Ultra-high performance concrete for deep sea floating wind power foundation and preparation method and application thereof

Abstract

This invention relates to the field of concrete building materials technology, and in particular to an ultra-high performance concrete for deep-sea floating wind turbine foundations, its preparation method, and its application, to alleviate the problem of cracking and seepage caused by biological erosion in existing deep-sea floating wind turbine foundations. It is composed of the following raw materials in parts by weight: 70-85 parts ordinary Portland cement; 15-30 parts magnesium oxychloride cement; 120-150 parts fine aggregate; 15-25 parts corundum powder; 25-40 parts ultrafine mineral admixtures; 8-15 parts densifying agent; 1.5-3.0 parts polycarboxylate superplasticizer; 0.05-0.2 parts defoamer; 5-12 parts multifunctional interface reinforcing agent; and nano-Fe3O4. 4 1-3 parts; steel fiber, by weight, 2.0-4.5 parts. The multifunctional interface reinforcing agent is formed by mixing 25-40 parts by weight of silver-zinc zeolite, 20-30 parts by weight of composite crystal nuclei, 15-25 parts by weight of zinc-loaded calcium sulfate whiskers, and 15-25 parts by weight of nano-copper-loaded boehmite, followed by high-speed shear dispersion. This invention achieves a balance between high-pressure impermeability and long-term stable ion release through the synergy of a dense reinforcing agent and a multifunctional interface reinforcing agent, ensuring engineering strength.

Description

Technical Field

[0001] This invention relates to the field of concrete building materials technology, and in particular to an ultra-high performance concrete for deep-sea floating wind power foundations, its preparation method and application. Background Technology

[0002] As offshore wind power expands from nearshore to deep-sea areas, floating wind turbine foundations have become the mainstream technology. Floating foundations operate in extreme environments characterized by high hydrostatic pressure, low temperatures, and dynamic fatigue loads, placing stringent demands on the mechanical properties, impermeability, and long-term durability of concrete materials. Ultra-high performance concrete, with its exceptionally high mechanical strength and excellent impermeability, is considered the ideal material for floating wind turbine foundations.

[0003] In recent years, scholars both domestically and internationally have conducted extensive research on UHPCs for deep-sea environments. Regarding high-pressure water densification technology, the addition of ultrafine mineral admixtures and nanomaterials has reduced capillary connectivity. Some studies have employed high-temperature sintering and rapid quenching processes to prepare highly active mineral phases, which are then continuously filled into the pores through secondary hydration reactions. Researchers have developed various strategies to prevent high-pressure water from penetrating along the fiber interface, including nano-CSH nuclei-induced hydration, silane coupling agent chemical grafting, and hydrophobic polymer coatings. In terms of fiber hybrid reinforcement, the hybridization of long and short fibers and fibers with different geometries has been widely reported. Tertiary fiber hybridization has become a standard technique in the UHPC field, with its reinforcement mechanism being the hierarchical control of cracks at different fiber scales.

[0004] However, scholars have discovered that the corrosive effect of deep-sea microorganisms on concrete materials has long been overlooked. Barotropic microorganisms such as sulfate-reducing bacteria and iron bacteria, widely present in deep-sea environments, can colonize and reproduce within the pores of concrete. Their metabolic activities significantly alter the chemical environment of the pore solution, inducing irreversible phase transitions and dissolution of cement hydration products. This bio-induced mineral phase transition is an internal self-destructive mechanism that cannot be resolved by simply relying on densification strategies. In the corrosive environment of deep-sea microorganisms, the fiber-matrix interface region, due to the presence of micropores and microcracks, becomes a preferential channel for microbial colonization and the penetration of metabolic products. Microbial activity in the interface region accelerates interfacial debonding, leading to premature loss of fiber reinforcement and decreased strength.

[0005] The study also found that existing ultra-high performance concrete used in deep-sea wind power foundations faces an inherent contradiction: increasing impermeability and density requires reducing porosity and connectivity, while maintaining long-term antibacterial ion release depends on a certain degree of pore connectivity as ion migration channels. Excessive density leads to the physical sequestration of antibacterial agents, with the release rate approaching zero; retaining interconnected pores allows high-pressure seawater infiltration, accelerating ion loss, both of which result in a significant decline in antibacterial function. How to simultaneously achieve high-pressure impermeability and long-term stable ion release is the technical problem that this invention aims to solve. Summary of the Invention

[0006] This invention provides an ultra-high performance concrete to alleviate the problem of cracking and seepage caused by biological erosion in existing deep-sea floating wind power foundations.

[0007] To alleviate the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0008] A high-performance concrete for deep-sea floating wind turbine foundations comprises the following raw materials in parts by weight: 70-85 parts ordinary Portland cement; 15-30 parts magnesium oxychloride cement; 120-150 parts fine aggregate; 15-25 parts corundum powder; 25-40 parts ultrafine mineral admixture; 8-15 parts densifying agent; 1.5-3.0 parts polycarboxylate superplasticizer; 0.05-0.2 parts defoamer; 5-12 parts multifunctional interface reinforcing agent; 1-3 parts nano-Fe3O4; and 2.0-4.5 parts steel fiber.

[0009] The multifunctional interface enhancer is composed of the following four components mixed in parts by weight: 25-40 parts of silver-zinc zeolite; 20-30 parts of composite crystal nuclei; 15-25 parts of zinc-loaded calcium sulfate whiskers; and 15-25 parts of nano-copper-loaded boehmite.

[0010] It should be noted that the densifying agent in this invention is mainly used to regulate the pore structure of concrete, improve impermeability, and enhance the migration stability of antibacterial ions; it is not the sole source of antibacterial activity. The silver-zinc zeolite, composite nuclei, zinc-loaded calcium sulfate whiskers, and nano-copper-loaded boehmite in the multifunctional interface reinforcing agent respectively provide Ag... + Zn 2+ and Cu 2+ The release source is that the material can still exhibit a certain antibacterial effect even without the addition of a densifying agent; however, due to the relatively interconnected pore structure, high-pressure seawater can more easily penetrate and accelerate ion loss, resulting in a significant decrease in long-term impermeability and performance retention rate after deep-sea immersion.

[0011] Furthermore, the silver-zinc zeolite is a Na-Y or Na-X zeolite processed with Ag. + and Zn 2+ The Ag:Zn molar ratio was 1:2-1:5 and the total metal ion loading was 8-15 wt% obtained by calcination after ion exchange.

[0012] Furthermore, the composite crystal nucleus incorporates Zn in situ during the process of creating nano-CSH crystal nuclei via a co-precipitation method. 2+ Preparation, Zn 2+ The mass ratio of the composite crystal to CSH is 1:50-1:20, and the particle size of the composite crystal nucleus is ≤50 nm.

[0013] Furthermore, the zinc-loaded calcium sulfate whiskers use calcium sulfate nanocrystals as a framework, and Zn is incorporated through surface adsorption or co-precipitation. 2+ Zn is loaded on the surface and internal defects of whiskers. 2+ The loading is 5-10 wt%, the diameter of the calcium sulfate nanocrystals is 50-200 nm, and the aspect ratio is 20-50.

[0014] Furthermore, the copper-loaded boehmite uses nano-boehmite as a carrier to transfer Cu through ion exchange or surface complexation. 2+ Fixed on the surface and between layers of boehmite, Cu 2+ The loading is 5-8 wt%, and the nanoboehmite particle size is 20-50 nm.

[0015] Furthermore, the densifying agent is composed of ultrafine slag powder, nano alumina, silica fume and diatomaceous earth in a mass ratio of 5:2:2:1, and is mixed and ground by an air jet mill to a specific surface area ≥1200 m² / kg; wherein the specific surface area of ​​the ultrafine slag powder is ≥800 m² / kg, the particle size of the nano alumina is ≤50 nm, and the diatomaceous earth is activated by calcination at 600℃.

[0016] Furthermore, the magnesium oxychloride cement is made by mixing lightly calcined active MgO and microsilica powder at a mass ratio of 1:0.8-1.2, and adding water glass as a reaction promoter; the water glass modulus is 2.0-3.3, and the amount added is 2-5% of the mass of lightly calcined active MgO.

[0017] Furthermore, the nano-Fe3O4 has a particle size of 20-50 nm and is prepared by co-precipitation.

[0018] Furthermore, the ultrafine mineral admixture is made by mixing metakaolin, rice husk ash, tuff, and mineral powder in a mass ratio of 2.0-4.0:0.5-1.5:1.5-3.0:3.0-6.0, and then grinding with a grinding aid until the specific surface area is ≥800 m² / kg; the amount of grinding aid added is 0.02-0.10% of the mass of the mixed powder.

[0019] A method for preparing ultra-high performance concrete includes the following steps:

[0020] (1) Put ordinary silicate cement, magnesium oxide cement, corundum powder, ultrafine mineral admixture, densifying agent and nano Fe3O4 into a mixer and dry mix to obtain mixed powder.

[0021] (2) Weigh out the silver-zinc zeolite, composite crystal nuclei, zinc-loaded calcium sulfate whiskers and nano-copper-loaded boehmite according to the mass fraction and then mechanically premix them. Then place them in a high-speed shear mixer and shear and disperse them for 1-5 min at 2000-5000 r / min to obtain a multifunctional interface enhancer.

[0022] (3) Add the multifunctional interface enhancer, fine aggregate and steel fiber to the mixed powder obtained in step (1) and continue to dry mix;

[0023] (4) Add the polycarboxylate superplasticizer and defoamer to water, stir and dissolve evenly to obtain a liquid component;

[0024] (5) Add the liquid component from step (4) to the mixture obtained in step (3) in multiple portions, stirring after each addition, and then put the resulting mixture into a mold and vibrate to shape it.

[0025] (6) After demolding, the specimens are placed under standard curing conditions and cured until the specified age.

[0026] The beneficial effects of this invention are analyzed as follows:

[0027] The ultrafine slag powder, nano-alumina, and diatomaceous earth in the densifying agent are filled through multi-scale gradation. First, the originally interconnected capillary pores at the micron or even submicron level are compressed to the 100nm level. At the same time, the moderate volume expansion generated by the hydration of magnesium oxycephalolithic cement compensates for the inherent shrinkage of the cement substrate and avoids the formation of new microcracks induced by shrinkage stress. At this scale, the viscous resistance of high-pressure water decreases with the pore size, and the seepage resistance of high-pressure water in the capillary pores increases significantly, reducing the continuous seepage channels and thus reducing the water permeability coefficient. It should be emphasized that this process does not completely eliminate nanoscale pores, but retains them as channels for the slow diffusion of antibacterial ions. This invention differs from the core design concept of extreme densification, that is, while ensuring high pressure impermeability, it reserves the necessary molecular diffusion path for ion release.

[0028] This invention achieves a balance between high-pressure impermeability and long-term stable ion release through the synergistic effect of a densifying agent and a multifunctional interface enhancer. The ultrafine slag powder, nano-alumina, and diatomaceous earth in the densifying agent are filled through multi-scale gradation, progressively dividing and blocking the originally interconnected capillary pores at the micron and even submicron levels. However, relying solely on densification can lead to excessive pore blockage, causing antibacterial ions to lose their migration pathways. It should be noted that the compression of pores by the densifying agent in this invention does not uniformly compress all pores into a single narrow nano-scale region, but rather narrows the pore size distribution from a micron-scale broad peak to a submicron-scale distribution through multi-scale particle gradation, while retaining a small number of nano-sized micropores as molecular diffusion pathways for ion migration. At this point, the zinc-loaded calcium sulfate whiskers in the multifunctional interface enhancer, with their submicron diameter and micron length, act as ion bridges in some of the incompletely filled pore channels. The zinc-loaded calcium sulfate whiskers are distributed in the matrix pores and the interface transition zone, and can serve as Zn... 2+The slow-release carrier helps prolong the ion release pathway and improves the erosion resistance of the interface region; while the composite nucleus and nano-copper-loaded boehmite directly penetrate the dense, inaccessible gel pore network. Silver-zinc zeolite, due to its larger size, can provide initial antibacterial activity. At these scales, high-pressure seawater cannot form continuous flow due to significantly increased viscous resistance, but Ag... + Zn 2+ Cu 2+ Antibacterial ions can still achieve sustained release to a certain extent. Detailed Implementation

[0029] Preparation method of silver-zinc zeolite: Na-Y type zeolite with a silica-to-alumina ratio of 5.2 and an average particle size of 2 μm was placed in a muffle furnace and calcined at 400℃ for 2 h to remove adsorbed water from the pores. The activated zeolite was then added to a mixed aqueous solution containing 0.1 mol / L AgNO3 and 0.5 mol / L Zn(NO3)2. + With Zn 2+ The molar ratio was 1:5, and the solid-liquid ratio was 1:10 g / mL. The ion exchange reaction was carried out with stirring in an 80℃ constant temperature water bath for 6 h. After the reaction, the mixture was filtered, washed three times with deionized water, and the filter cake was dried at 105℃ for 2 h. It was then transferred to a muffle furnace and calcined at 450℃ for 2 h at a heating rate of 5℃ / min. After cooling to room temperature in the furnace, the mixture was ground through a 200-mesh sieve to obtain silver-zinc zeolite.

[0030] Preparation method of composite nuclei: In-situ introduction of Zn using co-precipitation method. 2+ Preparation of nano-CSH composite crystal nuclei. Ca(NO3)2·4H2O and Na2SiO3·9H2O were dissolved in deionized water to prepare 0.5 mol / L Ca(NO3)2 and 0.5 mol / L Na2SiO3 solutions with a Ca / Si molar ratio of 1.0. 500 mL of Ca(NO3)2 solution was taken, and Zn(NO3)2 solid was added to it, so that Zn... 2+ The ratio of Zn to the target CSH mass is 1:35, i.e., according to Zn 2+ Add Zn(NO3)2 at a CSH mass ratio of 1:35. Transfer the solution to a 1L three-necked flask, adjust the pH to 12.5 with 1M NaOH, and mechanically stir at 300 r / min in a 25℃ constant temperature water bath. Add 500mL of Na2SiO3 solution dropwise to the above Ca(NO3)2 and Zn2 mixture at a rate of 5 mL / min. 2+In the mixture, the pH was maintained within the range of 12.5 ± 0.2 during the dropwise addition. After the dropwise addition was complete, the reaction was stirred for another 2 h. After the reaction was completed, the suspension was centrifuged at 8000 r / min for 15 min, the supernatant was discarded, and the precipitate was washed three times with deionized water, centrifuged after each wash. The washed precipitate was placed in a vacuum drying oven and dried at 50℃ and -0.09 MPa for 24 h to obtain a light gray powder.

[0031] Preparation method of copper-loaded boehmite nanoparticles: Using boehmite nanoparticles as a carrier, Cu is immobilized by ion exchange method. 2+ Nano-boehmite was prepared via a hydrothermal method: 0.2 mol Al(NO3)3·9H2O and 0.5 mol urea were dissolved in 500 mL of deionized water, transferred to a hydrothermal reactor, and reacted at 180℃ for 12 h. After natural cooling, the mixture was centrifuged, and the precipitate was washed three times each with deionized water and anhydrous ethanol, and then dried at 80℃ for 12 h to obtain nano-boehmite. Transmission electron microscopy revealed its morphology to be flake-like with an average particle size of 30 nm, and its X-ray diffraction pattern was consistent with the γ-AlOOH standard card. 5 g of nano-boehmite was dispersed in 100 mL of 0.15 mol / L Cu(NO3)2 solution, and the pH was slowly adjusted to 6.5 with a 1:10 volume ratio of dilute ammonia. The reaction was carried out in a 60℃ constant temperature water bath with stirring at 250 r / min for 3 h. The pH was monitored and maintained at 6.5 ± 0.1 during the reaction. After the reaction is complete, filter the solution and wash the filter cake repeatedly with deionized water until Cu is undetectable in the filtrate using Na2S solution. 2+ No black CuS precipitate was formed. The sample was dried at 80℃ for 12 h, ground through a 200-mesh sieve, and copper-loaded boehmite nanoparticles were obtained. Cu content was determined by flame atomic absorption spectrometry. 2+ The load is 6.5 wt%.

[0032] Preparation of zinc-loaded calcium sulfate whiskers:

[0033] Calcium sulfate nanocrystals were prepared using calcium sulfate dihydrate as raw material via a hydrothermal method. Calcium sulfate dihydrate and deionized water were mixed at a solid-liquid ratio of 1:20, and a crystal form control agent (such as magnesium chloride, added at 2% of the calcium sulfate mass) was added. The mixture was transferred to a hydrothermal reactor and reacted at 140℃ for 4 hours. After the reaction, the mixture was allowed to cool naturally, filtered, washed three times with deionized water, and dried at 80℃ for 12 hours to obtain calcium sulfate nanocrystals. SEM observation showed that the whisker diameter was approximately 80 nm and the aspect ratio was approximately 30. 10 g of the above calcium sulfate nanocrystals were dispersed in 200 mL of a 0.1 mol / L Zn(NO3)2 solution, and the pH was adjusted to 6.0 with dilute ammonia. The mixture was stirred at 200 rpm for 2 hours in a 50℃ water bath. After the reaction, the mixture was filtered and washed with deionized water until no Zn was detected in the filtrate. 2+(Tested with Na2S solution), dried at 105℃ for 6 hours, to obtain zinc-loaded calcium sulfate whiskers.

[0034] Preparation of the multifunctional interface reinforcing agent: Silver-zinc zeolite, composite crystal nuclei, zinc-loaded calcium sulfate whiskers, and nano-copper-loaded boehmite were weighed according to their mass proportions. These four components were added to a high-speed shear mixer and premixed at 500 r / min for 2 min, followed by high-speed shear dispersion at 3000 r / min for 2 min to obtain the multifunctional interface reinforcing agent. The obtained multifunctional interface reinforcing agent can be dry-mixed with cement, magnesium oxychloride cement, corundum powder, ultrafine mineral admixtures, densifying agents, and nano-Fe3O4 during concrete mixing, or added after premixing of the powders and continued dry-mixing.

[0035] Magnesium oxychloride cement is produced by mixing lightly calcined active MgO and silica fume at a mass ratio of 1:1.0, with water glass added as a reaction accelerator, and then mixing at high speed for 10 minutes until homogeneous. Tests showed that under standard curing conditions, the 3-day expansion rate of this magnesium oxychloride cement was 0.08%, the 7-day expansion rate was 0.12%, and the 28-day expansion rate was 0.15%. The expansion behavior was mainly concentrated in the early stage, and tended to stabilize in the later stage, indicating that it can effectively compensate for the shrinkage of the cementitious substrate without causing excessive expansion and cracking in the later stage.

[0036] Test method description:

[0037] The chloride ion diffusion coefficient is referenced to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete";

[0038] The impermeability grade was determined according to the stepwise pressure method in GB / T 50082-2009;

[0039] Compressive strength and flexural strength were determined in accordance with GB / T 17671-2021.

[0040] Antimicrobial activity test of sulfate-reducing bacteria: The test strain was sulfate-reducing bacteria *Desulfovibriodesulfuricans*, and the culture medium was Postgate B. Specimens were processed into cubic samples with dimensions of 20 mm × 20 mm × 20 mm. After surface cleaning and sterilization, they were placed in sterile simulated seawater and immersed at 25 ℃ for 28 days to obtain the specimen extract. A culture of sulfate-reducing bacteria in the logarithmic growth phase was diluted with sterile Postgate B medium to approximately 1.0 × 10^6 CFU / mL. An equal volume of the specimen extract was mixed with the sulfate-reducing bacteria culture and incubated anaerobically at 35 ℃ for 24 h. After incubation, the culture was serially diluted with sterile Postgate B medium from 10^-1 to 10^-6. Appropriate dilutions were spread onto Postgate B agar plates and incubated anaerobically at 35 ℃. The colony count was then performed. Using sulfate-reducing bacteria suspension not mixed with the specimen extract as a blank control group, the inhibition rate was calculated according to the following formula:

[0041] Antibacterial rate (%) = [(N0 - N1) / N0] × 100%

[0042] In the formula, N0 is the number of colonies in the blank control group, in CFU / mL; N1 is the number of colonies after the specimen is treated with the extract, in CFU / mL.

[0043] Example 1

[0044] The composition includes 78 parts ordinary silicate cement, 22 parts magnesium oxychloride cement, 135 parts fine aggregate, 20 parts corundum powder, 32 parts ultrafine mineral admixture, 12 parts densifying agent, 2.2 parts polycarboxylate superplasticizer, 0.12 parts defoamer, 8.5 parts multifunctional interface reinforcing agent, 2 parts nano-Fe3O4, and 3.5 parts steel fiber. The fine aggregate is quartz sand with a particle size of 0.1-0.5 mm; the corundum powder particle size does not exceed 10 μm; the ultrafine mineral admixture has a specific surface area of ​​not less than 800 m² / kg; the polycarboxylate superplasticizer has a solid content of 40% and a water reduction rate of not less than 35%; the defoamer is polyether-modified organosilicon; the nano-Fe3O4 is prepared by co-precipitation method with an average particle size of 35 nm; and the steel fiber is straight, 13 mm long, 0.2 mm in diameter, and has a tensile strength of not less than 2800 MPa. The multifunctional interface enhancer is formed by mechanically premixing 32 parts by mass of silver-zinc zeolite, 25 parts by composite crystal nuclei, 20 parts by mass of zinc-loaded calcium sulfate whiskers, and 23 parts by mass of nano-copper-loaded boehmite, followed by high-speed shear dispersion.

[0045] The ultrafine mineral admixture used in this embodiment has a ratio of metakaolin: rice husk ash: tuff: mineral powder = 3.5:1.2:2.5:5.0, with a specific surface area of ​​820 m² / kg. The densifying agent has a specific surface area of ​​1220 m² / kg. The mass ratio of lightly calcined MgO to microsilica in the magnesium oxychloride cement is 1:0.9, and the amount of water glass added is 3.5% of the mass of MgO.

[0046] The preparation method includes the following steps:

[0047] The first step is powder premixing: ordinary silicate cement, magnesium oxide cement, corundum micro powder, ultrafine mineral admixture, densifying agent, and nano Fe3O4 are put into a double planetary mixer and dry-mixed for 3 minutes at a stirring speed of 45 r / min to ensure that each powder component is evenly dispersed.

[0048] The second step is the pre-dispersion of the multifunctional interface enhancer: Weigh out 32 parts of silver-zinc zeolite, 25 parts of composite crystal nuclei, 20 parts of zinc-loaded calcium sulfate whiskers, and 23 parts of nano-copper-loaded boehmite. Add the above components to a high-speed shear mixer, premix for 2 min at 500 r / min, and then disperse at 3000 r / min for 2 min to obtain the multifunctional interface enhancer.

[0049] The third step is aggregate mixing: add the multifunctional interface enhancer, fine aggregate and steel fiber to the mixed powder from the first step, and continue dry mixing for 2 minutes.

[0050] Step 4, preparation of liquid components: Add polycarboxylate superplasticizer and defoamer to deionized water accounting for 75% of the total water volume. Adjust the fluidity of the remaining 25% of water during the mixing process. The water-cement ratio is 0.16-0.20.

[0051] Step 5, mixing and molding: Add the liquid component from step 4 to the mixture from step 3 in two batches, stirring for 2 minutes after each addition, for a total stirring time of 5 minutes at a stirring speed of 60 r / min. Pour the mixture into a mold, vibrate it on a vibrating table for 30 seconds, cover the surface with a plastic film, and let it stand at 20±2℃ for 24 hours before demolding.

[0052] Step 6, curing: After demolding, the specimens are placed in a standard curing room and cured to the specified age. The curing temperature is 20±2℃ and the relative humidity is not less than 95%.

[0053] Test results: 28-day compressive strength 147.3 MPa, 28-day flexural strength 28.6 MPa, chloride ion diffusion coefficient 0.32 × 10⁻⁶ MPa. -12 m 2 / s, impermeability grade P12

[0054] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 CFU / mL, the colony count after treatment with the extract in this example was 1.1 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 87.2%.

[0055] Long-term immersion test simulating deep-sea environment: Specimens cured for 28 days were placed in a high-pressure seawater immersion device with a hydrostatic pressure of 10 MPa and a temperature of 4±1℃. The artificial seawater formula conformed to ASTM D1141. After immersion for 180 days, the specimens were removed and tested. The compressive strength retention rate was 91.2%, and the chloride ion diffusion coefficient was 0.35×10⁻⁶. -12 m 2 / s, impermeability grade P12.

[0056] Example 2

[0057] The difference between this embodiment and Embodiment 1 lies in the different mass fractions of the raw materials, while the preparation method remains the same. The specific composition is as follows: 72 parts ordinary silicate cement, 28 parts magnesium oxychloride cement, 140 parts fine aggregate, 22 parts corundum micro powder, 36 parts ultrafine mineral admixture, 10 parts densifying agent, 2.5 parts polycarboxylate superplasticizer, 0.15 parts defoamer, 10 parts multifunctional interface reinforcing agent, 2.5 parts nano-Fe3O4, and 4.0 parts steel fiber. The multifunctional interface reinforcing agent contains: 28 parts silver-zinc zeolite, 28 parts composite crystal nuclei, 22 parts zinc-loaded calcium sulfate whiskers, and 22 parts nano-copper-loaded boehmite.

[0058] The preparation parameters for silver-zinc zeolite, composite crystal nuclei, zinc-loaded calcium sulfate whiskers, and nano-copper-loaded boehmite are consistent with those in Example 1.

[0059] Test results: 28-day compressive strength 151.2 MPa, 28-day flexural strength 29.1 MPa, chloride ion diffusion coefficient 0.28 × 10⁻⁶ -12 m 2 / s, impermeability grade P12.

[0060] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 CFU / mL, the colony count after treatment with the extract in this example was 7.8 × 10⁻⁶. 4 CFU / mL, with an antibacterial rate of 90.9%.

[0061] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 92.5%, and the chloride ion diffusion coefficient was 0.31×10⁻⁶. -12 m 2 / s, impermeability grade P12.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 1 is that silver-zinc zeolite is not added to the multifunctional interface reinforcing agent; the remaining components and their mass proportions are exactly the same as in Example 1. Specific composition: 78 parts ordinary silicate cement, 22 parts magnesium oxide cement, 135 parts fine aggregate, 20 parts corundum micro powder, 32 parts ultrafine mineral admixture, 12 parts densifying agent, 2.2 parts polycarboxylate superplasticizer, 0.12 parts defoamer, 8.5 parts multifunctional interface reinforcing agent, 2 parts nano-Fe3O4, and 3.5 parts steel fiber. The multifunctional interface reinforcing agent is a mixture of 25 parts composite crystal nuclei, 20 parts zinc-loaded calcium sulfate whiskers, and 23 parts nano-copper-loaded boehmite, totaling 68 parts by mass, which, after conversion according to the proportions of Example 1, is taken as 8.5 parts.

[0064] The preparation method is the same as in Example 1.

[0065] Test results: 28-day compressive strength 141.5 MPa, 28-day flexural strength 26.8 MPa, chloride ion diffusion coefficient 0.45×10⁻⁶ -12 m 2 / s, impermeability grade P12.

[0066] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 The CFU / mL count of the comparative sample treated with the extract was 6.7 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 22.1%.

[0067] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 82.5%, and the chloride ion diffusion coefficient was 0.68 × 10⁻⁶. -12 m 2 / s, the impermeability grade drops to P10.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that no composite crystal nucleus is added to the multifunctional interface enhancer; the remaining components and mass proportions are exactly the same as in Example 1. The multifunctional interface enhancer is a mixture of 32 parts silver-zinc zeolite, 20 parts zinc-loaded calcium sulfate whiskers, and 23 parts nano-copper-loaded boehmite, with a total mass of 75 parts, which is 8.5 parts after being converted according to the proportions of Example 1.

[0070] The preparation method is the same as in Example 1.

[0071] Test results: 28-day compressive strength 133.6 MPa, 28-day flexural strength 24.9 MPa, chloride ion diffusion coefficient 0.68 × 10⁻⁶ -12 m 2 / s, impermeability grade P10.

[0072] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶.5 The CFU / mL count of the comparative sample treated with the extract was 5.4 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 37.2%.

[0073] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 76.8%, and the chloride ion diffusion coefficient was 1.05 × 10⁻⁶. -12 m 2 / s, the impermeability grade drops to P8.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that zinc-loaded calcium sulfate whiskers are not added to the multifunctional interface enhancer; the remaining components and mass proportions are exactly the same as in Example 1. The multifunctional interface enhancer is a mixture of 32 parts silver-zinc zeolite, 25 parts composite crystal nuclei, and 23 parts nano-copper-loaded boehmite, with a total mass of 80 parts, which is 8.5 parts after being converted according to the proportions of Example 1.

[0076] The preparation method is the same as in Example 1.

[0077] Test results: 28-day compressive strength 137.2 MPa, 28-day flexural strength 25.7 MPa, chloride ion diffusion coefficient 0.52 × 10⁻⁶ -12 m 2 / s, impermeability grade P12.

[0078] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 The CFU / mL count of the comparative sample treated with the extract was 4.8 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 44.2%.

[0079] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 79.3%, and the chloride ion diffusion coefficient was 0.78 × 10⁻⁶. -12 m 2 / s, the impermeability grade drops to P10.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that the multifunctional interface enhancer does not contain nano-copper-loaded boehmite; the remaining components and mass fractions are exactly the same as in Example 1. The multifunctional interface enhancer is a mixture of 32 parts silver-zinc zeolite, 25 parts composite crystal nuclei, and 20 parts zinc-loaded calcium sulfate whiskers, with a total mass of 77 parts, which is 8.5 parts after being converted according to the proportions of Example 1.

[0082] The preparation method is the same as in Example 1.

[0083] Test results: 28-day compressive strength 139.8 MPa, 28-day flexural strength 26.3 MPa, chloride ion diffusion coefficient 0.48 × 10⁻⁶ -12 m 2 / s, impermeability grade P12.

[0084] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 The CFU / mL count of the comparative sample treated with the extract was 3.9 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 54.7%.

[0085] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 81.0%, and the chloride ion diffusion coefficient was 0.72×10⁻⁶. -12 m 2 / s, the impermeability grade drops to P10.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 1 is that no densifying agent is added; the remaining components and mass fractions are exactly the same as in Example 1.

[0088] The preparation method is the same as in Example 1.

[0089] Test results: 28-day compressive strength 128.4 MPa, 28-day flexural strength 23.5 MPa, chloride ion diffusion coefficient 1.25 × 10⁻⁶ -12 m 2 / s, impermeability grade P8.

[0090] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 The CFU / mL count of the comparative sample treated with the extract was 3.2 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 62.8%.

[0091] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 68.5%, and the chloride ion diffusion coefficient was 2.15 × 10⁻⁶. -12 m 2 / s, the impermeability grade drops to P6.

[0092] Comparative Example 6

[0093] The difference between this comparative example and Example 1 is that magnesium oxychloride cement is not added; instead, it is replaced with an equal amount of ordinary Portland cement. Specifically, the composition is: 100 parts of ordinary Portland cement (78 parts originally plus 22 parts replaced), with the remaining components and their proportions identical to those in Example 1.

[0094] The preparation method is the same as in Example 1.

[0095] Test results: 28-day compressive strength 131.2 MPa, 28-day flexural strength 24.1 MPa, chloride ion diffusion coefficient 0.82 × 10⁻⁶ -12 m 2 / s, impermeability grade P10.

[0096] Antibacterial test: The colony count in the blank control group was 8.6 × 10⁻⁶. 5 The CFU / mL count of the comparative specimen treated with the extract was 4.1 × 10⁻⁶. 5 CFU / mL, with an antibacterial rate of 52.3%.

[0097] Long-term immersion test in simulated deep-sea environment: After immersion for 180 days, the compressive strength retention rate was 74.2%, and the chloride ion diffusion coefficient was 1.18 × 10⁻⁶. -12 m 2 / s, the impermeability grade drops to P8.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of ultra-high performance concrete for deep-sea floating wind turbine foundations, characterized in that, The raw material composition includes the following parts by weight: 70-85 parts ordinary Portland cement; 15-30 parts magnesium oxychloride cement; 120-150 parts fine aggregate; 15-25 parts corundum powder; 25-40 parts ultrafine mineral admixture; 8-15 parts densifying agent; 1.5-3.0 parts polycarboxylate superplasticizer; 0.05-0.2 parts defoamer; 5-12 parts multifunctional interface reinforcing agent; 1-3 parts nano Fe3O4; and 2.0-4.5 parts steel fiber. The multifunctional interface enhancer is formed by mixing 25-40 parts by mass of silver-zinc zeolite, 20-30 parts by composite crystal nuclei, 15-25 parts by mass of zinc-loaded calcium sulfate whiskers, and 15-25 parts by mass of nano-copper-loaded boehmite, followed by high-speed shear dispersion.

2. The ultra-high performance concrete according to claim 1, characterized in that, The silver-zinc zeolite is a Na-Y or Na-X zeolite processed with Ag. + and Zn 2+ The Ag:Zn molar ratio was 1:2-1:5 and the total metal ion loading was 8-15 wt% obtained by calcination after ion exchange.

3. The ultra-high performance concrete according to claim 2, characterized in that, The composite nucleus is in-situ introduced with Zn during the process of nano-CSH nucleation via co-precipitation. 2+ Preparation, Zn 2+ The mass ratio of the composite crystal to CSH is 1:50-1:20, and the particle size of the composite crystal nucleus is ≤50 nm.

4. The ultra-high performance concrete according to claim 3, characterized in that, The zinc-loaded calcium sulfate whiskers use calcium sulfate nanocrystals as a framework and incorporate Zn through surface adsorption or co-precipitation. 2+ Zn is loaded on the surface and internal defects of whiskers. 2+ The loading is 5-10 wt%, the diameter of the calcium sulfate nanocrystals is 50-200 nm, and the aspect ratio is 20-50.

5. The ultra-high performance concrete according to claim 4, characterized in that, The copper-loaded boehmite uses nano-boehmite as a carrier to transfer Cu through ion exchange or surface complexation. 2+ Fixed on the surface and between layers of boehmite, Cu 2+ The loading is 5-8 wt%, and the nano-boehmite particle size is 20-50 nm.

6. The ultra-high performance concrete according to claim 5, characterized in that, The densifying agent is composed of ultrafine slag powder, nano alumina, silica fume and diatomaceous earth in a mass ratio of 5:2:2:1, and is mixed and ground by an air jet mill to a specific surface area ≥1200 m² / kg; wherein the specific surface area of ​​the ultrafine slag powder is ≥800 m² / kg, the particle size of the nano alumina is ≤50 nm, and the diatomaceous earth is activated by calcination at 600℃.

7. The ultra-high performance concrete according to claim 6, characterized in that, The magnesium oxy-cement is made by mixing lightly calcined active MgO and microsilica powder at a mass ratio of 1:0.8-1.2, and adding water glass as a reaction promoter. The water glass modulus is 2.0-3.3, and the amount added is 2-5% of the mass of lightly calcined active MgO.

8. The ultra-high performance concrete according to claim 7, characterized in that, The nano-Fe3O4 has a particle size of 20-50 nm and is prepared by co-precipitation.

9. The ultra-high performance concrete according to claim 8, characterized in that, The ultrafine mineral admixture is made by mixing metakaolin, rice husk ash, tuff, and mineral powder in a mass ratio of 2.0-4.0:0.5-1.5:1.5-3.0:3.0-6.0, adding grinding aid and grinding to a specific surface area ≥800 m² / kg, with the amount added being 0.02-0.10% of the mass of the mixed powder.

10. A method for preparing ultra-high performance concrete as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) Put ordinary silicate cement, magnesium oxide cement, corundum powder, ultrafine mineral admixture, densifying agent and nano Fe3O4 into a mixer and dry mix; (2) Weigh the silver-zinc zeolite, composite crystal nuclei, zinc-loaded calcium sulfate whiskers and nano-copper-loaded boehmite according to the mass fraction and mechanically premix them. Then place them in a high-speed shear mixer and shear and disperse them for 1-5 min at 2000-5000 r / min to make the components uniformly dispersed and obtain a multifunctional interface enhancer. (3) Add the multifunctional interface enhancer, fine aggregate and steel fiber obtained in step (2) to the mixed powder in step (1) and continue to dry mix; (4) Add the polycarboxylate superplasticizer and defoamer to the water and stir until dissolved; (5) Add the liquid component from step (4) to the mixture from step (3) in multiple portions, stirring after each addition, and then fill the mixture into a mold and vibrate to shape it. (6) After demolding, the specimens are placed under standard curing conditions and cured until the specified age.