Rapid repair material suitable for low-temperature environment ocean engineering as well as preparation method and application of rapid repair material

Abstract

The invention discloses a rapid repair material suitable for ocean engineering in a low-temperature environment as well as a preparation method and application thereof, and belongs to the technical field of ocean engineering. The repairing material comprises the following components in percentage by mass: 1.0%-1.6% of light calcined magnesia at 1000 DEG C, 19.0%-24.0% of dead calcined magnesia at 1700 DEG C, 6.5%-8.0% of monopotassium phosphate, 1.7%-2.5% of boric acid, 5.0%-7.0% of hydrogen-based mineral phase conversion iron tailing powder, 51.9%-56.5% of iron tailing sand, 1.5%-1.7% of wollastonite powder, 0.1%-0.2% of a water reducing agent and 6.1%-7.3% of water. According to the invention, light calcined magnesia at 1000 DEG C, dead calcined magnesia at 1700 DEG C and monopotassium phosphate are used to construct a magnesium potassium phosphate cement system, boric acid is used as a retarder, and a polycarboxylic acid water reducer is used as a plasticizer; the hydrogen-based mineral phase conversion iron tailing powder is used as an admixture, the wollastonite powder is used as a fiber micro-aggregate, and the iron tailings are used as a fine aggregate, so that the compactness, the structural strength and the hardness of a hardened body are improved, and the high-performance requirement of ocean engineering rapid repair in a low-temperature environment is met.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, specifically relating to a rapid repair material suitable for marine engineering in low-temperature environments, its preparation method, and its application. Background Technology

[0002] Marine engineering projects in frigid regions operate in complex environments characterized by high salinity, high humidity, tidal fluctuations, low temperatures, and physical erosion, making their durability a global challenge. Concrete structures and components, as well as natural reefs, are prone to damage and cracking in marine environments, leading to structural failure. To meet the all-weather repair requirements of marine engineering projects in frigid regions, the repair materials used must possess characteristics such as rapid setting and hardening, high early strength, good low-temperature hydration performance, good water resistance, and good salt corrosion resistance.

[0003] Common repair materials used in marine engineering fall into two main categories: organic and inorganic. Organic repair materials are typically composite adhesives using polymers as binders. Common examples include polymer-modified cementitious materials such as acrylic emulsion mortar, epoxy mortar, and phenolic resin, as well as pure polymer-based repair materials such as polyurethane and epoxy resin. Inorganic repair materials mainly include special cements and some modified cementitious materials. These traditional repair materials have significant problems in terms of setting and hardening, construction period, early strength, corrosion resistance, freeze-thaw cycle resistance, and low-temperature hydration characteristics, making them unsuitable for the complex repair requirements of marine engineering projects in frigid regions.

[0004] Potassium magnesium phosphate (MPP) cementitious materials are a newly emerging class of cementing materials in recent years. Their main components include magnesium oxide, potassium dihydrogen phosphate, admixtures, water, aggregates, and retarders. They exhibit rapid setting and hardening, high strength, and corrosion resistance. Therefore, MPP cementitious materials are one of the preferred choices for rapid repair in low-temperature marine engineering environments. During the setting and hardening process of MPP cementitious materials, H₂PO₄ in the liquid phase... 4- Ions make the cement paste weakly acidic, accelerating the formation of magnesium. 2+ Release of ions, Mg 2+ These hydrated magnesium ions undergo a complexation reaction with water molecules to form positively charged "hydrosols," and then react with H2PO4. 4- K + An acid-base reaction occurs, producing hydration products such as magnesium phosphate, and the exothermic reaction further accelerates the hydration process. As the hydration products gradually increase, they expand and destroy the protective layer, releasing more Mg. 2+Upon entering the liquid phase, a reaction occurs, forming a gel. Simultaneously, hydration product crystal nuclei are continuously generated, grown, and cross-linked, making the gel denser and ultimately forming a high-mechanical-performance hardened body with K-type struvite as the main hydration product. Compared to traditional magnesium phosphate cement, it exhibits better stability and possesses certain resistance to sulfate and chloride corrosion and salt freezing. However, its poor water stability is a key technical problem limiting its application. The accelerated dissolution and decomposition of its hydration products in flowing water environments leads to a significant decrease in the strength and durability of the hardened body. This clearly cannot efficiently meet the repair requirements of low-temperature marine engineering.

[0005] The master's thesis, "Study on Basic Mechanical Properties and Durability of Concrete Repair Materials for Splash Zones" (Fang Xiaoliang, Dalian University of Technology, June 2024), used ammonium dihydrogen phosphate and overburned magnesium oxide to prepare magnesium phosphate cement as a repair material for bridge piers damaged in splash zones. This material exhibits rapid strength development, excellent impact resistance, good resistance to chloride ion penetration, and good frost resistance. The material formulation in that thesis differs significantly from that of this invention, as does the cementitious system, and it does not address the use and mechanism of action of lightly calcined magnesium oxide. The master's thesis, "Study on the Influence of Low-Quality Fly Ash on the Hydration Process, Microstructure and Performance of Magnesium Phosphate Cement" (Du Jiaheng, Qingdao University of Technology, May 2025), used fly ash with different unburned carbon and sulfur contents to prepare composite cementitious materials in magnesium phosphate cement. While this thesis also focuses on magnesium phosphate cement, it differs significantly from the cementitious system described in this invention. The fly ash used in that thesis primarily acts as a filler and compactor in the hardening system, and it does not explicitly address the hydration mechanism of magnesium phosphate cement under retarded conditions. This is significantly different from the mechanism of action of hydrogen-based mineral phase conversion iron tailings powder in the hydration process used in this invention, and it also does not address the use and mechanism of action of lightly calcined magnesium oxide. The thesis, "Preparation and Performance Study of Magnesium Phosphate Cement-Based Repair Materials under Negative Temperature Environments" (Luo Xuanzhang, Southwest University of Science and Technology, May 2023), uses modified magnesium oxide to improve the working performance of magnesium phosphate cement-based repair materials under negative temperatures. The research formulation includes potassium dihydrogen phosphate, sodium dihydrogen phosphate, bentonite, and borax. Although this literature uses potassium dihydrogen phosphate, sodium dihydrogen phosphate plays a major role in the two-component phosphate, focusing on the workability and low-temperature hydration performance of magnesium phosphate cement paste under sodium silicate modification conditions, without addressing the issue of admixtures and seawater corrosion resistance. This differs significantly from the material mechanism and technical purpose of this invention. The literature "Influence of silica fume on the early performance of magnesium phosphate cement and analysis of micropore structure" (Wang Shouyuan et al., Concrete, 2025, 429(07), 163-167) uses silica fume to modify magnesium phosphate cement and discusses the influence of different admixture amounts on matrix properties. This literature selects silica fume as an admixture, whose main role is filling and pozzolanic properties in the later alkaline environment. This is significantly different from the activation and hardening mechanism of hydrogen-based mineral phase conversion iron tailings powder in the acidic environment formed by early potassium dihydrogen phosphate dissolution in this invention, and it also does not involve the use and mechanism of light-burned magnesium oxide. The literature “Influence of mineral admixtures on the rheological properties and early properties of potassium magnesium phosphate cement paste” (Tang Yunjie et al., Materials Reports, 2025, No. 39(11), 23020128-1-6) uses fly ash, silica fume and quartz powder to modify magnesium phosphate cement. The mechanism of action of these admixtures as admixtures is also significantly different from that of this invention.

[0006] In summary, the preparation and application of the above-mentioned magnesium phosphate cements are as follows: (1) magnesium phosphate cements are prepared by reacting recalcined magnesium oxide with phosphate ions in an acidic environment; (2) the phosphates used include H3PO4, NH4H2PO4, KH2PO4, NaH2PO4 and AlH2(PO4)2; (3) silica fume, fly ash, metakaolin and other admixtures are used as admixtures for magnesium phosphate cements to reduce the heat of hydration and the hydration rate, and participate in the hydration reaction when the hydration environment is alkaline in the later stage, thereby improving the later strength; (4) boric acid, borates or borax are used as retarder for magnesium phosphate cements; (5) magnesium phosphate cements are used for the rapid repair of highways, splash zones and other projects. As a type of magnesium phosphate cement, the water resistance problem of potassium magnesium phosphate cement is a technical problem that restricts its application. The existing technology mainly uses admixtures and other methods to improve the material density, thereby reducing the dissolution rate of hydration products. The material performance requirements for concrete engineering or natural rock structure repair in frigid marine environments encompass a wide range of aspects, including low-temperature hydration, construction period, early strength, later strength, corrosion resistance, abrasion and impact resistance, water resistance, and salt-freezing resistance. While existing magnesium phosphate cement materials are superior to other materials such as silicate cement and organic resins, significant problems remain. Conventional technical performance enhancement methods cannot meet the durability requirements of marine engineering repair in low-temperature environments. Therefore, there is an urgent need to develop durable and reliable potassium magnesium phosphate repair materials to address the material needs for engineering repairs under such harsh conditions in frigid marine environments. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, one of the objectives of this invention is to provide a rapid repair material suitable for marine engineering in low-temperature environments. This material employs a potassium magnesium phosphate cement hardening system, achieving rapid hardening in low-temperature environments and high durability in marine environments through three aspects: hydration process control, volume stability regulation, hardened body densification, and self-defense against salt and water erosion. This meets the high-performance requirements for rapid repair of marine engineering in low-temperature environments.

[0008] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0009] A rapid repair material suitable for marine engineering in low-temperature environments comprises the following components by mass percentage: 1.0%~1.6% lightly calcined magnesia at 1000℃, 19.0%~24.0% recalcined magnesia at 1700℃, 6.5%~8.0% potassium dihydrogen phosphate, 1.7%~2.5% boric acid, 5.0%~7.0% hydrogen-based mineral phase conversion iron tailings powder, 51.9%~56.5% iron tailings sand, 1.5%~1.7% wollastonite powder, 0.1%~0.2% water-reducing agent, and 6.1%~7.3% water.

[0010] This invention constructs a potassium magnesium phosphate cementing system using lightly calcined magnesium oxide (1000℃), recalcined magnesium oxide (1700℃), and potassium dihydrogen phosphate. The lightly calcined magnesium oxide (1000℃) and the recalcined magnesium oxide (1700℃) participate in the hydration reaction together, resulting in diverse crystal forms and morphologies of the hydration products. This ensures rapid early strength growth of the hardened system under conditions of -10℃ to 0℃. Simultaneously, the appropriately dense crystal structure of the lightly calcined magnesium oxide (1000℃) and its rate of reaction with water to form magnesium hydroxide ensure that the homologous expansion cycle (both the expansion source and the cementing material are composed of magnesium oxide) effectively compensates for the hardening shrinkage of the potassium magnesium phosphate cementing system without significantly negatively impacting the formation of the hardened structure. Furthermore, it avoids interference from non-homogeneous expansion components on the hydration process and the influence of hydration products. In the initial stage of slurry hardening, the liquid phase pH is acidic, and this acidic environment has a significant activating effect on the hydrogen-based mineral phase conversion iron tailings powder. As the slurry hardens, the pH of the system gradually changes to alkaline, and the hydrogen-based mineral phase conversion iron tailings powder participates in the secondary hydration reaction, producing a significant positive effect on the later strength and volume stability of the potassium magnesium phosphate cementing system. Furthermore, the acidic activation in the early stage of hydration further enhances the potential hydraulic properties of the hydrogen-based mineral phase conversion iron tailings powder. This characteristic of reacting in the same process as the main cementing system is beneficial to the stability of the microstructure of the hydration products. Compared with other active admixtures such as fly ash and silica fume, which can only react under alkaline conditions and not under acidic conditions, the hydrogen-based mineral phase conversion iron tailings powder of this invention has significant advantages. Iron tailings, due to their high content of quartz and silicate minerals and high structural hardness, can replace natural sand and quartz sand as fine aggregate in repair materials. Furthermore, they share the same origin as hydrogen-based mineral-phase-transformed iron tailings powder, which is beneficial for the formation of a homogeneous hardened body structure. This effectively improves the structural strength and hardness of the repair material, enhances surface wear resistance, and increases resistance to seawater erosion. The microfiber morphology of wollastonite powder effectively reduces shrinkage tendency during the hardening process of the potassium magnesium phosphate cementing system, particularly controlling the generation and propagation of microcracks in the plastic stage. This is significant for the density of the hardened repair material and can significantly improve its durability under seawater impact, immersion, and salt freezing conditions. After the repair material hardens, in a seawater immersion environment, chloride salts and other substances infiltrating the system with seawater can undergo a magnesium oxychloride cementing reaction with residual unreacted magnesium oxide, producing new cementing substances. This effectively seals existing microcracks, forming an active defense against erosion and penetration, thereby further improving the durability of the repair material in harsh marine environments.

[0011] Calcination temperature significantly affects the crystal structure, reactivity, and surface morphology of lightly calcined and heavily calcined magnesium oxide (MgO). This invention utilizes the reactivity of 1700℃ heavily calcined MgO, simultaneously meeting the requirements for construction and hydration hardening performance. Excessively high calcination temperatures lead to prolonged low-temperature reaction times and increased structural defects, while excessively low calcination temperatures result in excessively rapid hydration and a short construction cycle, failing to meet practical requirements. Simultaneously, this invention utilizes the micro-expansion characteristics of 1000℃ lightly calcined MgO to compensate for the shrinkage of the cementitious system, reducing microcracks and forming a magnesium oxychloride system under seawater infiltration conditions, actively defending against seawater erosion. Excessively low calcination temperatures cause the early-stage calcined MgO reaction to be too rapid, its expansibility being consumed during the plastic stage, failing to effectively compensate for the shrinkage after hydration hardening of the potassium magnesium phosphate cementitious system.

[0012] Preferably, the mass ratio of the 1000℃ lightly calcined magnesium oxide to the 1700℃ recalcined magnesium oxide is (1~1.5):(19.5~20).

[0013] Preferably, before use, lightly calcined magnesium oxide at 1000℃ and recalcined magnesium oxide at 1700℃ are mixed and then ground to a specific surface area of ​​300m². 2 / kg~350m 2 / kg.

[0014] Preferably, the fineness of the hydrogen-based mineral phase conversion iron tailings powder is 1500~1600 mesh.

[0015] Preferably, the fineness modulus of the iron tailings is 1.7 to 1.9.

[0016] Preferably, the fineness of the wollastonite powder is 300-500 mesh.

[0017] Another object of the present invention is to provide a method for preparing the aforementioned rapid repair material, comprising the following steps:

[0018] S1. The 1000℃ light-burned magnesium oxide and the 1700℃ re-burned magnesium oxide are mixed and then ground to a specific surface area of ​​300 m². 2 / kg~350m 2 / kg, to obtain mixture A;

[0019] S2. Mix the boric acid, hydrogen-based mineral phase conversion iron tailings powder and water-reducing agent evenly, add an appropriate amount of water and stir evenly to obtain mixture B;

[0020] S3. Mix potassium dihydrogen phosphate, iron tailings sand and wollastonite powder evenly to obtain mixture C;

[0021] S4. Mix mixture A, mixture B and mixture C together, and add to the remaining water and mix evenly to obtain the rapid repair material.

[0022] In the preparation method of this invention, step S1 first uses mechanical force to refine the 1000°C lightly calcined magnesium oxide and the 1700°C recalcined magnesium oxide while thoroughly mixing them; the surface of the refined magnesium oxide particles is roughened, and their total surface area increases. This facilitates the acceleration of the dissolution and reaction process in the next stage.

[0023] Step S2 involves mixing boric acid, hydrogen-based mineral phase conversion iron tailings powder, and a water-reducing agent. Since boric acid, as a retarding component in the potassium magnesium phosphate cement system, has high reaction efficiency and its dosage is far lower than that of borax used in other literature, directly mixing it with magnesium oxide would make it difficult to ensure the uniformity of the chemical reaction. The water-reducing agent improves the workability of the slurry, ensuring that the prepared slurry can still effectively meet construction requirements under low water consumption conditions; similarly, the dosage of this component is also very small. After hydrogen-based mineral phase conversion, the surface roughness of the iron tailings particles is significantly improved, and the unsaturation of Si-O bonds is significantly increased, enhancing their potential complexation and reactivity. Therefore, mixing boric acid, hydrogen-based mineral phase conversion iron tailings powder, and the water-reducing agent first allows the hydrogen-based mineral phase conversion iron tailings powder to act as an efficient carrier, enabling more uniform dispersion of boric acid and polycarboxylate water-reducing agent. This benefits the uniformity of the solid-liquid mixture B prepared with water and the balance of the reaction. Meanwhile, the pre-contact of hydrogen-based mineral phase conversion iron tailings powder with boric acid can increase its surface acidity. After the subsequent addition of water, a high acid concentration zone is formed on the surface of the particles in the solid-liquid mixture B. Unlike other active admixtures that can only be hydrated under alkaline conditions, hydrogen-based mineral phase conversion iron tailings powder can react under both alkaline and acidic conditions, which further helps the admixture to exert its hydration-assisted effect.

[0024] Step S3 involves mixing potassium dihydrogen phosphate, iron tailings sand, and wollastonite powder. Potassium dihydrogen phosphate is a major component in the potassium magnesium phosphate cement hydration system, and its dosage far exceeds that of boric acid and polycarboxylate superplasticizer. The small particle size of the hydrogen-based mineral phase conversion iron tailings powder makes it unsuitable as a dispersion carrier. Furthermore, premixing it with boric acid and polycarboxylate superplasticizer easily leads to agglomeration, which is detrimental to the uniform distribution of boric acid and polycarboxylate superplasticizer, resulting in a severe concentration gradient during subsequent liquid-phase reactions, which is detrimental to the homogeneity of the initial hydration reaction. Iron tailings particles are the largest in the system and are used in the largest quantity, making them suitable as a dispersion carrier for potassium dihydrogen phosphate. Wollastonite powder is an inert substance, but its microstructure is fibrous, making it highly prone to agglomeration; similarly, it is not suitable for premixing with the hydrogen-based mineral phase conversion iron tailings powder. After being effectively dispersed, wollastonite powder acts as a thickener in the slurry, which can improve the uniformity and stability of the slurry. In the hardened body, it can reduce the tendency to crack, improve dimensional stability, and especially restrain plastic cracks.

[0025] Preferably, in step S2, the mass of water added is 30% to 40% of the total mass of boric acid, hydrogen-based mineral phase conversion iron tailings powder, and water-reducing agent.

[0026] Another object of the present invention is to provide the application of the aforementioned rapid repair material in the repair of cement concrete or natural reefs in tidal zones of frigid regions.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] (1) This invention uses 1000℃ lightly calcined magnesium oxide, 1700℃ heavily calcined magnesium oxide and potassium dihydrogen phosphate to construct a potassium magnesium phosphate cement system, which diversifies the crystal form and morphology of hydration products, optimizes the hydration process, and ensures rapid hardening of the repair material by homologous expansion and fibrous particle constraint, while effectively controlling the generation and expansion of microcracks and improving the volume stability of the hardened body; and in the marine environment, it can generate active defense against seawater penetration and improve durability; the preparation mechanism has strong technical logic and the synergistic effect of each component is high, thus providing a new material for rapid repair of marine engineering in low temperature environment.

[0029] (2) The repair material of the present invention uses hydrogen-based mineral phase conversion iron tailings powder as an admixture. Compared with other active admixtures, hydrogen-based mineral phase conversion iron tailings, due to its inherent potential complexing and reactivity, participates in the reaction during both the acidic stage in the early stage and the alkaline stage in the later stage of hydration in the potassium magnesium phosphate cementing system, thus participating in the hydration hardening reaction throughout the entire hydration cycle. This further helps the admixture to exert its hydration-assisted effect, optimizes the microstructure of the hardened body of the repair material, and effectively improves the early and late strength of the repair material.

[0030] (3) The materials used in this invention are readily available and include solid wastes such as hydrogen-based mineral phase conversion iron tailings and iron tailings sand, which are harmless to the human body and will not cause other pollution to the environment while alleviating the pressure of solid waste discharge.

[0031] (4) The present invention has low requirements for equipment conditions, and existing equipment conditions can meet the requirements without specific modification or upgrade. It does not require complex mechanical equipment, has strong process adaptability, reliability and universality, and does not generate a lot of noise and has low energy consumption.

[0032] (5) The technical indicators of the repair material of the present invention, such as setting time, mechanical properties and dimensional stability, are outstanding, so that it can be widely used in various marine engineering projects. It solves the technical problems of high difficulty in repairing marine engineering projects in low temperature environment, short operation cycle and poor durability after repair, and has significant economic and technical benefits.

[0033] In summary, compared to the magnesium phosphate cement and marine engineering repair materials mentioned in the background technology, this invention uses 1000℃ light-burned magnesium oxide, 1700℃ heavy-burned magnesium oxide, and potassium dihydrogen phosphate to construct a potassium magnesium phosphate cementing system. Hydrogen-based mineral phase conversion iron tailings powder participates in the reaction, reinforcement, and regulation throughout the hydration process of the system. 1000℃ light-burned magnesium oxide serves as a homologous expansion component to regulate the volume stability of the hardened body. Wollastonite powder is used as fibrous micro-aggregate to improve structural stability, flexural strength, and impact toughness. Iron tailings are used as fine aggregate to improve the density, structural strength, and hardness of the hardened body. Through these technical means, the comprehensive performance of the material is improved, exhibiting strong process adaptability, reliability, and universality. It can effectively solve the problem of marine engineering repair in low-temperature environments, without generating significant noise and with low energy consumption. The constituent materials and the hardened body used in the repair construction are harmless to the human body and will not cause other pollution to the environment. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The rapid repair material of the present invention, suitable for marine engineering in low-temperature environments, comprises the following components in the indicated mass percentages: 1.0%~1.6% lightly calcined magnesia at 1000℃, 19.0%~24.0% recalcined magnesia at 1700℃, 6.5%~8.0% potassium dihydrogen phosphate, 1.7%~2.5% boric acid, 5.0%~7.0% hydrogen-based mineral phase conversion iron tailings powder, 51.9%~56.5% iron tailings sand, 1.5%~1.7% wollastonite powder, 0.1%~0.2% water-reducing agent, and 6.1%~7.3% water.

[0036] Rapid repair of marine engineering projects in low-temperature environments faces technical challenges such as low-temperature operation, tidal construction, rapid early strength growth under sub-zero temperatures, prevention of shrinkage cracking, resistance to wave erosion, resistance to seawater corrosion, and resistance to salt freezing. To address these challenges, this invention provides a novel potassium magnesium phosphate cementing system. Using mechanical force, it refines 1000℃ light-burned magnesium oxide and 1700℃ heavy-burned magnesium oxide while thoroughly mixing them. This mixture is then combined with potassium dihydrogen phosphate to form the potassium magnesium phosphate cementitious matrix. Boric acid is used as a retarder, polycarboxylate superplasticizer to adjust workability, hydrogen-based mineral phase conversion iron tailings powder as an active admixture, and iron tailings sand as aggregate. Through hydration process and volume stability control, densification of the hardened body, and self-defense against salt and water erosion, the repair material achieves rapid hardening in low-temperature environments and high durability in marine environments.

[0037] The method for preparing the rapid repair material of the present invention includes the following steps:

[0038] S1. The 1000℃ light-burned magnesium oxide and the 1700℃ re-burned magnesium oxide are mixed and then ground to a specific surface area of ​​300 m². 2 / kg~350m 2 / kg, to obtain mixture A;

[0039] S2. Mix the boric acid, hydrogen-based mineral phase conversion iron tailings powder and water-reducing agent evenly, add water accounting for 30%~40% of the total mass of boric acid, hydrogen-based mineral phase conversion iron tailings powder and water-reducing agent, stir evenly to obtain mixture B;

[0040] S3. Mix potassium dihydrogen phosphate, iron tailings sand and wollastonite powder evenly to obtain mixture C;

[0041] S4. Mix mixture A, mixture B and mixture C together, and add to the remaining water and mix evenly to obtain the rapid repair material.

[0042] The method provided by this invention does not have specific requirements for the relevant equipment. The appropriate equipment can be determined based on the actual conditions of existing grinding and mixing equipment.

[0043] This invention first grinds lightly calcined magnesia at 1000℃ and recalcined magnesia at 1700℃ to the required fineness (e.g., specific surface area of ​​300 m²) using equipment such as a disc crusher or ball mill. 2 / kg~350m 2 / kg), and mixed evenly. Depending on the environmental conditions and usage requirements of the repair material, the content of lightly calcined magnesia at 1000℃ should be adjusted within the range of 1.0% to 1.6%, and the content of recalcined magnesia at 1700℃ should be adjusted within the range of 19.0% to 24.0%. The grinding fineness requirement is not high, and the energy consumption required is relatively low, which can meet the requirements of subsequent processes. It should be noted that if the fineness is further increased, the particles are more likely to agglomerate, their elasticity tends to increase, the grinding and mixing efficiency is significantly reduced, and the energy consumption is too high, which is not worthwhile.

[0044] The surface roughness of hydrogen-based mineral phase conversion iron tailings powder is high, and the unsaturation of Si-O bonds is significantly improved. Its particle size of 1500-1600 mesh provides sufficient potential for complexation and reaction, making it suitable as a dispersion carrier. It is dispersed and mixed uniformly with boric acid and polycarboxylate superplasticizer using equipment such as a drum mixer. The specific mixing time depends on the specific equipment type and operating parameters. Boric acid, as a retarding component in the potassium magnesium phosphate cement system, has its dosage adjusted within the specified range according to the application temperature and construction cycle requirements of the repair material. The role of polycarboxylate superplasticizer is to improve the workability of the slurry; its dosage can be adjusted within the specified range according to specific construction requirements. After mixing, a planetary isostatic shaft mixer is used to prepare solid-liquid mixture B. The amount of water added is adjusted according to the uniformity of the slurry and suitability for the next process. Generally, the slurry fluidity should reach above 250 mm, corresponding to a water addition of 30%-40% of the total mass of boric acid, hydrogen-based mineral phase conversion iron tailings powder, and polycarboxylate superplasticizer. Hydrogen-based mineral phase transformation iron tailings powder not only improves the homogeneity of solid-liquid mixtures, but also forms a high acid concentration zone on the particle surface. Furthermore, it can react under both acidic and alkaline conditions in the later stages of hydration, which further enhances the hydration-assisted effect of the admixture.

[0045] Potassium dihydrogen phosphate, iron tailings sand, and wollastonite powder are mixed evenly using equipment such as a drum mixer. The specific mixing time depends on the specific equipment type and operating parameters. The particle size of the iron tailings sand should meet the requirements for effectively dispersing both potassium dihydrogen phosphate and wollastonite powder particles. Its fineness modulus can be adjusted within the range of 1.7 to 1.9, preferably 1.8. The preferred fineness of the wollastonite powder is 400 mesh. It acts as a thickener in the slurry, improving its uniformity and stability. In the hardened body, it can reduce the tendency to crack, improve dimensional stability, and especially restrain plastic cracks.

[0046] Solid mixture A, containing 1000℃ lightly calcined magnesia and 1700℃ recalcined magnesia, solid-liquid mixture B, containing boric acid, hydrogen-based mineral phase transformation iron tailings powder, polycarboxylate superplasticizer, and water, and solid mixture C, containing potassium dihydrogen phosphate, iron tailings sand, and wollastonite powder, are mixed together in a planetary isobaric mixer. The remaining water is then added and mixed thoroughly. A hand-held mixer can also be used on-site. The resulting slurry should be applied within 30 minutes of preparation.

[0047] In the following specific implementation cases, the model parameters and procurement sources of the raw materials used are shown in Table 1.

[0048] Table 1. Type parameters and procurement sources of raw materials used in the embodiments of the present invention.

[0049]

[0050] Example 1

[0051] This embodiment provides a rapid repair material suitable for marine engineering in low-temperature environments, comprising the following components by mass percentage: 1.5% lightly calcined magnesia at 1000℃, 19.5% recalcined magnesia at 1700℃, 8.0% potassium dihydrogen phosphate, 2.5% boric acid, 7.0% hydrogen-based mineral phase conversion iron tailings powder, 52.9% iron tailings sand, 1.7% wollastonite powder, 0.2% water-reducing agent, and 6.7% water;

[0052] The preparation method of the rapid repair material in this embodiment includes the following steps:

[0053] S1. Lightly calcined magnesium oxide at 1000℃ and recalcined magnesium oxide at 1700℃ are ground and mixed evenly using a ball mill to obtain a solid mixture A with a specific surface area of ​​300 m². 2 / kg;

[0054] S2. Mix boric acid, hydrogen-based mineral phase conversion iron tailings powder and polycarboxylate superplasticizer evenly, add water accounting for 38% of the total mass of boric acid, hydrogen-based mineral phase conversion iron tailings powder and superplasticizer, stir evenly to obtain solid-liquid mixture B;

[0055] S3. Mix potassium dihydrogen phosphate, iron tailings sand and wollastonite powder evenly to obtain solid mixture C;

[0056] S4. Mix solid mixture A, solid-liquid mixture B and solid mixture C, and add to the remaining water and mix evenly to obtain the rapid repair material.

[0057] Example 2

[0058] The rapid repair material in this embodiment is basically the same as that in Embodiment 1, except that the specific surface area of ​​solid mixture A in step S1 is 350 m². 2 / kg.

[0059] Example 3

[0060] The rapid repair material in this embodiment is basically the same as that in Embodiment 1, except that the mass percentage of magnesium oxide lightly calcined at 1000℃ in step S1 is 1.0%, and the mass percentage of magnesium oxide recalcined at 1700℃ is 20.0%.

[0061] Example 4

[0062] The rapid repair material in this embodiment is basically the same as that in Embodiment 1, except that the mass percentage of hydrogen-based mineral phase conversion iron tailings powder is 5% and the mass percentage of iron tailings sand is 54.9%.

[0063] Example 5

[0064] The rapid repair material in this embodiment is basically the same as that in Embodiment 1, except that the mass percentage of boric acid is 2.0% and the mass percentage of iron tailings sand is 53.4%.

[0065] Example 6

[0066] The rapid repair material in this embodiment is basically the same as that in Embodiment 1, except that the mass percentage of wollastonite powder is 1.5% and the mass percentage of iron tailings sand is 53.1%.

[0067] Comparative Example 1

[0068] The rapid repair material in this comparative example is basically the same as that in Example 1, except that: in step S1, 1000°C lightly calcined magnesium oxide is not used, and the mass percentage of 1700°C recalcined magnesium oxide is 21.0%.

[0069] Comparative Example 2

[0070] The rapid repair material in this comparative example is basically the same as that in Example 1, except that an equal amount of fly ash is used to replace the hydrogen-based mineral phase conversion iron tailings powder.

[0071] Comparative Example 3

[0072] The rapid repair material in this comparative example is basically the same as that in Example 1, except that an equal amount of polyacrylonitrile fiber is used instead of wollastonite powder.

[0073] Comparative Example 4

[0074] The rapid repair material in this comparative example is basically the same as that in Example 1, except that an equal amount of iron tailings powder of the same fineness is used to replace the hydrogen-based mineral phase transformation iron tailings powder.

[0075] Comparative Example 5

[0076] The rapid repair material in this comparative example is basically the same as that in Example 1, except that in step S1, an equal amount of 900°C lightly calcined magnesium oxide is used instead of 1000°C lightly calcined magnesium oxide.

[0077] Comparative Example 6

[0078] The rapid repair material in this comparative example is basically the same as that in Example 1, except that in step S1, an equal amount of magnesium oxide re-fired at 1600℃ is used instead of magnesium oxide re-fired at 1700℃.

[0079] Comparative Example 7

[0080] The rapid repair material in this comparative example is basically the same as that in Example 1, except that in step S1, an equal amount of magnesium oxide re-fired at 1800℃ is used instead of magnesium oxide re-fired at 1700℃.

[0081] Experimental Example: Performance Evaluation of Rapid Repair Materials for Marine Engineering in Low-Temperature Environments

[0082] The performance of the rapid repair materials for marine engineering in low-temperature environments prepared in the above embodiments and comparative examples was evaluated.

[0083] 1. Performance Testing Methods

[0084] (1) Condensation time test

[0085] The setting time of rapid repair materials for marine engineering in low-temperature environments was tested according to the method requirements in JC / T2537-2019 "Magnesium Phosphate Repair Mortar";

[0086] (2) Flowability test

[0087] The test was conducted in accordance with the requirements of GB / T 2419-2005 "Test Method for Flowability of Cement Mortar".

[0088] (3) Mechanical property testing

[0089] The test was conducted in accordance with the requirements of GB / T 17671-2021 "Test Method for Strength of Cement Mortar".

[0090] (4) Freeze resistance test

[0091] The single-sided salt freezing method was used, and the test was conducted in accordance with the requirements of GBT50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete".

[0092] (5) Drying shrinkage test

[0093] The test was conducted according to the requirements of JC / T2537-2019 "Magnesium Phosphate Repair Mortar".

[0094] (6) Abrasion resistance test

[0095] The test was conducted according to the requirements of JC / T2537-2019 "Magnesium Phosphate Repair Mortar".

[0096] 2. Test Results

[0097] The test results for setting time, fluidity, mechanical properties, frost resistance, shrinkage, and abrasion resistance are shown in Table 2 below.

[0098] Table 2 Performance test results of the repair materials in each embodiment and comparative example

[0099]

[0100] Based on the test results in Table 2, and by comparing Examples 1 and 2, it can be seen that changing the specific surface area of ​​the mixture of lightly calcined magnesia at 1000℃ and recalcined magnesia at 1700℃ will significantly affect the setting time, fluidity, mechanical properties (including compressive strength at 1.5h, 3d, 28d, and 3h at -5℃), freeze resistance, and drying shrinkage of the rapid repair material for marine engineering in low-temperature environments.

[0101] By comparing Examples 1 and 3, it can be seen that changing the mass ratio of lightly calcined magnesia at 1000℃ to heavily calcined magnesia at 1700℃ will affect the setting time, fluidity, mechanical properties (including compressive strength at 1.5h, 3d, 28d, and 3h at -5℃), freeze resistance, shrinkage rate, and wear resistance of the rapid repair material for marine engineering in low-temperature environments.

[0102] Comparing Examples 1 and 4, it can be seen that changing the amount of hydrogen-based mineral phase conversion iron tailings powder has a significant impact on the mechanical properties (including compressive strength at 1.5h, 3d, 28d, and 3h at -5℃), freeze resistance, and drying shrinkage rate of the rapid repair material for marine engineering in low-temperature environments.

[0103] By comparing Examples 1 and 5, it can be seen that changing the amount of boric acid significantly affects the setting time and early strength of rapid repair materials for marine engineering in low-temperature environments.

[0104] By comparing Examples 1 and 6, it can be seen that changing the amount of wollastonite powder significantly affects the shrinkage rate and wear resistance of the rapid repair material for marine engineering in low-temperature environments.

[0105] Based on the above comparison, the rapid repair materials for marine engineering in low-temperature environments provided by the present invention in Examples 1 to 6 still have relatively superior performance.

[0106] Comparing Example 1 and Comparative Example 1, it can be seen that the absence of 1000℃ lightly calcined magnesium oxide significantly and adversely affects the mechanical properties, shrinkage rate, freeze resistance, and abrasion resistance of the repair material, and also has a certain impact on setting time and flowability. This indicates that 1000℃ lightly calcined magnesium oxide is irreplaceable in the repair material of this invention. Its hydration expansion compensates for shrinkage, effectively controls the generation and propagation of microcracks, and can play an active defense role under seawater infiltration, significantly affecting the dimensional stability and durability of rapid repair materials for marine engineering in low-temperature environments.

[0107] Comparing Example 1 and Comparative Example 2, it can be seen that hydrogen-based mineral phase conversion iron tailings powder, as an admixture, performs significantly better than fly ash. Comparing Example 1 and Comparative Example 3, it can be seen that wollastonite powder has a significantly better shrinkage reduction effect than polyacrylonitrile fiber. Comparing Example 1 and Comparative Example 4, it can be seen that after replacing hydrogen-based mineral phase conversion iron tailings powder with ordinary iron tailings powder, the performance of the repair material deteriorates significantly in all aspects.

[0108] Comparing Example 1 and Comparative Example 5, it can be seen that lowering the calcination temperature of lightly calcined magnesia leads to a reduction in the setting time of the repair material, deterioration of its mechanical properties and freeze resistance, and a significant increase in shrinkage. This is because the lower calcination temperature reduces the density of lightly calcined magnesia, significantly accelerating its dissolution rate. It expands rapidly during the plastic stage of the slurry, failing to effectively compensate for the volume shrinkage of hard-burned magnesia after solidification.

[0109] By comparing Example 1 and Comparative Examples 6 and 7, it can be seen that both excessively high and excessively low calcination temperatures of recalcined magnesium oxide adversely affect the setting time and mechanical properties of the repair material. Excessively low calcination temperatures result in insufficiently dense crystal structure of the recalcined magnesium oxide, an excessively rapid reaction rate, and unsuitable workability. Excessively high calcination temperatures reduce the reactivity of the recalcined magnesium oxide, significantly slowing the reaction rate and significantly slowing the increase in low-temperature setting and hardening strength.

[0110] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rapid repair material suitable for marine engineering in low-temperature environments, characterized in that, The composition includes the following components by mass percentage: 1.0%~1.6% light-burned magnesia at 1000℃, 19.0%~24.0% dark-burned magnesia at 1700℃, 6.5%~8.0% potassium dihydrogen phosphate, 1.7%~2.5% boric acid, 5.0%~7.0% hydrogen-based mineral phase conversion iron tailings powder, 51.9%~56.5% iron tailings sand, 1.5%~1.7% wollastonite powder, 0.1%~0.2% water-reducing agent, and 6.1%~7.3% water.

2. The rapid repair material according to claim 1, characterized in that, The mass ratio of the 1000℃ lightly calcined magnesium oxide to the 1700℃ recalcined magnesium oxide is (1~1.5):(19.5~20).

3. The rapid repair material according to claim 1, characterized in that, Before use, mix 1000℃ light-burned magnesium oxide and 1700℃ re-burned magnesium oxide and grind them to a specific surface area of ​​300m². 2 / kg~350m 2 / kg.

4. The rapid repair material according to claim 1, characterized in that, The fineness of the hydrogen-based mineral phase conversion iron tailings powder is 1500~1600 mesh.

5. The rapid repair material according to claim 1, characterized in that, The fineness modulus of the iron tailings is 1.7 to 1.

9.

6. The rapid repair material according to claim 1, characterized in that, The fineness of the wollastonite powder is 300~500 mesh.

7. A method for preparing the rapid repair material according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The 1000℃ light-burned magnesium oxide and the 1700℃ re-burned magnesium oxide are mixed and then ground to a specific surface area of ​​300 m². 2 / kg~350m 2 / kg, to obtain mixture A; S2. Mix the boric acid, hydrogen-based mineral phase conversion iron tailings powder and water-reducing agent evenly, add an appropriate amount of water and stir evenly to obtain mixture B; S3. Mix potassium dihydrogen phosphate, iron tailings sand and wollastonite powder evenly to obtain mixture C; S4. Mix mixture A, mixture B and mixture C together, and add to the remaining water and mix evenly to obtain the rapid repair material.

8. The preparation method according to claim 7, characterized in that, In step S2, the mass of water added is 30% to 40% of the total mass of boric acid, hydrogen-based mineral phase conversion iron tailings powder, and water-reducing agent.

9. The application of the rapid repair material according to any one of claims 1 to 6 in the repair of cement concrete or natural reefs in tidal zones of frigid regions.

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