Epoxy modified cement-based material as well as preparation method and application thereof

Abstract

The invention provides an epoxy modified cement-based material, the epoxy modified cement-based material comprises an organic phase structure and inorganic crystals, and the inorganic crystals are radially distributed on the surface of the organic phase structure; the organic phase structure is a spherical or sphere-like structure with the diameter of 3-15 microns; the inorganic crystal is of a needle-shaped, rod-shaped or sheet-shaped structure with the length being 0.3-3 microns and the diameter being 0.05-0.5 microns. The epoxy modified cement-based material disclosed by the invention shows good adhesion and dispersion resistance under water or in a humid environment, can realize rapid underwater construction, and keeps stable performance for a long time under harsh conditions such as a marine environment and a humid environment; the engineering requirements of multiple fields such as building structure repairing, underwater repairing, rapid first-aid repair, ocean protection and road and bridge engineering are met, and the integration of high strength, high toughness, strong interface bonding and long-acting durability is realized.

Description

An epoxy-modified cement-based material, its preparation method and application Technical Field

[0001] This invention relates to the field of cement-based composite materials and building materials technology, specifically to an epoxy-modified cement-based material, its preparation method, and its application. Background Technology

[0002] Cement-based materials are the most widely used building materials in the world, occupying a core position in infrastructure construction. However, pure cement-based materials have inherent defects such as high brittleness, poor toughness, low tensile strength, and susceptibility to cracking. Furthermore, with the extension of service life, many concrete structures exhibit defects such as cracks, erosion, and steel reinforcement corrosion, seriously affecting the safety and durability of the structures. Therefore, there is an urgent need to develop high-performance repair and protection materials to meet the engineering needs of building structure repair and reinforcement, underwater concrete repair, road and bridge maintenance, and marine engineering protection.

[0003] Polymer-modified cement is one of the important technical approaches to improve the performance of cement-based materials. Epoxy resin, due to its excellent mechanical properties, bonding properties, and durability, is widely used in the field of cement modification. Currently, epoxy-modified cement materials mainly come in the following forms: solvent-based epoxy-cement composites, waterborne epoxy emulsion-cement composites, and epoxy resin directly mixed with cement. Solvent-based epoxy-cement composites, which dissolve epoxy resin in an organic solvent and then mix it with cement, have high strength and bonding properties, but suffer from problems such as explosive polymerization caused by organic solvent volatilization, poor workability, and poor resistance to long-term exposure to humid or underwater environments, thus limiting their application. Waterborne epoxy emulsion-cement composites use commercially available waterborne epoxy emulsions mixed with cement. Waterborne epoxy uses water instead of organic solvents, offering advantages such as environmental friendliness, good workability, and room-temperature curing. However, it suffers from drawbacks including a long curing cycle, slow early strength development, insufficient epoxy-cement compatibility, and unstable interfacial bonding. It typically takes several hours to several days to reach the required strength, making it unsuitable for rapid repairs and emergency maintenance. Direct epoxy resin-cement mixing involves mixing unemulsified epoxy resin directly with cement. Due to the hydrophobicity and high viscosity of epoxy resin, it is difficult to disperse evenly in cement slurry, easily forming large clumps. This results in uneven material properties, weak interfacial bonding, poor repeatability, and an inability to achieve the synergistic effect between epoxy and cement.

[0004] The core issue with the aforementioned epoxy-modified cement materials lies in the interfacial bonding between epoxy resin (the organic phase) and cement (the inorganic phase). Traditional methods rely primarily on physical mixing of epoxy resin and cement, lacking proactive design and precise control of the interfacial microstructure. This leads to problems such as high randomness in interfacial bonding, insufficient synergistic effects, poor performance stability, and a lack of control methods. The randomness of interfacial bonding makes the interfacial morphology between epoxy and cement uncontrollable, resulting in large fluctuations in interfacial bonding strength. The organic and inorganic phases act independently, failing to fully realize the synergistic enhancement effect. Weak interfaces make the material prone to failure modes such as interfacial cracking and debonding during long-term service. Existing technologies lack systematic methods for controlling the interfacial microstructure, making it impossible to customize material properties according to application requirements.

[0005] In recent years, materials science research has shown that the macroscopic properties of composite materials largely depend on their microstructure, especially the interfacial structure. Optimizing performance through microstructure design has become an important direction in materials research. However, in the field of epoxy-modified cement, research on the formation mechanism and control methods of microstructure remains insufficient. Existing technologies have failed to effectively address scientific and technological issues such as how to construct microstructures with specific morphologies in epoxy-cement systems, how to achieve effective bonding between the epoxy organic phase and the cement inorganic phase at the microscale, how to achieve precise microstructure design through process parameter control, and how to establish a correlation mechanism between preparation process, microstructure, and macroscopic properties.

[0006] In specific applications, such as underwater concrete repair, marine engineering protection, and rapid emergency repair, even higher requirements are placed on materials. Materials must exhibit excellent adhesion and anti-dispersion properties underwater or at damp interfaces, reach usable strength within a short time to meet emergency repair needs, maintain long-term performance stability under harsh conditions such as marine and humid environments, and form a strong bond with the old concrete substrate to prevent interfacial debonding failure. These requirements further increase the technical difficulty of developing high-performance epoxy-modified cementitious materials.

[0007] Epoxy resin emulsification technology offers a new approach to solving the aforementioned problems. Emulsification technology can uniformly disperse hydrophobic epoxy resin in the aqueous phase as tiny droplets, improving the dispersibility of epoxy in cement slurry. However, existing research on epoxy emulsification mainly focuses on emulsion stability and particle size control. Systematic and in-depth research is still lacking on key scientific issues such as the behavior of emulsified epoxy droplets during cement hydration, the formation mechanism of interfacial microstructure, and how to regulate the microstructure through emulsification parameters to achieve performance optimization.

[0008] During their long-term research on cement-based composite materials, the inventors discovered that when epoxy resin is dispersed in water and mixed with cement using a specific emulsification method, the epoxy emulsion droplets can act as heterogeneous nucleation sites during cement hydration, inducing the directional growth of cement hydration products on their surface to form a unique spherical core-crystal shell composite microstructure. This structure significantly enhances the mechanical interlocking and chemical bonding at the epoxy-cement interface, resulting in a substantial improvement in the overall performance of the material. More importantly, by controlling the emulsification parameters and curing conditions, the size of the spherical structure, the growth morphology of the crystals, and other microscopic characteristics can be precisely controlled, thereby achieving customized design of material properties. This discovery provides a novel technical approach for the microstructure design of epoxy-modified cement materials, possessing significant scientific and application value.

[0009] Therefore, there is an urgent need to provide a technical solution that can actively regulate the microstructure of the epoxy-cement interface, significantly improve the comprehensive performance of materials, and has a simple and feasible process, so as to meet the engineering needs of multiple fields such as building structure repair, underwater repair, and marine protection.

[0010] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0011] The purpose of this invention is to provide an epoxy-modified cementitious material to solve or alleviate the problems existing in the prior art.

[0012] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides an epoxy-modified cementitious material, wherein the epoxy-modified cementitious material comprises an organic phase structure and inorganic crystals, wherein the inorganic crystals are radially distributed on the surface of the organic phase structure; the organic phase structure is a spherical or near-spherical structure with a diameter of 3-15 μm; the inorganic crystals are needle-like, rod-like, or plate-like structures with a length of 0.3-3 μm and a diameter of 0.05-0.5 μm.

[0013] Preferably, the inorganic crystals cover more than 60% of the surface of the organic phase structure; more preferably, the spacing between the spherical or near-spherical structures is 5-50 μm.

[0014] The present invention also provides a method for preparing the above-mentioned epoxy modified cementitious material, wherein the epoxy modified cementitious material comprises the following components by weight: 8-30 parts of epoxy resin, 80-150 parts of cement, emulsifier, and 15-60 parts of water, wherein the amount of emulsifier is 1-20% of the weight of epoxy resin, and the preparation method includes the following steps: (1) Emulsification step: adding epoxy resin and emulsifier to water for emulsification treatment to obtain emulsified epoxy liquid, wherein the emulsification treatment causes the epoxy resin to form droplets with an average particle size of 1-30 μm and uniformly dispersed in the aqueous phase; (2) Mixing step: mixing the emulsified epoxy liquid with cement and stirring for 3-10 minutes to obtain a uniform mixed slurry; (3) Curing step: after the mixed slurry is formed, curing it for 3-28 days under the conditions of temperature 15-35℃ and relative humidity ≥70%.

[0015] Preferably, the weight ratio of epoxy resin to cement is (0.08-0.25):1; more preferably, the weight ratio of epoxy resin to cement is (0.10-0.20):1; and even more preferably, the weight ratio of epoxy resin to cement is (0.12-0.18):1.

[0016] Preferably, in step (1): the emulsification process is carried out by mechanical stirring, with a stirring rate of 3000-15000 rpm, an emulsification time of 5-20 minutes, an emulsification temperature of 20-30℃, and an average particle size of the emulsion droplets of 2-20 μm; or, the emulsification process is carried out by ultrasonic dispersion, with an ultrasonic power of 200-800 W, an ultrasonic frequency of 20-40 kHz, an emulsification time of 3-15 minutes, an emulsification temperature of 20-30℃, and an average particle size of the emulsion droplets of 1-15 μm.

[0017] Preferably, the emulsifier is selected from one or more of the following: (a) anionic surfactants: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyether sulfate; (b) nonionic surfactants: fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene polyoxypropylene block copolymer; (c) amphoteric surfactants: lecithin, betaine; the amount of the emulsifier is 1-5% of the weight of the epoxy resin; preferably, the emulsifier is a nonionic surfactant, and the amount is 2-4% of the weight of the epoxy resin; preferably, the epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin or a mixture thereof; more preferably, the technical indicators of the epoxy resin are: epoxy value: 0.40-0.55 eq / 100g, viscosity (25℃): 10000-20000 m Softening point: 8-16℃; Preferably, the cement is one or more of the following: ordinary Portland cement (PO 42.5, PO 52.5), rapid-hardening Portland cement (RPO 42.5), sulfoaluminate cement (grade 42.5, grade 52.5); More preferably, the cement is ordinary Portland cement PO 42.5 or rapid-hardening Portland cement RPO 42.5.

[0018] Preferably, the preparation method further includes one or more of the following components: (a) aggregate: river sand, quartz sand or manufactured sand, with a particle size of 0.15-5 mm, and an amount of 20-100 parts by weight; (b) curing agent: selected from one or more of polyetheramine D230, polyetheramine D400, modified aliphatic amine, and modified cycloaliphatic amine, and an amount of 10-30% of the weight of epoxy resin; (c) setting regulator: selected from one or more of lithium carbonate, lithium sulfate, triethanolamine, and citric acid, and an amount of 0.2-3% of the weight of cement; (d) reinforcing fiber: polypropylene fiber or glass fiber, with a length of 6-12 mm, and an amount of 0.2-2% of the weight of cement.

[0019] Preferably, in step (3): the curing conditions are: standard curing: temperature 20±2℃, relative humidity ≥95%, curing time 7-28 days; or rapid curing: temperature 30±2℃, relative humidity ≥90%, curing time 3-7 days; during the curing process, the crystal growth on the surface of the epoxy spherical structure follows the following rules: curing 1-3 days: crystals begin to germinate, length 0.1-0.5μm; curing 3-7 days: crystals grow rapidly, length 0.5-2μm; curing 7-28 days: crystal growth tends to stabilize, length 1-3μm.

[0020] Preferably, the preparation steps are as follows: Step (1): Add epoxy resin and emulsifier to water, stir with a high-speed stirrer at 3000-15000 rpm for 5-20 minutes, or use an ultrasonic disperser at 200-800W power for 3-15 minutes to obtain a milky white stable emulsified epoxy liquid with an average droplet diameter of 1-30 μm; Step (2): Mix the emulsified epoxy liquid prepared in step (1) with cement, stir for 3-10 minutes until the slurry is uniform and free of lumps; Step (3): Pour the slurry into a mold to form a shape, during which cement hydration crystals gradually grow on the surface of the epoxy spherical structure to form a "spherical core-crystal shell" composite microstructure; Preferably, in step (2), it is mixed with 20-100 parts of aggregate.

[0021] This invention also provides applications of the above-mentioned epoxy-modified cement-based materials, including: (a) building structure repair and reinforcement, especially concrete crack repair and steel reinforcement corrosion repair; (b) underwater or humid environment concrete repair, including seawalls, docks, dams, and bridge piers; (c) rapid repair and emergency repair, requiring more than 50% of the design strength to be achieved within 6 hours; (d) protective coatings for corrosion protection in marine and chemical environments; and (e) road and bridge repair materials, including road surface repair, bridge deck paving, and expansion joint repair.

[0022] Compared with the closest prior art, the technical solution of this invention has the following beneficial effects: In the epoxy-modified cement-based material of this invention, the epoxy resin is dispersed in the aqueous phase as uniform droplets with an average particle size of 1-30 μm through a precisely controlled emulsification process. These emulsified droplets act as heterogeneous nucleation sites in the cement paste, inducing the directional growth of cement hydration products on their surface, forming a unique spherical core-crystal shell composite microstructure. Compared with traditional direct epoxy mixing or commercially available aqueous emulsions, this invention achieves precise design of the microstructure by actively controlling the emulsification parameters, resulting in a narrow particle size distribution of the epoxy spherical structure with a coefficient of variation of less than 0.3. The micromorphology of different batches of materials is highly consistent, with a particle size deviation of less than 15%, proving that this microstructure is an inevitable result of the process conditions rather than an accidental phenomenon, thereby ensuring the stability and repeatability of the material performance.

[0023] The epoxy-modified cementitious material of this invention constructs a unique organic-inorganic hybrid interface through needle-like, rod-like, or plate-like cement hydration crystals grown on the surface of a spherical structure. These crystals, with a length of 0.3-3 μm and a diameter of 0.05-0.5 μm, grow radially outward from the surface of the spherical structure, achieving a surface coverage of ≥60%. This radial crystal layer not only provides strong mechanical bonding but also achieves a robust microscale bond between the organic and inorganic phases through chemical bonding between the epoxy groups, hydroxyl groups, and other functional groups on the epoxy resin surface and the cement hydration products. The interfacial bonding strength can reach over 3.0 MPa, which is 50-120% higher than that of materials directly mixed with unemulsified epoxy, significantly enhancing the overall performance of the material. This unique interfacial structure effectively solves the problem of weak interfacial bonding between the organic and inorganic phases in traditional epoxy-modified cementitious materials, allowing the two phases to fully exert a synergistic reinforcing effect.

[0024] The epoxy-modified cementitious material of this invention achieves customized design of material properties through a systematic microstructure control method. By adjusting emulsification parameters such as stirring speed of 3000-15000 rpm, ultrasonic power of 200-800 W, and emulsifier dosage of 1-5%, the particle size distribution of the spherical structure can be precisely controlled. Increasing the stirring speed or the emulsifier dosage can reduce the average particle size of the spherical structure from 15 μm to 3 μm. By adjusting curing conditions such as curing temperature of 20-30℃, humidity ≥70%, and time of 3-28 days, the growth morphology of crystals on the surface of the spherical structure can be controlled. At a curing temperature of 20℃, the crystals are slender needle-like with an aspect ratio of 6-10:1; at a curing temperature of 30℃, the crystals are short rod-like with an aspect ratio of 3-5:1. Adding setting-regulating components such as lithium carbonate of 0.5-2% can increase the crystal growth rate by 30-80%. This controllable microstructure design provides a technical basis for customizing materials according to the performance requirements of different application scenarios.

[0025] The epoxy-modified cementitious material of this invention exhibits superior performance. Compared with pure cementitious materials, its compressive strength after 28 days is increased by 12-45%, its flexural strength after 28 days is increased by 18-55%, its interfacial bond strength is increased by 20-65%, its fracture energy is increased by 35-75%, its chloride ion permeability coefficient is reduced by 25-60%, and its freeze-thaw cycle resistance is increased by 40-80%. These significant performance improvements stem from the enhanced interface provided by the spherical core-crystal shell composite microstructure. The epoxy spherical structure, dispersed within the cement matrix, acts as a flexible phase, effectively absorbing and dispersing stress, thus improving the material's toughness and crack resistance. Meanwhile, the densely distributed radial crystals on the surface effectively transfer stress to the surrounding matrix through mechanical interlocking and chemical bonding, achieving synergistic load-bearing between the organic and inorganic phases. The epoxy-modified cementitious material of this invention exhibits good adhesion and anti-dispersion properties in underwater or humid environments, enabling rapid underwater construction. It maintains stable performance under harsh conditions such as marine and humid environments, meeting the engineering needs of multiple fields such as building structure repair, underwater repair, rapid emergency repair, marine protection, and road and bridge engineering. It achieves the integration of high strength, high toughness, strong interfacial bonding, and long-term durability. Attached Figure Description

[0026] Figure 1 is an overall microscopic morphology view of the epoxy-modified cementitious material prepared in Example 1, with scanning parameters: FoV 25.4 μm, magnification 5000x, scale bar 5 μm; Figure 2 is the interface morphology of the spherical structure and cement matrix in the epoxy-modified cementitious material prepared in Example 1, with scanning parameters: FoV 18.1 μm, magnification 7000x, scale bar 2 μm; Figure 3 is a typical spherical core-crystal shell composite microstructure of the epoxy-modified cementitious material prepared in Example 1, with scanning parameters: FoV 6.35 μm, magnification 20000x, scale bar 1 μm; Figure 4 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 1; Figure 5 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 2; Figure 6 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 3; Figure 7 is a microstructure diagram of the epoxy-modified cementitious material prepared in Example 4, with scanning parameters: FoV 25.4 μm, 5000x, scale bar 5 μm. 6.35 μm, magnification 20000x, scale bar 1 μm; Figure 8 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 4; Figure 9 is the microstructure of the epoxy-modified cementitious material prepared in Example 5, scanning parameters: FoV 25.4 μm, magnification 5,000x, scale bar 5 μm; Figure 10 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 5; Figure 11 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 6; Figure 12 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 7; Figure 13 is the XRD pattern of the epoxy-modified cementitious material prepared in Example 8; Figure 14 is the XRD pattern of the material prepared in Comparative Example 1; Figure 15 is the XRD pattern of the material prepared in Comparative Example 2; Figure 16 is the XRD pattern of the material prepared in Comparative Example 3; Figure 17 is the XRD pattern of the material prepared in Comparative Example 4; Figure 18 is the XRD pattern of the material prepared in Comparative Example 5; Figure 19 is a comparison of the XRD spectra of Comparative Example 1 and Example 1; Figure 20 is a comparison of the XRD spectra of Examples 1, 4, and 6; Figure 21 is a comparison of the XRD spectra of Comparative Examples 1-3 and Example 1. Detailed Implementation

[0027] 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 them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0028] 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.

[0029] During their long-term research on cement-based composite materials, the inventors discovered that when epoxy resin is dispersed in an aqueous phase to form micron-sized droplets using a precisely controlled emulsification process and then mixed with cement for curing, these emulsion droplets do not simply exist as a dispersed phase in the cement paste, but rather exhibit the function of heterogeneous nucleation sites. During cement hydration, the surface of the epoxy spherical structure can induce the directional growth of cement hydration products, forming needle-like, rod-like, or plate-like crystals. These crystals grow radially outward from the surface of the spherical structure, constructing a unique spherical core-crystal shell composite microstructure. This structure not only significantly enhances the mechanical interlocking of the epoxy-cement interface but also achieves a strong bond between the organic and inorganic phases at the microscale through the chemical bonding between the functional groups on the epoxy resin surface and the cement hydration products. More importantly, by systematically controlling the emulsification parameters and curing conditions, the particle size distribution of the spherical structure, the growth morphology of the surface crystals, and the interfacial bonding characteristics can be precisely controlled, thereby enabling customized design of material properties. If this principle of microstructure regulation can be applied to the design and preparation of cement-based materials, especially in the research on interface enhancement and performance optimization, it will help solve or improve the above-mentioned problems existing in current epoxy-modified cement materials.

[0030] The epoxy-modified cementitious material of the present invention comprises an organic phase structure and inorganic crystals, wherein the inorganic crystals are radially distributed on the surface of the organic phase structure; the organic phase structure is a spherical or near-spherical structure with a diameter of 3-15 μm; the inorganic crystals are needle-like, rod-like, or plate-like structures with a length of 0.3-3 μm and a diameter of 0.05-0.5 μm. The coverage of the inorganic crystals on the surface of the organic phase structure is more than 60%; preferably, the spacing between the spherical or near-spherical structures is 5-50 μm.

[0031] The epoxy-modified cementitious material of the present invention has the following microstructural characteristics: Observed under scanning electron microscopy at magnification of 5000-20000x, the material comprises: (a) spherical or near-spherical epoxy phase structures with a diameter of 3-15 μm, and a number density of... (b) Needle-like, rod-like, or plate-like inorganic crystals with a length of 0.3-3 μm and a diameter of 0.05-0.5 μm are grown on the surface of the spherical structure, and the crystals are cement hydration products; (c) The crystals are radially distributed with a surface coverage of ≥60%, forming a "spherical core-crystal shell" composite morphology; (d) The spherical structure and the surrounding cement matrix form a mechanical interlocking interface through the surface crystals, and the interface bonding strength is ≥3.0 MPa.

[0032] The present invention characterizes the crystals on the surface of the spherical structure by the following methods: (a) X-ray diffraction analysis (XRD): the crystalline phases contain ettringite (AFt), calcium hydroxide ( (a) One or more of calcium silicate hydrate (CSH); (b) Energy dispersive spectroscopy (EDS): the spherical structure surface is enriched with Ca, Si, Al, and O elements, and the Ca / Si molar ratio is 1.5-3.5; (c) Fourier transform infrared spectroscopy (FTIR): A Si-O stretching vibration peak appears at [location missing], in [location missing] Appear at place The OH stretching vibration peak.

[0033] The present invention discloses a method for preparing an epoxy-modified cementitious material, wherein the epoxy-modified cementitious material comprises the following components in parts by weight: 8-30 parts of epoxy resin (e.g., 8, 10, 12, 15, 18, 20, 25, or 30 parts), 80-150 parts of cement (e.g., 80, 90, 100, 110, 120, 130, 140, or 150 parts), 0.4-6 parts of emulsifier (e.g., 0.4, 0.8, 1.2, 2, 3, 4, 5, or 6 parts), and 15-60 parts of water (e.g., 15, 20, 25, 30, 35, 40, 50, or 60 parts). The amount of emulsifier used is 1-20% of the weight of epoxy resin (e.g., 1%, 2%, 3%, 4%, 5%, 10%, 15% or 20%). The preparation method includes the following steps: (1) Emulsification step: adding epoxy resin and emulsifier to water and performing emulsification treatment to obtain emulsified epoxy liquid. The emulsification treatment causes the epoxy resin to form droplets with an average particle size of 1-30 μm that are uniformly dispersed in the aqueous phase; (2) Mixing step: mixing the emulsified epoxy liquid with cement and stirring for 3-10 minutes to obtain a uniform mixed slurry; (3) Curing step: after the mixed slurry is formed, curing it for 3-28 days (e.g., 3 days, 7 days, 14 days, 21 days or 28 days) under the conditions of temperature 15-35℃ (e.g., 15℃, 20℃, 25℃, 30℃ or 35℃) and relative humidity ≥70% (e.g., 70%, 80%, 90% or 95%).

[0034] The preferred weight ratio of epoxy resin to cement is (0.08-0.25):1 (e.g., 0.08:1, 0.10:1, 0.15:1, 0.20:1, 0.25:1), more preferably (0.10-0.20):1, and most preferably (0.12-0.18):1.

[0035] In the epoxy-modified cementitious material of the present invention, the epoxy resin is formed into uniform droplets with an average particle size of 1-30 μm through a precisely controlled emulsification process. These droplets serve as heterogeneous nucleation sites in the cement paste, inducing the cement hydration products to grow radially on their surface, thereby constructing a unique spherical core-crystal shell composite microstructure. This significantly enhances the mechanical interlocking and chemical bonding of the epoxy-cement interface, achieving efficient synergy between the organic and inorganic phases.

[0036] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, the epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin, or a mixture thereof. The technical specifications of the epoxy resin are: epoxy value of 0.40-0.55 eq / 100g (e.g., 0.40 eq / 100g, 0.42 eq / 100g, 0.45 eq / 100g, 0.48 eq / 100g, 0.50 eq / 100g, 0.52 eq / 100g, or 0.55 eq / 100g), and viscosity of 10,000-20,000 m³ at 25°C. (e.g., 10000 m) 12000 m 15000 m 18000 m or 20000 m The softening point of epoxy resin is 8-16℃ (e.g., 8℃, 10℃, 12℃, 14℃, or 16℃). The epoxy value reflects the reactivity and cross-linking density of the epoxy resin. A low epoxy value results in an insufficiently dense cross-linked network after curing, leading to insufficient material strength. A high epoxy value results in excessively high resin viscosity, making emulsification and dispersion difficult and increasing curing shrinkage. Viscosity affects the ease of emulsification and droplet stability. Epoxy resin with too low viscosity is prone to agglomeration in cement paste, making it difficult to form stable spherical structures. Excessively high viscosity makes emulsification difficult, requiring greater shear force and a longer emulsification time. The softening point affects the flowability and processing performance of epoxy resin at different temperatures. Epoxy resin with too low a softening point has excessive flowability at room temperature, which is detrimental to the stability of emulsion droplets. A too high softening point requires higher processing temperatures, increasing energy consumption and operational difficulty.

[0037] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, the emulsifier is selected from one or more of anionic surfactants, nonionic surfactants, and amphoteric surfactants. Anionic surfactants include sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium fatty alcohol polyether sulfate, etc. Nonionic surfactants include fatty alcohol polyoxyethylene ethers such as AEO-3, AEO-7, and AEO-9; alkylphenol polyoxyethylene ethers; sorbitan fatty acid esters such as the Span series and Tween series; and polyoxyethylene polyoxypropylene block copolymers such as the Pluronic series, etc. Amphoteric surfactants include lecithin and betaines, etc. The amount of the emulsifier is 1-5% (e.g., 1%, 2%, 3%, 4%, or 5%) of the epoxy resin weight. Preferably, the emulsifier is a nonionic surfactant, and the amount is 2-4% (e.g., 2%, 2.5%, 3%, 3.5%, or 4%) of the epoxy resin weight. The choice of emulsifier is crucial to the formation and stability of emulsion droplets. Anionic surfactants have strong emulsifying capabilities, but may fail in cement pastes with high ionic strength. Nonionic surfactants are insensitive to ionic strength and exhibit better stability in cement pastes. Amphoteric surfactants show good emulsifying effects over a wide pH range. Insufficient emulsifier dosage leads to incomplete emulsification, resulting in large and unevenly distributed epoxy droplets that are prone to aggregation and unable to form stable spherical structures. While excessive emulsifier dosage can improve emulsification, excess emulsifier may remain in the cement matrix, potentially introducing excessive air bubbles, reducing the material's density, and interfering with the normal hydration process of cement, thus affecting the final performance of the material. Furthermore, the emulsifier-to-water ratio affects the emulsion concentration and droplet stability.

[0038] In the preparation method of the epoxy-modified cementitious material of the present invention, the emulsification step is the key to forming a spherical core-crystal shell composite microstructure. Emulsification can be performed by mechanical stirring or ultrasonic dispersion. The emulsification conditions for mechanical stirring are: stirring speed of 3000-15000 rpm (e.g., 3000 rpm, 5000 rpm, 8000 rpm, 10000 rpm, 12000 rpm, or 15000 rpm), emulsification time of 5-20 minutes (e.g., 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, or 20 minutes), emulsification temperature of 20-30℃ (e.g., 20℃, 22℃, 25℃, 28℃, or 30℃), and an average droplet size of 2-20 μm (e.g., 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm). The emulsification conditions for ultrasonic dispersion are as follows: ultrasonic power 200-800W (e.g., 200W, 300W, 400W, 500W, 600W, 700W, or 800W), ultrasonic frequency 20-40kHz (e.g., 20kHz, 25kHz, 30kHz, 35kHz, or 40kHz), emulsification time 3-15 minutes (e.g., 3 minutes, 5 minutes, 8 minutes, 10 minutes, 12 minutes, or 15 minutes), emulsification temperature 20-30℃ (e.g., 20℃, 22℃, 25℃, 28℃, or 30℃), and the average droplet size of the resulting emulsion is 1-15μm (e.g., 1μm, 3μm, 5μm, 8μm, 10μm, 12μm, or 15μm). Temperature control is crucial during emulsification to avoid localized overheating; an ice-water bath can be used for cooling. After emulsification, a milky white stable emulsion is obtained with an average droplet size of 1-30 μm. After standing for 30 minutes, no obvious stratification or sedimentation should be observed, indicating that the emulsion has good stability.

[0039] From the perspective of emulsification mechanism, mechanical stirring generates shear force through high-speed rotation, breaking epoxy resin into tiny droplets and dispersing them in the aqueous phase. The stirring rate directly affects the magnitude of the shear force and the droplet size. Too low a stirring rate will result in insufficient shear force, making it difficult to fully break down the epoxy resin, resulting in large and unevenly distributed droplets. While too high a stirring rate can produce smaller droplets, the excessive shear force may disrupt the already formed stable emulsion structure, leading to droplet aggregation or breakage, and introducing a large number of air bubbles, reducing the quality of the emulsion. This differs from conventional cement mixing (which can use even higher speeds). Ultrasonic dispersion achieves emulsification through the cavitation effect and strong local shear force generated by ultrasound in the liquid. The ultrasonic power and frequency jointly determine the emulsification effect. Too low an ultrasonic power will not produce a sufficient cavitation effect, resulting in poor emulsification. Too high an ultrasonic power may lead to excessive local temperature rise, affecting the stability of the emulsion and even causing pre-curing of the epoxy resin. The ultrasonic frequency affects the size and distribution of cavitation bubbles. When the frequency is too low, the cavitation bubbles are large but few in number, while when the frequency is too high, the cavitation intensity weakens. The present invention selects a frequency range of 20-40kHz to achieve the best balance between cavitation intensity and emulsification efficiency.

[0040] Emulsification time has a significant impact on droplet size distribution and emulsion stability. Insufficient emulsification time leads to incomplete emulsification, resulting in a wide droplet size distribution and numerous large droplets. These large droplets are prone to aggregation or sedimentation during subsequent mixing and curing with cement, failing to form a uniformly distributed spherical structure. While excessively long emulsification times yield smaller, more narrowly distributed droplets, they increase energy consumption and production costs. Furthermore, prolonged high-intensity emulsification may lead to emulsifier decomposition or epoxy resin oxidation, reducing emulsion quality. Controlling the emulsification temperature is equally crucial. Too low a temperature results in high epoxy resin viscosity, making emulsification difficult and energy-intensive. Too high a temperature may cause pre-reaction of the epoxy resin or thermal degradation of the emulsifier. This invention selects a temperature range of 20-30℃ to ensure appropriate epoxy resin fluidity while avoiding the adverse effects of high temperatures.

[0041] The particle size distribution of spherical structures can be precisely controlled by adjusting emulsification parameters. Increasing the stirring speed from 3000 rpm to 15000 rpm gradually reduces the average particle size of the spherical structures from 15 μm to 3 μm. Increasing the emulsifier dosage from 1% to 5% reduces the average particle size of the spherical structures from 12 μm to 5 μm, and significantly improves the uniformity of the particle size distribution. Compared with mechanical stirring, ultrasonic dispersion can produce droplets with smaller particle size and narrower distribution because the cavitation effect of ultrasound provides stronger local shear force, resulting in more thorough breakup of the epoxy resin.

[0042] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, the cement is one or more of ordinary Portland cement, rapid-hardening Portland cement, and sulfoaluminate cement. The preferred strength grade of the ordinary Portland cement is... 42.5 or 52.5, the preferred strength grade of rapid-hardening Portland cement is... 42.5, the preferred strength grade for sulfoaluminate cement is 42.5 or 52.5. Different types of cement have different types of hydration products and growth rates, which affect the morphology and growth characteristics of crystals on the surface of spherical structures. The main hydration products of ordinary Portland cement are calcium silicate hydrate (CSH) gel and calcium hydroxide. The moderate hydration rate is conducive to stable crystal growth. Rapid-hardening silicate cement has a faster early hydration rate and strength development, and can form surface crystals in a shorter time, making it suitable for rapid repair applications. The main hydration product of sulfoaluminate cement is ettringite (AFt), which has a slender needle-like crystal morphology. The ettringite crystals grown on the surface of the spherical structure can provide stronger mechanical interlocking.

[0043] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, it may further include 20-100 parts by weight of aggregate (e.g., 20, 30, 40, 50, 60, 80, or 100 parts). The aggregate is river sand, quartz sand, or manufactured sand, with a particle size of 0.15-5 mm (e.g., 0.15 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm). The addition of aggregate can improve the workability of the material, reduce costs, and provide skeletal support. Insufficient aggregate will fail to provide adequate skeletal support, resulting in poor volume stability and large shrinkage deformation. Excessive aggregate will reduce the cementitious material content, affecting the material's bonding performance and strength. The selection of aggregate particle size should be determined according to the application scenario. For repair materials, fine aggregate of 0.15-2 mm is preferred to ensure the material's density and surface quality. For structural reinforcement materials, medium-coarse aggregate of 2-5 mm can be used to improve the material's volume stability and economy.

[0044] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, a curing agent may also be added, in an amount of 10-30% (e.g., 10%, 15%, 20%, 25%, or 30%) of the epoxy resin weight. The curing agent is selected from one or more of polyetheramine D230, polyetheramine D400, modified aliphatic amines, and modified cycloaliphatic amines. The addition of the curing agent can promote the cross-linking and curing reaction of the epoxy resin, shorten the curing time, and improve early strength. Polyetheramine curing agents have good hydrophilicity and can maintain high curing activity in humid environments, making them particularly suitable for underwater or humid repairs. Insufficient curing agent will lead to incomplete curing of the epoxy resin, leaving unreacted epoxy groups and affecting the final properties of the material. Excessive curing agent, while accelerating the curing speed, will lead to excessively rapid heat release, generating large curing stress, and may also make the material brittle and reduce its toughness.

[0045] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, a setting regulator may also be added, at a dosage of 0.2-3% (e.g., 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3% by weight of cement). The setting regulator is selected from one or more of lithium carbonate, lithium sulfate, triethanolamine, and citric acid. The setting regulator can adjust the hydration rate and setting time of cement, affecting the growth rate and morphology of crystals on the surface of the spherical structure. Lithium carbonate and lithium sulfate are cement hydration promoters, which can accelerate the hydration reaction, promote rapid crystal growth, and increase the crystal growth rate by 30-80%. Triethanolamine has both a setting-promoting effect and can improve the fluidity of the paste. Citric acid is a retarder, which can delay cement hydration and is suitable for applications requiring longer operating times. Insufficient setting regulator will result in an insignificant setting-regulating effect, while excessive dosage will excessively alter the cement hydration process, potentially leading to abnormal setting time or reduced final strength.

[0046] In a preferred embodiment of the epoxy-modified cementitious material of the present invention, reinforcing fibers may also be added, at a dosage of 0.2-2% (e.g., 0.2%, 0.5%, 1%, 1.5%, or 2%) of the total weight of the cementitious material. The reinforcing fibers are polypropylene fibers or glass fibers, with a length of 6-12 mm (e.g., 6 mm, 8 mm, 10 mm, or 12 mm). The reinforcing fibers form a three-dimensional network structure in the material, which can effectively limit the generation and propagation of cracks and improve the toughness and impact resistance of the material. Insufficient fiber dosage will result in insignificant reinforcing effect, while excessive dosage will lead to fiber clumping and uneven dispersion, thus reducing material performance and affecting the fluidity and workability of the slurry. The fiber length should be matched with the application thickness of the material; too short a length results in weak anchoring and poor reinforcing effect, while too long a length makes it difficult to disperse evenly and easily leads to clumping.

[0047] In the preparation method of the epoxy-modified cementitious material of the present invention, the stirring speed and time should be carefully controlled when mixing the freshly prepared emulsified epoxy liquid with cement in the mixing step. Excessive stirring speed will damage the stability of the emulsion droplets, leading to droplet aggregation or breakage; insufficient stirring speed will result in uneven mixing. The preferred stirring method is to use a planetary mixer or a handheld electric mixer, with the speed controlled at 300-500 rpm and the stirring time at 3-10 minutes. If aggregates are added, the cement and aggregates should be dry-mixed evenly first, and then the emulsified epoxy liquid should be added and stirred. If optional components such as curing agents, setting modifiers, or reinforcing fibers are added, they should be added sequentially in the order of curing agent-setting modifier-fiber, stirring for 2-3 minutes after each component is added to ensure even dispersion. After stirring, a uniform mixed slurry should be obtained, free of obvious lumps and with good fluidity.

[0048] In the preparation method of the epoxy-modified cementitious material of this invention, the curing step is crucial for the growth of crystals on the surface of the spherical structure. The microstructural evolution during the curing process is unique: the spherical epoxy droplets formed by emulsification act as heterogeneous nucleation sites, inducing the directional growth of crystals from cement hydration products on their surface. This is the core mechanism of this invention. The preferred curing conditions are a temperature of 20±2℃, relative humidity ≥95%, and a curing time of 7-28 days. These are standard curing conditions that ensure sufficient cement hydration and stable crystal growth. In the initial curing stage (1-24 hours), the slurry gradually solidifies and hardens; vibration and impact should be avoided. In the middle curing stage (1-7 days), the cement hydrates rapidly, and crystals begin to grow on the surface of the spherical structure; constant temperature and humidity conditions should be maintained. In the later curing stage (7-28 days), the crystals continue to grow and gradually stabilize, and the material strength continues to increase. For rapid repair applications, a rapid curing condition of 30±2℃, relative humidity ≥90%, and curing time of 3-7 days can be used. This can achieve over 50% of the design strength within 3 days and over 80% within 7 days. During the curing process, avoid violent vibrations or movement to maintain a stable distribution of the emulsion droplets.

[0049] Curing temperature significantly affects the growth morphology of crystals on the surface of spherical structures. When the curing temperature is within the range of 20-30℃, the cement hydration rate is moderate, crystal growth is stable, and the formed crystals are slender needle-like with an aspect ratio of (6-10):1. This crystal morphology provides a larger specific surface area and stronger mechanical interlocking. When the curing temperature is within the range of 30-40℃, the cement hydration rate accelerates, and crystal growth is faster, but the formed crystals are short rod-like with an aspect ratio of (3-5):1. The crystal length increases, but the morphology becomes coarser. Too low a curing temperature significantly delays cement hydration and crystal growth. Below 15℃, the hydration reaction is extremely slow, crystal growth is insufficient, and the interfacial bonding strength is affected. Too high a curing temperature leads to excessively rapid hydration, disordered crystal growth, and may also cause rapid moisture evaporation, resulting in drying shrinkage cracks.

[0050] Curing humidity is crucial for maintaining continuous cement hydration and preventing drying shrinkage cracking. A relative humidity of ≥70% is the minimum requirement for normal cement hydration, but for superior performance, a relative humidity of ≥90% is preferred. Insufficient humidity leads to rapid evaporation, incomplete cement hydration, hindered surface crystal growth, drying shrinkage cracks, and a significant decrease in strength and durability. Sufficient curing humidity ensures adequate moisture supply to the spherical surface, allowing for continuous growth of cement hydration products, achieving a crystal coverage of over 60%, and forming a dense crystalline shell.

[0051] The coverage rate of inorganic crystals on the surface of organic phase structures in this invention refers to the percentage of the surface area covered by inorganic crystals relative to the total surface area of ​​spherical or near-spherical organic phase structures, as observed by scanning electron microscopy (SEM) at a magnification of 10,000-20,000x. The specific measurement method is as follows: SEM images of representative spherical or near-spherical structures are selected, and the crystal-covered areas are binarized using image analysis software (such as ImageJ). The ratio of the crystal-covered area to the visible surface area of ​​the structure is calculated. At least 10 spherical structures are statistically analyzed for each sample, and the average value is taken as the coverage rate. A coverage rate ≥ 60% indicates that most of the surface area of ​​the spherical structure is covered by inorganic crystals, forming a relatively dense crystal shell.

[0052] The curing time affects the degree of crystal growth and the final properties. During the curing process, crystal growth on the surface of the spherical structure follows these patterns: During 1-3 days of curing, crystals begin to germinate, reaching a length of 0.1-0.5 μm; at this stage, the number of crystals is small, and the coverage is low. During 3-7 days of curing, crystals grow rapidly, reaching a length of 0.5-2 μm; the number of crystals increases significantly, and the coverage increases to 40-60%. During 7-28 days of curing, crystal growth tends to stabilize, reaching a length of 1-3 μm; the coverage reaches over 60%, forming a dense crystal shell. Insufficient curing time leads to insufficient crystal growth, low coverage, and insufficient interfacial bonding strength. Extending the curing time to 28 days allows for sufficient crystal growth, achieving optimal material properties; however, further extending the curing time no longer significantly improves performance and is no longer necessary from economic and time perspectives.

[0053] The formation mechanism of the spherical core-crystal shell composite microstructure can be understood as follows: during cement hydration, the surface of the epoxy spherical structure provides heterogeneous nucleation sites. The epoxy groups, hydroxyl groups, and other functional groups on the epoxy resin surface can interact with calcium ions in the cement paste. Adsorption and complexation of silicate ions lower the nucleation energy barrier of cement hydration products, allowing them to preferentially nucleate on the surface of the spherical structure. As the hydration reaction proceeds, the nucleated crystals gradually grow. Due to the relatively uniform distribution of nucleation sites across the surface of the spherical structure, the crystals grow radially outward, ultimately forming a composite morphology of spherical core-crystal shell. In this structure, the epoxy spherical core provides flexibility and toughness, while the surface crystal shell provides rigidity and strength. The two are firmly bonded through interfacial chemical bonding and mechanical interlocking, significantly enhancing the synergistic effect between the organic and inorganic phases.

[0054] Precise control of the crystal morphology on the surface of spherical structures can be achieved by adjusting curing conditions. Adding setting-regulating components such as lithium carbonate (0.5-2%) can promote cement hydration, increasing crystal growth rate by 30-80%, increasing crystal quantity, and improving coverage. Increasing curing temperature can accelerate crystal growth rate but will change the aspect ratio of the crystals. Extending curing time can increase crystal length and crystallinity, resulting in stronger interfacial bonding. This controllable microstructure design provides a technological basis for customizing materials according to the performance requirements of different application scenarios.

[0055] This invention also proposes the application of an epoxy-modified cementitious material with a spherical-radial composite microstructure. As described above, the epoxy-modified cementitious material is particularly suitable for the repair and reinforcement of building structures, including concrete crack repair, steel reinforcement corrosion repair, and structural surface defect repair; underwater or humid environment concrete repair, including the repair of hydraulic structures such as seawalls, docks, dams, and bridge piers; rapid repair and emergency repair, requiring at least 50% of the design strength to be achieved within 6 hours, for emergency repairs or rapid traffic reopening; high-performance protective coatings for corrosion protection in marine and chemical environments; and road and bridge repair materials, including road surface repair, bridge deck paving, and expansion joint repair. The material of this invention exhibits excellent performance in these applications, achieving integrated rapid construction and long-term protection, meeting the engineering needs of different scenarios.

[0056] The main raw materials used in the following examples are sourced from: Bisphenol A type epoxy resin, Nan Ya Epoxy Resin Co., Ltd., model E-51, epoxy value 0.48-0.54 eq / 100g, viscosity 12000-16000 m 25℃; Bisphenol F type epoxy resin, Bluestar Chemical New Materials Co., Ltd., model F-51, epoxy value 0.50-0.56 eq / 100g; Nonionic surfactant, BASF, trade name Pluronic F-68, polyoxyethylene-polyoxypropylene block copolymer; Sodium dodecyl sulfate, Sinopharm Chemical Reagent Co., Ltd., chemically pure; Ordinary silicate cement, Conch Cement Co., Ltd., strength grade P.O 42.5; Rapid-hardening silicate cement, Qingdao Kremer New Building Materials Technology Co., Ltd., strength grade RPO 42.5; Sulfoaluminate cement, Tangshan Polar Bear Building Materials Co., Ltd., strength grade 42.5; River sand, particle size 0.15-2.5mm, fineness modulus 2.6; Polyetheramine D230, Huntsman Chemical Trading Co., Ltd.; Modified aliphatic amine curing agent. Qingdao Kremer New Building Materials Technology Co., Ltd.; Lithium carbonate, Tianqi Lithium Corporation, battery grade; Triethanolamine, Sinopharm Chemical Reagent Co., Ltd., analytical grade; Citric acid, Shandong Yingxuan Industrial Co., Ltd., food grade; Polypropylene fiber, 6mm in length, Bekaert AG, Belgium; Glass fiber, 12mm in length, China Jushi Co., Ltd.

[0057] Example 1 The epoxy-modified cementitious material of this example is prepared from the following components by weight: 15 parts of bisphenol A type epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.45 parts of nonionic surfactant Pluronic F-68, 30 parts of deionized water, and 50 parts of river sand.

[0058] The bisphenol A type epoxy resin has an epoxy value of 0.50 eq / 100g and a viscosity of 14000 m. 25℃.

[0059] The preparation method of this embodiment includes the following steps: Step 1, 0.45 parts of Pluronic F-68 emulsifier are added to 30 parts of deionized water and stirred at room temperature for 5 minutes until completely dissolved. Then, 15 parts of bisphenol A epoxy resin are added, and the mixture is stirred at 8000 rpm for 12 minutes using a high-speed stirrer. The emulsification temperature is controlled at 25°C to obtain a milky white stable emulsion. Sampling and observation show that the average particle size of the emulsion droplets is 8 μm, the particle size distribution is uniform, and no obvious stratification occurs after standing for 30 minutes.

[0060] Step two, mix 100 parts of ordinary Portland cement Dry mix with 50 parts river sand in a mixing tank for 2 minutes, then add the emulsified epoxy liquid prepared in step one, and stir with a planetary mixer at 400 rpm for 5 minutes to obtain a uniform slurry with good flowability and no obvious lumps.

[0061] Step 3: Pour the slurry into a standard mold measuring 40mm×40mm×160mm, vibrate it on a vibrating table for 30 seconds to remove air, and smooth the surface. Immediately place the mold into a standard curing chamber, and cure it under the following conditions: temperature 20±2℃, relative humidity above 95%. After curing for 28 days, demold the mold to obtain epoxy-modified cementitious material test blocks.

[0062] Observation of the curing process: The slurry solidified and hardened after 1 day of curing; there were no cracks on the surface of the material after 3 days of curing; the strength increased significantly after 7 days of curing; and the material was completely hardened after 28 days of curing, with a smooth and dense surface.

[0063] Microstructural Characterization: Test blocks cured for 28 days were broken, and fresh cross-sections were observed using a scanning electron microscope (SEM). As shown in Figures 1-3: At 5000x magnification, multiple spherical structures are uniformly dispersed within the cement matrix. The diameter of the spherical structures is 6-10 μm, and the spacing between adjacent spherical structures is 15-30 μm. The fibrous network structure formed by cement hydration products and the spatial distribution relationship between the spherical structures and the surrounding matrix can also be observed. At 7000x magnification, needle-like and rod-like crystals (0.5-2 μm in length) growing on the surface of the spherical structures can be clearly observed extending radially outwards, intertwining with the surrounding cement hydration product fiber network to form a mechanical interlocking interface. The figures show the transition relationship between the epoxy spherical core, the surface crystalline layer, and the cement matrix. Under 20,000x magnification, needle-like crystals were clearly observed densely growing on the surface of the spherical structure. These crystals ranged in length from 1.0 to 2.0 μm and in diameter from approximately 0.1 to 0.3 μm. The crystals grew radially outwards from the surface of the spherical structure, covering about 70% of the surface, forming a typical spherical core-crystal shell composite morphology. Energy dispersive spectroscopy (EDS) analysis revealed that the core of the spherical structure was enriched in C and O elements, indicating an epoxy phase, while the surface crystals were enriched in Ca, Si, Al, and O elements, suggesting cement hydration products. The XRD results are shown in Figure 4, revealing the following main phases in the material: characteristic diffraction peaks of ettringite (AFt) appear at 2θ = 9.1°, 15.8°, and 22.9°, indicating the formation of ettringite crystals during cement hydration; characteristic diffraction peaks of portlandite (CH) appear at 2θ = 18.0°, 34.1°, 47.1°, and 50.8°; and a strong diffraction peak of quartz (Q) appears at 2θ = 26.6°, originating from river sand. A diffuse peak of hydrated calcium silicate (CSH) appears near 2θ=29.4°.

[0064] Compared with Comparative Example 1 (pure cement-based material, Figure 14), the XRD pattern of Example 1 showed a relatively enhanced intensity of the ettringite peak (the peak intensity at 9.1° increased by about 28%), indicating that the presence of the emulsified epoxy spherical structure promoted the formation of ettringite crystals, which is consistent with the result observed by SEM of densely packed needle-like crystals on the surface of the spherical structure.

[0065] Performance test results: The compressive strength after 28 days was 58.5 MPa, an increase of 15.8% compared to 50.5 MPa for pure cement-based materials. The flexural strength after 28 days was 9.8 MPa, an increase of 22.5% compared to 8.0 MPa for pure cement-based materials. The interfacial bond strength with the old concrete substrate was 3.2 MPa, an increase of 28.0% compared to 2.5 MPa for pure cement-based materials. The chloride ion permeability coefficient was 1.8 × 10⁻⁶. - ¹² m² / s, compared to 2.8 × 10⁻⁶ for pure cement-based materials. - ¹² m² / s decreased by 35.7%.

[0066] The surface coverage test method in this embodiment is as follows: (1) Select a clearly visible complete spherical structure in a SEM image with a magnification of 20,000 times; (2) Process the image using the image analysis software ImageJ; (3) First, select the visible surface area of ​​the spherical structure and measure its total area. (4) Binarize the image to distinguish the crystal-covered area (the needle-like protrusions with higher gray values) from the uncovered smooth area (the area with lower gray values); (5) Calculate the area of ​​the crystal-covered region. (6) Calculate coverage = (7) Perform the above measurements on at least 5 different spherical structures of the same sample and take the average value. The coverage of the 5 spherical structures measured in Example 1 were 68%, 72%, 71%, 69%, and 70%, respectively, with an average value of 70%.

[0067] Example 2 The epoxy-modified cementitious material of this example is prepared from the following components by weight: 15 parts of bisphenol A type epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.45 parts of nonionic surfactant Pluronic F-68, 30 parts of deionized water, and 50 parts of river sand.

[0068] The only difference between this embodiment and Example 1 is that ultrasonic dispersion is used for emulsification in step 1; all other steps are the same as in Example 1. In the preparation method of this embodiment, step one uses ultrasonic dispersion: 0.45 parts of Pluronic F-68 emulsifier are added to 30 parts of deionized water and stirred at room temperature for 5 minutes until completely dissolved. Then, 15 parts of bisphenol A epoxy resin are added, and an ultrasonic disperser is used with an ultrasonic power of 500W and an ultrasonic frequency of 25kHz. The mixture is ultrasonically treated for 8 minutes under ice-water bath conditions, with the emulsification temperature controlled below 25℃, resulting in a milky white stable emulsion. Sampling and observation showed that the average particle size of the emulsion droplets was 5μm, the particle size distribution was more uniform, the coefficient of variation was 0.22, and no stratification occurred after standing for 30 minutes.

[0069] Microstructure characterization: Under 20,000x magnification, the spherical structures had a diameter of 4-7 μm, which is smaller and more uniform than that in Example 1. The spacing between adjacent spherical structures was 10-25 μm, and the number density was approximately [missing information]. Needle-like crystals grow on the surface of the spherical structure. The crystals are 0.8-1.8 μm in length and about 0.08-0.25 μm in diameter. The crystals are more dense and the surface coverage is about 75%.

[0070] The XRD results are shown in Figure 5, indicating that the phase composition is basically the same as that of Example 1, mainly including ettringite (AFt), calcium hydroxide (CH), quartz (Q), and hydrated calcium silicate (CSH). Compared with Example 1, the XRD spectrum of Example 2 shows the following characteristics: the relative intensity of the ettringite peak (2θ=9.1°) is slightly increased, approximately 1.08 times that of Example 1; the half-width at half-maximum (FWHM) of each diffraction peak is slightly decreased, indicating better crystallinity. These differences are attributed to the smaller (4-7 μm) and more uniformly distributed spherical structures formed by ultrasonic emulsification, which provide more nucleation sites, promoting the uniform growth of hydrated product crystals and improving crystallinity.

[0071] Performance test results: The compressive strength after 28 days was 60.2 MPa, an increase of 19.2% compared to pure cement-based materials. The flexural strength after 28 days was 10.5 MPa, an increase of 31.3% compared to pure cement-based materials. The interfacial bond strength was 3.5 MPa, an increase of 40.0% compared to pure cement-based materials. The chloride ion permeability coefficient was... Compared to pure cement-based materials, the content is reduced by 46.4%. Compared to Example 1, the spherical structures obtained by ultrasonic emulsification are smaller and more uniform, and have better interfacial bonding performance.

[0072] Example 3 The epoxy-modified cementitious material with a spherical-radial composite microstructure in this example is prepared from the following components in parts by weight: 20 parts of bisphenol A epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.6 parts of nonionic surfactant Pluronic F-68, 35 parts of deionized water, and 50 parts of river sand.

[0073] In this embodiment, the weight ratio of epoxy resin to cement is 0.20:1, which is higher than the 0.15:1 in Example 1.

[0074] In the preparation method of this embodiment, step one uses mechanical stirring: 0.6 parts of Pluronic F-68 emulsifier are added to 35 parts of deionized water and stirred at room temperature for 5 minutes until completely dissolved. Then, 20 parts of bisphenol A epoxy resin are added, and the mixture is stirred at 10,000 rpm for 15 minutes using a high-speed stirrer. The emulsification temperature is controlled at 25°C to obtain a stable emulsion with an average droplet size of 6 μm. Steps two and three are similar to those in Example 1, with curing conditions of 20±2°C and relative humidity above 95% for 28 days.

[0075] Microstructure characterization: Under 20,000x magnification, the spherical structures have a diameter of 5-9 μm and a number density of approximately [missing information]. The number of spherical structures is greater than in Example 1. A mixture of rod-shaped and needle-shaped crystals grows on the surface of the spherical structures, with a crystal length of 1.2-2.5 μm and a diameter of approximately 0.15-0.40 μm, resulting in a surface coverage of approximately 68%. Due to the higher epoxy content, the number of spherical structures increases, and the spacing between adjacent spherical structures decreases to 8-20 μm.

[0076] The XRD test results are shown in Figure 6, which show that the phase composition is the same as that in Example 1, mainly consisting of ettringite (AFt), calcium hydroxide (CH), quartz (Q) and hydrated calcium silicate (CSH).

[0077] Compared to Example 1, the XRD pattern of Example 3 exhibits the following characteristics: the relative intensity of the ettringite peaks (2θ = 9.1°, 15.8°, 22.9°) is significantly enhanced, with the peak intensity at 9.1° being approximately 1.15 times that of Example 1; the intensity of the CSH diffuse peak near 29.4° increases, and the peak shape is more pronounced; the intensity of the calcium hydroxide peak decreases relatively. This is because Example 3 has a higher epoxy content (epoxy / cement = 0.20:1), resulting in an increased number density of spherical structures. This provides more heterogeneous nucleation sites. The increased formation of ettringite and CSH, along with the consumption of more calcium hydroxide for secondary hydration reactions, indicates that the epoxy spherical structure effectively promotes the deep hydration of cement.

[0078] Performance test results: The compressive strength after 28 days was 63.8 MPa, an increase of 26.3% compared to pure cement-based materials. The flexural strength after 28 days was 11.2 MPa, an increase of 40.0% compared to pure cement-based materials. The interfacial bond strength was 3.8 MPa, an increase of 52.0% compared to pure cement-based materials. The chloride ion permeability coefficient was... Compared to pure cement-based materials, it is reduced by 53.6%. The fracture energy is 125 N / m, which is 78.6% higher than the 70 N / m of pure cement-based materials, and the toughness is significantly improved.

[0079] Example 4 The epoxy-modified cementitious material with a spherical-radial composite microstructure in this example is prepared from the following components in parts by weight: 15 parts of bisphenol A epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.45 parts of nonionic surfactant Pluronic F-68, 30 parts of water, 50 parts of river sand, 3 parts of polyetheramine D230 curing agent, and 0.5 parts of lithium carbonate.

[0080] This embodiment adds a curing agent and a setting regulator to the basic embodiment of embodiment 1.

[0081] In this embodiment, step one is the same as in Example 1, using mechanical stirring to prepare the emulsified epoxy liquid. In step two, during mixing, 100 parts cement, 50 parts river sand, and 0.5 parts lithium carbonate are first dry-mixed until homogeneous. Then, the emulsified epoxy liquid and 3 parts polyetheramine D230 curing agent are added, and the mixture is stirred at 400 rpm for 8 minutes until homogeneous. Step three, the curing conditions are the same as in Example 1.

[0082] Observation during the curing process: Due to the addition of lithium carbonate accelerator and epoxy curing agent, the material's early strength development is faster. The compressive strength reaches 35 MPa after 1 day of curing, 50 MPa after 3 days of curing, 60 MPa after 7 days of curing, and reaches the final strength after 28 days of curing.

[0083] Microstructure characterization: As shown in Figure 7, observed under 20,000x magnification, the spherical structure has a diameter of 6-10 μm, similar to Example 1. The crystals grown on the surface of the spherical structure are more dense, with a crystal length of 1.5-2.8 μm and a diameter of approximately 0.12-0.35 μm. The crystal growth rate is faster, and the surface coverage reaches over 80%. The accelerating effect of lithium carbonate increases the crystal growth rate by approximately 50%, significantly increases the number of crystals, and strengthens the interfacial bonding.

[0084] The XRD results are shown in Figure 8. The phase composition is similar to that of Example 1, but the relative content of each phase has changed significantly: the intensity of the ettringite peaks (2θ = 9.1°, 15.8°, 22.9°) is significantly enhanced, with the peak intensity at 9.1° being approximately 1.35 times that of Example 1; the intensity of the CSH peak (2θ = 29.4°) is significantly increased, and the peak shape is sharper; the intensity of the calcium hydroxide peaks (2θ = 18.0°, 34.1°) is relatively reduced; and the intensity of the quartz peak remains basically unchanged. These changes are attributed to the addition of lithium carbonate accelerator (0.5% cement weight) in Example 4. Lithium carbonate, as a cement hydration accelerator, accelerates the... The reaction with gypsum produces ettringite, which in turn promotes... Hydration generates more CSH gel. XRD results are consistent with SEM observations showing "more dense crystalline spheres on the surface, with a coverage exceeding 80%", which also explains the rapid early strength development in this example (35 MPa at day 1, 50 MPa at day 3).

[0085] Performance test results: The compressive strength at 28 days is 65.5 MPa, a 29.7% increase compared to pure cement-based materials. The flexural strength at 28 days is 11.8 MPa, a 47.5% increase compared to pure cement-based materials. The interfacial bond strength is 4.0 MPa, a 60.0% increase compared to pure cement-based materials. The compressive strength at 3 days is 50 MPa, and at 7 days it is 60 MPa, demonstrating rapid early strength development, making it suitable for rapid repair applications. The chloride ion permeability coefficient is... It reduces permeability by 60.7% compared to pure cement-based materials and has excellent impermeability.

[0086] Example 5: The epoxy-modified cementitious material with a spherical-radial composite microstructure of this example is prepared from the following components in parts by weight: 15 parts of bisphenol A type epoxy resin, rapid-hardening silicate cement. 42.5 (100 parts total), nonionic surfactant Pluronic F-68 (0.45 parts total), water (30 parts), river sand (50 parts), lithium carbonate (1.0 part).

[0087] This embodiment uses fast-hardening cement and increases the amount of setting regulator to achieve rapid curing.

[0088] In the preparation method of this embodiment, steps one and two are similar to those in Example 1. The emulsification method is mechanical stirring at 8,000 rpm for 12 minutes. Step three adopts rapid curing conditions: the mold is placed in a curing chamber with a temperature of 30±2℃ and a relative humidity of over 90%, and demolded after curing for 7 days.

[0089] Observation during curing: Due to the use of fast-setting cement and a high amount of lithium carbonate, the material sets and hardens very quickly. Initial setting occurs in 6 hours, final setting in 12 hours, and the compressive strength reaches 38 MPa after 1 day of curing, 55 MPa after 3 days, and 62 MPa after 7 days, basically reaching the strength level of ordinary curing after 28 days.

[0090] Microstructure characterization: As shown in Figure 9, under 20,000x magnification, the spherical structure has a diameter of 6-11 μm. Due to the high curing temperature, the crystals growing on the surface of the spherical structure are short rod-shaped, with a length of 0.8-1.5 μm and a diameter of approximately 0.20-0.45 μm, with an aspect ratio of approximately 3-5:1, which is thicker and shorter than the needle-like crystals grown at room temperature. The crystal growth rate is very fast, with a surface coverage of approximately 65%. Eettsonite, the main hydration product of rapid-hardening cement, grows rapidly on the surface of the spherical structure, forming a dense crystalline layer.

[0091] The XRD test results are shown in Figure 10. This is due to the use of rapid-hardening silicate cement. 42.5, the phase composition differs from the example using ordinary Portland cement: the ettringite peaks (2θ=9.1°, 15.8°, 22.9°) have very high intensity, especially the main peak at 9.1°, which is approximately 1.42 times stronger than in Example 1; the calcium hydroxide peaks (2θ=18.0°, 34.1°) have relatively high intensity, reflecting the rapid hydration characteristics of the rapid-hardening cement; the CSH peak (2θ=29.4°) has significant intensity, indicating that although the curing time is short (7 days), the degree of hydration is already high; there may be a small amount of unhydrated silicate mineral residual peaks. In rapid-hardening cement... and With a high content and rapid hydration rate, hydration products are rapidly generated under the action of lithium carbonate accelerator (1.0%). XRD results show that a hydration degree similar to that of ordinary cement after 28 days of curing can be achieved after 7 days of curing, which is consistent with the performance test results (7-day compressive strength of 62 MPa).

[0092] Performance test results: The compressive strength after 7 days is 62.0 MPa, equivalent to the strength after 28 days of curing in Example 1, representing an approximately 4-fold increase in strength development rate. The flexural strength after 7 days is 10.0 MPa. The interfacial bond strength is 3.3 MPa. The compressive strength after 3 days of curing reaches 55 MPa, exceeding 50% of the design strength and meeting the requirements for rapid repair. The chloride ion permeability coefficient is... This embodiment is applicable to repair projects that require rapid construction and quick commissioning.

[0093] Example 6 The epoxy-modified cementitious material with a spherical-radial composite microstructure in this example is prepared from the following components in parts by weight: 18 parts of bisphenol F type epoxy resin, 110 parts of sulfoaluminate cement grade 42.5, 0.54 parts of nonionic surfactant Tween-80, 40 parts of water, 40 parts of quartz sand, 0.33 parts of triethanolamine, and 0.6 parts of polypropylene fiber.

[0094] This embodiment uses bisphenol F type epoxy resin and sulfoaluminate cement. The epoxy value of the bisphenol F type epoxy resin is 0.52 eq / 100g. The amount of the nonionic surfactant Tween-80 is 3% of the weight of the epoxy resin. The length of the polypropylene fiber is 6mm.

[0095] In the preparation method of this embodiment, step one adopts mechanical stirring: 0.54 parts of Tween-80 emulsifier are added to 40 parts of deionized water, stirred and dissolved, and then 18 parts of bisphenol F epoxy resin are added. The mixture is stirred at 12,000 rpm for 18 minutes using a high-speed stirrer at an emulsification temperature of 25°C to obtain a stable emulsion with an average droplet diameter of 4 μm.

[0096] Step 2: Dry mix 110 parts of sulfoaluminate cement, 40 parts of quartz sand and 0.33 parts of triethanolamine evenly, add the emulsion from Step 1, stir at 400 rpm for 5 minutes, and finally add 0.6 parts of polypropylene fiber and continue stirring for 2 minutes to disperse the fiber evenly.

[0097] Step 3: After the slurry is formed, it is cured for 14 days at a temperature of 20±2℃ and a relative humidity of over 95%.

[0098] Microstructure characterization: Under 20,000x magnification, the spherical structures were observed to have a diameter of 4-8 μm, exhibiting small size and uniform distribution. Numerous slender needle-like crystals, 1.8-3.0 μm in length and approximately 0.05-0.20 μm in diameter, with an aspect ratio of 10-15:1, grew on the surface of the spherical structures. XRD analysis confirmed that these needle-like crystals were primarily ettringite (AFt), a characteristic hydration product of sulfoaluminate cement. The ettringite needle-like crystals exhibited a dense, radial growth pattern, covering over 85% of the surface and forming a very dense crystal shell, the most densely grown crystal layer among all examples. The fibers were uniformly dispersed within the matrix, forming a three-dimensional network structure with the spherical structures and the cement matrix.

[0099] The XRD test results are shown in Figure 11. Due to the use of grade 42.5 sulfoaluminate cement, the phase composition differs significantly from that of silicate cement: the ettringite peaks (2θ=9.1°, 15.8°, 22.9°, 25.5°, 27.8°) are very strong, the strongest among all examples, with the main peak intensity at 9.1° being approximately 1.85 times that of Example 1. This is because the main hydration product of sulfoaluminate cement is ettringite; residual peaks of anhydrous calcium sulfoaluminate (Ye'elimite) appear at 2θ=23.1°, 29.1°, and 31.9°, indicating that some minerals have not been fully hydrated; the calcium hydroxide peak is relatively weak, which is a typical characteristic of sulfoaluminate cement; the quartz peak (2θ=26.6°) is present, originating from quartz sand aggregate; the CSH peak is relatively weak because the C2S content in sulfoaluminate cement is low.

[0100] The XRD results and SEM observations are in high agreement—the needle-like crystals grown on the surface of the spherical structure in Example 6 are ettringite, with a length of 1.8-3.0 μm and a surface coverage of up to 85%, making it the densest crystal growth among all examples. This explains why Example 6 has the highest interfacial bond strength (4.2 MPa).

[0101] Performance test results: The compressive strength after 14 days was 68.5 MPa, a 24.5% increase compared to the 55 MPa of pure sulfoaluminate cement-based material. The flexural strength after 14 days was 12.5 MPa, a 47.1% increase compared to the 8.5 MPa of pure sulfoaluminate cement-based material. The interfacial bond strength was 4.2 MPa, the highest among all examples, thanks to the strong mechanical interlocking effect of the acicular crystals of ettringite. The fracture energy was 145 N / m, with significantly improved toughness due to the addition of fibers and the formation of a dense crystalline layer. The freeze-thaw cycle resistance was 320 cycles, a 77.8% increase compared to the 180 cycles of pure sulfoaluminate cement-based material.

[0102] Example 7 The epoxy-modified cementitious material with a spherical-radial composite microstructure in this example is prepared from the following components in parts by weight: 25 parts of bisphenol A epoxy resin, 120 parts of ordinary silicate cement PO 52.5, 0.75 parts of anionic surfactant sodium dodecyl sulfate, 45 parts of water, 60 parts of river sand, 6 parts of modified fatty amine curing agent, and 0.36 parts of citric acid.

[0103] This embodiment uses cement with a high epoxy content and a high strength grade. Citric acid is used as a retarder to extend the working time.

[0104] In the preparation method of this embodiment, step one adopts ultrasonic dispersion: 0.75 parts of sodium dodecyl sulfate are added to 45 parts of deionized water, stirred and dissolved, and then 25 parts of bisphenol A epoxy resin are added. An ultrasonic disperser is used with an ultrasonic power of 600W and an ultrasonic frequency of 30kHz. The mixture is ultrasonically treated for 10 minutes under ice-water bath conditions to obtain a stable emulsion with an average droplet size of 3μm and a narrow particle size distribution.

[0105] Step two: Dry mix 120 parts of ordinary Portland cement PO 52.5, 60 parts of river sand, and 0.36 parts of citric acid until homogeneous. Add the emulsion from step one and 6 parts of modified fatty amine curing agent, and stir at 400 rpm for 8 minutes until homogeneous. Due to the addition of a retarder, the initial setting time of the slurry is extended to 4 hours, providing ample workability.

[0106] Step 3: After the slurry is formed, it is cured for 28 days at a temperature of 20±2℃ and a relative humidity of over 95%.

[0107] Observation during curing process: Due to the addition of citric acid retarder, the early strength development of the material was slow. The compressive strength was only 25 MPa after 1 day of curing, but it rapidly increased to 58 MPa after 7 days of curing, and reached the final strength of 72 MPa after 28 days of curing. The later strength development was good.

[0108] Microstructure characterization: Under 20,000x magnification, the spherical structures have a diameter of 3-7 μm, are small in size, and are very uniformly distributed, with a number density of approximately [missing information]. This is the highest density among all embodiments. The surface of the spherical structure is covered with slender needle-like crystals, with a length of 1.0-2.2 μm and a diameter of approximately 0.08-0.25 μm. The crystals are neatly arranged, and the surface coverage is approximately 70%. Due to the high epoxy content and small particle size, the spherical structures are densely distributed, with the spacing between adjacent spherical structures being only 5-15 μm.

[0109] The XRD test results are shown in Figure 12. The phase composition is similar to that of Example 1, mainly including ettringite (AFt), calcium hydroxide (CH), quartz (Q) and CSH. The ettringite peaks (2θ=9.1°, 15.8°, 22.9°) have high intensity, and the peak intensity at 9.1° is about 1.25 times that of Example 1. The CSH peak (2θ=29.4°) has significantly enhanced intensity and obvious peak shape. The calcium hydroxide peaks (2θ=18.0°, 34.1°, 47.1°) have moderate intensity. The quartz peak (2θ=26.6°) has high intensity, reflecting the increased amount of river sand (60 parts).

[0110] Example 7 uses PO 52.5 high-strength grade cement, which Higher content and stronger hydration activity. Simultaneously, the higher epoxy content (25 parts) and the fine, uniform spherical structure formed by ultrasonic emulsification (3-7 μm, number density) contribute to its superior properties. This provides a large number of nucleation sites. Although the added citric acid retarder delayed early hydration, it resulted in more complete hydration in the later stages, greater CSH formation, and a final compressive strength of 72 MPa, the highest among all examples.

[0111] Performance test results: The compressive strength after 28 days was 72.0 MPa, a 20.0% increase compared to the 60 MPa of pure PO 52.5 cement-based material, making it the highest compressive strength among all examples. The flexural strength after 28 days was 13.0 MPa, a 44.4% increase compared to pure cement-based material. The interfacial bond strength was 4.1 MPa. The fracture energy was 138 N / m. The chloride ion permeability coefficient was... It exhibits excellent impermeability. The material boasts superior overall performance, making it suitable for high-performance repair and protection projects.

[0112] Example 8 The epoxy-modified cementitious material with a spherical-radial composite microstructure of this example is prepared from the following components in parts by weight: 12 parts of bisphenol A epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.36 parts of nonionic surfactant Pluronic F-68, 28 parts of water, 70 parts of river sand, and 1.2 parts of glass fiber.

[0113] This embodiment uses a lower epoxy content and a higher aggregate content. The glass fiber length is 12 mm.

[0114] In the preparation method of this embodiment, step one adopts mechanical stirring: 0.36 parts of Pluronic F-68 are added to 28 parts of water, dissolved, and then 12 parts of bisphenol A epoxy resin are added. The mixture is stirred at 6000 rpm for 10 minutes to obtain a stable emulsion with an average droplet diameter of 10 μm.

[0115] Step 2: Dry mix 100 parts cement and 70 parts river sand evenly, add the emulsion from Step 1, stir at 350 rpm for 5 minutes, and finally add 1.2 parts glass fiber. Continue to stir at low speed for 3 minutes to avoid fiber breakage and ensure even dispersion.

[0116] Step 3: After the slurry is formed, it is cured for 28 days at a temperature of 20±2℃ and a relative humidity of over 95%.

[0117] Microstructure characterization: Under 20,000x magnification, the spherical structures have a diameter of 8-14 μm, which is relatively large, and the number density is approximately 3 × 10⁻⁶. 4The surface of the spherical structure is covered with a mixture of needle-like and rod-like crystals, with a length of 0.8-1.8 μm and a diameter of approximately 0.15-0.40 μm, and a surface coverage of approximately 60%. The glass fibers are uniformly dispersed in the matrix, and hydration products are also attached to the fiber surface, showing good bonding with the matrix.

[0118] The XRD test results are shown in Figure 13, which show that the phase composition is basically the same as that of Example 1: the intensity of the ettringite peaks (2θ=9.1°, 15.8°, 22.9°) is moderate, similar to that of Example 1; the intensity of the calcium hydroxide peaks (2θ=18.0°, 34.1°, 50.8°) is more obvious; the intensity of the quartz peak (2θ=26.6°) is the highest, reflecting the large amount of river sand used (70 parts); and the intensity of the CSH peak (2θ=29.4°) is moderate.

[0119] Example 8 has a lower epoxy content (12 parts, epoxy / cement = 0.12:1) and a lower number density of spherical structures. The relatively large particle size (8-14 μm) limits its effect on promoting cement hydration, and the XRD pattern shows little difference from the pure cement system. However, the addition of glass fiber (1.2 parts) in this embodiment significantly improves the material's toughness (fracture energy 155 N / m), making it suitable for repair projects requiring high toughness.

[0120] Performance test results: The compressive strength after 28 days is 55.0 MPa, an increase of 8.9% compared to pure cement-based materials. The flexural strength after 28 days is 10.2 MPa, an increase of 27.5% compared to pure cement-based materials. The interfacial bond strength is 3.0 MPa. The fracture energy is 155 N / m. Due to the addition of longer glass fibers, the toughness has been significantly improved, increasing by 121% compared to pure cement-based materials. The material exhibits excellent impact resistance and is suitable for repair projects requiring high toughness.

[0121] Comparative Example 1: This comparative example is a pure cement-based material, comprising the following components by weight: 100 parts of ordinary Portland cement P.O42.5, 30 parts of water, and 50 parts of river sand. No epoxy resin or emulsifier was added.

[0122] Preparation method: Mix 100 parts cement and 50 parts river sand evenly, add 30 parts water, stir for 5 minutes to obtain a uniform slurry, and cure for 28 days at a temperature of 20±2℃ and a relative humidity of over 95% after molding.

[0123] Microstructure characterization: Under 20,000x magnification, no spherical structure was observed; only the conventional morphology of cement hydration products was observed, mainly flocculent CSH gel, hexagonal plate-like calcium hydroxide crystals, and a small amount of needle-like ettringite crystals. The hydration products were randomly distributed and did not form a special microstructure.

[0124] The XRD test results are shown in Figure 14. As a reference sample of pure cement-based material, the phase composition is typical of silicate cement hydration products: the ettringite peaks (2θ=9.1°, 15.8°) are weak, with only a small amount of ettringite formed; the calcium hydroxide peaks (2θ=18.0°, 34.1°, 47.1°, 50.8°) are strong and are one of the main crystalline phases; the quartz peak (2θ=26.6°) is strong and is the strongest peak; and the CSH peak (2θ=29.4°) is diffuse.

[0125] Compared with the embodiments, the peak intensity of ettringite in Comparative Example 1 was significantly lower. This is because, in the absence of an emulsified epoxy spherical structure, the nucleation and growth of cement hydration products are homogeneous nucleation, lacking the induction effect of heterogeneous nucleation sites. The ettringite crystals are randomly dispersed in the matrix and cannot form the characteristic microstructure of a spherical core-crystal shell.

[0126] Performance test results: 28-day compressive strength is 50.5 MPa, 28-day flexural strength is 8.0 MPa, interfacial bond strength is 2.5 MPa, and chloride ion permeability coefficient is [not specified]. The fracture energy is 70 N / m. As a benchmark, the strength and toughness of the pure cement-based material are significantly lower than those of the example with added emulsified epoxy.

[0127] Conclusion: Comparative Example 1 demonstrates the necessity of adding epoxy resin to improve material performance. Without the addition of epoxy resin, a spherical core-crystal shell composite microstructure cannot be formed, and the material's strength, toughness, interfacial adhesion, and impermeability are significantly lower than those of the examples.

[0128] Comparative Example 2: This comparative example is a direct mixture of unemulsified epoxy resin and cement, comprising the following components by weight: 15 parts bisphenol A type epoxy resin, 100 parts ordinary Portland cement PO 42.5, 30 parts water, and 50 parts river sand. No emulsifier was used; the epoxy resin was mixed directly with the cement without emulsification treatment.

[0129] Preparation method: 100 parts cement and 50 parts river sand were dry-mixed evenly. 15 parts bisphenol A epoxy resin were directly added to 30 parts water and stirred at 1,000 rpm for 10 minutes. Due to the hydrophobicity and high viscosity of the epoxy resin, a stable emulsion could not be formed, and the epoxy resin floated on the water surface in large lumps. This mixture was then forcibly added to the cement and sand and stirred at 400 rpm for 10 minutes, resulting in a heterogeneous slurry with visible epoxy resin lumps. After molding, it was cured for 28 days at a temperature of 20±2℃ and a relative humidity of over 95%.

[0130] Microstructure characterization: Under 500x magnification, the epoxy resin was observed to be aggregated in large blocks, ranging in size from tens to hundreds of micrometers, with extremely uneven distribution. Under 20,000x magnification, there were obvious interfacial gaps between the epoxy block structure and the cement matrix, indicating weak interfacial bonding. The characteristic spherical structure and surface crystal growth of this invention were not observed. The surface of the epoxy blocks was smooth, with almost no cement hydration products adhering to them. Some areas had excessively high epoxy content, while others had no epoxy at all, indicating extremely uneven material composition.

[0131] The XRD test results are shown in Figure 15. The phase composition is similar to that of Comparative Example 1, but it has the following characteristics: the intensity of the ettringite peak (2θ=9.1°) is very weak, even lower than that of Comparative Example 1; the intensity of the calcium hydroxide peak (2θ=18.0°, 34.1°) is relatively high; the quartz peak (2θ=26.6°) is the strongest peak; and the intensity of the CSH peak (2θ=29.4°) is relatively low.

[0132] In Comparative Example 2, epoxy resin was directly mixed with cement without emulsification. The epoxy formed large aggregates (50-300 μm), resulting in weak interfacial bonding with the cement matrix. These large epoxy aggregates not only failed to serve as nucleation sites but also hindered normal hydration in the surrounding area, leading to a decrease in the overall hydration level. XRD results showed that the addition of unemulsified epoxy did not promote the formation of cement hydration products; on the contrary, it had a slight negative impact, which is consistent with the performance test results (compressive strength 48 MPa, lower than the 50.5 MPa of pure cement).

[0133] Performance test results: The compressive strength after 28 days was 48.0 MPa, lower than the 50.5 MPa of pure cement-based materials, a decrease of 4.9%. The flexural strength after 28 days was 7.2 MPa, lower than the 8.0 MPa of pure cement-based materials, a decrease of 10.0%. The interfacial bond strength was 1.8 MPa, only 56.3% of that in Example 1. When the specimen failed, the epoxy block and the cement matrix separated at the interface, proving that the interfacial bond was extremely weak. The chloride ion permeability coefficient was... Because of the interfacial gaps between the epoxy block and the matrix, the seepage channels are increased, resulting in a decrease in impermeability. The material properties are unstable, with the coefficient of variation in strength reaching 18% for the same batch of test blocks.

[0134] Conclusion: Comparative Example 2 demonstrates the necessity of the emulsification process. Unemulsified epoxy resin cannot be uniformly dispersed in cement slurry, forming large agglomerates with weak interfacial bonding with the cement matrix. It cannot form a spherical core-crystal shell composite microstructure, thus failing to improve material performance and instead causing performance degradation due to interfacial defects.

[0135] Comparative Example 3 uses a commercially available waterborne epoxy emulsion, which, by weight, comprises the following components: 30 parts of commercially available waterborne epoxy emulsion, 100 parts of ordinary silicate cement PO 42.5, and 50 parts of river sand. The waterborne epoxy emulsion is a commercially available product with a solid content of 50% and a droplet size of approximately 2-5 μm.

[0136] Preparation method: Mix 100 parts cement and 50 parts river sand evenly, add 30 parts water-based epoxy emulsion, stir at 400 rpm for 5 minutes to obtain a uniform slurry, and cure for 28 days at a temperature of 20±2℃ and a relative humidity of over 95% after molding.

[0137] Microstructural characterization: Under 20,000x magnification, spherical structures were observed dispersed within the cement matrix, with diameters of 2-5 μm, consistent with the droplet size of commercial emulsions. However, crystal growth on the surface of the spherical structures was sparse, with crystal lengths of only 0.2-0.8 μm and diameters of approximately 0.10-0.30 μm. The number of crystals was low, and the surface coverage was only about 30-40%, far lower than the over 60% of the embodiments of this invention. The surface of the spherical structures was relatively smooth, without the formation of a dense crystalline shell. The reason for this may be that commercial waterborne epoxy emulsions contain a large amount of stabilizers, thickeners, and other additives. These additives coat the droplet surface, hindering the nucleation and growth of cement hydration products on the surface of the spherical structures.

[0138] The XRD test results are shown in Figure 16. The phase composition is similar to that of Example 1, but the peak intensities are different: the intensity of the ettringite peaks (2θ=9.1°, 15.8°, 22.9°) is between that of Comparative Example 1 and Example 1, and the peak intensity at 9.1° is about 0.75 times that of Example 1; the calcium hydroxide peaks (2θ=18.0°, 34.1°) have high intensity; the quartz peak (2θ=26.6°) is the strongest peak; and the CSH peak (2θ=29.4°) has moderate intensity.

[0139] Comparative Example 3 used a commercially available water-based epoxy emulsion. Although it could form spherical structures (2-5 μm), the emulsion contained a large amount of stabilizers, thickeners, and other additives. These additives coated the droplet surface, partially hindering the nucleation and growth of cement hydration products on the spherical surface. Therefore, the increase in peak strength of ettringite was less than that of the example using the emulsification method of this invention. The XRD results were consistent with the SEM observation of "surface crystal coverage of only 30-40%". Performance test results: The compressive strength at 28 days was 53.5 MPa, an increase of 5.9% compared to pure cement-based materials, a much smaller increase than the 15.8% in Example 1. The flexural strength at 28 days was 8.8 MPa, an increase of 10.0% compared to pure cement-based materials, also significantly smaller than the 22.5% in Example 1. The interfacial bond strength was 2.7 MPa, only 84.4% of that in Example 1. The chloride ion permeability coefficient was... The improvement in impermeability is limited.

[0140] Conclusion: Comparative Example 3 demonstrates the superiority of the emulsification method of this invention. Although commercial waterborne epoxy emulsions can also form spherical structures in cement, the crystal growth on the surface of the spherical structures is sparse due to the influence of additives in the emulsion, failing to form the dense crystalline shell characteristic of this invention, resulting in a significantly weaker interface reinforcement effect compared to this invention. This invention, through a simple emulsifier system and precisely controlled emulsification process, enables the epoxy spherical structure surface to fully induce the growth of cement hydration products, forming a dense crystalline layer, with an interfacial bonding strength approximately 18.5% higher than that of commercial emulsion systems.

[0141] Comparative Example 4: The comparative example was stirred at a low speed, resulting in insufficient emulsification. By weight, it included the following components: 15 parts of bisphenol A epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.45 parts of nonionic surfactant Pluronic F-68, 30 parts of water, and 50 parts of river sand.

[0142] The only difference between this comparative example and Example 1 is that the emulsification step uses low-speed stirring: 0.45 parts of emulsifier are dissolved in 30 parts of water, then 15 parts of epoxy resin are added, and emulsification is carried out by stirring at a low speed of 1500 rpm for 15 minutes. Due to the excessively low stirring speed and insufficient shear force, the resulting emulsion has poor quality, a wide droplet size distribution, an average particle size of about 30 μm, and a large number of large droplets with a particle size of 50-100 μm. After standing for 10 minutes, obvious stratification occurs.

[0143] Microstructure characterization: At 5,000x magnification, the spherical structures exhibited highly uneven size distribution, ranging in diameter from 5 μm to 50 μm, a difference of nearly 10 times. At 20,000x magnification, the small spherical structures showed good surface crystal growth, but the large spherical structures showed uneven surface crystal growth, with some areas exhibiting crystal growth while others remained smooth and crystal-free. During the curing process, the large droplets also underwent partial aggregation, forming even larger epoxy aggregates. The material exhibited numerous internal pores and poor density.

[0144] The XRD test results are shown in Figure 17. The phase composition is the same as that of Example 1, but the characteristics are as follows: the intensity of the ettringite peaks (2θ=9.1°, 15.8°) is similar to that of Comparative Example 1, with a slight increase; the intensity of the calcium hydroxide peaks (2θ=18.0°, 34.1°, 50.8°) is relatively high; the quartz peak (2θ=26.6°) is the strongest peak; and the intensity of the CSH peak (2θ=29.4°) is moderate.

[0145] Comparative Example 4, using low-speed stirring (1500 rpm), resulted in incomplete emulsification, leading to a wide droplet size distribution (5-100 μm) and a large number of large droplets. These large droplets have a small specific surface area, providing limited nucleation sites and thus having a weak promoting effect on cement hydration. The XRD pattern showed no significant increase in the intensity of the ettringite peak, consistent with the performance test results (compressive strength 51 MPa, only 0.9% higher than pure cement). This indicates that precise control of emulsification parameters is crucial for forming an effective spherical core-crystal shell microstructure.

[0146] Performance test results: The compressive strength after 28 days was 51.0 MPa, only 0.9% higher than that of pure cement-based material, showing a negligible improvement. The flexural strength after 28 days was 8.3 MPa, an increase of 3.8%. The interfacial bond strength was 2.6 MPa, only 81.3% of that in Example 1. The material properties are unstable; the coefficient of variation for strength of the same batch of test blocks reached 15%, demonstrating the inhomogeneity of the microstructure. The chloride ion permeability coefficient was... .

[0147] Conclusion: Comparative Example 4 demonstrates the importance of precisely controlling emulsification parameters. When the stirring rate is too low, emulsification is insufficient, resulting in large and unevenly distributed droplets that cannot form a uniform and stable spherical structure. Consequently, the improvement in material properties is minimal and the stability is poor. This invention, by controlling the stirring rate within the range of 3000-15000 rpm, can form droplets with uniform particle size, ensuring the uniform distribution of the spherical structure and the stability of its performance.

[0148] Comparative Example 5: This comparative example does not use an emulsifier and, by weight, includes the following components: 15 parts bisphenol A type epoxy resin, ordinary silicate cement. 42.5 (100 parts total), water (30 parts), river sand (50 parts).

[0149] The difference between this comparative example and Example 1 is that no emulsifier is added. In the preparation method, 15 parts of epoxy resin are directly added to 30 parts of water and stirred at 8000 rpm for 15 minutes. Although high-speed stirring is used, the epoxy resin cannot form a stable emulsion due to the lack of an emulsifier to reduce interfacial tension. During stirring, the epoxy is sheared into droplets, but after stirring stops, it quickly agglomerates into large lumps and cannot maintain a stable dispersion. When this unstable mixture is forcibly mixed with cement and sand, obvious epoxy lumps are visible in the slurry.

[0150] Microstructure characterization: Similar to Comparative Example 2, the epoxy forms large, unevenly distributed aggregates with weak interfacial bonding with the cement matrix, and does not form a spherical core-crystal shell composite microstructure.

[0151] The XRD test results are shown in Figure 18. The phase composition is similar to that of Comparative Example 2: the intensity of the ettringite peak (2θ=9.1°) is very weak; the intensity of the calcium hydroxide peaks (2θ=18.0°, 34.1°, 47.1°) is relatively high; the intensity of the quartz peak (2θ=26.6°) is the strongest; and the intensity of the CSH peak (2θ=29.4°) is relatively low.

[0152] Comparative Example 5 did not use an emulsifier. Although high-speed stirring (8000 rpm) was employed, the epoxy resin failed to form a stable emulsion due to the lack of an emulsifier to reduce interfacial tension, and the droplets rapidly coalesced after stirring stopped. Therefore, the microstructure and XRD pattern of the material were essentially the same as those of Comparative Example 2 (direct mixing of unemulsified epoxy). The XRD results demonstrate that an emulsifier is a necessary condition for the formation of stable emulsion droplets, and high-speed stirring alone cannot replace the role of an emulsifier.

[0153] Performance test results: The compressive strength after 28 days was 49.0 MPa, lower than that of pure cement-based materials, a decrease of 3.0%. The flexural strength after 28 days was 7.5 MPa, a decrease of 6.3%. The interfacial bond strength was 1.9 MPa, only 59.4% of that in Example 1. The coefficient of variation for performance reached 20%.

[0154] Conclusion: Comparative Example 5 demonstrates the necessity of the emulsifier. Without an emulsifier, even with high-speed stirring, a stable emulsion cannot be formed, the epoxy resin cannot be uniformly dispersed in the cement slurry, and the characteristic microstructure of this invention cannot be formed; instead, the material properties deteriorate. This invention, by adding an appropriate amount of emulsifier, enables epoxy droplets to be stably dispersed in the aqueous phase, laying the foundation for the subsequent formation of a spherical core-crystal shell composite microstructure.

[0155] Comparative Example 6 was prepared by weight of the following components: 15 parts of bisphenol A epoxy resin, 100 parts of ordinary silicate cement PO 42.5, 0.45 parts of nonionic surfactant Pluronic F-68, 30 parts of water, and 50 parts of river sand.

[0156] The only difference from Example 1 is that an emulsifier was added, but no emulsification step (high-speed stirring or ultrasonic dispersion) was performed; instead, low-speed mixing was carried out directly.

[0157] Preparation method, step one (direct mixing without emulsification): Add 0.45 parts of Pluronic F-68 emulsifier to 30 parts of deionized water, and stir at low speed of 300 rpm for 5 minutes at room temperature to dissolve the emulsifier. Then add 15 parts of bisphenol A type epoxy resin, and continue stirring at low speed of 300 rpm for 5 minutes. Due to the lack of high-speed stirring or ultrasonic dispersion, the shear force is insufficient, and the epoxy resin cannot be broken into tiny droplets. Although the emulsifier reduces the interfacial tension, the epoxy resin still floats on the water surface in large clumps, failing to form a stable emulsion.

[0158] Step 2: Dry mix 100 parts of ordinary Portland cement PO 42.5 with 50 parts of river sand for 2 minutes, then add the epoxy-water mixture from Step 1 and stir at 400 rpm for 5 minutes. Because the epoxy resin is not emulsified and dispersed, obvious epoxy resin clumps are visible in the slurry, and the distribution is uneven.

[0159] Step 3: Pour the slurry into a standard mold of 40mm×40mm×160mm, vibrate to remove air, smooth the surface, and cure for 28 days at a temperature of 20±2℃ and a relative humidity of over 95%.

[0160] Low magnification (500x): The epoxy resin appears as irregular, large aggregates, ranging in size from 50 μm to 300 μm, with extremely uneven distribution. Compared to Comparative Example 2 (without emulsifier), the edges of the epoxy blocks are slightly rounded, but the overall structure remains a large aggregate without forming a spherical structure.

[0161] High magnification (20,000x): There is a clear interfacial gap between the epoxy block structure and the cement matrix, with a width of about 0.5-2 μm; only a very small amount of cement hydration products are attached to the surface of the epoxy block, with a coverage of <10%; the spherical core-crystal shell composite microstructure characteristic of this invention was not observed; a thin film formed by emulsifier residue can be seen in some areas, but it failed to promote interfacial bonding. Compared with Comparative Example 2: After adding emulsifier, the edge morphology of the epoxy block was slightly improved, but since it was not emulsified and formed micron-sized droplets, the emulsifier could not play its due role, and the interfacial bonding state was basically the same as that of Comparative Example 2.

[0162] Comparative Example 6 demonstrates that both the emulsifier and the emulsification process are necessary to form the characteristic microstructure of this invention. Adding the emulsifier alone without high-speed stirring or ultrasonic dispersion fails to break the epoxy resin into micron-sized droplets; the epoxy remains in large aggregates, essentially the same as Comparative Example 2 (no emulsifier, no emulsification). Performance test results show that the performance indicators of Comparative Example 6 are similar to those of Comparative Example 2, and all are lower than those of pure cement-based materials (Comparative Example 1), further demonstrating the necessity of the emulsification process of this invention.

[0163] Experimental test method: Compressive strength test: According to the standard method of GB / T 17671-2021, a standard test block of 40mm×40mm×160mm was used to test the compressive strength for 28 days on a pressure testing machine, and the average value of 3 test blocks in each group was taken.

[0164] Flexural strength test: According to the standard method of GB / T 17671-2021, a standard test block of 40mm×40mm×160mm was used to test the flexural strength for 28 days on a flexural testing machine, and the average value of 3 test blocks in each group was taken.

[0165] Interfacial bond strength test: According to the standard method of GB / T 50728-2011, the material was coated on the surface of the old concrete base layer with a thickness of 10mm. After curing for 28 days, the interfacial bond strength was tested by pull-out method. The average value of 5 test points in each group was taken.

[0166] Chloride ion permeability coefficient test: The chloride ion diffusion coefficient was determined by the NEL method according to the standard method of JTG / T 3310-2019. The specimen size was a cylinder with a diameter of 100 mm and a thickness of 50 mm. The test was conducted after curing for 28 days.

[0167] Fracture energy test: The three-point bending beam method was adopted. The specimen size was 40mm×40mm×160mm, the span was 120mm, the prefabricated notch depth was 20mm, the loading rate was 0.05mm / min, the load-deflection curve was measured, and the fracture energy was calculated.

[0168] Freeze-thaw cycle test: According to the standard method of GB / T 50082-2009, the rapid freezing method was used, with 3 test blocks in each group, and the number of cycles was recorded when the compressive strength loss reached 25% or the mass loss reached 5%.

[0169] Microstructure characterization: Test blocks cured to the specified age were broken, and fresh fracture surfaces were obtained. After gold sputtering, the microstructure was observed using a scanning electron microscope (SEM) at magnifications of 5000-20000x. Parameters such as the diameter of the spherical structure, the length of the surface crystals, and the coverage were measured. The phase composition of the crystals was analyzed using X-ray diffraction (XRD). Elemental distribution was analyzed using energy dispersive spectroscopy (EDS).

[0170] Test Results Summary: The following table summarizes the main performance metrics for all embodiments and comparative examples:

[0171] As shown in the table above, the epoxy-modified cementitious materials in Examples 1-8 all exhibited significant performance improvements. Compressive strength increased by 8.9-29.7% compared to pure cementitious materials, flexural strength increased by 22.5-47.5%, interfacial bond strength increased by 20.0-68.0%, and chloride ion permeability decreased by 35.7-64.3%. In all examples, a characteristic spherical core-shell composite morphology was observed in the microstructure, with spherical particle sizes of 3-15 μm, surface crystal lengths of 0.8-3.0 μm, and crystal coverage of 60-85%.

[0172] Example 2, using ultrasonic emulsification compared to mechanical stirring in Example 1, resulted in smaller, more uniform spherical structures with superior interfacial bonding. Example 3, by increasing the epoxy content, increased the number of spherical structures, significantly improving the material's toughness. Example 4, by adding a curing agent and setting regulator, achieved rapid early strength development, suitable for quick repairs. Example 5, using fast-hardening cement and rapid curing, achieved the strength level of ordinary curing (28 days) in just 7 days. Example 6, using sulfoaluminate cement, saw dense growth of ettringite needle-like crystals on the surface of the spherical structures, achieving a maximum interfacial bond strength of 4.2 MPa. Example 7, using high epoxy content and high-strength cement, exhibited the best overall performance, with a compressive strength of 72 MPa. Example 8, although with a lower epoxy content, significantly improved toughness through the addition of glass fiber.

[0173] The performance of Comparative Examples 1-5 was significantly worse than that of the Example. The pure cement-based material of Comparative Example 1 lacked a spherical core-shell structure, and its performance indicators were at the baseline level. Comparative Examples 2 and 5, due to the lack of emulsifiers or emulsification processes, exhibited large-scale epoxy aggregation and extremely weak interfacial bonding, resulting in a decline in performance. While the commercially available aqueous epoxy emulsion of Comparative Example 3 could form a spherical structure, the surface crystal growth was sparse, and the performance improvement was far less than that of this invention. The low-speed emulsification in Comparative Example 4 led to uneven spherical structure size, resulting in only a slight performance improvement and poor stability.

[0174] By comparing the XRD spectra in Figures 19-21, it can be found that: (1) the promoting effect of emulsified epoxy on cement hydration (Figure 19): compared with Comparative Example 1, the relative intensity of the ettringite peak (2θ=9.1°) in Example 1 increased by about 28%, and the intensity of the CSH peak also increased, proving that the spherical structure of emulsified epoxy effectively promoted the generation of cement hydration products as heterogeneous nucleation sites, especially the preferential nucleation and growth of needle-shaped ettringite crystals.

[0175] (2) The regulating effect of setting accelerator and cement type on crystal growth (Figure 20): The peak intensity of ettringite in Examples 1, 4, and 6 showed an increasing trend (1:1.35:1.85), indicating that the addition of lithium carbonate setting accelerator can accelerate the formation of ettringite, while the use of sulfoaluminate cement can significantly increase the ettringite content. This provides a basis for controlling the type and density of crystals on the surface of spherical structures through formulation design.

[0176] (3) Necessity and superiority of emulsification process (Figure 21): The peak intensity of ettringite in Comparative Examples 1-3 and Example 1 is ranked as follows: Comparative Example 2 ≈ Comparative Example 1 < Comparative Example 3 < Example 1. Direct mixing of unemulsified epoxy (Comparative Example 2) has no promoting effect on cement hydration; commercial waterborne epoxy emulsion (Comparative Example 3) has a certain promoting effect but the effect is limited (peak intensity increased by 15%); the emulsification method of the present invention (Example 1) has the most significant promoting effect (peak intensity increased by 28%), which proves the superiority of the present invention in precisely controlling the emulsification process.

[0177] In summary, the XRD analysis results systematically verified the core mechanism of this invention from the perspective of crystal phase composition: through a precisely controlled emulsification process, epoxy resin is formed into uniformly dispersed micron-sized spherical droplets. These droplets serve as heterogeneous nucleation sites in the cement paste, inducing the directional growth of cement hydration products (mainly ettringite) on its surface, forming a unique spherical core-crystal shell composite microstructure, thereby significantly improving the interfacial bonding performance and comprehensive mechanical properties of the material.

[0178] In summary, the epoxy-modified cement-based material with a spherical-radial composite microstructure provided by this invention utilizes a precisely controlled emulsification process to allow epoxy droplets to act as heterogeneous nucleation sites within the cement slurry. This induces the directional growth of cement hydration products on the surface of the spherical structure, forming a unique spherical core-crystal shell composite microstructure, significantly enhancing the mechanical bonding and chemical adhesion at the epoxy-cement interface. The material exhibits high strength, high toughness, strong interfacial adhesion, and excellent durability, and its microstructure can be precisely controlled through emulsification parameters and curing conditions. In contrast, the comparative example without an emulsification process cannot form this microstructure, and its performance even decreases. The comparative example without the precisely controlled emulsification method of this invention exhibits an uneven microstructure and limited performance improvement. The material of this invention has broad application prospects in building structure repair, underwater restoration, rapid repair, marine protection, and road and bridge engineering, and possesses significant engineering application value.

[0179] 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. An epoxy-modified cementitious material, characterized in that: The epoxy-modified cementitious material comprises an organic phase structure and inorganic crystals, wherein the inorganic crystals are radially distributed on the surface of the organic phase structure; the organic phase structure is a spherical or near-spherical structure with a diameter of 3-15 μm; and the inorganic crystals are needle-like, rod-like, or plate-like structures with a length of 0.3-3 μm and a diameter of 0.05-0.5 μm.

2. The epoxy-modified cementitious material according to claim 1, characterized in that: The inorganic crystals cover more than 60% of the surface of the organic phase structure; preferably, the spacing between the spherical or near-spherical structures is 5-50 μm.

3. A method for preparing an epoxy-modified cementitious material as described in claim 1, characterized in that: The epoxy-modified cementitious material comprises the following components by weight: 8-30 parts epoxy resin, 80-150 parts cement, emulsifier, and 15-60 parts water, wherein the amount of emulsifier is 1-20% of the weight of epoxy resin. The preparation method includes the following steps: (1) Emulsification step: adding epoxy resin and emulsifier to water for emulsification treatment to obtain emulsified epoxy liquid, wherein the emulsification treatment causes the epoxy resin to form droplets with an average particle size of 1-30 μm that are uniformly dispersed in the aqueous phase; (2) Mixing step: mixing the emulsified epoxy liquid with cement and stirring for 3-10 minutes to obtain a uniform mixed slurry; (3) Curing step: after the mixed slurry is formed, curing it for 3-28 days under the conditions of temperature 15-35℃ and relative humidity ≥70%.

4. The preparation method according to claim 3, characterized in that: The weight ratio of epoxy resin to cement is (0.08-0.25):1; preferably, the weight ratio of epoxy resin to cement is (0.10-0.20):1; more preferably, the weight ratio of epoxy resin to cement is (0.12-0.18):

1.

5. The preparation method according to claim 3, characterized in that: In step (1): the emulsification process is carried out by mechanical stirring, with a stirring rate of 3000-15000 rpm, an emulsification time of 5-20 minutes, an emulsification temperature of 20-30℃, and an average droplet size of 2-20 μm; or, the emulsification process is carried out by ultrasonic dispersion, with an ultrasonic power of 200-800 W, an ultrasonic frequency of 20-40 kHz, an emulsification time of 3-15 minutes, an emulsification temperature of 20-30℃, and an average droplet size of 1-15 μm.

6. The preparation method according to any one of claims 3-5, characterized in that: The emulsifier is selected from one or more of the following: (a) anionic surfactants: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyether sulfate; (b) nonionic surfactants: fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene polyoxypropylene block copolymer; (c) amphoteric surfactants: lecithin, betaine; the amount of the emulsifier is 1-5% of the weight of the epoxy resin; preferably, the emulsifier is a nonionic surfactant, and the amount is 2-4% of the weight of the epoxy resin; preferably, the epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin or a mixture thereof; the technical indicators of the epoxy resin are: epoxy value: 0.40-0.55 eq / 100g, viscosity (25℃): 10000-20000m Softening point: 8-16℃; Preferably, the cement is one or more of the following: ordinary Portland cement (PO 42.5, PO 52.5), rapid-hardening Portland cement (RPO 42.5), sulfoaluminate cement (grade 42.5, grade 52.5); Preferably, the cement is ordinary Portland cement PO 42.5 or rapid-hardening Portland cement RPO 42.

5.

7. The preparation method according to any one of claims 3-5 further comprises one or more of the following components: (a) aggregate: river sand, quartz sand or manufactured sand, with a particle size of 0.15-5 mm, and an amount of 20-100 parts by weight; (b) curing agent: selected from one or more of polyetheramine D230, polyetheramine D400, modified aliphatic amine, and modified cycloaliphatic amine, and an amount of 10-30% by weight of epoxy resin; (c) setting regulator: selected from one or more of lithium carbonate, lithium sulfate, triethanolamine, and citric acid, and an amount of 0.2-3% by weight of cement; (d) reinforcing fiber: polypropylene fiber or glass fiber, with a length of 6-12 mm, and an amount of 0.2-2% by weight of cement.

8. The preparation method according to claim 3, characterized in that: In step (3): the curing conditions are: standard curing: temperature 20±2℃, relative humidity ≥95%, curing time 7-28 days; or rapid curing: temperature 30±2℃, relative humidity ≥90%, curing time 3-7 days; during the curing process, the crystal growth on the surface of the epoxy spherical structure follows the following rules: curing 1-3 days: crystals begin to germinate, length 0.1-0.5μm; curing 3-7 days: crystals grow rapidly, length 0.5-2μm; curing 7-28 days: crystal growth tends to stabilize, length 1-3μm.

9. The preparation method according to claim 3, characterized in that, The preparation steps are as follows: Step (1): Add epoxy resin and emulsifier to water, stir at 3000-15000 rpm for 5-20 minutes using a high-speed stirrer, or use an ultrasonic disperser at 200-800W power for 3-15 minutes to obtain a milky white stable emulsified epoxy liquid with an average droplet diameter of 1-30 μm; Step (2): Mix the emulsified epoxy liquid prepared in step (1) with cement, stir for 3-10 minutes until the slurry is uniform and free of lumps; Step (3): Pour the slurry into a mold to form a shape, during which cement hydration crystals gradually grow on the surface of the epoxy spherical structure to form a "spherical core-crystal shell" composite microstructure; Preferably, in step (2), it is mixed with 20-100 parts of aggregate.

10. Applications of epoxy-modified cementitious materials as described in claim 1 or 2: including, (a) building structure repair and reinforcement, especially concrete crack repair and steel reinforcement corrosion repair; (b) underwater or humid environment concrete repair, including seawalls, docks, dams, and bridge piers; (c) rapid repair and emergency repair, requiring the achievement of more than 50% of the design strength within 6 hours; (d) protective coatings for corrosion protection in marine and chemical environments; and (e) road and bridge repair materials, including road surface repair, bridge deck paving, and expansion joint repair.

Images