Anti-crack concrete and preparation method thereof

Abstract

The invention relates to the technical field of concrete, and provides anti-crack concrete and a preparation method thereof.The anti-crack concrete is prepared from, by weight, 280-350 parts of cement, 50-80 parts of mineral admixture, 1000-1200 parts of gravel, 650-850 parts of sand, 6.0-10.0 parts of water reducing agent, 16-20 parts of expanding agent, 10-25 parts of fiber and 140-160 parts of water; the fiber is a nano-modified PVA fiber and is formed by grafting SiO2 nano-particles with the particle size of 20 nm on the surface of the PVA fiber, and the grafting amount is 3%-5%. The PVC fibers are subjected to nano modification, SiO2 nanoparticles with the particle size of 20 nm are grafted to the surfaces of the PVC fibers, a low-surface-energy dispersion layer is formed on the surfaces of the PVA fibers, the agglomeration resistance of the PVA fibers is improved, agglomeration generated when the PVC fibers are used for preparing the anti-crack concrete is reduced, and then the anti-crack performance of the concrete is improved.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a crack-resistant concrete and its preparation method. Background Technology

[0002] As the main material of modern buildings, concrete's crack resistance directly affects the service life and safety of buildings. During the hardening process, traditional concrete will shrink in volume due to plastic shrinkage, autogenous shrinkage and thermal shrinkage. When the shrinkage stress exceeds the tensile strength, cracks will form, leading to a decrease in durability and seriously affecting the structural durability and safety, especially in high temperature and dry environments. In order to solve the problem of cracking of traditional concrete, fibers and expansion agents are widely used in concrete to improve its crack resistance. The commonly used solutions include: (1) adding fibers to concrete, such as adding steel fibers or synthetic fibers alone, or adding steel fibers and synthetic fibers in combination to exert their synergistic effect. However, there are problems such as steel fibers being easy to rust, poor dispersibility, and weak bonding with the cement matrix interface. In addition, synthetic fibers are difficult to disperse. When the content of traditional PVA fibers exceeds 1.0%, severe agglomeration occurs, which will lead to a concrete strength loss of more than 15%. (2) By adjusting the mix proportion, the amount of cement in the concrete can be appropriately reduced, and the proportion of mineral admixtures such as fly ash can be appropriately increased to reduce the early heat of hydration of the concrete and reduce cracks caused by temperature stress. However, when the proportion of admixtures is high, the early strength of the concrete is relatively low, the demolding time becomes longer, and improper curing makes the concrete more prone to cracking. (3) Adding an expansive agent to the concrete can reduce the probability of cracks caused by volume shrinkage through micro-expansion. However, expansive agents (such as calcium sulfoaluminate) depend on curing conditions, and their expansion efficiency is unstable. Excessive use will lead to strength loss. At the same time, a single expansive agent mainly compensates for shrinkage through chemical reaction, which is difficult to completely suppress cracks in the plastic stage. In addition, CaO-type expansive agents have a violent early expansion but a rebound in shrinkage in the later stage, with a 28-day shrinkage rate as high as 120%. (4) Adding fibers and expansive agents to the concrete can play a synergistic role. However, when fibers and expansive agents are simply compounded, the expansion stress and the fiber restraint effect are mismatched, which can easily cause local stress concentration and induce cracks. Summary of the Invention

[0003] The purpose of this invention is to solve at least one technical problem in the background art and to provide crack-resistant concrete and its preparation method.

[0004] To achieve the above objectives, the present invention provides a crack-resistant concrete, comprising the following raw materials in parts by weight: 280-350 parts cement, 50-80 parts mineral admixtures, 1000-1200 parts crushed stone, 650-850 parts sand, 6.0-10.0 parts water-reducing agent, 16-20 parts expansion agent, 10-25 parts fiber, and 140-160 parts water. The fiber is a nano-modified PVA fiber, which is formed by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of the PVA fiber, with a grafting amount of 3% to 5%.

[0005] According to one aspect of the invention, the cement is ordinary Portland cement with a strength grade of 42.5.

[0006] According to one aspect of the present invention, the mineral admixture is formed by compounding fly ash microspheres and silica fume in a 1:1 mass ratio.

[0007] According to one aspect of the invention, the crushed stone is 5-25 mm in size and has a porosity of ≤42%.

[0008] According to one aspect of the invention, the sand is medium sand from zone II.

[0009] According to one aspect of the invention, the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of more than 28%.

[0010] According to one aspect of the invention, the expanding agent is a dual-source expanding agent composed of 50%~70% calcium oxide and 30%~50% calcium sulfoaluminate.

[0011] To achieve the above objectives, the present invention also provides a method for preparing the above-mentioned crack-resistant concrete, comprising: Nano-modified PVA fibers were prepared by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of PVA fibers. Weigh out the following ingredients in the specified proportions: cement, mineral admixtures, crushed stone, sand, water-reducing agent, expanding agent, nano-modified PVA fiber, and water. Add cement, mineral admixtures, crushed stone, sand, and expansion agent into the mixer and mix for 2-3 minutes; During the dry mixing process, nano-modified PVA fibers are added by vibration sieving to prevent clumping; Dissolve the water-reducing agent in the mixing water, then add it to the mixer and continue mixing for 1-2 minutes until a uniformly mixed concrete is formed.

[0012] According to one aspect of the present invention, the preparation of nano-modified PVA fibers, formed by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of PVA fibers, comprises: (1) Pretreatment of PVA fibers: Hydroxyl and carboxyl groups are introduced on the fiber surface by alkaline etching to activate the fiber. After activation, the fiber is ultrasonically cleaned with deionized water for 10 min and vacuum dried at 60℃ to constant weight. (2) Functionalized SiO2 nanoparticles: 20 nm SiO2 was dispersed in an ethanol solution to prepare a suspension. Then 3-aminopropyltriethoxysilane was added to the suspension and stirred evenly. The mixture was reacted at 60 °C for 2 h to generate amino or double bond active groups on the surface of SiO2. (3) Grafting: The pretreated PVA fibers were immersed in a functionalized SiO2 dispersion, and the photoinitiator benzophenone was added. The grafting reaction was initiated by ultraviolet irradiation for 30 min. (4) Cleaning and curing: Use deionized water to ultrasonically remove ungrafted SiO2 particles, dry at 80°C, and calcine at 500°C for 1 hour to strengthen the interfacial bonding and form nano-modified PVA fibers.

[0013] According to the present invention, silica fume fills the concrete interface transition zone, reduces the porosity of the interface transition zone, improves the bond strength between cement paste and aggregate, and enhances the concrete's ability to resist shrinkage stress. At the same time, fly ash vitrified microspheres have a lubricating effect, which can provide lubrication between the significantly angular expansion agent particles, reduce the local enrichment of the expansion agent, and achieve a uniform effect of the expansion agent's micro-expansion in the concrete.

[0014] PVC fibers are prone to agglomeration. By nano-modifying PVC fibers and grafting 20nm SiO2 nanoparticles (3%~5%) onto their surface, a low surface energy dispersion layer is formed on the PVA fiber surface, which improves the anti-agglomeration ability of PVA fibers. This helps reduce the agglomeration of PVC fibers when preparing crack-resistant concrete, thereby improving the crack resistance of concrete. In addition, the nano-SiO2 on the fiber surface reacts with CSH gel in concrete to form Si-O-Ca bonds, which significantly improves the interfacial bonding strength between PVA fibers and cement paste in concrete.

[0015] Single-component expanding agents exhibit only a phased, micro-expansion effect, making it difficult to achieve a full-age expansion effect. By adjusting the ratio of calcium oxide and calcium sulfoaluminate, the expanding agent achieves controllable expansion throughout its lifespan. Calcium oxide expands rapidly from 3 to 7 days to compensate for plastic shrinkage, while calcium sulfoaluminate continuously exerts its expanding effect from 14 to 28 days to counteract drying shrinkage.

[0016] According to the present invention, nano-SiO2 is used to modify PVA fibers to improve the anti-agglomeration property of PVA fibers and significantly improve the interfacial bond strength between PVA fibers and cement paste in concrete, which is beneficial to improving the crack resistance of concrete. This invention achieves controllable expansion by adjusting the ratio of calcium oxide and calcium sulfoaluminate. Calcium oxide expands rapidly from 3 to 7 days to compensate for plastic shrinkage, while calcium sulfoaluminate continues to exert its expansion effect from 14 to 28 days to counteract drying shrinkage.

[0017] This invention uses silica fume to fill the interface transition zone, and fly ash microspheres to reduce the local enrichment of the expansion agent, reduce the porosity of the concrete interface transition zone, improve the bond strength between cement paste and aggregate in the concrete, and improve the crack resistance of the concrete.

[0018] This invention significantly improves the crack resistance of concrete through the synergistic effect of the physical crack-inhibiting effect of modified PVA fibers and the chemical shrinkage compensation effect of composite expansion agents. Attached Figure Description

[0019] Figure 1 The flowchart schematically illustrates a method for preparing crack-resistant concrete according to one embodiment of the present invention. Detailed Implementation

[0020] The invention will now be discussed with reference to exemplary embodiments. It should be understood that the described embodiments are merely intended to enable those skilled in the art to better understand and thus implement the invention, and are not intended to imply any limitation on the scope of the invention.

[0021] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment".

[0022] To achieve the above objectives, the present invention provides a crack-resistant concrete, comprising the following raw materials in parts by weight: 280-350 parts cement, 50-80 parts mineral admixtures, 1000-1200 parts crushed stone, 650-850 parts sand, 6.0-10.0 parts water-reducing agent, 16-20 parts expansion agent, 10-25 parts fiber, and 140-160 parts water. The fiber is a nano-modified PVA fiber, which is formed by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of the PVA fiber, with a grafting amount of 3% to 5%.

[0023] Furthermore, according to one embodiment of the present invention, the cement is ordinary Portland cement with a strength grade of 42.5.

[0024] Furthermore, according to one embodiment of the present invention, the mineral admixture is formed by compounding fly ash microspheres and silica fume in a 1:1 mass ratio.

[0025] Furthermore, according to one embodiment of the present invention, the crushed stone is 5~25mm crushed stone with a porosity ≤42%.

[0026] Furthermore, according to one embodiment of the present invention, the sand is medium sand from zone II.

[0027] Furthermore, according to one embodiment of the present invention, the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of more than 28%.

[0028] Furthermore, according to one embodiment of the present invention, the expanding agent is a dual-source expanding agent composed of 50%~70% calcium oxide and 30%~50% calcium sulfoaluminate.

[0029] According to the above-mentioned scheme of the present invention, silica fume fills the concrete interface transition zone, reduces the porosity of the interface transition zone, improves the bond strength between cement paste and aggregate, enhances the concrete's ability to resist shrinkage stress, and at the same time, fly ash vitrified microspheres have a lubricating effect, which can provide lubrication between the significantly angular expansion agent particles, reduce the local enrichment of expansion agent, and realize the uniform effect of micro-expansion of expansion agent in concrete.

[0030] Nano-SiO2 is modified with APTES silane coupling agent to introduce -NH2 or double bond active groups to achieve surface functionalization. After modification, SiO2 dehydrates and condenses with -OH of PVA molecular chain under weak acid conditions to form Si-OC covalent bond. At the same time, through the synergistic effect of sol impregnation-hydrogen bond adsorption-heat treatment, a physical-chemical double bond interface is constructed. After grafting treatment, SiO2 nanoparticles are anchored on the surface of PVA fiber with a low surface energy dispersion layer of 10~30 nm. Its beneficial effects include: (1) SiO2 crosslinks with PVA chain to form a three-dimensional skeleton to inhibit molecular chain slippage and significantly improve the tensile strength and modulus of PVA fiber; (2) Nano-SiO2 particles have high melting point and good thermal conductivity, which can maintain structural stability in high temperature environment, thereby preventing PVA fiber from thermal degradation or deformation at high temperature and improving the thermal stability of PVA fiber; (3) The shell of nano-SiO2 particles with chemical inertness and good corrosion resistance can resist external chemical erosion and prevent PVA The chemical degradation or structural damage of the fiber in the chemical environment improves the chemical corrosion resistance of PVA fiber; (4) The nano-SiO2 on the surface of PVA fiber reacts with CSH gel in concrete to generate Si-O-Ca bonds, which significantly improves the interfacial bonding strength between PVA fiber and cement stone in concrete; (5) SiO2 nanoparticles form a low surface energy dispersion layer on the surface of PVA fiber, which weakens the influence of van der Waals forces, suppresses electrostatic adsorption, improves the anti-agglomeration ability of PVA fiber, and helps to reduce the agglomeration of PVC fiber when preparing crack-resistant concrete.

[0031] Single-component expanding agents exhibit only a phased, micro-expansion effect, making it difficult to achieve a full-age expansion effect. By adjusting the ratio of calcium oxide and calcium sulfoaluminate, the expanding agent achieves controllable expansion throughout its lifespan. Calcium oxide expands rapidly from 3 to 7 days to compensate for plastic shrinkage, while calcium sulfoaluminate continuously exerts its expanding effect from 14 to 28 days to counteract drying shrinkage.

[0032] Furthermore, to achieve the above objectives, the present invention also provides a method for preparing the above-mentioned crack-resistant concrete, such as... Figure 1 As shown, the preparation method includes: Nano-modified PVA fibers were prepared by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of PVA fibers. Weigh out the following ingredients in the specified proportions: cement, mineral admixtures, crushed stone, sand, water-reducing agent, expanding agent, nano-modified PVA fiber, and water. Add cement, mineral admixtures, crushed stone, sand, and expansion agent into the mixer and mix for 2-3 minutes; During the mixing process of dry mix (cement, mineral admixtures, crushed stone, sand, and expansion agent), nano-modified PVA fibers are added to the mixed dry mix through a vibrating sieve to prevent clumping. Dissolve the water-reducing agent in the mixing water, then add it to the mixer and continue mixing for 1-2 minutes until a uniformly mixed concrete is formed.

[0033] Furthermore, according to one embodiment of the present invention, nano-modified PVA fibers are prepared by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of the PVA fibers, comprising: (1) Pretreatment of PVA fibers: hydroxyl (-OH) and carboxyl (-COOH) groups are introduced on the fiber surface by alkaline etching (5% NaOH solution) to activate the fiber. After activation, the fiber is ultrasonically cleaned with deionized water for 10 min and vacuum dried at 60℃ to constant weight. (2) Functionalized SiO2 nanoparticles: 20 nm SiO2 was dispersed in an ethanol solution (volume ratio of ethanol:water = 7:3) to prepare a suspension. Then, 3-aminopropyltriethoxysilane (APTES) was added to the suspension and stirred evenly. The mixture was reacted at 60 °C for 2 h to generate amino or double bond active groups on the surface of SiO2. (3) Grafting: The pretreated PVA fibers were immersed in a functionalized SiO2 dispersion (concentration 4%~6%), and the photoinitiator benzophenone (0.5wt%) was added. The grafting reaction was initiated by ultraviolet light (wavelength 365nm) for 30min. (4) Cleaning and curing: Use deionized water to ultrasonically remove ungrafted SiO2 particles, dry at 80°C, and calcine at 500°C for 1 hour to strengthen the interfacial bonding and form nano-modified PVA fibers.

[0034] According to the above-described scheme of the present invention, nano-SiO2 is used to modify PVA fibers, thereby improving the anti-agglomeration property of PVA fibers and significantly enhancing the interfacial bond strength between PVA fibers and cement paste in concrete, which is beneficial to improving the crack resistance of concrete. This invention achieves controllable expansion by adjusting the ratio of calcium oxide and calcium sulfoaluminate. Calcium oxide expands rapidly from 3 to 7 days to compensate for plastic shrinkage, while calcium sulfoaluminate continues to exert its expansion effect from 14 to 28 days to counteract drying shrinkage.

[0035] This invention uses silica fume to fill the interface transition zone, and fly ash microspheres to reduce the local enrichment of the expansion agent, reduce the porosity of the concrete interface transition zone, improve the bond strength between cement paste and aggregate in the concrete, and improve the crack resistance of the concrete.

[0036] This invention significantly improves the crack resistance of concrete through the synergistic effect of the physical crack-inhibiting effect of modified PVA fibers and the chemical shrinkage compensation effect of composite expansion agents.

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are merely one preferred embodiment of the invention and are only used to explain the invention. They do not limit the scope of protection of the invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] The following examples and comparative examples include: Cement: Ordinary Portland cement with a strength grade of 42.5; Crushed stone: 5~25mm granite crushed stone, with a porosity of 41%; Sand: Manufactured sand from Zone II, with a fineness modulus of 2.8 and a stone powder content of 4.7%; Water-reducing agent: Polycarboxylate retarder high-performance water-reducing agent, with a water reduction rate of 29%; Water: tap water.

[0039] The embodiments also include: Mineral admixture: It is a mixture of SF90 grade silica fume and fly ash microspheres in a 1:1 mass ratio; Expanding agent: An expanding agent composed of 50% calcium oxide and 50% calcium sulfoaluminate; Modified PVA fiber: 15μm in diameter and 6mm in length, modified with SiO2 particles with a particle size of 20nm.

[0040] The comparative examples also include: Mineral admixtures: fly ash; Expanding agent: Calcium oxide type expanding agent; PVA fiber: 15μm in diameter, 6mm in length, unmodified.

[0041] Example 1 A method for preparing crack-resistant concrete includes the following steps: weighing 350 parts of cement, 70 parts of mineral admixture (silica fume: fly ash microspheres = 1:1), 1060 parts of crushed stone, 735 parts of sand, 7.0 parts of water-reducing agent, 18 parts of composite expansion agent, 20 parts of modified PVA fiber, and 155 parts of water; pouring the powder into a mixer and mixing for 2 minutes; during the dry mixing process, adding nano-modified PVA fiber by vibrating sieve; then pre-dissolving the water-reducing agent in the mixing water and adding it to the mixer; continuing to mix for 2 minutes until the concrete is uniformly mixed; covering with a film for 24 hours and then standard curing for 28 days.

[0042] Example 2 A method for preparing crack-resistant concrete includes the following steps: weighing 340 parts of cement, 75 parts of mineral admixture (silica fume: fly ash microspheres = 1:1), 1060 parts of crushed stone, 735 parts of sand, 7.3 parts of water-reducing agent, 20 parts of composite expansion agent, 18 parts of modified PVA fiber, and 155 parts of water; pouring the powder into a mixer and mixing for 2 minutes; during the dry mixing process, adding nano-modified PVA fiber by vibrating sieve; then pre-dissolving the water-reducing agent in the mixing water and adding it to the mixer; continuing to mix for 2 minutes until the concrete is uniformly mixed; covering with a film for 24 hours and then standard curing for 28 days.

[0043] Comparative Example 1 Compared with Example 1, Comparative Example 1 differs in that the mineral admixture (silica fume: fly ash microspheres = 1:1) is replaced with an equal amount of fly ash, the composite expanding agent is replaced with an equal amount of calcium oxide expanding agent, and the modified PVA fiber is replaced with an equal amount of PVA fiber.

[0044] Comparative Example 2 Compared with Example 2, Comparative Example 2 differs in that the mineral admixture (silica fume: fly ash microspheres = 1:1) is replaced with an equal amount of fly ash, the composite expanding agent is replaced with an equal amount of calcium oxide expanding agent, and the modified PVA fiber is replaced with an equal amount of PVA fiber.

[0045] The properties of the concrete prepared in the examples and comparative examples were tested as follows: (1) Early crack resistance: Tested according to the current national standard GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete"; (2) 56d resistance to chloride ion penetration (electric flux, chloride ion diffusion coefficient): tested according to the current national standard GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete"; (3) Restricted expansion rate: Tested according to Appendix B of the current national standard "Technical Specification for Application of Concrete Admixtures" GB / T 50119-2013; (4) 28d compressive strength: tested according to the current national standard GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0046] The experimental results are shown in Table 1.

[0047] Table 1. Concrete performance test results As shown in Table 1, compared with Comparative Examples 1 and 2, the total crack area per unit area of ​​Examples 1 and 2 decreased by 74% and 76%, respectively; the 56-day electrical flux decreased by 39% and 45%; and the 56-day chloride ion diffusion coefficient decreased by 31% and 35%, respectively. Furthermore, because the comparative examples used calcium oxide-type expansive agents, their 14-day restricted expansion rate in water was higher than that of the examples. However, as the curing time continued to increase, the 14-day restricted expansion rate in water to 28-day restricted expansion rate in air of the comparative examples decreased significantly compared to the comparative examples. This indicates that the composite calcium oxide and calcium sulfoaluminate of this invention can ensure the expansive agent exerts a sustained expansion effect. This invention significantly improves the crack resistance of concrete by nano-modifying PVA fibers, filling with the mineral admixture ITZ, and combining with an expansive agent.

[0048] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

[0049] It should be understood that the sequence number of each step in the invention and its embodiments does not absolutely imply the order of execution. 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 invention.

Claims

1. Crack-resistant concrete, characterized in that, The raw materials include the following components in parts by weight: 280-350 parts cement, 50-80 parts mineral admixtures, 1000-1200 parts crushed stone, 650-850 parts sand, 6.0-10.0 parts water-reducing agent, 16-20 parts expansion agent, 10-25 parts fiber, and 140-160 parts water. The fiber is a nano-modified PVA fiber, which is formed by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of the PVA fiber, with a grafting amount of 3% to 5%.

2. The crack-resistant concrete according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of 42.

5.

3. The crack-resistant concrete according to claim 1, characterized in that, The mineral admixture is formed by compounding fly ash microspheres and silica fume in a 1:1 mass ratio.

4. The crack-resistant concrete according to claim 1, characterized in that, The crushed stone is 5~25mm in size and has a porosity of ≤42%.

5. The crack-resistant concrete according to claim 1, characterized in that, The sand is medium sand from Zone II.

6. The crack-resistant concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of over 28%.

7. The crack-resistant concrete according to any one of claims 1-6, characterized in that, The expanding agent is a dual-source composite of 50%~70% calcium oxide and 30%~50% calcium sulfoaluminate.

8. The method for preparing crack-resistant concrete according to any one of claims 1-7, characterized in that, include: Nano-modified PVA fibers were prepared by grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of PVA fibers. Weigh out the following ingredients in the specified proportions: cement, mineral admixtures, crushed stone, sand, water-reducing agent, expanding agent, nano-modified PVA fiber, and water. Add cement, mineral admixtures, crushed stone, sand, and expansion agent into the mixer and mix for 2-3 minutes; During the dry mixing process, nano-modified PVA fibers are added by vibration sieving. Dissolve the water-reducing agent in the mixing water, then add it to the mixer and continue mixing for 1-2 minutes until a uniformly mixed concrete is formed.

9. The preparation method according to claim 8, characterized in that, The preparation of nano-modified PVA fibers involves grafting SiO2 nanoparticles with a particle size of 20 nm onto the surface of the PVA fibers, including: (1) Pretreatment of PVA fibers: Hydroxyl and carboxyl groups are introduced on the fiber surface by alkaline etching to activate the fiber. After activation, the fiber is ultrasonically cleaned with deionized water for 10 min and vacuum dried at 60℃ to constant weight. (2) Functionalized SiO2 nanoparticles: 20 nm SiO2 was dispersed in an ethanol solution to prepare a suspension. Then 3-aminopropyltriethoxysilane was added to the suspension and stirred evenly. The mixture was reacted at 60 °C for 2 h to generate amino or double bond active groups on the surface of SiO2. (3) Grafting: The pretreated PVA fibers were immersed in a functionalized SiO2 dispersion, and the photoinitiator benzophenone was added. The grafting reaction was initiated by ultraviolet irradiation for 30 min. (4) Cleaning and curing: Use deionized water to ultrasonically remove ungrafted SiO2 particles, dry at 80°C, and calcine at 500°C for 1 hour to strengthen the interfacial bonding and form nano-modified PVA fibers.

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