JP5204021B2 - Corrosion sensor unit and installation method of corrosion sensor - Google Patents

Description

  The present invention relates to a corrosion sensor unit for detecting a corrosive environment of a reinforcing bar in a reinforced concrete structure and a method for installing the corrosion sensor.

  Conventionally, a sensor for grasping the state of a concrete structure is known. For example, Patent Document 1 is formed by covering a base material made of a metal or an alkali-soluble metal that is more easily corroded than the metal of the detection object under the usage environment of the detection object, and covering at least a part of the base material, A corrosion sensor is disclosed that includes a detection unit formed by a coating made of a metal that corrodes under the environment in which the detection target is used, and a base material for holding the detection unit.

  Patent Document 2 discloses a corrosion sensor used for diagnosing the progress of corrosion of a steel material embedded in a concrete structure. This corrosion sensor is a corrosion detection unit and has a detection member laid in the vicinity of the measurement object or the measurement object, and measures the corrosion of the metal detection member and measures the electrical characteristics of the detection member. To detect. Then, the corrosion detection result is wirelessly transmitted to the reading device. With this configuration, the corrosion of the detection member can be detected 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, and the steel sheath tube is corroded. .

JP 2007-163324 A JP 2006-337169 A

  However, the conventional corrosion sensor is basically designed on the assumption that the sensor portion directly faces the corrosion factor. When these sensors are installed in a concrete structure, there is a possibility that the sensor part may be damaged when placing concrete. Further, there is a case where a gap is formed in the vicinity of the sensor unit, and accurate detection may be hindered. Moreover, in the corrosion detection sensor which used the fine iron wire as the sensor part, since the iron member used as a sensor part may rust before being embedded, it was necessary to prevent the iron member from being rusted. Moreover, when attaching to the existing concrete structure, a concrete structure will be destroyed locally (hole drilling), and a sensor will be installed, but the problem similar to the above also existed in this case. Furthermore, if the corrosive factor is, for example, chloride ions, penetration in concrete proceeds by diffusion. For this reason, it is desirable to install the sensor unit so that it can detect the corrosion factor from any direction.

  This invention is made in view of such a situation, protects a sensor part, avoids the coarse space | gap near a sensor part, and detects the corrosive environment of the reinforcement in a reinforced concrete structure correctly. It is another object of the present invention to provide a corrosion sensor unit and a corrosion sensor installation method that can facilitate the installation work of the sensor unit and can shorten the work process.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the corrosion sensor unit of the present invention is a corrosion sensor unit for detecting a corrosive environment of a reinforcing bar in a reinforced concrete structure, and is formed of a concrete, mortar, or paste in a cylindrical shape having a first diameter. A hardened cement body, a sensor unit that is installed on a side surface of the first hardened cement body, detects a penetration state of a corrosion factor that corrodes a reinforcing bar into concrete, and outputs data indicating the penetration state of the corrosion factor; A transmitting unit that is installed on any one smooth end surface of the first hardened cement body and wirelessly transmits data output from the sensor unit; and the first hardened cement body, the sensor unit, and the transmitting unit. Coated with concrete, mortar or paste, and formed into a cylindrical shape having a second diameter larger than the diameter of the first hardened cement body. It is characterized by comprising a second cement body that is, a.

  Thus, since the sensor unit is installed on the side surface of the first hardened cement body, it is possible to accurately detect the diffused corrosion factor. In addition, since the second hardened cement body covers the first hardened cement body, the sensor unit, and the transmission unit, the protection function of the sensor unit is greatly improved, and it is installed in the concrete to be inspected. Becomes easy. When the sensor part is an iron member, the sensor part is covered with a non-conductive coating because it is placed in an alkaline environment in the concrete. As a result, it becomes difficult to rust compared with a sensor part not placed inside the concrete, and handling is easy.

  (2) Moreover, the corrosion sensor unit of this invention WHEREIN: The said sensor part is formed with the iron foil, It is characterized by the above-mentioned.

  Thus, since the sensor part is formed of iron foil, the sensor part can be made flexible. As a result, the sensor unit can be installed on the side surface of the first hardened cement body with the same curvature as the side surface of the first hardened cement body. Thereby, it becomes possible to detect the corrosive environment of the reinforcing bar in the reinforced concrete structure no matter which direction the corrosion factor penetrates by diffusion.

  (3) Further, the corrosion sensor installation method of the present invention is a corrosion sensor installation method for detecting the corrosion environment of a reinforcing bar in a reinforced concrete structure, and is a cylindrical shape having a first diameter made of concrete, mortar or paste. A first hardened cement body formed into a shape, and a state of penetration of the corrosive factor that corrodes the reinforcing bar into the concrete is detected on a side surface of the first hardened cement body, and the permeated state of the corrosive factor is determined. A step of installing a sensor unit that outputs data, a step of installing a transmission unit that wirelessly transmits the data output by the sensor unit on one of the smooth end faces of the first hardened cement body, The first hardened cement body, the sensor unit, and the transmitter are covered with concrete, mortar, or paste, and the first hardened cement body A step of producing a second hardened cement body formed into a cylindrical shape having a second diameter larger than the diameter, and a drilling hole obtained by core boring the second cement hardened body with the concrete of the structure to be detected. And at least a step of embedding and integrating in the part.

  Thus, since the sensor unit is installed on the side surface of the first hardened cement body, it is possible to accurately detect the diffused corrosion factor. In addition, since the second hardened cement body covers the first hardened cement body, the sensor unit, and the transmission unit, the protection function of the sensor unit is greatly improved, and it is installed in the concrete to be inspected. Becomes easy. When the sensor part is an iron member, the sensor part is covered with a non-conductive coating because it is placed in an alkaline environment in the concrete. As a result, it becomes difficult to rust compared with a sensor part not placed inside the concrete, and handling is easy. Further, since the second hardened cement body is embedded in a hole drilling portion obtained by core boring the concrete to be detected, workability can be improved.

  According to the present invention, since the sensor unit is installed on the side surface of the first hardened cement body, it is possible to accurately detect the diffused corrosion factor. In addition, since the second hardened cement body covers the first hardened cement body, the sensor unit, and the transmission unit, the protection function of the sensor unit is greatly improved, and it is installed in the concrete to be inspected. Becomes easy. When the sensor part is an iron member, the sensor part is covered with a non-conductive coating because it is placed in an alkaline environment in the concrete. As a result, it becomes difficult to rust compared with a sensor part not placed inside the concrete, and handling is easy.

It is a perspective view which shows the state which installed the sensor part and the transmission part in the 1st cement hardening body. It is a figure which shows the 2nd cement hardening body which coat | covered the 1st cement hardening body in which the sensor part and the RFID tag were installed, and the 1st cement hardening body in which the sensor part and the RFID tag were installed with concrete. It is a figure which shows a mode that the 2nd cement hardening body 14 is inserted in the drilling part 31 provided in the concrete frame 30. FIG. It is a figure which shows the procedure which manufactures a corrosion sensor unit. It is a figure which shows an example of the installation method of the corrosion sensor unit which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a state in which a sensor unit 11 and an RFID tag 12 as a transmission unit are installed on a first hardened cement body 10. As shown in FIG. 1, the sensor part 11 is installed along the side surface of the 1st hardened | cured material 10 shape | molded cylindrically with concrete, mortar, or a paste. The sensor unit 11 is formed of iron foil. For this reason, the sensor unit 11 becomes flexible, and the sensor unit 11 can be installed on the side surface of the first cement cured body 10 with the same curvature as the side surface of the first cement cured body 10. Thereby, it becomes possible to detect the corrosive environment of the reinforcing bar in the reinforced concrete structure no matter which direction the corrosion factor penetrates by diffusion. In addition, an RFID tag 12 as a transmission unit is provided on one bottom surface of the first hardened cement body 10. The sensor unit 11 and the RFID tag 12 are connected by a lead wire 13.

  FIG. 2 shows a concrete cement, mortar, or paste in which the first hardened cement body 10 in which the sensor unit 11 and the RFID tag 12 are installed and the first hardened cement body 10 in which the sensor unit 11 and the RFID tag 12 are installed. It is a figure which shows the 2nd cement hardening body 14 coat | covered with. FIG. 3 is a view showing a state in which the second hardened cement body 14 is inserted into the drilled hole portion 31 provided in the frame concrete 30. As shown in FIG. 3, the second hardened cement body 14 is inserted into the drilled hole portion 31 and the repair mortar is filled on the second hardened cement body 14 so as to have the same height as the structure surface S. To do.

[Corrosion sensor unit shape and dimensions]
The shape of the corrosion sensor unit according to the present embodiment is preferably a cylindrical shape that matches the shape of a general-purpose core boring. The dimensions of the cylinder may be arbitrary, but in normal core boring, it is implemented with specific dimensions such as φ50 mm, φ75 mm, φ100 mm, φ125 mm, and φ150 mm. The implementation range may be implemented up to about φ25 mm to φ200 mm. The diameter of these cores is about several mm smaller, and after being inserted into the drilled hole portion or before insertion, a paste or mortar for adhesion to the concrete is applied and integrated.

  The diameter of the corrosion sensor unit is not particularly limited as long as it can be integrated. For example, when the diameter is 30 mm with respect to a hole with a diameter of 100 mm, there is a high possibility that the adhesion layer is too thick to properly detect the invasion of corrosion factors into the concrete. It is not preferable. For this reason, the thing which has a diameter smaller by several mm than a drilling part is preferable. For example, if the distance from the surface of the second hardened cement body 14 to the sensor unit 11 is x and the distance (gap) between the surface of the second hardened cement body 14 and the inner surface of the concrete frame is d, d <x It is preferable to install so that. However, the gap d has a limit in reducing the integration with the housing. This is because an adhesive material such as cement paste and non-shrink grout is applied and integrated during the integration. Therefore, d is set as a dimension of x or less with 1 mm being the lower limit.

  That is, it is set so as to satisfy 1 mm <d <x.

  The length of the corrosion sensor unit can be arbitrarily set according to the depth position of the frame concrete to be inspected and the communication distance of the RFID tag 12. For example, when it is desired to set the sensor unit 11 to be 50 mm from the surface of the concrete frame, the sensor unit 11 should be inserted at a position where the central part of the unit is 30 mm by using a drilling depth of 80 mm and a unit height of 60 mm. In this case, the position is 50 mm from the surface. Even when the hole is deep, the depth position can be adjusted by inserting the corrosion sensor unit after filling the mortar to the required depth position in advance. By combining the depth of the drilling portion, the length of the unit, and the sensor installation position in the unit, the sensor portion can be brought to an arbitrary depth position.

[Sensor dimensions and shape]
The sensor unit 11 uses an iron foil sensor, and can be installed in the circumferential direction of the first hardened cement body 10 to detect a corrosion factor regardless of directionality. Therefore, the base material of the sensor unit 11 is preferably a sheet material made of a highly flexible resin material. Specifically, a resin generally used for a base material called a flexible substrate, such as a PET material (polyethylene terephthalate) or polyimide, is preferable because of good workability. The iron foil sensor is integrated with the base material, and is arranged in a pattern shape such as a strip shape, a step shape, or a wave shape, and is bent in the circumferential direction with respect to the mortar unit. Thus, it can be said that the foil material can be arranged with a certain curvature. As the dimension, the sensor part width is about 0.2 mm to about several tens of mm, the length can be arbitrarily set according to the circumferential length of the unit, and the thickness is about 0.01 mm to 1 mm. Even if the width is less than 0.2 mm, there is no problem as long as the detection sensitivity can be maintained. This can be detected, but it becomes difficult to obtain information on the penetration depth of the corrosion factor.

  The circumferential length is preferably a length that allows the entire circumference of the cylinder to be one week long, because it corresponds to the entire direction of the cross section. However, the length of the circumferential direction is not necessarily required. However, a quarter length is not a big problem. As the minimum length, if it is longer than the maximum aggregate dimension length (for example, 20 mm) of the embedded concrete, the length of the sensor portion is acceptable (see FIGS. 1 and 2).

[Tag antenna location]
In the RFID tag 12 installed on the first hardened cement body 10, the antenna for wireless communication is installed on the upper end surface of the cylindrical first hardened cement body 10. The orientation is set so as to be parallel to the upper end surface of the cylinder or parallel to the concrete surface. The embedding depth from the upper end surface of the cylinder may be arbitrary, but a range of about several mm to several tens mm is preferable. The size of the antenna may be arbitrary as long as it can be embedded in the second hardened cement body 14. In general, the larger the antenna, the easier it is to increase the communication distance. Therefore, it is preferable to use a large antenna as long as it can be embedded in the mortar and ensure durability.

[Relationship between concrete, mortar and paste]
[Definition]
Concrete refers to cement, water, fine aggregate, coarse aggregate, and an admixture added as necessary, which are mixed and mixed by other methods or hardened. The mortar means a cement, water, fine aggregate, and an admixture material added as necessary, which are mixed and mixed by other methods or cured. The paste refers to a cement, water, and an admixture that is added as necessary, which constitutes a constituent material, and these are kneaded and mixed by other methods or cured. The fine aggregate refers to an aggregate that passes through all of the 10 mm screen and passes through the 5 mm screen by 85% or more. Coarse aggregate is an aggregate that remains 85% or more by mass on a 5 mm screen.

[Relationship]
The interrelationship between concrete, mortar and paste is as follows. Concrete is the highest level concept and has the largest range. Among concrete, mortar does not contain coarse aggregate, and mortar does not contain fine aggregate is paste.

[Cement used]
Since the concrete forming the first cement hardened body 10 and the second cement hardened body 14 may greatly differ in permeability depending on the corrosion factor, it is preferable to select a cement material used in the structural concrete. As a premise, there is no problem in using the cement used in the target structural concrete as long as the permeability can be equalized while ensuring the strength by combining the structural concrete and water cement ratio, etc., rather preferable . In general concrete, since the ratio of ordinary Portland cement is high, it is described below based on ordinary Portland cement.

For example, when the corrosion factor is chloride ion, penetration of chloride ion is generated when the cement reacts with water when the aluminate phase (C ₃ A) and ferrite phase (C ₄ AF) are large in the cement. The proportion of calcium aluminate hydrate increases as hydrated. When calcium aluminate hydrate comes into contact with chloride ions, a part of it forms Friedel's salt (insoluble salt) that immobilizes the chloride ions. Therefore, when compared with concrete of the same strength level, the penetration of chloride ions is slow. Moreover, it is known that the penetration of chloride ions is suppressed in concrete using blast furnace cement (= mixed cement) including blast furnace slag.

On the contrary, a cement with a small amount of C ₃ A can easily penetrate chloride ions, and commercially available ones include low heat Portland cement, medium heat Portland cement, sulfate resistant Portland cement and the like. Further, the type is not particularly limited as long as it is a cement that has a small content ratio of C ₃ A and C ₄ AF and does not contain a large amount of mixed material.

  On the other hand, when the corrosion factor is carbon dioxide, since the mechanism is different from the salinity, the cement that affects the permeability to the coated mortar is different. Reinforcement corrosion due to the neutralization of concrete due to carbon dioxide occurs due to a decrease in the pH of the concrete. The progress of carbon dioxide diffusion is such that the concrete pH decreases due to the carbonation of calcium hydroxide (about 12.6), the corrosion of steel (corrosion progresses at pH 9-10). Proceed to. Accordingly, the speed of neutralization varies depending on the amount of calcium hydroxide produced by the reaction of cement with water.

  Calcium hydroxide is a major hydrate of cement and is always produced by ordinary cement, so it is generally difficult to describe the speed of neutralization depending on the cement type, but the amount of calcium hydroxide produced or the amount that can be produced From this point of view, it can be said that a cement with a smaller amount of generation has a lower resistance to neutralization. Therefore, examples of the cement with the least amount of calcium hydroxide produced include blast furnace cement and fly ash cement, which are mixed cements. Mixed cement is cement in which blast furnace slag, fly ash, etc. are mixed with cement. The above mixed material does not produce calcium hydroxide, but rather reacts with calcium hydroxide and hardens, so the amount of calcium hydroxide is relative. Less.

  As the mortar for forming the first cement hardened body 10 and the second cement hardened body 14, it is relatively preferable to use a mixed cement such as a blast furnace cement or a fly ash cement, or a low heat blast furnace cement or a medium heat fly ash cement. It is considered preferable. Moreover, it is not limited to a commercial item, The cement manufactured by changing the mixing ratio etc. of a mixing material may be sufficient.

That is, the following cement is preferably used in the present embodiment.
(1) When the water cement ratio is equivalent (physical properties / permeability equivalent), use cement used in the target structure, ordinary cement, or cement with higher permeability.
(2) When the water cement ratio is small or when it is desired to improve the sensitivity, and chloride ions are taken into consideration, there are low heat Portland cement, medium heat Portland cement, sulfate resistant Portland cement and the like. The type of C ₃ A and C ₄ AF is not particularly limited as long as it is a cement containing a small amount of C ₃ A and C ₄ AF and does not contain a large amount of mixed material.
(3) When the water cement ratio is small or when it is desired to further improve the sensitivity, and when carbon dioxide (neutralization) is taken into account, there are blast furnace cement, fly ash cement and the like.

The chemical composition is as follows. The names such as aluminate (C ₃ A) and ferrite (C ₄ AF) are names used for cement minerals, and the description in JIS and the like is tricalcium aluminate, which is described as “3CaO · Al ₂ O ₃ ”. . Other major constituent minerals of cement include C ₃ S, C ₂ S, and C ₄ AF. Alite (C ₃ S) is tricalcium silicate and is described as “3CaO.SiO ₂ ”. Also, belite (C ₂ S) is dicalcium silicate and is described as “2CaO · SiO ₂ ”. Ferrite (C ₄ AF) is iron tetracalcium aluminate and is described as “4CaO · Al ₂ O ₃ · Fe ₂ O ₃ ”.

The specified values of C ₃ A described in the JIS R 5210 Portland cement standard are as follows.
Low heat Portland cement: Tricalcium aluminate mineral composition 6% or less Medium heat Portland cement: Tricalcium aluminate mineral composition 8% or less Sulfate resistant Portland cement: Tricalcium aluminate mineral composition 4% or less There is no upper limit for tricalcium aluminate.

上記の表において、構成鉱物の合計割合が１００％にならないのは、セメント製造で添加される粉砕助剤、石こう、５％以下で認められるＪＩＳ規定の混合材（石灰石微粉末、高炉スラグ、フライアッシュなど）があることによる。これらを全て足すと１００％となる。 An example of a commonly used mineral composition of cement is shown below.

In the above table, the total proportion of the constituent minerals does not reach 100% because of the grinding aid added in cement production, gypsum, JIS-stipulated mixed material recognized at 5% or less (limestone fine powder, blast furnace slag, fly Ash etc.). Adding all of these results in 100%.

  Blast furnace cement refers to “blast furnace cement” of JIS R 5211. Further, in the present specification, in addition to the above, cement obtained by mixing JIS A6206 “Blast Furnace Slag Fine Powder for Concrete” as a mixing material is also included. The fly ash cement is JIS R 5213 “fly ash cement”. Moreover, in this specification, in addition to the above, the cement which mixed the thing prescribed | regulated by JIS A6201 "fly ash for concrete" as a mixing material is also included.

[Concrete strength]
The strength of concrete is determined by the ratio of water to cement (water / cement mass ratio) if the materials used are the same. For this reason, generally, the strength of concrete is set by the water cement ratio or the cement water ratio. This relationship has been confirmed to be proportional and is directly proportional to strength in the case of cement water ratio. Also, regarding the material permeability (mass transfer), the water cement ratio is defined as a large factor, and if the cement type is the same, this becomes the dominant factor.

  However, since the strength varies depending on the aggregate used, it is difficult to perfectly match the strength even under the same water-cement ratio (the proportional line intercepts are different). Since the mortar forming the first hardened cement body 10 and the second hardened cement body 14 is managed and manufactured in a factory, a specific aggregate is used to check the strength for each water cement ratio, The relationship between cement ratio and strength is confirmed in advance, and a proportional straight line is obtained. From this relationship, the mortar for forming the first hardened cement body 10 and the second hardened cement body 14 so as to have a water cement ratio equal to or higher than the strength of the target structure concrete and close to the water cement ratio of the target structure. Set the water-cement ratio. Here, even if the strength is the same, if the water cement ratio is larger than that of the target structural concrete, the water cement ratio is made the same (the strength is not a problem).

In this embodiment, the strength of concrete is determined as follows.
(1) The strength of the mortar forming the first hardened cement body 10 and the second hardened cement body 14 is equal to or higher than that of the target structural concrete.
(2) The water cement ratio of the mortar forming the first hardened cement body 10 and the second hardened cement body 14 is maximized under the condition that satisfies the above (1) and is equal to or lower than the water cement ratio of the target structural concrete. .

(Example 1) When the target structural concrete has a strength of 36 N / mm ² and a water-cement ratio of 52.5%, the mortar forming the first cement cured body 10 and the second cement cured body 14 has a strength. If it is 40 N / mm ² or more and the water cement ratio needs to be 55% or less, the water cement ratio of the mortar forming the first cement cured body 10 and the second cement cured body 14 is 52.5%. And set.

(Example 2) When the target structural concrete has a strength of 36 N / mm ² and a water cement ratio of 57.5%, the mortar forming the first hardened cement body 10 and the second hardened cement body 14 has a strength If it is 40 N / mm ² or more and the water cement ratio needs to be 55% or less, the water cement ratio of the mortar forming the first cement cured body 10 and the second cement cured body 14 is set to 55%. To do.

  Since the water-cement ratio is known for a new structure, the above method is used. The same applies to existing concrete where the mixing information such as water cement ratio is known. On the other hand, when the blending information is unknown, installation to the existing structure involves core removal, so test the removed concrete core and confirm the strength level. From here, for example, by multiplying the strength level of the existing concrete by a safety factor of about 20%, the strength level of the mortar forming the first cement cured body 10 and the second cement cured body 14 is set, From there the water cement ratio is determined. In this case, although the water cement ratio of the target concrete is unknown, there is no problem because the water cement ratio is calculated by multiplying the strength by the safety factor.

  This is because the water cement ratio is considered to be substantially the same or small. Since the strength of existing concrete has increased over time, the ratio of water to cement in the mortar that forms the first hardened cement body 10 and the second hardened cement body 14 designed with short-term strength when combined with the strength level Is often smaller and is multiplied by a safety factor.

[Mortar formulation]
The mortar formulation is indicated by the mass of the constituent material per unit volume. The conditions for selecting the formulation are material type (water, cement, aggregate), water cement ratio (mass ratio), and unit aggregate volume ratio (ratio of aggregate volume to unit volume). In general, the water may be tap water, or JIS compatible water. It is preferable to set the water cement ratio (mass) of the mortar in the range of 20% to 70% and the unit aggregate volume ratio (vol) in the range of about 0% to 75% according to the target concrete.

  The water cement ratio is most preferably equal to the water cement ratio of the concrete to be inspected, and may be set to be smaller by about 0 to 10%. The unit aggregate volume is closer to concrete as the ratio is higher, but the workability is also lowered. On the contrary, if the ratio is low, the workability is improved, but the physical properties are separated and the material is easily separated. It can be set in consideration of the softness, compactness, installation position of the corrosion sensor, etc., and can be set in the range of 0% to 75%, preferably in the range of 30% to 65%. The following table shows blending conditions and blending examples of mortar paste. Note that the W / C of the target concrete is 57.5%.

ここでは、中庸熱ポルトランドセメント（密度３．２１ｇ／ｃｍ^３）、砕砂（密度：２．６０ｇ／ｃｍ^３）を使用する。

Here, medium heat Portland cement (density 3.21 g / cm ³ ) and crushed sand (density: 2.60 g / cm ³ ) are used.

  As the mortar for forming the first hardened cement body 10 and the second hardened cement body 14, a plurality of blends can be prepared in advance, and a suitable mortar can be selected. The following table shows an example of the range of application of the water cement ratio of the mortar forming the first cement cured body 10 and the second cement cured body 14. It is also possible to set more finely than the following table.

対象のコンクリートの水セメント比が不明の場合、調査によってある程度の範囲で推定することができる。そのため、上記の表のような選択基準でモルタルを選択することも可能である。

If the water-cement ratio of the target concrete is unknown, it can be estimated to a certain extent by investigation. Therefore, it is possible to select mortar based on the selection criteria as shown in the above table.

[Diffusion coefficient and sensor location]
When the corrosion factor is, for example, chloride ion or carbon dioxide, the penetration into mortar and concrete proceeds by diffusion. For this reason, the diffusion coefficient is a direct measure of the corrosive environment of the reinforcing bars in the reinforced concrete structure. Since the diffusion coefficient of mortar and concrete varies depending on the materials used, the composition, and the environment, it is not easy to determine the diffusion coefficient in a strict sense, but the apparent diffusion coefficient can be determined by tests and investigations. Except for environmental conditions, the diffusion coefficient depends on the material composition, so the mortar quality may be set by the diffusion coefficient.

When the detection target of the corrosion sensor is salt, use a cement with a small amount of C ₃ A as the cement type, and when the detection target is carbon dioxide, use a low alkali cement or mixed cement. And the apparent diffusion coefficient of carbon dioxide tends to increase. For this reason, it is effective in improving the detection sensitivity. Further, if the water cement ratio in the blending is set to the same level or close, the diffusion coefficient can be made close. In addition, the position of the corrosion sensor embedded in the mortar forming the first hardened cement body 10 and the second hardened cement body 14 should be set as close to the surface as possible within a range that ensures workability and protection. In this case, the detection sensitivity is improved. Diffusion of salt and carbon dioxide occurs in the concrete to be detected and the corrosion sensor-embedded mortar, and can be detected by the corrosion sensor. For diffusion, the reach of the factor is determined according to time using the concentration difference as a driving force. In other words, shortening the distance can be a direct way to shorten the arrival time of the diffusion factor.

  The distance from the surface to the sensor portion is preferably about 2 mm to 20 mm, more preferably about 2 mm to 10 mm, and still more preferably about 2 mm to 5 mm. Within the above range, even if the water-cement ratio is slightly smaller than that of the symmetric concrete, the time order from the penetration of the corrosion factor to the reinforcement corrosion in the concrete structure (several numbers) Compared with years to several decades), it is possible to give sufficient detection sensitivity to contribute to maintenance (detection sensitivity within months to years). As described above, it is most preferable that the concrete to be detected and the water cement ratio of the mortar forming the first cement cured body 10 and the second cement cured body 14 are equal. Since there are various diffusion coefficients such as a salt diffusion coefficient and a carbon dioxide diffusion coefficient (neutralization rate coefficient), any of them may be set according to the application.

[Manufacturing method of unit]
FIG. 4 is a diagram showing a procedure for manufacturing the corrosion sensor unit. Here, an example of a method for manufacturing a corrosion sensor unit to be inserted into a drilled hole having been subjected to core boring having a diameter of 50 mm and a depth of 120 mm will be described. First, the inner cylindrical portion of the mortar serving as a base, that is, the first cement hardened body 10 is manufactured as φ40 mm. Specifically, a general-purpose cylinder φ50 mm × 100 mm height mold 40 is prepared, and a Teflon (registered trademark) hollow cylinder A (outer diameter φ49.8 mm, inner diameter φ40 mm, height) to which mortar does not adhere. 100 mm) is inserted, and the mortar is driven up to a height of 80 mm (step S1). After the placement and the mortar has hardened (for example, one week later), the Teflon (registered trademark) cylinder A and the mortar cylinder are taken out to obtain the first hardened cement body 10 (step S2).

  Next, the RFID tag 12 having the sensor unit 11 and the antenna is attached to a predetermined surface of the first hardened cement body 10, and the sensor unit 11 and the RFID tag 12 are connected by the lead wire 13 (step S3). Since these connection portions tend to be a drawback of durability during long-term use, they are sufficiently covered with a waterproof / moisture-proof material such as a silicon material or a styrene rubber material. Thereafter, a Teflon (registered trademark) hollow cylinder B (outside diameter 49.8 mm, inner diameter φ46 mm, height 100 mm) is inserted into a mold 41 having a diameter of 50 mm and a height of 100 mm, and the sensor unit 11 and the like are already installed. The hardened body 10 (φ40) is inserted (step S4). Thereafter, a gap is made with a mortar using sand having a small maximum particle diameter so that the height becomes 100 mm. The mortar is cured for about one week, after which the formwork is removed and a unit of φ46 mm is completed (step S5).

  Since the corrosion sensor unit according to the present embodiment can be manufactured in a factory using the above-described method, quality and accuracy are ensured, and in the measurement in concrete, the variation in the detection data of the sensor unit 11 is reduced. Can be suppressed. That is, it is possible to provide a corrosion sensor unit with less uncertainty.

[Example of installation method]
FIG. 5 is a diagram illustrating an example of an installation method of the corrosion sensor unit according to the present embodiment. Core boring is performed at a location to be detected in the frame concrete 30 of the existing structure. At this time, a drilled portion 31 that is cored for sampling purposes may be used. The corrosion sensor unit (second cement hardened body 14) manufactured by the above method is inserted into the hole 31. Here, in order to adhere to the concrete body 30, paste / mortar may be applied to the outer surface of the second hardened cement body 14 in advance and then inserted, or after insertion, the paste / mortar is press-fitted. May be. After the installation, the surface of the drilled hole portion 31 is repaired with the repair mortar 32 because there is a possibility that a corrosion factor may enter.

[Detection method]
After the corrosion sensor unit (second cement hardened body 14) is inserted into the drilled hole 31, diffusion of corrosion factors occurs between the concrete frame 30 and the corrosion sensor unit as time passes. For example, if it is a chloride ion, it permeates into the unit, and the supply of moisture and oxygen causes corrosion in the iron foil of the sensor unit 11. By detecting the deformation of the sensor unit 11, the corrosive environment of the concrete frame 30 can be determined. For example, even if a corrosion disconnection occurs in the sensor unit 11 on the surface side, the penetration depth of the corrosive environment can be determined if no deformation occurs in the sensor unit on the back side. In addition, if the date of completion of the structure is known, from the relationship between time and penetration depth, about the future penetration of the corrosive environment, for example, the time to reach the position of the reinforcing bar, etc. It is possible to predict the future after several decades. As a result, it is possible to examine measures for extending the life of the structure through planned repairs and repair work.

  It can also be used to determine the effects of structural repairs and repairs. This can be done by embedding this sensor during construction.For example, the corrosion sensor unit according to this embodiment is buried in the hole drilled during the preliminary survey before repair work, and the effect of the construction can be improved. In addition to confirming, it will be possible to conduct long-term monitoring after construction.

  As described above, according to the present embodiment, since the sensor unit 11 is installed on the side surface of the first hardened cement body 10, it is possible to accurately detect the diffused corrosion factor. In addition, since the second hardened cement body 14 covers the first hardened cement body 10, the sensor unit 11, and the RFID tag 12 with concrete, the protection function of the sensor unit 11 is dramatically improved, and the inspection target Easy to install in concrete. Further, when the sensor unit 11 is an iron member, the sensor unit 11 is covered with a non-conductive coating because the sensor unit 11 is placed in an alkaline environment in the concrete. As a result, it becomes difficult to rust compared with a sensor part not placed inside the concrete, and handling is easy.

DESCRIPTION OF SYMBOLS 10 1st cement hardening body 11 Sensor part 12 RFID tag 13 Lead wire 14 2nd cement hardening body 30 Concrete body 31 Drilling part 32 Repair mortar 40, 41 Formwork

Claims (3)

A corrosion sensor unit for detecting a corrosive environment of reinforcing steel in a reinforced concrete structure,
A first hardened cement body formed into a cylindrical shape having a first diameter with concrete, mortar or paste;
A sensor unit that is installed on a side surface of the first hardened cement body, detects a penetration state of the corrosion factor that corrodes a reinforcing bar into the concrete, and outputs data indicating the penetration state of the corrosion factor;
A transmitter that wirelessly transmits data output from the sensor unit, which is installed on any one smooth end surface of the first cement cured body;
The first cement hardened body, the sensor unit, and the transmitter are covered with concrete, mortar, or paste, and are formed into a cylindrical shape having a second diameter larger than the diameter of the first cement hardened body. A corrosion sensor unit comprising: a second hardened cement body.   The corrosion sensor unit according to claim 1, wherein the sensor unit is formed of iron foil. A method of installing a corrosion sensor for detecting a corrosive environment of a reinforcing bar in a reinforced concrete structure,
Producing a first hardened cement body formed into a cylindrical shape having a first diameter with concrete, mortar or paste;
On the side of the first hardened cement body, detecting a penetration state of the corrosion factor that corrodes the reinforcing bar into the concrete, and installing a sensor unit that outputs data indicating the penetration state of the corrosion factor; and
On the smooth end surface of any one of the first cement hardened body, installing a transmission unit that wirelessly transmits the data output by the sensor unit;
The first cement hardened body, the sensor unit, and the transmitter are covered with concrete, mortar, or paste, and are formed into a cylindrical shape having a second diameter larger than the diameter of the first cement hardened body. Producing a second hardened cement body;
A method of installing a corrosion sensor, comprising at least a step of embedding and integrating the second hardened cement body in a drilled portion obtained by core boring the concrete of the structure to be detected.

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