Method for evaluating salt damage deterioration in concrete structure, method for predicting and evaluating alkali-silica reaction in concrete structure and electrochemical corrosion control method

Abstract

To provide a salt damage deterioration evaluation method for concrete structures for evaluating a salt damage deterioration state of a steel material disposed in concrete of the concrete structure, an alkali silica reaction prediction / evaluation method for concrete structures capable of predicting and evaluating a progress degree of an alkali silica reaction (ASR) of the concrete structure by a simple method, and an electrochemical corrosion control method for determining necessity of energization processing by acquiring a corrosion state of the concrete structure and the progress degree of the ASR.SOLUTION: A method for evaluating salt damage deterioration in a concrete structure includes the steps of: collecting fine powder obtained by pulverizing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete; preparing a mixture formed by mixing the fine powder with pure water; measuring an ion composition of the mixture; and calculating a Cl- / OH- molar ratio from the ion composition of the measured mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating salt damage deterioration of a concrete structure, a method for predicting and evaluating alkali-silica reaction of a concrete structure, and an electrochemical corrosion prevention method. [Background technology]

[0002] Traditionally, concrete structures such as reinforced concrete (RC) and prestressed concrete (PC), in which reinforcing bars or prestressing steel bars are placed within concrete, have been used to construct civil engineering structures such as roads and railways, specifically bridge substructures, bridge girders, underground or semi-underground structures such as tunnels, and culverts. Reinforced concrete (RC) is a building material that combines high compressive strength with high tensile strength reinforcing bars, thereby achieving both compressive and tensile strength. Prestressed concrete (PC) is a building material in which prestressing steel bars (PC wires, PC bars, PC strands, etc.) are placed within the concrete, creating a situation in which a reverse force is applied before the load is applied to the concrete member, thereby preventing tensile stress from being generated in the concrete and suppressing cracking.

[0003] In concrete structures, salt damage can cause corrosion of the steel materials placed inside the concrete. This corrosion of the steel materials accelerates the deterioration of the concrete structure, significantly reducing its durability. Therefore, electrochemical repair methods without destruction have been proposed and implemented as methods for repairing deteriorated concrete structures (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6586000 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-227578 Summary of the Invention [Problem to be solved by the invention]

[0005] By carrying out repairs using electrochemical methods such as those disclosed in Patent Documents 1 and 2, desalination of concrete structures can be carried out non-destructively and efficiently. However, in electrochemical methods, alkali metal ions such as sodium contained in concrete are attracted to the cathode in the concrete and accumulate around the reinforcing steel (steel), which is the cathode, and alkali-silica reaction (hereinafter sometimes referred to as "ASR") may begin. In concrete structures such as bridges, there are areas where the amount of rebar is different, so there are areas where the rebar (steel) is dense and areas where the rebar (steel) is sparse. In areas where the rebar (steel) is sparse, the amount of current per rebar surface area is high, so alkali ions accumulate in the concrete near the rebar (steel), and hydroxide ions (OH - ) is produced, creating a highly alkaline environment. As a result, when ASR accelerates, alkaline silica gel is produced, which absorbs water and expands, causing problems such as cracking, peeling, and spalling of the concrete.

[0006] Based on the above, the present invention aims to provide a salt damage deterioration evaluation method for evaluating the salt damage deterioration state of steel materials placed within the concrete of a concrete structure, a method for predicting and evaluating alkali-silica reaction (ASR) that can grasp the predictive evaluation of the progress of the alkali-silica reaction (ASR) in a concrete structure using a simple method, and an electrochemical corrosion protection method for determining the need for electrical treatment by grasping the corrosion state and the progress of ASR in a concrete structure. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the present inventors have come up with the following invention and found that the above problems can be solved. [1] A process of collecting fine powder obtained by crushing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete, a process of preparing a mixed solution by mixing the fine powder with pure water, a process of measuring the ion composition of the mixed solution, and a process of determining Cl from the measured ion composition of the mixed solution. - / OH - and calculating the molar ratio. [2] The method for evaluating salt-damaged deterioration of a concrete structure according to [1], wherein the mass ratio of the fine powder to the pure water in the mixed liquid is 1:1 to 1:3. [3] The method for evaluating salt damage deterioration of a concrete structure according to [1] or [2], wherein the particle size of the fine powder is 150 μm or less. [4] The above Cl - / OH - The molar ratio is obtained by measuring the ionic composition of the mixed solution made from the fine powder collected from the concrete near the reinforcing bars of the concrete structure. A method for evaluating salt damage deterioration of a concrete structure described in any one of [1] to [3]. [5] The above Cl - / OH - The method for evaluating salt-damage deterioration of a concrete structure according to any one of [1] to [4], further comprising the step of evaluating the degree of salt-damage deterioration of the concrete structure based on the molar ratio. [6] A process of collecting fine powder obtained by crushing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete, a process of preparing a mixed solution by mixing the fine powder with pure water, a process of measuring the ion composition of the mixed solution, and a process of detecting Li from the measured ion composition of the mixed solution. + / Na + and calculating the molar ratio. [7] The method for predicting and evaluating an alkali-silica reaction of a concrete structure according to [6], wherein a mass ratio of the fine powder to the pure water in the mixed solution is 1:1 to 1:3. [8] The method for predicting and evaluating alkali-silica reaction of a concrete structure according to [6] or [7], wherein the particle size of the fine powder is 150 μm or less. [9] Li + / Na + The method for predicting and evaluating alkali-silica reaction of a concrete structure according to any one of [6] to [8], wherein the molar ratio is obtained by measuring the ion composition of the mixed solution using the fine powder collected from the concrete near the surface of the concrete structure.

[10] Li + / Na + The method for predicting and evaluating alkali-silica reaction of a concrete structure according to any one of [6] to [9], further comprising a step of evaluating prediction of alkali-silica reaction of the concrete structure based on a molar ratio.

[11] An electrochemical corrosion protection method comprising an anode material and an electrolyte solution holding material holding an electrolyte solution, an electrode installed on the surface of the concrete as an external electrode, a reinforcing bar embedded inside the concrete as an internal electrode, and applying a direct current between the external electrode and the internal electrode, wherein the Cl calculated by the method for evaluating salt damage degradation of a concrete structure according to any one of [1] to [5] is - / OH - The Li molar ratio calculated by the alkali-silica reaction prediction evaluation method for concrete structures according to any one of [6] to

[10] + / Na + and a step of evaluating the current treatment based on at least one of the molar ratios.

[12] The above Cl - / OH - The electrochemical corrosion protection method according to

[11] , wherein the current treatment is evaluated as completed when the molar ratio is 1.5 or less, and the current treatment is evaluated as incomplete when the molar ratio is greater than 1.5.

[13] Li + / Na + The electrochemical corrosion protection method according to

[11] or

[12] , wherein the current treatment is evaluated as completed when the molar ratio is 1.0 or more, and the current treatment is evaluated as incomplete when the molar ratio is less than 1.0. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a salt damage deterioration evaluation method for evaluating the salt damage deterioration state of steel materials placed within the concrete of a concrete structure, an alkali silica reaction prediction evaluation method that can grasp the prediction evaluation of the progress of alkali silica reaction (ASR) in a concrete structure in a simple manner, and an electrochemical corrosion protection method that determines the need for electrical current treatment by grasping the corrosion state and the progress of ASR in a concrete structure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a partial cross-sectional view of an electrochemical corrosion protection system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in more detail below with reference to embodiments.

[0011] [Method for evaluating salt damage deterioration of concrete structures] The method for evaluating salt damage deterioration of a concrete structure according to an embodiment of the present invention includes a step of collecting fine powder, a step of preparing a mixed solution, a step of measuring the ion composition, and a step of measuring Cl - / OH - and calculating the molar ratio. The method for evaluating salt-damage deterioration of a concrete structure according to an embodiment of the present invention may further include a step of evaluating the degree of salt-damage deterioration.

[0012] <Process for collecting fine powder> The step of collecting fine powder is a step of collecting fine powder obtained by pulverizing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete. In the step of collecting fine powder, the concrete of the concrete structure to be measured is pulverized using a pulverizer such as a drill to generate and collect fine concrete powder. In this specification, "fine powder" refers to particles with a particle size of 150 μm or less.

[0013] The concrete fine powder may be collected from any location in the concrete of a concrete structure, but when evaluating the corrosion of steel materials placed in concrete, it is preferable to use fine powder collected by crushing concrete near the reinforcing bars.In this specification, "concrete near the reinforcing bars" refers to concrete within 10 mm of the reinforcing bars in a concrete structure.

[0014] The cement used in the concrete that makes up concrete structures is not particularly limited, and examples include various cements such as normal, early-strength, ultra-early-strength, low-heat, and moderate-heat cements; various blended cements made by mixing these cements with blast furnace slag, fly ash, or silica fume; environmentally friendly cements (eco-cements) made from municipal waste incineration ash or sewage sludge incineration ash; and commercially available fine particle cements. It is also possible to use various cements and blended cements that have been finely powdered. Furthermore, cements that have been adjusted by increasing or decreasing the amount of components normally used in cement (such as gypsum) can also be used. In the present invention, it is preferable to select ordinary Portland cement or high-early-strength Portland cement from the viewpoints of heat of hydration, drying shrinkage, and filling properties.

[0015] The cement used in this invention has a Blaine specific surface area of ​​2,500 cm from the viewpoint of production cost and strength development. 2 / g or more 7,000cm 2 / g or less, and 2 / g or more 6,000cm 2 / g or less is more preferable, and 2 / g or more 4,500cm 2 It is more preferable that the saturation coefficient is 1 / g or less. The Blaine specific surface area value is determined in accordance with JIS R 5201:2015 (physical testing methods for cement).

[0016] The concrete that makes up concrete structures contains chloride ions (Cl -From the viewpoint of improving the penetration resistance of the concrete and suppressing salt damage, it is preferable to include latent hydraulic substances such as blast furnace slag (cooled blast furnace slag, granulated blast furnace slag), steelmaking slag (converter slag, electric furnace slag), fly ash, silica fume, metakaolin, pulp sludge incineration ash, sewage sludge incineration ash, volcanic glass fine powder, and waste glass powder. One or more types of latent hydraulic substances may be used in combination.

[0017] The concrete structure of the present invention may be a concrete structure that constitutes an existing building such as a civil engineering structure such as a road or a railway, specifically a bridge substructure, a bridge girder, an underground structure such as a tunnel or a semi-underground structure, or a culvert. The concrete structure of the present invention may also be a concrete structure that is constructed when a new building is constructed.

[0018] <Process for preparing the mixed liquid> The step of preparing a mixed solution is a step of preparing a mixed solution by mixing the collected fine powder with pure water. In the step of preparing a mixed solution, the collected fine powder and pure water are placed in a container such as a beaker, and the mixture is stirred using a stirrer or other agitator to obtain a mixed solution. In this embodiment, it is preferable to use only the supernatant liquid of the mixed liquid. The mixed liquid is left standing for a certain period of time, causing the fine powder to precipitate. The supernatant liquid of the mixed liquid after standing for a certain period of time does not contain the fine powder, but is a liquid in which the ionic components from the fine powder are dissolved, making it easy to measure the ionic composition.

[0019] The mass ratio of the fine powder to pure water in the prepared mixture is preferably 1:1 to 1:3, more preferably 1:1 to 1:2.5, and even more preferably 1:1 to 1:2. When the mass ratio of the mixture is within the above range, the accuracy of salt damage deterioration evaluation of concrete structures can be improved.

[0020] <Step of measuring ion composition> The step of measuring the ion composition is a step of measuring the ion composition of the prepared mixed liquid. In the step of measuring the ion composition, specifically, the Cl content of the supernatant of the prepared mixture is - Ion concentration and OH - Measure the ion concentration. - The method for measuring the ion concentration is JIS A 6204 "Testing methods for chemical admixtures for concrete" Appendix A (regulations) Chloride ions (Cl) contained in chemical admixtures. - ) amount, the potentiometric titration method is used. - The ion concentration is measured by the back titration method using bromothymol blue as an indicator, in accordance with the Cement Association Standard Test Method JCAS I-04 "Method for analyzing water-soluble components of cement."

[0021] <Cl - / OH - Step for calculating the molar ratio Cl - / OH - The process of calculating the molar ratio is carried out by determining the Cl from the ion composition of the measured mixed solution. - / OH - This is the step of calculating the molar ratio. Cl - / OH - In order to increase the accuracy of salt damage deterioration evaluation of concrete structures, the molar ratio should be obtained by measuring the ion composition of a mixed solution made from fine powder collected from concrete near the reinforcing bars of a concrete structure.

[0022] Cl - / OH - The molar ratio is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less. - / OH - When the molar ratio is equal to or less than the upper limit, it can be determined that the degree of deterioration due to salt damage of the steel material placed in the concrete of the concrete structure is low.

[0023] <Process for evaluating the degree of salt damage> The process of evaluating the degree of salt damage is - / OH -This is a process for evaluating the degree of salt damage of a concrete structure based on the molar ratio. In the step of evaluating the degree of salt damage deterioration, the method for evaluating the degree of salt damage deterioration is, for example, - / OH - When the molar ratio is 1.5 or less, the risk of salt damage deterioration is evaluated as low, and when it is more than 1.5, the risk of salt damage deterioration is evaluated as high.

[0024] According to the method for evaluating salt-damage deterioration of a concrete structure according to this embodiment, the salt-damage deterioration state of steel materials placed in the concrete of a concrete structure can be easily evaluated. Furthermore, according to the method for evaluating salt-damage deterioration of concrete structures according to this embodiment, it is possible to collect fine powder of concrete at the construction site without using a separate test specimen, and to evaluate the degree of salt-damage deterioration using the collected fine powder, thereby achieving high evaluation accuracy.

[0025] [Prediction and evaluation method for alkali-silica reaction in concrete structures] The method for predicting and evaluating alkali-silica reaction of a concrete structure according to an embodiment of the present invention includes the steps of collecting fine powder, preparing a mixed solution, measuring the ion composition, and Li + / Na + and calculating the molar ratio. The method for predicting and evaluating alkali-silica reaction of a concrete structure according to the embodiment of the present invention may further include a step of evaluating the prediction of alkali-silica reaction.

[0026] <Process for collecting fine powder> The step of collecting the fine powder is substantially the same as the step of collecting the fine powder in the salt damage deterioration evaluation method described above, and therefore, a description of the same steps will be omitted.

[0027] The concrete fine powder may be collected from any location of the concrete in a concrete structure, but when evaluating the prediction of alkali-silica reactivity of a concrete structure, it is preferable to use fine powder collected by crushing concrete near the surface.In this specification, "concrete near the surface" refers to concrete within 20 mm from the surface of the concrete structure.

[0028] <Process for preparing the mixed liquid> The process for preparing the mixture is substantially the same as the process for preparing the mixture in the salt-damage degradation evaluation method described above, and therefore, a description of the same will be omitted.

[0029] The mass ratio of the fine powder to pure water in the prepared mixture is preferably 1:1 to 1:3, more preferably 1:1 to 1:2.5, and even more preferably 1:1 to 1:2. When the mass ratio of the mixture is within the above range, it is possible to increase the accuracy of the prediction evaluation of the progress of alkali-silica reaction (ASR) in concrete structures.

[0030] <Step of measuring ion composition> The step of measuring the ion composition is a step of measuring the ion composition of the prepared mixed liquid. In the process of measuring the ion composition, specifically, the Li + Ion concentration and Na + Measure the ion concentration. + Ion concentration and Na + The ion concentration was measured by adding dilute hydrochloric acid to the supernatant of the prepared mixture to make it an acidic solution (pH 3 or less), and measuring the Li concentration in the pH-adjusted acidic solution. + Ion concentration and Na + The ion concentration is measured using an atomic absorption spectrophotometer.

[0031] <Li + / Na + Step for calculating the molar ratio Li + / Na +The process of calculating the molar ratio is carried out by determining the ion composition of the measured mixture. + / Na + This is the step of calculating the molar ratio. Li + / Na + In order to improve the accuracy of predictive assessment of the degree of progression of alkali-silica reaction (ASR) in concrete structures, it is advisable to use the molar ratio obtained by measuring the ionic composition of a mixture made from fine powder collected from concrete near the surface of the concrete structure.

[0032] Li + / Na + The molar ratio is preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.4 or more. + / Na + When the molar ratio is equal to or greater than the above lower limit, it can be predicted that the degree of progression of alkali-silica reaction (ASR) in the concrete structure will be low.

[0033] <Process for evaluating alkali-silica reaction prediction> The process of evaluating the alkali-silica reaction prediction is + / Na + This is a process for evaluating the alkali-silica reaction prediction of concrete structures based on the molar ratio. In the step of evaluating the alkali-silica reaction prediction, the alkali-silica reaction prediction can be evaluated by, for example, calculating Li + / Na + When the molar ratio is 1.0 or more, it is evaluated that the progress of the alkali-silica reaction is inhibited, and when it is less than 1.0, it is evaluated that there is a high possibility that the alkali-silica reaction will proceed.

[0034] According to the method for predicting and evaluating alkali-silica reaction of a concrete structure according to this embodiment, it is possible to predict and evaluate the degree of progress of alkali-silica reaction (ASR) of a concrete structure in a simple manner. Furthermore, according to the method for predicting and evaluating alkali-silica reaction of concrete structures according to this embodiment, it is possible to collect fine powder of concrete at the construction site without using a separate test specimen, and use the collected fine powder to evaluate the progress of alkali-silica reaction (ASR), thereby achieving high evaluation accuracy.

[0035] [Electrochemical corrosion prevention method] The electrochemical corrosion protection method according to the embodiment of the present invention includes a step of evaluating the current application treatment. The electrochemical corrosion protection method according to the embodiment of the present invention can be applied to any of the electrochemical corrosion protection methods such as the desalination method, the re-alkalization method, the electrodeposition method, and the cathodic protection method, and is not limited to these electrochemical corrosion protection methods.

[0036] <Process for evaluating the energization treatment> The process of evaluating the current treatment is carried out by using Cl calculated by the above-mentioned method for predicting and evaluating alkali-silica reaction in concrete structures. - / OH - The Li calculated by the molar ratio and the above-mentioned alkali-silica reaction prediction evaluation method for concrete structures + / Na + This is a step of evaluating the necessity of energization treatment based on at least one of the molar ratios.

[0037] In the process of evaluating the current treatment, Cl - / OH - When the molar ratio is equal to or less than the threshold, the energization treatment is evaluated as complete, and when it is greater than the threshold, the energization treatment is evaluated as incomplete. - / OH - If the molar ratio is equal to or less than the threshold value, it is determined that the salt damage deterioration of the steel material placed in the concrete of the concrete structure has been improved, and the energization treatment can be completed. - / OH - If the molar ratio exceeds the threshold value and it is determined that the energization treatment is incomplete, it is advisable to conduct the energization treatment again and go through the process of evaluating the energization treatment again.

[0038] Cl - / OH - The threshold molar ratio is preferably 1.5, more preferably 1.3, and even more preferably 1.1. - / OH - By setting the molar ratio threshold to the above value, it is possible to determine that the degree of deterioration due to salt damage of the steel placed in the concrete of a concrete structure has decreased, and it is possible to determine that the current application process has been completed.

[0039] In the process of evaluating the current treatment, Li + / Na + If the molar ratio is equal to or greater than the threshold, the energization process is evaluated as complete, and if it is less than the threshold, the energization process is evaluated as incomplete. + / Na + If the molar ratio is equal to or greater than the threshold value, it is determined that the alkali-silica reaction is not proceeding, and the energization treatment can be completed. + / Na + If the molar ratio is less than the threshold value and it is evaluated that the energization treatment is incomplete, it is advisable to carry out the energization treatment again and go through the process of evaluating the energization treatment again.

[0040] Li + / Na + The threshold value of the molar ratio is preferably 1.0, more preferably 1.2, and even more preferably 1.4. + / Na + When the molar ratio threshold value is within the above range, it is possible to predict that the degree of progress of alkali-silica reaction (ASR) in the concrete structure has decreased, and it is possible to determine the completion of the energization treatment.

[0041] An electric current treatment system used for the electric current treatment will be described below. An example of an electric current treatment system will be described using Fig. 1. The electric current treatment system shown in Fig. 1 includes an anode material 21 and an electrolyte solution holding material 22 that holds an alkaline electrolyte solution, an electrode placed on the surface side of concrete 10 is an external electrode 20, a steel material buried inside the concrete 10 is an internal electrode 30, a direct current is passed between the external electrode 20 and the internal electrode 30, and the electrified concrete 10 is the electric current treatment area. The anode material 21 constituting the external electrode 20 and the steel material (internal electrode 30) buried inside the concrete 10 are each connected to wiring material 23 such as an electric cable, and by supplying DC current from a DC power supply device 24 to the wiring material 23, DC current can be passed between the external electrode 20 and the internal electrode 30.

[0042] <<Anode material>> The anode material 21 constituting the external electrode 20 may be selected from a material that is highly corrosion-resistant and conductive, such as titanium, a titanium alloy, platinum, or a metal plated with these metals. Other examples of the anode material 21 include carbon materials such as carbon fiber and carbon rod, and conductive polymers. The anode material 21 is preferably a net-shaped, mesh-shaped or sheet-shaped conductive material, such as a titanium mesh or a carbon fiber sheet.

[0043] <<Electrolyte holding material>> The electrolyte solution holding material 22 constituting the external electrode 20 may be a nonwoven fabric made of a hydrophilic material, a nonwoven fabric that has been treated to be hydrophilic, or felt. Nonwoven fabrics made from hydrophilic materials are nonwoven fabrics made from raw materials that are inherently hydrophilic, such as regenerated fibers such as rayon and cupra, and natural fibers such as cotton, and which have been subjected to a predetermined hydrophilic treatment. Hydrophilically treated nonwoven fabrics are nonwoven fabrics manufactured from synthetic fibers such as olefin-based fibers (e.g., polyethylene or polypropylene), polyester-based fibers, or polyamide-based fibers. Hydrophilic treatment can be performed by polymerizing the synthetic fibers in the presence of a compound having a hydrophilic group, such as an oxidation product of polyethylene glycol, during the synthetic fiber manufacturing process, or by treating the synthetic fibers with a metal salt such as stannous chloride to partially dissolve the surface, making them porous, and then depositing a metal hydroxide, thereby making the synthetic fibers swell or porous, and then applying capillary action to make them hydrophilic. Felt is wool or other animal fibers that have been shrunk into a sheet.

[0044] The method for producing the nonwoven fabric is not particularly limited, and various nonwoven fabrics obtained by appropriate processing methods such as the spunlace method, spunbond method, thermal bond method, meltblown method, and needle punch method can be used.

[0045] The thickness of the electrolyte solution retention material 22 is preferably 2 to 15 mm, more preferably 2 to 10 mm, and even more preferably 2 to 5 mm. When the thickness of the electrolyte solution retention material 22 is equal to or greater than the above-mentioned lower limit, the electrolyte solution retention is ensured and the material has excellent mechanical strength. On the other hand, when the thickness of the electrolyte solution retention material 22 is equal to or less than the above-mentioned upper limit, the material can be easily adhered to the surface of the concrete 10.

[0046] The density of the electrolyte holding material 22 is 200 to 500 g / m 2 It is preferable that the density is 300 to 400 g / m 2 It is more preferable that the density of the electrolyte solution holding material 22 is equal to or greater than the above lower limit, thereby ensuring the retention of the electrolyte solution. On the other hand, when the density of the electrolyte solution holding material 22 is equal to or less than the above upper limit, the weight can be reduced and handling is excellent.

[0047] The water retention capacity of the electrolyte retention material 22 is 0.1 to 1.5 ml / cm from the viewpoint of keeping the concrete 10 in a moist state. 3 It is preferable to set the concentration to 0.4 to 0.8 ml / cm. 3 The water retention capacity of the electrolyte retention material 22 can be calculated using the following formula. Water retention capacity (ml / cm 3 ) = (wet mass (g) - bone dry mass (g)) / volume of electrolyte holding material (cm 3 ) The specific gravity of water is not taken into consideration and 1g is calculated as 1ml.

[0048] <<Electrolyte solution>> The electrolyte that constitutes the electrolyte solution reduces the electrical resistance of the concrete 10 by penetrating into the concrete 10, allowing electricity to flow more easily, and any solution containing positive and negative ions is sufficient. Specifically, an aqueous solution in which various alkali metal salts or alkaline earth metal salts are dissolved as solutes in water as a solvent is preferably used as the electrolyte solution. Examples of alkali metal salts and alkaline earth metal salts include carbonates, nitrates, nitrites, sulfates, borates, hydroxides, chlorides, etc. of lithium, sodium, potassium, magnesium, calcium, etc.

[0049] The electrolyte solution is preferably circulated by being supplied to the electrolyte solution holding material 22 from an electrolyte solution storage tank (not shown) that stores the electrolyte solution, then returned to the electrolyte solution storage tank, and again supplied from the electrolyte solution storage tank to the electrolyte solution holding material 22. During this electrolyte solution circulation process, it is preferable to measure and monitor the pH of the electrolyte solution. This is because the liquid property of the electrolyte may change over time, so it is preferable to manage the liquid property at predetermined intervals.

[0050] In the energization treatment using the above-described energization treatment system, a direct current is applied between the outer electrode 20 and the inner electrode 30 to remove chloride ions (Cl ) from the concrete 10. - ) can be removed by migrating it to the external electrode 20 side. This action allows the alkaline electrolyte solution to be electro-penetrated into the concrete 10 toward the steel material side, restoring the alkalinity of the neutralized concrete 10, and the neutralized region can be made into an electrically-treated region.

[0051] In the current application process, the current density of the DC current flowing between the external electrode 20 and the internal electrode 30 on the surface of the concrete is 0.1 to 5 A / m 2 It is preferable that the current is 0.5 to 4.5 A / m 2 More preferably, it is 1 to 4 A / m 2It is more preferable that the current density of the direct current on the surface of the concrete is within the above range, so that the re-alkalization treatment can be carried out efficiently.

[0052] In the electric current treatment, the pH of the electric current treatment area is preferably 10 or more, more preferably 10.5 or more, and even more preferably 11 or more. When the pH of the electric current treatment area is equal to or more than the above lower limit, the steel material in the concrete structure exhibits a good rust prevention effect.

[0053] According to the electrochemical corrosion protection method of this embodiment, it is possible to determine whether or not energization treatment is necessary by understanding the state of corrosion of the concrete structure and the degree of ASR progression. [Example]

[0054] The present invention will be explained in more detail below using experimental examples, but the present invention is not limited to the following experimental examples as long as it does not deviate from the gist of the present invention.

[0055] [Experimental Example] A test specimen of a concrete structure in which steel materials (rebar, diameter φ13mm) placed within the concrete had deteriorated due to salt damage was prepared, and an external electrode (anode material: titanium alloy, electrolyte solution holding material: nonwoven fabric, electrolyte solution: 22% LiNO3 + 1.3% Li2CO3 aqueous solution = 1:2) was placed on the surface of the test specimen, and a direct current (1A) was passed between the external and internal electrodes for 56 days to perform electrochemical corrosion protection treatment. In a concrete structure specimen that had undergone electrochemical corrosion protection treatment, immediately before (5 days before) energization, during (28 days after) energization, and immediately after (1 day after) energization, fine powder was collected from the concrete near the rebar and near the surface between the external and internal electrodes by drilling with a concrete drill. Then, 12.5 g of the collected fine powder and 25 ml of pure water at room temperature (23°C) were placed in a 50 ml beaker and stirred with a stirrer for 3 minutes to prepare a mixture. The mixture was then left to stand for 5 minutes to allow the fine powder to settle, and the supernatant liquid was obtained. The ionic composition of the supernatant liquid of the mixture prepared using the fine powder of the concrete near the reinforcing bars was Cl. - Ion concentration and OH - Measure the ion concentration and Cl - / OH - The calculated molar ratios are shown in Table 1. In addition, the ion composition of the supernatant liquid of the mixture prepared using the fine powder of the collected near-surface concrete was Li. + Ion concentration and Na + ion concentration was measured, and Li + / Na + The calculated molar ratios are shown in Table 2.

[0056] [Table 1]

[0057] [Table 2]

[0058] As shown in Table 1, by applying electricity, the deterioration of concrete structures caused by salt damage can be repaired, and the Cl - / OH - The molar ratio decreases. - / OH -By understanding the molar ratio, it is possible to determine the degree of repair required for concrete structures deteriorated by salt damage, and therefore to determine whether or not electrical current treatment using electrochemical corrosion protection methods is necessary. In addition, as shown in Table 2, Li + / Na + The molar ratio increases. + / Na + As the molar ratio increases, the progression of alkali-silica reaction (ASR) in concrete structures is predicted. + / Na + By understanding the molar ratio, it is possible to predict the extent of ASR progression, and therefore determine whether or not electrical current treatment is required for electrochemical corrosion protection. [Explanation of symbols]

[0059] 10. Concrete 20 External electrode 21 Anode material 22 Electrolyte holding material 23 Wiring material 24 DC power supply 30 Internal electrode

Claims

1. A step of crushing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete to obtain fine powder; a step of preparing a mixed solution by mixing the fine powder with pure water; measuring the ion composition of the mixture; From the measured ion composition of the mixture, Cl － / OH － and calculating the molar ratio.

2. 2. The method for evaluating salt damage deterioration of a concrete structure according to claim 1, wherein a mass ratio of the fine powder to the pure water in the mixed liquid is 1:1 to 1:

3.

3. 2. The method for evaluating salt damage deterioration of a concrete structure according to claim 1, wherein the particle size of the fine powder is 150 μm or less.

4. The Cl － / OH － The method for evaluating salt damage deterioration of a concrete structure described in claim 1, wherein the molar ratio is obtained by measuring the ionic composition of the mixed liquid made from the fine powder collected from the concrete near the reinforcing bars of the concrete structure.

5. The Cl － / OH － The method for evaluating salt-damage deterioration of a concrete structure according to claim 1, further comprising the step of evaluating the degree of salt-damage deterioration of the concrete structure based on the molar ratio.

6. A step of crushing concrete of a concrete structure in which reinforcing bars are embedded inside the concrete to obtain fine powder; a step of preparing a mixed solution by mixing the fine powder with pure water; measuring the ion composition of the mixture; From the measured ion composition of the mixed solution, Li ＋ / Na ＋ and calculating the molar ratio.

7. 7. The method for predicting and evaluating an alkali-silica reaction of a concrete structure according to claim 6, wherein a mass ratio of the fine powder to the pure water in the mixed solution is 1:1 to 1:

3.

8. 7. The method for predicting and evaluating alkali-silica reaction of a concrete structure according to claim 6, wherein the particle size of the fine powder is 150 μm or less.

9. The Li ＋ / Na ＋ 7. The method for predicting and evaluating alkali-silica reaction of a concrete structure according to claim 6, wherein the molar ratio is obtained by measuring the ion composition of the mixed solution made of the fine powder collected from the concrete near the surface of the concrete structure.

10. The Li ＋ / Na ＋ The method for predicting and evaluating alkali-silica reactivity of a concrete structure according to claim 6, further comprising the step of evaluating the prediction of alkali-silica reactivity of the concrete structure based on the molar ratio.

11. An electrochemical corrosion protection method comprising: an anode material and an electrolyte solution holding material holding an electrolyte solution; an electrode placed on the surface of the concrete as an external electrode; a reinforcing bar embedded inside the concrete as an internal electrode; and an electric current treatment for passing a direct current between the external electrode and the internal electrode; The Cl calculated by the method for evaluating salt damage deterioration of a concrete structure according to any one of claims 1 to 5. － / OH － The molar ratio and the Li calculated by the alkali-silica reaction prediction evaluation method for a concrete structure according to any one of claims 6 to 10 ＋ / Na ＋ and a step of evaluating the current treatment based on at least one of the molar ratios.

12. The Cl － / OH － The electrochemical corrosion protection method according to claim 11, wherein the current treatment is evaluated as completed when the molar ratio is 1.5 or less, and the current treatment is evaluated as incomplete when the molar ratio is greater than 1.

5.

13. The Li ＋ / Na ＋ The electrochemical corrosion protection method according to claim 11, wherein the current treatment is evaluated as completed when the molar ratio is 1.0 or more, and the current treatment is evaluated as incomplete when the molar ratio is less than 1.0.

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