Device for detecting water seepage height in concrete impermeability test

Abstract

The invention relates to the technical field of concrete impermeability detection, in particular to a device for detecting the water seepage height of a concrete impermeability test. When the water seepage height of the concrete changes, the concrete serves as an interpolar medium of a capacitor, and the capacitance value can change along with the water seepage height, so that the water seepage height is tested. Through the implementation of the device, two tests of a step-by-step pressurization method and a water seepage height method can be completed within one experiment time, full-automatic detection can be completely realized, human intervention is not needed, the test time of the water seepage height method is greatly saved, and the working efficiency and the detection data quality are improved. The defects that in the prior art, a water seepage height method is complex in operation and low in efficiency are overcome.

Description

[0001] This invention is a divisional application of the patent application "Method, Device and System for Detecting Water Penetration Height in Concrete Impermeability Test" with the application number "2025102605242" and the filing date of March 6, 2025. Technical Field

[0002] This invention relates to the technical field of concrete impermeability detection, and particularly to a device for detecting the water penetration height in a concrete impermeability test. Background Art

[0003] The main methods for concrete impermeability tests mainly include the water penetration height method and the step-by-step pressure method, which are used to detect the water penetration resistance of ordinary concrete.

[0004] For the water penetration height method, the production of specimens needs to follow specific standards. There are strict regulations on the maximum nominal size of aggregates, specimen size, flatness of the bearing surface, etc. The specimens are required to be cured under standard curing conditions until the specified age. Before the test, the specimens are sealed. The sides of the specimens need to be sealed with materials such as melted paraffin to ensure the accuracy of the test. The test process starts from 0.1 MPa, and the water pressure is increased by 0.1 MPa every 8 hours until water seepage occurs in 3 out of 6 specimens, then the test is terminated. The specimens taken out from the impermeability tester are placed on a press, and two steel spacer bars with a diameter of 6 m should be placed at the center of the upper and lower end faces of the specimens along the diameter direction, and it should be ensured that they are in the same vertical plane. Then start the press and split the specimens into two halves along the longitudinal section. After the specimens are split, use a waterproof pen to trace the water marks. Place the trapezoidal plate on the split surface of the specimens, and use a steel ruler to measure the water penetration height values of 10 measuring points at equal intervals along the water marks. The readings should be accurate to 1 mm. When reading, if a certain measuring point is blocked by aggregates, the arithmetic mean of the water penetration heights near both ends of the aggregates can be used as the water penetration height of this measuring point.

[0005] The step-by-step pressure method is also used to determine the water penetration resistance of ordinary concrete. The production, curing and sealing treatment of specimens are the same as those of the water penetration height method. The test process starts from a low water pressure, gradually increases the water pressure, and each pressure level is maintained for a certain period of time until the predetermined pressure is reached or obvious water seepage is observed. Record the water seepage situation at each pressure level and the number of specimens that finally do not show water seepage to calculate the impermeability grade of the concrete.

[0006] Generally speaking, both the water penetration height method and the step-by-step pressure method can evaluate the impermeability performance of concrete. After the water penetration height method test is completed, use a press to split the specimens into two halves along the longitudinal section, and use a steel ruler to measure the water penetration height values of 10 measuring points at equal intervals along the water marks, which can accurately judge the water seepage situation of each specimen and has higher accuracy than the step-by-step pressure method.

[0007] However, after the water seepage height method test is completed, it is time-consuming and laborious to use a press to split the test piece in half along the longitudinal section and then evaluate the water seepage situation, which restricts the wide application of this method to a certain extent. Summary of the Invention

[0008] In order to overcome the defects of the complex operation and low efficiency of the water seepage height method in the above-mentioned prior art, the present invention provides a method for detecting the water seepage height of a concrete impermeability test, which realizes the rapid detection of the water seepage height, avoids the cumbersome process of splitting the test piece with a press for measurement, effectively saves time and reduces costs.

[0009] A method for detecting the water seepage height of a concrete impermeability test provided by the present invention regards the concrete test piece and the internal water seepage as the dielectric between the poles of a capacitor, arranges a capacitance sensor for clamping the concrete test piece around the concrete test piece, and the capacitance sensor is insulated from the concrete test piece; then calculates the water seepage height according to the capacitance value.

[0010] Preferably, it is applicable to a parallel plate capacitor, and the parallel plate capacitor is arranged horizontally up and down for clamping the concrete test piece during detection;

[0011] The method first fits the relationship between the capacitance value and the water seepage height of the concrete test piece with a calibration sample. The water seepage height calculated by combining the known capacitance value and the relationship is denoted as the fitted water seepage height value, and the water seepage height calculated by combining the known capacitance value and the theoretical formula is denoted as the theoretical water seepage height value; constructs a ratio change curve of the fitted water seepage height value and the theoretical water seepage height value under different capacitance values on the calibration sample;

[0012] Then, a parallel plate capacitor is used to detect the concrete test piece to be measured, the measured capacitance value is obtained, the theoretical water seepage height value of the concrete test piece to be measured is calculated, and the target ratio corresponding to the measured capacitance value is found by looking up the ratio change curve, and the product of the target ratio and the theoretical water seepage height value of the concrete test piece to be measured is calculated as the water seepage height detection result of the concrete test piece to be measured.

[0013] Preferably, the relationship is expressed as: h = a + b·ln(C) -4 ; where a and b are fitting parameters to be determined, C is the capacitance value, and h is the water seepage height.

[0014] Preferably, the theoretical formula is expressed as:

[0015]

[0016] where h s is the theoretical water seepage height value; ε1 is the dielectric constant of the water-seeped concrete, ε2 is the dielectric constant of the dry concrete; H is the height of the test piece; S is the area of the plate; C is the capacitance value.

[0017] Preferably, a ring-shaped capacitor is used to detect the capacitance value of the concrete specimen. The two clamping plates of the ring-shaped capacitor are symmetrically arranged on the left and right sides of the concrete specimen and clamp the concrete specimen. The water seepage height detection model applicable to the ring-shaped capacitor is as follows:

[0018]

[0019] Wherein, h is the water seepage height; ε1 is the dielectric constant of the water-seeped concrete; ε2 is the dielectric constant of the dry concrete; H is the height of the specimen; C is the measured capacitance value; α is the opening angle of the ring-shaped capacitor; ξ is the correction coefficient.

[0020] Preferably, the correction coefficient is obtained by fitting on the calibration samples.

[0021] Preferably, the value range of the opening angle α is [85°, 89.5°].

[0022] A device for detecting the water seepage height of a concrete impermeability test proposed by the present invention includes a capacitor structure, a capacitance testing instrument and a computer; the computer stores a water seepage height detection model corresponding to the capacitor structure. The capacitor structure uses the concrete specimen as the medium, the capacitance testing instrument is used to detect the capacitance value of the capacitor structure, and the computer obtains the capacitance value measured by the capacitance testing instrument and substitutes it into the water seepage height detection model for calculating the water seepage height;

[0023] When the capacitor structure is a flat capacitor composed of two plate members, the water seepage height detection model is as follows:

[0024] h = f s,C ·h s

[0025] Wherein, h is the water seepage height; h s is the theoretical value of the water seepage height calculated by substituting the detected capacitance value into the theoretical model; let C - f s be the correction function representing the ratio f s relationship between the fitting value and the theoretical value of the water seepage height of the concrete specimen under different capacitance values; f s,C represents the ratio f s corresponding to the detected capacitance value on the correction function C - f s ;

[0026] When the capacitor structure is a ring-shaped capacitor composed of two clamping plates, the water seepage height detection model is as follows:

[0027]

[0028] Wherein, h is the water seepage height; ε1 is the dielectric constant of the water-seeped concrete; ε2 is the dielectric constant of the dry concrete; H is the height of the specimen; C is the measured capacitance value; α is the opening angle of the ring-shaped capacitor; ξ is the correction coefficient.

[0029] A system for detecting the water seepage height in the concrete impermeability test proposed by the present invention includes a memory and a processor. A computer program is stored in the memory, and the processor is connected to the memory. The processor is configured to execute the computer program to implement the method for detecting the water seepage height in the concrete impermeability test.

[0030] A storage medium proposed by the present invention stores a computer program, and when the computer program is executed, it is used to implement the method for detecting the water seepage height in the concrete impermeability test.

[0031] The advantages of the present invention are as follows:

[0032] A method for detecting the water seepage height in the concrete impermeability test proposed by the present invention utilizes the characteristic that when the water seepage height in the concrete changes and the concrete serves as the dielectric between the electrodes of a capacitor, the capacitance value will change with the water seepage height to measure the water seepage height. The implementation of the present invention can complete the two tests of the step-by-step pressure method and the water seepage height method within the time of one experiment, fully realizing automatic detection without human intervention, greatly saving the test time of the water seepage height method, and improving work efficiency and the quality of test data.

[0033] The present invention utilizes the characteristic that during the concrete impermeability test, the concrete specimen can be clamped by a capacitor to perform capacitance measurement, which is convenient and fast, without splitting the concrete for observation, improving the efficiency of concrete detection and reducing the operation cost and difficulty.

[0034] The present invention proposes two capacitor structures and capacitance measurement methods, namely a flat capacitor and an encircling capacitor, in combination with the characteristic that concrete specimens are usually frustum-conical. Corresponding water seepage height detection models are proposed for different capacitance measurement methods, providing multiple ways for the capacitance detection of concrete specimens, facilitating selection according to the environment; at the same time, it is also convenient to verify the test results through different detection methods. Description of the Drawings

[0035] Figure 1 It is a flowchart of a method for detecting the water seepage height in the concrete impermeability test;

[0036] Figure 2 It is a schematic diagram of a flat capacitor;

[0037] Figure 3 It is a schematic diagram of the detection state of a flat capacitor;

[0038] Figure 4 It is a schematic diagram of the detection state of an encircling capacitor;

[0039] Figure 5 It is an angle display;

[0040] Figure 6It is the on-site of flat capacitor test;

[0041] Figure 7 It is for the display of fitting function;

[0042] Figure 8 It is for the display of detection error shown in Table 2 of Example 1;

[0043] Figure 9 It is for the display of detection error shown in Table 3 of Example 1;

[0044] Figure 10 It is the on-site of toroidal capacitor test;

[0045] Figure 11 It is for the display of detection error shown in Table 4 of Example 2;

[0046] Figure 12 It is for the display of detection error shown in Table 5 of Example 2;

[0047] Figure 13 It is for the display of detection error shown in Table 6 of Example 2. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0049] Refer to Figure 1 , the present invention takes the concrete specimen and the internal water seepage therein as the dielectric between the electrodes of a capacitor, arranges a special capacitance sensor around the concrete specimen. When the height of the internal water seepage in the concrete changes, the dielectric constant of the dielectric between the electrodes of the capacitor changes, resulting in a change in the capacitance value. Through testing, it is found that the change in the capacitance value shows a certain linear change law with the height of the water seepage. Therefore, the water seepage height in the concrete impermeability test can be quickly realized through the solution of the present invention, avoiding the cumbersome process of splitting the specimen with a press for measurement, effectively saving time and reducing costs.

[0050] The present invention provides two capacitor structures.

[0051] The first capacitor structure is composed of plate members 1 arranged up and down and parallel to each other, which is simply called a flat capacitor, as Figure 3 shown.

[0052] The flat capacitor is a basic and important electronic component, which is widely used in various circuits. The several key parameters involved in the capacitance value C of the flat capacitor include: the relative dielectric constant ε of the inter-electrode insulating dielectric er , the vacuum permittivity ε0, the plate area S, and the plate spacing d. For specific reference, see Figure 2 ; These parameters jointly determine the capacitance of the capacitor, that is, its ability to store charge. The calculation formula for a parallel-plate capacitor is:

[0053]

[0054] It can be seen from the above formula that the main factors affecting the capacitance of the capacitor are as follows:

[0055] 1. Different types of insulating media (such as air, mica, glass, etc.) will affect the permittivity;

[0056] 2. The area size of the upper and lower plates of the capacitor;

[0057] 3. The distance between the upper and lower plates of the capacitor.

[0058] When using a parallel-plate capacitor to detect the water seepage height of a concrete specimen, the two plate members 1 of the parallel-plate capacitor are arranged vertically on the two end faces of the concrete specimen, so that the two plate members 1 are horizontally arranged and clamp the concrete specimen 2 vertically. The result is as Figure 3 shown. It should be noted that the concrete specimen 2 and the two plate members 1 are insulated from each other.

[0059] In this way, the plate area is fixed, and the plate distance is the height of the concrete specimen. When the concrete specimen is infiltrated by water, the comprehensive permittivity of the medium between the electrodes is changed. The higher the water seepage height, the greater the water content, the greater the comprehensive permittivity of the medium between the electrodes, and the larger the capacitance value of the capacitor. On the contrary, the lower the water seepage height, the smaller the water content, and the smaller the comprehensive permittivity of the medium between the electrodes.

[0060] When using a parallel-plate capacitor to test the water seepage height, the water seepage height can be calculated through the water seepage height detection model shown in the following formula (1).

[0061]

[0062] Among them, h is the water seepage height; ε1 is the permittivity of the water-seeped concrete, ε2 is the permittivity of the dry concrete; H is the height of the concrete specimen; C is the capacitance value measured by the parallel-plate capacitor; S is the plate area; Let C-f s be the correction function representing the ratio relationship between the fitting value and the theoretical value of the water seepage height of the concrete specimen under different capacitance values; f s,C represents the value of f s when the capacitance value is C.

[0063] Among them, ε1 and ε2 can be obtained by looking up the table.

[0064] The correction function C-f sThe acquisition includes the following steps.

[0065] S11. Construct a detection environment, and determine the height H of the concrete specimen and the plate area S of the flat capacitor; measure the capacitance of the concrete specimen using the flat capacitor in the detection environment; the two plates of the flat capacitor are horizontally arranged and clamp the concrete specimen up and down, and the plates are insulated from the concrete specimen;

[0066] S12. Obtain the calibration sample (h, C p ) of the concrete specimen, where h is the water seepage height of the concrete specimen set during calibration, and C p is the capacitance value of the concrete specimen when the water seepage height is h set during calibration; specifically, the capacitance of the concrete specimen can be measured first, and then split to measure the water seepage height to obtain the calibration sample (h, C p );

[0067] S13. Fit the relationship between the water seepage height h and the calibration capacitance C p as the water seepage height fitting formula.

[0068] Specifically, in this embodiment, the water seepage height fitting formula can be set as h = a + b·ln(C p ) -4 , so as to fit the parameters a and b based on the calibration sample.

[0069] S14. Calculate the theoretical value h p of the water seepage height of the concrete specimen corresponding to the calibration capacitance C s ;

[0070]

[0071] where h s is the theoretical value of the water seepage height; ε1 is the dielectric constant of the water-seeped concrete, ε2 is the dielectric constant of the dry concrete; H is the height of the specimen; S is the plate area;

[0072] S15. Obtain the correction function C - f s , that is, construct the correlation curve of the ratio f s of the water seepage height h to the theoretical height h s with respect to the capacitance C p , f s = h / h s .

[0073] The second capacitor structure is an annular capacitor composed of two clamping plates 3 as electrode plates. The annular capacitor is arranged on the outer periphery of the concrete specimen, and the two clamping plates 3 clamp the concrete specimen left and right and are insulated from the concrete specimen; a gap is reserved between the two clamping plates 3, and the two clamping plates 3 are symmetrically arranged about the concrete specimen left and right, as Figure 4As shown, where the dashed line 4 represents the water level line.

[0074] The second capacitor structure can be equivalent to the first capacitor structure, and its influencing parameters are the same as those of the parallel-plate capacitor. When the water seepage height of the concrete specimen changes, the comprehensive dielectric constant of the dielectric between the capacitors changes. The higher the water seepage height, the greater the water content, the greater the comprehensive dielectric constant of the dielectric between the electrodes, and the larger the capacitance value of the capacitor. On the contrary, the same linear change occurs in the law.

[0075] For the cylindrical concrete specimen, the clamping plate 3 is provided with an arc surface structure attached to the circumferential surface of the concrete specimen. At this time, the water seepage height of the concrete specimen can be calculated according to the water seepage height detection model shown in the following formula (2).

[0076]

[0077] h is the water seepage height; ε1 is the dielectric constant of the water-seeped concrete; ε2 is the dielectric constant of the dry concrete; H is the height of the specimen; C is the measured capacitance value; α is the opening angle of the slotted ring-shaped capacitor, as shown in Figure 5; ξ is the correction coefficient, which can be specifically obtained by sample fitting.

[0078] Specifically, the fitting method of the correction coefficient ξ is as follows: First, obtain the calibration sample (h, C p ) of the concrete specimen, and then let C = C p Substitute the calibration sample into formula (2) to fit the correction coefficient ξ.

[0079] The above water seepage height detection model will be verified in combination with specific embodiments below.

[0080] Embodiment 1

[0081] In this embodiment, a parallel-plate capacitor is used for measurement to verify formula (1).

[0082] In this embodiment, a simulated concrete specimen container made of acrylic material is fabricated. The inner volume of the container is the same as the volume of the standard concrete specimen, with a height of 150 mm, a lower bottom circle diameter of 185 mm, and an upper bottom circle diameter of 175 mm.

[0083] The experimental settings are as follows:

[0084] Capacitance test instrument: The test level is 1 V, and the test frequency is 1 kHz;

[0085] Parallel-plate capacitor: The plate is made of an aluminum sheet with an area of 300×300 mm and a thickness of 2 mm;

[0086] Medium inside the container: Sand and water;

[0087] During the experiment, the water level in the container was separated up and down by a thin film to control the water level line, that is, the seepage height; the part above the thin film was dry sand, and the part below the thin film was a sand-water mixture.

[0088] The experimental scheme was carried out in 5 steps.

[0089] Step 1: There was no water in the acrylic specimen container. Use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0090] Step 2: Put water at a height of 1 / 4 of the volume in the acrylic specimen container. Use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0091] Step 3: Put water at a height of 2 / 4 of the volume in the acrylic specimen container. Use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0092] Step 4: Put water at a height of 3 / 4 of the volume in the acrylic specimen container. Use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0093] Step 5: Fill the acrylic specimen container with water. Use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0094] First, perform a data calibration, repeat the above experiment, record the data twice and take the average value, and then perform formula calculation. Figure 6 This is the on-site picture at 3 / 4 water level in this implementation.

[0095] Perform data calibration on this scheme, and the recorded data is shown in Table 1 below.

[0096] Table 1: Capacitance values at different water levels

[0097] Serial number Water level h (mm) <![CDATA[Capacitance value C p (pF)]]> 1 0 8.158 2 37.5 8.995 3 75 10.878 4 112.5 15.307 5 150 49.177

[0098] Perform data fitting on the above calibration data to obtain:

[0099] h = a + b·ln(C p ) -4

[0100] Determine the parameters a = 167.3 and b = -3124.2. The calibration data and the fitting function are as Figure 7 shown. In this embodiment, the formula (1-1) is used to calculate the theoretical water level value at different capacitance values C p to calculate the ratio of the actual water level value to the theoretical water level value at different capacitance values C p and construct a correction function C-f s .

[0101] In this embodiment, perform 2 more tests, collect data, and use the seepage height detection model shown in formula (1) to back-calculate the water level. The results are shown in Table 2, Table 3, andFigure 8 , Figure 9 as shown in

[0102] Table 2: Statistical Results of Inverse Calculation Error in the First Experiment

[0103]

[0104] Table 3: Statistical Results of Inverse Calculation Error in the Second Experiment

[0105]

[0106]

[0107] It can be seen that the error in this embodiment is always lower than 3%, which proves the reliability of the method.

[0108] Embodiment 2

[0109] In this embodiment, an annular capacitor is used for measurement to verify formula (2).

[0110] The simulated concrete specimen container and the capacitance testing instrument in this embodiment are as shown in Embodiment 1. The medium in the container is sand and water. A thin film is provided at the water level for water seepage isolation, so that the part above the film is dry sand and the part below the film is a sand-water mixture.

[0111] The clamping plate 3 of the annular capacitor is an arc-shaped copper sheet attached to the outer periphery of the simulated concrete specimen container, with an area of 150×295 mm and a thickness of 0.3 mm. When testing, the opening angle α of the annular capacitor is 89°.

[0112] In this embodiment, first, a calibration sample (h, C p ) is obtained and substituted into formula (2), and the fitting correction coefficient ξ is 8.5; then, formula (2) is verified according to the measured capacitance value in the experiment.

[0113] The experimental scheme steps are as follows.

[0114] Step 1: There is no water in the acrylic specimen container, and the capacitance value at this time is measured and recorded using the capacitance testing instrument;

[0115] Step 2: The water level with a volume of 1 / 4 height is placed in the acrylic specimen container, and the capacitance value at this time is measured and recorded using the capacitance testing instrument;

[0116] Step 3: The water level with a volume of 2 / 4 height is placed in the acrylic specimen container, and the capacitance value at this time is measured and recorded using the capacitance testing instrument;

[0117] Step 4: The water level with a volume of 3 / 4 height is placed in the acrylic specimen container, and the capacitance value at this time is measured and recorded using the capacitance testing instrument;

[0118] Step 5: Fill the acrylic specimen container with water to the full level, and use a capacitance testing instrument to measure the capacitance value at this time and record it.

[0119] Repeat the above experiment, record the data three times, and back-calculate the water level based on the measured capacitance value in combination with Formula (2). The results are shown in Table 4 - Table 6 and Figures 11 - 13 as follows.

[0120] Table 4: Statistical Data of the First Detection in Example 2

[0121]

[0122] Table 5: Statistical Data of the Second Detection in Example 2

[0123]

[0124] Table 6: Statistical Data of the Third Detection in Example 2

[0125]

[0126]

[0127] From the above three detection results, it can be seen that when using the ring-shaped capacitor for testing, the error is always lower than 6%; however, it can be seen from Figures 11 - 13 that the linear characteristic of the ring-shaped capacitor is more significant, which is better than that of the flat capacitor. It can be seen that the ring-shaped capacitor is more suitable for practical applications.

[0128] Of course, for those skilled in the art, the present invention is not limited to the details of the above exemplary embodiments, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0129] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0130] The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. A device for detecting water seepage height in concrete anti-seepage test, characterized in that: It includes a capacitor structure, a capacitance testing instrument and a computer; the computer stores a water seepage height detection model corresponding to the capacitor structure, the capacitor structure uses a concrete test piece as a medium, the capacitance testing instrument is used to detect the capacitance value of the capacitor structure, the computer obtains the capacitance value measured by the capacitance testing instrument and substitutes it into the water seepage height detection model to calculate the water seepage height; When the capacitor structure is a flat plate capacitor consisting of two plates, the water seepage height detection model is: h=f s,C ·h s Where, h is the water seepage height; h s Substitute the detection capacitance value into the theoretical model to calculate the theoretical value of water seepage height; let Cf s To characterize the ratio of the fitted value to the theoretical value of the water seepage height of the concrete specimen under different capacitance values, f s The correction function of the relationship; f s,C Denotes the correction function Cf s The ratio f corresponding to the upper detection capacitance value s ; When the capacitor structure is an enveloping capacitor consisting of two clamping plates, the water seepage height detection model is: Among them, ε1 is the dielectric constant of permeable concrete; ε2 is the dielectric constant of dry concrete; H is the specimen height; C is the measured capacitance value; α is the opening angle of the enveloping capacitor; ξ is the correction coefficient.

2. The device for detecting water seepage height in concrete anti-seepage test according to claim 1, characterized in that: Among them, ε1 is the dielectric constant of permeable concrete, ε2 is the dielectric constant of dry concrete; H is the specimen height; S is the plate area; C is the capacitance value.

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