JPH1181502A - Anti-corrosion method of reinforcement in reinforced concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion of reinforcing bars with electric current flowing in sequence such as flame spray film - concrete - reinforcement - conductor - flame spray film by flame spraying metals to the surfaces of reinforced concretes to form the film, and electrically connecting this film and reinforcing bars with the conductor to generate electromotive force for battery operation. SOLUTION: Flame spray materials such as zinc, aluminum, titanium, etc., are scattered as melt particles on the surfaces of reinforced concretes 1 by a flame spray gun, and the melt particles are sprayed on the concretes 1 to form a flame spray film 2. The flame spray film 2 is electrically connected to reinforcing bars 3 with a conductor 4, and the concretes 1 are made as electrolyte to constitute a battery making the flame spray film 2 and reinforcing bars 3 as both poles. Then, a direct current flows along the suggested route of flame spray film 2 - concretes 1 - reinforcing bars - conductor - flame spray film with electromotive force generated by battery operation, and a resin coating layer 7 is formed in the surface of the flame spray film 2. Accordingly, the corrosion of the reinforcing bars in the reinforced concretes can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing corrosion of reinforcing steel in reinforced concrete, and more particularly, to a method for reducing the life of a reinforced concrete structure by applying a corrosion protection treatment to a reinforced concrete structure at a relatively simple and low cost. The present invention relates to a method for preventing the corrosion of reinforcing steel in reinforced concrete, which is of great interest to the field of construction of reinforced concrete structures, mainly civil engineering and construction, and to the users of the construction industry.

[0002]

2. Description of the Related Art Reinforced concrete structures constituting breakwaters, piers, bridge girders, buildings, and the like are susceptible to corrosion of reinforced concrete in reinforced concrete during long-term use, resulting in reduced strength as reinforced concrete. Function of a reinforced concrete structure due to a decrease in bonding strength between steel and concrete, and the need for long-term construction work and high costs to perform large-scale repair or renovation of the structure . Corrosion of rebars is caused by seawater, rainwater, etc., which enter the concrete through the concrete surface or concrete cracks during operation, and water contained in the concrete, which acts on the iron to cause electrochemical corrosion. Things. Therefore, various anticorrosion methods have conventionally been adopted. For example: (l) painting on reinforced concrete surfaces. This method aims at preventing the infiltration of moisture from the surface of reinforced concrete, but requires repainting due to deterioration of the coating film due to long-term use. In addition, it has no effect on moisture originally contained in concrete. (2) Electrochemical corrosion protection by attaching a metal plate such as zinc to the surface of reinforced concrete. In this method, a metal having a natural potential lower than that of iron, such as zinc, aluminum, titanium, or an alloy thereof, is attached to the surface of reinforced concrete, and the metal and the reinforcing steel are electrically connected to each other by a conductive wire. The use of a DC power supply or the use of affixed metal and rebar as both poles, with the electromotive force generated by the battery action using concrete as the electrolyte,
The current flowing along this route in the closed circuit returning to the adhered metal-concrete-rebar-conductor-applied metal electrochemically prevents corrosion of the rebar. As this method, various methods have been devised for fixing the concrete surface and the metal to be adhered uniformly over a large area while maintaining electrical connection, but the construction cost is relatively high. (3) Anticorrosion treatment on the reinforcing bar surface. . The surface of the rebar is coated in advance with an electrically insulating material such as vinyl or other synthetic resin, ceramic, etc., making it impossible for current to flow out or in from the surface of the rebar, causing electrochemical corrosion. Although there is a method to prevent the reinforced concrete from being caused, generally, a weak portion is interposed between the reinforcing bar and the concrete and impairs the soundness of the reinforced concrete. . A possible method is to coat the rebar surface in advance with a method such as plating with a zinc alloy, aluminum alloy, etc., and to rust-proof the rebar.However, as in general, the weak parts of the zinc alloy, aluminum alloy, etc. are mixed with concrete. In addition, if there is a non-plated portion or a damaged portion practically, electrochemical corrosion is intensively applied to these portions to shorten the life of the reinforcing bar. . The above and the above are costly.

[0003]

The present invention relates to the method of item (2) exemplified as the prior art,
Instead of sticking a metal plate or an alloy plate having a lower natural potential than iron to the concrete surface as shown in the item (2), a film of the metal is formed on the concrete surface. In the present invention, thermal spraying of a metal material to the surface of concrete is employed as a method of forming this coating, and while obtaining the same effect in terms of technology as affixing a metal plate, the simplicity of construction,
They try to gain an advantage in terms of cost. That is, the present invention is a method for preventing corrosion of reinforcing steel in reinforced concrete having the following configuration. (1) In a method for preventing corrosion of reinforcing steel in reinforced concrete, a metal whose natural potential is lower than iron is sprayed on the surface of reinforced concrete to form a film thereof, and this film and the reinforcing steel are electrically connected to each other by a conductive wire. The sprayed coating and the reinforcing steel are used as both poles, and the electromotive force generated by the battery action using concrete as an electrolyte causes the current flowing along the spray coating-concrete-rebar-conductive wire-sprayed coating to electrochemically corrode the reinforcing steel. A method for preventing corrosion of reinforcing steel in reinforced concrete, characterized by preventing corrosion. (2) In a method of preventing corrosion of reinforcing steel in reinforced concrete, a metal whose natural potential is lower than iron is sprayed on the surface of reinforced concrete to form a film thereof, and an external DC power supply is connected between the film and the reinforcing steel by a conductor. Corrosion of reinforcing steel in reinforced concrete characterized by electrically intervening and electrically connecting to prevent electrochemically corrosion of reinforcing steel by current flowing along the route of thermal spray coating-concrete-rebar-conductor-spray coating. How to prevent. (3) The reinforcing steel in the reinforced concrete according to the above (1) or (2), wherein the thickness of the thermal spray coating is 1 mm or less to prevent peeling of the thermal spray coating from the concrete surface as the thermal spray base material. How to prevent corrosion. (4) The bonding strength between the thermal spray coating and the concrete surface as the thermal spray substrate is improved by setting the lower limit of the surface roughness of the thermal spray substrate concrete to Rz (10 point average roughness) 20 μm. The method for preventing corrosion of reinforcing steel in reinforced concrete according to any one of (1) to (3). (5) The method for preventing corrosion of reinforcing steel in reinforced concrete according to any one of (1) to (4), wherein a resin coating layer is provided on the surface of the thermal spray coating. (6) The method for preventing corrosion of reinforcing steel in reinforced concrete according to any one of (1) to (4), wherein a transparent resin coating layer is provided on the surface of the thermal spray coating. (7) The method for preventing corrosion of reinforcing steel in reinforced concrete as described in (5) or (6), wherein the resin coating layer is water-resistant. (8) The method for preventing corrosion of reinforcing steel in reinforced concrete according to any one of the above (1) to (7), wherein a resin coating layer is provided on the surface of the joint between the thermal spray coating and the conductive wire. .

[0004]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sprayed coating 2 on a surface of a reinforced concrete 1 by spraying a metal material having a natural potential lower than that of iron.
FIG. 2 is a cross-sectional view showing a state in which the thermal sprayed coating 2 and the reinforcing bar 3 are electrically connected to each other by the conductive wire 4. (1) Principle of Corrosion Protection By using a reinforced concrete structure in the state shown in FIG. 1, a battery having a sprayed film 2 and a reinforcing bar 3 as both electrodes using concrete 1 as an electrolyte is formed, and a sprayed film 2-concrete 1 is formed by electromotive force. -DC current flows along the route of the reinforcing bar 3-the conductive wire 4-the thermal spray coating 2 (hereinafter, this current is referred to as anticorrosion current). Due to this anticorrosion current, the reinforcing bar is always reduced, but not oxidized, that is, does not corrode. This method is known as a galvanic anode protection method. The reference electrode 5 is buried in concrete in advance in order to use the reference electrode 5 as a potential reference when measuring the potential of the reinforcing bar as necessary. FIG. 2 shows a method of inserting a DC power supply 6 in the middle of the conducting wire 4 of FIG. 1 and supplying an anticorrosion current by the power supply 6, which is known as an “external power supply type” cathodic protection technique. Is almost the same as (2) Thermal spraying technology Thermal spraying technology is well known as a simple method of forming a film having functions such as wear resistance and heat resistance on the surface of a material.
In the present invention, as shown in FIG. 3, an electric arc, a gas flame, a plasma jet, or the like is used as a heat source in the thermal spray gun 10,
By this heat, a sprayed material such as a wire, a rod, powdered Zn, ZnAl alloy, or Al having a required function is melted and scattered as melted particles 11, and this is spread on the surface of the base material (concrete) 1. The sprayed coating 2 is formed by spraying and depositing. The bond between the thermal spray coating 2 and the surface of the substrate 1 is generally a mechanical bond, and the bonding strength between the thermal spray coating 2 and the surface of the substrate 1 due to the entanglement of the molten thermal spray particles 11 with minute irregularities on the surface of the substrate. Have gained. Therefore, in terms of the bonding strength, the roughness of the substrate surface is large but preferable.

(3) Material and Shape of Thermal Spraying Material As described in (1) "Principle of Corrosion Protection", in order to prevent corrosion of reinforcing steel in concrete, thermal spraying for forming thermal spray coating 2 is performed. The material may be any material as long as the natural potential is lower than that of iron. Therefore, in the present invention, the material of the thermal spraying material family may be zinc, aluminum, titanium or an alloy containing these as a main component. Further, the shape of the thermal spray material may be any of a wire, a rod, and a powder as long as it is appropriate for the thermal spray gun and the heat source to be used. (4) Thermal Spray Heat Source As described in (2) “Thermal Spraying Technique”, the heat source for melting the thermal spray material includes an electric arc, a gas flame, and the like.
There is a plasma jet or the like, but in the present invention, any one may be used as long as it is appropriate for the thermal spray material to be used. (5) Thickness of thermal spray coating The thickness of the thermal spray coating is not particularly limited in thermal spraying. However, since the bond between the thermal spray coating 2 and the surface of the substrate 1 is a mechanical bond, if the thermal spray coating 2 is too thick, the thermal spray coating is deformed due to residual stress, and the thermal spray coating 2 and the substrate 1 are bonded. 1 may peel off. Therefore, in practice, it is desirable that the thickness of the thermal spray coating be 1 mm at the maximum. (6) Surface Roughness of Concrete As described in (2) “Thermal Spraying Technique”, in order to improve the bonding strength between the thermal spray coating 2 and the substrate 1, that is, the concrete surface, the surface roughness of the concrete 1 is required. The higher the degree, the better. The lower limit required for the surface roughness of concrete is Rz (10 point average roughness: according to JIS B0601) 20 μm.

[0006]

EXAMPLES Examples and comparative examples of the present invention will be described below. . Test specimen (a) Concrete substrate The test concrete substrate is 300 mm x 300 mm x 6
A test piece of 0 mm was prepared, and the test contents and thermal spraying method of the specimen were as shown in Table 1. The series was A to C series and D series. A 19mm diameter round steel bar (SGD400) is placed as a reinforcing bar 3 in a concrete substrate like this,
The lead reference electrode 5 for monitoring the corrosion state of the reinforcing bar 3 and the anticorrosion effect was embedded. The preparation of the concrete used is as shown in Table 2. In the D series, 0.3% NaCl was mixed in with a concrete mass ratio of 0.3% in order to provide an easily corrosive environment. That is, 100
× NaCl / (C + W + S + G + NaCl) = Fresh concrete mixed with 0.3 amount of NaCl was poured into molds of various materials. After placing the fresh concrete, after curing for one week in a curing room at room temperature 20 ° C ± 2 ° C and relative humidity 60 ± 10%, the mold was removed from the mold and about 40 days.
Cured in the above curing room.

[0007]

[Table 1]

[0008]

[Table 2]

(B) Thermal spraying Thermal spraying on the concrete substrate 1 cast and cured as described above was performed by two types of arc spraying and flame spraying, and pure zinc (Zn) wire was used as the sprayed metal. In addition, the thing which used the zinc aluminum alloy (Zn + 5% Al) by arc spraying was also tested. The distance between the surface of the concrete substrate (base material) 1 and the tip of the thermal spraying device (thermal spray gun 10) was set to about 25 cm (FIG. 3).

[0010] Measurement method (a) Measurement of concrete surface roughness Using a stylus-type measuring device, measurement was performed at a cutoff value of 2.5 mm and an evaluation length of 12.5 mm, and Rz (10-point average roughness JIS)
B0601). (B) Thickness Measurement of Thermal Sprayed Film The thickness was measured with an Erichsen film thickness meter. (C) Adhesion strength test of thermal sprayed coating Determined by a Kenken-type tensile tester. Position P shown in FIG.
At 1 and P2, the adhesive strength between the sprayed surface 2 and the substrate 1 was measured. (D) Measurement of concrete surface moisture content The moisture content was measured using an electric resistance mortar moisture meter.
The test was performed in three settings: a saturated state, standing in the open air for three days from the saturated state, and a dry state. (E) Heat-cooling repetition test For the measurement of strain, a strain gauge was attached to a predetermined position of the specimen shown in FIG. That is, waterproof strain gauges MG1, MG2 are provided at predetermined positions MP1, MP2 of the metal spray coating.
The test was performed by disposing waterproof strain gauges CG1 and CG2 at predetermined positions CP1 and CP2 of the base material 1, respectively. Heat-cooling repetition (0 to 90 ° C.) was performed, and an adhesive strength test was performed after 100 cycles. (F) Cathodic protection test All thermal spray coatings were applied with a target thickness of 500 μm. Specimens of salt water spraying were installed in a corrosion test tank where salt water sprinkling 5 hours and drying 19 hours were repeated as a single cycle. The rebar potential using the electrodes was measured. Further, at the point of time when 122 days of energization had passed, the circuit was opened and the amount of reversion of the rebar potential was measured.

[0011] Measurement Results (a) Concrete Surface Roughness and Adhesiveness of Thermal Sprayed Film FIG. 7 shows the relationship between concrete surface roughness and adhesive strength of the thermal sprayed film in Formulations I and II shown in Table 2. As can be understood from the figure, the adhesive strength increased as Rz increased up to Rz of 50 to 100 μm, and became almost constant as Rz increased. Formulation II has a higher overall adhesive strength than Formulation I, depending on the strength of the underlying concrete. (B) Concrete Surface Water Content and Adhesion of Thermal Sprayed Coating FIG. 8 shows the relationship between concrete surface water content and adhesive strength of the sprayed coating. There was no correlation between moisture content and adhesive strength. (C) Thermal spray coating thickness and adhesiveness FIG. 9 shows the relationship between the thermal spray coating thickness and the adhesive strength. The adhesive strength decreased as the film thickness increased. Despite the effect of the film thickness, the overall adhesion strength of the flame spraying was high. (D) Heat-cooling repetition test FIG. 10 shows the results of strain measurement in the heat-cooling repetition test.
It can be seen that the strain behavior of the concrete and the thermal spray coating is consistent and follows. The adhesive strength after the test was also 1.76, 2.
The value was as high as 63 MPa. (E) Cathodic protection FIG. 11 shows the change over time in the current density. FIG. 12 shows the amount of reversion of the rebar potential when the circuit is opened and the amount of current immediately before the circuit is opened. The shift amount of the rebar potential due to the galvanic anodic action in all the specimens satisfied the 100 mV shift anticorrosion standard. (F) Conclusion The following was confirmed from the above. . As the surface roughness Rz increases, the adhesive strength increases,
When Rz is 50 to 100 μm or more, it becomes a constant value depending on the background strength. . The underlayer moisture content does not affect the adhesion of the thermal spray coating. . As the film thickness increases, the adhesive strength decreases. . It shows good adhesion even after a heat-cooling cycle. . Both the sprayed coatings for the salt water spraying and the inland outdoor environment satisfied the 100 mV shift corrosion protection standard.

In the above description, the thermal spray coating formed on the surface of the concrete substrate is exposed as it is, but this thermal spray coating is often left in a harsh natural environment such as a coast or a place of acid rain precipitation. In such a case, the thermal spray coating itself is corroded and no longer functions as an electrode. Therefore, in the improved present invention, a resin coating layer is further formed on the surface of the thermal spray coating to prevent corrosion of the thermal spray coating and increase durability. Also, particularly at the joint between the thermal spray coating and the conductor, the corrosion resistance is poor, and there is a danger that both will peel off. FIGS. 13 and 14 show a specific configuration for solving the above problems. That is, the resin coating layer 7 is formed on the surface of the thermal spray coating 2 by spray painting or brush painting. The resin coating layer is water resistant,
Those having excellent chemical resistance, weather resistance and the like are preferable, and acrylic resin, epoxy resin, fluororesin, silicon resin, etc. are used. 2 is preferable because it can be seen through and the aesthetics can be secured for a long period of time.

[0013]

According to the present invention, the formation of a coating on a concrete surface by thermal spraying can be performed even on a reinforced concrete structure having a large surface area such as a breakwater, a pier, a bridge girder, or a building having a complicated shape. Construction can be performed simply and inexpensively, and more excellent effects can be obtained than by pasting a metal plate or the like of the prior art. Thus, the corrosion prevention of the reinforcing steel in the reinforced concrete can be realized in terms of technology and economy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing a state in which a metal sprayed film is formed on a surface of a reinforced concrete according to one embodiment of the present invention, and the sprayed film and a reinforcing bar are electrically connected by a conductive wire.

FIG. 2 is an explanatory cross-sectional view in which a DC power supply is interposed between the conductors of FIG. 1;

FIG. 3 is an explanatory view of a method for forming a thermal spray coating on a substrate surface using a thermal spray gun.

FIG. 4 is a plan view and a side view of a state in which a reinforcing bar is arranged in a concrete substrate and a lead reference electrode for monitoring a corrosion state and an anticorrosion effect of the reinforcing bar is buried.

FIG. 5 is an explanatory diagram showing a state in which a strain gauge is attached to the surface of a test specimen for a repeated hot-cooling test.

FIG. 6 is an electric circuit diagram for measuring a rebar potential in a concrete substrate.

FIG. 7 is a diagram showing the relationship between concrete surface roughness and the adhesive strength of a thermal spray coating.

FIG. 8 is a diagram showing the relationship between the water content of the concrete surface and the adhesive strength of the thermal spray coating.

FIG. 9 is a diagram showing the relationship between the thickness of a sprayed coating and the adhesive strength.

FIG. 10 is a view showing a strain amount measurement result in a thermal cooling repetition test.

FIG. 11 is a graph showing the change in current density over time showing the results of the cathodic protection test.

FIG. 12 is an explanatory diagram showing the amount of reversion of the rebar potential when the circuit is opened and the amount of current immediately before the circuit is opened.

FIG. 13 is a cross-sectional explanatory view of a state in which a metal material is sprayed on the surface of a reinforced concrete to form a sprayed coating, the sprayed coating is electrically connected to a reinforcing bar by a conductive wire, and a resin concrete layer is provided on the sprayed coating. .

FIG. 14 shows a DC power supply interposed between the conductors of FIG.
FIG. 4 is an explanatory cross-sectional view of a state in which a resin concrete layer is provided on the thermal spray coating.

[Explanation of symbols]

 1: Concrete (base material, reinforced concrete), 2: Thermal spray coating, 3: Reinforcement, 4: Conductor wire, 5: Reference electrode, 6: DC power supply, 7: Resin coating layer, 10: Thermal spray gun, 11: Melt particles

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuo Kondo 7-18-8 Doimachi, Amagasaki-shi, Hyogo Incorporated Foundation Kinki High Energy Processing Technology Research Laboratory (72) Inventor Yutaka Yoshida 4 Higashi-Namba-cho, Amagasaki-shi, Hyogo No. 18-6, Yoshida Steel Works (72) Inventor Yukio Arashi 1-10-20 Higashi Tenma, Kita-ku, Osaka City Matsumura Guminai Co., Ltd. (72) Inventor Hideo Urano, Higashi Tenma, Kita-ku, Osaka City No. 1-10-20 Matsumura Gumi Co., Ltd. (72) Inventor Takao Kashiwagi 1-10-20 Higashi Tenma, Kita-ku, Osaka City No. 1 Matsumoto Guminai Co., Ltd. 7-1-8, Kinkicho Kinki High Energy Processing Technology Research Institute (72) Inventor Jun Takaishi 7-1-8, Doimachi, Amagasaki City, Hyogo Prefecture Kinki High Energy Processing Technology Research Institute (72) Inventor Koichi Minami 7-1-8 Doimachi, Amagasaki City, Hyogo Prefecture Inside Kinki High Energy Processing Technology Research Institute (72) Inventor Akira Omori 12-5-516 Enomachi, Suita City (72) Inventor Toru Kurumi Osaka City No. 1-2-10, Doshin, Kita-ku (72) Nobuaki Miyao 20-19, Narita-Higashi-cho, Neyagawa-shi, Osaka

Claims (8)

[Claims] In a method for preventing corrosion of reinforcing steel in reinforced concrete, a metal having a natural potential lower than that of iron is sprayed on a surface of the reinforced concrete to form a film thereof, and the film and the reinforcing steel are electrically connected by a conductive wire. The sprayed coating and the reinforcing bar are used as both poles, and the electromotive force generated by the battery action using concrete as the electrolyte causes the current flowing along the route of the sprayed coating, the concrete, the reinforcing bar, the conductor, and the sprayed coating to electrochemically form the reinforcing bar. A method for preventing corrosion of reinforcing steel in reinforced concrete, characterized by preventing corrosion. 2. A method for preventing corrosion of reinforcing steel in reinforced concrete, wherein a metal having a natural potential lower than that of iron is sprayed on the surface of the reinforced concrete to form a film, and the film and the reinforcing steel are connected to each other by an external direct current through a conductive wire. Electrically connected with a power supply interposed, thermal spray coating-concrete-reinforcing steel-conductor-
A method for preventing corrosion of reinforcing steel in reinforced concrete, wherein the corrosion of reinforcing steel is electrochemically prevented by an electric current flowing along the path of the thermal spray coating. 3. The corrosion of reinforcing steel in reinforced concrete according to claim 1 or 2, wherein the thickness of the thermal spray coating is 1 mm or less to prevent peeling of the thermal spray coating from the concrete surface which is the thermal spray base material. How to prevent. 4. The bonding strength between the thermal spray coating and the concrete surface as the thermal spray base material is improved by setting the lower limit of the surface roughness of the thermal spray substrate concrete to Rz (10 point average roughness) 20 μm. The method for preventing corrosion of reinforcing steel in reinforced concrete according to any one of claims 1 to 3. 5. The method for preventing corrosion of reinforcing steel in reinforced concrete according to claim 1, wherein a resin coating layer is provided on the surface of the thermal spray coating. 6. The method for preventing corrosion of reinforcing steel in reinforced concrete according to claim 1, wherein a transparent resin coating layer is provided on the surface of the thermal spray coating. 7. The method for preventing corrosion of reinforcing steel in reinforced concrete according to claim 5, wherein the resin coating layer is water-resistant. 8. The method for preventing corrosion of reinforcing steel in reinforced concrete according to claim 1, wherein a resin coating layer is provided on the surface of the joint between the thermal spray coating and the conductive wire.