CN113075390A - Concrete internal moisture and chloride ion synchronous transmission sensing device - Google Patents
Concrete internal moisture and chloride ion synchronous transmission sensing device Download PDFInfo
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 title claims abstract description 66
- 230000005540 biological transmission Effects 0.000 title claims abstract description 27
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- 238000012360 testing method Methods 0.000 claims abstract description 53
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
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- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Inorganic materials O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 6
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/38—Concrete; Lime; Mortar; Gypsum; Bricks; Ceramics; Glass
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Abstract
The invention discloses a device for synchronously transmitting and sensing water and chloride ions in concrete, which comprises an electric signal control module, a multi-gradient in-situ monitoring sensor, an electric signal acquisition module and a data analysis and storage module, wherein the multi-gradient in-situ monitoring sensor is designed based on the electrical and electrochemical principles and is used for in-situ testing the synchronous transmission of the water and the chloride ions in the concrete; according to the difference of the dielectric constant of different water content test blocks, the moisture permeation process in the concrete can be represented by directly measuring the capacitance value of the concrete, through arranging the multi-gradient sensor, the transmission process of moisture and chloride ions in the concrete is monitored, the speed and the depth of moisture and chloride ion transmission are obtained, the test basis is provided for further disclosing the synchronous transmission mechanism of the moisture and the chloride ions in the concrete, the scheme is simple in structural design principle, small in environmental influence, rapid in test result, stable and reliable in test result, and high practical value and popularization value are achieved.
Description
Technical Field
The invention belongs to the technical field of civil engineering material performance test equipment, and particularly relates to a device for synchronously transmitting and sensing water and chloride ions in concrete.
Background
Currently, reinforced concrete is the building material with the largest usage worldwide, but the concrete structure often cannot reach the design service life due to insufficient durability, and for concrete in service in extreme environments, such as marine concrete, the concrete structure often faces more serious durability problems, and the newly-built bridge and the seaport concrete structure can be seriously degraded in durability after being used for less than 15 years.
The results of the study show that the durability of marine concrete is often deteriorated by water and Cl-The transport of ions is relevant. The concrete is a porous and hydrophilic material, external moisture can enter the concrete through capillary absorption, and simultaneously a large amount of soluble harmful media such as chloride ions, carbon dioxide, sulfate ions and the like are carried. Although moisture transports foreign harmful substances into concrete, related studies show that the penetration depth of moisture is not consistent with the invasion depth of chloride ions, the transmission speed and the invasion depth of harmful substances are lower than that of water, and the transmission speeds of different substances are different.
The chloride ions can change the pH value of concrete and dissolve a steel bar passivation film, so that the method is one of the main reasons for the deterioration of the durability of the reinforced concrete, and the research on the mechanism and the process of chloride ion transmission has important significance for improving the durability of coastal concrete structures. Generally, chloride in the external environment is firstly dissolved in water and is carried into the surface layer of the concrete by the capillary absorption of the concrete. Due to the filtering effect of the concrete, water firstly enters deeper concrete, chloride ions are gathered on the surface layer of the concrete, the concentration of the chloride ions is gradually increased, and the chloride ions are diffused to the deeper concrete under the action of the concentration gradient force. However, the further diffusion of the chloride ions is affected by various factors, such as chloride ion concentration, moisture permeation speed, moisture distribution and the like, and no sensing device for detecting the synchronous transmission of moisture and chloride ions exists at present. A plurality of experts and scholars at home and abroad try to disclose a water asynchronous transmission mechanism, but at present, no reliable method is available for effectively mastering the actual water and internal ion transmission process at the same time. The inside moisture content of concrete generally accessible relative humidity characterizes, adopts humidity transducer monitoring concrete inside humidity usually, and common sensor includes: resistance type humidity-sensitive sensors, capacitance type humidity-sensitive sensors, and the like. However, the linearity and environmental pollution of the humidity-sensitive element are poor, and when the environmental humidity is monitored, the humidity-sensitive sensor needs to be exposed in a high-alkaline environment in concrete for a long time, and is easy to be polluted to influence the measurement accuracy and long-term stability of the humidity-sensitive sensor. Moreover, the actual installation process is complicated, and due to the sensor technology and other reasons, the measurement results of the relative humidity in the concrete by different scholars are greatly different. The existing sensors are difficult to realize the monitoring of the whole service life of the concrete, and particularly, the sensors are easy to damage in the pouring process. Concrete moisture measurement has been an internationally recognized problem.
The determination of the content of chloride ions in concrete can be divided into destructive detection and nondestructive detection according to the sampling mode. Common test methods: ion chromatography, chemical titration, spectrophotometry, etc. are destructive tests and the sample processing process is complex. In nondestructive detection, the silver/silver chloride sensor as an ion selective electrode shows good Nernst response to chloride ions in a solution, and the concentration of the chloride ions in the concrete solution can be directly obtained according to the potential change of the electrode. And the silver/silver chloride electrode has quick response to the concentration of the chloride ions, and can obtain the concentration of the chloride ions in a very short time.
The asynchronous moisture transmission mechanism is an important ring for mastering the durability deterioration principle of the concrete structure, and is favorable for accurately predicting the service life of the structure and taking timely repair measures. A plurality of experts and scholars at home and abroad try to disclose a water asynchronous transmission mechanism, but at present, no reliable method is available for effectively mastering the actual water and internal ion transmission process at the same time.
Disclosure of Invention
The method and the device provided by the invention have the characteristics of simple operation and accurate test result, and can realize the monitoring of the synchronous transmission of the in-situ moisture and the chloride ions of the concrete.
The invention is realized by adopting the following technical scheme: a synchronous transmission sensing device for water and chloride ions in concrete comprises an electric signal control module, a multi-gradient in-situ monitoring sensor, an electric signal acquisition module and a data analysis and storage module which are sequentially connected, wherein the electric signal control module is used for controlling electric signals applied to the multi-gradient in-situ monitoring sensor, and the electric signal acquisition module is used for acquiring water, temperature and chloride ion content information monitored by the multi-gradient in-situ monitoring sensor and analyzing and processing the information based on the data analysis and storage module;
many gradients normal position monitoring sensor includes U type support frame and sets up multiunit condenser, temperature sensor and a plurality of chloride ion sensor on U type support frame, and every group condenser includes two parallel arrangement capacitance polar plates on U type support frame lateral wall, chloride ion sensor includes inlayer basal portion and outer protective layer, and the inlayer basal portion includes first layer concrete semi-permeable membrane layer, the cyclic annular AgCl layer in second layer and the central basicity that is encircleed by cyclic annular AgCl layer and gelatinizes layer, the cyclic annular Ag layer in third layer and by the central MnO that cyclic annular Ag layer encircleed from last to down in proper order2A fourth epoxy layer;
still be provided with rather than the vertically on the U type support frame and adjust the pole, adjust the pole and adopt the stainless steel screw, the fixed dead lever that is provided with U type support frame parallel on adjusting the pole, the dead lever is used for fixed many gradients normal position monitoring sensor, sets up fixation nut on adjusting the pole to adjust the height of dead lever and then realize many gradients and measure, condenser and chloride ion sensor set up along the length direction of U type support frame in turn.
Further, the outer protection layer is a PVA pipe, the outer protection layer and the inner base portion are sealed through an alkaline sealant, the first concrete semipermeable membrane is formed by mixing crushed wood chips, cement and water and then maintaining in a humid environment, the second AgCl layer and the alkaline gel layer are separated through a rubber insulation layer, the AgCl layer is prepared through a powder pressing method, and the alkaline gel layer is a mixture of calcium hydroxide and water; third Ag layer and MnO2Separated by rubber insulating layers, MnO2Is prepared by a powder pressing method.
Furthermore, the electric signal control module comprises a power supply, an inverter and a processor, wherein the power supply is converted into direct current through the inverter to provide stimulation current for the multi-gradient in-situ monitoring sensor, and the processor comprises a voltage controller for controlling the voltage magnitude and the output sequence of the stimulation current.
Furthermore, the capacitor plates are made of copper sheets, the surfaces of the copper sheets are covered with insulating PVA layers, the capacitor plates which are opposite and parallel to each other form a group of capacitors, and each group of capacitors are connected in parallel to test the concrete capacitance values at different gradient positions, so that the water content at corresponding points is obtained.
Further, the principle of obtaining the water content of the concrete according to the tested capacitance value is as follows:
1) installing the multi-gradient in-situ monitoring sensor on a reinforcement cage, pouring concrete, and testing to obtain the capacitance C of a certain point P after maintenance is finishedP；
2) Preparing a concrete test block with the same proportion as the monitored concrete, placing the concrete test block in an environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95 percent for curing for a plurality of days (such as one month), soaking the concrete test block in water for curing for a plurality of days (at least 4 days), wiping the surface water clean after the curing is finished, testing the capacitance on the surface of the concrete test block, and recording the capacitance as Zs；
3) Putting the concrete test block into a high-temperature oven to be dried to constant weight, testing the surface capacitance of the concrete test block, and recording as ZdIf the capacitance value of the corresponding test point P is CPThe concrete water content θ was:
compared with the prior art, the invention has the advantages and positive effects that:
the moisture and chloride ion synchronous transmission sensing device provided by the scheme is designed based on the electrical and electrochemical principles, is quick in response to moisture content and chloride ion content, is stable in test result, and can be used for monitoring moisture and chloride ion synchronous transmission in-situ test concrete; according to the difference of dielectric constants of test blocks with different water contents, the capacitance value of concrete can be directly measured to represent the water permeation process in the concrete, the transmission process of water and chloride ions in the concrete is monitored by arranging a multi-gradient sensor, the transmission speed and the transmission depth of the water and the chloride ions are obtained, and a test basis is provided for further revealing the synchronous transmission mechanism of the water and the chloride ions in the concrete;
simultaneously, the multi-gradient capacitor and the multi-gradient chloride ion sensor are connected in parallel and can be used independently, the multi-gradient capacitor can be used for testing moisture permeation rate and moisture content change in concrete, the multi-gradient chloride ion sensor can be used for monitoring erosion depth and concentration change of chloride ions in concrete, the principle is simple, the effect of environmental influence is small, the test result is rapid, the test result is stable and reliable, and the device has high practical value and popularization value.
Drawings
FIG. 1 is a schematic block diagram of a sensing device according to an embodiment of the present invention;
FIG. 2 is a schematic three-dimensional structure and binding diagram of a device for synchronously transmitting and sensing moisture and chloride ions according to an embodiment of the present invention, where (a) is a schematic three-dimensional structure and (b) is a schematic binding diagram;
FIG. 3 is a schematic cross-sectional view of a device for sensing moisture and chloride ion simultaneous transmission according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an internal circuit connection of a device for synchronously transmitting and sensing moisture and chloride ions according to an embodiment of the present invention;
FIG. 5 is a schematic cross-sectional structure diagram of a chloride ion sensor according to an embodiment of the present invention.
Detailed Description
In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be further described with reference to the accompanying drawings and examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those described herein, and thus, the present invention is not limited to the specific embodiments disclosed below.
Embodiment 1, this embodiment disclose a concrete inside moisture and chloride ion synchronous transmission perception device, as shown in fig. 1, including the signal of telecommunication control module, many gradients in situ monitoring sensor, the signal of telecommunication collection module and data analysis and the storage module that connect gradually, it is specific:
the electric signal control module comprises a power supply, an inverter and a processor, wherein the power supply is an external power supply, the inverter is used for converting alternating current into direct current and providing direct current for equipment corresponding to the multi-gradient in-situ monitoring sensor, the processor is used for controlling the voltage, meanwhile, each group of capacitors are sequentially and independently electrified, and other capacitors do not work. For example to the capacitor PC1 when current is applied, the other capacitor (P)C2，PC3) The multi-gradient capacitance sensor does not work, the voltage of the output stimulation current is 1-5V, the output of stimulation voltage signals is controlled by a voltage controller, and the stimulation voltage signals are sequentially connected with the capacitance pole plates of the multi-gradient capacitance sensor through leads.
The multi-gradient in-situ monitoring sensor comprises a multi-gradient capacitor (P)C1、P C2，PC3) Temperature sensor (P)Tem) And a multi-gradient chloride ion sensor (P)Cl1、PCl2) Temperature sensor PTemPT1000 thermal resistance is used to test the temperature of concrete.
The electric signal acquisition module is used for acquiring voltage on the multi-gradient chloride ion sensor and converting the voltage into digital quantity, 5 times of average filtering of acquisition results is performed on data acquisition of each time, data are gathered to the data analysis and storage module through the 485 bus after the data acquisition is completed, for example, the stimulation current output and the stimulation current I are controlled through the electric signal control moduleinIs a sine wave, and an electrical signal I is transmitted through an electrical signal input endinIs delivered to a capacitor PC1, correspondingly, the capacitor 1 at the electric signal output end generates induced current, the signal acquisition module acquires current signals, other capacitors do not work at the moment, and after the signal acquisition module acquires the current signals, the electric signal control module controls the capacitor P C2 delivering current electric signals with same intensity and collecting capacitor P at electric signal output end C2, generating induction current, sequentially inputting stimulation current to other capacitors and collecting corresponding electric signals; temperature sensor and multi-gradient power supplyAfter the volume sensor collects temperature and humidity data, the data are directly converted into digital quantity, then the data conversion result is summarized to the data analysis and storage module through the IIC bus, and the voltage value of the data collected by the capacitor is converted into a water content value by the data analysis and storage module, so that final data are stored.
As shown in fig. 2 and 3, the structure of the multi-gradient in-situ monitoring sensor is schematically illustrated, and includes a U-shaped support frame 1 (which may be made of stainless steel); the adjusting rod 2, the fixed rod 3 and the fixed nut 4; the temperature sensor comprises a temperature sensor 5, a capacitor 7, a chloride ion sensor 6 and a multi-core lead 8, wherein the U-shaped support frame 1 is used for fixing the capacitor 7, the chloride ion sensor 6 and the temperature sensor 5, the capacitor 7 is composed of two parallel copper sheets, a layer of insulating PVA material covers the surfaces of the copper sheets to form capacitor plates, as shown in figure 4, the mutually opposite parallel capacitor plates are a group of working capacitors, the relative distance of the working capacitors is about 10cm, and the adjacent distance of the capacitors on the same side is about 5 cm.
The aperture of a plurality of installation regulation poles has been reserved on U type support frame 1, the aperture diameter is about 8mm, can supply regulation pole 2 to pass, combine shown in fig. 2 and 3, adjust the connected mode of pole 2 and dead lever 3 for the welding, adjust the height of dead lever 3 through fixation nut 4 on every regulation pole 2, dead lever 3 is used for fixed multi-gradient in situ monitoring sensor, it is shown in fig. 2(b) to be ligatured on the reinforcing bar in advance before concrete structure pours, the position of multi-gradient in situ monitoring sensor is adjusted to the height of adjusting dead lever 3 through fixation nut 4.
In addition, in this embodiment, the chloride ion sensor 6 is divided into four layers, as shown in fig. 5, wherein the outermost layer is a protective layer, which is a PVA tube with a diameter of 1.5cm, the PVA is sealed with an alkaline sealant, and the interior thereof is sequentially provided with a first concrete semi-permeable film layer, a second annular AgCl layer, a cake-shaped alkaline gel layer, a third annular Ag layer, and a cake-shaped MnO layer from top to bottom2A layer and a fourth layer of epoxy resin; the first concrete semipermeable membrane is formed by mixing broken wood chips, cement and water and then maintaining in a humid environment, the second concrete semipermeable membrane comprises an annular AgCl layer and a cake-shaped alkaline gel layer, the AgCl layer and the alkaline gel layer are separated through a rubber insulating layer, and the AgCl layer is formedThe preparation method comprises the steps of preparing by a powder pressing method, wherein a cake-shaped alkaline gel layer is a mixture of calcium hydroxide and water, and a third layer is an annular Ag layer and cake-shaped MnO2Layers, likewise separated by a rubber insulation layer, MnO2The preparation method comprises the following steps of (1) preparing by a powder pressing method; the fourth layer is an epoxy resin layer and is used for connecting and fixing the lead and the sensor electrode, and the multi-core lead is connected with the acquisition equipment through the aviation plug.
The principle of measuring the water content in concrete by dielectric constant is explained in detail below:
the capacitance is defined as:
C＝εS/(4πkd)；
in the formula, S is the opposite area of two parallel capacitor plates; k is the electrostatic force constant; d is the distance between two metal plates; ε represents a dielectric constant. When a medium exists between two stages of the capacitor, the medium can generate induced charges when an electric field is applied to the medium to weaken the electric field, so that the capacitance value is reduced, the relative dielectric constants of different substances are different, wherein epsilon is influenced by the conductivity of the medium between the capacitor plates, the relative dielectric constant of water is about 80 and is far greater than that of dry concrete (about 6-8); it has also been determined in the prior art that concrete capacitance changes exhibit a good linear relationship with moisture content. In this embodiment, the calculation of the water content of the concrete at a certain point P in the actual engineering is performed according to the following steps:
1) installing the multi-gradient in-situ monitoring sensor on a reinforcement cage, pouring concrete, basically finishing maintenance, and testing to obtain the capacitance C of a certain point PP；
2) Preparing a round cake concrete test block with the same ratio as the monitoring concrete, wherein the diameter is 100mm, the height is 50mm, placing the round cake concrete test block into an environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95 percent for curing for 21 days, soaking the round cake concrete test block into water for curing for 7 days, wiping the surface water clean after the curing is finished, testing the capacitance of the round surface of the round cake concrete by using a universal meter, and recording the capacitance as Zs；
3) Then putting the test block into a 105 ℃ oven to be dried to constant weight, testing the surface capacitance of the concrete round cake concrete round, and recording as ZdIf the capacitance value of the corresponding test point P is CPThe concrete water content θ was:
in this embodiment, the multi-gradient capacitive sensor tests capacitance values of different gradients of concrete through a plurality of pairs of capacitors, each pair of capacitors works independently and sequentially measures, wherein the positive electrode of each capacitor is connected with an electric signal control device to receive a stimulation current, the capacitance plate at the other end outputs an electric signal, the electric signal is connected with a data acquisition device, and the water content of a corresponding measuring point is obtained through the formula.
The multi-gradient chloride ion sensor can quickly sense the change of the content of chloride ions in concrete through the structural design, and the principle of testing the concentration of the chloride ions is as follows:
the AgCl layer is a slightly soluble salt, and the following electrode reaction occurs in concrete pore solution:
according to the Nernst response principle, when the potential is balanced, the electrode potential can be expressed by the following formula:
in the formula (I), the compound is shown in the specification,
standard potential for Ag/AgCl, (0.2224V); r is an ideal gas constant (8.314J. mol)-1·K-1) (ii) a T is the temperature of the test environment, K; f is the Faraday constant (96485.3℃ mol)-1)；αClFor Cl in an ambient medium-Activity of (c).
According to the scheme, the moisture penetration process in the concrete can be represented by directly measuring the capacitance value of the concrete according to the difference of the dielectric constants of test blocks with different water contents, and the moisture invasion depth and the moisture content change are monitored by monitoring the change of the capacitance value of the concrete in the moisture penetration process through the multi-gradient capacitor. The principle is simple, the influence by the environment is small, the test result is rapid, the test result is stable and reliable, and a test basis is provided for further revealing the asynchronous transmission mechanism of the moisture and chloride ions in the concrete. Meanwhile, the multi-gradient capacitor and the multi-gradient chloride ion sensor are connected in parallel and can be used independently, the multi-gradient capacitor can be used for testing the water penetration rate and the water content change in concrete, and the multi-gradient chloride ion sensor can be used for monitoring the erosion depth and the concentration change of chloride ions in the concrete.
Specifically, in operation, the method is implemented by the following steps:
1. before the concrete member is poured, the multi-gradient water monitoring sensor is bound on a steel bar in the concrete member, and before the concrete member is buried, the gradients of a capacitor and a chloride ion sensor on the sensor are adjusted through an adjusting rod 2;
2. the stimulation current and the output electric signal of the multi-gradient in-situ monitoring sensor are transmitted through a multi-core wire, one end of the multi-core wire is connected with the multi-gradient in-situ monitoring sensor, and a joint is reserved when the other end of the multi-core wire is poured and is connected with the aviation plug socket;
3. the functions of the electric signal control module, the electric signal acquisition module and the data analysis and storage module can be realized by the same portable device, the portable device outputs stimulation current and acquires electric signals through the multi-core wire, and the multi-core wire at the other end is connected with the aerial plug. The portable equipment is connected with the sensor embedded in the concrete through the aerial plug, and the moisture content in the concrete can be monitored at variable time.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.
Claims (5)
1. A synchronous transmission sensing device for water and chloride ions in concrete is characterized by comprising an electric signal control module, a multi-gradient in-situ monitoring sensor, an electric signal acquisition module and a data analysis and storage module which are sequentially connected, wherein the electric signal control module is used for controlling electric signals applied to the multi-gradient in-situ monitoring sensor, and the electric signal acquisition module is used for acquiring water, temperature and chloride ion content information monitored by the multi-gradient in-situ monitoring sensor and analyzing and processing the information based on the data analysis and storage module;
many gradients normal position monitoring sensor includes U type support frame (1) and sets up multiunit condenser (7), temperature sensor (5) and a plurality of chloride ion sensor (6) on U type support frame, and every group condenser (7) includes two parallel arrangement capacitance polar plates on U type support frame (1) lateral wall, chloride ion sensor (6) include inlayer basal portion and outer protective layer, and the inlayer basal portion includes first layer concrete semi-permeable membrane layer, the cyclic annular AgCl layer in second floor and the central basicity that is encircleed by cyclic annular AgCl layer from last to down in proper order and gelatinizes layer, the cyclic annular Ag layer of third layer and the central MnO that is encircleed by cyclic annular Ag layer2A fourth epoxy layer;
still be provided with rather than vertically on U type support frame (1) and adjust pole (2), adjust pole (2) and go up fixed being provided with dead lever (3) parallel with U type support frame (1), dead lever (3) are used for fixed multi-gradient normal position monitoring sensor, adjust and set up fixation nut (4) on pole (2) to adjust the height of dead lever (3) and then realize multi-gradient measurement, condenser (7) and chloride ion sensor (6) set up along the length direction of U type support frame (1) in turn.
2. The device for synchronously transmitting and sensing the water content and the chloride ions in the concrete according to claim 1, wherein the outer protective layer is a PVA pipe, the outer protective layer and the inner base part are sealed by an alkaline sealant, the first concrete semipermeable membrane is formed by mixing crushed wood chips, cement and water and curing in a humid environment, the second AgCl layer and the alkaline gel layer are separated by a rubber insulating layer, the AgCl layer is prepared by a powder pressing method, and the alkaline gel layer is prepared by calcium hydroxide and waterA blend; third Ag layer and MnO2Separated by rubber insulating layers, MnO2Is prepared by a powder pressing method.
3. The device for synchronously transmitting and sensing the water content and the chloride ions in the concrete according to claim 1, wherein the electric signal control module comprises a power supply, an inverter and a processor, the power supply is converted into direct current through the inverter to provide stimulation current for the multi-gradient in-situ monitoring sensor, and the processor comprises a voltage controller for controlling the voltage magnitude and the output sequence of the stimulation current.
4. The device for synchronously transmitting and sensing the concrete internal moisture and the chloride ions according to claim 1, wherein the capacitor plates are copper sheets, the surfaces of the copper sheets are covered with insulating PVA layers, the mutually opposite and parallel capacitor plates form a group of capacitors, and each group of capacitors are mutually connected in parallel to test the concrete capacitance values at different gradients so as to obtain the moisture content at corresponding points.
5. The device for synchronously transmitting and sensing the water content in the concrete and the chloride ions according to claim 4, wherein the principle of obtaining the water content of the concrete according to the tested capacitance value is as follows:
1) installing the multi-gradient in-situ monitoring sensor on a reinforcement cage, pouring concrete, and testing to obtain the capacitance C of a certain point P after maintenance is finishedP；
2) Preparing a concrete test block with the same proportion as the monitored concrete, placing the concrete test block in an environment with the temperature of 20 +/-2 ℃ and the relative humidity of more than 95 percent for curing for a plurality of days, soaking the concrete test block in water for curing for more than four days, wiping the surface water after the curing is finished, testing the capacitance on the surface of the concrete test block, and recording the capacitance as Zs；
3) Putting the concrete test block into a high-temperature oven to be dried to constant weight, testing the surface capacitance of the concrete test block, and recording as ZdIf the capacitance value of the corresponding test point P is CPThe concrete water content θ was:
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| PCT/CN2022/071217 WO2022199224A1 (en) | 2021-03-22 | 2022-01-11 | Sensing apparatus for synchronous transport of moisture and chloride ions inside concrete |
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| CN114279937A (en) * | 2021-12-29 | 2022-04-05 | 山东交通学院 | Concrete structure anti-permeability nondestructive testing device |
| WO2022199224A1 (en) * | 2021-03-22 | 2022-09-29 | 青岛理工大学 | Sensing apparatus for synchronous transport of moisture and chloride ions inside concrete |
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