JP4819558B2 - Method of cathodic protection for reinforced concrete structure and cathodic protection structure - Google Patents

Description

  The present invention relates to a technique for preventing corrosion of reinforcing bars in a reinforced concrete structure.

Conventionally, cathodic protection has been widely employed to prevent corrosion of reinforcing bars in reinforced concrete structures such as building columns and piers. The conventional anti-corrosion method used for corrosion protection of reinforced concrete structures is to equalize the potential difference of iron by connecting the surface of the concrete to the anode of the DC power supply unit and flowing a weak DC current toward the reinforcing bar on the cathode side. This is to prevent corrosion of the reinforcing bars.
As such an anti-corrosion method, a carbon fiber non-woven fabric or carbon powder coated sheet is attached to the surface of a reinforced concrete structure and connected to the anode of the DC power source, and the reinforcing bar in the reinforced concrete structure is connected to the cathode of the DC power source. Technology to be performed (Patent Document 1), similarly, a technique in which a carbon fiber sheet provided on the surface of a reinforced concrete structure is connected to the anode of a DC power source and the reinforcing bar in the reinforced concrete structure is connected to a cathode of the DC power source (Patent Document 2) And the technique which coat | covers a carbon fiber sheet with the oxidation-resistant metal which has a passive film, for example, nickel, is disclosed in the above-mentioned cathodic protection method (patent document 3).
JP 2003-27607 A JP 2004-27709 A JP 2004-190119 A

  However, as disclosed in Patent Document 1 and Patent Document 2, when the carbon fiber sheet is connected to the anode of the DC power source to perform corrosion prevention, the conductive resistance of the carbon fiber sheet is gradually deteriorated as the energization time elapses. There is a risk that the voltage increases and the current cannot be supplied. In addition, when carbon is used as an electrode, it has been confirmed that the inside of the carbon will be discolored (“Electrical protection system using lightweight FRP panel and conductive material”, concrete structure repair, reinforcement, upgrade symposium paper) Report Collection, Volume 2, Society of Materials Science, P197-202, October 2002), I am concerned about the durability of the electrode.

Further, even when the carbon fiber sheet is coated with nickel as disclosed in Patent Document 3, there is a possibility that there is a problem in durability as in the case of the carbon fiber sheet alone disclosed in Patent Documents 1 and 2 ( "Study on current-carrying performance in the anti-corrosion of nickel-coated carbon fiber sheets", Concrete Engineering Papers, No. 1, Vol27, P1531 to 1536, June 2005).
The present invention has been made in view of the above-described problems, and an object thereof is to provide an anticorrosion structure having durability that can be used as an anticorrosion method for an anticorrosion method and a corrosion prevention method for a reinforced concrete structure having excellent durability. And

In order to achieve the above object, the present invention takes the following technical means.
That is, the cathodic protection method according to the present invention is a cathodic protection method for a reinforced concrete structure, wherein the sheet material formed of synthetic resin fibers and conductive metal wires is used for the reinforced concrete using a conductive adhesive. The terminal for integrating with the structure and energizing the conductive metal wire is attached.
Preferably, the conductive adhesive is an epoxy resin containing carbon powder.
Preferably, the synthetic resin fiber is an aramid fiber, and the conductive metal wire is a titanium wire.

The cathodic protection structure according to the present invention is an cathodic protection structure used for cathodic protection of a reinforced concrete structure, and a sheet material knitted into a sheet shape using synthetic resin fibers and conductive metal wires. Have.
Preferably, it has a conductive adhesive for integrating the sheet material into the reinforced concrete structure.
Preferably, the synthetic resin fiber is an aramid fiber, and the conductive metal wire is a titanium wire.

  Preferably, the conductive adhesive is an epoxy resin containing carbon powder.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion prevention method of the reinforced concrete structure excellent in durability, and the durable cathodic protection structure which can be used as an anode for cathodic protection can be provided.

FIG. 1 to FIG. 3 are views showing an anticorrosion structure according to the present invention.
The anti-corrosion structure is a sheet formed by knitting yarn made of aramid fibers (hereinafter sometimes referred to as “aramid fibers”). When aramid fibers are knitted, titanium wires are knitted simultaneously to impart conductivity. Has been.
In FIG. 1, the anticorrosion structures 1a, 1b, 1c are unidirectional sheets formed by so-called plain weaving of aramid fiber yarns 2, ..., 2 and titanium wires 3, ..., 3 are yarns 2, ..., 3. Double knitted along 2 In FIG. 1A, the titanium wires 3,..., 3 are knitted in a doubled manner with the yarns 2,. In FIG. 1B, the titanium wires 3,..., 3 are knitted in a doubled manner with the yarns 2,. In FIG. 1 (c), the titanium wires 3,..., 3 are double knitted with all the aramid fiber threads 2,.

  In FIG. 2, the anticorrosion structures 1Ba, 1Bb are each of the warp yarns 2, ..., 2 and the weft yarns 2, ..., 2 being tightly knitted, and the warp yarns 2, ..., 2 and the weft yarns 2, ..., 2 are Each is a two-way sheet that crosses three yarns in the other direction and crosses the next one. The titanium wires 3,..., 3 are knitted with double warp yarns 2,..., 2 at appropriate intervals (FIG. 2 (a)), or weft yarns 2,. Are knitted (FIG. 2B). 1 and warp yarns 2,..., 2 and weft yarns 2,..., 2 or all at appropriate intervals, respectively, like warp prevention structures 1a and 1b shown in FIG. Titanium wires 3,..., 3 may be knitted in double and double.

  3, the anticorrosion structures 1Ca and 1Cb are formed by combining aramid fiber threads 2,..., 2 and titanium wires 3,. In FIG. 3A, the titanium wires 3,..., 3 are wound around the warp yarns 2,..., 2 while connecting the warp yarns 2,. Titanium wires 3,..., 3 may be wound around the weft yarns 2,..., 2 and the weft yarns 2,. In FIG. 3B, the titanium wires 3,..., 3 are knitted together with the weft yarns 2,. In the mesh-shaped cathodic protection structure, like the cathodic protection structures 1a and 1b shown in FIG. 1, the warp yarns 2,..., 2 and the weft yarns 2,. .., 2 and weft yarns 2...

As the aramid fibers 2,..., 2 used for the cathodic protection structure, for example, para-aramid fibers KEVLAR (registered trademark) manufactured by Toray DuPont Co., Ltd. are used. 1-3, a bundle of 0.1 mm thick single fibers (one fiber) is used for the aramid fibers 2,... .., 3 having a diameter of 0.1 mm is used. Considering the ease of weaving into the aramid fiber, it is preferable to use a titanium wire having substantially the same diameter as the single fiber of the aramid fiber.
Since the aramid fiber 2 itself is excellent in insulation, there is no risk of leakage or the like, and when combined with the titanium wire 3, it is possible to concentrate the current on the portion to be energized.

1 to 3, the braiding density of the titanium wires 3,..., 3 in the cathodic protection structures 1a, 1b, 1c, 1Ba, 1Bb, 1Ca, 1Cb is preferably 1 cm to 10 cm, and preferably 3 cm to 10 cm. More preferred. Here, the “weave density of the titanium wire” refers to the interval between the adjacent titanium wires 3 and 3 that are knitted. In order not to increase the raw material cost excessively, the density of the titanium wire 3 to be knitted is preferably about 30 / m ² . In addition, the titanium wire 3 is arranged at equal intervals in each direction in order to make the current density distribution on the surface of the work object uniform when used along the warp and along the weft. It is preferable to knit as described above.

The anticorrosion structures 1a, 1b, 1c, 1Ba, 1Bb, 1Ca, 1Cb are sheet materials in the present invention.
Other synthetic fibers such as polyamide fibers (nylon: registered trademark), polyester fibers, and polypropylene fibers may be used in place of the aramid fibers. In addition to synthetic fibers, high-strength fibers such as glass fibers and carbon fibers can be used. Since the anticorrosion structure is woven with titanium wire, it can have sufficient durability as an electrode even when carbon fiber is used.

Further, another good conductive metal such as copper may be used instead of the titanium wire.
Next, the reinforced concrete structure in which the anticorrosion structure is constructed will be described.
4 is a schematic view of a cross section 4 of a reinforced concrete structure used for a floor of a building, FIG. 5 is a cross sectional view taken along the line AA in FIG. 4, and FIG. It is sectional drawing.
The cathodic protection structure used in FIGS. 4 to 6 is the cathodic protection structure 1Ca shown in FIG. In the construction of the reinforced concrete structure 4 in FIG. 4, first, the main reinforcement 5 and the reinforcing bars 6,..., 6 crossing the main reinforcement 5 are arranged, and after the concrete 7 is poured into the formwork, the foundation is cured for several days. It is formed. When the concrete 7 is hardened, the conductive adhesive 8 is applied to the concrete 7 surface, and the surface of the concrete 7 is covered with the anticorrosion structure 1Ca from the applied conductive adhesive 8. The conductive adhesive 8 is applied enough to spread over the entire anticorrosion structure 1Ca and protrude from the mesh-like surface. After covering the surface of the concrete 7 with the anticorrosion structure 1Ca, the conductive adhesive 8 may be applied to the surface of the anticorrosion structure 1Ca again.

Before the conductive adhesive 8 is cured, the distributor is placed on the anticorrosion structure 1Ca so that the longitudinal direction is perpendicular to the direction in which the titanium wires 3, ..., 3 of the anticorrosion structure 1Ca are knitted. A plurality of 9 are arranged. The plurality of distributors 9, 9, 9 are connected in parallel by a conductive wire 10. By using the distributors 9, 9, 9, current can be efficiently applied to the titanium wires 3,..., 3 of the anticorrosion structure 1 Ca as compared with the case where only the conductive adhesive 8 is interposed.
After the conductive adhesive 8 is cured, a mold is assembled outside the anticorrosion structure 1Ca, and the anode protective concrete 11 is poured into it, and the anticorrosion structure 1Ca, the distributors 9, 9, 9 and the conductive wire 10 are improved along with the appearance improvement. May be protected.

A cathode terminal 12 is connected to the main reinforcement 5 or the reinforcing reinforcement 6 by welding, and one end of the cathode terminal 12 is embedded in the concrete 7 so as to be exposed on the surface of the reinforced concrete structure 4. A reference electrode 13 is attached to the concrete 7. Moreover, the conducting wire 10 is connected to the anode terminal 14 and installed so that one end of the anode terminal 14 is exposed on the surface. The cathode terminal 12 is connected to the cathode of the DC power supply 15, and the anode terminal 14 is connected to the anode of the DC power supply 15.
The conductive adhesive 8 is cured to form FRP (Fiber Reinforced Plastics) together with the mesh-shaped cathodic protection structure 1Ca, and functions as a reinforcing material that increases the strength of the reinforced concrete structure 4.

Instead of the anticorrosion structure 1Ca, other anticorrosion structures 1a, 1b, 1c, 1Ba shown in FIG. 3 (b), FIG. 1 (a) to (c), and FIG. 2 (a), (b). , 1Bb, 1Cb can be used.
The galvanic protection of the reinforced concrete structure 4 is performed in the same manner as the known galvanic protection. That is, a current value determined based on the potential measured by the reference electrode 13 embedded in the reinforced concrete structure 4 is applied to the anode terminal 14 by the DC power source 15 to suppress the generation of corrosion current in the reinforced concrete structure 4. By doing so, corrosion of the reinforcing bars (the main reinforcing bars 5 and the reinforcing bars 6, ..., 6) is prevented.

At this time, as shown in FIG. 6, the conductive adhesive layer 8 in the reinforced concrete structure 4 surrounds the titanium wires 3,..., 3 of the cathodic protection structure 1Ca, and the titanium wires 3,. Fill the gap with 7. Therefore, the conductive adhesive 8 layer functions to increase the electrical conductivity between the distributor 9 and the titanium wires 3, 3, 3 and the electrical conductivity between the titanium wires 3, 3, 3 and the concrete 7.
The conductive adhesive 8 used here is obtained by mixing conductive carbon powder into an epoxy resin widely used as an adhesive. The mixing amount of the carbon powder is determined to be equal to or lower than the volume resistivity (1 × 10 ² to 1 × 10 ⁴ Ω · cm ² ) of the concrete 7. FIG. 7 is a diagram showing the relationship between the carbon powder mixing rate in the adhesive and the volume resistivity. The “carbon powder mixing rate” here refers to the weight percentage of the carbon powder contained when the conductive adhesive 8 (mixture) is taken as 100.

As shown in FIG. 7, the volume resistivity of the conductive adhesive 8 can be made substantially equal to the volume resistivity of the concrete 7 by setting the mixing ratio of the carbon powder to 50 to 58%. Thus, the volume resistivity of the conductive adhesive 8 can be adjusted by adjusting the amount of carbon powder mixed in the adhesive.
By using an epoxy resin having an excellent adhesive strength as an adhesive, it is possible to bond with the work of removing dirt adhering to the surface of concrete 7 during construction and the work of smoothing the surface, and a conductive material layer and an adhesive layer There is no need to repaint. Therefore, the construction period can be shortened and the construction cost can be reduced.

FIG. 8 is a cross-sectional view of a reinforced concrete structure 4B used for a pillar or the like as viewed from the direction of the arrow.
As the reinforced concrete structure 4B, an anticorrosion structure 1Ca shown in FIG. 3A is used. In the construction of the reinforced concrete structure 4B, like the reinforced concrete structure 4 in FIG. 4, the column main bars 5B,..., 5B and the column main bars 5B,. Lateral reinforcement bars 6B are assembled, and concrete 7B is poured into the mold, and then cured for several days to form columns. After the concrete 7B is cured, the conductive adhesive 8 is applied to the surface of the concrete 7B, and the surface of the concrete 7B is covered with the anticorrosion structure 1Ca from above the applied conductive adhesive 8. In FIG. 8, the cathodic protection structure 1Ca covers the surface of the concrete 7B such that the titanium wires 3,..., 3 are the same as the longitudinal direction of the column main bars 5B,. The procedure for applying the conductive adhesive 8 is the same as that for the reinforced concrete structure 4 described above.

Before the conductive adhesive 8 is cured, a plurality of distributors 9B are arranged on the anticorrosion structure 1Ca in a direction perpendicular to the direction in which the titanium wires 3, ..., 3 of the anticorrosion structure 1Ca are knitted. The plurality of distributors 9B, 9B, 9B are connected in parallel by a conducting wire 10B.
After the conductive adhesive 8 is cured, a mold is assembled on the outer periphery, the anode protective concrete is poured into it, and cured for several days to protect the anticorrosion structure 1Ca, the distributors 9B, 9B, 9B and the conductor 10B while improving the appearance. May be.

A cathode terminal 12B is connected to the lateral reinforcing bar 6B in advance, and an anode terminal 14B is connected to the distributor 9B, and one end of each is exposed on the surface.
A reference electrode is electrically insulated and attached to both the reinforcing bar and the anticorrosion structure 1Ca on the concrete 7B. The cathode terminal 12B is connected to the cathode of the DC power source 15 and the anode terminal 14B is connected to the anode of the DC power source 15.
Also in the reinforced concrete structure 4B, the conductive adhesive 8 functions as a reinforcing material that forms FRP together with the anticorrosion structure 1Ca and increases the strength of the reinforced concrete structure 4B.

The anti-corrosion structures 1a, 1b, 1c, 1Ba, 1Bb, 1Ca, 1Cb should be used not only for the new reinforced concrete structures 4 and 4B as described above, but also for repairing and reinforcing existing reinforced concrete structures. Can do. And when repairing and reinforcing an existing reinforced concrete structure, the conductive adhesive 8 is used to attach the reinforced concrete structure to the reinforced concrete structure as in the new installation.
FIG. 9 is a diagram comparing the amount of depolarization between the anticorrosion structure 1Ca and the carbon fiber sheet, FIG. 10 is a diagram showing a measuring procedure of the depolarization amount, and FIG. 11 is an electric diagram based on the anticorrosion structure 1Ca and other sheet materials. It is a figure which shows an energization voltage temporal change with a corrosion-proof structure.

The measurement of the instant-off potential of the reinforcing bar was performed by creating a specimen 16 shown in FIG.
The specimen 16 is obtained by winding an electro-corrosion-proof structure 1Ca around an outer periphery of a concrete cylinder 18 having a diameter of about 100 mm and a height of about 200 mm in which a reinforcing bar 17 is built, and fixing the structure with a conductive adhesive 8. The anticorrosion structure 1Ca is wound so that the titanium wire 3 forms a substantially circle in the circumferential direction in FIG. The reinforcing bar 17 is connected to the anode of the DC power source 20 by a conducting wire 19, and the cathodic protection structure 1 </ b> Ca is connected to the cathode of the DC power source 20 through the distributor 21.

The energization of the specimen 16 is performed for 10 minutes at each current density while changing the applied current density. Then, with reference to FIG. 10B, the potential of the reinforcing bar is measured by the measurement electrode 22 and the potential measuring device 23. Measurement is performed at each current density. The electric potential measuring device 23 is a portable rebar corrosion meter (SRI-CM-III type) manufactured by Shikoku Research Institute.
As a result of the potential measurement, as shown in FIG. 9, the cathodic protection structure 1 </ b> Ca exhibits the same degree of polarization performance as the carbon fiber sheet that has been proven as the cathodic protection of reinforced concrete structures. Thus, the anticorrosion performance is comparable.

The nickel-coated sheet in FIG. 11 is obtained by plating nickel on the surface of a carbon fiber non-woven fabric or by knitting carbon fiber subjected to nickel plating into a sheet shape.
As shown in FIG. 11, the voltage of the anticorrosion structure 1Ca and Comparative Examples 1 and 2 increases in the same way until the energization time is 20 days, but after 20 days, the anticorrosion structure 1Ca is Compared with Comparative Examples 1 and 2, the increase in voltage was very small, and it was possible to energize without any trouble even after 100 days. In addition, no abnormality was observed on the surface and inside of the anticorrosion structure 1Ca, and the durability superior to those of Comparative Examples 1 and 2 was exhibited.

The cathodic protection structure according to the present invention exhibits a corrosion prevention effect of a reinforced concrete structure that is inferior to existing various sheets used for cathodic protection, and has higher durability than existing various sheets.
In addition, since the anticorrosion structure according to the present invention can be used to reinforce a reinforced concrete structure, it is first constructed on the reinforced concrete structure for the purpose of reinforcement, and corrosion of the reinforced concrete structure is promoted. When it becomes clear that there is a risk that the anti-corrosion will occur, the anti-corrosion can be easily carried out without performing the anti-corrosion work again.

Since the cathodic protection structure according to the present invention does not use carbon fiber as an electrode for cathodic protection, it can be expected to improve the life as an electrode, that is, the durability. In addition, because it is mainly made of deformable aramid fibers, it can handle structures with complex shapes compared to conventional methods of attaching titanium mesh electrodes and reinforcing them with mortar, and is light and easy to handle. .
In the above-described embodiment, each structure or the entire structure of the anticorrosion structures 1a, 1b, 1c, 1Ba, 1Bb, 1Ca, 1Cb, and the anticorrosion structures 1a, 1b, 1c, 1Ba, 1Bb, 1Ca, 1Cb, The shape, dimensions, number, material, and the like can be appropriately changed in accordance with the spirit of the present invention.

  The present invention can be used to prevent corrosion of reinforcing bars in reinforced concrete structures.

It is a figure which shows the cathodic protection structure which concerns on this invention. It is a figure which shows the cathodic protection structure which concerns on this invention. It is a figure which shows the cathodic protection structure which concerns on this invention. It is the schematic of the cross section of a reinforced concrete structure used for the foundation etc. of high-rise building. It is AA arrow sectional drawing of FIG. It is BB arrow sectional drawing of the site | part P of FIG. It is a figure which shows the relationship between the carbon powder mixing rate to an adhesive agent, and volume resistivity. It is arrow sectional drawing of the reinforced concrete structure used for a pillar etc. It is the figure which compared the amount of depolarizations of an anti-corrosion structure and a carbon fiber sheet. It is a figure which shows the measuring point of a depolarization amount. It is a figure which shows the time-dependent change of the energization voltage of an anticorrosion structure and another sheet material.

Explanation of symbols

1 Sheet material (Corrosion-proof structure)
2 Synthetic resin fiber (aramid fiber)
3 Conductive metal wire (titanium wire)
4,4B Reinforced concrete structure 8 Conductive adhesive

Claims (7)

An anticorrosion construction method for a reinforced concrete structure,
A sheet material formed by synthetic resin fibers and conductive metal wires is integrated into the reinforced concrete structure using a conductive adhesive,
An anticorrosion construction method, comprising: attaching a terminal for energizing the conductive metal wire. The cathodic protection method according to claim 1, wherein the conductive adhesive is an epoxy resin containing carbon powder. The synthetic resin fiber is an aramid fiber,
The cathodic protection method according to claim 1 or 2, wherein the conductive metal wire is a titanium wire. An anticorrosion structure used for the anticorrosion of a reinforced concrete structure,
An anticorrosion structure comprising a sheet material knitted into a sheet shape using a synthetic resin fiber and a conductive metal wire. The cathodic protection structure according to claim 4, further comprising a conductive adhesive for integrating the sheet material into the reinforced concrete structure. The synthetic resin fiber is an aramid fiber,
The conductive metal wire is a titanium wire;
The cathodic protection structure according to claim 4 or 5. The cathodic protection structure according to claim 6, wherein the conductive adhesive is an epoxy resin containing carbon powder.

Images