JP6621611B2 - Corrosion detection method - Google Patents

Description

  The present invention relates to a technique for detecting a corrosion state of a steel material.

  2. Description of the Related Art Conventionally, as a technique for detecting a corrosive environment, an electrical corrosion sensor that detects electrical characteristics that change when a fine wire such as iron corrodes is known (for example, Patent Document 1 and Patent Document 2). Moreover, as a method of detecting corrosion of a reinforcing bar, a strain gauge is attached to the reinforcing bar in the concrete structure, and the strain when the reinforcing bar is damaged is detected (Patent Document 3). On the other hand, conventionally, an optical fiber sensor for detecting strain generated in a structure has been proposed. For example, in Patent Document 4, an optical fiber sensor shaped in a spiral shape is attached to a structure to be measured, and a change in light propagation characteristics of the optical fiber sensor is measured by an electro-optical measurement device. Thereby, when a displacement arises in a structure, it is possible to measure the displacement without destroying the structure.

  In Patent Document 5, a tape member that is wound around a spacer member and wound spirally inside an concrete structure, and an optical fiber that is wound along the tape member are used. This makes it possible to detect shear cracks in the concrete member.

JP-A-8-0945557 JP 2012-145330 A Japanese Patent No. 4975420 JP 2000-097647 A Japanese Patent No. 4008623

  As a method for detecting corrosion in a reinforced concrete structure, the self-potential method has been conventionally known, but this method must be measured by connecting the cable and the internal rebar through the concrete surface. In addition, there is a problem that measurement cannot be performed unless the concrete surface is sufficiently wet. Furthermore, when the surface of the structure is a resin-based paint or tile finish, it cannot be measured.

  In addition, conventionally known electrical corrosion sensors are affected by transmission loss, electromagnetic interference, etc., and when monitoring constantly, current flows during measurement, which accelerates corrosion of the sensor itself. There are drawbacks. In addition, the detection due to corrosion breakage of these iron wires and iron foils cannot capture the electrical characteristics over time, and it is difficult to evaluate the degree of subsequent progress only by detecting that it has become a corrosive environment. It is.

  In addition, in order to measure the strain of steel material due to corrosion, when a strain gauge is directly attached to the steel material or a strain gauge is installed in the vicinity of the steel material, the measuring instrument, adhesive, etc. will cover the steel material. Therefore, it may affect the occurrence of corrosion and may not be able to accurately detect corrosion. Furthermore, if corrosion occurs in the portion, the strain gauge may be peeled off, and measurement may not be possible, or correct results may not be obtained even if measurement is possible.

  On the other hand, the method of directly winding an optical fiber around a reinforcing bar in a structure is to dispose the optical fiber over the entire structure and detect damage or deformation of the structure, and does not detect a corrosive environment.

  This invention is made | formed in view of such a situation, and it aims at providing the corrosion detection method which can detect the corrosion environment of steel materials early and correctly using an optical fiber sensor.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the corrosion detection method of the present invention is a corrosion detection method for detecting a corrosive environment of a steel material, wherein an optical fiber sensor is fixed directly on the outer periphery of the steel material, and based on a change in characteristics of light waves propagating in the optical fiber sensor. Then, the strain due to corrosion of the steel material is detected.

  Thus, since the optical fiber sensor is directly fixed to the outer periphery of the steel material, the optical fiber sensor can be directly provided on the steel material without processing the steel material. Since the optical fiber is a thin wire, the corrosive environment can be detected early without blocking the corrosion factor. Further, it becomes possible to accurately detect strain due to corrosion.

  (2) In the corrosion detection method of the present invention, the steel material is a deformed reinforcing bar having ribs and nodes on the surface, and the optical fiber sensor is fixed along at least one node or rib of the deformed reinforcing bar. Features.

  As described above, the steel material is a deformed reinforcing bar having ribs and nodes on the surface, and the optical fiber sensor is fixed along at least one node or rib of the deformed reinforcing bar, so that it can be positioned on the concrete surface side. This makes it possible to detect a corrosion factor that has permeated from the concrete surface at a relatively early stage. Moreover, since an optical fiber sensor can be affixed as it is to a deformed bar, processing of a deformed bar becomes unnecessary. In addition, by continuously attaching optical fiber sensors to multiple nodes, it becomes possible to distinguish between strain caused by corrosion and strain that is not, ie, strain caused by temperature or external force. It becomes possible to remove the influence of strain. As a result, only distortion due to corrosion can be detected with high accuracy.

  (3) Further, in the corrosion detection method of the present invention, a part of the steel material is cut or polished to form a cutting / polishing part, and an optical fiber sensor is fixed to the cutting / polishing part.

  In this way, a part of the steel material is cut or polished to form the cutting / polishing part, and the optical fiber sensor is fixed to the cutting / polishing part, so that the detection sensitivity can be increased. In addition, it becomes possible to make a cutting and grinding | polishing part rust most easily among steel materials by removing the black skin and rust of some steel materials.

  (4) Further, in the corrosion detection method of the present invention, the steel material is a deformed reinforcing bar having ribs and nodes on a surface thereof, and the ribs and nodes of the deformed reinforcing bar are cut or polished to form a cutting / polishing portion, An optical fiber sensor is fixed to the cutting / polishing portion.

  In this way, the ribs and nodes of the deformed reinforcing bars are cut or polished to form a smooth cutting / polishing portion, and the optical fiber sensor is fixed to the cutting / polishing portion, so that there is no gap and the detection sensitivity is increased. It becomes possible. In addition, by removing the black skin and rust of the cutting / polishing part, it becomes possible to make the cutting / polishing part most susceptible to rust among the deformed reinforcing bars.

  (5) Further, in the corrosion detection method of the present invention, a coating layer made of a hardened cement body is provided between the steel material and the optical fiber sensor.

  Thus, since the coating layer which consists of a cement hardening body is provided between steel materials and the said optical fiber sensor, it becomes easy to fix an optical fiber sensor by eliminating an unevenness | corrugation by a cement hardening body. In addition, when it is wound directly on a reinforcing bar, it cannot be detected unless corrosion occurs at the location where the optical fiber sensor is in contact, but the vicinity of the corrosion location expands as a whole by sandwiching the hardened cement as a coating layer. Therefore, it becomes easy to detect corrosion regardless of the position of corrosion. Here, the water cement ratio of the hardened cement body is preferably 80% or less. This is because if the cement hardened body is soft, the expansion is transmitted to the optical fiber sensor slowly.

  (6) Moreover, the corrosion detection method of this invention coat | covers the said optical fiber sensor with a cement hardening body, It is characterized by the above-mentioned.

  In this way, the portion where the optical fiber sensor is fixed is covered with the cement hardened body. As the cement hardened body, cement paste or mortar that is alkaline and becomes porous after solidification can be used. The cement hardened body has a water cement ratio equivalent to or higher than that of the concrete of the reinforced concrete structure, for example, preferably 60% or more. As a result, the hardened cement body functions to prevent corrosion of the reinforcing bars until the corrosion factor reaches, to fix the position of the optical fiber sensor after manufacture, and to protect the optical fiber sensor at the time of placement. Furthermore, since the hardened cement body has a more porous structure than the concrete of the reinforced concrete structure, it does not hinder the passage of corrosion factors from the concrete surface to the reinforcing bars. As the cement material to be used, ordinary cement may be used, or fast-hardening cement may be used. By appropriately blending the cement hardened body and designing the cement material, the cement hardened body can be made into a property that allows easy penetration of corrosion factors such as chloride ions.

  According to the present invention, early detection of a corrosive environment is possible. Further, it becomes possible to accurately detect strain due to corrosion.

It is a figure which shows Example 1 which concerns on this invention. It is a figure which shows Example 2 which concerns on this invention. It is a figure which shows Example 3 which concerns on this invention. It is a figure which shows Example 3 which concerns on this invention. It is a figure which shows Example 4 which concerns on this invention. It is a figure which shows Example 5 which concerns on this invention. It is a figure which shows Example 6 which concerns on this invention. It is a figure which shows Example 6 which concerns on this invention. It is a figure which shows Example 7 which concerns on this invention. It is a figure which shows Example 8 which concerns on this invention. It is a figure which shows schematic structure of the test body which concerns on this verification example. It is a figure which shows the example of a detection of the corrosion sensor which concerns on this verification example. It is a figure which shows the example of a detection of the corrosion sensor which concerns on this verification example.

  As a corrosion detection method according to the present embodiment, a case where an optical fiber sensor is wound around the outer periphery of a steel material in concrete is illustrated. In this corrosion sensor, it is possible to detect the corrosive environment of the steel material itself. When the steel material is corroded, distortion due to volume expansion of the corrosion product occurs. By detecting this strain with a measuring instrument such as a data logger via an optical fiber sensor, whether the concrete interior is in a corrosive environment, whether a corrosive factor has invaded, and whether the steel is corroded. Diagnosis is possible. As the steel material, a steel material used in a structure may be used, or a steel material may be separately prepared and a corrosion sensor may be installed. Separately, when installing a corrosion sensor by preparing steel materials, fix it to the actual rebar with a cable tie and so that the sensor does not move or fall off during construction. When using the steel material used for the structure, it is not necessary to separately prepare or attach the steel material.

  FIG. 1 is a diagram showing a first embodiment according to the present invention. In the first embodiment, the optical fiber sensor 62 is directly wound around the round steel 60. As a result, the optical fiber sensor 62 can be provided directly on the steel material without processing the steel material. As a result, early detection of the corrosive environment becomes possible. Further, it becomes possible to accurately detect strain due to corrosion.

  As the optical fiber sensor, an FBG sensor or the like can be used. When the optical fiber sensor 62 is wound around the round steel 60, the optical fiber sensor 62 may be arranged in a straight line or bend in a wave shape, but preferably spiral so as to circulate, Or wrap it in a loop. As the number of laps increases, the corroded portion and the optical fiber overlap each other, so detection is performed earlier. However, if the number of laps is excessive, the arrival of the corrosion factor on the round steel 60 is hindered. When the optical fiber sensor 62 is wound around the round steel 60, it is wound so as to be in close contact with each other, and preferably a tensile force is applied, and both ends are fixed with an adhesive. Thereby, both the expansion side and the contraction side strain can be measured. After that, concrete is placed, and the expansion due to corrosion of the reinforcing bars is detected by measuring strain with a data logger. In addition, although it was set as the round bar 60 here, the said arrangement | positioning can also be performed to the deformed reinforcing bar 65.

  FIG. 2 is a diagram showing a second embodiment according to the present invention. In the second embodiment, a deformed reinforcing bar 65 is used. In FIG. 2, the deformed reinforcing bar 65 is provided with ribs 66 at positions above and below the paper surface. Further, the deformed reinforcing bar 65 is provided with a plurality of nodes 67 protruding from the surface and provided at predetermined intervals. In the second embodiment, the optical fiber sensor 62 is fixed to the top portion of the node 67. When the optical fiber sensor 62 is fixed, it is fixed at two adhesion points 69 as shown in FIG. Moreover, the location where the optical fiber sensor 62 is fixed is installed toward the surface of the concrete. Thus, since the optical fiber sensor 62 is fixed to the top part of the node 67, it can be brought close to the concrete surface at a place where deterioration is a concern. This makes it possible to detect corrosion at a relatively early stage. Moreover, in Example 2, since the optical fiber sensor 62 is arrange | positioned as it is to the deformed reinforcing bar 65, the process of the deformed reinforcing bar 65 becomes unnecessary. In addition, by removing the black skin and rust of the node 67, the portion of the deformed reinforcing bar 65 where the optical fiber sensor 62 is fixed may be most easily rusted.

  3A and 3B are diagrams showing a third embodiment according to the present invention. FIG. 3A is a diagram illustrating the deformed reinforcing bar 65 from the direction in which the rib 66 is positioned above and below the paper surface, and FIG. 3B is a diagram illustrating the deformed reinforcing bar 65 from any one direction of the rib 66. In the third embodiment, the optical fiber sensor 62 is continuously arranged with respect to the plurality of nodes 67. As shown in FIG. 3A, in each node 67, the optical fiber sensor 62 is bonded at two bonding points 69, respectively. As described above, by arranging the optical fiber sensors 62 at the plurality of nodes 67, a portion where rust is generated and a portion where no rust is generated at the initial stage when the corrosive environment is generated. Then, it becomes possible to discriminate between distortion caused by corrosion and distortion not caused, that is, distortion caused by temperature or external force, thereby eliminating the influence of distortion caused by temperature or external force. As a result, only distortion due to corrosion can be detected with high accuracy. Moreover, in Example 3, since the optical fiber sensor 62 is arrange | positioned as it is to the deformed reinforcing bar 65, a process becomes unnecessary. In addition, by removing the black skin and rust of the node 67, the portion of the deformed reinforcing bar 65 where the optical fiber sensor 62 is fixed may be most easily rusted.

  FIG. 4 is a diagram showing a fourth embodiment according to the present invention. In Example 4, the deformed reinforcing bar 65 is provided with the cutting / polishing portion 70 by cutting or polishing a part of the rib 66. The optical fiber sensor 62 is disposed along the cutting / polishing unit 70, and the cutting / polishing unit 70 is set toward the surface of the concrete. Thereby, it becomes possible to detect the corrosion factor which invaded from the concrete surface at an early stage. It should be noted that, by removing the black skin and rust of the cutting / polishing section 70, it becomes possible to make the cutting / polishing section 70 most susceptible to rust among the deformed reinforcing bars 65. Moreover, it becomes possible to prolong the measurement period by carrying out a rust prevention process about the adhesion part 69. FIG.

  FIG. 5 is a diagram showing a fifth embodiment according to the present invention. In Example 5, a part of the deformed reinforcing bar 65 was shaped like a round steel by cutting or polishing a part of the deformed reinforcing bar 65, and the cutting / polishing part 71 was provided. The optical fiber sensor 62 is installed in the cutting / polishing unit 71. Thereby, the optical fiber sensor 62 can be easily wound, and the arrangement method can be the same as in the first embodiment. By removing the black skin and rust of the cutting / polishing part 71, the cutting / polishing part 71 among the deformed reinforcing bars 65 is most likely to rust, so that the detection sensitivity can be increased. Moreover, it becomes possible to prolong the measurement period by carrying out a rust prevention process about the adhesion part 69. FIG.

  6A and 6B are diagrams showing a sixth embodiment according to the present invention. In Example 6, as shown in FIG. 6B, a cutting / polishing portion 73 is provided in a part of the deformed reinforcing bar 65 by continuously cutting or polishing any one of the plurality of nodes 67. It was. FIG. 6B shows an example in which three nodes 67 are continuously cut. The cutting / polishing portion 73 may be provided along the rib 66 as shown in FIG. 6A. The optical fiber sensor 62 is affixed along the cutting / polishing portion 73, and the cutting / polishing portion 73 is set toward the surface of the concrete. It becomes possible to detect the corrosion factor that has entered from the concrete surface at an early stage. In addition, by removing the black skin and rust of the cutting / polishing part 73, the cutting / polishing part 73 of the deformed reinforcing bars 65 can be most easily rusted. Moreover, it becomes possible to prolong the measurement period by carrying out a rust prevention process about the adhesion part 69. FIG.

  FIG. 7 is a diagram showing a seventh embodiment according to the present invention. In Example 7, the coating layer 72 was provided between the deformed reinforcing bar 65 and the optical fiber sensor 62. The coating layer 72 is composed of a hardened cement body such as mortar. The mortar may be made with a blend of water cement ratio similar to that of concrete, or may be made with a more porous blend. Preferably, the water cement ratio is 80% or less. This is because when the covering layer 72 is provided between the deformed reinforcing bar 65 and the optical fiber sensor 62, if the hardened cement body is soft, the transmission of expansion of the deformed reinforcing bar 65 due to corrosion to the optical fiber sensor 62 becomes slow.

  The water cement ratio should be equal to or higher than that of concrete in reinforced concrete structures so as not to hinder the passage of corrosion factors from the concrete surface to the reinforcing bars. For example, the water cement ratio is 60% or more. It is preferable that Moreover, you may mix | blend an admixture, a thickener, and a fiber with mortar etc. so that separation and bleeding may not arise. The coating layer 72 preferably has a thickness of 3 to 15 mm so that the irregularities of the deformed reinforcing bar 65 are not uneven and are not cracked. However, the present invention is not limited to these.

  As described above, since the coating layer 72 is provided and the unevenness can be eliminated regardless of the location of the deformed reinforcing bar 65, the optical fiber sensor 62 can be disposed at any location. Moreover, since the whole site | part including a mortar expands when the deformed reinforcing bar 65 corrodes, it becomes easy to detect the displacement by corrosion including the corroded place.

  FIG. 8 is a diagram showing an eighth embodiment according to the present invention. In FIG. 8, the left side of the paper surface has a configuration in which the deformed reinforcing bar 65 is provided with the covering portion 74, but is characterized in that the optical fiber sensor 62 is wound in a state where the mortar is not cured. In this case, the optical fiber sensor 62 is sunk into the mortar. Thus, the mortar can also function as an adhesive, and the adhesive point 69 may not be provided or temporarily fixed.

  On the other hand, in FIG. 8, the right side with respect to the paper surface is a mode in which a covering portion 74 is formed with a hardened cement body at a portion where the optical fiber sensor 62 is fixed. As for the method of fixing the optical fiber sensor 62, any one of the first to seventh embodiments may be used. It is possible to make the mortar function as an adhesive, and the adhesive point 69 may not be provided or may be temporarily fixed.

  As the cement hardened body of this embodiment, cement paste or mortar that is alkaline and becomes porous after solidification can be used. The cement hardened body has a water cement ratio equivalent to or higher than that of the concrete of the reinforced concrete structure, for example, preferably 60% or more. As the cement material to be used, ordinary cement may be used, or fast-hardening cement may be used. By appropriately blending the cement hardened body and designing the cement material, the cement hardened body can be made into a property that allows easy penetration of corrosion factors such as chloride ions. Moreover, you may mix | blend an admixture, a thickener, and a fiber with mortar etc. so that separation and bleeding may not arise. The covering layer 74 preferably has a thickness of 3 to 15 mm so as not to crack.

  Thereby, the hardened cement body constituting the covering portion 74 prevents corrosion of the reinforcing bar until the corrosion factor reaches, fixes the position of the optical fiber sensor 62 after manufacture, and protects the optical fiber sensor 62 at the time of placing. Fulfills the function of Furthermore, since the hardened cement body is more porous than or equal to the concrete of the reinforced concrete structure, it does not hinder the passage of corrosion factors from the concrete surface to the reinforcing bars.

  In the cutting or polishing in the above embodiment, the deformed reinforcing bar 65 is taken as an example, but the present invention is not limited to this, and a part of the round steel 60 may be cut or polished. Further, the coating layer 72 and the coating portion 74 of the hardened cement body take the deformed reinforcing bar 65 as an example, but the present invention is not limited to this, and the coating layer 72 or the optical fiber sensor 62 between the round steel 60 and the optical fiber sensor 62 is used. A covering portion 74 may be provided.

  In all of the above embodiments, a dummy sensor can be used. That is, an optical fiber sensor is manufactured in the same manner as in the above embodiment, but the dummy sensor has a rust preventive treatment on the entire surface. Then, a strain caused by factors other than corrosion may be detected using a dummy sensor, and the strain detected by the optical fiber sensor may be corrected. Thereby, for example, it becomes possible to remove the influence of temperature distortion and the like. As for the dummy sensor, there is a method in which the reinforcing bar or the covering portion where the optical fiber sensor is arranged is coated with an epoxy resin or the like to prevent neutralization or deterioration factors from entering and to prevent corrosion of the internal carbon steel. Moreover, when providing a some detection part like Example 3, you may give a rust prevention process to the one part.

[Verification example]
FIG. 9 is a diagram showing the concept of the corrosion detection method according to the present embodiment using a test specimen. As shown in FIG. 9, the test body 40 is configured by winding an optical fiber sensor 51 around a steel bar 50 and covering with a hardened cement body 52 such as mortar. With respect to the test body 40, the vertical fog is 20 mm, and the horizontal fog is 10 mm. Although FIG. 9 shows an example in which the optical fiber sensor 51 is wound once with respect to the steel bar 50, the case where it is wound three times will also be verified. Next, a specific verification example of the test body 40 is shown.

  JIS G 3108 SGD3M was used as the polished steel bar. The method of winding the optical fiber around the polished steel bar is under certain tension, for example, after confirming that some tensile strain has occurred during winding, and then winding the wire with CN (manufactured by Tokyo Sokki). Fixed. An optical fiber sensor (FBG sensor) having the specifications shown in Table 2 was used. In addition, it is preferable to detect corrosion based on the difference in strain behavior of the dummy sensor, and it is expected that the influence of volume change and moisture content of the coated mortar will appear in the strain. The body was made.

  Next, the covering mortar will be described. The materials used for the mortar are as shown in the following table.

  Next, the composition of the mortar is as shown in the following table.

なお、上記の表中、「Ｂ」とは、「Ｃ」と「Ｌ」とを混合したものである。

In the above table, “B” is a mixture of “C” and “L”.

[Mortar mixing method]
The mortar used for the test body was kneaded using a “mortar mixer (2 L kneading) manufactured by Maruto Manufacturing Co., Ltd.”. The mixing procedure is as follows. The mortar was kneaded in a constant temperature and humidity chamber at 20 ± 2 ° C. and a humidity of 50% or more.

  Put mortar into a PVC mold (inner diameter φ40 mm × height 50 mm, or inner diameter φ40 mm × height 65 mm), put a steel bar wrapped with optical fiber in the center, and then in the same constant temperature and humidity chamber After curing for 3 hours, it was cured at 20 ° C. and a humidity of 95% or more for 7 days and demolded.

  Specimen 40 under corrosive environment (temperature 40 ° C., immersed in NaCl: 10% aqueous solution for 1 day, humidity 60% dried for 3 days, again immersed in NaCl: 10% aqueous solution for 1 day, and thereafter dried at 60% humidity) The change in wavelength was measured using a measuring instrument (manufactured by Watanabe Seisakusho Co., Ltd.). In the immersion of NaCl: 10% aqueous solution, the portion up to 30 mm from the lower end of the test specimen (45 mm from the lower end of the specimen in the case of 3 windings) was so immersed that the NaCl aqueous solution did not enter from the optical fiber lead-out portion. . The dummy specimen used here was the same specimen as the corrosion sensor without using a steel bar that does not corrode experimentally, and was immersed in pure water that does not corrode instead of using the NaCl aqueous solution.

  Using the following equation, the wavelength was converted to strain, and the change in strain due to corrosion was confirmed.

ここで、ε：ひずみ（μ）、λ：測定時の波長（ｎｍ）、λ*：初期波長（ｎｍ）である。

Here, ε: strain (μ), λ: wavelength at the time of measurement (nm), and λ *: initial wavelength (nm).

  FIG. 10A is a graph showing the relationship between elapsed time and strain in a corrosive environment. In the verification example with one winding shown in FIG. 10A, since the samples were immersed in salt water or water on the 1st and 4th, the strain temporarily changed due to temperature change or mortar water absorption, but the dummy specimen also changed in the same way. This is not due to corrosion. On the 16th, the strain amount of the test specimen and the dummy test specimen deviated. Then, when the covering mortar of the test body was removed, it was confirmed that the steel bar was corroded.

  The verification example with 3 windings shown in FIG. 10B is an example in which measurement is started after the temperature becomes constant and measurement is continued after corrosion. Corrosion cracks occurred on the 45th measurement day, and expansion stopped. It has been proved that it is possible to continuously capture the expansion due to corrosion until cracking occurs.

  From this verification example, it was proved that the optical fiber sensor that detects the strain wound around the iron member detects the strain generated by the corrosion of the iron member. Therefore, it can be seen that the corrosion sensor of the present invention can also detect the strain caused by the corrosion of the steel material.

  As described above, according to the present embodiment, early detection of a corrosive environment is possible. Further, it becomes possible to accurately detect strain due to corrosion.

40 Specimen 50 Bar Steel 51 Optical Fiber Sensor 52 Mortar 60 Round Steel 62 Optical Fiber Sensor 65 Deformed Reinforcement 66 Rib 67 Node 69 Adhesive Points 70, 71, 73 Cutting / Polishing Part 72 Covering Layer 74 Covering Part

Claims (6)

A corrosion detection method for detecting a corrosive environment of a steel material,
Fix the optical fiber sensor directly on the outer periphery of the steel material,
A corrosion detection method, comprising: detecting strain associated with volume expansion due to corrosion of the steel material based on a change in characteristics of light waves propagating in the optical fiber sensor. The corrosion detection method according to claim 1 , wherein a process of making a portion on the outer periphery of the steel material where the optical fiber sensor is fixed easily rusted is performed . A corrosion detection method for detecting a corrosive environment of a steel material,
Directly fixing the optical fiber sensor along at least one node or rib of the deformed reinforcing bar having ribs and nodes on the surface;
A corrosion detection method , comprising: detecting strain due to corrosion of the steel material based on a change in characteristics of a light wave propagating in the optical fiber sensor . The steel material is a deformed reinforcing bar having ribs and nodes on the surface,
Cutting or polishing the ribs and nodes of the deformed reinforcing bar to form a cutting / polishing part,
The corrosion detection method according to claim 1, wherein an optical fiber sensor is fixed to the cutting / polishing portion.   The corrosion detection method according to any one of claims 1 to 4, wherein a coating layer made of a hardened cement is provided between the steel material and the optical fiber sensor.   The corrosion detection method according to claim 1, wherein the optical fiber sensor is covered with a hardened cement body.

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