Graphite phase carbon nitride fireproof coating, and application and application method thereof

Abstract

The application relates to the technical field of tunnel fireproof materials, and provides a graphite phase carbon nitride fireproof coating and application and application method thereof.The coating comprises the following components in mass fractions: 40-60 parts of alkali-activated cement, 2-4 parts of redispersible latex powder, 2-4 parts of polyvinyl alcohol, 11-14 parts of expanded vermiculite, 11-14 parts of expanded perlite, 5-7 parts of sepiolite, 1-3 parts of hollow floating bead, 2-4 parts of magnesium hydroxide, 5-8 parts of aluminum hydroxide, and 0.5-2 parts of g-C3N4.The graphite phase carbon nitride fireproof coating provided by the application has excellent fireproof performance, anti-cracking performance, working performance, anti-permeation performance, superior thermal stability and chemical stability, a bonding strength of 0.31 MPa, a fire resistance limit of 3.1 h, and an efficiency of visible light catalytic removal of NO x of 232 mu mol / (h.m 2 ).

Description

[0001] This application is a divisional application. The original application number is 202211639839.0, the application date is December 20, 2022, and the invention title is "A graphite phase carbon nitride fire retardant coating and its application and application method". Technical Field

[0002] This invention relates to the field of tunnel fireproof materials technology, and in particular to a graphite phase carbon nitride fireproof coating and its application and application method. Background Technology

[0003] The preparation of tunnel fireproof coatings involves a large amount of cement materials. The "two grinding and one firing" process for ordinary silicate cement clinker emits significant amounts of carbon dioxide, severely hindering the achievement of the "dual carbon" target (carbon reduction and emission reduction). Patent CN201310157218.3 discloses a tunnel fireproof coating composed of geopolymer, expanded perlite, expanded vermiculite, brucite fiber, sepiolite, hydroxymethyl cellulose, and fatty alcohol sulfonate air-entraining agent. The geopolymer is composed of silica fume, kaolin, calcium-based bentonite, calcium oxide, sodium carbonate, sodium chloride, sodium sulfate, and low-calcium fly ash. This coating exhibits high bonding strength and excellent fire resistance. However, the high proportion of geopolymer and the complex preparation method hinder cost reduction. Patent CN201710401285.3 discloses an alkaline slag tunnel fireproof coating and its preparation method using a composite activator. The coating is composed of slag, polypropylene fiber, redispersible latex powder, polyvinyl alcohol, expanded vermiculite, expanded perlite, sepiolite, hollow cenospheres, magnesium hydroxide, and aluminum hydroxide, using water glass and neutral sodium salt as composite activators. This coating is environmentally friendly and possesses high bonding strength, good fire resistance, and freeze-thaw resistance. However, the addition of water glass shortens the drying time of the fireproof coating, affecting normal construction. On the other hand, with the progress of industrialization, a large amount of harmful and toxic pollutants are continuously emitted into the environment. Among them, nitrogen oxides (NOx) in automobile exhaust... x The massive emissions of NO have not only caused various environmental problems, but also posed a threat to human health. x With increasing emissions, traditional physicochemical treatment methods are no longer sufficient to meet the demands of modern society. Therefore, there is an urgent need to develop a method that can reduce carbon emissions and promote NO reduction. x A new type of fireproof coating for tunnels that purifies the environment. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide a graphite phase carbon nitride fire-retardant coating, its application and application method.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a graphitic carbon nitride fire-retardant coating comprising the following components in parts by weight:

[0007] Alkali-activated cement 40-60 parts, redispersible latex powder 2-4 parts, polyvinyl alcohol 2-4 parts, expanded vermiculite 11-14 parts, expanded perlite 11-14 parts, sepiolite 5-7 parts, hollow cenospheres 1-3 parts, magnesium hydroxide 2-4 parts, aluminum hydroxide 5-8 parts, g-C3N 40.5-2 parts.

[0008] Preferably, the alkali-activated cement comprises the following components in parts by weight: 85-95 parts of precursor and 5-15 parts of alkali activator;

[0009] The mass ratio of slag to nickel slag in the precursor is 30-40:60-70;

[0010] The mass ratio of potassium hydroxide to sodium carbonate in the alkaline activator is 40-50:50-60.

[0011] Preferably, the redispersible latex powder has a particle size of 125-145 mesh and a specific gravity of 7.5-8.5 mL / g; the polyvinyl alcohol has a particle size of 90-110 mesh.

[0012] Preferably, the expanded vermiculite has a particle size of 0.5–2 mm and a bulk density of 480–580 kg / m³. 3 The expanded perlite has a particle size of 2-4 mm and a bulk density of 65-85 kg / m³. 3 The density of the sepiolite is 600-700 kg / m³. 3 The hollow cenospheres have a particle size of 0.6–1.2 mm and a bulk density of 380–480 kg / m³. 3 .

[0013] Preferably, the magnesium hydroxide has an average particle size of 65–85 μm, and the aluminum hydroxide has an average particle size of 12–18 μm.

[0014] Preferably, the preparation method of g-C3N4 includes the following steps:

[0015] Melamine and ammonium chloride were mixed and then calcined and ground sequentially to obtain g-C3N4.

[0016] Preferably, the mass ratio of melamine to ammonium chloride is 4-8:20-40;

[0017] The calcination heating rate is 2-4℃ / min, the target calcination temperature is 500-600℃, and the holding time to reach the target temperature is 3.5-4.5h; the particle size of the grinding is 0.05-5μm.

[0018] The present invention also provides the application of the graphite phase carbon nitride fire-retardant coating in tunnels.

[0019] The present invention also provides a method for applying the graphite-phase carbon nitride fire-retardant coating in tunnels, comprising the following steps:

[0020] The graphite phase carbon nitride fire-retardant coating is mixed with water and applied and cured sequentially to obtain a fire-retardant coating.

[0021] Preferably, the mass ratio of water to graphite phase carbon nitride fire-retardant coating is 70-90:100; the thickness of the fire-retardant coating is 18-22 mm; the curing temperature is 18-22°C; and the curing time is 26-30 days.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention provides a graphitic carbon nitride fireproof coating that does not use silicate cement in its raw materials, thus avoiding the carbon dioxide release problem caused by the decomposition of calcium carbonate during silicate cement production, reducing the greenhouse effect and lowering carbon emissions; this invention uses a cheaper potassium hydroxide and sodium carbonate composite activator instead of the commonly used NaOH activator, reducing costs; this invention uses cheaper nickel slag to partially replace slag, realizing the utilization of solid waste from slag and nickel slag, reducing environmental pressure.

[0024] 2. In the graphite-phase carbon nitride fire-retardant coating provided by this invention, the composite activator contains K + Its high activity can improve the fire resistance of the coating; the graphite phase carbon nitride fire retardant coating provided by the present invention has better fire resistance, crack resistance, workability and impermeability, and low drying shrinkage; the fire retardant coating provided by the present invention has better thermal stability and chemical stability, and exhibits higher corrosion resistance to strong acids and strong alkalis.

[0025] 3. This invention provides a graphitic carbon nitride fire-retardant coating. Because nickel slag has lower activity than mineral slag and its hydration products form more slowly, it does not extensively coat the surface of g-C3N4, thus not inhibiting the photocatalytic effect of g-C3N4. The fire-retardant coating provided by this invention has excellent photocatalytic performance and can purify NO in the air. xThe effect is that the reaction conditions are mild (no special requirements such as temperature and pressure), the reaction speed is fast, the stability is high, and only photons are consumed in the reaction process, which has good environmental benefits. The fireproof coating provided by the present invention has a higher visible light utilization rate. Compared with the traditional photocatalyst TiO2, which can only undergo photocatalytic reaction under ultraviolet light, g-C3N4 broadens the utilization of the spectrum and effectively realizes the response and absorption of visible light, making it more suitable for air purification under lamplight in non-sunlight and highly polluted areas such as tunnels.

[0026] 4. The graphite-phase carbon nitride fire-retardant coating provided by this invention has a bonding strength of 0.31 MPa, a fire resistance limit of 3.1 h, and can remove NO by visible light catalytic removal. x The efficiency reached 232 μmol / (h·m 2 ). Detailed Implementation

[0027] This invention provides a graphitic carbon nitride fire-retardant coating comprising the following components in parts by weight:

[0028] Alkali-activated cement 40-60 parts, redispersible latex powder 2-4 parts, polyvinyl alcohol 2-4 parts, expanded vermiculite 11-14 parts, expanded perlite 11-14 parts, sepiolite 5-7 parts, hollow cenospheres 1-3 parts, magnesium hydroxide 2-4 parts, aluminum hydroxide 5-8 parts, g-C3N 40.5-2 parts.

[0029] In this invention, alkali-activated cement, redispersible latex powder, and polyvinyl alcohol are used as binders; expanded vermiculite, expanded perlite, sepiolite, and hollow cenospheres are used as thermal insulation materials; and magnesium hydroxide and aluminum hydroxide are used as additives. The polyvinyl alcohol is preferably a cold-soluble type.

[0030] In this invention, the mass fraction of alkali-activated cement is 40-60 parts, preferably 45-55 parts, and more preferably 48-52 parts.

[0031] In this invention, the redispersible latex powder is 2 to 4 parts by mass, preferably 2.5 to 3.5 parts, and more preferably 2.7 to 3.3 parts.

[0032] In this invention, the mass fraction of polyvinyl alcohol is 2 to 4 parts, preferably 2.5 to 3.5 parts, and more preferably 2.7 to 3.3 parts.

[0033] In this invention, the mass fraction of expanded vermiculite is 11 to 14 parts, preferably 12 to 13 parts, and more preferably 12.2 to 12.8 parts.

[0034] In this invention, the mass fraction of expanded perlite is 11 to 14 parts, preferably 12 to 13 parts, and more preferably 12.2 to 12.8 parts.

[0035] In this invention, the sepiolite is used in 5 to 7 parts by weight, preferably 5.5 to 6.5 parts, and more preferably 5.7 to 6.3 parts.

[0036] In this invention, the hollow float beads are 1 to 3 parts by mass, preferably 1.5 to 2.5 parts, and more preferably 1.7 to 2.3 parts.

[0037] In this invention, the mass fraction of magnesium hydroxide is 2 to 4 parts, preferably 2.5 to 3.5 parts, and more preferably 2.7 to 3.3 parts.

[0038] In this invention, the mass fraction of aluminum hydroxide is 5 to 8 parts, preferably 6 to 7 parts, and more preferably 6.2 to 6.8 parts.

[0039] In this invention, the mass fraction of g-C3N4 is 0.5 to 2 parts, preferably 1 to 1.5 parts, and more preferably 1.2 to 1.3 parts.

[0040] In this invention, the alkali-activated cement comprises the following components in parts by weight: 85-95 parts of precursor and 5-15 parts of alkali activator.

[0041] In this invention, the precursor is preferably 85 to 95 parts by mass, more preferably 87 to 93 parts by mass, and even more preferably 89 to 91 parts by mass.

[0042] In this invention, the mass fraction of the alkali activator is preferably 5 to 15 parts, more preferably 7 to 13 parts, and even more preferably 9 to 11 parts.

[0043] In this invention, the mass ratio of slag to nickel slag in the precursor is preferably 30-40:60-70, more preferably 32-38:62-68, and even more preferably 34-36:64-66.

[0044] In this invention, the mass ratio of potassium hydroxide to sodium carbonate in the alkaline activator is preferably 40-50:50-60, more preferably 42-48:52-58, and even more preferably 44-46:54-56.

[0045] In this invention, the particle size of the redispersible latex powder is preferably 125-145 mesh, more preferably 130-140 mesh, and even more preferably 132-138 mesh; the specific gravity is preferably 7.5-8.5 mL / g, more preferably 7.7-8.3 mL / g, and even more preferably 7.9-8.1 mL / g; the particle size of the polyvinyl alcohol is preferably 90-110 mesh, more preferably 95-105 mesh, and even more preferably 98-102 mesh.

[0046] In this invention, the particle size of the expanded vermiculite is preferably 0.5–2 mm, more preferably 1–1.5 mm, and even more preferably 1.1–1.4 mm; the bulk density of the expanded vermiculite is preferably 480–580 kg / m³. 3 A further preferred value is 500–560 kg / m³. 3 More preferably, it is 520–540 kg / m³. 3 The expanded perlite preferably has a particle size of 2-4 mm, more preferably 2.5-3.5 mm, and even more preferably 2.7-3.3 mm; the expanded perlite preferably has a bulk density of 65-85 kg / m³. 3 Further preferred is 70-80 kg / m 3 More preferably 72-78 kg / m 3 The preferred bulk density of the sepiolite is 600–700 kg / m³. 3 A further preferred value is 620–680 kg / m³. 3 More preferably, it is 640–660 kg / m 3 The hollow cenospheres preferably have a particle size of 0.6–1.2 mm, more preferably 0.8–1.0 mm, and even more preferably 0.85–0.95 mm; the hollow cenospheres preferably have a bulk density of 380–480 kg / m³. 3 Further preferred is 400–460 kg / m³ 3 More preferably, it is 420–440 kg / m³. 3 .

[0047] In this invention, the average particle size of the magnesium hydroxide is preferably 65-85 μm, more preferably 70-80 μm, and even more preferably 72-78 μm; the average particle size of the aluminum hydroxide is preferably 12-18 μm, more preferably 14-16 μm, and even more preferably 14.5-15.5 μm.

[0048] In this invention, the preparation method of g-C3N4 includes the following steps:

[0049] Melamine and ammonium chloride were mixed and then calcined and ground sequentially to obtain g-C3N4.

[0050] In this invention, the mass ratio of melamine to ammonium chloride is preferably 4-8:20-40, more preferably 5-7:25-35, and even more preferably 5.5-6.5:27-33.

[0051] In this invention, the sample is taken out after calcination, allowed to cool naturally, and then ground.

[0052] In this invention, the heating rate of the calcination is preferably 2-4℃ / min, more preferably 2.5-3.5℃ / min, and even more preferably 2.7-3.3℃ / min; the target temperature of the calcination is preferably 500-600℃, more preferably 520-580℃, and even more preferably 540-560℃; the holding time to reach the target temperature is preferably 3.5-4.5h, more preferably 3.7-4.3h, and even more preferably 3.9-4.1h; the target cooling temperature is preferably 20-30℃, more preferably 22-28℃, and even more preferably 24-26℃; the particle size of the grinding is preferably 0.05-5μm, more preferably 1-4.5μm, and even more preferably 2-3.5μm.

[0053] The present invention also provides the application of the graphite phase carbon nitride fire-retardant coating in tunnels.

[0054] The present invention also provides a method for applying the graphite-phase carbon nitride fire-retardant coating in tunnels, comprising the following steps:

[0055] The graphite phase carbon nitride fire-retardant coating is mixed with water and applied and cured sequentially to obtain a fire-retardant coating.

[0056] In this invention, the mixing is preferably performed by first mixing the alkali activator with water, and then adding other components.

[0057] In this invention, it is preferable to perform a base cleaning and water spraying process before applying the coating. The base cleaning involves removing dust, residue, and oil stains from the surface of the tunnel inner wall; the water spraying process involves spraying water onto the wall surface and then letting it dry until the surface is dry; the number of coating applications is preferably 2 to 4, more preferably 3.

[0058] In this invention, after the coating is applied, it is observed whether there is any peeling. If there is peeling, it needs to be recoated and then cured to obtain a fireproof coating.

[0059] In this invention, the mass ratio of water to graphite phase carbon nitride fire-retardant coating is preferably 70-90:100, more preferably 75-85:100, and even more preferably 77-83:100; the thickness of the fire-retardant coating is preferably 18-22 mm, more preferably 19-21 mm, and even more preferably 19.5-20.5 mm; the curing temperature is preferably 18-22°C, more preferably 19-21°C, and even more preferably 19.5-20.5°C; and the curing time is preferably 26-30 days, more preferably 27-29 days, and even more preferably 27.5-28.5 days.

[0060] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] 6g of melamine and 30g of ammonium chloride were thoroughly mixed, heated to 550℃ at a heating rate of 3℃ / min and held for 4 hours. After the holding time was completed, the mixture was naturally cooled to 25℃. The sample was then ground to obtain g-C3N4 with a particle size of 0.1μm.

[0063] Mix 6 kg of alkali activator (the mass ratio of potassium hydroxide to sodium carbonate in the alkali activator is 2:3) with 80 kg of water, then add 34 kg of precursor (the mass ratio of slag to nickel slag in the precursor is 2:3), 4 kg of redispersible latex powder with a specific gravity of 7.5 mL / g and a particle size of 125 mesh, 4 kg of cold-soluble polyvinyl alcohol with a particle size of 90 mesh, and 14 kg of polyvinyl alcohol with a particle size of 0.5 mm and a bulk density of 488 kg / m³. 3 Expanded vermiculite, 14kg, with a particle size of 2mm and a bulk density of 65kg / m³. 3 Expanded perlite, 7kg has a bulk density of 611kg / m³. 3 The sepiolite, with a particle size of 0.6 mm and a bulk density of 387 kg / m³, has a density of 387 kg / m³. 3 Hollow cenospheres, 4 kg of magnesium hydroxide with an average particle size of 65 μm, 8 kg of aluminum hydroxide with an average particle size of 12 μm, and 2 kg of g-C3N4 with a particle size of 0.1 μm were used to obtain a graphitic phase carbon nitride fire-retardant coating.

[0064] Clean the dust, residue, and oil stains from the surface of the inner wall of the tunnel. Spray water to moisten the surface of the wall and let it dry until there is no water on the surface. Then, manually apply the prepared fireproof coating to the surface of the inner wall of the tunnel in two coats. Observe whether there is any peeling. If there is any peeling, it needs to be touched up. Finally, cure at 20℃ for 28 days to obtain a fireproof coating with a thickness of 19mm.

[0065] The basic properties of the graphite-phase carbon nitride fire-retardant coating obtained in this embodiment were determined according to GB28375-2012 "Fire-retardant Coatings for Concrete Structures". Furthermore, based on the international standard for photocatalytic gas purification, ISO / DIS22197–1, a self-made visible light photocatalytic method was used to remove NO. x The testing apparatus was used to evaluate the air purification performance of the graphite-phase carbon nitride fire-retardant coating. The adhesive strength of the graphite-phase carbon nitride fire-retardant coating obtained in this embodiment was 0.24 MPa, the fire resistance limit was 3.1 h, and the visible light photocatalytic removal of NO... x The efficiency is 232 μmol / (h·m 2 ).

[0066] Example 2

[0067] 5g of melamine and 29g of ammonium chloride were thoroughly mixed, heated to 580℃ at a heating rate of 3.5℃ / min and held at that temperature for 4.2 hours. After the holding time was completed, the mixture was naturally cooled to 27℃. The sample was then ground to obtain g-C3N4 with a particle size of 2.5μm.

[0068] Mix 5 kg of alkali activator (the mass ratio of potassium hydroxide to sodium carbonate in the alkali activator is 9:11) with 85 kg of water, then add 45 kg of precursor (the mass ratio of slag to nickel slag in the precursor is 7:13), 3 kg of redispersible latex powder with a specific gravity of 8 mL / g and a particle size of 135 mesh, 3 kg of cold-soluble polyvinyl alcohol with a particle size of 100 mesh, and 13 kg of polyvinyl alcohol with a particle size of 1 mm and a bulk density of 531 kg / m³. 3 Expanded vermiculite, 13kg, with a particle size of 3mm and a bulk density of 75kg / m³. 3 Expanded perlite, 6kg has a bulk density of 656kg / m³. 3 The sepiolite, with a particle size of 0.9 mm and a bulk density of 434 kg / m³, weighs 2 kg. 3 Hollow cenospheres, 3 kg of magnesium hydroxide with an average particle size of 75 μm, 6 kg of aluminum hydroxide with an average particle size of 15 μm, and 1 kg of g-C3N4 with a particle size of 2.5 μm were used to obtain a graphitic phase carbon nitride fireproof coating.

[0069] Clean the dust, residue, and oil stains from the surface of the inner wall of the tunnel. Spray water to moisten the surface of the wall and let it dry until there is no water. Then, manually apply the prepared fireproof coating to the surface of the inner wall of the tunnel in three coats. Observe for any peeling. If any peeling occurs, it needs to be recoated. Finally, cure at 19.5℃ for 27 days to obtain a fireproof coating with a thickness of 20mm.

[0070] The basic properties of the graphite-phase carbon nitride fire-retardant coating obtained in this embodiment were determined according to GB28375-2012 "Fire-retardant Coatings for Concrete Structures". Furthermore, based on the international standard for photocatalytic gas purification, ISO / DIS22197–1, a self-made visible light photocatalytic method was used to remove NO. x The testing apparatus was used to evaluate the air purification performance of the graphite-phase carbon nitride fire-retardant coating. The adhesive strength of the graphite-phase carbon nitride fire-retardant coating obtained in this embodiment was 0.27 MPa, the fire resistance limit was 2.9 h, and the visible light photocatalytic removal of NO... x The efficiency is 141 μmol / (h·m 2 ).

[0071] Example 3

[0072] 7.5g of melamine and 36g of ammonium chloride were thoroughly mixed, heated to 520℃ at a heating rate of 2.5℃ / min and held at that temperature for 3.7 hours. After the holding time was completed, the mixture was naturally cooled to 24℃. The sample was then ground to obtain g-C3N4 with a particle size of 5μm.

[0073] Mix 3 kg of alkali activator (the mass ratio of potassium hydroxide to sodium carbonate in the alkali activator is 1:1) with 75 kg of water, then add 57 kg of precursor (the mass ratio of slag to nickel slag in the precursor is 3:7), 2 kg of redispersible latex powder with a specific gravity of 8.5 mL / g and a particle size of 145 mesh, 2 kg of cold-soluble polyvinyl alcohol with a particle size of 110 mesh, and 11 kg of polyvinyl alcohol with a particle size of 2 mm and a bulk density of 576 kg / m³. 3 Expanded vermiculite, 11kg, with a particle size of 4mm and a bulk density of 85kg / m³. 3 Expanded perlite, 5kg has a bulk density of 696kg / m³. 3 The sepiolite has a particle size of 1.2 mm and a bulk density of 472 kg / m³. 3 Hollow cenospheres, 2 kg of magnesium hydroxide with an average particle size of 85 μm, 5.5 kg of aluminum hydroxide with an average particle size of 18 μm, and 0.5 kg of g-C3N4 with a particle size of 5 μm were used to obtain a graphitic phase carbon nitride fireproof coating.

[0074] Clean the dust, residue, and oil stains from the surface of the inner wall of the tunnel. Spray water to moisten the surface of the wall and let it dry until there is no water. Then, manually apply the prepared fireproof coating to the surface of the inner wall of the tunnel in two coats. Observe for any peeling. If peeling occurs, recoat the affected area. Finally, cure at 20.5℃ for 28.5 days to obtain a fireproof coating with a thickness of 21mm.

[0075] The basic properties of the graphite-phase carbon nitride fire-retardant coating obtained in this embodiment were determined according to GB28375-2012 "Fire-retardant Coatings for Concrete Structures". Furthermore, based on the international standard for photocatalytic gas purification, ISO / DIS22197–1, a self-made visible light photocatalytic method was used to remove NO. x The testing apparatus was used to evaluate the air purification performance of the graphite-phase carbon nitride fire-retardant coating. The graphite-phase carbon nitride fire-retardant coating obtained in this embodiment showed a bond strength of 0.31 MPa, a fire resistance limit of 2.7 h, and visible light photocatalytic removal of NO. x The efficiency is 87 μmol / (h·m 2 ).

[0076] Comparative Example 1

[0077] Mix 3 kg of alkali activator (the mass ratio of potassium hydroxide to sodium carbonate in the alkali activator is 1:1) with 75 kg of water, then add 57 kg of precursor (the mass ratio of slag to nickel slag in the precursor is 3:7), 2 kg of redispersible latex powder with a specific gravity of 8.5 mL / g and a particle size of 145 mesh, 2 kg of cold-soluble polyvinyl alcohol with a particle size of 110 mesh, and 11 kg of polyvinyl alcohol with a particle size of 2 mm and a bulk density of 576 kg / m³. 3 Expanded vermiculite, 11kg, with a particle size of 4mm and a bulk density of 85kg / m³. 3 Expanded perlite, 5kg has a bulk density of 696kg / m³. 3 The sepiolite has a particle size of 1.2 mm and a bulk density of 472 kg / m³. 3 Hollow cenospheres, 2 kg of magnesium hydroxide with an average particle size of 85 μm, 5.5 kg of aluminum hydroxide with an average particle size of 18 μm, and 0.5 kg of titanium dioxide were used to obtain a titanium dioxide fire-retardant coating.

[0078] Clean the dust, residue, and oil stains from the surface of the inner wall of the tunnel. Spray water to moisten the surface of the wall and let it dry until there is no water. Then, manually apply the prepared fireproof coating to the surface of the inner wall of the tunnel in two coats. Observe for any peeling. If peeling occurs, recoat the affected area. Finally, cure at 20.5℃ for 28.5 days to obtain a fireproof coating with a thickness of 21mm.

[0079] The basic properties of the titanium dioxide fire-retardant coating obtained in this comparative example were determined according to GB28375-2012 "Fire-retardant Coatings for Concrete Structures". Furthermore, based on the international standard for photocatalytic gas purification, ISO / DIS22197–1, a self-made visible light photocatalytic method was used to remove NO. x The testing apparatus was used to evaluate the air purification performance of titanium dioxide fire-retardant coatings. The results showed that the titanium dioxide fire-retardant coating had a bond strength of 0.29 MPa, a fire resistance limit of 2.6 h, and achieved visible light photocatalytic removal of NO. x The efficiency is 57 μmol / (h·m 2 ).

[0080] As can be seen from the above embodiments, the present invention provides a graphitic carbon nitride fire-retardant coating with excellent fire resistance, crack resistance, workability, impermeability, and superior thermal and chemical stability. The bonding strength reaches 0.31 MPa, the fire resistance limit reaches 3.1 h, and it exhibits visible light photocatalytic removal of NO. x The efficiency reached 232 μmol / (h·m 2 ).

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A graphite-phase carbon nitride fire-retardant coating, characterized in that, It contains the following components: Alkali-activated cement 40kg, redispersible latex powder 4kg, polyvinyl alcohol 4kg, expanded vermiculite 14kg, expanded perlite 14kg, sepiolite 7kg, hollow cenospheres 3kg, magnesium hydroxide 4kg, aluminum hydroxide 8kg, g-C3N4 2kg; The alkali-activated cement comprises the following components: 34 kg of precursor and 6 kg of alkali activator; The mass ratio of slag to nickel slag in the precursor is 2:3; The mass ratio of potassium hydroxide to sodium carbonate in the alkaline activator is 2:3; The preparation method of the g-C3N4 includes the following steps: Melamine and ammonium chloride were mixed and then calcined and ground sequentially to obtain g-C3N4. The mass ratio of melamine to ammonium chloride is 6:30; The calcination heating rate is 3℃ / min, the target calcination temperature is 550℃, and the holding time to reach the target temperature is 4h; the particle size of the grinding is 0.1μm.

2. The graphite-phase carbon nitride fire-retardant coating as described in claim 1, characterized in that, The redispersible latex powder has a particle size of 125 mesh and a specific gravity of 7.5 mL / g; the polyvinyl alcohol has a particle size of 90 mesh.

3. The graphite-phase carbon nitride fire-retardant coating as described in claim 2, characterized in that, The expanded vermiculite has a particle size of 0.5 mm and a bulk density of 488 kg / m³. 3 The expanded perlite has a particle size of 2 mm and a bulk density of 65 kg / m³. 3 The density of the sepiolite is 611 kg / m³. 3 The hollow cenospheres have a particle size of 0.6 mm and a bulk density of 387 kg / m³. 3 .

4. The graphite-phase carbon nitride fire-retardant coating as described in claim 3, characterized in that, The magnesium hydroxide has an average particle size of 65 μm; the aluminum hydroxide has an average particle size of 12 μm.

5. The application of the graphite phase carbon nitride fire-retardant coating according to any one of claims 1 to 4 in tunnels.

6. The method for applying the graphite-phase carbon nitride fire-retardant coating according to any one of claims 1 to 4 in tunnels, characterized in that, Includes the following steps: The graphite phase carbon nitride fire-retardant coating is mixed with water and applied and cured sequentially to obtain a fire-retardant coating.

7. The application method as described in claim 6, characterized in that, The mass ratio of water to graphite phase carbon nitride fire-retardant coating is 80:100; the thickness of the fire-retardant coating is 19 mm; the curing temperature is 20°C; and the curing time is 28 days.