A mass concrete self-energizing curing system for low temperature environment

Abstract

This invention discloses a self-storing energy storage curing system for large-volume concrete in low-temperature environments. The system controls the inflation and deflation of a variable insulation unit through a central control system, enabling the energy storage layer to efficiently absorb the heat of hydration of the large-volume concrete while maintaining insulation. Furthermore, once the energy storage layer has absorbed sufficient heat of hydration, it can promptly release the heat to the outside. When the energy storage layer regains its heat absorption capacity, it can re-insulate, efficiently absorbing the heat of hydration of the large-volume concrete. During this repeated heat absorption and release process, the temperature difference between the surface and interior of the large-volume concrete remains within a small range. This invention achieves heat extraction from large-volume concrete using only a variable insulation unit and an energy storage layer, while maintaining relatively uniform surface and interior temperatures. It also reduces energy consumption, labor, and material costs, and shortens the curing cycle.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a self-storing energy curing system for large-volume concrete in low-temperature environments. Background Technology

[0002] Massive concrete structures have large cross-sectional dimensions, characterized by their extra-long, extra-thick, and extra-wide dimensions. Due to their massive volume, a significant amount of heat from cement hydration accumulates internally. Since concrete has poor thermal conductivity, this leads to uneven temperature distribution between the internal and external surfaces of the massive concrete structure. This results in differences in strength development between the internal and external parts of the structure. Particularly during the construction of massive concrete structures in cold environments, the surface concrete temperature drops rapidly, halting cement hydration and significantly limiting surface strength development. Furthermore, the water in the surface concrete freezes, causing irreversible frost heave damage, leading to unstable construction quality and severely impacting the long-term service performance of the concrete. Therefore, determining the appropriate curing method for massive concrete structures in cold environments to effectively control their overall temperature is a crucial engineering issue.

[0003] In practical engineering, temperature control methods for large-volume concrete in cold environments mainly include two aspects. First, the heat of hydration accumulated inside the large-volume concrete needs to be reduced or effectively dissipated. Common methods include lowering the concrete's initial pour temperature, reducing the volume of concrete poured at one time, adding low-heat-of-hydration admixtures, pre-embedding hot water pipes, and increasing the concrete's thermal conductivity. Second, to prevent slow strength development or even frost damage to the surface concrete, an external heat source needs to be constructed for curing. Common methods for constructing external heat sources include heated enclosures and electric heating. These two methods allow the heat of hydration accumulated inside the large-volume concrete to be dissipated to the outside, while the outer surface concrete is protected from the cold environment. However, traditional methods for curing large-volume concrete in cold environments involve huge energy, labor, and material costs, drastically increasing curing costs and posing fire hazards. Furthermore, because the external heat source provides a higher curing temperature environment for the large-volume concrete structure, a longer time is required to cool the concrete before removing the formwork and the external heat source to prevent cracking caused by excessive temperature differences between the low-temperature environment and the concrete surface, significantly extending the construction period.

[0004] Phase change materials (PCMs) are thermal energy storage materials with near-isothermal heat storage and release characteristics. Placing PCMs in the curing layer of large-volume concrete can effectively improve the uniform temperature development of the entire concrete structure. However, in cold environments, even with good insulation, the curing process of large-volume concrete structures still requires a significant amount of time to allow the overall concrete structure to cool down before demolding. To achieve rapid cooling and accelerate construction, insulation capacity must be reduced, leading to the rapid loss of heat stored in the PCMs within the curing layer. This causes a rapid drop in the surface temperature of the concrete, potentially resulting in freezing and excessive temperature differences between the inside and outside of the large-volume concrete, leading to uneven strength development. Existing methods for temperature control of large-volume concrete using PCMs still struggle to balance the contradiction between the rapid heat dissipation from the interior of the concrete and the prevention of surface freezing damage in cold environments. Furthermore, there are currently few methods to guide the design of PCMs used in curing formwork based on the actual low-temperature environment of the application area to achieve optimal temperature uniformity control of the large-volume concrete. Summary of the Invention

[0005] This invention provides a self-storage curing system for large-volume concrete in low-temperature environments. This curing system can more efficiently make the internal and external temperatures of large-volume concrete more uniform, ensuring more consistent strength development of large-volume concrete, saving curing time, and consuming less energy.

[0006] This invention provides a self-storing energy storage curing system for large-volume concrete in low-temperature environments, comprising:

[0007] A variable insulation unit is used to achieve insulation and heat release through inflation and deflation.

[0008] An energy storage layer, located on the lower surface of the variable insulation unit, is used to absorb, store, and release the heat of hydration of large-volume concrete through the phase change of the phase change material inside the energy storage layer.

[0009] A template layer is located between the energy storage layer and the large-volume concrete.

[0010] The temperature acquisition system is used to detect the temperature of the upper and lower surfaces of the energy storage layer, as well as the surface and interior of the large-volume concrete.

[0011] The central control system is connected to the temperature acquisition system and the variable insulation unit. When the temperature difference between the surface and interior of the large-volume concrete exceeds the set temperature threshold, the variable insulation unit is controlled to inflate to achieve insulation, allowing the hydration heat of the large-volume concrete to be transferred to the energy storage layer. It is also used to release the energy storage unit when the energy stored in the energy storage layer is higher than the upper limit, releasing the heat of the energy storage layer to the outside. Furthermore, when the energy stored in the energy storage layer is lower than the lower limit, the variable insulation unit is controlled to inflate again to achieve insulation, allowing the energy storage layer to continue absorbing the hydration heat of the large-volume concrete, thereby maintaining the temperature difference between the surface and interior of the large-volume concrete within the temperature threshold.

[0012] Preferably, the variable insulation unit includes an air pump, an air pump, and a variable insulation layer;

[0013] The air pump is connected to the variable insulation layer through a vent pipe and is also connected to the central control system. The air pump is used to inflate the variable insulation layer with air based on the instructions of the central control system when the temperature difference between the surface and the interior of the large-volume concrete is greater than the set temperature critical value or when the stored energy in the energy storage layer is lower than the lower limit, so that the variable insulation layer can achieve the insulation function.

[0014] The air pump is connected to the variable insulation layer via a vent pipe and to the central control system. When the energy stored in the energy storage layer exceeds the upper limit, the air pump is used to extract the gas in the variable insulation layer based on the instructions of the central control system, so that the energy storage layer can release the stored energy to the outside.

[0015] This invention controls the air pump and the air pump through a central control system, enabling the variable insulation layer to adjust the insulation and heat release based on the energy storage of the energy storage layer and the temperature difference between the surface and the interior of the large-volume concrete. This can efficiently maintain the heat absorption capacity of the energy storage layer, thereby keeping the temperature difference between the interior and the surface of the large-volume concrete at a small level.

[0016] Preferably, the variable insulation layer is an inflatable / deflated airbag, and an infrared reflective coating is applied or disposed on the side of the variable insulation layer near the energy storage layer. Further, the infrared reflective coating is aluminum foil.

[0017] Preferably, the material of the inflatable airbag is polyethylene, rubber, or nylon fabric.

[0018] The inflatable airbag provided by this invention has a high-pressure function, good sealing effect and mechanical properties, good chemical properties and temperature, can withstand high air pressure, has excellent heat preservation ability, and is suitable for concrete curing.

[0019] This invention utilizes an infrared reflective coating to reflect infrared radiation, preventing heat from the internal energy storage layer from radiating to the external environment. The channels through which the energy storage layer dissipates heat to the outside can be summarized into two types: contact heat exchange with the variable insulation layer and radiative heat dissipation. Based on the proposed curing structure, without the infrared reflective coating, when the variable insulation layer is fully inflated and reaches its maximum insulation capacity, the energy storage layer will continuously radiate heat to the outside. If the heat dissipation is too high, the insulation effect of the variable insulation layer will be lost.

[0020] Preferably, the energy storage layer is obtained by mixing a shaped functional polymer and a phase change material, wherein the phase change material is an organic phase change material and / or an inorganic hydrated salt phase change material.

[0021] More preferably, the organic phase change material is paraffin wax, polyethylene glycol, fatty acids, and their eutectic systems, and the inorganic hydrated salt phase change material is a eutectic system of calcium chloride hexahydrate, magnesium nitrate hexahydrate, calcium chloride dodecahydrate, disodium hydrogen phosphate dodecahydrate, and sodium carbonate decahydrate.

[0022] This invention utilizes the rapid energy absorption of phase change materials during the phase change process. With the synergistic effect of the variable insulation layer, it can efficiently absorb the heat of hydration of large-volume concrete. At the same time, in conjunction with the heat insulation function of the variable insulation layer to reduce air venting, the absorbed energy can be efficiently released through phase change. Compared with the existing technology of installing drainage pipes, it can more efficiently discharge the heat of hydration to the outside.

[0023] Preferably, when the energy stored in the energy storage layer is higher than the upper limit, the temperature of the upper surface of the energy storage layer is higher than the first critical temperature, which is the phase change temperature of the phase change material + 2°C.

[0024] When the energy release causes the energy in the energy storage layer to fall below the lower limit, the temperature of the lower surface of the energy storage layer is lower than the second critical temperature, which is the phase change temperature of the phase change material -2℃.

[0025] The set temperature threshold is 20-30℃.

[0026] This invention, by setting a first critical temperature, a second critical temperature, and a temperature critical value, makes the internal temperature of large-volume concrete more uniform, and at the same time can more efficiently dissipate the heat of hydration to the outside.

[0027] Preferably, the thickness of the energy storage layer for:

[0028]

[0029] Among them, C1, A and These are the specific heat capacity, density, surface area, and second critical temperature of the energy storage layer. The time required for the insulation layer to be completely filled. The local average minimum temperature for the month in the area where the project is being constructed. λ is the lowest temperature that the concrete or equipment can tolerate, and λ is the thermal conductivity of the energy storage layer.

[0030] Preferably, the template layer is a wooden template or a steel template.

[0031] Preferably, the temperature acquisition system includes a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, and a multi-channel temperature acquisition instrument;

[0032] The first temperature sensor is located on the upper surface of the energy storage layer and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the upper surface of the energy storage layer to the multi-channel temperature acquisition instrument.

[0033] The second temperature sensor is located on the lower surface of the energy storage layer and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the lower surface of the energy storage layer to the multi-channel temperature acquisition instrument.

[0034] The third temperature sensor is located in the shallow layer of the large-volume concrete and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the large-volume concrete surface to the multi-channel temperature acquisition instrument.

[0035] The fourth temperature sensor is located inside the large-volume concrete and is connected to a multi-channel temperature acquisition instrument to transmit the detected internal temperature of the large-volume concrete to the multi-channel temperature acquisition instrument.

[0036] The multi-channel temperature acquisition instrument is connected to the central control system and is used to send the temperature of the upper and lower surfaces of the energy storage layer, as well as the surface and interior of the large-volume concrete, to the central control system.

[0037] More preferably, the shallow layer of the large-volume concrete is a concrete layer located 2 to 10 cm away from the outer surface of the concrete.

[0038] More preferably, the fourth temperature sensor is located inside the large-volume concrete, and the "inside" refers to any position within a range of 10-20 cm from the geometric center of the large-volume concrete.

[0039] More preferably, the third and fourth temperature sensors are mounted on the reinforcing bars.

[0040] Preferably, the dimensions of the large-volume concrete are between 1m×1m×1m and 10m×10m×10m.

[0041] On the other hand, the present invention also provides a method for curing large-volume concrete using the aforementioned self-storing energy-saving curing system for large-volume concrete in low-temperature environments, comprising:

[0042] When the temperature difference between the near center and near the surface of the large-volume concrete is detected to be greater than the upper critical value, the central control system controls the air pump to work, giving full play to the insulation capacity of the variable insulation layer, gradually reducing the temperature difference between the inside and outside of the large-volume concrete, and the heat of hydration of the concrete is gradually transferred to the energy storage layer.

[0043] When the temperature difference between the inside and outside of the large-volume concrete is less than the lower critical value, and the surface temperature of the energy storage layer near the variable insulation layer is higher than the first critical temperature value, the central control system's air pump will work, causing the insulation capacity of the variable insulation layer to gradually decrease, and the heat stored in the energy storage layer to gradually diffuse to the external environment.

[0044] When the surface temperature of the energy storage layer near the formwork layer is lower than the second critical temperature value, the central control system controls the air pump to work, and the insulation capacity of the variable insulation layer gradually increases, so that the energy storage layer continues to absorb the heat released by the hydration of concrete.

[0045] The energy storage layer provided by this invention is a composite phase change material with a low phase change temperature, huge heat storage capacity, stable thermophysical and chemical properties, and can be reused multiple times. This energy storage layer is charged by absorbing the heat of hydration of concrete. When the energy storage layer fully undergoes phase change and absorbs a large amount of heat, and the temperature difference between the inside and outside of the concrete is reasonable, the variable insulation layer begins to reduce its insulation capacity, causing the heat from the energy storage layer to gradually dissipate to the outside. When the energy storage layer fully undergoes phase change and releases a large amount of latent heat of phase change, the variable insulation layer begins to increase its insulation capacity, preventing heat loss from the energy storage layer. Throughout the curing process of large-volume concrete, the curing layer maintains a temperature environment conducive to effective strength growth for the concrete structure. The phase change material in the energy storage layer can be flexibly and diversely selected; a suitable phase change material can be chosen based on the large-volume concrete structure being cured. Various organic or inorganic phase change materials with suitable phase change temperatures can be used as phase change materials in the energy storage layer.

[0046] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention can determine the thickness of the energy storage layer in the curing layer according to the average temperature of the local construction site, making the curing process safe and cost-effective, and providing guidance for the curing of large-volume concrete in on-site construction.

[0047] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention can effectively reduce the temperature difference between the inside and outside of large-volume concrete, prevent cracking caused by excessive temperature difference inside the large-volume concrete, and greatly reduce safety hazards.

[0048] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention can achieve stable cooling of concrete, rapidly reduce the temperature difference between concrete and the external environment, shorten demolding time, and improve the turnover efficiency of formwork.

[0049] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention eliminates the need for an external heat source during the curing process. The entire curing process is safe and free from fire risks, and it saves a significant amount of materials and energy costs, which is beneficial for energy conservation, reducing carbon emissions, and environmental friendliness.

[0050] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention requires no human supervision during the curing process. The curing layer can ensure that the large-volume concrete structure is always within a reasonable temperature range throughout the entire curing process. It can ensure that the temperature difference between the inside and outside of the large-volume concrete does not become too large, while also ensuring that the entire large-volume concrete structure is always in a temperature environment for rapid strength development, thus ensuring construction quality and reducing labor costs.

[0051] The self-storage curing system for large-volume concrete in low-temperature environments provided by this invention has a wide range of applications and can be used for winter construction of large-volume concrete in most cold regions of my country.

[0052] In summary, the present invention provides a self-storing curing layer and temperature control method for large-volume concrete in low-temperature environments, which is suitable for winter construction of large-volume concrete in cold regions. It enables the overall temperature and strength of the large-volume concrete structure to develop uniformly, avoids frost damage to the concrete structure, and ensures that the heat accumulated inside the large-volume concrete structure can be stably transported outward. This not only shortens the curing cycle and speeds up the construction progress, but also helps to improve the construction quality and enhance the stability of the construction quality.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] This invention controls the inflation and deflation of the variable insulation unit through a central control system, enabling the energy storage layer to efficiently absorb the heat of hydration of large-volume concrete while maintaining insulation. It can also release the heat to the outside in a timely manner after the energy storage layer has absorbed sufficient heat of hydration, and then re-insulate when the energy storage layer regains its heat absorption capacity. In the repeated heat absorption and release process, the temperature difference between the surface and the interior of the large-volume concrete is always kept within a small range.

[0055] Compared with existing technologies, this invention can achieve the heat of hydration of large-volume concrete by using only a variable insulation unit and an energy storage layer. At the same time, the surface and internal temperatures are relatively uniform, and the energy consumption, labor and materials are all reduced, while saving the curing cycle. Attached Figure Description

[0056] Figure 1 A schematic diagram of a self-storing energy storage curing system for large-volume concrete in low-temperature environments is provided as a specific embodiment of the present invention.

[0057] Figure 2A flowchart of a self-storage maintenance temperature control method provided in a specific embodiment of the present invention;

[0058] Figure 3 This is a graph showing the curing temperature versus curing time in Embodiment 2 of the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0060] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0061] This invention provides a self-storing energy storage curing system and temperature control method for large-volume concrete in low-temperature environments. It controls the transport of the hydration heat of the large-volume concrete itself, optimizes the design of phase change materials according to the actual low-temperature environment of different regions, and achieves uniform temperature control of the large-volume concrete without the need for an external heat source, thus preventing freezing damage and promoting rapid strength development.

[0062] Specific implementation method one: Combining Figures 1 to 3 This implementation method is described below.

[0063] This embodiment is a self-storing energy storage curing system for large-volume concrete in low-temperature environments, including a variable insulation layer 201, an energy storage layer 202, a formwork layer 203, an air pump 101, an air extraction pump 102, a temperature acquisition system, and a central control system. In use, the inner layer of the formwork layer 203 is tightly attached to the concrete, the outer layer of the formwork layer is the energy storage layer 202, and the outer side of the energy storage layer is the variable insulation layer 201. The variable insulation layer, energy storage layer, and formwork layer, arranged from the outside in, constitute the curing layer of the concrete.

[0064] a. The formwork layer is made of wood or steel;

[0065] b. The variable insulation layer is an inflatable / deflatable airbag, which is made of high-pressure polyethylene, rubber, nylon fabric, etc. It has good sealing effect and mechanical properties, stable chemical properties, can withstand high air pressure, and has excellent thermal insulation capabilities, making it suitable for concrete curing. An infrared reflective coating is applied or provided on the surface of the variable insulation layer near the energy storage layer. In this embodiment, the infrared reflective coating uses a layer of aluminum foil to reflect infrared rays and prevent heat from the internal energy storage layer from radiating to the external environment.

[0066] In a specific embodiment of the present invention, the variable insulation layer 201 is connected to an air pump 101 and an air pump 102. The air pump and the air pump are respectively used to inflate and deflate the variable insulation layer to adjust its insulation capacity. Before the concrete is poured, the variable insulation layer is filled with gas, so that the insulation capacity of the variable insulation layer is maximized.

[0067] In a specific embodiment of the present invention, the air duct of the air pump 101 and the air pump 102 are sealed at the contact points with the variable insulation layer to prevent gas leakage from the variable insulation layer.

[0068] In some embodiments, two circular openings are cut at two points on the side of the inflatable airbag, and two ventilation tubes are inserted into the air bubble film through these two openings. The connection between the ventilation tubes and the air bubble film is sealed with epoxy resin, tape or other adhesive material to ensure that no air leakage occurs at the connection.

[0069] c. A phase change material is encapsulated in the energy storage layer 202. The phase change material is preferably an organic phase change material and / or an inorganic hydrated salt phase change material with a low phase change temperature.

[0070] In this embodiment, the preparation process of the phase change material in the energy storage layer 202 is as follows:

[0071] The inorganic hydrated salt phase change material and the shaping functional polymer were mixed at a mass ratio of 0.93:0.07. The mixing sequence was as follows: first, the inorganic hydrated salt phase change material was heated and fully melted into a liquid state. Then, the inorganic hydrated salt phase change material was heated and stirred at high speed using a paddle electric stirrer. During the stirring process, the shaping functional polymer was slowly added to the solution. After the polymer was completely added, the mixture was heated and stirred at high speed until it became a uniformly colored gel-like mixture. Then, the heating and stirring were stopped.

[0072] d. The temperature acquisition system includes a multi-channel temperature acquisition unit 300 and at least four temperature sensors; the multi-channel temperature acquisition unit 300 is used to acquire temperature through the temperature sensors. The at least four temperature sensors include a first temperature sensor 301, a second temperature sensor 302, a third temperature sensor 303, and a fourth temperature sensor 304; wherein:

[0073] The first temperature sensor 301 is disposed on the surface of the energy storage layer near the variable insulation layer;

[0074] The second temperature sensor 302 is disposed on the surface of the energy storage layer near the template layer;

[0075] The third temperature sensor 303 is located near the surface of the concrete close to the formwork layer. The near surface refers to the shallow surface layer of the concrete, and its distance from the outer surface of the concrete is 2~10cm.

[0076] The fourth temperature sensor 304 is located near the center of the concrete. Near the center means the location is close to the geometric center of the concrete space, which is 10~20cm away from the geometric center of the concrete.

[0077] Preferably, the third and fourth temperature sensors are installed on the reinforcing bars, which is beneficial to improving the timeliness of temperature data acquisition due to the excellent heat transfer performance of the reinforcing bars.

[0078] e. The central control system is used to receive data from the multi-channel temperature acquisition instrument and control the operation of the air pump and the air extraction pump.

[0079] The working process of the self-storing energy storage curing system for large-volume concrete in low-temperature environments described in this embodiment is as follows:

[0080] During the concrete curing process, the central control system receives signals from the temperature sensor in real time.

[0081] When the temperature near the center of the large-volume concrete is too high and the temperature near the surface is too low, that is, when the temperature difference between the near center and the near surface of the large-volume concrete is greater than the upper critical value of the temperature difference, the central control system controls the air pump to work, so that the insulation capacity of the variable insulation layer can be fully utilized, the external low temperature environment is isolated, and the temperature difference between the inside and outside of the large-volume concrete is gradually reduced, and the heat of hydration of the concrete is gradually transferred to the energy storage layer.

[0082] When the temperature difference between the inside and outside of the large-volume concrete is less than the lower critical value, and the surface temperature of the energy storage layer near the variable insulation layer is higher than the first critical temperature value, the central control system's air pump will work, causing the insulation capacity of the variable insulation layer to gradually decrease, and the heat stored in the energy storage layer to gradually diffuse to the external environment.

[0083] When the surface temperature of the energy storage layer near the template layer is lower than the second critical temperature value, the central control system controls the air pump to work, and the insulation capacity of the variable insulation layer gradually increases until it reaches its full potential, so that the energy storage layer can continue to absorb the heat released by the hydration of concrete.

[0084] Repeat the above steps.

[0085] Because the phase change process of the phase change material in the energy storage layer is approximately isothermal, it can continuously provide a high-temperature insulation environment for the large-volume concrete to prevent it from freezing during curing. At the same time, it can intermittently, in large quantities, and efficiently transfer the heat accumulated inside the concrete to the outside, ensuring that the temperature difference between the inside and outside of the large-volume concrete is not too large during curing. This avoids the problem of unstable construction quality caused by uneven overall strength development of the large-volume concrete, thus ensuring rapid strength development of the large-volume concrete and achieving a stable temperature drop. It also quickly reduces the temperature difference between the concrete surface and the external environment, thereby achieving the dual purpose of ensuring the construction quality of the large-volume concrete and rapid demolding.

[0086] The critical temperature difference between the interior and exterior of the large-volume concrete provided by this invention is 20~30℃, that is, the upper critical temperature difference between the center and surface of the concrete is 30℃, and the lower critical temperature difference is 20℃; the first critical temperature of the energy storage layer is the phase change temperature T of the phase change material in the energy storage layer. m,pcm +2℃, the second critical temperature of the energy storage layer is the phase transition temperature T of the phase change material in the energy storage layer. m,pcm -2℃.

[0087] Specific Implementation Method Two: Combining Figure 2 This implementation method is described below.

[0088] This embodiment describes a temperature control method for self-storing curing of large-volume concrete in low-temperature environments, including the following steps:

[0089] Step 1: Initialize the central control system.

[0090] Step 2: The central control system collects the temperature at the energy storage surface near the template layer and the surface of the energy storage layer near the variable insulation layer, as well as the temperature difference between the surface and the center of the large-volume concrete structure.

[0091] Step 3: The central control system compares the temperature difference between the near surface and near center of the large-volume concrete structure with the critical temperature difference value, and the surface temperature of the energy storage layer near the variable insulation layer with the first critical temperature value. If the temperature difference is lower than the lower critical temperature difference value, and the surface temperature of the energy storage layer near the variable insulation layer is higher than the first critical temperature value, then proceed to step 4; otherwise, return to step 2.

[0092] Step 4: The central control system controls the air pump to work, while controlling the air pump to stop working.

[0093] Step 5: The central control system compares the surface temperature of the energy storage layer near the template layer with the second critical temperature value. If the surface temperature of the energy storage layer near the template layer is lower than the second critical temperature value, proceed to step 5. If the surface temperature of the energy storage layer near the template layer is higher than the second critical temperature value, return to step 4.

[0094] Step Six: The central control system controls the air pump to work and controls the air pump to stop working, then returns to Step Two.

[0095] In practice, the temperature control method for self-storage curing of large-volume concrete in low-temperature environments realizes the working process of a self-storage curing system for large-volume concrete in low-temperature environments.

[0096] The critical temperature difference between the interior and exterior of the large-volume concrete is 20-30℃, and the first critical temperature of the energy storage layer is the phase change temperature T of the phase change material in the energy storage layer. m,pcm +2℃, the second critical temperature of the energy storage layer is the phase transition temperature T of the phase change material in the energy storage layer. m,pcm -2℃.

[0097] The phase transition temperature of the phase change material in the energy storage layer needs to be determined by testing the thermal and physical properties of the prepared energy storage layer. The phase transition temperature, specific heat capacity, and density of the energy storage layer are obtained through the tests. Specific implementation method three:

[0099] This embodiment describes a method for designing the thickness of an energy storage layer.

[0100] The air extraction pump extracts air from the variable insulation layer. As the air in the variable insulation layer is gradually extracted, the insulation capacity gradually decreases until the air in the variable insulation layer is completely expelled. At this point, the insulation capacity of the variable insulation layer will almost fail, and the heat stored in the energy storage layer will begin to dissipate rapidly to the external environment. The temperature of the energy storage layer should always be kept above the minimum tolerable temperature of the concrete or equipment. Before the curing layer is used, the thickness of the energy storage layer needs to be designed to ensure that the central control system of the curing layer will not fail and to guarantee the construction quality of the concrete.

[0101] The energy storage layer thickness design method described in this embodiment includes the following steps:

[0102] Based on the law of conservation of energy, the energy storage layer and the variable insulation layer are considered as a whole. During the process of the variable insulation layer recovering its insulation capacity until it reaches its maximum capacity, the sensible heat absorbed by the energy storage layer and the variable insulation layer is dissipated to the external environment through heat transfer and radiation. The equation for the total sensible heat dissipated by the energy storage layer and the variable insulation layer during the heat dissipation process is as follows:

[0103]

[0104] in, It is the total sensible heat lost by the energy storage layer and the variable insulation layer. It is the sensible heat lost by the energy storage layer. It is the sensible heat lost by the variable insulation layer.

[0105] Based on the lowest average temperature at the construction site that month Specific heat capacity of energy storage layer ,density Cross-sectional area A, phase transition temperature The time it takes for the air pump to completely fill the insulation layer. The above formula can be further derived as follows:

[0106]

[0107] in, This is the lowest tolerable temperature for concrete or equipment, typically taken as 5°C; C1, A1, b1 and These are the specific heat capacity, density, and coverage area of ​​the energy storage layer. Figure 1 The area in the horizontal direction), thickness, and second critical temperature value, i.e. -2℃; C2, ρ2, A2, and b(t) are the specific heat capacity, density, coverage area, and thickness of the variable insulation layer as a function of time, respectively; the coverage area of ​​the energy storage layer is equal to that of the variable insulation layer, and A1 = A2 = A; For the external heat dissipation efficiency of the energy storage layer, To improve the external heat dissipation efficiency of the insulation layer.

[0108] The external heat dissipation efficiency can be further elaborated, and the above formula can be expressed as:

[0109]

[0110] R1 is the temperature of the variable insulation layer, R2 is the thermal resistance of the energy storage layer, and R(T) is the thermal resistance function of the variable insulation layer over time. During the process of the air pump inflating the variable insulation layer, air at the same temperature as the ambient temperature is continuously injected into the layer. Therefore, the temperature of the variable insulation layer during this process can be considered approximately equal to the ambient temperature. Since the bubble wrap material in the variable insulation layer is too thin, the sensible heat it stores is negligible, and the following relationship can be obtained:

[0111] =0, =0

[0112] The above relation can then be further simplified as follows:

[0113]

[0114] R1 can be further expanded as follows:

[0115]

[0116] Where λ is the thermal conductivity of the energy storage layer, therefore, the above relationship can be further expanded as follows:

[0117]

[0118] This formula allows for a rough calculation of the minimum temperature that the energy storage layer must withstand to ensure it is not lower than that of the concrete or equipment. Furthermore, specifically, this inequality can be expressed as:

[0119]

[0120] This formula can be used to obtain the minimum design value of the energy storage layer thickness under different construction climate conditions.

[0121] As demonstrated by sample testing, this invention is suitable for curing large-volume concrete in low-temperature environments. The following embodiments are described in conjunction with the aforementioned advantages of this invention:

[0122] Example 1: In cold regions, the average minimum temperature in December is -11℃. A eutectic hydrated salt was selected as the phase change material, and a shaped functional polymer was used as the supporting material to encapsulate the phase change material. The resulting composite phase change material had a phase change temperature of 25℃, a latent heat of phase change of 196.7 J / g, a thermal conductivity of 0.3163 J / g·m·K for the energy storage layer, and a cross-sectional area of ​​2*2m² for both the insulation layer and the energy storage layer. 2 Substitute into the formula:

[0123]

[0124] Therefore, in this region with its low temperature environment, a thinner energy storage layer can ensure that the curing temperature provided by the curing layer to the concrete during the curing process is always higher than the lowest temperature that the concrete can tolerate.

[0125] Example 2: Following the calculation process and temperature conditions of Example 1, with a storage layer thickness of 2.6 cm, the structure with dimensions of 2*2*2m was designed. 3 The large-volume concrete was cured using the curing layer and temperature control method described in this invention. A comparison was made with the commonly used heated enclosure method for large-volume concrete in low-temperature environments, where the heated enclosure method provides a temperature atmosphere of 10°C for the concrete structure. Figure 3 As shown in the test results, the use of the curing layer described in this invention for curing concrete structures, compared with the traditional heated shed curing method, ensures that the temperature difference between the inside and outside of the concrete remains small, and the curing temperature provided by the curing layer to the concrete is always maintained above the effective temperature for concrete strength development. At the same time, the internal temperature of the concrete drops rapidly and stably, enabling rapid demolding, improving construction efficiency, and ensuring construction quality.

[0126] This invention may have other embodiments. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A mass concrete self-energizing curing system for cryogenic environments, characterized in that, include: A variable insulation unit is used to achieve insulation and heat release through inflation and deflation. An energy storage layer, located on the lower surface of the variable insulation unit, is used to absorb, store, and release the heat of hydration of large-volume concrete through the phase change of the phase change material inside the energy storage layer. A template layer is located between the energy storage layer and the large-volume concrete. The temperature acquisition system is used to detect the temperature of the upper and lower surfaces of the energy storage layer, as well as the surface and interior of the large-volume concrete. The central control system is connected to the temperature acquisition system and the variable insulation unit. When the temperature difference between the surface and the interior of the large-volume concrete exceeds the set temperature threshold, the variable insulation unit is controlled to inflate to achieve insulation, allowing the hydration heat of the large-volume concrete to be transferred to the energy storage layer. It is also used to release the heat of the energy storage layer to the outside when the energy stored in the energy storage layer is higher than the upper limit. Furthermore, when the energy stored in the energy storage layer is lower than the lower limit, the variable insulation unit is controlled to inflate again to achieve insulation, allowing the energy storage layer to continue absorbing the hydration heat of the large-volume concrete, thereby maintaining the temperature difference between the surface and the interior of the large-volume concrete within the temperature threshold. When the energy stored in the energy storage layer is higher than the upper limit, the temperature of the upper surface of the energy storage layer is higher than the first critical temperature, which is the phase change temperature of the phase change material + 2℃. When the energy release causes the energy in the energy storage layer to fall below the lower limit, the temperature of the lower surface of the energy storage layer is lower than the second critical temperature, which is the phase change temperature of the phase change material -2℃. The set temperature threshold is 20-30℃.

2. A mass concrete self-energizing curing system for cryogenic environments according to claim 1, characterized in that, The variable insulation unit includes an air pump, an air extraction pump, and a variable insulation layer; The air pump is connected to the variable insulation layer through a vent pipe and is also connected to the central control system. The air pump is used to inflate the variable insulation layer with air based on the instructions of the central control system when the temperature difference between the surface and the interior of the large-volume concrete is greater than the set temperature critical value or when the stored energy in the energy storage layer is lower than the lower limit, so that the variable insulation layer can achieve the insulation function. The air pump is connected to the variable insulation layer via a vent pipe and to the central control system. When the energy stored in the energy storage layer exceeds the upper limit, the air pump is used to extract the gas in the variable insulation layer based on the instructions of the central control system, so that the energy storage layer can release the stored energy to the outside.

3. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 2, characterized in that, The variable insulation layer is an inflatable airbag, and an infrared reflective coating is applied or provided on the side of the variable insulation layer near the energy storage layer.

4. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 3, characterized in that, The material of the inflatable airbag is polyethylene, rubber, or nylon fabric.

5. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 1, characterized in that, The energy storage layer is obtained by mixing a shaped functional polymer and a phase change material, wherein the phase change material is an organic phase change material and / or an inorganic hydrated salt phase change material.

6. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 1, characterized in that, The template layer is a wooden template or a steel template.

7. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 1, characterized in that, The temperature acquisition system includes a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, and a multi-channel temperature acquisition instrument; The first temperature sensor is located on the upper surface of the energy storage layer and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the upper surface of the energy storage layer to the multi-channel temperature acquisition instrument. The second temperature sensor is located on the lower surface of the energy storage layer and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the lower surface of the energy storage layer to the multi-channel temperature acquisition instrument. The third temperature sensor is located in the shallow layer of the large-volume concrete and is connected to a multi-channel temperature acquisition instrument to transmit the detected temperature of the large-volume concrete surface to the multi-channel temperature acquisition instrument. The fourth temperature sensor is located inside the large-volume concrete and is connected to a multi-channel temperature acquisition instrument to transmit the detected internal temperature of the large-volume concrete to the multi-channel temperature acquisition instrument. The multi-channel temperature acquisition instrument is connected to the central control system and is used to send the temperature of the upper and lower surfaces of the energy storage layer, as well as the surface and interior of the large-volume concrete, to the central control system.

8. The self-storing energy storage curing system for large-volume concrete in low-temperature environments according to claim 1, characterized in that, The dimensions of the large-volume concrete are between 1m×1m×1m and 10m×10m×10m.

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