Push forward type pressure construction method for cast high-doped steel fiber UHPC structure

Abstract

The present application belongs to the field of concrete construction, and particularly relates to a front pushing type pressurized construction method for pouring a high-mixing-amount steel fiber UHPC structure; the method comprises using a construction device, and the construction device comprises a wet material bin, a connecting hose, a hard insertion pipe, a pressurizing pump and a blocking device; the construction method comprises the following steps: step A, arranging the hard insertion pipe; step B, connecting the connecting hose with the hard insertion pipe, and pressurized pouring of UHPC wet material; step C, during the pouring process, pulling the hard insertion pipe upward, but the bottom outlet of the hard insertion pipe is maintained at a position 15-50 cm below the top surface of the wet material; step D, changing the connecting hose to be connected with the hard insertion pipe II, and pressurized pouring of UHPC wet material from the hard insertion pipe II; and step E, repeating the pouring steps until the concrete pouring is completed. The present application can effectively solve the problems of steel fiber clumping, surface easy wind-drying and shell formation, late cold joint and low construction efficiency in the traditional high-mixing-amount steel fiber UHPC construction process.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high performance concrete construction, specifically relating to a forward-pushing pressure construction method for casting high-content steel fiber UHPC structures. Background Technology

[0002] High-fiber reinforced concrete (UHPC) structures generally refer to ultra-high performance concrete (UHPC) structures with a volume content of 2% or higher. This type of UHPC is widely used in projects requiring high flexural strength, such as bridge decks and protective structures. Currently, the main construction method for pouring high-fiber reinforced concrete UHPC structures is the covering method, where each subsequent pour of concrete is placed on top of the previous pour, layer by layer or section by section. This method is used because high-fiber reinforced concrete UHPC has relatively poor fluidity. When pouring large areas, it's impossible to use a forward-pushing construction method where concrete is poured in one spot, causing the UHPC to accumulate near the pouring point. Frequent changes to the pouring point are necessary, hence the covering method. However, practical construction of high-fiber reinforced concrete UHPC has revealed the following disadvantages: 1) UHPC materials generally have a low water-cement ratio, making the poured UHPC surface very prone to dehydration and crusting. Cold joints can occur between two pours, severely affecting construction quality. This problem is unavoidable during the covering method of pouring concrete because it is difficult to continuously supply UHPC during on-site construction. There will be a time interval between two pours, causing the UHPC surface to crust over. Even if the concrete can be continuously supplied, the large surface area of ​​the spread UHPC during large-area pouring makes it impossible to cover the previously poured UHPC surface with freshly mixed UHPC in a short time, thus the problem of UHPC surface crusting and forming cold joints will still exist. 2) To prevent UHPC crusting and forming cold joints, some construction units use the method of vibrating and stirring to break up the hardened surface crust while covering and pouring, but this method is inefficient, especially for structures with dense reinforcement or complex structures. 3) High-content steel fiber UHPC will almost inevitably experience some degree of steel fiber clumping during wet mixing. In the traditional covering method of pouring concrete, the wet UHPC material is poured directly, so the clumped steel fibers will be poured into the structure and easily get stuck near the reinforcement, affecting the construction quality.

[0003] In response to the above problems, relevant literature was consulted, and the following prior technical solutions were found. Although they can solve some of the problems, they also have corresponding drawbacks.

[0004] Chinese invention patent CN202510164499.8 provides a UHPC anti-gravity pressurized casting device and its construction process. The device includes: a template system comprising an outer template placed on a bottom template platform, with an inner template fixedly arranged inside the outer template; a pressurized grouting device including a hopper for loading UHPC mixture, a propulsion cylinder for driving grouting, and a control module for controlling the grouting pressure and speed of the propulsion cylinder; and a grouting connecting hose whose inlet end is connected to the grout outlet of the propulsion cylinder, and at least one outlet end of the grouting connecting hose is connected to the bottom of the outer template for grouting into the cavity between the inner and outer templates. This invention addresses the problems of difficult casting, insufficient compaction, and poor surface quality in existing UHPC thin-walled components and complex-shaped components by employing negative pressure vibration technology. The casting process is convenient and easy to operate, resulting in dense casting and high surface quality, achieving high-quality construction and molding of UHPC thin-walled components and complex-shaped components.

[0005] This invention avoids the problems of surface drying and crusting leading to cold joints and low construction efficiency associated with the covering method by using a bottom-mounted anti-gravity pressurized casting method. However, it also introduces new problems: high-fiber reinforced polycarbonate (UHPC) has poor fluidity, and using this method would result in enormous external pressure during construction, placing high demands on the formwork system and machinery. This would significantly increase construction costs for large-area casting, making it unsuitable for widespread use in actual construction. This method is only suitable for the mass production of small UHPC components, and it does not solve the problem of steel fiber clumping. Therefore, this solution cannot be used in the engineered cast-in-place construction of high-fiber reinforced polycarbonate (UHPC).

[0006] Chinese invention patent application CN202211435284.8 discloses a method for large-area cast-in-place construction of UHPC structures, including: preparing formwork, reinforcing steel, and mixing concrete; concrete pouring: firstly, the saturated vapor pressure, air vapor pressure, and wind speed of the UHPC surface are monitored in real time on site, the surface water loss of the UHPC structure at different molding times is calculated, a water loss time history curve is plotted, the water loss time history curve is written into a programmable logic controller, and then real-time intelligent automatic water replenishment is performed during concrete pouring; concrete curing: firstly, a steam curing shed is set up, and the concrete curing process includes a steam curing process in which the curing temperature and relative humidity inside the shed are monitored in real time on site. UHPC components prepared using the method described in this invention can completely avoid the problems of surface water loss during the pouring process and the failure to control temperature and humidity in real time during steam curing, which lead to a decline in component performance. UHPC components prepared using the method described in this invention have excellent appearance quality and strong structural performance.

[0007] This invention prevents the formation of a hard crust on the UHPC surface by intelligently replenishing water. However, this method has the following problems: The solution mainly prevents UHPC surface dehydration and crust formation by spraying water mist onto the concrete surface. If the nozzle is far from the pouring surface, uneven water mist spraying is easily affected by external environmental factors, resulting in unsatisfactory effects. If the nozzle is close to the pouring surface, concrete may clog the nozzle, making it difficult to guarantee the implementation effect. Furthermore, frequent water mist spraying on the UHPC surface increases the water-cement ratio of the UHPC on the pouring surface, thereby reducing the strength of the UHPC and seriously affecting the construction quality. In addition, this method is not applicable to the construction of UHPC structures with high steel fiber content.

[0008] Chinese utility model patent CN202422112489.3 provides a UHPC cover plate layered casting equipment, including a frame, a mixing component on one side of the top of the frame, a steel feeding component on one side of the mixing component, a conveying component below the frame, a movable material feeding component between the frame and the conveying component, a movable grouting component on one side of the material feeding component, the moving direction of the material feeding component being perpendicular to the moving direction of the grouting component, the frame including a top frame, a transition chamber below the top frame, a material pump at the bottom of the transition chamber, and a flexible connecting pipe below the material pump. Through automated equipment, the steel fibers are effectively dispersed and oriented, ensuring the structural performance of the UHPC cover plate, enabling real-time monitoring of the entire casting process, and solving the problem of uneven steel fiber distribution in traditional UHPC cover plates.

[0009] The patent addresses the issue of uniform distribution of steel fibers in UHPC, but it only relates to a device and method for layered casting of UHPC cover plates, which cannot be adapted to large-volume UHPC structures. The patent also does not involve a forward-pressurized construction method for large-volume UHPC structures with high steel fiber content.

[0010] Therefore, there is still a need in this field for a forward-pressurized construction method for casting high-fiber reinforced polycarbonate (UHPC) structures. Summary of the Invention

[0011] This invention addresses the problems of steel fiber clumping, easy drying and crust formation on the surface leading to cold joints and low construction efficiency during the construction of high-fiber reinforced concrete (UHPC) structures. It proposes a forward-pushing pressure construction method that can effectively solve the above problems.

[0012] This invention provides a forward-push pressurized construction method for casting high-fiber reinforced polycarbonate (UHPC) structures. The method includes a construction device comprising a wet silo, a connecting hose, and a rigid insert connected in sequence. A pressurized pump is installed on the connecting hose. The rigid insert comprises at least two hollow tubes. An obstruction device is installed upstream of the connecting hose to prevent the agglomeration of steel fibers in the UHPC wet silo. The construction method includes the following steps: Step A: First, complete the construction and acceptance of the formwork and reinforcing steel, then arrange the rigid inserts. The UHPC structure is divided into one or more construction areas based on its horizontal area and into one or more layers based on its thickness. The first construction area of ​​the first layer from bottom to top is divided into n casting areas, n≥2, and a rigid insert is installed on at least two adjacent casting areas. The distance between the rigid inserts in two adjacent casting areas is less than or equal to L, where L=8~15m. The bottom end of each rigid insert is first set at a distance from the UHPC... At a point h above the bottom surface of the PC structure, h ≥ 10cm, the pressure from the pressurizing pump is sufficient to allow the UHPC wet material to flow to the edge of a single casting area; Step B: Connect the connecting hose to the rigid insert one, and start the pressurizing pump to pressurize and cast the UHPC wet material; Step C: During casting, pull the rigid insert upwards, but the bottom outlet of the rigid insert always remains at a position S below the top surface of the wet material, S = 15~50cm; Step D: When the wet material flows naturally from the rigid insert one to the rigid insert two, and the rigid insert... When the thickness of the wet material at the second rigid insertion tube is not less than d (d = 7~15cm), disconnect the connection between the connecting hose and the first rigid insertion tube, and connect it to the second rigid insertion tube instead. Pressurize and pour the UHPC wet material from the second rigid insertion tube. Step E: Repeat the pouring steps until the first construction area of ​​the first layer is completed. If the first layer includes multiple construction areas, then complete the pouring of all construction areas of the first layer. If the UHPC structure includes multiple layers, repeat the pouring steps until the concrete pouring of all layers is completed.

[0013] In one specific embodiment, the rigid cannula is a steel cannula.

[0014] In one specific embodiment, the length of the rigid cannula is 80-98% of the thickness of each layer of the UHPC structure, or 80-98% of the overall thickness of the UHPC structure.

[0015] In one specific embodiment, the outer diameter of the rigid insertion tubes is smaller than the minimum spacing between the reinforcing bars in the template, so that the rigid insertion tubes can be smoothly inserted into the UHPC structure.

[0016] In one specific implementation, the rigid cannula is vertically arranged, and the thickness of each layer of the UHPC structure in step A is less than or equal to 5m.

[0017] In one specific implementation, in step A, a rigid insertion tube is set at the center of at least two adjacent pouring areas, and h = 10 to 20 cm.

[0018] In one specific implementation, in step C, S = 25~50cm.

[0019] In one specific embodiment, the top of the rigid cannula is provided with a first connecting structure, and the downstream end of the connecting hose is provided with a second connecting structure for quick and secure connection with the first connecting structure.

[0020] In one specific implementation, both the first connecting structure and the second connecting structure are threaded structures.

[0021] In one specific embodiment, the blocking device is a wire mesh, and the mesh size of the wire mesh is no more than 2 cm.

[0022] Beneficial effects: This invention proposes a forward-push pressure construction method for casting high-fiber UHPC structures, which can effectively solve the problems of steel fiber clumping, easy surface drying and shelling leading to cold joints and low construction efficiency that occur in the traditional high-fiber UHPC construction process. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the construction device described in this invention.

[0024] Figure 2 This is a schematic diagram of the planar layout of multiple rigid cannulas in this invention.

[0025] Figure 3 This is a schematic diagram of the pouring steps of the construction method described in this invention.

[0026] In the diagram: 1-Formwork, 2-Reinforcing bar, 3-Rigid insert, 4-Connecting hose, 5-Pressure pump, 6-Wet silo, 31-Rigid insert one, 32-Rigid insert two, 33-Rigid insert three, 34-Rigid insert four, 35-Rigid insert five, 36-Rigid insert six. Detailed Implementation

[0027] This invention provides a forward-push pressurized construction method for casting high-fiber reinforced polycarbonate (UHPC) structures, such as... Figure 1As shown, the construction method includes the use of a construction device, which includes a wet material silo 6, a connecting hose 4, and a rigid insert 3 connected in sequence. A pressure pump 5 is installed on the connecting hose 4, and the rigid insert 3 includes at least two tubes, both of which are hollow. An obstruction device for preventing the agglomeration of steel fibers in the UHPC wet material is installed upstream of the connecting hose 4. The construction method includes the following steps: Step A, first complete the construction and acceptance of the formwork 1 and the reinforcing bars 2, then arrange the rigid insert 3; the UHPC structure is divided into one or more sections based on its horizontal area. Multiple construction areas are divided into one or more layers based on their thickness. The first construction area of ​​the first layer from bottom to top is divided into n pouring areas, n≥2, and a rigid insertion pipe 3 is set on at least two adjacent pouring areas. The distance between the rigid insertion pipes 3 of two adjacent pouring areas is less than or equal to L, where L=8~15m. The bottom end of each rigid insertion pipe 3 is first set at a distance h above the bottom surface of the UHPC structure, where h≥10cm, so that the delivery pressure of the pressure pump can make the UHPC wet material flow to the edge of a single pouring area. A planar layout of multiple rigid insertion pipes is shown in the diagram. Figure 2 Step B: Connect the connecting hose 4 to the rigid insertion tube 31, and start the pressure pump 5 to pressurize and pour the UHPC wet material. (See...) Figure 3 (a) In step C, during the pouring process, the rigid insert 3 is pulled upwards, but the bottom outlet of the rigid insert 3 is always kept at a position S below the top surface of the wet material, S=15~50cm, see Figure 3 (b) Step D: When the wet material flows naturally from rigid tube 1 31 to rigid tube 2 32, and the thickness of the wet material at rigid tube 2 32 is not less than d, where d = 7~15cm, disconnect the connecting hose 4 from rigid tube 1 31 and connect it to rigid tube 2 32 instead. Apply pressure and cast the UHPC wet material from rigid tube 2 32. See [link to relevant documentation]. Figure 3 (c) and (d) in the above; Step E, repeat the pouring steps until the first construction area of ​​the first floor is completed; if the first floor includes multiple construction areas, then complete the pouring of all construction areas of the first floor; if the UHPC structure includes multiple floors, repeat the pouring steps until the concrete pouring of all floors is completed.

[0028] In this invention, the connecting hose is used to connect the rigid tubing and the pressure pump, and to transport wet UHPC material with high steel fiber content.

[0029] In step A of this invention, only two rigid tubes 3 can be initially installed in the first construction area of ​​the first layer. After the connecting hose 4 is connected to the second rigid tube 32, the first rigid tube 31 is pulled out and inserted into the position of the third rigid tube 33, and so on. Alternatively, all the rigid tubes 3 can be installed in the first construction area of ​​the first layer, for example, including 6 to 20 rigid tubes 3. In this case, after the construction at the second rigid tube 32 is completed, the connecting hose 4 is directly connected to the third rigid tube 33 and construction is carried out at this location. Alternatively, some rigid tubes can be arranged in the first construction area of ​​the first layer first, and the other rigid tubes in the construction area can be arranged when the corresponding construction is nearing completion. For example... Figure 2 First, rigid cannulas 1 (31), 2 (32), 3 (33), 4 (34), 5 (35), and 6 (36) are installed.

[0030] In step C of this invention, external forces, including manual or mechanical forces, can be used to vertically set the rigid cannula 3, and during construction, external forces, including manual or mechanical forces, can be used to vertically move the rigid cannula 3 upward.

[0031] In step C of this invention, the rigid insertion tube 3 can also be spot welded to the template 1 or the reinforcing bar 2. When the concrete reaches a certain thickness, the spot weld connection is disconnected, the rigid insertion tube 3 is moved up a certain distance, and then it is spot welded to the template 1 or the reinforcing bar 2.

[0032] In step D of this invention, the connection between the connecting hose 4 and the rigid insertion tube 31 is disconnected and replaced with the rigid insertion tube 32. The rigid insertion tube 31 can be pulled out of the UHPC wet material or left in it to eventually form part of the UHPC structure.

[0033] In step D of this invention, as the wet material is continuously pushed forward (i.e., horizontally expanding outwards from the outlet of the rigid tube), it also accumulates upwards at the rigid tube under pressure. Therefore, it is necessary to pull the rigid tube upwards, so that the forward-pushing construction of concrete can be completed with only the smallest possible delivery pressure. This method avoids the disadvantage of traditional pressurized pouring requiring extensive reinforcement of the formwork. In other words, if the rigid tube is not pulled upwards in time during construction, the impact force of the concrete pouring on the formwork and reinforcing steel will also increase when the concrete pouring pressure increases. Therefore, the support system including the formwork and reinforcing steel needs to be more robust, which will result in unnecessary waste of formwork and reinforcing steel.

[0034] In this invention, after step E, the concrete surface is smoothed and polished before entering the concrete curing stage.

[0035] In one specific embodiment, the rigid cannula 3 is vertically arranged, and the thickness of each layer of the UHPC structure in step A is less than or equal to 5m.

[0036] In this invention, when the thickness of the UHPC structure is, for example, 9m, it is generally constructed by casting in two layers, and the length of the rigid tube 3 is, for example, 4.5m or 8.5m; when the thickness of the UHPC structure is, for example, 3m, the length of the rigid tube 3 is, for example, 2.7m.

[0037] In this invention, the slump expansion of the high-fiber reinforced polycarbonate (UHPC) wet mix is ​​large, generally not less than 70 cm. A pressure pump is used to apply a certain pouring pressure to the UHPC wet mix, causing it to flow forward. This allows the later-poured UHPC to be "squeezed" into the previous layer, pushing the already poured UHPC forward. The initially crusted surface remains on the outermost layer of the UHPC wet mix, preventing the formation of new surface crusts and thus eliminating construction cold joints. Furthermore, the applied pouring pressure results in a fast flow rate of the UHPC wet mix, achieving high pouring efficiency. In addition, the barrier device in the construction apparatus solves the problem of high-fiber reinforced polycarbonate clumping affecting construction.

[0038] In summary, this invention relates to a forward-push pressurized construction method for casting high-fiber reinforced polycarbonate (UHPC) structures. The method includes a construction device comprising a wet material silo, a connecting hose, a rigid insert, a pressurizing pump, and a blocking device. The construction method includes: Step A, arranging the rigid insert; Step B, connecting the connecting hose to the first rigid insert and pressurizing the UHPC wet material; Step C, during casting, pulling the rigid insert upwards, but maintaining the bottom outlet of the rigid insert 15-50 cm below the top surface of the wet material; Step D, connecting the connecting hose to a second rigid insert and pressurizing the UHPC wet material from the second rigid insert; Step E, repeating the casting steps until the concrete is poured. This invention effectively solves the problems of steel fiber clumping, easy surface drying and crusting leading to cold joints, and low construction efficiency that occur during traditional high-fiber reinforced polycarbonate (UHPC) construction.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A forward-push pressurized construction method for casting high-fiber reinforced polycarbonate (UHPC) structures, characterized in that, The construction method includes the use of a construction device, which comprises a wet material silo (6), a connecting hose (4), and a rigid insert (3) connected in sequence. A pressure pump (5) is installed on the connecting hose (4), and the rigid insert (3) comprises at least two tubes, both of which are hollow. An obstruction device for blocking the agglomerated steel fibers in the UHPC wet material is installed upstream of the upstream end of the connecting hose (4). The construction method includes the following steps: Step A: First, complete the construction acceptance of the template (1) and the reinforcing steel (2), and then arrange the rigid insert pipe (3); the UHPC structure is divided into one or more construction areas according to its horizontal area, and into one or more layers according to its thickness; the first construction area of ​​the first layer from bottom to top is divided into n pouring areas, n≥2, and a rigid insert pipe (3) is set on each of at least two adjacent pouring areas, the distance between the rigid insert pipes (3) of two adjacent pouring areas is less than or equal to L, L=8~15m; the bottom end of each rigid insert pipe (3) is first set at a distance h above the bottom surface of the UHPC structure, h≥10cm, so that the conveying pressure of the pressurizing pump can make the UHPC wet material flow to the edge of a single pouring area; Step B: Connect the connecting hose (4) to the rigid insert (31) and start the pressure pump (5) to pressurize and pour the UHPC wet material; Step C: During the pouring process, pull the rigid tube (3) upwards, but the bottom outlet of the rigid tube (3) is always kept at a position S below the top surface of the wet material, S=15~50cm; Step D: When the wet material flows naturally from the first rigid insertion tube (31) to the second rigid insertion tube (32), and the thickness of the wet material at the second rigid insertion tube (32) is not less than d, where d = 7~15cm, disconnect the connection between the connecting hose (4) and the first rigid insertion tube (31), and connect it to the second rigid insertion tube (32) instead. Pressurize and cast the UHPC wet material from the second rigid insertion tube (32). Step E: Repeat the pouring steps until the first construction area of ​​the first floor is completed; if the first floor includes multiple construction areas, then complete the pouring of all construction areas of the first floor; if the UHPC structure includes multiple floors, repeat the pouring steps until the concrete pouring of all floors is completed.

2. The construction method according to claim 1, characterized in that, The rigid cannula is a steel cannula.

3. The construction method according to claim 1, characterized in that, The length of the rigid cannula (3) is 80-98% of the thickness of each layer of the UHPC structure, or 80-98% of the overall thickness of the UHPC structure.

4. The construction method according to claim 1, characterized in that, The outer diameter of the rigid insertion tube (3) is smaller than the minimum steel bar spacing between the steel bars (2) inside the template (1), so that the rigid insertion tube (3) can be smoothly inserted into the UHPC structure.

5. The construction method according to claim 1, characterized in that, The rigid cannula (3) is set vertically, and the thickness of each layer of the UHPC structure in step A is less than or equal to 5m.

6. The construction method according to claim 1, characterized in that, In step A, a rigid insertion tube (3) is set at the center of at least two adjacent pouring areas, and h = 10~20cm.

7. The construction method according to claim 1, characterized in that, In step C, S = 25~50cm.

8. The construction method according to claim 1, characterized in that, The top of the rigid cannula (3) is provided with a first connecting structure, and the downstream end of the connecting hose (4) is provided with a second connecting structure for quick and stable connection with the first connecting structure.

9. The construction method according to claim 8, characterized in that, Both the first and second connection structures are threaded structures.

10. The construction method according to any one of claims 1 to 9, characterized in that, The barrier device is a wire mesh, and the mesh size of the wire mesh is no more than 2cm.

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