Temperature-controllable early-age authigenic shrinkage testing device and method for cement-based material

Abstract

The invention discloses a temperature-controllable cement-based material early-age authigenic shrinkage testing device and method.The device comprises a shell, a temperature control module, a measurement and control module and a data processing module, the measurement and control module transmits temperature data acquired by the temperature control module to the data processing module in real time and compares the temperature data with a preset temperature, and the data processing module sends the temperature data to the shell; the control module is used for controlling the temperature control module to regulate and control the liquid phase temperature; the measurement and control module is located in the gas area of the sealing cavity and comprises a plurality of solid rods, a corrugated pipe and a displacement sensor, every three solid rods form a group and are of an inverted triangular structure, multiple groups of inverted triangular structures are arranged in the sealing cavity in the length direction of the sealing cavity at intervals, and the two ends of each inverted triangular structure are fixed to the inner wall of the sealing cavity; the number of the corrugated pipes and the displacement sensors is in one-to-one correspondence with the number of the inverted triangular structures, the corrugated pipes are arranged above the inverted triangular structures, and the displacement sensors are arranged on the corrugated pipes.

Description

Technical Field

[0001] The present invention belongs to the technical field of building material detection, and in particular relates to a temperature-controllable cement-based material early-age autogenous shrinkage testing device and method. Background Art

[0002] Autogenous shrinkage is a major cause of cracking in cement-based materials at very early and early ages. Therefore, studying crack resistance at early and very early ages is crucial for preventing structural cracking, improving durability, and reducing subsequent repair and maintenance costs. However, testing cement-based materials at very early and early ages still presents significant challenges. Current autogenous shrinkage testing methods cannot simultaneously achieve high-precision temperature control and high-precision monitoring of autogenous shrinkage values. Therefore, developing a novel device and test method for testing the early autogenous shrinkage of cement-based materials to achieve high-precision temperature control and high-precision monitoring of autogenous shrinkage values ​​at very early and early ages is of great significance.

[0003] Currently, many methods for measuring autogenous shrinkage have been proposed or standardized. However, due to different definitions of autogenous shrinkage among researchers and the different national standards they rely on, different test methods have emerged. Current test methods make it difficult to accurately evaluate the autogenous shrinkage development of cement-based materials, monitor the autogenous shrinkage of cement-based materials at early and very early ages, and conveniently and quickly study the autogenous shrinkage development of cement-based materials under different constant temperature conditions.

[0004] The length measurement method is the primary method for measuring early-stage shrinkage of cementitious materials. However, this method requires that the cementitious materials be tested after initial or final setting, typically starting at the initial setting time. Therefore, this method cannot monitor the autogenous shrinkage of cementitious materials before initial setting.

[0005] In China, the autogenous shrinkage of concrete is typically measured using the shrinkage test device specified in GB / T 50082-2009, "Test Methods for Long-Term Properties and Durability of Ordinary Concrete." However, this method can only measure the autogenous shrinkage of cement-based materials after initial or final setting and does not provide high-precision temperature control.

[0006] While the American standard ASTM C157, "Standard Test Method for Length Change of Hardened Hydraulic-Cement, Mortar, and Concrete," considers temperature changes due to the heat released by cement hydration, it still has some significant limitations. While the standard mentions the need to consider the effects of temperature, it typically monitors the specimen temperature through embedded temperature sensors and corrects for length changes using the coefficient of thermal expansion. While this method can partially eliminate measurement errors caused by temperature fluctuations, the selection of the coefficient of thermal expansion is subject to uncertainty, especially at early ages when internal temperature fluctuations within the material are significant, potentially leading to significant errors. This method does not strictly control the specimen temperature during testing. In actual testing, cementitious materials experience temperature increases due to the release of heat from hydration, especially during the initial stages of hardening (early ages). This results in alternating thermal expansion and contraction within the material. Without strict temperature control, the measurement results may not accurately reflect the autogenous shrinkage behavior of the cementitious material.

[0007] While the US ASTM C1698 standard, "Standard Test Method for Autogenous Strain of Cement Paste and Mortar," requires that specimens be placed in an oil bath for temperature-controlled measurement, ASTM C1698 treats the oil bath temperature as constant, assuming that this environment stabilizes the temperature of the cementitious material. However, in reality, the oil bath itself can experience slight temperature fluctuations. Especially during extended testing, even small temperature changes can affect the autogenous shrinkage behavior of the cementitious material. These temperature fluctuations, while potentially minor, can cause subtle thermal expansion or contraction within the material, thereby affecting the accuracy of the test results. Furthermore, the standard does not simultaneously measure and record the relationship between temperature changes and autogenous shrinkage. Since the autogenous shrinkage of cementitious materials is directly affected by temperature fluctuations, especially at early ages, the interaction between temperature and autogenous shrinkage is complex. The inability to monitor temperature and autogenous shrinkage simultaneously in real time significantly impacts subsequent accurate calculations.

[0008] Chinese patents CN202210864899.6, "Device and method for synchronously monitoring ultrasonic and autogenous shrinkage characteristics during the hardening process of a paste," and CN202110367299.4, "Method for testing autogenous shrinkage properties of cement-based materials," fail to consider temperature control. While Chinese patent CN201410330986.9, "Autogenous shrinkage measurement device and method capable of eliminating the influence of hydration heat of cement-based materials," considers temperature variations during cement-based material testing, it still fails to achieve high-precision temperature control, and in the relevant examples, the temperature still rises by approximately 1.27°C.

[0009] The temperature-stress test is an emerging testing method that can simulate the entire process from concrete pouring to cooling, while also considering the effects of factors such as the concrete pouring temperature, ambient temperature, and various constraints on the crack resistance of concrete panels. However, this method requires high-precision autogenous shrinkage data during data processing. Therefore, before using the temperature-stress test method, it is necessary to accurately characterize the relationship between the autogenous shrinkage of cement-based materials and their age and temperature. In current research and applications, there is no clear and recognized conclusion regarding the autogenous shrinkage deformation of concrete at early ages. Furthermore, research equipment is not standardized, and there are no test equipment and methods specifically addressing this issue.

[0010] In summary, the test methods covered by current standards present several pressing challenges in practice. First, precise control and measurement of specimen temperatures at different constant temperatures: Current autogenous shrinkage tests often lack sufficient precision in temperature control and measurement. This results in test results being affected by temperature fluctuations, making it difficult to accurately assess the true impact of temperature on autogenous shrinkage. New methods and devices enable precise control and measurement of specimen temperature, providing stable and reliable experimental data. Second, current research and testing methods lack the ability to simultaneously measure temperature and autogenous shrinkage, failing to comprehensively and instantly record subtle temperature changes and autogenous shrinkage. Therefore, a new testing system is needed that can simultaneously monitor temperature and autogenous shrinkage in real time and rapidly characterize the relationship between these two factors and age. This requires a test device and method capable of rapidly acquiring data and performing real-time analysis to promptly understand and predict the autogenous shrinkage behavior of cementitious materials under different conditions. Third, monitoring autogenous shrinkage at very early and early ages is challenging. Because the physical and mechanical properties of cementitious materials change dramatically at these ages, conventional testing methods struggle to capture subtle shrinkage changes. Therefore, it is necessary to develop more sensitive and high-precision monitoring equipment and technologies to accurately record the dynamic process of early spontaneous contraction. Summary of the Invention

[0011] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a temperature-controllable cement-based material early-age autogenous shrinkage test device and method. The present invention can systematically study the relationship between temperature, maturity and autogenous shrinkage under the condition of precise temperature control, which helps to fill the gaps in existing research, promote the in-depth understanding of the autogenous shrinkage mechanism of cement-based materials, and provide a scientific basis for anti-cracking design in engineering practice. The present invention adopts a method of strictly controlling the working environment temperature of the test sample, and realizes precise control and measurement of the sample temperature and deformation through the design of the temperature control module and the measurement and control module. Compared with the existing technology, this patent has higher temperature accuracy, higher data measurement accuracy, and more intelligent operation.

[0012] The technical solution adopted in the present invention is:

[0013] A first aspect of the present invention relates to a temperature-controllable cement-based material early-age autogenous shrinkage testing device, characterized in that it includes a housing, a temperature control module, a measurement and control module, and a data processing module. A sealing cover is provided at the upper end of the housing. The temperature control module and the measurement and control module are both disposed in a sealed cavity within the housing. The lower portion of the sealed cavity is a liquid region, and the upper portion is a gas region. The measurement and control module transmits temperature data collected by the temperature control module to the data processing module in real time, and compares the temperature data with a preset temperature to control the temperature control module to regulate the liquid phase temperature.

[0014] The temperature control module includes a thermostat, a fan, and a temperature sensor. The thermostat is located in the liquid and releases or absorbs heat to allow the liquid to reach a preset temperature. The fan is located in the gas area to accelerate internal gas flow to maintain a consistent gas temperature and accelerate heat exchange between the gas and liquid phases to maintain the same gas and liquid phase temperatures. Temperature sensors are respectively provided in the liquid and gas areas to collect real-time gas and liquid phase temperatures.

[0015] The measurement and control module is located in the gas area of ​​the sealed cavity and includes several solid rods, bellows and displacement sensors. Every three solid rods form a group and form an inverted triangle structure. The lower solid rod is separated from the liquid area below by more than 5 cm to ensure that there is enough space for air to flow. Multiple groups of inverted triangle structures are arranged at intervals along the length direction of the sealed cavity, and the two ends are fixed on the inner wall of the sealed cavity respectively; the number of bellows and displacement sensors set corresponds to the number of inverted triangle structures. The bellows are placed above the inverted triangle structure, and the displacement sensor is set on the bellows.

[0016] Furthermore, plugs for sealing the sample inside the bellows are respectively provided at both ends of the bellows, wherein the displacement sensor is installed on the plug at one end, and a magnet is provided on the plug at the other end for fixing the bellows and concentrating the deformation of the bellows caused by the self-shrinkage of the cement-based material on the end where the bellows is connected to the displacement sensor probe; the bellows is placed on the two solid rods on the upper part of each group of inverted triangle structures, and the two upper solid rods are in contact with the side walls of the bellows.

[0017] Furthermore, the displacement sensor is fixed on the housing and arranged along the long axis direction of the bellows and aligned with the plug of the bellows, and the probe of the displacement sensor is tightly fitted with the plug of the bellows.

[0018] Furthermore, the data processing module includes an operation panel, a data processor, a data storage device and a data output port; wherein:

[0019] An operation panel is provided on the outer surface of the housing and is used to set the preset temperature, sample number, sampling interval and test end judgment criteria;

[0020] A data processor is used to read the temperature data of the temperature sensor in real time and control the working state of the temperature control module, that is, to control the heating or cooling of the thermostat and the working condition of the fan to maintain the temperature of the device at a preset temperature;

[0021] A data storage device for storing test data, wherein the test data includes a preset temperature, a sample number, a sampling interval, a test end judgment standard, temperature data of a temperature sensor, autogenous shrinkage data of a displacement sensor, and a test age corresponding to the temperature data and the autogenous shrinkage data set through an operation panel;

[0022] Data output port, outputs the test data in the data memory to other external devices.

[0023] Furthermore, the temperature range of the liquid controlled by the thermostat is 10°C to 60°C.

[0024] Furthermore, the solid rod is made of a hard material with a low linear expansion coefficient; the length of the solid rod is 470±5 mm.

[0025] Furthermore, the size of the corrugated part of the bellows is Φ29×(420±5) mm.

[0026] A second aspect of the present invention relates to a temperature-controllable method for testing the early-age autogenous shrinkage of cement-based materials, characterized in that it comprises the following steps:

[0027] S1. Material pre-temperature

[0028] S11, the preset temperature is input through the operation panel of the data processing module, the device starts working, the data processing module reads the temperature sensor reading in real time, and controls the working conditions of the thermostat and fan to make the temperature inside the device close to the preset temperature;

[0029] S12, when the internal temperature of the device reaches the preset temperature, the raw materials required for the test are weighed in advance, sealed, and placed on the inverted triangle structure, and pre-heated for 12 to 24 hours to allow the raw materials to reach the preset test temperature;

[0030] S2. Casting and molding

[0031] S21, fully mixing the raw materials after pre-constant temperature according to the required mix ratio to form the cement-based material required for the test;

[0032] S22, pouring the evenly mixed cement-based material into the corrugated pipe, vibrating or tapping the corrugated pipe with a vibration table to ensure that the cement-based material is fully filled into the inner cavity of the corrugated pipe, and sealing the corrugated pipe with a plug after ensuring that bubbles in the material are eliminated;

[0033] S23, check that the length of the corrugated part of the bellows is within 420±5mm. If the length exceeds the range, it can be adjusted by increasing or decreasing the content of cement-based material in the bellows;

[0034] S3. Test device assembly

[0035] S31, move the sealed bellows horizontally into the interior of the device and place the bellows on the two upper middle bars of the same group, tightly adhering to the housing at one end of the non-displacement sensor, while ensuring that the bellows contacts the side walls of the two solid bars;

[0036] S32, adjust the position of the displacement sensor so that the probe of the displacement sensor fits tightly against the bellows plug, and ensure that the displacement sensor has a measurement range of -10mm to 10mm;

[0037] S4. Test the early autogenous shrinkage of cement-based materials under different temperature constant temperature conditions

[0038] S41, after assembly is completed, the data processing module begins to synchronously read the temperature sensor and displacement sensor readings in real time, and performs comprehensive analysis and processing on the data through the built-in operating system. The data processing method refers to the calculation method in Section 8.2.5 of GB / T50082-2024 "Standard for Test Methods for Long-term Properties and Durability of Ordinary Concrete", and forms a time-temperature-strain value coupling curve;

[0039] S42: When the time reaches the preset age time, the device stops working and the test is completed.

[0040] The working principle of the present invention is as follows: through the collaboration of multiple modules, the present invention can monitor and adjust the temperature state of the material during the experiment in real time and accurately measure the autogenous shrinkage of cement-based materials. Specifically, the present invention can set the preset temperature, sample number, sampling interval and test end judgment standard through the operation panel of the data processing module. The preset temperature is the temperature that needs to be maintained during the test, the sampling interval is the frequency at which the device reads the temperature and autogenous shrinkage value, and the test end judgment standard is the total preset duration of the test. The data processor can read the temperature data of the temperature sensor in real time and control the working state of the temperature control module, that is, control the heating or cooling of the thermostat and control the working condition of the fan to maintain the temperature of the device at the preset temperature. The data processor can also synchronously collect the temperature data of the temperature sensor and the autogenous shrinkage data of the displacement sensor in real time and store them in a data storage device. The test data is stored in the data storage device. The test data in the data storage device can be output to other devices, such as a USB flash drive, through the data output port.

[0041] The innovation of this invention lies in its ability to conduct autogenous shrinkage tests at different constant temperature levels, enabling precise control and measurement of specimens at these temperatures. Through precise temperature regulation and high-precision measuring instruments, the system ensures specimen stability at the set temperature, thereby reducing the impact of environmental factors on test results. This precise control and measurement capability makes test results more reliable and consistent, and is of great significance for studying the relationship between temperature, autogenous shrinkage, and age.

[0042] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0043] 1. The present invention is rationally designed and easy to implement: It fully considers the needs of practical applications and operational convenience; its structure and functional layout are optimized, making the implementation and operation of the entire system simple and efficient. Both device installation and daily operation can be carried out smoothly, reducing the operational difficulty for users.

[0044] 2. The present invention implements intelligent control: It is equipped with a data processing module that can automatically control the temperature control module and the measurement and control module to complete the entire process of early-age autogenous shrinkage testing of cement-based materials. The intelligent control system reduces the need for manual intervention and improves the automation level and test efficiency of the test. The user only needs to set basic parameters, and the system can automatically execute the relevant test steps, making the operation convenient and user-friendly.

[0045] 3. The present invention implements autogenous shrinkage testing at different constant temperature levels: The present invention can achieve precise control and measurement of samples at different constant temperature levels; through precise temperature regulation and high-precision measuring instruments, the system ensures the stability of the sample at the set temperature, thereby reducing the interference of environmental factors on the test results; this precise control and measurement capability makes the test results more reliable and consistent, and is of great significance for studying the relationship between temperature, autogenous shrinkage, and age.

[0046] 4. The present invention can provide stable and reliable test data by precisely controlling and measuring the sample temperature. The combination of stable test conditions and high-precision measuring instruments ensures the accuracy and repeatability of the data, which provides a solid foundation for subsequent data analysis and conclusions, and helps to improve the scientific nature and reliability of the research.

[0047] 5. The present invention enables real-time synchronous data monitoring and rapid parameter characterization. It features real-time synchronous monitoring of temperature and autogenous shrinkage, and can rapidly characterize the relationship between these two factors and age. The data processing module rapidly acquires and processes real-time data. Through advanced data analysis techniques, the system can instantly analyze and predict the autogenous shrinkage behavior of cement-based materials under different conditions. This real-time monitoring and rapid characterization capability helps better understand changes in material properties, supporting scientific decision-making and optimized design.

[0048] 6. The present invention enables precise monitoring of the autogenous shrinkage of cement-based materials at the very early and early stages: by recording in detail the dynamic process of early autogenous shrinkage starting from the mixing of cement-based materials, the system can provide comprehensive data support; this is of great significance for understanding the early deformation characteristics of cement-based materials and predicting their performance in actual engineering applications, helping to optimize material design and construction processes, and improving project quality and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is an isometric view of the present invention.

[0050] Figure 2 It is a top view of the present invention.

[0051] Figure 3 It is a front view of the present invention.

[0052] Figure 4 It is a cross-sectional view of the measurement and control module and the temperature control module of the present invention.

[0053] Figure 5 This is a partial enlarged view of the bellows of the present invention.

[0054] Figure 6 This is a principle block diagram of the temperature control module of the present invention.

[0055] Figure 7 It is a working schematic diagram of the device of the present invention.

[0056] Figure 8 The autogenous shrinkage development of five cement-based materials with different mix ratios at a constant temperature of 30°C.

[0057] Figure 9 The autogenous shrinkage development of five cement-based materials with different mix ratios at a constant temperature of 40°C. DETAILED DESCRIPTION

[0058] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0059] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0060] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with exemplary embodiments.

[0061] Example 1

[0062] refer to Figures 1 to 5 The present invention provides a temperature-controllable cement-based material early-age autogenous shrinkage testing device, comprising a housing 1, a temperature control module 2, a measurement and control module 3, and a data processing module 4. A sealing cover plate 5 is provided at the upper end of the housing 1. The temperature control module 2 and the measurement and control module 3 are both disposed in a sealed cavity within the housing 1. The lower portion of the sealed cavity is a liquid region, and the upper portion is a gas region. The measurement and control module 3 transmits temperature data collected by the temperature control module 2 to the data processing module 4 in real time, and compares the temperature data with a preset temperature to control the temperature control module 2 to regulate the liquid phase temperature.

[0063] The temperature control module 2 includes a thermostat 21, a fan 22, and a temperature sensor 23. The thermostat 21 is located in the liquid and allows the liquid to reach a preset temperature by releasing or absorbing heat. The fan 22 is located in the gas area to accelerate the internal gas flow to maintain a consistent gas temperature and accelerate the heat exchange between the gas phase and the liquid phase to maintain the gas phase temperature consistent with the liquid phase temperature. Temperature sensors 23 are respectively provided in the liquid area and the gas area to collect the gas phase temperature and the liquid phase temperature in real time.

[0064] The measurement and control module 3 is located in the gas area of ​​the sealed cavity and includes several solid rods 31, bellows 32 and displacement sensors 33. Every three solid rods 31 form a group and form an inverted triangle structure. The lower solid rod is separated from the liquid area below by more than 5 cm to ensure that there is enough space for air to flow. Multiple groups of inverted triangle structures are arranged at intervals along the length direction of the sealed cavity, and the two ends are respectively fixed on the inner wall of the sealed cavity; the number of bellows 32 and displacement sensors 33 corresponds to the number of inverted triangle structures. The bellows are placed above the inverted triangle structure, and the displacement sensor 33 is arranged on the bellows 32.

[0065] In this embodiment, both ends of the bellows 32 are provided with plugs 34 for sealing the sample inside the bellows, wherein the displacement sensor 33 is installed on the plug 321 at one end, and the plug at the other end is provided with a magnet 35 for fixing the bellows 32 and concentrating the deformation of the bellows caused by the self-shrinkage of the cement-based material on the end connected to the displacement sensor probe; the bellows is placed on the two solid rods on the upper part of each group of inverted triangle structures, and the two upper solid rods are in contact with the side walls of the bellows.

[0066] In this embodiment, the displacement sensor 33 is fixed on the housing 1 and is arranged along the long axis direction of the bellows 32 and aligned with the plug of the bellows 33 . The probe of the displacement sensor 33 fits tightly with the plug of the bellows 32 .

[0067] Specifically, as shown in the figure Figure 1 、 Figure 2 、 Figure 4 and Figure 5 As shown, the displacement sensor is secured as follows: the main body of the displacement sensor is outside the housing. The sensor's probe and measuring rod penetrate the housing through a small hole in the housing and fit tightly against the bellows' plug. Simultaneously, the sensor's sleeve is secured with tiny bolts on the housing, keeping the entire displacement sensor relatively fixed to the housing.

[0068] In this embodiment, the data processing module 4 includes an operation panel 41, a data processor 42, a data storage 43 and a data output port 44; wherein:

[0069] An operation panel 41 is provided on the outer surface of the housing 1 and is used to set the preset temperature, sample number, sampling interval and test end judgment standard;

[0070] The data processor 42 is used to read the temperature data of the temperature sensor in real time and control the working state of the temperature control module, that is, to control the heating or cooling of the thermostat and the working condition of the fan to maintain the temperature of the device at a preset temperature;

[0071] A data memory 43 is used to store test data, including a preset temperature, a sample number, a sampling interval, a test end judgment standard, temperature data of the temperature sensor, autogenous shrinkage data of the displacement sensor, and a test age corresponding to the temperature data and the autogenous shrinkage data set through the operation panel;

[0072] The data output port 44 outputs the test data in the data memory 43 to other external devices.

[0073] In this embodiment, the temperature range of the liquid controlled by the thermostat 21 is 10°C to 60°C.

[0074] In this embodiment, the solid rod 31 is made of a hard material with a low linear expansion coefficient, such as Invar or other hard material with a low linear expansion coefficient; the length of the solid rod is 470±5 mm.

[0075] In this embodiment, the size of the corrugated portion of the bellows 32 is Φ29×(420±5) mm.

[0076] Example 2

[0077] refer to Figures 6 to 9 The present invention provides a temperature-controllable method for testing the early autogenous shrinkage of cement-based materials, comprising the following steps:

[0078] S1. Material pre-temperature

[0079] S11, the preset temperature is input through the operation panel of the data processing module, the device starts working, the data processing module reads the temperature sensor reading in real time, and controls the working conditions of the thermostat and fan to make the temperature inside the device close to the preset temperature;

[0080] S12, when the internal temperature of the device reaches the preset temperature, the raw materials required for the test are weighed in advance, sealed, and placed on the inverted triangle structure, and pre-heated for 12 to 24 hours to allow the raw materials to reach the preset test temperature;

[0081] S2. Casting and molding

[0082] S21, fully mixing the raw materials after pre-constant temperature according to the required mix ratio to form the cement-based material required for the test;

[0083] S22, pouring the evenly mixed cement-based material into the corrugated pipe, vibrating or tapping the corrugated pipe with a vibration table to ensure that the cement-based material is fully filled into the inner cavity of the corrugated pipe, and sealing the corrugated pipe with a plug after ensuring that bubbles in the material are eliminated;

[0084] S23, check that the length of the corrugated part of the bellows is within 420±5mm. If the length exceeds the range, it can be adjusted by increasing or decreasing the content of cement-based material in the bellows;

[0085] S3. Test device assembly

[0086] S31, move the sealed bellows horizontally into the interior of the device and place the bellows on the two upper middle bars of the same group, tightly adhering to the housing at one end of the non-displacement sensor, while ensuring that the bellows contacts the side walls of the two solid bars;

[0087] S32, adjust the position of the displacement sensor so that the probe of the displacement sensor fits tightly against the bellows plug, and ensure that the displacement sensor has a measurement range of -10mm to 10mm;

[0088] The above step 3 should be completed within 15 minutes of starting to mix the cement-based materials.

[0089] S4. Test the early autogenous shrinkage of cement-based materials under different temperature constant temperature conditions

[0090] S41, after assembly is completed, the data processing module begins to synchronously read the temperature sensor and displacement sensor readings in real time, and performs comprehensive analysis and processing on the data through the built-in operating system. The data processing method refers to the calculation method in Section 8.2.5 of GB / T50082-2024 "Standard for Test Methods for Long-term Properties and Durability of Ordinary Concrete", and forms a time-temperature-strain value coupling curve;

[0091] S42: When the time reaches the preset age time, the device stops working and the test is completed.

[0092] The working principle of the present invention is as follows: through the collaboration of multiple modules, the present invention can monitor and adjust the temperature state of the material during the experiment in real time and accurately measure the autogenous shrinkage of cement-based materials. Specifically, the present invention can set the preset temperature, sample number, sampling interval and test end judgment standard through the operation panel of the data processing module. The preset temperature is the temperature that needs to be maintained during the test, the sampling interval is the frequency at which the device reads the temperature and autogenous shrinkage value, and the test end judgment standard is the total preset duration of the test. The data processor can read the temperature data of the temperature sensor in real time and control the working state of the temperature control module, that is, control the heating or cooling of the thermostat and control the working condition of the fan to maintain the temperature of the device at the preset temperature. The data processor can also synchronously collect the temperature data of the temperature sensor and the autogenous shrinkage data of the displacement sensor in real time and store them in a data storage device. The test data is stored in the data storage device. The test data in the data storage device can be output to other devices, such as a USB flash drive, through the data output port.

[0093] In this example, the autogenous shrinkage of five cement-based materials with different mix ratios was tested at constant temperatures of 30°C and 40°C according to the autogenous shrinkage test method for cement-based materials. The temperature-autogenous shrinkage-age relationship can be derived and processed to form the following data: Figures 8 and 9 The data can be used to scientifically and accurately evaluate the autogenous shrinkage development of cement-based materials at different constant temperature levels, thereby better studying and predicting the relationship between temperature, autogenous shrinkage and age, and helping to evaluate the crack resistance of cement-based materials at early ages.

[0094] In this embodiment, the mix ratios of five cement-based materials with different mix ratios are shown in Table 1.

[0095] Table 1 Example mix ratio

[0096]

[0097] This invention enables real-time monitoring of the autogenous shrinkage of cement-based materials at both very early and early ages, starting from the moment of casting. In this example, the test was performed at an early age, enabling real-time monitoring of autogenous shrinkage from the moment the cement-based material was cast. This test achieved high precision, measuring differences in autogenous shrinkage development under different mix ratios and constant temperature environments.

[0098] The present invention has a reasonable design, is easy to use and operate, has high test accuracy and high reliability, and can more scientifically and accurately evaluate the autogenous shrinkage development of cement-based materials at different constant temperature levels, thereby better studying and predicting the relationship between temperature-autogenous shrinkage-age, and helping to evaluate the crack resistance of cement-based materials at early ages. It has good use effect and high promotion and application value.

[0099] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A temperature-controllable cement-based material early age autogenous shrinkage testing device, characterized in that: It includes a housing, a temperature control module, a measurement and control module, and a data processing module. A sealing cover is provided on the upper end of the housing. The temperature control module and the measurement and control module are both provided in a sealed cavity inside the housing. The lower part of the sealed cavity is a liquid area, and the upper part is a gas area. The measurement and control module transmits the temperature data collected by the temperature control module to the data processing module in real time, and compares it with the preset temperature to control the temperature control module to regulate the liquid phase temperature. Among them: The temperature control module includes a thermostat, a fan, and a temperature sensor. The thermostat is located in the liquid and releases or absorbs heat to allow the liquid to reach a preset temperature. The fan is located in the gas area to accelerate internal gas flow to maintain a consistent gas temperature and accelerate heat exchange between the gas and liquid phases to maintain the same gas and liquid phase temperatures. Temperature sensors are respectively provided in the liquid and gas areas to collect real-time gas and liquid phase temperatures. The measurement and control module is located in the gas area of ​​the sealed cavity and includes several solid rods, bellows and displacement sensors. Every three solid rods form a group and form an inverted triangle structure. The lower solid rod is separated from the liquid area below by more than 5 cm to ensure that there is enough space for air to flow; multiple groups of inverted triangle structures are arranged at intervals along the length direction of the sealed cavity, and the two ends are respectively fixed on the inner wall of the sealed cavity; the number of bellows and displacement sensors set corresponds to the number of inverted triangle structures. The bellows are placed above the inverted triangle structure, and the displacement sensor is set on the bellows.

2. A temperature-controllable cement-based material early age autogenous shrinkage testing device as claimed in claim 1, characterized in that: Both ends of the bellows are respectively provided with plugs for sealing the sample inside the bellows. The displacement sensor is installed on the plug at one end, and a magnet is provided on the plug at the other end to fix the bellows and concentrate the deformation of the bellows caused by the self-shrinkage of the cement-based material on the end connected to the displacement sensor probe; the bellows are placed on the two solid rods on the upper part of each group of inverted triangle structures, and the two upper solid rods are in contact with the side walls of the bellows.

3. A temperature-controllable cement-based material early age autogenous shrinkage testing device as claimed in claim 1, characterized in that: The displacement sensor is fixed on the housing and is arranged along the long axis direction of the bellows and aligned with the plug of the bellows. The probe of the displacement sensor is tightly fitted with the plug of the bellows.

4. A temperature-controllable cement-based material early age autogenous shrinkage testing device as claimed in claim 1, characterized in that: The data processing module includes an operation panel, a data processor, a data storage device and a data output port; wherein: An operation panel is provided on the outer surface of the housing and is used to set the preset temperature, sample number, sampling interval and test end judgment criteria; A data processor is used to read the temperature data of the temperature sensor in real time and control the working state of the temperature control module, that is, to control the heating or cooling of the thermostat and the working condition of the fan to maintain the temperature of the device at a preset temperature; A data memory for storing test data, wherein the test data includes a preset temperature, a sample number, a sampling interval, a test end judgment standard, temperature data of a temperature sensor, autogenous shrinkage data of a displacement sensor, and a test age corresponding to the temperature data and the autogenous shrinkage data set through the operation panel; Data output port, outputs the test data in the data memory to other external devices.

5. The temperature-controllable cement-based material early-age autogenous shrinkage testing device according to claim 1, characterized in that: The temperature range of the liquid controlled by the thermostat is 10°C to 60°C.

6. The temperature-controllable cement-based material early-age autogenous shrinkage testing device according to claim 1, characterized in that: The solid rod is made of a hard material with a low linear expansion coefficient; the length of the solid rod is 470±5 mm.

7. The temperature-controllable cement-based material early-age autogenous shrinkage testing device according to claim 1, characterized in that: The size of the corrugated part of the bellows is Φ29×(420±5) mm.

8. A temperature-controlled method for testing the early autogenous shrinkage of cement-based materials, characterized in that: The following steps are involved: S1. Material pre-temperature S11, the preset temperature is input through the operation panel of the data processing module, the device starts working, the data processing module reads the temperature sensor reading in real time, and controls the working conditions of the thermostat and fan to make the temperature inside the device close to the preset temperature; S12, when the internal temperature of the device reaches the preset temperature, the raw materials required for the test are weighed in advance, sealed, and placed on the inverted triangle structure, and pre-heated for 12 to 24 hours to allow the raw materials to reach the preset test temperature; S2. Casting and molding S21, fully mixing the raw materials after pre-constant temperature according to the required mix ratio to form the cement-based material required for the test; S22, pouring the evenly mixed cement-based material into the corrugated pipe, vibrating or tapping the corrugated pipe with a vibration table to ensure that the cement-based material is fully filled into the inner cavity of the corrugated pipe, and sealing the corrugated pipe with a plug after ensuring that bubbles in the material are eliminated; S23, check that the length of the corrugated part of the bellows is within 420±5mm. If the length exceeds the range, it can be adjusted by increasing or decreasing the content of cement-based material in the bellows; S3. Test device assembly S31, move the sealed bellows horizontally into the interior of the device and place the bellows on the two upper middle bars of the same group, tightly adhering to the housing at one end of the non-displacement sensor, while ensuring that the bellows contacts the side walls of the two solid bars; S32, adjust the position of the displacement sensor so that the probe of the displacement sensor fits tightly against the bellows plug, and ensure that the displacement sensor has a measuring range of -10mm to 10mm; S4. Test the early autogenous shrinkage of cement-based materials under different temperature constant conditions S41, after the assembly is completed, the data processing module starts to read the temperature sensor and displacement sensor readings in real time and synchronously, and performs comprehensive analysis and processing on the data through the built-in operating system to form a time-temperature-strain value coupling curve; S42: When the time reaches the preset age time, the device stops working and the test is completed.

Images