than 5 parts by weight, the appropriate texture (slick feeling) and the matte feeling are not sufficiently exhibited, while when it exceeds 30 parts by weight, the first layer and the second layer are applied when the coating material is applied twice. It is not preferable because the adhesiveness of the layers decreases. The fluororesin powder is added to the coating material by water-dispersing it with a disperser such as a sand mill using a dispersion resin such as a water-soluble resin or a surfactant to remove coarse particles and then adding it to the coating material. It can be done by doing.

In the present invention, the silica powder (B) and the fluororesin powder (C) are used in a weight ratio of 2: 1 to 1: 4, preferably 1: 1 to 1: 2. preferable. When the amount of silica powder is less than the weight ratio, the matte feeling is insufficiently expressed, while on the other hand, the fluorine-based resin powder is used in the weight ratio.
A small amount is not preferable because not only the texture (slick feeling) and matte feeling are insufficient, but also the alkali resistance, water resistance and weather resistance of the coating film deteriorate.

The water-based waterproof coating material of the present invention comprises the above (A),
An aqueous clear containing components (B) and (C),
Further, it may contain a fungicide and / or an algaeproofing agent, if necessary.

As the antifungal agent and / or antialgal agent, any conventionally known one can be used without particular limitation as long as it does not impair the transparency of the coating material, for example, 3- (3,4-dichlorophenyl) -1. , 1-Dimethylurea (commonly known as diuron or DCMU), 3- (3,4-dichlorophenyl) -1
-Methyloxy-1-methylurea (commonly called linuro
n) and other dichlorophenylurea compounds; 2-methylthio-4-t-butylamino-6-cyclopropylamino-1,3,5-triazine and other triazine-thio compounds; 2- (4-thiazolyl) -benzimidazo- (Commonly known as thiabenzol), 2-methoxycarbonylaminobenzimidazole, and the like, and examples of commercially available products include "Biocut" (manufactured by Dainippon Ink and Chemicals, Inc.),
"Moniside" (manufactured by Takeda Pharmaceutical Co., Ltd.), "Prevent-
("Made by Bayer Japan"), and these may be used alone or in combination of two or more.

The content of the antifungal agent and / or the algae preventive agent is 0. 0 based on 100 parts by weight of the solid content of the component (A).
5 to 5 parts by weight, preferably 1 to 2 parts by weight are suitable.
These can be dispersed in water using a dispersion resin such as a water-soluble resin or a surfactant and added to the coating material.

If necessary, the water-based waterproof coating material of the present invention may further contain a paint additive such as an antifoaming agent, an antiseptic agent, a thickening agent, an antifreezing agent, a film-forming aid, and an organic solvent for transparency. It can be added within a range that does not impair it.

In the surface finishing method of the present invention, the undercoat material is applied to the surface of the exposed concrete, and after drying, the aqueous waterproof coating material obtained as described above is applied.

The above-mentioned undercoating material blocks water-absorbing portions such as fine spots and pinholes on the concrete surface to impart water repellency and waterproofness. It can be used, for example, the above-mentioned alkylalkoxysilane compound and low-molecular-weight organosiloxane compound are dispersed, emulsified and dissolved in an aqueous medium, and the alkylalkoxysilane compound and fluoroalkylalkoxysilane compound are dissolved and diluted with an organic solvent. Things are included.

The coating of the undercoat material is carried out by a conventionally known coating means such as roller coating, brush coating, spray coating and the like, and the coating amount thereof is usually from 0.05 to
It is about 0.15 kg / m ² .

The above-mentioned water-based waterproof coating material is also applied by a conventionally known coating means such as roller coating, brush coating, spray coating, etc. The coating amount is usually 0.08.
It is about 0.16 kg / m ² · times.

[0030]

EXAMPLES The present invention will be described in more detail with reference to examples. In the following, "part" and "%" mean "part by weight" and "% by weight", respectively.

Production Example 1 A 2 liter four-necked flask was equipped with a condenser, a thermometer,
A dropping funnel was attached, 50 parts of deionized water and 2 parts of sodium dodecylbenzenesulfonate were charged, and after replacing the internal air with nitrogen, the internal temperature was raised to 82 ° C. with stirring to dissolve it. In a separate container, add 20 parts of deionized water, 3.5 parts of sodium dodecyl benzene sulfonate, and 0.15 parts of ammonium peroxydisulfate, and stir well to foam.
Among them, 7.5 parts of cyclohexyl methacrylate, 21.9 parts of methyl methacrylate, 7.5 parts of n-butyl acrylate, 12.9 of 2-ethylhexyl acrylate.
And 0.2 part of 1,6-hexanediol diacrylate were added and stirred to prepare an emulsion, which was continuously added dropwise over 2 hours. After finishing the dropping, 1 at 82 ℃
Stir for hours.

Next, 20 parts of deionized water, 3.5 parts of sodium dodecylbenzene sulfonate and 0.15 part of ammonium peroxydisulfate were added in a separate container, and the mixture was well stirred to foam, and cyclohexylmethacrylate was added thereto. -To 7.5 copies,
27.5 parts of methyl methacrylate, 4.5 parts of n-butyl acrylate, 5 parts of 2-ethylhexyl acrylate,
2.5 parts of diacetone acrylamide, 2 parts of 2-hydroxyethyl acrylate, and 1 part of acrylic acid were added to the monomer mixture and stirred to form an emulsion, which was allowed to take 2 hours in the above reaction vessel. Was continuously added dropwise. 82 ° C after completion of dropping
After stirring for 2 hours, the mixture was cooled to 40 ° C. to obtain a copolymer emulsion.

Next, while maintaining the temperature at 25 ° C., the pH of the system was adjusted to 7 with aqueous ammonia, 10 parts of phenyltrimethoxysilane was added, and the mixture was stirred for about 1 hour. Then, the reaction container was heated to 80 ° C. and reacted for 3 hours to obtain an aqueous emulsion (A-1). The solid content concentration of the emulsion was 53%, and the particle size was 0.15 μm.

Production Examples 2 to 4 Each of the aqueous emulsions (A-2) was prepared in the same manner as in Production Example 1 except that the composition of the monomer and silane compound at each stage was changed as shown in Table 1. ) ~ (A-4)
Got These property values are also shown in Table 1.

[0035]

[Table 1]

Preparation of Aqueous Waterproof Coating Material Examples 1 to 11 and Comparative Examples 1 and 2 Aqueous waterproof coating materials were obtained by stirring and mixing with the compounding compositions shown in Table 2. (Note 1) to (Note 9) in Table 2 are as follows.

(Note 1) "KP3000S": Silicone resin emulsion, manufactured by Japan Synthetic Rubber Co., Ltd., solid content concentration 45
% (Note 2) "Polydurex G633": Silicone resin emulsion, manufactured by Asahi Kasei Co., solid content concentration 46% (Note 3) "Sephralcoat WH351D": Fluororesin, Central Glass Co., solid content concentration 45 % (Note 4) "Sylysia 400": Silica powder, particle size 7μ
m, Fuji Silysia's (Note 5) "Shamrock LF": Fluorine resin powder, particle size 5 μm, Shamrock Technology's (Note 6) "Biocut HG": Anti-algae and antifungal agent, large Nippon Ink Chemical Co., Ltd. (Note 7) "SN Defoma-318": Defoamer, San Nopco (Note 8) "Adecan UH420": Thickener, Asahi Denka Kogyo (Note 9) "Kyowanol D": film-forming auxiliary, manufactured by Kyowa Hakko Co., Ltd.

[0038]

[Table 2]

Coating Examples 12 to 24 and Comparative Examples 3 and 4 A flexible plate of 70 × 150 × 5 mm was prepared as a base plate, the undercoat material of was selected as shown in Table 3, and the coating amount was 0.08 to 0.1 kg. Roller coating in the range of / m ²
After drying at room temperature (20 ° C.) for 1 day, the water-based waterproof coating material obtained in the above Examples and Comparative Examples was selected as shown in Table 3, and the coating amount was 0.1 to 0.12 kg by a wheel roller. Each test piece was obtained by applying twice in the range of / m ² and drying in a curing room at room temperature and a humidity of 65% for 2 weeks.

Comparative Example 5 As a base plate, a flexible plate of 70 × 150 × 5 mm was roller coated with a coating amount of 0.08 to 0.1 kg / m ² and dried at room temperature for 1 day, and then "Aresgar-
De Crystal "(Kansai Paint Co., Ltd., a wet color prevention coating material)
Was coated with a roller at a coating amount of 0.12 to 0.15 kg / m ² and dried for 1 day.
F clear "(a fluororesin clear paint manufactured by Kansai Paint Co., Ltd.) applied by a roller at an amount of 0.12 to 0.13 kg.
/ M ² was applied twice, and dried in a curing room at room temperature and a humidity of 65% for 2 weeks to obtain a test body.

Comparative Example 6 A 70 × 150 × 5 mm flexible plate as a base plate was coated with a roller in a coating amount range of 0.08 to 0.1 kg / m ² and dried at room temperature for 1 day, followed by “Bonflon AC Dry”. "Intermediate coating" (Urethane-based intermediate coating by Asahi Glass Coat Andresin Co., Ltd.) applied by a roller at an amount of 0.1 to 0.1
Painted in the range of ² kg / m ² and dried for 1 day, and then "Bonflon AC # 1100 clear" (Asahi Glass Co-
Fluorine resin clear paint manufactured by Toandresin Co., Ltd. was applied twice with a roller at an application amount of 0.1 to 0.11 kg / m ^{2 and then} in a curing room at room temperature and a humidity of 65%. A test body was obtained by drying for a week.

Each of the obtained test pieces was subjected to the following performance test and evaluated. The results are shown in Table 3.

(Undercoating material) "Alesgard pulsar": manufactured by Kansai Paint Co., Ltd., water-repellent undercoating material "Aqua Acyl 200S": manufactured by Sumitomo Seika, water-repellent undercoating material "Epocrete MH-15": Japan Epoxy type underlayer reinforcing agent manufactured by Catalyst Co., Ltd. (performance test) (* 1) Gloss: 60 ° The reflectance was measured.

(* 2) Water resistance: Each test body was visually evaluated for the state of the coating film after being immersed in a constant temperature running water bath at room temperature of 20 ° C. for 7 days.

⊚: No abnormality ○: Very slight blistering, discoloration, etc., but no problem in practical use △: Blistering, discoloration, etc. partially observed ×: Remarkably blistering, discoloration (* 3) ) Alkali resistance: Each sample was immersed in a water tank filled with a saturated aqueous solution of calcium hydroxide at room temperature of 20 ° C. for 30 days, and the state of the coating film was visually determined.

⊚: No abnormality ○: Slight blistering, discoloration, gloss change, etc. are observed, but there is no problem in practical use △: Swelling, discoloration, gloss change, etc. are partially observed ×: Blistering, discoloration, gloss change, etc. (* 4) Interlayer adhesion: The adhesion between the first and second application of the water-based waterproof coating material twice on each test piece was measured according to JIS K 5
The test was performed according to 400 crosscuts. The part that was difficult to see was confirmed with a magnifying glass.

⊚: No peeling was observed at all ○: Peeling was observed on a part of the coating film due to the cutter-scratch, but there was no problem in practical use Δ: Peeling was observed on the coating film of 25% or less ×: 25 % Peeling is observed in the coating film exceeding 5% (* 5) Accelerated weathering resistance: Each test piece was sunshine weathered.
The film was put on a meter for 2000 hours, and the state of the coating film was visually judged.

⊚: No abnormality ○: Blisters, discoloration, gloss change, peeling, etc. are slightly observed, but there is no problem in practical use Δ: Blisters, discoloration, gloss change, peeling, etc. are partially observed ×: Blisters, discoloration Remarkably, gloss change, peeling, etc. are recognized (* 6) Wetting colorability: It was visually determined whether or not a wet color feeling was caused by coating with respect to the hue of the flexible plate before coating.

⊚: No change at all ○: Wet color is slightly observed but there is no problem in practical use Δ: Blackish and wet color is seen ×: Completely different from the hue of the flexible plate before coating Strongly blackish (* 7) Odor during coating: The organic solvent odor during coating was evaluated.

[0050] ⊚: No solvent odor ◯: Slight solvent odor is felt, but there is no problem in practical use △: Solvent odor is clearly felt ×: Strong solvent odor and uncomfortable

[0051]

When the water-based waterproof coating material of the present invention is applied for finishing the surface of an exposed concrete, a coating film excellent in alkali resistance, water resistance and weather resistance is formed to prevent deterioration of the concrete. Not only can it be prevented, but it can also impart a unique texture and a high-quality finished texture.

[0052]

[Table 3]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 5/14 C09D 5/14 127/12 127/12 F term (reference) 4D075 CA38 DA06 DB12 DC03 EA06 EA13 EB16 EB43 EB56 EC03 EC54 EC60 4J038 CD092 CD101 CD121 DL031 HA446 KA20 MA02 MA08 MA10 PA07 PC04

Claims (7)

[Claims] 1. An aqueous waterproof coating material comprising (A) an aqueous silicone resin and / or an aqueous fluorine resin, (B) silica powder, and (C) a fluorine resin powder. 2. A polysiloxane composite aqueous emulsion in which the resin (A) has a core part which is a cross-linked polymer and a shell part which is a non-cross-linked polymer which covers the core part and which has polysiloxane near the surface of the shell. The water-based waterproof coating material according to claim 1. 3. The content of the silica powder (B) is the resin (A).
The water-based waterproof coating material according to claim 1, which is 5 to 20 parts by weight with respect to 100 parts by weight of the solid content. 4. A content (C) of a fluorine resin powder.
Is 5 to 30 relative to 100 parts by weight of the solid content of the resin (A).
The water-based waterproof coating material according to claim 1, which is parts by weight. 5. Silica powder (B) and fluororesin powder
The water-based waterproof coating material according to claim 1, wherein (C) is used in a weight ratio of 2: 1 to 1: 4. 6. The water-based waterproof coating material according to claim 1, which contains an antifungal agent and / or an antialgal agent. 7. An undercoating material is applied to the surface of an exposed concrete, and after drying, (A) an aqueous silicone resin and / or
Alternatively, a method for finishing the surface of an exposed concrete is characterized in that an aqueous waterproof coating material containing an aqueous fluororesin, (B) silica powder, and (C) fluororesin powder is applied.