A testing device for highway cement mortar solidification experiment

Abstract

The application relates to the technical field of cement mortar solidification testing, and discloses a testing device for highway cement mortar solidification experiments, which comprises supporting legs, a testing table is arranged on the top of the supporting legs, a rebound test assembly and a pressurizing mechanism are arranged on the outer walls of the testing table, a test mold shell is arranged on the top of the testing table, an adjustable positioning group is arranged on the inner wall of the test mold shell, and an external control box assembly is arranged on the top of the adjustable positioning group. After the resistivity dynamic monitoring of the whole cement mortar solidification process is completed, the resistivity monitoring system is systematically calibrated through the back-stepping method combined with the constant current input mode, so that the systematic errors caused by various interference factors are stripped, the accuracy and effectiveness of the monitoring data are ensured, and the problems that the contact resistance generated by the contact between the electrode and the cement mortar, the line impedance of the wire itself and the electrode polarization effect lead to errors in the resistivity monitoring data in the actual monitoring process are solved.

Description

Technical Field

[0001] This invention relates to the field of cement mortar solidification testing technology, specifically to a testing device for cement mortar solidification experiments on highways. Background Technology

[0002] The setting test of cement mortar for highways is a crucial step in road construction and maintenance. It is mainly used to evaluate the setting time (initial setting, final setting), early strength development, and volume deformation (shrinkage / expansion) of the mortar.

[0003] The existing testing equipment for cement mortar setting experiments on highways is prone to the following problems during testing: The electrode positioning is inflexible and lacks adaptability. In existing technologies, electrodes mostly adopt a fixed pre-embedded structure, which cannot adjust the electrode spacing and insertion depth according to the differences in mold size and cement mortar mix ratio. They can only be adapted to a single mold size and specific test conditions, resulting in poor versatility and failing to meet the resistivity monitoring needs in different scenarios. Furthermore, the electrodes are prone to displacement, affecting the monitoring accuracy. During the cement mortar solidification process, shrinkage and deformation occur, and the mold may also deform slightly, causing the electrodes to easily shift with the mortar shrinkage and mold deformation. This results in poor contact between the electrodes and the cement mortar, introducing contact resistance and interfering with the accuracy of resistivity monitoring data, leading to increased monitoring errors. In addition, in existing technologies, if the electrode position needs to be adjusted, the mold must be disassembled and the electrodes re-embedded, which is a complex, time-consuming, and labor-intensive process. It cannot achieve rapid adjustment of the electrode position, reducing the efficiency of experimental operations, especially unsuitable for scenarios involving continuous testing of multiple sets of specimens. In existing testing devices for cement mortar setting experiments on highways, the electrode wires, ultrasonic probe signal lines, temperature and humidity sensor wires, rebound hammer signal lines, and other wires are all scattered, making them prone to tangling and pulling. This not only affects the convenience of experimental operation but also may affect signal transmission accuracy due to poor contact and mutual interference, leading to deviations in monitoring data. Furthermore, in current technology, the locations where the wires pass through the mold lack effective sealing structures, relying only on simple gap sealing methods. This results in insufficient mold sealing, allowing moisture during the cement mortar setting process to easily leak through the gaps. At the same time, external dust and moisture can easily enter the mold, affecting the normal setting process of the cement mortar. This process leads to distortion of test data such as resistivity and strength, and is susceptible to electromagnetic interference, resulting in unstable signal transmission. In existing technologies, various types of conductors lack effective electromagnetic shielding measures. Electromagnetic signals in the experimental environment (such as electromagnetic radiation from other equipment) can easily interfere with signal transmission in the conductors, causing fluctuations in core monitoring data such as voltage, resistivity, and ultrasonic velocity, affecting the stability and accuracy of test data. At the same time, the scattered wiring lacks unified storage and labeling, making it difficult to quickly locate faults when they occur, resulting in low efficiency in troubleshooting and maintenance. Furthermore, messy wiring increases the probability of conductor damage, reduces the lifespan of equipment, and hinders the continuity of experiments. Current technologies only monitor resistance / resistivity, failing to distinguish between the intrinsic resistance of cement mortar and various system interference resistances such as contact resistance, line impedance, electrode polarization, and circuit temperature drift. The monitored resistance value is the total measured resistance including all interference factors, not the true resistance of the mortar itself. This leads to significant deviations in resistivity monitoring data, failing to accurately reflect the internal structural evolution of cement mortar during solidification. Furthermore, it cannot provide reliable data support for initial and final setting determination and strength correlation analysis. Moreover, it cannot calibrate the acquisition accuracy of the constant current source output current and voltage acquisition unit, nor can it calculate system correction coefficients. The monitoring data remains in a state of "uncalibrated and unverified," making its accuracy unverifiable and hindering experimental repeatability. The existing technology suffers from poor performance, making it impossible to compare data from different batches and equipment, thus hindering the formation of reliable experimental conclusions. Furthermore, it can only collect resistance monitoring data in real time and cannot comprehensively correct the measured data throughout the entire cement mortar solidification process. As the experiment progresses, the influence of interference factors such as contact resistance and line impedance will continue to accumulate, leading to a gradual increase in the error of monitoring data in the early, middle, and late stages. Especially in the mortar hardening stage, it is impossible to correct the data through calibration, ultimately causing the experimental data to lose its reference value. It is also impossible to obtain the true resistivity data of the mortar itself through calibration, resulting in the inability to effectively link and analyze it with auxiliary test data such as ultrasonic velocity, rebound strength, and press compressive strength. Only the resistance change can be monitored individually. In summary, the existing technology not only has obvious pain points in electrode positioning and circuit storage, but more importantly, it only sets up a simple resistance detection function, which leads to distorted resistance monitoring data, low reliability, and error accumulation. It cannot be linked with auxiliary test data and cannot meet the needs of accurate monitoring and calibration of cement mortar solidification process; therefore, it needs to be improved. Summary of the Invention

[0004] This invention provides a testing device for the solidification experiment of cement mortar for highways, which solves the problems mentioned in the background art.

[0005] The present invention provides the following technical solution: a test device for the solidification test of cement mortar for highways, including a support leg, a test platform installed on the top of the support leg, a rebound test component and a pressurization mechanism respectively provided on the outer wall of the test platform, a test mold shell installed on the top of the test platform, an adjustable positioning group provided on the inner wall of the test mold shell, and an external control box component provided on the top of the adjustable positioning group. The rebound test assembly includes a positioning plate, a drive motor is fixedly installed on the outer wall of the positioning plate, a lead screw is fixedly mounted on the power output shaft of the drive motor, a bracket is threadedly connected to the outer wall of the lead screw, an electric telescopic cylinder is installed on the top of the bracket, a rebound hammer is fixedly mounted on the telescopic end of the electric telescopic cylinder, and a spring hammer is provided on the inner wall of the rebound hammer. The pressurizing mechanism includes an oil storage tank, an inner wall of which is provided with a pump body, one end of a delivery pipe is installed on the outer wall of the pump body, and a pressure head is installed on the other end of the delivery pipe. An oil outlet hole is opened at the bottom of the pressure head.

[0006] As a preferred embodiment of the present invention: an independent controller is installed on the outer wall of the test bench, a support frame is mounted on the top of the test bench, a press hydraulic cylinder is mounted on the top of the support frame, limit guide rods are installed at both ends of the press hydraulic cylinder, an ultrasonic pulse velocity tester is installed on one side of the outer wall of the test mold shell, and a temperature and humidity recorder is mounted on the other side of the outer wall of the test mold shell, a sandwich layer is provided at the bottom of the inner wall of the test bench, and electrode posts are installed on the inner wall of the adjustable positioning group.

[0007] As a preferred embodiment of the present invention: the drive motor, the electric telescopic cylinder, and the rebound spring are all electrically connected to the main control logic calibration unit, and the bracket slides on the top of the test bench.

[0008] As a preferred embodiment of the present invention: the outer wall of the oil storage tank is provided with an oil inlet hole, an alarm is installed on the outer wall of the oil storage tank, and a liquid level sensor is installed on the inner wall of the oil storage tank at the end away from the alarm.

[0009] As a preferred embodiment of the present invention: the liquid level sensor and the alarm are electrically connected, the top of the lower pressure head is connected to the telescopic end of the hydraulic cylinder of the press, and there are two pump bodies and two delivery pipes, which are symmetrically arranged at both ends of the lower pressure head.

[0010] As a preferred embodiment of the present invention: the adjustable positioning assembly includes a positioning slide rail, both outer walls of the positioning slide rail are provided with mounting holes, a slidable electrode seat is slidably connected to the outer wall of the positioning slide rail, a locking bolt is installed on the inner wall of the mounting hole, a limit block is installed on the top of the slidable electrode seat, a cylinder is provided on the top of the limit block, a push rod is fixedly mounted on the telescopic end of the cylinder, a positioning plate is provided on the outer wall of the push rod, and an elastic clamping member is slidably connected to the inner wall of the limit block.

[0011] As a preferred technical solution of the present invention: there are four adjustable positioning groups, and the four adjustable positioning groups are symmetrically distributed on the inner wall of the mold shell. The push rod is electrically connected to the main control logic calibration unit. The sliding electrode seat moves on the outer wall of the mounting hole through the locking bolt. The adjustable positioning group is made of polytetrafluoroethylene.

[0012] As a preferred technical solution of the present invention: the external control box assembly includes a top cover, and the top of the top cover is respectively equipped with a circuit storage box, a constant current source module, a standard resistor module, a main control logic calibration unit, a mode switching switch, a voltage acquisition unit and a data storage unit. The bottom of the circuit storage box is provided with an integrated wire hole, and the inner wall of the integrated wire hole is inlaid with a sealing ring.

[0013] As a preferred technical solution of the present invention: the top cover is located above the test mold shell, the mode switching switch adopts a multi-channel electromagnetic relay structure, and the mode switching switch is connected to the output terminal of the constant current source module, the lead wire of the electrode post and the standard resistor module through shielded wires respectively. The control terminal of the mode switching switch is connected to the main control logic calibration unit. The standard resistor module is provided with an anti-interference shielding shell, and the two ends of the standard resistor module are connected to the mode switching switch and the voltage acquisition unit through shielded wires respectively. The sealing ring is made of high temperature and aging resistant silicone. The inner wall of the circuit storage box and the interior of the integrated wire hole are provided with an electromagnetic shielding layer, and the electromagnetic shielding layer is made of copper foil.

[0014] The present invention has the following beneficial effects: 1. The testing device for cement mortar setting experiment of this highway, after completing the dynamic monitoring of resistivity throughout the cement mortar setting process, systematically calibrates the resistance monitoring system by combining the reverse calculation method with constant current input. This eliminates systematic errors caused by various interference factors, ensuring the accuracy and effectiveness of the monitoring data. It solves the problem that in the actual monitoring process, the contact resistance generated by the contact between the electrode and the cement mortar, the line impedance of the conductor itself, the electrode polarization effect, and the circuit temperature drift caused by the temperature change of the experimental environment will all cause errors in the resistivity monitoring data. If calibration and correction are not performed, it will directly affect the accuracy of the initial setting and final setting judgment, and thus affect the reliability of the test conclusions of subsequent mortar mix optimization, construction temperature control and crack prevention control. Meanwhile, the device adopts a fully automated calibration process design, which can complete the entire calibration work without manual intervention. The main control logic calibration unit can automatically receive the monitoring completion signal from the resistance monitoring system and automatically trigger the calibration process. There is no need to disassemble the electrodes. After the electrode pairs are embedded in the cement mortar specimen, they do not need to be disassembled from monitoring to calibration. This avoids damage to the structure of the cement mortar specimen during disassembly, ensuring that the specimen can be used for subsequent performance tests, and also reduces the operational errors and time consumption caused by manual disassembly and reinstallation of electrodes. The calibration efficiency is high, and the total time of a single calibration is short. The core links such as voltage acquisition, data calculation, and data correction are all automatically completed by the main control logic calibration unit, which significantly shortens the calibration cycle and improves the efficiency of the entire experiment.

[0015] 2. This testing device for the solidification experiment of cement mortar for highways is symmetrically arranged on both sides of the inner wall of the mold shell via positioning slide rails, along the height direction of the mold. The height can be adjusted by locking bolts to meet the resistivity monitoring requirements of mortar at different depths. The electrode holder is made of conductive silicone material to tightly clamp the electrodes, ensuring close contact between the electrodes and the mortar, while buffering the stress generated by the solidification shrinkage of the mortar and preventing electrode displacement. The connection between the electrodes and the wires is equipped with a locking joint with a threaded locking structure and conductive spring, ensuring a firm connection between the wires and the electrodes, eliminating contact resistance interference caused by loose contact, and enabling adjustable electrode spacing and height. It solves the problems of electrode displacement and wire loosening. Electrode position adjustment can be completed without disassembling the mold, making it convenient to operate and effectively improving electrode contact stability, reducing systematic errors caused by contact resistance, adapting to different mold specifications and testing requirements, and making it more practical.

[0016] 3. The test device for cement mortar solidification experiment of highway uses an integrated structure of integrated storage, sealing protection and electromagnetic shielding through the line storage box. This solves the problems of messy lines, poor sealing and susceptibility to electromagnetic interference of the existing device. It realizes the neat storage of the line and the sealed protection of the test mold. At the same time, it reduces the impact of electromagnetic interference on signal transmission, improves the overall stability and test accuracy of the device, and facilitates line maintenance.

[0017] 4. This testing device for the solidification test of cement mortar for highways ensures test accuracy and avoids data deviation by releasing lubricating oil at the bottom of the pressure head. The automatic release of lubricating oil forms a stable oil film on the bottom surface of the pressure head, reducing sliding friction between the pressure head and the specimen surface, ensuring uniform and stable loading, and avoiding fluctuations in loading force caused by uneven friction. This ensures accurate calculation of the actual compressive strength of the cement mortar. Furthermore, automatic lubrication effectively reduces wear on the surface of the pressure head, preventing deformation and scratches caused by long-term dry friction. It also eliminates the need for frequent grinding and replacement of the pressure head, extending its overall service life, reducing maintenance costs, and replacing manual application of lubricating oil. This avoids problems such as uneven application and omissions, reduces manual operation steps, lowers the labor intensity of operators, and prevents interference from manual operation in the testing process, ensuring a smooth and continuous testing process and improving overall experimental efficiency. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the structure on the other side of the present invention; Figure 3 This is a schematic diagram of the independent controller structure of the present invention; Figure 4 This is a schematic diagram of the cross-sectional structure of the present invention; Figure 5 This is a schematic diagram of the external control box assembly structure of the present invention; Figure 6 This is a schematic diagram of the adjustable positioning component structure of the present invention; Figure 7 This is a schematic diagram of the rebound test component structure of the present invention; Figure 8 This is a schematic diagram of the pressurization mechanism of the present invention.

[0019] In the diagram: 1. Support leg; 2. Test bench; 3. Independent controller; 4. Rebound test assembly; 5. Support frame; 6. Press hydraulic cylinder; 7. Limiting guide rod; 8. Pressing mechanism; 9. Test mold shell; 10. Interlayer; 11. Adjustable positioning group; 12. External control box assembly; 13. Ultrasonic pulse velocity tester; 14. Temperature and humidity recorder; 15. Electrode post; 401. Positioning plate; 402. Drive motor; 403. Lead screw; 404. Bracket; 405. Electric telescopic cylinder; 406. Rebound spring; 407. Impact hammer; 801. Oil reservoir; 802. Pump body; 803. Delivery pipe; 804. Lower pressure head; 805. Oil outlet; 806. Oil inlet; 807. Alarm; 808. Liquid level sensor; 1101. Positioning slide rail; 1102. Mounting hole; 1103. Sliding electrode base; 1104. Locking bolt; 1105. Limiting block; 1106. Cylinder; 1107. Push rod; 1108. Positioning plate; 1109. Elastic clamping element; 1201 Top cover; 1202 Cable management box; 1203 Integrated wiring hole; 1204 Sealing ring; 1205 Constant current source module; 1206 Standard resistor module; 1207 Main control logic calibration unit; 1208 Mode switching switch; 1209 Voltage acquisition unit; 12010 Data storage unit. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figures 1-8 A test device for the solidification test of highway cement mortar includes a support leg 1, a test platform 2 installed on the top of the support leg 1, a rebound test component 4 and a pressurization mechanism 8 respectively provided on the outer wall of the test platform 2, a test mold shell 9 installed on the top of the test platform 2, an adjustable positioning group 11 provided on the inner wall of the test mold shell 9, and an external control box component 12 provided on the top of the adjustable positioning group 11. The rebound test assembly 4 includes a positioning plate 401, a drive motor 402 is fixedly installed on the outer wall of the positioning plate 401, a lead screw 403 is fixedly assembled on the power output shaft of the drive motor 402, a bracket 404 is threadedly connected to the outer wall of the lead screw 403, an electric telescopic cylinder 405 is installed on the top of the bracket 404, a rebound hammer 406 is fixedly assembled on the telescopic end of the electric telescopic cylinder 405, and a spring hammer 407 is provided on the inner wall of the rebound hammer 406. The pressurizing mechanism 8 includes an oil storage tank 801, an inner wall of which is provided with a pump body 802, and an outer wall of the pump body 802 is provided with one end of a delivery pipe 803, and the other end of the delivery pipe 803 is provided with a pressure head 804, and the bottom of the pressure head 804 is provided with an oil outlet hole 805.

[0022] In a preferred embodiment: an independent controller 3 is installed on the outer wall of the test bench 2, a support frame 5 is installed on the top of the test bench 2, a press hydraulic cylinder 6 is installed on the top of the support frame 5, limit guide rods 7 are installed at both ends of the press hydraulic cylinder 6, an ultrasonic pulse velocity tester 13 is installed on one side of the outer wall of the test mold shell 9, and a temperature and humidity recorder 14 is installed on the other side of the outer wall of the test mold shell 9, a sandwich 10 is provided at the bottom of the inner wall of the test mold shell 9, and an electrode post 15 is installed on the inner wall of the adjustable positioning group 11. In the above structure, the ultrasonic pulse velocity tester 13 uses a pair of transmitting and receiving probes, symmetrically installed on the outer wall of the mold shell 9, effectively avoiding the obstruction and interference of the ultrasonic signal by the electrode posts 15; and the probe installation position is flush with the inner wall of the mold shell 9, ensuring that the probe is in close contact with the outer wall of the mold, and the ultrasonic transmission efficiency can be improved by using a coupling agent to reduce signal attenuation, which is convenient for subsequent data linkage analysis; while the temperature and humidity recorder 14 uses an embedded installation, which is buried inside the cement mortar specimen, avoiding the polarization effect of the electrode posts 15 from affecting the sensor reading, ensuring close contact with the mortar, and being able to sense the temperature and humidity changes inside the specimen in real time. At the same time, the sensor probe of the temperature and humidity recorder 14 is insulated to effectively avoid forming a conductive circuit with the electrode posts 15, interfering with resistance monitoring, ensuring stable data acquisition, and making it convenient for operators to view real-time temperature and humidity data.

[0023] In the above structure, the drive motor 402 is started, which causes the lead screw 403 to rotate, thereby driving the bracket 404 to move along the direction of the lead screw 403 on the top of the test platform 2, thereby adjusting the position of the rebound hammer 406 on the top of the mold. At the same time, the electric telescopic cylinder 405 is started, which allows the height of the rebound hammer 406 to be adjusted so that the surface of the hammer 407 can contact the top of the mold, thus facilitating the adjustment of the height of the rebound hammer 406.

[0024] In a preferred embodiment: the drive motor 402, the electric telescopic cylinder 405, and the rebounder 406 are all electrically connected to the main control logic calibration unit 1207, and the bracket 404 slides on the top of the test bench 2.

[0025] In the above structure, the compressive strength of cement mortar after solidification is estimated by the rebound distance after the impact hammer 407 strikes the surface of the mortar specimen. This non-destructive testing complements resistivity monitoring, ultrasonic testing, and press testing, enabling rapid monitoring of strength at different stages of solidification. Furthermore, the rebound hammer 406 is height-adjusted via an electric telescopic cylinder 405 to ensure the axis of the impact hammer 407 is perpendicular to the test surface of the specimen, ensuring uniform impact force. The rebound test is divided into two stages: The first stage, from the initial setting to the final setting, is a period of significant fluctuation in the resistivity curve, used to monitor the intensity growth trend, and is tested every thirty minutes. Secondly, from final setting to complete hardening, the resistivity curve is continuous and stable, which is used to accurately calculate the compressive strength. It is carried out simultaneously with the press test of hydraulic cylinder 6 of the press to ensure that the data can be compared and verified. First, adjust the height and position of the rebound hammer 406 to ensure that the axis of the impact hammer 407 is perpendicular to the test surface of the specimen, the impact hammer 407 is in a free state, and the impact surface is in close contact with the specimen surface. Then, start the rebound hammer 406 to control the impact hammer 407 to impact the specimen surface with a preset force. After the impact, the impact hammer 407 rebounds due to the reaction force of the specimen. Because the impact hammer 407 has a built-in displacement sensor, the rebound distance of the impact hammer 407 is collected in real time. (Unit: mm) Each test point was tested three times consecutively. Abnormal rebound distances with a deviation from the average value exceeding ±5% were removed. The arithmetic mean of the remaining valid data was taken as the final rebound distance for that test point. After completing the test at the three test points, take the three test points. The average value is taken as the overall rebound distance of the specimen. Simultaneously record the temperature and humidity data of the temperature and humidity recorder 14 at this time for subsequent intensity estimation and correction; Compressive strength calculation based on rebound distance: Combining the characteristics of cement mortar and the requirements of specifications, a calculation formula is established by fitting the relationship between rebound distance and compressive strength, achieving accurate conversion from rebound distance to compressive strength. The specific formula and explanation are as follows: Basic calculation formula: ,in: : Compressive strength of cement mortar calculated from rebound distance (unit: MPa); Average rebound distance of the entire specimen (unit: mm); The internal temperature and humidity correction value of the specimen during testing is the internal temperature of the specimen collected by the temperature and humidity recorder 14. (°C) and humidity (%) is calculated; The corrected formula is: ; Correction notes: When the rebound distance If the mortar strength is too low, it indicates that the test needs to be repeated; when When calculating, the results need to be multiplied by a correction factor of 0.95 to avoid overestimating the intensity; temperature and humidity correction values... The value range is -0.5 to 0.5, which is used to eliminate the influence of temperature and humidity deviations from the standard environment on the rebound distance and strength; Calculation example: If the test yields the average rebound distance of the entire specimen... Internal temperature of the specimen ,humidity Substitute into the formula to calculate: The first step is to calculate the temperature and humidity correction values: ; The second step is to calculate the compressive strength: ; Compressive strength calculated from rebound Actual compressive strength of the hydraulic cylinder 6 of the press during press testing The corrected resistivity data and the ultrasonic velocity data of the ultrasonic pulse velocity tester 13 are analyzed together. If the deviation between the two exceeds ±8%, the rebound test operation and the fitting coefficient value need to be checked again. At the same time, the calculation formula is corrected in combination with temperature and humidity data to ensure the accuracy of the rebound calculation results, thus forming a complete testing system of "non-destructive monitoring and destructive testing".

[0026] In a preferred embodiment: an oil inlet 806 is provided on the outer wall of the oil tank 801, an alarm 807 is installed on the outer wall of the oil tank 801, and a liquid level sensor 808 is installed on the inner wall of the end of the oil tank 801 away from the alarm 807. In the above structure, the cement mortar mold that has completed resistance monitoring and calibration is disassembled, the solidified cement mortar specimen is taken out, and placed directly below the hydraulic cylinder 6 of the press. The height of the lower pressure head 804 is adjusted by the signal transmitted by the independent controller 3 so that the distance between the lower pressure head 804 and the specimen height is adapted. At this time, the pump body 802 can be started, so that the pump body 802 draws the lubricating oil on the inner wall of the oil storage tank 801 to the inner wall of the delivery pipe 803 and delivers it to the inner wall of the lower pressure head 804. It is then released through the oil outlet 805 to the bottom of the lower pressure head 804, so that there is a small amount of lubricating oil at the bottom of the lower pressure head 804, reducing the contact between the lower pressure head 804 and the specimen. The friction between them; place the specimen stably at the center of the bottom of the lower pressure head 804, adjust the position of the specimen to ensure that the center of the specimen is aligned with the center of the lower pressure head 804, and avoid eccentric pressure application; then start the hydraulic cylinder 6 of the press to begin uniform loading, and record the loading force data and the corresponding specimen deformation in real time during the loading process, and simultaneously record the environmental and internal temperature and humidity data of the temperature and humidity recorder 14; when the specimen shows obvious damage and the loading force reaches its peak and begins to decrease, stop loading and record the maximum loading force; after the test is completed, slowly unload, take out the damaged specimen, clean the surface of the lower pressure head 804, and prepare for the next set of specimens to be tested; Calculate the compressive area A (unit: mm²) based on the recorded maximum loading force and the preset size of the specimen, and substitute it into the compressive strength calculation formula. Calculate the actual compressive strength of cement mortar (Unit: MPa); After the calculation is completed, the compressive strength data, the corrected resistivity data, and the ultrasonic velocity data are linked for analysis to establish the correlation between the three, further verify the cement mortar solidification quality, and provide data support for subsequent mortar mix optimization.

[0027] In a preferred embodiment: the level sensor 808 is electrically connected to the alarm 807, the top of the lower head 804 is connected to the telescopic end of the hydraulic cylinder 6 of the press, and there are two pump bodies 802 and two delivery pipes 803, and the two pump bodies 802 and two delivery pipes 803 are symmetrically arranged at both ends of the lower head 804. In the above structure, releasing lubricating oil at the bottom of the pressure head 804 ensures testing accuracy and avoids data deviation. Automatic lubrication forms a stable oil film on the bottom surface of the pressure head 804, reducing sliding friction between the pressure head 804 and the specimen surface. This ensures a uniform and stable loading process with consistent force, preventing fluctuations in loading force due to uneven friction. It also ensures accurate calculation of the actual compressive strength of the cement mortar. Furthermore, automatic lubrication effectively reduces wear on the surface of the pressure head 804, preventing deformation and scratches caused by long-term dry friction. It also eliminates the need for frequent grinding and replacement of the pressure head 804, extending its overall service life and reducing maintenance costs. Moreover, it replaces manual lubrication, avoiding uneven application and omissions, reducing manual operation steps, lowering the labor intensity of operators, and preventing interference from manual operation in the testing process. This ensures a smooth and continuous testing process and improves overall experimental efficiency.

[0028] In a preferred embodiment: the adjustable positioning assembly 11 includes a positioning slide rail 1101, with mounting holes 1102 on both outer walls of the positioning slide rail 1101, a slidable electrode seat 1103 slidably connected to the outer wall of the positioning slide rail 1101, a locking bolt 1104 installed on the inner wall of the mounting hole 1102, a limit block 1105 installed on the top of the slidable electrode seat 1103, a cylinder 1106 provided on the top of the limit block 1105, a push rod 1107 fixedly mounted on the telescopic end of the cylinder 1106, a positioning plate 1108 provided on the outer wall of the push rod 1107, and an elastic clamping member 1109 slidably connected to the inner wall of the limit block 1105. In the above structure, the constant current source module 1205 can output a constant standard current of preset magnitude with fluctuation not exceeding ±0.5%. The voltage acquisition unit 1209 can simultaneously acquire the measured voltage across the electrode post 15. and the standard voltage across the standard resistor module 1206 After removing outliers with a deviation exceeding ±5% from the average, the arithmetic mean is taken as the final calculation parameter. The standard resistor module 1206 has a known resistance value. The factory-calibrated fixed values ​​can be directly used as the calculation benchmark; the main control logic calibration unit 1207 is responsible for receiving the parameters output by each structure, executing the calculation process, completing data correction and storage, and ensuring that the calculation process is automated and accurate; The structural stability and constant resistivity of cement mortar in the later stages of solidification can trigger the calibration process. The resistance monitoring system continuously monitors the resistivity changes of the cement mortar. When the resistivity curve of the cement mortar remains consistently stable, it is determined that the cement mortar has entered the stable hardening stage. The resistance monitoring system sends a monitoring completion signal to the main control logic calibration unit 1207. The main control logic calibration unit 1207 automatically triggers the calibration process, and the control device switches from dynamic monitoring mode to calibration mode, cutting off irrelevant circuits in the monitoring loop to ensure the independence and stability of the calibration loop. This lays the foundation for subsequent current input, voltage acquisition, and calculation. The main control logic calibration unit 1207 sends a control command to the constant current source module 1205 to set a constant standard current. The specific value controls the constant current source module 1205 to start and output the constant standard current. Simultaneously, the current stability is monitored in real time. If fluctuations exceed the range, adjustments are made immediately until the current stabilizes. Subsequently, the stable constant standard current is switched to the mode switching switch 1208. Electrode post 15, embedded inside the stabilized and hardened cement mortar, is inserted to form a complete calibration test circuit. At this time, the current in the circuit... Keep it constant to provide stable current parameters for subsequent measured resistance calculations; Under constant standard current After the calibration test circuit is stably connected, the voltage acquisition unit 1209 immediately starts, synchronously acquiring the actual voltage signal across electrode post 15. Data acquisition is completed according to preset acquisition rules. The acquired raw voltage data is then filtered to remove abnormal data, and the arithmetic mean of the remaining valid data is taken to obtain the final measured voltage. (Unit: V) Based on Ohm's law ( The main control logic calibration unit 1207 automatically performs the total measured resistance calculation. The calculation formula is as follows: ,in To calibrate the total measured resistance of the circuit (unit: Ω), the total resistance value can be obtained, including the resistance of the cement mortar body, the contact resistance between the electrode post 15 and the cement mortar, the impedance of the conductor line and the equivalent resistance of the circuit temperature drift. This clarifies the overall impact of the error and provides basic data for subsequent removal of interference factors and back-calculation of the theoretical resistance. After the total measured resistance calculation is completed, the main control logic calibration unit 1207 activates the control mode switching switch 1208, switching the constant standard current output by the constant current source module 1205 to... Switching from electrode post 15 to standard resistor module 1206 ensures the current magnitude remains constant, followed by voltage acquisition unit 1209 acquiring... Following a consistent rule, the voltage signal across the standard resistor module 1206 is collected, filtered, outlier data is removed, and the average value is calculated to obtain the standard voltage. (Unit: V); First, the constant standard current is deduced by working backward from Ohm's law. The actual value is calculated using the following formula: ,in The known rated resistance (in Ω) of the standard resistor module 1206 can be calibrated. The actual value is used to eliminate errors caused by small fluctuations in the constant current source, providing current parameters for subsequent theoretical resistance calculation. Then, based on the principle that "resistance is proportional to voltage under the same constant current," the theoretical resistance of the cement mortar body after removing interference is calculated. The calculation formula is: ,in The theoretical resistance (unit: Ω) only reflects the actual resistance of the cement mortar itself. It is used to obtain the actual resistance value of the cement mortar itself and to provide a benchmark for subsequent calculation of system correction coefficients and correction of monitoring data. Complete theoretical resistance calculation Total measured resistance After calculation, the main control logic calibration unit 1207 calculates the correction coefficient and quantifies the system error magnitude. The calculation formula is as follows: ,in The system correction coefficient directly reflects the degree of influence of system errors—when When the error is 0, it indicates that there is no systematic error; when the error is 10, it indicates that there is no systematic error. If the error is found, it indicates that there is an error, and the monitoring data needs to be corrected using this coefficient. This provides a unified correction standard for the correction of resistivity monitoring data throughout the solidification process, ensuring that all errors in the monitoring data are effectively eliminated. Subsequently, the main control logic calibration unit 1207 retrieves the measured resistivity data of the entire cement mortar solidification process stored in the resistance monitoring system. (Unit: Ω·M), using correction coefficients The measured resistivity values ​​at each time point are corrected overall, and the correction calculation formula is as follows: ,in The corrected resistivity value (unit: Ω·M) can truly reflect the resistivity change pattern during the cement mortar solidification process. This ensures that the corrected resistivity data can reflect the internal structural evolution of cement mortar from the fluid state, plastic state to the hardened state, providing reliable data support for the accurate determination of the initial and final setting times and subsequent optimization of mortar mix proportions, as well as construction temperature control and crack prevention. All calculations are derived based on mature Ohm's law and proportional relationships. The parameter acquisition method is clear, the calculation process is repeatable, and it is compatible with the hardware structure and calibration process of this device. It can effectively eliminate systematic errors caused by contact resistance, line impedance, electrode polarization and circuit temperature drift, ensure the accuracy and reliability of resistivity monitoring data, and control the error in determining the initial setting and final setting times within a reasonable error range. It provides core technical support for the accurate testing of highway cement mortar setting experiments.

[0029] In a preferred embodiment: there are four adjustable positioning groups 11, and the four adjustable positioning groups 11 are symmetrically distributed on the inner wall of the mold shell 9. The cylinder 1106 is electrically connected to the main control logic calibration unit 1207. The sliding electrode seat 1103 moves on the outer wall of the positioning slide rail 1101 through the locking bolt 1104. The adjustable positioning group 11 is made of polytetrafluoroethylene. In the above structure, by inserting the locking bolt 1104 into different mounting holes 1102, the height of the sliding electrode seat 1103 can be adjusted to different heights, so that the device can meet the resistivity monitoring requirements of mortar at different depths. When the cylinder 1106 is started, the push rod 1107 can drive the positioning plate 1108 to rotate, and the elastic clamping member 1109 slides on the inner wall of the limiting block 1105 to clamp the bottom of the electrode post 15. Since the elastic clamping member 1109 is made of conductive silicone, it tightly clamps the electrode post 15, ensuring that the electrode post 15 is in close contact with the mortar, while buffering the stress generated by the solidification and shrinkage of the mortar, and preventing the electrode post 15 from shifting. The connection between the electrode post 15 and the wire is provided with a locking joint, which adopts a threaded locking structure and is used in conjunction with a conductive spring to ensure that the connection between the wire and the electrode post 15 is firm, effectively reducing the problem of contact resistance interference caused by loose contact.

[0030] In a preferred embodiment: the external control box assembly 12 includes a top cover 1201, on the top of the top cover 1201 respectively mounted a cable storage box 1202, a constant current source module 1205, a standard resistor module 1206, a main control logic calibration unit 1207, a mode switching switch 1208, a voltage acquisition unit 1209 and a data storage unit 12010, and an integrated wire hole 1203 is provided at the bottom of the cable storage box 1202, and a sealing ring 1204 is embedded in the inner wall of the integrated wire hole 1203; In the above structure, the constant current source module 1205 employs a high-precision programmable constant current source, enabling it to provide a stable and unfluctuating constant standard current during calibration, thus avoiding errors in resistance calculation caused by current fluctuations. Furthermore, the constant current source module 1205 can be programmed to set the output current according to experimental requirements, ensuring it meets the resistance calibration needs of hardened highway cement mortar of different strength grades. Its output terminal is electrically connected to the resistance monitoring electrode post 15 and the standard resistance module 1206 via a mode switching switch 1208. Simultaneously, the surface of the constant current source module 1205 is equipped with a current adjustment interface (for presetting the constant standard current). The current stability data is fed back to the main control logic calibration unit 1207 in real time. The monitoring circuit and the calibration circuit are quickly switched through the action of the mode switching switch 1208 to ensure the continuity of the calibration process. The standard resistor module 1206 uses a high-precision, low-temperature-coefficient metal film standard resistor with high resistance stability. The resistance fluctuation does not exceed ±0.05% within the experimental temperature range. This module is electrically connected to the constant current source module 1205 and the voltage acquisition unit 1209. During the calibration process, it serves as a reference load to back-calculate the theoretical resistance value and eliminate the influence of various interference factors. The voltage acquisition unit 1209 uses a high-precision differential voltage acquisition chip, and its sampling rate is consistent with the resistivity acquisition rate of the resistance monitoring system to ensure the synchronization and consistency of the acquired data. The acquisition end of the voltage acquisition unit 1209 is electrically connected to both ends of the electrode post 15 and both ends of the standard resistance module 1206 through shielded wires. The shielded wires can effectively reduce the influence of external electromagnetic interference on the voltage signal. This unit can synchronously acquire the actual voltage at both ends of the electrode post 15 and the standard voltage at both ends of the standard resistance module 1206 during the calibration process. After the acquired data is filtered, it is transmitted to the main control logic calibration unit 1207 for subsequent resistance calculation and error analysis. The main control logic calibration unit 1207 uses a PLC controller and is connected to the constant current source module 1205, mode switching switch 1208, standard resistance module 1206, voltage acquisition unit 1209, and data storage unit 12010 via a bus. The main control logic calibration unit 1207 has a communication interface on its surface for linkage with the resistance monitoring data storage unit 12010, enabling data transmission, calculation, and correction. This achieves bidirectional signal transmission and automated process control. Upon receiving the monitoring completion signal from the resistance monitoring electrode 15, it automatically triggers the calibration process; sends current output commands to the constant current source module 1205 to control the output and stabilization of a constant standard current; receives voltage data transmitted from the voltage acquisition unit 1209, performs filtering and average value calculations; calculates the measured resistance, theoretical resistance, and correction coefficients; and retrieves monitoring data from the data storage unit 12010 to complete data correction, re-storage, and curve updates. It also has a manual calibration trigger function to meet calibration needs in special experimental scenarios. Furthermore, the calibration results of this device are repeatable, improving the traceability of experimental data. By using a mode switching switch 1208, the monitoring circuit and calibration circuit can be quickly switched. During the switching process, the current stability is controlled within ±0.5%, ensuring the independence and stability of the calibration circuit. The main control logic calibration unit 1207 can synchronously store the corrected resistivity data and various parameters in the calibration process, realizing full traceability of experimental data, which is convenient for subsequent experimental review, data verification, and experimental conclusion verification. After repeated calibration, the deviation of the calibration results stabilizes, ensuring the consistency and reliability of experimental data. Because the wiring storage box 1202 is made of transparent insulating material, it is easy to see the internal wiring connection status. The wiring storage box 1202 also has partitioned slots inside, used to store electrode wires, ultrasonic signal wires, and temperature and humidity sensor wires respectively, preventing wire tangling. An integrated wire-passing hole 1203 is also provided at the same position on the top of the top cover 1201 and the bottom of the wiring storage box 1202. Wires pass through the integrated wire-passing hole 1203 in a concentrated manner, ensuring a tight fit between the sealing ring 1204 and the wires, achieving a sealed protection for the test mold and preventing moisture leakage and the entry of dust and water vapor. An electromagnetic shielding layer is provided on the inner wall of the wiring storage box 1202 and inside the integrated wire-passing hole 1203, which can effectively shield against external electromagnetic interference and ensure stable signal transmission.

[0031] In a preferred embodiment: the top cover 1201 is located above the test mold shell 9; the mode switching switch 1208 adopts a multi-channel electromagnetic relay structure; the mode switching switch 1208 is connected to the output terminal of the constant current source module 1205, the lead wire of the electrode post 15, and the standard resistor module 1206 through shielded wires; the control terminal of the mode switching switch 1208 is connected to the main control logic calibration unit 1207; the standard resistor module 1206 is provided with an anti-interference shielding shell; and the two ends of the standard resistor module 1206 are connected to the mode switching switch 1208 and the voltage acquisition unit 1209 through shielded wires; the sealing ring 1204 is made of high temperature and aging resistant silicone; the inner wall of the circuit storage box 1202 and the interior of the integrated wire hole 1203 are provided with an electromagnetic shielding layer, and the electromagnetic shielding layer is made of copper foil. In the above structure, by taking advantage of the stable internal structure and constant resistivity of cement mortar in the later stage of solidification, the theoretical resistance value that only reflects the resistance of cement mortar body is calculated by using the standard resistance module 1206 with known resistance value as a reference. The theoretical resistance value is compared with the measured resistance value that includes various interference factors to calculate the system correction coefficient. Then, the resistivity data of the entire monitoring process is corrected to achieve system calibration. Moreover, it does not require disassembling the electrode column 15 and does not damage the specimen structure. The operation is simple and the calibration accuracy is high. When the electrode post 15 is energized, the main control logic calibration unit 1207 monitors the resistance in real time and continuously monitors the resistivity change of the cement mortar. When the resistivity curve of the cement mortar remains stable for 30-60 minutes without significant fluctuations, it is determined that the cement mortar has completed the solidification process and entered the stable hardening stage. At this time, the resistance monitoring sends a monitoring completion signal to the main control logic calibration unit 1207, which automatically triggers the calibration process after receiving the signal. The control mode switching switch 1208 switches the mode from dynamic monitoring mode to calibration mode, and cuts off the irrelevant circuits of the monitoring circuit to ensure the independence and stability of the calibration circuit. At this time, a constant standard current is applied, and the main control logic calibration unit 1207 sends a control command to the constant current source module 1205 to set the constant standard current. The specific value controls the constant current source module 1205 to start and output the constant standard current. During the current output process, the constant current source module 1205 provides real-time feedback on current stability data, and the main control logic calibration unit 1207 monitors current fluctuations to ensure that the current fluctuation does not exceed ±0.5%. If the fluctuation exceeds the range, an adjustment command is immediately issued until the current stabilizes. Subsequently, the constant current source module 1205 uses the mode switching switch 1208 to output a stable constant standard current. The current is fed into the electrode post 15 for resistance monitoring. Since the electrode post 15 is located inside the cement mortar that has been embedded in advance and stabilized and hardened, the current passes through the electrode post 15 to form a complete calibration test circuit inside the cement mortar, which provides a basis for subsequent voltage acquisition and resistance calculation. Under constant standard current After the calibration test circuit is stably connected, the voltage acquisition unit 1209 immediately starts and synchronously acquires the actual voltage across the electrode post 15. To avoid voltage data anomalies caused by accidental factors, the acquisition time was set to approximately ten minutes, with a sampling frequency of once every 100ms. Throughout the acquisition process, the voltage acquisition unit 1209 performed real-time filtering on the acquired raw voltage data to remove abnormal data caused by electromagnetic interference and instantaneous fluctuations during contact. After acquisition, the arithmetic mean of the remaining valid data was taken as the final measured voltage value. According to Ohm's law ( The main control logic calibration unit 1207 calculates the total measured resistance of the calibration circuit. The calculation formula is: And the total measured resistance It is not the actual resistance of the cement mortar itself, but the total resistance value that includes the resistance of the cement mortar itself, the contact resistance between the electrode post 15 and the cement mortar, the line impedance of the wire itself, and the equivalent resistance caused by the temperature drift of the circuit. After the measured voltage is acquired, the main control logic calibration unit 1207 activates the control mode switch 1208, switching the constant standard current output by the constant current source module 1205 to the standard current. Switch from electrode post 15 to standard resistor module 1206, ensuring the current magnitude remains constant (still [value]). Subsequently, the voltage acquisition unit 1209 synchronously acquires the standard voltage across the standard resistor module 1206. The data acquisition method is consistent with the actual voltage measurement method. After removing outlier data, the average value is taken to obtain the final standard voltage value. Due to the resistance value of the standard resistor module 1206 It is known that, according to Ohm's law, the constant standard current can be calculated first. Actual size ( ), and then combined with the collected measured voltage This leads to the theoretical resistance calculation, which only reflects the actual resistance of the cement mortar itself. The calculation formula is: The theory calculates resistance By leveraging the reference function of the standard resistor module 1206, the influence of various interference factors such as contact resistance, line impedance, and temperature drift is effectively eliminated, and the resistance characteristics of the cement mortar body after stable hardening are truly reflected, providing an accurate reference for subsequent error correction. The main control logic calibration unit 1207 calculates the total measured resistance. The theoretical resistance obtained by reverse calculation By comparing the two, the system correction coefficient is calculated using the ratio of the two values. Correction coefficient The calculation formula is This coefficient directly reflects the magnitude of the systematic error. If it is true, then there is no error; if If the resistance monitoring data is not corrected, the main control logic calibration unit 1207 will then call the resistivity monitoring data of the entire cement mortar solidification process stored in the resistance monitoring data storage unit 12010 via the bus, and use the correction coefficient to correct the data. The measured resistivity values ​​at each time point are corrected overall using the following formula: ,in This is the corrected resistivity value. To monitor the measured resistivity values ​​during the process, after correction, the main control logic calibration unit 1207 restores the corrected resistivity data to the data storage unit 12010, and updates the resistivity-time evolution curve to ensure that the curve can truly reflect the resistivity change law of the cement mortar solidification process. Thus, the calibration work of the entire resistance monitoring can be completed. This device achieves high overall calibration accuracy, effectively ensuring the authenticity of monitoring data and providing reliable support for determining initial and final setting times. Furthermore, through the combination of multi-dimensional high-precision components and reverse logic design, it achieves precise error isolation. By comparing the measured voltage with the standard voltage, it can isolate various system interferences such as the contact resistance between electrode post 15 and cement mortar, conductor impedance, electrode polarization effect, and equivalent resistance caused by circuit temperature drift. This ensures that the calculated theoretical resistance value truly reflects the inherent resistance characteristics of the cement mortar. By extending the voltage acquisition time, using high-frequency sampling, removing abnormal data, and calculating the arithmetic mean, the impact of random errors on the calibration results is further reduced. This allows the error in determining the initial and final setting times of cement mortar to be controlled within a reasonable range, effectively solving the problem of inaccurate initial and final setting determination due to excessive errors in traditional resistance monitoring.

[0032] Working principle: When using this device, adjust the position of the sliding electrode base 1103 on the positioning slide rail 1101, and insert the sliding electrode base 1103 into the inner wall of the mounting hole 1102 through the locking bolt 1104, so that the height of the sliding electrode base 1103 is half the height of the test mold shell 9. Then, the main control logic calibration unit 1207 sends a signal to start the cylinder 1106, so that the extension end of the cylinder 1106 drives the push rod 1107 to move. This allows the positioning plate 1108 to rotate, causing the elastic clamping member 1109 to slide on the inner wall of the limit block 1105. This allows the three elastic clamping members 1109 to clamp and position the electrode post 15, ensuring that the electrode post 15 is tightly clamped. At this time, the ultrasonic pulse speed can be increased. The tester 13 is started, and a pressure sensor is embedded in the probe of the ultrasonic pulse velocity tester 13. Then, the probe angle of the ultrasonic pulse velocity tester 13 is adjusted (the initial angle is perpendicular to the side wall of the mold shell 9) to ensure that the coupling agent storage tank at the bottom of the probe faces the mold shell 9. A small amount of petroleum jelly is applied as a coupling agent. The pressure sensor is started to stabilize the pressure between the probe and the side wall of the mold shell 9 at 0.1-0.3 MPa. The temperature and humidity sensor of the temperature and humidity recorder 14 is embedded in the preset position of the mold shell 9, that is, the center position of the specimen. It is ensured that the sensor probe is completely wrapped in the cement mortar area to be poured later, and the sensor wire passes through the integrated wire hole 1203 and is inserted into the corresponding slot in the inner wall of the wire storage box 1202. The adjustable positioning group 11, ultrasonic pulse velocity tester 13, and temperature and humidity recorder 14 are activated sequentially to confirm that each device is operating normally. This ensures that the electrode post 15, fixed by the adjustable positioning group 11, continuously collects resistivity data of the cement mortar specimen while energized. The acquisition frequency is consistent with that of the voltage acquisition unit 1209, and the resistivity change curve over time is recorded in real time. The elastic clamping element 1109 of the adjustable positioning group 11 can buffer the stress generated by the solidification and shrinkage of the mortar, ensuring that the electrode post 15 does not shift and is in close contact with the mortar, avoiding interference from contact resistance in the monitoring data. The main control logic calibration unit 1207 receives the resistivity data in real time, stores it in the data storage unit 12010, and monitors data fluctuations to prepare for subsequent calibration processes. At this time, the main control logic calibration unit 1207 transmits a signal, enabling the temperature and humidity recorder 14 to synchronously collect temperature and humidity data of the specimen's interior and the environment. It samples every 100ms, removes abnormal data, and takes the arithmetic mean, recording temperature and humidity changes in real time. Meanwhile, the sensor inside the mold shell 9 accurately senses the temperature and humidity inside the mortar, while a backup sensor monitors the ambient temperature and humidity. Both data are stored synchronously, providing environmental parameter basis for subsequent data correction. If the temperature and humidity deviate from the standard range, the experimental environment is adjusted promptly to ensure stable test conditions. The ultrasonic pulse velocity tester 13 continuously transmits ultrasonic signals to the cement mortar specimen through the probe, receives the reflected signals after penetrating the specimen, and collects ultrasonic velocity data in real time. The pressure sensor monitors the contact pressure between the probe and the mold shell 9 in real time. If the pressure is lower than 0.1MPa, the main control logic calibration unit 1207 will issue a warning signal, allowing the operator to adjust the pressure promptly to ensure the probe always contacts the mold shell 9 with appropriate force, reducing ultrasonic signal attenuation. The ultrasonic velocity data is stored in real time for subsequent analysis in conjunction with resistivity and strength data, reflecting the degree of mortar structure densification. From initial setting to final setting: When the cement mortar surface is observed to lose its fluidity and begin to solidify, this is the initial setting state. At this time, the main control logic calibration unit 1207 can send a signal to start the drive motor 402, rotate the lead screw 403, and move the support 404 to a preset position on the outer wall of the lead screw 403. At this time, the telescopic end of the electric telescopic cylinder 405 drives the rebound hammer 406 to move to the preset position. The rebound hammer 406 is then started, and the impact hammer 407 performs a rebound test every 30 minutes. During each test, the position of the support 404 can be adjusted to ensure that the axis of the impact hammer 407 is perpendicular to the test surface of the specimen and is at different test points, so that the impact surface is in close contact with the specimen surface. Each test point is tested three times consecutively. After removing outliers, the average value is taken, and the rebound distance at this time point is recorded for analysis of the strength growth trend. During the test, the support 404 can keep the rebound hammer 406 stable and avoid vibration causing deviation in the rebound distance acquisition. The resistance monitoring system continuously monitors the resistivity change curve. When the curve remains stable for 30-60 minutes with fluctuations not exceeding a preset value, it is determined that the cement mortar has entered the stable hardening stage. The resistance monitoring system sends a monitoring completion signal to the main control logic calibration unit 1207. The main control logic calibration unit 1207 automatically triggers the calibration process, causing the control device to switch from dynamic monitoring mode to calibration mode, cutting off irrelevant circuits in the monitoring loop to ensure the independence and stability of the calibration loop. Simultaneously, the temperature and humidity recorder 14 records the internal temperature and humidity data of the specimen and the environment at this time for subsequent data correction reference. The main control logic calibration unit 1207 sends a control command to the constant current source module 1205 to select an appropriate constant standard current based on the resistance range of the hardened cement mortar. The system controls the constant current source module 1205 to start and output the current; it monitors the current stability in real time, and if the current fluctuation exceeds ±0.5%, it immediately adjusts the constant current source parameters until the current stabilizes; subsequently, it uses the mode switching switch 1208 to switch the stable current... The electrode post 15, which is fixed by the adjustable positioning group 11, is connected to form a complete calibration test circuit to ensure that the current in the circuit remains constant. After a constant standard current is stably applied to the circuit, the voltage acquisition unit 1209 immediately starts and acquires the actual voltage signal across the electrode post 15 according to preset rules. The acquired raw voltage data is filtered to remove abnormal data with a deviation from the average value exceeding ±5%. The arithmetic mean of the remaining valid data is then taken to obtain the final measured voltage. Based on Ohm's law ( The main control logic calibration unit 1207 automatically calculates the total measured resistance. (Unit: Ω), this resistance value includes the resistance of the cement mortar itself, contact resistance, line impedance and equivalent resistance of circuit temperature drift, and is used to subsequently eliminate interference factors; After the total measured resistance is calculated, the main control logic calibration unit 1207 activates the control mode switching switch 1208, which outputs the constant current source module 1205. Switching from electrode post 15 to standard resistor module 1206 ensures the current magnitude remains constant; voltage acquisition unit 1209 is used for acquisition. Following a consistent rule, the voltage signal across the standard resistor module 1206 is collected, filtered, outlier data is removed, and the average value is calculated to obtain the standard voltage. (Unit: V); Based on Ohm's law, the reverse calculation is performed. The actual value ( The system first calibrates the constant current source to correct for errors caused by minute fluctuations. Then, based on the principle that "resistance is proportional to voltage under the same constant current," it reverse-engineers the theoretical resistance of the cement mortar after removing interference. (Unit: Ω), this resistance value only reflects the actual resistance of the mortar itself; At this point, the correction coefficient is calculated and the resistivity data is corrected: the main control logic calibration unit 1207 calculates the correction coefficient. The magnitude of the system error is quantified; subsequently, the measured resistivity data of the entire solidification process stored in the resistance monitoring system are retrieved. (Unit: Ω·M), using correction coefficients The measured resistivity values ​​at each time point are corrected overall using the following formula: The corrected resistivity value is obtained. The corrected resistivity data is re-stored to data storage unit 12010, and the resistivity-time evolution curve is updated synchronously; if The deviation from 1 is too large ( or We re-examined the voltage acquisition and current stabilization processes, analyzed the causes of errors based on temperature and humidity data, and recalculated the correction coefficients. Verification of calibration results: After completing the data correction, the corrected resistivity data is initially compared with the ultrasonic velocity data collected at the same time. If the two change trends are consistent, with resistivity increasing and ultrasonic velocity increasing synchronously, it indicates that the calibration result is valid. If the trends are inconsistent, the calibration process and equipment status are re-checked to ensure that the corrected resistivity data is accurate and reliable. At this point, confirm that the cement mortar is completely hardened, i.e., the resistivity curve remains stable for more than 60 minutes. Combined with temperature and humidity data, confirm that the curing time for the specimen is no less than 24 hours to avoid incomplete solidification leading to test data deviations or specimen damage. Then, activate the rebound hammer 406. Rotating the lead screw 403 will move the support 404, allowing the rebound hammer 406 to move to the central area of ​​the specimen as the test area, avoiding the electrode post 15 and the sensor installation position. Select three test points for each specimen. Adjust the height of the rebound hammer 406 using the electric telescopic cylinder 405, ensuring that the axis of the impact hammer 407 is perpendicular to the test surface of the specimen, the impact hammer 407 is in a free state, and the impact surface is in close contact with the specimen surface. Activate the impact hammer 407 to impact the specimen surface with a preset force. The displacement sensor built into the impact hammer 407 will collect the rebound distance in real time. Each test point was tested three times consecutively. Abnormal data with a deviation from the average value exceeding ±5% were removed, and the arithmetic mean of the remaining valid data was taken as the rebound distance of that test point. Three test points After all measurements are completed, the average of the three values ​​is taken as the overall springback distance of the specimen. The real-time data of the temperature and humidity recorder 14 is recorded synchronously, and the compressive strength is calculated by substituting it into the preset calculation formula and compared with the subsequent press test data for verification. Calculate temperature and humidity correction values ​​based on temperature and humidity data. , Substitute into the basic calculation formula ; (Conventional fitting coefficients:) ), calculate the compressive strength of cement mortar; if Retest; if The calculated result is then corrected by multiplying it by 0.95. After the rebound test is completed, the compressive strength destructive test is carried out: disassemble the outer shell 9 of the test mold, take out the fully hardened cement mortar specimen, clean the surface of the specimen to ensure that the surface of the specimen is flat and undamaged, place the specimen stably at the center of the bottom of the lower pressure head 804, adjust the posture of the specimen to ensure that the center of the specimen is aligned with the center of the lower pressure head 804, and avoid eccentric force during the pressure application process. Send a signal through the independent controller 3 to start the pump 802 in the oil storage tank 801. The pump 802 delivers the lubricating oil in the oil storage tank 801 to the lower pressure head 804 through the delivery pipe 803, and drips evenly onto the contact surface between the lower pressure head 804 and the specimen through the oil outlet 805 at the bottom to form a stable oil film and reduce the sliding friction between the two. After the lubricating oil is applied, start the hydraulic cylinder 6 of the press and control it to load at a constant speed to avoid instantaneous damage to the specimen and data distortion caused by excessive loading. During loading, record the loading force data and the corresponding specimen deformation in real time, and simultaneously collect environmental and internal temperature and humidity data from the temperature and humidity recorder 14 for subsequent compressive strength calculation correction. When the specimen shows obvious damage and crack propagation, and the loading force reaches its peak and begins to decline continuously, stop loading immediately and record the maximum loading force at this time. (Unit: N); Calculate the compressive area A (unit: mm²) based on the recorded maximum loading force and the preset size of the specimen, and substitute it into the compressive strength calculation formula. Calculate the actual compressive strength of cement mortar (Unit: MPa), this value is compared with the rebound test strength. Corrected resistivity data The ultrasonic pulse velocity tester 13 collects ultrasonic velocity data and performs linkage analysis to establish the correlation between the four. If the deviation between any two sets of data exceeds ±8%, the corresponding test link needs to be re-checked to investigate operational errors, equipment failures or environmental interference factors, and ensure the consistency of all test data. After the compression test is completed, the hydraulic cylinder 6 of the press is slowly unloaded, the damaged specimen is removed, the residual lubricating oil and specimen debris on the surface of the lower pressure head 804 are cleaned, and the pump body 802 is turned off. At the same time, the rebound hammer 406, ultrasonic pulse velocity tester 13, temperature and humidity recorder 14 and other equipment are turned off. All test data, calibration parameters, and corrected resistivity curves are synchronously stored in the data storage unit 12010 through the main control logic calibration unit 1207, which is convenient for subsequent experimental review, data verification and test conclusion verification. Finally, the device is reset: the sliding electrode seat 1103 is adjusted to the initial position and fixed with the locking bolt 1104; the control cylinder 1106 is retracted, causing the elastic clamping member 1109 to loosen, the electrode column 15 is removed and cleaned and stored; the bracket 404 is moved to the initial position at one end of the lead screw 403, and the electric telescopic cylinder 405 is retracted to reset the rebound spring 406; the lubricating oil level in the oil tank 801 is checked. If the level sensor 808 detects that the level is lower than the preset value, the alarm 807 will issue a warning. At this time, lubricating oil is added through the oil inlet 806 to ensure the device operates normally next time. This completes the entire test process for the road cement mortar solidification experiment.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended technical solutions and their equivalents.

Claims

1. A testing device for the solidification experiment of cement mortar for highways, comprising a support leg (1), characterized in that: The top of the support leg (1) is equipped with a test platform (2), the outer wall of the test platform (2) is respectively provided with a rebound test component (4) and a pressurizing mechanism (8), the top of the test platform (2) is equipped with a test mold shell (9), the inner wall of the test mold shell (9) is provided with an adjustable positioning group (11), and the top of the adjustable positioning group (11) is provided with an external control box component (12). The rebound test assembly (4) includes a positioning plate (401), a drive motor (402) is fixedly installed on the outer wall of the positioning plate (401), a lead screw (403) is fixedly mounted on the power output shaft of the drive motor (402), a bracket (404) is threadedly connected to the outer wall of the lead screw (403), an electric telescopic cylinder (405) is installed on the top of the bracket (404), a rebound hammer (406) is fixedly mounted on the telescopic end of the electric telescopic cylinder (405), and a spring hammer (407) is provided on the inner wall of the rebound hammer (406). The pressurizing mechanism (8) includes an oil storage tank (801), the inner wall of the oil storage tank (801) is provided with a pump body (802), one end of the delivery pipe (803) is installed on the outer wall of the pump body (802), and the other end of the delivery pipe (803) is provided with a pressure head (804), and the bottom of the pressure head (804) is provided with an oil outlet hole (805).

2. The testing device for the solidification test of highway cement mortar according to claim 1, characterized in that: An independent controller (3) is installed on the outer wall of the test bench (2). A support frame (5) is installed on the top of the test bench (2). A press hydraulic cylinder (6) is installed on the top of the support frame (5). Limiting guide rods (7) are installed at both ends of the press hydraulic cylinder (6). An ultrasonic pulse velocity tester (13) is installed on one side of the outer wall of the test mold shell (9), and a temperature and humidity recorder (14) is installed on the other side of the outer wall of the test mold shell (9). A sandwich layer (10) is provided at the bottom of the inner wall of the test bench (2). An electrode column (15) is installed on the inner wall of the adjustable positioning group (11).

3. The testing device for the solidification test of highway cement mortar according to claim 1, characterized in that: The drive motor (402), electric telescopic cylinder (405), and rebounder (406) are all electrically connected to the main control logic calibration unit (1207), and the bracket (404) slides on the top of the test bench (2).

4. The testing device for the solidification test of highway cement mortar according to claim 1, characterized in that: The outer wall of the oil storage tank (801) is provided with an oil inlet hole (806), an alarm (807) is installed on the outer wall of the oil storage tank (801), and a liquid level sensor (808) is installed on the inner wall of the oil storage tank (801) at the end away from the alarm (807).

5. The testing device for the solidification test of highway cement mortar according to claim 4, characterized in that: The liquid level sensor (808) is electrically connected to the alarm (807). The top of the lower pressure head (804) is connected to the telescopic end of the hydraulic cylinder (6) of the press. There are two pump bodies (802) and two delivery pipes (803), and the two pump bodies (802) and two delivery pipes (803) are symmetrically arranged at both ends of the lower pressure head (804).

6. The testing device for the solidification test of highway cement mortar according to claim 1, characterized in that: The adjustable positioning assembly (11) includes a positioning slide rail (1101). Mounting holes (1102) are provided on both outer walls of the positioning slide rail (1101). A slidable electrode seat (1103) is slidably connected to the outer wall of the positioning slide rail (1101). A locking bolt (1104) is installed on the inner wall of the mounting hole (1102). A limit block (1105) is installed on the top of the slidable electrode seat (1103). A cylinder (1106) is provided on the top of the limit block (1105). A push rod (1107) is fixedly assembled on the telescopic end of the cylinder (1106). A positioning plate (1108) is provided on the outer wall of the push rod (1107). An elastic clamping member (1109) is slidably connected to the inner wall of the limit block (1105).

7. The testing device for the solidification test of highway cement mortar according to claim 6, characterized in that: There are four adjustable positioning groups (11), and the four adjustable positioning groups (11) are symmetrically distributed on the inner wall of the test mold shell (9). The push rod (1107) is electrically connected to the main control logic calibration unit (1207). The sliding electrode seat (1103) moves on the outer wall of the mounting hole (1102) through the locking bolt (1104). The adjustable positioning group (11) is made of polytetrafluoroethylene.

8. The testing device for the solidification test of highway cement mortar according to claim 1, characterized in that: The external control box assembly (12) includes a top cover (1201), on the top of which are respectively installed a cable storage box (1202), a constant current source module (1205), a standard resistor module (1206), a main control logic calibration unit (1207), a mode switching switch (1208), a voltage acquisition unit (1209), and a data storage unit (12010). The bottom of the cable storage box (1202) is provided with an integrated wire hole (1203), and the inner wall of the integrated wire hole (1203) is inlaid with a sealing ring (1204).

9. The testing device for the solidification test of highway cement mortar according to claim 8, characterized in that: The top cover (1201) is located above the test mold shell (9). The mode switching switch (1208) adopts a multi-channel electromagnetic relay structure. The mode switching switch (1208) is connected to the output terminal of the constant current source module (1205), the lead wire of the electrode post (15), and the standard resistor module (1206) through shielded wires. The control terminal of the mode switching switch (1208) is connected to the main control logic calibration unit (1207). The standard resistor module (1206) is provided with an anti-interference shielding shell. The two ends of the standard resistor module (1206) are connected to the mode switching switch (1208) and the voltage acquisition unit (1209) through shielded wires. The sealing ring (1204) is made of high temperature and aging resistant silicone. The inner wall of the circuit storage box (1202) and the interior of the integrated wire hole (1203) are provided with an electromagnetic shielding layer, which is made of copper foil.

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