Drying shrinkage testing device under low air pressure and large temperature difference

Abstract

The utility model discloses a drying shrinkage testing device under low air pressure and large temperature difference. The drying shrinkage testing device comprises a testing box, a vacuumizing assembly, a heating assembly and a refrigerating assembly. The test box is equivalent to a drying shrinkage curing humidity control box and is also used for placing a test piece, the length of the test piece is recorded before placement, after the test piece is placed, the vacuumizing assembly maintains a low-pressure environment which is close to the air pressure environment of the Tibet Plateau, and the heating assembly and the refrigerating assembly act at intervals to form a large-temperature-difference environment. The large-temperature-difference environment is close to the day and night temperature difference value of the Tibet Plateau. According to the drying shrinkage testing device under the low air pressure and the large temperature difference, the accuracy of a cement mortar test piece test is improved by simulating a low air pressure and large temperature difference environment. The device is applied to the field of cement mortar testing.

Description

Technical Field

[0001] The utility model relates to the field of cement mortar testing, and particularly relates to a drying shrinkage testing device under low air pressure and large temperature difference. Background Art

[0002] The dry shrinkage test method of cement mortar is used to evaluate the mechanical properties of cement. Generally, it is used to test the strength of cement, made into specimens in accordance with the specified method, cured in accordance with the specified method, and the compressive strength and flexural strength at 3d and 28d are measured respectively. The strength grade of cement is determined according to the measurement results.

[0003] However, due to the complexity of the engineering environment of the Sichuan-Tibet Railway, the extreme natural environment is likely to have an adverse impact on the drying shrinkage of specimens. The conventional dry shrinkage test method of cement mortar cannot fully show the influence of the extreme natural environment on the test, resulting in a large deviation between the test results and the actual results, seriously affecting the project quality. Content of the Utility Model

[0004] The utility model aims to solve at least one of the technical problems existing in the prior art. For this purpose, the utility model provides a drying shrinkage testing device under low air pressure and large temperature difference, which can simulate the extreme natural environment and improve the accuracy of test results.

[0005] According to the drying shrinkage testing device under low air pressure and large temperature difference of the embodiment of the utility model, it includes:

[0006] A test chamber, having a test cavity for testing;

[0007] A vacuum pumping assembly, communicated with the test cavity, for controlling the air pressure in the test cavity to a preset air pressure, and the preset air pressure is less than the standard atmospheric pressure;

[0008] A heating assembly, for heating the temperature in the test cavity to a first preset temperature C1;

[0009] A refrigeration assembly, for refrigerating the temperature in the test cavity to a second preset temperature C2, and C1 - C2 ≥ 10°C.

[0010] The drying shrinkage test device under low air pressure and large temperature difference according to the embodiments of the present utility model has at least the following beneficial effects: Place the made cement mortar specimen in the test chamber and keep the test chamber airtight. Adjust the air pressure in the test chamber to the preset air pressure through the vacuum pumping assembly. The preset air pressure is lower than the standard atmospheric pressure to simulate a low air pressure environment. Then, heat the temperature in the test chamber to the first preset temperature through the heating assembly. After keeping warm for a period of time, cool the temperature in the test chamber to the second preset temperature through the refrigeration assembly. A large temperature difference is formed between the second preset temperature and the first preset temperature to simulate the large temperature difference in the extreme natural environment, so that the specimen completes the test in the extreme natural environment. The surface of the specimen in the test chamber is closer to the actual performance of the specimen in the extreme natural environment, improving the accuracy of the test results.

[0011] According to some embodiments of the present utility model, the first preset temperature is 60 °C and the second preset temperature is -20 °C.

[0012] According to some embodiments of the present utility model, the test chamber includes a box body with an opening and a box door capable of closing the opening. The box door is provided with an annular sealing ring, and the annular sealing ring surrounds the opening. The outer wall of the test chamber is provided with a heat insulation layer.

[0013] According to some embodiments of the present utility model, the test chamber is provided with an exhaust port and a control valve communicated with the exhaust port. The control valve can control the opening and closing of the exhaust port.

[0014] According to some embodiments of the present utility model, it further includes: a first circulation fan, and the first circulation fan is communicated with the test chamber.

[0015] According to some embodiments of the present utility model, it further includes: a temperature detection element, and the temperature detection element is used to detect the temperature in the test chamber.

[0016] According to some embodiments of the present utility model, it further includes: an elongation gauge. The elongation gauge is arranged in the test chamber. The elongation gauge includes a clamp and a measuring instrument. The clamp is used to clamp both ends of the sample to be tested, and the measuring instrument is fixed at one end of the sample to be tested to detect the change amount of the sample to be tested.

[0017] According to some embodiments of the present utility model, the test chamber is provided with an observation port communicating the test chamber and the outside and a transparent observation element arranged in the observation port. The observation element seals the observation port and is used to observe the inside of the test chamber.

[0018] According to some embodiments of the present utility model, the test chamber is further provided with a heating chamber surrounding the test chamber. The heating assembly is arranged in the heating chamber and is used to heat the test chamber.

[0019] According to some embodiments of the present utility model, it further includes: a second circulation fan, and the second circulation fan is communicated with the heating chamber.

[0020] Additional aspects and advantages of the present utility model will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present utility model. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following further describes the present utility model in conjunction with the drawings and embodiments, where:

[0022] Figure 1 is an overall schematic diagram of a drying shrinkage test device under low air pressure and large temperature difference according to an embodiment of the present utility model;

[0023] Figure 2 is an internal structure schematic diagram of a drying shrinkage test device under low air pressure and large temperature difference according to an embodiment of the present utility model;

[0024] Figure 3 is a front view schematic diagram of a drying shrinkage test device under low air pressure and large temperature difference according to an embodiment of the present utility model;

[0025] Reference numerals in the drawings:

[0026] Test chamber 100; test cavity 110; box body 120; box door 130; exhaust port 140; observation window 150; heating chamber 160;

[0027] Vacuum pumping assembly 200;

[0028] Heating assembly 300;

[0029] Refrigeration assembly 400; evaporator 410; drying filter 420; condenser 430; compressor 440; capillary 450;

[0030] First circulation fan 500;

[0031] Length comparator 600; fixture 610; measuring gauge 620;

[0032] Second circulation fan 700;

[0033] Test piece 800. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The embodiments of the present utility model are described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present utility model and should not be construed as a limitation of the present utility model.

[0035] In the description of the present utility model, it should be understood that with regard to the orientation description, such as the orientation or positional relationship indicated by "upper", "lower", etc., it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present utility model.

[0036] In the description of the present utility model, "several" refers to one and more than one, and "multiple" refers to two and more than two. If there is a description of "first" and "second", it is only for the purpose of distinguishing technical features, and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0037] In the description of the present utility model, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present utility model in combination with the specific content of the technical solution.

[0038] In the conventional production method of cement mortar in the cement mortar dry shrinkage test method, the preparation of the mortar is carried out according to GB177.

[0039] The prepared mortar is filled into the test mold with nail heads at both ends in two layers. After the first layer of mortar is filled into the test mold, first use a small knife to compact it back and forth, especially on both sides of the nail head. If necessary, it can be compacted several more times. Then use a scraping board to scrape off the mortar more than 3 / 4 of the height of the test mold. Then use a 23mm×23mm square rammer to start from the inside of the nail head and ram 10 times in sequence from one end to the other end, return and ram 10 times, for a total of 20 ramming times. Then use a notched rammer to ram 2 times on both sides of the nail head. Then fill the remaining mortar into the mold, and use a small knife to level it evenly. The depth of the knife scratching should penetrate the surface of the first layer of mortar. Then use a 23mm×23mm rammer to start from one end and ram 12 times in sequence, ram back and forth 24 times (each time when ramming, first touch the rammer on the surface of the mortar and then ram forcefully. The ramming should be uniform and stable, and no stamping is allowed). After ramming is completed, use a small knife to dial the mortar at the edge of the test mold back into the test mold and scrape it flat with a triangular scraper. Then number it and place it in a curing box at a temperature of 20±3°C and a relative humidity of more than 90% for curing.

[0040] The specimen shall be demolded 24 ± 2 h after water addition. Then the specimen shall be cured in water at a temperature of 20 ± 2 °C. If demolding is difficult, the demolding time can be extended. The extended time shall be noted in the test report and deducted from the water curing time. After the specimen has been cured in water for 2 days, it shall be taken out of the water, the surface moisture and the dirt on the nail head shall be wiped off with a wet cloth, and the initial reading shall be measured with a length comparator. Before using the length comparator, it shall be calibrated with a calibration rod, and it can be used for measuring the specimen only when it is confirmed that its zero point is correct (the zero point is a reference number, not necessarily zero). After measuring the initial reading, the zero point shall be rechecked with the calibration rod. When the zero point changes by more than ±1 grid, the whole batch of specimens shall be redetermined. Then the specimen shall be moved to the grid bars in the dry shrinkage curing humidity control box for curing. There shall be a gap between specimens. The specimens taken out of the water in the same batch can be placed in one curing unit, and at most two groups of specimens taken out of the water at the same time can be placed. 0.5 kg of the medicine for controlling the relative humidity shall be placed on the medicine tray for each group. Generally, potassium thiocyanate solid can be used as the medicine, or other salts that can control the specified relative humidity can also be used, but substances harmful to humans and the environment shall not be used. Close the unit latch to make it airtight and isolated from the outside. The ambient temperature around the box shall be controlled at 20 ± 3 °C. At this time, the medicine shall be able to make the relative humidity in the unit (50 ± 4%). The dry shrinkage specimens can also be cured under conditions that can meet the specified relative humidity and temperature, but it shall be specifically stated in the test report. When there are contradictions in the results, the results of curing in the dry shrinkage curing humidity control box shall prevail.

[0041] Starting from the time when the specimen is placed in the box, at 4 d, 11 d, 18 d, and 25 d (i.e., at 7 d, 14 d, 21 d, and 28 d from the time of molding), the length shall be measured respectively. Note: The measuring age can be increased or decreased and changed as necessary according to the curve graph of the dry shrinkage rate of different types of cement changing with age. The length measurement of the specimen shall be carried out in a laboratory at 17 °C to 25 °C. The length comparator can be used only after being kept at a constant temperature in the laboratory temperature. The upper and lower positions of the specimen in the length comparator shall be the same for all ages. When reading, the specimen shall be rotated left and right to make the nail head of the specimen and the length comparator contact correctly, and the pointer swing shall not be greater than 2 small grids. The reading shall be recorded to 0.005 mm. After the measurement is completed, the zero point shall be calibrated with the calibration rod. When the zero point changes by more than ±1 grid, the whole batch of specimens shall be re-measured.

[0042] Refer to Figures 1 to 3As shown in the figure, a drying shrinkage test device under low air pressure and large temperature difference according to an embodiment of the present utility model includes: a test chamber 100, a vacuum pumping assembly 200, a heating assembly 300, and a refrigeration assembly 400. The test chamber 100 is equivalent to a dry shrinkage curing humidity control chamber and is also used to place the specimen 800. The length of the specimen 800 is recorded before placement. After the specimen 800 is placed, the vacuum pumping assembly 200 maintains a low air pressure environment, which is close to the air pressure environment of the Qinghai-Tibet Plateau. The heating assembly 300 and the refrigeration assembly 400 act alternately to form a large temperature difference environment, which is close to the numerical value of the day-night temperature difference of the Qinghai-Tibet Plateau. The drying shrinkage test device under low air pressure and large temperature difference in this embodiment improves the accuracy of the test of the cement mortar specimen 800 by simulating the low air pressure and large temperature difference environment.

[0043] In this embodiment, the test chamber 100 has a test cavity 110 for testing. The test chamber 100 is generally rectangular in shape, and the test cavity 110 is also rectangular in shape. The size inside the test cavity 110 can accommodate the specimen 800. The number of specimens 800 can be one or multiple. Of course, the test chamber 100 can also be spherical in shape, and the test cavity 110 is also spherical in shape, or the test chamber 100 is spherical in shape and the test cavity 110 is rectangular in shape. The shapes of the test chamber 100 and the test cavity 110 can be selected according to actual needs. For the shapes of the test chamber 100 and the test cavity 110, this embodiment does not make specific restrictions.

[0044] The vacuum pumping assembly 200 is connected to the test cavity 110 and is used to control the air pressure in the test cavity 110 to a preset air pressure, and the preset air pressure is less than the standard atmospheric pressure; the vacuum pumping assembly 200 includes a vacuum pump and a vacuum pipeline connecting the vacuum pump and the test cavity 110. The vacuum pump extracts the gas in the test cavity 110 through the vacuum pipeline, so that the air pressure in the test cavity 110 is maintained at the preset air pressure. The preset air pressure is lower than the standard atmospheric pressure, and the standard atmospheric pressure is 101.325 kPa. Moreover, the preset air pressure is close to the air pressure of the Qinghai-Tibet Plateau, and the range of the preset air pressure is 78.9 kPa to 92 kPa.

[0045] The heating assembly 300 is used to heat the temperature in the test cavity 110 to the first preset temperature C1. The heating assembly 300 can be electrically heated by means of resistance heating. Of course, the heating assembly 300 can also be heated by other means, and this embodiment does not make specific restrictions on this. Among them, the upper limit temperature of the heating assembly 300 is 60 °C, and the first preset temperature C1 can be 60 °C or lower than 60 °C.

[0046] The refrigeration component 400 is used to cool the temperature in the refrigeration test chamber 110 to a second preset temperature C2, where C1 - C2 ≥ 10°C; the refrigeration component 400 includes an evaporator 410, a dryer filter 420, a condenser 430, a compressor 440, and a capillary tube 450. After the power is turned on, the compressor 440 starts to operate. The refrigerant is sucked into the compressor 440, compressed, and then discharged into the condenser 430. The refrigerant gas dissipates heat through the condenser 430. The condensed refrigerant saturated liquid flows through the dryer filter 420 to filter out moisture and impurities, and then flows into the capillary tube 450 for throttling and pressure reduction. Finally, it reaches the evaporator 410 to start absorbing heat and reducing the temperature in the test chamber 110. Among them, the lower limit temperature of the condensation component is -20°C, and the second preset temperature C2 can be -20°C or higher than -20°C.

[0047] Specifically, after the heating component 300 heats at a high temperature for 12 hours, it switches to low-temperature maintenance for 12 hours. Of course, the high-temperature duration and the low-temperature duration can be the same or different. In addition, the high-temperature duration can be selected between 1 hour and 24 hours, and the low-temperature duration can be selected between 1 hour and 24 hours.

[0048] It should be understood that the made cement mortar specimen 800 is placed in the test chamber 110, and the test chamber 110 is kept airtight. The air pressure in the test chamber 110 is adjusted to the preset air pressure through the vacuum pumping component 200. The preset air pressure is lower than the standard atmospheric pressure to simulate a low-pressure environment. Then, the temperature in the test chamber 110 is heated to the first preset temperature through the heating component 300. After keeping warm for a period of time, the temperature in the test chamber 110 is cooled to the second preset temperature through the refrigeration component 400. A large temperature difference is formed between the second preset temperature and the first preset temperature to simulate the large temperature difference in the extreme natural environment, so that the specimen 800 can complete the test in the extreme natural environment. The surface of the specimen 800 in the test chamber 110 is closer to the actual performance of the specimen 800 in the extreme natural environment, improving the accuracy of the test results.

[0049] In addition, the drying shrinkage test device under low pressure and large temperature difference can also include an operating system, and an operation panel is provided outside the test box 100. The operation panel is electrically connected to the controller, and the controller is electrically connected to the heating component 300 and the refrigeration component 400. The user can control the heating component 300 and the refrigeration component 400 through the operation panel, or control the test according to a preset program. For example, preset to heat for 12 hours first, then cool for 12 hours, and repeat the cycle 25 times, which can realize the automatic test of the workpiece.

[0050] Refer to Figure 3As shown, in some specific embodiments of the present utility model, the test chamber 100 includes a box body 120 with an opening and a box door 130 capable of closing the opening. The box door 130 is provided with an annular sealing ring that surrounds the opening, and the outer wall of the test chamber 100 is provided with a heat insulation layer.

[0051] It should be understood that the opening is opened through the box door 130 to place the test piece 800 into the test cavity 110. When the box door 130 closes the opening, the gap between the box door 130 and the box body 120 is sealed through the annular sealing ring, improving the sealing performance of the test cavity 110, so that a low-pressure environment can be maintained inside the test cavity 110. In this embodiment, a heat insulation layer is provided on the outer wall of the box body 120, and the box door 130 is also provided with a heat insulation layer to reduce the heat exchange between the box body 120 and the outside, reduce the energy consumption in the box body 120, and be more energy-efficient.

[0052] In this embodiment, the box body 120 is provided with glass wool as the heat insulation layer, and the box door 130 is also provided with glass wool as the heat insulation layer. The outer shell of the box body 120 is made of cold-rolled steel plate and painted on the surface to prevent rust.

[0053] Refer to Figure 1 and Figure 2 As shown, in some specific embodiments of the present utility model, the test chamber 100 is provided with an exhaust port 140 and a control valve connected to the exhaust port 140, and the control valve can control the opening and closing of the exhaust port 140.

[0054] It should be understood that when it is necessary to adjust the first preset temperature to the second preset temperature, or the second preset temperature to the first preset temperature, the test chamber 100 communicates the outside and the test cavity 110 through the exhaust port 140, so that the test cavity 110 can exchange heat of excess heat and cold air with the outside air, improve the heat exchange efficiency of the gas in the test cavity 110, and save energy.

[0055] Refer to Figure 1 and Figure 2 As shown, in some specific embodiments of the present utility model, the drying shrinkage test device under low air pressure and large temperature difference further includes: a first circulation fan 500, and the first circulation fan 500 is connected to the test cavity 110.

[0056] It should be understood that when the exhaust port 140 is opened, the first circulation fan 500 accelerates the heat exchange between the test cavity 110 and the outside air. When the exhaust port 140 is closed, the first circulation fan 500 accelerates the heat distribution of the heating component 300 in the test cavity 110, and the second circulation fan 700 accelerates the cooling capacity distribution of the refrigeration component 400 in the test cavity 110, making the temperature distribution in the test cavity 110 more uniform and the test effect better.

[0057] In some specific embodiments of the present utility model, the drying shrinkage test device under low air pressure and large temperature difference further includes: a temperature detection component, which is used to detect the temperature inside the test chamber 110.

[0058] It is understandable that by detecting whether the temperature inside the test chamber 110 reaches the required temperature, such as the first preset temperature or the second preset temperature, it is convenient for the user to adjust the heating component 300 or the refrigeration component 400, thereby improving the accuracy of the test.

[0059] In this embodiment, the drying shrinkage test device under low air pressure and large temperature difference further includes: a pressure detection component to detect the air pressure inside the test chamber 110, so as to improve the accuracy of the test.

[0060] Refer to Figure 1 And Figure 2 As shown, in some specific embodiments of the present utility model, the drying shrinkage test device under low air pressure and large temperature difference further includes: an extensometer 600. The extensometer 600 is arranged inside the test chamber 110. The extensometer 600 includes a clamp 610 and a measuring gauge 620. The clamp 610 is used to clamp both ends of the sample to be tested, and the measuring gauge 620 is fixed to one end of the sample to be tested to detect the change amount of the sample to be tested.

[0061] It is understandable that the extensometer 600 is used for the length detection of the test piece 800. When the test piece 800 shrinks, the test piece 800 drives the measuring gauge 620 to change. The measuring gauge 620 can directly display the length change of the test piece 800, and the user can directly record the reading of the measuring gauge 620, making the recording of test data more convenient without taking out the test piece 800 inside the test chamber 110. In this embodiment, the measuring gauge 620 can be a dial gauge or a micrometer. In addition, a layer of resilient cushion is added to the bottom of the test chamber 110, and the extensometer 600 reduces the slight fluctuations caused by external factors during the test through the resilient cushion, protects the integrity of the test piece 800, and reduces the test data error.

[0062] Refer to Figure 3 As shown, in some specific embodiments of the present utility model, the test box 100 is provided with an observation port communicating the test chamber 110 with the outside and a transparent observation member arranged inside the observation port. The observation member seals the observation port and is used to observe the inside of the test chamber 110.

[0063] It should be understood that at the specified time, such as 4d, 11d, 18d, 25d, the reading of the measuring table 620 can be directly observed through the transparent observation member of the observation port without opening the box door 130. The recording of test data is more convenient. Moreover, when recording test data, the measurement environment in the test chamber 110 will not be affected, the accuracy of the test is higher, the test chamber 110 does not exchange heat with the external environment, and the test chamber 110 can maintain a stable test environment, saving energy.

[0064] Referring to Figure 1 and Figure 2 As shown, in some specific embodiments of the present invention, the test chamber 100 further includes a heating chamber 160 surrounding the test chamber 110. The heating assembly 300 is disposed in the heating chamber 160 and is used to heat the test chamber 110.

[0065] It should be understood that a separate heating chamber 160 is provided in the test chamber 110, and the test chamber 110 is heated through the heating chamber 160. The temperature rise process of the test chamber 110 is more stable, avoiding the rapid temperature rise from affecting the state of the test piece 800 and improving the accuracy of the test results.

[0066] In this embodiment, the control system controls the heating rate to be 1 - 3 °C / min. The side wall between the heating chamber 160 and the test chamber 110 is made of a material with excellent thermal conductivity to improve the heat transfer efficiency and save energy consumption. The material of the side wall can be aluminum alloy. The heating assembly 300 is a stainless steel heating tube, which generates heat after being powered on.

[0067] Referring to Figure 1 and Figure 2 As shown, in some specific embodiments of the present invention, the low - air - pressure and large - temperature - difference drying shrinkage test device further includes: a second circulation fan 700, and the second circulation fan 700 is communicated with the heating chamber 160.

[0068] It should be understood that the second circulation fan 700 accelerates the air flow in the heating chamber 160, distributes the heat generated by the stainless steel heating tube evenly in the heating chamber 160, and through the heat exchange between the hot air flow and the side wall, the temperature in the test chamber 110 rises. In this embodiment, the second circulation fan 700 is a centrifugal fan.

[0069] The above - mentioned embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to the above - mentioned embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A drying shrinkage test device under low air pressure and large temperature difference, characterized in that Comprising: A test chamber having a test cavity for testing; A vacuum pumping assembly connected to the test cavity for controlling the air pressure in the test cavity to a preset air pressure, the preset air pressure being less than the standard atmospheric pressure; A heating assembly for heating the temperature in the test cavity to a first preset temperature C1; A refrigeration assembly for refrigerating the temperature in the test cavity to a second preset temperature C2, C1 - C2 ≥ 10°C.

2. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that: The first preset temperature is 60°C and the second preset temperature is -20°C.

3. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that: The test chamber includes a box body having an opening and a box door capable of closing the opening. The box door is provided with an annular sealing ring that surrounds the opening, and the outer wall of the test chamber is provided with a heat insulation layer.

4. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, wherein: The test chamber is provided with an exhaust port and a control valve connected to the exhaust port, and the control valve can control the opening and closing of the exhaust port.

5. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that, Further comprising: A first circulation fan, the first circulation fan being connected to the test cavity.

6. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that, Further comprising: A temperature detection component for detecting the temperature in the test cavity.

7. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that Further comprising: An extensometer, the extensometer being disposed within the test cavity. The extensometer includes a clamp and a measuring gauge. The clamp is used to clamp both ends of a sample to be tested, and the measuring gauge is fixed to one end of the sample to be tested to detect the change amount of the sample to be tested.

8. The drying shrinkage test device under low air pressure and large temperature difference according to claim 7, wherein: The test chamber is provided with an observation port communicating the test cavity with the outside and a transparent observation member disposed within the observation port. The observation member seals the observation port and is used to observe the inside of the test cavity.

9. The drying shrinkage test device under low air pressure and large temperature difference according to claim 1, characterized in that: The test chamber is further provided with a heating cavity surrounding the test cavity. The heating assembly is disposed within the heating cavity and is used to heat the test cavity.

10. The drying shrinkage test device under low air pressure and large temperature difference according to claim 9, characterized in that Further comprising: A second circulation fan, the second circulation fan being connected to the heating cavity.

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