Method for attaching oxygen barrier sheet to tunnel concrete structure

Abstract

To provide a method for attaching an oxygen barrier sheet to a tunnel concrete structure, which is highly cost-effective and economically effective in preventing rust on an internal steel material.SOLUTION: In a method for attaching an oxygen barrier sheet to a tunnel concrete structure, an oxygen barrier sheet 1 is applied to an inner surface 10a of a tunnel concrete structure 10 with a closed cross section to block oxygen from entering the concrete and prevent rusting of an internal reinforcing steel material 11. The oxygen barrier sheet 1 is applied only to a predetermined area near the internal reinforcing steel material 11 on the inner surface 10a of the tunnel concrete structure 10, and is not applied to the remaining part of the inner surface 10a.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for attaching an oxygen barrier sheet to a tunnel concrete structure. [Background technology]

[0002] Conventionally, in order to prevent corrosion of reinforcing steel bars, such as internal reinforcing steel bars in concrete structures, paint has been applied to the surface of the concrete structure and then coated with resin, creating a shielding material that blocks the intrusion of air (oxygen) from the surface.

[0003] For example, Patent Document 1 discloses a structural member in which the surface of a concrete structure is coated with an epoxy resin paint to act as a shielding material and inhibit corrosion of reinforcing steel (see paragraphs

[0030] to

[0037] of the specification of Patent Document 1, Figure 2 of the drawings, etc.).

[0004] However, in the invention described in Patent Document 1, because the resin paint is applied on-site where the concrete structure is to be installed, there is a possibility of pinholes and other construction defects occurring, which allow oxygen to penetrate into the structure, making it impossible to completely prevent corrosion of the concrete structure. For this reason, it is conceivable to attach a resin sheet, which can be produced in a factory, to the surface of the concrete structure to block oxygen from penetrating into the interior of the concrete structure.

[0005] On the other hand, Patent Document 2 discloses that in order to prevent concrete pieces from peeling off from concrete structures such as bridges, tunnels, and elevated roads, a multilayer sheet for preventing concrete from peeling off is adhered to the surface of the concrete structure to reinforce the structure (see claim 1 in the claims of Patent Document 2, paragraphs

[0015] to

[0026] in the specification, and Figures 1 to 3 in the drawings, etc.).

[0006] However, the multilayer sheet for preventing concrete spalling described in Patent Document 2 is attached to the entire surface of a concrete structure where spalling is likely to occur in order to prevent concrete pieces from spalling, and although it is assumed that it also has a certain degree of oxygen blocking effect, the extent to which the resin sheet is attached and the extent of its rust prevention effect on the internal reinforcing steel material have not been confirmed.

[0007] Furthermore, Patent Document 3 discloses that a membrane structure building is covered with a laminated sheet in which a transparent fiber-reinforced resin sheet in which a glass fiber fabric is impregnated with a matrix resin is laminated with a fluororesin layer containing an ultraviolet absorber with excellent weather resistance, thereby imparting flame retardancy and weather resistance (see Claim 1 in the scope of claims of Patent Document 3, paragraphs

[0014] to

[0077] in the specification, Figure 1 in the drawings, etc.).

[0008] However, the laminated sheet described in Patent Document 3 is also attached to the entire surface of the structure to which it is attached in order to provide the structure with fire resistance and weather resistance, and like the multilayer sheet for preventing concrete spalling described in Patent Document 2, the area to which the laminated sheet is attached and the extent of its rust prevention effect on the internal reinforcing steel material have not been confirmed.

[0009] In particular, in tunnel concrete structures such as box culverts, which have a rectangular, circular, semicircular, or elliptical cross section and are blocked by ground or water, resulting in very little oxygen supply from the outside, the direction in which oxygen can be supplied is limited, so if a resin sheet were to be attached to the entire inner surface facing the closed internal space in order to block the intrusion of oxygen for rust prevention, the construction area would be unnecessarily large, resulting in increased costs. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-285764 [Patent Document 2] Patent No. 7007081 [Patent Document 3] Patent No. 6330810 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention was devised in consideration of the above-mentioned problems, and its object is to provide a method for attaching oxygen-blocking sheets to tunnel concrete structures that is cost-effective and can economically achieve rust prevention effects for internal steel materials. [Means for solving the problem]

[0012] The method for attaching oxygen-blocking sheets to tunnel concrete structures according to the first invention is a method for attaching oxygen-blocking sheets to the inner surface of a tunnel concrete structure with a closed cross section, thereby blocking oxygen from entering the concrete and preventing corrosion of the internal reinforcing steel, and is characterized in that the oxygen-blocking sheet is attached only to a predetermined area near the internal reinforcing steel on the inner surface of the tunnel concrete structure, and is not attached to the remaining part of the inner surface.

[0013] The second invention relates to a method for attaching an oxygen barrier sheet to a tunnel concrete structure, in the first invention, wherein the oxygen barrier sheet has an oxygen gas permeability of 0 mg / (cm after attachment. 2 · Day) or more 3.6 × 10 -3 mg / (cm 2 · The characteristic is that it is less than 100%.

[0014] The third invention relates to a method for attaching oxygen-blocking sheets to tunnel concrete structures, and is characterized in that, in the second invention, the specified range is a distance from the axis of the internal reinforcing steel to the end of the oxygen-blocking sheet of 50 mm to 200 mm.

[0015] The fourth invention relates to a method of attaching oxygen-blocking sheets to tunnel concrete structures, and is characterized in that, in the third invention, the specified range is a coverage rate of the inner surface of the section of the tunnel concrete structure where the internal reinforcing steel is arranged, of 31.6% or more and 75.4% or less.

[0016] The fifth invention relates to a method for attaching oxygen-blocking sheets to tunnel concrete structures, and is characterized in that, in the third invention, the specified range is from the axis of the internal reinforcing steel material to within 1 / 4 of the installation spacing of the internal reinforcing steel material. [Effects of the Invention]

[0017] According to the first to fifth inventions, the oxygen-blocking sheet is attached only to a specified area near the internal reinforcing steel on the inner surface of the tunnel concrete structure, and is not attached to the remaining part of the inner surface, so that rust prevention effects for the internal steel can be achieved cost-effectively and economically. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic perspective view showing a state in which an oxygen barrier sheet according to an embodiment of the present invention is attached to the inner surface of a tunnel concrete structure. [Figure 2] Figure 2 is a diagram showing the analytical conditions for the FEM analysis used to confirm the oxygen diffusion status in concrete. [Figure 3] FIG. 3 shows test specimens for Case 1(a) to Case 4(d). [Figure 4] FIG. 4 shows test specimens for Case 5(e) to Case 7(g). [Figure 5] FIG. 5 is a diagram showing the analysis results, with color gradation representing the amount of oxygen reached by the test specimen after a predetermined time. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a method for attaching an oxygen barrier sheet to a tunnel concrete structure according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0020] <Oxygen barrier sheet attachment method> The oxygen-barrier sheet attachment method for a tunnel concrete structure according to this embodiment (hereinafter simply referred to as the oxygen-barrier sheet attachment method) will be described using Figure 1. The oxygen-barrier sheet attachment method according to this embodiment is suitably applied to a tunnel concrete structure 10 such as a box culvert with a rectangular, circular, semicircular, or elliptical cross section, which is isolated by ground or water and has very little oxygen supply from the outside (outer surface). Figure 1 is a schematic perspective view showing an oxygen-barrier sheet 1 according to this embodiment attached to the inner surface of a tunnel concrete structure 10.

[0021] The oxygen-blocking sheet application method according to this embodiment is a method of applying an oxygen-blocking sheet 1 to the inner surface of a tunnel concrete structure 10 with a closed cross section to block oxygen from entering the concrete interior and prevent the internal reinforcing steel material 11 from rusting.

[0022] The oxygen barrier sheet according to the present invention is a sheet in which oxygen permeation per unit area over a certain period of time is equal to or less than a predetermined mass, and the oxygen barrier sheet 1 according to this embodiment is a special laminate sheet (HB sheet manufactured by Sho-Bond Material Co., Ltd.) in which reinforcing fibers are impregnated with an adhesive and then a weather-resistant resin is laminated. This oxygen barrier sheet 1 is attached to the surface of a tunnel concrete structure 10 with a two-component solventless epoxy resin primer 2, which is then cured, and then attached with a two-component epoxy resin impregnating adhesive 3. The entire sheet (taking into account the oxygen barrier properties of the adhesive and primer) has a thickness of 25.2 cm. 3 / m 2 ·24h·ATM.

[0023] Here, the atm is ignored as normal atmospheric pressure, and oxygen is assumed to be an ideal gas, with the mass per molecule being 32g / 22.4L=0.00143g / cm 3When calculated as above, the oxygen barrier performance of the oxygen barrier sheet 1 attached to the tunnel concrete structure 10 is 3.6 × 10 -3 mg / (cm 2 However, the oxygen barrier performance of the concrete surface coating specified by NEXCO is an oxygen gas permeability of 5.0 x 10 -2 mg / (cm 2 The oxygen barrier performance of the oxygen barrier sheet of the present invention attached to a tunnel concrete structure is determined to be 5.0 × 10 or less of the oxygen gas permeability specified in the same standard. -2 mg / (cm 2 ・day) or less. Of course, the lower limit is 0 mg / (cm 2 ·Day).

[0024] In the oxygen barrier sheet attachment method according to this embodiment, the oxygen barrier sheet 1 is attached only to a predetermined area near the internal reinforcing steel on the inner surface of the tunnel concrete structure 10, and the oxygen barrier sheet 1 is not attached to the rest of the inner surface. This is because the oxygen barrier sheet 1 can be used effectively, and the rust prevention effect on the internal steel can be achieved cost-effectively and economically.

[0025] Specifically, the specified range for attaching the oxygen barrier sheet 1 is a distance of 50 mm to 200 mm from the axis of the internal reinforcing steel material 11 of the tunnel concrete structure 10 to the end of the oxygen barrier sheet 1 (see Figures 3 and 4). From the analysis results described below, it is believed that when the protrusion distance of the oxygen barrier sheet 1 from the internal reinforcing steel material 11 is 45.8 mm or more, the speed at which oxygen reaches the structure can be slowed to a certain extent compared to full coverage, and that there is a corrosion-inhibiting effect due to oxygen blocking. On the other hand, if the protrusion distance exceeds 200 mm, there is not much difference from covering the entire inner surface of the tunnel concrete structure 10 with the oxygen barrier sheet 1, and it is not cost-effective or economical.

[0026] Furthermore, the specified range for attaching the oxygen barrier sheet 1 is preferably set so that the distance from directly above the axis of the internal reinforcing steel 11, which is the target of corrosion protection for the tunnel concrete structure 10, to the edge of the oxygen barrier sheet 1 is within 1 / 4 of the installation interval (pitch) of the internal reinforcing steel 11. This is because it is more cost-effective and economical than full coverage, and the analysis results described below show that a certain degree of oxygen barrier performance is achieved even when the oxygen barrier sheet 1 is attached only to a portion of the inner surface of the tunnel concrete structure 10. However, the specified range for attaching the oxygen barrier sheet 1 can also be set within 98 / 200 = 49 / 100 of the installation interval of the internal reinforcing steel 11. This is because a certain cost reduction effect is achieved compared to full coverage.

[0027] In other words, the specified range for attaching the oxygen barrier sheet 1 is a range in which the coverage rate of the inner surface of the section of the tunnel concrete structure 10 where the internal reinforcing steel material 11 to be rust-prevented is located is 31.6% to 75.4% or less. Similarly, from the analysis results described below, it is believed that when the coverage rate of the oxygen barrier sheet 1 of the inner surface of the section of the tunnel concrete structure 10 where the internal reinforcing steel material 11 is located is 31.6% or more, the speed at which oxygen reaches the tunnel concrete structure 10 can be slowed to a certain extent, and there is a corrosion-inhibiting effect due to oxygen blocking, but when the coverage rate exceeds 75.4%, it is not cost-effective and is not economical.

[0028] According to the oxygen-blocking sheet attachment method for tunnel concrete structures of this embodiment described above, the oxygen-blocking sheet 1 is attached only to a specified area near the internal reinforcing steel material 11 on the inner surface 10a of the tunnel concrete structure 10, and the oxygen-blocking sheet is not attached to the remaining part of the inner surface, so that rust prevention effects for the internal steel material can be achieved cost-effectively and economically.

[0029] <Analysis results> Next, we will explain the results of an FEM analysis using the finite element method, which was conducted to confirm the state of oxygen diffusion in concrete when the aforementioned oxygen barrier sheet 1 was attached partially or completely to reinforced concrete. This analysis was conducted by simulating the state of oxygen diffusion using FEM analysis, taking into account various conditions of prior art such as "Method for predicting the corrosion rate of rebar in concrete based on oxygen diffusion theory," published in the Proceedings of the Japan Society of Civil Engineers, No. 648 / V-47, 1-8, May 2000.

[0030] As shown in Figure 2, the analysis conditions were as follows: the initial oxygen concentration in the concrete was 9.31 × 10 6 ×g / cm 3 (See Table 1 in the paper) = 9.31 × g / m 3 , the oxygen diffusion coefficient of concrete is 10 5 cm 2 / s (see the paper above) = 10 9 m 2 / s, and the oxygen diffusion coefficient of the oxygen barrier sheet 1 is 10 13 m 2 / s, and the oxygen concentration permeability of the epoxy resin coating is 0g / m 3 Figure 2 is a diagram showing the analysis conditions for the FEM analysis used to confirm the oxygen diffusion status in concrete.

[0031] The analysis model was based on a test specimen measuring 200 mm wide x 350 mm long x 50 mm thick, with reinforcing bars (deformed steel bars) placed 55 mm from one end in the longitudinal direction with a covering thickness of 20 mm as internal reinforcing steel to be protected from rust, as shown in Figures 3 and 4. Figure 3 shows the test specimens for Cases 1(a) to 4(d), and Figure 4 shows the test specimens for Cases 5(e) to 7(g).

[0032] As shown in Figure 3, Case 1 (a) is a specimen without the oxygen barrier sheet 1 (coverage rate 0%), Case 2 (b) is a specimen covered with the oxygen barrier sheet 1 from one end of the specimen directly above the rebar to a position 65 mm from the end in the longitudinal direction (coverage rate 18.6%), Case 3 (c) is a specimen covered with the oxygen barrier sheet 1 from one end of the specimen 50 mm beyond the rebar to a position 110.8 mm from the end in the longitudinal direction (coverage rate 31.6%), and Case 4 (d) is a specimen covered with the oxygen barrier sheet 1 from one end of the specimen 100 mm beyond the rebar to a position 162.8 mm from the end in the longitudinal direction (coverage rate 31.6%). As shown in Figure 4, Case 5(e) was covered with oxygen barrier sheet 1 from one end of the test specimen 150 mm beyond the rebar to a position 213.7 mm in the longitudinal direction (coverage rate 61.0%), Case 6(f) was covered with oxygen barrier sheet 1 from one end of the test specimen 200 mm beyond the rebar to a position 264 mm in the longitudinal direction (coverage rate 75.4%), and Case 7(g) was covered entirely with oxygen barrier sheet 1 from one end of the test specimen 285 mm beyond the rebar to a position 285 mm in the longitudinal direction (coverage rate 100.0%).

[0033] The analysis results, which show the amount of oxygen that reaches the rebar after 500 hours (500 hours) to 2500 hours (2500 hours) for each specimen, are shown in Figure 5 and Table 1. Figure 5 is a diagram showing the analysis results of the amount of oxygen that reaches each specimen after a specified time using color gradation, and Table 1 is a table showing the analysis results of the amount of oxygen that reaches each part of each specimen after a specified time using numerical values.

[0034] [Table 1]

[0035] The corrosion area ratio of the fully coated specimen in Case 7(g) after 2,500 hours was 19.9%, and the amount of oxygen reached was 4.63 g / m 3 On the other hand, the corrosion area ratio of the specimen in Case 4(d), which was covered up to a position 100 mm beyond the rebar, was 44.4% after 2,500 hours, and the amount of oxygen reached was 6.60 g / m 3 It was.

[0036] In contrast, the amount of oxygen reached after 500 hours in Case 3(c), a specimen covered up to 50 mm beyond the rebar, was 2.90 g / m 3 The oxygen content of the specimen in Case 4(d), which was covered up to 100 mm beyond the rebar, after 1,000 hours was 3.22 g / m 3 In Case 5(e), the amount of oxygen reached after 1,500 hours in the specimen coated up to 150 mm beyond the rebar was 3.72 g / m 3 The oxygen content of the specimen in Case 6(f), which was covered up to 200 mm beyond the rebar, after 2,000 hours was 4.27 g / m 3 In both cases, the amount of oxygen reached after 2,500 hours for the fully coated specimen in Case 7(g) was 4.63 g / m 3 This indicates that the oxygen barrier performance is at a certain level compared to the case of full coating.

[0037] Therefore, as described above, the predetermined range for attaching the oxygen barrier sheet 1 in the oxygen barrier sheet attachment method according to the embodiment of the present invention is a distance of 50 mm to 200 mm from the axis of the reinforcing bar (internal reinforcing steel material 11) to the end of the oxygen barrier sheet 1 (see Figures 3 and 4). In terms of coverage, the predetermined range for attaching the oxygen barrier sheet 1 is a coverage range of 31.6% to 75.4% of the inner surface of the section where the reinforcing bars of the concrete structure are placed.

[0038] The specified range for attaching the oxygen barrier sheet 1 is set so that the distance from the axis of the reinforcing bars, which are the object of rust prevention protection in the tunnel concrete structure, to the edge of the oxygen barrier sheet 1 is within 1 / 4 of the spacing between the reinforcing bars. This is because a certain cost reduction effect is observed compared to when the entire surface is covered.

[0039] In other words, according to the above-mentioned oxygen-blocking sheet application method, the oxygen-blocking sheet 1 is applied only to a specified area near the reinforcing bars on the inner surface of the tunnel concrete structure, and the oxygen-blocking sheet is not applied to the remaining part of the inner surface, so that rust prevention effects on the internal steel material can be achieved cost-effectively and economically.

[0040] Although the method for attaching an oxygen barrier sheet to a tunnel concrete structure according to the embodiment of the present invention has been described in detail above, the above-described and illustrated embodiments are merely specific examples for carrying out the present invention, and therefore the technical scope of the present invention should not be construed as being limited by these. [Explanation of symbols]

[0041] 1: Oxygen barrier sheet 2:2-component solvent-free epoxy resin primer (primer) 3: Two-component epoxy resin impregnated adhesive (adhesive) 10: Tunnel concrete structure (concrete structure) 10a:Inside 11: Steel bars (internal reinforcing steel)

Claims

1. An oxygen barrier sheet attachment method for a tunnel concrete structure, in which an oxygen barrier sheet is attached to the inner surface of a tunnel concrete structure whose cross section is closed, to block oxygen from entering the concrete interior and prevent rusting of the internal reinforcing steel material, The oxygen barrier sheet is attached only to a predetermined area near the internal reinforcing steel material on the inner surface of the tunnel concrete structure, and the oxygen barrier sheet is not attached to the remaining part of the inner surface. A method for attaching oxygen-blocking sheets to tunnel concrete structures, characterized by the above.

2. The oxygen barrier sheet has an oxygen gas permeability of 0 mg / (cm 2 ・Sun) or more 3.6 x 10 -3 mg / (cm 2 ・Days) or less 2. The method for attaching an oxygen barrier sheet to a tunnel concrete structure according to claim 1,

3. The predetermined range is a distance from the axis of the internal reinforcing steel material to the end of the oxygen barrier sheet of 50 mm to 200 mm.

3. The method for attaching an oxygen barrier sheet to a tunnel concrete structure according to claim 2, wherein

4. The predetermined range is a coverage rate of the inner surface of the section of the tunnel concrete structure where the internal reinforcing steel material is arranged, of 31.6% or more and 75.4% or less.

4. The method for attaching an oxygen barrier sheet to a tunnel concrete structure according to claim 3,

5. The predetermined range is from the axis of the internal reinforcing steel material to within 1 / 4 of the installation interval of the internal reinforcing steel material.

4. The method for attaching an oxygen barrier sheet to a tunnel concrete structure according to claim 3,

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