Concrete early cracking crack testing device and measuring method

Abstract

The invention discloses a concrete early cracking crack test device and a measurement method, the device comprises an environment main box body, a bottom plate of the environment main box body is connected with a clamping groove, and an anti-cracking test mold is fixed through the clamping groove; an image acquisition unit, a temperature control air supply box, a humidity control box and a load unit are also arranged in the environment main box body; the image acquisition unit, the temperature control air supply box, the humidity control box and the load unit are all connected with an instrument control module. The measuring method comprises the following steps: firstly, starting the temperature control air supply box and the humidity control box, then pouring concrete into the rectangular frame to form a test piece, and pushing the anti-crack test mold into the clamping groove for fixing; when the test piece reaches final setting, the fixing screws are removed, and the hydraulic cylinder is started to apply load force to the test piece; an image of the test piece is acquired through the image acquisition unit and processed, and crack information in the image is obtained through calculation. According to the invention, temperature, humidity, wind and stress under different conditions can be provided according to test requirements, and the accuracy of test results is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering, and in particular relates to a concrete early cracking crack test device. The invention also relates to a concrete early cracking crack measurement method. Background Art

[0002] The early cracking test of concrete is an important method to assess the risk of cracking of concrete in the early stage of hardening. The test results can provide a basis for the optimization of concrete mix ratio. However, the current early cracking test device connects the concrete specimen to the steel bars on the mold and accelerates the shrinkage of the concrete through an external fan to detect the crack resistance of the concrete panel. The test temperature, humidity and wind speed are clearly stipulated in the GB / T50082-2009, SL / T352-2020 and DL / T5150-2017 specifications. However, the stress state that can be provided by the above-mentioned existing test methods is relatively single, which makes it impossible to accurately simulate the performance of the concrete panel in resisting cracking during actual operation, affecting the accuracy of the final test results.

[0003] On the other hand, after the test, the crack width generated in the test needs to be measured. The crack width is based on the maximum width of each crack. Finally, the average crack area and the number of cracks per unit area are used as test results to evaluate the crack resistance of concrete. However, in the existing concrete early cracking test, the observation of cracks usually uses a scale magnifying glass and manual visual inspection to read the crack width, number and other information, resulting in the calculation of crack information only accurate to the millimeter level, which is difficult to reflect the real crack resistance of concrete materials, especially the details of tiny cracks. Summary of the invention

[0004] The invention aims to provide a concrete early cracking crack test device, which can provide temperature, humidity, wind speed and stress under different conditions according to test requirements, so as to improve the accuracy of test results.

[0005] Another object of the present invention is to provide a method for measuring early cracking of concrete, by collecting crack images and analyzing the images, to obtain detailed information of tiny cracks.

[0006] The first technical solution adopted by the present invention is that the concrete early cracking crack test device comprises an environmental main box body, a card slot is connected to the bottom plate of the environmental main box body, and an anti-cracking test mold fixed by the card slot is arranged in the environmental main box body; An image acquisition unit is arranged on the inner side of the main environmental box body relative to the anti-crack test mold, and the image acquisition unit is connected to the top of the main environmental box body. A temperature-controlled air supply box and a humidity control box are also installed on the inner side wall of the main environmental box body, and load units are arranged on the opposite sides of the anti-crack test mold, and the load units are connected to the inner side wall of the main environmental box body; The image acquisition unit, the temperature-controlled air supply box, the humidity control box and the load unit are all connected to the instrument control module through lines.

[0007] The first technical solution of the present invention is also characterized in that: The image acquisition unit includes a camera moving track fixed on the top of the main environmental box, a camera bracket is movably connected in the camera moving track, a camera is connected to the end of the camera bracket away from the camera moving track, and the camera lens faces the anti-crack test mold; camera fill lights are also arranged on both sides of the camera moving track.

[0008] The temperature-controlled air supply box comprises a shell, which is fixedly connected to the inner side wall of the main environment box, a temperature sensor is arranged on the outer side of the shell, a heater and a refrigerator are arranged in parallel in the shell, and air curtain fans are arranged at the air outlets of the heater and the refrigerator, and the lateral air outlet of the air curtain fan faces the anti-cracking test mold; The shell and the main environment box are provided with through holes for air to enter relative to the air inlets of the heater and the refrigerator.

[0009] The humidity control box includes a humidifier and a dehumidifier arranged in parallel, and the humidifier and the dehumidifier are fixedly connected to the inner wall of the main environmental box body; a water tank is arranged at the bottom of the humidifier and the dehumidifier, and the air outlet of the humidifier and the dehumidifier is located at the top of the humidifier and the dehumidifier.

[0010] The load unit comprises a hydraulic cylinder, which is connected to a hydraulic rod through a hydraulic pipeline, one end of the hydraulic rod is fixedly connected to the inner wall of the environment main box, and the other end is connected to a test mold fixture.

[0011] The anti-crack test mold includes a test mold bottom plate, the test mold bottom plate is clamped with the clamping slot, and a plurality of support plates are arranged on the test mold bottom plate to form a rectangular frame, and the plurality of support plates are connected to the test mold bottom plate by fixing screws; A plurality of steel bars are inserted into the support plate, and the axial direction of the steel bars is parallel to the test mold bottom plate. A pair of support plates arranged oppositely are inserted with clamps, and the clamps are movably connected with the test mold fixtures on the corresponding sides.

[0012] The instrument control module is fixed to the outer wall of the main environmental box. The instrument control module is provided with a power start / stop button and an emergency stop button. The instrument control module is also provided with a control panel for data display and operation. The instrument control module is also connected to the host computer through a signal.

[0013] An environmental chamber door is connected to one side of the environmental main chamber body, the environmental chamber door is located in the notch direction of the card slot, and a door handle is fixedly connected to the environmental chamber door; Exhaust and heat dissipation holes are provided on the environmental chamber door and the side wall of the environmental main chamber body opposite to the environmental chamber door.

[0014] The second technical solution adopted by the present invention is a method for measuring early cracking of concrete, which specifically includes the following steps: Step 1: Start the temperature-controlled air supply box and the humidity control box to make the environment inside the main environment box meet the test requirements; Step 2, pouring concrete into the rectangular frame formed by the support plate to form a test piece, and pushing the anti-cracking test mold into the slot for fixing, ensuring that the chuck is engaged with the test mold fixture; Step 3, after the specimen reaches final setting, remove the fixing screws of the two support plates with the chucks, start the hydraulic cylinder, and apply a load force to the specimen through the chuck connected to the test mold fixture; Step 4: The crack image of the specimen is collected by the image acquisition unit, and the image is transmitted to the host computer through the instrument control module for image processing to calculate the crack width, number of cracks and crack area in the image.

[0015] The second technical solution of the present invention is also characterized in that: The calculation formulas for the crack width, crack number and crack area in step 4 are specifically shown as follows: ; ; ; ; In the formula, δ is the actual width of each pixel, L is the actual length of the specimen in the image, in mm; m is the number of pixels contained in the specimen length L, in mm, N mean is the average number of medium cracks, x is the number of the pixel reference line, n is the total number of pixel columns, n x For the x The label value of the crack on the pixel reference line; w mean is the average crack width, Q xi For the x The reference line i The number of pixels contained in a crack label, l is the total number of pixels of the crack, S is the crack area of ​​the specimen.

[0016] The beneficial effects of the present invention are: (1) The concrete early cracking test device of the present invention controls the temperature, humidity and wind speed inside the main environmental box through a temperature-controlled air supply box and a humidity control box, thereby realizing concrete service simulation under different environments, making the cracks generated in the concrete closer to the situation in the actual environment, and improving the accuracy of the test results.

[0017] At the same time, the present invention can apply axial stress to the test piece through the hydraulic rods on both sides, simulating the crack resistance of the concrete test piece under different stress states, so that the test environment is more close to the real environment.

[0018] (2) The method for measuring early cracking of concrete of the present invention uses an image processing unit to photograph cracks generated in the specimen at different positions, and transmits the photographed images to a host computer for image processing through an instrument control module. The processed images can accurately obtain the crack width, number of cracks and crack area generated in the specimen under the test environment, thereby accurately reflecting the actual crack resistance of the concrete material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a concrete early cracking crack testing device of the present invention; Figure 2 It is a rear view of the concrete early cracking crack testing device of the present invention; Figure 3 It is a structural schematic diagram of a temperature-controlled air supply box in a concrete early cracking crack test device of the present invention; Figure 4 It is a structural schematic diagram of a humidity controller in a concrete early cracking crack test device of the present invention; Figure 5 It is a structural schematic diagram of an image acquisition unit in a concrete early cracking crack test device of the present invention; Figure 6 It is a schematic diagram of the structure of the load unit in the concrete early cracking crack test device of the present invention; Figure 7 It is a structural schematic diagram of the anti-cracking test mold in the concrete early cracking crack test device of the present invention.

[0020] In the figure, 101. main environmental box, 102. environmental box door, 103. door handle, 104. bottom plate, 105. card slot, 106. exhaust heat dissipation hole; 201. temperature control air supply box, 202. heater, 203. refrigerator, 204. air curtain fan, 205. horizontal air outlet, 206. temperature sensor; 301. humidity control box, 302. humidifier, 303. dehumidifier, 304. air outlet, 305. water tank; 401. image acquisition unit, 402. camera camera, 403. camera bracket, 404. camera moving track, 405. camera fill light; 501. load unit, 502. test mold fixture, 503. hydraulic rod, 504. hydraulic cylinder, 505. hydraulic pipeline; 601. anti-crack test mold, 602. test mold bottom plate, 603. steel bar, 604. support plate, 605. fixing screw, 606. chuck; 701. instrument control module, 702. power start and stop button, 703. emergency stop button, 704. control panel. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] Example 1 The concrete early cracking crack test device of the present invention is as follows Figure 1 As shown, it includes an environmental main box 101, a power supply for providing kinetic energy to the electrical equipment is arranged in the environmental main box 101, a card slot 105 is connected to the bottom plate 104 of the environmental main box 101, and an anti-crack test mold 601 fixed by the card slot 105 is arranged in the environmental main box 101; An image acquisition unit 401 is arranged on the inner side of the main environmental box 101 above the anti-crack test mold 601, and the image acquisition unit 401 is connected to the top of the main environmental box 101. A temperature-controlled air supply box 201 and a humidity control box 301 are also installed on the inner side wall of the main environmental box 101. Load units 501 are arranged on opposite sides of the anti-crack test mold 601, and the load units 501 are connected to the inner side wall of the main environmental box 101. The power supply, image acquisition unit 401, temperature-controlled air supply box 201, humidity control box 301 and load unit 501 are all connected to the instrument control module 701 through lines.

[0023] Furthermore, if Figure 2As shown, the instrument control module 701 is fixed to the outer wall of the main environmental box 101, and a power start / stop button 702 and an emergency stop button 703 are provided on the instrument control module 701. The power start / stop button 702 and the emergency stop button 703 can be used to control the start / stop of the power supply and the forced power off in an emergency state.

[0024] The instrument control module 701 is also provided with a control panel 704 for data display and operation. The instrument control module 701 is also connected to a host computer (such as a computer, a control system) via a signal.

[0025] The instrument control module 701 serves as a bridge between the host computer and the instrument equipment. The host computer sends instructions to the instrument control module 701 through software, and then the module converts the instructions into signals that the instrument equipment can understand and execute, thereby realizing remote operation and automatic control of the instrument equipment.

[0026] Furthermore, an environmental chamber door 102 is connected to one side of the environmental main chamber body 101 . The environmental chamber door 102 is located in the notch direction of the card slot 105 . A door handle 103 is fixedly connected to the environmental chamber door 102 .

[0027] Exhaust and heat dissipation holes 106 are formed on the environmental chamber door 102 and the side wall of the environmental main chamber body 101 opposite to the environmental chamber door 102 .

[0028] That is, the concrete early cracking crack test device of the present invention can adjust the temperature and humidity inside the environment main box 101 and the wind speed blowing across the surface of the test piece through the temperature-controlled air supply box 201 and the humidity control box 301, thereby realizing the simulation of test conditions under different environments. The load unit 501 can apply a load force to the test piece from one side of the test piece, thereby simulating the required real environmental conditions and improving the accuracy of the test results.

[0029] Finally, the image acquisition unit 401 takes images of the cracked specimen at different positions, and the images are transmitted to the host computer for processing through the instrument control module 701 to obtain the data of the cracks generated in the test.

[0030] Example 2 The concrete early cracking crack test device of the present invention comprises an environmental main box 101, a power supply for providing kinetic energy to electrical equipment is arranged in the environmental main box 101, a card slot 105 is connected to the bottom plate 104 of the environmental main box 101, and an anti-cracking test mold 601 fixed by the card slot 105 is arranged in the environmental main box 101; An image acquisition unit 401 is arranged on the inner side of the main environmental box 101 above the anti-cracking test mold 601. The image acquisition unit 401 is connected to the top of the main environmental box 101. A temperature-controlled air supply box 201 and a humidity control box 301 are also installed on the inner wall of the main environmental box 101.

[0031] Furthermore, load units 501 are provided on opposite sides of the anti-crack test mold 601, and the load units 501 are connected to the inner wall of the main environmental box 101; the power supply, image acquisition unit 401, temperature-controlled air supply box 201, humidity control box 301 and load unit 501 are all connected to the instrument control module 701 through lines.

[0032] Furthermore, if Figure 3 As shown, the temperature-controlled air supply box 201 includes a shell, which is fixedly connected to the inner wall of the main environment box 101, a temperature sensor 206 is arranged on the outer side of the shell, a heater 202 and a refrigerator 203 are arranged in parallel in the shell, and air curtain fans 204 are arranged at the air outlets of the heater 202 and the refrigerator 203, and the lateral air outlet 205 of the air curtain fan 204 faces the anti-cracking test mold 601; The shell and the air inlet of the main box 101 relative to the heater 202 and the refrigerator 203 are both provided with through holes for air to enter.

[0033] That is, the temperature inside the environmental main box 101 is detected by the temperature sensor 206. When the internal temperature needs to be adjusted, the wind curtain fan 204 is started to draw external air into the heater 202 or the refrigerator 203 to heat or cool the air, and then blow it into the interior of the environmental main box 101 through the horizontal air outlet 205, thereby achieving cooling or heating of the interior of the environmental main box 101.

[0034] The temperature sensor 206 , the air curtain fan 204 , the heater 202 and the refrigerator 203 are all connected to the instrument control module 701 through lines.

[0035] Furthermore, if Figure 4 As shown, the humidity control box 301 includes a humidifier 302 and a dehumidifier 303 arranged in parallel, and the humidifier 302 and the dehumidifier 303 are fixedly connected to the inner wall of the main environmental box 101; a water tank 305 is arranged at the bottom of the humidifier 302 and the dehumidifier 303, and the air outlet 304 of the humidifier 302 and the dehumidifier 303 is located at the top of the humidifier 302 and the dehumidifier 303.

[0036] The humidifier 302 and the dehumidifier 303 are both connected to the instrument control module 701 through lines.

[0037] On the other hand, the humidity control box 301 can also include an outer shell, which is fixedly connected to the inner wall of the main environmental box 101; the inner bottom of the outer shell serves as a water tank 305, and a parallel humidifier 302 and a dehumidifier 303 are arranged above the water tank 305, and a through hole is opened on the top of the outer shell as an air outlet 304 of the humidifier 302 and the dehumidifier 303.

[0038] Since the humidifiers 302 and dehumidifiers 303 usually purchased on the market have built-in humidity sensors, there is no need to install a humidity sensor separately. When the humidity inside the environmental main box 101 needs to be adjusted, one of the devices is started according to the humidity displayed by the humidifier 302 or the dehumidifier 303 to adjust the humidity inside the environmental main box 101.

[0039] Example 3 On the basis of Example 2, Figure 5 As shown, the image acquisition unit 401 of the concrete early cracking crack test device of the present invention includes a camera moving track 404 fixed to the top of the environmental main box 101, a camera bracket 403 is movably connected in the camera moving track 404, and a camera 402 is connected to the end of the camera bracket 403 away from the camera moving track 404, and the lens of the camera 402 faces the anti-cracking test mold 601; camera fill lights 405 are also arranged on both sides of the camera moving track 404.

[0040] Furthermore, the camera moving track 404 used in this embodiment is S-shaped, so that the images captured by the camera 402 when moving along the camera moving track 404 are closely fitted, which facilitates the integrity of the final synthesized overall image and improves the accuracy of image analysis. A driving mechanism and a slider are installed inside the camera moving track 404, and the driving mechanism drives the slider to slide along the track. The camera bracket 403 is relatively fixedly connected to the slider, so that the camera bracket 403 can change its position along the camera moving track 404.

[0041] Specifically, the driving mechanism usually includes a motor, which is a DC motor or a stepper motor. The motor is connected to a transmission mechanism. The transmission mechanism currently usually adopts belt drive, screw drive and gear drive. Since this technology is an existing mature technology, it will not be described in detail in this plan.

[0042] Furthermore, the camera moving track 404, the camera 402 and the camera fill light 405 are all connected to the instrument control module through lines, and the instrument control module 701 is controlled to realize timed photography.

[0043] Example 4 On the basis of Example 2, Figure 6 As shown, the load unit 501 of the concrete early cracking crack test device of the present invention includes a hydraulic cylinder 504, which is connected to a hydraulic rod 503 through a hydraulic pipeline 505. One end of the hydraulic rod 503 is fixedly connected to the inner wall of the environmental main box 101, and the other end is connected to a test mold fixture 502.

[0044] like Figure 7As shown, the anti-crack test mold 601 includes a test mold bottom plate 602, which is engaged with the card slot 105, and a plurality of support plates 604 are arranged on the test mold bottom plate 602 to form a rectangular frame, and the plurality of support plates 604 are connected to the test mold bottom plate 602 by fixing screws 605; A plurality of steel bars 603 are inserted into the support plate 604, and the axial direction of the steel bars 603 is parallel to the test mold bottom plate 602. A chuck 606 is inserted into a pair of oppositely arranged support plates 604, and the chuck 606 is movably connected to the test mold fixture 502 on the corresponding side.

[0045] The clamp 606 is composed of a steel bar and a connector. The shape of the connector matches the shape of the slot of the test mold fixture 502. The steel bar of the clamp 606 passes through the support plate 604 and is located inside the rectangular frame. When the concrete is poured in the rectangular frame, the steel bar 603 and the clamp 606 are pre-embedded in the concrete. After the clamp 606 is clamped with the test mold fixture 502, even if the test mold fixture 502 applies a pulling force to the clamp 606, the clamp 606 cannot be pulled out of the test piece.

[0046] Example 5 The method for measuring early concrete cracking of the present invention adopts the above-mentioned early concrete cracking test device and specifically comprises the following steps: Step 1, start the temperature-controlled air supply box 201 and the humidity control box 301 to make the environment in the main box 101 meet the test requirements; Step 2, pouring concrete into the rectangular frame formed by the support plate 604 to form a test piece, and pushing the anti-cracking test mold 601 into the slot 105 for fixing, ensuring that the clamp 606 is clamped with the test mold fixture 502; Step 3, after the specimen reaches final setting, remove the fixing screw 605, start the hydraulic cylinder 504, and pull the chuck 606 through the test mold fixture 502 to apply a load force to the specimen; Step 4: The crack image of the specimen is collected by the image collection unit 401, and the image is transmitted to the host computer through the instrument control module 701 for image processing to calculate the crack width, crack number and crack area in the image.

[0047] Furthermore, after the crack image acquisition of the specimen is completed, the temperature-controlled air supply box 201 and the humidity control box 301 are turned off.

[0048] Furthermore, the processing of the image includes binarization processing.

[0049] Example 6 The method for measuring early concrete cracking of the present invention adopts the above-mentioned early concrete cracking test device and specifically comprises the following steps: Step 1, start the temperature-controlled air supply box 201 and the humidity control box 301, and set the wind speed, temperature and humidity required for the test on the control panel 704 so that the environment in the test box meets the test requirements; Step 2: pour concrete into the rectangular frame formed by the support plate 604 to form a test piece, and push the anti-cracking test mold 601 into the card slot 105 for fixation. During the pushing process, adjust the position of the test mold fixture 502 of the load unit 501 to ensure that the clamp 606 penetrates into the slot of the test mold fixture 502; Step 3, retract the hydraulic rod 503, and control the mold test fixture 502 to move toward the hydraulic rod 503 until the chuck 606 is engaged with the mold test fixture 502; Step 4: After the specimen reaches final setting, remove the fixing screws 605 to loosen the support plates 604 on both sides; Step 5, start the hydraulic cylinder 504, and control the piston movement area of ​​the hydraulic cylinder 504 through the control panel 704 to ensure that the load force applied by the test mold fixture 502 to pull the chuck 606 to the test piece meets the test requirements; Step 6, setting the camera 402 to move automatically along the track for acquisition, the camera 402 is 30cm~50cm away from the surface of the specimen, the illumination of the camera fill light 405 is between 20lx~40lx to ensure the clarity of the acquired image, and the crack image of the specimen is acquired through the image acquisition unit 401; Step 7, close the temperature control air supply box 201 and the humidity control box 301, and control the test mold fixture 502 to move toward the test piece until it is out of the clamping state, and take out the anti-cracking test mold 601; at the same time, the image is transmitted to the host computer through the instrument control module 701, and the host computer merges the images collected by the camera 402 to form an overall image, and then performs binarization processing on the overall image; Step 8: The crack width, number of cracks and crack area of ​​the crack image are calculated by the number of cracks in each pixel column and the number of pixels representing cracks in the binary image. The specific calculation formulas are shown in the following formulas (1), (2), (3) and (4): (1); (2); (3); (4); In the formula, δ is the actual width of each pixel, L is the actual length of the specimen in the image, in mm; m is the number of pixels contained in the specimen length L, in mm, N mean is the average number of medium cracks, xis the number of the pixel reference line, n is the total number of pixel columns, n x For the x The label value of the crack on the pixel reference line; w mean is the average crack width, Q xi For the x The reference line i The number of pixels contained in a crack label, l is the total number of pixels of the crack, S is the crack area of ​​the specimen.

[0050] Furthermore, the image is binarized by MATLAB software. Image binarization belongs to the prior art. First, if it is a color image, it must be grayed and converted into a gray image to reduce the amount of calculation; then the threshold is determined, which can be determined manually based on empirical observation, based on image grayscale histogram distribution analysis, or by using adaptive threshold methods; then the image pixel grayscale values ​​are compared based on the selected threshold, and pixels greater than or equal to the threshold are assigned white, and pixels less than the threshold are assigned black, thereby separating the foreground and background; finally, post-processing can be performed according to the situation, such as using morphological operations to remove noise, median filtering to smooth edges, etc., so as to obtain a more ideal binary image, which provides a convenient basis for subsequent processing such as target recognition and image analysis.

[0051] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0052] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0053] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Concrete early cracking crack test device, characterized in that: It comprises an environmental main box (101), a bottom plate (104) of the environmental main box (101) being connected to a card slot (105), and an anti-cracking test mold (601) fixed by the card slot (105) is arranged inside the environmental main box (101); An image acquisition unit (401) is arranged on the inner side of the main environmental box (101) above the anti-cracking test mold (601), and the image acquisition unit (401) is connected to the top of the main environmental box (101). A temperature-controlled air supply box (201) and a humidity control box (301) are also installed on the inner side wall of the main environmental box (101). Load units (501) are arranged on opposite sides of the anti-cracking test mold (601), and the load units (501) are connected to the inner side wall of the main environmental box (101); The image acquisition unit (401), the temperature-controlled air supply box (201), the humidity control box (301), and the load unit (501) are all connected to an instrument control module (701) via lines.

2. The concrete early cracking crack testing device according to claim 1 is characterized in that: The image acquisition unit (401) comprises a camera moving track (404) fixed to the top of the environment main box (101), a camera bracket (403) being movably connected inside the camera moving track (404), a camera (402) being connected to an end of the camera bracket (403) away from the camera moving track (404), the lens of the camera (402) facing the anti-cracking test mold (601); camera fill lights (405) are also arranged on both sides of the camera moving track (404).

3. The concrete early cracking crack testing device according to claim 1 is characterized in that: The temperature-controlled air supply box (201) comprises a shell, the shell is fixedly connected to the inner wall of the main environment box (101), a temperature sensor (206) is arranged on the outer side of the shell, a heater (202) and a refrigerator (203) are arranged in parallel in the shell, air curtain fans (204) are arranged at the air outlets of the heater (202) and the refrigerator (203), and the lateral air outlet (205) of the air curtain fan (204) faces the anti-cracking test mold (601); The shell and the main environment box (101) are provided with through holes for air to enter at the air inlets of the heater (202) and the refrigerator (203).

4. The concrete early cracking crack testing device according to claim 1 is characterized in that: The humidity control box (301) comprises a humidifier (302) and a dehumidifier (303) arranged in parallel, wherein the humidifier (302) and the dehumidifier (303) are fixedly connected to the inner wall of the main environment box (101); a water tank (305) is arranged at the bottom of the humidifier (302) and the dehumidifier (303), and the air outlets (304) of the humidifier (302) and the dehumidifier (303) are located at the top of the humidifier (302) and the dehumidifier (303).

5. The concrete early cracking crack testing device according to claim 1 is characterized in that: The load unit (501) comprises a hydraulic cylinder (504), wherein the hydraulic cylinder (504) is connected to a hydraulic rod (503) via a hydraulic pipeline (505), wherein one end of the hydraulic rod (503) is fixedly connected to the inner wall of the environment main box (101), and the other end is connected to a test mold fixture (502).

6. The concrete early cracking crack testing device according to claim 5 is characterized in that: The anti-cracking test mold (601) comprises a test mold bottom plate (602), the test mold bottom plate (602) is clamped with the clamping groove (105), a plurality of support plates (604) are arranged on the test mold bottom plate (602) to enclose a rectangular frame, and the plurality of support plates (604) are connected to the test mold bottom plate (602) via fixing screws (605); A plurality of steel bars (603) are inserted into the support plate (604), and the axial direction of the steel bars (603) is parallel to the test mold bottom plate (602). A clamp (606) is inserted into a pair of oppositely arranged support plates (604), and the clamp (606) is movably connected to the test mold fixture (502) on the corresponding side.

7. The concrete early cracking crack testing device according to claim 1 is characterized in that: The instrument control module (701) is fixed to the outer wall of the main environment box (101); a power start / stop button (702) and an emergency stop button (703) are provided on the instrument control module (701); a control panel (704) for data display and operation is also provided on the instrument control module (701); and the instrument control module (701) is also connected to a host computer via a signal.

8. The concrete early cracking crack testing device according to claim 1 is characterized in that: An environmental chamber door (102) is connected to one side of the environmental main chamber (101); the environmental chamber door (102) is located in the notch direction of the card slot (105); and a door handle (103) is fixedly connected to the environmental chamber door (102); Exhaust and heat dissipation holes (106) are provided on the environmental chamber door (102) and the side wall of the environmental main chamber body (101) opposite to the environmental chamber door (102).

9. A method for measuring early cracking of concrete, characterized in that: The concrete early cracking crack test device according to any one of claims 1 to 8 is used, and specifically comprises the following steps: Step 1, starting the temperature-controlled air supply box (201) and the humidity control box (301) to make the environment inside the main environment box (101) meet the test requirements; Step 2, pouring concrete into the rectangular frame formed by the support plate (604) to form a test piece, and pushing the anti-cracking test mold (601) into the slot (105) to fix it, ensuring that the clamp (606) is clamped with the test mold fixture (502); Step 3, after the specimen reaches final setting, remove the fixing screws (605) of the two support plates (604) with the chuck (606), start the hydraulic cylinder (504), and apply a load force to the specimen through the test mold fixture (502) connected to the chuck (606); Step 4, collecting the crack image of the specimen through the image collection unit (401), and transmitting the image to the host computer through the instrument control module (701) for image processing, and calculating the crack width, crack number and crack area in the image.

10. The method for measuring early concrete cracks according to claim 9, characterized in that: The calculation formulas for the crack width, crack number and crack area in step 4 are specifically shown as follows: ； ； ； ； In the formula, δ is the actual width of each pixel, L is the actual length of the specimen in the image, in mm; m is the number of pixels contained in the specimen length L, in mm, N mean is the average number of medium cracks, x is the number of the pixel reference line, n is the total number of pixel columns, n x For the x The label value of the crack on the pixel reference line; w mean is the average crack width, Q xi For the x The reference line i The number of pixels contained in a crack label, l is the total number of pixels of the crack, S is the crack area of ​​the specimen.

Images