JPH0826466B2 - Electrocorrosion method for rebar - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

TECHNICAL FIELD The present invention relates to a method for preventing corrosion of reinforcing bars of a reinforced concrete structure, and more particularly to a galvanic anode type cathodic protection method.

[Prior art]

The corrosion reaction of a metal in a water-existing environment is an electrochemical reaction in which an oxidation reaction (anode reaction) in which a metal releases an electron and a reduction reaction (cathode reaction) in which an electron is received simultaneously proceed. Therefore, it is possible to prevent corrosion by changing the metal potential, and the methods of galvanic protection are roughly classified into a galvanic anode method that utilizes the natural potential difference of metals and an external power source method that supplies power from the outside. The conventional method of galvanic protection for reinforcing bars in concrete is to install an electrode on the concrete surface that serves as an anode, and use the reinforcing bar as a cathode to force it from the outside via concrete through the concrete. An external power supply system that supplies a current to the general was common.

[Problems to be Solved by the Invention]

However, the external power supply method has the following problems. (1) It is necessary to install electrodes on a concrete surface in a wide range, and the installation requires a great deal of time and labor. (2) Compared with normal cathodic protection against metal, the electrical resistance of concrete is large, so a large power supply device is required. (3) The electrical resistance of concrete changes depending on the environment in which the concrete structure is installed, but the amount of electricity supplied must be adjusted accordingly, which complicates the equipment and includes equipment costs and running costs. The cost will be enormous. On the other hand, in the case of the conventional galvanic anode method in which the sacrificial anode is placed away from the reinforcing bar serving as the cathode, the electrical resistance of the concrete is high. There was a construction problem. It is an object of the present invention to provide a method of cathodic protection for reinforcing bars, which has no such problems despite the galvanic anode method and can eliminate the above-mentioned drawbacks of the external power source method.

[Means for Solving the Problems]

In the present invention, the self-potential train than the surface of the reinforcing bar is directly coated with a base metal to form auxiliary metal bars such as distribution bars that form the anode metal layer, and the main bars to be protected are brought into contact with the main bars. The main reinforcement is protected against corrosion by using the cathode and auxiliary reinforcement as sacrificial anodes.

[Action]

Auxiliary reinforcing bars such as distribution bars having an anodic metal layer formed by metal coating are arranged in the vicinity of the main reinforcing bars which are sacrificial anodes and require corrosion protection, and these reinforcing bars directly constitute the cathodic protection network. Therefore, despite the galvanic anode method, the anticorrosion effect is good, and the electrolytic corrosion can be economically achieved without requiring any special work other than the conventional reinforced concrete construction. Also, the metal coated auxiliary rebar can be protected by the coating layer.

【Example】

An embodiment of the present invention will be described below. Reinforcing bars of reinforced concrete products are generally composed of main reinforcing bars whose required sectional force is determined from the design sectional strength and tensile strength of the reinforcing bars, and distribution bars, stirrup bars, and strip reinforcing bars that evenly distribute the stress acting on the main reinforcing bars. Etc. are divided into auxiliary reinforcing bars. Also,
There is also an assembly bar to secure the position of the reinforcing bar. Therefore, when the main rebar is the rebar for corrosion protection, the surface of the rebar 1 which is the distribution rebar as shown in FIG. The anode metal layer 2 is formed by coating. The thickness of the anode metal layer 2 is appropriately set according to the thickness of the reinforcing bar 1 and the installation environment. Figure 1 shows an example of bar arrangement, and metal-coated rebar 1
The main metal bars 3 are laid in a grid pattern using the
Is brought into contact with the surface of the main rebar 3, and the intersections are bound as shown in FIG. 2, for example. In this case, a galvano battery in which the distribution bar 1 serves as an anode and the main reinforcement 3 serves as a cathode is formed through the intersection of the distribution bar 1 and the main rebar 3, and the main rebar 3 is protected by galvanic anode method. . Further, the distribution bar 1 becomes, so to speak, a sacrificial rebar, but since it is itself covered with the anode metal layer 2, it is protected from corrosion. 4 (A) and (B) show an example applied to the column portion 4 of the reinforced concrete structure. When the strip reinforcing bars 6 are arranged around the main reinforcing bars 5 in contact with them, an anode metal layer as shown in FIG. 2 is formed on the strip reinforcing bars 6, and the main reinforcing bars 5 are protected against corrosion by using this as a sacrificial anode. To do. FIG. 5 is an example applied to the slab portion 7 and the beam portion 8 of the reinforced concrete structure. For the slab portion 7, the anode metal layer is formed on the distribution bar 9 to protect the main rebar 10, and for the beam portion 8 Main reinforcing bar 12 by forming anode metal layer on stirrup bar 11
To prevent corrosion. Particularly in the case of beams and slabs, the lower side is difficult to dry, and water and salt due to seawater splash are also concentrated here (see FIG. 6).
Further, as shown in FIG. 7, since the quality of the concrete on the lower side of the reinforcing bar 13 is inferior to that of other portions due to the breathing water 15 due to the water separation in the concrete 14, this portion is particularly apt to rust. Therefore, by disposing the sacrificial rebar as described above in such a place, effective corrosion prevention is possible.

【The invention's effect】

The present invention has the following effects. By simply assembling the main rebar and auxiliary rebars such as distribution bars as usual, a galvanic anode type cathodic protection circuit is formed, so the construction cost and construction period can be greatly reduced compared to the conventional one. No running cost is required. Corrosion can be effectively prevented against main rebars such as beams and slabs that are easily affected by moisture and salt. In addition to being able to prevent the main rebar from being corroded by auxiliary rebars such as distribution bars, the auxiliary rebar can also be protected by the anode metal layer coated directly on the surface.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of bar arrangement according to the present invention, FIG. 2 is an enlarged plan view of a part thereof, FIG. 3 is an enlarged sectional view of a reinforcing bar on which an anode metal layer is formed, and FIG. 4 (A), ( B) is a longitudinal sectional view and a transverse sectional view of an example applied to a column portion of a reinforced concrete structure, FIG. 5 is a sectional view of an example applied to a slab portion and a beam portion, and FIGS. 6 and 7 are beams and slabs. FIG. 6 is an explanatory view for explaining that the reinforcing bars of FIG. 1 ... Reinforcing bar, 2 ... Anode metal layer, 3, 5, 10 ... Main reinforcing bar, 6
...... Reinforcing bar, 9 ...... Strengthening bar, 11 ...... Stirrup bar.

Claims (1)

[Claims] 1. A main rebar, wherein auxiliary rebar such as distribution bar having an anode metal layer formed by directly coating the surface of the rebar with a base metal having a self-potential series is brought into contact with the main rebar to be protected by corrosion. A cathodic protection method for reinforcing bars, characterized in that the main reinforcing bars are protected by using as a cathode and auxiliary reinforcing bars as sacrificial anodes.