Weather-resistant external wall panel and preparation method thereof

Abstract

The invention relates to a weather-resistant outer wall panel which is formed by curing cement slurry. The cement slurry is prepared from the following components in percentage by weight: 25 to 35 percent of cement, 35 to 48 percent of quartz sand, 3 to 10 percent of secondary fly ash, 3 to 7 percent of silica fume, 0.6 to 3 percent of water reducing agent, 0.1 to 1 percent of defoaming agent, 0.8 to 2 percent of lithium salt exciting agent, 1 to 1.5 percent of graphene oxide grafted carbon fiber, 0.05 to 1.5 percent of carboxymethyl cellulose, 0.5 to 1 percent of nano TiO2, 0.05 to 0.1 percent of carbon black, 0.5 to 1 percent of phosphate flame retardant and 1 to 3 percent of compound inhibitor. 1.5-4% of a fluorocarbon modified acrylic emulsion, 0.05-0.5% of sodium gluconate, and 10-15% of water; the sum of the percentages of the components is 100%, and the compound inhibitor comprises a combination of molybdate and zinc powder. The external wall panel prepared by the invention has the advantages of high compressive strength, breaking strength, flame retardance, acid corrosion resistance, ultraviolet aging resistance, low long-term performance degradation rate and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a weather-resistant exterior wall panel and a preparation method thereof. Background Art

[0002] As the construction industry continues to develop, exterior wall panels, as key materials for building facades, have a direct impact on the safety, aesthetics and durability of buildings.

[0003] While existing exterior wall panels on the market can meet basic usage requirements, they still suffer from numerous performance shortcomings under complex climatic and environmental conditions. In industrially polluted areas, conventional exterior wall panels are susceptible to corrosion from corrosive gases such as acid rain and sulfur dioxide, causing the surface material to decompose and peel. In high-humidity environments, water vapor penetration weakens the panel's internal structure, shortening its service life. Long-term ultraviolet radiation can cause the panel material to age and fade, severely impacting the decorative effect. Furthermore, existing exterior wall panels generally suffer from insufficient compressive and flexural strength, making them susceptible to breakage when subjected to external forces. Furthermore, some panels exhibit poor flame retardancy, posing a fire safety hazard. These performance deficiencies not only increase building maintenance costs but can also lead to safety incidents.

[0004] Therefore, the development of a new type of weather-resistant exterior wall panel and its preparation method that can effectively enhance the resistance to acid and alkali corrosion, sulfur dioxide erosion, water vapor penetration, and ultraviolet aging, while improving the compressive strength, flexural resistance and flame retardancy has become an important issue that needs to be urgently addressed in the field of building materials. Summary of the Invention

[0005] (1) Technical issues to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a weather-resistant exterior wall panel and a preparation method thereof. The exterior wall panel has the advantages of high compressive strength, flexural strength, flame retardancy, acid corrosion resistance, UV aging resistance and low long-term performance decay rate. It solves the technical problems of low strength of existing exterior wall panel materials, resistance to acid gas corrosion, poor weather resistance and aging resistance, and flame retardancy, thereby improving the durability of the exterior wall panel.

[0007] (2) Technical solution

[0008] The invention provides a weather-resistant exterior wall panel, which is formed by curing cement slurry. The cement slurry has the following formula, calculated by mass percentage: 25-35% of cement, 35-48% of quartz sand, 3-10% of secondary fly ash, 3-7% of silica fume, 0.6-3% of water reducer, 0.1-1% of defoamer, 0.8-2% of lithium salt activator, 1-1.5% of graphene oxide grafted carbon fiber, 0.05-1.5% of carboxymethyl cellulose, 0.5-1% of nano-TiO2, 0.05-0.1% of carbon black, 0.5-1% of phosphate flame retardant, 1-3% of composite inhibitor, 1.5-4% of fluorocarbon modified acrylic emulsion, 0.05-0.5% of sodium gluconate, and 10-15% of water. The sum of the percentages of the aforementioned components is 100%, and the composite inhibitor comprises a combination of molybdate and zinc powder.

[0009] According to a preferred embodiment of the present invention, the water-cement ratio of the cement slurry is 0.38-0.46, and the mortar-sand ratio is 0.85-0.93. The water-cement ratio is the mass ratio of water to cement. The mortar-sand ratio is the mass ratio of the gel material (cement + fly ash + silica fume) to sand.

[0010] According to a preferred embodiment of the present invention, the cement is a mixture of one or more of grades 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R, and is low-heat cement or medium-heat cement; the silica fume particle size is 0.1-0.2 μm, and the silicon content is greater than 90%; the diameter of the graphene oxide grafted carbon fiber is 5-20 μm, and the length is 6-10 mm; the quartz sand particle size is less than 1 mm; and the quartz sand particle size of 40-70 mesh accounts for 60%.

[0011] Low-heat cement and medium-heat cement have lower hydration heats than ordinary Portland cement. Hydration heat refers to the amount of heat released during the hydration reaction between cement and water. Ordinary Portland cement has hydration heats of 50-80 kcal / g of cement after 7 and 28 days, respectively. Cement with a hydration heat lower than that of ordinary Portland cement is designated as low-heat or medium-heat cement.

[0012] By optimizing the quartz sand particle size and grading to achieve a 60% proportion of 40-70 mesh, the particle packing density is optimized, shrinkage cracks are reduced, and the mechanical strength, corrosion resistance, and drilling crack resistance of the panel are improved. The silica fume particle size is 0.1-0.2μm, and the silicon content is greater than 90%. Mineral admixtures such as fly ash and silica fume can improve the microstructure of the cement paste, increase early strength, shorten curing and demolding time, and enhance the panel material's later crack resistance.

[0013] The diameter of graphene oxide grafted carbon fiber (CF-GO) is 5-20μm and the length is 6-10mm; shorter fibers can be better dispersed and evenly distributed, thereby effectively improving the crack resistance and overall mechanical properties of the panel material.

[0014] According to a preferred embodiment of the present invention, the lithium salt activator is a combination of 0.1-0.3% LiOH and 0.7-1.7% Li2CO3; the Li2O content in the lithium salt activator is ≥95%.

[0015] Among them, LiOH can quickly stimulate the hydration reaction activity of cement, fly ash and silica fume, and Li2CO3 is used for long-term stability. The combination of the two lithium salts can balance the early and late strengths. LiOH is 0.1-0.3%, which can quickly provide a high alkaline environment (pH>13), dissolve tricalcium silicate and tricalcium aluminate in cement, accelerate early hydration, generate more CSH gel, and avoid flash setting. Li2CO3 can slowly release CO3 2- With Li + , and Ca in cement 2+ The reaction generates Li2Ca(CO3)2, which fills the pores and stabilizes the later strength development. The lithium salt activator Li2O content is ≥95%, avoiding impurities (such as K + 、Na + ) and other side effects.

[0016] According to a preferred embodiment of the present invention, the water reducer is a high-performance polycarboxylic acid water reducer (a pale yellow liquid) with a water reduction rate of 25-30%. This water reducer also serves as a fiber dispersant. The water reducer reduces the amount of water added, lowering the water-cement ratio (0.38-0.46), improving the panel material's performance while reducing shrinkage due to water evaporation.

[0017] According to a preferred embodiment of the present invention, the defoamer is a polyether defoamer (a colorless, transparent liquid) with a solids content of 40-50%. The defoamer can reduce the number of pores in the product, making the panel material surface smoother and more compact after polishing. This not only facilitates the printing of pattern layers or the composite decorative film layer, but also improves the panel material's resistance to environmental and weathering erosion, and enhances its flexural and compressive strengths.

[0018] According to a preferred embodiment of the present invention, the composite inhibitor is a combination of molybdate and zinc powder, with molybdate accounting for 0.5-1.5% and the balance being zinc powder; or the composite inhibitor is a combination of molybdate, zinc powder and zinc phosphate, with molybdate accounting for 0.5-1.5%, zinc phosphate accounting for 0.5-1%, and the balance being zinc powder. The combination of molybdate and zinc powder in the composite inhibitor can synergistically inhibit electrochemical corrosion and resist acidic gases (SO2 / NO x ); Adding a small amount of zinc phosphate to replace part of the zinc powder helps to form a more stable passivation film (Zn3(PO4)2), and the corrosion resistance against acid rain (pH=3) is improved by more than 30%.

[0019] According to a preferred embodiment of the present invention, the phosphate flame retardant is a combination of ammonium polyphosphate and bisphenol A bis(diphenyl phosphate). The phosphate flame retardant works synergistically with cement slurry to make the panel meet the GB 8624-2012A2 non-flammable standard. Ammonium polyphosphate APP and bisphenol A bis(diphenyl phosphate) BDP are both polymeric phosphate flame retardants. Compared with other phosphate flame retardants, they have the advantages of low migration and high thermal stability. They are suitable for exterior wall panel materials, have good weather resistance and no precipitation risk, and are halogen-free, low toxic, low smoke and low dripping. In addition, these two flame retardants also have the following synergistic flame retardant mechanisms: ① Complementary gas phase-condensation mechanism

[0020] APP: Decomposes under heat to generate polyphosphoric acid (dehydrating agent) and ammonia (oxygen dilution), promoting the formation of carbon layer (condensed phase flame retardant);

[0021] BDP: Releases phosphorus radicals (PO·) at high temperatures, capturing H· / OH· radicals in the combustion chain reaction (gas phase flame retardant).

[0022] After compounding, the limiting oxygen index (LOI) can reach more than 35% (pure APP is about 28%, pure BDP is about 30%).

[0023] ② Carbon layer strengthening and stability improvement

[0024] The carbon layer generated by APP is porous and fragile, while the aromatic ring structure of BDP can be cross-linked into a dense graphitized carbon layer that is resistant to high-temperature erosion (the residual carbon rate is significantly increased at 1000°C).

[0025] According to a preferred embodiment of the present invention, the fluorocarbon-modified acrylic emulsion is prepared by mixing methyl methacrylate (MMA) monomer, butyl acrylate (BA) monomer, a fluorinated monomer, an emulsifier, and water, and stirring to form a first emulsion; adding one-third of the first emulsion and a portion of the initiator to a reactor, and reacting at 60-75°C for 0.5-1.5 hours to form a seed emulsion; slowly adding the remaining first emulsion and initiator dropwise to the reactor over 2-3 hours, gradually heating the reactor to 80-85°C during the addition process to uniformly embed the fluorinated monomer into the polymer chains; cooling to 40°C, adjusting the pH to 7-8, and filtering to obtain an emulsion with a solids content of 40-50%. Fluorocarbon-modified acrylic emulsions can replace low-temperature aqueous emulsions, improving the material's UV resistance, stain resistance, elasticity, and adaptability to temperature changes.

[0026] MMA and BA monomers provide film-forming properties and flexibility. Preferably, the fluorinated monomer is perfluoroalkyl ethyl acrylate or dodecafluoroheptyl methacrylate, with the weight percentage of the fluorinated monomer in the polymer controlled at 5-15%. A higher percentage can lead to decreased emulsion stability. Fluorocarbon-modified acrylic emulsions serve as film-forming agents, combined with nano-TiO2 / SiO2, achieve thermal insulation, self-cleaning, and anti-fouling properties.

[0027] The combination of fluorocarbon-modified acrylic emulsion and graphene oxide grafted carbon fiber (CF-GO) gives the panel material both rigidity enhancement and flexibility toughening, which can significantly improve the crack resistance of the panel material. It can be dispersed in the cement slurry to absorb and disperse stress, reduce the occurrence and development of cracks, and avoid cracks in the panel material during drilling or installation.

[0028] In a second aspect, the present invention also relates to a method for preparing the above-mentioned weather-resistant exterior wall panel, which comprises:

[0029] S1. Stirring and mixing a water reducer, a phosphate flame retardant, graphene oxide grafted carbon fiber, a fluorocarbon modified acrylic emulsion, and 30-40% water to obtain a mixture A;

[0030] S2. Dry-mixing cement, quartz sand, secondary fly ash, silica fume, composite inhibitor, nano-TiO2, and carbon black silica fume to obtain a mixture B;

[0031] S3, mixing mixture A, mixture B, defoamer, lithium salt activator, carboxymethyl cellulose, sodium gluconate, and remaining water to obtain a first cement slurry;

[0032] S4. Pour the first cement slurry into a mold, flatten it in the mold with high-frequency vibration under vacuum, press it into shape at a pressure of 1.5-3 MPa, and steam cure it at 60-80° C. for 6-8 hours;

[0033] S5. Apply the second cement slurry to the surface 1-2 mm. The second cement slurry is made by adding 1% fluorocarbon-modified acrylic emulsion and 0.5-1% silica fume to the first cement slurry, and reducing the cement or quartz sand by 1.5-2% accordingly. Continue to cure at 37-42°C steam for 30-40 hours.

[0034] S6, demoulding, grinding and polishing to obtain the weather-resistant exterior wall panel.

[0035] (3) Beneficial effects

[0036] The present invention adopts cement, quartz sand, secondary fly ash and silica fume as the basic skeleton, and combines them with functional additives (lithium salt activator, graphene oxide grafted carbon fiber, etc.) to form a multi-dimensional performance control system, introduces fluorocarbon modified acrylic emulsion and nano-TiO2 to achieve surface weathering protection; improves structural strength and corrosion resistance through graphene oxide grafted carbon fiber and composite inhibitors; phosphate flame retardants and sodium gluconate synergistically optimize fire protection and construction performance.

[0037] Among them, fluorocarbon modified acrylic emulsion can form a low surface energy, UV-resistant fluorocarbon protective film on the surface of the panel, blocking the penetration of gases such as acid rain and SO2, while inhibiting polymer aging caused by ultraviolet rays. Nano-TiO2 uses the photocatalytic effect to decompose surface pollutants. Its nano-scale particle size fills the pores, improves the density of the matrix, and reduces the water vapor penetration path; anatase TiO2 has a strong absorption effect on ultraviolet rays and delays material aging. Composite inhibitor (molybdate + zinc powder): Molybdate forms a passivation film on the metal surface, and zinc powder provides electrochemical protection through the sacrificial anode effect. The two work together to inhibit the rust of steel bars inside the panel and resist acidic media such as acid rain (SO2 / NO x )erosion.

[0038] The lamellar structure of graphene oxide forms a "bridge-network" reinforcement system with carbon fibers. The carbon fibers bear the tensile load, while graphene oxide improves interfacial adhesion through π-π conjugation, thereby enhancing the compressive and flexural strength of the panel material. Lithium salt activators promote the pozzolanic reaction of active admixtures such as silica fume and fly ash, generating more CSH gels that fill pores and refine the crystal structure, improving matrix density and toughness. The lithium salt activator uses a combination of LiOH and Li2CO3 to balance early and late strength and reduce the risk of efflorescence. A low water-cement ratio to mortar-sand ratio reduces the porosity of the cement paste and, in combination with a polycarboxylate superplasticizer, reduces water consumption, resulting in a dense microstructure and improved compressive strength and impermeability.

[0039] Phosphate flame retardants decompose upon heating to form an expanded char layer, isolating oxygen and heat transfer while releasing non-combustible gases to dilute the concentration of combustible gases, achieving a flame retardant effect. Carboxymethyl cellulose and sodium gluconate are used to regulate the cement hydration rate, improve the workability of the slurry, reduce cracking during the molding process, and enhance later strength development.

[0040] When preparing the panel material, the surface slurry increases the content of fluorocarbon emulsion and silica fume to form a dense protective layer, strengthen the gradient structure of the skeleton layer, and enhance the surface's corrosion resistance. Vacuum vibration molding and staged steam curing (60-80°C initial curing + 37-42°C final curing) are used, combining dry mixing and wet dispersion processes to ensure uniform distribution of components and sufficient hydration of the cement, resulting in superior overall panel performance, including density, mechanical strength, and weather resistance. DETAILED DESCRIPTION

[0041] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific embodiments.

[0042] The weather-resistant exterior wall panel provided by the present invention is formed by curing cement slurry. The cement slurry has the following formula, calculated by mass percentage: 25-35% cement, 35-48% quartz sand, 3-10% secondary fly ash, 3-7% silica fume, 0.6-3% water reducer, 0.1-1% defoamer, 0.8-2% lithium salt activator, 1-1.5% graphene oxide grafted carbon fiber, 0.05-1.5% carboxymethyl cellulose, 0.5-1% nano-TiO2, 0.05-0.1% carbon black, 0.5-1% phosphate flame retardant, 1-3% composite inhibitor, 1.5-4% fluorocarbon modified acrylic emulsion, 0.05-0.5% sodium gluconate, and 10-15% water. The sum of the percentages of the aforementioned components is 100%, and the composite inhibitor comprises a combination of molybdate and zinc powder.

[0043] The above components have the following synergistic relationship:

[0044] (1) Weather resistance and strength synergy: The surface film formation of fluorocarbon emulsion and the filling effect of silica fume and nano-TiO2 reduce external erosion. The lithium salt activator and silica fume improve the density of the matrix, enhance the resistance to UV aging and weather resistance. The strength retention rate after 800h UV aging is above 90%.

[0045] (2) Anti-corrosion and anti-cracking synergy: The composite inhibitor prevents the corrosion and expansion of steel bars, and graphene oxide grafted carbon fiber inhibits matrix cracking.

[0046] (3) Flame retardant-mechanical property balance: Phosphate flame retardants are dispersed in the cement matrix at the nanometer level, forming a "flame retardant-protective" composite layer with fluorocarbon emulsion, thereby increasing the oxygen index to above 28%.

[0047] The preparation method of the weather-resistant exterior wall panel is as follows:

[0048] S1. Stirring and mixing a water reducer, a phosphate flame retardant, graphene oxide grafted carbon fiber, a fluorocarbon modified acrylic emulsion, and 30-40% water to obtain a mixture A;

[0049] S2. Dry-mixing cement, quartz sand, secondary fly ash, silica fume, composite inhibitor, nano-TiO2, and carbon black silica fume to obtain a mixture B;

[0050] S3, mixing mixture A, mixture B, defoamer, lithium salt activator, carboxymethyl cellulose, sodium gluconate, and remaining water to obtain a first cement slurry;

[0051] S4. Pour the first cement slurry into a mold, flatten it in the mold with high-frequency vibration under vacuum, press it into shape at a pressure of 1.5-3 MPa, and steam cure it at 60-80° C. for 6-8 hours;

[0052] S5. Apply the second cement slurry to the surface 1-2 mm. The second cement slurry is made by adding 1% fluorocarbon-modified acrylic emulsion and 0.5-1% silica fume to the first cement slurry, and reducing the cement or quartz sand by 1.5-2% accordingly. Continue to cure at 37-42°C steam for 30-40 hours.

[0053] S6, demoulding, grinding and polishing to obtain the weather-resistant exterior wall panel.

[0054] The curing process uses (60-80℃, 6-8h) instead of room temperature curing to reduce internal defects and improve early strength. The content of silica fume and fluorocarbon emulsion is increased in the surface layer (1-2mm) to form a dense protective layer and enhance the durability of the panel material. The total curing time of the panel is preferably 48h, matching the characteristics of the lithium salt excitation system to prevent early cracking. Vacuum vibration molding is mainly used to fully discharge the bubbles in the slurry, making the slurry more dense and reducing the porosity. Segmented curing promotes the full generation of CSH gel. Combined with the formula design, the panel's flexural strength reaches 12-15MPa, far exceeding traditional cement panels (8-10MPa). Improve panel strength and corrosion resistance.

[0055] The fluorocarbon-modified acrylic emulsion used in the following examples contains a fluorinated monomer, perfluoroalkylethyl acrylate FA-C6, with a polymer content of 10% and an emulsion solid content of 45%. The preparation process is as follows: the main monomer (MMA and BA in a 1:1 ratio), the fluorinated monomer FA-C6, SDS, and water are mixed and stirred at 2000 rpm for 30 minutes to form a stable pre-emulsion. One-third of the pre-emulsion and 30% of the initiator (ammonium persulfate APS) are added to a reactor and reacted at 75°C for 1 hour to produce a seed emulsion. The remaining pre-emulsion and the initiator (70% ammonium persulfate APS) are slowly added dropwise over a 3-hour period, and the temperature is gradually raised to 85°C to uniformly embed the fluorinated monomer into the polymer chains. The temperature is then lowered to 40°C, the pH is adjusted to 7-8, and the mixture is filtered to obtain the fluorocarbon-modified acrylic emulsion.

[0056] The present invention is further described below in conjunction with preferred embodiments.

[0057] Example 1

[0058] This embodiment provides a method for preparing a weather-resistant exterior wall panel, which includes:

[0059] (1) Prepare raw materials

[0060] The composition of the first cement slurry is as follows: cement: 26% (medium-heat cement with the designation 52.5R is selected);

[0061] Quartz sand: 45% (particle size less than 1mm, of which 40-70 mesh particle size accounts for 60%); secondary fly ash: 7%; silica fume: 5.85% (particle size 0.1-0.2μm, silicon content >90%); water reducer: 0.6% (polycarboxylic acid high-performance water reducer, water reduction rate 28%); defoamer: 0.1% (polyether defoamer, solid content 45%); lithium salt activator: 0.8% (composed of 0.1% LiOH and 0.7% Li2CO3, Li2O content ≥95%); graphene oxide grafted carbon fiber: 1% (diameter 10μm, length 8mm); carboxymethyl cellulose: 0.05%; nano-TiO2: 0.5%; carbon black: 0.05%;

[0062] Phosphate flame retardant: 0.5% (combination of APP and BDP); composite inhibitor: 1% (combination of 0.5% molybdate and 0.5% zinc powder); fluorocarbon-modified acrylic emulsion: 1.5%; sodium gluconate: 0.05%; water: 10%. The water-cement ratio is 0.38, and the mortar-sand ratio is 0.86.

[0063] (2) The preparation process is as follows:

[0064] ① A water reducer, a flame retardant, graphene oxide grafted carbon fiber, a fluorocarbon modified acrylic emulsion, and 40% water were stirred and mixed to obtain a mixture A.

[0065] ② Dry-mix cement, quartz sand, secondary fly ash, silica fume, composite inhibitor, nano-TiO2 and carbon black to obtain mixture B.

[0066] ③ Mix mixture A, mixture B, defoamer, lithium salt activator, carboxymethyl cellulose, sodium gluconate, and the remaining water, and stir to obtain a first cement slurry.

[0067] ④ Pour the first cement slurry into the mold, flatten it with high-frequency vibration in the mold under vacuum, press it into shape under a pressure of 2MPa, and cure it in 70℃ steam for 7h.

[0068] ⑤ Apply the second cement slurry on the surface 1-2mm. The second cement slurry is made by adding 1% fluorocarbon modified acrylic emulsion and 0.8% silica fume to the first cement slurry, reducing the cement by 1.3% and the quartz sand by 0.5%. Continue to cure in 40℃ steam for 35h.

[0069] S6. Demolding, grinding and polishing to obtain the weather-resistant exterior wall panel with a thickness of 4 cm.

[0070] Example 2

[0071] The formula of the first cement slurry of this embodiment is: cement: 29% (medium-heat cement with grade 42.5R is selected); quartz sand: 41.85%; secondary fly ash: 4%; silica fume: 5%; water reducer: 1% (polycarboxylic acid high-performance water reducer, water reduction rate 28%); defoamer: 0.2% (polyether defoamer, solid content 45%); lithium salt activator: 1% (composed of 0.1% LiOH and 0.7% Li2CO3, Li2O content ≥95%); graphene oxide grafted carbon fiber: 1.5%; carboxymethyl cellulose: 0.35%; nano-TiO2: 1%; carbon black: 0.05%; phosphate flame retardant: 0.5% (a combination of APP and BDP); composite inhibitor: 1% (a combination of 0.5% molybdate and 0.5% zinc powder); fluorocarbon modified acrylic emulsion: 1.5%; sodium gluconate: 0.05%; water: 12%. The water-cement ratio is 0.41, and the mortar-sand ratio is 0.91. The raw material specifications and preparation process are shown in Example 1.

[0072] Example 3

[0073] The formula of the first cement slurry of this embodiment is as follows: cement: 32% (medium-heat cement with the designation 42.5R is selected); quartz sand: 42%; secondary fly ash: 3%; silica fume: 3%; water reducer: 0.6% (polycarboxylic acid high-performance water reducer, water reduction rate 28%); defoamer: 0.2% (polyether defoamer, solid content 45%); lithium salt activator: 1% (composed of 0.1% LiOH and 0.7% Li2CO3, Li2 O content ≥95%); graphene oxide grafted carbon fiber: 1.2%; carboxymethyl cellulose: 0.1%; nano-TiO2: 0.5%; carbon black: 0.05%; phosphate flame retardant: 0.5% (a combination of APP and BDP); composite inhibitor: 1.5% (a combination of 0.5% molybdate and 0.5% zinc powder); fluorocarbon-modified acrylic emulsion: 1.5%; sodium gluconate: 0.05%; water: 12.8%. The water-cement ratio is 0.4, and the mortar-sand ratio is 0.90. For raw material specifications and preparation process, refer to Example 1.

[0074] Example 4

[0075] The formula of the cement slurry in this embodiment is the same as that in Example 1. In the preparation process, the panel material is formed in a mold at one time, and its surface layer is not subjected to a second cement slurry coating treatment; that is, the composition of the surface layer and the lower layer of the entire panel material remains consistent.

[0076] Example 5

[0077] The first cement slurry of this embodiment is formulated as follows: 30% cement (52.5R medium-heat cement), 42% quartz sand, 4% secondary fly ash, 4% silica fume, 1.2% polycarboxylate superplasticizer, 0.1% polyether defoamer, 1.2% lithium salt activator (0.2% LiOH + 1.0% Li2CO3), 1.2% graphene oxide grafted carbon fiber, 0.05% carboxymethyl cellulose, 0.5% nano-TiO2, 0.08% carbon black, 0.8% phosphate flame retardant (APP + BDDP), 1.2% composite inhibitor (0.6% molybdate + 0.4% zinc powder + 0.2% zinc phosphate), 1.5% fluorocarbon-modified acrylic emulsion, 0.05% sodium gluconate, and 12.12% water. The water-cement ratio is 0.40, and the mortar-sand ratio is 0.90. For the raw material specifications and preparation process, refer to Example 1.

[0078] Example 6

[0079] The first cement slurry of this embodiment has the following formula: 29.6% cement (62.5R medium-heat cement), 42% quartz sand, 4.4% secondary fly ash, 5% silica fume, 1.5% polycarboxylate superplasticizer, 0.1% polyether defoamer, 1.0% lithium salt activator (0.1% LiOH + 0.9% Li2CO3), 1.2% graphene oxide grafted carbon fiber, 0.05% carboxymethyl cellulose, 0.5% nano-TiO2, 0.06% carbon black, 0.7% phosphate flame retardant (APP + BDDP), 1.4% composite inhibitor (0.8% molybdate + 0.3% zinc powder + 0.3% zinc phosphate), 1.2% fluorocarbon-modified acrylic emulsion, 0.05% sodium gluconate, and 11.24% water. The water-cement ratio is 0.38, and the mortar-sand ratio is 0.93. For the raw material specifications and preparation process, refer to Example 1.

[0080] Comparative Example 1

[0081] In this comparative example, the graphene oxide grafted carbon fibers and nano-TiO2 used in Example 1 were omitted, and the proportion of secondary fly ash was increased accordingly. The remaining composition was the same as in Example 1.

[0082] Comparative Example 2

[0083] In this comparative example, the composite inhibitor used in Example 1 was deleted, and the proportion of silica fume was increased accordingly; the lithium salt activator was replaced with a mixed alkaline activator consisting of water glass and sodium hydroxide. The remaining compositions are the same as in Example 1.

[0084] Comparative Example 3

[0085] In this comparative example, the fluorocarbon-modified acrylic emulsion used in the cement slurry formulation of Example 1 was replaced with a common low-temperature aqueous emulsion. The remaining composition is the same as in Example 1.

[0086] Comparative Example 4

[0087] In this comparative example, the "phosphate flame retardant" used in Example 1 was replaced with a combination of TPP and RDP. The remaining composition is the same as in Example 1.

[0088] The panel materials (4 cm) prepared in the above-mentioned embodiments and comparative examples were tested for properties such as artificial weathering, SO2 corrosion test, compressive strength, flexural strength, limiting oxygen index (LOI), freeze-thaw cycle, color difference (ΔE), and crack width. The test methods are shown in Table 1:

[0089] Table 1:

[0090]

[0091]

[0092] The test results are shown in Table 2:

[0093]

[0094] In summary, the exterior wall panel materials prepared according to the various embodiments of the present invention have the following technical advantages:

[0095] 1. Weather resistance: Through the synergy of fluorocarbon coating and nano-TiO2, the panel can withstand artificial climate aging for ≥1000h, and there is no powdering or cracking on the surface.

[0096] 2. Resistance to acidic gas corrosion: After exposure to an environment with a SO2 concentration of 100ppm and a humidity of 90% for 120 days, the mass loss rate is ≤3%, which is significantly better than traditional cement panels (loss rate of 10-15%).

[0097] 3. Compressive and flexural strength: The compressive strength reaches 50-60MPa, and the flexural strength is 12-15MPa, which can meet the load-bearing requirements of the exterior walls of high-rise buildings.

[0098] 4. Anti-ultraviolet and crack resistance: Nano-TiO2 and graphene oxide grafted carbon fiber work together to make the panel's color difference ΔE ≤ 3 under ultraviolet light, and the crack resistance level reaches level three (crack width ≤ 0.1mm).

[0099] 5. Balance of comprehensive performance: good flame retardant performance and long-term durability (anti-freeze-thaw cycles ≥ 300 times).

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A weather-resistant exterior wall panel formed by curing cement slurry, characterized in that: The cement slurry comprises, by mass percentage, 25-35% cement, 35-48% quartz sand, 3-10% secondary fly ash, 3-7% silica fume, 0.6-3% water reducer, 0.1-1% defoamer, 0.8-2% lithium salt activator, 1-1.5% graphene oxide grafted carbon fiber, 0.05-1.5% carboxymethyl cellulose, 0.5-1% nano-TiO2, 0.05-0.1% carbon black, 0.5-1% phosphate flame retardant, 1-3% composite inhibitor, 1.5-4% fluorocarbon modified acrylic emulsion, 0.05-0.5% sodium gluconate, and 10-15% water; the sum of the percentages of the aforementioned components is 100%, and the composite inhibitor comprises a combination of molybdate and zinc powder.

2. The weather-resistant exterior wall panel according to claim 1, characterized in that: The water-cement ratio of the cement slurry is 0.38-0.46, and the mortar-sand ratio is 0.85-0.

93.

3. The panel material according to claim 2, characterized in that: The cement is a mixture of one or more of grades 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R, and is low-heat cement or medium-heat cement; the silica fume particle size is 0.1-0.2 μm, and the silicon content is greater than 90%; the diameter of the graphene oxide grafted carbon fiber is 5-20 μm, and the length is 6-10 mm; the quartz sand particle size is less than 1 mm; and the quartz sand particle size of 40-70 mesh accounts for 60%.

4. The weather-resistant exterior wall panel according to claim 1, characterized in that: The lithium salt activator is a combination of 0.1-0.3% LiOH and 0.7-1.7% Li2CO3; the content of Li2O in the lithium salt activator is ≥95%.

5. The weather-resistant exterior wall panel according to claim 1, characterized in that: The composite inhibitor is a combination of molybdate and zinc powder, with molybdate accounting for 0.5-1.5% and the balance being zinc powder; or the composite inhibitor is a combination of molybdate, zinc powder and zinc phosphate, with molybdate accounting for 0.5-1.5%, zinc phosphate accounting for 0.5-1%, and the balance being zinc powder.

6. The weather-resistant exterior wall panel according to claim 1, characterized in that: The phosphate flame retardant is a combination of ammonium polyphosphate and bisphenol A bis(diphenyl phosphate).

7. The weather-resistant exterior wall panel according to claim 1, characterized in that: The preparation method of the fluorocarbon-modified acrylic emulsion comprises the following steps: mixing methyl methacrylate (MMA) monomer, butyl acrylate (BA) monomer, fluorine-containing monomer, emulsifier and water, and stirring to form a first emulsion; adding 1 / 3 of the first emulsion and a portion of an initiator to a reactor, reacting at 60-75° C. for 0.5-1.5 hours to generate a seed emulsion; slowly dropping the remaining first emulsion and initiator into the reactor over 2-3 hours, gradually heating the reactor to 80-85° C. during the dropping process to uniformly embed the fluorine-containing monomer into polymer chains; cooling to 40° C., adjusting the pH to 7-8, and filtering to obtain an emulsion with a solid content of 40-50%.

8. The weather-resistant exterior wall panel according to claim 7, characterized in that: The fluorine-containing monomer is perfluoroalkyl ethyl acrylate or dodecafluoroheptyl methacrylate, and the mass proportion of the fluorine-containing monomer in the polymer is controlled to be 5-15%.

9. The weather-resistant exterior wall panel according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid high-performance water reducing agent with a water reduction rate of 25-30%; the defoaming agent is a polyether defoaming agent with a solid content of 40-50%.

10. The method for preparing the weather-resistant exterior wall panel according to any one of claims 1 to 9, characterized in that: It includes: S1. Stirring and mixing a water reducer, a phosphate flame retardant, graphene oxide grafted carbon fiber, a fluorocarbon modified acrylic emulsion, and 30-40% water to obtain a mixture A; S2. Dry-mixing cement, quartz sand, secondary fly ash, silica fume, composite inhibitor, nano-TiO2, and carbon black silica fume to obtain a mixture B; S3, mixing mixture A, mixture B, defoamer, lithium salt activator, carboxymethyl cellulose, sodium gluconate, and remaining water to obtain a first cement slurry; S4. Pour the first cement slurry into a mold, flatten it in the mold with high-frequency vibration under vacuum, press it into shape at a pressure of 1.5-3 MPa, and steam cure it at 60-80° C. for 6-8 hours; S5. Apply the second cement slurry to the surface 1-2 mm. The second cement slurry is made by adding 1% fluorocarbon-modified acrylic emulsion and 0.5-1% silica fume to the first cement slurry, and reducing the cement or quartz sand by 1.5-2% accordingly. Continue to cure at 37-42°C steam for 30-40 hours. S6, demoulding, grinding and polishing to obtain the weather-resistant exterior wall panel.

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