Method of reinforcing existing structures using sprayed UHPC

Abstract

This invention relates to the field of building construction technology, specifically to a method for reinforcing existing structures using sprayed UHPC. The method comprises the following steps: S1, cleaning the surface of the existing structure to be reinforced, and inserting anchor bars with hook structures into the cleaned surface; S2, installing a spraying pipe and spraying UHPC onto the surface to be reinforced until the desired thickness is reached, then stopping the spraying; S3, fabricating a reinforcing mesh, hanging the mesh on the anchor bars, and securing the mesh with the hook structures; S4, spraying UHPC onto the surface again until the required thickness is achieved; S5, repeating steps S2 to S4 sequentially until the surface is reinforced, correcting the surface, and curing it to complete the reinforcement of the existing structure. This application provides an extremely simple and convenient method for reinforcing existing structures, offering excellent reinforcement results with guaranteed strength, and without significantly increasing the self-weight of the existing structure.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a method for reinforcing existing structures using sprayed UHPC. Background Technology

[0002] In recent years, my country has made tremendous achievements in infrastructure construction, with a continuous increase in the number of permanent structures such as bridges, tunnels, and buildings in service. These existing structures not only face continuous effects from traffic loads, sunlight, and high temperatures, but also endure accidental impacts such as overloading, earthquakes, mudslides, and collisions, making structural performance and durability issues increasingly prominent. Furthermore, during the construction of existing structures, temporary structures such as foundation pit supports and tunnel linings are often used for protection to reduce safety risks. These temporary structures frequently require rapid reinforcement to cope with emergencies such as cracking and excessive deformation of the supports and linings. Therefore, to improve the reliability, applicability, and durability of both permanent and temporary structures, economical and feasible reinforcement technologies are gradually being applied on a large scale.

[0003] In the field of structural reinforcement, the main methods employed are cross-section enlargement, steel plate bonding, fiber bonding, and prestressed reinforcement. Steel plate bonding and fiber bonding require applying high-performance adhesives and then bonding steel plates or fiber cloths. However, these adhesives have slow strength development and are prone to aging, while steel plates and fiber cloths are expensive and have poor durability. Prestressed reinforcement is generally only suitable for vertically loaded structures such as beam bridges and is not applicable to piers, building frames, foundation pit support, tunnel linings, etc., thus its application scope is relatively limited. Cross-section enlargement is the most widely used method, which involves adding a new layer of concrete to the surface of the structure to be reinforced to achieve the desired reinforcement. For example, the Chinese invention patent with patent number "CN201710635339.2" entitled "Reinforcement Structure for Concrete Floor Slabs" describes a reinforcement structure that involves spraying concrete under a concrete floor slab and connecting the concrete floor slab and the sprayed concrete into a whole using steel strands. The steel strands are cup-shaped, with the upper end of the inclined section fixed to angle steel by anchors; spacers are placed between the horizontal section of the steel strands and the concrete floor slab; sprayed concrete is placed between the steel strands and the bottom of the concrete floor slab; a steel plate is placed under the steel strands, embedded in a concrete column, and prestressed struts are placed on top of the steel plate; a rubber pad is placed between the concrete floor slab and the steel plate at the edge of the concrete floor slab. This reinforcement structure strengthens the concrete floor slab by spraying concrete onto its lower surface and using steel strands to reinforce both the concrete floor slab and the sprayed concrete. This reinforcement method is relatively simple and has a good reinforcement effect. However, it can only be applied to relatively simple structures. For some cases with high reinforcement requirements, the above reinforcement structure is not suitable. The main reason is that the reinforcement structure can only increase the reinforcement strength by increasing the thickness of the shotcrete. After reinforcement, the self-weight of the structure increases significantly, the reinforcement effect is relatively poor, and the shotcrete in this reinforcement structure does not have a good consolidation effect, resulting in limited structural strength. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for reinforcing existing structures using sprayed UHPC.

[0005] The technical solution of this invention is: a method for reinforcing existing structures using sprayed UHPC, which is carried out according to the following steps:

[0006] S1. Clean the surface of the existing structure to be reinforced, and insert anchor bars with hook structure into the cleaned surface to be reinforced.

[0007] S2. Install the spray pipe and spray UHPC onto the surface to be reinforced using the spray pipe. Stop spraying once the sprayed UHPC reaches the set thickness.

[0008] S3. Make a steel mesh, hang the steel mesh on the anchor bars, and fix the steel mesh by hook structure;

[0009] S4. Spray UHPC onto the surface to be reinforced again until the required thickness is achieved;

[0010] S5. Proceed with steps S2 to S4 in sequence until the surface to be reinforced is completed. Repair the surface to be reinforced and perform maintenance to complete the reinforcement of the existing structure.

[0011] According to the method for reinforcing an existing structure using sprayed UHPC provided in this application, the method of implanting an anchor bar with a hook structure into the cleaned surface to be reinforced in step S1 includes: implanting an anchor bar into the cleaned surface to be reinforced, wherein the hook structure includes at least one short rod; the short rod is installed on the part of the anchor bar that protrudes from the surface to be reinforced, wherein when the surface to be reinforced is a vertical end face, the short rod is located at the upper end of the anchor bar and the angle between the short rod and the anchor bar is not greater than 90°, and when the surface to be reinforced is a horizontal end face, the angle between the short rod and the anchor bar is 90°.

[0012] According to the method for reinforcing an existing structure using sprayed UHPC provided in this application, the method of hanging the steel mesh on the anchor bar in step S3 includes: hooking the steel mesh on the anchor bar so that the short rod and the steel mesh bars are hooked together along the length of the anchor bar.

[0013] According to the method for reinforcing existing structures using sprayed UHPC provided in this application, a steel mesh is hooked onto an anchor bar, so that the connection point between the short rod and the anchor bar is in contact with the node of the steel mesh.

[0014] According to the method for reinforcing an existing structure by spraying UHPC provided in this application, step S2, the method of spraying UHPC onto the surface to be reinforced using a spraying pipe includes: spraying UHPC onto the surface to be reinforced, observing the length of the exposed portion of the anchor bar, and stopping the spraying when the distance between the outer surface of the sprayed UHPC and the connection point between the short rod and the anchor bar along the length of the anchor bar is just equal to the thickness of the steel mesh to be hooked. At this time, the thickness of the UHPC sprayed on the surface to be reinforced is the set thickness.

[0015] According to the method for reinforcing an existing structure using sprayed UHPC provided in this application, the method of installing the spray pipe in step S2 includes: installing a quick-setting agent inlet pipe on the nozzle, connecting the inlet end of the nozzle to a hydrocyclone, installing a compressed air inlet pipe on the hydrocyclone, arranging a first reducer pipe, a second reducer pipe, and a third reducer pipe with progressively increasing diameters on one side of the inlet end of the hydrocyclone, connecting the small end of the first reducer pipe to the hydrocyclone, connecting the large end of the first reducer pipe to the small end of the second reducer pipe through a spray pipe, connecting the large end of the second reducer pipe to the small end of the third reducer pipe, and connecting the inlet end of the third reducer pipe to a UHPC supply device through a straight pipe.

[0016] According to the method for reinforcing an existing structure using jet-propelled UHPC provided in this application, the cyclone separator is a bent pipe structure, and the angle between the axis of the nozzle on the outlet side of the cyclone separator and the axis of the first variable diameter pipe on the inlet side of the cyclone separator is in the range of 100 to 150°.

[0017] According to the method for reinforcing an existing structure by spraying UHPC provided in this application, after the spray pipe is assembled, the nozzle outlet end of the spray pipe is facing the surface to be reinforced, so that the angle between the spraying direction of the nozzle and the surface to be reinforced is 75-105°, the distance between the nozzle and the surface to be reinforced is 0.6-1.2m, and the speed of the UHPC sprayed by the nozzle is controlled to be 15-45m / s.

[0018] According to the method for reinforcing existing structures using sprayed UHPC provided in this application, in step S2, the UHPC sprayed onto the surface to be reinforced comprises cement, silica fume, cenospheres, stone powder, microfiber steel fibers, and a thixotropic agent. The cement is high-belite silicate cement with a strength of not less than 42.5; the silica fume has an SiO2 content greater than 90% and a specific surface area greater than 20,000 m². 2 / kg; the average particle size of the cenospheres is 1-5 μm, and the specific surface area is greater than 2500 m² / kg. 2 / kg; the CaCO3 content of the stone powder is greater than 95%, and the average particle size is not greater than 80nm; the thixotropic agent includes attapulgite; the attapulgite is a gel powder with an average particle size of 5-15μm.

[0019] According to the method for reinforcing an existing structure using sprayed UHPC provided in this application, the method for cleaning the surface of the existing structure to be reinforced in step S1 includes: roughening the surface to be reinforced until the aggregate is exposed, rinsing the surface to be reinforced with clean pressurized water or compressed air to remove loose aggregate, slag and powder from the surface to be reinforced.

[0020] The advantages of this application are: 1. This application sprays the surface to be reinforced in stages. Before spraying, rebar is installed on the surface to be reinforced. The rebar is used to hook the steel mesh, and then the steel mesh is sprayed into the UHPC to form a reinforced concrete structure. The steel mesh and the rebar form the skeleton structure of the concrete, which enhances the structural strength of the reinforcement layer and the connection strength between the reinforcement layer and the existing structure. Sufficient strength can be achieved with a very small thickness, avoiding the problems of large increase in the self-weight of the structure after reinforcement and poor reinforcement effect. Moreover, the method of this application is applicable to various scenarios and has great promotional value.

[0021] 2. The rebar installation method of this application is simple. By arranging bent short rods at the ends of the rebars, the rebar mesh is hooked on the short rods, avoiding the problem of difficulty in fixing the rebar mesh in some application scenarios, which greatly improves the efficiency of the reinforcement process. The rebar mesh can be set in a suitable position, which improves the structural strength of the entire reinforcement layer.

[0022] 3. The connection method between the steel mesh and the anchor bar in this application is extremely simple. By hooking the short rod to the steel mesh bar, the steel mesh can be restricted to the set position and supported at the same time, which facilitates the subsequent spraying of UHPC. The entire spraying reinforcement process is simple, easy to operate, and the reinforcement strength is guaranteed.

[0023] 4. When the steel mesh is hooked onto the anchor bar in this application, the nodes of the steel mesh are in contact with the connection point between the short bar and the anchor bar, which minimizes the area of ​​the steel mesh, anchor bar, and short bar projected onto the surface to be reinforced, so that UHPC can be easily sprayed onto the surface to be reinforced through the steel mesh, resulting in a better reinforcement effect.

[0024] 5. The reinforcement process of this application is multiple spraying reinforcement. During the initial spraying reinforcement, the UHPC is sprayed so that the distance between the sprayed UHPC and the connection point of the short rod and anchor bar is just enough to lay the steel mesh. The steel mesh is confined between the initial sprayed UHPC and the short rod. The positioning effect of the steel mesh is excellent, and the structural strength of the reinforcement layer is fully guaranteed.

[0025] 6. This application uses a specific injection pipe for UHPC injection. The injection pipe has a simple structure, is easy to install and use, can be moved on its own and put into use at any time, and can be freely extended and flexibly adjusted. Combined with the fast hardening and early strength characteristics of UHPC, it is especially suitable for emergency repair projects after impact loads such as earthquakes, debris flows, and impacts.

[0026] 7. A bent cyclone separator is provided between the nozzle and the first reducing pipe in this application. The bent cyclone separator facilitates the flow of UHPC in the spray pipe. At the same time, this structure connects the nozzle and the first reducing pipe for easy installation, so that UHPC can flow and spray at a set angle, thereby improving the spraying effect of the entire spray pipe.

[0027] 8. This application uses a special spraying method with a spray pipe, and the spraying angle, spraying distance and spraying speed of UHPC have been optimized. The sprayed UHPC has a certain impact force and can adhere closely to the surface to be reinforced. This allows the fine UHPC slurry to penetrate into the micropores of the structure, which can ensure the interfacial bonding performance between the UHPC used for reinforcement and the existing structure. Shallow roughening or no roughening is sufficient to meet the stress requirements, minimizing the damage to the existing structure and the amount of roughening work.

[0028] 9. This application optimizes the composition of the sprayed UHPC. The UHPC contains no coarse aggregate, minimizing the obstruction effect of rebar and steel mesh on the sprayed UHPC, thus reducing the area of ​​holes on the back of the rebar and steel mesh and improving the reinforcement effect. The UHPC matrix contains a large number of short and fine steel fibers, giving the reinforcement layer in the tension zone excellent crack resistance and impact toughness, significantly improving the beam's bending reinforcement performance, the pier's resistance to debris flow erosion, and its impact resistance. UHPC has high tensile and compressive strength; under the same reinforcement effect, its reinforcement layer thickness is much smaller than that of ordinary concrete reinforcement layers, minimizing the impact of reinforcement work on the existing structure's self-weight, dimensions, and appearance, achieving lightweight reinforcement. UHPC possesses extremely excellent durability (chloride ion diffusion coefficient is only 0.01 times that of conventional concrete). The UHPC reinforcement layer can serve as a reliable protective layer for existing structures, greatly slowing down the deterioration process and thus extending the structure's lifespan.

[0029] 10. This application cleans the surface of the existing structure to be reinforced. The cleaning method is simple. The spray reinforcement process does not require the installation or removal of formwork. The interface roughening and rebar installation process does not require traffic interruption. Moreover, UHPC has a fast strength development speed (the compressive strength can reach more than 50MPa in 24 hours), which can greatly shorten the time of traffic interruption due to reinforcement construction and minimize the interference with traffic along the route.

[0030] This application presents an extremely simple and convenient method for reinforcing existing structures. It provides excellent reinforcement results, ensures reinforcement strength, and does not significantly increase the self-weight of existing structures. It has great potential for widespread application. Attached Figure Description

[0031] Figure 1 This application includes a schematic diagram of rebar installation on the surface to be reinforced (vertical surface to be reinforced);

[0032] Figure 2: Schematic diagram of the initial spraying of UHPC on the surface to be reinforced (vertical surface to be reinforced);

[0033] Figure 3 This application presents a schematic diagram of the initial spraying of UHPC onto the surface to be reinforced (vertical surface to be reinforced).

[0034] Figure 4 This application includes a schematic diagram of the steel mesh installation (vertical surface to be reinforced);

[0035] Figure 5 This application includes a frontal schematic diagram of the steel mesh installation (vertical surface to be reinforced);

[0036] Figure 6 : A schematic diagram of the completed spraying of the reinforcement layer in this application (vertical surface to be reinforced);

[0037] Figure 7 : Schematic diagram of the injection pipe structure of this application;

[0038] Wherein: 1—jetting pipe; 11—nozzle; 12—accelerator inlet pipe; 13—cyclone separator; 14—compressed air inlet pipe; 15—first reducer; 16—second reducer; 17—third reducer; 18—jetting pipe; 19—straight pipe;

[0039] 2—Anchor bar; 3—Short rod; 4—Steel mesh. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0041] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0044] This application relates to a method for reinforcing existing structures using sprayed UHPC. The method primarily involves spraying UHPC onto the surface of the existing structure to be reinforced, forming a reinforcement layer. This reinforcement layer effectively increases the thickness or cross-sectional area of ​​the existing structure, thereby improving its overall structural strength and achieving the reinforcement objective. During the spraying of UHPC onto the reinforcement layer, this application also installs rebar and steel mesh 4 on the surface to be reinforced. The rebar and steel mesh 4 form the steel reinforcement skeleton of the reinforcement layer, resulting in a reinforcement layer that is equivalent to a reinforced concrete structure, providing greater strength reinforcement with a relatively small thickness.

[0045] Specifically, the method for reinforcing existing structures according to this application can be carried out according to the following steps:

[0046] S1. Clean the surface of the existing structure to be reinforced, and then insert anchor bars 2 with hook structures into the cleaned surface. Figure 1 As shown;

[0047] The purpose of cleaning the surface of the existing structure to be reinforced is to remove loose aggregate, slag and powder on the surface to be reinforced, so as to avoid affecting the subsequent rebar installation. At the same time, the loose structure will also cause the reinforcement layer to be loosely connected with the surface to be reinforced, affecting the reinforcement effect of the entire reinforcement layer. Therefore, it is necessary to clean the surface to be reinforced in the early stage of reinforcement.

[0048] The purpose of installing rebar on the surface to be reinforced is to facilitate the subsequent hooking of the steel mesh 4 in a suitable position. At the same time, the installation of rebar also enhances the tightness of the connection between the entire reinforcement layer and the existing structure. The rebar will also form a steel skeleton structure of the entire reinforcement layer together with the steel mesh 4.

[0049] S2. Install the spray nozzle and use it to spray UHPC onto the surface to be reinforced. Figure 2 As shown, spraying stops once the UHPC to be sprayed reaches the set thickness. Figure 3 As shown;

[0050] Because the UHPC sprayed in this application is a specific material, a special spraying pipe is used to spray the UHPC to achieve the best spraying effect. The process of constructing the reinforcement layer in this application involves multiple sprayings. The initial spraying stops once the set thickness is reached, and the steel mesh 4 needs to be installed.

[0051] S3. Fabricate the reinforcing mesh 4, hang the reinforcing mesh 4 on the anchor bar 2, and fix the reinforcing mesh 4 through the hook structure, such as... Figure 4 and 5 As shown;

[0052] The steel mesh 4 is actually a mesh-like structure in which longitudinal and transverse bars are connected in an interlaced manner. The steel mesh 4 is hooked at a set position at a distance from the surface to be reinforced by the anchor bars 2. Whether spraying the vertical surface to be reinforced or the horizontal surface to be reinforced, the hook structure on the anchor bars 2 can fix the steel mesh 4 very well.

[0053] S4. Spray UHPC onto the surface to be reinforced again until the required thickness is achieved;

[0054] If the reinforcement layer is a single-layer steel mesh 4, then only two sprayings of UHPC are needed to form the required reinforcement layer. The first spraying is to the set thickness. After the steel mesh 4 is hung on the anchor bar 2, the second spraying of UHPC is carried out to complete the construction of the reinforcement layer.

[0055] If the reinforcement layer is constructed as a multi-layer steel mesh 4, the number of UHPC spraying times needs to be designed according to the number of steel mesh 4. Each additional layer of steel mesh 4 requires one more UHPC spraying time. For example, if two layers of steel mesh 4 are used, the two layers of steel mesh 4 are arranged parallel to each other and spaced apart in the length direction of the anchor bar 2. After the initial spraying of UHPC reaches the set thickness, the first layer of steel mesh 4 is hung on the anchor bar 2, and then the second layer of UHPC is sprayed onto the first layer of steel mesh 4. Then the second layer of steel mesh 4 is hung on the anchor bar 2, and then the third layer of UHPC is sprayed onto the second layer of steel mesh 4 to form a reinforcement layer of the required thickness.

[0056] S5. Follow steps S2 to S4 sequentially until the reinforcement of the surface to be reinforced is complete. Figure 6 As shown, the surface is modified and reinforced and then cured to complete the reinforcement of the existing structure.

[0057] Once all the UHPC spraying is completed and the required thickness is achieved, the surface of the reinforced layer formed by the sprayed UHPC needs to be corrected, which is essentially repairing and smoothing it, and then curing is performed.

[0058] In some embodiments of this application, this embodiment optimizes the above step S1. In step S1, the method for cleaning the surface to be reinforced of the existing structure is as follows: roughen the surface to be reinforced until the aggregate is exposed, and use clean pressurized water or compressed air to rinse the surface to be reinforced to remove loose aggregate, slag and powder from the surface to be reinforced.

[0059] The surface to be reinforced is cleaned using pressurized water or compressed air. This method is highly effective and efficient, quickly removing loose parts from the surface and facilitating subsequent UHPC spraying and rebar installation.

[0060] In a further embodiment of this application, the method of anchoring the rebar in step S1 above is optimized. Specifically, anchor bars 2 are implanted into the cleaned surface to be reinforced. The hook structure includes at least one short rod 3, which is installed on the portion of the anchor bar 2 that protrudes from the surface to be reinforced. When the surface to be reinforced is a vertical end face, the short rod 3 is located at the upper end of the anchor bar 2, and the angle between the short rod 3 and the anchor bar 2 is no greater than 90°. When the surface to be reinforced is a horizontal end face, the angle between the short rod 3 and the anchor bar 2 is 90°. Figures 1-6 As shown.

[0061] The number of short rods 3 is determined based on the number of steel mesh 4. For example, if there is one layer of steel mesh 4, then one short rod 3 can be set on the anchor bar 2. If there are two layers of steel mesh 4, then two short rods 3 need to be set on the anchor bar 2 at intervals along the length of the anchor bar 2. The number of short rods 3 corresponds one-to-one with the number of steel mesh 4.

[0062] Short rod 3 and anchor bar 2 are perpendicular to each other. When short rod 3 is used on the vertical surface to be reinforced, it is positioned above anchor bar 2, facilitating the hooking of steel mesh 4. When short rod 3 is used on the horizontal end face, it is sufficient to ensure that short rod 3 and anchor bar 2 intersect perpendicularly. However, in either case, it is necessary to ensure that all short rods 3 on the surface to be reinforced face have the same orientation, as this facilitates the hanging of steel mesh 4.

[0063] This application uses a short rod 3 to hook the steel mesh 4. In a preferred case, the short rod 3 intersects the anchor bar 2 at 90°. This can be done by first forming a perpendicular intersecting structure between the anchor bar 2 and the short rod 3 and then inserting it into the surface to be reinforced. Alternatively, the straight anchor bar 2 can be inserted into the surface to be reinforced and then the short rod 3 can be installed on the anchor bar 2. In either case, as long as the function of hooking the steel mesh 4 is satisfied, it is acceptable.

[0064] Although this application limits the hook structure to the short rod type 3, it is not limited to this only type. Other types of structures are acceptable as long as they can meet the hook requirements.

[0065] In step S3 above, it is mentioned that the reinforcing mesh 4 is hung on the anchor bar 2. Specifically, the reinforcing mesh 4 is hooked onto the anchor bar 2, so that the short rod 3 and the reinforcing mesh 4 are hooked together along the length of the anchor bar 2. Figure 4 and 5 This hooking method is relatively simple. The mesh size of the reinforcing mesh 4 is larger than the length of the short rod 3. When dealing with the reinforcing mesh 4, the mesh size of the reinforcing mesh 4 is passed through the short rod 3, and the reinforcing mesh 4 can be easily hooked onto the anchor bar 2 and the short rod 3. For the vertical surface to be reinforced, after the reinforcing mesh 4 is hung on the anchor bar 2, the anchor bar 2 is the supporting structure of the reinforcing mesh 4, and the short rod 3 is the limiting structure. For the horizontal surface to be reinforced, the short rod 3 is the supporting structure of the reinforcing mesh 4, and the anchor bar 2 is the limiting structure.

[0066] Furthermore, the reinforcing mesh 4 is hooked onto the anchor bar 2, so that the connection point between the short rod 3 and the anchor bar 2 is in contact with the node of the reinforcing mesh 4. This method brings the node of the reinforcing mesh 4 as close as possible to the connection point between the short rod 3 and the anchor bar 2, which facilitates the sprayed UHPC passing through the mesh of the reinforcing mesh 4, reduces obstruction to the sprayed UHPC, and improves the spraying effect.

[0067] In other embodiments of this application, the method of spraying UHPC onto the surface to be reinforced using a spray pipe in step S2 above has been optimized. UHPC is sprayed onto the surface to be reinforced, and the length of the exposed portion of the anchor bar 2 is observed. When the distance along the length of the anchor bar 2 between the outer surface of the sprayed UHPC and the connection point between the short rod 3 and the anchor bar 2 is exactly equal to the thickness of the steel mesh 4 to be hooked, spraying is stopped. At this point, the thickness of the UHPC sprayed onto the surface to be reinforced is the set thickness. Figure 4 As shown, in this embodiment, to avoid the reinforcing mesh 4 becoming indistinguishable from the initially sprayed UHPC, an additional... Figure 4 In the process, there is a gap between the two. In actual operation, there is no gap between the steel mesh 4 and the initial reinforcement layer A formed by the initial spraying of UHPC. Similarly, there is no gap between the steel mesh 4 and the short rod 3.

[0068] The reinforcing mesh 4 is positioned precisely between the short rod 3 and the initial sprayed UHPC. This ensures that the reinforcing mesh 4 is properly positioned between the two, preventing the subsequent second spraying from altering its position along the length of the anchor bar 2. This guarantees that the reinforcing mesh 4 remains in the correct position, thus ensuring the strength of the constructed reinforcement layer structure.

[0069] In some embodiments of this application, the method of installing the injection pipe in step S2 above has been optimized, specifically, as follows: Figure 7As shown, this embodiment employs a special spray pipe for UHPC spraying. The spray pipe 1 includes a nozzle 11, which is the end portion for spraying UHPC. The nozzle 11 is a hollow pipe structure, and a quick-setting agent inlet pipe 12 is installed on the nozzle 11 to inject quick-setting agent into the UHPC inside the nozzle 11. The inlet end of the nozzle 11 is connected to a hydrocyclone 13, and a compressed air inlet pipe 14 is installed on the hydrocyclone 13. By injecting compressed air into the hydrocyclone 13, the flow velocity of UHPC in the spray pipe 11 is increased, enhancing the spraying effect and avoiding pipe blockage. A first reducer 15, a second reducer 16, and a third reducer 17 with progressively increasing diameters are arranged on one side of the inlet end of the hydrocyclone 13. The small end of the first reducer 15 is connected to the hydrocyclone 13. The large end of the first reducer 15 and the small end of the second reducer 16 are connected by a spray pipe 18. The large end of the second reducer 16 is connected to the small end of the third reducer 17. The inlet end of the third reducer 17 is connected to the UHPC supply device through a straight pipe 18.

[0070] Adjacent pipes are connected by pipe clamps and rubber rings, allowing for disassembly and installation as needed, thus enabling modification of the spray pipes according to the actual spraying range. In use, UHPC enters from the straight pipe 19 into the third reducer 17, then sequentially through the second reducer 16, the spray pipe 18, and the first reducer 15 before entering the hydrocyclone 13. Compressed air is injected into the hydrocyclone 13 to mix with the UHPC and drive it into the nozzle 11. The accelerator enters the nozzle 11 through the accelerator inlet pipe 12 and mixes evenly with the UHPC before being sprayed onto the surface to be reinforced.

[0071] In this embodiment, the hydrocyclone is a bent pipe structure. The angle between the axis of the nozzle 11 on the outlet side of the hydrocyclone 13 and the axis of the first reducing pipe 15 on the inlet side of the hydrocyclone 13 is within the range of 100° to 150°. The purpose of this arrangement is to enable the UHPC to flow at the set angle and avoid pipe blockage.

[0072] The specific spraying method is as follows: after the spray pipe 1 is assembled, the outlet end of the nozzle 11 of the spray pipe 1 is facing the surface to be reinforced, so that the angle between the spraying direction of the nozzle 11 of the spray pipe 1 and the surface to be reinforced is 75-105°, the distance between the nozzle 11 and the surface to be reinforced is 0.6-1.2m, and the speed of the UHPC sprayed by the nozzle is controlled to be 15-45m / s.

[0073] By optimizing the spraying angle, spraying distance, and spraying speed of UHPC, the sprayed UHPC has a certain impact force, which can adhere closely to the surface to be reinforced. This allows the fine UHPC slurry to penetrate into the micropores of the structure, ensuring the interfacial bonding performance between the UHPC used for reinforcement and the existing structure. Shallow roughening or no roughening is sufficient to meet the stress requirements, minimizing the damage to the existing structure and the amount of roughening work.

[0074] In a preferred embodiment of this application, the UHPC used in this embodiment is an optimized formulation based on existing UHPC. Specifically, the UHPC in this embodiment includes cement, silica fume, cenospheres, stone powder, microfiber steel fibers, and a thixotropic agent. The cement is high-belite silicate cement with a strength of not less than 42.5; the silica fume has a SiO2 content greater than 90% and a specific surface area greater than 20,000 m². 2 / kg; the average particle size of the cenospheres is 1-5 μm, and the specific surface area is greater than 2500 m² / kg. 2 / kg; the CaCO3 content of the stone powder is greater than 95%, and the average particle size is not greater than 80nm; the thixotropic agent includes attapulgite; attapulgite is a gel powder with an average particle size of 5-15μm.

[0075] The specific configurations are shown in Table 1:

[0076] Table 1: Proportioning of UHPC Sprayed Material

[0077]

[0078] The injection performance is shown in Table 2:

[0079] Table 2: Performance Comparison of Sprayed UHPC under Casting and Spraying Conditions

[0080]

[0081] Compared with existing cast-in-place molding, the spraying process of this application can increase the compressive strength of UHPC by 10.6%–13.6%, the flexural strength by 16.6%–17.9%, and the axial tensile strength by 8.9%–14.3%. The thickness of a single spraying reaches 23 cm, with a horizontal rebound rate of <5%, and no flow or overall detachment. The reinforcement layer can effectively restrain the development and extension of cracks, increasing the cracking load of reinforced beams by 28%–54% and the failure load by 34%–41%, and the failure load of reinforced columns by 63%. Compared with the process of directly spraying to a specified thickness in a single application, the cracking load of reinforced beams using the optimized process is increased by about 20%, and the failure load is increased by 1.5%, which is of great significance for improving the durability during the operational period.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for reinforcing existing structures using sprayed UHPC, characterized in that: Follow these steps: S1. Clean the surface of the existing structure to be reinforced, and insert anchor bars with hook structure into the cleaned surface to be reinforced. S2. Install the spray pipe and spray UHPC onto the surface to be reinforced using the spray pipe. Stop spraying once the sprayed UHPC reaches the set thickness. S3. Make a steel mesh, hang the steel mesh on the anchor bars, and fix the steel mesh by hook structure; S4. Spray UHPC onto the surface to be reinforced again until the required thickness is achieved; S5. Proceed with steps S2 to S4 in sequence until the surface to be reinforced is completed. Repair the surface to be reinforced and perform maintenance to complete the reinforcement of the existing structure. In step S1, the method of inserting anchor bars with hook structures into the cleaned surface to be reinforced includes: inserting anchor bars into the cleaned surface to be reinforced, wherein the hook structure includes at least one short rod; the short rod is installed on the part of the anchor bar that protrudes from the surface to be reinforced, wherein when the surface to be reinforced is a vertical end face, the short rod is located at the upper end of the anchor bar and the angle between the short rod and the anchor bar is not greater than 90°, and when the surface to be reinforced is a horizontal end face, the angle between the short rod and the anchor bar is 90°; In step S2, the method of installing the injection pipe includes: installing a quick-setting agent inlet pipe on the nozzle, connecting the inlet end of the nozzle to a hydrocyclone, installing a compressed air inlet pipe on the hydrocyclone, arranging a first reducer pipe, a second reducer pipe, and a third reducer pipe with progressively larger diameters on one side of the hydrocyclone inlet end, connecting the small end of the first reducer pipe to the hydrocyclone, connecting the large end of the first reducer pipe to the small end of the second reducer pipe through a grouting pipe, connecting the large end of the second reducer pipe to the small end of the third reducer pipe, and connecting the inlet end of the third reducer pipe to the UHPC supply device through a straight pipe; The UHPC sprayed to the surface to be reinforced in the step S2 comprises cement, silica fume, floating bead, stone powder, micro steel fiber and thixotropic agent, the cement is high belite Portland cement with strength not less than 42.5 grade; the silica fume has SiO2 content greater than 90%, specific surface area greater than 20000 m 2 / kg; the floating bead has average particle size of 1-5 μm, specific surface area greater than 2500 m 2 / kg; the stone powder has CaCO3 content greater than 95%, average particle size not greater than 80 nm; the thixotropic agent comprises attapulgite; the attapulgite is gel powder with average particle size of 5-15 μm; In step S3, the method of hanging the steel mesh on the anchor bar includes: hooking the steel mesh onto the anchor bar so that the short rod and the steel mesh bars are hooked together along the length of the anchor bar.

2. The method for reinforcing existing structures using sprayed UHPC as described in claim 1, characterized in that: Hook the steel mesh onto the anchor bar so that the connection point between the short rod and the anchor bar is in contact with the node of the steel mesh.

3. A method for reinforcing existing structures using sprayed UHPC as described in any one of claims 1 to 2, characterized in that: In step S2, the method of spraying UHPC onto the surface to be reinforced using a spray pipe includes: spraying UHPC onto the surface to be reinforced, observing the length of the exposed portion of the anchor bar, and stopping the spraying when the distance between the outer surface of the sprayed UHPC and the connection point between the short rod and the anchor bar along the length of the anchor bar is just equal to the thickness of the steel mesh to be hooked. At this time, the thickness of the UHPC sprayed on the surface to be reinforced is the set thickness.

4. The method for reinforcing existing structures using sprayed UHPC as described in claim 1, characterized in that: The hydrocyclone has a bent pipe structure, and the angle between the axis of the nozzle on the outlet side of the hydrocyclone and the axis of the first variable diameter pipe on the inlet side of the hydrocyclone is in the range of 100~150°.

5. A method for reinforcing existing structures using sprayed UHPC as described in claim 1 or 4, characterized in that: After the spray pipe is assembled, position the nozzle outlet end of the spray pipe facing the surface to be reinforced, so that the angle between the spray direction of the nozzle and the surface to be reinforced is 75~105°, the distance between the nozzle and the surface to be reinforced is 0.6~1.2m, and control the speed of the UHPC sprayed by the nozzle to be 15~45m / s.

6. The method for reinforcing existing structures using sprayed UHPC as described in claim 1, characterized in that: In step S1, the method for cleaning the surface of the existing structure to be reinforced includes: roughening the surface to be reinforced until the aggregate is exposed, rinsing the surface to be reinforced with clean pressurized water or compressed air to remove loose aggregate, slag and powder from the surface to be reinforced.

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