A method for rapidly repairing a marine pier based on self-excitation prestressed 3DTRC

Abstract

The application discloses a bridge pier repairing method based on self-excitation prestress 3DTRC, which comprises the following steps: 1) cleaning the bridge pier to be repaired; 2) coating a first magnesium phosphate / iron aluminate cement composite slurry on the surface after cleaning; 3) arranging a three-dimensional netted heat-shrinkable fiber fabric on the surface of the uncured first magnesium phosphate / iron aluminate cement composite slurry, and prefilling a first iron aluminate cement modified magnesium phosphate cement powder or pouring a second iron aluminate cement modified magnesium phosphate cement slurry prepared on site in the three-dimensional netted heat-shrinkable fiber fabric; 4) self-compacting under heat excitation; and 5) hardening and self-compacting under water injection or water containing in the composite cement net slurry to complete the bridge pier repairing. The self-excitation prestress repairing system based on the fast-hardening magnesium phosphate cement / iron aluminate cement composite cement and the heat-shrinkable three-dimensional spacing fabric generates the prestress in situ in the constructed repairing body, thereby promoting the realization of the repairing and reinforcing double targets of the bridge pier, and the application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering concrete structure repair and protection technology, specifically involving a rapid repair method for marine bridge piers based on self-excited prestressed 3DTRC. Background Technology

[0002] Bridge piers in marine environments are subjected to multiple harsh effects over long periods, including chloride ion corrosion, sulfate corrosion, wet-dry cycles, and wave-carried sand erosion. This easily leads to problems such as concrete cover peeling and steel reinforcement corrosion, seriously threatening structural safety and service life. Repair work in this area is strictly limited by the tidal cycle, with a very short low-tide construction window (typically only 2-4 hours). Existing repair techniques mostly use ordinary or high-performance concrete, which suffers from slow setting and hardening, low early strength, insufficient bond with old concrete, and poor corrosion resistance, making effective repairs impossible within the window period. Repairs often fail because the repaired structure is submerged in seawater before it has fully hardened, creating new weak points in durability.

[0003] There is an urgent need to develop an integrated rapid repair technology that can adapt to ultra-short construction windows, possess ultra-early strength, high corrosion resistance, strong adhesion, and actively improve the long-term service performance of bridge piers. Summary of the Invention

[0004] This invention aims to address the challenges and shortcomings of short construction windows in marine tidal zones, weak bonding at traditional repair interfaces, and easy failure at fabric joints. It provides a repair method that is quick to construct, has excellent performance, and can provide continuous active reinforcement to bridge piers after repair. The method utilizes a three-dimensional fabric composite material (3DTRC) system based on rapid-hardening magnesium phosphate cement / aluminoferrite cement composite cement and heat-shrinkable three-dimensional spacer fabric to generate prestress in situ within the constructed repair body, thereby promoting the dual goals of repairing and strengthening bridge piers.

[0005] To achieve the above solution, the technical solution adopted by the present invention includes: A bridge pier repair method based on self-excited prestressed 3DTRC includes the following steps: 1) Clean the bridge piers to be repaired; 2) Apply the first magnesium phosphate / aluminoferrite composite cement slurry to the cleaned surface; 3) A three-dimensional mesh heat-shrinkable fiber fabric is set on the surface of the uncured first magnesium phosphate / aluminate iron composite cement slurry, and the three-dimensional mesh heat-shrinkable fiber fabric is pre-filled with the first magnesium phosphate / aluminate iron composite cement powder or the second magnesium phosphate / aluminate iron composite cement slurry mixed on site is poured in. 4) Thermally activated self-compacting; Water spraying was used to activate the three-dimensional mesh heat-shrinkable fiber fabric of pre-magnesium phosphate / aluminoferrite composite cement powder, which underwent hydration hardening and self-compacting molding under sprayed water conditions to complete the bridge pier repair. A three-dimensional mesh heat-shrinkable fiber fabric for the magnesium phosphate / aluminate iron composite cement slurry mixed on-site was used to hydrate, harden, and self-compact under water-containing conditions in the composite cement slurry to complete the bridge pier repair.

[0006] In the above scheme, the three-dimensional mesh heat-shrinkable fiber fabric includes a three-dimensional mesh heat-shrinkable spacer fabric matrix and a water-soluble PVA nonwoven fabric disposed on one side close to the structure to be repaired (the side in contact with the pier to be repaired), and a water-permeable and slurry-resistant heat-shrinkable fiber nonwoven fabric encapsulation layer disposed on the other side opposite it; the four edges of the three-dimensional mesh heat-shrinkable fiber fabric are sealed by heat-pressing fusion or sewing to prevent leakage of the internal filling powder or injected slurry.

[0007] Furthermore, steps 3) and 4) can be carried out in stages according to the working conditions, with differentiated processes adopted based on the depth of damage to the bridge pier surface: a. For shallow damage (depth ≤ 2cm) on the interface to be repaired; a repair process of pre-filled composite cement powder + water spray activation is adopted; the bridge pier is covered with the resulting flexible fabric board after pre-filling aluminoferrite / magnesium phosphate composite cement dry powder in a three-dimensional mesh heat shrinkable fiber fabric, and then external water spray is performed to induce hydration and complete the repair. b. For deep damage (depth > 2cm) on the surface to be repaired: a temporary formwork + on-site grouting repair process is adopted, specifically including the following steps: except for the grouting surface (top surface) reserved by 3DTRC and the surface to be repaired in contact with the pier, the other surfaces of the three-dimensional fabric are sealed with heat-shrinkable fiber non-woven fabric; the above-mentioned pre-treated three-dimensional mesh fiber fabric is wrapped around the area of ​​the concrete pier to be repaired, and a high-rigidity formwork is used for temporary support, and the bottom of the formwork is sealed to avoid bursting and leakage of grout during grouting; then magnesium phosphate / aluminoferrite Composite cement is mixed with water on-site to form a slurry. This slurry has a setting time of 30-90 minutes (adjustable), high fluidity, and self-compacting properties. It can be fully poured into the repair cavity formed between the three-dimensional mesh heat-shrinkable fiber fabric that surrounds the bridge pier and the pier. After the 3DTRC has hardened rapidly and reached a strength of 40.0 MPa or higher (generally 2-3 hours), the temporary fixing template is removed (the heat-shrinkable fiber non-woven fabric on the outer surface of the 3DTRC can prevent the cement-based slurry from overflowing and avoid the modified magnesium phosphate cement slurry from sticking to the template) so that it can be reused and the repair work can be completed quickly.

[0008] During the self-compacting molding process described above, the resulting composite material system automatically enters the intelligent response stage; the hydration and heat release of the introduced cementitious material triggers the shrinkage of the heat-shrinkable fibers, forming pre-compression stress inside the set repair layer, and transforming it into radial hoop constraint force on the bridge pier concrete through the bonding interface between the repair layer and the bridge pier concrete; the entire system can obtain sufficient strength to resist tidal erosion within minutes to hours, completing rapid repair.

[0009] In the above solution, the cleaning steps include roughening and washing.

[0010] Furthermore, the cleaning process also includes removing rust from exposed steel bars.

[0011] In the above scheme, when the three-dimensional mesh heat shrinkable fiber fabric is wrapped around the bridge pier, its seams are connected by a zipper-like structure. The specific operation of the zipper-like structure is as follows: the edges of both ends of the fabric are pre-made into complementary teeth (such as rectangular teeth), interlocked on site, and then sewn and fixed with high-strength fiber thread (such as PBO thread). Subsequently, the modified cement slurry is applied to the sewn area for sealing.

[0012] In the above scheme, the magnesium phosphate / aluminate iron cement comprises magnesium phosphate cement component and aluminate iron cement, with aluminate iron cement accounting for 25-45% of the total mass of the composite cement (aluminate iron cement + magnesium phosphate cement component).

[0013] Furthermore, the ferroaluminate cement is a high-ferroaluminate sulfoaluminate cement, which possesses rapid hydration and exothermic properties, and has a specific surface area ≥350 m². 2 / kg, Fe2O3 mass percentage is 5-15wt%; the magnesium phosphate cement component contains calcined magnesium oxide and phosphate (potassium dihydrogen phosphate or ammonium dihydrogen phosphate), and the magnesium-phosphorus molar ratio is 4-8:1.

[0014] Furthermore, the magnesium phosphate / aluminoferrite composite cement also contains a retarder (borax, calcium lactate, etc.), with an external admixture percentage of 0.2-5.0% (preferably 1.5-3.0%).

[0015] Furthermore, the magnesium phosphate / aluminoferrite composite cement also contains an early strength agent (such as lithium salt early strength agent), with an external admixture mass percentage of 0.1-1.0% (preferably 0.2-0.5%).

[0016] Furthermore, the water-cement ratio of the first magnesium phosphate / aluminate ferrophosphate composite cement is higher than that of the second aluminate ferrophosphate cement modified magnesium phosphate cement.

[0017] Furthermore, the water-cement ratio of the first magnesium phosphate / aluminate iron composite cement is 0.16-0.20 to ensure that the grout has good substrate wettability and permeability; the water-cement ratio of the second magnesium phosphate / aluminate iron composite cement (as the grouting repair body) is 0.13-0.15 to ensure that sufficient heat peaks are generated during grout hydration to stimulate fabric shrinkage and obtain high early strength.

[0018] Furthermore, the first magnesium phosphate / aluminate ferrophosphate composite cement paste is applied to the surface of the bridge pier (concrete matrix and reinforcing steel) within 20 minutes after preparation. The applied paste mainly plays a triple role: a) as a super strong interface adhesive; b) as an immediate protective layer for the reinforcing steel (rust-inhibiting primer for reinforcing steel); c) providing a good bonding substrate for subsequent 3DTRC; d) using the heat released by its rapid hydration as the initial heat source to stimulate the shrinkage of the subsequent three-dimensional mesh heat-shrinkable fibers, preventing insufficient heat shrinkage at the interface due to heat loss.

[0019] In the above scheme, the thickness of the coated magnesium phosphate / aluminate iron composite cement paste is 1-3 mm.

[0020] In the above scheme, the components and their weight percentages in the iron aluminate cement modified magnesium phosphate cement include: 55-75 parts magnesium phosphate cement component and 25-45 parts iron aluminate cement component.

[0021] Furthermore, the second aluminoferrite cement-modified magnesium phosphate cement slurry is injected into the three-dimensional mesh heat-shrinkable fiber fabric within 30 minutes after preparation.

[0022] In the above scheme, the thickness of the three-dimensional mesh heat-shrinkable fiber fabric is less than 5cm.

[0023] Furthermore, the thickness of the three-dimensional mesh heat-shrinkable fiber fabric is 0.5-5.0 cm (preferably 1.0-3.0 cm).

[0024] Furthermore, in the three-dimensional mesh heat-shrinkable fiber fabric, the average pore size of the water-permeable and slurry-resistant heat-shrinkable nonwoven sealing layer is 15-45 μm.

[0025] In the above scheme, the heat shrinkage trigger temperature of the three-dimensional mesh heat shrink fiber fabric is 55-80℃.

[0026] In the above scheme, the main spinning fiber used in the matrix of the three-dimensional mesh heat-shrinkable fiber fabric is heat-shrinkable polymer fiber, which can produce 5-15% linear shrinkage when the set heat shrinkage temperature is reached.

[0027] Furthermore, the heat-shrinkable polymer fiber material can be selected from one or more of the following: high-shrinkage polyester (PET, molecular weight 20,000~30,000; boiling water shrinkage rate ≥15%, dry heat shrinkage rate at 60℃ ≥5%), polypropylene (PP), and polyamide (PA).

[0028] Furthermore, the molecular weight of the polypropylene is 180,000-350,000; and the molecular weight of the polyamide is 20,000-50,000.

[0029] Furthermore, the heat-shrinkable polypropylene fiber (PP) possesses excellent alkali resistance (strength retention ≥95% after immersion in an alkaline solution at pH 13 for 72 hours) and low-temperature heat-shrinkage characteristics (5-10% area shrinkage at 60-80℃). The high-shrinkage polyester (PET) fiber undergoes alkali-resistant modification treatment and possesses heat-shrinkage properties that coordinate with the deformation of the three-dimensional mesh fabric (shrinkage rate ≥5% at 60-80℃), ensuring that the sealing layer can shrink synchronously with the skeleton during the heat-activated process, avoiding surface wrinkling or peeling.

[0030] Furthermore, the areal density of the three-dimensional mesh heat-shrinkable fiber fabric is 450-650 g / m³. 2 The porosity is >90%, and the total porosity is 80-95%.

[0031] Furthermore, the heat shrinkage rate of the water-permeable, slurry-blocking, heat-shrinkable fiber nonwoven fabric encapsulation layer is 15-25% (80℃×30min), the initial shrinkage temperature is 50-55℃ (to avoid accidental shrinkage under high summer temperatures), the maximum shrinkage temperature is 75-85℃ (matching the peak heat release of modified cement hydration), the air permeability is 120-150mm / s, the longitudinal tensile strength is ≥120N / 5cm, and the average pore size is 15-45μm (effectively blocking cement particles from overflowing).

[0032] Furthermore, the thickness ratio of the three-dimensional mesh heat-shrinkable spacer fabric matrix, the water-permeable and slurry-resistant heat-shrinkable fiber nonwoven fabric encapsulation layer, and the water-soluble PVA nonwoven fabric is (80-120):(23-25):1.

[0033] Furthermore, the method for preparing the three-dimensional mesh heat-shrinkable spacer fabric includes the following steps: 1) Preparation and low-temperature setting of three-dimensional mesh spacer fabric matrix: Industrial filaments of heat-shrinkable polymer fibers are used as warp and weft yarns, and high-modulus polymer monofilaments (selected from polypropylene PP, polyester PET, or polyamide PA monofilaments, with a diameter of 0.15-0.30 mm) are used as spacer yarns. The fabric is then woven in three dimensions on a double-needle bed Raschel warp knitting machine. The resulting fabric is then subjected to low-temperature relaxation heat setting treatment, with the setting temperature controlled at 100-110℃. This process fixes the fabric shape while maximizing the preservation of the fiber's heat shrinkage potential at higher temperatures (>55℃) in the future, resulting in a three-dimensional mesh spacer fabric matrix with heat-sensitive properties. 2) Preparation of functional nonwoven fabrics: Water-soluble PVA nonwoven fabric (dissolution temperature 20-40℃) was selected as the inner bonding layer material (close to the structure to be repaired); water-permeable and slurry-resistant heat-shrinkable fiber nonwoven fabric was selected as the outer sealing layer (water-facing side). 3) Composite packaging process: Using hot-pressing or needle-punching processes, water-soluble PVA nonwoven fabric and heat-shrinkable permeable and pulp-resistant nonwoven fabric are respectively laminated onto the contact pier surface and water-facing surface of the three-dimensional mesh spacer fabric matrix obtained in step 1); during the lamination process, the temperature is controlled to be lower than the shrinkage initiation temperature of the fibers, and finally an encapsulated three-dimensional mesh heat-shrinkable spacer fabric is obtained.

[0034] In the above scheme, when the three-dimensional mesh heat-shrinkable fiber fabric is wrapped around the bridge pier, its seams adopt a zipper-like connection method. First, the edges of both ends of the fabric are pre-made into complementary tooth shapes, which are interlocked and then sewn together with high-strength fiber threads (such as PBO or ultra-high molecular weight polyethylene threads with a molecular weight of 2 million to 6 million). Then, the iron aluminate cement modified magnesium phosphate cement slurry is applied to the sewn area for sealing. This can effectively solve the problems of stress concentration, alignment difficulties, and local wrinkles or uneven force transmission that may occur during heat shrinkage in traditional flat-edge overlaps, and construct an interlocking toothed overlap interface based on the zipper interlocking mechanism.

[0035] Furthermore, the specific construction steps of the zipper-like structure include: For the longitudinal edges of the two ends of the three-dimensional mesh heat-shrinkable fiber fabric used for connection, complementary serrated or wavy interfaces are pre-processed; that is, one end is a continuous convex tooth, and the other end is a groove that matches its shape and size. The tooth angle and height are designed in coordination with the fabric mesh size.

[0036] The above connection method enables the edges of the two ends of the fiber fabric to be precisely aligned and interlocked, which greatly increases the effective overlap area and mechanical interlocking force.

[0037] Furthermore, the specific connection construction process for the three-dimensional mesh heat-shrinkable fiber fabric includes: Step 1: Alignment and meshing; At the bridge pier site, the pre-treated edges of both ends of the three-dimensional fabric are aligned and meshed together to form a preliminary closed and tightly fitted ring structure.

[0038] Step 2: High-strength suture fixation; along the center line of the interlocking seam, use high-performance fiber thread (such as PBO or ultra-high molecular weight polyethylene thread) that is alkali-resistant and seawater corrosion-resistant to continuously suture or braid and lock, firmly binding the "teeth" and "groove" together; this step is completed before 3DTRC fixation and watering or grouting.

[0039] Step 3: Integrated sealing and reinforcement; immediately after suturing, apply a layer of aluminoferrite cement-modified magnesium phosphate cement grout to the interlocking area; the introduced grout can play the following roles: a) Penetration reinforcement: It penetrates into the suture holes and fabric interlocking gaps, and after curing, it forms a high-strength "adhesive nail", which significantly enhances the integrity and shear resistance of the interface area.

[0040] b) Active corrosion protection: This cement grout has excellent resistance to chloride ion penetration and chemical erosion, forming a seamless and permanent anti-corrosion sealing layer at the interface that is consistent with the properties of the repair body material, fundamentally eliminating the possibility of seawater intrusion from the interface.

[0041] c) Smooth stress transition: This ensures a smooth transition in stiffness between the interface area and the adjacent area, guaranteeing that the prestress can be transmitted uniformly and continuously during subsequent thermally activated shrinkage, forming a complete "hoop force ring".

[0042] The principles of this invention include: 1) Multifunctional composite cementitious materials: It is obtained by combining rapid-hardening magnesium phosphate cement (MPC) components with aluminoferrite cement (FAC), and the mechanism of action includes the following: Microstructure optimization and corrosion resistance: The amorphous hydrated calcium sulfoaluminate gel, C-(A)-SH gel, iron glue, and aluminum glue generated by the hydration of FAC components can effectively encapsulate and refine the struvite crystals, the main hydration product of MPC, filling pores and blocking seepage channels, fundamentally improving the compactness, water resistance, and abrasion resistance of the composite cementitious system; at the same time, these hydration products can chemically adsorb and solidify Cl in seawater. - SO4 2- Irreactive ions.

[0043] Built-in energy source and exciter: Unlike traditional silicate cement, which releases hydration heat slowly (usually requiring 10-24 hours to reach peak) and is susceptible to insufficient temperature rise due to environmental heat dissipation, the FAC component used in this invention has a "burst" concentrated heat release characteristic. It can rapidly release huge amounts of heat in a short time (e.g., 10-30 minutes) after contact with water, effectively overcoming the heat dissipation effect of the thin-walled repair layer and rapidly raising the internal temperature of the system to the fiber shrinkage threshold (55-80℃). This instantaneous high temperature is the key to driving the heat-shrinkable fiber to generate effective shrinkage and establish prestress during the plastic-hardening transition period of the slurry, effectively solving the technical problem that the thermal effect of traditional cement cannot trigger heat-shrinkable fabrics in a short time.

[0044] 2) Intelligent Response Enhancement Skeleton: It employs a three-dimensional continuous mesh fabric woven from heat-shrinkable high-modulus polymer fibers. The fabric is flexible and morphologically stable at room temperature. When the temperature rises to its designed trigger threshold (e.g., 40-90℃), the fibers undergo molecular chain reconstruction, driving the entire mesh structure to produce significant macroscopic shrinkage and output high shrinkage force.

[0045] 3) Formation and dual / synergistic effects of endogenous thermally activated prestress 1. Thermal activation: When the cementitious material comes into contact with water, the rapid hydration and exothermic properties of the aluminoferrite cement (FAC) component cause the internal temperature of the 3DTRC to rise to the shrinkage trigger temperature of the fiber in a short time (e.g., 3-10 min).

[0046] Upon heating, the three-dimensional fabric undergoes uniform macroscopic shrinkage, generating a strong shrinkage force. At this time, the MPC / FAC composite cement paste has already formed a high-strength hardened body through early hydration, and forms a strong interfacial transition zone with the fiber network through mechanical interlocking and chemical bonding. This strong interface acts as a crucial stress transfer bridge, efficiently transferring the shrinkage force and producing a dual synergistic effect: On the one hand (internal self-compacting): the shrinkage force is transferred to the hardened repair layer body and transformed into uniform pre-compression stress. This stress can significantly refine the internal pore structure of the cement stone and heal micro-defects, which is conducive to the self-compacting of the material, thereby greatly improving the repair layer's impermeability, corrosion resistance and impact resistance.

[0047] On the other hand (active external confinement): through the radial contraction of the entire repair layer, the force is transferred to the internal pier structure to be repaired, forming an active radial "confinement constraint force". This constraint force can effectively limit the lateral deformation of the pier concrete and inhibit the propagation of existing cracks, thereby significantly improving the integrity, bearing capacity and seismic performance of the pier.

[0048] Compared with the prior art, the beneficial effects of the present invention include: 1. A novel technical approach was first proposed and implemented, which utilizes the heat of hydration of the cementitious material itself as an energy source to stimulate the shrinkage of intelligent fibers, thereby establishing prestress in situ within the composite material and on the structure to be repaired. This approach is significantly different from existing repair techniques that require external tensioning or heating.

[0049] 2. Collaborative design and functional integration of the material system: The rapid-hardening magnesium phosphate cement / aluminoferrite cement composite cement is endowed with the dual functions of microstructure modifier and internal prestressing excitation source. Combined with the rapid-hardening characteristics of magnesium phosphate cement and the intelligent response of heat-shrinkable fiber, an intelligent composite material system with self-driving and self-reinforcing properties is formed.

[0050] 3. Dual performance enhancement path: The generated prestress not only acts directly on the repair material to achieve self-compactment, but also acts on the bridge pier and other structures to be repaired to generate active hoop reinforcement; the mechanism can improve the performance at both the microscopic and macroscopic levels of the material and the component, significantly improving the repair effect.

[0051] 4. Extremely simple and efficient construction: It provides two flexible construction solutions, namely pre-filled powder and on-site grouting, neither of which requires complex procedures such as traditional rebar installation and steel mesh binding; the entire process can be completed within a single low tide period (usually 3-6 hours), effectively solving the time window problem of tidal zone repair.

[0052] 5. Constructing long-term and proactive protection capabilities: Forming a multi-dimensional protection system based on strong interfacial bonding, steel bar passivation protection, high corrosion resistance of the repair body, and active constraint on the structure to be repaired, which can significantly inhibit the development of defects and greatly extend the service life of the repaired bridge piers. Attached Figure Description

[0053] Figure 1 A schematic diagram of a concrete bridge pier repaired with 3DTRC sleeves.

[0054] Figure 2 This is a schematic diagram of the zipper-type interface structure and connection structure of the three-dimensional fabric of the present invention; wherein, (a) is the complementary tooth shape prefabricated at the edge of the interface; (b) is the physical interlocking and alignment of the fabrics on both sides; (c) is the mechanical sewing and locking using high-strength fiber thread; and (d) is a schematic diagram of the chemical sealing and reinforcement state after applying modified slurry. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] The raw material specifications used in the following embodiments are as follows: Calcinated magnesium oxide (MgO): Calcination temperature 1500℃, specific surface area 350m² 2 / kg, average particle size 45μm, activity time 90s; Potassium dihydrogen phosphate (KH2PO4): industrial grade, white crystalline powder, purity ≥98%; Ferroaluminate cement (FAC): selected ferric sulfoaluminate cement (Fe2O3 mass percentage approximately 10wt%), 42.5 rapid hardening grade, initial setting time 15min, specific surface area 380m² 2 / kg; Retarder: Borax, purity ≥99%.

[0057] In the following embodiments, the three-dimensional mesh heat-shrinkable spacer fabric matrix used was prepared using the following process: 1) Raw material selection: The warp and weft yarns are made of commercially available high-shrinkage modified polyester (PET) industrial filament (purchased from Jiangsu Hengli Chemical Fiber Co., Ltd., product model: HSP-1000, specification 1000D / 192F, boiling water shrinkage rate 45-50%), utilizing its high shrinkage force generated by heating; the spacer yarn (Z-direction yarn) is made of commercially available high-modulus polypropylene (PP) monofilament (Sinopec, grade Y2600, diameter 0.18-0.25mm, tensile modulus ≥3.5GPa) to provide excellent compressive support. 2) Three-dimensional knitting: The knitting is carried out using an E22-level double-needle bed Raschel warp knitting machine, employing a "1-through-1-gap" yarn threading method to form a large mesh structure on the surface; the ground comb uses a combination of chain knitting and weft weft weaving, and the middle comb bars (spacer yarns) use a "V" shaped interlacing to connect the upper and lower surfaces; the knitting density is controlled as follows: longitudinal density 10-12 rows / cm, transverse density 14-16 rows / cm; the fabric thickness is controlled to 15±1mm by adjusting the warp feed; 3) Low-temperature pre-setting: The fabric is passed through a setting machine, and the pre-setting temperature is set to 100-110℃ (lower than the conventional 160℃ setting temperature to preserve the shrinkage potential of the fibers), with a processing time of 60 seconds; The fabric prepared by the above process can rapidly generate an area shrinkage rate of 8-12% when exposed to a heat source above 60°C, effectively matching the hydration exothermic peak value of the modified cement described in this invention.

[0058] The preparation method of the magnesium phosphate / aluminoferrite composite cement powder and slurry includes the following steps: 1) Dry material premixing: Weigh the calcined magnesium oxide, potassium dihydrogen phosphate, aluminoferrite cement and retarder (borax) according to the designed mass ratio; place the above dry powder components in a mechanical mixer and dry mix for 3-5 minutes in an anhydrous environment until the powder color is uniform, to obtain composite cement dry material (magnesium phosphate / aluminoferrite composite cement powder). 2) Slurry preparation: Add the measured water (according to the set water-cement ratio) to the mixing pot, turn on the mixer at low speed, and slowly add the composite cement dry material obtained in step 1). Mix at low speed (200-500 r / min) for 30-60s, then switch to high speed (1000-2000 r / min) for 90-120s until a uniform slurry (magnesium phosphate / aluminoferrite composite cement slurry) with good fluidity and no agglomerated particles is formed. It can be used for brushing or grouting immediately. Example 1

[0059] A bridge pier repair method based on self-excited prestressed 3DTRC is proposed for shallow surface defects (depth ≤ 2cm) of bridge piers in marine splash zones. The specific working conditions are as follows: the bridge pier to be repaired is located in an area with frequent tidal rise and fall, and there is a large area of ​​spalling of the surface concrete protective layer, with an average spalling depth of about 15mm, and the reinforcement has not yet been deeply exposed; the construction window is only 3 hours during low tide. A rapid and lightweight repair solution is proposed to address the above operating conditions. The specific repair steps include: 1) Material preparation: Matrix formulation: Magnesium phosphate / ferroaluminate composite cement (MPC-FAC) system is adopted; wherein, the MPC component (molar ratio of reburned magnesium oxide: potassium dihydrogen phosphate = 4:1) accounts for 70%, and FAC (high iron sulfoaluminate cement) accounts for 30%; 2.0% borax retarder is further added; and the magnesium phosphate / ferroaluminate composite cement is mixed evenly. Fabric components: A three-dimensional mesh heat-shrinkable spacer fabric matrix with a thickness of 15mm is selected (preparation method is the same as above); Flexible panel prefabrication: In the factory, the obtained MPC-FAC dry powder is uniformly filled into the fabric gaps using a vibrating table, controlling the powder filling density to be 1.2-1.4 g / cm³. 3 (That is, for a 15mm thick fabric, the filler surface density is approximately 18-21kg / m²) 2 This ensures that the internal void filling rate of the fabric reaches over 95%. The inner side of the fabric (contacting the bridge pier surface) is hot-pressed with a layer of commercially available water-soluble PVA nonwoven fabric (20℃ cold water quick-dissolving type, surface density 30-45g / m²). 2 (Supplied by Kuraray Co., Ltd. of Japan), with a thickness of 0.1~0.2mm; The outer surface (water-facing side) is hot-pressed with a layer of commercially available permeable and pulp-resistant PP nonwoven fabric (areal density 60-80g / m²). 2 With an average pore size of 30-50μm and a thickness of 0.3-0.5mm, this product is supplied by Shandong Taian Lude Engineering Materials Co., Ltd. (heat-shrinkable type, made of polypropylene, density 80g / m³). 2Meanwhile, the PP nonwoven fabric has heat shrinkage characteristics that match the internal skeleton (shrinkage rate of 6~10% at 80℃), to ensure that it can shrink synchronously with the three-dimensional fabric skeleton during the heat excitation process and avoid surface wrinkling. After the upper and lower layers of nonwoven fabric are laminated, the edges of the fabric board are fused and sealed using a hot pressing process to create a closed pre-filled powder flexible board. Then, the edges of the two ends of the pre-made flexible board to be connected are cut into complementary serrations (50mm wide and 30mm deep) to form a zipper-like interface.

[0060] 2) On-site construction steps: Surface preparation: Use a high-pressure water gun to clean the marine organisms and loose layer on the surface of the bridge pier, and then apply a layer of MPC-FAC interface grout (water-binder ratio 0.18) with a thickness of about 1.0~2.0 mm to act as an adhesive and sealant for the underlying layer.

[0061] Encasing application: While the interface slurry is wet, the obtained flexible plate is wrapped around the surface of the bridge pier to be repaired; wherein, the inner PVA non-woven fabric dissolves rapidly after contacting the wet interface, allowing the dry powder to come into direct contact with the interface layer. Interface connection: The two ends of the flexible plate are engaged with teeth and quickly sewn together with PBO high-strength thread for fixation.

[0062] Water spray activation: Fresh water is continuously sprayed onto the outer surface of the powder board using an atomizing spraying device (designed water-to-binder ratio of 0.15); the water penetrates through the outer PP non-woven fabric, activating the internal dry powder. Hydration hardening and self-compacting molding are carried out under the sprayed water conditions to complete the bridge pier repair.

[0063] The specific implementation effects of this embodiment include the following: Thermal activation: Within 5 minutes after water spraying, a violent hydration reaction occurred inside the board, and the monitored temperature rose to 68°C, successfully triggering the thermal shrinkage of the fabric.

[0064] Self-compacting: The normal compressive force generated by the shrinkage of the fabric tightly presses the slurry onto the surface of the bridge pier, eliminating the need for vibration.

[0065] Rapid hardening: The repair layer initially sets within 10 minutes, reaches a compressive strength of 28.5 MPa after 2 hours, and an interfacial bond strength of 4.4 MPa. It already possesses sufficient erosion resistance before being submerged by high tide.

[0066] Durability: Tests show that its chloride ion diffusion coefficient is only 0.15 × 10⁻⁶ after 90 days. -12 m 2 / s (significantly better than ordinary marine concrete), and no early shrinkage microcracks were observed on the surface, confirming the system's excellent resistance to seawater erosion and impermeability. Example 2

[0067] A bridge pier repair method based on self-excited prestressed 3DTRC is proposed to address the repair requirements of deep structural damage (depth > 2cm) or severe exposed rebar. The specific working condition is as follows: the bridge pier to be repaired has been hit by a ship and has been corroded for a long time, with local deep concrete loss (depth about 50mm), and the rebar is completely exposed and corroded. The cross section needs to be restored and the structure reinforced. The specific repair steps include: 1) Material preparation: Matrix formulation: The proportion of aluminoferrite cement (FAC) in the magnesium phosphate / aluminoferrite composite cement described in Example 1 is adjusted to 40% to ensure sufficient and uniform heat transfer in thicker sections; The water-cement ratio of magnesium phosphate / aluminoferrite composite cement was set at 0.14, and it was prepared on-site as a highly fluid slurry.

[0068] Fabric assembly: A hollow, heat-shrinkable, three-dimensional spacer fabric is selected (the difference from Example 1 is that it is not filled with composite cement powder), and the thickness specification matches the depth of the defect.

[0069] Interface prefabrication: It also uses a factory-prefabricated zipper-style interface design with complementary tooth profiles.

[0070] 2) On-site construction steps: Base surface and reinforcement treatment: Remove loose concrete and perform simple rust removal on exposed reinforcement.

[0071] Functional primer: Apply a thick layer of MPC-FAC mortar with the same proportion as in Example 1 to the surface of old concrete and reinforcing steel (but control the coating thickness to 2.0~3.0mm to enhance the rust-inhibiting effect); utilize its phosphating effect to convert the residual rust on the surface of the reinforcing steel into a passivation film, achieving rust removal-free or weak rust removal construction.

[0072] Enclosure installation: Install three-dimensional fabric, perform toothed interlocking and PBO thread stitching at the seams, and apply high-viscosity MPC-FAC slurry (using the same solid components as the grouting material, but adjusting the water-to-binder ratio to 0.10-0.12 to ensure thixotropic non-sagging) to seal the seams.

[0073] Grouting: Install lightweight, segmented templates (such as fiberglass templates) on the outside of the fabric and seal the bottom; pump the above-mentioned high-fluidity grout (water-to-binder ratio of 0.14) into the cavity until the grout fills the cavity and slightly overflows from the top, using the grout's own weight to achieve self-compactment.

[0074] The bridge pier was repaired by hydration hardening and self-compacting under water conditions introduced by the high-fluidity MPC-FAC slurry, and the temporary formwork was removed.

[0075] The specific implementation effects of this embodiment include the following: Thermo-mechanical coupling: The heat release peak is reached about 20 minutes after the slurry is injected, with the core temperature reaching as high as 78°C. At this time, the slurry is in a plastic state, and the fabric shrinks strongly when heated.

[0076] Bidirectional reinforcement: The shrinkage force of the fabric squeezes the slurry inward on the one hand, expelling internal air bubbles (self-compacting effect), making the hardened repair extremely dense; on the other hand, it forms a radial active hoop prestress of up to 3.1MPa on the bridge pier.

[0077] Mechanical properties: After 3.5 hours of demolding, the compressive strength reaches 38MPa (and can reach more than 85MPa in the later stage). The interface between the old and new parts exhibits the "parent body fracture" mode, indicating that perfect structural integration has been achieved.

[0078] Repair layer durability: Tests showed that its chloride ion diffusion coefficient was as low as 0.12 × 10⁻⁶ days. -12 m 2 / s, the mass loss rate after 72 hours of simulated wave-driven sand erosion was only 0.6%, which confirms the system's excellent resistance to seawater erosion and wear in deep restoration. Example 3

[0079] A bridge pier repair method based on self-excited prestressed 3DTRC is proposed for large-diameter bridge piers (e.g., diameter > 2m) that cannot be wrapped with a single sheet of fabric. The specific working condition is as follows: the diameter of the bridge pier to be repaired is 2.5m, the width of a single sheet of three-dimensional fabric is insufficient to wrap around the pier, and there is severe peeling of the protective layer (depth > 2cm). The specific repair steps include: 1) Material preparation: The same MPC-FAC grouting material system as in Example 2 is used; 3 heat-shrinkable three-dimensional fabric sheets are selected, each with a width of about 2.8m (allowing for shrinkage and splicing allowance).

[0080] Interface prefabrication: In the factory, the edges of three pieces of fabric are cut into complementary rectangular teeth (50mm wide and 30mm deep) to form a zipper tooth structure.

[0081] On-site construction steps: Surface preparation: After roughening, apply MPC-FAC interface paste to the entire surface (the coating thickness is controlled at 1.0~2.0mm to ensure sufficient wetting of the interface).

[0082] Splicing sleeve: Three pieces of fabric are spliced ​​together on the surface of the bridge pier in sequence; at each seam, the teeth are interlocked and a handheld electric sewing machine is used with 1mm PBO (poly-p-phenylenebenzodioxazole) high-strength thread to make a continuous Z-shaped stitch to form a closed ring sleeve.

[0083] Joint sealing: Apply high-viscosity MPC-FAC slurry (same as in Example 2) to the three longitudinal joints, covering a width of 100mm and a thickness of 2mm, so that it penetrates into the seam gaps and forms a "chemical pin".

[0084] Formwork support and grouting: Segmented formwork is set up on the outside, and high-fluidity MPC-FAC grout is poured in (same as in Example 2). The grouting volume is controlled at 1.05 to 1.10 times the theoretical repair cavity volume. During construction, the grout is continuously pumped until the cavity is completely filled and slightly overflows from the top of the formwork to ensure that no air bubbles remain.

[0085] The bridge pier was repaired by hydration hardening and self-compacting under water conditions introduced by the high-fluidity MPC-FAC slurry.

[0086] Implementation Results: The exothermic hydration of the slurry (peak temperature 75℃) induces fabric shrinkage. Due to the use of a zipper-like interlocking assembly method, the stress at the three seams is uniform, and the slippage, opening, or localized bulging common in traditional overlapping methods is avoided. After demolding, the repair layer forms a perfect integral ring, and the tensile strength at the seams reaches over 90% of the fabric's inherent strength. Example 4

[0087] A bridge pier repair method based on self-excited prestressed 3DTRC is proposed for low-temperature construction environments. The specific working conditions are as follows: the construction environment temperature is 5℃ (winter splash zone), the sea wind is strong, and the tide is about to rise, and the repair needs to be completed within 3 hours. The specific repair steps include: 1) Material Adjustment: To counteract the inhibition of chemical reactions by the low temperature environment and ensure that the fabric shrinkage threshold (55℃) is reached, the MPC-FAC matrix formulation is adjusted: the proportion of aluminoferrite cement (FAC) in the cementitious material is increased to 45%, and an additional 0.5% of lithium salt early strength agent is added. A temporary insulating film (PE film) is wrapped around the outside of the fabric to reduce the heat being carried away by the cold air.

[0088] Construction steps: Use the same "pre-filled powder board" process as in Example 1 (suitable for shallow repair). Implementation results:

[0089] After activation by water spray, despite the ambient temperature being only 5°C, the core temperature of the repair layer rapidly climbed to 62°C within 15 minutes thanks to the high hydration heat release of FAC and the heat preservation of the PE film, successfully triggering the thermal shrinkage of the fabric.

[0090] The repair layer fully sets within 40 minutes, and its compressive strength reaches 32 MPa after 2 hours. In contrast, ordinary repair mortar typically requires more than 24 hours to fully set at 5°C, failing to meet the tidal window requirements. Comparative Example 1

[0091] A traditional epoxy mortar repair method (no heat shrinkage, no MPC-FAC) uses commercially available high-performance marine epoxy repair mortar, applied manually, without an internal three-dimensional fabric skeleton.

[0092] The results show that the traditional epoxy mortar repair method has problems such as slow construction, strict water control (epoxy is afraid of water) and long curing time. Comparative Example 2

[0093] A common 3DTRC repair method (without heat shrinkage and no internal heat) is constructed in a manner similar to that of Example 1, except that a non-heat shrinkable ordinary polyester three-dimensional spacer fabric is used and ordinary magnesium phosphate cement is used for filling (without FAC and low heat release).

[0094] Construction results show that the introduced fiber fabric only plays a passive restraint role and cannot generate active prestress (the measured radial prestress is about 0 MPa); and the interface lacks high temperature excitation and physical clamping force, and the interface bonding strength is only 1.8 MPa (far lower than the 4.4 MPa described in Example 1), resulting in a limited increase in the ultimate bearing capacity of the pier (only about 22%). Comparative Example 3

[0095] A single hydration heat repair method (with endogenous heat but no chemical synergy); its application method is roughly the same as that of Example 1, except that the matrix material is replaced with rapid-hardening sulfoaluminate cement mortar (strength grade 42.5, water-binder ratio 0.35, with high hydration heat characteristics) and does not contain magnesium phosphate components.

[0096] Construction results show that although the heat of hydration of sulfoaluminate cement (peak temperature of approximately 65°C) successfully triggered fabric shrinkage, generating a similar radial clamping force, the interfacial bond strength was only 1.2 MPa (far lower than the 4.4 MPa described in Example 1) due to the lack of the unique acid-base chemical bonding and phosphate film mechanism of magnesium phosphate cement system. In long-term durability testing, the chloride ion diffusion coefficient was high due to the presence of microscopic weak zones at the interface. Comparative Example 4

[0097] A modified construction method based on the traditional overlapping interface (zipperless interface) is provided. The materials and processes are the same as in Example 2, but the three-dimensional fabric interface adopts the traditional overlapping method with an overlap width of 20cm, which is simply tied with wire.

[0098] Construction results show that: doubling the thickness at the overlap leads to uneven protective layer thickness; during heat shrinkage, slippage occurs at the overlap, resulting in severe prestress loss.

[0099] Table 1. Comparison of the effects of repaired bridge pier concrete structures in the examples and comparative examples.

[0100] Results Analysis (1) Analysis of interfacial bonding performance: The bond strength of the repaired structures obtained in Examples 1-4 all exceeded 4.0 MPa, and the failure mode was mostly "fracture of the old concrete matrix" rather than interfacial delamination. The bond strength of Comparative Example 1 (epoxy mortar) on the damp substrate decreased significantly (only 1.5 MPa); Comparative Example 2 (ordinary 3DTRC) lacked the physical bonding generated by thermal shrinkage and relied solely on chemical bonding, resulting in a lower strength (1.8 MPa).

[0101] This is based on the dual synergy of chemical penetration (forming "root" anchoring) of MPC-FAC slurry and physical clamping force (normal stress) generated by heat-shrinkable fabric.

[0102] (2) Analysis of the bearing capacity and seismic performance of bridge piers: The repaired structure obtained in Example 2 showed a 59% increase in load-bearing capacity and a ductility coefficient of 6.2 (indicating excellent seismic performance). Comparative Example 4, although using the same material system as this invention, only showed a +28% increase in load-bearing capacity. This is because slippage occurred at the lap joint during thermal shrinkage, resulting in a prestress loss exceeding 50%, demonstrating the necessity of the zipper-type interface for maintaining circumferential restraint.

[0103] Comparative Example 2 (without heat shrink) only has passive constraints, and the improvement is limited (+22%).

[0104] The above results show that the endogenous thermally activated prestressing mechanism constructed in this invention can effectively exert the "active confinement" effect; the prestress formed can effectively constrain the lateral expansion of the core concrete and delay failure.

[0105] (3) Durability (resistance to chloride ions and impact abrasion) analysis: Advantages of this invention: The chloride ion diffusion coefficient in the example group is as low as 0.12-1.4×10⁻⁶. -12 m 2 / s, with an impact and abrasion loss rate of less than 1%, exhibiting excellent resistance to chloride ion corrosion.

[0106] Mechanism support: Self-compacting effect: Fabric shrinkage compresses the unhardened slurry inside, expelling tiny air bubbles and refining the pore structure.

[0107] Chemical chlorination: FAC hydration products (such as ettringite) can chemically adsorb chloride ions, fundamentally blocking corrosion.

[0108] In comparison: Due to uneven heating, the repair layer of Comparative Example 3 (external heating source) was "tight on the outside and loose on the inside", with high internal porosity and poor durability (diffusion coefficient 4.2); Although Comparative Example 1 (epoxy mortar) was dense, it was prone to leakage channels due to poor bonding at the interface in a humid environment, and the epoxy material was not as resistant to impact and abrasion as inorganic cementitious materials.

[0109] (4) Environmental adaptability (low temperature environment) analysis: The performance of Example 4 at 5°C (strength, durability) is comparable to that of Example 1 at room temperature, proving that the "self-heating" mechanism achieved by adjusting the FAC ratio can completely overcome the impact of low temperature on construction quality, which is unmatched by traditional cold construction materials.

[0110] (5) Analysis of resistance to sulfate attack: Examples 1-4 all exhibited sulfate resistance ratings exceeding KS150 (no damage was observed at the end of the test). The hydration products (mainly struvite) of the introduced magnesium phosphate cement (MPC) component did not undergo an expansive reaction with sulfates, and the gel formed by the hydration of the FAC component was extremely dense. This invention introduces high-iron sulfoaluminate cement (FAC) to functionalize the magnesium phosphate cement system, constructing a unique "exothermic relay-chemical chlorination" synergistic mechanism, specifically including: 1. Exothermic Relay and Temperature Field Construction: In the initial stage of the reaction, the MPC component rapidly undergoes an acid-base reaction to generate the MKP crystal framework, providing ultra-early strength performance on an hourly basis and releasing the first wave of hydration heat. Subsequently, the FAC component is thermally activated under a heating environment, rapidly hydrating with the remaining water and releasing a second wave of concentrated heat. This "dual-source exothermic relay" effect effectively overcomes the heat dissipation problem of thin-layer repair, ensuring that the internal temperature of the system can stably reach the fiber shrinkage threshold.

[0111] 2. Microscopic Density and Chemical Chlorine Fixation: The abundant amorphous hydrated calcium sulfoaluminate gel, CSH gel, and unique iron-rich gel phase generated by FAC hydration fill the voids in the MKP crystal framework, forming a dense "gel-encapsulated crystal" structure. More importantly, the iron-rich gel phase has excellent chloride ion binding capacity, enabling it to adsorb and solidify corrosive ions in seawater in situ, thus endowing the repair layer with marine environmental adaptability surpassing that of traditional MPC materials. In contrast, Comparative Example 1 (ordinary repair mortar) and Comparative Example 3 (simple sulfoaluminate system) exhibit corrosion resistance of only around KS90 under sulfate attack due to the secondary expansion or interfacial exfoliation of ettringite.

[0112] (6) Analysis of chloride ion permeation resistance (90d diffusion coefficient): The chloride ion diffusion coefficient of Example 2 of this invention is as low as 0.12 × 10⁻⁶. -12 m 2 / s, reaching the impermeability level of "Ultra-High Performance Concrete (UHPC)". In the composite repair system described in this invention, "intrinsic thermal activation" drives fabric shrinkage, generating strong self-compacting compressive stress on the internal matrix, which is beneficial for forcibly closing microcracks; at the same time, the chemical bonds formed by the MPC-FAC grout at the interface block the "interfacial seepage channels".

[0113] Comparative Example 3 (without MPC chemical bonding) also exhibits heat-shrinkable prestress, but due to weak interfacial adhesion, chloride ions easily penetrate along the interface between the old and new layers, resulting in a diffusion coefficient (4.2 × 10⁻⁶). -12 m 2 / s) is much higher than that of the example; Comparative Example 2 (without heat shrinkage) has poor impermeability due to the lack of self-compacting effect and the presence of micropores inside.

[0114] (7) Analysis of impact and abrasion resistance: The impact and abrasion resistance of Example 2 is as high as 232 h / (kg / m). 2 ), is a traditional repair material (Comparative Example 1, 35h / (kg / m) 2 More than 6 times that of the substrate. The three-dimensional fabric introduced in this invention acts as a high-strength and tough skeleton to limit the peeling of the substrate (similar to "reinforcement"), while the pre-compression stress generated by heat shrinkage makes the surface material "tight", making it extremely difficult to be worn by mud and sand carried by waves.

[0115] In contrast, Comparative Example 4 (traditional overlap) suffered from prestress loss at the joint and uneven surface, resulting in the joint edge failing first in the impact and abrasion test, leading to a significant decrease in overall impact and abrasion resistance.

[0116] This invention presents an internally generated thermally activated prestressed 3DTRC marine splash zone bridge pier repair system. Through a cross-scale organic combination of material micro-chemical mechanisms (MPC-FAC hydration exothermics) and macro-structural construction (heat-shrinkable fabric sleeve + zipper-type interface), it successfully solves the bottleneck problem of traditional marine repair technologies in achieving both rapid hardening and early strength, high-strength interfacial bonding, and active structural reinforcement under ultra-short tidal windows, and effectively eliminates weak points at joints. This technical solution is flexible, mature, and stable, possessing extremely high engineering application value and socio-economic benefits.

[0117] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible embodiments. Therefore, any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for repairing bridge piers based on self-excited prestressed 3DTRC, characterized in that, Includes the following steps: 1) Clean the bridge piers to be repaired; 2) Apply the first magnesium phosphate / aluminoferrite composite cement slurry to the cleaned surface; 3) A three-dimensional mesh heat-shrinkable fiber fabric is set on the surface of the uncured first magnesium phosphate / aluminate iron composite cement slurry, and the three-dimensional mesh heat-shrinkable fiber fabric is pre-filled with the first aluminate iron cement modified magnesium phosphate cement powder or the second magnesium phosphate / aluminate iron composite cement slurry mixed on site is poured in. 4) Thermally activated self-compacting; Water spraying was used to activate the three-dimensional mesh heat-shrinkable fiber fabric of pre-filled magnesium phosphate / aluminoferrite composite cement powder, which underwent hydration hardening and self-compacting molding under water spraying conditions to complete the bridge pier repair. A three-dimensional mesh heat-shrinkable fiber fabric for the magnesium phosphate / aluminate iron composite cement slurry mixed on-site was used to hydrate, harden, and self-compact under water-containing conditions in the composite cement slurry to complete the bridge pier repair.

2. The bridge pier repair method according to claim 1, characterized in that, The three-dimensional mesh heat-shrinkable fiber fabric includes a three-dimensional mesh heat-shrinkable spacer fabric matrix, a water-soluble PVA nonwoven fabric disposed on one side close to the structure to be repaired, and a water-permeable and slurry-resistant heat-shrinkable fiber nonwoven fabric encapsulation layer disposed on the opposite side.

3. The bridge pier repair method according to claim 1, characterized in that, Steps 3) and 4) can be carried out in stages according to the working conditions, with differentiated construction processes adopted based on the depth of damage to the bridge pier surface: a. For shallow damaged interfaces with a damage depth ≤2cm, a repair process using pre-filled composite cement powder and water-activated spraying is adopted; b. For deep-damaged interfaces with a damage depth >2cm: a repair process is adopted, which involves building a support template, first installing a three-dimensional mesh heat-shrinkable fiber fabric, and then injecting a second magnesium phosphate / aluminate iron composite cement grout on site.

4. The bridge pier repair method according to claim 1, characterized in that, When the three-dimensional mesh heat-shrinkable fiber fabric is wrapped around the bridge pier, its seams are connected by a zipper-like structure. The specific construction and connection steps of the zipper-like structure include: pre-forming the two ends of the three-dimensional mesh heat-shrinkable fiber fabric into complementary tooth shapes, interlocking them during on-site construction, and sewing and fixing them with high-strength fiber thread. Then, magnesium phosphate / aluminate iron composite cement slurry is applied to the sewn area for sealing.

5. The bridge pier repair method according to claim 1, characterized in that, The magnesium phosphate / aluminate iron cement comprises magnesium phosphate cement components and aluminate iron cement, with the aluminate iron cement accounting for 25-45% of the total mass of the composite cement.

6. The bridge pier repair method according to claim 1, characterized in that, The ferroaluminate cement is a high-iron type sulfoaluminate cement with a specific surface area ≥350m². 2 / kg, Fe2O3 mass percentage is 5-15wt%; the magnesium phosphate cement component contains calcined magnesium oxide and phosphate, and the magnesium-phosphorus molar ratio is 4-8:

1.

7. The bridge pier repair method according to claim 1, characterized in that, The water-cement ratio of the first magnesium phosphate / aluminate iron composite cement is higher than that of the second magnesium phosphate / aluminate iron composite cement; the water-cement ratio of the first magnesium phosphate / aluminate iron composite cement is 0.16-0.20; the water-cement ratio of the second magnesium phosphate / aluminate iron composite cement is 0.13-0.

15.

8. The bridge pier repair method according to claim 1, characterized in that, The heat shrinkage trigger temperature of the three-dimensional mesh heat-shrinkable fiber fabric is 55-80℃; the spinning fiber used is a heat-shrinkable polymer fiber; the areal density is 450-650 g / m³. 2 The porosity is >90%, and the total porosity is 80-95%.

9. The bridge pier repair method according to claim 8, characterized in that, The heat-shrinkable polymer fiber material is one or more of high-shrinkage polyester, polypropylene, and polyamide.

10. The bridge pier repair method according to claim 1, characterized in that, The method for preparing the three-dimensional mesh heat-shrinkable spacer fabric includes the following steps: 1) Preparation and low-temperature setting of three-dimensional mesh spacer fabric matrix: Industrial filaments of heat-shrinkable polymer fiber material are used as warp and weft yarns, and high-modulus polymer monofilaments are used as spacer yarns to perform three-dimensional weaving; the resulting fabric is subjected to low-temperature relaxation heat setting treatment at a setting temperature of 100-110℃ to obtain a three-dimensional mesh spacer fabric matrix with heat-sensitive properties. 2) Composite packaging process: Using hot-pressing or needle-punching processes, water-soluble PVA nonwoven fabric and heat-shrinkable permeable and pulp-resistant nonwoven fabric are respectively laminated onto the side of the three-dimensional mesh spacer fabric matrix obtained in step 1) that is close to the bridge pier structure to be repaired and the opposite side; during the lamination process, the temperature is controlled to be lower than the shrinkage initiation temperature of the fibers, and finally the three-dimensional mesh heat-shrinkable spacer fabric is obtained.

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