CN214097166U - Concrete corrosion state detection system - Google Patents

Abstract

The utility model discloses a concrete corrosion state detection system, which is characterized in that the system comprises a control detection module, an optical module and a cavity module; the control detection module comprises an oscilloscope, a photoelectric detector, a laser energy meter, a computer and a spectrometer; the oscilloscope is connected with the photoelectric detector and used for monitoring the output signal of the laser, and the laser energy meter is used for monitoring the actual energy of the laser output by the laser; the optical module comprises a laser, a first spectroscope used for transmitting part of laser light to the photoelectric detector, a second spectroscope used for transmitting part of laser light to the laser energy meter, a reflecting mirror, a first plano-convex lens, a dichroic mirror, a second plano-convex lens and a collecting optical fiber, wherein the first plano-convex lens and the second plano-convex lens are respectively positioned on two sides of the dichroic mirror; the cavity module comprises a closed air chamber and an optical window arranged on the closed air chamber.

Description

Concrete corrosion state detection system

Technical Field

The utility model belongs to the technical field of laser diagnosis, concretely relates to LIBS detecting system for concrete corrosion state detects.

Background

In the operation process of nuclear power plants, corrosion of concrete structures becomes a key factor influencing the safe and stable operation of each power plant. All commercial nuclear power plants in China are built at sea, and chloride ions (Cl) in seawater^-) Can produce strong erosion action to concrete structure, arouse the corrosion of the inside reinforced concrete of structure, lead to the concrete to take place the fracture, destroy structural stability, in case take place structural damage in addition, light then lead to the foreign matter to get into the pipeline and cause equipment damage, heavy then lead to nuclear power plant cooling cycle water supply ability to reduce, bring very big risk to unit safe operation, influence nuclear power plant's steady operation.

The traditional measuring method aiming at the content of the concrete Cl ions is a chemical titration method, and the concrete needs to be sampled, measured and detected off line, so that the process is complicated, and the concrete structure is damaged, so that a novel nondestructive online monitoring and detecting means is urgently needed to detect, comprehensively evaluate and predict the corrosion degree of the structure.

Aiming at the high-radioactivity environment of a nuclear power plant, conventional detection means such as an X-ray photography technology, an ultrasonic technology and an eddy current technology can only be applied to a shutdown stage and a non-operation stage, and long-distance online measurement cannot be realized. Recently developed remote on-line detection techniques include acoustic emission techniques and electrochemical techniques, which have their respective limitations: if acoustic emission technology is available, only the pressure wave signal emitted by the material undergoing destruction can be detected, and the service life of the material cannot be evaluated and predicted; electrochemical techniques require small amplitude electrical signal perturbations to be added to the nuclear power system, which can adversely affect the system.

The Laser Induced Breakdown Spectroscopy (hereinafter referred to as LIBS) is a Spectroscopy technique that is based on the interaction between high-power pulsed Laser and a sample to be measured to generate transient plasma, high-temperature and high-density plasma radiates characteristic spectral lines with different wavelengths, and qualitative or quantitative analysis is realized on the sample to be measured by analyzing the characteristic spectral lines of atoms or ions in the plasma emission spectrum.

Compared with the conventional detection means, the strong remote online detection capability of the LIBS technology cannot be achieved by the conventional detection means; the LIBS technology only contacts the surface of a sample in an optical contact manner in the detection process, the mass of the sample ablated in the detection process is only microgram magnitude, the whole system is not affected at all, the analysis result can be obtained in real time, the accuracy is high, the analysis speed is high, and the LIBS technology has obvious advantages in the on-line monitoring technology of the nuclear power station.

Disclosure of Invention

In view of the above, in order to overcome the defects of the prior art and achieve the above object, the present invention is directed to a system for detecting the corrosion state of concrete, which can realize rapid and accurate detection without destroying the sample to be detected.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a detection system for a concrete corrosion state comprises a control detection module, an optical module and a cavity module;

the control detection module comprises an oscilloscope, a photoelectric detector, a laser energy meter, a computer and a spectrometer; the oscilloscope is connected with the photoelectric detector and used for monitoring the output signal of the laser, and the laser energy meter is used for monitoring the actual energy of the laser output by the laser; in some embodiments of the present invention, the control detection module further comprises an ICCD (Integrated Charge Coupled Device) and a programmable pulse delay generator;

the optical module comprises a laser, a first spectroscope used for transmitting part of laser light to the photoelectric detector, a second spectroscope used for transmitting part of laser light to the laser energy meter, a reflecting mirror, a first plano-convex lens, a dichroic mirror, a second plano-convex lens and a collecting optical fiber, wherein the first plano-convex lens and the second plano-convex lens are respectively positioned on two sides of the dichroic mirror; the collecting optical fiber is used for transmitting the light transmitted by the second plano-convex lens into the spectrometer;

the cavity module comprises a closed air chamber and an optical window arranged on the closed air chamber.

The displacement platform can drive the sample to be measured to move in the horizontal direction and the vertical direction, is fixedly arranged on the bottom surface inside the closed air chamber and is connected with an electric signal of the electric controller outside the closed air chamber. The electric controller is electrically connected with a computer through electric signals, the displacement of the displacement platform on X, Y, Z aspects can be remotely and electrically controlled through software, and the control precision can reach 10 mu m. The displacement platform is adopted to drive the sample to be detected to move during detection, so that the two-dimensional scanning LIBS detection of the penetration surface of the concrete sample to be detected is realized, the two-dimensional spectrum information of the concrete penetration surface with the scanning precision of 0.1mm (the distance between adjacent scanning points) can be obtained, and the critical penetration depth with the content of chlorine exceeding the standard can be determined.

According to some preferred embodiments of the present invention, the laser, the first beam splitter, the second beam splitter and the reflector in the optical module are located in the same optical path; the mirror surfaces of the first spectroscope and the second spectroscope are arranged in parallel, and the mirror surface of the reflector is perpendicular to the mirror surface of the first spectroscope or the second spectroscope. Specifically, the mirror surfaces of the first beam splitter and the second beam splitter form an included angle of 135 degrees with the output laser optical axis of the laser, and the mirror surface of the reflector forms an included angle of 45 degrees with the output laser optical axis of the laser.

According to some preferred aspects of the invention, the first plano-convex lens, the dichroic mirror and the second plano-convex lens are located in the same optical path; and the mirror surfaces of the first plano-convex lens and the second plano-convex lens are both vertical to the optical axis of the output laser of the laser. The dichroic mirror and the output laser optical axis of the laser form an included angle of 45 degrees; the first plano-convex lens is installed on one side of the reflecting surface of the dichroic mirror, and the second plano-convex lens is installed on one side of the transmitting surface of the dichroic mirror. The diameter of the first plano-convex lens is 25.4mm, and the focal length is 100 mm; the diameter of the second plano-convex lens is 12.7mm, and the focal length is 40 mm.

According to some preferred embodiments of the invention, the laser is a picosecond laser. Specifically, in some embodiments of the present invention, the picosecond laser is Nd: YAG picosecond laser, the output laser wavelength is 1064nm, the frequency is 10Hz, the pulse width FWHM is 30 +/-3 ps, the maximum pulse energy is 30mJ, and the diameter of the laser beam is 6 mm. Because its pulse width is on the order of picoseconds, the power density of its laser is higher. Therefore, compared with nanosecond laser, the laser can better excite the chloride ions on the surface of the concrete sample to form plasma.

According to some preferred implementation aspects of the utility model, the cavity module still including set up in displacement platform in the sealed air chamber, the sample that awaits measuring is placed displacement platform's top, displacement platform is used for driving the sample that awaits measuring removes.

According to some preferred implementation aspects of the utility model, control detection module is still including being used for control displacement platform removes electric controller, electric controller with the computer is connected, and through signal cable with displacement platform connects.

According to some preferred implementation aspects of the utility model, air inlet and gas outlet have been seted up to the upper wall of airtight gas chamber, the air inlet is used for communicating with the inert gas air supply. And the air pressure in the sealed air chamber is controlled to be 800-. The filling of inert gas is favorable for improving the signal-to-noise ratio of the LIBS spectrum, greatly weakens the intensity of the background spectrum, and further improves the detection limit of chlorine.

According to some preferred embodiments of the invention, the inert gas is helium or argon.

According to some preferred embodiments of the invention, the focal position of the laser beam focus is set within 5mm below the surface of the sample to be measured. In some embodiments, the laser beam focus position is set 2mm below the surface of the concrete sample to be tested during the breakdown-induced plasma generation process when the laser is focused on the surface of the concrete sample to be tested. On one hand, the laser energy density in unit area is higher due to the smaller focusing light spot, so that the chlorine plasma on the surface of the concrete sample to be tested can be excited more conveniently; on the other hand, a larger focused spot has a larger ablation area and achieves higher ablation breakdown efficiency. This is the best choice in two aspects.

Owing to adopted above technical scheme, compare in prior art, the utility model discloses an useful part lies in: the utility model discloses a concrete corrosion state's detecting system has realized detecting the two-dimensional scanning LIBS of concrete sample osmotic surface that awaits measuring, compares traditional chemistry and titrates detection method's advantage and lie in: the detection speed is high, and the detection precision is high; by performing principal component analysis and cluster analysis on element information in LIBS spectra of different scanning points, aggregate components and cement components in a concrete sample to be detected can be accurately identified; the two-dimensional spectral information of the concrete penetration surface with the scanning precision of 0.1mm can be obtained, the critical penetration depth with the overproof chlorine element content can be easily determined, the chlorine element penetration path is deduced, and the concrete corrosion condition is more accurately reflected.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of a system for detecting a corrosion state of concrete according to an embodiment of the present invention;

FIG. 2 is a comparison graph of the measured chlorine plasma radiation spectrum lines of the detection system for the concrete corrosion state in the embodiment of the invention in the air atmosphere and the helium atmosphere;

FIG. 3 is a graph comparing the results of a test conducted by a test system of the present invention and a chemical titration conducted on a straight permeation line of a concrete sample immersed in a saturated sodium chloride solution for 15 days;

FIG. 4 is a flow chart of a method for detecting a corrosion state of concrete according to an embodiment of the present invention;

wherein: a 1-picosecond laser; 2-an oscilloscope; a 3-spectroscope; 4-a photodetector; 5-a spectroscope; 6-laser energy meter; 7-plano-convex lens; 8-a mirror; 9-an electric controller; 10-a signal cable; 11-an air inlet; 12-an aviation socket; 13-plasma plume; 14-concrete sample; 15-a three-dimensional displacement platform; 16-a closed air chamber; 17-a glass window; 18-air outlet; 19-plano-convex lens; 20-a computer; 21-a dichroic mirror; 22-a spectrometer; 23-ICCD; 24-a programmable pulse delay generator; 25-collecting fiber.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall belong to the protection scope of the present invention.

EXAMPLE 1 detection System for Corrosion State of concrete

Referring to fig. 1, the system for detecting the corrosion state of concrete in the present embodiment includes a control detection module, an optical module, and a cavity module; the control detection module comprises an oscilloscope 2, a photoelectric detector 4, a laser energy meter 6, an electric controller 9, a signal cable 10, a computer 20, a spectrometer 22, an ICCD23 and a programmable pulse delay generator 24; the optical module comprises a picosecond laser 1, a first spectroscope 3, a second spectroscope 5, a second plano-convex lens 7, a reflector 8, a first plano-convex lens 19, a dichroic mirror 21 and a collecting optical fiber 25; the cavity module includes: the air inlet 11, the aviation socket 12, the concrete sample 14, the three-dimensional displacement platform 15, the closed air chamber 16, the optical window 17 and the air outlet 18.

The picosecond laser 1, the first spectroscope 3, the second spectroscope 5 and the reflector 8 in the optical module are positioned on the same optical path, and the mirror surfaces of the first spectroscope 3 and the second spectroscope 5 and the output laser optical axis of the picosecond laser 1 form an included angle of 135 degrees; the mirror surface of the spectroscope 8 is perpendicular to the mirror surfaces of the first spectroscope 3 and the second spectroscope 5, and forms an included angle of 45 degrees with the output laser optical axis of the picosecond laser 1.

One path of laser output by the picosecond laser 1 penetrates through the first beam splitter 3 and is split into the photoelectric detector 4, and the photoelectric detector 4 is externally connected to the oscilloscope 2 and used for monitoring an output signal of the picosecond laser; the laser that permeates through the first spectroscope 3 continues to permeate through the second spectroscope 5, partial laser is split by the second spectroscope 5 and is sent to the laser energy meter 6, the laser energy meter 6 is externally connected to the computer 20, the proportion of the laser energy entering the laser energy meter 6 and the laser energy output by the picosecond laser 1 is measured in advance through experiments, and a corresponding splitting coefficient is set in the computer 20, so that the actual energy of the laser output by the picosecond laser 1 can be monitored.

The picosecond laser 1 used in this example was Nd: YAG picosecond laser, the output laser wavelength is 1064nm, the frequency is 10Hz, the pulse width FWHM is 30 +/-3 ps, the maximum pulse energy is 30mJ, and the diameter of the laser beam is 6 mm. The reason why the picosecond laser is used is that the pulse width of the picosecond laser is on the order of picoseconds, and the power density of the laser is higher. Therefore, the picosecond laser can better excite the chloride ions on the surface of the concrete sample to form plasma compared with the nanosecond laser.

The second plano-convex lens 7, the dichroic mirror 21 and the first plano-convex lens 19 in the optical module are positioned in the same other optical path, and the center of the second plano-convex lens 7, the center of the dichroic mirror 21 and the center of the first plano-convex lens 19 are positioned on the same straight line. The mirror surface of the dichroic mirror 21 and the optical axis of the output laser of the picosecond laser 1 form an included angle of 45 degrees, wherein the cut-off wavelength of the short-wave-pass dichroic mirror 21 is 805 nm; the first plano-convex lens 19 is installed on the reflection surface side of the dichroic mirror 21, and the second plano-convex lens 7 is installed on the transmission surface side of the dichroic mirror 21; wherein the first plano-convex lens 19 has a diameter of 25.4mm and a focal length of 100 mm. Wherein the diameter of the second plano-convex lens 7 is 12.7mm, and the focal length is 40 mm; the mirror surfaces of the first plano-convex lens 19 and the second plano-convex lens 7 are both perpendicular to the output laser optical axis of the picosecond laser 24.

The laser beam transmitted through the second beam splitter 5 is reflected by the reflecting mirror 8 and then directed to the dichroic mirror 21. Dichroic mirror 21 is a short-wave pass dichroic mirror with a diameter of 50.8mm and a cut-off wavelength of 805 nm. For light with the wavelength of 830-1300nm, the reflectivity of the dichroic mirror 21 can reach more than 96%; the light with the wavelength of 400-792nm can reach the light transmission rate of more than 90 percent. The parallel laser beam reflected by the dichroic mirror 21 is focused by the first plano-convex lens 19 and then passes through the optical window 17 in the cavity module, so that the focused laser enters the closed air chamber 16 for transmission.

The laser beam passing through the optical window 17 is focused onto the surface of the concrete sample 14, generating a plasma plume 13. Because the laser beam converged downwards by the first plano-convex lens 19 passes through the optical window 17 again, the refractive index of the medium is changed, and the optical path transmitted during laser focusing is prolonged, so that the distance between a laser beam focusing spot and the center of the first plano-convex lens 19 is slightly larger than the focal length of the first plano-convex lens by 100 mm.

Since the optical path is reversible, the photons emitted by the plasma plume 13 propagate out of the confined gas chamber 16 through the optical window 17; the plasma radiation photons start to travel back along the incident optical path, they are converted into parallel light by the first plano-convex lens 19, the parallel light propagates through the dichroic mirror 21 to the second plano-convex lens 7, is focused by the second plano-convex lens 7 into the collection fiber 25, and is input into the spectrometer 22.

The air inlet 11, the aviation socket 11, the optical window 17 and the air outlet 18 in the cavity module are all positioned on the wall surface of the closed air chamber 16; and the concrete sample 14 to be detected, the three-dimensional displacement platform 15 and the plasma plume 13 are all positioned in the closed gas chamber 16.

The upper wall surface of the closed air chamber 16 is respectively provided with an openable air inlet 11 and an openable air outlet 18, and the air inlet 11 and the air outlet 18 are connected with a helium gas cylinder through guide pipes. Before the detection of the sample to be detected is carried out, helium (He) is introduced into the closed air chamber 16 through the air inlet 11, and the original air in the closed air chamber 16 is discharged from the air outlet 18 until the closed air chamber 16 is completely filled with the helium. Because the air is composed of a series of element molecules, the LIBS emission spectrum line of the air can interfere with the chlorine emission spectrum line; the fluctuation of the intensity of the LIBS spectrum background signal is related to the laser breakdown of air, and the difficulty of detecting the spectrum of the chlorine element is further increased. Helium can improve the spectral signal-to-noise ratio, greatly weaken the intensity of a background spectrum and further improve the detection limit of chlorine.

The helium gas pressure within the closed gas chamber 16 is preferably controlled to be 1000 mbar. On the one hand, a high gas pressure leads to more gas in the environment and therefore to emission lines of greater intensity associated with the gas, which may interfere with and mask the lines of chlorine; on the other hand, at low gas pressures, the density of the emitted particles is low and the detected LIBS signal is low. The normalized spectral intensity increases with increasing gas pressure and starts to stabilize until 400mbar later, which corresponds to the dependence of the discharge parameters (e.g. electron density) on the pressure. Thus, the optimum working pressure within the closed gas chamber 16 is determined to be 1000mbar, since it is easier to stabilize the pressure at this value than to maintain it at a lower pressure. Fig. 2 is a comparison of plasma emission spectra of the spectra under air and helium atmospheres, and it can be seen that the measured chloride line intensity is significantly enhanced in the LIBS spectrum under helium atmosphere compared to the LIBS spectrum under no composite air atmosphere.

The three-dimensional displacement platform 15 used in the present embodiment is installed and fixed on the bottom surface inside the closed air chamber 16, and is electrically connected with the electric controller 9 outside the closed air chamber 16. The electric controller 9 is connected with the computer 20 through electric signals, and can remotely and electrically control the displacement of the three-dimensional displacement platform 15 on the X, Y, Z aspects through software, and the control precision can reach 10 micrometers.

The photoelectric switch sensor is arranged on the inner wall surface of the closed air chamber 16 and consists of a photoelectric switch transmitting end and a photoelectric switch collecting end, and the photoelectric switch sensor is mainly used for controlling the height of a sample to be measured. The light emitting diode in the emitting end of the photoelectric switch continuously emits light signals to the collecting end of the photoelectric switch, and the phototriode in the collecting end of the photoelectric switch converts the received light signals into electric signals to be transmitted to the computer 20. The photoelectric switch transmitting end and the photoelectric switch collecting end are arranged at the same height, and the light-emitting optical axis of the photoelectric detector is parallel to the surfaces of the three-dimensional displacement platform 15 and the concrete sample 14 to be detected. Preferably, the height of the light emission optical axis is set to be 2mm above the height of the focused focal position of the focused laser beam passing through the optical window 17.

In the detection process, a command is given to the electric controller 9 through the computer 20, the three-dimensional displacement platform 15 is controlled to drive the concrete sample 14 to be detected to slowly rise until the upper surface of the concrete sample 14 shields the light beam emitted by the photoelectric switch emitting end, the electric signal transmitted outwards by the photoelectric switch collecting end is changed, and meanwhile the computer 20 controls the three-dimensional displacement platform 15 to stop acting. At this time, the focal point of the laser beam passing through the optical window 17 is located 2mm below the surface of the concrete sample 14 to be measured.

The size of the focused light spot on the surface of the sample to be measured can be directly influenced by the position relation between the focused focus of the laser beam and the surface of the sample to be measured. On one hand, the laser energy density in unit area is higher due to the smaller focusing light spot, which is more beneficial to the chlorine plasma on the surface of the concrete sample 14 to be measured; on the other hand, a larger focused spot has a larger ablation area and achieves higher ablation breakdown efficiency. The laser beam focal point position is set 2mm below the surface of the concrete sample 14 to be tested in this application.

The aviation socket 12 in this embodiment is installed on the side wall surface of the airtight chamber 16, and functions to enable electrical signal connection between the components inside and outside the airtight chamber without affecting the airtightness of the airtight chamber. The 6 signal lines of the three-dimensional displacement platform in the closed air chamber 16 and the 2 signal lines of the photoelectric switch are integrated into a signal cable 10, pass through the aviation socket 12, and are respectively and electrically connected with the electric controller 9 and the computer 20 outside the closed air chamber 16.

In this embodiment, the preparation work before the two-dimensional scanning LIBS detection is as follows: turning on the indication light of the picosecond laser 1, and moving the position of the concrete sample 14 to be detected on the three-dimensional displacement platform 15, so that the indication light of the picosecond laser 1 falls on the position of the starting point of the two-dimensional scanning detection; the parameters of the programmable pulse delay generator 24 are set, the time delay of the light-emitting signal of the picosecond laser 1 and the gate width signal of the ICCD23 is changed, and the lifting of the three-dimensional displacement platform 15 is further finely adjusted through the computer 20, so that the signal-to-back ratio of the spectral intensity of the chlorine element characteristic spectral line at 837.6nm and the ordinate of the spectrogram are maximum when the software of the computer 20 is used for observing. The laser focusing position on the surface of the sample to be detected and the luminous intensity of the plasma can be observed through a micro camera or high-resolution monitoring arranged in the closed air chamber 16, and the electric controller 9 is conveniently controlled through the computer 20, so that the concrete sample 14 to be detected is adjusted in the three-dimensional direction, and the more remarkable effect of inducing the plasma through laser breakdown is obtained.

The spectrometer 22 will sample the ambient background spectrum before each measurement of the concrete sample 14 to be tested. During each measurement, the picosecond laser emits pulse laser for 100 times at a frequency of 10Hz, and a plasma spectrum generated by the laser breakdown on the surface of the concrete sample 14 to be measured each time is transmitted to the spectrometer 22 through a light path; the spectrometer 22 accumulates the collected spectra generated by the pulses of 100 times and transmits the accumulated spectra to the computer 22 for the user, the software can automatically analyze and compare the obtained spectral data with the LIBS element spectral information in the database, the obtained spectral data are provided for the element types and the corresponding spectral line intensities contained in the concrete sample 14 to be detected, and the chlorine content in the concrete sample 14 to be detected can be further determined through a calibration curve.

Example 2 detection method

As shown in fig. 4, in this embodiment, the two-dimensional scanning LIBS detection of the penetration surface of the concrete sample 14 to be detected by using the detection system for the corrosion state of concrete in embodiment 1 includes the following steps:

and S1, opening the closed air chamber 16, and placing the concrete sample 14 to be detected on the three-dimensional displacement platform 15.

And S2, closing the closed air chamber 16, introducing helium (He) into the closed air chamber 16 through the air inlet 11, discharging the original air in the closed air chamber 16 from the air outlet 18 until the closed air chamber 16 is completely filled with the helium, and controlling the air pressure in the closed air chamber 16 to be 1000 mbar.

And S3, issuing an instruction to the electric controller 9 through the computer 20, and controlling the three-dimensional displacement platform 15 to drive the concrete sample 14 to be tested to slowly rise until the upper surface of the sample to be tested shields the light beam emitted by the photoelectric switch emitting end in the closed air chamber 16, and stopping rising.

And S4, turning on the indicating light of the picosecond laser 1, controlling the movement of the three-dimensional displacement platform 15 in the X, Y direction, and adjusting the position of the concrete sample 14 to be detected on the xOy plane so that the indicating light of the picosecond laser 1 falls to the position of the starting point of the two-dimensional scanning detection.

And S5, adjusting the parameters of the optical signal emitted by the picosecond laser 1, the delay of the ICCD23 gate width signal and the height position of the fine adjustment three-dimensional displacement platform 15, so that the focal point of the laser beam is focused 2mm below the surface of the sample to be measured.

S6, observing the signal-to-back ratio of the spectral intensity of the chlorine element characteristic spectral line at 837.6nm and the ordinate of the spectrogram, carrying out the step of S7 if the signal-to-back ratio is high and the ordinate of the spectrogram has the maximum value, returning to the step of S5 if the signal-to-back ratio is low, and carrying out the step of S7 until the chlorine element characteristic spectral line with the high signal-to-back ratio and the ordinate of the spectrogram has the maximum value is observed.

And S7, setting the spectrum accumulation times of the spectrometer 22 on the computer 20, and setting the electric controller 9 to control the motion track, the motion interval and the motion speed of the three-dimensional displacement platform 15 in the X, Y direction to determine the scanning point.

And S8, sampling background light by using the spectrometer 22 in the control detection module, performing accumulation shooting at each position point, and controlling the three-dimensional displacement platform 15 to move the concrete sample 14 to be detected to the next scanning point to obtain the LIBS spectrum information of the two-dimensional scanning of the sample to be detected.

And S9, combining the LIBS detection experiment of the standard cement sample, quantitatively obtaining the two-dimensional scanning distribution information of the chlorine element on the penetration surface of the concrete sample 14 to be detected through the chlorine element standard calibration curve, and determining the penetration depth of the chlorine element of the concrete sample 14.

And S10, releasing helium in the closed air chamber 16, and controlling the three-dimensional displacement platform 15 to return to the initial position.

Fig. 3 is a comparison graph of detection results obtained by respectively using chemical titration and LIBS scanning on one straight penetration line of a concrete sample soaked in a saturated sodium chloride solution for 15 days by using the detection system in example 1 and the detection method in this example, and it can be seen that the content of chloride ions measured by the chemical titration method and the spectral intensity of chloride ions measured by the two-dimensional scanning LIBS method have high correlation and consistency. Since the corrosion threshold of chloride ions in concrete is 0.2wt.%, it can be concluded that the critical penetration depth of the penetration surface of the concrete sample 14, at which the chlorine content exceeds the standard, is about 18 mm. In the present embodiment, the critical penetration depth is defined as: in the concrete penetration surface, when the Cl ion concentration is equal to 0.2wt.%, the corresponding penetration depth.

The principle of the utility model is as follows:

the utility model provides a two-dimensional scanning LIBS detecting system and method for concrete corrosion state detects utilizes the two-dimensional scanning LIBS technique in the helium atmosphere, and two-dimensional element distribution information in the concrete that mainly used qualitative and quantitative analysis awaits measuring confirms the critical depth of penetration that chlorine element content exceeds standard, reflects out the concrete corrosion situation.

The utility model discloses a picosecond laser's pulse width is the picosecond magnitude, and the power density of its laser is higher. Therefore, the picosecond laser can better excite the chloride ions on the surface of the concrete sample to form plasma compared with the nanosecond laser.

The utility model discloses in the laser focusing punctures the induced plasma production in-process to the concrete surface that awaits measuring, set up 2mm department under the concrete sample surface that awaits measuring with laser beam focus position. On one hand, the laser energy density in unit area is higher due to the smaller focusing light spot, which is more beneficial to the chlorine plasma on the surface of the concrete sample 14 to be measured; on the other hand, a larger focused spot has a larger ablation area and achieves higher ablation breakdown efficiency. This is the best choice in two aspects.

The utility model discloses a to the two-dimensional scanning LIBS detection of the concrete sample infiltration face that awaits measuring, compare traditional chemistry and titrate detection method's advantage and lie in: the detection speed is high, and the detection precision is high; by performing principal component analysis and cluster analysis on element information in LIBS spectra of different scanning points, aggregate components and cement components in a concrete sample to be detected can be accurately identified; the two-dimensional spectral information of the concrete penetration surface with the scanning precision of 0.1mm can be obtained, the critical penetration depth with the overproof chlorine element content can be easily determined, the chlorine element penetration path is deduced, and the concrete corrosion condition is more accurately reflected.

The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose of the embodiments is to enable people skilled in the art to understand the contents of the present invention and to implement the present invention, which cannot limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered by the protection scope of the present invention.

Claims (10)

1. A detection system for a concrete corrosion state is characterized by comprising a control detection module, an optical module and a cavity module;

the control detection module comprises an oscilloscope, a photoelectric detector, a laser energy meter, a computer and a spectrometer; the oscilloscope is connected with the photoelectric detector and used for monitoring the output signal of the laser, and the laser energy meter is used for monitoring the actual energy of the laser output by the laser;

the optical module comprises a laser, a first spectroscope used for transmitting part of laser light to the photoelectric detector, a second spectroscope used for transmitting part of laser light to the laser energy meter, a reflecting mirror, a first plano-convex lens, a dichroic mirror, a second plano-convex lens and a collecting optical fiber, wherein the first plano-convex lens and the second plano-convex lens are respectively positioned on two sides of the dichroic mirror; the collecting optical fiber is used for transmitting the light transmitted by the second plano-convex lens into the spectrometer;

the cavity module comprises a closed air chamber and an optical window arranged on the closed air chamber.

2. The detection system according to claim 1, wherein the laser, the first beam splitter, the second beam splitter and the reflector in the optical module are located in the same optical path; the mirror surfaces of the first spectroscope and the second spectroscope are arranged in parallel, and the mirror surface of the reflector is perpendicular to the mirror surface of the first spectroscope or the second spectroscope.

3. The detection system according to claim 2, wherein the first plano-convex lens, the dichroic mirror, and the second plano-convex lens are located in the same optical path; and the mirror surfaces of the first plano-convex lens and the second plano-convex lens are both vertical to the optical axis of the output laser of the laser.

4. The detection system of claim 1, wherein the laser is a picosecond laser.

5. The system for detecting the corrosion state of concrete according to claim 1, wherein the cavity module further comprises a displacement platform disposed in the airtight air chamber, a sample to be tested is placed on the top of the displacement platform, and the displacement platform is used for driving the sample to be tested to move.

6. The system for detecting the corrosion state of concrete according to claim 5, wherein said control detection module further comprises an electric controller for controlling the movement of said displacement platform, said electric controller is connected with said computer and connected with said displacement platform through a signal cable.

7. The system for detecting the corrosion state of concrete according to claim 1, wherein the upper wall of the closed air chamber is provided with an air inlet and an air outlet, and the air inlet is used for being communicated with an inert gas source.

8. The system for detecting the corrosion state of concrete according to claim 7, wherein the inert gas is helium or argon.

9. The system for detecting the corrosion state of concrete according to claim 7, wherein the air pressure in the sealed air chamber is 800-1000mbar when the detection system detects the corrosion state of concrete.

10. The system for detecting the corrosion state of concrete according to claim 1, wherein the focal position of the laser beam focus is set within 5mm below the surface of the sample to be tested.

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