Bridge bottom crack filling material with penetration anchoring function and bridge bottom crack repairing method

Abstract

The application belongs to the field of civil engineering materials and bridge structure repair technology, and specifically relates to a bridge bottom crack filling material with a penetration anchoring function and a bridge bottom crack repair method, which comprises modified epoxy acrylate prepolymer, nano-silica sol, ultra-fine metakaolin, in-situ crystalline anchoring agent, penetration aid, retarding latent curing agent and water. The material forms a through filling structure in the crack through the synergistic effect of low-viscosity penetration and in-situ reaction anchoring, and constructs a double anchoring system of chemical bonding and micro-mechanical interlocking on the wall surface, thereby significantly improving the penetration depth, interfacial bonding strength and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering materials and bridge structure repair technology, specifically a bridge bottom crack filling material with penetrating anchoring function and a bridge bottom crack repair method. Background Technology

[0002] As bridges age, the problem of cracks at the bridge underside is becoming increasingly prominent, affecting not only structural safety but also accelerating steel corrosion and concrete deterioration. Traditional crack fillers rely primarily on physical filling or surface sealing, making it difficult to achieve effective penetration and deep anchoring within the cracks. This is especially problematic in areas with complex stresses and humid environments, such as the bridge underside, where poor adhesion and secondary cracking are likely to occur. Therefore, there is an urgent need to develop a crack filler for bridge undersides that combines excellent permeability and anchoring capabilities to improve repair durability and structural integrity.

[0003] A search revealed a Chinese patent (publication number CN116375443B) that discloses a self-healing composite material for bridge cracks and its preparation method. This patent uses components such as silicate cement, volcanic ash, epoxy-based hyperbranched polyborosiloxane, amino-containing hyperbranched polyurethane, and glass fiber tubes injected with self-healing active ingredients, aiming to improve the material's self-healing ability, compressive strength, and bonding performance. However, while this material system possesses certain self-healing capabilities, it primarily relies on the release of the repair agent through microcapsule rupture, resulting in limited initial penetration depth into the cracks. Furthermore, it lacks a specific anchoring mechanism designed for cracks at the bridge base. Although its bonding performance is high, it lacks active anchoring of the crack walls, making it prone to interfacial debonding under dynamic loads or vibration environments, hindering long-term stable structural repair.

[0004] A search revealed a Chinese patent (publication number CN109336525B) that discloses a bridge crack repair material with self-healing properties and its preparation method. This patent utilizes a synergistic dual-system approach combining organic (nano-zinc oxide-based asphalt) and inorganic (aluminate cement, Bonate) phases. It leverages the fluidity of asphalt to achieve a certain degree of penetration, while the inorganic phase provides structural strength. Although the material emphasizes "penetration performance," its organic phase primarily relies on the natural flow of asphalt, lacking penetration enhancers or capillary-driven design, resulting in insufficient penetration into micron-sized cracks or dry substrates. Furthermore, its anchoring effect relies solely on the mechanical interlocking of cement hydration products, without introducing chemical bonding or micromechanical anchoring structures. This leads to limited interfacial bonding strength with the original concrete matrix, particularly in high-stress areas such as the negative bending moment zone at the bridge bottom, making it difficult to resist interfacial delamination caused by repeated loading.

[0005] The above problems indicate that existing bridge crack repair materials still have significant shortcomings in terms of penetration depth, anchoring mechanism, and interface stability, making it difficult to meet the needs of efficient and durable repair of cracks at the bottom of bridges. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a bridge underpass crack filling material and a bridge underpass crack repair method with penetrating anchoring function. The material forms a penetrating filling structure inside the crack through the synergistic effect of a low-viscosity penetrating phase and an in-situ reactive anchoring phase, and constructs a dual anchoring system on the crack wall that combines chemical bonding and micromechanical interlocking, effectively improving the material's penetration depth into micro-cracks, interfacial bonding strength, and long-term service stability.

[0007] In a first aspect, the present invention provides a bridge under-floor crack filling material with penetrating and anchoring function, characterized in that, by weight, it comprises the following components: Modified epoxy acrylate prepolymer: 25-35 parts; Nano silica sol dispersion: 20-30 parts; Ultrafine metakaolin: 15-20 parts; Penetration enhancer: 3-5 parts; Water: 8-12 parts; In-situ crystallizing anchoring agent: 10-15 parts; Retarded latent curing agent: 2-4 parts.

[0008] Preferably, the in-situ crystalline anchoring agent comprises the following components by weight: Potassium aluminum sulfate: 40-50 parts; Sodium silicate: 30-40 parts; Nano titanium dioxide: 15-20 parts; Polyvinyl alcohol formaldehyde microspheres: 5-10 parts.

[0009] Preferably, the modified epoxy acrylate prepolymer is prepared by the following method: bisphenol A type epoxy resin is heated and melted, then acrylic acid and hydroquinone are added, the temperature is raised to 90-100℃ and stirred for 3-4 h under nitrogen protection, and then cooled to room temperature to obtain the modified epoxy acrylate prepolymer.

[0010] Preferably, the modified epoxy acrylate prepolymer has an epoxy value of 0.08-0.12 mol / 100g and a viscosity of 800-1200 mPa·s at 25°C.

[0011] Preferably, the nano-silica sol dispersion is prepared by the following method: commercially available silica sol is treated with a strong acid cation exchange resin until the conductivity is ≤50 μS / cm, and then the pH is adjusted to 4.5-5.5 with dilute hydrochloric acid to obtain a nano-silica sol dispersion with a particle size distribution of 8-15 nm.

[0012] Preferably, the ultrafine metakaolin is prepared by the following method: calcining kaolin in a muffle furnace at 750-800℃ for 1.5-3 h, cooling it, and then pulverizing it with an air jet mill until D90≤5 μm to obtain ultrafine metakaolin.

[0013] Preferably, the penetration enhancer is a compound of fluorocarbon surfactant and polyoxyethylene ether in a mass ratio of 1:2, and the HLB value of the penetration enhancer is 12-14.

[0014] Preferably, the retarded latent curing agent is an aliphatic polyamine encapsulated in microcapsules, with the capsule wall being polymethyl methacrylate; the core amine value of the retarded latent curing agent is ≥300 mg KOH / g, and the average particle size is 30-50 μm; the retarded latent curing agent begins to release active amines at temperatures above 60°C.

[0015] Preferably, the in-situ crystalline anchoring agent is prepared by the following method: potassium aluminum sulfate, sodium silicate, and nano titanium dioxide are mixed evenly in a dry environment, and then polyvinyl alcohol formaldehyde microspheres are added and stirred evenly. The stirring speed is controlled at 150-500 rpm and the stirring time is 5-15 min to obtain the in-situ crystalline anchoring agent.

[0016] Preferably, the polyvinyl alcohol formaldehyde microspheres are prepared by reacting an aqueous solution of polyvinyl alcohol with formaldehyde at 50°C for 2 h under hydrochloric acid catalysis, spray drying, and sieving out 50-100 μm particles to obtain polyvinyl alcohol formaldehyde microspheres with a surface grafting rate of 1.8 mmol / g.

[0017] Secondly, the present invention provides a method for repairing cracks at the bottom of a bridge, characterized by comprising the following steps: S1. Mixing of main ingredients: Modified epoxy acrylate prepolymer, nano silica sol dispersion, ultrafine metakaolin, penetration enhancer and water are added to a high-speed disperser and stirred to obtain the main ingredient slurry; S2. Addition of curing agent: After pre-mixing the retarding latent curing agent and the in-situ crystallizing anchoring agent evenly, slowly add them to the main material slurry and stir evenly under vacuum conditions to obtain the bridge bottom crack filling material. S3. Grouting construction: Several grouting holes are arranged along the direction of the crack at the bottom of the bridge. The grouting material is injected into the crack at the bottom of the bridge through the grouting holes in a bottom-to-top, hole-by-hole sealing manner. The grouting pressure is controlled at 0.2-0.4MPa and the spacing between grouting holes is not greater than 50 cm. S4. Curing reaction: After the grouting construction is completed, static curing is carried out under an ambient temperature of not less than 10℃, so that the crack filling material at the bottom of the bridge forms a flexible network skeleton inside the crack and condenses with hydroxyl groups on the concrete surface to form a covalent bond interface.

[0018] Preferably, in step S3, when the curing agent is added, the vacuum degree is -0.098 to -0.090 MPa, the stirring speed is 300-600 rpm, and the stirring time is 5-15 min.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention achieves active penetration of materials into the deep layers of cracks by constructing a low-viscosity, high-permeability matrix and an anchoring phase that can be polymerized / crystallized in situ, and forms a chemical-mechanical dual anchoring structure on the crack wall, thereby significantly improving the interfacial bonding strength and long-term service performance between the repair material and the matrix. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the injection and distribution relationship of the bridge bottom crack filling material of the present invention in the bridge bottom crack.

[0021] Figure 2 This is a schematic diagram illustrating the principle of the penetration and anchoring structure formed inside the crack by the bridge underpass crack filling material of the present invention.

[0022] Figure 3 This is a schematic diagram showing the relationship between the water absorption, swelling, rupture, and release of aldehyde groups in polyvinyl alcohol formaldehyde microspheres in in-situ crystalline anchoring agents.

[0023] Figure 4 This is a schematic diagram of the construction process of the bridge underside crack repair method of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are merely illustrative examples of the present invention, and the scope of protection of the present invention is not limited thereto. The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0025] A bridge underpass crack sealant with penetrating and anchoring properties, comprising the following components by weight: Modified epoxy acrylate prepolymer: 25-35 parts; Nano silica sol dispersion: 20-30 parts; Ultrafine metakaolin: 15-20 parts; Penetration enhancer: 3-5 parts; Water: 8-12 parts; In-situ crystallizing anchoring agent: 10-15 parts; Retarded latent curing agent: 2-4 parts. Example 2

[0026] A bridge underpass crack sealant with penetrating and anchoring properties, comprising the following components by weight: Modified epoxy acrylate prepolymer: 25-35 parts; Nano silica sol dispersion: 20-30 parts; Ultrafine metakaolin: 15-20 parts; Penetration enhancer: 3-5 parts; Water: 8-12 parts; In-situ crystallizing anchoring agent: 10-15 parts; Retarded latent curing agent: 2-4 parts; The in-situ crystalline anchoring agent, by weight, consists of the following components: Potassium aluminum sulfate: 40-50 parts; Sodium silicate: 30-40 parts; Nano titanium dioxide: 15-20 parts; Polyvinyl alcohol formaldehyde microspheres: 5-10 parts; in: The modified epoxy acrylate prepolymer was prepared by the following method: bisphenol A type epoxy resin was heated and melted, then acrylic acid and hydroquinone were added, the temperature was raised to 90-100℃ and stirred for 3-4 h under nitrogen protection, and then cooled to room temperature to obtain the modified epoxy acrylate prepolymer; the epoxy value of the modified epoxy acrylate prepolymer was 0.08-0.12 mol / 100g, and the viscosity at 25℃ was 800-1200 mPa·s; The nano-silica sol dispersion was prepared by the following method: commercially available silica sol was treated with a strong acid cation exchange resin until the conductivity was ≤50 μS / cm, and then the pH was adjusted to 4.5-5.5 with dilute hydrochloric acid to obtain a nano-silica sol dispersion with a particle size distribution of 8-15 nm. Ultrafine metakaolin is prepared by the following method: kaolin is calcined in a muffle furnace at 750-800℃ for 1.5-3h, cooled and then pulverized by an air jet mill to D90≤5 μm to obtain ultrafine metakaolin; The penetration enhancer is a compound of fluorocarbon surfactant and polyoxyethylene ether in a mass ratio of 1:2, and the HLB value of the penetration enhancer is 12-14. The retarded latent curing agent is an aliphatic polyamine encapsulated in microcapsules, with the capsule wall being polymethyl methacrylate; the core amine value of the retarded latent curing agent is ≥300 mg KOH / g, and the average particle size is 30-50 μm; the retarded latent curing agent begins to release active amines at temperatures above 60°C; The in-situ crystalline anchoring agent is prepared by the following method: potassium aluminum sulfate, sodium silicate, and nano titanium dioxide are mixed evenly in a dry environment, and then polyvinyl alcohol formaldehyde microspheres are added and stirred evenly. The stirring speed is controlled at 150-500 rpm and the stirring time is 5-15 min to obtain the in-situ crystalline anchoring agent. The polyvinyl alcohol formaldehyde microspheres are prepared by reacting polyvinyl alcohol aqueous solution with formaldehyde at 50℃ for 2 h under hydrochloric acid catalysis, spray drying, and sieving to obtain 50-100 μm particles, thus obtaining polyvinyl alcohol formaldehyde microspheres with a surface grafting rate of 1.8 mmol / g. Example 3

[0027] A bridge underpass crack sealant with penetrating and anchoring properties, comprising the following components by weight: Modified epoxy acrylate prepolymer: 30 parts; Nano silica sol dispersion: 25 parts; Ultrafine metakaolin: 18 parts; Penetration enhancer: 4 parts; Water: 10 parts; In-situ crystallizing anchoring agent: 12 parts; Retarded latent curing agent: 3 parts; The in-situ crystalline anchoring agent, by weight, consists of the following components: Potassium aluminum sulfate: 45 parts; Sodium silicate: 35 parts; Nano titanium dioxide: 18 parts; Polyvinyl alcohol formaldehyde microspheres: 8 parts; in: The modified epoxy acrylate prepolymer was prepared by the following method: Bisphenol A type epoxy resin was placed in a three-necked flask and heated to complete melting in an 80°C water bath. Acrylic acid and 0.3% hydroquinone by mass were added as polymerization inhibitors. The temperature was then raised to 95°C and a nitrogen protective atmosphere was introduced. The mechanical stirrer was turned on and the reaction was carried out at 300 rpm for 3.5 h. During the reaction, the epoxy value was measured by sampling and controlled within the range of 0.08-0.12 mol / 100g. At the same time, the viscosity at 25°C was measured by rotational viscometer and maintained between 800-1200 mPa·s. After the reaction was completed, the prepolymer was naturally cooled to room temperature to obtain the desired prepolymer. The nano-silica sol dispersion was prepared by the following method: a commercially available alkaline silica sol stock solution with a solid content of 20% was passed through a column packed with a strong acid cation exchange resin for sodium removal until the conductivity of the effluent was ≤50 μS / cm. The pH was then adjusted to 5.0 with dilute hydrochloric acid to obtain the nano-silica sol dispersion. The particle size distribution of the obtained product was concentrated in the range of 8-15 nm, which was used to prepare the inorganic reinforcing phase in the subsequent system. Ultrafine metakaolin is prepared by the following method: natural kaolin raw material is placed in a muffle furnace and calcined at a constant temperature of 780℃ for 2 h to remove the water of crystallization and form an amorphous active structure. After cooling, it is sent to an air jet mill for pulverization. The D90 particle size is controlled to be 4.2 μm and the specific surface area reaches ≥800 m² / kg, thereby obtaining a powder material with high pozzolanic activity and filling performance, namely ultrafine metakaolin. The penetration enhancer is a compound of fluorocarbon surfactant and polyoxyethylene ether in a mass ratio of 1:2, and the HLB value of the penetration enhancer is 12-14. The slow-setting latent curing agent is prepared by microencapsulating aliphatic polyamines: first, the aliphatic polyamine is dissolved in deionized water, and an appropriate amount of emulsifier is added to form an O / W type emulsion. Then, methyl methacrylate monomer and initiator are added, and in-situ polymerization is carried out at 70°C for 3 hours. The resulting microcapsules have an average particle size of 40 μm, the capsule wall material is polymethyl methacrylate, the encapsulation rate reaches 87%, and the amine value is 310 mg KOH / g. It can start to release active amine substances when the ambient temperature rises above 60°C to trigger the crosslinking reaction of the epoxy acrylate system. The in-situ crystalline anchoring agent was prepared by the following method: 45 parts by weight of potassium aluminum sulfate, 35 parts by weight of sodium silicate with a modulus of 3.0, and 18 parts by weight of anatase nano-titanium dioxide (particle size 15 nm) were weighed and mixed at low speed in a planetary ball mill in a dry environment for 10 min to ensure uniform dispersion without agglomeration; then 8 parts by weight of polyvinyl alcohol formaldehyde microspheres with a surface grafting rate of 1.8 mmol / g and a particle size range of 50-100 μm were added, and the stirring speed was adjusted to 300 rpm and mixing was continued for 10 min to avoid premature breakage of the microspheres due to excessive shear force, thus obtaining the in-situ crystalline anchoring agent; the preparation method of polyvinyl alcohol formaldehyde microspheres was as follows: polyvinyl alcohol aqueous solution was reacted with formaldehyde at 50℃ for 2 h under hydrochloric acid catalysis, and after spray drying, 50-100 μm particles were sieved to obtain polyvinyl alcohol formaldehyde microspheres with a surface grafting rate of 1.8 mmol / g; In practical applications, to fully and better utilize the effectiveness of the bridge underpass crack filling material, the bridge underpass crack filling material of this invention should be prepared and used immediately. To improve ease of use, the modified epoxy acrylate prepolymer, nano silica sol dispersion, ultrafine metakaolin, penetration enhancer, and water are usually mixed evenly according to the formula and sealed in container A as the main material slurry. The in-situ crystalline anchoring agent and the retarding latent curing agent are mixed evenly and sealed in container B. When repairing bridge underpass cracks, the materials in containers A and B are poured out and mixed to form the bridge underpass crack filling material of this invention, and then the bridge underpass crack filling material of this invention is immediately used for grouting construction. Example 4

[0028] For a method of repairing cracks under bridges, please refer to [link / reference]. Figure 4 It includes the following steps: S1. Mixing of Main Materials: According to the product formulation in Example 3, 30 parts of modified epoxy acrylate prepolymer, 25 parts of nano-silica sol dispersion, 18 parts of ultrafine metakaolin, 4 parts of penetration enhancer, and 10 parts of deionized water were added sequentially to a high-speed dispersion vessel and stirred at 800 rpm for 15 minutes to form a uniform, transparent, and low-viscosity main material slurry. Its viscosity at 25°C was measured to be 42 mPa·s, meeting the requirements for penetration into microcracks. Because the viscosity of the main material slurry after mixing is only 42 mPa·s at 25°C, and it contains a penetration enhancer composed of perfluorooctyl sulfonyl ethyl phosphate and nonylphenol polyoxyethylene ether, its surface tension is significantly reduced, allowing the bridge underside crack filling material to overcome the capillary resistance within the microcracks and spontaneously penetrate upwards along the cracks. The synergistic effect of the low viscosity and surface activity of the above-mentioned main material slurry is the key physical basis for achieving a penetration depth of over 15 cm.

[0029] S2. Adding curing agent: After pre-mixing 3 parts of retarded latent curing agent and 12 parts of in-situ crystallizing anchoring agent evenly, slowly add them to the main material slurry. Then, in a vacuum mixing device (vacuum degree -0.09 MPa), control the mixing speed at 500 rpm and mix for 8 minutes to prevent air from mixing in and causing bubble defects, thus obtaining the bridge bottom crack filling material.

[0030] S3. Grouting Construction: Cracks exist in the concrete bridge foundation, which are structural defects to be repaired; please refer to [link / reference needed]. Figure 1 Several grouting holes are laid out along the crack direction at the bottom of the bridge, with the spacing between adjacent grouting holes controlled to not exceed 50 cm. The grouting pipe is inserted into the bottom of the crack, and high-pressure air is used to blow away the floating dust inside the crack. Then, anhydrous ethanol is used to wipe the crack wall to remove oil and impurities, improving the efficiency of subsequent interface chemical reaction. The mixed bridge bottom crack filling material is injected into the storage tank of a special grouting pump. Continuous grouting is carried out from bottom to top and hole by hole in sequence. That is, the grouting pipe is connected to the current grouting hole, and a grouting pressure of 0.3 MPa is applied until the next adjacent grouting hole overflows with grout. Then, the current grouting hole is sealed with sealing tape and the operation is moved to the next grouting hole position to continue. The entire grouting process must ensure that the grout flows continuously and without interruption.

[0031] S4. Curing Reaction: After the grouting construction is completed, allow the material to cure statically for 24 hours at an ambient temperature not lower than 10℃. During this period, the material undergoes two consecutive but different curing stages. Please refer to [link / reference]. Figure 2 and Figure 3The first stage occurs in the early stage of grouting. As the ambient temperature rises or moisture evaporates, the microcapsules rupture, releasing aliphatic polyamines that trigger Michael addition and epoxy ring-opening cross-linking reactions in the epoxy acrylate prepolymer, forming a three-dimensional flexible network framework. The second stage relies on the slow diffusion of moisture inside the cracks, activating the reaction between potassium aluminum sulfate and sodium silicate in the in-situ crystalline anchoring agent, generating a large number of needle-like ettringite crystals. These crystals grow directionally along the crack walls and embed themselves in the microporous structure of the concrete, forming a physical interlocking effect. At the same time, nano-titanium dioxide catalyzes the oxidation and cross-linking of residual carbon-carbon double bonds in an alkaline environment, further enhancing the stability of the organic phase. Polyvinyl alcohol formaldehyde microspheres gradually absorb water and swell upon contact with moisture, eventually rupturing to release aldehyde groups, which undergo dehydration condensation reactions with hydroxyl groups on the concrete surface, constructing covalent bond interfaces of the -CO-Si- and -CO-Ca- types.

[0032] Throughout the implementation process, precise mass ratio control, strict process parameter setting, and a reasonable construction sequence ensured effective synergy between the low-viscosity penetrating phase and the in-situ reactive anchoring phase. Specifically, the modified epoxy acrylate prepolymer, as the main organic binder, provided excellent flexibility and adhesion; nano-silica sol and ultrafine metakaolin together constituted the inorganic filler phase, reducing the overall shrinkage rate of the system and enhancing early strength development; the penetration enhancer promoted the penetration of the slurry into the micron-level crack channels by reducing surface tension; the retarded latent curing agent ensured the material maintained fluidity during the construction window and initiated the cross-linking reaction at the appropriate time later; and the in-situ crystalline anchoring agent constructed a robust anchoring structure on the crack wall through multiple chemical and physical mechanisms. All the above components and process steps worked together to form a complete bridge underpass crack repair technology system, applicable to various concrete crack repair projects with widths ranging from 0.05 to 2 mm. Example 5

[0033] To enable those skilled in the art to fully understand and implement this invention, the specific implementation principles of this invention are further supplemented below with a specific application scenario.

[0034] After 15 years of service, multiple transverse cracks with widths ranging from 0.12 to 0.35 mm appeared on the bottom surface of the main beam of a certain city's elevated bridge. Located in the negative bending moment zone, the bridge was subjected to long-term vehicle dynamic loads and rainwater erosion. The transverse cracks were repaired using the bridge bottom crack filling material of Example 3 and the method of Example 4, as detailed below: Step 1: Before construction, grouting holes are drilled every 45 cm along the direction of each crack, and grouting pipe 4 is inserted to the bottom of the crack. Then, the interior of the crack is purged with 0.6 MPa high-pressure air to remove loose particles and dust. Next, the crack walls are repeatedly wiped with anhydrous ethanol-soaked cotton cloth to remove surface oil film and activate the silanol hydroxyl groups in the concrete matrix, providing active sites for subsequent covalent bond formation. This pretreatment ensures that the crack filler material at the bridge bottom can form effective chemical contact with the concrete bridge bottom matrix after injection, avoiding bonding failure due to interface contamination.

[0035] Step 2: Inject the uniformly mixed bridge underside crack filler into the storage tank of the two-component grouting pump. Continuous grouting is performed from bottom to top, sealing each hole sequentially. Grouting begins at a constant pressure of 0.3 MPa from the bottom of the crack through the grouting pipe, continuing until grout overflows from the next adjacent hole. The current hole is then sealed with sealing tape to prevent backflow and ensure no cavities remain inside the crack. The process is then moved to the next grouting hole to continue. The grout continuously fills the entire crack channel under the combined effect of pressure and capillary action.

[0036] Step 3: After the grouting construction is completed, allow it to stand for 24 hours under an ambient temperature of not less than 10℃ to enter the two-stage curing process.

[0037] Please see Figure 2 In the first stage (0-6 h), when the ambient temperature rises above 15°C, the polymethyl methacrylate microcapsules in the retarded latent curing agent rupture due to thermal expansion, releasing aliphatic polyamines. This triggers Michael addition and ring-opening reactions between the modified epoxy acrylate prepolymer and the epoxy resin, gradually forming a continuous epoxy acrylate crosslinking network. This network exhibits moderate flexibility, adapting to micro-strain under bridge under vibration loads and preventing brittle cracking. Simultaneously, moisture slowly diffuses inward through the crack walls, triggering an ion exchange reaction between potassium aluminum sulfate and sodium silicate in the in-situ crystalline anchoring agent, generating a large number of needle-like ettringite crystals. These crystals grow directionally along the microporous structure of the concrete, and their aspect ratio greater than 10:1 allows them to penetrate deep into the matrix pores and form a "pinning" effect, producing a significant micromechanical interlocking effect, thereby enhancing the interfacial shear resistance.

[0038] Please see Figure 3In the second stage (6-24 h), moisture further penetrates into the depths of the cracks, causing the polyvinyl alcohol formaldehyde microspheres to absorb water and swell. The accumulated internal osmotic pressure leads to the rupture of the microsphere shells, releasing free aldehyde groups. These aldehyde groups then undergo dehydration condensation reactions with the exposed silanol hydroxyl (≡Si-OH) and calcium hydroxyl (Ca-OH) groups on the concrete surface, forming stable -CO-Si- and -CO-Ca- covalent bond interfaces, respectively. This chemical bonding process is unaffected by subsequent wet-dry cycles, significantly enhancing interface durability. Simultaneously, the dispersed anatase nano-titanium dioxide in the system activates photocatalytic activity in the alkaline environment of the concrete (pH>12.5), promoting the oxidative crosslinking of residual carbon-carbon double bonds in the epoxy acrylate network, further densifying the organic phase structure and inhibiting the intrusion of moisture and chloride ions.

[0039] Through the orderly implementation of the above steps, the crack filling material at the bridge underside not only achieves continuous filling from the surface to the depth within the crack, but also simultaneously constructs a triple synergistic anchoring system at the interface. This system consists of an epoxy acrylate crosslinked network providing overall bonding, ettringite needle-like crystals providing micromechanical anchoring, and covalent bonds providing chemical bonding. This system enables the repaired specimen to achieve an interfacial shear strength of 3.5 MPa under standard testing conditions, far exceeding the 1.8-2.2 MPa of ordinary epoxy grouting materials. Furthermore, after undergoing 100 freeze-thaw cycles or 500,000 fatigue loading cycles, the strength retention rate still exceeds 90%, fully verifying the long-term anchoring capability of this invention under complex working conditions at the bridge underside.

[0040] All content not described in detail in the specification belongs to the prior art known to those skilled in the art, and the model parameters of each device are not specifically limited. Conventional construction and testing equipment can be used. Auxiliary control components not mentioned in this technical solution are not shown in the figure because they belong to the prior art, and will not be described here.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bridge underpass crack sealant with penetrating and anchoring function, characterized in that, By weight, it consists of the following components: Modified epoxy acrylate prepolymer: 25-35 parts; Nano silica sol dispersion: 20-30 parts; Ultrafine metakaolin: 15-20 parts; Penetration enhancer: 3-5 parts; Water: 8-12 parts; In-situ crystallizing anchoring agent: 10-15 parts; Retarded latent curing agent: 2-4 parts.

2. The bridge underpass crack filler material with penetrating anchoring function according to claim 1, characterized in that, The in-situ crystalline anchoring agent, by weight, consists of the following components: Potassium aluminum sulfate: 40-50 parts; Sodium silicate: 30-40 parts; Nano titanium dioxide: 15-20 parts; Polyvinyl alcohol formaldehyde microspheres: 5-10 parts.

3. The bridge underpass crack filler material with penetrating anchoring function according to claim 1, characterized in that, The modified epoxy acrylate prepolymer is prepared by the following method: bisphenol A type epoxy resin is heated and melted, then acrylic acid and hydroquinone are added, the temperature is raised to 90-100℃ and stirred for 3-4 h under nitrogen protection, and then cooled to room temperature to obtain the modified epoxy acrylate prepolymer.

4. The bridge bottom crack filling material with penetrating anchoring function according to claim 3, characterized in that, The modified epoxy acrylate prepolymer has an epoxy value of 0.08-0.12 mol / 100g and a viscosity of 800-1200 mPa·s at 25℃.

5. The bridge underpass crack filler material with penetrating anchoring function according to claim 1, characterized in that, The nano-silica sol dispersion is prepared by the following method: commercially available silica sol is treated with a strong acid cation exchange resin until the conductivity is ≤50 μS / cm, and then the pH is adjusted to 4.5-5.5 with dilute hydrochloric acid to obtain a nano-silica sol dispersion with a particle size distribution of 8-15 nm.

6. The bridge bottom crack filler material with penetrating anchoring function according to claim 1, characterized in that, The ultrafine metakaolin is prepared by the following method: kaolin is calcined in a muffle furnace at 750-800℃ for 1.5-3 h, cooled, and then pulverized by an air jet mill to D90≤5 μm to obtain ultrafine metakaolin.

7. A bridge underpass crack filler material with penetrating anchoring function according to claim 1, characterized in that, The penetration enhancer is a compound of fluorocarbon surfactant and polyoxyethylene ether in a mass ratio of 1:2, and the HLB value of the penetration enhancer is 12-14.

8. A bridge underpass crack filler material with penetrating anchoring function according to claim 1, characterized in that, The retarded latent curing agent is an aliphatic polyamine encapsulated in microcapsules, with the capsule wall being polymethyl methacrylate; the core amine value of the retarded latent curing agent is ≥300 mg KOH / g, and the average particle size is 30-50 μm; the retarded latent curing agent begins to release active amines at temperatures above 60°C.

9. A bridge underpass crack filler material with penetrating anchoring function according to claim 2, characterized in that, The in-situ crystalline anchoring agent is prepared by the following method: potassium aluminum sulfate, sodium silicate, and nano titanium dioxide are mixed evenly in a dry environment, and then polyvinyl alcohol formaldehyde microspheres are added and stirred evenly. The stirring speed is controlled at 150-500 rpm and the stirring time is 5-15 min to obtain the in-situ crystalline anchoring agent.

10. A bridge underpass crack filler material with penetrating anchoring function according to claim 2, characterized in that, The method for preparing the polyvinyl alcohol formaldehyde microspheres is as follows: polyvinyl alcohol aqueous solution and formaldehyde are reacted at 50°C for 2 h under hydrochloric acid catalysis, spray dried and then sieved to obtain 50-100 μm particles, thus obtaining polyvinyl alcohol formaldehyde microspheres with a surface grafting rate of 1.8 mmol / g.

11. A method for repairing cracks at the bottom of a bridge, characterized in that, Includes the following steps: S1. Mixing of main ingredients: Modified epoxy acrylate prepolymer, nano silica sol dispersion, ultrafine metakaolin, penetration enhancer and water are added to a high-speed disperser in sequence and stirred to obtain the main ingredient slurry; S2. Addition of curing agent: After pre-mixing the retarding latent curing agent and the in-situ crystallizing anchoring agent evenly, slowly add them to the main material slurry and stir evenly under vacuum conditions to obtain the bridge bottom crack filling material. S3. Grouting construction: Several grouting holes are arranged along the direction of the crack at the bottom of the bridge. The grouting material is injected into the crack at the bottom of the bridge through the grouting holes in a bottom-to-top, hole-by-hole sealing manner. The grouting pressure is controlled at 0.2-0.4 MPa and the spacing between grouting holes is not greater than 50 cm. S4. Curing reaction: After the grouting construction is completed, static curing is carried out under an ambient temperature of not less than 10℃, so that the crack filling material at the bottom of the bridge forms a flexible network skeleton inside the crack and condenses with hydroxyl groups on the concrete surface to form a covalent bond interface.

12. A method for repairing cracks at the bottom of a bridge according to claim 11, characterized in that, In step S3, when the curing agent is added, the vacuum degree is -0.098 to -0.090 MPa, the stirring speed is 300-600 rpm, and the stirring time is 5-15 min.

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