Shrinkage cracking test device for testing cement-based material

Abstract

The invention discloses a cement-based material shrinkage cracking test device, which comprises a base, a strain data acquisition instrument and a computer, the top end of the base is provided with an outer ring and an inner ring, the outer ring and the inner ring are used for manufacturing a test piece, the two sides of the outer part of the inner ring are fixedly connected with ribs, and the ribs are used for providing a cracking track for the test piece. Lifting handles are arranged on the two sides of the top end of the base, telescopic mechanisms, limiting mechanisms and clamping pieces are arranged on the lifting handles, each limiting mechanism comprises a tooth block and a plurality of ratchets, the telescopic mechanisms adjust the positions of the clamping pieces through clamping of the tooth blocks and the ratchets, and the clamping pieces are used for fixing the outer ring. Compared with an eccentric annular constraint test device, the device provided by the invention overcomes the defect of non-uniformity of the eccentric annular constraint test device, has geometric height symmetry, and overcomes the defect of offset of a crack cracking position caused by non-uniform distribution of stress at different angles of an eccentric ring; and the restraining uniformity of the circular ring on the mortar or concrete under the same radial thickness is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of cement-based material performance testing, in particular to a shrinkage cracking testing device for testing cement-based materials. Background Art

[0002] Shrinkage cracking of cement-based materials generally has two types: free shrinkage and constrained shrinkage. In free shrinkage, the cement-based material is not subject to any external force constraints, and the shrinkage is caused by water evaporation, hydration reaction, etc.; in constrained shrinkage, the cement-based material is subject to external constraints, and the volume change caused by the water and hydration reaction is constrained, and it cannot shrink freely. When the volume change is not subject to external constraints, tensile stress is generated inside the cement-based material. When the tensile stress is greater than its own tensile strength, the cement-based material may shrink and crack, thereby reducing the waterproofness, durability and bearing capacity of the structure, and shortening the life of the structure. Therefore, it is very important to evaluate the crack resistance of cement-based materials. Generally speaking, the test methods for evaluating the shrinkage and crack resistance of cement-based materials are mainly divided into free shrinkage methods and constrained shrinkage methods. Constrained shrinkage tests are mainly divided into plate constraint tests, ring constraint tests, strip constraint tests, etc. according to the different ways in which they constrain the shrinkage of cement-based materials.

[0003] After searching, the Chinese utility model patent with publication number CN220104611 U discloses a device for quickly evaluating the constrained shrinkage performance of cement-based materials, including a base plate, an inner ring and an outer ring. The inner ring is fixedly arranged on the base plate. The inner ring includes an inner semicircular ring and a semi-elliptical ring. The two ends of the semicircular ring are respectively fixedly connected to the two ends of the semi-elliptical ring in an integral manner. The outer ring is used to be placed on the base plate and is arranged colinearly with the axis of the inner semicircular ring. This application adopts the eccentric ring method for testing, but the eccentric constrained shrinkage test currently has some shortcomings: since the inner and outer rings of the device are fixedly connected to the base plate, this connection method determines that the positions of the inner and outer rings are fixed and cannot be changed, which results in the distance between the inner and outer rings cannot be changed. The eccentric constrained shrinkage test has the disadvantages of being unable to adjust the radial thickness of the inner and outer rings of the specimen and the single sensitivity of the specimen to cracking; and the eccentric constraint cannot complete the uniform annular shrinkage test, and cannot share the mold with the uniform annular constrained shrinkage test;

[0004] After searching, the Chinese invention patent with publication number CN1287149C discloses a testing device and application of the cracking and shrinkage performance of cement-based materials, including a mold (A) and a test circuit, a mold (B) and a measuring caliper placed on the same base plate. The mold specification of the device is single, so when conducting symmetrical circular ring constraint shrinkage tests and eccentric constraint shrinkage tests with different radial thicknesses, it is necessary to prepare multiple sets of different molds, which will lead to large errors in the comparison of test results between different molds; moreover, the test cost of using multiple sets of different test molds at the same time is high. Summary of the invention

[0005] In view of the above-mentioned prior art, the present invention provides a shrinkage cracking test device for testing cement-based materials, and the main technical problem to be solved is how to conveniently test the shrinkage strain change and cracking time of cement-based materials at different thicknesses.

[0006] To achieve the above object, the technical solution of the embodiment of the present invention is implemented as follows:

[0007] A shrinkage cracking test device for testing cement-based materials comprises a base, a strain data acquisition instrument and a computer. An outer ring and an inner ring are arranged on the top of the base. The outer ring and the inner ring are used to make a test piece. Ribs are fixedly connected to both sides of the outer portion of the inner ring. The ribs are used to provide a cracking track for the test piece. Handles are arranged on both sides of the top of the base. A telescopic mechanism, a limiting mechanism and a clamp are arranged on the handles. The limiting mechanism comprises a tooth block and a plurality of ratchets. The telescopic mechanism adjusts the position of the clamp by engaging the tooth block with the ratchets. The clamp is used to fix the outer ring.

[0008] Furthermore, the inner ring is fixedly connected to the middle of the top of the base, and three strain gauges are evenly spaced on the inner walls of both sides of the inner ring at the ribs along its height direction. The outer ring is outside the inner ring, and the three strain gauges are electrically connected to the strain data acquisition instrument, which is electrically connected to the computer. The ribs are in the shape of a triangular prism, and one of the three edges of the ribs faces the outer ring.

[0009] Furthermore, the outer ring is truncated cone-shaped and includes two mirror-symmetrical ring bodies, both sides of the two ring bodies are fixedly connected with connecting plates, the two connecting plates on the same side are provided with threaded through holes on the plate bodies, and the two connecting plates are threadedly connected with the same bolt at the two threaded through holes.

[0010] Furthermore, the handle is rotatably connected to the base through a damping shaft, and the handle includes a handle and two fixed sleeves on both sides thereof, the handle is fixedly connected to the top end between the two fixed sleeves, and the inner sides of the two fixed sleeves are slidably connected to connecting rods, the clip is fixedly connected to the top ends of the two connecting rods, the clip is arc-shaped, and a plurality of protrusions are provided on the inner side of the clip.

[0011] Furthermore, a rectangular opening is provided below the handle on the side where the two fixing sleeves are close to each other, and the two tooth blocks are respectively located at the two rectangular openings, and the ends of the two tooth blocks outside the fixing sleeves are fixedly connected with spring sheets, a connecting belt is fixedly connected between the two spring sheets at the ends close to the tooth blocks, and the ends of the spring sheets away from the tooth blocks are fixedly connected to the fixing sleeve.

[0012] Furthermore, the ratchets are equidistantly fixedly connected to the sides of the two connecting rods that are close to each other, and the ratchets are meshed with the tooth blocks, and the ratchets and the tooth blocks are two centrally symmetrical triangles.

[0013] Furthermore, a vibration motor is fixedly connected to one side of the top end of the base, and a plurality of gaskets are fixedly connected to the bottom end of the base.

[0014] Furthermore, circular openings are provided at the four outer corners of the bottom end of the base, and the base is slidably connected to support rods at the circular openings, the bottom ends of the four support rods are fixedly connected to the same base, and the top ends of the four support rods are fixedly connected to the same push plate, an electric lifting platform is fixedly connected to the middle part between the base and the base, and a pad is fixedly connected to the middle part of the top end of the base, and the diameter of the pad is larger than the bottom diameter of the outer ring.

[0015] Furthermore, a plurality of first through holes are equidistantly provided at the top of the base, and a hydraulic cylinder is fixedly connected to the top of the base at the outside of the first through hole, a second through hole is provided at one end of the hydraulic cylinder, and a piston rod is slidably connected to the hydraulic cylinder at the second through hole, one end of the piston rod inside the hydraulic cylinder is fixedly connected to the piston, and the other end of the piston rod is fixedly connected to a connecting plate, a plurality of mounting holes are provided on the plate body of the connecting plate, and screws are provided at the mounting holes of the connecting plate, the outer ring includes a plurality of arc plates arranged in a circle, the connecting plate is fixedly connected to the arc plate by screws, and a plurality of fixing piles are fixedly connected to the inner wall of the hydraulic cylinder on the side away from the piston.

[0016] The beneficial effects of the present invention are:

[0017] 1. Compared with the eccentric annular constraint test device, the present invention overcomes the disadvantage of the unevenness of the eccentric annular constraint test device. The device has high geometric symmetry, overcomes the disadvantage of the eccentric ring's crack position offset caused by the uneven stress distribution at different angles, and ensures the uniformity of the mortar or concrete's constraint on it by the ring at the same radial thickness; through the different diameters of the truncated cone shape, the constrained shrinkage cracking of cement-based materials with different radial thicknesses can be simulated on the same annular shrinkage test device. The test device is simple, convenient and easy to operate, which greatly reduces the cost of replacing outer rings of different sizes to carry out shrinkage constraint experiments; the adjustable handle can be used to carry the device and to maintain the stability of the outer ring, making the use of the device more convenient.

[0018] 2. When testing the shrinkage stress and strain of materials under different radial thickness constraint states, the present invention does not need to replace circular constraint molds of different sizes, and can simultaneously test the stress and strain changes of materials with different radial thicknesses. To compare the influence of radial thickness on the stress and strain of cement-based materials, it is only necessary to stick strain gauges at different radial positions to measure the stress and strain of different radial thicknesses on the same mold. At this time, the test results of comparing the influence of radial thickness on the shrinkage strain of cement-based materials under the circular constraint state are highly comparable and the result error is small. Compared with circular shrinkage specimens, there is no need to manually and multiple times adjust the radial thickness of the specimen, which breaks the shortcoming of the single cracking sensitivity of traditional circular specimens, and the cracking time of multiple groups of specimens with different radial thicknesses can be measured simultaneously on the same specimen.

[0019] 3. By setting up the vibration motor and the gasket, the vibration motor can accelerate the separation from the outer ring and the inner ring when the cement-based material needs to be removed, so as to ensure the convenience of using the device. The gasket can play a shock-absorbing and buffering effect under the base. Therefore, when the vibration motor is running, its vibration will not affect the overall stability of the device.

[0020] 4. This device divides the truncated cone-shaped outer ring into several arc-shaped pieces, and combines and separates all the arc-shaped pieces by hydraulic means, so that the outer ring and the test piece can be easily separated by reducing the contact area between each arc-shaped piece and the test piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A three-dimensional diagram of a shrinkage cracking test device for testing cement-based materials in Example 1 of the present application;

[0022] Figure 2 A front cross-sectional view of a handle of a shrinkage cracking test device for testing cement-based materials in Example 1 of the present application;

[0023] Figure 3 A three-dimensional diagram of a shrinkage cracking test device for testing cement-based materials in Example 2 of the present application;

[0024] Figure 4 A three-dimensional diagram of a shrinkage cracking test device for testing cement-based materials in Example 3 of the present application;

[0025] Figure 5 This is a front cross-sectional view of a shrinkage cracking test device for testing cement-based materials in Example 3 of the present application.

[0026] Description of Figure Numbers:

[0027] Base 1, handle 2, fixing sleeve 201, handle 202, outer ring 3, inner ring 4, rib 5, strain gauge 6, bolt 7, connecting plate 8, ratchet 9, connecting rod 10, tooth block 11, spring sheet 12, protrusion 13, clip 14, connecting belt 15, vibration motor 16, gasket 17, base 18, support rod 19, pad 20, connecting plate 21, hydraulic cylinder 22, piston rod 23, electric lifting platform 24, bolt 25, piston 26, fixing pile 27, push plate 28. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, the expression "some embodiments" is related to a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0029] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "inside", "outside", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0030] Example 1

[0031] See attached Figure 1-2The present application provides a shrinkage cracking test device for testing cement-based materials, comprising a base 1, a strain data acquisition instrument and a computer. The base 1 is square, with a length and a width of 450-500 mm. An outer ring 3 and an inner ring 4 are arranged on the top of the base 1. The outer ring 3 and the inner ring 4 are used to make a test piece. The material of the outer ring 3 is Q235 steel, with an upper inner diameter of 300-304 mm, a lower inner diameter of 370-380 mm, a thickness of 8-10 mm, and a height of 120-130 mm. Ribs 5 are fixedly connected to both sides of the outer side of the inner ring 4. The inner diameter of the inner ring 4 is 200-204 mm, and the thickness is 10-1 2mm, height 120-130mm, two ribs 5 are symmetrically arranged, the ribs 5 are used to provide a cracking trajectory for the specimen to induce concrete or mortar to crack at this position, the height of the ribs 5 is 10-12mm, the outer ring 3 and the inner ring 4 are at the same height as the ribs 5, and handles 2 are provided on both sides of the top of the base 1. The handles 2 are used to facilitate the transportation of the device. The handles 2 are provided with a telescopic mechanism, a limiting mechanism and a clip 14. The limiting mechanism includes a tooth block 11 and a plurality of ratchets 9. The telescopic mechanism adjusts the position of the clip 14 by the engagement of the tooth block 11 with the ratchet 9, and the clip 14 is used to fix the outer ring 3.

[0032] Preferably, the inner ring 4 is fixedly connected to the middle of the top of the base 1, and three strain gauges 6 are evenly spaced along the height direction of the inner walls of both sides of the inner ring 4 at the ribs 5, and the outer ring 3 is outside the inner ring 4. The three strain gauges 6 are electrically connected to the strain data acquisition instrument, and the strain data acquisition instrument is electrically connected to the computer. The rib 5 is in the shape of a triangular prism, and one of the three edges of the rib 5 faces the outer ring 3.

[0033] Preferably, the outer ring 3 is truncated cone-shaped and includes two mirror-symmetrical ring bodies, both sides of the two ring bodies are fixedly connected with connecting plates 8, threaded through holes are provided on the plate bodies of the two connecting plates 8 on the same side, and the two connecting plates 8 are threadedly connected with the same bolt 7 at the two threaded through holes. The two connecting plates 8 are connected by bolts 7 to fix the two ring bodies, thereby completing the assembly of the outer ring 3. Conversely, the outer ring 3 can be disassembled, thereby facilitating the removal of the test piece.

[0034] Preferably, the handle 2 is rotatably connected to the base 1 through a damping shaft. The handle 2 is tilted toward the outer ring 3 and the relative positions of the clip 14 and the handle 202 are adjusted so that the clip 14 can fit with the outer ring 3, thereby clamping and fixing the outer ring 3. The handle 2 includes a handle 202 and two fixing sleeves 201 on both sides thereof. The top end between the two fixing sleeves 201 is fixedly connected with the handle 202. When carrying the device, the handle 202 can be held and force can be applied, so that the device can be stably held. The inner sides of the two fixing sleeves 201 are slidably connected with connecting rods 10. The clip 14 is fixedly connected to the top ends of the two connecting rods 10. The clip 14 is arc-shaped, and a plurality of protrusions 13 are provided on the inner side of the clip 14. The material of the protrusion 13 is rubber, which can increase the friction between the clip 14 and the outer ring 3, thereby ensuring the stability of the former clamping and fixing the latter.

[0035] Preferably, a rectangular opening is provided on the side where the two fixing sleeves 201 are close to each other below the handle 202, the two tooth blocks 11 are respectively located at the two rectangular openings, and the ends of the two tooth blocks 11 outside the fixing sleeve 201 are fixedly connected with spring sheets 12, a connecting belt 15 is fixedly connected between the two spring sheets 12 at the ends close to the tooth blocks 11, and the ends of the spring sheets 12 away from the tooth blocks 11 are fixedly connected to the fixing sleeve 201. The ratchet teeth 9 are equidistantly fixedly connected to the side of the two connecting rods 10 that are close to each other, and the ratchet teeth 9 are meshed with the tooth block 11. The ratchet teeth 9 and the tooth block 11 are two centrally symmetrical triangular shapes. By engaging the ratchet teeth 9 at different positions with the tooth block 11, the length of the connecting rod 10 outside the fixed sleeve 201 can be changed to adjust the position of the clip 14. In normal conditions, the spring sheet 12 can maintain the engagement state of the tooth block 11 and the ratchet teeth 9 through its own elastic force, thereby ensuring the stability of the clip 14 after the position is adjusted. After pulling the connecting belt 15, the spring sheet 12 can be bent, and the tooth block 11 is separated from the ratchet teeth 9 at this time, so the connecting rod 10 is free to move in the fixed sleeve 201, so that the position of the clip 14 can be further adjusted.

[0036] Working principle: Apply the release agent to the outer surface of the inner ring 4 and the inner surface of the outer ring 3; pour the cement-based material between the inner ring 4 and the outer ring 3, vibrate and compact it, and smooth the surface of the cement-based material with a scraper. After forming, move the specimen into the test environment immediately, and connect the strain gauge 6 on the inner surface of the inner ring 4 to the strain gauge within two minutes, record the time and detect the strain value;

[0037] After 24 hours of specimen forming, unscrew the bolts 7 on the outer ring 3, remove the truncated cone-shaped outer ring 3, and seal the specimen surface with paraffin. Then, keep the specimen test curing environment unchanged, observe and record the strain value of the specimen and the crack position of the specimen. The time when the strain value suddenly changes is the cracking time of the specimen.

[0038] According to the monitoring results of the three strain gauges 6, the changes in the cracking time of the strain values ​​at different positions, such as the upper, middle and lower positions, can be compared to compare the changes in the cracking time of concrete under different radial thickness conditions;

[0039] The device can be carried during use with the help of the handle 2, and after the device is stabilized, the handle 2 can be pushed to tilt toward the outer ring 3, and then the clip 14 can be pushed toward the outer ring 3. In this case, the tooth block 11 can limit the ratchet 9, so the stability of the clip 14 after the position adjustment can be maintained by the connecting rod 10; after the device is used, the connecting belt 15 can be pulled, and the connecting belt 15 can pull the two spring sheets 12 to deflect outward, thereby separating the tooth block 11 from the ratchet 9. In this case, the connecting rod 10 can move freely in the fixing sleeve 201, so the clip 14 can be pulled to separate from the outer ring 3, thereby facilitating the removal of the outer ring 3.

[0040] Example 2

[0041] See attached Figure 3 The present application provides a shrinkage cracking test device for testing cement-based materials. Compared with Example 1, in order to facilitate the removal of the test block, a vibration motor 16 is fixedly connected to one side of the top of the base 1, and a plurality of gaskets 17 are fixedly connected to the bottom of the base 1.

[0042] Working principle: When it is necessary to remove the cement-based material from between the inner ring 4 and the outer ring 3, the vibration motor 16 can be started to use its vibration to cause the cement-based material to separate from the inner ring 4 and the outer ring 3, thereby further facilitating the removal of the cement-based material. When the vibration motor 16 is running, the rubber gasket 17 can provide a shock-absorbing and buffering effect for the base 1, thereby maintaining the overall stability of the device.

[0043] Example 3

[0044] See attached Figure 4-5The present application provides a shrinkage cracking test device for testing cement-based materials. In order to facilitate the disassembly and assembly of the outer ring 3, circular openings are opened at the four corners of the bottom outer side of the base 1, and the base 1 is slidably connected with a support rod 19 at the circular opening. The bottom ends of the four support rods 19 are fixedly connected to the same base 18, and the top ends of the four support rods 19 are fixedly connected to the same push plate 28. The push plate 28 has the same shape as the base 1 and is compatible. Hydraulic oil is provided in the interior of the hydraulic cylinder 22 and in the space above the push plate 28 in the base 1. Therefore, when the push plate 28 moves relative to the base 1, it can push or pull the hydraulic oil, so that The hydraulic oil in the base 1 and the hydraulic cylinder 22 can circulate with each other, thereby realizing the position adjustment of the piston 26. An electric lifting platform 24 is fixedly connected at the middle between the base 18 and the base 1. The electric lifting platform 24 is a miniature wedge-shaped electric lifting platform, and an ELPC series electric lifting slide can be used. A pad 20 is fixedly connected to the middle of the top of the base 1. The diameter of the pad 20 is larger than the bottom diameter of the outer ring 3. After the arc plate moves to the pad 20 and combines with each other to form the outer ring 3, the pad 20 can seal the bottom of the outer ring 3 so that no leakage will occur at the bottom of the outer ring 3 after pouring concrete.

[0045] Preferably, a plurality of first through holes are equidistantly provided on the outer side of the top end of the base 1, and a hydraulic cylinder 22 is fixedly connected to the top end of the base 1 at the outside of the first through hole, a second through hole is provided at one end of the hydraulic cylinder 22, and a piston rod 23 is slidably connected to the hydraulic cylinder 22 at the second through hole, one end of the piston rod 23 in the hydraulic cylinder 22 is fixedly connected to a piston 26, and the other end of the piston rod 23 is fixedly connected to a connecting plate 21, a plurality of mounting holes are provided on the plate body of the connecting plate 21, and screws 25 are provided at the mounting holes of the connecting plate 21, the outer ring 3 includes a plurality of arc plates arranged in a circle, and the connecting plate 21 is fixedly connected to the arc plate by screws 25, and a plurality of fixing piles 27 are fixedly connected to the inner wall of the hydraulic cylinder 22 on the side away from the piston 26, and the existence of the fixing piles 27 can limit the movement of the piston 26, thereby limiting its maximum displacement distance, thereby ensuring the stability of hydraulic transmission.

[0046] Working principle: When pouring concrete, the electric lifting platform 24 can be used to pull the base 1 down. At this time, the push plate 28 can push the hydraulic oil in the base, so that the hydraulic oil can enter the fixed pile 27 and push the piston 26 to move. The piston 26 can push several arc plates closer to each other through the piston rod 23 until the arc plates move onto the pad 20, and a complete annular outer ring 3 can be formed. In this case, concrete pouring can be carried out; and when the outer ring 3 needs to be removed, the electric lifting platform 24 can be used to push the base 1 up, so the push plate 28 can draw the hydraulic oil in the fixed pile 27 back into the base 1, and make the piston rod 23 pull the arc plates, so that several arc plates move away from each other, thereby realizing the separation of the outer ring 3 and the specimen.

[0047] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A shrinkage cracking test device for testing cement-based materials, comprising a base (1), a strain data acquisition instrument and a computer, characterized in that: An outer ring (3) and an inner ring (4) are provided at the top of the base (1), and the outer ring (3) and the inner ring (4) are used to make a test piece. Ribs (5) are fixedly connected to both sides of the outside of the inner ring (4), and the ribs (5) are used to provide a cracking track for the test piece. Handles (2) are provided on both sides of the top of the base (1), and a telescopic mechanism, a limiting mechanism and a clamping piece (14) are provided on the handles (2). The limiting mechanism includes a tooth block (11) and a plurality of ratchets (9). The telescopic mechanism adjusts the position of the clamping piece (14) by engaging the tooth block (11) with the ratchets (9), and the clamping piece (14) is used to fix the outer ring (3).

2. A shrinkage cracking test device for testing cement-based materials according to claim 1, characterized in that: The inner ring (4) is fixedly connected to the middle of the top of the base (1), and three strain gauges (6) are evenly spaced on the inner walls of both sides of the inner ring (4) at the ribs (5) along the height direction thereof; the outer ring (3) is located outside the inner ring (4); the three strain gauges (6) are electrically connected to a strain data acquisition instrument, and the strain data acquisition instrument is electrically connected to a computer; the ribs (5) are in the shape of a triangular prism, and one of the three edges of the ribs (5) faces the outer ring (3).

3. A shrinkage cracking test device for testing cement-based materials according to claim 1, characterized in that: The outer ring (3) is in a truncated cone shape and comprises two mirror-symmetrical ring bodies, both sides of the two ring bodies are fixedly connected with connecting plates (8), the plate bodies of the two connecting plates (8) on the same side are both provided with threaded through holes, and the two connecting plates (8) are threadedly connected with the same bolt (7) at the two threaded through holes.

4. A shrinkage cracking test device for testing cement-based materials according to claim 1, characterized in that: The handle (2) is rotatably connected to the base (1) via a damping shaft, and the handle (2) comprises a handle (202) and two fixing sleeves (201) located on both sides thereof, the handle (202) is fixedly connected at the top end between the two fixing sleeves (201), and the inner sides of the two fixing sleeves (201) are slidably connected to connecting rods (10), the clip (14) is fixedly connected to the top ends of the two connecting rods (10), the clip (14) is arc-shaped, and a plurality of protrusions (13) are provided on the inner side of the clip (14).

5. A shrinkage cracking test device for testing cement-based materials according to claim 4, characterized in that: A rectangular opening is provided at the bottom of the handle (202) on the side where the two fixing sleeves (201) are close to each other, and the two tooth blocks (11) are respectively located at the two rectangular openings, and the ends of the two tooth blocks (11) outside the fixing sleeve (201) are fixedly connected to spring sheets (12), a connecting belt (15) is fixedly connected between the two spring sheets (12) at the ends close to the tooth blocks (11), and the ends of the spring sheets (12) away from the tooth blocks (11) are fixedly connected to the fixing sleeve (201).

6. A shrinkage cracking test device for testing cement-based materials according to claim 5, characterized in that: The ratchet teeth (9) are fixedly connected at equal distances to the sides of the two connecting rods (10) that are close to each other, and the ratchet teeth (9) are meshed with the tooth block (11). The ratchet teeth (9) and the tooth block (11) are two centrally symmetrical triangle shapes.

7. A shrinkage cracking test device for testing cement-based materials according to claim 6, characterized in that: A vibration motor (16) is fixedly connected to one side of the top end of the base (1), and a plurality of gaskets (17) are fixedly connected to the bottom end of the base (1).

8. A shrinkage cracking test device for testing cement-based materials according to claim 1, characterized in that: Circular openings are provided at the four outer corners of the bottom end of the base (1), and the base (1) is slidably connected to a support rod (19) at the circular opening, the bottom ends of the four support rods (19) are fixedly connected to the same base (18), and the top ends of the four support rods (19) are fixedly connected to the same push plate (28), an electric lifting platform (24) is fixedly connected in the middle between the base (18) and the base (1), and a pad (20) is fixedly connected in the middle of the top end of the base (1), and the diameter of the pad (20) is larger than the bottom diameter of the outer ring (3).

9. A shrinkage cracking test device for testing cement-based materials according to claim 8, characterized in that: A plurality of first through holes are equidistantly formed on the outer side of the top of the base (1), and a hydraulic cylinder (22) is fixedly connected to the top of the base (1) outside the first through hole. A second through hole is formed at one end of the hydraulic cylinder (22), and a piston rod (23) is slidably connected to the hydraulic cylinder (22) at the second through hole. One end of the piston rod (23) inside the hydraulic cylinder (22) is fixedly connected to a piston (26), and the other end of the piston rod (23) is fixedly connected to a connecting plate (21). A plurality of mounting holes are formed on the plate body of the connecting plate (21), and screws (25) are provided at the mounting holes of the connecting plate (21). The outer ring (3) includes a plurality of arc plates arranged in a circle, and the connecting plate (21) is fixedly connected to the arc plates by screws (25). A plurality of fixing piles (27) are fixedly connected to the inner wall of the hydraulic cylinder (22) on a side away from the piston (26).

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