A method for temperature control of mass concrete placement

Abstract

The application discloses a temperature control method for mass concrete pouring, which comprises: temperature reduction treatment before concrete preparation; embedding a distributed temperature sensor before concrete pouring to monitor the internal temperature field of the concrete in real time; adopting a mobile distributor to cooperate with a step method layering and block pouring process; arranging a circulating water cooling system in the concrete, and dynamically adjusting the cooling water flow and temperature according to the temperature monitoring data; covering a heat preservation and moisture retention layer on the surface of the concrete, and setting a spraying system to spray in time according to the internal temperature feedback and external temperature. The method has the advantages of accurate temperature control, good crack prevention and treatment effect, high construction automation degree, improved structural durability, strong process adaptability, and remarkable synergistic cooling effect of materials and process. The method is suitable for mass concrete structures such as large foundations, dams and power station floors, and solves problems of excessive temperature stress and frequent temperature cracks caused by cement hydration heat.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology and relates to concrete pouring quality control technology in building construction, specifically a temperature monitoring and control method for the construction process of large-volume concrete pouring. Background Technology

[0002] During the hardening process of large-volume concrete, the hydration of cement generates a large amount of heat, causing a rapid rise in internal temperature. Simultaneously, the surface dissipates heat quickly, resulting in a significant temperature difference between the inside and outside. This can easily lead to temperature stress cracks, affecting structural safety and durability. Traditional temperature control methods rely heavily on experience in arranging cooling water pipes, lacking real-time monitoring and dynamic control. This can easily result in uneven cooling or over-cooling, and coupled with insufficient subsequent temperature stress compensation measures, it is difficult to fundamentally suppress crack formation. If traditional high-slump concrete pouring techniques are used, the high water consumption and similarly large heat of hydration further exacerbate the difficulty of temperature control. Summary of the Invention

[0003] This invention discloses a temperature control method for large-volume concrete pouring, addressing the shortcomings of existing technologies. The purpose of this invention is to provide a temperature control method for large-volume concrete pouring suitable for large foundations, dams, power station base slabs, and other large-volume concrete structures, solving problems such as excessive temperature stress and frequent temperature cracking caused by cement hydration heat.

[0004] This invention is achieved through the following technical solution:

[0005] A method for controlling the temperature during large-volume concrete pouring, characterized by comprising the following process steps:

[0006] (1) Cooling treatment before concrete preparation: Use medium-heat cement and HB7-3 type peak reducing agent to prepare concrete, reduce the heat of cement hydration and further reduce the concrete temperature peak; pre-cool coarse and fine aggregates with air cooling to control the aggregate temperature below 10℃; use ice flakes or ice water to replace part of the mixing water to control the concrete outlet temperature not higher than 12℃; and use low slump concrete mix proportion, water-cement ratio ≤0.46, control the slump to 90~110mm, water consumption 122kg / m³, cement consumption ≤200kg / m³, and add polycarboxylate-based high-efficiency water-reducing agent.

[0007] (2) Before concrete pouring, pre-embed distributed temperature sensors to monitor the internal temperature field of the concrete in real time;

[0008] (3) A mobile concrete placing machine is used in conjunction with a stepped, layered, and segmented pouring process;

[0009] (4) Install a circulating water cooling system inside the concrete and dynamically adjust the cooling water flow and temperature based on temperature monitoring data;

[0010] (5) Cover the concrete surface with a heat insulation and moisture retention layer and set up a spray system to spray in a timely manner based on the internal temperature feedback and the external temperature.

[0011] Furthermore, the pre-cooled aggregate is adopted in a closed aggregate bin and cooled by an in-bin air-cooling system; when using flake ice or ice water to replace part of the mixing water in concrete mixing, the amount of flake ice to replace part of the mixing water accounts for 30% to 50% of the total mass of mixing water, and the particle size of the flake ice is not greater than 10mm.

[0012] The stepped, layered, and block-based pouring method further describes the concrete pouring process, where concrete is poured in layers from bottom to top, with each layer consisting of stepped blocks. The pouring sequence is as follows: each layer begins with the pouring of the first-level step block A from one side of the bottom. Then, the second-level step block B, located above the first-level step block A, is poured. The area of ​​step block B is smaller than that of step block A, allowing step block A to retain an exposed edge area. Next, step block C, located on the same level as the first-level step block A, is poured. Then, the second-level step block D, located above the first-level step block C, is poured. Step block D allows step block C to retain an exposed edge area, continuing until the last step block at the top of the layer is reached. Adjacent blocks are poured in the same sequence from the first level upwards, following the pouring direction, until the entire surface of the poured layer is completed. After an interval of ≥48 hours, the next layer is poured using the same layered and block-based method. Each layer is ≤200cm thick, each step is 30cm~50cm thick, and the outward pouring length of each step block is 2m~3m.

[0013] Furthermore, the pre-embedded distributed temperature sensor includes three layers of temperature sensors evenly arranged along the central axis of the structure: the upper layer sensor is set 10cm below the top surface of the poured concrete, the middle layer sensor is set in the middle of the poured concrete section, and the lower layer sensor is set 10cm below the bottom surface of the poured concrete; the temperature data acquisition frequency is not less than once every 4 hours.

[0014] Furthermore, the circulating water cooling system consists of PE cooling pipes and intelligent control cooling units. The cooling pipes are arranged at intervals inside the concrete, with a longitudinal and transverse spacing of no more than 1.0m and an inner diameter of 28mm.

[0015] Furthermore, the heat insulation and moisture retention layer adopts a composite structure of "geotextile + flame-retardant heat insulation blanket" to cover the surface of the poured concrete. Spray pipes are arranged around the pouring concrete to reduce the temperature in the local space, ensuring that the humidity of the concrete surface is controlled above 90%, and the surface equivalent heat release coefficient is not greater than 2W / ㎡·℃.

[0016] Furthermore, the concrete uses medium-heat cement and incorporates HB7-3 type peak-shaving agent, with the dosage of peak-shaving agent being 0.5% to 1.5% of the total mass of cementitious materials.

[0017] Furthermore, the water-cement ratio of the low-slump concrete is no greater than 0.40, and a polycarboxylate-based high-efficiency water-reducing agent is used to adjust the workability of the concrete.

[0018] Furthermore, the stepped pouring method employs a mobile concrete placing machine to pour the concrete layer by layer, level by level, and block by block, with the material head covering time ≤3h to avoid the formation of cold joints.

[0019] Furthermore, the method of dynamically adjusting the cooling water flow rate and temperature based on temperature monitoring data includes the following:

[0020] (1) First stage, heating period: water is turned on immediately after pouring, with a flow rate of 1.5 to 2.1 m³ / h and a water temperature of 8 to 10℃. The direction of water flow is switched every 12 hours.

[0021] (2) Second stage, cooling period: continuous water supply, flow rate 0.6~1.2 m³ / h, dynamically adjusted ±25% according to the cooling rate, control daily cooling ≤2℃, water temperature adjusted according to temperature difference.

[0022] (3) The third stage, the stabilization period: intermittent water supply, 4 hours on and 4 hours off, flow rate < 0.5 m³ / h, water temperature 15℃, until the temperature difference between the concrete and the environment meets the standard.

[0023] This invention relates to a method for controlling the temperature of large-volume concrete pouring. The method uses medium-heat cement and HB7-3 peak-shaving agent to prepare the concrete, pre-cools the aggregates, and adds ice during mixing to effectively reduce the concrete's outlet temperature and adiabatic temperature rise threshold. It employs a low-slump concrete mix to reduce water consumption and heat of hydration. Distributed temperature sensors are embedded within the concrete to collect temperature data in real time. A mobile concrete placing boom combined with a stepped, layered pouring process controls the pouring speed and layer thickness, preventing cold joints. A circulating water cooling system is used to intelligently adjust cooling parameters based on monitoring data. Finally, a surface insulation and moisturizing system, along with a spray system, controls the surface temperature difference.

[0024] This invention discloses a method for temperature control of large-volume concrete, from initial cooling to intelligent regulation throughout the entire process. It reduces heat of hydration by using medium-heat cement and HB7-3 peak-shaving agent, lowers the initial concrete temperature by pre-cooling aggregates and adding ice during mixing, further reduces heat of hydration by using low-slump concrete to reduce mixing water and cement usage, and optimizes construction processes by using a mobile concrete placing boom and stepped pouring method. Combined with real-time monitoring, dynamic cooling, heat preservation and moisture retention, and post-construction compensation, this method achieves uniform control of the concrete temperature field throughout the entire process, fundamentally preventing temperature cracks.

[0025] The temperature control method for large-volume concrete pouring of the present invention has the following beneficial effects.

[0026] 1. Precise temperature control: Through real-time monitoring and intelligent adjustment, uniform control of the internal temperature field of concrete is achieved, and the temperature difference between the inner and outer surfaces of concrete is controlled within 25℃.

[0027] 2. Excellent crack prevention effect: Combining medium-heat cement, peak-shaving agent, cooling and insulation, it systematically reduces temperature stress and significantly reduces temperature cracks.

[0028] 3. High degree of automation in construction: The temperature sensor is linked with the cooling system to achieve unattended intelligent temperature control, reducing labor costs and operational errors.

[0029] 4. Improved structural durability: Effectively controls cracks and improves the integrity and service life of concrete structures.

[0030] 5. Strong process adaptability: The stepped pouring process and the mobile concrete placing boom work together, which can not only efficiently adapt to the complex structure pouring needs of large-scale projects such as hydropower stations, but also effectively reduce the probability of cold joints in construction through continuous pouring operations, thus ensuring the quality of concrete pouring.

[0031] 6. The synergistic cooling effect of materials and processes is significant: the peak temperature rise of medium-heat cement is 8℃~12℃ lower than that of ordinary Portland cement after 3 days, and the heat of hydration is reduced by 25%~35% after 7 days; the HB7-3 type peak shaving agent further delays the temperature peak by about 40 hours, and the peak temperature rise is reduced by another 6℃~15℃; low slump concrete reduces water consumption and reduces the heat of hydration per cubic meter by 20%~25%. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the temperature control system for large-volume concrete pouring according to the present invention.

[0033] Figure 2 This is a cross-sectional view of the distributed temperature sensor arrangement of the present invention.

[0034] Figure 3 This is a piping layout diagram of the circulating water cooling system of the present invention.

[0035] Figure 4 This is a schematic diagram of the heat preservation, moisture retention and spraying system of the present invention.

[0036] Figure 5 This is a schematic diagram of the step method construction process of the present invention.

[0037] In the diagram, 1 is the intelligent cooling unit, 2 is the system water inlet pipe, 3 is the gate valve, 4 is the cooling water outlet main pipe, 5 is the cooling water return column pipe, 6 is the water inlet head, 7 is the regulating hose, 8 is the cooling water pipe inside the chamber, 9 is the vertical spacing of the cooling water pipes, 10 is the horizontal spacing of the cooling water pipes, 11 is the insulation blanket, 12 is the spray pipe, and 13 is the geotextile; A, B, ... represent the layered and segmented pouring sequence. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. These specific embodiments are further explanations of the principles of the present invention and are not intended to limit the present invention in any way. Any technology that is the same as or similar to the present invention does not exceed the scope of protection of the present invention.

[0039] The temperature control method for large-volume concrete pouring of the present invention includes the following methods.

[0040] I. Concrete Cooling Preparation.

[0041] (1) Medium-heat silicate cement is used, with a hydration heat of ≤293kJ / kg in 7 days. Compared with ordinary silicate cement (hydration heat of ≥350 kJ / kg in 7 days), it can reduce the peak temperature rise of concrete by more than 10℃ and effectively control temperature cracks in large-volume concrete.

[0042] (2) Adding HB7-3 type peak shaving agent, the dosage is 0.5% to 1.5% of the total mass of cementitious material, can delay the hydration heat temperature peak by about 40 hours and reduce the temperature rise peak by 6℃ to 15℃ over 3 days.

[0043] (3) Coarse and fine aggregates are transported to a closed cooling chamber and continuously cooled to below 10°C by the air-cooling system inside the chamber.

[0044] (4) The mixing plant is equipped with an ice-making tower. 30% to 50% of the water consumption per cubic meter is replaced by -5℃ flake ice with a particle size of ≤10mm.

[0045] (5) Use low slump concrete mix proportion, water-cement ratio ≤0.46, slump controlled at 90~110mm, water consumption 122kg / m³, cement consumption ≤200kg / m³, and add polycarboxylate-based high-efficiency water-reducing agent to ensure workability.

[0046] (6) The concrete discharge temperature is controlled at 12±3℃.

[0047] II. Sensor Arrangement and Casting Process.

[0048] (1) The pre-embedded distributed temperature sensors include three layers of temperature sensors evenly arranged along the central axis of the structure: the upper layer sensor is set 10cm below the top surface of the poured concrete, the middle layer sensor is set in the middle of the poured concrete section, and the lower layer sensor is set 10cm below the bottom surface of the poured concrete; in this example, the embedment depths are 10cm, 100cm, and 190cm, respectively, and the data acquisition frequency is once every 4 hours. Figure 2 As shown.

[0049] (2) A mobile concrete placing boom (arm span ≥ 30m) is used in conjunction with the stepped pouring method: The stepped pouring method involves pouring concrete in layers from bottom to top, with each layer divided into stepped blocks. The pouring sequence is as follows: each layer starts from the bottom side, pouring the first level A step block, then pouring the second level B step block above the first level A step block. The area of ​​step block B is smaller than that of step block A, allowing step block A to retain an exposed edge area; then pouring the C step block of the same level next to the first level A step block, then pouring the second level D step block above the first level C step block. Step block D allows step block C to retain an exposed edge area, up to the last step block at the top of the layer; pouring in the same sequence from the first level upwards until the entire surface of the pouring layer is completed; after an interval of ≥ 48 hours, the next layer is poured using the same stepped pouring method; where each layer thickness is ≤ 200cm, each level thickness is 30cm~50cm, and the outward pouring length of the step block is 2m~3m. Figure 5 As shown.

[0050] III. Cooling System Layout.

[0051] The cooling water pipes are made of PE material, with a horizontal and vertical spacing of 1.0m, an inner diameter of 28mm, and a single length of ≤250m.

[0052] IV. Intelligent Temperature Control Stage.

[0053] (1) First stage, heating period: water is turned on immediately after pouring, with a flow rate of 1.5 to 2.1 m³ / h and a water temperature of 8 to 10℃. The direction of water flow is switched every 12 hours.

[0054] (2) Second stage, cooling period: continuous water supply, flow rate 0.6~1.2 m³ / h, dynamically adjusted ±25% according to the cooling rate, control daily cooling ≤2℃, water temperature adjusted according to temperature difference.

[0055] (3) The third stage, the stabilization period: intermittent water supply, 4 hours on and 4 hours off, flow rate < 0.5 m³ / h, water temperature about 15℃, until the temperature difference between the concrete and the environment meets the standard.

[0056] 5. Surface heat preservation and moisture retention.

[0057] The composite covering process of "geotextile water-locking + flame-retardant thermal insulation blanket" is adopted; relying on the temperature control monitoring system, when the temperature difference between the internal temperature of the concrete and the external ambient temperature collected by the temperature sensor exceeds 20℃, the control center automatically triggers the spray curing system to continuously maintain the relative humidity of the concrete surface ≥90%, and finally achieves the temperature control target of equivalent heat release coefficient ≤2W / ㎡・℃, effectively suppressing temperature cracks on the concrete surface.

Claims

1. A method for controlling the temperature during large-volume concrete pouring, characterized in that, The following processes are included: (1) Cooling treatment before concrete preparation: Use medium-heat cement and HB7-3 type peak reducing agent to prepare concrete, reduce the heat of cement hydration and further reduce the concrete temperature peak; pre-cool coarse and fine aggregates with air cooling to control the aggregate temperature below 10℃; use flake ice or ice water to replace part of the mixing water to control the concrete outlet temperature not higher than 12℃; use low slump concrete mix proportion, water-cement ratio ≤0.46, control the slump to 90~110mm, water consumption 122kg / m³, cement consumption ≤200kg / m³, and add polycarboxylate-based high-efficiency water-reducing agent; (2) Before concrete pouring, pre-embed distributed temperature sensors to monitor the internal temperature field of the concrete in real time; (3) A mobile concrete placing machine was used in conjunction with the step method for layered and segmented pouring; (4) Install a circulating water cooling system inside the concrete and dynamically adjust the cooling water flow and temperature based on temperature monitoring data; (5) Cover the concrete surface with a heat insulation and moisture retention layer and set up a spray system to spray in a timely manner based on the internal temperature feedback and the external temperature.

2. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The pre-cooled aggregate is cooled by an internal air-cooling system in a closed aggregate bin. When using flake ice or ice water to replace part of the mixing water in concrete mixing, the amount of flake ice to replace part of the mixing water accounts for 30% to 50% of the total mass of the mixing water, and the particle size of the flake ice is not greater than 10mm.

3. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The stepped, layered, and block-based pouring method involves pouring concrete in layers from bottom to top, with each layer consisting of stepped blocks. The pouring sequence is as follows: each layer begins with the pouring of the first-level step block A from one side of the bottom. Then, the second-level step block B, located above the first-level step block A, is poured. The area of ​​step block B is smaller than that of step block A, allowing step block A to retain an exposed edge area. Next, step block C, located on the same level as the first-level step block A, is poured. Then, the second-level step block D, located above the first-level step block C, is poured, allowing step block C to retain an exposed edge area. This continues until the last step block at the top of the layer. Adjacent blocks are poured in the same sequence from the first level upwards, following the pouring direction, until the entire surface of the poured layer is completed. After an interval of ≥48 hours, the next layer is poured using the same step-by-step method. Each layer is ≤200cm thick, each step is 30cm~50cm thick, and the outward pouring length of each step block is 2m~3m.

4. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The pre-embedded distributed temperature sensor includes three layers of temperature sensors evenly arranged along the central axis of the structure: the upper layer sensor is set 10cm below the top surface of the poured concrete, the middle layer sensor is set in the middle of the cross section of the poured concrete, and the lower layer sensor is set 10cm below the bottom surface of the poured concrete; the temperature data acquisition frequency is not less than once every 4 hours.

5. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The circulating water cooling system consists of PE cooling pipes and intelligent control cooling units. The cooling pipes are arranged at intervals inside the concrete, with a longitudinal and transverse spacing of no more than 1.0m and an inner diameter of 28mm.

6. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The thermal insulation and moisture retention layer adopts a composite structure of "geotextile + flame-retardant thermal insulation blanket" to cover the surface of the poured concrete. Spray pipes are arranged around the pouring concrete to reduce the temperature in the local space, ensuring that the surface humidity of the concrete is controlled above 90%, and the surface equivalent heat release coefficient is not greater than 2W / ㎡·℃.

7. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The concrete uses medium-heat cement and incorporates HB7-3 type peak-shaving agent, with the dosage of peak-shaving agent being 0.5% to 1.5% of the total mass of cementitious materials.

8. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The water-cement ratio of the low-slump concrete is no greater than 0.40, and a polycarboxylate-based high-efficiency water-reducing agent is used to adjust the workability of the concrete.

9. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that: The stepped pouring method employs a mobile concrete placing machine to pour the concrete layer by layer, level by level, and block by block, with the material head covering time ≤3h to avoid the formation of cold joints.

10. The method for controlling the temperature of large-volume concrete pouring according to claim 1, characterized in that... The method of dynamically adjusting cooling water flow and temperature based on temperature monitoring data includes the following: (1) First stage, heating period: water is turned on immediately after pouring, with a flow rate of 1.5 to 2.1 m³ / h and a water temperature of 8 to 10℃. The direction of water flow is switched every 12 hours. (2) Second stage, cooling period: continuous water supply, flow rate 0.6~1.2m³ / h, dynamically adjusted ±25% according to the cooling rate, control daily cooling ≤2℃, water temperature adjusted according to temperature difference; (3) The third stage, the stabilization period: intermittent water supply, 4 hours on and 4 hours off, flow rate < 0.5 m³ / h, water temperature 15℃, until the temperature difference between the concrete and the environment meets the standard.

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