High ductility basalt fiber concrete and method for preparing the same

Abstract

This application relates to the field of building materials, specifically disclosing a high-ductility basalt fiber concrete and its preparation method, comprising cementitious materials, fiber mixtures, water, and admixtures. The fiber mixture includes polyethylene fibers and modified basalt fibers. The modified basalt fibers are prepared by the following method: basalt fibers are soaked in a calcium solution, and carbonates are added dropwise under alkaline conditions for in-situ mineralization to generate nano-calcium carbonate whiskers. These whiskers are then deposited by electrophoresis in a first suspension and then in a second suspension to obtain modified basalt fibers. The preparation method includes the following steps: mixing the cementitious materials and the fiber mixture to obtain a preliminary mixture; mixing water and admixtures and adding the preliminary mixture; stirring to obtain high-ductility basalt fiber concrete. This application has the characteristics of improving the interfacial bonding strength between basalt fibers and the concrete matrix, resulting in a high-performance concrete material with better ductility and strength.

Description

Technical Field

[0001] This application relates to the field of building materials, and more specifically, to a high-ductility basalt fiber concrete and a method for its preparation. Background Technology

[0002] In concrete structure applications, fiber materials are commonly added to improve the crack resistance and ductility of concrete structures. Polyethylene fiber is widely used in concrete modification due to its excellent toughening effect, effectively improving the ultimate elongation and crack resistance of concrete. However, polyethylene fiber is formed by polymerizing ethylene, a monomer produced from petroleum cracking, into polyethylene through processes such as melt spinning. It is a non-renewable fossil resource, and its high carbon footprint makes it difficult to meet the requirements of green building and sustainable development. Therefore, finding an environmentally friendly and high-performance fiber has become a research hotspot.

[0003] Basalt fiber, as a natural inorganic fiber, possesses characteristics such as high strength, high temperature resistance, corrosion resistance, and environmental friendliness, and is considered a potential concrete reinforcing material. However, the smooth surface of basalt fiber results in poor interfacial bonding with the cement matrix, causing the fiber to easily slip out of the matrix or become impossible to pull out under stress, thus failing to fully realize its reinforcing effect. Specifically, this manifests as a significant decrease in the ultimate elongation of concrete, exacerbated stress concentration, and overall mechanical properties, especially tensile strength and ductility, failing to reach the expected levels.

[0004] In the prior art, in order to improve the interfacial properties between basalt fiber and concrete, chemical treatments such as silane coupling agent treatment are usually used to enhance the surface activity of the fiber. However, the treatment effect is limited and it is difficult to achieve a synergistic improvement in high strength and high ductility, which limits its large-scale application in practical engineering.

[0005] Therefore, it is of great significance to provide new solutions for high-performance concrete materials that can significantly improve the interfacial bond strength between basalt fibers and the concrete matrix, as well as enhance the ductility and strength of concrete. Summary of the Invention

[0006] In order to improve the interfacial bonding strength between basalt fiber and concrete matrix, and thus obtain high-performance concrete materials with better ductility and strength, this application provides a high-ductility basalt fiber concrete and its preparation method.

[0007] In a first aspect, this application provides a high-ductility basalt fiber reinforced concrete, which adopts the following technical solution:

[0008] A high-ductility basalt fiber concrete includes cementitious materials, fiber mixture, water and admixtures, wherein the fiber mixture comprises polyethylene fibers and modified basalt fibers in a mass ratio of 1:(2-3);

[0009] Modified basalt fibers are prepared by the following method: basalt fibers are first soaked in a calcium solution, and carbonates are added dropwise under alkaline conditions to generate nano-calcium carbonate whiskers in situ. Then, a first transition layer is formed by electrophoretic deposition in a first suspension containing silica fume and nano-silica. A second transition layer is formed by electrophoretic deposition in a second suspension containing nano-silica and carboxylated carbon nanotubes, thus obtaining modified basalt fibers.

[0010] By adopting the above technical solution, the surface of basalt fiber is relatively smooth, and its interfacial adhesion with cement matrix is ​​weak. In this application, basalt fiber is first generated into nano-calcium carbonate whiskers through in-situ mineralization. The three-dimensional anchoring structure formed by the nano-calcium carbonate whiskers significantly enhances the mechanical interlocking force between the fiber and the cement matrix. Moreover, the presence of nano-calcium carbonate whiskers enables the nano-calcium carbonate whiskers to disperse and transfer stress during the concrete stress process, reducing stress concentration and interfacial debonding, and improving the ductility of concrete. In addition, nano-calcium carbonate whiskers serve as heterogeneous nucleation sites for cement hydration products, which helps the hydration products grow in an orderly manner on the whisker surface, improving the mechanical properties of the interfacial transition zone. This solves the problem of low ductility caused by the weak interfacial layer between traditional basalt fiber and cement matrix as a stress concentration point, thereby improving the ductility of concrete.

[0011] Based on this, the basalt fibers are further subjected to an electrophoretic deposition process. First, a high-rigidity transition layer is formed using silica fume and nano-silica. Then, a tough transition layer is formed using nano-silica and carboxylated carbon nanotubes. This achieves a gradient structure between the fiber and the cement matrix, effectively alleviating the sudden change in interfacial stress and further dispersing stress concentration, thus improving the interfacial crack resistance. Ultimately, the concrete prepared in this application has both high strength and better ductility.

[0012] Optionally, high-ductility basalt fiber reinforced concrete comprises the following raw materials in parts by weight:

[0013] 90-100 parts cement, 20-30 parts fly ash, 10-20 parts silica fume, 5-10 parts stone powder, 160-180 parts sand, 8-15 parts fiber mixture, 30-40 parts water and 0.5-1 parts admixture.

[0014] Optionally, the modified basalt fiber is prepared by the following method:

[0015] S1. Basalt fibers are first ultrasonically cleaned in dilute hydrochloric acid solution for 20-30 min, then soaked in calcium chloride solution with a molar concentration of 0.1-0.3 mol / Ld for 1.5-2.5 h. Then, sodium carbonate and sodium bicarbonate buffer solution is added to adjust the pH to 8.5-9. Then, the temperature is raised to 30-35℃, and 0.5-0.6 mol / L sodium carbonate solution is added dropwise. After reacting for 2 h, the temperature is raised to 55-65℃ and kept at that temperature for 3-4 h to obtain the initial modified basalt fibers.

[0016] S2. Soak the initially modified basalt fiber in an ethanol solution of silane coupling agent for 1-1.5 hours;

[0017] S3. Using the modified basalt fiber after step S2 as the cathode, apply a voltage of 10-12V to the first suspension containing silica fume and nano silica, deposit for 10-15 minutes to form the first transition layer, and then place it in the second suspension containing nano silica and carboxylated carbon nanotubes, apply a voltage of 5-8V, deposit for 3-5 minutes to form the second transition layer.

[0018] S4. After step S3 is completed, vacuum dry at 100-120℃ for 2-3 hours to obtain modified basalt fiber.

[0019] By employing the above technical solution, basalt fibers are first ultrasonically cleaned in dilute hydrochloric acid to remove surface impurities and introduce hydroxyl active sites. Then, they are soaked in a calcium chloride solution to form an initial calcium adsorption layer, providing nucleation sites for the growth of calcium carbonate whiskers. Next, the initial system pH is controlled at 8.5-9, and sodium carbonate is added to raise the pH to 10-10.5, generating calcite-type calcium carbonate whiskers and forming a three-dimensional anchoring structure, achieving mineralization. After mineralization, the fibers are further treated with a silane coupling agent solution, covalently bonding the whiskers to the fiber surface and reducing subsequent detachment. Finally, a gradient transition layer is formed by electrophoretic deposition through a gradient slurry, buffering the gradient elastic modulus and thus achieving stress gradient buffering.

[0020] Optionally, in the preparation of modified basalt fibers, in step S3, the first suspension is prepared by mixing silica fume and nano-silica at a mass ratio of (2.8-3.2):1 and dispersing them in an ethanol-water solution containing 0.3-0.5 wt% polyethyleneimine, and the solid content of the first suspension is 15-20 wt%.

[0021] The second suspension is made by mixing nano-silica and carboxylated carbon nanotubes at a mass ratio of (4-5):1 and dispersing them in an aqueous solution containing 0.2-0.3 wt% dodecyl dimethyl benzyl ammonium chloride. The solid content of the second suspension is 8-10%.

[0022] By adopting the above technical solution, the large difference in elastic modulus between the fiber and the cement matrix can easily lead to stress concentration at the interface, causing debonding or microcracks. In this application, a gradient transition interface is formed on the fiber surface, and the first suspension uses silica fume as the main skeleton, with a small amount of nano silica filling the pores to construct a high-rigidity support layer, which forms a mechanical interlock with the calcium carbonate whiskers on the fiber surface to ensure the load-bearing capacity of the interface. Polyethyleneimine, as a cationic dispersant, prevents the agglomeration of silica fume and nano silica through electrostatic repulsion, ensuring the stability of the first suspension.

[0023] The second suspension, mainly composed of nano-silica, forms a strong interfacial bond with the cement matrix. Carboxylated carbon nanotubes form a flexible interface through crack deflection and pull-out effects, acting as a flexible bridge to further disperse stress and avoid interface cracking caused by stress concentration. Ultimately, the formation of the above transition interface achieves stress buffering, resulting in concrete with high strength and high ductility. Furthermore, the cationic dispersant in the first and second suspensions facilitates the electrophoretic deposition of nano-silica and other particles on basalt fibers.

[0024] Optionally, in the preparation of modified basalt fibers, the volume ratio of calcium chloride solution to sodium carbonate solution in step S1 is 1:(2-5).

[0025] In step S2, the mass concentration of the silane coupling agent in the ethanol solution is 0.3-0.5 wt%, and the ethanol solution is obtained by mixing ethanol and water in a volume ratio of (6-7):(3-4).

[0026] Optionally, during the preparation of modified basalt fibers, nano-silica in the second suspension is added after modification treatment. The modification treatment involves first impregnating the nano-silica in a graphene oxide solution and then amination treatment.

[0027] By adopting the above technical solution, the nano-silica in the second suspension undergoes the aforementioned modification treatment. First, the nano-silica is impregnated in a graphene oxide solution. The hydroxyl groups on the nano-silica form chemical bonds with the carboxyl functional groups of graphene oxide, thus achieving a composite. Utilizing the nanosheet interweaving effect of graphene oxide, stress can be effectively dispersed, crack propagation can be prevented, and the toughness of the second transition layer can be improved. Furthermore, when concrete is under stress, the modified basalt fibers can more effectively transfer the stress to the surrounding matrix, allowing the matrix to better perform its load-bearing capacity, thereby improving the overall strength of the concrete. Moreover, the better toughness of the second transition layer causes crack deflection or branching when cracks propagate within the concrete, more effectively preventing further crack development and improving ductility.

[0028] Then, it undergoes amylation treatment, utilizing its surface-active amino groups to react with the carboxyl groups of graphene oxide and carboxylated carbon nanotubes to form chemical bonds, reducing the risk of debonding at the transition layer interface, forming a strong interfacial bond to ensure effective stress transfer, and improving the toughness of the transition layer. Moreover, the introduction of amino groups can enhance the pozzolanic activity of nano-silica, causing it to react with calcium hydroxide in cement hydration products to generate more hydrated calcium silicate gel, which not only fills the pores but also strengthens the interfacial transition zone between the fiber and the cement matrix, improving the density and strength of concrete, and thus improving the overall performance of concrete.

[0029] Optionally, the specific operation of the nano-silica modification treatment in the second suspension is as follows:

[0030] Nano-silica was first placed in a graphene oxide solution with a mass concentration of 5-10 wt% and ultrasonically treated for 30-40 min to obtain a mixed suspension. Then, an ethanol solution of vinyltriethoxysilane was added to the mixed suspension, mixed for 30-40 min, and filtered to obtain the initial modified nano-silica.

[0031] Then, the pre-modified nano-silica was immersed in the modification solution for 1-2 hours and then dried to obtain the final product. The modification solution was prepared from the following raw materials in parts by weight:

[0032] The modified solution is prepared by mixing 4-6 parts glycidyl methacrylate, 3-5 parts maleic anhydride, 0.1-0.3 parts dicyclohexylcarbodiimide, 1-2 parts N-oleo-1,3-propanediamine, 0.5-0.8 parts PAMAM, 3-5 parts chitosan, 10-15 parts ethanol and 8-12 parts water, and the pH value of the modified solution is 5.5-6.

[0033] By adopting the above technical solution, nano-silica is first ultrasonically treated in a graphene oxide solution to form a composite structure of nano-silica and graphene oxide. The nanosheet structure of graphene oxide is used for toughening. Then, an ethanol solution of vinyltriethoxysilane is added to introduce carbon-carbon unsaturated double bonds into the composite structure of nano-silica and graphene oxide. During the impregnation treatment in the modification solution, the vinyl groups in glycidyl methacrylate in the modification solution react with the unsaturated double bonds in nano-silica to introduce epoxy groups. Finally, the introduction of epoxy groups in the transition layer is combined with the cement matrix through epoxy-calcium ion coordination bonds to improve the bonding strength.

[0034] The addition of maleic anhydride to the modified liquid introduces carboxyl groups into nano-silica, which then react with PAMAM under the action of dicyclohexylcarbodiimide, introducing multiple amino groups. This facilitates the subsequent formation of gel with hydration products in the cement matrix, improving the interfacial bonding between basalt fibers and the cement matrix. The addition of N-oleo-1,3-propanediamine, as a long-chain aliphatic diamine, interacts with the hydroxyl groups on the surface of nano-silica, introducing amino groups while reducing the aggregation of nano-silica using its long-chain aliphatic structure, further improving the dispersion of nano-silica in the second suspension. Moreover, it can chemically react with carboxylated carbon nanotubes, ultimately forming a denser cross-linked structure in the second transition layer. This results in a tough transition layer with better load-bearing capacity, ultimately leading to superior overall performance of the concrete.

[0035] Optionally, during the modification treatment of nano-silica in the second suspension, the mass ratio of nano-silica to graphene oxide solution is 1:(5-6), and the amount of vinyltriethoxysilane added is 8-12 wt% of nano-silica;

[0036] The initial mass ratio of modified nano-silica to modified liquid is 1:(6-8).

[0037] Optionally, the length of polyethylene fiber is 8-12 mm, and the length of basalt fiber is 9-11 mm.

[0038] Secondly, this application provides a method for preparing high-ductility basalt fiber reinforced concrete, employing the following technical solution:

[0039] A method for preparing high-ductility basalt fiber concrete includes the following steps: mixing cementitious materials with fiber mixture to obtain a preliminary mixture; mixing water and admixtures and adding them to the preliminary mixture; stirring to obtain high-ductility basalt fiber concrete.

[0040] In summary, this application has the following beneficial effects:

[0041] 1. In this application, basalt fibers are first mineralized in situ to generate nano-calcium carbonate whiskers. The three-dimensional anchoring structure formed by the nano-calcium carbonate whiskers significantly enhances the mechanical interlocking force between the fibers and the cement matrix. Moreover, the presence of nano-calcium carbonate whiskers enables the nano-calcium carbonate whiskers to disperse and transfer stress during the concrete stress process, reducing stress concentration and interfacial debonding, and improving the ductility of concrete. In addition, nano-calcium carbonate whiskers serve as heterogeneous nucleation sites for cement hydration products, which helps the hydration products grow in an orderly manner on the whisker surface, improving the mechanical properties of the interfacial transition zone. This solves the problem of low ductility caused by the weak interfacial layer between traditional basalt fibers and the cement matrix as a stress concentration point, thereby improving the ductility of concrete.

[0042] 2. The basalt fibers are further subjected to an electrophoretic deposition process. First, a high-rigidity transition layer is formed by silica fume and nano-silica. Then, a tough transition layer is formed by nano-silica and carboxylated carbon nanotubes. This achieves a gradient structure between the fiber and the cement matrix, effectively alleviating the sudden change in interfacial stress and further dispersing stress concentration, thus improving the interfacial crack resistance. Finally, the concrete prepared in this application has high strength and better ductility. Detailed Implementation

[0043] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0044] Unless otherwise specified, all percentages in the following preparation examples and embodiments are mass percentages.

[0045] In the following preparation examples, the carboxylated carbon nanotubes used are carboxylated multi-walled carbon nanotubes from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., model XFM09, with a carboxyl content of 2.56 wt%.

[0046] The following preparation examples illustrate the preparation of modified basalt fibers.

[0047] Preparation Example 1

[0048] A method for preparing modified basalt fiber includes the following steps:

[0049] S1. Basalt fibers with a length of 9-11 mm and a diameter of 12-15 μm were first ultrasonically cleaned in a 9% dilute hydrochloric acid solution (ultrasonic power of 100 W) for 25 min. Then, they were soaked in a 0.2 mol / L calcium chloride solution for 2 h. Then, sodium carbonate and sodium bicarbonate buffer solution was added to adjust the pH to 8.5. The temperature was raised to 30℃, and 0.5 mol / L sodium carbonate solution was added dropwise. After reacting for 2 h, the temperature was raised to 60℃ and kept at that temperature for 3.5 h to obtain the initial modified basalt fibers.

[0050] The volume ratio of calcium chloride solution to total added sodium carbonate solution is 1:3.

[0051] S2. The modified basalt fiber was soaked in an ethanol solution containing silane coupling agent KH-570 for 1 hour and then dried. The mass concentration of silane coupling agent in the ethanol solution was 0.4 wt%, and the ethanol solution was obtained by mixing ethanol and water in a volume ratio of 7:3.

[0052] S3. Ethanol and water are mixed at a volume ratio of 1:1, and then polyethyleneimine is added. The mass percentage of polyethyleneimine in the ethanol-water solution is 0.4 wt%. Then, silica fume and nano-silica are mixed at a mass ratio of 3:1 and dispersed in the ethanol-water solution containing polyethyleneimine to obtain a first suspension with a solid content of 18 wt%.

[0053] Similarly, a solution of dodecyl dimethyl benzyl ammonium chloride with a mass concentration of 0.2 wt% was prepared by dispersing dodecyl dimethyl benzyl ammonium chloride in water. Then, nano-silica and carboxylated carbon nanotubes were mixed at a mass ratio of 4.5:1 and dispersed in the solution of dodecyl dimethyl benzyl ammonium chloride to obtain a second suspension with a solid content of 9%.

[0054] Then, the modified basalt fiber after step S2 is used as the cathode. First, a voltage of 10V is applied in the first suspension containing silica fume and nano silica. After deposition for 15 minutes, the first transition layer is formed. Then, it is placed in the second suspension containing nano silica and carboxylated carbon nanotubes. A voltage of 5V is applied and deposition is carried out for 4 minutes to form the second transition layer.

[0055] After step S4 and step S3 are completed, the modified basalt fiber is obtained by vacuum drying at 110℃ for 2.5h.

[0056] Preparation Example 2

[0057] A method for preparing modified basalt fiber includes the following steps:

[0058] S1. Basalt fibers with a length of 9-11 mm and a diameter of 12-15 μm were first ultrasonically cleaned in a dilute hydrochloric acid solution with a mass concentration of 8% (ultrasonic power of 100 W) for 30 min. Then, they were soaked in a calcium chloride solution with a molar concentration of 0.1 mol / L for 2.5 h. Then, sodium carbonate and sodium bicarbonate buffer solution was added to adjust the pH to 8.5, the temperature was raised to 30 °C, and 0.5 mol / L sodium carbonate solution was added dropwise. After reacting for 2 h, the temperature was raised to 55 °C and kept at that temperature for 4 h to obtain the initial modified basalt fibers.

[0059] The volume ratio of calcium chloride solution to total added sodium carbonate solution is 1:2.

[0060] S2. The modified basalt fiber was soaked in an ethanol solution containing silane coupling agent KH-570 for 1 hour and then dried. The mass concentration of silane coupling agent in the ethanol solution was 0.3 wt%, and the ethanol solution was obtained by mixing ethanol and water in a volume ratio of 6:4.

[0061] S3. Ethanol and water are mixed at a volume ratio of 1:1, and then polyethyleneimine is added. The mass percentage of polyethyleneimine in the ethanol aqueous solution is 0.3 wt%. Then, silica fume and nano-silica are mixed at a mass ratio of 2.8:1 and dispersed in the ethanol aqueous solution containing polyethyleneimine to obtain a first suspension with a solid content of 15 wt%.

[0062] Similarly, a solution of dodecyl dimethyl benzyl ammonium chloride with a mass concentration of 0.2 wt% was prepared by dispersing dodecyl dimethyl benzyl ammonium chloride in water. Then, nano-silica and carboxylated carbon nanotubes were mixed at a mass ratio of 4:1 and dispersed in the solution of dodecyl dimethyl benzyl ammonium chloride to obtain a second suspension with a solid content of 8%.

[0063] Then, the modified basalt fiber after step S2 is used as the cathode. First, a voltage of 10V is applied in the first suspension containing silica fume and nano silica. After deposition for 15 minutes, the first transition layer is formed. Then, it is placed in the second suspension containing nano silica and carboxylated carbon nanotubes. A voltage of 5V is applied and deposition is carried out for 5 minutes to form the second transition layer.

[0064] S4. After step S3 is completed, vacuum dry at 100℃ for 3 hours to obtain modified basalt fiber.

[0065] Preparation Example 3

[0066] A method for preparing modified basalt fiber includes the following steps:

[0067] S1. Basalt fibers with a length of 9-11 mm and a diameter of 12-15 μm were first ultrasonically cleaned in a 10% dilute hydrochloric acid solution (ultrasonic power of 100 W) for 20 min. Then, they were soaked in a 0.3 mol / L calcium chloride solution for 1.5 h. Then, sodium carbonate and sodium bicarbonate buffer solution was added to adjust the pH to 9.0. The temperature was raised to 35 °C, and 0.6 mol / L sodium carbonate solution was added dropwise. After reacting for 2 h, the temperature was raised to 65 °C and kept at that temperature for 3 h to obtain the initial modified basalt fibers.

[0068] The volume ratio of calcium chloride solution to total added sodium carbonate solution is 1:5.

[0069] S2. The modified basalt fiber was soaked in an ethanol solution containing silane coupling agent KH-570 for 1.5 h and then dried. The mass concentration of silane coupling agent in the ethanol solution was 0.5 wt%, and the ethanol solution was obtained by mixing ethanol and water in a volume ratio of 7:3.

[0070] S3. Ethanol and water are mixed at a volume ratio of 1:1, and then polyethyleneimine is added. The mass percentage of polyethyleneimine in the ethanol aqueous solution is 0.3 wt%. Then, silica fume and nano-silica are mixed at a mass ratio of 3.2:1 and dispersed in the ethanol aqueous solution containing polyethyleneimine to obtain a first suspension with a solid content of 20 wt%.

[0071] Similarly, a solution of dodecyl dimethyl benzyl ammonium chloride with a mass concentration of 0.3 wt% was prepared by dispersing dodecyl dimethyl benzyl ammonium chloride in water. Then, nano-silica and carboxylated carbon nanotubes were mixed at a mass ratio of 5:1 and dispersed in the solution of dodecyl dimethyl benzyl ammonium chloride to obtain a second suspension with a solid content of 10%.

[0072] Then, the modified basalt fiber after step S2 is used as the cathode. First, a voltage of 12V is applied in the first suspension containing silica fume and nano silica. After deposition for 10 minutes, the first transition layer is formed. Then, it is placed in the second suspension containing nano silica and carboxylated carbon nanotubes. An 8V voltage is applied and deposition is carried out for 3 minutes to form the second transition layer.

[0073] After step S4 and step S3 are completed, vacuum dry at 120℃ for 2 hours to obtain modified basalt fiber.

[0074] Preparation Example 4

[0075] A method for preparing modified basalt fibers is provided, following the method in Preparation Example 1, except that the nano-silica in the second suspension in step S3 is added after the following modification treatment:

[0076] Nano-silica was first placed in an 8 wt% graphene oxide solution and ultrasonically treated (ultrasonic power 200W) for 35 min to obtain a mixed suspension. The mass ratio of nano-silica to graphene oxide solution was 1:5.5.

[0077] Then, an ethanol solution of vinyltriethoxysilane was added to the mixed suspension, and after mixing for 35 minutes, the mixture was filtered to obtain pre-modified nano-silica. The amount of vinyltriethoxysilane added was 10 wt% of the nano-silica. The ethanol solution of vinyltriethoxysilane was obtained by mixing vinyltriethoxysilane with ethanol and water at a volume ratio of 7:3. The amount of ethanol added was 3.5 times the mass of vinyltriethoxysilane.

[0078] A modification solution was prepared by mixing 5 kg glycidyl methacrylate, 4 kg maleic anhydride, 0.2 kg dicyclohexylcarbodiimide, 1.5 kg N-oleo-1,3-propanediamine, 0.6 kg PAMAM, 3-5 kg ​​chitosan, 12 kg ethanol, and 10 kg water. The pH of the modification solution was adjusted to 6. The pre-modified nano-silica was then immersed in the modification solution for 1.5 h and dried to obtain modified nano-silica. The mass ratio of pre-modified nano-silica to modification solution was 1:7.

[0079] The modified nano-silica was then used to prepare a second suspension.

[0080] Preparation Example 5

[0081] A method for preparing modified basalt fibers is provided, following the method in Preparation Example 1, except that the nano-silica in the second suspension in step S3 is added after the following modification treatment:

[0082] Nano-silica was first placed in a 5 wt% graphene oxide solution and ultrasonically treated (ultrasonic power 200W) for 30 min to obtain a mixed suspension. The mass ratio of nano-silica to graphene oxide solution was 1:5.

[0083] Then, an ethanol solution of vinyltriethoxysilane was added to the mixed suspension, and after mixing for 30 minutes, the mixture was filtered to obtain pre-modified nano-silica. The amount of vinyltriethoxysilane added was 8 wt% of the nano-silica. The ethanol solution of vinyltriethoxysilane was obtained by mixing vinyltriethoxysilane with ethanol and water at a volume ratio of 7:3. The amount of ethanol added was 3 times the mass of vinyltriethoxysilane.

[0084] A modification solution was prepared by mixing 4 kg glycidyl methacrylate, 3 kg maleic anhydride, 0.1 kg dicyclohexylcarbodiimide, 1 kg N-oleo-1,3-propanediamine, 0.5 kg PAMAM, 3 kg chitosan, 10 kg ethanol, and 8 kg water. The pH of the modification solution was adjusted to 5.5. The pre-modified nano-silica was then immersed in the modification solution for 1 hour and dried to obtain modified nano-silica. The mass ratio of pre-modified nano-silica to modification solution was 1:6.

[0085] The modified nano-silica was then used to prepare a second suspension.

[0086] Preparation Example 6

[0087] A method for preparing modified basalt fibers is provided, following the method in Preparation Example 1, except that the nano-silica in the second suspension in step S3 is added after the following modification treatment:

[0088] Nano-silica was first placed in a 10wt% graphene oxide solution and ultrasonically treated (ultrasonic power 200W) for 40 minutes to obtain a mixed suspension. The mass ratio of nano-silica to graphene oxide solution was 1:6.

[0089] Then, an ethanol solution of vinyltriethoxysilane was added to the mixed suspension, and after mixing for 40 minutes, the mixture was filtered to obtain pre-modified nano-silica. The amount of vinyltriethoxysilane added was 12 wt% of the nano-silica. The ethanol solution of vinyltriethoxysilane was obtained by mixing vinyltriethoxysilane with ethanol and water at a volume ratio of 7:3. The amount of ethanol added was 4 times the mass of vinyltriethoxysilane.

[0090] A modification solution was prepared by mixing 6 kg of glycidyl methacrylate, 5 kg of maleic anhydride, 0.3 kg of dicyclohexylcarbodiimide, 2 kg of N-oleo-1,3-propanediamine, 0.8 kg of PAMAM, 5 kg of chitosan, 15 kg of ethanol, and 12 kg of water. The pH of the modification solution was adjusted to 6. The pre-modified nano-silica was then immersed in the modification solution for 2 hours and dried to obtain modified nano-silica. The mass ratio of pre-modified nano-silica to modification solution was 1:8.

[0091] The modified nano-silica was then used to prepare a second suspension.

[0092] Preparation Example 7

[0093] A method for preparing modified basalt fiber is carried out according to the method in Preparation Example 4, except that glycidyl methacrylate is not added to the modified solution during the nano-silica modification treatment in the second suspension.

[0094] Preparation Example 8

[0095] A method for preparing modified basalt fiber is carried out according to the method in Preparation Example 1, except that graphene is added to the second suspension. The graphene is directly mixed with nano-silica and then added to a solution of dodecyl dimethyl benzyl ammonium chloride to obtain the second suspension. The mass ratio of graphene to nano-silica is the same as the mass ratio of graphene oxide to nano-silica in Preparation Example 4.

[0096] Comparative Preparation Example 1

[0097] A method for preparing modified basalt fibers is carried out according to the method in Preparation Example 1, except that in step S3, the initially modified basalt fibers only undergo electrophoretic deposition in a first suspension to form a first transition layer, and then step S4 is performed.

[0098] Comparative Preparation Example 2

[0099] A method for preparing modified basalt fibers is carried out according to the method in Preparation Example 1, except that the initial modified basalt fibers in step S3 are directly electrophoretically deposited in the second suspension to form a second transition layer, without being treated in the first suspension, and then the operation in step S4 is performed.

[0100] Comparative preparation example 3

[0101] A method for preparing modified basalt fiber is carried out according to the method in Preparation Example 1, except that steps S1 and S2 are not performed, and step S3 is performed directly.

[0102] Comparative preparation example 4

[0103] A method for preparing modified basalt fiber is carried out according to the method in Preparation Example 1, except that step S3 is not performed, and step S4 is performed directly after step S2.

[0104] The following examples are examples of high-ductility basalt fiber reinforced concrete.

[0105] In the following examples, the cement used is P.O.52.5R ordinary Portland cement; the sand used is medium sand with a fineness modulus of 2.6-2.9; the admixture used is polycarboxylate superplasticizer of model CP1200 from Nanjing Xinyi Synthetic Technology Co., Ltd.; the fly ash used is Class I fly ash of type F; the stone powder has a particle size of 0.15-5mm; and the polyethylene fiber has a length of 8-12mm and a diameter of 15-18μm.

[0106] Example 1

[0107] A method for preparing high-ductility basalt fiber reinforced concrete includes the following steps:

[0108] 95 kg of cement, 25 kg of fly ash, 15 kg of silica fume, 8 kg of stone powder, and 170 kg of sand were mixed, and then 12 kg of fiber mixture was added and stirred to obtain a preliminary mixture. The fiber mixture included polyethylene fiber and modified basalt fiber in a mass ratio of 1:2.5. The modified basalt fiber was the modified basalt fiber obtained in Preparation Example 1.

[0109] Mix 35 kg of water and 0.8 kg of admixture, then add to the initial mixture and stir to obtain high-ductility basalt fiber concrete.

[0110] Example 2

[0111] A method for preparing high-ductility basalt fiber reinforced concrete includes the following steps:

[0112] 90 kg of cement, 20 kg of fly ash, 10 kg of silica fume, 5 kg of stone powder and 160 kg of sand were mixed, and then 8 kg of fiber mixture was added and stirred to obtain a preliminary mixture. The fiber mixture included polyethylene fiber and modified basalt fiber in a mass ratio of 1:2. The modified basalt fiber was selected from the modified basalt fiber prepared in Preparation Example 2.

[0113] Mix 30 kg of water and 0.5 kg of admixture, then add to the initial mixture and stir to obtain high-ductility basalt fiber concrete.

[0114] Example 3

[0115] A method for preparing high-ductility basalt fiber reinforced concrete includes the following steps:

[0116] 100 kg of cement, 30 kg of fly ash, 20 kg of silica fume, 10 kg of stone powder and 180 kg of sand were mixed, and then 15 kg of fiber mixture was added and stirred to obtain a preliminary mixture. The fiber mixture included polyethylene fiber and modified basalt fiber in a mass ratio of 1:3. The modified basalt fiber was selected from the modified basalt fiber prepared in Preparation Example 3.

[0117] 40 kg of water and 1 kg of admixture were mixed and then added to the initial mixture. The mixture was stirred to obtain high-ductility basalt fiber concrete.

[0118] Examples 4-8

[0119] A method for preparing high-ductility basalt fiber concrete is carried out according to the method in Example 1, except that the modified basalt fiber is selected from the modified basalt fibers prepared in Examples 4-8.

[0120] Comparative Examples 1-4

[0121] A method for preparing high-ductility basalt fiber concrete is carried out according to the method in Example 1, except that the modified basalt fiber is selected from the modified basalt fibers prepared in Comparative Preparation Examples 1-4.

[0122] Comparative Example 5

[0123] A method for preparing high-ductility basalt fiber concrete is carried out according to the method in Example 1, except that the modified basalt fiber is replaced with an equal amount of basalt fiber.

[0124] Performance testing

[0125] The concrete prepared in the above embodiments and comparative examples was tested for ultimate elongation and initial crack tensile strength in accordance with JC / T 2461-2018 "Test Method for Mechanical Properties of High Ductility Fiber Reinforced Cement-Based Composite Materials" to characterize its ductility. Then, the prepared concrete was made into standard cubic specimens of 100mm×100mm×100mm. After standard curing for 28 days, its compressive strength was tested. The test results of the above items are shown in Table 1 below.

[0126] Table 1:

[0127]

[0128] Referring to the test results in Table 1 above, it can be seen that this application significantly improves the interfacial bond strength between the fiber and the cement matrix through the synergistic effects of three-dimensional anchoring, gradient transition, and interface toughening of nano-calcium carbonate whiskers, resulting in concrete with both high ductility and high strength. Referring to the test results of Examples 1 and 4-6, during electrophoretic deposition, the nano-silica in the second suspension, after being combined with graphene oxide and then subjected to amination treatment, exhibits significantly improved ductility and better mechanical properties. The amination treatment further facilitates the formation of a denser cross-linked structure, enhancing the load-bearing capacity of the concrete. Combining the test results of Example 7, when glycidyl methacrylate was not added to the modified liquid in Example 7, its ductility and mechanical properties were reduced. The introduction of epoxy groups helps to enhance the interfacial bonding between the fiber and the cement matrix through epoxy group and calcium ion bonding, thereby improving the concrete performance. Combining the test results of Example 8, in Example 8, graphene oxide was directly added to the second suspension. Compared with adding it after being combined with nano-silica in Example 4, it can be seen that the ductility and mechanical properties in Example 8 were reduced. When graphene is added directly, although its sheet structure can provide a certain toughening effect, the direct chemical bonding between graphene, nano-silica and fiber leads to weak interfacial bonding force, affecting the overall toughness.

[0129] Combining the test results of Example 1 with those of Comparative Examples 1 and 2, it can be seen that when electrophoretic deposition is performed directly in silica fume and nano-silica without the gradient interface transition described in this application, the stress abrupt change at the interface leads to a decrease in ductility and strength. Combining the test results of Comparative Examples 3 and 4, when basalt fiber modification is performed without in-situ mineralization to form nano-calcium carbonate whiskers and then directly electrophoretically deposited, its ductility and strength are reduced. When three-dimensional anchored calcium carbonate whiskers are formed on the basalt fiber, it is more conducive to the mechanical interlocking force of the fiber in the cement matrix and improves its crack resistance. Combining the test results of Comparative Example 5, it can be seen that when basalt fiber is added directly without modification, its ductility and strength are low due to the weak interfacial bonding between the basalt fiber and the cement matrix.

[0130] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-ductility basalt fiber-reinforced concrete, comprising cementitious materials, fiber mixtures, water, and admixtures, characterized in that: The fiber mixture comprises polyethylene fiber and modified basalt fiber in a mass ratio of 1:(2-3); Modified basalt fibers are prepared by the following method: basalt fibers are first soaked in a calcium solution, and carbonates are added dropwise under alkaline conditions to generate nano-calcium carbonate whiskers in situ. Then, a first transition layer is formed by electrophoretic deposition in a first suspension containing silica fume and nano-silica. A second transition layer is formed by electrophoretic deposition in a second suspension containing nano-silica and carboxylated carbon nanotubes, thus obtaining modified basalt fibers.

2. The high-ductility basalt fiber reinforced concrete according to claim 1, characterized in that: High-ductility basalt fiber reinforced concrete comprises the following raw materials in parts by weight: 90-100 parts cement, 20-30 parts fly ash, 10-20 parts silica fume, 5-10 parts stone powder, 160-180 parts sand, 8-15 parts fiber mixture, 30-40 parts water and 0.5-1 parts admixture.

3. The high-ductility basalt fiber reinforced concrete according to claim 1, characterized in that: Modified basalt fibers are prepared by the following method: S1. Basalt fibers are first ultrasonically cleaned in dilute hydrochloric acid solution for 20-30 min, then soaked in calcium chloride solution with a molar concentration of 0.1-0.3 mol / L for 1.5-2.5 h. Then, sodium carbonate and sodium bicarbonate buffer solution is added to adjust the pH to 8.5-9. Then, the temperature is raised to 30-35℃, and sodium carbonate solution with a molar concentration of 0.5-0.6 mol / L is added dropwise. After reacting for 2 h, the temperature is raised to 55-65℃ and kept at that temperature for 3-4 h to obtain the initial modified basalt fibers. S2. Soak the modified basalt fiber in an ethanol solution containing a silane coupling agent for 1-1.5 hours; S3. Using the modified basalt fiber after step S2 as the cathode, apply a voltage of 10-12V to the first suspension containing silica fume and nano silica, deposit for 10-15 minutes to form the first transition layer, and then place it in the second suspension containing nano silica and carboxylated carbon nanotubes, apply a voltage of 5-8V, deposit for 3-5 minutes to form the second transition layer. S4. After step S3 is completed, vacuum dry at 100-120℃ for 2-3 hours to obtain modified basalt fiber.

4. The high-ductility basalt fiber reinforced concrete according to claim 3, characterized in that: In the preparation of modified basalt fibers, in step S3, the first suspension is prepared by mixing silica fume and nano-silica at a mass ratio of (2.8-3.2):1 and dispersing them in an ethanol aqueous solution containing 0.3-0.5 wt% polyethyleneimine. The solid content of the first suspension is 15-20 wt%. The second suspension is made by mixing nano-silica and carboxylated carbon nanotubes at a mass ratio of (4-5):1 and dispersing them in an aqueous solution containing 0.2-0.3 wt% dodecyl dimethyl benzyl ammonium chloride. The solid content of the second suspension is 8-10%.

5. The high-ductility basalt fiber reinforced concrete according to claim 3, characterized in that: In the preparation of modified basalt fibers, the volume ratio of calcium chloride solution to sodium carbonate solution in step S1 is 1:(2-5). In step S2, the mass concentration of the silane coupling agent in the ethanol solution is 0.3-0.5 wt%, and the ethanol solution is obtained by mixing ethanol and water in a volume ratio of (6-7):(3-4).

6. The high-ductility basalt fiber reinforced concrete according to claim 1, characterized in that: During the preparation of modified basalt fibers, nano-silica in the second suspension is added after modification treatment. The modification treatment involves first impregnating the nano-silica in a graphene oxide solution and then amination treatment.

7. The high-ductility basalt fiber reinforced concrete according to claim 6, characterized in that: The specific operation of the nano-silica modification treatment in the second suspension is as follows: Nano-silica was first placed in a graphene oxide solution with a mass concentration of 5-10 wt% and ultrasonically treated for 30-40 min to obtain a mixed suspension. Then, an ethanol solution of vinyltriethoxysilane was added to the mixed suspension, mixed for 30-40 min, and filtered to obtain the initial modified nano-silica. Then, the pre-modified nano-silica was immersed in the modification solution for 1-2 hours and then dried to obtain the final product. The modification solution was prepared from the following raw materials in parts by weight: The modified solution is prepared by mixing 4-6 parts glycidyl methacrylate, 3-5 parts maleic anhydride, 0.1-0.3 parts dicyclohexylcarbodiimide, 1-2 parts N-oleo-1,3-propanediamine, 0.5-0.8 parts PAMAM, 3-5 parts chitosan, 10-15 parts ethanol and 8-12 parts water, and the pH value of the modified solution is 5.5-6.

8. The high-ductility basalt fiber reinforced concrete according to claim 7, characterized in that: During the modification treatment of nano-silica in the second suspension, the mass ratio of nano-silica to graphene oxide solution was 1:(5-6), and the amount of vinyltriethoxysilane added was 8-12 wt% of nano-silica. The initial mass ratio of modified nano-silica to modified liquid is 1:(6-8).

9. The high-ductility basalt fiber reinforced concrete according to claim 1, characterized in that: The length of polyethylene fiber is 8-12mm, and the length of basalt fiber is 9-11mm.

10. A method for preparing high-ductility basalt fiber reinforced concrete as described in any one of claims 1-9, characterized in that: Includes the following steps: A preliminary mixture is prepared by mixing cementitious materials and fiber mixtures. Water and admixtures are then mixed and added to the preliminary mixture. After stirring, high-ductility basalt fiber concrete is obtained.

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