Concrete Structures, Concrete Inspection Systems, and RFID Devices

Abstract

This concrete structural body comprises concrete, and an RFID device contained in the concrete. The RFID device comprises a capsule, and an RFID tag which is disposed inside the capsule, operates upon receipt of a prescribed call signal, and transmits a prescribed response signal. The capsule is configured such that a rupture exposing the RFID tag to the outside of the capsule occurs if an external force exceeding a prescribed force is applied. The RFID tag is configured to change to an incommunicable state upon coming into contact with a component of the atmosphere.

Description

[Technical field]

[0001] The present disclosure relates to a concrete structure equipped with an RFID device, a concrete inspection system that inspects a concrete structure using an RFID device, and an RFID device. [Background technology]

[0002] For example, Patent Document 1 discloses a system that uses multiple sensors to detect the condition of a concrete structure in order to periodically inspect the concrete structure, which makes it possible to perform periodic inspection of the concrete structure without performing tapping diagnosis by hand. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-22687 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of the system described in Patent Document 1, in order to periodically inspect the concrete structure, it is necessary to supply power to the multiple sensors installed in the concrete structure, and it is also necessary to install wiring in the concrete structure to supply power to the sensors.

[0005] Therefore, an object of the present disclosure is to perform periodic inspection of a concrete structure without installing sensors that require a power supply and wiring that supplies power to the sensors in the concrete structure. [Means for solving the problem]

[0006] In order to solve the above technical problem, according to one aspect of the present disclosure, Concrete and an RFID device contained within the concrete; The RFID device includes a capsule and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal and transmits a predetermined response signal; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; A concrete structure is provided, wherein the RFID tag is configured to change to an incommunicable state upon contact with an atmospheric component.

[0007] According to another aspect of the present disclosure, A concrete inspection system for inspecting a concrete structure, comprising: an RFID device contained in the concrete of the concrete structure; A communication device that wirelessly communicates with the RFID device, The RFID device, a capsule; and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal from the communication device and transmits a predetermined response signal to the communication device; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; A concrete inspection system is provided, wherein the RFID tag is configured to change to an incommunicable state when it comes into contact with a component in the air.

[0008] According to another aspect of the present disclosure, Capsules and an RFID tag disposed within the capsule, which receives a predetermined call signal, is activated, and transmits a predetermined response signal; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; An RFID device is provided, wherein the RFID tag is configured to change to an incommunicable state upon contact with an atmospheric component. Effect of the Invention

[0009] According to the present disclosure, periodic inspection of a concrete structure can be performed without installing sensors that require a power supply and wiring that supplies power to the sensors in the concrete structure. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of an RFID device according to a first embodiment of the present disclosure. [Diagram 2] Cross-section of the RFID device shown in Figure 1 [Diagram 3] FIG. 1 is a diagram showing an example of a concrete structure having an RFID device according to a first embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram of a concrete inspection system for inspecting a concrete structure according to a first embodiment of the present disclosure. [Diagram 5] Block diagram showing the configuration of the concrete inspection system [Figure 6A] Cross-section of a portion of a concrete structure before an abnormality occurred [Figure 6B] Cross-sectional view of a part of a concrete structure immediately after an abnormality occurred [Figure 6C] Cross-section of a part of a concrete structure some time after an abnormality occurred [Figure 7] FIG. 13 is a perspective view of an RFID device according to a second embodiment of the present disclosure. [Figure 8] Cross-section of the RFID device shown in Figure 7 [Figure 9] 1 is a top view of an RFID tag according to another embodiment of the present disclosure. [Figure 10] FIG. 11 is a cross-sectional view of an RFID device including an RFID tag according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0012] (Embodiment 1) Fig. 1 is a perspective view of an RFID device according to a first embodiment of the present disclosure, and Fig. 2 is a cross-sectional view of the RFID device shown in Fig. 1. The XYZ coordinate system in the figure is for facilitating understanding of the present disclosure, and is not intended to limit the present disclosure.

[0013] 1 and 2, an RFID (Radio-Frequency IDentification) device 10 according to the first embodiment has a substantially cylindrical shape, and includes an RFID tag 12 and a capsule 14 that houses the RFID tag 12. Although a substantially cylindrical shape is illustrated here, it may be a polygonal prism.

[0014] The RFID tag 12 is a device that performs wireless communication at a predetermined frequency. In the first embodiment, the RFID tag 12 is a so-called passive device that does not have a power source.

[0015] As shown in FIG. 2, the RFID tag 12 includes an IC chip 16 and two pole-shaped antenna members 18A and 18B. In the case of the first embodiment, the IC chip 16 is mounted on a substrate 20 such as a flexible substrate, and one end of each of the antenna members 18A and 18B is attached to the substrate 20. The other end of each of the antenna members 18A and 18B is supported by the capsule 14. The IC chip 16 and the antenna members 18A and 18B are electrically connected via conductor patterns 22A and 22B on the substrate 20. Specifically, the input / output terminals 16a and 16b of the IC chip 16 are electrically connected to the antenna members 18A and 18B via the conductor patterns 22A and 22B, respectively. The IC chip 16 and the antenna members 18A and 18B may be connected in a direct current manner or may be capacitively coupled. Here, the ends of the antenna members 18A and 18B are exemplified as being supported by the capsule 14, but this is not limited thereto, and the antenna members 18A and 18B may not be fixed to the capsule. Alternatively, it may be partially filled with adhesive, which is a design choice determined by the size of the capsule and the device inside.

[0016] The IC chip 16 is a chip-shaped electronic component having various elements built into a semiconductor substrate made of a semiconductor such as silicon. The IC chip 16 is configured to output a corresponding response signal (corresponding current) when a predetermined call signal (corresponding current) is input. In the case of the first embodiment, the response signal contains identification information unique to the RFID tag.

[0017] In the case of the first embodiment, the antenna members 18A and 18B are made of a corrodible material, such as iron or aluminum, for the reason to be described later. In the case of the first embodiment, the antenna members 18A and 18B are arranged on the same straight line to form a dipole antenna having an antenna length L0. The antenna length L0 is set to half the wavelength of a predetermined frequency. The antenna members 18A and 18B constituting the dipole antenna do not have to be linear, and may have other shapes, such as a meandering shape, as long as the antenna length L0 is half the predetermined frequency. The antenna members may be formed integrally with the substrate 20. In this case, the antenna members 18A and 18B are not provided, and the antenna is patterned on the substrate 20.

[0018] In such an RFID tag 12, when the antenna members 18A, 18B receive radio waves of a predetermined frequency (i.e., a call signal), a current is generated that flows from the antenna members 18A, 18B to the IC chip 16. The current activates the IC chip 16, and the IC chip 16 outputs a response signal (corresponding current) to the antenna members 18A, 18B. The antenna members 18A, 18B then transmit radio waves corresponding to the response signal.

[0019] 2, the capsule 14 is in the shape of a cylinder with a bottom, and includes a sealed space 14a for accommodating the RFID tag 12. For example, the capsule 14 for hermetically accommodating the RFID tag 12 is produced by accommodating the RFID tag 12 in a cylindrical member, and then melting both ends of the cylindrical member to seal the internal space of the cylindrical member.

[0020] First, the capsule 14 is made of a material that is permeable to radio waves transmitted and received by the RFID tag 12 therein. The capsule 14 is also made of a material that is impermeable to substances such as oxygen and moisture that corrode the antenna members 18A and 18B toward the sealed space 14a that houses the RFID tag 12. Furthermore, the capsule 14 is configured such that, when an external force exceeding a predetermined force is applied, it breaks and communicates between the sealed space 14a and the outside, for reasons that will be described later. In consideration of these factors, the capsule 14 is preferably made of a brittle material, and more preferably made of glass that does not substantially deteriorate over time in the natural environment.

[0021] Fig. 3 is a diagram showing an example of a concrete structure having an RFID device according to the first embodiment of the present disclosure, Fig. 4 is a schematic diagram of a concrete inspection system according to the first embodiment of the present disclosure for inspecting a concrete structure, and Fig. 5 is a block diagram showing a configuration of the concrete inspection system.

[0022] 3 and 4 show an example of a concrete structure 30 having an RFID device 10. In the case of the first embodiment, the concrete structure 30 is a concrete building constituting an inner surface portion of a tunnel. A plurality of RFID devices 10 are randomly included in the concrete structure 30.

[0023] The concrete structure 30 is a structure formed by hardening concrete 32 containing at least cement, water, and sand. The concrete structure 30 may contain reinforcing bars in some cases. A plurality of RFID devices 10 are mixed into the concrete 32 before it hardens, i.e., before it is poured. When the concrete 32 hardens and dries sufficiently, the concrete structure 30 containing the plurality of RFID devices 10 randomly is produced. Note that, although an example in which the RFID devices 10 are mixed into the concrete and hardened has been shown here, it is also possible to make a hole at a predetermined position after the concrete hardens, insert the RFID device 10, and then seal it again with concrete or resin.

[0024] 4 and 5, a concrete inspection system 50 for inspecting a concrete structure 30 includes a plurality of RFID devices 10 in the concrete structure 30, and an inspection device 52 for detecting an abnormality in the concrete structure 30 based on a response signal transmitted from the RFID device 10. The inspection device 52 includes a communication device 54 for wirelessly communicating with the RFID device 10, and a calculation device 56 for detecting an abnormality in the concrete structure 30. In the case of the first embodiment, since the concrete structure 30 is a tunnel, the inspection device 52 is mounted on a moving body M such as a vehicle or a drone.

[0025] The communication device 54 of the inspection device 52 wirelessly communicates with each of the RFID devices 10 in the concrete structure 30. In the case of the first embodiment, the communication device 54 includes at least three communication antennas 58 installed at different positions in order to identify the three-dimensional position of each of the RFID devices 10. Based on the output timing of a call signal and the reception timing of a response signal from each of the communication antennas 58 from the RFID devices 10, the distance between the RFID device 10 and each of the communication antennas 58 can be identified. In addition, based on these identified distances and the installation positions of the communication antennas 58, the three-dimensional position of the RFID device 10 can be identified.

[0026] The arithmetic device 56 of the inspection device 52 is, for example, a computer configured with a processor such as a CPU and a storage device that stores programs, etc. The processor operates according to the programs stored in the storage device, whereby the arithmetic device 56 can execute the following various operations.

[0027] First, the arithmetic device 56 controls the communication device 54 to cause the communication device 54 to perform wireless communication with each of the multiple RFID devices 10. As a result, the communication device 54 transmits a call signal of a predetermined frequency to each of the RFID devices 10, and each of the RFID devices 10 that receives the call signal transmits a response signal to the communication device 54.

[0028] After wireless communication is performed, the arithmetic device 56 acquires, from the communication device 106, response signals from each of the RFID devices 10 and information on the timing of receiving the response signals. Based on this information acquired from the communication device 54 and prestored information on the installation positions of the communication antennas 58 of the communication device 54, the arithmetic device 56 calculates the three-dimensional position of each of the RFID devices 10. Note that since the response signals from the multiple RFID devices 10 each contain different identification information, it is possible to calculate the three-dimensional position of each of the RFID devices 10.

[0029] After calculating the three-dimensional position of each of the RFID devices 10, the calculation device 56 creates a distribution map of the multiple RFID devices 10 based on the calculation result. The calculation device 56 creates a three-dimensional distribution map of the multiple RFID devices 10 in the concrete structure 30 by using, for example, 3D CAD data of the concrete structure 30 acquired in advance. That is, a distribution map of the communicable RFID devices 10 is created.

[0030] By using such a distribution map of the RFID devices 10, it becomes possible to detect abnormalities in the concrete structure 30.

[0031] Specifically, a reference distribution map of RFID devices 10 is created immediately after the concrete structure 30 is completed (i.e., when no abnormalities have occurred in the concrete structure 30). A distribution map of RFID devices 10 is also created when the concrete structure 30 is inspected periodically thereafter. If, as a result of comparing the reference distribution map with the distribution map created during inspection, there is an RFID device 10 that exists in the reference distribution map but not in the distribution map created during inspection, then an abnormality such as displacement or cracking has occurred in the part of the concrete structure 30 where the RFID device 10 exists. This will be described in detail.

[0032] Fig. 6A is a cross-sectional view of a portion of a concrete structure before an abnormality occurs, Fig. 6B is a cross-sectional view of a portion of a concrete structure immediately after an abnormality occurs, and Fig. 6C is a cross-sectional view of a portion of a concrete structure some time after the abnormality occurs.

[0033] 6A , when no abnormality such as displacement or cracks occurs, the RFID device 10 in the concrete structure 30 is in a state in which it can wirelessly communicate with the communication device 54 of the inspection equipment 52. In other words, the antenna members 18A, 18B of the RFID tag 12 of the RFID device 10 maintain an antenna length L0 that allows them to receive a call signal of a predetermined frequency from the communication device 54.

[0034] As shown in FIG. 6B, when an abnormality such as a localized displacement D or crack C occurs in the concrete structure 30, the capsule 14 of the RFID device 10 present in the occurrence portion is destroyed. Specifically, due to the occurrence of the abnormality in the concrete structure 30, an external force such as a compressive force or a shear force acts on the capsule 14, and as a result, the capsule 14 is destroyed. Due to this destruction, the sealed space 14a of the capsule 14 communicates with the outside, and the RFID tag 12 is exposed to the outside of the capsule 14. As a result, oxygen, moisture W, and the like can enter the capsule 14. It should be noted that immediately after the occurrence of the abnormality in the concrete structure 30, the RFID tag 12 is still in a state in which communication is possible.

[0035] Immediately after the capsule 14 is broken, oxygen and moisture W that have entered the capsule 14 start to corrode at least a part of the current path of the RFID tag 12, in the case of the first embodiment, the antenna members 18A and 18B. When the corrosion progresses to a certain extent, as shown in FIG. 6C, the antenna members 18A and 18B are partially disconnected. As a result, the antenna length of the antenna members 18A and 18B becomes an antenna length L1 that is shorter than the antenna length L0 before the corrosion started. Alternatively, the corrosion of the antenna members 18A and 18B significantly deteriorates the conductivity, and the performance as an antenna is significantly deteriorated. Therefore, even if a radio wave (call signal) of a predetermined frequency from the communication device 54 reaches the antenna members 18A and 18B, no current is generated from the antenna members 18A and 18B toward the IC chip 16, and the IC chip 16 does not operate. As a result, the RFID tag 12 cannot respond to the call signal from the communication device 54 (cannot transmit a response signal).

[0036] In this way, when the capsule 14 is destroyed due to the occurrence of an abnormality in the concrete structure 30, the RFID device 10 will eventually become unable to communicate. In other words, the position of the RFID device 10 that is unable to communicate corresponds to the part of the concrete structure 30 where the abnormality has occurred. Therefore, by performing wireless communication with multiple RFID devices 10 in the concrete structure 30 as a periodic inspection of the concrete structure 30 and thereby identifying the RFID devices 10 that are unable to communicate, it is possible to detect abnormalities in the concrete structure 30.

[0037] In the case of the first embodiment, the RFID tag 12 may become unable to communicate due to phenomena other than the antenna length of the antenna members 18A and 18B being shortened by corrosion, or the antenna itself being corroded and its conductivity deteriorating, causing it to no longer function as an antenna. For example, the input / output terminals 16a and 16b of the IC chip 16 may be short-circuited to each other due to moisture W that has entered the broken capsule 14. Since such phenomena are also caused by the occurrence of an abnormality in the concrete structure 30, the abnormality in the concrete structure 30 can be detected. That is, the RFID tag 12 is configured to change to a state in which communication is impossible when it comes into contact with components in the air, particularly oxygen and moisture W. In addition to or instead of making the antenna members 18A and 18B from a material that is easily corroded, the conductor patterns 22A and 22B on the substrate 20 may be made from a material that is easily corroded. When the conductor patterns 22A and 22B corrode, the electrical connection between the antenna members 18A and 18B and the IC chip 16 is cut, and the RFID tag 12 becomes unable to communicate.

[0038] Furthermore, the inspection device 52 of the concrete inspection system 50 may notify the inspector of the occurrence of an abnormality in the concrete structure 30 and the part where the abnormality occurred via an output device such as a display. In this case, the calculation device 56 of the inspection device 52 identifies RFID devices 10 that have transitioned from a communicable state to an incommunicable state based on a reference distribution map showing the distribution of communicable RFID devices 10 created immediately after the completion of the concrete structure 30 and a distribution map showing the distribution of communicable RFID devices 10 created during regular inspection. The position of the identified RFID device 10 is notified to the inspector via the output device as the part of the concrete structure 30 where the abnormality occurred.

[0039] Furthermore, in order to inspect such a concrete structure 30, it is preferable that the antenna members 18A, 18B of the RFID tag 12 of the RFID device 10 are made of a material that can be corroded by components in the air, particularly iron that is easily corroded by oxygen and moisture, and aluminum, the corrosion of which can be accelerated by applying a specific plating. However, when the antenna members 18A, 18B are made of such a material, it may be necessary to apply plating to ensure the desired high frequency characteristics. In this case, it is preferable to form a porous precious metal plating layer, for example a gold plating layer, on the surface of the antenna members 18A, 18B.

[0040] Generally, iron corrodes in normal air. Furthermore, even aluminum, which has high corrosion resistance, can be corroded by plating it with a precious metal due to the formation of a stable oxide film in normal air. When a precious metal such as gold is plated on a metal base material with a relatively high ionization tendency such as aluminum, zinc, or iron, the parts of the metal base material exposed through defective parts of the plating are significantly corroded by local cell action due to the difference in ionization tendency between them. This phenomenon progresses very significantly in the presence of oxygen or moisture. Conversely, corrosion hardly occurs in a state where the moisture concentration or oxygen concentration is extremely low. When gold plating with a thickness of 0.5 μm or less is applied to the surfaces of antenna members 18A and 18B made of materials such as iron or aluminum, a porous gold plating layer is formed. As a result, the surfaces of antenna members 18A and 18 are partially exposed to the outside, and antenna members 18A and 18B are easily corroded through the exposed parts. Due to such a porous gold plating layer, antenna members 18A and 18B are easily corroded in the air while having the desired high-frequency characteristics. In addition, there may be another plating layer between the gold plating layer and the surface of the antenna members 18A, 18B. For example, when the antenna members 18A, 18B are made of aluminum and a gold plating layer is formed on the surface, a nickel plating layer may be formed between them. Usually, nickel plating is used to prevent corrosion due to local cell action, but it is common to set the thickness of nickel plating to 5 μm or more for gold plating on aluminum to prevent corrosion due to local cell action. Therefore, considering the susceptibility of the antenna members 18A, 18B to corrosion, it is preferable that the nickel plating layer is thin. When the antenna members 18A, 18B are made of aluminum, the nickel plating layer can be corroded if it is, for example, 5 μm or less thick. Sulfur dioxide gas is also considered as an atmospheric component that corrodes metals. In particular, when silver plating is used, sulfurization progresses and its electrical performance decreases. The RFID tag 12 is designed so that the parts that perform the electrical function in this way actively lose their function when they come into contact with oxygen or moisture in the air.

[0041] Furthermore, in order to carry out such an inspection of the concrete structure 30, the capsule 14 of the RFID device 10 needs to have a strength that does not break due to the drying shrinkage of the concrete 32. Specifically, the concrete 32 shrinks when it dries. The shrinkage causes a compressive force to act on the capsule 14 as an external force. Therefore, the capsule 14 does not break due to the compressive force caused by the drying shrinkage of the concrete 32, but needs to break when an external force exceeding a predetermined force that is the same as or slightly larger than the compressive force is applied. For example, in the case of the first embodiment, the capsule 14 made of glass has a strength (e.g., a wall thickness) that can withstand the compressive force caused by the drying shrinkage of the concrete 32. Alternatively, the capsule 14 may be made of a resin material that elastically deforms when subjected to an external force equal to or smaller than the compressive force caused by the drying shrinkage of the concrete 32, and plastically deforms when subjected to an external force greater than the compressive force.

[0042] It is not a big problem that some of the capsules 14 in the plurality of RFID devices 10 are destroyed by the drying shrinkage of the concrete 32. This is because the RFID devices 10 that are not destroyed and capable of communication immediately after the concrete 32 dries and the concrete structure 30 is completed are used to inspect the concrete structure 30.

[0043] According to the first embodiment as described above, periodic inspection of a concrete structure can be performed without installing sensors requiring a power supply and wiring for supplying power to the sensors in the concrete structure.

[0044] (Embodiment 2) The second embodiment differs from the first embodiment in terms of the RFID device.

[0045] Fig. 7 is a perspective view of an RFID device according to the second embodiment of the present disclosure, and Fig. 8 is a cross-sectional view of the RFID device shown in Fig. 7.

[0046] As shown in Fig. 7 and Fig. 8, the capsule 114 of the RFID device 110 is substantially cylindrical and has a plurality of circumferential grooves 114b. When an external force acts on the capsule 114, stress is concentrated in the circumferential grooves 114b. That is, the circumferential grooves 114b function as a stress concentration portion of the capsule 114. Such circumferential grooves 114b make the capsule 114 more likely to break at the circumferential grooves 114b. In addition, by adjusting the width and depth of the circumferential grooves 114b, the breaking strength of the capsule 114 can be adjusted. As a result, the capsule 114 can be broken at a desired portion and by a desired external force.

[0047] In the case of the second embodiment, the RFID tag 112 accommodated in the sealed space 114a of the capsule 114 includes an IC chip 116 and a substrate 120 on which the IC chip 116 is mounted. On the substrate 120, antenna patterns 118A and 118B and a matching circuit pattern 124 are formed as conductor patterns. The matching circuit pattern 124 is a circuit that matches the impedance of the IC chip 116 and the impedance of the antenna patterns 118A and 118B at a predetermined frequency.

[0048] The antenna patterns 118A and 118B and the matching circuit pattern 124 are made of a corrodible material, such as iron, aluminum, etc. The substrate 120 is made of a material that has low resistance to strong alkali, that is, is easily decomposed by a strong alkaline liquid, such as polyimide.

[0049] According to the RFID device 110 of the second embodiment, when the capsule 114 is broken, the antenna patterns 118A, 118B and the matching circuit pattern 124 corrode. When at least one of the antenna patterns 118A, 118B and the matching circuit pattern 124 is broken due to corrosion, the RFID tag 112 cannot communicate. When at least one of the antenna patterns 118A, 118B and the matching circuit pattern 124 is locally thinned due to corrosion (when the resistance value is locally increased), impedance matching at a predetermined frequency cannot be achieved, and the RFID tag 112 cannot communicate. When a short circuit occurs in the matching circuit pattern 124 due to moisture, impedance matching at a predetermined frequency cannot be achieved, and the RFID tag 112 cannot communicate.

[0050] Furthermore, if reinforcing bars are present in a concrete structure, the substrate 120 will decompose, causing the antenna patterns 118A, 118B and the matching circuit pattern 124 on the substrate 120 to collapse, making the RFID tag 112 unable to communicate.

[0051] Specifically, when reinforcing bars are present in a concrete structure, the concrete has a strong alkalinity of, for example, pH 12 to 13 in order to suppress corrosion of the reinforcing bars. This is because calcium hydroxide is generated by a hydration reaction between the constituent materials of the concrete and the water used in preparing the concrete. When the capsule 114 is broken, the strong alkaline water, i.e., the calcium hydroxide aqueous solution, penetrates into the capsule 114, and the infiltrated calcium hydroxide aqueous solution decomposes the substrate 120. When the substrate 120 decomposes, the antenna patterns 118A and 118B and the matching circuit pattern 124, which have lost support from the substrate 120, cannot maintain their shapes and lose their electrical functions.

[0052] In addition, a specific liquid or a specific gas different from air may be enclosed in the capsule 114 together with the RFID tag 112. For example, an inert gas such as nitrogen gas may be enclosed. In this case, the inert gas flows out simultaneously with the destruction of the capsule 114, and the corrosion of the RFID tag 112 progresses rapidly. In addition, for example, a specific liquid may be enclosed in the capsule 114. That is, a liquid capacitance is disposed between the RFID tag 112 and the communication device. While the liquid is present, the RFID device 110 and the communication device can communicate at a predetermined resonant frequency (communication frequency), but when the capsule 114 is destroyed and the liquid flows out, the resonant frequency of the RFID device 110 changes, and the RFID device 110 cannot communicate with the communication device.

[0053] As in the above-mentioned embodiment 1, the present embodiment 2 as well makes it possible to perform comprehensive inspection of a concrete structure without installing sensors that require power supply and wiring that supplies power to the sensors in the concrete structure.

[0054] Although the present disclosure has been described above with reference to the above-mentioned embodiment, the present disclosure is not limited to this embodiment.

[0055] For example, in the case of the above-mentioned first embodiment, as shown in Fig. 1, the capsule 14 of the RFID device 10 is substantially cylindrical, but the shape of the capsule 14 is not limited to this. The capsule can have various shapes. However, in consideration of the ease of destruction, a lump shape, especially a spherical shape, which is unlikely to cause stress concentration and is unlikely to be destroyed by compression or shear, is not very suitable as a capsule shape.

[0056] Regarding the breaking strength of the RFID device capsule, the capsule shapes of the multiple RFID devices contained in the concrete structure may be different so that the breaking strength is different. This makes it possible not only to identify the location where the displacement or crack has occurred in the concrete structure, but also to estimate the extent of the displacement or crack.

[0057] In the case of the above-mentioned first embodiment, as shown in FIG. 2, the capsule 14 of the RFID device 10 has a hollow structure and includes an enclosed space 14a. The RFID tag 12 is accommodated in the enclosed space 14a. However, the embodiment of the present disclosure is not limited to this. For example, the capsule may have a solid structure and the RFID tag may be embedded in the capsule. In other words, it is sufficient that the RFID tag is disposed in the capsule.

[0058] Furthermore, in the case of the above-mentioned first embodiment, as shown in FIG. 2, the antenna members 18A and 18B of the RFID tag 12 of the RFID device 10 configure a dipole antenna. However, the embodiment of the present disclosure is not limited to this. The antenna of the RFID tag may be an antenna of another shape, such as a monopole antenna. That is, the RFID device according to the present disclosure can take various forms.

[0059] Fig. 9 is a top view of an RFID tag according to another embodiment of the present disclosure, and Fig. 10 is a cross-sectional view of an RFID device including an RFID tag according to another embodiment.

[0060] 9 and 10, RFID tag 212 includes IC chip 216 and substrate 220 such as a glass epoxy substrate. IC chip 216 is not directly mounted on substrate 220, but is mounted on substrate 220 via flexible substrate 226. Specifically, IC chip 216 is mounted on flexible substrate 226 on which a matching circuit and the like are formed, and modularized. Modularized IC chip 216 is mounted on substrate 220. Note that IC chip 216 may be directly mounted on substrate 220 as long as impedance matching can be achieved between IC chip 216 and antenna patterns 218A and 218B without a matching circuit.

[0061] In addition, antenna patterns 218A and 218B having significantly different antenna lengths are formed on the substrate 220. The latter has a longer antenna length. Therefore, the antenna pattern 218B contributes more to determining the resonant frequency (communication frequency) of the RFID tag 212.

[0062] The RFID tag 212 is housed in a glass cylindrical member having a bottom 214a, and is enclosed in the cylindrical member, i.e., capsule 214, by melting and closing an opening edge 214b of the cylindrical member with laser light. The inner diameter φ of the cylindrical member (i.e., capsule 214) is slightly larger than the width s1 of the RFID tag 212. In addition, the depth D of the cylindrical member is sufficiently larger than the length s2 of the RFID tag 212. As a result, when the opening edge 214b is melted and closed with laser light, the RFID tag 212 can be sufficiently separated from the opening edge 214b to be melted so as not to be affected by heat.

[0063] Moreover, the RFID tag 212 is fixed to the bottom 214a of the capsule 214 via an adhesive 228 such as a silicone adhesive. A part of the antenna pattern 218A penetrates the adhesive 228. That is, a part of the antenna pattern 218A that does not contribute much to determining the resonance frequency of the RFID tag 212 is disposed in the adhesive 228. As a result, the RFID tag 212 can perform wireless communication at a resonance frequency determined by the antenna length of the antenna patterns 218A and 218B, with almost no effect from the capacitance of the adhesive 228.

[0064] Like the RFID device 210 according to this other embodiment, the RFID device according to the present disclosure can take various forms depending not only on the conditions of use but also on the manufacturing method.

[0065] Furthermore, in the case of the above-mentioned first embodiment, the RFID tag 12 of the RFID device 10 is configured to receive a predetermined call signal, activate, and transmit a predetermined response signal. However, the embodiment of the present disclosure is not limited to this. For example, the RFID tag of the RFID device may be configured to store information transmitted from an external communication device. This allows the RFID tag to hold information such as the inspection date and inspector of the concrete structure.

[0066] In addition, in the case of the above-mentioned first embodiment, as shown in Fig. 3 and Fig. 4, the concrete structure 30 is a concrete building and is the inner surface part of a tunnel. However, the embodiment of the present disclosure is not limited to this. The concrete structure may be a concrete building such as a bridge pier or a levee. Furthermore, the concrete structure is not limited to a concrete building and may be a building material such as a concrete block.

[0067] In addition, in the case of the above-mentioned first embodiment, as shown in FIG. 4, the RFID device 10 is used by being embedded in the concrete of the concrete structure 30. The object in which the RFID device 10 is embedded is not limited to concrete. The RFID device may be embedded in an object that transmits radio waves and causes localized displacement. For example, multiple RFID devices may be buried in the soil of a slope. In this case, when the RFID device becomes unable to communicate, it is found that a displacement of a degree sufficient to cause an external force to destroy the capsule has occurred in the soil part in which the RFID device is present. This makes it possible to detect a precursor of a landslide on a slope.

[0068] That is, various aspects of the present disclosure are as follows.

[0069] A first aspect is a concrete structure comprising concrete and an RFID device contained within the concrete, the RFID device comprising a capsule and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal and transmits a predetermined response signal, the capsule being configured such that when an external force exceeding a predetermined force is applied to the capsule, it will be destroyed and the RFID tag will be exposed to the outside of the capsule, and the RFID tag is configured to change to a state in which communication is disabled when it comes into contact with a component in the air.

[0070] A second aspect is the concrete structure of the first aspect, wherein at least a portion of the current path of the RFID tag is made from a material that is corrodible by components in the atmosphere.

[0071] A third aspect is the concrete structure of the second aspect, wherein the current path of the RFID tag has a porous precious metal plating layer on a surface thereof.

[0072] A fourth aspect is a concrete structure of the second or third aspect, in which the RFID tag includes an IC chip and an antenna electrically connected to the IC chip as the current path, and the antenna is made of a material that can be corroded by components in the atmosphere.

[0073] A fifth aspect is a concrete structure of the fourth aspect, in which the RFID tag includes a matching circuit as the current path for impedance matching between the IC chip and the antenna, and the matching circuit is made of a material that can be corroded by components in the atmosphere.

[0074] A sixth aspect is a concrete structure according to any one of the first to fifth aspects, wherein the capsule of the RFID device is made from a material that breaks when an external force exceeding the predetermined force is applied.

[0075] A seventh aspect is the concrete structure of any one of the first to sixth aspects, wherein the encapsulation of the RFID device is provided with a stress concentrating portion at which stress is concentrated.

[0076] An eighth aspect is the concrete structure of any one of the first to seventh aspects, wherein the encapsulation of the RFID device is made from glass.

[0077] A ninth aspect is a concrete inspection system for inspecting a concrete structure, comprising: an RFID device contained in the concrete of the concrete structure; and a communication device that performs wireless communication with the RFID device, wherein the RFID device has a capsule and an RFID tag that is disposed within the capsule, is activated upon receiving a predetermined call signal from the communication device, and transmits a predetermined response signal to the communication device, wherein the capsule is configured such that when an external force exceeding a predetermined force is applied to the capsule, it is destroyed and the RFID tag is exposed to the outside of the capsule, and the RFID tag is configured to change to a state in which communication is disabled when it comes into contact with a component in the air.

[0078] A tenth aspect is an RFID device comprising: a capsule; and an RFID tag that is placed within the capsule, activates upon receiving a predetermined call signal, and transmits a predetermined response signal, wherein the capsule is configured such that when an external force exceeding a predetermined force is applied to the capsule, it is destroyed and the RFID tag is exposed to the outside of the capsule, and the RFID tag is configured to change to a state in which communication is disabled when it comes into contact with a component in the atmosphere. [Industrial Applicability]

[0079] The present disclosure is applicable to the inspection of objects such as concrete where localized displacements need to be detected.

Claims

1. Concrete and an RFID device contained within the concrete; The RFID device comprises a capsule and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal and transmits a predetermined response signal; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; A concrete structure, wherein the RFID tag is configured to change to a state in which communication is disabled when it comes into contact with a component in the air.

2. The concrete structure of claim 1 , wherein at least a portion of the current path of the RFID tag is made from a material that is corrodible by atmospheric constituents.

3. The concrete structure according to claim 2 , wherein the current path of the RFID tag has a porous precious metal plating layer on a surface thereof.

4. the RFID tag includes, as the current path, an IC chip and an antenna electrically connected to the IC chip; 4. The concrete structure according to claim 2 or 3, wherein the antenna is made of a material that is corrodible by atmospheric constituents.

5. the RFID tag includes a matching circuit for achieving impedance matching between the IC chip and the antenna as the current path, 5. The concrete structure of claim 4, wherein the matching circuit is made from a material that is corrodible by atmospheric constituents.

6. The concrete structure of claim 1 , wherein the encapsulation of the RFID device is made from a material that breaks when an external force exceeding the predetermined force is applied thereto.

7. The concrete structure of claim 1 , wherein the encapsulation of the RFID device comprises a stress riser where stress is concentrated.

8. The concrete structure of claim 1 , wherein the encapsulation of the RFID device is made from glass.

9. A concrete inspection system for inspecting a concrete structure, comprising: an RFID device contained in the concrete of the concrete structure; A communication device that wirelessly communicates with the RFID device, The RFID device comprises: a capsule; and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal from the communication device and transmits a predetermined response signal to the communication device; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; A concrete inspection system configured such that the RFID tag changes to an incommunicable state when it comes into contact with a component in the air.

10. Capsules and an RFID tag disposed within the capsule, which is activated upon receiving a predetermined call signal and transmits a predetermined response signal; The capsule is configured such that, when an external force exceeding a predetermined force is applied to the capsule, the capsule is broken and the RFID tag is exposed to the outside of the capsule; An RFID device, wherein the RFID tag is configured to change to an incommunicable state when exposed to an atmospheric component.

Images