Method for installing an anode for cathodic protection and structure for cathodic protection

Abstract

To provide a method of installing an anode for electrolytic protection suitable for electrolytic protection of concrete by an external power supply system, capable of easily installing the anode for electrolytic protection without damaging the concrete and without short-circuiting with conductive materials in the concrete.SOLUTION: Formwork auxiliary materials 12 having a longitudinal direction in one direction are installed in pairs at a predetermined interval on a surface of concrete 10 housing reinforcing bars functioning as cathodes for electrolytic protection. Conductive mortar is applied between a pair of the formwork auxiliary materials 12. Further, a primary anode 16 is arranged so as to be embedded in the conductive mortar. The conductive mortar is dried to form a conductive mortar layer 14 including the primary anode 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a method for installing an anode for cathodic protection and an anode structure for cathodic protection, and more particularly to a method for installing an anode for cathodic protection and an anode structure suitable for cathodic protection of concrete using an external power supply system. [Background technology]

[0002] As for methods of cathodic protection of concrete using an external power supply, methods in which the primary anode is placed on a surface, linearly, or at a point are generally known. The method of placing the primary anode on a surface is not widely used these days due to issues such as poor adhesion to the overlay mortar and the need to remove a large portion of the protective coating applied to the concrete surface.

[0003] The point-type arrangement method offers the best ease of installation among the three methods, but it is also prone to problems caused by design errors, such as an insufficient number of primary anodes. For this reason, the number of times the point-type arrangement method is used has decreased recently.

[0004] The linear arrangement method is the most widely adopted method recently because it does not require the complete removal of the protective coating mentioned above and offers excellent workability. As an example of a linear arrangement method, Patent Document 1 below discloses a method in which grooves are dug in the concrete and primary anodes are embedded within them. This method allows for the stable installation of primary anodes on the surface of the concrete. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-371390 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the above construction method described in Patent Document 1 inevitably causes some damage to the concrete when embedding the primary anode. Furthermore, if conductive foreign matter, such as reinforcing bar binding wire, is exposed in the groove created to embed the primary anode, the primary anode may short-circuit with that foreign matter, potentially accelerating the galvanic corrosion of the concrete.

[0007] This disclosure was made to solve the problems described above, and its primary objective is to provide a method for installing an anode for cathodic protection that allows for the simple installation of an anode for cathodic protection without damaging the concrete or short-circuiting it with conductive materials within the concrete. Furthermore, a second objective of this disclosure is to provide an anode structure for cathodic protection that can be easily installed without damaging concrete and has an anode that does not short-circuit with conductive material embedded in concrete. [Means for solving the problem]

[0008] The first aspect is a method for installing an anode for cathodic protection to achieve the above objective by realizing cathodic protection of concrete using an external power supply system, The process involves installing formwork support materials, each having a longitudinal direction in one direction, in pairs at predetermined intervals on the surface of concrete containing reinforcing bars that function as the cathode for the aforementioned cathodic protection, The process involves applying conductive mortar between the pair of formwork support materials, The steps include: positioning the primary anode so as to be embedded in the conductive mortar; The steps include drying the conductive mortar to form a conductive mortar layer containing the primary anode, It is desirable to include it.

[0009] Furthermore, the second embodiment is an anode structure for cathodic protection to achieve cathodic protection of concrete using an external power supply system, A conductive mortar layer is formed on the surface of the concrete containing the reinforcing steel that functions as the cathode for the aforementioned cathodic protection, with the longitudinal direction being one of the directions. The conductive mortar layer comprises a primary anode having a longitudinal direction in the one direction, The conductive mortar layer is Having an electrical resistivity of 0.5 kΩcm or less, It is desirable that either only one is formed on the surface of the concrete, or that multiple are formed on the surface of the concrete at intervals of 50 cm to 2 m. [Effects of the Invention]

[0010] According to the first or second aspect of this disclosure, an anode for cathodic protection can be easily installed without damaging the concrete or short-circuiting it with conductive materials within the concrete. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an overview of the cathodic protection anode structure of Embodiment 1 of the present disclosure. [Figure 2] This figure shows an overview of the method for installing an anode for cathodic protection according to Embodiment 1 of this disclosure. [Figure 3] This is a flowchart illustrating the flow of the method for installing an anode for cathodic protection according to Embodiment 1 of this disclosure. [Figure 4] Figure 4(A) shows a first example of a formwork support material that can be used in Embodiment 1 of this disclosure. Figure 4(B) shows a second example of a formwork support material that can be used in Embodiment 1 of this disclosure. Figure 4(C) shows a third example of a formwork support material that can be used in Embodiment 1 of this disclosure. Figure 4(D) shows a fourth example of a formwork support material that can be used in Embodiment 1 of this disclosure. [Figure 5] This figure illustrates an example of a conductive mortar composition that can be used in Embodiment 1 of this disclosure. [Figure 6] Figure (1) illustrates the conditions for measuring the characteristics of the cathodic protection installation structure of Embodiment 1 of this disclosure. [Figure 7] Figure (2) illustrates the conditions for measuring the characteristics of the cathodic protection installation structure of Embodiment 1 of this disclosure. [Figure 8] FIG. 8(A) shows the characteristics of the first comparative example (the formulation of No. 1 shown in FIG. 5). FIG. 8(B) shows the characteristics of the second comparative example (the formulation of No. 2 shown in FIG. 5). FIG. 8(C) shows the characteristics of the first structural example (the formulation of No. 6 shown in FIG. 5) that can be used in Embodiment 1 of the present disclosure. FIG. 8(D) shows the characteristics of the second structural example (the formulation of No. 8 shown in FIG. 5) that can be used in Embodiment 1 of the present disclosure.

Mode for Carrying Out the Invention

[0012] Embodiment 1. [Configuration of Embodiment 1] FIG. 1 is a diagram showing an overview of the electric anti-corrosion anode structure of Embodiment 1 of the present disclosure. The structure shown in FIG. 1 includes a structure of concrete 10. The concrete 10 contains reinforcing bars not shown. These reinforcing bars are arranged inside the concrete 10, for example, in a mesh shape, in order to obtain a desired strength.

[0013] FIG. 1 shows a state in which two formwork auxiliary materials 12 are installed on the surface of the concrete 10 so as to be paired. The formwork auxiliary material 12 is a rod-shaped member having a longitudinal direction in one direction. The pair of formwork auxiliary materials 12 are arranged such that the distance between them is a constant value of about 20 to 50 mm. Further, the formwork auxiliary material 12 has a height of about 10 mm.

[0014] A conductive mortar layer 14 is formed between the paired formwork auxiliary materials 12. The conductive mortar layer 14 is configured such that its electrical resistivity is 0.5 kΩcm or less. Further, since the conductive mortar layer 14 is formed between the formwork auxiliary materials 12, it has a width of 20 to 50 mm and a height of about 10 mm.

[0015] A primary anode 16 is embedded in the conductive mortar layer 14. The primary anode 16 is composed of, for example, a titanium ribbon mesh anode, a titanium grid anode, an MMO titanium tape anode, a platinum-based anode, or a platinum alloy wire anode. The primary anode 16 is given a width of, for example, about 10 mm. The width of the conductive mortar layer 14, that is, a width of about 20 to 50 mm, is set to be at least twice the width of the primary anode 16.

[0016] In this embodiment, the conductive mortar layer 14 functions as a secondary anode for achieving cathodic protection of the concrete 10 using an external power supply. In other words, both the primary anode 16 and the conductive mortar layer 14 function as anodes for achieving the above-mentioned cathodic protection.

[0017] The reinforcing steel embedded in the concrete 10 is subjected to a corrosive environment, for example, when water seeps into the concrete 10. When corrosion of the reinforcing steel progresses in such an environment, electron movement occurs between the concrete 10 and the reinforcing steel. By applying a voltage to the concrete 10 with the reinforcing steel as the cathode to prevent this electron movement, the corrosion of the reinforcing steel can be prevented. In this embodiment, the function of cathodic protection to prevent corrosion of the reinforcing steel is realized by applying a voltage from an external power source between the primary anode 16 and the reinforcing steel.

[0018] [Construction method of Embodiment 1] The following describes the construction method for forming the structure shown in Figure 1, with reference to Figures 2 to 4. Figure 2 shows that in this embodiment, the primary anode 16 is embedded in the conductive mortar layer 14. Figure 3 is a flowchart illustrating the flow of the cathodic protection anode installation method in this embodiment.

[0019] As shown in Figure 3, in the construction method of this embodiment, first, the anticorrosive coating applied to the surface of the concrete 10 is removed (step 100). Generally, the surface of the concrete 10 is coated with anticorrosive coating. In order to efficiently apply voltage between the anode and cathode of the electrochemical protection, that is, between the conductive mortar layer 14 and the primary anode 16 in this embodiment and the reinforcing steel, it is desirable that the conductive mortar layer 14 be in direct contact with the concrete 10 without the anticorrosive coating in between. For this reason, in step 100, the anticorrosive coating is removed from the area where the conductive mortar layer 14 is to be installed.

[0020] In this embodiment, multiple conductive mortar layers 14 are arranged on the surface of the concrete 10 at 50 cm intervals. Therefore, the peeling treatment in step 100 is performed at multiple locations on the surface of the concrete 10 at 50 cm intervals.

[0021] Once the above process is complete, formwork support materials 12 are then installed on the surface of the concrete 10 (step 102). The formwork support materials 12 are placed on both sides of the area from which the anticorrosion coating has been removed. Specifically, in this embodiment, multiple pairs of formwork support materials 12 are installed on the surface of the concrete 10 at 50 cm intervals.

[0022] Examples of formwork support materials 12 that can be used in this embodiment are shown in Figure 4. These are all general-purpose products that can be easily obtained on the market. However, the formwork support materials 12 are not limited to these, as long as they can be easily fixed to the surface of the concrete 10.

[0023] Figure 4(A) is a perspective view of the "adhesive-backed backing material" 12-1. The adhesive-backed backing material is a rectangular prism material having an adhesive surface on one side to which adhesive is applied. The adhesive surface is covered with release paper that can be easily peeled off. The adhesive-backed backing material 12-1 can function as a formwork support material 12 by peeling off the release paper and positioning it so that the adhesive surface is in contact with the concrete 10.

[0024] Figure 4(B) is a perspective view of the "plastic molding material" 12-2. Figure 4(C) is a perspective view of the L-shaped plastic angle 12-3. Figure 4(D) is a perspective view of the T-shaped plastic angle 12-4. These can be attached to the corresponding parts of the concrete 10 with adhesive and function as formwork support materials 12.

[0025] As shown in Figure 3, once the formwork support material 12 is installed, the foundation of the conductive mortar layer 14 is formed (step 104). Specifically, the conductive mortar, before it dries, is embedded between the pair of formwork support materials 12 using a trowel, spatula, caulking gun, etc. It is desirable to embed the primary anode 16 closer to the concrete 10 than the center of the conductive mortar layer 14. For this reason, it is desirable that the foundation formed in step 104 be thinner than 5 mm.

[0026] Next, the primary anode 16 is embedded in the base portion of the conductive mortar layer 14 (step 106). Then, the finishing treatment of the conductive mortar layer 14 is carried out, that is, the work of applying conductive mortar in layers on top of the primary anode 16 between the pair of formwork support materials 12 is performed (step 108).

[0027] Subsequently, after waiting for the conductive mortar layer 14 to dry and harden, the formwork support material 12 is removed from the surface of the concrete 10 (step 110). This results in a structure on the surface of the concrete 10 in which multiple dried and hardened conductive mortar layers 14 are arranged at 50 cm intervals.

[0028] In this disclosure, the formwork support material 12 is removed after the conductive mortar layer 14 has hardened, but this disclosure is not limited to this. If the formwork support material 12 is an adhesive backing material 12-1, a plastic molding material 12-2, or an L-shaped plastic angle 12-3, the process in step 110 above may be omitted, and the formwork support material 12 may be left on the surface of the concrete 10.

[0029] [Conductive mortar mix design] In this embodiment, it is necessary to adjust the composition of the conductive mortar layer 14 so that the electrical resistivity (volume resistivity) is 0.5 kΩcm or less. The electrical resistivity of the conductive mortar can be adjusted by the amount of admixture mixed into the base material. As admixtures, metal-based, carbon-based, and metal oxide-based conductive fillers, or ionic conductive electrolytes can be used. Specifically, graphite can be used as a conductive filler. As electrolytes, alkali metal salts or alkaline earth metal salts of chlorides, bromides, nitrates, nitrites, and organic carboxylates can be used alone or in combination.

[0030] Figure 5 shows the relationship between the mixing ratio and electrical resistivity when an electrolyte is used as an admixture. Figures 5-5 show comparative examples that cannot be used in this embodiment. On the other hand, figures 6-10 show mixing ratios that can be used in this embodiment. However, figures 6-10 in Figure 5 are merely examples of mixing ratios, and the mixing ratios of the conductive mortar used in this embodiment are not limited to these. As described above, conductive fillers can be used as admixtures in addition to electrolytes, and conductive mortar may be adjusted by other mixing ratios as long as an electrical resistivity of 0.5 kΩcm or less is achieved with admixtures below the solubility limit.

[0031] [Measurement results of corrosion protection current distribution] Next, with reference to Figures 6 to 8, the relationship between the electrical resistivity of the conductive mortar layer 14 and the corrosion-preventive current distribution flowing inside the concrete 10 will be explained.

[0032] Figure 6 shows the structure of the concrete specimen 10 used to measure the corrosion protection current distribution. The specimen shown in Figure 6 has a nominal strength of 24 N / mm 2 Slump 12cm, air volume 4.5%, chloride ion content 10kg / m 3 It is made using concrete and D13 deformed reinforcing bars. This test specimen is formed into a square with sides of 1000 mm.

[0033] The mix proportion of the test piece of concrete 10 is specifically as follows. W / C: 59.5% s / a: 46.4% Unit amount of W: 162 kg / m 3 C: 272 kg / m 3 S: 856 kg / m 3 G: 1023 kg / m 3 Admixture: 272 kg / m 3 Salt content: 5 kg / m 3

[0034] As shown in FIG. 6, reinforcing bars 18 are arranged in a grid pattern in the test piece of concrete 10. The vertical reinforcing bars 18 and the horizontal reinforcing bars 18 are arranged at intervals of 200 mm respectively. A part of the reinforcing bar 18 extends outside the test piece for energization.

[0035] FIG. 7 shows the arrangement of the anode 20 and the electrode 22 provided in the test piece of concrete 10. The anode 20 is composed of a conductive mortar layer 14 and a primary anode 16 embedded therein. The anode 20 is provided at a position 50 mm away from one side of the test piece and parallel to that side. Therefore, it is separated by 950 mm from the opposite side to the anode 20.

[0036] Nine electrodes 22 are arranged in the test piece. As shown in the figure, the electrodes 22 are arranged at equal intervals within a square area of 600 mm on one side located at the center of the test piece. The electrodes 22 are provided to measure the potential (hereinafter referred to as "polarization amount") at the site where each is arranged.

[0037] FIG. 8 shows that the current density between the anode 20 and the reinforcing bar 18 is 2 mA / m 2The distribution of polarization observed in the concrete 10 test specimen when a voltage is applied accordingly is shown. Specifically, Figures 8(A) and (B) show the polarization amounts when comparative examples No. 1 and No. 2 shown in Figure 5 are used as the conductive mortar layer 14, respectively. Figures 8(C) and (D) show the polarization amounts when invention No. 6 and No. 8 shown in Figure 5 are used as the conductive mortar layer 14.

[0038] In Figures 8(A) to 8(D), "V**" indicates that the polarization is between (**)mV and {(**)+20}mV. For example, "V20" in Figure 8(A) indicates that the polarization of the area with that sign is between 20 and 40mV. Similarly, "V40" indicates that the polarization of the area with that sign is between 40 and 60mV.

[0039] In external power supply type cathodic protection, the control standard is that the polarization amount must be 100mV or more in response to the above voltage application. In the distribution shown in Figure 8(A), only about 1 / 3 of the test specimen (V140, V120, V100) meets this standard. Also, in the distribution shown in Figure 8(B), only about 1 / 2 of the test specimen (V160, V140, V120, V100) meets the above standard.

[0040] In contrast, Figures 8(C) and 8(D) show that a polarization of 100 mV or more can be obtained in all areas of the test specimen. In other words, with the anode structure of this embodiment, in which the electrical resistance of the conductive mortar layer 14 is 0.5 kΩcm or less, a polarization that satisfies the control standard can be generated even at a distance of 1 m from the anode 20. For this reason, with the anode structure of this embodiment, a sufficient corrosion protection effect can be obtained over the entire surface of the concrete 10 even if the distance between anodes 20 is up to about 2 m.

[0041] As described above, in this embodiment, anodes 20, that is, conductive mortar layer 14 and primary anode 16, are arranged on the surface of the concrete 10 at 50 cm intervals. Therefore, with this structure, a sufficient corrosion protection effect can be obtained over the entire surface of the concrete 10 with ample margin. Note that the 50 cm interval is a preferred value set with a margin, and the interval can be widened to 1 m, or even up to 2 m.

[0042] [Effects of Embodiment 1] As described above, the anode installation method of this embodiment allows for the installation of the cathodic protection anode 20 without digging a groove in the concrete 10. It is far easier to attach the formwork support material 12 to the surface of the hard concrete 10 and fill it with mortar using a trowel, spatula, caulking gun, etc., than to dig a groove in the hard concrete 10. For this reason, according to this embodiment, the anode 20 can be installed with high workability without damaging the concrete 10 or causing a short circuit with the reinforcing bars 18.

[0043] Furthermore, according to the anode installation method of this embodiment, since the conductive mortar layer 14 has high conductivity, the installation spacing of the primary anodes 16 can be significantly wider than conventional spacings. Specifically, by setting the electrical resistivity of the conductive mortar layer 14 to 0.5 kΩcm or less, the spacing of the primary anodes 16, which is generally 20 to 30 cm, can be widened to 50 to 100 cm or more, or approximately three times or more. As a result, both material costs and construction costs are reduced, and the construction costs of cathodic protection methods, which are generally considered to be expensive repair methods, can be significantly reduced.

[0044] Furthermore, since the spacing between the primary anodes 16 can be significantly wider than in the current configuration, this embodiment allows for a cleaner appearance of the concrete structure. Moreover, for short beams with a width of approximately 50 to 100 cm, sufficient effect can be obtained by installing just one primary anode 16.

[0045] [Modified example of Embodiment 1] Incidentally, in the above-described embodiment 1, the base portion of the conductive mortar layer 14 formed in the lower layer of the primary anode 16 and the finishing portion of the conductive mortar layer 14 placed on top of the primary anode 16 are made of the same material. However, this disclosure is not limited to this, and the base portion and the finishing portion may be made of different materials.

[0046] In other words, the base portion of the conductive mortar layer 14 is in contact with the concrete 10 below, making it susceptible to damage such as cracks occurring in the underlying concrete 10. When cracks or other damage occur in the conductive mortar layer 14 as a result, anode products, which have a color similar to rust on steel, are easily formed. Although anode products do not significantly affect the effectiveness of cathodic protection, their rust-like appearance can easily give the impression that cathodic protection is not working, leading to complaints from clients.

[0047] In the structure of this embodiment, the base portion of the conductive mortar layer 14 may be made of a material with excellent crack-following properties. Specifically, a re-emulsifying powder resin or a liquid polymer dispersion may be used for the base portion. Alternatively, a lightweight aggregate such as obsidian perlite or perlite may be used for the base portion. Using such a material can reduce the static elastic modulus of the base portion and suppress the formation of anode products.

[0048] Furthermore, in the above-described embodiment 1, the conductive mortar layer 14 is finished so that its cross-section is rectangular, but this disclosure is not limited to this. For example, the conductive mortar layer 14 may be finished so that its cross-section is curved, square, trapezoidal, semicircular, or a combination thereof.

[0049] Furthermore, in the above-described embodiment 1, multiple conductive mortar layers 14 are arranged at 50 cm intervals, but this disclosure is not limited thereto. For example, conductive mortar may be uniformly applied to the surface of the concrete 10 to form a conductive mortar layer 14 that covers the entire surface of the concrete 10. Alternatively, an aqueous solution containing the above-described electrolyte at a concentration of 50% by weight or more may be uniformly applied to the surface of the concrete 10. Moreover, an aqueous solution of 1-10% by weight of Nafion with 1-10% by weight of photocatalyst added may be applied to the surface of the concrete 10 alone or in combination with the above-described electrolyte aqueous solution. [Explanation of Symbols]

[0050] 10 Concrete 12 Formwork support materials 14. Conductive mortar layer 16 Primary anode 18 Reinforcement bars 20 Anode

Claims

1. A method for installing an anode for cathodic protection to achieve cathodic protection of concrete using an external power supply system, The process involves installing formwork support materials, each having a longitudinal direction in one direction, in pairs at predetermined intervals on the surface of concrete containing reinforcing bars that function as the cathode for the aforementioned cathodic protection, The process involves applying conductive mortar between the pair of formwork support materials, The steps include: positioning the primary anode so as to be embedded in the conductive mortar; The steps include drying the conductive mortar to form a conductive mortar layer containing the primary anode, A method for installing an anode for cathodic protection, including the installation method.

2. The step of applying the conductive mortar is, A step of forming the foundation portion with the conductive mortar so as to be in contact with the concrete, The process includes forming a finishing portion with conductive mortar on the base portion and the primary anode placed thereon, The method for installing an anode for cathodic protection according to claim 1, wherein the base portion is made of a material with a lower static elastic modulus than the finishing portion, thereby providing excellent ability to follow cracks in the concrete.

3. The method for installing an anode for cathodic protection according to claim 1, wherein the conductive mortar layer has an electrical resistivity of 0.5 kΩcm or less.

4. The method for installing an anode for cathodic protection according to claim 3, wherein in the step of installing the pair of formwork support materials, a plurality of pairs of the formwork support materials are installed on the surface of the concrete at intervals of 50 cm to 2 m.

5. A method for installing an anode for cathodic protection according to any one of claims 1 to 4, further comprising the step of removing the formwork auxiliary material from the surface of the concrete after the conductive mortar layer has been formed.

6. An anode structure for cathodic protection to achieve cathodic protection of concrete using an external power supply system, A conductive mortar layer is formed on the surface of the concrete containing the reinforcing steel that functions as the cathode for the aforementioned cathodic protection, with the longitudinal direction being one of the directions. The conductive mortar layer comprises a primary anode having a longitudinal direction in the one direction, The conductive mortar layer is Having an electrical resistivity of 0.5 kΩcm or less, An anode structure for cathodic protection, which is formed as a single unit on the surface of the concrete, or which is formed as a multiple unit on the surface of the concrete at intervals of 50 cm to 2 m.

7. The conductive mortar layer is The foundation portion in contact with the aforementioned concrete, Including the base portion and the finishing portion formed on the primary anode, The cathodic protection anode structure according to claim 6, wherein the base portion is made of a material with a lower static elastic modulus than the finishing portion, thereby providing excellent crack-following properties for the concrete.

8. The cathodic protection anode structure according to claim 6 or 7, comprising a pair of formwork auxiliary materials arranged to sandwich the conductive mortar layer.

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