A recycled carbon fiber for reinforcing ultra-high performance concrete and a method of manufacturing the same

Abstract

This invention relates to the fields of ultra-high performance concrete and functional fiber preparation technology, and particularly to a recycled carbon fiber for reinforcing ultra-high performance concrete and its preparation method. The steps are as follows: S1: Mix and stir quartz sand and recycled carbon fiber to obtain mixture 1; S2: Add cement, silica fume, and fly ash to mixture 1 sequentially and stir to obtain mixture 2; S3: Mix water and water-reducing agent evenly and add them to mixture 2 in two batches to obtain an ultra-high performance concrete mixture. This invention provides a recycled carbon fiber for reinforcing ultra-high performance concrete and its preparation method. By pretreating the recycled carbon fiber according to a reasonable feeding sequence, the dispersibility between short-cut carbon fibers can be improved, effectively solving the problem of uneven dispersion of short-cut carbon fibers in the ultra-high performance concrete matrix; by changing the curing method and increasing the curing temperature, the hydration reaction in the matrix can be effectively promoted, and the mechanical strength of the ultra-high performance concrete can be improved.

Description

Technical Field

[0001] This invention relates to the fields of ultra-high performance concrete and functional fiber preparation technology, and in particular to a recycled carbon fiber for reinforcing ultra-high performance concrete and its preparation method. Background Technology

[0002] Recycled carbon fiber not only possesses the mechanical properties, corrosion resistance, and high-temperature resistance of virgin carbon fiber, but also offers significant environmental and cost advantages. Currently, ultra-high performance concrete using steel fibers suffers from poor durability in highly corrosive environments. Replacing steel fibers with recycled carbon fiber can eliminate the deterioration and corrosion problems of steel fiber reinforced concrete, extending its service life and expanding its application range. However, regarding the order of fiber incorporation, later incorporation is often chosen for economic reasons, while earlier incorporation is preferred for its advantages in fiber dispersion and composite material performance. Therefore, the actual fiber incorporation order should be determined based on application requirements and cost considerations.

[0003] To address this issue, a method for preparing ultra-high performance recycled carbon fiber for concrete reinforcement is designed, providing a technical solution to the aforementioned technical problems. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for preparing ultra-high performance recycled carbon fiber for concrete reinforcement and a method for preparing the same, in order to solve the technical problems mentioned in the background.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement, characterized by the following steps: S1: Mix and stir the quartz sand and recycled carbon fiber to uniformly disperse the recycled carbon fiber, and obtain mixture 1; S2: Add cement, silica fume and fly ash to mixture 1 in sequence and stir to obtain mixture 2; S3: After mixing water and water-reducing agent evenly, add them to mixture 2 in two batches to obtain ultra-high performance concrete mixture; S4: Pack the mixture into a box and vibrate it on a vibrating table until no air bubbles are released.

[0006] In a preferred embodiment of the method for preparing ultra-high performance concrete reinforcement recycled carbon fiber provided by the present invention, the stirring time in step S1 is 3 minutes; the stirring time in step S2 is 3 minutes.

[0007] In a preferred embodiment of the method for preparing ultra-high performance concrete reinforcement recycled carbon fiber provided by the present invention, in step S3, after the water and water-reducing agent are mixed evenly, 2 / 3 of the total water volume after mixing is first added to mixture 2 and stirred for 3 minutes, and then the remaining 1 / 3 of the total water volume after mixing is added to mixture 2 and stirred for 2 minutes.

[0008] In a preferred embodiment of the method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement provided by the present invention, in step S1, the recycled carbon fiber is chopped to a length of 10 mm and added at a dosage of 1 part of the total volume of concrete.

[0009] As a preferred embodiment of the method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement provided by the present invention, it further includes a high-temperature curing step, as follows: The molded specimens were heated to 90℃ at a rate of 20℃ / h, and then steam-cured at a constant temperature for 48h. After that, they were naturally cooled to room temperature and then water-cured at 20℃ for 7d or 28d.

[0010] A type of recycled carbon fiber for ultra-high performance concrete reinforcement, with the following formulation: The ingredients are: 16-20 parts cement, 16-30 parts fly ash, 18-30 parts silica fume, 1.0-1.3 parts quartz sand, 1.5-3 parts water-reducing agent, 0.5-1.5 parts recycled carbon fiber, and a water-cement ratio of 0.18-0.22.

[0011] As a preferred embodiment of the ultra-high performance concrete reinforcement recycled carbon fiber provided by the present invention, the quartz sand is a mixture of 40-70 mesh and 20-40 mesh quartz sand in a mass ratio of 1:1.

[0012] It is clear without a doubt that the technical problems to be solved by the present invention can be solved by the above-described technical solutions of the present invention.

[0013] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects: This invention provides a recycled carbon fiber for reinforcing ultra-high performance concrete and its preparation method. By pretreating the recycled carbon fiber through a reasonable feeding sequence, the dispersibility between short-cut carbon fibers can be improved, effectively solving the problem of uneven dispersion of short-cut carbon fibers in the ultra-high performance concrete matrix. By changing the curing method and increasing the curing temperature conditions, the hydration reaction in the matrix can be effectively promoted, and the mechanical strength of the ultra-high performance concrete can be improved. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a schematic diagram of the ultra-high performance concrete reinforcement recycled carbon fiber obtained in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the recycled carbon fiber for reinforcing ultra-high performance concrete obtained in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the ultra-high performance concrete reinforcement recycled carbon fiber obtained in Embodiment 3 of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0018] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0019] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0020] Example 1 This invention provides a recycled carbon fiber for reinforcing ultra-high performance concrete. By mass percentage, its raw material composition consists of 16-20 parts of P·O42.5 cement, 16-30 parts of Class I fly ash (F grade), 18-30 parts of silica fume with SiO2 content ≥85%, 1.0-1.3 parts of quartz sand, 1.5-3 parts of water-reducing agent, and 0.5-1.5 parts of recycled carbon fiber, with a water-cement ratio of 0.18-0.22.

[0021] Preferably, the quartz sand is a mixture of 40-70 mesh and 20-40 mesh quartz sand in a mass ratio of 1:1.

[0022] In this embodiment, the 28-day compressive strength of the recycled carbon fiber reinforced ultra-high performance concrete is not less than 130 MPa.

[0023] Preferably, by weight percentage, the raw material components include 18 parts cement, 20 parts fly ash, 25 parts fly ash, 20 parts silica fume, 25 parts silica fume, 1 part silica fume, 1.2 parts silica fume, 1.3 parts silica fume, 2 parts water-reducing agent, 2.5 parts water-reducing agent, 3 parts water-reducing agent, and 0.5 parts recycled carbon fiber, 1 part recycled carbon fiber, 1.5 parts recycled carbon fiber, and 1.5 parts recycled carbon fiber.

[0024] refer to Figure 1 The preparation method is disclosed, and the mix proportions of various materials in ultra-high performance concrete are obtained using the single-variable method. The steps are as follows: Quartz sand and recycled carbon fiber are mixed and stirred evenly to obtain mixture 1; Preferably, the recycled carbon fiber is chopped to a length of 10 mm and added at a dosage of 1 part of the total volume of concrete. The recycled carbon fiber has a tensile strength ≥4000 MPa, a tensile modulus ≥245 GPa, an elongation at break ≥1.71 parts, and a carbon content ≥95 parts.

[0025] Cement, silica fume and fly ash are mixed and stirred to obtain cementitious material mixture 2; Mix water and water-reducing agent to obtain mixture 3; Mixture 1 is stirred for 3 minutes, mixture 2 is added and stirred for 3 minutes, then 2 / 3 of mixture 3 is added and stirred for 3 minutes, and finally the remaining 1 / 3 of mixture 3 is added and stirred for 3 minutes to obtain ultra-high performance reinforced carbon fiber. The recycled carbon fiber for ultra-high performance concrete reinforcement obtained in this embodiment is as follows: Figure 2 As shown.

[0026] Example 2 The difference from Embodiment 1 above is: The preparation method steps are as follows: Recycled carbon fiber was mixed with water and stirred to obtain mixture 1; Cement, silica fume and fly ash are mixed and stirred to obtain cementitious material mixture 2; Mixture 1 is stirred for 3 minutes, then mixture 2 is added and stirred for 3 minutes, then quartz sand is added and stirred for 3 minutes, and finally water-reducing agent is added and stirred for 3 minutes to obtain ultra-high performance concrete reinforcement recycled carbon fiber.

[0027] The recycled carbon fiber for ultra-high performance concrete reinforcement obtained in this embodiment is as follows: Figure 3 As shown.

[0028] Example 3 The difference from Embodiment 1 above is: The preparation method steps are as follows: Cement, silica fume, and fly ash are mixed and stirred to obtain cementitious material mixture 1; Mix water and water-reducing agent to obtain mixture 2; Mixture 1, mixture 2 and quartz sand are poured in sequentially and stirred together for 8 minutes. Finally, recycled carbon fiber is added and stirred evenly for 6 minutes to obtain recycled carbon fiber for ultra-high performance concrete reinforcement.

[0029] The recycled carbon fiber for ultra-high performance concrete reinforcement obtained in this embodiment is as follows: Figure 4 As shown.

[0030] Through Examples 1 to 3 and their corresponding Figures 2-4 The comparison revealed that, in Example 2, although the fibers dispersed well in water during the mixing process, the carbon fibers' high water absorption made it difficult to mix and form the cementitious material mixture afterward. In Example 3, it was easily observed that the cementitious material mixture had already formed a slurry during the mixing process. Since the fibers had already been added and had a high viscosity, the fibers were unevenly dispersed within the slurry. Using the mixing method of Example 1, it was found that drying the quartz sand significantly reduced the moisture content and viscosity of the fibers, allowing for effective and uniform dispersion of the agglomerated fibers during dry mixing. The subsequent addition of cementitious materials allowed the cement, silica fume, and fly ash to effectively penetrate into the pores of the fiber bundles under dry mixing, resulting in more uniform dispersion.

[0031] Example 4 Based on the above embodiment one, the following is disclosed: It also includes high-temperature curing steps: Select a heating rate of 20℃ / h and maintain the temperature at 90℃ for 48 hours for high-temperature steam curing.

[0032] Preferably, after 48 hours of steam curing, the water is naturally cooled to room temperature and then cured in water at a constant temperature of 20°C for 7 days / 28 days. The compressive strength after 28 days is not less than 130 MPa.

[0033] Example 5 Based on the raw materials proposed in Examples 1 to 3 above, the corresponding proportions and sources of the raw materials are provided.

[0034] ① Source of materials Silica fume: Silica fume from a manufacturer in Henan Province was selected, with a SiO2 mass fraction of 96.2 parts and a specific surface area of ​​19.1 m². 2 / g.

[0035] Cement: Jidong brand PO 42.5 silicate cement from Jilin Jinyu Jidong Environmental Protection Technology Co., Ltd. was selected. Density: 3000 kg / m³ 3 .

[0036] Recycled carbon fiber: Short-cut carbon fiber (dosage: 1 part; length: 13 mm).

[0037] Water-reducing agent: This is a high-performance polycarboxylate water-reducing agent produced by a technology company in Shanxi Province. It is a light yellow oily liquid with a water reduction rate of >25 parts and a solid content of 39 parts.

[0038] Water: Tap water is used.

[0039] Quartz sand: Quartz sand produced by a manufacturer in Hebei Province, with a SiO2 content of 98 parts.

[0040] Table 1: Performance Indicators of Quartz Sand

[0041] ② Prepare the mixture according to the provided materials. The mix proportions are shown in Table 2. A total of 11 mix proportion tests were conducted, designated as test groups 1 to 11. The compressive strength of each group of specimens was tested at 7 days and 28 days, and the data are listed in Table 2.

[0042] Table 2. Mix proportions of recycled carbon fiber for ultra-high performance concrete reinforcement (unit: kg / m³) 3 )

[0043] Table 3. Performance test results of recycled carbon fiber for ultra-high performance concrete reinforcement.

[0044] According to the test results in Table 3, the application of recycled carbon fiber in this embodiment of the application can significantly improve the compressive strength of ultra-high performance concrete.

[0045] In summary, the method for preparing recycled carbon fiber for reinforcing ultra-high performance concrete of this application can effectively avoid the bonding phenomenon between fiber bundles and improve the dispersibility between short-cut recycled carbon fibers by selecting a reasonable feeding and mixing sequence and ratio, so that they are uniformly dispersed in the ultra-high performance concrete matrix. Through reasonable high-temperature steam curing and room temperature curing, the internal structure of the ultra-high performance concrete matrix can be effectively improved, crack generation can be reduced, and the compressive strength of ultra-high performance concrete can be effectively enhanced.

[0046] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement, characterized in that, The steps are as follows: S1: Mix and stir quartz sand and recycled carbon fiber to obtain mixture 1; S2: Add cement, silica fume and fly ash to mixture 1 in sequence and stir to obtain mixture 2; S3: After mixing water and water-reducing agent evenly, add them to mixture 2 in two batches to obtain ultra-high performance concrete mixture; S4: Pack the mixture into a box and vibrate it on a vibrating table until no air bubbles are released.

2. The method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement according to claim 1, characterized in that, The stirring time in step S1 is 3 minutes; the stirring time in step S2 is 3 minutes.

3. The method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement according to claim 1, characterized in that, In step S3, after the water and water-reducing agent are mixed evenly, 2 / 3 of the total water volume is first added to mixture 2 and stirred for 3 minutes, and then the remaining 1 / 3 of the total water volume is added to mixture 2 and stirred for 2 minutes.

4. The method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement according to claim 1, characterized in that, In step S1, the recycled carbon fiber is chopped to a length of 10 mm and added at a dosage of 1 part of the total volume of concrete.

5. The method for preparing recycled carbon fiber for ultra-high performance concrete reinforcement according to claim 1, characterized in that, It also includes a high-temperature curing step, as follows: The molded specimens were heated to 90℃ at a rate of 20℃ / h, and then steam-cured at a constant temperature for 48h. After that, they were naturally cooled to room temperature and then water-cured at 20℃ for 7d or 28d.

6. A type of recycled carbon fiber for ultra-high performance concrete reinforcement, characterized in that, The following are the matching examples: The ingredients are: 16-20 parts cement, 16-30 parts fly ash, 18-30 parts silica fume, 1.0-1.3 parts quartz sand, 1.5-3 parts water-reducing agent, 0.5-1.5 parts recycled carbon fiber, and a water-cement ratio of 0.18-0.

22.

7. The recycled carbon fiber for ultra-high performance concrete reinforcement according to claim 6, characterized in that, The quartz sand is a mixture of 40-70 mesh and 20-40 mesh quartz sand in a mass ratio of 1:1.

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