JP7032722B2 - Reinforced concrete corrosion evaluation method - Google Patents

Description

The present invention relates to a method for evaluating corrosion of reinforcing bars in reinforced concrete.

Corrosion of reinforcing bars in reinforced concrete can be stopped by applying anticorrosion technology to prevent its progress. Therefore, the technique of detecting the corrosion of the reinforcing bar of the reinforced concrete at an early stage and measuring the degree thereof is important for suppressing the corrosion of the reinforcing bar of the reinforced concrete, and the so-called natural potential method and the polarization resistance method are well known. The natural potential method is a method of measuring corrosion from the potential of the reinforcing bar surface that changes due to the corrosion of the reinforcing bar. The polarization resistance method is a method of estimating the corrosion rate of a reinforcing bar from the polarization resistance by utilizing the fact that the corrosion rate of the reinforcing bar and the reciprocal of the polarization resistance are in a proportional relationship.

However, both the natural potential method and the polarization resistance method require the measuring instrument to be electrically connected to the reinforcing bars in the reinforced concrete, and it is necessary to partially break the reinforced concrete to expose a part of the internal reinforcing bars to the outside. .. Therefore, the natural potential method and the polarization resistance method have a problem in terms of workability and a problem that the structure and aesthetics of the reinforced concrete are impaired.

As an example of the conventional technique for solving such a problem, a technique called non-contact electric pulse response analysis (CEPRA) for measuring corrosion of reinforcing bars of reinforced concrete using a method called Wenner's four-electrode method is known (for example,). See Patent Document 1, Non-Patent Documents 1 and 2). According to the prior art, it is not necessary to partially break the reinforced concrete to expose a part of the internal reinforcing bars to the outside, and it is possible to measure the corrosion of the reinforcing bars of the reinforced concrete in a non-destructive manner.

International Publication No. 2015/172231

“Connection-less Electrical Pulse Response Analysis (CEPRA) test method for corrosion rate measurement”, [online], [Search on March 16, 2017] Internet <URL: http://www.giatecscientific.com/wp-content /uploads/2015/12/CEPRA-Technology.pdf> "Technology to know the corrosion of reinforcing bars in concrete completely non-destructively", [online], KEYTEC Co., Ltd. homepage, [Search on April 4, 2017] Internet <URL: http://www.key-t.co. jp / resources / icor />

However, since the above-mentioned conventional technique is a method of applying a step voltage to the surface of reinforced concrete, the impedance measurement accuracy decreases as the depth of the reinforcing bar (reinforcing bar cover) increases, and the corrosion of the reinforcing bar of the reinforced concrete becomes highly accurate. There is a problem that it becomes difficult to evaluate. In addition, since outdoor concrete placed in various natural environments is affected by, for example, salt, its impedance-frequency characteristics are often slightly different and not uniform. Further, the above-mentioned conventional technique does not consider that the impedance-frequency characteristics of concrete are different from each other, and there is a possibility that the corrosion of the reinforcing bars of reinforced concrete cannot be evaluated with high accuracy due to the influence of the impedance-frequency characteristics of concrete.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a method for evaluating reinforced concrete reinforcing bar corrosion that can evaluate the corrosion of reinforced concrete reinforcing bars with high accuracy.

<First aspect of the present invention>
In the first aspect of the present invention, two detection probes are arranged at predetermined intervals on the surface of the reinforced concrete to be measured in parallel with the reinforcing bar in the reinforced concrete to be measured, and the two detection probes are arranged. Two current probes are arranged one by one on both outer sides of the needle at the predetermined intervals, an AC current is passed between the two current probes, and the two detections are detected while changing the frequency of the AC current. The voltage between the probes is measured, the relationship between the frequency of the AC current and the impedance is acquired as the first measurement data, and the direction perpendicular to the reinforcing bar in the reinforced concrete to be measured is on the surface of the reinforced concrete to be measured. The two detection probes are arranged at the predetermined intervals on the same line on the surface of the portion of the reinforced concrete to be measured where there is no reinforcing bar, and the two detection probes are placed on both outer sides of the two detection probes. The current probes are arranged one by one at the predetermined intervals, an AC current is passed between the two current probes, and the voltage between the two detection probes is measured while changing the frequency of the AC current. Then, the relationship between the frequency and the impedance of the AC current is acquired as the second measurement data, and the subtraction value or the division value of the impedance of the first measurement data at the impedance of the second measurement data is obtained for each frequency. Reinforcement corrosion evaluation of reinforced concrete, which evaluates the corrosion of the reinforcing bar in the reinforced concrete to be measured based on the difference between the maximum value in the low frequency region and the minimum value in the high frequency region of the subtracted value or the divided value. The method.

Although concrete is generally known as an insulator, it has conductivity due to a small amount of ions. In addition, a volume component due to the electric double layer is formed between the sound reinforcing bar surface and the concrete surface. The capacitance component of this electric double layer decreases as the electric double layer is destroyed and lost due to corrosion. The difference between the maximum impedance in the low frequency region and the minimum impedance in the high frequency region of the first measurement data changes depending on the capacitance component of the electric double layer, and therefore changes depending on the degree of corrosion of the reinforcing bar. Therefore, the degree of corrosion of the reinforcing bar of the reinforced concrete to be measured can be evaluated from the difference between the highest impedance value in the low frequency range and the lowest impedance value in the high frequency range of the first measurement data.

On the other hand, it can be said that the second measurement data is the impedance-frequency characteristics of the concrete itself of the reinforced concrete to be measured. Therefore, the first measurement data and the second measurement data are compared, specifically, the difference or ratio between the first measurement data and the second measurement data, that is, the impedance of the first measurement data and the impedance of the second measurement data. By obtaining the subtracted value or the divided value for each frequency and evaluating based on the subtracted value or the divided value, the contribution of the reinforcing bar in the first measurement data excluding the impedance-frequency characteristic peculiar to the reinforced concrete to be measured. Can be accurately identified. As a result, it is possible to measure the change in the capacitance component due to the electric double layer formed between the reinforcing bar surface and the concrete surface with high accuracy, so that the degree of corrosion of the reinforcing bar of the reinforced concrete to be measured can be evaluated with high accuracy. ..

As a result, according to the first aspect of the present invention, it is possible to provide an effect of providing a method for evaluating reinforced concrete rebar corrosion that can evaluate the corrosion of reinforced concrete rebar with high accuracy.

< Second aspect of the present invention>
The second aspect of the present invention is the depth from the surface of the reinforced concrete to be measured to the reinforcing bar based on the lowest value of the impedance in the high frequency region of the first measurement data in the first aspect of the present invention described above. This is a method for evaluating reinforced concrete corrosion of reinforced concrete.

The lowest value of impedance in the high frequency region of the first measurement data changes depending on the depth from the surface of the reinforced concrete to the reinforcing bar. Further, the minimum value of impedance in the high frequency range of the first measurement data hardly depends on the degree of corrosion of the reinforcing bar. Therefore, the depth from the surface of the reinforced concrete to be measured to the reinforcing bar can be estimated with high accuracy based on the lowest value of the impedance in the high frequency region of the first measurement data. As a result, according to the second aspect of the present invention, there is no need for a device for measuring the depth from the surface of the reinforced concrete to be measured to the reinforcing bar, such as a reinforcing bar exploration device by an electromagnetic wave radar method. Be done.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for evaluating reinforced concrete reinforcing bar corrosion that can evaluate the corrosion of reinforcing bars of reinforced concrete with high accuracy.

The front view which illustrated the structure of the measuring apparatus used for carrying out this invention. Top view of the samples of sample numbers 1 to 6 used in the verification experiment. Front view of the sample of sample numbers 1 to 6 used in the verification experiment. Top view of the sample of sample numbers 7 to 12 used in the verification experiment. Front view of the sample of sample numbers 7 to 12 used in the verification experiment. A list showing the composition of the sample used in the verification experiment. The graph which illustrated the impedance-frequency characteristic of the reinforcing bar of the sample of sample numbers 1-6. A graph showing the difference between the highest impedance value in the low frequency range and the lowest impedance value in the high frequency range in relation to the corrosion rate. The graph which illustrated the impedance-frequency characteristic of the reinforcing bar of the sample of a sample number 7-12. The graph which showed the impedance in the low frequency region (frequency 0.01Hz) corresponding to the rebar depth. Top view of the samples of sample numbers 1 to 6 used in the verification experiment. The graph which illustrated the impedance-frequency characteristic and the phase-frequency characteristic in the sample of the sample No. 1 having a reinforcing bar depth of 54 mm.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
It is needless to say that the present invention is not particularly limited to the examples described below, and various modifications can be made within the scope of the invention described in the claims.

First, the configuration of the measuring device used for carrying out the present invention will be described with reference to FIG.
FIG. 1 is a front view illustrating the configuration of a measuring device used in carrying out the present invention.
Here, the direction indicated by the reference numeral X in the drawings of the present application is a direction parallel to the surface of the reinforced concrete 20 and a direction parallel to the reinforcing bar 21 of the reinforced concrete 20. In the drawings of the present application, the direction indicated by reference numeral Y is a direction parallel to the surface of the reinforced concrete 20 and a direction orthogonal to the reinforcing bar 21 of the reinforced concrete 20. In the drawings of the present application, the direction indicated by reference numeral Z is a direction orthogonal to the surface of the reinforced concrete 20.

The measuring device used for carrying out the present invention is a device for measuring the impedance-frequency characteristics of the reinforced concrete 20 to be measured by using the so-called Wenner four-electrode method. The measuring devices include a first detection probe 11, a second detection probe 12, a first current probe 13, a second current probe 14, a potential difference measuring device 15, an AC power supply device 16, a current measuring device 17, and a control unit 18. To prepare for.

The first detection probe 11 and the second detection probe 12 are arranged in contact with the surface of the reinforced concrete 20 to be measured at predetermined intervals a. The first current probe 13 and the second current probe 14 are arranged on both outer sides of the first detection probe 11 and the second detection probe 12 in contact with the surface of the reinforced concrete 20 to be measured. More specifically, the first current probe 13 is arranged outside the first detection probe 11 at a position separated by a predetermined interval a, and the second current probe 14 is located outside the second detection probe 12. It is arranged at a position separated by a predetermined interval a. That is, the first detection probe 11, the second detection probe 12, the first current probe 13, and the second current probe 14 are on the same line in the X direction at regular intervals a at regular intervals a, and the reinforced concrete 20 to be measured. It is placed in contact with the surface. As the first detection probe 11, the second detection probe 12, the first current probe 13, and the second current probe 14, various ones can be used as long as the conductivity can be ensured. For example, a wet sponge and a metal needle are combined. A material, a sheet having conductivity, or the like can be used.

The potential difference measuring device 15 is connected to the first detection probe 11 and the second detection probe 12, and measures the potential difference and the phase between the first detection probe 11 and the second detection probe 12. More specifically, in the potential difference measuring device 15, the potential at the point where the first detection probe 11 is in contact with the surface of the reinforced concrete 20 to be measured and the second detection probe 12 are in contact with the surface of the reinforced concrete 20 to be measured. It is a device for measuring the potential difference V and the phase with the potential of the point.

The AC power supply device 16 is connected to the first current probe 13 and the second current probe 14. The AC power supply device 16 is a device for passing an AC current between the first current probe 13 and the second current probe 14, and is an AC power supply capable of variably setting the frequency of the AC current. The current measuring device 17 is a device that measures the current value I and the frequency of the alternating current flowing between the first current probe 13 and the second current probe 14.

The control unit 18 controls the AC power supply device 16 to change the frequency of the AC current flowing between the first current probe 13 and the second current probe 14, while changing the frequency of the first detection probe 11 and the second detection probe 14. The potential difference V between the needle 12 and the needle 12 is measured to acquire the relationship between the frequency of the alternating current and the impedance ρ. The impedance ρ may be measured by, for example, an impedance meter having a sufficiently high input impedance. Further, in Wenner's four-electrode method, the impedance ρ of the sample in an infinite half-space with a uniform medium can be calculated from the following equation (1).
ρ = 2πaV / I ・ ・ ・ (1)
The range in which the frequency of the alternating current is changed is, for example, about 0.001 Hz to 10 KHz. Further, for example, in order to shorten the measurement time, the measurement is limited to a specific frequency range including at least a frequency range of 1 Hz or less as a low frequency range and a frequency range of 10 to 1000 Hz as a high frequency range. May be good.

Next, a method for evaluating reinforced concrete corrosion of the reinforced concrete 20 according to the present invention will be described.

First, on the surface of the reinforced concrete 20 to be measured, parallel to the reinforcing bar 21 in the reinforced concrete 20 to be measured (on the same line in the X direction directly above the reinforcing bar 21), the first detection probe 11 and the second detection probe 12 are arranged at predetermined intervals a, and one first current probe 13 and one second current probe 14 are arranged at predetermined intervals a on both outer sides of the first detection probe 11 and the second detection probe 12. In this state, an alternating current is passed between the first current probe 13 and the second current probe 14, and the frequency of the alternating current is changed between the first detection probe 11 and the second detection probe 12. The potential difference V is measured, and the relationship between the frequency of the alternating current and the impedance ρ is acquired as the first measurement data.

Next, on the surface of the reinforced concrete 20 to be measured, in the direction orthogonal to the reinforcing bar 21 in the reinforced concrete 20 to be measured (on the same line in the Y direction), or the same surface of the portion of the reinforced concrete 20 to be measured without the reinforcing bar 21. The first detection probe 11 and the second detection probe 12 are arranged on the line at predetermined intervals a, and the first current probe 13 and the second detection probe 13 and the second detection probe 12 are arranged on both outer sides of the first detection probe 11 and the second detection probe 12. The current probes 14 are arranged one by one at predetermined intervals a. In this state, an alternating current is passed between the first current probe 13 and the second current probe 14, and the frequency of the alternating current is changed between the first detection probe 11 and the second detection probe 12. The potential difference V is measured, and the relationship between the frequency of the alternating current and the impedance ρ is acquired as the second measurement data.

The difference between the maximum value of the impedance ρ in the low frequency region and the minimum value of the impedance ρ in the high frequency region of the first measurement data changes depending on the capacitance component formed by the electric double layer formed between the surface of the reinforcing bar 21 and the concrete surface. , Will change depending on the degree of corrosion of the reinforcing bar 21. Therefore, the degree of corrosion of the reinforcing bar 21 of the reinforced concrete 20 to be measured can be evaluated from the difference between the maximum value of the impedance ρ in the low frequency region and the minimum value of the impedance ρ in the high frequency region of the first measurement data.

On the other hand, it can be said that the second measurement data is the impedance-frequency characteristic of the concrete itself of the reinforced concrete 20 to be measured. Therefore, by comparing the first measurement data and the second measurement data, for example, by evaluating the difference between the first measurement data and the second measurement data, the impedance-frequency characteristics peculiar to the reinforced concrete 20 to be measured are excluded. Therefore, the contribution of the reinforcing bar 21 in the first measurement data can be accurately specified. As a result, changes in the capacity component due to the electric double layer formed between the surface of the reinforcing bar 21 and the surface of the concrete can be measured with high accuracy, so the degree of corrosion of the reinforcing bar 21 of the reinforced concrete 20 to be measured can be evaluated with high accuracy. can do.

Further, the minimum value of the impedance ρ in the high frequency region of the first measurement data changes according to the depth from the surface of the reinforced concrete 20 to the reinforcing bar 21. Further, the minimum value of the impedance ρ in the high frequency region of the first measurement data hardly depends on the degree of corrosion of the reinforcing bar 21. Therefore, the depth from the surface of the reinforced concrete 20 to be measured to the reinforcing bar 21 can be estimated with high accuracy based on the lowest value of the impedance ρ in the high frequency region of the first measurement data.

Next, the verification experiment of the present invention conducted by the inventor of the present invention will be described with reference to FIGS. 2 to 12.

FIG. 2 is a plan view of the samples of sample numbers 1 to 6 used in the verification experiment, and FIG. 3 is a front view thereof. FIG. 4 is a plan view of the samples of sample numbers 7 to 12 used in the verification experiment, and FIG. 5 is a front view thereof. FIG. 6 is a list showing the composition of the sample used in the verification experiment.

As the samples of sample numbers 1 to 6 (FIGS. 2 and 3), a plurality of reinforced concrete 20 having a width L1, a length L2, and a height L3 in which one reinforcing bar 21M was embedded at a depth D1 were prepared. The width L1 was 300 mm, the length L2 was 300 mm, and the height L3 was 100 mm. The distance L4 from the side end of the reinforced concrete 20 to the reinforcing bar 21M was set to 150 mm. The diameter d of the reinforcing bar 21M is 16 mm. Here, in the samples of sample numbers 1 to 6, when the distance from the front surface of the reinforced concrete 20 to the reinforcing bar 21M is 30 mm, the distance from the back surface of the reinforced concrete 20 to the reinforcing bar 21M is 54 mm. The measurement is performed when the depth D1 of the reinforcing bar 21M is 30 mm, and the measurement on the back surface of each sample is measured when the depth D1 of the reinforcing bar 21M is 54 mm. That is, by measuring the depth D1 of the reinforcing bar 21M by turning over the sample of 30 mm, the measurement of the sample having the depth D1 of the reinforcing bar 21M of 54 mm is also performed. Of the reinforcing bars 21M of the samples of sample numbers 1 to 6, those having a corrosion rate of 0 wt% are reinforcing bars without corrosion, and those having a corrosion rate of 1 to 5 wt% are energized after concrete casting to accelerate corrosion. It is a reinforcing bar that is artificially corroded by making it.

As samples of sample numbers 7 to 9 (without reinforcing bars 21M in FIGS. 4 and 5), a plurality of reinforced concrete 20 having a width L1, a length L2, and a height L3 in which two reinforcing bars 21L and 21R were embedded were prepared. The width L1 was 300 mm, the length L2 was 300 mm, and the height L3 was 100 mm. The distance (distance) L5 from one end of the concrete 20 to the reinforcing bar 21L was 75 mm, and the distance (distance L5 + spacing L5) from the reinforcing bar 21L to the reinforcing bar 21R was 150 m. The diameter d of the two reinforcing bars 21L and 21R was set to 16 mm. The depth D2 of the reinforcing bar 21R was 10 mm, and the depth D4 of the reinforcing bar 21L was 50 mm. Of the reinforcing bars 21L and 21R of the samples of sample numbers 7 to 9, those having a corrosion rate of 0 wt% are reinforcing bars without corrosion, and those having a corrosion rate of 1 to 2 wt% are energized and corroded after concrete casting. It is a reinforcing bar that has been artificially corroded by accelerating.

As samples of sample numbers 10 to 11 (those having the same depth of reinforcing bars in FIGS. 4 and 5), three reinforcing bars 21L, 21M, and 21R are embedded at equal intervals, and the width L1, the length L2, and the height L3 are embedded. A plurality of reinforced concrete 20 of the above were prepared. The width L1 was 300 mm, the length L2 was 300 mm, and the height L3 was 100 mm. The distance L5 between the three reinforcing bars 21L, 21M, and 21R was set to 75 mm. The diameters d of the three reinforcing bars 21L, 21M, and 21R were all 16 mm. The depth of each of the three reinforcing bars 21L, 21M, and 21R was set to 30 mm. Among the reinforcing bars 21L, 21M, 21R of the samples of sample numbers 10 to 11, those having a corrosion rate of 0 wt% are reinforcing bars without corrosion, and those having a corrosion rate of 1 to 5 wt% are energized after concrete casting. It is a reinforcing bar that has been artificially corroded by accelerating the corrosion.

As a sample of sample number 12 (FIGS. 4 and 5), a plurality of reinforced concrete 20 having a width L1, a length L2, and a height L3 in which three reinforcing bars 21L, 21M, and 21R were embedded at equal intervals were prepared. The width L1 was 300 mm, the length L2 was 300 mm, and the height L3 was 100 mm. The distance L5 between the three reinforcing bars 21L, 21M, and 21R was set to 75 mm. The diameters d of the three reinforcing bars 21L, 21M, and 21R were all 16 mm. The depth D2 of the reinforcing bar 21R was 10 mm, the depth D3 of the reinforcing bar 21M was 30 mm, and the depth D4 of the reinforcing bar 21L was 50 mm. The corrosion rate of the reinforcing bars 21L, 21M, and 21R of the sample of sample No. 12 is 1%, and each reinforcing bar is a reinforcing bar that artificially causes corrosion by energizing after concrete casting and accelerating the corrosion.

The inventor of the present invention conducted a verification experiment to acquire "first measurement data" using the above-mentioned samples of sample numbers 1 to 12. More specifically, the first detection probe 11 and the second detection probe 12 are parallel to the surface of the reinforced concrete 20 of the sample numbers 1 to 12 along the reinforcing bars 21L, 21M, 21R in the reinforced concrete 20 to be measured. Are arranged at predetermined intervals a (positions shown by reference numerals P2 and P3), and the first current probe 13 and the second current probe 14 are placed on both outer sides of the first detection probe 11 and the second detection probe 12. The pieces were arranged at predetermined intervals a (positions shown by reference numerals P1 and P4). In this state, an alternating current is passed between the first current probe 13 and the second current probe 14, and the frequency of the alternating current is changed between the first detection probe 11 and the second detection probe 12. The potential difference V was measured to obtain the relationship between the frequency of the alternating current and the impedance ρ for each of the reinforcing bars 21L, 21M, and 21R of sample numbers 1 to 12.

7 and 8 show the results of verification experiments using the samples of sample numbers 1 to 6. FIG. 7 is a graph illustrating the impedance-frequency characteristics of the reinforcing bars 21M of the samples of sample numbers 1 to 6. FIG. 8 is a graph showing the difference between the highest value of impedance ρ in the low frequency range and the lowest value of impedance ρ in the high frequency range in association with the corrosion rate.

9 and 10 show the results of verification experiments using the samples of sample numbers 7 to 12. FIG. 9 is a graph illustrating the impedance-frequency characteristics of the reinforcing bars 21L, 21M, and 21R of the samples of sample numbers 7 to 12. FIG. 10 is a graph showing the impedance ρ in the low frequency region (frequency 0.01 Hz) in association with the reinforcing bar depth.

From the graphs of FIGS. 7 and 8, when the reinforcing bar depth of the reinforcing bar 21M is 30 mm and 54 mm, the maximum value of the impedance ρ in the low frequency range and the high frequency range are increased as the corrosion rate of the reinforcing bar 21M increases. It can be seen that the difference from the lowest value of the impedance ρ in is decreasing. Therefore, it can be seen that the degree of corrosion of the reinforcing bar 21M of the reinforced concrete 20 can be evaluated from the difference between the maximum value of the impedance ρ in the low frequency range and the minimum value of the impedance ρ in the high frequency range.

On the other hand, in FIG. 9, the frequency of the reinforcing bar 21R having a depth D2 of sample number 7 of 10 mm (L7R in FIG. 9) and the reinforcing bar 21R having a depth D2 of sample number 8 of 10 mm (L8R in FIG. 9) are 10 Hz. The values of impedance ρ in are almost the same corresponding to the depth of the reinforcing bar, but the values of impedance ρ of both reinforcing bars differ greatly toward lower frequencies (0.01 Hz). Since the only difference between the two reinforcing bars is the presence or absence of corrosion, it can be seen from the graph of FIG. 9 that the deviation in the value of the impedance ρ in the low frequency region is caused by the corrosion. Further, from the graph of FIG. 10 in which the value of the impedance ρ of 0.01 Hz is the vertical axis, it can be seen that the difference in the value of the impedance ρ is small even if the depth of the reinforcing bar changes when there is no corrosion. Further, from the graph of FIG. 10, it can be seen that the value of the impedance ρ at a frequency of 0.01 Hz correlates with the depth of the reinforcing bar when corrosion is present even at 1% in the reinforcing bar. That is, the value of the impedance ρ when the frequency is around 0.01 Hz is roughly classified according to the presence or absence of corrosion, and if there is corrosion, it depends on the depth of the reinforcing bar. In consideration of such a relationship, it becomes possible to comprehensively judge the corrosion of the reinforcing bar of the reinforced concrete 20.

Further, from the graph of FIG. 7, the minimum value of the impedance ρ in the high frequency region changes according to the reinforcement depth of the reinforcing bar 21M, and the minimum value of the impedance ρ in the high frequency region hardly depends on the degree of corrosion of the reinforcing bar 21M. You can see that. Similarly, from the graph of FIG. 9, the minimum value of the impedance ρ in the high frequency region changes according to the reinforcing bar depth of the reinforcing bars 21L, 21M, 21R, and the minimum value of the impedance ρ in the high frequency region is the reinforcing bars 21L, 21M. It can be seen that it does not depend much on the degree of corrosion of 21R. Therefore, it can be seen that the depth from the surface of the reinforced concrete 20 to be measured to the reinforcing bar 21 can be estimated based on the lowest value of the impedance ρ in the high frequency region.

FIG. 11 is a plan view of the samples of sample numbers 1 to 6 used in the verification experiment, and is a first detection probe 11, a second detection probe 12, and a first current probe 13 in a direction orthogonal to the reinforcing bar 21. The state in which the second current probe 14 is arranged is illustrated.

The inventor of the present invention conducted a verification experiment to further acquire "second measurement data" using the above-mentioned sample (corrosion rate 0 wt%) having a reinforcing bar depth of 54 mm of sample number 1. More specifically, the first detection probe 11 and the second detection probe 12 are placed on the surface of the reinforced concrete 20 of the sample having a reinforcing bar depth of 54 mm of sample number 1 in a direction orthogonal to the reinforcing bar 21M in the reinforced concrete 20. Arranged at predetermined intervals a (positions shown by the symbols P2V and P3V), one first current probe 13 and one second current probe 14 are provided on both outer sides of the first detection probe 11 and the second detection probe 12. They were arranged at predetermined intervals a (positions shown by reference numerals P1V and P4V). In this state, an alternating current is passed between the first current probe 13 and the second current probe 14, and the frequency of the alternating current is changed between the first detection probe 11 and the second detection probe 12. The relationship between the frequency and impedance ρ of the alternating current, and the frequency and phase change of the alternating current (relative to the phase of the current I) for each of the reinforcing bars 21L, 21M, and 21R of sample numbers 1 to 12 by measuring the potential difference V and the phase of The relationship of the phase difference of the potential difference V) was acquired.

FIG. 12 is a graph illustrating impedance-frequency characteristics and phase-frequency characteristics in a sample having a reinforcing bar depth of 54 mm of sample number 1. Here, the graph shown by the solid line in FIG. 12 is a graph of impedance-frequency characteristics, and the graph shown by a broken line is a graph of phase-frequency characteristics. Further, in FIG. 12, the graph with the characters “L1-54 mm parallel” shows the first detection probe 11, the second detection probe 12, and the first current probe in the sample with the reinforcing bar depth of 54 mm of sample number 1. 13 is a graph of the case where the 13 and the second current probe 14 are arranged in parallel along the reinforcing bar 21M in the reinforced concrete 20 (FIG. 2) (first measurement data). On the other hand, in FIG. 12, the graph with the letters "L1-54 mm orthogonal" shows the first detection probe 11, the second detection probe 12, and the first current probe in the sample with the reinforcing bar depth of 54 mm of sample number 1. It is a graph of the case where the needle 13 and the second current probe 14 are arranged in the direction orthogonal to the reinforcing bar 21M in the reinforced concrete 20 (FIG. 11) (second measurement data).

From the phase-frequency characteristics (broken line graph) in FIG. 12, when four probes are arranged in parallel along the reinforcing bar 21M, the maximum phase value is around 0.5 Hz, while the four probes are located. It can be seen that when the needle is arranged in the direction orthogonal to the reinforcing bar 21M, the phase change hardly occurs. The difference between these two phase graphs is considered to be the effect of the reinforcing bar 21M. The reinforcing bar 21M of the sample with the reinforcing bar depth of 54 mm of sample No. 1 is a healthy reinforcing bar having a corrosion rate of 0 wt% and no corrosion. Then, as the corrosion of the reinforcing bar 21M progresses, the capacitance component due to the electric double layer between the reinforcing bar surface and the concrete surface is gradually lost, and the difference in impedance-frequency characteristics (difference between the first measurement data and the second measurement data) becomes. It is thought that it will become smaller. Therefore, from the graph of FIG. 12, the reinforced concrete 20 to be measured is measured by comparing the first measurement data and the second measurement data, for example, by evaluating the ratio or difference between the first measurement data and the second measurement data. It can be seen that the contribution of the reinforcing bar 21 in the first measurement data can be accurately specified by excluding the impedance-frequency characteristics peculiar to.

11 1st detection probe 12 2nd detection probe 13 1st current probe 14 2nd current probe 15 Potential difference measuring device 16 AC power supply device 17 Current measuring device 18 Control unit 20 Reinforced concrete 21, 21L, 21M, 21R Reinforcing bar

Claims (2)

Two detection probes are arranged at predetermined intervals on the surface of the reinforced concrete to be measured in parallel with the reinforcing bars in the reinforced concrete to be measured, and two currents are applied to both outer sides of the two detection probes. Place the probes one by one at the predetermined intervals,
An alternating current is passed between the two current probes, the voltage between the two detection probes is measured while changing the frequency of the alternating current, and the relationship between the frequency of the alternating current and the impedance is determined. Acquired as 1 measurement data,
The two detection probes are placed on the surface of the reinforced concrete to be measured in a direction orthogonal to the reinforcing bar in the reinforced concrete to be measured, or on the same line on the surface of the portion of the reinforced concrete to be measured where there is no reinforcing bar. The two current probes are arranged at predetermined intervals, and the two current probes are arranged one by one on both outer sides of the two detection probes at the predetermined intervals.
An alternating current is passed between the two current probes, the voltage between the two detection probes is measured while changing the frequency of the alternating current, and the relationship between the frequency of the alternating current and the impedance is determined. 2 Acquired as measurement data,
The subtraction value or the division value of the impedance of the first measurement data at the impedance of the second measurement data is obtained for each frequency, and the subtraction value or the division value is the highest value in the low frequency region and the high frequency region . A method for evaluating reinforcing bar corrosion in reinforced concrete, which evaluates corrosion of reinforcing bars in the reinforced concrete to be measured based on the difference from the minimum value. In the method for evaluating reinforced concrete corrosion of reinforced concrete according to claim 1 , the depth from the surface of the reinforced concrete to be measured to the reinforcing bar is estimated based on the lowest value of the impedance in the high frequency region of the first measurement data. Reinforcement corrosion evaluation method.

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