Green low-carbon multi-scale organic fiber reinforced UHPC tube and preparation method thereof

Abstract

The invention discloses a green low-carbon multi-scale organic fiber reinforced UHPC (Ultra High Performance Concrete) tube and a preparation method thereof. The UHPC tube comprises a UHPC matrix, and continuous organic fiber grids and organic chopped fibers are arranged in the UHPC matrix; the organic chopped fibers comprise microcosmic fine fibers and macroscopic crude fibers; the diameter of the microscopic fine fiber is about 10-20 microns, and the length of the microscopic fine fiber is 5-15 mm; the diameter of the chopped macroscopic crude fibers is 0.2-0.5 mm, and the length of the chopped macroscopic crude fibers is 5-30 mm; the organic chopped fibers are uniformly dispersed in the UHPC matrix; the continuous organic fiber grids are arranged in the circumferential direction of the UHPC pipe, and the distance between the continuous organic fiber grids and the outer edge face of the UHPC pipe ranges from 1.0 cm to 10 cm. The microcosmic fine fibers, the macroscopic crude fibers and the continuous organic fiber grids form a three-dimensional network structure which is connected with one another and has a multi-scale effect in the UHPC matrix. According to the invention, the multi-scale organic fiber material is combined with the UHPC, so that the UHPC pipe which is green, low-carbon, light, capable of being assembled, high in bearing capacity, excellent in crack resistance, outstanding in durability and high in economic benefit is formed, and the UHPC pipe has a wide application prospect in civil engineering.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering materials, and particularly relates to a green and low-carbon multi-scale organic fiber reinforced UHPC assembled pipe and its preparation technology. Background Art

[0002] Ultra-high performance concrete (UHPC) has gradually become an important material in the field of civil engineering due to its dense microstructure and excellent mechanical properties, showing broad application prospects in fields such as bridges, buildings, and underground engineering. Especially in pipeline structures, UHPC pipes are highly recognized for their long-term stability in extreme environments due to their advantages such as light weight, high strength, low permeability, and high crack resistance, and are widely used in bridge drainage systems, ocean engineering, and municipal pipe galleries. However, there are still many challenges in the reinforcement design, autogenous shrinkage, low-carbon characteristics, and economy of existing UHPC pipes.

[0003] First of all, UHPC has become a key material in modern construction engineering due to its excellent mechanical properties and durability, and is widely used in fields such as bridges, high-rise buildings, and marine structures. However, the high density and low porosity of UHPC lead to significant autogenous shrinkage and self-drying during the early hydration process, which may cause cracks that seriously affect its long-term performance and structural safety. Solving these problems is crucial for the wider adoption and application of UHPC. Research shows that adding an appropriate amount of fiber to UHPC is an effective way to reduce early autogenous shrinkage and drying shrinkage.

[0004] Secondly, the metal fibers commonly used in traditional UHPC formulations, although excellent in improving the tensile strength and toughness of UHPC, have a significant impact on the environment during the production process and pose challenges in terms of recycling after disposal. In addition, the cost of UHPC is too high, and the cost of steel fibers accounts for about 35% of the total cost of UHPC. Therefore, there is an urgent need to find a green, low-carbon, environmentally friendly, and economically advantageous fiber substitute to reinforce UHPC.

[0005] In addition, although configuring steel bars in UHPC pipes is a common strengthening measure that can significantly improve the bearing capacity of the pipes, the corrosion problem still cannot be avoided. At the same time, the introduction of steel bars has limited improvement in the crack resistance of the material, while crack resistance is precisely one of the core advantages of UHPC in extreme environments. Therefore, simply relying on steel bar configuration or steel fiber reinforcement is difficult to meet the multiple performance requirements of UHPC pipes in complex environments.

[0006] Based on the above background, developing a new type of reinforcement technology that can solve the problems of high price, easy corrosion, and environmental unfriendliness of steel fibers, improve the reinforcement efficiency, reduce costs, and significantly enhance the overall mechanical properties has become a key research direction. In recent years, multi-scale organic fiber composite reinforcement technology has shown significant advantages in the field of materials science. By optimizing the material properties at different scales, the synergistic effect of organic fiber reinforcement can be achieved, which can not only improve the crack resistance and toughness but also enhance the impact resistance, bending resistance, and durability of the pipeline. Therefore, introducing multi-scale organic fiber reinforcement technology into the design of UHPC high-durability prefabricated pipes has important engineering value and application prospects. Thus, the present invention proposes a green and low-carbon multi-scale organic fiber reinforced UHPC prefabricated pipe and its preparation technology, aiming to optimize the distribution of organic fibers through multi-scale reinforcement technology, improve the crack resistance, durability, and bearing capacity of UHPC pipes, overcome the defects in the existing technology, and meet the usage requirements in complex service environments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a multi-scale organic fiber reinforced UHPC prefabricated pipe with green and low-carbon, light weight and high strength, and high durability characteristics and its preparation method in view of the deficiencies of the above-mentioned existing technologies.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: A green and low-carbon multi-scale organic fiber reinforced UHPC pipe, comprising a UHPC matrix, in which a continuous organic fiber grid and organic chopped fibers are arranged; the organic chopped fibers include micro-fine fibers and macro-coarse fibers; the diameter of the micro-fine fibers is about 10-20 μm, and the length is between 5-15 mm; the diameter of the chopped macro-coarse fibers is between 0.2-0.5 mm, and the length is between 5-30 mm; the organic chopped fibers are evenly dispersed in the UHPC matrix; the mesh size of the continuous organic fiber grid is between 5×5 mm and 50×50 mm, and the grid thickness is between 0.5-5 mm; the continuous organic fiber grid is arranged along the circumferential direction of the UHPC pipe, and the distance between the continuous organic fiber grid and the outer surface of the UHPC pipe is 1.0-10 cm; the micro-fine fibers, macro-coarse fibers, and continuous organic fiber grid form a three-dimensional network structure with multi-scale effects that are connected to each other in the UHPC matrix.

[0009] The continuous organic fiber grid in the UHPC high-durability prefabricated pipe is mainly prepared from sisal, flax, coconut, bamboo fiber, and wood fiber.

[0010] The organic fiber grid includes continuous organic fibers and a polymer resin matrix, and the fiber volume fraction is more than 50%.

[0011] The polymer resin matrix in the continuous organic fiber grid may be epoxy resin, vinyl resin or phenolic resin.

[0012] The micro fine fibers may be one or more of sisal, flax, coconut, bamboo fibers and wood fibers; the short-cut macro thick organic fibers are one or more of sisal, flax, coconut, bamboo fibers and wood fibers.

[0013] One or more layers of the organic fiber grid may be laid in the UHPC pipe, and local strengthening may also be carried out according to the stress conditions; the volume fraction of the short-cut micro organic fine fibers in the UHPC pipe is 0.5% - 1.0%; the volume fraction of the short-cut macro organic thick fibers in the UHPC pipe is between 1% - 4%.

[0014] The organic fiber grid is prepared from continuous fibers by a weaving process or a molding process, and different fibers can be used in different directions according to the stress requirements; both the micro fine organic fibers and the macro thick organic fibers in the short-cut organic fibers are prepared by a cutting process.

[0015] The water-binder ratio of the UHPC is controlled at 0.2 - 0.25, the average powder particle size is less than 20μm, and the average aggregate particle size is less than 1.5mm; the UHPC cement paste is prepared by mixing the following raw materials in parts by weight: 1 part of cement, 0.25 - 0.3 part of silica fume, 1.1 - 1.2 parts of sand, 0.3 - 0.4 part of mineral powder, 0.02 - 0.04 part of high-range water reducer, and 0.2 - 0.25 part of water.

[0016] When manufacturing the UHPC high-durability prefabricated pipe, first position the organic fiber grid in the mold using positioning pieces, then pour the organic fiber-reinforced UHPC mixture, and at the same time reserve anchor holes and grouting holes and embed anchor bolts.

[0017] Before being placed in the mold, the organic fiber grid needs to be tied into a circular net according to the preset pipe diameter. The material used for tying is nylon rope. After tying, epoxy resin is applied at the joint and cured at room temperature for 3 days.

[0018] After the UHPC pipe is poured, it is demolded after 24h of high-temperature steam curing, and then transferred to natural curing for more than 28 days.

[0019] The UHPC pipe includes a groove end and a convex groove end. Anchor holes are provided at the groove end, anchor bolts are embedded at the convex groove end. The grouting holes reserved around the groove end include anchor hole grouting holes and sealing groove grouting holes. When connecting pipe segments, insert the convex groove end of the upper pipe segment into the groove end of the lower pipe segment, insert the anchor bolts into the anchor holes, and then grout from the reserved grouting holes to fill the anchor holes and the sealing grooves with grouting material.

[0020] The high-strength grouting material is a high-strength non-shrinking grouting material, which can achieve rapid curing, high strength and good compactness.

[0021] As can be seen from the above technical solutions, the present invention has the following advantages: (1) Innovative reinforcing material system: The present invention uses organic short fibers and organic continuous fiber grid materials that are green, low-carbon, lightweight, high-strength, and have excellent mechanical properties to replace traditional steel fibers, completely solving the corrosion problem of steel fibers in highly corrosive environments and significantly improving the low-carbon characteristics of the pipeline. At the same time, it effectively avoids problems such as high material costs, weight increase, and difficult mixing and preparation caused by excessive steel fiber content. Through the directional reinforcement design of the organic fiber grid material, the direction, position, and number of layers of the fiber grid can be optimized according to the actual stress characteristics of the pipeline, fully realizing the performance potential of the reinforcing material and enhancing the flexibility and pertinence of the structural design.

[0022] (2) Multi-scale fiber reinforcement effect: The multi-scale organic fiber reinforcement technology proposed by the present invention combines the micro-crack resistance of short-cut micro organic fibers, the macro-crack resistance of short-cut macro organic fibers, and the macro-structural strengthening function of continuous organic fiber grids to synergistically improve the performance of UHPC pipes in aspects such as micro-crack control, macro-crack suppression, and ultimate bearing capacity. This reinforcement form realizes the optimization of material properties at different scales and significantly improves the overall mechanical properties and long-term stability of the pipeline under complex load conditions.

[0023] (3) Green and low-carbon production and optimized resource utilization: The present invention uses green and low-carbon organic fiber materials to replace traditional steel fibers (the continuous organic fiber grid and short-cut organic fibers are cost-effective (about 10-30% of the cost of steel fibers), have a low carbon footprint (the carbon emissions are only 5-20% of that of steel fibers), significantly reducing energy consumption and carbon emissions during the production process and reducing environmental pollution. In addition, organic fiber materials are renewable and degradable, contributing to resource recycling and waste reduction, and thus showing a low carbon footprint throughout the life cycle. By optimizing the material usage efficiency and reducing waste, the present invention not only improves the environmental performance of the product but also promotes the development of green and low-carbon building materials in the field of civil engineering, having important ecological benefits and sustainable development value.

[0024] (4) Prefabricated construction and efficient connection: The present invention realizes the segmental splicing of UHPC pipes through the anchor bolt grouting technology, simplifies the construction process, improves the construction efficiency, and ensures the reliable connection of the continuous pipe gallery structure. This prefabricated construction method is not only applicable to complex engineering environments but also reduces the on-site construction difficulty, contributing to the popularization and application of UHPC pipes in large-scale projects.

[0025] In summary, the UHPC high-durability prefabricated pipe of the present invention exhibits excellent advantages in terms of low carbonization, light weight, high durability, and high performance. Its innovative multi-scale organic fiber reinforcement system and prefabricated construction method not only provide a new technical solution for the application of UHPC pipes in fields such as bridges, marine engineering, and municipal pipe galleries, but also effectively reduce material and construction costs and significantly improve engineering benefits. In addition, the use of green and low-carbon organic fiber materials further optimizes resource utilization and reduces carbon emissions, promoting the sustainable development of civil engineering. This technical solution has broad application prospects and can meet the multiple requirements of future projects for high performance, low carbon, and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic structural diagram of the green and low-carbon multi-scale organic fiber-reinforced UHPC pipe of the present invention; Figure 2 is Figure 1 A-A sectional view of; Figure 3 is Figure 2 Enlarged schematic B-B sectional view of; Figure 4 Schematic diagram of multi-scale organic fiber reinforcement mechanism; Figure 5 Detail schematic diagram of the organic fiber grid; Figure 6 Schematic diagram of tying the annular net of the organic fiber grid; Figure 7 Schematic diagram of the connection between the grouting hole and the anchor hole; Figure 8 Schematic diagram of the pipe segment splicing joint; Figure 9 External schematic diagram of the pipe segment splicing; Figure 10 Internal structure schematic diagram at the pipe segment splicing location.

[0027] Wherein: 1 is the microscopic fine organic fiber; 2 is the macroscopic thick organic fiber; 3 is the organic fiber grid; 4 is UHPC; 5 is the groove end; 6 is the convex groove end; 7 is the anchor hole; 8 is the anchor rod; 9 is the anchor hole grouting hole; 10 is the sealing groove grouting hole; 11 is the microscopic crack; 12 is the macroscopic crack; 13 is the longitudinal limb of the organic grid; 14 is the transverse limb of the organic grid; 15 is the organic fiber; 16 is the resin polymer; 17 is the mesh hole; 18 is the nylon rope; 19 is the splicing joint; 20 is the sealing groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following combines Figures 1 to 7A further detailed clarification is made on the specific embodiments of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, those skilled in the art's various equivalent modifications of the present invention all fall within the scope defined by the appended claims of this application. The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified; the materials used in the embodiments of the present invention can all be obtained from commercial channels unless otherwise specified.

[0029] Specifically, as Figures 1 to 10 shown, a green and low-carbon multi-scale organic fiber-reinforced UHPC pipe is composed of microscopic fine organic fibers 1, macroscopic thick organic fibers 2, organic fiber grids 3, and UHPC 4, and grooves 5 and protrusions 6, anchor holes 7, anchor hole grouting holes 9, sealing groove grouting holes 10, and anchor bolts 7 are provided at both ends of the pipe.

[0030] In the embodiments of the present invention, green and low-carbon multi-scale organic fibers are used as the reinforcing materials for UHPC, which can effectively improve the mechanical properties of UHPC pipes. The microscopic fine fibers 1 are sisal fibers, the bamboo fibers have a diameter of about 15 μm and a length of 10 mm; the short-cut macroscopic thick fibers 2 are bamboo fibers, with a diameter of about 0.2 mm and a length of about 25 mm; the short-cut organic fibers are evenly dispersed in the UHPC matrix; the continuous organic fiber grid 3 is a sisal fiber grid, with a mesh size of 30×30 mm and a grid thickness of 2 mm; the microscopic fine organic fibers 1, macroscopic thick organic fibers 2, and the organic fiber grid 3 are matched through the above dimensions, so as to form a three-dimensional network structure with multi-scale effects connected to each other in the UHPC matrix. See Figure 3 , which not only realizes the improvement of the crack resistance and bearing capacity of UHPC pipes from micro to macro, but also can improve the comprehensive crack resistance of UHPC pipes through the overall synergistic performance of the three-dimensional network structure. As Figure 4 shown, among them, the microscopic fine organic fibers 1 mainly inhibit the microscopic cracks 11 inside the UHPC and effectively improve the initial crack load of the UHPC; the macroscopic thick organic fibers 2 and the organic fiber grid 3 can effectively inhibit the development of the macroscopic cracks 12 inside the UHPC and improve the post-crack capacity of the UHPC pipe; at the same time, during the continuous expansion of the macroscopic cracks, the longitudinal and transverse limbs of the organic fiber grid can also effectively bear the load and improve the bearing capacity of the UHPC pipe, including the circumferential bearing capacity and the longitudinal bending bearing capacity of the pipe.

[0031] In the embodiments of the present invention, the organic fiber grid is prepared by a weaving process or a molding process from continuous sisal fibers, and is composed of grid longitudinal limbs 13 and transverse limbs 14 to form mesh holes 17, as Figure 3As shown; taking the grid longitudinal limb 13 as an example, it contains organic fibers 15 and resin polymers 16 inside, and the volume fraction of the organic fibers is greater than 50%. The macroscopic thick organic fibers 2 are short fibers cut from continuous thick organic fibers, and the microscopic thin organic fibers 1 are cut from continuous fiber filaments.

[0032] In the embodiment of the present invention, the volume dosage of the microscopic thin organic fibers 1 is 0.5%, and the volume dosage of the macroscopic thick organic fibers 2 is 3%. The mass ratio of silica fume, sand, mineral powder, high-range water reducer and water is 0.3:1.0:0.4:0.03:0.2. Weigh the microscopic thin organic fibers 1, the macroscopic thick organic fibers 2 and the weight of each component material of UHPC according to this weight ratio. After weighing, mix the dry mixture evenly for standby. Make an organic fiber grid annular net according to the preset pipe diameter, tie the lap joint at the end, overlap two mesh holes of the grid, and tie it with nylon rope 18, then apply epoxy resin at the tied place and cure it at room temperature for 3 days to ensure a reliable fiber grid lap joint, as Figure 4 shown.

[0033] In the embodiment of the present invention, a steel formwork is used for the preparation of the UHPC pipe, and the positions of the anchor holes, anchor bars and grouting holes are set during formwork erection; at the same time, grid positioning plates are set at both ends of the formwork. Place the tied and fixed fiber grid annular net into the formwork according to the positioning position.

[0034] In the embodiment of the present invention, water and water reducer are added to the evenly mixed fiber-reinforced UHPC dry mixture, stirred evenly and then poured into the mold, and the pouring mold is placed on a vibrating table and vibrated sufficiently to make the UHPC paste in the mold dense. After pouring, demold after steam curing for 24h, and then place it in the natural environment for curing until 28 days.

[0035] In the embodiment of the present invention, the UHPC pipe includes a groove end 5 and a convex groove end 6, as Figure 1 shown; anchor holes 7, anchor hole grouting holes 9 and sealing groove grouting holes 10 are provided at the groove end 5, and the anchor hole grouting holes 9 and the anchor holes 7 are connected through, as Figure 5 shown; anchor bars 8 are embedded at the convex groove, and the anchor bars are threaded to increase the bond between the anchor bars and the matrix concrete to ensure reliable connection. When connecting the UHPC pipes, the convex groove end 6 of the upper pipe is inserted into the groove end 5 of the lower pipe, the anchor bar 8 is inserted into the anchor hole 7, and then grouting is carried out from the anchor hole grouting hole 9, and the grouting material fully fills the anchor hole 7 to ensure the effective connection of the anchor; at the same time, grouting is carried out from the sealing groove grouting hole 10 to make the grouting material fully fill into the sealing groove 20 to form a splicing joint 17 with good sealing performance, as Figure 6 and 7 shown; the grouting material used is a high-strength non-shrinking grouting material, and it is cured naturally for at least 7 days after grouting.

Claims

1. A green, low-carbon, multi-scale organic fiber-reinforced UHPC tube, comprising a UHPC matrix, characterized in that: A continuous organic fiber grid and organic chopped fibers are arranged in the UHPC matrix; the organic chopped fibers include microscopic fine fibers and macroscopic coarse fibers; the diameter of the microscopic fine fibers is about 10-20 μm, and the length is between 5-15 mm; the diameter of the chopped macroscopic coarse fibers is between 0.2-0.5 mm, and the length is between 5-30 mm; the organic chopped fibers are uniformly dispersed in the UHPC matrix; the mesh size of the continuous organic fiber grid is between 5×5 mm and 50×50 mm, and the grid thickness is between 0.5-5 mm; the continuous organic fiber grid is arranged along the circumference of the UHPC tube, and the distance between the continuous organic fiber grid and the outer edge surface of the UHPC tube is 1.0-10 cm; the microscopic fine fibers, the macroscopic coarse fibers and the continuous organic fiber grid form a three-dimensional network structure with multi-scale effect that is connected to each other in the UHPC matrix.

2. The green, low-carbon, multi-scale organic fiber reinforced UHPC pipe according to claim 1, characterized in that: The volume fraction of the microscopic fine fibers in the UHPC matrix is ​​0.2% to 1.0; the volume fraction of the macroscopic coarse fibers in the UHPC matrix is ​​1% to 4%.

3. The green, low-carbon, multi-scale organic fiber reinforced UHPC pipe according to claim 1, characterized in that: The organic fiber grid is laid in multiple layers in the UHPC tube, and the spacing between adjacent layers is 5-10 cm.

4. The green, low-carbon, multi-scale organic fiber reinforced UHPC pipe according to claim 1, characterized in that: The organic fiber grid comprises continuous organic fibers and a polymer resin matrix, and the volume fraction of the organic fibers is more than 50%.

5. The green, low-carbon, multi-scale organic fiber reinforced UHPC pipe according to claim 4, characterized in that: The polymer resin matrix in the organic fiber grid is epoxy resin, vinyl resin or phenolic resin.

6. The green, low-carbon, multi-scale organic fiber reinforced UHPC tube according to any one of claims 1 to 5, characterized in that: The microscopic fine fibers are one or more of sisal, flax, coconut, bamboo fibers and wood fibers; the short-cut macroscopic coarse fibers are one or more of sisal, flax, coconut, bamboo fibers and wood fibers.

7. The green, low-carbon, multi-scale organic fiber reinforced UHPC tube according to any one of claims 1 to 5, characterized in that: The UHPC pipe includes a groove end and a convex groove end, an anchor hole is reserved at the groove end, a threaded anchor rod is embedded in the convex groove end, and grouting holes are reserved around the groove end.

8. The green, low-carbon, multi-scale organic fiber reinforced UHPC tube according to any one of claims 1 to 5, characterized in that: The water-binder ratio of the UHPC matrix is ​​controlled between 0.2 and 0.25, the average powder particle size is less than 20 μm, and the average aggregate particle size is less than 1.5 mm.

9. The green, low-carbon, multi-scale organic fiber reinforced UHPC tube according to any one of claims 1 to 5, characterized in that: The UHPC matrix is ​​prepared by mixing the following raw materials in parts by weight: 1 part of cement, 0.25-0.3 parts of silica fume, 1.1-1.2 parts of sand, 0.3-0.4 parts of mineral powder, 0.02-0.04 parts of high-efficiency water reducing agent, and 0.2-0.25 parts of water.

10. The method for preparing a green, low-carbon, multi-scale organic fiber reinforced UHPC tube according to any one of claims 1 to 9, characterized in that: The organic chopped fibers are dispersed in the UHPC cement paste according to the volume fraction to form a grouting material; A continuous organic fiber grid is used to enclose the ring; Positioning the enclosed annular continuous organic fiber grid in the mold using a positioning sheet; The grouting material is poured into the mold and the mold is removed after curing.

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