JP2019167611A - Electric protection structure of concrete structural body, and electric protection method - Google Patents

Abstract

To evenly control corrosion of whole concrete structural body in an electric protection structure of the structural body.SOLUTION: There is provided the electric protection structure of a concrete structural body including a concrete layer 10 having reinforcing steels 12 built-in. On the surface of the concrete layer 10, a primary anode 14 is disposed via an insulation layer, and a semiconductive layer 16 is provided so as to cover the primary anode 14 and concrete layer 10. Besides, a direct-current power source 18 impressing an electric voltage between the primary anode 14 as an anode and the reinforcing steel 12 is provided, and a homogeneous electric resistivity is given to the semiconductive layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an anticorrosion structure and an anticorrosion method for a concrete structure, and more particularly to an anticorrosion structure and an anticorrosion method for a concrete structure effective for preventing corrosion of reinforcing bars inside a concrete layer.

  Japanese Patent Application Laid-Open No. 2012-67360 discloses an anticorrosion structure for a concrete structure using an anticorrosion electrode. In this structure, the concrete structure includes a concrete layer in which a reinforcing bar is installed. The anticorrosion electrode is a conductive material formed in a long shape, and is installed so that one surface thereof is in contact with the surface of the concrete layer.

  A sheet body is further arranged on the surface of the concrete layer. A sheet | seat body is arrange | positioned so that the surface of a concrete layer may be covered including an anticorrosion electrode. A sheet | seat body is a member which forms the outer surface of a concrete structure, and has waterproofness.

  In the above structure, a direct current voltage is applied between the anticorrosion electrode and the reinforcing bar so that the anticorrosion electrode serves as an anode. Corrosion of rebars involves the movement of electrons. According to said voltage application, the movement of the electron can be prevented and the corrosion progress of the reinforcing bar can be prevented. For this reason, according to the said conventional structure, corrosion of the reinforcing bar in concrete can be prevented stably for a long period of time.

JP 2012-67360 A

  In the above conventional structure, a plurality of cathodic protection electrodes are arranged on the surface of the concrete layer at substantially regular intervals. If a voltage is applied to the anticorrosion electrodes arranged in this way, a high potential tends to concentrate in the vicinity thereof, and potential unevenness occurs on the surface of the concrete layer. If the surface potential becomes uneven, the anticorrosion current flowing inside the concrete layer also becomes uneven. If non-uniformity occurs in the anti-corrosion current, non-uniformity also occurs in the anti-corrosion effect of the reinforcing bars. For this reason, the conventional structure described above leaves room for further improvement in preventing corrosion of the entire concrete structure evenly.

The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide an anticorrosion structure suitable for preventing corrosion of the entire concrete structure without unevenness.
Moreover, this invention makes it the 2nd objective to provide the cathodic protection method suitable for carrying out the corrosion prevention of the whole concrete structure uniformly.

  In order to achieve the first object, a first invention is an electric corrosion protection structure for a concrete structure including a concrete layer containing a reinforcing bar, the primary anode being disposed so as to cover a part of the concrete layer. An insulating layer that is interposed between and insulates between the primary anode and the concrete layer, a semiconductive layer disposed so as to cover the concrete layer together with the primary anode, and the primary anode as an anode And a direct current power source for applying a voltage between the primary anode and the reinforcing bar, and the semiconductive layer has a uniform electrical resistivity.

  In order to achieve the second object, the second invention is an anticorrosion method for a concrete structure including a concrete layer containing a reinforcing bar, wherein the insulating layer covers a part of the concrete layer. A step of disposing a primary anode via the step, a step of forming a semiconductive layer so as to cover the concrete layer together with the primary anode after the disposition of the primary anode, and the primary anode serving as an anode. Connecting a DC power source to a primary anode and the reinforcing bar, wherein the semiconductive layer has a uniform electrical resistivity.

  According to the first or second invention, the primary anode is disposed on the surface of the concrete layer via the insulating layer. For this reason, in the present invention, the anticorrosion current does not flow directly from the primary anode to the concrete layer. The primary anode in the present invention is in direct contact with the semiconductive layer. Further, the semiconductive layer is in direct contact with the concrete layer at a portion not covered with the primary anode. For this reason, the semiconductive layer functions as a secondary electrode, and the anticorrosion current flowing out from the primary anode reaches the surface of the concrete layer through the semiconductive layer. Since the semiconductive layer has a uniform electrical resistivity, the anticorrosion current spreads over a wide range in the semiconductive layer, and a uniform electric field distribution can be created in the entire concrete structure. For this reason, according to the present invention, the anticorrosion current does not flow in the vicinity of the primary anode, and as a result, the entire concrete structure can be appropriately anticorrosive.

It is a figure for demonstrating the outline | summary of the cathodic protection structure used in Embodiment 1 of this invention. It is the figure which expanded and represented the cross section of the concrete structure shown in FIG. It is the figure which illustrated the polymer component for cement mixing which can be used in Embodiment 1 of this invention. It is the figure which illustrated the inorganic type electroconductive filler which can be used in Embodiment 1 of this invention. It is the figure which illustrated surfactant which can be used in Embodiment 1 of the present invention. It is the figure which showed a mode that the passive film of a reinforcing bar was destroyed with chlorine. It is the figure which showed a mode that a corrosion current generate | occur | produced with corrosion of a reinforcing bar. It is a figure for demonstrating the relationship between corrosion of a reinforcing bar and electric potential. It is a figure for demonstrating the principle in which a corrosion-proof electric current lose | disappears a corrosion current. It is a flowchart of the cathodic protection method used in Embodiment 1 of the present invention. It is the figure which contrasted and represented the anticorrosion current in Embodiment 1 of this invention, and the anticorrosion current in a comparative example. It is the figure which represented the phenomenon which arises at the time of water leakage by contrasting with the structure in Embodiment 1 of this invention, and the structure in a comparative example. It is the figure which represented the phenomenon which arises at the time of drying by contrasting with the structure in Embodiment 1 of this invention, and the structure in a comparative example. It is a figure which shows the structure of the modification of the primary anode which can be used for the cathodic protection structure of Embodiment 1.

Embodiment 1 FIG.
[Electrical protection structure of Embodiment 1]
FIG. 1 is a diagram for explaining the outline of the cathodic protection structure used in Embodiment 1 of the present invention. The structure shown in FIG. 1 includes a concrete layer 10. A plurality of reinforcing bars 12 are built in the concrete layer 10. The reinforcing bars 12 in the present embodiment are arranged in a lattice pattern inside the concrete layer 10.

  A plurality of primary anodes 14 are arranged on the surface of the concrete layer 10. The primary anode 14 is an elongated ribbon-like conductive material, and is arranged in parallel at regular intervals on the entire surface of the concrete layer 10. In the present embodiment, specifically, an MMO titanium tape having a function of transferring current only on one side is used as the primary anode 14. The primary anode 14 is disposed so that the surface that does not receive and transmit current faces the concrete layer 10. The interval between the primary anodes 14 can be set as appropriate within a range of 10 to 50 cm, and is set to 50 cm in this embodiment.

  The concrete layer 10 and the primary anode 14 are covered with a semiconductive layer 16. As a result, the primary anode 14 is in contact with the semiconductive layer 16 on the surface that receives and transmits current. The semiconductive layer 16 is in direct contact with the surface of the concrete layer 10 in a region where the primary anode 14 is not present. The semiconductive layer 16 is a layer that functions as a secondary anode, and desirably has a uniform electrical resistivity belonging to a range of 0.005 Ωm or more and less than 1.0 Ωm. Furthermore, the semiconductive layer 16 desirably has a uniform thickness of about 3 to 10 mm. In the present embodiment, the electrical resistivity of the semiconductive layer 16 is adjusted to 0.5 Ωm over the entire area. The thickness of the semiconductive layer 16 is adjusted to 5 mm over the entire area.

  The structure shown in FIG. 1 further includes a DC power supply 18. The cathode 20 of the DC power supply 18 is connected to the reinforcing bar 12. The anode 22 of the DC power source 18 is connected to the primary anode 14. Therefore, the reinforcing bar 12 is equipotential with the cathode 20, while the primary anode 14 is equipotential with the anode 22. As a result, a voltage generated by the DC power source 18 is applied between the reinforcing bar 12 and the primary anode 14 so that the primary anode 14 side has a high potential.

  FIG. 2 is an enlarged view showing a cross section of the concrete structure shown in FIG. 1 as viewed in the direction of arrow II shown in FIG. As shown in FIG. 2, the primary anode 14 is installed on the surface of the concrete layer 10 via an insulating layer 24. The insulating layer 24 can be composed of an organic adhesive having an insulating property or a double-sided tape. The insulating layer 24 desirably has a function of preventing the permeation of water.

  The semiconductive polymer cement composition used as the material of the semiconductive layer 16 is mainly composed of (1) an inorganic binder, (2) a polymer component, and (3) an inorganic conductive filler. 4) An auxiliary component containing a foaming surfactant is further included.

(1) The inorganic binder contains at least one of cement, blast furnace slag fine powder, and pozzolanic substance. As the cement, any of Portland cement, mixed cement, white cement, ultrafine particle cement, high belite cement, ultrafast cement, and alumina cement can be used alone or in combination.

(2) As a polymer component, all polymers for cement admixture except a liquid polymer can be used. Specifically, the polymer component used in the present embodiment includes at least one of an aqueous polymer dispersion and a re-emulsifying powder resin. The aqueous polymer dispersion is a liquid substance containing about 35 to 45% solids in the liquid, while the re-emulsified powder resin is a substance containing almost 100% solids. FIG. 3 illustrates polymer components that can be used in this embodiment. However, in FIG. 3, “liquid polymer” is hatched to indicate that “liquid polymer” cannot be used in this embodiment. The polymer component is desirably prepared within a range of 15 to 45 wt% in terms of solid content with respect to the inorganic binder. According to this adjustment, the adhesion strength of the semiconductive layer 16 can ensure 1.5 N / mm ² or more at a material age of 28 days.

(3) The inorganic conductive filler is composed of at least one conductive material of carbon, metal, metal oxide, and metal coating. FIG. 4 exemplifies inorganic conductive fillers that can be used in the present embodiment, together with their respective shapes. The metal coating system is a structure in which a base filler such as mica is covered with a coating material such as nickel. In the present embodiment, a carbon-based conductive filler is mixed in the semiconductive layer 16. The electrical resistivity of the semiconductive layer 16 is adjusted by the mixing rate of the conductive filler. The inorganic conductive filler is desirably mixed within a range of 40 to 250 wt% with respect to the inorganic binder. According to this weight ratio, a filler distribution in which adjacent inorganic conductive filler particles come into contact with each other is realized, and a uniform electric field distribution can be formed over the entire semiconductive layer 16. At this time, the electrical resistivity of the semiconductive layer 16 is a value within 0.005 to 1.0 Ωm.

(4) As an auxiliary component, in addition to the surfactant, an expansion material, a fiber material, and silica sand can be included. The expansion material is added to suppress shrinkage of the semiconductive layer 16 during drying. The fiber material is added for the purpose of preventing cracks on the surface of the semiconductive layer 16. Silica sand is added for the purpose of increasing the thickness of the layer that can be applied in a single operation.

  The surfactant is added for the first purpose to improve pumpability, sprayability, and workability when the semiconductive layer 16 is formed by spraying the semiconductive polymer cement composition. In the present embodiment, a foaming activator is used as the surfactant. FIG. 5 illustrates surfactants that can be used in this embodiment. When a foaming surfactant is mixed and bubbles are entrained in the semiconductive polymer cement composition, the composition can be reduced in weight. And by weight reduction, the workability of the said composition's pumpability and iron holding | suppressing improves. Furthermore, when foam resulting from the surfactant is involved in the semiconductive polymer cement composition, the electrical resistivity of the semiconductive layer 16 is reduced as compared with the case where no surfactant is added. For this reason, in this embodiment, desired electrical efficiency is obtained with a small amount of conductive filler, and the semiconductive layer 16 can be formed at low cost.

  The weight ratio of the foaming surfactant to the inorganic binder is desirably uniform within a range of 0.3 to 3.0 wt%. According to this weight ratio, the specific gravity of the semiconductive polymer cement composition at the time of kneading can be suppressed to 1.5 or less, and the workability of the composition can be further enhanced.

[Principle of cathodic protection]
Next, the principle of cathodic protection will be described with reference to FIGS.
FIG. 6 shows how the passive film 26 of the reinforcing bar 12 is broken by chlorine. In an alkaline environment in the concrete, a passive film 26 is formed on the surface of the reinforcing bar 12. The passive film 26 is extremely dense and protects the surface of the rebar 12 from corrosion. However, when the concrete is neutralized or mixed with chloride ions, the passive film 26 is destroyed as shown in FIG. At the location where the passive film 26 is broken, the rebar 12 becomes active and easily corrodes.

FIG. 7 shows a state in which a corrosion current is generated with the corrosion of the rebar 12 in the active state. Corrosion may occur in the rebar 12 at the location where the passive film 26 is broken. When corrosion of the reinforcing bar 12 proceeds, an anodic reaction in which iron is ionized and a cathodic reaction in which oxygen is reduced proceed on the surface as shown in the following equations (1) and (2), respectively. As a result, corrosion currents 28 and 30 as shown in FIG. 7 flow inside the reinforcing bar 12 and the concrete layer 10.
Fe → Fe ²⁺ + 2e ⁻ (1)
2e ⁻ + H ₂ O + (1/2) O ₂ → 2OH ⁻ (2)

  FIG. 8 shows a state where a corrosion battery is formed on the reinforcing bar 12. As shown in FIG. 8, when corrosion occurs in the reinforcing bar 12, the potential of the corroded portion is lower than the potential of the surrounding healthy portion. Due to this potential difference, a corrosion battery is formed inside the reinforcing bar 12, and an electron flow from the corroded part to the healthy part occurs.

  FIG. 9 shows a state in which a voltage that cancels the corrosion battery is applied to the reinforcing bar 12. As described above, in the present embodiment, the cathode 20 and the anode 22 of the DC power supply 18 are connected to the reinforcing bar 12 and the primary anode 14, respectively. The primary anode 14 is in electrical contact with the semiconductive layer 16 that functions as a secondary anode. According to such a configuration, an electric field is generated between the anode (the primary anode 14 and the semiconductive layer 16) and the reinforcing bar 12, and as a result, the anticorrosion directed from the primary anode 14 to the reinforcing bar 12 through the concrete layer 10. A current 32 is generated. Thereby, electrons are evenly distributed over the entire region of the reinforcing bar 12, and the electric potential of the reinforcing bar 12 is equal throughout the region. As a result, the movement of electrons from the corroded portion to the healthy portion is prevented, and the progress of corrosion of the reinforcing bars 12 is suppressed. According to the present embodiment, the progress of corrosion of the reinforcing bars 12 can be prevented by such a principle.

[Electrical protection method of Embodiment 1]
FIG. 10 is a flowchart of the cathodic protection method used in this embodiment. In addition, this flowchart is for demonstrating the process performed after formation of the concrete layer 10. FIG.

  In the construction method shown in FIG. 10, a preparatory work is first performed (S100). Specifically, installation work such as verification electrodes and drain terminals is performed. Next, a substrate processing work and a marking work are performed.

  Next, an anode installation work is performed (S102). Here, first, the concrete surface is washed (S102-2). Thereby, the surface of the concrete layer 10 is cleaned. Next, a primary anode installation work is performed (S102-4). Specifically, the MMO titanium tape to be the primary anode 14 is bonded to the concrete layer 10 with an insulating organic adhesive or double-sided tape. At this time, the MMO titanium tape is bonded to the concrete layer 10 on a surface where no current is transferred.

  Next, a semiconductive layer coating work is performed (S102-6). In this embodiment, prior to this step, the above-described polymer cement composition including (1) inorganic binder, (2) polymer component, (3) inorganic conductive filler, and (4) auxiliary component is prepared. Is done. This polymer cement composition is adjusted so as to exhibit an electrical resistivity of 0.5 Ωm when dried to form the semiconductive layer 16. In this step, the polymer cement composition is applied to the concrete layer 10 by spraying or ironing so that a 5 mm semiconductive layer 16 is formed. After this process is finished, next, a surface protection work is performed (S102-8).

  When the above steps are completed, a wiring plumber is performed (S104). Here, construction related to wiring and piping necessary for connecting the DC power source 18 to the reinforcing bar 12 and the primary anode 14 is performed.

  Next, a DC power source installation work is performed (S106). Thereby, the cathode 20 and the anode 22 of the DC power source 18 are connected to the reinforcing bar 12 and the primary anode 14, respectively. By performing the above construction, the anticorrosion structure shown in FIG. 1 is realized.

[Effect of Embodiment 1]
(Uneven corrosion protection current)
FIG. 11 (A) shows the flow of anticorrosion current generated inside the cathodic protection structure realized by the present embodiment. FIG. 11B shows the flow of the anticorrosion current generated inside the anticorrosion structure realized by a general titanium ribbon mesh method.

In the titanium ribbon mesh method, an anticorrosion structure is formed by the following procedure.
(1) The vicinity of the surface of the concrete layer 10 is cut to form a space 34 for embedding the anode.
(2) A titanium ribbon mesh 36 is disposed in the space 34 as an anode. The titanium ribbon mesh 36 can transmit and receive current at least on the surface of the reinforcing bar 12 side.
(3) After the titanium ribbon mesh 36 is disposed, the space 34 is backfilled with a mortar 38.

The concrete forming the concrete layer 10 and the mortar used for space backfilling generally have an electrical resistivity of about 10 ² to 10 ⁴ Ωm. As described above, the maximum electrical resistivity allowed for the semiconductive layer 16 in this embodiment is 10 Ωm. Therefore, the titanium ribbon mesh 36 shown in FIG. 11B is surrounded by a member having an electrical resistivity 10 times or more that of the semiconductive layer 16 in the present embodiment.

  As shown in FIG. 11B, when the titanium ribbon mesh 36 (anode) is uniformly surrounded by concrete having a high electric resistivity, the anticorrosion current 32 is unevenly distributed in a region where the titanium ribbon mesh 36 exists. And easy to distribute. In addition, in the configuration shown in FIG. 11B, the titanium ribbon mesh 36 can send and receive current on the surface facing the reinforcing bar 12. For this reason, according to such a configuration, the anticorrosion current tends to concentrate locally in the vicinity of the titanium ribbon mesh 36.

  As shown in FIG. 11A, in the cathodic protection structure of the present embodiment, the surface of the concrete layer 10 is covered with a semiconductive layer 16. The semiconductive layer 16 exhibits a sufficiently small electric resistivity as compared with concrete. Furthermore, in the structure of this embodiment, the primary anode 14 transmits and receives current only on the surface that does not face the reinforcing bar 12. For this reason, the anticorrosion current 32 can flow through the semiconductive layer 16 having a low electrical resistivity to a sufficiently separated region. As a result, according to this structure, as shown in FIG. 11A, the anticorrosion current can be circulated not only in the vicinity of the primary anode 14 but also in a region away from the primary anode 14.

  In particular, in the anticorrosion structure of this embodiment, the semiconductive layer 16 is given a low electrical resistivity of 0.5 Ωm. The semiconductive layer 16 having an electrical resistivity of 0.005 Ωm or more and less than 1.0 Ωm realizes substantially the same potential distribution as a conductor under the condition that a minute current such as an anticorrosion current flows. Can do.

  In order to suppress corrosion of the reinforcing bar 12, it is desirable that the electric potential of the reinforcing bar 12 is made uniform over a wide range. And in order to equalize the potential of the reinforcing bar 12 over a wide range, it is desirable that the anticorrosion current flows through the interior of the concrete layer 10 over a wide range. As described above, according to the structure of the present embodiment, the anticorrosion current can be uniformly distributed and distributed over a wide range of the concrete layer 10. For this reason, according to the structure of this embodiment, the anticorrosion effect excellent in the wide area | region inside the concrete layer 10 can be acquired.

(Water leakage resistance)
FIG. 12A is a diagram for explaining a phenomenon when water leakage 40 occurs in the concrete layer 10 in the cathodic protection structure of the present embodiment. Moreover, FIG. 12 (B) is a figure for demonstrating the phenomenon when the water leak 42 arises in the concrete layer 10 in the anticorrosion structure implement | achieved by the titanium ribbon mesh construction method.

  The concrete structure assumed in the present embodiment can be used for a wall surface of a cave that accommodates a power transmission line and a gas pipe. In a use environment such as a cave, water leakage may occur in the concrete layer 10.

  As shown in FIG. 12 (B), a boundary exists between the mortar 38 and the concrete layer 10 in the general anticorrosion structure by the titanium ribbon mesh method. The water leakage 42 generated along the cracks in the concrete layer 10 is likely to enter this kind of boundary. In the configuration shown in FIG. 12B, the water leak 42 that has entered from the boundary can pass through the mortar 38 and reach the titanium ribbon mesh 36. The electrical resistivity of the water leak 42 is much smaller than that of concrete. For this reason, if the water leak 42 reaches the titanium ribbon mesh 36, an excess current 44 flows from the titanium ribbon mesh 36 through the water leak 42. When such an excess current 44 is generated, acid is generated inside the concrete and the deterioration of the concrete is promoted. Furthermore, if some of the titanium ribbon meshes 36 generate excess current 44, the anticorrosion current 46 flowing out from the other titanium ribbon meshes 36 will be insufficient. Thus, the cathodic protection structure shown in FIG. 12 (B) does not have high resistance to the water leakage 42.

  In the cathodic protection structure of this embodiment shown in FIG. 12A, the primary anode 14 is attached to the surface of the concrete layer 10 via the insulating layer 24. According to such a configuration, even if the water leak 40 enters between the concrete layer 10 and the semiconductive layer 16, the water does not reach the primary anode 14. For this reason, in the cathodic protection structure of this embodiment, even if water leakage 40 occurs in the concrete layer 10, it is difficult for excessive current to be generated from the primary anode 14. If no excessive current is generated, the deterioration of the concrete is not promoted, and the anticorrosion current from some primary anodes 14 is not insufficient. Thus, the cathodic protection structure of the present embodiment can impart high water leakage resistance to the concrete structure.

(Drying resistance)
FIG. 13A is a diagram for explaining a phenomenon that occurs when the cathodic protection structure of the present embodiment is placed in a dry environment. FIG. 13B is a diagram for explaining a phenomenon that occurs when the anticorrosion structure realized by the titanium ribbon mesh method is placed in a dry environment.

  In the cathodic protection structure shown in FIG. 13B, the surface of the concrete layer 10 is directly released to the atmosphere. For this reason, if this structure is placed in a dry environment, drying of the concrete layer 10 proceeds with time. Inside the concrete layer 10, moisture also functions as a medium for circulating electricity. For this reason, the more the concrete layer 10 is dried, the smaller the anticorrosion current 46 flowing through the concrete layer 10. As a result, in the structure shown in FIG. 13B, there may occur a situation where a sufficient anticorrosion effect cannot be obtained in a dry environment.

  In the cathodic protection structure of this embodiment shown in FIG. 13A, the surface of the concrete layer 10 is covered with the semiconductive layer 16. Since the semiconductive layer 16 mainly distributes electricity using a conductive filler as a medium, it exhibits a stable electrical resistivity without being affected by the degree of drying. Moreover, since the semiconductive layer 16 functions as an anti-drying film, the concrete layer 10 in the present embodiment does not become excessively dry even when placed in a dry environment. For this reason, according to the cathodic protection structure of the present embodiment, the anticorrosion current can be stably distributed even in a dry environment. If the anticorrosive current flows stably, the anticorrosive effect of the reinforcing bars 12 can be stably obtained. Thus, the cathodic protection structure of the present embodiment can impart high drying resistance to the concrete structure.

(Excellent workability)
In the above-described titanium ribbon mesh method, a lifting operation for providing a space 34 for embedding the titanium ribbon mesh 36 on the surface of the concrete layer 10 and a backfilling operation for the space 34 are required. It is not always easy to perform these operations in a narrow space such as a cave. In the cathodic protection method of the present embodiment, there is no need to perform such a hanging work or backfilling work. In this respect, the construction method of the present embodiment has excellent characteristics as compared with the titanium ribbon mesh construction method even when the work is carried out in a narrow space such as a cave.

[Modification of Embodiment 1]
FIG. 14 shows a configuration of a modified example of the primary anode that can be used in the cathodic protection structure of the first embodiment. More specifically, FIG. 14A is a diagram showing the modified primary anode 50 in plan view. FIG. 14B is a cross-sectional view showing the primary anode 50 as viewed in the direction of arrow BB shown in FIG.

  The primary anode 50 shown in FIG. 14 includes a tape layer 52 made of MMO titanium tape. A mesh layer 54 is formed on the surface of the tape layer 52. Like the MMO titanium tape, the mesh layer 54 is made of titanium and has a mesh structure. The primary anode 50 has a width of about 20 mm, for example. On the other hand, each rhombus-shaped opening provided in the mesh layer 54 has a diagonal length of about 3 mm in the longitudinal direction and a diagonal length of about 1.5 mm in the short direction.

  A double-sided tape constituting the insulating layer 56 is affixed to the back surface of the tape layer 52. The thicknesses of the tape layer 52 and the mesh layer 54 are about 0.07 mm and about 0.3 mm, respectively. On the other hand, the thickness of the insulating layer 56 is about 0.4 mm. These dimensions are merely examples, and the structure of the primary anode 50 is not limited to these.

  The primary anode 50 shown in FIG. 14 is used such that the insulating layer 56 is in contact with the concrete layer 10 (see FIG. 2) and the mesh layer 54 is in contact with the semiconductive layer 16 (see FIG. 2). According to such a structure, when the semiconductive layer 16 enters each opening of the mesh layer 54, the contact area between the two is ensured, and as a result, the contact strength between the two can be ensured. For this reason, when the primary anode 50 is used, the stability and durability of the cathodic protection structure can be enhanced.

DESCRIPTION OF SYMBOLS 10 Concrete layer 12 Reinforcing bar 14,50 Primary anode 16 Semiconductive layer 18 DC power supply 20 Cathode 22 Anode 24, 56 Insulating layer 32, 46 Corrosion protection current 54 Mesh layer

Claims (5)

An anticorrosion structure of a concrete structure including a concrete layer containing a reinforcing bar,
A primary anode disposed to cover a portion of the concrete layer;
An insulating layer interposed between the primary anode and the concrete layer to insulate them;
A semiconductive layer arranged to cover the concrete layer with the primary anode;
A DC power source for applying a voltage between the primary anode and the reinforcing bar, using the primary anode as an anode, and
The anticorrosion structure for a concrete structure, wherein the semiconductive layer has a uniform electrical resistivity.   2. The anticorrosion structure for a concrete structure according to claim 1, wherein the semiconductive layer has a uniform electrical resistivity belonging to a range of 0.005 Ωm or more and less than 1.0 Ωm. The semiconductive layer is
An inorganic binder containing at least one of cement, blast furnace slag fine powder, and pozzolanic material;
A polymer component comprising at least one of an aqueous polymer dispersion and a re-emulsifying powder resin;
An inorganic conductive filler composed of at least one conductive material of carbon, metal, metal oxide, and metal coating;
An auxiliary component containing a foaming surfactant,
3. The anticorrosion structure for a concrete structure according to claim 1, comprising: The primary anode is an elongated ribbon electrode,
4. The electric corrosion-proof structure for a concrete structure according to claim 1, wherein the insulating layer is formed in the same shape as the primary anode. 5. An anticorrosion method for a concrete structure including a concrete layer containing a reinforcing bar,
A step of disposing a primary anode through an insulating layer so as to cover a part of the concrete layer;
Forming a semiconductive layer so as to cover the concrete layer together with the primary anode after the placement of the primary anode;
Connecting a direct current power source to the primary anode and the reinforcing bar so that the primary anode becomes an anode,
An electric corrosion protection method for a concrete structure, wherein the semiconductive layer has a uniform electrical resistivity.

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