JPH0572476B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a galvanic anode member for cathodic protection of steel materials in reinforced concrete structures that are constantly exposed to the atmosphere, and a method for cathodic protection of reinforced concrete structures using the same. [Prior art] Normally, in reinforced concrete structures exposed to the atmosphere, macrocells (corrosion batteries) are formed due to defects in the concrete, non-uniformity in density, and differences in geometric structure, and this causes damage to the structure. The steel inside is corroded, and due to corrosion expansion of the steel,
There are structural defects in which cracks occur in the concrete and corrosion of the steel progresses. It is known that this phenomenon is further accelerated when the structure is exposed to the influence of salt. Cathodic protection is the most effective method for preventing corrosion of steel materials in such reinforced concrete structures. Conventional cathodic protection methods, for example, when protecting reinforced concrete for bridge decks, involve digging grooves in the concrete of the bridge deck at intervals of 127 to 457 mm, installing zinc ribbons (5 mm square), and applying mortar or concrete. There is a method of filling the grooves, or laying mortar (about 13 mm thick) on the bridge deck, and drilling many φ22 mm holes before the mortar hardens (perforation rate 60).
%) There is a method of laying zinc plates over the entire surface of the floor slab and covering it with concrete (this method is applied to the floor surface). [Problems to be solved by the invention] The above-mentioned method of laying zinc ribbons in the grooves does not provide sufficient anti-corrosion current due to insufficient surface area of the zinc, so this method is limited to laying zinc plates. has the following problems. *Problems in construction (1) Difficult to install on ceilings and walls. (2) Even if the zinc plate is fixed to the ceiling or wall by some method and covered with mortar, there is a risk that the mortar will peel off over time. (Adhesion of mortar on smooth zinc plate surface) (3) By supplying anti-corrosion current, the zinc will be consumed, but re-repair will be a major undertaking. *Performance issues (1) The grounding resistance of the anode is large. This tendency becomes even more pronounced as zinc is consumed and zinc oxides and hydroxides accumulate at the interface with mortar. (The galvanic anode method uses the potential difference between zinc and steel to prevent corrosion, and since the specific resistance of concrete in the atmosphere is high, it is desirable to lower the resistance at the zinc/mortar interface.) [Problem] Means for Solving the Problems] The present invention provides a galvanic anode member for preventing corrosion of steel materials in reinforced concrete structures, in which a protection plate, a waterproofing material, a galvanic anode plate, and a water retention material are sequentially and integrally laminated from the outside. A galvanic anode member for corrosion protection of reinforced concrete, characterized in that it can be attached to a reinforced concrete surface with an anchor bolt, and a galvanic anode member that can be attached to a concrete surface with an anchor bolt to provide electricity for reinforced concrete structures. This problem is solved by anti-corrosion method. Preferably, the anchor bolt is made of metal, and the anchor bolt is electrically connected to the galvanic anode plate. [Function] As described above, the galvanic anode member of the present invention has the protection plate, waterproof material, galvanic anode plate, and water retention material integrally laminated in advance, so it is easy to transport and can be easily carried on ceilings and walls. It can be easily installed and repaired when the galvanic anode becomes worn out. Furthermore, the resistance between the anode plate and the mortar can be lowered, and the potential difference between the anode plate and the steel material can be effectively utilized. Further, such an anode member is sized to be easily transportable and is attached to the concrete surface of the structure with anchor bolts, thereby facilitating construction and enabling simpler and more effective cathodic protection. When a metal anchor bolt is used, the metal anchor bolt can be protected against electrolytic corrosion, and the anchor bolt can have a long service life. In this case, if a metal anchor bolt is installed in reinforced concrete, there is a high probability that the metal anchor bolt and steel (rebar)
The corrosion prevention effect of the steel material is further improved. Next, each component will be explained. The protection plate in the present invention is a plate that is rigid so that when the anode plate is fixed to the concrete surface with anchor bolts, the entire surface of the anode plate comes into contact with the concrete surface with uniform surface pressure, and it is also resistant to external shocks. , to protect the anode plate, and can be made of FRP, asbestos slate, fiber-reinforced concrete plate, corrosion-resistant metal plate, etc. The waterproof material blocks water, oxygen, and salt from penetrating through the protective plate or from the gap between the protective plate and the anode plate, and prevents self-corrosion of the anode plate. Further, it is more desirable if the waterproof material itself has adhesive properties and has the function of adhering the anode plate and the protection plate and the function of alleviating the physical impact applied to the protection plate. For example, a rubber asphalt sheet is most suitable, but double-sided adhesive tape or the like may also be used. The galvanic anode plate is made of Zn, Al, Mg alloy, etc., which acts as a sacrificial anode.
Zn alloys are preferred. For example, a zinc plate with a thickness of 1 to 2 mm is used, and the thickness is appropriately selected from within the above range depending on the corrosion protection period. The water retaining material eliminates the gap between the anode plate and the concrete surface, lowers the electrical resistance at this interface, and also prevents an increase in resistance due to the accumulation of corrosion products on the anode plate. This water retaining material is preferably a material that is plastic, retains moisture even in the atmosphere, and has electrical conductivity. For example, a product prepared by kneading bentonite and a hygroscopic electrolyte with water, specifically aluminum silicate hydrate, metal sulfate, and magnesium chloride, is used in Japanese Patent Application No. 158484/1984 (Patent Application No. For example, there is a back file as shown in Japanese Patent No. 2-8383). Since this type of backing film has fluidity, when it is applied to a wall surface, etc., it is effective to sandwich a nonwoven fabric or the like between the backing films to prevent sagging. Further, as another water retaining material, a super absorbent sheet containing a super absorbent polymer can be used. For example, sheets made by sandwiching pulp and highly water-absorbing polymer powder such as polyacrylic acid between two sheets of water-supplying paper or non-woven fabric have the advantage of the fast absorption speed of the pulp and the excellent absorption of the polymer. It has a strong holding power and is easier to install compared to back-filing because it is made into a sheet. [Example] The galvanic anode member according to the present invention was applied to the back of reinforced concrete girders and deck slabs of a bridge superstructure to provide cathodic protection of steel in reinforced concrete. Multiple plates of anode members sized to be portable by hand were placed on the surface to be protected against corrosion. Each anode member is provided with mounting holes. The structure of such an anode member is shown in FIG. That is, as an anode member, a 6 mm thick flexible plate (asbestos slate) 3 is used as a protective plate, and a 1 mm thick double-sided adhesive rubber asphalt sheet 4 as a waterproof material is attached to the flexible plate 3. A zinc plate 5 as a galvanic anode plate was adhered. Although the thickness of the zinc plate 5 was set to 1 mm, it may be selected as appropriate depending on the designed service life. Before attaching such an anode member to the concrete surface, a backing film 6 was applied to the zinc plate 5 in advance to a thickness of 5 mm as a water retaining material. Anchor bolts 2 are installed in advance to match the holes for attaching such an anode member.
The anchor bolt 2 and the zinc plate 5 were electrically connected by a connecting nut 8 via a washer 7 with teeth. Furthermore, place the anode member on the concrete surface with a plate 9.
The head of the bolt 2 and the nut 10 were protected by a cap 11. Note that it is desirable that the thickness of the backing film 6 be made thicker if the target concrete surface has irregularities or small steps. When the backing film is applied to a vertical surface, a nonwoven fabric is interposed in the backing film to prevent the backing film from sagging. Each of the anode members arranged in this way was sequentially connected by lead wires, and the last (end) lead wire was connected to the reinforcing steel. In addition, in order to confirm the anti-corrosion effect, reference electrodes were buried in the concrete behind some of the girders and deck slabs, and these lead wires and the lead wires of nearby anode members and reinforcing bars were raised to an accessible location. The potential of the reinforcing bars can be measured at any time. The present inventors have confirmed that when anchor bolts are driven by the method of the present invention, the bolts come into contact with the reinforcing bars 1/5 of the time. By electrically connecting the washer 7 and the connecting nut 8, there is an advantage that not only is corrosion of the bolt prevented, but also the step of connecting the lead wire to the reinforcing bar can be omitted. Thus, when we measured the potential of the reinforcing steel, we found that the first
The anticorrosion effect shown in the table was confirmed.

〔Effect of the invention〕

As explained above, according to the galvanic anode member of the present invention and the electrode corrosion protection method using the same, it can be applied to ceiling surfaces and vertical surfaces, which was extremely difficult or impossible with the conventional galvanic anode method. It has the effect of being easy to construct. In addition, this method of fixing divided small-area anode members with anchor bolts does not require large-scale equipment or machinery, and can be easily applied to objects with poor working environments, such as bridges and the lower part of bridges. have an effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of the configuration of a galvanic anode member according to the present invention and a case where the same is constructed on a reinforced concrete surface. 1... Concrete, 2... Anchor bolt,
3... Flexible board, 4... Rubber asphalt sheet, 5... Zinc plate, 6... Back foil, 7
... Toothed washer, 8 ... Connection nut, 9
...Plate, 10...Mounting nut, 11...Cap.

Claims (1)

[Claims] 1. In a galvanic anode member for preventing corrosion of steel materials in a reinforced concrete structure, a protective plate,
A galvanic anode member for corrosion protection of reinforced concrete, characterized in that a waterproofing material, a galvanic anode plate, and a water retention material are sequentially and integrally laminated, and can be attached to a reinforced concrete surface with anchor bolts. 2. A method for cathodic protection of steel materials in a reinforced concrete structure, which comprises attaching the galvanic anode member according to claim 1 to a concrete surface with an anchor bolt. 3. The cathodic protection method according to claim 2, wherein the anchor bolt is made of metal and is electrically connected to a galvanic anode plate.