Concrete test piece, production method for concrete test piece, and method for measuring hydrogen content

Abstract

The present invention comprises concrete (11) that has a planar first surface, metal (12) that is embedded in the first surface, and a nickel film or a palladium film that is formed on the first surface that includes the metal (12).

Description

Concrete specimen, manufacturing method of concrete specimen, and method for measuring hydrogen content

[0001] The present invention relates to a concrete specimen, a method for manufacturing a concrete specimen, and a method for measuring the amount of hydrogen.

[0002] Steel bars are buried inside reinforced concrete structures such as infrastructure facilities. Because reinforced concrete structures are located outdoors, hydrogen generated by corrosion reactions penetrates into the metal of the steel bars. As the amount of hydrogen that penetrates into the metal increases, the metal deteriorates and the probability of fracture increases. Therefore, methods are being developed to non-invasively inspect the deterioration of steel bars by measuring the amount of hydrogen that penetrates into the metal.

[0003] As a method for measuring the amount of hydrogen that penetrates into a metal, for example, a testing device disclosed in Non-Patent Document 1 is known.

[0004] In the testing device disclosed in Non-Patent Document 1, one surface of a metal plate to be tested is placed in a corrosive environment as a hydrogen entry surface. The other surface of the metal plate is placed in a sodium hydroxide solution as a hydrogen detection surface. Hydrogen that has entered the metal plate from the hydrogen entry surface diffuses inside the metal plate and reaches the hydrogen detection surface. When the hydrogen reaches the hydrogen detection surface, it is electrochemically forcibly ionized in the sodium hydroxide solution. A current due to electrons released when the hydrogen is ionized is detected, and the amount of hydrogen that has entered the metal plate can be calculated based on the detected current value.

[0005] Sakai et al., "Proposal of a Dynamic Monitoring Interval Adjustment Method for Agent-Based Monitoring Systems," IEICE Technical Report, vol. 119, no. 299, ICM2019-22, pp. 7-12, November 2019.

[0006] However, the test device disclosed in Non-Patent Document 1 uses a metal foil or a metal plate as the test object for the hydrogen permeation test, and does not mention using concrete with a metal plate embedded therein (hereinafter referred to as a "concrete specimen") as the test object.

[0007] In addition to its role as a test object, the metal plate also serves as a partition to prevent leakage of the sodium hydroxide solution that comes into contact with the hydrogen detection surface. Because concrete is permeable to sodium hydroxide solution, even if a concrete specimen can be placed in the test device, the sodium hydroxide solution will leak. This has created the problem of making it impossible to conduct hydrogen permeation tests using concrete specimens.

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a concrete specimen capable of preventing permeation of sodium hydroxide solution, a method for manufacturing a concrete specimen, and a hydrogen amount measurement method capable of measuring the amount of hydrogen that penetrates into metal in a concrete specimen.

[0009] A concrete specimen of one embodiment of the present invention comprises concrete having a planar first surface, a metal embedded in the first surface, and a metal film containing the metal deposited on the first surface.

[0010] A method for manufacturing a concrete specimen according to one aspect of the present invention includes the steps of: cutting a concrete block having metal embedded inside the concrete along a plane that includes the metal to generate concrete pieces; and forming a metal film on the metal at the cut surface of the concrete piece and on the concrete.

[0011] One aspect of the hydrogen amount measurement method of the present invention is a method for measuring the amount of hydrogen that penetrates into the metal of the above-mentioned concrete specimen, and includes the steps of immersing the first surface of the concrete in a sodium hydroxide solution, placing the second surface opposite the first surface in an outdoor environment, and detecting the current flowing in the sodium hydroxide solution, and calculating the amount of hydrogen that penetrates into the metal based on the detected current.

[0012] According to the present invention, it is possible to prevent permeation of sodium hydroxide solution and measure the amount of hydrogen that penetrates into metal in a concrete specimen.

[0013] FIG. 1A is a cross-sectional view of a concrete block in which metal is embedded. FIG. 1B is an explanatory diagram showing a cut surface L1 when cutting a concrete block to create a concrete specimen. FIG. 1C is a cross-sectional view of a concrete piece cut at the cut surface L1. FIG. 2A is an explanatory diagram that schematically shows an apparatus that forms a metal film on the cut surface of a concrete piece using a vacuum deposition method. FIG. 2B is an explanatory diagram that shows a concrete specimen formed by forming a metal film. FIG. 3 is an explanatory diagram that schematically shows the configuration of a hydrogen content measuring device. FIG. 4 is an explanatory diagram that shows a state in which a sodium hydroxide solution comes into contact with a first surface of a concrete specimen.

[0014] An embodiment of the present invention will be described below with reference to the drawings. A concrete specimen according to this embodiment is manufactured by cutting a concrete block in which a metal is embedded along a plane containing the metal to generate concrete pieces, and then forming a metal film of nickel, palladium, or the like on the cut surface of the concrete piece. The concrete specimen is placed in a test device with the surface on which the metal film is formed as the hydrogen detection surface (first surface, described below) and the surface opposite the hydrogen detection surface as the hydrogen penetration surface (second surface, described below), and the amount of hydrogen that penetrates into the metal is measured. This will be described in detail below.

[0015] Fig. 1A is a cross-sectional view of a concrete block with embedded metal, Fig. 1B is an explanatory diagram showing a cut surface L1 when cutting the concrete block to create a concrete specimen, and Fig. 1C is a cross-sectional view of a concrete piece obtained by cutting the concrete block at the cut surface L1. Fig. 2A is an explanatory diagram showing a process for forming a metal film on the cut surface of the concrete piece, and Fig. 2B is an explanatory diagram showing a concrete specimen formed by forming the metal film.

[0016] Hereinafter, the steps of the method for manufacturing a concrete specimen according to the embodiment will be described with reference to FIGS. 1A, 1B, 1C, 2A, and 2B.

[0017] First, as shown in Fig. 1A, a concrete block 41 is prepared in which a metal 12 is embedded inside concrete 11. The metal 12 is, for example, iron (Fe). Note that Fig. 1A shows an example of using a concrete block 41 in which the entire periphery of the metal 12 is covered with concrete 11, but the concrete block 41 only needs to have at least a portion of the metal 12 covered with concrete 11. Also, in Fig. 1A, the metal 12 and the concrete 11 have a rectangular parallelepiped shape, but they may have a shape other than a rectangular parallelepiped.

[0018] Next, as shown in Fig. 1B, a planar cutting plane L1 including the metal 12 is set on the concrete block 41, and the concrete block 41 is cut along this cutting plane L1. As a result, concrete pieces 41a are generated by dividing the concrete block 41 into two pieces, as shown in Fig. 1C. That is, the concrete piece 41a has a shape in which the metal 12 is exposed in the center and is surrounded by concrete 11.

[0019] 2A, the concrete piece 41a shown in FIG. 1C is inserted into a vacuum container 31, and a metal film is formed by vacuum deposition on the surfaces of the metal 12 and the concrete 11. The metal film may be made of, for example, nickel (Ni) or palladium (Pd).

[0020] Specifically, a metal such as nickel (Ni) or palladium (Pd) is placed in the evaporation source 32, and the metal is heated and evaporated in the vacuum container 31, thereby forming a metal film on the surfaces of the metal 12 and concrete 11. Note that the method for forming the metal film is not limited to vacuum deposition, and other film formation methods such as sputtering and CVD may also be used.

[0021] As a result, as shown in Fig. 2B, a concrete specimen 10 (hereinafter abbreviated as "specimen 10") is produced in which metal 12 is embedded in the surface of concrete 11 and metal film 13 is formed on the surfaces of concrete 11 and metal 12. In the following, the surface of specimen 10 on which metal film 13 is formed (the lower surface of specimen 10 shown in Fig. 2B) will be referred to as the first surface, and the surface opposite to the first surface (the upper surface of specimen 10 shown in Fig. 2B) will be referred to as the second surface.

[0022] That is, the concrete specimen 10 according to this embodiment is composed of concrete 11 having a planar first surface, metal 12 embedded in the first surface, and a metal film 13 formed on the first surface including the metal 12.

[0023] In addition, the concrete specimen 10 according to this embodiment is manufactured by cutting a concrete block 41 having metal 12 embedded inside the concrete 11 along a plane including the metal 12 to generate a concrete piece 41a, and forming a metal film 13 on the metal 12 at the cut surface of the concrete piece 41a and on the concrete 11.

[0024] In this embodiment, the specimen 10 manufactured by the above procedure is used to measure the amount of hydrogen that penetrates into the metal 12. A method for measuring the amount of hydrogen will be described below.

[0025] 3 is a schematic diagram illustrating a measurement device 100 used to measure the amount of hydrogen. As shown in FIG. 3, the measurement device 100 includes a first cell 23, a second cell 24, a first current detector 21, a second current detector 22, and a fixture 28.

[0026] The inside of the first cell 23 is an environment in which hydrogen can penetrate. The inside of the first cell 23 is, for example, an outdoor environment. The outdoor environment is an outside air environment having a given temperature and humidity.

[0027] The second cell 24 is filled with a sodium hydroxide solution 14 .

[0028] The specimen 10 is placed at the connection between the first cell 23 and the second cell 24 and is hermetically fixed by a fixture 28. The specimen 10 is positioned so that its first surface is exposed to the second cell 24 side and its second surface is exposed to the first cell 23 side. In other words, the first surface of the specimen 10 is immersed in the sodium hydroxide solution 14.

[0029] The first current detector 21 is connected to a reference electrode RE1, a counter electrode CE1, and a sample electrode WE connected to the specimen 10, which are provided in the first cell 23. The first current detector 21 measures the current flowing in the first cell based on the voltages generated at the electrodes RE1, CE1, and WE.

[0030] The second current detector 22 is connected to a reference electrode RE2, a counter electrode CE2, and a sample electrode WE connected to the specimen 10, which are provided in the second cell 24. The second current detector 22 measures the current flowing through the sodium hydroxide solution 14 filled in the second cell based on the voltages generated at the electrodes RE2, CE2, and WE.

[0031] FIG. 4 is an explanatory diagram showing the state in which the first surface of the specimen 10 comes into contact with the sodium hydroxide solution 14.

[0032] As shown in Figure 4, a metal film 13 is formed on the surfaces of the metal 12 and concrete 11 that constitute the test specimen 10. That is, a metal film 13 such as a nickel film or a palladium film is formed on the first surface of the test specimen 10. The nickel film and the palladium film do not allow the sodium hydroxide solution 14 to pass through. Therefore, the sodium hydroxide solution 14 filled in the second cell 24 does not pass through the concrete 11. Therefore, it is possible to prevent the sodium hydroxide solution 14 from leaking to the first cell 23 side.

[0033] Next, we will explain the principle of measuring the amount of hydrogen using the above-mentioned measurement device 100. As shown in Figure 3, the second surface of the specimen 10 (the left surface in Figure 4) is exposed to the outdoor environment within the first cell 23.

[0034] Some of the hydrogen present in the first cell 23 penetrates into the concrete 11 from the second surface of the specimen 10 and reaches the surface (the left surface in FIG. 4 ) of the metal 12. Furthermore, some of the hydrogen that reaches the surface of the metal 12 penetrates into the interior of the metal 12 and diffuses, reaching the first surface (the right surface in FIG. 4 ) of the metal 12.

[0035] The hydrogen that reaches the first surface is ionized in the sodium hydroxide solution 14, and electrons are released by the ionization reaction. The second current detector 22 measures the current flowing through the sodium hydroxide solution 14.

[0036] Based on the current measured by the second current detector 22, the amount of hydrogen that has penetrated into the metal 12 of the specimen 10 can be calculated.

[0037] In this way, the amount of hydrogen that penetrates into metal (reinforcing bars) that are embedded in concrete can be measured using the concrete specimen 10 that simulates a reinforced concrete structure.

[0038] Thus, the concrete specimen 10 of this embodiment comprises concrete 11 having a planar first surface, metal 12 embedded in the first surface, and a metal film 13 formed on the first surface including the metal 12.

[0039] In the concrete specimen 10 according to this embodiment, a metal film 13 is formed on the first surface, which is the surface on the hydrogen detection side, so that when measuring the amount of hydrogen using the measuring device 100, the sodium hydroxide solution 14 filled in the second cell 24 can be prevented from permeating the concrete 11 and leaking to the first cell 23 side.

[0040] Therefore, it is possible to easily measure the amount of hydrogen in metals embedded in concrete, such as in reinforced concrete structures. According to this embodiment, it is possible to non-invasively measure the corrosion state of reinforcing bars embedded in concrete.

[0041] Furthermore, in the concrete specimen 10 according to this embodiment, nickel (Ni) or palladium (Pd) is used as the metal film formed on the surface of the concrete 11, which more reliably prevents leakage of the sodium hydroxide solution 14. Furthermore, by forming a metal film of nickel or palladium, it is possible to improve the detection sensitivity of hydrogen.

[0042] Furthermore, in this embodiment, a method such as vacuum deposition is used to form the metal film 13 on the surfaces of the concrete 11 and the metal 12. Therefore, since a method of forming a metal film of nickel, palladium, or the like by plating is not used, the problem of the plating solution seeping into the concrete can be avoided.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention.

[0044] REFERENCE SIGNS LIST 10 Concrete specimen 11 Concrete 12 Metal 13 Metal film 14 Sodium hydroxide solution 21 First current detector 22 Second current detector 23 First cell 24 Second cell 28 Fixture 31 Vacuum container 32 Evaporation source 41 Concrete block 41a Concrete piece 100 Measuring device

Claims

1. A concrete specimen comprising: concrete having a planar first surface; metal embedded in the first surface; and a metal film containing the metal and formed on the first surface.

2. The concrete specimen according to claim 1, wherein the metal film contains nickel or palladium.

3. A method for manufacturing a concrete specimen, comprising the steps of: cutting a concrete block having metal embedded inside the concrete along a plane including the metal to generate concrete pieces; and forming a metal film on the metal on the cut surface of the concrete piece and on the concrete.

4. The method for manufacturing a concrete specimen according to claim 3, wherein the step of forming the metal film forms the metal film by vacuum deposition.

5. The method for manufacturing a concrete specimen according to claim 3 or 4, wherein the metal film contains nickel or palladium.

6. A method for measuring the amount of hydrogen that penetrates into the metal of a concrete specimen as defined in claim 1 or 2, comprising the steps of: immersing the first surface of the concrete in a sodium hydroxide solution, placing the second surface opposite the first surface in an outdoor environment, and detecting the current flowing in the sodium hydroxide solution; and calculating the amount of hydrogen that penetrates into the metal based on the detected current.