Low-temperature-resistant underwater 3D printing concrete and construction method thereof

Abstract

The application provides a low-temperature-resistant underwater 3D printing concrete material. The application further provides a preparation method of the low-temperature-resistant underwater 3D printing concrete material. The application also provides a construction method of the low-temperature-resistant underwater 3D printing concrete material. The application further provides a use of the low-temperature-resistant underwater 3D printing concrete material in a low-temperature environment building facility. The low-temperature-resistant underwater 3D printing concrete material and the construction method thereof can break through the low-temperature restricted area, have excellent material performance, are high in construction efficiency and energy saving, have a wide application prospect, and can realize free-form and automatic construction in a cold water environment such as a polar region and a deep sea.

Description

Technical Field

[0001] This invention belongs to the technical field of building materials and polar engineering and intelligent construction, and relates to a low-temperature underwater 3D printed concrete and its construction method. Specifically, it relates to a 3D printed concrete material designed for low-temperature water environments such as polar regions and deep seas, and its supporting automated construction method. Background Technology

[0002] With the deepening of marine development and polar scientific research, the need for engineering construction in low-temperature waters (usually below 5°C), such as under ice and in the deep sea, is becoming increasingly urgent. 3D printing technology, with its advantages of template-free, automated, and digital construction, is considered a revolutionary technology for underwater engineering. Among existing technologies, Chinese patent CN 110723949 A discloses an underwater 3D-printed concrete and its construction method. Its technical solution focuses on improving the material's anti-dispersion properties and molding strength in room-temperature water by adding components such as water-based epoxy resin and flocculants. Another Chinese patent, CN 107311561 B, uses polymer materials such as polysaccharides and polyacrylamide as core anti-dispersion agents, and utilizes their thixotropic properties to give the slurry the characteristics of flowing during extrusion and solidifying when stationary, thereby achieving layer-by-layer deposition molding. This patent provides detailed quantitative performance data, offering a reference for verifying material performance.

[0003] However, the aforementioned existing technologies all have serious environmental limitations. They are mainly designed for ambient temperature aquatic environments and cannot be effectively applied in low-temperature cold water environments ranging from 0°C to 5°C. Under low-temperature conditions, the hydration reaction rate of concrete decreases sharply, the setting time is significantly prolonged, and the early strength development is extremely slow. This causes the printed slurry to collapse easily under the influence of water flow or its own gravity, making it impossible to form a stable structure.

[0004] On the other hand, traditional low-temperature concrete construction typically relies on overall heating of the environment or the use of large amounts of antifreeze. This is not only energy-intensive and impractical in open subglacial waters, but the release of large amounts of chemicals could also damage the fragile polar ecosystem. Currently, there is a lack of 3D-printed concrete materials and construction methods that can be directly printed in low-temperature water, set rapidly, and possess excellent freeze-thaw resistance. This severely restricts the automated construction process of polar and deep-sea engineering.

[0005] Therefore, there is an urgent need for a 3D-printed concrete material that can be used in low-temperature water environments, and to stably and reliably print robust structures with sufficient mechanical properties using a low-energy, high-efficiency, and highly automated construction method. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-temperature underwater 3D printed concrete and its construction method. The concrete material prepared by this invention can maintain good pumpability, underwater anti-dispersion and rapid setting ability in a cold water environment of 0℃~5℃. After molding, it has excellent early strength and frost resistance. The construction method provided by this invention achieves low-energy consumption and high-efficiency low-temperature underwater automated construction through local microenvironment temperature control.

[0007] To achieve the above and other related objectives, the first aspect of the present invention provides a low-temperature underwater 3D printing resistant concrete material, comprising the following components by weight:

[0008] 100 parts of cementitious material;

[0009] 70-120 parts fine aggregate;

[0010] 1-15 parts of low-temperature resistant composite additive;

[0011] Alkali-resistant fiber: 0.15-1.0 parts;

[0012] 20-40 parts water.

[0013] Preferably, the low-temperature underwater 3D printing concrete material comprises the following components by weight:

[0014] 100 parts of cementitious material;

[0015] Fine aggregate 80-110 parts; specifically, 80-90 parts, 90-100 parts, 100-110 parts;

[0016] Low-temperature resistant composite additive: 5-12 parts; specifically, 5-8 parts, 8-10 parts, or 10-12 parts.

[0017] Alkali-resistant fiber: 0.2-0.8 parts; specifically, 0.2-0.4 parts, 0.4-0.6 parts, or 0.6-0.8 parts.

[0018] 25-35 parts water.

[0019] Preferably, the cementing material is selected from at least one of sulfoaluminate cement or silicate cement.

[0020] More preferably, the cementing material includes sulfoaluminate cement and silicate cement.

[0021] More preferably, the weight ratio of the sulfoaluminate cement to the silicate cement is 70-80:20-30.

[0022] More preferably, the compressive strength of the sulfoaluminate cement is P·O42.5 grade.

[0023] More preferably, the silicate cement is high early-strength silicate cement. The high early-strength silicate cement is a silicate cement with high compressive strength and an early compressive strength development rate significantly higher than that of ordinary cement.

[0024] More preferably, the high early strength silicate cement has a compressive strength of P·O52.5 grade.

[0025] The cementitious material is a mixture of sulfoaluminate cement and high early strength silicate cement in a specific ratio to ensure rapid hydration at low temperatures.

[0026] Preferably, the fine aggregate is natural quartz sand.

[0027] Preferably, the particle size distribution of the fine aggregate has fractal characteristics, and its fractal dimension D value is 2.1-2.4.

[0028] The particle size distribution of the fine aggregate has been optimized, and the fractal dimension of its particle size distribution is controlled within a specific range to reduce frost heave sensitivity.

[0029] Preferably, the low-temperature resistant composite additive is selected from at least one of an early-strength agent, an antifreeze agent, a water-reducing agent, or an anti-dispersing agent.

[0030] More preferably, the low-temperature resistant composite additive includes an early-strength agent, an antifreeze agent, a water-reducing agent, and an anti-dispersing agent.

[0031] More preferably, the low-temperature resistant composite additive comprises, by weight, the following components:

[0032] Early-strength agent 1-3 parts;

[0033] 2-5 parts antifreeze;

[0034] 1-2 parts water-reducing agent;

[0035] 1-2 parts of anti-dispersant.

[0036] More preferably, the early strength agent is selected from at least one of sodium sulfate or lithium sulfate.

[0037] More preferably, the antifreeze is selected from at least one of calcium formate or triethanolamine. The antifreeze is a chlorine-free antifreeze.

[0038] More preferably, the water-reducing agent is a polycarboxylate superplasticizer.

[0039] More preferably, the anti-dispersant is selected from at least one of aqueous epoxy resin, cellulose ether or polyacrylamide.

[0040] More preferably, the performance requirements of the waterborne epoxy resin are as follows: it is a milky white or light yellow liquid in appearance, with a solid content of not less than 50%, a viscosity of 500-2000 mPa·s at 25°C, and a bonding strength to a damp concrete substrate of not less than 2.0 MPa.

[0041] More preferably, the viscosity of the cellulose ether at 20°C is 40,000-60,000 mPa·s.

[0042] More preferably, the cellulose ether accounts for 1-3% by mass in the aqueous solution of the above-mentioned concrete material, preferably 2%. The cellulose ether has excellent water retention and anti-dispersion properties, and can significantly improve the cohesiveness of the slurry.

[0043] More preferably, the polyacrylamide is anionic polyacrylamide.

[0044] More preferably, the polyacrylamide has a molecular weight of 8-12 million. The polyacrylamide can rapidly form a flocculation network in water through the bridging effect of its long-chain molecules, significantly improving the anti-dispersibility and stability of the slurry underwater.

[0045] The low-temperature resistant composite additive is scientifically formulated from early-strength agents, chlorine-free antifreeze agents, high-efficiency water-reducing agents, and anti-dispersing agents. These work synergistically to activate low-temperature activity, prevent ice crystal damage, and ensure underwater molding stability.

[0046] Preferably, the alkali-resistant fiber is selected from at least one of polyvinyl alcohol (PVA) fiber or polypropylene (PP) fiber.

[0047] More preferably, the polyvinyl alcohol fiber has the following performance requirements: a length of 10-15 mm, a diameter of 30-50 μm, a tensile strength of not less than 1500 MPa, and an elastic modulus of not less than 38 GPa. The polyvinyl alcohol fiber also exhibits good alkali resistance and dispersibility in a cementitious matrix.

[0048] More preferably, the polypropylene fiber has the following performance requirements: length of 10-15 mm, specific gravity of 0.91 g / cm³, and tensile strength of not less than 400 MPa. The polypropylene fiber exhibits excellent chemical resistance and hydrophobicity, which helps to inhibit plastic shrinkage cracking.

[0049] Preferably, the water is tap water or deionized water.

[0050] The second aspect of this invention provides a method for preparing low-temperature underwater 3D printing resistant concrete material, using the formulation of the low-temperature underwater resistant 3D printing resistant concrete material provided in the first aspect of this invention, including the following steps:

[0051] 1) Dry-mix the cementitious materials and fine aggregates according to the proportions to obtain the first mixture;

[0052] 2) Add low-temperature resistant composite additives and water to the first mixture and wet mix to obtain the second mixture;

[0053] 3) Add alkali-resistant fiber to the second mixture and continue stirring until homogeneous to provide the required material.

[0054] In steps 1), 2), or 3), the dry mixing, wet mixing, and continued stirring are all carried out in a mixer.

[0055] In step 1), the dry mixing time is 2-3 minutes.

[0056] In step 1), the stirring speed of the dry mixing is 30-50 r / min.

[0057] In step 2), the wet mixing time is 80-100s, preferably 90s.

[0058] In step 2), the stirring speed for the wet mixing is 60-80 r / min.

[0059] In step 3), the stirring time is 80-100s, preferably 90s.

[0060] In step 3), the stirring speed for continued stirring is 40-60 r / min.

[0061] A third aspect of this invention provides a construction method for low-temperature underwater resistant 3D printed concrete material, comprising the following steps:

[0062] A) Load the slurry of the low-temperature underwater 3D printing concrete material prepared by the method provided in the second aspect of the present invention into a 3D printing device, and place the printing nozzle at the printing starting point of the target water area.

[0063] B) Start the 3D printing equipment, and after locally heating the printing nozzle, slurry is extruded for continuous layer-by-layer printing. The structure is formed after solidification.

[0064] In step A), the 3D printing equipment is a conventionally used 3D printer.

[0065] In step A), the water temperature of the target water body is 0-5℃. Continuous printing and rapid setting of concrete are achieved in a cold water environment of 0℃ to 5℃.

[0066] In step A), the printing starting point is the existing foundation structure or the surface of the previous layer of cured concrete.

[0067] In step B), the temperature of the locally heated printhead is 10-20°C.

[0068] In step B), the local heating is achieved by using an electric heating element built into the nozzle or by coaxially spraying warm water around the nozzle. This maintains the local ambient temperature of the sprayed concrete slurry at 10-20°C.

[0069] In step B), the speed of the continuous layer-by-layer printing is 10-40 mm / s.

[0070] In step B), the interlayer interruption time of the continuous layer-by-layer printing is ≤15min.

[0071] The core of the above construction method lies in the "micro-environment temperature control" strategy during the printing process. This strategy involves immersing the printing nozzle in a target cold water area of ​​0℃ to 5℃. Simultaneously with material extrusion, a momentary, localized temperature zone (10℃ to 20℃) is created for the freshly extruded concrete strip through a heating element built into the nozzle or a coaxial jet of warm water (e.g., 15℃) around the nozzle. This temperature zone is sufficient to instantly activate the cement's hydration reaction, allowing it to complete its initial setting before being completely cooled by the surrounding cold water. This ensures good adhesion between layers and the immediate stability of the printed structure.

[0072] The fourth aspect of this invention provides the use of a low-temperature underwater resistant 3D-printed concrete material in building facilities in a low-temperature underwater environment.

[0073] Preferably, the building facilities in the low-temperature underwater environment are related to polar research stations or space bases.

[0074] More preferably, the related buildings and facilities of the polar research station include, but are not limited to, the foundation of the research station in the Arctic and Antarctic regions, underwater observation platforms, under-ice structure repair, and the construction of deep-sea space stations.

[0075] More preferably, the space base is a lunar base. Related architectural facilities of the lunar base include, for example, a lunar base ice dome.

[0076] As described above, the low-temperature underwater 3D printed concrete and its construction method provided by the present invention have the following beneficial effects:

[0077] (1) The present invention provides a low-temperature resistant underwater 3D printed concrete and its construction method, which can break through the low temperature forbidden zone and realize concrete 3D printing in the icy water environment of 0℃~5℃, solving the fundamental problem that the material does not solidify, has no strength, and is easily damaged by freezing at low temperature.

[0078] (2) The present invention provides a low-temperature underwater 3D printed concrete and its construction method. The material prepared by it has excellent performance. The concrete material prepared can achieve a compressive strength of more than 15MPa under low temperature water for 24 hours, and a strength of C40 grade for 28 days. Moreover, the frost resistance grade meets the requirements of polar environment.

[0079] (3) The present invention provides a low-temperature resistant underwater 3D printed concrete and its construction method, which is highly efficient and energy-saving in construction. The innovative "micro-environment temperature control" printing method only requires local heating of a small amount of material at the moment of extrusion. Compared with heating a large area of ​​water, the energy consumption is reduced by more than 99%, and the thermal disturbance to the environment is minimal.

[0080] (4) The low-temperature underwater 3D printed concrete and its construction method provided by the present invention have broad application prospects and provide feasible automated construction solutions for the foundation of scientific research stations, underwater observation platforms, ice structure repair and deep-sea space station construction in the Arctic, Antarctic and other regions.

[0081] (5) The present invention provides a low-temperature resistant underwater 3D printed concrete and its construction method, which solves the problem that existing underwater 3D printing technology cannot be effectively constructed in low-temperature and harsh environments through the systematic design of material formulation and the innovative combination of construction technology. The prepared concrete material has excellent low-temperature early strength, freeze-thaw resistance and underwater anti-dispersion properties; the construction method provided achieves low-energy consumption and high-efficiency automated construction through local micro-environment temperature control, providing key material and technical support for moldless construction in cold water environments such as polar regions and deep seas. Detailed Implementation

[0082] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0083] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0084] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0085] Example 1

[0086] A low-temperature underwater 3D printing concrete material, by weight, comprises the following components: 100 parts cementitious material (including 70 parts of P·O42.5 grade sulfoaluminate cement and 30 parts of P·O52.5 grade high early strength silicate cement), 90 parts fine aggregate: natural quartz sand (fractal dimension D=2.25), 8 parts low-temperature resistant composite admixture (including 2 parts sodium sulfate, 3 parts calcium formate, 1.5 parts polycarboxylate superplasticizer, and 1.5 parts waterborne epoxy resin), 0.5 parts polyvinyl alcohol (PVA) fiber, and 30 parts water. The waterborne epoxy resin is a pale yellow liquid with a solid content of not less than 50%, a viscosity of 1000 mPa·s at 25℃, and a bond strength to a damp concrete substrate of not less than 2.0 MPa. The polyvinyl alcohol fiber has a length of 13 mm, a diameter of 40 μm, a tensile strength of not less than 1500 MPa, and an elastic modulus of not less than 38 GPa.

[0087] The preparation method of the above-mentioned low-temperature underwater 3D printing concrete material is as follows:

[0088] (1) First, dry mix the cementitious material and fine aggregate for 2 minutes at a speed of 40 r / min to obtain the first mixture.

[0089] (2) Add low-temperature resistant composite additive and water to the first mixture and wet mix for 90s at a speed of 70r / min to obtain the second mixture.

[0090] (3) PVA fiber was added to the second mixture and stirred for 90 seconds at a speed of 50 r / min until uniform, to obtain sample 1# of low-temperature underwater 3D printing concrete material, which can be applied to the construction of the ice dome of the lunar base.

[0091] Example 2

[0092] A low-temperature underwater 3D printing resistant concrete material, by weight, comprises the following components: 100 parts cementitious material (including 80 parts of P·O42.5 grade sulfoaluminate cement and 20 parts of P·O52.5 grade high early strength silicate cement), 100 parts fine aggregate: natural quartz sand (fractal dimension D=2.20), 10 parts low-temperature resistant composite admixture (including 1 part lithium sulfate, 4 parts triethanolamine, 2 parts polycarboxylate superplasticizer, and 3 parts a mixture of cellulose ether and polyacrylamide, with a weight ratio of cellulose ether to polyacrylamide of 1:1), 0.6 parts polypropylene (PP) fiber, and 28 parts water. The cellulose ether has a viscosity of 50,000 mPa·s at 20℃. The polyacrylamide is anionic with a molecular weight of 10 million. The polypropylene fiber has a length of 12 mm, a specific gravity of 0.91 g / cm³, and a tensile strength of not less than 400 MPa.

[0093] The preparation method of the above-mentioned low-temperature underwater 3D printing concrete material is the same as that in Example 1, and a sample 2# of the low-temperature underwater 3D printing concrete material is obtained, which can be applied to the construction of the Antarctic research station.

[0094] Compare with Example 1

[0095] The concrete formula for room-temperature underwater 3D printing, based on existing technology and referencing the formula in Chinese Patent CN110723949A, does not contain specific antifreeze or low-temperature early-strength components. Its specific components are: 75 parts silicate cement, 16 parts ultrafine slag powder (specific surface area not less than 800 m² / kg), 100 parts fine aggregate: natural quartz sand, 27 parts water, 15 parts water-based epoxy resin, 2.2 parts polycarboxylate-based high-efficiency water-reducing agent, 0.2 parts retarder: sodium gluconate, 0.7 parts flocculant: cationic polyacrylamide, and 0.6 parts polypropylene fiber. The performance requirements for the water-based epoxy resin are the same as in Example 1, and the performance requirements for the polypropylene fiber are the same as in Example 2.

[0096] The preparation method of the above-mentioned 3D printed concrete material at room temperature underwater is as follows: The components except polypropylene fiber and half of the water are stirred at 1200 r / min for 100 s, then the remaining water is added and stirred at 1200 r / min for 70 s, then the polypropylene fiber is added and stirred at 1200 r / min for 100 s to obtain control material sample 1.

[0097] Compare with Example 2

[0098] Based on Control Example 1, a commercially available chloride-based antifreeze agent (5 parts calcium chloride) was simply added, while other components remained unchanged, to simulate the traditional antifreeze concrete approach. The preparation method was the same as Control Example 1, resulting in Control Material Sample 2.

[0099] Test Example 1

[0100] Material samples 1# and 2# prepared in Examples 1 and 2, along with control material samples 1# and 2 prepared in Control Examples 1 and 2, were loaded into a 3D printing device. The printing nozzle was placed at the printing starting point in a target cold water area with a water temperature of 2℃±1℃. The 3D printing device was started, and the printing nozzle was locally heated by the built-in heating element to maintain the local ambient temperature of the sprayed concrete slurry at 15℃. The slurry was extruded and printed layer by layer continuously at 30mm / s, with an interlayer interruption time of ≤15min. After solidification, the structure was formed. At the same time, its key performance was tested, and the test performance results are shown in Table 1 below.

[0101] As shown in Table 1, Examples 1 and 2, employing the technical solutions of this invention, exhibit excellent comprehensive performance in a low-temperature underwater environment at 2°C. They not only print smoothly but also solidify rapidly, achieving an early strength exceeding 15 MPa within 24 hours, ensuring structural safety. The 28-day strength reaches C40 or higher, demonstrating superior frost resistance and fully meeting the requirements for use in polar environments. Comparative Example 1 (existing room-temperature technology) completely failed in low-temperature water; the cement did not hydrate, and the material could not solidify, proving that existing technology cannot be directly applied to low-temperature environments. Comparative Example 2 (simple addition of antifreeze) promoted solidification to some extent, but the early strength was extremely low, and the later strength development was insufficient, resulting in poor frost resistance and surface spalling. This indicates that simple antifreeze measures cannot solve the fundamental problems of insufficient cement hydration kinetics and poor structural stability at low temperatures.

[0102] Table 1 Comparison of the performance of each formulation in a 2℃ underwater environment.

[0103] Performance indicators Example 1 Example 2 Compare with Example 1 Compare with Example 2 Printability Good, continuous discharge Good, continuous discharge Unable to form, slurry spills Poor material discharge can easily cause blockages. Initial setting time (h) 1.5 1.2 > 48 (Non-condensing) 3.5 24-hour underwater compressive strength (MPa) 16.8 18.5 0 2.1 28-day underwater compressive strength (MPa) 42.5 45.2 - 15.7 (Surface peeling) Freeze-thaw resistance rating (rapid freeze-thaw cycle) F150 F200 - F25

[0104] Compare with Example 3

[0105] A control material, by weight, comprises the following components: 100 parts cementitious material (including 50 parts of P·O42.5 grade sulfoaluminate cement and 50 parts of P·O52.5 grade high early strength silicate cement), fine aggregate: 50 parts natural quartz sand (fractal dimension D=1.8), 4.5 parts low-temperature resistant composite admixture (including 0.5 parts sodium sulfate, 1 part calcium formate, 2.5 parts polycarboxylate superplasticizer, and 0.5 parts waterborne epoxy resin), 0.1 parts polyvinyl alcohol (PVA) fiber, and 18 parts water. The performance requirements for the waterborne epoxy resin and polyvinyl alcohol (PVA) fiber are the same as in Example 1.

[0106] The preparation method of the above control material is the same as in Example 1, and control material sample 3 is obtained.

[0107] Compare with Example 4

[0108] A control material, by weight, comprises the following components: 100 parts cementitious material (including 40 parts of P·O42.5 grade sulfoaluminate cement and 60 parts of P·O52.5 grade high early strength silicate cement), 60 parts fine aggregate (fractal dimension D=2.7), 16 parts low-temperature resistant composite admixture (including 4 parts sodium sulfate, 6 parts calcium formate, 0.5 parts polycarboxylate superplasticizer, and 5.5 parts waterborne epoxy resin), 1.1 parts polyvinyl alcohol (PVA) fiber, and 42 parts water. The performance requirements for the waterborne epoxy resin and polyvinyl alcohol (PVA) fiber are the same as in Example 1.

[0109] The preparation method of the above control material is the same as that in Example 1, and control material sample 4 is obtained.

[0110] Compare with Example 5

[0111] The material sample 1# obtained in Example 1 was loaded into the 3D printing equipment. The printing nozzle was placed at the printing starting point of the target cold water area with a water temperature of 2℃±1℃. The 3D printing equipment was started, and the slurry was extruded for continuous layer-by-layer printing at 30mm / s. The interlayer interruption time of continuous layer-by-layer printing was ≤15min. After solidification, the structure was formed.

[0112] Test Example 2

[0113] Material sample 1# prepared in Example 1 and control material samples 3 and 4 prepared in Comparative Examples 3 and 4 were 3D printed according to the construction method in Test Example 1. Material sample 1# prepared in Example 1 was 3D printed according to the construction method in Comparative Example 5. The key performances were tested, and the test performance results are shown in Table 2 below.

[0114] Table 2

[0115] Performance indicators Example 1 Compare with Example 3 Compare with Example 4 Compare with Example 5 Printability Good, continuous discharge Poor quality; the slurry is too dry, making extrusion difficult. Poor quality, prone to clogging, excessive fluidity Unable to form, the slurry rapidly disperses in cold water. Initial setting time (h) 1.5 > 24 > 12 > 48 (Non-condensing) 24-hour underwater compressive strength (MPa) 16.8 < 1.0 < 0.5 — 28-day underwater compressive strength (MPa) 42.5 < 10.0 < 5.0 (Severely Stratified) — Freeze-thaw resistance rating (rapid freeze-thaw cycle) F150 F0 F0 —

[0116] As shown in Table 2, the superior performance of this invention is the result of the synergistic effect of a specific material formulation and a specific construction method. The material compositions of Comparative Examples 3 and 4 exceeded the optimization range defined by this invention, resulting in poor printability, inability to form an effective structure, and severely insufficient mechanical properties and frost resistance. Although Comparative Example 5 used the optimized material of this invention, it lacked the crucial "microenvironment temperature control" construction step, causing the material to fail to solidify and form in low-temperature water, resulting in performance failure similar to the prior art (Comparative Example 1). Only when the specific material formulation of this invention is combined with a specific construction method (as in Example 1) can good printability, rapid solidification, excellent early strength, and frost resistance be achieved in a low-temperature water environment.

[0117] In summary, this invention, through the systematic innovative design of material components and the ingenious combination of construction methods, successfully solves a series of technical challenges in low-temperature underwater 3D printing, demonstrating significant advancement and practicality.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A construction method for 3D printed concrete material, comprising the following steps: A) Prepare slurry from 3D printed concrete material, load it into the 3D printing equipment, and place the printing nozzle at the starting point of the printing process in the target water area; B) Start the 3D printing equipment, and after locally heating the printing nozzle, slurry is extruded for continuous layer-by-layer printing. The structure is formed after solidification. In step A), the water temperature of the target water area is 0-5℃; In step B), the temperature of the locally heated printhead is 10-20°C; The 3D printed concrete material comprises the following components by weight: 100 parts of cementitious material; 70-120 parts fine aggregate; 1-15 parts of low-temperature resistant composite additive; Alkali-resistant fiber: 0.15-1.0 parts; 20-40 parts water; The cementing material is selected from at least one of sulfoaluminate cement or silicate cement.

2. The construction method for 3D printed concrete material according to claim 1, characterized in that, Includes one or more of the following conditions: A1) The cementitious materials include sulfoaluminate cement and silicate cement; A2) The fine aggregate mentioned is natural quartz sand; A3) The particle size distribution of the fine aggregate has fractal characteristics, and its fractal dimension D is 2.1-2.4; A4) The low-temperature resistant composite additive is selected from at least one of the following: early strength agent, antifreeze agent, water-reducing agent or anti-dispersing agent; A5) The alkali-resistant fiber is selected from at least one of polyvinyl alcohol fiber or polypropylene fiber; A6) The water mentioned is tap water or deionized water.

3. The construction method for 3D printed concrete material according to claim 2, characterized in that, Includes one or more of the following conditions: B1) In item A1), the weight ratio of the sulfoaluminate cement to the silicate cement is 70-80:20-30; B2) In item A4), the low-temperature resistant composite admixture includes an early-strength agent, an antifreeze agent, a water-reducing agent, and an anti-dispersing agent; B3) In item A4), the early strength agent is selected from at least one of sodium sulfate or lithium sulfate; B4) In item A4), the antifreeze is selected from at least one of calcium formate or triethanolamine; B5) In item A4), the water-reducing agent is a polycarboxylate superplasticizer; B6) In item A4), the anti-dispersant is selected from at least one of waterborne epoxy resin, cellulose ether or polyacrylamide; B7) In item A5), the performance requirements of the polyvinyl alcohol fiber are: length of 10-15 mm, diameter of 30-50 μm, tensile strength of not less than 1500 MPa, and elastic modulus of not less than 38 GPa. B8) In item A5), the performance requirements for the polypropylene fiber are: length 10-15 mm, specific gravity 0.91 g / cm³. 3 The tensile strength is not less than 400 MPa.

4. The construction method for 3D printed concrete material according to claim 3, characterized in that, In item B2), the low-temperature resistant composite additive, by weight, includes the following components: 1-3 parts of early strength agent, 2-5 parts of antifreeze agent, 1-2 parts of water reducing agent, and 1-2 parts of anti-dispersing agent.

5. The construction method for a 3D printed concrete material according to claim 1, characterized in that, The method for preparing the 3D printed concrete material includes the following steps: 1) Dry-mix the cementitious materials and fine aggregates according to the proportions to obtain the first mixture; 2) Add low-temperature resistant composite additives and water to the first mixture and wet mix to obtain the second mixture; 3) Add alkali-resistant fiber to the second mixture and continue stirring until homogeneous to provide the required material.

6. The construction method for 3D printed concrete material according to claim 5, characterized in that, Step 1) includes one or more of the following conditions: 11) The dry mixing time is 2-3 minutes; 12) The stirring speed for the dry mixing is 30-50 r / min.

7. The construction method for 3D printed concrete material according to claim 5, characterized in that, Step 2) includes one or more of the following conditions: 21) The wet mixing time is 80-100 seconds; 22) The stirring speed for the wet mixing is 60-80 r / min.

8. The construction method for 3D printed concrete material according to claim 5, characterized in that, Step 3) includes one or more of the following conditions: 31) The stirring time is 80-100 seconds; 32) The stirring speed for continued stirring is 40-60 r / min.

9. The construction method for 3D printed concrete material according to claim 1, characterized in that, Includes one or more of the following conditions: C1) In step B), the speed of the continuous layer-by-layer printing is 10-40 mm / s; C2) In step B), the interlayer interruption time of the continuous layer-by-layer printing is ≤15min.

10. The use of a construction method for a 3D-printed concrete material according to any one of claims 1-9 in building facilities in a low-temperature underwater environment.