Preparation method and application of al2o3 modified ultrahigh molecular weight polyethylene fiber

Abstract

The application relates to the application field of high polymer materials in concrete for corrosion prevention of marine and coastal buildings, and particularly relates to a preparation method and application of Al2O3 modified ultrahigh molecular weight polyethylene fiber; the preparation method comprises the following steps: S1, ultrahigh molecular weight polyethylene fiber is subjected to oxidation treatment and drying; S2, the oxidized ultrahigh molecular weight polyethylene fiber is soaked in a coupling agent solution for hydrolysis, and then taken out for drying; S3, an aluminum salt, nitric acid and water are mixed to obtain a hydrolysis solution; the coupling agent grafted ultrahigh molecular weight polyethylene fiber is immersed in the hydrolysis solution; after stirring and reaction, the Al2O3 modified ultrahigh molecular weight polyethylene fiber is prepared. The prepared modified fiber is mixed into cement mortar, so that the combination capacity for chlorine ions can be improved, the durability of concrete in a high-chloride environment can be prolonged, interface cracks can be reduced, the mechanical properties of the concrete can be improved, and the service life can be prolonged.

Description

Technical Field

[0001] This invention relates to the application of polymer materials in concrete for corrosion protection in marine and coastal construction, specifically to a method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber and its application. Background Technology

[0002] In marine engineering construction, reinforced concrete components face durability challenges due to the high chloride content in aggregates such as sea sand and coral sand, which are constantly exposed to high chloride conditions after service. Chloride ion corrosion and penetration are common problems. Both endogenous and exogenous chloride ions readily undergo electrochemical reactions on the steel reinforcement surface, damaging the passivation film and causing corrosion, leading to a significant reduction in the durability of reinforced concrete and a shortened service life. In recent years, significant progress has been made in improving the performance of reinforced concrete structures by incorporating reinforcing fibers into cement mortar. Ultra-high molecular weight polyethylene (UHMWPE) fiber, as a high-strength and high-toughness material, is widely used for crack-resistant reinforcement of concrete structures. However, the interfacial bonding between single fibers and cement mortar is poor, and it cannot resist chloride ion corrosion of the steel reinforcement. Summary of the Invention

[0003] This invention overcomes the shortcomings of existing technologies by providing a method for preparing Al2O3-modified ultra-high molecular weight polyethylene fibers and their applications. Compared to methods that directly add nano-inorganic particles and single fibers to cement mortar, Al2O3 particles are attached to the fiber surface as a coating before being added to the cement mortar. This not only effectively avoids problems such as easy agglomeration of nanoparticles, which leads to poor cement crack resistance, but also solves the problems of poor durability caused by internal and external chloride ion penetration corrosion of steel bars and weak interfacial adhesion of composite materials by using a one-step method.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber, comprising the following steps: S1. Oxidize the ultra-high molecular weight polyethylene fiber to obtain oxidized ultra-high molecular weight polyethylene fiber, and then dry it. S2. Oxidized ultra-high molecular weight polyethylene fiber is soaked in a coupling agent solution for hydrolysis, then removed and dried to obtain coupling agent-grafted ultra-high molecular weight polyethylene fiber. S3. Aluminum salt, nitric acid and water are mixed to obtain a hydrolysis solution; the coupling agent-grafted ultra-high molecular weight polyethylene fiber is impregnated in the hydrolysis solution; after stirring and reaction, Al2O3 modified ultra-high molecular weight polyethylene fiber is prepared; and then dried and dispersed.

[0005] As a further limitation of the technical solution of the present invention, the oxidation treatment in step S1 is liquid phase oxidation treatment or electrochemical oxidation treatment; the drying method is one of natural air drying, atmospheric pressure heating drying, vacuum drying and freeze drying.

[0006] As a further limitation of the technical solution of the present invention, the oxidation system for liquid-phase oxidation treatment is at least one of nitric acid, sulfuric acid, H2O2, sodium hydroxide, and oxalic acid, with a concentration range of 0~100wt% and not 0, and a preset temperature range of 0~100℃. o C is not 0, and the time range is 0~50h and is not 0.

[0007] As a further limitation of the technical solution of the present invention, the electrolyte solution for electrochemical oxidation treatment is one of sodium hydroxide, ammonium bicarbonate, diammonium phosphate, triammonium phosphate, ammonium phosphate, sulfuric acid, and nitric acid, with a solution concentration of 0 mol / L to 20 mol / L and not equal to 0; the applied voltage is 0 to 50 V and not equal to 0; and the current density is 0.01-200 A / cm². 2 The time range is 0-50h and is not 0.

[0008] As a further limitation of the technical solution of the present invention, the coupling agent solution in step S2 is an aqueous solution of amino-based silane coupling agent, epoxy-based silane coupling agent, vinyl silane coupling agent, mercaptosilane coupling agent, or methacryloyloxysilane coupling agent; the mass ratio of coupling agent to water is 0.1:100 to 10:100, the hydrolysis time is 0 to 50 h and not 0, and the preset temperature range is 0 to 50 °C. o C is not 0.

[0009] As a further limitation of the technical solution of the present invention, the aluminum salt in step S3 is one of aluminum sec-butoxide, aluminum isopropoxide, organic low-alkyl groups, and inorganic aluminum salts; the molar ratio of aluminum salt, nitric acid, and water is 1:0.01~0.6:10~200; and the mixing temperature of the aluminum salt, nitric acid, and water is 0~100°C. o C; stirring reaction time: 0~12h; drying temperature: 40~100℃ o C. The drying method is one of the following: natural air drying, atmospheric pressure heating drying, vacuum drying, and freeze drying.

[0010] The present invention also provides Al2O3 modified ultra-high molecular weight polyethylene fiber obtained by the above preparation method.

[0011] The present invention also provides the application of the above-mentioned Al2O3 modified ultra-high molecular weight polyethylene fiber in the preparation of concrete with chloride ion curing and crack resistance functions.

[0012] As a further limitation of the application, the concrete includes component A and component B; Component A comprises the following raw materials in the following mass ratios: 1 part cement, 0.01-0.2 parts silica fume, 0.5-2 parts quartz sand, and 0.35-0.55 parts water; Component B is Al2O3 modified ultra-high molecular weight polyethylene fiber, the fiber length is 3~100mm; the added mass of the fiber accounts for 0.5%~8% of the mass of the cement.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention involves oxidizing ultra-high molecular weight polyethylene (UHMWPE) fibers and preferentially attaching a silane coupling agent layer to their surface. Al₂O₃ is then introduced onto the UHMWPE fiber surface via a sol-gel method. Compared to traditional methods that directly add nano-inorganic particles or single fibers to cement mortar, this approach effectively avoids problems such as nanoparticle agglomeration leading to poor cement crack resistance. Furthermore, through interaction with cement and the formation of surface calcium aluminate / calcium silicate and Friedel salts, it addresses the issues of poor durability caused by internal and external chloride ion penetration leading to steel corrosion, as well as weak interfacial adhesion in composite materials. Attached Figure Description

[0014] Figure 1 This is a morphology diagram of the Al2O3-modified ultra-high molecular weight polyethylene fiber product prepared in Example 1.

[0015] Figure 2 The image shows the surface morphology of the modified fiber prepared in Example 1 immersed in a calcium chloride solution under a saturated calcium hydroxide solution.

[0016] Figure 3 The graph shows the chlorine-fixing capacity of the modified fibers prepared in Example 1 when immersed in different calcium chloride solutions under saturated calcium hydroxide solution.

[0017] Figure 4 The images show the interfacial performance evaluation diagrams of the modified fiber-modified cement composites prepared in Examples 1-7. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. Example 1

[0019] A method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber includes the following steps: Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 5 mm were selected and placed in a 10 wt% nitric acid solution, and stirred at a constant temperature of 30 °C for 10 h. After the reaction was completed, the fibers were removed, thoroughly rinsed with deionized water, and then air-dried to obtain oxidized UHMWPE fibers. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (the mass ratio of coupling agent to water was 0.5:100) and hydrolyzed at 30 °C for 5 h. The fibers were then removed and air-dried to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. 3) An aluminum salt hydrolysate solution was prepared at 30 °C with a molar ratio of aluminum sec-butoxide:nitric acid:water of 1:0.2:200. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and dried at 60 °C to finally obtain Al2O3 gel-coated modified UHMWPE fibers.

[0020] The morphology of the prepared fiber product is shown in the attached figure. Figure 1 As shown in the attached figure, the fiber was immersed in calcium chloride solutions of different concentrations under saturated calcium hydroxide solution, and the surface morphology of the fiber was as follows. Figure 2 As shown, the chlorine-fixing capacity is shown in the appendix. Figure 3 .

[0021] like Figure 1 The surface morphology of ultra-high molecular weight polyethylene fibers modified with Al2O3 is shown. Obvious granular or flaky deposits are visible on the fiber surface, unevenly distributed with localized agglomeration, which is directly related to the size of the aluminum salt hydrolysis and deposition during the experimental steps. First, oxidation treatment introduces oxygen-containing functional groups such as hydroxyl, ether, and carbonyl groups onto the fiber surface; subsequently, coupling agent treatment enhances interfacial activity, forming CO-Si groups; then, in the hydrolysis solution of aluminum salt and nitric acid, Al2O3 precursors are deposited on the fiber surface, forming Si-O-Al groups, ultimately resulting in an observable rough coating.

[0022] Figure 2 The image shows the surface morphology of the modified fiber prepared in Example 1 immersed in a calcium chloride solution under a saturated calcium hydroxide solution. After being exposed to an alkaline chloride environment, a dense secondary reaction layer forms on the fiber surface. This layer is covered by calcium oxide crystals with regular geometric shapes (cubic or plate-like), which can react with cement to solidify chloride ions, thereby improving the durability of concrete in a chloride environment.

[0023] Figure 3This graph shows the chloride-binding capacity of the modified fibers prepared in Example 1 when immersed in different calcium chloride solutions under saturated calcium hydroxide solution. As the initial chloride concentration increases from 0.3 mol / L to 1.0 mol / L, the chloride-binding capacity of the fibers shows a continuous upward trend. When the concentration increases from 0.3 mol / L to 0.5 mol / L, the increase in chloride-binding capacity is relatively slow. When the concentration increases from 0.5 mol / L to 0.8 mol / L, the chloride-binding capacity increases significantly. This upward trend continues in the range of 0.8 mol / L to 1.0 mol / L. Overall, the higher the initial chloride concentration, the stronger the chloride ion binding capacity of the modified fibers.

[0024] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 1, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 2

[0025] A method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber includes the following steps: Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 10 mm were selected and placed in a 10 wt% nitric acid solution, and stirred at a constant temperature of 60 ℃ for 10 h. After the reaction was completed, the fibers were removed, thoroughly rinsed with deionized water, and then dried at 60 ℃ for 12 h to obtain oxidized UHMWPE fibers. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (the mass ratio of coupling agent to water was 0.5:100) and hydrolyzed at 30 °C for 5 h. The fibers were then removed and vacuum dried to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 30 °C with a molar ratio of aluminum sec-butoxide:nitric acid:water of 1:0.2:200. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and dried at 60 °C to obtain Al₂O₃ gel-coated modified UHMWPE fibers.

[0026] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 2, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 3

[0027] Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 20 mm were selected and placed in a 30 wt% hydrogen peroxide solution, and stirred at a constant temperature of 60 °C for 10 h. After the reaction was completed, the fibers were removed, thoroughly rinsed with deionized water, and then dried at 60 °C for 12 h to obtain oxidized UHMWPE fibers. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) (the mass ratio of coupling agent to water was 3:100) and hydrolyzed at 30 °C for 5 h. The fibers were then removed and air-dried to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 60 °C with a molar ratio of aluminum isopropoxide:nitric acid:water of 1:0.4:200. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and dried at 60 °C to obtain Al₂O₃ gel-coated modified UHMWPE fibers.

[0028] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 3, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 4

[0029] Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 10 mm were selected and placed in a 30 wt% sodium hydroxide solution, and stirred at a constant temperature of 60 °C for 20 h. After the reaction was completed, the fibers were removed, thoroughly rinsed with deionized water, and then naturally dried to obtain oxidized UHMWPE fibers. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (coupling agent to water mass ratio of 3:100) and hydrolyzed at 30 °C for 10 h. The fibers were then removed and dried at 60 °C for 12 h to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 60 °C with a molar ratio of aluminum isopropoxide:nitric acid:water of 1:0.4:100. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and dried at 70 °C to obtain Al₂O₃ gel-coated modified UHMWPE fibers.

[0030] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 4, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 5

[0031] Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 70 mm were selected and placed at the anode of an electrochemical reaction. A 0.5 mol / L ammonium bicarbonate solution was used as the electrolyte, and a certain voltage (10 V) was applied across the electrodes for electrochemical oxidation treatment. The current density was 10 A / cm². 2 After reacting for 3 hours, the fiber was removed and rinsed with deionized water, and then dried at 60 °C for 12 hours to obtain oxidized ultra-high molecular weight polyethylene fiber. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (coupling agent to water mass ratio of 3:100) and hydrolyzed at 30 °C for 10 h. The fibers were then removed and dried at 60 °C for 24 h to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 60 °C with a molar ratio of aluminum isopropoxide:nitric acid:water of 1:0.4:100. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and air-dried at room temperature to obtain Al2O3 gel-coated modified UHMWPE fibers.

[0032] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 5, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 6

[0033] Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 70 mm were selected and placed at the anode of the electrochemical reaction. A 3 mol / L ammonium bicarbonate solution was used as the electrolyte, and an electrochemical oxidation treatment was performed by applying a certain voltage (20 V) to both ends. The voltage was 20 A / cm². 2 After reacting for 3 hours, the fiber was removed and rinsed with deionized water, and then dried at 60 °C for 12 hours to obtain oxidized ultra-high molecular weight polyethylene fiber. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (coupling agent to water mass ratio of 5:100) and hydrolyzed at 30 °C for 10 h. The fibers were then removed and air-dried to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 60 °C with a molar ratio of aluminum isopropoxide:nitric acid:water of 1:0.4:100. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and air-dried at room temperature to obtain Al2O3 gel-coated modified UHMWPE fibers.

[0034] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 6, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 . Example 7

[0035] Ultra-high molecular weight polyethylene (UHMWPE) fibers with a length of 70 mm were selected and placed at the anode of an electrochemical reaction. A 3 mol / L sodium hydroxide solution was used as the electrolyte, and an electrochemical oxidation treatment was performed by applying a certain voltage (20 V) to both ends. The voltage was 20 A / cm². 2After reacting for 6 h, the fiber was taken out and rinsed with deionized water, and then dried at 60 °C for 12 h to obtain oxidized ultra-high molecular weight polyethylene fiber. The above-mentioned oxidized fibers were immersed in an aqueous solution of γ-aminopropyltriethoxysilane (KH550) (coupling agent to water mass ratio of 5:100) and hydrolyzed at 30 °C for 10 h. The fibers were then removed and air-dried at room temperature to obtain silane coupling agent-grafted ultra-high molecular weight polyethylene fibers. An aluminum salt hydrolysate solution was prepared at 60 °C with a molar ratio of aluminum isopropoxide:nitric acid:water of 1:0.4:100. Subsequently, ultra-high molecular weight polyethylene (UHMWPE) fibers grafted with a silane coupling agent were impregnated in this hydrolysate solution and stirred for 10 h. After the reaction was complete, the fibers were removed and air-dried at room temperature to obtain Al2O3 gel-coated modified UHMWPE fibers.

[0036] The modified fibers prepared above are used to prepare concrete, including the following steps: The modified fiber obtained in Example 7, cement, silica fume, quartz sand, and water were weighed in a ratio of 0.6:100:1:50:35. The fiber was added to the cement slurry in batches and stirred for 4-8 minutes to ensure uniform fiber dispersion. After stirring, the mixture was placed in a mold, vibrated for 1-2 minutes to form the product, and then cured. The product was then demolded to obtain the final product. The mechanical property test results of the obtained product are shown in the appendix. Figure 4 .

[0037] Figure 4 The diagram shows the interfacial performance evaluation of the modified fiber-modified cement composites prepared in Examples 1-7. It can be seen that after Al2O3 surface modification, the interfacial bonding strength between ultra-high molecular weight polyethylene fibers and the cement matrix is ​​significantly improved. The interfacial bonding strength of the unmodified fibers is only 1.04 MPa, while the strength values ​​of all modified examples (1-7) are significantly improved, with Example 1 reaching the optimal value of 1.74 MPa, an increase of approximately 67% compared to the unmodified fibers. This strengthening effect mainly stems from the dual effect of the Al2O3 coating on the modified fiber surface and its reaction products: on the one hand, the coating introduces micro-roughness (… Figure 1 This enhances the mechanical anchoring between the fiber and the matrix; on the other hand, the products generated in the alkaline environment of cement ( Figure 2 This promotes chemical bonding in the interfacial region. Overall, the significant improvement in interfacial bonding strength provides a key mechanical basis for the modified fibers to perform crack bridging and stress transfer functions in cement composites.

Claims

1. A method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber, characterized in that, Includes the following steps: S1. Oxidize the ultra-high molecular weight polyethylene fiber to obtain oxidized ultra-high molecular weight polyethylene fiber, and then dry it. S2. Oxidized ultra-high molecular weight polyethylene fiber is soaked in a coupling agent solution for hydrolysis, then removed and dried to obtain coupling agent-grafted ultra-high molecular weight polyethylene fiber. S3. Aluminum salt, nitric acid and water are mixed to obtain a hydrolysis solution; the coupling agent-grafted ultra-high molecular weight polyethylene fiber is impregnated in the hydrolysis solution; after stirring and reaction, Al2O3 modified ultra-high molecular weight polyethylene fiber is prepared; and then dried and dispersed.

2. The method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, The oxidation treatment in step S1 is either liquid-phase oxidation or electrochemical oxidation; the drying method is one of natural air drying, atmospheric pressure heating drying, vacuum drying, and freeze drying.

3. The method for preparing Al2O3-modified ultra-high molecular weight polyethylene fiber according to claim 2, characterized in that, The oxidation system for liquid-phase oxidation treatment consists of at least one of nitric acid, sulfuric acid, H₂O₂, sodium hydroxide, and oxalic acid, with a concentration ranging from 0 to 100 wt% and not being zero, and a preset temperature range of 0 to 100 °C. o C is not 0, and the time range is 0~50h and is not 0.

4. The method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber according to claim 2, characterized in that, The electrolyte solution for electrochemical oxidation treatment is one of sodium hydroxide, ammonium bicarbonate, diammonium phosphate, triammonium phosphate, ammonium phosphate, sulfuric acid, and nitric acid, with a concentration of 0 mol / L to 20 mol / L and not zero. The applied voltage is 0 to 50 V and not zero, and the current density is 0.01-200 A / cm². 2 The time range is 0-50h and is not 0.

5. The method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, The coupling agent solution in step S2 is an aqueous solution of amino-based silane coupling agent, epoxy-based silane coupling agent, vinyl silane coupling agent, mercaptosilane coupling agent, or methacryloxysilane coupling agent; the mass ratio of coupling agent to water is 0.1:100 to 10:100, the hydrolysis time is 0 to 50 hours and not zero, and the preset temperature range is 0 to 50 degrees Celsius. o C is not 0.

6. The method for preparing Al2O3 modified ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, The aluminum salt mentioned in step S3 is one of aluminum sec-butoxide, aluminum isopropoxide, organic low-alkyl aluminum salt, and inorganic aluminum salt; the molar ratio of aluminum salt, nitric acid, and water is 1:0.01~0.6:10~200; the mixing temperature of the aluminum salt, nitric acid, and water is 0~100°C. o C; stirring reaction time: 0~12h; drying temperature: 40~100℃ o C. The drying method is one of the following: natural air drying, atmospheric pressure heating drying, vacuum drying, and freeze drying.

7. Al2O3 modified ultra-high molecular weight polyethylene fiber obtained by the preparation method according to any one of claims 1-6.

8. The application of Al2O3 modified ultra-high molecular weight polyethylene fiber according to claim 7 in the preparation of concrete with chloride ion curing and crack resistance functions.

9. The application according to claim 8, characterized in that, The concrete comprises component A and component B; Component A comprises the following raw materials in the following mass ratios: 1 part cement, 0.01-0.2 parts silica fume, 0.5-2 parts quartz sand, and 0.35-0.55 parts water; Component B is Al2O3 modified ultra-high molecular weight polyethylene fiber, the fiber length is 3~100mm; the added mass of the fiber accounts for 0.5%~8% of the mass of the cement.

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