Water-borne epoxy resin-sulphoaluminate cement composite repairing material and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a waterborne epoxy resin-sulphoaluminate cement composite repairing material and a preparation method thereof. The water-borne epoxy resin-sulphoaluminate cement composite repairing material disclosed by the invention is prepared from the following components in parts by weight: 10 to 20 parts of water-borne epoxy resin, 40 to 60 parts of sulphoaluminate cement, 0.5 to 1 part of nano modified lignosulfonate, 0.2 to 0.6 part of nano hybrid polyvinyl alcohol, 0.1 to 0.5 part of a retarder, 0.05 to 0.3 part of an early strength agent and 12 to 25 parts of water. The water-borne epoxy resin-sulphoaluminate cement composite repairing material is suitable for hydraulic buildings with high requirements on repairing quality and durability, such as cross-sea bridges, seaport wharfs, hydropower stations and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to a water-based epoxy resin-sulphoaluminate cement composite repair material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of marine engineering and water conservancy engineering, underwater repair materials need to have excellent bonding strength, durability, self-leveling, self-compacting, thixotropy, and early strength and rapid hardening, etc. However, the traditional underwater repair materials such as ordinary cement-based materials and polymer modified cement-based materials generally have poor rheological properties, difficult to control setting time, and slow strength development, etc., which are difficult to meet the construction requirements in complex underwater environments. The self-leveling performance ensures that the material can fully fill the defects during flat construction; the thixotropic performance ensures that the material will not sag and lose during vertical construction; and the early strength and rapid hardening characteristics can ensure that the repair material obtains sufficient strength in a short time, reducing the erosion damage of water flow to the newly repaired area. Especially in complex underwater environments, the construction performance of the material is directly related to the repair effect. However, the traditional underwater repair materials generally have a series of technical problems. Although the ordinary cement-based material is low in cost, it has poor rheological properties, short initial setting time, long final setting time, and slow strength development, which is difficult to meet the requirements of underwater repair engineering. In recent years, the development of polymer modified cement-based materials has improved the performance of ordinary cement-based materials to some extent, but still cannot solve the fundamental problems of rheological regulation and setting time optimization.

[0003] The core challenge faced by current underwater repair materials is the flexible regulation of rheological properties. The existing technology cannot realize the precise regulation of material rheological properties according to the construction scene requirements. In the flat construction scene, the material needs to have excellent fluidity and self-leveling ability (according to the “GB / T 50448-2015 Technical Specification for Application of Cement-based Grouting Materials”, the fluidity should be ≥250mm), while maintaining the underwater anti-dispersion property to ensure full filling of the repair area; while in the vertical construction scene, the material needs to have high thixotropy and anti-flowing performance to prevent sagging and loss (vertical construction requires high thixotropy to prevent flowing, and the industry reference value of thixotropic index is TI≥1.5; the thixotropic index is tested by a rotary rheometer, and is the area ratio of the rising speed curve to the falling speed curve), while still maintaining sufficient underwater anti-dispersion ability. The application of traditional rheological regulators in water-based epoxy-sulphoaluminate cement systems has significant limitations: on the one hand, simply increasing the fluidity will lead to a decrease in the material's resistance to water flow dispersion, making it difficult to maintain the integrity of the underwater structure; on the other hand, enhancing the thixotropy often comes at the cost of fluidity, affecting the material's penetration and filling effect in complex working conditions.

[0004] In addition, the setting time regulation and strength development of existing underwater repair materials also have significant deficiencies. The initial setting time of ordinary cement-based materials is too short, usually only a few minutes, which limits the construction operation window; while the final setting time is too long, often taking several hours, which delays the strength formation and makes it difficult to meet the rapid repair requirements. Although the polymer modified material can accelerate hardening by adding early strength agent, the long-term durability is often sacrificed, leading to secondary cracking of the repaired structure. There is a lack of a regulation system that can achieve precise balance between initial setting and final setting in the prior art, while also considering the switching requirements of rheological properties according to different construction scenarios. SUMMARY

[0005] The purpose of the present application is to provide a water-based epoxy resin-sulphoaluminate cement composite repair material and a preparation method thereof, in order to help solve or improve the problem that existing underwater repair materials are difficult to meet the construction requirements in complex underwater environments.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solution: a water-based epoxy resin-sulphoaluminate cement composite repair material, by weight fraction, comprising the following components: water-based epoxy 10-20 parts, sulphoaluminate cement 40-60 parts, nano-modified lignin sulfonate 0.5-1 part, nano-hybrid polyvinyl alcohol 0.2-0.6 part, retarder 0.1-0.5 part, early strength agent 0.05-0.3 part and water 12-25 parts.

[0007] Preferably, the nano-modified lignin sulfonate is prepared by chemically bonding sodium lignin sulfonate with nano-silicon dioxide through a first silane coupling agent; the amount of nano-silicon dioxide is 3wt%-15wt% of the mass of sodium lignin sulfonate, and the particle size of nano-silicon dioxide is 20-50nm.

[0008] Preferably, the nano-modified lignin sulfonate is prepared by the following method: A1, adding nano-silicon dioxide to a sodium lignin sulfonate solution, ultrasonic dispersion to obtain a first mixed solution; A2, adding a first silane coupling agent dropwise to the first mixed solution, and stirring during the dropwise addition; A3, heating the mixture obtained by step A2 and constant temperature stirring reaction; A4, after the reaction is completed, spray drying to obtain the nano-modified lignin sulfonate.

[0009] Preferably, in step A2, the mass ratio of the first silane coupling agent to sodium lignin sulfonate is (0.06-0.3):100; in step A3, the temperature of the constant temperature stirring reaction is 45-65℃, and the reaction time is 1.5-4.5h.

[0010] Preferably, the nano-hybrid polyvinyl alcohol is prepared by grafting polyvinyl alcohol with nano-montmorillonite via a second silane coupling agent; the mass ratio of the nano-montmorillonite to the polyvinyl alcohol is 3wt%-15wt%.

[0011] Preferably, the nano-hybrid polyvinyl alcohol is prepared by a method comprising the following steps: B1, dispersing polyvinyl alcohol in deionized water, stirring under heating to form a clear polyvinyl alcohol solution; B2, dispersing nano-montmorillonite in water, treating with ultrasonic waves to obtain a nano-montmorillonite suspension; B3, adding a second silane coupling agent to the nano-montmorillonite suspension, stirring at 60°C for 2h to obtain a functionalized nano-montmorillonite suspension; B4, mixing the functionalized nano-montmorillonite suspension with the polyvinyl alcohol solution, adding ammonium persulfate as an initiator, reacting at 60-80°C under nitrogen for 3.5-6h; B5, after the reaction is completed, centrifuging, washing and drying the obtained solid to obtain the nano-hybrid polyvinyl alcohol.

[0012] Preferably, in step B2, the power of ultrasonic treatment is 450-550W, the frequency is 15-20kHz, and the ultrasonic treatment time is 25-35min; in step B3, the amount ratio of the second silane coupling agent to polyvinyl alcohol is (3-12)mL:100g.

[0013] Preferably, the set retarder is citric acid, and the early strength agent is calcium fluosilicate.

[0014] Preferably, the fineness of the sulphoaluminate cement is ≤300m² / kg, the initial setting time of the sulphoaluminate cement is 15-20min, and the final setting time is 25-30min.

[0015] The application also provides a preparation method of the water-based epoxy resin-sulphoaluminate cement composite repair material as described above, which adopts the following technical scheme: the preparation method of the water-based epoxy resin-sulphoaluminate cement composite repair material as described above comprises the following steps: (1) preheating and stirring the water-based epoxy resin and the water-based curing agent in the water-based epoxy respectively at 40-50°C for 10-15min; (2) dissolving nano-modified lignosulfonate in at least part of the water first, then adding the nano-hybrid polyvinyl alcohol, and stirring to obtain a first solution; (3) dissolving a set retarder in at least part of the water first, then adding an early strength agent, and stirring to obtain a second solution; (4) adding the first solution and the second solution to the sulphoaluminate cement, stirring uniformly, then adding the water-based epoxy resin and the water-based curing agent obtained by step (1), and continuing to stir uniformly to obtain the water-based epoxy resin-sulphoaluminate cement composite repair material.

[0016] Beneficial effects: The water-based epoxy resin-sulphoaluminate cement composite repair material of the present application significantly improves the performance of underwater repair material, and solves the technical problems of traditional materials in rheological property regulation, setting time optimization and comprehensive performance improvement. The nano-modified lignosulfonate in the water-based epoxy resin-sulphoaluminate cement composite repair material of the present application is prepared by chemical bonding of sodium lignosulfonate and nano-silicon dioxide through a first silane coupling agent. Sodium lignosulfonate acts as a high-efficiency water reducing agent to reduce the water consumption of cement paste and improve the fluidity. The high specific surface area and surface activity of nano-silicon dioxide enhance the particle dispersibility and interfacial bonding force. The chemical bonding of the two forms a stable nano-composite structure, which makes the material exhibit excellent dispersion resistance and fluidity in underwater environment. The nano-hybrid polyvinyl alcohol is prepared by grafting polyvinyl alcohol and nano-montmorillonite through a second silane coupling agent. Polyvinyl alcohol provides viscosity and rheological stability, and the layered structure of nano-montmorillonite endows the material with high thixotropy and anti-sagging ability. The grafting of the two forms a hybrid network, which further enhances the structural stability of the material. The synergistic effect of the two realizes flexible regulation of rheological property.

[0017] In the water-based epoxy resin-sulphoaluminate cement composite repair material of the present application, the use of citric acid (retarder) and calcium fluosilicate (early strength agent) in combination with the synergistic optimization of the two nano components establishes a “retarding-fast hardening” regulation system. Citric acid delays the hydration process of cement by forming a complex with Al 3+ , Ca 2+ in cement, ensuring sufficient construction operation window; calcium fluosilicate accelerates the rapid hydration of sulphoaluminate cement to speed up the strength development. The nano-modified lignosulfonate and the nano-hybrid polyvinyl alcohol further optimize this system. Nano-silicon dioxide and nano-montmorillonite act as crystal nuclei to promote the generation of hydration products, improve the microstructure of cement paste, and enhance the early hydration process and long-term durability (28-day compressive strength ≥ 58 MPa). The synergistic effect of this “retarding-fast hardening” system and the two nano components not only meets the demand for underwater rapid repair, but also avoids the problem of sacrificing long-term durability caused by traditional early strength agents.

[0018] In the water-based epoxy resin-sulphoaluminate cement composite repair material of the present application, the water-based epoxy resin and the sulphoaluminate cement form a dense composite network through physical interpenetration and chemical crosslinking, improving the bonding strength (≥ 2.4 MPa) and impermeability; the nano-modified lignosulfonate and the nano-hybrid polyvinyl alcohol enhance the interface and regulate the rheology through the nano-scale interface, optimizing the dispersibility and stability of the paste; citric acid and calcium fluosilicate regulate the hydration process, and the two nano components further enhance the microstructure through crystal nucleus effect and micro-filling. The synergistic effect of organic-inorganic and macro-micro makes the material have high bonding strength, self-compacting property, early strength and fast hardening characteristics, and excellent durability, which is significantly better than traditional cement-based or polymer-modified materials.

[0019] The preparation process of the water-based epoxy resin-sulphoaluminate cement composite repair material is simple, raw materials are widely available, the cost is moderate, the ratio of components and the synthesis process have a large adjustment space, and the engineering requirements can be flexibly adjusted, and the water-based epoxy resin-sulphoaluminate cement composite repair material is particularly suitable for high-quality and durability requirements of underwater construction such as cross-sea bridges, harbor wharfs, hydropower stations and the like. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein for explanation. Figure 1 The cement setting and hardening time and compressive strength (3d and 28d) test results of Example 1, Example 2 and Comparative Example 3, Comparative Example 4 and Comparative Example 6 are shown in the following figures. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0022] The present application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0023] The present application provides a water-based epoxy resin-sulphoaluminate cement composite repair material to solve the problem that the existing underwater repair material cannot meet the construction requirements in complex underwater environment.

[0024] The present application found in the research that the contradiction between high flow and low impact resistance and high thixotropy and low flow plasticity of the traditional rheological modifier in the application of the water-based epoxy-sulphoaluminate cement system is essentially due to the insufficient interfacial compatibility between organic additives and inorganic phases, which leads to the difficulty of the system to realize the rheological property self-adaptive adjustment under dynamic construction conditions. Especially in the underwater repair scene, the material not only needs excellent flow plasticity when pouring to ensure sufficient compaction, but also requires sufficient structural stability before solidification to resist water erosion.

[0025] The water-based epoxy-sulphoaluminate cement composite repair material of the embodiment of the present application comprises, by weight fraction, the following components: water-based epoxy 10-20 parts (for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts or 20 parts), sulphoaluminate cement 40-60 parts (for example, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts), nano-modified lignin sulfonate 0.5-1 part (for example, 0.5 part, 0.6 part, 0.8 part or 1 part), nano-hybrid polyvinyl alcohol 0.2-0.6 part (for example, 0.2 part, 0.3 part, 0.4 part, 0.5 part or 0.6 part), retarder 0.1-0.5 part (for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part or 0.5 part), early strength agent 0.05-0.3 part (for example, 0.05 part, 0.1 part, 0.2 part, 0.25 part or 0.3 part) and water 12-25 parts (for example, 12 parts, 16 parts, 20 parts, 22 parts or 25 parts).

[0026] The nano-modified lignin sulfonate and the nano-hybrid polyvinyl alcohol in the water-based epoxy-sulphoaluminate cement composite repair material of the present application help to achieve the regulation of rheological properties. For a flat construction scene, by increasing the content of the nano-modified lignin sulfonate and reducing the proportion of the nano-hybrid polyvinyl alcohol, the self-leveling performance of the material can be significantly improved. This is because the sulfonic acid groups in the nano-modified lignin sulfonate produce electrostatic repulsion and steric hindrance effect on the cement particles, and the surface-bonded nano-silica further enhances the fluidity of the material under shear stress by providing additional dispersion points and enhancing the stability of the hydration film. In contrast, in the vertical construction scene, the content of the nano-hybrid polyvinyl alcohol needs to be increased and the proportion of the nano-montmorillonite in it needs to be increased, so that the material exhibits high thixotropy. This is because the hybrid network structure formed by polyvinyl alcohol and nano-montmorillonite can quickly rebuild a three-dimensional network to form a thixotropic gel in a static state, but when subjected to shear, the network is destroyed, causing the viscosity to drop and the material to become easy to construct. At the same time, the synergistic effect of the rapid hydration of the sulphoaluminate cement and the two nano components achieves a controllable switch from "high flow" to "high thixotropy" through crystal nucleus effect and microstructure rearrangement, meeting the needs of different construction scenes.

[0027] Preferably, the mass ratio of the nano-modified lignin sulfonate to the nano-hybrid polyvinyl alcohol is (2.67-5):1. When the mass ratio of the nano-modified lignin sulfonate to the nano-hybrid polyvinyl alcohol is (2.67-5):1, it helps to improve the fluidity of the water-based epoxy-sulphoaluminate cement composite repair material of the present application, and thus the water-based epoxy-sulphoaluminate cement composite repair material of the present application is more suitable for flat construction scenes.

[0028] Preferably, the mass ratio of the nano-modified lignin sulfonate to the nano-hybrid polyvinyl alcohol is 1:1. When the mass ratio of the nano-modified lignin sulfonate to the nano-hybrid polyvinyl alcohol is 1:1, the thixotropy of the water-based epoxy resin-metakaolin cement composite repair material of the present application is improved, and the water-based epoxy resin-metakaolin cement composite repair material of the present application is more suitable for facade construction scenes.

[0029] In a preferred embodiment of the water-based epoxy resin-metakaolin cement composite repair material of the present application, the nano-modified lignin sulfonate is prepared by chemically bonding sodium lignin sulfonate and nano-silicon dioxide with a first silane coupling agent (preferably, the first silane coupling agent is vinyl trimethoxysilane); the amount of nano-silicon dioxide is 3wt%-15wt% (for example, 3wt%, 5wt%, 8wt%, 10wt%, 12wt% or 15wt%) of the sodium lignin sulfonate. If the amount of nano-silicon dioxide is too large, the excess nano-silicon dioxide is prone to agglomeration, which increases the viscosity of the system, hinders the dispersion of cement particles, and reduces the compressive strength; if the amount of nano-silicon dioxide is too small, the nano-silicon dioxide is not sufficient to effectively bond the sodium lignin sulfonate, resulting in poor dispersibility and reduced fluidity.

[0030] In a preferred embodiment of the water-based epoxy resin-metakaolin cement composite repair material of the present application, the nano-modified lignin sulfonate is prepared by the following method: A1, adding nano-silicon dioxide to a sodium lignin sulfonate solution, ultrasonically dispersing uniformly to obtain a first mixed solution; A2, adding a first silane coupling agent to the first mixed solution dropwise while stirring; A3, heating the mixture obtained by step A2 and stirring at a constant temperature to react; A4, after the reaction is completed, the nano-modified lignin sulfonate is obtained by spray drying.

[0031] In a preferred embodiment of the waterborne epoxy resin-sulfoaluminate cement composite repair material of the present invention, in step A2, the mass ratio of the first silane coupling agent to sodium lignin sulfonate is (0.06-0.3):100 (e.g., 0.06:100, 0.08:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, or 0.3:100); in step A3, the constant temperature stirring reaction temperature is 45-65°C (e.g., 45°C, 50°C, 55°C, 60°C, or 65°C), and the reaction time is 1.5-4.5 hours (e.g., 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or 4.5 hours). Among them, if the amount of the first silane coupling agent is too small, the chemical bonding between the sodium lignin sulfonate and the nano-silica will be insufficient, the interfacial bonding force will be weak, the dispersibility of the nano-silica will be reduced, it will be easy to agglomerate, and it will not be able to effectively play its role as a hydration nucleus and enhance fluidity; this will cause the material's anti-dispersion and fluidity in an underwater environment to decrease, thereby affecting the rheology and stability of the repair material; if the amount of the first silane coupling agent is too large, the excess silane coupling agent may cause excessive cross-linking, resulting in excessive occupation of the active sites on the surface of the sodium lignin sulfonate, reducing its compatibility with the cement matrix; in addition, too much coupling agent may trigger side reactions, generate unnecessary by-products, increase material costs, and at the same time may reduce the water-reducing and dispersion effects of the nano-modified lignin sulfonate, affecting the overall performance of the repair material.

[0032] If the reaction temperature in step A3 is too high, the chemical bonding reaction between the first silane coupling agent and the sodium lignin sulfonate may be too rapid, resulting in an uneven composite structure and even causing partial degradation or denaturation of the sodium lignin sulfonate. This will reduce the stability and functionality of the nano-modified lignin sulfonate, affect its dispersibility and water-reducing effect in the cement matrix, and ultimately lead to a decrease in the anti-dispersion and mechanical properties of the repair material. If the reaction temperature in step A3 is too low, the chemical bonding reaction rate between the first silane coupling agent and the sodium lignin sulfonate will be slowed down, the bonding efficiency will be reduced, and it will be difficult to form a stable nano-composite structure. This will result in insufficient surface modification of the nano-silica and poor particle dispersibility, affecting the rheological properties and underwater anti-dispersion properties of the material.

[0033] If the reaction time of step A3 is too long, the first silane coupling agent may overreact, consuming too many active sites or inducing side reactions to generate unnecessary polymers. This will reduce the surface activity of the nano-modified lignin sulfonate and its chemical bonding ability with the cement matrix, thereby affecting the rheological properties and strength of the repair material. If the reaction time of step A3 is insufficient, the chemical bonding between the first silane coupling agent and the sodium lignin sulfonate will be incomplete, the surface modification effect of the nano-silica will be poor, and the particles will easily agglomerate. This will reduce the material's anti-dispersion and fluidity, affecting the construction performance and mechanical properties of the underwater repair material.

[0034] In the preferred embodiment of the water-based epoxy-sulphoaluminate cement composite repair material of the present application, the nano-hybrid polyvinyl alcohol is prepared by grafting polyvinyl alcohol with nano-montmorillonite via a second silane coupling agent (preferably, the second silane coupling agent is vinyl trimethoxysilane); the amount of nano-montmorillonite is 3wt%-15wt% (for example, 3wt%, 5wt%, 8wt%, 10wt%, 12wt% or 15wt%) of the polyvinyl alcohol. If the proportion of nano-montmorillonite is too high, the dispersibility of the montmorillonite in the polyvinyl alcohol solution will decrease, and the nano-hybrid polyvinyl alcohol will be prone to agglomeration, which will reduce the uniformity and stability of the nano-hybrid polyvinyl alcohol. Too much montmorillonite can make the material system too rigid, and the rheological property will be poor, which will affect the flowability of the repair material. In addition, too much montmorillonite can weaken the flexible network structure of the polyvinyl alcohol, reduce the thixotropy and underwater dispersion resistance of the material, and increase the loss rate in water. If the proportion of nano-montmorillonite is too low, the structural activity of the polyvinyl alcohol cannot be effectively enhanced, and it is difficult to form a stable three-dimensional network structure. This will result in insufficient rheological regulation ability of the nano-hybrid polyvinyl alcohol, and the repair material will be prone to dispersion loss in underwater environment, and the dispersion resistance and stability will decrease. At the same time, the crystal nucleus effect of the montmorillonite will be insufficient, which will affect the generation of cement hydration products and the early strength development.

[0035] In the preferred embodiment of the water-based epoxy-sulphoaluminate cement composite repair material of the present application, the nano-hybrid polyvinyl alcohol is prepared by the following steps: B1, dispersing polyvinyl alcohol in deionized water, heating and stirring to form a clear polyvinyl alcohol solution; B2, dispersing nano-montmorillonite in water, and treating with ultrasonic waves (to exfoliate the clay sheets) to obtain a nano-montmorillonite suspension; B3, adding a second silane coupling agent to the nano-montmorillonite suspension, and stirring at 60°C for 2h, using vinyl trimethoxysilane to functionalize the surface of the clay sheets exfoliated from the nano-montmorillonite, thereby enhancing the reactivity with the polyvinyl alcohol, to obtain a functionalized nano-montmorillonite suspension; B4, mixing the functionalized nano-montmorillonite suspension with the polyvinyl alcohol solution, adding ammonium persulfate as an initiator, and reacting at 60-80°C (for example, 60°C, 65°C, 70°C, 75°C or 80°C) under nitrogen for 3.5-6h (for example, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h); B5, after the reaction is completed, centrifuging, washing and drying the obtained solid, to obtain the nano-hybrid polyvinyl alcohol. If step B2 is omitted, since the nano-montmorillonite naturally has a layered structure, the layers will be tightly stacked without ultrasonic treatment, which will make it difficult to uniformly disperse in water, and it will not be able to effectively react with the second silane coupling agent, thereby reducing the grafting rate and hybridization effect of the polyvinyl alcohol, and finally significantly reducing the thixotropy, sag resistance and mechanical strength of the material (such as reducing the thixotropic index and increasing the loss rate in water), which will affect the stability of underwater construction and the repair effect.

[0036] In Step B4, too high a reaction temperature can cause ammonium persulfate to decompose too quickly, resulting in too high a concentration of free radicals, uncontrolled grafting reaction, and excessive byproducts or uneven grafting structure. In addition, high temperature can cause partial degradation or denaturation of polyvinyl alcohol, reducing its rheological regulation ability and flexible network structure, and affecting the thixotropy and underwater stability of the repair material. If the reaction temperature is too low, the decomposition rate of ammonium persulfate will be slowed down, and the generation of free radicals will be insufficient, resulting in incomplete grafting reaction between the vinyl-functionalized montmorillonite and the polyvinyl alcohol. This will reduce the structural stability and functionality of the nano-hybrid polyvinyl alcohol, and affect the rheological properties and dispersion resistance of the repair material. In Step B4, if the reaction time is too long, it can cause excessive free radical reaction initiated by ammonium persulfate, generating excessive grafted polymers or byproducts, reducing the uniformity and functionality of the nano-hybrid polyvinyl alcohol. In addition, long-time reaction can consume the active sites of polyvinyl alcohol, weaken its chemical bonding ability with the cement matrix, and affect the mechanical properties and underwater stability of the repair material. If the reaction time is insufficient, it will result in incomplete grafting reaction, low degree of chemical bonding between the vinyl-functionalized montmorillonite and the polyvinyl alcohol, and difficulty in forming a stable three-dimensional network structure. This will reduce the rheological regulation ability and dispersion resistance of the nano-hybrid polyvinyl alcohol, and affect the workability and strength of the repair material in underwater environment.

[0037] In a preferred embodiment of the water-based epoxy resin-sulfoaluminate cement composite repair material of the present application, in Step B2, the power of ultrasonic treatment is 450-550 W (e.g., 450 W, 480 W, 500 W, 520 W, or 550 W), the frequency is 15-20 kHz (e.g., 15 kHz, 16 kHz, 17 kHz, 18 kHz, 19 kHz, or 20 kHz), and the ultrasonic treatment time is 25-35 min (e.g., 25 min, 28 min, 30 min, 32 min, or 35 min); in Step B3, the ratio of the amount of the second silane coupling agent to the amount of polyvinyl alcohol is (3-12) mL:100 g (e.g., 3 mL:100 g, 5 mL:100 g, 8 mL:100 g, 10 mL:100 g, or 12 mL:100 g). If the amount of the second silane coupling agent is too small, insufficient grafting of the montmorillonite surface will result in insufficient reaction with polyvinyl alcohol, making the hybrid structure loose, the thixotropy poor, and the mechanical strength low; while too much amount will cause the silane coupling agent to self-polymerize into a glue that hinders effective bonding, resulting in abnormal increase in the viscosity of the material and possible side effects.

[0038] In the preferred embodiment of the present application, the preparation method of the nano-modified lignin sulfonate salt comprises the following steps: A1, taking 100g of sodium lignin sulfonate, adding 900g of deionized water, stirring until completely dissolved, and preparing a 10 wt% solution; A2, adding 3-15g of nano-silicon dioxide (particle size 20-50nm, content 3wt%-15wt%), ultrasonic dispersion for 15-50 minutes to ensure uniform dispersion; A3, slowly adding 0.06-0.3g of the first silane coupling agent, controlling the dropping speed to be 0.05g / min, and keeping stirring during the dropping process; A4, heating the mixture to 45-65℃, constant temperature stirring reaction for 1.5-4.5 hours to promote chemical bonding; A5, after the reaction is completed, nano-modified lignin sulfonate powder is obtained by spray drying (inlet temperature 175-195℃, outlet temperature 75-90℃), and is ready for use.

[0039] In the preferred embodiment of the present application, the preparation method of the nano-hybrid polyvinyl alcohol comprises the following steps: B1, dissolving 100g of polyvinyl alcohol in 500mL of deionized water, stirring (300rpm) at 90℃ for 2h to form a clear solution; B2, dispersing 3g-15g of nano-montmorillonite in 100mL of water, and stirring (500W, 20kHz) for 30 minutes with ultrasonic waves to exfoliate the clay sheets of the nano-montmorillonite (the clay sheet refers to the exfoliated layer sheet of the nano-montmorillonite); B3, adding 3mL-12mL of the second silane coupling agent to the nano-clay suspension, and stirring at 60℃ for 2 hours to functionalize the surface of the clay sheets obtained by exfoliating the nano-montmorillonite with the second silane coupling agent, thereby enhancing the reactivity with the polyvinyl alcohol; B4, mixing the functionalized nano-clay suspension with the polyvinyl alcohol solution, adding 0.5g of ammonium persulfate (APS) as an initiator, and reacting at 60-80℃ for 3.5-6 hours under nitrogen to graft the nano-clay onto the polyvinyl alcohol through vinyl-hydroxyl interaction; B5, centrifuging at a speed of 8000rpm for 10 minutes, washing with ethanol, and drying at 60℃ for 12 hours to obtain nano-hybrid polyvinyl alcohol powder.

[0040] In the preferred embodiment of the present application, the water-based epoxy resin-sulfoaluminate cement composite repair material, the retarder is citric acid, and the early strength agent is calcium fluosilicate.

[0041] In the present application, the interaction between citric acid and calcium fluosilicate at the molecular and chemical level forms precise regulation of the hydration process of sulfoaluminate cement. Citric acid forms a stable complex with Al 3+ and Ca 2+ in cement through its carboxyl group, delaying the nucleation of ettringite at the initial stage of hydration, thereby prolonging the initial setting time to 25-30 minutes to provide an adequate operation window for construction. At the same time, SiO3 2-Si-O-C bond with epoxy resin. As the pH rises, the complex of citric acid dissociates to release Ca 2+ F produced by the decomposition of calcium fluosilicate - and SiO3 2- Synergistically promotes the rapid nucleation and growth of ettringite crystals in the later hydration stage, accelerating the final setting process. At the same time, the epoxy group forms a chemical bond with the modified cement particles, i.e. ≡Si-O-CH2-CH(OH)-CH2-, and the low Ca / Si ratio C-S-H gel formed in the later stage interlocks with the polyvinyl alcohol in the nano-hybrid polyvinyl alcohol, accelerating the final setting process. This chemical synergy between citric acid and calcium fluosilicate not only achieves precise balance between initial and final setting times, but also significantly improves the early hydration process. In contrast, traditional retarders such as boric acid have single adjustment effect and are difficult to form synergy with early strength agents; oxalic acid has strong corrosiveness and damages the durability of the matrix; the regulation precision of tartaric acid is limited; and although sodium gluconate has a lower cost, it is not as precise as citric acid in regulating the hydration process in the sulphoaluminate cement system. Similarly, traditional early strength agents such as calcium chloride or sodium sulfate have low cost, but are prone to cause matrix erosion in underwater environments, and cannot form a molecular synergy mechanism similar to citric acid-fluorosilicate calcium. Through the specific ratio of citric acid to fluorosilicate calcium, combined with the microstructure optimization of nano-modified lignosulfonate and nano-hybrid polyvinyl alcohol, the invention achieves comprehensive improvement of rheological properties, setting time and strength.

[0042] In the preferred embodiment of the water-based epoxy-sulphoaluminate cement composite repair material of the invention, the water-based epoxy is composed of a water-based epoxy resin and a water-based curing agent, and the main components are -O-(CH2CH2O) n -H and H2N-(CH2)2-NH-(CH2CH2O) n -H, the mass ratio of water-based epoxy resin to water-based curing agent is 1:1, and the solid content is 45%.

[0043] In the preferred embodiment of the water-based epoxy-sulphoaluminate cement composite repair material of the invention, the fineness of the sulphoaluminate cement is ≤300 m² / kg, the initial setting time of the sulphoaluminate cement is 15-20 min, and the final setting time is 25-30 min.

[0044] The application further provides a preparation method of the water-based epoxy resin-metasulphoaluminate cement composite repair material, and the preparation method comprises the following steps: (1) preheating and stirring the water-based epoxy resin and the water-based curing agent in the water-based epoxy respectively at 40-50 DEG C (for example, 40 DEG C, 42 DEG C, 44 DEG C, 46 DEG C, 48 DEG C or 50 DEG C) for 10-15 min (for example, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min); (2) dissolving the nano-modified lignosulfonate in at least part of the water first, then adding the nano-hybrid polyvinyl alcohol and stirring uniformly to obtain a first solution; (3) dissolving the retarding agent in at least part of the water first, then adding the early strength agent and stirring uniformly to obtain a second solution; (4) adding the first solution and the second solution into the metasulphoaluminate cement, then adding the water-based epoxy resin and the water-based curing agent obtained in the step (1) after uniform stirring, and continuing to stir uniformly to obtain the water-based epoxy resin-metasulphoaluminate cement composite repair material.

[0045] If the step of preheating the water-based epoxy is omitted, the water-based epoxy may not be fully dispersed, resulting in the presence of undispersed resin particles in the material, which affects the uniformity and performance of the material. Meanwhile, preheating helps to activate the epoxy resin and ensure sufficient reaction with the cement. If the preheating temperature is too low, the activation degree of the water-based epoxy is insufficient, which will slow down the reaction speed with the cement; if the preheating temperature is too high, the resin may partially denature or degrade, affecting its performance. If the preheating time is too short, the active functional groups are not fully activated, affecting the interfacial bonding with the cement; if the preheating time is too long, the epoxy resin may partially pre-cure, and excessive activation may cause the epoxy groups to react prematurely, consuming active sites. In step (2), the selection of the feeding order of the nano-modified lignosulfonate and the nano-hybrid polyvinyl alcohol can ensure that the nano-modified lignosulfonate fully exerts its dispersing effect, while the nano-hybrid polyvinyl alcohol usually needs longer time to dissolve, and if it is added first, it may hinder the uniform dispersion of the lignosulfonate due to swelling and thickening.

[0046] The water-based epoxy resin-metasulphoaluminate cement composite repair material and the preparation method thereof will be described in detail through specific examples.

[0047] The test methods in the following examples are as follows: 1. Initial setting time and final setting time: A Vicat apparatus is used, the test needle diameter is 1.13 mm, the test mold diameter is 50 mm, and the height is 50 mm. After the material is stirred with water, it is loaded into the test mold and placed in a constant temperature and humidity box (temperature 20±1 DEG C, humidity ≥90%). The initial setting time is the time corresponding to the state that the test needle is 4±1 mm away from the bottom plate; the final setting time is the time required when there is no ring mark on the surface of the test body.

[0048] 2. Bonding strength with substrate: Prepare a concrete test block, apply the repair material to the surface, and cure for the specified time. Using a bond strength tester, bond the puller to the repair layer and load until failure. Bond strength = maximum tensile force / bond area.

[0049] 3. Water loss rate: Gently place the sample in a container of clean water. Measure the turbidity of the water sample using a turbidimeter at specific time points (e.g., 1 minute, 5 minutes, 10 minutes, 30 minutes, etc.). This indirectly assesses material loss by measuring the turbidity of suspended particles in the water.

[0050] 4. Thixotropic index: The shear stress changes of cement-based materials at different shear rates were measured by a rotational rheometer. The shear stress-shear rate curves during the speed increase and speed decrease processes were compared to calculate the thixotropic index.

[0051] 5. Fluidity: Use a standard flow ring (a cylinder with an inner diameter of 30 mm and a height of 50 mm), place the ring on a glass plate, fill it with repair material, lift the ring vertically, and measure the diameter of the material spread after 30 seconds. Measure in two perpendicular directions and take the average value.

[0052] Example 1 The waterborne epoxy resin-sulphoaluminate cement composite repair material of this embodiment comprises the following components in parts by weight: 15 parts of water-based epoxy (the mass ratio of water-based epoxy resin and water-based curing agent is 1:1), 50 parts of sulfoaluminate cement, 0.8 parts of nano-modified lignin sulfonate (the amount of nano-silica is 12wt% of sodium lignin sulfonate), 0.3 parts of nano-hybrid polyvinyl alcohol (the amount of nano-montmorillonite is 4wt% of polyvinyl alcohol), 0.3 parts of citric acid, 0.1 parts of calcium fluorosilicate, and 20 parts of water.

[0053] The preparation method of the nano-modified lignin sulfonate is as follows: A1. Take 100g of sodium lignin sulfonate, add 900g of deionized water, and stir until completely dissolved to prepare a 10wt% solution. A2. Add 12g of nano-silica (particle size 20-50nm, the amount of nano-silica is 12wt% of the sodium lignin sulfonate) and ultrasonically disperse for 40 minutes to ensure uniform dispersion. A3. Slowly add 0.24g of the first silane coupling agent (vinyltrimethoxysilane) dropwise at a rate of 0.05g / min, while stirring continuously. A4. Heat the mixture to 60°C and stir at this constant temperature for 4 hours to promote chemical bonding. A5. After the reaction is completed, spray dry (inlet temperature 190°C, outlet temperature 85°C) to obtain the nano-modified lignin sulfonate powder, which is set aside.

[0054] The preparation method of the nanohybrid polyvinyl alcohol is as follows: B1, 100 g of polyvinyl alcohol (molecular weight 60-120 kg) is added to 500 mL of deionized water, heated to 90°C, and stirred (300 rpm) for 2 hours to form a clear solution. B2, 4 g of nanomontmorillonite (interlayer spacing 1-2 nm, content 4 wt%) is dispersed in 100 mL of deionized water, ultrasonic stirring (500 W, 20 kHz) for 20 minutes to exfoliate the clay platelets (the clay platelets are obtained by exfoliating the nanomontmorillonite after ultrasonic treatment). B3, 4 mL of a second silane coupling agent (vinyltrimethoxysilane) is added to the nanomontmorillonite suspension, and stirred at 55°C for 1.5 hours to functionalize the surface of the clay platelets with vinyl groups. B4, the functionalized nanomontmorillonite suspension is mixed with the polyvinyl alcohol solution, and 0.4 g of ammonium persulfate (APS) is added as an initiator, and the mixture is reacted at 65°C for 3.5 hours under nitrogen protection to graft through vinyl-hydroxyl interactions. B5, centrifugation at 8000 rpm for 10 minutes, washing with ethanol 3 times, and drying at 60°C for 12 hours to obtain nanohybrid polyvinyl alcohol powder, which is ready for use.

[0055] The preparation method of the water-based epoxy resin-sulfoaluminate cement composite repair material of the present embodiment comprises the following steps: (1) the underwater epoxy resin in the water-based epoxy and the water-based curing agent are respectively preheated and stirred at 45°C for 15 min; (2) the nanomodified lignosulfonate is first dissolved in at least part of the water, and then the nanohybrid polyvinyl alcohol is added and stirred for 5 min to obtain a first solution; (3) the retarder (citric acid) is first dissolved in at least part of the water, and then the early strength agent (calcium fluorosilicate) is added and stirred uniformly to obtain a second solution; (4) the first solution and the second solution are added to the sulfoaluminate cement, and after stirring uniformly, the water-based epoxy resin and the water-based curing agent obtained by step (1) are added, and the stirring is continued for 5 min to obtain the water-based epoxy resin-sulfoaluminate cement composite repair material of the present embodiment.

[0056] The water-based epoxy resin-sulfoaluminate cement composite repair material is poured and cast in a test mold (used to shape the water-based epoxy resin-sulfoaluminate cement composite repair material) underwater, and after shaping, it is cured in an environment with a constant temperature of 20°C and a humidity of not less than 95% to the target age.

[0057] Then the performance indicators thereof are detected. The performance thereof is measured according to the relevant standards as follows: Fluidity: 280 mm, thixotropic index: 1.5, initial setting time: 1.2 h, final setting time: 1.8 h, compressive strength (3 days): 41 MPa, compressive strength (28 days): 60 MPa, bonding strength: 2.8 MPa, loss rate in water: 1.5%.

[0058] The water-based epoxy-sulphoaluminate cement composite repair material of the embodiment can be used for flat repair work in the water environment of coastal areas.

[0059] Embodiment 2 The water-based epoxy-sulphoaluminate cement composite repair material of the embodiment comprises the following components by weight: Water-based epoxy 15 parts (the mass ratio of water-based epoxy resin and water-based curing agent is 1:1), sulphoaluminate cement 50 parts, nano-modified lignin sulfonate 0.5 parts (the amount of nano-silicon dioxide is 5wt% of sodium lignin sulfonate), nano-hybrid polyvinyl alcohol 0.5 parts (the amount of nano-montmorillonite is 12wt% of polyvinyl alcohol), citric acid 0.3 parts, calcium fluorosilicate 0.1 parts, and water 20 parts.

[0060] The preparation method of the nano-modified lignin sulfonate is as follows: A1, 100g of sodium lignin sulfonate is added to 900g of deionized water and stirred until completely dissolved to prepare a 10wt% solution. A2, 5g of nano-silicon dioxide (particle size 20-50nm, content 5wt%) is added and ultrasonically dispersed for 20 minutes (power 500W, frequency 20kHz). (3) 0.1g of the first silane coupling agent (vinyl trimethoxysilane) is slowly added dropwise, and the dropping speed is controlled at 0.05g / min. Stirring is maintained during the dropping process. (4) The mixture is heated to 50℃ and stirred at constant temperature for 2 hours to promote chemical bonding. (5) Spray drying (inlet temperature 180℃, outlet temperature 80℃) is performed to obtain nano-modified lignin sulfonate powder, which is ready for use.

[0061] The preparation method of the nano-hybrid polyvinyl alcohol is as follows: B1, 100g of polyvinyl alcohol is added to 500mL of deionized water and heated to 90℃, and stirred (300rpm) for 2 hours to form a clear solution. B2, 12g of nano-montmorillonite (interlayer spacing 1-2nm, content 12wt%) is dispersed in 100mL of deionized water and ultrasonically stirred (500W, 20kHz) for 40 minutes to exfoliate the clay sheets (the clay sheets are obtained by exfoliating the nano-montmorillonite after ultrasonic treatment). B3, 10mL of the second silane coupling agent (vinyl trimethoxysilane) is added to the nano-montmorillonite suspension and stirred at 65℃ for 2.5 hours to functionalize the surface of the clay sheets. B4, the functionalized nano-montmorillonite suspension is mixed with the polyvinyl alcohol solution, 0.6g of ammonium persulfate (APS) is added, and the reaction is carried out at 75℃ for 5 hours under nitrogen protection to graft through vinyl-hydroxyl interaction. B5, centrifugation is performed at 8000rpm for 10 minutes, and the product is washed with ethanol for 3 times and dried at 60℃ for 12 hours to obtain nano-hybrid polyvinyl alcohol powder, which is ready for use.

[0062] The preparation method of the water-based epoxy resin-metasulphoaluminate cement composite repair material of the embodiment comprises the following steps: (1) preheat and stir the water-based epoxy resin and the water-based curing agent in the water-based epoxy respectively at 45°C for 15 min; (2) dissolve the nano-modified lignosulfonate in at least part of the water first, then add the nano-hybrid polyvinyl alcohol, and stir for 5 min to obtain a first solution; (3) dissolve the retarder (citric acid) in at least part of the water first, then add the early strength agent (calcium fluosilicate), and stir uniformly to obtain a second solution; (4) add the first solution and the second solution to the metasulphoaluminate cement, add the water-based epoxy resin and the water-based curing agent treated in step (1) after uniform stirring, and continue to stir for 5 min, thereby obtaining the water-based epoxy resin-metasulphoaluminate cement composite repair material of the embodiment.

[0063] The repair material is poured into a test mold (for molding the water-based epoxy resin-metasulphoaluminate cement composite repair material) underwater, and is cured at a constant temperature of 20°C and in an environment with a humidity of no less than 95% to the target age.

[0064] Then, the performance indicators of the repair material are detected. The performance of the repair material is measured according to relevant standards and is as follows: Thixotropy index: 2.2, fluidity: 180 mm, initial setting time: 1.0 h, final setting time: 1.7 h, compressive strength (3 days): 44 MPa, compressive strength (28 days): 65 MPa, bonding strength to substrate: 3.2 MPa, and loss rate in water: 1.0%.

[0065] Embodiment 3 The water-based epoxy resin-metasulphoaluminate cement composite repair material of the embodiment comprises the following components by weight: Water-based epoxy 18 parts (the mass ratio of water-based epoxy resin to water-based curing agent is 1:1), metasulphoaluminate cement 55 parts, nano-modified lignosulfonate 1.0 part (the amount of nano-silicon dioxide is 15 wt% of sodium lignosulfonate), nano-hybrid polyvinyl alcohol 0.2 part (the amount of nano-montmorillonite is 3 wt% of polyvinyl alcohol), citric acid 0.4 part, calcium fluosilicate 0.15 part, and water 22 parts.

[0066] The preparation method of the nano-modified lignosulfonate of the embodiment is the same as that of embodiment 1, except that 15 g of nano-silicon dioxide is added in step A2 and ultrasonic dispersion is performed for 50 min, 0.3 g of the first silane coupling agent (vinyl trimethoxysilane) is added dropwise in step A3, heating is performed to 65°C for constant temperature stirring for 4.5 h in step A4, and the inlet temperature of the spray dryer is 195°C and the outlet temperature is 90°C in step A5.

[0067] The preparation method of the nanohybrid polyvinyl alcohol of the present example is the same as that of Example 1, except that 3 g of nanomontmorillonite is added in Step B2, and ultrasonic stirring is performed for 15 min; 3 mL of the second silane coupling agent (vinyl trimethoxysilane) is added dropwise in Step B3, and stirring is performed at 50°C for 1 h; 0.3 g of ammonium persulfate is added in Step B4, and reaction is performed under nitrogen protection at 60°C for 3 h, to complete grafting.

[0068] The preparation method of the aqueous epoxy resin-metasalt cement composite repair material of the present example is the same as that of Example 1.

[0069] The repair material is poured into a test mold (for molding the aqueous epoxy resin-metasalt cement composite repair material) under water, and after molding, curing is performed at 20°C under a constant temperature and humidity of no less than 95% until the target age.

[0070] Subsequently, various performance indicators thereof are detected. The performance is measured according to relevant standards as follows: Fluidity: 300 mm, initial setting time: 1.4 h, final setting time: 2.1 h, compressive strength (3 days): 42 MPa, compressive strength (28 days): 58 MPa, bonding strength with the substrate: 2.6 MPa, loss rate in water: 1.8%.

[0071] Example 4 The aqueous epoxy resin-metasalt cement composite repair material of the present example comprises the following components in parts by weight: Aqueous epoxy 12 parts (the mass ratio of the aqueous epoxy resin and the aqueous curing agent is 1:1), metasalt cement 45 parts, nanomodified lignosulfonate 0.6 parts (the amount of nanosilicon dioxide is 3 wt% of the sodium lignosulfonate), nanohybrid polyvinyl alcohol 0.6 parts (the amount of nanomontmorillonite is 15 wt% of the polyvinyl alcohol), citric acid 0.2 parts, calcium fluorosilicate 0.07 parts, and water 18 parts.

[0072] The preparation method of the nanomodified lignosulfonate of the present example is the same as that of Example 1, except that 3 g of nanosilicon dioxide is added in Step A2, and ultrasonic dispersion is performed for 15 min; 0.06 g of the first silane coupling agent (vinyl trimethoxysilane) is added dropwise in Step A3; heating is performed to 45°C for constant temperature stirring for 1.5 h in Step A4; the inlet temperature of the spray drying is 175°C, and the outlet temperature is 75°C in Step A5.

[0073] The preparation method of the nanohybrid polyvinyl alcohol of the present example is the same as that of Example 1, except that 15 g of nanomontmorillonite is added in Step B2, and ultrasonic stirring is performed for 50 min; 12 mL of the second silane coupling agent (vinyl trimethoxysilane) is added dropwise in Step B3, and stirring is performed at 70°C for 3 h; 0.8 g of ammonium persulfate is added in Step B4, and reaction is performed under nitrogen protection at 80°C for 6 h, to complete grafting.

[0074] The preparation method of the water-based epoxy resin-sulphoaluminate cement composite repair material of the present example is the same as that of Example 1.

[0075] The water-based epoxy resin-sulphoaluminate cement composite repair material is cast in a test mold (for molding the water-based epoxy resin-sulphoaluminate cement composite repair material) under water, and after molding, it is cured in an environment with a constant temperature of 20°C and a humidity of no less than 95% until the target age.

[0076] Subsequently, the various performance indicators thereof are detected. The performance thereof is measured according to relevant standards as follows: Thixotropy index: 2.8, fluidity: 160 mm, initial setting time: 1.1 h, final setting time: 1.9 h, compressive strength (3 days): 49 MPa, compressive strength (28 days): 68 MPa, bonding strength to substrate: 3.1 MPa, loss rate in water: 1.1%.

[0077] Comparative Example 1 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example differs from the raw material components of Example 1 in that the nano-modified lignin sulfonate is replaced by ordinary sodium lignin sulfonate, and the rest of the preparation method is the same as that of Example 1.

[0078] Comparative Example 2 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example differs from the raw material components of Example 2 in that the nano-hybrid polyvinyl alcohol is replaced by ordinary polyvinyl alcohol, and the rest of the preparation method is the same as that of Example 2.

[0079] Comparative Example 3 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example differs from the raw material components of Example 1 in that citric acid is replaced by oxalic acid as a retarder, and the rest of the preparation method is the same as that of Example 1.

[0080] Comparative Example 4 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example differs from the raw material components of Example 1 in that calcium fluorosilicate is replaced by calcium chloride as an early strength agent, and the rest of the preparation method is the same as that of Example 1.

[0081] Comparative Example 5 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example differs from the raw material components of Example 1 in that sulphoaluminate cement is replaced by ordinary Portland cement, and the rest of the preparation method is the same as that of Example 1.

[0082] Comparative Example 6 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example is different from the raw material components of Example 1 in that no water-based epoxy is added, and the rest of the preparation method is the same as that of Example 1.

[0083] Comparative Example 7 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example is different from the raw material components of Example 1 in that the nano-modified lignosulfonate is replaced by ordinary sodium lignosulfonate and 12% of the mass of ordinary sodium lignosulfonate of nano-silicon dioxide (the total amount of ordinary sodium lignosulfonate and nano-silicon dioxide is 0.8 parts), and the rest of the preparation method is the same as that of Example 1.

[0084] Comparative Example 8 The water-based epoxy resin-sulphoaluminate cement composite repair material of the present comparative example is different from the raw material components of Example 2 in that the nano-hybrid polyvinyl alcohol is replaced by polyvinyl alcohol and 12% of the mass of polyvinyl alcohol of nano-montmorillonite (the total amount of polyvinyl alcohol and nano-montmorillonite is 0.5 parts), and the rest of the preparation method is the same as that of Example 2.

[0085] Experimental Example The performance of the repair materials of the above examples and comparative examples was tested, and the test results are shown in Figure 1 and Table 1 below: Figure 1 The cement setting and hardening time and compressive strength (3d and 28d) test results of Example 1, Example 2 and Comparative Example 3, Comparative Example 4, Comparative Example 6 are shown in the figure. As can be seen from the figure, the 28-day compressive strength (60-65MPa) of Examples 1 and 2 is significantly higher than that of Comparative Example 3, Comparative Example 4 and Comparative Example 6, and the initial setting time (1.0-1.2h) and final setting time (1.7-1.8h) are more reasonable, reflecting the relationship between setting time and cement strength development, which not only ensures the construction operability, but also realizes the rapid hardening. In comparison, Comparative Example 3 (oxalic acid retarder) and Comparative Example 4 (calcium chloride early strength agent) have insufficient material synergy, low strength and unbalanced setting time, while Comparative Example 6 (without water-based epoxy) has similar setting time, but the mechanical properties are significantly reduced, which verifies the key role of the nano-modified component and the water-based epoxy in improving the comprehensive performance.

[0086] Table 1

[0087] In summary, the present application realizes the overall optimization of the performance of underwater repair materials. The nano-modified lignin sulfonate forms a unique nano-composite structure through the chemical bonding of sodium lignin sulfonate and nano-silicon dioxide, significantly improving the fluidity, compressive strength and dispersion resistance. The high specific surface area of nano-silicon dioxide enhances the electrostatic repulsion and steric hindrance effect between cement particles, and also acts as a hydration nucleus to promote the densification of C-S-H gel. The nano-hybrid polyvinyl alcohol forms a reversible three-dimensional network structure through the grafting of polyvinyl alcohol and nano-montmorillonite, significantly improving the thixotropy and underwater stability. The layered structure not only physically blocks the penetration of moisture, but also participates in the hydration reaction through silicon hydroxyl groups, thereby strengthening the mechanical properties.

[0088] In terms of setting regulation, the polycarboxyl structure of citric acid can form stable complexes with Ca 2+ , Al 3+ , delaying the initial hydration, and gradually decomposing to release ions in the middle stage, achieving the precise balance of "retardation-fast hardening". The synergistic calcium fluorosilicate releases F - , SiO3 2- and Ca 2+ ions to accelerate the hydration of aluminate phase and promote the generation of C-S-H gel, while avoiding the corrosion risk of chloride ions. The interpenetrating network structure of the rapid hydration characteristics (main phase of ettringite) of sulphoaluminate cement and water-based epoxy resin further synergizes the chemical bonding of epoxy groups and cement hydroxyl groups to significantly enhance the bonding strength, while the hydrophobic membrane effect of the resin reduces the loss rate in water.

[0089] The present application optimizes the rheological properties, hydration process and interface structure of the repair material at the molecular scale through nano-modification, organic-inorganic hybridization and ion synergistic mechanism, solves the key problems such as the difficulty of setting regulation of traditional materials, and realizes the breakthrough of high-performance underwater repair materials.

Claims

1. A waterborne epoxy resin-sulphoaluminate cement composite repair material, characterized in that: Calculated by weight, it includes the following components: 10-20 parts of waterborne epoxy, 40-60 parts of sulphoaluminate cement, 0.5-1 parts of nano-modified lignin sulfonate, 0.2-0.6 parts of nano-hybrid polyvinyl alcohol, 0.1-0.5 parts of retarder, 0.05-0.3 parts of early strength agent and 12-25 parts of water.

2. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 1, characterized in that: The nano-modified lignin sulfonate is prepared by chemically bonding sodium lignin sulfonate and nano-silicon dioxide via a first silane coupling agent; The amount of the nano-silicon dioxide used is 3wt%-15wt% of the mass of the sodium lignin sulfonate, and the particle size of the nano-silicon dioxide is 20-50nm.

3. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 2, characterized in that: The nano-modified lignin sulfonate is prepared by a method comprising the following steps: A1. Add nano-silica to the sodium lignin sulfonate solution and disperse it evenly by ultrasonication to obtain a first mixed solution; A2. adding a first silane coupling agent dropwise to the first mixed solution while stirring; A3, heating the mixture obtained in step A2, and stirring the mixture at a constant temperature; A4. After the reaction is completed, the product is spray-dried to obtain the nano-modified lignin sulfonate.

4. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 3, characterized in that: In step A2, the mass ratio of the first silane coupling agent to sodium lignin sulfonate is (0.06-0.3):100; In step A3, the constant temperature stirring reaction temperature is 45-65° C., and the reaction time is 1.5-4.5 h.

5. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 1, characterized in that: The nano hybrid polyvinyl alcohol is prepared by grafting polyvinyl alcohol and nano montmorillonite via a second silane coupling agent; The mass ratio of the nano-montmorillonite to the polyvinyl alcohol is 3 wt % to 15 wt %.

6. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 5, characterized in that: The nano-hybrid polyvinyl alcohol is prepared by a method comprising the following steps: B1. Disperse polyvinyl alcohol in deionized water, heat and stir to form a clear polyvinyl alcohol solution; B2, dispersing the nano-montmorillonite in water and treating it with ultrasound to obtain a nano-montmorillonite suspension; B3, adding a second silane coupling agent to the nano-montmorillonite suspension and stirring at 60° C. for 2 h to obtain a functionalized nano-montmorillonite suspension; B4. Mix the functionalized nano-montmorillonite suspension with the polyvinyl alcohol solution, add ammonium persulfate as an initiator, and react at 60-80°C under nitrogen for 3.5-6 hours; B5. After the reaction is completed, centrifuge the solid, wash and dry it to obtain the nano-hybrid polyvinyl alcohol.

7. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 6, characterized in that: In step B2, the ultrasonic treatment power is 450-550W, the frequency is 15-20kHz, and the ultrasonic time is 25-35min; In step B3, the ratio of the second silane coupling agent to polyvinyl alcohol is (3-12) mL:100 g.

8. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 1, characterized in that: The retarder is citric acid, and the early strength agent is calcium fluorosilicate.

9. The waterborne epoxy resin-sulphoaluminate cement composite repair material according to claim 1, wherein: The fineness of the sulphoaluminate cement is ≤300m² / kg, the initial setting time of the sulphoaluminate cement is 15-20min, and the final setting time is 25-30min.

10. The method for preparing the waterborne epoxy resin-sulphoaluminate cement composite repair material according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Preheat the waterborne epoxy resin and waterborne curing agent in the waterborne epoxy at 40-50°C and stir for 10-15 minutes; (2) dissolving the nano-modified lignin sulfonate in at least a portion of water, then adding the nano-hybrid polyvinyl alcohol, and stirring uniformly to obtain a first solution; (3) dissolving the retarder in at least part of the water, then adding the early strength agent and stirring evenly to obtain a second solution; (4) Adding the first solution and the second solution to the sulphoaluminate cement, stirring evenly, adding the waterborne epoxy resin and waterborne curing agent obtained by the treatment in step (1), and continuing to stir evenly to obtain the waterborne epoxy resin-sulphoaluminate cement composite repair material.

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