JP2006337169A - Corrosion sensor, sheath tube, sheath tube jointing member, and corrosion sensor unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion sensor, a sheath tube, a sheath tube jointing member, and a corrosion sensor unit, capable of easily measuring corrosion of reinforcing bars at low cost, without causing infiltration of salinity etc into concrete or damaging aesthetic appearance. <P>SOLUTION: The corrosion sensor, used for diagnosing the state of progress of corrosion of steel products buried in concrete structures, is provided with both a corrosion detection part having a member for detection underlaid in an object to be measured or in the vicinity of the object to be measured for detecting corrosion of the member for detection made of metal, by measuring the electrical characteristics of the member for detection and a radio communication part for transmitting the detected results of corrosion to a reading device by radio. It is thereby possible to detect the corrosion of the member for detection, on the basis of the changes in the electrical characteristics and predict the occurrence of corrosion in steel products, such as reinforcing bars, PC steel wires, or sheath tube made of steel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technical field for diagnosing the progress of corrosion of steel materials such as reinforcing bars, PC steel wires, and steel sheath pipes embedded in a concrete structure.

  Conventionally, as a corrosion diagnosis method for reinforcing steel bars, a method of measuring the corrosion degree of reinforcing steel bars by measuring the natural potential of unpainted reinforcing steel in concrete in C876-87 of ASTM (American Society for Testing and Materials) (for example, Patent Document 1). In a healthy concrete structure, the reinforcing bars are passivated due to strong alkalinity, and the natural potential is about −100 mV to −200 mV (CSE). In the above method, the corrosion progresses as the reinforcing bars are activated by the intrusion and neutralization (carbonation) of chloride, and the potential changes in the base direction (increases in the negative direction) as the corrosion progresses. The probability of corrosion is diagnosed based on the measured value of this natural potential.

  Patent Document 1 discloses a method of diagnosing the corrosion probability or degree of corrosion of a reinforcing bar in a concrete structure by measuring a natural potential. In this method, the measured natural potential is corrected by the moisture content of the concrete in the cover part of the concrete structure, corrected by the presence or absence of salt in the concrete, and corrected by the carbonation depth of the concrete. Diagnose the corrosion probability or degree of corrosion with high accuracy.

In addition, a method is known in which the potential of a reinforcing bar is measured through a transmission cable in concrete to remove the influence of the concrete on the cover (for example, see Patent Document 2). Among them, a technique is known in which a corrosion state of a PC steel material is detected by burying a wire for inspection in advance and measuring the resistance and current of the wire (see, for example, Patent Document 3 and Patent Document 4).
Japanese Patent No. 3096240 Japanese Patent No. 2511234 Japanese Patent Laid-Open No. 8-94557 Japanese Patent No. 3205291

  However, the method for measuring a natural potential as described in Patent Document 1 has a problem that uncertain factors are large, and there are variations in actual diagnosis results and lack of reliability. Since the natural potential of the reinforcing bar is measured through the cover on the concrete surface, it does not necessarily indicate the true potential of the corrosion point of the reinforcing bar. In addition, various factors affect the measured value, which causes the potential to fluctuate.

  Of the main factors that are thought to affect the measured values, the ones that have the greatest effect are the electrochemical and resistance factors. Electrochemical factors are due to non-uniformity in the chemical and physical properties of concrete, and resistance factors are due to resistance of the concrete itself and the surface carbonation layer. These causes depend on the moisture content and the salinity.

  As described above, since the potential varies variously depending on the properties of the cover portion, the situation determined by the measurement of the natural potential does not match the actual corrosion situation, and the above measurement method lacks reliability. In addition, such a method is not an efficient diagnostic method because it takes time and labor to measure the moisture content of concrete, the salt content of concrete, and the carbonation depth of concrete.

  Corrosion detection, on the other hand, uses wireless technology to eliminate the effects of corrosion factors such as salt, oxygen, water, carbon dioxide, sulfate ions, and acidic substances that may enter through transmission cables, and to improve aesthetics. Although a method is conceivable, in the detection method using wireless technology, how to secure electric power for operating the corrosion sensor is an important issue.

  There are methods to use a battery as a power source for the corrosion sensor or to rectify radio waves supplied to the corrosion sensor from the outside and use it as a power source. In order to reduce the influence of radio wave attenuation due to the increase in distance, it is necessary to reduce the power consumption of the corrosion sensor as much as possible. Conventional measurement of natural potential and measurement of corrosion factors have a problem of large power consumption, and a corrosion state detection method and prediction method suitable for using wireless technology have been desired.

  The present invention has been made in view of such circumstances, and a corrosion sensor, a sheath tube, and a sheath tube joint member capable of detecting a corrosion state of steel material or the like with low power consumption that enables application of wireless technology. And it aims at providing a corrosion sensor unit. As a secondary matter, corrosion of reinforcing steel can be measured easily and at low cost without impairing the aesthetic appearance, without causing salt or the like to enter the concrete through the transmission cable.

  (1) In order to achieve the above object, a corrosion sensor according to the present invention is a corrosion sensor used for diagnosing the progress of corrosion of a steel material embedded in a concrete structure, and includes a measurement object or the above-described object. Corrosion detection unit having a metal detection member laid near the object to be measured, and detecting the corrosion of the detection member by measuring the electrical characteristics of the detection member with low power consumption And a wireless communication unit for wirelessly transmitting the corrosion detection result to the reading device.

  Thus, the corrosion sensor of the present invention lays a metal detection member in the vicinity of the measurement object or the measurement object, and detects the corrosion of the detection member by measuring electrical characteristics with a small amount of power consumption. . In general, the resistance of a metal material is extremely small, and it is possible to detect the corrosion state of the metal material by passing a very small amount of current through the metal material at a low voltage. From this, it is possible to detect the corrosion of the detection member from the change in the electrical characteristics, and it is possible to predict whether or not the corrosion of the steel material such as the reinforcing bar, the PC steel wire, and the steel sheath tube has occurred. . As a result, based on the grasped information, it is possible to accurately determine the necessity of repair of the structure and formulate construction guidelines in a short time, and to maintain and maintain the concrete structure in a healthy state.

  In addition, although it described that the member for a detection was laid in the measurement object or the vicinity of the said measurement object, the vicinity mentioned here is the circumference | surroundings of each of a reinforcing bar, PC steel wire, a steel sheath pipe, and a concrete covering part. Corresponds to (cover concrete part).

  Moreover, electrical resistance, potential difference, etc. are mentioned as an electrical characteristic detected in order to grasp | ascertain the corrosion state of the member for a detection.

  Further, the corrosion sensor of the present invention wirelessly transmits the detection result of corrosion to the reader. Thereby, the labor for measurement preparation can be reduced and the preparation period can be shortened. Furthermore, since it is only necessary to hold the reader at the time of measurement, it is possible to eliminate the complexity of wiring.

  In addition, since there is no need to install a transmission cable or the like from the vicinity of the measurement object to the concrete surface, there is no loss of aesthetics, and there is no invasion of corrosion factors for reinforcing steel corrosion through the wiring path, resulting in durability. Can be improved.

  Also, by providing the corrosion sensor of the present invention near the measurement object, various factors given by the cover concrete can be eliminated from the measured electrical characteristics. Furthermore, it is possible to eliminate the need for a dedicated expensive measuring instrument and to increase the accuracy of detecting the corrosion status of the steel material at a low cost.

  (2) Further, in the corrosion sensor of the present invention, the detection member is composed of two or more metal wires having different types or diameters of materials, and the metal wires are respectively connected in series to a resistance element. It is characterized by.

  Thus, the corrosion sensor of the present invention uses metal wires of different types depending on the resistance against corrosion, or uses a plurality of types of metal wires depending on the diameter. Thereby, it becomes possible to grasp | ascertain the degree of corrosion in steps, and it becomes possible to estimate the degree of corrosion of steel materials.

  (3) Further, in the corrosion sensor of the present invention, the corrosion detection unit is provided in the vicinity of the detection member, and has a cathode member made of a metal having a potential higher than that of the detection member. The detection member and the cathode member are electrically connected, and the cathode member plays a role of a cathode with respect to the detection member.

  As described above, the corrosion sensor according to the present invention has a cathode member made of a noble metal as a material in the vicinity of the detection member. Therefore, when corrosion of the detection member proceeds, Corrosion current flows between the cathode material. Thereby, the corrosion of the member for detection can be detected by detecting the corrosion current, and the degree of corrosion of the steel material can be predicted. For example, by calculating the corrosion current density from the surface area of the steel material, it is possible to grasp the corrosion status of the steel material or predict the future progress status.

Moreover, it becomes possible to grasp | ascertain the penetration | invasion condition of deterioration factors, such as chlorine ion which degrades steel materials, etc. earlier (4) Moreover, the sheath pipe | tube of this invention is used for the grout construction of a prestressed concrete structure, The corrosion sensor according to any one of the above, wherein the detection member is provided along the outer peripheral surface and / or the inner peripheral surface of the sheath tube main body.

  As described above, the sheath tube of the present invention detects corrosion of the detection member by providing the detection member along the outer peripheral surface or the inner peripheral surface of the sheath tube main body and measuring the electrical characteristics thereof. This makes it possible to predict whether or not corrosion of the sheath tube or the PC steel wire in the sheath tube has occurred.

  (5) Moreover, the sheath pipe joint member of the present invention is a sheath pipe provided with the corrosion sensor according to any one of the above, which is used to connect the sheath pipes used for grouting the prestressed concrete structure. The joint member is characterized in that the detection member is provided along the outer peripheral surface and / or the inner peripheral surface of the sheath tube joint member main body.

  As described above, the sheath pipe joint member of the present invention detects the corrosion of the detection member by providing the detection member along the outer peripheral surface or the inner peripheral surface of the joint member main body and measuring the electrical characteristics thereof. . This makes it possible to predict whether or not corrosion of the sheath tube or the PC steel wire in the sheath tube has occurred. In particular, since there is a high possibility that a corrosion factor enters the sheath tube from the joint portion of the joint member, it is effective to give such a function to the joint member.

  (6) Moreover, the corrosion sensor unit of the present invention is a corrosion sensor unit having any one of the above-described corrosion sensors, and a mounting portion that allows the corrosion sensor to be attached to and detached from the installation target. The detection member is provided on the member surface of the mounting portion.

  As described above, since the corrosion sensor unit of the present invention has an attachment portion that enables the above-described corrosion sensor to be attached to and detached from the installation target, it is easy to install the corrosion sensor, correct the installation position, and the like. Thereby, the labor for measurement preparation before placing concrete can be reduced, and the preparation period can be shortened.

  According to the corrosion sensor of the present invention, a metal detection member is laid in the vicinity of the measurement object or the measurement object, and corrosion of the detection member is detected by measuring electrical characteristics. Thereby, it is possible to detect the corrosion of the detection member from the change in the electrical characteristics, and it is possible to predict whether or not the steel material such as the reinforcing bar, the PC steel wire, the steel sheath tube, or the like is corroded. As a result, based on the grasped information, it is possible to accurately determine the necessity of repair of the structure and formulate construction guidelines in a short time, and to maintain and maintain the concrete structure in a healthy state.

  Further, the corrosion sensor of the present invention wirelessly transmits the detection result of corrosion to the reader. Thereby, the labor for measurement preparation can be reduced and the preparation period can be shortened. Furthermore, since it is only necessary to hold the reader at the time of measurement, it is possible to eliminate the complexity of wiring.

  In addition, since there is no need to install a transmission cable or the like from the vicinity of the measurement object to the concrete surface, there is no loss of aesthetics, and there is no invasion of corrosion factors for reinforcing steel corrosion through the wiring path, resulting in durability. Can be improved.

  Also, by providing the corrosion sensor of the present invention near the measurement object, various factors given by the cover concrete can be eliminated from the measured electrical characteristics. Furthermore, it is possible to eliminate the need for a dedicated expensive measuring instrument and to increase the accuracy of detecting the corrosion status of the steel material at a low cost.

  Further, according to the sheath tube of the present invention, the detection member is provided along the outer peripheral surface or the inner peripheral surface of the sheath tube main body, and corrosion of the detection member is detected by measuring the electrical characteristics thereof. This makes it possible to predict whether or not corrosion of the sheath tube or the PC steel wire in the sheath tube has occurred.

  Further, according to the sheath pipe joint member according to the present invention, the detection member is provided along the outer peripheral surface or the inner peripheral surface of the joint member main body, and the electrical characteristics are measured to detect the corrosion of the detection member. To do. This makes it possible to predict whether or not corrosion of the sheath tube or the PC steel wire in the sheath tube has occurred. In particular, since there is a high possibility that a corrosion factor enters the sheath tube from the joint portion of the joint member, it is effective to give such a function to the joint member.

  In addition, according to the corrosion sensor unit according to the present invention, since the corrosion sensor has a mounting portion that allows the corrosion sensor to be attached to and detached from the installation target, it is easy to install the corrosion sensor, correct the installation position, and the like. Thereby, the labor for measurement preparation before placing concrete can be reduced, and the preparation period can be shortened.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, in order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

(Embodiment 1)
FIG. 1 is a block diagram showing an electrical configuration of the corrosion sensor 1. The corrosion sensor 1 communicates information regarding detected corrosion to the outside of the concrete by communicating with the reader via electromagnetic waves. The corrosion sensor 1 includes a corrosion detection unit 2 and a wireless communication unit 3. The corrosion detection unit 2 includes a sensor circuit 10 and a characteristic detection unit 5, and the characteristic detection unit 5 includes a sensor interface circuit 20 and a detection circuit 30 a of the RFID IC 30. The sensor circuit 10 includes metal wires A _{1 to An} (detection members) and resistance elements R _{1 to} R _n .

  The corrosion sensor 1 lays a metal detection member in the vicinity of the measurement object or the measurement object, and detects the corrosion of the detection member by measuring electrical characteristics with a small amount of power consumption. In general, the resistance of a metal material is extremely small, and it is possible to detect the corrosion state of the metal material by passing a very small amount of current through the metal material at a low voltage.

The resistance element is used for the purpose of improving detection accuracy such as the presence or absence of corrosion of the metal wires A _{1 to An} (detection members), the change in the corrosion state, or the identification of the corrosion location.

  The sensor interface circuit 20 is a circuit that connects the sensor circuit 10 and the RFID IC 30. The RFID IC 30 includes a detection circuit 30a and a wireless communication circuit 30b. The detection circuit 30a applies a voltage to the sensor circuit 10 and detects electrical characteristics between the terminals 10a and 10b. The electrical characteristics include voltage (potential difference) between the terminals 10a and 10b, electrical resistance, impedance, capacitance, and the like, and these can be detected. In this embodiment, the voltage between the terminals 10a and 10b is detected. The wireless communication circuit 30b wirelessly transmits the detection result of the detection circuit 30a to the external reading device via the antenna 40. Here, the sensor interface circuit 20 and the detection circuit 30 a of the RFID IC 30 constitute the characteristic detection unit 5, and the radio communication circuit 30 b and the antenna 40 of the RFID IC 30 constitute the radio communication unit 3.

The metal wires A _{1 to An} are laid in the vicinity of the measurement object or the measurement object. The measurement object is, for example, a reinforcing bar, a PC steel wire, a steel sheath tube, or the like. For example, it may be laid on the surface of an insulating steel sheath tube with an insulator such as a resin film interposed therebetween, or may be attached to the outer periphery of a resin sheath tube through which a PC steel wire is inserted. Thereby, various factors given by the cover concrete can be excluded from the measured electrical characteristics. Furthermore, it is possible to eliminate the need for a dedicated expensive measuring instrument and to increase the accuracy of detecting the corrosion status of the steel material at a low cost. Although metal lines A ₁ to A _n are shown as being more in FIG. 1, may be only one.

Metal wire A ₁ to A _n in the case of applying the sheath tube grout construction of the present invention is provided along one of at least the outer peripheral surface or inner peripheral surface of the sheath tube body used in the grout construction. FIG. 2 is a front view of a sheath tube 50 in which metal wires A _{1 to} A ₄ are laid on the outer periphery of a resin sheath tube main body 51. Metal wires A _{1 to} A ₄ are directly wound around the outer periphery of the sheath tube main body 51. At both ends of the metal wire _A 1 to A ₄ is an end of the lead wire _L 1 ~L ₄ is connected, the other end of the lead wire _L 1 ~L ₄ is connected to a sensor interface circuit 20 (not shown). As described above, the sheath tube 51 is provided with the metal wires A _{1 to} A ₄ along the outer peripheral surface or the inner peripheral surface of the sheath tube main body 51 and measures the electrical characteristics thereof, whereby the metal wires A _{1 to} A ₄ are measured. Detect corrosion of. Thereby, since the progress of the corrosion of the metal wires A _{1 to} A ₄ can be detected, it is possible to predict whether or not the sheath tube or the PC steel wire in the sheath tube is corroded.

FIG. 3 is a front view of the sheath tube joint member 52 in which the metal wires A _{1 to} A ₄ are laid on the outer periphery of the joint member main body 53 for joining the sheath tubes. Metal wires A _{1 to} A ₄ are arranged and wound around the outer periphery of the joint member main body 53 in parallel. At both ends of the metal wire _A 1 to A ₄ is an end of the lead wire _L 1 ~L ₄ is connected, the other end of the lead wire _L 1 ~L ₄ is connected to a sensor interface circuit 20 (not shown). As described above, the sheath pipe joint member 52 is provided with the metal wires A _{1 to} A ₄ along the outer peripheral surface or the inner peripheral surface of the joint member main body 53 and measures the electrical characteristics thereof, whereby the metal wires A ₁ to A ₄ are measured. detecting the corrosion of a _4. Thereby, since the progress of the corrosion of the metal wires A _{1 to} A ₄ can be detected, it is possible to predict whether or not the sheath tube or the PC steel wire in the sheath tube is corroded. In particular, since there is a high possibility that a corrosion factor enters the sheath tube from the joint portion of the joint member 52, it is effective to give the joint member 52 such a function.

  In addition, work efficiency can be improved compared with attaching the corrosion sensor 1 on the construction site by producing the sheath pipe | tube or joint member to which the corrosion sensor 1 was previously attached, and carrying to a construction place of concrete.

The metal wires A _{1 to An} are made of the same metal as the steel material in the concrete structure to be measured. If the concrete structure is an ordinary reinforced concrete structure, use an iron wire (JIS G3532) or a mild steel wire (JIS G 3505). In the case of a prestressed concrete structure, it is preferable to use a PC steel wire (JISG 3536) or a piano wire (JISG 3502). However, the material of the metal wire A ₁ to A _n are not limited to, it may be a known variety of wire.

Diameter of the metal wire _A 1 to A _n can be anything in the range of 0.01 to 1.0 mm. However, the shape of the detection member is not necessarily a line. The detection member is not limited to a metal wire, and it is also possible to use a thin metal plate that is more easily corroded than steel.

  The material for the detection member may be anything, but the material is more susceptible to corrosion than the material of the reinforcing bar, PC steel, and steel sheath tube, in other words, the potential is lower than that of the reinforcing bar, PC steel material, and steel sheath tube. Is preferred.

The metal wire A ₁ to A _n is not limited to the cross section is circular, it is also possible to use any of various shapes such as oval or strip. Examples of the electrical characteristics to be detected in order to grasp the corrosion state of the metal wire include impedance including electric resistance and potential difference. In addition, since the longer metal wire can cover a wider range, the detection accuracy becomes higher. Moreover, the adhesiveness of concrete can be improved by changing the magnitude | size of a diameter by the position in one metal wire. In that case, since corrosion is detected in the thin portion, it is possible to increase the sensitivity by repeatedly providing the thin portion.

Thus, it is possible to detect the corrosion of metal wire A ₁ to A _n from a change in electrical properties, rebar, PC steel wire, is possible to predict whether the corrosion of steel materials such as steel sheath tube has occurred It becomes possible. As a result, based on the grasped information, it is possible to accurately determine the necessity of repair of the structure and formulate construction guidelines in a short time, and to maintain and maintain the concrete structure in a healthy state.

Resistive element _R 1 to R _n are connected in series to the metal wire _A 1 to A _n. Thereby, when a metal wire corrodes, since resistance value goes up, corrosion of a metal wire is detectable. For example, the resistance element _R 1 as the resistance value _r 1 ~r _n of to R _n, the resistance value of the sensor circuit 10 in the absence of corrosion _{r 1 r 2 ··· r n /} (r 1 + r 2 + it is a ··· + _{r n),} when the metal wire _{a n} that are connected in series is disconnected to the resistance element _{R n,} the resistance value of the sensor circuit _{10, r 1 r 2 ··· r n} -1 / (R ₁ + r ₂ +... + R _n-1 ), and the resistance increases. Therefore, corrosion can be detected by detecting the resistance value. Incidentally, a resistor R ₁ to R _n without connecting to the metal wire A ₁ to A _n, may detect corrosion by the resistance of the metal wire itself. In the configuration shown in FIG. 1, although the sensor circuit 10 includes a plurality of metal lines A ₁ to A _n, may be provided with a single metal wire.

By thus connecting the resistor element _R 1 to R _n in the metal wire _A 1 to A _n, a slight corrosion state of the metal wire _A 1 to A _n current flowing through the metal wire _A 1 to A _n is even slightly It is possible to detect with high accuracy. Furthermore, by connecting the resistor element _R 1 to R _n in the metal wire _A 1 to A _n, the power consumed by the metal wire _A 1 to A _n and a resistor _R 1 to R _n is small, the detection member Can reduce power consumption.

In order to reduce the power consumption, it is preferable to combine the resistance elements R _{1 to} R _n so that the resistance value of the entire detection member is increased. The resistance value of the entire detection member is preferably in the range of 10 kΩ to 1 MΩ, for example. If it is less than 10 kΩ, the amount of current flowing through the detection member increases, and the power consumption consumed by the detection member increases. On the other hand, if it is greater than 1 MΩ, the amount of current flowing through the detection member decreases, but the voltage associated with the entire detection member increases and the power consumption increases.

The metal wires can be arranged not only in parallel but also in a stepped shape or a circumferential shape with respect to the depth direction. Stepwise along the direction of arrival of corrosion factor, by placing a metal wire A ₁ to A _n, because it is corroded from the metal wire near the outside of the concrete structure, corrosion degradation time of the steel of the concrete structure in Can be predicted more accurately. Note that circumferential metal wires A _{1 to An} having different radii may be arranged stepwise along the radial direction of the pipe or the reinforcing bar to be measured.

FIG. 4 is a block diagram showing an electrical configuration of the corrosion sensor 55 using the metal wires B _{1 to} B _n having different diameters. Thus, by using a plurality of metal wires having different materials, thicknesses and lengths as the metal wires, it becomes possible to accurately predict the corrosion state of the steel material or the like. Thereby, it becomes possible to grasp | ascertain the degree of corrosion in steps, and it becomes possible to estimate the degree of corrosion of steel materials. In this case, it is possible to detect which metal wire is corroded from the resistance value of the sensor circuit 10 by grasping the resistance value of each of the resistance elements R _{1 to} R _{n in} advance.

FIG. 5 is a block diagram showing an electrical configuration of the corrosion sensor 57 in which the sensor circuit 10 of the corrosion detection unit 2 is configured as an R-2R circuit. In the sensor circuit 10, the metal wires A _{1 to An} and the sensor interface circuit 20 are connected by resistance elements P _{1 to} P _n and Q. Corrosion sensor 57, a resistive element _R 1 to R _n series-connected metal wire _A 1 to A _n are arranged in parallel a plurality of metal wire _A 1 to A _n by measuring the electrical resistance or the potential difference of the sensor circuit 10 Make sure that is corroded or corroded. In this case, by utilizing the R-2R circuit, it is possible to determine the location of the corroded metal wire A ₁ to A _n.

  The detection circuit 30a of the RFID IC 30 measures an electrical characteristic such as a resistance value or a potential of the sensor circuit 10. The detection circuit 30a includes various circuits necessary for measuring electrical characteristics, such as a high output current circuit, an inverting amplifier circuit, an in-phase amplifier circuit, a voltage follow circuit, an integration amplifier circuit, a comparison operation circuit, and a comparison operation for hysteresis characteristics. Various resistance elements, capacitors, coils and the like are incorporated so as to constitute a circuit, a multivibrator circuit, a current-voltage conversion circuit, and the like. When measuring a potential difference, a small potential difference can be amplified by using an operational amplifier, and the potential difference can be detected more accurately.

  The memory of the detection circuit 30a includes a ROM that stores an operating system that performs overall control, an EEPROM or FRAM that stores programs for rewriting data and detecting the state of structures, and a RAM that records detected information. It consists of An ID number of the sensor unit may be mounted in the memory, or information on the position where the structure is embedded is written in the RAM from the reading device, and the information may be read by the reading device together with the information detected by the sensor.

  The wireless communication unit 3 includes a wireless communication circuit 30 b of the RFID IC 30 and an antenna 40. On the one hand, the wireless communication circuit 30b processes the information sent from the detection circuit 30a so that it can be wirelessly transmitted. On the other hand, the wireless communication circuit 30b transmits the instruction received from the reading device via the antenna 40 to the detection circuit 30a.

  The radio communication circuit 30b of the RFID IC 30 includes a modulation circuit, a charging / power supply unit, a memory, and the like. This power supply unit may be of a type equipped with a battery, or may be of a so-called battery-less type, that is, having a power storage function and temporarily storing an induced voltage due to electromagnetic waves supplied from the outside. good. The memory included in the wireless communication circuit 30b includes a ROM that stores an operating system that performs overall control, an EEPROM that stores programs for detecting data rewriting and the state of structures, and a RAM that records detected information. Etc. An ID number of the sensor may be mounted in the memory, or information related to the embedded position of the structure may be written in the RAM from the reading device, and the information may be read by the reading device together with the information detected by the sensor.

  As described above, the corrosion sensor 1 wirelessly transmits the detection result of corrosion to the reading device by the function of the RFID IC 30 or the like. Thereby, the labor for measurement preparation can be reduced and the preparation period can be shortened. Furthermore, since it is only necessary to hold the reader at the time of measurement, it is possible to eliminate the complexity of wiring.

  In addition, since there is no need to install a transmission cable or the like from the vicinity of the measurement object to the concrete surface, there is no loss of aesthetics, and there is no invasion of corrosion factors for reinforcing steel corrosion through the wiring path, resulting in durability. Can be improved.

  The RFID IC 30 includes a control unit such as a power rectifier circuit, a modulation / demodulation device, a charging / power source unit, a memory, and a CPU. The memory stores a unique identification number registered in advance, information from the outside, a record of state changes in the concrete structure, and other necessary information. The power supply unit may have a power storage function and temporarily store a dielectric voltage from an electromagnetic wave supplied from the outside. The CPU and control unit control the corrosion detection unit 2. For example, the CPU performs data processing of transmission / reception signals, digital conversion of analog information of the sensor unit, power supply control, and other data processing.

  The antenna 40 transmits and receives information wirelessly to and from the reading device. The antenna 40 is made of metals, carbon fiber, ferrite, or the like. For the antenna 40, it is desirable to use a hollow winding, a magnetic winding, or a substrate formed by using a printing technique, and the above material is sandwiched between films such as PET. Also good. As the antenna 40, a ring-shaped, rod-shaped, or disk-shaped antenna may be used.

  The reading device consists of an antenna, a modulation / demodulation device, a memory, a CPU, and a power supply unit for supplying power, and outputs information from the corrosion detection unit directly or data processing to other devices as necessary. Let In that case, it is good also as performing via an external output terminal.

  Next, an installation method and an operation method of the corrosion sensor 1 configured as described above will be described.

First, a plurality of metal wires A _{1 to An} are attached to the sheath tube at intervals in the length direction. Next, the sheath tube to which the metal wires A _{1 to An} are attached is arranged at a predetermined position according to the design of the structure or the situation at the site. Concrete is placed and cured to fill the sheath tube. Then, a PC steel material is inserted into the sheath tube and is tensioned using a jack or the like. Next, a grout material is injected into the sheath tube. In this way, the corrosion sensor 1 is installed inside the concrete.

  After the concrete hardens or during a certain period, the corrosion sensor 1 is operated by holding the reader over the position where the antenna is embedded. The corrosion sensor 1 that has received the signal from the reading device applies a predetermined voltage generated by the operation of the RFID IC 30 to the sensor circuit 10. The sensor interface circuit 20 detects a potential difference or a resistance value of the sensor circuit 10 and performs signal amplification. The RFID IC 30 modulates a signal to be transmitted and transmits corrosion information to the reader via the antenna 40. In this way, the corrosion sensor 1 is operated.

(Embodiment 2)
In the above embodiment, although the laying directly metal lines A ₁ to A _n on the outer circumference of sheath tube body 51, a mounting portion for mounting detachably a metal wire A ₁ to A _n in the sheath pipe or the like corrosion sensor It may be provided as a corrosion sensor unit. To be detachable means to be formed so that it can be fitted or inserted.

FIG. 6 is a front view showing the attachment portion 61 of the corrosion sensor unit 60, and FIG. 7 is a perspective view showing the attachment portion 61 of the corrosion sensor unit 60. The mounting portion 61, the metal wire _D 1 to D ₅ is laid, the metal wires _D 1 to D ₅ is connected to the lead wire _L 1 ~L ₅ respectively.

The attachment portion 61 has a shape similar to the outer shape of the sheath tube so as to be fitted to the outer shape of the sheath tube. Metal wire _D 1 to D ₅ are on the outer periphery of the mounting portion 61 are laid in parallel, when there is corrosion of the metal wire _D 1 to D ₅ are electricity sensor interface circuit 20 by a lead wire _L 1 ~L ₅ The information of the characteristic is transmitted.

As described above, by providing the dedicated mounting portion 61 so that the corrosion sensor can be attached to and detached from the installation target, and by installing the metal wires D _{1 to} D ₅ on the surface of the mounting portion 61, the sheath tube, the steel material Or, it is possible to attach the corrosion sensor to any location of the reinforcing bar. As a result, it becomes possible to grasp the corrosion state of the location to be measured efficiently at low cost. In addition, it becomes easy to install the corrosion sensor and correct the installation position. Thereby, the labor for measurement preparation before placing concrete can be reduced, and the preparation period can be shortened.

The attachment portion is not limited to the shape shown in FIG. 7, and may be an attachment portion on a flat plate. FIG. 8 is a perspective view showing the mounting portion 71 on the flat plate of the corrosion sensor unit 70. The mounting portion 71, the metal wire _E 1 to E ₅ is laid, the metal wires _E 1 to E ₅ is connected to the lead wire _L 1 ~L ₅ respectively.

  In addition to such a mounting portion, a corrosion sensor unit may be formed by laying a metal wire on the surface of a disk-shaped spacer used by inserting a reinforcing bar. In that case, a metal wire is laid in a circular shape by providing a groove on the outer peripheral surface of the disk shape. In addition, you may provide a groove | channel in the bottom surface in any one of disk shape, and may lay a metal wire in the periphery shape.

(Embodiment 3)
In the above-described embodiment, the electrical characteristic detected by the sensor circuit 10 is the resistance value of the resistance element or the potential difference caused by the resistance element. However, the corrosion current may be detected by providing a cathode member near the metal wire. Moreover, the sensitivity of corrosion detection may be increased by advancing the progress of corrosion by using a cathode member.

  FIG. 9 is a block diagram showing an electrical configuration of the corrosion sensor 80 that detects the corrosion current. In the corrosion sensor 80, by arranging a metal wire 81 (cathode member) having a potential higher than that of the metal wire in the vicinity of the metal wire, the metal wire 81 serves as a cathode, and the corrosion of the metal wire proceeds. It is what you use. Thereby, it becomes possible to grasp | ascertain the penetration | invasion condition of deterioration factors, such as a chlorine ion which degrades steel materials etc. earlier.

A battery in which a battery in which a metal anode part and a cathode part can be clearly distinguished is formed is called a macro cell, and a current flowing between both electrodes is called a corrosion current (macro cell current). Healthy concrete exhibits strong alkalinity (pH = 12 to 13), and a dense passive film having a thickness of 2 to 6 mm is formed on the inner steel surface, thereby protecting the steel from corrosion. However, when this passive film is destroyed by chloride ions (Cl ⁻ ) that have permeated into the concrete, a reaction in which the steel material is ionized (oxidation reaction: anode reaction) proceeds, and oxygen is reduced on a healthy steel surface. Reaction (reduction reaction: cathode reaction) proceeds. These reactions proceed simultaneously, resulting in a potential difference in which the anode part has a base potential and the cathode part has a noble potential. At the same time, a current (corrosion current) flows through the concrete from the anode part to the cathode part, and corrosion of the steel progresses. .

By this principle utilizing such, placing the noble metal wire 81 in potential than the metal wire A ₁ to A _n in vicinity of the metal wire (cathode member), progressive corrosion of the metal wire A ₁ to A _n It is possible to grasp the penetration state of deterioration factors such as chlorine ions that deteriorate steel materials.

Further, by disposing the metal wire _A 1 to A metal wire in the vicinity of the _{n A} 1 to A noble metal wire potential than _n 81 (cathode member), the metal wire _A 1 to A _n and the noble metal Corrosion current flows between This corrosion current is greatly affected by the resistance formed by the concrete. When concrete contains a lot of salt and moisture, the resistance of the concrete decreases and the corrosion current increases, but when the concrete does not contain a lot of salt and moisture, the resistance of the concrete increases and the corrosion current does not increase. Get smaller. By measuring this corrosion current and calculating the corrosion current density from the surface area of the steel material, it is possible to grasp the corrosion status of the steel material or predict the future progress status.

When the metal wires A _{1 to An} are iron, alloys of various metals such as nickel, tin, lead, copper, platinum, gold, and stainless steel can be used as the noble metal wire (cathode member). The electrical characteristics measured by the sensor circuit include a potential difference between the reinforcing bar and the metal wire.

  Next, the present invention will be specifically described with reference to examples.

  The experiment was conducted assuming a post-tension type T-type prestressed concrete (hereinafter referred to as PC concrete) having a girder length of 32 m and four PC steel materials (tensile materials) of 12S12.7B arranged in the girder. In the assumed PC concrete, a sheath tube made of steel and having an outer diameter of 68 mm is embedded, and an experiment for detecting the sheath tube corrosion was performed.

  In PC concrete designed according to the road bridge specifications, girder reinforcement was performed, followed by the sheath tube. The corrosion sensor 1 uses a metal wire wound around the outer periphery of a sheath tube body 51 as shown in FIG. 2, and the used metal wires are one each of 0.1 mm and 0.3 mm thick mild steel wires. A total of two were used.

  The corrosion sensor 1 was attached to one of the four sheath tubes arranged in the beam. The attached corrosion sensor 1 includes an RFID chip including another type of sensor, a modulation / demodulation circuit, a CPU, a memory and a sensor control unit, an antenna, and a power storage unit. A frequency of 13.56 MHz was used for communication between the corrosion sensor 1 and the reader.

  After the corrosion sensor 1 was attached, concrete was cast and steam curing was performed to remove the mold. Then, after curing for 2 weeks, PC steel was inserted, and it was tense. The grout used for filling was manufactured using a commercially available grout admixture with a water cement ratio of 45%. One month after the injection of the grout, the potential difference of the metal wire was measured using a reader while intermittently spraying salt water on the concrete specimen.

  As a result, the potential difference of the sensor was 2V from the start of the test to the 355th day, but showed a 1V potential difference on the 356th day. When the concrete specimen was split and the fine wires were examined, rust was observed on the entire metal wire with a thickness of 0.1 mm. This confirmed that the metal wire was corroded.

  An experiment was conducted as follows for corrosion inside a concrete yard (cross section: 600 mm × 600 mm) of a stock yard constructed near the coast.

First, after assembling the reinforcing bars, as shown in FIG. 10, the corrosion sensor 90 was attached to the reinforcing bars 94, the formwork was installed, and the concrete was placed. The corrosion sensor 90 is formed by providing _four iron wires F _{1 to} F ₄ as metal wires for corrosion detection on the surface of the RFID tag 91. The diameters of the iron wires F _{1 to} F ₄ are 0.1 mm, 0.5 mm, 1.0 mm, and 2.0 mm, respectively. By connecting resistance elements having resistance values of 2 KΩ, 3 KΩ, 5 KΩ, and 7 KΩ to the iron wires F _{1 to} F ₄ , and using resistance values that do not overlap with each other, the thickness of the wire when corroded I was able to tell if it was corroded. The resistance values that do not overlap each other are, for example, prime numbers. The RFID tag 91 is not equipped with a battery, and is integrated with a reinforcing bar 94 by a spacer 95 and a fitting metal 96 as shown in FIG. The RFID tag 91 and the spacer 95 are bonded by an adhesive such as an epoxy resin. As shown in FIG. 11, the RFID tag 91 was installed so that the distance between the concrete surface 97 and the surface of the RFID tag 91 was 20 mm with respect to the 50 mm cover of the reinforcing bar.

It held up reading device from the concrete surface 97 after the lapse of 5 years has elapsed and after 10 years from the construction, by measuring the current applied to the iron wire F ₁ to F _4, to confirm the presence or absence of cleavage of iron wire F ₁ to F _4. Five years later, 0.1 mm iron wire F ₁ corroded, and 10 years later, 0.1 mm iron wire F ₁ , 0.5 mm iron wire F ₂ and 1.0 mm iron wire F ₃ corroded. It was confirmed. Since the iron wire is corroded by the infiltrated salinity and the infiltration of the salinity is considered to follow diffusion, it can be assumed that the infiltration depth of the salinity is proportional to the square root of time. Since the salinity has penetrated to the position of 20 mm in 5 years, the time (year) when the salinity penetrates to the depth of 50 mm and corrosion of the reinforcing bar starts can be calculated by (2.236 × 50/20) ² It can be estimated that 31 years after construction. On the other hand, the corrosion rate was 0.5 × 0.5 × 3.14 / 5 and 0.157 mm ² / year or more because the iron wire having a diameter of 1.0 mm was corroded in 5 years from 5 to 10 years. Can be guessed.

  In this way, it is possible to estimate the corrosion time of the reinforcing bar by using the corrosion sensor so that the metal wire is arranged at a certain depth against the reinforcing bar cover, and the corrosion rate can be changed by changing the wire diameter. Can be estimated. In addition, it is possible to estimate the delamination time of concrete due to corrosion expansion from the corrosion rate, which is useful for formulating repair times and future maintenance plans.

It is a block diagram which shows the electrical structure of the corrosion sensor which concerns on this invention. It is a front view of the sheath tube which laid the metal wire (detection member) on the outer periphery of the sheath tube body. It is a front view of a sheath pipe joint member in which a metal wire (detection member) is laid on the outer periphery of the joint member main body. It is a block diagram which shows the electrical structure of the corrosion sensor which concerns on this invention. It is a block diagram which shows the electric constitution of the corrosion sensor which comprised the sensor circuit as an R-2R circuit. It is a front view which shows the attachment part of the corrosion sensor unit which concerns on this invention. It is a perspective view which shows the attachment part of the corrosion sensor unit which concerns on this invention. It is a perspective view which shows the attachment part of the corrosion sensor unit which concerns on this invention. It is a block diagram which shows the electrical structure of the corrosion sensor which concerns on this invention. It is a perspective view which shows the corrosion sensor which concerns on this invention. It is a figure which shows the corrosion sensor embed | buried under concrete.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Corrosion sensor 2 Corrosion detection part 3 Wireless communication part 5 Characteristic detection part 10 Sensor circuit 10a, 10b Terminal 20 Sensor interface circuit 30 RFIDIC
30a Detection circuit 30b Wireless communication circuit 40 Antenna 50 Sheath tube 51 Sheath tube body 52 Sheath tube joint member 53 Joint member body 55 Corrosion sensor 57 Corrosion sensor 60 Corrosion sensor unit 61 Mounting portion 70 Corrosion sensor unit 71 Mounting portion 80 Corrosion sensor 81 Metal Wire (Cathode member)
90 Corrosion sensor 91 RFID tag 94 rebar 95 spacer 96 fitting bracket 97 the concrete surface _{A 1 -A n, B 1 -B} n, D 1 -D 5, E 1 -E 5 metal wire (detection member)
R ₁ -R _n , P ₁ -P _n , Q resistive element L ₁ -L ₅ lead wire F ₁ -F ₄ iron wire (detection member)

Claims (6)

A corrosion sensor used for diagnosing the progress of corrosion of steel materials embedded in a concrete structure,
A corrosion detection unit that has a metal detection member laid near the measurement object or the measurement object, and detects corrosion of the detection member by measuring electrical characteristics of the detection member When,
A corrosion sensor comprising: a wireless communication unit configured to wirelessly transmit the corrosion detection result to a reader. The detection member is composed of two or more metal wires having different types or diameters of materials,
The corrosion sensor according to claim 1, wherein each of the metal wires is connected in series to a resistance element. The corrosion detector has a cathode member made of a metal having a potential higher than that of the detection member, and the cathode member is installed in the vicinity of the detection member,
The said detection member and the said member for cathodes are electrically connected, The said member for cathodes plays the role of a cathode with respect to the said member for detection, The Claim 1 or Claim 2 characterized by the above-mentioned. Corrosion sensor. A sheath tube in which the corrosion sensor according to any one of claims 1 to 3 is used for grout construction of a prestressed concrete structure,
The sheath member, wherein the detection member is provided along an outer peripheral surface and / or an inner peripheral surface of a sheath tube main body. A sheath pipe joint member provided with the corrosion sensor according to any one of claims 1 to 3, which is used to connect sheath pipes used for grout construction of a prestressed concrete structure,
The sheath tube joint member, wherein the detection member is provided along an outer peripheral surface and / or an inner peripheral surface of the sheath tube joint member main body. A corrosion sensor unit comprising: the corrosion sensor according to any one of claims 1 to 3; and an attachment portion that allows the corrosion sensor to be attached to and detached from an installation target.
The corrosion sensor unit, wherein the detection member is provided on a member surface of the attachment portion.

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