Low-vacuum environment concrete creep test system and test method thereof

Abstract

The application discloses a low-vacuum environment concrete creep test system, which comprises a main controller and a vacuum box body, wherein a compression-bending integrated concrete creep test device is arranged in the vacuum box body, a temperature adjusting system is arranged in the vacuum box body, the temperature adjusting system comprises a temperature sensor, a heating pipe and a cooling pipe arranged in the vacuum box body, and a vacuum control system is arranged in the vacuum box body. In addition, the application discloses a low-vacuum environment concrete creep test method, wherein compression load and bending load are applied to the concrete to be tested under a low-vacuum environment, and the creep deformation of the concrete under the load and the creep recovery deformation of the concrete under unloading are calculated. The low-vacuum environment concrete creep test system and the test method thereof can test under a low-vacuum environment and apply the compression load and the bending load simultaneously, and are more in line with the actual engineering structure.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials technology, specifically to a low-vacuum environment concrete creep testing system and its testing method. Background Technology

[0002] As human activity expands spatially, concrete, as the most widely used building material, is being designed for higher strength and increasingly applied in more extreme environments. Due to the needs of high-altitude infrastructure construction, initial explorations of vacuum pipeline rail transit systems, and the conception and experimentation of space concrete, the engineering applications of concrete under low-pressure and vacuum conditions are increasing, and the atmospheric pressure of the environments in which it may serve in the future will become increasingly lower. Creep is an important property of concrete, referring to the phenomenon of deformation gradually increasing over time under continuous load. It is a significant factor affecting abnormal deformation (such as warping and deflection), cracking, and prestress loss in large-span engineering structures such as bridges. Environmental temperature and humidity conditions are important factors affecting concrete creep deformation; both decreased humidity and increased temperature increase concrete creep deformation. According to Dalton's law of partial pressures, the rate of water evaporation is inversely proportional to atmospheric pressure. Low vacuum environments produce a strong drying effect on concrete, causing it to gradually dry or dehydrate, accelerating the growth of creep. Simultaneously, the increased vacuum also alters the stress state of internal components, thus affecting concrete creep deformation and the normal service life of engineering structures. Investigating the evolution of creep deformation in concrete under long-term vacuum conditions is of great significance for the design and service life prediction of concrete structures under low vacuum conditions.

[0003] Currently, there are many testing devices for concrete shrinkage or tensile creep under complex environments with multiple factors such as temperature and humidity. However, existing devices are all conducted under normal pressure, and there is no testing device for concrete creep under long-term low pressure or low vacuum conditions. In addition, concrete in actual structures is usually under complex loading states such as compression, tension, or bending, while the concrete under test in existing creep tests is usually only subjected to compression or tensile loads, and the test results cannot reflect the actual engineering structure. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a low-vacuum environment concrete creep testing system and test method, which on the one hand enables experimental testing in a low-vacuum environment, and on the other hand enables simultaneous application of compressive load and bending load to the concrete under test.

[0005] The present invention solves the above problems through the following technical means:

[0006] A low-vacuum environment concrete creep testing system and its testing method include a main controller, a vacuum chamber, and a compression-bending integrated concrete creep testing device installed in the vacuum chamber. The compression-bending integrated concrete creep testing device is electrically connected to the main controller, and a temperature control system is installed inside the vacuum chamber.

[0007] Furthermore, the integrated compression-bending concrete creep testing device includes a compression force application mechanism for applying compressive load to the concrete under test and a bending force application mechanism for applying bending load to the concrete under test. A longitudinal pressure sensor is arranged along the longitudinal direction of the concrete under test, a transverse pressure sensor is arranged along the transverse direction of the concrete under test, a strain sensor is arranged along the compression deformation direction of the concrete under test, and a displacement sensor is arranged below the concrete under test. The longitudinal pressure sensor, transverse pressure sensor, strain sensor, and displacement sensor are all electrically connected to the main controller.

[0008] Furthermore, the compression force application mechanism includes a transverse tie rod with external threads and a left end plate, a spring, a left pressure plate, a right pressure plate, and a right end plate sequentially sleeved on the transverse tie rod from left to right. The left pressure plate and the right pressure plate are used to place the concrete to be tested, and a hydraulic jack is provided between the right pressure plate and the right end plate. Both sides of the left end plate, the left pressure plate, the right pressure plate, and the right end plate are fixed to the transverse tie rod by fixing bolts.

[0009] Furthermore, the bending force application mechanism includes a rotating support rod, an L-shaped lever fixed on the rotating support rod and rotatable around the rotating support rod, the upper end of the L-shaped lever being horizontally positioned to apply a bending load to the concrete to be tested, the lower end of the L-shaped lever being vertically positioned and connected to the lever load application component, and also includes a bending load support positioned at the bottom of the concrete to be tested.

[0010] Furthermore, the lever load application component includes a force-applying lever, a lever bracket for supporting the force-applying lever, a weight placed on the force-applying lever and movable along the force-applying lever, the end of the force-applying lever away from the weight being connected to the lower end of the L-shaped lever via a rope, and also includes a fixed pulley for changing the direction of the force on the rope.

[0011] Furthermore, it also includes a traction bracket mounted on the linear motion mechanism. The traction bracket is connected to the weight via a flexible rope. The weight is moved on the force-applying lever by the traction bracket. The linear motion mechanism is controlled by a main controller.

[0012] Furthermore, a vacuum control system is installed inside the vacuum chamber. The vacuum control system includes a vacuum pump and a vacuum pressure sensor installed inside the vacuum chamber. The vacuum pump is connected to the vacuum chamber through a vacuum tube, and a vacuum control valve is installed on the vacuum tube. The vacuum pressure sensor, vacuum pump, and vacuum control valve are all electrically connected to the main controller.

[0013] Furthermore, the temperature control system includes a temperature sensor, a heating element, and a cooling element disposed in the vacuum chamber, all of which are electrically connected to the main controller.

[0014] Furthermore, it also includes a hydraulic pump station system and an oil pipeline, wherein the hydraulic pump station system is connected to the hydraulic jack via the oil pipeline, and the hydraulic pump station system is electrically connected to the main controller.

[0015] A method for testing concrete creep in a low-vacuum environment includes the following steps:

[0016] Place the concrete to be tested on the bending load support, adjust the fixing bolts so that both ends of the concrete to be tested contact the left pressure plate and the right pressure plate respectively, and at the same time make the longitudinal pressure sensor and the transverse pressure sensor contact the concrete to be tested; fix the strain sensor and the displacement sensor on the concrete to be tested.

[0017] The main controller preloads stress onto the concrete to be tested, controls the jack to apply compressive creep stress of 20% of the target value to the concrete, and controls the linear motion mechanism to drive the traction bracket, thereby pulling the weight to move on the force lever and applying bending creep stress of 20% of the target value to the concrete. The values ​​of the strain sensor and displacement sensor are checked. If the deformation difference between the left and right sides of the concrete to be tested is less than 10%, the test continues; otherwise, the load is removed and reloaded.

[0018] After preloading is completed, the ambient temperature and vacuum level are set by the main controller, and compressive creep stress and flexural creep stress of the same target value are applied. The deformation information of the concrete to be tested is collected in real time. After the load is maintained until the required age, the load is unloaded and the deformation information after unloading is recorded. The creep deformation of the concrete under low vacuum environment and the creep recovery deformation under unloading are calculated.

[0019] The beneficial effects of this invention are:

[0020] The low-vacuum environment concrete creep testing system of the present invention includes a main controller, a vacuum chamber, and a compression-bending integrated concrete creep testing device disposed within the vacuum chamber. The compression-bending integrated concrete creep testing device is electrically connected to the main controller. A temperature regulation system is installed inside the vacuum chamber. A vacuum control system is installed inside the vacuum chamber to adjust the vacuum level of the test chamber to meet the required vacuum environment for the test. The compression-bending integrated concrete creep testing device includes a compression force application mechanism and a bending force application mechanism for simultaneously applying compressive and bending loads to the concrete under test. Multiple sensors are also provided to facilitate the acquisition of experimental data outside the vacuum chamber. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 This is a schematic diagram of the structure disclosed in a preferred embodiment of the present invention;

[0023] Figure 2 yes Figure 1 Rear view;

[0024] Figure 3 This is the first isometric view of the integrated compression-bending concrete creep testing device;

[0025] Figure 4 This is the second isometric view of the integrated compression-bending concrete creep testing device;

[0026] Figure 5 yes Figure 3 The front view;

[0027] Figure 6 yes Figure 3 Top view;

[0028] Figure 7 yes Figure 3 Side view;

[0029] Figure 8 This is a structural diagram of a vacuum chamber assembly;

[0030] Figure 9 This is a schematic diagram of the main controller and hydraulic pump station system;

[0031] Figure 10 yes Figure 9 A diagram of the back of the car;

[0032] Figure 11 Schematic diagram of the pipeline section. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] like Figures 1-11 As shown, a low-vacuum environment concrete creep testing system includes a main controller 1 and a vacuum chamber 2. The vacuum chamber houses an integrated compression-bending concrete creep testing device 3. The vacuum chamber also includes a temperature control system 4, comprising a temperature sensor 403, a heating element 401, and a cooling element 402, all housed within the vacuum chamber 2. A vacuum control system is also installed within the vacuum chamber, comprising a vacuum pump 501 and a vacuum pressure sensor 502, both housed within the vacuum chamber. The vacuum pump is connected to the vacuum chamber via a vacuum pipe 503, which is equipped with a vacuum control valve 504. The integrated compression-bending concrete creep testing device, the vacuum control system, and the temperature control system are all electrically connected to the main controller.

[0037] In this embodiment, the vacuum chamber provides the necessary vacuum environment for the testing device, and the temperature control system regulates the temperature within the vacuum chamber. The integrated compression-bending concrete creep testing device can simultaneously apply compressive and flexural creep stresses to the concrete under test. This system can effectively simulate the influence of different vacuum environments on concrete creep. A main controller controls the testing environment to generate the required vacuum and temperature, simulating the working environment of concrete in vacuum pipelines and high-altitude, low-pressure environments, thus enabling better testing of the creep performance of concrete under these conditions.

[0038] The integrated compression-bending concrete creep testing device includes a compression force application mechanism 301 and a bending force application mechanism 302. The compression force application mechanism includes a transverse tie rod 301-1 with external threads and a left end plate 301-2, a spring 301-3, a left pressure plate 301-4, a right pressure plate 301-5, and a right end plate 301-6, which are sequentially sleeved on the transverse tie rod from left to right. The left pressure plate and the right pressure plate are used to place the concrete to be tested. A hydraulic jack 301-7 is provided between the right pressure plate and the right end plate. Both sides of the left end plate, the left pressure plate, the right pressure plate, and the right end plate are fixed to the transverse tie rod by fixing bolts 301-8.

[0039] Preferably, the bending force application mechanism includes a rotating support rod 302-1, an L-shaped lever 302-2 fixed to the rotating support rod and rotatable around the rotating support rod, the upper end of the L-shaped lever being horizontally positioned to apply a bending load to the concrete block, the lower end of the L-shaped lever being vertically positioned and connected to the lever load application assembly 302-3, and also includes a bending load support 302-4 positioned at the bottom of the concrete to be tested, the bending load support being used to support the concrete to be tested in the vertical direction. The lever load application assembly includes a force application lever 302-3-1, a lever bracket 302-3-2 for supporting the force application lever, and a weight 302-3-3 placed on the force application lever and movable along the force application lever, the end of the force application lever away from the weight being connected to the lower end of the L-shaped lever via a rope 302-3-4, and also includes a fixed pulley 302-3-5 for changing the direction of the force on the rope. It also includes a traction bracket 302-3-6 set on the linear motion mechanism. The traction bracket is connected to the weight by a flexible rope. The weight is pulled by the traction bracket to move on the force lever. The linear motion mechanism is controlled by a main controller. The linear motion mechanism can be a lead screw slider mechanism or an electric push rod.

[0040] Specifically, a fixed pulley 302-3-5 is fixed to the bottom platform 307. A rope connected to the lower end of the L-shaped lever passes through the bottom of the fixed pulley and connects upwards to one end of the force-applying lever 302-3-1. A weight 302-3-3 is placed at the other end of the force-applying lever. During the test, the weight is moved by the traction bracket. The pressure exerted by the weight on the force-applying lever at different positions is then converted into tension through the rope and transmitted to the lower end of the L-shaped lever. The L-shaped lever can rotate around the rotating support rod, so a bending load can be applied to the concrete under test at the upper end of the L-shaped lever. The two ends of the rotating support rod are fixed to the left end plate and the right end plate, respectively. Applying the bending load from above the concrete under test avoids interference with the bending load support and displacement sensor 306 below the concrete under test.

[0041] The compression loading mechanism applies compressive loads to the concrete under test, while the bending loading mechanism applies bending loads. This system can achieve dual loading of compressive and bending creep loads, further simulating the complex stress load conditions of actual concrete in real working environments, overcoming the shortcomings of concrete creep testing that only applies a single compressive or bending load.

[0042] A longitudinal pressure sensor 303 is installed along the longitudinal direction of the concrete to be tested, a transverse pressure sensor 304 is installed along the transverse direction of the concrete to be tested, a strain sensor 305 is installed along the direction of compression deformation of the concrete to be tested, and a displacement sensor 306 is installed below the concrete to be tested. All the longitudinal, transverse, strain, and displacement sensors are electrically connected to the main controller. These sensors allow for the rapid acquisition of experimental data such as pressure, displacement, and strain, solving the problem of difficult data acquisition in low-vacuum environments.

[0043] Preferably, the system also includes a hydraulic pump station system 6 and an oil pipeline. The hydraulic pump station system is connected to the hydraulic jack 301-7 via the oil pipeline, and the hydraulic pump station system is electrically connected to the main controller. The main controller regulates the hydraulic jack by controlling the hydraulic pump station system, outputting the pressure required for the experimental test.

[0044] Preferably, the main controller includes a computer host 101 and a line control terminal 102. The computer host and the line control terminal are electrically connected. The line control terminal is then electrically connected to the integrated concrete creep testing device, the vacuum control system, and the temperature regulation system. The various lines inside the vacuum chamber are connected to the line control terminal through line delivery pipes. The oil delivery pipes of the hydraulic pump station system are also connected to the hydraulic jack through line delivery pipes.

[0045] In this embodiment, multiple vacuum chambers 2 are connected in parallel to form a vacuum chamber group. Each vacuum chamber is equipped with an integrated compression-bending concrete creep testing device 3 and a temperature control system 4. The vacuum branch pipes 503-1 of each vacuum chamber converge into a main vacuum pipe 503-2 and connect to a vacuum pump 501. Each vacuum branch pipe is equipped with a vacuum control valve 504. In actual use, the vacuum chamber group can use a large main chamber, which is divided into multiple independent chambers by partitions 201. Each independent chamber is equipped with a door 202, and the door has a transparent observation area 202-1, which allows for real-time observation of the conditions inside each chamber. The strength of the main chamber and each partition should be able to withstand the pressure generated by different chambers.

[0046] Based on the low-vacuum environment concrete creep testing system disclosed in the embodiments of the present invention, a method for testing the creep of concrete in a low-vacuum environment is provided, including the following steps:

[0047] Step 1: Place the concrete to be tested on the bending load support, adjust the fixing bolts so that both ends of the concrete to be tested contact the left pressure plate and the right pressure plate respectively, and at the same time, make the longitudinal pressure sensor and the transverse pressure sensor contact the concrete to be tested.

[0048] Step 2: Fix the strain sensor and displacement sensor onto the concrete to be tested.

[0049] Step 3: The main controller preloads the concrete to be tested with stress, controls the jack to apply a compressive creep stress of 20% of the target value to the concrete, and controls the linear motion mechanism to drive the traction bracket, thereby pulling the weight on the force lever to apply a bending creep stress of 20% of the target value to the concrete. Check the values ​​of the strain sensor and displacement sensor. If the deformation difference between the left and right sides of the concrete is less than 10%, continue the test; otherwise, remove the load and reload.

[0050] Step 4: After preloading is completed, the ambient temperature and vacuum level are set through the main controller, and compressive creep stress and flexural creep stress of the same target value are applied, and the deformation information of the concrete to be tested is collected in real time.

[0051] Step 5: After maintaining the load to the required age, remove the load and continue recording the deformation information after unloading. Step 6: Calculate the creep deformation of the concrete under loading and the creep recovery deformation under unloading in a low vacuum environment. This yields the creep test data of the concrete under test in a low vacuum environment.

[0052] In summary, the low-vacuum environment concrete creep testing system and its testing method of this embodiment can, on the one hand, conduct experimental tests in a low-vacuum environment, and on the other hand, apply compressive load and bending load to the concrete under test simultaneously.

[0053] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0054] Furthermore, if the present invention discloses or relates to mutually fixedly connected components or structural parts, then unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured using a casting process) (except where it is obviously impossible to use an integral molding process).

[0055] Furthermore, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in this invention include states or shapes that are similar to, analogous to, or close to those states or shapes. Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured using a one-piece molding process.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-vacuum environment concrete creep testing system, characterized in that: It includes a main controller (1), a vacuum chamber (2) and a pressure-bending integrated concrete creep testing device (3) installed in the vacuum chamber. The pressure-bending integrated concrete creep testing device is electrically connected to the main controller. A temperature regulation system (4) is installed in the vacuum chamber. The integrated compression-bending concrete creep testing device (3) includes a compression force application mechanism (301) for applying compressive load to the concrete to be tested and a bending force application mechanism (302) for applying bending load to the concrete to be tested. A longitudinal pressure sensor (303) is arranged along the longitudinal direction of the concrete to be tested, a transverse pressure sensor (304) is arranged along the transverse direction of the concrete to be tested, a strain sensor (305) is arranged along the compression deformation direction of the concrete to be tested, and a displacement sensor (306) is arranged below the concrete to be tested. The longitudinal pressure sensor, transverse pressure sensor, strain sensor, and displacement sensor are all electrically connected to the main controller. The compression force application mechanism (301) includes a transverse tie rod (301-1) with external threads and a left end plate (301-2), a spring (301-3), a left pressure plate (301-4), a right pressure plate (301-5), and a right end plate (301-6) sequentially sleeved on the transverse tie rod from left to right. The left pressure plate and the right pressure plate are used to place the concrete to be tested. A hydraulic jack (301-7) is provided between the right pressure plate and the right end plate. Both sides of the left end plate, the left pressure plate, the right pressure plate, and the right end plate are fixed to the transverse tie rod by fixing bolts (301-8). The bending force application mechanism includes a rotating support rod (302-1), an L-shaped lever (302-2) fixed on the rotating support rod and rotatable around the rotating support rod, the upper end of the L-shaped lever being horizontally set to apply bending load to the concrete block, the lower end of the L-shaped lever being vertically set and connected to the lever load application component (302-3), and also includes a bending load support (302-4) set at the bottom of the concrete to be tested.

2. The low-vacuum environment concrete creep testing system according to claim 1, characterized in that: The lever load application assembly includes a force-applying lever (302-3-1), a lever bracket (302-3-2) for supporting the force-applying lever, and a weight (302-3-3) placed on the force-applying lever and movable along the force-applying lever. The end of the force-applying lever away from the weight is connected to the lower end of the L-shaped lever via a rope (302-3-4). It also includes a fixed pulley (302-3-5) for changing the direction of force on the rope.

3. The low-vacuum environment concrete creep testing system according to claim 2, characterized in that: It also includes a linear motion mechanism and a traction bracket (302-3-6) mounted on the linear motion mechanism. The traction bracket is connected to the weight by a flexible rope, and the linear motion mechanism is controlled by a main controller.

4. The low-vacuum environment concrete creep testing system according to claim 3, characterized in that: The vacuum chamber is equipped with a vacuum control system, which includes a vacuum pump (501) and a vacuum pressure sensor (502) installed in the vacuum chamber. The vacuum pump is connected to the vacuum chamber through a vacuum tube (503), and a vacuum control valve (504) is installed on the vacuum tube. The vacuum pressure sensor, vacuum pump and vacuum control valve are all electrically connected to the main controller.

5. The low-vacuum environment concrete creep testing system according to claim 4, characterized in that: The temperature control system (4) includes a temperature sensor (403), a heating tube (401), and a cooling tube (402) installed in the vacuum chamber. The temperature sensor, heating tube, and cooling tube are all electrically connected to the main controller.

6. The low-vacuum environment concrete creep testing system according to claim 5, characterized in that: It also includes a hydraulic pump station system (6) and an oil pipeline, wherein the hydraulic pump station system is connected to a hydraulic jack (301-7) via the oil pipeline and is electrically connected to the main controller.

7. A method for testing the creep of concrete in a low-vacuum environment using the low-vacuum environment concrete creep testing system as described in claim 6, characterized in that: Includes the following steps: Place the concrete to be tested on the bending load support, adjust the fixing bolts so that both ends of the concrete to be tested contact the left pressure plate and the right pressure plate respectively, and at the same time make the longitudinal pressure sensor and the transverse pressure sensor contact the concrete to be tested; fix the strain sensor and the displacement sensor on the concrete to be tested. The main controller preloads stress onto the concrete to be tested, controls the jack to apply compressive creep stress of 20% of the target value to the concrete, and controls the linear motion mechanism to drive the traction bracket, thereby pulling the weight to move on the force lever and applying bending creep stress of 20% of the target value to the concrete. The values ​​of the strain sensor and displacement sensor are checked. If the deformation difference between the left and right sides of the concrete to be tested is less than 10%, the test continues; otherwise, the load is removed and reloaded. After preloading is completed, the ambient temperature and vacuum level are set through the main controller, and compressive creep stress and flexural creep stress of the same target value are applied. The deformation information of the concrete to be tested is collected in real time. After the loading is maintained until the required age, the load is unloaded and the deformation information after unloading continues to be recorded. Calculate the creep deformation of concrete under loading and the creep recovery deformation under unloading in a low vacuum environment.

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