JPH06235080A - Corrosion preventive method for concrete structure by thermally sprayed metallic film - Google Patents

Abstract

PURPOSE:To optimize the supply of protective current and to improve a corrosion preventive effect and corrosion preventive life by changing the film thicknesses of thermally sprayed metallic films according to the surface area and corrosion condition of reinforcing bars and electrically insulating the these films in each of the respective film thickness blocks with an external power source system. CONSTITUTION:The film thicknesses of the thermally sprayed metallic films formed on the surfaces of the concrete structure are changed according to the various values of the surface area of the reinforcing bars or the corrosion condition in the respective parts of the structure. The thermally sprayed metallic films are electrically insulated in each of the blocks varying in the film thicknesses and the required DC current is passed in each of these blocks. As a result, the protective current is passed at the large current density in the parts of the reinforcing bars where the surface area is large or the corrosion is intensive and at the small current density in the parts of the reinforcing bar where the area is small or the corrosion is slight. Then, the adequate corrosion preventive effect is exhibited according to the various values of the surface areas and corrosion condition of the reinforcing bars and since the consumption of the thermally sprayed films increases in proportion to the energizing current, the life over the entire part of the thermally sprayed films is averaged and the corrosion preventive life, etc., are prolonged.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pier, a road bridge, a pier,
The present invention relates to a method of performing galvanic protection of a reinforced concrete structure such as a building structure with a metal spray coating.

[0002]

2. Description of the Related Art In recent years, there has been a problem that the reinforcing bars in a reinforced concrete structure are corroded by the intrusion of salt contained in fine aggregates or sea salt particles. As an anticorrosion measure, the electrocorrosion method has been attracting attention.A galvanic anode method in which a surface of a concrete structure is sprayed with a metal spray coating having a potential lower than that of reinforcing bars, or a metal spray coating is used as the positive electrode of a DC power supply device. An external power supply method is known, in which the connection is made and the rebar is connected to the negative electrode of the DC power supply device to allow a direct current to flow into the rebar.However, in the conventional external power supply system, the front surface of the metal sprayed coating is a single circuit of the DC power supply device. Was connected to.

[0003]

Therefore, in the external power supply system, the current supplied to any portion of the metal spray coating is constant. As a result, the corrosion prevention current is insufficient and the corrosion prevention effect is not sufficient at the part where the surface area of the reinforcing bar in the concrete structure is large or the corrosion is severe. Increasing the value increases the elution rate of the entire metal spray coating and shortens the corrosion protection life.

The present invention solves the above problems and supplies an anti-corrosion current to the metal spray coating on the surface of the concrete structure depending on the surface area of the reinforcing bars in the concrete structure and the corrosion rate. The present invention is intended to provide a method for preventing corrosion of a concrete structure that has both sufficient corrosion resistance and sufficient corrosion protection life.

[0005]

According to the present invention, the film thickness of a metal sprayed coating formed on the surface of a concrete structure is changed according to the size of the surface area of the reinforcing bars in each part of the concrete structure and / or the corrosion condition. Is electrically insulated from the metal sprayed coating in each of the different sections, and a required direct current is passed through each of the sections.

[0006]

The present invention increases the film thickness of the metal sprayed coating on a portion of the concrete structure having a large surface area of the reinforcing bars or a portion that is severely corroded, and it is applied to a portion of the concrete structure having a small surface area of the reinforcing bars or a portion having a slight corrosion. The thickness of the film is reduced to electrically insulate the sections having different thicknesses, and the DC power supply device is provided with a circuit according to the film thickness, or the DC power supply apparatus is provided according to the film thickness. By electrically connecting a DC power supply device or a DC power supply circuit to a part of the rebar with a large surface area or a part with severe corrosion, an anticorrosion current is applied with a large current density, and a part of the rebar with a small surface area or a small amount of corrosion Since the anticorrosion current can be applied to a large area with a small current density, it is possible to obtain an appropriate anticorrosion effect according to the size of the surface area of the reinforcing bar in the concrete structure and the corrosion condition. Since consumption is increasing in proportion to the applied current, the life of the entire thermal spray coating is averaged, it becomes possible to extend the corrosion life.

For example, regarding a bridge, for a beam having a large surface area of reinforcing bars and severe corrosion due to salt damage, the film thickness of the metal spray coating is made thicker than that of the other part, and the beam part and other parts are Is connected to the DC power supply via separate circuits, and the metal sprayed coating on the beam is supplied with an anticorrosion current with a larger current density than the other parts, so that the surface of the concrete structure and the corrosion condition can be adjusted. The proper anticorrosion effect can be enhanced, and the life of the entire metal spray coating can be averaged.

[0008]

Example: Water: cement: sand: gravel ratio of 0.5: 1:
2: 4, using concrete mixed with chloride at a ratio of 5 kg / m ² , a concrete block of 1 m × 2 m × 10 cm was manufactured, and a reinforcing bar having a diameter of 19 mm was placed in a section of 1 m × 1 m on each side. It is buried by the amount that the surface area of the reinforcing bar occupies the same area as the concrete surface area (hereinafter referred to as section A), and the other 1 m x 1 m section has a reinforcing bar with a diameter of 19 mm, and the surface area of the reinforcing bar is twice the surface area of the concrete. Was buried (hereinafter referred to as Section B). After curing this concrete block for 2 months, a zinc sprayed coating was uniformly sprayed to a thickness of 100 μm on the A partition surface of the A partition except the 10 cm width of the B partition side, and the entire surface of the B partition and the A partition The surface of 10 cm width on the B section side is uniformly sprayed with a zinc sprayed coating to a thickness of 200 μm to prevent premature wear of the zinc sprayed coating near the end of the B section on the A section side and average the life of the entire sprayed coating. It was Then, in each of the A and B sections of this concrete block, as shown in FIG.
Electrodes for potential measurement were embedded in the holes provided at three places, and the spontaneous potential was measured.

Next, the zinc sprayed coating and the positive electrode of the DC power supply device are connected by an electric wire, and the reinforcing bar and the negative electrode of the DC power supply device are connected by an electric wire. A current of / m ² was applied, and one week later, the potential of the rebar immediately after the termination of energization and the potential of the rebar 4 hours after the termination of energization were measured using the potential measuring electrodes. As a result, as shown in Table 1, it was found that in the A section, the potential measuring electrodes at three locations showed a polarization amount of 100 mV or more, indicating that the reinforcing bars were well protected, but in the B section, three locations. 100m for all electrodes
A value below V is shown, indicating that the corrosion protection for the reinforcing bars was not sufficient.

[0010]

[Table 1]

On the other hand, the zinc spray coating is electrically insulated at the boundary between the A and B compartments, and the zinc spray coatings in the A and B compartments are connected to the positive electrodes of the separate circuits of the DC power supply device by electric wires to reinforce and rebar. Connect the negative electrode of the power supply device with an electric wire and apply a current of 5 mA / m ² to the rebar from the zinc sprayed coating in the A section and a current of 10 mA / m ² to the rebar from the zinc sprayed coating in the B section. Then, one week later, the potential of the rebar immediately after the stop of energization and the potential of the rebar 4 hours after the stop of energization were measured by the potential measuring electrodes. As shown in Table 2, the results show that the potential measurement electrodes in both A and B sections showed a polarization amount of 100 mV or more,
It can be seen that a good anticorrosion effect was obtained on average.

[0012]

[Table 2]

[0013]

EFFECT OF THE INVENTION The present invention adopts the above-mentioned constitution and forms a metal spray coating thicker than other portions on the surface of a concrete structure requiring a large anticorrosion effect, so that the anticorrosion current can be increased at a large current density. By flowing, the desired anticorrosion effect can be secured, and as a result, the life of the entire metal spray coating can be averaged, so that a metal spray coating of the same thickness can be formed and the current density of the same magnitude can be formed. Compared with the conventional method of applying the anticorrosion current, the economic effect is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing an embedding position of a potential measuring electrode of a concrete block used in an example.

Claims (1)

[Claims] 1. The metal sprayed coating formed on the surface of the concrete structure is changed in accordance with the surface area of the reinforcing bars in each part of the concrete structure and / or the corrosion condition, and the metal sprayed coating is divided into sections having different film thicknesses. Is electrically insulated, and a required direct current is applied to each of the compartments.