A bridge pier column fireproofing system based on phase change material and a method of use

Abstract

The application relates to the field of building structure fireproof technology, and provides a bridge pier column fireproof system based on a phase change material and a use method. The fireproof system specifically comprises an expansion adhesive layer, a functional layer and an outer protective layer; the functional layer is sleeved outside a column body of the bridge pier column and is bonded with the column body through the expansion adhesive layer; the outer protective layer is sleeved outside the functional layer; the functional layer comprises a plurality of functional rings arranged in the axial direction; the functional rings are composed of a plurality of first functional blocks and a plurality of second functional blocks and are annularly spliced and have self-locking structures therebetween; the self-locking structures are used for providing circumferential prestress when the expansion adhesive layer expands; and the first functional blocks and the second functional blocks are both encapsulated with the phase change material. The encapsulation of the phase change material and the structural stability are unified, the structural integrity and continuity of the phase change functional layer in the whole fire process are ensured, and therefore the stability and the final fireproof reliability of the fireproof system are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of fire protection technology for building structures, and in particular to a fire protection system for bridge piers based on phase change materials and its application method. Background Technology

[0002] Currently, fire protection technologies for concrete building structures primarily rely on passive insulation. Common solutions include spraying fire-retardant coatings onto the structural surface, wrapping with fire-resistant panels (such as rock wool boards or fire-resistant concrete boards), or pouring fire-resistant concrete layers. The core principle of these technologies is to utilize the low thermal conductivity and high thermal inertia of the materials themselves to slow down the transfer of heat to the internal concrete.

[0003] Bridges are crucial hubs in transportation networks, and their structural safety is paramount. As primary load-bearing components, the performance of bridge piers under fire directly impacts the safety of the entire bridge. Under sustained high temperatures, the mechanical properties of concrete deteriorate significantly, easily leading to insufficient structural load-bearing capacity and destructive collapse. Therefore, implementing effective fire protection measures for bridge piers is essential to ensuring the safe operation of bridges during fires.

[0004] However, traditional technical solutions have some inherent drawbacks when applied to special components such as bridge piers. Fire resistance is strongly correlated with the thickness and weight of the protective layer, making it difficult to balance both. To achieve a high fire resistance rating, very thick fire-retardant coatings or boards are often required, which not only significantly increases the dead load on the bridge but may also affect the clearance height of the space beneath it, and is also very costly. Secondly, the structural integrity of assembled fire-resistant boards is difficult to guarantee under fire conditions. Traditional fire-resistant boards are usually installed using adhesives or simple mechanical anchoring. Under the high temperatures and thermal shock of a fire, the boards themselves may deform, warp, or even crack, and the joints between the boards can easily become weak points for flame and heat intrusion. Once the fire-resistant layer is partially damaged or detached, the high-temperature heat flow will directly act on the concrete itself, causing failure and significantly reducing the overall protective effect.

[0005] The application of phase change energy storage technology in building fire protection is still immature. Although phase change materials (PCMs) have been widely studied due to their ability to absorb a large amount of latent heat during phase change, thereby achieving efficient temperature control, current applications are mostly focused on energy-saving temperature regulation of building envelopes. When applying them to building structural fire protection, how to effectively combine PCMs with fire-resistant structures, how to ensure their structural stability and continuous function in a fire, and how to balance fire resistance, mechanical properties, and ease of construction remain pressing technical challenges that need to be addressed. Summary of the Invention

[0006] To address the aforementioned issues, this invention aims to provide a fireproof system for bridge piers based on phase change materials and its application method. This system effectively combines phase change materials with fireproof structures, ensuring structural stability and continuous function during fires, while also offering high ease of construction.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A fireproof system for bridge piers based on phase change materials includes an expansion bonding layer, a functional layer, and an outer protective layer. The functional layer is annularly fitted around the outside of the bridge pier and bonded to the pier via the expansion bonding layer. The outer protective layer is annularly fitted around the functional layer and serves to radially limit the functional layer and provide mechanical protection. The functional layer includes multiple functional rings arranged axially. Each functional ring is composed of multiple staggered first functional blocks and multiple second functional blocks joined together in a ring, with adjacent first and second functional blocks having a self-locking structure. The self-locking structure is used to circumferentially limit the first and second functional blocks and provide circumferential prestress when the expansion bonding layer expands. Both the first and second functional blocks are encapsulated with phase change material.

[0009] This design utilizes a three-layer structure working synergistically to achieve highly efficient fire protection for bridge piers. The phase change material within the functional layer undergoes a phase change under high fire temperatures, absorbing a large amount of heat and significantly slowing the temperature rise rate in the core area of ​​the pier, maintaining the mechanical properties of the concrete structure within its design fire resistance limit, and playing a core fire-resistant role. The modular design, with its segmented and ring-shaped sections, facilitates on-site installation, maintenance, and replacement. The expanding adhesive layer expands when heated, not only filling the initial gaps to ensure effective heat transfer to the functional layer but also generating radial thrust. The outer protective layer provides radial constraint and routine mechanical and environmental protection to the functional layer. The self-locking structure utilizes the radial thrust generated by the expanding adhesive layer, converting it into circumferential prestress on the functional blocks. This ensures that the functional blocks not only do not loosen during a fire but are instead tightly bound together, guaranteeing the integrity and continuous protective capability of the fire protection system.

[0010] Preferably, the self-locking structure includes a first wedge block; the first wedge block is disposed on both sides of the first functional block, and the second functional block has first wedge grooves on both sides corresponding to the first wedge block.

[0011] This design concretizes the self-locking structure into the engagement of the first wedge block and the first wedge groove, effectively transmitting radial force to circumferential force. When the inner expansion adhesive layer expands due to heat, generating radial thrust on the functional block, this thrust acts on the inclined surface of the first wedge block. This radial force has a circumferential component along the contact surface direction; this circumferential component is the circumferential prestress applied to the functional ring. It enables the entire functional ring to passively self-lock and tighten, preventing gaps between functional blocks that could allow flames or heat to penetrate, thus ensuring the integrity of the fireproof structure. This structure is simple, reliable, and easy to manufacture, enabling passive and adaptive locking under fire conditions.

[0012] Preferably, the first functional block is provided with a first fastening platform on both sides, and a second wedge block is provided on the first fastening platform; the second functional block is provided with a second fastening platform corresponding to the first fastening platform, and a second wedge groove corresponding to the second wedge block is provided on the second fastening platform.

[0013] This design places the second wedge block and the second wedge groove on the first and second engagement platforms, respectively. The first and second engagement platforms interlock, forming a stepped lap surface that goes beyond the contact of the wedge-shaped inclined surfaces, adding a shear surface perpendicular to the radial direction. This allows the functional blocks to resist more complex stresses, preventing misalignment or shear failure between functional blocks, and further enhancing the structural stability and reliability of the entire functional ring under high temperatures and external forces.

[0014] Furthermore, the functional layer also includes a limiting component for axially limiting multiple functional rings.

[0015] This design improves the stability and integrity of multiple functional rings along the axial direction (i.e., the pier height direction) by incorporating limiting components. It prevents relative slippage, tilting, or even detachment of the functional rings, which could lead to weak points or partial failures in the fire protection system. Axial limiting, by connecting multiple functional rings in series, enhances the continuity and integrity of the fire protection system along the pier height direction.

[0016] Furthermore, multiple limiting components are evenly arranged along the circumference of the functional layer. Each limiting component includes: two limiting anchors, which are respectively located at both ends of the functional layer in the axial direction; and a limiting rope connecting the two limiting anchors. The first functional block and the second functional block are both provided with through holes that cooperate with the limiting rope.

[0017] This design specifically defines one implementation method for the limiting components. By pre-setting through holes in the functional blocks, the limiting ropes can pass through all the functional rings, and axial prestress is applied by tensioning the limiting anchors at both ends. This method not only reliably fixes all the functional rings together, preventing their axial displacement, but also ensures a tight fit between the functional rings through the applied axial prestress, eliminating vertical gaps and further enhancing the thermal performance of the fire protection system. Evenly arranging multiple limiting components circumferentially allows for a more uniform distribution of axial prestress, avoiding localized stress concentrations and ensuring the overall system's stress balance and structural stability.

[0018] Furthermore, both the first and second functional blocks are cast from cement-based phase change composite materials.

[0019] This design, using cement-based phase change composite materials as the matrix material for functional blocks, offers multiple advantages. First, cement-based materials possess excellent fire resistance and durability, exhibiting good compatibility with the concrete of bridge piers and columns, enabling a stable bond. Second, uniformly dispersing and encapsulating the phase change material within the cement matrix effectively prevents leakage and loss of the material in its molten state, while simultaneously improving its heat transfer efficiency. Furthermore, casting allows for the easy manufacture of functional blocks with self-locking structures, simplifying the molding process and controlling costs.

[0020] Furthermore, the raw materials for cement-based phase change composite materials include mPCM (microencapsulated phase change material) powder, sulfoaluminate cement, quartz sand, PVA (polyvinyl alcohol) fiber, admixtures, and water.

[0021] Furthermore, the mix proportion of the cement-based phase change composite material is, by weight, 25% mPCM powder, 40% sulfoaluminate cement, 30% quartz sand, 1.5% PVA fiber and 0.5% polycarboxylate superplasticizer, with a water-cement ratio of 0.35.

[0022] This specially designed mortar aims to achieve a balance between fire resistance, mechanical properties, and workability. 25% mPCM powder ensures a sufficiently high latent heat of phase change to provide core energy storage, temperature control, and fire resistance. Using 40% sulfoaluminate cement as a binder enables rapid hardening and early strength, shortening the production cycle, and its low alkalinity helps protect the stability of PVA fibers and mPCM. 1.5% PVA fiber provides crack resistance and toughening, significantly improving the composite material's impact resistance and toughness, preventing brittle fracture under fire or external force. Modular design, consisting of multiple first and second functional blocks, effectively avoids quality defects such as cracks in large-volume mortar precast components, and facilitates precast component transportation and assembly.

[0023] The addition of 0.5% polycarboxylate superplasticizer as an admixture satisfies the workability requirements at a low water-cement ratio (0.35), facilitating the production and molding of cement-based phase change composite materials.

[0024] As a preferred option, the bridge pier fire protection system also includes an insulation layer located between the functional layer and the outer protective layer, which is used to reduce heat transfer and provide flexible protection for the functional layer.

[0025] This design further optimizes the fire protection system. Its functions are twofold: First, as an additional thermal barrier, it slows the rate of heat transfer from the outside to the functional layer, preventing the phase change material within the functional layer from undergoing a phase change prematurely or too quickly. This preserves the "heat absorption period" of the phase change material during the most intense phase of the fire, improving the efficiency and effective duration of heat absorption. Second, the insulation layer, made of flexible or semi-rigid materials (such as aerogel felt, ceramic fiber felt, rock wool, etc.), acts as a buffer, protecting the functional blocks from impacts or vibrations that may be transmitted from the outer protective layer. It can also accommodate minor displacements caused by thermal expansion and contraction between layers, improving the overall durability and reliability of the system.

[0026] This application also provides a method for using the bridge pier fire protection system as described above, including:

[0027] S1: Prefabricate multiple first function blocks and multiple second function blocks;

[0028] S2: Apply an expansion bonding layer evenly to the outer surface of the bridge pier column;

[0029] S3: Multiple first functional blocks and multiple second functional blocks are joined together in a ring on the surface of the expansion adhesive layer to form a functional ring;

[0030] S4: Following step S3, splice multiple functional rings along the axial direction of the bridge pier column to complete the installation of the functional layer;

[0031] S5: Install an outer protective layer on the outside of the functional layer.

[0032] In summary, this application has at least one of the following beneficial effects:

[0033] 1. This application employs a three-layer collaborative design consisting of an expansion bonding layer, a modular functional layer, and an outer protective layer. In particular, it constructs an expansion prestressing and "fire-activated" self-reinforcing stability protection system between the functional blocks of the functional layer. The radial expansion force generated by the expansion bonding layer can be transformed into circumferential prestress on the functional ring through a self-locking structure, achieving adaptive locking and overall reinforcement of the functional layer. It also allows for further locking under thermal expansion during fire. This achieves a unified approach to the encapsulation of phase change materials and structural stability, ensuring the structural integrity and continuity of the phase change functional layer throughout the fire process, thereby significantly improving the stability and ultimate fire protection reliability of the fire protection system.

[0034] 2. Modular design, convenient application and good economy. The functional layer of this application adopts a modular splicing concept of "functional block → functional ring → functional layer", which allows all core components to be prefabricated in the factory in a standardized manner. On-site operations are simplified to dry or semi-dry assembly, which significantly shortens the construction cycle and reduces the requirements for on-site construction conditions. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 This is a schematic diagram of a bridge pier fire protection system based on phase change materials, which is an optional embodiment of the present invention.

[0037] Figure 2 This is a cross-sectional view of a bridge pier fire protection system based on phase change materials, which is an optional embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the structure of an optional functional layer in an embodiment of the present invention;

[0039] Figure 4 for Figure 3 Enlarged diagram of section A in the middle;

[0040] Figure 5 This is a schematic diagram of the structure of the first functional block of a self-locking structure, which is an optional embodiment of the present invention.

[0041] Figure 6 This is a schematic diagram of the structure of the second functional block of an optional self-locking structure according to an embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram of the structure of the first functional block of another optional self-locking structure in an embodiment of the present invention;

[0043] Figure 8This is a schematic diagram of the structure of the first functional block of another optional self-locking structure in an embodiment of the present invention;

[0044] Figure 9 This is a schematic diagram of the installation of the first and second functional blocks of another optional self-locking structure in an embodiment of the present invention;

[0045] Figure 10 This is a schematic diagram of an optional intelligent temperature control system according to an embodiment of the present invention;

[0046] Figure 11 This is a flowchart illustrating the usage method of a bridge pier fire protection system based on phase change materials, which is an optional embodiment of the present invention.

[0047] Figure 12 The test results show the thermal insulation effect of the functional layer and thermal insulation layer in the embodiments of the present invention.

[0048] The components are: 1. Expansion adhesive layer; 2. Functional layer; 21. Functional ring; 211. First functional block; 212. Second functional block; 221. First wedge block; 222. First wedge groove; 223. First fastening platform; 224. Second fastening platform; 225. Second wedge block; 226. Second wedge groove; 23. Limiting component; 3. Outer protective layer; 4. Heat insulation layer. Detailed Implementation

[0049] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0050] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "front end", "rear end", "inner side", "outer side", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0051] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] Example 1

[0053] This embodiment provides a fire protection system for bridge piers based on phase change materials, such as... Figures 1 to 4 As shown, the structure includes an expansion bonding layer 1, a functional layer 2, and an outer protective layer 3. The functional layer 2 is encircled by the outer surface of the bridge pier column, and is bonded to the column via the expansion bonding layer 1. The outer protective layer 3 is encircled by the functional layer 2, and its main function is to provide radial restraint and control for the functional layer 2, and to provide routine mechanical impact protection and environmental isolation for the internal functional layer 2. The functional layer 2 is a modular structure, comprising multiple functional rings 21 arranged along the axial direction of the column. Each functional ring 21 is composed of multiple staggered first functional blocks 211 and multiple second functional blocks 212, joined together circumferentially. A self-locking structure is provided between adjacent first functional blocks 211 and second functional blocks 212. The core function of the self-locking structure is that when the internal expansion bonding layer 1 expands and generates radial thrust, this structure cleverly converts this radial force into circumferential prestress acting on the entire functional ring 21, thereby circumferentially restraining the first functional blocks 211 and second functional blocks 212. Through the synergistic effect of the three-layer structure, circumferential and radial restraints are achieved, enabling highly efficient fire protection for bridge piers. The phase change material within functional layer 2 undergoes a solid-liquid phase change under high fire temperatures, absorbing a significant amount of latent heat. This significantly delays heat transfer to the core area of ​​the pier, reducing the temperature gradient across the pier cross-section and helping to maintain the mechanical properties of the concrete structure within its design fire resistance limit, thus playing a core fire-resistant role. The modular design, with its segmented and ring-shaped sections, facilitates prefabrication, transportation, and on-site installation, and also allows for later repair and replacement of damaged sections. After expansion, the expanding adhesive layer 1 not only fills any small gaps that may exist during initial installation, ensuring a tight fit between the column and functional layer 2 for effective heat transfer, but also generates a crucial radial thrust on functional layer 2. The outer protective layer 3 provides radial restraint to functional layer 2, offering reaction force support for the mechanical transformation of the self-locking structure. The self-locking structure utilizes the radial thrust generated by the expansion bonding layer 1 to transform passive expansion force into active circumferential prestress, making each functional block not only less prone to loosening during a fire, but also more tightly bound together, thereby improving the stability and continuous protection capability of the fire protection system.

[0054] Specifically, the outer protective layer 3 can be made of galvanized steel sheet, aluminum alloy sheet, or stainless steel sheet with a thickness of 1.0mm to 3.0mm. Reinforcing ribs are formed through a pressing process to improve overall rigidity. In this embodiment, it is assembled on-site from two semi-circular modules. A robust connection structure is provided at the longitudinal joint of the arc-shaped module. Angle steel flanges with through holes are pre-embedded or welded to the edge of the outer protective layer 3. During assembly, high-strength, high-temperature resistant bolts (such as A2-70 stainless steel bolts) are used to securely connect the flanges of adjacent modules.

[0055] In some embodiments, bolts are pre-embedded on the outer surface of the first functional block 211 or the second functional block 212 to connect with the outer protective layer 3.

[0056] As a preferred implementation of the self-locking structure, such as Figure 5 and Figure 6 As shown, the self-locking structure includes a first wedge block 221; the first wedge block 221 is disposed on both sides of the first functional block 211 and corresponds to the first wedge grooves 222 disposed on both sides of the second functional block 212. Specifically, the self-locking structure is the mechanical engagement of the first wedge block 221 and the first wedge grooves 222, achieving effective transmission of radial force to circumferential force. When the inner expansion adhesive layer 1 expands due to heat, generating a radial thrust on the functional block, this thrust acts on the inclined surface of the first wedge block 221. According to the principle of force decomposition, this radial thrust can be decomposed into a normal component perpendicular to the wedge contact surface and a circumferential component along the contact surface direction. This circumferential component is the circumferential prestress applied to the functional ring 21, which enables the entire functional ring 21 to generate a passive, adaptive locking tendency, resisting deformation that may be caused by high temperature, preventing gaps between functional blocks from allowing flames or high-temperature smoke to enter, thereby ensuring the integrity of the fireproof structure. This wedge-shaped structure has a simple design, is easy to cast, has a reliable working principle, and can achieve passive self-locking under fire conditions.

[0057] As another preferred embodiment of the self-locking structure, such as Figures 7 to 9 As shown, the first functional block 211 has a first fastening platform 223 on both sides, and the second wedge block 225 is disposed on the first fastening platform 223; correspondingly, the second functional block 212 has a second fastening platform 224 corresponding to the first fastening platform 223, and the second wedge groove 226 is disposed on the second fastening platform 224. The second wedge block 225 and the second wedge groove 226 are respectively disposed on the interlocking first fastening platform 223 and the interlocking fastening platform 224 to form a stepped overlapping surface. This design does not rely on the wedge-shaped inclined surface for circumferential fastening, but uses the shear force surface perpendicular to the radial direction for circumferential tightening, while the wedge structure is used to provide multiple shear force surfaces and a stable fastening structure. When the functional ring 21 is subjected to complex stresses, especially torsional or shear stresses, these shear surfaces can provide additional shear resistance, enabling the functional blocks to resist more complex stresses and effectively preventing misalignment, slippage or shear failure between the functional blocks. This further enhances the structural stability and reliability of the entire functional ring 21 under high temperature and external force.

[0058] Furthermore, the functional layer 2 also includes a limiting component 23 for axially limiting the multiple functional rings 21. The purpose of setting the limiting component 23 is to improve the stability and integrity of the functional layer 2, which is composed of multiple independent functional rings 21 stacked together, in the axial direction (i.e., the height direction of the pier). Without axial limiting, under the influence of factors such as installation process, structural self-weight, vehicle vibration load, or thermal deformation caused by fire, the functional rings 21 may slide relative to each other, tilt, or even fall off, resulting in weak links or partial failures in the fire protection system. By setting the limiting component 23, multiple separate functional rings 21 can be effectively connected in series into a whole structure, which helps to improve the continuity and integrity of the fire protection system along the height direction of the pier.

[0059] In some embodiments, multiple limiting components 23 may be uniformly arranged along the circumference of the functional layer 2. Each limiting component 23 may include: two limiting anchors, respectively located at both ends of the functional layer 2 (e.g., the top surface of the top functional ring 21 and the bottom surface of the bottom functional ring 21); and a limiting rope, with its two ends connected to the two limiting anchors respectively. Correspondingly, the first functional block 211 and the second functional block 212 are both provided with through holes for the limiting rope to pass through. This is a specific embodiment of the limiting component 23. By pre-setting through holes on the functional blocks, the limiting rope can smoothly pass through all functional rings 21, and after installation, axial prestress is applied to the entire functional layer 2 by tensioning the limiting rope and fixing the limiting anchors. This axial prestress not only reliably fastens all functional rings 21 together, effectively preventing their axial displacement, but also makes the end faces of each functional ring 21 fit tightly together, helping to eliminate or reduce vertical gaps between rings, and further enhancing the airtightness and thermal performance of the fire protection system. By uniformly arranging multiple (e.g., 3 to 4) limiting components 23 along the circumference, the axial prestress can be distributed more evenly along the circumferential direction, avoiding local stress concentration and ensuring the force balance and structural stability of the entire system. The limiting ropes can be made of materials such as steel strand or high-strength fire-resistant fiber rope.

[0060] Optionally, to improve the positional stability between multiple limiting rings, a slot structure is provided between the limiting rings, which can be easily implemented by pre-designing the top and bottom shapes of the first functional block 211 and the second functional block 212.

[0061] Furthermore, both the first functional block 211 and the second functional block 212 are cast from cement-based phase change composite materials. Cement-based phase change composite materials, as the matrix material for the functional blocks, offer multiple technical advantages. First, cement-based materials are inorganic non-metallic materials with good fire resistance and chemical durability. Their coefficient of thermal expansion is close to that of concrete in bridge piers, resulting in low thermal stress when combined, thus forming a stable interface. Second, uniformly dispersing and solidifying phase change materials such as microcapsule phase change materials (mPCM) in the form of aggregates or admixtures within the cement matrix effectively prevents leakage and loss of the phase change materials after heating and melting. Simultaneously, the dense cement matrix provides a good heat transfer medium for the phase change materials, contributing to improved phase change energy storage efficiency. The casting process allows for convenient and precise manufacturing of functional blocks with complex geometric features such as wedge structures, first interlocking platforms 223 and 224, through holes, and slots. The molding process is mature and conducive to large-scale production and cost control.

[0062] Furthermore, the raw materials for the cement-based phase change composite material may include: mPCM powder, sulfoaluminate cement, quartz sand, PVA fiber, admixtures, and water. More specifically, a recommended mix proportion (by weight) is: 25% mPCM powder, 40% sulfoaluminate cement, 30% quartz sand, 1.5% PVA fiber, and 0.5% polycarboxylate superplasticizer, with a water-cement ratio controlled at 0.35. This specific mix proportion aims to achieve an optimized balance between the material's fire resistance, mechanical properties, and workability. It should be noted that the raw materials for precast mortar components are widely available and influenced by geographical environment, climate, and other external conditions. Therefore, routine tests should be conducted for specific applications, and appropriate adjustments should be made to this mix proportion to meet construction requirements. Obviously, performance can also be improved by conducting routine tests and adding other admixtures.

[0063] The 25% mPCM powder content ensures a sufficiently high latent heat of phase change while avoiding excessive weakening of the material's mechanical properties, thus providing the core energy storage, temperature control, and fireproofing effects. Using 40% sulfoaluminate cement as a binder leverages its rapid hardening and early strength characteristics to shorten the production and curing cycle of the functional blocks; its lower alkalinity also helps protect the long-term stability of PVA fibers and part of the mPCM wall material. The addition of 1.5% PVA fibers as randomly distributed reinforcing ribs forms a three-dimensional network in the cement matrix, effectively inhibiting the generation and propagation of microcracks, significantly improving the impact resistance and fracture toughness of the composite material, and preventing brittle failure under fire, explosion, or external forces. The functional layer 2 is designed as a splicing of multiple first functional blocks 211 and second functional blocks 212, effectively avoiding quality defects such as cracking caused by the heat of hydration and drying shrinkage of large-volume cement-based precast components, and also facilitating the transportation and on-site assembly of precast components. Adding 0.5% polycarboxylate superplasticizer as an admixture can give fresh mortar good fluidity and workability while maintaining a low water-cement ratio (0.35).

[0064] Specifically, the expansion bonding layer 1 is preferably a cement-based expansion material, specifically a cement-based material to which calcium sulfoaluminate or calcium oxide-based expansion agents are added. In this embodiment, the expansion bonding layer 1 is composed of sulfoaluminate cement and ordinary silicate cement in a mass ratio of 4:5, quartz powder, HCSA high-efficiency expansion agent, polycarboxylate superplasticizer, and water. This expansion bonding layer 1 can stably bond with the bridge pier substrate and the first functional block 211 and the second functional block 212 prepared from the cement-based phase change composite material; and the expansion rate can be precisely controlled by adjusting the dosage of the expansion agent through conventional experiments, thereby ensuring that the functional layer 2 has a stable and predictable preload.

[0065] In a preferred embodiment, the bridge pier fire protection system may further include a thermal insulation layer 4, located between the functional layer 2 and the outer protective layer 3. Adding the thermal insulation layer 4 further optimizes the overall performance of the fire protection system. On one hand, the thermal insulation layer 4 acts as an additional thermal barrier, effectively slowing down the rate of heat transfer from the external fire scene to the internal functional layer 2. This prevents the phase change material within the functional layer 2 from undergoing phase change prematurely and too quickly in the early stages of a fire, preserving its latent heat absorption capacity during the most intense and hottest phase of the fire. This improves the utilization efficiency of the phase change material's heat absorption and the effective fire resistance time of the entire system. On the other hand, the thermal insulation layer 4 is typically made of flexible or semi-rigid refractory materials, such as aerogel felt, ceramic fiber felt, and rock wool. These materials, in addition to their low thermal conductivity, also possess excellent compression resilience and cushioning properties. They can protect the rigid functional blocks from mechanical impacts or vibrations that may be transmitted from the outer protective layer 3, and effectively adapt to thermal expansion and contraction deformation caused by drastic temperature differences between materials, reducing interlayer stress and contributing to improved overall system durability and reliability.

[0066] Example 2

[0067] Based on Example 1, this example integrates an intelligent temperature control system to form an intelligent fire prevention system with active monitoring and early warning functions. Specifically, the following modules are added.

[0068] The intelligent temperature control system may include a temperature sensing system and a control and communication unit, and the specific control process is as follows: Figure 10 As shown.

[0069] Specifically, the temperature sensing system is responsible for collecting real-time temperature data from the fire protection system and key locations on the piers. In this embodiment, a K-type armored thermocouple, known for its stable performance, fast response, and high-temperature resistance in industrial temperature measurement, is preferably used as the temperature sensor. To achieve comprehensive and accurate monitoring, the sensor deployment locations may include:

[0070] 1. Located inside functional layer 2: Sensors are embedded in functional blocks at different heights and circumferential positions, with their temperature probes close to the core area of ​​the phase change material (PCM). Sensors in this location are primarily used to monitor the operating status of the PCM, such as the temperature plateau, heat absorption rate, and temperature distribution within functional layer 2 during the phase change process, to verify whether the fire protection function has been effectively activated.

[0071] 2. Sensors are installed close to the outer surface of the concrete pier: The sensors at this location are mainly used to monitor the actual heat flow boundary conditions transmitted to the surface of the pier, and are key measuring points for evaluating the instantaneous heat insulation effect of the fire protection system.

[0072] It should be noted that, to ensure the long-term reliability of the sensor at this location during the construction of the expansion bonding layer 1 (cement-based expansion grout) and its subsequent expansion process, a preferred protective installation method can be adopted: Before applying the expansion bonding layer 1, a small protective sleeve (e.g., a thin-walled stainless steel pipe with a temperature measuring hole or a U-shaped metal trough) is fixed to the planned temperature measuring point on the outer surface of the concrete of the pier column by adhesive bonding or clips. Then, the temperature measuring end of the armored thermocouple is inserted into the protective sleeve, ensuring good contact between its measuring head and the surface of the pier column. Finally, the expansion bonding layer 1 is applied or poured. In this way, the expansion and extrusion pressure generated by the expansion bonding layer 1 during solidification and heating is mainly borne by the external protective sleeve, thereby effectively avoiding direct impact on the sensor body and ensuring the accuracy of the temperature measurement data and the reliability of the sensor.

[0073] 3. Embedded within the pier concrete: Before installing the fire protection system, sensors with a depth of 50mm to 100mm are embedded in the concrete protective layer of the pier's critical stress sections. These sensors serve as key safety monitoring points, directly monitoring temperature changes in the core concrete area.

[0074] All sensor signal lines can be gathered through pre-reserved cable trays into a waterproof junction box located at the bottom of the pier for easy connection and maintenance.

[0075] The control and communication unit is the central processing unit, responsible for data processing, logical judgment, and information reporting. This unit can be installed entirely within a control box with a protection rating of at least IP65, and fixed in a safe and easily accessible location near the pier or bridge. Specifically, it may include:

[0076] Signal conditioning module: Since thermocouples generate weak voltage signals at the millivolt level, this module is used to receive signals from various sensors, perform necessary filtering to eliminate electromagnetic interference, amplify the signals through a high-precision operational amplifier, and perform cold junction compensation according to the ambient temperature to output an accurate and stable temperature signal.

[0077] Logic Controller: Preferably, an industrial-grade programmable logic controller (PLC) or a highly reliable embedded microprocessor can be used. It internally stores preset control logic and acquires temperature values ​​from all measurement points in real time via a high-speed A / D converter. This logic can be set with multiple alarm thresholds. For example, when the temperature value collected from any sensor located inside or on the surface of the pier concrete exceeds a warning threshold (e.g., 60°C, which is far below the concrete damage temperature), the controller determines it is in the early stages of a fire and sends a primary alarm to the remote monitoring center via the communication module. When the temperature value detected from a sensor inside the concrete exceeds a critical threshold (e.g., 300°C), the controller determines that structural safety is under serious threat and triggers the highest-level emergency alarm.

[0078] Wireless communication module: To achieve remote data transmission, a 4G / 5G DTU (Data Transmission Unit) module or an NB-IoT module is preferred in applications with strict power consumption requirements. This module connects to the logic controller via a serial port or network interface, and sends the collected real-time temperature data, device status information, and triggered alarm information in a common JSON data format to a designated remote monitoring server via the public network on a scheduled basis or immediately upon alarm triggering.

[0079] Power Module: The design of the power module is crucial to ensure uninterrupted operation of the system under extreme conditions such as fires and power outages. A "municipal power supply + backup battery" scheme can be adopted, where the system is powered by the mains and charges the battery under normal circumstances, and automatically and seamlessly switches to battery power when the mains power is interrupted. In remote bridges without mains power, an independent power supply scheme of "solar panels + energy storage batteries" can also be used.

[0080] For those skilled in the art, other intelligent temperature control systems can also be used to monitor the prevention and control system of this application.

[0081] Example 3

[0082] In this embodiment, the cement-based phase change composite material of Example 1 is verified.

[0083] Specifically, microencapsulated phase change materials (mPCM) with a phase change temperature of 180℃~220℃ are selected. The capsule wall material is melamine-formaldehyde resin or polymethyl methacrylate, the core material is paraffin, and the particle size distribution is 5μm~50μm.

[0084] The mPCM powder was mixed at a mass ratio of 25% with 40 wt% sulfoaluminate cement, 30 wt% quartz sand, 1.5 wt% PVA fiber, and 0.5 wt% polycarboxylate superplasticizer, with a water-cement ratio of 0.35. After mixing, the mixture was poured into "phase change thermal insulation mortar boards" of predetermined dimensions. A comparative example (Example 1) without mPCM powder was also prepared. The performance of the two mixtures was tested and compared, and the test results are shown in Table 1 below.

[0085] Table 1 Comparison of the performance of phase change thermal insulation mortar boards

[0086]

[0087] As can be seen, although the compressive strength of the phase change insulation mortar board provided in this application is reduced, its thermal inertia is significantly improved. This mix ratio achieves an optimal balance between ensuring sufficient structural strength of the board (to support modular installation) and excellent fire resistance. The reduction in strength is acceptable because it is installed as a functional layer within the sleeve and does not function as a load-bearing component.

[0088] To further verify the beneficial effects of this application, standard fire resistance tests were conducted on the following protection schemes in accordance with GB / T 9978.1 Fire Resistance Test Method for Building Components. The concrete pier column specimens used in the test had a cross-sectional size of 200mm × 200mm and a concrete strength grade of C40. See Table 2.

[0089] Table 2 Results of fire resistance performance comparison test

[0090]

[0091] Analysis of experimental conclusions:

[0092] When the critical temperature for concrete mechanical properties reaches 300℃, the fire resistance time of this embodiment far exceeds that of the two traditional technologies (126 min and 101 min), demonstrating a significant improvement. This fully proves that the fire protection effect brought by the technical solution of this application is excellent.

[0093] The total protective thickness is 50mm (30mm functional layer + 20mm insulation layer), which is comparable to that of Comparative Example B (50mm concrete slab). However, the fire resistance performance of this invention is significantly improved. The synergistic effect of "phase change heat storage" and "high-efficiency insulation" is excellent.

[0094] The temperature rise curves of Comparative Examples 2 and 3 are smooth, which is a typical characteristic of passive insulation. However, the long-term temperature plateau that appears in the curve of the embodiment of the present invention directly verifies the intelligent working process of the phase change temperature control module actively absorbing heat and dynamically delaying the temperature rise during a fire.

[0095] Example 4

[0096] Unlike Example 1, this example does not use cement-based phase change composite materials. The first and second functional blocks encapsulate the PCM in a container. Specifically, a composite hydrated salt (e.g., a mixed phase change material primarily composed of sodium acetate trihydrate) with a phase change temperature of 150°C ± 10°C or paraffin with a specific melting point is selected. The encapsulation container is preferably made of aluminum alloy or stainless steel sheet. Molten PCM is poured into the encapsulation container under vacuum or atmospheric pressure and then sealed.

[0097] Without altering the necessary structure of the first and second functional blocks, other phase change material encapsulation methods can be used in other embodiments.

[0098] Example 5

[0099] This embodiment provides a specific installation and usage method for a bridge pier fire protection system based on phase change materials as described in Embodiment 1. Specifically, as... Figure 11 As shown, it includes the following steps:

[0100] S1: Prefabricate multiple first function blocks and multiple second function blocks;

[0101] Before formal installation, all functional modules are manufactured and prepared at the factory. This includes:

[0102] According to the design drawings, the cement-based phase change composite material formula (e.g., 25% mPCM, 40% sulfoaluminate cement, etc.) described in Example 1 is used to produce the required quantity and precise size of the first and second functional blocks, which are equipped with self-locking structures (such as wedge structures, interlocking platforms), limit rope through holes and slot structures, by casting, vibrating and curing in molds.

[0103] Prepare the outer protective layer module, the dry powder required for the expansion adhesive layer, the limiting components, and all kinds of fasteners required for installation.

[0104] S2: Apply an expansion bonding layer evenly to the outer surface of the bridge pier column;

[0105] Clean the outer surface of the bridge piers that require protection, removing dust, oil, and loose concrete. If the pier surface is too smooth, it can be roughened or treated with a concrete bonding agent to enhance the adhesion of the expansion bond layer.

[0106] According to the predetermined ratio, the dry powder of the expansion bonding layer is mixed with water and stirred evenly to form a slurry. Then, the slurry is evenly applied to the treated outer surface of the pier column.

[0107] S3: Multiple first functional blocks and multiple second functional blocks are joined together in a ring on the surface of the expansion adhesive layer to form a functional ring;

[0108] Starting from the bottom of the pier, while the expansion bonding layer is still in a plastic state, take the prefabricated first and second functional blocks, and press their inner arc surfaces tightly onto the surface of the expansion bonding layer. Using the self-locking structure between the functional blocks, the first and second functional blocks are staggered and spliced ​​along the circumference of the pier until a complete and closed functional ring is formed.

[0109] If the design uses limiting ropes for axial limiting, then when splicing the first functional ring, the bottom ends of multiple limiting ropes need to be pre-anchored to the bottom limiting anchor, and the ropes should be passed through the pre-reserved through holes in the functional block from bottom to top.

[0110] S4: Following step S3, splice multiple functional rings along the axial direction of the bridge pier column to complete the installation of the functional layer;

[0111] Following the method in step S3, continue assembling new functional rings above the already installed functional rings. The pre-set slot structures at the top and bottom of the functional blocks can be used for alignment, ensuring the alignment and overlap between the upper and lower functional rings. Continue stacking and assembling ring by ring from bottom to top until the designed protective height is reached, completing the installation of the entire functional layer.

[0112] After all functional rings are installed, the top of the limiting rope passing through all functional blocks is connected to the top limiting anchor, and the designed preload is applied to the limiting rope using a dedicated tensioning device. Once the preload is reached, the limiting anchor is locked, completing the application of axial prestress to the entire functional layer.

[0113] S5: Install an outer protective layer on the outside of the functional layer.

[0114] Alternatively, if the design includes an insulation layer, the insulation material (such as aerogel felt) is first tightly wrapped around the outside of the functional layer.

[0115] Assemble the outer protective layer. Fit the semi-circular outer protective layer module around the functional layer (or insulation layer). Align the pre-set angle steel flanges on both sides of the module, insert high-strength, high-temperature resistant bolts, and tighten them alternately and evenly to the specified torque using a torque wrench to ensure the outer protective layer can tightly and firmly restrain the internal structure. If there are bolts connecting the functional blocks to the outer protective layer, these should also be fixed in this step.

[0116] At this point, the entire fire protection system for bridge piers based on phase change materials has been installed. Modular prefabrication and efficient on-site assembly ensure installation quality and enable the fire protection system to achieve the desired technical effects.

[0117] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A fire protection system for bridge piers based on phase change materials, characterized in that, include: The functional layer (2) is wrapped around the outside of the bridge pier column and is bonded to the column by an expansion adhesive layer (1); An outer protective layer (3) is fitted around the functional layer (2) to radially limit the functional layer (2) and provide mechanical protection; The functional layer (2) includes a plurality of functional rings (21) arranged axially. The functional ring (21) is composed of multiple first functional blocks (211) and multiple second functional blocks (212) arranged in a staggered manner and spliced ​​together in a ring, and there is a self-locking structure between adjacent first functional blocks (211) and second functional blocks (212); The self-locking structure includes a first wedge block (221); The first wedge block (221) is disposed on both sides of the first functional block (211), and the second functional block (212) is provided with a first wedge groove (222) corresponding to the first wedge block (221) on both sides. Both the first functional block (211) and the second functional block (212) are encapsulated with phase change materials.

2. The bridge pier fire protection system based on phase change materials according to claim 1, characterized in that, The first functional block (211) is provided with a first fastening platform (223) on both sides, and a second wedge block (225) is provided on the first fastening platform (223); The second functional block (212) is provided with a second fastening platform (224) corresponding to the first fastening platform (223), and the second fastening platform (224) is provided with a second wedge groove (226) corresponding to the second wedge block (225).

3. The bridge pier fire protection system based on phase change materials according to claim 1, characterized in that, The functional layer (2) also includes a limiting component (23) for axially limiting the plurality of the functional rings (21). Multiple limiting components (23) are uniformly arranged circumferentially along the functional layer (2), and each limiting component (23) includes: Two limiting anchors are respectively located at both ends of the axial direction of the functional layer (2); A limiting rope connects the two limiting anchors; The first functional block (211) and the second functional block (212) are both provided with through holes that cooperate with the limiting rope.

4. The bridge pier fire protection system based on phase change materials according to claim 1, characterized in that, Both the first functional block (211) and the second functional block (212) are made of cement-based phase change composite material.

5. The bridge pier fire protection system based on phase change materials according to claim 4, characterized in that, The raw materials for the cement-based phase change composite material include: mPCM powder, sulfoaluminate cement, quartz sand, PVA fiber, admixtures, and water.

6. The bridge pier fire protection system based on phase change materials according to claim 5, characterized in that, The mixing ratio of the cement-based phase change composite material is as follows, by weight: 25% mPCM powder, 40% sulfoaluminate cement, 30% quartz sand, 1.5% PVA fiber, 0.5% polycarboxylate superplasticizer, and a water-cement ratio of 0.

35.

7. The bridge pier fire protection system based on phase change materials according to claim 1, characterized in that, The bridge pier fire protection system also includes a heat insulation layer (4) located between the functional layer (2) and the outer protective layer (3), the heat insulation layer (4) being used to reduce heat transfer and provide protection for the functional layer (2).

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