Maritime work cement-based material floating structure protection layer and preparation method thereof

Abstract

The invention provides a maritime work cement-based material floating structure protection layer and a preparation method thereof, and relates to an ocean engineering material. The maritime work cement-based material floating structure protection layer comprises a surface layer and a bottom layer, and a cementing material of the surface layer is composed of cement, mineral powder, nano SiO2 and calcium carbonate whiskers according to the mass ratio of 40: 43-47: 9-11: 4-6; basalt fibers are doped into the surface layer, and the volume mixing amount of the basalt fibers is controlled to be 1.5%-2.5%; the bottom layer is formed by mixing cement, silica fume, metakaolin, quartz sand powder and elastic latex powder according to the mass ratio of 60: (9-11): (9-11): (9-11): (9-11); and an iron gauze is embedded in the bottom layer. The thickness of the surface layer is 3-5 mm, and the thickness of the bottom layer is 3-5 mm. The maritime work cement-based material floating structure is better optimized through the protective layer, a more stable and durable floating platform for mariculture and the like can be provided, and the development requirements of deep and far sea ocean engineering are better met.

Description

Technical Field

[0001] The present invention relates to the field of marine engineering materials, and in particular to a marine cement-based material floating structure protective layer and a preparation method thereof. Background Art

[0002] With the continuous deepening of marine resource development, facilities such as marine aquaculture are facing increasingly severe challenges from the marine environment. Marine concrete structures are susceptible to wave impact, chloride ion penetration, freeze-thaw cycles and other effects in the marine environment, resulting in a decline in structural performance and a shortened service life. Concrete in the splash zone and tidal range zone is most affected by the marine environment and is also the area most prone to damage and destruction. On the other hand, with the rapid rise of emerging industries such as marine ranching, the number of floating structures built with cement-based materials is increasing. These structures are more susceptible to the impact and erosion of the ocean's wind, waves and current environment, and are more prone to damage and destruction. It is also necessary to find technical solutions for rapid repair and reinforcement.

[0003] Most cement-based floating marine structures utilize high-strength and ultra-high-strength cement concrete, typically with strengths exceeding 100 MPa. As we all know, the higher the strength of concrete, the greater its brittleness and the higher the risk of cracking. Furthermore, floating structures are typically thin-shell (thin-walled) and large in area, further increasing the risk of structural cracking. my country's first large-scale cement-based floating wind turbine base underwent years of research to address this cracking issue. The key reason for the difficulty in addressing cracking in high-strength, thin-shell concrete structures is the extremely low tensile deformation rate of cement-based materials. While chemical admixtures, mineral admixtures, and steel fibers can improve the toughness and ultimate tensile strain of cement-based materials, the improvement is minimal, and the crack resistance in marine environments is still orders of magnitude lower.

[0004] Cement-based marine floating structures will inevitably be subjected to impacts and collisions during their service, and may suffer local damage. This requires appropriate cement-based materials for rapid repair (underwater repair if necessary), and the repaired area should be as flat and coordinated as possible, which means that the thickness of the repair material should not be too thick, but it should be able to provide good protection for the main structure.

[0005] Given these two requirements, it is imperative to develop a protective layer for floating offshore structures that exhibits excellent substrate bonding, tensile deformation properties, impact resistance, and impermeability. The superior tensile deformation performance provided by the protective layer is crucial for protecting the main structure from cracking.

[0006] To address the need for protection, weight reduction, and life extension for marine concrete and cement-based floating structures, a variety of protective coatings and structural layers have emerged. Representative examples include CN112597562A, which discloses a crack control method for components with concrete protective layers. This patent utilizes fiber-reinforced ultra-high-performance concrete (UHPC) with different types of cementitious materials as a protective layer. This significantly reduces the thickness of the protective layer for cement-based floating structures while also providing corrosion and fire protection. However, this patent determines the protective layer thickness based on the maximum strain at the edge of the tensile zone at maximum operating load, without considering the chemical effects of ion diffusion in marine environments. Furthermore, the patent does not address the protective layer's preparation process, the interface deformation coordination between two different cement-based materials, or the chemical compatibility between different cementitious materials.

[0007] In addition, patent CN113185895A discloses a coating material, its preparation method, and its application in marine concrete surface protection. CN118271883A discloses a high-toughness, high-durability marine concrete protective coating and its preparation method. These coatings, whose main components include fast-setting and hardening cement and lamellar silicate minerals (such as metakaolin), can provide protection for marine cement-based floating structures from marine corrosion. However, due to their long application and setting times, these coating materials are not suitable for rapid on-site repair and reinforcement, especially for cement-based floating structures underwater. From a durability perspective, since these coatings are primarily based on organic polymers, the durability of these repair materials under high ultraviolet radiation conditions in the ocean is also a concern.

[0008] In summary, in-depth research and improvement of the crack resistance and impermeability of floating structures of marine cement-based materials are urgent needs for the development of emerging industries such as marine aquaculture. Summary of the Invention

[0009] In view of this, the present invention proposes a marine cement-based material floating structure protective layer and a preparation method thereof to solve the above problems.

[0010] The technical solution of the present invention is achieved as follows: a protective layer for a floating structure made of a marine cement-based material, comprising a surface layer and a bottom layer, wherein the cementitious material of the surface layer comprises cement, mineral powder, nano-SiO2, and calcium carbonate whiskers in a mass ratio of 40:43-47:9-11:4-6; basalt fiber is incorporated into the surface layer, with the volume content controlled at 1.5% to 2.5%; the bottom layer comprises cement, silica fume, metakaolin, quartz sand powder, and elastic latex powder in a mass ratio of 60:9-11:9-11:9-11:9-11; wire mesh is embedded in the bottom layer; the thickness of the surface layer is 3-5 mm, and the thickness of the bottom layer is 3-5 mm.

[0011] Furthermore, the thickness of the surface layer is 4-5 mm, and the thickness of the bottom layer is 4-5 mm.

[0012] Furthermore, epoxy microcapsules are added to the surface layer in an amount of 2% to 3% of the cement mass.

[0013] Furthermore, the basalt fiber is reinforced with chopped basalt fibers, and the fiber length is 5 to 10 mm.

[0014] Furthermore, modified brucite fiber with a cement mass percentage of 0.9%-1.1% is added to the bottom layer.

[0015] Furthermore, the preparation method of the modified brucite fiber includes the following steps: adding brucite fiber to a 0.8-1.2 mol / L acetic acid solution, with the mass ratio of brucite fiber to acetic acid solution being 1:8-12, and stirring at 45-55°C for 3-4 hours to obtain a dispersion liquid I; mixing (2,6-dichlorobenzenesulfonylamino)-acetic acid and DMF at a mass ratio of 1:9-11 to obtain an intermediate solution II; adding the intermediate solution II dropwise to the dispersion liquid I, with the volume ratio of the intermediate solution II to the dispersion liquid I being 1:9-11, stirring at 75-85°C for 2-4 hours, and then stirring at 25-35°C for 8-10 hours, filtering, collecting the filter cake, washing, and vacuum drying to obtain the modified brucite fiber.

[0016] Furthermore, the wire mesh is a serrated wire mesh, the wire diameter of the wire mesh is 0.2-1.0 mm, the mesh size is 5-10 mm, and the height of the serrations is less than the thickness of the protective layer.

[0017] Furthermore, the cement is silicate cement or sulphoaluminate cement.

[0018] Furthermore, the invention comprises a surface layer and a bottom layer, wherein the cementitious material of the surface layer comprises cement, mineral powder, nano-SiO2, and calcium carbonate whiskers in a mass ratio of 40:43-47:9-11:4-6; basalt fiber is incorporated into the surface layer, and the volume content of the basalt fiber is controlled to be 1.5% to 2.5%; epoxy microcapsules are also incorporated into the surface layer, and the amount of epoxy microcapsules is 2% to 3% of the mass of the cement; the bottom layer comprises cement, silica fume, metakaolin, quartz sand powder, and elastic latex powder in a mass ratio of 60:9-11:9-11:9-11:9-11; modified brucite fiber is also added to the bottom layer at a cement mass percentage of 0.9%-1.1%; and a zigzag wire mesh is embedded in the bottom layer.

[0019] The present invention also provides a method for preparing a protective layer of a floating structure of a marine cement-based material, comprising the following steps: (1) Preparation and pouring of surface mixture: First, mix cement, mineral powder, nano-SiO2, calcium carbonate whiskers and water, and control the water-binder ratio to 0.18-0.22; then add basalt fiber; finally, add epoxy microcapsules, stir, and then pour; (2) Preparation and pouring of the bottom mixture: Cement, quartz sand powder, silica fume, metakaolin and rubber powder are mixed in proportion, first dry-mixed, then water is added and stirred to form a uniform fluid slurry; modified brucite fiber is added to the fluid slurry and stirred continuously for 2 to 3 minutes; when the slurry is evenly spread and reaches the pouring height, the wire mesh is evenly placed on the surface of the slurry. The wire mesh sinks due to vibration. When the wire mesh sinks to 45%-55% of its own height, the vibration molding stops, leaving part of the zigzag wire mesh exposed outside.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a prefabricated ultra-thin protective layer made of cement-based composite materials, particularly suitable for the protection, rapid repair, and reinforcement of cement-based floating structures (including ultra-high-performance cement-based floating structures) in marine engineering. Specifically, it involves a prefabricated thin-walled sheet reinforced with basalt fiber and synthetic fiber fabric, based on a Portland cement or sulfoaluminate cement matrix. This prefabricated protective layer has a thickness of less than 10 mm, is cuttable and bendable, and exhibits high ultimate elongation and impermeability. This protective layer can be adhered to the formwork during the construction of a new floating structure and naturally blends in with the main structure during casting. When repairing an existing structure, the protective layer can be adhered to the damaged surface using cement slurry, epoxy structural adhesive, or other adhesives, thereby achieving the purpose of repair and reinforcement.

[0021] The present invention better optimizes the floating structure of marine cement-based materials through the protective layer, can provide a more stable and durable floating platform for marine aquaculture, etc., and better meet the development needs of deep-sea marine engineering.

[0022] The protective layer of the present invention has the following advantages: (1) The protective layer of the present invention can provide effective protection for the steel materials in the concrete structure of marine engineering and the cement-based floating structure while reducing the thickness of the protective layer by more than half. This is of great significance for reducing the deadweight of the cement-based floating structure, improving the bearing capacity of the floating structure, and improving safety.

[0023] (2) The protective layer provided by the present invention has excellent tensile deformation capacity. Therefore, the surface has a strong crack resistance. Even if cracks occur in the main structure, they will not be reflected to the surface through the protective layer. This protective function is not available in ordinary concrete protective layers.

[0024] (3) The materials used in the protective layer of the present invention include micro-level fibers (calcium carbonate whiskers, modified brucite fibers) and macro-level fibers, which work synergistically to form a strong constraint mechanism for cracking behaviors at different scales, giving the entire protective layer good crack resistance and anti-seepage capabilities.

[0025] (4) The present invention uses a serrated wire mesh, which economically and effectively solves the connection problem between the prefabricated protective layer and the main structure. The wire mesh is embedded at both ends of the new and old materials to connect the new and old materials into a whole.

[0026] (5) The protective layer provided by the present invention can be used in the form of a permanent template for the manufacture of new structures, and can also be used in the form of a veneer for the repair and reinforcement of old structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : A plan view of a structural diagram of a protective layer of a cement-based floating structure, wherein: 1 is a fiber-reinforced cement matrix; 2 is a galvanized zigzag wire mesh; Figure 2 : A cross-sectional view of a schematic diagram of a protective layer structure of a cement-based floating structure, wherein: 1 is a fiber-reinforced cement matrix; 2 is a galvanized zigzag wire mesh; Figure 3 : Schematic diagram of a protective layer used for repairing an old structure, in which 101 is a surface layer; 102 is a bottom layer; 3 is a bonding filling layer; Figure 4 : Schematic diagram of a protective layer used for exterior protection of a new structure, wherein 101 is a surface layer; 102 is a bottom layer; and 4 is a main body of a floating structure. DETAILED DESCRIPTION

[0028] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0029] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0030] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0031] DMF Chinese meaning: N,N-dimethylformamide.

[0032] Example The ultra-thin protective layer provided by the present invention is a layered structure consisting of two layers, namely a surface layer and a bottom layer.

[0033] 1. Layered structure of the protective layer (1) Surface structure: This surface layer will be the exterior of the structure and will be in direct contact with the environmental medium. The thickness of this layer is 3-5 mm. Its cementitious material is composed of silicate cement: mineral powder: nano-SiO2: calcium carbonate whiskers in a mass ratio of 40:45:10:5. The volume content of basalt fiber is controlled at 1.5% to 2.5%.

[0034] Adding a certain proportion of nano-SiO2 to the surface layer of the present invention can fill the gaps between cement particles, improve the density and strength of the surface layer, and at the same time synergize with silicate cement to enhance the sufficiency of the cement hydration reaction and improve the durability of the surface layer; calcium carbonate whiskers are fibers at the microscopic level, and adding a certain proportion of calcium carbonate whiskers can greatly improve the density and toughness of the cement matrix; adding a certain proportion of basalt fibers in the surface layer plays a role in strengthening and toughening, effectively suppressing microcracks, and improving the elongation and crack resistance of the surface layer.

[0035] To further enhance the self-healing ability of microcracks on the protective layer's surface, epoxy microcapsules are added to the surface cement matrix (at a level of 2% to 3% of the cement's mass). When cracks appear in the protective layer, the epoxy microcapsules rupture under stress, releasing epoxy resin. The epoxy resin reacts with moisture in the cement matrix and, after solidifying, fills the cracks, achieving self-healing function and effectively preventing further crack expansion and seawater infiltration.

[0036] (2) Substructure: The bottom surface of the substructure will be combined with the main structure. This layer is 3-5 mm thick and is made of a mixture of silicate cement, silica fume, metakaolin, quartz sand powder, and elastic latex powder in a mass ratio of 60:10:10:10:10, and modified brucite fiber is added at a cement mass percentage of about 1%.

[0037] The invention provides a base layer in which a certain amount of silica fume and metakaolin are introduced, which can significantly enhance the activity of the middle layer, improve the microstructure of the cement matrix, and increase the density and strength of the material; the addition of a certain amount of ground quartz sand powder can increase the volume stability; the addition of elastic latex powder gives the base layer good elasticity and flexibility, can effectively buffer and absorb external stress, and reduce the risk of cracking of the protective layer caused by deformation of the base layer or temperature changes; at the same time, it forms a good bond with the surface layer and the middle layer, thereby improving the overall stability of the protective layer; and the incorporation of a certain amount of modified brucite fiber can enhance the flexibility of the cement matrix of the base layer.

[0038] In the underlying structure, there is a galvanized zigzag wire mesh embedded in it, and the other half of the wire mesh is exposed on the surface of the cement matrix. The wire mesh used in the present invention is a grid woven from galvanized iron wires, which is formed by rolling equipment to form a three-dimensional grid with a zigzag shape. The diameter of the wire mesh wire is 0.2~1.0mm, the mesh size is 5~10mm, and the height of the zigzag is slightly less than the thickness of the protective layer. Compared with steel wire mesh, the wire mesh used in the present invention is not only cheap and easy to press, but also has mechanical properties that meet the requirements. 2. Preparation method of protective layer (1) Preparation of modified brucite fiber: add brucite fiber to 0.8~1.2mol / L acetic acid solution, the mass ratio of brucite fiber to acetic acid solution is 1:8~12, stir at 45~55℃ for 3~4h to obtain dispersion I; mix (2,6-dichlorobenzenesulfonylamino)-acetic acid and DMF at a mass ratio of 1:9-11 to obtain intermediate solution II; add intermediate solution II dropwise to dispersion I, the volume ratio of intermediate solution II to dispersion I is 1:9~11, stir at 75-85℃ for 2~4h, and then stir at 25~35℃ for 8~10h, filter, collect the filter cake, wash, and vacuum dry to obtain modified brucite fiber.

[0039] In this example, brucite fiber was added to a 1.0 mol / L acetic acid solution at a mass ratio of brucite fiber to acetic acid solution of 1:10, and the mixture was stirred at 50°C±5°C for 3.5 hours to obtain a dispersion liquid I; (2,6-dichlorobenzenesulfonylamino)-acetic acid and DMF were mixed at a mass ratio of 1:10 to obtain an intermediate solution II; the intermediate solution II was added dropwise to the dispersion liquid I at a volume ratio of 1:10 to the dispersion liquid I, and the mixture was stirred at 80°C±5°C for 3 hours and then at 30°C±5°C for 9 hours. The mixture was filtered, the filter cake was collected, washed, and vacuum dried to obtain modified brucite fiber.

[0040] (2) Preparation and pouring of surface mixture: The surface cement matrix is reinforced with short-cut basalt fibers with a fiber length of 5-10 mm. First, silicate cement, mineral powder, nano-SiO2, and calcium carbonate whiskers are mixed with water in proportion, with the water-cement ratio controlled at about 0.2. A high-efficiency water reducer can be added to adjust the mixture to produce a highly fluid and uniform slurry. Secondly, short-cut basalt fibers are added to the slurry and stirred at variable speeds to fully disperse the fibers. Finally, epoxy microcapsules are added and poured after appropriate stirring. During pouring, the mold is placed on a vibration table and vibrated while pouring. The vibration frequency is adjusted to a range that fully eliminates bubbles.

[0041] (3) Preparation and pouring of the bottom layer mixture: Cement, quartz sand powder, silica fume, kaolin and rubber powder are mixed in proportion, first dry-mixed, then water is added and stirred until a uniform high-fluidity slurry is formed. Modified brucite fiber is added to the fluid slurry and stirred continuously for 2-3 minutes. During the pouring process of the above slurry, a vibration table is also used, but the frequency is lower than that of the previous layer. When the second layer of slurry is evenly spread and reaches the pouring height, the pre-prepared galvanized zigzag wire mesh is evenly placed on the surface of the slurry. The wire mesh gradually sinks with the vibration. When the wire mesh sinks to about half of its own height, the vibration forming stops. At this time, half of the galvanized zigzag wire mesh is exposed.

[0042] The protective layer structure of the cement-based material floating structure of the present invention is as follows Figure 1-2 As shown, Figure 1 For the plan view, Figure 2 It is a cross-sectional view, in which a fiber reinforced cement matrix 1 (i.e., surface layer 101 + bottom layer 102) and a galvanized zigzag wire mesh 2 are embedded in the bottom layer 102.

[0043] The protective layer of the present invention can be used to repair the main body of old marine engineering cement-based floating structures. When repairing old structures, the protective layer can be adhered to the damaged surface of the structure through cement slurry, epoxy structural adhesive, etc., thereby achieving the purpose of repair and reinforcement. Figure 3 As shown, the surface layer 101 is in direct contact with seawater, waves, and sea breeze, and the bottom layer 102 is connected to the main body of the old floating structure through the bonding filling layer 3.

[0044] The protective layer of the present invention can be applied to the main body of new marine engineering cement-based floating structures. The protective layer can be pasted on the formwork when the new floating structure main body is constructed, and when the floating structure main body is poured, the protective layer will naturally merge into one. Figure 4 As shown, the surface layer 101 is in direct contact with seawater, waves, and sea breeze, and the bottom layer 102 is directly adhered to the floating structure body 4 as a whole.

[0045] Test example An ultra-thin protective layer for a marine floating structure was prepared according to the steps of the above embodiment, and its basic properties were tested. The results are shown in Table 1.

[0046] Among them, this test uses a wire mesh with a wire diameter of 0.5mm and a mesh size of 8mm; this test uses basalt fiber reinforced with short-cut basalt fiber, with a fiber length of 5~10mm and a volume content of 2.0%; this test uses epoxy microcapsules added in an amount of 2.5% of the mass of the silicate cement in the surface layer.

[0047] Taking ordinary C30 concrete as the object, protective layers of different thicknesses were adhered to it, and then the electric flux test and bending performance test were carried out. The results are shown in Table 2.

[0048] Two research groups with different thicknesses were designed: research group 1: 7 mm thick protective layer, of which the surface layer thickness was 3.5 mm and the bottom layer thickness was 3.5 mm; research group 2: 9 mm thick protective layer, of which the surface layer thickness was 4.5 mm and the bottom layer thickness was 4.5 mm.

[0049] Table 1 shows the mechanical property test results of the 7 mm and 9 mm thick multifunctional protective layers. Table 2 shows the comparative results of the flexural toughness and chloride ion corrosion resistance of the unprotected concrete matrix and the concrete matrix protected with the 7 mm and 9 mm thick multifunctional protective layers at 7 days. The flexural toughness was measured by a four-point bending test on a specimen measuring 40 mm × 40 mm × 160 mm. The chloride ion corrosion resistance was evaluated according to the electric flux method in the "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete" (GB / T 50082-2024). The results are shown in the figure below. Figure 2 shown.

[0050] Table 1

[0051] Table 2

[0052] The results show that the cement-based material composite protected by the protective layer having a thickness of 7-10 mm according to the present invention has good mechanical properties, effectively improves its bending toughness, and improves its crack resistance and chloride ion corrosion resistance.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A protective layer of a floating structure of a marine cement-based material, characterized in that: Includes surface and bottom layers; The cementitious material of the surface layer includes cement, mineral powder, nano-SiO2 and calcium carbonate whiskers in a mass ratio of 40:43-47:9-11:4-6; basalt fiber is added to the surface layer, and its volume content is controlled at 1.5% to 2.5%; The bottom layer comprises cement, silica fume, metakaolin, quartz sand powder and elastic latex powder mixed in a mass ratio of 60: 9-11: 9-11: 9-11: 9-11; The bottom layer is embedded with wire mesh; The thickness of the surface layer is 3-5 mm, and the thickness of the bottom layer is 3-5 mm.

2. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: The thickness of the surface layer is 4-5 mm, and the thickness of the bottom layer is 4-5 mm.

3. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: Epoxy microcapsules are added to the surface layer in an amount of 2% to 3% of the mass of the cement in the surface layer.

4. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: The basalt fiber is reinforced with short-cut basalt fibers, and the fiber length is 5-10 mm.

5. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: Modified brucite fiber is added to the bottom layer, and the amount of the modified brucite fiber added is 0.9%-1.1% of the mass percentage of cement in the bottom layer.

6. The protective layer of the marine cement-based floating structure according to claim 5, characterized in that: The preparation method of the modified brucite fiber comprises the following steps: adding brucite fiber to a 0.8-1.2 mol / L acetic acid solution at a mass ratio of brucite fiber to acetic acid solution of 1:8-12, stirring at 45-55°C for 3-4 hours to obtain a dispersion liquid I; mixing (2,6-dichlorobenzenesulfonylamino)-acetic acid and DMF at a mass ratio of 1:9-11 to obtain an intermediate solution II; adding the intermediate solution II dropwise to the dispersion liquid I at a volume ratio of the intermediate solution II to the dispersion liquid I of 1:9-11, stirring at 75-85°C for 2-4 hours, and then stirring at 25-35°C for 8-10 hours, filtering, collecting the filter cake, washing, and vacuum drying to obtain the modified brucite fiber.

7. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: The wire mesh is a zigzag wire mesh, the wire diameter of the wire mesh is 0.2-1.0 mm, the mesh size is 5-10 mm, and the height of the zigzags is less than the thickness of the protective layer.

8. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: The cement is silicate cement or sulphoaluminate cement.

9. The protective layer of the marine cement-based floating structure according to claim 1, characterized in that: The invention comprises a surface layer and a bottom layer, wherein the cementitious material of the surface layer comprises cement, mineral powder, nano-SiO2 and calcium carbonate whiskers in a mass ratio of 40:43-47:9-11:4-6; basalt fiber is added to the surface layer in a volume ratio controlled at 1.5% to 2.5%; epoxy microcapsules are added to the surface layer in an amount of 2% to 3% of the cement mass; The bottom layer is made of cement, silica fume, metakaolin, quartz sand powder and elastic latex powder in a mass ratio of 60: 9-11: 9-11: 9-11: 9-11; modified brucite fiber is added to the bottom layer with a cement mass percentage of 0.9%-1.1%; and a zigzag wire mesh is embedded in the bottom layer.

10. The method for preparing the protective layer of the marine cement-based floating structure according to claim 9, characterized in that: The following steps are involved: (1) Preparation and pouring of surface mixture: First, mix cement, mineral powder, nano-SiO2, calcium carbonate whiskers and water, and control the water-binder ratio to 0.18-0.22; then add basalt fiber; finally, add epoxy microcapsules, stir, and then pour; (2) Preparation and pouring of the bottom mixture: Cement, quartz sand powder, silica fume, metakaolin and rubber powder are mixed in proportion, first dry-mixed, then water is added and stirred to form a uniform fluid slurry; modified brucite fiber is added to the fluid slurry and stirred continuously for 2 to 3 minutes; when the slurry is evenly spread and reaches the pouring height, wire mesh is evenly placed on the surface of the slurry. The wire mesh sinks due to vibration. When the wire mesh sinks to 45%-55% of its own height, the vibration molding is stopped, leaving the wire mesh partially exposed.

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