A high-ductility cement-based composite material for marine engineering and its preparation method

Abstract

This invention provides an ultra-high ductility cement-based composite material for marine engineering and its preparation method. The ultra-high ductility cement-based composite material comprises, by weight, the following raw materials: 250-500 parts cement clinker, 400-600 parts fly ash, 200-300 parts mineral powder, 100-150 parts silica fume, 160-240 parts metakaolin, 600-900 parts quartz sand, 10-20 parts organic synthetic fiber, 20-30 parts organic rust inhibitor, 180-240 parts water, and 1-8 parts water-reducing agent. The organic rust inhibitor provided by this invention can inhibit steel corrosion and chloride ion intrusion into concrete through the dual effects of binding chloride ions and forming a passivation film, thereby improving concrete durability. By controlling the mix proportions of the four mineral admixtures and the dosage of the synthetic fiber component, the concrete can better balance high strength, high ductility, high durability, high flowability, and excellent resistance to deformation.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an ultra-high ductility cement-based composite material for marine engineering and its preparation method. Background Technology

[0002] High-ductility concrete (HDC), also known as engineering cementitious composite (ECC), is a high-performance fiber-reinforced cementitious material. It exhibits multi-crack characteristics, strain hardening properties, and excellent crack control. Under bending and tensile loads, due to the bridging effect of the fibers, cracks can propagate stably, demonstrating significant multi-crack characteristics and strain hardening behavior. Based on these properties, HDC has become a new research hotspot. As a structural material, functionally graded material, and repair and reinforcement material, it can be used in seismic structures, shotcrete, highways, railways, port terminals, and other concrete structures requiring high toughness and durability.

[0003] In marine engineering construction, the preparation of high-ductility, large-volume concrete typically utilizes materials such as high-strength steel bars, high-performance concrete, and high-strength steel fibers. Under the high-temperature, high-humidity, and high-salinity service environment, these metallic materials are primarily susceptible to corrosion by chlorides and other harmful substances. Chloride penetration mainly relies on the diffusion effect of chloride ion concentration gradients in the concrete capillary fluid. In the marine environment, high concentrations of chloride ions diffuse from the marine environment into the concrete and penetrate the surface of the steel bars, forming chemical and electrochemical corrosion between the steel bars and concrete. This damages the passivation film on the steel bar surface, leading to a significant decline in the surface condition and mechanical properties of the steel. Over long-term service, steel bar corrosion and damage, stress concentration within the concrete causing localized expansion, and impaired bonding between the concrete and steel bars can lead to concrete cracking. This can even threaten the safety of the engineering structure and induce safety accidents.

[0004] In addition, concrete structures in projects such as offshore platforms are subjected to repeated wave loads and scouring, thus requiring concrete to have good impact resistance and fatigue resistance. Furthermore, with the frequent occurrence of disasters such as earthquakes and typhoons, which cause huge losses to infrastructure, higher requirements will be placed on the toughness and durability of large-volume concrete structures for infrastructure. Summary of the Invention

[0005] To address the need to improve the impermeability, corrosion resistance, and durability of high-ductility concrete in marine service environments, this section aims to provide an ultra-high ductility cement-based composite material for marine engineering and its preparation method.

[0006] On one hand, the present invention provides an ultra-high ductility cement-based composite material for marine engineering, comprising the following raw materials by weight: 250-500 parts of cement clinker, 400-600 parts of fly ash, 200-300 parts of mineral powder, 100-150 parts of silica fume, 160-240 parts of metakaolin, 600-900 parts of quartz sand, 10-20 parts of organic synthetic fiber, 20-30 parts of organic rust inhibitor, 180-240 parts of water, and 1-8 parts of water-reducing agent;

[0007] The organic rust inhibitor has the following molecular structure:

[0008] .

[0009] Furthermore, the cement clinker is either sulfoaluminate cement or ordinary Portland cement, with a strength grade of 42.5 or higher; the fly ash is Grade I fly ash with a specific surface area ≥350 m². 2 / kg; the silica content in the silica fume is ≥92%; the mineral powder is S95 grade mineral powder with a specific surface area ≥400m². 2 / kg; the metakaolin is obtained by calcining kaolin at 700~900℃ for 2~4h and grinding it to a specific surface area >350m². 2 / kg.

[0010] Fly ash, silica fume, slag powder, and metakaolin exhibit a pozzolanic effect, promoting the formation of more hydrated calcium silicate gel and enhancing the bond between concrete particles. Silica fume and metakaolin have even higher activity, rapidly increasing concrete density, improving impermeability, and significantly reducing chloride ion diffusion. The lower density of silica fume also acts as a filler and lubricant, optimizing microporous structure and reducing porosity.

[0011] Furthermore, the quartz sand has a particle size of 100-200 mesh; the water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of ≥25%.

[0012] Unlike manufactured sand, quartz sand has a certain degree of activity and can be hydrated, which can further reduce the porosity between cement and aggregates and increase the density of concrete. Quartz sand can also form crystallization centers, causing crystals to crystallize around the quartz powder / sand during cement hydration and promoting crystal growth, thus improving the integrity of aggregates and cementitious materials and the mechanical properties of concrete.

[0013] Furthermore, the organic synthetic fiber is selected from at least one of polyvinyl alcohol (PVA) fiber, polypropylene (PP) fiber, polyethylene (PE) fiber, and polyoxymethylene (POM) fiber.

[0014] Organic synthetic fibers themselves have certain tensile strength and modulus, do not change the chemical properties and composition of other materials in concrete, greatly improve the ductility of concrete, and obtain better mechanical properties such as impermeability, crack resistance, tensile strength, and bending resistance. Moreover, synthetic fibers have good affinity and bonding force with concrete, and are easy to distribute evenly in concrete, enhancing the interfacial bonding force.

[0015] Furthermore, the organic rust inhibitor is obtained by: 1) replacing N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine with cis-3,4-dichlorocyclobutene under alkaline conditions; 2) reacting the substituted product with DOTA-thiol under photoinitiator and ultraviolet irradiation conditions.

[0016] The molar ratio of the reaction between N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine and cis-3,4-dichlorocyclobutene is 1:(2.01~2.2); the molar ratio of the reaction between the substituted product and DOTA-mercapto is 1:(2.1~2.4).

[0017] Furthermore, the alkaline reagent is at least one of triethylamine, pyridine, N-diisopropylethylamine, sodium carbonate, and potassium carbonate, and the amount used is 1.05 to 1.2 times the molar amount of cis-3,4-dichlorocyclobutene; the photoinitiator is at least one of benzoin dimethyl ether, dimethylaminonaphthalene, azobisisobutyronitrile, benzoyl tert-butyl peroxide, and methyl ethyl ketone peroxide, and the amount used is 2 to 3 times the molar equivalent of cis-3,4-dichlorocyclobutene.

[0018] This invention improves the performance of concrete for marine engineering from two aspects. First, by selecting low-permeability siliceous aggregates such as fly ash, silica fume, slag powder, and metakaolin, the integrity and density of the concrete are improved, reducing porosity and defects, thereby reducing shrinkage cracking, minimizing water and salt penetration, and improving the durability of the concrete structure. The incorporation of high-modulus organic synthetic fibers enhances the fatigue resistance and impact resistance of the concrete. Second, a novel organic corrosion inhibitor is developed. On the one hand, its polar groups enhance the interfacial bonding between the concrete and synthetic fibers due to their compatibility with organic fibers and cementitious materials. On the other hand, it exerts a corrosion-inhibiting effect, chemically binding Fe ions in the reinforcing steel to form a metal passivation protective layer. Simultaneously, it binds penetrating anions through electrostatic adsorption, effectively preventing the migration of chloride ions and other harmful ions in the porous phase of the concrete.

[0019] On the other hand, the present invention provides a method for preparing the above-mentioned ultra-high ductility cement-based composite material for marine engineering, comprising the following steps:

[0020] Measure the appropriate weight proportions of cement, fly ash, silica fume, metakaolin, and mineral powder and dry mix them in a mixer for 2-3 minutes to obtain a mixed cementitious material; then slowly add organic synthetic fibers in batches along the mixing direction and continue dry mixing for 1-2 minutes; then add water, water-reducing agent, and organic rust inhibitor, and wet mix for 2-5 minutes until the mortar mixture is fluid; pour and vibrate the mortar mixture into shape, let it stand for 24 hours to demold, and cure it under standard conditions for 28 days to obtain ECC concrete.

[0021] To ensure uniform mixing of low-slump three-grade concrete, the mixing time of the mixer should be set to no less than 130 seconds. During the concrete pouring process, the slump of the concrete at the outlet and discharge port should be strengthened, and the vibration state of the concrete entering the formwork should be closely monitored to ensure that no laitance or bleeding occurs after the concrete is vibrated.

[0022] In this invention, the stirring, grinding, and calcining equipment used can be selected from existing equipment based on actual usage conditions, and there are no special requirements for the equipment model.

[0023] This invention also provides the application of the above-mentioned ultra-high ductility cement-based composite material for marine engineering in the outer protective layer of large-volume concrete in marine engineering.

[0024] The beneficial effects of this invention are:

[0025] In this invention, the organic rust inhibitor used contains carboxylic acid, tertiary amine, secondary amine, nitrogen heterocycle, and sulfur group. On the one hand, the amino group can react with Cl... - Electrostatic physical adsorption forms an adsorption layer on the surface of the steel bars, effectively preventing Cl from forming. - On the one hand, the amino, sulfur, and oxygen groups contain a large density of lone pair electrons, which can coordinate with Fe atoms to form strong chemical adsorption, creating a dense passivation protective film. This dual adsorption further inhibits charge transfer during corrosion, improves the stability and density of the protective film on the steel reinforcement surface, effectively inhibits metal corrosion, and enhances concrete durability. Furthermore, the rust inhibitor molecules are highly hydrophilic, allowing them to quickly penetrate and diffuse to the surface of concrete or steel reinforcement, inhibiting corrosion of both and extending the service life and durability of high-ductility concrete steel reinforcement used in large-volume marine engineering structures.

[0026] In this invention, the use of a large amount of mineral admixtures in the cementitious materials achieves the secondary utilization of industrial wastes such as fly ash, slag powder, silica fume, and kaolin. Furthermore, it contributes to the density and low porosity of the concrete, improving its impermeability and crack resistance. The synthetic fiber component, within its limited dosage range, can better integrate with the cementitious materials, enabling the concrete to achieve a good balance of high strength, high ductility, high fluidity, and excellent resistance to deformation and fatigue. Ultimately, this results in ultra-high ductility mass concrete that meets the requirements for high compressive strength, flexural strength, and impact toughness for marine engineering construction. Attached Figure Description

[0027] Figure 1 This is the 1H NMR spectrum of the organic rust inhibitor synthesized in this invention. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] The sources and properties of the raw materials used are as follows:

[0030] 42.5 high belite sulfoaluminate cement, supplied by Tangshan Arctic Bear Building Materials Co., Ltd., conforms to standard Q / TBJX25; its main technical indicators are shown in Table 1. Sulfoaluminate cement is a type of cement clinker with early strength, rapid hardening, low alkalinity, micro-expansion, and self-stressing properties, made primarily of anhydrous calcium sulfoaluminate (C4A3S) and dicalcium silicate (C2S), with appropriate amounts of limestone and gypsum as additives.

[0031] Table 1 Main Technical Indicators of Ordinary Sulfoaluminate Cement

[0032]

[0033] PO 42.5R ordinary Portland cement, supplied by China Resources Cement Holdings Limited, conforms to the standard GB175-2007. Its main technical indicators are shown in Table 2. Ordinary Portland cement is a cement clinker made primarily from Portland cement clinker, with the addition of active admixtures and an appropriate amount of gypsum, and is produced through fine grinding.

[0034] Table 2 Technical Specifications of Ordinary Portland Cement

[0035]

[0036] Grade I fly ash, fineness (45) m The residue on the sieve (m) is 8%, supplied by Guodian Shenneng Huayingshan Power Generation Co., Ltd.; S95 slag powder is alkali slag grinding supplied by Xiangtan Iron and Steel Co., Ltd. Yangchun New Iron and Steel Co., Ltd.; silica fume, particle size 0.17. m m, fineness (45) m The residue on the sieve (m) is 3%, and the technical specifications provided by Guizhou Ferroalloy Plant are shown in Table 3.

[0037] Table 3 Physical and technical properties of mineral powder, fly ash and silica fume

[0038]

[0039] Metakaolin is obtained by calcining kaolin at 850℃ for 3 hours, and its specific surface area after grinding is 398 m². 2 / kg, with an average particle size of 15.32. m m.

[0040] The chemical composition of the four mineral admixtures is shown in Table 4.

[0041] Table 4 Chemical composition of mineral admixtures (wt.%)

[0042]

[0043] Quartz sand, 80-120 mesh, 99.5% silica content, Mohs hardness 7, provided by Foshan Nanhai District Shitouyuan Building Materials Store. Its main technical indicators are shown in Table 5.

[0044] Table 5 Technical Specifications of Quartz Sand

[0045]

[0046] DUK-8 PVA fiber, with a diameter of 15 m m, 9mm in length, tensile strength 1990MPa, elongation at break 4~8%, elastic modulus 3.5GPa, provided by Guangdong Zhongtian Port Bridge Construction Engineering Co., Ltd.

[0047] PE monofilament short fiber, with a diameter of 15 m The product is m in length, 9mm in diameter, with a tensile strength of 390MPa, an elongation at break of 3.5~3.75%, and an elastic modulus of 5.1GPa. It was provided by Shandong Haosen Construction Engineering Co., Ltd.

[0048] HY-453 PP monofilament staple fiber, diameter 18 m m, length 9mm, tensile strength 570Mpa, elongation at break 15~20%, elastic modulus 4.3GPa, moisture absorption <0.1%, provided by Shandong Hongyao Copper Co., Ltd.

[0049] POM monofilament short fiber, diameter 37 m m, length 9mm, tensile strength 1000Mpa, elongation at break 30%, elastic modulus 15GPa, moisture absorption <0.1%, provided by Shanghai Shenxiang Concrete Fiber Co., Ltd.

[0050] PVA fiber is non-toxic and pollution-free, possesses excellent sunlight resistance, and exhibits good resistance to acidic and alkaline environments, making it suitable for various concrete application environments. It not only improves the frost resistance, abrasion resistance, and carbonation resistance of concrete, but also...

[0051] PP and PE fibers have low density, are insoluble in water, and have good resistance to acid, alkali, and salt corrosion. POM fibers inherit the high strength and high modulus of conventional copolymerized polyoxymethylene, resistance to organic solvents and salt solutions, resistance to strong alkali corrosion, and weather resistance. They have extremely strong resistance to alkaline solutions, seawater, and solvents.

[0052] Polycarboxylate superplasticizer, Sika (China) Co., Ltd., specific technical specifications are shown in Table 6.

[0053] Table 6 Technical Specifications of Polycarboxylate Superplasticizer

[0054]

[0055] In some embodiments of the present invention, the rust inhibitor used is synthesized by the following steps:

[0056] 1) 120 mL of dichloromethane was added to a 250 mL round-bottom flask equipped with a constant-pressure dropping funnel and a magnetic stirrer and placed in a 0 °C constant-temperature bath. 0.05 mol of N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine and 0.12 mol of triethylamine were added. After thorough stirring, 40 mL of a separately prepared dichloromethane solution containing 0.12 mol of cis-3,4-dichlorocyclobutene was slowly added dropwise to the flask over 1 hour. The mixture was stirred at 0 °C for 9 hours. After the reaction was complete, dichloromethane was added for dilution, the mixture was filtered, and repeatedly washed with saturated sodium chloride solution and deionized water until the organic phase was neutral. The organic phase was separated and collected, modified with anhydrous magnesium sulfate for 24 hours, filtered, and the dichloromethane was removed by rotary evaporation. The crude product was purified by silica gel column chromatography to obtain 167 g of the substituted product, with a yield of 85.2%.

[0057] 2) In a 500 mL beaker equipped with a mechanical stirrer, add 0.02 mol of the substituted product, 0.45 mmol of DOTA-mercapto, and 150 mL of anhydrous DMAc. After mixing thoroughly, add 0.04 mmol of 1,8-bis(dimethylaminonaphthalene) as a catalyst and stir to dissolve. Irradiate the mixture under a UV lamp (Intelli-Ray 600 UV curing oven, UV lamp irradiation distance 15 cm) at room temperature for 20 min to obtain a viscous mixture. After removing DMAc under vacuum, precipitate the mixture in 10 times its volume of diethyl ether to remove unreacted reactants and catalyst. Dry the precipitate under vacuum at 60 °C for 24 h to obtain the rust inhibitor, with a yield of 96.6%. The 1H NMR spectrum (400 MHz, deuterated chloroform) of the rust inhibitor molecules was measured using an AVANCE superconducting NMR spectrometer from Bruker, Germany. The results are shown in [Figure number missing]. Figure 1 .

[0058] Examples 1-12

[0059] Examples 1-12 provide an ultra-high ductility cement-based composite material for marine engineering, and the weight proportions of the raw materials used are shown in Table 7. In Examples 1-4, the amount of water is increased synchronously with the amount of cement to control the same water-cement ratio; the cement type in Examples 1-11 is ordinary sulfoaluminate cement, and the cement type in Example 12 is ordinary silicate cement.

[0060] Table 7. Raw material proportions (parts by weight) for ultra-high ductility cement-based composite materials used in marine engineering

[0061]

[0062] According to the dosage shown in Table 7, measure the corresponding weight parts of cement, fly ash, silica fume, metakaolin, and mineral powder in sequence and dry mix them in a mixer for 2-3 minutes to obtain a mixed cementitious material; then slowly add organic synthetic fibers in batches along the mixing direction and continue dry mixing for 1-2 minutes; then add water, water-reducing agent, and organic rust inhibitor, and wet mix for 3-5 minutes until the mortar mixture is fluid; pour and vibrate the mortar mixture into shape, let it stand for 24 hours to demold, and cure it under standard conditions for 28 days to obtain high ductility concrete.

[0063] Comparative Examples 1-2

[0064] High-ductility concrete was obtained by replacing the rust inhibitor provided in this invention with commercially available CPA corrosion inhibitor (purchased from Guangdong Jinlida Materials Technology Co., Ltd.) and KFS-1 type corrosion inhibitor (purchased from Guangxi Hengyong Building Materials Co., Ltd.), respectively, under the same conditions as in Example 2.

[0065] CPA corrosion inhibitor is an organic quaternary ammonium salt-based organic rust inhibitor, a grayish-white powder with a total alkali content of <0.4%; KFS-1 concrete corrosion inhibitor is a rust inhibitor formulated with surfactants, inorganic salts, and organic additives. The technical specifications for both are shown in Table 8, and the applicable standard is GB / T23439-2017 "Concrete Expansion Agent".

[0066] Table 8 Technical Specifications of Two Commercially Available Rust Inhibitors

[0067]

[0068] Comparative Example 3

[0069] Unlike Example 2, the amount of rust inhibitor used was reduced to 10 parts by weight.

[0070] Comparative Examples 4-5

[0071] Unlike Example 2, the synthetic fibers were in parts by weight of 2 parts and 25 parts respectively.

[0072] The concrete obtained in Examples 1-12 and Comparative Examples 1-5 were subjected to relevant tests, and the test results are summarized in Table 9.

[0073] Tensile properties: Tested using an MTS 10T universal testing machine, in accordance with JC / T 2461-2018 "Test Methods for Mechanical Properties of High-Ductility Fiber-Reinforced Cementitious Composites". Specimens were 100mm × 100mm × 100mm cubes, with displacement-controlled loading at a rate of 0.2mm / min.

[0074] Equivalent flexural strength, equivalent flexural toughness, flexural strength, and compressive strength were determined according to the performance indicators in the Technical Specification for Application of High-Ductility Concrete (DB62 / T 3159-2019). For compressive strength, 100mm×100mm×100mm cube specimens were used with a loading rate of 1.2MPa / s; for flexural strength, 100mm×100mm×400mm prism specimens were used with a loading rate of 0.2mm / min.

[0075] Chloride ion penetration resistance: The test was conducted according to the method for chloride ion penetration resistance test in GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Concrete".

[0076] Rebar corrosion rate: Referring to JGJ / T192-2009 "Technical Specification for Application of Rebar Corrosion Inhibitor", Q235 steel bars with a diameter of 6mm and a length of 1.2cm were embedded in concrete. After molding, the formwork was removed 72 hours later. After standard curing for 7 days, the concrete specimens were dried in an 80℃ oven for 24 hours. After cooling to room temperature, they were placed in a chloride ion solution (prepared with 5% sodium chloride + 95% water) for corrosion testing. The corrosion was accelerated by electric current for 28 days. Then, the concrete was broken up, the steel bars were removed, and the corroded steel bars in the bonded section were cut off. The corrosion products were cleaned with hydrochloric acid. The cleaned steel bars were weighed, and the mass of corrosion loss was calculated. The steel bar corrosion rate was then calculated (corrosion rate = (mass of uncorroded steel bars of a fixed length - mass of steel bars after removing corrosion products) / mass of uncorroded steel bars of a fixed length × 100%).

[0077] Table 9. Test results of relevant properties of high-ductility concrete

[0078]

[0079] The data in the table above shows that the performance indicators of the concrete in Comparative Examples 1 and 2 are all inferior to those in Example 2. This is particularly evident in the corrosion resistance and Cl-resistance of the reinforcing steel. -In terms of penetration performance, the rust inhibitor provided by this invention contains carboxylic acid, tertiary amine, nitrogen heterocycle, sulfur group, oxygen group and heterocycle, and has a better rust-inhibiting effect than the quaternary ammonium salt type rust inhibitor of Comparative Example 1 and the inorganic rust inhibitor of Comparative Example 2. Moreover, the mechanical properties are further optimized by increasing the dosage of the rust inhibitor. This is because the rust inhibitor of this invention has good affinity with synthetic organic fibers and cementitious materials, which can increase the bonding force and integrity of fibers, concrete and rust inhibitor.

[0080] Examples 1-4 demonstrate that the proportions of fly ash, mineral powder, silica fume, and metakaolin have a certain impact on the crack resistance and corrosion resistance of concrete. Silica fume, on the one hand, has the lowest density, which can fill micropores, improve the interface structure, and its smooth surface reduces internal friction and increases the fluidity of the mixture. On the other hand, its pozzolanic activity is the highest, which, within a certain dosage range, is beneficial to the increase of compressive strength in concrete. Metakaolin contains silica and alumina, which easily break bonds and bond in concrete to form a three-dimensional aluminosilicate gel, helping to improve compressive strength. However, both have high activity; excessive dosage can cause the concrete to harden too quickly, easily produce delamination or defects, increase the voids between granular materials, and be detrimental to the overall density and strength enhancement of the concrete. In Example 4, the silica fume content was close to 10%, and in Example 1, the metakaolin content exceeded 15%, resulting in insufficient mechanical properties of the concrete. The mineral powder coating on the surface of cement particles acts as an isolation layer, slowing down the overlap of cement hydration products. Fly ash, with its spherical particles, has a small specific surface area, low water adsorption capacity, and weaker activity than the other three materials, allowing for effective control of the concrete hydration rate as needed. Considering the above test results and construction costs, the concrete produced using the material proportions in Example 2 exhibits superior overall performance.

[0081] Comparing the results of Examples 2, 5-6, and 4-5, within the synthetic fiber dosage range limited by this invention, increasing the amount of synthetic fiber can improve the toughness and ductility of concrete; it also improves flexural and bending strength. Organic synthetic fibers possess high strength, elastic modulus, and moderate elongation at break, which can effectively inhibit plastic cracking and drying shrinkage in concrete, thereby improving its toughness and ductility. In Comparative Example 4, the synthetic fiber dosage was too low, resulting in brittle concrete with insufficient ductility, larger cracks at failure, and lower tensile toughness. In Comparative Example 5, the excessive synthetic fiber and fiber agglomeration caused low fluidity and defects in the concrete, significantly reducing compressive strength. Regarding the optimal selection of different synthetic fibers, Examples 2 and 7-9 showed that PVA and POM-doped concrete had higher toughness and corrosion resistance than PP and PE-doped concrete. This is because PP and PE have lower modulus and density, and their hydrophobic surfaces make them prone to agglomeration and floating. PVA fibers have good dispersibility in water, are not prone to sticking together, and can be evenly distributed in concrete; POM fibers have good thermal stability, extremely low water absorption, and can be used stably for a long time in high temperature or hot water; they are not decomposed by microorganisms, do not adsorb plankton in seawater, and do not grow mold.

[0082] A comparison of Examples 2 and 12 shows that ordinary sulfoaluminate cement is more effective than ordinary silicate cement in producing corrosion-resistant, highly ductile concrete. Compared to ordinary silicate cement, ordinary sulfoaluminate cement lacks the easily corroded tricalcium aluminate (C3A) and tricalcium silicate (C3S), thus exhibiting better corrosion resistance. Sulfoaluminate cement also possesses frost resistance, high impermeability, and lower requirements for production conditions and ambient temperature, allowing for production in low-latitude regions or during cold seasons.

[0083] This invention enhances the density of concrete by adjusting the formula and rationally controlling the proportion of four admixtures; it adjusts the ductility and toughness of concrete by adjusting the fiber ratio; and it effectively improves the concrete's resistance to chloride ion erosion and the steel reinforcement's resistance to corrosion by adding a multifunctional rust inhibitor, thus ensuring the quality of concrete projects and improving the durability and safety of buildings. It can be widely applied in the outer protective layer of marine engineering projects.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An ultra-high ductility cementitious composite material for marine engineering, characterized in that, The raw materials include, by weight parts, cement clinker 250-500 parts, fly ash 400-600 parts, mineral powder 200-300 parts, silica fume 100-150 parts, metakaolin 160-240 parts, quartz sand 600-900 parts, organic synthetic fiber 10-20 parts, organic rust inhibitor 20-30 parts, water 180-240 parts, water reducing agent 1-8 parts; the organic rust inhibitor is obtained by: 1) substitution of N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine with cis-3,4-dichlorocyclobutene under an alkali reagent to obtain a substitution product; 2) click reaction of the substitution product with DOTA-thiol under a photoinitiator and ultraviolet irradiation conditions; The molar ratio of the N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine to cis-3,4-dichlorocyclobutene is 1:(2.01-2.2); the molar ratio of the substitution product to DOTA-thiol is 1:(2.1-2.4); The organic rust inhibitor has the following molecular structure: 。 2. An ultra-high ductility cementitious composite material for marine engineering according to claim 1, wherein, The cement clinker is one of sulphoaluminate cement and ordinary portland cement, and the strength grade is 42.5 and above; the fly ash is grade I fly ash, and the specific surface area is ≥350m 2 / kg; the silica fume contains ≥92% of silicon dioxide; the mineral powder is S95 grade mineral powder, and the specific surface area is ≥400m 2 / kg; and the metakaolin is obtained by calcining kaolin at 700-900℃ for 2-4h and grinding to a specific surface area of >350m 2 / kg.

3. An ultra-high ductility cementitious composite material for marine engineering according to claim 1, wherein The particle size of the quartz sand is 80-200 mesh; the water reducing agent is a polycarboxylic acid water reducing agent, and the water reducing rate is ≥25%.

4. An ultra-high ductility cementitious composite for marine engineering according to claim 1, wherein The organic synthetic fiber is at least one of polyvinyl alcohol fiber, polypropylene fiber, polyethylene fiber, and polyformaldehyde fiber.

5. An ultra-high ductility cementitious composite for marine engineering according to claim 4, wherein The alkali reagent is at least one of triethylamine, pyridine, N-diisopropyl ethylamine, sodium carbonate, and potassium carbonate, and the amount is 1.01-1.2 times the molar amount of cis-3,4-dichlorocyclobutene; the photoinitiator is at least one of benzoin dimethyl ether, bisdimethylaminonaphthalene, azobis isobutyronitrile, benzoyl tert-butyl peroxide, and methyl ethyl ketone peroxide, and the amount is 2-3 times the molar equivalent of cis-3,4-dichlorocyclobutene.

6. A method of preparing a UHPC for marine engineering according to any one of claims 1 to 5, characterized in that, The following steps are included: The corresponding weight parts of cement, fly ash, silica fume, metakaolin, and mineral powder are measured and dry-mixed in a mixer for 2-3 min to obtain a mixed cementitious material; then the organic synthetic fiber is slowly added in batches along the mixing direction, and dry-mixing is continued for 1-2 min; then water, water reducing agent, and organic rust inhibitor are added, and wet-mixing is performed for 3-5 min until the mortar mixture is in a fluid state; the mortar mixture is poured and vibrated to form a mold, and is left to stand for 24 h before demolding, and is standard cured for 28 d to obtain a high ductility concrete.

7. Use of the ultra-high ductility cement-based composite material for marine engineering according to any one of claims 1-5 in the outer protective layer of marine engineering mass concrete.

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