CN111896466A - Embedded concrete durability monitoring sensor - Google Patents
Embedded concrete durability monitoring sensor Download PDFInfo
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- CN111896466A CN111896466A CN202010611102.2A CN202010611102A CN111896466A CN 111896466 A CN111896466 A CN 111896466A CN 202010611102 A CN202010611102 A CN 202010611102A CN 111896466 A CN111896466 A CN 111896466A
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- G01N17/02—Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement
Abstract
The invention relates to an embedded concrete durability monitoring sensor, which is poured in a concrete protective layer of a reinforced concrete structure and consists of 6 multiplied by n rows of electrodes, wherein each row of 6 electrodes consists of 3 reinforcing steel bars and 3 reference electrode bars which are alternately arranged; the n rows of electrodes are arranged in a flush manner near the inner ends of the steel bars in the reinforced concrete structure, and the outer ends of the n rows of electrodes are sequentially provided with height differences along the arrangement direction of the rows; the outer ends of the highest row of electrodes extend to the lower part of the outer surface of the concrete protective layer, and the outer ends of the lowest row of electrodes are lower than the outermost layer of steel bars in the service concrete; the inner end of each electrode is welded with a flexible lead, and all the flexible leads are integrated into a lead bundle and are welded and connected with pins in the lead box through numbers; and epoxy resin coatings are coated on the outer surface of each electrode except the upper end section and the welding part of the electrode and the flexible lead. The invention can simultaneously obtain information of different depths of the concrete structure and has high accuracy of monitoring information.
Description
Technical Field
The invention belongs to the field corrosion monitoring technology of reinforced concrete structures, and particularly relates to an embedded concrete durability monitoring sensor.
Background
The durability of the reinforced concrete structures is receiving great attention as building structures in various aspects of national economy and national defense construction. Among them, the early destruction of reinforced concrete structures caused by corrosion of steel bars has become a disaster which is generally concerned by countries in the world. Professor metta, university of california, usa, points out at the international conference on concrete durability: "the cause of concrete damage in the world today, in descending order, is: corrosion, freezing damage and physical and chemical action of the steel bars. He definitely ruled out "rebar corrosion" as the first factor affecting concrete durability. The corrosion of the steel bars in concrete causes a great number of problems in buildings, bridges, wharfs and other structures using reinforced concrete, and brings about huge economic losses. Therefore, in the current concrete structure monitoring technology, monitoring the corrosion state of the steel bars in the concrete structure is an important technical content.
In a newly-built concrete structure, the concrete pore liquid around the reinforcing steel bars is alkaline, and the alkaline environment enables the surfaces of the reinforcing steel bars to form stable passive films and inhibits the further corrosion of the reinforcing steel bars. Along with the interaction between the environment and the concrete, including carbonization, acid rain, and the invasion of chloride ions in the marine environment, the composition of the pore solution in the concrete is changed, which is mainly shown in that the pH value of the pore solution is reduced, the concentration of the chloride ions is increased, and the like. These changes can destroy the stability of the passivation film on the surface of the reinforcing steel bar, so that the reinforcing steel bar is deactivated and activated, and the corrosion speed of the reinforcing steel bar is accelerated. The increase in corrosion products further destabilizes the concrete material, leading to cracking failure of the concrete. From the service of a newly-built concrete structure, the concrete continuously interacts with the environment, and the erosive substances gradually expand towards the direction of the steel bars from the surface of the concrete. The rate of such expansion varies with environmental and concrete composition factors. Therefore, to ensure the safe service of the concrete structure, the erosion depth of the concrete aggressive substance needs to be effectively monitored, and data support is provided for the prevention and repair work.
According to the electrochemical process change principle of the concrete structure and the steel bar in the deterioration process, a corresponding sensor can be designed to monitor the durability of the reinforced concrete structure. In recent years, researchers in various countries design and develop various sensors based on corrosion electrochemical principles by combining the corrosion mechanism of steel bars in concrete, and the sensors can effectively detect and monitor the reinforced concrete structure. At present, the embedded type trapezoidal anode sensor reported at home and abroad, such as a reinforcement corrosion long-term monitoring sensor in a reinforced concrete member, CN 100454000C, proposed by Shanghai university of transportation, can monitor reinforcement corrosion for a long time and can directly measure a carrier, namely reinforcement, in which corrosion occurs in real time. "a steel reinforced concrete buried corrosion sensor, CN 101706408A", also a steel reinforced concrete buried corrosion sensor, is proposed by building university, and the sensor is provided with 4 pairs of corrosion couples, hollow bars, a base and connecting wires. The installation in concrete before the concrete is poured allows long-term monitoring of the reinforced concrete structure from the early stage. The sensors are all based on the principle of galvanic corrosion, an anode galvanic couple and a cathode galvanic couple are arranged in the sensors, and the degradation degree of the concrete is judged by measuring corrosion data of the galvanic couples according to different degrees of corrosion of the concrete during measurement. However, the steel bar corrosion monitoring sensor based on the macroscopic galvanic couple cell principle monitors the galvanic corrosion current between the anode and the inert cathode and does not directly measure the corrosion rate of the steel bar. From the structure of the sensor, the sensor has the advantages of complex structure, large volume and introduction of materials such as plastics, stainless steel and the like, which have certain influence on the strength of a concrete structure. Based on the defects, the invention provides a simple and effective embedded concrete structure sensor.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the embedded concrete durability monitoring sensor which is simple in structure, can simultaneously obtain information of different depths of a concrete structure and is high in accuracy of monitoring information.
The above object of the present invention is achieved by the following technical solutions:
an embedded concrete durability monitoring sensor, characterized in that: the monitoring sensor is poured in a concrete protective layer of the reinforced concrete structure; the monitoring sensor consists of 6 multiplied by n rows of electrodes, each 6 rows of electrodes consists of 3 steel bars and 3 reference electrode bars, wherein the type of the steel bars is the same as that of the steel bars in the service concrete; 3 reinforcing steel bars and 3 reference electrode bars in each row are sequentially and alternately arranged according to the space; the n rows of electrodes are arranged in a flush manner near the inner ends of the steel bars in the reinforced concrete structure, and the outer ends of the n rows of electrodes are sequentially provided with height differences along the arrangement direction of the rows; the outer ends of the highest row of electrodes extend below the outer surface of the concrete protective layer, and the outer ends of the lowest row of electrodes are lower than the outermost layer of steel bars in the service concrete; the inner end of each electrode is welded with a flexible lead, all the flexible leads are integrated into a lead bundle and are welded and connected with pins in a lead box through numbers, the lead box is embedded in a reinforced concrete structure or fixed outside the reinforced concrete structure in a mode that an interface end is exposed, and a sealing cover is arranged at the interface end; the outer surface of each electrode except the upper end section and the welding part of the electrode and the flexible lead are coated with epoxy resin coatings.
Further: the reference electrode rod is a zinc rod.
Further: the flexible lead adopts a copper lead with a sheath; and a high polymer material sheath is sleeved outside the integrated wire bundle.
Further: according to the thickness of the concrete protective layer, the height difference between adjacent rows of the n rows of electrodes is 2mm-8mm, the row spacing of the n rows of electrodes is 2mm-10mm, and the distance between the steel bars in each row of electrodes and the reference electrode bar is 3mm-10 mm.
The invention has the advantages and positive effects that:
1. the steel bars used by the sensor have the same type as the on-site service steel bars, so that the corrosion information of the service steel bars can be truly reflected, the reflected information is real and reliable, and errors caused by different types of the steel bars are avoided.
2. The sensor provided by the invention has a simple structure, does not contain other plastic or metal parts, and therefore, cannot influence the performance of a nearby concrete protective layer.
3. The sensor provided by the invention is provided with the zinc bar as a reference electrode, so that the real information of the corrosion condition of the steel bar in different service stages can be measured. Meanwhile, the sensor with three groups of steel bars/zinc bars can avoid errors generated by a single group of sensors.
4. The height difference array structure is introduced in the invention, so that the information of different depths of the concrete structure can be obtained simultaneously, and the corrosion information of the periphery of the serving steel bar is convenient to compare.
5. The application introduces the array type steel bar/zinc bar electrode, can introduce various measuring means to measure, including electrochemical impedance spectrum measurement, electrochemical noise measurement, corrosion potential measurement, corrosion current measurement and the like, and can feed back the corrosion state of the serving steel bar by multiple information.
Drawings
FIG. 1 is a reference view of a sensor array of the present invention in use disposed in reinforced concrete;
fig. 2 is a schematic diagram of a sensor array structure according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments, which are illustrative, not restrictive, and the scope of the invention is not limited thereto.
An embedded sensor for monitoring durability of concrete is disclosed, please refer to fig. 1-2, and its invention points are: the monitoring sensor 1 is cast in a concrete protective layer 101 of a reinforced concrete structure. The monitoring sensor consists of 6 x n rows of electrodes, each row of 6 electrodes consists of 3 steel bars 1.1 and 3 reference electrode bars 1.2, wherein the steel bars have the same type as the steel bars 102 in the service concrete, and the sizes of the steel bars and the reference electrode bars can be determined according to the size of a concrete structure and the thickness of a protective layer and can be used within the range of 3mm-10 mm. Wherein n is the number of rows, the size of n depends on the thickness of the concrete protective layer, and the thicker the protective layer is, the larger the value of n is, and the value can be selected within the range of 3-20. The 3 reinforcing bars and the 3 reference electrode bars in each row are alternately arranged in sequence according to the intervals, three groups of measuring systems are actually formed by staggered arrangement, and the distance between the reinforcing bars and the reference electrode bars of each group of measuring systems is too far, so that the electrochemical measurement of the reinforcing bars is not facilitated. Each row is composed of 3 steel bars and 3 reference electrode bars, so that the validity of data is guaranteed, and analysis and judgment can be more effectively carried out through the reproducibility of three groups of data. The n rows of electrodes are arranged in a flush manner near the inner ends of the steel bars in the reinforced concrete structure. The outer ends of the n rows of electrodes are sequentially provided with height differences along the arrangement direction of the rows, the height differences are marked by h in the attached drawings, the height differences can be determined according to the thickness of the concrete protective layer and the service environment service life, and the range of the height differences can be 2mm-8 mm. The outer ends of the highest row of electrodes extend below the outer surface of the concrete protective layer, preferably, the size of the electrodes is about 1mm away from the outer surface of the concrete protective layer, and the outer ends of the highest row of electrodes are used as initial calibration parameters. The outer end of the lowest row of electrodes is lower than the outermost layer of steel bars in the service concrete, the row of electrodes can reflect the final corrosion information of the steel bars, and if the positions of the steel bars are corroded, the whole concrete is in a warning state.
A flexible lead 2 is welded to the inner end of each electrode, and the flexible lead is preferably a copper lead with a sheath. All flexible wires are integrated into a wire bundle 3 and are connected with pins in a lead box 4 through welding by numbers. The integrated wire bundle is further sleeved with a high polymer material sheath to protect the wire bundle. The lead box is pre-buried in the reinforced concrete structure or fixed outside the reinforced concrete structure in a mode that the interface end is exposed. Specifically, the lead boxes are needle type interfaces which correspond to the sensor arrays one to one, the lead boxes are installed at positions where wind and rain are sheltered according to the actual condition of a concrete structure, and the sealing covers are installed at the interface ends of the lead boxes, so that contact corrosion failure of pins and the external environment is avoided. The outer surface of each electrode except the upper end section and the welding part of the electrode and the flexible lead are coated with epoxy resin coatings.
The reference electrode rod is preferably a zinc rod. In the alkaline system, the activity of zinc is relatively stable, and the electrode potential is relatively stable, so that the zinc rod is preferable. Other metal materials such as indium and silver are also available, but the cost is high, and the materials are not ideal, and zinc is convenient and easy to obtain. A carbon rod in nonmetal is also acceptable, but the strength is not good and the carbon rod is easy to break.
The following embodiments are used as examples to illustrate the selection of parameters of the sensor, the installation of the sensor, and the monitoring of the sensor as follows:
firstly, according to the type of the steel bar in the site construction design, the steel bar with the same type is selected as the steel bar in the sensor. And simultaneously, the row number and the height difference h of the sensor array are determined according to the thickness of a concrete structure design protective layer and the service life. In this embodiment, the concrete is a large concrete bridge structure, the thickness of the concrete protective layer is 80mm, and the service life is 50 years. The number of the array rows is 10, the height difference between every two rows in the array is 8mm, and the lowest row in the array is lower than the steel bars in the service concrete. So as to reflect the service state of the concrete around the steel bar in the whole service period.
The concrete structure in this embodiment is a large structure, the bonding strength is required, and the steel bars and the zinc bars in the sensor array can be selected from the size with a larger diameter, wherein the steel bars and the zinc bars with a diameter of 10mm are selected. And (4) cutting the steel bars and the zinc bars with different sizes according to the height difference of the array, wherein the length of the steel bars and the zinc bars in the lowest row is 100 mm. Polishing the surfaces of the steel bar and the zinc bar, welding one end of the steel bar and the zinc bar with a copper wire, removing oil with a solvent, cleaning and drying, and coating the welding part of the wire, the steel bar and the zinc bar and the whole periphery except the section of the other end with epoxy resin.
The sensor array is then fixed by the iron wire according to the height difference, the distance between the steel bars and the zinc bars is 10mm, and the distance between the rows is also 10 mm. And the conducting wires of the steel bars and the zinc bars are integrated into a wire bundle and are welded and connected with pins in the lead box through numbers. The connection validity of each wire was checked by resistance measurement.
During concrete structure pouring construction, the sensor and the lead box are placed according to the preset position, and the positions of the lead bundles are reasonably arranged, so that the impact of mortar is avoided. When pouring, a small amount of concrete mortar and small stones are poured, and each space of the array is carefully filled, so that the array is ensured to be full of the concrete mortar and stones. After the die is removed, the corrosion potential of each steel bar in the array is measured for the first time through the junction box, so that the effectiveness of the connection is checked, and meanwhile, the first measurement data is recorded, so that reference data is provided for subsequent monitoring.
The embedded concrete durability monitoring sensor has the advantages of small volume, easy material taking, convenient processing and small influence on the concrete structure; the structure is simple and firm, the service life is long, and relevant corrosion information in the service reinforced concrete can be truly reflected. The device is installed in concrete before concrete pouring, can carry out long-term multi-information monitoring on the reinforced concrete structure, and comprises electrochemical impedance spectrum measurement, electrochemical noise measurement, corrosion potential measurement, corrosion current measurement and the like, and the monitored environment is the same as the environment of the serving reinforced concrete. In electrochemical measurement, three groups of steel bars and zinc bars respectively form three electrode systems. The corrosion potential is measured by using a zinc bar as a reference electrode and measuring the corrosion potential of the steel bar through a potentiometer in a constant potential instrument. The noise spectrum measurement is to establish the relationship between the potential change and the corrosion state through mathematical transformation by acquiring the change curve of the corrosion potential of the steel bar in a certain time period along with the time. And measuring the corrosion current, wherein the zinc rod is used as a reference electrode and an auxiliary electrode and can be obtained by linear polarization.
Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.
Claims (4)
1. An embedded concrete durability monitoring sensor, characterized in that: the monitoring sensor is poured in a concrete protective layer of the reinforced concrete structure; the monitoring sensor consists of 6 multiplied by n rows of electrodes, each 6 rows of electrodes consists of 3 steel bars and 3 reference electrode bars, wherein the type of the steel bars is the same as that of the steel bars in the service concrete; 3 reinforcing steel bars and 3 reference electrode bars in each row are sequentially and alternately arranged according to the space; the n rows of electrodes are arranged in a flush manner near the inner ends of the steel bars in the reinforced concrete structure, and the outer ends of the n rows of electrodes are sequentially provided with height differences along the arrangement direction of the rows; the outer ends of the highest row of electrodes extend below the outer surface of the concrete protective layer, and the outer ends of the lowest row of electrodes are lower than the outermost layer of steel bars in the service concrete; the inner end of each electrode is welded with a flexible lead, all the flexible leads are integrated into a lead bundle and are welded and connected with pins in a lead box through numbers, the lead box is embedded in a reinforced concrete structure or fixed outside the reinforced concrete structure in a mode that an interface end is exposed, and a sealing cover is arranged at the interface end; the outer surface of each electrode except the upper end section and the welding part of the electrode and the flexible lead are coated with epoxy resin coatings.
2. The embedded concrete durability monitoring sensor of claim 1, wherein: the reference electrode rod is a zinc rod.
3. The embedded concrete durability monitoring sensor of claim 1, wherein: the flexible lead adopts a copper lead with a sheath; and a high polymer material sheath is sleeved outside the integrated wire bundle.
4. The embedded concrete durability monitoring sensor of claim 1, wherein: the height difference between adjacent rows of the n rows of electrodes is 2mm-8mm, the row distance of the n rows of electrodes is 2mm-10mm, and the distance between the reinforcing steel bars and the reference electrode bars in each row of electrodes is 3mm-10 mm.
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| CN202010611102.2A CN111896466A (en) | 2020-06-30 | 2020-06-30 | Embedded concrete durability monitoring sensor |
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| CN202010611102.2A CN111896466A (en) | 2020-06-30 | 2020-06-30 | Embedded concrete durability monitoring sensor |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1438478A (en) * | 2003-03-20 | 2003-08-27 | 上海交通大学 | Method for detecting corrosion of concrete bar in reinforced concrete |
| CN1945278A (en) * | 2006-10-12 | 2007-04-11 | 上海交通大学 | Long term monitoring sensor for steel bar corrosion in steel concrete member |
| CN101706408A (en) * | 2009-11-27 | 2010-05-12 | 厦门大学 | Reinforced concrete embedded type corrosion sensor |
| CN212748688U (en) * | 2020-06-30 | 2021-03-19 | 国网天津市电力公司电力科学研究院 | Embedded concrete durability monitoring and sensing device |
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- 2020-06-30 CN CN202010611102.2A patent/CN111896466A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1438478A (en) * | 2003-03-20 | 2003-08-27 | 上海交通大学 | Method for detecting corrosion of concrete bar in reinforced concrete |
| CN1945278A (en) * | 2006-10-12 | 2007-04-11 | 上海交通大学 | Long term monitoring sensor for steel bar corrosion in steel concrete member |
| CN101706408A (en) * | 2009-11-27 | 2010-05-12 | 厦门大学 | Reinforced concrete embedded type corrosion sensor |
| CN212748688U (en) * | 2020-06-30 | 2021-03-19 | 国网天津市电力公司电力科学研究院 | Embedded concrete durability monitoring and sensing device |
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