Twisted steel fiber ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses twisted steel fiber ultra-high performance concrete and a preparation method thereof, and the twisted steel fiber ultra-high performance concrete comprises the following raw materials by weight: 80-90 parts of cement, 20-26 parts of silica fume, 10-15 parts of coarse aggregate, 100-120 parts of quartz sand, 2.5-4 parts of a superplasticizer, 15-25 parts of water, 9-16 parts of twisted steel fiber, 3-5 parts of nano calcium carbonate, 2-3 parts of an expanding agent, and 4-5 parts of straight steel fiber. The cement is selected from PO52.5 ordinary Portland cement, and the quartz sand with the particle size of 30% being 0.1-0.3 mm and the quartz sand with the particle size of 70% being 0.3-0.6 mm are mixed, and the invention relates to the technical field of concrete preparation. According to the twisted steel fiber ultra-high performance concrete and the preparation method thereof, the twisted steel fiber ultra-high performance concrete is outstanding in corrosion resistance, compression resistance, tension resistance, shear resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete preparation, and in particular to a twisted steel fiber ultra-high performance concrete and a preparation method thereof. Background Art

[0002] In today's construction engineering field, as infrastructure construction continues to develop towards high-rise, large-span, heavy-load and harsh environment service, the performance requirements for building materials are becoming increasingly stringent. Traditional concrete has inherent defects such as low tensile strength and poor durability, especially when facing complex corrosive media and long-term mechanical effects, and is difficult to meet the high standards of modern engineering.

[0003] On the one hand, in coastal areas, chemical parks and other environments, buildings are exposed to long-term erosion by seawater and chemical solutions. The steel bars inside ordinary concrete are very easy to rust, causing volume expansion, resulting in cracking and spalling of the concrete, and a sharp drop in the structural bearing capacity, which seriously threatens the safety and service life of the project. According to statistics, the cost of infrastructure maintenance and reconstruction caused by concrete corrosion problems is as high as tens of billions of yuan each year.

[0004] On the other hand, concrete in structures like long-span bridges and high-rise buildings must withstand enormous tensile, compressive, and shear stresses. Conventional concrete's tensile strength is typically only about 1 / 10 of its compressive strength. When subjected to tension or shear, it often cracks prematurely, making it unable to effectively transfer loads. This limits structural design and necessitates extensive reinforcement, increasing costs and construction complexity.

[0005] To overcome these challenges, the industry continues to explore the path of technological innovation in high-performance concrete. Researchers focus on key links such as optimizing the combination of raw materials, regulating microstructures, and improving preparation processes. By introducing ultra-fine active mineral admixtures such as silica fume and nano-calcium carbonate, the gaps between cement particles are filled, the pore structure is optimized, and the density of concrete is improved, thereby enhancing its anti-permeability and corrosion resistance. The addition of steel fibers, especially twisted steel fibers, with their unique shape and good anchoring effect, effectively restrains the expansion of cracks after the concrete matrix is ​​loaded and cracked, and bears tensile and shear stresses, significantly improving the tensile and shear toughness of the concrete. Admixtures such as high-efficiency water reducers, expansion agents, ultraviolet absorbers, and antioxidants are used in combination to optimize working performance, compensate for shrinkage, and resist environmental aging factors.

[0006] This invention came into being in this technical context. It aims to systematically study the effects of different raw material ratios and preparation processes on the performance of twisted steel fiber ultra-high performance concrete, and provide engineering practice with a series of concrete solutions with excellent corrosion resistance, high strength in tension, compression and shear resistance, to fill the performance gap between traditional concrete and complex engineering requirements, and to promote the vigorous development of modern construction. Summary of the Invention

[0007] To achieve the above objectives, the present invention is implemented through the following technical scheme: a twisted steel fiber ultra-high performance concrete and a preparation method thereof, composed of the following raw materials by weight, including: 80-90 parts of cement, 20-26 parts of silica fume, 10-15 parts of coarse aggregate, 100-120 parts of quartz sand, 2.5-4 parts of high-efficiency water reducer, 15-25 parts of water, 9-16 parts of twisted steel fiber, 3-5 parts of nano-calcium carbonate, 2-3 parts of expansion agent, 4-5 parts of straight steel fiber, 10-15 parts of modified rubber reinforcing filler, 0.5-0.8 parts of ultraviolet absorber, and 0.3-0.5 parts of antioxidant.

[0008] Preferably, the cement is P·O52.5 ordinary Portland cement, and the particle size of the quartz sand is a mixture of 30% 0.1-0.3 mm and 70% 0.3-0.6 mm.

[0009] Preferably, the high-efficiency water reducer is a polycarboxylic acid water reducer with a solid content of 20%.

[0010] Preferably, the twisted steel fiber has a length of 15 mm, a diameter of 0.2 mm, an aspect ratio of 75, a twisting angle of 30°-60°, and a surface that has been specially roughened.

[0011] Preferably, the particle size of the nano calcium carbonate is 20-50 nm.

[0012] Preferably, the expansion agent is a calcium sulfoaluminate expansion agent, the ultraviolet absorber is a benzotriazole, and the antioxidant is a hindered phenol.

[0013] Preferably, the method comprises the following steps: The first step is to pre-mix the dry materials. Pour the cement, silica fume, coarse aggregate, quartz sand, nano calcium carbonate, expansion agent, and prepared modified rubber reinforcing filler into a forced mixer and stir at 60-80r / min for 2 minutes to make the dry materials preliminarily mixed; The second step is to mix the admixture with water. In another container, the high-efficiency water reducer, ultraviolet absorber, antioxidant and water are fully stirred and mixed to form an admixture aqueous solution; The third step is to mix the wet materials. Slowly pour the aqueous solution of the admixture into the dry materials being stirred. At the same time, adjust the mixer speed to 100-120r / min and stir for 3 minutes to fully wet the materials and form a uniform slurry. Step 4: Add and stir the steel fibers. First, evenly sprinkle the straight steel fibers into the slurry and stir for 1 minute. Then slowly add the twisted steel fibers and continue stirring at medium speed for 3-4 minutes to ensure that the steel fibers are evenly dispersed in the concrete without obvious agglomeration. Step 5: Discharging and molding. After mixing is completed, the concrete is immediately discharged and poured into a pre-prepared mold. Vibration, screeding and other molding operations are performed in accordance with relevant standards, and then maintenance is carried out.

[0014] Preferably, the modified rubber reinforcing filler is composed of the following raw materials by weight, including: 30-35 parts of natural rubber, 20-25 parts of styrene-butadiene rubber, 12-16 parts of carbon black, 3-5 parts of white carbon black, 8-7 parts of modified nano-carbon tubes, 2-6 parts of coupling agent, 1.5-2.5 parts of anti-aging agent, 1.2-1.8 parts of cross-linking agent, 1.2-2.4 parts of accelerator, 0.8-1.6 parts of stearic acid, 0.8-1.8 parts of zinc oxide, and 2-6 parts of glycidyl methacrylate.

[0015] Preferably, the preparation method of the modified rubber reinforced filler is as follows: Step 1: Pretreatment of carbon nanotubes: Add an appropriate amount of multi-walled carbon nanotubes to a mixed acid solution consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, with a weight ratio of carbon nanotubes to the mixed acid of 1:12. Ultrasonic treatment was performed in an ultrasonic oscillator for 2.5 hours at 45°C. After ultrasonic treatment, the mixture was repeatedly washed with copious amounts of deionized water until neutral, and then dried in a vacuum drying oven at 70°C for 24 hours. Step 2: Silane coupling agent modification of carbon nanotubes. The acidified carbon nanotubes were added to a toluene solution containing a silane coupling agent KH-550 (at a weight ratio of 1:6 to the carbon nanotubes). The concentration of the silane coupling agent in the toluene solution was 4%. Under nitrogen protection, the mixture was refluxed and stirred for 5 hours at 120°C. After the reaction, the carbon nanotubes were washed several times with toluene and then dried in a vacuum drying oven at 90°C for 12 hours. Step 3: Graft copolymerization reaction of carbon nanotubes with rubber monomers and anti-aging agents. The carbon nanotubes modified with a silane coupling agent are added to a solution containing a mixture of styrene and butadiene monomers (with a weight ratio of 1:1.8 to carbon nanotubes), an initiator benzoyl peroxide (with a weight ratio of 1:120 to rubber monomers), a hindered amine light stabilizer 770 (with a weight ratio of 1:25 to rubber monomers), and glycidyl methacrylate (with a weight ratio of 1:10 to rubber monomers). The mixture is stirred and reacted at 75°C for 4 hours. After the reaction is completed, the mixture is washed several times with ethanol to obtain modified carbon nanotubes. Step 4: Rubber mixing to prepare a modified rubber reinforcing filler. Natural rubber and styrene-butadiene rubber are blended on an open mill, the temperature is controlled at 45°C, and the mixing time is about 6 minutes. Carbon black and white carbon black are added to the blended rubber, and the mixing is continued for 12 minutes to uniformly disperse the filler in the rubber matrix. Modified nanocarbon tubes and silane coupling agent KH-550 are added and mixed at 55°C for 4 minutes to further enhance the interfacial bonding between the filler and the rubber. An anti-aging agent is added and mixed at 50°C for 4 minutes to uniformly disperse it in the rubber system. Finally, sulfur, thiazole accelerator M, stearic acid and zinc oxide are added, and a vulcanization cross-linking reaction is carried out at 150°C for about 12 minutes to form a modified rubber reinforcing filler with high toughness, corrosion resistance, high strength and good aging resistance.

[0016] The present invention provides a twisted steel fiber ultra-high performance concrete and a preparation method thereof. It has the following beneficial effects: This twisted steel fiber ultra-high performance concrete and its preparation method have outstanding performance in corrosion resistance. Through the synergistic effect of carefully formulated raw material combinations, especially nano-calcium carbonate, calcium sulfoaluminate expansion agents, benzotriazole ultraviolet absorbers, hindered phenol antioxidants and other functional ingredients, a solid protective barrier can be built inside the concrete. When used in corrosive environments such as marine engineering buildings in coastal areas and factory facilities in chemical parks, it can effectively delay or even prevent the erosion of the internal steel structure of the concrete by external corrosive media. Compared with traditional concrete, its rust rate is greatly reduced, and the tensile and shear strengths have made a qualitative leap. The unique twisted steel fibers cooperate with an appropriate amount of straight steel fibers. When the concrete is under tension or shear, the steel fibers rely on their own good tensile properties and their interaction with the concrete. The strong anchoring effect between the soil matrix can promptly bear the tension and shear forces, and restrain the generation and expansion of cracks. Based on the reasonable raw material ratio, the core ingredients such as P·O52.5 ordinary Portland cement, silica fume, quartz sand, etc. are tightly combined to form a concrete matrix with extremely high density. The preparation process of the present invention is scientific and reasonable and has good operability. The raw materials are mixed in steps and the stirring rate and time are precisely controlled. This not only ensures the uniform dispersion of the raw materials and avoids quality problems such as steel fiber agglomeration, but also fully stimulates the chemical reaction between the various components to achieve the optimal performance of concrete. It provides a solid technical guarantee for large-scale industrial production and on-site construction applications, and effectively improves the efficiency of engineering construction. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] In a first embodiment, the present invention provides a technical solution: a twisted steel fiber ultra-high performance concrete, comprising the following raw materials by weight: 80 parts of PO52.5 ordinary Portland cement, 20 parts of silica fume, 10 parts of coarse aggregate, 100 parts of quartz sand, 2.5 parts of a polycarboxylic acid-based water reducer with a solid content of 20%, 15 parts of water, 9 parts of twisted steel fibers, 3 parts of nano-calcium carbonate, 2 parts of a calcium sulfoaluminate expansion agent, 4 parts of straight steel fibers, 0.5 parts of a benzotriazole ultraviolet absorber, and 0.3 parts of a hindered phenol antioxidant; The preparation method of twisted steel fiber ultra-high performance concrete comprises the following steps: The first step is to pre-mix the dry materials. Pour the cement, silica fume, coarse aggregate, quartz sand, nano calcium carbonate and expansion agent into a forced mixer and stir at 70r / min for 2 minutes to make the dry materials preliminarily mixed. The second step is to mix the admixture with water. In another container, the high-efficiency water reducer, ultraviolet absorber, antioxidant and water are fully stirred and mixed to form an admixture aqueous solution; The third step is to mix the wet materials. Slowly pour the aqueous solution of the admixture into the dry materials being stirred. At the same time, adjust the mixer speed to 110r / min and stir for 3 minutes to fully wet the materials and form a uniform slurry. Step 4: Add and stir the steel fibers. First, evenly sprinkle the straight steel fibers into the slurry and stir for 1 minute. Then slowly add the twisted steel fibers and continue stirring at medium speed for 3 minutes to ensure that the steel fibers are evenly dispersed in the concrete without obvious agglomeration. Step 5: Discharging and molding. After mixing is completed, the concrete is immediately discharged and poured into a pre-prepared mold. Vibration, screeding and other molding operations are performed in accordance with relevant standards, and then maintenance is carried out.

[0019] In a second embodiment, the present invention provides a technical solution: a twisted steel fiber ultra-high performance concrete, comprising the following raw materials by weight: 85 parts of PO52.5 ordinary Portland cement, 23 parts of silica fume, 12 parts of coarse aggregate, 110 parts of quartz sand, 3 parts of a polycarboxylic acid-based water reducer with a solid content of 20%, 20 parts of water, 12 parts of twisted steel fibers, 4 parts of nano-calcium carbonate, 2.5 parts of a calcium sulfoaluminate expansion agent, 4.5 parts of straight steel fibers, 0.6 parts of a benzotriazole ultraviolet absorber, and 0.4 parts of a hindered phenol antioxidant; The preparation method of twisted steel fiber ultra-high performance concrete comprises the following steps: The first step is to pre-mix the dry materials. Pour the cement, silica fume, coarse aggregate, quartz sand, nano calcium carbonate and expansion agent into a forced mixer and stir at 70r / min for 2 minutes to make the dry materials preliminarily mixed. The second step is to mix the admixture with water. In another container, the high-efficiency water reducer, ultraviolet absorber, antioxidant and water are fully stirred and mixed to form an admixture aqueous solution; The third step is to mix the wet materials. Slowly pour the aqueous solution of the admixture into the dry materials being stirred. At the same time, adjust the mixer speed to 110r / min and stir for 3 minutes to fully wet the materials and form a uniform slurry. Step 4: Add and stir the steel fibers. First, evenly sprinkle the straight steel fibers into the slurry and stir for 1 minute. Then slowly add the twisted steel fibers and continue stirring at medium speed for 3 minutes to ensure that the steel fibers are evenly dispersed in the concrete without obvious agglomeration. Step 5: Discharging and molding. After mixing is completed, the concrete is immediately discharged and poured into a pre-prepared mold. Vibration, screeding and other molding operations are performed in accordance with relevant standards, and then maintenance is carried out.

[0020] In a third embodiment, the present invention provides a technical solution: a twisted steel fiber ultra-high performance concrete, characterized by being composed of the following raw materials by weight: 90 parts of PO52.5 ordinary Portland cement, 26 parts of silica fume, 15 parts of coarse aggregate, 120 parts of quartz sand, 4 parts of a polycarboxylic acid-based water reducer with a solid content of 20%, 25 parts of water, 16 parts of twisted steel fibers, 5 parts of nano-calcium carbonate, 3 parts of a calcium sulfoaluminate expansion agent, 5 parts of straight steel fibers, 0.8 parts of a benzotriazole ultraviolet absorber, and 0.5 parts of a hindered phenol antioxidant; The preparation method of twisted steel fiber ultra-high performance concrete comprises the following steps: The first step is to pre-mix the dry materials. Pour the cement, silica fume, coarse aggregate, quartz sand, nano calcium carbonate and expansion agent into a forced mixer and stir at 70r / min for 2 minutes to make the dry materials preliminarily mixed. The second step is to mix the admixture with water. In another container, the high-efficiency water reducer, ultraviolet absorber, antioxidant and water are fully stirred and mixed to form an admixture aqueous solution; The third step is to mix the wet materials. Slowly pour the aqueous solution of the admixture into the dry materials being stirred. At the same time, adjust the mixer speed to 110r / min and stir for 3 minutes to fully wet the materials and form a uniform slurry. Step 4: Add and stir the steel fibers. First, evenly sprinkle the straight steel fibers into the slurry and stir for 1 minute. Then slowly add the twisted steel fibers and continue stirring at medium speed for 3 minutes to ensure that the steel fibers are evenly dispersed in the concrete without obvious agglomeration. Step 5: Discharging and molding. After mixing is completed, the concrete is immediately discharged and poured into a pre-prepared mold. Vibration, screeding and other molding operations are performed in accordance with relevant standards, and then maintenance is carried out.

[0021] In a fourth embodiment, the present invention provides a technical solution: compared with the first embodiment, 10 parts more of the modified rubber reinforcing filler are added in step 1, and the other raw material ratios and preparation steps are the same as those of the first embodiment. The preparation steps of the modified rubber reinforcing filler include: Step 1: Pretreatment of carbon nanotubes: Add an appropriate amount of multi-walled carbon nanotubes to a mixed acid solution consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, with a carbon nanotube to mixed acid ratio of 1:12 (weight ratio). Ultrasonic treatment is performed in an ultrasonic oscillator for 2.5 hours at a temperature of 45°C. After ultrasonic treatment, the mixture is repeatedly washed with a large amount of deionized water until neutral, and then dried in a vacuum drying oven at 70°C for 24 hours. Step 2: Silane coupling agent modification of carbon nanotubes: The acidified carbon nanotubes were added to a toluene solution containing a silane coupling agent, KH-550, at a weight ratio of 1:6 to the carbon nanotubes. The concentration of the silane coupling agent in the toluene solution was 4%. The mixture was stirred under reflux for 5 hours at 120°C under nitrogen protection. After the reaction, the carbon nanotubes were washed several times with toluene and then dried in a vacuum drying oven at 90°C for 12 hours. Step 3, graft copolymerization reaction of carbon nanotubes with rubber monomer and anti-aging agent, adding the carbon nanotubes modified with silane coupling agent to a solution containing a mixture of styrene and butadiene monomers, initiator benzoyl peroxide, hindered amine light stabilizer 770 and glycidyl methacrylate, the weight ratio of the mixture to the carbon nanotubes is 1:1.8, the weight ratio of benzoyl peroxide to the rubber monomer is 1:120, the weight ratio of hindered amine light stabilizer 770 to the rubber monomer is 1:25, and the weight ratio of glycidyl methacrylate to the rubber monomer is 1:10, stirring and reacting at 75°C for 4 hours. After the reaction is completed, washing with ethanol several times to obtain modified carbon nanotubes; Step 4: Rubber mixing to prepare a modified rubber reinforcing filler. Natural rubber and styrene-butadiene rubber are blended on an open mill, the temperature is controlled at 45°C, and the mixing time is about 6 minutes. Carbon black and white carbon black are added to the blended rubber, and the mixing is continued for 12 minutes to uniformly disperse the filler in the rubber matrix. Modified nanocarbon tubes and silane coupling agent KH-550 are added and mixed at 55°C for 4 minutes to further enhance the interfacial bonding between the filler and the rubber. Hindered amine light stabilizer 770 is added and mixed at 50°C for 4 minutes to uniformly disperse it in the rubber system. Finally, sulfur, thiazole accelerator M, stearic acid and zinc oxide are added, and a vulcanization cross-linking reaction is carried out at 150°C for about 12 minutes to form a modified rubber reinforcing filler with high toughness, corrosion resistance, high strength and good aging resistance.

[0022] In a fifth embodiment, the present invention provides a technical solution: compared with the second embodiment, 12 parts of modified rubber reinforcing filler are added in step 1, and the other raw material ratios and preparation steps are the same as those of the second embodiment. The preparation steps of the modified rubber reinforcing filler include: Step 1: Pretreatment of carbon nanotubes: Add an appropriate amount of multi-walled carbon nanotubes to a mixed acid solution consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, with a carbon nanotube to mixed acid ratio of 1:12 (weight ratio). Ultrasonic treatment is performed in an ultrasonic oscillator for 2.5 hours at a temperature of 45°C. After ultrasonic treatment, the mixture is repeatedly washed with a large amount of deionized water until neutral, and then dried in a vacuum drying oven at 70°C for 24 hours. Step 2: Silane coupling agent modification of carbon nanotubes: The acidified carbon nanotubes were added to a toluene solution containing a silane coupling agent, KH-550, at a weight ratio of 1:6 to the carbon nanotubes. The concentration of the silane coupling agent in the toluene solution was 4%. The mixture was stirred under reflux for 5 hours at 120°C under nitrogen protection. After the reaction, the carbon nanotubes were washed several times with toluene and then dried in a vacuum drying oven at 90°C for 12 hours. Step 3, graft copolymerization reaction of carbon nanotubes with rubber monomer and anti-aging agent, adding the carbon nanotubes modified with silane coupling agent to a solution containing a mixture of styrene and butadiene monomers, initiator benzoyl peroxide, hindered amine light stabilizer 770 and glycidyl methacrylate, the weight ratio of the mixture to the carbon nanotubes is 1:1.8, the weight ratio of benzoyl peroxide to the rubber monomer is 1:120, the weight ratio of hindered amine light stabilizer 770 to the rubber monomer is 1:25, and the weight ratio of glycidyl methacrylate to the rubber monomer is 1:10, stirring and reacting at 75°C for 4 hours. After the reaction is completed, washing with ethanol several times to obtain modified carbon nanotubes; Step 4: Rubber mixing to prepare a modified rubber reinforcing filler. Natural rubber and styrene-butadiene rubber are blended on an open mill, the temperature is controlled at 45°C, and the mixing time is about 6 minutes. Carbon black and white carbon black are added to the blended rubber, and the mixing is continued for 12 minutes to uniformly disperse the filler in the rubber matrix. Modified nanocarbon tubes and silane coupling agent KH-550 are added and mixed at 55°C for 4 minutes to further enhance the interfacial bonding between the filler and the rubber. Hindered amine light stabilizer 770 is added and mixed at 50°C for 4 minutes to uniformly disperse it in the rubber system. Finally, sulfur, thiazole accelerator M, stearic acid and zinc oxide are added, and a vulcanization cross-linking reaction is carried out at 150°C for about 12 minutes to form a modified rubber reinforcing filler with high toughness, corrosion resistance, high strength and good aging resistance.

[0023] In a sixth embodiment, the present invention provides a technical solution: compared with the third embodiment, 15 parts more of a modified rubber reinforcing filler is added in step 1, and the other raw material ratios and preparation steps are the same as those of the third embodiment. The preparation steps of the modified rubber reinforcing filler include: Step 1: Pretreatment of carbon nanotubes: Add an appropriate amount of multi-walled carbon nanotubes to a mixed acid solution consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, with a carbon nanotube to mixed acid ratio of 1:12 (weight ratio). Ultrasonic treatment is performed in an ultrasonic oscillator for 2.5 hours at a temperature of 45°C. After ultrasonic treatment, the mixture is repeatedly washed with a large amount of deionized water until neutral, and then dried in a vacuum drying oven at 70°C for 24 hours. Step 2: Silane coupling agent modification of carbon nanotubes: The acidified carbon nanotubes were added to a toluene solution containing a silane coupling agent, KH-550, at a weight ratio of 1:6 to the carbon nanotubes. The concentration of the silane coupling agent in the toluene solution was 4%. The mixture was stirred under reflux for 5 hours at 120°C under nitrogen protection. After the reaction, the carbon nanotubes were washed several times with toluene and then dried in a vacuum drying oven at 90°C for 12 hours. Step 3, graft copolymerization reaction of carbon nanotubes with rubber monomer and anti-aging agent, adding the carbon nanotubes modified with silane coupling agent to a solution containing a mixture of styrene and butadiene monomers, initiator benzoyl peroxide, hindered amine light stabilizer 770 and glycidyl methacrylate, the weight ratio of the mixture to the carbon nanotubes is 1:1.8, the weight ratio of benzoyl peroxide to the rubber monomer is 1:120, the weight ratio of hindered amine light stabilizer 770 to the rubber monomer is 1:25, and the weight ratio of glycidyl methacrylate to the rubber monomer is 1:10, stirring and reacting at 75°C for 4 hours. After the reaction is completed, washing with ethanol several times to obtain modified carbon nanotubes; Step 4: Rubber mixing to prepare a modified rubber reinforcing filler. Natural rubber and styrene-butadiene rubber are blended on an open mill, the temperature is controlled at 45°C, and the mixing time is about 6 minutes. Carbon black and white carbon black are added to the blended rubber, and the mixing is continued for 12 minutes to uniformly disperse the filler in the rubber matrix. Modified nanocarbon tubes and silane coupling agent KH-550 are added and mixed at 55°C for 4 minutes to further enhance the interfacial bonding between the filler and the rubber. Hindered amine light stabilizer 770 is added and mixed at 50°C for 4 minutes to uniformly disperse it in the rubber system. Finally, sulfur, thiazole accelerator M, stearic acid and zinc oxide are added, and a vulcanization cross-linking reaction is carried out at 150°C for about 12 minutes to form a modified rubber reinforcing filler with high toughness, corrosion resistance, high strength and good aging resistance.

[0024] The performance test method of twisted steel fiber ultra-high performance concrete is as follows: Corrosion resistance test method: Accelerated corrosion test methods were used to simulate the performance changes of concrete in a harsh corrosive environment. The specimens that had expired were immersed in a specific corrosive solution. The corrosive solution was a 3.5% sodium chloride solution to simulate the seawater corrosion environment. The immersion device should have good sealing properties to prevent the volatilization of the solution from affecting the test concentration. The specimen should be completely immersed in the solution, and the ratio of solution volume to specimen surface area should be 20:1 to ensure sufficient supply of corrosive medium. The specimens were removed every seven days to observe changes in their appearance and record any signs of corrosion, such as rust and peeling, on the surface. An ultrasonic detector was also used to measure changes in the specimens' internal structure. Parameters such as wave velocity and amplitude were used to reflect the density and damage of the concrete, and to assess the evolution of the concrete's corrosion resistance over time. After 90 days of corrosion testing, the specimens were broken and the corrosion rate of the steel bars inside the concrete was determined by chemical analysis. The corrosion rate was quantified by the ratio of the corrosion mass loss to the original steel bar mass. The lower the corrosion rate, the higher the corrosion resistance of the concrete.

[0025] Tensile strength test method: Use a universal material testing machine to perform tensile strength tests. Before the test, ensure that the testing machine's range and accuracy meet the requirements and that it has been calibrated. The cured specimens are processed into standard tensile specimens. The clamping parts at both ends of the specimens should be flat and smooth to ensure uniform force during the tensile process and avoid local stress concentration that may cause premature failure of the specimens. When installing the specimen, ensure that it is on the axial centerline of the testing machine. The clamping force of the upper and lower clamps is moderate, which can not only firmly fix the specimen but also prevent additional damage to the specimen. Start the testing machine and apply tension at a constant loading rate of 0.5 MPa / s until the specimen breaks. The tensile strength of the concrete was calculated by dividing the maximum tensile force at fracture by the original cross-sectional area of ​​the specimen. The unit was MPa. The average of the test results of multiple parallel specimens in each group of embodiments or comparative examples was taken as the final tensile strength value to reduce the experimental error.

[0026] Compressive strength test method: The compressive strength test also uses a universal material testing machine. Before the test, the equipment status is checked and calibrated; Prepare a standard cubic compression test specimen with a size of 150mm×150mm×150mm, and a flat surface; Place the specimen at the center of the pressure plate of the testing machine. Adjust the testing machine so that the upper and lower pressure plates are in close contact with the surface of the specimen. Apply pressure slowly and uniformly during loading at a loading rate of 0.3 MPa / s until the specimen fails. Record the maximum load value when the specimen is destroyed, and calculate the compressive strength of the concrete using the formula compressive strength = failure load / bearing area. The unit is MPa. Similarly, the average value of the test results of each group of specimens is taken as the final compressive strength index, reflecting the compressive bearing capacity of concrete with different formulas.

[0027] Flexural strength test method: An electric flexural testing machine is used for flexural strength testing, and the testing machine needs to be calibrated before the test.

[0028] Prepare standard prismatic flexural test specimens with dimensions of 150mm×150mm×550mm. During the specimen forming process, ensure that the surface is flat and the edges are vertical. Place the specimen on the support of the flexural testing machine with the side of the specimen facing upwards. Adjust the position of the specimen to ensure that it is located in the center of the support, and set the support spacing to 450mm. Start the testing machine and apply vertical load at a constant loading rate of 0.05 Pa / s, slowly increasing the load until the specimen breaks; According to the failure load recorded during the test and the cross-sectional dimensions of the specimen, the flexural strength value of the concrete was calculated using the flexural strength calculation formula. Similarly, the test results of each group of parallel specimens were statistically analyzed, and the average value was taken as the basis for the final flexural strength assessment.

[0029] The test results between the embodiments and the comparative examples obtained according to the above-mentioned detection method are as follows: According to the above test results, it can be seen that the raw material ratio in the sixth embodiment is the optimal ratio of the present invention.

[0030] Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field and related fields without making creative efforts should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention shall be implemented in accordance with conventional means in the field unless otherwise specified or limited.

Claims

1. A twisted steel fiber ultra-high performance concrete, characterized in that: The invention is composed of the following raw materials by weight: 80-90 parts of cement, 20-26 parts of silica fume, 10-15 parts of coarse aggregate, 100-120 parts of quartz sand, 2.5-4 parts of high-efficiency water reducer, 15-25 parts of water, 9-16 parts of twisted steel fiber, 3-5 parts of nano calcium carbonate, 2-3 parts of expansion agent, 4-5 parts of straight steel fiber, 10-15 parts of modified rubber reinforcing filler, 0.5-0.8 parts of ultraviolet absorber and 0.3-0.5 parts of antioxidant.

2. The twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The cement is P·O52.5 ordinary Portland cement, and the particle size of the quartz sand is a mixture of 30% 0.1-0.3 mm and 70% 0.3-0.6 mm.

3. The twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The high-efficiency water reducer is a polycarboxylic acid water reducer with a solid content of 20%.

4. The twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The twisted steel fiber has a length of 15 mm, a diameter of 0.2 mm, an aspect ratio of 75, a twisting angle of 30°-60°, and a surface that has been specially roughened.

5. The twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The particle size of the nano calcium carbonate is 20-50 nm.

6. The twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The expansion agent is a calcium sulfoaluminate expansion agent, the ultraviolet absorber is a benzotriazole, and the antioxidant is a hindered phenol.

7. The method for preparing twisted steel fiber ultra-high performance concrete according to claim 1, characterized in that: The steps include: The first step is to pre-mix the dry materials. Pour the cement, silica fume, coarse aggregate, quartz sand, nano calcium carbonate, expansion agent and prepared modified rubber reinforcing filler into a forced mixer and stir at 60-80r / min for 2 minutes. Step 2: Mix the admixture with water. In another container, stir and mix the high-efficiency water reducer, ultraviolet absorber, antioxidant and water thoroughly. The third step is to mix the wet materials. Slowly pour the aqueous solution of the admixture into the dry materials being stirred. At the same time, adjust the mixer speed to 100-120r / min and stir for 3 minutes. Step 4: Add and stir the steel fibers. First, sprinkle the straight steel fibers evenly into the slurry and stir for 1 minute. Then, slowly add the twisted steel fibers and continue stirring at medium speed for 3-4 minutes. Step 5: Discharging and molding. After mixing is completed, the concrete is immediately discharged and poured into a pre-prepared mold. Vibration, screeding and other molding operations are performed in accordance with relevant standards, and then maintenance is carried out.

8. The method for preparing twisted steel fiber ultra-high performance concrete according to claim 7, characterized in that: The modified rubber reinforcing filler is composed of the following raw materials by weight: 30-35 parts of natural rubber, 20-25 parts of styrene-butadiene rubber, 12-16 parts of carbon black, 3-5 parts of white carbon black, 8-7 parts of modified nano-carbon tubes, 2-6 parts of coupling agent, 1.5-2.5 parts of anti-aging agent, 1.2-1.8 parts of cross-linking agent, 1.2-2.4 parts of accelerator, 0.8-1.6 parts of stearic acid, 0.8-1.8 parts of zinc oxide, and 2-6 parts of glycidyl methacrylate.

9. The method for preparing twisted steel fiber ultra-high performance concrete according to claim 8, characterized in that: The preparation method of the modified rubber reinforced filler is as follows: Step 1: pretreatment of carbon nanotubes; Step 2: Modification of carbon nanotubes with silane coupling agent; Step 3: Graft copolymerization reaction of carbon nanotubes, rubber monomer and anti-aging agent; Step 4: Rubber mixing to prepare modified rubber reinforcing filler.