Precast concrete member crack repairing method

Abstract

The invention discloses a precast concrete member crack repairing method, and relates to a precast concrete member repairing technology. Comprising the following steps: acquiring crack characteristics, planning grouting hole sites, performing drilling operation according to marked hole sites, performing crack cleaning, performing grouting and bubble removal operation in a vacuum environment, conveying a repaired component into a dry maintenance area, and maintaining. According to the method, a three-dimensional model in the fracture is reconstructed through data acquired by a detection instrument, accurate diagnosis of the shape, depth and internal cavity of the fracture is realized, and the hole position and the grouting sequence are planned accordingly, so that the fracture is fully filled; and meanwhile, pre-vacuumizing and a vacuum negative-pressure environment are adopted, so that gas and moisture in the slurry are discharged, and high compactness of a restoration body is ensured, so that the mechanical property of a restoration area is remarkably improved, the time required by subsequent maintenance is shortened, and the restoration efficiency is improved.

Description

Technical Field

[0001] This invention relates to the repair technology of precast concrete components, specifically a method for repairing cracks in precast concrete components. Background Technology

[0002] Precast concrete components are prone to cracking during manufacturing, transportation, or installation due to factors such as temperature stress, drying shrinkage, or external loads. These cracks not only affect the appearance of the components but, more importantly, reduce their load-bearing capacity, durability, and impermeability, posing a potential threat to structural safety.

[0003] Existing common repair methods include pressure grouting, which involves injecting prepared grout under high or low pressure. However, air and moisture in the grout cannot be effectively expelled, easily forming air bubbles and cavities within the cracks, resulting in an insufficiently dense repair structure and affecting the repair effect. Furthermore, the inability to expel moisture leads to a long subsequent drying and curing period, thus affecting the product delivery speed. To address this, we provide a method for repairing cracks in precast concrete components. Summary of the Invention

[0004] The purpose of this invention is to provide a method for repairing cracks in precast concrete components.

[0005] The technical problem solved by this invention is: (1) The existing pressure grouting method cannot effectively remove air and moisture from the grout, resulting in air bubbles and cavities in the crack after repair, and the repair body is not dense; (2) Residual moisture after repair leads to a long drying and maintenance period, which affects the repair efficiency.

[0006] This invention can be achieved through the following technical solution: a method for repairing cracks in precast concrete components, the method comprising the following steps: Step 1: Obtain fracture characteristics and plan grouting hole locations. An industrial vision camera is used to acquire images of cracks on the surface of the component, and an ultrasonic detector is used to acquire a three-dimensional model of the inside of the crack. Based on the model, the locations of grouting points and vacuum venting holes are determined. Step 2: Drill holes according to the marked hole positions and clean the cracks. Drill holes at the grouting point and vacuum venting hole, clean the surface and interior of the crack, cover with a sealing film and install the grouting interface and vacuum venting interface. Step 3: Perform grouting and defoaming operations in a vacuum environment. First, a vacuum is drawn to create negative pressure. Then, grout is injected in order from deep to shallow, using the negative pressure to expel air bubbles and moisture. Finally, high-pressure holding and curing are carried out. Step 4: Transfer the repaired components to the drying and curing area for further curing. The hot air blowing and spraying operations are alternated by a liftable curing hood to accelerate the curing of the slurry and its bonding with the components.

[0007] A further technical improvement of the present invention is that: the grouting points in step one include key grouting points and auxiliary grouting points: Key points for grouting include the center point of the cavity inside the fracture, the intersection of the fracture, and the projection point of the deepest point of the fracture onto the surface where the fracture is located. Grouting auxiliary points are grouting points that are manually added at fixed intervals; The vacuum vent is located at the projection point of the crack end on the surface where the crack is located.

[0008] A further technical improvement of the present invention is that, in step one, when the determined hole spacing is less than a set threshold, the holes are retained according to the priority of vacuum exhaust hole > grouting point corresponding to cavity > deepest point of crack > intersection point of crack.

[0009] A further technical improvement of the present invention is as follows: In step two, all drilled holes must be connected to the bottom of the fissure, and compressed air guns are used to blow air into the fissure from the vacuum exhaust port to clean the impurities inside the fissure. Then, multiple layers of transparent plastic film are covered and sealed, and sealing gaskets and glass glue are set at the grouting interface and vacuum extraction interface through the film for secondary sealing. The vacuum pumping interface mentioned in step two is connected to the vacuum pump through a transparent pipe, and the pipe is equipped with a polytetrafluoroethylene microporous membrane as a selective permeation membrane.

[0010] A further technical improvement of the present invention is as follows: In step three, the negative pressure environment of the pre-vacuum operation is maintained at -0.08MPa ~ -0.1MPa for 5 to 10 minutes; the low-pressure grouting pressure is 0.2 to 0.3MPa and the flow rate is 20 to 50 ml / min; the high-pressure holding pressure is 0.4 to 0.5MPa and the holding time is 15 to 20 minutes.

[0011] A further technical improvement of the present invention is that, in step three, the timing for transitioning from the sequential grouting stage to the pressure-holding and curing stage is as follows: when pure, bubble-free grout appears stably in the transparent connecting pipe connected to the vacuum exhaust port, it indicates that the crack filling is complete, and the stable appearance of pure, bubble-free grout means that the grout level in the transparent connecting pipe does not fluctuate.

[0012] A further technical improvement of the present invention is that the method is based on a repair track system, which includes a flaw detection zone, a crack pretreatment zone, a gap filling grouting zone and a drying curing zone arranged in sequence. Each zone is equipped with corresponding execution equipment. The precast concrete components are transported by a carrier vehicle and precisely positioned in each zone to complete the corresponding process. The equipment includes industrial vision cameras, ultrasonic detectors, drilling equipment, grouting equipment, vacuum pumps, liftable curing hoods, and spraying and heating devices inside them.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a combination of industrial vision and ultrasonic detection to reconstruct a three-dimensional model of the inside of the crack, enabling accurate diagnosis of the crack's morphology, depth, and internal cavity. Subsequently, based on the model, the location of the grouting holes and the venting holes, as well as the grouting sequence, are planned, achieving precise grouting from the deepest point upwards, ensuring that the crack is completely and uniformly filled with grout.

[0014] 2. This invention creates ideal conditions for the expansion, rising, and rupture of air bubbles in the grout by pre-vacuuming and grouting under vacuum negative pressure, and effectively removes them through a vacuum system. Combined with the subsequent high-pressure holding process, this greatly reduces air bubbles and defects within the repair body, ensuring high density of the repair body and thus significantly improving the mechanical properties of the repaired area.

[0015] 3. The pre-vacuuming process in this invention removes most of the air and moisture in the cracks. The negative pressure environment also promotes the precipitation and extraction of moisture during the grouting process, which greatly reduces the amount of moisture that needs to be removed in the subsequent curing stage. Combined with active hot air drying and spray curing in the curing area, a fast and efficient curing mechanism is formed, which greatly shortens the time of the entire repair process and improves the repair efficiency. Attached Figure Description

[0016] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the method execution flow of the present invention; Figure 2 This is a schematic diagram of the repair track system of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0019] Please see Figure 1-2As shown, a method for repairing cracks in precast concrete components is implemented based on a streamlined repair track system. This repair track system includes four areas: a data acquisition and inspection area, a crack pretreatment area, a grouting area, and a drying and curing area. Each area of ​​the repair track system is equipped with corresponding facilities. Specifically, data acquisition equipment, including an industrial vision camera and an ultrasonic detector, is installed in the data acquisition and inspection area; a three-axis drilling device is installed in the crack pretreatment area; a vacuum generator (such as a vacuum pump) and grouting equipment are installed in the grouting area; in the drying and curing area, multiple tracks are arranged side by side and can branch off from the main track. In addition, a liftable curing hood is installed in the curing area, which is equipped with electric heating fans and spray facilities to accelerate the drying of moisture and the overall curing process. The repair track system is equipped with a carrier vehicle that can move on the track. Precast concrete components (precast concrete slabs are used in this embodiment) are loaded on the carrier vehicle for transportation and positioned in various areas, and the repair process is carried out in real time in the corresponding areas.

[0020] The entire crack repair method includes the following steps: Step 1: Obtain fracture characteristics and plan grouting hole locations. An industrial vision camera is used to acquire images of the surface of a concrete component with cracks, and to determine the shape and direction of the cracks on the corresponding surface. According to the shape and orientation of the corresponding crack, the probes of the ultrasonic detector are deployed at the corresponding positions. The probes are deployed in an array. The echo time and amplitude of the sound waves excited at different angles are collected by the probes to obtain the reflection intensity of the sound waves at the reflection point. Points with different brightness intensities are marked to obtain multiple two-dimensional point sets of different cross sections. The three-dimensional model of the internal region of the crack is obtained by fitting the model using the interpolation method. Based on the three-dimensional model, the morphology, depth, and internal cavity state of the crack can be accurately determined in three-dimensional space; Prioritize marking the locations with internal cavities and fissures, with the deepest point of the fissure as the key grouting locations, and use the projection points of the cavity center point, fissure intersection point, and the deepest point of the fissure onto the surface as the key grouting points. The projection point on the surface at the end of the fissure serves as the vacuum vent. Since drilling is required at the above points, the minimum distance between adjacent holes is limited. If two holes are less than the specified distance, one of the holes is retained. The priority principle for retention is: The projection point of the vacuum exhaust hole is retained according to the priority of the grouting key point corresponding to the cavity position > the grouting key point corresponding to the deepest point of the crack > the grouting key point corresponding to the intersection of the crack. Subsequently, along the direction of the crack and the distribution of key grouting points, auxiliary grouting points were manually marked at regular intervals to avoid situations where the distance between two grouting points was too long, resulting in poor grout flow and incomplete pouring.

[0021] Step 2: Drill holes according to the marked hole positions and clean the cracks. The precast concrete slabs marked at the locations are moved to the crack pretreatment area using a carrier vehicle. Then, drilling equipment is used to drill holes at the corresponding locations. The depth of the drilled holes is generally 2 / 3 of the thickness of the precast concrete slab. It should be noted that all grouting holes and vacuum venting holes must be connected to the bottom of the crack.

[0022] After drilling the hole, use an angle grinder to clean the surface on both sides of the crack direction with a certain width to make the surface flat, and at the same time grind the corners on the same cross section smooth. Then, compressed air guns are used to blow air into the cracks through the vacuum exhaust port, causing the dust, scum, and loose particles inside to escape from the cracks under the impact of the airflow. After cleaning, multiple layers of transparent plastic film are rolled up and covered on both sides of the crack to seal the space where the crack is located. The transparent plastic film is then pierced at the corresponding hole position, and the grouting interface and vacuum extraction interface are installed and fixed. Sealing gaskets are placed at the interface positions and secondary sealing is performed with glass glue to ensure that each interface is firmly sealed to the hole wall. Both the grouting interface and the vacuum extraction interface are connected to control valves. The vacuum extraction interface is connected to a vacuum pump through a transparent pipe. A selective permeation membrane is installed in the transparent pipe to separate water vapor and air bubbles in the grout and prevent the grout from contaminating the vacuum pump. Specifically, the selective permeation membrane is a polytetrafluoroethylene microporous membrane.

[0023] Step 3: Perform grouting and defoaming operations in a vacuum environment. S31. Connect the vacuum pump to the vacuum pumping port and start the vacuum pump to perform a pre-vacuuming operation: In this state, close the grouting interface, start the vacuum pump, and perform a vacuuming operation on the constructed crack-sealed space. Maintain the vacuum for 5 to 10 minutes, keeping the negative pressure environment between -0.08 MPa and -0.1 MPa, to extract as much air and moisture as possible from the cracks and grouting channels.

[0024] S32. Based on the three-dimensional model, mark the grouting sequence according to the depth position of the crack in the vertical direction of the grouting port, that is, start grouting from the grouting port corresponding to the deepest part of the crack, and grout in sequence as the depth becomes shallower; open the vacuum pumping valve of the corresponding area during grouting, and the grout flows rapidly into the depth of the crack under the combined action of the positive pressure of grouting and the negative pressure of vacuum. S33. Since any stirred slurry will inevitably contain a large number of micro air bubbles, the negative pressure environment in which the air bubbles enter the crack causes the volume of the micro air bubbles in the slurry to expand rapidly, rise and grow larger, and break in the process. The gas escaped from these broken air bubbles is discharged under the action of negative pressure suction. During grouting, air bubbles and excess water in the grout are drawn into the vacuum pipe and discharged into the collection tank under negative pressure. The flow of the grout is observed through a transparent plastic film. When the grout flows to the next grouting port, the flow rate of the previous grouting port is reduced, and the grouting port is opened to continue grouting. When pure, bubble-free grout appears stably in the transparent connecting pipe connected to the vacuum exhaust port at the end of the crack, it indicates that the crack has been basically filled. The grouting operation in the above process is carried out at low pressure and low speed, generally with a positive grouting pressure of 0.2~0.3MPa and a flow rate of 20-50ml / min. S34. Increase the grouting pressure to a high-pressure state (0.4~0.5MPa), while maintaining a low-speed grouting, and maintain positive pressure grouting and vacuum negative pressure for 15~20 minutes to achieve complete filling and pressure-holding curing of the grout in the crack. Under the dual action of positive and negative pressure, the grout further bleeds, shrinks and densifies, ensuring the final strength of the repair.

[0025] S35. After initial curing is completed, turn off the vacuum pump and grouting equipment, and remove the above-mentioned interfaces and sealing plastic film.

[0026] Step 4: Transport the precast concrete with the gaps filled to the dry curing area for curing. Upon entering the drying and curing area, a liftable curing hood is used to cover the inside, and an electric heating fan is activated to blow hot air onto the entire surface of the precast slab to accelerate the evaporation of moisture. Subsequently, through repeated spraying and drying operations, the grout in the crack is completely bonded to the concrete on both sides, thus completing the entire crack repair process. Afterward, an angle grinder is used for appropriate grinding and trimming.

[0027] It should be noted that, for the stability and convenience of the drilling and coating of the transparent film, The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for repairing cracks in precast concrete components, characterized in that, The method includes the following steps: Step 1: Obtain fracture characteristics and plan grouting hole locations. An industrial vision camera is used to acquire images of cracks on the surface of the component, and an ultrasonic detector is used to acquire a three-dimensional model of the inside of the crack. Based on the model, the locations of grouting points and vacuum venting holes are determined. Step 2: Drill holes according to the marked hole positions and clean the cracks. Drill holes at the grouting point and vacuum venting hole, clean the surface and interior of the crack, cover with a sealing film and install the grouting interface and vacuum venting interface. Step 3: Perform grouting and defoaming operations in a vacuum environment. First, a vacuum is drawn to create negative pressure. Then, grout is injected in order from deep to shallow, using the negative pressure to expel air bubbles and moisture. Finally, high-pressure holding and curing are carried out. Step 4: Transfer the repaired components to the drying and curing area for further curing. The hot air blowing and spraying operations are alternated by a liftable curing hood to accelerate the curing of the slurry and its bonding with the components.

2. The method for repairing cracks in precast concrete components according to claim 1, characterized in that, The grouting points mentioned in step one include key grouting points and auxiliary grouting points: Key points for grouting include the center point of the cavity inside the fracture, the intersection of the fracture, and the projection point of the deepest point of the fracture onto the surface where the fracture is located. Grouting auxiliary points are grouting points that are manually added at fixed intervals; The vacuum vent is located at the projection point of the crack end on the surface where the crack is located.

3. The method for repairing cracks in precast concrete components according to claim 2, characterized in that, In step one, when the determined hole spacing is less than the set threshold, the holes are retained according to the priority of vacuum exhaust hole > grouting point corresponding to cavity > deepest point of crack > crack intersection point.

4. The method for repairing cracks in precast concrete components according to claim 1, characterized in that, In step two, all drilled holes must be connected to the bottom of the fissure, and compressed air guns are used to blow air into the fissure from the vacuum exhaust port to clean the impurities inside the fissure. Then, multiple layers of transparent plastic film are covered and sealed, and sealing gaskets and glass glue are installed through the film to install the grouting interface and vacuum extraction interface for secondary sealing. The vacuum pumping interface mentioned in step two is connected to the vacuum pump through a transparent pipe, and the pipe is equipped with a polytetrafluoroethylene microporous membrane as a selective permeation membrane.

5. The method for repairing cracks in precast concrete components according to claim 1, characterized in that, In step three, the negative pressure environment of the pre-vacuum operation is maintained at -0.08MPa ~ -0.1MPa for 5 to 10 minutes; the low-pressure grouting pressure is 0.2 to 0.3MPa and the flow rate is 20 to 50 ml / min; the high-pressure holding pressure is 0.4 to 0.5MPa and the holding time is 15 to 20 minutes.

6. A method for repairing cracks in precast concrete components according to claim 5, characterized in that, In step three, the timing for transitioning from the sequential grouting stage to the pressure-holding and curing stage is as follows: when pure, bubble-free grout appears stably in the transparent connecting pipe connected to the vacuum exhaust port, it indicates that the crack filling is complete, and the stable appearance of pure, bubble-free grout means that the grout level in the transparent connecting pipe does not fluctuate.

7. The method for repairing cracks in precast concrete components according to claim 1, characterized in that, This method is based on a repair track system, which includes a flaw detection zone, a crack pretreatment zone, a gap filling and grouting zone, and a drying and curing zone set up in sequence. Each zone is equipped with corresponding execution equipment. The precast concrete components are transported by a carrier vehicle and precisely positioned in each zone to complete the corresponding process. The equipment includes industrial vision cameras, ultrasonic detectors, drilling equipment, grouting equipment, vacuum pumps, liftable curing hoods, and spraying and heating devices inside them.

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