JP2003120041A - Repair method for concrete deteriorated by salt damage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repair method for concrete deteriorated by salt damage that can prevent reinforcement corrosion after repair and fully secure the adhesive property of cross-section restoration mortar at a repaired part. SOLUTION: In this repair method for concrete deteriorated by salt damage, concrete in the part to be restored of a concrete structure is chipped, and then a nitrite solution is applied to the adhesion interface of a chipped part and cross-section restoration mortar and the whole surface of the exposed reinforcement surface. After polymer cement mortar is applied, cross-section restoration is carried out using the cross-section restoration mortar.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for repairing a concrete structure deteriorated by salt damage or a concrete structure possibly deteriorated by salt damage.

[0002]

2. Description of the Related Art Conventionally, as a method of repairing a concrete structure deteriorated by salt damage, after removing the concrete in the deteriorated portion, the adhesion of the cross-section restoration mortar is secured to the surface of the concrete cross-section. In order to prevent this, water-spraying and primer application are performed.If exposed reinforcing bars are present, after removing rust, resin-based rust preventives, polymer cement rust preventives, rust conversion paint rust preventives, etc. A method of applying a rust material and then applying a cross-section restoration mortar is widely used.

However, in general, at the boundary between the reinforcing bar inside the repaired concrete and the healthy reinforcing bar, the self-potential, which is a parameter indicating the corrosion tendency of the reinforcing bar, changes extremely, and this part is the center. ,
A relatively large cell (electrical circuit) may be formed and corrosion called macrocell corrosion may progress, and this tendency becomes particularly strong when a resin-based rust preventive material is applied. Also, if polymer cement-based rust preventives or rust conversion paint rust preventives are used, and if cross-section restoration cannot be continued due to the process, the surface of the reinforced anti-corrosion bar will be further Rust may occur. Further, when a polymer cement-based rust preventive material having a low polymer / cement ratio is used, it may not be possible to secure sufficient adhesion between the cross-section restoration mortar and the reinforcing bar.

Further, when chloride ions penetrate deeply and there are high-concentration chloride ions that have penetrated deeper than the flared portion, these high-concentration chloride ions are concentrated after the cross-section restoration mortar is constructed. It is a problem that the action of the gradient causes the steel to come back to the vicinity of the reinforcing bar again and cause corrosion of the reinforcing bar.

[0005]

The main object of the present invention is to:
Method that can solve the above-mentioned problems in the repair method of salt damage deteriorated concrete using cross-section restoration mortar, that is,
It is an object of the present invention to provide a repairing method that can prevent corrosion of reinforcing bars after repairing and can sufficiently secure the adhesiveness of the cross-section restoration mortar in the repaired portion.

[0006]

Means for Solving the Problems The present inventor has conducted extensive studies to solve the above problems. As a result, after scraping off the concrete of the deteriorated part of the concrete structure deteriorated by salt damage, after applying the nitrite aqueous solution to the exposed reinforcing bar surface and the entire bonding interface between the scraped part and the cross-section restoration mortar , Furthermore, according to the method of applying polymer cement mortar on the application surface of the nitrite aqueous solution and then repairing it using the cross-section restoration mortar, at the boundary between the rebar inside the repaired concrete and the rebar inside healthy concrete. , It was found that the natural potential of the reinforcing bar can be changed stepwise from the joint interface part to the inside of the sound concrete, and the spontaneous potential can be prevented from changing extremely and the macrocell corrosion can be suppressed. It was Furthermore, according to such a repair method, the adhesiveness between the scraped-off portion and the surface of the reinforcing bar and the cross-section restoration mortar is greatly improved, and chloride ion permeation occurs at the adhesive interface between the scraped-off portion and the restoration mortar. Even when a barrier layer is formed and there is a high concentration of chloride ions that have penetrated deeper than the barbed portion, these high concentration of chloride ions return to the vicinity of the rebar due to the action of the concentration gradient and cause corrosion of the rebar. It has been found that it is possible to prevent the deterioration of concrete and the generation of rust for a long period of time. The present invention has been completed based on these findings.

That is, the present invention provides the following method for repairing salt-damaged concrete. 1. After scraping off the concrete of the repaired part of the concrete structure, apply an aqueous nitrite solution to the adhesive interface between the scraped part and the cross-section repairing mortar, and the entire surface of the exposed reinforcing bar, and then apply polymer cement mortar. A method for repairing salt-damaged concrete, which comprises applying cross-section restoration using mortar to restore cross-section after application. 2. 2. The polymer cement mortar contains 20 to 50 parts by weight of a polymer for admixing cement with respect to 100 parts by weight of cement, and the coating thickness of the polymer cement mortar is 0.5 to 3 mm. Method of repairing salt-damaged concrete. 3. Furthermore, polymer cement mortar is cement 1
2 parts by weight of the aqueous nitrite solution in terms of solid content with respect to 00 parts by weight.
The method for repairing salt-damaged concrete according to item 1 or 2 above, which comprises 10 to 10 parts by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the repairing method of the present invention, first, according to a conventional method, a concrete structure deteriorated by salt damage, or a concrete structure whose deterioration is predicted to progress,
Peel off the concrete in the area to be repaired. Depending on the degree of deterioration of the concrete, the area to be scraped off should be removed by scraping the concrete around the rusted part of the steel material, or if there are cracks or defects in the concrete. Just take off. Further, even if such deterioration cannot be confirmed, a portion that is considered to be potentially deteriorated may be similarly removed as necessary.

Next, an aqueous nitrite solution is applied to the joint interface between the stripped portion and the cross-section restoration mortar and the entire surface of the reinforcing bar exposed by the stripping.

Generally, at the interface between the exposed part of the reinforcing bar and the reinforcing bar existing inside the sound concrete, the self-potential, which is a parameter indicating the corrosion tendency of the reinforcing bar, changes extremely after the construction of the cross-section restoration mortar. Macrocell corrosion is likely to proceed. In the method of the present invention, not only the surface of the rebar exposed by the deburring, but by applying an aqueous nitrite solution to the entire joint interface between the deburred part and the cross-section restoration mortar, the exposed rebar and the inside of the sound concrete are A sufficient amount of nitrite aqueous solution will be applied to the interface with the existing rebar, and nitrite will permeate from the joint interface to the inside of healthy concrete, and the spontaneous potential of the rebar can be changed stepwise. As a result, it is possible to prevent the spontaneous potential from changing extremely and suppress macrocell corrosion.

As the nitrites, alkali metal nitrites such as lithium nitrite, sodium nitrite and potassium nitrite, and alkaline earth metal nitrites such as calcium nitrite and magnesium nitrite can be used. The concentration of the nitrous acid aqueous solution is not particularly limited, but is usually 10
It may be used as an aqueous solution having a concentration of about 50% by weight.

The coating amount of the aqueous nitrite solution is not particularly limited, but is preferably about ²⁰ to 200 g / m ^{2 in} terms of solid content. If the coating amount is less than this range, the effect of gradually changing the spontaneous potential is not sufficiently exerted, while if the coating amount is too large, the effect is hardly improved, resulting in high cost. It is an economy.

Next, polymer cement mortar is applied to the portion to which the aqueous nitrite solution has been applied.

Usually, when there are high-concentration chloride ions that have penetrated deeper than the flared portion, after the cross-section restoration mortar is constructed, these high-concentration chloride ions are again in the vicinity of the reinforcing bar due to the action of the concentration gradient. However, according to the method of sequentially applying the nitrite aqueous solution and the polymer cement mortar, a barrier layer for chloride ion permeation is formed at the adhesive interface of the repair mortar, and migration of chloride ion occurs. Can be suppressed, and it is possible to prevent the corrosion of the reinforcing bar in the repaired portion.

Further, by applying the polymer cement mortar after applying the nitrite aqueous solution, the applied nitrite permeates into the sound concrete at the interface between the exposed rebar and the rebar existing inside the sound concrete. The effect of doing is improved.

Further, according to the method of sequentially applying the nitrite aqueous solution and the polymer cement mortar and then repairing the cross section, the adhesiveness between the scraped-off portion and the surface of the reinforcing bar and the cross-section repairing mortar is greatly improved. Further, even when the cross section cannot be continuously repaired due to the repair process, it is possible to prevent further rusting on the surface of the reinforcing bar.

The type of polymer cement mortar is not particularly limited, and various types of polymer cement mortar can be used. In particular, it is preferable to use a polymer cement mortar containing 20 to 50 parts by weight of a polymer for admixing cement with 100 parts by weight of cement, and a polymer mortar containing 25 to 50 parts by weight of a polymer for admixing cement is used. Is more preferable. When the polymer cement mortar having a polymer content within such a range is used, a barrier layer excellent in the effect of suppressing the movement of chloride ions and excellent in adhesion can be formed.

The coating thickness of the polymer cement mortar is not particularly limited, but it is preferably applied so as to be about 0.5 to 3 mm, more preferably about 1 to 3 mm. When the coating thickness is within this range, a particularly excellent blocking effect against chloride ions is exhibited. If the coating thickness is insufficient, the blocking effect against chloride ions tends to be insufficient,
On the other hand, if the coating thickness is too thick, no further effect can be obtained, which is uneconomical.

In such a polymer cement mortar,
The cement that can be used is not particularly limited, and examples thereof include Portland cement (normal, early strength, super early strength, sulfate resistance, moderate heat, low heat), mixed cement (blast furnace cement, fly ash cement, silica cement), White portland cement or the like can be used. Further, as the admixture for cement, blast furnace slag fine powder, fly ash, silica fume, limestone powder, etc. may be used. Furthermore, if necessary, calcium sulfaluminate (C
SA) type expansion material may be added.

As the polymer for admixture with cement, liquid polymer emulsion, rubber latex, powdery re-emulsified powder resin, etc. can be used. In particular, when the re-emulsified powder resin is used, there is no need for on-site weighing and quality control becomes easy. In addition, empty cans of containers containing liquid materials such as Ito cans do not appear as waste materials. As the re-emulsified powder resin, for example, vinyl acetate vinyl versatate resin,
Acrylic / vinyl acetate vinyl versatate resin, polyacrylic ester resin, etc. can be used.

Further, it is preferable to add an aqueous nitrite solution to the polymer cement mortar. By adding nitrite into the polymer cement mortar, the sulfite gradually migrates to the concrete part due to the effect of the concentration gradient, and the effect of stepwise transition of the self-potential of the reinforcing bar is compensated for. The rust effect is improved. As the nitrite aqueous solution, the same nitrite aqueous solution as described above can be used. By adding nitrite into the polymer cement mortar, the sulfite gradually migrates to the concrete part due to the effect of the concentration gradient, and the effect of stepwise transition of the self-potential of the reinforcing bar is compensated for. The rust effect is improved. In order to exert such effects, it is preferable to add about 2 to 10 parts by weight of the aqueous nitrite solution as a solid content to 100 parts by weight of cement. If the addition amount is insufficient, the effect of the addition of nitrite may not be sufficiently exhibited, while if the addition amount exceeds the above range, no further effect can be obtained, which is uneconomical.

Among the other components to be added to the polymer cement mortar, the fine aggregates include silica sand Nos. 6 to 7 and cold water stones 222M to 70M, or fine aggregates having a relatively small particle size, or silica stone powder or limestone powder. Fine powder such as can be used. The amount of fine aggregate is usually 1 with respect to 100 parts by weight of cement.
The amount is preferably about 0 to 500 parts by weight, and is about 50 to 2
It is more preferable that the amount is about 100 parts by weight.

In addition, as a thickener, cellulose ether type (methyl cellulose), acrylic copolymer type (polyacrylamide), biopolymer type (curdlan,
A thickening agent such as welan gum may be mixed. The addition amount of the thickener is usually 5 to 100 parts by weight of cement.
The amount is preferably about 50 parts by weight, more preferably about 10 to 30 parts by weight. Further, fluidizing agents such as lignin sulfonate, naphthalene sulfonate, melamine sulfonate, and polycarboxylate may be used. The amount of superplasticizer added is usually 100% cement.
The amount is preferably about 5 to 300 parts by weight, and more preferably about 30 to 100 parts by weight, relative to the parts by weight. In addition, an antifoaming agent can be added in an amount of about 5 to 50 parts by weight, preferably about 10 to 30 parts by weight, based on 100 parts by weight of cement.

The amount of water to be added to the polymer cement is usually about 30 to 80 parts by weight with respect to 100 parts by weight of cement.

After the polymer cement mortar is applied by the above-mentioned method, the cross-section restoration mortar is used to restore the cross section, whereby the salt-damaged concrete can be repaired.

There is no particular limitation on the cross-section repairing method,
All you have to do is follow the usual method. For example, cross-section restoration mortar may be applied by a known method such as trowel coating, spraying, or form injection method.

There is no particular limitation on the type of cross-section restoration mortar that can be used, and any conventionally used one can be appropriately used depending on the repaired portion.

[0028]

According to the concrete repairing method of the present invention, the following remarkable effects are exhibited. (1) Macrocell corrosion can be prevented at the boundary between the reinforcing bar inside the repaired concrete and the healthy reinforcing bar. (2) Cross-section restoration Sufficient adhesion between the mortar and the reinforcing bar can be secured. (3) Even if chloride ions penetrate deeply and there are high-concentration chloride ions that have penetrated deeper than the splinter, these high-concentration chloride ions are re-introduced by the action of the concentration gradient. It is possible to suppress returning to the vicinity. (4) Even when the rustproofed reinforcing bar is exposed to the air, it is possible to prevent rusting on the surface thereof.

[0029]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 Architectural Institute of Japan "Durability Survey / Diagnosis of Reinforced Concrete Buildings and Guidelines for Repair (Draft)" Appendix 1.3 As a method for accelerating corrosion of reinforcing steel in the quality standard (Draft) of rust preventive materials for repairing reinforced concrete Correspondingly, a corrosion test was conducted by the following method.

First, a steel bar for reinforced concrete having a diameter of 10 mm and a length of 240 mm is fixed to the center of a steel frame of 100 × 100 × 400 mm, and ordinary Portland cement, 6
S / C = 2.0, W / C = 0.6 with No. dry silica sand
Place 5 mortar, and then at 20 ℃ 80% RH for 1 day, 2
Curing was performed in water at 0 ° C. for 6 days and at 20 ° C. and 60% RH for 7 days to prepare a cured mortar. NaCl was added to the mortar so that the amount of Cl ⁻ was 3 kg / m ³ .

With respect to the hardened body after curing, a depth of about 50 mm was cut off from a bottom surface of one side of the center portion having a length of 120 mm and a width of 100 mm, and a part of the steel bar embedded in the mortar specimen was removed. Exposed.

The cured mortar thus partially peeled off was repaired by the following methods, and then a corrosion acceleration test and an outdoor exposure test were performed. FIG. 1 shows a repair method showing a schematic shape of a cured mortar body including a stripped portion. As a repair method, a 25% aqueous solution of lithium nitrite (trade name: reflex α on the entire surface of the stripped surface and the exposed reinforcing bar surface). , Sumitomo Osaka Cement Co., Ltd.) coating amount 600g /
After coating with m ² (solid content 150 g / m ² ), a coating amount of polymer cement mortar (rust preventive material) of the following composition is 150 g
/ M ² was applied. The applied polymer cement mortar had a thickness of about 2 mm. (Polymer cement mortar composition) Ordinary cement 50 parts by weight Silica sand 6 50 parts by weight Lion GRLC-C material (styrene-butadiene synthetic rubber latex, solid content 45%) 30 parts by weight (polymer / cement ratio = 27%) Lithium nitrite 25% aqueous solution (Refre α, manufactured by Sumitomo Osaka Cement Co., Ltd.) 10 parts by weight (solid content of nitrite / cement ratio = 5%) Water 40 parts by weight Light weight ultra-fast cement mortar (trade name: Lion GRLC, Sumitomo Osaka Cement) (Corporation) was used to repair the cross section of the part that had been picked up by iron coating.

Regarding the test body repaired by the above method,
Pre-curing (CO ₂ pressurization accelerated neutralization 72 hours, 30 ° C drying 7
After carrying out pressure infiltration with NaCl aqueous solution for 3 hours), put it in a polyethylene bag and "heat at 80 ° C for 24 hours, remove from the bag and dry at 30 ° C for 24 hours, at 20 ° C, add 2.5% sodium chloride aqueous solution. 50 cycles of dry and wet cycles, each cycle consisting of "immersion for 24 hours", were performed.

After the completion of 50 cycles, the test piece was split and the rebar was taken out, and the corrosion grade was visually determined. Corrosion grades are: I: sound to slight rust on the surface, II: rust on the surface, III: surface rust, partial floating rust, IV: full surface rust, rust adheres mortar, V: expansive rust, Judgment was made based on each criterion of cross-section defect. After that, the rusted area of the reinforcing bar was measured separately for the base material portion and the repaired portion, and the rusted area ratio of the reinforcing steel bar was calculated as% with the effective area of the reinforcing bar of the base material portion or the repaired portion as 100.

Further, with respect to the repaired mortar, the amount of salt transferred from the base concrete was measured.

An outdoor exposure test was conducted for 7 days on the above-mentioned test piece whose section was repaired, and after 1 day, 3 days and 7 days.
The condition of the surface of the test body was visually observed after each day.

The above results are shown in Tables 2 and 3 below. Comparative Examples 1 to 4 With respect to the mortar hardened body that was partially peeled off in the same manner as in Example 1, after treating the fishing surface and the reinforcing bar surface by each method shown in Table 1 below, the same procedure as in Example 1 was performed. Repaired the cross section.

Thereafter, a corrosion acceleration test and an outdoor exposure test were conducted in the same manner as in Example 1.

The test results are shown in Tables 2 and 3 below.

The method for treating the flapping surface and the reinforcing bar surface is as follows. (Water) Coating amount 150g / m ² (Primer coating) Acrylic polymer dispersion (Trade name: Lion Bond, Sumitomo Osaka Cement Co., Ltd.)
Manufactured, solid content 45%) 3 times diluted solution coating amount 150g / m
² (Applying chelate reaction type rust preventive material) Reflesavinone (Sumitomo Osaka Cement Co., Ltd.) was applied at an application amount of 150 g / m ² (polymer cement mortar application) Same as Example 1

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[Brief description of drawings]

FIG. 1 is a drawing showing a schematic shape of a test piece used in Example 1.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigehiro Ando             28 Sumitomo Osaka, 6-6 Rokubancho, Chiyoda-ku, Tokyo             Inside Cement Co., Ltd. (72) Inventor Kenji Miyawaki             28 Sumitomo Osaka, 6-6 Rokubancho, Chiyoda-ku, Tokyo             Inside Cement Co., Ltd. (72) Inventor Keiichi Osaki             28 Sumitomo Osaka, 6-6 Rokubancho, Chiyoda-ku, Tokyo             Inside Cement Co., Ltd. F-term (reference) 2E176 AA01 BB15

Claims (3)

[Claims] 1. A nitrite aqueous solution is applied to the bonded interface between the scraped-off portion and the cross-section restoration mortar and the entire surface of the exposed reinforcing bar after the concrete in the restored portion of the concrete structure is scraped off, and then A method for repairing salt-damaged concrete, comprising applying polymer cement mortar and then performing cross-section restoration using cross-section restoration mortar. 2. A polymer cement mortar is cement 1.
20 to 20 parts by weight of the polymer for admixing cement with 100 parts by weight
The method for repairing salt-damaged concrete according to claim 1, wherein the content of the polymer cement mortar is 0.5 to 3 mm. 3. The polymer cement mortar further contains 2 to 10 parts by weight of the aqueous nitrite solution in terms of solid content with respect to 100 parts by weight of cement.
A method for repairing salt damage-deteriorated concrete according to.