JP4015933B2 - Method for manufacturing concrete structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode body used for corrosion protection of steel materials such as steel bars and steel bars of concrete structures, and more particularly to a structure of an anode electrode used for an external power source type anticorrosion method.
[0002]
[Prior art]
Ancient humans have used a large amount of iron (Fe) as a metal that exists in large quantities on the earth, can be refined relatively easily, has good workability, is inexpensive and stable. However, in recent years, corrosion of steel and steel bars in an acidic environment and rebar in concrete structures has become a social problem. This is because the chemical properties of iron (Fe) used as steel structures and reinforcing bars are covered with a thin passive film of iron oxide on the surface under normal circumstances, but are stable. This is because, in an acidic environment due to the environment or environmental pollution, the passive film is destroyed, oxidation proceeds to the inside, and finally a situation that leads to destruction of the structure occurs.
[0003]
This has been recognized for a long time, and as a countermeasure, means for preventing corrosion such as plating of a different metal on the surface of iron has been implemented. There are two ways to do this: zinc (Zn) and tin (Sn), which have different chemical properties (ionization tendency) from iron (Fe), and the former is known as a tin plate and the latter as a tin plate. ing. The tin plate is plated with zinc which is more ionized than iron (which is more likely to corrode) to corrode zinc before iron itself, and at the expense of zinc to protect iron from corrosion. The tin plate is plated with tin that has a lower ionization tendency (harder to corrode) than iron, so that there is a difference in that the iron plate itself is covered and the iron is protected from corrosion.
[0004]
In recent years, the mechanism of metal corrosion has been elucidated, and an anti-corrosion technology that prevents the corrosion electrically by combining dissimilar metals with different chemical properties by actively utilizing the inherent chemical properties (natural potential difference) of metals. Has been developed. There are two types of cathodic protection techniques, the galvanic anode method and the external power supply method, both of which use iron as a cathode and a different metal as an anode.
[0005]
The galvanic anode method uses a sacrificial electrode piece of zinc, aluminum alloy, magnesium alloy, etc., which has a higher ionization tendency than iron (as a low potential), as an anode, and is attached to an iron corroded body. For example, it is immersed in seawater to form an electrical circuit. When this electric circuit is formed, current flows due to the inherent potential difference of the metal, and the anode such as zinc, which has a higher ionization tendency than iron, ionizes and elutes, and the corrosion of iron, which is the object to be protected, is sacrificed at the sacrifice of the anode. Is prevented. Although this method has advantages such as easy installation and no special equipment, there is a drawback that it is necessary to periodically replace the sacrificial anode metal piece and it is difficult to control.
[0006]
In the external power source system, it is desirable to use a metal having a lower ionization tendency than iron of the corrosion-protected body, for example, a noble metal such as platinum, but since it is expensive, platinum-plated titanium wire, lead alloy, graphite or the like is used as the anode piece. Then, lead wires are drawn out from the object to be protected and the anode piece, connected to a DC power source, and a corrosion current is passed from the power source to prevent corrosion of the object to be protected. The anticorrosion control can be easily performed by controlling the output voltage of the DC power supply. There is an advantage that the maintenance of the power source is required, but the electrode body is not required to be replaced.
[0007]
The present inventor has disclosed a technique of applying an external power supply type anticorrosion technique to a bridge girder. This technique is a technique in which an insoluble electrode filament of a platinum-plated titanium wire is applied as an anode and stretched by applying tension to the electrode filament so as to maintain a certain distance from a steel material that is an anticorrosive material (see, for example, Patent Document 1). ). This is because the anticorrosion current that flows when the distance between the electrodes fluctuates becomes non-uniform and inhibits the anticorrosion effect. Conventional electrodes have been used in the form of fine wires, fine wires woven in a mesh shape, or thin ribbon shapes. These electrodes have a problem in that they have a small rigidity and are easily deformed so that they are arranged at a uniform distance from the object to be protected.
[0008]
Conventionally, an expanded insoluble metal mesh with an anti-corrosion anode material attached to the periphery of the expanded insoluble metal mesh and an electrical connection terminal attached to the periphery is embedded in the conductive coating with the terminals exposed. An anode material for cathodic protection is known (for example, see Patent Document 2). That is, in an external electrode type anticorrosion technique, an insoluble metal mesh made of expanded metal is known.
[0009]
Equipped with an anode encased in a concrete block containing ion-conducting cement, with a valve metal core encased in an active layer and protruding on both sides, fixed in reinforced concrete, and placed around the rebar for curing. There is a reinforced concrete protection technology in which a core and a reinforcing bar are connected to a DC power source. (For example, refer to Patent Document 3). Here, the electrodes are fixed in reinforced concrete. However, use of the anode electrode body as a spacer is not described.
[0010]
[Patent Document 1]
JP-A-6-158365 (page 2-3, FIGS. 4 to 6)
[Patent Document 2]
Japanese Utility Model Publication No. 5-56955 (page 1-2, Fig. 1)
[Patent Document 3]
US Pat. No. 5,609,748 (March 11, 1997) (column 1-4, FIG. 2)
[0011]
[Problems to be solved by the invention]
The present invention can be easily arranged, can maintain a uniform distance from the object to be protected, and can be used for a concrete structure using an anode electrode body in which the object to be protected and the electrode are not in direct contact. An object is to provide a manufacturing method.
[0012]
[Means for Solving the Problems]
The present invention is an electrode made of a thin metal plate, or an electrode formed by weaving a fine metal wire in a mesh shape into a strip shape, and covering a non-consumable electrode mainly composed of Ti with mortar or concrete, and having a length of about 1 m, An anode electrode body is manufactured in which a square bar having an electrode cross-sectional area of about 0.1 cm ² and a mortar thickness of about 2.5 cm is formed, and a connecting piece having an exposed end of the electrode is provided on the longitudinal end face of the square bar. The method of manufacturing a concrete structure is characterized in that a reinforcing bar is incorporated using the anode electrode body as a spacer, a side mold is built, and a concrete structure is manufactured.
[0013]
An electrode made of a known expanded metal may be used instead of the electrode made of the metal thin plate or the electrode formed by woven metal fine wires in a mesh shape into a band shape.
[0014]
Further, instead of using the anode electrode body as a spacer, the anode electrode body may be bound and fixed to a reinforcing bar.
[0015]
The anode electrode is assumed to connected ones having a length of about 1m to length, the electrode cross-sectional area 0.1 cm ² about, mortar thickness 2.5cm about. The spacer is suitable because the distance between the anode electrode and the reinforcing bar is constant.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an anode electrode body 1 according to an embodiment of the present invention. The strip electrode 2 is covered with a mortar 3 in a square bar shape. The strip electrode 2 may be formed by weaving fine metal wires in a mesh shape, may be formed of a thin metal plate, or may be an expanded metal. From the viewpoint of easy manufacture and easy handling, the length of the anode electrode body 1 is formed to about 1 m. The cross-sectional area of the strip electrode may be about 0.1 cm ² , for example. The thickness is about 2.5 cm. The end of the electrode is exposed from the end of the square bar to form the connection piece 4, and when the electrode body is disposed on the structure, the connection pieces 4 are connected to each other by means such as spot welding and used as the desired length do it. As the electrode metal, an electrode in which a titanium (Ti) fine wire having a higher natural potential and higher durability than the iron (Fe), which is an anticorrosive object, is formed in a mesh (grid) shape was used, but the material is limited to this. is not. The electrode metal that can be used may be any material that has a higher potential than iron, and nickel, tin, lead, copper, silver, gold, platinum, etc., and their alloy materials and plating materials should be selected in consideration of cost. That's fine.
[0017]
FIG. 2 is a cross-sectional view of the bridge girder 10 and is an arrangement view of anode electrode bodies when a new girder is manufactured. The anode electrode body 1 is disposed in the concrete near the bottom surface of the bridge girder 10. This is because when the bridge girder 10 is manufactured, the anode electrode body 1 covered with mortar is connected to a predetermined length on the bottom form of the bridge girder 10, and the girder is required by using the anode electrode body 1 as a spacer. A rebar 11 and a PC steel material 12 are incorporated, a side mold is built, and concrete 13 is cast and molded by a normal method. Instead of using the anode electrode body 1 as a spacer, the anode electrode body 1 may be fixed to the reinforcing bar 11 with a binding wire, and a separate spacer may be used.
[0018]
FIG. 3 shows a reference example in which the anode electrode body 1 is applied to repair a concrete girder 10 from which concrete has been peeled off due to corrosion of reinforcing bars. The concrete 13 of the spar 10 at the peeling part is removed, and the reinforcing bars 11 and the PC steel material 12 are derusted. If necessary, apply anti-corrosion coating, and insert the insert 15 into the sound concrete and attach the mold 14 to restore the normal concrete section with bolts 16, and fill the aggregate 17 and filling mortar for repair. This is an example. In this case, the anode electrode body 1 was embedded for corrosion prevention so that the corrosion of the reinforcing steel bars after repair did not recur.
[0019]
FIG. 4 is an explanatory view of an external anti-corrosion method using the anode electrode body 1 of the present invention. Lead wires 24 and 25 are pulled out from the anode electrode embedded in the concrete 13 and the structural reinforcing bar 11 of the concrete girder 10, respectively, and connected to a DC power source 21 installed outside. The lead wire 24 of the electrode of the anode electrode body 1 is connected to the plus (+) terminal 22 of the DC power source 21, and the lead wire 25 from the reinforcing bar 11 is connected to the minus (−) terminal 23 of the DC power source 21. By doing so, the anticorrosion current flows from the positive side of the DC power supply 21 to the anode electrode 1 and corrosion of the reinforcing bars 11 is prevented. If the DC power source 21 needs to have a large capacity, a commercial AC power source may be rectified and used.
[0020]
The above is an example applied to a concrete girder, but it is possible to prevent corrosion of reinforcing bars of other concrete structures as well as girder. Furthermore, the present invention is not limited to a concrete structure, and it is possible to prevent corrosion of the steel member itself by arranging an anode electrode on the steel member of the steel structure.
[0021]
【The invention's effect】
The anode electrode body of the present invention uses an external power source type anode electrode using titanium having a natural potential higher than that of a reinforcing bar, and is composed of a strip-shaped metal plate, or a strip-shaped electrode in which metal fine wires are woven in a mesh shape or an expanded metal. The electrode is covered with a mortar or concrete in the form of a square bar, and the end of the electrode is exposed from the longitudinal end face of the square bar to form a connecting piece. By covering with the mortar, the electrode itself directly contacts the reinforcing bar. Therefore, it is possible to ensure an accurate gap between the electrodes, to allow a uniform corrosion-proof current to flow, and to surely prevent corrosion of an object to be protected such as a reinforcing bar.
[Brief description of the drawings]
FIG. 1 is a perspective view of an anode electrode body according to an embodiment.
FIG. 2 is a cross-sectional view of a bridge girder.
FIG. 3 is an explanatory view of an example applied to repair of a concrete girder in which concrete is peeled off due to corrosion of reinforcing bars.
FIG. 4 is an explanatory diagram of an external power supply type anti-corrosion method using an anode electrode body.
[Explanation of symbols]
1 Anode electrode body 2 Electrode 3 Covering body (mortar or concrete)
4 Connection piece 10 Concrete girder (bridge girder)
11 Reinforcing bar 12 PC steel 13 Concrete 14 Form 15 Insert 16 Bolt 17 Aggregate 21 DC power source 22 (+) Electrode terminal 23 (-) Electrode terminals 24, 25 Lead wire

Claims (2)

An electrode made of a thin metal plate, or an electrode formed by weaving fine metal wires in a mesh shape into a band shape, and covering a non-consumable electrode mainly composed of Ti with mortar or concrete, and having a length of about 1 m and an electrode cross-sectional area of 0 An anode electrode body in which a square bar having a thickness of about 1 cm ² and a mortar thickness of about 2.5 cm is formed and a connecting piece having an exposed end of the electrode is provided on the longitudinal end surface of the square bar is manufactured. A method for producing a concrete structure, characterized by incorporating a reinforcing bar with a body as a spacer, building a side mold, and producing a concrete structure.   2. The method for producing a concrete structure according to claim 1, wherein an electrode made of expanded metal is used in place of the electrode made of the thin metal plate or the electrode formed by woven metal fine wires in a mesh shape into a band shape.

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