A hybrid fiber-reinforced cementitious composite material and its preparation method

Abstract

This invention relates to a hybrid fiber engineering cement-based composite material and its preparation method. The composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150-200 parts modified PVA fiber, 0-50 parts recycled tire steel fiber, 50-70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener. This invention leverages the advantages of fiber blending to improve the mechanical and durability properties of ECC (Extractable Cemented Carbide), and the resulting cement-based material also possesses self-healing capabilities under humid conditions. By using recycled tire steel fiber to partially replace modified PVA fiber in the preparation of hybrid fiber ECC, the preparation cost of ECC is reduced while ensuring strain hardening performance, resulting in certain economic advantages. The reuse of waste tires and bio-keratin improves the utilization rate of solid waste, achieving sustainable development of resources and the environment, and thus possessing certain environmental advantages.

Description

Technical Field

[0001] This invention relates to the technical field of building materials, and in particular to a hybrid fiber-reinforced cement-based composite material and its preparation method. Background Technology

[0002] Engineering cementitious composites (ECCs) are fiber-reinforced composites within a cement matrix. They possess high tensile strength, high ductility, and high energy absorption capacity. The fiber incorporation improves the brittleness of concrete, significantly enhancing its durability and dynamic mechanical properties. Currently, ECCs are widely used in the construction of airports, railways, bridges, dams, tunnels, and nuclear power plants to address the problem of concrete cracking and brittle failure under dynamic loads. ECCs exhibit strain hardening characteristics after the first crack appears under tensile stress, followed by the appearance of multiple microcracks. These microcracks are typically less than 100 μm wide and can self-heal under humid conditions, with an ultimate tensile strain exceeding 2%. However, a significant factor limiting the widespread application of ECCs is their high manufacturing cost. Summary of the Invention

[0003] The present invention aims to address the shortcomings of the prior art by providing a hybrid fiber engineering cement-based composite material and its preparation method.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A hybrid fiber-reinforced cementitious composite material is made from the following raw materials in parts by weight:

[0006] 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150-200 parts modified PVA fiber, 0-50 parts recycled tire steel fiber, 50-70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0007] The method for preparing modified PVA fibers is as follows:

[0008] S1. Weigh 10g of vinyltriethoxysilane, add 5g of deionized water and stir at 150r / min at room temperature for 12h to obtain hydrolysate A.

[0009] S2. Weigh 15g of nano-silica and put it into 50mL of toluene. Stir at 300r / min at room temperature for 2h and then disperse by ultrasonication for 30min to obtain dispersion B.

[0010] S3. Hydrolysate A is slowly injected into dispersion B and refluxed in a fume hood for 6 hours at a ventilation temperature of 50°C to obtain mixture C. Then, 1g of triethylenediamine is added and stirred at 300r / min at room temperature for 30s. After the mixture is homogeneous, PVA fiber is added and modified at 110°C for 1.5 hours to obtain modified PVA fiber.

[0011] The specific method for recycling steel fibers from tires through screening is as follows:

[0012] P1. Place three types of screens with apertures of 1.25mm, 0.6mm and 0.3mm on the vibrating table in the upper, middle and lower positions respectively;

[0013] P2. Spread the recycled tire steel fibers evenly on the top layer of the screen to avoid insufficient fiber vibration due to the accumulation of recycled tire steel fibers. Start the vibration table and vibrate for 1 minute. Discard the recycled tire steel fibers left on the top layer of the screen.

[0014] P3. Spread the recycled tire steel fibers left on the middle layer screen back onto the top layer screen, start the vibrating table to vibrate for 1 minute, and discard the recycled tire steel fibers left on the top layer screen.

[0015] P4. Spread the recycled tire steel fibers left on the bottom screen back onto the middle screen, start the vibrating table and vibrate for 1 minute. Finally, discard the recycled tire steel fibers left on the bottom screen and keep the recycled tire steel fibers on the middle screen to obtain recycled tire steel fibers.

[0016] Sources of biological keratin include animal hair, animal keratin, and discarded fur products;

[0017] The preparation method of biological keratin is as follows:

[0018] Y1. The source material of biological keratin is crushed, washed and formed into a stable emulsion. After removing impurities, it is dried in a drying oven for 24 hours to obtain fibrin.

[0019] Y2. Mix 2g of fibrin, 0.6mol / L sodium metabisulfite, 9mol / L urea, and 0.12mol / L sodium dodecyl sulfonate at a bath ratio of 1:50. Heat the mixture to 70°C in a constant temperature water bath and stir at low speed for 12 hours to dissolve and react, thus obtaining a mixed solution.

[0020] Y3. The mixed solution was filtered, dialyzed, and freeze-dried to obtain biological keratin.

[0021] The fine aggregate is quartz sand with an average particle size of 130μm and a maximum particle size of 250μm.

[0022] The thickener is methylcellulose.

[0023] The water-reducing agent is a 38% polycarboxylate high-performance water-reducing agent.

[0024] Iron tailings powder was prepared by grinding the iron tailings using a ball mill. The iron tailings were high-silica type. The grinding parameters were as follows: ball mill speed 350 r / min; ball-to-material ratio 4:1; average ball diameter 8.70 mm; and ball gradation selected. The grinding time is 3 hours.

[0025] The preparation method of the above-mentioned hybrid fiber engineering cementitious composite material includes the following steps:

[0026] Z1. Weigh out the cement, iron tailings powder and fine aggregate and pour them into the mixer and dry mix for 2 minutes to ensure that the dry materials are evenly distributed and to avoid stratification due to differences in density and particle size of the dry materials.

[0027] Z2. Slowly add the weighed water to the mixing pot, continue stirring for 2 minutes, then add the water-reducing agent and stir for 2 minutes. After stirring evenly, add the thickener.

[0028] Z3. Slowly add modified PVA fiber and bio-keratin and stir for 3 minutes. Then add the sieved recycled tire steel fiber and continue stirring until the fiber is evenly distributed. The total stirring time is controlled within 14 minutes to obtain the mixture.

[0029] Z4. After mixing, pour the mixture into a mold and place it on a vibrating table for full vibration. After sealing with a film, place it at room temperature of 18-22℃ for 24 hours, then demold and place it in a standard curing room. Curing is carried out for 28 days at 18-22℃ and 95% relative humidity to obtain hybrid fiber engineering cement-based composite material.

[0030] The beneficial effects of this invention are as follows: This invention leverages the hybrid advantages of fibers to improve the mechanical and durability properties of ECC, and the resulting cement-based material also possesses self-healing capabilities under humid conditions; by using recycled tire steel fibers to partially replace modified PVA fibers in the preparation of hybrid fiber ECC, the preparation cost of ECC is reduced while ensuring strain hardening performance, thus exhibiting certain economic advantages; the reuse of waste tires and biological keratin improves the utilization rate of solid waste, achieving sustainable development of resources and the environment, thus possessing certain environmental advantages. Detailed Implementation

[0031] The principles and features of the present invention are described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The advantages and features of the present invention will become clearer from the following description.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] The present invention will be further described below with reference to specific embodiments:

[0034] A hybrid fiber-reinforced cementitious composite material is made from the following raw materials in parts by weight:

[0035] 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150-200 parts modified PVA fiber, 0-50 parts recycled tire steel fiber, 50-70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0036] The rapid development of the automotive industry has generated a large number of waste tires, but the utilization rate of these tires is low, not exceeding 60%. Common disposal methods include landfill, incineration, or shredding for reuse, but these methods produce harmful substances that pollute the air and soil. Therefore, the rational utilization of waste tires is receiving increasing attention. After shredding and sorting, waste tires can yield recycled tire steel fiber (RTSF), rubber granules, and recycled tire polymer fibers.

[0037] Considering that steel fiber reinforced concrete (SFT) exhibits the most stable mechanical properties among fiber-reinforced concretes, with high tensile and compressive strengths, this paper proposes using RTS fibers to partially replace PVA fibers in the preparation of hybrid fiber ECC. This reduces the preparation cost of ECC while maintaining strain-hardening performance and improving its mechanical properties. Furthermore, it suggests incorporating a certain amount of bio-keratin into the ECC to enhance water retention at concrete cracks, further increasing the self-healing ability of the hybrid fiber ECC and achieving sustainable development in terms of resources and the environment.

[0038] The method for preparing modified PVA fibers is as follows:

[0039] S1. Weigh 10g of vinyltriethoxysilane, add 5g of deionized water and stir at 150r / min at room temperature for 12h to obtain hydrolysate A.

[0040] S2. Weigh 15g of nano-silica and put it into 50mL of toluene. Stir at 300r / min at room temperature for 2h and then disperse by ultrasonication for 30min to obtain dispersion B.

[0041] S3. Hydrolysate A is slowly injected into dispersion B and refluxed in a fume hood for 6 hours at a ventilation temperature of 50°C to obtain mixture C. Then, 1g of triethylenediamine is added and stirred at 300r / min at room temperature for 30s. After the mixture is homogeneous, PVA fiber is added and modified at 110°C for 1.5 hours to obtain modified PVA fiber.

[0042] The specific method for recycling steel fibers from tires through screening is as follows:

[0043] P1. Place three types of screens with apertures of 1.25mm, 0.6mm and 0.3mm on the vibrating table in the upper, middle and lower positions respectively;

[0044] P2. Spread the recycled tire steel fibers evenly on the top layer of the screen to avoid insufficient fiber vibration due to the accumulation of recycled tire steel fibers. Start the vibration table and vibrate for 1 minute. Discard the recycled tire steel fibers left on the top layer of the screen.

[0045] P3. Spread the recycled tire steel fibers left on the middle layer screen back onto the top layer screen, start the vibrating table to vibrate for 1 minute, and discard the recycled tire steel fibers left on the top layer screen.

[0046] P4. Spread the recycled tire steel fibers left on the bottom screen back onto the middle screen, start the vibrating table and vibrate for 1 minute. Finally, discard the recycled tire steel fibers left on the bottom screen and keep the recycled tire steel fibers on the middle screen to obtain recycled tire steel fibers.

[0047] Sources of biological keratin include animal hair, animal keratin, and discarded fur products;

[0048] The preparation method of biological keratin is as follows:

[0049] Y1. The source material of biological keratin is crushed, washed and formed into a stable emulsion. After removing impurities, it is dried in a drying oven for 24 hours to obtain fibrin.

[0050] Y2. Mix 2g of fibrin, 0.6mol / L sodium metabisulfite, 9mol / L urea, and 0.12mol / L sodium dodecyl sulfonate at a bath ratio of 1:50. Heat the mixture to 70°C in a constant temperature water bath and stir at low speed for 12 hours to dissolve and react, thus obtaining a mixed solution.

[0051] Y3. The mixed solution was filtered, dialyzed, and freeze-dried to obtain biological keratin.

[0052] The fine aggregate is quartz sand with an average particle size of 130μm and a maximum particle size of 250μm.

[0053] The thickener is methylcellulose.

[0054] The water-reducing agent is a 38% polycarboxylate high-performance water-reducing agent.

[0055] Iron tailings powder was prepared by grinding the iron tailings using a ball mill. The iron tailings were high-silica type. The grinding parameters were as follows: ball mill speed 350 r / min; ball-to-material ratio 4:1; average ball diameter 8.70 mm; and ball gradation selected. The grinding time is 3 hours.

[0056] The preparation method of the above-mentioned hybrid fiber engineering cementitious composite material includes the following steps:

[0057] Z1. Weigh out the cement, iron tailings powder and fine aggregate and pour them into the mixer and dry mix for 2 minutes to ensure that the dry materials are evenly distributed and to avoid stratification due to differences in density and particle size of the dry materials.

[0058] Z2. Slowly add the weighed water to the mixing pot, continue stirring for 2 minutes, then add the water-reducing agent and stir for 2 minutes. After stirring evenly, add the thickener.

[0059] Z3. Slowly add modified PVA fiber and bio-keratin and stir for 3 minutes. Then add the sieved recycled tire steel fiber and continue stirring until the fiber is evenly distributed. The total stirring time is controlled within 14 minutes to obtain the mixture.

[0060] Z4. After mixing, pour the mixture into a mold and place it on a vibrating table for full vibration. After sealing with a film, place it at room temperature of 18-22℃ for 24 hours, then demold and place it in a standard curing room. Curing is carried out for 28 days at 18-22℃ and 95% relative humidity to obtain hybrid fiber engineering cement-based composite material. Specific Implementation Example 1

[0062] A hybrid fiber-based cementitious composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 175 parts modified PVA fiber, 50 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0063] The chemical composition (%) of cement and iron tailings powder is shown in Table 1. The physical and mechanical properties of recycled tire steel fiber and modified PVA fiber are shown in Table 2. The unit price, carbon content and energy consumption of raw materials for engineering cement-based composite materials are shown in Table 3.

[0064] Table 1. Chemical composition (%) of cement and iron tailings powder as cementitious materials

[0065]

[0066] Table 2 Physical and mechanical properties of recycled tire steel fibers and modified PVA fibers

[0067]

[0068] Table 3 Unit price, carbon content and energy consumption index of raw materials for cement-based composite materials in engineering

[0069]

[0070]

[0071] The preparation method of the above-mentioned hybrid fiber engineering cementitious composite material includes the following steps:

[0072] Z1. Weigh out the cement, iron tailings powder and fine aggregate and pour them into the mixer and dry mix for 2 minutes to ensure that the dry materials are evenly distributed and to avoid stratification due to differences in density and particle size of the dry materials.

[0073] Z2. Slowly add the weighed water to the mixing pot, continue stirring for 2 minutes, then add the water-reducing agent and stir for 2 minutes. After stirring evenly, add the thickener.

[0074] Z3. Slowly add modified PVA fiber and bio-keratin and stir for 3 minutes. Then add the sieved recycled tire steel fiber and continue stirring until the fiber is evenly distributed. The total stirring time is controlled within 14 minutes to obtain the mixture.

[0075] Z4. After mixing, pour the mixture into a mold and place it on a vibrating table for full vibration. After sealing with a film, place it at room temperature (20±2℃). After 24 hours, demold it and place it in a standard curing room (20±2℃, relative humidity of 95%) for 28 days to obtain a hybrid fiber engineering cement-based composite material. Specific Implementation Example 2

[0077] A hybrid fiber-based cementitious composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150 parts modified PVA fiber, 50 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0078] The specific preparation method of the hybrid fiber engineering cement-based composite material is the same as that in Specific Example 1. Specific Implementation Example 3

[0080] A hybrid fiber-based cementitious composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 200 parts modified PVA fiber, 60 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0081] The specific preparation method of the hybrid fiber engineering cement-based composite material is the same as that in Specific Example 1. Specific Implementation Example 4

[0083] A hybrid fiber engineering cement-based composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 175 parts modified PVA fiber, 25 parts recycled tire steel fiber, 70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0084] The specific preparation method of the hybrid fiber engineering cement-based composite material is the same as that in Specific Example 1. Specific Implementation Example 5

[0086] A hybrid fiber engineering cement-based composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150 parts modified PVA fiber, 50 parts recycled tire steel fiber, 70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

[0087] The specific preparation method of the hybrid fiber engineering cement-based composite material is the same as that in Specific Example 1.

[0088] Comparative Example 1

[0089] A cement-based composite material is made from the following raw materials in parts by weight: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 5 parts water-reducing agent, and 1 part thickener.

[0090] According to GB / T 17671-2020 "Test Method for Strength of Cement Mortar", GB / T 2419-2005 "Test Method for Flowability of Cement Mortar" and GB / T 50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", the properties of the composite materials in specific examples 1-5 and comparative example 1 were tested, as shown in Tables 4, 5 and 6. Among them, the static splitting tensile strength test used a cylindrical specimen with a diameter of 100mm × 200mm.

[0091] Table 4 Test results of physical and mechanical properties of composite materials

[0092]

[0093] Table 5. Test results of uniaxial tensile properties and single-crack tensile properties of composite materials.

[0094]

[0095] Table 6. Total cost, carbon content, and energy consumption indicators of composite materials

[0096]

[0097] The advantages of the hybrid fiber-reinforced cementitious composite material of the present invention are as follows:

[0098] By leveraging the hybrid advantages of fibers, the mechanical and durability properties of ECC are improved, and the resulting cement-based material also possesses self-healing capabilities under humid conditions. Using recycled tire steel fibers to partially replace modified PVA fibers in the preparation of hybrid fiber ECC reduces the preparation cost of ECC while ensuring strain hardening performance, thus offering certain economic advantages. The reuse of waste tires and biological keratin improves the utilization rate of solid waste, achieving sustainable development of resources and the environment, and thus offering certain environmental advantages.

[0099] The present invention has been described above with reference to specific embodiments. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A hybrid fiber-reinforced cementitious composite material, characterized in that, Made from the following parts by weight of raw materials: 500 parts cement, 1000 parts iron tailings powder, 400 parts water, 500 parts fine aggregate, 150-200 parts modified PVA fiber, 0-50 parts recycled tire steel fiber, 50-70 parts bio-keratin, 5 parts water-reducing agent, and 1 part thickener.

2. The hybrid fiber-reinforced cementitious composite material according to claim 1, characterized in that, The method for preparing modified PVA fibers is as follows: S1. Weigh 10g of vinyltriethoxysilane, add 5g of deionized water and stir at 150r / min at room temperature for 12h to obtain hydrolysate A. S2. Weigh 15g of nano-silica and put it into 50mL of toluene. Stir at 300r / min at room temperature for 2h and then disperse by ultrasonication for 30min to obtain dispersion B. S3. Hydrolysate A is slowly injected into dispersion B and refluxed in a fume hood for 6 hours at a ventilation temperature of 50°C to obtain mixture C. Then, 1g of triethylenediamine is added and stirred at 300r / min at room temperature for 30s. After the mixture is homogeneous, PVA fiber is added and modified at 110°C for 1.5 hours to obtain modified PVA fiber.

3. The hybrid fiber-reinforced cementitious composite material according to claim 2, characterized in that, The specific method for recycling steel fibers from tires through screening is as follows: P1. Place three types of screens with apertures of 1.25mm, 0.6mm and 0.3mm on the vibrating table in the upper, middle and lower positions respectively; P2. Spread the recycled tire steel fibers evenly on the top layer of the screen to avoid insufficient fiber vibration due to the accumulation of recycled tire steel fibers. Start the vibration table and vibrate for 1 minute. Discard the recycled tire steel fibers left on the top layer of the screen. P3. Spread the recycled tire steel fibers left on the middle layer screen back onto the top layer screen, start the vibrating table to vibrate for 1 minute, and discard the recycled tire steel fibers left on the top layer screen. P4. Spread the recycled tire steel fibers left on the bottom screen back onto the middle screen, start the vibrating table and vibrate for 1 minute. Finally, discard the recycled tire steel fibers left on the bottom screen and keep the recycled tire steel fibers on the middle screen to obtain recycled tire steel fibers.

4. The hybrid fiber-reinforced cementitious composite material according to claim 3, characterized in that, Sources of biological keratin include animal hair, animal keratin, and discarded fur products; The preparation method of biological keratin is as follows: Y1. The source material of biological keratin is crushed, washed and formed into a stable emulsion. After removing impurities, it is dried in a drying oven for 24 hours to obtain fibrin. Y2. Mix 2g of fibrin, 0.6mol / L sodium metabisulfite, 9mol / L urea, and 0.12mol / L sodium dodecyl sulfonate at a bath ratio of 1:

50. Heat the mixture to 70°C in a constant temperature water bath and stir at low speed for 12 hours to dissolve and react, thus obtaining a mixed solution. Y3. The mixed solution was filtered, dialyzed, and freeze-dried to obtain biological keratin.

5. The hybrid fiber-reinforced cementitious composite material according to claim 4, characterized in that, The fine aggregate is quartz sand with an average particle size of 130μm and a maximum particle size of 250μm.

6. The hybrid fiber-reinforced cementitious composite material according to claim 5, characterized in that, The thickener is methylcellulose.

7. The hybrid fiber-reinforced cementitious composite material according to claim 6, characterized in that, The water-reducing agent is a 38% polycarboxylate high-performance water-reducing agent.

8. The hybrid fiber-reinforced cementitious composite material according to claim 7, characterized in that, Iron tailings powder was prepared by grinding the iron tailings using a ball mill. The iron tailings were high-silica type. The grinding parameters were as follows: ball mill speed 350 r / min; ball-to-material ratio 4:1; average ball diameter 8.70 mm; and ball gradation selected. The grinding time is 3 hours.

9. A method for preparing a hybrid fiber-reinforced cementitious composite material as described in any one of claims 1-8, characterized in that, The preparation steps are as follows: Z1. Weigh out the cement, iron tailings powder and fine aggregate and pour them into the mixer and dry mix for 2 minutes to ensure that the dry materials are evenly distributed and to avoid stratification due to differences in density and particle size of the dry materials. Z2. Slowly add the weighed water to the mixing pot, continue stirring for 2 minutes, then add the water-reducing agent and stir for 2 minutes. After stirring evenly, add the thickener. Z3. Slowly add modified PVA fiber and bio-keratin and stir for 3 minutes. Then add the sieved recycled tire steel fiber and continue stirring until the fiber is evenly distributed. The total stirring time is controlled within 14 minutes to obtain the mixture. Z4. After mixing, pour the mixture into a mold and place it on a vibrating table for full vibration. After sealing with a film, place it at room temperature of 18-22℃ for 24 hours, then demold and place it in a standard curing room. Curing is carried out for 28 days at 18-22℃ and 95% relative humidity to obtain hybrid fiber engineering cement-based composite material.

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