JP5443888B2 - Cathodic protection method for concrete structures by galvanic anode method - Google Patents

Description

  The present invention mainly relates to a galvanic anode type cathodic protection method used in civil engineering / architectural concrete structures. In this technique, the amount of the anticorrosive current is suppressed to a certain value or less, and the early blistering or peeling of the metal sprayed film is eliminated or reduced.

  In recent years, there has been a demand for an electrochemical corrosion protection method for the purpose of preventing corrosion of reinforcing bars, PC steel, and steel frames in concrete as a measure to prolong the life and durability of concrete structures.

  Conventionally, as one of the electrochemical corrosion prevention methods, a metal having a lower potential than the steel material inside the concrete is sprayed onto the concrete surface, and the corrosion current is supplied from the sprayed metal to the steel material inside the concrete using the difference in ionization tendency. In addition, there is a galvanic anode method that prevents rusting of the steel material inside the concrete or significantly reduces the corrosion rate.

  The galvanic anode method for concrete structures uses a difference in the ionization tendency of iron, such as zinc, aluminum, magnesium, indinium, and their alloys and pseudo-alloys, installed on the concrete surface to prevent corrosion of steel inside the concrete. Supply current. Therefore, the amount of anticorrosion current cannot be controlled depending on the environment of the concrete structure, the moisture content of the concrete, and the properties such as fogging.

  In order to improve this problem, a method has been proposed in which a DC converter boosts or reduces pressure to obtain an output voltage of an arbitrary value, secures an effective potential difference, and increases the anticorrosion current in the galvanic anode method (Patent Literature). 1).

  However, this method is a method for increasing the galvanic anode-type anticorrosion current, and no measures are taken to suppress the galvanic anode-type anticorrosion current. There is a problem that problems such as swelling and peeling occur.

  In addition, as a measure to suppress swelling and peeling of the sprayed anode type sprayed metal film, a primer layer having a rough surface is formed by applying a primer containing aggregate in advance to the concrete surface to which the metal sprayed film is sprayed. A method for improving the adhesion strength of a metal sprayed film has been proposed (see Patent Document 2).

  However, with this method, although the adhesion strength is improved, the anticorrosion current flowing from the metal sprayed film to the inside of the concrete cannot be controlled, and in the environment where the flow is easy and the chloride surface contains chloride ions, There was a problem that the metal sprayed film was swollen or peeled off early after the construction due to the volume expansion caused by the generated or ionized metal hydroxide.

  On the other hand, by applying a mortar containing lithium nitrite that suppresses electrical resistance, which is called conductive polymer cement mortar, measures have been proposed to suppress the reduction or inactivation of the anode over the long term (patent) Reference 3).

  However, this conductive polymer cement mortar covers the periphery of the anode after the anode is installed (see paragraph [0003]), and is not applied in advance to the concrete surface to which the metal sprayed film as the anode is sprayed. When this is applied in advance as described above, the anticorrosion current flowing from the metal sprayed film to the inside of the concrete becomes larger than necessary, and conversely due to the generation of gas in the metal sprayed film part and the volume expansion due to the ionized metal oxide. There is a problem that the metal sprayed film swells or peels off at an early stage after construction.

  Further, Patent Document 3 states that “In the anticorrosion method, an anode is provided on the concrete surface of a concrete structure and the anode is installed and protected, so that a protective material having excellent adhesion to concrete is required. Polymer cement mortar is used as a protective material with good adhesion to concrete, but it has a drawback that it is lower in conductivity than ordinary cement mortar, and there is a problem in using it in an anticorrosion method. It is not intended to use polymer cement mortar in order to suppress the anticorrosion current flowing from the metal sprayed film as the anode into the concrete.

  Furthermore, a mortar containing carbon fiber has also been proposed as a conductive polymer cement mortar used in the cathodic protection method (see Patent Document 4).

  However, the conductive polymer cement mortar containing the carbon fiber is used as a counter electrode (anode) excellent in workability and durability in the anticorrosion method (see paragraphs [0001] and [0002]), It has not been suggested to use it to control the anticorrosion current flowing from the metal sprayed film, which is the anode, into the concrete.

  In addition, a method has been proposed in which a surface treatment material containing a lithium salt is applied to the concrete surface to improve the electrical conductivity of the concrete and supply a corrosion-proof current uniformly and efficiently (see Patent Document 5).

  However, even in this method of applying a surface treatment material containing lithium salt to the concrete surface, the anticorrosion current flowing from the metal sprayed film to the inside of the concrete becomes larger than necessary, and conversely the generation of gas and ionization of the metal sprayed film part. Due to the volume expansion due to the metal hydroxide, there is a problem that problems such as swelling and peeling of the metal sprayed film occur early after the construction.

JP-A-9-31673 JP-A-5-331922 JP 2005-281037 A Japanese Patent Laid-Open No. 7-206502 JP 2006-232559 A

  The present invention is intended to solve the above-described problems, and in galvanic anode type cathodic protection for concrete structures, the metal sprayed film installed on the concrete surface is prevented from bulging or peeling, or greatly reduced. Thus, it is an object of the present invention to suppress the deterioration rate of the metal sprayed film, maintain the corrosion protection of the concrete structure, and extend the life of the structure.

The present invention employs the following means in order to solve the above problems.
(1) to the concrete surface Te cathodic protection method odor galvanic anode method of supplying a protection current concrete inside the steel by by spraying a metal having a large ionization tendency than iron to form a metal spray coating, prior Symbol metal spraying film is one formed by thermally spraying a zinc-aluminum pseudo alloy, means to install a cement mortar between the sprayed metal layer and the concrete surface, the aluminum thin film during the previous SL metal sprayed coating and the concrete surface taking steps to install electrical resistance material means installing, or between the metal sprayed film and the concrete inside the steel material Hairyutan terminal of the circuit portion for electrically connecting, said sprayed metal layer and the concrete inside the steel protective current density flowing between the a cathodic protection method in Turkey Nkurito structure to suppress the 80 mA / m ² or less per concrete area.
(2) The anticorrosion method according to (1), wherein the cement mortar is at least one selected from a polymer cement mortar, a fiber-containing cement mortar, and a polymer and fiber-free cement mortar.

  According to the present invention, the amount of anticorrosion current flowing into the concrete from the metal sprayed film that becomes the anode placed on the concrete surface is suppressed, the amount of gas generated on the anode surface and the amount of oxide generated in the anode material are suppressed, By suppressing the swelling / peeling of the sprayed film, it is possible to prevent corrosion of the concrete structure over a long period of time.

It is the schematic which shows the example of the cathodic protection method which provided the means to install cement mortar between a metal sprayed film and the concrete surface. It is a schematic diagram showing an example of a cathodic protection method in which taking steps to place a thin film of A Ruminiu arm between the metal sprayed coating and the concrete surface. Is a schematic diagram showing an example of a cathodic protection method in which taking steps for installing electrical resistance material Hairyutan terminal of the circuit portion which electrically connects the metal sprayed film and inside the concrete steel.

(Explanation of symbols)
1: Cement mortar 2: Rough surface forming agent 3: Aluminum single metal thin film 4: Zinc / aluminum pseudo alloy metal sprayed film 5: Sealing agent 6: Deformed bar 7: Concrete 8: IV wire 9: Drain terminal 10: Non-resistance ammeter 11: Electrical resistance material

Hereinafter, the present invention will be described in detail.
The present invention provides an anti-corrosion method using a galvanic anode method as a countermeasure against early bulging, peeling and anode consumption of a metal spray film to be an anode formed by spraying a metal having a higher ionization tendency than iron (1) By installing (applying) cement mortar (one or more types selected from polymer cement mortar, fiber-containing cement mortar, and polymer and fiber-free cement mortar) between the metal spray coating and the concrete surface, the anticorrosion current is suppressed. to it, (2) at Rukoto be installed aluminum thin film between the metal sprayed coating and the concrete surface, inhibiting the corrosion current, electrical connection between (3) metals sprayed coating and the concrete inside the steel the electrical resistance material is placed Hairyutan terminal of the circuit portion, suppressing the protection current, more ways of either a metal sprayed film Swelling and peeling are eliminated or greatly reduced to suppress the deterioration rate of the metal sprayed film.

  In the present invention, the polymer cement mortar applied to the concrete surface adopted as the first means contains cement, sand, polymer, short fiber, admixture (admixture), etc., and has an appropriate adhesion strength. It is a material with high crack resistance. Although there are no particular limitations on the proportion and type of cement, sand, polymer, short fiber, and admixture (admixture), the following can be used.

  The cement is not particularly limited, and various portland cements specified in JIS R 5210, various mixed cements specified in JIS R 5211, JIS R 5212, and JIS R 5213, and specified in JIS. One or more selected from blast furnace cement, fly ash cement, silica cement, limestone powder mixed filler cement, and alumina cement manufactured with the above admixture mixing rate can be used.

  Although it does not specifically limit as a polymer, Usually, it is used for mixing with cement, and both powdery form and liquid can be used. As the types of polymer emulsions, for example, polymers for blending cement (polymer dispersion) specified in JIS A 6203 can be used, and rubbers such as acrylonitrile / butadiene rubber, styrene / butadiene rubber, chloroprene rubber, and natural rubber. Latex, ethylene / vinyl acetate copolymer, polyacrylic acid ester, vinyl acetate vinyl versatate copolymer, and acrylic acid ester copolymer represented by styrene / acrylic acid ester copolymer and acrylonitrile / acrylic acid ester. Examples thereof include a polymer, an epoxy resin, and a liquid polymer represented by an unsaturated polyester resin. One or more selected from these can be used.

The short fiber is not particularly limited, but is usually used for cement mixing, and commercially available organic fibers and inorganic fibers can be used. Examples of the fiber include vinylon fiber, acrylic fiber, nylon fiber, polypropylene fiber, polyethylene fiber, aramid fiber, carbon fiber, glass fiber, cellulose fiber, rock wool, alumina fiber, basalt fiber, and steel fiber.
One or more selected from these can be used.
Of these, organic fibers such as vinylon fibers and nylon fibers are preferable.

  The admixture (agent) is a shrinkage reducing agent or an expansion material. The shrinkage reducing agent suppresses drying shrinkage of the mortar, and is not particularly limited, and a commercially available one can be used. For example, a compound having a surfactant activity such as an alcohol, a lower alcohol alkylene oxide derivative, a glycol, a glycol ether / amino alcohol derivative, or a polyether can be used. The swelling agent gives a reduction in curing shrinkage and gives chemical prestress, and is not particularly limited, and uses calcium sulfoaluminate-based or lime-based and composites of these calcium sulfoaluminate-based and lime-based materials. be able to.

  In the present invention, fluidizing agent, air entraining agent, rust preventive agent, thickener, clay mineral, pozzolanic material, latent hydraulic material, rapid hardening agent, quick setting agent, antifoaming, as long as performance is not adversely affected Various cement admixtures such as additives, antibacterial agents, and rosin derivatives can be added.

  The fiber-containing cement mortar is a polymer to which no polymer is added. However, as with the polymer cement mortar, there are no particular restrictions on the composition and type of the components. The same cement, fiber and admixture (agent) can be used. In the same manner as described above, fluidizing agents, air entraining agents, rust inhibitors, thickeners, clay minerals, pozzolanic materials, latent hydraulic materials, quick hardening agents, quick setting agents, as long as they do not adversely affect performance. Various cement admixtures such as antifoaming agents, antibacterial agents, and rosin derivatives can be added.

  Cement mortar containing no polymer and fiber (hereinafter abbreviated as “cement mortar”) is not particularly limited with respect to the proportion and type of components, like polymer cement mortar and fiber-containing cement mortar. . The same cement and admixture (agent) as described above can be used. In the same manner as described above, fluidizing agents, air entraining agents, rust inhibitors, thickeners, clay minerals, pozzolanic materials, latent hydraulic materials, quick hardening agents, quick setting agents, as long as they do not adversely affect performance. Various cement admixtures such as antifoaming agents, antibacterial agents, and rosin derivatives can be added.

  The blending ratio of cement, sand, polymer, short fiber, etc. can be 40 to 300 parts by weight of sand, 0 to 5 parts by weight of polymer, and 0 to 5 parts by weight of short fibers with respect to 100 parts by weight of cement.

  Before entering the galvanic anode type anticorrosion process, at least one selected from polymer cement mortar, fiber-containing cement mortar, and cement mortar is applied to the concrete surface, and a ground treatment is performed.

The coating thickness of polymer cement mortar, fiber-containing cement mortar, and cement mortar is about 1 mm to 100 mm, and the concentration of anticorrosion current is prevented by covering the concrete surface. The adhesion strength with concrete is important to be 0.5 N / mm ² or more, and it is necessary to have an appropriate adhesion strength.

In the present invention, as a second means, an aluminum thin film is placed between a metal sprayed film formed by spraying a metal having a higher ionization tendency than iron and the concrete surface . Aluminum has a greater ionization tendency than iron (less oxide formation) long term oxidation hardly compared to zinc Ru metal der.
As metals that have a higher ionization tendency than iron , generally used metals include zinc, zinc alloys, aluminum, aluminum alloys, indium, copper, and copper alloys. Here, the zinc alloy is an alloy obtained by mixing Zn as a main component and at least one kind of metal such as Al, Cu, Mg, Fe, In, etc., and the aluminum alloy is mainly composed of Al. An alloy obtained by mixing at least one kind of metal such as Zn, Mg, Cr, Si, In, etc., and a copper alloy is mainly composed of Cu, Ni, Zn, Sn, Al, In it had a resulting alloy obtained by mixing at least one metal selected from such. In the present invention, that to form a sprayed coating layer by zinc-aluminum pseudo alloy of Zn / Al = 90 / 10~50 / 50 ( weight ratio). The reason is that the sprayed coating layer formed of a zinc-aluminum pseudo-alloy is excellent in corrosion resistance, has a large cohesive failure force, is dense, and does not easily generate blisters. The zinc-aluminum pseudo-alloy is a state in which zinc and aluminum do not form an alloy structure, and zinc fine particles and aluminum fine particles are irregularly overlapped to form a zinc-aluminum alloy in appearance. This zinc / aluminum pseudo-alloy coating can be formed by performing arc spraying using a sprayed wire of zinc and aluminum and by low temperature spraying such as arc spraying in a reduced pressure.
Although the thickness of a metal sprayed film is not limited, It can be set as 50 micrometers-1000 micrometers.

In the present invention, aluminum is used as the metal used for the thin film placed between the metal sprayed film and the concrete surface . Aluminum (less oxide formation) long term hard oxidation as compared to zinc metal. The thickness of the aluminum thin film is not limited, but can be 10 μm to 300 μm. For example, the amount of anticorrosion current is suppressed by spraying aluminum to several tens of μm.

  In the present invention, as a third means, an electric resistance material is installed in a circuit portion (drain terminal) that electrically connects between the metal sprayed film installed on the concrete surface and the steel material inside the concrete, and the amount of anticorrosion current is set. Let it be suppressed.

  Any method can be used alone or in combination, and the determination is made according to the amount of chloride ions in the concrete, the amount of moisture in the concrete, and the surrounding environment of the concrete structure.

  Hereinafter, the present invention will be described in more detail based on experimental examples, but the present invention is not limited thereto.

(Experimental example 1)
Concrete specimens (7) were prepared with the composition shown in Table 1, and deformed reinforcing bars (6) were embedded. The polymer cement mortar or fiber-containing cement mortar or cement mortar (manufactured by Denki Kagaku Kogyo Co., Ltd.) (1) is applied with 3 mm (adhesion strength 1.0 N / mm ² ), and a rough surface forming agent (Dai Nippon Paint ( Co., Ltd. (2) was prepared, and a zinc / aluminum pseudo-alloy was sprayed to form a metal sprayed film (4), and a specimen treated with a sealing agent (Dai Nippon Paint Co., Ltd.) (5) was prepared. (See Fig. 1) Using this specimen, galvanic anode-type cathodic protection was carried out, and the metal sprayed film serving as the anode was subjected to a comparative study of swelling and peeling.

<Materials used>
・ Cement (C): Portland cement (manufactured by Electrochemical Industry Co., Ltd.)
・ Fine aggregate (S): Hokuriku stone cooperatives ・ Coarse aggregate (G): Hokuriku stone cooperatives ・ Water: tap water ・ Admixture: water reducing agent ・ NaCl: industrial use ・ Polymer cement mortar (electrochemical industry) (Made by)
(Cement: 100 parts by mass, polyacrylate polymer: 0.1 parts by mass, vinylon fiber: 0.02 parts by mass, sand: 50 parts by mass)
・ Cement mortar with fiber (manufactured by Denki Kagaku Kogyo Co., Ltd.)
(Cement: 100 parts by mass, nylon fiber: 0.06 parts by mass, sand: 180 parts by mass)
・ Cement mortar (manufactured by Electrochemical Industry Co., Ltd.)
(Cement: 100 parts by mass, sand: 200 parts by mass)

<Measurement method>
A non-resistance ammeter (made by Hokuto Denko Co., Ltd.) (10) is installed on the discharge terminal part (9) via the IV wire (8), and the corrosion protection flows between the metal sprayed film (4) and the reinforcing bar (6). The current was measured. Further, the state of swelling / peeling of the metal sprayed film was visually observed. The specimen was exposed to the marine environment for 2 years.

  Table 2 shows the results of the amount of anticorrosion current and the results of swelling / peeling. Specimen Nos. 1-1 and 1-2, No. 1-3 and No. 1-4, No. 1-5 and No. 1-6, No. 1-7 and No. 1-8 The difference in the anticorrosion current density is due to the difference in temperature and humidity conditions.

From the results shown in Table 2, the corrosion current density was suppressed to 80 mA / m ² or less by applying polymer cement mortar, fiber reinforced cement mortar, or cement mortar before the anticorrosion process using the galvanic anode. It can be seen that the occurrence of swelling and peeling of the metal sprayed film is suppressed.

(Experimental example 2)
Concrete specimens (7) were prepared using the same materials as in Experimental Example 1 and blended as shown in Table 3, and the deformed reinforcing bars (6) were embedded. A metal sprayed film (3) of 50 μm aluminum alone is provided on the rough surface forming agent (2), and a metal sprayed film (4) of a zinc / aluminum pseudo-alloy is formed thereon, and a sealing agent (5 ) Was prepared (see FIG. 2). Using this specimen, the amount of anticorrosion current was compared with the swelling and peeling of the metal sprayed film. The measurement was performed in the same manner as in Experimental Example 1.

  Table 4 shows the results of the amount of anticorrosion current and the results of swelling / peeling. The difference in the corrosion protection current density between specimen numbers No.2-1 and No.2-2, No.2-3, No.2-4, and No.2-5 is due to the difference in temperature and humidity conditions.

From the test results in Table 4, by applying a metal sprayed film of aluminum alone on the concrete surface side after applying the rough surface forming agent, the corrosion protection current density is suppressed to 80 mA / m ² or less, and the metal sprayed film It can be seen that peeling is suppressed.

(Experimental example 3)
Concrete specimens (7) were prepared using the same materials as in Experimental Example 1 and blended as shown in Table 5, and the deformed reinforcing bars (6) were embedded (see FIG. 3). An electric resistance material (11) is connected to a circuit portion (drain terminal) (9) for electrically connecting the metal spray film (4) on the anode side installed on the concrete surface and the steel material (6) inside the concrete (7). It was installed and visually examined for the amount of anticorrosion current and the swelling / peeling of the metal sprayed film. The measurement was performed in the same manner as in Experimental Example 1.

Table 6 shows the results of the anticorrosion current amount and the results of the swelling and peeling. The difference in the corrosion protection current density between specimen numbers No. 3-1 and No. 3-2, No. 3-3, No. 3-4 and No. 3-5 depends on the difference in temperature and humidity conditions.

From the test results in Table 6, by installing an electrical resistance material at the discharge terminal part, the corrosion-proof current density by the galvanic anode method is suppressed to 80 mA / m ² or less, and the swelling and peeling of the metal sprayed film are suppressed. I can see that

  The technique of devising the concrete surface preparation of the present invention, the layer structure of the sprayed metal and the electric circuit has the above-mentioned effects, and can be usefully used in the cathodic protection method of the galvanic anode method. It can be used as a technique to prevent the sprayed film from swelling and peeling.

Claims (2)

In a cathodic protection method using a galvanic anode method, in which a metal sprayed film is formed by spraying a metal that has a higher ionization tendency than iron on the concrete surface to supply a corrosion-preventing current to the steel material inside the concrete, the metal sprayed film is made of zinc / aluminum. It is formed by thermal spraying a pseudoalloy, means for installing cement mortar between the metal sprayed film and the concrete surface, means for installing a thin film of aluminum between the metal sprayed film and the concrete surface, or the above Take measures to install an electric resistance material at the drain terminal of the circuit part that electrically connects the metal sprayed film and the steel material inside the concrete, and reduce the density of the corrosion protection current flowing between the metal sprayed film and the steel material inside the concrete. An anticorrosion method for concrete structures, characterized in that it is controlled to 80 mA / m ² or less per concrete area .   2. The cathodic protection method according to claim 1, wherein the cement mortar is at least one selected from polymer cement mortar, fiber-containing cement mortar, and polymer and fiber-free cement mortar.