JP2018172950A - Method for inhibiting deterioration of reinforced concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for suppressing deterioration of reinforced concrete, which can suppress deterioration of reinforced concrete while being simple. Further, the present invention provides a method for suppressing deterioration of reinforced concrete, which is simple but can suppress deterioration of reinforced concrete, and changes in appearance before and after construction are difficult to understand. SOLUTION: A step of injecting a specific aqueous solution into a crack 4 of deteriorated reinforced concrete 1, a specific amount of a specific aqueous solution is applied to the surface of the reinforced concrete 1, a polymer cement slurry is injected into the crack 4, and then the reinforced concrete. A specific water repellent material is applied to the surface of 1. No paint is applied to the surface of the reinforced concrete 1 coated with the water repellent material. [Selection diagram] Fig. 1

Description

  The present invention relates to a method for suppressing deterioration of reinforced concrete. Specifically, the present invention relates to a method for suppressing deterioration of reinforced concrete that easily suppresses further deterioration of deteriorated reinforced concrete.

  If the reinforced concrete deteriorates severely, remove the deteriorated concrete, remove the rust of the exposed reinforcing bars, apply rust prevention treatment (applying a rust inhibitor), and then repair the cross-sectional defect part of the concrete with mortar or concrete And such repair methods have been proposed (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1). However, since such full-scale repair work is large and costly, it is rarely performed promptly after the discovery of the deterioration, and investigation, diagnosis, repair design, construction plan is considered, and the necessary budget is required. In many cases, actual construction is carried out after securing the above. For this reason, there is a case where the time has passed since the discovery of the deterioration until the full-scale restoration work is performed, and the deterioration proceeds. Therefore, there has been a demand for a simple method that can suppress deterioration until full-scale repair work is performed. In the repair work of reinforced concrete, a technique of applying a rust preventive aqueous solution to the reinforced concrete surface without removing the concrete, applying a silicon-based and / or silane-based primer, and further applying a paint is proposed (for example, Patent Document 3). reference.). In addition, when a reinforced concrete structure that requires repair work is a historical building in a tourist spot, a deterioration suppressing technique that does not feel a change in appearance is desired.

JP 2003-120041 A Japanese Patent Laid-Open No. 02-92883 JP-A-62-074090

Ed., Architectural Institute of Japan, “Durability investigation / diagnosis and repair guideline (draft) / commentary explanation of reinforced concrete buildings”, 1st edition, 1st edition, Architectural Institute of Japan, January 25, 1997, p. 29-34, 104-111

  An object of this invention is to provide the deterioration suppression method of the reinforced concrete which can suppress deterioration of a reinforced concrete while being simple. Another object of the present invention is to provide a method for suppressing deterioration of reinforced concrete that is capable of suppressing deterioration of reinforced concrete while being simple and in which changes in appearance before and after construction are difficult to understand.

As a result of diligent studies to solve the above problems, the present inventors have injected a specific aqueous solution into the cracked reinforced concrete, and applied a specific amount of the specific aqueous solution to the surface of the reinforced concrete, and the polymer cement slurry is applied to the crack. It discovered that the said subject could be solved by inject | pouring and then apply | coating a specific material to the surface of this reinforced concrete, and completed this invention. That is, the present invention is a method for suppressing deterioration of reinforced concrete represented by the following (1) or (2).
(1) After performing the step of injecting a calcium nitrite aqueous solution into cracks of deteriorated reinforced concrete and the step of applying a calcium nitrite aqueous solution to the surface of the reinforced concrete at a coating amount of 50 to 300 g / m ² , It is characterized by comprising a step of injecting a polymer cement slurry and subsequently applying a silane-based water repellent material having a viscosity of 0.5 to 50 mPa · s to the surface of the reinforced concrete at a coating amount of 100 to 400 g / m ^2. To suppress deterioration of reinforced concrete.
(2) The method for inhibiting deterioration of reinforced concrete according to (1) above, wherein no paint is applied to the surface of the reinforced concrete coated with a silane-based water repellent material.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration suppression method of the reinforced concrete which can suppress deterioration of a reinforced concrete is obtained easily. Further, according to the present invention, it is possible to obtain a method for suppressing deterioration of reinforced concrete that can suppress deterioration of reinforced concrete while being simple, and in which change in appearance before and after construction is difficult to understand.

It is typical B-B 'sectional drawing which shows a reinforced concrete test body. It is typical A-A 'sectional drawing showing a reinforced concrete specimen. It is a typical top view which shows a reinforced concrete test body.

The method for inhibiting deterioration of reinforced concrete according to the present invention includes a step of injecting a calcium nitrite aqueous solution into cracks of deteriorated reinforced concrete (step A), and a calcium nitrite aqueous solution is applied to the surface of the reinforced concrete at a coating amount of 50 to 300 g / m ² . A silane-based water repellent material having a viscosity of 1 to 10 mPa · s on the surface of the reinforced concrete, which is performed after the step (step C) of injecting polymer cement slurry into the crack It is characterized by comprising a step (step D) of applying a coating amount of 200 to 400 g / m ² .

  The calcium nitrite aqueous solution used in the present invention preferably has a calcium nitrite concentration of 25% by mass or more. The aqueous calcium nitrite solution functions as a rust inhibitor. Similarly, when a lithium nitrite aqueous solution that functions as a rust preventive agent is used in place of the calcium nitrite aqueous solution, lithium nitrite is highly deliquescent and the concrete surface after application is difficult to dry. This is not preferable because it impedes the impregnation of the material into the concrete.

  The method of injecting the calcium nitrite aqueous solution into the cracked reinforced concrete in the above step A is not particularly limited, but for example, a method of injecting with a low-pressure injector, a tip filled with a calcium nitrite aqueous solution or a caulking gun or the like A method of extruding and filling a calcium nitrite aqueous solution from the hole provided in the tip with the tip of the thinned container pressed against the crack, and a sprayer while bringing the nozzle part of the sprayer filled with the calcium nitrite aqueous solution close to the crack Preferred examples include the method of spraying the cracks by operating and the method of filling by tracing the cracks with a brush dipped in an aqueous calcium nitrite solution. If the crack length is as long as 1m or more, the surface layer of the crack is caulked with silicone, etc., and a syringe-type low-pressure injector filled with calcium nitrite aqueous solution is installed in several places of the crack, and low-pressure injection (by low-pressure injection method) Injection) is preferable because the calcium nitrite aqueous solution easily penetrates into the reinforcing bar portion.

Although the method of applying the calcium nitrite aqueous solution to the surface of the reinforced concrete in the above step B is not limited, it is preferable because application with a brush, application with a roller, or spraying with a sprayer is good in work efficiency and easy to grasp the application amount. Can be mentioned. Moreover, the coating amount of the calcium nitrite aqueous solution in the process B is 50 to 300 g / m ² . If it is less than 50 g / m < ² >, the rust prevention effect of a rebar is hard to be acquired and the deterioration inhibitory effect of a reinforced concrete is easy to be insufficient. Further, if it exceeds 300 g / m ² , the moisture contained may inhibit the penetration of the silane-based water repellent material into the concrete in the step D, and the deterioration suppressing effect of the reinforced concrete may be insufficient. The coating amount of the calcium nitrite aqueous solution in step B is preferably 50 to 200 g / m ² .

  The polymer cement slurry used in the above step C may be a slurry containing cement and a polymer for cement as a binder and further containing water. The cement contained in the polymer cement slurry may be a hydraulic cement, for example, various Portland cements such as ordinary Portland cement, early strength Portland cement, white Portland cement, eco cement, alumina cement, fly ash cement and blast furnace cement. And a rapid hardening cement such as a super-hard cement. The cement polymer contained in the polymer cement slurry includes synthetic rubber such as styrene / butadiene copolymer, chloroprene rubber, acrylonitrile / butadiene copolymer or methyl methacrylate / butadiene copolymer, natural rubber, polyethylene and polypropylene. Such as polyolefin, polychloropyrene, polyacrylate, styrene / acrylic copolymer, all acrylic copolymer, polyvinyl acetate, vinyl acetate / acrylic copolymer, vinyl acetate / acrylic acid ester copolymer, modified vinyl acetate , Ethylene / vinyl acetate copolymer, ethylene / vinyl acetate / vinyl chloride copolymer, vinyl acetate vinyl versatate copolymer, acrylic / vinyl acetate / veova (trade name of vinyl t-decanoate), etc. Vinyl acetate resin, Examples thereof include synthetic resins such as saturated polyester resins, polyurethane resins, alkyd resins and epoxy resins, bitumens such as asphalt and rubber asphalt, preferably synthetic resins, more preferably styrene / butadiene copolymers, or polyacrylic. Acrylic resins such as acid esters, styrene / acrylic copolymers, and all acrylic copolymers. As a polymer cement slurry used in the above-mentioned process C, the mass ratio (P / C) of the polymer for cement to the mass of cement contained is preferably 10% to 30%, more preferably 20% to 30%. Moreover, as a polymer cement slurry used in the said process C, water cement ratio (W / C) is preferable 25 to 50%, and 30 to 40% is more preferable. The polymer cement slurry preferably has an average particle size of 0.1 to 50 μm, more preferably 0.5 to 10 μm, and still more preferably 1 to 8 μm.

  The method of injecting the polymer cement slurry into the cracked reinforced concrete in the above step C is not limited. For example, a method of injecting with a low-pressure injector, a syringe filled with the polymer cement slurry, or a container with a thin tip such as a caulking gun is used. A method in which the polymer cement slurry is extruded and filled from the hole provided in the tip while the tip is pressed against the crack, and the sprayer is operated while the nozzle portion of the sprayer filled with the polymer cement slurry is brought close to the crack to spray the crack. Preferred examples include a method, a method of filling by tracing a crack with a brush dipped in a polymer cement slurry, and the like. If the crack length is as long as 1m or more, the surface layer of the crack is caulked with silicone, etc., and low pressure injection (injection by low pressure injection method) is installed by installing syringe type low pressure injectors filled with polymer cement slurry at several places of the cracks. ) Is preferable because it is easy to fill the entire crack with the polymer cement slurry and to prevent the intrusion of deterioration factors such as water, chloride, acid gas and the like.

  If polymer cement slurry is injected into the cracks of dry concrete, dryout may occur and the polymer cement slurry may not be filled into fine cracks. However, after injecting the calcium nitrite aqueous solution into the cracks in the above step A, the polymer cement slurry is injected. By doing so, the calcium nitrite aqueous solution works like a lubricant, and the polymer cement slurry can be filled up to fine cracks. In addition, if calcium nitrite is contained in the polymer cement slurry, there is a possibility that calcium nitrite having anti-corrosive performance may not reach the reinforcing bar, so a calcium nitrite aqueous solution that suppresses corrosion of the reinforcing bar and a crack to be integrated with the concrete The polymer cement slurry that physically plugs the cracks is injected separately from the cracks.

In the present invention, the silane-based water repellent material is a water repellent material mainly composed of silane and / or siloxane, and is modified with various functional groups such as alkyl modification, epoxy modification, amino modification, and amide modification. Or what has siloxane as a main component may be sufficient. The silane water-repellent material used in the step D may be one having a viscosity of 0.5 to 50 mPa · s. When the viscosity exceeds 50 mPa · s, the penetration into the concrete is inhibited, and the effect of suppressing the deterioration of the reinforced concrete is insufficient. Moreover, since the frequency | count of application | coating for apply | coating a predetermined amount increases that a viscosity is less than 0.5 mPa * s, working efficiency is bad. The silane water repellent material used in the present invention preferably has a viscosity of 0.8 to 40 mPa · s, and preferably has a viscosity of 1 to 35 mPa · s because the number of coatings can be reduced and the permeability to concrete is excellent. More preferred. The silane water repellent material preferably has an active ingredient of 95% or more. The coating amount of the silane-based water repellent material in the process D is 100 to 400 g / m ² . 100 g / m is less than ² insufficient deterioration suppressing effect of reinforced concrete, 400 g / m ² greater than the coating work troublesome but 400 g / m ² Beyond silane water repellent to be applied water and chloride There is a problem that the permeation suppression effect of such deterioration factors does not change. A more preferable coating amount of the silane water repellent material is 150 to 400 g / m ² . If a paint is applied to the surface coated with the silane water repellent material, the appearance changes before and after the construction, which is not preferable.

  The method of applying the silane-based water repellent material to the surface of the reinforced concrete in the step D is not limited, but a preferable example is that application with a brush, application with a roller, or spraying with a sprayer is good in work efficiency and easy to grasp the application amount. As mentioned. In addition, when the silane-based water repellent material is applied to the surface of the reinforced concrete in the step D, the calcium nitrite aqueous solution applied in the step B may permeate the concrete surface and the surface may be dried. Furthermore, it is preferable that the polymer cement slurry injected in step C is cured.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[Example 1]
<Accelerated deterioration test>
Concrete (W / C: 65%, unit chloride ion content) on a 100x100x400mm formwork in which steel bars with a diameter of 16mm and a length of 400mm are installed at an equal distance from the bottom plate and 30mm from the long horizontal plate. 2 kg / m ³ , compressive strength: 38 N / mm ² ) was filled, and water curing was performed at 20 ° C. until the age of 28 days after demolding the next day. After curing, the reinforcing bars were energized and electrocorrosion was carried out until cracks with a width of about 1 mm occurred on the surface (test surface) formed by the bottom plate of the mold. Thereafter, the reinforced concrete subjected to air curing (temperature: 20 ° C., humidity: 60%) for 28 days was used in the accelerated deterioration test as a simulated specimen (base material) of the deteriorated reinforced concrete. FIG. 1 shows a schematic BB ′ sectional view of a simulated specimen (base material) of iron-degraded reinforced concrete. FIG. 2 shows a schematic AA ′ cross-sectional view of a simulated specimen (base material) of deteriorated reinforced concrete. FIG. 3 shows a schematic plan view of a simulated specimen (base material) of deteriorated reinforced concrete.

  Table 1 shows the coating material 1 on the test surface of the base material after filling the test surface of the prepared base material with the crack injection material 1 into the cracks generated by electric corrosion by injection by the low pressure injection method (step A). The application amount was applied with a brush (step B). Thereafter, the crack injection material 2 was filled into the crack by injection by a low pressure injection method (step C). After the crack injection material 2 was cured, the application amount shown in Table 1 was applied to the test surface of the base material (step D).

The materials used for the crack injection material and the coating material in the test are shown below.
A1: Calcium nitrite aqueous solution (concentration: 30% by mass)
A2: Lithium nitrite aqueous solution (concentration: 40% by mass)
B: Polymer cement slurry (cement polymer: SBR synthetic resin emulsion, cement: ordinary Portland cement, P / C: 27%, W / C: 33%, average particle diameter of contained binder: 4 μm)
C1: Silane-based water-repellent material-based water-repellent material (active ingredient: 95% by mass or more, viscosity: 2 mPa · s)
C2: Silane-based water-repellent material-based water-repellent material (active ingredient: 95% by mass or more, viscosity: 35 mPa · s)
C3: Silane-based water-repellent material-based water-repellent material (active ingredient: 80% by mass or more, viscosity: about 2000 mPa · s)
C4: Silane-based water-repellent material-based water-repellent material (active ingredient: 90% by mass or more, viscosity: about 700 mPa · s)

With respect to the simulated specimens repaired by the repair method shown in Table 1, the appearance of the repaired simulated specimens after 50 cycles and 100 cycles was observed with the following test cycle as one cycle.
Test cycle: Immerse in a 10% by mass aqueous sodium chloride solution for 1 day. Then left in the atmosphere at 20 ° C for 2 days.
The results are shown in Table 1. The evaluation criteria at this time were as follows.
・ Evaluation criteria ○: No change in appearance (No change in shape that can be confirmed visually (no occurrence of new cracks), good)
△: New crack occurred (crack width: less than 0.1 mm, there is a problem)
×: New crack generation (crack width: 0.1 mm or more and less than 0.3 mm, defective), rust soup generation (total area: less than 4 cm ² )
XX: Severe deterioration occurred (crack width: 0.3 mm or more or total area of rust juice is 4 cm ² or more, defective)

  The test level corresponding to the example of the present invention was simple and sufficiently suppressed deterioration. In addition, the test body of the test level corresponding to the example of the present invention showed almost no change in appearance before and after the repair.

[Example 2]
<Impregnation depth test of water repellent material>
After applying the coating material 1 in Example 1 to concrete, the impregnation depth of the coating material 2 into the concrete when the coating material 2 is applied is JSCE-K 571 “Surface impregnating material test method (draft)”. Measured accordingly. Concrete had the same composition as that used in Example 1, and the size of the specimen was 100 × 100 × 100 mm. Evaluation of the test result of the impregnation depth of the coating material 2 (silane-based water repellent material) is shown in Table 2 together with the coating conditions of the coating material 1 and the coating material 2. The evaluation criteria at this time are shown below.
・ Evaluation criteria ○: Impregnation depth 3.5mm or more (good)
Δ: impregnation depth of less than 2 to 3.5 mm (insufficient)
×: Impregnation depth less than 2.0 mm (defect)

  The level (test Nos. 11 to 14) in which the coating material was applied to the concrete surface under the same conditions as in the example in Example 1 was that the coating material 2 (silane-based water repellent material) was impregnated at an impregnation depth of 3.5 mm or more. Thus, it is considered that the test-level specimen subjected to the repairing method (the method for suppressing deterioration of reinforced concrete) corresponding to the example of Example 1 was sufficiently suppressed in deterioration.

  The present invention can suppress the progress of deterioration of a deteriorated reinforced concrete structure by a simple operation.

1 Simulated specimen of reinforced concrete (base material)
2 Surface formed by bottom plate of mold (test surface)
3 Reinforcement 4 Cracks caused by electric corrosion 5 Concrete

Claims (2)

After performing a step of injecting a calcium nitrite aqueous solution into cracks of deteriorated reinforced concrete and a step of applying a calcium nitrite aqueous solution to the surface of the reinforced concrete at a coating amount of 50 to 300 g / m ² , a polymer cement slurry is applied to the cracks. Of reinforced concrete, comprising the step of applying a silane-based water repellent material having a viscosity of 0.5 to 50 mPa · s to the surface of the reinforced concrete at a coating amount of 100 to 400 g / m ² . Deterioration suppression method.   2. The method of inhibiting deterioration of reinforced concrete according to claim 1, wherein no paint is applied to the surface of the reinforced concrete coated with a silane water repellent material.

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