Device and method for measuring the adiabatic temperature rise of concrete

Abstract

Device for measuring the adiabatic temperature rise of concrete, characterized in that the device comprises a sample container (1), an adiabatic box (2) and a temperature measuring cannula (3), wherein the sample container (1) and the adiabatic box (2) are spherical, wherein the sample container (1) is embedded in the adiabatic box (2), wherein a vacuum exists between the sample container (1) and the adiabatic box (2), wherein the outside of the adiabatic box (2) is provided with a thermal insulation layer, wherein one end of the multiple temperature measuring cannulas (3) is connected to the sample container (1) and the other end of the multiple temperature measuring cannulas (3) is distributed on a spherical surface concentric with the sample container (1) inside the sample container (1), and wherein the inside of the temperature measuring cannula (3) is provided with an internal temperature measuring device (4).wherein the outer wall of the sample container (1) is provided with a container-external temperature measuring device (5) and a heating device (6), wherein the container-internal temperature measuring device (4), the container-external temperature measuring device (5) and the heating device (6) are each connected to a data acquisition and control system (7).

Description

Field of invention

[0001] The present application relates to the technical field of experimental devices, in particular to a device and a method for measuring the adiabatic temperature rise of concrete. State of the art

[0002] The influence of concrete's exothermic properties on its structural durability has received increasing attention, particularly the temperature rise of mass concrete. According to the definition in the standard construction rules for concrete mixes JG / T55-2000, mass concrete refers to a concrete structure with a minimum size of 1 meter or greater. Furthermore, the internal and external temperature difference of the concrete is expected to be too large due to the heat of hydration of the cement, leading to cracking in the concrete structure. Current practical experience shows that many concrete structures previously considered unsuitable for use with such structures frequently exhibit cracking due to temperature rise.For this reason, the American Concrete Association also believes that the size of cast-in-place concrete must conform to standards to address the problem of heat of hydration and the resulting volume deformation, thereby minimizing the effects on cracking. It can be described as mass concrete, and temperature control measures must be implemented. Therefore, it is evident that the issue of concrete temperature rise has always been a concern both domestically and internationally. By measuring the adiabatic temperature rise of concrete, its hydration and heat release capacity can be assessed.

[0003] Comparable experimental devices are known from publications US 2021 / 0003522A1, CN 109974899A and JP 2020-106377A.

[0004] Currently, the standard method for measuring the adiabatic temperature rise of concrete primarily involves a device for measuring the adiabatic temperature of concrete. This device consists of an adiabatic curing box, shaped like a cuboid or cylinder, and a sample container with a matching inner shape. The adiabatic box completely surrounds the sample container and has a structure similar to Chinese characters. The adiabatic hardening chamber provides an adiabatic environment to ensure that the sample does not exchange heat with the outside world. The temperature of the adiabatic chamber and the sample is monitored in real time by a thermometer in the chamber and a thermometer placed on the sample. The data is fed into the computer for feedback control, ultimately generating a temperature-time curve.

[0005] The curve obtained through this measurement method can be used to quantitatively describe the temperature change of the adiabatic temperature rise process of concrete. However, the main reasons for the low measurement accuracy are the following: 1) Sample shape: The sample container is generally a cuboid or cylinder. The distance of each point on the cross-sectional boundary of the cuboid from the geometric center is not the same, and the thermal boundary conditions of each geometric boundary are inconsistent, resulting in a non-uniform internal temperature of the sample. The temperature measurement data are strongly related to their position, so this is not the true sample temperature. 2) Adiabatic Environment: The so-called adiabatic system is a system that does not exchange heat with the outside world, representing an ideal physical model. According to the principles of thermodynamics, a temperature difference is a sufficient and necessary condition for heat exchange. Therefore, the adiabatic box ensures that the internal and external temperatures of the sample container are consistent, thus isolating heat transfer. Current adiabatic boxes are primarily made of steel plates, and their thermal conductivity is too high. Due to the need to control the temperature of the adiabatic chamber via a heater, there is an airflow within the chamber.Temperature control is achieved through temperature monitoring and feedback adjustment of the adiabatic chamber and the sample. However, the accuracy of the temperature measurement is affected by factors such as the position of the measurement point, the slow response of the heating temperature control, poor temperature control accuracy, and uneven heating. These factors influence the adiabatic effect. 3) Test duration: As the amount of concrete mixed with fly ash and other external admixtures increases, the adiabatic temperature rise of the concrete increases significantly in the later stages. Currently, the adiabatic temperature rise test is only performed for 28 days, and the rate of increase in concrete temperature decreases in the later stages, making it difficult to guarantee test accuracy. Object of the invention

[0006] The purpose of this application is to provide a device and method for measuring the adiabatic temperature rise of concrete, thereby overcoming the shortcomings of the prior art described above. The device exhibits good adiabatic action, bringing the measured temperature closer to the actual value, thus enabling highly accurate measurements in long-term tests, which is an important basis for theoretical analysis and engineering practice.

[0007] The present application is achieved through the following technical solutions: The present application discloses a device for measuring the adiabatic temperature rise of concrete, the device comprising a sample container, an adiabatic box, and a temperature measuring cannula, wherein the sample container and the adiabatic box are spherical, wherein the sample container is embedded in the adiabatic box, wherein a vacuum exists between the sample container and the adiabatic box, wherein the outside of the adiabatic box is provided with a thermal insulation layer, wherein one end of the multiple temperature measuring cannulas is connected to the sample container and the other end of the multiple temperature measuring cannulas is distributed on a spherical surface concentric with the sample container inside the sample container, wherein the inside of the temperature measuring cannula is provided with an internal temperature measuring device, and wherein the outer wall of the sample container is provided with an external temperature measuring device and a heating device.wherein the internal temperature measuring device, the external temperature measuring device and the heating device are each connected to a data acquisition and control system.

[0008] Preferably, the adiabatic box is multilayered and a vacuum exists between the adjacent adiabatic boxes.

[0009] Preferably, the sample container and the adiabatic box are made of a thermal insulation material.

[0010] Preferably, the sample container comprises a lower container hemisphere, an upper container hemisphere, and an upper container cover, wherein the lower container hemisphere is detachably connected to the upper container hemisphere, wherein the upper container hemisphere is detachably connected to the upper container cover, wherein one end of the multiple temperature measuring cannulae is connected to the upper container cover and the other end of the multiple temperature measuring cannulae is evenly distributed on the spherical surface concentric to the sample container. that the adiabatic box comprises a lower box hemisphere, an upper box hemisphere and an upper box cover, wherein the lower box hemisphere is detachably connected to the upper box hemisphere, and wherein the upper box hemisphere is detachably connected to the upper box cover. that several columns are connected between the lower container hemisphere and the lower box hemisphere.

[0011] Preferably, it is further provided that a sealing disc is arranged between the lower container hemisphere and the upper container hemisphere, between the upper container hemisphere and the upper container cover, between the lower box hemisphere and the upper box hemisphere, and between the upper box hemisphere and the upper box cover.

[0012] Preferably, the upper box cover is further provided with a socket and a suction valve, wherein the socket is connected to the container's internal temperature measuring device, the container's external temperature measuring device and the heating device, and wherein the suction valve is provided with a pressure detection device.

[0013] Preferably, the power outlet should be an aviation power outlet.

[0014] Preferably, the temperature measuring cannula comprises a connecting tube and a temperature measuring tip, wherein one end of the connecting tube is connected to the sample container and the other end of the connecting tube is detachably connected to the temperature measuring tip, wherein the container-internal temperature measuring device is connected to the temperature measuring tip.

[0015] Preferably, the connecting pipe is made of a thermal insulation material, and the temperature measuring tip is made of a temperature-sensitive material.

[0016] The present application discloses a method for measuring the adiabatic temperature rise of concrete using the above device for measuring the adiabatic temperature rise of concrete, comprising the following steps: Injecting concrete into the sample container; arranging the container's internal temperature measuring device inside the temperature measuring cannula; wiring the container's internal temperature measuring device, the container's external temperature measuring device, and the heating device to the respective data acquisition and control system; sealing the sample container as a whole and subsequently placing it in the adiabatic box; vacuuming between the adiabatic box and the sample container to seal the entire assembly; Real-time reading of the concrete's internal temperature by the container's internal temperature measuring device; real-time reading of the sample container's external temperature by the container's external temperature measuring device; reading and comparing a temperature difference value between the internal and external temperatures by the data acquisition and control system and comparing the temperature difference value with a preset threshold; controlling the heating device by the data acquisition and control system to begin heating until the temperature difference value exceeds the threshold, or if the temperature difference value exceeds the threshold.

[0017] Compared to the prior art, the present application has the following advantageous technical effects: The present application discloses a device for measuring the adiabatic temperature rise of concrete. The sample container and the adiabatic box have a spherical structure, which facilitates embedding and assembly. More importantly, every position of the spherical surface is equivalent, and the temperature is expressed uniformly. The temperature-measuring end of the temperature-measuring cannula is distributed on a spherical surface concentric with the sample container, so that an accurate temperature value can be obtained with a uniform expression, while simultaneously reducing the variation in measurements due to different arrangement positions. A vacuum exists between the sample container and the adiabatic box, which reduces heat transfer between the concrete sample and the external environment and improves the adiabatic effect.The adiabatic effect is further enhanced by the thermal barrier layer outside the adiabatic box. If a temperature difference occurs inside and outside the sample container, the heating device can raise the temperature outside the sample container to compensate for the internal and external temperature difference, thus ensuring the adiabatic effect during the test process and improving test accuracy. During the test process, the data acquisition and control system handles the recording of temperature data inside and outside the sample container and the switching on / off of the heating device. This results in a high degree of automation and reduces labor, enabling highly precise measurements in long-term tests, which provides an important basis for theoretical analysis and engineering practice.

[0018] Furthermore, it is provided that the adiabatic box has a multi-layered structure, with a vacuum between the adjacent adiabatic boxes, thus enabling test applications with higher adiabatic requirements to be met.

[0019] Furthermore, it is planned that the sample container and the adiabatic box will be made of a thermal insulation material, thereby improving the adiabatic effect and the accuracy of the test data.

[0020] Furthermore, it is provided that the sample container and the adiabatic box have a structural design with the upper hemisphere and the lower hemisphere, which facilitates embedding, assembly and disassembly.

[0021] Furthermore, it is also provided that a sealing disc is arranged at the connection between the components, thereby ensuring tightness and improving the adiabatic effect.

[0022] Furthermore, it is also provided that the internal temperature measuring device, the external temperature measuring device and the heating device are integrated at the socket to reduce the complicated operation of the wiring, thereby facilitating the integration and plugging in of the line, whereby the vacuum level can be monitored in real time by the pressure detection device, so that the adiabatic box can be inflated and cooled as required.

[0023] Furthermore, it is planned that the socket will be an aviation socket, which offers a fast connection and good reliability.

[0024] Furthermore, it is also provided that the temperature measuring cannula has a removable connecting tube and a removable temperature measuring tip structure, which facilitates manufacturing and maintenance.

[0025] Furthermore, it is provided that the connecting pipe consists of a thermal insulation material, and the temperature measuring tip consists of a temperature-sensitive material, thereby ensuring that the temperature of the temperature measuring point can be accurately recorded by the container's internal temperature measuring device with the temperature measuring tip, and improving the accuracy of the data.

[0026] The method for measuring the adiabatic temperature rise of concrete is carried out by the above device for measuring the adiabatic temperature rise of concrete according to the present application, which brings the measured temperature closer to the actual value, so that highly precise measurements can be ensured by compensating for the internal and external temperature difference in long-term tests, which has good application potential. Brief description of the drawings Fig. Figure 1 is an exploded view diagram of a device for measuring the adiabatic temperature rise of concrete according to the present application; Fig. Figure 2 is a diagram illustrating the use of a device for measuring the adiabatic temperature rise of concrete according to the present application; Fig. Figure 3 is a schematic diagram of a device for measuring the adiabatic temperature rise of concrete according to the present application; Fig. Figure 4 is a block diagram of the measurement principle according to the present application. Description of preferred embodiments

[0027] The present application is described in more detail below in conjunction with drawings and specific embodiments, the content of which is more of an interpretation than a limitation of the present application: The device for measuring the adiabatic temperature rise of concrete according to the present application comprises a sample container 1, an adiabatic box 2, and a temperature measuring cannula 3. Both the sample container 1 and the adiabatic box 2 are spherical and are simple pressure vessels designed and manufactured in accordance with the relevant national standards, as described in Fig. Figure 2 shows the sample container 1 embedded in the adiabatic box 2, and a vacuum exists between the sample container 1 and the adiabatic box 2. Depending on the adiabatic requirements, a multi-layered adiabatic box 2 can be arranged, and a vacuum can exist between adjacent adiabatic boxes 2. The sample container 1 and the adiabatic box 2 are made of a thermal insulation material such as G10 fiberglass and resin rolled composite, polytetrafluoroethylene, etc. The outer surface of the adiabatic box 2 is provided with a thermal insulation layer, the thermal insulation layer being made of a material with good thermal insulation properties and a soft texture, such as cotton, foam plastic, etc.

[0028] One end of the multiple temperature measuring cannulas 3 is connected to the sample container 1, and the other end of the multiple temperature measuring cannulas 3 is distributed on a spherical surface concentric with the sample container 1 within the sample container 1. In a preferred embodiment of the present application, the temperature measuring cannula 3 comprises a connecting tube 3-1 and a temperature measuring tip 3-2, wherein one end of the connecting tube 3-1 is connected to the sample container 1 and the other end of the connecting tube 3-1 is screwed to the temperature measuring tip 3-2, and the container-internal temperature measuring device 4 is connected to the temperature measuring tip 3-2, as shown in Fig. Figure 3 shows the connecting tube 3-1, which is made of a thermal insulation material, preferably polytetrafluoroethylene. The temperature measuring tip 3-2 is made of a temperature-sensitive material, preferably copper.

[0029] The inner surface of the temperature measuring cannula 3 is provided with an internal temperature measuring device 4, and the outer wall of the sample container 1 is provided with an external temperature measuring device 5 and a heating device 6. The internal temperature measuring device 4, the external temperature measuring device 5, and the heating device 6 are each connected to a data acquisition and control system 7. The data acquisition and control system 7 comprises a data acquisition card and a host computer. The host computer is equipped with data processing software such as LabVIEW. The measured values ​​of the internal temperature measuring device 4 and the external temperature measuring device 5 can be read by the data acquisition card, converted into an electrical signal, and transmitted to the host computer.After processing by the data processing software, the host computer transmits the control signal to the data acquisition card. The heating level is controlled by adjusting the operating voltage and current of the heating device 6.

[0030] In a preferred embodiment of the present application, the sample container 1 comprises a lower container hemisphere 1-1, an upper container hemisphere 1-2, and an upper container cover 1-3, wherein the lower container hemisphere 1-1 is detachably connected to the upper container hemisphere 1-2 by flanges and connecting bolts, wherein the upper container hemisphere (1-2) is detachably connected to the upper container cover 1-3 by flanges and connecting bolts, wherein one end of the multiple temperature measuring cannulae 3 is connected to the upper container cover 1-3, and the other end of the multiple temperature measuring cannulae 3 is evenly distributed on the spherical surface concentric with the sample container 1, as shown in Fig.Figure 1 shows that the side of the upper container hemisphere 1-2 is provided with a handle. The adiabatic box 2 comprises a lower box hemisphere 2-1, an upper box hemisphere 2-2, and an upper box cover 2-3, wherein the lower box hemisphere 2-1 is detachably connected to the upper box hemisphere 2-2 by flanges and connecting bolts, and the upper box hemisphere 2-2 is detachably connected to the upper box cover 2-3 by flanges and connecting bolts. The side of the upper box hemisphere 2-2 is provided with a handle. Several columns are connected between the lower container hemisphere 1-1 and the lower box hemisphere 2-1. A concentric fixed connection is achieved by a one-to-one correspondence between the pivot point on the outer wall of the lower container hemisphere 1-1 and the lower box hemisphere 2-1.

[0031] A sealing disc can be arranged between the lower container hemisphere 1-1 and the upper container hemisphere 1-2, between the upper container hemisphere 1-2 and the upper container cover 1-3, between the lower box hemisphere 2-1 and the upper box hemisphere 2-2, and between the upper box hemisphere 2-2 and the upper box cover 2-3 to improve the sealing performance of the device. The upper box cover 2-3 is provided with a socket and a vent valve. The internal container temperature measuring device 4, the external container temperature measuring device 5, and the heating device 6 are integrated into the socket. The socket is preferably an aviation-grade socket. The vent valve is provided with a pressure detection device for monitoring the vacuum level and for inflating and cooling the adiabatic box.

[0032] The method for measuring the adiabatic temperature rise of concrete using the device for measuring the adiabatic temperature rise of concrete comprises the following steps: Before testing, the individual components are separated, which facilitates the necessary inspection and cleaning. The number of required layers of the adiabatic box 2 is determined according to the test requirements. First, the lower box hemisphere 2-1 and the lower container hemisphere 1-1 of each layer are installed sequentially. The lower container hemisphere 1-1 is connected to the upper container hemisphere 1-2. Concrete is injected into the sample container 1. The internal container temperature measuring device 4 is positioned in the temperature measuring cannula 3. The upper container cover 1-3, which is attached to the temperature measuring cannula 3, is tightly connected to the upper container hemisphere 1-2. The internal container temperature measuring device 4, the external container temperature measuring device 5, and the heating device 6 are each wired. The external power supply and the data acquisition and control system 7 are connected to the power outlet.The upper box hemisphere 2-2 is connected to the lower box hemisphere 2-1. The upper box cover 2-3 is then connected to the upper box hemisphere 2-2. A vacuum is created between the adiabatic box 2 and the sample container 1 via a suction valve to seal the assembly. The suction valve is closed.

[0033] Generally, due to the setting and temperature rise of the concrete, the internal temperature of sample container 1 is always higher than the external temperature of sample container 1. This temperature difference leads to spontaneous heat dissipation from the concrete. Heat dissipation is not adiabatic; therefore, preventing heat dissipation is key to the adiabatic test. During the test process, the multi-layered adiabatic box 2, the vacuum environment, and the thermal barrier work together to largely prevent heat dissipation from the sample to the outside.

[0034] The internal temperature of the concrete is read in real time by the internal temperature measuring device 4. The external temperature of the sample container 1 is read in real time by the external temperature measuring device 5. The temperature difference between the internal and external temperatures is read and compared by the data acquisition and control system 7, and this temperature difference is compared to a preset threshold. If the temperature difference exceeds the threshold, such as 0.1 °C, the heating device 6 is controlled by the data acquisition and control system 7 to begin heating in order to equalize the internal and external temperature difference until the temperature difference does not exceed the threshold, thus ensuring the adiabatic effect during the test process.

[0035] Once the test is complete, all that is required is to dismantle the equipment and clean the concrete in sample container 1 for the next test.

[0036] It should be noted that the above is only part of the embodiments of the present application. Equivalent modifications made according to the system described in the present application fall within the scope of protection of the present application. The person skilled in the technical field to which the present application belongs can replace the specific examples described in a similar manner. As long as these replacements do not deviate from the structure of the present application or do not go beyond the scope defined in this claim, they fall within the scope of protection of the present application. Reference sign 1 sample container 1-1 Lower container hemisphere 1-2 Upper container hemisphere 1-3 Top container cover 2 Adiabatic Box 2-1 Lower Box Hemisphere 2-2 Upper box hemisphere 2-3 Top box cover 3 temperature measuring cannula 3-1 Connecting pipe 3-2 Temperature measuring tip 4. Internal container temperature measuring device 5 Container external temperature measuring device 6 Heating device 7. Data acquisition and control system.

Claims

[1] Device for measuring the adiabatic temperature rise of concrete, characterized bythat the device comprises a sample container (1), an adiabatic box (2) and a temperature measuring cannula (3), wherein the sample container (1) and the adiabatic box (2) are spherical, wherein the sample container (1) is embedded in the adiabatic box (2), wherein a vacuum exists between the sample container (1) and the adiabatic box (2), wherein the outside of the adiabatic box (2) is provided with a thermal insulation layer, wherein one end of the multiple temperature measuring cannulas (3) is connected to the sample container (1) and the other end of the multiple temperature measuring cannulas (3) is distributed on a spherical surface concentric with the sample container (1) inside the sample container (1), that the inside of the temperature measuring cannula (3) is provided with an internal temperature measuring device (4), wherein the outer wall of the sample container (1) is provided with an external temperature measuring device (5) and a heating device (6),wherein the internal temperature measuring device (4), the external temperature measuring device (5) and the heating device (6) are each connected to a data acquisition and control system (7). [2] Device for measuring the adiabatic temperature rise of concrete according to claim 1, characterized by , that the adiabatic box (2) is multilayered and that a vacuum exists between the adjacent adiabatic boxes (2). [3] Device for measuring the adiabatic temperature rise of concrete according to claim 1, characterized by , that the sample container (1) and the adiabatic box (2) are made of a thermal insulation material. [4] Device for measuring the adiabatic temperature rise of concrete according to claim 1, characterized bythat the sample container (1) comprises a lower container hemisphere (1-1), an upper container hemisphere (1-2) and an upper container cover (1-3), wherein the lower container hemisphere (1-1) is detachably connected to the upper container hemisphere (1-2), wherein the upper container hemisphere (1-2) is detachably connected to the upper container cover (1-3), wherein one end of the multiple temperature measuring cannulae (3) is connected to the upper container cover (1-3) and the other end of the multiple temperature measuring cannulae (3) is evenly distributed on the spherical surface concentric with the sample container (1), that the adiabatic box (2) comprises a lower box hemisphere (2-1), an upper box hemisphere (2-2) and an upper box cover (2-3), wherein the lower box hemisphere (2-1) is detachably connected to the upper box hemisphere (2-2), and wherein the upper box hemisphere (2-2) is detachably connected to the upper box cover (2-3). is,that several columns are connected between the lower container hemisphere (1-1) and the lower box hemisphere (2-1). [5] Device for measuring the adiabatic temperature rise of concrete according to claim 3, characterized by , that a sealing disc is arranged between the lower container hemisphere (1-1) and the upper container hemisphere (1-2), between the upper container hemisphere (1-2) and the upper container cover (1-3), between the lower box hemisphere (2-1) and the upper box hemisphere (2-2) and between the upper box hemisphere (2-2) and the upper box cover (2-3). [6] Device for measuring the adiabatic temperature rise of concrete according to claim 3, characterized by, that the upper box cover (2-3) is provided with a socket and a suction valve, wherein the socket is connected to the container internal temperature measuring device (4), the container external temperature measuring device (5) and the heating device (6), wherein the suction valve is provided with a pressure detection device. [7] Device for measuring the adiabatic temperature rise of concrete according to claim 6, characterized by that the socket is an aviation socket. [8] Device for measuring the adiabatic temperature rise of concrete according to claim 1, characterized by, that the temperature measuring cannula (3) comprises a connecting tube (3-1) and a temperature measuring tip (3-2), wherein one end of the connecting tube (3-1) is connected to the sample container (1) and the other end of the connecting tube (3-1) is detachably connected to the temperature measuring tip (3-2), wherein the container-internal temperature measuring device (4) is connected to the temperature measuring tip (3-2). [9] Device for measuring the adiabatic temperature rise of concrete according to claim 7, characterized by , that the connecting pipe (3-1) is made of a thermal insulation material, wherein the temperature measuring tip (3-2) is made of a temperature-sensitive material. [10] Method for measuring the adiabatic temperature rise of concrete using the device for measuring the adiabatic temperature rise of concrete according to any one of claims 1 to 9, characterized by that the procedure includes the following steps: Injecting concrete into the sample container (1); positioning the container's internal temperature measuring device (4) inside the temperature measuring cannula (3); wiring the container's internal temperature measuring device (4), the container's external temperature measuring device (5), and the heating device (6) to the data acquisition and control system (7); sealing the sample container (1) as a whole and subsequently placing it in the adiabatic box (2); vacuuming between the adiabatic box (2) and the sample container (1) to seal the entire assembly; reading the internal temperature of the concrete in real time by the container's internal temperature measuring device (4); reading the external temperature of the sample container (1) in real time by the container's external temperature measuring device (5);Reading and comparing a temperature difference value between the indoor temperature and the outdoor temperature by the data acquisition and control system (7) and comparing the temperature difference value with a preset threshold value; controlling the heating device (6) by the data acquisition and control system (7) to start heating until the temperature difference value does not exceed the threshold value, or if the temperature difference value does exceed the threshold value.

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