1. The bare concrete protective agent is characterized by comprising a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 40-60 parts of fluorocarbon resin emulsion, 2-6 parts of film-forming agent, 2-3 parts of silane coupling agent, 2-3 parts of thickening agent, 0.1-0.2 part of defoaming agent, 1-1.5 parts of dispersing agent, 5-10 parts of cosolvent and 30-50 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 5-7 parts of modified graphene-loaded titanium dioxide powder, 9-12 parts of polydimethylsiloxane and 30-50 parts of toluene.

2. The bare concrete protective agent according to claim 1, wherein the preparation process of the modified graphene-loaded titanium dioxide powder comprises the following steps:

under the stirring state, slowly adding tetrabutyl titanate into ethanol, uniformly mixing to obtain solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:3-4,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 6-8, the content of titanium dioxide reaches 0.5-1.5 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

3. The bare concrete protective agent according to claim 2, wherein the preparation process of the amine-modified branched silane graphene oxide comprises the following steps:

adding 15-20 parts of branched silane modified graphene oxide into 500 parts of water in 300-50 ℃, uniformly stirring by ultrasonic dispersion, slowly adding 4-6 parts of hydrazine hydrate after controlling the temperature to be 40-50 ℃, then heating to 100-105 ℃, reacting for 20-30min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

4. The bare concrete protective agent according to claim 3, wherein the preparation process of the branched silane modified graphene oxide comprises the following steps:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 4-6 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

5. The bare concrete protectant according to any one of claims 1-4, wherein the film former is any one of an acrylic resin film former or a butadiene resin film former.

6. The bare concrete protectant according to any one of claims 1-4, wherein the silane coupling agent is any one of KH-550, KH-560, KH-570, and KH-792.

7. The bare concrete protectant according to any of claims 1-4, wherein the co-solvent is propanol or isopropanol; the dispersant is stearic acid monoglyceride.

8. The bare concrete protectant according to any one of claims 1-4, wherein: the thickening agent is one or two of hydroxypropyl methyl cellulose, sodium carboxymethyl cellulose and hydroxyethyl cellulose; the defoaming agent is one of polyoxyethylene polyoxypropylene amine ether and polyoxypropylene polyoxyethylene glycerol ether.

9. A construction method of the bare concrete protective agent is characterized in that: the method comprises the following steps:

uniformly mixing the raw materials in the seal base coat component according to the proportion in claim 1 to obtain the seal base coat, wherein the proportion is 20-100 mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

uniformly mixing the raw materials in the photocatalytic top coat component according to the proportion in claim 1 to obtain the photocatalytic top coat, and uniformly mixing the raw materials on the surface of the sealing bottom coat according to the proportion of 30-120 mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

10. The construction method of the bare concrete protective agent according to claim 9, characterized in that: before the sealing primer is coated, the construction method further comprises the steps of washing and removing particles and dust on the surface of the fair-faced concrete and fully drying.

Background

With the rapid development of society, concrete structures play an increasingly important role in urban construction. As a new concrete which is newly emerged in recent years, the fair-faced concrete receives more and more attention due to the unique concrete texture and color.

Fair-faced concrete is also called decorative concrete, so that it is named for its very good decorative effect. The concrete is cast once without any external decoration, and the natural surface effect of cast-in-place concrete is directly adopted as a veneer, so that the surface is flat and smooth, the color is uniform, the edges and corners are clear, and no damage and pollution are caused. Because a plurality of micro pores exist in the concrete, the concrete is easy to absorb water, and dirt is formed on the surface of the concrete due to the erosion of rainwater, so that the appearance of the concrete is influenced; the acidic substances can neutralize the concrete, so that the strength of the concrete is reduced, and the problems of cracks, saltpetering, discoloration and the like occur, thereby affecting the service life of the building. Therefore, it is necessary to coat a protective agent on the surface of the fair-faced concrete to reduce the water absorption of the fair-faced concrete and improve the durability of the fair-faced concrete.

The bare concrete protecting agent is prepared with silane cross-linking small molecular resin with carbon functional group capable of combining with organic material and hydrolytic silicon functional group capable of combining with inorganic material as base material, and through special technological cross-linking with other high performance resin and special assistants. The existing fair-faced concrete protective agent mostly forms a compact protective layer on the surface of concrete so as to achieve the aim of dewatering. However, the common protective agent can only achieve a common hydrophobic effect, and in the long-term use process, the concrete is often decomposed due to the breeding of mold, and meanwhile, the photocatalytic degradation effect of the common protective coating is realized only by doping titanium dioxide functional powder, and the photocatalytic effect of the titanium dioxide functional powder still has certain limitation.

Disclosure of Invention

The invention provides a bare concrete protective agent and a construction method thereof, aiming at the problems that the concrete is decomposed due to the breeding of mould in the long-time use process of the common protective agent in the prior art, and the photocatalytic degradation of toxic substances of the common protective coating is realized only by doping titanium dioxide functional powder, so that the limitation exists.

The invention is realized by the following technical scheme:

the invention provides a bare concrete protective agent in a first aspect, which comprises a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 40-60 parts of fluorocarbon resin emulsion, 2-6 parts of film-forming agent, 2-3 parts of silane coupling agent, 2-3 parts of thickening agent, 0.1-0.2 part of defoaming agent, 1-1.5 parts of dispersing agent, 5-10 parts of cosolvent and 30-50 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 5-7 parts of modified graphene-loaded titanium dioxide powder, 9-12 parts of polydimethylsiloxane and 30-50 parts of toluene.

As a further illustration of the present invention, the preparation process of the modified graphene-loaded titanium dioxide powder comprises the following steps:

under the stirring state, slowly adding tetrabutyl titanate into ethanol, uniformly mixing to obtain solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:3-4,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 6-8, the content of titanium dioxide reaches 0.5-1.5 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

As a further illustration of the present invention, the preparation process of the amine-modified branched silane graphene oxide comprises the following steps:

adding 15-20 parts of branched silane modified graphene oxide into 500 parts of water in 300-50 ℃, uniformly stirring by ultrasonic dispersion, slowly adding 4-6 parts of hydrazine hydrate after controlling the temperature to be 40-50 ℃, then heating to 100-105 ℃, reacting for 20-30min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

As a further illustration of the present invention, the preparation process of the branched silane-modified graphene oxide comprises the following steps:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 4-6 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

As a further illustration of the invention, the film-forming agent is any one of an acrylic resin film-forming agent or a butadiene resin film-forming agent.

As a further explanation of the present invention, the silane coupling agent is any one of KH-550, KH-560, KH-570 and KH-792.

As a further illustration of the present invention, the co-solvent is propanol or isopropanol; the dispersant is stearic acid monoglyceride.

As a further illustration of the invention, the thickener is one or two of hydroxypropyl methyl cellulose, sodium carboxymethyl cellulose and hydroxyethyl cellulose; the defoaming agent is one of polyoxyethylene polyoxypropylene amine ether and polyoxypropylene polyoxyethylene glycerol ether.

The second aspect of the invention provides a construction method of the bare concrete protective agent, which comprises the following steps:

uniformly mixing the raw materials in the sealing bottom coating component according to the proportion to obtain the sealing bottom coating, wherein the mixing ratio is 20-100 mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

uniformly mixing the raw materials in the photocatalytic top coat component according to the proportion to obtain the photocatalytic top coat, and uniformly mixing the raw materials on the surface of the sealing bottom coat according to the ratio of 30-120 mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

As a further illustration of the invention, the construction method further comprises the steps of washing and removing particles and dust on the surface of the fair-faced concrete and fully drying before the sealing primer is coated.

Compared with the prior art, the invention has the following beneficial technical effects:

the sealing bottom coating component of the bare concrete protective agent provided by the invention contains fluorocarbon resin emulsion, fluorocarbon resin takes a firm C-F bond as a framework, compared with other resins, the fluorocarbon resin has better heat resistance, chemical resistance, cold resistance, low-temperature flexibility, weather resistance, electrical property and the like, and has non-adhesion property and non-wettability due to good crystallinity, so that the sealing bottom coating containing fluorocarbon resin has good compactness and hydrophobicity, can prevent concrete from being corroded by acid, alkali, salt, grease and the like, and can effectively prevent the surface of concrete from being carbonized.

On the other hand, the sealing bottom coating formed by fluorocarbon resin can also play a good bearing role for the photocatalytic surface coating on the sealing bottom coating, so that the photocatalytic surface coating which depends on the sealing bottom coating and contains the modified graphene loaded titanium dioxide powder has good weather resistance, and the photocatalytic degradation effect of the photocatalytic surface coating is well exerted.

In addition, the photocatalytic surface coating containing the modified graphene-loaded titanium dioxide powder can inhibit microorganisms such as lichen, algae and mold from growing on the surface of the fair-faced concrete by virtue of a photocatalytic sterilization effect, maintain the long-term surface cleanness of the fair-faced concrete, and meanwhile, can effectively degrade harmful substances of formaldehyde by virtue of photocatalysis, so that the toxicity on the surface of the fair-faced concrete is reduced.

The preparation and use of the modified graphene-loaded titanium dioxide powder are an important component in the invention, the modified graphene oxide is used as an adsorptive base material, then the titanium dioxide is loaded on the base material, and the photocatalytic property of the titanium dioxide is combined with the adsorptive base material, so that the photocatalytic surface coating can absorb formaldehyde and has the capability of photocatalytic degradation of the formaldehyde, thereby greatly improving the sterilization and disinfection effects of the photocatalytic surface coating;

when the graphene oxide is modified, the active functional groups on the surface of the graphene oxide are sequentially modified with dendritic polyphenyl dimethylsilane and hydrazine hydrate, the graphene oxide is subjected to two-step chemical modification, the polarity of the surface of the graphene oxide is reduced, the surface characteristics of the graphene oxide are improved, the problems that the small molecular graphene is difficult to disperse and uneven in dispersion in a system are solved, and the graphene oxide modified by amine can have strong adsorption performance, so that a strong adsorption basis is provided for the toxicity adsorption of a photocatalytic surface coating.

When the titanium dioxide load modified graphene oxide is carried out, the method is realized by adopting an in-situ grafting mode, but the titanium dioxide hydrosol prepared by the common hydrolysis method of the n-butyl titanate has the defects of easy agglomeration, wide particle size range and the like, so that the dialysis treatment is doped in the common in-situ grafting mode, and compared with the titanium dioxide hydrosol obtained by simple hydrolysis after the dialysis treatment, the particle size of the titanium dioxide hydrosol product is reduced, the particle size is uniform, and more beneficial photocatalysis performance is shown.

Detailed Description

In order that the above objects, features and advantages of the present invention may be more clearly understood, the present invention will be described in detail below with reference to specific embodiments. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

Providing a bare concrete protective agent, which comprises a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 40 parts of fluorocarbon resin emulsion, 2 parts of acrylic resin film-forming agent, 2 parts of KH-550 silane coupling agent, 2 parts of hydroxypropyl methyl cellulose thickener, 0.2 part of polyoxyethylene polyoxypropylene amine ether defoamer, 1.5 parts of stearic acid monoglyceride dispersant, 10 parts of propanol cosolvent and 50 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 5 parts of modified graphene-loaded titanium dioxide powder, 9 parts of polydimethylsiloxane and 50 parts of toluene.

Specifically, the preparation process of the modified graphene loaded titanium dioxide powder comprises the following steps:

step 1: preparing branched silane modified graphene oxide:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 4 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

Step 2: preparing amine modified branched silane graphene oxide:

adding 15 parts of the branched silane modified graphene oxide prepared in the step 1 into 300 parts of water, ultrasonically dispersing and stirring uniformly, then controlling the temperature to be 40-50 ℃, slowly adding 4 parts of hydrazine hydrate, heating to 100 ℃, reacting for 20min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

And step 3: modified graphene loaded titanium dioxide powder:

under the stirring state, slowly adding tetrabutyl titanate into ethanol, uniformly mixing to obtain solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:3,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 6, the content of titanium dioxide reaches 0.5 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

The construction process of the bare concrete protective agent comprises the following steps:

step 1: washing to remove particles and dust on the surface of the fair-faced concrete and fully drying

Step 2: uniformly mixing the raw materials in the sealing bottom coating component according to the proportion to obtain the sealing bottom coating, wherein the mixing ratio is 20mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

and step 3: uniformly mixing the raw materials in the photocatalytic top coat component according to the proportion to obtain the photocatalytic top coat, and uniformly mixing the raw materials on the surface of the sealing bottom coat according to the ratio of 30mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

Example 2

Providing a bare concrete protective agent, which comprises a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 48 parts of fluorocarbon resin emulsion, 3 parts of butadiene resin film-forming agent, 2.5 parts of KH-560 silane coupling agent, 2.5 parts of sodium carboxymethylcellulose thickening agent, 0.15 part of polyoxypropylene polyoxyethylene glycerol ether defoamer, 1.2 parts of stearic acid monoglyceride dispersant, 7 parts of isopropanol cosolvent and 42 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 6 parts of modified graphene-loaded titanium dioxide powder, 10 parts of polydimethylsiloxane and 37 parts of toluene.

Specifically, the preparation process of the modified graphene loaded titanium dioxide powder comprises the following steps:

step 1: preparing branched silane modified graphene oxide:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 5 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

Step 2: preparing amine modified branched silane graphene oxide:

adding 17 parts of the branched silane modified graphene oxide prepared in the step 1 into 400 parts of water, ultrasonically dispersing and stirring uniformly, then controlling the temperature to be 45 ℃, slowly adding 5 parts of hydrazine hydrate, heating to 102 ℃, reacting for 23min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

And step 3: modified graphene loaded titanium dioxide powder:

under the stirring state, slowly adding tetrabutyl titanate into ethanol, uniformly mixing to obtain solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:3.5,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 7, the content of titanium dioxide reaches 1 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

The construction process of the bare concrete protective agent comprises the following steps:

step 1: washing to remove particles and dust on the surface of the fair-faced concrete and fully drying

Step 2: uniformly mixing the raw materials in the sealing bottom coating component according to the proportion to obtain the sealing bottom coating, wherein the mixing ratio is 50mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

and step 3: uniformly mixing the raw materials in the photocatalytic topcoat composition according to the proportion to obtain the photocatalytic topcoat, and uniformly mixing the raw materials on the surface of the sealing undercoat according to the ratio of 60mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

Example 3

Providing a bare concrete protective agent, which comprises a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 53 parts of fluorocarbon resin emulsion, 4 parts of butadiene resin film-forming agent, 2.5 parts of KH-570 silane coupling agent, 2.5 parts of sodium carboxymethylcellulose thickening agent, 0.15 part of polyoxyethylene polyoxypropylene amine ether defoamer, 1.2 parts of stearic acid monoglyceride dispersant, 8 parts of propanol cosolvent and 37 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 6 parts of modified graphene-loaded titanium dioxide powder, 11 parts of polydimethylsiloxane and 43 parts of toluene.

Specifically, the preparation process of the modified graphene loaded titanium dioxide powder comprises the following steps:

step 1: preparing branched silane modified graphene oxide:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 5 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

Step 2: preparing amine modified branched silane graphene oxide:

adding 18 parts of the branched silane modified graphene oxide prepared in the step 1 into 400 parts of water, ultrasonically dispersing and stirring uniformly, then controlling the temperature to be 45 ℃, slowly adding 5 parts of hydrazine hydrate, heating to 102 ℃, reacting for 25min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

And step 3: modified graphene loaded titanium dioxide powder:

under the stirring state, slowly adding tetrabutyl titanate into ethanol, uniformly mixing to obtain solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:3.5,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 7, the content of titanium dioxide reaches 1 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

The construction process of the bare concrete protective agent comprises the following steps:

step 1: washing to remove particles and dust on the surface of the fair-faced concrete and fully drying

Step 2: uniformly mixing the raw materials in the sealing bottom coating component according to the proportion to obtain the sealing bottom coating, wherein the mixing ratio is 70mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

and step 3: uniformly mixing the raw materials in the photocatalytic topcoat composition according to the proportion to obtain the photocatalytic topcoat, and uniformly mixing the raw materials on the surface of the sealing undercoat according to the ratio of 90mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

Example 4

Providing a bare concrete protective agent, which comprises a sealing bottom coating component and a photocatalytic top coating component;

the sealing bottom coating comprises the following raw materials in parts by mass: 60 parts of fluorocarbon resin emulsion, 6 parts of butadiene resin film-forming agent, 3 parts of KH-792 silane coupling agent, 3 parts of hydroxyethyl cellulose thickener, 0.1 part of polyoxypropylene polyoxyethylene glycerol ether defoamer, 1 part of stearic acid monoglyceride dispersant, 5 parts of isopropanol cosolvent and 30 parts of water;

the photocatalytic topcoat composition comprises the following raw materials in percentage by mass: 7 parts of modified graphene-loaded titanium dioxide powder, 12 parts of polydimethylsiloxane and 50 parts of toluene.

Specifically, the preparation process of the modified graphene loaded titanium dioxide powder comprises the following steps:

step 1: preparing branched silane modified graphene oxide:

measuring a proper amount of dendritic polyphenyldimethylsilane, and adding the dendritic polyphenyldimethylsilane into a THF solvent for dissolving, wherein the volume ratio of the dendritic polyphenyldimethylsilane to the THF solvent is 1: 15;

after the dendritic polyphenyl dimethylsilane is dissolved, sequentially adding graphene oxide and vinyl triethoxysilane, and ultrasonically dispersing and stirring for 6 hours; the mass ratio of the graphene oxide to the vinyltriethoxysilane is 10:1, and the ratio of the graphene oxide to the dendritic polyphenyl dimethylsilane is 1g:10 mL;

and centrifugally separating the powder, and drying in vacuum to obtain the branched silane modified graphene oxide.

Step 2: preparing amine modified branched silane graphene oxide:

adding 20 parts of the branched silane modified graphene oxide prepared in the step 1 into 500 parts of water, ultrasonically dispersing and stirring uniformly, then controlling the temperature to be 50 ℃, slowly adding 6 parts of hydrazine hydrate, heating to 105 ℃, reacting for 30min, filtering and separating to obtain an amine modified branched silane graphene oxide crude product;

and washing the amine modified branched silane graphene oxide crude product with toluene, and drying to obtain the amine modified branched silane graphene oxide.

And step 3: modified graphene loaded titanium dioxide powder:

under the stirring state, slowly adding tetrabutyl titanate into ethanol and uniformly mixing to obtain a solution A, wherein the volume ratio of the tetrabutyl titanate to the ethanol is 1:4,

slowly adding the solution A into an ammonia solution with the pH value being more than 9 under the stirring state, wherein the volume ratio of the solution A to the ammonia solution is 1:1, and then hydrolyzing at 40 ℃ to obtain a solution B;

slowly adding amine modified branched silane graphene oxide into the solution B under the stirring state, wherein the ratio of the n-butyl titanate to the amine modified branched silane graphene oxide is 2mL to 1g, keeping the temperature at 40 ℃ and reacting for 12h to obtain modified graphene loaded titanium dioxide gel,

dialyzing the modified graphene loaded titanium dioxide gel to separate impurities, so that the pH value reaches 8, the content of titanium dioxide reaches 1.5 wt%,

drying the modified graphene loaded titanium dioxide gel after dialysis treatment to obtain powder, and then placing the powder in a heating furnace to keep the temperature at 300 ℃ for 1.5h to obtain the modified graphene loaded titanium dioxide powder.

The construction process of the bare concrete protective agent comprises the following steps:

step 1: washing to remove particles and dust on the surface of the fair-faced concrete and fully drying

Step 2: uniformly mixing the raw materials in the sealing bottom coating component according to the proportion to obtain the sealing bottom coating, wherein the mixing ratio is 100mL/m²Coating the sealing primer on the surface of the bare concrete according to the proportion of the components, and fully drying and curing to form the sealing primer;

and step 3: uniformly mixing the raw materials in the photocatalytic top coat component according to the proportion to obtain the photocatalytic top coat, and uniformly mixing the raw materials on the surface of the sealing bottom coat according to the ratio of 120mL/m²The photocatalytic topcoat is coated according to the proportion of the above components, and the photocatalytic topcoat is formed after full drying and curing.

The sealing bottom coating component of the bare concrete protective agent provided by the invention contains fluorocarbon resin emulsion, fluorocarbon resin takes a firm C-F bond as a framework, compared with other resins, the fluorocarbon resin has better heat resistance, chemical resistance, cold resistance, low-temperature flexibility, weather resistance, electrical property and the like, and has non-adhesion property and non-wettability due to good crystallinity, so that the sealing bottom coating containing fluorocarbon resin has good compactness and hydrophobicity, can prevent concrete from being corroded by acid, alkali, salt, grease and the like, and can effectively prevent the surface of concrete from being carbonized.

On the other hand, the sealing bottom coating formed by fluorocarbon resin can also play a good bearing role for the photocatalytic surface coating on the sealing bottom coating, so that the photocatalytic surface coating which depends on the sealing bottom coating and contains the modified graphene loaded titanium dioxide powder has good weather resistance, and the photocatalytic degradation effect of the photocatalytic surface coating is well exerted.

In addition, the photocatalytic surface coating containing the modified graphene-loaded titanium dioxide powder can inhibit microorganisms such as lichen, algae and mold from growing on the surface of the fair-faced concrete by virtue of a photocatalytic sterilization effect, maintain the long-term surface cleanness of the fair-faced concrete, and meanwhile, can effectively degrade harmful substances of formaldehyde by virtue of photocatalysis, so that the toxicity on the surface of the fair-faced concrete is reduced.

The preparation and use of the modified graphene-loaded titanium dioxide powder are an important component in the invention, the modified graphene oxide is used as an adsorptive base material, then the titanium dioxide is loaded on the base material, and the photocatalytic property of the titanium dioxide is combined with the adsorptive base material, so that the photocatalytic surface coating can absorb formaldehyde and has the capability of photocatalytic degradation of the formaldehyde, thereby greatly improving the sterilization and disinfection effects of the photocatalytic surface coating;

when the graphene oxide is modified, the active functional groups on the surface of the graphene oxide are sequentially modified with dendritic polyphenyl dimethylsilane and hydrazine hydrate, the graphene oxide is subjected to two-step chemical modification, the polarity of the surface of the graphene oxide is reduced, the surface characteristics of the graphene oxide are improved, the problems that the small molecular graphene is difficult to disperse and uneven in dispersion in a system are solved, and the graphene oxide modified by amine can have strong adsorption performance, so that a strong adsorption basis is provided for the toxicity adsorption of a photocatalytic surface coating.

When the titanium dioxide load modified graphene oxide is carried out, the method is realized by adopting an in-situ grafting mode, but the titanium dioxide hydrosol prepared by the common hydrolysis method of the n-butyl titanate has the defects of easy agglomeration, wide particle size range and the like, so that the dialysis treatment is doped in the common in-situ grafting mode, and compared with the titanium dioxide hydrosol obtained by simple hydrolysis after the dialysis treatment, the particle size of the titanium dioxide hydrosol product is reduced, the particle size is uniform, and more beneficial photocatalysis performance is shown.

Testing the formaldehyde adsorption performance:

placing the modified graphene loaded titanium dioxide powder obtained in the embodiments 1-4 of the invention into brownDropping quantitative formaldehyde solution into the gas collecting bottle above the gas bottle, heating to volatilize completely, wherein the initial concentration of gaseous formaldehyde in the gas collecting bottle is 400 mg × m^-3(ii) a Measuring the formaldehyde adsorption performance of an adsorption sample obtained by loading titanium dioxide powder on four groups of modified graphene by adopting a formaldehyde analyzer;

after the test is finished, the four groups of adsorption samples are irradiated for 5 hours in the sun, then the formaldehyde adsorption is continuously measured, and the specific surface area of the four groups of adsorption samples is measured by adopting a specific surface area analyzer.

The results in the table show that the modified graphene-supported titanium dioxide powder provided by the invention has excellent formaldehyde adsorption performance, so that the modified graphene-supported titanium dioxide powder has good formaldehyde adsorption performance for modifying a photocatalytic coating in a protective agent.

The specific measurement results are shown in the following table:

testing of photocatalytic efficiency:

preparing four parts of bare concrete protective agent according to the above examples 1-4, preparing a group of commercially available bare concrete protective agent, selecting five groups of bare concrete test pieces with the same properties, the diameter of 30mm and the thickness of 10mm, respectively coating the four parts of bare concrete protective agent prepared in the examples 1-4 and one part of commercially available bare concrete protective agent according to the same coating mode and proportion to obtain 1-5 samples, and carrying out photocatalytic efficiency determination after the groups are cured for one week;

the photocatalytic efficiency of the sample was determined as follows:

the test uses NO with a gas concentration of 10ppm as a photocatalytic object and measures the concentration of NO using a gas analyzer. Placing 1-4 samples in a closed and light-transmitting experimental device, and placing a xenon lamp light source at a position opposite to the 1-4 samples;

firstly, the gas is introduced until the concentration is 0.3ppm, then the reaction is stopped, and after the reaction is kept still and stabilized for 40 minutes, the gas concentration is recorded as an initial value P₀(ii) a Then starting timing after turning on the light source to obtain the gas concentrations P of four time nodes of 30min, 60min, 90min and 120min respectively_iI is 1,2,3, 4; photocatalytic efficiency v_iThe calculation formula of (2) is as follows: v. of_i＝(P ₀-P _i)/P ₀X 100%, the calculation results are shown in the following table.

As can be seen from the table above, the bare concrete protective agent provided by the invention has good photocatalytic effect, and the photocatalytic performance of the bare concrete protective agent is far superior to that of common commercial bare concrete protective agents.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.