JP3040613B2 - Corrosion protection method for reinforced concrete structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion method for a reinforced concrete structure, and more particularly to an external power supply type anticorrosion method capable of effectively protecting a reinforcing bar of a reinforced concrete structure from corrosion for a long period of time. Is a method for preventing reinforced concrete structures from being corroded.

[0002]

2. Description of the Related Art Reinforcing bars are usually embedded in concrete structures for reinforcement. However, this rebar
Corrosion occurs due to the neutralization of concrete or the effect of salt contained in the concrete material, and chloride ions and sulfate ions contained in the water that enters the concrete. Rebar has the disadvantage that its function as a reinforcing material is lost in a relatively short time. Therefore, conventionally, in order to prevent corrosion of reinforcing steel, (a) a method of applying an anticorrosion paint to the surface of a concrete structure, (b) a method of electrolytic protection using a galvanic anode method, and (c) an electrolytic protection method using an external power supply method. A method was used. However, in the method (a) of coating the anticorrosion paint on the surface of the concrete structure, the physical strength of the coating film formed by the anticorrosion paint is not sufficiently strong, so that the coating film is easily damaged. There is a drawback that the corrosion factor is inferior to long-term corrosion protection because the corrosion factor invades from the part.
(B) The cathodic protection method using the galvanic anode method is easy to maintain, and when applied to marine concrete structures immersed in seawater, the electrical resistance of the concrete itself is small, the anticorrosion current flows easily, and the anticorrosion method is used. However, when applied to land concrete structures in the air, the electrical resistance of the concrete itself is high, so the anticorrosion current does not easily flow, and as a result, the anticorrosion properties cannot be sufficiently exhibited. . On the other hand, (c) the anticorrosion method using an external power supply system is excellent in long-term anticorrosion of rebar because the applied voltage can be freely adjusted even for a concrete structure in the atmosphere, and is widely used. Is coming.

[0003] As the external power supply system, (i) a conductive paint system and (ii) a reticulated anode system are known as typical systems. However, both systems are difficult to construct and have poor workability. There is. That is, (i) the conductive paint system is a method in which a narrow groove is dug in the surface of concrete, and a platinum-plated titanium wire and a conductive resin for its protection are filled therein as a primary anode, and a carbon-based material as a secondary anode. Alternatively, it is a method of applying a nickel-based conductive paint to the concrete surface, but it is difficult to apply it to concrete structures with complicated shapes, and it takes a lot of man-hours to dig a groove on the concrete surface, and the workability is poor. In addition, the coating film tends to be blistered and peeled, and the platinum-plated titanium wire is expensive. On the other hand, in the (ii) reticulated anode system, in the system of the above (i), the primary anode directly connected to the power source is arranged in a reticulated manner on the concrete surface so as to make the current distribution to the reinforcing bar uniform and the secondary anode is omitted. It is an anode system. In other words, a method of arranging a titanium expanded type mesh with a platinum-based metal oxide coating on the concrete surface or a carbon-based expanded type mesh with a surface treatment, and coating the mortar on the mesh is used. However, there is a drawback in that it is difficult to work, the workability is poor, there is a problem in the durability of the overlay mortar, peeling tends to occur over time, and the cost of the anode material is high.

[0004]

The present invention can be easily applied to a reinforced concrete structure having a complicated shape, has good workability, and is inexpensive. An object of the present invention is to provide a method for preventing corrosion of a reinforced concrete structure, which can provide excellent corrosion protection for a long period of time that is not inferior to that of a concrete structure.

[0005]

Means for Solving the Problems The present inventors have studied the problems of such an external power supply system, and have excellent workability and low cost while utilizing the features of the cathodic protection method using the external power supply system. The present invention has been completed as a result of research for developing a long-term anticorrosion method for a reinforced concrete structure.
Therefore, the present invention forms a primer layer having a rough surface by applying a primer containing aggregate to the surface of a reinforced concrete structure, and forms aluminum, an aluminum alloy or a zinc-aluminum pseudo-alloy on the primer layer. A method for preventing corrosion of a reinforced concrete structure, comprising forming a sprayed coating layer by spraying, using the sprayed coating as an anode, using a reinforcing bar in the concrete structure as a cathode, and applying a DC voltage between the two to flow an anticorrosion current. Is provided. Hereinafter, the present invention will be described in detail.
The primer used in the present invention contains an aggregate and a binder as essential components, and further contains a solvent (or a dispersion medium), a pigment, and various additives as necessary.

The aggregate used in the present invention has an average particle diameter of about 10 to 200 μm, preferably 30 to 100 μm, and can form sharp irregularities on the surface of the primer layer. Examples of the aggregate include metals and alloys having the same ionization tendency as the thermal spray coating material, various metals and alloys having at least a surface insulated, oxides thereof (eg, aluminum oxide and iron oxide), and nitrides. And silicon carbide, silicon carbide, boron nitride, and a plastic powder that does not dissolve in the solvent in the primer. The amount of the aggregate is about 30 to 300% by volume based on the binder,
Preferably 65 to 150% by volume, pigment volume concentration (PV
About 25 to 75%, preferably 40 to 60% is suitable as C). The surface of the primer layer formed on the concrete structure is made to have an appropriate surface roughness, preferably a surface roughness (Rz) specified in JIS B-0601, of about 40 to 150 μm by an aggregate contained in the primer. Due to the roughness, a sprayed coating having good workability and excellent adhesion can be formed on the surface of the reinforced concrete structure without blasting.

[0007] As the binder used in the present invention, conventional binders for paints can be used without particular limitation as long as they are excellent in drying property, water resistance, adhesion and the like, and examples thereof include: , Chlorinated rubber, alkyd resin, one-pack normally dry resin such as vinyl resin, epoxy resin, unsaturated polyester resin, acryl-urethane resin, polyester-
Two-part curable resin such as urethane resin (used together with a curing agent)
In the present invention, a two-pack type epoxy resin having particularly good water resistance and adhesion is preferable. Examples of the solvent (or dispersion medium) to be added as needed include ordinary organic solvents for coatings such as xylene, toluene, butanol, methyl ethyl ketone, and butyl acetate, and water, and can be mentioned as pigments. Is an extender such as barium sulfate, calcium carbonate, and talc; and a coloring pigment such as titanium oxide and carbon black.Examples of the additives include an antifoaming agent, an anti-sagging agent,
And dispersants. It is preferable to add 0 to 50% by weight of a solvent (or a dispersion medium) and 0 to 30% by weight of a pigment to the weight of the primer. The primer used for coating may be of any form such as an organic solvent type, an aqueous type or a liquid solventless type.

Next, aluminum, an aluminum alloy, or a zinc-aluminum pseudo alloy can be used as a thermal spray coating material for forming a thermal spray coating layer serving as an anode used in the present invention. In addition, zinc is known as a typical thermal spray coating material, but zinc is easily consumed by white rust and the like, and even if a protective coating is applied thereon, blisters and the like are liable to be generated and the purpose is to provide long-term corrosion protection. This is not suitable in the present invention. The aluminum alloy contains at least 50% by weight of aluminum and contains Cr, Si, Fe, N
This is an alloy obtained by mixing at least one kind of metal such as i, Sn, and Zn. The thermal spray coating formed of aluminum or an aluminum alloy has the advantage of less wear because the surface of aluminum itself is oxidized to form a stable and dense coating. The zinc-aluminum pseudo alloy is
Zinc and aluminum, Zn: Al = 85: 15-30:
This is a pseudo alloy containing 70 (weight ratio). Thermal spray coatings formed from a zinc-aluminum pseudo-alloy have the advantage that they have high cohesive strength, are dense, and do not easily form blisters. In addition, a zinc-aluminum pseudo alloy refers to a state in which zinc and aluminum do not form an alloy structure, zinc fine particles and aluminum fine particles overlap irregularly, and a zinc-aluminum alloy is apparently formed. The zinc-aluminum pseudo-alloy coating can be formed by using a spray wire of zinc and aluminum and performing arc spraying by a low-temperature spraying method such as an arc spraying method under reduced pressure.
FIG. 1 is a characteristic partial sectional side view of a typical reinforced concrete structure subjected to anticorrosion treatment by the method of the present invention. Based on this figure, a method of preventing corrosion of a reinforced concrete structure of the present invention will be described. The surface of the concrete structure 1 in which the reinforcing bar 2 is embedded as a reinforcing material is subjected to removal of extraneous matter such as dust and oil, if necessary, and then the primer is applied and dried to form a primer layer 3. The primer is applied by a conventional coating means such as a spray, a brush or a roller, and the applied amount is about 20 to 4
00 g / m ² , preferably 40 to 200 g / m ² .

Conventionally, in order to improve the adhesion of the metal spray coating, a method of blasting the surface of the substrate to be sprayed and roughening the surface has been generally used. When applied to the surface of a structure, dust is generated, deteriorating the work environment and surrounding environment, and the surface hardness of the concrete structure is lower than that of steel, etc., and concrete aggregates may fall off the surface. However, there was a problem that it was difficult to obtain a rough surface having sharp irregularities with sharp angles as in the case of blasting the steel material surface, and as a result, it was not possible to form a sprayed coating having excellent adhesion, but the present invention employs a blasting method. Instead, a primer containing aggregate was applied to overcome this problem. On the semi-dried or completely dried primer layer 3 thus obtained, aluminum, an aluminum alloy or a zinc-aluminum pseudo alloy is sprayed to form a sprayed coating layer 4 serving as an anode. In the case of aluminum or an aluminum alloy, there are a gas flame spraying method, an electric arc spraying method, a low-temperature spraying method using a reduced pressure arc spraying machine, and the like, and any method may be used in the present invention. If the temperature of the sprayed particles is high, the primer layer may be burned out.
A low-temperature spraying method using an arc spraying machine under reduced pressure disclosed in, for example, Japanese Patent No. 67472 is desirable.

The low-temperature thermal spraying method using the reduced pressure arc spraying machine utilizes a low-temperature air flow that is jetted into a cylindrical shape, and continuously applies a metal wire under an environment in which a central portion is reduced in pressure from a peripheral portion. In the same way, the arc is melted, and at the same time, it is sucked into the forward jet stream, pulverized, rapidly cooled, and in a liquid supercooled state,
This is a method of spraying the sprayed metal particles on the primer layer. In the case of a zinc-aluminum pseudo alloy, thermal spraying is performed by the low-temperature thermal spraying method as described above. The thickness of the thermal spray coating layer 4 formed on the primer layer 3 is about 20 to 200 μm, especially 3 μm.
It is preferably from 0 to 150 μm. However, even if the film thickness is, for example, about 1000 μm, there is no problem at all and only the quality becomes excessive. Thermal spray coating layer 4 thus formed
And the reinforcing bar 2 are connected via a power source 6 with a conductive material 5 which is a lead wire such as a copper wire whose surface is insulated and coated. The present invention thus forms a sprayed coating layer constituting an anode on a reinforced concrete surface via a primer layer, and uses a reinforcing bar as a cathode to apply a DC voltage from a power supply between the reinforcing bar and the sprayed coating layer, thereby preventing corrosion current. To prevent corrosion of the reinforcing steel buried in the concrete structure. The DC voltage is such that the potential of the rebar is −1000 mV to −550 mV (based on a saturated Ag / AgCl electrode), preferably −900 mV to −60.
It is appropriate to add so that it becomes 0 mV. FIG.
In the figure, reference numeral 7 denotes various electrodes such as a saturated glaucomatous electrode or an Ag / AgCl electrode, and 8 denotes a voltmeter, which is provided for measuring the electric potential of the reinforcing bar. The corrosion prevention method of the reinforced concrete structure of the present invention is as described above,
In order to prevent wear of the thermal spray coating due to rust, it is desirable to apply a protective coating by applying various anticorrosive paints, polymer cements, etc. on the thermal spray coating layer. The method of the present invention can be applied to various types of reinforced concrete structures such as bridges and tunnels on land, as well as newly or existing marine reinforced concrete structures.

[0011]

According to the method of the present invention, construction can be easily performed even on a reinforced concrete structure having a complicated shape, and it is possible to efficiently perform an external power supply type of electrolytic protection at a low cost.
In addition, it is possible to obtain a reinforced concrete structure excellent in long-term anticorrosion property, which is not inferior to that of the conventional external power supply type anticorrosion method. In addition, the present invention forms a rough surface by applying a primer to the surface of a reinforced concrete structure,
Excellent adhesion of thermal spray coating, and it is not necessary to roughen the surface of reinforced concrete structure by performing blasting before thermal spraying as in the past, so that environmental pollution due to dust generated by blasting can be prevented, and The effect that the working time can be greatly reduced is obtained.

[0012]

The present invention will be described in more detail with reference to the following examples. <Primer> Epoxy resin [Epiclon 4051: trade name of Dainippon Ink and Chemicals, Inc .: epoxy equivalent 950] 1
80 g of xylene and 60 of methyl ethyl ketone
and 25 g of butanol were added and dissolved, and 10 g of a polyamide resin (Epicure 892: manufactured by Celanese: active hydrogen equivalent: 133) was added.
275 g of polyamide resin solution (resin solid content capacity 100 cm
³ ) and silicon carbide having an average particle diameter of 48 μm [Green silicon carbide CG320: trade name, manufactured by Nagoya Abrasive Equipment Co., Ltd .: specific gravity
3.16] 221 g (particle volume 70 cm ³ , PVC 41%) was sufficiently stirred to prepare a primer. <Reinforced Concrete Specimen> A deformed reinforcing bar with the designation D13 specified in JIS G3112 is covered with a 20 mm cover and 6 bars each.
A reinforced concrete specimen (height x length x width = 900 x 9) was embedded with a total of 12 rods, and a lead wire was attached to the end of the reinforcing rod as shown in Fig. 1 and an Ag / AgCl electrode was embedded.
00 × 100 mm).

The concrete is usually Portland cement, water / cement = 60/40 (weight ratio), sand / concrete aggregate = 54/46 (weight ratio),
The unit cement amount was 320 kg / m ³ . In order to suppress the influence of the edge effect, the four sides other than the side on which the thermal spray coating was applied were applied with a solventless epoxy resin paint and sealed. However, the back surface opposite to the surface on which the thermal spray coating was applied was not treated. [Example 1] The surface of a reinforced concrete specimen was washed with high-pressure water and cleaned, and then the primer was air-sprayed at 50 g /
m ² and air-dried for 2 hours to form a primer layer having a surface roughness (Rz) of 60 μm. Next, an aluminum wire rod was sprayed on the primer layer using an arc spraying machine under reduced pressure (PA-100 manufactured by Pan Art Craft Co., Ltd.) to form a sprayed coating layer having a thickness of 80 μm. The above-mentioned lead wire attached to the end of a reinforcing bar serving as the anode and the cathode as the sprayed coating layer was connected via a power source as shown in FIG. In the above thermal spraying, low temperature thermal spraying was performed on an aluminum wire rod having a diameter of 1.1 mm under the conditions of a line speed of 5 m / min, a voltage of 17 V, a current of 120 A, an air pressure of 6 kg / cm ² , an air flow rate of 1 m ³ / min, and a spray distance of 20 cm.

Example 2 After a primer layer was formed in the same manner as in Example 1, zinc-aluminum was applied on the primer layer using an arc spraying machine under reduced pressure (PA-100 manufactured by Pan Art Craft Co., Ltd.). Pseudo alloy [Zn / Al = 72/28
(Weight ratio)], a test specimen was prepared in the same manner as in Example 1 except that an acrylic resin polymer semeton paint was applied thereon to form a protective coating of 100 μm. In addition, the said thermal spraying is carried out by transferring a zinc wire and an aluminum wire having a diameter of 1.1 mm at a carrying speed of 6 m / min.
Current 120A, air pressure 6kg / cm ² , air flow rate 1m ³ / min,
Low-temperature spraying was performed under the condition of a spraying distance of 20 cm. Comparative Example 1 An aluminum sprayed coating layer was formed in the same manner as in Example 1 except that the surface was roughened by sandblasting instead of forming the primer layer on the surface of the reinforced concrete test specimen. A lead wire attached to the end of the reinforcing bar serving as a cathode was connected via a power supply. [Comparative Example 2] A titanium mesh (aperture 35 ×
70 mm), and an acrylic resin-based polymer cement mortar was troweled thereon to form a 20 mm protective layer. A lead wire attached to an end of a reinforcing bar serving as the anode and the cathode as the cathode was connected via a power source.

With respect to the specimens obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the potential of the reinforcing bar was monitored by an Ag / AgCl electrode embedded in advance at the position of the reinforcing bar so that the value was constantly -800 mV. The following cycle test was carried out while adjusting the amount of current and supplying current. <Cycle test method> After leaving in a constant temperature room at a relative humidity of 60% and a temperature of 20 ° C for 24 hours, 2% in a 3% saline solution at 50 ° C.
Assuming that the step of dipping for 4 hours was one cycle, 100 cycles were performed. The self-potential measurement after 100 cycles, the current density measurement for each cycle (using a microammeter), the appearance observation, and the rusting area ratio of the reinforcing steel after the 100 cycle test were performed. The results are shown in Table 1.

[0016]

[Table 1] Table 1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Examples Comparative examples Test items ━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━ 1 2 1 2 No processing ━━━━━━━━━━━━━━━━━自然 Natural potential after 100 cycles -165 -170 -500 -180 -485 (Unit: mV) ━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━ Current density (unit: μA / cm ² ) 5 cycles 12 12 11 12 −10 〃 12 11 12 10 −20 〃 10 10 11 11 − 40 〃 8 9 9 10 − 60 〃 9 8 7 8 − 80 〃 8 8 6 8 − 100 〃 7 8 4 8 − ━━━━━━━━━━━━━━━━━━

Appearance 5 cycles No abnormality No abnormality No abnormality No abnormality No abnormality No abnormality 10 〃 Same as above Same as above Same as above 20 〃 Same as above Same as above Same as above Spray less than 5% Many occurrences 80 〃 Same as above Thermally sprayed film Same as above Cracked about 10% peeled off Enlarged 100 〃 Same as above Thermal sprayed film Same as above About 20% peeled off ━━━━━━━━━━━━━━━━━━━錆 Rebar rust area ratio 5> 5> Approx. 15 5> 95 <(Unit:%) ━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━

As is clear from Table 1, Examples 1 and 2, which were protected by the method of the present invention, were inexpensive, had good workability, and had good corrosion resistance, as compared with Comparative Example 2 using a conventional mesh anode system. It was almost equivalent. The blasted Comparative Example 1 was inferior in adhesion, the thermal spray coating was peeled off, and the long-term corrosion resistance was inferior. In the untreated test specimen, cracks occurred in the concrete, and rust was generated on almost the entire surface of the reinforcing bar.

[Brief description of the drawings]

FIG. 1 is a partial side sectional view of a reinforced concrete structure subjected to anticorrosion treatment by the method of the present invention. DESCRIPTION OF SYMBOLS 1 Concrete structure 2 Reinforcing bar 3 Primer layer 4 Thermal spray coating layer 5 Lead wire 6 Power supply 7 Electrode 8 Voltmeter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 13/20 C23C 4/06 E04B 1/62 E04C 5/01

Claims (2)

(57) [Claims] 1. A primer layer having a rough surface is formed by applying a primer containing an aggregate to the surface of a reinforced concrete structure, and aluminum, an aluminum alloy or a zinc-aluminum pseudo-alloy is sprayed on the primer layer. Forming a sprayed coating layer by using the sprayed coating as an anode, using a reinforcing bar in the concrete structure as a cathode, applying a DC voltage between the two, and flowing an anticorrosion current, the method for preventing corrosion of a reinforced concrete structure. . 2. The method for preventing corrosion of a reinforced concrete structure according to claim 1, wherein a protective coating is provided on the thermal spray coating layer.