A construction method for large-volume beam concrete pouring

Abstract

The present application relates to the technical field of water transport engineering, and discloses a large-volume cross beam concrete pouring construction method, which comprises the following steps: S1, a preparation stage: prefabricating a partitioned active temperature control integrated bed jacking frame, the integrated bed jacking frame is divided into at least three independent temperature control loop areas along the longitudinal direction of the cross beam; S2, a precooling and pouring stage: starting the central temperature control center to precool the partitioned active temperature control integrated bed jacking frame; S3, a dynamic thermal field gradient management stage: after the concrete pouring is completed, the A area, the B area and the C area of the integrated bed jacking frame are controlled through the central temperature control center; S4, a demolding stage: after the concrete meets the demolding condition, the partitioned active temperature control integrated bed jacking frame is demolded and transported as a whole. Through the partitioned control mechanism, the tensile stress concentration of the constraint end area is effectively inhibited, the constraint crack problem caused by the longitudinal temperature gradient is solved, and the one-time overall pouring of the concrete is realized.

Description

Technical Field

[0001] This invention relates to the field of waterway engineering technology, specifically a method for constructing large-volume crossbeams using concrete pouring. Background Technology

[0002] In large-scale port and wharf projects, massive concrete structures, such as wharf beams, large foundations, and panels, are key load-bearing components of the wharf's main structure. Due to the enormous volume of concrete, the hydration process of the cement releases a large amount of heat, causing a rapid increase in the internal temperature of the structure. If left uncontrolled, significant temperature gradients will form between the concrete core and surface, as well as between different parts of the structure, leading to thermal stresses exceeding the early tensile strength of the concrete and causing structural cracking. Especially in marine chloride-corrosion environments, these temperature cracks can become rapid channels for the invasion of harmful ions, seriously affecting the safety and long-term durability of the structure.

[0003] Existing technologies typically address both materials and processes. For example, low-heat cement or admixtures such as fly ash are used to reduce the total heat of hydration, or cooling water pipes are embedded inside the concrete, and the surface is sprayed or covered for curing to dissipate heat and reduce the temperature difference between the inside and outside. However, these conventional measures have significant limitations. Existing temperature control methods mostly focus on controlling the temperature difference between the concrete core and surface, while for long, narrow structures like beams, the longitudinal temperature gradient is often ignored. Due to differences in heat dissipation conditions and constraint states, significant longitudinal temperature differences arise between the unconstrained areas of the beam (such as mid-span) and the constrained end areas (such as the connection with large pile foundations or already cast structural sections), leading to huge tensile stresses at the constrained ends. This is a major cause of longitudinal or diagonal cracks in the structure, but existing technologies lack effective control methods for this.

[0004] Current construction methods often employ layered casting, but this not only prolongs the construction period but also easily creates cold joints between layers, becoming weak points in structural durability. The internal pre-embedded cooling water pipe solution is not only cumbersome to arrange and has high initial material costs, but it may also interfere with dense reinforcing steel, affecting construction quality. Meanwhile, external spray cooling is inefficient, and in the salt spray environment of dock construction, directly using seawater or ordinary water for cooling will increase corrosion of metal formwork and temperature control piping systems, affecting the stability and reliability of temperature control. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for concrete pouring of large-volume beams, which solves the problem of insufficient longitudinal temperature gradient control in existing technologies, leading to temperature cracks easily occurring at the constraint ends.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing large-volume crossbeams using concrete pouring, comprising the following steps;

[0007] S1. Preparation stage: Prefabricate a zoned active temperature control integrated frame. The integrated frame is divided into at least three independent temperature control loop areas along the longitudinal direction of the crossbeam, including a mid-span area A and two constraint end areas B and C. The zoned active temperature control integrated frame is hoisted and fixed and connected to the central temperature control center.

[0008] S2. Pre-cooling and pouring stage: The central temperature control center is activated to pre-cool the zoned active temperature control integrated jig, reducing the surface temperature of its bottom mold to 15-20℃; a large volume of concrete is poured into the zoned active temperature control integrated jig in one go.

[0009] S3, Dynamic Thermal Gradient Management Stage: After the concrete pouring is completed, the integrated formwork in zones A, B, and C is controlled by the central temperature control center to perform the following temperature control steps:

[0010] Peak heat removal: Within 0-24 hours after pouring, a cooling medium of 5-10℃ is pumped into all temperature control loop areas for powerful cooling;

[0011] Gradient stress control: Within 24-72 hours after pouring, zone A, zone B and zone C are controlled separately. Through sensor data feedback, the temperature difference between the concrete core and the bottom formwork surface is kept at 20-25℃ or below, and the longitudinal temperature difference between the core of zone A and the core of zones B and C is kept at 5-8℃ or below.

[0012] Controlled synchronous cooling: Within 72-120 hours after pouring, the zoned active temperature control integrated frame guides the overall cooling of the concrete structure, with the overall cooling rate controlled at 0.3-0.5℃ / hour or less.

[0013] S4. Demolding stage: After the concrete meets the demolding conditions, the partitioned active temperature control integrated jig is demolded as a whole and transported.

[0014] Preferably, the mass concrete in step S2 is C50 grade low heat of hydration concrete, and its cementitious material has a density of 350-400 kg / m³. 3 It consists of P.LH42.5 low-heat silicate cement and Class I fly ash of type F accounting for 15-25% of the total cementitious materials; the water-cement ratio is controlled at 0.32-0.38.

[0015] Preferably, the cooling medium used in step S3 is a composite water-based anti-corrosion coolant, the components of which, by mass percentage, include: 25-40% ethylene glycol, 0.1-0.3% benzotriazole, 0.2-0.5% sodium molybdate, and the balance deionized water.

[0016] Furthermore, ethylene glycol is used to provide the antifreeze and thermal properties of the medium, while benzotriazole and sodium molybdate, as a composite corrosion inhibitor system, can effectively inhibit the electrochemical corrosion of the integrated frame's internal metal pipes by the cooling medium, ensuring the long-term stable operation of the temperature control system.

[0017] Preferably, step S1 includes placing Pt100 platinum resistance temperature sensors at the geometric center of the beam reinforcement cage, at a distance of 50-100mm from the top surface of the bottom formwork, and at a distance of 50-100mm from the top surface, and connecting the signals of the sensors to the central temperature control center to provide sensor data feedback.

[0018] Furthermore, the arrangement method can accurately monitor the highest core temperature point and key data representing the internal and external temperature differences, providing necessary closed-loop feedback data for gradient stress control in step S3.

[0019] Preferably, the specific operation of the zone control in step S3 is as follows: the central temperature control center maintains the inlet temperature of the cooling medium in zone A at 10-18℃, and dynamically adjusts the flow rate of the cooling medium in zones B and C or raises its inlet temperature to 15-22℃, so as to actively reduce the cooling rate of zones B and C, thereby achieving the control of the longitudinal temperature difference.

[0020] Furthermore, heat accumulates fastest in zone A (mid-span), requiring strong cooling; while zones B / C (constrained ends) reduce their cooling rate by actively increasing the temperature of the cooling medium (or reducing the flow rate), making their cooling behavior consistent with that of zone A, thereby achieving active control of the longitudinal temperature difference.

[0021] Preferably, in step S2, the temperature of the large-volume concrete entering the formwork is controlled within the range of 25-30℃, and continuous pouring is carried out using a layer thickness of 300-500mm and a stepped approach.

[0022] Furthermore, controlling the temperature upon entering the mold is one of the measures to reduce initial heat; while the step-by-step continuous pouring method is a necessary means to cooperate with the one-time integral pouring process of this invention, avoid the generation of construction cold joints, and ensure the integrity of the structure.

[0023] Preferably, the main body of the zoned active temperature control integrated frame in step S1 is a tubular truss structure, and its load-bearing main truss is made of seamless steel pipe. The hollow cavity of the seamless steel pipe is the cooling medium channel of the temperature control circuit area.

[0024] Preferably, the demolding conditions in step S4 include:

[0025] The strength of concrete test blocks cured under the same conditions reached 75-85% of the design strength;

[0026] The difference between the core temperature of the concrete and the daily average temperature of the construction site environment is reduced to 15-20℃ or below.

[0027] Preferably, in step S4, after demolding, the surface of the beam is covered with a plastic film and geotextile, and water is sprayed to keep it moist for a period of not less than 14-21 days.

[0028] Preferably, the maintenance process includes anti-corrosion construction on the surface of the beam, using epoxy-based anti-corrosion coating by roller or spray to achieve a total dry film thickness of 400-500μm.

[0029] This invention provides a method for constructing large-volume horizontal beams using concrete pouring. It offers the following advantages:

[0030] 1. This invention, by setting gradient stress regulation, performs zonal regulation on the mid-span A zone and the constrained end B and C zones, controls the internal and external temperature difference between the concrete core and surface, actively controls the longitudinal temperature difference between the mid-span zone and the constrained end zone, effectively suppresses the tensile stress concentration of the beam in the constrained end zone, and solves the problem of constrained cracks caused by longitudinal temperature gradient.

[0031] 2. This invention employs a zoned active temperature control integrated jig, combined with a complete thermal field management program that includes peak heat removal, gradient stress regulation, and controlled synchronous cooling. This enables highly efficient and precise heat removal capabilities, making it possible to cast large volumes of concrete in a single, integral pour. This eliminates the construction cold joint problem caused by traditional layered pouring processes and significantly improves the integrity and durability of the formed structure.

[0032] 3. This invention integrates load-bearing and temperature control functions by adopting a zoned active temperature control integrated jig and preferably using the hollow cavity of the tubular truss structure as a cooling channel. At the same time, the use of a composite water-based anti-corrosion coolant containing benzotriazole and sodium molybdate can effectively inhibit the corrosion of the internal metal pipes of the jig by the cooling medium, prevent system blockage or failure, and ensure the long-term stable and reliable operation of the temperature control method during the construction period. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Please see the appendix Figure 1 This invention provides a method for constructing large-volume crossbeams using concrete pouring, including:

[0036] Example 1

[0037] S1. Preparation Stage: Prefabricate a "zonal active temperature control integrated jig," the main body of which is a tubular truss structure. The main load-bearing truss uses seamless steel pipes, and the hollow cavity serves as a cooling medium channel. The jig is longitudinally divided into three independent temperature control loop areas: mid-span zone A, constraint-end zone B, and constraint-end zone C. The integrated jig is hoisted and fixed, and connected to a central temperature control center. Pt100 platinum resistance temperature sensors are installed at the geometric center within the beam reinforcement cage, 75mm from the top surface of the bottom formwork, and 75mm from the top surface, and connected to the central temperature control center.

[0038] S2, Pre-cooling and casting stage:

[0039] Concrete preparation: C50 grade low heat of hydration concrete is prepared, the components (per cubic meter) of which include: P.LH42.5 low heat of hydration silicate cement 375 kg / m³ 3 Class F, Grade I fly ash: 93.75 kg / m³ 3 (468.75 kg / m³ of cementitious material) 3 (20% of the total content); the water-cement ratio is controlled at 0.35.

[0040] Pre-cooling: Activate the central temperature control center to pre-cool the integrated jig, reducing the surface temperature of its bottom mold to 18°C.

[0041] Pouring: The above-mentioned concrete is poured into the integrated formwork in one go. The concrete temperature is controlled at 28℃ when it enters the formwork, and continuous pouring is carried out in layers of 400mm thickness in a stepped manner.

[0042] S3, Dynamic Thermal Gradient Management Stage:

[0043] Cooling medium preparation: A composite water-based anti-corrosion coolant is used, the components of which, by mass percentage, include: 32% ethylene glycol, 0.2% benzotriazole, 0.35% sodium molybdate, and the balance deionized water.

[0044] Temperature control steps:

[0045] Peak heat removal: Within 0-24 hours after pouring, pump the cooling medium at 8°C to all temperature control loop areas.

[0046] Gradient stress control: Zoned control is implemented within 24-72 hours after pouring. The central temperature control center maintains the inlet temperature of the cooling medium in zone A at 14℃, and dynamically adjusts the flow rate of the cooling medium in zones B and C to raise their inlet temperatures to 18℃. During this period, sensor data feedback ensures that the maximum temperature difference between the concrete core and the bottom formwork surface remains at 22℃, and the maximum longitudinal temperature difference between the core of zone A and the core of zones B / C remains at 6℃.

[0047] Controlled synchronous cooling: Within 72-120 hours after pouring, the integrated formwork guides the overall cooling of the concrete structure, with the overall cooling rate controlled at 0.4℃ / hour.

[0048] S4. Demolding and subsequent processes:

[0049] Demolding: The demolding conditions are met when the strength of the concrete test blocks cured under the same conditions reaches 80% of the design strength, and the difference between the core temperature of the concrete and the daily average temperature of the construction site environment drops to 18℃. The integrated formwork is then demolded as a whole and transported.

[0050] Curing: Immediately after demolding, cover the surface of the beam with plastic film and geotextile, and spray water to keep it moist for 17 days.

[0051] Corrosion protection: After curing, epoxy-based anti-corrosion coating is applied to the surface of the beam by roller coating to achieve a total dry film thickness of 450μm.

[0052] Example 2

[0053] S1. Preparation stage: The same partitioned active temperature control integrated jig and central temperature control center as in Example 1 are used. Pt100 platinum resistance temperature sensors are installed at the geometric center of the beam reinforcement cage, 50mm from the top surface of the bottom formwork, and 50mm from the top surface, and connected to the central temperature control center.

[0054] S2, Pre-cooling and casting stage:

[0055] Concrete preparation: C50 grade low heat of hydration concrete is prepared, the components (per cubic meter) of which include: P.LH42.5 low heat of hydration silicate cement 350kg / m³ 3 Class F, Grade I fly ash: 61.76 kg / m³ 3 (411.76 kg / m³ of cementitious material) 3 (15%); the water-cement ratio is controlled at 0.32.

[0056] Pre-cooling: Activate the central temperature control center to pre-cool the integrated jig, reducing the surface temperature of its bottom mold to 15°C.

[0057] Pouring: The above-mentioned concrete is poured into the integrated formwork in one go. The concrete temperature is controlled at 25℃ when it enters the formwork, and continuous pouring is carried out in layers of 300mm thickness in a stepped manner.

[0058] S3, Dynamic Thermal Gradient Management Stage:

[0059] Cooling medium preparation: A composite water-based anti-corrosion coolant is used, the components of which, by mass percentage, include: 25% ethylene glycol, 0.1% benzotriazole, 0.2% sodium molybdate, and the balance deionized water.

[0060] Temperature control steps:

[0061] Peak heat removal: Within 0-24 hours after pouring, pump the cooling medium at 5°C to all temperature control loop areas.

[0062] Gradient stress control: Zoned control is implemented within 24-72 hours after pouring. The central temperature control center maintains the inlet temperature of the cooling medium in zone A at 10℃ and dynamically adjusts the flow rate of the cooling medium in zones B and C to raise their inlet temperatures to 15℃. During this period, sensor data feedback ensures that the maximum temperature difference between the concrete core and the bottom formwork surface remains at 20℃, and the maximum longitudinal temperature difference between the core of zone A and the core of zones B / C remains at 5℃.

[0063] Controlled synchronous cooling: Within 72-120 hours after pouring, the integrated formwork guides the overall cooling of the concrete structure, with the overall cooling rate controlled at 0.3℃ / hour.

[0064] S4. Demolding and subsequent processes:

[0065] Demolding: The demolding conditions are met when the strength of the concrete test blocks cured under the same conditions reaches 75% of the design strength, and the difference between the core temperature of the concrete and the daily average temperature of the construction site environment drops to 15℃. The integrated formwork is then demolded as a whole and transported.

[0066] Curing: Immediately after demolding, cover the surface of the beam with plastic film and geotextile, and spray water to keep it moist for 14 days.

[0067] Corrosion protection: After curing, epoxy-based anti-corrosion coating is sprayed onto the surface of the beam to achieve a total dry film thickness of 400μm.

[0068] Example 3

[0069] S1. Preparation stage: The same partitioned active temperature control integrated jig and central temperature control center as in Example 1 are used. Pt100 platinum resistance temperature sensors are installed at the geometric center of the beam reinforcement cage, 100mm from the top surface of the bottom formwork, and 100mm from the top surface, and connected to the central temperature control center.

[0070] S2, Pre-cooling and casting stage:

[0071] Concrete preparation: C50 grade low heat of hydration concrete is prepared, the components (per cubic meter) of which include: P.LH42.5 low heat of hydration silicate cement 400 kg / m³ 3 Class F, Grade I fly ash: 133.33 kg / m³ 3 (533.33 kg / m³ of cementitious material) 3 (25%); the water-cement ratio is controlled at 0.38.

[0072] Pre-cooling: Activate the central temperature control center to pre-cool the integrated jig, reducing the surface temperature of its bottom mold to 20°C.

[0073] Pouring: The above-mentioned concrete is poured into the integrated formwork in one go. The concrete temperature is controlled at 30℃ when it enters the formwork, and continuous pouring is carried out in layers of 500mm thickness in a stepped manner.

[0074] S3, Dynamic Thermal Gradient Management Stage:

[0075] Cooling medium preparation: A composite water-based anti-corrosion coolant is used, the components of which, by mass percentage, include: 40% ethylene glycol, 0.3% benzotriazole, 0.5% sodium molybdate, and the balance deionized water.

[0076] Temperature control steps:

[0077] Peak heat removal: Within 0-24 hours after pouring, pump the cooling medium at 10°C to all temperature control loop areas.

[0078] Gradient stress control: Zoned control is implemented within 24-72 hours after pouring. The central temperature control center maintains the inlet temperature of the cooling medium in zone A at 18℃ and dynamically adjusts the flow rate of the cooling medium in zones B and C to raise their inlet temperatures to 22℃. During this period, sensor data feedback ensures that the maximum temperature difference between the concrete core and the bottom formwork surface remains at 25℃, and the maximum longitudinal temperature difference between the core of zone A and the core of zones B / C remains at 8℃.

[0079] Controlled synchronous cooling: Within 72-120 hours after pouring, the integrated formwork guides the overall cooling of the concrete structure, with the overall cooling rate controlled at 0.5℃ / hour.

[0080] S4. Demolding and subsequent processes:

[0081] Demolding: The demolding conditions are met when the strength of the concrete test blocks cured under the same conditions reaches 85% of the design strength, and the difference between the core temperature of the concrete and the daily average temperature of the construction site environment drops to 20℃. The integrated formwork is then demolded as a whole and transported.

[0082] Curing: Immediately after demolding, cover the surface of the beam with plastic film and geotextile, and spray water to keep it moist for 21 days.

[0083] Corrosion protection: After curing, epoxy-based anti-corrosion coating is applied to the surface of the beam by roller coating to achieve a total dry film thickness of 500μm.

[0084] Comparative Example 1;

[0085] Compared with Example 1, the difference is that in the gradient stress control stage, the A, B and C areas are not controlled separately. Instead, just like in the peak heat removal stage, the 8°C cooling medium is pumped uniformly to all three temperature control loop areas. The rest is the same.

[0086] Comparative Example 2;

[0087] Compared with Example 1, the difference is that the controlled synchronous cooling stage is omitted, while the rest are the same.

[0088] Comparative Example 3;

[0089] The difference compared to Example 1 is that the cementitious material was replaced with ordinary Portland cement 468.75 kg / m³. 3 The rest are the same.

[0090] Comparative Example 4;

[0091] Compared with Example 1, the difference is that the cooling medium components are replaced with 32% ethylene glycol and the balance deionized water, and do not contain the two corrosion inhibitors benzotriazole and sodium molybdate, while the rest are the same.

[0092] Comparative Example 5;

[0093] Compared with Example 1, the difference is that after the central temperature control center is started, concrete pouring begins immediately when the surface temperature of the bottom mold is at ambient temperature, without waiting for it to drop to 18°C. All other aspects are the same.

[0094] Test Example 1: Comparison Test of Dynamic Thermal Field Gradient Control Effect

[0095] Experimental description:

[0096] This test case aims to verify the effects of key components (low heat of hydration concrete) and key process steps (precooling, zoned control) on three core temperature indicators of large-volume beams during the hardening process in this invention (Example 1). , , The overall control effect.

[0097] Test groups: The process schemes of Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 5 were selected as test groups.

[0098] Example 1 (Complete Scheme of the Invention);

[0099] Comparative Example 1 (No zone control: unified cooling for zones A / B / C);

[0100] Comparative Example 3 (non-low heat of hydration: ordinary Portland cement was used);

[0101] Comparative example 5 groups (no pre-cooling: bottom mold not cooled).

[0102] Data collection:

[0103] During the construction process of the above four groups according to their respective plans, the temperature data within 0-120 hours is automatically monitored and continuously recorded by the central temperature control center through the Pt100 platinum resistance temperature sensor installed inside the crossbeam reinforcement cage in stage S1, and the sensor installed on the surface of the bottom formwork.

[0104] Data processing: After data collection is completed, the following three indicators are extracted and calculated from the databases of each group:

[0105] Core peak temperature ( ): The highest temperature reading monitored by the beam geometric center sensor within 0-72 hours.

[0106] Maximum internal and external temperature difference ( : The maximum value of the difference between the reading of the geometric center sensor and the reading of the bottom mold surface sensor within 24-72 hours (gradient stress control stage).

[0107] Maximum longitudinal temperature difference ( : The maximum absolute value of the difference between the sensor reading at the core of zone A (geometric center of the cross-section) and the sensor reading at the core of zone B or C (geometric center of the constraint end zone) within 24-72 hours (gradient stress control stage).

[0108] The experimental data are shown in Table 1;

[0109] Table 1: Test data on the effect of dynamic thermal field gradient control

[0110]

[0111] Summarize

[0112] Table 1 shows the test data reflecting the influence of different process parameters on the internal temperature field of concrete. A comparison with Comparative Example 3 shows that using ordinary Portland cement leads to a higher core peak temperature (…). The temperature reached 76.2℃, significantly higher than the 58.7℃ in Example 1. This is attributed to the higher heat release during hydration of ordinary cement. Consequently, the maximum internal and external temperature difference ( The temperature also rose to 34.6℃, exceeding the control target. The results indicate that the low heat of hydration gelling material selected in this invention is a prerequisite for effectively controlling the total heat release.

[0113] The data compared with Comparative Example 5 shows that omitting the bottom formwork pre-cooling step resulted in a higher initial temperature baseline after concrete pouring, which directly led to a higher core peak temperature ( ) and maximum internal and external temperature difference ( The temperatures rose to 65.4℃ and 28.3℃ respectively. The data indicates that the pre-cooling of the bottom mold in step S2 is an effective measure to reduce the initial heat of the system and ensure that the subsequent internal and external temperature differences meet control requirements. Compared with Comparative Example 1, this clearly reveals the mechanism of zoned temperature control. Comparative Example 1 uses a uniform cooling strategy, and its maximum longitudinal temperature difference ( The temperature reached 15.8℃, far exceeding the control target; while Example 1 controlled this value at 6.3℃ through zoned regulation. This data shows that uniform cooling cannot solve the longitudinal temperature gradient problem caused by uneven heat dissipation and end constraints. In the gradient stress regulation stage, this invention uses differentiated cooling power for the mid-span zone (zone A) and the constrained end zones (zones B and C), which is the core technology for controlling the longitudinal temperature difference below 8℃.

[0114] Test Example 2: Comparison Test of Structural Integrity and Crack Suppression Effect

[0115] Experimental description:

[0116] This test case aims to directly verify the final effect of the complete process of the present invention (Example 1) in suppressing temperature cracks by inspecting the surface condition of the final formed beam.

[0117] Test Groups:

[0118] Example 1, along with Comparative Examples 1, 2, and 3, which had critical defects in temperature control or material selection, were selected as the test group.

[0119] Example 1 (Complete Scheme of the Invention);

[0120] Comparative Example 1 (no zoned control);

[0121] Comparative Example 2 (uncontrolled synchronous cooling);

[0122] Comparative examples: 3 groups (using ordinary Portland cement).

[0123] Testing steps:

[0124] After the beams in the above four groups have been constructed according to their respective plans and have met the demolding conditions of stage S4, the following inspection steps shall be performed:

[0125] Visual inspection: Conduct a systematic visual inspection of all surfaces of each beam, especially the sides and top surfaces of the two constraint end areas B and C.

[0126] Crack calibration and measurement:

[0127] Using a crack width observation instrument, all temperature cracks found during inspection with a width greater than 0.05 mm were measured and recorded. The location, direction, and maximum width of each crack were recorded.

[0128] Data processing: Compile the on-site inspection results and statistically analyze the following two core indicators for the crossbeams of each group:

[0129] The total number of visible temperature cracks and the total number of cracks with a width greater than 0.05 mm on the beam surface are shown.

[0130] Maximum crack width (mm): The maximum width among all recorded cracks.

[0131] The experimental data are shown in Table 2;

[0132] Table 2: Test data on structural integrity and crack suppression effect

[0133]

[0134] Summarize

[0135] No visible temperature cracks were observed in the beam of Example 1, indicating that the process effectively maintained the stress level of the concrete below its tensile strength throughout the hardening process. In contrast to Comparative Example 3, the specimen using ordinary Portland cement developed nine cracks, with the maximum width reaching 0.27 mm. This result is directly related to the excessively high core peak temperature and large internal-external temperature difference in Test Example 1. The high heat and high gradient generated tensile stress exceeding the material's capacity, leading to structural cracking.

[0136] The specimen in Comparative Example 1 showed three cracks with a maximum width of 0.18 mm in the constrained end region. This phenomenon is consistent with the longitudinal temperature difference of up to 15.8℃ observed in Test Example 1. There is a clear correspondence. Data confirms that the failure to control the longitudinal temperature gradient is the direct cause of tensile stress concentration and eventual cracking in the constrained end area; 11 narrow network cracks appeared on the surface of the specimen in Comparative Example 2. This was due to the thermal shock effect caused by the sudden cessation of cooling after 72 hours, resulting in a rapid drop in ambient temperature on the concrete surface. This result indicates that the controlled synchronous cooling step set in the later stage of temperature control in this invention is necessary to prevent surface cracking caused by excessively rapid cooling rates.

[0137] Test Example 3: Comparative Test of the Corrosivity of Cooling Medium to the System

[0138] Experimental description:

[0139] This test case aims to verify the corrosion inhibition performance of the composite water-based anti-corrosion coolant used in the present invention (Example 1) on the internal pipeline (seamless steel pipe) of the zoned active temperature control integrated frame.

[0140] Test Groups:

[0141] Example 1 group: The coolant formulated in Example 1 (containing 32% ethylene glycol, 0.2% benzotriazole, 0.35% sodium molybdate and the balance deionized water) was used.

[0142] Comparative Example 4: The coolant formulated in Comparative Example 4 was used (containing 32% ethylene glycol and the balance deionized water, without corrosion inhibitors).

[0143] Experimental steps:

[0144] Specimen preparation: Select steel of the same material as the main truss of the integrated jig (seamless steel pipe) to prepare 4 standard corrosion hanging plates (75mm×13mm×2mm in size), and weigh them accurately (to 0.1mg) after grinding, cleaning and drying.

[0145] Simulated circulation: Prepare two identical benchtop dynamic circulation loop devices. Inject the coolant from Example 1 and Comparative Example 4 into the two loops respectively. Suspend two pre-weighed corrosion plates in each loop.

[0146] Accelerated testing: Start the circulation pumps of both loops to simulate the working conditions of the S3 stage, so that the coolant circulates within the temperature range of 5℃ to 22℃ for 500 hours.

[0147] Data Acquisition: After the test, visually inspect the appearance of the coolant in both circuits. Remove the coolant strips, chemically clean them (to remove corrosion products), dry them, and then weigh them accurately again.

[0148] Data processing: Based on the weight loss of the pads before and after the test, the surface area of ​​the pads, and the test time, the average corrosion rate is calculated, with units of mg / (dm³). 2 ·day).

[0149] The experimental data are shown in Table 3;

[0150] Table 3: Comparative Test Data on Corrosion of Cooling Media

[0151]

[0152] Summarize

[0153] Comparative Example 4 (without corrosion inhibitor) showed an average corrosion rate of 38.82 MDD. After testing, the liquid exhibited a distinct reddish-brown turbidity, accompanied by flocculent precipitates. Both this phenomenon and the data indicate that ethylene glycol aqueous solution has significant electrochemical corrosiveness to the carbon steel material used in the integrated jig, and the precipitate is a corrosion product.

[0154] Example 1 (the coolant of this invention) exhibited an average corrosion rate of only 2.19 MDD under the same accelerated testing conditions. The liquid remained clear and transparent before and after the test. Data comparison confirmed that the corrosion rate of Example 1 was reduced by more than an order of magnitude compared to Comparative Example 4 (corrosion inhibition rate of approximately 94.4%). This clearly demonstrates that the benzotriazole and sodium molybdate compounded in the components of this invention, as a composite corrosion inhibitor system, can form an effective passivation protective layer on the steel surface, thereby greatly inhibiting the occurrence of corrosion reactions. The zoned active temperature control integrated jig is the core system component enabling the implementation of the method of this invention. The structural integrity and unobstructed flow channels of its internal hollow pipes are prerequisites for achieving precise thermal field management. The composite water-based anti-corrosion coolant components of this invention can effectively prevent the jig pipes from becoming blocked or perforated due to corrosion, which is a necessary technical guarantee for ensuring the long-term, stable, and reliable operation of the technical solution of this invention in engineering applications.

Claims

1. A method for constructing large-volume horizontal beams using concrete pouring, characterized in that, Includes the following steps: S1. Preparation stage: Prefabricate a zoned active temperature control integrated frame, which is divided into at least three independent temperature control loop areas along the longitudinal direction of the crossbeam, including a mid-span area A and two constraint end areas B and C. Hoist and fix the zoned active temperature control integrated frame and connect it to the central temperature control center. The main body of the partitioned active temperature control integrated frame in step S1 is a tubular truss structure, and its load-bearing main truss is made of seamless steel pipe. The hollow cavity of the seamless steel pipe is the cooling medium channel of the temperature control circuit area. S2, Pre-cooling and pouring stage; The central temperature control center is activated to pre-cool the partitioned active temperature control integrated jig, reducing the surface temperature of its bottom mold to 15-20℃; A large volume of concrete is poured into the partitioned active temperature control integrated jig in one go; S3, Dynamic Thermal Gradient Management Stage; After the concrete pouring is completed, the integrated formwork's A, B, and C zones are controlled by the central temperature control center to perform the following temperature control steps: Peak heat removal: Within 0-24 hours after pouring, a cooling medium of 5-10℃ is pumped into all temperature control loop areas for powerful cooling; Gradient stress control: Within 24-72 hours after pouring, zone A, zone B and zone C are controlled separately. Through sensor data feedback, the temperature difference between the concrete core and the bottom formwork surface is kept at 20-25℃ or below, and the longitudinal temperature difference between the core of zone A and the core of zones B and C is kept at 5-8℃ or below. Controlled synchronous cooling: Within 72-120 hours after pouring, the zoned active temperature control integrated frame guides the overall cooling of the concrete structure, with the overall cooling rate controlled at 0.3-0.5℃ / hour or less. The specific operation of the zone control in step S3 is as follows: the central temperature control center maintains the inlet temperature of the cooling medium in zone A at 10-18℃, and dynamically adjusts the flow rate of the cooling medium in zones B and C or raises its inlet temperature to 15-22℃, so as to actively reduce the cooling rate of zones B and C, thereby achieving the control of the longitudinal temperature difference. S4. Demolding stage: After the concrete meets the demolding conditions, the partitioned active temperature control integrated jig is demolded as a whole and transported.

2. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, The large-volume concrete in step S2 is C50 grade low-heat-of-hydration concrete, and its cementitious material has a density of 350-400 kg / m³. 3 It consists of P.LH42.5 low-heat silicate cement and Class I fly ash of type F accounting for 15-25% of the total cementitious materials; the water-cement ratio is controlled at 0.32-0.

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3. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, The cooling medium used in step S3 is a composite water-based anti-corrosion coolant, whose components, by mass percentage, include: 25-40% ethylene glycol, 0.1-0.3% benzotriazole, 0.2-0.5% sodium molybdate, and the balance being deionized water.

4. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, Step S1 includes installing Pt100 platinum resistance temperature sensors at the geometric center of the beam reinforcement cage, at a distance of 50-100mm from the top surface of the bottom formwork, and at a distance of 50-100mm from the top surface. The signals of the sensors are then connected to the central temperature control center to provide sensor data feedback.

5. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, In step S2, the temperature of the large-volume concrete entering the formwork is controlled within the range of 25-30℃, and continuous pouring is carried out by layering with a thickness of 300-500mm and using a stepped approach.

6. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, The demolding conditions in step S4 include: The strength of concrete test blocks cured under the same conditions reached 75-85% of the design strength; The difference between the core temperature of the concrete and the daily average temperature of the construction site environment is reduced to 15-20℃ or below.

7. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 1, characterized in that, In step S4, after demolding, the surface of the beam is covered with plastic film and geotextile, and water is sprayed to keep it moist and cured for no less than 14-21 days.

8. The method for constructing a large-volume horizontal beam using concrete pouring according to claim 7, characterized in that, After the maintenance is completed, anti-corrosion construction is carried out on the surface of the beam, using epoxy-based anti-corrosion coating by roller or spray to achieve a total dry film thickness of 400-500μm.

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