A modified fiber and its preparation method and application

Abstract

The present application relates to the field of composite material technology, and in particular to a modified fiber and its preparation method and application. The modified fiber includes a fiber matrix, a hydrophilic layer, and a mineralized surface layer. The hydrophilic layer covers the fiber matrix, and the mineralized surface layer covers the hydrophilic layer. The mineralized surface layer contains silicate and silicon dioxide and is amorphous and / or microcrystalline. The hydrophilic layer, as an intermediate layer, is conducive to improving the degree of bonding with the other two layers and improving the overall structural stability of the modified fiber. The mineralized surface layer is an inorganic mineralized layer, which can improve the compatibility of the modified fiber and concrete materials and promote mutual penetration. The modified fiber can be used in concrete materials to further improve mechanical strength, durability, and resistance to microbial erosion. The preparation method includes performing a hydrophilic modification treatment on the surface of the fiber matrix to form a hydrophilic layer on the surface of the fiber matrix to obtain a hydrophilic fiber; and depositing a silicate raw material on the surface of the hydrophilic fiber to form a mineralized surface layer covering the hydrophilic fiber.

Description

Technical Field

[0001] The present application relates to the technical field of composite materials, and in particular to a modified fiber and a preparation method and application thereof. Background Art

[0002] To improve the mechanical strength of concrete, existing research has explored incorporating fibers into concrete, such as those made of PET, PA, PC, PVC, PP, and PS. However, these fibers are not highly compatible with concrete, and their synergistic effects are limited.

[0003] There are also studies in the prior art on fiber modification and its subsequent use in concrete materials. For example, the 2022 master's thesis of Fujian Forestry University, "Preparation and Performance Research of PET Waste Fiber Reinforced Aerated Concrete", records that dopamine hydrochloride is used to polymerize and modify the surface of PET fibers, and then used in aerated concrete to improve the mechanical properties of concrete materials. In addition, there are other prior arts that record technical solutions for modifying and activating the fiber surface and further using it in concrete. However, the combination effect of the modified fibers and concrete materials in these methods still needs to be improved, and the improvement in the mechanical properties of concrete materials is still limited. Moreover, depending on the usage scenario, many concrete materials also have certain requirements for durability and resistance to microbial erosion, and the above methods have no significant improvement in these aspects. Summary of the Invention

[0004] The purpose of this application is to provide a modified fiber and a preparation method thereof, aiming to solve the problems in the prior art of low compatibility of fibers used in concrete materials, low mechanical strength, durability, and low bioerosion resistance.

[0005] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0006] In a first aspect, the present application provides a modified fiber, comprising:

[0007] Fiber matrix;

[0008] A hydrophilic layer, wherein the hydrophilic layer covers the fiber matrix;

[0009] A mineralized surface layer, the mineralized surface layer covers the hydrophilic layer, and the mineralized surface layer contains silicates and silicon dioxide, and the silicates and silicon dioxide are in amorphous and / or microcrystalline form.

[0010] The modified fiber of the present application includes a three-layer structure of inner, middle and outer layers such as a fiber matrix, a hydrophilic layer and a mineralized surface layer, wherein the hydrophilic layer as an intermediate layer is conducive to improving the degree of bonding with the other two layers and improving the structural stability of the modified fiber as a whole. The mineralized surface layer contains silicates and silicon dioxide in amorphous and / or microcrystalline form, which belongs to the inorganic mineralized layer, and can improve the compatibility of the modified fiber with the concrete material and promote mutual penetration. Compared with existing modified fibers, the modified fiber of the present application can be used in concrete materials to further improve the mechanical strength, and can also improve the durability and resistance to microbial erosion of concrete materials.

[0011] In a second aspect, the present application provides a method for preparing the modified fiber of the above application, comprising the following steps:

[0012] Performing hydrophilic modification on the surface of the fiber matrix to form a hydrophilic layer on the surface of the fiber matrix to obtain hydrophilic fibers;

[0013] The silicate raw material is deposited on the surface of the hydrophilic fiber to form a mineralized surface layer covering the hydrophilic fiber to obtain the modified fiber.

[0014] The preparation method of the present application first hydrophilically modifies the fiber matrix to obtain hydrophilic fibers, forming a tightly bound hydrophilic layer on the fiber matrix surface, and then deposits the modified fibers to form a mineralized surface layer tightly bound to the hydrophilic layer. The modified fibers thus obtained form a three-layer structure comprising a fiber matrix, a hydrophilic layer, and a mineralized surface layer. These fibers exhibit good compatibility with concrete materials, promoting mutual penetration. Their use in concrete materials can improve the mechanical strength, durability, and resistance to microbial erosion of the concrete materials. The preparation method is process-controllable, and the resulting modified fibers have stable structures and physicochemical properties.

[0015] In a third aspect, the present application provides a modified concrete containing the modified fiber of the above application, or containing the modified fiber prepared by the preparation method of the modified fiber of the above application.

[0016] The modified concrete of the present application contains the modified fiber of the above-mentioned application, so the modified fiber has good compatibility with the concrete material, promotes mutual penetration, can improve the mechanical strength of the modified concrete material, and can also improve the durability and resistance to microbial erosion of the modified concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 Schematic diagram of the dopamine redox autopolymerization reaction in the method for preparing the modified fiber according to an embodiment of the present application;

[0019] Figure 2 is a SEM image of the interface between the PET fiber and concrete in Comparative Example B1;

[0020] Figure 3 is a SEM image of the interface between the modified PET fiber and concrete in Example B1;

[0021] Figure 4 is an SEM image of the interface of the PET fiber taken out from the concrete in Comparative Example B1;

[0022] Figure 5 This is a SEM of the interface where the modified PET fiber in Example B1 was removed from concrete;

[0023] Figure 6 It is the XRD pattern of the concrete components of Examples B1, B9, B10, the blank group, and Comparative Examples B1, B4, and B9. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0025] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0026] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0027] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0029] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass in the examples of this application may be μg, mg, g, kg, etc., which are mass units known in the chemical industry.

[0030] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0031] A first aspect of an embodiment of the present application provides a modified fiber, which includes a fiber matrix, a hydrophilic layer and a mineralized surface layer, wherein the hydrophilic layer covers the fiber matrix, the mineralized surface layer covers the hydrophilic layer, and the mineralized surface layer contains silicate and silicon dioxide, and the silicate and silicon dioxide are in amorphous and / or microcrystalline form.

[0032] Among them, amorphous refers to the glassy or non-crystalline state; microcrystalline morphology refers to the fact that the number of unit cells in each grain is small, the repetition period is small, and the small crystals formed are small in scale.

[0033] The modified fiber of the embodiment of the present application includes a three-layer structure of inner, middle and outer layers such as a fiber matrix, a hydrophilic layer and a mineralized surface layer, wherein the hydrophilic layer as an intermediate layer is conducive to improving the degree of bonding with the other two layers, thereby improving the structural stability of the modified fiber as a whole. The mineralized surface layer contains silicates and silicon dioxide in amorphous and / or microcrystalline form, which belongs to an inorganic mineralized layer and can improve the compatibility of the modified fiber with the concrete material and promote mutual penetration. Compared with existing modified fibers, the modified fiber of the embodiment of the present application can be used in concrete materials to further improve the mechanical strength, and can also improve the durability and resistance to microbial erosion of concrete materials.

[0034] About fiber matrix:

[0035] In some embodiments, the diameter of the fiber matrix can be 15 to 30 μm; in exemplary embodiments, this can include, but is not limited to, any value or range between any two values ​​of 15 μm, 20 μm, 25 μm, and 30 μm. In some embodiments, the length of the fiber matrix can be approximately 6 mm. Fiber matrices of these diameters and lengths have a certain mechanical strength, thus imparting corresponding mechanical strength to the modified fiber.

[0036] In some embodiments, the fiber matrix can include at least one of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), carbon fiber, and glass fiber, and PET is optional. The fiber matrix of these types of materials has a certain mechanical strength and can also be tightly combined with the hydrophilic layer, giving the modified fiber corresponding mechanical strength and structural stability, and can be used for modification in concrete materials.

[0037] About the hydrophilic layer:

[0038] The primary function of the hydrophilic layer is to hydrophilically modify the fiber matrix, forming hydrophilic fibers together with the fiber matrix to better bond with the mineralized surface layer, enhancing the bonding between the three layers and resulting in a modified fiber. The hydrophilic layer may contain a hydrophilic substance or a hydrophilic group to impart hydrophilicity. In some embodiments, the hydrophilic layer contains at least one of amino and hydroxyl groups, which exhibit excellent hydrophilic properties and facilitate close bonding between the fiber matrix and the mineralized surface layer.

[0039] In some embodiments, the hydrophilic layer contains polydopamine, which is a product obtained by polymerization of dopamine and contains hydrophilic groups such as amino groups and hydroxyl groups, which further facilitates the hydrophilic layer to be tightly bonded to the fiber matrix and the mineralized surface layer.

[0040] In some embodiments, the mass content of the hydrophilic layer in the modified fiber can be 0.5% to 5%; in exemplary embodiments, it can include, but is not limited to, any value of 0.5%, 1.0%, 2.0%, 3.0%, or 5.0%, or a range between any two values. These mass contents of the hydrophilic layer impart good hydrophilicity to the modified fiber, allowing it to function as an intermediate layer, tightly bonding the fiber matrix and the mineralized surface layer. In contrast, if the hydrophilic layer is not present as an intermediate layer and the mineralized surface layer is applied directly to the fiber matrix, the bond between the two layers is weak and easily detached, making it difficult to obtain a structurally stable modified fiber.

[0041] About the mineralized surface:

[0042] The mineralized surface layer, containing silicates and silicon dioxide in amorphous and / or microcrystalline forms, is an inorganic mineralized layer that firmly bonds with the hydrophilic layer. This layer also improves the compatibility of the modified fiber with concrete, promoting mutual penetration. Therefore, compared to existing modified fibers, the use of modified fibers in concrete can further enhance mechanical strength, durability, and resistance to microbial attack.

[0043] In some embodiments, the mineralized surface layer comprises 3% to 10% by weight of the modified fiber; in exemplary embodiments, this may include, but is not limited to, any value of 3%, 5%, 7%, 9%, or 10%, or a range between any two values. These mineralized surface layer contents impart improved compatibility between the modified fiber and concrete, promoting interpenetration and further enhancing the mechanical strength, durability, and resistance to microbial attack of the concrete.

[0044] In some embodiments, the mass ratio of silicate to silicon dioxide is 1:(1-4); in exemplary embodiments, it may include but is not limited to any ratio of 1:1, 1:2, 1:3, 1:4 or a range between any two ratios. These mass ratios of silicate and silicon dioxide are beneficial to improving the compatibility of the mineralized surface layer and the concrete material, promoting mutual penetration, and further improving the above-mentioned properties of the modified fiber.

[0045] In some embodiments, the silicate in the mineralized surface layer includes at least one of sodium silicate, ethyl silicate, potassium silicate, and magnesium silicate. These mineralized surfaces are beneficial to improving the degree of bonding with the hydrophilic layer, and can also improve the compatibility with concrete materials, promote mutual penetration, and improve the above-mentioned properties of the modified fiber for concrete. Sodium silicate is optional. Not only does it have the above-mentioned ideal properties, but it also does not introduce impurity ions that affect the properties of the concrete material.

[0046] The second aspect of the present application provides a method for preparing the modified fiber of the above application embodiment, comprising the following steps:

[0047] S10. The fiber matrix is ​​subjected to a hydrophilic modification treatment to form a hydrophilic layer on the surface of the fiber matrix to obtain a hydrophilic fiber;

[0048] S20. Depositing the silicate raw material on the surface of the hydrophilic fiber to form a mineralized surface layer covering the hydrophilic fiber to obtain a modified fiber.

[0049] The preparation method of the embodiment of the present application first hydrophilically modifies the fiber matrix to obtain hydrophilic fibers, forming a tightly bonded hydrophilic layer on the surface of the fiber matrix, and then depositing the modified fiber to form a mineralized surface layer tightly bonded to the hydrophilic layer to obtain the modified fiber. As a result, the modified fiber forms a three-layer structure of fiber matrix, hydrophilic layer, and mineralized surface layer, which has good compatibility with concrete materials, promotes mutual penetration, and can be used in concrete materials to improve the mechanical strength, durability, and resistance to microbial erosion of concrete materials. The preparation method is process-controllable, and the modified fiber structure and physicochemical properties are stable.

[0050] Step S10 is a step of subjecting the fiber matrix to a hydrophilic modification treatment.

[0051] Before the hydrophilic modification treatment, the fiber matrix can be cleaned to remove possible impurities. In an exemplary embodiment, the fiber matrix can be dispersed in deionized water and ultrasonically cleaned for 30 minutes, and then dried. In an exemplary embodiment, the fiber matrix can be placed in an oven and dried at 60°C to constant weight to obtain a clean fiber matrix.

[0052] The fiber matrix is ​​subjected to a hydrophilic modification treatment to form a hydrophilic layer containing a hydrophilic substance or a hydrophilic group on the surface of the modified fiber. The hydrophilic modification treatment can be performed with a material containing hydroxyl groups and / or amino groups, thereby activating the fiber matrix to obtain a hydrophilic fiber. In some embodiments, the hydrophilic modification treatment includes the steps of dispersing the fiber matrix in a dopamine solution and performing a polymerization reaction. Dopamine is a catecholamine containing catechol and ethylamine groups. The structure of catechol is a benzene ring with two adjacent hydroxyl groups bonded to it. The structural formula is shown in A below:

[0053]

[0054] Therefore, dopamine is rich in hydrophilic groups such as hydroxyl and amino groups. After mixing with the fiber matrix, it can hydrophilically modify the fiber matrix and activate the fiber matrix. In addition, in an aerobic reaction environment, dopamine can undergo a series of complex spontaneous redox reactions to generate a variety of intermediates, some of which will polymerize to form polydopamine. Since the above reactions involve many types, we will focus on Figure 1As an example, the reaction process of one type of dopamine redox polymerization reaction is described. First, the hydroxyl group on the dopamine is oxidized to a carbonyl group. Subsequently, a series of redox reactions occur, and ethylamine also forms a nitrogen-containing heterocycle, forming an intermediate product containing groups such as indole. Finally, polydopamine is self-polymerized. Polydopamine is rich in hydrophilic groups such as hydroxyl, amino, and imino (-NH-) groups, and spontaneously forms a highly hydrophilic film layer, namely the hydrophilic layer. Furthermore, this redox autopolymerization reaction causes the intermediate product and the generated polydopamine to adhere tightly to the surface of the fiber matrix, facilitating a close bonding between the hydrophilic layer and the fiber matrix.

[0055] In some embodiments, since dopamine is unstable in environments such as air, various modified dopamines with good stability can be selected as the dopamine raw material. In exemplary embodiments, dopamine hydrochloride can be used. The pH of the dopamine solution can be 8.5 to 9.0; in exemplary embodiments, it can include but is not limited to any value of 8.5, 8.6, 8.7, 8.8, 8.9, or 9.0, or a range between any two values, with 8.8 being the preferred value. Dopamine solutions with these pH values ​​can further enhance the hydrophilic modification effect of dopamine on the fiber matrix, facilitating the redox polymerization reaction of dopamine to form a hydrophilic layer that tightly binds to the fiber matrix. Furthermore, dopamine polymerization is strongly affected by pH. At a pH of 8.8, the oxidation and polymerization rates of dopamine are rapid. The hydrophilic layer formed by polydopamine at a pH of 8.8 has good adhesion and can evenly coat the surfaces of various fiber matrices. In exemplary embodiments, dopamine can be first prepared into a solution, and then Tris-HCl buffer can be added to adjust the pH to the above range.

[0056] In some embodiments, the concentration of the dopamine solution can be adjusted to 1-4 g / L. In exemplary embodiments, the concentration can include, but is not limited to, any value of 1 g / L, 2 g / L, 3 g / L, or 4 g / L, or a range between any two values, with 2 g / L being an option. Dopamine solutions having such concentrations are beneficial for further enhancing the hydrophilic modification effect of dopamine on the fiber matrix, facilitating the redox polymerization reaction of dopamine to form a hydrophilic layer that is tightly bound to the fiber matrix.

[0057] In some embodiments, the mass ratio of the fiber matrix to dopamine is (0.8-0.95):1. In exemplary embodiments, this ratio may include, but is not limited to, any value or range between any two values ​​of 0.8:1, 0.85:1, 0.9:1, and 0.95:1. These mass ratios are beneficial for further enhancing the hydrophilic modification effect of dopamine on the fiber matrix, facilitating the redox autopolymerization reaction of dopamine to form a hydrophilic layer that is tightly bound to the fiber matrix.

[0058] In some embodiments, the polymerization reaction time is 12 to 48 hours. In the exemplary examples, it may include but is not limited to 12 hours, 18 hours, 24 hours, 27 hours, 30 hours, and 48 hours. In some embodiments, the above-mentioned polymerization reaction can be carried out by adding the fiber matrix to the dopamine solution and stirring evenly, and then standing to cause spontaneous redox polymerization reaction; or ultrasonic dispersion can be further performed after standing to fully promote the hydrophilic modification effect of dopamine on the fiber matrix, fully promote the redox polymerization reaction of dopamine, promote the uniformity of the modification degree at different positions on the fiber matrix, and promote the uniformity of the thickness of the hydrophilic layer at different positions. In the exemplary example, it can be allowed to stand for 24 hours first, and then ultrasonic dispersion can be performed for 30 minutes. The power of ultrasonic dispersion can be 100 to 500W, and can be optionally 100W, so that the dopamine modification is uniform.

[0059] Step S20 involves a deposition process to form a mineralized surface layer. This deposition process forms an inorganic mineralized surface layer on the surface of the hydrophilic fiber. This deposition process tightly bonds the resulting mineralized surface layer with the hydrophilic layer, improving the structural stability of the resulting modified fiber. Furthermore, the inorganic mineralized surface layer enhances the compatibility of the resulting modified fiber with concrete, promoting mutual penetration. Application to concrete can improve the mechanical strength, durability, and resistance to microbial attack of the concrete.

[0060] In some embodiments, the deposition treatment includes the step of immersing the hydrophilic fiber in a solution of a silicate raw material to carry out a reaction. The silicate raw material can deposit a mineralized surface layer containing silicate and silicon dioxide on the surface of the hydrophilic fiber to form a mineral inorganic layer. In the exemplary embodiment, the silicate raw material can include at least one of sodium silicate, ethyl silicate, potassium silicate, and magnesium silicate, and sodium silicate can be selected, with the chemical formula of Na2O·nSiO2, where n is 1 to 4; the selection of sodium silicate as the silicate has the following beneficial effects: sodium silicate is easily hydrolyzed and deposits a mineralized surface layer containing sodium silicate and silicon dioxide on the surface of the hydrophilic fiber, and it will not introduce impurity ions when used in concrete. In the exemplary embodiment, the sodium silicate can be sodium metasilicate, with the chemical formula of Na2SiO3. After sodium metasilicate is dissolved in water, the following hydrolysis reaction will first occur:

[0061] Na2SiO3+3H2O→2NaOH+Si(OH)4

[0062] Sodium metasilicate decomposes into silicic acid and sodium hydroxide, Si(OH)4 and NaOH. The sodium hydroxide dissolves in the solvent or is later removed by rinsing. Silicic acid, also known as orthosilicic acid, has the chemical formula Si(OH)4 and is an unstable compound that undergoes rapid condensation reactions. The condensation reaction between silicic acid molecules forms silicon-oxygen chains or ring structures of varying lengths, ultimately forming a deposit of silicon dioxide. Therefore, water molecules are generated during the condensation process, forming silicon-oxygen bonds:

[0063] Si(OH)4→SiO2+2H2O

[0064] As the reaction proceeds, the formed SiO2 can be deposited on the surface of the hydrophilic fiber, and some of the sodium silicate raw material will also co-deposit to form a silicate layer, which is tightly bound to the hydrophilic layer. The material in this silicate layer is mainly amorphous and / or microcrystalline, with a certain degree of porosity and crystallinity. These properties can be adjusted and optimized by controlling the reaction conditions such as pH, reaction time, and temperature.

[0065] In some embodiments, the concentration of the solution of the silicate raw material is 0.45 to 1 mol / L. Optionally, the concentration is any value of 0.45 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, or a range between any two values. Solutions of silicate raw materials with these concentrations are beneficial to promoting the above-mentioned deposition reaction and forming a mineralized surface layer.

[0066] In some embodiments, the pH of the silicate raw material solution is between 10 and 12. Optionally, the pH is 10. In exemplary embodiments, the pH may include, but is not limited to, any value of 10, 10.5, 11, 11.5, or 12, or a range between any two values. Solutions of silicate raw materials having these pH values ​​are beneficial for promoting the aforementioned deposition reaction and forming a mineralized surface layer. In some embodiments, a solution of silicate raw material can be prepared at a certain concentration and its pH measured. If the pH is too high, dilute acid can be added to adjust the pH to within an appropriate range.

[0067] In some embodiments, the hydrophilic fiber is immersed in the silicate raw material solution for a reaction at a temperature of 20 to 50° C. In some embodiments, the hydrophilic fiber is immersed in the silicate raw material solution for a reaction time of 12 to 48 hours. In some exemplary embodiments, the hydrophilic fiber can be immersed in the silicate raw material solution and allowed to settle naturally, or it can be subjected to ultrasonic dispersion treatment for 30 minutes to allow the silicate raw material to fully react and settle to obtain a uniform mineralized surface layer, thereby obtaining the modified fiber.

[0068] The preparation method of steps S10 and S20 simulates the mineralization process in the natural environment, can use mild raw materials and reaction conditions, and has good environmental friendliness.

[0069] After all of the above reactions are complete, the modified fiber can be removed from the silicate solution and rinsed with plenty of deionized water to remove any unreacted residual chemicals and byproducts, such as the sodium ions generated by the hydrolysis reaction. Finally, the rinsed modified fiber can be dried. In this example, drying can be performed in an oven at 60°C to obtain a clean modified fiber.

[0070] A third aspect of the embodiments of the present application provides a modified concrete containing the modified fiber of the above embodiments of the application, or containing the modified fiber prepared by the preparation method of the modified fiber of the above embodiments of the application.

[0071] The modified concrete of the embodiment of the present application contains the modified fiber of the embodiment of the above-mentioned application. Therefore, the modified fiber has good compatibility with the concrete material, promotes mutual penetration, can improve the mechanical strength of the modified concrete material, and can also improve the durability and resistance to microbial erosion of the modified concrete.

[0072] In some embodiments, the modified concrete is a cement-based modified concrete to further improve the compatibility of the modified fiber in the modified concrete and promote mutual penetration. The mass content of the modified fiber in the modified concrete can be 1% to 5%; in the exemplary embodiment, it can include but is not limited to any value of 1%, 2%, 3%, 4%, 5% or a range between any two values.

[0073] In some embodiments, in addition to modified fibers, the modified concrete may also include Portland cement, and may also include at least one of auxiliary cementitious materials (fly ash, silica fume, etc.), a water reducer, and aggregate. In some embodiments, 3D printed concrete may be further prepared, and the modified concrete may include the following components in parts by weight:

[0074]

[0075]

[0076] Among them, the mass proportion of silicate cement may include but is not limited to any value of 580 parts, 600 parts, 620 parts, 640 parts, and 660 parts, or a range between any two values; the mass proportion of auxiliary cementitious material may include but is not limited to any value of 260 parts, 267 parts, 274 parts, and 280 parts, or a range between any two values; the auxiliary cementitious material may include fly ash and silica fume, the mass ratio of fly ash to silica fume may be about 2:1, the mass proportion of fly ash may be 175-185 parts, and the mass proportion of silica fume may be 85-95 parts; the mass proportion of water reducer may include but is not limited to any value of 3.3 parts, 3.4 parts, and 3.5 parts, or a range between any two values; the mass proportion of aggregate may include but is not limited to any value of 1300 parts, 1330 parts, 1360 parts, and 1400 parts, or a range between any two values; the mass proportion of modified fiber may include but is not limited to any value of 2.2 parts, 5 parts, 7 parts, 9 parts, and 11.5 parts, or a range between any two values. The modified concrete of these components in parts by mass can improve the mechanical strength, durability, resistance to microbial erosion and other properties of the modified concrete; and after adding an appropriate amount of water, it has good fluidity, pumpability, buildability, molding speed and mechanical strength. It can be further used as a raw material for 3D printing concrete for pouring and 3D printing, and can prepare 3D printed concrete structures with enhanced mechanical properties.

[0077] After testing, the concrete structure obtained after pouring the modified concrete includes at least one of the following characteristics:

[0078] (1) 28-day compressive strength is 64-73 MPa;

[0079] (2) 28-day flexural strength is 9-11 MPa;

[0080] (3) The tensile strength after 28 days is 2.8-3.2 MPa;

[0081] (4) The chloride ion diffusion rate is (5~8.2)×10 -12 m 2 / Second;

[0082] (5) The 28-day anti-microbial erosion performance is characterized by a pH value of 10.9 to 11.5. Among them, anti-microbial erosion performance refers to the fact that the metabolism of microorganisms such as sulfur-oxidizing bacteria (SOB), sulfate-reducing bacteria (SRB), nitrifying bacteria, and Fusarium species can easily cause concrete corrosion and destroy structures such as CSH in concrete. The typical manifestation is that the pH value of concrete decreases, continuously providing conditions for the growth and reproduction of microorganisms such as sulfur-oxidizing bacteria. When the pH value in concrete is high and stable, it can be considered that the anti-microbial erosion performance is high.

[0083] Therefore, combined with the above test results, it can be seen that the modified concrete made from modified fibers has high mechanical strength, and also has strong durability and resistance to microbial erosion, and can be used in environments with high service requirements, such as lakes, rivers, oceans and other scenes.

[0084] The following describes the details in conjunction with specific embodiments.

[0085] Example A1

[0086] This embodiment provides a modified fiber and a preparation method thereof. The modified fiber includes a PET fiber matrix, a hydrophilic layer and a mineralized surface layer. The hydrophilic layer covers the PET fiber matrix, and the mineralized surface layer covers the hydrophilic layer. The mineralized surface layer contains sodium silicate and silicon dioxide, and the sodium silicate and silicon dioxide are in amorphous and microcrystalline forms.

[0087] The preparation method comprises the following steps:

[0088] S1. Dopamine modified fiber matrix:

[0089] 1.6 g of dopamine hydrochloride powder was mixed and dissolved in 800 mL of deionized water, and then the pH was adjusted to 8.8 with Tris-HCl buffer. The concentration of the prepared dopamine hydrochloride modified solution was 2 g / L.

[0090] PET fibers with a diameter of about 25 μm and a length of about 6 mm were ultrasonically cleaned in deionized water for 30 minutes, and then dried in a 60°C oven to constant weight to remove possible impurities. 15 g of the dried PET fibers were placed in the above-mentioned dopamine hydrochloride modification solution, stirred thoroughly with a glass stirring rod, exposed to air, and modified for 24 hours. The fibers were then transferred as a whole into an ultrasonic reactor, and dopamine was uniformly dispersed on the surface of the PET fibers for 30 minutes by ultrasonic action, thereby promoting uniform adsorption of dopamine on the fiber surface to obtain hydrophilic fibers.

[0091] S2. Formation of mineralized surface layer:

[0092] First, prepare 1 liter of 0.5 mol / L sodium metasilicate solution. According to the molecular weight of sodium metasilicate (about 122.06 g / mol), 61.03 grams of sodium metasilicate (Na2SiO3) is required, and the balance is water as a solvent; then slowly add dilute hydrochloric acid dropwise to a pH of 10 to obtain the sodium metasilicate solution for modification;

[0093] The hydrophilic fiber was immersed in the adjusted sodium metasilicate solution and ultrasonically dispersed for 30 minutes. After the reaction was completed, the modified fiber was taken out from the solution and washed with a large amount of deionized water to remove unreacted chemicals and by-products. Finally, the modified fiber was dried in an oven at 60°C to obtain a clean modified fiber.

[0094] Example A2

[0095] This embodiment provides a modified fiber and a preparation method thereof, which differs from Example A1 only in that the pH of the sodium metasilicate solution is adjusted to 12 with dilute hydrochloric acid in step S2, and all other aspects are the same.

[0096] Example A3

[0097] This embodiment provides a modified fiber and a preparation method thereof, which differs from Embodiment A1 only in that the pH of the sodium metasilicate solution is adjusted to 9 with dilute hydrochloric acid in step S2, and all other aspects are the same.

[0098] Example A4

[0099] This embodiment provides a modified fiber and a preparation method thereof. The only difference from Example A1 is that the sodium metasilicate in step S2 is replaced with sodium orthosilicate, whose chemical formula is Na4SiO4. Similarly, 1 liter of 0.5 mol / L sodium orthosilicate solution is first prepared. All other aspects are the same.

[0100] Example A5

[0101] This embodiment provides a modified fiber and a preparation method thereof. The only difference from Example A1 is that the sodium metasilicate in step S2 is replaced with potassium silicate, whose chemical formula is K2SiO3. Similarly, 1 liter of 0.5 mol / L potassium silicate solution is first prepared. All other aspects are the same.

[0102] Example A6

[0103] This embodiment provides modified fibers and a preparation method thereof. The only difference from Example A1 is that the ultrasonic dispersion treatment for 30 min in step S2 is replaced by immersing the hydrophilic fibers in an adjusted sodium metasilicate solution, stirring evenly with a glass rod, and then standing for 24 h. All other aspects are the same.

[0104] Example A7

[0105] This embodiment provides modified fibers and a preparation method thereof, which differs from embodiment A1 only in that in step S1 , ultrasonic treatment is not performed after the static modification for 24 hours, and all other aspects are the same.

[0106] Example A8

[0107] This embodiment provides a modified fiber and a preparation method thereof, which differs from Example A1 only in that the pH value of the dopamine hydrochloride solution is adjusted from 8.8 to 8.5 in step S1, and all other aspects are the same.

[0108] Comparative Example A1

[0109] This comparative example provides a fiber material and a preparation method thereof, which differs from Example A1 only in that the PET fiber provided in step S1 is directly used as the fiber material without any modification treatment.

[0110] Comparative Example A2

[0111] This comparative example provides a fiber material and a preparation method thereof, which differs from Example A1 only in that step S2 is not included, and the dopamine hydrophilic modified PET fiber prepared in step S1 is directly used as the fiber material, and all other aspects are the same.

[0112] Comparative Example A3

[0113] This comparative example provides a fiber material and a preparation method thereof, which differs from Example A1 only in that the dopamine hydrophilic modification treatment in step S1 is not included, and the PET fiber in step S1 is directly used in step S2 to be immersed in the adjusted sodium metasilicate solution. Other aspects are the same.

[0114] The differences between the above cases are recorded in Table 1 below:

[0115] Table 1

[0116] Case Silicate solution pH Silicate types Other differences from Example A1 Example A1 10 Sodium metasilicate / Example A2 12 Sodium metasilicate / Example A3 9 Sodium metasilicate / Example A4 10 Sodium orthosilicate / Example A5 10 Potassium silicate / Example A6 10 Sodium metasilicate The hydrophilic fiber was placed in the silicate solution for 24 hours. Example A7 10 Sodium metasilicate Only stand in dopamine solution for 24 hours without ultrasonic treatment Example A8 10 Sodium metasilicate The pH of the dopamine solution was changed from 8.8 to 8.5 Comparative Example A1 / / PET fiber, unmodified Comparative Example A2 / / No silicate deposition Comparative Example A3 10 Sodium metasilicate No dopamine modification

[0117] The modified fibers provided in Examples A1 to A8 and the fiber materials provided in Comparative Examples A1 to A3 were used in 3D printing concrete materials and mixed according to the following mass parts:

[0118]

[0119]

[0120] A modified concrete was obtained, wherein fly ash and silica fume were auxiliary cementitious materials, a polycarboxylate high-performance water reducer was used as the water reducer, and quartz sand was used as the aggregate. The modified concrete was then mixed with water at a water-cement ratio of 0.3, and concrete components with the same structure were produced by pouring and 3D printing. The concrete component produced using the modified fiber provided in Example A1 is designated as Example B1, the concrete component produced using the modified fiber provided in Example A2 is designated as Example B2, and so on, up to the concrete component produced using the fiber material provided in Comparative Example A3, which is designated as Comparative Example B3.

[0121] Then, the fiber dosage in Example B1 was changed to 6.7, recorded as Concrete Component Example B9, the fiber dosage in Example B1 was changed to 11.1, recorded as Concrete Component Example B10, the fiber dosage in Comparative Example B1 was changed to 6.7, recorded as Concrete Component Comparative Example B4, and the fiber dosage in Comparative Example B1 was changed to 11.1, recorded as Concrete Component Comparative Example B5.

[0122] Related performance tests and result analysis

[0123] 1. Morphology analysis:

[0124] The concrete components of Examples B1 to B10 and Comparative Examples B1 to B5 were subjected to scanning electron microscopy to obtain SEM images; wherein, Figure 2 This is a diagram of the interface between the PET fiber and concrete in Comparative Example B1;

[0125] Figure 3 is a diagram of the interface between the modified PET fiber and concrete in Example B1, Figure 3 The MPET-24 in the text refers to the modified fiber, which was soaked in the dopamine solution for 24 h. Figure 4 This is a diagram showing the interface of the PET fiber removed from concrete in Comparative Example B1; Figure 5 This is the interface diagram of the modified PET fiber taken out from concrete in Example B1. Figure 5 The MPET-24 in the figure refers to the modified fiber, which was soaked in the dopamine solution for 24 h.

[0126] from Figure 2 、 Figure 3 It can be seen that compared with directly using PET fibers in concrete, the modified PET fibers in Example B1 have better compatibility with concrete materials. Because the modified PET fibers are hydrophilic modified and deposited, the mineralized surface layer formed is fully compatible with the concrete material and has penetrated each other. The interface has become blurred and difficult to clearly separate. Figure 4 、 Figure 5 It can be seen that the mineralized surface layer of the modified PET fiber in Example B1 has penetrated into the concrete material. A lot of concrete material remains on the removed modified PET fiber, and part of the mineralized surface layer has also penetrated into the concrete material. However, the surface of the PET fiber in Comparative Example B1 is intact in the concrete material, and is not fully compatible with or mutually penetrated into the concrete material.

[0127] 2.XRD analysis:

[0128] The modified fibers or fibers were taken out from the concrete components of Examples B1 to B10 and Comparative Examples B1 to B5, as well as the concrete components of the blank group. The components of the interface where the modified fibers were taken out of the concrete were analyzed by X-ray diffractometer. The obtained XRD patterns are shown in FIG. Figure 6 As shown, from Figure 6 It can be seen that the modified fibers of various embodiments are fully compatible with the interface of concrete, which includes a variety of crystalline components, including a variety of components in concrete and microcrystalline components in the mineralized surface layer of the modified fibers.

[0129] 3. Mechanical properties test:

[0130] After pouring and printing, the concrete components were cured using a computer electronic universal testing machine (YAW-300b) at a loading speed of 2.4 kN / s to measure their compressive and tensile strengths. The tests were conducted at different ages: 3 days, 7 days, and 28 days. The results are shown in Table 2 below. The blank group in Table 2 is a control group in which no fiber was added.

[0131] Table 2

[0132]

[0133]

[0134] 4. Durability test:

[0135] Using the chloride ion penetration resistance test, according to the requirements of GB / T 50082-2009, a cylindrical mortar specimen with a diameter of 100 mm x 100 mm was first prepared. After the specimen was cast, it was demolded 24 hours later and placed in a standard curing room for immersion in deionized water for curing. To ensure that the specimen met the requirements of the chloride ion penetration resistance test, the cylindrical specimen was processed 7 days before the test to ensure that it met the standard dimensions required by the testing instrument. The specific steps are as follows:

[0136] (1) After taking out the cylindrical specimen, cut a cylinder with a height of 50±2mm from its middle part for testing. The end close to the casting surface is used as the test surface exposed to the chloride ion solution, and its surface is marked.

[0137] (2) The cut specimens were polished using water sandpaper and then continued to be immersed in deionized water until the curing age reached 28 days.

[0138] (3) After the curing period, take out the treated mortar specimens, clean the surface debris, and wipe off excess moisture on the surface.

[0139] (4) Use a vernier caliper to accurately measure the diameter and height of the specimen with a measurement accuracy of 0.1 mm.

[0140] (5) Place the specimen in a vacuum water saturator for water saturation. First, reduce the air pressure to 1 kPa within 5 minutes and maintain it for 3 hours. Then, while continuing to operate the vacuum pump, inject saturated calcium hydroxide solution until the specimen surface is completely immersed. After the specimen is immersed in the solution for 1 hour, return it to normal pressure and continue to immerse it for another 20 hours.

[0141] (6) Remove the test piece, dry the surface with a hair dryer at the cold air block, and then install it in the RCM test device. Inject 0.3 mol / L NaOH and 10% NaCl solution into the anode and cathode respectively to ensure that the liquid levels of the solutions inside and outside the rubber sleeve are consistent.

[0142] (7) Conduct an electrically accelerated chloride ion rapid migration test at an initial voltage of 30 V. Adjust the voltage based on the initial current. Record the initial and final solution temperatures at the anode and the final current.

[0143] (8) After the test is completed, the cylindrical specimen is removed, the scale or sediment on the surface is removed and rinsed with deionized water. The specimen is divided into two halves along the axial direction and 0.1 mol / L AgNO3 solution is immediately sprayed on the fracture surface for color development.

[0144] (9) After the surface is dry, the cross section of the cylindrical specimen is divided into 10 equal parts along the diameter. The outline of the chloride ion penetration is marked with a marker pen, and the penetration depth of the chloride ions is measured with a vernier caliper to an accuracy of 0.1 mm.

[0145] (10) According to GB / T 50082-2009, the calculation formula for the chloride ion migration coefficient of concrete is:

[0146]

[0147] Among them, D RCM is the chloride ion migration coefficient, accurate to 0.1×10 -12 m 2 / s; U is the absolute value of the voltage used in the experimental test process (V); T represents the average value of the initial and final temperatures of the anode solution (°C); L represents the thickness of the specimen (mm, accurate to 0.1mm); X d It represents the average value of chloride ion penetration depth (mm, accurate to 0.1mm); t is the duration of the test power-on, t is 24h.

[0148] The chloride ion penetration resistance, i.e., durability, corresponding to 28 days of curing was measured by the above method. The results are shown in Table 3 below. The smaller the chloride ion penetration rate, the better the durability.

[0149] 4. Anti-microbial erosion test:

[0150] The pH distribution of concrete specimens at different depths was measured using a powder suspension method. To measure pH, for Example B1, multiple samples, each at least 3 mm thick, were taken from concrete components that had been cured for 28 days. Samples were taken from different depths and locations after curing to assess overall pH changes and characterize antimicrobial performance. Each sample was ground into a fine powder, ensuring uniform grinding. The ground concrete powder was then mixed with deionized distilled water at a 1:1 solid-to-liquid ratio. For every gram of concrete powder, 1 ml of water was added. The mixture was stirred for 5 minutes to ensure thorough mixing. The pH of each suspension was measured using a calibrated pH probe, ensuring the suspension was allowed to settle sufficiently to allow solid particles to settle. The results were averaged to obtain the pH value for Example B1, which was used to characterize antimicrobial performance. Antimicrobial performance was measured using this method for other examples and comparative examples. The results are shown in Table 3 below. Higher pH values ​​indicate better antimicrobial performance. The blank control group in Table 3 represents a blank control group without fiber addition.

[0151] Table 3

[0152] Case <![CDATA[Chloride ion penetration rate (m 2 / s)]]> Anti-microbial erosion performance (pH value) Example B1 <![CDATA[7.2×10 -12 ]]> 11.3 Example B2 <![CDATA[7.3×10 -12 ]]> 11.1 Example B3 <![CDATA[7.2×10 -12 ]]> 11.0 Example B4 <![CDATA[7.3×10 -12 ]]> 11.1 Example B5 <![CDATA[7.5×10 -12 ]]> 11.1 Example B6 <![CDATA[7.6×10 -12 ]]> 11.2 Example B7 <![CDATA[7.5×10 -12 ]]> 11.1 Example B8 <![CDATA[7.7×10 -12 ]]> 11.1 Example B9 <![CDATA[5×10 -12 ]]> 11.5 Example B10 <![CDATA[8.2×10 -12 ]]> 10.9 Blank group <![CDATA[20.2×10 -12 ]]> 9.7 Comparative Example B1 <![CDATA[15.4×10 -12 ]]> 9.9 Comparative Example B2 <![CDATA[15.6×10 -12 ]]> 10.5 Comparative Example B3 <![CDATA[17.2×10 -12 ]]> 10.2 Comparative Example B4 <![CDATA[17.3×10 -12 ]]> 10.1 Comparative Example B5 <![CDATA[18.4×10 -12 ]]> 9.9

[0153] From Table 1, Table 2, and Table 3, it can be seen that in each embodiment, the fiber matrix surface is modified by dopamine polymerization to form a hydrophilic layer, and silicate is deposited on the surface to form a mineralized surface layer. When used in concrete materials, the mechanical strength can be further improved, and the durability and resistance to microbial erosion of the concrete material can also be improved. In contrast, the fiber matrix of each comparative example is not modified, or lacks hydrophilic layer modification, or lacks mineralized surface modification, and the relevant properties are affected. Compared with Comparative Examples B1, B4, and B5, Examples B1, B9, and B10, respectively, add 2.2 parts, 6.7 parts, and 11.1 parts of modified fibers to the concrete. The performance of the concrete using the modified fibers is significantly better than that of the concrete adding conventional PET fibers.

[0154] The pH value of the dopamine solution is 8.8, and the use of ultrasonic dispersion treatment is beneficial to further improve the performance of the modified fiber. The selection of sodium metasilicate as silicate, the control of the pH value of the solution, and the use of ultrasonic dispersion treatment are all beneficial to further improve the performance of the modified fiber.

[0155] Moreover, a comparison of Examples B1, B9, and B10 shows that adding modified fibers of appropriate quality to concrete materials is also beneficial to improving relevant properties of the concrete materials.

[0156] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A modified fiber, characterized in that: For concrete materials, the modified fiber comprises: Fiber matrix; A hydrophilic layer, wherein the hydrophilic layer covers the fiber matrix, and the material of the hydrophilic layer is polydopamine; A mineralized surface layer covers the hydrophilic layer, and the mineralized surface layer contains silicate and silicon dioxide, and the silicate and silicon dioxide are in amorphous and / or microcrystalline form.

2. The modified fiber according to claim 1, characterized in that: The silicate comprises at least one of sodium silicate, ethyl silicate, potassium silicate and magnesium silicate; and / or The mass content of the mineralized surface layer in the modified fiber is 3% to 10%; and / or The mass ratio of the silicate to silicon dioxide is 1:(1-4).

3. The modified fiber according to claim 1 or 2, characterized in that: The mass content of the hydrophilic layer in the modified fiber is 0.5% to 5%; and / or The diameter of the fiber matrix is ​​15 to 30 μm; and / or The fiber matrix includes at least one of polyethylene terephthalate, polypropylene, polyethylene, carbon fiber, and glass fiber.

4. A method for preparing the modified fiber according to any one of claims 1 to 3, characterized in that: The steps include: The fiber matrix is ​​subjected to a hydrophilic modification treatment to form the hydrophilic layer on the surface of the fiber matrix to obtain a hydrophilic fiber; The silicate raw material is deposited on the surface of the hydrophilic fiber to form the mineralized surface layer covering the hydrophilic fiber, thereby obtaining the modified fiber.

5. The method for preparing the modified fiber according to claim 4, characterized in that: The hydrophilic modification treatment includes the steps of dispersing the fiber matrix in a dopamine solution and performing a polymerization reaction; wherein, The pH of the dopamine solution is 8.5-9.0; and / or The mass ratio of the fiber matrix to the dopamine is (0.8-0.95):

1.

6. The method for preparing the modified fiber according to claim 5, characterized in that: The pH of the dopamine solution is 8.8; and / or The polymerization reaction time is 12 to 48 hours; and / or The concentration of the dopamine solution is 1-4 g / L.

7. The method for preparing the modified fiber according to any one of claims 4 to 6, characterized in that: The deposition process includes the step of soaking the hydrophilic fiber in a solution of the silicate raw material to react; wherein, The silicate raw material includes at least one of sodium silicate, ethyl silicate, potassium silicate and magnesium silicate; and / or The concentration of the silicate raw material solution is 0.45 to 1 mol / L; and / or The pH of the solution of the silicate raw material is 10 to 12; and / or The reaction time of soaking the hydrophilic fiber in the solution of the silicate raw material is 12 to 48 hours.

8. A modified concrete, characterized in that: A modified fiber comprising the modified fiber according to any one of claims 1 to 3, or a modified fiber prepared by the method for preparing the modified fiber according to any one of claims 4 to 7.

9. The modified concrete according to claim 8, characterized in that The composition comprises the following components in parts by weight:

10. The modified concrete according to claim 8 or 9, characterized in that: The modified concrete includes at least one of the following features (1) to (5): (1) 28-day compressive strength is 64-73 MPa; (2) 28-day flexural strength is 9-11 MPa; (3) The tensile strength after 28 days is 2.8-3.2 MPa; (4) The chloride ion diffusion rate is (5~8.2)×10 -12 m 2 / Second; (5) The 28-day antimicrobial erosion performance was characterized by a pH value of 10.9 to 11.5.

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