Hybrid fiber toughened charcoal concrete proportioning composition and preparation method

Abstract

The invention discloses a mixed fiber toughened charcoal concrete proportioning composition and a preparation method. The material is prepared from cement, fly ash, biochar, quartz sand, bamboo fibers, polyvinyl alcohol fibers (PVA fibers) and a water reducing agent. The preparation method comprises the following steps: firstly, carrying out fixed-length treatment on the bamboo fibers, carrying out pre-wetting, stirring and drying treatment on the PVA fibers, and then physically mixing the pretreated PVA fibers and the bamboo fibers according to the mass ratio of (1.75-1.85): 1 to form hybrid fibers with good dispersity; uniformly mixing cement, fly ash, biochar and quartz sand, adding water and a water reducing agent, and stirring to form basic slurry; and finally, adding the hybrid fibers into the basic slurry in batches according to 1.8%-2.2% of the volume of the basic slurry, stirring until the fibers are uniformly dispersed, and compacting, forming and curing to obtain the final material. The concrete is endowed with excellent toughness by constructing a composite system of the biochar and the specific pretreated fibers and utilizing the synergistic effect of the biochar and the specific pretreated fibers, and meanwhile, the carbon sequestration function of the concrete is also increased.

Description

Technical Field

[0001] This invention relates to the field of concrete preparation technology, and in particular to a mixed fiber-reinforced biochar concrete material mix composition and preparation method. Background Technology

[0002] Concrete, as the most widely used building material globally, is extensively applied in civil engineering due to its high compressive strength and durability. However, concrete's inherent brittleness, low tensile strength, and susceptibility to cracking severely impact structural safety and service life. To overcome these shortcomings, traditional methods typically involve incorporating steel fibers or synthetic fibers into concrete. However, this often leads to increased costs, increased weight, and environmental problems such as the difficulty in degrading synthetic fibers.

[0003] With the deepening of green building and sustainable development concepts, the search for environmentally friendly and high-performance natural fiber-reinforced materials has become a research hotspot in the industry. Bamboo fiber, as a widely available and renewable natural plant fiber, possesses lightweight, high specific strength, and good toughness. Introducing it into concrete matrices can effectively bridge cracks and transfer stress, thereby significantly improving the material's toughness and crack resistance. However, bamboo fiber is prone to degradation in strongly alkaline cement-based environments, leading to a deterioration in its mechanical properties. Furthermore, the interfacial bond strength between bamboo fiber and the cement matrix is ​​relatively weak. These problems severely restrict the long-term durability and large-scale engineering application of bamboo fiber reinforced concrete.

[0004] On the other hand, biochar, a carbon-rich material produced by the pyrolysis of biomass under anaerobic conditions, is beginning to show potential in the field of building material modification due to its porous structure, high specific surface area, and excellent chemical stability. Studies have shown that incorporating biochar into concrete can optimize the cement hydration process, refine the pore structure, and may have a certain toughening effect on the matrix. However, the improvement in concrete toughness by using biochar alone is limited and cannot meet the requirements for high crack resistance.

[0005] Currently, most existing technologies apply bamboo fiber or biochar as independent modifying components in concrete. However, research on organically combining the two to prepare high-performance concrete is still lacking. Therefore, there is an urgent need to develop an innovative fiber-biochar composite toughening technology to meet the dual requirements of modern engineering structures for both concrete toughness and environmental friendliness. Summary of the Invention

[0006] To address the problems of high brittleness, easy cracking, and high carbon emissions in existing concrete materials, this invention provides a biochar concrete material composition and preparation method that synergistically toughens bamboo fiber and PVA fiber. By compounding bamboo fiber and PVA fiber in a specific ratio, this invention significantly improves the toughness and crack resistance of concrete while effectively reducing carbon emissions.

[0007] This invention provides a mixed fiber-reinforced biochar concrete mix composition, comprising: The components in the hybrid fiber-reinforced biochar concrete are as follows by weight: 400-410 parts cement, 600-610 parts fly ash, 100-110 parts biochar, 510-520 parts quartz sand, 510-520 parts water, 10-15 parts water-reducing agent, and 1.8%-2.2% hybrid fiber by volume. Preferably, the biochar is derived from plant-based materials such as bamboo, rice husks, and corn stalks, and its particle size distribution meets the following requirements: D10=4-4μm, D50=20-25μm, D90=50-55μm. The main oxides and their contents are: silicon dioxide 17%-19%, calcium oxide 26%-29%, aluminum oxide 6%-9%, magnesium oxide 2%-4%, and loss on ignition 60%-70%. Preferably, the bamboo fiber is prepared by a chemical desorption method, with a cellulose content of 70%-75%, hemicellulose of 18-22%, lignin of 2%-4%, a density of 1.4 g / cm³, a diameter of 0.15 mm-0.25 mm, a tensile strength of 1.27 ± 0.063 GPa, and a Young's modulus of 72.6 ± 4.9 GPa; Preferably, the PVA fiber has a density of 1.3 g / cm³, a diameter of 40 μm, a length of 12 mm, a tensile strength of 1.8 GPa, and a Young's modulus of 34.3 GPa. Preferably, the quartz sand has a particle size of 60-80 mesh; the water-reducing agent is a polycarboxylate high-performance water-reducing agent; the cement is 42.5 ordinary Portland cement; and the fly ash is grade I fly ash.

[0008] The method for preparing the hybrid fiber includes: Fiber pretreatment and compounding: bamboo fiber is cut to a fixed length, and PVA fiber is pre-wetted, stirred and dried; the pretreated PVA fiber and bamboo fiber are physically mixed at a mass ratio of (1.75-1.85):1 to obtain hybrid fiber. Preferably, the fixed-length shearing process involves cutting the bamboo fibers into uniform lengths of 1.8 mm. The pre-wetting, stirring, and drying process is as follows: polyvinyl alcohol fibers are placed in water and stirred at 400 rpm for 10-15 minutes, filtered out, and dried at 50°C until the mass change between two consecutive tests does not exceed 1%; The specific steps of the physical mixing are as follows: bamboo fiber is placed in a sealed container, and pretreated polyvinyl alcohol fiber is added in four batches. After each addition, the mixture is shaken and mixed for 1 minute. After all the fibers are added, the mixture is shaken and mixed for another 3-5 minutes.

[0009] This invention utilizes a multi-component composite formulation of bamboo fiber and PVA fiber, combined with a specific amount of biochar, to achieve a significant synergistic toughening effect in a cement matrix. Four-point bending performance tests were conducted on specimens measuring 200 mm × 45 mm × 15 mm according to GB / T 50081 standard. The results (see...) Figure 5 This material maintains a high flexural strength of 4.3 MPa while exhibiting a vertical ultimate deflection of up to 15 mm. This performance is far superior to ordinary concrete and single-fiber reinforced systems, indicating that the material possesses the ability to absorb enormous deformation energy before failure, achieving a transformation from typical "brittle failure" to "plastic deformation" mode, demonstrating excellent toughness and crack resistance reserves. Furthermore, by using renewable bamboo fiber and biochar derived from plant matrix, it partially replaces energy-intensive cement, improving the material's mechanical properties while simultaneously achieving carbon reduction and environmental friendliness goals. While endowing concrete with superior mechanical properties, it significantly reduces the material's carbon footprint, aligning with the development direction of green building materials and sustainable civil engineering, achieving a balance between environmental benefits and high performance. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the specific embodiments of the present invention or related technologies, the accompanying drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Figure 1 This is the mix proportion of hybrid fiber-reinforced biochar concrete according to a preferred embodiment of the present invention. Figure 2 This is a flowchart illustrating the preparation method of hybrid fiber-reinforced biochar concrete material according to a preferred embodiment of the present invention. Figure 3 To illustrate the particle size distribution of cement, biochar, and fly ash raw materials according to a preferred embodiment of the present invention, Figure 4 The phase composition of cement, biochar, and fly ash raw materials according to a preferred embodiment of the present invention is as follows: Figure 5 Four-point bending test of hybrid fiber-reinforced biochar concrete according to a preferred embodiment of the present invention. Detailed Implementation The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0012] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0013] Application Examples A mixed fiber-reinforced biochar concrete mix design and preparation method, comprising: The hybrid fiber-reinforced biochar concrete material comprises the following components: cement, fly ash, biochar, quartz sand, bamboo fiber, PVA fiber, and water-reducing agent. The specific material specifications are as follows: The cement used is ordinary Portland cement with a strength grade of 42.5; the fly ash used is Grade 1 fly ash; the biochar raw materials are derived from plant-based materials such as bamboo, corn stalks, and coconut shells, with a particle size distribution of D10=4-5μm, D50=20-25μm, and D90=50-55μm, wherein the oxide types and contents are: silicon dioxide 17%-19%, calcium oxide 26%-29%, aluminum oxide 6%-9%, magnesium oxide 2%-4%, and loss on ignition 60%-70%; the bamboo fiber is characterized by: cellulose content 70%-75%, hemicellulose 18-22%, lignin 2%-4%, density 1.45g / cm³, diameter 0.15mm-0.25mm, tensile strength 1.27 ± 0.063 GPa, and Young's modulus 72.6 ± 4.9 GPa; the PVA fiber is characterized by: density 1.3g / cm³, diameter 40... μm in diameter, 12 mm in length, tensile strength 1.8 GPa, Young's modulus 34.3 GPa; the water-reducing agent is a polycarboxylate high-performance water-reducing agent.

[0014] Fiber pretreatment and compounding: Bamboo fiber and PVA fiber are pretreated separately, and the treated fibers are physically mixed according to a set weight ratio to obtain hybrid fibers; The fiber pretreatment and mixing are carried out according to the following steps: bamboo fibers are uniformly cut to a length of 1.8 mm; PVA fibers are placed in water and stirred at 400 rpm for 10-15 minutes to fully disperse them, then filtered out and dried in a 50℃ oven. During the drying process, the mass is measured every hour until two consecutive mass changes do not exceed 1%, which is considered to be the drying endpoint. This treatment helps to improve the compatibility of PVA fibers with the slurry; the PVA fibers treated above are weighed with bamboo fibers at a mass ratio of (1.75–1.85):1, and then the bamboo fibers are placed in a sealed container. 1 / 4 part of the pretreated PVA fibers are added in batches, and the mixture is shaken and mixed for 1 minute after each addition. After all the pretreated PVA fibers have been added, the mixture is shaken and mixed for another 3–5 minutes to finally obtain the hybrid fiber.

[0015] Mix 400-410 parts cement, 600-610 parts fly ash, 100-110 parts biochar, and 510-520 parts quartz sand, and stir at 200 rpm for 5-10 minutes to form a uniform dry mix; add 510-520 parts water and 10-15 parts water-reducing agent to the dry mix, and stir at 400 rpm for 5-10 minutes to obtain a uniform base slurry.

[0016] Mixed fibers, comprising 1.8%-2.2% of the total concrete volume, are added to the base slurry in four batches under a stirring condition of 300 rpm. After each batch of fibers is added, stirring continues for 1-2 minutes. After all fibers have been added, stirring continues until the fibers are macroscopically and uniformly dispersed in the slurry. The uniformly mixed slurry is poured into a mold, and the surface is smoothed with a scraper. It is then transferred to a vibrating table for continuous vibration for at least 5 minutes or until no air bubbles are released from the slurry surface. After curing, the mixed fiber-reinforced biochar concrete is obtained.

[0017] Comparative Example 1: The difference between this comparative example and the application example is that the 1.8%-2.2% volumetric blended fiber is replaced with 1.8%-2.2% volumetric pretreated PVA fiber, and the volumetric blend of bamboo fiber is 0%. The remaining components and preparation conditions are the same as those in the application example.

[0018] Comparative Example 2: The difference between this comparative example and the application example is that the 1.8%-2.2% volumetric blended fiber is replaced with 1.8%-2.2% volumetric bamboo fiber of fixed length, and the volumetric blend of PVA fiber is 0%. The remaining components and preparation conditions are the same as those in the application example.

[0019] Comparative Example 3: The difference between this comparative example and the application example is that the part ratio of cement, fly ash, biochar, and quartz sand is (510-520):(600-610):0:(510-520). The remaining components and preparation conditions are the same as in the application example.

[0020] The materials prepared in the application examples and Comparative Examples 1 to 3 were subjected to four-point bending performance tests according to the method specified in GB / T 50081. The specimen size used for the test was 200 mm × 45 mm × 15 mm, and four parallel specimens were set up for each group of experiments. The results are shown below:

[0021] Note: Data in the table are expressed as mean ± standard deviation. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hybrid fiber-reinforced biochar concrete, characterized in that, It is made from raw materials containing the following components: cement, fly ash, biochar, quartz sand, bamboo fiber, polyvinyl alcohol fiber (hereinafter referred to as PVA fiber), water reducing agent and water.

2. A method for preparing hybrid fibers, characterized in that, Includes the following steps: Fiber pretreatment and compounding: bamboo fiber is cut to a fixed length, and PVA fiber is pre-wetted, stirred and dried. Pretreated PVA fibers and bamboo fibers were physically mixed at a mass ratio of (1.75-1.85):1 to obtain hybrid fibers.

3. The hybrid fiber-reinforced biochar concrete according to claim 1, characterized in that: The biochar is a plant-based material such as bamboo, rice husk, and corn stalk, with a particle size distribution satisfying: D10=4-5μm, D50=20-25μm, D90=50-55μm. The main oxides and their contents are: silicon dioxide 17-19%, calcium oxide 26-29%, aluminum oxide 6-9%, magnesium oxide 2-4%, and loss on ignition 60%-70%. The bamboo fiber is extracted using a chemical desorption method, with a cellulose content of 70%-75%, hemicellulose of 18-22%, lignin of 2%-4%, a density of 1.4 g / cm³, a diameter of 0.15 mm-0.25 mm, a tensile strength of 1.27 ± 0.063 GPa, and a Young's modulus of 72.6 ± 4.9 GPa. The PVA fiber has a density of 1.3 g / cm³, a diameter of 40 μm, a length of 12 mm, a tensile strength of 1.8 GPa, and a Young's modulus of 34.3 GPa. The quartz sand has a particle size of 60-80 mesh; the water-reducing agent is a polycarboxylate high-performance water-reducing agent; the cement is 42.5 ordinary Portland cement; and the fly ash is grade I fly ash.

4. The preparation method according to claim 2, characterized in that: The fixed-length shearing process involves cutting bamboo fibers into uniform lengths of 1.8 mm. The pre-wetting, stirring, and drying process is as follows: polyvinyl alcohol fibers are placed in water and stirred at 400 rpm for 10-15 minutes, filtered out, and dried at 50°C until the mass change between two consecutive tests does not exceed 1%; The specific steps of the physical mixing are as follows: bamboo fiber is placed in a sealed container, and pretreated polyvinyl alcohol fiber is added in four batches. After each addition, the mixture is shaken and mixed for 1 minute. After all the fibers are added, the mixture is shaken and mixed for another 3-5 minutes.

5. The mix proportion of the hybrid fiber-reinforced biochar concrete according to claim 1, characterized in that: The raw materials for preparing the concrete include, by weight, 400-410 parts cement, 600-610 parts fly ash, 100-110 parts biochar, 510-520 parts quartz sand, 510-520 parts water, and 10-15 parts water-reducing agent. The amount of the hybrid fiber is 1.8%-2.2% of the total volume of the concrete.

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