Grout filling method

Abstract

To provide a grout filling method capable of allowing grout to pass without problem even when there is a narrow void having a diameter of about 3 mm in a cavity part, and capable of reliably filling all regions in the cavity part with grout.SOLUTION: An injection port 3 is formed in a cavity part 12 in the skeleton of a concrete structure, an exhaust port 4 is formed at a position above the injection port 3, the tip of an injection pipe 5 is connected to the injection port 3, the base end part of the injection pipe 5 is connected to a pump 8 (electric grout pump), and grout is discharged from the pump 8 to fill the grout from the lower side to the upper side of the cavity. When the water powder ratio is 45% or less and low viscosity grout or ultra-low viscosity grout is used and the injection pressure exceeds 0.4 MPa during the injection operation, the output of the pump 8 is adjusted so that the injection rate is 2 L / min or less and the injection pressure is within the range of 0.4-0.8 MPa.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for filling cavities present in a concrete structure with grout, and more particularly to a method for filling cavities including narrow gaps in a sheath through which PC steel members are inserted in an existing post-tensioned prestressed concrete (PC) structure. [Background technology]

[0002] When the framework of a PC structure is constructed using the post-tensioning method, PC grout is injected into the sheath through which the PC steel bars are inserted from a grout hose properly connected to the ends of the sheath, filling the entire space within the sheath without any gaps. However, bleeding of the PC grout filled in the sheath can cause insufficient filling, leaving cavities in the sheath. If such cavities are left unattended, the PC steel bars exposed in the cavities may corrode due to the infiltration of rainwater, etc.

[0003] Therefore, when cavities remain in the sheath, repair work (re-injection of PC grout) is carried out to inject new PC grout into the sheath to fill the cavities in order to suppress corrosion of the PC steel. Various techniques have been proposed as methods for re-injecting PC grout into cavities in the sheath (Patent Documents 1 to 5, etc.).

[0004] For example, Patent Document 1 discloses a method in which multiple holes are formed to access a cavity, and the air inside is sucked out through one of the holes while PC grout is injected through the other hole, while Patent Document 2 discloses a method in which a container containing PC grout is held at a position higher than the cavity, and the PC grout is injected into the cavity by gravity flow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-23567 A [Patent Document 2] JP 2013-249636 A [Patent Document 3] JP 2013-241762 A [Patent Document 4] JP 2013-249637 A [Patent Document 5] JP 2018-105063 A [Patent Document 6] JP 2019-143394 A Summary of the Invention [Problem to be solved by the invention]

[0006] The cavities remaining in the sheath often have a complex appearance and may contain, for example, narrow gaps of about 3 mm in diameter. If such narrow gaps are present in the cavity when re-injecting the PC grout, there is a problem that the injected PC grout will become clogged in the narrow gaps due to the dry-out phenomenon, etc., and will not be able to pass through.

[0007] The present invention is intended to solve the problems associated with the conventional technology as described above, and aims to provide a grout filling method that can pass grout through a cavity without any problems, even when a narrow gap of about 3 mm in diameter is present in the cavity, and can reliably fill the entire area of ​​the cavity with grout. [Means for solving the problem]

[0008] The grout filling method of the present invention involves forming an injection port in a cavity within the framework of a concrete structure and forming a discharge port at a position above the injection port, connecting the tip of an injection pipe to the injection port, connecting the tip of a discharge pipe to the discharge port, connecting the base end of the injection pipe to an electric grout pump, and delivering grout from the electric grout pump to fill the cavity from the lower side to the upper side with grout. The method is characterized in that a low-viscosity or ultra-low-viscosity grout with a water-powder ratio of 45% or less is used, and when the injection pressure exceeds 0.4 MPa during the injection operation, the output of the electric grout pump is adjusted so that the injection rate is 2 L / min or less and the injection pressure is within the range of 0.4 to 0.8 MPa.

[0009] It is preferable to dispose the exhaust thin pipe so that its tip is located at the top of the cavity through the exhaust port, and in this case, when the height of the grout in the cavity exceeds the position of the exhaust port and the grout overflows from the exhaust pipe, it is preferable to temporarily stop the electric grout pump, close the exhaust pipe, and prevent the grout from being discharged from the exhaust pipe, and then resume the injection work to fill the area above the exhaust port with grout. It is also preferable to perform the injection work continuously without interruption from the start of the injection work until the grout is discharged from the exhaust pipe. Effect of the Invention

[0010] The grout filling method of the present invention can pass through narrow gaps of about 3 mm in diameter without any problems even when the cavity to be filled with grout has a cavity, by monitoring the injection pressure, etc. and appropriately adjusting the pump output according to the situation, and can reliably fill the entire area of ​​the cavity with grout. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram of a grout filling method according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of the grout filling method according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing the configuration of a test piece 20 (cross section of a thin tube 21, etc.) used in the "test using a thin tube" carried out by the inventors of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the "grout filling method" according to the present invention will be described with reference to the attached drawings. Fig. 1 is an explanatory diagram of a grout filling method according to a first embodiment of the present invention. Here, as an example of the grout filling method, a method of filling (re-injecting) PC grout into a cavity 12 when a cavity 12 exists inside a sheath 2 for a PC steel member arranged in a skeleton 1 of a PC structure (such as a PC girder of a bridge) due to insufficient filling of the PC grout will be described. Note that in Fig. 1, for convenience, the PC steel member inserted into the sheath 2 is omitted.

[0013] First, a drill (or other means) is used to drill holes from the outer surface (side, bottom, etc.) of the body 1 toward the hollow portion 12 of the sheath 2, and an inlet 3 and an outlet 4 (both of which are holes penetrating the sheath 2) are formed in the sheath 2 inside the body 1. The inlet 3 is formed near the bottom end of the hollow portion 12 (preferably within 1.5 m (e.g. 0.5 m) from the bottom end), and the outlet 4 is set at a position above the inlet 3 near the top end of the hollow portion 12 (preferably within 1.5 m (e.g. 0.5 m) from the top end).

[0014] After drilling, if necessary, a rust inhibitor is injected through the injection port 3 and the discharge port 4. Specifically, the powdered rust inhibitor is injected and pressed into the cavity 12 from the injection port 3 (or the discharge port 4) at a pressure of 0.15 MPa or more, and is then pumped through the cavity 12. In this case, the rust inhibitor can be delivered to a range of about 1.5 m from the injection port 3 (or the discharge port 4), and the rust inhibitor can be attached to the surface of the PC steel material exposed in the cavity 12.

[0015] Next, an injection pipe 5 (grout hose) is connected to the injection port 3, and a discharge pipe 6 (grout hose) is connected to the discharge port 4. The injection port 3 and the injection pipe 5 can be connected, for example, by the following method. First, as shown in FIG. 2, the tip of the connection pipe 15 (aluminum pipe) is inserted into a drilled hole 18 formed from the outer surface of the skeleton 1 toward the injection port 3, and the gap between the opening of the drilled hole 18 and the outer circumferential surface of the connection pipe 15 is filled with a putty material 17 (resin putty, etc.) to fix the connection pipe 15. Next, the injection pipe 5 is attached to the base end of the connection pipe 15 protruding outward from the drilled hole 18, and fixed with a hose band 16. The discharge port 4 and the discharge pipe 6 can be connected in the same manner. In addition, an exhaust thin pipe 7 is arranged in the discharge port 4. Specifically, as shown in FIG. 1, the tip of the pipe is arranged so as to pass through the discharge port 4 and be positioned at the top of the cavity 12 (in the example of FIG. 1, near the fixing part 11 of the PC steel). Then, air is fed into either the injection pipe 5 or the discharge pipe 6 to confirm that air can be circulated between the injection port 3 and the discharge port 4.

[0016] It is preferable that the injection tube 5 and the exhaust tube 6 have an inner diameter of 12 to 25 mm (19 mm in this embodiment), and the exhaust thin tube 7 has an inner diameter of 4 to 6 mm (4 mm in this embodiment).

[0017] The base end of the injection pipe 5 is connected to a pump 8 (electric grout pump), and a flow meter 9 is placed in the middle of the injection pipe 5 (between the pump 8 and the structure 1). Cocks 10 are placed between the pump 8 and the flow meter 9, and between the flow meter 9 and the structure 1. The pump 8 used should be one that does not generate pulsation and whose discharge speed can be adjusted. The flow meter 9 used should be one that can measure speed (flow rate) and pressure.

[0018] Next, a low-viscosity or ultra-low-viscosity grout with a water-powder ratio of 45% or less is prepared and fed into the pump 8. Note that "low-viscosity grout" means grout whose rheology test value (JSCE-F531 / JP funnel flow time) in accordance with the standards of the Japan Society of Civil Engineers (Japan Society of Civil Engineers, a public interest incorporated association) is in the range of 6 to 14 seconds, and "ultra-low-viscosity grout" means grout whose value is in the range of 3.5 to 6 seconds.

[0019] Then, when the cock 10 is opened and the pump 8 is operated, the grout is sent from the pump 8 through the injection pipe 5 toward the sheath 2 and injected (pressed) into the cavity 12 through the injection port 3. When this injection operation is continued, the grout is filled from the lower side (the area near the injection port 3) to the upper side in the cavity 12, and in response, the air in the cavity 12 is sequentially discharged to the outside through the discharge pipe 6 and the exhaust thin pipe 7.

[0020] As the injection operation progresses, when the height of the grout in the cavity 12 exceeds the position of the discharge port 4, the grout flows into the discharge pipe 6. When the grout subsequently overflows from the discharge pipe 6, the cock 10 is closed, the pump 8 is temporarily stopped, and the injection operation is interrupted. Note that, by the fact that the grout has been discharged from the discharge pipe 6, it can be confirmed that the cavity 12 has been completely filled with grout from the area near the injection port 3 to the area near the discharge port 4.

[0021] Next, the exhaust pipe 6 is closed so that no grout is discharged from the exhaust pipe 6, and then the injection work is resumed to fill the remaining area (the area above the exhaust port 4 in the cavity 12) with grout. At this time, the remaining air in the cavity 12 is sequentially discharged to the outside from the exhaust pipe 7. Then, once the grout has been discharged from the exhaust pipe 7, the exhaust pipe 7 is closed so that no grout is discharged. Note that, by discharging the grout from the exhaust pipe 7, it can be confirmed that the entire area in the cavity 12 has been reliably filled with grout. Then, the cock 10 is closed, and the pump 8 is stopped (injection work completion).

[0022] During the injection work, the injection pressure, injection speed, and injection amount (accumulated amount) of the grout are monitored by the flow meter 9, and the output of the pump 8 is adjusted so that the injection pressure does not exceed 0.8 MPa from the start to the end of the injection work. If the injection pressure exceeds 0.4 MPa during the injection work, the output of the pump 8 is adjusted so that the injection speed is 2 L / min or less and the injection pressure is within the range of 0.4 to 0.8 MPa. After the start of the injection work, the injection work is performed continuously without interruption until the grout is discharged from the discharge pipe 6.

[0023] In addition, when there is no narrow gap in the region between the injection port 3 and the discharge port 4 (the space in the sheath 2), the monitoring of the injection pressure and the adjustment of the output of the pump 8 as described above are not necessarily required, but it is difficult to know in advance whether a narrow gap exists. In addition, when a narrow gap with a diameter of about 3 mm exists in the region between the injection port 3 and the discharge port 4, it is difficult to make the grout flow into and pass through such a narrow gap by the conventional method. In the grout filling method according to the present invention, by monitoring the injection pressure and the like and appropriately adjusting the output of the pump 8 according to the situation, even if a narrow gap exists, it is possible to pass through them without any problem, and the entire region of the cavity 12 can be reliably filled with grout.

[0024] To explain this in more detail, the inventors of the present invention have found that when low-viscosity or ultra-low-viscosity grout with a water-powder ratio of 45% or less is continuously supplied by an electric pump 8 (electric grout pump) to be forced into a narrow gap with a diameter of about 3 mm, the injection pressure exceeds 0.4 MPa. Therefore, if the injection pressure exceeds 0.4 MPa during the injection work, it can be determined that a narrow gap with a diameter of about 3 mm exists in the region between the injection port 3 and the discharge port 4, and by monitoring the injection pressure, it is possible to grasp the timing when the grout injected into the sheath 2 starts to flow into the narrow gap with a diameter of about 3 mm.

[0025] In addition, when low viscosity or ultra-low viscosity grout with a water-powder ratio of 45% or less is injected into narrow gaps in an absolutely dry state with a diameter of approximately 3 mm, if the injection pressure is less than 0.4 MPa, it becomes difficult to pass the grout through the narrow gap due to insufficient pressure, and it has been confirmed that if the injection pressure is more than 0.8 MPa, blockages may occur, making it difficult to pass through the narrow gap.

[0026] According to the grout filling method of the present invention, even if narrow gaps of about 3 mm in diameter are present in the hollow portion 12 of the sheath 2 to be filled, the grout can pass through the narrow gap without any problems by adjusting the pump 8 so that the injection pressure is within the range of 0.4 to 0.8 MPa at the time when the grout begins to flow into the narrow gap, and the grout can be reliably filled into the entire area of ​​the hollow portion 12.

[0027] It has been confirmed that the injection pressure can be controlled to 0.8 MPa or less by adjusting the pump 8 so that the injection rate is 2 L / min or less. Therefore, if the injection pressure exceeds 0.4 MPa during injection work, the effect of passing through narrow gaps and reliably filling the grout can be expected by adjusting the injection rate to 2 L / min or less.

[0028] Such adjustment of the pump 8 can be performed by an operator visually checking the flow meter 9 and manually operating the pump 8, or the flow meter 9 can output signals of the measurement values ​​of the injection pressure and injection rate, which can be processed by a control means (computer) and the pump 8 can be automatically controlled based on the measurement values.

[0029] Here, as an embodiment of the present invention, a method for reinjecting PC grout into the inside of the sheath 2 for PC steel placed within the body 1 of a PC structure has been described. However, the application of the present invention is not limited to PC structures, and it can also be applied to cases where grout is filled into cavities present within the body of concrete structures other than PC structures. EXAMPLES

[0030] Here, the results of an experiment conducted by the inventors to confirm the effect of the "grout filling method" according to the present invention will be described as an example. First, a number of test specimens 20 were prepared that reproduced "cavities including narrow gaps" that may exist in the sheath for PC steel of a PC structure (see FIG. 2). These test specimens 20 were made by connecting two transparent pipes 22, 23 (length 1000 mm, inner diameter 13 mm) to both longitudinal sides of a small diameter pipe 21 (length 2000 mm) with a continuous narrow gap 26 (diameter 3 mm) formed inside (total length 4000 mm), and were used while fixed in a state inclined at 30° as shown in FIG. 2.

[0031] The small diameter tube 21 was produced by inserting a 3 mm diameter core (inner core) into the inside of a metal pipe with an outer diameter of 19 mm, holding it in the center, injecting PC grout into the pipe, and then removing the core after it hardened, thereby forming a grout section 25 (in an absolute dry state) and a narrow gap 26 with a diameter of 3 mm inside the metal pipe 24, as shown in Figure 2.

[0032] In addition, two types of PC grout, α and β, were prepared with the compositions shown in the table below. [Table 1]

[0033] A pump 8 and a flow meter 9 were then connected to the lower end of the test specimen 20, and a test (a test using a thin pipe) was conducted in which the PC grout α or β was injected from the lower side to the upper side of the test specimen 20. Note that during the test, the injection method and other conditions were appropriately changed for each test specimen 20. The results of the test using the thin pipe are shown below.

[0034] [Table 2]

[0035] Regarding test specimens 20a to 20c The PC grout α was continuously injected using an electric pump 8 (electric grout pump), and the output of the pump 8 was adjusted so that the injection pressure did not exceed 0.8 MPa. Specifically, the output of the pump 8 was adjusted so that the injection rate of the PC grout was about 2 to 5 L / min, and the injection work was started. After the injection work started, the injection pressure was measured before the PC grout reached the thin pipe 21. In all of the test specimens 20a to 20c, the injection pressure was 0.4 MPa or less, but after the PC grout began to flow into the thin pipe 21, it exceeded 0.4 MPa. After that, the output of the pump 8 was adjusted so that the injection rate was 2 L / min or less.

[0036] As a result, in all of the test specimens 20a to 20c, the PC grout passed through the thin pipe 21 and flowed out to the transparent pipe 23 above. The injection pressure of the PC grout during passage through the thin pipe 21 (from the start of flow into the thin pipe 21 to the flow out to the transparent pipe 23) was in the range of 0.4 to 0.8 MPa. This confirmed that in order to inject low-viscosity PC grout α into the narrow gap 26 in an absolute dry state with a diameter of 3 mm and pass it through without any problems, it is effective to adjust the output of the pump 8 so that the injection pressure is in the range of 0.4 to 0.8 MPa, and to adjust the output of the pump 8 so that the injection rate is 2 L / min or less after the injection pressure exceeds 0.4 MPa.

[0037] Regarding test specimens 20d to 20f The PC grout β was continuously injected using an electric pump 8 (electric grout pump), and the output of the pump 8 was adjusted so that the injection pressure did not exceed 0.8 MPa. Specifically, the output of the pump 8 was adjusted so that the injection rate of the PC grout was about 2 to 5 L / min, and the injection work was started. After the injection work started, the injection pressure was measured before the PC grout reached the small diameter pipe 21. In all of the test specimens 20d to 20f, the injection pressure was 0.4 MPa or less, but after the PC grout began to flow into the small diameter pipe 21, it exceeded 0.4 MPa. After that, the output of the pump 8 was adjusted so that the injection rate was 2 L / min or less.

[0038] As a result, in all of the test specimens 20d to 20f, the PC grout passed through the thin pipe 21 and flowed out to the transparent pipe 23 above. The injection pressure of the PC grout during passage through the thin pipe 21 (from the start of flow into the thin pipe 21 to the flow out to the transparent pipe 23) was in the range of 0.4 to 0.8 MPa. This confirmed that in order to inject the ultra-low viscosity PC grout β into the narrow gap 26 in an absolute dry state with a diameter of 3 mm and pass it through without any problems, it is effective to adjust the output of the pump 8 so that the injection pressure is in the range of 0.4 to 0.8 MPa, and to adjust the output of the pump 8 so that the injection rate is 2 L / min or less after the injection pressure exceeds 0.4 MPa.

[0039] Regarding the 20g test specimen The PC grout β was injected using an electric pump 8 (electric grout pump). After the injected PC grout started to flow into the small diameter pipe 21, the injection pressure exceeded 0.4 MPa. Thereafter, in order to avoid a sudden increase in the injection pressure, the pump 8 was operated intermittently to perform intermittent injection.

[0040] After the PC grout started to flow into the small diameter pipe 21, the injection pressure reached 1.0 MPa, and it became impossible to inject any more PC grout. At this point, the injection work was stopped, and after the injected PC grout hardened, the small diameter pipe 21 was cut in the longitudinal direction, and it was confirmed that the injected PC grout had reached a position 1200 mm from the bottom end (at this point, blockage had occurred). This confirmed that if the PC grout was intermittently injected before it had finished passing through the narrow gap 26, the injection pressure would instead increase sharply, and that in order for the PC grout to pass through the narrow gap 26 in an absolute dry state with a diameter of 3 mm, the injection pressure must be reduced to less than 1.0 MPa.

[0041] Regarding test piece 20h The PC grout β was injected using a manual pump 8. After the PC grout started to flow into the small diameter pipe 21, it became impossible to inject any more PC grout after a while. At this point, the injection work was stopped, and after the injected PC grout hardened, the small diameter pipe 21 was cut along its length, and it was confirmed that the injected PC grout had reached a position 400 mm from the bottom end (a blockage had occurred at this point). The injection pressure reached 0.4 MPa after the PC grout started to flow into the small diameter pipe 21, but did not exceed this pressure. It was confirmed that an injection pressure greater than 0.4 MPa was required to pass through the narrow gap 26 with a diameter of 3 mm, and that it was difficult to obtain sufficient injection pressure with the manual pump 8. [Explanation of symbols]

[0042] 1:Structure, 2: Sheath, 3: Inlet, 4: Outlet, 5: Injection tube, 6: Discharge pipe, 7: Exhaust tube, 8: Pump, 9:Flowmeter, 10: Cook, 11: Fixing section, 12: Cavity part, 13: Existing grout, 14:PC steel material, 15: connecting pipe, 16: Hose band, 17: Putty material, 18: Drilling, 20, 20a-20h: test specimen, 21: Small diameter tube, 22, 23: transparent pipe, 24: Metal pipe, 25: Grout section, 26: Narrow gap,

Claims

1. A method for filling a cavity in a skeleton of a concrete structure with grout by forming an injection port in the cavity and forming a discharge port at a position above the injection port, connecting a tip of an injection pipe to the injection port, connecting a tip of a discharge pipe to the discharge port, connecting a base end of the injection pipe to an electric grout pump, and delivering grout from the electric grout pump to fill the cavity from a lower side to an upper side, comprising: Use low-viscosity or ultra-low-viscosity grout with a water-powder ratio of 45% or less. A grout filling method characterized in that, when the injection pressure exceeds 0.4 MPa during injection work, the output of the electric grout pump is adjusted so that the injection rate is 2 L / min or less.

2. The grout filling method according to claim 1, characterized in that if the injection pressure exceeds 0.4 MPa during the injection operation, the output of the electric grout pump is adjusted so that the injection pressure is within the range of 0.4 to 0.8 MPa.

3. 2. The grout filling method according to claim 1, wherein the exhaust thin pipe is disposed so that its tip is positioned at the top of the cavity through the exhaust port.

4. 4. The grout filling method according to claim 3, characterized in that when the height of the grout in the cavity exceeds the position of the discharge outlet and the grout overflows from the discharge pipe, the electric grout pump is temporarily stopped, the discharge pipe is closed so that the grout is not discharged from the discharge pipe, and then the injection work is resumed to fill the area above the discharge outlet with grout.

5. 5. The grout filling method according to claim 4, wherein the grout injection is carried out continuously without interruption from the start of the injection until the grout is discharged from the discharge pipe.

Images