Hybrid fiber ultra-high performance concrete and preparation method thereof

Abstract

The present invention discloses a hybrid fiber ultra-high performance concrete and a preparation method thereof, which belongs to the field of concrete technology. The ultra-high performance concrete comprises the following components by mass: 600-800 parts of cementitious materials, 300-500 parts of reinforcing fibers, 300-500 parts of quartz sand, 10-20 parts of water reducers, and 20-30 parts of nano-silicon dioxide. The present invention adopts the above-mentioned hybrid fiber ultra-high performance concrete and a preparation method thereof, and through a reasonable raw material ratio, as well as the synergistic effect of steel fiber and PVA fiber, significantly improves the mechanical properties of concrete, and the industrial waste pretreatment and carbonization curing process reduces porosity, greatly reduces the chloride ion diffusion coefficient, and enhances the impermeability and corrosion resistance of concrete; at the same time, realizes the resource utilization of industrial waste, not only solves its processing problems, but also reduces production costs, in line with the concept of sustainable development.

Description

Technical Field

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

[0002] While concrete technology continues to advance, conventional concrete faces limitations in key performance areas such as strength and durability, making it difficult to meet the stringent high-performance requirements of large-scale building structures, marine engineering projects, and infrastructure in harsh environments. Traditional reinforcement methods are reaching a bottleneck in improving strength, and the application of new reinforcement materials is becoming a key breakthrough. Regarding durability, concrete is susceptible to environmental corrosion, with prominent issues such as chloride ion penetration-induced steel corrosion and structural damage caused by freeze-thaw cycles. Industrial waste disposal also presents challenges, as large-scale accumulation not only consumes land resources but also poses a risk of environmental pollution. Summary of the Invention

[0003] The purpose of the present invention is to provide a hybrid fiber ultra-high performance concrete and a preparation method thereof. Through a reasonable raw material ratio, that is, ordinary Portland cement is matched with a specific proportion of fly ash, steel slag powder, and waste glass powder in the cementitious material, and the synergistic effect of steel fiber and PVA fiber, the mechanical properties of the concrete are significantly improved. The industrial waste pretreatment and carbonization curing process reduces the porosity, greatly reduces the chloride ion diffusion coefficient, and enhances the impermeability and corrosion resistance of the concrete; at the same time, the resource utilization of industrial waste is realized, which not only solves its treatment problem but also reduces production costs, in line with the concept of sustainable development.

[0004] To achieve the above objectives, the present invention provides a hybrid fiber ultra-high performance concrete, which includes the following components, calculated by mass: 600-800 parts of cementitious material, 300-500 parts of reinforcing fiber, 300-500 parts of quartz sand, 10-20 parts of water reducer, and 20-30 parts of nano-silicon dioxide.

[0005] Preferably, the cementitious material includes ordinary Portland cement and industrial waste, wherein the industrial waste includes fly ash, steel slag powder and waste glass powder, and their mass ratio is (3-5):(2-4):(1-2), and the reinforcing fiber includes steel fiber and PVA fiber, and the volume ratio of steel fiber to PVA fiber is (2.5-3.5):1.

[0006] The method for preparing the hybrid fiber ultra-high performance concrete described above comprises the following steps:

[0007] S1. Pre-treatment of industrial waste;

[0008] S2, dry mix cementitious materials and quartz sand;

[0009] S3, adding fiber and wet mixing;

[0010] S4. Forming and curing.

[0011] Preferably, the specific operation of S1 is:

[0012] S11. The steel slag powder is activated in two stages: first, the steel slag powder is ball-milled with a ball-to-material ratio of 8:1. The specific surface area of ​​the steel slag powder after ball milling is ≥650m 2 / kg, then mix the ball-milled steel slag powder with sodium sulfate-triethanolamine solution at a mass ratio of 2-3%, stir and react at 60-70℃ for 2-3h, and then dry to a moisture content of ≤1%;

[0013] S12, acid-washing and pre-carbonizing the waste glass powder: crushing the waste glass to a particle size of ≤0.3 mm to obtain waste glass powder, then soaking the waste glass powder in 5% citric acid for 1-2 hours, placing the acid-washed waste glass powder in a closed reactor, and introducing CO2 gas for carbonization. The pressure in the reactor is 0.2-0.3 MPa, and the temperature is 20-30° C. After carbonization for 5-7 hours, a nano-calcium carbonate coating is generated. After carbonization, the waste glass powder is dried at 100-120° C. for 2 hours, and particles ≤0.15 mm are sieved;

[0014] S13. Pre-treating the fly ash: separating the fly ash through an air classifier, and selecting ultrafine fly ash with a particle size of ≤20 μm.

[0015] Preferably, the specific operation of S2 is:

[0016] S21, ordinary Portland cement and 30% quartz sand are put into a planetary mixer and stirred;

[0017] S22: After the mixing is completed, pretreated fly ash, activated steel slag powder, pickled waste glass powder and remaining quartz sand are added to the planetary mixer, and the speed of the planetary mixer is increased to continue mixing;

[0018] S23. After the mixing is completed, add nano-silicon dioxide and pre-carbonized waste glass powder to the planetary mixer, increase the speed of the planetary mixer and continue to mix until the mixture is uniform.

[0019] Preferably, in S21, the stirring rate of the planetary mixer is 20-30 r / min, and the stirring time is 3-5 min;

[0020] In S22, the stirring rate of the planetary mixer is 50-70 r / min, and the stirring time is 5-8 min;

[0021] In S23, the stirring rate of the planetary mixer is 90-100 r / min, and the stirring time is 2-3 min;

[0022] The stirring temperatures of S21, S22 and S23 are all 25-35°C.

[0023] Preferably, the specific operation of S3 is:

[0024] S31, evenly spreading the steel fibers into the mixture through a vibrating feeder, and starting an electromagnetic device in a planetary mixer to perform low-speed stirring so that the steel fibers are oriented and distributed along the direction of the magnetic field;

[0025] S32. Premix the PVA fiber and the water reducer, and spray them into a planetary mixer through a high-pressure atomizing nozzle. Simultaneously, turn on the ultrasonic generator to break up the agglomeration of the PVA fiber, and perform high-speed stirring to obtain a mixed slurry.

[0026] Preferably, in S31, the end of the steel fiber is hook-shaped, and the aspect ratio is (60-80):1;

[0027] In S32, the water-binder ratio of PVA fiber and water-reducing agent is (0.16-0.2):1, the frequency of the ultrasonic generator is 30-50kHz, the power is 5000-6000W, the stirring rate of the planetary mixer is 100-130r / min, and the stirring time is 8-10min.

[0028] Preferably, the specific operation of S4 is:

[0029] S41, injecting the mixed slurry into the mold and continuously applying pressure;

[0030] S42, after demoulding, placing in a steam curing box for constant temperature curing, then performing temperature curing, and then performing temperature curing to obtain a sample;

[0031] S43. The sample is transferred to a carbonization chamber for curing. After carbonization, a silane coupling agent is sprayed on the surface to seal the pores.

[0032] Preferably, in S41, the applied pressure is a vertical pressure of 0.3-0.5 MPa, which lasts for 3-5 minutes;

[0033] In S42, the constant temperature curing temperature is 70-90°C, the constant temperature curing time is 12-36h, the rising temperature curing temperature is 100-110°C, the rising temperature curing time is 12-24h; the cooling curing temperature is 50-70°C, and the cooling curing time is 12-24h;

[0034] In S43, the CO2 concentration in the carbonization chamber is 15-30%, the temperature is 20-30°C, the humidity is 60-80%, the curing time is 36-72h, and the concentration of the silane coupling agent is 4-6%.

[0035] Therefore, the present invention adopts the above-mentioned hybrid fiber ultra-high performance concrete and its preparation method, which has the following beneficial effects:

[0036] (1) By combining ordinary Portland cement with fly ash, steel slag powder, and waste glass powder in a specific mass ratio in the cementitious material, and synergistically reinforcing steel fiber and PVA fiber in an appropriate volume ratio, it can withstand greater loads and is suitable for heavy-load structures;

[0037] (2) The industrial waste pretreatment and carbonization curing process reduces the porosity of concrete, effectively blocks the entry of corrosive media such as chloride ions, improves density and impermeability, prevents internal steel bars from rusting, improves corrosion resistance in harsh environments, and extends the service life of the structure;

[0038] (3) The rational use of industrial wastes such as fly ash, steel slag powder and waste glass powder in concrete can not only solve the problem of their disposal, but also reduce the cost of concrete production and reduce dependence on natural resources, which is in line with the concept of green environmental protection and sustainable development.

[0039] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further illustrated by the following examples.

[0041] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0042] Example 1

[0043] The present invention provides a hybrid fiber ultra-high performance concrete, which comprises the following components, calculated by mass: 700 parts of cementitious materials (cement, fly ash, steel slag powder, and waste glass powder in a mass ratio of 5:3:2:1), 400 parts of reinforcing fibers (the volume ratio of steel fiber to PVA fiber is 3:1), 400 parts of quartz sand, 15 parts of a water reducer, and 25 parts of nano-silicon dioxide.

[0044] The preparation method comprises the following steps:

[0045] 1. Preprocessing:

[0046] Steel slag powder is ball-milled to a specific surface area of ​​680m 2 / kg, add 3% sodium sulfate-triethanolamine solution and activate at 65℃ for 2.5h;

[0047] Waste glass powder was soaked in 5% citric acid for 1.5 h, pre-carbonized with 0.25 MPa CO2 for 6 h, dried and sieved to 0.1 mm;

[0048] Fly ash is air-classified to 15 μm.

[0049] 2. Dry mixing:

[0050] Put ordinary Portland cement and 30% quartz sand into a planetary mixer and stir at 25 r / min for 4 min;

[0051] After the mixing is completed, add the pretreated fly ash, activated steel slag powder, pickled waste glass powder and remaining quartz sand into the planetary mixer, increase the speed of the planetary mixer to 60r / min and mix for 7 minutes;

[0052] After the mixing is completed, nano-silica and pre-carbonized waste glass powder are added to the planetary mixer, and the speed of the planetary mixer is increased to 95 r / min and stirred for 3 minutes to ensure that the mixture is evenly mixed.

[0053] 3. Wet mixing:

[0054] Steel fibers with an aspect ratio of 70:1 are evenly sprinkled into the mixture through a vibrating feeder, and the electromagnetic device in the planetary mixer is started to provide a 0.4T magnetic field. Low-speed stirring is performed at a rate of 40r / min to orient the steel fibers along the direction of the magnetic field.

[0055] PVA fiber and water reducer were premixed at a water-binder ratio of 0.18:1 and sprayed into a planetary mixer through a high-pressure atomizing nozzle. At the same time, the ultrasonic generator was turned on, and 50kHz, 5500W ultrasound was used to break the agglomeration of the PVA fiber. The mixed slurry was obtained by high-speed stirring at 120r / min for 9 minutes.

[0056] 4. Maintenance:

[0057] The mixed slurry was injected into the mold and a vertical pressure of 0.4 MPa was continuously applied for 4 min;

[0058] After demoulding, the sample was placed in a steam curing box at a constant temperature of 80°C for 24 hours, then heated to 105°C for 18 hours, and then cooled to 60°C for 18 hours to obtain the sample.

[0059] The sample was transferred to a carbonization chamber for curing. The CO2 concentration in the carbonization chamber was 25%, the temperature was 25°C, and the curing time was 60 h. After carbonization, 5% silane coupling agent was sprayed on the surface to seal the pores.

[0060] Example 2

[0061] The present invention provides a hybrid fiber ultra-high performance concrete, which includes the following components, calculated by mass: 600 parts of cementitious materials (cement, fly ash, steel slag powder, and waste glass powder in a mass ratio of 4:4:3:1.5), 450 parts of reinforcing fibers (the volume ratio of steel fiber to PVA fiber is 2.8:1), 450 parts of quartz sand, 18 parts of water reducer, and 28 parts of nano-silicon dioxide.

[0062] The preparation method comprises the following steps:

[0063] 1. Preprocessing:

[0064] Steel slag powder is ball-milled to a specific surface area of ​​680m 2 / kg, add 2% sodium sulfate-triethanolamine solution and activate at 70℃ for 3h;

[0065] Waste glass powder was soaked in 5% citric acid for 1.5 h, pre-carbonized with 0.3 MPa CO2 for 7 h, dried and sieved to 0.1 mm;

[0066] Fly ash is air-classified to 15 μm.

[0067] 2. Dry mixing:

[0068] Put ordinary Portland cement and 30% quartz sand into a planetary mixer and stir at 25 r / min for 4 min;

[0069] After the mixing is completed, add the pretreated fly ash, activated steel slag powder, pickled waste glass powder and remaining quartz sand into the planetary mixer, increase the speed of the planetary mixer to 60r / min and mix for 7 minutes;

[0070] After the mixing is completed, nano-silica and pre-carbonized waste glass powder are added to the planetary mixer, and the speed of the planetary mixer is increased to 95 r / min and stirred for 3 minutes to ensure that the mixture is evenly mixed.

[0071] 3. Wet mixing:

[0072] Steel fibers with an aspect ratio of 70:1 are evenly sprinkled into the mixture through a vibrating feeder, and the electromagnetic device in the planetary mixer is started to provide a 0.4T magnetic field. Low-speed stirring is performed at a rate of 40r / min to orient the steel fibers along the direction of the magnetic field.

[0073] PVA fiber and water reducer were premixed at a water-binder ratio of 0.18:1 and sprayed into a planetary mixer through a high-pressure atomizing nozzle. At the same time, the ultrasonic generator was turned on, and 50kHz, 6000W ultrasound was used to break the agglomeration of the PVA fiber. The mixed slurry was obtained by high-speed stirring at 130r / min for 10min.

[0074] 4. Maintenance:

[0075] The mixed slurry was injected into the mold and a vertical pressure of 0.4 MPa was continuously applied for 4 min;

[0076] After demoulding, the sample was placed in a steam curing box at a constant temperature of 90°C for 36 hours, then heated to 110°C for 24 hours, and then cooled to 70°C for 24 hours to obtain the sample.

[0077] The sample was transferred to a carbonization chamber for curing. The CO2 concentration in the carbonization chamber was 25%, the temperature was 25°C, and the curing time was 60 h. After carbonization, 5% silane coupling agent was sprayed on the surface to seal the pores.

[0078] Example 3

[0079] The present invention provides a hybrid fiber ultra-high performance concrete, which comprises the following components, calculated by mass: 800 parts of cementitious materials (the mass ratio of cement to industrial waste is 1:1, and the mass ratio of fly ash, steel slag powder, and waste glass powder is 3:4:2), 350 parts of reinforcing fibers (the volume ratio of steel fiber to PVA fiber is 3.5:1), 300 parts of quartz sand, 20 parts of water reducer, and 30 parts of nano-silicon dioxide.

[0080] The preparation method comprises the following steps:

[0081] 1. Preprocessing:

[0082] Steel slag powder is ball-milled to a specific surface area of ​​720m 2 / kg, add 3% sodium sulfate-triethanolamine solution and activate at 65℃ for 2.5h;

[0083] Waste glass powder was soaked in 5% citric acid for 1.5 h, pre-carbonized with 0.25 MPa CO2 for 6 h, dried and sieved to 0.1 mm;

[0084] Fly ash is air-classified to 15 μm.

[0085] 2. Dry mixing:

[0086] Put ordinary Portland cement and 30% quartz sand into a planetary mixer and stir at 25 r / min for 4 min;

[0087] After the mixing is completed, add the pretreated fly ash, activated steel slag powder, pickled waste glass powder and remaining quartz sand into the planetary mixer, increase the speed of the planetary mixer to 60r / min and mix for 7 minutes;

[0088] After the mixing is completed, nano-silica and pre-carbonized waste glass powder are added to the planetary mixer, and the speed of the planetary mixer is increased to 100 r / min and stirred for 3 minutes to ensure that the mixture is evenly mixed.

[0089] 3. Wet mixing:

[0090] Steel fibers with an aspect ratio of 70:1 are evenly sprinkled into the mixture through a vibrating feeder, and the electromagnetic device in the planetary mixer is started to provide a 0.4T magnetic field. Low-speed stirring is performed at a rate of 40r / min to orient the steel fibers along the direction of the magnetic field.

[0091] PVA fiber and water reducer were premixed at a water-binder ratio of 0.18:1 and sprayed into a planetary mixer through a high-pressure atomizing nozzle. At the same time, the ultrasonic generator was turned on to break the agglomeration of the PVA fiber with 50kHz ultrasound, and a mixed slurry was obtained by high-speed stirring at 120r / min for 9min.

[0092] 4. Maintenance:

[0093] The mixed slurry was injected into the mold and a vertical pressure of 0.4 MPa was continuously applied for 4 min;

[0094] After demoulding, the sample was placed in a steam curing box at a constant temperature of 80°C for 24 hours, then heated to 105°C for 18 hours, and then cooled to 60°C for 18 hours to obtain the sample.

[0095] The sample was transferred to a carbonization chamber for curing. The CO2 concentration in the carbonization chamber was 25%, the temperature was 25°C, and the curing time was 72 hours. After carbonization, 6% silane coupling agent was sprayed on the surface to seal the pores.

[0096] Comparative Example 1

[0097] The concrete in Comparative Example 1 includes the following components: 700 parts of cementitious material (pure cement), 400 parts of reinforcing fiber (only steel fiber), 400 parts of quartz sand, 15 parts of water reducing agent, and 25 parts of nano-silicon dioxide.

[0098] The preparation method differs from Example 1 in that: there is no pretreatment step of industrial waste, dry mixing is a single stirring of 50 r / min for 10 minutes, curing is standard curing without carbonization treatment, and other conditions are the same.

[0099] The concrete obtained from Examples 1 to 3 and Comparative Example 1 was tested for compressive strength and flexural strength according to the method in GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", and the test results are shown in Table 1.

[0100] Table 1 Compressive strength and flexural strength test results

[0101] ;

[0102] As can be seen from Table 1, the compressive strength and flexural strength of Examples 1 to 3 are all higher than those of Comparative Example 1, indicating that the pretreatment of industrial waste and the synergistic effect of steel fiber and PVA fiber significantly improve the mechanical properties of concrete.

[0103] The concrete obtained in Examples 1 to 3 and Comparative Example 1 was subjected to the ASTM C1202 rapid chloride ion penetration method. The concrete was immersed in a 3.5% NaCl solution for 28 days to obtain its chloride ion diffusion coefficient. The results are shown in Table 2.

[0104] Table 2 Chloride ion diffusion coefficient

[0105] ;

[0106] As can be seen from Table 2, the chloride ion diffusion coefficients of Examples 1 to 3 are much lower than that of Comparative Example 1, indicating that the pretreatment of industrial waste and the carbonization curing process significantly reduce the porosity, improve the density and anti-permeability of concrete, and effectively prevent corrosion and improve its corrosion resistance.

[0107] Therefore, the present invention adopts the above-mentioned hybrid fiber ultra-high performance concrete and its preparation method, and through a reasonable raw material ratio, that is, ordinary Portland cement and a specific proportion of fly ash, steel slag powder, and waste glass powder in the cementitious material, as well as the synergistic effect of steel fiber and PVA fiber, the mechanical properties of concrete are significantly improved. The industrial waste pretreatment and carbonization curing process reduces the porosity, greatly reduces the chloride ion diffusion coefficient, and enhances the impermeability and corrosion resistance of concrete; at the same time, it realizes the resource utilization of industrial waste, which not only solves its treatment problem but also reduces production costs, in line with the concept of sustainable development.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A hybrid fiber ultra-high performance concrete, characterized by: The composition comprises the following components by weight: 600-800 parts of cementitious material, 300-500 parts of reinforcing fiber, 300-500 parts of quartz sand, 10-20 parts of water reducing agent, and 20-30 parts of nano-silicon dioxide; The cementitious material includes ordinary Portland cement and industrial waste, wherein the industrial waste includes fly ash, steel slag powder and waste glass powder, and the mass ratio thereof is (3-5):(2-4):(1-2); the reinforcing fiber includes steel fiber and PVA fiber, and the volume ratio of steel fiber to PVA fiber is (2.5-3.5):1; The preparation method of steel slag powder is as follows: firstly, the steel slag powder is ball-milled with a ball-to-material ratio of 8:

1. The specific surface area of ​​the steel slag powder after ball milling is ≥650m 2 / kg, then mix the ball-milled steel slag powder with sodium sulfate-triethanolamine solution at a mass ratio of 2-3%, stir and react at 60-70℃ for 2-3h, and then dry to a moisture content of ≤1%; The preparation method of waste glass powder is as follows: waste glass is crushed to a particle size of ≤0.3 mm to obtain waste glass powder, and then the waste glass powder is soaked in 5% citric acid. After soaking for 1-2 hours, the acid-washed waste glass powder is placed in a closed reactor and introduced with CO2 gas for carbonization. The pressure in the reactor is 0.2-0.3 MPa and the temperature is 20-30°C. After carbonization for 5-7 hours, a nano-calcium carbonate coating layer is generated. After carbonization, the waste glass powder is dried at 100-120°C for 2 hours, and particles of ≤0.15 mm are sieved. The preparation method of fly ash is as follows: the fly ash is separated by an air flow classifier, and ultrafine fly ash with a particle size of ≤20 μm is selected.