Prestressed concrete bridge hole grouting simulation test method

Abstract

This invention relates to a simulation test method for grouting of prestressed concrete bridge ducts, characterized by the following specific test steps: S1: Test design; S2: Equipment and material preparation; S3: Test commencement. This method addresses the problem that common duct grouting construction techniques, processes, and requirements cannot meet the needs of new grouting materials and equipment, such as "grouting from the lowest point." Some construction techniques have theoretical flaws, such as "flushing the duct before grouting and blowing away accumulated water with high-pressure air," and some lack reliable theoretical and practical basis. Therefore, it is necessary to study the influencing factors of duct grouting construction techniques based on current grouting materials, summarize the main factors affecting duct grouting quality, and propose an operable grouting process method.

Description

Technical Field

[0001] This invention relates to the field of grouting simulation test of prestressed concrete bridge ducts, and more particularly to a method for grouting simulation test of prestressed concrete bridge ducts. Background Technology

[0002] The quality of prestressed duct grouting plays a crucial role in the durability of prestressed bridges. According to relevant surveys, grouting quality problems can lead to steel strand corrosion, loss of prestress, and a significant reduction in bridge lifespan, sometimes reaching only 10% of the design service life. Therefore, countries worldwide have conducted extensive research on prestressed duct grouting processes, materials, and finished product testing. In recent years, the material properties of duct grouting have been significantly improved, achieving zero bleeding, zero shrinkage, and high durability.

[0003] Although the performance of grouting materials has been greatly improved, and grouting equipment has become increasingly advanced, even reaching the level of intelligence, the construction technology, process, and requirements for duct grouting have remained largely unchanged. Some construction technology requirements are practically impossible to implement on the front lines, such as "grouting from the lowest point." Other requirements are theoretically flawed, such as "flushing the duct before grouting and blowing away accumulated water with high-pressure air." Still others lack reliable theoretical and practical basis. Given these reasons, it is necessary to study the influencing factors of duct grouting construction technology based on current grouting materials, summarize the main reasons affecting duct grouting quality, and propose operable grouting process methods. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a simulation test method for grouting of prestressed concrete bridge ducts, which can solve the problem that the general existing duct grouting construction process is difficult to operate on the construction site.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a simulation test method for grouting of prestressed concrete bridge ducts, the innovation of which is as follows: the specific test is as follows:

[0006] S1: Test Design: Design multiple tests, and the purpose of the test should be included in the design of multiple tests; grouting range, pressure stabilization time, settling time, secondary pressure stabilization time, pressure stabilization pressure, and corresponding parameters of the bleeding channel;

[0007] S2: Equipment and Material Preparation: 1 set of automatic grouting trolley; 1 set of high-power, high-capacity air compressor; 6 sets of transparent 55mm inner diameter pressure-resistant pipes, 25 meters long; 1 set of 55mm inner diameter corrugated pipes, 25 meters long; 8 meters of 25*90 flat corrugated pipes; 18 strands of 25 meters of steel strand; 3 strands of 8 meters of steel strand; test bracket; high-speed grout mixer; electronic scale; 1 set of cement grout testing equipment; 5 2.5L-30L capacity tanks; weights for equipment calibration; cement; grouting agent; epoxy resin mortar;

[0008] S3: Start the test: The laboratory takes raw materials from the site and uses a high-speed mixer to prepare the slurry at the simulated test site according to the construction mix ratio. The performance index of the cement slurry is obtained. All subsequent grouting simulation tests shall be conducted according to this index to eliminate the difference between the test conditions and the actual simulation and construction environment conditions. The cement slurry mix ratio in the simulation test is: cement: grouting agent: water = 1:0.1:0.31. The test shall be conducted in one go according to the test sequence number and settings, and the relevant data shall be recorded.

[0009] Furthermore, the experimental design consisted of six groups of tests; Test 1: Purpose: To simulate the process requirements of simultaneously pressurizing, stabilizing, and sealing the seepage channels; Grouting range: 0.5-0.7 MPa; Stabilization time: 3 min; Settling time: 8 min; Secondary stabilization time: 3 min; Stabilizing pressure: 0.7 MPa; No seepage channels; Test 2: Purpose: To simulate the extremely irresponsible practices of grouting construction personnel, where the pipe is filled with thick grout under natural pressure and grouting is stopped immediately for sealing; Grouting range: 0 MPa; Stabilization time: 0 min; No pressure in the seepage channels; Test 3: Purpose: To simulate the large-circulation grouting process; Grouting range: 0.5-0.7 MPa; Stabilization time: 3 min; Settling time: 8 min; Secondary stabilization time: 3 min; Stabilizing pressure: 0.7 MPa. MPa; No bleeding channel; Test 4: Purpose: The steel strand end of the grout outlet is not sealed, leaving a bleeding channel; Grouting range 0.5-0.7MPa; Pressure stabilization time 3min; Settling time 8min; Secondary pressure stabilization time 3min; Pressure stabilization pressure 0.7 MPa; Bleeding channel reserved at the outlet; Test 5: Purpose: To verify the actual situation of "using compressed air to blow out all the water in the duct" in the bridge code; Test 6: Purpose: To examine the cement grout condition after repeated pressurization and bleeding in the concrete pipe; Grouting range 0.8-1.0MPa; Pressure stabilization time 3min; Settling time 8min; Secondary pressure stabilization time 3min; Pressure stabilization pressure 1 MPa; Bleeding channel present.

[0010] The advantages of this invention are:

[0011] 1) According to the test method in this invention, it can be concluded that regardless of the grouting process used, the pipeline is basically dense and meets the function of protecting the prestressing tendons, provided that the initial index of the cement grout is qualified. When pressurized and stabilized, the quality of the cement grout in the pipeline after solidification is not improved compared with the quality of the cement grout after solidification in the pipeline under normal pressure. In particular, under the premise of pressurization and stabilization but no water seepage channel, the quality of the cement grout before and after solidification is significantly reduced. Therefore, if pressurization and stabilization are necessary, it is very necessary to leave a water seepage channel during grouting.

[0012] 2) In this invention, the water accumulation in the compressed air discharge pipe, as specified in the standard, cannot achieve the expected effect. Therefore, water accumulation in the duct should be avoided as much as possible before grouting. Unless there are special circumstances, it is not advisable to clean the pipe with water before grouting. Taking temporary sealing measures at the pipe ends in advance to prevent foreign objects and curing water from entering the pipe is a worthwhile method to promote. The current low water-cement ratio cement grout pressurization and water seepage poses a significant threat to the cement grout setting quality after grouting. For pipes in special locations, repeated overpressure and pressurization should be explicitly prohibited to prevent the cement grout from "losing water" and failing to set properly. In the process of duct grouting quality management, the quality management of the cement grout is the key to ensuring grouting quality. The grouting process needs to be systematically studied based on the performance of existing grouting materials, pipe type, length, and other factors, and more scientific and feasible regulations should be made. This is another key point in ensuring grouting quality. Attached Figure Description

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0014] Figure 1 This is an experimental design table for a simulated test method of grouting in prestressed concrete bridge ducts according to the present invention;

[0015] Figure 2 This is a schematic diagram of the test specimen for the simulated test method of grouting in the prestressed concrete bridge duct of the present invention.

[0016] Figure 3 This is a schematic diagram of test specimen 3 of the grouting simulation test method for prestressed concrete bridge ducts according to the present invention.

[0017] Figure 4 This is a schematic diagram of test specimen 4 of the prestressed concrete bridge duct grouting simulation test method of the present invention.

[0018] Figure 5 The cement grout performance indicators are simulated in the grouting simulation test method for prestressed concrete bridge ducts according to the present invention.

[0019] Figure 6This is a test record diagram of high-pressure water removal test 5, which is a simulation test method for grouting of prestressed concrete bridge ducts according to the present invention. Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. 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, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] A simulation test method for grouting of prestressed concrete bridge ducts is described below:

[0027] S1: Experimental Design: Design multiple experiments, including the experimental objective; grouting range, stabilization time, settling time, secondary stabilization time, stabilization pressure, and corresponding parameters for the bleeding channels; such as... Figure 1 As shown;

[0028] S2: Equipment and Material Preparation: 1 set of automatic grouting trolley; 1 set of high-power, high-capacity air compressor; 6 sets of transparent 55mm inner diameter pressure-resistant pipes, 25 meters long; 1 set of 55mm inner diameter corrugated pipes, 25 meters long; 8 meters of 25*90 flat corrugated pipes; 18 strands of 25 meters of steel strand; 3 strands of 8 meters of steel strand; test bracket; high-speed grout mixer; electronic scale; 1 set of cement grout testing equipment; 5 2.5L-30L capacity tanks; weights for equipment calibration; cement; grouting agent; epoxy resin mortar;

[0029] S3: Start the test: The laboratory takes raw materials from the site and uses a high-speed mixer to prepare the slurry at the simulated test site according to the construction mix ratio. The performance index of the cement slurry is obtained. All subsequent grouting simulation tests shall be conducted according to this index to eliminate the difference between the test conditions and the actual simulation and construction environment conditions. The cement slurry mix ratio in the simulation test is: cement: grouting agent: water = 1:0.1:0.31. The test shall be conducted in one go according to the test sequence number and settings, and the relevant data shall be recorded.

[0030] Experiment 1:

[0031] A. Take one 25-meter transparent plastic rigid pipe with a pressure resistance of 1 MPa. Arrange it according to the N1 steel strand duct layout for a 25-meter prestressed precast box girder. Secure both ends with unions and anchor plates. Thread three prestressed steel strands through the pipe, and seal the anchor plates at both ends, leaving only the grout inlet and outlet ports open. During the test, grout is introduced through the inlet port, and the valve at the outlet port is opened, allowing grout to enter from only one end. After the grout fills to the outlet port, close the valve and begin pressure stabilization for 3 minutes at a pressure of 0.5 MPa-0.7 MPa. Perform a second pressure stabilization at an interval of 8-10 minutes, stabilizing for 3 minutes at a pressure of 0.5 MPa-0.7 MPa.

[0032] During the experiment, 10 kg of water was injected into the pipe, and then a dye was injected using a syringe to observe the mixing of cement slurry and water.

[0033] B. Open the grout outlet and slowly replenish the grout inlet. Take about 2.5 liters of cement grout from the end of the grout outlet and 10 meters away to conduct a consistency test. Make 3 sets of 40×40×160mm specimens for each test. Then, continue to open the grout outlet and pressurize the grout until the fresh cement grout completely replaces the cement grout that entered the pipe for the first time.

[0034] C. After repeating step A, close the valves at both ends to finish grouting.

[0035] Experiment 2:

[0036] like Figure 2 As shown: Take a 25-meter transparent plastic rigid pipe with a pressure resistance of 1 MPa. Arrange it according to the N1 steel strand duct of a 25-meter prestressed precast box girder. Both ends are fixed to the anchor plates with unions. Thread three prestressed steel strands through it, and seal the anchor plates at both ends, leaving only the grout inlet and outlet ports. During the test, grout is introduced through the inlet port, and the valve at the outlet port is opened. Grout is introduced from one end only. After the grout fills to the outlet port, the valve is closed, and the grouting is completed.

[0037] Experiment 3:

[0038] Take two 25-meter transparent plastic rigid pipes, with a pressure resistance of 1 MPa, and arrange them according to the N1 steel strand duct layout for a 25-meter prestressed precast box girder. Secure both ends to the anchor plates using unions. Thread three prestressed steel strands through the pipes. Connect the grout outlets using high-pressure hoses. Seal all four ends with anchor plates, leaving only openings A and B. Figure 3 As shown; during the test, grout is introduced at end A, and the valve at end B is opened, allowing grout to enter from only one end. After the grout fills to end B, the valve is closed, and pressure stabilization begins. This stabilization lasts for 3 minutes at a pressure of 0.5 MPa-0.7 MPa. A second pressure stabilization is performed every 8-10 minutes for 3 minutes at a pressure of 0.5 MPa-0.7 MPa. Finally, the valves at both ends are closed, and the grouting process is complete.

[0039] Experiment 4:

[0040] Take two 25-meter transparent plastic rigid pipes, with a pressure resistance of 1MPa, and arrange them according to the N1 steel strand duct layout for a 25-meter prestressed precast box girder. Both ends are secured to anchor plates using unions. Thread three prestressed steel strands through the pipes. Connect the grout outlet using a high-pressure hose. At end B, connect the anchor to the anchor plate using four bolts. Secure the prestressed steel strands with clamps and seal the anchors with epoxy mortar. When sealing the anchors, leave the leading edge of the prestressed steel strands exposed above the anchor. Seal the anchor plates at both ends, leaving openings A and B, and the ends of the steel strands as shown. Figure 4As shown. Grout is introduced at end A, and the valve at end B is opened, allowing grout to enter from only one end. Once all water has been drained and the grout level is the same as the grout at the inlet, the valve at end B is closed, and pressure stabilization begins. Stabilize the pressure for 3 minutes at 0.5 MPa-0.7 MPa. Check for water seepage in the steel strands at end B. Perform a second pressure stabilization every 8-10 minutes for 3 minutes at 0.5 MPa-0.7 MPa. Finally, close the valves at both ends; grouting is complete.

[0041] Experiment 5:

[0042] Take a 25-meter corrugated pipe and lay it out according to the N1 steel strand pipeline of a 25-meter prestressed precast box girder. Inject 5 kg and 10 kg of water into the pipe respectively. Use a V1.05 / 12.5 type air compressor with an air storage capacity of 1.05 cubic meters and a rated maximum pressure of 1.25 MPa. Use an air pipe with an outer diameter of 55 mm to tightly connect one end to the corrugated pipe. Close the air compressor outlet valve, start the air compressor and open the valve to inflate when the pressure gauge shows 0.8 MPa. Inflate for 5 minutes. Use a container to collect the water in the pipe blown out by the high-pressure air at the other end of the pipe and weigh it.

[0043] Experiment 6:

[0044] To facilitate inspection by chiseling, this test simulated the negative bending moment duct of a precast box girder. A flat pipe with dimensions of 2×3.5m-25mm*90mm was pre-embedded in the concrete for grouting. This simulated the inspection of the cement grout after two pressurization and stabilization cycles. Considering that in actual construction, the negative bending moment flat pipe has a small pressure area during concrete pouring, and the relatively small cross-sectional area for grouting after the steel strands are tensioned, which could affect grout flow, and that overpressure often occurs during actual grouting, and that the corrugated galvanized steel strip has large gap variations under pressure, theoretically allowing seepage water to intermittently penetrate through the steel strip and be absorbed by the concrete, the pressure control range for the simulation test was 0.8-1.0MPa, with a stabilization pressure controlled at 1.0MPa, and two pressurization and stabilization tests were conducted.

[0045] In summary:

[0046] like Figure 5As shown: Under non-pressurized conditions, the performance indicators of the cement grout at the inlet and outlet of the pipeline are basically the same; however, under pressurized conditions and without leaving a bleeding channel, the performance of the cement grout at the outlet of both single-pipe and double-pipe circulating grouting systems deteriorates significantly, with its consistency changing from 15s at the inlet to 9s. This indicates that the cement grout bleeds under pressure of 0.5-0.7MPa. When there is no bleeding channel, the performance of the cement grout at the end of the pipeline inevitably decreases. That is, under pressure, the cement grout bleeds, and the bleed moves towards the outlet along the pressure direction, causing a change in the water-cement ratio of the cement grout within the channel, resulting in a bleeding rate of approximately 2.2% at the end of the cement grout after 3 hours. Further indoor testing and calculations showed that using this raw material, maintaining the original mix ratio, and adjusting its fluidity using the water addition method until the fluidity reaches 9s, the water-cement ratio of the cement grout is 0.36.

[0047] like Figure 6 The experiment demonstrates a practical verification of the requirement in bridge regulations to "blow out all accumulated water from the ducts using compressed air." The test employed rented high-pressure, continuous air supply equipment. The results show that the requirement to "blow out all accumulated water from the ducts using compressed air" is problematic. Firstly, it's difficult to find such large-scale equipment on construction sites. Secondly, even if such equipment were used, a certain amount of water would inevitably remain in the ducts. The reason is simple: when the water level in the pipe is below a certain point, the water cannot continue to move forward and be discharged when the high-pressure air is blown out and the channels created above the water allow for its passage. Increasing the pressure further did not yield significant results. Analysis of the 3-day flexural and compressive strength results of the cement grout shows that regardless of the grouting method used, the requirements of the "Technical Specification for Construction of Highway Bridges and Culverts" (JTG / T F50-2011) are met. However, under pressure without water seepage channels, the 3-day flexural and compressive strengths decreased to 73% and 87%, respectively.

[0048] In Experiment 1, a certain amount of dyed water was injected into the pipeline. During the grouting process, it was found that due to the low viscosity and good fluidity of the cement grout, the cement grout and water fused quickly. Up to 9.5L of cement grout that was fully fused with water was discharged from the end of the pipeline. Therefore, when using a large circulation grouting method and when there is water accumulation in the pipeline, sufficient attention must be paid, especially the need to clean the pipeline with clean water before grouting. If the substandard grout is not completely removed, grouting quality problems will inevitably occur.

[0049] Experiment 2 simulated the extremely irresponsible practices of grouting construction workers: the pipes were filled with thick grout under natural pressure, and grouting was stopped immediately for sealing. Under natural pressure of 0.1-0.3 MPa, the cement grout filling the pipes did not show any significant abnormalities in filling degree after setting; in fact, the interior of the cement grout appeared denser. Using the original grouting process, the quality of the cement grout in the pipes decreased to varying degrees. Due to limitations of previous technology, water seepage was allowed in cement grout under both normal and pressurized conditions. At that time, pressurization and stabilization could accelerate the occurrence of water seepage and partially alleviate the shrinkage caused by natural water seepage in the later stages of the pipe, leading to the exposure of prestressing tendons at the high points of the pipe ends. This practice was reasonable for the cement grout technical specifications at the time. However, when cement grout specifications are improved, achieving no water seepage and slight expansion under normal pressure, simply increasing and stabilizing pressure seems to lack theoretical basis and may even damage the originally high-quality cement grout.

[0050] Experiment 3 simulated the large-circulation grouting process, and its results were basically the same as those of Experiment 1. However, when the cement grout that had set at the outlet was inspected for damage, it was found that its quality was significantly inferior to that of the imported cement grout.

[0051] In Experiment 4, the steel strand end of the grout outlet was not sealed, leaving a water seepage channel. The results showed that this was better than Experiment 3. Therefore, if pressurized and stable grouting is used, it is necessary to leave a water seepage channel.

[0052] Experiment 6 was a practical verification of the theoretical inference that excessive bleeding of cement grout in a flat pipe located in the top slab area due to overpressure and repeated pressurization could lead to poor cement grout setting quality. This experiment was a simulation of grouting in a concrete pipe on-site. Considering the impact on the structure, only one flat pipe was simulated. After two pressurization and stabilization cycles, the grout was inspected at a distance of 3 meters from the grouting port after a 5-minute interval. At this time, the cement grout had completely lost its plasticity and was dry. The inspection showed that after repeated pressurization and stabilization, some of the bleeding water flowed out from the end, and some intermittently bled out from the steel strip, indicating severe bleeding. Theoretically, cement requires about 24% water to fully hydrate, while the water-cement ratio of the cement grout in the duct grouting is only 0.26-0.28. At this point, the actual excess water in the cement grout is very little. If excessive bleeding occurs due to improper grouting process, it will affect the setting quality of the cement grout in the pipe, and in severe cases, local cement grout may fail to set properly.

[0053] Those skilled in the art should understand that this 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 this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for simulating the grouting of a prestressed concrete bridge duct, characterized in that: The specific experiment is as follows: S1: Test Design: Design multiple tests, and the purpose of the test should be included in the design of multiple tests; grouting range, pressure stabilization time, settling time, secondary pressure stabilization time, pressure stabilization pressure, and corresponding parameters of the bleeding channel; S2: Equipment and Material Preparation: 1 set of automatic grouting trolley; 1 set of high-power, high-capacity air compressor; 6 sets of transparent 55mm inner diameter pressure-resistant pipes, 25 meters long; 1 set of 55mm inner diameter corrugated pipes, 25 meters long; 8 meters of 25*90 flat corrugated pipes; 18 strands of 25 meters of steel strand; 3 strands of 8 meters of steel strand; test bracket; high-speed grout mixer; electronic scale; 1 set of cement grout testing equipment; 5 2.5L-30L capacity tanks; weights for equipment calibration; cement; grouting agent; epoxy resin mortar; S3: Start of Test: The laboratory takes raw materials from the site and prepares the grout using a high-speed mixer at the simulated test site according to the construction mix ratio. The performance indicators of the cement grout are obtained. All subsequent grouting simulation tests shall be conducted according to these indicators to eliminate the differences between the test conditions and the actual simulation and construction environment conditions. The cement grout mix ratio in the simulation test is: cement:grouting agent: water = 1:0.1:0.

31. The test shall be conducted in one go according to the test sequence number and settings, and the relevant data shall be recorded. The experimental design consisted of six groups of experiments; Experiment 1: Objective: To simulate the process requirements of pressurizing, stabilizing, and sealing the bleeding channels simultaneously; Grouting range: 0.5-0.7 MPa; Stabilization time: 3 min; Settling time: 8 min; Secondary stabilization time: 3 min; Stabilizing pressure: 0.7 MPa; No bleeding channels; Experiment 2: Objective: To simulate the extremely irresponsible practices of grouting construction personnel, filling the pipe with thick grout under natural pressure and then stopping grouting to seal it; Grouting range: 0 MPa; Stabilization time: 0 min; No pressure in the bleeding channels; Experiment 3: Objective: To simulate a large-circulation grouting process; grouting range: 0.5-0.7 MPa; pressure stabilization time: 3 min; settling time: 8 min; secondary pressure stabilization time: 3 min; stabilizing pressure: 0.7 MPa; no water seepage channel; Experiment 4: Objective: The steel strand end at the grout outlet is not sealed, leaving a water seepage channel; grouting range: 0.5-0.7 MPa; pressure stabilization time: 3 min; settling time: 8 min; secondary pressure stabilization time: 3 min; stabilizing pressure: 0.7 MPa; water seepage channel reserved at the outlet; Experiment 5: Objective: To verify the actual use of compressed air to blow out all the water in the duct in the bridge code; Test 6: Objective: To test the cement slurry condition after repeated pressurization and water seepage in the concrete pipes; Grouting range: 0.8-1.0 MPa; Pressure stabilization time: 3 min; Standing time: 8 min; Second pressure stabilization time: 3 min; Pressure stabilization pressure: 1 MPa; Water seepage channels are present.

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