JP6529847B2 - Diffusion coefficient estimation method - Google Patents

Description

  The present invention relates to a diffusion coefficient estimation method.

In some cases, the diffusion coefficient of mass transfer in the ground (bedrock, soil, etc.), concrete, etc. may be estimated.
For example, if the mobility of chloride ions is evaluated by measuring the diffusion coefficient of chloride ions infiltrated into concrete, the durability of concrete against salt damage can be confirmed. In particular, in the case of a concrete member (steel reinforced concrete, steel reinforced concrete, steel fiber reinforced concrete, etc.) in which steel is used as a reinforcing material, if salt penetrates, the steel inside will expand due to corrosion, and cracks may occur in the concrete. Therefore, it is necessary to understand the mobility of chloride ions.

As a method of measuring the diffusion coefficient in concrete, for example, a method of applying a voltage to concrete to evaluate the movement of salt in a non-steady state (see Non-Patent Document 1) or evaluating the movement of salt in the steady state Methods (see Non-Patent Document 2) and the like.
Further, in Patent Document 1, as a method of predicting a long-term diffusion state based on a short-term diffusion state, after infiltrating chemical species into concrete, the chemical species in the concrete are colored to allow penetration of the chemical species. Discloses a method of measuring the concentration of chemical species at an arbitrary distance and time using a prediction equation of the concentration of chemical species determined based on the measurement result.

JP, 2012-202731, A

NT BUILD 492, "Chloride Migration Coefficient from Non-steady State Migration Experiment", Nordtest, Finland, 1999. "Test method of effective diffusion coefficient of chloride ion in concrete by electrophoresis (Draft) (JSCE-G571-2013)" Concrete Standard Specification [Criteria Edition], Japan Society of Civil Engineers, 2013

Since Non-Patent Document 1 uses a conversion formula for ordinary concrete, it prescribes concrete using only portland cement, and cement other than portland cement, for example, blast furnace cement and fly ash cement It was unsuitable for the measurement of the diffusion coefficient of concrete using mixed cement such as.
Moreover, since the measuring method of the diffusion coefficient of nonpatent literature 2 needs to be made to soak in a solution until salt content penetrates a concrete sample, time is required until a measurement result is obtained. In particular, in the case of dense concrete such as high-strength concrete (diffusion coefficient is 1/20 or less of that of ordinary concrete), it takes more than a year for salt to penetrate. Therefore, it was unsuitable for the measurement of the diffusion coefficient of a precise concrete member.
Furthermore, if the applied voltage is increased to shorten the application time, the concrete sample generates heat and can not perform accurate measurement. There is a risk that water is electrolyzed near the electrodes to generate hydrogen gas.
Moreover, even if the prediction method of the diffusion coefficient of Patent Document 1 is applied to dense concrete such as high-strength concrete (a diffusion coefficient is 1/20 or less of that of ordinary concrete), it is difficult to measure the colored area, It is difficult to measure the diffusion coefficient accurately.

  From such a point of view, the present invention has an object to propose a diffusion coefficient estimation method which makes it possible to estimate the diffusion coefficient with high accuracy in a short period of time without being limited to the property of the specimen. .

  In order to solve the above problems, the diffusion coefficient estimation method of the present invention comprises a preparation step of immersing a specimen in an ion solution in a test cell in which a cathode and an anode are disposed; DC voltage applied to the cathode and the anode Applying the ion solution to the specimen for a predetermined period in the state of applying a voltage, measuring the concentration distribution of anions and cations having permeated the specimen, and And D. estimating the diffusion coefficient of one of the ions, wherein in the estimation step, the concentration distribution of the other ion, which is the counter ion of the one ion, is used in the estimation step. Estimate the depth of penetration of the ion and fit the concentration distribution of the one ion in a range deeper than the depth to the penetration formula of the ion by the potential gradient It is a symptom.

According to such a diffusion coefficient estimation method, since the anions and cations do not penetrate until they penetrate the specimen but are divided into predetermined periods, the test period is significantly shortened compared to the conventional diffusion coefficient estimation method. can do.
Further, since the diffusion coefficient is estimated by excluding the concentration distribution of one of the ions in the range in which the other ion penetrates, it is possible to measure the diffusion coefficient of ions with higher accuracy.
The diffusion coefficient estimation method according to the present invention can be applied to estimation of diffusion coefficients of concrete, rock, soil, pottery and the like. For example, if the diffusion coefficient of concrete is estimated according to the present invention, the progress of salt damage of a concrete member can be estimated, and if the diffusion coefficient of rock is estimated, the transition of material to the rock (diffusion state) is estimated can do.

Before the measurement step, a permeation confirmation step of confirming the penetration depth of the anion or the cation may be provided. As a method of confirming the penetration depth of the target ion into the sample, for example, a fluorescent X-ray elemental analyzer may be used.
When the specimen is a concrete specimen, the cathode side of the concrete specimen in the test cell is filled with a sodium chloride solution in the preparation step, and the anode side of the concrete specimen is filled with water. If the sodium oxide solution is filled, the diffusion coefficient of chloride ions penetrating into the concrete can be estimated.
In the permeation confirmation step in the case where the specimen is a concrete specimen, silver nitrate may be sprayed onto the concrete specimen to confirm the permeation depth of chloride ions infiltrated into the concrete specimen, The penetration depth of chloride ions into the concrete sample may be confirmed using a fluorescent X-ray elemental analyzer.
Furthermore, if the concentration distribution of the anion and the cation is measured by a wavelength dispersive electron probe microanalyzer (EPMA: Electron Probe Micro Analyzer) in the measurement step, the ion concentration distribution in the test body can be simplified and high. Accuracy can be measured.

  According to the diffusion coefficient estimation method of the present invention, it is possible to estimate the diffusion coefficient with high accuracy in a short period of time without being limited to the property of the specimen.

It is a schematic diagram of the test device concerning the embodiment of the present invention. (A) A perspective view schematically showing a test piece, (b) a cross-sectional view showing a coloration example of the test piece, (c) a cross-sectional view showing an example of a measurement result by EPMA. It is a graph which shows the measurement example of EPMA, Comprising: (a) is distribution of Cl ion and Na ion, (b) is distribution of Cl ion and fitting curve.

First Embodiment
In the first embodiment, the case of estimating the diffusion coefficient of chloride ions in dense concrete (high strength concrete or the like) will be described.
The diffusion coefficient estimation method of the present embodiment includes a preparation step, an application step, a penetration confirmation step, a measurement step, and an estimation step.
The preparation step is a step of placing the specimen 1 in the test cell 2 as shown in FIG. In the present embodiment, four specimens 1, 1, 1, 1 are tested respectively, and the diffusion coefficient is estimated using three of them.
The specimen 1 is collected from the concrete member to be measured. Specifically, first, a concrete core may be collected from a concrete member, and then a cylindrical specimen 1 may be cut out from the concrete core. In the present embodiment, four cylindrical test pieces 1 of φ100 mm × 50 mm are cut out from one concrete core. In addition, the shape dimension of the specimen 1, the formation method, and the number are not limited, and may be set as appropriate.

  The specimen 1 is placed so as to shield the center of the test cell 2. The cylindrical surface (side surface) of the sample 1 is coated with a resin so that the solution does not penetrate from the side surface of the sample 1. In addition, the kind of resin which coats the side of sample 1 is not limited. Moreover, the water stopping method of the side surface of the sample 1 is not limited to coating of resin.

The test cell 2 of the present embodiment is made of a cylindrical member made of acrylic, but the material and shape of the test cell 2 are not limited.
A cathode 4 and an anode 5 connected to a DC power supply 3 are disposed in the test cell 2.
In the present embodiment, the cathode 4 is provided on one side (left side in FIG. 1) of the specimen 1 and the anode 5 is provided on the other side (right side in FIG. 1). The cathode 4 and the anode 5 may be arranged in the opposite manner.

After placing the specimen 1 in the test cell 2, the ion solutions 6, 7 are injected into the test cell 2, and the specimen 1 is immersed in the ion solutions 6, 7. In this embodiment, one surface side (cathode 4 side) of the specimen 1 is filled with a sodium chloride solution (1.8 mol / L) 6, and the other surface side (anode 5 side) of the specimen 1 is sodium hydroxide solution (0 Fill with 7 mol / L) 7. The type of ion solution to be injected into the test cell 2 and the concentration of each ion solution are not limited.
The depth of the ion solutions 6 and 7 is the depth to which the whole of the specimen 1 is immersed.

The applying step is a step of applying a DC voltage to the cathode 4 and the anode 5.
When a direct current voltage is applied to the cathode 4 and the anode 5, mass transfer from the ion solution (sodium chloride solution 6) toward the inside of the specimen 1 starts by a potential gradient from the cathode 4 to the anode 5.
In the present embodiment, a voltage of 30 V is applied for 14 days to 91 days, but the magnitude of the voltage and the period for applying the voltage (the time for the ion solution to permeate the specimen 1) are not limited. The application time of the sample 1 used for estimation of the diffusion coefficient (time to allow the ion solution to permeate) depends on the result of the permeation confirmation step (the permeation state of the chloride ion of the sample 1 for 14 days). Set (see Table 1).

The permeation confirmation step is a step of confirming the permeation depth of chloride ion (anion) and sodium ion (cation).
In the present embodiment, the penetration depth is confirmed for the specimen 1 with an application time of 14 days.
The specific procedure is as follows.
First, as shown in FIG. 2A, a cylindrical specimen 1 is cut into two specimen pieces 10 and 10 (only one specimen piece 10 is shown in the drawing).
Next, silver nitrate is sprayed on the cut surface 11 of one of the test pieces 10. When silver nitrate is sprayed on the cut surface 11, the specimen 1 is discolored due to a color reaction between chloride ions and silver nitrate (see FIG. 2 (b)).

Subsequently, the approximate depth (penetration depth) of the colored area 12 by silver nitrate appearing on the cut surface 11 is confirmed (visually observed). Then, the application time (period in which the ion solution is allowed to permeate in the application step) of the specimen 1 used to estimate the diffusion coefficient is set by the average penetration depth (thickness) of the colored area 12 (see Table 1).
In the present embodiment, the penetration depth was confirmed with respect to the specimen 1 with an application time of 14 days, and the application time to each specimen 1 used for estimation of the diffusion coefficient was set as shown in Table 1. The application time is not limited to the time (days) in Table 1, and may be set as appropriate. Moreover, the application time of the sample used for a permeation | transmission confirmation process is not limited to 14 days, What is necessary is just to set suitably. Moreover, the confirmation method of permeation | transmission of chloride ion is not limited to silver nitrate spray. If visual confirmation is difficult, the permeation may be confirmed by a handheld X-ray fluorescence elemental analyzer.

When the penetration depth for 14 days of application time is 3 mm or less, as shown in Table 1, the diffusion coefficient is estimated using specimen 1 for 56 days, 74 days, and 91 days of application time.
Here, when the penetration depth for 14 days of application time is 3 mm or less, confirmation of the penetration depth of chloride ion (permeation confirmation step) is performed using silver nitrate also for specimen 1 for 56 days of application time. Do. In the present embodiment, when the penetration depth of chloride ions at an application time of 56 days is 3 mm or less, the diffusion coefficient is less than the estimated addition (less than 6 × 10 ⁻¹⁵ m ² / s in the present embodiment) It is estimated that the test is ended (the test of application time 74 days, 91 days is not performed).

When the penetration depth for 14 days of application time is more than 3 mm and 10 mm or less, the diffusion coefficient is estimated using the specimen 1 of 14 days, 28 days and 56 days of application time.
On the other hand, when the penetration depth for 14 days of application time is more than 10 mm and 20 mm or less, the diffusion coefficient is estimated using the specimen 1 of 14 days, 21 days and 28 days of application time.
Furthermore, when the penetration depth for 14 days of application time exceeds 20 mm, the diffusion coefficient is estimated by the diffusion coefficient measurement by the conventional steady flow.

A measurement process is a process of measuring concentration distribution of chloride ion (anion) and sodium ion (cation) which penetrated sample 1.
In the present embodiment, the concentration distribution of chloride ions and sodium ions is obtained using the wavelength dispersive electron probe microanalyzer (EMPA) for the specimen 1 for which the application process has been performed according to the application time set in the permeation confirmation process. taking measurement.
In addition, the measuring method (apparatus used for a measurement) of the concentration distribution of a chloride ion and a sodium ion is not limited to the method of using EMPA. For example, it can be measured by a known wet analysis or instrumental analysis technique according to the target element using a sample which has been cut or cut sequentially from the surface in contact with the ion solution and recovered.
Here, when the average penetration depth of the colored area 12 is in the range of 3 mm to 20 mm, when the measurement step is performed for the sample 1 with an application time of 14 days, the sample piece 10 used in the permeation confirmation step The other test piece 10 which is a pair is used.

In this embodiment, as shown to Fig.2 (a), the 50x50x10 mm test piece 13 cut out from the cut surface 11 of the test piece 10 is used for the measurement of density | concentration distribution.
First, the test piece 13 is vacuum dried to impregnate the resin, and then the analysis surface (surface) of the test piece 13 is mirror-polished to deposit carbon, and then the concentration distribution of chloride ion and sodium ion is measured by EMPA Do.
According to EMPA, as shown in FIG. 2 (c), it can be confirmed that chloride ions 61 permeate from the cathode side toward the anode side.
In this embodiment, measurement points determined to be aggregate in concrete are removed from the measurement result of concentration distribution. Although the removal method of the measurement point determined to be aggregate is not limited, for example, it is removed by determining based on the difference in composition and concentration of elements of aggregate and cement hardened body (cement paste) in the periphery. Can. In addition, although the extraction operation of a cement hardened body (cement paste) is not essential, the fluctuation | variation of content of the object component by the presence or absence of aggregate can be made small, and estimation with high precision is attained.
The concentrations of chloride ion and sodium ion are determined by the calibration curve method. Then, as shown in FIG. 3 (a), the concentration of chloride ions and sodium ions averaged at a distance of 0.1 mm from the surface on the cathode side is taken along the horizontal axis as the distance from the permeation surface of the sodium chloride solution. The contents of chloride ion and sodium ion are plotted on the vertical axis.

The estimation step is a step of estimating the diffusion coefficient of chloride ions.
The estimation of the diffusion coefficient of chloride ion is performed by fitting the concentration distribution of chloride ion to the ion penetration formula (Formula 1) by the potential gradient.

The fitting of the concentration distribution of chloride ion (Cl) to equation 1 is a range (fitting range A2) deeper than the depth (excluded range A1) at which sodium ion (Na 2 O), which is the counter ion of chloride ion, penetrates Use the concentration distribution in (see Figure 3).
The depth to which sodium ions permeated is estimated from the concentration distribution of sodium ions shown in FIG. 3 (a). In this embodiment, as shown in FIG. 3B, a range of about 4 mm from the cathode side end face of the specimen 1 is excluded range A1, and a range deeper than about 4 mm from the cathode side end face is fitting range A2 as chloride. The concentration distribution of the object ion is fitted to Equation 1.

Here, when the concentration distribution of chloride ions penetrates (diffuses) using only the potential gradient as a driving force (in accordance with Equation 1), sodium ions do not permeate (diffuse) from the cathode side.
However, as shown in FIG. 3A, as a result of measurement by EMPA, penetration of sodium ions from the cathode side was confirmed. The concentration of sodium ion is high on the surface side of the specimen 1 and is almost constant in the other range. In addition, since chloride ion also showed remarkable permeation like sodium ion in a range where sodium ion intrusion was remarkable, it is appropriate to think that this penetrated by electroosmosis. In addition, this cause is not limited to electro-osmosis, and when the type of the sample and the type of the ion solution used in the test are different, the surface of the sample 1 has the opposite polarity to the electrode due to different causes. It does not reject the penetration of ions.
Therefore, when fitting it to Formula 1 of concentration distribution of a chloride ion, the concentration distribution of the chloride ion of the depth (exclusion range A1) which sodium ion penetrated is excluded.
In the determination of exclusion range A1, comparison with the internal concentration where permeation of sodium ion is not observed, or approximation of the distribution state by an applicable function, the point where divergence starts in the vicinity of the surface and concentration which is a constant value inside Can be the boundary of the exclusion range.

Equation 1 is an equation obtained by assuming that the transport of chloride ions in concrete follows the Nernst-Planck equation.
That is, assuming that the potential gradient inside the concrete is constant and ignoring the advection term in the Nernst-Prank equation, the equation 2 holds.
On the other hand, the change of the concentration c (x, t) of the chloride ion at an arbitrary time t and position x can be expressed as Formula 3 using a flux J.
And Formula 4 is obtained by Formula 2 and Formula 3.

Here, initial conditions c (x, t) = 0, x> 0, t = 0, boundary conditions c (x, t) = c0 (chloride ion concentration of concrete on the cathode side surface), x = 0, t Equation 5 is obtained by solving Equation 4 under the conditions of> 0, c (x, t) = 0, x → ∞, and >>t> 0.
Since the applied voltage (30 V) of the present embodiment is sufficiently large, the first term of the right side of Equation 5 can be regarded as zero. Therefore, equation 1 is obtained from equation 5.
Therefore, the diffusion coefficient D can be calculated by fitting the average concentration distribution of chloride ions obtained by the EMPA test to Equation 1.

  Fitting is performed on each of the test pieces 1 in which chloride ions are infiltrated according to the application time shown in Table 1, and the diffusion coefficient D is estimated. In the present embodiment, the diffusion coefficient D (average value and range) of the concrete member is estimated by calculating the diffusion coefficient D for each of the three test pieces 1 in which the application time is changed. In addition, the number of specimens used for estimation of the diffusion coefficient is not limited.

According to the diffusion coefficient estimation method of the present embodiment, the chloride ion does not penetrate until it penetrates the specimen 1, but is divided and infiltrated for a predetermined period (see Table 1). In comparison, the test period can be significantly shortened.
In addition, since the concentration distribution in the range where sodium ions permeated is excluded to estimate the diffusion coefficient of chloride ions, it becomes possible to measure the ion concentration distribution with higher accuracy.

Second Embodiment
In the second embodiment, the case of estimating the diffusion coefficient of iodine in the bedrock will be described.
The diffusion coefficient estimation method of the present embodiment includes a preparation step, an application step, a penetration confirmation step, a measurement step, and an estimation step.
The preparation step is a step of placing the specimen 1 in the test cell 2 as shown in FIG.
The specimen 1 is formed by cutting it out of rock.

After placing the specimen 1 in the test cell 2, the ion solutions 6, 7 are injected into the test cell 2, and the specimen 1 is immersed in the ion solutions 6, 7. In this embodiment, one surface side (cathode 4 side) of the specimen 1 is filled with a potassium iodide solution (500 mg / L) 6 and the other surface side (anode 5 side) of the specimen 1 is filled with ion exchange water 7. The type of ion solution to be injected into the test cell 2 and the concentration of each ion solution are not limited.
The details of the other preparation steps are the same as the contents shown in the first embodiment, so the detailed description will be omitted.

The applying step is a step of applying a DC voltage to the cathode 4 and the anode 5.
When a DC voltage is applied to the cathode 4 and the anode 5, an ionic solution (potassium iodide solution 6) penetrates the specimen 1 by a potential gradient from the cathode 4 to the anode 5.
In the present embodiment, a voltage of 15 V is applied, but the magnitude of the voltage and the period of applying the voltage (the time for causing the ion solution to permeate the specimen 1) are not limited.

The permeation confirmation step is a step of confirming the permeation depth of iodine ion (anion).
In the present embodiment, the penetration depth of the specimen 1 with an application time of 1 day is confirmed using a handheld fluorescent X-ray apparatus. In addition, the confirmation method of permeation of an iodine ion is not limited.
Application time The application time of the specimen 1 used for estimation of the diffusion coefficient (period for allowing the ion solution to permeate in the application process) is set by the penetration depth (thickness) of iodine ions for 1 day.

A measurement process is a process of measuring concentration distribution of iodine ion (anion ion) and potassium ion (cation ion) which penetrated sample 1.
In the present embodiment, the concentration distribution of iodine ion and potassium ion is measured using the wavelength dispersive electron probe microanalyzer (EMPA) for the sample 1 for which the application process is performed according to the application time set in the permeation confirmation process. Do.
In addition, the measuring method (apparatus utilized for a measurement) of the concentration distribution of an iodine ion and potassium ion is not limited to the method of using EMPA.
The details of the method of measuring the concentration distribution using EMPA are the same as the contents shown in the first embodiment, so the detailed description will be omitted.
When the concentration distribution of iodine ion and potassium ion is measured, the distance distribution from the permeation surface of potassium iodide solution is taken as abscissa and the concentration distribution of iodine ion and potassium ion is taken as ordinate. Plot above.

The estimation step is a step of estimating the diffusion coefficient of iodine ion.
The diffusion coefficient of iodine ion is estimated by fitting the concentration distribution of iodine ion to the ion penetration formula (Formula 1) by the potential gradient.
In fitting of the concentration distribution of iodine ion (I) to equation 1, concentration in the range (fitting range A2) deeper than the depth (exclusion range A1) where potassium ion (K), which is counter ion of iodine ion, penetrated Use distribution.

According to the diffusion coefficient estimation method of the present embodiment, the diffusion coefficient of iodine in the rock can be easily estimated.
The substance to be estimated by the diffusion coefficient estimation method is not limited to iodine.

Third Embodiment
In the third embodiment, the case of estimating the diffusion coefficient of chloride ions in the soil will be described.
The diffusion coefficient estimation method of the present embodiment includes a preparation step, an application step, a penetration confirmation step, a measurement step, and an estimation step.
The preparation step is a step of placing the specimen 1 in the test cell 2 as shown in FIG.
The specimen 1 is formed by compacting bentonite or the like.

After placing the specimen 1 in the test cell 2, the ion solutions 6, 7 are injected into the test cell 2, and the specimen 1 is immersed in the ion solutions 6, 7. In this embodiment, one surface side (cathode 4 side) of the specimen 1 is filled with a sodium chloride solution (1.8 mol / L) 6, and the other surface side (anode 5 side) of the specimen 1 is sodium hydroxide solution (0 Fill with 7 mol / L) 7. The type of ion solution to be injected into the test cell 2 and the concentration of each ion solution are not limited.
The details of the other preparation steps are the same as the contents shown in the first embodiment, so the detailed description will be omitted.

The applying step is a step of applying a DC voltage to the cathode 4 and the anode 5.
When a DC voltage is applied to the cathode 4 and the anode 5, an ionic solution (sodium chloride solution 6) penetrates the specimen 1 by a potential gradient from the cathode 4 to the anode 5.
In the present embodiment, a voltage of 15 V is applied, but the magnitude of the voltage and the period of applying the voltage (the time for causing the ion solution to permeate the specimen 1) are not limited.

The permeation confirmation step is a step of confirming the permeation depth of chloride ion (anion).
In the present embodiment, the penetration depth of the specimen 1 with an application time of 1 day is confirmed using a handheld fluorescent X-ray apparatus. In addition, the confirmation method of permeation of chloride ion is not limited.
Application time The application time of the specimen 1 used for estimation of the diffusion coefficient (period for allowing the ion solution to permeate in the application process) is set according to the penetration depth (thickness) of chloride ions for 1 day.

The details of the measurement process and the estimation process are the same as the contents shown in the first embodiment, so the detailed description will be omitted.
According to the diffusion coefficient estimation method of the present embodiment, the diffusion coefficient of chloride ions in the soil can be easily estimated.
The substance permeating the soil estimated by the diffusion coefficient estimation method is not limited to the chloride ion.

Fourth Embodiment
In the fourth embodiment, the case of estimating the diffusion coefficient of chloride ions in ceramic will be described.
The diffusion coefficient estimation method of the present embodiment includes a preparation step, an application step, a penetration confirmation step, a measurement step, and an estimation step.
The preparation step is a step of placing the specimen 1 in the test cell 2 as shown in FIG.
The specimen 1 is made of ceramic sintered at about 1000 ° C. In addition, the material which comprises the specimen 1 is not limited.

After placing the specimen 1 in the test cell 2, the ion solutions 6, 7 are injected into the test cell 2, and the specimen 1 is immersed in the ion solutions 6, 7. In this embodiment, one surface side (cathode 4 side) of the specimen 1 is filled with a sodium chloride solution (1.8 mol / L) 6, and the other surface side (anode 5 side) of the specimen 1 is sodium hydroxide solution (0 Fill with 7 mol / L) 7. The type of ion solution to be injected into the test cell 2 and the concentration of each ion solution are not limited.
The details of the other preparation steps are the same as the contents shown in the first embodiment, so the detailed description will be omitted.

The details of the application process, the permeation confirmation process, the measurement process, and the estimation process are the same as the contents described in the third embodiment, and thus the detailed description is omitted.
According to the diffusion coefficient estimation method of the present embodiment, the diffusion coefficient of chloride ions in ceramic can be easily estimated.
In addition, the substance which permeates into the pottery estimated by the diffusion coefficient estimation method is not limited to the chloride ion.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiment, and each component described above can be modified as appropriate without departing from the spirit of the present invention.
For example, in the above embodiment, silver nitrate is sprayed onto the specimen 1 in the permeation confirmation step, and the case where the permeation depth of chloride ions is confirmed by confirming the range of the discolored portion has been described. The method of confirming the depth is not limited. That is, the material to be sprayed or applied to the specimen 1 may be determined according to the material of the ion to be measured. Moreover, in the permeation confirmation process, it is not necessary to necessarily carry out by confirmation of the colored area. Furthermore, the permeation confirmation step may be performed as necessary, and may be omitted.

Although the said embodiment demonstrated the case where extract | collected a specimen from the existing concrete member, the collection method of a specimen is not limited. For example, if a specimen formed with a predetermined composition is used, it is possible to estimate in advance the diffusion coefficient in concrete of the concrete structure to be newly constructed.
The properties of the material (specimen) whose diffusion coefficient is to be estimated by the diffusion coefficient estimation method of the present invention and the substance that penetrates the material are not limited to those described in the above embodiments.

1 test object 2 test cell 3 direct current power source 4 cathode 5 anode 6 sodium chloride solution (ion solution)
7 Sodium hydroxide solution (ionic solution)

Claims (6)

In the test cell in which the cathode and the anode are disposed, a preparation step of immersing the specimen in an ionic solution;
Applying the ion solution to the sample for a predetermined period in a state where a direct current voltage is applied to the cathode and the anode;
Measuring the concentration distribution of anions and cations which have penetrated the specimen;
An estimation step of estimating a diffusion coefficient of any one of an anion and a cation.
In the estimation step, the depth of penetration of the other ion is estimated from the concentration distribution of the other ion which is a counter ion of the one ion, and the concentration distribution of the one ion in a range deeper than the depth is calculated. A diffusion coefficient estimation method characterized by fitting to a penetration equation of ions by a potential gradient.   The diffusion coefficient estimation method according to claim 1, further comprising a permeation confirmation step of confirming the penetration depth of the anion or the cation into the specimen before the measurement step.   The diffusion coefficient estimation method according to claim 2, wherein in the permeation confirmation step, the permeation depth is confirmed using a fluorescent X-ray elemental analyzer. The sample is a concrete sample,
In the preparation step, a sodium chloride solution is injected to the cathode side of the concrete specimen in the test cell, and a sodium hydroxide solution is injected to the anode side of the concrete specimen. Diffusion coefficient estimation method. Before the measurement step, a penetration confirmation step of confirming the penetration depth of the chloride ion that has permeated into the concrete specimen is provided,
5. The diffusion coefficient estimating method according to claim 4, wherein silver nitrate is sprayed to the concrete specimen in the permeation confirmation step, or the confirmation is performed using a fluorescent X-ray elemental analyzer.   The diffusion coefficient estimation method according to any one of claims 1 to 5, wherein in the measurement step, the distribution of the anion and the cation is measured by a wavelength dispersive electron probe microanalyzer. .

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