A device for testing the restricted shrinkage and expansion performance of concrete

Abstract

The present invention discloses a device for testing the restricted shrinkage and expansion performance of concrete, which includes a bottom plate, a fixed end plate, a movable end plate and two sets of lever testing mechanisms. The bottom plate is horizontally arranged. The lower part of the fixed end plate is connected to one end of the bottom plate. The lower part of the movable end plate is movably connected to a pushing mechanism arranged on the bottom plate. The movable end plate and the fixed end plate are arranged opposite to each other, and the distance between them can be adjusted by the pushing mechanism. Lever testing mechanisms are respectively connected to both the fixed end plate and the movable end plate. A concrete specimen integrally cast with a longitudinal restrictor is arranged between the two lever testing mechanisms. The two ends of the longitudinal restrictor are testing ends, and the two testing ends respectively contact the lower parts of the two lever testing mechanisms. The beneficial effects of the present invention are as follows: It can measure the deformation value of compensated shrinkage concrete in real time, eliminate the human error in the testing process, improve the credibility and measurement accuracy of the measured value, is simple to operate, and reduces the labor intensity of the staff.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete testing, and particularly relates to a device for testing the restricted shrinkage and expansion performance of concrete. Background Art

[0002] With the development of the fields of super high-rise buildings and infrastructure, the application of mass concrete is becoming more and more common. However, the self-shrinkage of mass concrete is relatively large and cracks are likely to occur. Therefore, using compensated shrinkage concrete is a relatively effective technical means to reduce and prevent concrete cracking. Testing the restricted expansion rate of compensated shrinkage concrete is an important technical index, which directly determines the compensated shrinkage ability of concrete.

[0003] Currently, two testing methods are generally adopted in China: One is to use a complete set of test equipment such as specimens with longitudinal restrictors, a comparator, a standard rod, and a bracket during the testing process. After the concrete with longitudinal restrictors is cured to a certain age, the concrete specimens are placed on the comparator bracket calibrated with the standard rod. After the measurement is completed, the concrete specimens are placed back in the constant temperature pool for curing until the next test age. This process is repeated, with complex operations, time-consuming and laborious. Moreover, each time of centering is prone to human errors due to problems such as the testing orientation, the sinking of the measuring connecting rod, and the unevenness of the concrete surface, affecting the measurement accuracy; while the other method requires firmly installing the measuring connecting rod, the bracket, and the longitudinal restrictor with fastening screws during the testing process. The installation process is relatively complex and is prone to loosening in the actual process. At the same time, the measurement point is not the central axis of the specimen, and the credibility of the test results cannot be guaranteed. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for testing the restricted shrinkage and expansion rate of compensated shrinkage concrete with a simple structure and high measurement accuracy in view of the deficiencies of the prior art.

[0005] The technical solution adopted by the present invention is as follows: A device for testing the restricted shrinkage and expansion performance of concrete includes a bottom plate, a fixed end plate, a movable end plate, and two groups of lever testing mechanisms. The bottom plate is horizontally arranged. The lower part of the fixed end plate is connected to one end of the bottom plate. The lower part of the movable end plate is movably connected to a pushing mechanism arranged on the bottom plate. The movable end plate and the fixed end plate are arranged opposite to each other, and the distance between them can be adjusted by the pushing mechanism. Lever testing mechanisms are respectively connected to both the fixed end plate and the movable end plate. Between the two lever testing mechanisms is a concrete specimen cast integrally with a longitudinal restrictor. The two ends of the longitudinal restrictor are test ends, and the two test ends are respectively in contact with the lower parts of the two lever testing mechanisms.

[0006] According to the above solution, the lever testing mechanism includes a lever, a micrometer, and a spring strip. The lever is arranged vertically, and the middle part of the lever is hinged to the bracket through a pin shaft. The bracket is connected to the inner side of the corresponding end plate, and the upper and lower ends of the lever can rotate around the middle part thereof; the micrometer is fixedly installed on the top of the corresponding end plate, and the measuring rod of the micrometer contacts the upper end of the lever; the spring strip is sleeved on the guide shaft, and one end of the guide shaft is connected to the corresponding end plate.

[0007] According to the above solution, gaskets are provided on the inner sides of the lower parts of the levers of the two sets of lever testing mechanisms, and the two testing ends of the longitudinal limiter are respectively in contact with the lower parts of the two lever testing mechanisms through the gaskets.

[0008] According to the above solution, a flange plate is installed on the top of the fixed end plate and / or the movable end plate, the micrometer is fixed on the flange plate, and the measuring rod of the micrometer passes through the flange plate and contacts the gasket on the upper part of the lever.

[0009] According to the above solution, the pushing mechanism includes an adjusting end plate, an adjusting screw, and an adjusting nut. The adjusting end plate is installed on the bottom plate outside the movable end plate. One end of the adjusting screw passes through the base plate and is threadedly connected to the movable end plate; the other end of the adjusting screw is adapted to the adjusting nut.

[0010] According to the above solution, the distance between the lower end of the lever and the pin shaft is greater than the distance between the upper end of the lever and the pin shaft, and the distances between the centers of the upper and lower gaskets of the same lever and the pin shaft are equal.

[0011] According to the above solution, the centers of the gaskets at the lower parts of the two levers are aligned with the center line of the concrete specimen, and the centers of the gaskets at the upper parts of the two levers are aligned with the central axes of the measuring rods of the two micrometers.

[0012] According to the above solution, the gasket is made of hard copper alloy; the lever is made of hard alloy steel.

[0013] According to the above solution, the width of the bottom plate is greater than the width of the longitudinal limiter; the maximum distance between the fixed end plate and the movable end plate is greater than the distance between the two measuring ends of the longitudinal limiter, and the heights of the fixed end plate and the movable end plate are not less than twice the width of the longitudinal limiter.

[0014] The beneficial effects of the present invention are as follows: The device of the present invention can measure the deformation value of the compensated shrinkage concrete in real time, eliminate the human error in the testing process, improve the credibility and measurement accuracy of the measurement value, and the device can also be used for the real-time measurement of the expansion and shrinkage performance of the concrete specimen in water, with simple operation and reduced labor intensity of the staff; The present invention is used as an ordinary specific length meter, and after centering with a standard rod, it measures the length of the compensated shrinkage concrete at a specified age, which is convenient, reliable, and simple to use. Description of the Drawings

[0015] Figure 1It is a schematic structural diagram of a specific embodiment of the present invention.

[0016] Figure 2 It is the front view of this embodiment.

[0017] Figure 3 It is the top view of this embodiment.

[0018] Figure 4 It is the side view of this embodiment.

[0019] Figure 5 It is the front view with a longitudinal limiter.

[0020] Figure 6 It is the front view of the test compensated shrinkage concrete specimen of this embodiment.

[0021] Wherein: 1. Bottom plate; 2. Fixed end plate; 3. Movable end plate; 4. Adjusting end plate; 5. Lever; 6. Pin shaft; 7. Spring piece; 8. Guide shaft; 9. Dial gauge; 9.1 Measuring rod; 10. Flange plate; 11. Gasket; 12. Adjusting nut; 13. Adjusting screw; 14. Fastening bolt; 15. Bracket; 16. Concrete specimen; 17. Longitudinal limiter. Specific embodiments

[0022] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The following will describe in detail a concrete restricted shrinkage and expansion rate test device and method of the present invention in conjunction with the specific structure and principle.

[0024] As Figures 1 to 4 shown, a concrete restricted shrinkage and expansion performance test device includes a bottom plate 1, a fixed end plate 2, a movable end plate 3 and two sets of lever test mechanisms. The bottom plate 1 is horizontally arranged. The lower part of the fixed end plate 2 is connected to one end of the bottom plate 1. The lower part of the movable end plate 3 is movably connected to a pushing mechanism arranged on the bottom plate 1. The movable end plate 3 is arranged opposite to the fixed end plate 2, and the distance between the two can be adjusted by the pushing mechanism. Lever test mechanisms are respectively connected to both the fixed end plate 2 and the movable end plate 3. Between the two lever test mechanisms is a concrete specimen 16 cast integrally with a longitudinal limiter 17. The two ends of the longitudinal limiter 17 are test ends, and the two test ends are respectively in contact with the lower parts of the two lever test mechanisms.

[0025] Preferably, the lever testing mechanism includes a lever 5, a dial indicator 9, and a spring strip 7. The lever 5 is vertically arranged, and the middle of the lever 5 is hinged to the bracket 15 (hinged by a pin shaft 6). The bracket 15 is connected to the inner side of the corresponding end plate (fixed end plate 2 or movable end plate 3). The upper and lower ends of the lever 5 can rotate around its middle part. The dial indicator 9 is fixedly installed on the top of the corresponding end plate (fixed end plate 2 or movable end plate 3), and the measuring rod of the dial indicator 9 contacts the upper end of the lever 5. The spring strip 7 is sleeved on the guide shaft 8. One end of the guide shaft 8 is connected to the corresponding end plate (fixed end plate 2 or movable end plate 3), and the length of the guide shaft 8 is less than the distance between the outer side of the lever 5 (the side of the spring strip 7) and the inner side of the corresponding end plate (the side of the spring strip 7) when the lever 5 is in the vertical state, so as to prevent the guide shaft 8 from affecting the rotation of the lever 5 and then affecting the measurement result.

[0026] Preferably, gaskets 11 are provided on the inner sides of the lower parts of the levers 5 of the two sets of lever testing mechanisms, and the two test ends of the longitudinal limiter 17 are respectively in contact with the lower parts of the two lever testing mechanisms through the gaskets 11.

[0027] Preferably, a flange plate 10 is installed on the top of the fixed end plate 2 and / or the movable end plate 3. The dial indicator 9 is fixed on the flange plate 10 through a fastening bolt 14. The measuring rod 9.1 of the dial indicator 9 passes through the flange plate 10 and contacts the gasket 11 on the upper part of the lever 5.

[0028] Preferably, the pushing mechanism includes an adjusting end plate 4, an adjusting screw 13, and an adjusting nut 12. The adjusting end plate 4 is installed on the bottom plate 1 outside the movable end plate 3. One end of the adjusting screw 13 passes through the base plate and is threadedly connected to the movable end plate 3. The other end of the adjusting screw 13 is adapted to the adjusting nut 12. When the adjusting nut 12 rotates to adjust the bolt, the movable end plate 3 can move along the bottom plate 1, and then the distance between the movable end plate 3 and the fixed end plate 2 can be adjusted.

[0029] In this embodiment, the bottom plate 1 is located at the bottom of the device and is fixedly connected to the fixed end plate 2 and the adjusting end plate 4 at both ends respectively. The width of the bottom plate 1 is slightly wider than the width of the concrete restricted expansion rate test specimen in the relevant design specifications (the concrete specimen 16 with the longitudinal restrictor 17 is the concrete restricted expansion rate test specimen, and the width of the concrete restricted expansion rate test specimen is generally 10 cm); the maximum distance between the fixed end plate 2 and the movable end plate 3 is greater than the distance between the tips of the measuring heads at both ends of the longitudinal restrictor 17 (i.e., the end of the measuring end) in the relevant design specifications, and the height is not less than twice the width of the longitudinal restrictor 17. The lever 5 is made of hard alloy steel and is provided with a through hole for passing through the pin shaft 6 in the middle (the clearance between the pin shaft 6 and the through hole is ≤10 μm after the pin shaft 6 is inserted into the through hole). The distance between the lower end of the lever 5 and the pin shaft 6 is greater than the distance between the upper end of the lever 5 and the pin shaft 6, so that it can be in a vertical state when not subjected to external forces. The distances between the centers of the upper and lower gaskets 11 of the same lever 5 and the pin shaft 6 are equal, and both are greater than the width of the longitudinal restrictor 17. And when the lever 5 is in a vertical state, the centers of the lower gaskets 11 of the two levers 5 are aligned with the center line of the concrete specimen, and the centers of the upper gaskets 11 of the two levers 5 are aligned with the central axis of the measuring rods of the two dial gauges 9. The bracket 15 is a "Y"-shaped opening structure, and the lever 5 is located inside the opening end of the bracket 15 and is hinged through the pin shaft 6. The guide shaft 8 is arranged at the lower end of the fixed end plate 2 or the movable end plate 3, and the spring piece 7 is sleeved on the guide shaft 8. The spring piece 7 can only deform along its axis; the stiffness coefficient of the spring piece 7 is not less than 10 N / mm, and the length of the spring piece 7 when not subjected to axial force (i.e., the natural length) is more than 1 mm greater than the distance between the lever 5 and the fixed end plate 2 / movable end plate 3 when the lever 5 is vertical. The adjusting end plate 4 is fixed to the bottom plate 1, and the adjusting end plate 4 is provided with threaded holes for the adjusting bolts to pass through. By rotating the adjusting bolts, the movable end plate 3 can be finely adjusted to move slightly parallel to the bottom plate 1, and then the distance between the movable end plate 3 and the fixed end plate 2 can be adjusted. The gasket 11 is made of hard copper alloy. The inner side of the gasket 11 is fixed on the lever 5, and the outer side of the gasket 11 is the contact surface, and the contact surface is smooth. The longitudinal restrictor 17 is a common existing concrete longitudinal restrictor, mainly including a measuring rod in the middle and limit plates at both ends. The concrete is poured between the two limit plates, as Figure 5 shown.

[0030] In this embodiment, the concrete specimen 16 with the longitudinal restrictor 17 is the concrete restricted expansion rate test specimen. The working principle of this embodiment is: adjust the movable end plate 3 so that the distance between the movable end plate 3 and the fixed end plate 2 is greater than the total length of the concrete restricted expansion rate test specimen (i.e., the concrete specimen 6 with the longitudinal restrictor 17); place the concrete restricted expansion rate test specimen on the bottom plate 1 (as Figure 6As shown in the figure, the central axes of the longitudinal limiter 17 and the centers of the gaskets 11 at the lower ends of the two levers 5 are collinear, so that one measuring end of the longitudinal limiter 17 contacts the lower gasket 11 of the lever 5 on the fixed end plate 2 (at this time, the lever 5 is vertical); adjust the adjusting bolt, and the movable end plate 3 moves towards the fixed end plate 2 until the lower gasket 11 of the lever 5 connected to the movable end plate 3 contacts the other measuring end of the longitudinal limiter 17. At this time, the spring piece 7 is in a compressed state. Insert the dial indicators 9 at both ends into the holes of the flange plate 10, and the tip (i.e., the measuring rod) of the dial indicator 9 abuts against the upper gasket 11 of the lever 5. At the same time, adjust the fastening bolt 14 to fix the dial indicator 9 and record the reading of the dial indicator 9; after a period of time, if the concrete specimen 16 expands or shrinks, since the spring piece 7 always presses the lower gasket 11 of the lever 5 against the measuring end of the longitudinal limiter 17, even a small change will cause the lower part of the lever 5 to rotate around the pin shaft 6 in the middle, and at the same time, the reading of the upper dial indicator 9 will also change accordingly; since the distances from the upper and lower gaskets 11 to the pin shaft 6 are equal, and the distance length is much larger than the expansion or contraction value of the concrete, it can be considered that the change in the value of the upper dial indicator 9 can reflect the length change value of the concrete specimen 16. Record the reading of the dial indicator 9, and the difference between the readings of the dial indicator 9 before and after is the length change of the concrete specimen 16, that is, the concrete has shrunk or expanded; the shrinkage or expansion performance of the concrete specimen 16 can be understood according to the length change of the concrete specimen 16.

[0031] When it is necessary to measure the shrinkage and expansion performance of the concrete specimen 16 in water, place the test device in a water tank, install and measure the specimen according to the above method, and read the reading of the dial indicator 9 in real time without taking the specimen in and out repeatedly. This embodiment can also be used as an ordinary comparator. After calibrating with a standard rod, measure and record according to the above method, and take the sum of the three average values.

[0032] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for testing the restricted shrinkage and expansion performance of concrete, characterized in that, It includes a bottom plate, a fixed end plate, a movable end plate and two groups of lever testing mechanisms. The bottom plate is horizontally arranged. The lower part of the fixed end plate is connected to one end of the bottom plate. The lower part of the movable end plate is movably connected to a pushing mechanism provided on the bottom plate. The movable end plate is arranged opposite to the fixed end plate, and the distance between them is adjusted by the pushing mechanism. The fixed end plate and the movable end plate are respectively connected with a lever testing mechanism. Between the two lever testing mechanisms is a concrete specimen cast integrally with a longitudinal restrictor. The two ends of the longitudinal restrictor are testing ends, and the two testing ends respectively contact the lower parts of the two lever testing mechanisms. The lever testing mechanism includes a lever, a dial gauge and a spring plate. The lever is vertically arranged. The middle part of the lever is hinged to a bracket through a pin shaft. The bracket is connected to the inner side of the corresponding end plate. The upper and lower ends of the lever rotate around its middle part. The dial gauge is fixedly installed on the top of the corresponding end plate, and the measuring rod of the dial gauge contacts the upper end of the lever. The spring plate is sleeved on a guide shaft, and one end of the guide shaft is connected to the corresponding end plate. Gaskets are provided on the inner sides of the lower parts of the levers of the two groups of lever testing mechanisms. The two testing ends of the longitudinal restrictor respectively contact the lower parts of the two lever testing mechanisms through the gaskets. The gasket is made of hard copper alloy; the lever is made of hard alloy steel. The distance between the lower end of the lever and the pin shaft is greater than the distance between the upper end of the lever and the pin shaft. The distances between the centers of the two gaskets on the upper and lower parts of the same lever and the pin shaft are equal. The stiffness coefficient of the spring plate is not less than 10 N / mm, and the natural length of the spring plate when not subjected to an axial force is more than 1 mm greater than the distance between the lever and the fixed end plate / movable end plate when the lever is vertical.

2. The concrete restricted shrinkage and expansion performance testing device according to claim 1, characterized in that, A flange plate is installed on the top of the fixed end plate and / or the movable end plate. The dial gauge is fixed on the flange plate, and the measuring rod of the dial gauge passes through the flange plate and contacts the gasket on the upper part of the lever.

3. The concrete restricted shrinkage and expansion performance testing device according to claim 2, wherein The pushing mechanism includes an adjusting end plate, an adjusting screw and an adjusting nut. The adjusting end plate is installed on the bottom plate outside the movable end plate. One end of the adjusting screw passes through the bottom plate and is threadedly connected to the movable end plate. The other end of the adjusting screw is adapted to the adjusting nut.

4. The concrete restricted shrinkage and expansion performance testing device according to claim 1, wherein, The centers of the gaskets on the lower parts of the two levers are aligned with the center line of the concrete specimen, and the centers of the gaskets on the upper parts of the two levers are aligned with the central axes of the measuring rods of the two dial gauges.

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