Preparation method of ultra-high performance concrete pipe pile

Abstract

The invention provides a preparation method of an ultra-high-performance concrete tubular pile, and relates to the technical field of concrete tubular piles, and the preparation method comprises the following steps: filling a mold filled with first UHPC with second UHPC, carrying out centrifugal molding, and carrying out steam curing to obtain the ultra-high-performance concrete tubular pile, the slump expansion degree of the second UHPC concrete is smaller than that of the first UHPC concrete, the slump expansion degree of the first UHPC concrete is 300-600 mm, at least 80% of the metal fibers in a pile body of the prepared ultra-high performance concrete pipe pile are evenly distributed in the axial direction of the UHPC concrete pile body, the metal fibers are parallel to the axial direction, and compared with a common C80 common pipe pile, the content of the metal fibers in the pile body of the prepared ultra-high performance concrete pipe pile is greatly reduced. The anti-cracking bending moment of the prepared UHPC pipe pile is improved by 90% or above, and the ultimate bending moment is improved by 38% or above. The technical problem of poor bending resistance caused by non-uniform fiber distribution in the ultra-high performance concrete pipe pile prepared in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete pipe piles, in particular to a preparation method of an ultra-high performance concrete pipe pile. BACKGROUND

[0002] China has a vast territory and complex and diverse natural environments, and pile foundations are served in complex and diverse environments, and chloride ion erosion environments in the ocean and near the sea are very common. The degree of erosion damage of concrete structures in the marine environment is influenced by the synergistic effect of regional environment, material properties and erosion medium, and the most serious is in the splash zone and the tidal zone. The core mechanism is the combined effect of chloride ion penetration, sulfate expansion and physical damage. Among them, the chloride ion in seawater can destroy the passivation film of the steel bar, leading to steel corrosion, and the sulfate may react with the components in the cement to generate expansive products, leading to cracking of the concrete; in the splash zone, the dry-wet cycle accelerates the penetration of chloride ions (Cl⁻), and at the same time, the salt crystallization expansion (such as the generation of gypsum and ettringite) leads to cracking of the concrete. The corrosion of erosive ions under these environmental conditions will cause damage to the pile body that cannot be ignored, seriously affecting the quality of the pile body, endangering the bearing capacity and various properties of the pile body, and with the extension of time, the damage phenomenon will continue to worsen, bringing serious safety hazards and seriously threatening the safety of the superstructure of the marine engineering. With the improvement of the requirements of marine engineering on bearing capacity and durability, it is urgent to design pile types that meet the requirements of different application scenarios to serve the development of the marine infrastructure industry. For example, in offshore wind power projects, the original steel pipe pile has been gradually replaced by large-diameter PHC pipe pile due to the fast corrosion rate of steel in high-salt fog and high-humidity environments, the difficulty of maintenance and other factors, but the application and development of ordinary PHC pipe pile in the marine field are restricted by factors such as low compressive and tensile strength and limited corrosion resistance.

[0003] Ultra-high performance concrete (UHPC) is the most innovative engineering material in recent decades, which breaks through the performance bottleneck of traditional concrete and represents a new direction for the development of future concrete materials. If UHPC is used in pipe piles, it can greatly improve the ultimate bearing capacity, bending toughness and durability of the pipe piles, realize lightweight design of the pipe pile structure, shorten the construction period and reduce the engineering cost; at the same time, it can also form a steel-UHPC composite structure (such as a bridge deck and an offshore platform) with high bearing capacity and corrosion resistance, solving the fatigue and corrosion problems of traditional steel structures, but the difference in density between the metal fiber and ordinary concrete will cause the metal fiber to be unevenly distributed in the pipe pile, thereby greatly reducing the bending resistance.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] One of the purposes of the present application is to provide a preparation method of an ultra-high performance concrete pipe pile to solve the technical problem of poor bending resistance caused by uneven distribution of fibers in the ultra-high performance concrete pipe pile prepared in the prior art.

[0006] The second purpose of the present application is to provide an ultra-high performance concrete pipe pile.

[0007] In order to achieve the above-mentioned purposes of the present application, the following technical solutions are adopted: In a first aspect, the present application provides a preparation method of an ultra-high performance concrete pipe pile, comprising filling a mold filled with a first UHPC concrete with a second UHPC concrete, centrifugal forming, and obtaining the ultra-high performance concrete pipe pile through steam curing. The slump spread of the second UHPC concrete is less than the slump spread of the first UHPC concrete, and the slump spread of the first UHPC concrete is 300-600 mm.

[0008] Further, the slump spread of the second UHPC concrete is ≤300 mm. Preferably, the slump spread of the second UHPC concrete is 200-300 mm.

[0009] Further, the metal fiber content of the first UHPC concrete and the second UHPC concrete is independently 2.1% v / v-4.0% v / v. Preferably, the diameter of the metal fiber is 0.1-0.3 mm. Preferably, the aspect ratio of the metal fiber is 50-100. Preferably, the tensile strength of the metal fiber is >1000 MPa.

[0010] Further, the centrifugal forming comprises centrifugal forming under low-speed, medium-low-speed, medium-speed, medium-high-speed and high-speed centrifugal conditions in sequence. The low-speed centrifugal condition is 50-80 r / min, the medium-low-speed centrifugal condition is 100-170 r / min, the medium-speed centrifugal condition is 210-280 r / min, the medium-high-speed centrifugal condition is 320-360 r / min, and the high-speed centrifugal condition is 390-460 r / min.

[0011] Further, the low-speed centrifugal time is 2-6 min, the medium-low-speed centrifugal time is 1-2 min, the medium-speed centrifugal time is 1-2 min, the medium-high-speed centrifugal time is 1.5-4 min, and the high-speed centrifugal time is 5-20 min.

[0012] Further, the steam curing comprises temperature rising curing for 1.5-3 h and constant temperature curing for 5-15 h.

[0013] Further, the temperature rising maintenance for 1.5-3h includes gradually rising from 30-45℃ to a constant temperature, and the rising time is 1.5-3h; the rising rate is 10-15℃ / h; and the constant temperature is 60-90℃.

[0014] Further, the filling mode of the concrete includes mold opening and material laying or mold closing and material pumping.

[0015] Further, the mold opening and material laying include sequentially performing twice material laying, mold closing, prestress tensioning and entering into a centrifugal forming process. Preferably, the mold closing and material pumping include sequentially performing mold closing, prestress tensioning of the steel reinforcement cage, twice material laying and entering into a centrifugal forming process.

[0016] In the second aspect, the application provides an ultra-high performance concrete pipe pile prepared by the above preparation method.

[0017] The application provides a preparation method of an ultra-high performance concrete pipe pile, and at least 80% of the metal fibers in the pile body of the prepared ultra-high performance concrete pipe pile are uniformly distributed along the axial direction of the UHPC concrete pile body, and the metal fibers are parallel to the axial direction. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The schematic diagram of the overall structure of the ultra-high performance concrete pile prepared in Embodiment 1 of the application is shown in the figure. Figure 2 The schematic diagram of the cross-sectional structure of the ultra-high performance concrete pile prepared in Embodiment 1 of the application is shown in the figure. Figure 3 The schematic diagram of the cross-sectional structure of the ultra-high performance concrete pile prepared in Embodiment 1 of the application is shown in the figure. Figure 2 The schematic diagram of the enlarged structure at position A in the figure is shown in the figure. Figure 4 The product cross-sectional photo of the ultra-high performance concrete pile prepared in Embodiment 1 of the application is shown in the figure.

[0020] Figure legend: 1-UHPC concrete pile body; 2-metal fiber; 3-main reinforcement; 4-stirrup. DETAILED DESCRIPTION

[0021] Unless otherwise defined, scientific and technical terms used in connection with the present application shall have the meanings that are commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear; however, in the event of any latent ambiguity, definitions provided herein take precedent over any dictionary or extrinsic definition. In this application, the use of "or" means "and / or" unless specifically stated otherwise, e.g., "comprising A or B" means "comprising A or B or both". Also, the use of "comprising" or "including" or other forms for "comprise" or "including" is intended to be non- limiting.

[0022] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the scope of protection of the present application.

[0023] In one aspect of the present application, a preparation method of an ultra-high performance concrete pipe pile is provided, comprising filling a second UHPC concrete in a mold filled with a first UHPC concrete, centrifugal forming, and obtaining the ultra-high performance concrete pipe pile through steam curing. The slump spread of the second UHPC concrete is less than that of the first UHPC concrete, and the slump spread of the first UHPC concrete is 300-600 mm.

[0024] Since the slump spread of the second UHPC concrete is less than that of the first UHPC concrete, at least 80% of the metal fiber content in the pile body of the ultra-high performance concrete pipe pile prepared by the above method is uniformly distributed along the UHPC concrete pile body 1 axial direction, and the metal fiber is parallel to the axial direction. Compared with the ordinary C80 ordinary pipe pile, the crack resistance bending moment of the UHPC pipe pile prepared by the present application is increased by more than 90%, and the ultimate bending moment is increased by more than 38%; and the production efficiency time of the ordinary pouring method component can be increased by more than 1 times; the compactness of the concrete component is improved, and the overall performance strength of the component is improved. The technical problem of poor bending resistance caused by uneven distribution of fibers in the ultra-high performance concrete pipe pile prepared in the prior art is solved, and the production efficiency is high, the forming quality is high, the durability is good, it is suitable for large-scale industrialization and mechanization production, the residual slurry amount is small, and it can be recycled without additional treatment.

[0025] In some specific embodiments, the slump spread of the second UHPC concrete is ≤300 mm.

[0026] In some specific embodiments, the slump spread of the second UHPC concrete is 200-300 mm.

[0027] In some specific embodiments, the metal fiber content of the first and second UHPC concrete is independently 2.1% v / v to 4.0% v / v; in some specific embodiments, the diameter of the metal fiber is 0.1 to 0.3 mm; in some specific embodiments, the aspect ratio of the metal fiber is 50 to 100; in some specific embodiments, the tensile strength of the metal fiber is >1000 MPa.

[0028] In some specific embodiments, the metal fiber content of the first and second UHPC concrete is independently 2.1% v / v to 4.0% v / v; in some specific embodiments, the diameter of the metal fiber is 0.1 to 0.3 mm; in some specific embodiments, the aspect ratio of the metal fiber is 50 to 100; in some specific embodiments, the tensile strength of the metal fiber is >1000 MPa.

[0029] In some specific embodiments, the metal fiber content of the first and second UHPC concrete is independently 2.1% v / v to 4.0% v / v; in some specific embodiments, the diameter of the metal fiber is 0.1 to 0.3 mm; in some specific embodiments, the aspect ratio of the metal fiber is 50 to 100; in some specific embodiments, the tensile strength of the metal fiber is >1000 MPa.

[0030] In some specific embodiments, the metal fiber content of the first and second UHPC concrete is independently 2.1% v / v to 4.0% v / v; in some specific embodiments, the diameter of the metal fiber is 0.1 to 0.3 mm; in some specific embodiments, the aspect ratio of the metal fiber is 50 to 100; in some specific embodiments, the tensile strength of the metal fiber is >1000 MPa.

[0031] In some specific embodiments, the centrifugal forming includes sequentially centrifugal forming under low-speed, medium-low-speed, medium-speed, medium-high-speed and high-speed centrifugal conditions; the low-speed centrifugal condition is 50 to 80 r / min, the medium-low-speed centrifugal condition is 100 to 170 r / min, the medium-speed centrifugal condition is 210 to 280 r / min, the medium-high-speed centrifugal condition is 320 to 360 r / min, and the high-speed centrifugal condition is 390 to 460 r / min.

[0032] The centrifugal process can further reduce the water-binder ratio of the UHPC concrete, improve the compactness of the concrete member, and thus improve the overall performance strength of the member. In some specific embodiments, the low-speed centrifugal time is 2 to 6 min; the medium-low-speed centrifugal time is 1 to 2 min; the medium-speed centrifugal time is 1 to 2 min; the medium-high-speed centrifugal time is 1.5 to 4 min; and the high-speed centrifugal time is 5 to 20 min.

[0033] In some specific embodiments, the centrifugal forming includes sequentially centrifugal forming under low-speed, medium-low-speed, medium-speed, medium-high-speed and high-speed centrifugal conditions; the low-speed centrifugal condition is 50 to 80 r / min, the medium-low-speed centrifugal condition is 100 to 170 r / min, the medium-speed centrifugal condition is 210 to 280 r / min, the medium-high-speed centrifugal condition is 320 to 360 r / min, and the high-speed centrifugal condition is 390 to 460 r / min.

[0034] The medium-low speed centrifugation time can be, but is not limited to, 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min or 2 min, or any value between 1 and 2 min.

[0035] The medium speed centrifugation time can be, but is not limited to, 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min or 2 min, or any value between 1 and 2 min.

[0036] The medium-high speed centrifugation time can be, but is not limited to, 1.5 min, 1.8 min, 2 min, 2.3 min, 2.5 min, 2.8 min, 3 min, 3.3 min, 3.5 min, 3.8 min or 4 min, or any value between 1.5 and 4 min.

[0037] The high speed centrifugation time can be, but is not limited to, 5 min, 7 min, 9 min, 11 min, 13 min, 15 min, 17 min, 19 min or 20 min, or any value between 5 and 20 min.

[0038] In some specific embodiments, the steam curing comprises temperature rising curing for 1.5 to 3 hours and constant temperature curing for 5 to 15 hours.

[0039] The temperature rising curing time can be, but is not limited to, 1.5 hours, 2.0 hours, 2.5 hours or 3.0 hours, or any value between 1.5 and 3.0 hours.

[0040] The constant temperature curing time can be, but is not limited to, 5 hours, 7.5 hours, 10 hours, 12.5 hours or 15 hours, or any value between 5 and 15 hours.

[0041] In some specific embodiments, the temperature rising curing for 1.5 to 3 hours comprises temperature rising from 30 to 45 °C to constant temperature curing, and the temperature rising time is 1.5 to 3 hours; the temperature rising rate is 10 to 15 °C / h; and the constant temperature is 60 to 90 °C.

[0042] In some specific embodiments, the filling of the concrete comprises open mold placement or closed mold pumping. In some specific embodiments, the open mold placement comprises, in sequence, two times of placement, mold closing, prestress tensioning and entering into the centrifugal molding process; in some specific embodiments, the closed mold pumping comprises, in sequence, mold closing, prestress tensioning of the steel cage, two times of placement and entering into the centrifugal molding process.

[0043] According to another aspect of the present invention, there is provided an ultra-high performance concrete pipe pile, which is produced by the above-mentioned preparation method.

[0044] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0045] To better compare the flexural capacity of ultra-high performance concrete piles prepared under different conditions, the following examples all use UHPC concrete composed of aggregate, cementitious material, admixture, water, and metal fiber as raw materials. To meet different slump requirements, the proportions of each component are slightly adjusted.

[0046] Preparation method of the first UHPC concrete or the second UHPC concrete: first, add aggregate and stir for 2 minutes, add cementitious material and mix and stir for 3 minutes, add admixture and about 90% water and stir for 3 minutes, add the remaining water according to the state of the concrete, and when the concrete is in a slurry state, sprinkle in fiber and continue stirring for 2 minutes, the total time is about 10 minutes; when the fiber is evenly dispersed and the concrete state meets the requirements, it can be taken out of the machine for pouring.

[0047] Among them, the aggregate is machine-made sand; the cementitious material includes 70% silicate cement, 10% cement pozzolanic material and 20% granulated blast furnace slag powder; the admixture is a high-performance polycarboxylic acid water reducer; the metal fiber is made of fine copper-plated steel fiber with a diameter of 0.2mm, an aspect ratio of 65, and a tensile strength of 2000MPa.

[0048] Example 1 A method for preparing ultra-high performance concrete pipe piles comprises the following steps: Step 1, concrete preparation: The first UHPC concrete includes the following components in mass percentage: 47.0% aggregate, 42.0% cementitious material, 0.5% admixture, 5.2% water, and the balance being metal fiber, which is equivalent to a metal fiber volume content of 2.1% v / v.

[0049] The second UHPC concrete includes the following components in mass percentage: aggregate 47.5%, cementitious material 42.4%, admixture 0.5%, water 4.3%, and the balance is metal fiber, which is equivalent to a metal fiber volume content of 2.1% v / v.

[0050] The slump expansion of the first UHPC concrete is 600 mm; the slump expansion of the second UHPC concrete is 300 mm.

[0051] Step 2, concrete pouring: placing the steel cage (main reinforcement 3 and stirrup 4) in the centrifuge mold, sequentially pouring the first UHPC concrete and the second UHPC concrete, and manually cleaning the excess concrete on the pipe mold edge after pouring.

[0052] Step 3, centrifugal forming: sequentially forming at low speed, medium-low speed, medium speed, medium-high speed, and high speed; the low speed is 65 r / min, the medium-low speed is 130 r / min, the medium speed is 260 r / min, the medium-high speed is 320 r / min, and the high speed is 390 r / min. The low-speed centrifugal time is 5 min; the medium-low-speed centrifugal time is 2 min; the medium-speed centrifugal time is 2 min; the medium-high-speed centrifugal time is 2 min; and the high-speed centrifugal time is 10 min.

[0053] Step 4, steam curing: gradually increasing the temperature from 45°C to 60°C for 1.5 h, the rate of temperature increase is 10°C / h, and then curing at 60°C for 15 h to obtain the ultra-high performance concrete pipe pile, as shown in Figures 1-4 The thickness of the UHPC concrete pile body 1 is 12.5 cm, and the metal fibers 2 are uniformly distributed along the UHPC concrete pile body 1 in the axial direction at a dosage of at least 80%, and the metal fibers are parallel to the axial direction.

[0054] In this embodiment, the filling concrete is mold opening and material distribution. Specifically, the mold opening and material distribution includes two times of material distribution, mold closing, prestressed tension, and entering the centrifugal forming process; the mold closing and material pumping includes mold closing, prestressed tension of the steel cage, and entering the centrifugal forming process after two times of material distribution.

[0055] Example 2 A method for preparing an ultra-high performance concrete pipe pile, comprising the following steps: Step 1, concrete preparation: The first UHPC concrete includes the following components by mass percentage: aggregate 47.0%, cementitious material 42.0%; admixture 0.5%; water 5.2%, and the balance is metal fiber, which corresponds to a metal fiber volume dosage of 2.1% v / v.

[0056] The second UHPC concrete includes the following components by mass percentage: aggregate 47.0%, cementitious material 40.5%; admixture 0.4%; water 4.5%, and the balance is metal fiber, which corresponds to a metal fiber volume dosage of 3.0% v / v.

[0057] The slump flow of the first UHPC concrete is 300 mm; and the slump flow of the second UHPC concrete is 100 mm.

[0058] Step 2, concrete pouring: placing the steel cage (main reinforcement 3 and stirrup 4) in the centrifuge mold, sequentially pouring the first UHPC concrete and the second UHPC concrete, and manually cleaning the excess concrete at the pipe mold edge after pouring is completed.

[0059] Step 3, centrifugal forming: sequentially forming at low speed, medium-low speed, medium speed, medium-high speed and high speed; the low speed is 80 r / min, the medium-low speed is 170 r / min, the medium speed is 280 r / min, the medium-high speed is 320 r / min, and the high speed is 390 r / min. The low speed centrifugal time is 2 min; the medium-low speed centrifugal time is 1 min; the medium speed centrifugal time is 1 min; the medium-high speed centrifugal time is 1.5 min; and the high speed centrifugal time is 15 min.

[0060] Step 4, steam curing: gradually increasing the temperature from 45℃ to 60℃ for 1.5h, the rate of temperature increase is 10℃ / h, and then curing at 60℃ for 15h to obtain the ultra-high performance concrete pipe pile. The thickness of the UHPC concrete pile body 1 is 12.5cm.

[0061] In this embodiment, the filling concrete is pumped in the closed mold. Specifically, the open mold material includes two times of material distribution, mold closing, prestress tensioning, and entering the centrifugal forming process; the closed mold pumping includes mold closing, prestress tensioning of the steel cage, and two times of material distribution, and then entering the centrifugal forming process.

[0062] Example 3 A preparation method of an ultra-high performance concrete pipe pile, comprising the following steps: Step 1, concrete preparation: The first UHPC concrete includes the following components by mass percentage: aggregate 45.0%, cementitious material 43.0%; admixture 0.6%; water 6.1%; and metal fiber volume content 2.1%.

[0063] The second UHPC concrete includes the following components by mass percentage: aggregate 46.0%, cementitious material 39.0%; admixture 0.4%; water 4.6%; and metal fiber volume content 4.0%.

[0064] The slump flow of the first UHPC concrete is 550mm; and the slump flow of the second UHPC concrete is 200mm.

[0065] Step 2, concrete pouring: placing the steel cage (main reinforcement 3 and stirrup 4) in the centrifuge mold, sequentially pouring the first UHPC concrete and the second UHPC concrete, and manually cleaning the excess concrete at the pipe mold edge after pouring is completed.

[0066] Step 3, centrifugal forming: sequentially at low speed, medium-low speed, medium speed, medium-high speed and high speed centrifugal forming; low speed is 50 r / min, medium-low speed is 100 r / min, medium speed is 265 r / min, medium-high speed is 360 r / min, high speed is 460 r / min. The low speed centrifugal time is 6 min; the medium-low speed centrifugal time is 2 min; the medium speed centrifugal time is 2 min; the medium-high speed centrifugal time is 4 min; the high speed centrifugal time is 20 min.

[0067] Step 4, steam curing: curing at 45℃ to 60℃ gradually for 1.5h, the rate of temperature rising is 10℃ / h, then curing at 60℃ for 15h to obtain the ultra-high performance concrete pipe pile. The thickness of the UHPC concrete pile body 1 is 12.5cm.

[0068] In the embodiment, the filling concrete is mold opening and material laying. Specifically, the mold opening and material laying sequentially includes twice material laying, mold closing, prestress tensioning, and entering the centrifugal forming process; the mold closing and material laying sequentially includes mold closing, prestress tensioning of the steel reinforcement cage, and twice material laying, and then entering the centrifugal forming process.

[0069] Example 4 Compared with Example 1, the difference is that the volume content of the metal fiber in the first UHPC concrete is 1.5%; the volume content of the metal fiber in the second UHPC concrete is 2.0%, and other components and contents are adjusted accordingly, and the slump spread is unchanged.

[0070] Comparative Example 1 Compared with Example 1, the difference is that the slump spread of the second UHPC concrete is greater than that of the first UHPC concrete, and the slump spread of the second UHPC concrete is 620mm, wherein the mass percentage of the cementitious material is 42.0%, the mass percentage of the admixture is 0.5%, and the mass percentage of the water is 5.5%.

[0071] Comparative Example 2 Compared with Example 1, the difference is that the slump spread of the first UHPC concrete is 700mm; wherein the mass percentage of the cementitious material is 41.0%, the mass percentage of the admixture is 0.4%, and the mass percentage of the water is 6.3%.

[0072] Comparative Example 3 Compared with Example 1, the difference is that the slump spread of the first UHPC concrete is 200mm.

[0073] The mass percentage of the cementitious material is 43.0%, and the mass percentage of the water is 4.2%.

[0074] Comparative Example 4 Compared with Example 1, the difference is that the slump spread of the second UHPC concrete is 450mm.

[0075] wherein the mass percentage of cementitious material is 42.0% and the mass percentage of water is 4.7%.

[0076] Comparative Example 5 Comparative to Example 1, the difference is in step 3, centrifugal forming: sequentially in low speed, medium speed, and high speed centrifugal forming; low speed is 65 r / min, medium speed is 130 r / m, high speed is 390 r / min. Low speed centrifugal time is 5 min; medium speed centrifugal time is 6 min; high speed centrifugal time is 15 min.

[0077] Comparative Example 6 Comparative to Example 1, the difference is in step 3, centrifugal forming: sequentially in low speed, medium speed, and high speed centrifugal forming; low speed is 65 r / min, medium speed is 130 r / m, high speed is 390 r / min. Low speed centrifugal time is 5 min; medium speed centrifugal time is 6 min; high speed centrifugal time is 15 min.

[0078] Comparative Example 7 Comparative to Example 1, the difference is in step 3, centrifugal forming: sequentially in low speed, medium speed, and high speed centrifugal forming; low speed is 65 r / min, medium speed is 130 r / m, high speed is 390 r / min. Low speed centrifugal time is 5 min; medium speed centrifugal time is 6 min; high speed centrifugal time is 15 min.

[0079] Bending resistance detection According to the bending test detection method of GB13476 prestressed concrete pipe pile specified by the pre-tensioning method, the bending resistance of ABφ500x125x10 concrete piles prepared in Examples 1-4 and Comparative Examples 1-7 was detected, and PHC pipe pile was selected as a control group, and two repeated tests were performed, and the average value was taken, and the results are shown in Table 1.

[0080] Table 1

[0081] As shown in Table 1, Examples 1-4 are all better than the PHC pipe pile, and compared with Example 1, the bending resistance of Example 4 is reduced due to the reduced amount of metal fiber, but is still higher than that of the PHC pipe pile, which shows that the bending resistance of the pipe pile of Example 1 is not only related to the amount of metal fiber, and even if the amount of metal fiber is low, the bending resistance of the pipe pile prepared by this method is still improved; Comparative Examples 1-7 show that the slump spread of the first UHPC concrete and the second UHPC concrete and different centrifugal molding processes all have a significant impact on the bending resistance of the concrete pile.

[0082] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing ultra-high performance concrete pipe piles, characterized in that: The method includes filling a mold filled with a first UHPC concrete with a second UHPC concrete, centrifugally forming the mold, and steam curing the mold to produce an ultra-high performance concrete pipe pile. The slump expansion of the second UHPC concrete is smaller than that of the first UHPC concrete, and the slump expansion of the first UHPC concrete is 300-600 mm.

2. The preparation method according to claim 1, characterized in that The slump expansion of the second UHPC concrete is ≤300 mm; Preferably, the slump expansion of the second UHPC concrete is 200-300 mm.

3. The preparation method according to claim 1, wherein The metal fiber content of the first UHPC concrete and the second UHPC concrete is independently 2.1% v / v to 4.0% v / v; Preferably, the diameter of the metal fiber is 0.1-0.3 mm; Preferably, the aspect ratio of the metal fiber is 50-100; Preferably, the tensile strength of the metal fiber is greater than 1000 MPa.

4. The preparation method according to claim 1, characterized in that The centrifugal forming includes centrifugal forming under centrifugal conditions of low speed, medium-low speed, medium speed, medium-high speed and high speed in sequence; The low-speed centrifugation condition is 50~80r / min, the medium-low-speed centrifugation condition is 100~170r / min, the medium-speed centrifugation condition is 210~280r / min, the medium-high-speed centrifugation condition is 320~360r / min, and the high-speed centrifugation condition is 390~460r / min.

5. The preparation method according to claim 4, characterized in that The low-speed centrifugation time is 2~6 minutes; the medium-low-speed centrifugation time is 1~2 minutes; the medium-speed centrifugation time is 1~2 minutes; the medium-high-speed centrifugation time is 1.5~4 minutes; and the high-speed centrifugation time is 5~20 minutes.

6. The preparation method according to claim 1, characterized in that The steam curing includes temperature rising curing for 1.5 to 3 hours and constant temperature curing for 5 to 15 hours.

7. The preparation method according to claim 6, characterized in that The 1.5-3h temperature raising and curing includes gradually raising the temperature from 30-45°C to a constant temperature, and the heating time is 1.5-3h; The heating rate is 10-15°C / h; The constant temperature is 60-90°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that The methods of filling concrete include spreading in open molds or pumping in closed molds.

9. The preparation method according to claim 8, characterized in that The mold opening and distributing process includes two distributing steps, mold closing, prestressing, and centrifugal forming. Preferably, the mold closing and material pumping process includes, in sequence, mold closing, prestressing the steel cage, and entering the centrifugal molding process after two material laying processes.

10. An ultra-high performance concrete pipe pile, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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