A test device for bond strength of fresh concrete

Abstract

This utility model discloses a bonding strength testing device for freshly mixed concrete, including a CNC system, and further comprising: a main frame with a material container positioning groove at its bottom; a material container with its bottom installed in the positioning groove; a power mechanism located in the upper part of the main frame for driving a transmission mechanism to move vertically; a transmission mechanism connected to the power mechanism; a tension sensor with its upper end connected to the lower end of a lifting component on the transmission mechanism; and a test piece detachably connected to the lower end of the tension sensor via a quick-release assembly; wherein both the power mechanism and the tension sensor are connected to the CNC system. This utility model solves the problems of tension direction deviation, insufficient measurement accuracy, water absorption interference from the test piece, and limitations of single-dimensional testing in the prior art, enabling rapid and accurate evaluation of the bonding performance between freshly mixed concrete and the top and sidewalls of the surrounding rock in tunnel construction scenarios.

Description

Technical Field

[0001] This utility model relates to a test device for the bond strength of freshly mixed concrete, belonging to the technical field of wet-sprayed concrete performance testing. Background Technology

[0002] In tunnel engineering, initial support is a crucial step in ensuring construction safety and the stability of the surrounding rock. Shotcrete, as a core component of initial support, together with steel arches, steel mesh, and anchor bolts, constitutes the initial support system. Its construction process involves spraying freshly mixed concrete at high speed through pipes under the action of compressed air onto the excavated tunnel rock wall (the sprayed surface), and then instantly compacting it with impact.

[0003] Currently, wet shotcrete technology has become the mainstream form of shotcrete construction for the initial support of tunnels due to its advantages such as low dust concentration in the working environment and good uniformity of concrete quality. However, the inherent characteristics of wet shotcrete process determine that a certain amount of concrete rebound will inevitably occur during the spraying process. This rebound phenomenon brings about several significant problems. (1) Increased economic costs: Rebound material is usually difficult to recycle effectively, resulting in direct waste of concrete materials and significantly increasing construction costs. (2) Occupational health hazards: Rebound material disperses in the air, increasing the dust concentration in the working environment and posing a serious threat to the respiratory health of on-site construction personnel. (3) Engineering quality risks: The proportion of coarse aggregate in the rebound material is usually high, which means that the actual cementitious material content and sand ratio of the concrete effectively sprayed onto the sprayed surface are relatively higher. This change in composition will increase the shrinkage tendency of hardened concrete, thereby increasing its cracking risk and ultimately having an adverse effect on the long-term durability of the support structure.

[0004] In-depth research shows that the rebound rate of wet-mixed shotcrete is closely related to its adhesion performance to the sprayed surface in its fresh state. During the spraying process, when concrete is sprayed at high speed onto the surrounding rock or other substrate surface, the concrete must temporarily adhere to the sprayed surface (such as rock, existing concrete, or support structure) based on its own adhesive ability before the accelerator can induce sufficient bond strength in the cement paste. If the initial bond strength between the fresh concrete and the sprayed surface is insufficient, the sprayed concrete layer may locally debond under gravity, peeling off in sheet or block form, thus causing rebound. Therefore, scientifically controlling the adhesion performance of the fresh concrete (enhancing the bond strength with the sprayed surface) is an effective way to reduce the rebound rate of shotcrete.

[0005] However, the core dilemma currently facing engineering practice lies in the lack of standardized devices and methods for objectively and quantitatively testing the adhesion properties of fresh concrete. Construction workers primarily rely on empirical observation (such as visually assessing the concrete's "viscosity" and its adhesion to the shovel) or indirect indicators (such as slump) to subjectively judge its performance, which is highly ambiguous and uncertain. This lack of quantitative testing methods severely restricts the accurate prediction of the spraying performance of fresh concrete, making it difficult to achieve the goal of proactively controlling the rebound rate based on material performance optimization. This poses a significant obstacle to improving the efficiency of wet-mixed sprayed concrete construction, reducing costs, ensuring worker health, and maintaining project quality.

[0006] A search revealed a Chinese utility model patent, publication number CN 116698735 A, which discloses a test device and method for testing the adhesion force of sprayed concrete. The device includes a mold, a test plate, a support frame, a rope assembly, and a tension assembly. During the test, the test plate is attached to the surface of freshly mixed concrete. One end of the rope assembly is fixedly connected to the top of the test plate, and the other end passes through a pulley mechanism and is connected to the tension assembly. Through the rope assembly, the tension assembly applies tension to the test plate, thereby determining the magnitude of the adhesion force between the test plate and the freshly mixed concrete. However, the device has the following shortcomings: (1) The tensile component and the test plate are connected by a flexible method, which makes it difficult to ensure that the tensile direction is perpendicular to the test plate during each test, thus affecting the comparability of the test results; (2) The tensile testing device has a relatively simple structure, which may not be able to accurately capture the maximum adhesion force between the test plate and the fresh concrete, affecting the measurement accuracy; (3) The test plate is a rock sheet, which is absorbent and will interfere with the test results of the adhesion force; (4) The adhesion force measured by the device can only reflect the adhesion performance between the fresh concrete and the top of the tunnel surrounding rock, and cannot reflect the adhesion performance between it and the tunnel sidewall.

[0007] Therefore, the key to solving the above-mentioned technical problems lies in developing a rapid and accurate test device for measuring the bond strength of freshly mixed concrete. Utility Model Content

[0008] In view of the many defects and shortcomings of the above-mentioned background technology, this utility model has made improvements and innovations, aiming to provide a fresh concrete bonding force testing device to solve the problems of tensile force direction deviation, insufficient measurement accuracy, water absorption interference of test specimens and single-dimensional testing limitations in the existing technology, so as to realize rapid and accurate evaluation of the bonding performance between fresh concrete and the top and side walls of the surrounding rock in tunnel construction scenarios.

[0009] To solve the above problems and achieve the above-mentioned utility model objectives, this utility model provides a test device for the bond strength of freshly mixed concrete, which is achieved by adopting the following design structure and the following technical solution:

[0010] A device for testing the bond strength of freshly mixed concrete includes a numerical control system and further includes:

[0011] The main frame has a material holding bucket positioning groove at the bottom inside the main frame;

[0012] The bottom of the material container is installed in the positioning groove of the material container;

[0013] The power mechanism is located in the upper part of the main frame and is used to drive the transmission mechanism to move vertically.

[0014] Transmission mechanism, which connects to the power mechanism;

[0015] The upper end of the tension sensor is connected to the lower end of the lifting component on the transmission mechanism;

[0016] The test piece is detachably connected to the lower end of the tension sensor via a quick-release assembly.

[0017] The power mechanism and the tension sensor are both connected to the CNC system.

[0018] Preferably, the main frame includes a base and a vertical frame connected above the base, wherein the material container positioning groove is opened in the middle of the base, and several bayonets are circumferentially connected on the material container positioning groove.

[0019] Preferably, the bottom outer periphery of the material container is provided with several flanges that are adapted to each of the slots, and the wall of the material container is marked with concrete filling height scale lines;

[0020] The power mechanism includes: a motor connected to one end of the base plate inside the main frame; and a power supply connected to the base plate inside the main frame.

[0021] The power supply is connected to the motor, the tension sensor, and the CNC system.

[0022] Preferably, the motor is a servo motor.

[0023] Preferably, the transmission mechanism includes:

[0024] The coupling is connected at its upper end to the output end of the motor.

[0025] The upper end of the ball screw is connected to the lower end of the coupling;

[0026] A lead screw nut is embedded in one end of the lifting component and extends through the lifting component.

[0027] The guide rails are symmetrically connected in pairs to both ends inside the vertical frame;

[0028] The lifting component has sliders connected to its four corners, and each slider is slidably connected to the guide rail at the corresponding end.

[0029] The lower end of the ball screw is threadedly connected to the screw nut.

[0030] Preferably, the ball screw and the guide rails on both sides form a rigid transmission structure, which is used to forcibly limit the lifting trajectory to the vertical direction.

[0031] Preferably, the tension sensor is a high-precision tension sensor, and the upper end of the high-precision tension sensor is detachably installed to the lower middle part of the lifting component via a connector;

[0032] Preferably, the quick-connect assembly includes: a quick-connect male connector whose lower end is connected to the upper end of the test piece; a quick-connect female connector whose upper end is connected to the lower end of the tension sensor; the quick-connect male connector and the quick-connect female connector are snapped together as an integral structure.

[0033] Preferably, the CNC system includes an integrated display screen, a control panel, and a data processing module, used to control test parameters, automatically calculate, and output the adhesion force value.

[0034] In this invention, the data processing module includes a pre-set formula for calculating the adhesive force: transverse adhesive force σ h =F h / A, longitudinal adhesion force σ z =F z / 2A, where F h F z denoted as peak tensile force, and A as the area of ​​the test specimen.

[0035] Preferably, the test piece includes:

[0036] The transverse test piece includes a transverse test plate and connecting rods that are inclinedly connected to the four corners above the transverse test plate. The non-connecting ends of the four connecting rods are respectively connected to the lower part of the quick-release assembly, and the quick-release assembly is vertically located at the upper center of the transverse test plate.

[0037] The longitudinal test piece includes a longitudinal test plate and two fixing rods that are inclinedly connected to the upper ends of the transverse test plate. The non-connecting ends of the two fixing rods are respectively connected to the lower part of the quick-release assembly, and the quick-release assembly is vertically located at the upper middle part of the longitudinal test plate.

[0038] When the transverse test specimen is preloaded, the test surface is parallel to the concrete surface; when the longitudinal test specimen is inserted into the concrete, the test surface is perpendicular to the concrete surface.

[0039] The beneficial effects of this utility model compared with the prior art are:

[0040] 1. This utility model effectively achieves precise control of the lifting speed by incorporating a servo motor, ensuring that it remains strictly within the set value range. This avoids deviations in adhesive force measurement caused by speed fluctuations and completely solves the problems of large tension fluctuations and high data dispersion in existing technologies.

[0041] 2. This utility model ensures more precise power transmission between the servo motor and the ball screw by setting a coupling; at the same time, it adopts a high-precision centering installation method to force the coaxiality of the motor shaft and the ball screw, prevent guide rail wear caused by off-center load, and effectively suppress the high-frequency vibration generated during the start and stop of the servo motor, thereby improving the stability of the tension sensor data.

[0042] 3. This utility model, by setting up a ball screw and guide rails, forms a rigid constraint between the ball screw and the double-sided guide rails, ensuring absolutely vertical lifting and completely solving the problem of skewed pulling force direction caused by traditional flexible transmission.

[0043] 4. This utility model is equipped with a high-precision tensile sensor and uses a high-resolution strain gauge sensor, which can accurately detect the peak tensile force at the moment of concrete bond failure.

[0044] 5. This utility model, by incorporating quick-installation components and adopting a quick-disassembly structure, significantly reduces the installation and disassembly time of transverse / longitudinal test pieces, thereby significantly improving on-site testing efficiency.

[0045] 6. This utility model uses transverse and longitudinal test specimens, where the transverse test specimen is used to accurately simulate the bonding performance between the tunnel arch and wet shotcrete, and the longitudinal test specimen is used to realistically reproduce the bonding performance between the tunnel sidewall and wet shotcrete, thereby achieving synchronous quantitative evaluation of the bidirectional bonding performance of shotcrete "top-sidewall" using a single device.

[0046] 7. This utility model, by setting a positioning groove for the material container and adopting a precision-machined snap-fit ​​groove structure, forces the center of the material container to be coaxially aligned with the lifting axis, effectively avoiding non-vertical force phenomena caused by the offset of the container body.

[0047] 8. This utility model ensures that the concrete filling height remains consistent each time it is filled by setting a concrete filling height scale line; this scale line also serves as a leveling reference, which helps to obtain a smooth concrete surface and avoids local stress concentration caused by uneven surface, thereby realizing the transformation of fluid fresh concrete into a standardized test sample with controllable geometric parameters, providing a repeatable metrological basis for bond strength testing.

[0048] 9. This utility model is equipped with a numerical control system that integrates servo drive, tension sensing and data processing modules to achieve closed-loop control of the entire process of "pre-compression-lifting-peak capture-result output".

[0049] 10. This utility model significantly improves the efficiency and reliability of on-site testing, providing key technical support for optimizing wet sprayed concrete mix proportions, reducing rebound rate, and ensuring construction quality and efficiency. Attached Figure Description

[0050] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings, wherein:

[0051] Figure 1 This is a diagram showing the usage state of this utility model;

[0052] Figure 2 This is one of the overall structural schematic diagrams of this utility model;

[0053] Figure 3 This is the second schematic diagram of the overall structure of this utility model;

[0054] Figure 4 This is a partial structural schematic diagram of the present invention;

[0055] Figure 5 This is a utility model Figure 4 Exploded view;

[0056] Figure 6 This is a schematic diagram of the host frame structure of this utility model;

[0057] Figure 7 This is a schematic diagram showing the connection relationship between the quick-assembly component and the test piece of this utility model;

[0058] Figure 8 This is a schematic diagram showing the connection relationship between the quick-release male connector of this utility model and the transverse test piece;

[0059] Figure 9 This is a schematic diagram showing the connection relationship between the quick-release male connector of this utility model and the longitudinal test piece;

[0060] Figure 10 This is one of the usage state diagrams of another design structure of this utility model;

[0061] Figure 11 This is another design structure of this utility model in use, shown in the second diagram.

[0062] Figure 12 This is one of the schematic diagrams of the overall structure of another design of this utility model;

[0063] Figure 13 This is another schematic diagram of the overall structure of this utility model;

[0064] In the figure, the numbers are: 1—main frame 1, 11—base 11, 12—vertical frame 12, 13—material container positioning groove 13, 14—leveling anchor screw 14.

[0065] 2—Containing bucket 2, 21—Graduation line 21;

[0066] 3—Power mechanism 3, 31—Motor 31, 32—Power supply 32;

[0067] 4—Transmission mechanism 4, 41—Coupling 41, 42—Ball screw 42, 43—Screw nut 43, 44—Guide rail 44, 45—Lifting component 45;

[0068] 5—Tension sensor 5;

[0069] 6—Quick-connect component 6, 61—Quick-connect male connector 61, 62—Quick-connect female connector 62;

[0070] 7—Test piece 7, 71—Transverse test piece 71, 711—Transverse test plate 711, 712—Connecting rod 712, 72—Longitudinal test piece 72, 721—Longitudinal test plate 721, 722—Fixing rod 722;

[0071] 8—CNC system 8, 81—Integrated display screen 81, 82—Control panel 82;

[0072] 9—Concrete 9. Detailed Implementation

[0073] To make the technical means, inventive features, objectives, and effects of this utility model readily understandable, the technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0074] In summary, a more specific embodiment of this utility model is as follows:

[0075] Example 1

[0076] As attached Figure 1-9 As shown, a test device for the bond strength of freshly mixed concrete includes a numerical control system 8, and further includes:

[0077] Main frame 1, with a material holding bucket positioning groove 13 at the bottom of the main frame 1;

[0078] Material container 2, the bottom of material container 2 is installed in material container positioning groove 13;

[0079] The power mechanism 3 is located in the upper part of the main frame 1 and is used to drive the transmission mechanism 4 to move vertically.

[0080] Transmission mechanism 4 is connected to power mechanism 3;

[0081] The upper end of the tension sensor 5 is connected to the lower end of the lifting member 45 on the transmission mechanism 4;

[0082] Test piece 7 is detachably connected to the lower end of the tension sensor 5 via quick-release assembly 6;

[0083] The power mechanism 3 and the tension sensor 5 are both connected to the CNC system 8.

[0084] In this invention, the CNC system 8 is an existing product that can be purchased from the market. The CNC system 8 is a programmable logic controller, a PLC, or a PC.

[0085] Furthermore, the main frame 1 includes a base 11 and a vertical frame 12 connected above the base 11, wherein a material container positioning groove 13 is opened in the middle of the base 11, and several bayonets are circumferentially connected on the material container positioning groove 13.

[0086] In this utility model, the base 11 is made of steel welded together, the vertical frame 12 is connected to the base 11 by bolts, the motor 31 and coupling 41 are installed on the top, and the coaxiality error between the motor output shaft and the ball screw 42 is ≤0.02mm.

[0087] Furthermore, the bottom outer periphery of the material container 2 is provided with several flanges that are adapted to each slot, and the wall of the material container 2 is marked with concrete filling height scale line 21.

[0088] The power mechanism 3 includes: a motor 31, which is connected to one end of the bottom plate inside the main frame 1; and a power supply 32, which is connected to the bottom plate inside the main frame 1.

[0089] The power supply 32 is connected to the motor 31, the tension sensor 5, and the CNC system 8.

[0090] In this utility model, motor 31 is a servo motor; motor 31 outputs power vertically downward, and the speed controller on the motor adjusts the speed range from 0.1 to 2 mm / s; the depth of the bayonet is 5 mm, and the width matches the bottom flange of the material container 2 to ensure that there is no loosening after the bayonet is fixed.

[0091] Furthermore, the transmission mechanism 4 includes:

[0092] Coupling 41, the upper end of which is connected to the output end of motor 31;

[0093] Ball screw 42, the upper end of which is connected to the lower end of coupling 41;

[0094] A lead screw nut 43 is embedded in one end of the lifting member 45 and is disposed through the lifting member 45.

[0095] Guide rail 44 is symmetrically connected to both ends of the interior of vertical frame 12 in pairs;

[0096] The lifting component 45 has sliders connected to its four corners, and each slider is slidably connected to the guide rail 44 at the corresponding end.

[0097] The lower end of the ball screw 42 is threadedly connected to the screw nut 43.

[0098] In this utility model, the ball screw 42 and the double-sided guide rails 44 form a rigid transmission structure, which forcibly limits the lifting trajectory to the vertical direction. The parallelism of the ball screw 42 and the double-sided guide rails 44 is ≤0.05mm. The screw nut 43 is rigidly connected to the lifting member 45 by bolts to ensure that the vertical lifting trajectory deviation is ≤0.1mm / m.

[0099] Furthermore, the tension sensor 5 is a high-precision tension sensor, and the upper end of the high-precision tension sensor is detachably installed to the lower middle part of the lifting member 45 via a connector;

[0100] The quick-connect assembly 6 includes: a quick-connect male connector 61 whose lower end is connected to the upper end of the test piece 7; a quick-connect female connector 62 whose upper end is connected to the lower end of the tension sensor 5; the quick-connect male connector 61 and the quick-connect female connector 62 are snapped together as an integral structure.

[0101] The numerical control system 8 includes an integrated display screen 81, a control panel 82, and a data processing module, which are used to control test parameters, automatically calculate and output the adhesion force value;

[0102] The data processing module includes a pre-set formula for calculating adhesive force: transverse adhesive force σ. h =F h / A, longitudinal adhesion force σ z =F z / 2A, where F h F z denoted as peak tensile force, and A as the area of ​​the test specimen.

[0103] In this invention, the tension sensor 5 is an S-shaped tension sensor, coaxially fixed between the lifting component 45 and the quick-release female head 62. The display screen 81, control panel 82, and data processing module are all integrated into the CNC system 8 and installed at the front of the main frame 1 for easy operation.

[0104] Specifically, the test piece 7 includes:

[0105] The transverse test piece 71 includes a transverse test plate 711 and connecting rods 712 that are inclinedly connected to the four corners above the transverse test plate 711. The non-connecting ends of the four connecting rods 712 are respectively connected to the lower part of the quick-release assembly 6, and the quick-release assembly 6 is vertically located at the upper center of the transverse test plate 711.

[0106] The longitudinal test piece 72 includes a longitudinal test plate 721 and fixed rods 722 that are inclinedly connected to the two ends above the transverse test plate 721. The non-connecting ends of the two fixed rods 722 are respectively connected to the lower part of the quick-release assembly 6, and the quick-release assembly 6 is vertically located at the upper middle part of the longitudinal test plate 721.

[0107] When the transverse test specimen 71 is subjected to preload, the test surface is parallel to the concrete surface; when the longitudinal test specimen 72 is inserted into the concrete, the test surface is perpendicular to the concrete surface.

[0108] In this utility model, the length of the longitudinal test plate 721 is less than the concrete filling height scale line 21 of the material container 2, and the width of the longitudinal test plate 721 is less than the inner diameter of the material container 2; the outer circle diameter of the transverse test plate 711 is slightly smaller than the inner diameter of the material container 2.

[0109] In the transverse test piece 71, the transverse test plate 711 has dimensions of 100mm×100mm×5mm and is connected to the quick-release male connector 61 by 4 connecting rods 712, with an included angle of 45° to uniformly transmit the tensile force.

[0110] In the longitudinal test piece 72, the longitudinal test plate 721 has dimensions of 100mm×100mm×5mm and is connected to the quick-connect male connector 61 by two fixing rods 722. Furthermore, the surfaces of the longitudinal test plate 721 and the transverse test plate 721 are sandblasted to simulate the rough surface of the surrounding rock of the tunnel.

[0111] Example 2

[0112] As attached Figure 10-13 As shown, it is basically the same as in Embodiment 1, except that leveling screws 14 are connected to the four corners of the bottom of the main frame 1.

[0113] Specifically, the surface of the main frame 1 is leveled by adjusting the leveling screws 14, with the error controlled within ±0.1°.

[0114] In this utility model, leveling screws 14 are connected to the four corners of the bottom of the main frame 1.

[0115] Alternatively, the leveling structure includes a screw and an adjusting nut threaded onto the screw, wherein one end of the screw is fixedly connected to the bottom of the frame, and the other end of the screw is threaded onto a base, which is circular or square.

[0116] Therefore, during use, the leveling structure at the bottom of the main frame can adapt to complex environments, enabling the testing device to adapt to different terrains and environmental conditions. This ensures that the equipment maintains good operating condition under various conditions, thereby improving the accuracy of measurement or operation and avoiding errors caused by unevenness.

[0117] The specific usage steps are as follows:

[0118] Step S1: Leveling device, pour freshly mixed concrete into the material container 2 up to the scale line 21, vibrate and scrape it level, and fix the material container 2;

[0119] Step S2: Select the transverse bond strength test mode on the CNC system 8, install the transverse test piece 71, and apply pre-pressure after the tension is set to zero to make the test surface adhere to the concrete.

[0120] Step S3: Based on step S2, the CNC system 8 controls the vertical lifting at a constant rate, and records the peak tension F. h Automatically calculate the transverse adhesion force σ h =F h / A;

[0121] Step S4: Switch to longitudinal bond strength test mode on CNC system 8, install longitudinal test piece 72, set the tension to zero, and insert it vertically into the concrete to the set depth;

[0122] Step S5: Based on step S4, the CNC system 8 controls the vertical lifting at a constant rate, and records the peak tension F. z Automatically calculate longitudinal adhesion force σ z =F z / 2A.

[0123] Specifically, the transverse adhesion test mode and the longitudinal adhesion test mode were each repeated 3 times;

[0124] The rules for determining the values ​​are as follows: if the difference between the maximum or minimum value and the median value is ≤10% of the median value, take the arithmetic mean; if the difference between a single value is >10% but ≤15% of the median value, take the median value; if the difference between both values ​​is >15% of the median value, the test is invalid.

[0125] Furthermore, the pre-pressure of the CNC system 8 is set to 30-70N, and the holding time is 10-15 seconds; the constant lifting rate during the transverse adhesion test is 0.1-0.5mm / s; and the constant lifting rate during the longitudinal adhesion test is 0.5-2mm / s.

[0126] In this utility model, when in use, the depth of the freshly mixed concrete in the container 2 is set so that the top surface of the longitudinal test plate 721 is flush with the concrete surface.

[0127] During the transverse adhesion test:

[0128] Step S1: First, level the main frame 1. Then, pour C25 wet sprayed concrete with a water-cement ratio of 0.46 into the material container 2 up to the scale line 21. Vibrate the container wall 10 times with a rubber hammer, smooth the surface with a scraper, and fix the material container 2 into the positioning groove 13 of the material container.

[0129] Step S2: Select the transverse bond strength test mode on the CNC system 8, install the transverse test piece 71, and apply pre-pressure after the tension is set to zero to make the test surface adhere to the concrete.

[0130] The operator first installs the transverse test piece 71, and then locks the quick-connect male connector 61 onto the quick-connect female connector 62;

[0131] The control panel of the integrated display screen 81 on the CNC system 8 is set as follows: mode is lateral test, preload is 50N, holding time is 10 seconds, and lifting speed is 0.3mm / s;

[0132] Start-up test: Set the tension value to zero. The output shaft of motor 31 drives ball screw 42 to rotate through coupling 41. Ball screw 42 then drives screw nut 43 connected to it to move. Screw nut 43 then drives lifting component 45 connected to it to move along four guide rails 44. This causes the transverse test plate 711 connected below lifting component 45 to come into contact with the surface of concrete 9. The CNC system 8 controls motor 31 to move transverse test component 71 until it is vertically lifted and detached. Tension sensor records peak tension F. h =16.36N; The data processing module automatically calculates: σ h =16.36N / 0.1m×0.1m=1636Pa.

[0133] Step S3: Data Verification

[0134] The results of the three repeated tests were 1636 Pa, 1763 Pa, and 1654 Pa, respectively. The difference between the maximum value and the median value was 1763-1654 / 1654=6.6%, and the difference between the minimum value and the median value was 1654-1636 / 1654=1.1%, both of which were less than 10%. The arithmetic mean was taken as 1684 Pa.

[0135] During longitudinal adhesion testing:

[0136] Step S1: Sample preparation

[0137] Similar to the concrete in Example 3, the material is first refilled and vibrated, the surface is leveled with a scraper, and the material container 2 is fixedly attached to the material container positioning groove 13.

[0138] Step S2: Testing Process

[0139] Replace the transverse test piece 71 with the longitudinal test piece 72, and lock the quick-release male connector 61 on the longitudinal test piece 72 onto the quick-release female connector 62.

[0140] The control panel of the integrated display screen 81 on the CNC system 8 is set as follows: mode is longitudinal test, rest time is 10 seconds, and lifting speed is 1.0 mm / s.

[0141] Start-up test: Set the tension value to zero. The output shaft of motor 31 drives ball screw 42 to rotate through coupling 41. Ball screw 42 then drives screw nut 43 connected to it to move. Screw nut 43 then drives lifting component 45 connected to it to move along four guide rails 44. This causes the longitudinal test plate 721 connected below the lifting component 45 to be inserted to a depth where the top surface of the longitudinal test plate 721 is flush with the surface of concrete 9. Lift vertically until release. Tension sensor records peak tension F. z =17.68N; The data processing module calculates this automatically.

[0142] σ z =17.68N / 20.1m×0.1m=884Pa.

[0143] Step S3: Data Verification

[0144] The test results were repeated three times: 884 Pa, 946 Pa, and 962 Pa. The difference between the maximum value and the median value was 962-946 / 946=1.7%, and the difference between the minimum value and the median value was 946-884 / 946=6.6%, both of which were less than 10%. The arithmetic mean was taken as 931 Pa.

[0145] The above embodiments demonstrate that this invention solves problems such as tensile force direction deviation and limited testing dimensions, achieving accurate quantitative evaluation of the bonding performance of wet-mixed shotcrete to the top and sidewalls of the surrounding rock in the plastic state during tunnel engineering. The device is highly portable and suitable for rapid on-site optimization of mix proportions, providing data support for controlling the rebound rate of wet-mixed shotcrete and improving the quality and economy of tunnel support engineering.

[0146] In this utility model, the length of the longitudinal test plate 721 is less than the concrete filling height scale line 21 of the material container 2, and the width of the longitudinal test plate 721 is less than the inner diameter of the material container 2; the outer circle diameter of the transverse test plate 711 is slightly smaller than the inner diameter of the material container 2.

[0147] In this invention, the bond strength testing device for freshly mixed concrete also includes a method for testing the bond strength of freshly mixed concrete, the method comprising the following steps:

[0148] Step S1: Leveling device, pour freshly mixed concrete into the material container 2 up to the scale line 21, vibrate and scrape it level, and fix the material container 2;

[0149] Step S2: Select the transverse bond strength test mode on the CNC system 8, install the transverse test piece 71, and apply pre-pressure after the tension is set to zero to make the test surface adhere to the concrete.

[0150] Step S3: Based on step S2, the CNC system 8 controls the vertical lifting at a constant rate, and records the peak tension F. h Automatically calculate the transverse adhesion force σ h =F h / A;

[0151] Step S4: Switch to longitudinal bond strength test mode on CNC system 8, install longitudinal test piece 72, set the tension to zero, and insert it vertically into the concrete to the set depth;

[0152] Step S5: Based on step S4, the CNC system 8 controls the vertical lifting at a constant rate, and records the peak tension F. z Automatically calculate longitudinal adhesion force σ z =F z / 2A.

[0153] Specifically, the transverse adhesion test mode and the longitudinal adhesion test mode were each repeated 3 times;

[0154] The rules for determining the values ​​are as follows: if the difference between the maximum or minimum value and the median value is ≤10% of the median value, take the arithmetic mean; if the difference between a single value is >10% but ≤15% of the median value, take the median value; if the difference between both values ​​is >15% of the median value, the test is invalid.

[0155] More specifically, the pre-pressure of the CNC system 8 is set to 30-70N, and the holding time is 10-15 seconds; the constant lifting rate during the transverse adhesion test is 0.1-0.5mm / s; and the constant lifting rate during the longitudinal adhesion test is 0.5-2mm / s.

[0156] In this utility model, when in use, the depth of the freshly mixed concrete in the container 2 is set so that the top surface of the longitudinal test plate 721 is flush with the concrete surface.

[0157] In this invention, the data processing module includes a pre-set formula for calculating the adhesive force: transverse adhesive force σ h =F h / A, longitudinal adhesion force σ z =F z / 2A, where F h F z denoted as peak tensile force, and A as the area of ​​the test specimen.

[0158] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this utility model without departing from its technical solution shall still fall within the protection scope of this utility model.

Claims

1. A fresh concrete cohesion test apparatus comprising a numerical control system (8), characterised in that, Also includes: The main frame (1) has a material holding bucket positioning groove (13) at the bottom inside the main frame (1); The bottom of the material container (2) is installed in the material container positioning groove (13); The power mechanism (3) is located in the upper part of the main frame (1) and is used to drive the transmission mechanism (4) to move vertically. Transmission mechanism (4), which is connected to power mechanism (3); The upper end of the tension sensor (5) is connected to the lower end of the lifting member (45) on the transmission mechanism (4); Test piece (7) is detachably connected to the lower end of the tension sensor (5) via quick-release assembly (6); The power mechanism (3) and the tension sensor (5) are both connected to the numerical control system (8).

2. The fresh concrete bond strength testing device of claim 1, wherein, The main frame (1) includes a base (11) and a vertical frame (12) connected above the base (11). The material container positioning groove (13) is opened in the middle of the base (11), and several bayonet openings are circumferentially connected on the material container positioning groove (13).

3. The fresh concrete bond strength testing device of claim 1, wherein, The bottom outer periphery of the material container (2) is provided with several flanges that are adapted to each slot, and the wall of the material container (2) is marked with concrete filling height scale line (21); The power mechanism (3) includes: a motor (31), which is connected to one end of the bottom plate inside the main frame (1); and a power supply (32), which is connected to the bottom plate inside the main frame (1). The power supply (32) is connected to the motor (31), the tension sensor (5), and the numerical control system (8), respectively.

4. The fresh concrete bond strength testing device of claim 3, wherein, The motor (31) is a servo motor.

5. The bonding strength testing device for freshly mixed concrete according to claim 1, characterized in that, The transmission mechanism (4) includes: Coupling (41), the upper end of which is connected to the output end of motor (31); The upper end of the ball screw (42) is connected to the lower end of the coupling (41); A lead screw nut (43) is embedded in one end of the lifting member (45) and the lead screw nut (43) passes through the lifting member (45); Guide rails (44) are symmetrically connected in pairs to both ends inside the vertical frame (12); The lifting component (45) has sliders connected to its four corners, and each slider is slidably connected to the guide rail (44) at the corresponding end. The lower end of the ball screw (42) is threadedly connected to the screw nut (43).

6. The fresh concrete bond strength testing device of claim 5, wherein, The ball screw (42) and the guide rails (44) on both sides form a rigid transmission structure, which is used to force the lifting trajectory to be vertical.

7. The fresh concrete bond strength testing device of claim 1, wherein, The tension sensor (5) is a high-precision tension sensor, and its upper end is detachably installed to the lower middle part of the lifting member (45) via a connector.

8. The fresh concrete bond strength testing device of claim 1, wherein, The quick-release assembly (6) includes: a quick-release male connector (61) whose lower end is connected to the upper end of the test piece (7); a quick-release female connector (62) whose upper end is connected to the lower end of the tension sensor (5); the quick-release male connector (61) and the quick-release female connector (62) are snapped together as an integral structure.

9. The bonding strength testing device for freshly mixed concrete according to claim 1, characterized in that, The numerical control system (8) includes an integrated display screen (81), a control panel (82), and a data processing module, used to control test parameters, automatically calculate and output the adhesion force value.

10. The fresh concrete bond strength testing device of claim 1, wherein, The test piece (7) includes: The transverse test piece (71) includes a transverse test plate (711) and connecting rods (712) that are inclinedly connected to the four corners above the transverse test plate (711). The non-connecting ends of the four connecting rods (712) are respectively connected to the lower part of the quick-release assembly (6), and the quick-release assembly (6) is vertically located in the upper middle part of the transverse test plate (711). The longitudinal test piece (72) includes a longitudinal test plate (721) and fixed rods (722) that are inclinedly connected to the upper ends of the transverse test plate (721). The non-connecting ends of the two fixed rods (722) are respectively connected to the lower part of the quick-release assembly (6), and the quick-release assembly (6) is vertically located at the upper middle part of the longitudinal test plate (721). When the transverse test piece (71) is subjected to preload, the test surface is parallel to the concrete surface; when the longitudinal test piece (72) is inserted into the concrete, the test surface is perpendicular to the concrete surface.

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