A mass concrete temperature monitoring device and monitoring method

Abstract

The application provides a mass concrete temperature monitoring device and a monitoring method, which comprise a protection pipe, a bottom seal, a seal, a filling slurry, a scale line, a plurality of temperature sensors and a reading instrument; the protection pipe is configured as a pipe body structure with through ends, the material of the protection pipe is selected from heat-conducting materials, and the outer surface of the protection pipe is provided with the scale line; the bottom seal is blocked at the bottom end of the protection pipe; the filling slurry fills the protection pipe, and the filling slurry is a mixture of bentonite, water, volcanic ash and fly ash; the plurality of temperature sensors are embedded in the filling slurry in the protection pipe according to the set scale line positions; the seal is blocked at the open end of the protection pipe, and the seal is detachably sealed and waterproofly connected with the open end of the protection pipe; the reading instrument is connected with the temperature sensors and used for reading the readings of the temperature sensors, and the device is embedded in concrete for temperature monitoring. The scheme has the advantages of protecting the safety of the sensors, replacing and recycling the sensors, high monitoring accuracy and stable performance.

Description

Technical Field

[0001] This invention relates to the field of water conservancy construction engineering technology, specifically to a temperature monitoring device and method for large-volume concrete. Background Technology

[0002] Mass concrete refers to large-volume concrete structures with a minimum geometric dimension of 1 meter, or concrete that is expected to develop harmful cracks due to temperature changes and shrinkage caused by the hydration of cementitious materials. It is very common in hydraulic dams. Its main characteristics are large volume, small surface area, concentrated heat release from cement hydration, and rapid internal heating. When there is a large temperature difference between the inside and outside of the concrete, temperature cracks can occur, affecting structural safety and normal use.

[0003] Therefore, the impact of temperature stress on concrete quality has received widespread attention in the construction industry. Nowadays, various concrete temperature control measures are constantly being optimized and improved, but the goal is the same: to reduce the internal and external temperature difference of large-volume concrete, thereby reducing temperature stress and avoiding the occurrence of temperature cracks.

[0004] To obtain accurate data on the internal and external temperature changes of large-volume concrete, corresponding requirements have been put forward for concrete temperature monitoring. Currently, the state has also published relevant standards for temperature monitoring of large-volume concrete, such as the "Technical Specification for Temperature Measurement and Control of Large-Volume Concrete" and the "Construction Specification for Large-Volume Concrete," highlighting the importance of temperature monitoring for large-volume concrete.

[0005] Current technologies for monitoring the temperature rise of large-volume concrete include:

[0006] Adiabatic temperature rise test is mostly used to detect the maximum temperature rise of concrete before construction.

[0007] Temperature sensors are pre-embedded during the pouring of large-volume concrete. They are mainly used to detect temperature changes inside the concrete during construction and to provide timely warnings. If necessary, measures can be taken to reduce the temperature difference between the inside and outside of the concrete.

[0008] During construction, temperature sensors are pre-embedded according to design requirements to accurately determine the temperature variation patterns within the concrete. Currently, temperature sensors can be directly placed into the concrete or protected before embedding. Direct impact from concrete or direct contact between the sensor and the vibrator should be avoided. Temperature readings can be taken manually or automatically using a temperature reading instrument, both methods meeting the requirements for temperature measurement.

[0009] However, during actual construction, the temperature sensors embedded in the concrete may be damaged to varying degrees due to factors such as construction skill and protection capabilities, resulting in missing temperature monitoring data, temperature monitoring failure, and unsatisfactory temperature warning effect.

[0010] Furthermore, the temperature sensor cannot be recycled after temperature monitoring is completed, resulting in a waste of resources. Summary of the Invention

[0011] The purpose of this invention is to address the shortcomings of existing technologies by providing a large-volume concrete temperature monitoring device that can protect the temperature sensor, especially from direct impact and direct contact with the vibrator, and is recyclable.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is: a large-volume concrete temperature monitoring device, comprising a protective tube, a bottom seal, a top seal, a filling grout, a marking line, multiple temperature sensors, and a reading instrument;

[0013] The protective tube is configured as a tube structure with both ends open. The material of the protective tube is a thermally conductive material. The outer surface of the protective tube is marked with a line indicating the axial dimension of the protective tube.

[0014] The bottom seal is applied to the bottom end of the protective tube, and the bottom seal is connected to the protective tube in a sealed and waterproof manner.

[0015] The filling grout fills the protective pipe. The filling grout is a mixture of bentonite, water, and volcanic ash / fly ash. The mass content of bentonite in the filling grout is 3% to 8% of the volcanic ash / fly ash, and the mass ratio of water to volcanic ash / fly ash is 0.8 to 1.2. The water bleeding rate of the filling grout is 2%. The filling grout is fluid, has plasticity, and does not solidify at high temperatures below 80°C.

[0016] Multiple temperature sensors are embedded in the filling grout inside the protective tube at the set marked positions;

[0017] The seal is applied to the open end of the protective tube, and the seal is detachably and waterproofly connected to the opening of the protective tube.

[0018] The reader is connected to each temperature sensor to read the readings of each temperature sensor.

[0019] Based on the above, the protective pipe is a PVC pipe or a metal pipe.

[0020] Based on the above, among the multiple temperature sensors, the temperature sensor located at the bottom is ≥3cm away from the bottom seal, and the highest position of the protective tube is higher than the concrete surface.

[0021] Based on the above, the bottom seal is sealed to the bottom of the protective tube using at least one of cement mortar, epoxy mortar, and paraffin wax. The bottom seal is waterproofed to the bottom of the protective tube using waterproof tape, and the height of the bottom seal is ≤3cm.

[0022] Based on the above, the sealing is achieved by using at least one of waterproof tape, plastic film, transparent tape, and paraffin wax to waterproofly seal the opening end of the protective tube.

[0023] Based on the above, the number of temperature sensors is 3-6, and the diameter of the protective tube is 28-30mm.

[0024] A method for monitoring the temperature of large-volume concrete, comprising the aforementioned large-volume concrete temperature monitoring device, wherein monitoring is performed through the following steps:

[0025] Step 1) Determine the number of temperature sensors and the embedment depth of each temperature sensor according to the specifications of the large volume concrete to be monitored. Determine the length and diameter of the protective tube according to the number of temperature sensors and the embedment depth. Then, prefabricate the protective tube with the bottom sealed and prefabricate multiple temperature sensors with the set embedment depth and tie them together for use.

[0026] Step 2) Install the protective pipe in the concrete slab, and control the installation elevation and sag;

[0027] Step 3) Prepare the filling slurry. Let the filling slurry stand for at least 24 hours to ensure that the preparation performance is stable. After stirring evenly again, fill it into the protective tube and gently tap the protective tube to remove air bubbles from the filling slurry.

[0028] Step 4) Place the bundled temperature sensors into the protective tube, use the external markings on the protective tube to determine and calibrate the embedment depth of the temperature sensors, and then seal the tube.

[0029] Step 5) The large volume of concrete begins to be poured. After the pouring is completed, the temperature sensor readings are read at set intervals. If the temperature difference between the inside and outside of the concrete exceeds the specification requirements, an early warning message is issued. If the temperature sensor is found to be damaged or after the monitoring is completed, the seal is opened and the temperature sensor is replaced or recycled.

[0030] Based on the above, the mass ratio of water, volcanic ash and bentonite is 1:1:0.05.

[0031] Based on the above, the temperature sensor is installed on the central axis of the concrete sump, and the protective tube coincides with the central axis of the concrete sump.

[0032] Based on the above, in step 3), the filling slurry is first subjected to a high-temperature test below 80°C after preparation to ensure that it can maintain fluidity under high temperature conditions for a long time.

[0033] This invention has outstanding substantive features and significant progress compared to the prior art. Specifically, this invention has the following advantages:

[0034] 1. The protective tube creates a safe monitoring environment for the temperature sensor, effectively preventing direct impact from concrete on the temperature sensor and direct contact with the vibrator, thus protecting the temperature sensor from damage.

[0035] 2. The protective tube provides a longitudinally extended and relatively independent monitoring space for the temperature sensor. By utilizing the thermal conductivity of the protective tube and the filling grout, accurate monitoring of large-volume concrete can be achieved.

[0036] 3. The enclosed environment provided by the protective tube can prevent the filling slurry from losing moisture, ensuring the stability of the filling slurry's performance, and thus ensuring the stability of the temperature sensor's monitoring.

[0037] 4. Fill the protective tube with a relatively viscous yet fluid filling slurry. After the temperature sensor is damaged or monitoring ends, the seal can be opened to replace or recycle the temperature sensor.

[0038] 5. Designed markings allow for precise placement of temperature sensors at specific embedment depths, enabling temperature detection at specific depths. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the temperature monitoring device for large-volume concrete in this invention.

[0040] In the diagram: 1. Protective tube; 2. Bottom seal; 3. Filling grout; 4. Marking line; 5. Sealing; 6. Temperature sensor; 7. Reading instrument. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0042] like Figure 1 As shown, a temperature monitoring device for large-volume concrete includes a protective tube 1, a bottom seal 2, a sealing opening 5, a filling grout 3, a marking line 4, multiple temperature sensors 6, and a reading instrument 7.

[0043] The protective tube 1 is configured as a tube structure with both ends open. The material of the protective tube 1 is a thermally conductive material, such as metal or PVC. The outer surface of the protective tube 1 is provided with a marking line 4 indicating the axial dimension of the protective tube 1.

[0044] The bottom seal 2 is sealed at the bottom end of the protective tube 1. The bottom seal 2 and the protective tube 1 are sealed to the bottom of the protective tube by at least one of cement mortar, epoxy mortar, and paraffin wax. The bottom seal is waterproofed to the bottom of the protective tube by waterproof tape. The height of the bottom seal is ≤3cm.

[0045] The filling slurry 3 fills the protective pipe 1. The filling slurry 3 is a mixture of bentonite, water, and volcanic ash / fly ash. The mass content of bentonite in the filling slurry 3 is 3%~8% of the volcanic ash / fly ash, and the mass ratio of water to volcanic ash / fly ash is 0.8~1.2. The water bleeding rate of the filling slurry 3 is 2%. The filling slurry 3 is in a fluid state and has plasticity. It does not solidify at high temperatures below 80°C. In this application, the fluid state of the filling slurry 3 refers to a fluid state with a certain viscosity, rather than a fluid state like water. The emphasis is on slow flow because temperature difference will cause fluids like water to flow relatively quickly driven by temperature difference, while the filling slurry 3 is relatively viscous and not easily affected by temperature difference, thus ensuring its own stability.

[0046] Multiple temperature sensors 6 are embedded in the filling grout 3 inside the protective pipe 1 according to the set marking line 4. Among the multiple temperature sensors, the temperature sensor located at the bottom is ≥3cm away from the bottom seal, and the highest position of the protective pipe is higher than the concrete surface.

[0047] Temperature sensors are purchased as finished products and used in conjunction with the reading instrument. Generally, considering the size of large volumes of concrete, the wire length of the temperature sensor should not be less than 3m, and at the very least, not less than 1.1 times the length of the component in the direction of temperature measurement. When using the sensor, its length should be measured. During installation, the total length minus the length outside the protective conduit gives the internal length. Using this formula, the length of the temperature sensor inside the conduit is adjusted to ensure proper embedding within the concrete. Each installed temperature sensor should be numbered to prevent confusion.

[0048] The reading instrument can be either manually read or automatically recorded. Where possible, it is recommended to use an automatically recorded reading instrument and assign personnel to patrol and regularly check the temperature monitoring data. When this is not possible, a manually read reading instrument can be used, with a designated person taking readings according to a pre-determined schedule. Based on the reading results, timely warnings should be issued, and necessary measures should be taken to prevent temperature cracks in the concrete.

[0049] The seal 5 is sealed at the open end of the protective tube 1. The seal 5 and the opening of the protective tube 1 are connected in a waterproof and sealed manner using at least one of waterproof tape, plastic film, transparent tape, and paraffin wax. Its main purpose is to prevent the moisture in the filling slurry inside from evaporating.

[0050] The reading instrument 7 is connected to each temperature sensor 6 to read the readings of each temperature sensor 6. Specific implementation examples:

[0052] The Tanzanian hydroelectric power station is a roller-compacted concrete gravity dam, comprising approximately 1.5 million cubic meters of roller-compacted concrete and approximately 400,000 cubic meters of conventional concrete, the vast majority of which is large-volume concrete. During the construction of both roller-compacted and conventional concrete in this project, temperature sensors were used to monitor the temperature of the large-volume concrete. The device described in this embodiment was used and achieved good results, ensuring a high success rate in monitoring the temperature of the large-volume concrete, verifying the effectiveness of the temperature control measures, and optimizing the temperature control measures, thus playing a positive role in ensuring the construction quality of the large-volume concrete.

[0053] Specifically, the construction steps include the following:

[0054] Step 1) When using this invention to monitor the temperature of large-volume concrete, an iron pipe with a diameter of about 30mm is selected as the protective pipe. Three temperature sensors are installed in the upper, middle and lower parts of the pipe. The temperature sensors are respectively 5cm from the bottom of the concrete slab, in the middle and 10cm from the top surface of the slab.

[0055] Step 2) Install the temperature monitoring device on the central axis of the concrete silo number, 3m from the edge of the silo number, and use measuring instruments and protective pipe markings to control the installation elevation.

[0056] Step 3) uses a filling grout consisting of "water + volcanic ash + bentonite" with a mass ratio of water:volcanic ash:bentonite = 1:1:0.05. This filling grout has undergone static and high-temperature tests, proving that it can maintain a fluid state for an extended period at high temperatures. When using the grout, because it contains bentonite, it should be stirred and allowed to stand for 24 hours. After stirring again until homogeneous, it should be filled into a protective tube, and the tube should be gently tapped to remove air bubbles from the grout.

[0057] Step 4) Place the bundled temperature sensors into the protective tube, use the external markings on the protective tube to determine and calibrate the embedment depth of the temperature sensors, and then seal the tube.

[0058] Step 5) Begin pouring the large volume of concrete. After pouring, use a thermometer to take a reading. The temperature measured 1 hour after the thermometer is covered by concrete is taken as the starting temperature for temperature monitoring. Manual readings are then taken every hour thereafter. If the temperature difference between the inside and outside of the concrete exceeds the specified requirements, an early warning message is issued promptly, and necessary measures are taken. If the temperature sensor is found to be damaged or monitoring is completed, the seal is opened, and the temperature sensor is replaced or recycled.

[0059] After replacement, quickly reseal the pipe opening and then start taking readings. At this time, due to the replacement of the temperature sensor, the slurry filling the protective tube will flow up and down, which may cause abnormal changes in the readings of other temperature sensors. This is a normal phenomenon. Just continue to observe for 2 hours, and the temperature sensor readings will return to the normal range.

[0060] After temperature monitoring is completed, open the seal and remove the temperature sensor. If necessary, use cement grout to replace the filling grout inside the protective tube to complete the sealing of the protective tube.

[0061] Since the device does not affect the engineering structure and the concrete in this compartment needs to be poured upwards, after the monitoring was completed, the temperature sensor was removed and, without any special treatment, was poured directly into the concrete compartment during the construction of the next compartment.

[0062] By analyzing temperature monitoring results and calculations, we can obtain monitoring results such as the maximum temperature rise, surface-to-internal temperature difference, heating rate, and cooling rate of large-volume concrete. Using these results, we can evaluate the effectiveness of temperature control measures or take necessary temperature control measures to reduce the risk of temperature cracks in concrete.

[0063] Existing technologies for monitoring the temperature of large-volume concrete can obtain concrete temperature monitoring results, but they cannot handle the replacement of temperature sensors during the monitoring process or their recycling after the monitoring is completed. Using the device of this invention, in addition to obtaining accurate and reliable concrete temperature monitoring results, the replacement of damaged temperature sensors is considered, avoiding monitoring failures due to sensor damage and ensuring the success rate of large-volume concrete temperature monitoring. Through recycling, the single-use nature of the temperature sensor is increased to multiple cycles, reducing costs and increasing efficiency. Research was conducted on non-setting grout, using commonly used materials in project construction, to prepare a filling grout that maintains its flowability even after high temperatures and prolonged standing, providing a guarantee for the effectiveness of the device of this invention.

[0064] Finally, it should be noted that: the preferred embodiments of this patent have been described in detail above, but this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A mass concrete temperature monitoring device, characterised in that: The device comprises a protective tube, a bottom seal, a seal, a filling slurry, a scale, a plurality of temperature sensors and a reading instrument. The protective tube is configured as a tube structure with both ends through, and the material of the protective tube is selected from heat-conducting materials. The bottom seal is sealed and waterproofly connected with the protective tube. The filling slurry fills the protective tube, and the filling slurry is a mixture of bentonite, water and volcanic ash / pulverized coal ash. The plurality of temperature sensors are embedded in the filling slurry in the protective tube according to the set scale position. The seal is detachably sealed and waterproofly connected with the opening of the protective tube. The reading instrument is connected with each temperature sensor for reading the reading of each temperature sensor.

2. Mass concrete temperature monitoring device according to claim 1, characterized in that The protective tube is a PVC tube or a metal tube.

3. Mass concrete temperature monitoring device according to claim 1 or 2, characterized in that: The distance between the bottommost temperature sensor and the bottom seal is greater than or equal to 3 cm, and the highest position of the protective tube is higher than the surface height of the concrete.

4. A mass concrete temperature monitoring apparatus according to claim 3, characterised in that: The bottom seal is sealed and connected with the bottom of the protective tube by using at least one of cement mortar, epoxy mortar and paraffin, and is waterproofly connected with the bottom of the protective tube by using waterproof adhesive tape.

5. A mass concrete temperature monitoring apparatus according to claim 4, characterised in that: The seal is waterproofly and sealably connected with the opening end of the protective tube by using at least one of waterproof adhesive tape, plastic film, transparent adhesive tape and paraffin.

6. A mass concrete temperature monitoring apparatus according to claim 5, characterised in that: The number of temperature sensors is 3-6, and the diameter of the protective tube is 28-30 mm.

7. A method of mass concrete temperature monitoring, characterized by: The device for monitoring the temperature of mass concrete according to any one of claims 1-6 is monitored by the following steps: Step 1) According to the size of the mass concrete to be monitored, the number of temperature sensors and the embedding depth of each temperature sensor are determined, the length and diameter of the protective tube are determined according to the number and embedding depth of the temperature sensors, and then the protective tube with the bottom seal is prefabricated, and the plurality of temperature sensors with the set embedding depth are bound for use; Step 2) The protective tube is installed in the concrete bin, and the installation elevation and sag are controlled; Step 3) The filling slurry is prepared, the filling slurry is left to stand for at least 24 hours to determine the stable preparation performance, and then the filling slurry is filled into the protective tube after being stirred uniformly, the protective tube is tapped to remove the air bubbles in the filling slurry; Step 4) The plurality of temperature sensors after being bound are placed in the protective tube, the embedding depth of the temperature sensors is determined and calibrated by using the scale outside the protective tube, and the seal is performed; Step 5) The mass concrete is poured, after pouring is completed, the reading of the temperature sensors with time is read at the set interval, if the temperature difference between the inside and outside of the concrete exceeds the specification requirement, a warning information is sent, and if the temperature sensor is damaged or the monitoring is completed, the seal is opened, and the temperature sensor is replaced or recovered.

8. The mass concrete temperature monitoring method of claim 7, wherein: The mass ratio of the water, the volcanic ash and the bentonite is 1:1:0.

05.

9. The mass concrete temperature monitoring method of claim 8, wherein: The temperature sensor is installed on the central axis of the concrete bunker, and the protection tube coincides with the central axis of the concrete bunker.

10. The mass concrete temperature monitoring method of claim 9, wherein: In step 3, the filling slurry is tested at a high temperature below 80°C after being prepared, to ensure that the filling slurry can keep flowing for a long time under high temperature.

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