Fiber-reinforced UHPC decorative plate and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to a fiber-reinforced UHPC decorative plate and a preparation method thereof. The preparation method comprises the following steps: S1, adding Portland cement, mineral powder, fly ash, silica fume, quartz sand, composite fibers and water into a stirrer, stirring for 20-30 minutes, adding a water reducing agent and an air entraining agent, and uniformly stirring to obtain a mixture; the composite fiber is formed by compounding 2-6 parts by mass of silicon dioxide grafted polyvinyl alcohol fiber and 3-9 parts by mass of modified carbon fiber; and S2, a concrete release agent is evenly sprayed on the inner surface of a prefabricated mold, the UHPC obtained in the step S1 is poured into the prefabricated mold, demolding is conducted after vibration forming and curing are conducted, and the fiber-reinforced UHPC decorative plate is obtained and has the excellent mechanical property and durability.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a fiber-reinforced UHPC decorative panel and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the continuous development of building materials, ultra-high performance concrete (UHPC) has been widely used in the field of building decoration due to its excellent mechanical properties, durability, and aesthetics. Fiber-reinforced UHPC decorative panels, as a new type of building material, combine the advantages of UHPC with the characteristics of fiber reinforcement, possessing better crack resistance and toughness, making them widely used in exterior wall decoration, landscape facilities, and other applications.

[0003] However, existing technologies still present some specific problems in the preparation methods and applications of fiber-reinforced UHPC decorative panels. Firstly, the interfacial bonding performance between the fiber and the UHPC matrix is ​​a key factor affecting the performance of fiber-reinforced UHPC decorative panels. In existing technologies, the interfacial bonding strength between the fiber and the matrix sometimes fails to reach an ideal level, causing the fiber to easily pull out of the matrix under stress, rather than fully utilizing its tensile and reinforcing properties. This not only affects the mechanical properties of the material but may also lead to cracks or damage to the decorative panel during use. Although UHPC itself has high durability, the fiber may age, corrode, or degrade under long-term stress, moisture, or corrosive environments, thereby reducing the durability and service life of the decorative panel.

[0004] Therefore, we propose a fiber-reinforced UHPC decorative panel and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber-reinforced UHPC decorative panel and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a fiber-reinforced UHPC decorative panel includes the following steps: Step S1: Add silicate cement, mineral powder, fly ash, silica fume, quartz sand, composite fiber and water into a mixer and mix for 20-30 minutes. Then add water-reducing agent and air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 2-6 parts by weight of silica-grafted polyvinyl alcohol fiber and 3-9 parts by weight of modified carbon fiber. Step S2: Spray the concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, cure and demold to obtain fiber reinforced UHPC decorative panel.

[0007] A more optimized scheme is that the mixture comprises the following weight components: 300-500 parts silicate cement, 700-900 parts quartz sand, 70-90 parts mineral powder, 80-100 parts fly ash, 10-20 parts silica fume, 160-220 parts water, 20-50 parts water-reducing agent, 3-6 parts air-entraining agent, and 5-15 parts composite fiber.

[0008] A more optimized method for preparing the silica-grafted polyvinyl alcohol fiber is as follows: Nano-silica and toluene are stirred evenly and ultrasonically dispersed for 30-50 min. A mixed solution of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and deionized water is added and refluxed for 6-8 h. Triethylenediamine is added and mixed evenly. Polyvinyl alcohol fibers are then added and reacted at 110-120℃ for 2-5 h to obtain silica-grafted polyvinyl alcohol fibers.

[0009] In a more optimized scheme, the mass ratio of the nano-silica, toluene, 3-(2,3-epoxypropoxy)propyltrimethoxysilane and deionized water is 1:(25-30):(0.6-0.8):(0.3-0.5).

[0010] In a more optimized scheme, the amount of triethylenediamine used is 6-12% of the mass of nano-silica.

[0011] In a more optimized scheme, the amount of polyvinyl alcohol fiber used is 0.5-1.0 times the mass of nano-silica.

[0012] A more optimized approach is to prepare the modified carbon fiber using the following process: Step A: Place the pretreated carbon fiber in a concentrated nitric acid solution, heat it in an oil bath at 70-80℃ for 2-4 hours, then rinse it with deionized water until neutral, and dry it to obtain carboxylated carbon fiber. Step B: Mix polyethyleneimine and phosphate buffer evenly, adjust the pH of the system to 5.0-5.5 with nitric acid, add gallic acid and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 2-3 hours to obtain a modified polyethyleneimine solution; Step C: Immerse the carboxylated carbon fibers in a modified polyethyleneimine solution for 1-2 hours, remove and dry them, then immerse them in a graphene oxide solution for 2-4 hours, remove and dry them to obtain the modified carbon fibers.

[0013] In a more optimized scheme, in step A, the mass ratio of pretreated carbon fiber to concentrated nitric acid is 1:(2-4).

[0014] A more optimized approach is to prepare the pretreated carbon fiber as follows: place the carbon fiber in acetone, extract for 44-48 hours, and then wash and dry to obtain the pretreated carbon fiber.

[0015] In a more optimized scheme, the mass ratio of carbon fiber to acetone is 1:(20-40).

[0016] In a more optimized scheme, in step B, the mass ratio of polyethyleneimine, phosphate buffer, gallic acid and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimine is 1:(15-20):(0.5-0.8):(0.9-1.0), and the concentration of nitric acid is 1 mol / L.

[0017] In a more optimized scheme, in step C, the mass ratio of carboxylated carbon fiber, modified polyethyleneimine solution, and graphene oxide solution is 1:(10-20):(15-30), and the concentration of graphene oxide solution is 8-10 mg / mL.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a fiber-reinforced UHPC decorative panel and its preparation method. The composite fiber is obtained by grafting silica-grafted polyvinyl alcohol fibers with modified carbon fibers. The modified carbon fibers, with their high elastic modulus, serve as the "main skeleton," effectively bearing the load and improving tensile and compressive strength. The silica-grafted polyvinyl alcohol fibers significantly enhance the material's toughness, bending resistance, and fatigue resistance. The two components work synergistically, giving the composite fiber both toughness and strength. Under external forces, it effectively absorbs and disperses stress, reducing the material's tendency for brittle fracture and minimizing moisture penetration defects caused by cracking. This ensures the material's stability in humid environments, thereby improving the mechanical properties and durability of the ultra-high performance concrete (UHPC) decorative panel.

[0019] In this scheme, a layer of nano-silica particles is grafted onto the surface of polyvinyl alcohol (PVA) fibers using a chemical grafting method. Silica nanoparticles are often added to cement matrices and can undergo a hydration reaction with calcium hydroxide produced during cement hydration, generating a stable colloidal substance, CSH gel. This significantly improves the strength of the cement matrix and effectively enhances the interfacial interaction between PVA fibers and the cement matrix. Gallic acid (GA), rich in phenolic hydroxyl groups, reacts with polyethyleneimine (PEI) to form PEI-GA, which combines the strong positive adsorption properties of PEI with the high reactivity of the pyrogallol structure. The scheme selects modified polyvinyl... Ethyleneimide is used as a bridging agent to modify the surface of carbon fibers to improve the effective introduction of graphene oxide (GO). On the one hand, the oxygen-containing functional groups of GO promote the generation of hydration products on the carbon fiber surface, significantly improving its surface inertness and thus enhancing the adhesion between carbon fibers and hydration products. On the other hand, the rough structure of GO increases the contact area between carbon fibers and hydration products, effectively improving the interfacial compatibility between carbon fibers and cement matrix. In addition, GO sheets form a nanoscale physical barrier in the interfacial region, which greatly prolongs the path of water penetration (maze effect) and further reduces the permeability of the interfacial region. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, all quantities below are by weight. It should be noted that there are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples include (in this embodiment): Silicate cement: P·O 42.5 grade, sourced from Hunan Xindingli New Material Technology Co., Ltd.; Mineral powder: S95 grade mineral powder, sourced from Shandong Kefa Building Materials Co., Ltd.; Fly ash: Grade 1 fly ash, particle size 200-300 mesh, sourced from Jining Hengzhi New Building Materials Co., Ltd.; Silica fume: Model GWF13, particle size 350-400 mesh, sourced from Hebei Siruit Mineral Products Co., Ltd.; Quartz sand: particle size 40-70 mesh, sourced from Changxing Qingsheng Calcium Industry Co., Ltd.; Water-reducing agent: Polycarboxylate water-reducing agent, model PC-1030; Air-entraining agent: Sodium rosinate; Concrete Release agent: brand name Ausler AS-931; Polyvinyl alcohol fiber: length 8-12mm, single filament diameter 5μm, sourced from Nanjing Panier Technology Industry Co., Ltd.; Nano silica: particle size 20-30nm, sourced from Shanghai Xiaohuang Nanotechnology Co., Ltd.; Carbon fiber: T700 short-cut carbon fiber, length 3mm, sourced from Shanghai Lishuo Composite Materials Technology Co., Ltd.; Graphene oxide: model DN-20DY, average thickness 1-3nm, diameter 4-7μm, number of layers 2-5, sourced from Zhejiang Zhitai Nanomaterials Co., Ltd.

[0022] Example 1: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 300 parts silicate cement, 70 parts mineral powder, 80 parts fly ash, 10 parts silica fume, 700 parts quartz sand, 5 parts composite fiber, and 160 parts water to a mixer and mix for 20 minutes. Then add 20 parts water-reducing agent and 3 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 2 parts silica-grafted polyvinyl alcohol fiber and 3 parts modified carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Four parts of nano-silica and 100 parts of toluene were stirred evenly and ultrasonically dispersed for 30 min. A mixed solution of 2.4 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 1.2 parts of deionized water was added and refluxed for 6 h. 0.24 parts of triethylenediamine were added and mixed evenly. Then, 2 parts of polyvinyl alcohol fiber were added and reacted at 110 °C for 2 h to obtain silica-grafted polyvinyl alcohol fiber. The preparation process of modified carbon fiber is as follows: Step A: Place 3 parts of carbon fiber in 60 parts of acetone and extract for 44 hours. After washing and drying, pretreated carbon fiber is obtained. Place 3 parts of pretreated carbon fiber in 6 parts of concentrated nitric acid solution and heat in an oil bath at 70°C for 2 hours. Then rinse with deionized water until neutral and dry to obtain carboxylated carbon fiber. Step B: Mix 2 parts of polyethyleneimine and 30 parts of phosphate buffer evenly, adjust the pH of the system to 5.0 with 1 mol / L nitric acid, add 1 part of gallic acid and 1.8 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 2 h to obtain a modified polyethyleneimine solution. Step C: Immerse 3 parts of carboxylated carbon fiber in 30 parts of modified polyethyleneimine solution for 1 hour, remove and dry, then immerse in 45 parts of 8 mg / mL graphene oxide solution for 2 hours, remove and dry to obtain modified carbon fiber.

[0023] Example 2: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 400 parts silicate cement, 80 parts mineral powder, 90 parts fly ash, 15 parts silica fume, 800 parts quartz sand, 10 parts composite fiber, and 200 parts water to a mixer and mix for 25 minutes. Then add 30 parts water-reducing agent and 5 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 3 parts silica-grafted polyvinyl alcohol fiber and 7 parts modified carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Five parts of nano-silica and 140 parts of toluene were stirred evenly and ultrasonically dispersed for 40 min. A mixed solution of 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 2 parts of deionized water was added and refluxed for 7 h. 0.5 parts of triethylenediamine were added and mixed evenly. Then, 4 parts of polyvinyl alcohol fiber were added and reacted at 115 °C for 3 h to obtain silica-grafted polyvinyl alcohol fiber. The preparation process of modified carbon fiber is as follows: Step A: Place 7 parts of carbon fiber in 210 parts of acetone and extract for 46 hours. After washing and drying, pretreated carbon fiber is obtained. Place 7 parts of pretreated carbon fiber in 21 parts of concentrated nitric acid solution and heat in an oil bath at 75°C for 3 hours. Then rinse with deionized water until neutral and dry to obtain carboxylated carbon fiber. Step B: Mix 5 parts of polyethyleneimine and 100 parts of phosphate buffer evenly, adjust the pH of the system to 5.2 with 1 mol / L nitric acid, add 3.5 parts of gallic acid and 4.8 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 2.5 h to obtain a modified polyethyleneimine solution; Step C: Immerse 7 parts of carboxylated carbon fiber in 100 parts of modified polyethyleneimine solution for 1.5 hours, remove and dry, then immerse in 126 parts of 9 mg / mL graphene oxide solution for 3 hours, remove and dry to obtain modified carbon fiber.

[0024] Example 3: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 500 parts silicate cement, 90 parts mineral powder, 100 parts fly ash, 20 parts silica fume, 900 parts quartz sand, 15 parts composite fiber, and 220 parts water to a mixer and mix for 30 minutes. Then add 50 parts water-reducing agent and 6 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 6 parts silica-grafted polyvinyl alcohol fiber and 9 parts modified carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Six parts of nano-silica and 180 parts of toluene were stirred evenly and ultrasonically dispersed for 50 min. A mixed solution of 4.8 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 3 parts of deionized water was added and refluxed for 8 h. 0.72 parts of triethylenediamine were added and mixed evenly. Then, 6 parts of polyvinyl alcohol fiber were added and reacted at 120 °C for 5 h to obtain silica-grafted polyvinyl alcohol fiber. The preparation process of modified carbon fiber is as follows: Step A: Place 9 parts of carbon fiber in 360 parts of acetone and extract for 48 hours. After washing and drying, pretreated carbon fiber is obtained. Place 9 parts of pretreated carbon fiber in 36 parts of concentrated nitric acid solution and heat in an oil bath at 80°C for 4 hours. Then rinse with deionized water until neutral and dry to obtain carboxylated carbon fiber. Step B: Mix 9 parts of polyethyleneimine and 180 parts of phosphate buffer evenly, adjust the pH of the system to 5.5 with 1 mol / L nitric acid, add 7.2 parts of gallic acid and 9 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 3 h to obtain a modified polyethyleneimine solution; Step C: Immerse 9 parts of carboxylated carbon fiber in 180 parts of modified polyethyleneimine solution for 2 hours, remove and dry, then immerse in 270 parts of 10 mg / mL graphene oxide solution for 4 hours, remove and dry to obtain modified carbon fiber.

[0025] Comparative Example 1: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 400 parts silicate cement, 80 parts mineral powder, 90 parts fly ash, 15 parts silica fume, 800 parts quartz sand, 3 parts silica-grafted polyvinyl alcohol fiber and 200 parts water to a mixer and mix for 25 minutes. Then add 30 parts water-reducing agent and 5 parts air-entraining agent and mix evenly to obtain the mixture. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Five parts of nano-silica and 140 parts of toluene were stirred evenly and ultrasonically dispersed for 40 min. A mixed solution of 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 2 parts of deionized water was added and refluxed for 7 h. 0.5 parts of triethylenediamine were added and mixed evenly. Then, 4 parts of polyvinyl alcohol fiber were added and reacted at 115 °C for 3 h to obtain silica-grafted polyvinyl alcohol fiber. Comparative Example 1 is based on Example 2, but no modified carbon fiber was introduced in Comparative Example 1. The remaining process steps and reaction parameters are the same as in Example 2.

[0026] Comparative Example 2: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 400 parts silicate cement, 80 parts mineral powder, 90 parts fly ash, 15 parts silica fume, 800 parts quartz sand, 10 parts composite fiber, and 200 parts water to a mixer and mix for 25 minutes. Then add 30 parts water-reducing agent and 5 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 3 parts silica-grafted polyvinyl alcohol fiber and 7 parts carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Five parts of nano-silica and 140 parts of toluene were stirred evenly and ultrasonically dispersed for 40 min. A mixed solution of 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 2 parts of deionized water was added and refluxed for 7 h. 0.5 parts of triethylenediamine were added and mixed evenly. Then, 4 parts of polyvinyl alcohol fiber were added and reacted at 115 °C for 3 h to obtain silica-grafted polyvinyl alcohol fiber. Comparative Example 2 is based on Example 2, except that the modified carbon fiber is replaced with the same mass of carbon fiber, and the remaining process steps and reaction parameters are the same as in Example 2.

[0027] Comparative Example 3: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 400 parts silicate cement, 80 parts mineral powder, 90 parts fly ash, 15 parts silica fume, 800 parts quartz sand, 10 parts composite fiber, and 200 parts water to a mixer and mix for 25 minutes. Then add 30 parts water-reducing agent and 5 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 3 parts silica-grafted polyvinyl alcohol fiber and 7 parts modified carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. The preparation method of silica-grafted polyvinyl alcohol fibers is as follows: Five parts of nano-silica and 140 parts of toluene were stirred evenly and ultrasonically dispersed for 40 min. A mixed solution of 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 2 parts of deionized water was added and refluxed for 7 h. 0.5 parts of triethylenediamine were added and mixed evenly. Then, 4 parts of polyvinyl alcohol fiber were added and reacted at 115 °C for 3 h to obtain silica-grafted polyvinyl alcohol fiber. The preparation process of modified carbon fiber is as follows: Step A: Place 7 parts of carbon fiber in 210 parts of acetone and extract for 46 hours. After washing and drying, pretreated carbon fiber is obtained. Place 7 parts of pretreated carbon fiber in 21 parts of concentrated nitric acid solution and heat in an oil bath at 75°C for 3 hours. Then rinse with deionized water until neutral and dry to obtain carboxylated carbon fiber. Step B: Immerse 7 parts of carboxylated carbon fiber in 126 parts of 9 mg / mL graphene oxide solution for 3 hours, remove and dry to obtain modified carbon fiber; Comparative Example 3 was based on Example 2, but no modified polyethyleneimine solution was introduced. The remaining process steps and reaction parameters were the same as in Example 2.

[0028] Comparative Example 4: A method for preparing a fiber-reinforced UHPC decorative panel, comprising the following processes: Step S1: Add 400 parts silicate cement, 80 parts mineral powder, 90 parts fly ash, 15 parts silica fume, 800 parts quartz sand, 10 parts composite fiber, and 200 parts water to a mixer and mix for 25 minutes. Then add 30 parts water-reducing agent and 5 parts air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 8 parts silica-grafted polyvinyl alcohol fiber and 2 parts modified carbon fiber. Step S2: Spray concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, let it stand for 24 hours at a temperature of 25℃ and a relative humidity of 90%, demold, and obtain fiber reinforced UHPC decorative board. Comparative Example 4 is based on Example 2. In Comparative Example 4, the mass ratio of silica-grafted polyvinyl alcohol fiber to modified carbon fiber in the composite fiber is 8:2. The remaining process steps and reaction parameters are the same as in Example 2.

[0029] Experiment: Fiber-reinforced UHPC decorative panels obtained in Examples 1-3 and Comparative Examples 1-4 were used to prepare samples. Their properties were tested, and the results were recorded. Compressive strength test: The test was conducted according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The sample size was 150mm×150mm×150mm. The maximum load of the press was 2000kN and the loading rate was 0.5MPa / s. A uniform load was applied to each sample until failure, and the maximum failure load was recorded. Then the 28-day compressive strength was calculated. Three samples were used in each test group, and the final result was the average value.

[0030] Flexural strength test: The test was conducted according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The specimen was a prism specimen with a side length of 150mm×150mm×600mm. The loading speed was 0.10MPa / s. Three specimens were used in each test group, and the final result was the average value.

[0031] Water absorption test: The test was conducted in accordance with T / CBMF 172-2022 "Ultra-high performance concrete (UHPC) decorative products".

[0032] The test results are shown in Table 1.

[0033] Table 1 Performance test results of fiber-reinforced UHPC decorative panels Based on the data in the table above, the following conclusions can be clearly drawn: Compared with Examples 1-3, the compressive strength and flexural strength of the products obtained in Comparative Examples 1 and 2 decreased significantly, while the water absorption increased. This indicates that by introducing modified carbon fibers, the present invention can produce a significant synergistic reinforcement effect with silicon dioxide-grafted PVA fibers, thereby improving the overall performance of the material. Compared with unmodified carbon fibers, the modified carbon fibers prepared by the present invention have a better modification effect, effectively improving the chemical compatibility and interfacial bonding strength between the originally inert carbon fibers and the hydrophilic cement matrix.

[0034] Compared with Examples 1-3, the compressive strength and flexural strength of the product obtained in Comparative Example 3 decreased, while the water absorption rate increased. It can be seen that by introducing a modified polyethyleneimine solution, the present invention can construct a stable interface layer between carbon fiber and graphene oxide (GO), firmly anchoring GO to the fiber surface, thereby improving the mechanical properties and waterproof performance of the material.

[0035] Compared with Examples 1-3, the compressive strength and flexural strength of the product obtained in Comparative Example 4 decreased, while the water absorption rate increased. This indicates that the composite fiber prepared by the present invention is affected by its component ratio. By selecting the component ratio within the range mentioned above, it is ensured that the high modulus carbon fiber and the high toughness PVA fiber form a continuous and uniform three-dimensional network in the matrix, thereby simultaneously achieving the optimal synergy between mechanical properties and durability (low water absorption rate).

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a fiber-reinforced UHPC decorative panel, characterized in that: Includes the following steps: Step S1: Add silicate cement, mineral powder, fly ash, silica fume, quartz sand, composite fiber and water into a mixer and mix for 20-30 minutes. Then add water-reducing agent and air-entraining agent and mix evenly to obtain a mixture. The composite fiber is composed of 2-6 parts by weight of silica-grafted polyvinyl alcohol fiber and 3-9 parts by weight of modified carbon fiber. Step S2: Spray the concrete release agent evenly on the inner surface of the precast mold, pour the mixture obtained in step S1 into the precast mold, vibrate to form, cure and demold to obtain fiber reinforced UHPC decorative panel.

2. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 1, characterized in that: The mixture comprises the following components by weight: 300-500 parts silicate cement, 700-900 parts quartz sand, 70-90 parts mineral powder, 80-100 parts fly ash, 10-20 parts silica fume, 160-220 parts water, 20-50 parts water-reducing agent, 3-6 parts air-entraining agent, and 5-15 parts composite fiber.

3. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 1, characterized in that: The method for preparing the silica-grafted polyvinyl alcohol fiber is as follows: Nano-silica and toluene are stirred evenly and ultrasonically dispersed for 30-50 min. A mixed solution of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and deionized water is added and refluxed for 6-8 h. Triethylenediamine is added and mixed evenly. Polyvinyl alcohol fibers are then added and reacted at 110-120℃ for 2-5 h to obtain silica-grafted polyvinyl alcohol fibers.

4. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 3, characterized in that: The mass ratio of the nano-silica, toluene, 3-(2,3-epoxypropoxy)propyltrimethoxysilane and deionized water is 1:(25-30):(0.6-0.8):(0.3-0.5).

5. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 1, characterized in that: The preparation process of the modified carbon fiber is as follows: Step A: Place the pretreated carbon fiber in a concentrated nitric acid solution, heat it in an oil bath at 70-80℃ for 2-4 hours, then rinse it with deionized water until neutral, and dry it to obtain carboxylated carbon fiber. Step B: Mix polyethyleneimine and phosphate buffer evenly, adjust the pH of the system to 5.0-5.5 with nitric acid, add gallic acid and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 2-3 hours to obtain a modified polyethyleneimine solution; Step C: Immerse the carboxylated carbon fibers in a modified polyethyleneimine solution for 1-2 hours, remove and dry them, then immerse them in a graphene oxide solution for 2-4 hours, remove and dry them to obtain the modified carbon fibers.

6. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 5, characterized in that: In step A, the mass ratio of pretreated carbon fiber to concentrated nitric acid is 1:(2-4).

7. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 6, characterized in that: The preparation process of the pretreated carbon fiber is as follows: carbon fiber is placed in acetone and extracted for 44-48 hours. After washing and drying, pretreated carbon fiber is obtained.

8. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 5, characterized in that: In step B, the mass ratio of polyethyleneimine, phosphate buffer, gallic acid and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimine is 1:(15-20):(0.5-0.8):(0.9-1.0), and the concentration of nitric acid is 1 mol / L.

9. The method for preparing a fiber-reinforced UHPC decorative panel according to claim 5, characterized in that: In step C, the mass ratio of carboxylated carbon fiber, modified polyethyleneimine solution, and graphene oxide solution is 1:(10-20):(15-30), the concentration of graphene oxide solution is 8-10 mg / mL, and the solvent is deionized water.

10. A fiber-reinforced UHPC decorative panel prepared by the preparation method according to any one of claims 1-9.

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