A method for building thin-walled components based on cement-based 3D printing

Abstract

This invention discloses a method for constructing thin-walled components based on cement-based 3D printing, comprising the following steps: Step S1, placing cement-based material into the extrusion equipment of a concrete 3D printer; the extrusion equipment is equipped with a first temperature control system, which controls the temperature inside the extrusion equipment to 10℃±5℃; Step S2, setting the printing parameters of the extrusion equipment according to the model of the thin-walled component, and printing layer by layer from bottom to top on the printing platform using 3D printing technology to form an initial component; the printing platform is equipped with a second temperature control system, which is used to control the temperature of the cement-based material printed on the printing platform; Step S3, curing the initial component on the printing platform at 45℃±5℃ to obtain the thin-walled component. The construction method of this invention is applicable to printing thin-walled components in any temperature and humidity environment, with more than 100 stacked layers and a stacking height of more than 1m, and the resulting printed component has a stable structure.

Description

Technical Field

[0001] This invention relates to the field of cement-based 3D printing technology, and in particular to a method for constructing thin-walled components based on cement-based 3D printing. Background Technology

[0002] In recent years, cement-based 3D printing technology, based on extrusion and layer-by-layer deposition, has developed rapidly in the fields of architecture and civil engineering. Cement-based 3D printing technology is mostly used for printing irregular permanent templates (i.e., modular manufacturing) and landscape structures. Among them, modular manufacturing, taking advantage of the advantages of 3D printing, prints thin-walled irregular templates, inserts a steel cage (steel mesh, etc.), and then pours it into a whole, thereby improving the intelligence, economy, efficiency, and greenness of the manufacturing process. Landscape structures mainly include small and medium-span landscape arch bridges, tunnel entrance decorations, and landscape features. Currently, the height of a single thin-walled irregular printed component, i.e., a continuous and uninterrupted stacking of thin-walled components, is 0.5m to 1m. Moreover, existing thin-walled components are mostly solid or have an internal lattice structure to form a complete large structure or template. Such thin-walled components have complex shapes, extremely high precision requirements, and some thin-walled components also require ultra-thin walls.

[0003] The inherent properties of cement-based materials and the printing environment during the printing of thin-walled components can significantly affect the performance and fabrication efficiency of the finished product, making it difficult to achieve stable control of 3D printed structures. Traditional cement-based materials suffer from poor rheological and early mechanical properties, poor matching between the printing material and the extrusion device, and thixotropic slurries can negatively impact the mechanical properties of the printed structure, hindering their practical application in 3D printing technology. To meet the material requirements of 3D printing technology, some existing research has specifically developed cement-based materials suitable for 3D printing. These typically involve introducing auxiliary binders and clay materials or admixtures to regulate the rheology of 3D printed building materials, thereby stabilizing the 3D printed structure. Patent CN 111302709 A discloses an alkali-activated gelling material for 3D printing and its printing method. The alkali-activated gelling material consists of two parts: a particulate mixture and an alkali activator solution. The particulate mixture includes: 100 parts of alkali-activated powder; 0-5 parts of a coagulant; 0-0.5 parts of nanoparticles; 0.1-5 parts of chopped fibers; 100-220 parts of aggregate; and 5-20 parts of fine filler. The alkali activator solution includes: 100 parts of alkali solution; 0.0005-0.002 parts of surfactant; 0.0001-0.0005 parts of defoamer; and 0.0003-0.001 parts of stabilizer. The surfactant has a hydrophilic-lipophilic balance value of 7-9, resulting in a contact angle of 10-45° for the alkali activator solution. The printing method of this invention can achieve the printing of thin-walled components. Patent CN112125618A provides a high thixotropic 3D printing cement-based material, its preparation method, and its application. The raw materials of the cement-based material include the following components: 65-100 parts of composite cementitious component, 0.1-0.4 parts of porous carbon material, 1-3 parts of expanded perlite, 20-40 parts of quartz sand, 0.5-1.5 parts of thickener, 0.4-1.2 parts of water-reducing agent, and 30-50 parts of water. The high thixotropic 3D printing cement-based material proposed in this invention can well meet the continuity and extrusion properties required for 3D printing, thereby obtaining the low deformation and high mechanical properties required for 3D printing.

[0004] Besides the high requirements of 3D printing materials, a more significant issue is the poor compatibility between 3D printing technology and cement-based printing materials, making it difficult to achieve stable control over the structure and mechanical properties of thin-walled components. Current 3D printing technologies improve printing stability and success rates to some extent by reducing print head speed, increasing infill rate, or simultaneously printing multiple components in slices, thereby extending the printing time of a single layer. However, regardless of the method, breakpoints or material waste can occur, significantly reducing printing efficiency and component appearance quality, increasing assembly difficulty and the number of weak connection surfaces between printed components, potentially leading to unnecessary economic losses. The success rate of printed components is inversely proportional to the height of continuous stacking (number of layers stacked at once), the degree of irregularity (cantilever), the thinness of the wall (cross-sectional area of ​​any printed slice or number of parallel printed strips), and the travel speed of the printing tool. The success rate is also affected by materials and the printing environment. Therefore, there is a need to develop a 3D printing cement-based construction method for thin-walled components. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art, such as poor compatibility between 3D printing technology and cement-based printing materials, and the fact that the printing success rate is affected by materials and printing environment, making it difficult to achieve stable control of the structure and mechanical properties of thin-walled components. This invention provides a method for constructing thin-walled components based on cement-based 3D printing.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for constructing thin-walled components based on cement-based 3D printing includes the following steps:

[0008] Step S1: Place the cement-based material into the extrusion equipment of the concrete 3D printer; the extrusion equipment is equipped with a first temperature control system, which controls the temperature inside the extrusion equipment to be 10℃±5℃.

[0009] Step S2: Set the printing parameters of the extrusion equipment according to the model of the thin-walled component, and print layer by layer from bottom to top on the printing platform using 3D printing technology to form the initial component; the printing parameters include pumping speed, printing path, slice layer height, extrusion speed, travel trajectory speed, slice direction, filling mode, extrusion tool end, printing layer interval time, etc., the printing layer interval time is 10s to 300s, and the slice layer height is 10mm to 30mm; the printing platform is equipped with a second temperature control system, which is used to control the temperature of the cement-based material printed on the printing platform;

[0010] Step S3: Curing the initial component on the printing platform at 45℃±5℃ to obtain a thin-walled component.

[0011] The construction method of this invention uses cement-based materials to prepare thin-walled components, which have excellent extrudability and constructability. The extrusion equipment is equipped with a first temperature control system and the printing platform is equipped with a second temperature control system. The first temperature control system can control the temperature of the cement-based material in the extrusion equipment, which can avoid sudden changes in the composition and environmental conditions that may affect the slurry performance, thus causing problems such as blockage and material interruption. The second temperature control system controls the temperature of the cement-based material printed on the printing platform according to the material parameters. The setting of the second temperature control system can shorten the initial or final setting time of the cement-based material of the same height printing layer, avoiding excessive time difference, which may easily lead to cold joints between adjacent printing layers and reduce the overall performance of the thin-walled component. At the same time, the temperature on the printing platform can make the bottom printing layer support the upper printing layer, preventing the printing layer from collapsing and improving the success rate of printing thin-walled components with a large aspect ratio.

[0012] Further, the cement-based material comprises the following components in parts by weight: 40-80 parts silicate cement, 20-80 parts fly ash, 15-50 parts silica fume, 20-50 parts mineral powder, 100-210 parts quartz sand, 28.5-63 parts water, 0.20-0.40 parts water-reducing agent, 0.20-0.40 parts reinforcing fiber, 0.005-0.03 parts thickener, and 1-5 parts accelerator.

[0013] Furthermore, the fly ash is Class F Grade 1 fly ash, the mineral powder is S95 mineral powder, and the quartz sand has a mesh size of 40-80 mesh; the water-reducing agent is a high-efficiency polycarboxylate water-reducing agent, the reinforcing fiber is one or more of PVA fiber, basalt fiber, etc., the reinforcing fiber is an easily dispersible fiber, the thickener is hydroxyethyl methyl cellulose, and the quick-setting agent is one or two of powdered quick-setting agents such as calcium formate and lithium carbonate.

[0014] Furthermore, the method for preparing the cement-based material includes the following steps:

[0015] (1) Divide the components of the cement-based material into four groups, mix 2.85 to 6.3 parts of water and 0.005 to 0.03 parts of thickener in the first group, stir, and stir until the mixed solution is gel-like or has a certain viscosity to obtain the first solution;

[0016] (2) Put 40-80 parts of silicate cement, 20-80 parts of fly ash, 15-50 parts of silica fume and 20-50 parts of mineral powder into a vertical shaft mixer and mix thoroughly. Continue to add 0.2-0.4 parts of water-reducing agent, 0.2-0.4 parts of reinforcing fiber, 1-5 parts of quick-setting agent and 22.8-50.4 parts of water from the second group and stir. Then add the first solution to the well-mixed mixture and mix until it is evenly mixed to obtain the second solution.

[0017] (3) Add 2.85 to 6.3 parts of water and 100 to 210 parts of quartz sand from the fourth group to the second solution, stir, mix evenly, and obtain the cement-based material.

[0018] Furthermore, the cement-based material comprises the following components in parts by weight: 56 parts silicate cement, 20 parts fly ash, 15 parts silica fume, 20 parts mineral powder, 130 parts quartz sand, 35.2 parts water, 0.21 parts water-reducing agent, 0.21 parts reinforcing fiber, 0.016 parts thickener, and 3.75 parts accelerator.

[0019] Furthermore, the first temperature control system is installed on the pumping equipment, pumping pipeline, and extrusion tool end of the extrusion equipment. Distributed on the pumping equipment, pumping pipeline, and extrusion tool end, the first temperature control system can significantly extend the residence time and pumping length of the cement-based material within the pipeline or equipment by controlling the temperature of the pumping equipment and pumping pipeline. This effectively avoids the impact on the bonding between component layers caused by excessive differences in the setting time of cement-based materials stirred at different time points, or the significant changes in the cross-sectional dimensions of the printing strip due to material conditions caused by unstable extrusion pressure. This ensures the final shape of the thin-walled component and improves the success rate of component printing. Furthermore, the first temperature control system is a water-cooling device.

[0020] Furthermore, the stacking height of the thin-walled components is 1–3 m, and the wall thickness is 3 cm–10 cm. Even further, the stacking height of the thin-walled components is 1.4–2 m.

[0021] Furthermore, the printing parameters are set according to the shape and size of the printed component, and the shape of the extrusion tool end is circular or rectangular.

[0022] Furthermore, the second temperature control system controls the temperature of the cement-based material printed on the printing platform according to material parameters, including printing status, printing model height, printing environment temperature and humidity, equipment parameters, printing path, etc. Furthermore, the second temperature control system uses jet hot steam or cold air to achieve temperature control.

[0023] Further, in step S2, the temperature of the printing platform is linearly set according to the difficulty of printing the thin-walled component model. The difficulty of the thin-walled component model is determined by the interval time between printing layers under different continuous stacking heights and the stability of the underlying support structure. Different continuous stacking heights are divided into two levels: H≤50cm and H>50cm, where H is the height of the different continuous stacking heights. When the height of the different continuous stacking heights is used as a variable, the higher H is, the higher the construction requirements for the thin-walled component. The printing layer interval time refers to the interval between printing layers, which is divided into three levels: T≤15s, 120s≥T>15s, and T>120s, where T is the printing layer interval time. When the printing layer interval time is used as a variable, the larger T is, the higher the success rate of constructing the thin-walled component. The stability is determined by the proportion of the horizontal distance between the center lines of the two adjacent printing strips in the width of a single extrusion strip, the proportion of the height of the overhanging area in the one-time stacking height, and the location, combined with project information and facility foundation. The stability is mainly determined by the proportion of the horizontal distance between the center lines of the two adjacent printing strips in the width of a single extrusion strip.

[0024] The horizontal distance between the center lines of two adjacent printing strips in the upper and lower layers is the proportion of the width of a single extrusion strip. Q represents the distance percentage, y represents the horizontal distance between the center lines of adjacent print strips on the upper and lower layers, and x represents the distance between the center lines of adjacent print strips on the upper and lower layers.

[0025] For a single extrusion strip width, the distance percentage is divided into two levels: Q≤1 / 6 and Q>1 / 6. When the distance percentage is used as a variable, the smaller Q is, the smaller the overhang area percentage, the higher the position, the closed and symmetrical printed cross-section, and the higher the printing success rate of the thin-walled component. The proportion of the overhang area height in the one-time stacking height is the height percentage. P represents the height percentage, and h represents the height of the cantilever area. There are two levels: P > 0.5 and P ≤ 0.5.

[0026] When H ≤ 50cm and Q < 1 / 6, the temperature of the printing area on the printing platform is controlled to be 5–35°C by the second temperature control system. At this time, the printing difficulty of the thin-walled component does not need to be considered. The temperature of the printing area is controlled to ensure the normal operation of the extrusion equipment and the material can complete the solidification process.

[0027] When H > 50cm and Q ≤ 1 / 6, or when H ≤ 50cm and Q > 1 / 6, if T ≤ 15s and P > 0.5, and the printed cross-section is not closed or its symmetry is not obvious, the temperature of the printing area on the printing platform is controlled at 35℃ ± 5℃ by the second temperature control system; if T ≤ 15s or P > 0.5, the temperature of the printing area on the printing platform is controlled at 30℃ ± 5℃ by the second temperature control system; if 120s ≥ T > 15s, or P ≤ 0.5, the temperature of the printing area on the printing platform is controlled at 20℃ ± 5℃ by the second temperature control system; if T > 120s, the temperature of the printing area on the printing platform is controlled at 15℃ ± 5℃ by the second temperature control system. For the case where T > 120s, the temperature control is appropriately adjusted according to the initial setting time and printing state of the cement-based material under different temperatures and humidity conditions, which to some extent reduces the phenomenon of weak interlayer surfaces. It should be noted that the printing area refers to the area above the printing platform where the extrusion equipment travels, or the entire space occupied by the extrusion tool end during the component printing process. The temperature of the printing area is the average temperature.

[0028] Furthermore, in step S3, the thin-walled component is cured on the printing platform for 6 to 12 hours with humidity controlled between 50 and 95% to ensure that it meets the requirements for movement and is moved into the curing cover for subsequent curing.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The construction method of this invention uses cement-based materials to prepare thin-walled components, which have excellent extrudability and constructability. The extrusion equipment is equipped with a first temperature control system and the printing platform is equipped with a second temperature control system. The first temperature control system can control the temperature of the cement-based material in the extrusion equipment, which can avoid sudden changes in the composition and environmental conditions that may affect the slurry performance, thereby causing problems such as blockage and material interruption. The second temperature control system controls the temperature of the cement-based material printed on the printing platform according to the material parameters. The setting of the second temperature control system can shorten the initial or final setting time of the cement-based material of the same height printing layer, avoiding excessive time difference, which may easily lead to cold joints between adjacent printing layers and reduce the overall performance of the thin-walled component. At the same time, the temperature on the printing platform can make the bottom printing layer support the upper printing layer, preventing the printing layer from collapsing and improving the success rate of printing thin-walled components with a large aspect ratio.

[0031] 2. The construction method of the present invention is applicable to the printing of thin-walled components in any temperature and humidity environment, especially printing in low temperature environment. The number of stacked layers of the printed thin-walled components is greater than 100 and the stacking height is more than 1m. The resulting printed components have stable structures and the travel time of a single printed layer is less than 30s. Attached image description:

[0032] Figure 1This is a schematic diagram of the process for constructing thin-walled components based on cement-based 3D printing according to the present invention.

[0033] Figure 2 This is a three-dimensional structural diagram of the thin-walled, irregularly shaped hollow landscape column in Example 1;

[0034] Figure 3 This is a top view of the thin-walled, irregularly shaped hollow landscape column in Example 1;

[0035] Figure 4 This is a schematic diagram of the printing path for the thin-walled, irregularly shaped hollow landscape column in Example 1;

[0036] Figure 5 This is a field photo of the thin-walled, irregularly shaped hollow landscape column in Example 1. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0038] Example 1

[0039] This embodiment provides a method for constructing thin-walled components based on cement-based 3D printing. The printing uses a cement-based material, which comprises the following components by weight: 40-80 parts silicate cement, 20-80 parts fly ash, 15-50 parts silica fume, 20-50 parts mineral powder, 100-210 parts quartz sand, 28.5-63 parts water, 0.20-0.40 parts water-reducing agent, 0.20-0.40 parts reinforcing fiber, 0.005-0.03 parts thickener, and 1-5 parts accelerator. Specifically, the cement-based material composition is 56 parts silicate cement, 20 parts fly ash, 15 parts silica fume, 20 parts mineral powder, 130 parts quartz sand, 35.2 parts water, 0.21 parts water-reducing agent, 0.21 parts reinforcing fiber, 0.016 parts thickener, and 3.75 parts accelerator. In this embodiment, the fly ash is Class F Grade 1 fly ash, the mineral powder is S95 mineral powder, and the quartz sand has a mesh size of 40-80 mesh. The water-reducing agent is a high-efficiency polycarboxylate water-reducing agent, the reinforcing fiber is PVA fiber, which is easily dispersed, the thickener is hydroxyethyl methyl cellulose, and the viscosity used in this embodiment is 40,000. The quick-setting agent is calcium formate. The preparation method of the cement-based material includes the following steps:

[0040] (1) Divide the components of the cement-based material into four groups, mix 2.85 to 6.3 parts of water and 0.005 to 0.03 parts of thickener in the first group, stir, and stir until the mixed solution is gel-like or has a certain viscosity to obtain the first solution;

[0041] (2) Put 40-80 parts of silicate cement, 20-80 parts of fly ash, 15-50 parts of silica fume and 20-50 parts of mineral powder into a vertical shaft mixer and mix thoroughly for 60 seconds. Then add 0.2-0.4 parts of water-reducing agent, 0.2-0.4 parts of reinforcing fiber, 1-5 parts of quick-setting agent and 22.8-50.4 parts of water from the second group and mix for 60 seconds. Then add the first solution to the well-mixed mixture and mix until it is evenly mixed to obtain the second solution.

[0042] (3) Add 2.85 to 6.3 parts of water and 100 to 210 parts of quartz sand from the fourth group to the second solution, stir for 180 to 300 seconds, mix evenly, and obtain the cement-based material.

[0043] The cement-based material prepared above was subjected to performance testing. The test results are shown in Table 1 below. The data in the table show that the cement-based material has good extrudability and constructability.

[0044] Table 1 Performance test results of cement-based materials

[0045]

[0046] To test the mechanical properties of printed cement-based materials, the cement-based material was placed in the extrusion equipment of a concrete 3D printer for printing. The printed component served as the test piece, and the model parameters were set according to the test piece model. The extrusion tool end was circular with a diameter of 30 mm, the print head travel speed was 9.75 cm / s, and the pumping equipment screw rotation speed was 10 r / min. The printing path interval was 30 mm, and the layer height was set to 13 mm. Each layer of the model had 12 consecutive round-trip paths, and the vertical stacking number was 10 layers. After the test piece was allowed to stand naturally for 8 hours, it was cut into several 100 mm × 100 mm × 100 mm cube specimens according to the specified direction using a rock cutter, and the direction was marked on each specimen. At the same time, considering the rigor and accuracy of the test, the number and area of ​​weak surfaces were fixed as much as possible according to the cutting position. According to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete GB / T 50081~2002", three specimens were taken from different directions and the average value was taken, resulting in the data shown in Table 2. Meanwhile, according to the "Technical Specification for 3D Printing of Concrete T / CECS 786~2020", 15% of the test data exceeding the arithmetic mean difference was discarded, that is, the maximum and minimum values ​​were discarded and the average of the remaining data was taken (according to regulations, 67.5 and 46.9 were discarded), resulting in the data shown in Table 3. The data in Tables 2 and 3 both indicate that the cement-based materials used in this embodiment can meet the compressive strength requirement of over 50 MPa for the printed specimens.

[0047] Table 2 Compressive Strength Data of Test Specimens

[0048]

[0049] Table 3C 60 Compressive strength data sheet for printed cubes

[0050]

[0051] The cement-based material prepared above was then used for printing thin-walled components. Figures 2-3 This embodiment demonstrates the thin-walled component printed in this example. The component is a thin-walled, irregularly shaped hollow landscape column with a stacking height of 1502 mm and a wall thickness of 40 mm. The designed printing path is a single continuous path stacking, with a layer height of 12 mm, for a total of 125 layers. The printing path is as follows: Figure 4 As shown.

[0052] The extrusion equipment's pumping devices, pumping pipelines, and extrusion tool ends are equipped with a first temperature control system. This first temperature control system is a water-cooling device or other cooling device; no specific limitation is made here. A second temperature control system controls the temperature of the cement-based material being printed on the printing platform based on material parameters, including printing status, printing model height, ambient temperature and humidity, equipment parameters, and printing path. This second temperature control system uses jet hot steam or cold air to achieve temperature control. In this embodiment, distance percentage... A continuous stacking height H > 50cm was used in a single operation. The layer-to-layer interval T was 13s, and the slice height was 10mm–30mm. The printing area temperature on the printing platform was controlled at 30℃±5℃ via a second temperature control system. Printing was performed on a heated printing platform (platform surface temperature 60℃), with the actual printing area temperature controlled at 28℃±2℃. The ambient printing temperature was 5–10℃. Based on the model dimensions, a 25mm diameter circular nozzle was selected, with a pump pressure of 0.4MPa and a nozzle travel speed of 0.13m / s. The cement-based material was printed layer by layer from bottom to top on the printing platform, completing the hollow column in one operation and forming the initial component. The resulting initial component is shown below. Figure 5 As shown. The final printing time was 27 minutes and 5 seconds, consistent with the design estimate.

[0053] The initial components were cured on the printing platform at 45℃±5℃ to obtain thin-walled components. The top diameter, height, and wall thickness of the thin-walled irregular hollow column component were completely consistent with the design model. Furthermore, the printed surface quality was excellent, with smooth corners and no obvious defects. Even after being placed normally for 90 days, the surface quality of the hollow column remained good, with a smooth texture. This demonstrates that by controlling the printing parameters during the printing process, thin-walled components with good structural and mechanical properties can be prepared. Cement-based materials can be used to print thin-walled irregular landscapes in low-temperature environments and have high stacking capacity.

[0054] Example 2

[0055] This embodiment is similar to Embodiment 1, except that the printing environment temperature during the printing of thin-walled irregular-shaped hollow landscape columns is 15-20℃. The top layer diameter, height, and wall thickness of the printed thin-walled components are completely consistent with the design model, and there are no obvious defects between layers. This shows that the construction method of the present invention is not affected by the printing environment and can improve the success rate of thin-walled components.

[0056] Comparative Example 1

[0057] This embodiment is similar to Embodiment 1, except that the cement-based material used in this embodiment is 3D printed concrete, a commercially available product from a certain company.

[0058] Under the set printing parameters, printing was performed on the printing platform at a pump pressure of 0.8 MPa. The first print reached 62 layers before overturning. Therefore, the print head travel speed was reduced to T = 25 s, and the top layer diameter and height of the hollow column were changed to 455 mm and 1465 mm respectively, allowing sufficient time for material to solidify. Multiple attempts were needed to barely complete the modified hollow column; however, the total printing time, excluding failure time, was 52 minutes and 5 seconds, twice as long as the original model. Furthermore, due to excessive material mixing time and multiple re-printing cycles, the print surface quality was poor, the extruded strips were discontinuous, and there were many obvious defects. The success rate was also low, and the printing environment was extremely sensitive, requiring minimal disturbance to the print head and hollow column.

[0059] Comparative Example 2

[0060] This embodiment is similar to Embodiment 1, except that the cement-based material composition used in this embodiment is 56 parts silicate cement, 9 parts fly ash, 14.5 parts silica fume, 20.5 parts mineral powder, 130 parts quartz sand, 35.2 parts water, 0.21 parts water-reducing agent, 0.21 parts reinforcing fiber, 0.016 parts thickener, and 0.16 parts quick-setting agent.

[0061] Printing was performed using the same parameters as in Example 1. During printing, the pump pressure was 0.4 MPa, demonstrating the material's good pumpability. However, the bottom printed layer failed to withstand the load of the upper layer and overturned during the printing of the 49th layer, resulting in printing failure. One reason for this was that the cement-based material in this mix had a low static yield stress and a long setting time at low temperatures, making it unable to complete the setting process within the specified time. Another reason was that the bottom printed material could not withstand the weight of the upper material and the extrusion pressure from the locally eccentric printhead, ultimately leading to lateral overturning during the printing process.

[0062] Comparative Example 3

[0063] This embodiment is similar to Embodiment 1, except that the cement-based material composition used in this embodiment is 77 parts silicate cement, 15 parts fly ash, 8 parts silica fume, 130 parts quartz sand, 35.2 parts water, 0.21 parts water-reducing agent, 0.21 parts reinforcing fiber, 0.016 parts thickener, and 1.25 parts quick-setting agent.

[0064] Printing was performed using the same parameters as in Example 1. During the printing process, the pump pressure was 0.4 MPa, demonstrating the material's good pumpability. However, the entire material overturned when printing the 30th layer, failing to complete the printing process. This indicates that the proportions of cement, accelerator, and other components in the composite material are still relatively small, resulting in a high water-cement ratio. Under low-temperature conditions, the material's setting time and static yield stress still cannot meet the application requirements, leading to lateral overturning during the printing process.

[0065] Comparative Example 4

[0066] This embodiment is similar to Embodiment 1, except that the printing platform in this embodiment does not have a second temperature control system. The printing environment temperature is 5-10℃, and the same parameters as in Embodiment 1 are used for printing. During the printing process, the pump pressure is 0.4MPa, demonstrating that the material has good pumpability. Compared to Comparative Examples 1-3, under the condition of disturbance around the printing environment (such as slight vibration caused by the movement of transport vehicles), the printed component overturned completely at the 105th layer, and printing was not completed. Printing was finally completed after the surrounding environment was kept as free of slight vibration as possible. This indicates that the composite material has a low water-cement ratio and suitable component proportions, possessing the performance to print thin-walled components. However, the low-temperature environment has a significant impact on the material's setting time, causing the success rate of the component to be greatly affected by the degree of surrounding disturbance, thus indirectly limiting the material's performance and application scenarios.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for building thin-walled components based on cement-based 3D printing, characterized in that, The thin-walled component has more than 100 stacked layers, a stacking height of more than 1m, and a wall thickness of 3cm to 10cm. The construction method includes the following steps: Step S1: Place the cement-based material into the extrusion equipment of the concrete 3D printer; the extrusion equipment is equipped with a first temperature control system, which controls the temperature inside the extrusion equipment to be 10℃±5℃. Step S2: Set the printing parameters of the extrusion equipment according to the model of the thin-walled component, and print layer by layer from bottom to top on the printing platform using 3D printing technology to form the initial component. The printing parameters include pump speed, printing path, slice layer height, extrusion speed, travel trajectory speed, extrusion tool end, and printing layer interval time. The printing layer interval time is 10s~300s, and the slice layer height is 10mm~30mm. The printing platform is equipped with a second temperature control system, which is used to control the temperature of the cement-based material printed on the printing platform. The temperature of the printing platform is set according to the difficulty of printing the thin-walled component model. The horizontal distance between the center lines of adjacent printing strips of the upper and lower layers is the proportion of the width of a single extrusion strip. Q represents the distance percentage, y represents the horizontal distance between the center lines of adjacent print strips in the upper and lower layers, x represents the width of a single extrusion strip, and the height percentage represents the proportion of the overhang area height in the total stack height. P represents the height percentage, h represents the height of the cantilevered area, and H represents the height of a single continuous stack. When H≤50cm and Q<1 / 6, the temperature of the printing area on the printing platform is controlled to be 5~35℃ by the second temperature control system; When H > 50cm and Q ≤ 1 / 6, or when H ≤ 50cm and Q > 1 / 6, if the printing layer interval time T ≤ 15s and P > 0.5, the temperature of the printing area on the printing platform is controlled to be 35℃ ± 5℃ by the second temperature control system; if T ≤ 15s or P > 0.5, the temperature of the printing area on the printing platform is controlled to be 30℃ ± 5℃ by the second temperature control system; if 120s ≥ T > 15s or P ≤ 0.5, the temperature of the printing area on the printing platform is controlled to be 20℃ ± 5℃ by the second temperature control system; if T > 120s, the temperature of the printing area on the printing platform is controlled to be 15℃ ± 5℃ by the second temperature control system. Step S3: Curing the initial component on the printing platform at 45℃±5℃ to obtain a thin-walled component.

2. The method for constructing thin-walled components based on cement-based 3D printing according to claim 1, characterized in that, The cement-based material comprises the following components in parts by weight: 40-80 parts silicate cement, 20-80 parts fly ash, 15-50 parts silica fume, 20-50 parts mineral powder, 100-210 parts quartz sand, 28.5-63 parts water, 0.20-0.40 parts water-reducing agent, 0.20-0.40 parts reinforcing fiber, 0.005-0.03 parts thickener, and 1-5 parts quick-setting agent.

3. The method for constructing thin-walled components based on cement-based 3D printing according to claim 2, characterized in that, The fly ash is Class F Grade 1 fly ash, the mineral powder is S95 mineral powder, and the quartz sand has a mesh size of 40-80 mesh; the water-reducing agent is a high-efficiency polycarboxylate water-reducing agent, the reinforcing fiber is PVA fiber or basalt fiber, the thickener is hydroxyethyl methyl cellulose, and the quick-setting agent is one or both of calcium formate and lithium carbonate.

4. The method for constructing thin-walled components based on cement-based 3D printing according to claim 2, characterized in that, The method for preparing the cement-based material includes the following steps: (1) Divide the components of the cement-based material into four groups, mix 2.85~6.3 parts of water and 0.005~0.03 parts of thickener in the first group, stir, and stir until the mixed solution is gel-like or has a certain viscosity to obtain the first solution; (2) Put 40-80 parts of silicate cement, 20-80 parts of fly ash, 15-50 parts of silica fume and 20-50 parts of mineral powder into a vertical shaft mixer and mix thoroughly. Then add 0.2-0.4 parts of water-reducing agent, 0.2-0.4 parts of reinforcing fiber, 1-5 parts of quick-setting agent and 22.8-50.4 parts of water from the second group and stir. Then add the first solution to the well-mixed mixture and mix until it is evenly mixed to obtain the second solution. (3) Add 2.85~6.3 parts of water and 100~210 parts of quartz sand from the fourth group to the second solution, stir, mix evenly, and obtain the cement-based material.

5. The method for constructing thin-walled components based on cement-based 3D printing according to claim 2, characterized in that, The cement-based material comprises the following components in parts by weight: 56 parts silicate cement, 20 parts fly ash, 15 parts silica fume, 20 parts mineral powder, 130 parts quartz sand, 35.2 parts water, 0.21 parts water-reducing agent, 0.21 parts reinforcing fiber, 0.016 parts thickener, and 3.75 parts quick-setting agent.

6. The method for constructing thin-walled components based on cement-based 3D printing according to claim 1, characterized in that, The first temperature control system is installed on the pumping equipment, pumping pipeline, and extrusion tool end of the extrusion equipment.

7. The method for constructing thin-walled components based on cement-based 3D printing according to claim 1, characterized in that, The stacking height of the thin-walled components is 1~3m.

8. The method for constructing thin-walled components based on cement-based 3D printing according to claim 1, characterized in that, The shape of the extrusion tool end is circular or rectangular.

9. The method for constructing thin-walled components based on cement-based 3D printing according to claim 1, characterized in that, The second temperature control system controls the temperature of the cement-based material being printed on the printing platform according to the material parameters, including printing status, printing model height, printing environment temperature and humidity, equipment parameters, and printing path.

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