Concrete repair liquid and concrete repair method

Abstract

To provide a concrete repairing liquid and a concrete repairing method, by which a workload is small and a fast impregnation rate into a concrete structure is fast.SOLUTION: Provided is a concrete repairing liquid containing nitrite salt, polyoxyalkylene alkyl ether-based surfactant, and water. The content of the polyoxyalkylene alkyl ether-based surfactant is preferably 0.01-1.0 mass%. The polyoxyalkylene alkyl ether-based surfactant is preferably polyoxyethylene alkyl ether, more preferably, polyoxyethylene lauryl ether. The nitrite salt is preferably lithium nitrite. The content of the nitrite salt is preferably 5-50 mass%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a concrete repair liquid and a concrete repair method for inhibiting rebar corrosion and alkali-aggregate reaction in a concrete structure by impregnating the concrete structure with an inhibitor such as an aqueous lithium nitrite solution. [Background technology]

[0002] In concrete structures such as walls, bridge piers, and breakwaters, corrosion of reinforcing bars in the concrete occurs due to the salt contained in the concrete and the drop in concrete pH (neutralization, carbonation) caused by carbon dioxide in the air, which results in cracks in the concrete structures.Alkali metal components such as sodium and potassium contained in the concrete react with aggregate to cause alkali aggregate reaction (ASR), which results in abnormal expansion inside the concrete structure and causes cracks.

[0003] Conventionally, as a method for inhibiting such rebar corrosion and alkali-aggregate reaction, a method of permeating a concrete structure with an aqueous solution of lithium nitrite or the like has been proposed. For example, Patent Document 1 describes an invention in which an inhibitor such as an aqueous solution of lithium nitrite is pressurized and injected through an injection hole provided in a concrete structure, thereby allowing the lithium nitrite or the like to permeate deeper into the concrete structure.

[0004] On the other hand, as a silicate-based surface impregnating material for impregnating concrete to modify (densify) the surface layer of the concrete, Patent Document 2 describes an invention relating to a silicate-based surface impregnating material that contains an alkali metal silicate and has a specific molar ratio. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-38347 A [Patent Document 2] Patent No. 6309140 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when injecting an inhibitor such as a lithium nitrite aqueous solution under pressure through an injection hole provided in a concrete structure as in the invention described in Patent Document 1, it is necessary to drill the injection hole and use an injection device, which is a heavy workload. There is also a method of applying an inhibitor such as a lithium nitrite aqueous solution to the surface of a concrete structure to impregnate it, but the penetration speed is insufficient. In addition, the silicate-based surface impregnation material described in Patent Document 2 does not directly inhibit rebar corrosion or alkali-aggregate reaction in concrete structures.

[0007] The present invention is intended to solve the above-mentioned problems of the conventional art, and provides a concrete repair liquid and a method for repairing concrete which reduce the workload and achieve a high rate of impregnation into concrete structures. [Means for solving the problem]

[0008] In order to solve the above problems, the concrete repair liquid of the present invention contains a nitrite, a polyoxyalkylene alkyl ether surfactant, and water.

[0009] The content of the polyoxyalkylene alkyl ether surfactant is preferably 0.01 to 1.0% by mass.

[0010] The polyoxyalkylene alkyl ether surfactant is preferably a polyoxyethylene alkyl ether.

[0011] The polyoxyalkylene alkyl ether surfactant is preferably polyoxyethylene lauryl ether.

[0012] The nitrite is preferably lithium nitrite.

[0013] The content of the nitrite is preferably 5 to 50% by mass.

[0014] The concrete repair method of the present invention is characterized in that the concrete is impregnated with the above-mentioned concrete repair liquid of the present invention. Effect of the Invention

[0015] According to the present invention, it is possible to provide a concrete repair liquid and a concrete repair method which reduce the workload and achieves a high rate of impregnation into concrete structures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The inventors of the present invention have studied methods for accelerating the impregnation speed of inhibitors that inhibit rebar corrosion and alkali-aggregate reaction in concrete structures, and have come up with a method of making a concrete repair liquid by adding a surfactant as a penetration assistant to the inhibitor. Then, tests were conducted while changing the type and content of the inhibitor and surfactant.

[0017] Nitrite can be used as an inhibitor for suppressing rebar corrosion and alkali-aggregate reaction. Lithium nitrite is preferred as the nitrite. The content of the nitrite is preferably 5 to 50 mass%, more preferably 15 to 40 mass%, and even more preferably 25 to 40 mass%.

[0018] As the surfactant, a polyoxyalkylene alkyl ether surfactant can be used. Examples of oxyalkylenes constituting the polyoxyalkylene alkyl ether include oxyethylene and oxypropylene. Examples of alkyl ethers constituting the polyoxyalkylene alkyl ether include lauryl ether, myristyl ether, palmityl ether, stearyl ether, and oleyl ether. As the polyoxyalkylene alkyl ether surfactant, polyoxyethylene alkyl ether is preferred, and polyoxyethylene lauryl ether is more preferred. The content of the polyoxyalkylene alkyl ether surfactant is preferably 0.01 to 1.0% by mass, more preferably 0.05 to 1.0% by mass, and even more preferably 0.05 to 0.5% by mass or 0.05 to 0.4% by mass.

[0019] The HLB value, which indicates the hydrophilicity or hydrophobicity of the surfactant, is, for example, 8-20, or 10-20, or 12-20.

[0020] The following description will be given based on examples. EXAMPLES

[0021] (Test Method) A surfactant was added as a penetration aid to an aqueous lithium nitrite solution to create a concrete repair liquid, which was then applied to the surface of mortar specimens. The penetration depth was measured three months after application.

[0022] (Concrete repair fluid) A 40% by mass aqueous solution of lithium nitrite [Inoue Shoji Co., Ltd., Procon (registered trademark) 40] was used as the base lithium nitrite aqueous solution. The surfactants used were those shown in Examples 1 to 4 and Comparative Examples 2 to 10 in Table 1, and were added at 0.1% by mass to the lithium nitrite aqueous solution. The surfactants (water reducing agents) shown in Comparative Examples 7 to 10 were added in an amount of 0.1% by mass as the active ingredient (solid content). The surfactant (water reducing agent) shown in Comparative Example 9 was not dissolved in the lithium nitrite aqueous solution, and therefore was not applied to the test specimen. In the table, Emulgen, Poise, Shin-Etsu Silicone, Surflon, Floric, Master Pozzolith, Mighty, and Accelerate are all registered trademarks.

[0023] [Table 1]

[0024] (Specimen) To eliminate the inhibition of penetration of the concrete repair liquid by coarse aggregate, the test specimens were 10 x 10 x 10 cm cube mortar test specimens, with the surface (upper surface) being the coating surface. The mortar ingredients were water, cement (C), and fine aggregate (S), with a water-cement ratio of 55.0% by mass and a sand-cement ratio of 2.5S / C. The ingredients were poured into a formwork immediately after mixing, and demolded when the material was 1 day old. After demolding, the material was cured underwater at 20°C until it was 28 days old, and then cured in air until it was 3 months old.

[0025] (Application of concrete repair liquid to test specimens) The concrete repair liquid was applied to the specimens when they were 3 months old. The application amount was 0.5 kg / m 2 (5 g for a 10 x 10 cm specimen coating surface).

[0026] (Measurement of Penetration Depth) The penetration depth was measured three months after the application of the concrete repair liquid. The test specimen was split vertically to the applied surface to obtain the measurement surface. A nitrite ion coloring liquid was applied to the measurement surface, and the depth from the applied surface to the discolored portion was measured and used as the penetration depth. TDI (2,4-toluene diisocyanate) was used as the nitrite ion coloring liquid. Five test specimens were used per example (comparative example), and the average value was calculated. In addition, for Examples 1 to 4, the nitrite ion content at each depth was measured (water extraction-ion chromatography method).

[0027] The test results are shown in Table 2.

[0028] [Table 2]

[0029] As shown in Table 2, the concrete repair liquids of Examples 1 to 4 penetrated deeper and had a faster impregnation rate than those of Comparative Examples 1 to 10. The nitrite ion content indicates the percentage of the total nitrite ions contained in the corresponding depth.

[0030] (Additional Exam) Of Examples 1 to 4, the concrete repair liquid of Example 4 (using Emulgen 150 as the surfactant), which gave the best results (higher nitrite ion content in deeper parts), was tested on concrete specimens. (Specimen) The specimen was a 10 x 10 x 10 cm cubic concrete specimen, with the surface (upper surface) used for coating. The concrete materials were water, cement (C), fine aggregate (S), and coarse aggregate (G). The water-cement ratio W / C was 65.0 mass%, the fine aggregate ratio s / a (the ratio of the fine aggregate volume to the total volume of fine aggregate and coarse aggregate) was 52.6 volume%, and the unit cement amount was 274 kg / m 3 The material was poured into the formwork immediately after mixing, and demolded on the first day of age. After demolding, the material was cured in water at 20°C until it was 28 days old, and then cured in air until it was 3 months old.

[0031] (Test Method) The conditions of the lithium nitrite aqueous solution used, the method of applying it to the test specimen, the method of measuring the penetration depth (method of measuring the nitrite ion content per depth), etc. were the same as those in Example 4. In Example 5, the amount of surfactant added was 0.1 mass%, and in Example 6, the amount of surfactant added was 0.3 mass%. In Comparative Example 11, no surfactant was added.

[0032] The test results are shown in Table 3.

[0033] [Table 3]

[0034] As shown in Table 3, the nitrite ion content at a depth of 10 to 20 mm of the concrete repair liquids of Examples 5 and 6 was relatively high compared to Comparative Example 11, indicating that the permeability was good.

[0035] As described above, the concrete repair liquid of the present invention improved the penetration rate in both mortar and concrete specimens, demonstrating the effectiveness of the invention.

[0036] As described above, the concrete repair liquid according to this embodiment requires less work, has a fast rate of impregnation into concrete structures, and can be applied to a method of repairing concrete.

[0037] The concrete repair liquid and the concrete repair method according to the embodiment of the present invention have been described above, but the present invention is not limited to the above-described embodiment, and various other modifications are possible.

Claims

1. A concrete repair liquid comprising lithium nitrite, a surfactant, and water, wherein the surfactant is polyoxyethylene lauryl ether, the lithium nitrite content is 5 to 50 mass %, and the polyoxyethylene lauryl ether content is 0.05 to 0.4 mass %.

2. A method for repairing concrete, comprising impregnating concrete with the concrete repair liquid according to claim 1.

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