Underwater concrete rapid repairing material and its preparation method

Abstract

The application provides a kind of underwater concrete rapid repair material, by weight fraction, including the following components: cementing material system 67-80 parts, dual functional graphene system 0.6-1.2 parts, intelligent curing adjustment system 3-5 parts, auxiliary additive 2-3 parts, filler system 20-25 parts and water 18-25 parts;The dual functional graphene system includes hydrophilic amino graphene and hydrophobic sulfhydryl reduced graphene oxide, and the mass ratio of the two is (1.2-1.8):(0.8-1.2);The intelligent curing adjustment system includes microcapsule coated temperature-sensitive coagulant 2-3 parts and in-situ whisker generation precursor 1-2 parts.The application realizes underwater rapid curing, strong bonding, high toughness, long-term protection integration, and provides a high-performance solution for the rapid repair and emergency repair of hydraulic and marine infrastructure.

Description

Technical Field

[0001] This invention relates to the field of underwater concrete repair technology, and in particular to an underwater concrete rapid repair material and its preparation method. Background Technology

[0002] As service life increases, the safety and durability of concrete structures in special environments such as marine and water conservancy projects deteriorate year by year. Affected by multiple factors such as seawater erosion, freeze-thaw cycles, wave impact, and chloride ion penetration, hydraulic and marine infrastructure such as port terminals, offshore platforms, cross-sea bridge piers, and water conservancy dams frequently suffer from cracks, spalling, and steel reinforcement corrosion. If timely repair measures are not taken, these defects will seriously threaten structural safety. To address the need for rapid repair of concrete structures in underwater or humid environments, there is an urgent need to develop high-performance repair materials that can rapidly cure underwater, strongly bond to wet substrates, and possess long-term durability.

[0003] Currently, underwater concrete repair materials mainly include ordinary cement mortar, polymer-modified mortar, and water-based epoxy-cement composite materials. Ordinary cement mortar is prone to dispersion and loss during underwater construction, has low bond strength with the old concrete interface, and a long setting time, making it difficult to meet the requirements for rapid repair. Although polymer-modified mortar improves the toughness and bonding performance of the material, the polymer is easily diluted in the underwater environment, significantly reducing the modification effect, and the material cost is relatively high. In recent years, water-based epoxy-cement composite materials have attracted attention due to their good underwater adhesion and water resistance, but they have problems such as long curing time (usually requiring several hours to several days), insufficient wet bond strength (only 50-60% of the dry state), and poor compatibility with cement systems, limiting their application in emergency repairs and underwater operations.

[0004] To improve the early strength of repair materials, rapid-hardening cementitious materials such as silicate cement and sulfoaluminate cement have been introduced into the field of underwater repair. Although these materials can harden quickly, they have inherent defects such as low tensile strength, high brittleness, and poor anti-dispersion properties underwater, especially in terms of bonding at wet interfaces. Water molecules form a "water film" at the interface between the old and new concrete, which seriously hinders the effective contact between the adhesive and the substrate, making the interface a weak link in the repair system, and the repair layer is prone to interfacial delamination failure.

[0005] In recent years, nanomaterial modification has become an important approach to improve the performance of cement-based materials. Graphene, as a two-dimensional nanomaterial, possesses an ultra-high specific surface area (theoretical value 2630 m²). 2With its high g / g density, excellent mechanical properties (Young's modulus of approximately 1 TPa), and unique layered structure, graphene has shown great potential in the modification of cement-based materials. However, existing research on graphene-modified cement-based materials mainly focuses on dry or conventional humid environments, with limited research on special underwater conditions. Unmodified graphene tends to agglomerate in cement pastes, making uniform dispersion difficult. While graphene oxide has good hydrophilicity, its oxygen-containing functional groups delay cement hydration and cannot solve the fundamental problem of weak adhesion at the wet interface. Furthermore, traditional fast-hardening systems are difficult to adapt to underwater temperature variations (4-30℃), curing too slowly at low temperatures and prone to cracking at high temperatures, lacking environmental adaptability.

[0006] The existing technology still has the following shortcomings: (1) The underwater initial setting time of the material is difficult to control precisely, and it cannot meet the construction requirements under different water depths, water temperatures and flow rates at the same time; (2) The bonding mechanism of the wet interface is unclear, and there is a lack of targeted interface reinforcement design, resulting in low interface fracture energy between the repair layer and the substrate; (3) The long-term durability of the material is insufficient, and its performance deteriorates rapidly under the action of corrosive media such as chloride salts and sulfates. After 3-5 years, the bond strength loss can reach 30-50%; (4) The material has poor toughness, poor impact resistance and fatigue resistance, and is prone to secondary cracking under wave load.

[0007] In summary, the goal is to develop a method that can rapidly cure underwater (initial setting time < 20 min), achieve high-strength wet bonding (wet bond strength > 2.5 MPa), possess temperature adaptability, and balance high strength (28-day compressive strength > 55 MPa) with high toughness (fracture energy > 350 J / m). 2 This new type of underwater concrete repair material, characterized by long-term durability (performance retention rate >90% over 3 years), is of significant practical importance and has broad application prospects for ensuring the safe operation of hydraulic and marine infrastructure.

[0008] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0009] The purpose of this invention is to provide an underwater concrete rapid repair material to solve or alleviate the problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] This invention provides an underwater concrete rapid repair material, comprising the following components: 67-80 parts of a cementitious material system, 0.6-1.2 parts of a bifunctional graphene system, 3-5 parts of an intelligent curing regulation system, 2-3 parts of auxiliary additives, 20-25 parts of a filler system, and 18-25 parts of water; the bifunctional graphene system comprises hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide, with a mass ratio of (1.2-1.8):(0.8-1.2); the intelligent curing regulation system comprises 2-3 parts of a microcapsule-encapsulated temperature-sensitive accelerator and 1-2 parts of an in-situ whisker generation precursor.

[0012] Preferably, the cementitious material system comprises 50-55 parts of silicate cement, 10-15 parts of sulfoaluminate cement, and 7-10 parts of ultrafine slag powder; the silicate cement is ordinary silicate cement or rapid-hardening silicate cement with a strength grade not lower than 52.5; the tricalcium aluminate content of the sulfoaluminate cement is ≥40%; and the specific surface area of ​​the ultrafine slag powder is ≥600 m². 2 / kg, with an activity index ≥95%.

[0013] Preferably, the auxiliary additives include 0.8-1.3 parts of a water-reducing agent, 0.4-0.8 parts of nano-silica, 0.15-0.3 parts of an defoamer, 0.25-0.5 parts of a cellulose ether, and 0.4-0.8 parts of an expanding agent; the water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 35-45%; the nano-silica has an average particle size of 15-30 nm and a specific surface area of ​​180-250 m². 2 / g; the defoamer is an organosilicon defoamer or a mineral oil defoamer; the cellulose ether is hydroxypropyl methylcellulose ether, with a viscosity of (3-8) ten thousand. The expanding agent is a calcium sulfoaluminate or calcium oxide expanding agent.

[0014] Preferably, the filler system comprises 12-18 parts of quartz sand and 6-10 parts of quartz powder; the quartz sand has a particle size of 35-80 mesh and an SiO2 content of ≥98%; the quartz powder has a particle size of 180-250 mesh and an SiO2 content of ≥99%.

[0015] Preferably, the microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 7-13°C, an encapsulation rate of 82-95%, and a wall thickness of 12-28 μm.

[0016] Preferably, the preparation method of the hydrophilic amino graphene includes the following steps: Step A1: Graphene oxide is dispersed in anhydrous ethanol at a concentration of 0.8-1.2 wt%, and ultrasonically dispersed for 20-40 min to obtain a graphene oxide dispersion for later use; Step A2: γ-aminopropyltriethoxysilane is added to the graphene oxide dispersion at a molar ratio of 1:(2-4), and the mixture is prepared at 55-65°C. Reflux for 5-7 hours to obtain an aminated intermediate for later use; Step A3: Add dopamine hydrochloride to the aminated intermediate, the amount of dopamine hydrochloride added is 0.4-0.6 wt% of the graphene oxide mass, adjust the pH value to 8.0-9.0 with sodium hydroxide solution, and stir at room temperature for 10-14 hours; Step A4: Centrifuge the product of step A3, wash with anhydrous ethanol 3-5 times, and freeze-dry under vacuum for 24-36 hours to obtain hydrophilic aminated graphene.

[0017] Preferably, the preparation method of the hydrophobic thiolized reduced graphene oxide includes the following steps: Step B1: Graphene oxide is dispersed in deionized water at a concentration of 1.0-1.5 wt%, and ultrasonically dispersed for 30 min to obtain an aqueous solution of graphene oxide for later use; Step B2: Ascorbic acid is added to the aqueous solution of graphene oxide at a mass ratio of 1:(4-6), and the mixture is reduced at 75-85℃ for 3-5 h. The C / O ratio is measured to reach 5.5-8.5 by XPS to obtain partially reduced graphene oxide for later use; Step B 3: After centrifugation and washing, the partially reduced graphene oxide is transferred to N,N-dimethylformamide solvent and ultrasonically dispersed for 20 min; Step B4: 3-mercaptopropyltrimethoxysilane is added to the dispersion in step B3, with a mass ratio of partially reduced graphene oxide to 3-mercaptopropyltrimethoxysilane of 1:(0.3-0.5), and the reaction is carried out at 115-125℃ for 7-9 h under nitrogen protection; Step B5: The product of step B4 is washed 4-6 times with tetrahydrofuran and vacuum dried at 55-65℃ for 12-18 h to obtain hydrophobic thiolized reduced graphene oxide.

[0018] Preferably, steps A2 and B4 are carried out in a reaction vessel equipped with a thermometer, a stirring device, nitrogen protection, reflux condensation and tail gas absorption device, and the stirring rate is 200-600 rpm; the ultrasonic power of steps A1 and B1 is 300-500W and the ultrasonic frequency is 40-60kHz; the vacuum freeze-drying temperature of step A4 is -50 to -40℃ and the vacuum degree is <10Pa; the vacuum drying vacuum degree of step B5 is <100Pa.

[0019] Preferably, the preparation method of the microcapsule-encapsulated thermosensitive coagulant includes the following steps: Step C1: Weigh the coagulant core material according to the mass percentage, wherein the coagulant core material includes 25-35% sodium aluminate, 20-30% aluminum sulfate, 3-7% lithium carbonate, and 35-45% nano calcium carbonate, mix and ball-mill to a D50 of 4-6 μm to obtain a core material mixture for later use; Step C2: Add the core material mixture to deionized water, wherein the mass ratio of the core material mixture to deionized water is 1:(3-5), add polyvinyl alcohol as a dispersant, wherein the amount of polyvinyl alcohol added is 1-3% of the mass of the core material, and stir to form a suspension; Step C Step 3: Adjust the pH of the suspension to 4.0-5.0 with hydrochloric acid solution, heat to 50-60℃, add melamine and formaldehyde solution, the molar ratio of melamine to formaldehyde is 1:(2-3), and the mass ratio of melamine to core material is (0.3-0.5):1; Step C4: React at 55-65℃ for 2.5-3.5h, adjust the pH to 7.0-8.0 with sodium hydroxide solution, and continue the reaction for 0.5-1h; Step C5: Cool to room temperature, filter, wash, dry at 45-55℃ to constant weight, and sieve to a particle size of 80-350μm to obtain microcapsule-coated temperature-sensitive coagulant.

[0020] Preferably, the preparation method of the in-situ whisker precursor includes the following steps: Step D1: Prepare magnesium nitrate solution and aluminum nitrate solution with a concentration of 0.4-0.6M respectively, mix them in a molar ratio of (1.5-2.5):(0.8-1.2) to obtain a mixed salt solution for later use; Step D2: Prepare sodium carbonate solution with a concentration of 0.8-1.2M for later use; Step D3: Add sodium carbonate solution dropwise to the mixed salt solution under vigorous stirring at 55-65℃. Add sodium carbonate solution, controlling the dropping rate to maintain the pH value at 9.5-10.5, with a molar ratio of mixed salt solution to sodium carbonate solution of 1:(0.25-0.35); Step D4: After the dropping is completed, age at 60℃ for 20-28h; Step D5: Filter and wash the product until the pH value of the filtrate is 6.5-7.5, dry at 75-85℃ for 8-12h, grind and pass through a 200-300 mesh sieve to obtain the in-situ whisker generation precursor.

[0021] The present invention also provides a method for preparing the above-mentioned underwater concrete rapid repair material, comprising the following steps: Step (1): Weigh the solid components of the cementitious material system, the intelligent curing adjustment system, the auxiliary additives, and the filler system according to the proportion, mix them, and dry mix them in a high-speed mixer for 2-4 minutes at a stirring speed of 800-1200 rpm to obtain a dry mixture for later use; Step (2): Add hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide to a water-reducing agent aqueous solution, wherein the mass concentration of the water-reducing agent in the water-reducing agent aqueous solution is 5-10%, and ultrasonically disperse for 10-20 minutes at an ultrasonic power of 350-450W; Step (3): Add nano-silica to the dispersion in step (2), and mechanically stir. Stir for 4-6 minutes at a stirring rate of 300-500 rpm to form a stable graphene suspension for later use; Step (4): Add the graphene suspension to the dry mixture and stir at low speed for 1.5-2.5 minutes at a stirring rate of 100-200 rpm; Step (5): Add the remaining water and liquid additives and stir at medium speed for 2.5-3.5 minutes at a stirring rate of 300-450 rpm; Step (6): Add the microcapsule-encapsulated thermosensitive coagulant and in-situ whiskers to generate precursors, and stir at high speed for 1.5-2.5 minutes at a stirring rate of 500-700 rpm to obtain a uniform slurry, which is the graphene-modified underwater concrete rapid repair material; The total preparation time is controlled within 8-12 minutes.

[0022] Preferably, step (1) uses a double-helix conical mixer or a planetary mixer for dry mixing; the ultrasonic frequency in step (2) is 40-60kHz; steps (4)-(6) use a planetary mixer for wet mixing, and the ambient temperature is controlled at 15-30℃ during the mixing process; in step (6), the microcapsule-encapsulated temperature-sensitive coagulant and the in-situ whisker precursor should be added in the last stage of the mixing process, and the mixture should be quickly and evenly stirred immediately after addition.

[0023] The present invention also provides the application of the above-mentioned rapid underwater concrete repair material in the repair of underwater concrete structures.

[0024] Preferably, the underwater concrete structure includes one or more of the following: port wharf, offshore platform, cross-sea bridge pier, hydraulic dam, underwater tunnel, and submarine pipeline base.

[0025] This invention also provides an underwater repair construction method for the above-mentioned underwater concrete rapid repair material, comprising the following steps: Step I: Cleaning the surface of the underwater concrete to be repaired, using underwater high-pressure water jet or mechanical grinding to remove loose layers, contaminants, and attached organisms, cleaning to the depth of exposing the solid base layer; Step II: Roughening the base layer surface, using underwater chisel or wire brush grinding to form a rough texture 3-5mm deep on the base layer surface, and rinsing it clean with water after roughening; Step III: Adjusting the water-cement ratio of the material according to the underwater ambient temperature and the water depth of the repair area: the water-cement ratio is 0.28-0.30 when the water temperature is 4-10℃, 0.29-0.31 when the water temperature is 10-20℃, and 0.29-0.31 when the water temperature is 20-28℃. The ratio is 0.30-0.32; Step IV: Prepare the repair material slurry according to the aforementioned preparation method; Step V: Inject the slurry into the repair area through an underwater pumping device or an underwater non-dispersible grouting pipe, with the injection speed controlled at 8-15 L / min, and the repair thickness per layer not exceeding 50 mm; Step VI: When the repair thickness exceeds 30 mm, the repair area contains exposed rebar, the repair area has a complex shape, or the water depth exceeds 10 m, use an underwater vibrating device to compact the repair material, with a vibration time of 10-30 s / m²; Step VII: After the repair is completed, allow it to cure naturally underwater, with an initial setting time of 4-18 min, a 24-hour strength reaching 45-55% of the design strength, and a 7-day strength reaching 80-90% of the design strength.

[0026] Preferably, in step I, the pressure of the underwater high-pressure water jet is 15-25 MPa; in step V, when the repair depth exceeds 50 mm, layered construction is adopted, with an interval of 15-30 min between each layer; in step VII, when the water temperature is below 10℃, the initial setting time is 10-18 min; when the water temperature is 10-20℃, the initial setting time is 6-12 min; when the water temperature is above 20℃, the initial setting time is 4-8 min.

[0027] Beneficial effects:

[0028] In the graphene-modified underwater concrete rapid repair material of this invention, a bifunctional graphene system constructs a unique "hydrophilic-hydrophobic" gradient transition interface layer through the synergistic effect of hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide. The amino and dopamine functional groups grafted onto the surface of the hydrophilic aminated graphene mimic the underwater adhesion mechanism of mussel byssal proteins. The catechol groups form stable coordination bonds with calcium ions on the cement matrix surface, hydrogen bonds with hydroxyl groups, and covalent bonds with siloxy groups in the underwater environment, achieving triple chemical bonding and significantly improving the material's wettability and initial adhesion to damp surfaces. The hydrophobic thiolized reduced graphene oxide forms a hydrophobic barrier in the interface transition region, effectively preventing water molecules from continuously penetrating into the interface and ensuring the long-term stability of the adhesive layer. This dual-function synergistic design enables the material's wet interface bonding strength to reach 2.5-3.2 MPa, which is more than 200% higher than that of ordinary repair materials. The wet bonding strength can reach more than 85% of that in the dry state, while traditional materials only reach 50-60%.

[0029] The graphene-modified underwater concrete rapid repair material of this invention further enhances interfacial properties through the bridging effect and directional arrangement mechanism of graphene nanosheets. During underwater curing, the osmotic pressure difference drives the layered graphene to oriented alignments at the interface between the old and new concrete. Vertically, it anchors itself into the micropores of the old concrete surface, while horizontally it bridges microcracks, forming a "anchoring-bridging" dual-reinforcement structure. This nanoscale interfacial reinforcement mechanism reduces the interfacial fracture energy from 80-120 J / m² for ordinary materials. 2 Increased to 350-450 J / m 2 The improvement is up to 300%, effectively solving the problem that the interface of traditional repair materials is a weak link.

[0030] The graphene-modified underwater concrete rapid repair material of this invention achieves temperature-adaptive rapid curing through an intelligent curing regulation system. Microencapsulated temperature-sensitive accelerators, using melamine-formaldehyde resin as the shell material and aluminate-sulfoaluminate composite accelerator core material, are designed with a glass transition temperature of 7-13℃. At a low temperature of 4℃, 15% of the accelerator is released within 1 hour for slow curing; at a normal temperature of 25℃, 80% of the accelerator is released within 1 hour for rapid curing, avoiding the problems of traditional rapid-setting agents failing at low temperatures or bursting at high temperatures. Simultaneously, this system utilizes the activating effect of chloride and sulfate ions in seawater on aluminates, increasing the curing speed in seawater environments by 30-40% compared to freshwater environments, fully utilizing the unique ionic composition of the marine environment. Through the dual triggering mechanism of temperature and salt ions, the underwater initial setting time of the material can be precisely controlled within the range of 4-18 minutes. The initial setting time is 10-18 minutes at 4℃, 6-12 minutes at 10-20℃, and 4-8 minutes above 20℃, which can adapt to the construction needs under different water depths, water temperatures, and flow rates.

[0031] This invention relates to a graphene-modified underwater concrete rapid repair material that constructs a three-dimensional toughening network through an in-situ whisker generation mechanism. The in-situ whisker generation precursor slowly hydrates in an alkaline cement environment to generate plate-like hydrotalcite nanocrystals. These crystals grow along the c-axis to form high aspect ratio nanowhiskers, with aspect ratios exceeding 50. These in-situ generated nanowhiskers interweave with graphene sheets in three-dimensional space to form a network structure. The graphene sheets provide high strength and stiffness in the plane, while the nanowhiskers provide toughness and crack deflection capability in the vertical direction. Their synergistic effect allows the material to maintain high strength while exhibiting excellent toughness. This composite reinforcement mechanism enables the material to achieve a 28-day compressive strength of 55-65 MPa, more than 50% higher than ordinary repair materials, while simultaneously achieving a flexural strength of 8-11 MPa and a 200% increase in fracture toughness, effectively overcoming the defects of traditional rapid-hardening cement-based materials, such as high brittleness and poor impact resistance.

[0032] The graphene-modified underwater concrete rapid repair material of this invention exhibits excellent performance, achieving initial setting underwater in 4-18 minutes, reaching 45-55% of its design strength after 24 hours, and 80-90% after 7 days. This reduces curing time by 60-70% compared to traditional products, meeting the needs of emergency repairs and rapid restoration. The material's chloride ion permeability coefficient is below 1000°C, more than 60% lower than ordinary repair materials, effectively resisting chloride ion corrosion in seawater. In accelerated aging tests simulating marine environments, the material retains over 90% of its bond strength after 3 years of service, while ordinary repair materials only retain 65-75%, demonstrating superior long-term durability. Through multiple innovative designs, including synergistic modification of bifunctional graphene, temperature adaptive control of the intelligent curing system, and a three-dimensional toughening mechanism using in-situ whiskers, this invention achieves integrated underwater rapid curing, strong adhesion, high strength and toughness, and long-term protection, providing a high-performance solution for rapid repair and emergency maintenance of hydraulic and marine infrastructure. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The various embodiments are provided by way of explanation of the present invention and not by way of limiting the present invention. In fact, those skilled in the art will understand that modifications and variations can be made to the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present invention include such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0034] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0035] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0036] This invention addresses at least one of the problems existing in current underwater concrete repair materials, namely slow underwater curing, low wet bonding strength, weak interfacial bonding, poor temperature adaptability, and insufficient long-term durability, and provides a rapid underwater concrete repair material, specifically a bifunctional graphene-modified repair material.

[0037] The inventors discovered that the core challenge in underwater concrete repair lies in the formation of a "water film" at the interface between old and new concrete, severely hindering effective contact between the adhesive and the substrate. Traditional modification methods either focus on increasing the material's hydrophilicity to promote wetting or on increasing its hydrophobicity to prevent water penetration, making it difficult to achieve both simultaneously. Inspired by the strong underwater adhesion mechanism of mussels and the two-dimensional nanostructure of graphene, if a "hydrophilic-hydrophobic" gradient transition interface layer can be constructed, ensuring both initial wetting and subsequent waterproofing, while simultaneously utilizing the bridging effect of graphene sheets to enhance the interface, it is expected to fundamentally solve the problem of weak adhesion at wet interfaces. Furthermore, by designing a smart curing system with dual salt excitation and temperature responses, combined with in-situ generation of nanocrystals to construct a three-dimensional toughening network, rapid curing, high strength, and high toughness can be synergistically improved simultaneously. Organically combining these innovative mechanisms can help solve or improve the aforementioned problems existing in current underwater concrete repair materials.

[0038] The underwater concrete rapid repair material of this invention comprises, by weight, the following components: 67-80 parts of a cementitious material system (e.g., 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, or 80 parts), 0.6-1.2 parts of a bifunctional graphene system (e.g., 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, or 1.2 parts), 3-5 parts of an intelligent curing adjustment system (e.g., 3, 3.5, 4, 4.5, or 5 parts), and 2-3 parts of auxiliary additives. The system comprises 3 parts (e.g., 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, or 3 parts), 20-25 parts (e.g., 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts) of filler system and 18-25 parts (e.g., 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts) of water; the bifunctional graphene system includes hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide, with a mass ratio of (1.2-1.8):(0.8-1.2); the intelligent curing regulation system includes microcapsule-encapsulated temperature-sensitive coagulant and in-situ whisker generation precursor.

[0039] In the underwater concrete rapid repair material of this invention, a bifunctional graphene system constructs a unique "hydrophilic-hydrophobic" gradient transition interface layer through the synergistic effect of hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide. The amino and dopamine functional groups grafted onto the surface of the hydrophilic aminated graphene mimic the underwater adhesion mechanism of mussel byssal proteins. The catechol groups form a triple chemical bond with the cement matrix surface in the underwater environment, consisting of coordination bonds, hydrogen bonds, and covalent bonds, significantly improving the initial adhesion and interfacial wettability of the material on damp surfaces. The hydrophobic thiolized reduced graphene oxide forms a hydrophobic barrier in the interfacial transition region. The thiol groups (-SH) work together with the partially reduced graphene framework to effectively prevent water molecules from continuously penetrating into the interface, ensuring the long-term stability of the adhesive layer. Through the directional arrangement of graphene nanosheets at the interface, they vertically anchor into the micropores of the old concrete and horizontally bridge microcracks, forming a "anchoring-bridging" dual-reinforcement structure, increasing the interfacial fracture energy by more than 300%.

[0040] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the hydrophilic aminated graphene is prepared by a method comprising the following steps: A1. Dispersing graphene oxide in anhydrous ethanol, wherein the graphene oxide concentration is 0.8-1.2 wt% (e.g., 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, or 1.2 wt%). A1. Graphene oxide dispersion is prepared by ultrasonic dispersion for 20-40 min (e.g., 20 min, 25 min, 30 min, 35 min, or 40 min) to obtain a graphene oxide dispersion for later use; A2. γ-aminopropyltriethoxysilane is added to the graphene oxide dispersion, with a molar ratio of graphene oxide to γ-aminopropyltriethoxysilane of 1:(2-4) (e.g., 1:2, 1:2.5, 1:3, 1:3.5, or 1:4), and refluxed at 55-65℃ (e.g., 55℃, 57℃, 60℃, 63℃, or 65℃) for 5-7 h (e.g., 5 h, 5.5 h, 6 h, 6.5 h, or 7 h) to obtain an amination intermediate for later use; A3. Dopamine hydrochloride is added to the amination intermediate, with the amount of dopamine hydrochloride added being 0.4-0.6 wt% of the mass of graphene oxide (e.g., 0.4 wt%, 0.45 wt%). A3. The product of step A3 is prepared by centrifugation, washed 3-5 times with anhydrous ethanol (e.g., 3, 4 or 5 times), and freeze-dried under vacuum for 24-36 hours (e.g., 24 hours, 28 hours, 32 hours or 36 hours) to obtain hydrophilic aminographene.

[0041] In the preparation of hydrophilic aminated graphene, amino groups are introduced on the surface of graphene oxide through silanization reaction, which not only maintains a certain degree of hydrophilicity but also provides active sites for reaction with cement hydration products. Subsequent dopamine grafting further enhances the underwater adhesion ability, and the catechol groups exhibit excellent adhesion performance in alkaline cement environment.

[0042] Preferably, step A2 is carried out in a reaction vessel equipped with a thermometer, a stirring device, nitrogen protection, reflux condensation, and tail gas absorption device, with a stirring rate of 200-600 rpm (e.g., 200 rpm, 300 rpm, 400 rpm, 500 rpm, or 600 rpm); the ultrasonic power of step A1 is 300-500 W (e.g., 300 W, 350 W, 400 W, 450 W, or 500 W), and the ultrasonic frequency is 40-60 kHz (e.g., 40 kHz, 45 kHz, 50 kHz, 55 kHz, or 60 kHz); the vacuum freeze-drying temperature of step A4 is -50 to -40°C (e.g., -50°C, -48°C, -45°C, -42°C, or -40°C), and the vacuum degree is <10 Pa.

[0043] More preferably, the degree of amino grafting of the hydrophilic amino graphene is 12-28% (e.g., 12%, 15%, 18%, 20%, 23%, 25% or 28%), which is the total content of all amino functional groups (including amino groups introduced by γ-aminopropyltriethoxysilane and amino groups introduced by dopamine) in the final product, calculated by integrating the CN peak area of ​​XPS; the particle size is 500-2000 nm (e.g., 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm or 2000 nm), determined by a laser particle size analyzer; and the water contact angle is less than 15° (e.g., 5°, 8°, 10°, 12° or 15°). Low amino grafting density (<12%) leads to insufficient chemical bonding sites with the cement matrix, resulting in decreased interfacial bonding strength. High amino grafting density (>28%) causes excessive hydrophilicity of the graphene surface, leading to excessive swelling in underwater environments and reduced interfacial stability. Furthermore, excessive grafting density disrupts the conjugated structure of graphene, reducing its mechanical reinforcing effect. Particle size control within the 500-2000 nm range is beneficial for uniform dispersion in the cement matrix; excessively small particle sizes tend to agglomerate, while excessively large particle sizes result in rapid sedimentation and difficulty in dispersion.

[0044] In a preferred embodiment of the graphene-modified underwater concrete rapid repair material of the present invention, the hydrophobic thiolized reduced graphene oxide is prepared by a method comprising the following steps: B1. Dispersing graphene oxide in deionized water, the graphene oxide concentration being 1.0-1.5 wt% (e.g., 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%). B2. Add ascorbic acid to the graphene oxide aqueous solution, with a graphene oxide to ascorbic acid mass ratio of 1:(4-6) (e.g., 1:4, 1:4.5, 1:5, 1:5.5 or 1:6), and reduce it at 75-85℃ (e.g., 75℃, 77℃, 80℃, 83℃ or 85℃) for 3-5 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours). The C / O ratio should be adjusted to 5.5-8.5 (e.g., 5.5, 6, 7, 7.5, 8 or 8.5) by XPS detection to obtain partially reduced graphene oxide, which is then set aside. B3. After centrifugation and washing, the partially reduced graphene oxide is transferred to N,N-dimethylformamide solvent and ultrasonically dispersed for 20 minutes. B4. Add ascorbic acid to the graphene oxide aqueous solution, with a graphene oxide to ascorbic acid mass ratio of 1:(4-6) (e.g., 1:4, 1:4.5, 1:5, 1:5.5 or 1:6), and reduce it at 75-85℃ (e.g., 75℃, 77℃, 80℃, 83℃ or 85℃) for 3-5 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours). 3-Mercaptopropyltrimethoxysilane is added to the dispersion of step B3, and the mass ratio of partially reduced graphene oxide to 3-mercaptopropyltrimethoxysilane is 1:(0.3-0.5) (e.g., 1:0.3, 1:0.35, 1:0.4, 1:0.45, or 1:0.5). The reaction is carried out under nitrogen protection at 115-125°C (e.g., 115°C, 117°C, 120°C, 123°C, or 125°C). B4. Wash the product of step B4 with tetrahydrofuran 4-6 times (e.g., 4, 5 or 6 times), and vacuum dry at 55-65°C (e.g., 55°C, 57°C, 60°C, 63°C or 65°C) for 12-18 hours (e.g., 12 hours, 14 hours, 16 hours or 18 hours) to obtain hydrophobic thiolized reduced graphene oxide.

[0045] The key to preparing hydrophobic thiolized reduced graphene oxide lies in precisely controlling the degree of reduction. When the C / O ratio is 5.5-8.5, the necessary oxygen-containing functional groups are retained to facilitate the subsequent thiolization reaction, while the hydrophobicity and conductivity of graphene are restored. The introduction of thiol groups further enhances the hydrophobicity and can chelate with heavy metal ions to improve the corrosion resistance of the material.

[0046] Preferably, step B4 is carried out in a reaction vessel equipped with a thermometer, a stirring device, nitrogen protection, reflux condensation, and tail gas absorption device, with a stirring rate of 200-600 rpm (e.g., 200 rpm, 300 rpm, 400 rpm, 500 rpm, or 600 rpm); the ultrasonic power of step B1 is 300-500 W (e.g., 300 W, 350 W, 400 W, 450 W, or 500 W), and the ultrasonic frequency is 40-60 kHz (e.g., 40 kHz, 45 kHz, 50 kHz, 55 kHz, or 60 kHz); and the vacuum drying vacuum degree of step B5 is <100 Pa (e.g., 20 Pa, 40 Pa, 60 Pa, 80 Pa, or 100 Pa).

[0047] More preferably, the thiol content of the hydrophobic thiolized reduced graphene oxide is 0.6-1.4 mmol / g (e.g., 0.6 mmol / g, 0.8 mmol / g, 1.0 mmol / g, 1.2 mmol / g, or 1.4 mmol / g), determined by the Ellman reagent colorimetric method; the water contact angle is 95-110° (e.g., 95°, 100°, 105°, or 110°). Wherein, too low a thiol content (<0.6 mmol / g) results in insufficient hydrophobicity and inability to effectively prevent water penetration; too high a thiol content (>1.4 mmol / g) makes it difficult for graphene to disperse in cement paste, and excessive thiol groups may oxidize into disulfide bonds in an alkaline environment, affecting the material's stability.

[0048] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the mass ratio of hydrophilic aminated graphene to hydrophobic thiolized reduced graphene oxide is (1.2-1.8):(0.8-1.2) (e.g., 1.2:0.8, 1.3:0.9, 1.5:1.0, 1.6:1.1, or 1.8:1.2). This mass ratio is designed based on the construction requirements of the interface gradient structure. The hydrophilic graphene content is slightly higher to ensure initial wetting and adhesion, while an appropriate amount of hydrophobic graphene is added to form a later waterproof layer. If the proportion of hydrophilic graphene is too high, although the initial adhesion is strong, the interface layer will absorb too much water and expand excessively in the underwater environment, leading to a decrease in bonding strength. If the proportion of hydrophobic graphene is too high, the initial wetting is insufficient, and it cannot fully contact the substrate, resulting in weak initial adhesion.

[0049] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the microencapsulated temperature-sensitive accelerator is prepared by a method comprising the following steps: C1. Weighing the accelerator core material by mass percentage, comprising 25-35% sodium aluminate (e.g., 25%, 27%, 30%, 32% or 35%), 20-30% aluminum sulfate (e.g., 20%, 23%, 25%, 27% or 30%), 3-7% lithium carbonate (e.g., 3%, 4%, 5%, 6% or 7%), and 35-45% nano-calcium carbonate (e.g., 35%, 38%, 40%, 42% or 45%), and ball milling the mixture to D. 50 C1. Obtain a core material mixture with a thickness of 4-6 μm and set aside; C2. Add the core material mixture to deionized water at a mass ratio of 1:(3-5) (e.g., 1:3, 1:3.5, 1:4, 1:4.5, or 1:5), add polyvinyl alcohol as a dispersant at 1-3% of the core material mass (e.g., 1%, 1.5%, 2%, 2.5%, or 3%), and stir to form a suspension; C3. Adjust the pH of the suspension to 4.0-5.0 with hydrochloric acid solution, heat to 50-60℃ (e.g., 50℃, 52℃, 54℃, 56℃, 58℃, or 60℃), and add melamine and formaldehyde solutions at a molar ratio of melamine to formaldehyde of 1:(2-3). (e.g., 1:2, 1:2.5, or 1:3), the mass ratio of melamine to core material is (0.3-0.5):1 (e.g., 0.3:1, 0.35:1, 0.4:1, 0.45:1, or 0.5:1); C4. React at 55-65℃ for 2.5-3.5h (e.g., 2.5h, 2.8h, 3h, 3.2h, or 3.5h), adjust the pH to 7.0-8.0 with sodium hydroxide solution (e.g., 7.0 or 8.0), and continue the reaction for 0.5-1h (e.g., 0.5h, 0.6h, 0.8h, or 1h); C5. Cool to room temperature, filter, wash, dry at 45-55℃ to constant weight, and sieve to a particle size of 80-350μm to obtain microcapsule-coated temperature-sensitive coagulant.

[0050] The core of the design of microencapsulated temperature-sensitive coagulant lies in the fact that the glass transition temperature of the melamine-formaldehyde resin shell is exactly within the common underwater temperature range. At low temperatures, the shell is in a glassy state, which is dense, hard, and has good encapsulation properties. When the temperature rises above Tg, the shell transforms into a highly elastic state, which increases permeability and allows the coagulant to be released, thus achieving temperature-adaptive curing.

[0051] Preferably, the glass transition temperature (Tg) of the microencapsulated temperature-sensitive accelerator is 7-13°C (e.g., 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, or 13°C), determined by differential scanning calorimetry (DSC); the encapsulation efficiency is 82-95% (e.g., 82%, 85%, 88%, 90%, 92%, or 95%), determined by Soxhlet extraction; and the wall thickness is 12-28 μm (e.g., 12 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, or 28 μm), observed and measured by scanning electron microscopy. A Tg that is too low (<7°C) will cause the material to cure too quickly in low-temperature environments during winter, resulting in a short application window; a Tg that is too high (>13°C) will result in slow curing at room temperature, failing to meet the needs of rapid repair. If the encapsulation rate is too low (<82%), the accelerator will leak more and the storage stability will be poor; if the wall thickness is too thin (<12μm), the mechanical strength will be insufficient and it will be easily damaged during the stirring process; if the wall thickness is too thick (>28μm), the release rate will be slow and the curing efficiency will be affected.

[0052] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the in-situ whisker generation precursor is prepared by a method comprising the following steps: D1. Preparing magnesium nitrate solution and aluminum nitrate solution with concentrations of 0.4-0.6M (e.g., 0.4M, 0.45M, 0.5M, 0.55M or 0.6M), respectively, in a molar ratio of (1.5-2.5):(0.8-1.2) (e.g., 1.5:0.8, 2:0.8, 2.5:0.8, ...). D1. Mix 1.5:0.8, 1.5:0.8, 1.5:1, 1.5:1.2, 2:0.8, 2:1, 2:1.2, 2.5:0.8, 2.5:1, or 2.5:1.2 to obtain a mixed salt solution for later use; D2. Prepare a sodium carbonate solution with a concentration of 0.8-1.2M (e.g., 0.8M, 0.85M, 0.9M, 0.95M, 1.0M, 1.1M, or 1.2M) for later use; D3. Heat at 55-65°C... Under conditions of vigorous stirring and at ℃ (e.g., 55℃, 57℃, 60℃, 63℃, or 65℃), sodium carbonate solution is added dropwise to the mixed salt solution, controlling the dropping rate to maintain the pH at 9.5-10.5 (e.g., 9.5, 10, or 10.5). The molar ratio of the mixed salt solution to the sodium carbonate solution is 1:(0.25-0.35) (e.g., 1:0.25, 1:0.3, or 1:0.35). D4. After the addition is complete, the mixture is aged at a constant temperature of 60℃. D5. Filter and wash the product until the pH of the filtrate is 6.5-7.5 (e.g., 6.5, 7 or 7.5), dry it at 75-85°C (e.g., 75°C, 77°C, 80°C, 83°C or 85°C) for 8-12 hours (e.g., 8 hours, 9 hours, 10 hours, 11 hours or 28-12 hours), grind it and pass it through a 200-300 mesh sieve to obtain the in-situ whisker generation precursor.

[0053] The precursor for in-situ whisker generation is layered double hydroxides (LDHs) precursor. Its layered structure is reconstructed in an alkaline cement environment through the "memory effect" and grows along the c-axis to form high aspect ratio nano whiskers. These whiskers interweave with graphene sheets to form a three-dimensional toughened network.

[0054] Preferably, the magnesium-aluminum molar ratio in the in-situ whisker formation precursor is (1.5-2.5):(0.8-1.2) (e.g., 1.5:0.8, 1.8:0.9, 2.0:1.0, 2.2:1.1, or 2.5:1.2). Controlling the magnesium-aluminum ratio within this range allows for the formation of a precursor with a typical hydrotalcite structure, which can stably exist in the alkaline environment of cement (pH>12) and slowly hydrate to form whiskers. If the magnesium-aluminum ratio is too low (<1.5:0.8), the generated whiskers have a small aspect ratio and poor toughening effect; if the magnesium-aluminum ratio is too high (>2.5:1.2), the precursor's stability in the cement paste decreases, leading to premature hydration and preventing in-situ formation.

[0055] More preferably, XRD diffraction analysis revealed that the characteristic diffraction peaks of the in-situ whisker precursor were located at 2θ = 11.5°±0.3°, 23.2°±0.3°, and 34.8°±0.3°, corresponding to the (003), (006), and (009) crystal planes of hydrotalcite. SEM observation showed that the precursor exhibited a hexagonal plate-like morphology with a plate diameter of 50-200 nm and a thickness of 5-15 nm. After hydration in an alkaline cement environment for 48 h, TEM observation revealed that the generated nanowhiskers had a length of 200-800 nm, a diameter of 5-15 nm, and an aspect ratio of 50-150.

[0056] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the cementitious material system comprises 50-55 parts of silicate cement, 10-15 parts of sulfoaluminate cement, and 7-10 parts of ultrafine slag powder; the silicate cement is ordinary silicate cement or rapid-hardening silicate cement with a strength grade not lower than 52.5; the sulfoaluminate cement has a tricalcium aluminate (C3A) content ≥40%; and the ultrafine slag powder has a specific surface area ≥600 m². 2 / kg, with an activity index ≥95%. In the cementitious material system, silicate cement provides long-term strength and durability, sulfoaluminate cement provides rapid curing capability and early strength, and ultrafine slag powder improves workability and provides potential hydraulic activity. The rapid setting mechanism of sulfoaluminate cement is that its contained ettringite (AFt) phase is rapidly generated in the early stage of hydration, and the setting accelerator released by microcapsules further accelerates this process. At the same time, it utilizes sulfate ions in seawater for activation, achieving an adjustable initial setting time of 4-18 minutes.

[0057] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the auxiliary additives include 0.8-1.3 parts of water-reducing agent (e.g., 0.8, 0.9, 1.0, 1.1, 1.2, or 1.3 parts), 0.4-0.8 parts of nano-silica (e.g., 0.4, 0.5, 0.6, 0.7, or 0.8 parts), 0.15-0.3 parts of defoamer (e.g., 0.15, 0.2, 0.25, or 0.3 parts), and 0.25-0.5 parts of cellulose ether (e.g., 0.25, 0.3, 0.35 parts). The water-reducing agent is a polycarboxylate superplasticizer with a solid content of 35-45% (e.g., 35%, 36%, 35%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%). The nano-silica has an average particle size of 15-30 nm (e.g., 15 nm, 20 nm, 25 nm, or 30 nm) and a specific surface area of ​​180-250 m². 2 / g (e.g., 180m) 2 / g、190m 2 / g、200m 2 / g、220m 2 / g、230m 2 / g、240m 2 / g or 250m 2 / g); the defoamer is an organosilicon defoamer or a mineral oil defoamer; the cellulose ether is hydroxypropyl methylcellulose ether with a viscosity of (3-8) ten thousand. (For example, 30,000) 40,000 50,000 60,000 70,000 Or 80,000 The expanding agent is a calcium sulfoaluminate or calcium oxide expanding agent. The water-reducing agent lowers the water-cement ratio while ensuring workability; nano-silica acts as both a graphene dispersion stabilizer and fills cement stone pores, increasing density; the defoamer eliminates air bubbles introduced by stirring, improving material density; cellulose ether provides water retention and anti-dispersion properties, crucial for underwater construction; and the expanding agent compensates for shrinkage and improves interfacial bonding force.

[0058] In a preferred embodiment of the underwater concrete rapid repair material of the present invention, the filler system comprises 12-18 parts of quartz sand (e.g., 12, 13, 14, 15, 16, 17, or 18 parts) and 6-10 parts of quartz powder (e.g., 6, 7, 8, 9, or 10 parts); the quartz sand has a particle size of 35-80 mesh (e.g., 35, 40, 45, 50, 60, 70, or 80 mesh) and an SiO2 content ≥98%; the quartz powder has a particle size of 180-250 mesh (e.g., 180, 200, or 250 mesh) and an SiO2 content ≥99%. The filler system adopts a coarse-fine gradation design, with quartz sand providing skeletal support and quartz powder filling the pores, jointly improving the material's density and volume stability, and reducing costs.

[0059] This invention also proposes a method for preparing an underwater concrete rapid repair material. The method for preparing the underwater concrete rapid repair material according to an embodiment of this invention includes the following steps: (1) Weighing the cementitious material system, the intelligent curing adjustment system, the solid components of the auxiliary additives, and the filler system according to the specified proportions, mixing them, and then dry-mixing them in a high-speed mixer for 2-4 minutes (e.g., 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, or 4 minutes) at a mixing speed of 800-1200 rpm (e.g., 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm) to obtain... (1) Dry mix and set aside; (2) Add hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide to the water-reducing agent aqueous solution, wherein the mass concentration of the water-reducing agent in the aqueous solution is 5-10% (e.g., 5%, 6%, 7%, 8%, 9% or 10%), and ultrasonically disperse for 10-20 min (e.g., 10 min, 12 min, 14 min, 16 min, 18 min or 20 min), with an ultrasonic power of 350-450 W (e.g., 350 W, 400 W or 450 W); (3) Add nano silica to the dispersion in step (2) and mechanically stir for 4-6 min (e.g., 4 min). (3) Stir at a speed of 300-500 rpm (e.g., 300 rpm, 400 rpm, or 500 rpm) for 1.5-2.5 min (e.g., 1.5 min, 2 min, or 2.5 min) to form a stable graphene suspension for later use; (4) Add the graphene suspension to the dry mix and stir at a low speed for 1.5-2.5 min (e.g., 1.5 min, 2 min, or 2.5 min) at a speed of 100-200 rpm (e.g., 100 rpm, 150 rpm, or 200 rpm); (5) Add the remaining water and liquid additive and stir at a medium speed for 2.5-3.5 min (e.g., 2 min, 4.5 min, 5 min, 5.5 min, or 6 min) to form a stable graphene suspension for later use; (6) Add the graphene suspension to the dry mix and stir at a low speed for 1.5-2.5 min (e.g., 1.5 min, 2 min, or 2.5 min) at a speed of 100-200 rpm (e.g., 100 rpm, 150 rpm, or 200 rpm); (7) Add the remaining water and liquid additive and stir at a medium speed for 2.5-3.5 min (e.g., 2 min, 4.5 min, 5 min, 5.5 min, or 6 min) at a speed of 300-500 rpm (e.g., 300 rpm, 400 rpm, or 500 rpm) to form a stable graphene suspension for later use; (5 min, 3 min or 3.5 min), stirring rate is 300-450 rpm (e.g. 300 rpm, 350 rpm, 400 rpm or 450 rpm); (6) add microcapsule-coated temperature-sensitive accelerator and in-situ whiskers to generate precursor, stir at high speed for 1.5-2.5 min (e.g. 1.5 min, 2 min or 2.5 min), stirring rate is 500-700 rpm (e.g. 5300 rpm, 600 rpm or 700 rpm) to obtain a uniform slurry, which is the underwater concrete rapid repair material; the total preparation time is controlled within 8-12 min.

[0060] The steps in the preparation method of the graphene-modified underwater concrete rapid repair material of the present invention are designed to: (1) help ensure uniform dispersion. The correct order of addition can ensure uniform dispersion of each component in the cement matrix. If graphene, which is prone to agglomeration, is added first, it will lead to difficulty in dispersion, form an uneven structure, cause unstable material performance, and insufficient strength in local areas; (2) help ensure the stability of microcapsules. Microcapsules must be added at an appropriate stage to avoid premature rupture under high shear stress. If added at the beginning of high-speed stirring, the microcapsules may be destroyed, the accelerator will be released prematurely, and the material will solidify prematurely; (3) (4) It also affects the control of temperature and time. The entire preparation process is controlled within 8-12 minutes to ensure sufficient mixing and avoid premature solidification of materials. In particular, microcapsules and precursors are added in the last stage. After addition, they are quickly stirred evenly and applied as soon as possible. (5) The segmented stirring rate design is beneficial to the process requirements of different stages. Low-speed mixing avoids damage to microcapsules, medium-speed stirring ensures uniform mixing, and high-speed stirring achieves final homogenization.

[0061] In a preferred embodiment of the preparation method of the underwater concrete rapid repair material of the present invention, step (1) is dry mixing using a double helical cone mixer or a planetary mixer; the ultrasonic frequency of step (2) is 40-60 kHz (e.g., 40 kHz, 45 kHz, 50 kHz, 55 kHz or 60 kHz); steps (4)-(6) are wet mixing using a planetary mixer, and the ambient temperature is controlled at 15-30 ℃ (e.g., 15 ℃, 20 ℃, 25 ℃, 28 ℃ or 30 ℃) during the mixing process; in step (6), the microcapsule-encapsulated temperature-sensitive accelerator and the in-situ whisker generation precursor should be added in the last stage of the mixing process, and after addition, the mixture should be quickly and evenly mixed immediately, and the construction should be completed within 5 minutes.

[0062] This invention also proposes an application of a rapid underwater concrete repair material, as described above, for the repair of underwater concrete structures, including one or more of port terminals, offshore platforms, cross-sea bridge piers, hydraulic dams, underwater tunnels, and submarine pipeline foundations. The rapid underwater concrete repair material of this invention is particularly suitable for complex working conditions where dewatering is not possible or rapid repair while submerged is required, achieving integrated rapid underwater construction and long-term protection.

[0063] The main raw materials used in the following examples were sourced from: Graphene oxide: Suzhou Carbon-Feng Graphene Technology Co., Ltd., sheet diameter 0.5-5μm, monolayer ratio >95%; γ-aminopropyltriethoxysilane: Dow Corning, purity ≥98%; Dopamine hydrochloride: Shanghai Aladdin Biochemical Technology Co., Ltd., purity ≥98%; 3-mercaptopropyltrimethoxysilane: Nanjing Nengde New Material Technology Co., Ltd., purity ≥95%; Ascorbic acid: Sinopharm Chemical Reagent Co., Ltd., analytical grade; Silicate cement: Conch brand. 52.5, Anhui Conch Cement Co., Ltd.; Sulfoaluminate cement: Tangshan Arctic Bear Building Materials Co., Ltd., C3A content 42%; Ultrafine slag powder: S95 grade, specific surface area 620m² 2 / kg, Wuhan Iron and Steel Group; Sodium aluminate: Sinopharm Chemical Reagent Co., Ltd., industrial grade; Aluminum sulfate: Tianjin Guangfu Fine Chemical Research Institute, chemically pure; Lithium carbonate: Tianjin Kemei Chemical Reagent Co., Ltd., analytical grade; Nano calcium carbonate: Guangdong Enping Lianwei Calcium Industry Co., Ltd., average particle size 80nm; Melamine: Jinan Hongshun Chemical Co., Ltd., industrial grade; Formaldehyde solution: Tianjin Fuyu Fine Chemical Co., Ltd., concentration 37%; Magnesium nitrate: Tianjin Damao Chemical Reagent Factory, analytical grade; Aluminum nitrate: Sinopharm Chemical Reagent Co., Ltd., analytical grade; Sodium carbonate: Tianjin Tianli Chemical Reagent Co., Ltd., analytical grade; Polycarboxylate superplasticizer: Jiangsu Bote New Material Co., Ltd., solid content 40%; Nano silica: Degussa, Aerosil 200, average particle size 12nm; Organosilicon defoamer: Dow Corning; Hydroxypropyl methylcellulose ether: Shandong Yousuo Chemical Technology Co., Ltd., viscosity 50000 Expansion agent: CSA-Ⅲ type, Tangshan Jidong Cement Co., Ltd.; Quartz sand: Lingshou County, Hebei Province, 40-70 mesh, SiO2 content 98.5%; Quartz powder: Fengyang County, Anhui Province, 200 mesh, SiO2 content 99.2%.

[0064] Example 1

[0065] An underwater concrete rapid repair material, by weight, comprises the following components: 52 parts silicate cement, 12 parts sulfoaluminate cement, 8 parts ultrafine slag powder, 0.5 parts hydrophilic aminated graphene, 0.3 parts hydrophobic thiolized reduced graphene oxide, 2.5 parts microencapsulated thermosensitive accelerator, 1.5 parts in-situ whisker generation precursor, 1.0 part polycarboxylate superplasticizer, 0.6 parts nano silica, 0.2 parts defoamer, 0.3 parts cellulose ether, 0.6 parts expansion agent, 15 parts quartz sand, 8 parts quartz powder, and 21 parts water.

[0066] The preparation method of hydrophilic amino-type graphene is as follows: Step A1: Graphene oxide is dispersed in anhydrous ethanol at a concentration of 1.0 wt%, and ultrasonically dispersed for 30 min at a power of 400 W and a frequency of 50 kHz to obtain a graphene oxide dispersion for later use; Step A2: γ-aminopropyltriethoxysilane is added to the graphene oxide dispersion at a molar ratio of 1:3, and the mixture is refluxed at 60 °C for 6 h. The stirring rate was 400 rpm to obtain an amination intermediate, which was set aside for later use. Step A3: Dopamine hydrochloride was added to the amination intermediate at an amount of 0.5 wt% of the graphene oxide mass. The pH was adjusted to 8.5 with sodium hydroxide solution, and the mixture was stirred at room temperature for 12 h. Step A4: The product from step A3 was centrifuged, washed four times with anhydrous ethanol, and freeze-dried under vacuum at -45℃ and <10 Pa for 30 h to obtain hydrophilic amination-modified graphene. The obtained hydrophilic amination-modified graphene had an amino grafting degree of 20%, a particle size of 1200 nm, and a water contact angle of 10°. The preparation method of hydrophobic thiolized reduced graphene oxide is as follows: Step B1: Graphene oxide is dispersed in deionized water at a concentration of 1.2 wt%, and ultrasonically dispersed for 30 min at a power of 400 W and a frequency of 50 kHz to obtain an aqueous solution of graphene oxide for later use; Step B2: Ascorbic acid is added to the aqueous solution of graphene oxide at a mass ratio of 1:5, and the mixture is reduced at 80 °C for 4 h. XPS analysis shows that the C / O ratio reaches 6.8, yielding partially reduced graphene oxide for later use; Step B3: Partially... After centrifugation and washing, the reduced graphene oxide was transferred to N,N-dimethylformamide solvent and ultrasonically dispersed for 20 min. Step B4: 3-Mercaptopropyltrimethoxysilane was added to the dispersion from Step B3, with a mass ratio of partially reduced graphene oxide to 3-mercaptopropyltrimethoxysilane of 1:0.4. The reaction was carried out at 120℃ for 8 h under nitrogen protection with a stirring rate of 400 rpm. Step B5: The product from Step B4 was washed five times with tetrahydrofuran and vacuum-dried at 60℃ and a vacuum degree <100 Pa for 15 h to obtain hydrophobic thiolized reduced graphene oxide. The obtained hydrophobic thiolized reduced graphene oxide had a C / O ratio of 7.0, a thiol content of 1.0 mmol / g, and a water contact angle of 102°.The preparation method of microencapsulated thermosensitive coagulant is as follows: Step C1: Weigh the coagulant core material according to the mass percentage, including 30% sodium aluminate, 25% aluminum sulfate, 5% lithium carbonate, and 40% nano calcium carbonate. After mixing, ball mill until D50 is 5μm to obtain the core material mixture for later use; Step C2: Add the core material mixture to deionized water, with a mass ratio of core material mixture to deionized water of 1:4. Add polyvinyl alcohol as a dispersant, with the amount of polyvinyl alcohol added being 2% of the mass of the core material. Stir to form a suspension; Step C3: Step C4: Adjust the pH of the suspension to 4.5 with hydrochloric acid solution, raise the temperature to 55℃, and add melamine and formaldehyde solutions. The molar ratio of melamine to formaldehyde is 1:2.5, and the mass ratio of melamine to core material is 0.4:1. Step C5: React at 60℃ for 3 hours, adjust the pH to 7.5 with sodium hydroxide solution, and continue the reaction for 0.8 hours. Step C6: Cool to room temperature, filter, wash, dry at 50℃ to constant weight, and sieve to a particle size of 200 μm to obtain microcapsule-encapsulated thermosensitive coagulant. The obtained microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 10℃, an encapsulation efficiency of 88%, a wall thickness of 20 μm, and a particle size of 200 μm. The preparation method of the in-situ whisker formation precursor is as follows: Step D1: Prepare 0.5M magnesium nitrate solution and aluminum nitrate solution respectively, mix them in a molar ratio of 2.0:1.0 to obtain a mixed salt solution for later use; Step D2: Prepare a 1.0M sodium carbonate solution for later use; Step D3: Under vigorous stirring at 60℃, add sodium carbonate solution dropwise to the mixed salt solution, control the adding rate to maintain the pH value at 10.0, and the molar ratio of the mixed salt solution to the sodium carbonate solution is 1:0.3; Step D4: After the addition is complete, age at 60℃ for 24 hours; Step D5: Filter and wash the product until the pH value of the filtrate is 7.0, dry it at 80℃ for 10 hours, grind it and pass it through a 250-mesh sieve to obtain the in-situ whisker formation precursor. The magnesium-aluminum molar ratio of the obtained in-situ whisker formation precursor is 2.0:1.0.

[0067] Preparation method: Prepared according to the aforementioned preparation method of underwater concrete rapid repair material, specifically: Step (1): Weigh the solid components of the cementitious material system, intelligent curing adjustment system, auxiliary additives, and filler system according to the proportion, mix them, and dry mix them in a planetary mixer for 3 minutes at a stirring speed of 1000 rpm to obtain a dry mix for later use; Step (2): Add hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide to the water-reducing agent aqueous solution, the mass concentration of the water-reducing agent in the water-reducing agent aqueous solution is 8%, and ultrasonically disperse for 15 minutes at an ultrasonic power of 400W; Step (3): Add the mixture from step (2) to the water-reducing agent aqueous solution. Nano-silica was added to the powder and mechanically stirred for 5 minutes at a stirring rate of 400 rpm to form a stable graphene suspension for later use; Step (4): The graphene suspension was added to the dry mixture and stirred at low speed for 2 minutes at a stirring rate of 150 rpm; Step (5): The remaining water and liquid additives were added and stirred at medium speed for 3 minutes at a stirring rate of 400 rpm; Step (6): Microcapsule-encapsulated thermosensitive coagulant and in-situ whiskers were added to generate precursors and stirred at high speed for 2 minutes at a stirring rate of 600 rpm to obtain a uniform slurry, which is the underwater concrete rapid repair material; The total preparation time was controlled within 10 minutes.

[0068] Example 2

[0069] An underwater concrete rapid repair material, by weight, comprises the following components: 50 parts silicate cement, 10 parts sulfoaluminate cement, 7 parts ultrafine slag powder, 0.4 parts hydrophilic aminated graphene, 0.2 parts hydrophobic thiolized reduced graphene oxide, 2 parts microencapsulated thermosensitive accelerator, 1 part in-situ whisker generation precursor, 0.8 parts polycarboxylate superplasticizer, 0.4 parts nano-silica, 0.15 parts defoamer, 0.25 parts cellulose ether, 0.4 parts expansion agent, 12 parts quartz sand, 6 parts quartz powder, and 18 parts water. Preparation method: The difference from the preparation method in Example 1 is that the dry mixing time is 2 min, the stirring speed is 800 rpm, the graphene is ultrasonically dispersed for 10 min at a power of 350 W, and the total preparation time is controlled within 8 min. Other parameters are the same as in Example 1.

[0070] The hydrophilic amino-coated graphene has an amino grafting degree of 12%, a particle size of 500 nm, and a water contact angle of 15°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 0.8 wt%, ultrasonic dispersion for 20 min, molar ratio 1:2, reflux temperature 55°C, reaction time 5 h, dopamine addition 0.4 wt%, pH 8.0, stirring for 10 h, washing 3 times, and freeze-drying for 24 h. The hydrophobic thiolized reduced graphene oxide has a C / O ratio of 5.5, a thiol content of 0.6 mmol / g, and a water contact angle of 95°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 1.0 wt%, ascorbic acid mass ratio 1:4, reduction temperature 75°C, reduction time 3 h, C / O ratio 5.5, thiol silane mass ratio 1:0.3, reaction temperature 115°C, reaction time 7 h, washing 4 times, drying temperature 55°C, and drying time 12 h. The microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 7°C, an encapsulation efficiency of 82%, a wall thickness of 12 μm, and a particle size of 80 μm. Its preparation method differs from Example 1 in that the core material composition is: 25% sodium aluminate, 20% aluminum sulfate, 3% lithium carbonate, and 45% nano-calcium carbonate; D50 is 4 μm; deionized water mass ratio is 1:3; polyvinyl alcohol is 1%; pH is 4.0; temperature is raised to 50°C; melamine to formaldehyde molar ratio is 1:2; melamine to core material mass ratio is 0.3:1; reaction time is 2.5 h; pH is 7.0; reaction continues for 0.5 h; drying temperature is 45°C; and particle size is 80 μm. The magnesium-aluminum molar ratio of the in-situ whisker precursor was 1.5:0.8. The preparation method differed from that in Example 1 in that: the salt solution concentration was 0.4M, the magnesium-aluminum molar ratio was 1.5:0.8, the sodium carbonate concentration was 0.8M, the reaction temperature was 55℃, the pH value was 9.5, the molar ratio was 1:0.25, the aging time was 20h, the pH value of the filtrate was 6.5, the drying temperature was 75℃, the drying time was 8h, and the solution was passed through a 200-mesh sieve.

[0071] Example 3

[0072] An underwater concrete rapid repair material, by weight, comprises the following components: 55 parts silicate cement, 15 parts sulfoaluminate cement, 10 parts ultrafine slag powder, 0.7 parts hydrophilic aminated graphene, 0.5 parts hydrophobic thiolized reduced graphene oxide, 3 parts microencapsulated thermosensitive accelerator, 2 parts in-situ whisker generation precursor, 1.3 parts polycarboxylate superplasticizer, 0.8 parts nano-silica, 0.3 parts defoamer, 0.5 parts cellulose ether, 0.8 parts expansion agent, 18 parts quartz sand, 10 parts quartz powder, and 25 parts water. Preparation method: The difference from the preparation method in Example 1 is that the dry mixing time is 4 min, the stirring speed is 1200 rpm, the graphene is ultrasonically dispersed for 20 min at a power of 450 W, and the total preparation time is controlled within 12 min. Other parameters are the same as in Example 1.

[0073] The hydrophilic amino-coated graphene has an amino grafting degree of 28%, a particle size of 2000 nm, and a water contact angle of 5°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 1.2 wt%, ultrasonic dispersion for 40 min, molar ratio 1:4, reflux temperature 65°C, reaction time 7 h, dopamine addition 0.6 wt%, pH 9.0, stirring for 14 h, washing 5 times, and freeze-drying for 36 h. The hydrophobic thiolized reduced graphene oxide has a C / O ratio of 8.5, a thiol content of 1.4 mmol / g, and a water contact angle of 110°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 1.5 wt%, ascorbic acid mass ratio 1:6, reduction temperature 85°C, reduction time 5 h, C / O ratio 8.5, thiol silane mass ratio 1:0.5, reaction temperature 125°C, reaction time 9 h, washing 6 times, drying temperature 65°C, and drying time 18 h. The microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 13℃, an encapsulation rate of 95%, a wall thickness of 28μm, and a particle size of 350μm. Its preparation method differs from Example 1 in that the core material composition is: sodium aluminate 35%, aluminum sulfate 30%, lithium carbonate 7%, nano-calcium carbonate 35%, D50 6μm, deionized water mass ratio 1:5, polyvinyl alcohol 3%, pH 5.0, temperature raised to 60℃, melamine to formaldehyde molar ratio 1:3, melamine to core material mass ratio 0.5:1, reaction time 3.5h, pH 8.0, further reaction time 1h, drying temperature 55℃, and particle size 350μm. The magnesium-aluminum molar ratio of the in-situ whisker precursor was 2.5:1.2. The preparation method differed from that in Example 1 in that: the salt solution concentration was 0.6M, the magnesium-aluminum molar ratio was 2.5:1.2, the sodium carbonate concentration was 1.2M, the reaction temperature was 65℃, the pH value was 10.5, the molar ratio was 1:0.35, the aging time was 28h, the pH value of the filtrate was 7.5, the drying temperature was 85℃, the drying time was 12h, and the solution was passed through a 300-mesh sieve.

[0074] Example 4

[0075] An underwater concrete rapid repair material, by weight, comprises the following components: 53 parts silicate cement, 13 parts sulfoaluminate cement, 9 parts ultrafine slag powder, 0.6 parts hydrophilic aminated graphene, 0.4 parts hydrophobic thiolized reduced graphene oxide, 2.8 parts microencapsulated thermosensitive accelerator, 1.8 parts in-situ whisker generation precursor, 1.1 parts polycarboxylate superplasticizer, 0.7 parts nano-silica, 0.25 parts defoamer, 0.4 parts cellulose ether, 0.7 parts expansion agent, 16 parts quartz sand, 9 parts quartz powder, and 23 parts water. Preparation method: The difference from the preparation method in Example 1 is that a double-spiral conical mixer is used for dry mixing for 3 minutes at a mixing speed of 1000 rpm and an ultrasonic frequency of 50 kHz. For wet mixing, a planetary mixer is used, and the ambient temperature is controlled at 22℃. Other parameters are the same as in Example 1.

[0076] The hydrophilic amino-coated graphene has an amino grafting degree of 22%, a particle size of 1500 nm, and a water contact angle of 8°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 1.1 wt%, ultrasonic dispersion is performed for 35 min, the molar ratio is 1:3.5, the reflux temperature is 62°C, the reaction time is 6.5 h, the dopamine addition is 0.55 wt%, the pH is 8.8, stirring is performed for 13 h, and freeze-drying is completed for 32 h. The hydrophobic thiolized reduced graphene oxide has a C / O ratio of 7.2, a thiol content of 1.2 mmol / g, and a water contact angle of 105°. Its preparation method differs from Example 1 in that: the graphene oxide concentration is 1.3 wt%, the ascorbic acid mass ratio is 1:5.5, the reduction temperature is 82°C, the reduction time is 4.5 h, the C / O ratio is 7.2, the thiol silane mass ratio is 1:0.45, the reaction temperature is 122°C, the reaction time is 8.5 h, and the drying temperature is 62°C for 16 h. The microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 11℃, an encapsulation rate of 90%, a wall thickness of 22μm, and a particle size of 280μm. Its preparation method differs from Example 1 in that the core material composition is: sodium aluminate 32%, aluminum sulfate 27%, lithium carbonate 6%, nano-calcium carbonate 38%, D50 5.5μm, deionized water mass ratio 1:4.5, polyvinyl alcohol 2.5%, pH 4.8, temperature raised to 58℃, melamine to formaldehyde molar ratio 1:2.8, melamine to core material mass ratio 0.45:1, reaction time 3.2h, pH 7.8, continued reaction for 0.9h, drying temperature 52℃, and particle size 280μm. The magnesium-aluminum molar ratio of the in-situ whisker precursor was 2.2:1.1. The preparation method differed from that in Example 1 in that: the salt solution concentration was 0.55M, the magnesium-aluminum molar ratio was 2.2:1.1, the sodium carbonate concentration was 1.1M, the reaction temperature was 62℃, the pH value was 10.2, the molar ratio was 1:0.32, the aging time was 26h, the pH value of the filtrate was 7.2, the drying temperature was 82℃, the drying time was 11h, and the solution was passed through a 280-mesh sieve.

[0077] Example 5

[0078] An underwater concrete rapid repair material, by weight, comprises the following components: 54 parts silicate cement, 14 parts sulfoaluminate cement, 8.5 parts ultrafine slag powder, 0.65 parts hydrophilic aminated graphene, 0.45 parts hydrophobic thiolized reduced graphene oxide, 2.6 parts microencapsulated thermosensitive accelerator, 1.6 parts in-situ whisker generation precursor, 1.2 parts polycarboxylate superplasticizer, 0.65 parts nano-silica, 0.22 parts defoamer, 0.35 parts cellulose ether, 0.65 parts expansion agent, 17 parts quartz sand, 8.5 parts quartz powder, and 22 parts water. Preparation method: Same as in Example 1, dry mixing time 3 min, stirring speed 1000 rpm, graphene ultrasonic dispersion 15 min, power 400 W, total preparation time controlled within 10 min. The underwater concrete rapid repair material of this embodiment has an interfacial fracture energy of 400 J / m. 2 After 3 years of service, the bonding strength retention rate was 92%. The hydrophilic aminated graphene, hydrophobic thiolized reduced graphene oxide, microencapsulated thermosensitive coagulant, and in-situ whisker generation precursor in this embodiment are the same as those in Example 1.

[0079] Example 5A

[0080] An underwater concrete rapid repair material comprises, by weight, the following components: 52.5 parts silicate cement, 12.5 parts sulfoaluminate cement, 8.5 parts ultrafine slag powder, 0.6 parts hydrophilic aminated graphene, 0.6 parts hydrophobic thiolized reduced graphene oxide, 2.6 parts microencapsulated thermosensitive accelerator, 1.7 parts in-situ whisker formation precursor, 1.05 parts polycarboxylate superplasticizer, 0.65 parts nano-silica, 0.22 parts defoamer, 0.35 parts cellulose ether, 0.65 parts expansion agent, 16 parts quartz sand, 8.5 parts quartz powder, and 22 parts water. Performance test results: flexural strength 8.5 MPa, interfacial fracture energy 380 J / m. 2 The preparation methods of hydrophilic aminated graphene, hydrophobic thiolized reduced graphene oxide, microencapsulated thermosensitive accelerator, in-situ whisker generation precursor, and underwater concrete rapid repair material in this embodiment are all the same as those in Example 1.

[0081] This embodiment employs an equal ratio of hydrophilic and hydrophobic graphene, exhibiting balanced overall performance. In the initial wetting stage, the equal amount of hydrophilic graphene provides sufficient underwater adhesion; the catechol groups form effective chemical bonds with the wet substrate, resulting in good initial adhesion strength. Simultaneously, the equal amount of hydrophobic graphene constructs an effective hydrophobic barrier in the interfacial transition region, preventing water molecules from continuously penetrating into the interface and ensuring the long-term stability of the adhesive layer. The equal ratio results in a more balanced thickness distribution of the "hydrophilic-hydrophobic" gradient transition interface layer, with the hydrophilic and hydrophobic layers each accounting for approximately 50% of the interface thickness, achieving a good balance between initial adhesion and long-term waterproofing. The wet interfacial adhesion strength reaches 2.85 MPa, which is above average compared to Examples 1-7, proving that the equal ratio is technically feasible and has excellent performance. The interfacial fracture energy reaches 380 J / m. 2 This demonstrates that the "pinning-bridging" dual enhancement mechanism of graphene sheets at the interface is fully utilized. This embodiment verifies the rationality and effectiveness of including equal amounts of hydrophilic and hydrophobic graphene in the mass ratio range, providing more formulation options for different construction environments and performance requirements.

[0082] 90-day long-term performance test results: After 90 days of underwater curing, the wet bond strength retention rate was 91%, and the chloride ion penetration resistance coefficient remained at 85°C. The water content in the interface transition zone was 6.5%, which is between the slightly hydrophilic ratio (5% water content in Example 1) and the theoretical calculation value. In a simulated seawater environment (chloride ion concentration 19000 ppm, water temperature 18°C), the bond strength retention rate reached 89% after 90 days of curing, demonstrating good long-term durability. In the freeze-thaw resistance test, after 50 freeze-thaw cycles, the bond strength loss was only 18%, which is better than the example with the slightly hydrophilic ratio. This example proves that the equal proportion not only performs well in initial performance but also fully meets the requirements for the repair of hydraulic and marine infrastructure in terms of long-term durability.

[0083] Example 6

[0084] A bifunctional underwater concrete rapid repair material synergistically modified with graphene differs from Example 1 only in that the mass ratio of hydrophilic aminated graphene to hydrophobic thiolized reduced graphene oxide is 1.2:0.8, while all other aspects remain the same as in Example 1. At this ratio, the proportion of hydrophilic graphene is at the lower limit, resulting in good initial wetting properties, but a slight decrease in long-term waterproofing performance.

[0085] Example 7

[0086] A bifunctional underwater concrete rapid repair material synergistically modified with graphene differs from Example 1 only in that the mass ratio of hydrophilic aminated graphene to hydrophobic thiolized reduced graphene oxide is 1.8:1.2, while all other aspects remain the same as in Example 1. This ratio represents the upper limit of the hydrophobic graphene proportion, resulting in excellent long-term waterproofing performance, but requiring a slightly longer initial wetting time.

[0087] Example 8

[0088] Underwater repair was performed using the formulation from Example 1. The water temperature was 6°C, and the water-cement ratio was adjusted to 0.28, meaning the cementitious material system remained at 72 parts, the water content was adjusted to 20.2 parts, and the contents of other components remained unchanged. The cleaning depth was increased to expose a solid base layer, and a roughening treatment was applied to create a 4mm deep rough texture. The repair material was injected using an underwater pump at a rate controlled at 10L / min, with a single-layer repair thickness of 45mm. Underwater vibration time was 20s / m². Performance test results showed that the microcapsule release rate decreased under low-temperature conditions. Reducing the water-cement ratio could appropriately increase the slurry viscosity and density, while still meeting the requirements for rapid repair.

[0089] Example 9

[0090] Using the formulation of Example 1, with a water temperature of 15℃ and a water-cement ratio adjusted to 0.30 (keeping the cementitious material system at 72 parts and the water content at 21.6 parts), the amounts of other components remained unchanged. All other construction parameters were the same as in Example 8. Performance test results showed that the curing rate was moderate under room temperature conditions, resulting in the best overall performance.

[0091] Example 10

[0092] Using the formulation of Example 1, with a water temperature of 26°C and a water-cement ratio adjusted to 0.32 (keeping the cementitious material system at 72 parts and the water content at 23.0 parts), the amounts of other components remained unchanged. The remaining construction parameters were the same as in Example 8. Performance test results showed that the microcapsules released rapidly under high-temperature conditions and cured quickly, but the application window needed to be shortened.

[0093] Example 11

[0094] Using the formulation from Example 3, repair work and curing were carried out in a simulated seawater environment (chloride ion concentration 19000 ppm, sulfate ion concentration 2700 ppm, pH=8.2, temperature 20℃). Performance test results showed that the initial setting time underwater was shortened by 25% compared to the freshwater environment. Chloride and sulfate ions in seawater have an activating effect on sulfoaluminate cement, significantly accelerating the curing reaction and verifying the material's excellent adaptability to the marine environment. After 90 days of seawater immersion, the bond strength retention rate reached 91%, and the chloride ion penetration resistance coefficient was 720℃.

[0095] Example 12

[0096] Using the formulation from Example 4, repair work was carried out at a water depth of 8m, a water temperature of 12℃, and a water pressure of approximately 1.8 bar. Underwater non-dispersible grouting pipes were used for injection, with the injection rate controlled at 12L / min. Layered application was employed, with each layer 40mm thick and a 20-minute interval between layers. The material exhibited excellent anti-dispersibility properties under deep water pressure, and the cellulose ether effectively prevented dilution and loss of the cement grout.

[0097] Comparative Example 1

[0098] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but the total amount of the bifunctional graphene system is only 0.4 parts (0.25 parts of hydrophilic aminated graphene and 0.15 parts of hydrophobic thiolized reduced graphene oxide), less than 0.6 parts. The remaining components and preparation methods are the same as in Example 1.

[0099] Analysis: Insufficient graphene content resulted in insignificant interfacial reinforcement; the wet bond strength decreased by 36% compared to Example 1, failing to form an effective "pinning-bridging" dual reinforcement structure. The interfacial fracture energy was only 180 J / m. 2 It is far lower than the 350-450 J / m of the example. 2 The underwater adhesion mechanism is imperfect, and the water film formed by water molecules at the interface cannot be effectively removed. After long-term immersion, the adhesion strength decreases by up to 45%, and after 3 years of service, the adhesion strength retention rate is only 62%, which does not meet the requirements for long-term durability.

[0100] Comparative Example 2

[0101] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but the total amount of the bifunctional graphene system is 1.5 parts (0.9 parts of hydrophilic aminated graphene and 0.6 parts of hydrophobic thiolized reduced graphene oxide), exceeding 1.2 parts. The remaining components and preparation methods are the same as in Example 1.

[0102] Analysis: Excessive graphene content led to severe agglomeration in the cement paste. Even after 15 minutes of ultrasonic dispersion, uniform dispersion could not be achieved, resulting in agglomerates with a size of 5-10 μm. These agglomerates became stress concentration points, consequently reducing the material's mechanical properties. Excessive graphene adsorbed large amounts of water-reducing agents and nano-silica, affecting the normal hydration of the cement and prolonging the initial setting time by 175%. The viscosity of the material mixture was also excessively high (reaching 35,000 ppm). It exhibits poor workability and is difficult to pump. After curing, it has numerous internal pores, resulting in decreased density and a 20% reduction in compressive strength compared to Example 1.

[0103] Comparative Example 3

[0104] An underwater concrete rapid repair material, by weight, has the same composition as Example 1, but the total amount of the intelligent curing adjustment system is only 2 parts (1.2 parts of microcapsule-encapsulated temperature-sensitive accelerator and 0.8 parts of in-situ whisker generation precursor), less than 3 parts. The remaining components and preparation method are the same as in Example 1. The fracture toughness of the material in this comparative example is only 60% of that in Example 1.

[0105] Analysis: Insufficient microencapsulated accelerator dosage weakens the temperature-adaptive curing ability. Initial setting time is extended to 42 minutes at 4℃ and still requires 18 minutes at 25℃, failing to meet the requirements for rapid repair. The accelerator release is insufficient to fully activate the rapid hydration of sulfoaluminate cement, resulting in a slow ettringite phase formation rate. Insufficient in-situ whisker precursor dosage leads to an incomplete three-dimensional toughening network, low whisker density, and insignificant synergistic toughening effect with graphene sheets. The material exhibits high brittleness, with a flexural strength of only 5.2 MPa, a 40% decrease compared to Example 1, and poor impact resistance.

[0106] Comparative Example 4

[0107] An underwater concrete rapid repair material, by weight, has the same composition as Example 1, but the total amount of the intelligent curing adjustment system is 6.5 parts (4 parts of microcapsule-encapsulated temperature-sensitive accelerator and 2.5 parts of in-situ whisker generation precursor), exceeding 5 parts. The remaining components and preparation methods are the same as in Example 1.

[0108] Analysis: Excessive use of microencapsulated accelerator led to excessively rapid curing, with an initial setting time of only 2 minutes at room temperature (20℃). This short construction window meant the material began to solidify before it could be pumped and vibrated properly, resulting in insufficient compaction. The concentrated release of hydration heat during rapid curing caused thermal stress and microcracks within the material. Excessive in-situ whisker precursors hydrated rapidly in the alkaline environment, resulting in overly dense whiskers that interfered with each other, hindering normal whisker growth. The average aspect ratio was only 25, far below the normal 50. Excessive whiskers occupied the internal space of the cement paste, increasing porosity, decreasing density, and reducing compressive strength by 23% compared to Example 1. While the material exhibited high early strength, its later strength growth was slow, almost ceasing after 7 days.

[0109] Comparative Example 5

[0110] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but uses only 0.8 parts of hydrophobic thiolized reduced graphene oxide and does not add hydrophilic aminated graphene. The remaining components and preparation method are the same as in Example 1.

[0111] Analysis: The lack of hydrophilic amino graphene caused the material to lose the key mechanism for simulating underwater adhesion of mussels. Hydrophobic graphene could not effectively wet the damp substrate; water molecules formed a stable water film at the interface with a thickness of 15-25 nm, severely hindering the contact between the repair material and the old concrete. The lack of amino and dopamine functional groups prevented the formation of triple chemical bonds (coordination, hydrogen, and covalent bonds), and the interface relied solely on physical interlocking, resulting in a 46% decrease in adhesion strength compared to Example 1. Initial adhesion was weak, and interfacial peeling easily occurred under water erosion. Although hydrophobic graphene provided some waterproofing, it could not compensate for the insufficient initial adhesion. After 28 days of underwater curing, obvious microcracks appeared at the interface, and the adhesion strength decreased to 1.1 MPa, with a retention rate of only 73%.

[0112] Comparative Example 6

[0113] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but uses only 0.8 parts of hydrophilic aminated graphene and does not add hydrophobic thiolized reduced graphene oxide. The remaining components and preparation method are the same as in Example 1.

[0114] Analysis: The lack of hydrophobic thiolized reduced graphene oxide prevented the formation of an effective hydrophobic barrier in the interfacial transition zone. Although the hydrophilic graphene provided good initial wetting and adhesion, and the initial bond strength was acceptable, the interfacial layer continuously absorbed water and swelled in a long-term underwater environment. Water molecules continuously penetrated into the interface through capillary action, reaching a penetration depth of 3-5 mm after 90 days. The water content in the interfacial transition zone was as high as 12%, far exceeding the less than 5% in Example 1. The high water content led to a continuous decline in the interfacial layer strength; after 90 days, the wet bond strength decreased to 1.6 MPa, a 33% decrease from the initial strength, and the retention rate after 3 years was expected to be only 55%. Resistance to chloride ion penetration was poor; chloride ions rapidly penetrated through the water-containing interfacial layer, with the penetration coefficient increasing by 47% compared to Example 1. The lack of a hydrophobic barrier also led to accelerated carbonization and insufficient interfacial durability.

[0115] Comparative Example 7

[0116] An underwater concrete rapid repair material, by weight, has the same composition as Example 1, but the mass ratio of hydrophilic aminated graphene to hydrophobic thiolized reduced graphene oxide is 3.0:0.5, exceeding (1.2-1.8):(0.8-1.2). The remaining components and preparation method are the same as in Example 1. Performance test results show that the bond strength decays to 1.7 MPa after 90 days.

[0117] Analysis: The excessively high proportion of hydrophilic graphene leads to an overly hydrophilic interface layer. Although initial wetting and adhesion properties are good, there is a lack of sufficient hydrophobic graphene to form a waterproof layer. The water contact angle in the interface transition zone is only 35°, far exceeding the ideal gradient distribution. Long-term immersion causes the interface layer to swell, with a volume expansion rate of 5.8%, generating expansion stress and inducing microcracks at the interface. Continuous water penetration leads to the dissolution and loss of cement hydration products in the interface region, increasing porosity. The interfacial fracture energy after 90 days is only 190 J / m. 2 Compared to Example 1, the yield was reduced by 53%. It exhibited poor freeze-thaw resistance, with a 62% loss in bond strength after 50 freeze-thaw cycles.

[0118] Comparative Example 8

[0119] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but the mass ratio of hydrophilic aminated graphene to hydrophobic thiolized reduced graphene oxide is 0.8:1.5, exceeding (1.2-1.8):(0.8-1.2). The remaining components and preparation method are the same as in Example 1.

[0120] Analysis: The excessively high proportion of hydrophobic graphene leads to insufficient initial wetting properties. Hydrophobic graphene struggles to spread fully underwater, exhibiting a contact angle of 85° with damp substrates, failing to effectively remove the interfacial water film. Insufficient hydrophilic graphene results in a low density of adhesive functional groups (amino and dopamine), reducing interfacial chemical bonding sites by 70%. Weak initial adhesion makes it prone to early debonding under water flow and its own weight. While the hydrophobic barrier effect is good and long-term waterproofing performance is excellent, it cannot compensate for the fundamental defect of insufficient initial adhesion. Numerous unfilled voids exist at the interface, with the effective bonding area only 65% ​​of that in Example 1, resulting in a 32% reduction in bonding strength compared to Example 1.

[0121] Comparative Example 9

[0122] An underwater concrete rapid repair material, by weight, has the same composition as Example 1, but without the addition of microencapsulated temperature-sensitive accelerator; the intelligent curing regulation system contains only 1.5 parts of in-situ whisker generation precursor. The remaining components and preparation method are the same as in Example 1.

[0123] Analysis: The lack of microencapsulated temperature-sensitive accelerators results in the material losing its temperature-adaptive rapid curing ability. At room temperature (15℃), the hydration rate of sulfoaluminate cement is slow, with an initial setting time extended to 45 minutes, failing to meet the needs of rapid repair and emergency maintenance. At a low temperature of 4℃, the initial setting time is further extended to over 90 minutes, limiting practical applications. The lack of accelerator activation leads to slow ettringite phase formation and slow early strength development; the 24-hour strength reaches only 28% of the design strength, and the 7-day strength is only 62%. While chloride and sulfate ions have some activating effect in seawater environments, the effect is far less than the targeted release of microencapsulated accelerators. During construction, the material remains underwater for a long time, causing partial dispersion and dilution of the cement paste, reducing density and affecting final performance. The lack of a temperature response mechanism prevents the material from automatically adjusting the curing rate according to actual working conditions, resulting in poor adaptability.

[0124] Comparative Example 10

[0125] An underwater concrete rapid repair material, by weight, has the same composition as in Example 1, but without the addition of in-situ whisker precursors. The intelligent curing regulation system contains only 2.5 parts of microencapsulated temperature-sensitive accelerator. The remaining components and preparation methods are the same as in Example 1.

[0126] Performance test results showed that the flexural strength was 5.8 MPa, and the fracture toughness was reduced by 55% compared with Example 1.

[0127] Analysis: The lack of in-situ whisker generation precursors prevented the construction of a whisker-graphene three-dimensional toughening network. Although the graphene sheets provided in-plane reinforcement, the lack of vertical whisker toughening resulted in severely insufficient material toughness. Flexural strength decreased by 28% compared to Example 1, and impact toughness decreased by 62%. The material exhibited high brittleness, easily fractured under dynamic loads, with rapid crack propagation and poor crack deflection. The absence of crack brittleness and pull-out effects from nanocrystals resulted in a fracture energy of only 160 J / m. 2 It is far lower than the 350-450 J / m of the example. 2 It is prone to secondary cracking under dynamic loads such as wave impact and ship collision. It exhibits poor fatigue resistance, with a fatigue life of only 40% of that in Example 1 under alternating loads. The microstructure reveals numerous internal cracks that propagate linearly, lacking whisker-like crack deflection and energy dissipation mechanisms.

[0128] Comparative Example 11

[0129] An underwater concrete rapid repair material is provided, using the formulation of Example 1, but the amino grafting degree in the preparation of the hydrophilic aminated graphene is only 8%, less than 12%. The remaining components and preparation method are the same as in Example 1.

[0130] Analysis: Insufficient amino grafting leads to a lack of active sites on the graphene surface. The low density of amino functional groups reduces chemical bonding sites with cement hydration products (mainly calcium hydroxide and CSH gel) by 65%. Dopamine grafting is also affected, and the low density of catechol groups hinders effective underwater adhesion. The number of coordination bonds, hydrogen bonds, and covalent bonds formed at the interface is insufficient, weakening the triple chemical bonding mechanism. Wet bond strength is 29% lower than in Example 1, with interfacial bonding relying mainly on physical intercalation and van der Waals forces, while the contribution of chemical bonding decreases from 75% in Example 1 to 45%. Prolonged immersion leads to hydrolysis at the interface, resulting in rapid bond strength decay; after 90 days, the bond strength retention rate is only 78%.

[0131] Comparative Example 12

[0132] An underwater concrete rapid repair material was developed, using the formulation of Example 1, but with an amino grafting degree of 35% exceeding 28% during the preparation of the hydrophilic aminated graphene. The remaining components and preparation method were the same as in Example 1. Performance test results showed that the bond strength decreased to 1.7 MPa after 90 days.

[0133] Analysis: Excessive amino grafting leads to excessive hydrophilicity of the graphene surface, reducing the water contact angle to 2°. In an underwater environment, the graphene sheets swell excessively, increasing in thickness from the normal 1-3 nm to 8-12 nm, resulting in decreased sheet stiffness. Excessive amino functional groups cause protonation of the graphene in an alkaline cement environment, increasing surface charge and enhancing electrostatic repulsion between sheets, making it difficult to form a stable oriented arrangement. Excessive grafting disrupts the conjugated π-electron structure of graphene, significantly reducing its intrinsic mechanical properties; Young's modulus drops from 1 TPa to 0.3 TPa. Prolonged immersion causes continuous water absorption at the interface layer, reaching a moisture content of up to 15%, leading to a continuous decrease in interface strength. Excessive organic functional groups slowly degrade in an alkaline environment, releasing small molecules that form micropores at the interface, reducing density. After 90 days, the bond strength retention rate is only 74%, lower than the over 90% in Example 1.

[0134] Comparative Example 13

[0135] An underwater concrete rapid repair material was developed, using the formulation of Example 1, but with a thiol content of only 0.4 mmol / g in the hydrophobic thiolized reduced graphene oxide, which is lower than 0.6 mmol / g. The remaining components and preparation method were the same as in Example 1. Performance testing results showed that the bond strength decreased to 2.0 MPa after 90 days.

[0136] Analysis: The low thiol content resulted in insufficient hydrophobicity. The water contact angle of the hydrophobic graphene was only 82°, lower than the required range of 95-110°, failing to form an effective hydrophobic barrier. The water permeation rate in the interface transition zone was 2.3 times that of Example 1, and the interface layer moisture content reached 9% after 90 days. The low thiol density resulted in weak chelation ability with heavy metal ions, leading to decreased corrosion resistance in seawater environments containing heavy metal pollution. The imperfect hydrophobic barrier allowed chloride ions to penetrate more easily through the interface layer, increasing the chloride ion permeation resistance coefficient by 35% compared to Example 1. After long-term service, continuous water permeation caused the dissolution and loss of hydration products in the interface layer, gradually weakening the bonding strength. The retention rate was only 77% after 90 days, and it is expected to be less than 70% after 3 years, failing to meet long-term durability requirements.

[0137] Comparative Example 14

[0138] An underwater concrete rapid repair material is disclosed, using the formulation of Example 1, but with a thiol content of 1.8 mmol / g in the hydrophobic thiolized reduced graphene oxide, exceeding 1.4 mmol / g. The remaining components and preparation method are the same as in Example 1. Performance test results: During material mixing, graphene dispersion was found to be difficult; even after ultrasonic dispersion for 20 minutes, significant agglomerates remained.

[0139] Analysis: Excessive thiol content drastically worsens the dispersibility of hydrophobic graphene in cement paste. Too many thiol functional groups make the graphene sheets excessively hydrophobic, with a water contact angle of up to 125°, making them difficult to wet and disperse in aqueous systems. Even with water-reducing agents and ultrasonic dispersion, agglomerates of 3-8 μm in size still form, which become defect sources and reduce material properties. Excessive thiols are unstable in alkaline cement environments (pH>12), and some thiols oxidize to disulfide bonds (-SS-), altering the surface properties of graphene and causing hydrophobicity to decay over time. Sulfides generated from thiol oxidation may react with calcium ions in alkaline environments to form calcium sulfide precipitates, affecting cement hydration. Excessive hydrophobicity also leads to poor interfacial compatibility between graphene and the cement matrix, resulting in numerous voids at the interface, reducing the effective reinforcing area, and lowering the compressive strength by 13% compared to Example 1.

[0140] Comparative Example 15

[0141] An underwater concrete rapid repair material is proposed, using the formulation of Example 1, but with a glass transition temperature (Tg) of 4°C for the microencapsulated temperature-sensitive accelerator, which is lower than 7°C. The remaining components and preparation method are the same as in Example 1. Performance test results: Under low winter conditions (4°C), the initial setting time underwater is only 2 minutes; under normal temperature conditions (20°C), the initial setting time is 3 minutes; and under high temperature conditions (28°C), the initial setting time is 2 minutes, indicating poor temperature adaptability.

[0142] Analysis: The excessively low glass transition temperature causes the microcapsules to enter a highly elastic state at low temperatures, significantly increasing the permeability of the shell material. At 4℃, the accelerator release rate reaches 85% within one hour, far exceeding the designed 15%, thus losing its temperature adaptive regulation function. Rapid curing at low temperatures leads to incomplete cement hydration, resulting in hydration products with poor crystallinity and low strength. The heat of hydration generated by rapid curing cannot be dissipated in time, easily creating temperature gradients during winter construction and causing thermal stress cracking. The construction window is too short; pumping, pouring, and vibration must be completed within 2 minutes after mixing, which is difficult in practice. The microcapsules cannot effectively preserve the accelerator at room temperature and high temperatures, resulting in poor storage stability and a shelf life of only 15 days for the premixed material. The temperature response characteristics fail; the curing time varies little at different temperatures, failing to automatically adjust according to actual working conditions, significantly reducing the material's environmental adaptability and reliability.

[0143] Comparative Example 16

[0144] An underwater concrete rapid repair material is disclosed, using the formulation of Example 1, but with a glass transition temperature (Tg) of 16°C for the microencapsulated temperature-sensitive accelerator, exceeding 13°C. The remaining components and preparation method are the same as in Example 1. Performance test results: At room temperature (20°C), due to the excessively high Tg (16°C), the microcapsule release is slow, extending the initial setting time underwater to 35 minutes; at low temperature (10°C), the initial setting time is 65 minutes; and at high temperature (28°C), the initial setting time is 18 minutes.

[0145] Analysis: The excessively high glass transition temperature causes the microcapsules to remain in a glassy state at room temperature, resulting in a dense and hard shell and an excessively slow release rate of the accelerator. At 20℃, the accelerator release rate is only 35% within one hour, far below the designed 80%, leading to slow curing and an extended initial setting time of 35 minutes, which cannot meet the needs of rapid repair. At a low temperature of 10℃, the microcapsules release almost no accelerator, with a release rate of less than 5% within one hour, resulting in extremely slow curing and an initial setting time exceeding one hour, severely limiting practical applications. Only at temperatures above 28℃ can the microcapsules respond normally and release the accelerator, but such high-temperature conditions are rarely encountered in underwater environments. The material has a narrow applicable temperature range, suitable only for high-temperature construction in summer, and cannot be used in winter and spring / autumn. Slow curing at low temperatures causes the material to remain in a plastic state for a long time, making it susceptible to erosion and dilution under water flow, resulting in decreased density. Poor temperature adaptability prevents the full utilization of the intelligent curing regulation system's advantages.

[0146] Comparative Example 17

[0147] An underwater concrete rapid repair material is disclosed, using the formulation of Example 1, but the encapsulation rate of the microencapsulated temperature-sensitive accelerator is only 75%, lower than 82%, and the wall thickness is 10 μm. The remaining components and preparation method are the same as in Example 1. Performance test results: After 7 days of storage, the initial setting time decreased from 8 minutes to 3 minutes, and after 14 days of storage, it decreased to 1.5 minutes, indicating extremely poor storage stability. The initial setting time of freshly mixed material (0 days of storage) underwater is 6 minutes.

[0148] Analysis: A low encapsulation rate means that 25% of the accelerator is not encapsulated or is incompletely encapsulated. These free accelerators are released prematurely during material mixing and storage, resulting in extremely poor storage stability. The low encapsulation rate is due to insufficient shell thickness (only 10μm) and poor shell density. The thin shell leads to insufficient mechanical strength, and approximately 15% of the microcapsules are destroyed during mixing, causing premature release of the accelerator. The free accelerator triggers cement hydration, causing the ready-mixed material to gradually harden during storage, resulting in a shelf life of only 7 days, far shorter than the 90 days in Example 1. Transportation and storage are difficult; the material must be mixed on-site, making factory pre-mixing and long-distance transportation impossible. The thin-walled microcapsules have poor stability in the alkaline environment of cement, and the shell is prone to alkaline hydrolysis, leading to slow release of the accelerator. The controllability and repeatability of the curing time are poor, resulting in large performance fluctuations between different batches of material and unstable quality.

[0149] Comparative Example 18

[0150] An underwater concrete rapid repair material was developed, using the formulation of Example 1, but with a magnesium-aluminum molar ratio of 1.0:1.0 for the in-situ whisker precursor, which is lower than the minimum magnesium ratio in the range of (1.5-2.5):(0.8-1.2). The remaining components and preparation method were the same as in Example 1. Performance testing results showed a flexural strength of 6.2 MPa and a 42% decrease in fracture toughness compared to Example 1.

[0151] Analysis: The imbalanced magnesium-aluminum ratio leads to an incomplete structure in the generated hydrotalcite precursor. The excessively low magnesium content results in an unstable hydrotalcite laminate structure, reduced interlayer spacing, and decreased anion exchange capacity. In an alkaline cement environment, the precursor reconstruction efficiency is low, with only 60% of the precursor effectively reconstructing and growing into whiskers. The generated whiskers are few in number and low in density, with an average aspect ratio of only 28, far below the designed 50. The whiskers are too short and insufficient in number to form an effective three-dimensional toughening network, resulting in poor interweaving with the graphene sheets and a weak synergistic toughening effect. The material exhibits poor crack deflection ability, a relatively straight crack propagation path, low crack propagation energy consumption, and a fracture energy of only 210 J / m. 2 The flexural strength and impact toughness are significantly reduced, the material is more brittle, and it is prone to brittle fracture under dynamic loads.

[0152] Comparative Example 19

[0153] An underwater concrete rapid repair material is disclosed, employing the formulation of Example 1, but with a magnesium-aluminum molar ratio of 3.5:0.8 for the in-situ whisker precursor, exceeding the highest magnesium proportion within the range of (1.5-2.5):(0.8-1.2). The remaining components and preparation method are the same as in Example 1. Performance testing results show a flexural strength of 6.8 MPa.

[0154] Analysis: Excessive magnesium content leads to decreased stability of the hydrotalcite precursor in cement paste. The high magnesium-to-aluminum ratio hydrotalcite laminate structure is prone to excessive dissolution in strongly alkaline environments (pH > 13), causing the laminate structure to collapse. The precursor rapidly hydrates after cement mixing, prematurely generating whiskers and hindering in-situ generation and directional growth. The early-generated whiskers are randomly distributed, resulting in poor interweaving with the graphene sheets and failing to form an effective three-dimensional network. Excessive magnesium ions react with cement hydration products to form magnesium hydroxide and brucite. These products are large in size, forming micropores within the hardened body and reducing density. Magnesium hydroxide is unstable in chloride environments and easily undergoes ion exchange, leading to decreased resistance to chloride ion penetration. Excessive whisker precursors also consume a large amount of alkalinity, lowering the pH of the cement paste and affecting normal cement hydration and the stability of graphene surface functional groups. The long-term stability and durability of the material decrease, with compressive strength reduced by 10% compared to Example 1.

[0155] Comparative Example 20

[0156] An underwater concrete rapid repair material is disclosed, using the formulation of Example 1, but the silicate cement in the cementitious material system is ordinary silicate cement with a strength grade of 42.5, lower than 52.5. The remaining components and preparation method are the same as in Example 1.

[0157] Analysis: The use of low-strength cement significantly reduces the mechanical properties and durability of the material. The 42.5 grade cement has low C3S and C2S content in its mineral composition, resulting in insufficient hydration activity, a slow hydration rate, and slow early strength development. The 7-day compressive strength is 18% lower than in Example 1, and the 28-day compressive strength is 20% lower. The CSH gel in the cement hydration products has low polymerization degree, weak gel strength, and reduced interfacial bonding with graphene. Low-strength cement has high porosity and poor density, providing channels for the penetration of harmful ions such as chloride and sulfate, increasing the chloride ion penetration resistance coefficient by 27% compared to Example 1. The cement stone has poor carbonation resistance, making it prone to rapid carbonization in marine atmospheres, leading to an increased risk of steel reinforcement corrosion. The wet bond strength decreases by 14%, resulting in insufficient long-term durability; the bond strength retention rate after 3 years of service is expected to be only 75%, lower than the over 90% in Example 1.

[0158] Comparative Example 21

[0159] An underwater concrete rapid repair material is provided, using the formulation of Example 1, but the tricalcium aluminate (C3A) content of the sulfoaluminate cement in the cementitious material system is only 32%, less than 40%. The remaining components and preparation method are the same as in Example 1.

[0160] Analysis: Insufficient tricalcium aluminate content significantly weakens the rapid setting effect. C3A is a key mineral in sulfoaluminate cement that rapidly hydrates to form ettringite, and its content directly affects the early strength development rate. Low C3A content results in less ettringite phase formation and a slower formation rate, extending the initial setting time to 18 minutes, a 125% increase compared to Example 1, failing to meet the basic requirements for rapid repair. Early strength development is slow, with the 24-hour strength reaching only 35% of the design strength, a 30% decrease compared to Example 1, severely impacting construction progress and subsequent procedures in emergency repair scenarios. Although microencapsulated accelerators can stimulate the hydration reaction, the insufficient C3A content limits the accelerator's effect, failing to achieve the expected rapid curing goal. While sulfate ions in seawater can promote ettringite formation, the activating effect is limited when C3A content is low. The material's rapid setting and hardening characteristics are weakened, losing its core advantage as a rapid repair material.

[0161] The performance test results of each embodiment and comparative example are shown in Table 1 below.

[0162] Table 1

[0163]

[0164] Note: (1) The water temperature is in parentheses after the initial setting time underwater. (2) “Freshly mixed” in Comparative Example 17 refers to the material that has just been mixed and has not been stored. This sample has poor storage stability, and the initial setting time is shortened to 3 min after 7 days of storage. (3) The values ​​with arrows represent “initial bond strength → bond strength after 90 days”, which are used to show samples with severe long-term degradation. For example: Comparative Example 6 (2.4→1.6): lack of hydrophobic graphene, good initial adhesion but long-term water absorption leads to a 33% decrease in strength; Comparative Example 7 (2.6→1.7): too high proportion of hydrophilic graphene, excessive swelling of the interface layer; Comparative Example 12 (2.3→1.7): too high amino grafting, continuous water absorption of the interface layer; Comparative Example 13 (2.6→2.0): too low thiol content, insufficient hydrophobic barrier.

[0165] Comprehensive analysis shows that the bifunctional graphene-modified underwater concrete rapid repair material of this invention, while maintaining the appropriate component ratios and preparation process, can achieve comprehensive performance including rapid underwater curing (initial setting time 4-18 min), strong adhesion (wet bond strength 2.5-3.2 MPa), high strength and toughness (28-day compressive strength 55-65 MPa), temperature adaptability, and durable impermeability (chloride ion permeability resistance 750-950°C, 90-day bond strength retention rate 88-94%). The absence of any key component, exceeding the specified dosage, or failure to meet quality standards will lead to a significant decline in material performance, failing to meet the actual needs of rapid repair and emergency maintenance of hydraulic and marine infrastructure.

[0166] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rapid underwater concrete repair material, characterized in that: By weight, it includes the following components: The mixture consists of 67-80 parts of a cementitious material system, 0.6-1.2 parts of a bifunctional graphene system, 3-5 parts of an intelligent curing and conditioning system, 2-3 parts of auxiliary additives, 20-25 parts of a filler system, and 18-25 parts of water. The bifunctional graphene system comprises hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide, with a mass ratio of (1.2-1.8):(0.8-1.2). The intelligent curing and regulating system includes 2-3 parts of microcapsule-encapsulated temperature-sensitive coagulant and 1-2 parts of in-situ whisker generation precursor; The preparation method of the hydrophilic aminated graphene includes the following steps: Step A1: Disperse graphene oxide in anhydrous ethanol at a concentration of 0.8-1.2 wt%, and sonicate for 20-40 min to obtain a graphene oxide dispersion for later use. Step A2: Add γ-aminopropyltriethoxysilane to the graphene oxide dispersion. The molar ratio of graphene oxide to γ-aminopropyltriethoxysilane is 1:(2-4). Reflux the reaction at 55-65℃ for 5-7 hours to obtain an aminated intermediate for later use. Step A3: Add dopamine hydrochloride to the amination intermediate. The amount of dopamine hydrochloride added is 0.4-0.6 wt% of the graphene oxide mass. Adjust the pH value to 8.0-9.0 with sodium hydroxide solution and stir at room temperature for 10-14 h. Step A4: The product from step A3 is centrifuged, washed 3-5 times with anhydrous ethanol, and freeze-dried under vacuum for 24-36 hours to obtain hydrophilic amino graphene. The preparation method of the hydrophobic thiolized reduced graphene oxide includes the following steps: Step B1: Disperse graphene oxide in deionized water at a concentration of 1.0-1.5 wt%, and ultrasonically disperse for 30 min to obtain an aqueous solution of graphene oxide for later use. Step B2: Add ascorbic acid to the aqueous solution of graphene oxide, with a mass ratio of graphene oxide to ascorbic acid of 1:(4-6). Reduce the graphene oxide at 75-85℃ for 3-5 hours. Detect the C / O ratio using XPS to obtain partially reduced graphene oxide for later use. Step B3: After centrifugation and washing, the partially reduced graphene oxide is transferred to N,N-dimethylformamide solvent and ultrasonically dispersed for 20 min. Step B4: Add 3-mercaptopropyltrimethoxysilane to the dispersion from Step B3. The mass ratio of partially reduced graphene oxide to 3-mercaptopropyltrimethoxysilane is 1:(0.3-0.5). React at 115-125℃ for 7-9 hours under nitrogen protection. Step B5: Wash the product from step B4 with tetrahydrofuran 4-6 times, and dry it under vacuum at 55-65℃ for 12-18 hours to obtain hydrophobic thiolized reduced graphene oxide.

2. The underwater concrete rapid repair material as described in claim 1, characterized in that: The cementitious material system includes 50-55 parts of silicate cement, 10-15 parts of sulfoaluminate cement, and 7-10 parts of ultrafine slag powder. The silicate cement is ordinary silicate cement or rapid-hardening silicate cement with a strength grade of not less than 52.

5. The tricalcium aluminate content of the sulfoaluminate cement is ≥40%; The ultrafine slag powder has a specific surface area ≥600m² / kg and an activity index ≥95%.

3. The underwater concrete rapid repair material as described in claim 1, characterized in that: The auxiliary additives include 0.8-1.3 parts of water-reducing agent, 0.4-0.8 parts of nano-silica, 0.15-0.3 parts of defoamer, 0.25-0.5 parts of cellulose ether, and 0.4-0.8 parts of expanding agent; The water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 35-45%. The average particle size of the nano-silica is 15-30 nm, and the specific surface area is 180-250 m² / g; The defoamer is an organosilicon defoamer or a mineral oil defoamer; The cellulose ether is hydroxypropyl methylcellulose ether with a viscosity of (30,000-80,000) mPa·s; The expanding agent is a calcium sulfoaluminate or calcium oxide expanding agent.

4. The underwater concrete rapid repair material as described in claim 1, characterized in that: The filler system comprises 12-18 parts of quartz sand and 6-10 parts of quartz powder; The quartz sand has a particle size of 35-80 mesh and a SiO2 content of ≥98%. The quartz powder has a particle size of 180-250 mesh and a SiO2 content of ≥99%.

5. The underwater concrete rapid repair material as described in claim 1, characterized in that: The microcapsule-encapsulated thermosensitive coagulant has a glass transition temperature (Tg) of 7-13℃, an encapsulation rate of 82-95%, and a wall thickness of 12-28μm.

6. The underwater concrete rapid repair material as described in claim 1, characterized in that: The degree of amino grafting of the hydrophilic aminated graphene is 12-28%, which is calculated by integrating the CN peak area using XPS; the thiol content of the hydrophobic thiolized reduced graphene oxide is 0.6-1.4 mmol / g, which is determined by the Ellman reagent colorimetric method.

7. The underwater concrete rapid repair material as described in any one of claims 1-6, characterized in that: The preparation method of the microcapsule-coated thermosensitive coagulant includes the following steps: Step C1: Weigh the coagulant core material according to the mass percentage. The coagulant core material includes 25-35% sodium aluminate, 20-30% aluminum sulfate, 3-7% lithium carbonate, and 35-45% nano calcium carbonate. After mixing, ball mill the mixture until the D50 is 4-6 μm to obtain the core material mixture for later use. Step C2: Add the core material mixture to deionized water, with a mass ratio of core material mixture to deionized water of 1:(3-5). Add polyvinyl alcohol as a dispersant, with the amount of polyvinyl alcohol added being 1-3% of the mass of the core material. Stir to form a suspension. Step C3: Adjust the pH of the suspension to 4.0-5.0 with hydrochloric acid solution, heat to 50-60℃, add melamine and formaldehyde solution, the molar ratio of melamine to formaldehyde is 1:(2-3), and the mass ratio of melamine to core material is (0.3-0.5):1; Step C4: React at 55-65℃ for 2.5-3.5h, adjust the pH to 7.0-8.0 with sodium hydroxide solution, and continue the reaction for 0.5-1h; Step C5: Cool to room temperature, filter, wash, dry at 45-55℃ to constant weight, and sieve to a particle size of 80-350μm to obtain microcapsule-encapsulated temperature-sensitive coagulant. or, The method for preparing the in-situ whisker precursor includes the following steps: Step D1: Prepare magnesium nitrate solution and aluminum nitrate solution with concentrations of 0.4-0.6M respectively, mix them in a molar ratio of (1.5-2.5):(0.8-1.2) to obtain a mixed salt solution for later use; Step D2: Prepare a sodium carbonate solution with a concentration of 0.8-1.2M for later use; Step D3: Under vigorous stirring at 55-65℃, add sodium carbonate solution dropwise to the mixed salt solution, controlling the dropping rate to maintain the pH value at 9.5-10.

5. The molar ratio of the mixed salt solution to the sodium carbonate solution is 1:(0.25-0.35). Step D4: After the addition is complete, age at a constant temperature of 60℃ for 20-28 hours; Step D5: Filter and wash the product until the pH of the filtrate is 6.5-7.5, dry it at 75-85℃ for 8-12 hours, grind it and pass it through a 200-300 mesh sieve to obtain the in-situ whisker generation precursor.

8. A method for preparing an underwater concrete rapid repair material as described in any one of claims 1-7, characterized in that: Includes the following steps: Step (1): Weigh the solid components of the cementitious material system, intelligent curing adjustment system, auxiliary additives and filler system according to the proportions, mix them and dry mix them in a high-speed mixer for 2-4 minutes at a stirring speed of 800-1200 rpm to obtain a dry mix for later use. Step (2): Add hydrophilic aminated graphene and hydrophobic thiolized reduced graphene oxide to the water-reducing agent aqueous solution. The mass concentration of the water-reducing agent in the aqueous solution is 5-10%. Disperse ultrasonically for 10-20 min. The ultrasonic power is 350-450W. Step (3): Add nano-silica to the dispersion in step (2), and mechanically stir for 4-6 minutes at a stirring rate of 300-500 rpm to form a stable graphene suspension for later use. Step (4): Add the graphene suspension to the dry mixture and stir at low speed for 1.5-2.5 min at a stirring rate of 100-200 rpm; Step (5): Add the remaining water and liquid additives, stir at medium speed for 2.5-3.5 minutes, with a stirring speed of 300-450 rpm; Step (6): Add microcapsule-encapsulated temperature-sensitive accelerator and in-situ whiskers to generate precursors, stir at high speed for 1.5-2.5 min at a stirring rate of 500-700 rpm to obtain a uniform slurry, which is the graphene-modified underwater concrete rapid repair material. The total preparation time is controlled within 12 minutes.

9. A method for preparing the underwater concrete rapid repair material as described in claim 8, characterized in that: Step (1) Dry mixing is performed using a double helical cone mixer or a planetary mixer; The ultrasonic frequency in step (2) is 40-60 kHz; Steps (4)-(6) use a planetary mixer for wet mixing, and the ambient temperature is controlled at 15-30℃ during the mixing process; In step (6), the microcapsule-encapsulated temperature-sensitive coagulant and the in-situ whisker precursor should be added in the final stage of the stirring process, and then immediately and quickly stirred until homogeneous.

10. The application of the underwater concrete rapid repair material as described in any one of claims 1-7 in the repair of underwater concrete structures.

11. The application according to claim 10, characterized in that: The underwater concrete structure includes one or more of the following: port terminals, offshore platforms, cross-sea bridge piers, hydraulic dams, underwater tunnels, and submarine pipeline foundations.

12. An underwater repair construction method, characterized in that: Includes the following steps: Step 1: Clean the underwater concrete surface to be repaired by using underwater high-pressure water jet or mechanical grinding to remove loose layers, contaminants and attached organisms, cleaning to the depth of the exposed solid base layer; Step II: Roughen the base surface by underwater chiseling or wire brushing to create a rough texture 3-5mm deep. Rinse with clean water after roughening. Step III: Adjust the water-cement ratio of the material according to the underwater ambient temperature and the water depth of the repair area: the water-cement ratio is 0.28-0.30 when the water temperature is 4-10℃, 0.29-0.31 when the water temperature is 10-20℃, and 0.30-0.32 when the water temperature is 20-28℃. Step IV: Prepare the repair material slurry according to the method described in claim 8 or 9; Step V: Inject the grout into the repair area using an underwater pumping device or an underwater non-dispersible grouting pipe. The injection speed should be controlled at 8-15 L / min, and the thickness of each repair layer should not exceed 50 mm. Step VI: When the repair thickness exceeds 30mm, the repair area contains exposed rebar, the repair area has a complex shape, or the water depth exceeds 10m, underwater vibration equipment is used to compact the repair material. The vibration time is 10-30s / m². Step VII: After the repair is completed, allow the water to cure naturally. The initial setting time is 4-18 minutes. The strength reaches 45-55% of the design strength in 24 hours and 80-90% of the design strength in 7 days.

13. The underwater repair construction method according to claim 12, characterized in that: In step I, the pressure of the underwater high-pressure water jet is 15-25 MPa; In step V, when the repair depth exceeds 50mm, layered construction is adopted, with an interval of 15-30 minutes between each layer; In step VII, when the water temperature is below 10℃, the initial setting time is 10-18 min; when the water temperature is 10-20℃, the initial setting time is 6-12 min; and when the water temperature is above 20℃, the initial setting time is 4-8 min.

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