Intelligent temperature control and crack prevention method for mass concrete construction in winter

Abstract

The application discloses an intelligent temperature control and crack prevention method for mass concrete winter construction, which comprises the following steps: step 1, thermal calculation, to determine the cooling pipe arrangement scheme and the warm shed scheme; step 2, laying the cooling pipe according to the cooling pipe arrangement scheme and burying the temperature measuring device; step 3, erecting the warm shed according to the warm shed scheme; step 4, pouring the concrete layer by layer; step 5, obtaining the concrete temperature through the temperature measuring device, and controlling the temperature and flow of the cooling pipe according to the concrete temperature to dynamically control the concrete; and step 6, curing and maintaining the concrete. The application constructs the temperature control system of 'external preservation and internal reduction' for the mass concrete, and controls the internal temperature rising range and the internal and external temperature difference in a bidirectional linkage mode, so that the generation of temperature stress is reduced, the appearance of temperature cracks is effectively prevented, the integrity and durability of the concrete structure are ensured, the early strength growth speed of the concrete is improved, the construction period is shortened, and the engineering cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of large-volume concrete construction technology, specifically to an intelligent temperature control and crack prevention method for large-volume concrete construction in winter. Background Technology

[0002] With the development of modern engineering construction towards large-scale, super high-rise, and long-span structures, the thickness and volume of concrete in foundation raft slabs and pile caps are increasing daily, making their construction a typical example of large-volume concrete. It is commonly used in high-rise buildings, large public buildings, and water conservancy projects—projects with high requirements for foundation bearing capacity and integrity—serving as the foundation of the building and evenly transferring the load of the superstructure to the foundation. Large-volume concrete foundations refer to foundation structures with large single-pour volumes and thick structural dimensions (usually ≥1m). During pouring, due to the heat of cement hydration, heat easily accumulates inside the concrete, creating excessive temperature differences between the inside and outside, leading to thermal stress and potentially harmful cracks. During winter construction, the lower ambient temperature further increases the temperature difference between the inside and outside of the concrete, making it highly susceptible to temperature cracks. These cracks not only affect the integrity and durability of the structure but can also, in severe cases, endanger structural safety, causing significant quality risks and economic losses to the project. Traditional methods for controlling the temperature of large-volume concrete in winter, such as single thermal insulation and curing measures, can reduce heat loss from the concrete surface to some extent, but have limited effect on controlling excessive internal temperature and temperature differences between the inside and outside of the concrete. On the other hand, relying solely on adjusting the concrete mix proportion to reduce the heat of hydration may affect the strength and other performance indicators of the concrete. Summary of the Invention

[0003] To address the aforementioned issues, this invention employs an "external protection and internal cooling" temperature control system for large-volume concrete. This system provides bidirectional, coordinated regulation of the internal temperature rise and the internal-external temperature difference within the concrete, reducing temperature stress, effectively preventing temperature cracks, and ensuring the integrity and durability of the concrete structure. Simultaneously, it accelerates the early strength development of the concrete, shortens the construction period, and reduces project costs, providing a reliable technical solution for large-volume concrete construction in winter.

[0004] Specifically, this invention discloses an intelligent temperature control and crack prevention method for large-volume concrete construction in winter, comprising:

[0005] Step 1: Thermal calculations to determine the cooling pipe layout and greenhouse design;

[0006] Step 2: Lay the cooling pipes according to the cooling pipe layout plan and install the temperature measuring device;

[0007] Step 3: Construct the greenhouse according to the greenhouse plan;

[0008] Step 4: Pour concrete in layers;

[0009] Step 5: Obtain the concrete temperature through a temperature measuring device, and control the temperature and flow rate of the cooling pipes based on the concrete temperature to achieve dynamic temperature control of the concrete.

[0010] Step 6: Insulate and cure the concrete.

[0011] Further, step 1 includes:

[0012] Step 11: Calculate the adiabatic temperature rise, temperature at each age, and maximum central temperature of the concrete;

[0013] Step 12: Determine the equivalent heat transfer coefficient between the cooling pipes and the concrete, and simulate the cooling effect under different cooling pipe layout schemes using finite element software to determine the optimal cooling pipe layout scheme.

[0014] Step 13: Calculate the heat load of the greenhouse to determine the greenhouse heating scheme;

[0015] Step 14: Establish a thermo-mechanical coupling model based on the adiabatic temperature rise of concrete, temperature at each age and the highest central temperature, the equivalent heat transfer coefficient between cooling pipes and concrete, and the heat load of the heated shed, and further optimize the cooling pipe layout scheme and the heated shed scheme.

[0016] Further, step 2 includes:

[0017] Step 21: Install several cooling loop units in the cooling pipes. The width of each cooling loop unit is 5 to 10 meters, and they are arranged in the middle of the concrete.

[0018] Step 22: The temperature measuring device includes several temperature sensors; mark several sets of temperature measuring points on the steel bars of the concrete, each set of temperature measuring points includes three sensing points: upper, middle and lower, and pre-embed each temperature sensor on the corresponding sensing point.

[0019] Furthermore, in step 21, when the concrete thickness is ≤3.0m, a single layer of cooling pipes is installed, and the length of each cooling loop unit is 150-200m;

[0020] When the concrete thickness is greater than 3.0m, the cooling pipes are arranged in multiple layers along the thickness direction, with a spacing of 1.5m between each layer of cooling pipes.

[0021] The cooling pipes are arranged in layers and zones according to the principle that cooling water flows from the thermal center to the edge zone.

[0022] Further, step 3 includes:

[0023] Step 31: Erecting the greenhouse frame;

[0024] Step 32: Lay and secure the tarpaulin;

[0025] Step 33: Arrange the heating equipment evenly inside the shed and hang temperature and humidity sensors in the shed to obtain the external temperature and humidity of the concrete.

[0026] Further, step 5 includes:

[0027] Step 51: Initial cooling operation: After the concrete has initially set, start the first water flow. The initial water flow rate should be 32-40 L / min and the flow velocity should not be less than 0.6 m / s to ensure a smooth start-up of the system.

[0028] Step 52: Peak cooling operation: When the temperature difference between the inside and outside of the concrete is less than the warning value of 25℃ and the difference between the water temperature and the inlet water temperature is 3℃~6℃, reduce the cooling water flow or temporarily stop the circulation to allow the internal temperature to develop naturally and avoid over-cooling; conversely, increase the cooling pipe flow to suppress the rise of the core temperature or accelerate its decline.

[0029] Step 53: Post-construction cooling operation: After the internal temperature of the concrete has exceeded the peak temperature rise and begins to stabilize and decrease, the concrete is cooled down.

[0030] Furthermore, in step 53, the daily cooling rate of the concrete is controlled within 1.5~2.0℃ / day.

[0031] Further, step 6 includes:

[0032] Step 61: Before pouring concrete, check the airtightness of the greenhouse and start the heating equipment in advance;

[0033] Step 62: After the concrete is poured, cover the concrete surface with plastic film and insulation material;

[0034] Step 63: Steam heating and curing: After the concrete has set, steam is supplied to the concrete surface at a rate not exceeding 10℃ / h for 4-6 hours.

[0035] Step 64: Steam constant temperature curing: The temperature is controlled at 50-60℃ for 12-16 hours;

[0036] Step 65: Steam cooling curing: Temperature drop ≤5℃ per hour, duration 6-8 hours.

[0037] Furthermore, in step 64, the steam equipment maintains a steam pressure of 0.05-0.1 MPa, a humidity of ≥95%, and a temperature difference between the center and the surface of ≤15℃.

[0038] The beneficial effects of this invention are:

[0039] (1) The present invention adopts “external heat preservation” and “internal cooling” to achieve temperature control during the curing period: a stable environment is provided before and after pouring and in the initial curing stage to ensure that the concrete is protected from freezing damage; the cooling pipe is introduced in the hardening stage to solve the problem of hydration heat. The two are seamlessly connected in time to form a temperature control system for the curing cycle.

[0040] (2) The present invention constructs a warm shed and maintains the temperature inside the shed to control the temperature and humidity of the concrete components, accelerates the cement hydration reaction, and reduces the temperature difference stress. It solves the problem of concrete freezing damage caused by low temperature in winter, avoids internal structural damage caused by ice crystal formation, and reduces the 28-day strength loss from 20% to less than 2%, shortening the curing cycle. In the long run, its heat preservation effect and construction continuity can significantly reduce the overall cost.

[0041] (3) The temperature data of different locations inside the large volume concrete is monitored in real time by a temperature measuring device, and the flow rate and water temperature of the cooling water are adjusted according to the temperature to remove the internal heat, reduce the peak value of hydration heat, balance the internal and external temperature difference, ensure that the difference between the inlet water temperature and the maximum temperature of the concrete is 15℃~25℃, and the difference between the outlet water temperature and the inlet water temperature is 3℃~6℃, thus reducing the temperature gradient. Attached Figure Description

[0042] Figure 1 This is a flowchart of the intelligent temperature control and crack prevention method for large-volume concrete construction in winter, as described in Example 1.

[0043] Figure 2 This is a plan view of the cooling pipe layout in Example 1;

[0044] Figure 3 This is a cross-sectional view of the cooling pipe layout in Example 1;

[0045] Figure 4 This is a plan view of the greenhouse layout in Example 1;

[0046] Figure 5 This is a cross-sectional layout diagram of the greenhouse in Example 1.

[0047] Figure label:

[0048] 1-Concrete; 21-Water inlet pipe, 22-Water tank, 23-Temperature control switch, 24-Heating rod, 25-Water pump, 26-Pressure stabilizing device, 27-Thermometer, 28-Cooling pipe, 29-Return water pipe; 31-Rock wool blanket, 32-Steam curing machine, 33-Hot air blower, 34-Steam curing machine air pipe, 35-Tartar cloth, 36-Plastic film, 37-Sealed foam board. Detailed Implementation

[0049] The present invention will be further described in detail below through specific embodiments.

[0050] Example 1

[0051] like Figure 1 As shown in the figure, this embodiment discloses an intelligent temperature control and crack prevention method for large-volume concrete construction in winter, including:

[0052] Step 1: Thermal calculations to determine the cooling pipe layout and greenhouse design;

[0053] Step 2: Lay the cooling pipes according to the cooling pipe layout plan and install the temperature measuring device;

[0054] Step 3: Construct the greenhouse according to the greenhouse plan;

[0055] Step 4: Pour concrete in layers;

[0056] Step 5: Obtain the concrete temperature through a temperature measuring device, and control the temperature and flow rate of the cooling pipes based on the concrete temperature to achieve dynamic temperature control of the concrete.

[0057] Step 6: Insulate and cure the concrete.

[0058] Further, step 1 includes:

[0059] Step 11: Calculate the adiabatic temperature rise, temperature at each age, and maximum central temperature of the concrete.

[0060] Adiabatic temperature rise formula: T max = (W*Q) / (c*ρ),

[0061] W: Amount of cementitious materials used in concrete (kg / m³);

[0062] Q: Total heat of hydration of cementitious materials (kJ / kg);

[0063] c: Specific heat capacity of concrete (kJ / (kg·℃));

[0064] ρ: Apparent density of concrete (kg / m³).

[0065] Formula for maximum internal temperature: T max =T j +T(t) *ξ(t),

[0066] T j Concrete pouring temperature (°C)

[0067] T(t): Adiabatic temperature rise of concrete at a certain age (°C);

[0068] ξ(t): Temperature drop coefficient.

[0069] Temperatures at each age can be derived using hydration heat models, temperature drop coefficient methods, etc., which will not be elaborated here. Through the above core thermal calculations, the peak temperature rise and its history are predicted in order to predict the highest central temperature and the rate of temperature rise.

[0070] Step 12: Determine the equivalent heat transfer coefficient between the cooling pipes and the concrete, and simulate the cooling effect under different cooling pipe layout schemes using finite element software to determine the optimal cooling pipe layout scheme.

[0071] Based on models of flow velocity, pipe material, and concrete thermal conductivity, the cooling effect under different pipe spacing, flow rate, and water flow duration is simulated using finite element software. The goal is to find the optimal pipe layout and water flow strategy that can meet the cooling rate and control the internal and external temperature difference.

[0072] Step 13: Calculate the heat load of the greenhouse to determine the greenhouse heating scheme.

[0073] (1) Basic heat loss of building envelope: Q1 = ∑(K*F*(t) n - t w ')*α),

[0074] K: Heat transfer coefficient of the building envelope (W / (m²·℃));

[0075] F: Heat transfer area (m²) of a single building envelope component.

[0076] t n The design calculation temperature (°C) inside the greenhouse is usually set according to the curing requirement of not less than 5°C;

[0077] t w ′:The outdoor design temperature (°C) for heating should be calculated using meteorological data such as the average temperature of the coldest month in the project location over the years, rather than the extreme minimum temperature;

[0078] α: Orientation correction factor for building envelope.

[0079] (2) Heat loss due to cold air infiltration: Q2=0.278*V*ρ w *c p * (t n -t w ′);

[0080] V: The volume of air per hour that cold air penetrates (m³ / h).

[0081] ρ w Outdoor air density (kg / m³);

[0082] c p Specific heat capacity of air at constant pressure (kJ / (kg·℃)).

[0083] (3) Total heat load of the greenhouse: Q′=(Q1+Q2)*(1+x ch +x f +x g );

[0084] Q′: Total heat load (kW) required for winter construction of the greenhouse;

[0085] x ch Orientation additional coefficient;

[0086] x f Wind force additional coefficient;

[0087] x g : High additional coefficient.

[0088] Step 14: Integrate the adiabatic temperature rise of concrete, temperatures at various ages and the highest central temperature, the equivalent heat transfer coefficient between cooling pipes and concrete, the heating load of the greenhouse, and their corresponding technical formulas into the finite element software to establish a thermo-mechanical coupling model. Temperature field analysis can simulate the combined effects of hydration heat, cooling water pipes, greenhouse insulation, and ambient air temperature; stress field analysis, based on the temperature field results and the time-varying E(t), calculates the total stress resulting from the superposition of temperature stress and shrinkage stress.

[0089]

[0090] σ: Total temperature stress in concrete (MPa);

[0091] T b Surface temperature (°C) inside the concrete casting;

[0092] Q1: Heat of hydration of cement in n1 days (kJ / kg);

[0093] Q2: Heat of hydration of cement in n2 days (kJ / kg);

[0094] c: Specific heat capacity of concrete (kJ / (kg·℃));

[0095] ρ: Density of concrete (kg / m³) 3 );

[0096] k1: Adjustment coefficient for heat of hydration of fly ash admixture;

[0097] k2: Adjustment coefficient for heat of hydration of slag powder;

[0098] w: per m 3 Concrete cementitious material dosage (kg / m) 3 );

[0099] m: A coefficient related to cement type, pouring temperature, etc.

[0100] T0: Concrete temperature upon placement (°C);

[0101] e: natural constant, with a value of approximately 2.71828;

[0102] h: The actual thickness of the concrete structure (m);

[0103] Hi(t, η): At age η: the relaxation coefficient of the constraint stress generated in the i-th calculation section when it continues to t;

[0104] The relationship between the heat of hydration and the thickness of the cast block at different ages;

[0105] t: Concrete age (d);

[0106] E0: Ultimate elastic modulus of concrete (GPa).

[0107] Optimization and Early Warning: Through repeated simulations, the cooling pipe layout and greenhouse design are optimized. During construction, real-time temperature data is fed back to the model for correction, and future stress development is predicted, enabling dynamic early warning and adjustment of water supply and insulation strategies, forming an intelligent closed-loop control.

[0108] The core idea of ​​intelligent temperature control is "prediction-control-verification": prediction is made in advance through precise thermal calculations and simulations, dynamic control is carried out in the process using the cooling system and insulation measures of the cooling pipeline, and the effect is verified afterward through temperature and stress monitoring.

[0109] Further, step 2 includes:

[0110] Step 21: As Figure 2-3 As shown, the cooling system consists of an inlet pipe 21, a water tank 22, a temperature control switch 23, a heating rod 24, a water pump 25, a pressure stabilizing device 26, a thermometer 27, cooling pipes 28, and a return pipe 29, achieving automatic regulation of water temperature and flow rate. The cooling pipes 28 are located inside the concrete 1, arranged in layers and zones according to the principle of cooling water flowing from the thermal center to the edge zone. Each layer consists of several cooling loop units, with a width of 5-10m, located in the middle of the concrete 1. The flow of circulating cooling water removes the heat generated by the cement hydration reaction, thereby reducing the internal temperature of the concrete 1, minimizing the temperature difference between the inside and outside, and preventing cracks caused by temperature stress.

[0111] The specific installation process is as follows:

[0112] 1) Cooling water pipe positioning and layout: Lay out the lines on the bottom layer of the foundation reinforcement that has been tied, and use ink lines or paint to accurately mark the plane position and direction of the cooling water pipes, using a "serpentine" or "loop" layout.

[0113] 2) Cooling pipe laying and connection:

[0114] Precast pipe sections are stacked according to their numbers and laid in numerical order during installation. When the concrete thickness 1 is ≤3.0m, the cooling pipe 28 is installed in one layer, with each cooling loop unit having a length of 150-200m. When the concrete thickness is >3.0m, the cooling pipe 28 is arranged in multiple layers along the thickness direction, with a spacing of 1.5m between each layer.

[0115] 3) When arranging the cooling system, install a pressure stabilizing device 26 at the inlet of the cooling pipes. Welds must undergo 100% penetration testing, achieving Level II compliance. Clean weld slag promptly after welding and perform anti-corrosion treatment. Connect the pipes into independent loops as designed, with each loop's length as similar as possible to ensure balanced water flow. Each loop should have clearly defined inlet and outlet, leading to the edge of the foundation or a pre-designated operating pit. After the cooling pipes are installed, conduct a water flow test to ensure unobstructed flow.

[0116] Step 22: The temperature measuring device includes several temperature sensors. According to the relevant temperature measuring point layout drawings, accurately mark the position of each temperature sensor on the corresponding steel bars. There are several groups of temperature measuring points, and each group of temperature measuring points includes three sensing points: upper, middle, and lower. One temperature sensor is placed at each sensing point.

[0117] The temperature measurement of the foundation concrete uses a JDC-2 portable building electronic thermometer, along with temperature sensing leads and probes. The temperature sensor is securely tied to the reinforcing steel at the predetermined location using insulating binding wire. During pre-embedding, the reinforcing steel can be used as a support. The sensor's temperature probe should be separated from the reinforcing steel and wrapped with a small piece of foam to prevent direct contact and reading distortion (reinforcing steel conducts heat quickly). For temperature measurement points at different depths, reinforcing steel supports of varying heights are used to ensure accurate vertical elevation of the sensor.

[0118] The system uses several temperature sensors to monitor temperature data at different locations inside the large-volume concrete in real time. Based on a preset temperature range, it automatically adjusts the flow rate and temperature of the cold water to ensure a uniform temperature drop within the concrete and keeps the temperature difference within acceptable limits. Depending on the maximum concrete temperature and the water temperature under natural conditions, it considers whether to heat the water in water tank 2, ensuring that the difference between the inlet water temperature and the maximum concrete temperature is 15℃~25℃, and the difference between the outlet water temperature and the inlet water temperature is 3℃~6℃.

[0119] Greenhouse structure such as Figure 4-5 As shown, step 3 includes:

[0120] Step 31: Erection of the greenhouse frame. Lay continuous scaffold boards or channel steel as base plates at the upright positions, starting from the corners and erecting the uprights one by one. The spacing between uprights is determined based on the unit weight of the cooling pipes, the dimensions of the foundation, and relevant specifications (usually 1.5m-2.0m). Insert the steel pipes of the uprights into the ground anchor bars and fix them with double fasteners. The verticality deviation of the uprights should be less than 1 / 200 of the frame height. The height of the uprights is determined based on the thickness of the foundation and insulation requirements, usually 1.5-2.0m above the foundation surface. Install horizontal crossbars at the top and middle of the uprights, connected with butt-joint fasteners, with a crossbar spacing ≤1.8m. Install diagonal braces at the four corners of the greenhouse, with the angle between the braces and the ground being 45°-60° to enhance the stability of the greenhouse. For large-area foundations, a truss structure can be installed at the top of the greenhouse, using welded or bolted steel pipes, spaced 3-4m apart. The truss is fixed to the uprights with U-shaped clips to ensure a firm connection.

[0121] Step 32: Install and secure the tarpaulin. The overlap width between tarpaulin sections should not be less than 200mm. Secure the overlap with special pressure strips and rivets, and seal the gaps with waterproof tape to prevent air and heat leakage. The bottom of the vertical tarpaulin must be firmly secured with long wooden blocks and weighed down with sandbags or heavy objects. The wooden blocks should be fixed to the ground with expansion bolts to prevent strong winds from lifting the tarpaulin.

[0122] 3) Entrance and Exit Treatment: Personnel entrances and material transport openings should be provided, and double-layered insulated door curtains should be installed with sufficient overlap. At the same time, openings reserved for concrete pump pipes, temperature measuring lines, cables, etc., must be tightly plugged with cotton felt or flexible materials and sealed with tape to minimize heat loss.

[0123] Step 33: Evenly distribute the steam curing machine 32 and hot air blower 33 inside the shed. The air outlets must not be directly pointed at the newly poured concrete surface or the tarpaulin; they should be directed towards passageways or unoccupied spaces to allow for uniform heating through air convection. Hang thermometers and hygrometers (temperature and humidity sensors) at representative locations inside the shed (diagonally, in the center, and near the air vents), approximately 1.5 meters high. Provide sufficient fire extinguishers as required, set up conspicuous safety warning signs, and install moisture-proof and explosion-proof lighting fixtures.

[0124] Step 51: After the concrete has been poured and initially set (approximately 4-12 hours), begin the initial water flow. Start with a small flow rate and proceed slowly to ensure a smooth system startup. Do not start too early, as this will hinder cement hydration and affect early strength; do not start too late, as this may cause you to miss the peak temperature rise. Based on the concrete temperature changes, temperature sensors will feed back the temperature data to the mechanical equipment. The heating equipment in the water tank will automatically start, providing water at a suitable temperature. The circulating water pump will adjust the water flow as needed to ensure the internal temperature of the concrete gradually decreases.

[0125] Step 52: Peak Cooling Operation: The core of the peak stage is controlling the maximum temperature difference between the inside and outside of the concrete. Mechanical equipment automatically collects data from temperature sensors and precisely adjusts the water flow and inlet water temperature. When the internal and external temperature difference approaches the warning value, the circulating water pump increases the cooling water flow rate to enhance internal heat dissipation and suppress the rise in core temperature or accelerate its decline. When the internal and external temperature difference is small, the cooling water flow rate is reduced, or even circulation is temporarily stopped, allowing the internal temperature to develop naturally and avoiding overcooling.

[0126] Step 53: Post-construction cooling: Once the internal temperature of the concrete has surpassed its peak and begun to stabilize, the focus shifts from "controlling the temperature difference between the inside and outside" to "controlling the cooling rate." The daily cooling rate of the concrete should be controlled within 1.5~2.0℃ / day. Excessive cooling can lead to excessive shrinkage stress in the concrete later on, potentially causing cracks. The internal temperature of the concrete should decrease gradually and slowly by progressively reducing the cooling water flow and increasing the inlet water temperature. Stopping the water supply should be a gradual process: first, stop heating the water in the tank, then circulate with low-temperature water, then circulate with room-temperature water for one day, and finally stop completely. Sudden water outages are strictly prohibited, as they can cause temperature rebound or sudden stress changes.

[0127] Furthermore, step 6 includes:

[0128] Step 61: Before pouring concrete 1, check the airtightness of the greenhouse. Ensure the tarpaulin 35 overlaps tightly and is secured with strips, ropes, or buckles. The bottom perimeter must be weighed down with heavy objects (such as sandbags or concrete blocks) to ensure close contact with the ground and prevent cold air intrusion. Set up necessary entrances and exits and install double-layered door curtains to reduce heat loss. At the same time, start the hot air blower 33 in advance to introduce hot air 33 into the greenhouse through the air supply pipe, allowing the hot air to circulate evenly.

[0129] Step 62: After the concrete 1 is poured, cover the surface of the concrete 1 with plastic film 36, closed foam board 37 (or insulation materials such as insulation blankets or flame-retardant cotton quilts), and rock wool quilt 31, ensuring a tight and thorough covering without any blind spots. Strengthen insulation in areas prone to heat loss, such as corners and edges.

[0130] Step 63: Steam Curing: After concrete 1 has set, steam is supplied to the surface of concrete 1 at a rate not exceeding 10℃ / h for 4-6 hours. Gradually increase the steam supply or hot air power to ensure a uniform temperature rise inside the shed, thus avoiding excessive thermal stress within the concrete. Simultaneously monitor the temperature difference between the interior and surface of the concrete.

[0131] Step 64: Steam Curing at Constant Temperature: The temperature is controlled at 50-60℃ for 12-16 hours. This stage provides the concrete with a constant, warm, and humid environment, allowing the concrete strength to increase continuously and rapidly. The steam curing machine 32 maintains a steam pressure of 0.05-0.1MPa, humidity ≥95%, and a temperature difference between the center and surface ≤15℃. Steam can be supplied intermittently if necessary to ensure the air is in a suitable temperature and humidity state.

[0132] Step 65: Steam Cooling Curing: Temperature reduction ≤ 5℃ per hour, duration 6-8 hours. The goal of this stage is to allow the concrete temperature to drop steadily to ambient temperature, avoiding shrinkage cracks caused by excessively rapid cooling. Reduce steam supply or lower the power of the hot air blower; do not abruptly shut off the heat source. Gradually close the steam valve to gradually cool the concrete, while maintaining insulation coverage to allow the concrete to cool slowly using the insulation properties of the structure. Insulation can only be removed after the surface temperature difference between the component and the ambient temperature is ≤ 20℃.

[0133] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A smart temperature control and crack prevention method for large-volume concrete construction in winter, characterized in that, include: Step 1: Thermal calculations to determine the cooling pipe layout and greenhouse design; Step 2: Lay the cooling pipes according to the cooling pipe layout plan and install the temperature measuring device; Step 3: Construct the greenhouse according to the greenhouse plan; Step 4: Pour concrete in layers; Step 5: Obtain the concrete temperature through a temperature measuring device, and control the temperature and flow rate of the cooling pipes according to the concrete temperature to achieve dynamic temperature control of the concrete. Step 6: Insulate and cure the concrete.

2. The method as described in claim 1, characterized in that, Step 1 includes: Step 11: Calculate the adiabatic temperature rise, temperature at each age, and maximum central temperature of the concrete; Step 12: Determine the equivalent heat transfer coefficient between the cooling pipes and the concrete, and simulate the cooling effect under different cooling pipe layout schemes using finite element software to determine the optimal cooling pipe layout scheme. Step 13: Calculate the heat load of the greenhouse to determine the greenhouse heating scheme; Step 14: Establish a thermo-mechanical coupling model based on the adiabatic temperature rise of concrete, temperature at each age and the highest central temperature, the equivalent heat transfer coefficient between cooling pipes and concrete, and the heat load of the heated shed, and further optimize the cooling pipe layout scheme and the heated shed scheme.

3. The method as described in claim 1, characterized in that, Step 2 includes: Step 21: Install several cooling loop units in the cooling pipes. The width of each cooling loop unit is 5 to 10 meters, and they are arranged in the middle of the concrete. Step 22: The temperature measuring device includes several temperature sensors; mark several sets of temperature measuring points on the steel bars of the concrete, each set of temperature measuring points includes three sensing points: upper, middle and lower, and pre-embed each temperature sensor on the corresponding sensing point.

4. The method as described in claim 3, characterized in that, In step 21, when the concrete thickness is ≤3.0m, a layer of cooling pipes is installed, and the length of each cooling loop unit is 150-200m; When the concrete thickness is greater than 3.0m, the cooling pipes are arranged in multiple layers along the thickness direction, with a spacing of 1.5m between each layer of cooling pipes.

5. The method as described in claim 3, characterized in that, The cooling pipes are arranged according to the principle that cooling water flows from the thermal center to the edge area.

6. The method as described in claim 1, characterized in that, Step 3 includes: Step 31: Erecting the greenhouse frame; Step 32: Lay and secure the tarpaulin; Step 33: Arrange the heating equipment evenly inside the shed and hang temperature and humidity sensors in the shed to obtain the external temperature and humidity of the concrete.

7. The method as described in claim 1, characterized in that, Step 5 includes: Step 51: Initial cooling operation: After the concrete has initially set, begin the initial water flow to ensure a smooth start-up of the system; Step 52: Peak cooling operation: When the temperature difference between the inside and outside of the concrete is less than the warning value of 25℃ and the difference between the water temperature and the inlet water temperature is 3℃~6℃, reduce the cooling water flow or temporarily stop the circulation to allow the internal temperature to develop naturally and avoid over-cooling; conversely, increase the cooling pipe flow to suppress the rise of the core temperature or accelerate its decline. Step 53: Post-construction cooling operation: After the internal temperature of the concrete has exceeded the peak temperature rise and begins to stabilize and decrease, the concrete is cooled down.

8. The method as described in claim 7, characterized in that, In step 53, the daily cooling rate of the concrete is controlled within 1.5~2.0℃ / day.

9. The method as described in claim 1, characterized in that, Step 6 includes: Step 61: Before pouring concrete, check the airtightness of the greenhouse and start the heating equipment in advance; Step 62: After the concrete is poured, cover the concrete surface with plastic film and insulation material; Step 63: Steam heating and curing: After the concrete has set, steam is supplied to the concrete surface at a heating rate of no more than 10℃ / h for a duration of 4-6 hours. Step 64: Steam constant temperature curing: The temperature is controlled at 50-60℃ for 12-16 hours; Step 65: Steam cooling curing: Temperature drop ≤5℃ per hour, duration 6-8 hours.

10. The method as described in claim 9, characterized in that, In step 64, the steam equipment maintains a steam pressure of 0.05-0.1 MPa, a humidity of ≥95%, and a temperature difference between the center and the surface of ≤15℃.

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