A method and device for detecting carbonation depth of concrete based on DIC technology

Abstract

The application provides a concrete carbonation depth detection method and device based on DIC technology, which comprises the following steps: (1) drilling a core sample on the surface of a concrete structure to be detected to obtain a standard test piece; (2) spraying a speckle pattern on the outer facade of the test piece and drawing a ring-shaped mark line at different height positions; (3) arranging at least one camera around the test piece and adjusting a DIC system support; (4) loading the test piece and synchronously shooting at least one camera to record a deformation image, so that a full-field strain deformation cloud chart of the outer facade of the test piece is obtained; (5) obtaining a maximum value of the concrete carbonation depth according to the strain deformation cloud chart mutation limit of the test piece and the ring-shaped mark line; and (6) repeating steps (4) to (5) to obtain the maximum value of the depth at least once, and calculating the average value of the concrete carbonation depth. The concrete carbonation depth detection method and device based on the DIC technology provided in the application are simple to operate and can improve the detection precision of the concrete carbonation depth.

Description

Technical Field

[0001] This invention relates to the field of concrete testing technology, and in particular to a method and equipment for detecting the carbonation depth of concrete based on DIC technology. Background Technology

[0002] Concrete carbonation is a multiphase physicochemical process. It is the process by which atmospheric carbon dioxide penetrates concrete and reacts with alkaline substances in the cement paste, causing the concrete to neutralize. After carbonation, the gel pores and some capillary pores of the concrete are blocked by the carbonation product calcium carbonate, increasing the concrete's density, strength, and modulus of elasticity. Therefore, the modulus of elasticity differs between the carbonated and uncarbonated regions of a concrete structure; that is, a gradient change in the modulus of elasticity exists in the critical region.

[0003] In the strength and durability testing of existing concrete structures, concrete carbonation parameters are a mandatory test item. Commonly used testing methods include local drilling with phenolphthalein indicator, thermal analysis, X-ray phase analysis, and electron probe microanalysis. Among these, the local drilling with phenolphthalein indicator is the most commonly used, simplest, and lowest-cost method. However, due to the need for local drilling on-site, it is easy to drill into coarse aggregate, making it impossible to accurately measure the carbonation depth with phenolphthalein indicator. Furthermore, the phenolphthalein indicator method can only measure areas with pH > 10, resulting in a certain degree of measurement error. The latter three methods are laboratory operations, which are relatively expensive and have requirements regarding sample size and analytical results. Additionally, since concrete strength testing specifications require the use of core drilling or rebound hammer methods, when using the rebound hammer method, core samples must be drilled from the concrete structure for axial compressive strength testing, and then the core sample compressive strength value is used to correct the rebound hammer test results.

[0004] Therefore, it is essential to find a method for detecting carbonation depth based on concrete core samples by utilizing the axial compressive strength test of concrete core samples. Summary of the Invention

[0005] This invention provides a method and device for detecting the carbonation depth of concrete based on DIC technology. It can accurately obtain the carbonation depth value of concrete during the concrete strength testing process. It can not only correct the strength value detected by the rebound method, but also predict the durability of concrete based on the carbonation depth value. It is of great significance for practical engineering applications. It is simple to operate, has high accuracy, and can take samples during the concrete strength testing process without the need for separate local damage detection of the concrete structure for measuring carbonation parameters.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] A method for detecting the carbonation depth of concrete based on DIC technology includes:

[0008] (1) Drill core samples from the surface of the concrete structure to be tested to obtain standard specimens;

[0009] (2) Spray a speckle pattern onto the outer surface of the specimen and draw circumferential marking lines at different height positions, wherein the different height positions are different positions along the longitudinal extension direction of the specimen;

[0010] (3) Arrange at least one camera around the specimen and adjust the DIC system bracket;

[0011] (4) Load the specimen and simultaneously capture images with at least one of the cameras to record deformation images. Based on DIC technology and photogrammetry technology, combine the deformation images captured by at least one of the cameras at the same time to obtain a full-field strain deformation cloud map of the specimen's exterior facade. The specimen is loaded to the target load value at a predetermined loading rate and unloaded after maintaining the load for a predetermined time.

[0012] (5) Based on the abrupt change limit of the strain deformation cloud diagram and the circumferential marking line of the specimen, obtain the maximum value of the concrete carbonation depth;

[0013] (6) Repeat (4) to (5) at least once to obtain the maximum value of the concrete carbonation depth, and calculate the average value of the concrete carbonation depth.

[0014] In some embodiments, before step (4), the specimen is placed on the base of the universal testing machine and the universal testing machine is adjusted, with the top surface of the specimen in close contact with the loading plate of the universal testing machine.

[0015] In some embodiments, during step (4),

[0016] The universal testing machine loads the specimen to the target load value at a preset loading rate, maintains the load for at least 3 minutes, and then unloads it. The target load value is at least 1 / 3 of the ultimate load value of the specimen.

[0017] The full-field strain deformation cloud map of the specimen's exterior facade is acquired collaboratively by at least one of the cameras. Based on DIC technology and photogrammetry, a unified measurement coordinate system is obtained, and the full-field strain deformation cloud map is obtained based on the correlation of speckle characteristics in the images before and after the specimen's deformation.

[0018] In some embodiments, step (5) of obtaining the maximum value of concrete carbonation depth based on the abrupt change limit of the strain deformation cloud diagram and the circumferential marking line of the specimen specifically includes:

[0019] 1) Using the strain deformation cloud map of the entire exterior surface of the specimen generated by the DIC testing system, the strain of each part of the exterior surface of the specimen can be obtained intuitively, and the boundary of obvious strain change can be quickly found in the strain deformation cloud map.

[0020] 2) Record the strain abrupt change limit furthest from the top surface of the specimen according to the circumferential marking lines, and record the number of marking lines n in the area;

[0021] 3) Since the elastic modulus of concrete is defined as stress divided by strain during the elastic stage of concrete, and stress is the force per unit area, the elastic modulus is inversely proportional to strain. Therefore, the strain changes at various parts of the specimen directly reflect the changes in the elastic modulus. Consequently, the strain changes at each part can reflect the carbonized and non-carbonated zones of the concrete. Based on the full-field strain-deformation cloud map obtained from the DIC testing system, the pixel coordinates P of the location of the strain abrupt change boundary furthest from the top surface of the specimen are obtained. m (x m y m The pixel coordinates of the upper and lower indicator lines where the strain abrupt change limit is located are P, respectively. i (x i y i ), P i+1 (x i+1 y i+1 Thus, the maximum carbonation depth d1 of the concrete specimen was obtained:

[0022] In some embodiments, in step (1), the core sample is a core sample used for testing the concrete strength, so as to avoid drilling a core sample again for testing the concrete carbonation parameters, thereby reducing damage to the main concrete structure. The height of the core sample is in the range of 60mm to 200mm, and the diameter is in the range of 60mm to 200mm.

[0023] In some embodiments, in step S2, the speckle pattern is a random black dot pattern, and the speckle pattern is sprayed to obtain a high-precision strain field.

[0024] In some embodiments, in step S2, the circumferential marking line is a marking line drawn along the longitudinal direction of the specimen at predetermined intervals around the outer surface of the specimen. The range of the circumferential marking line is between 3mm and 16mm. Based on the circumferential marking line, the distance from each part of the specimen to the top surface of the specimen is read.

[0025] In some embodiments, step (3) involves arranging cameras around the specimen and adjusting the DIC system support, including:

[0026] At least one camera is installed at 1 / 4 intervals along the circumference of the specimen. The shortest distance from the lens of at least one camera to the outer surface of the specimen is the same, and the optical axis of the lens is perpendicular to the outer surface of the specimen.

[0027] Calibrate at least one of the camera parameters;

[0028] Debugging DIC equipment and testing systems.

[0029] In some embodiments, in step (6), the average carbonation depth of the concrete is the average value after three repeated loading cycles. The average carbonation depth of the concrete in the specimen can be obtained from the following formula:

[0030] This invention also provides a concrete carbonation depth detection device based on DIC technology. Utilizing the aforementioned concrete carbonation depth detection method based on DIC technology, core samples are taken from the concrete to detect the concrete carbonation depth. The device includes:

[0031] A camera device, including at least one lens;

[0032] A loading device, in which the core sample is loaded, the loading device can load the core sample according to a preset program, and at least one lens surrounds the outer surface of the core sample;

[0033] The DIC testing device is connected to the imaging device. The DIC testing device obtains a full-field strain deformation cloud map through the deformation image of the core sample under load, so as to finally obtain the average value of concrete carbonation depth.

[0034] The beneficial effects brought about by the embodiments of the present invention are as follows:

[0035] In the above scheme, the present invention utilizes the difference in elastic modulus between the carbonized and non-carbonated zones of concrete in the axial compressive strength test of concrete core samples, as well as the relationship between elastic modulus and strain, to obtain a full-field strain deformation cloud map of the specimen's exterior surface using DIC technology and photogrammetry. Then, based on the circumferential markings on the specimen, the strain abrupt change boundary furthest from the top surface of the specimen is quickly located. Finally, based on the pixel coordinates of the circumferential markings and the boundary position, the maximum value of the concrete carbonation depth can be obtained. The operation is simple and has high accuracy.

[0036] In a further embodiment of the present invention, sampling can be performed during the concrete strength testing process. By utilizing the concrete strength testing process, the concrete carbonation depth value can be accurately obtained. This not only corrects the strength value detected by the rebound method, but also predicts the durability of concrete based on the carbonation depth value. This is of great significance for practical engineering applications, eliminating the need for separate local damage detection of the concrete structure due to the measurement of carbonation parameters. Attached Figure Description

[0037] The accompanying drawings illustrate some embodiments of the invention and, together with the specification, further serve to explain the principles of the invention and enable those skilled in the art to implement and use the invention.

[0038] Figure 1 A schematic flowchart of the concrete carbonation depth detection method based on DIC technology provided in an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of core sampling from concrete.

[0040] Figure 3 A schematic diagram of the concrete specimen treatment;

[0041] Figure 4 This is a schematic diagram of the full-field strain-deformation contour map of a concrete specimen.

[0042] Figure 5 This is a schematic diagram of the structure of a concrete carbonation depth detection device based on DIC technology provided in an embodiment of the present invention.

[0043] [Figure Labels]

[0044] 100. Concrete carbonation depth detection equipment based on DIC technology; 10. Imaging device; 20. Loading device; 01. Test core sample.

[0045] As shown in the figure, specific structures and devices are labeled in the figure to clearly illustrate the structure of the embodiments of the present invention. However, this is only for illustrative purposes and is not intended to limit the present invention to the specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs, and such adjustments or modifications are still included in the scope of the appended claims. Detailed Implementation

[0046] The present invention provides a method and device for detecting the carbonation depth of concrete based on DIC technology, with reference to the accompanying drawings and specific embodiments. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments; those skilled in the art can also use other alternative methods to implement some known technologies. Furthermore, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0047] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0048] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0049] It is understood that the meanings of “on”, “above”, and “above” in this invention should be interpreted in the broadest manner, such that “on” means not only “directly on” something, but also includes the meaning of being “on” something with an intervening feature or layer, and that “above” or “above” means not only “on” something, but also includes the meaning of being “on” something without an intervening feature or layer.

[0050] Furthermore, spatially related terms such as “below,” “under,” “lower,” “above,” and “upper” are used herein for convenience to describe the relationship of one element or feature to one or more other elements or features, as illustrated in the accompanying drawings. Spatially related terms are intended to cover different orientations in the use or operation of the device other than those depicted in the accompanying drawings. The device may be oriented in other ways, and the spatially related descriptive terms used herein can be interpreted similarly.

[0051] refer to Figure 1 As shown, this embodiment of the invention provides a method for detecting the carbonation depth of concrete based on DIC technology, including:

[0052] S100: Drill core samples from the surface of the concrete structure to be tested to obtain standard specimens;

[0053] S200: Spray a speckle pattern onto the outer surface of the specimen and draw circumferential marking lines at different height positions, wherein the different height positions are different positions along the longitudinal extension direction of the specimen;

[0054] S300: Arrange at least one camera around the specimen and adjust the DIC system bracket;

[0055] S400: Load the specimen and simultaneously capture images with at least one of the cameras to record deformation images. Based on DIC technology and photogrammetry technology, combine the deformation images captured by at least one of the cameras at the same time to obtain a full-field strain deformation cloud map of the specimen's exterior surface. The specimen is loaded to the target load value at a predetermined loading rate and unloaded after maintaining the load for a predetermined time.

[0056] S500: Based on the abrupt change limit of the strain deformation cloud diagram and the circumferential marking line of the specimen, obtain the maximum value of the concrete carbonation depth;

[0057] S600: Repeat steps S400 to S500 at least once to obtain the maximum value of the concrete carbonation depth, and calculate the average value of the concrete carbonation depth.

[0058] In the above embodiments, step S100 can be referred to Figure 2 and Figure 3 Understandably, the standard specimen can be a cylindrical concrete core sample as shown in the diagram. The specimen to be tested can be an existing concrete structure to be tested, or it can be collected from a sample taken during a concrete strength test. Since the specimen to be tested is collected from a sample taken during a concrete strength test, there is no need to conduct local damage testing on the concrete structure separately for measuring carbonation parameters. Furthermore, the test sample can be reused, making the operation simple and the cost low.

[0059] Combination Figure 2 and Figure 3 In step S200, the longitudinal extension direction of the specimen can be understood as the up-down direction. In the up-down direction, the specimen has different height positions. Circular marking lines are drawn at different height positions, which is equivalent to drawing scales on the specimen. This allows for intuitive observation of the distance between various parts of the specimen and the top surface of the specimen. The speckle pattern sprayed on the outer surface of the specimen can be dots or triangles to mark the points. Setting marking points can obtain a strain field with higher accuracy.

[0060] Combination Figure 5 In step S300, multiple cameras can be evenly arranged along the outer surface of the specimen to capture deformation images from multiple directions. In addition, multiple cameras can capture images simultaneously at the same time to obtain deformation images of the specimen at multiple different positions. Adjusting the DIC system bracket can adjust the angle between the multiple cameras and the outer peripheral surface of the specimen, which is beneficial to obtaining the expected deformation images.

[0061] In steps S400 and S500, due to the difference in elastic modulus between the carbonized and non-carbonated zones of the concrete structure, and considering the relationship between elastic modulus and strain, deformation images of the concrete cylindrical specimen under load are acquired using DIC technology. Multiple cameras are used for simultaneous measurement to obtain a full-field strain-deformation cloud map. This full-field strain-deformation cloud map can be referenced. Figure 4 Based on the limits of strain abrupt change locations in the strain cloud diagram and the circumferential marking lines of the cylindrical specimen, the strain abrupt change limit furthest from the top surface of the specimen can be quickly obtained. Then, based on the pixel coordinates of the upper and lower circumferential marking lines where the furthest strain abrupt change limit is located and the pixel coordinates of the abrupt change location point, the maximum value of the concrete carbonation depth can be obtained.

[0062] In step S600, steps S400 to S500 are repeated, and can be repeated three, four, five times, etc. When the number of repetitions reaches a certain level, the average value of concrete carbonation depth can be calculated by averaging the maximum value of concrete carbonation depth, and the resulting average value of concrete carbonation depth can more accurately reflect the actual depth of concrete carbonation.

[0063] In summary, this solution utilizes the concrete strength testing process for sampling to accurately obtain the concrete carbonation depth value. This not only corrects the strength value detected by the rebound method but also predicts the concrete durability based on the carbonation depth value, which is of great significance for practical engineering applications. This invention is simple to operate, highly accurate, and eliminates the need for separate local damage detection of the concrete structure to measure carbonation parameters, thus ensuring the integrity of the existing concrete structure.

[0064] In other embodiments, prior to step S400, it may be combined with Figure 5 The specimen is placed on the base of the universal testing machine, and the universal testing machine is adjusted. The top surface of the specimen is in close contact with the loading plate of the universal testing machine. This allows for both axial compressive strength testing of concrete core samples and simultaneous acquisition of deformation images through the lens.

[0065] In the above embodiment, in step S400,

[0066] The universal testing machine loads the specimen to the target load value at a preset loading rate, maintains the load for at least 3 minutes, and then unloads it. The target load value is at least 1 / 3 of the ultimate load value of the specimen.

[0067] The full-field strain deformation cloud map of the specimen's exterior facade is acquired collaboratively by at least one of the cameras. Based on DIC technology and photogrammetry, a unified measurement coordinate system is obtained, and the full-field strain deformation cloud map is obtained based on the correlation of speckle characteristics in the images before and after the specimen's deformation.

[0068] In the above embodiment, step S500, based on the abrupt change limit of the strain-deformation cloud map and the circumferential marking line of the specimen, obtains the maximum value of the concrete carbonation depth, specifically including:

[0069] 1) Using the strain deformation cloud map of the entire exterior surface of the specimen generated by the DIC testing system, the strain of each part of the exterior surface of the specimen can be obtained intuitively, and the boundary of obvious strain change can be quickly found in the strain deformation cloud map.

[0070] 2) Record the strain abrupt change limit furthest from the top surface of the specimen according to the circumferential marking lines, and record the number of marking lines n in the area;

[0071] 3) Since the elastic modulus of concrete is defined as stress divided by strain during the elastic stage of concrete, and stress is the force per unit area, the elastic modulus is inversely proportional to strain. Therefore, the strain changes at various parts of the specimen directly reflect the changes in the elastic modulus. Consequently, the strain changes at each part can reflect the carbonized and non-carbonated zones of the concrete. Based on the full-field strain-deformation cloud map obtained from the DIC testing system, the pixel coordinates P of the location of the strain abrupt change boundary furthest from the top surface of the specimen are obtained. m (x m y m The pixel coordinates of the upper and lower indicator lines where the strain abrupt change limit is located are P, respectively. i (x i y i ) P i+1 (x i+1 y i+1 Thus, the maximum carbonation depth d1 of the concrete specimen was obtained:

[0072]

[0073] In some embodiments, in step S100, the core sample is a core sample used for testing the concrete strength, so as to avoid drilling a core sample again for testing the concrete carbonation parameters, thereby reducing damage to the main concrete structure. The height of the core sample is in the range of 60mm to 200mm, and the diameter is in the range of 60mm to 200mm.

[0074] In one embodiment, in step S100, the core sample is drilled into a cylindrical structure with a height of 100mm and a diameter of 100mm, which is conducive to adapting to the test equipment and facilities in the laboratory, thereby ensuring the smooth progress of concrete carbonation parameter testing.

[0075] In another optional embodiment, in step S100, the core sample is drilled into a cylindrical structure with a height of 75mm and a diameter of 75mm, which is conducive to adapting to the test equipment and facilities in the laboratory, thereby ensuring the smooth conduct of concrete carbonation parameter testing.

[0076] In the above embodiment, in step S200, the speckle pattern is a random black dot pattern, and the speckle pattern is sprayed to obtain a high-precision strain field.

[0077] In addition, in step S200, the circumferential marking line is a marking line drawn along the longitudinal direction of the specimen at predetermined intervals around the outer surface of the specimen. The setting range of the circumferential marking line is between 3mm and 16mm. According to the circumferential marking line, the distance of each part of the specimen from the top surface of the specimen can be read, which makes the concrete carbonation depth detection provided in this embodiment more intuitive and convenient to operate.

[0078] In some embodiments, step S300 involves deploying cameras around the specimen and adjusting the DIC system support, including:

[0079] At least one camera is installed at 1 / 4 intervals along the circumference of the specimen. The shortest distance from the lens of at least one camera to the outer surface of the specimen is the same, and the optical axis of the lens is perpendicular to the outer surface of the specimen.

[0080] Calibrate at least one of the camera parameters;

[0081] Debugging DIC equipment and testing systems.

[0082] In the above embodiments, multiple cameras can be evenly arranged along the circumference of the specimen, thereby enabling the capture of deformation images from multiple directions. In addition, multiple cameras can capture images simultaneously at the same time, thereby obtaining deformation images of multiple different positions of the specimen. Adjusting the DIC system support can adjust the angle between the multiple cameras and the outer circumference of the specimen, which is beneficial for obtaining the expected deformation images.

[0083] In the above embodiment, in step S600, the average carbonation depth of the concrete is the average value after three repeated loading cycles. The average carbonation depth of the concrete specimen can be obtained from the following formula: Of course, as in the above embodiments, the average value of concrete carbonation depth can be the average value after four or five repeated loadings, and will not be listed one by one here.

[0084] In addition, combined Figure 5 The present invention also provides a concrete carbonation depth detection device 100 based on DIC technology, which uses the concrete carbonation depth detection method based on DIC technology as described above to take a test core sample 01 from the concrete to detect the concrete carbonation depth, characterized in that it includes:

[0085] The shooting device 10 includes at least one lens;

[0086] The loading device 20 is used to load the core sample 01. The loading device 20 can load the core sample 01 according to a preset program. At least one of the lenses surrounds the outer surface of the core sample 01.

[0087] The DIC testing device is connected to the imaging device. The DIC testing device obtains a full-field strain deformation cloud map by measuring the deformation image of core sample 01 under load, so as to finally obtain the average value of concrete carbonation depth.

[0088] The device described above can obtain a full-field strain deformation cloud map of the specimen's exterior surface using DIC technology and photogrammetry, based on the difference in elastic modulus between the carbonized and non-carbonized zones of concrete and the relationship between elastic modulus and strain, in the axial compressive strength test of concrete core samples. Then, based on the circumferential marking lines on the specimen, it can quickly find the strain abrupt change boundary furthest from the top surface of the specimen. Finally, based on the pixel coordinates of the circumferential marking lines and the boundary position, the maximum value of the concrete carbonation depth can be obtained.

[0089] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. The above descriptions are merely preferred embodiments of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for detecting the carbonation depth of concrete based on DIC technology, characterized in that, include: (1) Drill core samples from the surface of the concrete structure to be tested to obtain standard specimens; (2) Spray a speckle pattern onto the outer surface of the specimen and draw circumferential marking lines at different height positions, wherein the different height positions are different positions along the longitudinal extension direction of the specimen; (3) Arrange at least one camera around the specimen and adjust the DIC system bracket; (4) Load the specimen and simultaneously capture images with at least one of the cameras to record deformation images. Based on DIC technology and photogrammetry technology, combine the deformation images captured by at least one of the cameras at the same time to obtain a full-field strain deformation cloud map of the specimen's exterior facade. The specimen is loaded to the target load value at a predetermined loading rate and unloaded after maintaining the load for a predetermined time. (5) Based on the abrupt change limit of the strain deformation cloud diagram and the circumferential marking line of the specimen, obtain the maximum value of the concrete carbonation depth; (6) Repeat (4) to (5) at least once to obtain the maximum value of the concrete carbonation depth, and calculate the average value of the concrete carbonation depth.

2. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 1, characterized in that, Before step (4), the specimen is placed on the base of the universal testing machine and the universal testing machine is adjusted so that the top surface of the specimen is in close contact with the loading plate of the universal testing machine.

3. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 2, characterized in that, In step (4), The universal testing machine loads the specimen to the target load value at a preset loading rate, maintains the load for at least 3 minutes, and then unloads it. The target load value is at least 1 / 3 of the ultimate load value of the specimen. The full-field strain deformation cloud map of the specimen's exterior facade is acquired collaboratively by at least one of the cameras. Based on DIC technology and photogrammetry, a unified measurement coordinate system is obtained, and the full-field strain deformation cloud map is obtained based on the correlation of speckle characteristics in the images before and after the specimen's deformation.

4. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 3, characterized in that, Step (5) involves obtaining the maximum value of the concrete carbonation depth based on the abrupt change limit of the strain deformation cloud diagram and the circumferential marking line of the specimen. Specifically, this includes: 1) Using the strain deformation cloud map of the entire exterior surface of the specimen generated by the DIC testing system, the strain of each part of the exterior surface of the specimen can be obtained intuitively, and the boundary of obvious strain change can be quickly found in the strain deformation cloud map. 2) Record the strain abrupt change limit furthest from the top surface of the specimen according to the circumferential marking lines, and record the number of marking lines n in the area; 3) Since the elastic modulus of concrete is defined as stress divided by strain during the elastic stage of concrete, and stress is the force per unit area, the elastic modulus is inversely proportional to strain. Therefore, the strain changes at various parts of the specimen directly reflect the changes in the elastic modulus. Consequently, the strain changes at each part can reflect the carbonized and non-carbonated zones of the concrete. Based on the full-field strain-deformation cloud map obtained from the DIC testing system, the pixel coordinates P of the location of the strain abrupt change boundary furthest from the top surface of the specimen are obtained. m (x m y m The pixel coordinates of the upper and lower indicator lines where the strain abrupt change limit is located are P, respectively. i (x i y i ), P i+1 (x i+1 y i+1 Thus, the maximum carbonation depth d1 of the concrete specimen was obtained: .

5. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 1, characterized in that, In step (1), the core sample is a core sample used for testing the concrete strength, so as to avoid drilling a core sample again to test the concrete carbonation parameters, thereby reducing damage to the main concrete structure. The height of the core sample is in the range of 60mm to 200mm, and the diameter is in the range of 60mm to 200mm.

6. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 2, characterized in that, In step (2), the speckle pattern is a random black dot pattern, and the speckle pattern is sprayed to obtain a high-precision strain field.

7. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 6, characterized in that, In step (2), the circumferential marking line is a marking line drawn along the longitudinal direction of the specimen at predetermined intervals around the outer surface of the specimen. The setting range of the circumferential marking line is between 3mm and 16mm. According to the circumferential marking line, the distance of each part of the specimen from the top surface of the specimen can be read.

8. The method for detecting the carbonation depth of concrete based on DIC technology according to claim 1, characterized in that, Step (3) involves arranging cameras around the specimen and adjusting the DIC system support, which includes: At least one camera is installed at 1 / 4 intervals along the circumference of the specimen. The shortest distance from the lens of at least one camera to the outer surface of the specimen is the same, and the optical axis of the lens is perpendicular to the outer surface of the specimen. Calibrate at least one of the camera parameters; Debugging DIC equipment and testing systems.

9. The method for detecting the carbonation depth of concrete based on DIC technology according to any one of claims 1-8, characterized in that, In step (6), the average carbonation depth of the concrete is the average value after three repeated loading cycles. The average carbonation depth of the concrete specimen can be obtained from the following formula:

10. A concrete carbonation depth detection device based on DIC technology, comprising using the concrete carbonation depth detection method based on DIC technology as described in any one of claims 1 to 9, wherein core samples are taken from the concrete to detect the concrete carbonation depth, characterized in that, include: A camera device, including at least one lens; A loading device, in which the core sample is loaded, the loading device can load the core sample according to a preset program, and at least one lens surrounds the outer surface of the core sample; The DIC testing device is connected to the imaging device. The DIC testing device obtains a full-field strain deformation cloud map through the deformation image of the core sample under load, so as to finally obtain the average value of concrete carbonation depth.

Images