Ultra-high performance concrete member based on gradient phase change material layering and preparation method thereof

Abstract

The invention belongs to the field of ultra-high performance concrete temperature control, and particularly relates to an ultra-high performance concrete member based on gradient phase change material layering and a preparation method of the ultra-high performance concrete member. The ultra-high performance concrete member comprises an ultra-high performance concrete base body and at least three functional layers. The functional layers are sequentially arranged in the ultra-high performance concrete base body in the thickness direction of the ultra-high performance concrete member. Each functional layer contains a microencapsulated phase change material, and the phase change temperatures of the microencapsulated phase change materials in each functional layer are sequentially reduced in the thickness direction of the ultra-high performance concrete member. The at least three functional layers with different phase transition temperatures are arranged in the thickness direction in a gradient manner, so that accurate matching with the spatial and temporal distribution of the hydration heat of the ultra-high performance concrete is realized. The internal and external temperature difference of the component can be remarkably reduced, the occurrence time of a temperature peak value is delayed, early-stage temperature cracks are effectively inhibited, and the integrality and durability of the component are improved.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete temperature control technology, specifically to an ultra-high performance concrete component based on gradient phase change material stratification and its preparation method. Background Technology

[0002] Ultra-High Performance Concrete (UHPC), with its extremely high strength, excellent durability, and dense microstructure, is increasingly widely used in long-span bridges, nuclear power plant containment structures, marine engineering, and facilities requiring ultra-long service lives. However, the high amount of cementitious materials and low water-cement ratio of UHPC lead to intense and concentrated hydration reactions, resulting in a large release of hydration heat in the early stages. In large-volume or thick-section components, due to the low thermal conductivity of concrete, internal heat is difficult to dissipate effectively, causing the core area of ​​the structure to heat up rapidly after pouring, forming a significant hydration heat peak. Meanwhile, the surface layer of concrete is affected by ambient temperature, wind speed, and formwork heat dissipation, resulting in a smaller temperature rise and a faster cooling rate. The resulting internal and external temperature difference can easily exceed the limits specified in the code, easily inducing significant temperature gradient stress. When this stress exceeds the early tensile strength of the concrete, non-structural temperature cracks will appear inside or on the surface of the structure, not only damaging the appearance but also becoming channels for chloride ions, moisture, and corrosive media to penetrate, severely weakening the long-term durability and service life of the structure.

[0003] To control such temperature cracks, existing technologies often employ traditional temperature control measures such as pre-embedded cooling water pipes, the addition of mineral admixtures, or surface insulation. While pre-embedded cooling water pipes can actively remove internal heat, their construction process is complex, requiring precise pipe placement, water flow testing, and subsequent sealing, posing risks of pipe blockage, leakage, and impact on the overall integrity of the concrete. Mineral admixtures, such as fly ash and slag, can, to some extent, slow down the hydration rate and reduce total heat release, but often at the expense of the crucial early strength development of ultra-high performance concrete, hindering rapid demolding and optimized construction schedules. Surface insulation technology only slows down the surface heat dissipation rate and has no substantial effect on the peak high-temperature levels in the core area.

[0004] In recent years, phase change materials (PCMs) have been explored for inclusion in ultra-high performance concrete (UHVPCs) to improve their temperature control performance due to their latent heat storage properties. Current technologies typically involve uniformly incorporating microencapsulated PCMs into the overall UHVPC mixture to achieve uniform distribution. However, practical engineering applications have shown that this homogeneous incorporation method has failed to effectively achieve the expected temperature control effect in UHVPCs, generally exhibiting problems such as unstable temperature control and limited ability to suppress internal and external temperature differences, making it difficult to meet the stringent requirements for temperature crack control in large-volume UHVPC components.

[0005] Therefore, it is necessary to improve the temperature control performance of ultra-high performance concrete to effectively suppress temperature cracks in large-volume ultra-high performance concrete components. Summary of the Invention

[0006] (a) Technical problems to be solved To address the problems of unstable temperature control and limited ability to suppress internal and external temperature differences when uniformly incorporating phase change materials into ultra-high performance concrete in existing technologies, this invention provides an ultra-high performance concrete component based on gradient phase change material stratification and its preparation method.

[0007] (II) Technical Solution To achieve the above objectives, the main technical solutions adopted by the present invention include: An ultra-high performance concrete component based on gradient phase change material layering includes an ultra-high performance concrete matrix and at least three functional layers. The at least three functional layers are sequentially disposed in the ultra-high performance concrete matrix along the thickness direction of the ultra-high performance concrete component. Each functional layer contains microencapsulated phase change materials; Along the thickness direction of the ultra-high performance concrete component, the phase transition temperature of the microencapsulated phase change material in each functional layer decreases sequentially.

[0008] The ultra-high performance concrete component based on gradient phase change material layering as described above is preferably provided with three functional layers in the ultra-high performance concrete matrix, and the three functional layers are provided in the ultra-high performance concrete matrix in the form of precast thin plates.

[0009] In the ultra-high performance concrete component based on gradient phase change material layering as described above, preferably, the phase change temperatures of the microencapsulated phase change materials in the three functional layers are 50-70℃, 40-50℃, and 30-40℃, respectively.

[0010] As described above, in the ultra-high performance concrete component based on gradient phase change material stratification, preferably, the phase change temperature of the microencapsulated phase change material with the highest phase change temperature is 5-10℃ higher than the hydration environment temperature, and the phase change temperature of the microencapsulated phase change material with the lowest phase change temperature is 3-5℃ lower than the hydration environment temperature.

[0011] In the ultra-high performance concrete component based on gradient phase change material layering as described above, preferably, an ultra-high performance concrete transition layer with a thickness of 2-5 mm is also provided between adjacent functional layers.

[0012] The ultra-high performance concrete component based on gradient phase change material stratification as described above, preferably, has a particle size of 20-50 μm for the microencapsulated phase change material, and the microencapsulated phase change material includes a core material and a shell covering the surface of the core material. The core material is a paraffin-based phase change material, a fatty acid-based phase change material, or a eutectic salt-based phase change material, and the shell is an inorganic ceramic material.

[0013] As described above, the ultra-high performance concrete component based on gradient phase change material stratification preferably has a precast thin plate thickness of 10-30 mm. The raw materials for preparing the precast thin plate include ultra-high performance concrete and microencapsulated phase change material, with the amount of microencapsulated phase change material being 15-25% of the cement mass.

[0014] The present invention also provides a method for preparing the above-mentioned ultra-high performance concrete component, comprising the following steps: S1: Based on the hydration heat history of ultra-high performance concrete components, determine the number of functional layers in the components, the phase transition temperature of the microencapsulated phase change material in each functional layer, and the arrangement order of each functional layer. S2: Based on the phase transition temperature of the microencapsulated phase change material of each functional layer determined in step S1, prepare corresponding prefabricated thin plates doped with microencapsulated phase change materials. S3: Set up formwork according to the dimensions of the component, pour ultra-high performance concrete to form the base layer; S4: Before the initial setting of the base concrete, its surface is treated with interface treatment, then the first layer of precast thin plate is laid, and ultra-high performance concrete is poured on top of the precast thin plate to form a transition layer, and the transition layer is vibrated and compacted. S5: Repeat the process of interface treatment, laying precast thin slabs, pouring and vibrating the transition layer in step S4 until all precast thin slabs are laid and the corresponding transition layer is poured. S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components; S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

[0015] In the preparation method described above, preferably, in steps S4 and S5, interface treatment is performed by roughening the surface and spraying an interface adhesive.

[0016] (III) Beneficial Effects This invention constructs a gradient thermal response structure that highly matches the spatiotemporal distribution of hydration heat by sequentially setting at least three functional layers along the thickness direction in ultra-high performance concrete components, with the phase change temperature of the microencapsulated phase change materials contained in each functional layer decreasing sequentially from the inside to the outside along this direction. This arrangement breaks through the traditional technical path of homogeneous incorporation of phase change materials, no longer randomly dispersing the phase change materials throughout the matrix. Instead, based on the actual heat accumulation and dissipation laws inside the large-volume ultra-high performance concrete component, a high phase change temperature functional layer is configured in the inner region where the temperature peak is most significant to efficiently absorb early concentrated heat release; a medium-temperature functional layer is configured in the middle region where the temperature gradient changes drastically to slow down the heat transfer rate; and a low phase change temperature functional layer is configured in the outer region near the surface where heat dissipation is rapid to compensate for the shrinkage stress caused by the rapid cooling of the surface layer. Thus, the functional layers form a synergistic thermal buffer system in space, allowing the heat inside the component to be stored and released in stages and rhythmically, significantly reducing the instantaneous temperature difference and temperature gradient between the core area and the surface layer.

[0017] The gradient layered structure of this invention achieves precise coupling between phase change behavior and the hydration heat evolution process. This not only improves the response efficiency of phase change materials to critical temperature rise periods but also avoids the resource waste caused by premature melting and failure of low-phase-change-temperature phase change materials in the high-temperature core region or the long-term failure of high-phase-change-temperature phase change materials to trigger at the low-temperature surface. The structure of this invention can effectively reduce the peak internal and external temperature difference of large-volume ultra-high-performance concrete components, significantly delay the occurrence of temperature peaks, and greatly suppress the generation and development of early temperature cracks. Thus, without sacrificing early strength, increasing construction complexity, or relying on external energy intervention, it effectively improves the crack resistance and long-term durability of ultra-high-performance concrete components, providing a feasible, effective, and widely applicable new technological path for solving the temperature control problem of large-volume ultra-high-performance concrete. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the ultra-high performance concrete component based on gradient phase change material layering in this invention; Figure 2 This is a process diagram for the preparation of ultra-high performance concrete components in this invention. Detailed Implementation

[0019] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1As shown, this invention provides an ultra-high performance concrete component based on gradient phase change material layering, comprising an ultra-high performance concrete matrix and at least three functional layers. The at least three functional layers are sequentially disposed within the ultra-high performance concrete matrix along the thickness direction of the ultra-high performance concrete component, and each functional layer contains microencapsulated phase change material. Along the thickness direction of the ultra-high performance concrete component, the phase change temperature of the microencapsulated phase change material in each functional layer decreases sequentially.

[0021] This invention abandons the traditional approach of homogeneously incorporating phase change materials (PCMs) into concrete. Instead, based on the temperature field distribution characteristics of large-volume UHPC components during hydration—higher inside and lower outside—microencapsulated PCMs with different phase change temperatures are arranged in a gradient and structured manner along the thickness of the component as functional layers. This design allows the latent heat storage capacity of the PCMs to be precisely matched spatially and temporally with the release process of cement hydration heat, thereby efficiently and actively regulating the internal temperature of the component and suppressing thermal stress and crack formation.

[0022] Preferably, the present invention provides three functional layers in an ultra-high performance concrete matrix, and the three functional layers are provided in the ultra-high performance concrete matrix in the form of precast thin plates.

[0023] Preferably, the phase transition temperatures of the microencapsulated phase change materials in the three functional layers are 50-70℃, 40-50℃, and 30-40℃, respectively. This gradient design directly corresponds to the hydration heat history of UHPC: the early temperature peak in the core region is high, requiring a high-temperature phase change layer to undergo a phase transition within this range, absorbing a large amount of heat to suppress the peak. The temperature in the intermediate transition region is approximately 40-50℃, regulated by the intermediate-temperature layer. The surface temperature is easily affected by environmental fluctuations, and is buffered by the low-temperature layer.

[0024] More preferably, the microencapsulated phase change material with the highest phase change temperature has a phase change temperature 5-10°C higher than its hydration environment temperature. This ensures that it only begins to melt and absorb heat during the most intense heat accumulation phase, fully absorbing peak energy while avoiding premature phase change and exhaustion of latent heat. The microencapsulated phase change material with the lowest phase change temperature has a phase change temperature 3-5°C lower than its hydration environment temperature, allowing it to solidify and release heat promptly when the concrete surface begins to cool and shrink, effectively compensating for the tensile stress caused by temperature drop and suppressing early surface cracks. This invention, through a gradient reservation slightly higher than the peak value and slightly lower than the environment temperature, enables each functional layer to trigger phase change at its appropriate time in its respective position, significantly improving the utilization efficiency and temperature control stability of the PCM.

[0025] Further preferably, to improve the mechanical properties of the functional layers and their synergistic crack resistance with temperature control, steel fibers and / or PVA fibers can be incorporated into the precast thin plates of each functional layer. The preferred fiber volume fraction is 0.5-2.0%, the length can be 6-18 mm, and the aspect ratio is 50-100.

[0026] Microcapsule PCM is responsible for absorbing / releasing latent heat to alleviate temperature stress, while fibers bridge microcracks, transfer loads and dissipate fracture energy during thermal expansion and contraction. The two generate a stress coupling effect at the microscopic interface. Fibers constrain the melting expansion of PCM, and PCM buffers the thermal mismatch strain of fibers, which significantly improves the cracking energy of the functional layer itself, the initial crack strength of the component and the residual flexural strength, truly achieving the integrated design goal of temperature control for crack resistance and energy storage for toughening.

[0027] In this invention, each functional layer is preferably implemented in the form of a UHPC-PCM prefabricated thin plate, and its preparation method is as follows: 1. Material Proportioning: The UHPC matrix of the thin slab adopts the same proportion as the main component to ensure consistency of material properties. The dosage of microencapsulated PCM is controlled at 15-25% of the cement mass. This dosage range has been optimized to ensure significant temperature control without excessively affecting the mechanical properties and rheological properties of UHPC. The selected microcapsule particle size is 20-50μm, matching the particle size of fine aggregate in UHPC, allowing for uniform dispersion and avoiding local stress concentration. The microencapsulated phase change material in this invention includes a core material and a shell covering the surface of the core material. The core material can be a paraffin-based phase change material, a fatty acid-based phase change material, or a eutectic salt-based phase change material. The shell can be an inorganic ceramic material such as SiO2. The ceramic shell not only has good thermal stability and sealing properties but can also undergo a pozzolanic reaction with the silica fume in UHPC, thereby significantly enhancing the interfacial bonding force between the microcapsules and the concrete matrix and improving the overall durability of the thin slab.

[0028] 2. Thin Plate Manufacturing: First, premix the microcapsule PCM and UHPC dry mix for 30 seconds, then add the polycarboxylate superplasticizer in portions and stir at low speed for 2 minutes each time. Pour the mixture into a mold and vibrate to form the plate. Cover the surface with a film for curing to prevent moisture evaporation. Demold after 24 hours, then steam-cur at 90℃ for 48 hours to fully activate the strength of the UHPC. Finally, the surface of the precast thin plate can be sandblasted to create a certain roughness, enhancing the mechanical interlocking and bonding strength between the thin plate and the transition layer during subsequent construction. The thickness of the finished precast thin plate is 10-30 mm. If fiber composite thin plates are to be prepared, the selected type and dosage of fiber are premixed with the microcapsule PCM and UHPC dry mix during the dry mixing stage to ensure uniform fiber dispersion.

[0029] Between adjacent precast thin slabs, a 2-5 mm thick ultra-high performance concrete transition layer is provided. This transition layer is composed of UHPC without phase change materials. Its key functions are: first, as a bonding medium, ensuring a firm bond between the upper and lower precast thin slabs and achieving effective stress transfer; second, its extremely thin thickness design minimizes interference with the continuity of the overall temperature field; and third, preferably, the UHPC used in this transition layer has a higher fluidity than the matrix material of the precast thin slabs and the ultra-high performance concrete matrix of the entire component. This higher fluidity ensures that it can fully penetrate and encapsulate the rough surface of the precast thin slabs during casting, filling all micropores and providing a material basis for forming a dense, defect-free interface.

[0030] like Figure 2 As shown, the present invention also provides a method for preparing the above-mentioned ultra-high performance concrete component, comprising the following steps: S1: Before construction, a detailed thermodynamic simulation and hydration heat time history analysis are conducted on the target component. Calculations predict the temperature distribution curves along the thickness direction of the component at different time points after casting. Based on this analysis, the required number of functional layers, the phase transition temperature thresholds of each PCM layer (e.g., 50-70℃, 40-50℃, and 30-40℃ for three layers), and the specific arrangement sequence of each layer along the component's thickness direction are determined.

[0031] S2: Based on the different phase transition temperature requirements determined in step S1, prepare UHPC-PCM precast thin plates of corresponding specifications in batches, and classify and store them according to temperature gradients, such as high temperature, medium temperature, and low temperature, for later use. At the same time, prepare auxiliary materials: UHPC slurry with higher fluidity for casting the transition layer, and temperature sensors.

[0032] S3: Set up formwork according to the component dimensions, and then pour ordinary UHPC to form the base / bottom structure of the component. Use this base as the starting bearing surface of the entire gradient temperature control system.

[0033] S4: ① Interface treatment: Before the initial setting of the poured lower layer of concrete (initially the base layer, subsequently the transition layer of the previous cycle), roughen its surface and immediately and evenly spray epoxy-based interface adhesive. The application rate of epoxy-based interface adhesive is 0.2-0.3 kg / m². 2 Roughening the surface increases the surface area and provides mechanical interlocking points, while the interfacial adhesive can significantly enhance the chemical bond between new and old concrete, preventing interlayer debonding.

[0034] ② Laying functional thin slabs: Using a laser positioning system for guidance, the precast thin slabs corresponding to the current layer are hoisted and laid. During laying, attention should be paid to ensuring that the joints of adjacent thin slabs are staggered by a distance of ≥100mm to optimize stress distribution and avoid through joints.

[0035] ③ Embedded Sensors: As a preferred option, temperature sensors can be pre-embedded in the area where the functional layer is located during or after the laying of the thin slabs. The area where the high-temperature precast thin slabs are located is the core area, the area where the medium-temperature precast thin slabs are located is the middle area, and the area where the low-temperature precast thin slabs are located is the surface area. Two to three temperature sensors can be arranged in each of the core area, middle area, and surface area, with a spacing of about 500mm between the sensors. This is used to monitor the temperature gradient inside the components in real time during construction and curing, and to verify the temperature control effect.

[0036] ④ Pouring and Vibrating the Transition Layer: Immediately after each layer of precast thin slabs is laid in place, pour a 2-5mm thick layer of highly fluid UHPC transition layer grout on top. Then, use a high-frequency vibrator to thoroughly vibrate the transition layer for 30-60 seconds. The purpose of high-frequency vibration is to eliminate air bubbles in the grout, ensuring it completely and densely fills all uneven areas on the surface of the thin slab, achieving a tight bond between the thin slab and the transition layer.

[0037] Repeat the above cycle, laying each layer of precast thin slabs in the predetermined temperature gradient order, such as first the high-temperature layer, then the medium-temperature layer, and finally the low-temperature layer, and completing the construction of the corresponding transition layer, until all functional layers are laid.

[0038] S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components.

[0039] S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

[0040] Through the above-described structure and process, the present invention achieves the following significant effects: 1. The gradient phase change layer enables zoned management of the hydration thermal field, allowing phase change materials to operate within their most effective temperature ranges. This avoids energy waste and response lag during uniform mixing, significantly improving temperature control efficiency.

[0041] 2. By absorbing and releasing heat in layers, the temperature peaks and valleys inside the component are effectively leveled out, and the temperature difference between the core and the surface is controlled within a safe range, fundamentally reducing the risk of temperature cracks.

[0042] 3. The process of combining precast thin slabs with a high-flowability transition layer and high-frequency vibration ensures excellent bonding performance at the interlayer interface, enabling the gradient functional structure to form a solid whole with the UHPC matrix without affecting the final mechanical properties of the component.

[0043] 4. Prefabricated and modular construction methods improve engineering accuracy and efficiency; the embedded temperature sensors make the temperature control effect quantifiable and verifiable, realizing closed-loop control of construction quality.

[0044] This invention uses pre-embedded temperature sensors to monitor the evolution of the internal temperature field of the component in real time, and can dynamically optimize the activation sequence and spatial arrangement of each PCM functional layer accordingly. This enables the gradient phase change structure to actively adapt to complex working conditions such as sudden environmental changes, pouring temperature differences, and strong wind heat dissipation, thereby improving the flexibility and adaptability of temperature control response.

[0045] Furthermore, this invention can further link the temperature sensor network with external temperature control equipment to build an intelligent temperature control system that works in conjunction with PCM passive temperature regulation and external active control, forming complementary responses in key periods and key areas, and significantly enhancing the overall temperature control effect and reliability.

[0046] To further clarify the present invention and its technological advancements, the following description is provided in conjunction with specific embodiments and technical effects.

[0047] Example 1 This embodiment provides an ultra-high performance concrete component based on gradient phase change material layering, comprising an ultra-high performance concrete matrix and three functional layers. The three functional layers are arranged in precast thin slabs within the ultra-high performance concrete matrix. Along the thickness direction of the ultra-high performance concrete component, the phase change temperatures of the microencapsulated phase change materials in the three functional layers are 60℃, 45℃, and 35℃, respectively. The phase change temperature of the microencapsulated phase change material with the highest phase change temperature is 7℃ higher than its hydration environment temperature, while the phase change temperature of the microencapsulated phase change material with the lowest phase change temperature is 4℃ lower than its hydration environment temperature. A 4mm thick ultra-high performance concrete transition layer is provided between adjacent precast thin slabs.

[0048] The preparation method of the ultra-high performance concrete component in this embodiment is as follows: S1: Perform detailed thermodynamic simulation and hydration heat time history analysis on the target component to determine the required 3 functional layers, the phase change temperature threshold of each PCM layer, and the specific arrangement order of each layer in the component thickness direction.

[0049] S2: Based on the different phase change temperature requirements determined in step S1, UHPC-PCM precast thin slabs of corresponding specifications are prepared in batches. The specific preparation method is as follows: The UHPC matrix of the thin slab adopts the same proportion as the main component, and the dosage of microencapsulated PCM is controlled at 20% of the cement mass. The average particle size of the microcapsules is 30μm. The microencapsulated phase change material includes a core material and a shell covering the surface of the core material. The core material is a paraffin-based phase change material, and the shell is SiO2. The microencapsulated PCM and UHPC dry mix are premixed for 30s, and then polycarboxylate superplasticizer is added in batches and stirred at low speed for 2min. The mixture is injected into a mold and vibrated to form the shape, and the surface is covered with a film for curing. After 24h, the slab is demolded, and then cured with high-temperature steam at 90℃ for 48h. Then, the surface of the precast thin slab is sandblasted to obtain a precast thin slab with a thickness of 25mm. At the same time, auxiliary materials are prepared: a more fluid UHPC slurry for casting the transition layer.

[0050] S3: Set up formwork according to the component size, and then pour ordinary UHPC to form the base layer of the component.

[0051] S4: Before the initial setting of the poured lower layer of concrete, roughen its surface and immediately and evenly spray epoxy-based interface adhesive. The application rate of the epoxy-based interface adhesive is 0.25 kg / m². 2 Next, guided by a laser positioning system, the precast thin slabs corresponding to the current layer are hoisted and laid, with the joints of adjacent slabs staggered by ≥100mm. After each layer of precast thin slabs is laid in place, a 4mm thick, highly fluid UHPC transition layer grout is immediately poured on top. Subsequently, the transition layer is vibrated for 50 seconds using a high-frequency vibrator. This cycle is repeated until all functional layers are laid. During this step, temperature sensors are pre-embedded in the area where the functional layer is located while the thin slabs are being laid.

[0052] S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components.

[0053] S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

[0054] Example 2 This embodiment provides an ultra-high performance concrete component based on gradient phase change materials, comprising an ultra-high performance concrete matrix and three functional layers. The three functional layers are arranged in precast thin slabs within the ultra-high performance concrete matrix. Along the thickness direction of the ultra-high performance concrete component, the phase change temperatures of the microencapsulated phase change materials in the three functional layers are sequentially 50°C, 40°C, and 30°C. The phase change temperature of the microencapsulated phase change material with the highest phase change temperature is 5°C higher than its hydration environment temperature, while the phase change temperature of the microencapsulated phase change material with the lowest phase change temperature is 3°C lower than its hydration environment temperature. A 2mm thick ultra-high performance concrete transition layer is provided between adjacent precast thin slabs.

[0055] The preparation method of the ultra-high performance concrete component in this embodiment is as follows: S1: Perform detailed thermodynamic simulation and hydration heat time history analysis on the target component to determine the required 3 functional layers, the phase change temperature threshold of each PCM layer, and the specific arrangement order of each layer in the component thickness direction.

[0056] S2: Based on the different phase change temperature requirements determined in step S1, UHPC-PCM precast thin slabs of corresponding specifications are prepared in batches. The specific preparation method is as follows: The UHPC matrix of the thin slab adopts the same proportion as the main component, and the dosage of microencapsulated PCM is controlled at 15% of the cement mass. The average particle size of the microcapsules is 20μm. The microencapsulated phase change material includes a core material and a shell covering the surface of the core material. The core material is a fatty acid-based phase change material, and the shell is SiO2. The microencapsulated PCM and UHPC dry mix are premixed for 30s, and then polycarboxylate superplasticizer is added in batches and stirred at low speed for 2min. The mixture is injected into a mold and vibrated to form the shape, and the surface is covered with a film for curing. After 24h, the slab is demolded, and then cured with high-temperature steam at 90℃ for 48h. Then, the surface of the precast thin slab is sandblasted to obtain a precast thin slab with a thickness of 10mm. At the same time, auxiliary materials are prepared: a more fluid UHPC slurry for casting the transition layer.

[0057] S3: Set up formwork according to the component size, and then pour ordinary UHPC to form the base layer of the component.

[0058] S4: Before the initial setting of the poured lower layer of concrete, roughen its surface and immediately and evenly spray epoxy-based interface adhesive. The application rate of the epoxy-based interface adhesive is 0.2 kg / m². 2Next, guided by a laser positioning system, the precast thin slabs corresponding to the current layer are hoisted and laid, with the joints of adjacent slabs staggered by ≥100mm. After each layer of precast thin slabs is laid in place, a 2mm thick layer of highly fluid UHPC transition grout is immediately poured on top. Subsequently, the transition layer is vibrated for 30 seconds using a high-frequency vibrator. This cycle is repeated until all functional layers are laid. During this step, temperature sensors are pre-embedded in the area where the functional layer is located while the thin slabs are being laid.

[0059] S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components.

[0060] S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

[0061] Example 3 This embodiment provides an ultra-high performance concrete component based on gradient phase change materials, comprising an ultra-high performance concrete matrix and three functional layers. The three functional layers are arranged in precast thin slabs within the ultra-high performance concrete matrix. Along the thickness direction of the ultra-high performance concrete component, the phase change temperatures of the microencapsulated phase change materials in the three functional layers are 70°C, 50°C, and 40°C, respectively. The phase change temperature of the microencapsulated phase change material with the highest phase change temperature is 10°C higher than its hydration environment temperature, while the phase change temperature of the microencapsulated phase change material with the lowest phase change temperature is 5°C lower than its hydration environment temperature. A 5mm thick ultra-high performance concrete transition layer is provided between adjacent precast thin slabs.

[0062] The preparation method of the ultra-high performance concrete component in this embodiment is as follows: S1: Perform detailed thermodynamic simulation and hydration heat time history analysis on the target component to determine the required 3 functional layers, the phase change temperature threshold of each PCM layer, and the specific arrangement order of each layer in the component thickness direction.

[0063] S2: Based on the different phase change temperature requirements determined in step S1, UHPC-PCM precast thin slabs of corresponding specifications are prepared in batches. The specific preparation method is as follows: The UHPC matrix of the thin slab adopts the same proportion as the main component, and the dosage of microencapsulated PCM is controlled at 25% of the cement mass. The average particle size of the microcapsules is 50μm. The microencapsulated phase change material includes a core material and a shell covering the surface of the core material. The core material is a eutectic salt phase change material, and the shell is SiO2. The microencapsulated PCM and UHPC dry mix are premixed for 30s, and then polycarboxylate superplasticizer is added in batches and stirred at low speed for 2min. The mixture is injected into a mold and vibrated to form the shape, and the surface is covered with a film for curing. After 24h, the slab is demolded, and then cured with high-temperature steam at 90℃ for 48h. Then, the surface of the precast thin slab is sandblasted to obtain a precast thin slab with a thickness of 30mm. At the same time, auxiliary materials are prepared: a more fluid UHPC slurry for casting the transition layer.

[0064] S3: Set up formwork according to the component size, and then pour ordinary UHPC to form the base layer of the component.

[0065] S4: Before the initial setting of the poured lower layer of concrete, roughen its surface and immediately and evenly spray epoxy-based interface adhesive. The application rate of the epoxy-based interface adhesive is 0.3 kg / m². 2 Next, guided by a laser positioning system, the precast thin slabs corresponding to the current layer are hoisted and laid, with the joints of adjacent slabs staggered by ≥100mm. After each layer of precast thin slabs is laid in place, a 5mm thick, highly fluid UHPC transition layer grout is immediately poured on top. Subsequently, the transition layer is vibrated for 60 seconds using a high-frequency vibrator. This cycle is repeated until all functional layers are laid. During this step, temperature sensors are pre-embedded in the area where the functional layer is located while the thin slabs are being laid.

[0066] S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components.

[0067] S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

[0068] Examples 4-6 Examples 4-6 provide an ultra-high performance concrete component based on gradient phase change material layering. The preparation method is exactly the same as that of Example 1, but the difference is that steel fibers, PVA fibers, and steel fibers + PVA fibers are added only in the precast thin plate preparation stage. In Example 4, the fiber volume content is 1%, the fiber length is 12 mm, and the aspect ratio is 75. In Example 5, the fiber volume content is 0.5%, the fiber length is 18 mm, and the aspect ratio is 50. In Example 6, the fiber volume content is 2.0%, the fiber length is 6 mm, and the aspect ratio is 100.

[0069] Comparative Example 1 This comparative example uses the exact same UHPC mix ratio and total PCM dosage as Example 1, but the microcapsule PCM is uniformly incorporated into all the concrete mix, and PCM is uniformly incorporated into the entire component. The other construction and curing conditions are the same.

[0070] Nine temperature measuring points were arranged along the thickness direction of the components prepared in Examples 1-3 and Comparative Example 1, with three points each in the core area, middle area, and surface area. Temperature data were recorded over 72 hours. The results showed that the peak internal and external temperature difference of the components in Examples 1-3 was reduced by an average of about 10°C compared to Comparative Example 1, and the peak temperature time was delayed by an average of about 8 hours compared to Comparative Example 1. No visible cracks were found on the surface of the components in Examples 1-3 after 7 days of curing. In addition, the 28-day compressive strength of the components in Examples 1-3 was basically equivalent to that of the pure UHPC component without phase change material.

[0071] Under the same test conditions, the peak internal and external temperature difference, the time of occurrence of the temperature peak, and the surface crack state at 7 days in the components of Examples 4-6 were basically the same as those in Example 1.

[0072] Furthermore, three-point bending tests were conducted on the specimens prepared in Examples 4-6 at 7 days of age. The results showed that, compared with Examples 1-3, Examples 4-6 exhibited superior early crack resistance and deformation recovery. Specifically, the initial crack load of Examples 4-6 was increased by approximately 15-20% compared to Example 1, and the residual flexural strength was increased by approximately 21-23%. In addition, the 28-day compressive strength of Examples 4-6 was still not lower than that of Comparative Example 1, indicating that the fiber incorporation did not weaken the basic mechanical properties of the components.

[0073] The above data demonstrate that this invention, by embedding microencapsulated PCMs with different phase transition temperatures into a UHPC matrix in the form of prefabricated thin plates along the thickness direction, successfully achieves a dual match between the phase transition behavior and the hydration heat release process in both spatial location and time window. Compared to traditional homogeneous doping methods, this invention not only significantly improves the energy capture efficiency and response time of the PCM, but also fundamentally reconstructs the heat transfer path within the component. Therefore, without introducing external energy, reducing early strength, or increasing structural complexity, this invention effectively achieves efficient, reliable, and verifiable control of temperature cracks in large-volume UHPC components.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-performance concrete component based on gradient phase change material stratification, characterized in that, It includes an ultra-high performance concrete matrix and at least three functional layers; The at least three functional layers are sequentially disposed in the ultra-high performance concrete matrix along the thickness direction of the ultra-high performance concrete component. Each functional layer contains microencapsulated phase change materials; Along the thickness direction of the ultra-high performance concrete component, the phase transition temperature of the microencapsulated phase change material in each functional layer decreases sequentially.

2. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 1, characterized in that, The ultra-high performance concrete matrix is ​​provided with three functional layers, which are set in the ultra-high performance concrete matrix in the form of precast thin plates.

3. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 2, characterized in that, The phase transition temperatures of the microencapsulated phase change materials in the three functional layers are 50-70℃, 40-50℃, and 30-40℃, respectively.

4. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 1, characterized in that, The phase transition temperature of the microencapsulated phase change material with the highest phase transition temperature is 5-10℃ higher than the temperature of its hydration environment, while the phase transition temperature of the microencapsulated phase change material with the lowest phase transition temperature is 3-5℃ lower than the temperature of its hydration environment.

5. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 2, characterized in that, A 2-5mm thick ultra-high performance concrete transition layer is also provided between adjacent functional layers.

6. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 2, characterized in that, The microencapsulated phase change material has a particle size of 20-50 μm, and the microencapsulated phase change material includes a core material and a shell covering the surface of the core material. The core material is a paraffin-based phase change material, a fatty acid-based phase change material, or a eutectic salt-based phase change material, and the shell is an inorganic ceramic material.

7. The ultra-high performance concrete component based on gradient phase change material stratification according to claim 1, characterized in that, The thickness of the precast thin plate is 10-30mm, and the raw materials for preparing the precast thin plate include ultra-high performance concrete and microencapsulated phase change material. The amount of microencapsulated phase change material is 15-25% of the cement mass.

8. A method for preparing an ultra-high performance concrete component according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Based on the hydration heat history of ultra-high performance concrete components, determine the number of functional layers in the components, the phase transition temperature of the microencapsulated phase change material in each functional layer, and the arrangement order of each functional layer. S2: Based on the phase transition temperature of the microencapsulated phase change material of each functional layer determined in step S1, prepare corresponding prefabricated thin plates doped with microencapsulated phase change materials. S3: Set up formwork according to the dimensions of the component, pour ultra-high performance concrete to form the base layer; S4: Before the initial setting of the base concrete, its surface is treated with interface treatment, then the first layer of precast thin plate is laid, and ultra-high performance concrete is poured on top of the precast thin plate to form a transition layer, and the transition layer is vibrated and compacted. S5: Repeat the process of interface treatment, laying precast thin slabs, pouring and vibrating the transition layer in step S4 until all precast thin slabs are laid and the corresponding transition layer is poured. S6: Continue pouring ultra-high performance concrete to obtain ultra-high performance concrete molded components; S7: Curing ultra-high performance concrete molded components to obtain ultra-high performance concrete components.

9. The preparation method according to claim 8, characterized in that, In steps S4 and S5, the interface is treated by roughening the surface and spraying an interface adhesive.

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