Monitoring instrument and monitoring method for transverse non-uniform corrosion of reinforcing steel bar based on magnetic field

Abstract

The invention provides a monitoring instrument and a monitoring method for transverse non-uniform corrosion of a reinforcing steel bar based on a magnetic field, a reinforcing steel bar corrosion monitoring sensor is fixed at the periphery of the monitoring reinforcing steel bar, and the reinforcing steel bar corrosion monitoring sensor comprises a Hall sensor; the eight Hall sensors in the transverse direction of the reinforcing steel bar are used for in-situ monitoring magnetic field intensity changes around the reinforcing steel bar; the data acquisition unit is used for converting a voltage signal output by the steel bar corrosion monitoring sensor into a numerical signal and transmitting the numerical signal to the data processing system; and the data processing system receives the voltage signal data and records the voltage signal data in real time. The corrosion condition of the reinforcing steel bar in the reinforced concrete can be monitored in real time in a lossless and quantitative mode, and the method has the advantages of being easy to operate and high in precision. Therefore, the method has great development potential in engineering application.

Description

Technical Field

[0001] The invention provides a monitoring instrument and a monitoring method for transverse non-uniform corrosion of steel bars based on a magnetic field, and relates to the technical field of steel bar corrosion rate monitoring in the engineering field. Background Art

[0002] Reinforced concrete structures are widely used in civil engineering due to their many advantages. However, after chloride attack or concrete carbonization, the passive film is destroyed and the steel begins to corrode. At present, corrosion of steel bars in structures caused by chloride ion attack is relatively common, especially in coastal areas or areas in the north where deicing salt is frequently used. However, there is no absolute way to prevent corrosion; or some protective measures are expensive and cannot be applied to all projects. Therefore, regular inspection of building structures is necessary.

[0003] At present, there are many methods for detecting steel corrosion, all of which can be clearly divided into destructive detection and non-destructive detection. Since non-destructive detection methods do not cause additional damage to concrete structures, they are widely used in the study of reinforced concrete corrosion. There are two main types of sensors used for monitoring the durability of reinforced concrete in actual engineering projects: one is based on the principle of macroscopic batteries, such as the anode ladder sensor developed by the Institute of Civil Engineering of Aachen University of Technology in Germany and the CorroWatch sensor developed by FORCE in Denmark; the other is based on the principle of linear polarization, such as the ECI-2 durability monitoring sensor developed by VTI in the United States. In addition, there are many other sensors under development, such as fiber optic sensors, piezoelectric sensors, ultrasonic detection sensors, and new ground penetrating radars. The above sensors can basically determine qualitatively whether the steel bars are corroded. However, due to the complexity of the on-site environment, it is impossible to accurately and quantitatively analyze the deterioration of the durability of the steel bars. Therefore, it is impossible to obtain a comprehensive picture of the corrosion of reinforced concrete structures. There is still a lot of room for development in the durability monitoring of actual projects.

[0004] Based on magnetic medium and magnetic field theory, a magnetic field-based non-destructive dynamic monitoring instrument (MCD) for steel bars has been developed. The MCD instrument can non-destructively and quantitatively monitor the corrosion of steel bars in reinforced concrete in real time, and is also easy to operate and highly accurate. Before concrete pouring, the steel bars are placed in the test area of ​​the MCD sensor. The steel bars are in the magnetic circuit path of the MCD, so they have a positive effect on the magnetic field of the MCD. When reinforced concrete is in use, the steel bars are corroded by water, chloride ions and other substances. Due to the huge difference in magnetic conductivity between the steel bars and the corrosion products, the magnetic field around the steel bars also changes. The change of the magnetic signal will be captured by the Hall element, and the change of the magnetic signal will be converted into the steel bar corrosion rate through the calibration curve of the instrument itself. Therefore, MCD has great development potential in engineering applications. However, after more tests, it was found that the magnetic induction intensity measured by the MCD does not indicate the corrosion rate of the entire steel bar, but the corrosion of the side of the steel bar close to the measuring point, so the MCD can only be applied to the case of uniform corrosion of the steel bars. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art, such as the steel bar corrosion rate being tested only in the case of uniform corrosion. The present invention provides a magnetic field-based steel bar transverse non-uniform corrosion monitoring instrument and a testing method thereof.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] A monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field, comprising a steel bar corrosion monitoring sensor, a data collector and a data processing system;

[0008] The steel bar corrosion monitoring sensor is fixed to the periphery of the monitoring steel bar, and the steel bar corrosion monitoring sensor includes a Hall sensor; eight Hall sensors on the transverse direction of the steel bar are used to monitor the change of magnetic field intensity around the steel bar in situ;

[0009] The data collector converts the output voltage signal of the steel bar corrosion monitoring sensor into a numerical signal and transmits it to the data processing system;

[0010] The data processing system receives voltage signal data and records it in real time.

[0011] The steel bar corrosion monitoring sensor specifically comprises:

[0012] Silicon steel frame, used to form a magnetic field loop;

[0013] The central through hole of the silicon steel frame is the location for placing steel bars, and four permanent magnets are installed around the location for placing steel bars to generate a steady-state magnetic field;

[0014] There are also Hall element slots around the steel bar placement location for installing Hall elements; the Hall element is a SS495A Hall sensor that outputs the magnetic field changes caused by steel bar corrosion as voltage changes based on the Hall effect;

[0015] It also includes a data acquisition circuit board, which is an ADS1256IDB data acquisition board, used for collecting and transmitting the voltage signal of the Hall element;

[0016] A six-core cable connects the steel corrosion monitoring sensor to the data collector.

[0017] The data collector specifically includes:

[0018] The circuit board of the ADS1256 signal acquisition main chip converts the output voltage signal of the steel bar corrosion monitoring sensor into a numerical signal through four processes: sampling, holding, quantization and encoding;

[0019] RS232 USB to serial port chip realizes USB to serial port conversion, thereby connecting the data collector to the USB interface of the data processing system.

[0020] The data processing system specifically includes:

[0021] The monitoring instrument module automatically stores, processes and records in real time the voltage signal output by the steel corrosion monitoring sensor and displays it as a specific voltage value.

[0022] A method for monitoring transverse non-uniform corrosion of steel bars based on a magnetic field, using the monitoring instrument for transverse non-uniform corrosion of steel bars based on a magnetic field, comprises the following steps:

[0023] Step 1: Measure the voltage value of a type of steel bar when it is not corroded;

[0024] Step 2: corrode the steel bar, measure the voltage value of the steel bar after corrosion, and measure the corrosion rate of the steel bar at the same time;

[0025] Step 3: Repeat step 2 to establish the relationship between the steel bar corrosion rate and the measured voltage;

[0026] Step 4: Embed the steel corrosion monitoring sensor in the reinforced concrete component, measure the voltage value, and obtain the steel corrosion rate based on the relationship established in step 3.

[0027] Working principle:

[0028] The steel bar corrosion monitoring sensor includes four permanent magnets and a silicon steel frame. The permanent magnet itself can generate a fixed magnetic field. When combined with the silicon steel frame in the steel bar corrosion monitoring sensor, the magnetic flux will generate a magnetic circuit along the silicon steel frame and the air. The steel bar corrosion monitoring sensor forms a total of four magnetic circuits. When the steel bar is located in the test position in the middle of the steel bar corrosion monitoring sensor, that is, the air position on the magnetic circuit path, since the steel bar is a magnetic conductor and the air is a non-magnetic conductor, the presence of the steel bar interferes with the magnetic circuit of the steel bar corrosion monitoring sensor. The change of the magnetic circuit is detected by the Hall element in the steel bar corrosion monitoring sensor and output as a voltage signal. After being processed by the data acquisition device, it is displayed as a certain magnetic induction intensity value at the data processing system terminal. As the steel bar corrodes, the interference to the magnetic circuit changes, resulting in a change in the final output magnetic induction intensity value. In this way, a correlation between the steel bar corrosion rate and the magnetic induction intensity value is established, so as to achieve the purpose of quantitatively judging the steel bar corrosion rate by monitoring the magnetic induction intensity value.

[0029] Based on magnetic medium and magnetic field theory, the present invention can non-destructively and quantitatively monitor the corrosion of steel bars in reinforced concrete in real time, and has the characteristics of easy operation and high precision. Therefore, it has great development potential in engineering applications.

[0030] Compared with the prior art, the beneficial effects of the present invention are mainly manifested in:

[0031] 1. The steel bar corrosion monitoring sensor has a small structure, is easy to install and simple to operate.

[0032] 2. The steel bar corrosion monitoring sensor has eight measuring points around the steel bar cross section. The test results show that the magnetic induction intensity values ​​of the eight measuring points around the steel bar under different corrosion conditions can be respectively indicated. When the steel bar is transversely non-uniformly corroded, the corrosion condition of the steel bar cross section can be obtained through the magnetic induction intensity values ​​of the eight measuring points and converted into the steel bar corrosion rate.

[0033] 3. Before the steel corrosion monitoring sensor is embedded in reinforced concrete, the relationship between the amount of steel corrosion and the magnetic induction intensity value has been established. When applied in subsequent projects, the steel corrosion monitoring sensor embedded in reinforced concrete can quantitatively determine the corrosion of the steel bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the appearance of a steel bar corrosion monitoring sensor;

[0035] Figure 2 This is the internal structure diagram of the steel bar corrosion monitoring sensor;

[0036] Figure 3 This is the internal structure diagram of the steel bar corrosion monitoring sensor;

[0037] Figure 4Schematic diagram of the semi-immersion impressed current accelerated corrosion test. DETAILED DESCRIPTION

[0038] The specific technical solution of the present invention is described in conjunction with the accompanying drawings.

[0039] like Figures 1 to 3 As shown, a monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field includes a steel bar corrosion monitoring sensor 2, a data collector 4 and a data processing system;

[0040] The steel bar corrosion monitoring sensor 2 is fixed to the periphery of the monitoring steel bar, and the steel bar corrosion monitoring sensor 2 includes a Hall sensor; eight Hall sensors on the transverse direction of the steel bar are used to monitor the change of magnetic field strength around the steel bar in situ;

[0041] The data collector 4 converts the output voltage signal of the steel bar corrosion monitoring sensor 2 into a numerical signal and transmits it to the data processing system;

[0042] The data processing system receives voltage signal data and records it in real time.

[0043] The steel bar corrosion monitoring sensor 2 specifically includes:

[0044] Silicon steel frame 22, used to form a magnetic field loop;

[0045] The central through hole of the silicon steel frame 22 is a steel bar placement position 24, and four permanent magnets 21 are installed around the steel bar placement position 24 to generate a steady-state magnetic field;

[0046] A Hall element slot 23 is also provided around the steel bar placement position 24 for installing a Hall element 26; the Hall element 26 outputs the magnetic field change caused by steel bar corrosion as a voltage change according to the Hall effect;

[0047] It also includes a data acquisition circuit board 25, which is an ADS1256IDB data acquisition board for collecting and transmitting the voltage signal of the Hall element;

[0048] The six-core cable 3 connects the steel bar corrosion monitoring sensor 2 with the data collector 4.

[0049] The data collector 4 specifically includes:

[0050] The circuit board of the ADS1256 signal acquisition main chip converts the output voltage signal of the steel bar corrosion monitoring sensor 2 into a numerical signal through four processes: sampling, holding, quantization and encoding;

[0051] The RS232 USB to serial port chip realizes USB to serial port conversion, thereby connecting the data collector 4 to the USB interface of the data processing system.

[0052] The data processing system specifically includes:

[0053] The monitoring instrument module automatically stores, processes, and records in real time the voltage signal output by the steel bar corrosion monitoring sensor 2 and displays it as a specific voltage value.

[0054] A method for monitoring transverse non-uniform corrosion of steel bars based on a magnetic field, using the monitoring instrument for transverse non-uniform corrosion of steel bars based on a magnetic field, comprises the following steps:

[0055] Step 1: Measure the voltage value of a type of steel bar when it is not corroded;

[0056] Step 2: corrode the steel bar, measure the voltage value of the steel bar after corrosion, and measure the corrosion rate of the steel bar at the same time;

[0057] Step 3: Repeat step 2 to establish the relationship between the steel bar corrosion rate and the measured voltage;

[0058] Step 4: embed the steel bar corrosion monitoring sensor 2 in the reinforced concrete component, measure the voltage value, and obtain the steel bar corrosion rate based on the relationship established in step 3.

[0059] The implementation method of the present invention is specifically described below using 20mmHPB300 smooth round steel bars as an example.

[0060] 1. Prepare 2 steel bars with a length of 15 cm, measure the mass with an electronic scale, and calculate the mass of the middle 5 cm as m;

[0061] 2. Weld the wire on one side of the steel bar, then apply epoxy resin 5cm from both ends, and wrap it with waterproof tape after solidification, so that only the middle 5cm will be corroded. (The corrosion rate of the two ends of the steel bar corroded by electricity is quite different from that of the middle steel bar, so only the middle part is measured);

[0062] 3. The mass of the entire sample after measurement and processing is M0;

[0063] 4. Mark two points 1.5 cm on both sides of the center point of each steel bar, and measure the initial voltage value V0 with a steel bar corrosion monitoring sensor;

[0064] 5. As Figure 4 The data collector 4 is connected to the power supply 5 and the data processing system 6 of the data collector. The steel bar 1 is placed in a 5% NaCl solution. An auxiliary electrode 7 is also placed. The steel bar 1 and the auxiliary electrode 7 are respectively connected to the two poles of the power supply 8. The current density is 20A / m 2 , after every 24 hours, take out the corroded steel bar 1, use the steel bar corrosion monitoring sensor 2 to measure the post-rust voltage V11, V21, ..., V81 (the voltage of eight measuring points), then use the steel bar rust remover to remove the external rust layer, and after drying, use an electronic scale to measure the post-rust mass M1;

[0065] 6. Repeat step 5, record the post-rust voltage V12, ... V82, V13, ..., V83...; post-rust mass M2, M3... When the steel bar corrosion rate is close to 20%, the measurement ends.

[0066] 7. Use the formula (V0-Vi j ) / V0 is used to calculate the voltage change rate of the i measuring point in the jth cycle; (M0-Mi) / m is used to calculate the corrosion rate of the middle 5cm steel bars, and this value is used as the corrosion rate of the two calibration points of each steel bar.

[0067] 8. With the mass loss rate as the horizontal coordinate and the voltage change rate as the vertical coordinate, the voltage change rate and the corresponding mass loss rate of all points and all cycles are substituted to obtain the correlation between the voltage change rate and the mass loss rate of this type of steel bar. The obtained relationship is a nonlinear relationship: Among them, ΔU is the voltage change rate, Δm is the mass loss rate, and a, b, and c are nonlinear coefficients.

[0068] 9. When pouring reinforced concrete components, bury the steel corrosion monitoring sensor at the key points of the component (such as the mid-span of the bending beam), measure the voltage V0 of the monitoring point before corrosion, and measure the voltage Vi of the monitoring point again after the component has corroded for a certain period of time. j , calculate the voltage reduction rate, substitute it into the formula obtained in step 8, and get the corrosion rate of eight measuring points on the steel bar cross section, which respectively represent the corrosion conditions at different positions on the steel bar cross section, and then get the actual corrosion rate of the steel bar at this time.

[0069] 10. Use the measured steel corrosion rate to evaluate the concrete structure. When the steel corrosion rate is less than 5%, appropriate measures can be taken to prevent further corrosion of the steel. When the steel corrosion rate is greater than 5% and less than 10%, it is necessary to evaluate the components to see whether local maintenance is required. When the steel corrosion rate is greater than 10%, the components need to be maintained or replaced.

Claims

1. A monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field, characterized in that: It comprises a steel bar corrosion monitoring sensor (2), a data collector (4) and a data processing system; The steel bar corrosion monitoring sensor (2) is fixed to the periphery of the monitoring steel bar, and the steel bar corrosion monitoring sensor (2) comprises a Hall sensor; eight Hall sensors in the transverse direction of the steel bar are used to monitor the change of magnetic field intensity around the steel bar in situ; The data collector (4) converts the output voltage signal of the steel bar corrosion monitoring sensor (2) into a numerical signal and transmits it to the data processing system; The data processing system receives voltage signal data and records it in real time.

2. The monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field according to claim 1 is characterized in that: The steel bar corrosion monitoring sensor (2) specifically comprises: A silicon steel frame (22) for forming a magnetic field loop; The central through hole of the silicon steel frame (22) is a steel bar placement position (24), and four permanent magnets (21) are installed around the steel bar placement position (24) to generate a steady-state magnetic field; A Hall element slot (23) is also provided around the steel bar placement position (24) for installing a Hall element (26); the Hall element (26) outputs the magnetic field change caused by steel bar corrosion as a voltage change according to the Hall effect; It also includes a data acquisition circuit board (25), which is an ADS1256IDB data acquisition board, used for collecting and transmitting the voltage signal of the Hall element; The six-core cable (3) connects the steel bar corrosion monitoring sensor (2) and the data collector (4).

3. The monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field according to claim 1 is characterized in that: The data collector (4) specifically comprises: The circuit board of the ADS1256 signal acquisition main chip converts the output voltage signal of the steel bar corrosion monitoring sensor (2) into a numerical signal through four processes: sampling, holding, quantization and encoding; The RS232 USB to serial port chip realizes USB to serial port conversion, thereby connecting the data collector (4) to the USB interface of the data processing system.

4. The monitoring instrument for transverse non-uniform corrosion of steel bars based on magnetic field according to claim 1 is characterized in that: The data processing system specifically includes: The monitoring instrument module automatically stores, automatically processes, and records in real time the voltage signal output by the steel bar corrosion monitoring sensor (2) and displays it as a specific voltage value.

5. A method for monitoring transverse non-uniform corrosion of steel bars based on magnetic field, characterized in that: The monitoring instrument for transverse non-uniform corrosion of steel bars based on a magnetic field as claimed in any one of claims 1 to 4 comprises the following steps: Step 1: Measure the voltage value of a type of steel bar when it is not corroded; Step 2: corrode the steel bar, measure the voltage value of the steel bar after corrosion, and measure the corrosion rate of the steel bar at the same time; Step 3: Repeat step 2 to establish the relationship between the steel bar corrosion rate and the measured voltage; Step 4: embed the steel bar corrosion monitoring sensor (2) in the reinforced concrete component, measure the voltage value, and obtain the steel bar corrosion rate based on the relationship established in step 3.

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