Large-temperature-difference environment mass concrete cooling circulating water temperature control construction method
By using low-heat cement and fly ash or slag powder mix design in the large temperature difference environment of high-altitude and cold regions, combined with cooling water pipe network and dynamic temperature control system, the problem of controlling the internal and external temperature difference of concrete was solved, and the crack-resistant construction effect of concrete was achieved.
Patent Information
- Application Number
- CN202610270988.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-06
- Publication Date
- 2026-05-08
AI Technical Summary
In high-altitude and frigid regions with large temperature differences, existing cooling water circulation technology cannot effectively control the internal and external temperature differences of concrete, resulting in excessive temperature stress, which can easily cause concrete cracking and fail to meet the requirements for crack resistance and temperature control.
Low-heat cement is used as the main cementitious material, with fly ash or slag powder added. A crack-resistant mix design is used, and a closed-loop system is formed by combining a cooling water pipe network and temperature sensors. By dynamically adjusting the temperature and flow of the circulating water, combined with surface insulation measures, dynamic control of the internal temperature rise and internal and external temperature difference of the concrete is achieved.
It achieves full-process crack control during the construction of large-volume concrete, and improves the construction quality and crack resistance of concrete through differentiated cooling modes and scientific curing standards.
Smart Images
Figure CN121992954A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete construction technology, and in particular to a method for temperature control of cooling circulating water in large-volume concrete under large temperature difference environments. Background Technology
[0002] In high-altitude and frigid regions, the diurnal temperature range often exceeds 25°C. This drastic fluctuation is the primary direct factor contributing to temperature cracking in large-volume concrete. The heat released during concrete hydration raises the internal temperature, while the ambient temperature drops sharply below zero at night. This dual temperature gradient creates thermal stress that easily exceeds the tensile strength of the concrete, leading to cracks and affecting project quality. Existing cooling water circulation temperature control technology for large-volume concrete primarily reduces internal temperature peaks through pre-embedded cooling water pipes and unidirectional constant water flow. While effective under normal temperature differences, this static method has limitations when applied to high-altitude and frigid environments. While it can suppress temperature peaks during the day, the continuous low-temperature water flow combined with the cold environment at night accelerates internal cooling, widens the internal-external temperature difference, generates significant thermal stress, and induces concrete cracking, failing to meet the requirements for crack-resistant temperature control. Therefore, this invention proposes a construction method for cooling water circulation temperature control of large-volume concrete in environments with large temperature differences. Summary of the Invention
[0003] The purpose of this invention is to address the problem in the prior art where, during the day, the temperature peak can be suppressed, but when the environment suddenly cools down at night, the continuous low-temperature water circulation combined with the cold environment will accelerate internal cooling, widen the temperature difference between the inside and outside, generate huge temperature stress, induce concrete cracking, and fail to meet the requirements for crack resistance and temperature control. The invention proposes a construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences.
[0004] The technical solution of this invention: a construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences, comprising the following steps: S1. Using low-heat cement as the main cementing material, fly ash or slag powder is added to design and test the concrete mix proportion, and the final construction mix proportion is determined through crack resistance verification test. S2. Based on the thermal parameters of concrete under the construction mix ratio, a cooling water pipe network and temperature sensors are planned and pre-embedded in the large-volume concrete structure, and connected to external temperature control equipment to form a cooling circulation system. S3. Using the concrete mixed according to the construction mix ratio, control its pouring temperature and pour it in layers. After the concrete covers part of the cooling water pipes, start the cooling circulation system and begin temperature monitoring. S4. Based on real-time temperature monitoring data, dynamically adjust the temperature and flow rate of circulating water to control the internal temperature rise and internal-external temperature difference of concrete, and combine surface insulation measures for curing. S5. Once the concrete strength has increased to the required level and the temperature field has stabilized, stop the cooling system and remove the curing facilities.
[0005] Optionally, in step S1, the specific steps for determining the final construction mix proportion through crack resistance verification tests include: S11. Prepare concrete specimens according to the preliminarily determined mix proportions; S12. Place the specimen in a temperature cycling chamber to simulate the large temperature difference between day and night in high-altitude and cold regions for curing. S13. Use a crack observation instrument to regularly observe and record the cracking time, number of cracks and width of the specimen surface; S14. Using the observation results as the key evaluation index, compare the crack resistance performance of different mix proportions, and finally select the mix proportion with the lowest cracking risk as the construction mix proportion, which will be used for concrete mixing in subsequent steps.
[0006] Optionally, the temperature control program of the temperature cycling chamber is as follows: the highest temperature during the day is 15℃, the lowest temperature at night is -10℃, the heating and cooling rate is 2-3℃ / hour, and the single temperature cycle is 24 hours. The crack observation instrument is an electronic magnifying glass with a magnification of not less than 20 times and a measurement accuracy of 0.01mm. The observation frequency is on the 1st, 3rd, 7th, 14th and 28th day after the specimen is formed. When comparing the crack resistance performance of different mix proportions, a weighted comprehensive evaluation system is adopted with initial crack time of 0.3, total number of cracks of 0.2, maximum crack width of 0.3 and total crack area of 0.2. The mix proportion with the highest comprehensive crack resistance score and simultaneously meets the design compressive strength and frost resistance index is selected.
[0007] Optionally, in step S2, based on the adiabatic temperature rise prediction curve of the construction mix ratio and the site environmental conditions, the pipe diameter, layout spacing, and loop length of the cooling water pipes are calculated and determined. The construction parameters include the adiabatic temperature rise value, the time to reach the temperature peak, the thermal conductivity, and the specific heat capacity. The cooling water pipes are HDPE pipes with an outer diameter of 32mm and a wall thickness of 2.0mm. The layout spacing is 0.8m vertically and 1.2m horizontally. The length of a single loop is controlled within 250m. The temperature sensor is a PT1000 platinum resistance thermometer. The pipes are arranged in a three-dimensional grid pattern inside the concrete. The core high-temperature zone is arranged at a spacing of 1.0m×1.0m×0.8m, and the surface area is arranged with a denser spacing of 0.8m×0.8m. The cooling water pipe network is connected to the manifold in parallel. Each branch of the manifold is equipped with an independent regulating valve and flow meter, and is connected to a temperature control device with automatic data acquisition and control functions.
[0008] Optionally, in step S3, the specific steps for controlling the concrete pouring temperature and performing layered pouring include: S31. According to the construction mix ratio, the mixing water is heated to 60±5℃ at the mixing plant, and the aggregate is preheated to above 5℃ by hot air in the heat preservation shed. S32. Insulated tank trucks with double-layer insulated tanks are used to transport concrete, and the tanks are insulated during transportation. S33. During the pouring process, the time from concrete discharge to placement in the formwork should not exceed 90 minutes. A layered continuous pouring process should be adopted, with each layer controlled to a thickness of 50cm. The interval between layers should not exceed the initial setting time of the concrete. The vibration spacing should not exceed 50cm, and contact with cooling water pipes and temperature sensors should be avoided. When the concrete surface covers the first layer of cooling water pipes to a thickness of 50cm, the cooling circulation system should be immediately activated. The initial water temperature should be set 10-15℃ lower than the measured temperature of the concrete core area at that moment, and the flow rate should be controlled at 1.2-1.5m³. ³ / h, and automatically collect and record temperature data at each measuring point every 30 minutes.
[0009] Optionally, in step S4, the specific steps for dynamically adjusting the temperature and flow rate of the circulating water to control the internal temperature rise and internal-external temperature difference of the concrete include: S41. When the core temperature inside the concrete is detected to rise rapidly at a rate exceeding 2℃ / hour over a continuous 4-hour period, activate the high-flow-rate, low-temperature-difference cooling mode. Control the temperature difference between the inlet water and the highest internal temperature of the concrete within 10–15℃, while simultaneously increasing the cooling water flow rate to 1.8–2.2 m³ / h. 3 / h, to accelerate heat dissipation; S42. When the temperature at the core measuring point inside the concrete reaches its peak and begins to decline within 12 consecutive hours with a variation not exceeding ±0.5℃, switch to a low-flow-rate, high-temperature-difference cooling mode. Gradually reduce the difference between the inlet water temperature and the highest temperature inside the concrete to within 5–8℃, while simultaneously reducing the cooling water flow rate to 0.8–1.2 m³ / h. 3 / h, and control the concrete cooling rate within any 24-hour cycle to remain below 2℃ / day, in order to mitigate temperature shrinkage stress.
[0010] Optionally, in step S4, the specific steps for curing in conjunction with surface insulation measures include: S43. After the concrete has set, cover it with a plastic film with a thickness of not less than 0.12 mm to keep it moist, and the overlap between each film should be not less than 200 mm. S44. On top of the plastic film, tightly cover at least one layer of rock wool insulation blanket with a thermal conductivity of not more than 0.045 W / (m·K); S45. When the environmental forecast predicts rain or snow or the actual ambient temperature is below -15℃, add a layer of waterproof canvas on top of the insulation blanket and seal the seams with double pressure strips.
[0011] Optionally, in step S5, the specific steps for determining whether the concrete strength growth meets the requirements are as follows: S51. At the site, no less than 3 sets of test blocks cured under the same conditions shall be used for the construction mix ratio and tested for 3 days, 7 days and final strength respectively. After demolding, the test blocks shall be placed in a curing box that can synchronously reproduce the temperature changes and thermal insulation environment of the solid structure. S52. When the compressive strength test value of the test block reaches more than 75% of the design strength, and at the same time, the difference between the highest internal temperature and the lowest surface temperature of the concrete at all measuring points within 24 consecutive hours does not exceed 20℃, and the standard deviation of the temperature data at each measuring point during this period is less than 2℃, the removal conditions are deemed to be met.
[0012] Optionally, the cooling system can be shut down in stages or steps, starting with reducing the cooling water flow rate to 0.5 m³ / h in three separate steps over 24 hours. 3 / h, while raising the inlet water temperature to a value not exceeding 5℃ from the ambient temperature, then stop the circulating water pump but keep the monitoring system running. After 24 hours of confirming that the temperature data has no abnormal fluctuations, completely stop the system and orderly remove the surface curing facilities. After removal, the concrete surface still needs to undergo a 3-day visual inspection.
[0013] Compared with the prior art, the present invention has the following beneficial technical effects: This invention achieves full-process crack control in the construction of large-volume concrete by designing crack-resistant mix proportions, deploying systems based on thermal parameters, and implementing dynamic temperature-controlled curing. Through a phased dynamic control strategy, it adopts differentiated control modes with large flow rate and low temperature difference for the heating period and small flow rate and high temperature difference for the cooling period, respectively. This solves the technical problem that cooling technology cannot adapt to the large temperature difference environment at high altitudes. By setting dual criteria of strength index and temperature difference index, a scientific curing removal standard is established, thereby improving the construction quality and crack resistance of concrete. Attached Figure Description
[0014] Figure 1 A flowchart of the construction method for temperature control of cooling circulating water for large-volume concrete in a large temperature difference environment according to the present invention is provided. Figure 2 for Figure 1 Flowchart of S1; Figure 3 for Figure 1 Flowchart of S3 in the middle; Figure 4 for Figure 1 Flowchart of S4 in the middle; Figure 5 for Figure 1 The flowchart of S5 in the middle. Detailed Implementation
[0015] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0016] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.
[0017] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example
[0020] like Figure 1 and Figure 2 As shown, the temperature control construction method for cooling circulating water in large-volume concrete under large temperature difference environments proposed in this invention includes the following steps: S1. Using low-heat cement as the main cementitious material, fly ash or slag powder is added for concrete mix design and trial mixing. The fly ash is selected as Grade II or above, and the slag powder is selected as Grade S95 or above. The dosage is controlled at 30%-50% of the total cementitious material, and the fly ash content alone does not exceed 40%, and the slag powder content alone does not exceed 50%. The final construction mix proportion is determined through crack resistance verification test. In specific step S1, the steps for determining the final construction mix proportion through crack resistance verification tests include: S11. Based on the 3-5 preliminarily determined mix proportions with different admixtures and different water-cement ratios, prepare concrete specimens of the same size. Prepare no less than 3 specimens for each mix proportion to ensure the representativeness of the test data. S12. Place the specimen in a temperature cycling chamber and strictly simulate the large temperature difference between day and night in the high-altitude and cold region for curing. The curing period shall be no less than 28 days. During this period, the surface humidity of the specimen shall be kept no less than 90% to avoid the risk of cracking caused by the superposition of drying shrinkage and temperature difference shrinkage. S13. Use a crack observation instrument to regularly observe and record the cracking time, number and width of cracks on the surface of the specimen. When observing, adopt a multi-angle observation method, and pay special attention to stress concentration areas such as the corners and center of the surface of the specimen to avoid missing tiny cracks. S14. Using the observation results as the key evaluation index, compare the crack resistance performance of different mix proportions, and finally select the mix proportion with the lowest cracking risk as the construction mix proportion, which will be used for concrete mixing in subsequent steps.
[0021] Furthermore, the temperature control program of the temperature circulation chamber is as follows: the highest temperature during the day is 15℃, the lowest temperature at night is -10℃, the heating and cooling rate is 2-3℃ / hour, the heating rate does not exceed 3℃ / hour, and the cooling rate does not exceed 2℃ / hour to avoid excessive cooling and temperature stress. The single temperature cycle is 24 hours, and the continuous cycle maintenance is 28 days.
[0022] Furthermore, the crack observation instrument is an electronic magnifying glass with a magnification of not less than 20x and a measurement accuracy of 0.01mm. The observation frequency is on the 1st, 3rd, 7th, 14th and 28th day after the specimen is formed. In the first 7 days, one afternoon observation is added every day to focus on monitoring early cracking. When comparing the crack resistance performance of different mix proportions, a weighted comprehensive evaluation system is adopted with initial cracking time of 0.3, total number of cracks of 0.2, maximum crack width of 0.3 and total crack area of 0.2. The mix proportion with the highest comprehensive crack resistance performance score is selected, which also meets the design compressive strength, reaches 100% or more of the design strength grade and has a frost resistance grade of not less than F200. If there are cases with the same comprehensive score, the mix proportion with a smaller water-cement ratio and a more reasonable amount of cementitious material is given priority.
[0023] like Figure 1 and Figure 3 As shown in Figure S2, based on the thermal parameters of the concrete under the construction mix ratio, combined with the size, thickness and pouring zones of the large-volume concrete structure, a cooling water pipe network and temperature sensors are planned and pre-embedded in the large-volume concrete structure, and connected to external temperature control equipment to form a closed-loop cooling circulation system to ensure uniform cooling and accurate monitoring.
[0024] In specific step S2, based on the adiabatic temperature rise prediction curve of the construction mix proportion, the adiabatic temperature rise test is conducted. The test environment temperature is controlled at 20±2℃, and the on-site environmental conditions, including day-night temperature difference, ambient wind speed, and solar radiation intensity, are taken into account. Professional thermal calculation software, such as MidasGTS or ANSYS, is used to calculate and determine the pipe diameter, arrangement spacing, and loop length of the cooling water pipes to ensure that the cooling efficiency meets the temperature control requirements.
[0025] In addition, thermal parameters include adiabatic temperature rise, time to reach peak temperature, thermal conductivity, and specific heat capacity, wherein the adiabatic temperature rise shall not exceed 50°C, and the time to reach peak temperature shall not be earlier than 3 days after the completion of pouring.
[0026] The cooling water pipes are made of HDPE pipes with an outer diameter of 32mm and a wall thickness of 2.0mm. The spacing between them is 0.8m vertically and 1.2m horizontally. The length of a single loop is controlled within 250m, and the longest is no more than 300m, to avoid excessive cooling water temperature difference due to excessive loop length. The water pipe elbows are injection molded elbows of the same material, and the bending radius is not less than 5 times the pipe diameter to prevent water pipe damage.
[0027] The temperature sensor is a PT1000 platinum resistance thermometer with a measurement range of -50℃ to 150℃ and a measurement accuracy of ±0.1℃. It is arranged in a three-dimensional grid pattern inside the concrete. In the core high-temperature zone, at a distance greater than 1.5m from the surface, it is arranged at a spacing of 1.0m×1.0m×0.8m. In the surface area, within 0.5m from the surface, it is arranged at a denser spacing of 0.8m×0.8m. At least one ambient temperature measuring point is set in each pouring section.
[0028] The cooling water pipe network is connected to the manifold in parallel. Each branch of the manifold is equipped with an independent regulating valve and flow meter, and is connected to a temperature control device with automatic data acquisition, real-time alarm and automatic control functions. The temperature control device can preset temperature thresholds. When the monitored temperature exceeds the threshold, it will automatically trigger an alarm and adjust the cooling parameters.
[0029] like Figure 1 and Figure 4 As shown in Figure S3, use concrete mixed according to the construction mix ratio, control its pouring temperature and pour it in layers. After the concrete covers part of the cooling water pipes, start the cooling circulation system and begin temperature monitoring.
[0030] In specific step S3, the steps for controlling the concrete pouring temperature and performing layered pouring include: S31. According to the construction mix ratio, the mixing water is heated to 60±5℃ at the mixing plant, and the aggregate is preheated to above 5℃ by hot air in the heat preservation shed. S32. Insulated tank trucks with double-layer insulated tanks are used to transport concrete, and the tanks are insulated during transportation. S33. During the pouring process, the time from concrete discharge to placement in the formwork should not exceed 90 minutes. A layered continuous pouring process should be adopted, with each layer controlled to a thickness of 50cm. The interval between layers should not exceed the initial setting time of the concrete. The vibration spacing should not exceed 50cm, and contact with cooling water pipes and temperature sensors should be avoided. When the concrete surface covers the first layer of cooling water pipes to a thickness of 50cm, the cooling circulation system should be immediately activated. The initial water temperature should be set 10-15℃ lower than the measured temperature of the concrete core area at that moment, and the flow rate should be controlled at 1.2-1.5m³. 3 / h, and automatically collect and record temperature data at each measuring point every 30 minutes.
[0031] like Figure 1 and Figure 4 As shown in Figure S4, based on real-time temperature monitoring data, the temperature and flow rate of circulating water are dynamically adjusted to control the internal temperature rise and internal and external temperature difference of the concrete, while surface insulation measures are combined for curing.
[0032] In specific step S4, the steps for dynamically adjusting the temperature and flow rate of circulating water to control the internal temperature rise and internal-external temperature difference of the concrete include: S41. When the core temperature inside the concrete is detected to rise rapidly at a rate exceeding 2℃ / hour over a continuous 4-hour period, activate the high-flow-rate, low-temperature-difference cooling mode. Control the temperature difference between the inlet water and the highest internal temperature of the concrete within 10-15℃, while simultaneously increasing the cooling water flow rate to 1.8-2.2m³ / h. 3 / h, to accelerate heat dissipation; S42. When the temperature at the core measuring point inside the concrete reaches its peak and begins to decline within 12 consecutive hours with a variation not exceeding ±0.5℃, switch to a low-flow-rate, high-temperature-difference cooling mode. Gradually reduce the difference between the inlet water temperature and the highest temperature inside the concrete to within 5-8℃, while simultaneously reducing the cooling water flow rate to 0.8-1.2m³ / h. 3 / h, and control the concrete cooling rate to remain below 2℃ / day within any 24-hour cycle to mitigate temperature shrinkage stress. Step S4, which combines surface insulation measures with curing, includes the following specific steps: S43. After the concrete has set, cover it with a plastic film with a thickness of not less than 0.12 mm to keep it moist, and the overlap between each film should be not less than 200 mm. S44. On top of the plastic film, tightly cover at least one layer of rock wool insulation blanket with a thermal conductivity of not more than 0.045 W / (m·K); S45. When the environmental forecast predicts rain or snow or the actual ambient temperature is below -15℃, add a layer of waterproof canvas on top of the insulation blanket and seal the seams with double pressure strips.
[0033] like Figure 1and Figure 5 As shown in Figure S5, once the concrete strength has increased to the required level and the temperature field has stabilized, stop the cooling system and remove the curing facilities.
[0034] In specific step S5, the steps to determine whether the concrete strength growth meets the requirements are as follows: S51. At the site, no less than 3 sets of test blocks cured under the same conditions shall be used for the construction mix ratio and tested for 3 days, 7 days and final strength respectively. After demolding, the test blocks shall be placed in a curing box that can synchronously reproduce the temperature changes and thermal insulation environment of the solid structure. S52. When the compressive strength test value of the test block reaches more than 75% of the design strength, and simultaneously meets the condition that the difference between the highest internal temperature and the lowest surface temperature of the concrete at all measuring points within 24 consecutive hours does not exceed 20℃, and the standard deviation of the temperature data at each measuring point during this period is less than 2℃, the removal condition is deemed met. The cooling system is shut down in stages and steps. First, the cooling water flow rate is reduced to 0.5m³ in three stages within 24 hours. 3 / h, while raising the inlet water temperature to a value not exceeding 5℃ from the ambient temperature, then stop the circulating water pump but keep the monitoring system running. After 24 hours of confirming that the temperature data has no abnormal fluctuations, completely stop the system and orderly remove the surface curing facilities. After removal, the concrete surface still needs to undergo a 3-day visual inspection.
[0035] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.
Claims
1. A construction method for temperature control of cooling circulating water in large-volume concrete under large temperature difference environment, characterized in that, Includes the following steps: S1. Using low-heat cement as the main cementing material, fly ash or slag powder is added to design and test the concrete mix proportion, and the final construction mix proportion is determined through crack resistance verification test. S2. Based on the thermal parameters of concrete under the construction mix ratio, a cooling water pipe network and temperature sensors are planned and pre-embedded in the large-volume concrete structure, and connected to external temperature control equipment to form a cooling circulation system. S3. Using the concrete mixed according to the construction mix ratio, control its pouring temperature and pour it in layers. After the concrete covers part of the cooling water pipes, start the cooling circulation system and begin temperature monitoring. S4. Based on real-time temperature monitoring data, dynamically adjust the temperature and flow rate of circulating water to control the internal temperature rise and internal-external temperature difference of concrete, and combine surface insulation measures for curing. S5. Once the concrete strength has increased to the required level and the temperature field has stabilized, stop the cooling system and remove the curing facilities.
2. The construction method for temperature control of cooling circulating water for large-volume concrete in a large temperature difference environment according to claim 1, characterized in that, In step S1, the specific steps for determining the final construction mix proportion through crack resistance verification tests include: S11. Prepare concrete specimens according to the preliminarily determined mix proportions; S12. Place the specimen in a temperature cycling chamber to simulate the large temperature difference between day and night in high-altitude and cold regions for curing. S13. Use a crack observation instrument to regularly observe and record the cracking time, number of cracks and width of the specimen surface; S14. Using the observation results as the key evaluation index, compare the crack resistance performance of different mix proportions, and finally select the mix proportion with the lowest cracking risk as the construction mix proportion, which will be used for concrete mixing in subsequent steps.
3. The construction method for temperature control of cooling circulating water for large-volume concrete in a large temperature difference environment according to claim 2, characterized in that, The temperature control program of the temperature cycling chamber is as follows: the highest temperature during the day is 15℃, the lowest temperature at night is -10℃, the heating and cooling rate is 2-3℃ / hour, and the single temperature cycle is 24 hours. The crack observation instrument is an electronic magnifying glass with a magnification of not less than 20 times and a measurement accuracy of 0.01mm. The observation frequency is on the 1st, 3rd, 7th, 14th and 28th day after the specimen is formed. When comparing the crack resistance performance of different mix proportions, a weighted comprehensive evaluation system is adopted with initial crack time of 0.3, total number of cracks of 0.2, maximum crack width of 0.3 and total crack area of 0.
2. The mix proportion with the highest comprehensive crack resistance score and simultaneously meets the design compressive strength and frost resistance index is selected.
4. The construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences according to claim 1, characterized in that, In step S2, based on the adiabatic temperature rise prediction curve of the construction mix ratio and the site environmental conditions, the pipe diameter, layout spacing, and loop length of the cooling water pipes are calculated and determined. Construction parameters include adiabatic temperature rise value, time to reach peak temperature, thermal conductivity, and specific heat capacity. The cooling water pipes are HDPE pipes with an outer diameter of 32mm and a wall thickness of 2.0mm. The layout spacing is 0.8m vertically and 1.2m horizontally. The length of a single loop is controlled within 250m. The temperature sensor is a PT1000 platinum resistance thermometer, which is laid out in a three-dimensional grid pattern inside the concrete. The core high-temperature zone is laid out at a spacing of 1.0m×1.0m×0.8m, and the surface area is laid out with a denser spacing of 0.8m×0.8m. The cooling water pipe network is connected to the manifold in parallel. Each branch of the manifold is equipped with an independent regulating valve and flow meter, and is connected to a temperature control device with automatic data acquisition and control functions.
5. The construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences according to claim 1, characterized in that, In step S3, the specific steps for controlling the concrete pouring temperature and performing layered pouring include: S31. According to the construction mix ratio, the mixing water is heated to 60±5℃ at the mixing plant, and the aggregate is preheated to above 5℃ by hot air in the heat preservation shed. S32. Insulated tank trucks with double-layer insulated tanks are used to transport concrete, and the tanks are insulated during transportation. S33. During the pouring process, the time from concrete discharge to placement in the formwork should not exceed 90 minutes. A layered continuous pouring process should be adopted, with each layer controlled to a thickness of 50cm. The interval between layers should not exceed the initial setting time of the concrete. The vibration spacing should not exceed 50cm, and contact with cooling water pipes and temperature sensors should be avoided. When the concrete surface covers the first layer of cooling water pipes to a thickness of 50cm, the cooling circulation system should be immediately activated. The initial water temperature should be set 10-15℃ lower than the measured temperature of the concrete core area at that moment, and the flow rate should be controlled at 1.2-1.5m³. 3 / h, and automatically collect and record temperature data at each measuring point every 30 minutes.
6. The method for temperature control of cooling circulating water in large-volume concrete under large temperature difference environment according to claim 1, characterized in that, In step S4, the specific steps for dynamically adjusting the temperature and flow rate of circulating water to control the internal temperature rise and internal-external temperature difference of the concrete include: S41. When the core temperature inside the concrete is detected to rise rapidly at a rate exceeding 2℃ / hour over a continuous 4-hour period, activate the high-flow-rate, low-temperature-difference cooling mode. Control the temperature difference between the inlet water and the highest internal temperature of the concrete within 10–15℃, while simultaneously increasing the cooling water flow rate to 1.8–2.2 m³ / h. 3 / h, to accelerate heat dissipation; S42. When the temperature at the core measuring point inside the concrete reaches its peak and begins to decline within 12 consecutive hours with a variation not exceeding ±0.5℃, switch to a low-flow-rate, high-temperature-difference cooling mode. Gradually reduce the difference between the inlet water temperature and the highest temperature inside the concrete to within 5–8℃, while simultaneously reducing the cooling water flow rate to 0.8–1.2 m³ / h. 3 / h, and control the concrete cooling rate within any 24-hour cycle to remain below 2℃ / day, in order to mitigate temperature shrinkage stress.
7. The construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences according to claim 1, characterized in that, In step S4, the specific steps for curing in conjunction with surface insulation measures include: S43. After the concrete has set, cover it with a plastic film with a thickness of not less than 0.12 mm to keep it moist, and the overlap between each film should be not less than 200 mm. S44. On top of the plastic film, tightly cover at least one layer of rock wool insulation blanket with a thermal conductivity of not more than 0.045 W / (m·K); S45. When the environmental forecast predicts rain or snow or the actual ambient temperature is below -15℃, add a layer of waterproof canvas on top of the insulation blanket and seal the seams with double pressure strips.
8. The construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences according to claim 1, characterized in that, In step S5, the specific steps for determining whether the concrete strength growth meets the requirements are as follows: S51. At the site, no less than 3 sets of test blocks cured under the same conditions shall be used for the construction mix ratio and tested for 3 days, 7 days and final strength respectively. After demolding, the test blocks shall be placed in a curing box that can synchronously reproduce the temperature changes and thermal insulation environment of the solid structure. S52. When the compressive strength test value of the test block reaches more than 75% of the design strength, and at the same time, the difference between the highest internal temperature and the lowest surface temperature of the concrete at all measuring points within 24 consecutive hours does not exceed 20℃, and the standard deviation of the temperature data at each measuring point during this period is less than 2℃, the removal conditions are deemed to be met.
9. The construction method for temperature control of cooling circulating water for large-volume concrete in environments with large temperature differences according to claim 8, characterized in that, The cooling system was shut down in stages and in stages. First, the cooling water flow rate was reduced to 0.5 m³ / h in three separate steps over 24 hours. 3 / h, while raising the inlet water temperature to a value not exceeding 5℃ from the ambient temperature, then stop the circulating water pump but keep the monitoring system running. After 24 hours of confirming that the temperature data has no abnormal fluctuations, completely stop the system and orderly remove the surface curing facilities. After removal, the concrete surface still needs to undergo a 3-day visual inspection.