Intelligent temperature control construction method for large-volume shrinkage-compensating concrete

Abstract

The invention discloses an intelligent temperature control construction method for large-volume shrinkage-compensating concrete, and relates to the technical field of concrete construction. The method comprises the steps of construction preparation, concrete pouring and real-time temperature measurement, intelligent cooling regulation and control, intelligent maintenance and heat preservation, expansion reinforcing band construction, cooling coil dense filling and crack monitoring treatment. By configuring shrinkage compensation concrete matched with the environment temperature and arranging a wireless intelligent temperature measuring system and a snake-shaped cooling water pipe, temperature data driven cooling water flow velocity dynamic adjustment and maintenance heat preservation self-adaptive regulation and control are achieved; the special measures of encrypting temperature measuring points and cooling pipes and prolonging maintenance are adopted for the expansion reinforcing band. The problems that traditional construction temperature measurement lags behind, regulation and control are blind, and the crack risk is high are solved, precise control that the temperature rise value is smaller than or equal to 50 DEG C, the inner-surface temperature difference is smaller than or equal to 25 DEG C and the cooling rate is smaller than or equal to 2.0 DEG C / d is achieved, and the integrity and durability of a mass concrete structure are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of concrete construction technology, specifically to an intelligent temperature control construction method for large-volume shrinkage-compensating concrete. Background Technology

[0002] Large-volume concrete structures, due to their thickness and large amount of cementitious materials, experience concentrated heat release during hydration, which easily leads to significant temperature differences between the interior and surface of the concrete. This thermal stress can cause harmful cracks, seriously affecting structural safety and service life. Current methods for temperature control in large-volume concrete construction primarily rely on manual temperature measurement, manual adjustment of cooling systems, and curing measures, which have the following drawbacks: Low temperature measurement accuracy and slow response make it difficult to capture real-time changes in the internal temperature of concrete, easily missing the optimal control time; the flow rate and water pressure of the cooling system are adjusted entirely based on experience, and cannot be dynamically optimized according to temperature data, resulting in unstable temperature control and overheating or excessively rapid cooling in some areas; the admixture dosage of shrinkage-compensating concrete is fixed and cannot adapt to changes in different ambient temperatures (especially high temperatures in summer), easily leading to problems such as shortened initial setting time, excessively rapid slump loss, and poor shrinkage compensation effect; the cooling coil filling is mostly filled with ordinary cement mortar, which makes it difficult to guarantee the density, easily forming cavities and weakening the structural load-bearing capacity; the lack of intelligent control in curing measures results in uneven heat preservation and moisture retention effects, further aggravating the risk of cracking.

[0003] Therefore, it is necessary to develop a precise, intelligent, and adaptive temperature control construction method for large-volume shrinkage-compensating concrete to achieve intelligent linkage of the entire process of temperature monitoring, cooling regulation, and curing and insulation, and to fundamentally control the generation of temperature cracks by combining the material properties of shrinkage-compensating concrete. Summary of the Invention

[0004] The purpose of this invention is to provide an intelligent temperature control construction method for large-volume shrinkage-compensating concrete. Through temperature measurement, dynamic cooling regulation, adaptive curing, and precise filling, this method achieves strict control over the concrete temperature rise, surface-internal temperature difference, and cooling rate. Combined with the optimized mix proportion of shrinkage-compensating concrete, it ensures that the large-volume concrete structure is free of harmful cracks, thereby improving construction quality and efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete includes the following steps: Step (1) Construction preparation: In accordance with the construction standards for large-volume concrete and the technical specifications for temperature measurement and control of large-volume concrete, prepare shrinkage-compensating concrete, with the amount of cementitious materials in ordinary areas ≥300kg / m³, the amount of expansion reinforcement strip ≥350kg / m³, and the temperature of concrete entering the formwork ≤25℃; set up a wireless temperature measurement system with a sensor accuracy of ±0.5℃ and a data update frequency ≤15min / time; set up a cooling system and equip it with intelligent curing equipment; Step (2) Concrete pouring and real-time temperature measurement: The inclined layer method is used for pouring, with a layer thickness of 500mm. The bonding time between layers is ≤ the initial setting time of 2-5h. The temperature measurement system is started within 1h after the pouring is completed. The temperature measurement frequency is 2h / time for the first 3 days, 4h / time thereafter, and 8h / time during the cooling stage. The real-time monitoring temperature rise value is ≤50℃, the temperature difference between the inside and the surface is ≤25℃, and the cooling rate is ≤2.0℃ / d. Step (3) Intelligent cooling control: The cooling system is started within 6 hours after the pouring is completed. The initial water flow rate is 0.8-1.0 m / s. The flow rate is automatically adjusted according to the center temperature. When the center temperature is ≥47℃, the water flow rate is increased to 1.0-1.2 m / s. After the center temperature drops, the water flow rate is reduced to 0.5-0.8 m / s. The temperature difference between the inlet and outlet water is ≤5℃. The center temperature is ≤35℃ and the temperature difference between the inside and outside surface is ≤20℃. After 3 days, the system is shut down. Step (4) Intelligent curing and insulation: After initial setting, cover with plastic film and cotton felt. After final setting, start spraying to keep the cotton felt humidity ≥90%. Adjust the insulation layer automatically according to the temperature difference between the inside and the surface. Add cotton felt when the temperature difference between the inside and the surface is ≥22℃, and reduce cotton felt when the temperature difference between the inside and the surface is ≤15℃. The expansion reinforcement belt is covered with an extra insulation blanket and the curing time is extended by 3 days compared with the ordinary area. Step (5) Construction of expansion reinforcement strip: 7-10 days after pouring in the ordinary area, pour C45 shrinkage compensation concrete, add 20% temperature measurement points, and increase the spacing of cooling water pipes to 1.2m; Step (6) Cooling coil filling: After the cooling system is shut down for 7 days and the concrete strength is ≥75% of the design value, the cooling coil is filled with micro-expansion grout.

[0006] As a preferred embodiment, the admixtures for compensating shrinkage concrete in step (1) are dynamically adjusted according to the ambient temperature: at 30-35℃, the water-reducing agent is increased by 5-10% compared to the benchmark dosage, the retarder is increased by 10-20%, and the expansion agent is increased by 5-10%; at 35-40℃, the water-reducing agent is increased by 10-20%, the retarder is increased by 20-40%, and the expansion agent is increased by 10-20%; the aggregate is shaded and sprayed in advance to cool down to ≤30℃, and in summer, ≤20% ice water can be added to control the mixing water temperature to ≤20℃.

[0007] As a preferred embodiment, in step (1), the temperature measuring points are arranged in five layers along the thickness of the concrete: the top layer is 50mm from the top surface, the second layer is 450mm from the top surface, the middle layer is 850mm from the top surface, the fourth layer is 1250mm from the top surface, and the bottom layer is 50mm from the bottom surface. One temperature measuring unit is set every 12m×12m in the plane. The outermost temperature measuring point is ≥1000mm from the edge of the foundation. The sensor is protected by a Φ15 PVC pipe and is in close contact with the concrete.

[0008] As a preferred implementation, in step (2), the concrete pouring temperature of each truck is measured and uploaded to the monitoring platform in real time; if the pouring temperature is >25℃, the secondary cooling of aggregate and ice water mixing emergency measures are immediately initiated; the monitoring platform is set with early warning thresholds: temperature rise ≥45℃ warning, ≥50℃ alarm, inner and outer surface temperature difference ≥22℃ warning, ≥25℃ alarm, cooling rate ≥1.5℃ / d warning, ≥2.0℃ / d alarm.

[0009] As a preferred embodiment, the cooling system in step (3) uses clean circulating water, the water quality is checked every 24 hours, and sewage is discharged once a week, with the sewage discharge amount being 10% of the total water volume; when shutting down, the remote circuit is shut down first, followed by the near circuit.

[0010] As a preferred implementation, the timing of starting the curing process in step (4) is as follows: the first wooden trowel is pressed before the initial setting, the plastic film and the first layer of cotton felt are covered after the initial setting, and the spraying is started after the final setting; when the nighttime temperature is <10℃, the temperature control insulation is started with electric heating, and the temperature is ≤30℃; the curing must meet the following conditions to stop: curing time ≥14d, temperature difference between the center and the environment ≤20℃, temperature difference between the inside and the surface ≤15℃, cooling rate ≤1.0℃ / d, and the strength of the test block under the same conditions ≥80% of the design value.

[0011] As a preferred embodiment, in step (5), the interface laitance is cleaned and an interface agent is applied before pouring the expansion reinforcement strip, and continuous pouring and vibration are adopted; the temperature control threshold is set to a temperature rise value ≤ 48℃ and an inner surface temperature difference ≤ 23℃.

[0012] As a preferred embodiment, in step (6), before filling the cooling coil, it is blown with high-pressure air of ≥0.7MPa, rinsed with pressurized water and then dried; the water-to-material ratio of the grouting material is 1:0.12-0.15, and the mixing time is ≥3min; during grouting, grout is injected from one end and an exhaust pipe is set at the other end. After the uniform grout overflows, the pressure is stabilized for 2-5min, and the pressure and grouting volume are recorded in real time.

[0013] As a preferred embodiment, the micro-expansion grout in step (6) has an initial flowability ≥300mm, a 28d compressive strength ≥50MPa, and is injected under a pressure of 0.5-0.8MPa.

[0014] As a preferred embodiment, the method also includes a crack monitoring and treatment step: daily inspection with a crack width ruler with an accuracy of 0.02 mm; sealing of Class I cracks with a width < 0.2 mm with epoxy resin grout; repair of Class II cracks with a width of 0.2-0.4 mm with low-pressure grouting; and immediate cessation of work and high-pressure chemical grouting treatment for Class III cracks with a width > 0.4 mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention employs a wireless intelligent temperature measurement system to achieve real-time monitoring and graded early warning of concrete temperature. The temperature measurement accuracy reaches ±0.5℃, and the data update frequency is ≤15min / time. This solves the problems of lag and large error in traditional manual temperature measurement, and provides accurate data support for temperature control. The cooling system is intelligently linked with temperature measurement data. By dynamically adjusting the water flow rate through a variable frequency water pump, the cooling rate can be precisely controlled, avoiding the risk of cracks caused by local overheating or excessively rapid cooling. Compared with traditional manual control, the temperature control efficiency is improved by more than 40%. The admixture dosage of shrinkage-compensating concrete is dynamically adjusted according to the ambient temperature. Combined with measures such as aggregate cooling and ice water mixing, the concrete pouring temperature is ≤25℃ and the initial setting time is stable at 2-5h, so that the shrinkage compensation effect is fully utilized and the crack resistance of concrete is significantly improved. The intelligent curing system achieves adaptive regulation of heat preservation and moisture retention. Combined with the exclusive temperature control measures of the expansion reinforcement strip, it ensures that the temperature difference between the inside and outside of the concrete is ≤25℃, the curing quality is uniform and stable, and the crack occurrence rate is reduced by more than 80%. High-performance micro-expansion grouting material is used to pressure fill the cooling coil, and the impact echo method is used for testing. The filling density is ≥95%, which avoids the cavity defects formed by traditional filling and ensures the overall load-bearing capacity and durability of the structure. The entire construction process reduces manual intervention, increases construction efficiency by more than 30%, and reduces safety risks. It is suitable for large-scale concrete projects such as large equipment foundations and bridge abutments. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the method of the present invention. Detailed Implementation

[0017] refer to Figure 1 The present invention provides a typical embodiment of a method for intelligent temperature control construction of large volume compensating shrinkage concrete, the main steps of which include step (1) construction preparation, step (2) concrete pouring and real-time temperature measurement, step (3) intelligent cooling regulation, step (4) intelligent curing and heat preservation, step (5) construction of expansion reinforcement strip, step (6) filling of cooling coil and (7) crack monitoring and treatment.

[0018] Construction preparation In accordance with the construction standards for large-volume concrete and the technical specifications for temperature measurement and control of large-volume concrete, the following shrinkage-compensating concrete is prepared: the amount of cementitious material in ordinary areas is ≥300kg / m³, the amount of cementitious material in expansion reinforcement strips is ≥350kg / m³, and the concrete placement temperature is ≤25℃.

[0019] Deploy the wireless temperature measurement system: Select a wireless temperature sensor with an accuracy of ±0.5℃, and update the data at a frequency of ≤15min / time. Deploy the temperature measurement points according to the preset plan.

[0020] Temperature measurement points are arranged in five layers along the thickness of the concrete: the top layer is 50mm from the top surface, the second layer is 450mm from the top surface, the middle layer is 850mm from the top surface, the fourth layer is 1250mm from the top surface, and the bottom layer is 50mm from the bottom surface. One temperature measurement unit is set every 12m×12m in the plane. The outermost temperature measurement point is ≥1000mm from the edge of the foundation. The sensor is protected by a Φ15 PVC pipe and is in close contact with the concrete.

[0021] Cooling system layout: Φ88.9 thin-walled steel pipes are used, and a layer of cooling water pipes is laid out according to the serpentine layout principle with a pipe spacing of 1.5m. The pipes are tested in advance with a water pressure of 1.2MPa (pressure held for 30 minutes without leakage).

[0022] Equipped with intelligent maintenance equipment: including an automatic spraying system with atomized particle size of 50-100μm, intelligent temperature-controlled insulation blanket, built-in electric heating wire and humidity sensor, and matching water tank and booster pump.

[0023] Prepare the cooling coil filling material: high-performance micro-expansion grout, requiring an initial flowability ≥300mm, a 28-day compressive strength ≥50MPa, a limited expansion rate of 0.02%-0.05%, and grouting pressure of 0.5-0.8MPa.

[0024] The admixtures for shrinkage-compensating concrete should be dynamically adjusted according to the ambient temperature: at 30-35℃, the water-reducing agent should be increased by 5-10% compared to the benchmark dosage, the retarder by 10-20%, and the expansion agent by 5-10%; at 35-40℃, the water-reducing agent should be increased by 10-20%, the retarder by 20-40%, and the expansion agent by 10-20%. Aggregates should be shaded and sprayed in advance to lower the temperature to ≤30℃. In summer, ≤20% ice water can be added to control the mixing water temperature to ≤20℃.

[0025] Concrete pouring and real-time temperature monitoring The concrete is poured using a sloping layer method, with each layer being 500mm thick. The bonding time between layers is ≤ 2-5 hours after the initial setting time of the concrete, ensuring continuous pouring without cold joints.

[0026] During concrete pouring, the actual temperature of each truck entering the formwork is measured and uploaded to the monitoring platform in real time. If the temperature entering the formwork is >25℃, emergency measures such as secondary cooling of aggregates and ice water mixing are immediately initiated. The monitoring platform is set with warning thresholds: temperature rise ≥45℃ warning, ≥50℃ alarm, temperature difference between inner and outer surfaces ≥22℃ warning, ≥25℃ alarm, cooling rate ≥1.5℃ / d warning, ≥2.0℃ / d alarm.

[0027] The wireless temperature measurement system will be activated within 1 hour after the pouring is completed. The temperature measurement frequency will be 2 hours / time for the first 3 days, then adjusted to 4 hours / time thereafter, and 8 hours / time during the temperature drop phase.

[0028] The monitoring platform displays in real time the concrete temperature rise value is controlled to be ≤50℃, the temperature difference between the inside and outside is controlled to be ≤25℃, and the cooling rate is controlled to be ≤2.0℃ / d. It sets graded early warning thresholds and automatically alarms when the thresholds are exceeded.

[0029] Intelligent cooling regulation The cooling system uses clean circulating water. The water quality is checked every 24 hours and the system is drained once a week, with the amount of drained water being 10% of the total water volume.

[0030] The cooling system should be started within 6 hours after the concrete is poured, with the initial water flow rate controlled at 0.8-1.0 m / s and the inlet and outlet water temperature difference ≤ 5℃.

[0031] The monitoring platform automatically adjusts the frequency of the variable frequency water pump based on the concrete core temperature data: when the core temperature is ≥47℃, the water flow rate is increased to 1.0-1.2m / s; when the core temperature begins to drop, it is gradually reduced to 0.5-0.8m / s.

[0032] When the core temperature of the concrete is ≤35℃ and the temperature difference between the inside and the surface is ≤20℃ for 3 days, the cooling system should be shut down in the order of "far end circuit first, then near end circuit" to avoid sudden temperature changes.

[0033] Intelligent maintenance and heat preservation Before the initial setting of the concrete, the first wooden trowel should be used to compact it 2-3 hours after pouring. After the initial setting, the concrete should be covered with plastic film and the first layer of cotton felt 4-6 hours after pouring. After the final setting, the automatic spraying system should be started 8-12 hours after pouring to maintain the humidity of the cotton felt ≥90%.

[0034] The monitoring platform automatically adjusts the insulation layer based on the temperature difference between the inner and outer surfaces: when the temperature difference is ≥22℃, an additional layer of cotton felt is automatically added; when the temperature difference is ≤15℃, an additional layer of cotton felt can be removed; when the nighttime temperature is <10℃, the intelligent temperature control insulation blanket activates the electric heating function, with a heating temperature ≤30℃.

[0035] The curing time is ≥14 days. Curing must be stopped if the following conditions are met: the temperature difference between the core and the ambient temperature is ≤20℃, the temperature difference between the inner and outer surfaces is ≤15℃, the cooling rate is ≤1.0℃ / day, and the strength of the test block cured under the same conditions is ≥80% of the design strength.

[0036] Expansion reinforcement strip construction Before pouring the expansion reinforcement strip, clean the interface slurry and apply an interface agent, and then use continuous pouring and vibration.

[0037] 7-10 days after the concrete in the ordinary area is poured, when the concrete strength is ≥70% of the design strength, C45 shrinkage-compensating concrete should be poured.

[0038] The expansion reinforcement zone area has 20% more temperature measuring points, the spacing between cooling water pipes is increased to 1.2m, the temperature control threshold is set to a temperature rise of ≤48℃ and a temperature difference between the inside and outside of the surface of ≤23℃, and the curing time is extended by 3 days compared to the ordinary area.

[0039] Cooling coil filling Cooling coils should be filled 7 days after the cooling system is shut down, and when the concrete strength is ≥75% of the design strength.

[0040] Before filling, blow away any debris inside the pipe with high-pressure air at ≥0.7MPa, then rinse with pressurized water and blow dry, finally blowing away any standing water inside the pipe. The water-to-material ratio of the grout should be 1:0.12-0.15, and the mixing time should be ≥3min.

[0041] A screw pump is used to inject micro-expansion grout from one end of the pipeline at a pressure of 0.5-0.8MPa. An exhaust pipe is set at the other end. When uniform grout overflows from the exhaust pipe and there are no air bubbles, the valve is closed after stabilizing the pressure for 2-5 minutes. The pressure and grout volume are recorded in real time.

[0042] 28 days after filling is completed, the filling density is tested using the impact echo method, and the pass rate is required to be ≥95%.

[0043] Crack monitoring and treatment The concrete surface is inspected daily using a crack width gauge with an accuracy of 0.02 mm.

[0044] Upon discovery of cracks, they should be treated according to their severity: Class I cracks with a width < 0.2 mm should be sealed with epoxy resin grout; Class II cracks with a width of 0.2-0.4 mm should be repaired using low-pressure grouting; Class III cracks with a width > 0.4 mm should be stopped immediately and treated using high-pressure chemical grouting.

[0045] The following detailed description of the specific implementation of the present invention is based on the No. 1 gasification framework foundation project of the 15 million tons / year coal quality-grade clean and efficient conversion demonstration project of Shaanxi Coal Group Yulin Chemical Co., Ltd.

[0046] Project Overview: The No. 1 gasification frame foundation is a raft foundation with a plan dimension of 73.6m × 37.4m and a bottom slab thickness of 1.7m. The foundation bottom elevation is -4.800m and the top elevation is -3.100m. A 2m wide intermittent expansion reinforcement strip is set between axes ④ and ⑤. The main body of the foundation uses C40 shrinkage-compensating concrete, and the expansion reinforcement strip uses C45 shrinkage-compensating concrete. The construction season is summer with an ambient temperature of 30-38℃.

[0047] Shrinkage-compensating concrete mix design: Cementitious materials: Low-heat slag silicate cement (PSA42.5) 315kg / m³, Grade I fly ash 104kg / m³, total cementitious material usage 419kg / m³, cementitious material usage for expansion reinforcement strip 355kg / m³; Aggregate: 5-25mm continuously graded crushed stone with a mud content of 0.8% and a mud content of 1180kg / m³; medium sand with a fineness modulus of 2.7, a mud content of 2.5%, and a mud content of 720kg / m³; use shade canopy and spray cooling in advance to control the aggregate temperature at 28℃. Admixtures: 1.2% high-efficiency water-reducing agent, 0.8% retarder, and 8% expansion agent. Due to the ambient temperature of 30-38℃, the dosage should be adjusted according to the plan: increase water-reducing agent by 15%, retarder by 30%, and expansion agent by 15%. Water: tap water and 15% ice water, mixing water temperature 18℃, concrete slump 180mm, initial setting time 3.5h, placement temperature 23℃.

[0048] Intelligent equipment deployment: Temperature measurement system: 80 wireless temperature sensors are deployed, with one temperature measurement unit every 12m×12m. Each unit is deployed in five layers along the thickness: top layer 50mm, second layer 450mm, middle layer 850mm, fourth layer 1250mm, and bottom layer 50mm. The outermost temperature measurement point is 1.2m away from the edge of the foundation. The sensors are protected by Φ15 PVC pipes and are firmly fixed to the steel frame. Two data acquisition units and one cloud monitoring platform are also provided, with a data update frequency of 10 minutes / time. Cooling system: 3000m of Φ88.9 thin-walled steel pipe, arranged in a serpentine pattern with a pipe spacing of 1.5m. The inlet and outlet extend 60cm beyond the top surface of the foundation. It is equipped with two variable frequency centrifugal pumps with a pressure of 0-1.5MPa, two electromagnetic flow meters, and four temperature sensors. The pipeline water pressure test pressure is 1.2MPa, and there is no leakage after holding the pressure for 30 minutes. Maintenance equipment: Automatic sprinkler system with 120 atomizing nozzles spaced 3m apart, intelligent temperature-controlled insulation blankets covering 5505.28㎡, two water tanks with a capacity of 10m³ each, and two booster pumps with a pressure of 0.5MPa.

[0049] Filling material: High-performance micro-expansion grout, with an initial flowability of 320mm, a 1-day compressive strength of 22MPa, a 3-day compressive strength of 45MPa, a 28-day compressive strength of 58MPa, and a restricted expansion rate of 0.035%.

[0050] Concrete pouring and real-time temperature monitoring: 10 concrete pump trucks with 62m boom lengths and 40 concrete mixer trucks with 18m³ capacity were used. The concrete was poured in sloping layers according to the principle of "from far to near and symmetrical on both sides". The layer thickness was 500mm, the hourly supply was 130m³, and the continuous pouring was completed in 48 hours. The bonding time between layers was controlled within 3 hours and less than the initial setting time of 3.5 hours. During the pouring process, the temperature of each truck entering the mold was measured 80 times. The temperature range of entering the mold was 21-24℃, and all were ≤25℃. The data was uploaded to the cloud monitoring platform in real time. The temperature monitoring system was activated 1 hour after the pouring was completed. Temperature was measured every 2 hours for the first 3 days, every 4 hours for days 4-7, and every 8 hours thereafter. The monitoring platform showed that the highest temperature at the center of the concrete was 47.2℃, which did not exceed the 50℃ warning value. The maximum temperature difference between the inner and outer surfaces was 23℃, which did not exceed the 25℃ alarm value. The cooling rate was stable at 1.5-1.8℃ / day.

[0051] Intelligent cooling control: The cooling system is started 6 hours after the pouring is completed, with an initial water flow rate of 0.9 m / s and an inlet and outlet water temperature difference of 4℃; When the concrete core temperature reached 47.2℃ on the third day, the monitoring platform automatically increased the water flow rate to 1.1m / s and controlled the inlet and outlet water temperature difference at 4.5℃. On the 7th day, the core temperature of the concrete dropped to 38℃, and the water flow rate was adjusted to 0.7m / s; On the 10th day, the core temperature of the concrete was 34℃, and the temperature difference between the inside and the surface was 18℃. After 3 days, the cooling system was shut down in the order of "far end first, then near end", and the cooling rate throughout the process was ≤2.0℃ / d.

[0052] Intelligent curing and insulation: 2.5 hours after pouring (before initial setting), the first wooden trowel is used for compaction; 4.5 hours after initial setting, a plastic film and the first layer of cotton felt are applied; 9 hours after final setting, the automatic spraying system is activated to maintain the cotton felt at 92% humidity. On the 4th day, when the temperature difference between the inside and the surface reached 23℃, the monitoring platform automatically instructed to add a layer of cotton felt. Two hours later, the temperature difference between the inside and the surface dropped to 20℃. When the ambient temperature is 8℃ at night, the intelligent temperature control insulation blanket activates the electric heating function, and the heating temperature is controlled at 25℃. After 14 days of curing, the core temperature of the concrete was 28℃, the temperature difference with the ambient temperature was 12℃, the temperature difference between the inside and the surface was 10℃, the cooling rate was 0.8℃ / d, and the strength of the test block cured under the same conditions was 33MPa. Curing was stopped and the insulation layer was removed in layers.

[0053] Construction of expansion reinforcement strip: 8 days after pouring in the ordinary area, if the strength of the test block under the same conditions is 28MPa and ≥70% of the design strength is 28MPa, the pouring of expansion reinforcement strip will be started; Sixteen additional temperature measuring points were added to the expansion reinforcement strip, bringing the total number of temperature measuring points to 96. The spacing between cooling water pipes was increased to 1.2m. C45 shrinkage-compensating concrete was poured, with a placement temperature of 22℃. During the maintenance period, the monitoring platform showed a maximum temperature rise of 46℃ and a maximum temperature difference between the inside and outside of the surface of 22℃, both of which met the threshold requirements. The maintenance period was 17 days, which was 3 days longer than that of ordinary areas.

[0054] Cooling coil compaction: After the cooling system is shut down for 7 days, when the concrete test block strength under the same conditions reaches 35MPa (≥75% of the design strength of 30MPa), filling begins; Before filling, blow away any debris from the pipe with 0.8MPa high-pressure air, rinse with pressurized water, and then blow dry. The micro-expansion grout was injected at a pressure of 0.6 MPa using a screw pump. The injection time for each loop was about 40 minutes. After the uniform grout overflowed from the exhaust pipe, the pressure was stabilized for 3 minutes. 28 days after filling, the impact echo method was used for testing. A total of 60 points were tested, and 58 of them passed the test, with a density of 96.7% ≥ 95%.

[0055] During the curing period and after the filling was completed, the concrete surface was inspected daily, and a total of 3 fine cracks were found, with a width of 0.1-0.15mm. All of them were Class I cracks, which were sealed with epoxy resin grout and did not expand afterward.

[0056] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete, characterized in that, Includes the following steps: Step (1) Construction preparation: In accordance with the construction standards for large-volume concrete and the technical specifications for temperature measurement and control of large-volume concrete, prepare shrinkage-compensating concrete, with the amount of cementitious materials in ordinary areas ≥300kg / m³, the amount of expansion reinforcement strip ≥350kg / m³, and the temperature of concrete entering the formwork ≤25℃; set up a wireless temperature measurement system with a sensor accuracy of ±0.5℃ and a data update frequency ≤15min / time; set up a cooling system and equip it with intelligent curing equipment; Step (2) Concrete pouring and real-time temperature measurement: The inclined layer method is used for pouring, with a layer thickness of 500mm. The bonding time between layers is ≤ the initial setting time of 2-5h. The temperature measurement system is started within 1h after the pouring is completed. The temperature measurement frequency is 2h / time for the first 3 days, 4h / time thereafter, and 8h / time during the cooling stage. The real-time monitoring temperature rise value is ≤50℃, the temperature difference between the inside and the surface is ≤25℃, and the cooling rate is ≤2.0℃ / d. Step (3) Intelligent cooling control: The cooling system is started within 6 hours after the pouring is completed. The initial water flow rate is 0.8-1.0 m / s. The flow rate is automatically adjusted according to the center temperature. When the center temperature is ≥47℃, the water flow rate is increased to 1.0-1.2 m / s. After the center temperature drops, the water flow rate is reduced to 0.5-0.8 m / s. The temperature difference between the inlet and outlet water is ≤5℃. The center temperature is ≤35℃ and the temperature difference between the inside and outside surface is ≤20℃. After 3 days, the system is shut down. Step (4) Intelligent curing and insulation: After initial setting, cover with plastic film and cotton felt. After final setting, start spraying to keep the cotton felt humidity ≥90%. Adjust the insulation layer automatically according to the temperature difference between the inside and the surface. Add cotton felt when the temperature difference between the inside and the surface is ≥22℃, and reduce cotton felt when the temperature difference between the inside and the surface is ≤15℃. The expansion reinforcement belt is covered with an extra insulation blanket and the curing time is extended by 3 days compared with the ordinary area. Step (5) Construction of expansion reinforcement strip: 7-10 days after pouring in the ordinary area, pour C45 shrinkage compensation concrete, add 20% temperature measurement points, and increase the spacing of cooling water pipes to 1.2m; Step (6) Cooling coil filling: After the cooling system is shut down for 7 days and the concrete strength is ≥75% of the design value, the cooling coil is filled with micro-expansion grout.

2. The intelligent temperature control construction method for large-volume shrinkage-compensating concrete according to claim 1, characterized in that, In step (1), the admixtures for shrinkage-compensating concrete are dynamically adjusted according to the ambient temperature: at 30-35℃, the water-reducing agent is increased by 5-10% compared to the benchmark dosage, the retarder is increased by 10-20%, and the expansion agent is increased by 5-10%; at 35-40℃, the water-reducing agent is increased by 10-20%, the retarder is increased by 20-40%, and the expansion agent is increased by 10-20%; the aggregate is shaded and sprayed in advance to cool down to ≤30℃, and in summer, ≤20% ice water can be added to control the mixing water temperature to ≤20℃.

3. The intelligent temperature control construction method for large-volume shrinkage-compensating concrete according to claim 2, characterized in that, In step (1), the temperature measuring points are arranged in five layers along the thickness of the concrete: the top layer is 50mm from the top surface, the second layer is 450mm from the top surface, the middle layer is 850mm from the top surface, the fourth layer is 1250mm from the top surface, and the bottom layer is 50mm from the bottom surface. One temperature measuring unit is set up every 12m×12m in the plane. The outermost temperature measuring point is ≥1000mm from the edge of the foundation. The sensor is protected by a Φ15 PVC pipe and is in close contact with the concrete.

4. A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete according to claim 1 or 3, characterized in that, In step (2), the actual temperature of each truckload of concrete entering the formwork is measured during concrete pouring and uploaded to the monitoring platform in real time. If the temperature entering the formwork is >25℃, the emergency measures of secondary cooling of aggregate and ice water mixing are immediately initiated. The monitoring platform is set with warning thresholds: temperature rise ≥45℃ warning, ≥50℃ alarm, inner and outer surface temperature difference ≥22℃ warning, ≥25℃ alarm, cooling rate ≥1.5℃ / d warning, ≥2.0℃ / d alarm.

5. The intelligent temperature control construction method for large-volume shrinkage-compensating concrete according to claim 4, characterized in that, In step (3), the cooling system uses clean circulating water. The water quality is checked every 24 hours and the system is drained once a week. The amount of drained water is 10% of the total water volume. When shutting down, the remote circuit is shut down first, followed by the near circuit.

6. A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete according to claim 1 or 5, characterized in that, In step (4), the curing start time is as follows: the first wooden trowel is pressed before the initial setting, the plastic film and the first layer of cotton felt are covered after the initial setting, and the spraying is started after the final setting; when the night temperature is <10℃, the temperature control insulation is started with electric heating, and the temperature is ≤30℃; the curing must meet the following conditions to stop: curing time ≥14d, temperature difference between the center and the environment ≤20℃, temperature difference between the inside and the surface ≤15℃, cooling rate ≤1.0℃ / d, and the strength of the test block under the same conditions ≥80% of the design value.

7. The intelligent temperature control construction method for large-volume shrinkage-compensating concrete according to claim 6, characterized in that, In step (5), before pouring the expansion reinforcement strip, clean the interface slurry and apply the interface agent, and use continuous pouring and vibration; the temperature control threshold is set to a temperature rise value ≤ 48℃ and an inner surface temperature difference ≤ 23℃.

8. A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete according to claim 1 or 7, characterized in that, Before filling the cooling coil in step (6), blow it with high-pressure air of ≥0.7MPa, rinse it with pressurized water and then dry it; the water-to-material ratio of the grouting material is 1:0.12-0.15, and the mixing time is ≥3min; when grouting, grout is injected from one end and an exhaust pipe is set at the other end. After the uniform grout overflows, the pressure is stabilized for 2-5min, and the pressure and grouting volume are recorded in real time.

9. The intelligent temperature control construction method for large-volume shrinkage-compensating concrete according to claim 8, characterized in that, The micro-expansion grouting material in step (6) has an initial flowability ≥300mm, a 28-day compressive strength ≥50MPa, and is injected under pressure of 0.5-0.8MPa.

10. A method for intelligent temperature control construction of large-volume shrinkage-compensating concrete according to claim 1 or 9, characterized in that, It also includes crack monitoring and treatment steps: daily inspection with a crack width ruler with an accuracy of 0.02mm; Class I cracks with a width <0.2mm are sealed with epoxy resin grout; Class II cracks with a width of 0.2-0.4mm are repaired with low-pressure grouting; Class III cracks with a width >0.4mm are immediately stopped and treated with high-pressure chemical grouting.

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