Early crack resistance testing device for concrete

Abstract

The utility model discloses a concrete early-stage crack resistance testing device which comprises a test mold used for forming a concrete sample, the test mold comprises a frame and a crack induction unit, and the crack induction unit is detachably connected with the frame; the plastering mechanism is used for trowelling and finishing the surface of the concrete sample; a transportation platform of the flat car is provided with a lifting mechanism, and the lifting mechanism is provided with a test mold placing platform; the ventilation device comprises a bottom frame and a ventilation hood, the lower portion of the bottom frame is provided with the flat car containing space, the ventilation hood is installed on the upper portion of the bottom frame through a first telescopic rod, a fan is installed in the ventilation hood, and an anemograph and a hygrothermograph are installed below the ventilation hood; and the crack positioning observation mechanism is detachably mounted and fixed on the bottom frame of the ventilation device. The test mold is convenient to carry and disassemble, the wind speed, the temperature and the humidity can be monitored in real time, and cracks are convenient to observe and position.

Description

Technical Field

[0001] This utility model relates to a test device for early crack resistance of concrete. Background Technology

[0002] According to the requirements of GB / T 50082-2019 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" and DL / T 5150-2017 "Test Procedures for Hydraulic Concrete", it is necessary to test the early crack resistance of concrete specimens under constrained conditions. A flat, thin-plate steel mold with dimensions of 800*600*100mm is used for the test, with seven crack inducing devices arranged along its long side. The mold is part of the testing apparatus and is connected to the specimen during testing.

[0003] Early crack resistance tests were conducted in a constant temperature and humidity chamber at 20±2℃ and 60±5% relative humidity. Concrete molds were poured, shaped, and leveled. Immediately after 30 minutes, the fan position and speed were adjusted so that the wind speed at 100mm directly above the center of the specimen surface was 5±0.5m / s, with the wind direction parallel to the specimen surface and the crack inducing device. Cracks were measured 24±0.5 hours after the concrete mixing and water addition. Crack length was measured with a steel ruler, and the straight-line distance between the two ends of the crack was taken as the crack length. When there were two cracks on one cutting edge, their lengths were added together and counted as one crack. Crack width was measured using a reading microscope with at least 40x magnification, and the maximum width of each crack was also measured.

[0004] The test results are taken as the arithmetic mean of the average crack area of ​​two or more specimens as the measured value of the average crack area (number of cracks per unit area or total crack area per unit area) of the group of specimens.

[0005] Existing methods for testing the early crack resistance of concrete have the following drawbacks:

[0006] 1) The frame of the test mold is connected to the crack inducer by welding. The concrete sample cannot be directly removed and needs to be manually chiseled away, which is time-consuming and labor-intensive.

[0007] 2) The trial mold is heavy and difficult to move;

[0008] 3) The sample surface is uneven;

[0009] 4) It is inconvenient to test wind speed by manually holding the anemometer or by using a magnetic base to clamp it to a designated position;

[0010] 5) The temperature and humidity meter is fixed on the wall of the curing room, which deviates from the temperature and humidity around the sample, which may affect the crack development pattern of the concrete specimen.

[0011] 6) Cracks require a handheld magnifying glass for observation, and locating the cracks is difficult. Utility Model Content

[0012] The technical problem to be solved by this utility model is that, in view of the shortcomings of existing concrete early crack resistance testing devices, such as bulky test molds that are difficult to transport and disassemble, inconvenient wind speed testing, deviations in temperature and humidity testing, and difficulty in observing cracks, this utility model provides a concrete early crack resistance testing device that can facilitate sample transportation and sampling, and facilitates the measurement of wind speed, temperature and humidity, and cracks.

[0013] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0014] A device for testing the early crack resistance of concrete, comprising:

[0015] A mold for molding concrete specimens, the mold comprising a frame and a crack inducer, the crack inducer being detachably connected to the frame;

[0016] A finishing mechanism used to smooth and finish the surface of concrete samples.

[0017] A flatbed truck for transporting concrete samples, wherein a lifting mechanism is installed on the transport platform of the flatbed truck, and a mold placement platform is provided on the lifting mechanism;

[0018] A ventilation device for curing concrete samples by drying shrinkage includes a base frame and a ventilation hood. The lower part of the base frame is provided with a space for accommodating the flatbed cart. The upper part of the base frame is equipped with the ventilation hood via a first telescopic rod. A fan is installed inside the ventilation hood. An anemometer and a thermometer and hygrometer are installed below the ventilation hood.

[0019] The crack location observation mechanism for measuring cracks is detachably installed and fixed on the base frame of the ventilation device.

[0020] This invention utilizes a detachable mold to facilitate sample removal. Simultaneously, a flatbed cart allows for convenient early-stage crack-resistant specimen molding in the concrete mixing chamber. Once molded, the flatbed cart easily pushes the specimens to the drying shrinkage curing chamber, avoiding the arduous manual handling of the molds and samples, and facilitating manual observation of cracks. Furthermore, this invention installs an anemometer and a thermometer / hygrometer on the ventilation system, enabling real-time monitoring of wind speed and ambient temperature and humidity. The ambient temperature and humidity detection is accurate and without deviation. The crack positioning and observation mechanism is fixed to the base of the ventilation system, eliminating the need for a handheld magnifying glass to locate cracks and observe their width.

[0021] Furthermore, the crack inducer has a cavity in the middle, within which a screw is installed. A spring is fitted onto the screw, and the two ends of the screw are secured by bolts passing through the frame and compressing the spring. Thus, when disassembling the mold, simply loosening the bolts allows the frame to separate from the crack inducer under the action of the spring, facilitating the removal of the concrete sample.

[0022] Furthermore, the smoothing mechanism includes two retractable supports, a roller guide rail is installed between the two supports, a roller shaft is installed on the roller guide rail, and a push rod for driving the roller shaft is installed on the roller shaft. In this way, the height and level of the two supports and the roller guide rail can be adjusted by the retractable supports, thereby ensuring that the roller shaft smooths the surface evenly.

[0023] Furthermore, the lifting mechanism is an electric lifting mechanism, and the flatbed truck is equipped with a control switch for controlling the lifting mechanism's movement.

[0024] Furthermore, the crack location and observation mechanism includes a second telescopic rod, with a magnifying glass bracket hinged to the end of the second telescopic rod. A magnifying glass for crack measurement is installed inside the magnifying glass bracket. This allows for convenient adjustment of the magnifying glass's height and angle during crack measurement.

[0025] Furthermore, a rotary knob is installed on the hinge axis between the second telescopic rod and the magnifying glass bracket to facilitate adjustment of the measuring angle of the magnifying glass.

[0026] Compared with the prior art, the beneficial effects of this utility model are:

[0027] This invention utilizes a detachable mold to facilitate sample removal. Simultaneously, a flatbed cart allows for convenient early-stage crack-resistant specimen molding in the concrete mixing chamber. Once molded, the flatbed cart easily pushes the specimens to the drying shrinkage curing chamber, avoiding the arduous manual handling of the molds and samples, and facilitating manual observation of cracks. Furthermore, this invention installs an anemometer and a thermometer / hygrometer on the ventilation system, enabling real-time monitoring of wind speed and ambient temperature and humidity. The ambient temperature and humidity detection is accurate and without deviation. The crack positioning and observation mechanism is fixed to the base of the ventilation system, eliminating the need for a handheld magnifying glass to locate cracks and observe their width. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of an embodiment of the overall structure of this utility model used for dry shrinkage curing.

[0030] Figure 2 This is a schematic diagram of the prototype mold.

[0031] Figure 3 This is a schematic diagram showing the usage state of this utility model for applying a sample surface.

[0032] Figure 4 This is a schematic diagram of the crack location and observation mechanism.

[0033] Figure 5 This is a flowchart for conducting early crack resistance tests on concrete using this invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0035] In the description of this utility model, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0037] Please see Figure 1 - Figure 4 An embodiment of the concrete early crack resistance testing device of this utility model includes the following components:

[0038] A mold 1 for molding concrete specimens, the mold 1 including a frame 11 and a crack inducer 12, the crack inducer 12 being detachably connected to the frame 11 to facilitate the removal of the specimen;

[0039] Surface finishing mechanism 2 for smoothing and finishing the surface of concrete samples;

[0040] A flatbed truck 3 is used for transporting concrete samples. A lifting mechanism 31 is installed on the transport platform of the flatbed truck 3, and a mold placement platform is set on the lifting mechanism 31.

[0041] A ventilation device 4 for drying shrinkage curing concrete samples includes a base frame 41 and a ventilation hood 42. The lower part of the base frame 41 is provided with a flatbed trolley accommodating space 43. The upper part of the base frame 41 is equipped with the ventilation hood 42 through a first telescopic rod 44. A fan 45 is installed inside the ventilation hood 42. An anemometer 46 and a thermometer and hygrometer 47 are installed below the ventilation hood 42.

[0042] The crack location observation mechanism 5, used for measuring cracks, is detachably installed and fixed on the base frame 41 of the ventilation device 4.

[0043] In this embodiment, as Figure 2 As shown, the crack inducer 12 has a cavity in the middle, and a screw 13 is installed in the cavity. A spring (not shown in the figure) is fitted on the screw 13. The two ends of the screw 13 are fastened with bolts 14 that pass through the frame 11. When the bolts 14 are tightened, the spring is compressed. After the sample is formed, the bolts 14 are removed, and the frame 11 can be separated from the crack inducer 12 under the restoring force of the spring, so that the concrete sample can be taken out. The process does not require manual chiseling and cleaning.

[0044] like Figure 3 As shown, the finishing mechanism 2 includes two telescopic supports 21, with a roller guide rail 22 installed between the two supports 21. A roller shaft 23 is installed on the roller guide rail 22, and a push rod 24 for driving the roller shaft 23 is installed on the roller shaft 23. When using the finishing mechanism 2, first adjust the height of the two telescopic supports 21 and the level of the roller guide rail 22 (achieved by adjusting the height of the two telescopic supports 21). Then, push the flatbed cart 3 containing the test mold 1 under the finishing mechanism 2. After that, finely adjust the height of the telescopic supports 21 so that the roller guide rail 22 contacts the concrete sample. Then, the push rod 24 can be used to push the roller shaft 23 to move along the length of the test mold 1, thereby achieving the smoothing and finishing of the sample.

[0045] For ease of use, the lifting mechanism 31 is an electric lifting mechanism, and the flatbed trolley 3 is equipped with a control switch 32 for controlling the lifting mechanism 31.

[0046] like Figure 4 As shown, the crack positioning and observation mechanism 5 includes a second telescopic rod 51, with a magnifying glass bracket 52 hinged to the end of the second telescopic rod 51. A crack measuring magnifying glass 53 is installed inside the magnifying glass bracket 52, and a rotating knob 54 is installed on the hinge axis between the second telescopic rod 51 and the magnifying glass bracket 52.

[0047] like Figure 5 As shown, the detailed implementation steps for conducting early crack resistance testing of concrete using this invention include:

[0048] 1) Molding of early-stage crack-resistant concrete specimens

[0049] After the mixed concrete is poured into the mold 1 in the concrete mixing room, the concrete is immediately spread out and the height of the support 21 of the finishing mechanism 2 is adjusted according to the concrete slump. After tamping with a vibrator, the roller shaft 23 is pushed by the push rod 24 to level the concrete surface. Then, the mold 1 and the sample are pushed to the concrete drying shrinkage curing room by the flatbed truck 3.

[0050] 2) Sample curing and monitoring of wind speed, temperature and humidity

[0051] Install ventilation device 4 above mold 1 and specimen, and start ventilation device 4. Observe the anemometer 46 located above the center of specimen surface, adjust the wind speed of fan 45 to 5 m / s ± 0.5 m / s, and make the wind direction parallel to specimen surface and crack inducer 12. Adjust the existing concrete drying shrinkage curing temperature and humidity control equipment, and observe the temperature and humidity through thermometer and hygrometer 47, so that the specimen is at a temperature of 20℃ ± 2℃ and a relative humidity of 60% ± 5%.

[0052] 3) Crack observation

[0053] The cracks are measured 24 hours after the concrete mixing and water addition begins. When measuring the cracks, the lifting mechanism 31 is activated until the sample observation surface is in the optimal observation position for the tester. Then, the magnifying glass 53 is rotated to observe the cracks at each crack inductor 12. Mark the crack positions with a marker. Using the scale of the magnifying glass 53 (magnifying glasses with scales are readily available), the widest point of each crack is directly identified, and the maximum crack width is read. The crack length is measured with a steel ruler, and the straight-line distance between the two ends of the crack is taken as the crack length. For two cracks on the same cutting edge, the lengths of the two cracks are added together and converted into one crack.

[0054] The average crack area of ​​the sample (the number of cracks per unit area or the total crack area per unit area) is calculated based on the number of cracks, the length of each crack, and the maximum width.

[0055] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can make many possible variations and modifications to the technical solution of this utility model, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of this utility model. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this utility model without departing from the content of the technical solution of this utility model should fall within the protection scope of the technical solution of this utility model.

Claims

1. A device for testing the early crack resistance of concrete, characterized in that... include: A mold for molding concrete specimens, the mold comprising a frame and a crack inducer, the crack inducer being detachably connected to the frame; A finishing mechanism used to smooth and finish the surface of concrete samples. A flatbed truck for transporting concrete samples, wherein a lifting mechanism is installed on the transport platform of the flatbed truck, and a mold placement platform is provided on the lifting mechanism; A ventilation device for curing concrete samples by drying shrinkage includes a base frame and a ventilation hood. The lower part of the base frame is provided with a space for accommodating the flatbed cart. The upper part of the base frame is equipped with the ventilation hood via a first telescopic rod. A fan is installed inside the ventilation hood. An anemometer and a thermometer and hygrometer are installed below the ventilation hood. The crack location observation mechanism for measuring cracks is detachably installed and fixed on the base frame of the ventilation device.

2. The early-stage crack resistance testing device for concrete according to claim 1, characterized in that, The crack inducer has a cavity in the middle, a screw is installed in the cavity, a spring is fitted on the screw, and the two ends of the screw are fastened by bolts passing through the frame and compressing the spring.

3. The early-stage crack resistance testing device for concrete according to claim 1, characterized in that, The finishing mechanism includes two retractable supports, a roller guide rail is installed between the two supports, a roller shaft is installed on the roller guide rail, and a push rod for driving the roller shaft is installed on the roller shaft.

4. The early-stage crack resistance testing device for concrete according to claim 1, characterized in that, The lifting mechanism is an electric lifting mechanism, and the flatbed truck is equipped with a control switch for controlling the lifting mechanism's movement.

5. The early-stage crack resistance testing device for concrete according to claim 1, characterized in that, The crack location and observation mechanism includes a second telescopic rod, with a magnifying glass bracket hinged to the end of the second telescopic rod, and a magnifying glass for crack measurement installed inside the magnifying glass bracket.

6. The early-stage crack resistance testing device for concrete according to claim 5, characterized in that, A rotary knob is installed on the hinge shaft between the second telescopic rod and the magnifying glass bracket.

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