JP7227088B2 - Measurement method for measuring the inside of a specimen - Google Patents

Description

TECHNICAL FIELD The present invention relates to a measuring method for measuring the inside of a specimen for determining, for example, whether or not a cavity or the like exists inside a concrete product.

For example, when mixing aggregates for concrete, it is assumed that the concrete is in a "surface dry state (surface dry saturated state)", the density of the aggregates is obtained, and the aggregates are mixed according to various mixing designs. Here, the "surface dry state" is premised on a state in which the voids inside the compacted aggregate are filled with water and the surface of the aggregate does not contain water. .
In general, the flow cone method standardized in JIS A1109 is used to determine the surface dry state of aggregates. According to this, a flow cone having a truncated cone shape is filled with aggregate, rammed with a ramming rod to a predetermined hardness, and then the flow cone is gradually pulled upward to form the rammed bone. The state near the boundary where the material crumbles or does not crumble is judged as the surface dry state.

However, accurate data of collapsed aggregates are required for judging the surface dry state. In particular, an empirical rule is required to make an accurate judgment, and an inexperienced measurer may not be able to make an accurate judgment.
In particular, the above-mentioned flow cone method is carried out on sand, gravel, etc. called "natural aggregate", but in recent years, the supply of this "natural aggregate" has decreased, and many substitutes is used as aggregate. For example, so-called "low-grade" aggregates such as crushed sand, blast furnace slag, molten waste slag, and recycled aggregates are often used. These low-grade aggregates may have a glassy or porous surface, and may have surface drying properties that are distinctly different from those of natural aggregates. Therefore, in the flow cone method, it is particularly difficult to accurately determine the surface dry state of aggregates such as crushed sand.

For example, a method using a new standard flow cone for determining surface dryness formed with a size such as a free-standing angle or a wide diameter that is different from the shape of the flow cone standardized by JIS, and measuring the moisture content using infrared reflectance. (see Non-Patent Document 1), using changes in electrical resistance in dry and wet conditions (see Non-Patent Document 2), using centrifugal dehydration (see Non-Patent Document 3), and the like.

Kazuma Takeuchi, et al., ``Fundamental research on surface dry judgment test method for fine aggregate'', Proceedings of the Japan Concrete Institute, Vol. 25, No. 1, 2003, p77-p82 Daisuke Yamamoto, 4 others, ``Study on method for judging surface dryness of crushed sand as sea sand substitute aggregate'', 59th Annual Conference of Japan Society of Civil Engineers, September 2004, p491-492 Kazuo Suzuki, et al., ``Study on Simple Method for Determining Surface Dryness of Fine Aggregate,'' Proceedings of the 48th Cement Technology Conference, 1994, p.156-p.159 JP-A-2006-329801 Japanese Patent No. 6343708

In Non-Patent Document 1, flow cones formed with different self-supporting angles and sizes are used, and a certain amount of empirical rules are required to determine the surface dry state as in the past, and accurate reproducibility is required. It was difficult. In addition, it is necessary to appropriately select the optimum flow cone according to the type and properties of the aggregate, and it is necessary to prepare a plurality of types of flow cones in advance.
In particular, non-patent document 1, which utilizes infrared reflectance, uses two wavelengths: an infrared wavelength (1.46 μm) that is generally easily absorbed by water and an infrared wavelength (1.6 μm) that is difficult to be absorbed by water. Since it was calculated based on the data measured mainly for "Shirasu" as an aggregate, the effect on other low-grade aggregates was not disclosed.

In Non-Patent Document 2, various measurements were carried out using crushed sand as a sample to be measured, and by synthesizing various results, the flow cone method obtained the most appropriate result, and the other methods are Non-Patent Document The measurement results of No. 2 did not show particularly excellent characteristics.
In Non-Patent Document 3, it is possible to determine the surface dry state with high accuracy, but the target aggregate is set in a centrifuge and a centrifugal force of several G to several thousand G is applied depending on the sample. Therefore, the apparatus for judging the surface dryness becomes large-scaled, and is not suitable for simple judgment of the surface dryness.

On the other hand, in order to improve the durability of concrete structures at present, attention is paid to a construction method in which a silane-based surface impregnating material is applied to the surface and permeated to form a water-repellent layer inside the concrete.
By applying this water-repellent layer, it is possible to suppress the infiltration of water and to suppress the infiltration of degrading factors such as salt and water, thereby enhancing the durability of the concrete. For example, the "Hokkaido Development Bureau Road Design Guidelines" stipulates that the permeation depth should be 6 mm or more as a criterion for product selection of silane-based surface impregnating materials for countermeasures against frost damage. For this reason, when the surface impregnation method is applied, the quality of construction can be improved by managing with the formed water-repellent layer. Therefore, the present inventors proposed a method for estimating the thickness of the water-repellent layer of concrete by using the electrical change due to the level of water content.

In Patent Document 2, the present inventors consider two electrode plates having an electrode plate area as a pair, and the horizontal distance from the center position of the pair of electrode plates to the center position of the width of each electrode plate and the area of the pair of electrode plates A geometric coplanar electrode having a constant geometric coplanar electrode constant consisting of a ratio of is applied to the pair of the geometric coplanar electrodes, and a horizontal plane distance to the center position between the electrode plates and The characteristic of the linear function equation is obtained between the displayed value that depends on the capacitance, the slope of the characteristic of the linear function equation is used as the slope information related to the thickness of the water-repellent layer, and the capacitance depends on the We invented a measurement method that can measure the thickness of the water-repellent layer, in which the intercept of the displayed value is output as information related to the water content near the surface layer.
Thus, a measurement method for measuring a specimen in which even if the resistance value and the dielectric constant change with the water content, the effect of the water content does not change was presented.

However, when measured by applying current, the resistance value decreases depending on the temperature and composition, and the dielectric constant changes accordingly depending on the metal ions. Furthermore, the frequency characteristics of conductivity and dielectric constant also change depending on the water content. Therefore, there has been a demand for a method of measuring the inside of a specimen in which changes in electrical characteristics are small and disturbances in the electric field are easily detected depending on the position of the electrode plate, the area of the electrode plate, and the height of the applied voltage.

In particular, when concrete is cast, internal cavities such as janka (bean board) may be formed in the concrete below the window frame. Defects such as these cavities are difficult to grasp from the outside. In particular, even if the internal cavity is found while the formwork is being removed after the concrete has been placed, basic repairs cannot be carried out. Therefore, there has been a demand for a method for measuring the inside of a specimen that can detect cavities even during concrete placement.
Further, there has been a demand for a measuring method capable of detecting abnormalities in internal cavities of concrete, even during concrete placement, even with an embedded formwork that does not remove the concrete formwork.

In particular, in order to ensure the performance of the concrete structure, it is important that the concrete is densely filled in the formwork. Insufficient filling may occur due to factors such as unexpected troubles during transportation or construction of concrete, and defects such as junka on the surface of the formwork and internal cavities around the reinforcing bars may occur. These defects are difficult to detect during construction, and may become apparent only after the formwork is removed after the concrete has hardened.
Recently, from the aspect of productivity improvement, buried formwork made of concrete or mortar has been adopted so that stripping work can be omitted. In particular, it is not possible to grasp the state of concrete filling in the embedded formwork even after demolding. However, it is necessary to ensure integrity without creating a gap between the embedded formwork and the filling concrete, and it is necessary to confirm this in some way.

Therefore, the present invention provides a measurement method for measuring the inside of a test piece in which the results are not different depending on the electrical characteristics of the test piece, and even if the resistance value and dielectric constant change due to the moisture content, the effect is unlikely to appear. It is intended for

The measuring method for measuring the inside of a specimen according to the invention of claim 1 is equal ratio, in which a plurality of strip-shaped electrode plates made of a conductor and having the same aspect ratio and the same electrode plate area S are arranged side by side on an insulating sheet 10. The total area nS of the coplanar electrode plates 21 and 22 is arbitrarily selected, the selected equal ratio coplanar electrode plates 21 and 22 are short-circuited to form a pair of a positive electrode and a negative electrode, and the equal ratio coplanar electrode plates 21 and 22 are formed. A power supply e for applying a frequency of 100 Hz or more to the plane electrode plates 21 and 22, and a power supply e that rotates from the center position 0 between the pair of equal ratio coplanar electrode plates 21 and 22 to the center positions ± of the equal ratio coplanar electrode plates 21 and 22. The distance between the electrodes up to _s0 , that is, the electrode spacing t, is provided, and the mutual arrangement of the equal ratio coplanar electrode plates 21 and 22 is from the center position 0 of the equal ratio coplanar electrode plates 21 and 22 to πt , the capacitance between the pair of equal-ratio coplanar electrode plates 21 and 22 is calculated.
Even during concrete placement, the capacitance of the specimen (concrete) becomes lower due to the detection of cavities compared to concrete with a known standard capacitance. , the internal cavity of concrete can be detected even in an embedded mold without removing the concrete formwork.

Here, the equal ratio coplanar electrode plates 21 and 22 are strip-shaped electrode plates made of a conductor and having the same aspect ratio and the same area. The strip shape having the same aspect ratio and the same electrode plate area S may be either a square or a rectangle.
Further, the power source e applies a frequency of 100 Hz or more, which means that there should be no influence of noise from the commercial power source and no influence on the measured value of tan δ. Since the measurement environment is a wet place, the applied voltage is desirably 100 V or less because the measurement is performed without increasing the voltage as much as possible in order to prevent electric shock. The frequency is desirably in the range of 100 Hz or more and 30 MHz or less. If possible, it is desirable to use 1 MHz to 30 MHz.

For the pair of equal ratio coplanar electrode plates 21 and 22, the total area nS of the equal ratio coplanar electrode plates 21 and 22 is arbitrarily selected, and the selected equal ratio coplanar electrode plates 21 and 22 are They are short-circuited to form a pair of a positive electrode and a negative electrode.
Further, the electrode spacing t is defined by the distance from the center position O between the pair of equal ratio coplanar electrode plates 21 and 22 and the center position ±s ₀ of the pair of equal ratio coplanar electrode plates 21 and 22 to the other equal ratio coplanar electrode plate. It is the distance to the center position ±s ₀ of the electrode plates 21 and 22 .
Furthermore, if the equal-ratio coplanar electrode plates 21 and 22 are arranged as parallel plate electrodes, the distance between them is the facing average distance d. However, since the equal ratio coplanar electrode plates 21 and 22 are used, the mutual distance between the equal ratio coplanar electrode plates 21 and 22 is 2πd/2=πd. The distance πd is therefore the arithmetic mean value of the estimated depth of penetration of the electric field.

In the measuring method for measuring the inside of a specimen according to the invention of claim 2, a plurality of equal-ratio coplanar electrode plates 21 and 22, which are made of the conductor and have the same aspect ratio and the same electrode plate area S, are arranged side by side. In addition, since it is possible to detect filling defects in concrete from a plurality of angles with different combinations of the equal ratio coplanar electrode plates 21 and 22, detection can be performed without overlooking depending on the combination angle of the equal ratio coplanar electrode plates 21 and 22. It is possible. In particular, by setting the combined total area of the equal ratio coplanar electrode plates 21 and 22 to be S, 2S, 3S, . . Occurrence of poor filling in concrete can be estimated from the decrease in capacitance.

In the measuring method for measuring the inside of the specimen according to the invention of claim 3, the equal ratio coplanar electrode plates 21 and 22, which are made of conductors and have the same aspect ratio and the same electrode plate area S, are insulated. Since a plurality of types of the equal ratio coplanar electrode plates 21 and 22 are combined according to the combination of the number of the equal ratio coplanar electrode plates 21 and 22 formed on the substrate, it is possible to combine various types of equal ratio coplanar electrode plates 21 and 22 by short-circuiting. By combining a plurality of equal-ratio coplanar electrode plates 21 and 22 arranged side by side, the electrodes can be formed in a required form.
A specific area can be easily calculated by setting the combined total area of a plurality of equal ratio coplanar electrode plates 21 and 22 to be S, 2S, 3S, . . .

In the measuring method for measuring the inside of a specimen according to the invention of claim 4, a plurality of equal-ratio coplanar electrode plates 21 and 22 having the same aspect ratio and the same electrode plate area S are provided so that the front and back surfaces are made of an insulating material. Since the electrode plates 21 and 22 are molded with , both sides of the equal ratio coplanar electrode plates 21 and 22 can be placed in the formwork of the insulating concrete, and an internal cavity or the like is formed in the concrete while the concrete is being poured. It is possible to determine whether or not
In particular, since the equal ratio coplanar electrode plates 21 and 22 are molded with insulating material on the front and back surfaces, the equal ratio coplanar electrode plates 21 and 22 are placed inside and/or outside a styrene board, plywood formwork, or the like. 22 can be provided.

In the measuring method for measuring the inside of a specimen according to the first aspect of the invention, the total area nS of the equal ratio coplanar electrode plates 21 and 22 having the same aspect ratio and the same electrode plate area S is arbitrarily selected and selected. The equal ratio coplanar electrode plates 21 and 22 form a pair of positive and negative electrodes, and an alternating current with a frequency of 100 Hz or higher is applied to the pair of equal ratio coplanar electrode plates 21 and 22 . The distance from the center position 0 of the pair of equal ratio coplanar electrode plates 21 and 22 to the center position ±s ₀ of each equal ratio coplanar electrode plate 21 and 22, that is, the distance between the electrodes t, the equal ratio coplanar Assuming that the electric field reach distance when parallel plate electrodes are present at the center position ±s ₀ to πt between the electrode plates 21 and 22, the capacitance between the pair of equal-ratio coplanar electrode plates 21 and 22 is given by calculate.

By setting the total area of the equal ratio coplanar electrode plates 21 and 22 to be S, 2S, 3S, . Since the existence of internal cavities affects either of the equal ratio coplanar electrode plates 21 and 22, the value of the capacitance C[F] decreases.
The capacitance C[F]=ε・S/d is
However, C: capacitance [F] ε: dielectric constant [F/m]
S; electrode plate area [m ² ] d; average facing distance [m]
is.

Incidentally, the dielectric constant of water is 80.4
Dielectric constant of air 1.00×10 ^-12
Dielectric constant of synthetic resin 2~6×10 ³
, when the value of the capacitance C[F] decreases, the capacitance C[F] is calculated by ε·S/d. At this time, the dielectric constant of water has a large effect of 80 or more, and the dielectric constant of air has a small effect of 1/10 ¹² . , changes as the value of the capacitance C[F].

Further, by arbitrarily selecting the total area nS of the equal ratio coplanar electrode plates 21 and 22 and short-circuiting the selected equal ratio coplanar electrode plates 21 and 22 to each other, an arbitrary total area nS can be obtained.
A pair of a positive electrode and a negative electrode are formed, and an alternating current with a frequency of 100 Hz or more is applied to the pair of equal-ratio coplanar electrode plates 21 and 22 as the power source e, so that the influence of the commercial frequency power source can be eliminated. , the voltage value to be applied can be reduced. Also, by increasing the frequency, an accurate value can be detected as the capacitance C[F].
The mutual arrangement of the equal ratio coplanar electrode plates 21 and 22 is regarded as the electric field reaching distance in the case where the parallel plate electrodes are present at a radius πt from the center position O of the equal ratio coplanar electrode plates 21 and 22 . In principle, there is no contradiction.

The measuring method for measuring the inside of the specimen of the invention according to claim 2 is such that a plurality of equal ratio coplanar electrode plates 21 and 22 made of conductors and having the same aspect ratio and the same electrode plate area S are arranged side by side. By changing the combination of the coplanar electrode plates 21 and 22, for example, by changing the total area to S, 2S, 3S, . is formed, the influence of the existence of the internal cavity will appear at some angle, so it can be assumed that the cause of the small capacitance C [F] is the internal cavity, etc. . Also, even if the electric field is disturbed by reinforcing bars or the like, there is no significant difference in numerical values as a polygonal line approximation.
The mutual arrangement of the equal ratio coplanar electrode plates 21 and 22 is such that from the center position 0 to the center position ±s ₀ between the equal ratio coplanar electrode plates 21 and 22 πt is the electric field reaching distance where the parallel plate electrodes exist. It is assumed that it is an accurate description of the electric field strength in principle, and the error that can be obtained from the measured value is small.

In the measuring method for measuring the inside of a specimen according to the third aspect of the invention, a plurality of equal-ratio coplanar electrode plates 21 and 22 made of conductors and having the same aspect ratio and the same electrode plate area S are insulated. Since it is a combination of the equal ratio coplanar electrode plates 21 and 22 formed on the substrate, in addition to the effect described in claim 1 or 2, the equal ratio coplanar electrode plates 21 and 22 are formed on the surface of the insulating substrate. can be standardized. Therefore, if a plurality of equal ratio coplanar electrode plates 21 and 22 are formed on an insulating substrate, the total area of arbitrary equal ratio coplanar electrode plates 21 and 22 can be set to S, 2S, 3S, . . . can be formed.

In the measuring method for measuring the inside of a specimen according to the fourth aspect of the invention, a plurality of equal ratio coplanar electrode plates 21 and 22 made of conductors and having the same aspect ratio and the same electrode plate area S are arranged side by side. Since the front and back surfaces of the specimen are molded with an insulating material, the inside of the specimen according to any one of claims 1 to 3 is measured. It can also be used as a form in which it is arranged. Further, since the electrode plates 21 and 22 can be embedded in concrete, the front and back surfaces of the equal ratio coplanar electrode plates 21 and 22 are molded with a dielectric, so that they can be installed inside and/or outside a styrene board, plywood formwork, or the like. Equal ratio coplanar electrode plates 21, 22 can be provided. Of course, it is also possible to use the embedded formwork for embedding.

FIG. 1 is a basic illustration of the electrodes, in which (a) is a parallel plate electrode, (b) is a shallow electric field of the coplanar electrode plate, and (c) is a deep electric field. FIG. 2 is a basic explanatory diagram of a measuring method for measuring the inside of a specimen according to the embodiment of the present invention, the top being a plan view and the bottom being a cross-sectional view of the main part for explanation. FIG. 3 is an explanatory diagram showing a plan view of equal ratio coplanar electrode plates used in the measuring method for measuring the inside of the test piece according to the embodiment of the present invention, where (a) is a pair of equal ratio coplanar electrode plates. , (b) is ten pairs of equal-ratio coplanar electrode plates, and (c) is an explanatory view showing one form of use thereof. FIG. 4 is an explanatory diagram of visualization of the electric field density in the embodiment of the present invention. FIG. 5 is an explanatory diagram of a one-layer model of the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 6 is a confirmation characteristic diagram of a two-layer model of the formwork and test-like concrete of the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 7 is a confirmation characteristic diagram of a two-layer model of a mortar plate and a water-based gel with different thicknesses according to the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 8 is a confirmation characteristic diagram of a two-layer model of a mortar plate and a styrene board in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 9 is a confirmation characteristic diagram of a three-layer model of a formwork, a styrene board with different thicknesses, and an aqueous gel in a measuring method for measuring the inside of a specimen according to the embodiment of the present invention. FIG. 10 is a characteristic diagram for confirming that the mortar plate is limited to 100 [mm] in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 11 is a confirmation characteristic diagram of the two-layer model and the three-layer model of the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 12 is an explanatory diagram of the calculation of the capacitance of the two-layer model and the three-layer model of the measurement method for measuring the inside of the specimen according to the embodiment of the present invention. 13A and 13B are explanatory diagrams of the synthetic inclination and the measured inclination of the three-layer model of the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. 14A and 14B are explanatory diagrams of the synthetic inclination and the measured inclination of the three-layer model of the mortar and the styrene board in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. Fig. 15 is an example of synthetic inclination and measured values of (a) 100 mm, (b) 76 mm, and (c) 32 mm, assuming a mortar formwork for the measurement method for measuring the inside of the specimen according to the embodiment of the present invention. is an explanatory diagram of . FIG. 16 is an explanatory diagram showing that an internal cavity is not estimated in the measurement of the synthetic inclination and the actually measured inclination of the four-layer model of the measurement method for measuring the inside of the specimen according to the embodiment of the present invention. 17A and 17B are explanatory diagrams of the synthetic inclination and the measured inclination of the model when reinforcing bars are embedded in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. 18A and 18B are explanatory diagrams of model synthetic inclinations and measured inclinations when the reinforcing bars are laid in different directions in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 19 is an explanatory diagram of the reciprocal of the inclination and the thickness of the model of the styrene board and reinforcing bars in the aqueous gel of the measuring method for measuring the inside of the specimen according to the embodiment of the present invention. FIG. 20 is an explanatory diagram of the reciprocal of the inclination and the thickness of the reinforcing bars in the aqueous gel and the styrene board in the measuring method for measuring the inside of the specimen according to the embodiment of the present invention.

A measuring method for measuring the inside of a specimen according to an embodiment of the present invention will be described below with reference to the drawings. In addition, in the embodiment, the same symbols and the same reference numerals in the drawings denote the same or corresponding functional parts, so redundant description thereof will be omitted here.

[Embodiment]
First, the basic principle of the measuring method for measuring the inside of the specimen according to the present embodiment will be described.
As shown in FIG. 1(a), the electrode plate area S of a pair of electrodes is a parallel plate, and has a configuration to obtain a capacitance C [F] when a dielectric having a dielectric constant ε is sandwiched between them. ing. The parallel electrode plate area S is in a state in which the electrode plates are spaced apart by an average facing distance d between the parallel opposing electrode plates. At this time, the electrostatic capacitance C[F] with the electrode plate area S as a parallel plate is proportional to the electrode plate area S and the dielectric constant ε of the dielectric sandwiched between the electrode plates, and is proportional to the opposing average distance d between the electrode plates. There is a characteristic of being inversely proportional, and the capacitance C[F] is expressed by the following equation.
C=ε・S/d
where C[F] capacitance
S [m ² ] Electrode plate area
d[m] Opposing average distance
ε [F/m] is the permittivity of the dielectric between the electrode plates.

As the high-frequency power supply e applied between the electrode plate areas S, the inventors are accustomed to handling it, so a commercially available high-frequency capacitive moisture meter (HI-520: manufactured by , high-frequency capacitive (20 MHz)).
In the experiment of the inventors, when a high-frequency capacitive moisture meter is used in place of the LCR meter, as a result, it is necessary to consider the influence of the stray capacitance of the electrodes, etc. in a general LCR meter, but commercially available A high-frequency capacitive moisture meter was more useful.

When water is added to the aggregate of the test material, a phenomenon occurs in which the capacitance C increases as the water content increases. Normally, the capacitance C is approximated by "tan", which is the angle between "current Ir of the resistance component/current Ic of the capacitance component", from the dielectric loss tangent "tan δ". ceremony
tan δ ≈ Ir/Ic
becomes.
However, the value of the dielectric constant of water, which is about 80, changes with changes in temperature and also changes with the applied frequency. In addition, when water is added, a chemical reaction occurs, and changes depending on the application time and the like. This is largely due to the action of melting by ions.
Also, the capacitance is calculated by setting the capacitance C to C=ε·S/d, but the region sandwiched between the electrode plate areas S can also be regarded as a resistor.

Next, the electrode plates 21 and 22 shown in FIGS. 1(b) and 1(c) and FIG. 2 used in the embodiment of the present invention will be examined.
The inventors produced electrodes such that the ratio S/t between the electrode plate area S and the electrode interval t from the center position 0 of the center of the electrode plate of the electrode plate area S to the center position 0 of the other electrode plate is constant. bottom. An electrode having a constant ratio S/t between the electrode interval t and the electrode plate area S is called an "equal ratio coplanar electrode" here. Further, the electrode plates 21 and 22 are defined as the electrode spacing t, but may be a vertical plane or a predetermined inclination. Electrode plates 21 and 22 are equal ratio coplanar electrodes.
Here, the term "electrode spacing t" is used to clarify the difference from the average opposing distance d between the electrode plates. Here, S/t=const is referred to as a "equivalent coplanar electrode constant".
Note that the electrode spacing t ₁ between the shield electrode plates 23 and 24 does not affect the electrode plate area S, so a description thereof will be omitted.

Here, a value obtained by multiplying the electrode interval t by the circular constant π is set as the facing average distance d.
π・t=d
t = d/π
becomes.
therefore,
S/t=S·π/d
becomes. The circular constant π is constant, and the geometric coplanar electrode constant S/d is always constant.
Further, the capacitance C is constant according to C=ε·S/d, unless the dielectric constant ε, that is, the water content, changes in the depth direction.
As the electrode interval t is gradually increased, when the electric field reaches a portion with a high water content, the capacitance C changes for the first time, and the value at the changed position becomes the depth of the electric field.

Furthermore, the inventors investigated the equal ratio coplanar electrodes 21 and 22 .
The electrode plate length of the electrode S of the equal ratio coplanar electrodes 21 and 22 was fixed at 100 mm, and the electrode plate width was varied to obtain a equal ratio coplanar electrode constant S/t=100. In this case, since the electrode plate width cancels out the electrode spacing t, the opposing average distance d between the electrode plates and the electrode spacing t of the equal ratio coplanar electrodes 21 and 22 are the same (the opposing average distance d between the electrode plates = the electrode spacing t). Here, electrode plates having different electrode plate areas S of the pair of equal-ratio coplanar electrodes 21 and 22 are excluded.

A power source e of high frequency power (AC voltage) was applied to both electrode plate areas S, a belt-shaped electric field was generated in the meantime, and the capacitance C of the test material on this electric field was measured. The shape of the electric field is thought to be arc-shaped or elliptical depending on the boundary conditions, etc., but it is possible to evaluate the dielectric physical quantity up to a depth proportional to the electrode spacing (Tetsuro Tokoro: "By dielectric measurement with surface depth resolution Development of deterioration diagnosis technology for polymeric electrical insulating materials” 2004-2006 Scientific Research Grant Result Report”), the average distance d between opposing electrode plates and the depth of electric field reach It is assumed that the arc is simply proportional to the It was assumed that the electrode plates were arranged in parallel to allow the electric field to pass through the test material, and that the depth reached by the electric field was changed by changing the opposing average distance d of the electrode plates.

In addition, the capacitance (three-layer model) C composed of three layers, the sum of capacitance a, capacitance b, and capacitance c, is
1/a+1/b+1/c=1/d
becomes.
FIG. 4 was confirmed by the inventors, and proves that there is no contradiction in the premises of FIGS. 1(b) and 1(c). In FIG. 2, regardless of the widths of the upper layer portion U and the lower layer portion D, the average of the electric field is centered at the center position O, and the electric field reaching distance is This corresponds to a simple average distance.
In particular, unlike a current circuit, the state is similar to that of an electrostatic field that maintains the potential of the voltage of the power supply e. corresponds to the simple average distance in

As shown in FIG. 2, the permittivity ε of the dielectric naturally changes according to the water content. Also, the facing average distance d is the facing average distance length of the arc-shaped electric field. When the average facing distance d between the electrode plates is small, the electric field is applied to the upper layer U of the sample under test, and the capacitance C decreases as the average facing distance d between the electrode plates increases. When the electric field reaches the lower layer D having a high water content, the dielectric constant ε also changes.

Therefore, logically, it was thought that the inflection point of this test sample was the boundary between the upper layer portion U and the lower layer portion D. FIG.
The estimated value of the upper layer U at this time was close to the confirmed value confirmed by the actual measurement. However, if the upper layer U is thin, the point of inflection appears immediately, making it difficult to determine the point of inflection. Further, when the width of the electrode plate is narrowed for thickness measurement, there is a drawback that the accuracy is lowered. That is, it is presumed that the electric field affects the lower layer D side from the beginning.
Therefore, the inventors neglected the relationship between the upper layer portion U and the lower layer portion D, and used an analysis program in which the dielectric constant of the low water content layer was set to "0" and the thickness was changed. We observed the entire electric field that showed the relationship of t.

FIG. 4 is based on FIGS. 1(b) and 1(c). In FIG. 2, regardless of the widths of the upper layer portion U and the lower layer portion D, the average electric field is simply It corresponds to the average distance.
In particular, unlike a current circuit, the state is similar to that of an electrostatic field that maintains the potential of the voltage of the power source e. corresponds to the simple average distance in

In the experiment of the inventors, the electrode plate area S of the electrode plates 21 and 22 is
Electrode plate area S=9000 [mm ² ], electrode center interval t=90 [mm],
Electrode plate area S=5000 [mm ² ], electrode center interval t=50 [mm],
Electrode plate area S=2000 [mm ² ], electrode center interval t=20 [mm]
, the geometric coplanar electrode constant S/t=100. Further, the electrode interval t=20 to 90 [mm] can be varied.
In addition, the shield electrodes 23 and 24 in the central portion have an electrode plate area of S ₁ and an electrode interval of t ₁ . In this experiment, the electrode interval t was changed, and only the influence of the dielectric constant ε that changed with the measurement depth was measured.

FIG. 3(a) is a schematic plan view of FIG. 2 corresponding to an actual product. The insulating sheet 10 is, as shown in FIG. 3(a), a plastic film with a thickness of 0.1 to 5 [mm] that does not conduct electricity. The electrode plates 1a to 1j are joined with a synthetic adhesive, if possible. However, the electrode plates 1a to 1j and 1a to 1j attached to the insulating sheet ₁₀ shown in FIG. there is

The electrode plates 1a to 10j attached to the insulating sheet 10 shown in FIG. 3(b) have a central position ±s ₀ at the center. Each of the electrode plates 1a to 1j is bonded to the plastic film surface with a synthetic adhesive so that it can be peeled off. Further, each of the electrode plates 1a-10j in this embodiment consists of 10 pairs of electrode plates 1a-1j, but the present invention is not limited to this.
However, the electrode plates 1a to 10a and 1b to 10b attached to the insulating sheet ₁₀ shown in FIG. connected by a line. Further, the electrode plates 1a to 1j and the electrode plates 1a to 1j are wired so as to be detachable and short-circuited between the conductors of the printed circuit board in order to form desired pattern pairs.

The electrode plate group 1A is composed of the electrode plates 1a to 1j, and the electrode plate group 1B is composed of the electrode plates 1a to 1j. 1B has a symmetrical electrode arrangement. As shown in FIG. 3(c), the electrode plates 1a to 1j are formed by removing the electrode plates 1a and 1e from the electrode plate group 1A. is composed of electrode plates from which the electrode plates 1a and 1e are omitted. Short-circuiting plates 2A and 3A are provided under the electrode plates 1b to 1d and the electrode plates 1f to 1j, and two pairs of electrodes are formed by the shorting plates 2B and 3B.
The electrode plates 1a to 1j of the short-circuit plate 2A and the short-circuit plate 3A and the short-circuit plate 2B and the short-circuit plate 3B may be formed by short-circuiting the lower portions of the electrode plates 1a to 1j, and the electrode plate 1a and the electrode plate 1e may be omitted. . In any case, it suffices if the electrode plates 1a to 1j can be paired.

In Fig. 5, HYPERLINK "mailto: plywood formwork, mortar board, and styrene board are measured using a one-layer model in which upper layer 41 and lower layer 42 are integrated and qeZc4mw@.l94d<" upper layer U and lower layer D are integrated. did Since this is concrete, which is the same material, the capacitance C and dielectric constant ε should be the same.
As a result, the relationship between the distance between the electrodes and the capacitance was almost constant for the plywood formwork and the mortar plate. The slight change in properties only for the styrene board is considered to be caused by surface roughness and partial contact pressure differences. Just to make sure, the inventors repeated experiments only with the styrene board and confirmed that the capacitance C [pF] was specified as a specific value, and that it was a factor caused by the frequency.

Figure 6 shows the weight ratio of aqueous gel (87% water), polyvinyl alcohol (90%), and salt (3%) to create a test-like concrete that approximates the physical properties of concrete used as a two-layer model. bottom.
Experiments were carried out on a two-layer model of aqueous gel (87%) and the test-like concrete. FIG. 6 is an example of this, which is a two-layer model of aqueous gel and test-like concrete. Here, when the capacitance C [pF] is obtained, it becomes the capacitance proportional to the electrode interval t. That is, the output (capacitance) changes linearly. The similar concrete to be tested also has a linear characteristic, and it can be seen that the inclination tendency is the same for W=190 [Kg/m ³ ] and W=160 [Kg/m ³ ].

FIG. 7 is an illustration of a two-layer model of mortar board and water gel.
In FIG. 7, the result is the same even with two layers of mortar board and aqueous gel. However, as the thickness of the mortar plate increases, the capacitance decreases. It is believed that this is due to the addition of air grains in the vicinity of sand grains.
In FIG. 8, the relationship between the reciprocal of the slope of each straight line and the thickness of the mortar board and the styrene board is linear. That is, there is a proportional relationship between the reciprocal of the slope and the thickness.

As shown in FIG. 9, even if the form plate, the styrene board, and the aqueous gel are assumed to be a three-layer model, the same linear characteristic is obtained when the capacitance C [pF] is output. A styrene board, such as a 44 [mm] styrene board, has a smaller difference in capacitance as it becomes thicker. It can be seen that this change has the same characteristics as in FIG.

FIG. 10 shows the relationship between the slope γ and the measured value δ similarly synthesized using mortar plates with thicknesses of 32 mm, 76 mm and 100 mm. A linear relationship was obtained for the 32 mm and 76 mm thick mortar plates as well as the plywood formwork. The void thickness in the formwork can be estimated even for the formwork made of mortar or the like. However, with a mortar plate having a thickness of 100 mm, the inclination obtained by measurement was small, and estimation was difficult. It is necessary to increase the sensitivity by increasing the electrode plate area S and the electrode interval t.
As shown in FIG. 11, the relationship between the electrode spacing t, the capacitance, the two-layer model, and the three-layer model can also be shown in the two-layer model and the three-layer model.
Plywood formwork + aqueous gel is the two-layer model Y = aX + e, and the slope of the styrene board (11 mm) + aqueous gel is the two-layer model Y = bX + f.
Also, styrene board (styrene board) + plywood formwork + aqueous gel is a three-layer model Y = δX + g.

In FIG. 11, plywood formwork+aqueous gel is the slope of Y=aX+e of the two-layer model. In addition, the slope of the styrene board (11 mm) + aqueous gel is the two-layer model Y = bX + f. And, styrene board (styrene board) + plywood formwork + aqueous gel is actually measured inclination Y = δX + g of the three-layer model. Furthermore, c is the slope of the synthesized two-layer model.
Therefore, the capacitance is 1/a+1/b=1/c, which represents the slope γ of the combined two-layer model, and 1/a+1/b+1/c=1/δ is the combined slope of the three-layer model.

Further examination of the plywood formwork using FIG. 12 shows that the relationship between the synthetic inclination γ and the measured inclination δ is investigated. From FIG. was taken.
Therefore, an estimate of the void thickness was obtained from the linear relationship between the composite slope γ and the measured slope δ.

When the capacitance C [pF] is obtained from 1/α (plywood for formwork) + 1/β (air gap) = 1/γ (combined slope) in Fig. 14, the plywood for formwork has a constant slope α = 0 .128, and γ converted from the actually measured slope δ is 0.018,
1/0.128+1/β=1/0.018
1/β=47.7
becomes.
In the above formula, the thickness of the formwork plywood has a constant slope, and the slope was converted from the actually measured slope.
When 1/α is calculated from this formula, 1/β=47.7.
The resulting air gap thickness is 49.7.

In FIGS. 15A to 15C, a linear relationship was obtained between the synthetic slope γ and the measured value δ for both the 32 [mm] mortar plate and the 76 [mm] mortar plate. However, as shown in FIG. 14(c), the 100 [mm] mortar plate showed variations rather than specific numerical values.
Of course, in order to make the 100 [mm] mortar plate have a linear relationship, the width of the electrodes should be widened, the voltage should be increased, and the sensitivity should be increased.

FIG. 16 shows a four-layer model consisting of a formwork, aqueous gel, and aqueous gel with varying thicknesses of styrene boards. It is difficult to detect internal cavities because changes in the thickness of the styrene board cannot be detected.

FIG. 17 shows a model in which the direction in which the reinforcing bars are arranged and the direction of the electric field are the same. As the number of reinforcing bars increases, the reinforcing bars become paths for the electric field, and without the aqueous gel, the inclination increases.
In addition, in the case where aqueous gel is present, the reinforcing bar increases only in the area A and the reinforcing bar increases only in the gel area A, and the slope is small. In the case of no aqueous gel, the number of reinforcing bars increases in region B and the inclination is small. Reinforcing bars are embedded in the thickness of the styrene board.

FIG. 18 is a model in which the direction in which the reinforcing bars are arranged and the direction of the electric field are perpendicular to each other. As the number of reinforcing bars increases, the inclination is almost the same because the reinforcing bars are not parallel to the electric field.
In addition, in the case of the presence of the aqueous gel, the reinforcing bars are increased only in the area A and the area B, and no change occurs.
FIG. 19 shows a model in which the direction in which the reinforcing bars are arranged and the direction of the electric field are the same. As the number of reinforcing bars increases, the reinforcing bars become paths for the electric field, and the inclination increases without the aqueous gel.
Further, since the reinforcing bars are arranged in the aqueous gel, even if the thickness of the styrene board is changed in the area A, the reinforcing bars are embedded therein.

FIG. 20 shows the relationship between the styrene board and the reinforcing bars in the aqueous gel.
It is considered that the method of estimating the weighted state can be applied to the fog portion between the reciprocal of the slope and the unreinforced three-layer model.
In this way, the inventors fabricated equal ratio coplanar electrodes in which the ratios S, t between the electrode spacing t from the center s ₀ of the electrode to the center 0 of each electrode plate and the electrode plate area S are constant. It is possible to estimate the filling estimation method of concrete in the formwork using the capacitance, and it can also be applied to the mortar plate that simulates the embedded formwork, and it can also be applied to the influence of reinforcing bars. .

<1> Single-layer model Using a geometric coplanar electrode, the capacitance of a urethane-coated plywood formwork, mortar board, and styrene board was measured. Plywood formwork, embedded formwork, and voids are assumed respectively. Four plywood forms with a thickness of 12 mm and ten styrene boards with a thickness of 55 mm were stacked.
The mortar plate was a 1:3 mortar with a W/C ratio of 40% and a thickness of 100 mm. The plywood formwork was measured in an air-dried state. In order to reduce the influence of electrical noise from the surroundings, the specimen to be measured is placed on top of two sheets of polystyrene foam for heat insulation, and the electrodes are placed on top of it. A 2 kg weight was placed on the specimen to ensure close contact. Even if the electrode interval t to the electrode center 0 in each material was increased, the displayed value did not change and remained substantially constant. Even if S/d is constant, the electrode interval t to the electrode center 0 is increased, and the position where the electric field reaches is deepened, the capacitance remains the same if the dielectric constant ε does not change.

<2> Two-layer model (plywood formwork and concrete)
Assuming concrete in the formwork, the fresh concrete that was kneaded was placed in a plastic bag, and a plywood formwork was placed on it to measure the capacitance. Concrete was set to W/C=50% and two types of unit water content, 160 kg/m ³ and 190 kg/m ³ , were used. Table 1 shows the mix of concrete and mortar.

粗骨材は長良川産の玉砕石（最大寸法１５ｍｍ、表乾密度２．６２）を用い、細骨材には長良川産の粗砂（Ｆ．Ｍ．２．７６、表乾密度２．６１）と細砂（Ｆ．Ｍ．１．４３、表乾密度２．６０）を７：３の割合で混合したものを用いた。また、フレッシュコンクリートの静電容量は水分が水和に消費され変化する経時変化があるため、常に同じ条件で計測できるようフレッシュコンクリートを模した水性ゲルを作成した。

Coarse aggregate used is crushed stone from Nagaragawa (maximum size 15 mm, dry surface density 2.62), and coarse sand from Nagaragawa (FM 2.76, dry surface density 2.61) is used for fine aggregate. and fine sand (FM 1.43, surface dry density 2.60) at a ratio of 7:3. In addition, since the capacitance of fresh concrete changes over time as water is consumed for hydration, we created a water-based gel simulating fresh concrete so that measurements can always be made under the same conditions.

The aqueous gel is made of PVA (polyvinyl alcohol) and 87% of its mass is water. The electrostatic capacity of the aqueous gel containing 3% sodium chloride was about 220 [pF]. Concrete with a unit water content of 160 kg/m ³ was about 180 [pF], and that with a unit water content of 190 kg/m ³ was about 190 [pF]. A water-filled plastic bag was also used for the measurement, but the liquid was unstable and interfered with the measurement.
The measurement results are shown in FIG. A linear relationship was obtained between the capacitance C and the inter-electrode distance t for both concrete and aqueous gel.

In addition, when a two-layer model in which a plywood formwork with a small capacitance is placed on top of fresh concrete or water gel with a large capacitance, a slope appears. If the unit amount of water is large, the capacitance is also large, which is similar to the two-layer model measurement. In addition, although the capacitance of aqueous gel is larger than that of concrete, it does not change over time, so stable measurement is possible. I decided to use gel.

<3> Two-layer model (mortar board and styrene board)
A two-layer model was created by placing a mortar board and a styrene board on top of the aqueous gel, and the thickness of the mortar board and the layered thickness of the styrene board were varied. The thickness of the mortar plate was 18, 32, 47, 76 and 100 mm, and the thickness of the styrene board was 5.5 to 55 [mm] by stacking 1 to 10 sheets.
FIG. 10 shows part of the measurement results of the mortar plate. As with the plywood formwork, a linear relationship was obtained between the capacitance C and the electrode spacing t. The steeper the mortar plate, the smaller the slope of the straight line. The styrene board showed the same tendency. Table 2 shows the slope (a), intercept (b), and coefficient of determination (R2) of the straight line obtained by performing regression analysis on the measured values of the electrode spacing t and the capacitance C.

モルタル板及びスチレンボードの厚さが大きくなると直線の傾き(ａ)は小さくなり、反比例の関係となった。傾きの逆数１／ａを用いれば１／ａと厚さは正比例の関係になると考えられる。各厚さにおける直線の傾きの逆数１／ａとモルタル板及びスチレンボードの厚さとの関係を図８に示す。
各材料において傾きの逆数と厚さとには線形関係が得られた。
即ち、空隙の厚さと傾きβの関係を図８のように予め求めておけば，求めたｂの値から空洞の厚さが推定できる。厚さ３２ｍｍ，７６ｍｍ、１００ｍｍのモルタル板を用いて同様に合成した傾きγと実測値δとの関係を図１０に示す。厚さ３２ｍｍ，７６ｍｍのモルタル板でも合板型枠と同様に線形関係が得られた。モルタル等で作成された埋設型枠でも型枠中の空隙厚さが推定できる。しかし、厚さが１００ｍｍのモルタル板では測定で得られる傾きは小さくなり推定が困難であった。電極板面積Ｓや電極間隔ｔを大きくした電極にするなどして感度を上げ，更に、深い位置まで精度良くする必要がある。

As the thickness of the mortar board and the styrene board increased, the slope (a) of the straight line decreased, showing an inversely proportional relationship. If the reciprocal of the slope, 1/a, is used, it is considered that 1/a and the thickness are directly proportional to each other. FIG. 8 shows the relationship between the reciprocal 1/a of the slope of the straight line at each thickness and the thickness of the mortar board and the styrene board.
A linear relationship was obtained between the reciprocal of the slope and the thickness for each material.
That is, if the relationship between the thickness of the air gap and the slope β is obtained in advance as shown in FIG. 8, the thickness of the cavity can be estimated from the obtained value of b. FIG. 10 shows the relationship between the slope γ and the measured value δ similarly synthesized using mortar plates with thicknesses of 32 mm, 76 mm and 100 mm. A linear relationship was obtained for the 32 mm and 76 mm thick mortar plates as well as the plywood formwork. The void thickness in the formwork can be estimated even for the formwork made of mortar or the like. However, with a mortar plate having a thickness of 100 mm, the inclination obtained by measurement was small, and estimation was difficult. It is necessary to increase the sensitivity by increasing the electrode plate area S and the electrode interval t, and to improve the accuracy even at deep positions.

<4> Estimation of voids near the formwork of a three-layer model A styrene board that simulates voids is placed on top of the aqueous gel, and a plywood formwork is placed on top of it to form a three-layer model. was measured. The thickness of the gap was adjusted to 5.5 to 55 mm by changing the number of styrene boards sandwiched between the aqueous gel and the plywood formwork.

FIG. 11 shows the relationship between the electrode spacing t and the capacitance C. As shown in FIG. A linear relationship was obtained between the electrode spacing t and the capacitance C also in this three-layer model. The slope of the straight line decreased as the thickness of the styrene board increased.
Let a be the slope of the regression line between the plywood formwork and the water gel obtained from the two-layer model, and b be the slope of the regression line between the styrene board and the water gel obtained from each thickness of the styrene board. The slope γ was obtained as a three-layer model synthesized by the described formula.
Table 3 shows the measured values .delta. FIG. 12 shows the relationship between the combined slope γ and the measured value δ.

A linear relationship was obtained between the slope γ in the synthesized three-layer model and the slope δ measured. This relationship can be used to estimate the void thickness between the formwork and the concrete during construction. Since the standard thickness of the plywood formwork is constant, the inclination α is constant. When the thickness of the void (the thickness of the styrene board) is unknown, the value of the slope β can be obtained from the equation in FIG. 11 by obtaining the slope δ by actual measurement.
If the relationship between the thickness of the gap and the slope β is obtained in advance as shown in FIG. 8, the thickness of the cavity can be estimated from the obtained value of b. FIG. 10 shows the relationship between the slope γ and the measured value δ similarly synthesized using mortar plates with thicknesses of 32 mm, 76 mm and 100 mm. A linear relationship was obtained for the 32 mm and 76 mm thick mortar plates as well as the plywood formwork. The void thickness in the formwork can be estimated even for the formwork made of mortar or the like. However, with a mortar plate having a thickness of 100 mm, the inclination obtained by measurement was small, and estimation was difficult. It is necessary to increase the sensitivity by increasing the electrode plate area S and the electrode interval t, and to improve the accuracy even at deep positions.

<5> Estimation of cavities in the four-layer model Reinforcing bars as conductors. The effect on capacitance was investigated.
[1] A state in which concrete is not filled at all,
[2] Concrete is filled inside the formwork but does not reach the reinforcing bars.
[3] Concrete is filled up to the position of the reinforcing bars, but the cover part is not filled.
[1], [2], and [3] were examined with the rebars arranged parallel to the electric field, and only [2] was conducted with the rebars arranged perpendicular to the electric field.

17 to 19 show the arrangement of reinforcing bars. A space of 11×90 mm was provided between the two styrene boards when they were arranged parallel to the electric field, and 1 to 3 stainless steel round bars with a diameter of 10 mm were arranged as reinforcing bars.
In the state of arranging perpendicularly to the electric field, a gap of 11×11 mm was arranged between two styrene boards at intervals of 40 mm, and 1 to 7 round steels with a diameter of 10 mm were arranged.

In [1], 10 styrene boards were placed on the polystyrene foam, and a styrene board with a round bar and a plywood formwork were placed thereon for measurement. The area A from the mold surface to the center of the round steel is 11 mm.
In [2], a styrene board and a plywood formwork were placed on top of the aqueous gel. A styrene board was inserted between the styrene board on which the round steel was arranged and the aqueous gel and the plywood formwork, and the area A from the formwork to the center of the round steel and the area B from the center of the reinforcing bar to the aqueous gel were changed. The area A from the center of the reinforcing bar to the formwork and the area B from the center of the reinforcing bar to the aqueous gel are 11, 22 and 33 mm.
In [3], three round bars were placed in the center of a water-based gel with a thickness of 22 mm. Styrene boards were inserted between the water-based gel on which the round bars were arranged and the water-based gel used as the lower substrate, and between the upper plywood formwork. The relationship between the electrode spacing t and the capacitance C was determined, and the slope of the regression line was determined.
The results are shown in Tables 4 and 5.

In the state where concrete is not filled in the formwork from the formwork surface to the center of the reinforcing bar, that is, in the state without aqueous gel [1], the inclination increases with the presence of reinforcing bars, and increases as the number of reinforcing bars increases. In the state [2] where the concrete is filled inside the formwork but does not reach the reinforcing bars, when the area A from the formwork to the reinforcing bars is constant at 11 mm, the slope increases as the number of reinforcing bars increases. .

In addition, the slope increased as the region B from the center of the reinforcing bar to the aqueous gel increased. As shown in [2], the slope becomes smaller as the gap increases, but the opposite phenomenon appears when there are reinforcing bars. When the reinforcing bars were arranged orthogonally to the electric field, the inclination was almost the same regardless of the number of reinforcing bars. It is considered that the reinforcing bars in the formwork affect the capacitance measurement. However, the rebars used were only one kind of round steel with a diameter of 10 mm, and it is necessary to further study the influence of the rebars on the diameter of the rebars, the state of the rebar arrangement, and the like.

In the state where the concrete is filled up to the position of the reinforcing bar, that is, the state where the reinforcing bar is in the aqueous gel [3], if there is a gap between the reinforcing bar and the formwork, the thickness of the gap increases and the slope decreases. became. Compared to the case without reinforcing bars in Table 2, the decrease in slope with increasing thickness of the voids was smaller when there were reinforcing bars. A linear thickness was obtained. Even in the case of reinforced concrete, if the concrete is filled up to the position of the reinforcing bar, the presence of the reinforcing bar will affect the concrete.
When there is a gap between the reinforcing bar and the aqueous gel that serves as the substrate, the inclination is almost constant regardless of the thickness of the gap and the presence of the reinforcing bar. and the presence of voids did not appear.

As described above, the measuring method for measuring the inside of the specimen according to the present embodiment employs the strip-shaped electrode plates 21 and 22 made of conductors having the same aspect ratio and the same electrode plate area S, and the insulating sheet 10 . and the total area nS of the equal ratio coplanar electrode plates 21 and 22 are arbitrarily selected, and the equal ratio coplanar electrode plates 21 and 22 are mutually a power supply e that short-circuits the short-circuit plates 2A, 3A, 2B, and 3B according to selection to form a pair of positive and negative electrodes and applies an alternating current with a frequency of 100 Hz or more to the pair of equal-ratio coplanar electrode plates 21 and 22; The distance electrode interval t from the center position 0 of the pair of equal ratio coplanar electrode plates 21 and 22 to the center position ±s ₀ of each equal ratio coplanar electrode plate 21 and 22, and the equal ratio coplanar electrode The mutual arrangement of the plates 21 and 22 is regarded as the electric field reaching distance when parallel plate electrodes are present at the center position s ₀ to πt of the equal ratio coplanar electrode plates 21 and 22, and the equal ratio of the pair of equal ratio coplanar electrode plates 21 and 22 is The capacitance between the coplanar electrode plates 21 and 22 is calculated.

In the measuring method for measuring the inside of the specimen according to the present embodiment, the total area nS of the equal ratio coplanar electrode plates 21 and 22 having the same noise aspect ratio and the same electrode plate area S is arbitrarily selected and selected. The equal ratio coplanar electrode plates 21 and 22 form a pair of positive and negative electrodes, and an alternating current with a frequency of 100 Hz or higher is applied to the pair of equal ratio coplanar electrode plates 21 and 22 . With respect to the electrode distance t from the center position 0 of the pair of equal ratio coplanar electrode plates 21 and 22 to the center position ±s ₀ of each of the equal ratio coplanar electrode plates 21 and 22, the equal ratio coplanar electrode plates 21 and 22 The capacitance between the pair of equal-ratio coplanar electrode plates 21 and 22 is calculated by assuming that the electric field reaches the distance when parallel plate electrodes are present between the center positions ±s ₀ and πt of each other.

By setting the total area of the equal ratio coplanar electrode plates 21 and 22 to be S, 2S, 3S, . Since the existence of internal cavities affects either of the equal ratio coplanar electrode plates 21 and 22, the value of the capacitance C[F] decreases. Capacitance C[F]=ε·S/d.

Incidentally, the dielectric constant ε is the dielectric constant of synthetic resin > the dielectric constant of water > the dielectric constant of air. d. At this time, the dielectric constant of water has a large effect of 80 or more, and the dielectric constant of air has a small effect of 1/10 ¹² . , changes as the value of the capacitance C[F].

Further, by arbitrarily selecting the total area nS of the equal ratio coplanar electrode plates 21 and 22 and short-circuiting the selected equal ratio coplanar electrode plates 21 and 22 to each other, an arbitrary total area nS can be obtained.
A pair of a positive electrode and a negative electrode are formed, and an alternating current with a frequency of 100 Hz or more is applied to the pair of equal-ratio coplanar electrode plates 21 and 22 as the power source e, so that the influence of the commercial frequency power source can be eliminated. , the voltage value to be applied can be reduced. Also, by increasing the frequency, an accurate value can be detected as the capacitance C[F].
The mutual arrangement of the equal ratio coplanar electrode plates 21 and 22 is regarded as the electric field reaching distance in the case where the parallel plate electrodes are present at a radial length πt from the center position 0 of the equal ratio coplanar electrode plates 21 and 22 . In principle, there is no contradiction.
In the measuring method for measuring the inside of the specimen according to the present embodiment, a plurality of equal-ratio coplanar electrode plates 21 and 22 each having the same length-to-width ratio and the same electrode plate area S made of the conductor are arranged side by side. , the minimum value is made meaningful by the measurement with different combinations of the equal ratio coplanar electrode plates 21 and 22 .

In the measuring method for measuring the inside of the specimen according to the present embodiment, a plurality of equal ratio coplanar electrode plates 21 and 22 made of conductors and having the same aspect ratio and the same electrode plate area S are arranged side by side. Measurements were performed by changing the combination of the coplanar electrode plates 21 and 22, for example, by changing the total area to S, 2S, 3S, . If it is formed, the effect of the existence of the internal cavity will appear at some angle, so it can be assumed that the cause of the small capacitance C[F] is the internal cavity or the like. Also, even if the electric field is disturbed by reinforcing bars or the like, there is no significant difference in numerical values as a polygonal line approximation.
The mutual arrangement of the equal ratio coplanar electrode plates 21 and 22 is such that from the center position O of the equal ratio coplanar electrode plates 21 and 22 to the center position ±s ₀ to πt is the electric field reaching distance where the parallel plate electrodes exist. It is assumed that it is an accurate description of the electric field strength in principle, and the error that can be obtained from the measured value is small.

Furthermore, the measuring method for measuring the inside of the specimen according to the present embodiment uses a plurality of equal-ratio coplanar electrode plates 21 and 22 which are made of the conductor and have the same aspect ratio and the same electrode plate area S. is a combination of a plurality of types of equal ratio coplanar electrode plates 21 and 22 formed on an insulating substrate.

Furthermore, the measuring method for measuring the inside of the specimen according to the present embodiment employs a plurality of equal-ratio coplanar electrode plates 21 and 22 each made of a conductor and having the same aspect ratio and the same electrode plate area S. is a combination of the equal ratio coplanar electrode plates 21 and 22 formed on the insulating substrate. If a plurality of equal ratio coplanar electrode plates 21 and 22 are formed, the total area of any equal ratio coplanar electrode plates 21 and 22 can be formed as S, 2S, 3S, . can.

In the measuring method for measuring the inside of the specimen according to the present embodiment, a plurality of equal-ratio coplanar electrode plates 21 and 22 made of the conductor and having the same aspect ratio and the same electrode plate area S are arranged side by side. The front and back surfaces are molded with an insulating material.

In the measuring method for measuring the inside of the specimen according to the present embodiment, a plurality of equal-ratio coplanar electrode plates 21 and 22 made of conductors and having the same aspect ratio and the same electrode plate area S are arranged side by side. Since the front and back surfaces are molded with an insulating material, and the inside of the specimen is measured, it can be used as a configuration in which it is attached to a mold on the surface of the insulating substrate. Further, since the electrode plates 21 and 22 can be embedded in concrete, the front and back surfaces of the equal ratio coplanar electrode plates 21 and 22 are molded with a dielectric, so that they can be installed inside and/or outside a styrene board, plywood formwork, or the like. Equal ratio coplanar electrode plates 21, 22 can be provided. Of course, it is also possible to use the embedded formwork for embedding.

10 Insulating films 21, 22 Equal ratio coplanar electrode plate U Upper layer portion D Lower layer portion t Electrode spacing d Opposing average distance S Electrode plate area C Capacitance ε Permittivity S/t Equal ratio coplanar electrode constant

Claims (1)

a equal-ratio coplanar electrode plate formed by arranging a plurality of strip-shaped electrode plates made of a conductor and having the same aspect ratio and the same area on an insulating sheet;
The total area of the equal ratio coplanar electrode plates is arbitrarily selected, the equal ratio coplanar electrode plates are selectively short-circuited to form a pair of positive and negative electrodes, and the pair of equal ratio coplanar electrode plates are a power supply that applies alternating current with a frequency of 100 Hz or higher;
a distance t from the center position between the selected pair of equal-ratio coplanar electrode plates to the center position of each of the selected equal-ratio coplanar electrode plates;
The equal ratio coplanar electrode plate has front and back surfaces molded with an insulating material,
The mutual arrangement of the equal ratio coplanar electrode plates is regarded as the electric field reaching distance when parallel plate electrodes exist at πt from the center position of the equal ratio coplanar electrode plates, and the pair of equal ratio coplanar electrodes Calculate the capacitance between the electrode plates,
When the area S and the distance t are changed under the condition that the equal ratio coplanar electrode constant S/t, which is the ratio of the selected pair of equal ratio coplanar electrode plate areas S and the distance t, is constant. A measuring method for measuring the inside of a specimen, characterized by measuring a change in the capacitance.

Images