JP2006206953A - Method for installing anode for electric corrosion protection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently fit an anode for electric corrosion protection to a concrete structure such as a bridge girder and a pier, and to effectively prevent the electric short-circuit between the anode and a reinforcing rod arranged inside the concrete. <P>SOLUTION: A net-shaped member 1 composed of an insulating material is fitted so as to cover the surface of a reinforcing rod concrete member 10, and an anode 2 for electric corrosion protection as a member in which an electrically conductive material is formed in a net shape is fitted to the net-shaped member 1, so as to be superimposed. The net-shaped member and the anode are fitted by plastic nails driven into insertion holes provided at the concrete member. After the fitting of the net-shaped member and the anode, these are buried, and further, a mortar covering layer is formed by troweling so as to be stuck with the surface of the reinforcing rod concrete member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of installing an anode for electrocorrosion protection on a reinforced concrete member such as a bridge girder or a pier, and in particular, an anode for electrocorrosion prevention so as not to cause a short circuit between the anode for electrocorrosion protection and the reinforcing bar disposed in the reinforced concrete member. It is related with the method of installing.

When a reinforced concrete structure deteriorates, the corrosion of the reinforcing bars may cause cracks in the vicinity of the surface, resulting in peeling and dropping of the concrete pieces. This is because corrosion products are formed on the surface of the reinforcing bars due to the corrosion of the reinforcing bars arranged in the concrete, and this expands to cause cracks in the concrete on the surface side of the reinforcing bars, that is, the concrete at the cover, and peel off.
Corrosion of reinforcing bars is likely to occur due to the neutralization and salt damage of concrete. Particularly in a reinforced concrete structure in the marine environment, salt such as seawater penetrates into the concrete, and the reinforcing bars are extremely susceptible to corrosion. And when cracks occur on the surface, salt penetrates further and accelerates corrosion of the reinforcing bars.

  It is known that cathodic protection is effective as a means for preventing corrosion of reinforcing bars under extremely severe conditions such as reinforced concrete structures in the marine environment. In the case of cathodic protection, a reinforcing bar that is subject to corrosion prevention is used as a cathode, and an anode is provided to generate a negative potential at the cathode. There are a galvanic anode method and an external power supply method. In the galvanic anode method, there is a limit to the voltage that can be obtained, so it is common to use an external power supply method for reinforced concrete structures. In the external power supply system, an insoluble anode is arranged on the concrete surface, and a direct current is passed from an external direct current power source to the reinforcing bar inside the concrete via the anode. A negative potential is generated in the reinforcing bar due to the flow of electrons from the anode to the reinforcing bar, which is called an anticorrosion current, and the oxidation of the reinforcing bar is suppressed.

  As described in Non-Patent Document 1, a mesh-like electrode attached near the surface of a reinforced concrete structure is known as an anode used for electrocorrosion protection. For this anode, for example, a titanium mesh having a mesh interval of 25 to 75 mm is used. In this way, in the anticorrosion method in which the surface electrode is provided so as to cover the surface of the reinforced concrete, an appropriate anticorrosion current can be generated between all the reinforcing bars arranged in the concrete, effectively preventing corrosion. be able to.

On the other hand, Patent Document 1 describes a technique in which a groove is formed on the surface of a reinforced concrete structure, and a linear or strip electrode is embedded in the groove to form an anode. And if a groove is formed and an electrode is embedded, it may come into contact with a reinforcing bar in the concrete and electrically short-circuit, and in order to prevent this, a part of the linear electrode is covered with a mesh-like insulating member. It is supposed to be covered.
Edited by the Japan Elgard Association, Q & A for corrosion protection of concrete structures, Sankaido JP 2004-689132 A

The method of attaching a planar anode such as a mesh body to the surface of a concrete structure by the conventional anticorrosion technique as described above has the following problems.
When an anode is disposed on the surface of an existing concrete structure, the reinforcing bar disposed in the concrete and the anode may be electrically short-circuited. Generally, reinforcing bars are embedded in a concrete structure, and a cover thickness of a predetermined dimension is set from the reinforcing bars to the surface of the structure. However, the reinforcing bars may be arranged near the surface of the concrete structure due to inaccurate arrangement of the reinforcing bars or construction failure such as dropping of the spacer inserted between the molds when placing the concrete. And if sufficient cover thickness of concrete is not ensured, a part of reinforcing bar may be exposed on the surface. In addition, the rebars are bound to each other by binding wires made of mild steel or the like at the time of assembly, but if the processing of the binding wires is not appropriate, a part may be exposed on the surface of the concrete structure. Thus, when the reinforcing bars and the binding wires are exposed on the surface of the concrete structure, when the net-like anode as described in Non-Patent Document 1 is arranged along the surface of the concrete structure, the anode and The exposed reinforcing bars or binding wires come into contact with each other, and these are electrically short-circuited. When there is an electrical short circuit, when a voltage is applied between the reinforcing bar and the anode, the current concentrates on the contact portion, and a corrosion-proof current cannot be generated over a wide range.

  It is possible to prevent short circuit by inspecting the surface of the concrete structure before placing the anode in advance and applying insulation treatment to the exposed parts of the reinforcing bars and binding wires. It takes a lot of time and sometimes overlooks exposed parts. If an exposed part is overlooked and a short circuit is detected after construction, exploration and refurbishment of the short circuit part is required, and the burden of costs becomes extremely large.

  The present invention has been made in view of the circumstances as described above, and its purpose is to efficiently attach an anode for cathodic protection to a concrete structure such as a bridge girder or a pier, and in the anode and the concrete. It is an object of the present invention to provide a method for installing an anode for cathodic protection capable of effectively preventing the arranged reinforcing bars from being electrically short-circuited.

  In order to solve the above-mentioned problem, the invention according to claim 1 is for an anticorrosion, which is a member in which a mesh member made of an insulating material is attached so as to cover the surface of a reinforced concrete member, and a conductive material is formed in a mesh shape. A method of installing an anode for cathodic protection, comprising attaching an anode to the mesh member, embedding the mesh member and the anode, and forming a coating layer so as to adhere to the surface of the reinforced concrete member I will provide a.

In this method of installing an anode for cathodic protection, since the mesh member made of an insulating material is disposed between the mesh-like anode for cathodic protection and the reinforced concrete member, the anode does not directly contact the surface of the reinforced concrete member. . For this reason, even if the reinforcing bars and the binding wires arranged in the concrete are exposed on the surface, an electrical short circuit between the reinforcing bars and the anode can be reliably prevented. Then, the coating layer is formed so as to embed the mesh member and the anode made of an insulating material, and the material of the coating layer contacts and adheres to the surface of the concrete member, so that the mesh member and the anode are firmly held. At the same time, the anticorrosion current flows through the material forming the covering layer and the concrete. As a result, a positive charge is supplied to the reinforcing bars in the concrete, and corrosion is effectively prevented.
In addition, the material which forms a coating layer has a big adhesive force with respect to concrete, and the material which produces a weak corrosion-proof electric current is selected, and generally mortar or concrete is employ | adopted.

  The invention according to claim 2 is the method of installing an anode for cathodic protection according to claim 1, wherein the reinforced concrete member is a beam or a bridge girder, and the mesh member and the anode are arranged from a side surface to a lower surface or a side surface of the beam or bridge girder. From the top to the top, it shall be attached continuously beyond the apex.

In this method of installing the anode for cathodic protection, since the anode is continuously attached beyond the apex portion of the reinforced concrete member such as a beam or a bridge girder, a substantially uniform anticorrosive effect can be obtained in a region where the reinforcing bar may be corroded. In addition, by continuously attaching the insulative mesh member and the anode, a wide range of construction can be performed in a series of operations, and the construction management can be simplified.
In addition, the mesh member and the anode for cathodic protection used in this method have a planar shape, can be easily bent at any position, and can be easily applied continuously beyond the apex portion. it can.

  According to a third aspect of the present invention, in the method for installing an anticorrosion anode according to the first or second aspect, the mesh member has a mesh interval of 20 to 70 mm, and the diameter of the wire constituting the mesh is What is 1 mm-6 mm is used.

  In this method of installing an anode for cathodic protection, by setting the mesh interval of the mesh member and the diameter of the wire forming the mesh member within the above values, the anode separated from the surface of the concrete member via the mesh member. Can be effectively prevented from coming into contact with the concrete surface. In other words, by appropriately setting the mesh interval and the wire diameter, it is possible to prevent the anode from bending between the meshes and contacting the surface of the concrete member when the coating layer is formed.

  As described above, in the method for installing an anode for cathodic protection according to the present invention, by inserting an insulative mesh member between the anode and the surface of the concrete member, the reinforcing bar and the anode for cathodic protection are provided. It is possible to reliably prevent an electrical short circuit between the two. Therefore, it is possible to effectively protect the reinforcing bars in a wide range and to attach the anode efficiently.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The present invention is applied to suppress the progress of the bridge girder deterioration by electric corrosion protection when the bridge girder 10 of reinforced concrete or prestressed concrete as shown in FIG. In this example, an anode for cathodic protection is attached along the lower surface 10a of the bridge girder 10, the side surface 10b, and the lower surface 10c of the concrete slab formed between the girders, and a voltage is applied between these anodes and reinforcing bars. It is.

FIG. 1 is a cross-sectional view in the vicinity of the surface of a bridge girder where the anode is installed, and FIG. 2 is a conceptual diagram showing an installed state of the anode and a state of voltage application.
In the method of installing the anode for cathodic protection according to the present invention, the mesh member 1 made of an insulating material is attached so as to cover the surface of the bridge girder, that is, the concrete member 10, and the anode 2 for cathodic protection is placed on the mesh member 1. Install. Then, a mortar coating layer 3 is formed so as to embed the mesh member 1 and the anode 2, and is firmly attached to the surface of the concrete member 10. A voltage is applied between the anode 2 and the reinforcing bar 5 from the power supply device 9 provided outside.

  The mesh member 1 is made of an insulating material, such as plastics such as polyethylene, polyester, polyvinyl chloride, and acrylic, rubbers such as natural rubber and synthetic rubber, ceramics such as porcelain and ceramics, and others. A material made of a fluororesin or a combination thereof is used. The mesh spacing is preferably 20 to 70 mm, and the diameter of the wire constituting the mesh is preferably 1 mm to 6 mm.

  The mesh spacing and the wire diameter of the mesh member 1 are in contact with the concrete surface due to the flexure generated between the meshes even when the anticorrosion anode 2 attached to the mesh member 1 is pressed to the concrete surface side when the coating layer 3 is formed. It is desirable to set so that it does not occur.

  The anode 2 for cathodic protection is a member in which a conductive material is formed in a net shape. The material needs to be insoluble, and titanium is generally used. The mesh spacing is preferably 25 to 75 mm.

  The covering layer 3 protects the mesh member 1 and the anode 2 for cathodic protection, and firmly attaches the anode 2 and the mesh member 1 to the surface of the concrete member 10 so as to be integrated. It is desirable to use mortar or concrete as the material of the covering layer 3, and the thickness is about 20 mm to 80 mm. Moreover, the surface protective layer 4 by an epoxy resin etc. can be provided in the surface of this coating layer as needed.

Next, the process of installing the cathodic protection anode will be described.
First, damage of the concrete member 10 is confirmed visually. If damage such as cracking has occurred, epoxy resin is injected to suppress the progress of deterioration. When the concrete floats up due to the expansion of the product due to corrosion of the reinforcing bars 5, this portion is removed, and the mortar 6 is embedded as shown in FIG. When the deterioration of the cover part of the reinforcing bar 5 progresses and the strength of the concrete is reduced, the cover part is cut and removed. And the concrete member 10 is restored | repaired by providing a formwork and placing concrete.

When the concrete member 10 is repaired, as shown in FIG. 3B, the mesh member 1 made of an insulating material is attached so as to cover the surface thereof. The net-like member 1 is wound in a roll shape having a width of about 1 m, and the required length is cut and used during construction. For attaching the mesh member 1, a plastic nail 8 that is driven into an insertion hole 7 provided in the concrete member is used.
The plastic nail 8 has a head portion 8a having a flat surface and a shaft portion 8b protruding perpendicularly from the head portion. The shaft portion 8b has a plurality of enlarged diameter portions projecting in a node shape. Yes. The enlarged diameter portion is deformed by driving the shaft portion 8b into the insertion hole 7 having an inner diameter smaller than the maximum diameter of the enlarged diameter portion, and is strongly pressed and fixed to the inner peripheral surface of the insertion hole 7. . The mesh member 1 is locked to the head 8 a of the plastic nail 8 and driven into the insertion hole 7, whereby the mesh member 1 can be pressed against the surface of the concrete member 10 and held.

  Next, as shown in FIG. 4A, the anode 2 for anticorrosion is attached to the mesh member 1 in an overlapping manner. The anode 2 for the anticorrosion is also wound into a roll having a width of about 1 m, carried into the construction site, and cut to a length necessary for construction. As in the case of attaching the mesh member 1, the concrete member 10 is provided with an insertion hole 7 by a drill or the like, and the anode 2 for cathodic protection is superimposed on the mesh member 1 to hold the plastic nail 8 in the insertion hole 7. Fix by driving into. At this time, the plastic nail 8 is preferably driven close to a portion where the wire of the mesh-like anode 2 intersects the wire of the mesh-like member 1 made of an insulating material. This prevents the anode 2 from being directly pressed against the surface of the concrete member 10 by the plastic nail 8, and ensures that the surface of the concrete member 10 is exposed to reinforcing bars or binding wires and causes a short circuit. Can be prevented.

  In addition, the mesh member 1 and the anode 2 for cathodic protection are limited to a method in which only the mesh member 1 is fixed first and the anode 2 is fixed thereafter, as shown in FIG. 4 (a). Instead, the mesh member 1 made of an insulating material and the anode 2 may be overlapped and fixed simultaneously by the same plastic nail. Moreover, when the mesh member made of an insulating material is fixed first, the anode may be attached to the mesh member by bundling it with a clip or a binding wire.

  When the attachment of the mesh member 1 and the anode 2 made of an insulating material is completed, the covering layer 3 is formed so as to embed them and adhere to the surface of the concrete member 10 as shown in FIG. The coating layer 3 can be formed by troweling mortar. Moreover, when forming a coating layer thickly, you may provide a mold and cast concrete or mortar. When a surface protective layer is provided on the coating layer, an epoxy resin or the like is subsequently applied with a brush, a roller, or the like.

  As shown in FIG. 5, the anode 2 provided as described above is preferably attached so as to continue beyond the apex portion of the concrete member 10. Thus, by providing an anode continuously over the side surface 10b and the bottom surface 10a of the girder, an equivalent anticorrosion effect can be expected for the reinforcing bars disposed near the side surface and the bottom surface of the concrete member 10. And construction can be performed continuously, and efficient work becomes possible.

It is sectional drawing of the surface vicinity of the concrete member in which the anode was installed by the method based on this invention. It is a conceptual diagram which shows the state of the anode installed by the method based on this invention, and a voltage application. It is sectional drawing which shows the process in the installation method of the cathodic protection anode which is one Embodiment of this invention. It is sectional drawing which shows the process in the installation method of the cathodic protection anode which is one Embodiment of this invention. It is sectional drawing which shows the vertex part of the concrete member in which the anode was provided by the method based on this invention. It is an example of the concrete structure which can apply the installation method of the cathodic protection anode of this invention, Comprising: It is a schematic sectional drawing of the bridge girder which consists of reinforced concrete.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Net-like member which consists of insulating materials, 2: Anode, 3: Coating layer, 4: Surface protective layer, 5: Reinforcing bar, 6: Mortar, 7: Insertion hole, 8: Plastic nail, 9: Power supply device, 10 : Concrete member (bridge girder)

Claims (3)

Attach a mesh member made of an insulating material to cover the surface of the reinforced concrete member,
An anode for cathodic protection, which is a member formed of a conductive material in a mesh shape, is attached to the mesh member,
A method for installing an anode for cathodic protection, comprising embedding the mesh member and the anode and forming a coating layer so as to adhere to the surface of the reinforced concrete member.   The reinforced concrete member is a beam or a bridge girder, and the mesh member and the anode are attached continuously from the side surface to the bottom surface or from the side surface to the top surface of the beam or bridge girder, exceeding the apex portion. The installation method of the anode for electro-corrosion prevention of description. The anode for cathodic protection according to claim 1 or 2, wherein the mesh member has a mesh interval of 20 to 70 mm and a wire constituting the mesh has a diameter of 1 mm to 6 mm. Installation method.

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