JPH0977574A - Concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the deposition of a contaminant on the surface of a structure difficult and to easily wash away the contaminant, if deposited, with rain, etc., in the structure to be used as a building base material such as wall and column by forming specified surface layer and waterproof layer. SOLUTION: A hydrophilic surface layer 4 contg. a photocatalyst (e.g. titania) with the contact angle to water controlled preferably to <=10 deg., more preferably to <=5 deg., is formed on the surface of a concrete structure 1, and a waterproof layer 3 (e.g. polytetrafluoroethylene layer) is formed between the surface layer 4 and the concrete 1 surface or in the concrete 1. Besides, when a refinforcement 2 is arranged in the concrete structure 1, a waterproof layer is preferably formed on the surface of the reinforcement 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molded concrete boards such as PC boards (precast concrete boards), FRC boards (fiber reinforced concrete boards), ALC boards (lightweight cellular concrete boards) and extrusion molded cement boards, mortar and siding. The present invention relates to a cement-based outer wall material such as a board (flexible board, calcium silicate board, wood-based wood chip cement board, asbestos cement perlite board) or an outer wall board containing a cement filler, and further to a concrete structure including exposed concrete.

[0002]

2. Description of the Related Art Conventionally, concrete structures have been widely used as outer walls of buildings. Since such a concrete structure is exposed to rainwater, dirt adheres to it. It is considered that this stain is a mixture of combustion products such as carbon black, urban dust, and inorganic dust such as clay minerals (Yoshinori Tachibana, "Method for accelerating contamination of exterior wall finishing materials", Architectural Institute of Japan Structural Papers, 404th
No., October 1989, P15-24).

Since a large number of holes are present on the surface of the concrete structure, dirt will accumulate if nothing is done. Therefore, in the past, the surface of the concrete structure was painted and the like. The surface of the body is made water repellent to prevent dirt from adhering.

However, when the surface of the concrete structure is rendered water-repellent, muddy water or the like remains as water droplets on the surface, which is difficult to remove when it dries, and black streaky dirt becomes conspicuous over time. The dirt is composed of a hydrophobic substance such as carbon black which is a combustion product. Since the hydrophobic substance is more easily adapted to a hydrophobic base material than water, it is hard to be washed away by rainwater and stays on the surface of the material.

Therefore, recently, it has been reported that a hydrophilic resin coating is applied to the surface to exert an automatic cleaning effect (Polymer, Vol. 44, May 1995, P30).
7) is proposed. That is, by imparting hydrophilicity to the surface, a thin water film is formed on the surface to prevent dirt components from adhering and to easily wash away dirt with rainwater or the like.

It has also been proposed to paint buildings with hydrophilic graft polymers (Chemical Industry Daily 1995).
January 30th). Further, recently, many hydrophilic paints such as acrylic resin and acrylic silicone resin are commercially available.

[0007]

The water repellent coating is less effective against urban dust containing lipophilic components,
Contamination adheres over time and it is difficult to remove the adhered dirt.
Further, the contact angle of the hydrophilic graft polymer with water is 30.
４０40 °. On the other hand, the contact angle of inorganic dust such as clay mineral with water is 20 to 50 °. Therefore, the graft polymer cannot be said to be effective against inorganic dust.
Further, all of the commercially available hydrophilic paints such as acrylic resins have a contact angle with water of 50 to 70 ° and cannot prevent the stains due to the urban dust containing lipophilic components. Furthermore, all hydrophilic coatings have the drawback that their hydrophilicity deteriorates over time.

If the surface of the concrete structure is made hydrophilic to prevent dirt from adhering to it, the concrete structure itself is porous, so that the water adhering to the surface or the salt content contained in the water is concrete. There is a risk of seeping into the structure and corroding the concrete structure or the reinforcing bars inside.

[0009]

According to the present invention, in order to make it difficult for dirt to adhere to the surface of a concrete structure or to easily remove the adhered dirt by a self-cleaning action or the like, a water repellent property is applied to the surface of the concrete structure. In light of the recently announced fact that it is more effective to impart hydrophilicity than to impart it to the photocatalyst particles such as titanium oxide, in addition to the action of decomposing stains by a redox reaction, The present invention was made based on the fact that the present inventors uniquely found that it has the effect of making the surface hydrophilic (superhydrophilic).

Here, the decomposition action of the substance by the photocatalyst particles is based on an oxidation-reduction reaction, and when the photocatalyst particles are irradiated with ultraviolet rays or the like, photoexcitation causes electron-hole pairs, of which electrons generate surface oxygen. It is reduced to produce superoxide ions (O ₂ ⁻ ), and holes oxidize surface hydroxyl groups to produce hydroxyl radicals (· OH), and these extremely reactive active species (O ₂ ⁻ or The substance attached to the surface is decomposed by the redox reaction of (OH).

On the other hand, the hydrophilizing action of the photocatalyst particles newly discovered by the present inventors has not been completely clarified on its theoretical basis, but a hydroxyl group (O
H ^-) chemisorbed photocatalyst particle surface, or hydroxyl (OH ^-) is replaced with an organic group, further the hydroxyl (OH ^-)
It is considered that water molecules in the air are physically adsorbed and the amount of physically adsorbed water is increased, whereby the hydrophilicity of the surface is increased and a superhydrophilic surface is realized.

As a specific example, a case where the surface layer is made of a silicone resin having a Si--O bond will be described. Before the photocatalyst particles are irradiated with light, as shown in FIG.
Since the alkyl group (R) is bonded to the atom, the surface layer exhibits hydrophobicity. However, when the surface layer is irradiated with light having an energy higher than the band gap energy of the photocatalyst particles, as shown in FIG. the substitution (chemisorption), further the hydroxyl group - ^(OH) alkyl group (R) is a hydroxyl group by photocatalytic effect - exhibit hydrophilic water molecules in the air are physically adsorbed ^(OH).

[0013] In the above description, it is apparent that the decomposition and hydrophilization effect of a substance is completely different, if Shimese concrete examples, TiO ₂ anatase even TiO ₂ oxidation-reduction reaction However, rutile-type TiO ₂ shows almost no decomposition action of the substance based on the redox reaction. Also, among the photocatalysts, tin oxide does not show a decomposition effect of a substance based on a redox reaction. In these photocatalyst particles, the energy level of the conduction band is not sufficiently high, so that the reduction reaction does not proceed. As a result, the electrons excited by the photoexcitation in the conduction band become excessive, and the electron-hole pairs generated by the photoexcitation are oxidized and reduced. It is believed that they recombine without participating in the reaction. However, both rutile TiO ₂ and tin oxide exhibit a hydrophilizing action. Further, the photocatalytic layer needs to have a thickness of at least 100 nm in order to exhibit the decomposing action of the substance, but it is possible for the photocatalytic layer to exhibit a hydrophilizing action if it has a thickness of several nm or more. From these facts, it can be said that the decomposition action of the substance by the photocatalyst and the hydrophilization action are completely different.

The present invention was made based on the above findings, and the concrete structure according to the present invention has a hydrophilic surface layer containing photocatalyst particles formed on the surface thereof, and the surface layer and the concrete surface. A waterproof layer was formed between or in the concrete. When reinforcing bars are arranged inside the concrete structure, a waterproof layer may be formed on the surface of the reinforcing bars. Further, the preferable hydrophilicity is that the contact angle with water is 10 ° or less, more preferably 5 ° or less.

Here, the waterproof layer means a material capable of blocking pores of concrete and preventing permeation of water,
Specific examples include polytetrafluoroethylene (PTFE).

Titanium oxide is most preferable as the photocatalyst particles, but in addition to this, ZnO, SnO ₂ , SrTi are also used.
Examples thereof include metal oxides such as O ₃ , WO ₃ , Bi ₂ O ₃ and Fe ₂ O ₃ . It is considered that, since a metal element and oxygen are present on the surface, a hydroxyl group (OH ⁻ ) is easily adsorbed on the surface, and therefore, it is easy to exhibit hydrophilicity. The titanium oxide may be either anatase type or rutile type.

As a method for forming a hydrophilic surface layer containing photocatalyst particles (titania), amorphous titania is applied and crystallized, silica-containing titania is applied, tin oxide-containing titania is applied, and titania-containing silicone paint is applied. Etc.

The formation of amorphous titania is a method in which the surface to be coated is first coated with amorphous titania and then fired to cause a phase change to crystalline titania, and either of the following methods can be adopted. . (1) Hydrolysis and Dehydration Polycondensation of Organic Titanium Compounds Titanium alkoxides such as tetraethoxy titanium, tetraisopropoxy titanium, tetra n-propoxy titanium, tetrabutoxy titanium, tetramethoxy titanium, and hydrolyzed hydrochloric acid or ethylamine. After adding a decomposition inhibitor and diluting with an alcohol such as ethanol or propanol, the mixture is spray-coated, flow-coated, spin-coated, while the hydrolysis is partially or completely allowed to proceed. It is applied by dip coating, roll coating or other coating method, and dried at room temperature to 200 ° C. By drying, the hydrolysis of the alkoxide of titanium is completed to form titanium hydroxide, and a layer of amorphous titania is formed by dehydration-condensation polymerization of titanium hydroxide. Instead of titanium alkoxide, other organotitanium compounds such as titanium chelate or titanium acetate may be used. (2) Formation of amorphous titania by inorganic titanium compound Inorganic titanium compound such as TiCl ₄ or Ti (S
An acidic aqueous solution of O ₄ ) ₂ is applied by spray coating, flow coating, spin coating, dip coating, roll coating or other coating method, and dried at a temperature of 100 to 200 ° C. to perform hydrolysis and dehydration polycondensation, Form a layer of amorphous titania. Or it may form a layer of amorphous titania on the surface to be coated by chemical vapor deposition of TiCl _4. (3) Formation of amorphous titania by sputtering A target of metal titanium is irradiated with an electron beam in an oxidizing atmosphere to form a layer of amorphous titania on the surface to be coated.

Application of silica-containing titania is to form a layer of a mixture of titania and silica on the surface to be coated. The ratio of silica to the total of titania and silica is 5 to 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. The following method can be employed for forming the surface layer made of silica-containing titania. (1) A suspension containing particles of anatase type or rutile type titania and particles of silica is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Based on a mixture of a precursor of amorphous silica (for example, tetraalkoxysilane such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc.) and crystalline titania sol After applying to the surface of the material and hydrolyzing it as necessary to form silanol, heating at a temperature of about 100 ° C. or more and subjecting the silanol to dehydration polycondensation, the titania is bound with amorphous silica. Obtained surface layer (photocatalytic coating). In particular, if the dehydration condensation polymerization of silanol is performed at a temperature of about 200 ° C. or higher, the degree of polymerization of silanol can be increased, and the alkali resistance performance of the photocatalytic coating can be improved. (3) Dispersing silica particles in a solution of amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) Is applied to the surface of the base material, and the titanium compound is cooled to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which silica particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate. (4) Amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) in a solution of amorphous titania precursor (For example, tetraalkoxysilanes such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc., silanols which are hydrolysates thereof, or polysiloxanes having an average molecular weight of 3000 or less) And apply to the surface of the substrate. Then, these precursors are subjected to hydrolysis and dehydration polycondensation to form a thin film composed of a mixture of amorphous titania and amorphous silica. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The application of titania containing tin oxide is to form a layer of a mixture of titania and tin oxide on the surface to be coated. The ratio of tin oxide to the total of titania and tin oxide is 1 to 95 mol%, preferably 1 to 50 mol%. The following method can be adopted as a method for forming a surface layer made of titania mixed with tin oxide. (1) A suspension containing particles of anatase type or rutile type titania and particles of tin oxide is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Dispersion of tin oxide particles in a solution of a precursor of amorphous titania (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) The resulting suspension is applied to the surface of the substrate, and the titanium compound is heated to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which tin oxide particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The titania-containing silicone paint is applied by using a paint in which titania (photocatalyst particles) is dispersed in a film-forming element made of uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. . Specifically, when the photocatalyst is photoexcited after the above coating material is applied to the surface of the substrate and the coating film forming element is cured, the organic group bonded to the silicon atom of the silicone molecule is replaced with a hydroxyl group by the action of the photocatalyst. , The surface is made hydrophilic (superhydrophilic). This method has the advantages that the film-forming element can be cured at a relatively low temperature, can be applied as many times as necessary, and can be easily hydrophilized even by sunlight. Examples of the resin that cures at a temperature as low as room temperature include the following. Methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltrit-butoxysilane, ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, Ethyltriisopropoxysilane, ethyltri-t-butoxysilane, n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n
-Propyltriisopropoxysilane, n-propyltrit-butoxysilane, n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n
-Hexyltriisopropoxysilane, n-hexyltri-t-butoxysilane, n-decyltrichlorosilane,
n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-decyltriisopropoxysilane, n-decyltrit-butoxysilane, n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n
-Octadecyltriisopropoxysilane, n-octadecyltrit-butoxysilane, phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltrit-butoxysilane, tetrachloro Silane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldichloro Silane, diphenyldibromosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenylmethyldichlorosilane, phenylmethyl Dibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, triethoxyhydrosilane, tribromohydrosilane, trimethoxyhydrosilane, isopropoxyhydrosilane, tri-t-butoxyhydrosilane, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyl Triethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane, trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane ,
Trifluoropropyltri-t-butoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltrit-butoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyl Trimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltrit-butoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-ami Nopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltrit-butoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane,
β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and partial hydrolysates thereof or a mixture thereof can be used. In order to ensure good hardness and smoothness of the silicone resin film, it is preferable to contain 10 mol% or more of the three-dimensional crosslinked siloxane. In order to provide sufficient flexibility of the resin film while ensuring better hardness and smoothness, 2
It is preferable that the dimensional cross-linking siloxane content be 60 mol% or less. Further, in order to accelerate the rate at which the organic group bonded to the silicon atom of the silicone molecule is replaced with the hydroxyl group by photoexcitation, the organic group bonded to the silicon atom of the silicone molecule is n.
It is preferred to use silicones consisting of -propyl or phenyl groups. An organopolysilazane compound having a silazane bond can be used instead of the silicone having a siloxane bond.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a cross-sectional view of a concrete structure according to the present invention, in which the concrete structure 1 is provided with reinforcing bars 2 inside and a waterproof layer 3 is formed on the surface,
A hydrophilic surface layer 4 containing photocatalyst particles is formed on the waterproof layer 3.

The location where the waterproof layer 3 is provided is not limited to between the illustrated concrete structure 1 and the surface layer 4, and
It may be the inside of the concrete structure 1 or the surface of the reinforcing bar 2. Even when reinforcing bars are arranged, it is not necessary to provide a waterproof layer on the surface of the reinforcing bar as long as the waterproof layer functions sufficiently.

Next, concrete examples will be described. (Example) Concrete was cast on a test plate, and after one month, the surface of exposed concrete having a water content of 10% or less and a pH of 9 or less was used as a base. First, an undercoat was applied, and a paint containing a suction-preventing pigment or the like was applied. Next, an inorganic-organic composite type waterproof material having moisture permeability was applied as an intermediate layer. Next, the following two types of coating were separately applied onto the waterproof material on the concrete surface. Coating The titania sol was added to the silane coating so that the molar ratio of silica to titania was 1: 1. This paint was applied and dried. Painting The existing acrylic paint was applied and dried. As a solution for top coating, a mixture of titanium oxide sol, tetraethoxysilane, ethanol and water was used. This solution was applied and dried.

(Evaluation: Salt Water Spraying Test) Assuming salt damage due to salt breeze, a predetermined amount of 5% NaCl aqueous solution was repeatedly sprayed with a spray gun at regular intervals. The coated surface was peeled off with sandpaper, and the amount of NaCl in the base portion was quantified. As a result, the amount of Na in the comparative sample having no waterproof layer was obviously increased as compared with that before the test, whereas the sample to which the coating according to the present invention was applied (the above-mentioned coating and coating) was before the test. There was almost no increase in the amount of Na as compared with.

(Evaluation: Carbonated water dropping test) The test was conducted to accelerate the neutralization by carbon dioxide gas. Carbonated water was continuously added dropwise at a constant flow rate for one month. The pH of the comparative sample having no waterproof layer was lowered by 1 or more, and the neutralization was progressing, while the pH of the sample coated with the present invention (the above-mentioned coating and coating) was higher than that before the test. The decrease was only 0.5.

[0027]

As described above, according to the present invention, since a hydrophilic surface layer containing photocatalyst particles is formed on the surface of the concrete structure, the surface of the concrete structure is exposed as long as it is exposed to sunlight or the like. Can be kept hydrophilic. Further, since the surface of the concrete structure exhibits hydrophilicity, dirt hardly adheres, and the adhered dirt is washed away by rain or the like, so that the self-cleaning effect is exerted. And, according to the present invention, since the waterproof layer is formed between the surface layer and the concrete surface or inside the concrete, the disadvantage due to the formation of the hydrophilic surface layer, that is, the concrete is porous, is hydrophilic. The formation of the surface layer can prevent the disadvantage that water and salt contained in the surface layer enter to cause corrosion.

[Brief description of drawings]

1A is a conceptual diagram of a hydrophobic surface, and FIG. 1B is a conceptual diagram of a hydrophilic surface.

FIG. 2 is a sectional view of a concrete structure according to the present invention.

[Explanation of symbols]

1 ... Concrete structure, 2 ... Reinforcing bar, 3 ... Waterproof layer, 4 ...
A hydrophilic surface layer containing photocatalyst particles.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location E04C 2/04 E04C 2/04 D 5/02 5/02 E04F 13/14 102 8913-2E E04F 13 / 14 102A (72) Makoto Senkoku, 1-1 1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Equipment Co., Ltd. (72) Toshiya Watanabe 2-1-1, Nakajima, Kitakyushu, Kitakyushu, Fukuoka No. 1 Totoki Equipment Co., Ltd. (72) Inventor Atsushi Kitamura 2-1, 1-1 Nakajima, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture Totoki Equipment Co., Ltd.

Claims (2)

[Claims] 1. A concrete structure used as a building substrate such as a wall or a pillar, wherein the concrete structure has a hydrophilic surface layer containing photocatalyst particles formed on the surface thereof. A concrete structure characterized in that a waterproof layer is formed between the concrete surface and inside the concrete. 2. The concrete structure according to claim 1, wherein the concrete structure has reinforcing bars inside,
A concrete structure characterized in that a waterproof layer is formed on the surface of the reinforcing bar.