Method for detecting leakage of porous member

Abstract

To efficiently and accurately detect existence of deficiency that may cause leakage from a front surface to the backside in a porous member.SOLUTION: A leakage detection method of a porous member for detecting deficiency that causes leakage from a front surface of a porous member to the backside, includes an airtightness confirmation step of evaluating airtightness of an evaluation target area which has been set to a front surface of the porous member. In the airtightness confirmation step, a leak detection liquid is coated in the evaluation target area, and the periphery of the evaluation target area is provided with a seal portion and subjected to airtightness treatment, and the evaluation target area is then loaded with negative pressure.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for detecting leakage from a porous member, for detecting defects that may cause leakage from the surface to the back surface in a porous member such as a concrete structure. [Background technology]

[0002] Conventionally, one of the leak tests for steel ships and the like is the vacuum test stipulated in the Steel Ship Rules. The vacuum test is a test to evaluate the watertightness of steel ships by their airtightness. A test liquid is applied to the welded joints of the steel material, and negative pressure is applied to evaluate the watertightness by the presence or absence of foaming. This type of vacuum test can also be applied to concrete members.

[0003] For example, if a floating structure is constructed by pouring concrete joints, there is a possibility that water may leak from the outer surface to the hollow space through the joints. For this reason, the above-mentioned vacuum test is applied as necessary to detect the presence or absence of defects that may cause leakage. However, because concrete is a porous material, even if the airtightness of the floating structure's walls is sound and there are no problems with the airtightness inside and outside, air trapped inside the walls may cause bubbles to form on the surface, making it difficult to accurately detect defects that may cause leakage.

[0004] On the other hand, another method is to conduct an air permeability test, which is one of the tests to evaluate the density of concrete members, to detect the presence or absence of defects that may cause leakage. The air permeability test is a test to evaluate the density of concrete structure, and as disclosed in the prior art of Patent Document 1, for example, the Torrent method is a widely known method for measuring air permeability in actual structures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-238415 Summary of the Invention [Problem to be solved by the invention]

[0006] However, air permeability tests such as the Torrent method have a small test area of ​​only a few centimeters in diameter, so when applied to, for example, long joints in concrete structures, it requires a great deal of time and effort.

[0007] The present invention has been made in consideration of such problems, and its main purpose is to efficiently and accurately detect the presence or absence of defects in porous members that may cause leakage from the front surface to the back surface. [Means for solving the problem]

[0008] In order to achieve this object, the porous member leak detection method of the present invention is a porous member leak detection method that detects defects that may cause leakage from the surface to the back surface of the porous member, and includes an airtightness confirmation process that evaluates the airtightness of an evaluation target area set on the surface of the porous member, and is characterized in that the airtightness confirmation process applies a leak detection liquid to the evaluation target area, provides a sealing portion around it to make it airtight, and then applies a negative pressure to the evaluation target area.

[0009] The leak detection method of the present invention is characterized in that it includes a bubble reproduction step of, when bubbles are confirmed in the airtightness confirmation step, performing the airtightness confirmation step again to identify the location where bubbles have occurred.

[0010] The method for detecting leakage from a porous member of the present invention is characterized in that it includes an air permeability coefficient confirmation step in which, when the bubble generation position is identified in the airtightness confirmation step or the bubble generation reproduction step, an air permeability test is carried out at the bubble generation position and the air permeability coefficient is calculated.

[0011] The method for detecting leakage from a porous member of the present invention is characterized in that the porous member is a concrete member.

[0012] The method for detecting leakage from a porous member of the present invention is characterized in that the evaluation target area is a joint in the concrete member, and the sealing portion includes a strip-shaped sealing portion formed on both sides of the joint.

[0013] The method for detecting leakage from a porous member of the present invention is characterized in that a plurality of sections are set by dividing the joint in the longitudinal direction, and the airtightness confirmation step is carried out for each of the sections.

[0014] According to the leak detection method for porous members of the present invention, an airtight seal is formed around the evaluation area. This prevents outside air from entering the porous member from the surface surrounding the evaluation area when negative pressure is applied to the evaluation area. Therefore, by using testing equipment similar to that specified in the rules for steel ships to check for the occurrence of bubbles in the leak detection liquid applied to the evaluation area, it is possible to efficiently check the airtightness of the evaluation area.

[0015] Furthermore, if bubbles are found in the leak detection liquid, a bubble reproduction process is carried out in which the airtightness confirmation process is repeated to determine whether the bubbles are caused by outside air sucked in from the back side of the porous member, or pseudo-bubbles caused by gas contained within the porous member. This makes it possible to efficiently and accurately detect defects that may cause leaks, even if the evaluation target area is set to the porous member.

[0016] Furthermore, if the porous member is a concrete member and foaming due to air being drawn in from the backside is observed, an air permeability test is conducted at the specific location where foaming has occurred to evaluate the soundness of the concrete. This allows for efficient repair work, as if there is any doubt about the soundness, the specific location where foaming has occurred can be repaired.

[0017] Furthermore, if the area to be evaluated is a construction joint in a concrete member, a strip-shaped seal is provided along the construction joint to seal it airtight. Then, multiple sections are set along the length of the construction joint, and the airtightness check process is carried out for each section in turn. This makes it possible to efficiently detect defects that could cause leakage, even when the construction joint is long and large. [Effects of the Invention]

[0018] According to the present invention, by performing an airtight treatment in which a sealing portion is provided around the evaluation target area set on the surface of a porous member, it is possible to efficiently and accurately detect defects that may cause leakage from the surface to the back surface, even in porous members. [Brief explanation of the drawings]

[0019] [Figure 1] 3A to 3C are diagrams illustrating a method for detecting leakage from a porous member (airtightness confirmation step) according to an embodiment of the present invention. [Figure 2] 3A to 3C are diagrams illustrating a method for detecting leakage from a porous member (a step of checking the air permeability coefficient) according to an embodiment of the present invention. [Figure 3] 1 is a diagram showing an outline of a vacuum test and an air permeability test according to an embodiment of the present invention. FIG. [Figure 4] 1 is a diagram showing the flow of a method for detecting leakage from a porous member according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention is directed to detecting defects in porous members that may cause leakage from the front surface to the back surface. While the present invention is applicable to any porous member, in this embodiment, a concrete member constructed by pouring concrete in a joint is used as an example to detect whether or not there is a defect in the joint that may cause leakage, and details thereof will be described with reference to Figs. 1 to 4.

[0021] As shown in Figure 1(a), a concrete member 10 constructed by pouring concrete has a pouring joint 11 visible on its surface 12. If there is a defect in this pouring joint 11, such as poor construction, a water path may form from the surface 12 to the back surface 13 of the concrete member 10, as shown in Figure 3(a), which may result in water leakage.

[0022] Therefore, the construction joint 11 is set as the evaluation target area, and the presence or absence of defects that may cause water leakage is detected by a method for detecting leakage from a porous member. The procedure for detecting the presence or absence of defects that may cause water leakage in the construction joint 11 is explained below with reference to the flow shown in Figure 4.

[0023] <<<<Leak detection method>>>> ≪≪Preparation process: STEP1≫≫ First, as shown in Figure 1(a), strip-shaped seal portions 21 are provided on both sides of a construction joint 11 on the surface 12 of a concrete member 10. At this time, the pair of strip-shaped seal portions 21 are provided with a gap of about 1 to 2 cm between them. In other words, the construction joint 11, which is the area to be evaluated, is located in this gap.

[0024] The strip-shaped seal portion 21 is provided to prevent outside air from flowing in from the surface 12 of the concrete member 10 to the inside when negative pressure is applied to the pouring joint 11 in the airtightness confirmation process (STEP 2) described below. Therefore, the strip-shaped seal portion 21 is provided with a sufficient width and is made of a material that can cover the surface 12 and ensure airtightness. For example, latex paint is preferable as a material for the strip-shaped seal portion 21, and aluminum tape may also be attached.

[0025] <<Airtightness Check Process: STEP 2>> In the airtightness confirmation process, first, as shown in Figure 1(b), multiple sections A, B, C, D, etc. are set to divide the joint 11 in the longitudinal direction, and then a pair of end seal sections 22 are provided on both sides of section A, for example.

[0026] Similar to the strip seals 21, the pair of end seals 22 are also made large enough to prevent outside air from flowing in from the surface 12 of the concrete member 10 to the interior when negative pressure is applied to the joint 11, and are made of a material that can cover the surface 12 and ensure airtightness. The end seals 22 are preferably made of a removable material that restricts air permeability, such as aluminum tape.

[0027] In this way, the periphery of section A is made airtight with the seal section 20 consisting of the pair of end seal sections 22 and the above-mentioned strip-shaped seal section 21. After this, testing equipment 30 for vacuum testing is attached to section A, and the airtightness is confirmed by vacuum testing.

[0028] <Vacuum test> The vacuum test is carried out based on the vacuum test prescribed in the Rules for Steel Ships (in accordance with Annex 2.1.5 An1.4.4-6 of the Rules for Steel Ships Part B of the Nippon Kaiji Kyokai).

[0029] As shown in Figures 1(b) and 3(a), a leak detection liquid 31 is applied to the surface 12 within the compartment A surrounded by the seal portion 20. The leak detection liquid 31 is a material that foams when gas is released from the surface 12 within the compartment A. Since the Rules for Steel Ships do not specify foaming materials, this embodiment uses a foaming liquid that satisfies the specifications specified in the Non-Destructive Test - Foaming Leak Test Method (JIS Z2329:2019 Annex A).

[0030] Next, a container with an inspection window 32 to which a vent pipe 33 is attached is placed so as to cover section A. The vent pipe 33 is connected to a vacuum pump 34, and by operating this vacuum pump 34, air is sucked into the container with an inspection window 32 through the vent pipe 33, thereby applying a negative pressure to the inside of the container with an inspection window 32.

[0031] Air is suctioned into the inspection window-equipped vessel 32 until a predetermined negative pressure state (for example, 0.0020 to 0.026 MPa according to the rules for steel ships) is reached, and this negative pressure state is maintained for a predetermined time. As mentioned above, the periphery of compartment A is provided with a seal portion 20 to make it airtight. This makes it possible to prevent outside air from entering the interior through the surface 12 around compartment A, even if negative pressure is applied to compartment A using the above procedure.

[0032] Therefore, if bubbles are found in the leak detection liquid 31 within section A covered by the container 32 with an inspection window, the bubbles can be evaluated as being either caused by outside air sucked in from the back surface 13 of the concrete member 10, or as pseudo-bubbles caused by gas contained within the concrete member 10.

[0033] Furthermore, if no foaming occurs in the leak detection liquid 31, or if foaming occurs but it is clearly pseudo-foam, it can be determined that there are no defects within section A that could cause leakage.

[0034] In this case, the airtightness checking step in section A is completed, and as shown in FIG. 1(c), the airtightness checking step (STEP 2) is carried out in the adjacent section B in the same manner as above.

[0035] If it is not possible to determine whether the bubbles that have formed in the leak detection liquid 31 are pseudo-bubbles, or if it is highly likely that the bubbles are caused by outside air being sucked in from the back surface 13 of the concrete member 10 but the location cannot be identified, the bubbles reproduction process (STEP 3) described below is carried out.

[0036] <<Foaming Reproduction Process: STEP 3>> The foaming reproduction process checks the reproducibility of foaming based on, for example, the non-destructive test - foaming leak test method specified in the JIS standard (JIS Z2329:2019 8.6 Application of foaming liquid) and determines whether it is a pseudo-foam. Specifically, the container with inspection window 32 used in the previous airtightness confirmation process is removed, the air bubbles are removed, and the leak detection liquid 31 is applied to section A again. After this, the container with inspection window 32 is installed, and a negative pressure is applied inside the container with inspection window 32 using the procedure described above.

[0037] If no foaming occurs in the leak detection liquid 31 within section A covered by the container 32 with an inspection window, it is determined that the foaming that occurred during the airtightness confirmation process described above was pseudo-foam caused by gas contained in the concrete member 10, and it is assessed that there are no defects within section A that could cause leakage.

[0038] In this case, the airtightness checking step in section A is completed, and as shown in FIG. 1(c), the airtightness checking step (STEP 2) is continued in the adjacent section B in the same manner as above.

[0039] On the other hand, if the foaming occurring in the leak detection liquid 31 is reproducible and the foaming occurrence position P can be identified as shown in Figure 2(a), the air permeability coefficient confirmation step (STEP 4) described below is carried out in section A. If foaming occurs but the foaming occurrence position P cannot be identified, the foaming reproduction step (STEP 3) is repeated until it can be identified. Note that if the foaming occurrence position P can be identified in the airtightness confirmation step (STEP 2), the foaming reproduction step (STEP 3) may be omitted and the process may proceed to the air permeability coefficient confirmation step (STEP 4).

[0040] <<Air permeability coefficient confirmation process: STEP 4>> In the air permeability coefficient confirmation process, first, as shown in Figure 2(b), section A is covered with an air permeability test seal portion 23, except for a predetermined circular area (approximately 2 cm in diameter) including the identified bubble generation position P.

[0041] In this way, the periphery of the bubble generation position P is airtightly treated with the seal part 20 consisting of the seal part 23 for air permeability test and the pair of end seal parts 22 and the strip seal part 21. Like the end seal part 22, the seal part 23 for air permeability test is preferably made of a material that can cover the surface 12 to ensure airtightness and is also removable.

[0042] After this, an air permeability test device 40 is attached to the foaming occurrence position P, and an air permeability test, which is one of the tests for evaluating the soundness of concrete, is performed. In addition, the air permeability coefficient k is calculated, and the soundness of the area near the foaming occurrence position P is evaluated.

[0043] <Air permeability test> The air permeability test and calculation of the air permeability coefficient k are carried out based on the air permeability test using the seal method ("Development of a method for measuring the air permeability coefficient of concrete in actual structures," Concrete Engineering, Vol. 51, No. 4, April 2013).

[0044] As shown in FIG. 3(b), a chamber 41 to which a ventilation pipe 42 is attached is installed via a sealing material 46 such as putty so as to cover the foam generation position P, the periphery of which is airtightly sealed by the sealing portion 20.

[0045] The ventilation pipe 42 is connected to a vacuum pump 43 and is equipped with a differential pressure gauge 44 and a flow meter 45. In such a testing device 40 for an air permeability test, by operating the vacuum pump 43, the inside of the chamber 41 is suctioned through the ventilation pipe 42, and the air inside the chamber 41 is sucked out.

[0046] In this embodiment, the hemispherical surface having a radius r2 that is the shortest distance from the bubble generation position P to the outer edge of the seal portion 20 (the outer edge of the strip-shaped seal portion 21) is defined as the air permeable region V involved in the air permeation, and the air permeability coefficient k is calculated from the flow rate Q1 of air sucked out of the chamber 41 using the following equation (1).

[0047] JPEG2025136526000002.jpg17170 k: Air permeability coefficient η: Viscosity coefficient Q1: The flow rate of air sucked out from the suction port S (circular area including the bubble generation position P) P1: Measured pressure in the chamber P2: atmospheric pressure r1: Radius of suction port S (chamber) r2: The shortest distance from the bubble generation position P (joint) to the outer edge of the strip-shaped seal portion 21

[0048] In the sealing method, the hemispherical air permeable area V is generally set to be contained within the concrete member 10. However, in this embodiment, as shown in Fig. 3(b), the air permeable area V is set to extend beyond the back surface 13 of the concrete member 10. In other words, the shortest distance from the pouring joint 11 to the outer edge of the strip-shaped seal portion 21 (the width of the strip-shaped seal portion 21) is set to be greater than the thickness of the concrete member 10.

[0049] The soundness of the vicinity of the foaming occurrence position P is evaluated based on the calculated air permeability coefficient k and a preset reference air permeability coefficient T. The reference air permeability coefficient T can be, for example, a general air permeability coefficient of dense concrete that has been sufficiently cured.

[0050] If the calculated air permeability coefficient k exceeds the reference air permeability coefficient T, the area near the bubbling occurrence position P is evaluated as being of questionable integrity and as a defective area that may cause a leak. In this case, repair work is carried out in the area near the bubbling occurrence position P. After repair work has been carried out, the above leak detection method is repeated according to the procedure shown in Figure 4 until it is evaluated that there are no defects in section A that may cause a leak.

[0051] On the other hand, if the calculated air permeability coefficient k is equal to or lower than the reference air permeability coefficient T, the bubbling occurrence position P is evaluated as sound and no defects that could cause leakage are anticipated. If there are multiple bubbling occurrence positions P within section A, the air permeability coefficient confirmation step (STEP 4) is carried out for each of those positions.

[0052] If it is determined that no defects that may cause leakage are suspected for all of the bubble generation positions P identified within section A, the air permeability coefficient confirmation step (STEP 4) for section A is terminated. Then, as shown in Figure 1(c), the airtightness confirmation step (STEP 2) is carried out in the adjacent section B using the above procedure.

[0053] The above-mentioned work is carried out in all sections A, B, C, D, etc., and the construction joint 11, which is the area to be evaluated, is evaluated to see if there is any defect at the bubble generation position P that could cause leakage.

[0054] According to the above-described method for detecting leaks from a porous member, the sealing portion 20 is provided around the joint 11 to provide an airtight seal, thereby enabling the airtightness confirmation step (STEP 2) to be carried out based on the vacuum test prescribed in the Rules for Steel Ships, etc. Furthermore, once the foaming occurrence position P has been identified, the air permeability coefficient confirmation step (STEP 4) can be carried out using the sealing portion 20 based on the sealing method, which is widely known as an air permeability test for concrete.

[0055] This makes it possible to efficiently and accurately detect the presence or absence of defects that may cause leakage, even if the evaluation target area is porous and contains air on the surface 12 of the concrete member 10. Also, even if the construction joint 11 is long, dividing the construction joint 11 into multiple sections and implementing the porous member leakage detection method in each section can greatly improve the workability of leakage detection.

[0056] The method for detecting leakage from a porous member of the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0057] For example, in this embodiment, the case where the leak detection method is carried out in the order of sections A, B, C, D, etc., which divide the construction joint 11 longitudinally, is taken as an example. However, this is not limited to this, and any section may be randomly selected and the leak detection method may be carried out, or the leak detection method may be carried out in multiple sections simultaneously. Also, if the construction joint 11 is short, it does not necessarily have to be divided into multiple sections.

[0058] Furthermore, in this embodiment, the case where the evaluation target area is the construction joint 11 has been given as an example, but the present invention is not limited to this. For example, when cracks or damaged areas are found on the surface of the concrete member 10 by visual inspection or the like, the area including these may be set as the evaluation target area, and the leak detection method may be carried out according to the above procedure.

[0059] Furthermore, in this embodiment, in the airtightness confirmation process (STEP 2), the test equipment 40 for vacuum testing specified in the Rules for Steel Ships is used, and negative pressure is applied to the evaluation target area according to the specified procedure, but this is not limited to this, and negative pressure may be applied by other means. For example, the non-destructive test - foam leakage test method specified in the JIS standard (JIS Z2329:2019) may be used. [Explanation of symbols]

[0060] 10 Concrete members 1. Joint 2 surface 3 Back side 20 Seal part 21 Strip seal 22 End seal 23 Seal for air permeability test 30 Test equipment (for vacuum testing) 31 Leak detection liquid 32 Container with inspection window 33 Ventilation pipe 34 Vacuum pump 40 Test equipment (for air permeability testing) 41 Chamber 42 Ventilation pipe 43 Vacuum Pump 44 Differential pressure gauge 45 Flow meter 46 Encapsulating material V Air permeable area S suction nozzle P Bubbling occurrence position

Claims

1. A method for detecting leakage from a porous member, which detects a defect that may cause leakage from a surface to a back surface of the porous member, an airtightness confirmation step of evaluating the airtightness of an evaluation target area set on the surface of the porous member; The airtightness confirmation step includes: A method for detecting leaks in porous members, characterized in that a leak detection liquid is applied to the evaluation target area, a sealing portion is provided around the area to make it airtight, and then a negative pressure is applied to the evaluation target area.

2. The method for detecting leakage from a porous member according to claim 1, When foaming is confirmed in the airtightness confirmation step, A method for detecting leakage from a porous member, comprising a bubble reproduction step of performing the airtightness confirmation step again to identify the location where the bubble has occurred.

3. The method for detecting leakage from a porous member according to claim 1 or 2, When the bubble generation position is identified in the airtightness confirmation step or the bubble reproduction step, The method for detecting leakage from a porous member is characterized by including an air permeability coefficient confirmation step of conducting an air permeability test at the position where bubbling occurs and calculating the air permeability coefficient.

4. The method for detecting leakage from a porous member according to claim 1, A method for detecting leakage from a porous member, wherein the porous member is a concrete member.

5. The method for detecting leakage from a porous member according to claim 4, The evaluation target area is a construction joint of the concrete member, A method for detecting leakage from a porous member, wherein the sealing portion includes strip-shaped sealing portions formed on both sides of the joint.

6. The method for detecting leakage from a porous member according to claim 5, A plurality of sections are set to divide the joint in the longitudinal direction, A method for detecting leakage from a porous member, characterized in that the airtightness confirmation step is carried out for each of the compartments.

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