Basalt fiber reinforced cement-based material for underwater 3D printing, preparation method and underwater printing method of basalt fiber reinforced cement-based material

Abstract

The invention belongs to the technical field of underwater additive manufacturing, and particularly relates to a basalt fiber reinforced cement-based material suitable for underwater 3D printing, a preparation method and a printing method of the basalt fiber reinforced cement-based material. The material is prepared from sulphoaluminate cement, a mineral admixture, aggregate, basalt fiber, an anti-dispersing agent, a water reducing agent, a coagulation accelerator, water and the like according to a specific proportion, and by optimizing the component proportion and basalt fiber parameters, the anti-dispersing property, constructability and mechanical property of underwater printing concrete are remarkably improved; the material can be widely applied to 3D printing construction in the fields of ocean engineering, underwater repair and the like, and has excellent engineering applicability and environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of underwater additive manufacturing technology, specifically providing a basalt fiber reinforced cementitious material suitable for underwater 3D printing, its preparation method, and its underwater printing method. Background Technology

[0002] With the rapid development of marine resource development and near-shore engineering construction, the demand for underwater bridge piers, submarine pipelines, artificial reefs, and other structures is increasing. Traditional underwater construction methods, such as cofferdams, suffer from problems such as large project scale, long construction period, high cost, and significant personnel safety risks. Underwater 3D printing technology, as an intelligent construction method, can directly complete the structure forming underwater through printing equipment, greatly improving construction efficiency, but it places stringent requirements on the performance of printing materials.

[0003] Existing underwater printing of cement-based materials generally suffers from three major drawbacks: First, insufficient underwater anti-dispersion properties, leading to component separation after immersion in water and resulting in poor molding quality; second, a difficult balance between mechanical properties and printability, with high-flowability materials prone to collapse and high-stiffness materials difficult to extrude; and third, poor adaptability to marine environments, with seawater temperature changes and salinity erosion significantly degrading material strength. Basalt fiber, with its advantages of high strength, corrosion resistance, and good compatibility with cement-based materials, is widely used for concrete reinforcement. However, existing research lacks sufficient matching between fiber length and dosage, and systematic optimization for complex marine environments is insufficient.

[0004] Therefore, developing a basalt fiber reinforced cementitious material with excellent working performance, mechanical properties and environmental adaptability is of great significance for promoting the engineering application of underwater 3D printing technology. Summary of the Invention

[0005] This invention provides a basalt fiber reinforced cementitious material for underwater 3D printing with excellent anti-dispersion, printability and mechanical properties, its preparation method and its underwater printing method. This material can make up for the shortcomings of existing 3D printing materials in terms of anti-dispersion and mechanical properties in underwater, especially marine environments. It has excellent underwater anti-dispersion, printability and high mechanical strength, and good adaptability to complex underwater environments.

[0006] The first aspect of this application protects a basalt fiber reinforced cementitious material for underwater 3D printing, which, by weight, comprises the following components: 985-1015 parts of cementitious material, 445-455 parts of aggregate, 325-335 parts of water, 10-30 parts of basalt fiber, 2.4-2.6 parts of anti-dispersant agent, 3.7-3.9 parts of water-reducing agent, 0.9-1.1 parts of coagulant, and 29-31 parts of flocculant; The cementitious material is composed of 395-405 parts of sulfoaluminate cement, 245-255 parts of fly ash, and 345-355 parts of mineral powder.

[0007] Preferably, the antidispersant is hydroxypropyl methylcellulose.

[0008] Preferably, the water-reducing agent is polycarboxylic acid.

[0009] Preferably, the coagulant is lithium carbonate.

[0010] Preferably, the flocculant is an alkaline silica sol.

[0011] Preferably, the aggregate is river sand.

[0012] Preferably, the length of the basalt fiber is 3-6 mm.

[0013] The second aspect of this application protects a method for preparing a basalt fiber reinforced cementitious material for underwater 3D printing, comprising the following steps: (1) Pretreatment: Dry the aggregate to a moisture content of less than 1%, and disperse the basalt fiber for later use; (2) Ingredients: Weigh each component according to the proportions; (3) Dry mixing: Dry mixing of sulfoaluminate cement, mineral powder, fly ash and aggregate; (4) Wet mixing: Add water, water-reducing agent, coagulant accelerator and anti-dispersant agent and wet mix; (5) Dispersion and thickening: Add basalt fiber and continue stirring until a uniform mixture is formed. Finally, add flocculant to thicken the mixture to obtain the basalt fiber reinforced cementitious material.

[0014] The third aspect of this application protects an underwater printing method for basalt fiber reinforced cementitious material for underwater 3D printing. The basalt fiber reinforced cementitious material is loaded into a 3D printing device and extruded in an underwater environment. The printing layer height is 10-15 mm and the printing speed is 10-30 mm / s.

[0015] Beneficial effects The material has excellent underwater anti-dispersion properties, printability, and high mechanical strength, enabling it to adapt to 3D printing construction in underwater environments, especially complex seawater environments. It is also resistant to salt corrosion and temperature differences. The underwater 3D printed basalt fiber reinforced cementitious material of the present invention includes industrial waste mineral powder and fly ash, which are abundant, safe and environmentally friendly. (3) The preparation method of the underwater 3D printed basalt fiber reinforced cementitious material of the present invention is simple and easy to control. Attached Figure Description

[0016] The following figures are for illustrative purposes only and are not intended to limit the scope of the invention, wherein: Figure 1This is a printable performance test diagram of the material in Embodiment 2 of the present invention, wherein (a) the width of the test block is measured; and (b) the height of the test block is measured. Figure 2 This describes the underwater printing process of the material in Embodiment 2 of the present invention. Figure 3 The image shows the SEM image of the material in Example 2 of this invention, where (a) the bridging effect of the fibers and (b) the network structure formed by the fibers. Figure 4 This is a SEM image of the material in Comparative Example 2 of this invention; Figure 5 These are comparative XRD phase analysis spectra of the materials after curing in a simulated saline environment in Examples 2 and 3 of the present invention. Figure 6 These are printable performance test diagrams for some embodiments and comparative examples of the present invention; Figure 7 This is a diagram showing the ingredient ratios for some embodiments and comparative examples of the present invention. Detailed Implementation

[0017] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0018] To facilitate understanding of the present invention, a more complete description of this application will be provided below with reference to relevant embodiments. Preferred embodiments of the present application are given below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of this application will be achieved.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0020] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0021] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0022] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0023] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0024] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0025] In this application, unless otherwise specified, the terms "size," "particle size," and "diameter" generally refer to average values. In this application, "particle size" and "particle diameter" have the same definition, both representing the average particle size of spheres or spheroids.

[0026] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0027] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0028] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0029] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0031] Unless otherwise specified, all raw materials used in the following examples are commercially available.

[0032] The freshwater environment and mixing water used in this invention are both Jinzhou tap water.

[0033] This invention simulates a seawater environment: artificial seawater is prepared according to ASTM D1141-98 standard, with the following main salt contents (g / L): NaCl (24.54), MgCl2·6H2O (11.10), Na2SO4 (4.09), CaCl2·2H2O (1.54), and KCl (0.69). The total salinity is approximately 41.96 g / L. Care must be taken during preparation to avoid precipitation.

[0034] The sulfoaluminate cement used in this invention is grade R.SAC42.5, with a specific surface area of ​​400~420 m² / kg, a 3-day flexural strength ≥6 MPa, a 3-day compressive strength ≥45 MPa, an initial setting time of 8~12 min, and a final setting time of 13~17 min.

[0035] The mineral powder used in this invention is grade S95, with a density of 2.7~2.9 g / cm³, a specific surface area of ​​340~360 m² / g, and a glass content ≥85%. The fly ash used in this invention is Grade I fly ash, with a SiO2 content of 45-48% and an Al2O3 content of 44-47%. The maximum particle size of the river sand used in this invention is ≤1.2 mm, the apparent density is 2550~2600 kg / m³, the bulk density is 1450~1500 kg / m³, and the porosity is 42~43%. The basalt fiber used in this invention has a single filament diameter of 7~15 μm, a density of 2.63~2.65 g / cm³, an elastic modulus of 91~110 GPa, and a tensile strength of 3000~4800 MPa. The viscosity of the hydroxypropyl methylcellulose used in this invention is 200 Pa·s.

[0036] The first aspect of this application protects a basalt fiber reinforced cementitious material for underwater 3D printing, which, by weight, comprises the following components: 985-1015 parts of cementitious material, 445-455 parts of aggregate, 325-335 parts of water, 10-30 parts of basalt fiber, 2.4-2.6 parts of anti-dispersant agent, 3.7-3.9 parts of water-reducing agent, 0.9-1.1 parts of coagulant, and 29-31 parts of flocculant; The cementitious material is composed of 395-405 parts of sulfoaluminate cement, 245-255 parts of fly ash, and 345-355 parts of mineral powder.

[0037] This invention controls the basalt fiber content to approximately 2% of the cementitious material's mass, which significantly improves the material's strength and avoids stress concentration and increased porosity problems caused by high fiber content. This invention also optimizes key mix proportion parameters: water is 33% of the cementitious material's mass, ensuring slurry fluidity while preventing bleeding; aggregate is 45% of the cementitious material's mass, balancing skeletal support and extrusion performance; mineral powder is 35% of the cementitious material's mass, promoting later-stage strength development; and alkaline silica sol is 3% of the cementitious material's mass, effectively improving underwater anti-dispersion properties.

[0038] In some embodiments, the anti-dispersant is hydroxypropyl methylcellulose, used to improve the anti-dispersibility and plasticity of cement. Hydroxypropyl methylcellulose molecules are soluble in water and rapidly bind to water molecules through hydrogen bonds, significantly increasing the viscosity of the solution. This increased viscosity significantly slows the settling rate of cement solid particles, fundamentally solving the problem of stratification caused by gravity. Furthermore, hydroxypropyl methylcellulose molecules have water-retention properties, forming a three-dimensional network structure within the material that firmly "locks in" moisture, preventing excessive evaporation or absorption by the porous substrate. For cement-based materials, sufficient water retention is crucial for ensuring adequate cement hydration and achieving final strength, while also effectively preventing cracking and dusting caused by rapid water loss.

[0039] In some embodiments, the water-reducing agent is polycarboxylate. Polycarboxylate, as a water-reducing agent, can reduce water and cement usage, effectively lowering the yield stress of concrete. This allows the concrete to maintain good fluidity, cohesiveness, and water retention even with lower water usage, contributing to improved early and later strength of the concrete.

[0040] In some embodiments, the coagulant is lithium carbonate.

[0041] In some embodiments, the flocculant is an alkaline silica sol, used to improve the anti-dispersion properties of underwater 3D printed concrete.

[0042] In some embodiments, the aggregate is river sand.

[0043] In some embodiments, the basalt fibers have a length of 3-6 mm, including but not limited to 3 mm, 4 mm, 5 mm, and 6 mm. Preferably, when the basalt fibers are 6 mm long, the 6 mm fibers have a larger aspect ratio, making it easier for them to overlap and entangle with each other in the cement matrix, forming a denser fiber network. This network structure acts like a "skeleton" for concrete, effectively constraining the flow and deformation of the cement matrix, thereby significantly reducing the slump and dispersion of the concrete.

[0044] The second aspect of this application protects a method for preparing a basalt fiber reinforced cementitious material for underwater 3D printing, comprising the following steps: (1) Pretreatment: The aggregate is dried to a moisture content of less than 1% to completely eliminate its own moisture from interfering with the mix proportion, thereby accurately controlling the final water-cement ratio and ensuring the stability and reproducibility of the mechanical properties of concrete. Basalt fiber is dispersed for later use. Dispersion pretreatment of basalt fiber can effectively prevent it from agglomerating into clusters during mixing, thereby avoiding the formation of stress concentration points and ensuring its uniform distribution to achieve the best reinforcement and toughening effect.

[0045] (2) Ingredients: Weigh each component according to the proportions; (3) Dry mixing: Dry mixing of sulfoaluminate cement, mineral powder, fly ash and aggregate; In some embodiments, the dry mixing time is no less than 2 minutes to ensure uniform mixing of components. The cementitious system formed by dry mixing is mainly composed of sulfoaluminate cement, combined with S95 mineral powder and grade I fly ash. The activity activation effect of the mineral powder and the micro-aggregate filling effect of the fly ash are utilized to optimize the density of the slurry. The river sand is selected as fine aggregate with a maximum particle size ≤1.2 mm to ensure that the material can be smoothly extruded through the nozzle.

[0046] (4) Wet mixing: Add water, water-reducing agent, coagulant accelerator and anti-dispersant agent and wet mix; In some embodiments, the wet mixing time is not less than 3 minutes to ensure that the components are mixed evenly; in the wet-mixed admixture system, the anti-dispersant hydroxypropyl methylcellulose can improve water retention and anti-dispersibility, the polycarboxylate superplasticizer can improve fluidity, and the coagulant lithium carbonate can adjust the setting time.

[0047] (5) Dispersion and thickening: Add basalt fiber and continue stirring until a uniform mixture is obtained. Finally, add flocculant to thicken the mixture to obtain the basalt fiber reinforced cementitious material. The flocculant alkaline silica sol can enhance the underwater scouring resistance.

[0048] In some embodiments, the basalt fiber is added and stirred for at least 3 minutes to ensure good dispersion of the basalt fiber.

[0049] The third aspect of this application protects an underwater printing method for basalt fiber reinforced cementitious material for underwater 3D printing. The basalt fiber reinforced cementitious material is loaded into a 3D printing device and extruded in an underwater environment. The printing layer height is 10-15 mm and the printing speed is 10-30 mm / s. Example 1

[0050] A basalt fiber reinforced cementitious material for underwater 3D printing, comprising, by weight: 400 parts R.SAC42.5 sulfoaluminate cement, 350 parts S95 mineral powder, 250 parts Grade I fly ash, 450 parts river sand, 330 parts water, 20 parts 3mm basalt fiber, 2.5 parts hydroxypropyl methylcellulose, 3.8 parts polycarboxylic acid, 1 part lithium carbonate, and 30 parts alkaline silica sol.

[0051] Printing method: The mixture, i.e. the underwater 3D printing basalt fiber reinforced cement-based material, is loaded into a 3D printing device and extruded in an underwater environment. The printing layer height is 10~15 mm and the printing speed is 10~30 mm / s.

[0052] Curing: After printing, the material is placed in a standard freshwater environment for curing for 28 days, and then its performance is tested.

[0053] 1. Test methods for printability (1) Extrusion test Before testing, the hopper, mixing pump, and nozzle of the frame printer were moistened with water. After the water was completely drained, the well-mixed slurry was loaded into the hopper and printing was started. After the slurry was evenly and continuously extruded from the print head, a stopwatch was used to record 30 seconds. The mass of slurry extruded during this period was weighed and recorded as M, which represents the extrudability of the slurry formulation.

[0054] (2) Constructability experiment To systematically evaluate constructability, a model measuring 150 mm in length, 30 mm in width, and 75 mm in height was printed. Five layers were stacked in a layered manner, with each layer designed to be 15 mm high. Constructability tests were conducted using a 3D printing cement-based material mixed with water for 15 minutes. During printing, the printing speed and screw rotation were strictly controlled to eliminate the influence of process parameter fluctuations on the experimental results. After printing, dimensions were measured, and the tangent of the inclination angle α and the cross-sectional area ratio were calculated. Criteria for excellent constructability include top and bottom widths close to the design dimensions, a large inclination angle, and a cross-sectional area ratio close to 1, as shown in the attached diagram. Figure 1 As shown.

[0055] 2. Mechanical property testing methods After underwater printing, the specimens were left to stand in the water until they no longer deformed. They were then removed and pre-cut using a cutting machine to create cubes and prisms with dimensions of 40 mm x 40 mm x 160 mm each. These were then placed in different underwater environments for curing for 28 days. The cured specimens were then surface-polished using an angle grinder. Finally, the compressive and flexural strengths of the specimens were measured using an electronic universal testing machine.

[0056] From the appendix Figure 2 As can be seen, this mix proportion allows for proper stacking during underwater printing without collapse or deformation, resulting in excellent printing quality. Ultimately, it enables the achievement of higher printing heights and underwater printing methods. Example 2

[0057] Same as Example 1, except that 20 parts of 6 mm basalt fiber are used.

[0058] From the appendix Figure 3 (a) This indicates that the fibers, through bridging, delay the development of the main crack, thereby improving the mechanical strength of the specimen. (From the attached...) Figure 3(b) It can be seen that the three-dimensional network structure formed by fibers inside concrete can effectively inhibit crack penetration, thereby improving the overall mechanical properties of the specimen. The 6 mm fiber group showed more balanced and superior performance in the experiment. Its cross-sectional area ratio was generally good, approaching the ideal value of 1, while the height and width of the printed component were also relatively ideal. This indicates that the 6 mm fiber length has found a good balance point in underwater 3D printed concrete. The addition of 6 mm fibers can more effectively form a three-dimensional network structure inside the concrete. Compared with 3 mm fibers, 6 mm fibers have a larger aspect ratio, making it easier to overlap and entwine with each other in the cement matrix to form a denser fiber network. This network structure is like the "skeleton" of concrete, which can effectively constrain the flow and deformation of the cement matrix, thereby significantly reducing the slump and dispersion of concrete. Therefore, the 6 mm fiber group can achieve a cross-sectional area ratio close to 1, as well as relatively ideal printing height and width, which fully demonstrates the effectiveness of 6 mm fibers in improving the shape retention of underwater 3D printed concrete. Example 3

[0059] Similar to Example 2, except that after printing, the material was placed in a simulated seawater environment for 28 days (20 ℃, 25‰ salinity) for material performance testing.

[0060] Compared to freshwater curing, seawater curing gradually weakens the strength of concrete over time. This is because the main difference between seawater and freshwater is the high salt content in seawater, primarily chlorides and sulfates. These salts have a complex impact on the cement hydration process and the durability of concrete, thus affecting compressive and flexural strength. Seawater temperature plays a crucial role in regulating the hydration reaction and strength development of concrete.

[0061] From the appendix Figure 5 It can be seen that the hydrates produced by different underwater curing environments are different. Among them, the amount of ettringite produced in the seawater environment is higher than that in the freshwater curing conditions. This microscopic degradation mechanism is consistent with the previous compressive strength test results, that is, the strength of some mix proportion specimens decreased or growth was limited in the seawater environment. Comparative Example 1

[0062] Same as Example 1, except that no basalt fiber is added to the mixture. Comparative Example 2

[0063] Same as Example 1, except that 20 parts of 9 mm basalt fiber are used.

[0064] From the appendix Figure 4It can be seen that 9 mm fibers, due to their longer length, are more prone to fiber agglomeration and clustering under high admixture conditions. This is mainly because the longer fibers have a larger surface area, making them more susceptible to entanglement and electrostatic adsorption, thus leading to agglomeration. Fiber agglomeration can severely affect the uniformity and fluidity of concrete, and also weaken the overall strength of the specimens. Comparative Example 3

[0065] Same as Example 2, except that the amount of basalt fiber added is 10 parts by mass. Comparative Example 4

[0066] Same as Example 2, except that the amount of basalt fiber added is 30 parts by weight.

[0067] Depend on Figure 7 It can be seen that Example 2 exhibits the highest 28-day compressive and flexural strength at a 2% fiber content. This is because in Comparative Example 3, the fiber bridging and crack-preventing effects are not fully realized when the fiber content (1%) is too low; and in Comparative Example 4, the fiber agglomerates easily when the content is too high (3%), which negatively impacts matrix density and limits the improvement in compressive strength. In Example 2, at a 2% fiber content, the fibers form a uniform and dense bridging network, effectively inhibiting crack initiation and propagation. Its flexural strength significantly exceeds that of Comparative Example 3 (1%) and Comparative Example 4 (3%), demonstrating outstanding advantages in toughness and crack resistance.

[0068] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A basalt fiber reinforced cementitious material for underwater 3D printing, characterized in that, By mass parts, including the following components: cementitious material 985~1015 parts, aggregate 445~455 parts, water 325~335 parts, basalt fiber 10~30 parts, anti-dispersion agent 2.4~2.6 parts, water reducing agent 3.7~3.9 parts, accelerator 0.9~1.1 parts, flocculating agent 29~31 parts; The cementitious material is composed of sulphoaluminate cement 395~405 parts, fly ash 245~255 parts and mineral powder 345~355 parts.

2. Basalt fiber reinforced cementitious material for underwater 3D printing according to claim 1, characterized in that, The anti-dispersion agent is hydroxypropyl methyl cellulose.

3. The basalt fiber reinforced cementitious composite material for underwater 3D printing according to claim 1, characterized in that, The water reducing agent is polycarboxylic acid.

4. The basalt fiber reinforced cementitious composite material for underwater 3D printing according to claim 1, characterized in that, The accelerator is lithium carbonate.

5. The basalt fiber reinforced cementitious composite material for underwater 3D printing according to claim 1, characterized in that, The flocculating agent is basic silica sol.

6. The basalt fiber reinforced cementitious composite material for underwater 3D printing according to claim 1, characterized in that, The aggregate is river sand.

7. The basalt fiber reinforced cementitious composite material for underwater 3D printing according to any one of claims 1 to 6, characterized in that, The length of the basalt fiber is 3~6 mm.

8. A method for producing a basalt fiber reinforced cementitious material for underwater 3D printing according to any one of claims 1 to 7, characterized in that, Including the following steps: (1) Pretreatment: dry the aggregate to a water content of less than 1%, and disperse the basalt fiber for standby; (2) batching: take each component according to the proportion; (3) dry mixing: dry mixing sulphoaluminate cement, mineral powder, fly ash and aggregate; (4) wet mixing: add water, water reducing agent, accelerator and anti-dispersion agent for wet mixing; (5) dispersion and thickening: add basalt fiber and continue stirring until the mixture is uniform, and finally add flocculating agent to thicken to obtain the basalt fiber reinforced cement-based material.

9. An underwater printing method of the basalt fiber reinforced cementitious material prepared by the method of any one of claims 1 to 7 or the basalt fiber reinforced cementitious material prepared by the method of claim 8, characterized in that, The basalt fiber reinforced cement-based material is loaded into a 3D printing device, and extrusion printing is carried out in an underwater environment, with a printing layer height of 10~15 mm and a printing speed of 10~30 mm / s.

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